GIFT OF 
 
 V- NC\ 
 
(U*. , 
 
MANUAL 
 
 OF 
 
 CHEMICAL TECHNOLOGY 
 
 BY 
 
 RUDOLF VON WAGNER 
 
MANUAL 
 
 OP 
 
 CHEMICAL TECHNOLOGY 
 
 BY 
 
 RUDOLF VON WAGNER 
 
 II 
 
 TRANSLATED AND EDITED BY 
 
 SIR WILLIAM CROOKES, F.R.S. 
 
 PAST PRES. C.S., PRES. INST. E.E. 
 
 FROM THE THIRTEENTH ENLARGED GERMAN EDITION AS REMODELLED BY 
 
 DE FERDINAND FISCHER 
 
 WITH 596 ILLUSTRATIONS 
 REPRINTED 1897 
 
 NEW YORK 
 D. APPLETON & CO. 
 
 1, 3 & 5 BOND STREET 
 1897 
 
T P/ fs- 
 
PREFACE TO THE THIRTEENTH GERMAN EDITION. 
 
 IN the twelfth edition of this Manual, which appeared in 1886, I confined 
 myself to abridging or totally removing jhe obsolete matter in the eleventh 
 edition, which had been completed by Wagner shortly before his death, 
 October 4, 1880, and to inserting, or at least referring to, the improvements 
 effected in the last few years. 
 
 In the present edition the former arrangement of the subject-matter was 
 rejected, as it seems inadmissible to speak of nitric acid, explosives, and soda 
 before sulphuric acid ; to separate cotton from wool, whilst placing in juxta- 
 position leather, lucifer matches, and milk. 
 
 Technology (T^VJ?, Aoyoc) the doctrine of the industries which improve 
 materials is divided, for more ready comprehension, into Mechanical Technology, 
 which teaches us to modify the form of the crude material, and Chemical 
 Technology, the task of which is to alter the nature or the composition of the 
 materials. A strict separation of both parts of Technology is impracticable, 
 since Chemical Technology very often requires the help of mechanical arrange- 
 ments, especially in metallurgy, in the production and elaboration of glass, 
 earthenware, cements, and paper, in tissue-printing, &c. But in the arrangement 
 of the subject-matter in Mechanical Technology the manner in which the form 
 of bodies is modified is exclusively prominent, whilst in Chemical Technology the 
 chemical change of the material is the dominant point of view. The Mechanical 
 Technologist treats, e.g., the cutting of iron, wood, leather, and bread as if 
 in connection ; he presupposes the necessary knowledge of the material. The 
 Chemical Technologist must pursue the material in its various changes, pre- 
 supposing the mechanical auxiliaries which may be needed (e.g., the various 
 machines for comminution), or they must be treated in such a manner as not to 
 interfere with the survey of the chemical process. 
 
 452047 
 
<ri PREFACE TO THE THIRTEENTH GERMAN EDITION. 
 
 In every department of Technology fuel is indispensable, and it is therefore 
 discussed in the first place. 
 
 If we consider that Germany alone consumes every minute almost a 
 milliard of calories of the heat (or of energy) stored up in the state of fossil 
 fuel, we are justified, whilst no substitute can be thought of, in demanding 
 that more attention shall be paid to fuel than has been hitherto the case. 
 
 In Section II. the subdivisions on Potassium and Sodium, in III. those 
 on Water, Manures, and Thermo -chemistry, are entirely novel ; Section I. is 
 chiefly, and Section IV. entirely, new. As compared with the eleventh edition, 
 in that now submitted to the reader more than half the text and also the illus- 
 trations will be found new. It is hoped that this new edition will meet with 
 as favourable a reception as its predecessors. 
 
 F. FISCHER. 
 
 HAKOVEE, December 1888 
 
PREFACE TO THE ENGLISH EDITION. 
 
 THE present English version differs so widely from that which appeared in 
 May 1872, that it may be regarded as substantially a new work. It is 
 founded on the thirteenth German edition of 1888, brought out by Dr. 
 Ferdinand Fischer, and re-modelled in accordance with the many important 
 changes which have been recently effected in chemical industry. To these 
 reference has already been made in Dr. Fischer's Preface. 
 
 But further modifications have been found necessary. A treatise on pure 
 chemistry is of equal value the world over. But a Manual like the present 
 must be in many respects adapted to the conditions of the country where it is 
 written, and, if translated for use elsewhere, it requires modification. The prices 
 of raw materials, of fuel, and of labour have to be kept in view. The laws 
 of different countries interfere with industrial processes in different manners 
 and to a very different extent. Hence certain passages have been omitted as 
 inapplicable to conditions prevailing in Britain, and many notes have been 
 added, for which the Editor considers himself solely responsible. 
 
 Bibliographical references to works easily accessible to the English reader 
 are added either in the form of notes or in the text, the latter chiefly under 
 Silver (pp. 187 and 188) and Gold (pp. 189, 190, and 191). 
 
 Concerning the illustrations, it may be necessary to add that many of the 
 blocks, instead of being lettered for reference with plain printing characters, 
 are marked in script, and in some cases German words form part of the 
 figures. It has therefore been necessary to add to each such cut an " Explana- 
 tion of Terms/' which the Editor hopes will render it perfectly intelligible to 
 the reader. 
 
 Temperatures are almost entirely expressed on the Centigrade scale, the 
 
viii PREFACE TO THE ENGLISH EDITION. 
 
 freezing-point or zero = o, and the boiling-point of water = 100. Where 
 other scales are used, such as Fahrenheit, they are specially mentioned. 
 
 Weights and measures are given according to the metric system. 
 
 Specific gravities of liquids heavier than water are generally given on 
 TwaddelPs hydroinetric scale. This scale has the double advantage over that 
 of Baume", in that it does not exist in two or more modifications, and that it can 
 be converted into direct specific gravity by a very simple calculation, for which 
 the reader is referred to the tables at the end of the book. 
 
 WILLIAM CKOOKES. 
 
 LONDON, December 1891. 
 
TABLE OF CONTENTS. 
 
 SECTION I. 
 TECHNOLOGY OF FUEL. 
 
 PAG* 
 
 FUEL AND ITS TREATMENT . I 
 
 THERMOMETRY 2 
 
 History, 2 ; conspectus of ordinary thermometers, 2 ; mercurial thermometers, 2 ; naph- 
 thaline and benzophenone thermometers, 3 ; determination of boiling-point, 3 ; determina- 
 tion of high temperatures, 4 ; electric thermometers, 5 ; diffusion of heat, 5. 
 
 DETERMINATION OP THE VALUE OF FUELS 6 
 
 Sampling, 6 ; determination of ash, 7 ; the yield of coke, 7 ; determining the nitrogen by 
 Kjeldahl's process, 7 ; determining the carbon and hydrogen, 7 ; determining the volatile 
 sulphur, 8 ; wood, n ; air-dried wood, n ; degasified wood, 12. 
 
 MANUFACTURE OF WOOD CHARCOAL 12 
 
 Kiln, 12 ; Italian kiln, 13 ; Slavonian kiln, 13 ; Schwarten kiln, 13 ; sweating, full com- 
 bustion, slow smouldering, 13 ; carbonisation in South Germany, Russia, and Sweden, 
 13; charcoal ovens, 14; simplest kilns, 14; charring wood in retorts, 15; wood-tar in 
 Russia, 15; in Lower Austria, 15; in Bohemia, 15; Swedish " thermo-kettles," 16 ; yield 
 of crude acid tar and charcoal with different kinds of wood, 17. 
 
 PEAT . . . 18 
 
 Varying nature, 18; extraction, 18 ; percentages of water, 18; composition, 18 ; uses of 
 peat, 19. 
 
 LIGNITE (BROWN COAL, BOVEY COAL) .19 
 
 Experiments of Schinnerer and Morawski, A. Bartoli and G. Papasogli, 19 ; degree of com- 
 position to distinguish appearance of wood, 19 ; pitch-coal, 19 ; jet, 19 ; Cologne umber, 
 20 ; production of solar oil and paraffine, 20 ; average composition of lignites, 20 ; moisture, 
 20 ; applicability, 20 ; drying, 20 ; modes of treatment fire-plate ovens, 20 ; steam- 
 oven, 21 ; tube drying oven of Schulz, 21 ; hot-air oven, 22; desiccation by means of steam 
 and hot air, 22; fault of all systems, 22; "press-coal," 22; collecting space, 23; limit of 
 compression, 23. 
 
 COAL 23 
 
 Composition, 23 ; important localities in the United Kingdom, 23 ; Europe, 24 ; America, 
 24 ; British North America, 24 ; South Africa, 24 ; India, 24 ; China, 24 ; Japan, 24 ; Aus- 
 tralia, 24 ; researches of M. A. Carnot, 24 ; of Scheurer-Kestner, 24 ; quality of coal, 24 ; 
 combustion value, 24 ; Schwackhofer's experiments, 24 ; anthracite, 25 ; where found, 25 ; 
 analysis, 25 ; use, 25 ; Boghead coal, 25 ; where found, 25 ; composition, 25 ; Dr. Stenhouse's 
 analysis, 25 ; analysis of ash, 25 ; used as fuel in gas manufacture, &c. , 25 ; Hilt's classifi- 
 cation of coals, 26 ; L. Gruner on technical value of a coal, 26 ; E. Jensch's analysis, 26. 
 
 COKE 26 
 
 Object of making, 26 ; oven-coking, 27 ; closed coke-ovens, 27 ; coking of small coal, 27 ; 
 coke-oven used on the Saar, &c., 28 ; coke-oven of Appolt Bros., 28 ; combination of coke- 
 ovens with the Siemens heat reservoirs by G. Hoffmann, 30 ; coke-ovens at the Pluto Mine, 
 32 ; briquettes, block-coal, 35 ; moulded charcoal, 35 ; coal blocks, &c., 35. 
 
 b 
 
x TABLE OF CONTENTS. 
 
 PAGI 
 
 DEGASIFYING, GASIFYING, COMBUSTION 35 
 
 Application of the fuels, 35 ; degasifying, 36 ; products of degasification of coal, 36 ; of 
 wood, 36 ; time required, 38 ; H. Bunte's experiment, 39 ; Berthelot's researches, 39 ; 
 analyses of purified gas, 39 ; combustion value of the components of coal-gas, 39 ; bye- 
 products, 40 ; generator-gas, 41 ; coke-generators, 41 ; gas-fires, 41 ; gas-firing, 42 ; F. 
 Siemens' generator, 42 ; gasification of carbon, 43 ; introduction of watery vapour, 44 ; 
 water-gas, 45 ; method of making, 45 ; arrangements at Essen and Witkowitz, 46 ; gener- 
 ator-gas made at Essen, 47 ; determinations of carbonic acid, 48 ; cost of lighting by 
 water-gas, 48 ; applications in metallurgical operations, 49. 
 
 HEATING ARRANGEMENTS 50 
 
 Materials used, 50 ; method of combustion, 50 ; gas analysis, 50 ; W. Apel's apparatus, 50 ; 
 mode of use, 52 ; method of determining hydrogen and methan, 53 ; the analysis, 53 ; 
 lubricator for the cocks, 55 ; calculating various readings, 55 ; to preserve samples of gas, 
 56 ; loss of heat, 57 ; weight of sulphurous or sulphuric acid, &c., 57 ; best apparatus for 
 steam-boiler furnaces, &c., 58 ; steam-boiler firing, 58 ; size of grate, 58 ; control, 59 ; 
 heating experiments, 59 ; regulations for deciding on the duty of a steam boiler, 59 ; 
 evaporation and distribution of heat, 60; shape of grate, 60; smoke consumption, 61 ; 
 house heating, 61 ; object, 61 ; forms, 61 ; open fires, 61 ; stove heating, 61 ; results, 62 ; 
 stoves in Germany, 62 ; Russian stoves, 62 ; experiments with a tile stove, 63 ; hot-air 
 heating, 63 ; air entrance, 64 ; air-filter, 64 ; consumption of fuel, 65 ; water heating, 65 ; 
 steam heating, 65 ; best means of heating, 65 ; heating with coal gas, 65 ; expense, 65 ; 
 gas-firing, 66 ; air entrance, 66 ; system for lignite, 66 ; burners, 66 ; generator, 66 ; C. W. 
 Siemens' method, 66 ; Munich generator furnace of N. H. Schilling, 68 ; composition of 
 generator gases, 70 ; uses of gas-firing, 71. 
 
 LIGHTING-GAS 71 
 
 History, 71 ; production, 72 ; Stedman's retort furnace, 73 ; furnaces of Liegel and Klonne, 
 Hasse and Didier, 73 ; tar-firing, 73 ; reduced value of tar, 73 ; Korting's pulveriser, 73 ; 
 experiments with various kinds of coal, 74 ; purification of the gas, 75 ; the condenser, 75 ; 
 scrubber, 75; purifiers, 76; purifying with oxide of iron, 76; "Laming's mass," 76; 
 ammoniacal purifying, 76 ; Glaus' method, 76 ; F. C. Hill's modification, 77 ; examination, 
 78 ; amount of sulphur, 78 ; ammonia, 78 ; complete analysis of gas, 78 ; wood-gas, 79 ; 
 Lebon's " thermo-lamp," 79 ; resin-gas, 79 ; peat-gas, 79 ; oil-gas, 80; apparatus used, 80; 
 air-gas, 80. 
 
 MINERAL OIL 80 
 
 Ancient use of, 80 ; natural oil wells, 81 ; origin, 81 ; how obtained, 81 ; relative quantities 
 from different places, 82 ; Bradford oil, 82 ; natural gas, 82 ; where found, 82 ; composition, 
 82 ; manufacture, 84 ; upright wrought-iron boilers, 84 ; waggon boiler, 84 ; roller boiler, 
 85 ; fuel substitutes, 85 ; products of distillation, 86 ; cost of production, 86 ; uses of 
 residues, 86. 
 
 PABAFFINE AND SOLAR OIL INDUSTRY . 87 
 
 Paraffine when and how first obtained, 87 ; how now obtained, 87 ; manufacture, 87 ; 
 preparation of the tar, 87 ; arrangement of retorts, 87 ; condensation of the vapours of the 
 tar, 88 ; properties of tar, 89 ; quantity obtained, 89 ; mode of operating with the tar, 89 ; 
 distillation of the tar, 90 ; treatment of the products of distillation, 90 ; rectification of the 
 crude oils, 91 ; refining the crude paraffine, 91 ; Hubner's method of preparing paraffine, 
 92 ; yield of paraffine, 92 ; brown coal, 92 ; steam-tar, 93 ; purified paraffine, 93 ; applica- 
 tion, 93 ; solar oil, 94 ; " vulcanol,'' 94. 
 
 PRODUCTION OF LIGHT 94 
 
 Treatment of solids, 94. 
 
 PHOTOMETEY 95 
 
 Measuring the luminosity of a flame, 95 ; Bunsen's photometer, 95 ; various photometric 
 candles, 95 ; German, 95 ; Munich, 96 ; English, 96 ; carcel lamp, 96 ; Von Hefner- Alteneck's 
 proposed unit of light, 96 ; international conference unit, 97 ; Violle's method of producing 
 this unit, 97 ; apparatus for comparing platinum unit with carcel lamp, 97. 
 
 LIGHTING WITH CANDLES . 98 
 
 Various kinds, 98. 
 
TABLE OF CONTENTS. xi 
 
 MM 
 
 LIGHTING WITH LAMPS 98 
 
 Various oils used, 98 ; refining fatty oils, 98 ; ancient use and development of lamps, 99 ; 
 evaporating temperature of oils, 99 ; suction lamps, 100 ; the lamp of Schuster and Baer, 
 100; imperial lamps, 101 ; study lamps, 101 ; ligroine and sponge lamp, 101. 
 
 GAS LIGHTING 101 
 
 Materials for burners, 101 ; various classes of burners, 101 ; Fr. Siemens' regenerative 
 gas-burner, 101 ; Auer von Welsbach's burner, 103; Fahnehjelm's "globe-light," 103; 
 Gillard's "platinum gas," 103 ; the Drummond light, 104 ; H. Cohn, quantity of light for 
 reading, 104 ; cost of various kinds of illumination, 104 ; pollution and contamination of 
 the air, 104 ; economy of various lights, 104. 
 
 ELECTRIC LIGHT 105 
 
 Arc light, 105 ; Siemens and Halske's apparatus for measuring the light, 105 ; Von Hefner- 
 Alteneck's experiments, 106 ; intensity of light, 105. 
 
 SECTION II. 
 
 METALLURGY. 
 
 Chemical processes, 108 ; how metals are found, 108 ; dressing, 108 ; preparation, 108 ; smelting, 
 108 ; mixing, 109 ; furnace products, 109 ; slags, 109; various kinds of slags, no ; com- 
 position of slags, no; properties of metals, no ; melting and boiling point of metals, no ; 
 specific heat, 1 10 ; thermo-conductivity, in; hardness, 1 1 1 ; modification of the hard- 
 ness and tenacity of metals, 112 ; pliancy, 112 ; treatment of metals for manufacture, 113 ; 
 friction, 113 ; welding, 113. 
 
 IKON 113 
 
 Magnetic ironstone, 113 ; red ironstone and specular iron, 113 ; iron spar, 113 ; brown iron 
 ores, 114 ; bean ore, 114 ; bog iron ore, 114 ; Franklinite, 114 ; classification, 114. 
 
 CKUDE IRON 114 
 
 Roasted ores, 114; smelting in blast furnaces, 114; furnace building, 115; air heating, 
 115 ; air-heater of Whit well, 117; Macco's heater, 117; smelting process, 117; heat con- 
 ditions of the blast furnace, 117 ; processes of reduction, 118 ; experiments in the refining 
 process, 118; importance of silica, 119; melting-heat of crude iron, 119 ; melting-heat of 
 slags, 119; decomposition of the atmospheric moisture, 119 ; water and air used for re- 
 frigeration, 119 ; losses, 119 ; consumption of fuel, 120 ; average heat required for smelt- 
 ing, 121 ; proportion of cyanogen compounds in the gases and dust, 122 ; composition of 
 slags, 122 ; analyses of slags, 123 ; use, 123; crude iron, 123. 
 
 EXAMINATION OP IRON AND STEEL 124 
 
 Wohler's process, 124; for determining carbon, 124; for determining sulphur, 124 ; for 
 determining silicon, 124 ; for determining phosphorus, 124 ; analyses of crude iron, 124. 
 
 IKON FOUNDING 125 
 
 Various methods, 125 ; examination of Krigar furnaces, 125; analyses, 126 ; melting pig- 
 iron with lime and fluor spar, 126; good casting-iron, 126 ; reverberatory furnace, 126. 
 
 WROUGHT OR BAR IRON 127 
 
 Improved method of obtaining wrought iron, 127 ; value of the "direct" process, 128 ; 
 refining process, 129; hearth refining, 129; Swedish fining, 129 ; puddling, 129; puddling 
 furnace, 130 ; bar-iron, wrought or malleable iron, 131 ; chemical examination of bar-iron, 
 131 ; welding, 132 ; Siemens-Martin and Bessemer processes, 132. 
 
 STEEL 132 
 
 Composition, 132; how obtained, 132; rough steel or natural steel, 133; puddled steel, 
 133 ; Bessemer steel, 133 ; apparatus, 134 ; analysis, 136 ; basic process (of Thomas and 
 Gilchrist), 136; Finkener's experiments, 136; Hilgenstock's experiment, 137; the slag, 
 138; the Siemens- Martin process, 138; furnaces at Witkowitz, 139; basic hearth-smelt- 
 ing, 140 ; carbonisation steel, 142 ; sheer steel, 142 ; cast steel, 142 ; run steel, 143 ; infil- 
 tration of cast blocks, 143 ; steeling, 143 ; properties of steel, 143 ; Damascus steel, '144; 
 steel engraving, 144. 
 
xu TABLE OF CONTENTS. 
 
 PAGE 
 
 MANGANESE . . . ... . . 145 
 
 Occurrence, 145 ; preparation, 145. 
 
 COBALT *45 
 
 Occurrence, 145 ; cobalt colours, 145 ; smalts, 146 ; cobalt speiss, 146 ; cobalt ultra- 
 marine, 146; coeruleum, 146; Rinmann's or cobalt green, 146; pure protoxide of cobalt, 
 147 ; nitrite of protoxide of cobalt and potassa, 147 ; cobalt bronze, 147. 
 
 NICKEL X 47 
 
 Occurrence, 147 ; treatment before smelting, 147 ; dry process for nickel, 148 ; wet pro- 
 cess, 148 ; L. Mond's process for nickel, 149 ; composition of cast nickel, 149 ; colour, 149. 
 
 COPPER 15 
 
 Copper ores, 150; red copper ore, 150; tile ore, 150; azurite, 150; malachite, 150; 
 chalkosine, 150 ; copper slate, 150 ; enargite, 150 ; Fahl ores, 150 ; atakamite, 150; method 
 of obtaining copper from its ores, 150 ; production of copper in the dry way, 151 ; roast- 
 ing of the copper matte, 152 ; eliquation, 153 ; refining copper, 153 ; English system of 
 copper smelting, 154; smelting furnace, 154; white metal, 155 ; refining in the United 
 States, 155 ; copper ores worked in the Bessemer converter, 156 ; working crude regulus, 
 156 ; production of copper in the wet way, 157 ; Dotsch's process, 158 ; analysis of cement 
 copper, 158 ; fusion with a reducing flame, 159 ; poling, 159 ; general treatment of coppers 
 during refining, 160 ; composition of Mansfeld coppers, 160 ; tough poling, 160 ; obtaining 
 and refining copper by electricity, 161 ; Siemens and Halske's method, 162 ; machines at 
 Oker, 164 ; Hilarion Roux's machines, 165 ; properties of copper, 165 ; uses of copper, 165; 
 analysis of some samples of refined copper, 165 ; copper alloys, 166 ; bell-metal, 166 ; gun- 
 metal, 167 ; art-bronze, 167 ; phosphor-bronze, 167 ; brass, 167 ; alloys of brass, 167 ; bronze 
 colours, 168 ; German silver, 168 ; copper amalgam, 168. 
 
 LEAD 169 
 
 Production, 169 ; lead smelting furnace, 169 ; English process for the production of lead, 
 169 ; composition of the lead ore washings of the Upper Harz, 170 ; treatment of ores at 
 Mechernich, 171 ; flue-dust, 172 ; work-lead, 172 ; electric production of lead, 172 ; Keith's 
 process, 173; properties, 173; uses, 173; manufacture of small shot, 173; alloys, 174; 
 production of lead, 174. 
 
 SILVER 174 
 
 Where and how found, 174 ; extraction, 174; amalgamation, 175 ; various processes, 175 ; 
 American or wet process, 175 ; Kroncke's process, 176 ; extraction of silver by solution and 
 precipitation, 176; Augustin's process, 177; Ziervogel's process, 178; other procedures, 
 178; extraction of silver in the dry way, 178; the Pattinson process, 179; desilvering 
 lead, 1 80; Plattner's process, 180 ; desilvering work-lead by electricity, 185; fine- burning 
 silver, 185 ; total production of silver, 186 ; chemically pure silver, 186; silver alloys, 187 ; 
 silver assay, 187 ; silvering, 187 ; electro-plating, 188 ; oxidation of silver, 188. 
 
 GOLD 188 
 
 Occurrence, 188 ; different processes for extracting, 189 ; W. Crookes' process, 190 ; 
 Molloy's process, 191 ; Morgan and Longden's process, 191 ; Plattner's process, 192 ; 
 various modifications, 192 ; separation of gold, 194; Gutzkow's proposal, 194; properties, 
 J 95 5 g ld alloys, 195 ; gold proof, 195 ; gilding, 196 ; galvanic gilding, 197. 
 
 PLATINUM I9 7 
 
 Occurrence, 197 ; analysis of various ores, 197 ; extraction, 197 ; St. Claire Deville and 
 Debray's process, 198 ; properties, 198 ; platinum black, 198 ; manufacture, 198. 
 
 TIN 
 
 199 
 
 Tin-stone, 199 ; treatment of ore, 199 ; occurrence, 199 ; properties, 200 ; assay of tin ores, 
 200 ; uses, 200 ; tinning, 201. 
 
 ^ 
 
 BISMUTH 2OI 
 
 Occurrence, 201; treatment of ore?, 202 ; properties, 202 ; uses, 202. 
 
 ANTIMONY .... 202 
 
 Occurrence, 202 ; extraction, 203 ; smelting in Hungary, 204 ; electrolytic extraction, 204 ; 
 properties, 204 ; alloys, 205. 
 
TABLE OF CONTENTS. xiu 
 
 PAGE 
 
 ARSENIC . 205 
 
 Production, 205 ; arsenious acid, 205 ; arsenic acid, 206 ; realgar, 206 ; orpiment, 206. 
 
 MERCURY . 207 
 
 Occurrence, 207 ; production, 207 ; furnaces used, 208 ; the Knox-furnace, 209 ; quantity 
 and price, 211 ; furnace at Horzowitz, 211 ; properties, 211 ; detection, 212. 
 
 ZINC 212 
 
 Occurrence, 212 ; treatment, 212 ; Belgian system, 212 ; furnaces at Letmathe, 213 ; English 
 method, 214 ; production of zinc by electricity, 214 ; properties, 216 ; uses, 217. 
 
 CADMIUM 217 
 
 Properties, 217 ; occurrence, 218; treatment, 218; detection, 218. 
 
 POTASSIUM AND SODIUM 218 
 
 Production, 218 ; manufacture of sodium, 218 ; potassium, 220 ; cost of manufacture, 22 1 ; 
 uses, 221 ; electrolytic production of sodium, 221 ; price of potassium, 221. 
 
 ALUMINIUM 22. 
 
 Woehler's process for isolating, 221; Cowles Bros.' process, 222; result according t<> 
 Mehner, 222 ; according to Maberry, 222 ; Prof. Netto's process, 223 ; properties, 223 ; appli- 
 cations, 223 ; alloys, 223 ; aluminium bronze, 223. 
 
 MAGNESIUM 224 
 
 Occurrence, 224 ; production, 224 ; Bunsen's method, 224 ; modification by Graetzel, 225 ; 
 uses, 225. 
 
 SECTION III. 
 
 CHEMICAL MANUFACTURING INDUSTRY. 
 
 WATER AND ICE 226 
 
 Occurrence, 226 ; quantity, 226 ; distribution of rainfall, 226 ; composition, 226 ; impurities, 
 227 ; spring and well water, 227 ; examination of waters, 228 ; process used by W. Crookes, 
 W. Odling, and C. M. Tidy, 228 ; purification of water, 229 ; water for steam boilers, 229 ; 
 breweries, 230; distilleries, 230 ; starch works, 230; sugar works, 231 ; paper mills, 231 ; 
 tanneries, 231 ; manufacture of glue, 231 ; bleach and dye works, 231 ; water for municipal 
 and domestic supplies, 233 ; various kinds of soap to be used, 233 ; water used for baking, 
 234 ; washing the floors, &c., 234 ; in the construction of houses, 234 ; filtering water, 234 ; 
 speed of filtration, 235 ; effects of sand filtration, 236 ; analysis by Koch, 236 ; various 
 analyses, 237 ; softening water the Clarke process, 237 ; Bohlig's process, 238 ; E. de Haen's 
 process, 239 ; distillation, 239 ; of sea-water, 239 ; water mains, 240. 
 
 ARTIFICIAL MINERAL WATERS 241 
 
 Production, 241 ; ice, 242 ; uses in works, 242 ; artificial production, 242 ; evaporation ice 
 machines, 242 ; Pictet's machine, 243. 
 
 SULPHUR 244 
 
 Occurrence, 244 ; extraction, 244 ; distillation process, 245 ; fusion process, 245 ; refining, 
 245 ; apparatus, 246 ; Michel's apparatus, 246 ; Dujardin's apparatus, 247 ; sulphur from 
 iron pyrites, 247 ; sulphur from roasting copper ores, 248 ; gas sulphur, 248 ; from sul- 
 phurous acid and sulphuretted hydrogen, 248 ; from sulphurous acid and carbon, 249 ; 
 from sulphuretted hydrogen, 249 ; properties, 249-50 ; carbon disulphide, 249 ; sulphur 
 chloride, 251 ; sulphurous and sulphuric acids, 251 ; furnaces, 251 ; kilns used at the Oker 
 works, 252 ; pyrites kilns used at Marseilles, 253 ; Gerstenhofer roasting kilns, 254 ; Hasen- 
 clever and Helbig kiln, 255 ; plate furnace of Maletra, 255 ; roasting blende, 256 ; blende 
 furnace, 257 ; composition of the roasting gases, 259 ; liquid sulphurous acid, 259 ; proper- 
 ties, 260 ; applications, 260 ; calcium sulphite, 261 ; sodium thiosulphate, 261. 
 
 SULPHURIC ACID 262 
 
 Fuming sulphuric acid, 262 ; properties, 263 ; solid oil of vitriol, 263 ; ordinary sulphuric 
 acid, 263 ; lead chambers, 263 ; arrangements for collecting the nitrous vapours, 265 ; 
 denitration of the nitrose, 266 ; Gay-Lussac's denitrificator, 266 ; J. Glover's tower, 267 ; 
 Laurent's apparatus for raising sulphuric acid, 268 ; lead chamber process, 270 ; formation 
 
adv TABLE OF CONTENTS. 
 
 PAG* 
 
 of sulphuric acid in the lead chambers, 271 ; purification of chamber acid, 274 ; concentra- 
 tion of sulphuric acid, 275 ; concentration in leaden pans, 275 ; completion of concentra- 
 tion, 276 ; apparatus used in Britain, 277 ; at Muehlheim, 277 ; platinum still, 278 ; apparatus 
 of Johnson, Matthey & Co., 279; concentrator of Faure and Kessler, 280; composition, 
 281 ; modern proposals for manufacturing sulphuric acid, 281. 
 
 PROPERTIES OF SULPHURIC ACID 282 
 
 Specific gravity, 282 ; applications, 282. 
 
 POTASSIUM SALTS 283 
 
 Occurrence, 283 ; potassa salts from the Stassfurt salt mine, 283 ; preparation of potas- 
 sium chloride, 283 ; Mr. A. Frank's process, 283 ; Dupre's method, 284 ; manufacture of 
 Glauber's salts, 285 ; kainite, 286 ; production of potassium carbonate, 286 ; analysis of, 
 286 ; various processes, 287 ; salts of potassium from the ashes of plants, 287 ; value of 
 ash, 288 ; lixiviation of the ash, 289 ; boiling down the liquor, 289 ; calcination of crude 
 potash, 289 ; American potash, 290 ; salts of potassium from the treacle of beet-root sugar, 
 291 ; various analyses, 291 ; treatment of molasses, 292 ; salts of potassium from seaweeds, 
 295 ; French method, 295 ; Scotch mode, 295 ; Stanford's method, 296 ; salts of potas- 
 sium from the suint of wool, 297 ; Maumene' and Rogelet's patent, 297 ; caustic potash, 
 299 ; alkalimetry, 300 ; commercial potash, 300 ; Mohr's normal solution, 300 ; commer- 
 cial value, 300. 
 
 COMMON SALT AND SALT WORKS 302 
 
 Occurrence, 302 ; method of preparing common salt from sea water, 302 ; in salines, 303 ; 
 by freezing, 303 ; by artificial evaporation, 304 ; rock-salt, 304 ; composition, 304 ; mode 
 of working rock-salt, 305 ; salt-springs, 306 ; preparation of common salt from brine, 306 ; 
 concentrating the brine, 306 ; enriching by gradation, 306 ; faggot gradation, 306 ; boil- 
 ing down the brine, 307 ; properties of common salt, 307 ; uses of common salt, 309. 
 
 SODA 309 
 
 NATURAL SODA 309 
 
 Occurrence, 309 ; La Lagunilla, 309. 
 
 SODA FROM PLANTS 310 
 
 SODA OBTAINED BY CHEMICAL MEANS JJQ 
 
 The Leblanc process, 310; Gossage's patent, 311 ; salt-cake furnaces, 312 ; sulphate fur- 
 naces of Mactear, 312; Hargreaves and Eobinson's process for salt-cake, 313 ; hydro- 
 chloric acid, 313 ; properties, 313 ; applications, 314 ; sodium sulphate, 314; applications, 
 315 ; conversion of sulphate into crude soda, 315 ; rotating soda furnace, 317 ; conversion 
 of crude soda into purified soda, 318 ; lixiviation, 319 ; C. Desormes' apparatus, 319 ; 
 Durre's apparatus, 321 ; Shanks' apparatus, 321 ; treatment of lyes, 321 ; composition, 
 323 ; purification and concentration of the lye, 323 ; analysis of soda-lyes, 324 ; use of re- 
 verberatory, 325 ; producing soda crystals, 326 ; theory of the formation of soda, 328 ; 
 utilisation of the Leblanc soda-residues, 329 ; obtaining sulphur-lye, 330 ; Mond's recovery 
 process, 332 ; P. W. Hofmann's process, 334 ; Divers' process, 336 ; C. Opl's process, 337 ; 
 Chance's new process, 337 ; ammonia-soda process, 339 ; cryolite soda, 343 ; soda from 
 sodium sulphate, 343 ; caustic soda, 343 ; Lunge's advice for the oxidation of sulphides, 
 344 ; Deacon and Hurter's process, 345 ; sodium bicarbonate, 346. 
 
 CHLORINE, CHLORIDE OF LIME, AND CHLORATES . 347 
 
 Production, 347 ; apparatus at the Josephsthal paper works, 347 ; Dunlop's process, 347 ; 
 Gatty's process, 348 ; F. Kuhlmann's process, 348 ; Weldon's process, 348 ; obtaining 
 chlorine without manganese, 350 ; Deacon and Hurter's process, 350 ; MacDougal, Kawson, 
 and Shanks' process, 352 ; Vogel's method, 352 ; Peligot's method, 352 ; properties and 
 uses of chlorine, 358 ; chloride of lime, 358 ; liquid chloride of lime, 359 ; properties of 
 chloride of lime, 360; loss of value, 360 ; chlorometry, 361 ; Penot's test, 361 ; Wagner's 
 method, 361 ; Lunge's method, 362 ; chlorometric degrees, 363 ; chloride of alkali, 363 ; 
 potassium chlorate, 363 ; properties, 364 ; potassium perchlorate, 364. 
 
 BBOMINE _ -g- 
 
 Occurrence, 365 ; distillation, 365 ; A. Frank's process, 365 ; apparatus used at united 
 chemical works of Leopoldshall, 366 ; crude bromine, 369 ; properties and applications of 
 bromine, 368. 
 
TABLE OF CONTENTS. xv 
 
 PA&B 
 
 IODINE 3 68 
 
 Production, 368 ; from seaweed, 369 ; Allary and Pellieux' method, 370 ; Vitali's method, 
 370 ; properties and uses, 371. 
 
 NITRIC ACID AND NITRATES . 371 
 
 Soda saltpetre, 371 ; sodium nitrate, 372 ; potassium saltpetre, 373 ; occurrence of native 
 saltpetre, 373 ; mode of obtaining saltpetre, 373 ; treatment of the ripe saltpetre earth, 
 373 5 preparation of raw lye, 374; breaking up, 374; boiling down, 375 ; refining crude 
 saltpetre, 375 ; preparation of potassium nitrate from Chili saltpetre, 376 ; testing the salt- 
 petre, 378 ; Wagner's method, 378 ; uses of saltpetre, 379. 
 
 NITRIC ACID 379 
 
 Methods of manufacture, 379 ; bleaching, 380 ; condensation, 380 ; preparing chemically 
 pure, 381 ; densities, 382 ; technical applications, 383. 
 
 EXPLOSIVES 384 
 
 Gunpowder, 384 ; manufacture, 384 ; mechanical operations of powder manufacture, 384 ; 
 pulverising the ingredients, 384 ; mixing the ingredients, 385 ; caking and pressing the 
 powder, 385 ; granulation of the cake, and sorting the powder, 385 ; Congreve's granu- 
 lating machine, 386 ; polishing the granulated powder, 386; drying the powder, 386 ; sifting 
 the dust from the powder, 387 ; properties of gunpowder, 387 ; composition, 388 ; products 
 of combustion, 388 ; testing, 390 ; pyrotechnics, 390 ; chemical principles of pyrotechny, 
 390 ; the more commonly used firework mixtures, 390 ; saltpetre and sulphur mixture, 391 ; 
 grey-coloured mixture, 391 ; potassium chlorate mixtures, friction mixtures, percussion 
 powders, 391 ; mixture for igniting the cartridges of needle-guns, 391 ; heat-producing 
 mixtures, 392 ; coloured fires, 392 ; more recent explosives, 392 ; nitroglycerine, 393 ; 
 Nobel's dynamite, 395 ; gun-cotton, 395 ; properties of gun-cotton, 396 ; apparatus of Hess 
 for determining the chemical stability of explosives, 398 ; Alberts' examination of gun- 
 cotton, 397 ; collodion cotton, 398 ; fulminating mercury, 398 ; percussion-caps, 398. 
 
 AMMONIA 399 
 
 Preparation of liquid ammonia, 399 ; inorganic sources of ammonia, 400 ; organic sources 
 of, 401 ; Mallet's apparatus, 401 ; Lunge's apparatus, 401 ; H. Griineberg's apparatus, 402 ; 
 stairs column, 404 ; apparatus of J. Gareis, 405 ; ammonia from lant, 405 ; apparatus 
 contrived by Figuera, 406 ; ammonia from bones, 406 ; from beet-root, 407 ; technically 
 important ammoniacal salts, 407 ; ammonium sulphate. 409 ; ammonium carbonate, 409 ; 
 ammonium nitrate, 409 ; C. O. Harz, manurial value of ammoniacal salts, 410. 
 
 PHOSPHORUS 410 
 
 Preparation of phosphorus, 410 ; composition of bone ash, 410 ; burning the bones to ash, 
 411 ; decomposition of bone ash by sulphuric acid, 411 ; distillation of phosphorus, 412 ; 
 refining and purifying the phosphorus, 413 ; another process, 413 ; moulding the refined 
 phosphorus, 414 ; Fleck's process for obtaining phosphorus, 415 ; properties of phosphorus, 
 416; amorphous or red phosphorus, 416; Dr. Schrotter's experiment, 416; properties of 
 amorphous phosphorus, 417 ; production, 417. 
 
 MATCHES : PRODUCTION OP FIRE 417 
 
 Db'bereiner's hydrogen lamp, 417 ; phosphorus match, 417 ; manufacture of lucifer matches, 
 419 ; preparation of wooden splints, 419 ; preparation of the combustible composition, 420 ; 
 dipping and drying the splints, 421 ; dipping apparatus of Eoller, 422 ; matches with 
 amorphous phosphorus, 422 ; wax or vesta matches, 423 ; B. Forster and F. Wara's " non- 
 poisonous " match, 423 ; Zulzer's machine for cutting tapers, 424. 
 
 PHOSPHATES: MANURES 424 
 
 Poudrette, 424 ; guano, 424 ; bone meal, 425 ; precipitated tricalcium phosphate, 425 ; super- 
 phosphate, 425; coprolites, 426; double superphosphate, 426; preparation of solutions, 
 
 427. 
 
 BORIC ACID AND BORAX 427 
 
 Occurrence, 427 ; theory of the formation of native boric acid, 428 ; production, 428 ; 
 properties and uses, 429 ; borax, 429 ; from boric acid, 430 ; prismatic borax, 430 ; purify- 
 ing borax, 431 ; octahedral borax, 432 ; uses, 432 ; manufacture of borax in Germany, 433 ; 
 diamond boron or adamantine, 434 ; Wohler and H. Deville's observations, 434. 
 
 SALTS OP ALUMINIUM 435 
 
 Alum, 435 ; material of alum manufacture, 435 ; preparation of alum from alum stone (ist 
 group), 435 ; from alum shale and alum earths (2nd group), 436 ; preparation of alum, 436 ; 
 
rri TABLE OF CONTENTS. 
 
 * * 1 
 
 roasting the alum-earth, 436 ; lixiviation, 436 ; evaporation of the lye, 436 ; alum-flour, 
 437 ; washing and re-crystallisation, 437 ; preparation of alum from clay (3rd group), 437 ; 
 from cryolite, 438 ; decomposition of cryolite according to Thomsen's method, 438 ; decom- 
 position of cryolite with caustic lime by the wet way (Sauerwein's method), 438 ; decom- 
 position by sulphuric acid, 439 ; preparation of alum from bauxite, 439 ; from blast furnace 
 slag, 439; from felspar (4th group), 439; properties of alum, 440; ammonia alum, 440; 
 soda alum, 440 ; neutral or cubical alum, 441 ; aluminium sulphate, 441 ; composition, 441 ; 
 H. Fleck's analyses of cake-alum, 441 ; preparation of cake-alum, 442 ; sodium aluminate, 
 442 ; aluminium hydrate, 443 ; applications of alum and aluminium salts, 443. 
 
 ULTRAMARINE . 444 
 
 Haw materials, 444 ; manufacture, 444 ; preparation of sulphate ultramarine, 444 ; green 
 ultramarine, 445 ; Stolzel's analysis, 445 ; conversion of green into blue ultramarine, 446 ; 
 preparation of soda ultramarine, 446 ; of silica ultramarine, 446 ; siliceous blues from 
 Hirschberg works and from Marienberg works, 447 ; violet and red ultramarines, 447 ; 
 constitution of ultramarine, 447 ; properties, 448 ; adulterations, 448. 
 
 COMPOUNDS OP TIN AND ANTIMONY . 448 
 
 Mosaic gold, 448 ; tin crystals, 448 ; tin chloride, stannic chloride, 449 ; nitrate of tin, 449 ; 
 pink salt, 449 ; stannate of soda (sodium stannate), 449. 
 
 COMPOUNDS OP ANTIMONY 449 
 
 Antimony oxide, 449 ; black antimony sulphide, 449 ; Neapolitan yellow, 450 ; antimony 
 cinnabar, 450 ; pentasulphide, 450. 
 
 COMPOUNDS OP ARSENIC 450 
 
 Arsenic acid, 450 ; plant, 450 ; uses, 452 ; how tested, 452. 
 
 COMPOUNDS OF GOLD, SILVER, AND MERCURY 452 
 
 Cassius's purple, gold purple, 452 ; salts of gold, 452 ; salts of silver, silver nitrate, lunar 
 caustic, 452 ; marking ink, 452 ; mercurial compounds, 453 ; mercuric oxide, 453 ; mercuric 
 chloride, 453 ; cinnabar or vermilion, 453 ; red lead, 454. 
 
 COMPOUNDS OP COPPER . . 454 
 
 Copper sulphate, blue vitriol, blue stone, 454 ; preparation of blue vitriol, 454 ; double 
 vitriol, 455 ; applications of blue vitriol, 455 ; copper pigments, 455 ; Brunswick green, 
 455 ; Bremen blue or Bremen green, 456 ; Casselmann's green, 457 ; mineral green and blue, 
 457 ; oil blue, 457 ; Schweinfurt green or emerald green, 457 ; copper stannate, 458 ; ver- 
 digris, 458 ; applications of verdigris, 459 ; Egyptian blue, 459. 
 
 COMPOUNDS OP ZINC AND CADMIUM . . 459 
 
 Zinc white, 459 ; white vitriol, zinc sulphate, 460 ; zinc chromate, 460 ; zinc chloride, 460 ; 
 cadmium yellow, 461. 
 
 COMPOUNDS OP LEAD , : 461 
 
 Lead oxide, 461 ; massicot, 461 ; litharge, 461 ; minium, red lead, 461 ; lead peroxide, 462; 
 white lead, 462 ; methods of manufacture, 463 ; English, French, methods, 463 ; apparatus 
 used at Clichy, 463 ; improvements suggested, 464 ; theory of preparing white lead, 464 
 properties, 465 ; adulteration, 465 ; applications, 466 ; white lead from chloride of lead, 
 467 ; basic lead chloride as a substitute for white lead, 467 ; lead sulphate, 467 ; Cassel 
 yellow and Turner's yellow, 467. 
 
 COMPOUNDS OP MANGANESE AND CHROMIUM 467 
 
 Manganese, 467 ; testing the quality, 468 ; potassium permanganate, 468 ; uses, 468 ; 
 preparation, 468 ; chromates, 469 ; Jacquelain's method of preparation, 469 ; application 
 of potassium chromates, 470 ; sodium chromate, 470 ; chromic acid, 470 ; chrome yellow, 
 lead chromate, 470; chrome red, 471 ; chromic oxide or chrome green, 472; Guignet's 
 green, 472 ; chromic hydrate, 472 ; Dingler's green, 472 ; Casali green, 473 ; chrome alum, 
 473 5 chromium chloride, 473 ; basic ferric chromate, 473. 
 
 IBON COMPOUNDS, INCLUDING FERROCYANOGEN . . . 473 
 
 Copperas or green vitriol, 473 ; preparation as a bye-product in alum works, 473 ; in beds, 
 473 ; green vitriol from the residues of pyrites distillation, 473 ; from metallic iron and 
 sulphuric acid, 473 ; from spathic iron ore, 474 ; uses, 474 ; iron minium, 474 ; potassium 
 ferrocyanide, 474; theory of its formation, 475; applications of yellow prussiate, 476; 
 manufacture of ferrocyanide, 476 ; potassium ferricyanide, 477 ; preparation, 477 ; potas- 
 
TABLE OF CONTENTS. xvii 
 
 PAGE 
 
 slum cyanide, 477 ; Prussian blue, 477 ; neutral Berlin blue, 478 ; basic Berlin blue, 478 ; 
 old method of preparing Prussian blue, 478 ; recent methods of preparing Berlin blue, 479 ; 
 Turnbull's blue, 479 ; Berlin blue as a bye-product of the manufactures of coal-gas and 
 animal charcoal, 479 ; soluble Berlin blue, 479 ; pure Berlin blue, 479. 
 
 CONSPECTUS OF INORGANIC PIGMENTS 480 
 
 Whites, reds, yellows, 480 ; greens, blues, 481. 
 
 THEEMO-CHEMISTEY 481 
 
 Uses, 481 ; the unit used, 482 ; various heat-units, 482 ; production of chlorine, 483 ; 
 Deacon's oxidation process, 483 ; Pechiney's 'decomposition furnace, 483 ; various appli- 
 cations, 483. 
 
 SECTION IV. 
 
 THE ORGANIC CHEMICAL MANUFACTURES. 
 
 ALCOHOLS AND ETHERS 486 
 
 Methylic alcohol, 486 ; distillation, 486 ; uses, 487 ; ethyl alcohol, 487 ; percentage 
 hydrometers, 487 ; O. Hehner's alcohol tables, 488 ; chloroform, 490 ; apparatus used for 
 distilling, 490 ; Giinther's method, 491 ; production of iodoform, 491 ; chloral hydrate, 
 491 ; ether, 491. 
 
 ORGANIC ACIDS 491 
 
 Acetic acid, 491 ; various kinds of vinegar, 491 ; older method of vinegar making, 492 ; 
 quick vinegar making, 492 ; Singer's vinegar generator, 494 ; Michaelis' process, 494 ; 
 Pasteur, action of bacteria on the formation of vinegar from alcohol, 494 ; vinegar by 
 means of platinum black, 495 ; Dobereiner's process, 495 ; properties and examination of 
 vinegar, 496; acetometry, 496; apparatus for determining the value of vinegar, 496; 
 testing vinegar essence, 497 ; wood vinegar, 497 ; purifying wood vinegar, 497 ; principal 
 methods, 498 ; Stoltze's method, 498 ; formic acid, 498 ; butyric acid, 499 ; valerianic acid, 
 499 ; oxalic acid, 499 ; Thorn's method of obtaining, 499 ; Merz's method, 500 ; lactic acid, 
 500 ; tartaric acid, 500 ; Dieter's process, 501 ; yearly production of tartaric acid, 501 ; 
 citric acid, 502 ; benzoic acid, 502 ; sodium benzoate, 502 ; tannin, 502 ; uses, 502. 
 
 TREATMENT OP COAL-TAR 502 
 
 Specific gravity, 502 ; distillation of tar, 503 ; Lunge's process, 503 ; the stills, 505 ; cooler 
 for pitch, 507 ; Haussermann's analysis, 507 ; value of pitch, 507 ; light oil, 508 ; apparatus 
 used in English manufactories, 508; Coupler's apparatus, 509; apparatus for obtaining 
 pure benzene, 510; Bannow's boiling vessel, 510; benzene, 511 ; toluol, 511 ; the light 
 oil, 511 ; crude carbolic acid, 511 ; phenol, 512; cresol, 512 ; subliming chamber, 512 ; 
 naphthaline, 513 ; anthracene, 514. 
 
 ORGANIC COLOURING MATTERS 514 
 
 Red colours, 514; madder, 514; madder lake, 515 ; flowers of madder, 515 ; azale, 515 ; 
 garancine, 515 ; garanceux, 515 ; colorine, 516 ; safflower, 516 ; cochineal, 516 ; carthamine, 
 516 ; lac dye, 517 ; Tyrian purple, 517 ; weed colours, 517 ; less important red dyes, 518 ; 
 murexide, 518 ; red woods, 518 ; production of red ink, 518 ; brasilein, 518; adulteration 
 ofdyewoods, 519; blue colouring matters, 519; indigo, 519; properties of indigo, 520; 
 testing, 520; indigo blue, 521 ; artificial indigo, 522 ; logwood or campeachy, 522; litmus, 
 
 522 ; hematine, 522 ; turnesol rags, 522 ; yellow colouring matters, 522 ; fustic, 522 ; 
 young fustic, 522 ; annatto, 523 ; berries Persian, French, or Turkey, 523 ; turmeric, 
 
 523 ; weld or wold, 523 ; quercitron, 523 ; some other yellow dye-wares, 523 ; brown, green, 
 and black colours, 523 ; tannin ink, 524 ; inks, various, 524. 
 
 TAR COLOURS 524 
 
 Arrangement into natural groups, 524 ; mtro-compounds, 524 ; azo-colours, 524 ; indamines 
 and indophenoles, 525 ; saffranines, 525 ; indulines and nigrosines, 526 ; Schultz and 
 Julius' arrangement of colouring matters, 526. 
 
 BaiNzoL COLOURS 5 28 
 
 Nitro-benzol, 528 ; aniline, 528 ; composition of aniline oil, 530 ; pure aniline, 530 ; 
 toluidine, 530; aniline red (magenta), 530; arsenic acid process, 531; Schoop's melting- 
 
xviii TABLE OF CONTENTS. 
 
 PAGE 
 
 pot, 531 ; purification of crude magenta, 533 ; Coupier's process, 534 ; rosaniline, 535 
 aniline blue, 535 ; treatment, 536 ; De Laire and Girard's treatment, 536 ; aniline violet, 
 537 ; methyl violet, 537 ; aniline green, 537 5 fast green, 538 ; aniline yellow, 538 ; flav- 
 aniline, 538 ; aniline black, 538 ; formula, 538 ; jetoline, 538 ; benzaldehyd green or 
 malachite green, 539 ; preparation, 539 ; dimethyl aniline, 539 ; separation of oil and water, 
 539 ; Miihlhauser, manufacture of malachite green, 540 ; obtaining the leuko-base, 540 ; 
 production of liquid colour, 543 ; liquid green, 543 ; " navy blue," 543 ; brilliant green, 
 emerald green, new Victoria green, 543 ; acid green, 544 ; apparatus for producing leuko- 
 base, 544 ; for obtaining lead peroxide for oxidation, 545 ; acid green, 545 ; resorcine, 546 ; 
 fluoresceine colouring matters, 547 ; tetrabromfluoresceine, 547 ; dibromfluoresceine, 
 548 ; ethyltetrabromfluoresceine, 548 ; dibromdinitrofluoresceine, 548 ; tetraiodofluor- 
 esceine, 548; di-iodofluoresceine, 548 ; Miihlhauser's method of obtaining fluoresceine, 548 ; 
 utilisation of the residues, 55 1 ; eosine orange, 552 ; spirit cosine, 552 ; dinitrodi- 
 bromfluoresceine, 554 ; erythrosine B, 556 ; erythrosine G, 556 ; phloxine, 556 ; resorcine 
 blue, lacmoid, 557 ; auramines, 557 ; nitrosodimethyl aniline, 558 ; new blue, 558 ; gallo- 
 cyanine, 558 ; methylene blue, 558 ; zinc sulphide process, 562 ; Lauth's violet, 563 ; 
 Bernthsen's method, 563 ; induline, saffranine, phenosaffranine, neutral blue, giro fie, 
 imperial yellow, 564 ; phenol colouring matters, 564 ; picric acid, 564 ; phenyl brown, 
 565 ; flavaurine, 565 ; Victoria yellow, 565 ; aurine, 565 ; coralline, 565 ; azuline, 565 ; 
 quinoline, 565 j Dobner and Miller's experiment, 566 ; quinoline green, blue, red, yellow, 
 566 ; salicylic acid, 567 ; salicyl yellow, 567 ; naphthaline dye-stuffs, 567 ; distillation of 
 naphthaline, 569; phthalic acid, 570; naphthaline red, 570; Martius' yellow, 570; 
 naphthol yellow, 570; brilliant yellow, 570; sun gold, 570; naphthol green, 571 ; phen- 
 anthrenered, 571 ; anthracene colours, 571 ; alizarine, 571 ; changes in the melting process, 
 572 ; purpurine, 573 ; alizarine orange, 573 ; alizarine carmine, 573 ; alizarine blue,573 ; azo 
 dyes, 574; aniline yellow, 574; acid or fast yellow, 574 ; Bismarck brown, 574 ; benzopur- 
 purine, 575 ; a scarlet dye- ware, 576 ; chrysophanine, 577 ; croceine scarlet, 577 ; Biebrich 
 scarlet, 577 ; double brilliant scarlet, 578 ; woollen black, 578 ; Congo, 578 ; preparation 
 of mixed azo-dyes, 578 ; other organic colouring matters, 379 ; galleine, 579 ; ceruleine, 
 579; galloflavine, 580; the Baden Aniline Company's process, 580; styrogallol, 580; 
 tartrazine, 580; canarine, 580; murexide, 581 ; lampblack (soot), 581. 
 
 EXAMINATION OP COLOURING MATTERS 582 
 
 Treatment of sample, 582 ; Goppelsroeder's method, 582 ; acid colouring matters, 583. 
 
 ARTIFICIAL COLOURS SOLUBLE IN WATEB 584 
 
 Basic colouring matters, 584 ; acid colours, 584. 
 
 SOLID OR PASTY COLOURS, INSOLUBLE IN WATER 585 
 
 Treatment of dye-wares, 585 phasic colouring matters, 585 ; acid colouring matters 
 phthaleines, 587 ; sulphonised rosaniline derivatives, 587 ; nitro-colouring matters, 587 ; 
 benzido-azo colouring matters, 588 ; azo colours yellow orange, 589 ; Bordeaux reds, 589 ; 
 anthracene derivatives, 590 ; colouring matters insoluble in water, 591. 
 
 SECTION V. 
 
 MANUFACTURE 592 
 
 Antiquity, 592 ; composition, 592 ; soda glass, 593 ; potash glass, 593 ; Schott's experiments, 
 594 ; E. Weber's analyses, 594 ; Pelouze's glasses, 595 ; Lamy's attempts to introduce 
 thallium into glass, 595 ; Maes' optical glass, 595 ; bottle glass, 595 ; analysis of bottles, 
 596 ; lime-alumina glass, 596 ; phosphatic glass, 596 ; solubility of glass, 596 ; Emmerling's 
 analysis, 597; Kreusler, reactions of glass, 598 ; Stass's experiments, 598 ; Weber and Wiebe's 
 experiments, 598 ; devitrification, 598 ; coloured glasses, 598 ; hematinon, 598 ; aventurine 
 glass, 598 ; gold ruby glass, 599 ; red glass, 599 ; Venetian mosaic glass, 599 ; composition, 
 600 ; physical properties of glass, 600 ; raw materials used in glass making, 600 ; 
 bleaching, 601 ; utilisation of refuse glass, 602 ; melting vessels, 602 ; glass-furnace, 603 ; 
 Siemens' gas-oven, 604 ; manufacturing bottles, 605 ; tank furnaces, 606 ; Boetius' furnace, 
 607 ; glass melting, 607 ; melting the glass material, 607 ; clear melting, 607 ; cold- 
 
TABLE OF CONTENTS. six 
 
 rtm 
 
 stoking, 608 ; defects in glass, 608 ; various kinds of glass, 609 ; plate and window glass, 
 609; tools, 610; crown glass, 610 ; sheet, or cylinder glass, 611 ; plate glass, 612; 
 melting and clearing, 613 ; polishing, 613 ; silvering, 614 ; by precipitation, 614; platinis- 
 ing, 614 ; gilding, 614 ; bottle glass, 615 ; details of manufacture, 615 ; pressed and cast 
 glass, 616; hardened glass, 616 ; soluble glass, 617 ; water glass, 618 ; stereochromy, 618 ; 
 crystal glass, 619 ; polishing, 620 ; optical glass, 620 ; Rev. Mr. Harcourt's researches, 
 620 ; strass, 621 ; Donault-Wieland's analysis, 621 ; coloured glass and glass staining, 622 ; 
 satin glass, 623 ; painting on glass, 623 ; enamel, bone glass, alabaster glass, 624 ; cryolite 
 glass, 624 ; ice glass, 624 ; muslin glass, 625 ; glass relief, 625 ; iridescent glass, 625 ; filigree 
 or reticulated glass, 625 ; millifiore work, 625 ; glass pearls, 625 ; solid pearls, 625 ; blown 
 pearls, 626 ; glass etching, 626 ; sand blast machine, 628. 
 
 EAETHENWAEE OB CERAMIC MANUFACTURE 628 
 
 Weathering, 628 ; clays and their application, 628 ; felspar, 628 ; Seger's examination 
 of clays, 629 ; technical qualities, 629 ; colour, 629 ; plasticity, 629 ; kinds of clays, 630 ; 
 chemical composition, 631 ; analyses, 631 ; by Sir F. A. Abel, 631 ; potter's clay, 631 ; 
 fuller's earth, 631 ; marl, 632 ; loam, 633 ; behaviour of clays in working, 633 ; changes 
 of colour in burning, 634 ; efflorescences, 634 ; green eruptions, 634 ; black spots, 634 ; 
 Seger's examination of change of colour, 635 ; infusibility, 635 ; experiment determination 
 of the behaviour of clay under heat, 636 ; production of earthenware, 636 ; classification of 
 earthenware, 637 ; dense clay ware, 637 ; porous clay ware, 637 ; hard porcelain ; grinding 
 and mixing the material, 638 ; drying the mass, 638 ; kneading the dried mass, 639 ; 
 moulding, 639 ; potter's wheel, 639 ; moulding in plaster of Paris forms, 639 ; casting, 640 ; 
 preparation of porcelain articles without moulds, 640 ; drying the porcelain, 640 ; glazing, 
 640 ; porcelain glaze, 640 ; applying the glaze, 641 ; immersion, 641 ; dusting, 641 ; water- 
 ing, 641 ; volatilisation, 641 ; lustres and flowing colours, 641 ; capsule or sagger, 641 ; 
 porcelain kilns, 641 ; emptying the kiln and sorting the ware, 642 ; faulty ware, 642 ; 
 porcelain painting, 643 ; ornamenting the porcelain, 643 ; bright gilding, 643 ; silvering 
 and platinising, 644 ; lithophanie, 644 ; tender porcelain, 644 ; French fritte, 644 ; English 
 fritte, 644 ; Parian and Carrara, 645 ; stoneware, 645 ; ovens, 645 ; lacquered ware, 647 ; 
 fayence, 647 ; ornamenting fayence, 648 ; flowing colours, 648 ; lustres, 649 ; Etruscan 
 vases, 649 ; clay pipes, 649 ; water coolers, 649 ; common pottery, 650 ; burning, 650 ; brick 
 and tile making, 650; terra-cotta, 650; brick material, 651 ; preparation of the clays, 65 1 ; 
 "treading," 651; the furnace, 652; Bock's channel furnace, 655; gas-firing, 655; 
 Escherich's ring-furnace, 655 ; Mendheim's modification, 656 ; kilns, 656 ; clinkers, 
 roofing and flooring-tiles, 657 ; ballast, 657 ; fire-bricks, 657 ; crucibles, 659. 
 
 MORTARS, ETC 659 
 
 Substances used, 659 ; gypsum, 660 ; nature, 660 ; burning, 66 1 ; kilns, or burning ovens, 66 1 ; 
 grinding, uses, 662 ; casts, hardening, 663 ; lime, 664 ; properties, burning, 664 ; occasional 
 or periodic kilns, 665 ; continuous kilns, 666; kilns for burning lime and bricks, 667; pro- 
 perties of lime, 667 ; slacking, 667 ; mortar, 668 ; common, hardening, 668 ; hydraulic 
 mortar, 668; Roman, Portland cements, 669; analyses, 671 ; hardening hydraulic cement, 
 67 1 ; hardening Portland cements, 672 ; hydraulic admixtures, 674 ; puzzolane cements, 
 674 ; concrete, 675 ; mixed cements, 675. 
 
 SECTION VI. 
 
 ARTICLES OF FOOD AND CONSUMPTION. 
 
 STARCH AND DEXTRINE 676 
 
 Nature of starch, 676 ; sources, 678 ; starch from potatoes, 678 ; process of manufacture, 
 678 ; drying potato starch, 679 ; preparation of wheat starch, 679 ; without fermentation, 
 680 ; constituents and uses of commercial starch, 680 ; rice and maize starch, 68 1 ; chest- 
 nut and cassava starch, 68 1 ; arrowroot, 682 ; sago, 683; dextrine, 683; preparation, 684. 
 
 SUGAR 684 
 
 Grape sugar, 684 ; preparation, 686 ; boiling starch meal with dilute sulphuric acid, 686 ; 
 separation of sulphuric acid from the sugar solution, 687 ; evaporating and drying sugar 
 solution, 687 ; composition of starch sugar, 687 ; uses of grape sugar, 687 ; German starch 
 
xx TABLE OF CONTENTS. 
 
 PAIR 
 
 sugar, 688 ; maltose, 688 ; cane sugar, 689 ; the sugar-cane, 689 ; components, 689 ; pre- 
 paring raw sugar from, 690 ; expressing the juice, 690 ; refining and boiling, 690 ; varieties 
 of sugar, 691 ; molasses, 691 ; refining sugar, 691 ; beet sugar, 692 ; species of beet, 692 ; 
 chemical constituents, 693 ; saccharimetry, 693 ; Stockbridge's lixiviation apparatus, 694 ; 
 extraction of sugar from the root, 694 ; washing and cleansing the beets, 695 ; separating 
 the juice from the root, 695 ; a diffusion-battery, 697 ; composition and treatment of juice, 
 698 ; de-liming or saturating the juice with carbonic acid, 699 ; other methods, 699 ; 
 purifying with baryta, 700 ; filtration through animal charcoal, 700 ; Fichet's furnace, 701 ; 
 evaporation pans, 702 ; vacuum pans, 703 ; Derosne's apparatus, 703 ; Wellner and Jelinek's 
 apparatus, 704 ; separation of the crystals, 706 ; consumption sugar, 706 ; melis, 707 ; 
 sugar-candy, 707 ; beet treacle, 708 ; elution, 709 ; substitution and separation, 709 ; the 
 strontia process, 711 ; palm, maple, and sorghum sugar, 712. 
 
 FERMENTATION ARTS . . , , 712 
 
 Fermentation and yeast, 712; vinous fermentation, 713 ; yeast, 713; E. C. Hansen's ex- 
 periments with yeast, 714 ; Niigeli and Low, bottom yeast of beer, 717 ; conditions of 
 alcoholic fermentation, 718 ; dry yeast, 718 ; industries based on alcoholic fermentation, 719. 
 
 WINE MAKING 719 
 
 The vine and its cultivation, 720 ; vintage, 720 ; pressing the grapes, 720 ; centrifugal 
 machine, 721 ; chemical constituents of must, 721 ; the sugar of the grape, 722 ; fermenta- 
 tion of the grape juice, 723 ; drawing off and casking the wine, 723 ; constituents of wine, 
 723 ; average composition of wine, 724 ; ebullioscope of Tabarie, 725 ; of Malligandand Vidal, 
 725 ; of Amagat, 726 ; amount of alcohol in various wines, 726 ; analyses of wine-ash, 727 ; 
 diseases of wine, 727 ; souring of wine, 728 ; bittering, 728 ; Pasteuring, 728 ; hygrother- 
 mant of Ballo, 729 ; clearing or fining the wine, 730 ; residues from the production of 
 wine, 730 ; effervescing wines, 730 ; improving wine musts and artificial wines, 732 ; use 
 of freezing, 734 ; cider, 735 ; appendix, 735. 
 
 BEER BREWING 735 
 
 Materials, 735 ; grain, 735 ; hops, 736 ; quality of the hops, 737 ; substitutes for hops, 737 ; 
 malting, 738 ; softening or soaking the grain, 738 ; germination of softened grain, 739 ; 
 drying the germinated grain, 739 ; pneumatic malting, 740 ; Leicht's malt kiln, 741 ; 
 nitrogen in barleys and malt, 743 ; production of the wort, 744; preparation, 744 ; bruising 
 the malt. 745 ; mashing, 745 ; decoction and infusion method, 745 ; thick mash boiling, 
 746 ; Augsburg method, 747 ; infusion method, 747 ; extractives of the wort, 748 ; boiling 
 the wort, 748 ; adding the hops, 750; cooling the wort, 751 ; fermentation of the beer- 
 wort, 753 ; sedimentary fermentation, 754 ; after-fermentation in the casks, 755 ; surface 
 fermentation, 756 ; steam brewing, 757 ; constituents of beer, 757 ; beer testing, 758 ; 
 Balling's saccharometrical beer test, 759. 
 
 THE MANUFACTURE OP SPIRITS 760 
 
 Properties of alcohol, 760 ; raw materials, 761 ; saccharification, 762 ; mashing process, 
 762 ; Bohm's apparatus, 763 ; preparation of a vinous mash, 764 ; from cereals, 764 ; 
 spirits from sugar waste, 766 ; from wine and lees, 767 ; fermentation, 766 ; distillation, 
 767; apparatus, 768 ; Pistorius' apparatus, 768 ; Gall's, 770; Schwarz's, 771 ; Siemens', 772 ; 
 continuous distilling apparatus, 773 ; K. Ilge's apparatus, 775 ; purification of the crude 
 spirit, 779 ; yield of alcohol, 780. 
 
 FLOUR AND BREAD 781 
 
 Modes of bread making, 781 ; details, 781 ; mixing the dough, 782 ; kneading, 782 ; baking, 
 783 ; substitutes for yeast, 784 ; yield and composition of bread, 785 ; impurities and 
 adulterations, 785. 
 
 MILK, BUTTER, AND CHEESE 786 
 
 Milk, 786 ; whey, 787 ; lactose, 787 ; uses of milk, 787 ; condensed milk, 788 ; kefyr, 788 ; 
 koumiss, 788 ; butter, 788 ; chemical nature of butter, 789 ; composition of butter fats, 
 789 ; artificial butter, 789 ; margarine and oleomargarine, 789 ; cheese, 790 ; composition, 
 791 ; Payen's researches, 791 ; Lindt's, 791 ; E. Hornig's analyses, 792. 
 
 MEAT 792 
 
 Constituents of meat, 792 ; cooking, 793 ; broth, 793 ; boiling meat, 794 ; preservation of 
 meat, 794 ; by withdrawal of water, 795 ; salting, 795 ; Liebig's researches, 795 ; smoking 
 or curing meat, 796. 
 
 NUTRITION .^ 797 
 
 Effect of various kinds of diet, 797. 
 
TABLE OF CONTENTS. XT* 
 
 SECTION VII. 
 CHEMICAL TECHNOLOGY OF FIBRES. 
 
 PAGK 
 
 WOOL 798 
 
 Origin and properties of wool, 798 ; varieties, 801 ; cashmere, vicuna, alpaca, mohair, 801 ; 
 
 chemical composition, 80 1 ; analysis of various kinds of merino, 802 ; suint, 802 ; artificial 
 
 wool, 802 ; shoddy, mungo, 803. 
 BILK 803 
 
 Production, 803 ; sericiculture varieties of silk worms, 803 ; rearing and culture, 804 ; 
 
 chemical composition of silk, 804 ; manipulation of the silk, 805 ; sorting the cocoons, 805 ; 
 
 winding the silk, 805 ; throwing, 805 ; testing, 806 ; boiling the gum out of silk, 806 ; 
 
 means of distinguishing silk from wool and from vegetable fibres, 807. 
 VEGETABLE FIBRES 808 
 
 Flax, 808 ; hot-water cleansing, 809 ; retted flax, 809 ; beating or batting the flax, 809 ; 
 
 combing, 809 ; tow, 809 ; spinning, 809 ; weaving linen threads, 810 ; linen, 810; hemp, 810 ; 
 
 stalk fibre, 810 ; Chinese grass, 810 ; the great nettle, 811 ; ramie hemp, rhea grass, jute, 
 
 Bombay hemp, sun hemp, 8n ; leaf fibre, 811 ; New Zealand flaxes, 8n ; aloe, Manilla, 
 
 ananas, pikaba hemp, 812; cocoa-nut fibre, 812; cotton, 812; species of cotton, 813; 
 
 substitutes, 813 ; detecting cotton in linen fibres, 813; Kindt and Lehnert's tests, 813; 
 
 Stockhardt's test, 814 ; O. Zimmermann's test, 814 ; separation of animal and vegetable 
 
 fibres by singeing, 814 ; adulteration of cotton fabrics, 815. 
 BLEACHING ... 815 
 
 Grass bleach, 815 ; chlorine, 815; various methods of application, 816; Lunge, removing 
 
 last traces of bleaching agents, 816 ; Moyret's method, 817 ; Lauber's method, 817 ; cotton 
 
 bleaching, 817; H. Koechlin's method, 818 ; J. Thompson's method, 818 ; continuous 
 
 bleaching machine, 818; Mather-Thompson process, 819; linen bleaching, 820; Kolb's 
 
 method, 820 ; jute bleaching by Cross, 820 ; silk bleaching, 820 ; wool bleaching, 820. 
 
 DYEING AND TISSUE-FEINTING 821 
 
 Removing the solvent, 821 ; oxidation, 821 ; double decomposition, 821 ; mordants, 821 ; 
 turkey -red oil, 822 ; alumina mordants, 822 ; aluminium acetates and sulphacetates, 822 ; 
 
 ageing, 822 ; " dunging," 823 ; iron mordants, 823 ; nickel, 824; chrome, 824; tin, 825; 
 manganese, 825 ; antimony, 825 ; tannin, 825 ; apparatus, 826 ; colour-pans for laboratories, 
 826 ; machine for dyeing piece-goods and yarns, 828 ; Sulzer's machine, 829 ; dyeing 
 woollens, 829 ; blue dyeing, 829 ; indigo blue, 830 ; blue vats, 830 ; Saxony blue, 832 ; recovery 
 of indigo from rags, 832 ; Berlin blue, royal blue, 832 ; logwood and copperas blues, 833 ; 
 dyeing yellows, 833 ;'red dyeing, 833 ; green dyeing, 834 ; black dyeing, 834 ; silk dyeing, 835; 
 blue dyeing, 836 ; yellow dyes, 837 ; green dyes, 837 ; cotton dyeing, 837 ; Baden Aniline 
 Company's process, 837 ; C. and H. Koechlin's processes, 838 ; turkey red, 838 ; aniline black, 
 839 ; dyeing linen, 839 ; tissue-printing, 839 ; thickenings, 840 ; special care of colour- 
 mixer, 841 ; madder style, 842 ; madder printing, 843 ; Witz's method, 843 ; " padding 
 on mordants," 843 ; machine used, 843 ; printing with resists, 844 ; fatty resists, 844 ; 
 white resists, 844 ; coloured resists, 844 ; lapis style, 844 ; discharges, 845 ; China-blue 
 style, 845 ; pencil blue, 845 ; discharge style, 846 ; printing aniline blacks on dyed cottons, 
 846 ; steam colours, 847 ; Schlieper and Baum process for indigo printing, 847 ; Goppels- 
 roder, proposed use of electrolysis, 848 ; " coppering," 849 ; Barlow's process, 849 ; topical 
 or application colours, 849 ; topical black, 849 ; use of ultramarine in printing, 849 ; printing 
 with gold and silver, 849 ; with coal-tar colours, 850 ; Botsch, preparation of Congo colours, 
 850 ; finishing, 851 ; examination of dyed and printed textiles, 852 ; Lenz, Martin, Hutamel, 
 and Lepetit, detecting colouring matters on fibres, 852-61. 
 
 PAPER MANUFACTURE 853 
 
 History of paper, 853 ; materials used, 853 ; substitute for rags, 853 ; F. C. Keller, 
 mechanical wood-stuff, 860 ; chemical production of cellulose, 862 ; mineral additions to 
 rags, 865 ; manufacture of paper by hand, 865 ; cutting and cleaning the rags, 865 ; sepa- 
 ration of rags for half-stuff and whole-stuff, 866 ; stamp machine, 866 ; bleaching the pulp, 
 866 ; antichlore, 867 ; blueing, 867 ; sizing, 867 ; hand-made paper, 867 ; straining the 
 paper sheets, 867 ; pressing, 868 ; drying, 868 ; sizing, 868 ; preparing the paper, 868 ; 
 different kinds of paper, 869 ; machine paper, 869 ; manufacture, 869 ; paper-cutting 
 machine, 869 : pasteboard, 870 ; papier-mache, 870 ; coloured paper, 870 ; graphite paper, 
 871 ; parchment paper, 871 ; Fritsch's machine, 871. 
 
xxii TABLE OF CONTENTS. 
 
 SECTION VIII. 
 
 MISCELLANEOUS ORGANO-CHEMICAL ARTS AND MANUFACTURES. 
 
 PA&l 
 
 TANNING 873 
 
 Anatomy of animal skin, 873 ; red or bark tanning, 874 ; oak bark, 874 ; Biichner's re- 
 searches, 875 ; sumac, 875 ; dividivi, 875 ; nut galls, 876 ; valonia nuts, 876 ; Chinese 
 galls, 876 ; cutch, 876 ; kino, 877 ; estimation of the value of the tanning materials, 877 ; 
 the hides, 878 ; cleansing, 879 ; stripping off the hair, 880 ; swelling the hides, 880 ; the 
 tanning, 881 ; in bark, 881 ; in liquid, 882 ; quick tanning, 882 ; dressing or currying the 
 leather, 883 ; sole leather, 883 ; upper leather, 883 ; paring, 883 ; scraping or smoothing, 
 883 ; graining, 883 ; polishing with pumice-stone, 883 ; raising the grain with pommels of 
 cork, 883 ; smoothing with the Tawer's softening iron, 884 ; rolling, 884 ; finishing off, 884 ; 
 greasing, 884 ; yufts, jufts, or jufti, Russia leather, 884 ; morocco leather, 885 ; dressing 
 morocco, 885 ; cordwain, Cordovan leather, 885 ; lacquered leather, 885 ; alum tanning 
 tawing, 886 ; common tawing, 886 ; Hungarian tawing, 888 ; glove leather, 888 ; Knapp's 
 leather, 889 ; electrical tanning, 889 ; oil-tawing and wash-leather process, 890 ; parch- 
 ment, 891 ; velin, 891 ; shagreen, 891. 
 
 GLUE, SIZE, GELATINE 892 
 
 General observations, 892 ; leather glue, 893 ; treating with lime, 893 ; boiling the mate- 
 rials, 894 ; fractionated boiling, 894 ; moulding, 895 ; drying the glue, 895 ; bone glue, 
 896 ; boiling out the grease, 896 ; treating the bones with hydrochloric acid, 896 ; con- 
 version of the organic matter into glue, 896 ; liquid glue, 897 ; tests of quality of glue, 
 897. 
 
 SIZES 898 
 
 Isinglass, fish glue, 898 ; substitutes for glue, 899. 
 
 BONES 899 
 
 Bone-black, 900 ; properties of bone-black, 901 ; testing bone-black, 901 ; revivification of 
 charcoal, 902 ; substitutes for bone-black, 902. 
 
 FATS 903 
 
 Berthelot's series, 903 ; goose-grease, 904 ; fish oil, 904 ; important non-drying oils, 904 
 palm-oil, 904 ; bassia-oil, 904 ; olive oil, 905 ; rape and colza oil, 906 ; beech, 906 ; sesame, 
 906 ; earth-nut, 906 ; chief drying oils, 906 ; hemp, 906 ; nut, 906 ; cotton, 906 ; waxes, 
 
 906 ; beeswax, 906 ; white, 906 ; Chinese, 906 ; andaquies wax, 906 ; vegetable waxes, 
 
 907 ; Japan, 907 ; carnauba wax, 907 ; palm, 907 ; myrtle wax, 907 ; ucuhuba wax, 907 ; 
 lubricants, 907 ; to ascertain the fluidity of an oil, 908 ; varnishes, 908 ; linseed-oil var- 
 nishes, 908 ; for paper-hangings, 909 ; printing ink, 909 ; fat varnishes, 909 ; spirit varnish, 
 909 ; lacquers, 910 ; turpentine oil varnishes, 910 ; polishing the dried varnish, 910 ; Pet- 
 tenkofer's process for restoring pictures, 910 ; G. J. Mulder's researches, 911 ; linseed-oil 
 varnish cement, 911 ; cement for steam pipes, &c., 911 ; iron-putty, 911. 
 
 SOAP 911 
 
 Raw materials, 911 ; theory of saponifi cation, 911 ; Chevreul's researches, 911 ; Berthelot's 
 researches, 912 ; soft soaps, 912 ; hard soap, 912 ; grain soap, 912 ; smooth, 912 ; filled, 
 
 912 ; chief varieties of soap, 913 ; Mege-Mouries' process, 913 ; F. Knapp's researches, 
 
 913 ; German curd soap, 914 ; Dr. A. C. Oudemans' researches, 914 ; olive-oil soap, 914 ; 
 mottled soap, 914; Marseilles mottled soap, 914 ; oleic acid soap, 915;; Pitman's process, 915 ; 
 Morfit's arrangement, 915 ; resin-tallow soaps, 915 ; German palm-oil soap, 915 ; cocoa-nut 
 oil soap, 915 ; soft soap, 916 ; various other soaps, 917 ; toilet soaps, 917 ; modes of pre- 
 paring, 918 ; Windsor soap, 917 ; rose, 917 ; shaving, 917 ; lather, 917 ; palm or olive oil, 
 917 ; transparent soap, 918 ; glycerine soap, 918 ; uses of soap, 918 ; tests, 918 ; Dr. Leeds' 
 method for the examination of soap, 918; insoluble soaps, 918; calcium, magnesium, 
 aluminium soap, 918 ; manganese, zinc, mercury, silver, gold, platinum soaps, 919 ; washing 
 powders, extracts of soap, soap powders, &c., 919 ; adulteration of soap, 919. 
 
 STEARINE AND GLYCEEINE 921 
 
 Saponification with caustic lime, 921 ; A. Kind's method, 922 ; Messener's apparatus, 922 ; 
 Petit's apparatus, 922 ; saponification with a reduced proportion of lime and the use of high 
 
TABLE OF CONTENTS. xxiii 
 
 MM 
 
 pressure, 924 ; the Milly process, 924 ; Leon Droux's apparatus, 924 ; saponification with 
 sulphuric acid and subsequent distillation by means of steam, 926 ; with water and high 
 pressure, 929 ; Tilghman's apparatus, 929 ; manufacture of fatty acids by means of super- 
 heated steam and subsequent distillation, 930 ; process used by Price's Candle Company, 
 Limited, 930; Heckel's apparatus, 931 ; Korschelt's researches, 931 ; Bock's process, 932 ; 
 conversion of oleic acid into palmitic acid, 932 ; glycerine, 933 ; preparation, 933 ; distil- 
 lation, 934 ; freezing observed by W. Crookes, Sarg, and Woehler, 934 ; applications, 934 ; 
 " scheelising," 935. 
 
 ESSENTIAL OILS AND KESINS . 935 
 
 Preparation, 935 ; by pressure, 935 ; extraction, 936 ; properties and uses, 936 ; perfumery, 
 936 ; artificial perfumes, 936 ; preparation of cordials, 936 ; Mxirile's apparatus for the 
 extraction of ethereal oils, 938 ; resins, 938 ; sealing wax, 938 ; asphalte, 939 ; caoutchouc, 
 939; solvents of caoutchouc, 940 ; various sorts of, 940; preparation, 940; "Para," 941: 
 preparation and use of india-rubber, 941 ; vulcanised caoutchouc, 941 ; Goodyear's process, 
 942 ; gutta-percha, 942 ; solvents of, 943 ; uses, 943 ; mixture of gutta-percha and caout- 
 chouc, 944 ; balata, 944 ; celluloid, 944. 
 
 PBESERVATION OF WOOD ..." 944 
 
 Durability of wood, 944 ; attack of insects, 945 ; preservation of wood, 945 ; by drying, 
 946 ; elimination of the constituents of the sap, 946 ; air drains, 946 ; chemical alteration 
 of the constituents of the sap, 947 ; danger of kyanised wood, 947 ; Burnett's fluid, 947 ; 
 Bethell's method, 948 ; Payne's method, 948 ; mineralising wood, 948 ; Boucherie's method 
 of impregnation, 948. 
 
 APPENDIX. 
 
 USEFUL TABLES. 
 
 THEKMOMETEIC SCALES 949 
 
 To convert degrees Centigrade into degrees Fahrenheit, 949. 
 
 HYDROMETER TABLES 949 
 
 For converting Twaddell into direct specific gravity, 949 ; for converting direct specific 
 gravity into Twaddell, 949 ; conversion of the scale of Baume into degrees Tw., 949 ; scales 
 for liquids lighter than water, 950 ; Gay-Lussac's alcoholometer, 951 ; comparison of metric 
 system with English weights and measures, 952. 
 
 MEASURES OP CAPACITY 952 
 
 MEASURES OF LENGTH 952 
 
SECTION I. 
 TECHNOLOGY OF FUEL. 
 
 1. FUEL AND ITS TREATMENT. 
 
 UNDER fuel we understand those organic substances which, if suitably heated, 
 combine with the oxygen of the atmosphere, evolving light and heat, and forming 
 carbon dioxide and water.* The combustibles chiefly used for generating heat 
 wood, peat, lignite, and coal (which will be considered separately from the fatty 
 matters and mineral oils, used principally for the production of light) consist essentially 
 of cellulose, C 6 H 10 O 5 , and are derived from it as residues richer in carbon, after car- 
 bonic acid, water, and methane have been split off, as is shown in the following table, 
 calculated for average specimens free from moisture and ash : 
 
 
 Carbon 
 per cent. 
 
 Hydrogen 
 per cent. 
 
 Oxypen 
 (+K) 
 
 per cent. 
 
 Heat Value 
 in Thermic 
 Units.t 
 
 Wood . 
 
 49 
 
 6 
 
 45 
 
 4IOO 
 
 Peat 
 
 55 
 
 5 
 
 40 
 
 4500 
 
 Lignite . . 
 
 66 
 
 5 
 
 29 
 
 5700 
 
 Coal 
 
 S6 
 
 4 
 
 10 
 
 8000 
 
 Anthracite 
 
 94 
 
 3 
 
 3 
 
 820O 
 
 Cellulose is formed from carbonic acid and water under the action of the sun's 
 rays- 6CO, + 5 H 2 = C 6 H 10 5 + 6O 2 , 
 
 whilst in the combustion of cellulose 
 
 C 6 H 10 5 H- 60, m 6CO, + S H f O, 
 
 the same substances are re-constituted with the evolution of 5150 thermic units for 
 each kilo, of cellulose. Exactly the same quantity of heat must have been supplied by 
 the sun's rays for the formation of i kilo, cellulose from carbonic acid and water. 
 We therefore consume, not only the heat which is now being yielded by the sun, but 
 the solar heat which has been stored up for thousands of years in vegetable residues 
 (lignite, coal, &c.), a supply of power, heat, and light which is, without doubt, daily 
 decreasing, and must gradually become exhausted. 
 
 This should be a serious warning not to waste fuel, as is now frequently done, 
 or at any rate to attend to its thorough utilisation, so long as we have no other 
 means of producing work, heat, and light in sufficient quantity. The application of 
 water-power for the production of electricity is only a slight attempt in this 
 direction. 
 
 The importance, or rather, so far, the necessity of fuel for the whole of our 
 
 * This definition excludes chlorine in hydrogen, &c., as also sulphur, phosphorus, and the 
 metals. 
 
 t A thermic unit is that quantity of heat which raises i kilo, water from o to 1. The 
 mechanical equivalent of heat = 425 kilogrammetres. 
 
'.'V V : CHEMICAL TECHNOLOGY. [SECT, i, 
 
 y/an^'iD^oai 1 iatit-udes fctvetiior human life, justifies a more thorough attention 
 to the utilisation of fuel' than it has hitherto generally received. 
 
 THERMOMETRY. 
 
 History. The first thermometer is said to have been constructed by Galileo in 
 1556, but this is disputed, and the invention is currently ascribed to C. Drebble in 
 1638. It consisted of a globe with a tube welded on, and dipping with its open end 
 into a vessel containing a dilute solution of copper nitrate. Becher (1680) and 
 others improved this air thermometer by taking the pressure of the external air into 
 account. The first spirit thermometer was made about 1640 by Moriani, for the 
 Academy of Florence. Reaumur (1730) also used spirit ; Neston (1701), linseed oil ; 
 and Fahrenheit of Dantsic (1709) first used mercury. The first metallic thermometer 
 was constructed by Mortimer in 1746. Renaldini (1694) introduced the use of ice 
 and of boiling water for ascertaining the fixed points. 
 
 As Fahrenheit's thermometer is still almost exclusively used in Britain and North 
 America and elsewhere, in addition to the scale of Celsius (Centigrade), and that of 
 Reaumur (extensively used in the fermentation industries), it may not be superfluous to 
 remark that these scales may be converted into each other as follows : 
 
 F. = 9 / 4 R. + 32 - V,C. + 32; 
 R. - V. (F. - 32); 0. - /. (F. - 32) = 
 
 B. 
 
 Fahren- 
 heit. 
 
 Celsius. 
 
 Reaumur 
 (de Luc). 
 
 Celsius. 
 
 Reaumur 
 (de Luc). 
 
 Fahrenheit. 
 
 Re'aumur 
 (de Luc). 
 
 Celsius. 
 
 Fahrenheit. 
 
 - 20 
 
 - 28-88 
 
 - 23-11 
 
 - 20 
 
 - l6'0 
 
 - 4-0 
 
 - 2O 
 
 - 25*00 
 
 - 13-00 
 
 - 10 
 
 - 23-33 
 
 - 18-66 
 
 - IO 
 
 - 8-0 
 
 + 14-0 
 
 - 10 
 
 - I2-OO 
 
 + 9-50 
 
 O 
 
 - 1777 
 
 - 14-22 
 
 O 
 
 O'O 
 
 32-0 
 
 
 
 O'OO 
 
 32-00 
 
 IO 
 
 - I2'22 
 
 - 977 
 
 + 10 
 
 + 8-0 
 
 50-0 
 
 + 10 
 
 + 12-50 
 
 54-50 
 
 20 
 
 - 6-66 
 
 - 5 '33 
 
 2O 
 
 16-0 
 
 68-0 
 
 20 
 
 25-00 
 
 77-00 
 
 30 
 
 - I'll 
 
 - 8-00 
 
 30 
 
 24-0 
 
 86-0 
 
 30 
 
 37-50 
 
 99-50 
 
 40 
 
 + 4-44 
 
 + 3'55 
 
 40 
 
 32-0 
 
 104-0 
 
 40 
 
 50-00 
 
 I22'OO 
 
 50 
 
 lO'OO 
 
 8-00 
 
 5 
 
 40-0 
 
 I22'O 
 
 5 
 
 62-50 
 
 I44-50 
 
 60 
 
 I5-5S 
 
 12-44 
 
 60 
 
 48-0 
 
 I4O-O 
 
 60 
 
 75-00 
 
 I67-00 
 
 70 
 
 21-11 
 
 16-88 
 
 70 
 
 56-0 
 
 I58-0 
 
 70 
 
 87-50 
 
 189-50 
 
 80 
 
 26-66 
 
 21-33 
 
 80 
 
 64-0 
 
 I76-O 
 
 80 
 
 1 00 '00 
 
 212-00 
 
 90 
 
 32-22 
 
 2577 
 
 90 
 
 72-0 
 
 I94-0 
 
 90 
 
 112-50 
 
 234-50 
 
 100 
 
 3777 
 
 30-22 
 
 100 
 
 80-0 
 
 212-0 
 
 IOO 
 
 125-00 
 
 257-00 
 
 2OO 
 
 93 '33 
 
 74-66 
 
 2OO 
 
 160-0 
 
 392-0 
 
 20O 
 
 250-00 
 
 482-00 
 
 Conspectus of the Ordinary Thermometers. The numerous instruments devised for 
 measuring temperatures depend on the utilisation of the following phenomena : 
 
 1. Expansion of matter, solid, liquid, or aeriform. 
 
 2. Alteration of the state of aggregation. 
 
 3. Dissociation ; optical and acoustic phenomena. 
 
 4. Electric manifestations. 
 
 5. Distribution of heat. 
 
 i. The expansion of metals has been used, especially for the determination of high 
 temperatures.* All these metal thermometers or pyrometers axe untrustworthy. 
 
 The most important appliances for measuring heat are the mercurial thermometers. 
 For temperatures from 250 to 350 the space above the mercury should be filled 
 with nitrogen-gas. If this nitrogen is under increased pressure the thermometers can 
 be used up to 400 or even 430, and are the most accurate and convenient instru- 
 ments for measuring such temperatures. 
 
 Attention must be given to the variability of thermometers which is shown in 
 
 * Fischer, Chemische Technologic der Brennstoffe, pp. 7 and 313. 
 
SECT. I.] 
 
 THERMOMETRY. 
 
 two directions. On the one hand, the zero-point, and consequently the entire scale, 
 slowly rises, and on the other the indications after any exposure to a strong heat 
 experience a temporary depression. In these thermometers the transient influence of 
 subsequent heatings is in part marked by the temperature to which the instruments 
 are submitted in their manufacture. In old thermometers this latter effect is weakened. 
 Here there exists between the rise and the fall a relation, in as far as the magnitude of 
 the latter may be regarded to some extent as a standard for the rise to be subsequently 
 expected. To a large extent of this temporary fall there corresponds a large amount 
 of slow rise to be expected in the course of years. A constancy of the indications 
 sufficient for practical purposes can be counted on only if the temporary fall does not 
 exceed a certain limit, which for a heating up to 100 falls distinctly below o'i. The 
 magnitude of the fall depends essentially on the chemical nature of the glass. Ther- 
 mometers of very fusible potash-soda glass are subject to considerable variations, whilst 
 pure potash glass or pure soda glass behaves more satisfactorily, as it has been shown 
 by R. Weber and H. F. Wiebe.* The composition of three kinds of glass (Jena 
 normal glass), made by Abbe and Schott of Jena for mercurial thermometers with 
 
 an invariable zero, is : 
 
 i. ii. in. 
 
 . 67-50 ... 69-00 ... 52-0 
 
 Si0 2 
 
 Na.,0 
 
 ZnO 
 
 CaO 
 
 AL.O 
 
 BO, 
 
 K,0 
 
 14-00 
 7-00 
 7-00 
 2-50 
 
 2'OO 
 
 II. 
 
 69-00 
 14-00 
 
 7'OO 
 
 7 'oo 
 
 I'OO 
 
 2'OO 
 
 30-0 
 
 9-0 
 9-0 
 
 Although these thermometers are very decidedly superior to those previously 
 known, an occasional comparison of the zero (crushed ice) and the boiling point of 
 water should be made. For the latter determination attention must be paid to the 
 connection between the boiling-point of water and the atmospheric pressure : 
 
 Barometer. 
 720 millim. 
 73 
 740 
 
 75 
 760 
 
 770 
 
 780 
 
 Boiling-point. 
 98-49 
 98-88 
 99-26 
 
 99 '63 
 ioo-oo 
 100-36 
 100-73 
 
 Naphthaline and benzophenone are suitable for higher temperatures. The follow- 
 ing table gives the boiling-points of naphthaline and benzophenone at various pressures 
 in millimetres of mercury (reduced to o): 
 
 Naphthaline. 
 
 Benzophenone. 
 
 Temp. 
 
 Millimetres. 
 
 Temp. 
 
 Millimetres. 
 
 Temp. 
 
 Millimetres. 
 
 \ Temp. 
 
 Millimetres. 
 
 215-8 
 
 722-05 
 
 217-2 
 
 745'4i 
 
 303-8 
 
 72477 
 
 305-2 
 
 746-24 
 
 2l6'0 
 
 725-34 
 
 217-4 
 
 748-80 
 
 304-0 
 
 727-80 
 
 305-4 
 
 749-36 
 
 2l6'2 
 
 728-45 
 
 217-6 
 
 752-20 
 
 304-2 
 
 730-86 
 
 305-6 
 
 752-47 
 
 216-4 
 
 731'98 
 
 217-8 
 
 750-90 
 
 34'4 
 
 733-92 
 
 305-8 
 
 755-60 
 
 216-6 
 
 735-32 
 
 218-0 
 
 759-02 
 
 304-6 
 
 736-98 
 
 306-0 
 
 75874 
 
 216-8 
 
 738-67 
 
 218-2 
 
 762-46 
 
 304-8 
 
 740*06 
 
 306-2 
 
 761-90 
 
 217-0 
 
 742-03 
 
 2I8-4 
 
 765-91 
 
 305-0 
 
 743-14 
 
 308-4 
 
 765-09 
 
 In determining the boiling-point,^ the direct action of the vapours upon the 
 
 * Jahresber. 1885, p. 1234. 
 
 f Tliermometric Correction for the Projecting Thread. If in determination of temperature the 
 mercurial thread is not entirely exposed to the heat in question, the instrument will not give the 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 Fig. i. 
 
 thermometer case is to be avoided as far as possible, which is effected by inserting 
 
 the thermometer in a narrow tube of very thin sheet-metal, closed below (Fig. i). 
 
 An enclosure of the entire lower part of the thermometer in such a metal casing, 
 in contact with the atmosphere above, affords the advantage 
 (especially in determinations of boiling-points at reduced pres- 
 sures that the difference of the pressure existing within and 
 without the thermometer is very much smaller, and that conse- 
 quently a correction for the influence of the pressure upon the 
 height of the thermometer may be omitted. The compressibility 
 of the glass of the thermometer may be approximately ascertained 
 by determining one and the same temperature with a thermo- 
 meter in a perpendicular and then in a horizontal position. The 
 difference of the thermometer in these two determinations is 
 caused by the pressure of the mercurial column in the tube upon 
 its case when in an upright position. This effect is the greater 
 the longer the thermometer, and consequently the longer the 
 mercurial column at any given temperature. If the temperatures 
 found by a mercurial thermometer are to be calculated for an air 
 thermometer, the tables of Regnault are no longer available, since 
 different kinds of glass are now in use. 
 
 Air thermometers * are very accurate, but not well adapted to 
 practical purposes. 
 2. The determination of high temperatures by the fusion of metals and alloys has 
 
 been repeatedly attempted. Erhardt and Schertel recommend metal balls of from 100 
 
 to 150 milligrams of the following composition : 
 
 Composition. 
 
 Melting- 
 point. 
 
 Composition. 
 
 Melting- 
 point. 
 
 Composition. 
 
 Melting- 
 point. 
 
 per cent. 
 
 
 per cent. 
 
 
 per cent. 
 
 
 Silver 
 
 954 
 
 95Au 5?t 
 
 IIOO 
 
 65Au 35Pt 
 
 1285 
 
 8oAg 2oAu 
 
 975 
 
 90 10 
 
 1130 
 
 60 40 
 
 1320 
 
 60 40 
 
 995 
 
 85 15 
 
 1160 
 
 55 45 
 
 1350 
 
 40 60 
 
 1020 
 
 80 2O 
 
 1190 
 
 50 50 
 
 1385 
 
 20 So 
 
 1045 
 
 75 25 
 
 I22O 
 
 45 55 
 
 1420 
 
 Gold 
 
 1075 
 
 70 30 
 
 1255 
 
 Platinum 
 
 1775 
 
 The more recent determinations of melting-points by Violle are : 
 
 Ir 
 Pt 
 Pd 
 
 Cu 
 Au 
 Ag 
 
 1054 
 
 1035 
 
 954 
 
 correct indication. If we call the temperature to be determined T, the mean temperature of the 
 mercurial thread, T, and its length /, the thread, if entirely immersed in the temperature to be 
 measured, will be longer in the proportion i : i + a (T - r) if a denotes the co-efficient of expansion 
 of the mercury in the glass. Instead of / the length would be I + I a (T- r), or the number of degrees 
 which go to the unit of length being put = i>, then in place of v I in thermometer degrees the length 
 of the thread would be vl + vl a ( T- T} or the thermometer, if v I is put = n, indicate n . a (T- T). 
 If, therefore, we read off on the thermometer the temperature t, the real temperature of the space 
 
 in question T = t + n.a (T - T) or = - . The mean co-efficient of expansion of mercury 
 
 between o and 100 being assumed as 0*000181, and that of glass o > oooo26, a = 0*000155. The 
 mean temperature T of the thread is generally determined by hanging a small thermometer near 
 the middle of the thread, along with the one whose indications are to be corrected, and assuming 
 the temperature of the air read off on the former as the value of T, On account of the con- 
 ductivity of the mercurial thread, the value of r as thus determined is too small, and the calcu- 
 lated value of T is, therefore, too great. For shorter mercurial threads we insert, according to 
 Holtzmann, for compensating this error only 0*000135 instead of a, for long threads the value 
 of T must be specially determined for each thermometer as j ust given. 
 * F. Fischer's Chem. Technologic der Brennstoffe, pp. 32 and 319. 
 
SECT. 
 
 THERMOMETRY. 
 
 For high temperatures H. Seger recommends tetrahedra (normal cones) of mixed 
 glazes composed of felspar, marble, quartz, and Zettlitz kaolin according to the following 
 formulae : 
 
 No. 
 
 Chemical Formula: o'3K 2 0,o'7CaO, and 
 
 No. 
 
 Chemical Formula : o^KjjO.o^CaO, and 
 
 I 
 
 o-2Fe 2 3 ,o-3Al.,O 3 ,4SiO 2 
 
 ii 
 
 r2Al 2 3) i2SiO 2 
 
 2 
 
 o i Fe 2 O 3 ,o -4 Al 2 O 3 ,4Si0 2 
 
 12 
 
 i'4Al 2 O 3 ,i4SiO. 
 
 3 
 
 o - o5Fe 2 3 ,o -45 Al.,0 3 ,4Si0 2 
 
 13 
 
 i-6Al.,0 3 ,i6SiO; 
 
 4 
 
 o-5Al.,O 3 ,4SiO 2 
 
 14 
 
 i-8Al 2 0.,,i8Si<X 
 
 5 
 
 o-5Al 2 3 ,5Si0 2 
 
 15 
 
 2-iAl 2 3 ,2iSi(X 
 
 6 
 
 o-6AL,O 3 ,6Si0 2 
 
 16 
 
 2-4Al.,O 3 ,24SiO 2 
 
 7 
 
 o7ALA j ,7SiO, 
 
 17 
 
 27Al."O 3 ,27SiO., 
 
 8 
 
 o-8Al.,O 3 ,8Si0 2 
 
 18 
 
 3'iAL 2 3 ,3iSiO; 
 
 9 
 
 o-9AU),,9Si0 2 
 
 19 
 
 3'5Al,0 3 ,35Si0 2 
 
 10 
 
 i-oAL,O s ,ioSiO, 
 
 20 
 
 3- 9 Al 2 3) 3 9 Si0 2 
 
 Fig. 2. 
 
 The fusion of the cones indicates the temperatures between the melting-point of 
 90 parts gold and 10 parts of platinum i.e., about 1145 U P to * ne mog t intense glow 
 of a porcelain-furnace. If we call the range to be measured 600, each cone represents 
 a rise of about 30. It must be remembered that the cones for the higher figures show 
 phenomena of fusion more and more slowly. This is intelligible if we consider that at 
 higher temperatures the heat of the furnace rises more and more slowly on account of 
 the increasing losses of heat. The glazes also become more and more refractory, and sink 
 down less readily. In setting up the cones care must be taken that they always incline 
 to one and the same side, the open side of the form on which the number is impressed, 
 and which almost invariably comes upwards. The 
 cones are to be placed so that the sinking of the point 
 may be observed until it touches the fire-clay plate be- 
 neath. The Royal Porcelain Works at Berlin supply 
 i oo cones for 45. 6d. The cones act satisfactorily.* 
 
 3. The determinations of heat depending upon 
 dissociation, optical and acoustic phenomena seem to 
 have no future, t 
 
 4. Electric Thermometers. The best of these 
 devices is the electric pyrometer of C. W. Siemens. 
 As the author has satisfied himself by prolonged 
 experiments,! it is trustworthy, but it requires very 
 careful manipulation, and is costly (about ^25). 
 
 5. Diffusion of Heat. Among instruments of this 
 kind only the so-called calorimeters are trustworthy. 
 The author J[ recommends the following arrangement as 
 satisfactory : The cylinder of sheet-copper, A (Fig. 2), 
 145 mm. high and 50 mm. wide, is suspended in the 
 wooden case, B, which is provided with a convenient 
 handle. The space between the wood and the metal is 
 filled up with asbestos of a long fibre. The apparatus 
 is closed with a thin plate of brass which has a large 
 aperture, d, of 20 mm. diameter, for the stirrer, c, and 
 for introducing the metal cylinder, and a smaller one 
 for the thermometer, t. The normal thermometer 
 with a very small bulb for mercury, ranging from o 
 
 to 50, is graduated in o - i , so that it is possible to estimate o - oi. It is protected 
 against injury from the stirrer by a strap, a, of thin sheet-copper. The stirrer consists of 
 
 J Op. cit. p. 47. 
 
 * Jalir&sber. 1887, p. 30. 
 Op. cit. pp. 54 and 327. 
 
 t Brennstoffe, pp. 45 and 326. 
 || Op. cit. p. 61. 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 a round disc of copper soldered to a stout copper wire, which is melted into a glass rod, 
 serving as a handle. The copper vessel weighs, e.g., 35*9 grammes, and the stirrer with- 
 out the glass rod 6 '4 grammes ; hence the water- value of the calorimeter (specific heat of 
 copper 0-094) with the thermometer 4 grammes. For refrigerating there are used 246 
 grammes of water, so that the water-value of the calorimeter when full is 250 grammes. 
 For measuring the temperatures the author uses a platinum cylinder weighing 20 
 grammes, or a cast-iron cylinder of 12 mm. diameter and 20 to 22 mm. in length, weigh- 
 ing 20 grammes, and having two perforations. These cylinders are exposed to the heat, 
 which is to be determined in a small covered iron vessel, secured to an iron rod from 
 to i metre in length, and fitted with a wooden handle. They are then brought to the 
 calorimeter and dropped in through the aperture d. The metal cylinder falls regularly 
 upon the plate of the stirrer ; by moving this up and down, the heat is rapidly and 
 uniformly distributed through the water, so that within a minute the thermometer 
 shows the final temperature. Corrections for evaporation of water or difference of the 
 temperature of the outer air are not necessary. The temperature sought for appears 
 from the following table : 
 
 T. 
 
 i kilo. Water and i kilo. Metal 
 -*i 
 
 250 grammes Water and 
 20 grammes Metal t - <j 
 
 Difference per 10 
 
 
 for Iron. 
 
 for Platinum. 
 
 for Iron. 
 
 for Platinum. 
 
 for Iron. 
 
 for Platinum. 
 
 400 
 
 47 '4 
 
 13-6 
 
 3-8 
 
 I '09 
 
 O'I2 
 
 0-03 
 
 5OO 
 
 62-3 
 
 17-4 
 
 5-0 
 
 I '39 
 
 0-13 
 
 0-03 
 
 600 
 
 78-5 
 
 21 '2 
 
 6-3 
 
 170 
 
 0-14 
 
 o'O3 
 
 700 
 
 96-2 
 
 25-I 
 
 77 
 
 2'OI 
 
 0-15 
 
 0-03 
 
 800 
 
 1 15 '4 
 
 29 '2 
 
 9-2 
 
 2'34 
 
 0-17 
 
 0-03 
 
 900 
 
 136-4 
 
 33 '4 
 
 io - 9 
 
 2-67 
 
 0-18 
 
 0-04 
 
 IOOO 
 
 159-2 
 
 377 
 
 127 
 
 3-02 
 
 
 
 If the thermometer before the introduction of the cylinder marks i 1 , and afterwards 
 t ; and if the increase of temperature is consequently t t v the temperature sought 
 for is =T + . If, e.g., the water- value and the calorimeter are 250 grammes water, 
 the temperature of the water ^=12*0, and after the introduction of the iron cylinder 
 weighing 20 grammes, 2= 20-3, then t ^ = 8-3. The nearest value in the table, 77, 
 represents T = 760 ; for the remaining 0-6(8-3 77) there results 0-6:0-15=4, i.e., 
 40, to which = 20, so that the temperature sought for is 760. On using a platinum 
 cylinder weighing 20 grammes, let the temperature ^ be= 15*15, after introducing the 
 cylinder 17-98, consequently t ^ = 2-83 ; 2-67, according to the table, correspond to 
 900; to the residue 2-83 2-67 = 0-16 ; and 0-16 : 0*04 = 4, i.e., 40. Hence the total 
 temperature, 958. 
 
 According to more recent experiments by Pionchon,* the specific heat of iron abovo 
 660 is very irregular, so that the platinum cylinder is preferable. 
 
 DETERMINATION OF THE VALUE OF FUELS. 
 
 The value of fuel employed for the production of heat chiefly depends on the quan- 
 tity of heat liberated on combustion. Instead of determining this value it is often 
 customary to be satisfied with determining the water, the ash, the sulphur (especially 
 important in alkali works, smelting works, &c.), the nitrogen (especially for obtaining- 
 ammonia), further, the carbon and the hydrogen, so that the thermic value may be 
 calculated according to the formula of Dulong (p. 8). 
 
 Sampling. From every load, or every other load, barrow, basket, &c., of the coal 
 as delivered, a spadeful is thrown into a chest fitted with a cover ; the coal is then 
 broken up, mixed, and spread out on a level surface in a rectangular shape, and divided 
 into four parts by two diagonal cuttings. Two of these portions lying opposite to each 
 
 * Jahresber. 1887, p. 33. 
 
SECT, i.] DETERMINATION OF THE VALUE OF FUELS. 7 
 
 other are taken, away ; the two remaining are again comminuted and mixed until there 
 remains a sample of about 2 kilos., which is put into a closely stoppered bottle. For 
 more careful investigations it is advisable to take in the same manner an average sample 
 of the other half, and to examine it separately. As a loss of moisture is to be feared 
 during the process of sampling, smaller average samples are placed from time to time 
 in weighed test-glasses with glass stoppers to serve for the determination of water. 
 
 Samples of peat are taken in a corresponding manner. 
 
 The samples given in to the laboratory must be completely pulverised without 
 rejecting any portions which may be hard to comminute. The determination of 
 moisture must not be effected in open capsules, since many fuels become slowly oxidised 
 if heated in the air. For technical purposes about 20 grammes of the sample are heated 
 for two hours to 105 or 110 in an air-bath either between two watch-glasses or in a 
 crucible with a well-fitting cover, let cool, and weighed. The portion intended for 
 analysis is, if possible, to be allowed to dry in a current of nitrogen, or with the utmost 
 possible exclusion of air. 
 
 For the determination of its ash, 5 grammos of the pulverised fuel are incinerated in 
 a platinum capsule. In examining coal, the sample should first stand one or two hours 
 in an open capsule over a small flame, and be heated in a drying closet to about 130 ; 
 the incineration is then completed over a flame, which is gradually increased. Coke 
 and anthracite should be very finely powdered. 
 
 To determine the yield of coke, from i'8 to 2 grammes of powdered coal are heated 
 over a Bunseri burner in a platinum crucible with a well-fitting cover (the distance 
 between the mouth of the burner and the bottom of the crucible being 3 centimetres) 
 until flame no longer issues from under the cover.* 
 
 For determining the nitrogen by the Kjeldahl process, from 0-5 to i gramme of the 
 coal or coke, pulverised as finely as 
 
 possible (peat does not require pul- **& 3- 
 
 verising), is boiled for about three 
 hours with i gramme mercuric oxide 
 and 20 c.c. of sulphuric acid. When 
 cold there are added 120 c.c. soda- 
 lye, and i -6 gramme sodium sul- 
 phide (in solution), when the am- 
 monia is distilled off and determined 
 volumetrically. 
 
 For determining carbon and 
 hydrogen, the author uses a simple 
 combustion-furnace (Fig. 3). The 
 two end plates, b and p, are con- 
 nected below with the bottom plate, 
 
 and joined to each other above by the two iron rods, u, against which the tiles, s, 
 vest above, whilst they stand below in the grooves running along each side. By this 
 means the flames of the burners below, which are screened from currents of air by the 
 
 Fig. 4. 
 
 metal sheets placed on each side, are compelled completely to enfold the combustion 
 tube as it lies in the open, semi-cylindric channel, o. The combustion-tube (Fig. 4), of 
 
 * See Fischer, op. cit. p. 113. 
 
8 CHEMICAL TECHNOLOGY. [SECT. i. 
 
 very refractory glass, open at each end, contains between the two asbestos plugs, a, 
 wrapped in very thin platinum foil, a layer, n, of granular copper oxide. The platinum 
 boat, m, with the sample, is inserted, and the end of the tube u is connected with a 
 gas-holder of oxygen, and the other end, w, with the calcium-chloride tube, c. 
 
 When beginning a series of experiments, the combustion-tube is laid in the sheet 
 iron channel, o, the tiles are laid against the rods, u (Fig. 3), and as the layer of copper 
 oxide is heated to redness by the lamp, B, provided with three or four flat burners (for 
 the sake of distinctness the sheet-iron screens are here omitted), whilst a single Bunsen, 
 A, burner suffices for the other half of the tube. A current of atmospheric air is 
 drawn through for about ten minutes. The air has passed first through a flask with 
 potassa-lye, and then through another of undiluted sulphuric acid. The tube is then 
 let cool in the current. The stopper, u, is then removed, and the sample (about 300 
 milligrammes), previously dried at 110, is introduced in the platinum boat, the 
 stopper is again inserted, the calcium-chloride tube, c, is connected at the other end, 
 and the combustion is effected as usual in the current of oxygen. 
 
 The volatile sulphur is determined in a corresponding manner, but a larger sample 
 is used (0*8 to i gramme), and the combustion-tube contains asbestos in place of copper 
 oxide. The sulphurous and sulphuric acids formed are passed into bromiferous potassa- 
 lye and into hydrogen peroxide, and precipitated as barium sulphate. 
 
 If the fuel under examination contains c per cent, of carbon, h per cent, of 
 hydrogen, s per cent, of sulphur, o per cent, of oxygen, and w per cent, of water, 
 i kilo, of coal requires carbon (2*667 c + 8 h + so) : 100 kilos, or (2*667 c + 8 h + s 
 o) : (100 . 1*43) c.c. oxygen or (2-667 c + Sh + s- o) : (21. 1*43) c.c. of atmospheric air 
 for complete combustion, i kilo, coal of medium composition consists of 
 
 Carbon 80 per cent. 
 
 Hydrogen 4 
 
 Oxygen 8 
 
 Nitrogen i 
 
 Sulphur 2 
 
 Water 3 } , 
 
 Ash ...... 2 
 
 and requires, therefore, 2-667 . o'8 + 8-004 + 0*02 - o - o8 or (2-667 . 80 -i- 8-4 + 2 - 8) : 
 100 . 2-393 kilos, or 1*673 c.c. oxygen, or 8 c.c. of atmospheric air. 
 
 The thermic value according to Dulong's formula, referred to liquid water at o as 
 the product of combustion = 
 
 8100 c + 34220 (h - - ) + 2500 s : 
 100 heat-units, or referred for convenience to steam at 20 = 
 
 81000 + 28800 (ft j + 2500 s 600 w I: i oo heat-units. 
 
 Dulong's formula gives approximately accurate values for wood, peat, and lignite ; 
 for coal they are generally from 400 to 800 heat -units too small. Accurate values are 
 obtained only by determining the combustion- value (see p. 9). 
 
 In this determination of the combustion-value the author obtained the best possible 
 value by passing the gases evolved in the silver combustion vessel, A (Fig. 5), down- 
 ward through the tube i into the flat space, c, where, as the transverse section (see 
 accompanying figure) shows, they are compelled in the first place to go to the external 
 side, escaping finally by the flat tube, e. The combustion-chamber is secured by the 
 three feet, f, to the bottom of the copper refrigerating vessel, which is strongly 
 silvered, by corresponding projections. 
 
 The glass pieces, a and b, are connected with this silver apparatus at the water-level 
 by short caoutchouc pipes. The entrance tube, a, for the supply of oxygen, which has 
 
SECT, i.] DETERMINATION OF THE VALUE OF FUELS. 
 
 Fig. 5- 
 
 previously been dried, is prolonged by a bent tube of sheet-platinum, which has some 
 small apertures above. The platinum crucible, , can be coated below with asbestos 
 board to prevent too rapid refrigeration, and it is 
 covered with a net of platinum wire, u. The 
 gases evolved on the combustion of the sample 
 of coal rise through the platinum sieve, warm the 
 oxygen entering through the tube a, mix with it 
 as it enters through the openings in the platinum 
 tube, and are compelled by the annular plate, v, to 
 pass again through the hot wire net, u, along the 
 glowing side of the crucible, escaping downwards 
 through the aperture, i. The refrigeration at the 
 bottom, c, and the tube g is so complete that the 
 gases escape at the tube e scarcely o'i higher 
 than the temperature of the refrigerating water. 
 The gases for the determination of water and 
 carbonic acid pass through two calcium-chloride 
 tubes, three sets of potash bulbs, and then, for deter- 
 mining the substances which have not been per- 
 fectly burned, through a tube with ignited copper 
 oxide, and again through calcium chloride and 
 soda-lime. The residual oxygen is drawn into a 
 bell gas-holder, and can be used again. 
 
 The space, C, between the silvered copper 
 vessel, , and the wooden case, D, is filled with 
 glass-wool. The silvered lid, n, consists of two 
 halves, one of which has two semicircular openings 
 for the tubes a and b, an aperture for the ther- 
 mometer, t, and two for the silvered stirring 
 arrangement, m. The thermometer is graduated 
 in -^ degrees, so that o - oi may be accurately 
 read off by means of a telescope. 
 
 In order to decrease as far as possible the 
 communication of heat from the stirrer to it, the 
 two last apertures in the lid are fitted with small 
 
 ivory inlets, and the two wires which support the disc, r, are screwed at top into an 
 ivory support, m. To move the stirrer a silk cord, o, is passed over a pulley supported 
 by a brass strap (drawn here at one side for the sake of distinctness), so that during 
 an experiment the thermometer may be watched from a short distance by means of a 
 telescope, and the stirrer can be moved at the same time.* 
 
 * In order to find the water- value of the apparatus it was completely put together and filled 
 with 1500 grammes water at different temperatures e.g., temperature of the air, 14 '5; of the 
 water, 20 '5 ; and of the calorimeter 
 
 Empty I4'64 
 
 Filled, after 2 minutes 20-09 
 
 4 
 
 6 
 
 8 
 
 10 
 
 12 
 14 
 
 20-02 
 I9-97 
 
 I9-93 
 I9-90 
 I9-86 
 19-84 
 
 After 6 minutes the temperature was equalised, and then decreased at each reading by o'O3. 
 In order thus to heat the apparatus from 14-64 to 19-97 the water was cooled down from 20-5 to 
 
10 CHEMICAL TECHNOLOGY. [SECT. i. 
 
 With charcoal, peat, &c., no combustible residue remains in the crucible. In 
 order to examine the carbonaceous ash left by coal, the lower part of the crucible is 
 lined with thin sheet-platinum or asbestos paper, which, after the ignition is completed, 
 is introduced with its contents into a combustion-tube, when the combustible parts are 
 converted into carbonic acid and water, which are determined gravimetrically. 
 
 A part of the pre-existing water as well as that formed is volatilised in the condensa- 
 tion-tube, and a part escapes as vapour. According as the combustion-value is to be 
 referred to liquid or aeriform water, 610 heat-units must therefore be added or de- 
 ducted per gramme of water, which seems to have been hitherto neglected. After the 
 combustion is complete, the increase of weight in the calcium-chloride tubes gives the 
 quantity of the aeriform water. The combustion chamber is now, without being pre- 
 viously opened, again connected with the calcium-chloride tubes, carefully heated to 
 about 60, and dry air is passed through, which carries the watery vapour into the 
 calcium-chloride tubes for weighing. 
 
 In carrying out the experiment the calcium -chloride tubes and the potash appa- 
 ratus are weighed and connected suitably, the coal, which must have been dried at no 
 in a current of nitrogen, is weighed off in a covered crucible, which, after its lid has 
 been removed, is rapidly introduced into the dry combustion chamber, A, the lid is 
 screwed up, set in the calorimeter vessel, the tube b is connected with the absorp- 
 tion-tubes and the tube a with the oxygen tube ; 1500 grammes water are now poured 
 into the calorimeter vessel, the lid is put on, the stirrer is set in action, and the tem- 
 perature is read off. In about five minutes from i to i J litre dry oxygen per minute is 
 allowed to enter, i to 2 milligrammes of heavy charcoal splinters, ignited, are thrown 
 in through the tube a, and the thermometer is observed with the telescope whilst the 
 agitator is kept in action. If the combustion is completed in four or five minutes the 
 current of gas is moderated. In four to five minutes more the heat is equalised, so 
 that the final temperature may be read off. The absorption-tubes are weighed, and 
 the volatilised water and the residue of the combustion are examined as indicated. 
 Employed 874 milligrammes coal. 
 Obtained : 
 
 Carbonic acid, 2490 milligrammes, representing carbon . 679 milligrammes 
 Carbonic oxide, 32 ..... 14 
 
 Carbon in residue 16 
 
 Water, aeriform, 1 04 milligrammes) , , 
 liquid, 126 f nyarogen 
 
 769 
 25-5 
 
 
 
 26 '2 
 
 Hence is deduced the following composition of the coal, compared with the ultimate 
 analysis : 
 
 Calorimeter. Elementary Analysis. 
 
 Carbon . . . . 8i'i2 ... 80-91 
 
 Hydrogen . . . .3-00 ... 3-11 
 
 Nitrogen .... ... 0-91 
 
 Oxygen .... ... 7-14 
 
 Sulphur .... ... 0-51 
 
 Ash 7-21 .,. 7-42 
 
 19-97 or 20-03. The water- value is hence (0-47 x 1500) : 5-33 = 132 heat-units. As the mean 
 of five experiments conducted differently there was found the figure 124. The water-value of the 
 apparatus containing 1500 grammes is therefore 1624 heat-units. According to the author's subse- 
 quent experiments, it is preferable to fill the space Q with eider-down. If the exchange of tem- 
 perature between the apparatus and the external air is not to be brought into account, its 
 temperature is fixed so much below that of the air as it is higher after the experiment. 
 
SECT, i.] DETERMINATION OF THE VALUE OF FUELS. n 
 
 The temperature of the air was 14*9, that of the calorimeter i2'8i; the final 
 temperature reached in nine to ten minutes, i6'86. Hence we have the following 
 calculation : 
 
 Taken up by calorimeter, 4/05 x 1624 = 6577 heat-units 
 For CO, 16 x 2-4 = 77} 
 
 C, 16 x 8-1 = 130 j- . . 227 
 H, 07 x 28-8 = 20) 
 higher specific heat of the pro- 
 ducts of combustion 20 
 
 6824 
 
 For the water volatilised we must deduct 0-126x610 = 77 heat-units ; or per grammo 
 coal, 6747 : 0*874 = 7720 heat-units referred to watery vapour at 15 to 20, whilst 
 Dulong's formula (see p. 8) gives only (8i'i2 x 8100 + 2'i x 28800) : 100= 7175 heat- 
 units. Dulong's formula is consequently useless for mineral coal. With 1*4 per cent, 
 water we have (7720 : roi4) (1*4 x 6) = 7605 heat-units. The mean of three experi- 
 ments gave 7630 heat-units. 
 
 The combustion of coal is not quite perfect, but, as the products of combustion are 
 completely determined, and as the combustion- value of carbon monoxide and of hydrogen 
 is accurately known, the inaccuracy which may possibly arise is of the less importance, 
 as any error of moment is completely excluded by a comparison with the elementary 
 analysis. If it is desired to burn also the residue of the coal, this may be effected by 
 directing upon the coal a small hydrogen flame through a narrow platinum tube. Its 
 development of heat can be easily determined with accuracy.* 
 
 Wood. Wood is built up of cells and vessels which consist of cellulose, 6 H 10 O 5 
 (see section on Paper), and contain the vegetable juices. The latter contain, besides 
 water and the ingredients of ash (see Potash), various organic matters upon which the 
 composition of the different woods depends. The proportion of water in the different 
 woods is about 
 
 White beech 18*6 
 
 Birch 30-8 
 
 Cluster oak . . . . . . . . 347 
 
 Common oa k 35-4 
 
 White pine 37'I 
 
 Scotch fir 397 
 
 Red beech 397 
 
 Alder 41-6 
 
 Elm 44-5 
 
 Spruce fir .45-2 
 
 Air-dried wood contains 12 to 20 per cent, of water. The water diminishes the 
 value of the wood as fuel, not merely by taking up the room of combustible matter, but 
 also by requiring it to be evaporated. The following analyses show the average compo- 
 sition of wood : 
 
 * The objection that such small samples do not represent the true average is ill-founded. In 
 an elementary analysis still smaller quantities are employed. If, as is commonly done, we take 
 from a larger average sample, say of I kilo., two specimens of i gramme each for the calorimetric 
 determination and for the ultimate analysis, we have, in the agreement of the results, a much 
 better guarantee for accuracy than if we employed ico grammes for combustion, and were conse- 
 quently unable to determine the products of combustion and the residues with accuracy, whilst 
 the check of ultimate analysis is also wanting. 
 
12 
 
 CHEMICAL TECHNOLOGY. 
 
 SECT. I. 
 
 Kind. 
 
 Composition dried at 115. 
 
 Air-dry. 
 
 C. 
 
 H. 
 
 N. 
 
 o. 
 
 Ash. 
 
 Water. 
 
 Value of 
 i gramme.* 
 
 
 per cent. 
 
 per cent. 
 
 per cent. 
 
 per cent. 
 
 per cent. 
 
 per cent. 
 
 heat-units. 
 
 
 Oak . 
 
 50-22 
 
 5-99 
 
 0-09 
 
 43-42 
 
 0-28 
 
 I3-30 
 
 3990 
 
 
 Ash . ! 49-77 
 
 6-26 
 
 0-07 
 
 4337 
 
 0-53 
 
 II-80 
 
 4155 
 
 4 
 
 White beech , 49*48 
 
 6-17 
 
 O'o6 
 
 4377 
 
 0-52 
 
 1 2 -O2 
 
 4161 
 
 I 
 
 Beech, old 
 
 49-03 
 
 6-06 
 
 O'll 
 
 44-36 
 
 0-44 
 
 12-95 
 
 4168 
 
 -g \ young 
 
 49-14 
 
 6-16 
 
 0-09 
 
 44-07 
 
 0-54 
 
 I3-95 
 
 4101 
 
 $ 
 
 Birch 
 
 48-88 
 
 6-06 
 
 O'lO 
 
 44-67 
 
 0-29 
 
 II-83 
 
 4207 
 
 
 Pine. 
 
 50-36 
 
 5-92 
 
 0-05 
 
 43'39 
 
 0-28 
 
 12-17 
 
 4422 
 
 
 ^Spruce 
 
 50-31 
 
 6-20 
 
 0-04 
 
 43-08 
 
 0-37 
 
 1 1 -80 
 
 4485 
 
 
 Oak . 
 
 48-94 
 
 5-94 
 
 
 
 43-09 
 
 2-03 
 
 
 
 N 
 
 H 
 
 Beech 
 
 46*02 
 
 5-86 
 
 
 
 46-94 
 
 1-18 
 
 
 
 a - 
 
 41 
 
 Birch 
 
 48-89 
 
 6-19 
 
 
 
 44-93 
 
 0-99 
 
 
 
 o 
 ffi 
 
 Fir, old 
 
 49-87 
 
 6-09 
 
 
 
 43-4I 
 
 0-63 
 
 
 
 ' young 
 
 50*62 
 
 6-27 
 
 
 
 42-58 
 
 o-53 
 
 
 
 If wood is heated above 150, it is de-gasified; there escape water, carbon dioxide 
 and monoxide, hydrocarbons, then methylic alcohol, acetic acid, &c., whilst the residual 
 charcoal becomes richer in carbon as the temperature rises. Yiolette on heating wood 
 obtained at 
 
 No. 
 
 Temperature of Carbonising. 
 
 Composition of the Products (per Cent.). 
 
 C. 
 
 H. 
 
 O. 
 
 Ash. 
 
 I 
 
 I 5 .... 
 
 47-5I 
 
 6'12 
 
 46-29 
 
 0-18 
 
 2 
 
 2OO .... 
 
 51-82 
 
 3-99 
 
 43-96 
 
 0-23 
 
 3 
 
 270 .... 
 
 70-45 
 
 4-64 
 
 24-19 
 
 0-85 
 
 4 
 
 350 .... 
 
 76-64 
 
 4-14 
 
 18-44 
 
 0-61 
 
 5 
 
 Melting-point of antimony 
 
 81-64 
 
 1-96 
 
 I5-24 
 
 16 
 
 6 
 
 , silver . 
 
 81-97 
 
 2-30 
 
 14-15 
 
 60 
 
 7 
 
 , copper . 
 
 83-29 
 
 170 
 
 1379 
 
 "22 
 
 8 
 
 gold . 
 
 88-14 
 
 1-41 
 
 9-26 
 
 20 
 
 9 
 
 , steel 
 
 90-81 
 
 1-58 
 
 6-49 
 
 'IS 
 
 10 
 
 , iron 
 
 94'57 
 
 074 
 
 3-84 
 
 66 
 
 ii 
 
 , platinum 
 
 96-52 
 
 0-62 
 
 0-94 
 
 94 
 
 Samples i and 2 are very solid and imperfectly burned, since decomposition only 
 begins at these temperatures. No. 3 is red charcoal, which, if produced at this tem- 
 perature, begins to be friable, and is very readily combustible (300). No. 4 and all 
 the remainder are black charcoal. Nos. 6 10 are very black, dense, solid, and difficult 
 to ignite. No. 1 1 is so hard that it cannot be easily broken, and if let fall upon stone 
 it gives a metallic sound. It is very sparingly combustible, so that it only begins to 
 burn on direct contact with a flame, and is at once extinguished if taken out of the fire. 
 
 MANUFACTURE OF WOOD CHARCOAL. 
 
 If the products of distillation are not to be utilised,! the charring is effected in 
 kilns, but otherwise in retorts. 
 
 By a kiln we understand a heap of large pieces of wood piled up and covered with 
 earth, or with a mixture of earth and charcoal-dust. The logs of wood are laid either 
 
 * Not quite trustworthy. 
 
 t The formation of pyroligneous acid during the dry distillation of wood is described by Glauber 
 in his work Miraculum Mundi, in 1658. The earliest large charcoal-kilns were set in action in 
 1819 at Hausach in Baden, but were abandoned shortly after. The increased value of acetic acid 
 and the application of methylic alcohol (discovered by Taylor in 1812 as accompanying wood 
 vinegar) for the production of tar colours have latterly given scope for a more remunerative 
 utilisation of the products of the distillation of wood. 
 
SECT, i.] MANUFACTURE OF CHAKCOAL. 13 
 
 almost at right angles to the axis of the kiln, or horizontally, running out radially from 
 the axis. In the former case the kiln is termed standing, and in the other, lying. 
 
 An Italian kiln (Fig. 6) has for an axis a shaft consisting of three or four poles, 
 kept asunder by wedges, n, and consists of two or three layers of wood. The conical 
 mass is rounded off by blocks laid horizontally. 
 
 A Slavonian kiln (Fig. 7) is distinguished from the last-mentioned by its axis, 
 
 Fig. 6. Fig. 7. 
 
 which consists of a post driven in, and by the kindling passage, b, a channel leading to 
 the axis, by means of which the kiln is set burning. 
 
 The Schwarten kiln (Fig. 8), used in Norway, is composed of irregular planks. 
 Three of the largest form the axial shaft, a, 
 around which combustible matter is heaped, 
 and conically arranged heaps of the largest 
 wood loppings is superimposed, interspersed 
 with easily combustible matter. This heap 
 forms the nucleus of the kiln, against 
 which the planks are made to lean. The 
 horizontal heaps have the outward appear- 
 ance of the former, but the blocks of wood 
 are placed horizontally and radially. The 
 axis is either a shaft or a post, with a kindling passage, and the mound, when complete, 
 is covered with a layer of earth. 
 
 In charcoal-burning we have to distinguish three stages or phases ( i ) The sweating ; 
 (2) The full combustion ; (3) The slow smouldering. The kiln requires a larger supply 
 of air in its interior when first lighted, in order to effect the spreading of the fire, than 
 does one which has been burning for some time. To this end the foot of the heap is at 
 first quite or partially uncovered. As the fire spreads there is evolved watery vapour 
 mixed with products of the dry distillation of wood, which may form, by mingling 
 hydrocarbons with atmospheric air, mixtures resembling detonating gas, and, by 
 explosion, may occasion a partial displacement of the covering, or even a rupture of the 
 heap. By the rapid spread of the fire, by the actual consumption of a part of the 
 wood, and by the decrease of volume due to desiccation and charring, there are pro- 
 duced hollow spaces, which must be carefully filled up. As soon as the vapours escap- 
 ing at the foot of the mound take a lighter colour comes the stage of slow smouldering. 
 The access of air must be diminished, and for this purpose the mound is covered up 
 wherever it had become open. In about four days the larger portion of the wood is 
 charred. The fire must now be managed so that it spreads from the top downwards, 
 and from the centre towards the circumference. If the smoke from the draught-holes 
 becomes pale and blue, it is a sign of readiness, and the air-holes are closed. When the 
 heap is thus ready in all parts, it is left covered for about twenty-four hours, and let 
 cool whilst protected from the access of air. The mound is then dressed and extin- 
 guished. 
 
 The carbonisation of wood in heaps for horizontal works is especially practised in 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 South Germany, Russia, and Sweden. It differs from the process just described, as the 
 wood is gradually charred in portions, whilst the carbonised pieces are at once with- 
 drawn. The site of the kiln is a longish rectangular figure, the front and the back 
 being shorter than the two sides. The heap slopes upwards from the front to the back, 
 and the two sides are both secured by a row of strong perpendicular wooden posts so 
 
 that the two run 
 
 Jfjcy q 
 
 parallel. Figs. 9 
 and 10 show such a 
 heap, Fig. 9 in ele- 
 vation and Fig. 10 
 in section. The heap 
 is surrounded with 
 the posts, a, and 
 with shingles ; it has 
 a covering, h, and 
 at the foot a vacant 
 passage, b, for kind- 
 ling. As the fire advances, the charcoal produced at the front is withdrawn, the 
 burner having merely to see that the fire does not spread unequally. 
 
 Charcoal-ovens may be regarded as permanent walled mounds in which the heat for 
 
 charring is obtained, exactly 
 
 IO> as in the common kilns, by 
 
 the combustion of a part of 
 the wood with sparing access 
 of air. As compared with 
 the kilns with movable cover- 
 ings, they have the advan- 
 tage that the pyroligneous 
 acid and the tar can be better 
 and more completely sepa- 
 rated. On the other hand, 
 
 the charcoal obtained is said to be inferior both in quality and quantity to that from 
 the common kilns. 
 
 Fig. 1 1 shows one of the simplest kilns ; 
 
 Fig. n. 
 
 the wood to be charred is heaped up 
 either perpendicularly or horizontally. 
 The wood is introduced either by the 
 aperture, a, or the door, b. The 
 kindling passage extends from the 
 door to the middle of the sole i.e., 
 the floor of the kiln. Except a small 
 part of the doorway and of the open- 
 ing, , all apertures are bricked up, 
 and only re-opened when the charcoal 
 is withdrawn. After the wood has 
 got on fire sufficiently, b and a are 
 closed. The small openings in the 
 upper part of the oven correspond to 
 
 the smoke vents in the common kilns. In the charcoal-oven shown in Fig. 12 the 
 two doorways, a and b, serve for introducing the wood, and b is also used for taking 
 out the charcoal. The dampers are at c, and the volatile products are carried off to a 
 condenser by the iron pipe, d. During the process a and b are closed. The tar collects 
 chiefly on the floor of the oven and flows into a suitable recipient. Beneath the arched 
 doorway, b, there is a small aperture which serves as the entrance to the kindling pas- 
 
SECT. I.] 
 
 MANUFACTURE OF CHARCOAL. 
 
 sage. In the oven Fig. 13 the access of air takes place through the grating, r. The 
 wood is introduced through a and b, and the volatile products escape by the pipe, g. 
 
 In charring wood in retorts, the wood enclosed in iron or earthenware retorts is 
 heated from without, and arrangements are made for the escape and the complete utili- 
 sation of the volatile products. In some cases the production of tar, and in others that 
 
 Fig. 12. 
 
 g. 13- 
 
 Fig. 14. 
 
 of gas, is the chief object. In the tube-furnace the heating and charring of the enclosed 
 mass of wood is effected from within by means of ignited iron tubes, which traverse the 
 furnace, being placed externally in contact with a fire, and opening into a chimney. 
 Instead of passing the hot air and the flame through iron pipes, the wood may be at 
 once charred by the heated air if care be taken that the air and flame are deprived as 
 completely as possible of their oxygen. 
 
 If the chief object in charring wood is to obtain tar, a process adopted in Russia 
 may be employed with advantage. According to Hessel's description, the stems and 
 roots of coniferous trees, and preferably of such as are decaying, are chosen, split into 
 pieces, and used for building up the kiln. The site for the kiln (Fig. 14) is funnel- 
 shaped, and provided in its 
 middle with a cavity ; the 
 entire surface is coated with 
 clay and covered with roof- 
 ing shingles, over which 
 the tar flows towards the 
 middle, from whence it 
 passes through a pipe into 
 a vessel placed in a sub- 
 terranean vault. The wood 
 is piled up in these kilns in 
 six to eight layers, covered 
 with straw or dung, and 
 then with sand or earth. 
 When the kiln has been arranged, it is kindled at forty or fifty openings around its 
 base, which are afterwards choked with sand as soon as the fire has spread upwards 
 through the entire heap. In about six days, during which the filling is kept up con- 
 tinuously, the apex of the heap begins to sink in, and there appears a high, strong 
 flame. In ten to twelve days the removal of the tar begins, and is continued every 
 morning. As this process is simply a slow combustion from without inwards, which 
 is preceded by dry distillation and the formation of tar in the same direction, most of 
 the charcoal is consumed before the process reaches the axis of the kiln. 
 
 In Lower Austria (according to Thenius) wood-tar is obtained in a similar manner 
 from such wood of the black fir as yields little or no turpentine. In Bohemia, on 
 
i6 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 the contrary, there are used woods rich in resin, especially tree-stumps, which contain 
 many particles of resin. In Russia they obtain from 100 parts of wood 17-6 parts of 
 tar and 23-3 of charcoal. 
 
 Since 1853 the Swedish so-called " thermo-kettles " have been used in Russia, and 
 deserve to be preferred in every respect to kilns for charring. According to Hessel, 
 such a kettle (Fig. 15) consists of strong sheet-iron, and holds about 8 cubic metres. The 
 
 charge is introduced 
 
 X 5- through the man-hole, 
 
 g. The heat passes 
 from the fire, a, by 
 means of the flues, b, 
 round the side walls. 
 To bring the wood 
 rapidly to 100 a cur- 
 rent of steam is passed 
 into the kettle through 
 the pipe e. The tar, 
 which has already col- 
 lected in the kettle, 
 runs through the pipe c 
 
 to the store-cask, , whilst the tarry vapours arrive through d into the collector, B' ; 
 what is here condensed descends through h to B, and what remains as a vapour is 
 liquefied in the condensing apparatus, C. The combustible gases, which, however, 
 according to the author's experiments,* have only a low heating value, are led into 
 the fire-box. Besides tar, there are obtained, at the beginning of the distillation, oil 
 of turpentine, pyroligneous acid, and methylic alcohol. The residual charcoal is 
 quenched by means of steam, and taken out through the aperture, a. In Germany and 
 England horizontal iron retorts are chiefly used.f (See also Methylic Alcohol.) 
 
 
 Green. 
 
 Summer 
 Dry. 
 
 Dried. 
 
 Exsiccated. 
 
 Charred. 
 
 Loss per Cent. 
 
 
 
 
 
 
 
 
 
 
 Dried. 
 
 Exsiccated. 
 
 Charred. 
 
 
 >i 
 
 >^ 
 
 ite 
 
 ^3 
 
 >" 
 
 jr 
 
 >-, 
 
 S 
 
 
 
 
 Kind of Wood. 
 
 1 
 
 1 
 
 1 
 
 5? 
 
 5 
 
 i 
 
 i 
 
 1 
 
 
 8 
 
 
 
 B 
 
 
 
 8 
 
 
 
 C 
 
 
 o 
 
 CM 
 
 o 
 
 5 
 
 o 
 
 [T 
 
 _ 
 
 g 
 
 
 _ 
 
 a 
 
 
 
 _ 
 
 B 
 
 
 
 3 
 
 B 
 
 
 
 O 
 
 
 
 o 
 
 c 
 
 
 
 2 
 
 J5 
 
 "3 
 
 1 
 
 
 3 
 
 E 
 
 
 
 "3 
 
 
 
 1 
 
 1 
 
 1 
 
 
 o 
 
 1 
 
 >3 
 
 c 
 o 
 
 | 
 
 1 
 
 c 
 O 
 
 
 
 1 
 
 1 
 
 s 
 
 "o 
 H 
 
 
 02 
 
 C 
 
 go 
 
 
 00 
 
 
 02 
 
 
 
 . 
 
 
 
 E 
 
 
 
 
 
 
 
 
 
 p.c. 
 
 
 p.c. 
 
 
 p.c. 
 
 
 
 
 
 
 G 
 
 
 
 G 
 
 
 Oak 
 
 I -0745 
 
 0-9852 
 
 0*804 
 
 29*1 
 
 0-766 
 
 38-2 
 
 0-387 
 
 767 
 
 _ 
 
 3'i 
 
 6-1 
 
 0'2 
 
 6-813-3 
 
 6-0 
 
 17-0 
 
 35 ' 2 
 
 Ash 
 
 0-8785 
 
 0-8304 
 
 0771 
 
 19-6 
 
 0-746 
 
 29*1 
 
 0-371 
 
 77*9 
 
 - 
 
 4'? 
 
 8-4 
 
 - 
 
 8-616-5 
 
 7-0 
 
 25*0 
 
 477 
 
 Beech 
 
 I -0288 
 
 o - 8i6o 
 
 0-747 
 
 33 '5 
 
 0-700 
 
 417 
 
 0*319 
 
 82-3 
 
 - 
 
 4'3 
 
 8-4 
 
 - 
 
 7-5 14-4 
 
 6-5 
 
 22 -O 
 
 43*1 
 
 Fir 
 
 0-8734 
 
 0-7828 
 
 0-678 
 
 27-6 
 
 0-662 
 
 377 
 
 0-351 
 
 80-1' - 
 
 3 '4 
 
 67 
 
 0*2 
 
 6 '9 13 '5 
 
 9-0 
 
 26-5 
 
 50*8 
 
 Elm 
 
 O-9I66 
 
 0-7502 
 
 0-635 
 
 35'5 
 
 o-595 
 
 42*6 
 
 0-284 
 
 81-90-3 
 
 3 '4 
 
 7-0 
 
 0*1 
 
 
 9-0 
 
 20'0 
 
 41-4 
 
 Yew 
 
 0-9030 
 
 0-7106 
 
 0*696 
 
 24-6 
 
 0-642 
 
 35 '3 
 
 O'202 
 
 76-2 
 
 - 
 
 i 'i 
 
 
 0'5 
 
 4'3 8-9 
 
 10-5 
 
 8-0 
 
 19-6 
 
 Plane 
 
 O-92IO 
 
 0-7044 
 
 0-637 
 
 33'i 
 
 0-604 
 
 40 - 3 
 
 0-247 
 
 81*4 
 
 - 
 
 1-7 
 
 3'4 
 
 
 4'5 8-9 
 
 8-5 
 
 I3-0 
 
 307 
 
 Aspen 
 
 0-8809 
 
 0-6398 
 
 0-5I5 
 
 46-1 
 
 0*463 
 
 54-0 
 
 0-179 
 
 86-3 
 
 0-4 
 
 3-8 
 
 7*8 
 
 0*3 
 
 6-1 I2'I 
 
 7-0 
 
 I5-0 
 
 32-8 
 
 Larch 
 
 07633 
 
 0-61120-607 
 
 27 '3 
 
 o 560 
 
 34'3 
 
 0-238 
 
 77-1 
 
 0*23-4 
 
 6*9 
 
 0-4 
 
 5'2'io-S 
 
 8-5 
 
 10*5 
 
 267 
 
 White pine 
 
 O-8O4I 
 
 0-58780-529 
 
 37 '3 
 
 0*510 
 
 43-8 
 
 0*214 
 
 81-0 
 
 
 2 '3 
 
 4*6 
 
 0-4 
 
 5711-4 
 
 IO'O 
 
 I I'D 
 
 287 
 
 Lime 
 
 0-7690 
 
 0-5810 
 
 0-505 
 
 41-6 
 
 0*484 
 
 477 
 
 0-240 
 
 84-1 
 
 - 57 
 
 ii'i 
 
 0*1 
 
 8-816-9 
 
 8*0 
 
 25-5 
 
 48*9 
 
 Spruce 
 
 0-5266 
 
 0-4931 0-487 
 
 13-1 
 
 o-457 
 
 23*1 
 
 0-193 
 
 73'3 
 
 - 3'i 
 
 6*1 
 
 0-3 
 
 57 
 
 11-3 
 
 9*0 
 
 10-5 
 
 27*1 
 
 The experiments were made with cubes from the trunks of trees from seventy -five 
 to one hundred years old. For obtaining the wood in the state named " exsiccated " 
 (German durr) the attempt was first made to render the wood chemically dry. As this 
 was a failure, the cubes were placed, at the beginning of May, in the drying-room of a 
 inanufactory of inlaid-wood articles at Sulgenbach, near Berne. The results of this 
 *Jahresler. 1880, p. 417. t Ibi'l. 1866, p. 477; 1871, p. 659; 1880, p. 417; 1884^.453; l %%$ P-435- 
 
SECT. I.] 
 
 MANUFACTURE OF CHARCOAL. 
 
 exsiccation, continued for two months at gradually increasing temperatures, which in 
 the last fortnight reached 100, were at once determined by weight and measure. For 
 charring, the apparatus of the gunpowder works at Worblaufen was employed. The 
 cubes were carbonised in fixed retorts, and, after complete charring and cooling, they 
 were at once weighed and measured. 
 
 The yield of different kinds of wood on dry distillation has been determined by 
 Senff,* using a cast-iron retort of 60 centimetres in length and 20 in diameter. The 
 specimens of wood were air-dry. In order to determine the yield on slow and rapid 
 distillation, the retort was either first charged and closed and then submitted to a 
 small fire, or the wood was thrust into the ignited retort, which was then quickly 
 closed and strongly heated. For 4 to 6 kilos, of wood the slow charring took 
 six, and the rapid process only three, hours. When the distillation was complete, the 
 retort remained closed until quite cold. Immediately on opening, the residual char- 
 coal was weighed, and its increase of weight was determined after remaining for 
 several weeks in the air of an ordinary dwelling-room. In the distillate the tar and 
 the crude acid were separated by means of parting funnels, and the quantity of gas was 
 calculated as loss. As the amount of methylic alcohol could not be determined, and 
 as it generally corresponds to that of the pyroligneous acid, the results of experiments 
 are arranged according to the yield of acetic anhydride on slow charring. 100 kilos, 
 of air-dried wood gave the values laid down in the subjoined table ; s denotes slow, and 
 r rapid, action. 
 
 Kind of Wood. 
 
 1 
 
 H 
 
 kilos. 
 
 H 
 kilos. 
 
 Crude Acid. 
 
 
 
 a 
 'E 
 a 
 
 >? 
 
 I 
 kilos. 
 
 Charcoal. 
 
 i Gas not 
 3 Condensed. 
 
 kilos. 
 
 S 
 p.c. 
 
 i 
 
 o 
 kilos. 
 
 c 
 1 
 
 p.c. 
 
 Carpinus betulus, L. Stem . . s 
 
 52-40 
 
 475 
 
 47-65 
 
 13-50 
 
 6-43 
 
 25-37 
 
 6-09 
 
 22-23 
 
 r 
 
 48-52 
 
 5-55 
 
 42-97 
 
 12-18 
 
 5' 2 3 
 
 2047 
 
 10-03 
 
 31-01 
 
 Bhamnus f rangula, L. Peeled ) . a 
 
 52-79 
 
 7-58 
 
 45'2I 
 
 13-38 
 
 6-05 
 
 26-50 
 
 5-09 
 
 20-71 
 
 shoots J . r 
 
 4538 
 
 5-I5 
 
 40-23 
 
 11-16 
 
 4'49 
 
 22-53 
 
 6-85 
 
 32-09 
 
 Alnus glutinosa. Stem, peeled . s 
 
 
 6'39 
 
 44-14 
 
 13-08 
 
 577 
 
 3I-56 
 
 6-29 
 
 17-91 
 
 r 
 
 47-76 
 
 7-06 
 
 40-70 
 
 10-14 
 
 4-I3 
 
 21-11 
 
 9-52 
 
 
 Betula alba, L. Stem . . . s 
 
 5I-05 
 
 5'46 
 
 45-59 
 
 12-36 
 
 5-63 
 
 29-24 
 
 1-29 
 
 1971 
 
 r 
 
 42-98 
 
 3-24 
 
 39-74 
 
 11-16 
 
 4 "43 
 
 21-46 
 
 7-37 
 
 35-56 
 
 Sorbus aucuparia, L. Stem . s 
 
 5^54 
 
 7-43 
 
 44-11 
 
 1 2 '60 
 
 5-56 
 
 27-84 
 
 4-62 
 
 20-62 
 
 r 
 
 46-40 
 
 6-41 
 
 39-99 
 
 10-41 
 
 4-16 
 
 2O '2O 
 
 872 
 
 33-40 
 
 Fagus silvatica, L. Stem . . s 
 
 5I-65 
 
 5-85 
 
 45-80 
 
 11-37 
 
 5-21 
 
 26-69 
 
 4*61 
 
 21-66 
 
 r 
 
 44-35 
 
 4-90 
 
 39-45 
 
 978 
 
 3-86 
 
 21-90 
 
 8-45 
 
 3375 
 
 Fagus silvatica, L. Branch . . s 
 
 49-89 
 
 4-81 
 
 45-08 
 
 11-40 
 
 5-14 
 
 26-19 
 
 5-95 
 
 23-92 
 
 r 
 
 43-I4 
 
 2-90 
 
 40-24 
 
 10-89 
 
 438 
 
 2I-30 
 
 8-99 
 
 35-56 
 
 Populus tremula, L Stem . . s 
 
 47-44 
 
 6-90 
 
 40-54 
 
 12-57 
 
 5-10 
 
 25-47 
 
 
 27-09 
 
 r 
 
 46-36 
 
 6-91 
 
 39'45 
 
 11-04 
 
 436 
 
 21-33 
 
 
 
 32-31 
 
 Quercus robur, L. Stem . . . s 
 
 48-15 
 
 370 
 
 44'45 
 
 9-18 
 
 4-08 
 
 34-68 
 
 4-67 
 
 17-17 
 
 r 
 
 45-24 
 
 3"2o 
 
 42-04 
 
 8-19 
 
 3'44 
 
 2773 
 
 6-36 
 
 27-03 
 
 Pinus larix, L. Stem . . . s 
 
 51-61 
 
 9-30 
 
 42-3I 
 
 6-36 
 
 2-69 
 
 26-74 
 
 8-08 
 
 21-65 
 
 r 
 
 4377 
 
 5-58 
 
 38-19 
 
 5-40) 2-06 
 
 24-06 
 
 872 
 
 32-17 
 
 Pinus abies, L. Stem . . s 
 
 46-92 
 
 5-93 
 
 40-99 
 
 5'6i | 2-30 
 
 34-30 
 
 4-82 
 
 1878 
 
 r 
 
 46*35 
 
 6-20 
 
 40*15 
 
 4'44J 178 
 
 24-24 
 
 9*63 
 
 29-41 
 
 Pinus abies, L. Branch . . s 
 
 46-34 
 
 8-13 
 
 38-2I 
 
 5-82 
 
 2 '22 
 
 25-55 
 
 9]33 
 
 28-11 
 
 r 
 
 43-85 
 
 5-44 
 
 38-4I 
 
 4-20 
 
 1-61 
 
 23-35 
 
 
 32-80 
 
 Pinus abies, L. Bark . . s 
 
 40-53 
 
 6-99 
 
 33-54 
 
 3'34 
 
 I '12 
 
 30-24 
 
 
 
 29-23 
 
 r 
 
 37-8o 
 
 5-36 
 
 
 2-64 j o'86 
 
 3I-59 
 
 
 
 30-61 
 
 The yield of crude acid, tar, and charcoal does not vary essentially in the several 
 kinds of wood, but there is a difference in the percentage of acid in the crude acid, 
 and consequently in the yield of acetic anhydride. The wood of leaf -bearing trees is 
 more productive than that of the conifers ; the stem more than the branches, the wood 
 more than the bark, and sound wood more than that which is decayed. Rapid car- 
 
 * Jahresber. 1885, p. 433. 
 
 R 
 
18 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 bonisation produces more gas at the expense of the yield in tar and charcoal, the 
 distillate contains less acid, and the charcoal is more hygroscopic. 
 
 PEAT. 
 
 Peat * is the product of the spontaneous decomposition (decay) of plants, especially 
 swamp-plants, in many cases mixed with sand, loam, clay, lime, iron pyrites, ochres, 
 &c. Beds of peat are especially formed in places which possess a sufficient temperature 
 for the development of the plants, and standing waters, which during most of the year 
 cut off the peat from contact with the air. The chief swamp and peat plants are : 
 Eriophorum, Erica, Calluna, Ledum palustre, Hypnum, but above all Sphagnum, a plant 
 especially adapted for the production of peat, as it never entirely dies down, but con- 
 tinues growing and ramifying above whilst the lower parts are being converted into 
 peat. 
 
 The varying nature of peat depends in part on the different character of the plants 
 from which it is formed, on their more or less complete decomposition, and on the 
 nature of the earthy matter which becomes mixed with the vegetable tissues. The 
 pressure to which the peat is exposed during its formation has also an influence on the 
 density of the mass. According to the difference of the plants from which the peat has 
 been produced we may distinguish (i) bog-peat, consisting principally of species of 
 Sphagnum; (2) heath-peat, formed chiefly from the roots and stems of Erica and Calluna; 
 (3) meadow-peat, formed from grass and sedges ; (4) forest- or wood-peat, formed from 
 the wood of trees ; (5) sea-peat, formed from sea- weeds. 
 
 With reference to its extraction, it is distinguished as spade-peat, which is at once 
 dug out of the bogs in blocks; (2) strained and (3) pressed peat, obtained from paste- 
 like, swampy masses, too soft to admit of digging. If the mass is too liquid, as is some- 
 times the case in Holland, in Westphalia, and in Northern France, a part of the water 
 is strained off by means of a kind of net. To give the peat more solidity, it is some- 
 times submitted to pressure in presses of a special construction. 
 
 The percentage of water in recent peat is very high ; when air-dried, it still retains 
 15 to 20 per cent. The ash ranges from 2 to 20 per cent.; that with more mineral 
 matter is not worth getting. 
 
 The following analyses show the composition of peat : 
 
 Peat from 
 
 In ioo parts free from Ash 
 and Dry. 
 
 Ash in ioo parts 
 Dry Peat. 
 
 Water in 
 Air-dried Peat. 
 
 Authority. 
 
 C. 
 
 H. 
 
 N. 
 
 O. 
 
 Kolbermoor . 
 Markobach, Eheinpfalz 
 Steinwenden, 
 
 58-5I 
 63-87 
 58-70 
 60-40 
 
 59-84 
 58-69 
 60-48 
 59-92 
 6l'O2 
 
 6-17 
 6-46 
 7-04 
 5-96 
 577 
 6-97 
 6-10 
 6-61 
 577 
 
 0-88 
 i *6o 
 170 
 
 2'2I 
 
 2'54 
 1-45 
 
 0-88 
 1-26 
 0-81 
 
 34-44 
 28-07 
 
 32-56 
 31-30 
 3I-85 
 32-88 
 
 32-55 
 32-21 
 32-40 
 
 4'2I 
 
 2-70 
 2'04 
 5-58 
 973 
 
 I5-5 
 
 8-0 
 
 8-3 
 25-6 
 
 Wagner 
 Walz 
 
 
 V. Regnault 
 Vaux 
 Kane 
 
 Sullivan 
 
 England 
 Philipstown, light . 
 heavy 
 Bog of Allen, light . 
 heavy 
 
 According to Wolff, two samples of peat-ash from the Mark Brandenburg (I. and 
 II.), and according to R. Wagner, an ash from pressed peat from Kolbermoor, in Upper 
 Bavaria (III.), contain 
 
 * BIBLIOGRAPHY : Torfindmtrie und Moorcultur : B. and K. Birnbaum ; Braunschweig, 1880. 
 Torfwirthschaft Suddeutschland's und Oesterreich's : A. Hausding ; Berlin, 1878. Torf, Natur und 
 Bedeutung : A. Vogel ; Braunschweig, 1859. 
 
SECT, i.] LIGNITE (BKOWN COAL, BOVEY COAL). 19 
 
 i. ii. in. 
 
 Lime 15*25 ... 20-00 ... 18-37 
 
 Alumina 20-50 ... 47 'oo ... 45 -45 
 
 Ferric oxide f . . 5-50 ... 7-59 ... 7-46 
 
 Silica 41-00 ... 13-50 ... 20-17 
 
 Calcium phosphate with gypsum . . . 3-10 ... 2'6o 
 
 Alkali, phosphoric acid, sulphuric acid, &c. . ... ... 8-55 
 
 Uses of Peat. Peat as obtained in the ordinary manner is a fuel of low value, as it 
 takes up a large space in proportion to its combustive efficacy. This defect is certainly 
 reduced by pressing the peat, but this operation raises the price to such a degree that 
 it can be used only at or near the place of production. The peat charcoal obtained by 
 carbonising in closed receivers has found only a limited consumption, as it is too soft. 
 The dry distillation of peat for the production of paraffine and solar oil can now be 
 scarcely remunerative on account of the diminished price of these products. The same 
 may be said of the proposal to use peat as a source of ammonia. Loose peat finds a 
 limited employment in the manufacture of pasteboards, but it is now extensively used 
 as litter for stables.* 
 
 LIGNITE (BEOWN COAL, BOVEY COAL). 
 
 Lignite is wood modified by decay in contact with water, but the process of 
 decomposition is here much more advanced than in the case of peat. If we look merely 
 to chemical and physical properties, it is not possible to draw a sharp boundary between 
 coal and lignite. The geological and palseontological relations of a deposit supply data 
 for determining these fossil carbons. Every fossil coal which is more recent than the 
 chalk, and is met with in superjacent formations, is termed lignite ; every specimen' 
 found in formations older than the chalk must be regarded as a true coal. As the 
 proportion of nitrogen in coal is greater than that in lignite, the latter, if heated in a 
 test-tube, yields vapours which have an acid reaction from the predominance of acetic 
 acid. Coal, if similarly treated, yields vapours which have a basic reaction from the 
 presence of ammonia, aniline, lepidine, &c. Another proposed test is to heat the 
 sample in question, finely pulverised, with potassa-lye. Coal leaves the liquid colour- 
 less, whilst lignite imparts to it a brown colour owing to the formation of potassium 
 humate (and perhaps also phlobaphen), but we must except the lignites of the northern 
 Alpine tertiaries as soon as they assume the character of fatty coals. According to the 
 experiments of Schinnerer and Morawski (1872) on the action of melting caustic alkalies 
 upon lignite, there is always formed, along with other products, pyrocatechine, probably 
 formed by the decomposition of the phlobaphenes present in the lignite, which, on 
 treatment with a melting alkali, form at first protocatechuic acid and subsequently 
 pyrocatechine. 
 
 According to A. Bartoli and G. Papasogli, there are formed, on heating lignite 
 with sodium hypochlorite, carbonic acid, chloroform, oxalic and mellitic acids. Coal is 
 attacked much less readily, and yields no oxalic acid. 
 
 According to the degree of decomposition, we distinguish (i) the light-brown 
 fibrous lignite, of the appearance of wood, in which portions of stems, branches, and 
 roots may be plainly recognised (fossil or bituminous wood). (2) Pitch-coal, shining black 
 pieces of a conchoidal fracture, and without any distinctly perceptible trace of woody 
 structure. If the fracture is lustrous, such specimens are known as jet f or, in German, 
 
 * Peats containing iron pyrites (sometimes not free from traces of arsenic) cannot be used for 
 litter, as, when subsequently applied to the land, they prove destructive to vegetation. On the 
 same account they are unfit for use in sewage-treatment, the construction of filters for waste 
 waters, &c. [EDITOR.] 
 
 t Jet is the English word for gayat, and is derived from the Greek yaydres, through the 
 Vienchjayet,jais. A peculiarly fine deep-black lignite is found at Whitby and in the Cleveland 
 
20 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. 
 
 gagat. (3) The earthy lignite, a brown mass of decayed pulveriform vegetable matter. 
 It is used as a pigment, Cologne umber. Lignites suitable for the production of solar 
 oil and paraffine are found in Germany (Weissenfels and Zeitz in Prussia, Eschersleben 
 and Saarau in Silesia, Borna in Saxony). 
 
 The average composition of the lignites from different localities is : 
 
 Lignites from ; 
 
 ioo parts free from H 2 O S Ash 
 contain : 
 
 ioo parts 
 contain 
 Ash. 
 
 Authority. 
 
 C. 
 
 H. 
 
 O + N. 
 
 Gangelsberg, Berlin 
 Braunschweig 
 Prussian province, Saxoi y 
 Kingdom of Saxony 
 Hessen-Darmstadt . 
 Westerwald . 
 Kegensburg . 
 
 63-42 
 7172 
 65-01 
 65-93 
 57-63 
 66-35 
 6475 
 81-41 
 66-04 
 
 4-18 
 
 576 
 6 -20 
 6-03 
 6-06 
 S'43 
 5-5i 
 4'44 
 5 '30 
 
 32-20 
 22-50 
 2877 
 28-03 
 
 36-3I 
 28-21 
 2972 
 14-14 
 28-65 
 
 8-1 
 7-6 
 14-2 
 ii -6 
 0-6 
 
 9'3 
 4-0 
 
 7'3 
 3'4 
 
 F. Fischer 
 Varrentrapp 
 Bischoff 
 Baer 
 Liebig 
 Casselmann 
 
 Kiihnert 
 
 ordinary 
 * 
 
 IIO. 
 
 870. 
 
 350. 
 
 450. 
 
 About iooo c 
 
 66-34 . 
 4-34 
 
 23-38 
 
 O'I2 
 
 .. 69-64 .. 
 4-23 - 
 I9-25 
 
 74-92 .. 
 3-28 .. 
 . 14-40 .. 
 
 . 77-98 
 2*69 
 II'OI 
 
 ... 87-11 
 o'6i 
 ... 1-36 
 
 O'4I . 
 5-4I . 
 
 O'2I . 
 .. 6-67 . 
 
 .. 0-15 . 
 .. 7-25 . 
 
 . . trace 
 .. 8-32 
 
 ... 10-92 
 
 The moisture in freshly raised lignite amounts up to 60 per cent., that of air-dried 
 samples to 15 to 20 per cent. The combustion-value varies with their different com- 
 position so greatly that it must be determined in every special case either by elementary 
 analysis and calculation according to Dulong's formula (which only yields approximate 
 results), or by direct determination. 
 
 The applicability of lignite is greatly increased by drying and pressing. In order 
 to ascertain the behaviour of lignite on drying, the author dried at 150 a sample 
 of Gangelsberg lignite of the composition stated below as containing 60 per cent, of 
 water. If slowly cooled, spontaneous combustion took place. If air was excluded, the 
 sample, after being heated for one hour each to the following temperatures, had the 
 subjoined composition : 
 
 Carbon . 
 
 Hydrogen 
 
 Oxygen . 
 
 Nitrogen 
 
 Sulphur . 
 
 Ash ... 
 
 If treated with superheated steam at 350, water-gas was formed, i.e., coal was 
 gasified. Drying with superheated steam is, therefore, not to be recommended. 
 
 Among the approved systems now in use we may distinguish four (i) Fire-plate 
 ovens, in which the drying is effected by the products of combustion ; (2) Steam 
 ovens, which dry by steam ; (3) Hot-air ovens, in which desiccation is effected by heated 
 air ; (4) Jacobi ovens, which dry by means of steam and hot air. 
 
 Fire-plate ovens were first constructed by Biebeck, of Halle, early in the year 
 1870. They are now at action in all the briquette factories of Biebeck's mines, and 
 latterly they have been introduced in some new factories. They generally contain 
 fifteen to seventeen round cast-iron plates, of 4 metres in diameter, arranged above 
 each other (Figs. 16 and 17). An axle in the middle of the plates which revolves 
 when the oven is at work supports over each dlate two arms provided with sheet-iron 
 
 Hills in England, and in the Departments Aude and Hautes-Alpes. At Aude there existed down 
 to the seventeenth century a guild of makers of jet rosaries (patendtriers enjais). The jet industry 
 existed formerly at Balingen and Gmund in Wurtemberg. At present Whitby is celebrated for 
 the occurrence and the manufacture of jet. 
 
 * The lignite of Bovey Heathfield contains, according to Vaux, carbon, 67-9, hydrogen, 5-8, 
 oxygen and nitrogen, 24-8 per cent. [EDITOR.] 
 
SECT. I.] 
 
 LIGNITE (BROWN COAL, BOVEY COAL). 
 
 21 
 
 shovels fixed obliquely. On turning this axle the coal is moved and turned over by 
 means of the shovels, and in this manner conveyed over the plates. The shovels are 
 fixed in such a manner that on one plate the lignite is moved from within outwards, 
 Fie. 16. 
 
 Fig. 17. 
 
 and on the next one from the outside inwards. The lignite falls through notches from 
 plate to plate in such a manner that in the plates where the shovels work outwards the 
 fall is at the margins, but in the other plates near the middle. From the last plate the 
 lignite falls through a shoot into the store chest. The plates are in an externally quad- 
 rangular furnace of masonry, with a grate in front. The gases of combustion pass up 
 through a channel into the furnace, passing down over the plates and the lignite upon 
 them, and escape at the chimney along with the watery vapour. These ovens are 
 especially adapted for lignites which contain little bitumen for which a high temperature 
 is needed. They have the advantage that the heat can be raised at pleasure, but also 
 the defect that the proper drying of the lignite requires very close attention. Fires and 
 explosions are here more common than with other ovens, and hence they have not been 
 generally adopted. For dusty, adhesive, and smelling lignites they cannot be used. 
 
 Of the steam ovens, we mention first the steam-plate oven, similarly arranged to the 
 fire-plate oven, and with the same appliance for moving the lignite. The difference 
 is that the plates stand free in an open space, and that they are hollow and con- 
 structed of wrought iron. In drying, the interior of the plates is swept by steam. 
 The plates are supported on four hollow columns, two of which serve to convey steam 
 to and from the plates. The watery vapour escapes by a chimney erected on the oven. 
 A valuable improvement, first devised by Rowold, of Meuselwitz,* consists in inclosing 
 the oven in a sheet-iron case, by which the space in which the oven is set up is kept 
 free from dust and its working can be conveniently watched and regulated. The air 
 and the temperature in the oven-house is thus prevented from becoming unpleasant or 
 hurtful. This oven is suitable for most kinds of lignite, though not for those which 
 need a very high temperature. 
 
 The tube drying-oven of Schulz, of Halle (Figs. 18 and 19), is a cylinder in 
 which are a great number of smaller tubes ; it is therefore like a tubular boiler. It lies 
 on an incline, and revolves on its longitudinal axle. The axle is formed of two cones, 
 which are contracted towards the middle, where they are connected together. They are 
 hollow, and their covering surfaces are perforated. The steam for drying exhaust 
 steam from the engines is let into the upper cone, and, after having steamed through 
 the apertures, it escapes by the lower cone. On the higher front of the apparatus 
 there is a hopper from which the lignite falls into the tubes, gradually works through 
 
 * Jahresber. 1883, p. I2II. 
 
22 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. i.. 
 
 Fig. i 8. 
 
 Fig. 19. 
 
 in consequence of the rotation and the inclined position, and falls out at the lower 
 end. To carry off the condensed steam there are three escape-pipes at the lower end. 
 
 This apparatus can 
 boast a simpler 
 motory arrangement 
 than any other. It 
 has been recently set 
 up at Ackermann's 
 works at Bitter f eld, 
 and experience must 
 show if it has fur- 
 ther advantages, and 
 what, if any, defects 
 exist. According to 
 Jacobi's view, it is 
 suitable for dusty 
 lignite and such as is 
 of a uniform grain, 
 less suitable for unequal grains, and not at all for adhesive and tumid kinds. 
 
 The hot-air oven used in the third system (Fig. 20) consists essentially of sheet- 
 iron plates, arranged like a Venetian blind, through which 
 the lignite falls downwards ; an arrangement for emptying, 
 consisting of a metal sheet working up and down, effects 
 the gradual transit of the coal. The air for drying is 
 drawn in by ventilators in so-called wind-heaters, i.e., 
 tubular boilers, heated by the spare steam of the engines, 
 and forced through the oven in the opposite direction to 
 the lignite. 
 
 At Frose there are twenty-six such ovens, each 4 metres 
 long, 0*5 metre broad, and 5 metres high, which furnish, 
 every twenty-four hours, material for 700 hectokilos. 
 " press-coal." The temperature of the air forced in is on 
 the average 60 to 70. The oven is easily set in action, 
 and has few moving parts. As defects, must be mentioned 
 the high temperature in the oven-house, the dust, and the 
 
 irregular drying. For granular lignites, and such as do not need a strong heat, this 
 oven suits well, but not for those which retain a woody texture and swell up or become 
 adhesive. 
 
 The fourth system, desiccation by means of steam and hot air, has been evolved from 
 the third, an endeavour being made to remove its imperfections by means of steam- 
 pipes. As appears from Fig. 21, the Jacobi oven is merely a modification of the hot- 
 air oven. Instead of the internal wall of the Venetians, there are used pent- 
 angular or triangular tubes, by which steam is introduced, to assist in drying the 
 lignite. In addition, hot air is passed in by openings between the tubes. The 
 working and the moving arrangements are the same as in the hot-air oven. In 
 comparison with the latter it has the advantage that the desiccation is more uniform 
 and that a higher temperature can. be obtained ; in other respects it has the same 
 disadvantages. 
 
 All the drying arrangements described have the common grave fault that, in pro- 
 portion to the cost of installation, they effect far too little work. The manufacture of 
 " press-coal " (dried and compressed lignite) will not receive its full development, in- 
 volving a suitable utilisation of the deposits of lignite, until this defect is overcome. 
 
SECT, i.] COAL. 23 
 
 An important feature in drying lignite is the collecting space ; it is commonly under- 
 neath the ovens, or sometimes at one side or over the presses. Here the dried lignite 
 is collected and raised to the presses by means of spirals and elevators. This collecting 
 space has the important function of equalising the differences of the dried lignite 
 arising from variations in the proportion of moisture, different working of the ovens, 
 changes in the temperature of the hot air, &c., since good, marketable press-coals can 
 only be produced with certainty from uniform materials. The lignite goes on drying 
 in this space. It has been unjustly charged with being the source of frequent fires 
 and explosions, and latterly attempts have been made to abolish it. According to 
 experiments at Frose, the subsequent desiccation in this space is essential for the 
 production of good " press-coal." This is intelligible, since the lignite which comes 
 out of the oven at 46, rises in the collecting-room within eight hours to 70 75, 
 the correct temperature for the production of a good article. The fires arise mostly in 
 the ovens and the spirals ; a fire in the collecting-room is never formidable, unless 
 the burning material is moved, when it may become dangerous in consequence of 
 explosions. Whether such explosions are due to dust or gas, or both together, is still 
 a matter of dispute. According to Johanni's views we have, in the first place, an 
 explosion of dust, which may lead to a gas explosion if it becomes extensive. 
 
 Many kinds of lignite, after desiccation, must be crushed and sifted to yield a good 
 press-coal. This ensures a uniform grain, a further compensation of the temperatures 
 of the single parts, and the elimination of impurities. 
 
 The limit of compression of lignite differs according to its texture ; it is less when 
 the material is granular and greater when it is dusty. The average is assumed at 
 45 to 50 per cent. The thickness of press-coals ranges from 30 to 50 millimetres; 
 the transverse section of the smaller is 100 and of the larger no square centimetres. 
 The presses make sixty to eighty rotations per minute, and with each one press-coal is 
 produced. The pressure is estimated by "Wendland at 1200 to 1500 atmospheres, and 
 a similar value has been found experimentally. 
 
 The higher value of press-coal as compared with the original lignite appears from 
 the following figures : 
 
 Frose Lignite. Frose Press-coal. 
 
 Water 50*0 ... 16 per cent. 
 
 Combustible . . . .48*5 ... 74 
 
 There are at present in action in Germany 56 press-coal works, with about 142 
 presses, producing in 1885 about 8 million hectokilos. of press-coal. If we reckon 
 that 4 hectolitres of press-coal are produced by the consumption of i hectokilo. of fuel, 
 the manufacture of press-coal i.e., 32 million hectolitres consumes about y^th of 
 the German yield of lignite, which is 300 million hectolitres. The value of i hectokilo. 
 of press-coal at the spot is on the average o - 8 to o'9 of a shilling, and the cost of 
 manufacture, material included, o'6 to 07 of a shilling. 
 
 COAL. 
 
 The great importance of coal-mining appears from the following figures. The 
 quantity raised has increased almost threefold in twenty years. In 1885 Germany 
 raised 58,320,398 tons of coal, of the value of 303 million marks, and 15,355,117 
 tons of lignite, of the value of 40*4 million marks. This continued increase should 
 prompt the public to a more careful and thorough utilisation of this store of heat and 
 power. 
 
 Coal has been formed from lycopods, equisetacese, ferns, and other cryptogamous 
 plants. It occurs in the Devonian up to the forest clay, but especially in the carboni- 
 ferous formation. The most important localities of coal are, in Britain, the Scottish, 
 
24 CHEMICAL TECHNOLOGY. [SECT. i. 
 
 the Newcastle, the Lancashire and Staffordshire, the Welsh, and the Cumberland beds. 
 A deposit of coal has recently been discovered in Sussex, but its extent is not yet 
 known. Altogether the coal formation occupies about T Vth of the total surface of the 
 British Islands. Ireland is supposed to have possessed at one time very important 
 deposits of coal, which have been chiefly destroyed by denudation. In France the most 
 important coal-beds are those of the Loire, of Valenciennes, of Creusot and Blanzy, of 
 Aubin, and of Alais. In Belgium the carboniferous districts take up about -j^th. of the 
 total surface. In Germany there are the palatinate or Saar basins ; those of Aachen 
 and Liege, which lie partly in Belgium and partly in Germany ; the Westphalian 
 field at Essen, Bochum, and Ibbenbiiren ; the small beds of Merseberg ; the Silesian 
 deposits, extending to Gallicia and Cracow ; in Saxony, the beds of Zwickau and 
 the Plauen valley ; and in the Bavarian province of Upper Franconia, the field of 
 Stockheim. Austria, with the exception of Bohemia and South Hungary, yields 
 more lignite than coal. The production of coal in Spain, Italy, Russia, and Sweden is 
 unimportant. 
 
 In America the coal-fields of the United States are of vast importance. There 
 are three districts ; those of Pennsylvania, of Illinois, and the Western fields in 
 Iowa, Nebraska, and Texas occupying a total surface of at least 250,000 square kilo- 
 metres. 
 
 In British North America there are important coal-fields in the provinces of New 
 Brunswick and Nova Scotia, having areas of 8000 square miles. In British Columbia 
 there are also extensive coal deposits, the area of which has not been ascertained. In 
 the island of Trinidad a deposit of coal of superior quality occupies 318 square miles, 
 and is supposed to extend underneath the great pitch lake. The extent of coal in the 
 South American countries has still to be determined. 
 
 In South Africa coal is abundant. The British province of Natal contains more 
 coal than Britain ever did, and the fields extend into the Orange Free State. 
 
 India contains coal-fields of the area of 3500 square miles. As to the existence of 
 fossil fuel in Burmah we are still in doubt. China is probably richer in coal even than 
 the United States. The coal deposits of Japan and of Yesso are also of considerable 
 importance. The area occupied by the carboniferous system in Australia (Queensland 
 and New South Wales) is estimated at 240,000 square miles. 
 
 According to the researches of A. Carnot,* the quality of coal depends not merely 
 on its age and on the circumstances attending its formation, but on the kind of plants 
 from which it has been formed. According to Stein, the behaviour of coal on coking 
 does not depend on its elementary composition. 
 
 Scheurer-Kestner whose results are confirmed by the author shows that the com- 
 bustion-value of coal is considerably higher than Dulong's formula requires. 
 
 His most recent experiments with coal from Ronchamp (I.), from Altendorf on 
 the Ruhr (II.), and from Glamorgan (III.) gave 
 
 Carbon . ' . 
 Hydrogen . 
 Nitrogen . 
 Sulphur . . 
 
 Oxygen . . 
 Value . . . 9130 heat-units ... 9121 heat-units ... 8864 heat-units 
 
 Schwackhofer obtained the following results for the combustion-value of coal : 
 
 * Comptes-rendus, 99, p. 253. 
 
 I. 
 
 II. 
 
 III. 
 
 89*09 per cent. 
 
 ... 89-92 per cent. 
 
 ... 90-27 per cent. 
 
 5 '09 
 
 ... 4-11 
 
 ... 4-39 
 
 1-30 
 
 I -00 
 
 0-69 
 
 i -03 
 
 I'OO 
 
 ... 0-49 
 
 3 '49 
 
 - 3'97 
 
 4-16 
 
SECT. I.] 
 
 COAL. 
 
 Name of Coal. 
 
 C. 
 
 H. 
 
 0. 
 
 N. 
 
 H S 5 . 
 
 Ash. 
 
 Sul- 
 phur. 
 
 Heat- 
 units. 
 
 Wilczek, Ostrau 
 
 77-06 
 
 4 'So 
 
 1 1 '22 
 
 0-19 
 
 2-91 
 
 4'12 
 
 0-39 
 
 7758 
 
 Erzherzog-Albrecht, Ostrau 
 
 74-21 
 
 4-19 
 
 9-82 
 
 0-33 
 
 3-22 
 
 8-2 3 
 
 071 
 
 7443 
 
 Konigshutte, Prussia 
 
 70-38 
 
 4-07 
 
 1I-85 
 
 0-59 
 
 8-82 
 
 4-29 
 
 0-44 
 
 6920 
 
 Karwiner-Larisch, Ostrau 
 
 7372 
 
 4-25 
 
 10-39 
 
 0-31 
 
 3-96 
 
 7'37 
 
 0-50 
 
 7368 
 
 Morgenstern, Prussia 
 
 6i'io 
 
 3-I7 
 
 1 3 "93 
 
 0-41 
 
 9-07 
 
 12-32 
 
 0-57 
 
 5728 
 
 Hermenegilde, Silesia 
 
 71-02 
 
 4-17 
 
 11-46 
 
 0-18 
 
 2 '6O 
 
 10-57 
 
 0-21 
 
 6992 
 
 Dombrauer, Polnisch-Ostrau 
 
 74-69 
 
 4-23 
 
 12-42 
 
 0-07 
 
 3^3 
 
 5-56 
 
 0-50 
 
 7280 
 
 Carolinen, Prussia . 
 
 61-42 
 
 3-23 
 
 1 3 '64 
 
 0-24 
 
 7-29 
 
 14-18 
 
 078 
 
 5758 
 
 Gliickshilf I. , Waldenburg 
 
 70-50 
 
 3 '94 
 
 9-28 
 
 0-19 
 
 I "6O 
 
 14-49 
 
 0-63 
 
 6955 
 
 Jaklowetz, Silesia . 
 
 72-59 
 
 3-90 
 
 10-08 
 
 O'2O 
 
 2-40 
 
 10-83 
 
 o-35 
 
 7044 
 
 Waterloo, Prussia . 
 
 69-70 
 
 374 
 
 13-60 
 
 0-40 
 
 6-28 
 
 6-28 
 
 0-40 
 
 6571 
 
 Anthracite occurs chiefly in transition formations, especially between the strata of 
 clay-slate and of grey-wacke and between mica-slate and the beds by which it is inter- 
 sected. It is deep black, brittle, of conchoidal or irregular fracture, burns with a feebly 
 luminous but smokeless flame, does not soften in the fire, but often crackles and decre- 
 pitates. Jacquelain obtained the following results on the analysis of certain anthra- 
 cites : 
 
 From C. H. O. N. Ash. 
 
 Swansea . . 90-58 ... 3-60 ... 3*81 ... 0-29 ... 172 
 
 Sabl6 . . . 87-22 ... 2-49 ... I -08 ... 2-31 ... 6-90 
 
 Vizille . . . 94*09 ... 1-85 ... I -08 ... 2-85 ... 1-99 
 
 Isere-Dep. . . 94-00 ... 1*49 ... I'o8 ... 0-58 ... 4-00 
 
 Anthracite owes its superiority to other fuel to its cleanliness, hardness, and its 
 smokeless combustion. In Swansea and in some of the Eastern American States, 
 especially along the river Lehigh in Pennsylvania, it has been used since 1839 for the 
 reduction of iron ores in blast furnaces. It serves also in lime-burning, brick-burning, 
 in salt works, and as a domestic fuel. Since 1875 the attempt has been made to 
 convert anthracite into coke by breaking it up previously along with caking coal and 
 coke. 
 
 Boghead Coal, or Torbane Hill mineral, is found near Bathgate, at Rocksoles 
 near Airdrie, at Pirnie, Capeldrea, Kirkness, and Wemyss in Fife. The Torbane Hill 
 coal, famous for the unedifying litigation as to its nature, is considered the most 
 valuable coal known for gas-making. It is amorphous, with a conchoidal fracture, and 
 contains impressions of the stems and roots of Sigillaria. It yields a coke of little 
 value, and on dry distillation it gives off paramne, photogejxe, and solar oil, whilst true 
 coal produces anthracene, naphthaline, and benzene. 
 
 Its composition, according to Dr. Stenhouse, F.R.S., is 
 
 Carbon 
 
 Hydrogen 
 
 Nitrogen 
 
 Oxygen 
 
 Ash 
 
 6572 
 9-03 
 072 
 478 
 
 1975 
 
 The ash of Torbane Hill coal is stated by the same authority to contain- 
 
 Silica 5831 
 
 Alumina . . . . . . 33*65 
 
 Ferric oxide 7-00 
 
 Potash 0-84 
 
 Soda 0*41 
 
 Lime and sulphuric acid . . . traces 
 
 Boghead coal is used both as fuel for the manufacture of gas, and for the pro- 
 
26 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 duction of paraffine and lubricating oils. Other forms of brown cannels approximating 
 to the original Torbane Hill deposit, which is now nearly exhausted, are found at 
 Wemyss, at Rigside and near Lesmahagow in Lanark. 
 
 Hilt classifies coals according to their yield of coke, which ranges from 52 to over 
 90 per cent. 
 
 L. Gruner maintains that the technical value of a coal can be better ascertained by 
 proximate than by ultimate analysis. He distils the coal in a retort and incinerates 
 the residue. In true coals the combustion-value generally coincides with the quantity 
 of fixed carbon left after distillation ; this is less commonly the case with anthracites 
 and lignites. He distinguishes five kinds of coal (i) dry coal, with a long flame, yielding 
 50 to 60 per cent, of coke, which is powdery or at most fritted ; (2) fat or gas coal, with 
 a long flame, yielding 60 to 68 per cent, of coke, fused and tumid ; (3) smithy coal, 
 giving 68 to 74 per cent, of coke, fused and of mean density; (4) coking coal, with a 
 short flame, yielding 74 to 82 per cent, of a very compact coke with few blisters ; 
 (5) anthracites, giving 82 to 90 per cent, of a fritted or powdery coke. 
 
 The following analyses of the ash of Upper Silesian coals are taken from E. 
 Jensen : 
 
 
 
 
 
 
 
 6. 
 
 
 * 
 
 ' 
 
 3- 
 
 4- 
 
 5- 
 
 
 Sand 
 Si0 2 (soluble) 
 
 } 39-450 
 
 26-070 
 
 ( 3-860 
 (20-940 
 
 6-890 
 
 3 8 '340 
 
 6-430 
 28-2OO 
 
 9'2OO 
 27-450 
 
 Al.,0, 
 
 18-230 
 
 27-800 
 
 20*630 
 
 15-840 
 
 23-820 
 
 28-570 
 
 FeA 
 
 15-680 
 
 19-840 
 
 26 'O2O 
 
 19-270 
 
 18-580 
 
 10760 
 
 MnO 
 
 i '330 
 
 0-420 
 
 2-840 
 
 1-170 
 
 I-430 
 
 O-2OO 
 
 ZnO. 
 
 0-260 
 
 0-370 
 
 I'I2O 
 
 0*090 
 
 0-550 
 
 0-860 
 
 PbO. 
 
 O'O2I 
 
 0-069 
 
 0-058 
 
 0-037 
 
 O-O82 
 
 0-056 
 
 CdO 
 
 O'OOS 
 
 O'OOI 
 
 0-003 
 
 0-005 
 
 O-OO4 
 
 O'OO2 
 
 CaO. 
 
 6"O2O 
 
 11-150 
 
 6 - 4OO 
 
 2-160 
 
 3-290 
 
 7-450 
 
 MgO 
 
 2-440 
 
 4-210 
 
 4-690 
 
 0-810 
 
 0-870 
 
 2-000 
 
 Alkalies 
 
 2T70 
 
 0-760 
 
 2'98O 
 
 2'IOO 
 
 3-090 
 
 2-O9O 
 
 SO S (total) 
 
 I2-830 
 
 7-380 
 
 9-480 
 
 1 1 -840 
 
 I2'6lO 
 
 10-880 
 
 PA 
 
 I -290 
 
 1-480 
 
 0-850 
 
 1-090 
 
 0-970 
 
 0-230 
 
 The presence of copper is to be ascertained in coals used in iron smelting. Schulze* 
 detected thallium and lithium in coal. 
 
 Coke. The object of the coking of coal is (i) to increase the proportion of carbon 
 and thus to obtain a higher temperature; (2) to expel evil-smelling constituents 
 (especially for household consumption) ; (3) to deprive coal of the property of caking 
 together-, whereby the due access of air is hindered, especially in blast furnaces ; (4) to 
 expel a part of the sulphur always present in the form of iron sulphide. 
 
 Coking in heaps is very similar to charcoal-burning. On the spot selected there is 
 
 Fig. 22. 
 
 built a chimney shaft from i to i J metre in height, which serves for the axis of the 
 heap. It is 0-3 metre in diameter, and is provided with several rows of air-holes, by 
 
 * Jahresber. 1886, p. 1069. 
 
SECT. I.] 
 
 COKE. 
 
 27 
 
 which it is kept in connection with the heap of coal. The largest pieces of coal are 
 laid round the chimney and smaller pieces towards the circumference so as to round off 
 the heap (Fig. 22). The intervals between the lumps are filled up with small coal. 
 At the sole of the heap there are formed channels or air passages leading from the 
 circumference towards the shaft. At the bottom of the shaft there are laid dry chips 
 of wood, which are kindled from above. The heap is fired as long as smoke is given off, 
 the top of the chimney is then closed with an iron cover, and the mouths of the air- 
 channels are choked with earth. Sometimes cooling is promoted by the application of 
 cold water, which is erroneously thought to desulphurise the coke. The whole process 
 is very similar to charcoal-burning. 
 
 Oven-coking. At present coking is effected almost exclusively in special fur- 
 naces, coke-ovens, in which the management of the fire is easier, an excessive con- 
 sumption of the coal is more readily avoided, and the yield is in general greater. 
 The ovens in greatest use are that of Appolt, which may be regarded as a kind of 
 upright gas retort with openings for the escape of the gases, and latterly the Coppee 
 oven. 
 
 Of the closed coke-ovens of earlier construction may be mentioned one used at the 
 ironworks at Gleiwitz in Silesia, shown in section in Fig. 23. The cylindrical coke- 
 room, A, with a perforated arch above, is provided 
 with register-openings in the walls, o, which can be 
 closed from without by means of plugs. There are 
 also similar apertures in the sole, forming a kind of 
 grate. But the sole may be advantageously con- 
 structed solid if care be taken that the lowest row of 
 apertures is placed immediately above the sole. The 
 coal to be coked is introduced partly through the 
 opening, b, in the arch, and partly through the door, 
 a. First the larger pieces are inserted, though a 
 passage opening at the door is left free for the intro- 
 duction of burning coals. After the oven is filled up 
 to the lower part of the discharge-pipe, r, the door 
 
 is bricked up to the mouth of the kindling passage, all the register-openings are closed 
 except the lowest row, and the opening of the arch is closed with the iron cover, d. As 
 soon as the coals display an average redness through the register-holes of the lowest 
 row, these are closed and the next row is opened, which is the case in about ten hours - r 
 after another ten hours, the second row is closed ; after sixteen hours, the third ; and 
 after a further three hours, the fourth. The oven, when entirely closed, is let stand 
 twelve hours to cool ; the door, t, is then opened, the glowing cokes are drawn out with 
 a hook and at once extinguished 
 
 with water. The above furnace *' 2 4- 
 
 takes 2 tons of coal, and, on an 
 average of several months, it 
 yields 53 per cent, of coke by 
 weight or 74 by volume. The 
 gases and vapours escape through 
 the pipe, r, to a condensing appa- 
 ratus which serves for two adjacent 
 ovens. It liquefies and receives 
 the tarry vapours, letting the 
 gases escape. 
 
 The coking of small coal is effected on hearths arched over after the manner of a 
 baker's oven. The waste of the coal mines may be very advantageously utilised by 
 
28 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 coking, since the particles, when heated, cake together and yield as firm coke as does 
 lump coal. 
 
 In the coke- works on the Saar and at Sulzbach, as well as formerly in some iron- 
 works in Lorraine, ovens are employed as shown in section, Fig. 24 (p. 27), and, Fig. 25, 
 
 in ground plan. They are advan- 
 tageously distinguished from the 
 earlier coke-ovens (in which the 
 access of air took place through 
 chinks in the doors and the chim- 
 ney) by the circumstance that a 
 regular current of air takes place 
 through openings in the vault. 
 The sole of the oven is egg-shaped ; 
 the length is 3 metres, the breadth 
 2, the greatest internal height i 
 metre. The chimney, if metre 
 high, serves for introducing the 
 small coal. A peculiarity in this 
 furnace is the distribution of the 
 air-supply. At the height of 0*3 
 
 metre above the sole there runs a draught channel of horseshoe shape round the oven 
 space, and opens at o' on each side of the door, t. The air streaming into these open- 
 ings is distributed through nine cross-channels, o, and rushes into the oven space. 
 The door, t, closes the opening almost perfectly. A charge of i to i^ cubic metre of 
 small coal is coked in this oven in twenty-four to thirty hours. 
 
 Coke-oven of Appolt Bros. The first of these ovens was erected, in 1855, at St. Avoid 
 (German Lorraine). It is distinguished by the form of its standing shaft, which is 
 heated from without, whilst the heating of the oven shaft is effected merely by vapours 
 
 Fig. 26. 
 
 Fig. 27. 
 
 and gases evolved and ignited during the coking. Fig. 26 shows the section, and Fig. 27 
 a horizontal section on the line i to 2. In order that the heat may pass better into the 
 shafts, a, they are of a prolonged quadrangular section (0*45 and i' 24 metre by 4 metres 
 deep) ; and, the better to utilise the heat, every twelve shafts are united in two rows 
 to a general oven. The several shafts (whose walls are separated by hollow spaces, 6) 
 
SECT, i.] COKE. 29 
 
 are connected with each other and with the mantle by masonry ; the empty spaces are 
 also connected with each other. Each compartment has two apertures an upper one 
 by which the coal is introduced, and a lower through which the cokes are allowed to 
 drop out. In the lower part of the side wall of the compartments there are left between 
 the stones narrow slits, e, through which pass the gases and vapours, which are burnt 
 in the hollow spaces with the co-operation of the air which enters through 6. The heat 
 thus generated effects the coking of the coal in the interior of the compartments. 
 
 The products of combustion escape through the channels g and h. The draught is 
 regulated by the slide, fi. The channels g vent into a horizontal channel, *', and the 
 channels h intoj. The two channels i and j unite in the flue, k. The compartments 
 of the oven (Fig. 26) are contracted at their upper end by projecting stones, so that 
 there remains only a small opening, which is closed with an iron cover. This cover has 
 in the middle a pipe, through which a part of the gaseous and vaporous products of dis- 
 tillation can be led off. A tramway running along over every series of oven compart- 
 ments receives the truck, which each time brings to a compartment its charge of 1200 
 kilos, of coal. In the solid masonry below the oven there are two passages, in which 
 the trucks for receiving the coke travel on tram-lines. 
 
 In working the oven, wood fires are placed in the compartments, upon which coal is 
 then placed. The interior of the oven is rapidly heated by the combustion of the gases 
 which issue from the compartments through the slits, e. When the oven is hot enough 
 to effect the decomposition of the coal and the combustion of the volatile products, the 
 compartment is charged with coal, and the upper opening is closed by putting on its 
 cover and luting it down. Two hours later the same operation is repeated, and so on 
 until in the course of twenty-four hours all the compartments are charged. By that 
 time the coking in the first compartment is completed, and the coke is taken out. 
 When empty, the compartment is charged afresh, and two hours later the second com- 
 partment is in like manner emptied and re-charged. 
 
 The Appolt ovens are expensive to build, but each yields daily 1 2 tons of coke, and, 
 as there is scarcely any loss, the Duttweiler coal yields 66 to 6 7 per cent, of coke, whilst 
 in a horizontal oven it would give at most 6 1 per cent. A defect of the Appolt system 
 is, that the compartments in the middle of a row receive more heat than those at the 
 ends, and with the same kind of coal yield a denser coke, a circumstance which is dis- 
 turbing in metallurgical operations. 
 
 Of great importance are the coke-ovens arranged for securing the tar and ammonia. 
 The earliest furnace of this kind was constructed by Knab, and was heated from the 
 sole only. Carves in 1863 added heating from the sides, and Hiissener (1883) im- 
 proved the access of gas and air. In the fifty ovens erected on this plan in Gelsen- 
 kirchen, the retort is 9 metres long, conical in shape, 0*575 metre broad in the middle, 
 and i '8 metre high. Its available capacity is 88 per cent, of the total space, and it holds 
 5^ tons of dry, finely sifted coking coal, reckoning i cubic metre at 690 kilos. The 
 distillation has been in uninterrupted work since November 1882. At first there were 
 used finely sifted coals from Gelsenkirchen ; they were relatively too impure, not having 
 been washed. The sale was difiicult, and the impurities produced so much waste that 
 fat coal was chiefly used in place of gas coal. The time of preparing was at first seventy- 
 two hours, but by a better distribution of the gases in the channels it was gradually 
 reduced to fifty -two to fifty-six hours. la. order to insure a periodical regularity in 
 charging and emptying the retorts, these operations are effected within sixty hours. 
 The yield was 
 
 Gas Coal. Patty Coal. 
 
 Lump coke .... 61 700 per cent. ... 75 *oo per cent. 
 
 Small coke .... 3*500 ... 0*80 
 
 Dirt 9-180 ... 1*20 
 
 Tar 2720 ... 277 
 
 Ammonium sulphate . . 0*924 ,, ... i'io 
 
.3 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT, i, 
 
 Boiling between 80 and 100 
 100 and 140 
 
 Solvent naphtha . 
 Phenol, purified 
 Pure anthracene . 
 
 The tar is very thin; 100 kilos, yielded 58*83 distillate; 39*51 pitch distillate; 
 1*65 loss. A closer examination of the tar showed : Benzol, purified with sulphuric 
 acid and soda, and several times fractionated 
 
 . 0*59 per cent. 
 
 0-49 
 
 - 0-39 
 . i'37 
 . 0-95 
 
 whilst in gas-tars the maximum yield is only 0*25 to 0*3 per cent. 
 
 The crude gases have in the receiver above the oven a pressure = 2 mm. of water, 
 and a temperature of 75 to 80. The purified gases have a pressure = 90 to no mm. 
 of water, and a temperature of 15. The combustion gases contain on an average 
 
 Carbon dioxide 8'i per cent. 
 
 Carbon monoxide . . . . .0*4 
 Oxygen . . . . . . .0-3 
 
 and evaporate 0*91 to i kilo, water for each kilo, of coal put in the retorts. 
 
 G. Hoffmann (1884) combines the coke-ovens with the Siemens heat reservoirs. This 
 arx-angement was first introduced experimentally in the Silesian Coal and Coke Works 
 at Gottesberg, without a condensation apparatus for the gas, then with very perfect 
 -apparatus for liquefaction in an installation of twenty ovens at the Pluto Mine, near 
 
 Fig. 28. 
 
 Explanation of Terms. 
 
 Maschimnhaus 
 Ammoniakfabrik 
 
 ftaskuhler 
 Gaswascher 
 
 Windleitung 
 AmmoniaTc 
 Theervorrathe 
 
 Steam-engine house. 
 Ammonia-works. 
 Condensation. 
 Gas-coolers. 
 Gas-mixer. 
 Exhausters. 
 Ventilator. 
 Air-duct. 
 Ammonia- tank. 
 Tar-stores. 
 
 ttetortenofen 
 
 DrucklcituiHj 
 
 Sauffle.itiing 
 
 s 
 
 Schornstein 
 
 Maschinenseite 
 
 Vorlage 
 
 Koksofen 
 
 Koksseite 
 
 Ketort furnace. 
 
 Pressure-duct. 
 
 Suction-duct 
 
 Gasometer. 
 
 ( !himney. 
 
 Machinery shed. 
 
 Receiver. 
 
 ('oke-oven. 
 
 Coke-shed. 
 
SECT, i.] COKE. 31 
 
 Wanne, and in twenty ovens at the Gottesberg works. The results of these installa- 
 tions are so exceedingly favourable that at present 120 ovens have been built in 
 Germany with the same arrangement for securing the by-products. Fig. 28 shows 
 
 Fig. 29. 
 
 ^^ 
 
 V-U 
 
 r nr 
 
 S5 
 
 5 
 
 i 
 
 ::: -.::v 
 
 .-::::. 
 
 = 
 
 
 ^pi 
 
 ^: 
 
 
 w 
 
 . ^ ".:'.:: 
 
 -/.-:..:.. 
 
 
 
 -vv~ 
 
 :'::. 
 
 
 
 ^..~. 
 
 r-:-..i 
 
 
 
 
 S 
 
 
 
 '-.-::':':. 
 
 -..-.-;:: 
 
 
 
 ;:.' : ":. 
 
 L'v.'... 
 
 = 
 
 
 _J 
 
 E 
 
 < 
 
 L*_ 
 
 Fig. 30. Fig. 34. 
 
 the general arrangement of the ovens and condensation at the Pluto Mine, and 
 Figs. 29 to 34 represent the details. The coke-ovens, with vertical draughts in the 
 sidewalk,* are 9 metres long, a clear width of o'6 metre, a height of r6 metre, and 
 
 * See Jahresber. 1883, p. 1221. 
 
32 CHEMICAL TECHNOLOGY. [SECT. i. 
 
 the distance from middle to middle is 0-95 metre. In ordinary ovens without 
 arrangements for securing tar and ammonia there are openings in the coking cham- 
 bers through which the gases first pass into the lateral walls, and then into the channels 
 in the sole, and there burn along with atmospheric air. By this the combustion 
 chamber is heated sufficiently for the process. In the oven before us there is no 
 direct connection between the coking chamber and the wall. Besides the openings for 
 charging and emptying (which are closed during the process), this oven has only two 
 apertures, a, in the arch by which the gases evolved may escape. In the side wall of 
 the oven there is a channel, m, arranged, which passes over all the perpendicular 
 draughts of the side wall, and renders the connection possible. Each channel in the 
 sole is divided into two parts, s and S, in the longitudinal direction of the oven. 
 Each part is connected with two regenerators, which lie side by side. Of these g and G 
 serve to heat the gas to be expended in the combustion ; I and L serve to heat the air 
 required. These regenerators are long channels, set grate-like with stones so as to 
 expose a large surface. They pass underneath the entire group, and at their end are 
 the two air-heaters, I and Z, connected, by an alternating valve, either with the pipe for 
 introducing air or with the chimney. The gas-heaters, g and G, are likewise brought in 
 connection either with the gas-efflux pipe, or with the chimney, by means of an especial 
 alternating valve. When the ovens are hot, and have been charged with coal at/", the 
 gases of the coals which are coking escape by the aperture a into the ascending pipe, r, 
 and pass through the open valve, v, into the receiver, F. From hence they proceed to the 
 condensation arrangement, where they are cooled in the refrigerators, JT, and are washed 
 in the scrubbers, W (Figs. 32 to 34). The gases are then again forced from the con- 
 densors back to the ovens (by means of the same" blast, which has sucked them into 
 the refrigerators and occasioned their entire movement), and according to the position 
 of the alternating valve of the gas-pressure pipe, either to the regenerator g, or to the 
 one, G, on the other side. If we assume that the gas passes to g, the alternating valve 
 of the air-regenerators is placed so that the air blown in enters the regenerator L 
 This and the gas-regenerator g open in every oven through the adjacent apertures o 
 and d to the channel s in the sole. The total current of the gases in course of com- 
 bustion and of the hot products of combustion passes through the ascending channels 
 c into the horizontal channel m, and thence descend through the vertical flues, e, 
 into the channel S in the sole, where the spent gases escape to the chimney through the 
 air-regenerator L and the gas-regenerator G, and give off their remaining heat to the 
 grating of the regenerators. After about one hour, the two alternating valves are 
 reversed, and the current then takes the opposite way. The gas passes from the con- 
 densors into the gas-regenerator G, and the air into the air-regenerator L. The 
 combustion takes place in S. The current of gas, air, and of the products of combustion 
 passes through e towards m, and then through c towards s, and through the 
 regenerators I and g to the chimney. 
 
 Such is the original arrangement of the coke-ovens at the Pluto Mine ; but the 
 regeneration of the gas was abandoned at the very beginning, so that only the air was 
 heated, and on the following grounds : The proximity of the long gas- and air-regene- 
 rators may, in the possible case of leakage of their sides, lead to a mixture of air and gas 
 in the regenerators, and consequently to fusions in them, involving irregularities in 
 working. Further, at each reversion of the alternating valve the whole of the gas con- 
 tained in the regenerators is wasted, which, on account of their large size, demands con- 
 sideration. Besides, at the reversal, the escaping hot gas between the valve and the 
 chimney meets with the hot contents of the air-regenerator, when explosions may ensue. 
 Lastly, the volume of the air necessary for the combustion of the gas is about sixfold that 
 of the latter. It seems, therefore, simpler and more important to raise the large volume 
 of the air alone to a very high temperature rather than to heat, in addition, the small 
 
SECT, i.] COKE. 33. 
 
 volume of the gas and to withdraw the heat required for this purpose from the air. 
 Hence the two regenerators, as they lie side by side, are used for the air only, and the 
 gas is led out of the pipe, returning from the condensation either to n or N, according; 
 to the position of the alternating valve. In each oven a connection between the gas- 
 pressure tube and the channel in the sole is effected by means of a small pipe fitted 
 with a cock. The valve in the gas-pressure tube and that at the end of the air-regene- 
 rators are placed to correspond. When the gas passes through the pressure conductors 
 into the sole channels on one side, the air sweeps through the regenerators on the 
 same side into the same sole channels, and the combustion and the route taken by its 
 products are those already laid down. 
 
 At present, instead of two regenerators on each side, there is only a single one in use 
 on each side of the battery, serving merely for re-heating the air. By means of this 
 arrangement the air for combustion can be very rapidly and intensely heated. By 
 means of this " Siemens regeneration " the air at the Pluto Mine can be raised above 
 1000, and by using for combustion air so extremely hot it is possible to employ only 
 a part of the cold air returning from the condensation (impoverished by the loss of the 
 tar) in order to set the coking process in action and keep the ovens sufficiently hot. 
 It has been found in practice that there is no need to use all the gas for heating the 
 ovens, otherwise the combustion spaces would become too hot. Hence there is much 
 more gas than is needed for maintaining the coking process, the excess being daily 
 100 cubic metres per oven. The temperature is so high that the process, with a normal 
 charge (i.e., 5750 kilos, dry coal per oven), is completed in forty-eight hours ; the time is 
 often less. If the process is too rapid it is merely requisite to introduce less gas, so as 
 slightly to reduce the temperature and bring the time to forty-eight hours. The 
 process is quite under control, since both gas and air are forced in, and the quantities 
 of each can be accurately regulated. The quality of the coke is excellent, arid the 
 quantity is about 7 per cent, more than in the common ov^ns. 
 
 The gas-refrigerators, K (Figs. 32 and 33), are upright iron cylinders with iron 
 tubes, x, fixed in the top and the bottom. From the top piece, w, water flows down 
 through the iron pipes and cools the gas, which is passing between these cooling 
 tubes in the opposite direction. Several gas- coolers are connected together in such a 
 manner that the cooling water which flows down from the first gas-cooler enters the 
 second from above, whilst the gas travels in the opposite way. The gas, after its 
 escape from the oven in the ascending tube, has a temperature of 600 -7 00 ; in the 
 receiver 2oo-4oo, according to the distance from the ascending pipe. Before the 
 gas-coolers the heat is 75-i 20, and after them i7-3o. By cooling, the gas parts 
 with a large portion of tar and ammoniacal liquor, about 75 per cent, of the total 
 liquor which the condensation furnishes. In the scrubbers, W (Fig. 34), there are 
 arranged a great number of perforated metal sheets at distances of about 10 centi- 
 metres above each other. Upon the topmost, cold water is constantly dropping, so 
 that a drizzle of water-drops is always falling from sheet to sheet so as to meet the 
 ascending current of gas, which yields up its ammonia to the water. The ammoniacal 
 water flows off below, and if not sufficiently strong in ammonia is pumped up again 
 and again to meet the current of gas until it is strong enough to be saleable. Several 
 scrubbers are placed in connection, so that the gas in passing through them comes in 
 contact in the last with pure water only, and is enriched with ammonia in those 
 scrubbers into which the gas first enters. The scrubbers remove the 25 percent, of the 
 /tmmonia which still remained in the gas-coolers, and at the same time eliminate very 
 much tar. If the water employed in the scrubbers is sufficiently cold, the temperature 
 of the gas falls to 13. The separation of the tar and the ammoniacal liquor is effected 
 in cisterns by means of specific gravity. The ammoniacal water is enriched in the 
 scrubbers until it has a specific gravity of 4 -4'5 B e , representing 1-78 per cent, of 
 
 c 
 
34 CHEMICAL TECHNOLOGY. [ SECT - I - 
 
 ammonia. As the yield is about 14 per cent, of ammonia at 3, the yield of ammonia 
 calculated as ammonium sulphate is about i per cent, of the dry coal. 
 
 At the Pluto Mine the ammonia water is not converted into ammonium sulphate, 
 but sold as liquid ammonia according to its strength. The yield of tar is on the average 
 3^46 per cent, for the best working month, and 278 per cent, for the worst month, 
 calculated on the dry coal. These fluctuations are owing to the circumstance that 
 sometimes the supply of water for refrigeration is insufficient. The water needed 
 daily is 5 cubic metres per oven. 
 
 The proportion of the chief constituents of the tar (calculated as anhydrous) is, 
 According to the researches of Knublauch 
 
 Benzol 0^954-1 - o6 per cent. 
 
 Naphthaline 4 '270-5 '27 
 
 Anthracene 0-57 5-0 '64 
 
 Pitch about 50 
 
 A greater or less proportion of this pitch can be driven off on prolonged distillation. 
 The residue insoluble in glacial acetic acid or in benzene is 10 to 25 per cent, of the 
 tar. 
 
 In each oven there is a daily excess of TOO cubic metres of gas of the following 
 composition. It has about half the candle power of that of the Cologne Gasworks. 
 Small quantities of this gas are burnt for lighting, with very large burners. It may 
 .also serve for heating boilers, &c. It contains : 
 
 Coking Gas. Ccbgne Gas. 
 
 Benzol vapour . . . . o'6o ... 1^54 
 
 Ethylene i'6i ... 1*19 
 
 ELS 0-42 
 
 CO 2 . I 1-39 ... 0-87 
 
 CO 6-41 ... 5-40 
 
 H 52-69 ... 55 -oo 
 
 Methan 35'67 ... 36-00 
 
 Water 1-21 
 
 This gas, as a source of heat, has the advantage that it can be conveyed to a dis- 
 tance. The waste heat from the regenerators, which escapes into the chimney at 420, 
 can be very well used for heating boilers, perhaps most advantageously with the simul- 
 taneous combustion of the superfluous gas along with hot air from the cooling channels 
 of the coke-ovens or from the regenerators. Such a utilisation of the waste heat and 
 of the superfluous gas for heating boilers is about to be carried out at a Westphalian 
 coke-works. , 
 
 The return from collecting the by-products depends, independently of the construc- 
 tion of the ovens and the condensations, and of the careful working of the process, 
 essentially on the quality of the coal, i.e., its richness in gas, tar, and ammonia. Good 
 coking coals are especially adapted for the profitable collection of the by-products. If 
 we assume the price of tar to be 55. 60?. per 100 kilos., then for 10 tons of dry coal 
 the net returns in tar for a yield of 3^ per cent, will be 19*. $d. The yield of ammonia 
 from the Westphalian coal is in general about i per cent, of the dry coal, calculated as 
 ammonium sulphate. In Upper Silesia, the coal is richer in ammonia, and reaches 1-37 
 per cent, on the dry coal. If we take the market price for 100 kilos, ammonium sul- 
 phate as 27$. (it has since fallen to 2OS.-225.), and deducting 55. for the cost of manufac- 
 ture, the net returns per 10 tons dry coals (yielding 1*37 per cent, ammonium sulphate) 
 will be 30*. 6d. We may assume that a coke-oven fitted with all appliances for securing 
 the by-products will cost three to four times as much as a common coke-oven. Unless, 
 therefore, the returns of such an establishment are good, the costliness of the plant 
 stands in the way of a rapid extension of the system. 
 
SECT, i.] DEGASIFYING, GASIFYING, COMBUSTION. 35 
 
 It has never been found practicable to convert the total nitrogen of coal into 
 ammonia by dry distillation. Thus, W. Foster, on distilling a coal containing 173 per 
 cent, of nitrogen, obtained 14*51 per cent, of the total nitrogen as ammonia, 1-56 as 
 cyanogen, 35*26 in the gases, whilst 48*66 per cent, remained in the coke. Winkler* 
 calculates that 18,000,000 tons of coal are yearly coked, from which 58,600 tons of 
 ammonia might be obtained. 
 
 The cokes, when extracted from the ovens or retorts, are quenched with water. 
 The three main strata of a charge of coke take up water to very different degrees. 
 The porous top layer may absorb as much as 120 per cent, of its weight, the main 
 mass of the charge in the middle takes up only i per cent., and the bottom layer may 
 absorb 13 per cent. As a rule, we may assume that cokes gain 6 per cent, of their 
 weight if they are moistened with that quantity of water only which is needed to 
 quench them. Quenched cokes thrown when cold into water do not take up one-third 
 of the quantity which they do if thrown in when red hot. 
 
 Cokes, when properly burnt, form a uniform dense solid mass not easily broken or 
 crushed, and having no very large bubbles or blisters. Coke prepared in kilns from 
 baking coal has a surface like cauliflowers, and a melted appearance, not owing to fusion, 
 but to a fine division of carbon, which is separated out at high temperatures from the 
 hydrocarbons formed at the beginning of the process. The colour is a black-grey or 
 iron-grey with a dull metallic lustre. The sulphur in organic combination is only 
 driven off to a very slight extent on coking. 
 
 On account of its density and the absence of combustible gases, the combustibility 
 of coke is so slight that it requires for ignition a strong red heat and a concentrated 
 stream of air to maintain the fire. The combustion value ranges from 7000 to 8000 
 heat-units, according to the proportion of ash. 
 
 Briquettes ; Block-coal. Under this name is understood a fuel originally pulveru- 
 lent, such as coal-slack, sawdust, &c., mixed with a binding ingredient, such as tar or 
 clay, and pressed into blocks or brick-shaped masses. Here might rank pressed peat, 
 pressed lignite, and cakes of spent tan or dye-woods. 
 
 The moulded charcoal (Paris coal) consists of charcoal made coherent by means of 
 tar and re-charring. 100 kilos, of charcoal-dust are worked up with 33 to 40 litres of 
 coal-tar, and the mass is moulded into the form of cylinders. These cylinders are then 
 dried from thirty-six to forty-eight hours, and then charred in muffle furnaces. Here 
 belongs also the pressed charcoal (pyrolite), consisting of charcoal-dust, a little soda- 
 saltpetre, and a cohesive ingredient, such as dextrine or starch-paste. Such fuels are 
 <used in quantity in some countries for heating locomotives, for small household stoves, 
 for drying rooms in newly built houses, where the carbonic acid given off combines 
 with the lime of the mortar. A very imperfect fuel is the carbonatron introduced into 
 commerce by Nieske, and made of charcoal-dust. 
 
 Coal blocks, &c., consist of small coal and a binding agent mixed together and 
 pressed into shape. The binding materials are coal-tar, coal-pitch, hard and soft, 
 natural asphalt, potato starch, treacle, <fec. ; also gypsum, alum, soluble glass, &c. 
 
 DEGASIFYING, GASIFYING, COMBUSTION. 
 
 The important point in the application of the fuels already mentioned (wood, peat, 
 coal) is their behaviour when heated. 
 
 1. Heated alone: charring, coking, illuminating gas. 
 
 2. Heated with access of combined oxygen (H 2 O, CO 2 ) : water-gas. 
 
 3. With limited access of free oxygen (air) : generator-gas. 
 .4. With sufficient access of air : ordinary burning. 
 
 * Jahresber. 1884, p. 1249. 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 Gases, 
 20 to 35 per cent. 
 
 The processes under No. i are known as degasifying: those under 2 and 3 as 
 gasification, i and 2 take place with absorption of heat ; 3 and 4 with liberation of 
 heat. 
 
 Degasifying. If wood is heated, there escapes first the hygroscopic moisture ; at 
 about 170 a part of the carbon is given off as carbon dioxide, carbon monoxide, and 
 methan ; hydrogen and oxygen are split off as water, and there gradually appear the 
 constituents of methylic alcohol, &c., acetic acid, tar, &c., whilst the residual charcoal 
 becomes continually richer in carbon and in acetic acid. The following are the chief 
 products from degasifying wood : 
 
 Carbon dioxide 
 
 Carbon monoxide 
 
 Hydrogen 
 
 Methan, CH 4 
 ( Acetylene, C 2 H 2 
 ] Ethylene, C 2 H 4 
 
 Propylene, C S H 6 
 
 Butylene, C 4 H 8 
 I, Benzol, C 6 H 6 
 /Benzol, C 6 H 6 
 
 Toluol, C 7 H 8 
 
 Xylol, C 8 H 10 
 
 Styrolene, C 8 H 8 
 
 Naphthaline, C IO H g 
 
 Retene, C 1S H, 8 
 
 Paraffine, C^H^ to C., 2 H 43 
 , Pyrogallic dimethyl ether, C g H, a O, 
 \ Phenol, C fi H 6 O 
 
 Cresol, C.H 8 
 
 Phlorol, C 8 H 10 O 
 
 Pyrocatechine, C 6 H 6 O 2 
 
 / p TT Q 
 
 Methylesters of pyrocatechine I Q 7 ,r 8 fi 
 (guaiacol and homologues) 1 r , 8 iT lo n 2 
 w n i2 u 
 
 \Pyrogenous resins 
 fFurfurol, C 5 H 4 O 2 
 
 Formic acid, CH 2 O 2 
 
 Acetic acid, C 2 H 4 O 2 
 
 Propionic acid, C S H,.O 2 
 
 Butyric acid, C 4 H 8 O, 
 
 Valerianic acid, C S H 10 O., 
 
 Capronic acid, C 6 H 12 O 2 
 
 Crotonic acid, C 4 H 6 O.j 
 
 Angelicic acid, C S H 8 O 2 
 
 Aceton, C 3 H 6 O 
 
 Methyl acetate, C S H,.O, 
 
 Methylic alcohol, CH 4 
 
 Allylic alcohol, C 3 H 4 O 
 
 Methylamine, CH S N 
 
 Hydroccerulignon, C I5 H 18 O S 
 V Phenoles, guaiacoles, and pyrogenous resins 
 (Carbon 
 \ Hydrogen and oxygen 
 
 Ash 
 
 Tar, 
 3 to 9 per cent. 
 
 Wood vinegar, 
 
 water, &c., 
 35 to 45 P er cent - 
 
 Charcoal, 
 20 to 30 per cent. 
 
 The gases evolved on the distillation of beech wood contain, according to the author's 
 investigations, 58-65 per cent, carbon dioxide, 30-35 carbon monoxide, up to 5 per 
 cent, methan and 4 per cent, hydrogen. The combustion-value of these gases i 
 therefore trifling. The products of the distillation of peat are similar, but those of 
 lignite have a higher value. 
 
 The products of the degasification of coal are more completely known : 
 
SECT. I.] 
 
 DEGASIFYING, GASIFYING, COMBUSTION. 
 
 37 
 
 1. Coke. 
 
 II. 
 
 Illuminating 
 gas. 
 
 Luminiferous 
 ingredients. 
 
 Gases 
 
 Vapours 
 
 Diluents 
 
 Impurities 
 
 III. Ammoniacal 
 liquor 
 
 IV. Tar, according to Schultz and others : 
 
 Acetylene, C 2 H 2 
 Ethylene, C 2 H 4 
 Propylene, C S H 4 
 Butylene, C 4 H g 
 Allylene, C 3 H 4 
 Crotonylene, C 4 H 6 
 Terene, C 5 H g 
 Benzol, C 6 H 6 
 Thiophene, C 4 H 4 S 
 Styrolene, C S H 8 
 Naphthaline, C 10 H 8 
 Methylnaphthaline, C,,H 10 
 Fluorene, C ):j H 10 
 Fluoranthene, (J 15 H 10 
 Propyl, C 3 H 7 
 Butyl, C 4 H 9 
 Hydrogen 
 Methan, CH 4 
 Carbon monoxide, CO 
 Carbon dioxide, C0 2 
 Ammonia, NH S 
 Cyanogen, CN 
 Cyanmethyl, C 2 H,N 
 Sulphocyanogen, CNS 
 ( Hydrogen sulphide, SH 2 
 Sulphuretted hydrocarbons 
 Carbon disulphide, CS, 
 Carbon oxysulphide (?j, COS 
 Nitrogen 
 
 Ammonium carbonate, (NH 4 ),CO, 
 Ammonium sulphide, (NH 4 ) 2 S 
 Ammonium sulphocyanide, NH 4 CNS 
 Ammonium chloride, NH 4 C1 
 A mmonium cyanide, NH 4 CN 
 
 r 
 
 
 Name. 
 
 Formula. 
 
 Melting-point. 
 
 Boiling-point. 
 
 
 r 
 
 f i. Fatty Series. 
 
 
 
 
 
 
 Crotonylene * 
 
 C 4 H 6 
 
 liquid 
 
 25 
 
 
 
 Amylene 
 
 C 5 H 10 
 
 
 
 30 
 
 
 
 Hexylene 
 
 C 6 H 12 
 
 
 
 71 
 
 
 
 Hydrocarbon 
 
 V<fiv> 
 
 
 
 85 
 
 
 
 Jacobsen's hydrocarbon .... 
 
 1 
 
 
 
 150 
 
 
 
 Paraffine . . . . . . 
 
 t 
 
 solid 
 
 400 ? 
 
 
 
 2. Aromatic Series. 
 
 
 
 
 
 
 Benzol 
 
 C 6 H 6 
 
 + 3 
 
 81 
 
 
 
 Toluol 
 
 C 7 H 8 
 
 liquid 
 
 in 
 
 n 
 
 
 Orthoxylol 
 
 ^8^10 
 
 
 
 141 
 
 13 
 
 a 
 
 
 Metaxylol 
 
 
 ,, 
 
 141 
 
 a 
 
 3 
 
 Paraxylol 
 
 (J 
 
 15 
 
 J 37 
 
 
 o 
 ja 
 
 Styrol 
 
 ^8^8 
 
 liquid 
 
 146 
 
 a 
 
 o 
 
 a 
 
 Mesitylene 
 
 C 9 H 12 
 
 
 
 163 
 
 i 
 
 o , 
 
 2 
 
 Pseudocumol 
 
 
 
 
 169 
 
 1 
 
 o 
 
 Hemellithol 
 
 
 > 
 
 J 75 
 
 2 
 
 t*i 
 
 n 
 
 Terpene 
 
 Ci H I6 
 
 
 171 
 
 01 
 
 ^ 
 
 
 Cymol 
 
 ^10^14 
 
 i) 
 
 1 75 
 
 + 
 
 < 
 
 Tetramethylbenzol 
 
 
 
 
 
 
 
 Naphthaline hydride 
 
 CI O H IO 
 
 liquid 
 
 205 
 
 
 
 Naphthaline . . ... 
 
 ^lO^s 
 
 80 
 
 217 
 
 
 
 a-Methylnaphthaline 
 
 C n H IO 
 
 
 
 243 
 
 
 
 
 
 i2-? 
 
 24.1 '$ 
 
 
 
 Diphenyl 
 
 C, 2 H 10 
 
 J D 
 71 
 
 *+* 3 
 254 
 
 
 i 
 
 Berthelot's hydrocarbon .... 
 
 ? 
 
 85 
 
 26O 
 
 
 
 Aoenaphthene 
 
 Ci 2 H 10 
 
 99 
 
 280 
 
 
 i 
 
 Fluorene 
 
 C] 3 H 10 
 
 "3 
 
 294 
 
 
 
 Pbenanthrene 
 
 C, 4 H 10 
 
 IOO 
 
 340 
 
 
 
 Fluoranthen 
 
 C 15 H )0 
 
 109 
 
 above 360 
 
 
 
 Pseudophenanthrene 
 
 C, 8 H 12 
 
 "5 
 
 ,, 
 
 
 i 
 
 ^Anthracene . . . 
 
 C 14 H 10 
 
 213 
 
 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 Nime. 
 
 Formal*. 
 
 Melting-point. 
 
 Boiling-point. 
 
 f' 3. Bases. 2. Acids. I. Neutral compounds. 
 
 {> ' s 
 % B. Other neutral A. Hydro- 
 |f compounds. carbons. 
 
 Methylanthracene 
 Pyrene 
 Chrysene 
 Chrysogen 
 . Parachrysene 
 
 C 1B H IO 
 
 8 ? 
 i) 
 
 CS 2 
 C 2 H 6 O 
 C 2 H S N 
 
 C 12 H 9 N 
 C 16 H U N 
 C 4 H 4 S 
 C 6 H.S 
 
 H 2 S 
 CNH 
 CO, 
 C 2 H 4 2 
 C 6 H B 
 C 7 H 8 
 
 C 8 H I0 
 
 C 10 H 122 
 
 C^H,/), 
 
 
 
 C 7 H 6 2 
 
 NH S 
 
 C 6 H 5 N 
 C 4 H 5 N 
 C 6 H 7 N 
 C 7 H 9 N 
 C 8 H U N 
 C 6 H 7 N 
 C 9 H 1S N 
 C IO H I5 N 
 C n H 17 N 
 C 9 H,N 
 C 14 H 9 N 
 C 12 H 19 N 
 C n H n N 
 
 2OO 
 119 
 
 250 
 290 
 320 
 
 liquid 
 
 'o 
 238 
 330 
 
 liquid 
 
 17 
 42 
 
 liquid 
 36 
 
 215 
 
 121 
 
 gas 
 liquid 
 
 i 
 
 > 
 i 
 
 i 
 
 
 
 > 
 > 
 
 107 
 
 above 360 
 
 M 
 
 n 
 
 > 
 )> 
 
 47 
 78 
 82 
 
 IOO 
 
 u 35S 
 above 440 
 
 84 
 137 
 
 119 
 182 
 188 
 20 1 
 199 
 
 195 
 124 
 104 
 249 
 
 "5 
 126 
 
 179 
 182 
 1 88 
 
 211 
 230 
 
 239 
 240 
 
 251 
 257 
 360 + 
 
 Ethylic alcohol 
 Acetonitrile 
 Water 
 Carbazol 
 Phenylnaphthyl carbazol .... 
 Thiophene 
 /Ihioxene 
 
 /Hydrosulphuric acid 
 Hydrocyanic acid . . . . ''.', 
 Carbonic acid 
 
 Phenol . 
 
 Orthocresol 
 Metacresol 
 Paracresol . 
 Xylenol . 
 Isodurol . 
 
 |8-Pyrocresol 
 
 \Benzoic acid . . 
 
 /Ammonia 
 Pyridine 
 Pyrrol 
 
 
 Lutidine 
 Collidine 
 Aniline 
 Parvoline 
 Corindine . _ . 
 Rubidine 
 Quinoline . . . 
 
 Viridine ..... 
 Cryptidine 
 \Acridine 
 
 iigenous compounds ] p^ r P^ eE 
 
 . These products are modified according to the intensity and the duration of the heat. 
 Wright obtained from the same quantity of coal from 8-25 to 12 cubic metres of illu- 
 minating gas, according to the temperature used, and of the following composition : 
 
 Cubic metres. 
 Hydrogen 
 Carbon monoxide . 
 Methan . 
 
 Heavy hydrocarbons 
 , Nitrogen 
 
 Coal which, for complete degasifying, required six hours yielded gases of the follow- 
 ing composition after the times specified : 
 
 8-25. 
 
 9'7- 
 
 12. 
 
 38-09 per cent. 
 
 872 
 
 4377 P er cent. ... 
 ... 12-50 
 
 48^02 per cent. 
 13-96 
 
 4272 
 
 7'55 
 2-92 
 
 ... 34-50 
 ... 4-83 
 3'4Q 
 
 37o , 
 
 4'5i 
 2-81 
 
SECT. I.] 
 
 DEGASIFYING, GASIFYING, COMBUSTION. 
 
 
 . . 
 
 . , 
 
 . 
 
 . 
 
 
 10 rn nu s. 
 
 90 nu . 
 
 195 minutes. 
 
 
 Sulphuretted hydrogen 
 Carbon dioxide 
 
 1-30 
 2'2I 
 2O'IO 
 
 1-42 
 2'09 
 7.8-7.3 
 
 0-49 
 1-49 
 52-68 
 
 O'll 
 
 1-50 
 67-12 
 
 Carbon monoxide .... 
 
 6-19 
 C7-78 
 
 5-68 
 44'OT, 
 
 3 "u 
 6'2I 
 
 *V?4 
 
 6'12 
 
 22-58 
 
 Heavy hydrocarbons .... 
 Nitrogen 
 
 IO'62 
 2'2O 
 
 S-98 
 2'47 
 
 3'04 
 2'5S 
 
 1-79 
 0-78 
 
 H. Bunte* found the following composition of the purified gas during the dis- 
 tillation of Westphalian coal after the tenth period of fifteen minutes : 
 
 
 
 
 
 
 
 X 
 
 2 - 
 
 
 
 
 
 Carbon dioxide 
 
 1-8 
 
 2-0 
 
 i -i 
 
 07 
 
 07 
 
 Heavy hydrocarbons 
 
 6-0 
 
 4'2 
 
 2-4 
 
 I'4 
 
 I'2 
 
 Carbon monoxide . 
 
 8-3 
 
 7'4 
 
 6-8 
 
 6-6 
 
 67 
 
 Hydrogen 
 
 37'i 
 
 48-9 
 
 53'5 
 
 58-2 
 
 6ri 
 
 Methan ... - 
 
 45 '4 
 
 36'9 
 
 34'2 
 
 29-6 
 
 27-6 
 
 Nitrogen 
 
 I '4 
 
 0-6 
 
 2'O 
 
 3'5 
 
 27 
 
 The unpurified gas contained at the commencement 4 per cent, of carbonic acid, 
 and towards the end 1-4. 
 
 A large part of these products is derived directly from the coal, and another por- 
 tion from the original products as their mutual reaction increases with the height 
 and the duration of the temperature. Ethylene, e.g., is resolved into hydrogen and 
 naphthaline. 
 
 According to Berthelot's researches methan forms ethylene, propylene, and perhaps 
 the entire series of the polymeric hydrocarbons ; acetylene yields benzol and a poly- 
 meric series, (C 2 H 2 ) B , &c. 
 
 Watery vapour and carbonic acid also act upon coal, as mentioned below. 
 
 There are few complete analyses of purified gas known i.e., Heidelberg gas by R. 
 Bunsen, Konigsberg gas by Blochmann, and Hannover gas by Dr. Fischer : 
 
 
 
 Bunsen. 
 
 Blochmann. 
 
 Fine 
 
 ler. 
 
 I. 
 
 II. 
 
 Benzol, C d H 6 . 
 Propylene, C S H 8 
 Ethylene, O,H 4 
 Methan, CH 4 . 
 Hydrogen 
 Carbon monoxide 
 
 I '33 
 
 I '21 
 
 2 '55 
 34-02 
 46-20 
 8-88 
 3-01 
 0-65 
 2-15 
 
 0-66 
 0-72 
 
 2'OI 
 35^8 
 
 5275 
 4'00 
 I'4O 
 
 3-i8 
 
 0-69 
 
 0-37 
 2'II 
 
 37*55 
 46-27 
 H'19 
 
 0-81 
 trace 
 
 I '02 
 
 0'59 
 0-64 
 2-48 
 
 3875 
 47-60 
 
 7H2 
 0-48 
 O'O2 
 2 -O2 
 
 Oxygen 
 Nitrogen . 
 
 The combustion value of the components of coal-gas appears from the following 
 conspectus : 
 
 
 
 Water at o as Product of 
 
 Steam at 20 as Product of 
 
 
 Mol. 
 
 Combustion. 
 
 Combustion. 
 
 
 
 i Mol. 
 
 i Cubic Metre. 
 
 i Mol. 
 
 i Cubic Metre. 
 
 Benzol, C 6 H 6 . 
 
 78 
 
 790,000 
 
 35,400 
 
 757,600 
 
 34,000 
 
 Propylene, C,H d 
 
 42 
 
 501,200 
 
 22,500 
 
 468,800 
 
 21,000 
 
 Ethylene, C^ . 
 
 28 
 
 333,400 
 
 15,000 
 
 311,800 
 
 I4,OOO 
 
 Methan, CH 4 . 
 
 16 
 
 2I2,OOO 
 
 9,500 
 
 190,400 
 
 8,540 
 
 Hydrogen . 
 
 2 
 
 68,400 
 
 3,070 
 
 57,600 
 
 2,580 
 
 CO ... 
 
 28 
 
 68,OOO 
 
 3,050 
 
 68,000 
 
 3,050 
 
 Jahresber. 1887, p. 97. 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 For i cubic metre of coal-gas of mean composition there results the following 
 combustion value calculated for water at o and steam at 20 as products of com- 
 bustion : 
 
 
 Composition. 
 
 Combustion value. 
 
 
 Water. 
 Heat-units. 
 
 Steam at 20. 
 Heat-units. 
 
 Benzol 
 
 0-8 
 07 
 
 2 '3 
 36-0 
 
 48-0 
 
 8-0 
 
 283 
 157 
 
 345 
 3.420 
 
 1.473 
 244 
 
 272 
 
 147 
 322 
 
 3.074 
 1,238 
 244 
 
 Ethylene 
 Methan 
 H 
 
 CO 
 
 
 
 5.922 
 
 5.297 
 
 Now, 100 kilos, of good gas-coal (of about 8000 heat-units of combustion value) 
 with careful working yields 27 to 30 cubic metres of coal-gas, or i kilo, of coal gives 
 o'3 cubic metre of gas, representing about 1600 heat-units. The gas obtained on degasi- 
 fying coals represents, therefore, 20 per cent, of the total combustion value of the coal. 
 
 We have certainly as by-products from 100 kilos, of coal 50 to 70 kilos, of coke, of 
 which from 10 to 25 kilos, are consumed in heating the retorts, also tar, ammoniacal 
 liquor, and spent purifying mass, the value of all which is very fluctuating. If these 
 substances can be successfully utilised, the expense of the production of gas may 
 fall very low. This will appear from a comparison of the reports of the Cologne Gas- 
 works for the financial years April i, 1882-83 an( ^ 1886-87. 
 
 Total product 
 
 cubic metres 
 
 sold 
 
 1882-83. 
 
 13,447,780 
 12,387,191 
 1,058,489 
 
 Loss of gas .... 
 
 From 100 kilos, of Westphalian coal there were obtained : 
 
 1882-83. 
 298-48 
 
 1886-87. 
 16,963,630 
 15,605,456 
 
 1,357,374 
 
 6-87. 
 
 Gas .... 
 
 sold 
 
 Coke, saleable . 
 Tar . . . ; v 
 Ammonium sulphate . 
 
 Outgoings . 
 
 for coal 
 
 Coke . 
 Tar . 
 Ammonia . 
 Ammonium sulphate 
 
 cubic metres 
 
 kilos, 
 is 
 
 
 marks 
 > 
 
 Receipts : 
 marks 
 
 Total 
 
 274-94 
 
 60 roo 
 
 49-00 
 
 9-40 
 
 640,516 
 430,440 
 
 255.387 
 
 119,773 
 
 133,693 
 
 19,996 
 
 528,849 
 
 272-19 
 
 620-00 
 
 45 '4 
 
 lO'OO 
 
 985,126 
 
 575,551 
 
 294,340 
 31,988 
 91,281 
 17,293 
 
 405,602 
 
 Hence i cubic metre cost at the works, without including interest and cost 
 of mains, in 188283 only 0-83 pfennig (100 pfennige = is.) ; but in 188687 more 
 than 3 pfennige. The cause of this is that in 1882-83 the receipts for the by- 
 products exceeded the cost of coal by nearly 100,000 marks, but in 1886-87 ^ e ^ 
 short of the cost of coal by 170,000 marks. 100 kilos, of ammonium sulphate cost 
 in 1882, 40-85 marks, in 1885 only 22-90 marks; 100 kilos, of tar in 1878 were 
 worth 2'3 marks, in 1883, 5-5 marks, and in 1887. 2 marks. In 1881-82 it was even 
 
SECT, i.] DEGASIFYING, GASIFYING, COMBUSTION. 41 
 
 found advantageous to burn 20,077 cubic metres of gas under the retorts, and thus to 
 sell the main coke.* 
 
 The value of the by-products would probably fall still lower if gas was generally 
 used as a source of heat and power. This would be very difficult, since coals suitable 
 for the production of gas are relatively scarce. 
 
 Generator-gas. In order to gasify the coke which remains after the degasification 
 of the coal, oxygen must be supplied. This may be effected either with free oxygen 
 (atmospheric air) or with combined oxygen (water or carbonic acid). The following 
 reactions here come into play : 
 
 1. For forming carbon monoxide : C + O = CO = + 29,000 heat-units. 
 
 2. For carbon dioxide : C + O 2 = C0 2 = + 97,000 heat-units. 
 
 3. For gasification with carbon dioxide: C + CO 2 = 2 CO = 97,000+ 58,000 = 
 
 39,000 heat-units. 
 
 4. For decomposition with liquid water : C + H 2 = CO + H 2 = 68,400 + 29,000 
 
 39,400 heat-units, 
 
 but only 57,600 + 29,000 = 28,600 heat-units with watery vapour at about 20. 
 
 5. C + 2H 2 = C0 2 + 2H 2 = - 136,800 + 97,000 = - 39,800 heat-units if liquid water 
 was used, 
 
 but 115,200 + 97,000 = 28,200 with watery vapour at 20. 
 
 Of course the combustion value of the gases formed = 97,000 heat-units less heat of 
 formation. According to the equation of decomposition, No. 4, we obtain, e.g., from 
 12 kilos, carbon and 18 kilos, of water, 28 kilos, of carbon monoxide and 2 kilos, of 
 hydrogen, or, jointly, 68,000 + 68,400 = 97,000 + 39,400 heat-units. 
 
 Consequently, heat is produced only on the gasification of the carbon by free 
 oxygen ; if combined oxygen is used heat is absorbed, which must be supplied from 
 without (on gasifying in retorts) or in the coal itself, by the introduction of free 
 oxygen (air). The latter can take place separately or simultaneously. 
 
 In coke-generators the gasification should be arranged, as far as possible, in 
 accordance with the first equation, since the carbonic acid formed according to the 
 second has no more combustion value. The 28 kilos, or 22^3 cubic metres of carbon 
 monoxide formed on the gasification of 12 kilos, carbon have consequently a com- 
 bustion value of only 68,000 heat-units, instead of the 97,000 heat-units of the 
 original coal. The 29,000 heat-units are evolved in the generator, i.e., 30 per cent, 
 of the total combustion value of the coke is likewise utilised, if the gases enter into 
 the fire at their full heat, as is mostly the case in the coke-generators built into the 
 retort-ovens of gasworks. But they are entirely lost if the gas is let cool down to 
 the temperature of the air, as it would be doubtless requisite if gas were universally 
 introduced. 
 
 Most of the gas-fires introduced industrially allow a part of this heat to be lost. A 
 portion of the heat is even sacrificed, e.g., in the Siemens gas-firing used in glass- 
 works, iron furnaces, &c., in order to obtain a simple and regular working. 
 
 Independently of gasworks, we use in general for gas-firing, not coke, but coal. 
 The coals are first degasified, then gasified by the introduction of atmospheric oxygen, 
 so as to obtain a mixture of coal-gas and coke generator-gas. In Liirmann's generator 
 these two processes are kept as separate as possible. The coal is fed uninterruptedly 
 into the retort, A (Fig. 35), by mechanical power, and pushed forwards. By the 
 channels, D, escape the combustion-gases, which pass away from the fire still hot, in 
 order to furnish the heat required for the partial degasifying of the coal. The coke 
 
 * Of late years the value of tar has fallen so low that it has been sometimes profitable in England 
 to burn the tar under the retorts instead of selling it for the manufacture of tar products. 
 [EDITOK.] 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 formed is gasified in the shaft, b, by the atmospheric oxygen entering ; the gaseous 
 mixture formed escapes at (7. 
 
 In the gas-firing of Boetius, as shown in longitudinal and transverse section (Figs. 
 36 and 37), there lie beneath the hearth two generators, A. They are formed by 
 
 inclined planes, C, oblique 
 
 Fig. 35. gratings, />, and side-walls, 
 
 N, which are contracted up- 
 wards. The coal introduced 
 at B gives off its gas, the 
 coke is gasified upon the 
 grate, D, so that the gases 
 enter the flame-channel, A", 
 at a high temperature. The 
 atmospheric air introduced 
 through the side-channels, F, 
 is heated along the side- 
 walls, N, of the generator, 
 and in the horizontal chan- 
 nels, H t enters by a number 
 of lateral apertures into the 
 stream of gas ; the flame sur- 
 rounds the pots, G, whilst 
 the smoke-gases escape by 
 small chimneys, m. 
 
 The generator of F. Sie- 
 mens is in extensive use. The coal introduced through the shaft, A (Fig. 38), slides 
 gradually down upon the grate, p o, the slag formed is removed beneath, and the 
 mixed gases escape through the pipe, V U. 
 
 Fig- 36- Fig. 37. 
 
 According to the kind of coal employed and the manner of working, the composition 
 of generator-gas differs. A part of the coal-gas is decomposed, since coals before they 
 are degasified come in contact with the instreaming oxygen, and the gas is partially burnt. 
 Thereby the heavy hydrocarbons, and especially the hydrogen, are consumed. The 
 water formed is then again more or less completely decomposed by the ignited coke. If 
 the generator is worked hot, as is generally the case if no watery vapour is passed in 
 below, decomposition sets in, whereby the proportion of the heavy hydrocarbons is like- 
 
SECT. I.] 
 
 DEGASIFYING, GASIFYING, COMBUSTION. 
 
 43: 
 
 wise reduced. Hence it is intelligible that generator-gases contain so little heavy hydro- 
 carbons (about o'2 per cent.), so that it is 
 preferable not to determine them separately, 
 but along with the methan. 
 
 This does not complete the number of the 
 possible transformations. Watery vapour is 
 decomposed by carbon. According to Naumann 
 and Pistor, charcoal is partially converted into 
 carbon monoxide by dry carbon dioxide at 
 530 -5 60. Dry carbon dioxide is not reduced 
 to carbon monoxide even at 900. The action 
 of carbon monoxide upon water begins at about 
 600 with the formation of carbon dioxide and 
 hydrogen. But if mixtures of hydrogen and 
 carbon monoxide are heated with insufficient 
 proportions of oxygen, then, according to the 
 experiments of R. Bunsen, decidedly more 
 hydrogen is burnt than carbon monoxide, so 
 that the affinity of oxygen for hydrogen is 
 greater than for carbon monoxide. The pro- 
 cesses in the generator are therefore very com- 
 plicated, and but partially known. 
 
 The gases from the collecting-channels of eight Siemens generators at Essen have^ 
 according to the author's experiments, the following composition : 
 
 J 
 
 II. 
 
 III. 
 
 IV. 
 
 V. 
 
 Mean. 
 
 CO 2 . ....,] 6-99 
 
 5-50 
 
 5-89 
 
 3 '96 
 
 4-04 
 
 5'3) 
 
 CO . . 22-84 
 
 26-01 
 
 22 '6 1 
 
 24-02 
 
 23-01 
 
 237 r30'9 
 
 Methan . . ' 2-99 
 
 2-46 
 
 I'39 
 
 1-63 
 
 0-92 
 
 1-9) 
 
 H . . . . 10-30 
 
 8-02 
 
 5-50 
 
 4-83 
 
 3-92 
 
 6-5 
 
 N. . . . | 56-88 
 
 58-01 
 
 64-61 
 
 65-56 
 
 68 -i i 
 
 62-6 
 
 One kilo, of coal gave 4*52 cubic metres of generator-gas ; i cubic metre of this had 
 a combustion-value of 1053 heat-units; consequently, the 4/52 cubic metres had 4760 
 heat-units, whilst the coal expended had a combustion value of 7950 (steam at 20). 
 The gas, when cooled down to the temperature of the air, contained, therefore, only 
 60 per cent, of the combustion value of the coal, the rest having been expended on 
 heating the gas. 
 
 We lose here, therefore, not merely the considerable quantities of heat which the 
 exposed generators give off by conduction and radiation, but, further, 850 heat-units 
 for each kilo, of coal which the long channel gives off, whilst only about 140 heat-units 
 of the specific heat of the gas are led to the fire ; together, 4900 heat-units. This 
 loss, if coal is not very dear, is amply compensated by the simplification and the in- 
 creased certainty and uniformity of working. 
 
 The gasification of carbon by carbon dioxide occurs only as an auxiliary reaction, in 
 order to re-convert the carbon dioxide, formed in the generator, into carbon monoxide. 
 In gasifying carbon by watery vapour there are required almost exactly the same 
 quantities of heat whether CO + H 2 or CO 2 + 2H a are produced. Of course the gaseous 
 mixtures have almost the same combustion value if referred to liquid water. 
 
 According to equation 4 the decomposition of 18 kilos, of watery vapour at 20 re- 
 quires 28,600 heat-units. This circumstance comes into play in every generator, as 
 the atmospheric air introduced always contains watery vapour. It had been observed 
 long ago that by letting water into the ash-pit, especially in coke generators, the grates 
 
44 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 and the masonry of the generator are preserved, and the removal of slag is often 
 facilitated. In consequence, water or steam is often introduced under the grate 
 of the generator. If the generator is walled directly into the retort furnace, this intro- 
 duction of heat certainly involves a loss ; the higher the temperature of the escaping 
 gases, the greater this loss. Every 18 kilos, of water decomposed in the generator 
 carry away, according to equation 4, 39,400 heat-units, which the hydrogen formed 
 certainly liberates on combustion. But the reconstituted water carries off as steam of 
 1000 about 20,000 heat-units, and if heat reservoirs (regenerators) at 500 are used, 
 there is still a loss of about 1500 heat-units. Whether this loss is compensated by the 
 advantages depends on local conditions ; in general this will not be the case. But if 
 the watery vapour introduced is generated by the heat of the escaping combustion- 
 gases (which would otherwise be wasted) the loss will be smaller by 11,000 or 12,000 
 heat-units. It would entirely disappear only if watery vapour, produced without 
 expense, could be introduced into the generator at the same temperature at which the 
 combustion-gases pass away. 
 
 The introduction of watery vapour appears more favourable when the generator is 
 at a distance from the place of its application, so that a part (greater or smaller) of the 
 specific heat of the gas produced is given off to its surroundings. If the gas before use 
 is cooled down to the temperature of the air, its higher combustion value seems in the 
 first place an immediate gain, but this becomes the smaller the higher the tem- 
 perature at which the products of combustion escape, and the less is the refrigeration 
 of the generator-gas. The introduction of watery vapour into the generators cannot, 
 hence, be universally recommended, as in most cases it is connected with loss of heat. 
 Whether this waste is compensated by other advantages must depend on local circum- 
 stances. 
 
 Attempts have not been wanting to use generator- gases rich in hydrogen for the 
 Fig. 39. Fig. 40. 
 
 production of heat and power. This idea has been recently practically realised by 
 Dowson. The generator, (Figs. 39 and 40), has a double jacket, b, into which water 
 
SECT. I.] 
 
 WATER-GAS. 
 
 45 
 
 Fig. 41. 
 
 is driven. That part of the inner jacket exposed to the greatest heat is lined with 
 a fire-resisting material, c. From the lower part of the space, b, the water flows to 
 the lower part of the heating-worm, d, which is heated by a fire, and in which steam 
 is constantly evolved. A part of this 
 steam passes through the pipe e to the 
 space, 6, above the level of the water 
 which it contains. The other part of 
 the steam goes to the blast, /, through 
 which a mixture of air and steam is 
 blown into the fire of the gas generator. 
 The pressure of steam in b compels the 
 water under pressure to flow towards 
 the heating-worm, d ; the pressure in b 
 can be regulated by a valve. The 
 Backet of the space, b, is covered with 
 any bad conductor of water. The heat- 
 ing-worm, d, is also fitted with a jacket, 
 the lower part of which, enclosing the 
 worm, is screwed to the upper part, so 
 that the worm may be easily removed. 
 The gas coming from the generator 
 passes through the pipe g into the closed 
 scrubber, h, partly filled with water, into 
 which the pipe g dips, so as to be discon- 
 nected from the gas in the gas-holder, 
 and to wash the gas coming from a on 
 its way to the gas-holder. The scrubber 
 is divided into two parts by a partition, 
 which has an opening for the water, 
 near the bottom. The one compartment 
 receives the pipe g and a pipe i (Figs. 39 
 and 41), the latter of which leads to the 
 bottom of the scrubber j. The gas 
 
 passes through i into j, and ascends through the charge of coke into the gasometer, k. 
 From here it passes through the pipe downwards into the second compartment of the 
 scrubber h, whence it passes by another pipe to the place of its destination. The coke 
 which fills the scrubber j is kept moist by water, which is conveyed by the tube in to 
 thexradial tubes, n, fitted with perforations. The water trickles through the coke, 
 and flows through i to the scrubber h, whence it is carried out by the overflow, o 
 (Fig. 40). Instead of taking the water which is to be evaporated in the worm, d, from 
 the jacket, b, of the generator, it may be effected through the vessel placed above the 
 worm, d. 
 
 Water-gas. That steam passed over ignited coals forms hydrogen along with carbon 
 dioxide and monoxide has long been known. Hence the attempt has often been made 
 to heat charcoal, coke, or anthracite in retorts, upright or horizontal, and there to 
 introduce steam. As carbonic acid was principally formed along with hydrogen, it 
 \vas sought to remove the former by means of milk of lime or caustic soda. Such a 
 gas has been used at Narbonne for lighting, but the process has everywhere been 
 abandoned as not economical. 
 
 In order to render the water-gas process practicable, there were used, instead of 
 retorts heated from without, shaft furnaces into which air and watery vapour were 
 blown alternately. Such were the arrangements of Lowe, Strong, Dwight, and others, 
 
4 6 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 in use in many cities of North America. The process was adapted to European con- 
 -ditions by Schulz, Knaudt & Co., of Essen. 
 
 According to the arrangements at Essen and Witkowitz (V, Figs. 42 to 44), the 
 
 Fig. 42. Fig. 43. 
 
 JJ 
 
 ,4rbeitsplatte 
 
 Nach dent Gasbehalter 
 
 Explanation of Terms. 
 
 Working floor. 
 Scrubber. 
 
 Pipe leading to the 
 gasometer. 
 
 Wasstryekiiklter Schieber 
 Windleitung 
 Wasserverschluss 
 Nach den Kesseln 
 
 Generator. 
 
 Slide cooled by water. 
 
 Air-duct. 
 
 Water-joint 
 
 Duct leading to boilers* 
 
 steam, which can be regulated by a sliding valve, enters at D, a generator filled with 
 coke. The water-gas formed is led off below. The slide, S, kept cool by water, closes 
 the air- channel as scon as the gas-channel is open, and inversely. In the same manner 
 
SECT. I.] 
 
 WATER-GAS. 
 
 44. 
 
 AnsiM da \ \ Stemming 
 
 zum 
 
 the valve, d, fixed in the air-pipe below the point where the air enters W is closed as 
 soon as the gas-pipe is open. Thus, the air is doubly shut off to prevent explosions. 
 If the surfaces of the slide fit loosely, the small quantity of detonating gas puffs out at 
 the openings, a. In Witkowitz, during the hot blast, the upper part of the slide is fixed 
 so that the air- pipe is connected with the generator, the 
 throttle-valve is open, and the gas-valve of the generator, 
 G ; the pipe through which the gas passes to the scrubber 
 and the slide-valve, F, are closed. Whilst the gas is 
 being made, G and d are closed ; the upper part of the 
 slide shuts off the airway, and establishes the connection 
 from the generator to the scrubber; F is opened. The 
 connection between the gasometer and the generator is 
 then disturbed only by the water-joint, w, in the scrubber, 
 which amounts to 100 mm. Upon the slide, S, there are 
 screwed two uprights, on which is fixed an axle, 3S r This 
 axle is connected with the driving axle, sjg 2 . The levers 
 upon $g t move the upper part of S, and effect the opening 
 and shutting of d and of the slide in F. A lever wedged 
 upon j>2} 2 effects the opening and shutting of the gas- 
 valve of the generator ; *JJj 2 is turned by the hand wheel, 
 //. The arrangement is such that by turning H to one 
 side the upper part of S shuts the airway and opens the 
 gasway. At the same time d and G are closed and the 
 slide of F is opened. By turning to the other side, the 
 upper part of S closes the gas-channel and opens the air- 
 channel; at the same time d and G are opened and the 
 slide of F is closed. The workman has therefore merely 
 to turn the wheel, H, to correspond in order to set the 
 apparatus either for " gas-making " or " hot-blowing," and 
 no accident can happen from his inattention. At Wit- 
 kowitz two generators are in action, each holding 10 cubic 
 metres. Alternately steam is blown in for five minutes 
 (" gas-making ") and for ten minutes there is hot-blowing, 
 i.e., air is forced in. The generator-gas (Siemens-gas) 
 
 obtained on hot-blowing is burnt under four steam boilers, and the water-gas is used 
 for heating the Siemens-Martin furnaces. 
 
 For larger installations it is more advantageous to connect each two generators with 
 a, scrubber and a dust-collector (Figs. 44 and 46). 
 
 The generator-gas made at Essen produced 3690 cubic metres water-gas (July 21, 
 1887), and consumed 3256 kilos, coke. The composition of the coke was 
 
 . 84-8 
 
 Ansicht der Stetterunff gum Gene- 
 rator = Connection of the 
 scrubber with the generator. 
 
 C . 
 H . 
 NO 
 Ash 
 Water 
 
 2-1 
 
 io-6 
 
 2-0 
 
 The generator-gases had the following mean composition : 
 
 6 
 4-03 
 
 28-44 
 0-39 
 2 '2O 
 
 64-94 
 
 C0 2 
 CO 
 
 Methan 
 H . 
 
 N . 
 
 In i 
 
 7-04 
 23-68 
 
 0-44 
 
 2-95 
 65.89 
 
 10 Min. 
 I -6O 
 
 32-21 
 O'l8 
 2-JI 
 
 63-90 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 Determinations of carbonic acid effected at the generator gave 1*5 to 7*2 per cent. 
 The gases would have contained less carbonic acid if the blast had been less strong, 
 i cubic metre of these gases has a mean combustion- value of 950 heat-units and 
 contains 0718 kilo, carbon. The temperature of the gases rose to 505. After making 
 
 Fig. 45- 
 
 SdinittAB-CV-EF. 
 
 Explanation of Terms. 
 Section AB CD EF. 
 
 StaubsammUr 
 
 Scrubber. 
 Generator. 
 Dust chamber. 
 
 Wasseryas 
 Windsammler 
 
 Siemens-gas. 
 Water-gas. 
 Air chamber. 
 
 gas respectively for one, two and a half, and four' minutes, the water-gas had the 
 
 following mean composition : 
 
 C0 2 . 
 CO . 
 
 Methan 
 H 
 
 N 
 
 In i 
 
 1-8 
 
 45'2 
 
 I'l 
 
 44-8 
 7-1 
 
 2'5 
 
 3-0 
 
 44 -6 
 
 0-4 
 
 48-9 
 
 4 Min. 
 
 5-6 
 40-9 
 
 O'2 
 
 51-4 
 
 i kilo, of coke yielded 1*13 cubic metre of water-gas, representing 2970 heat-units, 
 and containing 1*13 x 0*477 x '5395 = 0*291 carbon. The remaining 0*557 kilo, of 
 carbon yielded 3*13 cubic metres of generator -gas. Of the 7000 heat-units of the coke 
 there are found in the \ 
 
 Water-gas 
 Generator-gas 
 
 2970 heat-units = 42 per cent. 
 2970 = 42 
 
 At Essen, to a small extent at Sulzer, and in some other places water-gas is used 
 to give light by means of Fahnehjelm's magnesium burner. Taking the cost of the 
 
SECT. 
 
 I.] 
 
 WATER-GAS. 
 
 49 
 
 mains into account, the price of water-gas would in many places be higher than that 
 of coal-gas, but in others lower lower even than petroleum. 
 
 Water-gas may find extensive application in metallurgical operations, in chemical 
 works, and in the laboratory, especially as it has the advantage of not depositing soot 
 on the apparatus to be heated, and of giving out a higher temperature. 
 
 Fig. 46. 
 GrwtdriR. 
 
 -f 
 
 StaubsbmjnZer. 
 
 Explanation of Terms. 
 GROUND PLAN. 
 
 Zum Gasometer 
 
 Scrubber 
 Generator 
 
 Pipe leading to 
 Gasometer. 
 Scrubber. 
 Generator. 
 
 Staubsammler 
 Siemens Leitung 
 
 Windsammler 
 
 Dust chamber. 
 Siemens-conduc- 
 tion. 
 Air-collector. 
 
 The use of water-gas will become more general as soon as it is produced from coal 
 instead of coke, since it appears irrational first to coke the coal in a separate apparatus. 
 A remunerative production of ammonia is, however, scarcely practicable in the direct 
 production of generator-gas and water-gas from coal, and that of tar (even at improved 
 prices) seems out of the question. 
 
 Whilst i kilo, of the best coal gives at the most o - 3 cubic metre of illuminating gas, 
 we obtain from i kilo, of common coke 1*13 cubic metre of water-gas and 3' 13 cubic 
 metres of generator-gas, which together contain 84 per cent, of the combustion value of 
 the coke used. If the coal is partially degasified, then at once gasified, and the 
 luminous gas mixed with the water-gas, we have a gas containing 
 
 Heavy hydrocarbons i per cent. 
 
 Methan ....... 8 
 
 Hydrogen 
 
 Carbon monoxide .... 
 
 Carbon dioxide .... 
 
 Nitrogen 
 
 and having a combustion value of about 3250 heat-units per cubic metre. Along with 
 this richer gas we have as by-products tar, ammonia, and cyanogen, as in common coal- 
 gas, and the corresponding proportion of generator-gas, as in the ordinary water-gas 
 process.* 
 
 * The great objection to water-gas has been its dangerous character. As will be seen from 
 the above analysis, it contains from 30 to upwards of 40 per cent, of the fearfully poisonous con- 
 
 D 
 
 48 
 
 37 
 3 
 3 
 
50 CHEMICAL TECHNOLOGY. [SECT. i. 
 
 HEATING ARRANGEMENTS. 
 
 If wood, peat, lignite, or coal is heated, it is degasified in the manner already 
 described. If atmospheric oxygen is present, and if the temperature is sufficiently high, 
 the gases take fire and burn with a luminous flame. The residual charcoal or coke does 
 not burn with a flame, but glows, the combustion taking place only on the surface. If 
 the air, after its oxygen has been completely converted into carbonic acid, remains in 
 contact with the fuel, and if the temperature is sufficient, the carbonic acid (carbon 
 dioxide) takes up another atom of carbon, C0 2 + C = 2CO, and forms carbonic oxide 
 (carbon monoxide). 
 
 In our ordinary fires, domestic or industrial, these processes take place simultane- 
 ously. To effect complete combustion there is required a sufficient supply of oxygen (or 
 air) and a sufficient temperature. 
 
 If oxygen is deficient, the combustion is imperfect ; from the charcoal or coke there 
 is formed carbon monoxide (a colourless gas) ; the gas produced on the degasifying of 
 wood or coal gives a smoky flame, as the hydrogen combines with the oxygen by prefer- 
 ence, so that the heavy hydrocarbons and the other constituents of tar liberate 
 more or less free carbon. If undecomposed particles of tar escape along with the soot, 
 it becomes adhesive, attaches itself to solids, and has a very unpleasant smell. If a fire 
 is to be smokeless, the complete combustion of the gases and the accompanying tarry 
 vapours must be effected ; degasified fuel burns without smoke. 
 
 For the complete combustion of the volatile matter, especially the tar, a sufficient 
 temperature is necessary. As this is lowered by the immediate withdrawal of heat by 
 cold surfaces, water, and superfluous air, the mixture of gases or vapours to be burnt must 
 not before complete combustion come in contact with cold surfaces (stoves should be 
 lined with fire-clay or stone, not with iron), and the fuel must be employed as dry as 
 possible (coal should not be moistened). It follows that the numberless proposals for 
 the combustion of smoke are useless. The formation of smoke can be prevented, but 
 smoke, when once formed, is so hard to burn that the task may be pronounced practically 
 impossible. 
 
 Gas Analysis. A correct estimate of a firing can be effected only on the basis of 
 .gas analysis. With the following apparatus, made by W. Apel, mechanician to the 
 University of Gb'ttingen, the author has executed thousands of gas analyses. 
 
 The lower part holding 45 c.c. of the burette, A (Fig. 47), used for measuring 
 the gas under examination, which is enclosed in a wide cylinder filled with water in 
 order to obviate fluctuations of temperature, is divided into tenths of a c.c., but the 
 upper part is graduated only into entire c.c. The thick glass capillary tube with 
 the glass cocks is fastened at both ends at i in a section of the partition, and at o in a 
 
 stituent, carbon monoxide, which, in good coal-gas, does not exceed 8 per cent. Hence a very 
 slight escape is sufficient to prove fatal. Two men at Leeds lost their lives from accidentally 
 inhaling air thus contaminated, and even the medical men commissioned to make an autopsy of 
 the bodies were rendered seriously ill. The danger is the greater as water-gas is, per se, inodorous, 
 so that a leakage is not detected as rapidly as is the case with ordinary coal-gas. For this evil a 
 remedy has been devised by Mr. W. Crookes, F.R.S., and Mr. F. I. Ricarde-Seaver, F.R.S.E. The 
 process, which is simple and inexpensive, is fully described in their patent, No. 10,164 of 1889. 
 They cause the water-gas, as at present produced, to pass at red heat over a mixture of caustic 
 soda and quicklime. The water in the soda is decomposed, its oxygen going to the carbon mon- 
 exide and converting it into carbonic acid, which latter instantly unites with the soda and lime, 
 while the hydrogen is liberated and takes the place of the carbon monoxide in the water-gas. 
 The mixture, when spent, can be revivified by dissolving out the carbonate of soda with water and 
 causticising it afresh in the ordinary manner. The poisonous character of the gas is thus entirely 
 removed without injury to its combustion value, and it can be easily enriched if required for 
 illuminating purposes. [EmTOB.] 
 
SECT; I.] 
 
 GAS ANALYSIS. 
 
 small support in the cover of the box. The four glass cocks close perfectly, and never 
 stick fast if handled in an intelligent manner. The cock tube is bent round at its front, 
 and connected with the U-tube, B, the limbs of which contain cotton-wool, whilst there 
 is a little water in the lower bend, in order to keep back any soot or dust, and to satu- 
 rate the aspirated gas with water before it is measured. The end of the three-way 
 cock which is turned backwards is connected by a caoutchouc tube with the caoutchouc 
 
 Fig. 47- 
 
 sucker, C, by means of which it is easy to fill the gas entrance tube and B with the 
 gases to be examined. The combination of the gases takes place in the U-shaped vessels, 
 D, E, and F, fixed below in notches and connected by short caoutchouc tubes with the 
 cock tube, and filled with glass tubes to increase the surfaces of contact. As the mark 
 m is above this point of connection, it is always moistened with the liquid concerned, 
 and is thus easily kept perfectly tight. The other end of the U-tube is closed with a 
 
52 CHEMICAL TECHNOLOGY. [SECT. i. 
 
 caoutchouc stopper containing a small glass tube, x ; the small tubes are connected in 
 common with a slack caoutchouc ball, holding about 200 c.c. to keep off oxygen. 
 
 When the apparatus is to be used, the cylinder inclosing the burette, A, and the flask, 
 L, are first filled with distilled water. To fill the three absorption bottles, the stoppers 
 with the glass tubes, x, and the caoutchouc ball, G, are taken off, and there is poured 
 into D about no c.c. potassa-lye of sp. gr. 1*20 to 1-28, so that it is about half full. 
 
 Further, we dissolve 18 grammes pyrogallol in 40 c.c. hot water, 70 c.c. of potassa- 
 lye of the above strength are added, and the mixture is poured into E, to take up 
 oxygen. For determining carbon monoxide, we place beforehand 35 grammes copper 
 chloride with 200 c.c. of strong hydrochloric acid and a few clippings of sheet-copper in 
 a well-stoppered bottle, and let them stand for two days with frequent shaking; 120 c.c. 
 of water are added, and the vessel F is charged from this solution. The three glass 
 cocks are closed, the cock c is set vertically, and the bottle L is lifted up so that the 
 water fills the burette, A, the cock c is turned a quarter to the left so that the second 
 aperture leads to the tube B, the cock of D is opened, the bottle L is lowered, and the 
 pinch-cock fixed upon the tube s is cautiously opened so that the potassa-lye rises to 
 the mark m when the cock is closed. In like manner the liquids of the two other 
 vessels are drawn up to the mark m, keeping the eye constantly fixed upon the ascend- 
 ing liquid. The three stoppers with the glass tubes, x, are then inserted air-tight. 
 Into the tube B there is first poured a little water, both limbs are loosely filled with 
 cotton-wool, the stoppers are re-inserted, and the little tube, n, is connected by a caout- 
 chouc tube with the glass tube, or at high temperatures with the porcelain tube, which 
 is luted with clay air-tight into the chimney, &c., in order to prevent the access of 
 atmospheric air. 
 
 To ascertain if the apparatus is air-tight, the cock c is placed vertically, the 
 caoutchouc pipe is pressed closely to the tube in the chimney either with the pinch- 
 cock or with the hand, and the pinch-cock of s is opened. The water-column in A 
 sinks a little, but it must then remain standing immovably. A continued slow 
 sinking must be remedied either by fitting the caoutchouc pipe more closely, or 
 pressing in the stoppers, or lubricating the glass taps with vaselin mixed with a little 
 paraffine. 
 
 After the burette, A, has been filled with water up to the mark 100, by lifting the 
 bottle L, the cock c is placed so that the connection of the aspirator, C, with the 
 chimney is established through the tube B, suction is effected by pressing C ten to 
 fifteen times, until the entire channel is filled with the gases in question. This is 
 best effected by pressing C with the left hand, closing the tube r with the thumb of 
 the right hand, letting the ball expand by opening the left hand, raising the thumb, 
 compressing C again, and so on until the object is effected. The cock c is then again 
 set vertically, the pinch-cock of s is opened, and the bottle L is lowered, so that the 
 burette, A, is filled to o with the gases to be examined ; thereupon c is again closed 
 by turning it a quarter to the left. The gas is now shut in between the four glass 
 cocks and the column of water in A. 
 
 For determining the carbon dioxide, the cock of D is opened, and L is raised with 
 the left hand, so that on opening the pinch-cock at s with the right hand the gas passes 
 over into D, L is lowered again until the potassa-lye in D reaches to the junction of 
 the flexible tube under m, and the gas is once more driven into the potassa vessel by 
 raising L. On lowering L and cautiously opening the pinch-cock, the potassa-lye is 
 again allowed to rise to the mark m, the glass cock is closed, the pinch-cock is opened, 
 the bottle L is held close to the burette so that the water in both vessels stands at an 
 equal height, the pinch-cock is again closed, and the residual volume is read off. 
 The level of the water shows directly the percentage of the carbonic acid by volume in 
 the gas. In the same manner the gas is passed two or three times into E, until no 
 
SECT. I.] 
 
 GAS ANALYSIS. 
 
 53 
 
 Fig. 48. 
 
 further decrease of volume ensues ; the reading gives the joint volume of carbon 
 dioxide and oxygen, whilst carbon monoxide is further absorbed by a similar treatment 
 in F. In ordinary fires it is generally needless to examine for carbon monoxide if a 
 few per cents, of oxygen have been found. 
 
 When the analysis is thus completed the cock c is again placed horizontally, L is 
 lifted, the pinch-cock is opened, and the water is let flow up to 100 in the burette, c is 
 again set vertically, the channel is again filled with the gas by means of C, and a fresh 
 determination is made. If, as is usual, no carbon monoxide is present, with a little 
 experience it will be found practicable to effect every five minutes an analysis accurate 
 to one-tenth per cent. 
 
 If after 100 to 200 analyses the absorption becomes sluggish, the vessels are 
 emptied by means of a siphon, rinsed with distilled water, and filled anew as before. 
 If by inattention the absorption liquid should rise in the cock-tube, the bottle L is 
 raised, the pinch-cock opened, and the solution 
 is thus rinsed back into the vessel by the dis- 
 tilled water. If this is not quite successful, 
 the flexible pipe, a, is taken off the cock c, the 
 latter is turned half way round, and, by lifting 
 L, water is let flow through the cock-tube and 
 the cock c (the others are closed) until perfectly 
 clean. If the water in the burette becomes im- 
 pure, it must be changed. Before putting the 
 apparatus away all the glass cocks must be 
 lubricated afresh with vaseline. 
 
 If in examining water-gas or generator-gas 
 we wish also to determine hydrogen and methan, 
 we may connect the apparatus above described 
 without a mercurial trough, as follows : The 
 working-tube, A (Fig. 48), is closed below with 
 a caoutchouc stopper having a glass tube, g (not 
 too narrow), which is fixed at v to the bottom 
 plate, and connected with a bottle of mercury, 
 F, by means of a strong flexible tube with a 
 screw pinch-cock. The platinum wires above 
 are fused in for electric ignition. The measur- 
 ing-tube, M, and the pressure-tube, D, are like- 
 wise connected with the bottle L by means of 
 a glass tube and a flexible pipe inserted by a 
 caoutchouc plug and secured to the bottom 
 plate. It is advisable to 
 fix a small brass cap round 
 the point of connection, e, 
 since it may otherwise 
 happen that, on exploding 
 the gaseous mixture by 
 means of an induction 
 spark, the caoutchouc con- 
 nection may spring off. 
 
 In executing the analy- 
 sis, the tubes A, M, D (the 
 
 latter up to O), are filled with mercury by raising the two bottles, the pinch-cocks on 
 the flexible pipes and the three glass cocks are closed, so that the end of the pipe a 
 
54 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 remains filled with water (or mercury), one of the drawn-out ends of the glass globe con- 
 taining the sample of gas is introduced, the point is broken off within the flexible pipe, 
 the other end is plunged into water and its point also is broken off, the cock d is turned 
 so as to make connection with the tube A, and the sample of gas is sucked over to A by 
 lowering the mercury bottle, F. The cocks d and h are now turned round 90, and the 
 needful quantity of gas is forced into the measuring-tube, M, by raising the mercury 
 bottle, F, and lowering the other bottle, L. If there is contained in the tube A a residue 
 of gas and any water which has been drawn over, they are forced outwards by the cock d. 
 The sample of gas is measured, 0*6 to o'8 c.c. of potassa-lye are introduced into the tube 
 A through the funnel, t, the sample of gas is passed over from M and A, and, after the 
 carbon dioxide has been absorbed, again to M. The potassa-lye is only allowed to rise 
 to a mark immediately before d, which can be seen during the calibration of the tube. 
 When the carbonic acid has been determined and the presence of oxygen tested with 
 pyrogallol, the tube A must be carefully cleansed up to the cock d, as otherwise after 
 the explosion a part of the carbonic acid formed is immediately dissolved and the con- 
 traction is thus rendered great. This is effected by pouring about 5 c.c. water into the 
 funnel, t, lowering the bottle F, and then lifting it so that the liquid flows off through 
 the flexible pipe, a, into a bottle connected by means of a short glass tube and a long 
 flexible pipe. This is repeated three or four times. If by inadvertence any potassa- 
 lye has passed beyond d up to h, or even to M, after the cleansing of the tube A has 
 been completed water is again let enter through the funnel, t ; F is raised until all air 
 has been removed through the cock n and the flexible pipe a, when the pinch-cock is 
 closed on a and the water is allowed to pass towards M by turning the cocks d and h 
 round for 90. Then the bottle L is raised and F is lowered, so that the sample of gas,, 
 the water, and some mercury pass over to A. When this is done the specimen of gas 
 is let return to M, the cock d is closed towards M as soon as the liquid almost touches. 
 it, then immediately also h, and the water is again let flow off through a. Care is 
 taken that the end of the flexible pipe a always remains filled with water or mercury. 
 A few drops of liquid should also remain in the funnel, t. The absorption of carbon 
 dioxide and oxygen is much promoted by letting the sample of gas pass ten or twelve 
 times from one tube to the other without the liquid touching the cock -tube. For this 
 purpose the bottles, F and L, are taken one in each hand and lowered alter- 
 nately, keeping the eye constantly upon the liquid as it ascends in A and M. 
 The oxygen required for burning the combustible gases is best obtained 
 electrolytically. This can be conveniently effected by means of A. W. Hof- 
 mann's apparatus for the decomposition of water, or with the U-tube (Fig. 
 49) fixed upon a simple foot and filled up to the cock with water containing 
 sulphuric acid. The point of the tube s (its platinum electrode is connected 
 with the positive pole of a Taucher battery) is placed in the end, a, of the 
 flexible tube, filled with water, and the oxygen is let pass over to A and 
 thence into the tube M. If the end of the tube a is completely filled with 
 mercury, the oxygen may be at once passed into M. After measurement, the 
 gaseous mixture is driven to A, the spark is passed, the contraction deter- 
 mined as usual, the carbon dioxide and the nitrogen are determined and cal- 
 culated as given below. If the gaseous mixture is not so far known that the 
 effect of the explosion may be judged with certainty in the first place, about 
 100 vols. are allowed to pass to A, the cocks d and h are closed, the 
 mercury-bottle F is set on the bottom plate of the apparatus, the pinch-cock 
 is opened so that the gas is strongly expanded, and the spark is let pass 
 over. It is then easily seen whether, on exploding the larger residue, a 
 diminution of pressure must be applied to reduce the force of the explosion. If the 
 gas contains less than 30 per cent, of combustible ingredients, it may be placed under 
 
 Fig. 49. 
 
SECT. I.] 
 
 GAS ANALYSIS. 
 
 55 
 
 an increased pressure ; if up to 3040 per cent., it should be exploded at the ordinary 
 atmospheric pressure ; up to 40-50 per cent., at a reduced pressure. 
 
 In manufacturing laboratories water may often be used in the bottle L, but 
 in F mercury is necessary. The tube D may be dispensed with ; M is graduated, not 
 in millimetres, but in 100 vols. ; the water level in the bottle L and the tube M is 
 placed at an equal height before reading off, so that as during the short time required 
 for an analysis the temperature and the height of the barometer may be regarded as 
 constant all calculations are needless. But as this latter advantage can only be 
 secured by placing the mercury in M and D exactly at the same height before each 
 reading, the author prefers the apparatus (Fig. 48) with mercury in both bottles. 
 
 As a lubricator for the cocks, the author recommends a mixture of melted caout- 
 chouc and vaseline. This is prepared by melting two parts of pure caoutchouc at the 
 lowest possible temperature in a covered porcelain crucible, adding one part of vaseline, 
 and stirring till cold. The readings are calculated for o and 1000 mm. pressure of 
 mercury according to 
 
 with the aid of the tables. 
 
 ___ _ - 
 1000 (i + (0-00366 x t] ) 
 
 Tension qftJie Vapour of Water according to jRegnault :- 
 i = temperature Centigrade; wi=tension in millimetres. 
 
 t. 
 
 m. 
 
 t. 
 
 m. 
 
 t. 
 
 m. 
 
 t. 
 
 m. 
 
 I2'0 
 
 10-46 
 
 I5-0 
 
 I2-7O 
 
 18-0 
 
 I5-36 
 
 21 -O 
 
 18-50 
 
 12*2 
 
 io - 6o 
 
 I5-2 
 
 12-86 
 
 18-2 
 
 I5-55 
 
 21'2 
 
 1872 
 
 I2'4 
 
 1073 
 
 I5-4 
 
 I3'03 
 
 18-4 
 
 1575 
 
 21-4 
 
 18-95 
 
 12*6 
 
 10-88 
 
 15-6 
 
 I3-20 
 
 18-6 
 
 I5-95 
 
 21'6 
 
 I9-19 
 
 12-8 
 
 1 1 -02 
 
 15-8 
 
 I3'37 
 
 18-8 
 
 16-15 
 
 21-8 
 
 1942 
 
 13-0 
 
 ii'i6 
 
 i6'o 
 
 I3-54 
 
 19-0 
 
 16-35 
 
 22'0 
 
 19-66 
 
 13-2 
 
 11-31 
 
 16-2 
 
 I3'7I 
 
 19-2 
 
 I6-55 
 
 22'2 
 
 19-90 
 
 3 '4 
 
 11-46 
 
 16-4 
 
 I3-89 
 
 19-4 
 
 1676 
 
 22'4 
 
 2O-I4 
 
 13-6 
 
 ii'6i 
 
 16-6 
 
 14-06 
 
 19-6 
 
 16-97 
 
 22'6 
 
 20-39 
 
 13-8 
 
 11-76 
 
 16-8 
 
 I4-24 
 
 19-8 
 
 I7-I8 
 
 22-8 
 
 20-64 
 
 14-0 
 
 11-91 
 
 17-0 
 
 I4-42 
 
 20 '0 
 
 I7-39 
 
 23-0 
 
 20-89 
 
 14-2 
 
 1 2 '06 
 
 17-2 
 
 14-61 
 
 2O '2 
 
 I7-6l 
 
 23-2 
 
 21-14 
 
 14-4 
 
 I2'22 
 
 I7-4 
 
 1479 
 
 20 '4 
 
 I7-83 
 
 23-4 
 
 21-40 
 
 14-6 
 
 I2-38 
 
 17-6 
 
 14-08 
 
 20 -6 
 
 I8-05 
 
 23-6 
 
 21-66 
 
 14-8 
 
 12-54 
 
 17-8 
 
 I5-I7 
 
 20-8 
 
 I8-27 
 
 23-8 
 
 21-92 
 
 Log. i + 0*00366 . t. 
 
 t. 
 
 log. 
 
 t. 
 
 log. 
 
 t. 
 
 log. 
 
 t. 
 
 log. 
 
 I2'O 
 
 0-01867 
 
 I5-0 
 
 0-02321 
 
 18*0 
 
 0-02771 
 
 21 *O 
 
 O-O32I6 
 
 I2'2 
 
 0-01897 
 
 I5-2 
 
 0-02351 
 
 18*2 
 
 0-02801 
 
 21'2 
 
 0*03246 
 
 I2'4 
 
 0-01928 
 
 I5-4 
 
 0*02381 
 
 18*4 
 
 0*02831 
 
 21*4 
 
 0*03275 
 
 I2'6 
 
 0-01958 
 
 I 5 -6 
 
 0-02411 
 
 18-6 
 
 0*02861 
 
 21*6 
 
 0*03305 
 
 12-8 
 
 0-01989 
 
 15-8 
 
 0-02441 
 
 18-8 
 
 0*02891 
 
 21*8 
 
 0*03334 
 
 13-0 
 
 0*02019 
 
 16-0 
 
 0-02471 
 
 19*0 
 
 0*02921 
 
 22*0 
 
 0*03363 
 
 13-2 
 
 O-02O49 
 
 16-2 
 
 0-02501 
 
 19-2 
 
 0*02951 
 
 22-2 ; 0*03393 
 
 I3'4 
 
 0*02079 
 
 16-4 
 
 0-02531 
 
 19-4 
 
 0-02980 
 
 22 '4 
 
 0*03422 
 
 13-6 
 
 O-O2IIO 
 
 16-6 
 
 0-02561 
 
 19-6 
 
 0-03009 
 
 22'6 
 
 0-03452 
 
 13-8 
 
 O-O2I4O 
 
 16*8 
 
 0*02591 
 
 19-8 
 
 0*03039 
 
 22 8 
 
 0*0348l 
 
 14*0 
 
 O-O2I7O 
 
 17*0 
 
 0*02621 
 
 20*0 
 
 0-03068 
 
 23-0 
 
 0-035IO 
 
 14-2 
 
 O'O22OO 
 
 17-2 
 
 0-02651 
 
 2O '2 
 
 0*03098 
 
 23-2 
 
 0*03539 
 
 14-4 
 
 O-O223O 
 
 17-4 
 
 0-02681 
 
 20-4 
 
 0-03128 
 
 23-4 
 
 0*03568 
 
 14-6 
 
 O-O226I 
 
 17-6 
 
 0-02711 
 
 20 -6 
 
 0-03157 
 
 23-6 
 
 0*03598 
 
 14-8 
 
 O-O229I 
 
 17*8 
 
 0-02741 
 
 20-8 
 
 0-03187 
 
 23-8 
 
 0-O3627 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 Reduction, of the Readies of the Barometer to o~ 
 
 B-6. 
 
 Correct. 
 
 B-6. 
 
 Correct. 
 
 B-4. 
 
 Correct. 
 
 40O 
 
 0-0684 
 
 600 
 
 0*1027 
 
 800 
 
 0-1369 
 
 420 
 
 0'O7I9 
 
 620 
 
 0-1061 
 
 820 
 
 0-1403 
 
 440 
 
 0-0753 
 
 640 
 
 o'io95 
 
 840 
 
 0-1437 
 
 460 
 
 0*0787 
 
 660 
 
 0-1129 
 
 860 
 
 OT47I 
 
 480 
 
 0-0821 
 
 680 
 
 0-1163 
 
 880 
 
 0-1506 
 
 500 
 
 0-0856 
 
 7OO 
 
 0-1198 
 
 900 
 
 0*1540 
 
 520 
 
 0-0890 
 
 72O 
 
 0*1232 
 
 920 
 
 0-1574 
 
 540 
 
 0-0924 
 
 740 
 
 0-1266 
 
 940 
 
 0-1608 
 
 560 
 
 0-0958 
 
 760 
 
 0-1300 
 
 960 
 
 0-1643 
 
 580 
 
 0-0992 
 
 780 
 
 0-1335 
 
 980 
 
 0-1677 
 
 E.g., in an analysis the reading of the barometer was 756*6 mm. at 20-8, so that, 
 with a correction of 2*7 mm. for the glass scale, B, = 753^9 mm. To the reading of the 
 measuring-tube, M, = 546-0, corresponds v, 5 53' 5. The position of the mercury in the 
 pressure tube, D, was also 546*0, consequently b-o, and as, at 20*8, e= 18*3 mm., 
 (B - b - e) = 735-6 mm. and V = 378*34, as 
 
 Log- 553 '5 
 Log. 735*6 
 Log. looo (i+ 0-00366 x 20'8) . 
 
 Therefore log. V . . . 
 andV 
 
 Collocated with the second reading : 
 
 M. v. D. 
 
 546-0 ... 553-5 ... 546-0 
 370-0 ... 378-8 ... 29-1 
 
 2-74312 
 2-86664 
 3-03187 
 
 2-57789 
 
 (B-6-6.) 
 735-6 
 
 V. 
 
 378-34 
 378-41 
 
 Mean 378-38 
 
 If the two readings do not agree to at least 0*4, there is an error, and the experi- 
 ment must be repeated. 
 
 Fig. 50. 
 
 Fig. 51- 
 
 In order to preserve samples of gas for a 
 length of time, the gas is drawn by means of 
 the small caoutchouc aspirator, C (Fig.47),through 
 a glass globe holding 100 c.c. (Fig. 50), and 
 sealed off before the lamp at c, c. In order to 
 
 Fig. 52. 
 
 Mauerwerk Masonry. 
 Mauer Wall. 
 
 perform this sealing even in the open air, the author uses a small oil lamp, n, with 
 a brass screen, shown in section (Fig. 51). The nozzle of the blow-pipe, e, is admitted 
 
SECT, i.] GAS ANALYSIS. 57 
 
 through a corresponding aperture, opposite to which is another opening through which 
 the blow-pipe flame issues. 
 
 The sample of gas must be drawn through a glass or porcelain tube (not iron), and 
 taken at a point where the gases are already mixed. In ordinary fires this takes place 
 where the gases of combustion leave the apparatus (steam boiler, &c.), and in any case 
 before the draught-slide, S (Pig- 52), as cold air is drawn in by the split in the 
 masonry. It is convenient to have fixed in the vault of the smoke-channel a tube, e, 
 2 or 3 c.m. in width, a piece of a gas-pipe, luting it well, and inserting in it, by 
 means of a caoutchouc plug, the thermometer, t, and the glass tube, r, for taking 
 specimens. The mercurial vessel of the thermometer (i metre in length) and the 
 lower aperture of the glass tube, r, should be in the middle of the current of gas, as 
 the figure shows. 
 
 The loss of heat in the smoke-gases appears from the following calculations. If 
 the gas-analyses made during an experiment show on the average k per cent, carbon 
 dioxide, o per cent, oxygen, and n per cent, nitrogen, the proportion of air consumed 
 to that theoretically required is, when the air contains x per cent, of oxygen and z per 
 cent, of nitrogen 
 
 x - (z o : n) n - (zo:x) 21 - (79 o : n) 
 
 for 2 1 per cent, oxygen ; i kilo, of the coal with o per cent, of carbon gives = 
 1-854 c : 100 = K cubic metre carbon dioxide (at o and 760 mm.), Ko : k = O cubic 
 metre and K n : k = N cubic metres of nitrogen. The quantity, W, of the watery 
 vapour contained in the smoke-gases is calculated from the moisture of the coal 
 (o-oi w), that formed by the combustion of the hydrogen (0-09 h), and that contained 
 in the air serving for combustion (v L/). The total quantity of the combustion-gases 
 from i kilo, of coal is therefore 
 
 K (o + n) 28 W 
 
 K + T H ITT + o cubic metre at o and 760 mm. 
 
 K 200 '4 o '005 
 
 or + 1-43 + 1-257 N + + W kilo. 
 
 100 100 
 
 If the smoke-gases contain carbon monoxide and hydrocarbons, it must be remem- 
 bered that, according to the formulae C + 2 = CO 2 , + = CO, and C + 2H,= CH 4 , 
 each cubic metre of these gases contains 0-5395 kilo, carbon. If the analysis shows 
 k per cent, carbon dioxide, d per cent, carbon monoxide, m per cent, methan, h per 
 cent, hydrogen, o per cent, oxygen, and n per cent, nitrogen, as well as per cubic 
 metre r kilo, carbon as soot, then i cubic metre of these gases contains 
 
 (k + d + m) 0-^395 , .. , 
 
 ^ ' ^^2 + r kilo, carbon, 
 
 100 
 
 and i kilo, of coal yields 
 
 cC : loo 
 
 100 
 in which we have 
 
 d + m 
 
 x 0-5395 + 
 
 = I cubic metre dry gcises, 
 
 Gk Kd Gd 
 
 = K cubic metre CO,,, -j- or CO, 
 
 Gm Gr A Go^ , G ra . 
 
 methan, H, O, and nitrogen. 
 
 The proportion of soot is so trifling that it may be neglected. 
 
 Sulphurous or sulphuric acid and the vapour of water may be calculated as above, 
 the weight of these gases being readily found with the aid of the following table : 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 ,- 
 
 
 
 
 
 
 
 
 
 Weight of 
 
 Specific Heat of 
 
 
 
 
 
 
 
 
 
 Specific Hent. 
 
 i Cubic Metre, 
 kilos. 
 
 i Cubic Metre. 
 
 CO., at 10 to isc 
 
 f 
 
 
 
 
 
 
 
 0*2091 
 
 1-9781 
 
 0-414 
 
 20C 
 
 > 
 
 
 
 
 
 
 
 0-2156 
 
 
 
 0-427 
 
 25< 
 
 > 
 
 
 
 
 
 
 
 O'222O 
 
 
 
 D'439 
 
 3oc 
 
 ) 
 
 
 
 
 
 
 
 O-228l 
 
 
 
 0-451 
 
 35< 
 
 > 
 
 
 
 
 
 
 
 0-234I 
 
 
 
 0-463 
 
 IOOC 
 
 ) 
 
 
 
 
 
 
 
 O-289I 
 
 
 
 0-572 
 
 I5cx 
 
 ) 
 
 
 
 
 
 
 
 0-3I80 
 
 
 
 0-629 
 
 2OOC 
 
 ) 
 
 
 
 
 
 
 
 03290 
 
 
 
 0-651 
 
 CO . 
 
 
 
 
 
 
 
 
 O-2450 
 
 I -2593 
 
 0-308 
 
 O 
 
 
 
 
 
 
 
 
 0-2175 
 
 I -4303 
 
 0-311 
 
 N 
 
 
 
 
 
 
 
 
 0-2438 
 
 I '2566 
 
 0-306 
 
 H 
 
 
 
 
 
 
 
 
 3-4090 
 
 0-0896 
 
 0-305 
 
 Steam 
 
 
 
 
 
 
 
 
 0-4805 
 
 0-8048 
 
 0-387 
 
 Methan (CH 4 ) 
 
 
 
 
 
 
 
 
 0-5929 
 
 07160 
 
 0-424 
 
 SO 2 . 
 
 
 
 
 
 
 
 
 0-ISS3 
 
 2-8640 
 
 0-445 
 
 The loss of heat by the higher temperature of the smoke-gases is found by multi- 
 plying the separate quantities of the gases by the specific heat and the excess of 
 temperature of the gases above the air serving for combustion. 
 
 The loss from incomplete combustion is found from the combustion value of the 
 unburnt coal in the cinders and the combustible ingredients, if any (carbon monoxide, 
 methan, hydrogen, soot), of the smoke-gases. 
 
 As an instance of the loss of heat by the imperfect combustion of i kilo, of coal, 
 the following figures may serve : 
 
 
 
 
 Combustion 
 
 
 f nil if* TVTAtrPs 
 
 
 VllllP 
 
 
 
 
 Heat-units. 
 
 CO . . 
 
 0-292 
 
 0-3680 
 
 893 
 
 Methan 
 
 0-073 
 
 0-0520 
 
 620 
 
 H 
 
 0-073 
 
 0-0065 
 
 I8 7 
 
 Soot . 
 
 
 0-0080 
 
 65 
 
 Carbon in cinders 
 
 
 
 0-0050 
 
 40 
 
 
 
 
 1805 
 
 On the basis of the experience which the author has collected in more than 4000 
 gas analyses, he considers the apparatus figured and described above (Fig. 47) the best 
 and the most convenient for judging of steam-boiler furnaces, domestic stoves, brick 
 and porcelain furnaces, ultramarine furnaces, and alkali furnaces, and as also well 
 adapted for examining blast-furnace and cupola gases, and of puddling furnaces ; and 
 even for examining the kiln-gases in sulphuric acid works, the saturation gases in sugar- 
 works, and for petroleum lamps and gas engines. In order to determine the small 
 quantities of combustible gases which occur in normal combustion-gases, even accurate 
 volumetric procedures are generally insufficient. Those with platinum coils (Orsat), 
 palladium-asbestos, &c., do more harm than good, as they lead to wrong conclusions. 
 In such cases gravimetric determinations must be made with a sample drawn directly 
 through the apparatus for a considerable time without the interposition of a gasometer. 
 But at the same time a volumetric test should be made every five or ten minutes with 
 the apparatus described above, in order to watch the progress of the combustion. 
 
 For gas fires the same apparatus is sufficient for ordinary control. Care must be 
 taken that the generator- gases contain a minimum of carbon dioxide along with much 
 carbon monoxide, whilst the gases escaping should contain a maximum of carbon 
 dioxide and no monoxide. 
 
 Steam-boiler Firing. By far the majority of steam boilers have too large a grate, 
 and work, in consequence, with a great excess of air, losing much heat in the chimney. 
 
SECT, i.] STEAM BOILER FIRING. 59, 
 
 The gases from a steam-boiler fire, for instance, contained i'8 per cent. C0 2 and 19 per 
 cent. O at 169, representing a loss of heat of 3921 heat-units, or 60 per cent, of the 
 total combustion value. After the masonry and the grate were thoroughly repaired, 
 and the strength of the draught was regulated according to the indications of gas 
 analyses, the gases contained 18*7 per cent, of carbon dioxide and 17 per cent, of 
 oxygen, corresponding to a loss of heat of only 508 heat-units, or 7 per cent. ! In 
 judging a fire it is necessary to look under the grate ; all the intervals between the 
 bars must be equally bright. 
 
 For ordinary control it is sufficient to determine the CO 3 and in three samples of 
 the gas taken in rapid succession. The more C0 2 (without CO) is present, the better 
 is the firing. For a coal fire n k + o must be about 20, if the combustion is complete. 
 In large works it is advisable to connect a narrow lead pipe with the pipe fixed in 
 the flue (inserting, however, a tuft of asbestos to keep back soot and dust), and to> 
 carry it into the laboratory. In order to take samples of gas at any time, so much gas 
 is first drawn off as the pipes will hold, and the sample is then taken. 
 
 In conducting heating experiments (which, according to the importance of the case, 
 should last from three to ten hours), six to twelve samples are taken hourly, deter- 
 mining their proportion of C0 2 and O, and of CO if present. If the gases contain 
 notable quantities of the latter, which is the case only in defective boiler furnaces, the 
 stoking must be altered, or samples of gas must be sealed up in bulbs and examined 
 for carbon monoxide, hydrogen, and hydrocarbon. The moisture and the temperature 
 of the air entering the fire-box should be determined hourly. 
 
 For deciding on the duty of a steam boiler by an evaporation experiment, which 
 should be continued at least for ten hours, the Association of German Engineers and 
 the Steam Boiler Association have agreed on the following regulations : 
 
 Before beginning the experiments, the boiler must be cleaned, examined within 
 and without, and tested for leakage; the flues are swept; the joints of the walls 
 pointed and plastered over. The boiler must then be kept for at least one day in, 
 normal work, in order that it may be in its ordinary permanent condition. 
 
 The level of the water and the pressure of steam are accurately noted at the com- 
 mencement of the experiments, and are kept all the time as uniform as possible. Th& 
 pressure of steam is gauged by the manometer, and noted every fifteen minutes. 
 
 The feed-water is either weighed or measured in tared vessels, the contents of which 
 are regulated according to the temperature. In accurate experiments weighing alone is 
 admissible. The feeding must be effected regularly, and with a minimum of interrup- 
 tion ; feeding must be avoided shortly before the beginning and the end of the experi- 
 ment. The temperature of the water is measured in the cistern, from which it i& 
 drawn every thirty minutes, and just before its entrance into the boiler. This must be 
 done with every feed. Feeding with injectors is permissible only when their supply of 
 steam is drawn from the boiler in question. 
 
 If simultaneously with the examination of the performance of the boiler there is 
 carried on an inquiry into the consumption of steam in a machine supplied by the 
 boiler, the use of steam pumps for feeding is inadmissible if they derive their steam 
 from the experimental boiler or if their waste steam comes in contact with the feed- 
 water. 
 
 All leakage from the boiler fittings and all water blown off must be caught and 
 taken into account. The weight of water thus ascertained must be recalculated as 
 feed-water at o and steam at 100. (See Table.) 
 
 In determining the consumption of water, care must be taken that the fire at the 
 beginning of the trial is charged and cleaned normally, ash and slag being removed 
 from the ash-box. If the ash cannot be removed, the residues therein should be 
 brought to a given level before and after the experiment. The fire must be in the 
 
6o 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 same condition at the end of the experiment as at the beginning. The duration of the 
 heating and the consumption of fuel are noted. The fuel consumed during the experi- 
 ment is to be weighed and suitably broken up. The fire is fed regularly. Slags and 
 ash are weighed and examined for the presence of combustible matter. 
 
 Experiments in which notable quantities of water have evidently been carried away 
 mechanically by the steam are useless. No accurate and trustworthy methods are 
 known for the determination of such water. 
 
 Evaporation experiments without a simultaneous examination of the smoke-gases 
 have little, if any, value. 
 
 The total evaporation-heat of water is, according to Regnault, = 606*5 + '35 ^ 
 
 Temperature t of 
 Saturated Steam. 
 
 Steam Tension 
 
 Pressure on i Square 
 Centimetre in Kilos. 
 
 Evaporation-heat. 
 
 in mm. 
 
 in Aim. 
 
 O 
 
 4-6 
 
 . 
 
 
 
 606-5 
 
 20 
 
 I7-4 
 
 . 
 
 
 
 612-6 
 
 40 
 
 54 '9 
 
 0-072 
 
 0-075 
 
 618-7 
 
 60 
 
 148-8 
 
 0-196 
 
 0-203 
 
 624-8 
 
 80 
 
 354-5 
 
 0-466 
 
 0-482 
 
 630-9 
 
 IOO 
 
 760-0 
 
 I'OOO 
 
 1-033 
 
 637-0 
 
 no 
 
 1075 '4 
 
 1-415 
 
 1-462 
 
 640-0 
 
 1 20 
 
 I49i '3 
 
 1-962 
 
 2-027 
 
 643-I 
 
 130 
 
 2030-3 
 
 2-671 
 
 2-760 
 
 646-1 
 
 140 
 
 2717-6 
 
 3-576 
 
 3^95 
 
 649-2 
 
 150 
 
 358I-2 
 
 4-712 
 
 4-869 
 
 652-2 
 
 1 60 
 
 4651*6 
 
 6'I2O 
 
 6-324 
 
 655-3 
 
 170 
 
 59617 
 
 7-844 
 
 8-105 
 
 658-3 
 
 1 80 
 
 7546-4 
 
 9-929 
 
 10-260 
 
 661-4 
 
 190 
 
 9442-7 
 
 12-425 
 
 12-834 
 
 664-4 
 
 Experiments executed by the author showed the following distribution of heat in 
 three boilers : 
 
 123-8 
 
 86-3 
 
 26-6 
 
 24-7 
 
 46-9 
 8-7 
 
 7790 
 
 ... 7720 . 
 
 .. 7630 
 
 74-9 
 
 ... 68-4 . 
 
 .. 83-6 
 
 2-1 
 
 ... 3'6 
 
 .. 0-9 
 
 
 
 
 
 .. 0-3 
 
 l6- 7 
 
 ... 19-3 . 
 
 .. 10-6 
 
 6-3 
 
 ... 8-7 . 
 
 .. 4-6 
 
 Coal to each square metre grate surface . kilos. 
 Water to each square metre of heating 
 
 surface 
 
 Combustion value of the coal determined 
 
 calorimetrically heat-units 
 
 Percentage of heat taken up in water . 
 
 Loss in cinders, &c per cent. 
 
 in gases imperfectly burnt ... 
 
 in higher temperature of the smoke-gases 
 
 by conduction and radiation . . 
 
 The grate of the boiler furnace should be easily cleaned ; hence all designs of 
 grates which obstruct such cleansing with the object of giving the air free and uniform 
 access to the fuel cannot be recommended e.g., that of Fletcher (Fig. 53). Those 
 
 with lateral projections on the bars, the so-called 
 
 ' 53- polygon grates, are to be rejected. For fuel which 
 
 does not cake, the oblique grates (e.g., Tenbrinck) 
 are worth attention, as here there occurs a partial 
 degasifying of the fuel as it slides downwards, and 
 thus the formation of smoke is to a great extent 
 prevented. 
 
 This object is more perfectly effected by the 
 so-called mechanical grates, which drive the fuel continuously into the fire-box, so 
 that the gases evolved in front pass over the ignited coke and are burnt. One of the 
 earliest arrangements of this kind is the chain grate. It is costly, soon wears out, 
 and has been gradually abandoned.* 
 
 * We have observed that it brings out a considerable quantity of imperfectly burnt fuel, ami 
 lets it fall into the ashes, as waste. [EDITOR.] 
 
SECT. I.] 
 
 HOUSE HEATING. 
 
 61 
 
 The arrangement of Dougal works well in practice.* All these devices, however, 
 are expensive and consume mechanical power. 
 
 It has been already remarked that the almost numberless devices for " smoke con- 
 sumption " are impracticable. Good gas-firing gets rid of smoke from the chimneys, 
 but it cannot be recommended for steam boilers. The best solution of the important 
 smoke problem is the substitution of coal-gas or water-gas burners for domestic fires, 
 and of the gas engine for the steam engine. This latter step will probably be very 
 generally adopted with the expiry of the Otto patent. f At Terni, near Rome, a mixture 
 of water-gas and generator-gas is used for a gas engine. For the production of 14*35 
 horse-power the engine consumes hourly ii'86 cubic metres water-gas and 36' 66 cubic 
 metres generator-gas, and works very satisfactorily. This is, per horse-power 
 
 0-83 cubic metre water-gas =2182 heat-units 
 2'55 generator-gas = 2422 
 
 or about 4600 heat-units. The same work, if performed with lighting-gas, would 
 require at least 0*9 cubic metre, representing 4770 heat-units. For producing the 
 above-named quantities of water-gas and generator-gas 075 kilo, of coke or coal will be 
 required, whilst for obtaining 0*9 cubic metre of coal-gas there would be consumed 
 3 kilos, of the best gas-coal (yielding only i -8 kilo, of coke as residue), whilst a steam 
 engine of the same power uses 4 kilos, of coals. There is besides the ease of distributing 
 the power from gas engines, so that they may claim the future both for small and 
 large industries. 
 
 House-heating. The object here in view is to heat dwelling-rooms, &c., uniformly, 
 with a minimum expenditure of fuel, and without rendering the 
 air impure. Hence all kinds of heating which do not carry off 
 the products of combustion are at once excluded e.g., the car- 
 bonatro stoves of A. Nieske, various coal-gas stoves, <fec. Such 
 arrangements testify to a marvellous thoughtlessness. 
 
 The forms of heating may be divided into separate arrange- 
 ments (fires and stoves) and collective arrangements (heating with 
 hot air, steam, or hot water). 
 
 Heating with open fires involves a great expenditure of fuel.f 
 The open fire is used in Germany only where appearance is aimed 
 at more than heating. The author cannot admit the alleged 
 advantages of heating with radiant heat. 
 
 Stove-heating is most common. To explain the action of an 
 iron stove we may take the diagram, Fig. 54. The fire-box, A, 
 -| metre in height, is lined with fire-clay ; the door to the fire- 
 box, a, with an oblique grate, and that to the ash-pit, B, are fitted 
 with screws, so that they may fit closely, as does also that through 
 which fuel is introduced, 6. The smoke-gases pass in the direc- 
 tion of the arrow through the top piece, C, and escape through 
 the sheet-iron pipe, D, to the chimney. 
 
 At the aperture, d, the thermometer, t (filled with nitrogen), is inserted for experi- 
 mental purposes by means of a good cork, the tube, e, leading to an apparatus for 
 
 a 
 
 * Dingier s Journal, 232, p. 346. 
 
 t Before coal-gas is used in the household it must be much cheaper, and before water-gas can 
 be safely introduced to warm our houses and cook our food it must be freed from carbon monoxide, 
 as already described. [EDITOR.] 
 
 $ Ninety per cent, of the heat generated being wasted. The recent " improvements " introduced 
 in England have been steps in the wrong direction. [EDITOR.] 
 
 Jahresber. 1887, p. 145. 
 
62 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 measuring the draught and the glass tube,/", which is connected with apparatus for the 
 analysis of the smoke-gases. These are thoroughly mixed by the bendings through 
 which they pass, so that specimens taken simultaneously at c have the same composition 
 to T ^ per cent. If anthracite is used, the gases have the composition given in the sub- 
 joined tables. 
 
 The results indicate a total loss of heat in the chimney of only 8 per cent., so that 
 92 per cent, of the heat remains in the room. 
 
 To obtain such favourable results the fire-room of all iron stoves must be lined 
 with fire-proof stone, or tiles of fire-clay. If the fuel touches the iron surfaces, com- 
 plete combustion is rarely possible. Further, the iron plates become overheated, so 
 that they allow carbonic oxide to permeate them, and they certainly singe all organic 
 dust, thus spoiling the air of the room. It would be desirable for the gases to descend 
 again in order to give off their heat still more completely through the sides of the 
 stove to the air of the room. 
 
 Time, 
 h. m. 
 
 C0 2 . 
 
 CO. 
 
 0. 
 
 N. 
 
 Temperature of 
 Escaping Gases. 
 
 Remarks. 
 
 2.50 
 
 I2'S 
 
 
 
 8-0 
 
 79 '5 
 
 240 
 
 Temperature in the laboratory, 12. 
 
 3-00 
 
 I2'6 
 
 
 
 7-9 
 
 79'5 
 
 241 
 
 i millimetre draught. 
 
 3.10 
 
 11 "5 
 
 
 
 9-1 
 
 79 '4 
 
 240 
 
 Fuel added, doors a and b closed. 
 
 3.20 
 
 u-8 
 
 trace 
 
 8-4 
 
 79-8 
 
 2O I 
 
 
 3-30 
 
 137 
 
 
 
 6-4 
 
 79 '9 
 
 234 
 
 
 3-40 
 
 14-1 
 
 
 
 6-2 
 
 797 
 
 242 
 
 
 3-50 
 
 I3'6 
 
 
 
 67 
 
 797 
 
 248 
 
 Fuel added. 
 
 4.00 
 
 I3-5 
 
 
 
 6-9 
 
 79-6 
 
 206 
 
 
 4.10 
 
 I3H 
 
 
 
 7-2 
 
 79 "4 
 
 229 
 
 
 4.20 
 
 i3'5 
 
 
 
 7-0 
 
 79 '5 
 
 248 
 
 
 4-30 
 
 13-1 
 
 
 
 7'4 
 
 79'5 
 
 247 
 
 
 4.40 
 
 I2'0 
 
 
 
 8-6 
 
 79 '4 
 
 246 
 
 
 If the stove is used full, the lower doors must be kept tightly closed, as otherwise 
 carbon monoxide may be formed, which, if the draught is defective, may pass out into 
 the room. The regulation of the supply of air is very important for the utilisation of 
 the heat. If, in the stove Fig. 54, the ash-pit door is opened, so that the air passes 
 through the horizontal grate into the fire-box, and also the door a, the temperature of 
 the escaping gases rises so rapidly that the thermometer has to be removed, whilst, in 
 accordance with the increased draught, the proportion of carbon dioxide falls, and the 
 loss of heat rises up to 40 per cent. 
 
 Hundreds of thousands of stoves in Germany which have imperfect doors or none 
 at all allow from 50 to 80 per cent, of the entire combustion value of the fuel to pass 
 up the chimney, a loss which amounts yearly to millions of marks. 
 
 Certain stoves, such as those of Sturm and Henschel, are not used or known in 
 Britain, and their description may therefore be omitted. 
 
 Earthenware stoves are generally built up of tiles. A Russian stove, e.g., is a 
 longish rectangular block, and has six smoke channels. Fig. 55 shows the plan, 
 Fig. 56 an elevation of the broad side, Fig. 57 of the narrow side, and Fig. 58 a 
 longitudinal section. From the fire-box covered with an arch, a, the fire rises up in 
 the flue i, descends again in flue 2, rises in 3, falls in 4, rises in 5, and falls in 6, 
 whence it escapes through the stove-pipe into the chimney. Near the connection of the 
 last flue with the stove-pipe a four-sided plate of cast iron (Figs. 59, 60, and 61) is 
 built in ; this plate has in the middle an aperture of 2 1 to 24 centimetres in diameter, 
 with an upright neck of 3 centimetres and an internally projecting margin of 2 centi- 
 metres. A cast-iron cover, a, provided with a handle, fits over the aperture, a second, 
 larger, cover, 6, with a projecting margin, fits over the neck and closes the whole. For 
 heating, the fire-box is filled with short pieces of wood, the wood is kindled, the door 
 
SECT. I.] 
 
 HOUSE HEATING. 
 
 being left open at first ; it is afterwards closed so that the air enters through its 
 apertures. 
 
 Experiments which the author carried out with a tile stove, 1*2 metre wide and 
 3 metres in height, showed that with a coal fire from 40 to 80 per cent, of the heat 
 escaped up the chimney, so that tile stoves are less suitable for giving out heat than 
 iron stoves. The surfaces which come in contact with the air of the room are kept 
 carefully free from sharp angles and roughnesses, and are covered with a glaze, all cir- 
 cumstances which impede the communication of heat as much as possible. Hence the 
 
 Fig- 55- 
 
 Fig. 58- 
 
 Fig. 56. 
 
 Fig- 57- 
 
 S I 
 
 Fig. 59- 
 
 Fig. 60. 
 
 Fig. 61. 
 
 gases pass into the chimney with about 100 more heat than that from the iron 
 stove (Fig. 55), the surface of which is covered with small ornaments in relief, and is 
 consequently well adapted for throwing off heat.* The loss of heat in tile stoves can 
 be diminished by carefully closing the doors. If the supply of heat to an iron stove 
 lined with fire-clay or tiles is properly regulated it retains the heat as long as a tile 
 stove. 
 
 Hot-air heating differs from stove heating by the circumstance that the fire is not 
 in the rooms to be heated, but outside, and often below them. As a specimen of a 
 successful arrangement of this kind the author describes that existing in his own 
 house. It has to supply six rooms with warm, pure air below, three dwelling-rooms, 
 A, B, C (Fig. 62) ; V, an ante-room ; D, kitchen ; above, one storey high (Fig. 63), A, 
 
 Tile stoves can of course be made with unglazed surfaces and small projecting ornaments. 
 
6 4 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. 
 
 library ; C, work-room ; D, laboratory. The heating arrangements are in the space 
 below B. 
 
 The air-entrance, K (Figs. 64-68), is underneath the veranda, on the south-western 
 
 Fig. 62. Fig. 63. 
 
 P Zufuhritngskana.!. 
 mAUufikanal. 
 B Rauchka.na.1. 
 
 Explanation of Terms. 
 
 Zvfulinmgskanal Access for air. 
 Abluftkanal Exit for air. 
 
 llaiichhanal 
 Ltiftschacht 
 
 Smoke channel. 
 Air shaft. 
 
 side of the house. The opening is covered with a wire grating, before which stands a 
 triple row of juniper bushes, so that all the coarser impurities are kept out. 
 
 The air-filter, F, is 2 metres wide, and has a total filtering surface of 50 square 
 metres. The arrangement is adapted for 5000 cubic metres air per hour, whilst the 
 
 Fig. 66. 
 
 heating itself requires only 2000 to 3000. Not the least disturbing influence has been 
 felt in the supply of air in three years. All the air entering has to pass through a 
 dense cotton tissue, which keeps back soot and dust. The air, freed from dust, passes 
 
SECT, i.] HEATING ARRANGEMENTS. 65 
 
 tnrough the channel, L, into the heating-room, becomes warmed in the tubes, C, and 
 passes at IT in to six vertical channels of smooth masonry (but not plastered), of which 
 five, as shown in Figs. 62 and 63, are placed in a niche of the corner room, and open 
 into the rooms 2 metres above the floor. From here the waste air escapes through 
 six shafts close above the floor. Coal is introduced at /, whilst the door t is opened 
 only to stir the fire ; the door a regulates the supply of air. 
 
 About 85 per cent, of the total combustion-value served to warm the rooms, and 
 5 to 7 per cent, more are not wasted, but serve to warm the staircase uniformly. 
 
 The greatest consumption of fuel in twenty-four hours was no kilos, of coal at art 
 outside temperature of 15 and a violent east wind with driving snow. At 4-3 
 and calm weather only 25 kilos, of coal were used. The objections raised against hot 
 air on the score of drying the air are completely groundless. 
 
 Water-heating. As is shown in the diagram, Fig. 67, the water heated in the 
 boiler, A, rises in the tube, c, up to d ; it becomes heavier again 
 by giving off' its heat in the pipes, f, laid down in the rooms, &c., Fig. 67. 
 
 to be heated, and flows back to the boiler. If the system of 
 pipes is left open at its highest point, e, no increase of pressure 
 can ensue, and we have a low-pressure water heating ; if the 
 system is closed so that the water may be heated to 1 80 -200 
 (Perkins' tubes), it is a high-pressure water heating. In the 
 latter case the pipes may be smaller, but there is the possibility 
 of an explosion. The warm water of artesian wells and that of 
 hot springs is used for heating conservatories, factories, &c. The 
 Catholic town church at Baden-Baden has been heated since 
 1867 by means of the hot springs in the neighbourhood, which 
 have a temperature of 67. 
 
 Steam heating may be effected either at low pressure (| atmosphere) or at high 
 pressure. In each case the steam passes into mains laid beneath the floors of the 
 buildings to be heated. Here it is liquefied by giving off' its latent (and a part of its 
 specific) heat, and flows back to the boiler. 
 
 All collective heating arrangements have the great advantage, as compared with 
 stoves and open fires, that they occasion no ash, soot, &c. They allow also of a great 
 economy of labour, as only a single fire has to be kept up to warm a great number of 
 rooms. They also admit of a more perfect utilisation of the fuel than do ordinary 
 stoves, and they enable a uniform and unchanging temperature to be kept more easily 
 than does any other kind of firing. 
 
 Hot-air heating involves the least initial outlay, is easily attended to, and, where 
 the ventilation is good, it produces a uniform heat in the rooms. It is not adapted for 
 distributing heat horizontally in large halls or long series of rooms, since hot air 
 should ascend vertically as nearly as possible. In such places steam or water heating 
 is preferable.* 
 
 Heating with Coal-gas. This is a very pleasant, but a very expensive, arrange- 
 ment, i cubic metre coal-gas evolves 5300 heat-units, watery vapour being one of the 
 products of combustion. Of this total, about 5000 heat-units are utilised. For a small 
 room during the entire winter the average demand for heat is 10,000 heat-units daily. 
 This requires 2 cubic metres of coal-gas, which may cost, according to the locality, from 
 
 * Hence steam or hot water is selected for heating museums, libraries, galleries of pictures, 
 conservatories, &c., where a uniform heat, strictly under control, is required in all parts. It must 
 be remembered that the mains should never be allowed to lie upon wood, still less sawdust, 
 shavings, &c., as, though the temperature may never exceed 100, wood thus heated gradually 
 undergoes a series of chemical changes which render it spontaneously combustible. The mains 
 should be supported upon firebricks. [EDITOR.] 
 
 E 
 
66 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 o'24 to 0-40 shilling, whilst in properly arranged hot-air heating the coal consumed 
 costs merely 0*03 to 0-04 shilling. In heating with stoves we have, on the other 
 hand, the trouble of feeding the fires, the inevitable dirt, and the difficulty of main- 
 taining an even temperature. 
 
 Gas-firing. Gas-firing is distinguished from ordinary firing by the circumstance 
 that the fuel is first gasified, and then burnt, atmospheric air being introduced at two 
 distinct places. The air required for gasifying enters the fuel through the grate. The 
 air (called secondary) needed for burning the gas thus formed enters the fire-box. 
 
 A system of gas-firing adapted for lignite is shown in Figs. 68 and 69. In this 
 
 Fig. 68. Fig. 70. 
 
 Sections 1-11. 
 
 JTnh Wood. 
 
 Arrangement, built by Heupel at the Aussee Saltworks, the boiling pans, Z, are 
 1 7' i metre long by 7-6 broad, so that each has a heating surface of 130 square metres, 
 for which three gas generators, A, with the grates, T and P, were placed equally dis- 
 tributed over the breadth of the pan. The regulation of the production of gas is 
 effected by means of tightly fitting air- valves in the door, E, in front of the ash-pit. 
 The apparatus for burning the gas, which is separated from the feeding shaft, A, by 
 means of a simple vault, consists of an almost horizontal grating, F, constructed of fire- 
 bricks, and of the vertical grating, e, between which is the true fire-box, 7?, and in 
 which vent the air-passages, n, are introduced in the side walls of the generator. The 
 gases evolved in the generator pass through the grating, F, into the fire-box, B (closed 
 above), where they mix with the air warmed against the stove sides and streaming in 
 from the air-channels, n, and are ignited. 
 
 The forms of burners by which a perfect combustion is effected are shown in the 
 wood-gas stove, Fig. 70. 
 
 If the generator does not stand directly under the fire-box, as in that of Boetius 
 (Fig. 36), gas-firing involves a loss of heat. As compensation, the combustion-air, 
 more rarely the air for gasification, is strongly heated by the waste heat. 
 
 C. W. Siemens effects the formation of gas in the generator by means of heated air 
 (Fig. 71). The fuel is introduced by the hopper, ; the gases are carried off through a 
 great number of channels arranged round the stove, and arrives at the ring-shaped 
 draught, c. which, as is shown by dotted lines and arrows, leads through d to the 
 furnace. The gases meet with the air rising from the regenerator pipes through the 
 channel I, and burn. After the flame has completed its work in the heating space of 
 the furnace, it passes out opposite to the entrance through apertures which lead the 
 gases through the channels &, to the regenerator flues, e, whence they ultimately 
 arrive at the chimney, S. The air required for the combustion of the gases arrives at 
 the regenerator through the openings, v, which lead to o, which in turn is in connection 
 
SECT. 
 
 HEATING ARRANGEMENTS. 
 
 67 
 
 at the other end with the channel I, already mentioned. A part of the air coming 
 from the regenerator flues may be led to the generator in order to volatilise the fuel 
 there, or, as shown in the figure, the air needed for this purpose may be heated in 
 
 Fig. 71. 
 
 separate tubes which lead to a blast, s, at the foot of the generator. The ashes, &c., fall 
 into a reservoir of water at the foot of the generator. The steam thus produced enters 
 
 Fig. 73- 
 
 Fig. 72. 
 
 the gas generator, where it is de- 
 composed on contact with the ignited 
 coal, and serves to enrich the gases. 
 
 The preliminary heating of the 
 air for gasification may be objec- 
 tionable in so far as it raises the 
 temperature in the gas generator, 
 and thus increases the action of 
 the slag upon the masonry. It is 
 of value only when the generator- 
 gases enter the fire-box at a high 
 temperature. 
 
 The preliminary heating of the 
 air for combustion is of much 
 greater importance. It is effected according to the procedure of Fr. Siemens by 
 
 Section I. 
 
 Section III. 
 
 passing the combustion- 
 gases which leave the fur- 
 nace at a high tempera- 
 ture through a grating of 
 stone (regenerator), and 
 then inverting the cur- 
 rent and causing the air 
 for combustion to ascend 
 through the ignited 
 stones. According to 
 another process the heat 
 of the combustion-gases 
 is transferred to the 
 ascending air by partition 
 walls (Figs. 72 and 73). 
 
 Fig- 74- 
 
68 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 Fig. 74 shows a longitudinal section through the trough and the regenerator of a 
 Siemens glass-melting furnace provided with regenerators of the first kind. Fig. 75 
 shows a horizontal section on V, VI, and Fig. 76 a transverse section on VII, VIII r 
 through the entire furnace, and Fig. 7 7 the section of a work-place. The four regene- 
 rators, 72, to 7? 4 , lie close 
 alongside each other, and 
 form a connected whole with 
 the furnace, thus reducing 
 the loss of heat by radiation 
 and conduction. The greater 
 part, A, of the regenerators 
 is lined with fire-stones, but 
 not the smaller portion, B, 
 separated by the wall, m. 
 This part, situate next to 
 the place for introducing the 
 materials, takes up the con- 
 stituents of the charge, so 
 that the regenerators, A, 
 remain clean ; these are 
 easily accessible from G, as 
 are the parts B from the 
 alternating valves, W. The 
 trough itself is an entire whole, in consequence of which repairs are seldom needed. 
 In the melted glass there float at the end of the furnace turned towards the work- 
 places, a, rings of stoneware, 
 whilst the flame sweeps 
 through the upper part, 0, 
 of the furnace, so that the 
 melting of the glass takes 
 place on the surface only. 
 The bottom, b, and the sides, 
 w, of the trough are, as 
 formerly, surrounded with 
 air refrigerators, e, in which 
 a brisk current of cold air 
 is kept up by means of the chimneys, s. 
 The trough is thus not only better pre- 
 served, but the glass is prevented from 
 passing through the joints. 
 
 As a good instance of the second method 
 of obtaining heat from the combustion- 
 gases we may take the so-called Munich generator furnace of N. H. Schilling (Figs. 78- 
 to 82). The heat necessary for gasifying the coke enters the aperture, A, which can be 
 Regulated with a slide, and mixes with the watery vapours rising up from the box, B. 
 The gaseous mixture traverses the channels c to c 3 , is heated by their sides, which in 
 turn are heated by the escaping smoke-gases, passes under the grate, D, and through 
 the ash-pit, w, into the burning stratum of fuel. The generator-gases formed pass 
 through the channel F to the furnace, and meet in the burners, G, with the air pre- 
 viously heated. The combustion-gases traverse the retort furnace in the direction 
 of the arrows, leave it at the end of channel z, and enter into the regeneration 
 system. The hot gases pass through channels o to o 3 , which lie between the channels 
 
 Fig. 77. 
 
J3ECT. I.] 
 
 HEATING ARRANGEMENTS. 
 
 69 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. 
 
 Fig. 82. 
 
 n to w,, for warming the combustion-air, then through channel o 4 , the walls of which 
 heat the mixture of gas and watery vapour passing to the generator, arrive under the 
 
 water-cistern, B, at r, and through s into the 
 smoke-pipe, 0. 
 
 For more rapidly transferring the heat from 
 the smoke-gases to the air moving towards the 
 furnace, and for securing the structure and 
 tight joints of the so-called regeneration, the 
 several channels are traversed by perforated 
 stones, which increase the heating surface. The 
 slide for regulating the draught in the chimney 
 is behind the regeneration, not behind the fur- 
 nace. The heating surface of the water-tank 
 beneath the generator is arranged so that the 
 quantity of steam which is sufficient for all 
 cases, 1000 to 1300 kilos., may be produced, 
 thus completely preventing the formation of 
 slag. To regulate the quantity of steam pro- 
 duced there is provided a valve, P, which can be 
 set at pleasure, thus moderating the tempera- 
 ture. If, on using coke with from 14 to 16 per 
 cent, of ash, the ash-pit has become filled in 
 about thirty -six hours with the residues of com- 
 bustion, they are removed as follows : Through 
 the openings, e, which are in general tightly 
 closed, there are thrust iron rods to catch the 
 fuel in the generator. The covers, R and S, are 
 removed, and the ash fallen upon the grate is 
 taken away. All the apertures for cleansing 
 are closed again. The water which has evaporated from B is renewed by a con- 
 tinual flow from v ; an overflow removes any superfluous water. In order, when 
 setting the furnace in action, to remove temporarily the regeneration there are 
 connecting channels, U, through which the smoke-gases may be passed at once to the 
 chimney. 
 
 Such furnaces have been in regular work at the Munich Gasworks since 1881. 
 Three series of observations, of several months each, gave the following results : 
 
 Yield of gas in twenty-four hours 2300 cubic metres 
 
 Coal distilled in twenty-four hours in eight retorts . . . 7350 kilos. 
 Coke consumed per furnace in twenty-four hours .... 800 
 
 Yield of gas per retort in twenty-four hours 287 cubic metres 
 
 Gas per furnace and charge in four hours 383 
 
 Gas from 100 kilos, of coal 31 
 
 Coal distilled per retort in twenty-four hours 919 kilos. 
 
 > -, and charge ...... 153 
 
 Consumption of coke (14 per cent, ash) per 100 kilos of coal dis- 
 tilled IO'9 
 
 Consumption of coke (14 per cent, ash) per 100 cubic metres of gas 45^8 
 
 The generator-gases contain as a mean 8'6 per cent, of carbon dioxide, 20-6 
 of carbon monoxide, 15 of hydrogen, and 55-8 of nitrogen. They enter the furnace 
 at about 1150. The combustion-gases contain 17 to 19 per cent, of carbon dioxide, 
 about 2-5 per cent, of oxygen or small quantities of carbon monoxide. They leave the 
 furnace at about 1400. After having traversed the flues o to o 3 , and given off a part 
 
 Section VII-VIJLI. 
 
SECT, i.] LIGHTING-GAS. 71 
 
 of their heat to the air ascending in the intervening channels, they still have a tempera- 
 ture of 900, whilst the combustion-air arriving at the furnace before entering the 
 channels m to m 4 , has become heated to iooo 1100. Passing further down, the 
 smoke-gases play round the channels c to c 3 , and heat the air passing to the generator 
 to 350 ; finally, on passing through the channels r, they produce the steam employed 
 in the generator, and enter the chimney at about 550. 
 
 An exit temperature of 1400 without regeneration would represent a loss of 64 
 per cent, of the heating value of the coke ; but by the regeneration process the smoke- 
 gases are cooled down to 550, and the loss is reduced to about 25 per cent. The heat 
 thus recovered is conveyed back to the furnace, 20 per cent, by the heated combustion- 
 air, 6 per cent, by the preliminary heating of the generator-air, about 5 per cent, is 
 used in evaporating water, whilst the rest is lost by conduction and radiation out- 
 wards.* 
 
 This latter way of recovering heat has the advantage that the direction of the 
 draught does not require to be changed every fifteen or thirty minutes. Care must be 
 taken that the divisions between the channels for air and combustion-gases are air- 
 tight, so that no disturbing intermixtures take place. This point has to be deter- 
 mined by the analysis of samples of gas taken from channels n v z, and r. 
 
 Gas-firing gives satisfaction in metallurgy, in glass manufacture, and in burning 
 clay and cement. 
 
 In industrial heating operations, the dissociation of the gases of combustion is 
 without importance. 
 
 LIGHTING-GAS. 
 
 History. As far back as 1727-1739, Clayton, Bishop of Cork, and Dr. Hales 
 observed the escape of gas on heating coal.f In 1767, Dr. Watson, Bishop of Llan- 
 daff, observed that combustible air could be conveyed through pipes. Pickel, Professor 
 of Chemistry at Wiirzburg, lighted up his laboratory in the gardens of the Julius 
 Hospital with gas obtained from bones, in 1876. About the same time Dundonald 
 made experiments at his country seat of Culross Abbey on lighting with coal-gas. The 
 first question for him had been the production of gas- tar as a by-product of the coke 
 manufacture. The workmen fixed iron tubes in the condenser in which the tar was 
 deposited, and kindled the escaping gas for light in the night. Strictly speaking, the 
 beginning of gas-lighting took place in 1792, when Murdoch lighted his house and 
 works at Redruth, in Cornwall, with gas obtained from coal. His process did not 
 become known on the Continent until about ten years subsequently ; hence the French 
 claim the invention for their countryman, Lebon, who in 1801 illuminated his house 
 and garden with gas produced from wood. The enterprise proved a complete failure, 
 on account of the feeble illuminating power of wood-gas, and was soon abandoned. The 
 first gas illumination on the large scale was installed by Murdoch in 1802, at the works 
 of Watt & Boulton, the Soho Foundry, near Birmingham. In 1804 he fitted up a 
 similar installation at a cotton-spinning establishment in Manchester. J From this 
 time the use of gas became extended. But for some time it was confined to factories. 
 Its introduction into daily life dates from 1812, when the streets of London were 
 lighted with gas. In 1824 gas-lighting was introduced into Hannover, and other 
 continental cities followed the example. The wood-gas introduced at Pettenkofer's 
 suggestion into Munich and other South German cities has probably been everywhere 
 
 * Dingler's Journal, 248, p. 27. 
 
 t Indeed, in 1659 Thomas Shirley is said to have ascribed the burning exhaldtions from the well 
 of Wigan to the subjacent coal-beds. 
 
 + Winzer, who converted his name into Winsor, is sometimes regarded as a discoverer of gas- 
 lighting, but he was merely the inventor of gas companies. 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 abandoned in favour of coal-gas. For small installations oil-gas and resin-gas are 
 convenient, as they require little purification. 
 
 For the production of lighting-gas, coal is hea,ted to whiteness in retorts, formerly 
 made of cast-iron, but latterly of fire-clay. As the source of heat, the residual coke is 
 used, being formerly burnt in common grates. During the last ten years the firing 
 has been improved, so that the consumption of fuel has been reduced one-half. In the 
 half-gas-firing of J. Hasse and M. Vacherot the fuel is introduced (Figs. 83-85) through 
 
 Fig. 83. 
 
 an opening, J3, provided with a tightly fitting door and laid upon the grate, A . Slags 
 and ashes are removed through the air-tight door, E. When both doors are closed the 
 combustion-air, regulated by the slide, F, into the furnace right and left at G, traverses 
 
 the channels in the direc- 
 tion of the arrows, and 
 passes through the slit J 
 to the left and right 
 under the grate. Where 
 circumstances permit, air 
 can also be introduced 
 xinder the flues M and 
 JV, and conveyed from 
 thence to the channels //. 
 The products of combus- 
 tion, after they have 
 passed uniformly through 
 the furnace, enter the 
 smoke flue, K, from 
 before backwards, down- 
 wards in L, in M from 
 behind forwards, and in 
 N in the reverse direction to the chimney. In this manner the products of com- 
 bustion give off a great part of their heat both to the air entering through the air- 
 channels H, and to evaporating the water in the tank, 0, under the grate. As the 
 fuel is packed high up on the grate and maintained at the same height, a complete 
 combustion does not take place, but there is formed a considerable percentage of 
 carbon monoxide, for the combustion of which a further supply of air is needful. This 
 secondary combustion-air enters from the back of the furnace at P, where its access is 
 
SECT. I.j 
 
 LIGHTING-GAS. 
 
 73 
 
 Fig, 87. 
 
 regulated by the slide, Q. It traverses the air channels, R, in the direction of the 
 arrows, and arrives through the slit S in contact with the gases coming from the com- 
 bustion hearth. The channels R are 
 heated by radiation from the surround- 
 ing masonry. The channels II may be 
 connected with the channels R in such 
 a manner that the air passes through H 
 into R. 
 
 In the retort furnace of Stedman, 
 provided with a gas-firing, the combus- 
 tion-gases, as shown in Figs. 86 and 87, 
 pass from A to E, or from a to e, down 
 into the chimney. The air for gasifica- 
 tion enters on both sides at J, traverses 
 the channels, i to 6, and enters into the 
 bed of coke at r. The air for combus- 
 tion enters at /, passes through // to 
 V, and meets with the generator-gases 
 at VI. 
 
 The furnaces of Liegel and Klb'nne, in which the generator is built into tho 
 furnace, have given satisfaction in practice. 
 
 The furnaces of Hasse and Didier have much similarity with the Munich furnace. 
 The air for gasifying 
 enters at P (Figs. 88 and 
 89), and is warmed in 
 channels left in the 
 masonry of the generator 
 outside the furnace. The 
 air for combustion enter- 
 ing at S, rises in the 
 channels, 0, whilst the 
 products of combustion 
 pass from the furnace 
 down through the chan- 
 nels, and yield the heat 
 necessary for producing 
 steam in the tank, D. 
 The steam passes under the grate of the generator. 
 
 Tar-firing. In consequence of the reduced value of tar and its products, it is in 
 many gasworks advantageous to use it as fuel. Tar 
 has a combustion-value of 8500 to 9000 heat-units, 
 and is blown into the fire in a state of fine division by 
 compressed air and steam. Kb'rting's pulveriser (Fig. 
 90) allows the steam to issue from four apertures of 
 i mm. in diameter. At a pressure of 3 atmospheres 
 these apertures let pass 5 '4 kilos, of steam, pulverising 
 30 kilos, of tar. At the exit the steam takes the tem- 
 perature of 100, is heated to the temperature of the 
 furnace, gives up heat to the retorts, and leaves the 
 furnace at about 1000. It thus occasions a loss of 
 heat corresponding to the rise of temperature from 
 100 to 1000, i.e., 900. Steam has a specific heat of 0-475 ^ 
 
 Fig. 90. 
 
 2'Aeer Tar. Dampf Steam. 
 
 to heat i kilo, of 
 
74 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 steam to i, 0*475 heat-unit is needed. To heat 5-4 kilos, to 900 there are needed 
 5*4 x 900 x o - 475 = 2 38'5 heat-units. From the 30 kilos, of tar burnt in this time 
 there are produced 260,000 heat-units, so that the loss as steam does not come to 
 0-9 per cent. At the Hannover Gasworks 100 kilos, of coal are degasified along with 
 13-5 kilos, of tar. Sometimes tar is let flow into the generator. 
 
 As already mentioned, the composition of the volatile matter given off on heating 
 coal fluctuates greatly. The Paris Gas Company experimented at their works at 
 La Villette with fifty-nine kinds of coal, and very carefully with twenty-three of the 
 same, using 36 tons of each. 
 
 The nitrogen was not determined, but assumed as i per cent, in each case ; all the 
 coals were grouped in five classes. 
 
 
 
 I 
 
 II 
 
 III 
 
 IV 
 
 V 
 
 
 
 
 
 
 
 
 
 [Oxygen ..... 
 
 5-56 
 
 6-66 
 
 771 
 
 lO'IO 
 
 11-70 
 
 Composition of 
 
 Hydrogen .... 
 
 5-06 
 
 S'37 
 
 5*40 
 
 5-53 
 
 5-64 
 
 coal. 
 
 
 88-^8 
 
 86.97 
 
 8 5 -89 
 
 8r^7 
 
 8 1 -66 
 
 
 
 I "OO 
 
 I'OO 
 
 I'OO 
 
 I-QO 
 
 I'OO 
 
 
 
 
 
 
 
 
 
 
 100 '00 
 
 lOO'OO 
 
 lOO'OO 
 
 lOO'OO 
 
 lOO'OO 
 
 
 Moisture . . . per cent. 
 
 2-17 
 
 2-70 
 
 3-31 
 
 4'34 
 
 6-17 
 
 Products of 
 
 [Volatile . 
 
 26-82 
 
 31-59 
 
 33-80 
 
 37'34 
 
 39-27 
 
 distillation. 
 
 Coke . . ,, 
 
 73-18 
 
 68-41 
 
 66 -20 
 
 62-66 
 
 6073 
 
 
 (Coal . ... 
 
 0*04 
 
 7-06 
 
 7 -2i 
 
 8-18 
 
 10-73 
 
 Ash in 
 
 Coke 
 
 12-35 
 
 10-32 
 
 10 -80 
 
 I3-05 
 
 17-76 
 
 
 rGas . cubic metres 
 
 30-13 
 
 31-01 
 
 30-64 
 
 2972 
 
 27-44 
 
 loo kilos, of 
 coal yield 
 
 . . kilos. 
 Coke 
 Tar . 
 
 13-70 
 77-81 
 3-90 
 
 15-08 
 74-70 
 4-65 
 
 15-81 
 72-31 
 5-08 
 
 16-95 
 68-96 
 
 5-48 
 
 17-00 
 67-36 
 5-59 
 
 
 lAmmoniacal liquor . 
 
 4-59 
 
 5'57 
 
 6-80 
 
 8-61 
 
 9-86 
 
 The gas, on a very imperfect examination, showed- 
 
 
 I 
 
 II 
 
 III 
 
 IV 
 
 y 
 
 
 
 
 
 
 
 Carbon dioxide . 
 
 1-470 
 
 1-580 
 
 1-720 
 
 2-790 
 
 3-130 
 
 monoxide 
 
 6-680 
 
 7-190 
 
 8-210 
 
 9-860 
 
 11-930 
 
 Hydrogen . 
 
 54-210 
 
 52-790 
 
 50-100 
 
 45-450 
 
 42-260 
 
 Methan + nitrogen 
 
 34-370 
 
 34-430 
 
 35-030 
 
 36-420 
 
 37-140 
 
 Benzoles 
 
 0-790 
 
 0-990 
 
 0-960 
 
 1-040 
 
 0-880 
 
 Other gases absorbed in bromine 
 
 2-480 
 
 3-020 
 
 3-980 
 
 4440 
 
 4-760 
 
 
 lOO'OOO 
 
 lOO'OOO 
 
 100 'OOO 
 
 IOO.OOO 
 
 loo-ooo 
 
 Specific gravity 
 
 0-352 
 
 0-376 
 
 0-399 
 
 0-441 
 
 0-482 
 
 Required per carcel . . litres 
 
 132-100 
 
 III -700 
 
 103-803 
 
 IO2-IOO 
 
 ioi'8oo 
 
 The Scottish cannels, the Boghead minerals, which produce no residue applicable as 
 fuel, and the Australian kerosene shales, which likewise leave no coke on distillation, 
 are almost exclusively used at gasworks to improve the gas from common coal, and are 
 added in proportions varying from 5 to 50 per cent. The following are the yields 
 obtained from these ingredients : 
 
 Coal. 
 
 Gas per 100 Kilos. 
 
 Luminous Power 
 of 150 Litres of 
 Gas. 
 
 Coke from 
 100 Kilos. 
 
 Scotch cannel ....... 
 
 30-4-35-2 
 
 18-1-43-4 
 
 30-65 
 
 Boghead. 
 
 
 
 
 Scotch 
 
 29-2-38-8 
 
 26-3-62-6 
 
 23-62 
 
 Australian 
 
 39-5-4I-5 
 
 48-0-53-6 
 
 30-36 
 
 Of the nitrogen in coal, according to Schilling, u to 17 per cent, are given off as- 
 ammonia, 57 to 70 per cent, are left in the coke, and the rest is not determined. 
 
LIGHTING-GAS. 
 
 75 
 
 Purification 'of the Gas. The crude gas evolved in the retorts rises through a wide 
 iron pipe, and enters by way of the bent tube, B C, the hydraulic main, D (Fig. 91),. 
 
 Fig. 91. Fig. 92. 
 
 Fig- 93- 
 
 which runs over the entire range of furnaces, so as to receive the delivery pipes of all 
 the retorts. Here a portion of the tar and the ammoniacal liquor are condensed, and 
 are run off only so far that the exit-pipes may plunge in to the depth of a few centi- 
 metres to prevent the gas from going back into the retorts. An exhauster is intro- 
 duced into the system, generally after the washing apparatus, to prevent over-pressure. 
 
 From the main the gas arrives at the condenser. This generally consists, as shown 
 in section (Fig. 92), of a series of vertical iron pipes, connected above by arched pipes, 
 and standing below on the rectangular cast-iron chest, P. The latter is divided into 
 compartments, both in length and breadth. Each compartment has an entrance pipe, 
 TO, and an exit pipe, n. The partitions do not reach 
 quite down to the bottom, so that the liquid which 
 closes the compartments can move freely through 
 the entire chest. In this chest the gas-liquor and 
 the tar are collected. The level of the liquid is 
 regulated by the exit tubes, d, through a pipe bent 
 as a siphon. The entrance pipes, which lead down- 
 wards, dip a little into the liquid, so that the gas 
 is compelled to pass through. 
 
 For separating the residue of tar and ammonia 
 the gas is conducted into a scrubber. It consists 
 generally of cylinders, A (Fig. 93), 3 or 4 metres 
 in height, filled with fragments of coke, upon which 
 a hollow rotating cross tube constantly sprinkles 
 water. The gas enters through the pipe, i, moves 
 upwards among the wet coke, passes down through 
 the tube, m, and then enters a second scrubber. 
 At the lowest part of the pipe there is an arrangement for removing the washing 
 water and the tar which collects in the receiver, M. Of late the gas is often caused 
 
7 6 CHEMICAL TECHNOLOGY. [SECT. i. 
 
 to pass through sieves which dip into water or over which water flows. For the 
 complete separation of the tar it is desirable that the gas should be compelled to 
 impinge repeatedly on cold surfaces. 
 
 Finally, the gas is led into the purifiers in order to remove carbon dioxide (other 
 than that combined with ammonia), sulphuretted hydrogen, carbon disulphide, ammo- 
 nium cyanide, &c. 
 
 The milk-of-lime purifier, introduced by Clegg, has been superseded by the dry- 
 lime purifier (moist calcium hydroxide). In order to give the slacked lime a loose 
 consistence, and to facilitate the passage of the gas to be purified, it is mixed with 
 sawdust, spent tar, &c. Such mixtures are so loose that they may be laid on sieves in 
 layers of 1 5 to 20 centimetres in thickness without presenting any important resistance, 
 and that, in five layers of 20 centimetres each and spread out in the purifiers, they do 
 not require a pressure of more than 2 or 3 centimetres of water. 
 
 According to Veley, the first product formed in this process is calcium hydro- 
 sulphate. Gas lime contains, along with unchanged calcium hydroxide and a little 
 calcium cyanide, calcium hydrosulphate in such quantity that gas lime is used by 
 tanners for unhairing hides. 
 
 Purifying with Oxide of Iron. Though copperas was proposed for removing 
 ammonium sulphide from gas, and used as early as 1835, Mallet (1840) was the 
 first to introduce metallic salts, and especially manganous chloride (which was then 
 produced extensively at the chloride of lime works), and also ferrous chloride for the 
 purification of gas on the large scale. 
 
 Of much greater importance is the so-called " Laming's mass," introduced by 
 Laming in 1847. As at present used, it consists of ferrous sulphate with lime, to 
 which sawdust is added to render the mass loose. The ferrous sulphate is converted, 
 with the lime, into ferrous oxide and calcium sulphate ; the original blackish-green 
 colour of the mixture is changed, by turning over and exposure to the air, to a red, when 
 we have a mixture of ferric hydroxide and gypsum. The mass is used in dry purifiers. 
 Since it has been observed that the lime is of no consequence, iron or manganese oxide, 
 or preferably bog-iron ore, is almost universally used instead of Laming's mass. It is 
 ground fine, mixed with an equal bulk of sawdust, moistened, and used for purifying. 
 Instead of the natural oxide, the residues from the reduction of nitrobenzol by means 
 of iron-filings (in the aniline manufacture) may be used. 
 
 According to R. Wagner, the ferric oxide of Laming's mass is first converted by 
 the hydrogen sulphide into iron sesquisulphide, and this compound then passes into 
 ferric oxide, giving up its entire amount of sulphur. 
 
 If Laming's mass has been in use for a long time, its efficacy falls off, since the 
 sulphur accumulates up to 40 per cent., and the particles are coated with a glutinous 
 layer, which prevents contact with the gas. From the exhausted mass the sulphur 
 can be recovered by fusion under water at high pressure or by extraction with carbon 
 disulphide ; or, after the ammoniacal salts and the iron cyanide (the latter in the form 
 of calcium ferrocyanide) have been removed by lixiviation, the mixture is roasted in 
 kilns, thus producing sulphurous acid for the manufacture of sulphuric acid ; and, on 
 the other hand, iron oxide, which may be employed anew in the purification of coal-gas. 
 
 For desulphurising coal-gas the mass of Lux has been found satisfactory. It consists 
 of 65 parts ferric hydroxide, 5 parts sodium carbonate, and 30 parts clay, sand, &c. 
 The recent mass takes sulphuretted hydrogen completely up at a velocity of 16 mm. 
 per second. For old, regenerated mass the limit is a velocity of 5 mm. per second. For 
 very 100 cubic metres of gas daily the purifiers must have at least a transverse section 
 of 0^23 square metre. 
 
 Ammoniacal Purifying. According to Glaus, the gas when freed as completely as 
 possible from tar passes through six scrubbers (Fig. 94). Almost all the carbon 
 
SECT. I.] 
 
 LIGHTING-GAS. 
 
 dioxide is removed in the first, A. In the second it loses the last trace of carbon dioxide, 
 together with the larger portion of hydrogen sulphide. At the upper end of this 
 scrubber, A v the ammonia arriving from the stills enters in a continuous current, and,, 
 flowing along with the partially 
 
 purified coal-gas, it passes into Fi g- 94- 
 
 the next scrubber, A r Here the 
 last trace of hydrogen sulphide is 
 removed, and at the same time a 
 great part of the carbon disulphide 
 contained in the crude gas is 
 eliminated. In the liquid con- 
 tained in this scrubber the chief 
 part of the ammonia is free, and 
 much of the rest exists as ammo- 
 nium sulphide. Hence the con- 
 ditions for removing carbon disulphide from crude gas in this scrubber are favourable. 
 However, in this washer alone there is not presented to the gas a sufficiently large 
 surface moistened with the liquid to effect the maximum possible removal of carbon 
 disulphide. On this account the contents (e.g., coke) of the fourth and fifth scrubbers, 
 which may be named carbon disulphide scrubbers, are kept moistened with a small 
 portion of the liquid from the bottom of the second or third scrubber. From the fifth 
 scrubber the gas passes into A. a . Here the last trace of ammonia is washed out and 
 the gas issues perfectly purified. Over this scrubber is a cistern into which the 
 exhausted liquid from the distillation of ammonia, after it has passed through a refri- 
 gerator, is pumped. 
 
 A quantity of ammonia is stored up in the scrubbers and in the apparatus for the 
 recovery of ammonia, thirty to fifty times larger than the quantity required for 
 taking up the impurities in the largest quantity of crude gas which passes hourly 
 through the scrubbers. 
 
 If only an open fire or enclosed steam were used for the distillation of the 
 ammoniacal liquid, after a short time it would become a saturated solution of cyanides 
 and would have to be removed from time to time. Hence the distillation is preferably 
 effected with open steam, for which the waste steam of the engine may be employed. 
 An essential feature in the purification of crude gas with ammonia is the recovery of 
 the cyanides. The liquid contains ammonium ferro-cyanide and sulpho-cyanide. 
 
 Whilst Glaus distils off the gas-liquor and passes the gaseous ammonia into the 
 scrubbers, F. C. Hills proposed to pump the liquor, freed from carbon dioxide and 
 hydrogen sulphide, direct into the scrubbers. In consequence of successive improve- 
 ments the two processes almost coincide, as appears from the following report by 
 Watts on Hill's process, as carried out by the South Metropolitan Gas Company. The 
 five scrubbers, A to A 4 (Fig. 94), are 1-3 metre in width and 6 metres in height ; the 
 sixth scrubber A 5 is 1*5 metre in diameter and 9 metres high. The crude gas enters the 
 first scrubber at a, passes through the tube e, to the following scrubbers, and escapes, 
 purified, at g. The drawn-out lines show the circulation of the liquid. The towers B are 
 0-6 metre broad and 4-5 metres high. To two of them steam is conveyed by the piped, 
 so that the liquid trickling through the towers (fitted up in the manner of scrubbers) 
 is warmed so much that carbon dioxide and hydrogen sulphide escape whilst the 
 ammonia is distilled off in the tower C. The washing liquid in the five scrubbers 
 contains : 
 
 A. A 4 . A 3 . A 2 . AI. 
 
 Ammonia . . .01 ... 1-5 ... 3'5 ... 5'o ... 4 - o 
 
 Sulphuretted hydrogen . .. o'i ... I'S ... 2'o ... i'5 
 
 Ammonium as carbonate ... ... i'O ... 3' 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 The gas-liquor on entering (I.) and leaving (II.) the decomposers B contained : 
 
 i. ii. 
 
 Ammonia . 4-50 ... 4-50 
 
 Ammonium as carbonate .... 4*00 ... i'io 
 Sulphuretted hydrogen . . . . 1-08 
 
 The crude gas contains o* i per cent, hydrocyanic acid, which forms this cyanide : 
 
 NH 4 CN + (NH 4 )S 2 = NH 4 CNS + (NH 4 ),S ; 
 then with carbon disulphide 
 
 (NH 4 ) 2 CS 3 - NH 4 CNS + 2 H 2 S. 
 
 The finished gas is stored in large bell-gasometers and conveyed for consumption in 
 cast-iron mains tarred. The distribution in houses, &c., is effected through wrought- 
 iron tubes, more rarely leaden ones. [In England lead and composition pipes are 
 unfortunately the most common]. Copper pipes are costly and may become dangerous 
 from the formation of acetylene copper: 
 
 Examination. For checking the process of manufacture the carbon dioxide is 
 determined with the apparatus already described. 
 
 The amount of sulphur is determined with the arrangement shown in Fig. 95. 
 The tube B, about 25 centimetres long, is secured by a cork to the lateral neck of the 
 "bottle A, which is also 25 centimetres high. The gas, accurately measured, is con- 
 veyed to the glass tube b on a small plate, and over its efflux 
 point there is an under glass tube e, which slides up and 
 down in a simple holder, so that the whole arrangement 
 represents a glass Bunsen burner. The supply of gas is so 
 arranged that about 20 litres are burnt hourly. Above the 
 repeatedly bent tube c, a small dropping vessel a is fixed, 
 by means of which during the experiment hydrogen per- 
 oxide, free from sulphuric acid and slightly ammoniaca!*, can 
 be let drop so slowly that every hour 2 c.c. may flow down 
 into the tube c to dissolve the last traces of the sulphurous 
 and sulphuric acids formed out of the gases of combustion 
 as they ascend. When about 100 litres of gas have thus 
 been consumed, the tubes B and c are taken off, rinsed out 
 with a little water, the contents of the bottle A, together with 
 the rinsings, are heated to boiling, acidified with hydrochloric 
 acid, and precipitated with barium chloride in the ordinary 
 manner. If the ambient air is not free from sulphuric acid 
 and hydrogen sulphide, the whole arrangement is fixed higher 
 and the interval at e is closed in a suitable manner, so that 
 no air can enter except through pumice, moistened with 
 strong potassa lye. One cubic metre of gas should not con- 
 tain more than o - 3-o'4 grain sulphur. In London 0-57 grain 
 sulphur per cubic metre is permitted ; in Leeds 0-45 grain ; 
 in Cologne 0*23 to 0*39. 
 
 For determining ammonia in purified gas 200 litres are 
 drawn through 10 c c. of decinormal hydrochloric acid, and 
 the excess of acid is titrated back. 
 The complete analysis of gas is effected with the author's apparatus, Fig. 48. 
 Carbon dioxide and oxygen are determined as already described, the tube A is re- 
 peatedly rinsed with water, which is drawn ofi at the cock d ; to remove the last traces 
 of water a few drops of sulphuric acid are allowed to enter A through the funnel t, 
 the mercurial column is lowered in A and the acid is driven out with mercury through 
 
SECT. I.] 
 
 LIGHTING-GAS. 
 
 79 
 
 the tube d. About 0-5 c.c. of strong fuming sulphuric acid is allowed to enter the 
 tube A through the funnel t, and then the sample of gas from the tube M. In about 
 three minutes the sample of gas is forced back into M, the sulphuric acid is let out 
 through the cock d ; the funnel t, and the tube A are repeatedly rinsed with water, and 
 the sample is measured in M. 
 
 Of this gas freed from CO 2 , O, and from heavy hydrocarbons, so much is let escape 
 through the three-way cock that there only remain 50-60 vols. (at ordinary pressure) 
 in the measuring tube M. 60 to 70 vols. oxygen, and about 150 vols. atmospheric air 
 (containing a known amount of oxygen), are allowed to enter, measured ; the mixture is 
 ignited by a spark between the platinum wires, the quantity of the residual gas is 
 determined and its proportion of CO a and O. 
 
 The composition of a sample of gas from the Hannover works was : 
 
 Benzol, C,.H 6 
 
 Propylene, C 3 H ( . 
 
 Ethylene, C,H 4 
 
 Methane, CH 4 
 
 H 
 
 CO 
 
 CO 2 . 
 
 O " . 
 
 N 
 
 0-69 
 0'37 
 
 2'II 
 
 37*55 
 46-27 
 II-I9 
 
 0-81 
 
 trace 
 
 i -or 
 
 For checking the production Lux recommends a continuous determination of the 
 specific gravity. The gas enters through the flexible pipe a (Fig. 96), the mercurial 
 joint and the narrow tube 
 
 into a hollow glass ball, fixed N 
 
 on ,one arm of a lever, and 
 escapes again at z. If the 
 gas becomes heavier, the ball 
 winks ; if lighter, it rises. 
 
 Wood-gas. Lebon, as 
 far back as 1799, busied 
 himself with the preparation 
 of illuminating gas from 
 wood. His " thermo-lamp " 
 was quickly abandoned, as 
 its light was not compar- 
 able with that of coal-gas. 
 Pettenkofer found in 1849 
 that if wood is carbonised 
 at a high temperature the 
 gas is more luminous. But, as already stated, even this superior wood-gas has been 
 generally superseded by coal-gas. 
 
 Resin-gas. Colophonium was temporarily used for the production of illuminating 
 gas in several cities in England and the Continent, but it has been given up. 
 
 Peat-gas. Purified peat-gas, according to Reisig, contains 
 
 Heavy hydrocarbons 
 
 Methan . 
 
 Hydrogen 
 
 Carbon monoxide . 
 
 C0 2 andH 2 S . 
 
 Nitrogen 
 
 I. 
 
 9-52 
 
 42-65 
 
 27-50 
 
 20-33 
 
 traces 
 
 II. 
 
 13-16 
 33-00 
 35-18 
 18-34 
 
 0-32 
 
 Peat-gas will probably never be used on a large scale. 
 
So 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. 
 
 i. 
 
 Oil-gas. If fats, paraffine oil, petroleum residues, &c., are strongly heated they are 
 almost entirely gasified, and form a heavy gas of great illuminating power. 
 
 For this purpose the apparatus of J. Pintsch is most generally used. He lets the 
 oil flow slowly down through a U-tube into the iron retort d (Figs. 97 and 98), falling 
 
 Fig. 97- 
 
 Fig. 98. 
 
 Sections I-II. 
 
 into the vessel, e, where it is 
 completely evaporated, thus 
 facilitating the cleansing of 
 the retorts. The vapours of 
 oil produced here and already 
 partially gasified, pass through 
 the connection, i, into the 
 lower cast-iron retort, /, in 
 which, for the promotion of 
 gasification there is inserted a 
 
 piece, s, of clay or iron, composed of discs connected by a longitudinal rod. The gas 
 passes, now, to deposit tarry vapours, through the pipe, </, to the receiver, h. The 
 pipe, g, is provided with ball joints, so as to follow the expansion of the retort. 
 Other devices have been proposed by Hirzel, Kiihnel, Macadam, and Briehm. 
 Oil-gas generally requires no particular purification. According to Hilger (1874), 
 paraffine- oil gas has the following composition : 
 
 Heavy hydrocarbons 
 Methan 
 Hydrogen . 
 Carbon monoxide 
 dioxide . 
 
 28-91 
 
 54 '92 
 
 5-65 
 
 8-94 
 
 0-82 
 
 Oil-gas compressed in iron cylinders at , a pressure of six to eight atmospheres is of 
 great value for lighting railway carriages. Oil-gas is also suitable for small installa- 
 tions. 
 
 Air-gas. If atmospheric air is saturated with the vapours of volatile hydrocarbons, 
 especially the so-called petroleum ether, it yields an illuminating gas which can only 
 l>e conveyed to short distances, and cannot bear low temperatures. 
 
 The uses of coal-gas are too familiar to need description.* 
 
 MINERAL OIL. 
 
 According to Herodotus, the mineral oil of the Island of Zante, which he names 
 pissasphaltum, was used for embalming corpses. Plutarch describes a burning pool 
 
 * W. J. Cooper has patented a process for improving the quality both of coal-gas and of coke, 
 by adding to the coal before distillation a quantity of lime. The coke as well as the gas is 
 alleged to be, to a great extent, freed from sulphur, so that the purification of the gas is much 
 simplified. Experimental working seems, in some cases, to have given satisfactory results, but we 
 <lo not know that the process has as yet been formally adopted by any gas company. 
 
SECT, i.] MINERAL OIL. 8t 
 
 of oil near Ecbatana, and Pliny and Dioscorides assert that the petroleum of Agri- 
 gentum, in Sicily, was used by the inhabitants for lighting purposes. The mineral oil 
 wells of Baku were known in pre-historical ages, and the same may be said of the 
 springs of Rangoon. The Hannoverian oil-wells were probably found by the first settlers 
 in that district, and their product was used as a lubricant and a medicine 500 years 
 ago. The small spring at Tegernsee has been known since 1430. But mineral oils 
 have first become of importance in commerce since 1879, when the deposits of North 
 America were systematically worked. 
 
 Several deposits in Hannover, Holstein, and Alsace have been discovered in 
 Germany. In the Austrian Empire the Galician springs are of importance, and 
 petroleum extends from Austrian Silesia, through Hungary, to Transylvania, as also 
 in Lower Austria, Salzburg, Carinthia, Tyrol, Croatia and Dalmatia. In Roumania 
 there is mineral oil to a considerable extent. In Russia, the springs of Baku appear 
 inexhaustible ; in some places fountains of oil shoot up to the height of 30 metres, and 
 flow away unutilised. 
 
 There are oil-springs in Burma (Rangoon), in Assam, and in the North-western 
 Provinces of India ; in Java and China. In Japan petroleum has been known to occur 
 for 1200 years, but it has only been collected during the last ten years; there are now 
 five refineries at work. Mineral oil has been found in South Australia and New 
 Zealand. The islands of Cuba, Trinidad, and Barbadoes produce petroleum, as do also 
 Mexico, Bolivia, Brazil, and the province Jujuy, in La Plata. North America is espe- 
 cially rich in petroleum. The oil region of Pennsylvania is a narrow belt of country 
 about 100 kilometres in length, between Lake Erie and Pittsburg. There is also an 
 important oil region in Canada. 
 
 Concerning the origin of petroleum, the most conflicting views have been advanced 
 by ehemists and geologists. Some authorities (Berthelot, Byasson, and Mendeleeff} 
 hold that it has been formed from inorganic materials. Dumas, Rose, and Bunsen 
 assume that mineral oil is derived from the hydrocarbons of the deposits of rock salt. 
 Gregory and Kobell asserted that it was a product of the distillation of coal, of which 
 anthracite is the solid residue. The predominating view at present is that petroleum 
 has been formed by the decomposition of organisms at low temperatures. Well, 
 Kruger, and Windakiewicz, ascribe to it a vegetable origin, whilst Hoefer, Bertels, 
 Miiller, and Fraas consider it as a product of the remains of animals. 
 
 Mineral oil is rarely obtained by mining. In North America deep borings are the 
 usual source, and the same system is extending in Hannover, Galicia, and at Baku. It 
 is noteworthy that the upper oil region of Pennsylvania, once so productive, has been 
 almost entirely exhausted in ten years, whilst the lower, more southern oil region, 
 which was only opened up in October 1865, now supplies all the petroleum exported 
 from Pennsylvania. The Canadian wells generally run dry in about three years. As 
 the total average yield of a well is 10,540 hectolitres, and as 15 per cent, of the borings 
 in Pennsylvania are unsuccessful, Hoefer calculates the cost of i hectolitre of crude oil 
 at the well at 5-8 shillings ; after carriage in a pipe line 6| shillings, or for a barrel of 
 42 gallons 2-58 dollars, so that in the years 1873 * J ^75> an( * a g a i n i n the first seven, 
 months of 1876, the oil proprietors were working at a decided loss. In Galicia, accord- 
 ing to Strippelmann, the cost of 100 kilos, of crude oil is 6'i shillings. 
 
 Hannover and Alsace yield but little oil ; Galicia produces yearly 800,000 hecto- 
 litres, and the Caucasus 4 millions. The production of crude oil in Pennsylvania rose 
 from 2000 barrels (at 159 litres) in 1859 to ten million barrels in 1874. In 1859 the 
 price was 20 dollars per barrel, and in 1874 it had fallen to 1*29 dollar. The total 
 exportation of the United States in 1886 and 1887 was : 
 
82 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 
 1886. 
 
 1887. 
 
 1887. 
 
 
 hectolitres. 
 
 hectolitres. 
 
 dollars. 
 
 Crude oil .... 
 Benzene .... . 
 Lighting oil ... . 
 Lubricating oil and Paraffine _. 
 Residues .... 
 
 289,320 
 54,223 
 1,793.750 
 52,111 
 7,556 
 
 305,640 
 46,786 
 1,759,108 
 77,091 
 ",325 
 
 5,HO,737 
 10,439,195 
 35,401,044 
 3,504,942 
 I4I>350 
 
 The total value was 
 
 1886. 
 1887. 
 
 47,016,095 dollars 
 45,231,988 
 
 ioo litres of crude oil yield on the average 76 litres of lighting oil, 12 litres of 
 gasoline, benzene, &c., 3 litres lubricating oil, and 9 litres of residues. 
 
 In Pennsylvania, where most of the wells are exhausted, boring is now not remune- 
 rative. The Bradford district, which for years produced more than the total consump- 
 tion in the world, furnishes now but little ; the total production in the remaining 
 districts is estimated at 58,000 barrels daily, while the world's consumption is now 
 daily 70,000 barrels. The consumption of mineral oil has increased not only in America 
 in 1882, 14,288,905 barrels but in India, China, Japan, England, France, Spain, 
 and along the Mediterranean. The increase from 1876 to 1882 is estimated at 150 per 
 cent., and the world's consumption for 1876 is taken at 10,000,000 barrels. 
 
 The Bradford oil now produced is not nearly so good as it v/as formerly obtained 
 from Parker's district in Pennsylvania. Of the latter, ioo barrels give 75 barrels of 
 refined oil, whilst ioo of the former yield only 66 barrels. The present so-called 
 refined oil is a product of very light and heavy oils ; a complete intermixture is not 
 always practicable. The lighter portions rise to the top and burn first ; whilst the 
 heavier oils collect at the bottom, and, if the wick is too thick and too compactly 
 woven, and if the burners are not very carefully cleaned, the light is unsatisfactory. 
 The American refineries are incessantly striving to remedy these evils. But it cannot 
 be denied that oils which have passed the German imperial test are often affected with 
 all these disadvantages. The consumption in Germany for 1882 was 2,001,136 barrels. 
 
 Natural Gas. The gases escaping from the oil wells at (i) Cherrytree, (2) Burns, 
 (3) Leechburg, (4) Harvey, and (5) Bloomfield, have, according to Sadtler and Wurtz, 
 the following composition : 
 
 
 
 
 
 
 
 
 ! 
 
 2 
 
 
 
 
 Carbon dioxide . 
 Carbon monoxide 
 Hydrocarbons (C n H 2n ) . 
 Methan (CHJ . 
 
 2-28 
 
 60-27 
 22" SO 
 
 0'34 
 
 trace 
 
 75 '44 
 6'io 
 
 0'35 
 0-26 
 0-56 
 89-65 
 4*70 
 
 0-66 
 trace 
 
 80-11 
 
 I 2 -CO 
 
 lO'II 
 
 2-94 
 82-41 
 
 Ethylhydrogen (C 2 H a ) . 
 Propylhydrogen (C 3 H 8 ) 
 Oxygen 
 
 Nitrogen 
 
 6-80 
 
 0-83 
 7-32 
 
 18-12 
 
 trace 
 
 4-39 
 
 trace 
 
 572 
 
 trace 
 
 0-23 
 4'3i 
 
 According to Fouque, these American gases belong to the series C n H 2n+2 ; these are 
 much used for heating steam boilers, for smelting furnaces, &c. 
 
 Mineral oil varies in consistence from a thin liquid to a butter-like fat ; its colour 
 ranges from that of water to black, and it has sometimes a blue fluorescence; the 
 specific gravity fluctuates between o'8 and o'96. 
 
 According to Boussingault, the oil from Bechelbronn contains hydrocarbons of the 
 series C n H 2W+2 , petrolene corresponds with the formula C 9 H 16 ; Blanchet and Sell found 
 in their researches compounds C^H^ and C B H 2JH ., ; Warren de la Rue and Miiller 
 found CjjHjn and C B H 2B+1 . The oil from Sehnde is C n H 2B , but, according to TJelsmann, 
 
SECT. I.] 
 
 MINERAL OIL. 
 
 it belongs to the series C n H 2rH _ r Bussenius obtained from the products boiling 
 between 90 and 140 a trinitropetrol C 8 H 7 (NO 2 ) 3 ; according to Eisenstuck, a mixture 
 chiefly of C 9 H 7 (N"O 2 ) 3 and C g H 7 (NOj) 3 . According to Le Bell, the mineral oil of the 
 Lower Rhine consists of hydrocarbons of the methan and ethylene series ; Joffre 
 detected in the mineral oil of Bruxiere de la Grue and Cordesse hydrocarbons absorbed 
 by sulphuric acid belonging to the series C n H 3B and others not absorbed of the series 
 C n H 2B+J , especially of C 8 H 18 to C^H^. In the Pennsylvanian oil Warren found 
 
 G 6 H 14 , Pelouze and Cahours 
 
 as the most volatile constituent C 5 H 12 , Lefebvre 
 
 C 4 H 10 and C 3 H 8 , Ronalds C 3 H 8 and C 2 H 6 . 
 
 According to Chandler and Schorlemmer, the oil contains the following hydro- 
 carbons : 
 
 Name (CHj i2 + 2 ). 
 
 Formula. 
 
 Boiling-point. 
 
 Specific Gravity. 
 
 Methan ........ 
 Ethan 
 
 CH 4 
 
 C 2 H 6 
 C S H 
 
 Gas 
 
 
 0*559 
 i x>^6 
 
 Butane 
 Pentane 
 
 C 4 H 10 
 
 C 5 H )2 
 
 i 
 
 30 
 
 0-600 
 0-628 
 
 Name. 
 
 Formula. 
 
 Boiling- 
 point. 
 
 Specific 
 Gravity. 
 
 Name (CnH 2 ). 
 
 Formula. 
 
 Boiling- 
 point. 
 
 Specific 
 Gravity. 
 
 Hexane 
 
 CH 14 
 
 69 
 
 0-664 
 
 Ethylene 
 
 C 2 H 4 
 
 Gas 
 
 0-978 
 
 Heptane 
 
 C 7 H I6 
 
 97'5 
 
 0-699 
 
 Propylene 
 
 C 3 H 8 
 
 -18 
 
 
 Octane 
 
 C S H 13 
 
 125 
 
 0-703 
 
 Butylene 
 
 C 4 H 8 
 
 + 3 
 
 
 Nonane 
 
 CgH^ 
 
 136 
 
 0741 
 
 Amylene . 
 
 C 5 H, 
 
 35 
 
 O'663 
 
 Dekane 
 
 C 10 Ho,, 
 
 158 
 
 0770 
 
 Hexylene . 
 
 C 6 H 12 
 
 69 
 
 
 Endekane 
 
 C,,H 24 
 
 182 
 
 0-765 
 
 Heptylene 
 
 C,H 14 
 
 95 
 
 
 Dodekane 
 
 C 12 H 2J 
 
 198 
 
 0776 
 
 Octylene . 
 
 C 8 H , B 
 
 104 
 
 
 Tridekane 
 
 (' H 
 V -13 rl 2S 
 
 216 
 
 0-792 
 
 Nonylene 
 
 C U H 18 
 
 140 
 
 
 Tetradekane 
 
 ^lAo 
 
 238 
 
 
 Dekatylene 
 
 Cl H'.0 
 
 160 
 
 
 Pentadekane 
 
 C 15 H 32 
 
 258 
 
 
 Endekatylenc 
 
 C 11 H 22 
 
 195 
 
 0782 
 
 
 ClgH.jg 
 
 
 
 Dodekatylene . 
 
 C 12 H 24 
 
 216 
 
 
 
 C 20 H 42 
 
 
 
 Dekatritylene . 
 
 Ci 3 H 2s 
 
 235 
 
 0791 
 
 
 C 23 H 4S 
 
 
 
 Cetene . 
 
 C i6 H a2 
 
 275 
 
 
 
 C^H^ 
 
 
 
 ? 
 
 ^20^40 
 
 
 
 Paraffine 
 
 C 27 H 5i 
 
 
 
 Cerotene 
 
 CH M 
 
 
 
 ti 
 
 CsoHffi. 
 
 370 
 
 
 Melene . . 
 
 CsoH,,, 
 
 375 
 
 
 Hemilian has furthur obtained from the Pennsylvanian oil a hydrocarbon melting 
 above 300, petrocen C 32 H 22 ; Rbttger separated from the fraction boiling between 
 55 and 65 a white body C 5 H 10 S0 3 . If the vapours of mineral oils boiling at low 
 temperatures are passed through ignited tubes, we obtain, according to Prunier, hydro- 
 carbons of the series 0,11^. 
 
 By fractionated distillation of the crude American oils the following average 
 products are obtained : 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Rhigolen 
 
 l*< 
 
 - 18 
 
 4Q 
 
 0-625 
 o-66s 
 
 
 IO'O 
 
 82-150 
 
 ' 3 
 
 0-7060-742 
 
 
 A'Q 
 
 
 
 Kerosene ........ 
 Paraffine oil ...... 
 
 55'0 
 
 iq-tr 
 
 - I6 7 
 
 too 
 
 0-804 
 0-85-088 
 
 Eesidue and loss . . . 
 
 IO'O 
 
 
 1 
 
 Other experiments show a very different percentage of products. 
 
8 4 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. i.. 
 
 Manufacture. According to Engler, 100 parts of crude oil contain 
 
 Pennsylvania. Galicia. Boumania. Alsace. 
 
 Easily volatile oils . 10-20 ... 3-6 ... 4 
 
 Lighting oils . . 60-75 ... 55-65 ... 60-70 ... 35~4O 
 
 Eesidues . . . 5-10 ... 30-40 ... 2 5~35 55~6o 
 
 The residues of the refineries at Baku are the most valuable ingredients, on account 
 of their suitability for lubricants. In these establishments Engler saw only the 
 following three forms of boilers : 
 
 (1) Upright wrought-iron boilers, of a cylindrical shape as tall as wide, with a 
 bottom arching upwards, and a common capital leading to the refrigerator. Capacity, 
 80 to 100 hecto-kilos, if filled from to ^. They are heated with naphtha residues. 
 
 (2) The so-called waggon-boiler (Figs. 99 and 100) consists of the chest-shaped 
 
 Fig. 99. 
 
 boiler of wrought-iron plates rivetted together. The largest size are 7 metres long, 
 4 metres wide, and 3 metres high from the lowest part of the bottom to the capital. 
 It has a bottom with three undulations, a top slightly arched upwards, and three 
 capitals, a, which carry away the vapours to the condenser ; b is a man-hole ; c are 
 exit supports for the residues. The inner arrangements of the boiler and the setting 
 with the flues, B and B v can easily be understood from the figures. From the burner, 
 r, of which there are always two side by side, and which open into the arched fire-flues, 
 B, B v the flame, for the protection of the bottom of the boiler, strikes first through 
 
 Fig. 101. 
 
 Fig. 102. 
 
 fire-proof vaults, turns at the end of the boiler, the bottom of which is here lined with 
 fire-clay tiles, again to the front, ascends and turns at both sides of the boiler, first 
 backwards and then downwards, and escapes into the chimney through the flue, 2 
 The distillation is assisted by the introduction of high-pressure steam. 
 
 If such a boiler (smaller size) contains 350 hecto-kilos., and is charged with 300 
 hecto-kilos. of crude oil, z| distillations can be effected in twenty-four hours, so that 
 700 to 800 hecto-kilos. of crude oil are distilled, which corresponds to a daily production of 
 
SECT. I.] MINERAL OIL. 85 
 
 200 to 250 hecto-kilos. of kerosene. The older setting in which the supporting walls 
 fitted into the depressions of the wave-shaped boiler, so that the three protuberances 
 lay free below and formed three fire-spaces, has been abandoned, as it caused a rapid 
 destruction of the bottom of the boiler. 
 
 3. Roller-boiler. Such a boiler is cylindrical, and is shown in Figs. 101 and 102. 
 The materials are wrought-iron plates, 10 mm. in thickness ; the length is from 5 to 
 6 metres, the diameter from 2 to 3 metres ; the smaller make, if filled to | or , hold 
 170 hecto-kilos. (=1000 pud.), the largest 270 hecto-kilos. It has not been found 
 practicable to exceed the latter size. The boiler, A, lies on bars, a, built into the wall, 
 and is further kept in its place by a number of flanges rivet ted to its sides. As a pro- 
 vision against boiling over, there is a large dome, B, from which the vapours escape 
 through an opening, c, into an iron conductor of the same width, by which they are 
 led to the refrigerator. The apparatus for burning residues is introduced at C ; its 
 flame strikes first through under the vault, passes at the opposite end over the vault 
 into the space C lt draws forward in the opposite direction directly under the boiler, 
 distributes itself here BO as to pass on both sides of the boiler in its original direction 
 through (7,, thus arriving into the common exit flue and into the chimney. If the 
 flames of the residues were let pass underneath the boiler without the protective vault, 
 the burner would have to be placed at least 175 metre below the bottom of the boiler, 
 on account of the intense heat. In most refineries a number of distilling boilers are 
 fixed side by side, and behind them runs a common tube with naphtha, from which 
 branch pipes, n, pass off for feeding the several boilers, as also a steam-pipe, d, with the 
 branch -pipe d v in order to assist the distillation in each by the introduction of high- 
 pressure steam. E is the outflow for the residues placed at the lowest point. The 
 man-hole serves for cleaning out the boiler. As condensers, water refrigerators are 
 uniformly used ; they are generally placed behind the distilling boilers, and connected 
 with the capitals by means of iron pipes, either directly or with the interposition of 
 one or more dephlegmators. 
 
 As wood and coal are wanting at Baku, the residues boiling at high temperatures 
 are largely used as fuel. For distilling 100 parts of crude F - 
 
 oil there are used 3 to 4 parts of these residues, called 
 by the Tartar workman " Massud," and by the Russians 
 " Astatki." 
 
 The combustion of these residues is effected by pulver- 
 ising them by means of high-pressure steam ; pulverising 
 by means of air does not answer. The air entering is sufficient for combustion, and 
 the temperature of the flames is enough to melt wrought-iron. Fig. 103 shows a 
 burner much used at Baku ; it consists of an iron tube, D, of the internal diameter 
 of 26 mm., flattened at its front end, so that there only remains a slit of to i 
 millimetre, through which the steam can pass. The residues are brought up through 
 the tube, N ; the thick oil running out at its end is distributed so as to flow down 
 over the steam slit, when it is finely pulverised and then burnt. The arrangement 
 of this burner under a boiler maybe seen from Figs. 99 and 100. 
 
 The chemical purification of the kerosene obtained on distillation is effected by 
 treatment with sulphuric acid, caustic soda, and water. The apparatus consists of two 
 iron receivers of a cylindrical shape, set above each other like steps. The bottoms are 
 shaped like funnels, with an outflow valve at the bottom, so that the contents of the 
 upper tank can conveniently flow into the lower, and from this, again, into the store 
 tank. The upper receiver, for treating the crude oil with sulphuric acid, is lined with 
 lead. 
 
 The " souring " of the oil is effected by an intimate mixture with strong sulphuric 
 acid containing at least 92 per cent, of monohydrate. The quantity used must be the 
 
86 CHEMICAL TECHNOLOGY. [SECT. i. 
 
 larger the more rapidly the oil has been distilled. In well-managed works it does not 
 exceed 0*9 per cent. The acid trickles in slowly through a ring of perforated tubes 
 with constant stirring, which is kept up for one and a-half to two hours; the oil 
 becomes heated, and sulphurous acid is given off. It is let settle ; the acid which col- 
 lects below is let off at a special branch-pipe, so that it may be used again, and the 
 kerosene is treated a second time with fresh acid. After this second souring follows a 
 washing process with cold water, which is not especially mixed with the oil, as the 
 separation would be too tedious. After settling for one hour, the oil is run off into the 
 lower tank for treatment with soda-lye. The lye is used first at sp. gr. 1*28 to i '35, and 
 then a weaker lye is introduced. The quantity of caustic soda used should not exceed 
 0*3 per cent. 
 
 An exactly neutral reaction is aimed at in many refineries. Water is not applied 
 after the soda process. To test kerosene for organic acids (derived from the oil), a 
 sample is shaken up with 2 per cent, of soda-lye at sp. gr. 1-2, let settle, and the clear 
 soda-liquid is acidified. The turbidity -arising shows the amount of the existing acid. 
 To ascertain if the treatment with sulphuric acid has been sufficient, a specimen is 
 shaken up with a few drops of soda-lye to form an emulsion, which by reflected light 
 must appear of a pure white without any yellow tinge. The colorimetric test is effected 
 with Stammer's colorimeter. A good burning oil is colourless and clear as water. 
 
 The photometric test is executed with Bunsen's photometer with the mirror com- 
 parison, the German normal candle being used as a standard. The distillation trial is 
 carried out with a Glinsky dephlegmater, filling the boiling flask each time with 250 cc. 
 of the oil, and taking two hours for the distillation working more slowly towards the 
 end. The flashing-point is determined with Abel's apparatus. Hitherto the limit in 
 Russia has been 28 to 30, but the manufacturers have resolved on a limit of 25. 
 
 The yield of the various products of the distillation differs according to the manner 
 of working. The more benzene and heavy oils are taken along with the true burning 
 oils boiling between 150 and 290 the higher is the yield of the latter and the 
 lower its quality. From numerous reports the following values may be taken : 
 
 Benzene with gasoline . . .5-7 per cent. 
 Kerosene I. (burning oil) . . . 27-33 
 Kerosene II. (solar oil) . . .5-8 
 Residues 50-60 
 
 In general, 3^ parts crude oil are used to obtain i part of kerosene. The quicker 
 the distillation the more abundant, but the poorer, is the product. At Nobel's refinery 
 the yield of kerosene of 32 flashing-point is 27 per cent.; of 50, 23 per cent. The 
 specific gravities for benzene are 0754, for gasoline 0787, for kerosene 0-820-0-822. 
 
 The cost of production for i hecto-kilo. (= 100 kilos.) burning oil (kerosene) are 
 
 Shillings. 
 3i hecto-kilos. crude naphtha . . . .1-78 
 
 Sulphuric acid 0*15 
 
 Caustic soda o'li 
 
 Wages 0-06 
 
 Management 0-07 
 
 Boiler repairs O'i8 
 
 Sinking fund, 15 per cent 0-24 
 
 2-59 
 
 Besides the kerosene there is 50 per cent. (17 hecto-kilos.) of residues, and 26 per 
 cent, of residues are used in heating the works. 
 
 The residues are especially adapted for the production of lubricating oils. These 
 oils are valuable from their viscosity, their resistance to cold, and their non-liability to- 
 spontaneous combustion. 
 
SECT, i.] THE PARAFFINE AND SOLAR OIL INDUSTRY. 87 
 
 Not merely kerosene, but the lighter products, gasoline, naphtha, and ligroine 
 are often burnt in lamps of special construction. The residues, as well as the 
 crude oil, may be heated in retorts for the production of gas. Compressed cymogen, 
 boiling at o, is used in the production of artificial ice ; Rhigolene Rhyolan, boiling at 
 1 8, serves as an anaesthetic; naphtha (petroleum-ether, or canadol) for extracting 
 fatty oils ; benzene for colours, varnishes, and for taking out spots, and the heavier oils 
 (vulcanol, vaseline, and valvoline) serve as lubricants. 
 
 THE PARAFFINE AND SOLAR OIL INDUSTRY. 
 
 Paraffine was first discovered in 1830 by Reichenbach in beech- wood tar, and 
 received its name from its disinclination to combine with other bodies. It was sub- 
 sequently obtained by the dry distillation of peat, lignite, Boghead coal, oil-shales, &c. 
 It occurs also in nature ready formed in mineral oil, which may contain from 6 to 40 
 per cent. ; in ozokerite (mineral wax) and in bitumen, or asphalte. The American 
 mineral oils contain little paraffine, but those of India (Rangoon tar) and of Java con- 
 tain large proportions. Warren de la Rue in 1854 obtained a patent for the extraction 
 of paraffine and hydrocarbons from mineral oils. The paraffine obtained as a residue in 
 refining the Pennsylvanian mineral oil is now met with in commerce and extensively 
 used under the name vaseline. It is employed in ointments, pomades, and for protect- 
 ing metal articles from oxidation. Very similar preparations are sold as " ozokerine " 
 and " Virginia." 
 
 Paraffine has been obtained for ten years from ozokerite. This mineral is found in 
 Galicia, on the northern slope of the Carpathians, in Roumania, Bulgaria, and various 
 places in Austria and Germany. It occurs also in Texas, Arizona, and Utah. 
 
 Paraffine is obtained in Scotland from asphalt. The bitumen of Trinidad, Cuba, 
 Canada, &c., forms a source for the preparation of paraffine and liquid fuels. 
 
 The manufacture of paraffine by the dry distillation of peat, lignite, oil-shales, &c., 
 resolves itself into two branches the preparation of tar, and the extraction from it of 
 photogen, solar oil and paraffine. The former process is difficult and important ; it is 
 now generally performed in upright retorts, preferably of fire-clay. 
 
 Preparation of the Tar. i. This operation is one of the most important and difficult 
 parts of the industry, and during the last fifty years many enterprises undertaken for 
 the application of fossil fuel to the preparation of illuminating materials have failed 
 solely on account of the imperfect preparation of the tar. The making of the tar is 
 carried on in retorts or in peculiarly constructed ovens, the distillation being in many 
 cases assisted by the application of superheated steam. The principle of the construc- 
 tion of the tar-oven is very simple, being that of a portion of fuel burning in the lower 
 part of the oven, a layer, more or less thick, of superincumbent fuel is submitted to a 
 slow carbonisation, resulting in the production of tar, which flows downwards, while 
 the gaseous products are lost. In order to prevent its violent combustion, the fuel is 
 covered with a layer of clay. But as experience has shown that this mode of distilla- 
 tion is not well suited for the production of tar intended to yield paraffine and the oils, 
 it is not generally in practice on the large scale, although it has the advantage of being a 
 continuous and uninterrupted process. According to report, an oven constructed by 
 L. Unger, the manager of a paraffine works at Dollnitz, near Halle, yields suitable pro- 
 ducts, while a saving is effected in labour as well as in the quantity of fuel required for 
 the distillation. 
 
 Horizontal retorts are frequently used for the preparation of tar, but experience 
 has taught that if in the construction of the furnaces containing the retorts tie 
 arrangement is similar to that of a gasworks where four to eight retorts are worked 
 in one furnace, no satisfactory results can be obtained, one of the reasons being that 
 
88 CHEMICAL TECHNOLOGY. [SECT. i. 
 
 the principles of gas- and of tar-making are entirely opposed. It appears to be neces- 
 sary to construct a furnace for every retort, and that the furnace should be of such 
 dimensions as to be suited to hold a retort 10 feet long, 30 inches wide, and 15 inches 
 high, forming in section a shallow oval. More recently there have been built in 
 Bohemia and elsewhere brickwork retorts, shaped somewhat like a baker's oven. These 
 seem to answer well, but are difficult to repair, although of small first cost. Vohl 
 observed that a quantity of 20 to 25 per cent, of water present in the fossil material 
 very greatly assists the formation and increases the yield of tar, owing to the super- 
 heated steam formed from the water during the distillation carrying off the vapours of the 
 tar rapidly from the hot retort. This has given rise to the construction of Lavender's 
 tar-producing apparatus, the principle of which is the same as that of Violetti's 
 wood-charring apparatus used for the preparation of the charcoal in gunpowder manu- 
 facture. Lavender's apparatus consists of an iron cylinder provided with holes at the 
 bottom for the purpose of admitting superheated steam, while to the top of the cylinder 
 a tube is fitted for carrying off the products of the distillation. It would appear that 
 L. Ramdohr's method of preparing tar from brown-coal by means of steam yields a tar 
 which contains 22 to 24 per cent, of paraffine, and 36 to 38 per cent, of oil. 
 
 Condensation of the Vapours of the Tar. The condensation of the products of the 
 dry distillation is one of the most important operations, and greatly influences the 
 yield of tar. Vohl has lately proved that even when the construction of the retorts is 
 not of the best, an average yield of tar may be obtained by attention to the condensa- 
 tion of the vapours. The complete condensation of the vapours of the tar is one of the 
 most difficult problems the paraffine and mineral oil manufacturer has to deal with, 
 while the means usually adopted for condensation, such as large condensing surfaces, 
 injection of cold water, and the like, have proved ineffectual. It has often been 
 attempted to condense the vapours of tar in the same manner as those of alcohol, but 
 there exist essential differences between the distillation of fluids and dry distillation. 
 In the former case the vapours soon expel all the air completely from the still and from 
 the condenser, and provided, therefore, that in reference to the size of the still and 
 bulk of the boiling liquid the latter be large and cool enough, every particle of vapour 
 must come into contact with the condensing surfaces. In the process of dry distilla- 
 tion the case is entirely different, because with the vapours, say of tar, permanent gases 
 are always generated. On coming into contact with the condensing surfaces, a portion 
 of the vapours is liquefied, leaving a layer of gas as a coating, as it were, on the con- 
 densing surface. The gas being a bad conductor of heat, prevents to such an extent 
 the further action of the condensing apparatus, that a large proportion of the vapours 
 is carried on and may be altogether lost. A sufficient condensation of the vapours of 
 tar can be obtained only by bringing all the particles of matter which are carried off 
 from the retorts into contact with the condensing surface, which need neither be very 
 large nor exceedingly cold, because the latent heat of the vapours of tar is small, and 
 consequently a moderately low temperature will be sufficient to condense these vapours 
 to the liquid state. The mixture of gases and vapours may be compared to an emul- 
 sion, such as milk, and as the particles of butter may be separated from milk by churn- 
 ing, so the separation of the vapours of tar from the gases can be greatly assisted by 
 the use of exhausters acting in the manner of blowing fans. It is of the utmost im- 
 portance in condensing the vapours of tar that the molecules of the vapours be kept in 
 continuous motion, and thus made to touch the sides of the condenser. The condenser 
 should not be constructed so that the vapours and gases can flow uninterruptedly in 
 one and the same direction. The temperature at which the distillation is conducted 
 greatly influences the yield of tar, and consequently of the paraffine and oil. As 
 regards the influence of the shape of the retorts and mode of distillation, H. Vohl made 
 the undermentioned comparative researches by distilling French and Scotch peat in 
 
SECT, i.] THE PARAFFINE AND SOLAK OIL INDUSTRY. 
 
 89 
 
 horizontal retorts (No. I.), in vertical retorts (No. II.), and in ovens somewhat like 
 coke-ovens (No. III.). 
 
 100 parts of peat yield of tar, 
 
 i. n. in. 
 
 French peat . . . 5-59 ... 4-67 ... 2-69 
 
 Scotch peat .... 9-08 ... 6-39 ... 4-16 
 
 The sp. gr. of the tar from the different kinds of apparatus was as follows : 
 
 i. IT. in. 
 
 French peat . . . 0-920 ... 0-970 ... roo6 
 Scotch peat . . . 0-935 0-970 ... 1-037 
 
 It appeal's from these results that horizontal retorts yield the largest, and ovens 
 the smallest, quantity of tar ; moreover, the duration of the operation of distilling is 
 shortest in horizontal retorts, which also yield less gas, while in the ovens both tar and 
 coke are burnt away to a considerable extent by the too great supply of oxygen. 
 
 Properties of Tar. The tar obtained from the retorts in distilling peat, brown-coal, 
 lignite, bituminous shales, Boghead coal, &c., at as low a temperature as possible, and 
 hardly higher than dull red-heat even towards the end of the operation, exhibits a 
 coffee-brown colour, generally an alkaline, but in some instances an acid, reaction, and 
 possesses the very penetrating odour characteristic of tar. By exposure to air the 
 colour of the tar becomes deeper, and sometimes even brownish-black. This tar often 
 semi-solidifies at a temperature of 9 to 6, owing to the paraffine it contains. The 
 sp. gr. varies from 0*85 to 0*93, and consequently the tar floats on water. The so- 
 called steam-tar, obtainedby the aid of superheated steam from brown-coal (according 
 to Ramdohr's plan, 1869) always has an acid reaction, and is completely saponified by 
 alkalies ; this tar becomes solid at a temperature of 55 to 60, and can therefore be 
 preserved in solid blocks in summer time. Its sp. gr. is 0*875. 
 
 As regards the quantity of tar obtained from 100 parts of raw material, the follow- 
 ing results are most general : 
 
 
 
 Sn Pi- 
 
 Crude 
 
 Paraffine. 
 
 
 
 
 
 per cent. 
 
 Foliated bituminous shale, Siebengebirge . . . .; 
 ,, Hesse 
 Brown-coal, Prussian Saxony . 
 .... 
 
 _> .... 
 
 2O'OO 
 
 25-00 
 7-00 
 
 lO'OO 
 
 6-00 
 5-00 
 
 II'OO 
 
 0-880 
 0-880 
 O^IO 
 O-92O 
 0-9I5 
 0'9IO 
 0-860 
 
 0-750 
 i-ooo 
 0-500 
 
 0750 
 0-500 
 0-250 
 
 Westerwald . . . . .'.- 
 Nassau 
 
 5-50 
 3-50 
 
 4-00 
 3'OO 
 
 O^IO 
 O^IO 
 O-9IO 
 O^IO 
 
 
 Frankfort 
 Lignite, Silesia 
 
 9-00 
 3-00 
 14-00 
 
 0-890 
 O-89O 
 0^70 
 
 0-250 
 
 I'OOO 
 
 Westphalia . . . .; 
 Schist, Wiirtemburg 
 
 Peat, Neumark . . . . v 
 
 5-00 
 
 9-63 
 5-00 
 9 -co 
 
 O-92O 
 
 0*975 
 O^IO 
 O-92O 
 
 0-050 
 0-124 
 0-330 
 
 O'O 
 
 Erzgebirge . ... 
 
 
 570 
 5-30 
 V86 
 
 O-902 
 0^5 
 
 0-350 
 
 0-400 
 
 
 7 -oo 
 
 
 
 
 3VOO 
 
 0-860 
 
 i i '4 
 
 Cannel coal, .... 
 
 
 
 i-i-3 
 
 I'OOO 
 
 Coarse coal, ,, ..... 
 
 9-00 
 
 O-9IO 
 
 I-I -25 
 
 Mode of Operating with the Tar. The first thing to be done with the crude tar 
 us to separate the water, which is effected by pumping the tar into the dehydrating 
 
9 o CHEMICAL TECHNOLOGY. [SECT. i. 
 
 apparatus. These apparatus consist of tanks of boiler-plate, placed within a larger tank, 
 so that a space of 10 centimetres intervenes, into which water is poured and maintained 
 by means of steam at a temperature of 60 to 80 for ten hours. After this time the 
 ammoniacal water and other impurities, together about one-third of the bulk of the 
 crude tar, have become separated, while the small quantity of water still adhering to 
 the tar is of no consequence in the further operations. The tar is decanted by opening 
 a stop-cock or valve placed near the top of the tank, and the ammoniacal water is 
 removed by opening a stop-cock at the bottom. 
 
 Specifically light tars are of course readily separated from the water, while heavy 
 tars are more difficult to deal with. If to the ammoniacal water of such tars salts are 
 added for instance, common salt, Glauber salt, chloride of calcium, and the like the 
 specific gravity of the water is increased, and the heavy tar more readily separated ; 
 but, according to Dullo, these means are either too expensive or do not quite answer the 
 purpose. The complete separation of the tar from the water is of the greatest import- 
 ance, because in the subsequent distillation the presence of water may cause the tar to 
 boil over and give rise to serious accidents by coming in contact with the fire under 
 the stills. 
 
 Distillation of the Tar. This operation is usually carried on in cast-iron stills large 
 enough to hold 20 cwt. of tar. In order to prevent the flame impinging on the bottom 
 of the still, it is protected by a fire-brick arch. The still is usually built in two separate 
 parts, which are joined with a flange and bolts, so that if the lower part is burnt out, 
 only that requires to be renewed. 
 
 The capitals of these stills are rather flat and the spout very wide. The vapours of 
 the various oils have a high density and low latent heat, so that these vapours have a 
 tendency to condense readily and flow back into the still ; therefore the capital is covered 
 with sand or ash, being bad conductors of heat. When the tar is thoroughly dehydrated, 
 the distillation proceeds quietly and without ebullition ; but if any water be mixed with 
 or adheres to the tar, the liquid in the still boils violently and is very apt to boil over. 
 At below 1 00 the tar loses the very volatile sulphide of ammonium and the pyrrhol 
 bases, while gases are evolved which ought to be allowed to escape by a safety-valve. 
 The true distillation begins at 1 00, yielding at first a distillate consisting of very strong 
 ammoniacal liquor and some light oils. The boiling-point of the tar is not constant, 
 the oil coming over uninterruptedly when the temperature has risen to above 200 ; 
 then the boiling-point becomes somewhat constant, while with the oil some water comes 
 over, due to the chemically combined water of the carbolic acid being set free. The 
 distillation then again becomes somewhat interrupted, and can be maintained only by 
 stronger firing of the retort. The oils now distilling over become solid on cooling, 
 owing to the large proportion of paraffine they contain. The distillation is continued 
 to dryness, the asphalt left in the still being removed after about four or five opera- 
 tions, and for this purpose the still is somewhat cooled, and the molten asphalt run off 
 by a tap at the bottom of the still. If the distillation is carried to dryness, some water 
 finally distils over, due to the decomposition of the organic matter. A still of 500 litres 
 capacity can be distilled off in twelve to fourteen hours, if the operation is pushed so far 
 as to decompose the asphalt, leaving only a carbonaceous residue ; but if the asphalt is 
 to be collected, the distillation must be stopped after eight to ten hours. The still is 
 separated from the condensing apparatus by a massive wall, through which the spout 
 of the capital is passed into the leaden worm, serving as a condenser, and kept cool by 
 being placed in a wooden tank filled with cold water. But as soon as the paraffine 
 magma begins to come over the water is allowed to become warm, in order to prevent 
 the paraffine solidifying in the worm. The gases which are evolved towards the end of 
 the distillation are carried off by a pipe communicating with the chimney. 
 
 Treatment of the Products of Distillation. The mixed products of raw oils 
 
SECT, i.] THE PARAFFINS AND SOLAR OIL INDUSTRY. 91 
 
 obtained by the distillation are poured into a large cast-iron cylinder and mixed with a 
 solution of caustic soda so as to cause the latter to act upon, and intimately combine 
 with, the acid substances (homologues of carbolic acid) simply termed creosote in the 
 works and pyroligneous acid, which impart an offensive odour and dark colour to the 
 oils. When the mixture of the oils and caustic soda solution has been effected, the 
 fluid is run into an iron tank and allowed to settle ; the creosote-soda is then removed, 
 and the oil washed with water to eliminate any adhering alkali. The crude oil is next 
 similarly treated with sulphuric acid for the purpose of removing basic substances, 
 which impart odour and colour. The quantity of acid to be used and the duration of 
 its action, aided sometimes by heat, depend upon the nature of the crude oil 5 per 
 cent, of acid of i"jo sp. gr. and five minutes' action are sometimes sufficient, while in 
 other cases 25 per cent, of acid will be required, and three hours' contact with the oil. 
 The action of the sulphuric acid should be carefully watched, as it may injure the 
 quality of the oil by decomposing some of the lighter hydrocarbons, whereby sulphur- 
 ous acid is given off. The mixture of acid and oil is allowed to settle ; the former is 
 run off, and the latter washed first with water, then with very dilute soda-lye, and is 
 finally poured into the rectifying stills. The solution of creosote-soda is neutralised 
 with the sulphuric acid from the preceding operation, the result being that crude 
 carbolic acid is obtained, which is used for various purposes ; such as impregnating 
 wooden railway sleepers, as a disinfecting material, or for preparing certain tar-colours. 
 More recently the creosote-soda has been used for gas manufacture, leaving a coke con- 
 taining soda, the soda being abstracted by lixiviation with water. 
 
 Rectification of the Crude Oils. This operation is conducted precisely as the distil- 
 lation of the tar. The oils are separated according to their greater or less volatility 
 and specific gravity, or are kept mixed, as parafline oil, at a sp. gr. of 0-833, and sent 
 as such to the market. When the oil which comes over begins to solidify on cooling or 
 exhibits a sp. gr. of o - 88 to 0*9, it is separately collected and placed in a cool situation 
 for the purpose of crystallising the paraffme. The vessels in which the parafline magma 
 is placed for the purpose of solidifying are rectangular iron tanks, fitted with a tap, or 
 are conical, sugar-loaf-shaped vessels, made of iron or wood, and from 1*6 to 2 metres 
 high, and i metre wide at the top, being provided with a tap for the purpose of remov- 
 ing the oily matter which has not solidified after the lapse of about two to four weeks. 
 This thick oil is next cooled to far below the freezing-point of water, in order to obtain 
 more parafline and other hydrocarbons mixed with it. Any still non -solidified matter is, 
 when it has a low specific gravity, again refined by distillation, and will yield parafline 
 oil ; but if its sp. gr. is high say from 0^925 to 0*940 it is used as a lubricating oil, 
 known abroad as Belgian waggon grease. 
 
 Refining the Crude Parafline. The crude parafline is in England sold to the 
 refiners, who are also paraffine-candle makers ; but on the Continent every manufacturer 
 of crude parafline refines his products and converts it into candles. The crude parafline, 
 so-called parafline butter, is treated in various ways : some manufacturers crystallise it 
 by the aid of cold, and press it for the purpose of removing any oil ; others, again, first 
 treat the crude material with caustic alkali-lye, next with sulphuric acid, and then again 
 distil it or leave it to crystallise. The caustic soda-lye removes from the parafline all the 
 acid substances and other impurities it may contain. The partly purified parafline is 
 now treated with 6 to 10 per cent, of sulphuric acid, whereby alkaline and resinous 
 matters are removed. The loss in bulk of the crude material by these operations 
 amounts to about 5 per cent. The purified parafline is next allowed to remain in a 
 very cool place for some three or four weeks, after which the nearly solid mass is 
 filtered, then submitted to the action of centrifugal machines, and finally strongly 
 pressed. The oil which is separated from the parafline is again distilled, yielding paraf- 
 fine oil and parafline butter. The solid parafline is molten, cast into blocks, and these 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 submitted to very powerful hydraulic pressure. The pressed cake is next treated at 
 1 80 with 10 per cent, of sulphuric acid for two hours, then washed with hot water, 
 again cast into blocks, again pressed, and then washed with a solution of caustic soda. 
 Instead of treating the paraffine with active agents, it has been proposed to use neutral 
 solvents for the removal of the oily materials ; for this purpose, benzol, light tar oils, 
 benzolene, and sulphide of carbon, have been employed in the following manner : The 
 crude paraffine is first hot-pressed, and the pressed mass fused with 5 to 6 per cent, of 
 the solvent ; having been again cast into blocks, these are pressed, and the operation 
 repeated if necessary. The paraffine having thus been made quite white and pure, is 
 again fused and treated with high-pressure steam, forced into the molten mass for the 
 purpose of volatilising the last traces of the solvents. The sulphide of carbon, first em- 
 ployed by Alcan (1858) for refining paraffine, is used in the following manner: The 
 paraffine is melted at the lowest possible temperature, then well mixed with 10 to 15 
 per cent, of sulphide of carbon, after which the cooled and solidified mass is strongly 
 pressed, the expressed fluid being submitted to distillation for the purpose of recovering 
 the sulphide of carbon. The paraffine is next fused and kept in liquid state for some 
 time for the purpose of eliminating the adhering sulphide of carbon. 
 
 Hubner's Method of Preparing Paraffine. Instead of following the preceding 
 method with the crude tar, Hubner treats it first with sulphuric acid, and next distils 
 the tar, separated from the acid, over quicklime. The crude paraffine obtained is 
 pressed, and then further refined by treating it with colourless brown-coal tar oil. The 
 advantages of this method by which one distillation is saved are : 
 
 a. A larger yield of paraffine. 
 
 jQ. A material of better quality and greater hardness than by the usual method. 
 
 With the paraffine the so-called paraffine oils are obtained ; but this industry has 
 been greatly crippled by the extensive importation of paraffine oils (really petroleum 
 oils) from America, so that the aim of the paraffine makers is to increase the yield of 
 paraffine. By Hubner's method of distillation over quicklime, 40 to 50 per cent, of 
 impurities (chiefly empyreumatic resins and creosote) are removed, which by the old 
 process are only got rid of at greater expense by the use of caustic soda. 
 
 Yield of Paraffine. As regards the yield of paraffine, paraffine oil, and lubricating 
 oil, from the various kinds of raw materials, we quote the following particulars. At 
 the Bernuthsfeld works, near Aurich, the excellent peat yields 6 to 8 per cent, of tar ; 
 20 per cent, of paraffine oil, of sp. gr. = 0-830 ; and 0*75 per cent, of paraffine. 
 H. Vohl obtained from 100 parts of peat-tar from the peat of undermentioned 
 localities : 
 
 1 
 
 1 . r 
 
 Paraffine Oil. 
 
 Lubricating 1 Oil. 
 
 
 i 
 
 Sp. gr. o'82o. 
 
 Sp. gr. o'86o. 
 
 
 \ 
 Celle (Hannover) 
 Coburg 
 
 34'6o 
 20-62 
 
 IQ-4 1 ? 
 
 36-00 
 26-57 
 19-54 
 
 8-01 
 3-12 
 3-31 
 
 ; Zurich (Switzerland) 
 
 I4"4O 
 
 8-66 
 
 0-42 
 
 Russia . ....... 
 
 2O*^Q 
 
 20 -30 
 
 3'36 
 
 Westphalia . 
 
 II'OO 
 
 19-48 
 
 2-25 
 
 Brown-Coal. In the works situated in the Weissenfels brown-coal mineral district, 
 275 to 300 Ibs. of the mineral yields 35 to 50 Ibs. of tar. 100 Ibs. of this tar 
 yield 8 to 10 Ibs. of hard paraffine suited for candle-making, and further 8 to 10 Ib. of 
 soft paraffine for use in stearine-candle making, as well as 43 Ibs. of paraffine oil. 
 Hubner's works at Rehmsdorf, near Zeitz, yield annually from 360,000 cwts. of brown- 
 coal, about 40,000 cwts. of tar, yielding 18,000 cwts. of crude oil, 4000 cwts. of refined 
 paraffine oil, and 6000 cwts. of paraffine. 
 
SECT, i.] THE PARAFFINE AND SOLAR OIL INDUSTRY. 93 
 
 i oo parts of retort-tar (in contradistinction to steam-tar) from brown-coal yield : 
 
 Brown Coal from 
 
 Paraffine Oil. 
 Sp. gr. o'82o. 
 
 Lubricating Oil. 
 Sp. gr. o - 86o. 
 
 Paraffine. 
 
 Analysed by 
 
 
 33-50 
 
 4O'OO 
 
 3 '3 
 
 \ 
 
 
 33'4I 
 
 40-06 
 
 67 
 
 
 
 17-50 
 
 26-2I 
 
 5-0 
 
 
 Oldisleben 
 
 1772 
 
 26-60 
 
 4'4 
 
 
 
 16*42 
 
 27-14 
 
 4'2 
 
 Wohl. 
 
 Der Rhon, Bavaria 
 
 IO-62 
 
 I9-37 
 
 I '2 
 
 
 Tilleda, Prussia ... 
 
 I6'66 
 
 18-05 
 
 4'4 
 
 
 Stockheim, near Diiren, Prussia 
 
 I7-SO 
 
 26-63 
 
 3'2 
 
 
 Bensberg, near Cologne 
 
 16-36 
 
 I9-S3 
 
 3-4 
 
 / 
 
 Tscheitch, Austro- Hungary . 
 
 9-04 
 
 28-86 
 
 3-2 
 
 
 Eger 
 
 9-14 
 
 54-00 
 
 5'2 
 
 C Miiller 
 
 Herwitz 
 
 22-OO 
 
 48-32 
 
 5 '2 
 
 
 Schobritz .. . 
 
 21-68 
 
 46-33 
 
 4'3 
 
 
 Ramdohr obtained (1869) from steam-tar from brown-coal on an average 
 
 '5 P er cent - fusin g afc 
 9 
 36 to 38 per cent, of oil. 
 
 22 to 24 per cent, paraffine , 
 \ 7 
 
 to 58;j and 
 " 47 ) 
 
 With careful management steam-tar may yield from 28 to 30 per cent, paraffine. 
 The quotations of the yield from cannel and Boghead coals vary very much. 100 
 parts of tar from bituminous shale were found to yield : 
 
 
 Mineral Oil. 
 
 Lubricating Oil- 
 
 Paraffine. 
 
 
 English bituminous shale 
 Bituminous shale from Romerickberg, Prussia 
 Westphalia 
 Oedingen on the Rhine . 
 
 24-28 
 25-68 
 27-50 
 18-33 
 
 40*00 
 43-00 
 13-67 
 38-33 
 
 O'I2 
 O'll 
 I'll 
 5.00 
 
 According to Miiller (1867), 100 parts of Galician mineral wax (ozokerite) yield 
 24 per cent, of paraffine and 40 per cent, of oil. 
 
 Paraffine when purified is a white, waxy, tasteless, and inodorous mass, slightly 
 greasy to the touch, harder than tallow, but softer than wax. Its sp. gr. varies from 
 0-869 to 0-943, and its specific heat = 0-683. If heated for days with access of air it 
 takes up oxygen and turns brownish. Its properties vary according to its origin. 
 Paraffine from the Boghead coal melts at 45, and is either crystalline or granular ; but 
 it has been known to melt at 80. Paraffine from Rangoon tar melts at 61, that from 
 peat at 47, that from ozokerite at 56 to 82. Paraffine seems to be a mixture of 
 hydrocarbons homologous with methan (of the formula CH 2 + 2 ), and especially of 
 members of this series containing more than 16 atoms of C. The softer paraffines have 
 the formulae C 18 H 40 , and C 20 H 42 ; whilst the harder varieties are C 21 H 44 and C 22 H 46 . 
 Grotowsky found in paraffine from Saxon lignite 3-4 per cent, of oxygen, and gave it 
 the formula C 32 H 33 O. 
 
 Paraffine is insoluble in water, but soluble in alcohol, ether, oil of turpentine, olive 
 oil, benzol, chloroform, and carbon disulphide. Acids and alkalies do not attack paraffine 
 at common temperatures ; neither does chlorine, but if it is allowed to act for some 
 time upon melted paraffine, hydrochloric acid is evolved, and chlorised products are 
 formed. If heated with bromine it forms hydrobromic acid in abundance, and with 
 sulphur sulphuretted hydrogen.* 
 
 Paraffine can be melted along with wax, stearine, and palniitine in any proportion. 
 
 The main application of paraffine is, of course, in the manufacture of candles. Its 
 minor uses are for saturating matches, greasing leather, preparing wax-papers, polish- 
 ing glazed-paper, &c. 
 
 * The latter reaction has been proposed as a means of obtaining sulphuretted hydrogen, abso- 
 lutely free from arsenic, for use e.g., in toxicological cases. 
 
94 CHEMICAL TECHNOLOGY. [SECT. i. 
 
 Along with paraffine, Eeichenbach discovered in tar eupion a very light mobile fluid, 
 which burns with aluminous flame. Its boiling-point varied from 47 to 169 so that 
 it was doubtless a mixture. 
 
 Solar Oil. Tar-oil can be resolved by further rectification into paraffine and into 
 oily liquids, which, after the acid and the heavy constituents are removed, occur in 
 commerce as a mixture under the names photogene, mineral oil, solar oil, paraffine 
 oil (which in England denotes the lamp oil obtained from the Boghead mineral). 
 These oils are very similar to petroleum oils and consist only of carbon and hydrogen. 
 When thoroughly purified they are colourless and have only a slight smell. 
 
 The mineral oils are thus distinguished photogene is a mixture of liquid hydro- 
 carbons of the ethase series (C^H^ + 2 ) especially of Leptase, C 7 H 16 and benzyl-hydride, 
 C 15 H 33 . It is a clear, very mobile liquid of sp. gr. 0*80 to o - 8i ; the earlier light 
 photogenesof 078 sp. gr. contain chiefly essences of sp. gr. 0720, boiling below 60. 
 They have hence been long ago proscribed as dangerous. The low-boiling oils from 
 lignite tar and mineral oil are sold by the names benzene (benzolene, naphtha, ligroine) 
 and are used for taking out fat and oil stains, for removing the grease of wool, as a 
 substitute for oil of turpentine, for enriching gas, &c. The solar oil, which is being 
 substituted as an illuminant for the photogenes and the fatty oils of the past, is a 
 clear oil, colourless and slightly yellowish, of sp. gr. 0-825 * '83O. The boiling-point 
 is on the mean 178. At 10 no solid paraffine should separate out. Its flashing 
 point is above 100. On fractionation no products having a flashing point below 70 
 should separate out. 
 
 Along with solar oil follows the pyrogene of Breitenlohner, obtained from the 
 residuary crude oils, having a sp. gr. of 0-895 to 0-945, which accumulate in the tar- 
 works. Pyrogene is a light wine-yellow oil of sp. gr. 0-825 to 0-845. 
 
 Lubricating oil, known also as "vulcanol," is a thick oil of sp. gr. 0*845 * 
 o'86o, and at low temperatures deposits abundance of fine crystals of paraffine. It is 
 formed in great quantities in the petroleum refineries and in the paraffine and solar 
 oil works. The vulcanol imported from America is not a distilled product, but a heavy 
 mineral oil decolorised by means of bone-black. Sometimes it is mixed with a few 
 per cents, of animal or vegetable fats. 
 
 The manufacture of mineral oil is developed simultaneously with that of paraffine. 
 Solar oil gives, in suitable lamps, a light equal in intensity to that of kerosene. It 
 has, however, an unpleasant smell and is apt to smoke.* 
 
 PRODUCTION OF LIGHT. 
 
 If solids are heated they become feebly luminous in the dark about 400 ; at 600 
 they are red-hot, at 90o-iooo white hot, whilst gases even at i5oo-2ooo do not 
 become luminous. The luminosity of flame is therefore not the ignition of the products 
 of combustion. If the gases arriving at combustion are more quickly mixed, the flame 
 becomes shorter, since the process is effected more rapidly, and at the same time 
 hotter, since less cold air is mixed with the products of combustion. In the same 
 manner, the flame becomes shorter and hotter if the gases are heated prior to 
 combustion. As the ascending products of combustion retain for a short time nearly 
 the temperature of the flame, the reverse behaviour would occur if the gases were 
 self-luminous. The light of the flame ceases at a sharply marked upper boundary, 
 and evidently coincides with the completion of the chemical action. This action 
 consequently, and not the ignition of the products of burning, must be the cause 
 of the light. 
 
 * It must seem strange that the author should have made no mention of the merits of the late 
 James Young in connection with the paraffine industry. The only mention of his name is in n 
 note giving the statistics of Young's Mineral Oil Company. [EDITOR.] 
 
SECT. I.] 
 
 PHOTOMETEY. 
 
 95 
 
 In the flame of a candle we may distinguish four layers. The dark nucleus is 
 formed by the gasification of the fuel (tallow, paraffine, &c.) rising up in the wick, 
 which may be kindled at the orifice of a fine glass tube cautiously inserted into the 
 flame. The rush of air is directed towards the axis of the flame, whence the blue portion 
 has a lower temperature. In the luminous layer the oxygen of the air is only in part 
 sufficient for combustion, whilst in the non-luminous veil externally the products of 
 the imperfect oxidation burn in an excess of air. 
 
 In opposition to the well-known theory of Davy that the luminosity of a flame is 
 due to particles of carbon ignited to whiteness by the combustion of the hydrogen, 
 Frankland and Tyndall maintain that the luminosity is due, not to the separation of 
 solid carbon, but to the presence of dense vapours of the higher hydrocarbons. 
 
 PHOTOMETRY. 
 
 Attempts at measuring the luminosity of a flame were made as early as 1700. 
 Lambert (1760) utilised the circumstance that an object illuminated by two flames 
 throws two shadows of unequal depth if the action of both flames upon the screen 
 receiving the shadows is unequal. Let C D (Fig. 104) be a white screen, before which 
 
 Fig. 104. 
 
 stands at some distance a thin round rod, blackened with soot, s, and let 1 be the one 
 and L the other source of light. The two lights are placed so that the two shadows of 
 the rod, a and b, do not coincide, but fall upon the screen, C D, at no great distance 
 from each other. The stronger light is then pushed so far from the screen, C D, that 
 the shadows are equally dark i.e., the shadow, b, is as strongly illuminated by the 
 light, L, as is the shadow, a, by the light, 1. The process is not adapted for accurate 
 measurements, but it is simple and easy, and may even now serve for the purposes 
 of daily life. 
 
 Bunsen's photometer is chiefly used for measuring different sources of light. It 
 consists of a paper screen stretched in a frame, and in the middle is a spot made trans- 
 lucent with wax or stearine. It appears light on a dark ground if the screen is 
 illuminated more strongly at the back than at the front, and in the reverse case dark 
 on a light ground. The normal flame is placed on one side of the screen, and on the 
 other the flame to be measured, and this is displaced until the spot nearly disappears. 
 If, e.g., the distance of the normal flame from the screen is 2 decimetres, and that of 
 the flame to be measured 8 decimetres, the latter = 8 2 : 2 2 16 candles. 
 
 During such measurements all other sources of light must be carefully excluded. 
 
 As unit, the flame of a candle is generally used. In Germany the photometric 
 candle has a diameter of 20 mm. ; it must be accurately cylindrical, and so long that 
 twelve candles weigh i kilo. The wicks must be twisted as uniformly as possible, of 
 
9 6 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 twenty-four threads of cotton, and, when dry, must weigh 668 m. grammes per metre 
 run. They are distinguished from other wicks by the introduction of a red thread. The 
 material must be paraffine, as pure as possible, congealing not under 55. The flame 
 must be 50 mm. in height. 
 
 In Munich there is used as the unit a stearine candle made from a stearine con- 
 taining 76 to 76^6 per cent, of carbon. It consumes hourly, according to Schilling, on an 
 average io'4 grammes stearine, and has a flame of 52 mm. in height. The English sper- 
 maceti candle has a wick platted of three strands,, 
 each containing seventeen threads ; it consumes 
 hourly 120 grains (7'78 grammes) spermaceti, the 
 height of the flame being 45 mm. In France the 
 carcel lamp is used, burning hourly 42 grammes 
 colza oil. 
 
 The relation of these normal flames is, accord- 
 ing to Schilling 
 
 Figs. 105 and 106. 
 
 German Candle. 
 
 Munich Candle. 
 
 English Candle. 
 
 Carcel Lamp. 
 
 IOOO 
 1128 
 
 887 
 IOOO 
 
 977 
 
 1 102 
 
 I O2 
 H5 
 
 1023 
 9826 
 
 907 
 8715 
 
 IOOO 
 9600 
 
 104 
 IOOO 
 
 Monier found i carcel = 7-5 German candles = 
 7'5 bougies d'etoile = 6'5 Munich candles = 8'3 
 English candles. If we compare with these 
 figures the experiments of Violle, we may be able 
 to compare the luminosity of paraffine and sper- 
 maceti candles. 
 
 According to the newest reports of the Ger- 
 man Normal Candle Commission, candles of paraf- 
 fine, stearine, and spermaceti give almost exactly 
 equal lights if the wicks and the height of the 
 flame are kept alike. 
 
 The conflicting statements concerning the 
 value of the normal candles induced Hefner- 
 Alteneck to propose the following unit of light 
 it is the light of a flame burning in pure motion- 
 less atmospheric air, arising from the section of a 
 massive wick saturated with amyl acetate. The 
 wick completely fills a round socket of nickel 
 silver of 8 mm. inner and 8*3 outer diameter, and 
 of 25 mm. length. The flame is 40 mm. in height, 
 measured from the margin of the wick-holder, and 
 is shown by the sight-line over the angles, a and 
 b (Figs. 105 and 106). It is arranged by look- 
 ing through the point of the flame to the angles, 
 a and b, upon which the light shows, and regu- 
 lating the height of the flame by turning the 
 milled head, S, so that the point of the bright nucleus of the flame just touches the 
 line from below. The angles, a and b, are kept bright. The wick does not extend 
 into the flame. Its nature has no effect upon the light as long as it fills up the socket, 
 and is able to suck up the fuel in sufficient excess. Hence it must not be pressed 
 too tightly into the socket. The wick consists of threads laid parallel to (and not 
 
SECT. I.] 
 
 PHOTOMETRY. 
 
 97 
 
 twisted or plaited) its length, so thick that it can be easily fitted to the diameter of 
 the socket. The wick is cut level and horizontal with sharp scissors. The quantity of 
 fuel in the lamp is not important, so long as the wick dips well in with all its threads. 
 From time to time the wick-holder must be cleaned from a thick brown deposit. The air 
 must be perfectly calm, as the slightest draught causes the point of the flame to rise 
 and sink. This light-unit is equal to an English spermaceti candle at a flame-height 
 of 43 mm. 
 
 The International Conference held in Paris in 1883-84 adopted as the unit of white 
 light the quantity of light radiated out by i square centimetre of pure melted platinum 
 at the temperature of solidification. 
 
 To produce this platinum light-unit, Violle used a platinum mlting-furnace of 
 lime which admits an oxy-hydrogen flame to play upon the platinum through its cover. 
 When all the platinum is fused the liquid mass has a much higher temperature than 
 its melting-point (1775), anc ^ * ne liquid metal is placed behind or under a double screen 
 with an aperture of a certain width, through which the light falls. The screen is 
 made of platinum or copper ; it is double, and is kept cool by a stream of cold water. 
 The light rays passing through the opening are thrown upon the photometer screen. 
 
 Fig. 107 shows the apparatus for comparing the platinum unit with the carcel 
 lamp, as constructed by Deleuil of Paris. The carcel, C, can be moved upon a sledge 
 
 Fig. 107. 
 
 before the screen, E, of a Foucault photometer. The rays coming from both sources 
 of light are separated by the screen, K. The apparatus for producing the platinum- 
 unit is on the left side. F is the Deville furnace, the lid of which is pushed back in 
 front to uncover the surface of the melted metal. D is the lid cooled with water, A 
 and A' the entrance and exit for water. The blowpipe is connected with the oxygen 
 gasometer, and the supply of common coal-gas by the pipes, O and H. The whole 
 smelting apparatus rests upon a little table, which can be fixed at any height by means 
 of the screw, g. The mirror, M, reflects back upon the screen of the photometer the 
 rays which have been let through from the cover. If the kind of light to be compared 
 e.g., a glow-lamp permits any desired position, the disc of the photometer is brought 
 to bear vertically upon the crucible containing the platinum ; if, as is usual, this is 
 impracticable, the rays proceeding from the metal bath must be deflected horizontally 
 by a mirror or a prism, as shown in Fig. 107. The co-efficient of absorption of 
 the mirror and the prism must of course be taken into account. When the adjustment 
 
 o 
 
9 8 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 
 has been effected, and the rays of both the sources to be compared fall upon the screen 
 of the photometer, an equal illumination is obtained by displacing either the screen or 
 one of the sources of light. The equality is very brief, as the melted metal cools, and 
 the emission of light rapidly decreases. The measurement must be effected whilst the 
 temperature and the light are constant. Violle gives the following comparison of the 
 measure of light : 
 
 
 Platinum- 
 unit. 
 
 Carcel. 
 
 French 
 Candle. 
 
 German 
 Candle. 
 
 English 
 Candle. 
 
 
 Platinum-unit . 
 
 I 
 
 2'08 
 
 16-100 
 
 l6'4OO 
 
 18-50 
 
 Carcel 
 
 0-481 
 
 I 
 
 7750 
 
 7-890 
 
 8-91 
 
 French stearine candle 
 
 0-062 
 
 0-130 
 
 I 
 
 I'O2O 
 
 *IS 
 
 German normal candle 
 
 o'o6i 
 
 0*127 
 
 0-984 
 
 I 
 
 I-I3 
 
 English candle 
 
 0-054 
 
 0-II2 
 
 0-870 
 
 0-886 
 
 I 
 
 Unfortunately, little is gained by proposing this international unit, as it cannot be 
 carried about like a standard measure of weight, but must be produced afresh on every 
 occasion, and requires preparations which will rarely be practicable. The amyl acetate 
 lamp appears most practical, and will probably in time supersede the other units. 
 
 Illumination is effected 
 
 1. By the combustion of solids made up in the form of candles, such as tallow, 
 stearine, paraffine, and wax. 
 
 2. By means of liquids burnt in lamps, either (a) liquid fats, rape oil, olive oil, or 
 train ; (b) volatile oils, petroleum, solar oil, camphine (purified oil of turpentine). 
 
 3. By gases which are either luminous in themselves, as coal- and oil-gas, or, like 
 water-gas, act by rendering solids incandescent, such as platinum, magnesia, zirconia, 
 <kc. 
 
 4. By electricity. 
 
 LIGHTING WITH CANDLES. 
 
 Wax candles appear not to have been made prior to the beginning of the fourth 
 century ; tallow candles made their appearance in the twelfth century ; spermaceti 
 candles in the beginning of the eighteenth century; stearine candles in 1834, and 
 paraffine candles in 1850.* 
 
 LIGHTING WITH LAMPS. 
 
 As liquid capable of serving for the production of light we have (a) the fatty oils, 
 (b) the volatile oils, which latter are either ethereal oils, such as camphine, products of 
 the treatment of the tar from lignite e.g., photogen and solar oil or oils supplied by 
 nature (petroleum and naphtha). Of the fatty oils the most common are rape, colza, 
 olive oil, train, and, more rarely, poppy oil. 
 
 In order to refine the fatty oils, they are mixed with 2 per cent, of sulphuric acid, 
 or a strong solution of zinc-chloride, and well shaken up. These reagents do not 
 attack the oil itself, but destroy all the mucilaginous and other foreign matter, and 
 separate it out. On washing with water, the acid and the zinc-chloride are removed, 
 
 * Notwithstanding the introduction of gas and of petroleum lamps, the demand for candles is 
 still increasing. The preparation of wicks and the process of moulding candles are mechanical 
 rather than chemical operations ; and, as much space will be required below for the introduction of 
 matter not contained in the German edition, they are omitted. A light obtained by the com- 
 bustion of magnesium wire must not be overlooked. It is certainly expensive, but it resembles 
 solar light more closely than even the electric light, and is therefore unequalled for use in the 
 tinctorial arts if it is required to match off colours after sunset, or in foggy or cloudy weather. 
 If metallic magnesium can be produced more cheaply, this light will have a great future. 
 
SECT, i.] LIGHTING WITH LAMPS. 99 
 
 and the oil is thus purified. Since the rise of the paraffine and petroleum industry the 
 importance of the fatty oils as sources of light has much declined. 
 
 Lamps were in use in pre-historical ages. Elegant as were the forms of those 
 employed by the Greeks and Romans, their construction was technologically most 
 imperfect. If we except a few empirically discovered improvements, such as the lamp- 
 glass (chimney) introduced by Quinquet, and the invention of the hollow circular wicks 
 by Argand in 1786, the construction of a normal lamp has been rendered possible by 
 the development of chemistry e.g., the theory of combustion and illumination, the 
 application of physical data to the supply of oil to the burner, and the determination 
 of the illuminating power of the lamp-flame, the refining of oils, and the supply of 
 solar oil and petroleum. In 1850 the camphine lamp was introduced, and, soon after, 
 the elegant but costly regulators and moderators. In the fifties began a struggle of the 
 oil-lamps among themselves, and at the same time against gas. In the sixties the 
 petroleum-lamp appeared, and has almost entirely superseded the oil-lamp. A lamp 
 contains the same parts as a candle the luminiferous material and the wick. In each 
 the material is liquid, and the difference is merely that in the candle, in the cup- 
 shaped depression round the wick, the fat (stearine, tallow, paraffine, &c.) is burnt in a 
 melted condition, whilst in a lamp the material is liquid at common temperatures, and 
 requires a vessel in which the liquid fuel is contained, so as to feed the flame con- 
 tinuously and as equally as possible. The great variety which we see in lamps 
 resolves itself into the character of the fuel, the form of the wick, and the manner of 
 supplying air to the flame, whether with or without a draught ; in the shape of the oil 
 cistern, its position with respect to the wick, and in the conveyance of the oil to the 
 wick, whether by capillarity alone or in connection with hydrostatic or mechanical 
 pressure. 
 
 Rape oil and mineral oil, whatever the character of the latter, differ in the fact 
 that the former at common temperatures does not evaporate. Hence it is inodorous, 
 and cannot be ignited. Only when it has been heated to such a degree that the 
 products of dry distillation, especially inflammable gases, are formed, do ign ion and 
 combustion of the oil take place. Mineral oil, even the so-called " inodorous " quality 
 of the factories, has a smell, and on prolonged exposure to the air it gradually loses 
 weight. At higher temperatures it evaporates, and may be distilled unchanged. At 
 a still greater heat it is gasified, and becomes chiefly illuminating gas. Refined rape 
 oil in a properly constructed lamp burns only in a gaseous form, and completely, yield- 
 ing merely the inodorous products, carbonic acid and watery vapour. Solar oil and 
 mineral oil are mixtures of various hydrocarbons. They begin to boil at 250, and at 
 higher temperatures are resolved into gaseous products, and into free carbon. The 
 proportion of carbon in mineral oils is far greater than in rape oil, as is here shown : 
 
 
 Per Cent. Composition. 
 
 i Kilo. 
 
 i Kilo yields : 
 
 Names. 
 
 
 
 
 for 
 
 Carbonic 
 
 Wntor 
 
 
 Carbon. 
 
 Hydrogen. 
 
 Oxygen. 
 
 Combustion. 
 
 Acid. 
 
 
 
 
 
 
 kilos. 
 
 kilos. 
 
 kilos. 
 
 Stearine 
 
 76*1 
 
 I2'5 
 
 11-4 
 
 2 '92 
 
 279 
 
 13 
 
 Rape oil 
 
 77 -2 
 
 I3'4 
 
 9 '4 
 
 3 '4 
 
 2-8 3 
 
 '21 
 
 Tallow 
 
 78-1 
 
 117 
 
 9 '3 
 
 2'9I 
 
 2-86 
 
 'OS 
 
 Spermaceti 
 
 8r6 
 
 12-8 
 
 5'6 
 
 3'14 
 
 2-99 
 
 'IS 
 
 Wax . 
 
 81-8 
 
 127 
 
 5'5 
 
 3'I4 
 
 3' 
 
 '14 
 
 Petroleum 
 
 85-2 
 
 14-8 
 
 
 3'45 
 
 3'12 
 
 '33 
 
 Paraffine 
 
 857 
 
 I4-3 
 
 
 
 3 '43 
 
 3'i4 
 
 29 
 
 Hence the first burns in the open air with a smoky flame, which, by the use of a 
 draught-glass, is at once rendered of a dazzling whiteness and strongly luminous, the 
 combustion of the excess of carbon being thus effected by the increased supply of air ; 
 whilst rape oil arrives at the flame only in a gasified condition, solar oil and the less 
 
IOO 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. 
 
 volatile part of petroleum, similar in its composition, enter the flame as a vapour. 
 Mineral oil lamps must therefore be so arranged that the combustion is effected as per- 
 fectly as possible, and that no trace of the malodorous vapour escapes unconsumed. 
 
 A normal lamp, whatever its fuel, must be so constructed that it gives out a maxi- 
 mum of light during a certain time, and that as uniformly as possible ; the light pro- 
 duced must also be utilised to the beet advantage. 
 
 Lamps may be classified according to the manner in which the fuel arrives at the 
 point where the light is to be evolved. Thus we have 
 
 (i) Suction lamps, in which the oil is brought up by capillary action alone from a 
 lower receiver. (2) Pressure lamps, in which a mechanical or physical arrangement 
 conveys the oil to the wick. Pressure lamps are again subdivided into (a) aerostatic 
 lamps, in which the principle of Heron's lamp comes into play ; (b) hydrostatic lamps, 
 depending on the principle of communicating tubes according to the levels of liquids of 
 different specific gravities in connected tubes ; (c) static lamps, in which the oil is 
 
 Fig. 108. 
 
 Fig. 109. 
 
 Fig. no. 
 
 driven up by a weight or a piston, and (d) mechanical 
 lamps, in which the oil is pumped up to the burner by 
 means of a train of wheel work or by the action of a 
 spring. 
 
 Mineral oil lamps always act on the principle of 
 suction, and they are now the only kind which require to 
 be described and figured. Of the older forms must be 
 mentioned that designed by R. Ditmar. It consists (Fig. 108) of a metal oil- holder, b, 
 which surrounds the wick-holder in the form of a ring, and is connected with the 
 latter merely by a horizontal tube in order to convey the oil to the wick. An aperture 
 closed by a perforated screw, a, serves to introduce the oil into the holder, 6. The 
 lamp has a circular wick and a double current of air ; it has a glass chimney con- 
 tracted at e, and resting on a movable support. The chief part of the luminous 
 flame, which should be altogether from 6-8 centimetres in height, is above the con- 
 tracted part. The oil-holder does not become appreciably heated. 
 
 In the lamp of Schuster and Baer of Berlin, intended for heavy oils (Figs. 109 
 and no) the air is supplied by means of a perforated box, e, an air-tube, v, within the 
 combustion tube and the perforated support of the disc. f. This lamp gives, with 
 solar oil, a bright white, steady, and perfectly inodorous flame. 
 
SECT. I.] 
 
 GAS LIGHTING. 
 
 JOI 
 
 The " Imperial lamps " recently introduced give an- ,ilb,iaiiB&ting power' up to 
 no candles. Their characteristic feature is that the air-pipe, G (Fig. in), passes 
 
 Fig. in. 
 
 Fig. 112. 
 
 through the oil-holder, F, with the wick, H. 
 The star-shaped piece, J3, with the disc, A, 
 regulates the distribution of air. 
 
 In study-lamps the radiant heat must be 
 guarded against. Schuster and Baer, in their 
 " normal hygienic lamp," surround the ordi- 
 nary cylinder, a (Fig. 112), with a second 
 cylinder, so that the dome, c, is kept cool by 
 the current of air ascending between both. 
 The ligroine and sponge lamp, proposed some thirty years ago, has not come into 
 general use. 
 
 GAS LIGHTING. 
 
 Burners for gas are constructed of iron, brass, porcelain, or steatite. Those of the 
 two latter materials are never choked in consequence of oxidation. The chief classes 
 of burners are the following : (i) The single-hole burner, a short, hollow cylinder, 
 closed at top with a plate having a fine aperture. (2) The slit-burner has in its button- 
 shaped top a cut like that made by a saw. The flame is flat, broader than high, and 
 is hence known as the bat's-wing burner. If two such burners are inclined towards 
 each other, so that the flames intersect each other, we have the twin-burner, which gives 
 out more light than the two flames of which it is composed. (3) The Manchester 
 burner a fish-tail has, instead of the slit of the bat's-wing, two apertures inclined 
 towards each other at an angle of 90. (4) In the Argand burner, chiefly used in 
 rooms, the flame consists of a circle of small rays, each issuing from a separate orifice. 
 (5) In the Dumas burner there is a circular slit instead of the circle of orifices. (6) In 
 the sun-burner, a number of slit-burners are so placed that the flames coalesce. 
 
 Of prominent importance are the so-called regenerative gas-burners, in which the 
 gas and the air are heated before ignition. The most widely known of these burners is 
 that of Fr. Siemens (Figs. 113 to 117), consisting of several upright receivers placed 
 one within the other. The air entering through the slits at a takes the way indicated by 
 
10? 
 
 '* CHEMICAL TECHNOLOGY. [SECT. i. 
 
 1 > 1 1. 
 
 i ,\ 
 
 arrows through the-exterual ^generation cells, d, in order to burn outside the porcelain 
 cylinder, z, with the gas escaping from the circular tubes, r, placed in the regenerator. 
 The products of combustion escape in part down through the hollow porcelain 
 Fig. 113. Fig. 114. Fig. 115. 
 
 Luft=Air. 
 
 Fig. 116. 
 
 Fig. 117. 
 
 cylinder, z, and the internal regenerator, s, through the support, g, into the flue which 
 
 (Fig. 113) leads up on the side of the main body into the chimney above the cylinder, z ; 
 
 Fig. 118. Fig. 119. Fig. 120. Fig. 121. 
 
 another part of the products of combustion passes directly upwards into the chimney, 
 whilst the latter is directly heated by a part of the products of combustion ; the portion 
 drawn downwards through the regenerator, s, serves to heat the air and the gases, 
 
SECT. I.] 
 
 GAS LIGHTING. 
 
 103 
 
 Fig. 122. 
 
 The heated air is especially divided and conducted by means of the so-called dis- 
 tributing-combs placed at and above he uorifices of the gas-pipes. 
 
 When it is required to throw the light downwards, the inverted regenerative 
 burner of Fr. Siemens is to be recommended. Here (Fig. 118) the gas-pipe, G, leads 
 into the horizontal gas-ring, R. This has on its lower side a number of small burner 
 tubes, r, screwed in or wedged in, which, as shown in Fig. 119, collect below to a 
 smaller circle. At the lowest and narrowest point of the circle formed by the burner 
 tubes, r, are their orifices, where the gas meets with the necessary air for combustion 
 brought from below (see the arrows) into the external mantle, M, and, with the gas, it 
 escapes downwards as flame. For the better joint conveyance of gas and air, the 
 inner mantle, m, has at its lower end a surface whereby the transverse section of the 
 transit is much contracted. (For further details see the inventor's English patents, 
 Nos. 13,701 and 13,788 for 1886.) 
 
 The regenerative slit burner of Fr. Siemens has an ordinary slit burner (Figs. 
 1 20 and 121) with a steatite orifice so arranged as to give a rounded flame. This 
 expands in the form of a shell beneath the reflector, c, provided with many fine 
 apertures, whilst the products of combustion escape through the circular opening, i, 
 into the cast-iron regenerator, b, and escape through the flue, d. The air drawn 
 through the openings of the screen passes, strongly heated, in the direction of the 
 arrows, through the bottle-shaped space, n, and the per- 
 forated reflector, c, to the flame. A part of the gas goes through 
 the tube, g, to the arrangement for lighting, h. This apparatus 
 surpasses in power and economy all the prior devices of Siemens 
 as well as of others. 
 
 Regenerative burners have also been designed by J. R. 
 Foster, and Wenham. 
 
 Auer von Welsbach deluminises coal-gas, burning it in a 
 Bunsen burner and igniting then in a cylindrical earthen 
 screen. In this arrangement the quantity of light decreases 
 rapidly, and the screen is easily broken, so that the general 
 adoption of that light is out of the question. 
 
 Fahnehjelm's " globe-light " has proved successful. A fish- 
 tail burner is fed with water-gas, and rods of magnesia, lime, 
 zirconia, kaolin, silica, &c., are ignited. If the iron comb, n 
 (Fig. 122), supporting two rows of magnesia rods, is set up, the 
 flame of the water-gas strikes between the rows of the rods and 
 ignites them to whiteness, when a powerful and perfectly white 
 light is radiated out. The mass of which the rods consist is chiefly burnt magnesia, 
 rendered plastic by means of starch and other suitable material. The arch supporting 
 the comb can be fixed lower or higher by means of a steel bar working on a tapped 
 spindle. 
 
 Gillard's "Platinum Gas." In 1846 Gillard established works in which hydrogen 
 was obtained for illuminating purposes. The hydrogen-flame was made to play 
 through a net-work of fine platinum wire, which was shortly heated to whiteness, and 
 rendered luminous. It was called in Paris "platinum-gas," and has been everywhere 
 abandoned. 
 
 Tesste du Motay obtained hydrogen by heating hydrated lime with coal. Oxygen 
 J p obtained by first heating pyrolusite with caustic soda to 450 in the air, forming 
 sodium manganate, and then passing superheated steam over the mixture, when the 
 reverse reaction takes place. 
 
 If the mixture of caustic soda and sesquioxide of manganese is heated in a current 
 of air, it is again converted into sodium manganate. The ignited oxyhydrogen gas 
 
104 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. i. 
 The process 
 
 thus obtainable was passed over small cylinders of magnesia or zirconia. 
 has been everywhere abandoned. 
 
 The Drummond light, obtained by exposing caustic lime to the flame of oxyhydro- 
 gen gas, has been everywhere superseded by the electric arc-light. 
 
 H. Cohn endeavoured to find the limit at what quantity of light it is still possible 
 to read and write without straining the eyes. He determined the time necessary, at 
 different grades of illumination, to read 36 hook-shaped figures at 6 metres distance, 
 stating whether the hooks were open upwards, downwards, to the right or to the left. 
 He found that with 
 
 I candle 0-12 hooks were read in 40-60 seconds with very many faults 
 5 candles 36 48-73 with many faults 
 
 10 36 30-60 ,, with some faults 
 
 20 36 22-26 correctly 
 
 50 36 l7- 2 5 i> as i n good daylight. 
 
 He determined also that in a minute twelve lines of newspaper print could be read 
 with ten candles, sixteen lines with fifty candles, as in the daylight ; ten candles are 
 therefore the lowest light which a work-room should have. 
 
 The following conspectus shows the cost of the chief kinds of illumination for 100- 
 candle hours : 
 
 How the Hourly Production of 100 Candles are required. 
 
 Thereby Evolved. 
 
 Kind of Light. 
 
 Quantity. 
 
 Price in Shil- 
 lings and lOOths 
 of a Shilling. 
 
 Water, 
 kilos. 
 
 Carbonic 
 Acid. 
 
 cub. met. 
 
 Heat. 
 
 ihermic-units. 
 
 Electricity, arc light . . . 
 glow light . 
 Gas, Siemens regen. burner . 
 Argand burner . . . 
 two-hole burner . . . 
 Petroleum, round burner 
 flat 
 Solar oil, Schuster and Baer's lamp 
 flat 
 
 O'09-O'25 h.p. 
 o '46-0 "85 
 0-35-0-56 c.m. 
 0'8-(2) 
 0'2-(8) 
 O'20 
 
 o'6o 
 
 0-28 
 
 o - 6o 
 
 o'43 
 0-70 
 077 
 077 
 077 
 0-92 
 
 I '00 
 
 O 'Ofo-O* 1 2O 
 O'150-O '3OO 
 
 o-o63-o'ioi 
 o' 144-0-360 
 0-360-1-440 
 0-040 
 
 0-120 
 
 0-062 
 
 0-132 
 0-413 
 
 0-672 
 
 1-390 
 
 2-700 
 
 3-080 
 1-660 
 
 I -600 
 
 0-86 
 2-14 
 
 O'22 
 0-80 
 
 0'37 
 0-80 
 0-52 
 0-85 
 0-99 
 0-89 
 
 0-88 
 1-04 
 1-05 
 
 traces 
 
 0*46 
 1-14 
 0-32 
 
 0-95 
 0-44 
 
 0'95 
 o - 6i 
 
 I'OO 
 I '22 
 
 I-I7 
 
 1-18 
 1-30 
 
 i'45 
 
 57-158 
 290-536 
 1,500 
 4,860 
 1 2, 1 50 
 2,4OO 
 7,20O 
 3.360 
 7,20O 
 4,2OO 
 6,800 
 9,20O 
 7,960 
 7,960 
 8,940 
 9,700 
 
 Kape oil (carcel) . . . . 
 (study lamp) . 
 
 
 Wax 
 
 
 
 
 As regards the pollution of the air, carbonic acid and watery vapour have to be 
 first considered. From the figures in the table, it follows that solar oil and mineral oil 
 give off the least carbonic acid and watery vapour, gas and tallow the most. In the 
 Siemens regenerative burner they are conveyed outside. 
 
 A contamination of the air with carbon monoxide and hydrocarbons is not to be 
 apprehended in the case of burners furnished with cylinders. Petroleum lamps smell 
 only if the flame is much too large or too small, or if the lamp is not kept clean. With 
 free-burning flames, as the air is rarely quite steady, a contamination of the atmosphere 
 with carbon monoxide is likely to occur. Coal-gas always contains sulphur, and yields 
 on combustion sulphurous and sulphuric acids, which act injuriously upon window- 
 plants, possibly upon the inhabitants, as well as upon books, pictures, articles of metal, 
 and upon curtains, &c. The mineral oils of commerce often contain sulphur. Ordinary 
 gas-lighting occasions more heat than oil -lighting. Among candles, those of tallow are 
 the least advantageous. 
 
 "Where economy is considered, solar oil, and especially petroleum, are to be employed ; 
 
Fig. 123. 
 
 SECT, i.] ELECTRIC LIGHT. I05 
 
 gas-lighting is dearer, and pollutes the air more, but it is convenient. When other 
 circumstances allow, gas-lights, with regenerative burners or electric glow-lamps, are 
 
 preferable, as they do not pollute the air, and give the least heat. For a study or 
 
 generally a working light the author prefers a good mineral oil lamp as giving the 
 steadiest flame. 
 
 ELECTRIC LIGHT. 
 
 The electric light is suited for large halls and gardens, where beauty is to be con- 
 sidered rather than economy. For lighting up streets, manufactories, and railway 
 stations, it is cheaper than gas only where a cheap motive power is available. 
 
 In estimating the arc-light, we must consider that with continuous currents the 
 positive carbon, which is always placed as the upper one, takes the form of a blunt 
 point, often with a small hollow in place of its point ; whilst the lower, negative car- 
 bon, remains pointed, or has in any case a very convex summit. At the lower point 
 only a small part is luminous, whilst by far the chief portion of the light comes from 
 the internal side of the concavity of the upper carbon, and is, of course, thrown entirely 
 downwards. This is best seen if the light is enclosed in a globe of translucent glass. 
 The upper part of the globe is comparatively dark ; 
 the lower very luminous except quite at its bottom, 
 where the shadow of the lower carbon is visible. 
 The limits between the two zones are never hori- **-, 
 zontal, but more or less slanting, especially when the 
 carbons are not quite straight. It is seen at once 
 that measurements of the free light in a horizontal 
 direction as was formerly customary give very 
 uncertain results. According as the naked light 
 happened to be measured from the one side or the % 
 other, it might be taken in the dark or the light 
 zone. 
 
 Fig. 123 shows the little apparatus with which 
 such measurements are conducted by the firm of 
 Siemens & Halske. It consists chiefly of a small mirror, S, fixed to a movable 
 curved arm, A. The supporter of the entire apparatus, I), can be fixed to an 
 electric lamp (of which only the upper part is shown) by means of the screw, R. This 
 is effected so that the prolongation of the axle on which the arm, A, turns, passes 
 through the arc. This prolongation is brought into the axis of the photometer (placed 
 at a distance), to which the arrows in the figure are pointing. The mirror, $, in every 
 one of its positions is equidistant from the arc, and so inclined that it reflects to the 
 photometer the rays falling from the arc upon its middle always at a right angle, 
 Z, p, o. Between tho photometer and the arc is the metal disc, B, which prevents the 
 passage of the direct rays to the photometer. On the other hand, the cone of rays 
 from the image of the arc in the mirror arrives unhindered at the photometer. The 
 inclination to the horizon at which these rays are emitted corresponds to the inclina- 
 tion of the arm, A. It is read off on the index, z, and the graduated dial, C. The 
 counterpoise, G, serves for the mirror and the arm, A, which is kept in each of its 
 positions by a slight friction. In order to deduce the absolute value from the measured 
 results, the co-efficient of absorption of the mirror must be ascertained and taken into 
 account. As the angle of reflection is always the same, this co-efficient does not vary ; it 
 may be determined once for all. For this purpose the mirror is turned downwards, 
 and the lamp is turned 90 round the perpendicular, so that the rays fall directly from 
 the arc towards the photometer in the same plane as they are to be previously or after- 
 wards measured by means of the mirror, also in horizontal radiation. The very trifling 
 
io6 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. . i. 
 
 alteration which the angle of incidence of the rays undergoes in the photometer in 
 consequence of the lateral application of the mirror is measured simultaneously, and 
 therefore compensated. 
 
 In Fig. 1 24 the intensities of light are shown graphically in the curve, a ; they are 
 measured by means of the apparatus Fig. 123, from a light having 9*4 amperes strength 
 of current and 45 volts difference of tension at the carbons. The upper carbon is 
 1 1 mm. and the lower 9 mm. in thickness. The line OB shows the horizontal, and 
 the source of light. The strengths of the light from onwards are plotted out upon 
 lines which have the same inclination as OB. The values given are the means of 
 many measurements ; indeed, in the measurement of the electric light we must never 
 be content with single observations, but must collect copious experience to escape very 
 glaring errors. From the course of this curve we see at once that the maximum of 
 light is given off at an angle of about 37 with the horizon, where it is more than six 
 times greater than in the horizontal plane. 
 
 But the case is complicated by the circumstance that in practical use the question 
 
 becomes involved by the enclosure of the light in 
 translucent globes or lanterns. These are used, 
 not merely to prevent dazzling, but chiefly be- 
 cause all the lower parts of the lamp, every 
 spoke of the lamp, and every irregularity in 
 clear glass would throw very sharp and ugly 
 shadows. In so-called mat and alabaster glass 
 the loss thus occasioned is 15 per cent., in opal 
 glass above 20, and milk glass above 30 per cent. 
 This loss of light is greatest in the direction 
 of the strongest rays, the inequalities of the 
 illumination being thus equalised at the cost of 
 the maxima. 
 
 Von Hefener-Alteneck made accurate ex- 
 periments with a larger mirror apparatus. The curve c (Fig. 124) thus ascertained 
 corresponds to a lantern of ground glass ; the curve b to a new globe of a glass not 
 very opaque. Reflectors placed above are of little value, as the smallest part of the 
 light is thrown upwards, so that the gain is trifling in comparison with the incon- 
 venience and the expense. 
 
 With reference to the values determined by the Paris Commission, and to the 
 assumption that i cubic metre of coal-gas yields hourly i horse-power, Voit has calcu- 
 lated the following table : 
 
 i cubic metre of gas yields 
 in a one-hole burner . 
 in an Argand burner . 
 in a small Siemens burner 
 in a large 
 
 in glow-lamps . 
 in arc-lamps 
 
 80-160 (mean) 
 250-750 
 
 45 units light 
 
 7o 
 141 
 145 
 110 
 
 490 
 
 Hence gas is used for lighting more appropriately (though not always more cheaply) 
 if it is burnt in a gas engine which drives a dynamo and feeds an electric lamp than if 
 it is used directly in a burner. 
 
 The disposable work in gas is not entirely utilised as light, but to a great degree as 
 heat. From other considerations, it appears that a body at higher temperatures emits 
 a greater proportion of external work as light, and a smaller as heat. It may therefore 
 be understood that i cubic metre of gas can develop larger quantities of light at the 
 higher temperatures of the above table. 
 
SECT, i.] ELECTRIC LIGHT. 107 
 
 We must notice the intensity of light. Two sources of light may send out the same 
 quantity of light, but one of them has a large and the other a small surface, so that the 
 former, from a given unit of surface, emits a smaller quantity of light than the other. 
 This light sent out from a superficial unit is called the intensity of the source of light. 
 If, for the sake of simplicity, we assume that each part of the surface of the two sources 
 of light emits the same quantity, we find the intensity by dividing the total light emitted 
 by the surface of the luminous body. The rays of the sun passing through an orifice 
 of o - 9 mm. diameter correspond, according to Sir W. Thomson, to 126 candles = about 
 20,000 candles per square centimetre. Moonlight is equal to the light of a normal 
 candle at the distance of 2*3 metres. 
 
 In this manner the luminosity of i square centimetre of surface is found : 
 
 Single-hole burner . . . . 0*06 candles 
 
 Argand ...... 0*30 
 
 Small Siemens ..... 0-38 
 
 Large ..... o'6o 
 
 Glow-lamps ' ..... 40x10 
 
 Arc-lamps ...... 484x10 
 
 * The glow-lamp, or incandescent lamp, is a mode of obtaining light by electric action 
 perfectly distinct from the arc light. It is well known that if in a good electric conductor, through 
 which a current is being passed, there is introduced a short piece, having a very high resistance, 
 we have in such a short piece, in accordance with Joule's law, a very considerable evolution of 
 heat, which, if the current is sufficiently powerful, renders it incandescent and luminous. If such 
 a short and resistant piece is enclosed in a vacuum, and if it is relatively long in proportion to 
 its diameter, so as to increase the resistance, we have, in substance, the glow lamp. A variety of 
 practical conditions are essential the vacuum, which should be very high, has to be enclosed in a 
 glass globe, or, more commonly, a pear-shaped vessel. This vessel must be so constructed that the 
 air may be readily exhausted, and be then sealed up so as to allow no entrance of air. The two 
 wires are also sealed into the neck of the vessel in such a manner that the current can pass from 
 the one to the other only by traversing the filament which is to be rendered incandescent. The 
 nature and preparation of this filament have been the critical points of the invention. The 
 earliest glow-lamps constructed, those, e.g., of Lontin de Clangy, King, and Lodyguine, had spiral 
 platinum wires, as had also those of Edison in his first attempts. The conclusion was soon reached 
 that a filament of carbon was preferable to one of metal, on account of its higher durability. 
 Wood charcoal, retort charcoal, &c., were successively tried, and in 1879 Edison prepared filaments 
 from carbonised bamboo. Other materials have since been used by Swan, Lane Fox, Crookes, and 
 others, such as gelatine, collodion, cotton, &c., the main condition being the production of a fibre 
 equally thick and strong throughout its entire length. Before carbonising, therefore, the fibres are 
 carefully examined with an apparatus capable of indicating the hundredth of a millimetre. They 
 are then charred in a fire-clay muffle, or in a Hessian crucible, every layer of fibres being covered 
 with charcoal dust or graphite. The crucible is then filled up with the same material, and the lid is 
 carefully luted on. When the luting is dry the crucibles are placed in the furnace and ignited for 
 five hours to iooo-i2OO . The higher and more uniform the heat the better is the quality of the fila- 
 ments. The specific resistances of the different materials, that of mercury being taken = i, are 
 
 Charred bamboo fibre ..... 62-56 
 
 Unprepared collodion carbon .... 39'9o 
 Prepared . ... 22*00 
 
 Chemical retort carbon ..... 7*17 
 
 Lamps are classified according to their luminous power. They are generally made to give the 
 light of 8, 10, 1 6, 20, 25, and 32 candles, those of i6-candle power being in greatest demand. 
 In gauging the lamps, accurate photometry is essential. Silvanus Thompson, instead of the grease 
 spot on the screen, uses two pieces of paraffine or milk glass, between which is laid a polished 
 slip of sheet silver. This arrangement is more convenient and more sensitive than the 
 fat spot. The duration, or, as it is technically called, the lifetime, of a glow-lamp varies, 
 according to the current used, from 300 to 2400 hours. The great recommendation of the glow- 
 lamp is its universal applicability. It gives off very little heat, does not contaminate the air with 
 the products of combustion, and reduces the risk of fire to a minimum. As compared with the 
 arc light, the glow-lamp has the advantage of absolute steadiness. 
 
SECTION II. 
 METALLURGY. 
 
 ONLY the chemical processes of metallurgy can here be discussed, as the mechanical 
 arrangements form a part of mechanical technology. 
 
 Few metals occur native; most of them are found in the mineral kingdom in 
 chemical combinations known as ores and as 
 
 (1) Elements : e.g., gold, platinum, bismuth, copper. 
 
 (2) Chlorides and fluorides : Compounds of the monovalent elements chlorine or 
 fluorine with metals (if heated with sulphuric acid, they give off HC1 or HF) e.g., 
 sodium chloride, carnallite, cryolite. 
 
 (3) Oxides : Oxygen compounds of the metals with or without hydrogen e.g., red 
 copper ore, hydroferrite, and anhydroferrite. 
 
 (4) Sulphides and corresponding compounds : Sulphur and arsenic-combinations of 
 the metals (if laid on ignited charcoal, they give off S0 2 or the odour of arsenic e.g., 
 iron-pyrites, galena, blende, proustite). 
 
 (5) Sulphates : Compounds of the general formula R U S0 4 (if melted upon charcoal 
 with soda, they give sodium sulphide ; heated with soda in a tube, their watery solution 
 gives with BaCl 2 , BaS0 4 insoluble in hydrochloric acid e.g., gypsum and heavy-spar). 
 
 (6) Borates : If heated on a platinum wire with H 2 SO 4 , they tinge the edge of the 
 flame a fine green e.g., boracite. 
 
 (7) Nitrates : Compounds of the general formula RjNOg (they are soluble in water, 
 and deflagrate on charcoal e.g., cubic nitre). 
 
 Dressing. Ores mostly require to be broken up and separated from foreign ores 
 and from the accompanying earthy or stony masses (gangue). This separation is, of 
 course, mechanical, and is often begun at the mine. The ores are generally sorted into 
 three heaps : the first heap is so rich that it can be at once smelted ; the second heap 
 contains medium ore, which, before smelting, has to be further freed from mechanical 
 impurities ; whilst the third heap consists chiefly of gangue, so that the little metal 
 which it contains is not worth the cost of extraction. 
 
 Preparation. By the above-mentioned dressing the ores are rendered rich enough 
 for further treatment. Before smelting, a preparation of the ores is often required, 
 which in some cases consists of exposure to the air weathering ; or in heating without 
 access of air burning ; or heating with access of air roasting. Weathering effects a 
 mechanical separation of the clay, shales, &c., from the nodules of ore, as it is chiefly 
 done in iron ores and calamine ; sometimes it effects also an oxidation of iron ores and 
 of accompanying pyrites to form copperas, which is then washed away by the rain. 
 Burning or calcination loosens the texture of certain ores, such as ironstone, calamine, 
 copper- shales, by expelling volatile matter such as water, carbon dioxide, bitumens, or 
 merely by the expansive power of heat. Roasting effects merely an oxidation e.g., 
 magnetic iron ore ; or a simultaneous expulsion of certain matters. Blende, e.g., on 
 roasting, yields zinc oxide and S0 2 (see Zinc), arsenides evolve arsenious acid, and 
 cinnabar is split up into mercury and sulphurous acid. Ores are in some cases 
 roasted with the addition of common salt (see Silver). 
 
 Smelting. Single kinds of ore are 'rarely smelted by themselves; in general, richer 
 
SECT. II.] 
 
 METALLURGY. 
 
 109 
 
 and poorer qualities are mixed together, so as to bring the whole to a medium standard. 
 Attention has also to be paid to the portions of gangue which still accompany the ore, so- 
 that the slag produced may be of a suitable quality. For this purpose, certain materials 
 are in most cases added, which are known as roasting materials (charcoal, coke, coal, 
 quicklime, and common salt) ; or as fluxes, quartz, and certain silicates (hornblende, 
 felspar, augite, chlorite, and old slags) ; calcareous minerals, such as limestone, fluor- 
 spar, gypsum, and heavy spar ; aluminous minerals, such as clay slate and clay, &c. ; saline 
 fluxes, such as potash, soda, borax, salt-cake, soda, saltpetre ; metallic additions, such as 
 iron (in the decomposition of cinnabar and galena), zinc (for the separation of silver from 
 lead), arsenic (for increasing the proportion of nickel and cobalt in speiss), iron-slack, red 
 and brown haematite in the puddling process; additions rich in such materials, as puddling- 
 slags,rich in ferrous oxide, and which act either by their proportion of oxygen (in puddling 
 iron), or by their iron as a precipitant (in separating lead from galena). Fluxes merely 
 promote the separation of the metal by increasing the fluidity of the melted mass, so that 
 the particles of metal may unite more easily. They may be arranged in three classes ( i ) 
 such as have little chemical action, but merely promote fusibility, such as fluor-spar, borax, 
 common salt ; (2) those which in addition have a reducing action, such as black flux (a mix- 
 ture of tartar and saltpetre) ; (3) those which act by absorbing either acids or bases. 
 
 Mixing is the operation by which the ore and the additional materials and fluxes are 
 mixed together. The quantity used in a period of twelve to twenty-four hours is called 
 the charge. 
 
 Furnace Products. The products of the smelting process are either (i) Metals 
 (educts). The degree of purity in the precious metals is expressed by fine (fine silver, 
 fine gold) ; in the base metals we speak of raw or crude metal, whilst a higher grade of 
 purity is indicated as refined. (2) Such furnace products as are not already contained in 
 the ores, but are formed by the reactions taking place during smelting, are many of them 
 articles of commerce, such as hard lead (antimonial and arsenical), spiegeleisen, the 
 various sorts of steel (such as Bessemer steel, cement steel, &c.), the arsenical products 
 (arsenious acid, orpiment, and realgar), antimony sulphide, &c. There are often also 
 by-products, which, if capable of further elaboration, are (3) intermediate products, or, 
 in the opposite case, (4) waste or dross. 
 
 The intermediate products are alloys, " teller silver," consisting of silver, copper, and 
 lead ; work-lead, lead containing some silver or copper ; black copper, consisting of 
 copper with iron and lead, &c. ; arsenides, speises ; carbides, crude iron and steel ; and 
 oxides, such as litharge. 
 
 Slags. The chief waste products of smelting-furnaces are slags, vitreous masses 
 resulting from most smelting processes, the most important of which are silicates, i.e., 
 compounds of silica with earths (especially lime, magnesia, alumina) and with 
 metallic oxides (ferrous and manganous oxides). In smelting processes they are 
 formed from the impurities never absent in the ores and in the admixtures, and sub- 
 serve the important task of protecting the metal as it is liberated from the oxidising 
 action of the blast. Their nature depends on their proportion of silica, whence they 
 are divided into sub-, mono-, bi-, and tri-silicates. The proportion of the oxygen of the 
 silica to that in the bases is as follows : 
 
 Proportion 
 ot O. 
 
 Metallurgical Name. 
 
 Old Equivalent. 
 
 New Atomic Weights. 
 
 Dualistic Formula. 
 
 Molecular Formula. 
 
 B. | A. 
 
 I =3 
 
 Trisilicate 
 
 R 2 Si 3 or R,,Si 9 
 
 2R0.3Si0 2 or 2R".,O s .9Si0 2 
 
 R u 2 Si,0 8 or R^Si.Og, 
 
 I : 2 
 
 Bisilicate . 
 
 RSi or RSi s 
 
 RO.Si0 2 or R 2 O s .3SiO, 
 
 RSiO s or R vi 2 Si 3 O 8 
 
 l:i| 
 
 Sesquisilicate . 
 
 R 4 Si, or R 4 Si 9 
 
 4RO.3Si0 2 or 4R a O 3 .9SiO s 
 
 R 4 Si 3 10 or R^SiAo 
 
 i : i 
 
 Monosilicate . 
 
 R 2 Si or R 2 Si, 
 
 2RiiO.SiO 2 or 2R 2 O r 3Si0 2 
 
 R 2 SiO 4 or R" 4 Si,0 I2 
 
 4:1 
 
 Subsilicate 
 
 R,Si or RSi 
 
 3RO.SiO 2 or R 2 O 3 .SiO 2 
 
 Rii s SiO 5 or RrfjSiO., 
 
no 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. ii. 
 
 Whilst in slags the degree of silication does not exceed the stage of a trisilicate, 
 and it is not yet ascertained whether trisilicates do not owe their high percentage of 
 silica to the presence of quartz, subsilicates may occur of various capacities of saturation. 
 Excesses of infusible bases, e.g., lime, are not uniformly distributed in the slag. 
 Aluminates are more rarely formed. 
 
 Slags are either vitreous or crystalline. From the latter, crystalline silicates often 
 separate, which exactly agree with natural minerals, e.g., augite, olivine, Wollastonite, 
 mica, idocrase, chrysolite, felspar, &c. The mixtures of the monosilicates generally 
 yield easily fusible (basic) silicates, whilst the bi- and tri-silicates are acid, and solidify 
 less readily. The phosphatic slags are of the greatest importance. 
 
 If a slag is to have an appropriate composition it should be (i) Specifically lighter 
 than the product to be obtained, so that it may cover the surface. (2) It must be homo- 
 geneous throughout, as otherwise the smelting process is not normal. (3) It must be 
 easily fusible, so that the particles of metal when separated out may easily sink down 
 through the liquid mass. (4) A chemical composition such that the slag cannot react 
 upon the product obtained. 
 
 Properties of Metals. The extraction of the various metals depends essentially on 
 their properties, and in the first place on their melting and boiling points. Arsenic, e.g., 
 melts only under pressure and not below redness, whilst it sublimes at 450 ; it is 
 therefore separated by distillation, not by smelting. Cadmium distils sooner than 
 zinc, and can therefore be removed from the latter by a separate condensation of the 
 portion which first volatilises. Cobalt, manganese, and platinum require the highest 
 temperatures for fusion. Even very small traces of foreign substances may affect the 
 melting-point, as may be seen in the subjoined table : 
 
 
 
 Melting-point. 
 
 Boiling-point. 
 
 Specific 
 Heat, 
 0-100. 
 
 Latent 
 Melting 
 Heat. 
 Heat- 
 units. 
 
 Heat of 
 Combustion. 
 
 Sp. Gr. 
 
 Product 
 of Com- 
 bustion. 
 
 Heat- 
 units 
 per 
 Kilo. 
 
 Aluminium . 
 
 600-850 
 
 above whiteness 
 
 O'2IO 
 
 
 
 
 
 
 
 2 '60 
 
 Antimony 
 
 425-450 
 
 1040-1050 
 
 0'050 
 
 
 
 
 
 
 
 6-70 
 
 Arsenic . 
 
 - 
 
 450 
 
 0-076 
 
 
 
 ABA 
 
 1030 
 
 570 
 
 Lead 
 
 326-335 
 
 1450-1600 
 
 O-O32 
 
 5'8 
 
 PbO 
 
 243 
 
 11-40 
 
 Cadmium 
 
 310-320 
 
 720-772 
 
 0-055 
 
 137 
 
 
 
 
 8-60 
 
 Iron, pnre 
 
 1600-1800 
 
 
 OTI4 
 
 
 FeO 
 
 1353 
 
 7-90 
 
 white, cast 
 
 1050-1100 
 
 
 
 
 
 33-o 
 
 
 
 
 7'6o 
 
 grey . 
 
 IIOO-I275 
 
 
 
 
 
 23-0 
 
 
 
 
 
 7'10 
 
 steel 
 
 1300-1400 
 
 
 
 O'll8 
 
 
 
 
 
 
 
 770 
 
 Gold . 
 
 1035-1250 
 
 
 
 0-032 
 
 
 
 
 
 
 
 19-30 
 
 Potassium 
 
 62 
 
 7I9-73I 
 
 
 
 
 
 K.,0 
 
 *745 
 
 0-87 
 
 Cobalt . 
 
 1500-1800 
 
 
 O'IO7 
 
 
 
 
 
 
 8-60 
 
 Copper . 
 
 1050-1300 
 
 
 
 0-093 
 
 
 
 f Cu 2 O 
 '( CuO 
 
 321) 
 593! 
 
 8-90 
 
 Magnesium . 
 
 700-800 
 
 above whiteness 
 
 0-245 
 
 
 
 MgO 
 
 6078 
 
 1-70 
 
 Manganese . 
 
 1900 
 
 
 
 O'I22 
 
 
 
 
 
 
 
 8-00 
 
 Sodium . 
 
 9 6 
 
 861-954 
 
 
 
 
 
 Nap 
 
 3293 
 
 0-98 
 
 Nickel . 
 
 1400-1600 
 
 
 
 0-IO9 
 
 
 
 
 
 
 8-90 
 
 Platinum 
 
 I775-200O 
 
 
 
 0-032 
 
 27-2 
 
 
 
 
 
 21-50 
 
 Mercury 
 
 -38-5 
 
 357 
 
 0-034 
 
 2-8 
 
 HgO 
 
 153 
 
 13-60 
 
 Silver . 
 
 954-1040 
 
 
 
 0-056 
 
 2I'I 
 
 Ag 2 
 
 27 
 
 10-50 
 
 Bismuth 
 
 260-270 
 
 1090-1450 
 
 0-030 
 
 I2'6 
 
 Bi 2 8 
 
 96 
 
 9-80 
 
 Zinc 
 
 412-420 
 
 930-954 
 
 0-094 
 
 28T 
 
 ZnO 
 
 1300 
 
 7-10 
 
 Tin 
 
 227-230 
 
 
 
 0-056 
 
 I3-3 
 
 SnO 
 
 574 
 
 7 '30 
 
 The specific heat of the metals generally increases with the temperature. Un- 
 fortunately, the determinations at high temperatures are either very uncertain or 
 altogether wanting. Thus Bystrb'm, e.g., found for iron at 1400 0-403, whilst 
 Pionchon found considerable variations in its specific heat. The latent melting heat 
 
SECT. II. J 
 
 METALLURGY. 
 
 and the combustion or reduction heats are known only for few metals and even 
 these determinations can only be regarded as approximative. We are therefore still 
 far from being able to calculate the various metallurgical processes, though we see from 
 the table that lead, bismuth, and tin are easily obtained, and that the separation of 
 mercury is easier than that of zinc. 
 
 If lead is reduced by carbon, with the formation of carbon monoxide, we have 
 for lead, - PbO + C = Pb + CO - (206 x 243 = 50,000) + 29,000 = - 21,000 heat-units, 
 therefore, for 206 kilos, of lead we need only 21,000 heat-units. But for magnesium, 
 MgO + C = Mg + CO - 146,000 + 29,000 = - 1 1 7,000 heat-units. In fact, the reduction 
 of magnesia by charcoal or coke is practically impossible. For zinc we have: 
 ZnO + C = Zn + CO 85,000 + 29,000 = 56,000 heat-units. For mercury only 
 HgO + C = Hg + CO 30,500 + 29,000 = - 1500 heat-units, so that in this case scarcely 
 any heat is required. 
 
 For accurate determinations the specific heats of the metals must be known at all 
 temperatures, as also the specific and latent heat of the residues, especially the slags, 
 the latent boiling-heat of the zinc, &c., which are not yet determined. 
 
 The thermo-conductivity of the metals is for a plate of i mm. in thickness for 
 each i difference of temperature of the two sides and i square metre per second, in 
 heat units : 
 
 Metnl. 
 
 Temperature. 
 
 Conductivity. 
 
 Temperature. 
 
 Conductivity. 
 
 Aluminium ...... 
 
 _^_ -^ ^_ ^_ 
 
 
 34 '4 
 
 100 
 
 36-2 
 
 Antimony . 
 
 
 
 4-2. 
 
 IOO 
 
 4' 
 
 Lead 
 
 o 
 
 8-4 
 
 IOO 
 
 7'6 
 
 Cadmium 
 
 o 
 
 22 '0 
 
 IOO 
 
 2O'4 
 
 Iron 
 
 o 
 
 W9 
 
 IOO 
 
 14-2 
 
 wrought, &c 
 
 o 
 
 2O'7 
 
 IOO 
 
 IT7* 
 
 Copper 
 
 o 
 
 *** / 
 98-2 
 
 IOO 
 
 1 3 / 
 83-3 
 
 Silver 
 
 o 
 
 IO9'6 
 
 
 
 Bismuth 
 
 o 
 
 [ 
 
 IOO 
 
 1-6 
 
 Zinc 
 
 o 
 
 *3'5 
 
 
 
 Tin 
 
 
 
 !5'3 
 
 IOO 
 
 14-2 
 
 (Glass 
 
 60 
 
 0-045) 
 
 
 
 The hardness of metals, as shown in their resistance to cutting, filing, boring, 
 turning, and planing, is given below, the hardness of lead being taken as unity : 
 
 Lead 
 
 Tin . . 
 Bismuth . 
 Cadmium 
 Gold 
 Zinc . 
 
 Silver 
 
 i-oo 
 
 173 
 
 3'34 
 
 6'95 
 
 10-70 
 
 11-70 
 
 I3-3Q 
 
 Aluminium 
 
 Copper 
 
 Platinum . 
 
 Wrought iron . 
 
 Steel 
 
 Cast iron, grey 
 
 17-30 
 19-30 
 24-00 
 60-70 
 61-40 
 64-00 
 
 Fig. 125. 
 
 Turner, for determining the hardness of metals, uses the arm of a lever, A, exactly 
 brought into equilibrium by the counterpoise, F, and the screw, G (Fig. 125), upon the 
 
 * At 275= 12-4 heat-unit,-. 
 
ii2 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 blade, B. The supporter, 0, rotates upon D, so that the diamond point, E, can be 
 pushed laterally on the piece of metal in question, J, which is held by K. The 
 diamond point is loaded by means of the weights, H and /, so that it leaves a distinct 
 scratch upon the metals. Results : 
 
 Hardness according Weight, 
 
 to Mohs. grammes. 
 
 Steatite ro ... i'o 
 
 Lead 1-5 ... ro 
 
 Tin 2-0 ... 2-5 
 
 Rock salt . 2 - o ... 4 - o 
 
 Zinc 2'5 ... 6~o 
 
 Copper, pure 2-5 ... 8*0 
 
 Calc. spar 3-0 ... I2'O 
 
 Soft iron ... 15-0 
 
 Fluorspar 4-0 ... 19x5 
 
 Steel for wheels 4-5 ... 20-24 
 
 Soft cast iron 4-5 . . . 20-24 
 
 Apatite . . . . . . . 5-0 ... 34-0 
 
 Hardest cast iron . . . . . ... 72-0 
 
 The resistance of the most important metals to rupture is expressed in kilos. 
 for i square mm. section as follows, according to Hugo Fischer : 
 
 Tin . . . . . .1 
 
 Lead ..... I 
 Gold . ... .11 
 
 Zinc 13 
 
 Aluminum . - . .14 
 Magnesium . . . .14 
 
 Silver . . , . .17 
 Platinum . . . .22 
 
 Copper 24 
 
 Iron 30 
 
 Nickel 48 
 
 Steel . .80 
 
 The resistance to pressure in kilos, per square mm. is 
 
 Lead 5 
 
 Bar iron ...... 30 
 
 Copper .- 57 
 
 Steel 55-79 
 
 The hardness and tenacity of metals are often greatly modified by small admixtures 
 and also by mechanical treatment ; most metals are rendered harder and more 
 tenacious by rolling, hammering, and drawing. This is the case with brass, iron, and 
 platinum ; less so with copper, silver, and gold, and not at all with tin and lead. As 
 increased hardness often means increased brittleness, it is sometimes necessary, in the 
 mechanical manipulation of iron and brass, to heat the metal under treatment from time 
 to time, so as to render it again soft and ductile, (i) If hardness accompanied by 
 elasticity is to be obtained, the metal is hammered, rolled, or drawn in the cold. (2) 
 The influence which the speed of cooling after ignition or fusion has upon the hardness 
 of a metal is particularly manifested in the case of steel and cast iron. (3) The tem- 
 perature to which the metal is raised before casting is not without influence upon 
 the hardness. If, e.g., tin is heated to incipient redness and then speedily cooled, the 
 objects cast become hard and sonorous ; hence tin for tin-foil, tin-paper, &c., which 
 must be soft and flexible, must not be heated above the melting-point. 
 
 "Very closely connected with the crystalline nature and hardness of metals come 
 malleability and ductility, collectively known as pliancy. This signifies the property 
 of metals to spread out into thin sheets under the hammer or between rollers. For 
 this purpose a certain softness is necessary, so that the metal may yield to a moderate 
 pressure or thrust, yielding to the force at the point of attack, but tenacity is also 
 needed to prevent the metal from losing its continuity. A hard, tenacious metal is 
 pliant only when tenacity and hardness are in the right proportion. The highest 
 degree of pliability is found in metals like silver, gold, and soft wrought iron. Soft- 
 
SECT. II.] IRON. tl ^ 
 
 ness, with deficient tenacity, as in lead, does not produce pliability. Antimony and 
 bismuth are brittle. 
 
 In order to convert the malleable metals into sheets they are beaten out with the 
 hammer or rolled between steel and chilled iron rollers. Those metals which can be 
 rolled are also capable of being drawn into wire, but the degree of ductility does not 
 always coincide with their degree of malleability or of being rolled. The metals are 
 the most malleable, reliable, or ductile in the following decreasing order : 
 
 Reliable. 
 Gold 
 Silver 
 Aluminium 
 Copper 
 Tin 
 
 Platinum 
 Lead 
 Zinc 
 Iron 
 Nickel 
 
 Malleable. 
 Lead 
 Tin 
 Gold 
 Silver 
 Aluminium 
 Copper 
 Platinum 
 Iron 
 
 Ductile. 
 Platinum 
 Silver 
 Iron 
 Copper 
 Gold 
 
 Aluminium 
 Nickel 
 Zinc 
 Tin 
 Lead 
 
 Closely connected with tenacity is the resistance to mechanical wear and tear, e.g. t 
 friction. This resistance is high in steel, and in cast-iron poor in silicon and rapidly 
 cooled on casting ; medium in wrought iron and in cast-iron cooled normally, in 
 platinum, silver, gold and aluminium ; slight in zinc, lead, and tin. The power of 
 resistance can be increased by suitable alloying with other metals, as lead with antimony, 
 silver and gold with copper. 
 
 Certain malleable metals, such as soft iron, nickel, and platinum, can be welded, i.e., 
 pieces of such metals after being softened by heat to a certain degree can be united into 
 one pjece by hammering and pressure. This can be effected in other metals only by 
 the use of a suitable solder. 
 
 IRON. 
 
 The most important iron-ores (iron stones) of commerce are : 
 
 (1) Magnetic Ironstone (Fe 3 4 ) ; it contains 72 per cent, of iron and is very widely 
 distributed, especially in northern countries, Canada, the United States, Russia, 
 Norway, and Sweden, in the crystalline slate formation. From this ore is obtained 
 the celebrated Swedish iron, e.g., that of Dannemora. Frequently it is accompanied by 
 pyrites, galena, copper pyrites, apatite, and other minerals, which reduce its value as 
 an iron ore. It is known by its black streak. 
 
 (2) Red Ironstone and Specular Iron (Fe 2 3 ) contains 69 per cent, of iron. Red iron- 
 stone, the massive or earthy variety of native ferric oxide, occurs in beds in primitive 
 formations and in quartz, granite, &c. It occurs also in transition formations, and, 
 according to its physical properties, it is known as haematite, iron-ochre, &c. It is found 
 mixed with silica (chamoisite), with alumina (red-clay iron ore), with compounds of 
 lime (minette). Iron glance is crystalline ferric oxide ; its most important deposit is 
 in Elba. All the red iron ores have a more or less decided iron colour and always a 
 red streak. 
 
 (3) Iron Spar (FeC0 3 with 48 per cent, of iron) contains almost invariably larger 
 or smaller proportions of manganese carbonate. It occurs in Styria and in Carinthia. 
 Kidney-shaped or globular iron spar is known as spherosiderite. It is also met with 
 as coaly iron ore, or black band (with 35 to 40 per cent, of iron). It is a mixture of 
 iron spar with coal and clay-slate deposited in the upper beds of the carboniferous 
 formation (Scotland, Westphalia). Clay ironstone, or clay band, especially in England, 
 Scotland, Westphalia, Silesia, and the Banate, is an intimate mixture of iron spar with 
 clayey minerals. 
 
 (4) Iron spar, when exposed to the action of air and of water containing carbonic 
 
 B 
 
ii 4 CHEMICAL TECHNOLOGY. [SECT, n- 
 
 acid, forms, as secondary products, brown iron ores (H 3 Fe 2 4 to H 6 Fe 2 O 6 ), which, 
 according to their physical properties, bear the names lepido-crocite, pyrosiderite, and 
 stilpnosiderite. These ores often contain calcium carbonate, silica, clay, &c. 
 
 (5) Bean ore, globular grains formed of concentric layers, occurs in some parts of 
 Germany and France in the jura formation. It consists either of silica, ferrous oxide 
 and water, or of brown hsematite and siliceous clay. 
 
 (6) Bog iron ore (limonite, meadow-ore) is found in the alluvium of the North 
 German Plain, in Holland, Denmark, Poland, and Southern Sweden, in peat bogs, 
 beneath the grass of meadows, and at the bottom of lakes. It is found in tuberous 
 and muddy masses of a brown or black colour, and consists of hydrated ferrous and 
 ferric oxides, manganic oxide, phosphoric acid, organic matter, and sand. The iron 
 which it yields is well suited for castings, as it is very fluid and fills the moulds well. 
 
 (7) Franklinite (Fe s 3 (ZnOMnO), with 45 per cent, of iron, 21 percent, of zinc, 
 and 9 of manganese, is used as an iron ore in New Jersey, yielding also zinc. 
 
 From a metallurgical point of view, iron ores are classified according as they are 
 easy or difficult to reduce and smelt. Among the former rank those which, after a 
 preparatory roasting, have a porous texture, so that they are easily reduced and 
 smelted in the furnace. This is the case with iron spar and brown ores, which lose on 
 roasting carbon dioxide and water respectively. Specular iron, red haematite, and 
 magnetic ore are hard to reduce. 
 
 The burnt ores from sulphuric acid works, after their copper, zinc, and silver have 
 been extracted in the moist way, are smelted for grey cast iron. 
 
 (1) Crude Iron. 
 
 In ancient times, and to a small extent even yet in some districts, a direct prepara- 
 tion of iron from its ores was very general. In this manner very pure and tough 
 bar-iron was obtained, but the process admitted only of a limited extension, and the 
 ores were imperfectly utilised. 
 
 The ores are roasted in heaps or in special kilns, in order to expel carbonic acid 
 and water, to make the mass more brittle and porous, and thus more susceptible to 
 reduction, and to convert any ferrous oxide present into the ferric state, so as to be less 
 readily convertible into slag. The ores, roasted or raw, are, if necessary, broken up by 
 means of stamps, rollers, or special crushing machines (such as Blake's ore-breaker) ; 
 the richer ores are mixed with lower qualities (assorted) in proportions which, accord- 
 ing to experience, yield the best returns. The coal acts in smelting as a source of 
 heat and (per se as well as in the state of carbon monoxide and dioxide) as a reducing 
 agent. In order to unite the reduced iron into a mass before smelting, materials are 
 added which combine with the gangue to form a readily fusible slag. This slag serves 
 for removing foreign matter, partly injurious to the quality of the iron, by facilitating 
 the coalescence of the reduced metallic particles, and by protecting the crude iron already 
 formed from the oxidising action of the blast. If silica is deficient, sand or quartz is 
 added ; if bases are wanting, limestone or fluor-spar is supph'ed. The charge as intro- 
 duced into the furnace should not contain more than 50 per cent, of iron. 
 
 The smelting process is almost exclusively executed in so-called blast furnaces. A 
 blast furnace is a round shaft-oven (Fig. 126), surrounded with a strong wall, A ; it is 
 15 to 30 metres in height, the inner part of which has the shape of two truncated cones 
 fixed to each other at their bases. The wall of the shaft, B, is enclosed by a second, A , 
 which joins up to the massive brickwork of the furnace. Between the two there is 
 left a space, which is filled up with a bad conductor of heat, such as ashes, and which 
 gives the necessary play-room for the expansion of the inner shaft by heat. The part 
 from B to C is the shaft ; that from D to E, the boshes ; the part B, where the 
 diameter is greatest, is the belly or upper part of the boshes. Below the boshes the 
 
SECT. II.] 
 
 IKON. 
 
 space contracts to F, the crucible or hearth. Here the smelting process takes place, 
 and here are, opposite to each other, apertures with conical tubes into which enter the 
 mouth-pieces or tuyeres of the pipes which supply the furnace with air. The open top or 
 mouth of the furnace, A, serves for introducing the charge. Such furnaces were 
 formerly built on a declivity, so that fuel and ore, &c., could be conveyed to the mouth 
 on a sloping road, or it was brought over the bridge P. The lower part of the hearth 
 is prolonged towards the front, forming the hearth-pan or fore-hearth, which is enclosed 
 by the dam-stone, M. This stone stands off a little from the wall and forms a slit, 
 
 Fig. 126. 
 
 the so-called tap-hole, which is stopped with clay during smelting, and serves afterwards 
 to discharge the molten metal and the slag. 
 
 Latterly, the furnaces are no longer built so massive. The bridge, w (Fig. 127), 
 leading to the top, and the upper wall of the furnace rest upon iron pillars. The 
 hot blast is introduced through a ring-shaped pipe, r, lying round the furnace through 
 tuyeres cooled by water. The furnace mouth is provided with a moveable cover ; ore, 
 coke, etc., are thrown into the funnel, e ; the cover is then raised for a moment to let 
 the charge slide down into the furnace, and it is then immediately closed, so that the 
 gases are compelled to pass through the top-piece, g, and the connecting pipes, to the 
 apparatus for heating the air, or to the boiler fires. 
 
 Air-Heating. One of the most important modern improvements has been the use 
 of the hot blast. The influence of the raised temperature of the air upon the con- 
 sumption of fuel arid the performance of the furnace is shown in the following table. 
 The addition of purple ore served for closing the joints of the funnel : 
 
n6 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. ii. 
 
 
 
 Charge per Ton of Crude Iron. 
 
 Silicon 
 
 Weekly Production. 
 
 Heat of Blast. 
 
 Coke. 
 
 Limestone. 
 
 Roasted Ore. 
 
 Purple Ore. 
 
 per Cent, in 
 Crude Iron. 
 
 metric tons. 
 
 
 kilos. 
 
 kilos. 
 
 kilo?. 
 
 kilos. 
 
 
 406 
 
 532 
 
 1209 
 
 584 
 
 2 39 8 
 
 18 
 
 2-4 
 
 415 
 
 631 
 
 "79 
 
 584 
 
 2408 
 
 18 
 
 2-6 
 
 456 
 
 702 1169 
 
 616 
 
 2408 
 
 18 
 
 2'5 
 
 568 
 
 722 
 
 1157 
 
 618 
 
 2400 
 
 18 
 
 2'5 
 
 465 
 
 760 
 
 1132 
 
 620 
 
 2388 
 
 18 
 
 2'6 
 
 The heating apparatus may consist either of a single chamber built of stone, serving 
 both for air and heating gas, and which works alternately and with interruptions, or 
 
 Fig. 128. 
 
 it may comprise two iron cham- 
 bers working continuously. 
 The stone apparatus bears a 
 higher temperature, but re- 
 quires a larger heating surface 
 in order that the variation of 
 temperature on changing may 
 be the smaller. Hence, they aue more expensive to erect, but eheaper to maintain, 
 though they require trustworthy attendants during the change. In the iron apparatus, 
 
SECT. II.] IRON. 
 
 the temperature of the air is limited (up to the point at which cast-iron softens), the 
 heating surfaces and the cost of erection are smaller ; the maintenance is more costly, 
 though the cleaning is easier. 
 
 The air-heater of Whitwell consists of a sheet-iron cylinder A (Fig. 128), lined with 
 fire-stone and fitted with partitions, a. The furnace gases led in through B pass 
 through the valve-box, C, into the first chamber, where they burn along with air which 
 is introduced simultaneously, and pass in the direction of the arrows through the 
 apertures, b, and the valve-box, D, to the flue, E. If the stone lining is sufficiently 
 heated the connection with B and E is closed, and blast-air is driven in, which takes 
 up the heat stored in the stones, and passes through F into the furnace. The top and 
 the floor are provided with apertures, e e, for cleaning. 
 
 In Macco's heater, the furnace gases pass through the flue, a (Figs. 129 and 130), 
 pass upwards in the chamber, b, of the apparatus, enter the grated chamber, 6, passing 
 downwards, and unite again in the lower chamber, e. Hence the gases pass into the 
 second grated compartment,/, in which they move upwards, arriving through the 
 aperture, g, into the last compartment of the apparatus, turning downwards and 
 escaping through the chimney, at i. Both immediately after entering the apparatus 
 at the lower part of compartment, 6, and in the lower middle compartment, e, 
 heated air is conveyed to the gases for their more complete combustion. The 
 air to be heated takes the opposite direction. By the use of the intermediate 
 chambers, d and /, a large heating surface is supplied and the air is raised to a high 
 temperature. 
 
 The Smelting Process. The furnace is heated first by kindling wood on the hearth 
 and then introducing the fuel (generally coke, sometimes anthracite, rarely crude coal) 
 until the entire shaft is filled with ignited matter. At the same time, the blast is 
 turned on and ore and fuel are introduced in successive layers. As the fuel burns, and the 
 ore and fluxes, &c., melt, the layers sink gradually down. The silica melts with the 
 earths and oxides, forming slag, whilst the reduced semi-liquid iron unites with carbon 
 to form an easily fusible crude iron. The melted iron collects at the bottom of the 
 hearth, and upon it floats the slag, which is let flow off. The liquid iron is from time 
 to time run off by opening the tap-hole, and conveyed to the moulds through a 
 channel prepared in the sand in front of the furnace. During tapping, the blast is 
 stopped. 
 
 Heat-conditions of the Blast Furnace. According to Liirman, we must not think 
 of the heat as being distributed in successive zones of the blast furnace. The charges 
 tend towards the axis of the melting column, and the gases to the circumference, so 
 that here the reactions take place more rapidly than in the middle. Heat is con- 
 sumed 
 
 (i) For the evaporation of water and for the escaping gases. Samples of gas are to 
 be taken where they are in a state of mixture. For the evaporated water it is not 
 sufficient to calculate 637 heat-units, but 
 
 Heat = 606-5 + 0-305 (100) + 0-48 (t- 100). 
 
 For the remaining gases the calculation is carried out in the usual manner. As to 
 the quantity of dust thrown off at the top, there are few trustworthy statements. 
 Independently of the character of the ores, the quantity of dust will depend on the 
 rapidity of the charges and the temperature of the furnace. At any rate, the escape 
 of dust is a cause of the expenditure of heat and the loss of material which must be 
 taken into account. No great error will be committed if we take as specific heat the 
 figure which has been established for porous refractory stones and fire-bricks (about 
 = o - 22), and multiply it by the temperature of the gas and the quantity of dust. For 
 5 per cent, of dust, or 50 kilos, per ton, and 100 as the temperature of the gas, the 
 quantity of heat would be 50 x 400 x 0*22 = 4400 heat-units per ton yield of crude iron. 
 
n8 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 For hotter working, 10 per cent, of dust, and a gas temperature of 600, we have 
 100 x 600 x o'22 = 13,200 heat-units. 
 
 (2) The liberation of carbonic acid from the carbonates of the ores and the additions 
 has a great influence on the entire character of the blast -furnace process. It absorbs a 
 very considerable quantity of heat, and the course of its evolution extends over a great 
 space in the furnace shaft. Where there are very abundant additions of limestone, 
 the liberation of carbonic acid extends down to the region of the smelting (strictly 
 speaking), and perhaps the last traces of the volatile constituent of the carbonates is 
 expelled only by the silica, which is already active in the formation of slag. It is decided 
 that the expulsion of carbonic acid in the blast furnace, though it probably begins at 
 800, requires for its completion about 1700, whence the final decomposition of the 
 carbonates takes place in the zone of the most dazzling white heat. 
 
 (3) Processes of Reduction. The most important compound of iron is the magnetic 
 oxide, Fe 3 4 . Here there must be utilised a reduction-heat of only 1648 heat-units, 
 instead of the mean value of 1887 heat-units proposed by Grimer for iron oxide; the 
 expenditure of heat per iron unit is certainly smaller. The decomposition heat of iron 
 carbonate, when split up into carbon dioxide, and ferrous oxide (half of which has to 
 be further oxidised to ferric oxide) has not been measured. Diirre takes in its place 
 the heat of calcium carbonate. The silicate is more important, as considerable portions 
 of slags undergo refining. For the combination-heat of ferrous oxide and silica there 
 are no accurate determinations. According to Tholander, 310 heat-units would be 
 calculated as the combination-heat of ferrous oxide and silica. For i kilo, of crude 
 iron, containing 95-5 per cent. Fe, there would then be 0-955 x 3 IC> or 296'! heat-units 
 used in the decomposition of silicate, besides the reduction-heat of the liberated ferrous 
 oxide (according to Favre and Silbermann, = 1352 heat-units). We see that the sum 
 1352 heat-units + 296-1 heat-units = 1648-1 heat-units coincide almost exactly with the 
 reduction heat of magnetic oxide, 1648 heat-units, whence we should conclude that a 
 pure ferrous silicate and the magnetic oxide are almost equally reducible if Tholander's 
 supposition is correct, and there remained on the i-eduction of ferrous silicate, metallic 
 iron and free silica. It is only, however, reduced to a small extent, whilst most of it 
 passes into the slag. Ferrous silicate is usually considered difficult to reduce, though 
 easily fusible, and, as it generally holds in solution variable quantities of magnetic oxide, 
 its reductibility cannot be pronounced great. For the manganese compounds we may 
 provisionally assume for Mn 3 O 4 = u / 8 x 1648 = 2264 heat-units; for Mn 2 3 n / 8 x 1887 - 
 2 595 heat-units; for sulphur from sulphur acids 3226 heat-units; for phosphorus from 
 phosphoric acid (P 2 5 ) 5747; from H 3 PO 4 = 9662 heat-units. Whether the lower 
 value is accurate must remain a question, and only the circumstance that also the 
 combination-heat of iron phosphide, as well as the heat evolved by the combination of 
 lime and magnesia with the slag cannot be determined, causes the proposal to use 5747 
 instead of 9662 heat-units to appear less questionable. 
 
 The heat capacity of the reduction products is known only in part, and it is hence 
 difficult to form a correct conception of the temperature at which phosphoric acid is 
 reduced. In any case, this reduction occurs at so high a temperature that it takes 
 place on the hearth of the furnace and in presence of solid carbon. Carbon monoxide 
 can scarcely be active here ; at least, laboratory experiments show that the phosphates 
 cannot be reduced by a current of carbon monoxide alone. How far the liquefied iron 
 in the blast furnace participates in the reduction of the phosphoric acid is hard to say. 
 
 Experiments in the refining process show that the prolonged contact of metallic 
 iron and phosphatic slags reduces the phosphoric iron contained in the latter to 
 phosphorus. On the other hand, the first experiments with the Thomas and Gilchrist 
 process have shown that dephosphorised iron covered with a phosphatic slag can take 
 up phosphorus again on treatment with highly carburetted iron (spiegel-eisen and 
 
SECT. II.] IRON". 119 
 
 ferromanganese), which can only have been isolated by the transit of carbon monoxide 
 through the layer of slag or in consequence of the action of the same compound upon 
 finely divided iron-phosphates in the liquid iron. All these processes, if further studied, 
 may lead to important conclusions on the behaviour of phosphoric acid in the blast 
 furnace. Arsenic acid scarcely comes into question. 
 
 Of especial importance is silica. As soon as from any cause a very infusible slag 
 is formed, or is intended to be formed, there is seen in the crude iron a separation of 
 graphite regularly preceded by the taking up of silicon. The medium for the reduction 
 of silicon is partly the silica in the slag, partly that of the furnace walls, though these 
 first yield silica for reduction. According to experiments on the reductibility of iron 
 ores, we must assume that a charge free from slag, i.e., without the addition of puddling 
 slags, as it is generally made up from brown iron ore, haematite and roasted iron-spar 
 for the production of Bessemer iron is chiefly reduced in the shaft, and that by means 
 of carbon monoxide, whilst a charge containing a large proportion of slags is reduced 
 only on the hearth in the state of complete fusion. 
 
 The nature of the slags is here nearly indifferent, since both in acid and in basic 
 slags, in those Avhere calcium silicates, and in those where aluminates predominate, the 
 iron takes up silicon and liberates carbon as soon as the temperature is high enough. 
 The reduction -heat with the combustion-heat of silicon may be estimated at 7830 heat- 
 units, referred to the silicon of crude iron. The reduction-heat of the earths and the 
 alkalies does not come under notice. 
 
 (4) Melting-heat of Crude Iron. Griiner has proposed mean values for practical 
 utilisation, to be applied when direct calorimetric determinations have not been 
 simultaneously made on the iron, the slag, the hot blast and the escaping gases. 
 These mean values are : 300 heat-units for grey cast iron, 275 for white cast iron, 25 
 of which may be considered as latent in the grey and 35 in the white iron. 
 
 (5) Melting -heat of Slags. The most comprehensive experiments have been made 
 by Akermann. For blast furnace slags he found 340-410 heat-units. The quantity 
 of heat ascertained at the furnace itself will always be greater than that found in an 
 unmelted slag, for in addition to the true melting-heat, the slag flowing out of the 
 furnace contains the sum of the heats of combination and decomposition, whilst in 
 measuring the heat in an unmelted slag, the mere melting-heat alone comes in question. 
 In slags worked for grey cast-iron we may assume 500 heat-units, and in those for 
 white iron 450 heat-units. 
 
 (6) Decomposition of the Atmospheric Moisture. Griiner in his calculations assumed 
 an atmospheric moisture of at least 0^0062 in his calculations. The influence of foggy or 
 wet weather, both upon the course of the process and the results, is sufficiently known to 
 every practical man, and shows that attention to the moisture of the air is justifiable. 
 
 (7) Water and Air used for Refrigeration. Some observers have attempted to 
 determine the quantities of heat which have been transmitted to the water and the 
 air used for refrigeration. 
 
 (8) Losses include all the heat expended upon the furnace itself. They can be 
 found only in and by subtracting all the known and determinable expenditures of heat 
 from the total heat produced, and in spite of repeated experiments they have not been 
 determined with certainty. There occurs in the first place a transfer of heat from 
 the interior of the furnace to the substance of the walls, which, in the layers next to 
 the interior, have almost the same temperature as the adjacent zone of the furnace. 
 A part of the heat is conveyed through the entire thickness of the walls according to 
 their conductivity, the size of the surface, &c., to the outer surface of the walls and 
 thence to the ambient air, partly by radiation and partly by conduction. This quantity 
 of heat can scarcely be regarded as total loss, since the interior of the furnace must of 
 necessity have the temperature of the process going on within. 
 
120 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 The consumption of fuel in the working of the blast-furnace depends essentially on 
 the reducibility of the ores. The experiments of Akermann and Sarnstrom prove that 
 ferric oxide is reduced by carbon monoxide to magnetite. Already, at 450 the 
 carbon monoxide may already contain 20 per cent, of carbon dioxide and still has a 
 reductive action upon the oxides ; at 900 the oxide loses oxygen even in carbonic 
 acid free from carbon monoxide. In order to deoxidise magnetite at 850, the gas 
 must not contain more than 3 vols. of carbon dioxide, and if the reaction is to be 
 effected at 300 to 350, the carbonic acid must not exceed 2 parts. To produce 
 ferrous oxide, not more than o - 5 part of carbonic acid must be present to i part of 
 carbon monoxide. 
 
 Hence, the smallest consumption of fuel for a blast-furnace may be calculated if it is 
 possible to effect the reduction of the ora with carbon monoxide exclusively. 
 
 According to the formula, 3CO + FeO = 2CO + C0 2 + Fe, for each mol. of iron there 
 must be present at least 3 mols. of carbon monoxide. If the ore higher up in the 
 furnace is in the stage of oxidation of- magnetite, then, according to the formula, 
 pCO + Fe 3 4 = 5CO + 4C0 2 + 3Fe, five parts carbon monoxide must be accompanied at 
 most by 4 parts of carbonic acid, whilst the same 5 parts of carbon monoxide, as far 
 as the reduction of magnetite is concerned, may be accompanied by at least 10 parts of 
 carbonic acid. If the ore consisted at first of oxide, the equation 3CO + Fe 2 O 3 = 
 3C0 2 -i- 2Fe signifies that the escaping gases, if the final reaction with carbon monoxide 
 is to be produced, must contain at least equal volumes of carbon monoxide and carbonic 
 acid, whilst oxide can be reduced to magnetite even with a gaseous mixture containing 
 20 parts of carbonic acid. Hence, it follows that the difficulties of reduction grow 
 enormously with the decreasing grades of oxidation of the iron, and that the final 
 reduction of ferrous oxide requires much more carbon monoxide than is necessary for 
 the partial reduction of the higher grades of oxidation. For the mere reduction of 
 the ore by means of carbon monoxide, there must be burnt by the blast at least 
 3C : Fe = 0*643 kilo, carbon. If we further consider the 4 per cent, of carbon taken up 
 by the raw iron, we have 0-657 carbon. If the ore was pure magnetite, then for 
 each kilo, of non-volatile carbon we should have at most 
 
 (3 x 56 + 4 x 16) : [(9 x 12) x (3 x 12 + 0-04 x 56) : (3 x 12)] = 2-03 kilos, 
 of pure magnetite ; then percentage of the escaping gases in carbonic acid and carbon 
 monoxide would be in volume o - 8o and in weight 1*26. If the ore was pure oxide, we 
 should have 
 
 (2 x 56 + 3 x 16) : [(6 x 12) x (3 x 12 + 0-04 x 56) : (3 x 12)] = 2'io kilos. 
 oxide, and the mixture of gas would be roo or 1*57. 
 
 If the reduction is thus to be effected by carbon monoxide alone, there must be 
 burnt with the air of the blast at least 64*3 kilos, of carbon to 100 kilos, of reduced 
 iron. But, contrary to expectation, this quantity in blast-furnaces is often smaller, 
 whilst the gases are not richer in oxide. Hence, it follows that the reduction is 
 effected not only by carbon monoxide, but also by carbon. The fear of loss of heat in 
 the carbon-reduction as compared with the oxide-reduction has been the cause that 
 the consumption of coal is now in that case less than it ever could have been in oxide 
 reduction. The lost heat is substituted by hotter air from the blast, whereby the crude 
 iron is rendered again poorer in carbon and richer also in silicon by overheating in the 
 moulds. 
 
 The consumption of fuel can scarcely be reduced lower in many cases. Fuel could 
 be further economised only by very hot air from the blast, with a simultaneous intro- 
 duction of carbon monoxide ; but this gas would have to be produced more cheaply 
 than in the blast furnace itself. The oxide gas must thereby not be mixed with 
 hydrogen, as Bell proposes, since this chiefly promotes reduction by carbon, to which 
 the supply of oxide gas would act antagonistically. 
 
SECT. II.] IRON. 121 
 
 The following calculation shows the average heat required for smelting crude iron 
 in charcoal furnaces. For comparison there are also given the corresponding values 
 which express the consumption of heat in smelting 100 kilos, of coke iron : 
 
 Consumption of Heat for 
 
 Swedish 
 
 Charcoal Furnaces, 
 heat-units. 
 
 Evaporation of moisture of fuel 8,155 
 
 Reduction of iron from ore 158,805 
 
 Saturation of reduced iron with carbon 
 Expulsion of carbonic acid from limestone 
 Its decomposition by carbon 
 Decomposition of moisture of air 
 
 of phosphoric acid and silica 
 
 Fusing crude iron 
 
 ,, slag 
 
 Heat escaping through masonry, estimated 
 Absorption by refrigerating water 
 Escape of heat in gases at mouth 
 
 9,600 
 
 7,105 
 
 7,36o 
 
 6,800 
 
 2,610 
 
 33,000 
 
 41,35 
 
 12,715 
 
 5-545 
 
 34,565 
 
 Cleveland 
 
 Coke Furnaces. 
 
 heat-units. 
 
 I,62O 
 165,540 
 
 7,20O 
 20,065 
 2O,8oo 
 I2,2OO 
 20,870 
 
 33,000 
 72,600 
 18,290 
 9,090 
 37,7io 
 
 Total heat-units required 327,610 
 
 Heat evolved, calculated according to composition, weight, 
 and temperature of fuel of escaping gases and of air . 318,175 
 
 419,005 
 
 423,860 
 
 Hence fully 30 per cent, more heat is required for smelting Cleveland irons than 
 for the richer haematites and magnetites of Sweden. The consumption of materials for 
 100 kilos, crude iron was as follows : 
 
 Fuel 
 
 Limestone 
 
 Ore 
 
 Temperature of blast 
 
 of escaping gases 
 
 Sweden. 
 97 -4 kilos. 
 I9-2 
 197-8 
 
 211 
 28Q 
 
 Cleveland. 
 IO2'O kilos. 
 
 46.9 
 2347 .. 
 563 
 262 
 
 It is known that the ore is the source of the oxygen which converts carbon mon- 
 oxide into carbon dioxide. In addition to the carbon dioxide thus formed, a certain 
 quantity is contributed by the limestone, and a further portion by the dissociation of 
 the carbon monoxide, since two equivalents of this gas are resolved into carbon dioxide 
 and carbon within the pores of the ore undergoing reduction. But as soon as the 
 carbonic acid exceeds a certain proportion, there sets in the temperature and other 
 circumstances permitting an opposite reaction : carbonic oxide is formed by the carbon 
 of the fuel. 
 
 The gases of the Cleveland blast furnaces, those especially of 23 to 24 metres in 
 height, are notable for the small quantity of carbonic acid contained in them below a 
 certain depth. The following examples illustrate this proposition for a furnace of the 
 capacity of 496 cubic metres 
 
 Beneath the Mouth. 
 
 No. I. 
 
 No. II. 
 
 CO,. 
 
 CO. 
 
 CO 2 . 
 
 CO. 
 
 5 metres 
 
 2'22 
 0-67 
 I'09 
 
 i'S 
 
 0-50 
 
 O'OO 
 
 0-81 
 
 34-08 
 35'" 
 3496 
 35 '24 
 35 '92 
 36-63 
 3770 
 
 2*25 
 
 073 
 I '00 
 
 0-49 
 
 O'OO 
 
 073 
 
 33-31 
 34-84 
 35-08 
 
 36-03 
 37-60 
 
 37-86 
 
 
 16 
 
 
 21'5 , 
 
 
 
 A charcoal blast furnace of 15-95 metres in height and 101 cubic metres capacity 
 .gave, in the average of two determinations 
 
122 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. ii. 
 
 co a . co. 
 
 3 "4 metres below mouth ..... 16*39 13*1 1 
 
 5'2 17-80 ... 10-89 
 
 7-0 9-60 ... 21-59 
 
 8-2 2-68 ... 30-66 
 
 10-4 ii'6o ... 20-06 
 
 Various samples of flue dust had the following composition : 
 
 
 KO. 
 
 NaO. 
 
 CaO. 
 
 MgO. 
 
 Fe 2 s - 
 
 MnO. 
 
 ZnO. 
 
 PbO. 
 
 Si0 2 . 
 
 A1 2 3 . 
 
 8. ZnS. 
 
 Gleiwitz . 
 
 . 12-28 
 
 12-58 
 
 6-15 
 
 5-87 
 
 9'5 
 
 0-3I 
 
 25-SI 
 
 1373 
 
 1772 
 
 3-94 
 
 O'24 
 
 Tarnowitz . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 35-65 
 
 10-64 
 
 I5-55 
 
 4-21 
 
 
 
 ? 
 
 . 17-05 
 
 9'53 
 
 2S-95 
 
 2-31 
 
 O'9I 
 
 0'37 
 
 I-30 
 
 
 
 24-05 
 
 10-90 
 
 171 
 
 Cleveland . 
 
 
 
 4-70 
 
 12-30 
 
 5-03 
 
 14-22 
 
 
 
 10-48 
 
 
 
 22'6O 
 
 8.20 
 
 0-17 1370 
 
 The proportion of cyanogen compounds in the gases and the dust deserves notice. 
 According to the views of Berthelot, there is first formed in the blast furnace potassium 
 acetylide, C,K,, which then combines directly with nitrogen to potassium cyanide, 
 2(CNK). How considerable may be the production of metallic cyanides in blast 
 furnaces worked with coal appears from an investigation by Bunsen and Playfair on 
 the English manufacture of crude iron, according to which 112*5 kilos, of potassium 
 cyanide were produced daily in a blast furnace. According to Bell, the following 
 quantities of potassium and sodium were found in combination with carbon dioxide, 
 oxygen, or cyanogen in i cubic metre of the gases of a Cleveland coke-blast furnace of 
 495 cubic metres capacity, and a height of 24*4 metres. The gases were drawn on six 
 successive days at the height of 2^44 metres above the hearth : 
 
 Potassium and sodium 
 Cyanogen . 
 
 I. 
 
 46-49 
 19-00 
 
 II. 
 
 30-17 
 12-93 
 
 III. 
 
 33-I5 
 17-32 
 
 IV. 
 
 21-09 
 
 V. 
 
 31-65 
 
 2C'6l 
 
 VI. 
 
 11.83 
 
 9-16 
 
 Average. 
 29.11 gramme 
 15-06 
 
 On the same days the escaping gases contained : 
 
 Potassium and sodium . 12-20 15*30 6*68 5-89 4*29 9-07 
 
 Cyanogen. . , . 4-00 6-60 3-57 2-91 1-79 377 
 
 Slags. The composition of the slag is, to an experienced eye, an important indica- 
 tion of the working of the furnace. The composition is, of course, widely different 
 e.g. : 
 
 
 Mariazell 
 (Styria). 
 
 Scotch. 
 
 
 Granular. 
 
 Vitreous. 
 
 Silica 
 Alumina 
 Manganous oxide 
 
 43-850 
 4-650 
 2'6lO 
 
 0-540 
 0-850 
 
 23-300 
 
 22-700 
 0-480 
 0-050 
 
 I'OIO 
 
 0-009 
 
 57-95 
 21-96 
 
 0-37 
 0-05 
 
 16-24 
 0'43 
 
 3-00 
 
 5271 
 21-44 
 0*64 
 0-36 
 
 19-13 
 370 
 
 2 -O2 
 
 
 
 Magnesia 
 Potash . 
 Soda 
 Calcium sulphide 
 Phosphoric acid 
 
 The crude grey iron from Mariazell, in Styria, belonging to the first slag contained : 
 
 Carbon . . . . . . . 0-354 
 
 Graphite . 2-837 
 
 Silicon 2-953 
 
 Sulphur 0-018 
 
 Phosphorus 0-045 
 
 Copper 0-220 
 
 Cobalt and nickel 0-013 
 
 Manganese 2.980 
 
SECT, ii.] IRON. 123, 
 
 The blast furnace works of Ougre"e exhibited at Antwerp the following analyses of 
 slags, together with the accompanying kinds of iron : 
 
 
 White 
 Iron. 
 
 Spiegel. 
 
 Spiegel 
 Bessemer. 
 
 Semi- 
 Bessemer. 
 
 Bessemer. 
 
 Bessemer, 
 Extra. 
 
 Thomas. 
 
 Crude Iron 
 for 
 Castings. 
 
 Crude Irons. 
 
 
 
 Grey, 
 
 
 Nucleus 
 
 Great 
 
 Radiating 
 
 
 
 
 
 
 
 Coarse, 
 with 
 Spiegel. 
 
 Fine 
 Grain. 
 
 Coarse, 
 Exterior 
 Fine. 
 
 Separa- 
 tion of 
 Graphite. 
 
 Specular, 
 Grey 
 Points. 
 
 Strong 
 Grey. 
 
 Carbon 
 
 4-400 
 
 5-800 
 
 5'ioo 
 
 4"OOO 
 
 4-500 
 
 4-500 
 
 4^25 
 
 3-987 
 
 Silicon 
 
 0*409 
 
 0-503 
 
 1-127 
 
 l'I21 
 
 2-463 
 
 2-845 
 
 0-807 
 
 1-307 
 
 Manganese 
 
 0-131 
 
 7-232 
 
 4-213 
 
 2-988 
 
 2*042 
 
 0-9-0-4 
 
 1-820 
 
 0-407 
 
 Sulphur 
 
 0-329 
 
 O'OOO 
 
 trace 
 
 trace 
 
 O-OI4 
 
 O'OIO 
 
 0-054 
 
 0-056 
 
 Phosphorus 
 
 1-528 
 
 0-892 
 
 0-223 
 
 0-093 
 
 0-060 
 
 0-048 
 
 2-344 ? 
 
 0-157 
 
 
 
 
 
 
 
 
 
 
 Slags. 
 
 Dark 
 Brown, 
 Firm. 
 
 Light 
 Green. 
 
 Light 
 Grey, 
 Firm. 
 
 Light 
 Grey. 
 
 Light 
 Crumb- 
 ling. 
 
 Crumb- 
 ling. 
 
 - 
 
 Chiefly 
 Crumb- 
 ling. 
 
 Silicon 
 
 3435 
 
 32-25 
 
 33-io 
 
 34-00 
 
 32-21 
 
 30-00 
 
 32-97 
 
 35-50 
 
 Alumina . 
 
 14-66 
 
 11-17 
 
 10-33 
 
 979 
 
 11-57 
 
 12-34 
 
 12-44 
 
 8- 7 2 
 
 Lime . 
 
 42-66 
 
 46-20 
 
 49-70 
 
 47-00 
 
 50-42 
 
 5I-00 
 
 47-95 
 
 46-50 
 
 Magnesia . 
 
 2'OO 
 
 2 -O2 
 
 i-34 
 
 3 "30 
 
 I'37 
 
 2'34 
 
 1-37 
 
 3 -20 
 
 Manganous oxide 
 
 0-92 
 
 5-07 
 
 2-04 
 
 2-32 
 
 0-85 
 
 0-30 
 
 2-26 
 
 1-58 
 
 Ferrous oxide 
 
 3 '30 
 
 o'6o 
 
 0-67 
 
 0-65 
 
 0-76 
 
 1-05 
 
 1-47 
 
 1-16' 
 
 Sulphur 
 
 1-42 
 
 2*52 
 
 2-69 
 
 I -80 
 
 272 
 
 273 
 
 1-42 
 
 1-64 
 
 Phosphorus 
 
 0*14 
 
 0'02 
 
 0-03 
 
 O'OI 
 
 O'OI 
 
 0-O2 
 
 0-08 
 
 O'O2 
 
 Blast furnace slags are used for the preparation of artificial stone, for road-making, 
 as a material for cement, for bottle-glass, for enamelling, for manures.* Slags, if not 
 basic, are also used for the manufacture of aluminous products.t 
 
 Crude Iron. The iron run off from the blast furnace contains carbon (both free, as 
 graphite, and in combination, as iron carbide), silicon, sulphur, phosphorus, manganese, 
 &c. According to the nature of the carbon, it is distinguished as white and grey crude 
 iron. 
 
 The white iron is distinguished by its silvery white colour, hardness, brittleness, 
 brightness, and high specific gravity (7-58 to 7-68). Its carbon is in a state of chemical 
 combination. Sometimes it displays prisms, and is then known as spiegel-eisen, which 
 is obtained from manganif erous iron spar. It may contain from 4 to 1 5 per cent, of 
 manganese. In the production of steel from such spiegel-eisen the manganese protects 
 the carbon against too rapid combustion. 
 
 Grey crude iron varies in colour from a light grey to a deep blackish grey, and is of 
 a granular or scaly texture. It is softer than white iron and more fusible. It contains 
 much graphite and little carbon in chemical combination. It is used for castings, as it 
 fills the moulds more sharply and cleanly than white iron, which hardens with blunt 
 extremities and a concave surface. White (especially manganiferous) crude iron is 
 particularly suited for the preparation of bar iron and steel (Bessemer steel). 
 
 The character of crude iron depends not merely on the charge, but on the tempera- 
 ture of the furnace and the way of working. White iron seems to be first formed in 
 the furnace, and to pass into grey iron at a very high temperature. If ore additions 
 (fluxes, &c.) and fuel are duly proportioned, the product is chiefly white iron, and the 
 slag is never dark. If the fuel is deficient, much ferrous oxide passes into the slag, 
 and gives it a dark colour. If there is an excess of fuel, grey iron is produced. 
 
 * This use is practicable only with the basic slags of the Thomas and Gilchrist process, which 
 are very rich in phosphates. 
 
 t E.g., crude aluminium chloride for the treatment of sewage. See J. W. Slater's process, 
 patent No. 12,830, A.D. 1884. It has been proposed to make bricks of slag, but houses, &c., built 
 of such material never become dry, as there is no interchange of air through the walls. 
 
124 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. ii. 
 
 (2) Examination of Iron and Steel. 
 
 The most important points to be determined are the quantities of carbon, silicon, 
 phosphorus, sulphur, manganese ; secondarily, those of tungsten and titanium. The 
 microscopic examination is acquiring importance.* 
 
 In determining total carbon in iron according to Wohler's process (heating the 
 sample in a current of chlorine, and burning the residue for converting the carbon into 
 carbon dioxide), we obtain, according to Gintl, defective values, as it is not possible by 
 ordinary means to obtain a current of chlorine absolutely free from oxygen, perhaps in 
 consequence of the formation of oxides of chlorine obtained during the action of hydro- 
 chloric acid upon manganese peroxide. This error is avoided by passing the current of 
 chlorine (freed from hydrochloric acid and watery vapour by washing and careful 
 drying) over a stratum of fragments of charcoal of about the size of lentils, about 
 10 centimetres in length, and kept at a red heat. The charcoal must have been 
 previously ignited in chlorine. The gas so purified is then allowed to act upon the iron, 
 which must be used as borings. Ullgren oxidises the carbon by means of chromic acid, 
 and weighs the carbonic acid produced ; Wiborgh determines it volumetrically. 
 
 For determining the carbon present as graphite the sample is generally dissolved in 
 dilute hydrochloric acid in the absence of air, when the residual carbon is washed out 
 and weighed. The combined carbon appears as a residue. Eggertz determines com- 
 bined carbon by dissolving the sample in nitric acid and comparing the solution with 
 known standards. The process is adapted for checking work. 
 
 For determining sulphur the sample is dissolved in nitric acid, and the sulphuric 
 acid formed is precipitated with barium chloride. Less accurate are the processes in 
 which the sample is dissolved in hydrochloric acid ; the sulphur being driven off as 
 hydrogen sulphide and conducted into metallic solutions. 
 
 For determining silicon 5 grammes of the sample are dissolved in nitric acid or 
 bromiferous hydrochloric acid, or in sulphuric acid with potassium chlorate ; it is then 
 evaporated to dryness, moistened with hydrochloric acid, dissolved, and the silica is 
 filtered off. 
 
 For determining phosphorus the sample is dissolved in nitric acid, evaporated to 
 dryness, slightly ignited, re-dissolved ; the phosphoric acid is precipitated with molybdic 
 acid, the precipitate dissolved in ammonia and reprecipitated with magnesia mixture. 
 
 The following analyses of crude iron may be appended : 
 
 
 
 n. 
 
 
 
 TV 
 
 
 
 
 
 . 
 
 
 IV. 
 
 . 
 
 Graphite 
 Combined carbon 
 
 0-086 
 
 3-156 
 
 1-347 
 
 } 6-05 
 
 Carbon 
 Sulphur 
 
 4-323 
 
 0-014 
 
 4-166 
 0-035 
 
 Phosphorus 
 
 0-459 
 
 0-842 
 
 6-37 
 
 Phosphorus 
 
 0-059 
 
 0-090 
 
 Sulphur 
 
 0-036 
 
 1-267 
 
 0-06 
 
 Silicon 
 
 0-997 
 
 0-584 
 
 Silicon 
 
 3-265 
 
 2-721 
 
 2-41 
 
 Manganese . 
 
 10-707 
 
 5-920 
 
 Manganese 
 
 0-388 
 
 2-401 
 
 6-28 
 
 Cobalt 
 
 trace 
 
 trace 
 
 Aluminium 
 
 0*028 
 
 
 
 0-08 
 
 Nickel 
 
 0-016 
 
 - 
 
 Chrome 
 
 0-027 
 
 
 
 Zinc . 
 
 
 
 Vanadium 
 
 O'OI2 
 
 
 
 Copper 
 
 0-066 
 
 0-046 
 
 Copper 
 
 0-OO9 
 
 
 
 Lead . 
 
 
 
 Arsenic 
 
 0-OI5 
 
 
 
 Potassium . 
 
 0-063 
 
 
 Antimony 
 
 O'OII 
 
 
 
 Aluminium 
 
 0-077 
 
 0-068 
 
 Cobalt and nickel 
 
 0-035 
 
 
 
 Calcium 
 
 0-091 
 
 trace 
 
 Zinc . 
 
 trace 
 
 
 
 Magnesium 
 
 0-045 
 
 0-058 
 
 Calcium 
 
 0-072 
 
 
 
 0-46 
 
 Titanium . 
 
 0.006 
 
 
 Magnesium 
 
 O'lOO 
 
 
 
 0*25 
 
 Arsenic 
 
 0-007 
 
 0-032 
 
 Titanium . 
 
 0-024 
 
 
 
 Antimony . 
 Tin . 
 
 0-004 1 
 
 0-026 
 
 
 
 
 
 Nitrogen 
 
 0*014 
 
 
 
 
 
 
 Oxygen (in slag) 
 
 0-665 
 
 
 * See Select Methods, by W. Crookes, F.K.S., pp. 145-195. 
 
SECT. II.] 
 
 IRON, 
 
 I2 5 
 
 I. is a black crude iron, according to Fresenius ; II. is a very grey crude iron from 
 Gartsherrie ; III. grey crude iron from bog-ore at Helbo (charcoal) ; IV. Spiegel iron, 
 from Lohe, according to Fresenius ; V. Spiegel -eisen from St. Louis. 
 
 The analysis of Gleiwitz coke iron has given the following results : 
 
 Spiegel, crude . 
 
 White 
 
 Finely granular 
 
 Coarse 
 
 c. 
 
 Si. 
 
 S. 
 
 p. 
 
 Mn. 
 
 3-35 
 
 ... 0-317 ... 
 
 0-030 . 
 
 1-29 
 
 ... 3-60 
 
 5'49 
 
 ... 0800 
 
 O'OIO . 
 
 .. 0-28 
 
 373 
 
 3-20 
 
 I'2IO ... 
 
 0-114 . 
 
 ,. 0-81 
 
 ... 1-70 
 
 4-38 
 
 ... 2'O2O ... 
 
 0-118 . 
 
 . . 0-90 
 
 ... 1-65 
 
 (3) Iron Founding. 
 
 Fig. 
 
 Although iron can be cast direct from the blast-furnace it is generally preferred 
 to re-melt the pigs ; this is effected either in crucibles in shaft- or cupola - 
 furnaces, or in reverberatories. The 
 cupola-furnaces are by far the most 
 generally used, the preference being 
 given in Germany to the design pro- 
 posed by Krigar. The cylindrical 
 shaft, a (Fig. 131), has a short cham- 
 ber, b ; the compressed air issues from 
 the ring-shaped channel, d, through 
 slits, f , into the melting-box, c, e. The 
 melted iron collects in the fore-hearth, 
 g, from which the slag can flow off at 
 s or t. The door, o, lined with fire- 
 clay, is provided with an aperture 
 above the out- flow channel, p. At q 
 there is an eye-hole, and at r an open- 
 ing for cleaning the slits. The lower 
 part of the furnace is, with the sheet- 
 metal screen, h, and stands on the 
 ribbed cast-iron plate, k, which lies on 
 the iron pillars, m. When the melt 
 is complete, the last residues are re- 
 moved through the trap door, n. In 
 the cupola-furnaces of Greiner and 
 Erpf the air enters through different 
 rows of tuyeres to burn the carbon 
 monoxide. 
 
 The author found on examining 
 Krigar furnaces that the ratio C0 3 : 
 CO in the escaping gases is now 2 to 
 3, whilst it was formerly about 0*8 ; the Consumption of coke per 100 kilos, iron is now 
 reduced from 20 to 6 kilos. The sulphur escapes partly in the gases, and in part, if 
 sufficient lime is present, it enters the slags, as the following analyses show : 
 
126 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. ii. 
 
 
 Slags from 
 Former 
 Times. 
 
 Slags from Hannoverian 
 Cupolas. 
 
 From 
 Spiegel. 
 
 Slags from Irons for Basic 
 Process. 
 
 
 HO, 
 
 60-05 
 
 5604 
 
 SS'oi 
 
 50-48 
 
 36-56 
 
 37-05 
 
 42-08 
 
 52-96 
 
 Al,6 3 
 
 lS-00 
 
 H-55 
 
 11-61 
 
 10-68 
 
 H-57 
 
 II-08 
 
 10-81 
 
 1 2 -80 
 
 Fe 2 3 
 
 
 
 
 
 
 
 
 
 
 
 0-85 
 
 1-25 
 
 FeO 
 
 4-61 
 
 IS'34 
 
 14-91 
 
 20-98 
 
 078 
 
 1-59 
 
 6-28 
 
 4-36 
 
 MnO 
 
 8-29 
 
 4'02 
 
 I -06 
 
 4-01 
 
 19-80 
 
 14-09 
 
 5-66 
 
 4-3I 
 
 CaO 
 
 6-29 
 
 9'74 
 
 I5-05 
 
 9-85 
 
 28-97 
 
 29-64 
 
 29-50 
 
 19-63 
 
 MgO 
 
 0-25 
 
 0-51 
 
 0-49 
 
 0-84 
 
 1-92 
 
 20-79 
 
 3-65 
 
 . 2'12 
 
 Ca . 
 
 } 0-41 
 
 O'2I 
 
 0-28 
 
 O'22 
 
 
 
 1-98 
 
 
 ) 
 
 S . 
 
 ) 0-33 
 
 O'I7 
 
 O'22 
 
 0-18 
 
 0-40 
 
 1-58 
 
 0-48 
 
 1 0-47 
 
 PA 
 
 
 
 
 
 
 
 
 0-04 
 
 O'lO 
 
 I '00 
 
 O'H 
 
 so s . 
 
 
 
 
 
 
 
 
 
 0*05 
 
 
 
 0-04 
 
 0-40 
 
 The iron present in the cupola slag is derived partly from the ash and partly from 
 the crude iron ; the latter is the more strongly oxidised the less carbon monoxide is 
 formed, as shown, e,g., in the slags of the Hannover cupolas. The richer the crude iron 
 is in manganese the more both the iron and the silicon are protected from oxidation. 
 
 The changes which iron undergoes on re-melting in the cupola were examined by 
 Ledebur : 
 
 
 Q 
 
 Si 
 
 
 Pll 
 
 P 
 
 
 
 
 
 
 
 Pig ... 
 
 After ist smelting 
 2nd 
 3rd 
 4th 
 
 4-I73 
 3-586 
 3-860 
 3763 
 3-686 
 
 1-528 
 
 1-447 
 I-370 
 I-378 
 I'334 
 
 2-084 
 I'599 
 1-399 
 1-038 
 0736 
 
 0-079 
 0-150 
 0-080 
 0-079 
 0-079 
 
 0-331 
 
 0-475 
 
 On melting pig-iron with lime and fluor-spar Rollet obtained : 
 
 
 ] 
 
 
 1 
 
 I. 
 
 I] 
 
 I. 
 
 
 Before 
 Smelting. 
 
 After 
 Smelting. 
 
 Before 
 Smelting. 
 
 After 
 Smelting. 
 
 Before 
 Smelting. 
 
 After 
 Smelting. 
 
 Ca 
 Si 
 Mn 
 S 
 P 
 
 3-500 
 0-900 
 I-300 
 O'220 
 O"O7O 
 
 3-500 
 0-380 
 0-815 
 0-015 
 OXK8 
 
 2*900 
 
 0-655 
 traces 
 
 0-375 
 
 O'^O 
 
 3-088 
 0-060 
 traces 
 0-015 
 O'o68 
 
 2-550 
 0-450 
 traces 
 0-520 
 I "Q"iO 
 
 2 '800 
 0'120 
 traces 
 0*040 
 0*4.1 c 
 
 
 
 
 
 
 
 
 Good casting-iron should contain as much carbon as possible, in the form of graphite, 
 and be consequently very coarse in grain (generally 3 to 3-5 per cent.) ; the manganese 
 should be low, not exceeding 0*75 per cent. A high proportion of silicon at least 
 2 per cent. is, according to Schmidt, indispensable. A low proportion of phosphorus 
 is advantageous, and i per cent, is the utmost limit. For castings which must have 
 great absolute strength the margin lies at 0*5 per cent. Sulphur must not exceed 
 <ro6 at the outside. 
 
 Melting in a reverberatory furnace has the advantage that the iron does not come 
 in contact with the coke or its ashes, and is consequently less modified than in the 
 cupola. On account of the high temperature required, only furnaces with a storage for 
 heat can be advantageous. The reverberatory designed by Fr. Siemens has a round 
 chamber K (Figs. 132 and 133), with a vault as shown by dotted lines. To the furnace 
 chamber there are joined two pairs of gas and air flues, F l and F 3 , situate high up in 
 the vault, leading down in such a manner from the furnace chamber, K, to the heat- 
 storage chamber, R, that the sides of the hearth are freely accessible. The chamber is 
 built upon pillars, and hence the furnace is accessible also from below. The furnace is 
 provided with doors, F, for introducing the metal to be melted, and with an upper and 
 .a lower tap-hole, S l and S s . The lower hole, S a , permits of the entire charge being 
 
SECT. II.] 
 
 IRON. 
 
 127 
 
 drawn off, whilst the upper tap-hole serves merely to draw off the upper portion of the 
 melted steel, together with the slag. The zone, Z, in contact with the slag, is without 
 
 Fig. 132. 
 
 Fig. 133- 
 
 an iron coating, and is hence accessible on all sides and can be repaired even during 
 work. 
 
 (4) Wrought or Bar Iron. 
 
 As already mentioned, wrought iron was formerly obtained by heating the ores 
 with charcoal upon a hearth and forging out the spongy iron thus produced. This so- 
 called " direct " process has been of late much improved, especially by Siemens, who 
 vised firstly a rotatory furnace and then a reverberatory (Figs. 134 to 137). The 
 bottom of the melting chamber forms a tank, s, to collect the melted metal, and one 
 side is a sloping hearth, /, upon which the mixture of ore, coal, and fluxes to be smelted 
 moves downwards. For the convenient introduction of this mixture, a slit, o, is left 
 free in the vault above the sloping hearth, and above it a space is set off, in which a 
 large quantity of the mixture can be collected and sink gradually down through the 
 slit as the charge already upon the hearth melts away. The tank, s, is fitted at 
 different heights with three tap-holes Z, Z^ and Z v the upper one being permanently 
 open and serving for the continued removal of the slag, Z, is the general tap-hole for 
 running off the melted iron from time to time, whilst the lowest hole, Z v is used only 
 
128 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. 
 
 if the furnace is to be completely emptied. Thus, a part of the iron-bath remains in 
 the furnace, so that the slag never touches the bottom of the tank, and the iron, which 
 is constantly being formed in the shape of fine globules, can sink down in the mass of 
 metal upon the hearth. In order to render the slag suitably mobile and to remove 
 impurities from the iron, lime, and potassium and sodium salts are added to the 
 
 Fig. 134- 
 
 Fig. 135- 
 
 Fig. 136 
 
 j^xpu 
 
 FIG. 134. Schnitt = Section A, B, a, b. 
 FIG. 135. Schnitt Section C, D, E, F. 
 
 Explanation of Terms. 
 
 a. b. FIG. 136. Schnitt = Section G, H", I, K,L, M. 
 
 FIG. 137. Schnitt = Section N, O, P, Q. 
 
 mixture, inot generally, but under certain circumstances. The addition of such salts" 
 renders the slag more fit for the glass manufacture. 
 
 Opinions on the value of the direct processes are very varied. Ledebur considers 
 them as unpromising. Westmann contests this view if the ores used contain at least 
 50 per cent of iron. For obtaining pig-iron, the following quantities of heat are 
 needful : 
 
 For reducing ores . . . . . . . 1588 
 
 expelling H 2 O and CO._, 158 
 
 reducing SiCX, and P..O.J 29 
 
 smelting iron and slags 774 
 
 To which come further for O '0428 kilo, carbon taken up 
 
 by the crude iron 173 
 
 Heat-units 2722 
 
 In the production of spongy iron the following items are dispensed with : 
 
 For expelling H 3 from fuel 82 
 
 carbon taken up by crude metal 173 
 
 reduction of SiO, and P..O 5 29 
 
 half heat expended in smelting . . . . . 372 
 
 Heat-units 
 
 656 = 24 % 
 
SECT, ii.] IRON. 129, 
 
 By far the largest quantity of bar-iron is prepared from crude iron. 
 
 Refining Process. This process depends on the removal by oxidation of the bulk of 
 the carbon and the other foreign matters, especially silicon, from crude iron. Only 
 white pig is used, as poor as possible in carbon, since before smelting it softens, remains 
 for a long time as a thin liquid, and hence presents a larger surface to the oxidising 
 agents. Its combined carbon burns more readily than the graphite of grey pig. This 
 process may be effected either (i) on a hearth (sometimes called the German pro- 
 cess), (2) in reverberatories (the puddling process), or (3) by forcing air into the 
 melted crude iron (the Bessemer process). 
 
 In the hearth-refining process, white pig is melted in the four-sided, depressed fire- 
 space, , of the hearth, b (Fig. 138), in such a manner that it is not exposed to the 
 blast until it is liquefied. The depression is lined with iron plates and receives the 
 necessary current of air through the 
 pipe, c. The fire-box is first filled with 
 glowing charcoal, the blast is turned 
 on, and the iron is laid upon the 
 hearth and pushed down into the 
 depression as it melts off at the 
 end. 
 
 The air of the blast constantly 
 burns the carbon of the crude iron to 
 carbonic acid, and thus effects its de- 
 carbonisation. The sand adhering to the pigs, the silica formed by the oxidation of 
 their silicon and that introduced by the ash of the charcoal, combine with the ferrous 
 oxide simultaneously formed to bisilicate, FeSi0 3 , the so-called "crude-slag" (68'8 
 per cent, ferrous oxide and 31*2 silica) which floats above the melted iron and is 
 run off from time to time, though the iron is never left quite uncovered. This slag, 
 mixed with anvil-dross (ferroso-ferric oxide), is used for the next operation to decarbonise 
 the iron. In fining, all the other foreign matters contained in the iron, such as phos- 
 phorus, &c., pass into the slag in the state of phosphoric acid, &c. After the iron 
 is melted the slag is drawn off, and the pieces of iron are exposed to the blast 
 whilst being frequently turned. The slag now being formed becomes the richer 
 in ferrous oxide as the metal becomes purer, and contains 73-7 per cent, ferrous 
 oxide and 21*4 silicic acid. It is never crystalline, but compact, of a dark grey colour, 
 and of a higher specific gravity than the crude slag. The whole mass of iron is made 
 semi-fluid by an increase of the temperature to promote the separation of the slag. 
 The fined lump (ball or bloom) is lifted out of the fire and brought under the lift- 
 hammer. By its blows all particles of slag are forced out. The bloom is then cut 
 into pieces, which are forged into bars. From 100 parts of pig iron there are obtained 
 on the average 70 to 75 parts of bar iron. 
 
 The Swedish fining process acts at once upon small portions of iron only. The 
 decarbonisatioii is effected by the oxygen of the air. Much fuel is consumed, and a 
 not inconsiderable part of the iron is oxidised, but the iron obtained contains no slag, 
 and is more compact. 
 
 The puddling process is, in fact, fining in a reverberatory furnace. In countries 
 where charcoal cannot be used for fining crude iron on account of its high price, coal is 
 used. As the immediate contact of coal with the iron must be avoided on account of 
 the sulphur which it contains, reverberatory or puddling furnaces are used for effecting 
 the elimination of the carbon. This is effected by agitation, either by hand or by 
 machinery, or by means of a revolving hearth. Thus we have hand puddling, machine 
 puddling, and rotatory puddling. 
 
 Preparatory to the puddling process is the refining, by which the free carbon is 
 
130 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. n. 
 
 brought into the combined state and the silicon is burnt. This refining consists in 
 re-melting upon a bed of coke under the action of a blast. A grey pig-iron contained 
 
 Before Refining. After Refining. 
 
 Carbon 
 
 Silicon 
 
 Sulphur 
 
 Phosphorus 
 
 Manganese 
 
 ro 
 
 o'5 
 07 
 
 O'2 
 
 0'2O 
 
 0x15 
 
 Fig. 139- 
 
 Hence it appears that the proportion of carbon in crude iron is not reduced by 
 refining, but the silicon is chiefly removed. 
 
 A puddling furnace is shown in front elevation in Fig. 139, and in Fig. 140 in 
 
 section. The hearth, A, is a rect- 
 angular iron chest, into which air 
 can stream in freely through the 
 grate, F. Upon this hearth there 
 is placed a layer of refining slag, 
 to which forge scales have been 
 added, and the mass is heated 
 until its surface is softened. The 
 pig-iron to be treated is heated 
 until it is soft, spread about over 
 the surface of the hearth by 
 means of a stirrer, and heated 
 with constant agitation (pud- 
 dling). The working door, D, can 
 be easily opened and closed. There 
 appear small blue flames of carbon 
 monoxide upon the pasty iron, and 
 the metal becomes stiffer and 
 tougher. The greater part of the slag 
 formed during puddling flows away from 
 the iron to the front of the furnace, down 
 the inclined plane, B, and it is let off 
 through an opening from time to time. 
 When the puddling is completed the iron 
 spread out on the hearth is collected into 
 balls arid freed from slag by the hammer. 
 By the access of the air or of oxy- 
 genous fire-gases to the molten crude iron 
 upon the hearth of the reverberatory, there is formed ferroso-ferric oxide, the oxygen 
 of which removes the carbon of the crude iron in the form of carbon monoxide, which 
 burns with a blue flame. As the mass is decarbonised it becomes less fusible, and 
 there are formed in its interior solid masses of wrought iron, which increase in quantity 
 and which are collected with the stirrer and slightly welded together. In practice the 
 process is not so simple, because (i) it is not possible to bring all the ferroso-ferric oxide 
 in contact with the carboniferous iron, so that oxide is easily left in the iron and prevents 
 the coherence of its parts. To remove this superfluous oxide, crude slag is added, 
 which is converted into refinery slag. The elimination of the oxide involves a loss of 
 iron of 4 to 5 per cent., to which must be added 5 per cent, more by the combustion 
 of the carbon ; (2) another difficulty arises from the presence of blast-furnace slag, and 
 of mechanically adhering silica, &c. During puddling the free silica unites with the blast- 
 furnace slag; if this comes in contact with the ferroso-ferric oxide with deficient 
 
 Fig. 140. 
 
SECT. II.] 
 
 IRON. 
 
 carbon, it gives its silica partially to the ferroso-ferric oxide, forming with it a refinery 
 slag, which adheres to the walls and the sole of the furnace, and a basic, very infusible 
 blast-furnace slag, which remains mixed with the iron. The puddling process, as at 
 present carried out, is quite unable to remove this slag. Recent studies of irons and 
 slags in the various stages of the puddling process have proved that, in puddling, the 
 oxidation of the combined carbon, silicon, sulphur, manganese, and iron, is effected 
 much more by the combined oxygen of the slag and the fluxes than by the free oxygen 
 of the air, which is especially active only at the period of melting. In the first portion 
 of time after melting, the iron re-dissolves the non-combined carbon. Hence, the 
 silicon is separated as silica, the proportion of combined carbon increases, and the 
 graphite diminishes. At the same time, much of the manganese is oxidised. After 
 this fining process is completed the boiling period sets in, with separation of carbon and 
 partial reduction of iron, when the particles of iron separated are in the state of steel. 
 In the third period, soft iron is formed with further decarbonisation, when the bulk of 
 the phosphorus is separated out as iron phosphide and ferric phosphate, and passes 
 into the slag. 
 
 Iron which contains too much phosphorus is purified by adding, during puddling, 
 the so-called " Schafhautel's mixture " (manganese, common salt, and clay). According 
 to Richter, litharge is better than manganese for oxidising the sulphur in crude iron. 
 Superheated steam has also been proposed for the removal of sulphur. The volatilisa- 
 tion of sulphur and phosphorus has also been attempted by the addition of fluor-spar 
 (Henderson's process), and of iodine compounds such as potassium iodide. Others add 
 soda. 
 
 The tendency to displace manual labour more and more led, firstly, to the con- 
 struction of the mechanical puddler, and, as the results were not completely satisfac- 
 tory, to the invention of rotatory puddling furnaces, among which that of Danks 
 (Fig. 141) deserves notice. The furnace, A, has a grate apparently similar to the 
 'Common puddling furnace, but the necessary 
 air is admitted also by a row of tuyeres, 
 placed above the grate. The rotatory 
 hearth, B, consists of cast-iron segments, 
 lined within with a mixture of iron-ore and 
 bauxite. The rotatory hearth has a two- 
 fold arrangement supporting two rails for 
 the rollers upon which the apparatus rests 
 movably, and a toothed wheel, E, to which 
 the motion is communicated by means of a 
 small engine. Whilst one opening of the 
 hearth is in contact with the furnace bridge, 
 the other serves for introducing the charge 
 and taking out the finished blooms. 
 
 Bar-iron, Wrought or Malleable Iron, has a light grey colour and a granular and 
 jagged fracture ; its specific gravity is 7'6o-7'9O, that of chemically pure iron being 
 7 844. Its carbon is from 0-20 to 0-84 per cent., traces of which only are in a state 
 of mechanical mixture. 
 
 Chemical examination of bar-iron give the following results (i) English bars 
 from South Wales, (2) soft bars from Magdesprung in the Harz, (3) Swedish Danne- 
 
 smora iron : 
 
 Iron . 
 
 Carbon 
 Silicon 
 Copper 
 Phosphorus 
 
 98-904 
 0-411 
 0-084 
 
 0-041 
 
 98-963 
 0-400 
 0-014 
 0-303 
 
 3- 
 
 98775 
 0-843 
 
 0-118 
 0-054 
 
1 32 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 Wrought iron, if heated to redness and plunged into cold water, does not become 
 harder and more brittle, and can still be forged. It is much softer than grey or 
 white pig, and can be easily filed, cut, planed, &c. It is far less fusible than crude 
 iron ; at a white heat it becomes so soft that two pieces can be united together by 
 hammering, pressing, or rolling. 
 
 Iron shares this property of welding with platinum, palladium, potassium, and 
 sodium. Iron is less easily welded the more carbon it contains. The bar-iron 
 obtained by fining and puddling is more or less contaminated with foreign matter. 
 If it contains sulphur, arsenic, and much copper, it is red short, i.e., it crumbles under 
 the hammer at a red heat ; silicon renders it hard and brittle, and the presence of 
 phosphorus makes it cold-short, i.e., it can be worked when hot, but when cold it breaks 
 on bending. Calcium renders iron incapable of being welded. Hard, crystalline sorts 
 are preferred for articles which have to resist friction and take a permanent polish. 
 Tough, stringy irons serve for parts of machinery, for chains and anchors, &c. 
 
 The puddling process has lost much, of its importance, and will probably be entirely 
 superseded by the Siemens-Martin and the Bessemer processes, both of which produce 
 steel as well as wrought iron. The treatment of 350 kilos, of iron in Danks' furnace 
 appears feeble in comparison with the manipulation of 10,000 kilos, in the Bessemer 
 converter. 
 
 STEEL. 
 
 Steel. This substance differs from crude pig-iron and from bar-iron in the amount 
 of carbon it contains : from crude iron, moreover, by being capable of welding ; and, 
 again, from bar-iron, by being comparatively readily fusible : in reference to the amount 
 of carbon present, steel holds a position between crude pig-iron and bar-iron. Recent 
 researches have revealed the fact that steel contains nitrogen ; but whether this element 
 really contributes to the peculiar properties of steel obtained from different sources is 
 not a definitely settled point. Steel is obtained of various qualities by a number of 
 processes, as will be seen in the following brief reference 
 
 a. Directly from iron ores 
 
 1 . By the reduction of iron ores directly with the aid of fuel (chiefly charcoal), 
 
 and a blast on the hearth, the steel being obtained in the form of lumps 
 (so-called natural steel). 
 
 2. By the heating of certain iron ores along with coal, but without fusion 
 
 (cementation steel from ores). 
 
 3. By the fusion of iron ores along with charcoal in crucibles (cast-steel from 
 
 ores). 
 
 6. By the partial decarbonisation of pig-iron (rough steel, furnace steel, or German 
 steel) 
 
 4. By the refining (partial decarbonisation) of pig-iron by means of charcoal 
 
 fuel on the hearth (sheer steel). 
 
 5. By treating pig-iron in reverberatory furnaces fed by coal or blast-furnace 
 
 gases as fuel (puddled steel). 
 
 6. By forcing air through molten cast-iron (Bessemer steel). 
 
 7. By heating cast-iron to redness along with substances which will effect 
 
 decarbonisation below the fusion-point of the metal ; if the substances 
 employed for partial decarbonisation are iron ores, the steel is called iron 
 ore steel. 
 
 8. By melting crude cast-iron with such substances as those just men- 
 
 tioned. 
 
 9. By treating crude cast-iron with sodium nitrate (Heaton steel, Hargreave 
 
 steel). 
 
BECT. ii.] STEEL. 133 
 
 c. By imparting carbon to bar or malleable iron 
 
 10. By ignition with carbonaceous matter, but without fusion (cementation 
 
 steel). 
 
 11. By fusion with charcoal (cast steel). 
 
 d. By combination of methods b and c, as in fluxed steel 
 
 12. By melting crude pig-iron and malleable iron together. 
 
 In India a kind of steel is still made directly from iron ores, and known as wootz 
 (as to the composition of this substance, see the Chemical News, vol. xxii. p. 46) ; 
 it is possessed of excellent qualities. The Japanese also understand the art of making 
 steel of most excellent quality by rather rough and primitive means. 
 
 According to the degree of hardness we distinguish mild and hard steel, and accord- 
 ing to its applications tool steel and machine steel. 
 
 The finery steel obtained by the partial decarbonisation of crude iron may be either 
 
 (1) Rough Steel or Natural Steel, prepared chiefly from the "crude steel-irons" a 
 crude iron prepared from iron spar, and made in Styria, Carniola, Carinthia, &c., also 
 as spiegeleisen, generally with charcoal, but partly with coke. Steel-fining is distin- 
 guished from iron-fining chiefly by the application of the blast, which is directed so 
 that the carbon may be burnt gradually, and the workman has it in his power to 
 interrupt the process at the moment when the steel is ready. 
 
 (2) Puddled Steel. Steel may be produced by the puddling process from very 
 different kinds of ore, and is furnished very cheaply for the wheels of locomotives, 
 railway carriages, and other large and heavy objects. 
 
 (3) Bessemer Steel. The pneumatic process invented by J. Bessemer, of Sheffield, in 
 1856, consists in forcing into liquid crude iron (whether direct from the blast furnace or 
 such as has been re-melted in cupola or reverberatory furnaces) a strongly compressed 
 blast of air. Without the addition of especial fuel a sufficient temperature is produced 
 by the combustion of silicon, manganese, and iron to maintain the process and form 
 ferro- silicate, which takes up f erroso-ferric oxide, and, as in the other refining processes, 
 exerts an oxidising action upon the carbon and other foreign matter. Phosphorus is 
 removed only by the basic process (Thomas & Gilchrist); sulphur to a small extent 
 only ; copper, nickel, and cobalt not at all. The process may be either continued until 
 wrought iron is formed (which may then be converted into steel by the addition of 
 spiegeleisen or ferro-manganese) or the carbon is removed only to the degree necessary 
 to form steel. 
 
 On account of the energetic oxidation, the process is much more rapid than the 
 fining on hearths and in reverberatories, and during the oxidation of the silicon a part 
 of the carbon is burnt off also. To treat 10 tons of crude iron by this process requires 
 from 10 to 20 minutes, whilst to puddle the same weight requires three days, and to 
 convert it on the hearth about three weeks. 
 
 The best crude iron for the Bessemer process in converters with an acid lining 
 (quartz, gannister) is a grey pig containing silicon and manganese, but as little phos- 
 phorus and manganese as possible. On forcing in strongly compressed air into this 
 liquid iron, the silicon and manganese, along with some iron, burn first, and yield so 
 high a temperature that it suffices to keep the mass liquid during the remainder of the 
 process. The presence of manganese, which is oxidised almost simultaneously with 
 silicon, retards the process. The behaviour of graphite in the first part of the process 
 is similar, as it has to be converted into combined carbon before it is oxidised. In 
 manganif erous grey pig the silicon seems to be chiefly combined with the manganese. In 
 white pig, poor in silicon and containing carbon only in a state of chemical combination, 
 the process is more rapid, which does not conduce to a good result. There is produced 
 a thickly liquid steel mixed with slag, which cannot be rendered compact by forging. 
 As a small percentage of sulphur is less hurtful in steel than in wrought-iron, good 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. n. 
 
 Fig. 142. 
 
 coke-pig may give satisfactory results, especially if manganese is present, which helps. 
 
 to remove sulphur, but not phosphorus. 
 
 The apparatus consists of a pear-shaped converter of sheet-iron, A (Fig. 142). It 
 
 is lined with a fire-proof mixture, and 
 turns on two horizontal points by means 
 of a toothed wheel, K, which catches into 
 a tQothed rod moved by the piston of a 
 hydraulic press. At the bottom of the retort 
 there is applied, by means of hydraulic 
 pressure, a wind-chest, M, from which 
 tuyeres with forty-nine to eighty-four aper- 
 tures convey the air, with thorcmgh distri- 
 bution, into the interior of the converter. 
 The blast streams out from the pipe, L, 
 through o, into a space round the pivot, 
 d, passes downwards in the pipe, e, and 
 enters the wind-chest, M, through the pipe, 
 D, which is secured to e by means of a 
 
 Fig. 143. 
 
 bent iron strap. The case, m, surrounding the pivot, d, rests upon the support, E r 
 and is connected with the tube,' o, by means of a stuffing box. 
 
 In working, the converter is first properly heated, and then from 3 to 10 tons of 
 iron melted in reverberatories, or cupolas, F (Fig. 143), are run in a channel through 
 the neck of the converter, J4, inclined more than 90 (and shown in Fig. 143 by dotted 
 
SECT, ii.] STEEL. 135 
 
 lines), in such a manner that it does not enter into and clog the tuyeres at the bottom, 
 The blast is turned on, and the converter is then raised to an upright position. The 
 blast must have so strong a pressure that it forces the iron out of the jets of the tuyeres, 
 and distributes itself in fine streams. In the first period which thus begins (fining 
 or slagging period), a temperature is produced exceeding the melting-point of wrought- 
 iron ; and silicon, manganese, and a part of the iron are oxidised ; a slag is produced 
 consisting of ferrous and manganous silicate ; and the graphite is converted into com- 
 bined carbon, but without the combustion of much of it. The indication for judging 
 the process is chiefly the flame issuing from the mouth of the converter, , into the 
 chimney, C D, the sparks and the matter thrown out, as well as the spectroscopic 
 character of the flame, and the appearance of samples taken. During the first four 
 minutes no flame is visible, in the next two minutes there appears a small pointed 
 flame, and, after six or eight minutes, an unsteady flame, with explosions. In these 
 three intervals of time there are seen, by means of the spectroscope, at first a faint 
 continuous spectrum from the sparks of ignited metal, then a light spectrum with 
 flashes of the sodium line, and, lastly, a bright spectrum with a permanent sodium 
 line, a red lithium line, and both the potassium lines. 
 
 With the explosions there begins the second period (the period of eruptions or 
 boiling), in which the carbon is burnt by the abundant formation of ferroso-ferric 
 oxide, in consequence of the more violent and copious formation of carbon monoxide ; 
 the mass rises up (boils), and slags and particles of iron are thrown forcibly out of the 
 neck of the retort. The flame becomes bright and dense, then bright, but less dense 
 below. With the spectroscope there are seen, in addition to the lines above mentioned, 
 bright carbon monoxide lines in the red, the green, and the blue, and the bright lines 
 in the green. In about fourteen minutes after the beginning of the process this period 
 is at an end. In the third period the bath has become quieter ; the eruptions have 
 ceased, and much iron is burnt along with the carbon still remaining ; this is indicated 
 by a brisk rain of sparks, whilst the flame becomes less vivid and smaller. With the 
 disappearance of the flame and the change of the green line of carbon monoxide into a 
 continuous spectrum, the carbon is consumed within about eighteen to twenty minutes. 
 The iron at the end of the third period is present as decarbonised iron (bar iron). If, 
 as is generally the case, the production of steel is intended, the fourth period begins. 
 For this purpose the blast is shut off, the converter is inclined, and so much liquid 
 manganiferous spiegeleisen or ferro-mangan is introduced at the neck as will produce 
 steel containing a given proportion of carbon. The converter is again placed upright, 
 and the masses are allowed to mix, or the blast is turned on again for a moment to 
 effect a more perfect intermixture. The converter is then turned to the right, and the 
 steel is poured into the pan, T, and thence, by means of the hydraulic crane, P, into the 
 moulds. By means of the wheels, S and K, the crane can be turned on the pivot, Q, 
 and the pan, T, tilted by means of q r. The iron screen, F, is to protect the workman, 
 and the counterpoise, U, keeps the plate, P, in equilibrium. The ferro-manganese is 
 not merely to supply carbon to the iron, which has been decarbonised by the Bessemer 
 process, but as the manganese present is more readily oxidised than the carbon, it is bo 
 keep the proportion of the latter constant. 
 
 Dahlems has followed the Bessemer process analytically in four Swedish establish- 
 ments. (See Table.) 
 
136 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. ii. 
 
 
 T 
 
 
 
 
 
 .Langshjt tan. 
 
 .Nykroppa. 
 
 ang ro. 
 
 es an ors. 
 
 Crude Iron. 
 
 
 Si 
 Mn 
 
 3 "94 
 1-14 
 
 o"6d. 
 
 4'35 
 0-88 
 I'lS 
 
 4-00 
 
 I'02 
 
 1-83 
 
 4'22 
 I -06 
 $12 
 
 Metal. 
 I. time 
 
 C 
 Si 
 
 2 min. 15 sec. 
 
 4 '02 
 
 0*04 
 
 2 min. 30 sec. 
 4'oi 
 
 O'lO 
 
 3 min. 
 
 4 '03 
 0-03 
 
 4 min. 1 5 sec. 
 
 4-02 
 0-43 
 
 Mn 
 
 O'I2 
 
 0-15 
 
 O'22 
 
 3-26 
 
 II. time 
 
 c 
 
 4 min. 30 sec. 
 
 I'lO 
 
 5 min. 30 sec. 
 
 I 'CO 
 
 4 min. 45 sec. 
 0-90 
 
 8 min. 35 sec. 
 1-30 
 
 Si .... 
 
 O'O^ 
 
 0-05 
 
 0-03 
 
 0'12 
 
 
 O'I2 
 
 1-15 
 
 O'I2 
 
 0-85 
 
 III. time 
 
 c 
 
 5 min. 30 sec. 
 0-05 
 
 6 min. 30 sec. 
 0-08 
 
 5 min. 45 sec. 
 
 O'lO 
 
 9 min. 20 sec. 
 '55 
 
 Si 
 
 O'OI 
 
 0-04 
 
 0-03 
 
 0-07 
 
 Mn 
 
 o - o6 
 
 0-08 
 
 0-09 
 
 o-43 
 
 Slag. 
 I. 
 
 3472 
 
 13-50 
 
 14*20 
 
 4-20 
 
 Mangan oxide .... 
 Magnesia ..... 
 
 1 3 '95 
 
 O"24 
 2 '60 
 
 2976 
 0-23 
 0-42 
 
 26-31 
 
 O"22 
 0-62 
 
 46-38 
 0-54 
 1-26 
 
 Alumina 
 
 078 
 4876 
 
 2-28 
 53-26 
 
 2-86 
 55-26 
 
 3-08 
 45 '87 
 
 II. 
 Fe O 
 
 2 1 '08 
 
 9 '34 
 
 18-52 
 
 6-24 
 
 Mn 2 O s 
 Magnesia 
 
 I3-48 
 0-30 
 3-25 
 
 2370 
 0-28 
 o'6o 
 
 31-01 
 
 0-14 
 0-38 
 
 52*26 
 0-29 
 0-70 
 
 Alumina 
 Silica 
 
 III. 
 Fe O 
 
 0-98 
 
 59 '92 
 
 3C-S2 
 
 3-90 
 62-34 
 
 7O'6O 
 
 2-70 
 47-20 
 
 "U '19 
 
 2-49 
 39 '07 
 
 9-4.1: 
 
 Mn 2 3 . 
 Magnesia 
 Lime 
 Alumina 
 Silica . 
 
 I2'29 
 O'2I 
 
 2'3S 
 
 072 
 48-48 
 
 21-39 
 
 O'2I 
 
 0-38 
 2-14 
 
 44^4 
 
 25 '43 
 
 O'll 
 
 0-32 
 
 2-24 
 40-50 
 
 48-92 
 0-46 
 
 I -00 
 
 2-94 
 37-63 
 
 In the basic process (of Thomas & Gilchrist), the converter is lined with a mixture 
 of burnt dolomite and tar. Besides freshly burnt lime is introduced into the heated 
 converter to about 10 per cent, of the intended charge of metal; the liquid iron is 
 then run in and the blast is turned on. 
 
 Finkener showed that first the proportion of silicon and manganese decreases, then 
 that of carbon, and lastly, that of phosphorus and manganese, if the latter has not 
 already disappeared along with the silicon. The removal of these substances is the 
 consequence of their oxidation, and of the property of the products of oxidation to 
 separate from the liquid iron which, however, can take place only when the substances 
 eliminated under the above circumstances have no especial decomposing action upon each 
 other. Experiments show that the carbon escapes chiefly as carbon monoxide, with 
 a small proportion of dioxide, which is such that the transit of carbon dioxide to the 
 iron is compensated by the carbon given to the iron by the carbon monoxide. The 
 proportion between carbon monoxide and carbonic acid may vary with the temperature 
 and the quality of the iron exposed to the action of the gaseous mixture, but the 
 carbonic acid does not entirely disappear except the proportion of carbon in the iron is 
 
SECT, ii.] STEEL. 137 
 
 very high. The phosphorus is oxidised to phosphoric acid along with iron enough to 
 form a ferrous phosphate, containing 3 mols. iron to i mol. of phosphoric acid. A com- 
 pound of phosphoric acid with a smaller proportion of iron cannot separate from the 
 liquid iron, as it would be decomposed. The silicon is converted into silicic acid, which, 
 like the phosphoric acid, enters into the slag as a ferrous compound, containing i mol. 
 silica to i at. iron or manganese. The oxygen entering into the liquid mass will at 
 first burn all the constituents with which it comes in contact, but of the compounds 
 formed only those will remain undecomposed which are equally fusible with the liquid 
 mass. As long as silicon is present the carbon will not decrease ; the carbon monoxide 
 as it is formed decomposes, forming silicate and metallic carbide. The iron silicide has 
 such a reducing action that it reduces a part of the iron present in the normal ferrous 
 silicate to the metallic state. The phosphate, which is more readily reduced, cannot 
 remain ; it is decomposed in contact with the metallic silicide to silicate and metallic 
 phosphide. A decrease of the phosphoric acid does not occur so long as silicon is 
 present. Iron is protected from oxidation by manganese, just as is phosphorus by 
 silicon ; the chief product of the oxidation is, in the beginning, manganous bisilicate. 
 After removal of the silicon, carbon monoxide appears, with a proportion of carbon 
 dioxide, which increases somewhat as the carbon dioxide decreases. Manganous and 
 ferrous phosphates are found in perceptible but not large quantities, and are chiefly 
 decomposed by the iron carbide which still exists. This reduction can only be ascribed 
 to the mixture of carbon monoxide and dioxide, on the supposition that the reducing 
 power of the mixture increases more rapidly as the temperature rises than that of iron 
 carbide. Against the assumption that carbon monoxide has a reducing action upon 
 ferrous phosphate, must be put the small proportion of phosphorus in the metallic 
 iron selected from different slags. If iron carbide is the reducing agent, the iron 
 phosphide formed immediately comes in contact with iron, and there is no inducement 
 for the formation of an iron rich in phosphorus. When the carbon has disappeared the 
 separation of the iron phosphate is effected. The iron sulphide remains undecomposed 
 even after the removal of the phosphorus. After the addition of spiegeleisen the pro- 
 portion of phosphorus increases by the reduction of ferrous phosphate by iron carbide. 
 Fig. 144 shows the changes taking place in iron, and Kg. 145 those in slag, according 
 to an experiment made at Horde. 
 
 According to Hilgenstock, the quadri-basic calcium phosphate, Ca 4 P 2 O 9 , is the sup- 
 porter of the basic process. In a crude iron which, when put into the converter, 
 contained 3 per cent, phosphorus, i per cent, manganese, 0^15 per cent, silicon, 2"j 
 carbon, and 0*15 sulphur, the silicon is soon removed, the combustion of the carbon 
 begins, and with it the oxidation of the manganese and the phosphorus, so that after 
 decarbonising it retains o'oi to 0*02 Si, o'io to 0*15 C, 0*2 to 0-3 Mn, i'5 to 2 P, and 
 o - 1 o to 0-128. After the dephosphorising process, during which the metal mostly 
 requires to be cooled, the bath retains Si, O'o8 to o'oi ; C, o'o6 to 0-14; Mn, 0-07 
 to 0-25 ; P, 0-05 to 0*07 ; S, o'o8 to 0-09, but as much as 0*3 per cent, of oxygen. 
 
 After the bath has been reduced by ferro-manganese, the finished steel contained 
 Si, o - o8 to o-oi ; C, o-io to 0-20 ; Mn, 0*35 to 0*45 ; P, 0-05 to 0-09, and S, 0-04 too-o6. 
 Among the oxidation products silicon as manganous silicate is not reduced at the 
 initial low temperature of the bath, or afterwards at a higher temperature as calcium 
 silicate by any constituents of the bath ; hence the rapid and almost total disappear- 
 ance of the silicon ; silicon if once oxidised remains in the slag as a basic silicate. 
 Carbon monoxide disappears without any noteworthy reductive action either upon 
 metal or slag, so that, save the action of the current of the air, we have only the 
 reactions of the two (igneous) liquids, the metal and the slag, to consider. At the 
 beginning of the dephosphorising process we have to do with them only. After the 
 bath is decarbonised the manganese is reduced to a few tenths and the phosphorus to 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. n. 
 
 one-half. The oxidation and separation of the phosphorus takes place as tribasic 
 ferrous phosphate. The iron phosphate is at once converted into calcium phosphate 
 by the more powerful base lime, and there is formed the quadri-basic phosphate, which 
 is not reduced by metallic iron. The liberated ferrous oxide is again reduced by 
 contact with phosphorus in the bath, so long as the proportions are suitable. If 
 there is from 0-5 to 0-3 per cent, of phosphorus in the bath no notable quantity of 
 
 Fig. 144. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 c 
 
 ^ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 ft 
 
 t-o 
 
 :* 
 P 
 
 t-o 
 Si 
 
 OS 
 
 MD 
 S 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 x , 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 1 
 
 ^ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ' C 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 s^ 
 
 
 
 \ 
 
 a 
 
 
 
 
 
 
 
 
 
 
 N 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 i 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 < 
 
 \\ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 I 
 
 s. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 V 
 
 
 
 
 
 
 
 
 
 
 
 
 I 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 i 
 
 
 
 
 
 
 \ 
 
 
 I 
 
 
 
 
 
 i 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 V 
 
 
 
 
 
 \ 
 
 
 
 
 \ 
 
 V 
 
 
 
 ~\ 
 
 
 ... 
 
 
 " 
 
 \" 
 
 
 \ 
 
 
 M 
 
 
 
 
 W ' 
 
 
 - 
 
 
 \ 
 
 
 Y 
 
 ,i ' 
 
 C 
 
 
 
 
 
 
 
 
 
 
 
 >. 
 
 _j . 
 
 5 " 
 
 S 
 
 
 
 
 
 
 
 
 
 
 
 A 
 
 ' 
 
 P 
 
 
 Fig. 145- 
 
 12. 14Min 
 
 ferrous oxide remains unreduced, and not until afterwards does the iron increase in 
 the slag. It is one of the grandest industrial reactions that in masses of crude iron 
 of the weight of ten tons the phosphorus in contact with three tons of slag is reduced 
 within a few minutes to some tenths per cent. 
 
 The Slag. The basic process yielded in 1886, in round numbers, 400,000 tons of 
 slag containing from 30 to 35 per cent, calcium phosphate ; its utility in agriculture is 
 therefore of the highest importance. At first the slag was prepared in a variety of 
 ways ; now it is simply ground to a fine powder, since experience has proved that it is 
 soluble in the soil. 
 
 In experiments on the value of the phosphoric acid in the " Thomas slags," Miircker 
 proved that when finely ground it had 56 per cent, of the efficacy of the soluble phos- 
 phoric acid in superphosphates, even on superior soils. On moorland soils it was of 
 equal value to the " precipitated phosphates." Slag has no injurious effects upon the 
 crops. The only condition is very fine grinding. 
 
 The Siemens-Martin Process. In this process the decarbonising agent is iron 
 oxide, iron ores, and iron waste. The crude iron is melted in a Siemens reverberatory, 
 and it is introduced into the bath, covered with a layer of slag, old iron, &c., until a 
 sample drawn shows that the entire mass has assumed the fibrous nature of bar-iron. 
 By adding a certain quantity of crude iron the entire mass is converted into steel. 
 The table on p. 140 shows the working of this Siemens- Martin process at the rolling 
 works at Graz. 
 
SECT. II. J 
 
 STEEL. 
 
 Very important experience has been gained with the use of water-gas ia this 
 process. The furnaces employed at Witkowitz have good heat-stoves (Figs. 1 46 to 149) ; 
 
 Fig. 146. 
 
 Fig. 147. 
 
 Fig. 148. 
 
 -lli'JCf) 
 
 SchnHt ARC1) Section ABCD 
 
 Gasletiung 
 Windleitunfi 
 
 Gas-pipiug 
 Air-pipe 
 
 Explanation of Terms. 
 R^ Schnitt ED 
 
 Kinyuss 
 
 Fig. 149. 
 
 Section ED. 
 Inflow. 
 
 they are round and enclosed with a sheet-metal screen ; the bottom is cooled with air,. 
 The vaults of the Martin furnaces can be lifted off. For this purpose a powerful cran& 
 is fixed between the two Martin furnaces, and it serves also to raise the steel pan to 
 the necessary level. Each gas tuyere has a cock connected by a rod to the rest in such 
 a manner that all the cocks can be turned at once. The two gas-pipes from which the 
 gas tuyeres branch off to each furnace have throttle valves. The air is forced by a 
 blast under a small bell, which always maintains the necessary pressure (no mm., equal 
 to the pressure of the gas). The air-pipes branch off in two arms at each furnace and 
 discharge into the furnace channels through which the flue-gases pass from the 
 regenerators to the chimney. Each of these channels can be shut alternately by the 
 slide, S, whilst the other is connected with the flue. 
 
140 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. n. 
 
 * 
 Charge. 
 
 
 Iro 
 
 Mn. 
 
 n. 
 Si. 
 
 
 Slag. 
 
 C. 
 
 SiOjj. 
 
 A1 2 3 . 
 
 MnO. 
 
 FeO. 
 
 CaO. 
 
 6.40 A.M., ist charge of 
 
 
 
 
 
 
 
 
 
 2100 kilos, white pig, 
 
 
 
 
 
 
 
 
 
 1500 grey pig, 
 
 
 
 
 
 
 
 
 
 1000 steel ends, 
 
 
 
 
 
 
 
 
 
 Sample when smelted .... 
 
 1-13 
 
 O'i4 
 
 O'OI 
 
 42-56 
 
 I -46 
 
 28-39 
 
 29-47 
 
 
 9.10 A.M., 2nd charge 
 
 
 
 
 
 
 
 
 
 500 kilos, hoop-iron, 
 
 
 
 
 
 
 
 
 
 500 ., turnings, 
 
 
 
 
 
 
 
 
 
 2000 old boiler plates 
 
 
 
 
 
 
 
 
 1000 old rails, 
 
 
 
 
 
 
 
 
 Sample when smelted . . . .0*69 
 
 O'll 
 
 
 
 42-94 
 
 I'53 
 
 22-23 
 
 3^47 
 
 
 11.20 A.M., 3rd charge 
 
 
 
 
 
 
 i 
 
 
 3900 kilos, old rails, 
 Sample 
 
 0*27 
 
 0-13 
 
 __ 
 
 48-03 
 
 1-76 
 
 18-48 
 
 30-I5 
 
 078 
 
 I2.2O P.M., Sample . O'2O : O'I2 
 
 
 
 47-87 
 
 2-34 I9-53 
 
 29-99 
 
 
 1.40 P.M., sample o'ia 
 
 0-08 
 
 
 
 48-90 
 
 2"OI 
 
 I9'37 
 
 28-88 
 
 
 1.45 P.M., added 120 kilos, silico 
 
 
 
 
 
 
 
 
 ferro-manganese, 
 
 
 
 
 
 
 
 
 Average sample of day's work . . ] 0*31 
 
 0-45 o.oi 
 
 49-63 
 
 
 
 20-89 
 
 25-42 
 
 
 In a water-gas Martin furnace 200 hectokilos of steel were produced in twenty-four 
 hours. The consumption of gas is about 8 cubic metres per minute. The air in the 
 regenerators is heated to 1200 to 1400, whilst the temperature in the furnace is near 
 the melting-point of platinum. The heat of the escaping gases behind the regenerators 
 
 Fig. 150. 
 
 Fig. 152. 
 
 Acid. 
 Basic. 
 
 is still 400 to 500 ; 60 cubic 
 metres of water-gas are 
 used for i oo kilos, of finished 
 steel, including the prelim- 
 inary heating, &c., of the 
 bottom. 
 
 In a common Siemens- 
 Martin stove 50 kilos, of 
 Ostrau coal are used for 100 
 kilos. Hence, for the same 
 amount of work, the water- 
 gas Martin furnace con- 
 sumes only 47 per cent, of 
 the quantity of heat which 
 an ordinary Siemens-Martin 
 furnace requires. 
 
 Basic Hearth-Smelting. This process promises to be of great importance now the 
 difficulties of producing a lining of magnesia have been overcome. Figs. 150 to 152 
 show a furnace suitable for charges of 1 2 tons. The vault, built of an acid stone, is 
 supported by a strong furnace frame, whilst the upper acid part of the hearth-walls 
 consists of separate parts built in boxes, which, if needful, e.g., for mending the furnace, 
 can be turned back on the arm, a, which rotates on the furnace-frame, or may be 
 
SECT. II.] 
 
 STEEL. 
 
 141 
 
 entirely changed. By this arrangement all strain is removed from the basic hearth- 
 walls a point of great importance, as basic materials are mostly very sensitive to 
 pressure. The basic stones consist of burnt dolomite, and are submitted to a pressure 
 of 150 tons on the flat side, and then immediately built into the furnace and heated as 
 quickly as possible. In small furnaces the basic walls reach up to the vault, otherwise 
 only up to the upper angle of the charging apertures; below the slag-line 8 to 10 per 
 cent, of sand is mixed with the basic mass. The upper, changeable part of the walls 
 (45 centimetres high) is built of 2000 ordinary acid stones, separated from the basic 
 lining by a layer of chrome iron and retort-coke, mixed with lime and tar. The vault, 
 consisting of 3000 acid stones, is luted with clay to the walls. 
 
 When the furnace has been duly heated it is charged with ore or anvil-dross and 
 lime, upon, which crude and wrought iron are laid. During heating care must be taken 
 that the slags are sufficiently basic. The duration of the heat is generally shorter than 
 that of an acid furnace, since the dephosphoration is complete as soon as the iron is 
 entirely melted. It might then be tapped, only that a higher temperature is necessary 
 for compact castings, and a further decarbonisation is often necessary. Hence it is 
 proposed to heat with water-gas, in the expectation of finishing a process in four 
 and a half hours. 
 
 Dolomite powder, raw or burnt, and mixed with 8 to 1 2 per cent, of sand, is used 
 for repairs. 
 
 Further experiments were made on a 5 -ton Martin furnace with a basic lining. Two 
 charges were melted of 60 parts crude iron, 30 parts granulated steel, and three parts 
 spiegeleisen, and a third of 70 crude iron, 30 steel, and 4 spiegeleisen. After the 
 mass was in flux a sample of metal and one of slag was drawn every half -hour, and 
 besides a sample of slag, A, after the charge was one-third melted, and another, B, 
 after it was two-thirds melted. 
 
 Metal. i. 
 
 2. 
 
 3- 
 
 4- 
 
 5. 1 6. 
 
 7- 
 
 8. 
 
 9- 
 
 10. 
 
 12. 
 
 13- 
 
 Steel. 
 
 C 1760 
 Si 10-075 
 P ii'400 
 Mn o-ioo 
 S 0-180 
 
 1-680 
 0-075 
 I-370 
 
 o-ioo 
 0-169 
 
 I-390 
 0-070 
 I-320 
 O'II5 
 0-I62 
 
 I-260 
 O-O9O 
 
 rno 
 
 0-090 
 0-150 
 
 Q-840^-5 100-400 
 0-080^-060 o - o6o 
 0-990:0-900 0-8 10 
 o-ioo 0-080 0-090 
 0-145 0-140 0-145 
 
 0-220 
 
 0-040 
 0700 
 
 0-075 
 0-147 
 
 O'OgO 
 0-035 
 0-62O 
 0-085 
 0-137 
 
 0-075 
 0-030 
 0-460 
 O'lOO 
 
 0-133 
 
 0-075 
 
 0-018 
 0-180 
 0-125 
 
 O'I2O 
 
 0-070 
 
 O'OIO 
 
 0-085 
 
 O'I2O 
 O'lII 
 
 0-140 
 trace 
 0-075 
 0-370 
 0-089 
 
 Slag. 
 
 A. 
 
 B. 
 
 i. 
 
 2. 
 
 3. 
 
 4- 
 
 5- 
 
 6. 
 
 7- 
 
 8. 
 
 13. 
 
 Si0 2 
 
 14-40 
 
 
 
 23-60 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 17-40 
 
 FeA 
 
 6-81 
 
 0-40 
 
 073 
 
 3'80 
 
 077 
 
 0-90 
 
 2-60 
 
 2-30 
 
 I -60 
 
 I-I7 
 
 1-64 
 
 FeO 
 
 44-20 
 
 21-50 
 
 8-07 
 
 675 
 
 7-28 
 
 6'2I 
 
 6-35 
 
 7-38 
 
 477 
 
 5-3I 
 
 4'53 
 
 ALA 
 
 6-80 
 
 
 
 7-00 
 
 
 
 
 
 
 
 
 
 
 
 
 
 7-50 
 
 MnO 
 
 2-04 
 
 
 
 8-15 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 4-60 
 
 CaO 
 
 14-00 
 
 
 
 38-10 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 44-00 
 
 MgO 
 
 0-84 
 
 
 
 1-28 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 2-80 
 
 PoO B 
 
 lO'OO 
 
 
 
 12-45 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 1575 
 
 Fe 
 
 38-90 
 
 17-09 
 
 679 
 
 7'93 
 
 6-10 
 
 5 '40 
 
 6-90 
 
 7-41 
 
 4-80 
 
 4-90 
 
 4 '63 
 
 The separation of the substances in question from the iron in the basic reverbera- 
 tory, the basic converter, and the puddling furnace is shown in the diagrams Figs. 153 
 to 155. The processes in the basic reverberatory have, as the lines show, the greatest 
 resemblance to those in the puddling furnace. The lines of phosphorus and sulphur 
 run in a similar manner, a difference existing only in the quantities of these sub- 
 stances eliminated. In the Siemens process 18 to 19 per cent, of phosphorus is 
 separated more than in the puddling furnace ; but the puddling furnace oxidises 5 per 
 cent, more sulphur than the basic reverberatory. In both furnaces almost the total 
 silicon and manganese are conveyed into the slag in the first two periods of time, and 
 about 40 per cent, of phosphorus is removed. The lines indicating the oxidation in 
 
142 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. ii. 
 
 Fig. 153- 
 
 the basic converter take a quite different course from those in the basic reverberatory, 
 although the results obtained by the oxidation are equal. The silicon line only 
 resembles that of the other processes. The separation of carbon in the basic reverbera- 
 tory is so irregular that it cannot be represented by a line. 
 
 Carbonisation Steel. The second principal kind of steel (cement steel) is produced 
 
 by the prolonged ignition of bar-iron 
 along with carbonaceous substances, 
 which generally contain at the same 
 time, nitrogen. To obtain normal 
 cement steel it is necessary to use 
 good bar -iron. The Swedish iron 
 (from magnetic ore and red haema- 
 tite) is brought in large quantities 
 to England for conversion into ce- 
 ment steel, as even the best English 
 iron is suitable only for ordinary 
 steels. 
 
 The process for the manufacture 
 of cement steel is as follows : The 
 iron bars are laid in layers, along 
 with the carbonaceous powder, in 
 earthen boxes, closed air-tight. Two 
 such boxes (a pair of pots) are placed 
 in a furnace which is fired with coal, 
 rarely with wood, and kept at a red 
 heat for one to three weeks. It is then let cool, and the bars are taken out. A 
 furnace contains about 15 tons of iron. About 5 per cent, of carbon penetrates by 
 molecular migration without the iron being fused ; the action of gases falls quite into 
 the background 
 
 Sheer Steel. Both crude and cement steel are very unequal in their composition, 
 and cannot therefore be used immediately, but must be rendered uniform by refining. 
 
 Fig- 154- 
 
 Explanation of Terms. 
 
 1'eriode von 4 Stunden Period of 4 hours. 
 
 Abscheidung in % 
 Kohlenstoff unbestimmt 
 Aiifnahme in % Ge&chmolzen 
 Zritcinheiten 
 fiasiacher Flammofen 
 
 Separation in per cents. 
 Carbon not determined. 
 Taken up in per cerrt. fused. 
 Units of time. 
 Basic reverberatory. 
 
 flasischer Converter 
 Abscheidung in % 
 Aufnahme in % 
 Zeiteinheiten 
 
 Basic converter. 
 Matter eliminated in per cents. 
 Matter taken up in per cunts. 
 Units of time. 
 
 Explanation of Terms. 
 
 I'uddelofen 
 Abscheidung in % 
 Aufnahme in % 
 
 Puddling furnace. 
 Matter eliminated in per cents. 
 Matter taken up in per cents. 
 Units of time. 
 
 To this end the crude bars are forged out to thin, flat slips, which are thrown into cold 
 water when red hot ; several of them are collected in a sheaf, heated to whiteness, and 
 again wrought out under the hammer or between rollers. For cement steel a simple 
 re-melting is more suitable. 
 
 Cast Steel. This material, so widely used in modern industry for the manufacture 
 
SECT. II.] 
 
 STEEL. 
 
 143 
 
 of cannons, tyres for railway wheels, axles, anchors, pump-rods, and for tools, is pro- 
 duced by re-melting finery steel, Martin steel, Bessemer metal, or carbonised steel. 
 Every desired property can be obtained by a due selection of materials. 
 
 The melting is effected in fire-proof crucibles (without a blast) in a fire of coke, or 
 in a coal reverberatory, or with a gas fire and Siemens regenerators. The melted 
 steel is cast in bars in iron moulds. When cold, the bars are again heated to redness, 
 wrought out under the hammer or between rollers. The metal thus treated is refined 
 cast steel. 
 
 Run Steel. This kind is formed by melting together crude iron and wrought-iron. 
 The quality of steel thus obtained (known in Italy as Glisenti steel) depends on the 
 quantity (and quality) of the wrought-iron used. 
 
 As a welding agent for cast steel, a mixture of borax with sal-ammoniac and potas- 
 sium ferrocyanide is in use. 
 
 A remarkable phenomenon is the infiltration of cast blocks. A steel block had 
 above and below the following compositions 
 
 Fe 
 
 C 
 
 Si 
 
 S 
 
 P 
 
 Mn 
 
 Top. 
 
 98-304 
 0760 
 
 traces 
 0-187 
 0-191 
 0-5S8 
 
 Bottom. 
 99-038 
 
 0-350 
 
 traces 
 
 0-044 
 
 0-044 
 
 lOO'OOO 99'990 
 
 Iron and steel castings not unfrequently contain hollows, the outer layer especially 
 containing numbers of bubbles, a (Fig. 156). The bubbles more in the interior arise 
 during progressive cooling, having a pear shape, with the point 
 turned outwards, and forming the series b. Other hollows, c, 
 appear in the midst of the casting, and decrease from above 
 downwards ; a and b arise from the liberation of gas dissolved 
 in the liquid metal, but c in consequence of the condensation of 
 the iron on becoming solid. Manganese, silicon, and magnesium 
 have been used as a remedy for these bubbles.* 
 
 Steeling. For certain technical purposes it is sufficient to 
 convert iron into steel superficially. This steeling or case hard- 
 ening is effected by cleaning the surface of the article with 
 emery, and heating it, along with a carbonaceous powder, in 
 an air furnace without a blast. Or the surface iron may be 
 steeled by covering it when red hot with potassium ferrocyanide 
 or with a mixture of clay and borax. 
 
 Properties of Steel. Steel is generally of a pale greyish- 
 white colour, moderate lustre, granular, and of homogeneous 
 fracture ; the better the sample the finer is the grain. The 
 granular texture of steel is characteristic ; good mild steel has 
 never the coarse grain of grey crude iron nor the fibrous texture 
 of wrought-iron. Hardened steel resembles in its fracture the finest silver, and the 
 grains can scarcely be distinguished with the naked eye. Like wrought-iron, it may 
 be cut and welded when hot, but it must be cautiously heated to avoid decarbonising. 
 It is fusible like cast-iron. Its specific gravity is 7-62 to 7*92, and is diminished on 
 tempering e.g., from 7*92 to 7*55. Its proportion of carbon varies from 0-25 to 2 
 per cent. With higher proportions of carbon, its solidity and hardness increase, but 
 its elasticity decreases. It contains no graphite. If quenched when ignited, it becomes 
 
 * A small addition of aluminium has latterly been found successful. 
 
144 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. ii. 
 
 harder and brittle, so as to scratch glass and resist the file. Polished steel assumes 
 various colours when gradually heated. These colours are used for determining the 
 temperature and the consequent degrees of hardness. For this purpose metallic baths 
 are used, heated to their melting-point. Into such melted metal the steel is plunged 
 until it assumes the temperature of the bath. The following table gives the com- 
 position of the baths found convenient for different kinds of cutting and piercing 
 instruments : 
 
 Instruments. 
 
 Metal Bath. 
 
 Heat. 
 
 Colour. 
 
 Lead. 
 
 Tin. 
 
 Lancets ..... 
 
 7'0 
 8-0 
 
 8-5 
 14-0 
 19-0 
 -48-0 
 50 'o 
 boiling li 
 
 4 
 4 
 
 4 
 
 4 
 4 
 4 
 
 2 
 
 nseed oil 
 
 220 
 
 228 
 232 
 
 254 
 265 
 288 
 292 
 316 
 
 pale yellow 
 straw colour 
 brown yellow 
 brown, purple spots 
 purple 
 light blue 
 royal blue 
 black blue 
 
 Penknives .... 
 Scissors and chisels 
 Axes, pocket-knives, plane-irons 
 Blades, watch-springs, crinoline steel 
 Daggers, gimlets, rapiers, fine saws 
 Hand-saws 
 
 The lower the heat of the steel, the harder, but the more brittle, it remains. It 
 cannot be denied that iron may be converted into steel by other substances besides 
 carbon, which may probably be replaced by its near ally, boron, and possibly by 
 silicon. 
 
 Admixtures of other materials confer upon steel valuable properties ; thus tungsten 
 steel owes its peculiar firmness to the presence of tungsten. Samples of tungsten steel 
 (I.) and tungsten iron (II.) had the following composition 
 
 Fe . 
 
 W . 
 
 Mn . 
 Co and Ni 
 
 Si . . 
 P 
 S 
 
 c 
 
 I. 
 
 85-000 
 11-028 
 
 1-493 
 
 trace 
 0-263 
 0-007 
 trace 
 2-147 
 
 99-938 
 
 II. 
 
 68-363 
 28-181 
 0-986 
 trace 
 0-233 
 0-008 
 trace 
 1-882 
 
 Similar assertions are made concerning titanium- and chromium-steels, but whether 
 with justice must remain for the present undecided. 
 
 A celebrated kind of steel is that of Damascus, used for the Damascus sword-blades, 
 though the raw material was brought from Cabul. If its surface is moistened with an 
 acid it displays an uneven veining, a property which is not lost by re-melting. Such 
 steel, Wootz, is made in India by the natives. Crude iron, obtained by a very 
 imperfect process, is broken up, mixed with 10 per cent, of the chipped wood of Cassia 
 auriculata, placed in a crucible, covered with leaves of Asdepia gigantea ; the crucible 
 is coated with moist clay and heated in a furnace for two and a half hours, at the 
 lowest available temperature. The steel thus obtained is re-heated before forging. 
 
 Two samples of Wootz had the following composition 
 
 Combined carbon ..... 4-333 
 Graphite 0-312 
 
 Si 
 S 
 Al 
 P 
 
 As 
 
 0-045 
 0-181 
 
 0-037 
 
 0*0167 
 
 0-0035 
 0*0006 
 trace 
 
 trace 
 
 Steel Engraving. For engraving and etching on steel there are used plates of 
 
SECT. II.] 
 
 COBALT. 
 
 cast steel, which are decarbonised on the surface, and after engraving are re-converted 
 into steel. 
 
 An excellent fluid for etching is a solution of 2 parts iodine and 5 parts potassium 
 iodide in 40 parts of water. 
 
 MANGANESE. 
 
 Occurrence. The most important ore of manganese is pyrolusite, Mn0 2 , often 
 spoken of in commerce simply as " manganese." It contains generally small quantities 
 of baryta ; silica and water, and sometimes larger proportions of nickel, cobalt, and 
 some thallium. Other manganese ores are braunite, Mn 2 3 , manganite, Mn 2 O 3 H 2 0, 
 hausmannite, in which the manganous oxide is in part replaced by potassa, baryta, 
 magnesia, and cuprous oxide, and manganese-spar, MnC0 3 . The manganese of commerce 
 is often a mixture of pyrolusite, hausmannite, braunite, &c. 
 
 Preparation. Manganese is prepared by reducing the ores in crucibles. Latterly 
 it has been obtained on the large scale along with a larger or smaller proportion of 
 iron as ferromanganese. Its preparation is effected in blast furnaces with a plentiful 
 addition of lime. Manganese has a great tendency to pass into the slags, so that in a 
 well-worked blast furnace from 40 to 50 per cent, of the manganese in the ores is to 
 be found in the slags, which contain from 6 to 9 per cent, of metallic manganese. Ta 
 extract more than 60 per cent, of the ores is rarely remunerative, as the consumption 
 of coke is very high and the spiegel acquires grey spots by taking up silicon. 
 
 
 
 
 
 
 
 
 
 
 Ferromanganese 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Crude 
 
 
 
 
 
 
 
 
 
 I. 
 
 II. 
 
 III. 
 
 Manganese. 
 
 c 
 
 
 
 
 
 
 
 
 6-21 
 
 6 '600 
 
 5-874 
 
 6-0-6-5 
 
 tti 
 
 
 
 
 
 
 
 
 0-28 
 
 0-093 
 
 0'2IO 
 
 0-5-1-2 
 
 P 
 
 
 
 
 
 
 
 . 
 
 0-06 
 
 0-300 
 
 0-305 
 
 
 Cu 
 
 
 
 
 
 
 
 
 0*14 
 
 
 
 O-O9O 
 
 
 Mn 
 
 
 
 
 
 
 
 
 69-64 
 
 8 1 -240 
 
 57-608 
 
 90-0-92-0 
 
 Fe 
 
 
 
 
 
 
 
 
 23-25 
 
 I2-OOO 
 
 35-03I 
 
 0-5-1-5 
 
 Co 
 
 
 
 
 
 
 
 
 
 
 
 
 O-O7O 
 
 
 Alloys of copper and manganese have been produced by Gersdorff and then by 
 Schroter, by heating a mixture of copper, manganic oxide, and carbon in a crucible. 
 They are very hard and take a polish ; their colour is white to rose. Manhes has 
 used them to reduce cuprous oxide in fining copper. Manganese-silver, an alloy of 80 
 parts copper, 1 5 manganese, and 5 zinc, is white, works well and takes a fine polish. 
 
 COBALT. 
 
 Cobalt is chiefly met with as speiss, CoAs 2 , and as cobalt glance, CoAsS. Recently 
 metallic cobalt has been prepared on a large scale at Iserlohn, and at Pfannenstiel, 
 near Aue (Saxony). It has a silvery white colour with a reddish cast, a higher lustre 
 than nickel, and polishes well. When obtained by electrolysis or by reduction as 
 a pure metal, it is flexible and ductile, but as found melted under ordinary circum- 
 stances it is porous and crystalline, and can neither be hammered nor rolled. This evil 
 is due, according to Fleitmann, to the absorption of carbon-monoxide, and can be removed 
 by the addition of o'i per cent, of magnesium. It fuses at a very high temperature. 
 At a white heat steel and iron may be welded together with cobalt, and iron, plated 
 on both sides with cobalt, can be rolled out very thin. It is slowly dissolved by 
 dilute acids ; more rapidly by nitric acid and aqua regia. 
 
 Cobalt Colours. The ores to be worked for cobalt colours are roasted, and are then 
 called safflor or zaffre. According to their purity, they are distinguished as ordinary 
 (SO), medium (MS), and fine (FS and FSB 1 ). They consist essentially of cobalt oxide. 
 
146 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 nickel, arsenic, with traces of manganese, and bismuth oxides, &c. In Sweden, zaffre 
 is prepared by precipitating a solution of cobaltous sulphate with a solution of potassium 
 carbonate. From zaffre are prepared : smalts, cobalt ultramarine, creruleum, Binmann's 
 green (cobalt green, or Saxon green), with which are connected cobalt yellow, cobalt 
 violet, and cobalt bronze. 
 
 Smalts. Glass is coloured blue by compounds of cobalt. If zaffre (impure 
 cobalt oxide) is fused with silica and potash, we obtain a deep-blue glass, which, 
 when finely ground, is known as smalts. The best sort, i.e., that richest in cobalt, is 
 called king's blue. According to Ludwig it contains : 
 
 Norwegian. German. 
 
 Couleur. Eschel. Coarse. 
 
 Si . . . . . 70-86 ... 66-20 ... 72-11 
 
 Co . . . . . 6-49 ... 6-75 ... 1-95 
 
 K and Na . . . 21-41 ... 16-31 ... i'8o 
 
 A1 2 S .... 0-43 ... 8-64 ... 20-04 
 
 It contains, besides, small quantities of ferrous and nickelous oxide, lime, arsenic 
 flcid, carbonic acid, and water, sometimes also lead. Soda cannot be used in place of 
 potash in the manufacture of smalts, as soda cobalt glasses have not a pure colour. 
 
 Smalts are used for blueing paper, linen, and starch, and for colouring and paint- 
 ing on glass and porcelain, and for enamels. 
 
 Cobalt Speiss. As in roasting cobalt ores the heat is not prolonged sufficiently 
 to oxidise the nickel present in the ores, it melts with the other metals and the 
 ansenic to a white mass, with a reddish cast, a strong metallic lustre, and a finely 
 granular fracture. It consists of 40 to 56 parts of nickel, 26 to 44 of arsenic, along with 
 copper, iron, bismuth, and sulphur. 
 
 Cobalt Ultramarine. This substance, also known as Thenard's blue, is a pigment 
 consisting of alumina and protoxide of cobalt. Curiously enough, this pigment has 
 been discovered and prepared at three several periods and localities by different people ; 
 first by Wenzel, at Freiberg, Saxony ; next by Gahn, at Fahlun, Sweden ; and lastly, 
 simultaneously at Paris and Vienna, by Thenard and von Leithener. The pigment is 
 prepared either by mixing solutions of alum and a salt of protoxide of cobalt, pre- 
 cipitating the mixture by a solution of carbonate of soda ; or by the decomposition of 
 aluminate of soda by means of chloride of cobalt. The ensuing precipitate, consisting 
 of an intimate mixture of hydrate of alumina and hydrate of protoxide of cobalt, is 
 first well washed, then dried, and heated for some time. The pigment thus produced 
 is, when seen in daylight, of course after pulverisation, very similar to ultramarine, 
 but by artificial light its colour is a dirty violet. It is, however, not acted upon by 
 acids, as distinguished from artificial ultramarine ; neither is it affected by alkalies nor 
 heat, as is copper or mineral blue. Cobalt ultramarine, chiefly under the denomination 
 of Thenard's blue, is employed as a paint in oil- and water-colours, and also for staining 
 glass and porcelain. 
 
 Cceruleum is a pigment prepared in England, exhibiting a bright blue colour, 
 not changing in artificial light, and consisting of stannate of protoxide of cobalt 
 (SnO 2 ,CoO), mixed with stannic acid and gypsum in the proportions, in 100 parts, of 
 49-6 of oxide of tin, i8'6 protoxide of cobalt, 31-8 gypsum. This pigment is not 
 affected by heat, or the action of dilute acids and alkalies ; nitric acid dissolves the 
 protoxide of cobalt, leaving the other ingredients, from which the gypsum may be 
 cleared by water. 
 
 Rinmann's, or Cobalt Green. This substance, also known as cobalt green, zinc 
 green, and Saxony green, is a compound similar to the cobalt ultramarine, for the 
 alumina of which oxide of zinc is substituted. This green is prepared by mixing a 
 solution of white vitriol with a solution of a salt of protoxide of cobalt, precipitating 
 by carbonate of soda, and washing, drying, and heating the precipitate. This pigment 
 
SECT, ii.] NICKEL. J47 
 
 when pure contains 88 per cent, of oxide of zinc and 1 2 per cent, of protoxide of cobalt. 
 It is not affected by strong heat, tinges the borax-bead blue, dissolves in warm hydro- 
 chloric acid, forming a blue colour, which, upon water being added, becomes a pale red. 
 Treated with caustic potassa, the oxide of zinc is dissolved, and may be detected, after 
 previous dilution with water, by the addition of a solution of sulphuret of potassium. 
 
 Pure Protoxide of Cobalt. This substance is occasionally employed for the pre- 
 paration of fine colours. It may be obtained by heating one part of previously 
 roasted and finely pulverised cobalt ore with two parts of sulphate of potassa until no 
 more sulphuric acid is given off. The fused mass, consisting of sulphate of potassa, 
 sulphate of protoxide of cobalt, and insoluble arsenical salts, is, when cooled, first 
 treated with water, and next digested with hydrated protoxide of cobalt to precipitate 
 any iron which may happen to be present, and in order to eliminate the oxide of that 
 metal the solution is filtered. It is next precipitated with carbonate of soda, and, 
 finally, the precipitate is washed and heated. 
 
 Nitrite of Protoxide of Cobalt and Potassa. This double salt, known by its 
 trade name of cobalt yellow, is obtained by mixing a solution of protoxide of cobalt 
 with nitrite of potassa; it is a yellow crystalline precipitate, perfectly insoluble in 
 water. M. Saint-Evre first investigated this body, and, struck with its beautifully 
 yellow colour, quite like that of purrhee (euxanthinate of magnesia), and with the 
 fact that cobalt yellow resists oxidising and sulphuretting influences, suggested its 
 applicability to artistic purposes. He prepares this pigment by precipitating with a 
 slight excess of potassa the double salt of protoxide of cobalt and potassa, obtaining a 
 rose-red-coloured protoxide of cobalt and potassa. Into this thickish magma deutoxide 
 of nitrogen gas is passed. According to Hayes, this pigment is readily obtained by 
 causing the vapours of hyponitric acid to pass into a solution of protonitrate of cobalt, 
 to which some potassa has been added ; the whole of the cobalt is then converted into 
 cobalt yellow. As the nitrite of protoxide of cobalt and potassa can be obtained even 
 from impure solutions of protoxide of cobalt, so as to be quite free from any nickel, iron, 
 &c., the use of this preparation of cobalt is preferable for glass and porcelain staining 
 when a pure blue is required. 
 
 Cobalt Bronze. This substance, a double salt of phosphate of protoxide of cobalt 
 and ammonia, prepared at Pfannenstiel, near Aue, in Saxony, has been but lately 
 brought into commerce. It is a violet-coloured powder, very much like the violet- 
 coloured chloride of chromium, and exhibits a strong metallic lustre. 
 
 NICKEL. 
 
 Nickel occurs in the following ores : Kupfer nickel, NiAs, antimony nickel, NiSb, 
 diosmose, NiAs 3 , and especially in the nickeliferous varieties of speiss cobalt, nickel 
 pyrites, NS, and nickel-antimony glance, NiS 2 + Ni (SbAs 2 ). In New Caledonia occurs 
 garnierite (pimelite or numeite), a nickel magnesium hydrosilicate (containing n to 
 1 6 per cent, of nickel), at present the most important ore of nickel. At Rewdansk, in 
 the Ural, there is found rewdanskite, a hydrated nickelous silicate. Often magnetic 
 pyrites and iron pyrites yield nickel, as does the cobalt-speiss of the blue colour works, 
 and certain products obtained in copper works e.g., nickel vitriol nickel is found in 
 many kinds of pyrolusite and in some magnetic irons. It was formerly obtained in 
 England from the residues of the chlorine stills. According to Gerland, i ton of pyro- 
 lusite yielded on an average 2'5 kilos, of nickel and 5 kilos, of cobalt. 
 
 A concentrative treatment has to precede the smelting of nickel ores. If nickel is 
 present as a sulphide, iron pyrites are used for concentration; if the nickel is an 
 arsenide, arsenic is employed. The product is in the former case matte, in the latter 
 speiss. From these nickeliferous products metallic nickel or its alloy with copper is 
 
148 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 obtained, either in the dry or the wet way. Hence the metallurgy of nickel is resolved 
 into 
 
 (I.) The concentration fusions, which aim at the accumulation of the nickel present 
 in an ore, either (a) in matte, (6) in speiss, or (c) in black copper ; 
 
 (II.) In the elimination of nickel or its alloy from the products of the concentration 
 fusions, which may be effected in the dry or the wet way. 
 
 Since it has been understood that by preparing nickel-copper alloys the most valu- 
 able properties of nickel its white colour and its resistance to chemical reagents are 
 masked, it is preferred to prepare pure nickel. 
 
 The concentration fusion of nickel ores is especially applicable if they occur among 
 iron pyrites. The ferric oxide produced by smelting the partially roasted ores with 
 quartz, or substances rich in silica, is chiefly slagged whilst the nickel, which is also 
 oxidised, but which is more readily reduced than ferric oxide, becomes metallic, and 
 collects in the matte formed from the undecomposed sulphides and the reduced sul- 
 phates. If the ore contains also copper, it concentrates in the matte more completely 
 than does the nickel. If too much ferrous oxide is present, a part of it is reduced to 
 metallic iron in contact with charcoal, and is either taken up in the matte or separates 
 out as nickeliferous pig iron. An improved result is obtained if the matte is concen- 
 trated in a reverberatory with the addition of quartz, heavy spar, and charcoal, forming 
 barium sulphide. This liberates baryta, and sulphurises the oxidised nickel and copper 
 contained in the charge, whilst the baryta combines with the quartz and the ferrous 
 oxide to form a very fusible slag. 
 
 At the Isabella Works at Dillenburg a nickeliferous sulphur and copper pyrites, 
 containing on an average 7*5 per cent, ofnickel, is first roasted, broken up with coke, 
 fused, roasted again, and finally smelted with the addition of slags, to form concentration 
 matte. In order to diminish the iron and yet leave so much sulphur that the matte 
 may be brittle and break easily, it is melted before the blast on the hearth, forming a 
 refinery matte, from which nickel or a nickel alloy may be produced in the wet way. 
 
 The methods hitherto devised for obtaining nickel in the dry way have not given 
 fully satisfactory results. In the wet way the first step is generally to roast the ores 
 or the nickeliferous furnace products in order to convert the iron present into an 
 iron oxide soluble in acids, and to render the nickel, copper, and cobalt soluble 
 either in water, as sulphates, or in acids, as oxides or basic salts. From the solution the 
 nickel is thrown down as oxide or as sulphide, and from the precipitate metallic nickel 
 or the alloy of copper and nickel is obtained. 
 
 The wet process for nickel consists of 
 
 (i) The preparation of the solution of nickel. If nickeliferous mattes are roasted, 
 there are first formed the sulphates of the four metals iron, copper, nickel, and cobalt, 
 which, at increasing temperatures, are decomposed at different degrees of heat : ferrous 
 and ferric sulphate the most easily, and cobalt sulphate with the greatest difficulty. 
 From the roasted mass the chief part of the nickel and cobalt are dissolved out in 
 water, as is also a little copper, whilst the iron and a part of the copper with a little 
 nickel and cobalt remain undissolved. From the residue, cuprous and nickelous oxides 
 may be extracted by acids. If the roasted mass is at once treated with hydrochloric 
 acid, copper oxide is dissolved rather than nickelous oxide, and nickelic and ferric 
 oxides may be extracted from the residue by hot concentrated acids. 
 
 From speiss arsenic may be removed and the nickel dissolved by igniting the roasted 
 speiss with a mixture of soda-saltpetre and soda, extracting the sodium arseniate with 
 water, treating the residue with sulphuric acid, when nickel and cobalt sulphates are 
 dissolved and ferric oxide is left. According to Wbhler's proposal, the arsenic can be 
 removed as a sulpho salt by melting the speiss with sodium sulphide and lixiviating the* 
 mass. 
 
SECT, ii.] NICKEL. 149 
 
 (2) The nickel is thrown down from the solution by fractionated precipitation with 
 chalk, which separates first iron and arsenic and then copper, so that only nickel 
 remains in solution, and is thrown down by means of milk of lime, free from iron. At 
 Joachimsthal the copper is removed from the acid solution by means of sulphuretted 
 hydrogen, the nickel is precipitated by potassium bisulphate in the state of sparingly 
 soluble potassium nickel sulphate, when cobalt, free. from nickel, remains in solution, 
 and can be thrown down by sodium carbonate. 
 
 (3) The conversion of the nickel precipitate into metallic nickel or copper nickel 
 can be effected thus : The hydrated nickelous oxide precipitated from the solution of 
 the metal by lime-water is separated by filtration and pressing so that it may be dried. 
 When dry, the precipitate is ground up with water, and washed with water containing 
 hydrochloric acid until all gypsum is removed ; the pure nickelous oxide stamped to a 
 stiff paste with rye-meal and beetroot treacle,* and cut into cubes of 1*5 to 3 centi- 
 metres in diameter. These cubes are dried rapidly and reduced to metal by heating 
 strongly in crucibles or upright fire-clay cylinders. This is easily effected in one and a 
 half hour, but pure nickel requires three hours of an intense white heat. Since the intro- 
 duction of galvano-nickeling, nickel is met with in commerce in ingots of great purity. 
 
 L. Mond has devised the following process for obtaining pure nickel. He finds that 
 the liquid and volatile compound of Ni and oxide of carbon has not a corresponding 
 Co compound. On passing the vapour of this liquid through a red-hot tube, the nickel 
 is deposited alone. 
 
 The New Caledonian nickel ores which are now the chief material of the French 
 nickel industry, consists of fine green hydrosilicates, and are free from arsenic and sulphur 
 and poor in copper and cobalt. In consequence of the difficulty of working these ores in 
 the dry way, Christofle treats them with hydrochloric acid, and precipitates the nickel 
 alone as oxalate, which is calcined in crucibles. On account of the high price of oxalic 
 acid, it is better to precipitate ferric oxide and alumina, and then nickel as oxide or 
 sesqui-oxide, but the removal of the sulphuric acid, introduced along with the commercial 
 hydrochloric acid, is difficult. The nickel thus obtained is very pure. Riche found in 
 it 9775 nickel, 1*25 carbon, 0*54 silicon, and 0*36 manganese. Subsequently Christofle 
 has introduced a mixed process : he separates the ore as well as possible from ferric 
 oxide in the wet way, and then reduces the purified ore in the dry way. 
 
 Samples of cast nickel have, according to Gard, the following composition : 
 C . . 0-530 ... i -104 ... 1-900 
 
 Si . . 0-303 ... 0-130 ... 0-255 
 
 Fe . . 0-464 ... 0-108 ... 0-301 
 
 Co . . 0.446 ... trace ... trace 
 
 S . . 0-049 0-266 ... 0-104 
 
 Ni . . 98-208 ... 98-392 ... 97 -440 
 
 loo-ooo ... loo-ooo ... loo-ooo 
 
 Nickel is almost silver white, with a faint yellowish cast, very infusible, extensible, 
 and capable of taking a polish. Its specific gravity is 8*97 to 9-26. When pure it may 
 be forged, rolled, and drawn to wire. The tenacity of nickel to that of iron is as 9 to 7. 
 It has a considerable resemblance to iron, but is distinguished by its greater resistance 
 to chemical agents. Hence, it is suitable for crucibles and other laboratory implements. 
 On account of its silvery colour and its resistance to the action of air, water, and many 
 acids, it is used for the manufacture of alloys resembling silver. It is a constituent of 
 the smaller coins in Germany, the United States, Brazil, &c. It serves also for coating 
 other metals. Its porosity and crystalline texture, when melted on the large scale, can 
 be removed by the addition of o - i per cent, of magnesium. At a white heat nickel 
 may be welded with steel and iron. 
 
 * The latter article is not fit for human consumption. 
 
1 5 o CHEMICAL TECHNOLOGY. [SECT. n. 
 
 COPPER. 
 
 Copper, one of the most common metals, was known in prehistorical ages.* The 
 Greeks and Romans obtained this metal chiefly from Cyprus, whence the name cuprum. 
 It occurs sometimes native, but more commonly as oxide and sulphide. 
 
 Copper Ores. Metallic or native copper occurs in quantity near Lake Superior, 
 where, in 1857, a mass was found weighing 450 tons, and measuring 13*75 metres in 
 length, by 6-7 in breadth, and z"j in thickness. It is also found in Peru, Bolivia, and 
 Chili, from which last country it is brought to England under the names of copper 
 sand and copper barilla (!), containing 60 to 80 per cent, of copper, and 20 to 40 percent, 
 of quartz. 
 
 Red Copper Ore, ruberite, or ruby copper, C\i 2 O, is found crystalline in regular 
 octohedra as well as massive and diffused. It occurs in Cornwall and in large quan- 
 tities in the Burraburra mine in South. Australia.! 
 
 Tile ore is an intimate mixture of cuprous oxide with iron ochres. 
 
 Azurite (cuprazurite, copper lazulite, or azure malachite), 2CuC0 3 .Cu(OH) 2 , is found 
 in beautiful blue crystals as well as massive and diffused. It is found in Cornwall, at 
 Chessy formerly, and in South Australia. 
 
 Malachite (a green copper carbonate), CuC0 3 .Cu(OH) 2 , occurs in oblique rhombic 
 crystals, or stalactitic and fibrous (Atlas ore), or massive (copper green), generally 
 mixed with azurite (Ural, South Australia, Canada). 
 
 Chalkosine (vitreous copper, copper glance), Cu 2 S, and phillipsine, or purple pyrites, 
 3Cu 2 S.Fe 2 S 3 , and copper pyrites, CuFeS 2 , are the most important sulphur compounds 
 used for the extraction of copper. Copper pyrites is often accompanied with iron 
 pyrites, arsenical pyrites, and fahl ore (grey copper), and also with silver, gold, and 
 nickel. 
 
 Copper slate is a bituminous marly slate finely interspersed with sulphuretted 
 copper ores. It occurs chiefly at Mansfeld, at Stollberg in the Hartz, and at Riechels- 
 dorf in Hessia. 
 
 Enargite, Cu 3 AsS 4 , is found at Manilla, in Peru, and in Hungary. 
 
 The Fahl ores (grey copper) are composed of copper sulphide with silver sulphide, 
 accompanied with arsenic and antimony sulphides. On account of the presence of 
 silver, they of ten rank among silver ores. They contain 14 to 41*5 per cent, of copper. 
 
 Atakamite, 3Cu(OH) 2 .CuCl 2 , contains 56 per cent, of copper. It is found in Chile 
 and other parts of the west coast of South America, as also in South Australia, and is 
 worked at Swansea. When ground to powder, it is brought from Peru under the 
 name " arsenillo," and is used for sprinkling sand (to take up ink). 
 
 Several atakamites contain iodine as copper iodide. Since 1869 important quantities 
 of copper have been obtained, in the wet way, from the burnt copper pyrites, the refuse 
 of the sulphuric acid manufacture. 
 
 Copper is obtained from its ores either by the dry or the wet way. 
 
 In spite of concentration, it is rarely practicable to enrich copper ores so that 
 they yield on smelting more than 8 to 10 per cent, of copper. Only pyritic 
 ores are prepared by roasting. When the ores to be roasted consist essentially of 
 copper pyrites, and are strongly contaminated with iron pyrites (sulphur ore), the 
 attempt is made to utilise a part of the escaping sulphur, and to concentrate the copper 
 (which often forms not more than 3 to 4 per cent, of the mixture) by means of nucleus 
 roasting. If a mixture of sulphur ore with a little copper ore is roasted, the copper 
 
 * It seems to have been used for tools and weapons prior to bronze, and, of course, before iron, 
 t It is also found at Chessy, in France, along with copper carbonate, in the Bannat, and in 
 Siberia in primitive rocks. 
 
SECT, ii.] COPPER. 151 
 
 retires into the middle of the lumps, whilst the outer coating, which can easily be 
 removed by mechanical means, consists of loose iron oxides very poor in copper.* 
 
 In certain cases the roasting is intended, not merely to expel sulphur, but to burn 
 off the bitumen with which some ores are interpenetrated e.g., the bituminous copper 
 shales. The fluxes in copper smelting are added, not only to make the charge more 
 fusible, but to promote the separation of the iron from the copper oxide. 
 
 (A) Production of Copper in the Dry Way. In pyritic ores this process is effected 
 either in shaft furnaces or in reverberatories. In the latter the reduction of the 
 copper oxide is effected by the sulphur itself. Thus the copper is more and more 
 concentrated in the matte, until it is possible to proceed to the decomposition of the 
 last portions of the sulphides. This decomposition is conducted by roasting the concen- 
 trated ore and its simultaneous smelting, whereon the air can have free access until 
 the sulphur is entirely eliminated. There is then always a formation of cuprous 
 oxide, so that the purified copper is in the state known as " overdone." In melting 
 copper ores in shaft furnaces the same process is followed, of first concentrating the 
 copper in a "copper matte ;" but the reduction of the copper oxide after roasting is 
 effected by means of charcoal, with which the charge of the shaft furnace is inter- 
 stratified. In shaft furnaces the product is never overdone or contaminated with 
 cuprous oxide, but always carboniferous copper. Consequently, malleable copper 
 is obtained neither by means of the shaft furnace nor the reverberatory, but the 
 means for rendering it fit to bear the hammer are completely different in the two 
 cases. 
 
 The treatment of pyritic ores in shaft furnaces consists in roasting the ores, 
 whereby a part of the sulphur, antimony, and arsenic is volatilised ; a part of the 
 metals present is converted into sulphates, arseniates, and antimoniates ; whilst a part 
 of the ore escapes roasting. In smelting the roasted mass with the addition of sub- 
 stances which form slag, the copper oxide is first converted to metallic copper ; whilst 
 the sulphates are again reduced to sulphides, which, with the metallic copper and the 
 sulphides remaining undecomposed, form a richer crude matte (copper matte) ; whilst a 
 speiss (antimonide and arsenide) is formed by the reduction of the existing metallic 
 arseniates and antimoniates. The remaining metallic oxides, especially ferrous oxide, 
 formed by reduction, combine with the fluxes to form slag. 
 
 By repeating the roasting and reducing processes there is ultimately obtained, 
 along with a small quantity of matte, metallic copper (crude or black copper) contami- 
 nated with foreign metals, from which it is freed by an oxidising fusion, in which the 
 foreign metals are partly volatilised as oxides and partly taken up in the slag. The 
 finished copper (rosette copper, disc copper) contains, as the roasting process has 
 generally been carried too far, cuprous oxide, by which its malleability is decreased. 
 By a rapid reducing fusion, and by remelting upon a hearth between charcoal, the 
 cuprous oxide is reduced, and there is formed malleable copper. 
 
 The crude smelting of the roasted ores to form crude matte (copper matte) is effected 
 in cupola furnaces. Fig. 157 shows the section of the cupola furnace, and Fig. 158 its 
 front elevation, with a removal of the front wall, to show the interior arrangements. 
 Fig. 159 shows the interior of the furnace. Through the apertures, t, there pass the 
 tuyeres of the blast. The liquid contents of the furnace flow through the two aper- 
 tures, o (eyes), situate above the sole, and two short channels into the two depressed 
 basins, C. As the roasted copper ore always contains iron oxide, a simply reducing 
 fusion might readily reduce the iron. To prevent this, substances capable of 
 forming slag (quartz or silicates) are added, so that the iron oxide, when reduced 
 to the ferrous state, combines with the silica present to yield a readily fusible slag. 
 
 * When the sulphur amounts to 30 per cent, or upwards, the ores should always be roasted in 
 kilns, not merely to utilise the sulphur, but to obviate the nuisance of escaping sulphur dioxide. 
 
152 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. n. 
 
 The cupric and cuprous oxide formed are reduced to metallic copper by the iron 
 sulphide present (^CuO + FeS = SO, + FeO + jCu). 
 
 During the formation of slag, sulphides separate out, and collect in the lower part 
 
 Fig. 157- 
 
 Fig. 158. 
 
 m m-mm w KM aM" 
 nfi tnnn tnnn innnn m || J i8 'nnn iui!iiimin_ni"H'n 
 
 Fig. 159- 
 
 of the furnace as copper matte (crude matte), amixture of copper sulphide, iron sulphide, 
 and other sulphides, containing on an average 32 percent, of copper. The slag formed 
 at the same time is the crude slag. 
 
 The roasting of the copper matte is to effect its complete oxidation and the removal 
 of the sulphur present. The matter resulting is melted in a cupola furnace with an 
 addition of slag, a process known as concentration work. The product is the concen- 
 tration matte, containing about 50 per cent, of copper ; it is thoroughly roasted off and 
 melted to black copper. If silver is present this is extracted prior to any further treat- 
 ment. This was effected formerly by amalgamation, but at present by the Ziervogel 
 process (see SILVER), if it is not preferred to separate the silver from the copper by the 
 eliquation process with lead. 
 
 In richer copper ores the concentration work is dispensed with, and the thoroughly 
 roasted copper matte is smelted at once as black copper (crude copper, yellow copper). 
 This takes place in cupola furnaces of less height than those used for smelting the 
 roasted ores. The sulphur of the matte has been so much diminished by roasting that 
 it can no longer take up the reduced copper. It separates out (along with a small 
 quantity of matte) as black copper, with 93 to 95 per cent, of copper. Black copper 
 from Mansfeld, according to Flach (1866), contained : 
 
 Copper . 
 
 Lead . 
 
 Zinc 
 
 Iron 
 
 Nickel and Cobalt 
 
 Silver . 
 
 Sulphur 
 
 93 '49 
 i '49 
 1-47 
 1-03 
 1-25 
 0-03 
 0-99 
 
 9975 
 
 The black copper, or crude copper, is freed from impurities (sulphur and foreign 
 metals) by a powerfully oxidising fusion, as the impurities are slagged more rapidly 
 than the copper. This process the finishing or cooking the black copper is carried 
 out (i) in a small finishing hearth, (2) in a large hearth or speiss-furnace, or (3) in a 
 draught flame furnace or refining furnace. 
 
 The finishing hearth is shown in section in Fig. 160, and in elevation in Fig. 161. 
 The hearth consists of masonry, on the upper surface of which is a hemispherical 
 depression, a, the hearth-pit with a cast-iron covering plate, 6. Black copper is melted 
 down with the addition of charcoal, using the blast, h. 
 
SECT. 11. J 
 
 COPPER. 
 
 '53 
 
 Sulphur, ars'enic, and antimony are volatilised ; ferric oxide and the other non 
 volatile oxides, along with cuprous oxide, separate out as slag in combination with silica 
 from the mass of the hearth, and collect on the surface of the copper, where it is drawn 
 off from time to time. When the copper is finished, the blast is turned off, the surface of 
 
 Fig. 1 60. Fig. 161. 
 
 the copper freed from charcoal and slag, and cooled by sprinkling with small coal so far 
 that it may be chilled superficially by means of water, without danger of an explosion. 
 There is thus formed a thin disk (rosette), which is lifted off and immediately quenched 
 in water to prevent the oxidation of the copper. Water is again sprinkled on, and another 
 disc lifted off until the hearth is almost empty. This work is called resetting, and the 
 metal obtained is rosette, or disc-copper. This operation is better conducted in large 
 blast-flame furnaces. The melting-hearth, A (Fig. 162), is provided with a fire-box, I, 
 and apertures, n, for the blast. When it is 
 finished, it is let off into the pan, B, and there 
 converted into rosettes in the manner already 
 described. As in this method the fuel is com- 
 pletely separated from the metal, the copper is more 
 completely purified than in the small hearth. 
 
 Eliquation. In working argentiferous copper 
 ores, the black copper before refining is submitted 
 to liquation, if it is not thought preferable to 
 employ the Ziervogel method (see SILVER). This 
 process depends on the principle that copper and 
 lead may be fused together, but they do not 
 remain combined on cooling. There is formed an alloy of much copper with little lead, 
 whilst the remaining lead separates out. The separation takes place chiefly in accord- 
 ance with specific gravity, the lowest stratum being argentiferous lead. If the liquid 
 mass is allowed to cool slowly, the lead flows out in combination with the silver, but on 
 rapid cooling there is formed an intimate mixture of both metals. The silver is 
 separated from the lead either by the refining process, by Pattinson's process, or by 
 means of zinc (see SILVER). 
 
 Copper, whether refined on a large or a small hearth, generally contains cuprous 
 oxide. If this oxide is present to the extent of 1*1 per cent., the metal is so deficient 
 in tenacity and malleability that it cannot be forged at common temperatures without 
 splitting at the edges. If it contains 1*5 cuprous oxide the decrease of tenacity is per- 
 ceptible, even when hot, and the copper is both cold and hot short. In this state it is 
 said in Germany to be " overdone." Such copper contaminated with cuprous oxide can 
 only recover its tenacity by the reduction of the oxide in order to become malleable. 
 
 The great wealth of Britain in coal the best fuel for the reverberatory process 
 probably first led to the idea of refining copper in reverberatories instead of shaft 
 furnaces. The chief English copper-works are at Swansea ; they obtain their ore from 
 the mines of Cornwall, North Wales, Westmoreland, the adjoining parts of Lancashire 
 . and Cumberland ; but very large quantities of ores imported from Australia, Chile, Peru, 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. ii. 
 
 Cuba, and Norway are also smelted. There are also copper works in Anglesea, Stafford- 
 shire, and South-west Lancashire. The English copper ores consist chiefly of copper 
 pyrites accompanied by iron pyrites, also stannine and arsenical pyrites and gangue. 
 
 The chief processes of the English system of copper smelting consist of (i) Calcin- 
 ing the pyritic copper ores ; (2) melting the roasted ores for coarse metal ; (3) roasting 
 or calcining the coarse metal ; (4) preparation of the concentrated white metal by melt- 
 ing the roasted coarse metal with richer ores; (5) preparation of the concentrated blre 
 metal by melting the calcined coarse metal with calcined ores of a medium percentage 
 of copper ; (6) preparation of a red and white metal by smelting the slags obtained in 
 the previous operations ; (7) calcination fusion of the blue metal No. 5, and production 
 of white extra-metal ; (8) calcination fusion of the white extra-metal, and production 
 of the concentrated metal ; (9) calcination of the ordinary white metal and the cupri- 
 ferous bottoms for the production of blister copper (black copper) ; (10) refining the 
 blister copper. 
 
 The fusion of the calcined ores for coarse metal is conducted in the smelting furnace 
 generally used at Swansea, and shown in Fig. 163. The hearth is contracted towards its 
 
 mouth, forming a kind of 
 
 ' l63 ' tray. The object of smelt- 
 
 ing the coarse metal by 
 the reverberatory process 
 is the separation of the 
 copper from the gangue, 
 and from a part of the 
 foreign metallic oxides 
 contained in the roasted 
 ore by means of a re- 
 ducing and dissolving 
 fusion. The sulphur is 
 of importance, since the 
 undecomposed sulphides 
 during fusion decompose 
 the oxides and the sul- 
 phates. Ferric oxide and iron sulphide are first converted into sulphur dioxide and 
 ferrous oxide, the latter often combining with the silica present to form slag. As the 
 heat rises the copper oxide is decomposed by the iron and copper sulphides with forma- 
 tion of ferric oxide and metallic copper, the latter of which partly dissolves in the 
 coarse metal, and is partly converted by the ferric cxide into cuprous oxide, which 
 becomes slagged at the highest temperature of the furnace. As the coarse metal and 
 the slags are brought into intimate contact in the fused mass by means of constant 
 stirring, the iron sulphide contained in the coarse metal and the cuprous oxide contained 
 in the slags undergo a double decomposition into copper sulphide and ferrous silicate, 
 so that the slagging of the copper is almost totally prevented. 
 
 The calcination of the coarse metal is mostly conducted in the same reverberatories 
 which serve for calcining the ores. The purpose of this calcination or roasting is 
 chiefly to oxidise the iron and to volatilise a part of the sulphur. A certain proportion 
 of sulphur in the calcination products is necessary, since otherwise the concentration 
 could not be effected without a loss of copper. 
 
 For the production of the concentrated white metal the roasted coarse metal is 
 charged along with rich copper ores, which contain scarcely any iron sulphide, but 
 copper sulphide, copper oxide, and quartz in such proportions that the iron pyrites is 
 oxidised by the oxygen of the oxides, whilst all the copper coalesces to metal, and the 
 iron oxidised to the ferrous state forms, with the quartz, ferrous silicate. The smelting 
 
SECT. II.] 
 
 COPPER. 
 
 '55 
 
 is conducted similarly to that of coarse metal. The concentrated white metal formed! 
 has almost the same composition as copper glance (Cu 2 S), and is run off into moulds of 
 sand. 
 
 The white metal is melted for blister copper. The metal is placed on the sole of a 
 furnace, which does not differ from the smelting furnace, and the fire is allowed to act 
 for twelve to twenty-four hours. At first the heat must not reach the melting-point, 
 but it is raised towards the end. By this process the sulphur is removed in the state 
 of sulphurous acid, and at the same time the impurities, such as arsenic, cobalt, nickel, 
 tin, iron, &c., are removed either by volatilisation alone or by oxidation and slagging. 
 Meantime the cuprous oxide and copper sulphide are mutually decomposed, forming 
 sulphur dioxide and metallic copper (2Cu 2 + Cu 2 S = S0 2 + 6Cu). The melted copper 
 is run off into moulds, and is covered on the surface with black bubbles, whence it& 
 name, blister copper. The fracture has also a porous, honeycombed aspect. Blister 
 copper is already moderately pure and almost free from sulphur, arsenic, and foreign 
 metals. The last stage of the English process is refining the blister copper, which is 
 effected on the sole of a reverberatory. The heat is gentle at first, to complete the 
 oxidation. After about six hours the copper is in flux. When it has been all melted 
 down into the sump, and the furnace is at a strong heat, the reddish slag, rich in 
 cuprous oxide, is drawn off. The surface of the molten copper is covered with charcoal 
 powder, and a wooden stirring rod, generally of birch, is thrust down into the liquid 
 metal. The object of this operation " poling " is the reduction of the cuprous oxide 
 by means of the gases evolved out of the cuprous oxide. The copper is then malleable. 
 
 For refining copper in the United States the native metal from Lake Superior is 
 almost exclusively used in the three works at Hancock, Detroit, and Pittsburg. Pure 
 copper and rich slag are obtained in a reverberatory. At Detroit and Hancock the 
 refinery slags are worked up in shaft furnaces for blister copper and poor slags. The 
 furnaces used at Lake Superior and Detroit, each for 10 tons of crude copper, are 
 4-3 metres in length ; the fuel is Ohio coal, giving out a long flame. The slag, formed 
 by smelting crude copper with cupriferous slags and limestone, containing mostly from 
 5 to 14 per cent, of copper, is drawn out four to six times, and finally freed from 
 copper in a reverberatory or a shaft furnace. Five slags from Pittsburg had the fol- 
 lowing composition : 
 
 
 
 
 
 
 
 
 
 j_ 
 
 II. 
 
 III. 
 
 IV. 
 
 V. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Cu 2 O 
 
 
 
 
 
 
 
 
 12*46 
 
 "'43 
 
 12 -OI 
 
 1 2 -O2 
 
 10-53 
 
 Cu 
 
 
 
 
 
 
 
 
 4-82 
 
 4 '93 
 
 5 '05 
 
 5-80 
 
 5 '44 
 
 Oin Ct 
 
 
 
 
 
 
 
 
 I '22 
 
 1-24 
 
 1-28 
 
 1-46 
 
 1-37 
 
 Zn 
 
 
 
 
 
 
 
 
 0'37 
 
 0-56 
 
 1-52 
 
 075 
 
 0'43 
 
 Ni 
 
 
 
 
 
 
 
 
 o - o6 
 
 
 
 0-47 
 
 0-18 
 
 0-08 
 
 MnO 
 
 
 
 
 
 
 
 
 0x15 
 
 0-04 
 
 0-15 
 
 0-13 
 
 O'I2 
 
 A1A 
 
 
 
 
 
 
 
 
 i57i 
 
 14-52 
 
 15-21 
 
 14-48 
 
 I5-36 
 
 CaO 
 
 
 
 
 
 
 
 
 I4-34 
 
 1475 
 
 1479 
 
 i5'25 
 
 11-81 
 
 MgO 
 
 
 
 
 
 
 
 
 4-07 
 
 3 '99 
 
 4-11 
 
 3-90 
 
 2'57 
 
 Si0 2 
 
 
 
 
 
 
 
 
 45 '32 
 
 46-94 
 
 45'Si 
 
 44*66 
 
 49'83 
 
 
 
 
 
 
 
 
 
 100*42 
 
 98-40 
 
 100-40 
 
 98-23 
 
 97 '54 
 
 The copper now contains about 0-72 per cent, of oxygen. It is further heated with 
 access of air through the arch, through the ash-door and the furnace bridge, and it is 
 constantly stirred. The slags produced, containing from 12 to 40 per cent, of copper, 
 are drawn off from time to time in order to add them to the next charge along with 
 the finery slags, until the copper is overdone, containing about i per cent, of oxygen. 
 It is now refined by means of poling, for the removal of the oxygen, the surface of the 
 metal being entirely cleared from slag, covered with charcoal and split wood, and the 
 pole introduced. Samples are taken every ten or fifteen minutes until black spots are 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. u. 
 
 no longer seen upon the fracture, which becomes fibrous and of a silky lustre. At 
 some works there is added during the refining 0-05 to 0-07 of lead, especially if the 
 copper is to be wrought into sheets, and the pole is then introduced as soon as the lead 
 distributed over the surface is melted. The poling is effected at the highest possible 
 temperature, and with the greatest possible exclusion of air. Over-poling renders the 
 copper brittle, light yellow, very shining, and mirror-like. Over-poled copper, appa- 
 rently containing carbon, still retains oxygen. In presence of much carbon and oxygen 
 there is formed carbon dioxide, which renders the copper porous. The withdrawal of 
 the copper (which is to be kept covered with charcoal) is effected with a flame as 
 neutral as possible, samples being frequently taken. 
 
 Manhes has carried out Holvay's proposal to work copper ores in the Bessemer 
 converter. The furnace consists essentially of a horizontal cylinder of sheet iron, A 
 (Figs. 164 and 165), lined with fire-proof stones acid or basic, which can be made to 
 revolve on its axis by means of rollers. The external apertures, c, of the wind-chest, c?, 
 are opposite to the air-pipes, e, and can be closed with plugs. At F there enters the 
 flame, which may be supplied from any kind of a fire-box, whilst the products of corn- 
 
 Fig. 164. 
 
 Fig. 165. 
 
 A 
 
 Fig. 166. Fig. 167. Fig. 168. 
 
 Mstion escape at G. When the apparatus is sufficiently heated it is brought up to the 
 furnace containing the melted ore, the cylinder is turned (the arched pieces, K, lying 
 upon the rollers, r) by means of the handle, IT, which catches into the circle of teeth, n, 
 fixed to the cylinder, until A takes the position shown in Fig. 166, and allows the 
 melted metal to run to the mouth, H. It may also be baled in with a ladle, or the 
 fusion may be effected in the cylinder itself by means of the flame striking in laterally. 
 After the apparatus is sufficiently filled it is removed to a fit place by turning the 
 wheels, R, which run on rails; the wind-chest is filled with compressed air or gas, 
 and the cylinder, A, is placed in a proper position (Figs. 167 and 168). According to 
 the action intended, the air flue, w, is connected with the recipient, V, so that the 
 powdery substances which it contains may be blown into the liquid mass. By suitably 
 inclining the melting furnace the slag, and afterwards the metal, can be run off 
 (Fig. 169). 
 
 For working crude regulus, it is run into the heated cylinder, A, from an ordinary 
 fixed smelting furnace ; the cylinder is moved to the proper place and turned until the 
 current of air passes through a sufficiently thick stratum of the liquid mass. The 
 
SECT, ii.] COPPER. 157 
 
 oxygen of the air combines with the sulphur, forming sulphurous acid ; and with the 
 other substances, forming oxides, which are carried with the gases to condensation 
 chambers, and are there precipitated. The sulphurous acid can be passed to the lead 
 chambers and converted into sulphuric acid. Of the ferric oxide formed, the greater 
 part remains in the bath, and would soon make the stone lining useless if silica were 
 not constantly blown in. Therefore, when the current of air begins, the recipient, U, 
 filled with silica, is connected with the air-pipe. As the more oxidisable substances 
 escape first, there remains in the cylinder only copper sub-sulphide, which may be plainly 
 seen by the colour of the flame. The cylinder is then turned so that the air is caused 
 to play more and more on the surface of the metals. From this moment the copper is 
 in excess as the sulphur is continually being burnt and separates out from the com- 
 bination. The copper, by reason of its superior density, sinks down below the remaining 
 copper sub-sulphide, and the tuyeres are gradually so raised that the air only enters 
 this sub-sulphide, which is thus gradually decomposed. There now remains in the cylinder 
 merely crude copper, which is run out or can serve for refining copper in the ordinary 
 manner. If the temperature is no longer sufficient, the cylinder may be heated afresh. 
 If it is noticed during working that all the iron is oxidised, no more silica is blown in. 
 The cylinder is turned to the position, Fig. 166, and the slag, if sufficiently liquid, is 
 run out. The current of air which then strikes the back of the bath on the surface 
 drives out the slag. With this apparatus very poor ores can be worked up, and refined 
 copper can be obtained. 
 
 For producing copper from oxidised ores, they are smelted down with coke in a 
 cupola furnace, after the addition of the fluxes necessary to produce an easily fusible 
 slag which takes up no copper. The blister copper is then refined, and is introduced in 
 commerce as rosette copper. At Chessy, near Lyon, malachite, azurite, and ruberite 
 are smelted. There is, however, a considerable loss of copper by slagging. In the 
 Siberian works on the Ural, sulphuretted copper ores and iron pyrites are added to 
 the oxidised copper ores. The copper is thus protected from slagging by the sulphur. 
 
 (B) Production of Copper in the Wet Way. This process is coming more and more 
 into use. The great ease with which copper is dissolved and precipitated from its 
 solutions suggested the moist way for obtaining copper when the dry way gave no 
 advantageous results on account of the poverty of the ores, or when it was desired to 
 utilise intermediate metallurgical and chemical products. 
 
 Cementation consists in precipitating copper from solutions of copper sulphate 
 (blue vitriol, blue stone) by means of metallic iron. Such waters occur in nature in 
 cupriferous districts. The metallic copper obtained by precipitating such solutions with 
 iron is known as cement copper. At the Amlwch copper works in Anglesea the 
 cement water is stored first in a large tank, to become clarified by the deposit of iron 
 ochre, and is then run into the cement pits, in which has been placed scrap-iron, &c., 
 for the decomposition of the copper sulphate. From time to time the sediments are 
 stirred up, and the turbid liquor, with all the deposit, is led into large sumps, in which 
 the mud is deposited and dried in a reverberatory drying furnace. It contains as 
 much as 50 per cent, of copper on an average 30 per cent. the chief constituent 
 being basic ferric sulphate. 
 
 Latterly the wet way for obtaining copper has been extensively used for the treat- 
 ment of poor ochre and pyritic copper ores, weathered pyrites, and burnt ores containing 
 copper pyrites. In general, the copper cannot be at once extracted by water or acids 
 from ores and furnace products, but preparatory operations are needed. In cupriferous 
 sulphur ores we use weathering or roasting (both oxidising and chlorising). The ores 
 to be extracted are sometimes sulphated by means of roasting-gases. For lixiviation 
 there are used, besides water, dilute hydrochloric or sulphuric acid, solutions of ferric 
 and ferrous chloride, and of common salt. Other solvents, such as ammonia, sodium 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. ii. 
 
 sulphite, and thiosulphate, have not given satisfaction. The precipitation of the 
 copper from its solutions is effected either by iron, or, as in Norway (Binding's 
 process), by sulphuretted hydrogen, the precipitated sulphide being afterwards con- 
 verted into copper sulphate or metallic copper. 
 
 Cupreous pyrites (as at Duisburg), after having given off their sulphurous acid by 
 roasting (for the manufacture of sulphuric acid), are freed from copper and silver in 
 the moist way ; the copper may be extracted by a solution of iron chloride and the 
 copper precipitated with iron sulphide. 
 
 In the Db'tsch process (worked at Rio Tinto) the pyrites are treated with ferric 
 chloride : CuS + Fe,Cl 6 = 2FeCl 8 + CuCl 2 + S and Cu 2 S + Fe 8 Cl 6 = 2FeCl 2 + Cu 2 Cl 2 + S. 
 The practical utility of these reactions is that the ferric chloride in solution preferably 
 attacks the cuprous sulphides, whilst the iron pyrites remain almost unchanged. 
 Instead of ferric chloride there may be used a solution of ferric sulphate and common 
 salt, which is distributed uniformly over the tops of the heaps. The solution penetrates 
 downwards and runs into a tank, where it settles, and is next led into the precipitating 
 tank. Before making up the heaps, 0-5 per cent, of common salt and an equal quantity 
 of ferric sulphate are mixed with the pyrites. The height of the heaps varies from 
 4 to 5 metres. By means of methodic lixiviation 1-34 per cent, of copper, that is, the 
 half of the 2'68 per cent, originally present, can be removed in four months ; in two 
 years, 2-2 per cent. ; whilst by the old process of roasting in free heaps and lixiviation 
 with pure water only, ri per cent, can be obtained in the same time. The cuprous 
 chloride is precipitated with iron ; the lye is treated with chlorine and used afresh. 
 The chlorine is obtained by igniting a mixture of sea-salt and iron sulphate with access 
 of air : 2FeS0 4 + 4NaCl + 30 = Fe 2 O 3 + 2Na 2 S0 4 + 4C1. 
 
 An average sample of cement copper obtained by the Witkowitz Mining and 
 Metallurgical Company, from the lixiviation of burnt ore, and also the crude copper 
 obtained by melting it in crucibles without additions, had, according to L. Schneider 
 {1884), the following composition: 
 
 Cement Copper. 
 
 Copper 
 
 Silver 
 
 Gold 
 
 Arsenic 
 
 Bismuth 
 
 Lead 
 
 Iron 
 
 1 1 -30 per cent. 
 0-521 
 trace 
 
 Ferrous chloride 
 Cobaltous chloride 
 Nickelous chloride 
 
 65-3I 
 0-19 
 
 0'45 
 1-18 
 
 0'20 
 
 Arsenious chloride 
 Lead sulphate 
 Sodium sulphate 
 Calcium sulphate 
 Magnesium sulphate 
 Water 
 
 0-32 
 
 
 Crude 
 92-752 per cent. 
 0-699 
 
 Copper. 
 Cobalt 
 Nickel 
 
 O'OOI 
 
 Zinc . . . 
 
 I-452 
 0-188 
 0760 
 3-1" 
 
 Phosphorus 
 Sulphur 
 Oxygen 
 
 o - i6 per cent. 
 
 0-29 
 
 0-07 
 
 1-32 
 
 2-19 
 
 3'39 
 
 5-32 
 
 0'59 
 
 2-98 
 
 0-178 per cent. 
 
 0-051 
 
 traces 
 
 0-055 
 
 0-190 
 
 0-360 
 
 All cement copper, in consequence of the treatment with iron, contains 
 generally considerable admixtures of basic ferric salts, which delay the refining, and 
 occasion a loss of copper, if chlorine is present. For the removal of these salts there 
 is required a mechanical preparation by washing, so that the proportion of copper is 
 raised to 94-05 or 95-93 There may besides be present, iron, antimony, arsenic, lead, 
 nickel, cobalt, lime, sulphuric acid, and chlorine (the last from 0-06 to 0-21 percent-.). 
 Blister copper, obtained chiefly from rich ores, contained in three samples 87-02 to 
 
SECT, ii.] COPPER. 159 
 
 94-31 copper, besides iron, antimony, arsenic, lead, nickel, cobalt, silver, and sulphur 
 the last from ro6 to 2*11 per cent. Cement copper may be combined with lime to 
 promote the formation of slag and to render the chlorine harmless. 
 
 The fusion with a reducing flame (the lateral draughts being closed), for the purpose 
 of volatilising antimony and arsenic, lasts from nine to fourteen hours, according to the 
 quality ; the treatment is then continued with open draughts, in order to slag the 
 foreign materials, producing either a thinly fusible slag (cement copper after treatment 
 with lime), or a basic, and merely fritted slag, containing iron and nickel, along with 
 which there appears, if the mass in fusion contains arsenic, antimony or lead. A slag 
 consists of nickel and lead antimoniates or arseniates, until a sufficiency of cuprous 
 oxide has been formed, and this in the period of reaction is decomposed with copper 
 sulphide, accompanied with strong effervescence (copper-rain) occasioned by the escape 
 of sulphurous acid, as follows : Cu 4 S + 2Cu 2 O = 6Cu 4- S0 2 . When the frothing and 
 b ubbling of the bath have ceased, the copper is more or less pure, but still contains 
 antimoniates and arseniates in such quantity that a purification with soda is advisable 
 for their removal, until a sample of the copper shows a crystalline fracture and a deep 
 red colour. The copper then contains cuprous oxide, is overdone and porous, in 
 consequence of sulphurous acid, which is still retained. Samples taken a short time 
 before the apparent completion of the period of reaction have an earthy, very porous 
 fracture, often of a greenish grey colour. After oxidation for some hours, and after the 
 still existing impurities have become slagged, the fracture is densely earthy and red ; on 
 further oxidation, corresponding to a proportion of 0-7 to i'o per cent, of oxygen, it is 
 crystalline and deep red. 
 
 Poling then follows to expel the gas until the samples taken have the required 
 compactness, shown by a finely earthy fracture. To render the copper ductile, the 
 oxygen is expelled by means of tough poling, the metallic bath being covered with 
 charcoal, with the draughts closed, and poled until the metal has a pure green colour, 
 and samples taken have a silky lustre at the fracture, can be forged at a red heat 
 without cracking, and at common temperature admit of stretching, bending, and 
 twisting, and have a fibrous fracture. Lots containing bismuth and lead must not be 
 over-poled, lest they entirely lose their oxygen, but only until a sample is sufficiently 
 tenacious to be used for common sheet-copper. After the metal has become malleable, 
 it is baled out, with iron ladles coated with clay, into moulds of iron or copper coated 
 with clay ; samples are often taken, and the poling is regulated accordingly. If the 
 poling gases (hydrogen and carbon monoxide) do not meet with sufficient oxygen for 
 combustion they may be absorbed by the copper, rendering it porous and unfit for 
 mechanical treatment. To prevent this absorption, especially in the case of copper 
 free from bismuth and lead, red phosphorus wrapped up in thin sheet-copper has been 
 used with success. According to Stahl, the phosphorus is best added to each lot of 
 copper poured into the mould. On examining the following refined coppers 
 
 I. II. III. IV. 
 
 Ou . . 99-365 ... 99*842 ... 99778 99'662 
 As . . 0-466 ... 0-052 ... 0-004 0-066 
 Sb . . trace ... ... ... 0-028 
 
 Fe . . O-OO4 O'OOI ... O'OO2 ... O'OO2 
 
 Ni . . o - oi6 ... 0-004 O'ooi ... trace 
 
 Co . 0-034 0-008 ... 0-003 ... trace 
 
 O . . 0-050 ... 0-062 ... 0-206 ... 0-042 
 
 S . . c'ooi 
 
 Pb . . 0-015 trace ... trace ... 0-043 
 
 Sn . . o'ooS ... ... Bismuth o - io2 
 
 Au . . ... 0-004 
 
 99 "959 99 "973 99 '994 99 '945 
 Sp gr. . . 8-904 ... 8-4*8 ... 8-908 ... 8-468 
 
160 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 the arseniferous copper I. was tougher than II. and III. ; the latter not tougher 
 than at common temperature, but in a red heat more easily forged and rolled than II. ; 
 IV. was both hot and cold short. This behaviour shows that corresponding quantities 
 of arsenic prevent the absorption of the poling gases, and thus give a denser copper, 
 which is tougher than the porous qualities, because the molecules remain more united, and 
 the intervening substances, in this case arsenic, in the quantities present do not exert 
 an injurious effect upon the properties of the copper. Whilst II., on account of its 
 larger percentage of copper and oxygen, might lead us to expect a higher degree of 
 toughness, its lower sp. gr. indicates porosity, whence the copper is in reality less 
 tough than II. The high precentage of copper and the considerable density of III. 
 render it fit to be forged and rolled at a red heat, but its proportion of oxygen is 
 enough to render it cold short on working at a common temperature. IV. is both hot 
 and cold short, on account of the presence of metallic bismuth. 
 
 In general, the coppers treated during refining for the partial removal of oxygen 
 with phosphorus, manganese, phosphide, &c., prove tougher and firmer than such as 
 have been poled tough. At the conclusion of the dense-poling, the copper contains 
 about 0-2 per cent, of oxygen, which allows it to be rolled and forged at a red heat, 
 but not at common temperatures. If an attempt is made to reduce the oxygen to 
 0*07 or 0*05 by continuous tough poling, in order to get rid of the cold shortness, the 
 metal absorbs pole gases to such an extent that it fulfils the required conditions even 
 less by its porosity than by the former presence of oxygen. Melted copper dissolves 
 gases (sulphur dioxide, hydrogen, and carbon monoxide), which are expelled by carbon 
 dioxide. At the Olper Works a sample of copper purposely over-poled was converted 
 into a very dense and tough copper by passing into it a current of carbon dioxide. 
 The absorption of gases involves the so-called rising or running of the copper. Bottcher 
 has found the cause of his phenomenon to be the absorption of sulphurous acid into 
 refined copper. As the copper cools, the gas becomes liberated again. It is formed by 
 the action of copper sulphide upon cuprous oxide : 2Cu_O + Cu 2 S = 3Cu, +- So r 
 
 Whilst, according to Ledebur, with the decrease of copper sulphide and cuprous oxide 
 in the metal-bath, the transformation of these substances is proportionately retarded, 
 Hampe shows that, in spite of the presence of oxygen, copper may contain copper 
 sulphide and sulphurous acid. 
 
 Three Mansfeld coppers had, e.g., the following composition : 
 
 i. ii. in. 
 
 Cu . . 98-9048 ... 99-5200 ... 99-6125 
 
 Ag . . 0*0287 0-0280 .. 0-0292 
 
 Pb . . 0*0208 ... 0-0232 ... 0*0200 
 
 As . . 0*0223 ... 0-0228 ... 0-0172 
 
 Sb . . 0-0059 ... 0-0031 ... 0-0023 
 
 Ni . . 0-2200 ... 0*2142 ... 0*2112 
 
 Fe . . 0-0029 ... 0-0039 ... 0-0039 
 
 O . . 0-7464 ... 0-1546 ... 0-0752 
 
 S . . 0-0036 ... O'OO2I ... 0*0024 
 
 99-9627 ... 99 -97 19 99 -9739 
 
 I. is overdone copper, after nine hours' melting and four hours' poling ; II., dense 
 refined copper after dense-poling for one and a half hour ; III., refined copper after 
 tough poling for one hour. 
 
 If the quantity of copper sulphide is sufficiently small it cannot be detected during 
 dense poling in the ladle samples, because a sufficiency of oxygen for transformation and 
 for the formation of sulphuric acid is wanting. It passes through the stage of tough 
 poling, and finally comes to be cast, but meets here with the newly formed cuprous oxide, 
 and form's with it sulphurous acid, which occasions the rising of the copper. This 
 
 
SECT, ii.] COPPER. 161 
 
 behaviour occurs if the dense poling stage is begun at that point which is indicated by 
 samples with a dense earthy fracture, since the proportion of oxide at this stage is mostly 
 not sufficient for conversion with all the copper sulphide, however uniformly the particles 
 are mixed by the poling, along with the demands of the reducing gases. If, on the 
 contrary, the dense poling has been begun at the point characterised by a crystalline 
 fracture, the proportion of oxygen of the cuprous oxide, which is formed more abund- 
 antly, suffices for complete conversion with the copper sulphide ; and the copper does 
 not rise on casting, if this is not produced by pole-gases or by sulphurous acid evolved 
 from pyritic fuel, which were absorbed by the copper after tough poling. This may be 
 ascertained by a sample before casting. That it is not always sulphurous acid which 
 occasions the rising of the copper, but that this phenomenon may be due to the pole- 
 gases (hydrocarbons, carbon monoxide, hydrogen), is proved by the fact that even the 
 best coppers, smelted with the best fuel, rise the more the longer the period of 
 toughening lasts. Stahl has shown that there was no trace of sulphur in some highly- 
 poled coppers which had risen. If the rising has been occasioned by sulphurous acid, 
 sulphur is, as a rule, still demonstrable in the copper. It is very difficult, whilst 
 ladling out the copper, to regulate the access of air so that all the combustible gases 
 are burnt, whilst the copper remains unchanged. If the supply of air is too scanty, 
 there is a reducing atmosphere in the furnace, the copper absorbs carbon monoxide, it 
 becomes porous, and it must be again rendered dense by oxidation or by the method 
 stated below. If the access of air is too free, the copper goes back, takes up oxygen, 
 and must be again poled until it is tough. Combustion gases are not absorbed, since 
 their ultimate products, carbon dioxide and watery vapour, are not absorbable. 
 
 The presence of oxygen, lead, arsenic, or phosphorus has a marked influence on 
 the density of copper. As the proportion of oxygen decreases on poling from 0*210 to 
 0*05 1 per cent., the porosity of the copper increases by taking up pole-gases. With a 
 proportion of oxygen of 0*160 per cent, the absorption of gases is just perceptible ; but 
 lower down it becomes very distinct, and as the oxidation of the copper increases its 
 density follows. An absorption of the gases makes itself perceived before the propor- 
 tion of oxygen has been reduced by tough poling as far as necessary for producing 
 sufficient toughness, and if the period of tough poling is too much prolonged the gas- 
 absorption goes to such an extent that the copper is worse than when it contained from 
 0*200 to 0*160 per cent, of oxygen. 
 
 The addition of lead is said to prevent the rising of copper from sulphurous acid, 
 becoming converted by the acid into lead sulphide and lead oxide, and also to 
 render the copper fitter for forging and rolling, by purifying it from antimony and 
 arsenic. According to Stahl, it condenses porous copper by dissolving therein, becoming 
 partly evaporated, and expelling the gases, just as do watery vapour and carbon dioxide. 
 An excess of lead added in refining makes the copper exfoliate on rolling. Under 
 certain circumstances arsenic prevents the absorption of the pole-gases and keeps the 
 copper dense. Such arsenif erous copper, obtained even after prolonged poling, has, along 
 with a low proportion of oxygen, the property of being better adapted for working 
 than less dense refined copper richer in oxygen, even up to a proportion of arsenic of 
 i per cent. Antimony acts similarly to arsenic. In copper free from lead and 
 bismuth, phosphorus, as a reducing agent, acts favourably upon the density of copper. 
 The porosity of copper occasioned by sulphurous acid or pole-gases is distinct from that 
 which arises during casting, by air bubbles carried along mechanically. 
 
 Obtaining and Refining Copper by Electricity. The installation erected by Mar- 
 chese for a company at Genoa consists of 20 Siemens machines for electrolysis, each of 
 which, with a tension of 15 volts and a current of 250 amperes, serves 12 baths. 
 A part of the ores to be treated are smelted, according to their nature, to a raw 
 matte, which serves in the process as an anode (positive pole), and consists of about 
 
 L 
 
162 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 30 per cent, copper, 30 sulphur, and 40 iron. Another portion of the ores is roasted to 
 produce a liquor containing as much copper sulphate as is necessary to utilise the iron 
 sulphate of the anodes for the electrolytic decomposition of the same solution of copper 
 sulphate. That part of the mineral which is reserved for anodes is melted to raw 
 metal in the ordinary manner. The crude metal is cast in thin plates corresponding 
 to the sizes of the troughs, and into each there is inserted a slip of copper to 
 effect the connection with the circuit. The kathodes (negative poles) are formed 
 of thin sheets of copper. The roasted ores are systematically lixiviated with the addi- 
 tion of sulphuric acid, in order to dissolve the metal present as oxide, and the solution 
 obtained, a mixture of copper and iron sulphate, is passed into cisterns. Copper sul- 
 phate is decomposed by the electric current, the copper being deposited upon the 
 kathodes ; at the same time the metallic sulphates forming the anodes are attacked ; 
 there are formed iron salts and sulphuric acid, which prevent the precipitation of iron 
 from the copperas (iron sulphate) and the development of hydrogen. In order to keep 
 the solution saturated and of correct composition, it is passed through the collecting 
 pipes from the separate baths to the cisterns for liquor, and thus a regular and constant 
 circulation is maintained between the baths and the cisterns. The tension required is 
 about one volt. The worn-out anodes are utilised for sulphur or sulphuric acid. If 
 the solution contains too much iron it is removed; the last traces of copper are 
 precipitated by the sulphuretted hydrogen evolved by the action of the liquor upon 
 the raw metal. In the same manner, the ferrous sulphate is reduced and the free 
 sulphuric acid is neutralised. The ferrous sulphate is crystallised out, if it is saleable, 
 by a suitable arrangement of the baths, a proper composition of the solution, and a 
 well-managed circulation ; the daily yield of pure copper is said to be 20 kilos, per 
 horse-power. 
 
 The diagram (Fig. 170) makes the succession of the operations more intelligible. 
 
 Siemens and Halske use as depolarising agent a liquid in connection with insoluble 
 anodes, and separate the salt of copper to be decomposed at the kathode from the 
 liquid to be oxidised at the anode of a non-metallic septum. The liquid submitted to 
 electrolysis consists of a solution of iron and copper sulphates, with the addition of 
 some free sulphuric acid to increase its conductivity, 
 
 If single decomposition cells are used, this liquid is best introduced, without inter- 
 ruption, near the bottom of the solution surrounding the kathode plates (Fig. 171); 
 it rises here whilst a part of the copper is deposited by the electric current at the 
 kathodes, Ou, and flows over the upper edge of the membrane, C, into the anode-spaces, 
 which it traverses in order to be drawn off again at the bottom, through JRa. 
 
 During this descent the ferrous sulphate is first decomposed into basic ferric 
 sulphate, and then, by taking up the sulphuric acid liberated in the decomposition of 
 the copper sulphate, it is converted into neutral ferric sulphate, which, on account of 
 its greater specific gravity, sinks to the bottom at the carbon rods or plates. The 
 liquid flowing off has therefore become poorer in copper and consists in part of neutral 
 ferric sulphate. This solution has the property of converting copper sub-sulphide, 
 copper mono-sulphide and copper oxide into copper sulphate. Hence, by the solution 
 of the two copper compounds, the ferric sulphate is reconverted into ferrous sulphate, 
 whilst the oxygen liberated oxidises the copper sulphide. By previously roasting the 
 copper pyrites at a gentle heat, a product has been obtained in which the copper exists 
 chiefly as copper hemi-sulphide and the iron as oxide, the latter, therefore, in a state in 
 which it is not attacked by ferric sulphate and very slightly by sulphuric acid, whilst 
 the copper hemi-sulphide is powerfully dissolved by the solution of ferric sulphate. 
 
 The process is continuous, the same liquid serving until it is rendered unfit for 
 galvano-deposition, by having taken up foreign metals. 
 
SECT. II.] 
 
 COPPER. 
 
 163 
 
 The chemical processes involved appear from the following equations : _ 
 i. xH 2 SO + 2 CuS0 + 4 FeSO 4 = 2 Cu + 2J Te 2 (S0 4 ) 3 + xH 2 S0 4 . 
 
 xH 8 SO 4 . 
 
 2. . xH 2 S0 4 + Cu 2 S + 2Fe 2 (S0 4 ) 3 = 2 CuS0 4 + 4 FeS0 4 + 
 
 b. CuO + H 2 SO 4 = CuSO 4 + H 2 O. 
 
 c. 3 CuO + Fe 2 (S0 4 ) 3 = 3 CuS0 4 + Fe 2 O 3 . 
 
 d. CuO + 2 FeS0 4 + H 2 = CuS0 4 + (Fe 2 3 + SO 3 ) + 
 
 Fig. 170. 
 
 Explanation of Terms. 
 Kupfererze Copper ores. 
 
 Schmelzen zu Kupferstein fiir Fusion to copper matte 
 
 Anoden 
 Riisten 
 Anoden 
 Gen'istete Erze 
 Kammersaure 
 Unverandecte Riickstande 
 Losuny imd Auslaugen 
 
 H 
 
 Cmcentriruny 
 Kreislauf 
 Bdder 
 Electrolyte 
 Schicefelsiiiirc 
 Chemisch. reines 
 Flatten 
 
 Kupfer in 
 
 Schicefel haltende Rilckstande 
 Xiederschlag von Kupfer, CuS, 
 
 Fiillung des Kupfers und Re- 
 
 duction 
 Kisenvitriol oder Ablauf 
 
 Eisenvitriol 
 Krystallisation 
 Rolunaterial 
 Verkaufliche Producte 
 Nebenproducte 
 
 for anodes. 
 
 Boasting. 
 
 Anodes. 
 
 Eoasted ores. 
 
 Chamber acid. 
 
 Unchanged residues. 
 
 Solution and Lixivia- 
 tion. 
 
 Concentration . 
 
 Circulation. 
 
 Baths. 
 
 Electrolyte. 
 
 Sulphuric acid. 
 
 Chemically pure cop- 
 per in plates. 
 
 Solution. 
 
 Sulphurous residues. 
 
 Precipitate of copper, 
 CuS. 
 
 Precipitation of cop. 
 per and reduction. 
 
 Copperas or waste 
 liquor. 
 
 Copperas. 
 
 Crystallisation. 
 
 Raw material. 
 
 Saleable products. 
 
 Bye-products. 
 
 On comparing the formulae i, and 2 a, we perceive that if the ore contains all its 
 copper in the form of a hemi-sulphide the electrolyte contains, after the transflux 
 of the lixivium, exactly the same quantity of copper sulphate, iron sulphate, and 
 sulphuric acid as before electrolysis, and is therefore completely regenerated and can 
 be again used for electrolysis. If, on the contrary, the copper is partly present in the 
 ore as oxide, it is seen from equations 2 b, c, and d that in this case after lixiviation the 
 electrolyte is richer in copper but poorer in iron than it was before electrolysis. 
 
 It need scarcely be mentioned that, instead of roasted copper pyrites, unroasted raw 
 matte in which the copper is almost exclusively present as hemi-sulphide may serve 
 for lixiviation. Here not only copper, but iron, is dissolved, so that a complete uni- 
 formity of the solution in copper and iron is not reached. 
 
164 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. n. 
 
 Fig. 171. 
 
 In the galvanic process described, no polarisation occurs, and the different position 
 of the anode and kathode in the series of tension does not occasion any counter electric 
 force. 
 
 Whilst, on using anodes of raw metal, there is required a potential difference of 
 about i '5 volt in the processes above described, there is needed a tension of only 0*7 
 volt for the same density of current. Whilst, further, in using anodes of copper 
 matte, about one-third of the current is used in other reductions and is consequently 
 wasted, there is here no loss of current. 
 
 For refining copper the distance of the electrodes is 5 centimetres, the density of 
 the current is 20 to 30 amperes per square metre of kathode surface, and the bath is a 
 solution of 1 50 grammes copper sulphate and 50 grammes sulphuric acid to i litre water. 
 The tension for the bath is o - i to o - 2 volt. Manganese, zinc, 
 iron, cadmium, tin, antimony, arsenic, lead, and bismuth pass 
 into the liquid, remaining in the mud at the anodes only 
 if insoluble compounds are formed. Silver, platinum, and 
 gold are deposited on the anode in the metallic state. It is 
 essential that the bath must remain acid and must be kept 
 constantly in motion. 
 
 \ | If the tension at the terminals of the dynamo is 1 5 volts, the 
 
 ^J) tension in the bath 0*25 we might put (15 : 0-25) = 60 baths 
 
 in series. For the sake of safety, 40 are used. If the dynamo 
 yields 240 amperes hourly, corresponding to 283*6 grammes 
 copper, we obtain in twenty -four hours in 40 baths, arranged 
 in series, 272 kilos. The work required is (240 x 1 5) : 736 = 4-9 
 horse-power in the dynamo or 6 horse-power in the engine. 
 If the tension in the bath, using plates of very impure copper 
 matte, and impure solutions, is 1*2 volt, so that only 10 baths 
 can be arranged in series, we obtain only one-fourth of the 
 quantity of copper from the same machine-power. 
 
 Explanation of Terms. 
 
 FUissigkeitshuhe Level of 
 liquid. 
 
 At Oker there are now 6 dynamos in action, 5 of the type C t and one C, 8 , each 
 of which daily deposits 250 to 300 kilos, of copper, with the expenditure of 7 to 8 horse- 
 power. The yearly output is therefore 500 to 600 tons of copper. The copper to 
 be refined has already undergone a furnace refining, and contains only g to ^ per cent, 
 of impurity. Nevertheless, the electrolytic process is financially remunerative, as the 
 removal of the last impurities considerably raises the value of the product. 
 
 The great advantage of the electrolytic process as compared with furnace-refining 
 is, that the precious metals, especially silver, do not pass into solution, but, as the 
 anode is gradually destroyed, they fall down into the mud. To obtain all the silver 
 present in the crude material, it is merely necessary to remove from time to time the 
 mud which collects, and to extract the silver. The greatest difficulty of the electrolytic 
 process lies in the behaviour of arsenic and antimony. They pass into solution, and 
 as soon as they exceed a certain proportion they begin to combine with the deposit of 
 copper, and render it hard and brittle. In order to meet this difficulty there is no 
 expedient except to purify the solution or to prepare a fresh solution in its stead. 
 Both the crude copper and the refined copper are used in plates i metre in length and 
 0-5 metre in breadth. The plates of crude copper.^ about 15 millimetres in thickness, 
 are fixed in boxes at the mutual distance of 10 to 15 centimetres, and plates of copper 
 are inserted between them as kathodes. 
 
 Each dynamo C t with a tension at the terminals of 3-5 volts, and a current of 1000 
 amperes in strength, works, as a rule, 1 2 baths introduced in series, the whole occupying 
 a space of 80 square metres. The dynamo C 18 gives a tension of 30 volts and a current 
 
SECT, ii.] COPPER. !6 5 
 
 of 1 20 amperes (or in other cases 15 volts and 240 amperes). It actuates at Oker 80 
 smaller baths. The room occupied, the quantity of liquor, the working-power, and the 
 deposit of copper are in this case quite similar to the arrangements with C L dynamos. 
 The expense, however, differs, and a decided advantage of the installation 18 is that the 
 baths can be placed at a considerable distance from the machine, which is not the 
 case with O r 
 
 Hilarion Roux, of Marseilles, has a 5 horse-power Gramme and 40 baths, with a 
 surface of anodes 900 square metres. The kathodes are only o - 5 millimetre in 
 thickness, and are fixed at the distance of 5 centimetres from the anodes. The 
 machine consumes daily 240 kilos, of coal and yields at 8 volts and 300 amperes 250 
 kilos, of purified copper or 10*4 kilos, hourly. The machine utilises 85 per cent, of 
 the power supplied = 3 19 kilogrammetres ; 240 of which, according to Gramme, are 
 spent in overcoming resistance, and 79 in transporting the metal between the poles ; 
 chemical work has not here to be performed. 
 
 In order to calculate the necessary expenditure of work, the potential difference 
 between both electrodes must be measured in a laboratory experiment, with that 
 density of current which has been found most favourable for general working, and with 
 the intended distances of the electrodes. If, e.g., the tension at the terminals of the 
 machine is 15 volts, and the tension at the bath 0*25 volt, we might, if we quite over- 
 look the resistance of conduction outside the baths, at most introduce (15 : 0*25) = 60 
 baths in a series, but 40 are generally found sufficient. If the machine at the above 
 tension gives a current of the strength of 240 amperes, representing 238-61 grammes 
 copper hourly, we obtain in 40 baths arranged in series 11*344 kilos, hourly, or in 
 twenty-four hours 272-26 kilos, of copper. The work consumed is (240 x 15) : 736 = 4-9 
 horse-power for a dynamo, or 6 horse- power for the steam-engine. Such an installation 
 takes up a surface of 80 square metres, and five months are required for producing a 
 copper plate of i centimetre in thickness, with a current of 20 amperes. 
 
 Properties of Copper. Copper is red, strongly lustrous, and, though consider- 
 ably hard, it is so ductile that it may be drawn out to very fine wires and rolled into 
 thin leaf. It has a granular fracture, a spec. gr. (pure) of 8*955 to 8*956 ; the best 
 commercial samples have only 8*2 to 8*5 ; it fuses rather less readily than silver. 
 Pure copper flows in a thin stream, which quickly solidifies ; if contaminated with cuprous 
 oxide, it flows more sluggishly and solidifies less rapidly. Melted copper has a peculiar 
 sea-green colour. For castings copper is not good, since it gives porous articles 
 full of air-bubbles, probably because cast too hot. At high temperatures, and with 
 access of air, copper burns with a fine green flame. If exposed to moist air, it 
 gradually becomes coated with copper hydrocarbonate, commonly but improperly 
 called verdigris. If heated with access of air, it takes at first rainbow colours, and 
 then becomes covered with a reddish-brown film of cuprous oxide, which by degrees 
 turns black, and on quenching the ignited metal in hot water, or on hammering or 
 bending, falls off in scales. 
 
 Copper is used for boiling-vessels and coolers in distilleries, breweries, and sugar- 
 works, for sheathing ships, for money, for rollers in tissue-printing, for making copper 
 sulphate, nitrate, and copper colours, for engraving, and especially in the production 
 of alloys. The Mining Journal estimates the quantity used yearly in cartridges at 
 7500 tons. 
 
 Among samples of refined copper examined in 1884 by Pupahl, two brands were 
 found unsuitable for brass castings, on account of their high percentage of arsenic : 
 
i66 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. ii. 
 
 Cu 
 O 
 Pb 
 Fe 
 
 Ni 
 
 Ag 
 
 Au 
 
 8 
 
 As 
 
 Sb 
 
 Wallaroo. 
 
 99795 
 0-127 
 0-004 
 
 O'OOI 
 
 0-039 
 0-015 
 
 Chm. Co. 
 
 Mansfelder R. 
 
 99-864 
 
 99'49i 
 
 O'I20 
 
 0-145 
 
 
 
 0-038 
 
 trace 
 
 O'OOI 
 
 0-002 
 
 ... O'2OI 
 
 0-028 
 
 0-031 
 
 trace 
 
 ... 
 
 99-981 
 
 trace 
 
 100*014 
 
 0-072 
 trace 
 
 99-979 
 
 Bede. 
 99-148 
 0-090 
 0-023 
 O'OOI 
 
 o'oSi 
 0-058 
 trace 
 0-005 
 0-600 
 
 O'OO2 
 
 100-008 
 
 Grange. 
 
 98-961 
 0-160 
 0-005 
 0-004 
 0*066 
 
 O'OIO 
 
 trace 
 0-766 
 
 O'OII 
 
 99-983 
 
 Copper obtained from Colorado ores contains, according to Eggleston (1883), 
 tellurium, which renders it brittle. 
 
 Cu 
 
 Au . 
 
 Ag . 
 
 Pb 
 
 Zn&Ni 
 
 Fe 
 
 S 
 
 Te 
 
 As 
 
 Slag . 
 
 Stone. 
 
 55-02 
 0-06 
 0-40 
 
 17-87 
 
 2'22 
 
 4'l8 
 
 2OX>2 
 
 O'I2 
 
 Black Copper. 
 
 97-120 
 
 0-132 
 0-777 
 0-070 
 0-130 
 0-236 
 0-093 
 0-006 
 1-270 
 
 98-090 
 
 0-128 
 0757 
 
 O'lOO 
 
 0-080 
 
 0-097 
 0-192 
 
 Eefined Copper. 
 99705 
 
 0-135 
 
 0-024 
 0-031 
 trace 
 0-083 
 0-091 
 
 Refined Mansfeld copper (1880) contains : 
 
 Cu 
 Ag 
 Pb 
 Fe 
 
 Ni 
 As 
 
 A. 
 
 99-394 to 99-550 
 0-028 0-030 
 0-043 0-103 
 0-025 0-132 
 0-239 0-275 
 
 B. 
 
 99-110 to 99-270 
 
 0-016 0-020 
 
 0-134 0-259 
 
 0-019 I. 0-024 
 
 0-314 0-405 
 
 o-ioi 0-144 
 
 The total production of copper in 1879 amounted to 149,000 tons, and in 1884 to 
 about 208,000 tons, of which the United States furnished 63,950, Chili 41,648, Spain 
 and Portugal 43,664 (chiefly from Eio Tinto), Australia 13,300, South Africa 5000, 
 and England only 2500. 
 
 Copper Alloys. Among the copper alloys, the most important are bronze, brass, 
 and nickel-silver, commonly called German silver. Bronze is an alloy of copper and 
 tin, or copper, tin, and zinc ; or, latterly, of copper and aluminium. By these addi- 
 tions copper is rendered more fusible, and hence easier to cast; denser, and thus 
 more susceptible of polish, it is also harder, more brittle, sonorous, and resonant, and 
 is (with the exception of the aluminium alloys) cheaper, and thus more suitable for a 
 variety of purposes. Lead renders bronze more fusible and denser, but has a great 
 disposition to separate out on the surface in combination with copper. Hence a per- 
 centage exceeding 3 per cent, is to be avoided. On slow cooling bronze becomes 
 soft and malleable, but on rapid cooling hard and brittle. A small addition of 
 phosphorus (0-12 to 0-7 6 ''per cent.) makes some of these alloys more homogeneous 
 and pliable. The chief kinds of bronze are bell-metal, gun-metal, art-bronze, 
 phosphor-bronze, and aluminium-bronze, the last of which will be described under 
 ALUMINIUM. 
 
 Bell-Metal, of spec. gr. 8-368, consists of 78 parts copper and 22 parts tin. It 
 must combine sonorousness with hardness and tenacity. It is a brittle metal, and its 
 treatment in the turning-lathe is therefore difficult. A bell must obtain its intended 
 sound in the casting, by its form and by its composition. It is an error to suppose 
 
SECT, ii.] COPPER. 167 
 
 that silver has to be mixed with bell-metal to yield a good sound. The alloy for 
 certain instruments of military music, such as cymbals, as well as of tom-toms and 
 gongs, is similar to bell-metal. 
 
 Gun-Metal consists, on an average, of 90 parts copper and 9 tin. It has the 
 defect of becoming gradually decomposed, either by a kind of eliquation, more fusible 
 alloys richer in tin separating out from less fusible parts richer in copper, or by 
 combustion, since tin burns more readily than copper, the alloy thus becoming poorer 
 in tin. 
 
 Art-Bronze, for statues, busts, decorations, &c., consists of copper and tin. It 
 must be so composed that when melted it fills up the mould completely, giving a clear, 
 sharp casting, which admits of being easily retouched, and takes a fine patina. A 
 normal bronze, according to Elster, consists of 86-6 copper, 6-6 tin, 3-3 lead, and 
 3'3 zinc - 
 
 Bronze is valued for its property of quickly becoming coated with a uniform fine 
 green layer of oxide (patina), the formation of which is often expedited by chemical 
 means. According to Weber, zinc hinders the formation of patina; he recommends 
 that copper, as free as possible from arsenic, should be used with tin alone. A bronze 
 statue having a remarkably fine patina consisted of 88'6 per cent, copper, 9-1 per cent, 
 tin, i -3 zinc, and 0*8 lead.* 
 
 Phosphor-Bronze (90 parts copper, 9 tin, and 0-5 to 075 phosphorus) was in- 
 vented in 1871 by C. Kiinzel. It has been latterly used for gun-metal, bell-metal, 
 art-bronze, for the bearings of axles, &c. The elasticity is considerably heightened and 
 its absolute tenacity is increased more than twofold by the introduction of phosphorus, 
 and the hardness is augmented to such a degree that some specimens resist the file. 
 The metal when melted flows well and fills the mould perfectly. 
 
 Brass. Zinc and copper combine with each other in all proportions, some of which 
 are well known as brass, and find numerous applications. The following are instances : 
 
 Cu. Zn. Pb. Sn. 
 
 Clock wheels . 60-66 ... 36.88 ... ... 1-35 
 
 Cast brass . . 6370 ... 33'5o ... 0-30 ... 3-50 
 
 Sheet brass . . 70*10 ... 29-90 
 
 Brass wire . . 71-89 ... 27-63 ... 0-85 
 
 In general, a reduction of the proportion of zinc gives the brass a darker and a redder 
 colour ; a larger proportion of zinc gives a paler and yellower metal. The larger the 
 proportion of copper the more extensile is the brass. When cold, brass is malleable 
 and can be rolled and drawn to wire. When hot, it easily breaks and cracks. A 
 malleable brass (yellow metal) which can be forged and rolled is obtained by melting 
 together 60 parts of copper with 40 of zinc. 
 
 Brass is superior to pure copper in several respects. It has a more pleasing colour, 
 does not oxidise so readily, is harder and stifier (whence its use for pins) ; has a lower 
 melting-point, and when melted flows more easily and does not become blistery ; hence, 
 and from its lower cost, it is preferred for castings. The addition of i or 2 per cent, 
 of lead makes the brass more suitable for turning ; it also files better, and does not 
 clog the file. 
 
 Brass was formerly manufactured by fusing together calamine with black copper 
 and charcoal. Now it is produced by melting metallic zinc with refined copper. 
 
 Alloys similar to brass are pinchbeck (tombak), containing 85 parts copper with 
 15 zinc. Spurious gold-leaf is made in Germany from 2 parts zinc and n copper. 
 
 Other alloys are prince's metal, similor, ore'ide, Mannheim gold, &c. Delta metal 
 is composed of 60 parts copper, 32-2 zinc, and 1*8 iron. Sterro-metal is similar in 
 
 * The formation of patina is now found to be due to the action of certain minute organisms. 
 [EDITOB.] 
 
168 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 composition, but much harder. Muntz's metal, used for sheathing ships, for bolts, 
 ships' nails, &c., consists of copper and zinc in proportions fluctuating between 50 per 
 cent, zinc to 63 copper and 37 zinc to 50 copper. The alloy for the bronze coinage 
 of France, Sweden, Britain, Spain, Russia, Norway, Greece, Servia, and Boumania 
 consists of 95 parts copper, 3-5 tin, and 1-5 zinc. In Denmark the alloy is 90 copper, 
 5 tin, and 5 zinc. The German bronze coins (2 and i pfennig pieces) consist of 95 
 copper, 4 tin, and i zinc. So-called white brass consists, like bath metal, of 55 copper 
 and 45 zinc. Button metal is composed of 20 copper and 80 zinc. 
 
 The Bronze colours used for bronzing objects of plaster or wood, as also for cast- 
 metal articles, in letter-press and lithographic printing, in lacquering, and in the manu- 
 facture of paper-hangings, &c., are made from the powders resulting from forging metals, 
 which are ground up and heated with oil, tallow, wax, or parafnne ; the colours which 
 they assume violet, red, orange, gold-colour, and green are due to superficial 
 oxidation.* 
 
 German silver (Argentan, Pakfong, Mail lech ort) is an alloy of copper, nickel, zinc, 
 or tin, which may be regarded as brass, with an addition of \ to | of nickel. It has 
 a yellowish white colour, a densely granular or jagged fracture, a spec. gr. of 8*4 to 
 8- 7, and it is harder than common brass, but almost equally extensile. It takes a 
 very high polish. In its preparation there are used zinc, copper, and nickel in a 
 comminuted state. The metals are put in a crucible, a part of the copper being 
 laid at the top and the rest at the bottom. The whole is then covered with charcoal 
 powder and melted. 
 
 German silver takes a fine polish, and remains for a long time unchanged on expo- 
 sure to the air ; it is less readily attacked by acid liquids than are copper and brass. 
 The proportions of the ingredients are copper 50 to 66 per cent., zinc 19 to 31, nickel 
 13 to 18*5. Latterly, smaller proportions of nickel are found in cheap sorts of German 
 silver. 
 
 German silver can scarcely be distinguished on the touch-stone from a silver- 
 alloy of 0-750. If the streak is moistened with nitric acid, it disappears more 
 rapidly than that of silver, and on the addition of a solution of sodium chloride, no 
 turbidity is produced. It is chiefly used in rolled sheets. Alfenide, used for candle- 
 sticks, milk-cans, tea services, forks, spoons, &c., is German silver electro-plated, 
 containing about 2 per cent, of silver. Other plated nickel alloys are Peru silver, 
 China, silver, Christofle, and Alpacca. Tiers Argent consists of 27-5 silver, 62^5 copper, 
 nickel, and zinc. 
 
 An alloy of nickel and silver has been used in Switzerland since 1850 for small 
 coinage. It contains pieces for 
 
 Silver. Copper. Zinc. Nickel. 
 
 20 raps ... 15 ... 50 ... 25 ... 10 
 
 1 ii . 10 ... 55 ... 25 ... 10 
 
 5 i. 5 ... 60 ... 25 ... 10 
 
 A metal formerly met with under the name Suhler-white copper, contained 88 
 parts copper, 875 nickel, 1-75 antimony. It was obtained from old slag-heaps, and is 
 the first nickel alloy which was used in the arts. 
 
 Copper Amalgam. A compound of 30 parts copper and 20 mercury, obtained 
 by moistening copper-powder with mercurous nitrate, covering with hot water, and 
 adding the required amount of mercury by grinding. It is also known as metallic 
 putty, and is a soft mass, which softens in a few hours. It is also (most injudi- 
 ciously) used for stopping hollow teeth. 
 
 * Bessemer has effected great improvements in the preparation of bronze colours. [EDITOR.] 
 
SECT. II.] 
 
 LEAD. 
 
 i6g 
 
 Fig. 172. 
 
 Fig. 173- 
 
 LEAD. 
 
 Lead has been known from the remotest antiquity. It rarely occurs native, but fre- 
 quently combined with sulphur, as galena (PbS), and as Bournonite, a lead and anti- 
 mony sulphide. The latter ore consists of lead 41*77 parts, copper 1 2*76, antimony 26 - oi, 
 and sulphur 19-46. It is worked for lead and copper. Lead is found also as cerus- 
 site, white lead ore (PbCO 3 ), pyromorphite, or green lead ore (3Pb 3 (PO 4 ) 2 + PbCl,), 
 mimetesite, a lead arseriiate (3Pb 3 (As0 4 ) 2 + PbCl 2 ), as Anglesito (lead sulphate, PbSO 4 ), 
 yellow lead ore (lead molybdate, PbMo0 4 ), and as crocoisite, or red lead ore (a lead 
 chromate, PbCr0 4 ). 
 
 Production. Lead is obtained almost exclusively from galena. Its extraction 
 depends on the behaviour of galena with metallic iron. If lead sulphide is heated with 
 metallic iron, there are formed iron sulphide and metallic lead : PbS + Fe = FeS + Pb. 
 The galena, previously freed from gangue by smelting or elutriation, is mixed with 
 granular iron and smelted down in a shaft-furnace. The products are metallic lead 
 and a lead matte. Instead of metallic iron, there may be used iron ores and slags, 
 which exert a desulphurising action by means of their oxygen. 
 
 Figs. 172, 173, and 174 show a lead smelting furnace (sump-furnace). The hearth 
 and the sump lie partly outside the furnace. The gases escaping from the shaft B, 
 before reaching the chimney T, pass through chambers in which they deposit the 
 particles of ore carried away by the blast o. 
 The assorted ores mixed with granular iron 
 are thrown into the furnace in alternate 
 layers. The liquid products collect in the 
 sump C. The products are slag floating 
 on the surface, argentiferous lead and lead 
 matte. The latter is either roasted and 
 worked up for vitriol or cement copper or 
 smelted with rich lead slags and granular 
 iron, and worked for lead. The slag as it 
 forms is allowed to flow off down an in- 
 clined plane until the sump is filled with 
 the other products. The tap-hole is then 
 opened, and the product run off into the 
 lower hearth. In this hearth the matter 
 as it congeals is taken off in discs ; the 
 subjacent work-lead is desilverised by the 
 Pattinson process. 
 
 The production of lead from galena by roasting in the reverberatory depends on 
 the behaviour of lead oxide and lead sulphate with galena. By the action of the 
 oxygen of the air, a part of the galena is oxidised to lead oxide and sulphurous acid, 
 whilst lead sulphate is also formed. By means of the oxygen of the lead sulphate and 
 the lead oxide the sulphur of the undecomposed part of the galena is oxidised and 
 removed : 2 PbO + PbS = 3 Pb + S0 2 ; PbS0 4 + PbS - 2Pb + 2 S0 2 . 
 
 If an excess of galena is present in the roasting process, there is formed lead 
 sub-sulphide (Pb 2 S), from which metallic lead is eliquated, whilst the residue takes up 
 more sulphur : Pb 2 S = PbS + Pb. 
 
 Upon this process, combined with the use of a reverberatory with a depressed 
 hearth, is founded the English process for the production of lead. The ordinary 
 arrangement of the reverberatories for melting lead ores in Derbyshire and Cumber- 
 land is shown in Fig. 175. The hearth, formed of slags fluxed together, rests on a 
 
170 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. ii. 
 
 Fig. 175- 
 
 Fig. 176. 
 
 massive wall. Its surface is inclined from all sides towards the tap-hole, from which 
 the lead flows down into the anterior crucible. The furnace has six doors o, three of 
 which are at the tapping side, and three at the back. The ores are let down through a 
 funnel T, capable of being closed down upon the hearth. In general 800 kilos, of 
 ore are introduced and worked up in six to seven hours. The consumption of coal is 
 
 about half the weight of the ore. The ore 
 is spread level over the hearth, and the doors 
 of the furnace are closed, that it may be 
 heated uniformly. In two hours they are 
 opened, until the smoke filling the furnace 
 has disappeared, when they are closed .and 
 a strong heat is given. Subsequently the 
 doors are opened for the second time and 
 the ore is alternately stirred through one or 
 other of the side doors. The mass becomes 
 pasty, and the lead runs off on all sides. The 
 stirring is kept up for an hour, and then 
 the mass becomes almost liquid. This liquefaction is promoted by additions of fluor- 
 spar. As soon as it is sufficiently fluid, the upper layer of the slag is run off 
 and caused to solidify by wetting with water. It is called 
 white slag ; it has an appearance like enamel, and it often con- 
 tains 22 per cent, lead sulphate. Coal is introduced through 
 the middle door to congeal the refractory and abundant slag, 
 which has remained upon the metal. Lastly the tap-hole is 
 opened, and the lead runs off into the tap-crucible. 
 
 At Alternau the lead ore washings of the Upper Harz, 
 containing 54-55 per cent, lead, o - o8 silver, 0^9 copper, 7-8 
 zinc, and 14-18 silica, are roasted in a reverberatory with one 
 hearth. For smelting there are used two shaft -furnaces (Figs. 
 176, 177), the shaft of which, A, rises from the form 4 metres in a width of 1*2 metre, 
 and then ends in a wrought-iron top-piece i metre in height, which expands above to 
 
 1 1 metre. Up to i metre above the form the shaft has a 
 gentle slope to form and rest, with which the front wall of 
 d, the furnace, runs parallel. A wrought-iron water re- 
 frigerator, e, which forms a jacket for the back wall of the 
 furnace, protects it against any corrosive action of the 
 charge, without having too strong a cooling action upon 
 the melting mass. 
 
 At present 4 tons of roasted ore are sorted with i ton of 
 raw slick, and these 5 tons are charged, according to the pro- 
 portion of silica and zinc, with i to 1*25 ton of puddling- 
 slag, i to 1-25 ton of extraction residues from Oker, and 
 0-75 to 1-5 ton lime, in all 3^25 to 3-5 of basic materials. 
 To this come slags from the same works as they may be 
 needed. From such a charge there are obtained 32 to 34 
 tappings each, with 50 kilos, of coke, and 60 such lots are 
 worked through in twenty-four hours, the pressure of the 
 blast being 14 to 20 millimetres of mercury. The slag 
 drawn off in the first quarter of 1882 contained 
 
 Fig. 177. 
 
SECT, ii.] LEAD. 171 
 
 Silica .... 30*32 
 
 Barium sulphate . . 0*19 
 
 Lead .... ri3 
 
 Copper . . . 0*18 
 
 Silver .... 0-0007 
 
 Antimony . . . 0-09 
 
 Ferrous oxide . . 35*72 
 
 Alumina . . . 3-20 
 
 Zinc oxide . . . 7-27 
 
 Manganous oxide . i'66 
 
 Cobalt and Nickel . traces 
 
 Lime . . _. .16-15 
 
 Potassa . . . 0-67 
 
 Soda . . . o'6i 
 
 Sulphur . . i -47 
 
 Phosphoric acid . . 2-04 
 
 If the proportion of metal in the slag is higher, it is a sign that more bases are 
 needed for the decomposition of the lead silicate. If separation takes place in the 
 sump of the furnace, and the slag falls below the normal amount, this indicates an 
 excess of basic additions. The influence of the zinc present, which interferes with the 
 course of the smelting, must be counteracted by decreasing the lime and increasing the 
 iron in the charge, and by the addition of slags from the same work. 
 
 At Mechernich the ores are roasted in eighteen furnaces with double sides, with 
 working-doors on both sides, and with rails laid on both the longer sides of the furnaces, 
 for the sake of possible working on the sole of the upper hearth. Each furnace is 
 15 metres long by 4 in breadth, and the whole length available for roasting is 
 24 metres, with a width of 3*1 metres. There is room to receive 50,000 to 55,000 kilos, 
 of ore, and the production of roasted ore is 8000 to 10,000 kilos, in twenty-four hours, 
 so that a lot of ore remains from five to six days in the furnace, which is always 
 kept full. The ore is kept constantly stirred up as it approaches the bridge. The 
 imperfectly liquefied mass is let off every six hours in a form made of rails laid together 
 in front of the furnace, and broken up when cold. There are used 15 per cent, of 
 fuel for the vitreous product, which resembles obsidian, and has the following 
 composition : 
 
 Lead . . 58*85 corresponding to PbS . . 3-47 
 
 PbO . . 60-57 
 Copper . . 0-38 Cu 2 S . . 0-48 
 
 Antimony . 0*22 
 
 Iron . . 2-70 
 
 Zinc . . 0-82 
 
 Nickel . . 0-75 
 
 Manganese . 0-36 
 
 Alumina . 4*80 
 
 Sb 2 S s . . 0*30 
 
 Fe 2 s . . 3-90 
 
 Zno .' . 1-05 
 
 NiO v . 0-92 
 
 Mn 2 g . . 0-51 
 
 A1 2 8 . . 4-80 
 
 Lime . . 0-31 CaO . . 0-31 
 
 Silica . . 23-65 SiO 2 . . 23-65 
 
 Sulphur . . o'66 
 
 The fumes given off in roasting traverse a system of chambers of 10,015 
 metres, and then a chimney 66 metres in height. The ore is melted in nine shaft- 
 furnaces of 7 metres in height and 4-8 metres in length. The height of the furnace- 
 shaft from the forms, which are placed in four bronze water-troughs, along the back 
 wall to the mouth of the funnel of the working-door is 3*8 metres ; the depth of the 
 level of the forms i'2 metre, with an enlargement to 1*5 metre at the top; the height 
 of the crucible, moulded of sweepings, is i metre. For letting off the lead are two 
 lateral tapping-channels opening into the crucible, 13 to 15 centimetres above its 
 bottom ; the tapping-hole for slags is 40 centimetres below the diameter of the forms. 
 Iron pots suspended in trucks serve to receive the slag in such a manner that it flows 
 over from a larger pot (interposed to keep back lumps of lead matte) into a smaller 
 one. The charges for the furnace are placed in tilting-trucks, which (with the 
 exception of the limestone) are raised by tackle to the level of the furnace-mouth. 
 The charge consists of 100 parts of roasted ore, 5 parts of furnace bottoms, 35 iron- 
 finery slags, 15 raw sparry iron, 45 limestone, 10 lead slags, and 25 coke. Of the nine 
 shaft-ovens only four are in regular work, which get through 282,400 kilos, of charge 
 in twenty-four hours, and yield 73,000 kilos, of work-lead. If the slag, which is daily 
 
172 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. ii. 
 
 PbS 
 
 Cu 2 S 
 
 Sb 2 S s 
 
 FeS 
 
 NiS 
 
 Si0 2 
 
 9-24 
 
 i'9S 
 0*40 
 
 32-34 
 0-40 
 0-31 
 
 tested in an iron crucible with borax, soda, and a little tartar, yields more than 0*7 lead, 
 it is re-smelted. The matte is ground, roasted, and mixed with the raw ores. 
 
 Matte. Lead Slag. Work-Lead. 
 
 Si0 2 . . 27*00 Silver . . 0-0215 0-0250 
 
 P 2 5 . . 3-79 Copper . . 0-13320-1396 
 
 A1 2 O, . . 5'6i Antimony . 0-2180 0-1586 
 
 CaO . . 20-30 Iron . . 0-030 0-014 
 
 Sulphur . . 1*26 Nickel . . trace 
 
 Lead . . 1-02 Zinc . . o'oo6 
 
 Copper . . 0-35 
 
 Antimony . trace 
 
 Iron . . 25-81 
 
 Manganese . 0-62 
 
 Flue-dust. According to Freudenberg, the deposit of flue-dust is proportional to 
 the temperature of the gases and the size of the surface of the walls. Hence the 
 deposit decreases more rapidly in the upper compartments of the chambers than in the 
 lower. The proportions of silver, zinc, and antimony are greatest near the furnace, 
 and decrease with the length of the flues. Samples taken contained 60-5 to 67 per 
 cent, of lead, 3-2 to 4*2 zinc, 0*003 silver, 14-1 to 14*8 sulphuric acid, 5-4 to 6'2 sulphur, 
 i to 2'i ferric oxide and alumina, 5-8 to 8 coal, 0-3 to o'4 antimony, o'i6 to 0*24 
 arsenic, and o'6 to 4-1 lime. It appears, further, that the quantities of metals deposited 
 in the smoke-channels as flue-dust are proportional to the square surface of the sides 
 of the flues. He recommends, therefore, that metal sheets, &c., should be suspended 
 parallel to the direction of the draught. Schlosser proposes the use of refrigerating 
 pipes, and Walker that of electricity, which latter process is said to have proved unsuc- 
 cessful. 
 
 Work-lead. The work-lead obtained contains silver, copper, antimony, &c. For 
 the separation of the silver, see SILVER. The litharge produced is either used as such 
 or reduced to metallic lead. The reduction is effected in a reverberatory, the litharge 
 being mixed on the hearth with charcoal. The lead thus obtained contains a little 
 copper, antimony, and perhaps some silver. It is therefore less soft than lead produced 
 from pure litharge. The composition of different sorts of Freiberg leads appears from 
 the following analyses by Reich : 
 
 
 i. 
 
 3. 
 
 3- 
 
 4- 
 
 & 
 
 Lead . 
 Arsenic 
 
 97-72 
 1-36 
 
 99-28 
 
 O'i6 
 
 87-60 
 7-90 
 
 90-76 
 1-28 
 
 87-60 
 0*40 
 
 Antimony 
 
 0-72 
 
 trace 
 
 2-8o 
 
 7'3i 
 
 1 1 -60 
 
 Iron 
 
 0-07 
 
 0-05 
 
 trace 
 
 0-13 
 
 trace 
 
 Copper 
 ^Silver . 
 
 0-25 
 0-49 
 
 0-25 
 0'53 
 
 0*40 
 
 o'35 
 
 trace 
 
 Electric Production of Lead. The process of Bias and Miest is based on the fact 
 that the native sulphides conduct electricity when they are compressed into plates, with 
 the aid of heat. To this end zinc blende, galena, &c., are comminuted to grains of about 
 5 millimetres in diameter, pressed into plates in metal moulds, under a pressure of 100 
 atmospheres, heated to 600 in a furnace, pressed again and quickly cooled, that they 
 may be easily extracted from the moulds. Plates of galena thus obtained are suspended 
 as anodes in a bath of lead nitrate. There is here little chemical work to be performed, 
 as, according to PbfNO,), + PbS = Pb(NO a ), + Fb + S, the work needed at the negative 
 pole for the decomposition of the lead nitrate is compensated at the positive pole, so 
 that chemical work is needed only for decomposing the lead sulphide; hence, for i kilo, 
 lead 18-328 : 207 = 89 heat-units. If we take into account resistance, transportation 
 
SKCT. ii.] LEAD. 173 
 
 of ions, &c., or only a 30 per cent, utilisation of the power of the machine, we should 
 have hourly for each horse-power 2 kilos, of lead and an equivalent quantity of sulphur. 
 Practically speaking, the matter is still involved in difficulties. 
 
 Keith's process for refining lead by electrolysis is carried out by the Electrometal 
 Refining Company of New York. In each of a set of 30 vats, i metre in height and 
 1*83 metre wide, there are immersed as kathodes 13 cylinders of thin sheet brass, 
 arranged concentrically, so that they are o'6i to 1*83 metre in diameter. They are 
 immersed to a depth of o'6 metre. The crude lead, smelted in a reverberatory, is 
 poured into 12 moulds 61 centimetres long, 15 broad, and 3 millimetres in thickness, to 
 form plates for the anodes. The solution of lead sulphate (nitrate ?) and sodium acetate 
 is forced from below continuously into the vats, through wooden pipes laid below the 
 vats, whilst it flows off above to be heated in a cistern to 38 by means of steam pipes, 
 and again conveyed to the vats, so that it is in constant circulation. The muslin bags 
 enclosing the anodes retain silver, along with arsenic, antimony, &c. The silver is 
 melted along with saltpetre and soda. The lead, before and after this treatment, has 
 the following composition : 
 
 Crude. Refined. 
 
 Lead 96*36 ... 99-9 
 
 Silver 0-554 ... 0-00007 
 
 Copper .... 0-315 ... o 
 
 Antimony .... 1-070 ... trace 
 
 Arsenic . . . .1-22 ... trace 
 
 Zinc and Iron . . . 0-489 ... o 
 
 If 12 h.-p. are used, 10 tons of lead are refined in 24 hours, in 48 vats, each containing 
 50 plates weighing each 16 kilos. Consequently, if i h.-p. requires 1*75 kilos, of coal 
 hourly, 67-1 kilos, of coal are used per ton of lead. 
 
 Properties. Lead as it occurs in commerce, refined and Pattinsonised, has a peculiar 
 light grey colour. It is little disposed to assume a crystalline texture, and has on its 
 fracture a uniformly melted appearance. In certain metallurgical processes it may be 
 obtained crystallised in the forms of the tesseral system (combination of cubes and 
 octahedra). Lead is distinguished by softness and flexibility ; hence, it has a somewhat 
 high degree of malleability, but little absolute tenacity. If freshly scraped or cut, it is 
 very brilliant, but it soon becomes dull on exposure to the air. It marks strongly on 
 the hands, on paper, and on linen fabrics. The spec. gr. of refined lead is 1 1*370 ; that 
 of cast lead, 11-352, and that of rolled lead, 11-358. In the manufacture of sheet lead 
 oxidation has to be avoided. Lead is one of the easily fusible metals ; it solidifies quietly, 
 i.e., without spirting, and with a concave surface. If heated almost to the melting- 
 point it becomes brittle, and breaks under the hammer in fragments of a peculiar rod- 
 like structure. If heated to a certain degree, it may be pressed into solid or hollow 
 cylinders : the former serve for projectiles and the latter for pipes, which are now 
 manufactured on a large scale. At a full white heat, and if air is excluded, it enters 
 into ebullition and evaporates. Lead takes up at most 1*5 per cent, of zinc and 0-07 per 
 cent, of iron, but so much the more copper as the temperature rises. 
 
 The uses of lead are very various. It is employed in the form of rolled plates for 
 roofing, for boiling-pans for sulphuric acid, copperas, and alum ; lead chambers in the 
 manufacture of sulphuric acid ; water- and gas-pipes and retorts ; in thin leaves for 
 wrapping up snuff; in the manufacture of small shot and bullets; in metallurgical 
 processes for the extraction of certain metals, e.g., silver and gold ; for the production 
 of sugar of lead, red lead, white lead, and other lead preparations. 
 
 Manufacture of Small Shot. Shot is remarkable as no moulds are needed in its 
 preparation. It consists of solidified drops of lead. The lead is not used pure, but 
 alloyed with a small quantity of arsenic, 0-3 to o - 8 per cent., which gives it the power 
 of granulating more easily. Too much arsenic gives the grains a flattened aspect, and 
 
i 7 4 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 too small a proportion renders them longish. The arsenic is added either as such, as 
 sulphide, or as arsenious acid. If it is used in the last state, the surface of the lead 
 is covered with charcoal powder, the heat raised to redness ; the arsenic, wrapped in 
 coarse paper, is placed in a basket of iron wire, plunged into the melted lead, and well 
 stirred. For granulating the lead there are used iron kettles, with a flat bottom, 
 provided, like a sieve, with round holes of equal diameter. If the lead were at once 
 poured into the kettles, there would be produced more oval than round grains. 
 There is therefore placed in the kettle a porous mass, which attaches itself to 
 the sides, and keeps the lead at such a temperature that it flows through, neither 
 too easily nor too tardily. The substance used is the dross drawn off from the surface 
 of the molten metal. As the liquid metal oozes through this mass, and flows in single 
 drops through the holes in the kettle, it takes a globular form in falling, like every 
 other liquid. The grains, congealed whilst falling from a great height, are received in 
 water which holds in solution in 100 parts 0-025 sodium sulphide. A thin film of 
 lead sulphide is thus formed round the grains, and defends them from oxidation. 
 
 Alloys. Soft solder, for tinmen, &c., consists of equal parts lead and tin ; organ- 
 pipe metal (96 parts of lead and 4 of tin) ; antifriction metal (4 tin, 5^ lead, and 
 i antimony) ; hard lead (an alloy of lead and antimony) ; the alloy for ships' nails (3 
 parts tin, 2 lead, i antimony) ; the calain of the Chinese, used in foil for lining tea- 
 chests (126 parts lead, 17' 5 tin, 1*25 copper, and a trace of zinc). Other alloys, such 
 as type-metal, are mentioned under ANTIMONY. 
 
 Production of Lead. The annual production of lead for the whole of Europe was, 
 in 1885, 330,000 to 350,000 tons, and that of North America 120,000 tons. The annual 
 average consumption of lead maybe estimated as: North America, 13 5,000 tons; 
 Britain, 115,000 ; France, 6500 ; Germany, 45,000 ; and the rest of the world, 100,000 
 tons : in all, 460,000 tons. The consumption in France for lead pipes and lead plates has 
 decreased to a very remarkable degree. 
 
 SILVER. 
 
 Silver occurs in nature very abundantly; partly metallic (usually auriferous); 
 partly combined with arsenic, antimony, tellurium, and mercury ; partly as sulphide, 
 mingled with other sulphides ; and partly as a chloride. The most abundant silver 
 ores are : Argyrose (silver glance), Ag 2 S ; argyrythrose (dark-red silver), Ag 3 SbS 3 ; 
 proustite (light-red silver), Ag 3 AsS 3 ; miargyrite, Ag 2 Sb s S 4 , with small proportions 
 of copper and iron; psaturose (prismatic melane glance, brittle silver sulphide), 
 CuAg 2 S + Sb 2 S 3 ; polybasite, [(Ag 2 SCu 2 S) 9 Sb 2 S 3 ] ; and freieslebenite [(FeS,ZnSCu 2 S) 4 , 
 Sb,S 3 + (PbSAg 2 S) 4 Sb 2 S 3 ]. 
 
 As chloride (horn silver), AgCl 2 , silver occurs in some quantity in Utah.* 
 
 Lastly, silver occurs in galena, which contains o'oi to 0-03, sometimes 0-5, rarely 
 i per cent. ; in copper ores, copper pyrites, chalkosine, and phillipsine, with 0-020 to 
 i 'i per cent, of silver; in cupriferous pyrites (from which, when burnt, silver and 
 copper are now obtained) ; in the fahl ores, in blende, and calamine. 
 
 Extraction. Silver is obtained 
 
 I. In the wet way. 
 
 1. By means of mercury amalgamation. 
 
 2. By solution and precipitation, on the systems of Augustin, Ziervogel, and 
 
 other procedures. 
 
 II. In the dry way. 
 
 1. Obtaining argentiferous lead. 
 
 2. Extraction of silver from argentiferous lead. 
 
 * Silver chloride exists in solution in sea water, but the quantity is so small that its extraction 
 is not remunerative. 
 
SECT, ii.] SILVER. 175 
 
 Silver is rarely smelted out from its ores, which can be undertaken only with such 
 as are rich in native silver. The silver thus obtained is mostly rich in gold, and is 
 submitted to the process of refining. 
 
 Amalgamation. The extraction of silver by means of mercury, or the amalga- 
 mation process, is followed in the case of very poor silver ores (argentiferous copper 
 matte, speiss, &c.). 
 
 In the process as formerly used in Europe, 10 per cent, of common salt was added 
 to the ores to be amalgamated, and the mixture was roasted to drive off antimony 
 and arsenic. By the mutual action of the salt and the roasted pyrites, were formed 
 sodium sulphide, ferric chloride, and escaping sulphurous acid ; further copper sulphate, 
 and ferric sulphate, which oxidised the untransformed part of the silver sulphide 
 to silver sulphate, being themselves reduced to cuprous and ferrous sulphates. By 
 the action of the residual salt were formed silver chloride and sodium sulphate. 
 The other metals present were, like the silver, converted into chlorides. When the 
 roasting was completed the brown mass was ground and placed in the amalgamation 
 vats, in which they were mixed with water, scrap iron, and mercury, and turned for 
 1 6 to 1 8 hours. The metals were precipitated on the iron and became amalgamated 
 with the mercury. 
 
 To explain the nature of the amalgamation process, let us suppose that a silver 
 ore : Cu 2 S, Ag 2 S, FeS + As 2 S 3 , Sb 2 S 3 , is being worked. After the roasting with salt there 
 are found CujCl., 2AgCl, Fe01 2 , 3Na 2 S0 4 , and As 2 3 , Sb 2 3 , 6S0 2 . 
 
 For the amalgamation vats there are produced by the joint action of the iron, 
 mercury, and water : 
 
 Cu 2 01 2 ,2AgCl,FeCl 2 + Na 2 S0 4 + 2Fe + nHg = Na 2 S0 4 + (Cu 2 ,Ag 2 ,nHg) + 3FeCl 3 . 
 The amalgam collects at the bottom of the vats, and is let off by means of a spigot 
 turning downwards, through straining cloths of ticking, into stone troughs. 
 
 In order to separate the superfluous mercury, the sack is tied at its mouth and 
 pressed between boards. The solid amalgam remaining in the bag, and containing about 
 1 1 per cent, of silver and 3 to 4 per cent, of copper, is laid on iron plates in the 
 apparatus for distilling mercury (q.v.). The cupriferous silver (plate silver) is left 
 behind. 
 
 The American, or wet amalgamation (patio process) is practised in Mexico, Peru, 
 Chile, Bolivia, and in the Western States of North America. The silver ores are stamped 
 whilst dry, and then finely ground with water. The stamped ore is conveyed to the 
 ore-mills (Ai'rastras) and ground with the addition of water. The thin mud is 
 conveyed to a court (patio) laid with stone flags slightly sloping, so that the rain- 
 water may run off. The ore-mud, to which from 2 to 5 per cent, of common salt 
 is added, is well trodden by mules or horses. After a few days there is added 
 magistral, roasted copper pyrites, therefore essentially copper sulphate. This is also 
 well trodden in, and by degrees mercury is added, about six times the weight of the 
 silver contained in the ore (Incorporation). The treading is continued on alternate 
 days for a term of two to five months, until the mass seems completely de-silvered. The 
 mud is then washed in cisterns of masonry to separate the amalgam, which is freed 
 from superfluous mercury by pressing in bags of ticking, and distilled at a reduced 
 pressure. 
 
 In the amalgamation process as generally followed in America, copper chloride and 
 silver, according to Rammelsberg, form cuprous chloride and silver chloride 
 
 2 CuCl 2 + 2 Ag = 2 AgCl + Cu 2 01 2 . 
 Silver sulphide is completely decomposed at a boiling heat by copper chloride 
 
 Ag 2 S + Cud, = 2AgCl + CuS. 
 
 Sodium chloride has a solvent action upon silver chloride and accelerates the process of 
 decomposition. Cuprous chloride and silver sulphide yield silver chloride and dicuprous 
 
176 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 sulphide : Ag 2 S + Cu 2 Cl 2 = 2AgCl + Cu 2 S. If cuprous chloride is previously dissolved 
 in sodium chloride the transformation is more rapid, but a quantity of silver chloride 
 remains in the liquid. If zinc is added to the separated mixture and the solution of 
 common salt is heated, there remains a mixture of z molecules silver and i molecule 
 Cu a S. Copper chloride and arsenic sulphide yield quickly copper sulphide and arsenious 
 chloride : As 2 S 3 + aOuCl, = 3CuS + 2 AsCl 3 . On the other hand, the greenish grey deposit 
 obtained by the action of copper chloride upon antimony sulphide, Sb 2 S 3 , contains, along 
 with sulphur and copper, much antimony, as also chlorine and oxygen, in consequence 
 of the decomposition of antimony chloride by water and formation of oxychloride. But 
 a great part of the antimony remains in the solution, which contains sulphuric acid. 
 As the analysis shows that the separated copper and chlorine exist in the same 
 proportions as in cuprous chloride, we may assume that the rest of the chlorine has 
 oxidised a part of the sulphur. Cuprous chloride and antimony sulphide behave in a 
 similar manner, but the copper seems to be present chiefly in the metallic state in 
 the matter deposited, which also contains antimony oxychloride and, on standing, 
 antimonic acid is deposited from the richly cupriferous nitrate. Both kinds of red 
 silver ore (argyrythrose and proustite) are decomposed by cupric chloride. In the 
 separated mass, which is black in the arsenical ore and grey in the antimonial, there 
 are found the silver, the antimony, but only half the arsenic. The silver is entirely 
 found as chloride in argyrythrose, but only to the extent of one half as proustite ; the 
 rest of the deposit consists of copper sulphide and free sulphur. 
 
 Among the usual modifications of the amalgamation process, one treats the ore with 
 water, salt, and mercury, in presence of iron or copper ; the other employs water, salt, 
 copper chloride, and mercury. The first method figures in the tina process, using a 
 wooden vat with an iron bottom, and, in the cazo-oder calderon process worked, with 
 the addition of salt, in wooden or stone vessels, and the washoe process, which requires 
 iron kettles and runners. The two latter methods require the aid of heat. 
 
 The second method comes into play in the patio process, above described ; and 
 characterised by the use of magistral. The choice of the two principal processes 
 depends on the chemical character of the ores. The first requires that the main mass 
 of the silver should be native, as is the case in the pacos in Peru, in the metas 
 calidos in Chile, and the Colorados in Mexico, which often contains silver chloride and 
 bromide. The silver is easily amalgamated, as are also the chloride and bromide if 
 copper or iron is present. The sulphur compounds existing at greater depths silver 
 glance, argentiferous fahl-ores, and pyrites must be treated by the patio process. 
 Though Rammelsberg's experiments prove that silver sulphide and argyrythrose can, 
 under favourable circumstances, be reduced by copper chloride, it is still very doubtful 
 whether this process can extract the whole of the silver from sulphur ores on the 
 large scale. 
 
 The Kroncke process, which has been in use in Northern Chile for some time, 
 consists in amalgamation, in vats, in which the agents are cuprous chloride, zinc, and 
 mercury. The air is almost excluded, and the amalgamation is effected within a few 
 hours. Experiments have shown that the sulphur ores can thus be completely decom- 
 posed, and the results of the process are described as very satisfactory. 
 
 Extraction of Silver "by Solution and Precipitation. The ores are here roasted, 
 either alone or after the addition of salt. For the latter method the roasting furnace 
 of Stetefeld has proved successful. The ore, mixed with from 2-5 to 18 per cent, of 
 sodium chloride, slides down in the shaft B (Fig. 178), from 9 to 14 metres in height, 
 meeting at the hot gases coming from the fires at 6f, whilst air enters at M. The 
 doors, P and 7?, serve for watching and regulating the process. The roasted ore is let 
 fall into the recipients, N, by opening a trap, C, at the bottom, and is here slowly cooled 
 to complete the chlorination. The gases escape through the shaft H, provided with 
 
SECT. II.] 
 
 SILVER. 
 
 177 
 
 man-holes, S, and additional fire, E, in order to deposit their flue-dust in the funnels, 
 F. With large furnaces and great quantities of ore operated upon, 50 per cent, of the 
 ore collects in the flue-dust chambers, of which 80 per cent, settles in the first compart- 
 ment. In order to effect the chlorination of any silver that has escaped the action of 
 chloride in the furnace, the flue-dust chambers are only emptied occasionally, the last 
 compartment once weekly. The escaping gases enter a chimney not less than 16 
 metres in height. In the same furnace the weight of ore worked iu 24 hours is 
 
 Fig. 178. 
 
 Fig. 179. 
 
 70 tons of ores poor in sulphur, 
 but only 30 tons of ores of such as 
 contain pyrites and blende. As 
 the roasting is very rapid the loss 
 of silver here is said to be smaller 
 than in a reverberatory. The 
 coarseness or fineness of the ore 
 is regulated by the manner in 
 which it is to be afterwards 
 treated. If the ore is intended 
 for amalgamation it must be 
 ground more finely than if it is 
 to be submitted to lixiviation 
 (with sodium thiosulphate) as mercury cannot be entirely washed out from coarsely 
 ground ores. The rotatory fvirnace of Bruckner is used in many places. The modi- 
 fication proposed by Arent (Fig. 179) has the object that in the part of the cylinder, 
 c, situated nearest to the fire, A, the ore is more heaped up than towards d. The 
 revolving furnace is filled through the hopper, e, and the aperture, o, and emptied 
 through p into the iron chest, k, or the recipient, f, provided with a sliding door, g. 
 The rotation is effected by the rollers, I, and the cast-iron rings, ra. 
 
 Augustiris Process. The most ancient hydro-metallurgical process for extracting 
 silver is that of Augustin the so-called salt lixiviation. It depends on the formation 
 of an easily soluble double chloride when silver chloride is brought in contact with 
 an excess of strong solution of common salt with the aid of heat, and on the power of 
 copper to expel the silver completely from the saturated solution of this compound. 
 The copper-matte, consisting chiefly of silver, copper, and iron sulphides, are reduced 
 to fine powder by stamping and grinding, and are roasted at first without salt. There 
 is then formed, first iron sulphate, then copper sulphate, and lastly, as the temperature 
 is raised, silver sulphate, by which time all the iron sulphate and a great part of the 
 copper sulphate are decomposed, so that the mixture at the end of this preliminary 
 
1 78 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 roasting consists of iron oxide, copper oxide, and small quantities of copper sulphate. 
 By continuous roasting with common salt the silver sulphate is converted into silver 
 chloride. The mass is then lixiviated with a hot saturated solution of salt, which 
 dissolves the silver chloride. From the liquid the silver is precipitated by metallic 
 copper, and the copper is recovered from the coppery solution by means of metallic 
 iron. 
 
 (For the extraction of silver from burnt pyrites see SULPHURIC ACID.) 
 
 Ziervoyel's Process. In this lixiviation process no salt is added on roasting. The 
 roast ore, consisting mainly of silver sulphate, a little copper sulphate, much copper 
 oxide and iron oxide is extracted with hot water, which dissolves the silver and copper 
 sulphates. From this solution silver is precipitated by metallic copper, and copper 
 sulphate is obtained as a by-product. 
 
 At Mansfeld this process has been in use for many years for desilverising copper 
 matte. The lixiviation is rapidly effected ; whence there is a less outlay for fuel and for 
 labour than in the Augustin process. On the other hand, the roasting is less easily 
 effected, richer materials are needed, and, as a rule, the residues are richer. In 
 presence of arsenic and antimony the Ziervogel process is inapplicable, since on 
 roasting there are formed silver arseniate and antimoniate, insoluble in water. The 
 presence of lead easily leads to fritting, which makes the roasting difficult. 
 
 Other Procedures. Of late ores of gold and silver have been extracted with 
 sodium thiosulphate (formerly known as hyposulphite of soda). This process is in 
 use in California and Nevada, after the ores have been roasted with 3 per cent, of 
 common salt : AgCl + Na 2 S 2 3 = NaCl + NaAgS 2 3 . The solution is mixed with a 
 solution of calcium sulphide : 
 
 2NaAgS 2 3 + 2NaCl + CaS = Ag 2 S + 2Na 2 S 2 3 + CaCl 2 . 
 
 The lye drawn off from the precipitated silver sulphide is used again. Care must 
 be taken that no excess of calcium sulphide is present, as this would subsequently 
 occasion a precipitation of the dissolved silver in the lye-vats in the state of silver 
 sulphide. Such silver would not be redissolved in the thiosulphate, and would conse- 
 quently be lost. If the ore contains gold it is preferable to use calcium thiosulphate. 
 This salt is prepared by boiling lime with sulphur, 3CaO+ 128= 2CaS 5 + CaS 2 3 , 
 letting the solution subside, and passing sulphurous acid into the clear lye till the sulphide 
 is converted into thiosulphate and a dilute solution of silver is no longer precipitated. 
 
 According to Russel, ores which contain silver in combination with arsenic and 
 antimony, and from which the precious metals cannot be extracted by lixiviation with 
 sodium thiosulphate, can be treated either at once or after mixing with thiosulphate, 
 with a solution produced by mixing thiosulphate with a solution of copper, preferably 
 copper sulphate. There is formed according to the equation : 
 
 4Na 2 S 2 3 + 2 CuS0 4 = aCuS,O,.Na,S,O, + 2Na 2 S0 4 + Na 2 S 2 3 , 
 a sodium copper thiosulphate, in which silver is easily substituted for copper. 
 
 Extraction of Silver in the Dry Way. The extraction of silver from its ores by 
 means of lead depends (a) On the property of lead to act upon silver sulphide with 
 formation of lead sulphide and separation of metallic silver. Other sulphides accom- 
 panying the silver, especially copper and iron sulphides, are less readily decomposed by 
 lead. The products of the fusion are argentiferous lead and a matte free from silver, 
 but containing lead, copper, and iron sulphides. The extraction of silver by lead is the 
 more complete the poorer are the ores in copper. 
 
 (b) On the decomposing action of lead oxide or lead sulphate upon silver sulphide : 
 
 Ag 2 S + 2PbO = Pb 2 Ag 2 + SO,. 
 
 (c) On the reducing action of lead upon silver oxide or silver sulphate : 
 
 3Pb + Ag 2 SO 4 = PbAg 2 + 2 PbO + S0 2 . 
 
 (d) On the greater affinity of silver for lead than for copper. If argentiferous 
 
.SECT, ii.] SILVER. 179 
 
 copper is melted up with lead there is formed an easily fusible argentiferous lead and 
 an alloy of copper and lead which melts with difficulty. The former can be separated 
 from the latter by eliquation. 
 
 To this process there are subjected genuine silver ores, roasted pyritic ores, argenti- 
 ferous copper and lead ores raw or roasted, and roasted argentiferous native arsenic. 
 The essential feature of the process is the treatment of the materials with melted lead. 
 An argentiferous work-lead is formed just as in the treatment of galenas containing 
 .silver. 
 
 The treatment of the work-lead may be effected (i) on the refiner's hearth, (2) by the 
 Pattinson process, and (3) by the Parkes process (by means of zinc). 
 
 The refining on the hearth turns on the fact that the readily oxidisable lead is 
 separated by a simple oxidising fusion from the non-oxidisable metals, care being taken 
 that the lead oxide formed is partly drawn off and partly absorbed into the pores of 
 the hearth. The surface of the metallic bath is oxidised as long as the alloy contains 
 lead, and the silver remains behind. 
 
 The hearth is a round reverberatory, with a fire-box F built up to it (Fig. 180). 
 
 'The hearth A is covered with a hood a, 
 
 Fig. 1 80 
 of sheet-iron, lined with fire-clay B which 
 
 can be raised or lowered by the arrange- 
 inent D. The hearth is made of lixi- 
 viated ashes, or preferably of calcareous 
 marl ; in the middle is a depression 
 to collect the silver. In the space sur- 
 rounding the health is the litharge-hole, 
 during working kept closed with the 
 same material of which the hearth is 
 made so far that it is on the same level 
 as the upper surface of the melted lead in 
 the furnace, so that the litharge formed 
 upon the metal may flow off. As soon as the quantity of the work-lead decreases the 
 mass in the litharge-hole is partially removed ; this channel-like depression is called 
 the litharge road. The hole P opposite the fire-bridge serves for introducing the 
 hearth-mass and the materials. The tuyeres of the blast open at a. 
 
 The refining is continued until the silver on the hearth is covered only with a thin 
 film of litharge, which disappears as rapidly as it is formed. The formation and dis- 
 appearance of the film is recognised by a play of colour the brightening of the silver. 
 
 As soon as this phenomenon is recognised the firing is ceased, the silver is cooled 
 by sprinkling with water, and lifted out of the furnace. The liquid lead-oxide flowing 
 off congeals on cooling to a foliaceous crystalline mass of a yellow or reddish- 
 yellow colour, litharge. 
 
 The Pattinson Process. The rule holds good that work-lead with a percentage of 
 silver less than 0-12 cannot be further refined by cupellation. The process indicated by 
 Pattinson (in 1883) is based on the phenomenon that if we melt a sufficient quantity 
 of lead in an iron kettle and let the liquid mass cool uniformly there are formed small 
 octahedral crystals which cohere at their ends. These crystals are much poorer in 
 silver than the original alloy, whilst the silver is concentrated in the part which 
 remains liquid. If we melt these crystals and proceed as before, there are again 
 formed crystals, which are still poorer than the foregoing. By a succession of such 
 separations the lead is resolved into two portions, a small part rich in silver, rich lead 
 (containing 0-5 to 1-5 per cent, of silver), and a larger portion, very poor lead (contain- 
 ing o-oo i to 0-003 per cent, of silver). As the limit up to which the lead can be 
 enriched by the Pattinson process, we may fix 2*5 per cent, of silver. 
 
i8o 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. IT. 
 
 A desilvering of lead by means of zinc was proposed by Parkes in 1850. 
 
 Work-lead is placed in an iron pan ; when melted 5 per cent, of melted zinc is 
 added, and after thorough stirring the mixture is let stand until the zinc congeals to a 
 cake, which is lifted off. The zinc in the earlier process was separated from the silver 
 by distillation. After the completion of the distillation the residue is taken out, 
 mixed with some lead, and refined on the hearth. According to a modification, intro- 
 duced by Cordurie, the zinc is oxidised by superheated steam (Zn -f H 2 = ZnO + H 2 ). 
 The zinkiferous work-lead left after being thus desilverised is freed from zinc by heat- 
 ing with lead chloride, as a mixture of lead sulphate and sodium chloride, then lead 
 chloride is formed (Zn + PbCL, = ZnCl 2 + Pb). According to Flach's proposal the zink- 
 iferous lead is treated with puddling slags in a shaft-furnace to scorify and volatilise 
 the zinc. The zinc process has become almost universal in Britain, France, and 
 Germany. 
 
 The advantages to which this process is indebted for its rapid introduction consist, 
 according to Plattner, especially in the circumstances that 
 
 1. The process does not require the work-lead to be previously refined, so far 
 
 as the removal of inconsiderable quantities of copper, arsenic, and 
 antimony is concerned ; 
 
 2. The work is effected with only small quantities of intermediate products ; 
 
 3. That it requires a smaller apparatus with fewer workmen and a reduced 
 
 outlay for fuel ; 
 
 4. That it effects the separation of silver from lead in much shorter time than 
 
 the Pattinson process ; 
 
 5. That it yields a decidedly smaller and proportionally richer quantity of rich 
 
 lead, to be refined ; and lastly, 
 
 6. That the process involves a more moderate loss of lead. 
 
 A further advantage of the Parkes process is that a minimum proportion of gold, 
 present in the work-lead, can be first extracted by a small addition of zinc, and a zinc 
 scum obtained which furnishes a small quantity of auriferous silver, whilst the 
 subsequent main quantity of silver extracted by a second treatment with zinc is free 
 from gold. 
 
 At the Mulden Works at Freiberg the Pattinson and Parkes processes are combined 
 in such a manner that the former process is interrupted in that pan where it is expected 
 that bismuth may be obtained, which passes into the rich lead. In the Pattinson 
 process there is here employed a battery of 9 cast-iron pans, each of 1-75 metre 
 diameter at top, 0*90 metre in depth, and receiving each a charge of 150 hectokilos. 
 For the Parkes process (Figs. 181-184) there are set up, with separate fires: 2 cast- 
 Fig. 181. 
 
 iron desilvering pans, a, of 1-98 metre top-diameter, i-o metre in depth, and each 
 holding 200 hectokilos.; 3 cast-iron hemispherical eliquation pans, b, of 0-55 metre; i 
 refining furnace, c with a fire-clay hearth 3 metres long, 2 metres wide and 0-45 metre 
 
SECT. II.] 
 
 SILVER. 
 
 181 
 
 deep for freeing the poor lead from zinc, and i cast-iron pan, d of 1-9 metre diameter 
 at top and i metre deep to receive the poor lead when freed from zinc. 
 
 The apparatus for the Parkes process is so united with the Pattinson apparatus 
 that the two desilvering pans and the three eliquation pans of the Parkes process, placed 
 at the same level, lie with their edge 2 metres higher than the edge of the Pattinson pans, 
 
 Fig. 182. 
 
 JL 
 
 so that the zinkiferous poor lead can be conveyed by means of syphons (Fig. 185) 
 whilst still liquid, into the following refining-furnace placed with its sole 2 metres 
 lower than the margin of the 
 desilvering pans. The pan for 
 the de-zinkified poor lead is built 
 in with its margin 10 centi- 
 metres below the sole of the 
 refining furnace. 
 
 From it the poor lead can be 
 led off through pipes (which can 
 be closed by a conical valve) and 
 a movable channel. It is then 
 run into cast iron moulds to give 
 it a form suitable for trade. The 
 conveyance of the lead from the 
 Pattinson battery and of other 
 refined work-leads, poor in silver, 
 to the level of the desilvering 
 pans is effected by a simple steam 
 lift. The last pan of the Pat- % 
 tinson battery is emptied of the 
 work-lead containing o'i per cent, of silver and destined for the Parkes process by means 
 of the Rosing steam-pump. For mixing in the zinc there is used an agitating scoop, 2-3 
 metres in length with 100 to 1 20 holes to let the lead drop through (Fig. 186) ; for lifting 
 off the zinc scum there is used a similar scoop with a shorter handle. For distilling 
 
182 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. ii. 
 
 the rich scum there are used two wind-furnaces (Fig. 187) with a round shaft 0-75 
 metre in width and 0^9 metre deep down to the level of the grate. On the movable 
 ring e, of angle iron and strong sheet iron lined with fire-clay lies a cover, f, of clay 
 plates resting in a ring of angle iron. The ring and the cover can be lifted off either 
 separately or jointly by means of pulleys. 
 
 The graphite crucible is 55 centimetres high, with sides 5 centimetres thick; the 
 
 Fig 185. 
 
 cover, of graphite, A, 20 centimetres; the graphite pipe, i, is 50 centimetres in length, 
 with sides 2-5 centimetres in thickness. The iron receiver k, ^ metre in height rests on 
 an iron bottom plate and has a movable lid. All the refined work-leads containing 
 more than 0*1 per cent of silver, if not worth separate treatment on the hearth, are 
 conveyed to a pan of the Pattinson battery, according to their proportion of silver, and 
 are there worked to a rich lead of 2 per cent, and a poor lead of o'i per cent. The 
 rich lead goes to the refinery hearth and the poor lead to the Parkes process. 
 
 To desilver this work-lead by means of zinc, after the lead has been fused in the 
 desilvering-pan, the solid pieces formed are lifted off with the scum scoop, until the 
 lead -bath has a perfectly clean surface. When the lead has been heated up to the melting 
 point of zinc (by means of a cover), the first addition of zinc takes place. When it 
 has been thoroughly stirred into the lead, the mixture of metals is left undisturbed 
 until a crust, about 3-4 centimetres in breadth, has been formed at the edge of the 
 pan. The zinc scum, which has come to the surface and covered it, must be lifted off 
 with the perforated scoop, letting the adhering lead carefully drop back. The zinc 
 scum from the first additions of zinc being rich in silver (rich scum) is transferred to 
 the adjacent eliquation pans, whilst the scum poorer in silver (poor scum), obtained 
 from the subsequent additions of zinc, is thrown into iron pans, and is afterwards 
 used in desilvering a fresh charge of work-lead, so as to utilise its zinc. At the same 
 time that the scum is removed, the fire under the pan is strengthened, in order to give 
 the lead the high temperature required for the next addition of zinc. The entire 
 treatment is repeated as often as additions of zinc are necessary, in order to extract the 
 silver from the work-lead, and convert it into poor lead. 
 
 After the (supposed) last skimming, the sides of the pan are carefully scraped with 
 a chisel, in order to remove any adhering scum and bring it to the surface, lest the 
 accuracy of the determination of silver in the poor lead should be endangered. An 
 intensified fire promotes the fusion of the scum. Before each fresh addition of lead the 
 
SECT, ii.] SILVER. !8 3 
 
 metallic bath is well stirred up, and several samples of lead are taken from the middle 
 with a sampling-spoon, cast into ingots, and tested for their contents of silver. If the 
 assay gives a result of o'ooi per cent, no more zinc is added, and the process is 
 regarded as complete. As soon as the zinkiferous poor lead has been rendered 
 sufficiently hot, it is drawn off from the pan (by means of the syphon, previously 
 heated and filled with melted lead) into the sheet-iron gutter, leading to the hearth of 
 the refining furnace, and the desilvering pan when empty is filled again for a new 
 operation. 
 
 Simultaneously with the desilvering, goes on the eliquation of the rich scum in 
 the first, and afterwards in the second, eliquation pan. The argentiferous zinkiferous 
 lead obtained by this process goes back, like the poor lead, to the desilvering process, 
 whilst the rich silver scum, which has been taken off, is reserved for distillation. The 
 average time needed for melting the work-lead and taking off the cakes is five hours, 
 and for each period of the desilvering, i.e., from one addition of zinc to the next, is 
 altogether five hours, namely : 
 
 hr. min. 
 
 Heating the lead-bath 115 
 
 Adding and melting zinc o 45 
 
 Stirring in zinc . . . . . . . o 30 
 
 Cooling metallic bath 20 
 
 Lifting off zinc scum o 30 
 
 As for the work-lead from the Pattinson process containing o'i per cent, of silver 
 at the most three additions of lead are sufficient ; the duration of the desilvering of 
 such work-lead, the time required until a zinkiferous poor lead is produced, may be 
 taken at the most as twenty hours. 
 
 Every charge of 200 hectokilos. (20 tons) of work-lead of the above-mentioned per- 
 centage of silver, with the additional use of the zinkiferous eliquation lead and the 
 poor scum, requires for desilvering, 215 kilos, of zinc, 100 kilos, for the first addition, 
 75 for the second, and 40 for the third. The addition of zinc required for desilvering 
 runs up to 1-485 per cent., whilst the actual consumption of zinc, deducting that 
 recovered on the distillation of the rich scum, is only 0-832 per cent., the original 
 proportion of silver o'i per cent., and the gold averaging 0*0004 per cent, of the work- 
 lead, is reduced after the first addition of zinc to 0-0250 silver and a trace of gold ; 
 after the second to <roo2o silver, and after the third to 0-0007 per cent, silver, and 
 no gold. As a rule, the decrease of the proportion of silver is most striking after 
 the first addition of zinc, whilst the last small quantities of silver are more difficult to 
 remove. The process is essentially abbreviated if the first addition of zinc is made as 
 large as practicable. The cost of the zinc is not increased, as there is effected an economy 
 in the subsequent additions of zinc, as well as in time. The gold generally disappears 
 after the first addition of the zinc, as it combines with the zinc more readily than does 
 silver. 
 
 Work-lead gives after desilvering the following products : 
 
 o - 35 per cent, cakes from melting, with an average contents of 0^0004 per cent, gold and o-io 
 
 per cent, silver, 
 
 2*25 per cent, rich scum for distillation, with an average contents of 0-0153 P er cent, gold, 
 4-0510 per cent, silver, 53-2 per cent, lead, 2'68 per cent, copper, and 397 per cent, zinc; 
 that is : 
 
 1-73 per cent, of rich scum I. with 0-0174 per cent, gold, and 4-670 silver, 
 0-31 per cent, rich scum II. with O"ooi6 per cent, gold, and 2-53 silver, 
 0-21 per cent, rich scum III. with a trace of gold, and 1-130 per cent, of silver, 
 besides 98-95 per cent, of zinkiferous poor lead for de-zinking with an average contents of 0-0007 
 per cent, of silver and 075 per cent. zinc. 
 
 There are returned to the process : 1-5 per cent, eliquated lead, containing on the 
 
1 84 CHEMICAL TECHNOLOGY. [ SECT - u - 
 
 average a trace of gold, 0*032 per cent, silver, and 1*3 per cent. zinc. Poor scum is 
 not formed because the zinc-scum obtained after the third addition of zinc gives on 
 eliquation the above rich scum III., containing a moderate amount of silver and 
 capable of useful distillation. The quantities of the eliquated rich scum increase with 
 the proportion of silver in the work-lead, and the silver in the rich scum increases 
 proportionally, whilst the lead in the normal case of eliquation remains at a limit of 
 76-80 per cent, and the zinc remains between 20-24. The quantities of poor scum 
 remain approximately equal in all sorts of work-lead, since the silver reduced in them 
 by repeated additions of zinc shows the essential variations, if the poor scum is drawn 
 off. The lead reaches, as a maximum, 90 per cent, and the zinc 6-9 per cent. The 
 yield of eliquated lead, with uniform management, keeps step with the quantities of 
 rich scum, and must increase or abate in a corresponding proportion, according as 
 more or less rich scum is taken off in consequence of the higher or lower proportion of 
 silver in the material. The silver in eliquated lead is uniformly moderate, since the 
 main quantity of the silver is kept back by the zinc remaining in the eliquated rich 
 scum, and the small quantities of silver in the eliquated lead are carried over only by the 
 zinc, which passes in. The zinc fluctuates between i and 1-5 per cent. The zinki- 
 ferous poor lead, if the process has been duly conducted, shows a constant proportion 
 f '75 P er cent, of silver, whatever quantities of zinc were required for desilvering 
 the work-lead. The total gold and copper of the work-lead will be found taken up in 
 the rich scum, so that all subsequent products are free from these two metals. 
 
 For L ae subsequent de-zinking in the refining furnace, the zinkiferous poor lead 
 which has gone down in temperature by removal from the desilvering-pan to the 
 refining furnace must be heated to, and maintained at, redness. There is soon formed 
 by the oxidising influence of the blast upon the surface of the lead-bath a film of lead 
 and zinc oxide, as a thin crust which must be drawn off with a crutch through the 
 working doors to keep the surface of the lead clean. This drawing off the films must 
 continue until pure litharge appears as the product of oxidation, when the de-zinking 
 process is at an end. The tap-hole in the refining furnace is then opened and the 
 lead is run off into the poor lead pan, which has been heated in the meantime. When 
 the cake floating upon the surface has been lifted off, the lead is finally run out 
 through the escape pipe at the bottom of the pan, and let off into iron moulds as the 
 pure lead of commerce. If two desilvering pans are worked simultaneously, the 
 de-zinking can at once begin in the refining furnace as soon as the former lot has been 
 let off into the poor-lead pan. 
 
 The films from the refining furnace and the lead-scum from the poor lead pan, as 
 soon as a sufficient quantity has been collected, are first returned to the refining 
 furnace, in order to smelt out of them a not unimportant quantity of lead, and then, 
 much reduced in weight and volume, they are used as a plumbiferous addition in the 
 treatment of the ore. The refiner's films, when ground, form a good pigment for 
 varnish -painting, and may thus be partially disposed of. The poor lead yields 94-2 
 per cent, commercial lead and 6-17 per cent, of refinery scum. The total de-zinking 
 process from running the poor lead into the refining process to letting off the de-zinked 
 lead requires a mean of nine hours. The original proportion of zinc (075 per cent.) 
 in the zinkiferous poor lead is reduced in three hours to 0*16, in five hours to o-oi, in 
 seven hours to 0-0008, and in nine hours to 0*0002 per cent. 
 
 For distilling the rich scum it is mixed (after being kept as clean as possible) 
 with i per cent, of coarse charcoal powder ; the bottom of the graphite crucible is then 
 covered with a thin layer of pieces of charcoal of the size of a walnut, and the crucible 
 is then filled up to the rim with rich scum. The cover, h, coated at its edge with a 
 moist lute (of i part clay, i part ground tiles, and i part ground coke) is placed upon 
 the crucible, connected with the receiver k (Fig. 187), and the furnace is filled with 
 
SECT, ii.] SILVER. !85 
 
 coke. When the distillation is at an end the receiver, containing the zinc which has 
 passed over in the shape of a lump, is moved away, the grate of the wind-furnace is 
 freed from slag and ashes, the ring and cover of the shaft are drawn away, and the 
 lid of the crucible is taken off as quickly as possible, since when cold it adheres fast to 
 the crucible and cannot be removed without the risk of breakage. As soon as the 
 crucible has ceased giving off fumes, the residue of the charcoal and the unreduced 
 scum floating on the surface of the separated rich lead are lifted off by means of a 
 perforated ladle, and the rich lead itself is baled out into cast-iron pans. After this is 
 completed, a small quantity of charcoal is again laid at the bottom of the crucible, and 
 a fresh lot is introduced. From the rich scum are obtained : 
 
 57'i7 per cent, rich lead, containing O'oi86 per cent, gold, and 7-35 per cent, silver. 
 
 5-85 per cent, crucible scrapings, containing 0-0112 per cent, gold, 4*608 per cent, silver, and 
 
 3'5 per cent, copper, 
 2 9'54 P er cent, metallic zinc, 
 6'35 per cent, zinc in 7-22 per cent, zinc-dust and scrapings. 
 
 With careful working, 50 per cent, of the zinc run over can be recovered, which 
 completely covers the costs of distillation. 
 
 From a work-lead containing 0*84 per cent, of auriferous silver there are obtained 
 {without reference to losses of metals on Pattinsonising) with 16 pans : 
 
 Rich lead ......... 41*0 per cent. 
 
 Commercial lead 49-0 
 
 Lead in intermediate products io'o 
 
 The first of these items contains 2*0 per cent, of gold and silver, the second crooi 
 And the third o'2. 
 
 Of the gold and silver there are found ! 
 
 96'6 per cent, in the rich lead, 
 o' i in the commercial lead, 
 2-3 in the intermediate products. 
 
 On Pattinsonising with nine pans, and treating the lead on the Parke process : 
 
 Rich lead 38*9 per cent, with 2' 14 per cent. 
 
 Commercial lead . . . 52-5 o'ooi 
 
 Lead in intermediate products. 8'6 o'i8 
 
 Of the gold and silver there occur : 
 
 99- 1 per cent, in the rich lead, 
 o'i in the commercial lead, 
 o'8 in the intermediate product. 
 
 This latter procedure is therefore more remunerative than the former. 
 
 Desilvering Work-Lead by Electricity. The electric refining of silver still occasions 
 difficulties. It is a hindrance that neither lead nor silver forms firm, sheet-like deposits, 
 but mostly dendritic concretions. Experiments for producing soft lead electrolytically 
 show that the difference of price between the two qualities does not at present open a 
 prospect for the electric process. 
 
 Fine-burning Silver. Silver as directly obtained from its ores, whether by amalga- 
 mation, or by lead-work, or by precipitation from its solutions by means of metallic 
 copper, still contains several per cents, of other metals. The process on the refining 
 hearth is never continued long enough for the complete oxidation of all other metals, and 
 the actual quantity left in the sample on brightening is sometimes as much as 9*5 per cent. 
 The purification of silver from all admixtures of other metals is called fine-burning. If 
 lead is present or forms the chief ingredient of the contaminating matters the fine- 
 burning is simply a prolonged refining conducted not on the large hearth of the refin- 
 
186 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 ing furnace but in a smaller space. If lead does not preponderate among the im- 
 purities, the silver receives an addition of lead before the oxidation is begun. Small 
 quantities of litharge are always produced in the process, but they are not allowed to 
 run off from the surface of the silver, but are absorbed by the mass (bone-ashes, marl) 
 of which the apparatus used in fine-burning is composed. We distinguish three kinds 
 of fine-burning, i.e. (i) in capsules or iron rings ; (2) in the muffle ; (3) in the reverbera- 
 tory, the last process is the simplest and most advantageous. 
 The production of gold and silver in the world in 1884 was : 
 
 Gold. Silver. 
 
 Kilos. Kilos. 
 
 Germany ." 555 ... 248,115 
 
 United States 46,343 ... 1,174,205 
 
 Russia 32,829 ... 9,336 
 
 Australia . 42,960 ... 2,788 
 
 Mexico 1,780 ... 655,868 
 
 Austrian Empire 1,658 ... 49,424 
 
 Sweden and Norway . . . . -19 ... 8,203 
 
 Italy 109 ... 432 
 
 Spain ... 3,562 
 
 Turkey . . .... . 10 ... 2,164 
 
 La Plata, 118 ... 10,109 
 
 Columbia ....... 5,802 ... 18,286 
 
 Bolivia 109 ... 384,985 
 
 Chili . . . ^7^ . . . 245 ... 128,106 
 
 Brazil . . . T- . . . 952 ... 
 
 Japan 256 ... 21,121 
 
 Africa . . . . . . 3,000 
 
 Venezuela 5,022 ... 
 
 Canada . 1,435 1)641 
 
 France ... 6,356 
 
 Peru 179 ... 45,909 
 
 143,381 ... 2,770,610 
 
 According to Soetbeer the total production of the world between the years 1493 and 
 1875 was : 
 
 Silver. Gold. Value in 
 
 Kilos. Kilos. million shillings. 
 
 Germany . . . 7,904,910 ... ... 1,422-9 
 
 Austria . . . 7,770,135 ... 460,650 ... 2,683-8 
 
 Rest of Europe . . 7,382,000 ... ... 1,328-8 
 
 Russia .... 2,428,940 ... 1,033,655 ... 3,32i'i 
 
 Africa .... ... 731,600 ... 2,041*2 
 
 Mexico .... 76,205,400 ... 265,040 ... 14,456-4 
 
 New Granada . . ... 1,214,500 ... 3,388-5 
 
 Peru .... 31,222,000 ... 163,550 ... 6,076-3 
 
 Bolivia .... 37,717,600 ... 294,000 ... 7,609-4 
 
 Chili .... 2,609,000 ... 263,000 ... 1,205-1 
 
 Brazil .... ... 1,037,050 ... 2,893-4 
 
 United States . . 5,271,500 ... 2,026,100 ... 6,601-7 
 
 Australia ... ... 1,812,000 ... 5,055-4 
 
 Otherwise . . . 2,000,000 ... 151,000 ... 783-0 
 
 180,511,485 ... 9,453,345 ... 58,857-0 
 
 Of this total value silver amounts to 32,492 and gold to 26,375 million (shillings). 
 Chemically pure silver is obtained by dissolving cupriferous silver in nitric acid, 
 precipitating the silver from the solution by means of sodium chloride or hydrochloric acid, 
 and reducing the silver chloride by introducing it into melting potassium carbonate or 
 igniting it with resin and potash. Silver chloride is reduced in the moist way by bringing 
 it in contact with zinc and dilute hydrochloric acid : AgCl, + Zn = ZnCl 2 + Ag. 
 
SECT. ii. J SILVER. 187 
 
 Gutzkow prepares fine silver by placing silver sulphate in a hot solution of ferrous 
 sulphate, when ferric sulphate and metallic silver are formed : AgS0 4 + 2FeS0 4 = 
 Fe 2 (S0 4 ) 3 4 Ag, which is washed, dried, and smelted. 
 
 Pure silver has a pure white colour and a strong lustre which is much heightened 
 by polishing. It is softer than copper, but harder than gold. It is extremely ductile 
 and malleable, in which respect it exceeds all other metals except gold. Yery small 
 admixtures of some metals decrease its ductility and malleability ; the presence of 
 copper, however, is not injurious, and that of gold is even beneficial. An admixture of 
 lead, antimony and selenium is very pernicious. If melted with charcoal, silver loses its 
 flexibility, but it may be melted in a graphite crucible without any change in its pro- 
 perties. The sp. gr. of silver is 10*5 ; by hammering it may be increased to ro'62. 
 At very high temperatures silver is volatilised. If melted with access of air, silver 
 absorbs oxygen, which as the metal solidifies escapes often with a noise and with the 
 projection of liquid silver (spitting, or spirting). If silver contains a trace of lead or 
 i per cent, of copper it solidifies quietly with a concave surface, as when cold it occupies 
 a smaller volume than when melted. It is not attacked by weak acids but dissolves in 
 nitric acid in the cold, and in strong sulphuric acid with the aid of heat. 
 
 Silver Alloys. Silver forms alloys with lead, zinc, aluminium, bismuth, tin, copper, 
 gold, and other metals, of which that with lead is important in the extraction of silver. 
 The most useful of its alloys are those with copper, since pure silver is too soft and is 
 scarcely ever wrought except alloyed with copper. The alloys are harder than silver. 
 
 The German silver coins contain o'goo of fine silver; the ore of the Latin monetary 
 union 0^900 and 0*835, those of Britain o'c)2$. 
 
 Silver Assay. In order to ascertain the fineness of an alloy, presuming that it 
 contains nothing but silver and copper, we may proceed (i) by the dry way, cupellation ; 
 or (2) by the moist way, titration ; or (3) by the hydrostatic method. 
 
 The process of cupellation requires too many niceties to be here adequately described. 
 The reader is, therefore, referred to : Mitchell's Manual of Practical Assaying, 6th 
 edition, edited by W. Crookes, F.R.S., pp. 601-634.* 
 
 The assay by the moist way, the titration method of Gay-Lussac, is more easily 
 executed and is accurate to -$^Q "5 per cent. Since it is known that 5*4274 grammes 
 of sodium chloride precipitate exactly i gramme of silver from solution, the fineness of a 
 dissolved alloy can be found by the use of the ordinary apparatus for titration. 
 
 Volhard uses for precipitating silver from an acid solution mixed with a little ferric 
 sulphate, ammonium sulphocyanide. As soon as all the silver is deposited as a sulpho- 
 cyanide, the red colour of iron sulphocyanide appears.f 
 
 For cases in which cupellation and titration are not admissible Karmarsch recommends 
 a hydrostatic assay in which the proportions of copper and silver are determined by 
 specific gravity. As copper and silver expand when alloyed, but alloys become the 
 denser the more they are exposed to mechanical pressure, there is here an uncertainty in 
 the very basis of the hydrostatic silver assay which renders it inapplicable for silver 
 which has been cast and subsequently worked, but only for silver coins. 
 
 Silvering. Silver-plating, or the coating of other metals with silver, can be effected 
 (i) by plating ; (2) by fire (fire-silvering) ; (3) in the cold way ; (4) in the wet way, and 
 (5) galvanically. In order to cover sheet-copper with a layer of silver the surface of 
 the copper is carefully cleaned and moistened with a solution of silver nitrate, which 
 produces a thin film of silver. Upon this film there is laid a plate of silver ; both are 
 heated and extended between rollers. Copper wire may be silvered by simply laying 
 sheet silver upon it and passing it, hot, through grooved rollers. 
 
 Silvering in the fire is effected by means of a silver-amalgam or a mixture of i part 
 
 * See also Select Methods in Chemical Analysis, by W. Crookes, F.E.S., p. 359. 
 
 t See also Mitchell s work above quoted, pp. 634 685 ; and Select Methods, p. 286. 
 
i88 CHEMICAL TECHNOLOGY. [SECT. 11. 
 
 precipitated silver, 4 parts sal-ammoniac, 4 parts sodium chloride, and ^ part of mercuric 
 chloride, which is rubbed upon the surface of the metal previously well cleaned. The 
 mercury is then expelled from the coating of amalgam by ignition. For silvering but- 
 tons there is used a paste of 48 parts sodium chloride, 48 parts zinc sulphate, i part 
 mercuric chloride, and 2 parts silver chloride. 
 
 For silvering in the cold the cleaned surface of the metal to be silvered is 
 rubbed by means of a cork with a mixture of equal parts silver chloride and sodium 
 chloride, | parts chalk, and 2 parts potash moistened with water, until the colour of silver 
 is produced as desired. According to W. Stein i part silver nitrate and 3 parts potas- 
 sium cyanide are rubbed together with water enough to form a thick paste, which is 
 quickly and uniformly rubbed on with woollen rags. To silver iron it must first be 
 coated with a layer of copper. 
 
 In silvering in the wet way the metal to be coated is placed in a boiling solution of 
 equal parts of tartar and common salt with ^ silver chloride until the silvering is sufficient. 
 
 For galvanic silvering (electro-plating), recently precipitated and well-washed 
 silver chloride is introduced into a solution of potassium cyanide (100 grammes cyanide 
 to one litre water), as long as it is taken up, and to this solution is added an equal 
 measure of solution of potassium cyanide.* Galvanic silvering is applicable upon 
 copper, bell-metal, brass, pinchbeck, cast- and bar-iron. Tin, zinc, and polished steel 
 must be previously coated with copper, if the silver is to be permanent. Articles made 
 of German silver, and Britannia metal, and electro-plated, known under the names 
 of " Alfenide " or China silver, occur in commerce, and have been already mentioned. 
 Upon one square metre of metallic surface there are deposited from i to 22, and even 
 240, grammes silver, so that the thickness of the stratum of silver varies from -5^5-5- 
 to y^, and even -%, of a millimetre. Galvano-plated articles sometimes further 
 receive a slight coating of palladium to preserve them from being blackened by the 
 action of hydrogen sulphide. 
 
 The black colouring of silver articles, sometimes in vogue, and called the oxidation 
 of silver is produced either by sulphur or by chlorine. The former agent gives a blue- 
 black tone, and the latter a brownish black. To obtain the sulphur colour the articles 
 are immersed in a solution of potassium sulphide. For the chlorine colour the silver 
 must be immersed in a solution of copper sulphate and sal-ammoniac. 
 
 GOLD. 
 
 Occurrence. Almost exclusively metallic, either in situ, in quartz rock, especially 
 along with quartz, pyrites, and hydroferrite ; also as gold-sand, in dust or grains, 
 leaflets, and rounded pieces (nuggets), in the sands of rivers or in alluvial soils, consist- 
 ing chiefly of clay and quartz-sand along with mica, water-worn fragments of syenite, 
 chloritic slate, grains of chrome iron and magnetic iron, spinel, garnet, &c. In the 
 metallic state it always contains more or less silver, as electrum. According to recent 
 analyses, native gold contains : 
 
 Transylvania. S. America. Siberia. California. Australia. 
 
 Gold .... 6477 ... 88-04 ... 86-50 ... 90-60 ... 99-2 and 957 
 
 Silver .... 35-23 ... 11-96 ... 13-20 ... 10-06 ... 0-43 3-8 
 
 Iron and other metals . ,.. ... 0-30 .. 0^34 ... 0-28 O'2 
 
 Gold is also often met with in native tellurium and silver telluride, sometimes in 
 argyrythrose and proustite, in iron pyrites, copper pyrites, in stibine, in blende, in 
 arsenical pyrites (e.g., that of Keichenstein in Silesia) and galena. The chief supplies 
 
 * The most useful form of battery for depositing silver is a modification of the Wollaston 
 battery. For the details of the process, and for methods of producing dead or bright surfaces at 
 pleasure, the reader may consult Electro-deposition of Metals, by A. Watt (Crosby Lockwood & Co.). 
 
SECT, ii.] GOLD. 189 
 
 of gold are obtained from the Ural, the United States (California, Nevada, Arizona, 
 Montana, Utah, and Colorado), from British Columbia, Nova Scotia, Mexico, Peru, and 
 Brazil, from Australia (especially Victoria, New South Wales, and Queensland), 
 Tasmania, New Zealand, and in Africa (Natal, the Transvaal, &c.). The Ural Moun- 
 tains and Siberia also yield much gold. 
 
 The gold deposits of India (the Wynaad and elsewhere) must in earlier ages have 
 yielded a large part of the treasures of Eastern kings, but in modern times their working 
 has not proved very remunerative. In the British Islands gold was formerly obtained in 
 considerable quantity. The placer mines of Croghan Kinshela, in county Wicklow, were 
 worked about the beginning of the present century. In 1795, a large nugget, weigh- 
 ing 2\\ oz., was picked up at the ford of Ballinasilloge, in a stream since known as the 
 Gold Mines River. The Government placers yielded 944 oz. of gold, whilst over 
 ;i 0,000 were paid for gold sold by private individuals. Geological authorities con- 
 sider it probable that vast quantities of auriferous sands still exist untouched under 
 the deep river accumulations in the valley of the Ovoca.* The South of Scotland at 
 one time produced gold, e.g.) the head waters of the Clyde, Tweed, and Annan. The 
 specimens lately obtained have served merely as curiosities. In Sutherland gold- 
 seeking was commenced in the years 1867 and 1868, and a certain amount of the 
 precious metal was found, but as all the works have been abandoned, the operations 
 cannot have proved remunerative. In North Wales, especially Merionethshire, the 
 result is of greater importance. A Welsh mine owner is known to have lent Charles I. 
 ^500,000 in Welsh gold at the beginning of the Civil War. Latterly and at present 
 mining is carried on in the Cefn Coch and Gwynfynydd mines. Some 6f the lode- 
 stuff raised gives 87 oz. per ton, but owing to the sulphuretted character of the mineral 
 no known method of working has proved fully successful.t 
 
 In the earlier days of all auriferous districts, gold was obtained in dust, 
 grains, scales, and nuggets, derived from the weathering of gold-bearing rocks and 
 found in shallow diggings in alluvial soils (placers), or procured by washing the sands 
 of river-beds or the deposits of floods. If such matter is dexterously washed and 
 shaken, the gold grains sink to the bottom on account of their superior gravity. 
 The more minute particles are, however, in such cases lost. 
 
 When water is plentiful the gold alluvium is washed by means of strong currents, 
 which wash the mud, sand, and shingle into large sluices, in which the particles of 
 gold sink to the bottom. This method involves, however, greater losses than washing 
 by hand or by machinery. In any case when the placer diggings and the washings in 
 a district are exhausted, the next method is grinding up the gold-quartz in specially 
 constructed mills. As it exists in particles often finer than flour, it has to be 
 extracted from the mass by means of mercury, either incorporated with the ground 
 ore, or presented in the form of amalgamated copper plates, which are fixed obliquely 
 in the long troughs in which the ore is ground up with water. From time to time 
 these plates are lifted out and scraped, and returned to the troughs after being re- 
 amalgamated. 
 
 There is, however, a distinction to be made in the character of gold-bearing quartz. 
 In some kinds the " free-milling " sorts the gold is easily, and, if the mechanical 
 arrangements have been properly constructed, completely taken up from the ground 
 mineral. Such free-milling quartz generally lies near the surface, where the rocks are 
 permeated by atmospheric air and water, and where consequently, in the lapse of ages, 
 the base metals and their compounds have been oxidised, decomposed, and washed 
 away, leaving the gold free. As the miner penetrates deeper he comes upon minerals 
 
 * See Kinahan, Quarterly Journal of /Science, April 1878, N. S., vol. viii. p. 289. 
 t For details the reader is referred to a paper on "British Gold, "by K. Hunt, F.R.S., Quarterly 
 Journal of Science, 1865. 
 
1 90 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 situate below the permanent water-line.* Here the gold cannot be readily extracted 
 by the amalgamation process, as it exists, if not combined, at least entangled among 
 blende, arsenical pyrites, galena, and antimony ores, so that it to a great extent 
 escapes the action of the mercury. Hence the gold actually extracted from a mineral 
 in practical working falls sadly short of the quantity found on assaying. Yery small 
 quantities of lead, copper, arsenic, or antimony quickly spoil the mercury, and render 
 it unable to take up the gold. Among the most successful expedients for combatting 
 this evil, ranks the use instead of pure mercury of sodium-amalgam as invented by 
 W. Crookes, F.R.S. 
 
 The presence of sodium keeps the mercury bright and active. This compound is 
 prepared in three modifications A, B, and C. Amalgam A is a combination of 
 3 parts sodium with 97 of mercury. The mixture is prepared as follows : A strong 
 iron flask with a narrow neck is bedded nearly up to the mouth in a sand-bath at 
 198 ; the materials are weighed out, the mercury is poured into the flask, and the 
 sodium is dropped in, taking pieces of the size of a pea each time, and using an iron 
 forceps. The action should be allowed to cease each time before a fresh portion is added, 
 When the whole of the sodium has been introduced, the amalgam is poured, whilst 
 still liquid, into a flat iron dish, and when cold is broken up and kept in a stoppered 
 jar. Amalgams B and C contain an addition of zinc, and are recommended for use. 
 
 Both from experiments and from practical working,! it appears that when sodium- 
 amalgam is used according to the instructions of the inventor, and is not expected to 
 dispense with all judgment on the part of the operator, it greatly facilitates the amalga- 
 mation of gold, which, it must be remembered, is not so easily taken up by mercury 
 as it is commonly believed. 
 
 Mr. W. Skey, analyst to the Geological Survey of New Zealand, J finds that 
 numerous samples of bright, clear-looking gold, of all degrees of fineness, refuse to 
 amalgamate on any part of their natural surfaces though taken direct from the 
 reef and untouched by hand ; that on such surface sulphur is always present ; 
 that native gold or gold in a pure state readily takes up sulphur from moist 
 sulphuretted hydrogen or ammonium sulphide and absorbs it directly when ad- 
 ministered in boiling water ; that surfaces so treated refuse to amalgamate, though no 
 apparent change can be observed ; geld so affected is rendered amalgamable by roasting 
 in an open fire, except copper is present to the extent of 7 per cent, or perhaps less, whilst 
 the same effect is produced by contact with potassium cyanide, chromic and nitric acids, 
 and chloride of lime acidified. The author is of opinion that this absorption is of a 
 chemical character. He has observed that iron sulphates in presence of air and water 
 decompose various metallic sulphides common in gold reefs, liberating sulphuretted 
 hydrogen. He has also proved that the action of sulphuretted hydrogen renders gold 
 non-amalgamable, and he suggests that much of the loss in extracting gold from auriferous 
 minerals of amalgamation depends on the presence of a thin film of sulphurised gold 
 which envelops the particles. 
 
 An immense quantity of gold is lost by being carried away in the form of tailings 
 too fine to be deposited in any practicable time. It is estimated that though the State 
 of California since '1848 has produced gold to the value of ^250,000,000, yet 
 more " has been wasted in milling and hydraulic mining by being washed down the 
 rivers and even to the ocean." An experienced Californian expert, quoted by Eissler, 
 states that in his experiments " gold has been taken up in distilled water so fine that it 
 could not precipitate in less than from five to ten minutes." Gold of this character 
 obviously cannot be saved in running streams. 
 
 * See Eissler's Metallurgy of Gold, Crosby Lockwood & Co. 
 
 t See Ure's Dictionary of Arts, Manufactures, and Mines, Longmans, vol. ii. p. 697. 
 
 Chemical News, vol. xxii. Dec. 9, 1870, p. 282. 
 
SECT, ii.] GOLD. 191 
 
 Great care must be observed in the " milling " process. If the ore is too coarse, a 
 proportion of the gold is certainly wasted, as many of the particles remain incrusted 
 with silica, and never come into actual contact with the mercury at all. On the 
 other hand, if the ore is crushed too fine, much of the gold will float instead of amal- 
 gamating, and is not arrested either by the amalgamated copper or silver plates, or by 
 the " blankets " suspended in the sluices. The pulp is generally caused to flow over 
 three sets of blankets. The first set are washed every twenty minutes, and the second 
 every two hours. 
 
 A so-called hydrogen amalgamation process perhaps more correctly styled an 
 electric process has been patented by Molloy, and is being worked in America by the 
 Hydrogen- Amalgam Company. The apparatus used consists of a shallow pan, i inch 
 in depth and 41^ inches in diameter, containing mercury to the depth of half-an- 
 inch. In the centre of this pan is a porous jar, so fixed that the mercury cannot enter 
 or displace it. Within the jar is a cylinder of lead and a solution of sodium sulphate. 
 This lead cylinder forms the anode, and is coupled with the positive pole of a small 
 dynamo, whilst the mercury is connected with the negative pole of the same machine. 
 As the current passes, hydrogen is evolved from the surface of the mercury, which 
 combines with a portion of it, forming a hydrogen-amalgam. According to the 
 statements of the Hydrogen-Amalgam Company, quoted by Eissler, this process 
 prevents the mercury from turning " sick " (losing its activity), and eflects an increased 
 yield of gold amounting to 10 per cent, at the expense of only threepence per ton for 
 electrical and mechanical force and labour. 
 
 To obviate the waste of gold and mercury and the losses involved in the ordinary 
 processes, Mr. W. Pritchard Morgan, M.P., and Mr. J. Needham Longden of 
 Sydney, have invented and patented a dry amalgamation process, in which water 
 is entirely dispensed with. This is in itself no small advantage in many parts of 
 Australia and Africa. The ore is first comminuted, not by grinding or stamping, but 
 by the " Jordan " pulveriser, which acts nearly in the manner of a Carr disintegrator, 
 and reduces the mineral to a powder, passing it through a sieve of 8100 meshes to 
 the square inch, or forty times as fine as is commonly done. This, in a wet process 
 would be fatal, as it would allow much of the gold to float, but where water is not 
 present it is an advantage, as it secures the contact of the gold with the mercury. 
 The mercury is applied dry and hot by means of a self-acting apparatus which ensures 
 perfect contact but which cannot be described intelligibly without the aid of a working 
 model. As the process is completed the ground ore is forced into the concentrating 
 chamber. Messrs. Jordan, Son & Comman, of Gracechurch Street, erected plant for 
 the process at Stratford Market, and found a considerably increased yield of gold with 
 a decrease of the working cost. It is needless to say that this process can be worked 
 with sodium amalgam, which, in the presence of antimony, would be found advan- 
 tageous.* 
 
 The following method of treating refractory gold ores, sulphides, tellurides, arsenio- 
 sulphides, &c., containing zinc, copper, iron, bismuth, and antimony has been devised 
 by W. Crookes, F.E.S. The object sought is to prevent the flouring and sickening of 
 the mercury and the tarnishing of the gold grains, which together involve a loss of 
 from 20 to 80 per cent, of the gold present as found on assay. Various methods for 
 preventing these evils have been suggested, but none of them have proved satisfactory. 
 Mr. Crookes submits the ores, tailings, sulphides, etc., to the joint action of a solution 
 of mercury cyanide, or of some other soluble salt of mercury, and of an alternating 
 electric current. The ore in question is reduced to a powder in the usual manner, 
 mixed with a solution of sulphate, nitrate, chloride, or cyanide of mercury, and a 
 rapidly alternating current of electricity is then passed through the mass either when 
 
 * For further particulars, the reader is referred to the Journal of Science, Third Series, vol. vi. 
 (1884) P- 4i6. 
 
i 9 2 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 at rest or when kept in a state of agitation. The bulk of the mass is not a very good 
 conductor of electricity, whilst the fine particles of gold disseminated through the mass 
 are excellent conductors. The poles may be made of iron or carbon, each being 
 alternately anode or kathode. Each alternation of the current causes mercury to be 
 precipitated on alternate surfaces of the particles of gold in the mass of ore, without re- 
 quiring the gold to be in metallic communication with either pole. The sizes of the 
 particles are not material, as the finest " flour " and " float " gold will be amalgamated 
 and thus weighted as well as the largest pieces. 
 
 An advantage incidental to the use of an alternating current is that the sudden 
 and the violent decompositions and recompositions alternating with great rapidity 
 cause the mass to become warm, thus greatly facilitating the decomposition. The efficient 
 action of the alternating current depends on the right adjustment of several variable 
 factors, e.g. (i) current density; (2) area of electrodes; (3) rate of alternations per second ; 
 (4) electric conductivity of the wet mixture of crushed ore and liquid. As this last 
 factor varies with every kind of ore the others will have to be ad justed in each separate 
 case to get the maximum effect. Hence no general directions can be given. 
 
 If it is impracticable to use an electric current the inventor employs a solution 
 of mercury cyanide or sulphate, either of which will superficially amalgamate the 
 particles of gold, though less rapidly than with the aid of the alternating current. The 
 reaction may be hastened somewhat by heating the mass. 
 
 When carrying out the process in this manner the inventor uses a solution of 
 2 or 3lbs. of mercury cyanide or sulphate, dissolved in 80 to 100 gallons of water. 
 
 In some cases he finds it advantageous to add to the mercury used in the subsequent 
 amalgamation process a little sodium amalgam as described in his specification No. 391 of 
 1865 or some of the modified amalgams described in his specification No. 2229 of 1865. 
 
 The points here claimed are the improvements in amalgamating and extracting gold, 
 which consist in submitting the ore to the joint action of a solution of mercurial salt 
 and an alternating electric current. Further, the improvement in amalgamating and 
 extracting gold, which consists in submitting the ore to the action of a solution of 
 mercury cyanide or sulphate, and lastly the improvement in the final amalgamating 
 process by using a solution of cyanide or sulphate of mercury, or an alternating electric 
 current, in conjunction with a solution of a mercurial salt. 
 
 The extraction of gold from gold-sands may be effected completely by fusion. The 
 sand is smelted with iron ore in blast furnaces with suitable fluxes, thus yielding auri- 
 ferous raw iron, from which the gold is subsequently extracted by means of sulphuric 
 acid. If gold is present in copper or lead ores they are roasted and washed. Auri- 
 ferous sulphides are sometimes roasted and smelted. The raw stone or matte thus 
 obtained is again roasted, melted afterwards along with litharge, which takes up the 
 gold present in the matte, and is separated on the refining hearth.* 
 
 Plattner devised a process for extricating gold from its minerals by means of 
 chlorine ; it has been improved by Deetkin, Kustel, Bruckner, Hears, and others. 
 The process of chlorination consists, generally speaking, of the following operations : 
 
 (i) The comminuted auriferous matter is perfectly oxidised, moistened with water, 
 and sifted into a wooden vat, coated with tar or resin and having a perforated false 
 bottom. It is then covered with a lid, which must fit well. Chlorine is liberated 
 below the false bottom, whether from a mixture of salt, pyrolusite, and sulphuric acid, 
 or from chloride of lime in contact with an acid, and allowed to penetrate the mass of 
 we from below. When the chlorine has pervaded the entire mass, the vat is closed at 
 the top, and allowed to stand for a few hours covered up. The lid is then removed 
 and water is added so as to fill it up on a level with the top of the ore. It is found that 
 
 * This process has not come into general use in America or Australia. 
 
SECT. ii.J GOLD. 193 
 
 the gold has been converted into a soluble terchloride, which is dissolved out with 
 water. Lastly, a solution of ferrous sulphate is added to the clear liquid, when the 
 gold is thrown down as a black or brown precipitate, which is collected, washed, and 
 melted down. 
 
 As a condition for success, sulphuretted ores must be carefully roasted before 
 chlorination, as must also be all minerals containing lead, beginning at a very low 
 temperature. Sulphates, if present, must be destroyed by roasting. No hydrochloric 
 acid gas must accompany the chlorine : hence in many cases it is advisable to generate 
 chlorine in a separate vessel, so that it may be washed in pure water before it is intro- 
 duced below the false bottom. 
 
 In the modification of the chlorine process devised by M. Their the chlorinator is an 
 iron barrel lined with lead, with a man-hole at one side for filling and emptying. A 
 ton of ore is introduced at a time, the barrel is partially filled with water ; about 20 Ibs. 
 of chloride of lime are introduced, followed by the roasted ore, and the proper quantity 
 of sulphuric acid about 25 Ibs. The man-hole is tightly closed, and the barrel is 
 caused to revolve until the gold is dissolved, which is generally effected in six hours. 
 The contents of the barrel are then rinsed out upon a filter. 
 
 For a full account of the various modifications of the chlorination process, of the 
 precautions required, and the utilisation of silver and other matter present, see Eissler's 
 work above-mentioned (chapters vi. and vii.). 
 
 The gold, as obtained by whatever process, contains small admixtures of other 
 metals, always including silver. The gold may be separated (i) By antimony 
 sulphide ; (2) by sulphur and litharge ; (3) by chlorine ; (4) by the quartation process ; 
 and (5) by sulphuric acid. 
 
 In the process of parting by antimony sulphide, the alloy of gold (containing at 
 least 60 per cent, of gold) is melted in a graphite crucible, and pulverised antimony 
 sulphide is then introduced. The melted mass is poured into an iron mould. When 
 cold, the mass is found separated into two layers, the upper, or plagma, consisting 
 of silver, copper, and antimony sulphides ; and the lower, being the regulus (gold anti- 
 monide). The latter is then roasted, and the residue of gold is melted with borax, 
 saltpetre, and powdered glass. 
 
 The operation with sulphur is a concentration, preparatory for separation in the 
 wet way, especially for quartation, the object being only to economise nitric acid. The 
 granulated alloy of gold is put in an ignited graphite crucible, along with one-seventh part 
 of powdered sulphur, and covered with powdered charcoal. It is kept first for two to two 
 and a half hours at a low red-heat, and is then heated to fusion. If the alloy contained 
 considerable proportions of gold, there is separated out a silver rich in gold, whilst but 
 little gold remains in the plagma. If the alloy was poor in gold, such a separation 
 takes place very imperfectly, or not at all. To effect this, litharge is sprinkled upon 
 the melted mass ; its oxygen converts a part of the sulphur into sulphurous acid, 
 whilst the liberated silver is eliminated along with the greater part of the gold. 
 
 For separating gold by means of chlorine the auriferous alloy, in fine grains or in 
 thin sheets, is stratified in a crucible, with so-called cement powder (consisting of 
 4 parts ground bricks, i part common salt, and i part ignited iron sulphate), and 
 exposed for several hours to a gradually increasing heat. By the action of the ferrous 
 sulphate upon the salt, chlorine is liberated, which converts the silver into chloride, 
 but does not attack the gold. The silver chloride is absorbed by the ground bricks. 
 When cold, the mass is boiled in water to recover the gold. In 1869 Miller founded 
 upon the property of chlorine not to attack gold at elevated temperatures a new 
 process for purifying gold, which has been successfully introduced at the Mints of 
 London, Sydney, and Philadelphia. Chlorine gas is introduced into the melted metal 
 through a stoneware pipe, and combines with the silver to form silver chloride, which 
 
i 9 4 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 vises to the surface of the melted gold ; the gold remains perfectly desilvered. 
 Instead of chlorine gas, bromine may be used. 
 
 Separation in the wet way, or quartation, derives its name from the traditional 
 assumption that in order to separate gold from silver in this manner the latter metal 
 must amount to three times the quantity of the latter. Pettenkof er has shown that two 
 parts of silver are sufficient if the acid is sufficiently strong, and the boiling is duly 
 prolonged. For this purpose the alloy is melted xip with the needful quantity of silver, 
 the mixed metal is granulated and covered in a platinum pan with nitric acid of 
 sp. gr. i '320, perfectly free from chlorine. Silver is dissolved, whilst the gold remains, 
 and is melted in a crucible with borax and saltpetre. The silver is thrown down from 
 the solution by means of copper or zinc. 
 
 The separation of gold by means of sulphuric acid is preferable to quartation, on 
 account of its simplicity and cheapness. The separation is effected most readily if the 
 alloy contains in 16 parts not much above 4 and not much less than 3 parts of gold. 
 The sulphuric acid used in the process must have the sp. gr. i - 848. The alloy is 
 placed in a suitable pan, and covered with sulphuric acid and heated. In twelve hours 
 the silver and the copper are completely dissolved : 
 
 AuAg 2 + 2 H 2 S0 4 = Au + Ag 2 S0 4 + S0 2 + 2 H 2 0. 
 
 When all the silver and copper are converted into sulphates, the solution is poured 
 into a leaden pan, and the silver sulphate, which congeals to a crystalline paste, is 
 taken out with an iron shovel and put in lead pans filled with hot water. The 
 precipitation of the sulphate is effected with slips of sheet-copper. The solution of 
 copper sulphate is neutralised as completely as possible with copper oxide, and worked 
 up as copper sulphate. The gold which remains undissolved is freed from accompanying 
 ferric oxide, copper sulphide, and lea*d sulphate, by boiling with sodium carbonate 
 and treatment with nitric acid, dried, and remelted with a little saltpetre. This 
 method of separation has rendered it possible to refine to advantage old cupriferous 
 silver containing or -^ per cent, of gold, as is often the case in old silver coins. 
 
 According to Gutzkow's proposal, there are worked up : gold ingots from California, 
 set at 2 parts gold and 3 parts silver and then granulated ; silver ingots from the 
 Comstock mine, containing 2 to 10 per cent, of gold, which are dissolved up at once 
 without granulating ; and, finally, silver in the form of bricks containing a considerable 
 proportion of copper from the amalgamation of the tailings, and from the mines of 
 Nevada. These bricks are smelted with so much fine silver that the proportion of 
 copper is reduced to 8 per cent. 
 
 There is used for dissolving the alloys a cast-iron pan, 66 centimetres in width and 45 
 centimetres in depth, made more capable of resisting acids by containing 2 to 4 per cent, 
 of phosphorus. It takes a charge of 100 to 150 kilos., which is introduced through 
 an opening in the dome capable of being closed with a slide. The gases and vapours 
 given off during dissolving are passed through a leaden pipe into a chamber lined with 
 lead plates, and from here through a tower into a lofty chimney. The sulphuric acid 
 put in at 1 68 Tw., is heated to a boil, and the alloy is added. The hot solution, floating 
 above the undissolved gold is syphoned off into a deep iron receiver, through an iron 
 pipe into sulphuric acid at the heat of 110, and of the strength of i23Tw. Of 
 this i cubic metre is required for every 200 kilos, of the alloy treated ; it is 
 obtained as a mother-liquor on the crystallisation of silver sulphates. As the liquid 
 cools, silver sulphate crystallises out, whilst copper sulphate remains in solution. 
 Upon the silver sulphate crystals a hot, saturated neutral solution of ferrous 
 sulphate is conducted, which first dissolves copper sulphate, then reduces the silver- 
 sulphate, takes up the free acid, and flows off, at first as a blue and then as a brown 
 liquid, until a green colour indicates the end of the reduction. The blue cupriferous 
 liquid is preserved separately from the brown liquid, in which there are still in 
 
ECT. II.] 
 
 GOLD. 
 
 solution 2-5 per cent., of silver. The reduction is complete in 3 to 4 hours. The 
 solution of ferric oxide is re-converted into a ferrous salt by the addition of waste 
 
 iron. 
 
 Chemically pure gold is obtained by dissolving gold in aqua reyia ; the solution is 
 separated from silver chloride, &c., by filtration; the filtrate is evaporated to dryness, 
 the remaining gold chloride is taken up in water, and the gold is precipitated by a 
 solution of ferrous sulphate : 2AuCl 3 + 6FeS0 4 = 2Au + 2Fe 2 (S0 4 ) 3 + Fe 2 Cl 6 . 
 
 Properties. Gold is yellow, but very small traces of other metals can modify its 
 colour. It takes a very high polish. In hardness it is little superior to lead, but it is 
 the most malleable and extensible of all metals. It possesses an absolute solidity 
 almost equal to that of silver. Its elasticity is unimportant, whence it is but little 
 ;sonorous. Its sp. gr. varies from 19^25 in the cast and unextended state, to 19*55, 
 and even to 19-6, when it has been condensed by mechanical manipulation. Gold fuses 
 at 1037 Deville, 1075 Erhard, and after casting it contracts strongly in the mould. 
 Melting gold shines with a sea-green colour. Its value is much increased by the fact 
 that it remains unaffected in the air, in sulphuretted gases (see Skey's observations, 
 p. 190), in water, and in contact with all acids, except aqua regia.* Of all metals 
 gold has the greatest tendency to combine with mercury. In thin leaves it is trans- 
 lucent with a blue or a green light according to its degree of tenuity. 
 
 Gold Alloys. Fine gold is not used in the arts on account of its softness; it is 
 employed only for (genuine) leaf gold, and for ornamenting glass and porcelain. Its 
 standard of fineness is expressed in this country in carats. Absolutely pure gold is 
 said to be 24 carats fine. An i8-carat gold is understood to contain 18 parts of fine 
 gold and 6 of copper or silver. The alloys containing copper have a more reddish and 
 those containing silver a more whitish yellow colour. 
 
 The quantity of gold used in ornamenting earthenware is far larger than it might be 
 supposed. In the year 1869 gold to the value of ^60,000 was used for this purpose 
 in England alone, chiefly in the Staffordshire potteries. 
 
 For melting gold and silver alloys the furnace of Booth is preferred (Figs. 188 
 and 189), as every loss of the precious metal is avoided. The melting furnace is enclosed 
 with iron plates and provided with an 
 iron ash-pit, A. In order to recover any 
 gold and silver which may adhere to the 
 furnace-bars, R, these are occasionally 
 melted and kept for a long time in a 
 liquid condition, so that gold or silver 
 may subside to the bottom. 
 
 All alloys of gold, when polished, dis- 
 play colours differing from that of pure 
 .gold ; they appear reddish or pale yellow. 
 In order to give to such alloys the intense 
 yellowness of pure gold they are boiled in a liquid (gold-colour) consisting of common 
 salt, saltpetre, and hydrochloric acid. The action of the " gold-colour " depends on its 
 property of dissolving by means* of the chlorine evolved a little gold from the 
 : surf ace of the object, and then re-depositing it as a thin film, so that the surface may 
 be richer in gold than the interior of the metal. The same object can be as well 
 effected by the galvanic gilding process. 
 
 Gold Proof. In oi'der to ascertain rapidly the fineness of a gold alloy, goldsmiths 
 make use of the touch-stone and the " touch needles." These are needles of gold 
 alloyed with different proportions of silver or copper. A mark is first made upon 
 
 * It is also soluble, according to Mitscherlich, in selenic acid, and according to Gay-Lussac, in 
 iodic acid. See also Notes on the Treatment of Gold Ores, by Fl. O'Driscoll, Assoc. M. Inst. C.E. 
 
 1'ig. 1 88. 
 
 Fig. 189. 
 
196 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 the stone with the article in question, which is then compared with marks made with 
 the different needles. The mark is then treated with dilute aqua regia, and the 
 quality is judged by the permanence, or the more or less rapid disappearance of the 
 streak. This process, of course, can merely give approximate results, and it must be 
 considered that the surface, especially of articles of jewellery, has in many cases been 
 made richer in gold by the processes above-mentioned. 
 
 The best proof is cupellation. For this purpose the auriferous granule is melted 
 up, according to its colour, with a triple, double, or equal weight of silver, and with 
 about ten times the quantity of lead. It is then assayed in the usual manner. The 
 argentiferous bead is flattened out, digested in nitric acid, the residual gold is washed,. 
 dried, and weighed. 
 
 Gilding. Gilding is effected either by gold-leaf, by plating in the wet way, by 
 tire gilding, or by the galvanic process. 
 
 Articles of wood, stone, cast-iron, ike., are gilt with leaf -gold. The gold leaf intended 
 for this process is obtained by casting fine gold in ingots, forging it out in plates, and 
 then rolling it into sheets. Twenty ducats yield sheet gold of 16 metres in length and 
 3 centimetres in width, which are cut up into quarters (so-called) of 3 centimetres in 
 length. These sheets are first beaten out between leaves of parchment, and then 
 between the exterior membrane of the caecum of the ox. The finished leaves are laid 
 in small books of very smooth paper rubbed with a little bole or ruddle to prevent the 
 gold leaves from adhering. The residues serve for preparing (genuine) gold bronze. 
 The objects to be gilt are first coated with a mixture of white lead and varnish or glue 
 and chalk, and then covered with gold leaf. Articles of iron and steel, such as the 
 blades of swords and the barrels of guns are first treated with nitric acid, heated until 
 they turn blue, and then covered with leaf gold. 
 
 Talmi gold (first introduced into commerce by the Parisian manufacturer Tallois), 
 is a yellow alloy of copper, coated with gold in the state of wire and sheets, and then 
 further wrought up. 
 
 Gilding in the cold way is effected by dissolving fine gold in aqua regia, dipping 
 linen rags in the solution, drying and burning them to tinder. The ash contains finely 
 divided gold and carbon which are rubbed by means of a cork dipped in salt water 
 upon the surface of the copper, brass, or silver to be gilt, and which must previously 
 have been cleansed and polished. 
 
 Gilding in the wet way is conducted by plunging the objects into a dilute solution 
 of gold chloride, or into a boiling mixture of dilute solution of gold chloride with a 
 solution of sodium carbonate. Iron and steel which are to be gilt in this way are first 
 coated with copper by immersion in a solution of copper sulphate. Articles of iron 
 which are to be gilt in the wet way, may first be corroded with nitric acid, brushed 
 over with a solution of gold chloride in ether, and heated. The action is almost instan- 
 taneous. A solution of gold chloride in sodium pyrophosphate has been recommended 
 as a bath for gilding in the wet way. 
 
 Gilding in the fire, especially for articles of bronze, brass, or silver, corresponds 
 very closely with silvering in the fire. The surface to be gilt is coated with a gold 
 amalgam, with the intervention of a solution of mercury in nitric acid, and the article 
 is then heated to expel the mercury, leaving the gold as a thin film adhering to its 
 surface. The gold amalgam used consists of two parts gold and one part mercury. 
 The gilding is either made brilliant by polishing or it is kept dead. If the gilding 
 is to have the reddish polish of gold alloyed with copper, the bronzes, after the 
 expulsion of the mercury, are dipped in melted gilders' wax (a mixture of wax, bole, 
 verdigris, and alum), and the wax is allowed to burn off over a charcoal fire. The 
 copper oxide of the verdigris is reduced to copper which combines with the gold to 
 form a reddish alloy. Iron and steel are previously coated with copper. 
 
SECT, ii.] PLATINUM. i 97 
 
 Galvanic Gilding. For preparing a gold bath 100 grammes of potassium cyanide are 
 dissolved in i litre of distilled water. For this solution 7 grammes of fine gold are 
 dissolved in aqua regia, cautiously evaporated to dryness, the residue taken up in a 
 little distilled water, and the liquid added to the solution of the cyanide. 
 
 PLATINUM. 
 
 Occurrence. Platinum is found only native and in small quantity in the so-called plati- 
 num-ore met with in Columbia and Peru, in alluvial deposits, and on the Ural, in the 
 form of small, rounded, steel-grey grains rarely nuggets of a metallic lustre. Re- 
 cently it has been found among gold-sand in California, in Oregon, Brazil, Haiti, 
 Australia, and Borneo, and very lately in the Norwegian parish of Roeraas, disseminated 
 in rocks, as also in the sands of the Ivalo River in northern Lapland.* 
 
 It was first discovered by the Spanish mathematician, Antonio d' Ulloa, in the 
 gold-bearing sand of the river Pinto in Choco (New Granada) ; it was at first taken 
 for silver, until in 1752 its distinct metallic character was recognised by Schaffer, the 
 Master of the Swedish Mint. 
 
 The ores occurring in commerce under the names of platinum ore, native platinum, 
 or crude platinum, are mixtures of platinum with palladium, rhodium, iridium, osmium, 
 ruthenium, iron, copper and lead, and contain also generally grains of osmium -iridium, 
 gold, chrome-iron, titanif erous iron, spinel, zircon, and quartz. 
 
 Platimim ores from Ural (I.), Columbia (II.), Choco (III.), Borneo (IV.), and 
 California (V.), contained : 
 
 I. II. III. IV. V. 
 
 Platinum . . 86-50 ... 84-30 ... 86'i6 .. 71*87 ... 5775 
 
 Rhodium . . 1^15 ... 3-46 ... 2'i6 ... ... 2-45 
 
 Iridium . . ... 1-46 ... 1-09 ... 7-92 ... 3-10 
 
 Palladium . no ... ro6 ... 0-35 ... 1-28 ... 0-25 
 
 Osmium-iridium . 1*14 ... ... 1*91 ... 8-43 ... 27^65 
 
 Osmium . . ... 1*03 ... 0^97 .. 0-48 ... o- 
 
 Copper . . o'45 ... 074 ... 0^40 ... 0^43 ... 0-20 
 
 Iron . . . 8-32 ... 5-31 ... 8-03 \ 
 
 Lime ... ... 0-12 ... - [ ... 8-40 ... 770 
 
 Quartz ... ... o'6o 
 
 The yearly supply of platinum is about 450 kilos, from the South American localities, 
 120 from Borneo, and 3600 from the Ural. 
 
 For the extraction of platinum from its ores they are first heated to redness and 
 covered with cold aqua regia to remove gold ; filtered, and the residue is again treated 
 with aqua regia in a retort. The liquid distilled off contains osmium, whilst the undis- 
 solved residue consists of osmium-iridium, ruthenium, chrome-iron and titanif erous iron, 
 whilst the solution contains palladium, platinum, rhodium, and a little iridium. The 
 solution is neutralised with sodium carbonate and mixed with a solution of potassium 
 cyanide, when the palladium is eliminated as a cyanide. The filtrate is concentrated- by 
 evaporation, and mixed with a saturated solution of ammonium chloride whereby 
 PtCl 4 2NH 4 Cl is thrown down along with a small quantity of iridium. For technical uses 
 the slight admixture of iridium is advantageous, as it confers upon the platinum the hard- 
 ness necessary for working. The double ammonium-platinum chloride is dried and ignited 
 leaving metallic platinum as a spongy mass (platinum sponge). This mass is then com- 
 pressed in iron cylinders with steel pistons at a red heat, repeating this operation until 
 the metal has the appearance of melted platinum, and is sufficiently dense for working. 
 
 According to Descotils, the platinum ores are to be smelted with 2 to 4 parts of 
 
 * It is very probable that platinum may have often been overlooked in California and Australia 
 in the earlier and pre-scientific days of gold-digging. 
 
I9 8 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 zinc, the homogeneous brittle mass powdered and sifted, the zinc and the chief part of 
 the iron dissolved out with dilute sulphuric acid, and the residue treated first with nitric 
 acid to extract iron, copper, and lead, and then with aqua regia, which dissolves the plati- 
 num, &c., much more easily on account of its finely divided state. The process is then, 
 completed in the usual manner. 
 
 In the process of H. Sainte Claire Deville and Debray lead is used to dissolve all 
 the metals of the platinum ore except osmium-iridium and iron. The ore is smelted in a 
 reverberatory with an equal weight of galena and a little glass, yielding a regulus, at 
 the bottom of which is the osmium-iridium, whilst a lead-slag floats on the surface of the 
 regulus. This platiniferous regulus is refined on the hearth, when all the foreign metals 
 are volatilised and absorbed into the hearth, whilst the platinum which remains is refined 
 in lime crucibles. The lime here acts upon all such impurities as silicon, iron, copper, 
 <fec., and converts them into fusible compounds, which withdraw into the porous mass of 
 the crucible. To fuse i kilo, of platinum there are required 100 litres oxygen and 300 
 litres of coal-gas. Still higher temperatures may be obtained with the electric smelting 
 furnace of W. Siemens which, however, has not yet been applied for this purpose. 
 
 Properties. Platinum is almost of a silvery-white but with a slight steel-grey cast, 
 it is shining, malleable, and ductile and so soft that it may be cut with shears. It may 
 be drawn out to wire which is almost microscopic. For this purpose a platinum wire 
 is coated with silver and drawn as finely as possible in the ordinary manner. It is 
 then treated with nitric acid, which dissolves off the silver and leaves the platinum 
 untouched. Its sp. gr. is 21*504. It can be welded and fused before the oxyhydrogen 
 blast. Platinum sponge and platinum black have the property of condensing gases in 
 their pores in extraordinary quantities. If hydrogen comes in contact with these 
 substances it combines with oxygen so as to form water by intervention of the platinum. 
 This combination is effected with so great a development of heat that the platinum 
 is ignited and hydrogen passed up against it takes fire. (Dobereiner's hydrogen lamp.) 
 
 Platinum black is platinum in a state of very fine division ; it is produced either by 
 boiling platinum sulphate with sodium carbonate and sugar, when the platinum blr.ck 
 is precipitated as a powder, or by melting together platinum and zinc, and dissolving 
 the alloy in dilute sulphuric acid. Platinum black possesses the property of condensing 
 gases in a still higher degree than spongy platinum, and serves thus for converting 
 alcohol into acetic acid. 
 
 Platinum may be worked up either by rolling or by fusion and casting. The 
 manufacture has been lately developed by Heraeus, of Hanau, and especially by 
 Matthey, of the firm of Johnson & Matthey, of London. It serves for chemical and 
 technical apparatus, which are not attacked by high temperatures or by most 
 substances. Still they must be treated with great care, and especially must not be ex- 
 posed to contact with fused caustic alkalies, melting saltpetre, free chlorine, aqua regia, 
 sulphur and sulphides, phosphorus, melted metals and easily reducible metallic oxides 
 (especially along with carbonaceous matter). The articles made of platinum are 
 sheets, wires, crucibles, spoons, nozzles for blow-pipes, points for lightning conductors, 
 retorts, forceps, pans for refineries and sulphuric acid works; it serves also in the 
 manufacture of galvanic elements, glow-lamps, and for coating copper capsules, 
 porcelain, stone-ware and glass. Platinum has been used for producing the standard 
 measures (copies of the original Paris metre) resolved on by the International Com- 
 mission of Weights and Measures. The standard measures, which were prepared by 
 Mr. Matthey (Johnson & Matthey), consist of an alloy of 90 parts platinum and 10 
 parts iridium, and are much harder than pure platinum. Similar alloys are now 
 preferred as the material for platinum crucibles. 
 
 In Russia, platinum was coined, from the year 1828, into 3, 6 and 12 rouble pieces. 
 In 1845, tne coining of these pieces (which had already consumed or wasted 14,250 
 kilos, of this indispensable metal) ceased, and the pieces already issued were called in. 
 
SECT. II. 
 
 199 
 
 In 1877, S. Kern found in the metal of platinum crucibles, made in Paris- 
 Platinum . _. . 9870 per cent. ... 97 -90 per cent. 
 Iridium . . . 0^56 ,, ... 1-40 ,, 
 
 Iron . . . 030 , 
 
 Copper . . . o - 22 ... 0-67 
 
 TIN. 
 
 Tin is one of the rarer metals. It never occurs native, but oxidised as cassiterite 
 or tin-stone, Sn0 2 or as stannine, tin sulphide, combined with other sulphides in tin 
 pyrites (2Cu 2 S + SnS 2 + 2FeS,ZnS)SnS 2 . 
 
 Tin-stone is found in situ in granite, syenite, mica-slate, porphyry, <fec., or in 
 secondary and alluvial deposits (wash-tin, tin sand, &c.) ; contains in addition to tin- 
 oxide, sulphur, arsenic, zinc, iron, copper, and other metals. It also occurs in the 
 sand of rivers as almost chemically pure stannic acid. Such tin, and that obtained 
 from washings, gives a much purer metal than vein-tin, as Nature has here already 
 executed a mechanical purification. The vein ores are first separated by stamping and 
 elutriation from the gangue and freed from sulphur, arsenic, and antimony by roasting. 
 
 According to the process in use at Altenberg in the Erzgebirge, the ore, after 
 roasting, is smelted in shaft-furnaces, 3 metres in height (Fig. 190, I. and II.). The 
 
 I. Fig. 190. 
 
 walls, constructed of granite, rest upon a founda- 
 tion of gneiss. The bottom stone, D, cojisists oi; 
 one piece, hollowed out to form a dish. The fore- 
 hearth, B, is connected by a tap-hole with an iron 
 pan ; the tuyere of the blast opens into the shaft 
 at o. The ore mixed with coal, coke or charcoal, is 
 placed in the shaft, A ; the reduced tin collects in the fore-hearth, B, whence it flows 
 into the pan, C. It contains iron and arsenic; from these impurities it is freed by 
 eliquation on a hearth covered with ignited fuel. The pure tin melts first, flows 
 through the fuel and collects on the tapping hearth, whilst a less fusible alloy of tin 
 with iron, &c., remains in grains, which the Saxon miners call " thorns." The slags, 
 which often contain 15 to 18 per cent, of tin, are smelted from time to time, yielding 
 tin and a residue which, like the " thorns," consists of an alloy of tin and iron. 
 
 The tin obtained in shaft furnaces is very pure, containing scarcely ^ per cent, of 
 foreign metals. It is known as grain tin. The less fusible alloy is re-melted and sold 
 as block tin. The presence of tungsten in fhe ores greatly interferes with the pro- 
 duction of pure tin. 
 
 Australia produces yearly 10 to 15,000 tons, Britain 10,000, the Straits (Malacca) 
 10,000, Banka and Billiton 9000, Tasmania 3-5000, Altenberg 150.* 
 
 * It is found in New Granada, but the Western hemisphere contributes practically nothing to 
 the commercial supply. Tin ores have also been worked in Central Asia, on the north and north- 
 west of Afghanistan, but nothing definite is known concerning the extent and the capabilities of 
 the deposits. 
 
200 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 Tin has a silvery colour, but with a bluish cast, and a perfect metallic lustre. 
 Next to lead it is the softest of the metals, but it possesses so much hardness that a 
 bar of tin, freely suspended, gives a sound if struck. If bent it creaks, the more 
 decidedly the higher its purity. Tin is very malleable, and can be wrought out to 
 very thin leaves. If rubbed it imparts a peculiar and very persistent smell to the 
 hands. The sp. gr. of pure tin is 7'28, but by hammering and rolling it can be raised 
 to 7-29.* If heated almost to its melting-point, it becomes brittle, and can be broken up 
 with the hammer. If used for castings, its lustre and tenacity depend entirely upon 
 its temperature at the moment of casting. If heated so strongly as to show in flowing 
 colours upon its surface, it appears striped after solidifying, and is called " red shoot." 
 If heated too little it is called " cold shoot", and has a dull surface. At a strong white 
 heat tin begins to boil and slowly evaporates. Melted tin becomes covered on its surface 
 with a grey film, consisting of stannous oxide and metallic tin. By continued fusion in 
 presence of air, tin is completely converted into a yellowish-white oxide, tin-ashes. On 
 exposure to the air tin gradually loses its lustre. 
 
 Assay of Tin Ores. For suitable methods we may refer the reader to " Select 
 Methods in Chemical Analysis," by W. Crookes, F.R.S., p. 403 ; for the determination 
 of lead in samples of tin, ibid. p. 409 ; for the separation of tin from copper, ibid. 
 p. 410 ; and for the commercial analysis of tinware, ibid. p. 413. 
 
 Uses. Tin is used in alloys (gun-metal, bronze, phosphor-bronze, bell-metal), and 
 formerly more than at present for domestic and table requisites, for the capitals of 
 stills, for cooling-apparatus, and tubs, dye-pans, and laboratory appliances. Tin is 
 used along with lead, because these alloys are harder than either of the constituents 
 alone, and resist wear better. By rolling and beating, tin is extended to tin-foil, the 
 stronger sort of which is used for lining mirrors so-called silvering and the thinner 
 kind for lining boxes, wrapping up chocolate, fancy soaps, sweetmeats, &c,f Stolzel 
 found in four qualities : 
 
 Tin . . 97-60 ... 97-81 .. 98-47 ... 96-21 
 
 Copper . 2-16 ... 1-23 ... 0-38 ... 0-95 
 
 Lead . . 0*04 ... 0-76 ... 0*84 ... 2-41 
 
 Iron . . o'li ... o'io ... 0-12 ... 0*09 
 
 Bismuth . trace ... ... .. 
 
 Nickel . .. ... ... 0-29 
 
 99'9i ... 99'90 ... 99'8r ... 99-95 
 
 False leaf silver is tin mixed with a little zinc, and beaten out to thin leaves. Tin 
 with small proportions of copper, antimony and bismuth, is often used for spoons, &c. 
 A similar alloy is Britannia-metal, used for spoons, candlesticks, coffee- and tea-pots, as 
 it approximates more to silver in its appearance than does tin ; it is harder, takes a 
 better polish, and is more easily wrought and rolled out to sheets. It consists of 90 
 parts of tin, with 10 of antimony, and generally small quantities of copper (0*09 to 
 0-8 per cent.) ; frequently i to 3 per cent, of zinc ; in one case, in an English 
 sample 1*83 per cent, of arsenic. Britannia-metal articles are sometimes silvered. 
 
 As the metals with which tin is likely to be contaminated accidentally or inten- 
 tionallyhave all a higher sp. gr. than tin, a determination of the sp. gr. of a sample 
 gives an indication of its purity. Alloys of tin and lead in the ordinary proportions 
 have the following specific gravities : 
 
 Sp. gr. 
 
 iSn + iPb . . . 8-864 
 iSn + 2Pb . . . 9-953 
 iSn + 3Pb . . . 9-9387 
 
 Sp. gr. 
 
 iSn + 4?b . . . 10-183 
 2Sn + iPb . . . 8-226 
 3Sn + iPb . . . 7-994 
 
 * Solid pieces of pure tin float upon a bath of melted tin, just as does ice upon water. 
 t There occur in commerce, however, tin-foils containing a large percentage of lead, and con- 
 sequently unfit for contact with articles of food. 
 
:SECT. II.] BISMUTH. 201 
 
 Tin-ash, mentioned above, is used in polishing glass and metals, and for giving a 
 white colour to enamels. 
 
 Tinning. The objects to be tinned are previously cleaned by scouring, washing, 
 or by acid liquids. The oxidation of the layer of tin to be applied is prevented by 
 means of resin and sal-ammoniac, which reduce immediately any oxide that has been 
 formed. Copper and wrought-iron are easily tinned, the vessel or other article to be 
 tinned being heated almost up to the melting-point of tin ; melted tin is then poured 
 upon it, and the metal is spread over the surface of the copper, &c., by means of a 
 bunch of tow, upon which sal-ammoniac has been scattered. Articles of brass, e.g., 
 pins, are boiled in tinned pans with granulated tin, and with a solution of potassium 
 bitartrate. The tinned articles are then rubbed with bran or sawdust. Sheet-iron, 
 which must be of the best quality, before tinning is very carefully cleansed with bran- 
 water which has turned sour, and with dilute sulphuric acid, plunged into melting 
 tallow, and then into melted tin. The tallow protects the tin from oxidation. After 
 the sheets are sufficiently coated with tin, they are taken out, cleared from any excess 
 of tin, and cleaned with bran.* 
 
 The clippings of tin-plate (tinners' waste), which contain 7 to 8 per cent, of tin, are 
 collected, freed from tin, and used as scrap-iron or worked up to ferrous sulphate. The 
 removal of the tin is sometimes effected by treatment with a mixture of nitric and 
 hydrochloric acids, and from the nearly neutral solution (which, of course, contains 
 iron chloride) the tin is thrown down by means of zinc. Or the tin waste is sus- 
 pended as an oxide in dilute sulphuric acid, the tin is deposited upon copper sheets 
 connected with the negative pole and may be taken off in plates, f 
 
 If tin-plates are corroded with acids, it often results that deposits of a nacreous 
 lustre appear on the surface, due to the crystallisation of the tin on rapid cooling. On 
 treatment with a mixture of 2 parts hydrochloric acid, i part nitric acid, and 3 parts 
 of water, the crystalline places are made apparent, which appear duller or brighter 
 according to the unequal reflection of the light. Crystalline surfaces may be produced 
 by the prolonged action of melted palmitic acid. Such tin-plate is called moire metal- 
 lique. They are found with large regular hexagons, others with squares, the small 
 crystals recalling the aspect of granite or gneiss ; others like mosses and ferns, large 
 trees or seaweeds, a strange regularity along with fantastic irregularity. Splendid effects 
 may be produced with the aid of lacquers, showing the lustre of many-coloured nacre, 
 along with the full colours of tortoise-shell, granite-like plates, apparently covered 
 'with elegant dendrites, the lustre of which is heightened by appropriate colours. 
 
 BISMUTH. 
 
 Bismuth ranks among the rarer metals. It is found at Schneeberg in the 
 Erzgebirge, in Peru, Chile, and Australia ; mostly native in cobalt and silver veins in 
 granite, gneiss, mica-slate, and in transition formations. It is also met with oxidised as 
 bismuth ochre, Bi 2 3 , and combined with sulphur as bismuthine, Bi 2 S 3 , or as cupreous 
 bismuth (containing 49*24 per cent, of bismuth). 
 
 The chief supply of bismuth is from the Saxon blue-colour works at Oberschlema 
 and Pfannenstiel, which are in possession of the great deposit of bismuth at Schnee- 
 berg. Formerly bismuth was obtained from its ores by eliquation, the mineral being 
 heated in iron pipes, laid in a sloping position, when the bismuth was liquefied, and 
 
 * Tern-plates are sheet-iron coated, not with pure tin, but with an alloy of tin and lead. Tern 
 Is employed for inferior wares, but should never be used for tins or cans for preserved milk, 
 meat, fruits, or vegetables, all of which act more or less upon the metals, and dissolve a quantity 
 of lead, which may in time have serious effects. It has also been found that in soldering up 
 canned provisions zinc chloride has been used instead of resin and with most serious effects. 
 
 f No process as yet known is perfectly satisfactory. Tern-waste is quite useless. 
 
202 CHEMICAL TECHNOLOGY. [SECT. u. 
 
 ran off. In this manner, only that part of the bismuth was obtained which was present 
 in the metallic state, and even this very incompletely. The rest, on the smelting of 
 the cobaltiferous residues, passed into the smalt- glass, when the bismuth collected in 
 the cobalt-speiss, and was again separated by eliquation. This imperfect process has 
 long ago been abandoned. 
 
 At the Saxon blue-colour works, all the bismuth and bismuth-cobaltic ores are first 
 roasted, and are then smelted in the crucibles of the smalt-glass furnaces, with the 
 addition of carbon, iron, and slag. The reduced metal beneath the slag forms two 
 very distinct layers, the upper, consisting of cobalt-speiss (cobalt-nickel and iron- 
 arsenides), the lower of bismuth. As the melting point of bismuth is very low, it is 
 run off in a liquid state as soon as the super jacent layer of speiss has solidified. 
 
 This crude bismuth is tolerably pure, containing only small quantities of iron, 
 cobalt, nickel, lead, silver, sulphur, and arsenic. The purification is effected by kindling 
 a wood fire on an iron plate, slightly sloping, and allowing the blocks of crude bismuth 
 to be slowly melted down. The refined bismuth, collected in an iron dish previously 
 warmed, is ladled out into hemispherical iron moulds, which have at the bottom the 
 arms of Saxony. These hemispheres weigh 10 to 12 kilos., and constitute the commer- 
 cial article. 
 
 At Freiberg bismuth is also obtained, in the wet way, from the litharge and ash 
 from silver refining. The ash is extracted with dilute hydrochloric acid. Basic bis- 
 muth chloride is precipitated from the solution by the addition of water, and is reduced 
 by melting in iron cmcibles with soda, charcoal, and glass. 
 
 The blue-colour works of Saxony produce yearly 18,000 kilos, of bismuth ; Freiberg, 
 2500; Johanngeorgenstadt, 1500; Altenberg, tjoo ; and Britain (from exotic ores), 
 2500 kilos. 
 
 Properties. Bismuth is a reddish -white metal, of a high lustre, a foliaceous tex- 
 ture, and so brittle that it may be pulverised. It is slighty malleable, if carefully 
 hammered. 
 
 The respective composition of Saxon (I.), Peruvian (II.), and Australian (III.) 
 
 bismuth is as follows : 
 
 I. ii. in. 
 
 Bismuth . . . 9977 ... 93'372 ... 94'iO3 
 
 Antimony ... ... 4'57o ... 2'62i 
 
 Arsenic ... ... ... 9*290 
 
 Copper . . . O'oS ... 2x358 ... i'944 
 
 Silver . . . 0-05 
 
 Sulphur . . o'oi ... ... 0-430 
 
 99-91 ... loo-ooo ... 99'388 
 
 Uses. Bismuth is used for alloys, melted as oxide, with boric and silicic acids, for 
 optical glasses, and of late to a considerable extent for porcelain colours, and, as basic 
 bismuth nitrate, for a cosmetic (blanc de /ard) ; also for medicinal purposes. Among 
 the chief alloys of bismuth are those with lead, tin, and cadmium. Newton's fusible 
 metal consists of 8 parts bismuth, 3 tin, and 5 lead, and melts at 64' 5. Rose's 
 metal consists of 2 bismuth, i lead, and i tin, and melts at 93*75. A small 
 addition of cadmium makes these alloys still more fusible. An alloy of 3 parts lead, 
 2 tin, and 5 bismuth, melts at 91 '66, and is suitable for obtaining cliches of woodcuts, 
 printing formes, stereotypes, &c. A similar alloy serves for metallic baths used in 
 tempering steel work, as also for pencils, used instead of graphite, upon paper prepared 
 with bone-ash. 
 
 ANTIMONY. 
 
 Occurrence. Antimony is found chiefly combined with sulphur, as stibine or 
 antimony-glance, Sb 2 S 3 , in beds and veins in granite and in crystalline slate and tran- 
 
SECT. II.] 
 
 ANTIMONY. 
 
 sition formations. It is also met with as antimony oxide, Sb 2 3 , in the minerals 
 valentinite (rhombic) and senarmontite (tessera!) . The latter occurs in great quantity 
 at Constantine (Algeria) and in Borneo. 
 
 Extraction. Antimony is chiefly obtained by fusion followed by desulphurising. 
 The smelting is effected in some districts, as at Wolsberg near Harzgerode, in crucibles,. 
 b, (Fig. 191). The bottoms are perforated and fixed upon smaller crucibles, c, which 
 are surrounded with hot sand or ashes. At both sides of the crucibles there are 
 draught -holes. In order the better to utilise the fuel, there is used in other places a 
 similar arrangement with two melting pots or crucibles, which are set on the hearth of 
 a reverberatory in such a manner that only the upper, charged crucibles are touched 
 by the flame. The lower crucibles are set outside the furnace in front of larger 
 crucibles in small vaults, and are connected with the furnaces by means of stone ware 
 pipes (Figs. 192 and 193). The eliquation of antimony sulphide can be effected most 
 rapidly when the ore as is done at Ramee in La Vendee, is placed directly upon the 
 sloping hearth of a reverberatory (Fig. 194) and care is taken that the antimony 
 
 Fig. 191. 
 
 Fig. 192. 
 
 Fig. 193. 
 
 Fig. 194. 
 
 sulphide, as it melts out of the ores, flows from the lowest point of the hearth through 
 the channel, e, to a receiver, f, placed outside the furnace. 
 
 After the ore is in a softened condition and a layer of slag has been formed, the 
 tap-hole is opened and the heat is raised. The sulphide remaining in the ore collects 
 beneath the slag and is let off after the end of the operation. 
 
 For obtaining antimony by tie roasting process, the sulphide is spread on the sole 
 of a reverberatory, and constantly turned over until it is chiefly converted into 
 antimony antimoniate. The roasted product is reduced in crucibles. Heating alone 
 would suffice for the reduction, as the roasted ore always contains un decomposed anti- 
 mony sulphide: 3Sb.,0 4 + 2Sb 2 S 3 = loSb + 6S0 2 . But as antimony oxide would 
 volatilise without a cover, the roasted ore is mixed with crude argol, or charcoal arid 
 soda. The regulus is allowed to cool slowly beneath the layer of slag, so as to acquire 
 that stellated crystalline surface which is preferred in trade. 
 
204 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 It is convenient to remove the sulphur from antimony sulphide by a precipitant 
 (iron, or spongy iron). But in the exclusive use of iron the result of the decomposition 
 is unfavourable, the separation of the iron sulphide from antimony being difficult, on 
 account of the approximate equality of their specific gravities. From this reason, and 
 to render the sulphide at once specifically lighter and more fusible, an alkaline carbonate 
 or sulphate is added. To 100 parts of antimony sulphide, 42 parts of iron waste 
 (wrought), 10 calcined salt-cake, and 3-2 parts of charcoal are found suitable proportions. 
 To obtain a regulus free from arsenic, 16 parts of the metal thus obtained (to which, 
 if not sufficiently ferriferous, 2 parts of iron sulphide may be added) are melted with 
 i part of antimony sulphide, and 2 parts of dry soda, and kept for an hour in fusion. 
 The regulus is melted a second time with i^, and a third time with i part of soda, 
 until the slag is of a light yellow. The presence of iron sulphide seems to be a con- 
 dition for the elimination of arsenic, as a compound is formed similar to arsenical 
 pyrites: FeS 2 + FeAs 2 . 
 
 At Banya in Hungary antimony is smelted in the blast furnace. 
 
 An electrolytic extraction of antimony can be effected, according to Borchers, by 
 decomposing a solution of 3*4 kilos. Sb 2 S 3 and 7-2 kilos. Na 2 S.9H 2 O corresponding 
 to the formula Sb 2 S 3> 3Na 2 S with the addition of 2 or 3 per cent, sodium chloride. The 
 resulting products were 2-435 kilos, antimony and in the solution 1*29 kilos. NaHS, 
 i -2 kilo. Na 2 S 2 and 1-563 Na 2 S 2 3< 5H 2 O. The process at the kathode seems to have 
 been according to the formula: Sb 2 S 3 -3Na 2 S + 3H 2 = Sb 2 + 6NaHS, and that at the 
 anode: 6NaHS + 3 = 3H 2 + 3Na 2 S 2 . 
 
 Very poor antimony ores may be worked to advantage, as antimony tersulphide is 
 easily soluble in very dilute solutions of sodium sulphide. To i mol. antimony 
 tersulphide there must be present in the liquid 3 mol. sodium sulphide. After the 
 former is dissolved, the liquid should mark 17 Tw. (if hot 12 to 14). About 3 per 
 cent, of sodium chloride, calculated on the entire quantity of the liquid, are added, 
 which helps to separate the dissolved iron sulphide and lessens the resistance on 
 electrolysis. If the solution remaining after the precipitation of the antimony is 
 worked up for sodium thiosulphate, the common salt separates out again on the final 
 evaporation. Iron vessels of any shape are used as decomposing cells and serve at the 
 same time as kathodes. If a vessel of quadrangular section is used, the kathode 
 surface may be increased by suspending in it iron plates. Between every two iron 
 plates a lead plate, insulated from the iron, is suspended as an anode. 
 
 Properties. The antimony of commerce contains arsenic, iron, copper, and sulphur. 
 It is purified by melting with antimony oxide, the oxide oxidises the iron and the 
 sulphur, and is reduced in the same proportion. Antimony is nearly of a silver white, 
 with a yellowish cast; it has a strong metallic lustre and a foliaceous crystalline 
 texture. Like its isomorphs arsenic and bismuth, it crystallises in distinct 
 rhombohedrons. Its sp. gr. is 6-712 and its melting point 430. 
 
 On solidifying, the melted metal does not expand. It is not extensible, very brittle, 
 and can be easily pulverised. It exceeds copper in hardness. The powder sold under 
 the name " iron black," and used for bronzing objects of plaster and papier mache, or 
 of cast zinc (by which they obtain the appearance of polished steel), is finely divided 
 antimony, obtained by precipitating a solution with zinc. 
 
 C. Himly found (1878) in three samples of commercial antimony : 
 
 Pb 
 S 
 
 As 
 Cu 
 
 Fe 
 
 Sb 
 
 
 . 0-34 
 
 0-34 
 
 O*I2 
 
 0-73 
 
 O*T I 
 
 . 
 
 0-09 
 
 0-36 
 
 1 i 
 
 0-09 
 
 
 O'OI 
 
 0'02 
 
 O'O2 
 
 . 
 
 . 0-35 
 
 0'34 
 
 0*16 
 
 
 
 . 98-98 
 
 98-8I 
 
 98-87 
 
SECT, ii.] ARSENIC. 205 
 
 For the assay of antimony ores and regulus the reader is referred to Mitchell & 
 Manual of Practical Assaying, 6th edit., edited by W. Crookes, F.K.S., pp. 556, 557,. 
 558; also to Select Methods in Chemical Analysis, by W. Crookes, F.R.S., 2nd edit., 
 pp. 396, 400, and 421. 
 
 Alloys. An admixture of antimony in general renders metals more lustrous, hard, 
 and brittle. "Hard lead" contains antimony up to 12 per cent. If, with Calvert 
 and Johnson, we take the hardness of lead as i, that of an alloy of 34-86 lead and 65-14 
 antimony = 11*7, and that of 86-50 lead and 13*50 antimony = 4. Thus, the hardness of 
 lead may be increased almost twelve-fold by the addition of antimony. Alloys con- 
 taining 17 to 20 per cent, of antimony form type-metal. Of the alloys of antimony and 
 tin Britannia metal is the most valuable. It consists of 10 parts antimony and 90 parts 
 tin. Similar alloys are pewter (89-3 tin, 7-1 antimony, r8 copper, and i'8 bismuth); 
 argentine (85.5 tin and 14-5 ant-:noiiy), sometimes used for spoons and forks; and 
 Ashbury metal (77*8 tin, 19-4 antimony, and 2'8 zinc), used for plummer blocks for 
 locomotives and for the spindles of turners' lathes. An alloy of 5 antimony, 5 nickel,. 
 2 bismuth, and 87-5 tin has been lately recommended. 
 
 The production of antimony is 
 
 Britain 2000 tons. 
 
 France 580 
 
 Austria-Hungary .... 800 
 
 Germany 650 
 
 Italy 100 
 
 Spain 8 
 
 ARSENIC. 
 
 Arsenic occurs either native, or associated with metals, sulphur, and metallic 
 sulphides. The oxides of arsenic never occur in nature is such quantity as to be of any 
 technical importance. Small quantities of arsenic are found in all pyrites, and thus 
 find their way into sulphuric acid. 
 
 Production. Arsenic is obtained by subliming native arsenic, or by heating 
 arsenical pyrites (mispickel), FeSAs, and mohsine, Fe 4 A 6 , or by reducing white 
 arsenic (arsenious acid) : As 2 3 + 3C = 3CO + As 2 . 
 
 It is met with in commerce in greyish-black, crystalline crusts of a metallic lustre, 
 and of sp. gr. 5-72. It evaporates at 180, and melts (in closed vessels) at higher 
 temperatures ; and sometimes contains 8 to 10 per cent, of arsenic sulphide. Pure 
 arsenic is used in the manufacture of shot, and for producing a light (by the combustion 
 of arsenic in oxygen) used in trigonometric and military telegraphic signalling under 
 the name of Bengal light. 
 
 Arsenious acid (arsenious anhydride, arsenteroxide, white arsenic) is obtained as a 
 by-product in working up arseniferous cobalt, nickel, silver, and tin ores, in the blue 
 colour works, in tin and silver furnaces, <fcc. ; the arsenical ores being roasted in rever- 
 beratories and the vapours being led into flues and chambers in order to condense the 
 arsenious acid. In Silesia arsenical pyrites are roasted expressly for the production of 
 arsenious acid. The sublimation is effected in iron kettles (a, Fig. 195), upon which are 
 set iron rings, b, c, d, and upon these again a dome, e, which is connected by means of 
 pipes with the chamber, i. Along with this chamber there are other chambers. After 
 all the joints and chinks have been luted up the sublimation begins. The heat must be 
 increased so that the arsenious acid collecting in the chamber, i, begins to soften. When 
 cold it appears as a perfect glass (arsenic glass) of a conchoidal fracture, vitreous lustre, 
 and transparency, which in time becomes white, porcelain-like, and of an opaline or 
 waxy lustre. Like the other preparations of arsenic, it is very poisonous. Sometimes 
 there occur in arsenious acid small quantities of antimony sulphide and oxide. 
 
206 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. ii. 
 
 Fig- i95- 
 
 Arsenious acid is used, dissolved in glycerine, as a mordant in calico printing ; it 
 serves also for purifying glass (especially crystal glass) during melting, for certain 
 arsenical preparations (alkaline arsenites, Schweinf urt green, and other copper colours), 
 as an antiseptic in stuffing the skins of animals [which is a dangerous blunder, as its 
 antiseptic power is not great], for producing certain tar-colours ; dissolved in hydrochloric 
 acid for producing a grey colour on brass, and sometimes for hardening iron. One 
 
 part of crystalline arsenious acid dissolves in 355 parts 
 of water at 15, whilst one part of the amorphous acid 
 takes only 108 parts of water for solution. 
 
 Arsenic Acid, H 3 As0 4 , is obtained by boiling arse- 
 nious acid in 4 parts of nitric acid of sp. gr. 1-35 and 
 evaporating the solution to dryness, or by passing 
 chlorine into arsenious acid suspended in water or dis- 
 solved in -hydrochloric acid. It is sometimes used 
 instead of tartaric acid in. calico printing, and, besides, 
 for preparing tar-colours, especially rosaniline or 
 magenta,* Acid sodium arseniate (sodium dihydro- 
 arseniate, NalI 2 As0 4 ), which is used in print works 
 in the " dunging process," in place of cow-dung, is 
 prepared by the cautious and prolonged heating of 
 36 pai'ts arsenious acid with 30 parts sodium ixitrate, 
 or by heating a mixture of dry sodium nitrate and 
 sodium arseniate. By saturating the solution of this 
 salt there is obtained the so-called " saturated arseniate 
 of soda " (disodium hydro-arseniate, Na,H AsO 4 . 1 2H,0), 
 which is also vised in dyeing and tissue printing. 
 
 Realgar, As 2 S 2 , is often found in crystals in mineral 
 veins, or is produced artificially by melting sulphur 
 with an excess of arsenic or arsenious acid, or, on the 
 large scale, by submitting arsenical pyrites to dis- 
 tillation, or lastly as formerly done in Freiberg 
 
 by melting the arsenic sulphide from the sulphuric acid works under increased 
 pressure, and purifying the crude glass by sublimation. Realgar is a ruby-red 
 mass of a conchoidal fracture, which, if mixed with saltpetre and ignited, burns, 
 giving off a brilliant white light. The mixture for white fire consists of 24 parts 
 saltpetre, 7 sulphur, and 2 realgar. 
 
 Orpiment, As,S 3 , is also found naturally, and is obtained artificially (as a mixture 
 of As,S 3 with arsenious acid) by melting together sulphur with arsenious acid or 
 realgar, or by the distillation of a corresponding mixture of arsenical and sulphur 
 pyrites. It forms massive, pale orange, transparent lumps (so-called yellow glass), 
 which always contain arsenious acid up to 97 per cent., so that the yellow arsenic 
 .sulphide obtained in the dry way may perhaps be regarded as an arsenic oxysulphide. 
 In the wet way it is obtained by precipitating a hydrochloric solution of arsenious 
 acid by sulphuretted hydrogen, or by decomposing sodium sulpharseniate (As a S 3 NaS 2 , 
 obtained by fusing arsenious acid with sulphur and sodium carbonate) with dilute 
 sulphuric acid, or lastly, by boiling a solution of arsenious acid in hydrochloric acid 
 with sodium thiosulphate. In the last manner it is produced of an especially fine 
 colour. Orpiment obtained in the wet way is used in oil-painting as a yellow pigment 
 under the name of King's yellow. It was used in dyeing for the reduction of indigo, 
 and it serves also, under the name of rusma, for the removal of superfluous hair. For 
 
 * Medlock process. 
 
SECT. 
 
 II.] 
 
 MERCURY. 
 
 207 
 
 this purpose a mixture of 9 parts of lime and i part of orpiment is made up into a paste 
 with water. Calcium hydrosulphate, prepared by passing sulphuretted hydrogen into 
 cream of iime until it takes a greyish-blue colour, is now used in preference. 
 
 MERCURY. 
 
 Occurrence. Mercury is found native, but chiefly as cinnabar, HgS, in beds and, 
 veins in crystalline slate rocks, in transition and Flotz formations, and is sometimes 
 found in secondary deposits in loose, rounded fragments. 
 
 The chief localities are Almaden, or Almadingas, in Spain (Silurian), where it was 
 raised in antiquity, and Idria, in Carniola (carboniferous). Cinnabar is also found in 
 the Bavarian Palatinate near Wolfstein ; on the Stahlberg, the Moschelandsberg, and 
 the Potsberg, near Kusel ; at Olpe, in Westphalia ; in some parts of Carinthia, Eisenerz, 
 in Styria ; Horzowitz, in Bohemia ; in several places in Hungary and Transylvania ; at 
 DalF alta, in Yenetia ; on the Ural ; in China and Japan ; in the district of Sarawak, 
 in Borneo ; in Mexico ; at Huancavelica, in Peru ; and in large quantities in California, 
 in transition formations.* 
 
 An impure cinnabar, mixed with earthy and bituminous matter, or a carboniferous 
 shale, rich in cinnabar and paraffine, is known as mercury-lime-ore, and is peculiar to 
 Carniola. A mercurial fahl- ore, containing from 2 to 15 per cent, of mercury, may also 
 be mentioned. 
 
 Production. At Idria the older shaft-furnaces are connected on both sides with a 
 series of condensation chambers. The 
 cinnabar is converted by the action of 
 atmospheric oxygen into sulphurous acid 
 and metallic mercury 
 
 HgS 4- 2O = 2S0 2 + Hg. 
 
 At the works in Idria there was used 
 in 1884 as fuel partly wood and partly 
 lignite. In the previous year there were 
 worked up 49,384-1 tons of ore, con- 
 taining on an average 0*95 per cent, of 
 mercury, besides 1044*2 tons of furnace 
 residues produced on the spot, and con- 
 taining on an average 10-12 per cent, 
 of mercury, and rubbish from the foun- 
 dations of old furnaces, 2968-3 tons, 
 containing 0^51 per cent, of mercury. 
 There were produced metallic mercury 
 
 4537-52 kilos., and intermediate products (stupps) 98-15 tons, containing 1053-2 kilos, 
 of mercury, or a total yield of 5590-72 kilos. Hence the average proportion of mercury 
 secured was 94-22 per cent. ; if we omit the working up of the stupp and the mercury 
 extracted from it, 94-06 per cent. ; or a loss of metal, in round numbers, of 6 per cent. 
 
 The arrangement for condensing mercurial fumes introduced at Idria in 1882 
 consists of four ranks of pipes, which are formed of three condenser-elements, 
 A (Fig. 196), each made up of two tubes, a, a twin-tube, 6, and a cut-off portion, c, all 
 fixed vertically upon the plates, v ; the pipes, a, are closed with lids, d, provided with 
 small openings for cleaning. The plate forms a part of the supporting surface for the 
 tubes, a, formed by an internal circular rib of b, and has an aperture by which it is 
 possible to get to the bottom of g, the box for receiving the stupp. The additional 
 
 * An extensive deposit of mercury is said to exist in the Transvaal, but no particulars are as 
 yet known. 
 
203 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. ii. 
 
 pieces of pipe, h, effect the communication between the pipes which bring and which 
 carry off the furnace-gases. All the cast-iron pipes, excepting c, and the boxes for 
 collecting the stupp, are lined with layers of cement-mortar 10 to 15 millimetres in 
 thickness, which has proved to be an excellent protection against the action of acid 
 vapours. The gases enter the condenser at e, descend in the pipe, a, turn into the 
 pipe, a, and rise in the second pipe, a, in order to traverse a similar course twice in the 
 following portions of the condenser. The products of condensation are a mixture of 
 finely divided mercury, particles of unburiit fuel, undecomposed hydrocarbons, ore, and 
 ashes, as also moisture from the ore, and the fuel. The condensed steam-water, 
 containing fluctuating quantities of soluble mercurial salts, is led into the wooden 
 chests, k, where also solid matter which has been swept over may be deposited, and 
 then into large cemented sumps, where it is sprinkled, in order to precipitate the mercury 
 from its salts, with a lye of sodium sulphide, and is then allowed to run off. The 
 stupp collecting under the water upon the sloping bottom of the chest, g, is raked upon 
 the plate, //, after the free mercury and the water have drained off into dishes or 
 chests. The mercury collecting at the deepest part of the chest runs off into i. The 
 refrigeration of the condenser is effected by water conveyed from above, and allowed to 
 (low down in a thin, uniform layer over the entire surface of the pipes, a and b ; it 
 then collects in the water-tight cistern formed by the plate nv, and escapes through a, 
 lateral channel to the drains. 
 
 Fig. 197. 
 
 Fig. 198. 
 
 At the Almaden works the mercurial vapours are condensed in aludels, pear-shaped 
 vessels of earthenware, open at both ends, and fixed together so that, as shown in 
 Fig. 197, the thinner end of one fits into the wider end of the other, forming long 
 rows after the joints have been luted together with clay and ashes. The cylindrical 
 shaft- furnace, A (Fig. 198), is divided into two compartments by a perforated vault. 
 The fire is made in the lower compartment and the ores are placed in the upper. 
 Large blocks of a sandstone containing cinnabar are placed at the bottom (containing 
 so little mercury that they do not admit of mechanical concentration), and upon these 
 are placed the rich ores. The vapours pass into twelve series of aludels. Each series 
 is 20 to 22 metres long and comprises 44 aludels. Consequently, there are in each 
 furnace 528 aludels. The series lie on an inclined plane. From the lowest aludel the 
 condensed mercury flows through the channel, g, into the stone cisterns, h. The 
 vapours riot condensed in the aludels are received in chambers, where they are 
 completely precipitated. The mercury mixed with soot is purified by allowing it to 
 flow down a slightly inclined plane ; the mercury flows fairly clean into a sump ; the 
 sooty dust is left behind and is distilled again. 
 
 The furnaces used in America for coarse-grained ores are very similar to those 
 devised at Idria, in 187 1 , by A. Exeli ; they are iron-clad shaft furnaces. The shaft, A y 
 
SECT. 
 
 II.] 
 
 MERCURY. 
 
 209- 
 
 (Figs. 1 99 and 200) with twelve view-holes, s, is 1-87 metre in diameter; the four upper 
 metres of the height are cylindrical, whilst the following 2-3 metres have the form of a 
 truncated cone. Beneath the three fire-boxes, f, at the side, are the exit apertures, . 
 The round part of the furnace is clad with iron, 5 millimetres in thickness, enclosing a 
 
 Fig. 199. 
 
 Fig. 200. 
 
 rough wall of ordinary bricks 0*12 metre thick, an 
 inner wall 0*33 metre thick, which, as well as 
 the filling between the two, is made of fire- 
 proof stones. The angular part of the furnace 
 is armed with cast-iron plates, well luted and 
 screwed down ; the cast-iron bottom plate slopes 
 down towards the middle. The arrangement 
 
 ;it the top of the furnace has a water joint, o'6 metre ; below the top are six 
 apertures at equal intervals which convey the gases and vapours by means of the system 
 of pipes, r ; the gases and vapours escape into a large cast-iron main, and from thence to 
 the condensers. In this system of pipes almost half the mercury collected is condensed. 
 The furnace shaft is filled completely, but a space of 1*2 to 1*5 metre in height is left 
 empty, where the vapours may collect. Every two hours at New-Almaden a fresh 
 charge of 720 kilos, of rich ore and 1-5 percent, of coke is introduced, so that 10 tons 
 
 Fig. 20 1. 
 
 are worked up daily with an expenditure of 2*7 cubic metres wood and the labour of 
 two men for twelve hours. 
 
 The Knox- furnace (Figs. 201 to 203) first constructed at Knoxville, Redington, 
 has been introduced at Sulfurbank, California, and Manhattan works, &c. The shaft- 
 furnace, A, 1 1 -7 metres high, and lined with fire-bricks, is constructed above and 
 telow of compact masonry, and is separated in its upper half by the five arches of 
 masonry, a, of which the lowest project furthest outwards past the chambers, 
 d and d, which are closed except one opening each (Fig. 203). The air-ducts, e, serve 
 
 o 
 
2IO 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. ii. 
 
 to cool the masonry, which is 2-5 metres in thickness. The sole of the chambers, d, 
 is protected against the penetration of the mercury by a strong iron plate. The charge of 
 the furnace consists of two to three parts lumps (from 0-06 to 0-2 in size), and one part 
 smalls ; if the smalls are plentiful and moist the yield sinks to sixteen and even twelve 
 tons daily. The shaft, which is closed at top with a bail-section, B, is charged with 
 55 tons of ore, and at the sloping mouth, c, one ton of dead ore is drawn out every 
 hour, whilst fresh ore is added at B. Thus the charge remains in the furnace for three 
 
 days. The grate, 
 d, lies 6 'i metres 
 below the top of 
 the furnace ; the 
 fire is stirred up 
 every half - hour. 
 The combustion 
 gases generated in 
 the fire-box enter 
 the ore through the 
 openings between 
 the arches, a, pass 
 along with the pro- 
 ducts of distillation 
 between the oppo- 
 site arches into the 
 space, d, and thence 
 through the pipe, 
 k, into the cast-iron 
 condensers, /. 
 These are rectan- 
 gular chests with a 
 sloping bottom 2*4 
 metres long, 074 
 
 Fig. 203. metre wide, and 1-5 to i - 8 
 
 metre high, connected 
 with each other by the 
 pipes, k. The covering 
 plates are turned up at 
 the edges and kept cool 
 with water, which runs 
 over and trickles down 
 the sides. The condensed 
 products collect in the 
 lowest parts of the bottom 
 plate. The wooden con- 
 densers in connection are 
 
 similarly arranged. The condensed products collect in the pans, IT, from which the 
 mercury is baled out into bottles. The acid water is run out into the recipients, P, in 
 which a little mercury deposits. The vapours which issue from the furnace are very hot, 
 so that the mercury condenses chiefly in the middle coolers. From the last condenser 
 the gases, when quite cold, are driven by means of a Roots' blast, Q (four of which, 
 along with the water-pump, S. a saw, &c., are driven by the engine, R\ into the wooden 
 channels, U, of o'6 by 075 metre section. After running 89 metres each, two of them 
 unite into a larger channe of i '2 by 1*5 metre section, which conveys the gases for 
 
 '.*___* i PI * y 
 
SECT. II.] 
 
 MERCURY. 
 
 211 
 
 Fig. 204. 
 
 350 metres to a four-sided wooden scrubber tower, 4-5 metres high, filled with pebbles, 
 over which water trickles. A furnace works up daily 96 tons of ore, and uses 36 cubic 
 metres of firewood. 
 
 In 1883 California yielded 46,725 bottles of mercury, 28,700 from New Almaden. 
 Between the years 1850-1883 California produced 1,357,403 bottles, each of 34*695 
 kilos, of mercury, Idria only 272,834, and Spain 1,044,139 bottles, each of 34*507 kilos. 
 The price of mercury in 1874 reached a maximum of 125. and fell in 1883 to a 
 minimum of 35. ; in consequence, in March 1884, 22 of the 27 furnaces in California 
 were out of work. In 1886 California yielded only 29,981 bottles. 
 
 At Horzowitz in Bohemia cinnabar containing clay iron ore is mixed with x to A its 
 weight of forge scales and charged in a bell-furnace (Fig. 204) upon iron plates or dishes 
 b &, which are secured to an iron support and covered with an iron bell, e, dipping into 
 water. The bell is placed in a fur- 
 nace shaft of masonry and ignited by 
 means of a coal fire. The mercury 
 descending collects in d. Each bell, 
 of which there are six in a furnace, 
 contains 25 kilos, of ore and 12 kilos, 
 of anvil scales ; from 30 to 36 hours 
 are required for the process. 
 
 The mines at Rosswalde near 
 Stahlberg, in the Palatinate (opened 
 in 1410), those at Landsberg, Pots- 
 berg, and Wolfstein contain cinnabar 
 diffused through sandstone. The pro- 
 portion of mercury is generally 0*005 
 -and sometimes o-oi per cent. To be 
 worth extraction, it must form ^i^ 
 part of the ore. The decomposition 
 of the cinnabar is conducted in iron 
 retorts, of which 30 to 50 are placed 
 in a galley-furnace. Lime is added 
 to the ore when mercurial fumes are 
 evolved, and there remains a mixture 
 of calcium sulphide, thiosulphate, and 
 sulphate. 
 
 The mercury works at Siele, near Castellazara, operate upon a very rich ore, partly 
 in Hahner shaft-furnaces and partly in muffle-furnaces. The neighbouring works at 
 Cornachino has two furnaces, each with three muffles of cast iron. Each is 27 metres 
 long, 64 centimetres wide, and 32 centimetres in height. They are charged with 140 
 kilos, of ore and 84 kilos, of lime, both broken up and well mixed. This quantity is 
 distilled off in six hours, so that the muffles are charged four times daily. 
 
 Details concerning the Chinese mercury mines are wanting. In 1782 a consider- 
 able quantity of mercury was exported from thence to South America. 
 
 Properties. Mercury has a strong metallic lustre and a white colour, with a faint 
 blueish cast. At common temperatures it is liquid ; it solidifies and becomes malleable 
 at ~ 35-5 an( l boils at 360 . Its sp. gr. is 1 3-5. It combines readily with lead, bismuth, 
 zinc, tin, silver, and gold, forming amalgams ; less readily with copper, and not at all, 
 under ordinary circumstances, with iron, nickel, cobalt, and platinum. On these 
 properties depend its applications for the separation of gold and silver from ores 
 (amalgamation) ; amalgams are used for coating mirrors, for fire gilding, and for the 
 friction-cushions of electrical machines. 
 
212 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 Mercury is used in various scientific and technical apparatus, barometers, thermo- 
 meters, levels, Sprengel pumps. &c. For directions for the detection of mercury in 
 minerals, and for the assay of mercurial ores, see Select Methods in Chemical Analysis, 
 by W. Crookes, F.R.S., pp. 292, 293, and 294. 
 
 ZINC. 
 
 Occurrence. Zinc never occurs in the metallic state, but combined with sulphur as 
 blende ZnS, and sometimes with small quantities of indium and gallium ; it is found 
 oxidised as calamine or zinc-spar, ZnC0 3 , and as electro-calamine, zinc silicate, 
 Zn 2 Si0 4 ,H 2 O. It is also found as willemite, an anhydrous zinc silicate, as red zinc ore, 
 or zinc oxide, coloured reddish by oxides of iron and manganese (spartalite), as 
 franklinite, Fe 2 Zri0 4 , as gahnite, Al 2 ZnO 4 and in some fahl-ores. 
 
 The distillation of zinc from calamine and roasted blende in muffles is practised in 
 Upper Silesia, at Stolberg near Aachen, in Westphalia, &c. The muffles are made upon 
 
 moulds, and consist of fire clay 
 
 Fig. 205. Fig. 206. and fragments of old muffles. 
 
 The front side of a muffle has 
 two openings ; the lower is 
 closed with a plate, a (Figs. 205 
 and 206), which is removed 
 when the residues of the pro- 
 cess have to be drawn out. 
 
 Above, a tube with an elbow joint is introduced, with an aperture which is closed at c, 
 during distillation, and through which the charge is introduced. The liquid zinc flows 
 out of d into the space below. The muffles are placed upon banks on the vaulted zinc 
 furnace on both sides of a long fire grate, so that they are wrapped in the flame as much 
 as possible. The zinc oxide formed at the beginning of the distillation contains nearly all 
 the cadmium oxide, and serves for the preparation of cadmium. At the outset, the con- 
 densers are so cool that the vapours of zinc condense in them, not to a liquid, but to a 
 solid, finely divided metal known as zinc powder. It contains about 98 per cent, of zinc, 
 and is used as a powerful reducing agent, especially in calico printing. The zinc drops, 
 afterwards formed in the old furnaces (drop zinc), are made to coalesce by remelting. 
 In the recent furnaces the zinc is collected as a liquid in clay receivers and is taken out 
 with iron ladles and poured into moulds. 
 
 Recently, gas-firing on the principle of Siemens or of Boetius has almost every- 
 where superseded grate-fires. In the latter case the furnace has two generators, a 
 (Figs. 207 and 208), so that the fire-gases from each generator pass through half the 
 furnace and then down in the middle through a common main shaft, or into the 
 flues, c, placed between the muffles, and then through a channel connecting the latter 
 into the main, d. The air required for gasification streams through the draught holes, b, 
 into the furnace ; the air for combustion is introduced through channels left in the 
 walls of the furnace. The greater part of them are led through the furnace-walls in 
 the reserved channels, n, in such a manner that this air meets the combustion gases, 
 which have been half burnt in the combustion shaft, and so burns it gradually and com- 
 pletly, in order to produce a uniform heat. In order to convey away the vapours, which 
 greatly annoy the workmen, the arch aoove the fore-cupels is provided with an exit 
 slit, s, opening into the channel, k, leading into a small chimney. 
 
 On the Belgian system the distillation of the zinc is effected in stoneware pipes 
 which lie in rows, over and alongside each other, slightly sloping. The pipes (Fig. 209) 
 are cylindrical, generally i metre long, 18 centimetres in internal diameter, and closed 
 at one end. The front opening of the pipes touches the front wall of the furnace and 
 serves for introducing the charge, drawing off the zinc vapours, and removing the 
 
SECT. II.] 
 
 ZINC. 
 
 213 
 
 residues. To each of these pipes there is attached a tube (Fig. 210), 25 centimetres in 
 length, and to it again a tube of sheet iron (Fig. 211) 20 centimetres long, or a larger 
 sheet iron receiver (coated within with clay), in which the zinc collects. Fig. 212 
 shows the section of a Belgian zinc furnace. The distilling tubes lie in ranks above 
 each other, slightly inclining. For this purpose there are left steps in the back wall, b d, 
 
 Explanation of Terms. 
 Schnitt I-II. = Section I. II. 
 
 Fig. 207. 
 
 Fig. 209. 
 
 Fig. 210. 
 
 Fig. 211. 
 
 Fig. 212. 
 
 of the furnace, upon which the closed ends of the pipes rest. Whilst the Belgian fur- 
 naces formerly worked up daily 200 kilos, of ore in 30 tubes, those of recent make, with 
 70 tubes, use up 1200 kilos. 
 
 According to Liebig, the zinc works of the Markisch-Westphalian Mining Union at 
 Letmathe have in action twenty-six zinc furnaces, with seventy-six retorts each. 
 Each furnace works up daily 1600 kilos, of ore (| bleude and ^ calamine), containing 
 
214 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. n. 
 
 on an average 45 per cent, of zinc, and produces 580 kilos, crude zinc. The con- 
 sumption of fuel is about 23 hectolitres heating coal and 8 hectolitres reducing-coal. 
 Three retorts are charged daily in each furnace. 
 
 The English method of obtaining zinc (Wales, Sheffield, Birmingham, Bristol) is 
 the so-called downward distillation in crucibles. The reducing furnaces are so con- 
 structed that six to eight crucibles, c (Fig. 213), can be placed upon the hearth. The 
 crucibles are made of fire-clay and are i| metre high. In the middle of the bottom 
 is a hole through which the zinc fumes pass into the condensing tubes. The charge is 
 introduced into the crucibles through a hole in the lid, which is left open for about two 
 hours after charging, until a blue flame shows that reduction is beginning. The 
 opening in the cover is then closed with a plate of fire-clay, the condensing pipe is 
 joined to the opening in the bottom of the crucible, and below it is placed the receiver 
 for the zinc, often filled with water, to prevent the zinc from spirting as it falls. The 
 distilling zinc collects in drops and in fine powder mixed with zinc oxide, and is 
 re-melted in iron vessels. The oxide which separates on the surface is skimmed off 
 and the zinc is run into moulds. This process, especially 
 at Swansea, has been latterly superseded by Belgian fur- 
 naces. 
 
 The production of zinc in blast furnaces has been at- 
 tempted without success, as the zinc is re-oxidised to zinc 
 oxide by the carbon dioxide. 
 
 From the receivers of the zinc distillation furnaces there 
 escapes, as the author has shown, carbon monoxide nearly in 
 a state of purity. This can be explained if the solid carbon 
 forms only carbon monoxide- 
 
 - 85,000 + 29,000 = - 56,000 heat units, 
 or if the carbon monoxide originally formed is reduced again 
 (C0 2 + C 2 CO), so that the original process would be 
 2ZnO + C = Zn 2 + CO 2 
 
 170,000 + 97,000 = 73,000 heat units. 
 The latter process takes up decidedly more heat than the 
 former, and is therefore very improbable. 
 
 The reduction of zinc is hence effected chiefly or exclusively by solid carbon. 
 For the production of 65 kilos, of zinc there are required theoretically only 56,000 
 heat units, or 860 heat units per kilo., corresponding to 0-12 kilo, of coal. In practice 
 twenty times the quantity of coal is required, so that the utilisation of heat is still very 
 imperfect. 
 
 Production of Zinc by Electricity. L. Letrange roasts blende at a low temperature 
 to convert it into zinc sulphate. The roasted ores are lixiviated in walled tanks, coated 
 with asphalte, A (Figs. 214 and 215), connected by pipes. The residues are worked up 
 for lead and silver if present, the solution of zinc sulphate is collected in the cistern, B, 
 and freed, if necessary, from iron, &c., and conveyed by the pumps, P, and the pipes, d, 
 to the precipitating tank, C. The kathodes, b, consists of thin sheet zinc, but polished 
 copper or brass may be used, from which the deposited zinc is easily removed. The 
 anodes, c, are of carbon, platinum, or lead. The lye rendered acid by the elimination 
 of the zinc flows away continuously through pipes, o, in order to be used for dissolving 
 fresh masses containing zinc oxide. If very pure calamine or zinc-ash is to be worked 
 up, it is mixed with carbon and suspended in the bath in a porous vessel as an anode. 
 
 Letrange fitted up such an installation for working up zinc-ash at his rolling milk 
 at St. Denis ; a second installation for blende containing lead and silver has been 
 erected in the Department du Var. When a stratum of metallic zinc, 4 to 5 millimetres. 
 
SECT. II.] 
 
 ZINC. 
 
 215 
 
 in thickness has been deposited upon the brass sheets serving as negative poles, a work- 
 man takes out the sheets and removes with a knife the zinc plate, which strips off like 
 a piece of leather. The metal thus obtained is re-melted. The process devised by 
 Letrange of converting the ores into sulphates by treatment with sulphurous acid and 
 precipitating them electrolytically would render it possible to utilise large quantities of 
 poor calamines. 
 
 According to Kosmann, there are obtained at St. Denis, in regular work from roasted 
 blende with i horse power, 8 kilos, of zinc every 12 houra ; consequently, with 1-4 kilo, 
 coal per hour and horse power, for i kilo, zinc, 2 - i kilos, coal; whilst in the zinc works 
 of Upper Silesia, there are consumed for i kilo, zinc, 2 kilos, coal for reduction, and 
 9-8 kilos, for heating. These statements appear doubtful, the assertion that 0*67 kilo, 
 of zinc is obtained hourly per horse power can only hold good in cases of soluble anodes. 
 For insoluble anodes the separation of 65 kilos, of zinc from the solution requires 
 170,000 heat units, consequently per kilo. 2615 heat units. Or as i horse-power hourly 
 (75 + 60 + 60): 428 = 631 heat-units, there are required at least 4 horse-power, or 
 7 horse-power (equivalent to 10 kilos, of coal) if only 50 to 60 per cent, of the power 
 of the machine is utilised. It must also be remembered that with feeble currents 
 hydrogen is always evolved. 
 
 Figs. 214 and 215. 
 
 In a solution of zinc sulphate of specific gravity 1*38 this escape of gas ceases if 
 about 0*5 gramme zinc are deposited per second on i square metre of polar surface 
 (corresponding to 16 amperes). For 10 per cent, solutions a density of current of 20-30 
 amperes is required per square metre. 
 
 Kiliani treats calamine, &c., with a solution of ammonia holding ammonium 
 carbonate in solution. The liquid is led into decomposition troughs, the zinc is deposited 
 at the kathode and oxygen is evolved at the anode. The kathodes are of zinc or brass ; 
 the anodes of sheet iron, The lye as it flows off is conveyed back into the closed 
 dissolving tanks. 
 
 If soluble anodes are used, much less work is required from the current. If when 
 decomposing a solution of zinc sulphate the anode consists of pure zinc, there are used 
 at the negative poles for each molecule of ZnS0 4 106,090 heat-units chemical work ; 
 but at the anode, exactly the same quantity is again developed, so that the current has 
 merely to undertake the mechanical work of conveying the ions from one pole to the 
 other. This mechanical work is expressed in the tension, or the development of heat. 
 Jahn has shown that notwithstanding the differences of the chemical work to be per- 
 
2 i6 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 formed by the current, the total loss of energy of the chain, e.g., by the oxide, zinc 
 sulphate, and copper sulphate is the same, as in the separation of i kilo, copper m 
 which 1807 heat-units are evolved, and of i kilo, zinc, 977 heat-units, corresponding 
 to: 
 
 Free Chem. 
 
 heat. work. 
 
 ZnS0 4 . . 63,210 + 106,090 = 169,306 heat-units. 
 
 CuSO 4 . . 114,744 + 59,96o = 170,704 >i 
 
 According to the process of Bias and Miest the bath for working up blende consists 
 of zinc sulphate ZnS0 4 + ZnS = Zn + S + ZnS0 4 . As much zinc as is deposited on 
 the kathode is dissolved at the anode, whilst the corresponding quantity of sulphur 
 is separated out and can be freed from the gangue found in the sediment. The blende 
 does not require to be roasted and the sulphate is obtained free. Less work is 
 required from the current than in former methods. Since, then, only the decom- 
 position of the zinc sulphide is in question, as 
 
 Zn | S0 4 - Zn | S 
 
 - 106,090 +106,090 - 41,326 = - 41,326 heat-units. 
 
 Hence, there is needed for i kilo, of zinc 41,326 : 65-5 = 63-1 heat units, whilst for 
 decomposing zinc chloride and sulphate more than double the chemical work is required. 
 Pure blende is a bad conductor ; the ordinary kind containing iron is better. 
 
 Luckow suspends in the bath a mixture of blende and coke, packed in boxes, but 
 hitherto with little success. 
 
 Siemens and Halske recommend their process for working up blende. There are 
 formed in the electrolytic decomposition cells zinc and ferric sulphide, according to the 
 equation : Zn SO 4 + 2Fe S0 4 = Zn + Fe 2 (S0 4 ) 3 . The ferric sulphate thus formed has 
 the property of dissolving zinc from sulphuretted zinc ores which have been slightly 
 roasted, according to the equation : 
 
 ZnS + Fe 2 (S0 4 ) 3 = ZnS0 4 + 2FeS0 4 + S. 
 
 A comparison of this and the former equation shows that after lixiviating slightly 
 roasted zinc sulphide ores with the oxidised electrolytic liquid, the proportion of zinc 
 and iron becomes as great as it was before electrolysis. Indeed, in this zinc pro- 
 cess the necessary difference of potential between the anode and the kathode of the 
 electrolytic bath is about twice as great as in the copper process previously de- 
 scribed. 
 
 Properties. Zinc is of a grey- white, slightly bluish colour, generally of a foliaceous 
 crystalline, but sometimes very finely foliated, texture, with a strong metallic lustre 
 on its surface. Colour, texture, and lustre vary in different directions, according as 
 the zinc is more or less contaminated with other metals. According to Bolley, zinc, cast 
 near its melting point and cooled rapidly, has the sp. gr. 7-178 ; if slowly cooled, 7*145 : 
 that cast at a red heat, if cooled rapidly, 7,109 ; if cooled slowly 7-120. By hammering 
 and rolling, the sp. gr. may be raised to 7-2, or even 7-3. Pure zinc is slightly extensile, 
 even at common temperatures, and can be rolled out to thin sheets without cracking at 
 the edges. This property is lost if it is even slightly contaminated with other metals, so 
 that ordinary zinc breaks under the hammer. It distils in a vacuum at 184. At about 
 500 it ignites in the air, and burns with a pale green luminous flame to zinc oxide (zinc 
 white). When heated, zinc expands considerably, more than any other technical metal 
 (from o to 100) by ^-^ in length ; if hammered, ^^. When melted, zinc on solidifying 
 contracts. In casting zinc, the iron moulds must be strongly heated, and the tempera- 
 ture of the melted zinc must not be raised too high, that the solidification may take place 
 gradually and at the smallest possible difference of temperature. The expansibility of 
 zinc reaches its maximum between 100 and 150, and even if contaminated with other 
 metals it can be extended at this temperature. Hence it is worked out to sheets with 
 
SECT, ii.] CADMIUM. 217 
 
 hot rollers. Above 150 the flexibility of zinc decreases, and at 200 it is so brittle 
 that it may beaten to powder. Zinc is oxidised by superheated steam : 
 
 H 2 O + Zn = ZnO + H a 
 
 a property which is used in separating lead from zinc. In moist air zinc becomes 
 coated with a film of oxide, which protects the subjacent parts from further oxidation. 
 On account of its ready oxidation by water and acids, it is unsuitable for milk-pails and 
 culinary utensils. An addition of 0*5 per cent of lead makes zinc more flexible, and 
 such small proportions are therefore commonly added to zinc intended for rolling. But 
 for zinc which is to be used for brass, even 0-25 per cent, of lead is very injurious, as it 
 seriously lessens the strength of the brass. A large proportion of iron renders zinc 
 brittle. For eliminating arsenic, L'Hote melts zinc with i to i| per cent, of anhy- 
 drous magnesium chloride. Commercial zinc can be freed from the greater part 
 of foreign metals by repeated fractional distillation, keeping apart the portion which 
 passes over first, and leaving the residue unvolatised. Traces of gallium and indium 
 are sometimes found in the zinc of commerce. 
 
 Zinc from the Georg Works of the Silesian Association (I.), the brand CH of the 
 same company (II.), from Giesche's successors (III.), an d of the Furnace Sagan (IV.), in 
 1885, contained, according to Schneider and Peterson, in 100 parts : 
 
 I. II. III. IV. 
 
 Pb . . 1-4483 ... 17772 ... 1-1921 ... 0-633 
 
 Fe . . 0-0280 ... 0-0280 ... 0-0238 ... 0-032 
 
 Cd . . 0-0245 ... ... ... 0-054 
 
 Cu . . O'ooo2 ... ... O'ooo2 ... trace 
 
 Ag . . 0-0017 ... trace ... 0*0007 trace 
 
 As . . trace 
 
 Sb ... trace ... trace 
 
 Bi . . ... ... trace 
 
 S . . trace ... 0*0020 ... trace ... trace 
 
 A method for determining the value of zinc powder, which is often contaminated 
 with zinc oxide, is to be found in Select Methods in Chemical Analysis, by W. Crookes, 
 F.E.S., 2nd edition, p. 121. 
 
 Uses. Zinc is applied in sheets for roofing, for gutters and spouts, for plates 
 and cylinders in galvanic batteries ; in alloys (brass, bronze, false gold-leaf) ; for de- 
 silvering work-lead, for generating hydrogen gas along with sulphuric or hydro- 
 chloric acid, for preparing zinc sulphide, zinc white, &c. Zinc precipitates copper, 
 silver, lead, &c., from their solutions. If zinc and iron are placed in contact, the latter 
 metal is protected from oxidation. Zinc is much used for castings, in place of bronze, 
 cast-iron, and even of wrought stone and wood. 
 
 From 1860 to 1884 the total production of zinc in Europe has increased from 
 97,896 to 257,767 tons. In 1884 America furnished 23,240 tons of zinc. 
 
 CADMIUM. 
 
 Cadmium almost constantly accompanies zinc in its ores, especially in the Silesian 
 calamine, and to a less extent in blende. 
 
 In some of its properties cadmium is intermediate between tin and zinc ; it is tin- 
 white, very brilliant, malleable and ductile, and gradually loses its lustre on exposure to 
 the air. It has the sp. gr. 8-6 ; it melts at 360, boils at 860 (Deville and Troost), 
 or according to Becquerel at 746-2, and can be easily distilled. It is met with in trade 
 in rods weighing from 60-90 grammes. Silesian calamine contains as much as 5 per 
 cent. ; calamine from Wiesloch more than 2 per cent.; blende from the Harz 0-35 to 079; 
 that from Przibram 1.78 per cent., that from Eaton in North America 3.2 per cent. The 
 cadmium of these ores is concentrated in the brownish smoke which appears at the 
 
2l8 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. ii. 
 
 beginning of the distillation of zinc. This fume, consisting of metallic zinc, zinc car- 
 bonate and cadmium, serves as the crude material for the preparation of cadmium. It 
 is reduced by means of wood charcoal in small cylindrical retorts of cast-iron provided 
 with conical receivers of sheet-iron. The metal found in these receivers is sold in the 
 shape of rods of the thickness of a finger. Cadmium may also be obtained from cad- 
 miferous zinc in the wet way by treatment with dilute hydrochloric acid. The zinc dis- 
 solves in the acid, and the cadmium is precipitated so long as zinc is present in excess. 
 The residue (which also contains any lead present) is concentrated as far as possible 
 and the cadmium is finally separated by distillation. 
 
 Silesia produces yearly about 2000 kilos, of cadmium. 
 
 If alloyed with lead, tin and bismuth it forms Wood's metal. An alloy of 10 parts 
 cadmium, 13*5 tin, 49^8 bismuth, and 26*7 lead melts at 70. The only preparation of 
 cadmium in use is the sulphide, CdS, a splendid and permanent yellow pigment (Jaune 
 brilliant) used by artists. It serves also for giving a bright yellow colour to toilet 
 soaps and for producing a blue colour in fireworks. It is best obtained by precipi- 
 tating a solution of cadmium sulphate with sodium sulphide, washing, pressing and 
 drying the precipitate. 
 
 For the detection of cadmium in ores and alloys and for its determination, the 
 reader is referred to Select Methods in Chemical Analysis, by W. Crookes, F.R.S., 2nd 
 edition, pp. 331-333. 
 
 POTASSIUM AND SODIUM. 
 
 The production of the alkali metals differs from that of zinc only by the greater 
 care required to preserve the metal from contact with the oxygen of the atmosphere. 
 For the manufacture of sodium, sodium carbonate is ignited with carbon : 
 
 273>o + 87,000 = 186,000 heat-units. 
 
 The separation of one kilo, of sodium requires, therefore, 4050 heat-units, decidedly 
 
 more than in the corresponding reduction 
 
 Fig. 216. o f metallic zinc from its oxide. With 
 
 potassium the case is similar : 
 
 281,000 +87,000 = 
 
 - 144,000 heat units. 
 For manufacturing sodium 30 kilos, of 
 dry sodium carbonate, 13 kilos, charcoal 
 and 5 kilos, chalk are intimately mixed 
 and placed in iron tubes, A (Fig 216), 1-2 
 metre long and 0*15 metre in diameter. 
 The front cover supports an iron escape- 
 tube leading to the flat iron receiver, v. 
 
 For protection against the destructive action of the fire the tube A is usually encased 
 in a wider fire-clay pipe. On heating to whiteness there escapes first carbonic oxide, 
 then sodium, which becomes liquefied in the receiver and falls into an iron vessel filled 
 with mineral oil (free from oxygen). 
 
 In this process there is obtained only about 40 per cent, of the theoretical yield, 
 since a part of the sodium is burnt and a large part escapes reduction on account of 
 the imperfect mixture. 
 
 Mactear gives the following estimate of cost for i kilo, sodium, 1887 : 
 
SECT. II.] 
 
 POTASSIUM AND SODIUM. 
 
 Wear and tear of furnace, &c 5-3 shillings 
 
 Loss of materials 27 
 
 Labour . . . . . . . .2-2 
 
 Fuel i -I 
 
 219 
 
 11-3 
 
 The recent proposal of Thompson, therefore, demands attention ; 4 parts of dry 
 sodium carbonate and 3 parts of tar are to be slowly heated to dull redness, the 
 pulverised melt is placed in a box of sheet-iron b (Figs. 217 and 218), 10 centimetres in 
 
 Fig. 217. 
 
 depth, and provided with a spout. 
 This is then placed in a fire-clay gas 
 retort (previously heated to full red- 
 ness) in such a manner that its spout 
 is close to the lid of the retort c, 
 which is then secured air-tight. Be- 
 hind the lid the retort is freely con- 
 nected by the aperture e with the 
 chamber g, which can be closed air- 
 tight by means of the door f. In 
 
 the chamber a receiver g is placed, below the spout of the box 6. From the chamber 
 g a tube h passes outwards, and gives free escape to the carbon monoxide which is 
 formed. The extinction of the flame of this gas shows the end of the process. The 
 metal flows into the receiver. It is taken out as soon as the flame of carbonic oxide is 
 extinct, and a fresh vessel is introduced. The box b is then removed and a freshly 
 charged box is put in its place. 
 
 Whilst the reduction is thus conducted the melt is prepared for further operations, 
 the mixture of carbonate and tar being put in the iron pots A, through the apertures 
 B, which can be closed with fireproof plates. These pots stand in the escape-flue for 
 the combustion gases which is enlarged at this point for the purpose and thus the 
 heat is utilised for preparing the melt. 
 
 Castner reduces sodium hydrate with so-called iron carbide, FeC 2 , obtained by 
 heating ferric oxide with tar. On heating 10 kilos, caustic soda and 2 kilos, carbide the 
 decomposition is said to be effected as follows : 
 
 4NaOH + FeC 2 - Na 2 CO 3 + Fe + 2H 2 4- CO + Na,. 
 
 The thermic relations would be : 
 
 For sodium hydrate 4 x 102,000= 
 ,, ,, carbonate . . 
 carbon monoxide . . 
 
 Heat-units. 
 - 408,000 
 + 273,000 
 + 29,000 
 
 106,000 heat-units. 
 This would be decidedly more favourable than the old process ; it must be con- 
 
220 CHEMICAL TECHNOLOGY. [SECT. u. 
 
 sidered that the heat liberated in the decomposition of FeC, comes in addition ; its 
 amount is not yet known. 
 
 According to Mactear, the mixture of sodium iiydrate and iron carbide is placed in 
 cast-steel crucibles in a furnace which is first gently heated for 30 minutes. The mass 
 melts, and much hydrogen escapes in bubbles, whilst the carbide remains suspended in 
 the melted soda. The crucible with its contents now in tranquil flux is lifted up and 
 introduced into the heating-chamber of the main distillatory furnace. The cover of 
 the crucible, which always remains in the furnace, has a convex border which fits into a 
 groove in the edge of the crucible. From the lid a bent tube passes to the condensing 
 apparatus, which has at its hinder end a small escape for the hydrogen evolved. It is 
 also provided with a rod for preventing any obstruction from being formed in the tube 
 during the distillation. 
 
 The gas given off at the beginning of the process is pure hydrogen. A sample 
 drawn shortly before the end of the process contained 95 hydrogen and 5 carbon 
 monoxide (which does not agree well with the above formula). A small excess of 
 carbide induces the formation of a little sodium peroxide in the residue. The quantity 
 of carbon monoxide formed is so little that it does not combine with the vapours of 
 sodium. Hence, the formation of the black compound is prevented, which is otherwise 
 apt to choke the exit-tube. The sodium obtained in this manner is pure. 
 
 After the completion of the process the contents of the crucible are poured out to 
 make room for a new charge. The average composition of the residue is : 
 
 Sodium carbonate . . . -77 per cent. 
 Sodium peroxide . . . 2 
 
 Carbon 2 
 
 Iron 19 
 
 In preparing potassium less carbide is used to prevent the formation of carbon 
 monoxide, and the distillation proceeds, it is said, smoothly. 
 
 The average weight of the residue of a mixture of 5'6 kilos, sodium carbonate 
 and i '97 kilos, carbide amounts to about 6 kilos. From this there are recovered 
 4-85 kilos, anhydrous sodium carbonate, corresponding to 3^ kilos, sodium hydrate at 
 76 per cent. 
 
 If the manufacture is carried on as above laid down, the yield (according to 
 Mactear) of 5'6 kilos, soda is 0*933 kilos, sodium. 
 
 On each charge the distillation lasts i^ hour. Thus, as the furnace receives three 
 crucibles it is possible to work up 3 x 5*6 kilos. = 16*8 kilos, sodium hydrate, and to 
 obtain 2"jg kilos, sodium and 14-5 kilos, sodium carbonate. The furnace yields daily 
 from 2687 kilos, sodium carbonate, 44-7 kilos, sodium, and 232*8 kilos, anhydrous 
 soda. 
 
 The estimated daily working-cost for a furnace using the quantities of sodium 
 hydrate and " carbide," is 
 
 2687 kilos, caustic soda 71 shillings 
 
 55-9 kilos, carbide 6 
 
 Labour . 20 
 
 Fuel 17 
 
 Cost of converting 232-8 kilos, of sodium carbonate 
 
 into hydrate 20 
 
 134 >i 
 
 Caustic soda recovered from 177-2 kilos. . .46 
 
 447 kilos, sodium cost nett . " . . 88 
 
 I kilo, sodium costs . 2 
 
SECT, ii.] ALUMINIUM. 221 
 
 As far as experience goes the wear and tear of the crucibles and the furnace is said 
 to be unimportant, as 200 operations can be effected with the same apparatus, the loss 
 for these items would be about 0-45 of a shilling on i kilo, sodium, or one-twelfth the 
 amount in the old process. The statement of Mactear 
 that a temperature of 830 is sufficient for the dis- Fig. 219. 
 
 tillation can scarcely be accurate.* 
 
 Sodium is an important reducing agent in the pre- 
 paration of aluminium, magnesium and silicon, as also 
 as of various organic compounds. 
 
 The electrolytic production of sodium has not yet 
 come into practical use. The oxygen compounds, as 
 well as the chloride, the> decomposition-heat of which 
 = 98^000 heat-units (calories), are not suitable mate- 
 rials. Concerning sodium fluoride, a by-product in 
 the production of aluminium, further experiments are 
 wanting. 
 
 The production of potassium is hitherto effected according to the old process for 
 sodium, but the oxygen must be still more carefully excluded. The potassium collects 
 in the receiver (Fig. 219), consisting of the two parts, d and s. When this is almost 
 full it is taken off, and plunged into mineral oil and purified by distillation. 
 
 The price of potassium is considerably higher than that of sodium, as there is 
 formed during its preparation a black explosive compound of potassium and carbon, 
 K G Cg0 6 , which diminishes the quantity of the yield and may occasion serious mischief. 
 This is said to be obviated by Castner's process. 
 
 ALUMINIUM. 
 
 Aluminium, in the form of alumina (aluminium oxide), is one of the most abun- 
 dant substances on the surface of the earth. It was first isolated by Woehler, by means 
 of the action of potassium upon aluminium chloride 
 
 It was for some time obtained only by the decomposition of aluminium-sodium 
 chloride by means of sodium. The double chloride is prepared by treating a mixture 
 of alumina with sodium chloride and tar with chlorine gas, in a retort at a red heat : 
 A1,O 3 + sCl, + 30 = A1 2 C1 6 + 3CO. 
 
 The aluminium chloride is volatilised as the double aluminium-sodium chloride, 
 and is condensed in a walled chamber, lined internally with earthenware. The double 
 chloride is decomposed by bringing it in contact with sodium on the sole of a rever- 
 beratory, when there ai*e formed free aluminium and a saline mass, consisting of the 
 double chloride and the excess of sodium chloride, which incloses the metallic 
 aluminium, f 
 
 * Weldon calculated the cost of sodium at 7. to 8s. per kilo., but the greater portion of this sum 
 is for the destruction of the retorts in which the process was then effected. Castner hopes to be 
 able to produce sodium at 25 cents per Ib. He effects the reduction by carbon diffused in alkali, 
 melting at moderate temperatures, or by means of a metallic carbide. Mierzinski and Jablochkoff 
 propose to obtain sodium by the electrolysis of sodium chloride. (See Aluminium, by Jos. W. 
 Richards, pp. 130-143.) 
 
 f A modification of this has been worked at Salindres, by A. R. Pechiney & Co., successors to 
 Henri Merle & Co. 
 
 The raw material is bauxite. This is first converted into sodium aluminate to get rid of the 
 accompanying iron (ferric oxide). From the solution of the aluminate hydrated alumina is thrown 
 down by a current of carbon dioxide and washed. The precipitate thus obtained is mixed with 
 carbon and sodium chloride, and this mixture is treated with chlorine gas to obtain the double 
 aluminium-sodium chloride which is finally decomposed by treatment with sodium. In this last 
 operation cryolite (the aluminium-sodium fluoride) is added. The production of aluminium at 
 
222 CHEMICAL TECHNOLOGY. [SECT. n. 
 
 The process of Cowles Brothers, which calls in the aid of electricity, and which is 
 rather adapted for the production of certain valuable alloys than of pure aluminium, 
 is thus described : 
 
 The inventors use a furnace, L (Fig. 220), the iron cover of which, N, contains 
 openings, n, for the escape of the carbon monoxide evolved. At the bottom is a 
 stratum of powdered coal, saturated with milk of lime, about a hand's-breadth in 
 depth. Over this is spread the mixture to be reduced, P, consisting of broken 
 corundum, mixed with fragments of charcoal and the requisite quantity of copper (i.e., 
 for the formation of bronze) in small grains. By means of a rectangular frame of 
 sheet-metal, it is arranged that the coarser materials lie only in the middle. The 
 electrodes, MM', which enter the hearth, serve for the production of a powerful 
 electric arc. They are blocks of carbon, 7-5 centimetres, in square sections of 75 centi- 
 metres in length. The furnace itself is i^ metre long and 0-3 metre broad and 
 deep. After the charge of ore, more charcoal is spread, in the first place, between the 
 wall of the hearth and the sheet-metal frame, and, after its removal as a layer, O', to 
 
 cover the whole. The furnace is then closed with its cover, and the current is passed 
 through. 
 
 According to Mehner, the machine used yields, at 907 i-otations, 1575 amperes and 
 47 volts. To prevent short-circuiting, strong resistances must be inserted at first. 
 In about one hour the reduction is complete. The aluminium bronze at the bottom of 
 the furnace contains 15 to 35 per cent, aluminium. In the layer of carbon above 
 there is said to exist an aluminium carbide. A dynamo of 100 electric horse-power 
 is said to produce in 20 hours 150 kilos, of a 10 per cent, aluminium bronze. A com- 
 pany at Lockport has bought a water-power of 1000 horse-power hours, and expects 
 to produce the aluminium alloys so cheaply that the aluminium contained in them will 
 cost only 35. 6d. a hope which is very sanguine. It is improbable that pure aluminium 
 will be produced in this manner at 4 to 5 shillings per kilo. 
 
 According to Maberry, the volatilisation of aluminium in this process may be pre- 
 
 Salindres has been from 2000 to 3000 kilos, yearly. The cost per kilo, is estimated at 69^ francs. 
 For the details of the processes, the reader is referred to Fremy's Encyloptdie Chimique. 
 
 A novelty was the introduction, as a raw material, of cryolite, A^Na^F,,. Its use is not free 
 from disadvantages, as the yield is relatively small ; the crucibles are attacked, and the aluminium 
 obtained is deficient in purity. 
 
 Webster's process, used at the Aluminium Crown Metal Works, at Hollywood, turns upon the 
 use of an exceptionally pure alumina. The inventor incorporates three parts pure alum with one 
 part of coal pitch, and heats to 200 or 260. After treatment, the particulars of which are found 
 in the author's patent, a product is obtained containing 8-41 per cent, of actual A1 2 O 3 , the cost of 
 which is said to fall below ^100 per ton. 
 
 From the by-products it was said that a blue dye was obtained which .served as a substitute 
 for indigo (!), and was worth 6s. per Ib. This colouring matter is a Prussian blue, which is of 
 course not without value. Beyond taking this pure alumina as a raw material, Webster's pro- 
 cedures do not seem to involve any novelty. The sodium produced is of excellent quality, but it is 
 too costly for extended uses. 
 
 For a number of proposed methods, none of which seem to have achieved any decided success, 
 the reader may consult Aluminium, by Jos. W. Eichards (pp. 178-189). 
 
SECT, ii.] ALUMINIUM. 223 
 
 vented by the presence of copper, tin, or iron. No electrolytic aluminium has yet 
 appeared in the market. 
 
 The process of Prof. Netto is carried out by the Alliance Aluminium Company at 
 Wallsend-on-Tyne. 
 
 These works at present comprise four reverberatories, arranged in two blocks, each 
 23 ft. by 8| ft. by 9 ft. high. Each furnace is charged from the top with a mixture of 
 cryolite and salt, which when melted is drawn off into a movable iron converter in 
 which the decomposition is effected. Sodium is thrown into the molten mass, which is 
 worked about with an iron dipper, until all action ceases. The slags are then run off 
 into an iron pot, and the aluminium is found in the shape of a " button" at the bottom 
 of the converter. The yield of metal is about 8 per cent, on the weight of cryolite, 
 and three parts of sodium are used to furnish one part of aluminium. The resulting 
 slag, sodium fluoride, on treatment with an oxygen salt of aluminium, forms an artifi- 
 cial cryolite, which serves for the production of aluminium as well as the natural 
 mineral. For producing i ton of aluminium there are required 12 tons cryolite, 12 
 tons common salt, 12 tons coke for heating, and 3 tons sodium. The by-products are 
 20 tons slag, containing 40 per cent, sodium fluoride, 15 per cent, of undecomposed 
 cryolite, and a trace of clay, the remainder being common salt. 
 
 Properties. Aluminium is greatly modified even by small quantities of other 
 metals. The common commercial metal has a slight bluish-white cast, intermediate 
 between the colours of tin and zinc. But the pure metal is almost absolutely white. 
 It is very malleable and ductile ; it can be beaten into leaf as thin as gold-leaf. When 
 cast it is as soft as silver, but by hammering and rolling it is rendered nearly as hard 
 as iron. Its specific gravity at 4 is, when cast, 2-56. According to Deville, it con- 
 ducts electricity eight times better than iron. The melting-point of the absolutely 
 pure metal is about 650, but ordinary commercial samples are about 815. It is 
 probably the most sonorous of all metals. 
 
 As regards its chemical properties, it is not oxidised by the action of air or water. 
 Unlike silver, it is not blackened by sulphuretted hydrogen. Nitric and sulphuric 
 acids scarcely affect it, but in hydrochloric acid or in solutions of the caustic alkalies it 
 dissolves readily. 
 
 Applications. From its combined lightness and strength aluminium is admirably 
 adapted for use in watch-making, for the frames of microscopes, spectroscopes, and 
 other delicate optical and physical instruments, and for many surgical appliances. It 
 will probably supersede all other metals for the production of bells, wind instruments, 
 and pianoforte wires. Its high conductive power for electricity, joined to its great 
 lightness, render it preferable to iron and copper for telegraph wires. This is especially 
 the case as regards field telegraphs. An aluminium wire extending three miles will 
 not weigh as much as copper wire of one mile. 
 
 Alloys. The alloys of aluminium are exceedingly important. An alloy of aluminium 
 and iron (Mitis metal) is said to be from 30 to 50 per cent, stronger than the iron from 
 which it is made, and is certainly free from porosity and from enclosed air-bubbles. Even 
 such small proportions of aluminium as o'2 per cent, greatly improve the quality of iron 
 and steel. " "Wasters " are almost unknown to ironfounders who use aluminium, and 
 very thin parts and sharp edges are thus cast with oase. 
 
 The aluminium bronzes, containing 2^, 5,-?i> an ^ i per cent, aluminium, accord- 
 ing to the purpose intended, are both useful and ornamental. For artillery, the 
 10 per cent, aluminium bronze is the metal par excellence, by reason of its hardness and 
 homogeneity, its high breaking-strain, its elasticity, and resistance to corrosion. This 
 10 per cent, bronze is not changed in its properties how often so ever it is re-cast. It 
 will not only take the place of phosphor-bronze, silicon-bronze, &c., but even of steel 
 .for ships' propellers, pistons, cylinders, cogged wheels, engine-fittings of most kinds, 
 
224 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. ii. 
 
 bearings, &c. Mierzinski is of opinion that in any part of a machine which is com- 
 monly made of steel, this bronze can be substituted. Its strength when hammered is 
 equal to the best steel. Soldering aluminium and its alloys was for some time a diffi- 
 culty, but the Alliance Aluminium Co. now supply a solder which works perfectly if 
 the instructions are followed. Aluminium can be welded electrically, and it has the 
 advantage of not clogging files. 
 
 MAGNESIUM. 
 
 Magnesium, which occurs in exhaustless quantities in sea-water as magnesium 
 chloride and bromide, and in carnallite, as sulphate in kieserite, schcenite, and kainite, 
 and as carbonate in magnesite and the dolomites, has only been included among the tech- 
 nical metals within the last twenty years. It is silvery white ; its recent fracture 
 appears either slightly crystalline, finely granular, or even fibrous. It is as hard as 
 calcareous spar, and becomes dull on exposure to the air. Slightly above its melting 
 point it takes fire, and burns to magnesia with a dazzling white light. Its sp. gr. 
 is =1743. 
 
 It has hitherto been produced exactly like aluminium, magnesium chloride, or 
 carnallite, being decomposed by heating in contact with sodium. 
 
 Until recently, it was prepared by the Magnesium Metal Company, at Patricroft, 
 near Manchester (conducted by Mellor) ; by the American Magnesium Company, at 
 Boston, U.S.A. (producing each 2500 kilos.) ; and in Paris (about 100 kilos.). 
 
 The magnesium of commerce is never pure, as is seen from the following analysis 
 (1872 and 1876). I. is English magnesium, and II. and III. are French samples : 
 
 Magnesium 
 
 Aluminium 
 
 Zinc 
 
 Iron 
 
 Carbon 
 
 Silicon 
 
 (I.) 
 
 96 '38 1 per cent. 
 0-342 
 
 0-673 
 
 O'I20 
 2-309 
 
 (II.) 
 92-357 per cent. 
 
 5-686 
 0-091 
 1-860 
 
 (in.) 
 
 93-620 per cent. 
 0-216 
 3-063 
 
 O'lOI 
 O'20I 
 2-421 
 
 Kg. 221. 
 
 In 1852 Bunsen prepared magnesium elect rolytically from magnesium chloride by 
 means of his zinc-carbon elements. As decomposing cell he used a porcelain crucible, 
 9 centimetres in height and 5 centimetres in width, divided into two halves by a 
 partition reaching down to half-depth. Through the cone were passed the two carbon 
 poles of the battery. The saw-like projections of the negative pole 
 served to hold the separated metal below the melting salt, as it 
 otherwise rises to the surface and ignites. The author was the 
 first to show that fused potassium-magnesium chloride (KMgCl 3 
 carnallite) is very suitable for the electrolytic separation of mag- 
 nesium, and that its combustion may be prevented by the intro- 
 duction of reducing-gases. 
 
 In order to heat the porcelain crucible to a red heat as uniformly 
 as possible, there were used two sheet iron rings, a and b (Fig. 221) 
 lined with asbestos pasteboard connected below by three strong wires 
 and resting on three feet, z. The cover, which is also lined below 
 with asbestos pasteboard, has an opening in which the crucible fits 
 when it rests upon a thick iron wire enclosed in the pipe-clay tube, 
 x. If a triple burner is placed below, the hot gases play uniformly 
 round the crucible, as they are compelled by the outer ring, b, to re-descend in the 
 direction of the arrows. When the double salt is melted, a round asbestos plate, v, is 
 put on and pressed firmly upon the edge of the crucible by the heavy cast iron ring, b. 
 The asbestos plate contains an earthen tube, o, in which have been bored several lateral 
 
SECT, ii.] MAGNESIUM. 225. 
 
 holes. In this earthen tube there is secured, by means of asbestos plates, the carbon 
 which serves as positive electrode, and the tube r, with a lateral appendage for 
 carrying off the chlorine. This form of tube was selected to obviate possible obstruc- 
 tions and, after lifting off the plug, to ascertain the development of chlorine by means 
 of a slip of litmus-paper. As negative pole is used an iron wire, e, 5 millimetres in 
 thickness, the lower end of which forms a ring round the carbon. Gas is very slowly 
 introduced through the tube g ; it has been dried over calcium chloride, and escapes 
 with the chlorine through the tube r. The magnesium melts in balls of the size of a 
 nut. Graetzel has modified this process by using the iron crucible as a negative 
 electrode, as Davy proposed for potassium. 
 
 Considerable quantities of magnesium are now so cheaply prepared by the elec- 
 trolysis of carnallite that the sodium process can no longer compete. 
 
 The technical uses of magnesium are not important. As an illuminating agent it 
 can be thought of only in special cases, for military purposes, &c. A Berlin firm 
 recommends for a white fire, shellac i part, 6 parts barium nitrate, and 2\ per cent, 
 magnesium powder. The shellac and the barium salt are melted together and ground. 
 For a red fire the mixture is similar, only for the 6 parts barium nitrate are substituted 
 5 parts strontium nitrate. 
 
SECTION III. 
 CHEMICAL MANUFACTURING INDUSTRY. 
 
 WATER AND ICE. 
 
 WATER occurs as rain-, spring-, river-, and sea-water. When, after sunset, objects 
 upon the earth's surface are cooled down below the dew-point, a part of the water 
 existing in a gaseous state in the air is precipitated upon such objects as dew, in the 
 form of small drops, or as hoar-frost if the temperature be below o. If a considerable 
 volume of air is cooled below its dew-point, the corresponding quantity of water is also 
 separated in minute drops, forming mists or clouds. These drops sink down slowly, 
 and if the lower strata of air are warmer and not yet saturated with water, they resume 
 the form of vapour. But they fall down upon the earth as rain or frozen as snow 
 and hail if the moisture in the lower strata of the atmosphere approaches the dew- 
 point. 
 
 The quantity of the atmospheric waters thus deposited is generally greatest within 
 the tropics and near the sea, and smallest towards the poles. Thus the mean height of 
 the rainfall is at 
 
 Madrid 
 Vienna 
 Petersburg . 
 Stockholm . 
 Berlin 
 Paris . 
 Hanover 
 
 The distribution of the rainfall in the seasons is very different. Autumnal rains 
 predominate in Britain, the west of France, the Netherlands, and Norway ; summer 
 rains in Germany, Denmark, and Sweden ; summer rains are absent in those parts of 
 Europe which He nearest Africa, i.e., southern France, Italy, Portugal, &c. 
 
 The quantity of rain in single years deviates very considerably from the general 
 average. Thus, at Frankfort the mean rainfall for thirty years is 60 centimetres, but 
 in 1864 it was only 36 centimetres, and in 1867, 144 centimetres. 
 
 About half this atmospheric water is directly returned to the air by evaporation ; 
 the remainder chiefly penetrates into the soil as far as the first impervious stratum 
 along which it flows in accordance with the law of gravitation, and is finally either 
 raised artificially in wells or comes to light in natural springs, and, in conjunction with 
 the surface drainage, is conveyed to[the sea in brooks and rivers. Generally a permeable 
 soil and shattered rocks are rich in springs, whilst a compact clay soil and a solid rock 
 formation yield only feeble springs. 
 
 Composition. Rain and snow contain the constituents of atmospheric air, nitrogen, 
 oxygen, carbon dioxide, and also the impurities of the atmosphere in proportion to 
 their respective solubilities. Rain-water collected upon clean surfaces can hence, in 
 many cases, be used in the chemical arts in place of distilled water. Water obtained 
 from roofs is at the commencement of wet weather often contaminated by dust, the 
 
 25 centimetres 
 
 London 
 
 . 63 centimetres 
 
 45 
 
 
 Rome . 
 
 . 78 
 
 46 
 
 
 Genoa . 
 
 . 118 
 
 5i 
 
 
 Bombay 
 
 . 198 
 
 57 
 
 
 Havanna 
 
 . 231 
 
 57 
 
 
 St. Domingo 
 
 273 
 
 58 
 
 
 
 
SECT. HI.] WATER AND ICE. 227 
 
 droppings of birds, &c. Water which has been preserved in cisterns, and which 
 in low, swampy, coast districts is used for all domestic purposes, is often very impure. 
 Among the impurities of the atmosphere sulphurous acid, chlorine, ammonia, and 
 nitric acid are the most important. 
 
 Sulphurous acid or sulphuric acid is especially due to coal fires. According to 
 Sendtner freshly fallen snow at Munich contained per kilo. 7 milligrammes total sulphuric 
 acid, the next day, 17 '6 milligrammes, in ten days 6 2' 2, and in sixteen days 91*8 milli- 
 grammes. Thus snow very quickly absorbs the sulphurous acid existing in the air of 
 towns, which soon passes into sulphuric acid. Such snow or rain is very injurious to 
 statues or monuments of marble placed in the open air. Angus Smith found at Liver- 
 pool 35 milligrammes sulphuric acid per litre of rain-water, at Manchester 50 milli- 
 grammes, at Newcastle-on-Tyne (among sulphuric acid works) 430 milligrammes, and 
 this chiefly in a free state. 
 
 The proportion of chlorine (or of chlorides) is of importance only on coasts. 
 The ammonia in rain-water is chiefly derived from processes of putrefaction, but also 
 from chimney gases, if the combustion is imperfect. Rain-water generally contains 
 from 0-5 to 5 milligrammes, but sometimes as much as 30 milligrammes per litre. 
 Snow after remaining a long time on the ground contains much ammonia. 
 
 Rain-water contains also from i to 10, but sometimes even 50 milligrammes 
 nitric acid, due either to the decomposition of organic matter, or formed by electric 
 discharges. 
 
 Spring- and Well- Water. The rain-water charged with these matters penetrates 
 chiefly into the soil when it does not immediately evaporate, and comes up to daylight 
 in springs, or is artificially raised in wells after taking up more or less of the 
 constituents of the strata which it has traversed. 
 
 In water it is common to distinguish the carbonic acid into that which forms, with the 
 existing metals, simple carbonates ; that which is half -combined, forming, with the car- 
 bonates, bicarbonates, and being capable of expulsion by boiling ; and that which again 
 is free, and merely dissolved in the water. In some springs, especiaDy in volcanic 
 districts (as the Eifel, the Laach lake, &c.), the water holds in solution carbonic acid, 
 in volumes several times exceeding its own. The ordinary well- and spring-waters owe 
 their carbonic acid in part to the atmosphere, but chiefly to the processes of putrefaction 
 -and decay taking place in the soil. Carbonic acid assists in the decomposition of 
 minerals, and forms calcium and magnesium bicarbonates, less frequently similar 
 compounds of iron, sodium, &c.,so that ordinary spring- waters contain only a relatively 
 small quantity of carbonic acid in a free state. Well-waters contain, as a rule, no free 
 carbonic acid, but often, in a greatly polluted soil, considerable quantities of 
 calcium and magnesium carbonate, and have, in consequence, a great transitory 
 hardness. 
 
 The quantities of lime, magnesia, alkalies, sulphuric acid, &c., vary very greatly 
 according to the nature of the soil. The less variable are the quantities of the products 
 of the decomposition of animal excretions, which in populous places penetrate into the 
 earth to a great depth. Such matters at ordinary temperatures and under the 
 influence of certain microscopic organisms, are quickly resolved into decomposition 
 products as yet but imperfectly known. In presence of atmospheric oxygen they 
 form carbonic acid, ammonia, and then nitrous and nitric acids. The phosphates, the 
 nitrogenous organic matters, and the ammonia are in part retained in the soil, and 
 conveyed to the roots of plants ; the chlorides, nitrates, and sulphates are carried away 
 by the water to the wells and springs. These changes take place especially in soils 
 covered with vegetation. Polluted waters after filtering through the soil contain much 
 more nitric nitrogen (nitrogen in the state of nitrous and nitric acid) than they did 
 previously. If nitrogenous organic substances are conveyed into a soil not covered with 
 
228 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 plants, then if the access of air is sufficient, the nitrogen of such organic matter and 
 the ammonia which has been formed are quickly converted, firstly into nitrous, and 
 then into nitric acid, which are taken up by the water in the soil, and conveyed into 
 the springs and wells. If sufficient oxidation cannot be effected, from scanty access of 
 air, when the absorptive power of the soil is exhausted, the ammonia and the putrescent 
 organic substances are taken up by the water. Water which springs out of the earth 
 remote from human habitation may be perfectly free from decomposing animal 
 products or may contain mere traces.* 
 
 The water of wells which reach down into the ground-waters of cities and are 
 partly fed by soakage from the street-sewers, the cess-pits, &c., contains impurities to a 
 serious degree. The proportion of sulphuric acid may reach i gramme per litre ; that 
 of ammonia 100 milligrammes, organic matter i gramme, and chlorine 90 centigrammes. 
 As the latter (except in marine or saliferous districts) is chiefly derived from the 
 sodium chloride of human excretions, its presence gives a valuable indication for 
 determining the character of a well-water. 
 
 The composition of river- waters is naturally very different according to the character 
 of the formations which they and their affluents traverse. Sea-water contains espe- 
 cially sodium and magnesium chlorides, calcium and magnesium sulphates ; potassium 
 compounds are found only in small quantities. Calcium carbonate is likewise scantily 
 present, often in mere traces ; near the coasts it is more abundant. Magnesium 
 carbonate is still more sparingly present. 
 
 It is impossible to pronounce a water fit or unfit for domestic uses unless we know 
 its origin and the surroundings of its source. It is by no means indifferent whether 
 the organic matter detected in a sample of water is derived from a peaty soil or from 
 a cess-pit. Here the presence of chlorine, ammonia, and nitrites gives valuable indica- 
 tions. So-called " standards " and limits are only of very local value. 
 
 Drinking-water should not be too hard, and its temperature should fluctuate little. 
 Examination of Waters. The reader will do well here to consult the following 
 works: Water Analysis, by J. A. Wanklyn and E. Th. Chapman; Volumetric 
 Analysis, by F. Sutton (latest edition, the section relating to the examination of 
 water) ; Select Methods in Chemical Analysis, by W. Crookes, F.R.S., p. 657, for esti- 
 mation of free oxygen in water, and p. 659, for an expeditious method of estimating 
 the temporary hardness. 
 
 It is a very prevalent error to say that the colour of water gives little help 
 towards ascertaining its quality. Water free from organic pollution has, if seen in 
 a sufficient volume, a peculiar blue colour. If contaminated with organic matter in 
 solution, it has a brownish or yellowish colour. The process in question, devised by 
 W. Crookes, W. Odling, and C. Meymott Tidy, is, in substance, as follows : Two 
 hollow glass wedges are filled, the one with a brown and the other with a blue solu- 
 tion. The blue solution is made by dissolving 5 grammes pure crystalline copper sul- 
 phate in i litre distilled water. For the brown solution dissolve ferric chloride and 
 cobalt chloride in distilled water in such proportions that i litre of the solution may 
 contain 07 gramme of metallic iron and 0-3 gramme of metallic cobalt. A very slight 
 excess of free hydrochloric acid must also be present. These two wedges are made to 
 slide across each other in front of a circular aperture in a sheet of metal. In this 
 manner any desired combination of brown and blue can be produced. Each prism is 
 graduated along its length from i to 40, the figures representing millimetres in thick- 
 ness of the solution at that particular part of the prism. On a level just below the 
 
 * Some savage tribes in Africa and South America have the dreadful custom of burying the 
 bodies of chiefs, &c., underneath a spring, or in the bed of a stream. Water containing no animal 
 pollution may be very dangerous in consequence of decomposing vegetable matter e.g., the- 
 drainage of rice-fields and the waters of mangrove thickets. EDITOB. 
 
SECT, in.] WATER AND ICE. 229 
 
 prisms is a 2-foot tube containing the water to be examined, and having in front of it 
 a, circular aperture of the same size as the one in front of the prisms. The stand 
 supporting the prisms and tube is placed horizontally in front of a uniformly lighted 
 window. The observer, standing a little distance off, sees two discs, the lower one 
 illuminated by light which has passed through 2 feet of the water, and the upper 
 one illuminated by light which has passed through the respective thicknesses of the 
 brown and blue solutions. By sliding the prisms sideways one way or the other, it is 
 easy to imitate with considerable accuracy the depth and tone of the colour of the 
 lower disc. A metal pointer fixed over the centre of the upper disc shows on the 
 prism scales the number of millimetres in thickness through which the light has 
 passed to produce a colour which corresponds to that of the water, and the results are 
 recorded thus : " February 2ist (New River), 20 : 21," meaning that on that date the 
 colour of New River water seen through a 2 -foot tube was represented by 20 milli- 
 metres of the brown and 21 millimetres of the blue solution. 
 
 Purification of Water. Water requires to be purified in various ways, according to 
 its original condition and the purposes to which it is to be ultimately applied. Sewage 
 and industrial waste waters, which generally occur together, may be treated by irriga- 
 tion, filtration, or precipitation. For the conditions under which these processes are 
 available, their drawbacks, and the manner of their execution, the reader may consult 
 Slater's Sewage Treatment and Purification (Whittaker). The compound processes of 
 precipitation may be considered as " inverse irrigation," as, instead of passing the 
 impure water through the soil, fresh portions of clay, peat, &c., are continually passed 
 through the sewage, and are then caused to subside (carrying with them the impuri- 
 ties they have absorbed) by the addition of a suitable salt of aluminium or iron. 
 
 Water for human consumption, for cookery, &c., should be as free as possible from 
 organic matter, and especially from micro-organisms. It is very doubtful in how far 
 this can be effected by any practicable filtration. The celebrated Chamberland filter, 
 used by Pasteur in his researches, effects the end desired, as far as microbia are con- 
 cerned, but very slowly. Precipitation with lime (see p. 237, Clarke process) removes 
 the germs (pathogenic and other) for a time, but they are apt to reappear if the clear 
 water is allowed to remain standing over the precipitate. From time immemorial the 
 Chinese have been in the habit of adding to the impure water which they use for 
 drinking small quantities of alum, letting the precipitate subside, and drawing off the 
 clear. Since this simple method has been introduced among the French troops in 
 Tonkin, the soldiers have suffered much less from dysentery a fact proving that alum 
 not merely removes the suspended earthy matters, but is also capable of eliminating 
 dissolved organic matter as any one practically acquainted with the art of dyeing 
 would expect and even organisms. Brautlecht (Slater's Sewage Treatment, p. 99) 
 even proposes the use of alum for detecting or removing the microbia in water. He 
 adds a few drops of a solution of a salt of aluminium to some of the suspected water, 
 allows the precipitate to settle, decants off the clear, redissolves the sediment in a few 
 drops of acetic acid, and searches for the organisms in the solution thus obtained. 
 
 Water for Steam-Boilers. In deciding on a water for steam purposes it must be 
 considered in how far it may corrode the boiler-plates or form solid deposits (crock). 
 Whilst the destruction of the boiler-plates from without depends on the action of 
 sulphurous acid, and of an excess of oxygen in the flue gases in presence of moisture ; 
 injuries to the boiler from within are to be sought for in the composition of the feed- 
 water. Magnesium chloride is especially destructive to the plates, and in sugar-works 
 it is found that treacle has an injurious action on the boilers. Feed-water containing 
 oily and fatty matter is unfit for use. 
 
 The chief compounds concerned in the formation of crock are calcium sulphate and 
 calcium and magnesium carbonates. 
 
230 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 The calcium sulphate separates according to the temperature and the proportion of 
 saline matter in the water, either as anhydrite or with water of crystallisation ; 
 magnesia is deposited as hydrate. Calcium hydrate also forms sol : d incrustations if, 
 e.g., too much milk of lime has been used in purifying the water. The prevention of 
 crock, which interferes with the heating of the water, is best done in a cistern before 
 it is pumped into the boiler, and may be effected by means of soda. The numerous 
 patented or secret anti-incrustation compositions should be regarded with suspicion, 
 as most of them are of little or no value. 
 
 Water for Breweries. If perhaps too great an influence upon the quality of beer 
 has been ascribed to the character of the water, yet recent experiments have proved 
 that certain constituents of water may act unfavourably upon softening the barley in 
 the mashing and the fermentation. 
 
 The use of water containing organic matter in course of decomposition is especially 
 objectionable. The organic matters attach themselves to the malt, carry on their 
 process of decomposition, induce putrefaction and mouldiness, and under certain circum- 
 stances may injure the fermentation of the wort obtained from such malt. Tannic,. 
 crenic, and apocrenic acids are hurtful. Water from woodlands and from rivers receiv- 
 ing the waste waters of tanneries should be used with caution.* Beer made with 
 water containing animal impurities will not keep. The drainage of the brewery itself 
 exerts an injurious effect upon the process of fermentation. 
 
 As regards the first products of decomposition, Lintner points out that as we justly 
 characterise their presence in drinking-water as suspicious, they should be used in 
 brewing and malting only in extreme cases and with caution. A malthouse which, 
 according to Lintner, worked with polluted water, had to contend with the mouldiness 
 of the malt, which disappeared as soon as a different and better supply of water was 
 obtained. 
 
 A considerable proportion of magnesia is objectionable. Concerning the presence 
 of lime, opinions are divided, but it has been ascertained that soft water effects the 
 swelling of the barley more quickly than such as is hard. But as soft water dissolves 
 out of the barley on steeping more extractive matter and salts than a calcareous water, 
 greater care is needed with the former. According to Griessmayer, soft water removes 
 from the grain of barley more phosphoric acid and potassium phosphate than does hard 
 water, forming within the grain insoluble phosphoric compounds which are subse- 
 quently re-dissolved by the lactic acid of the mash. On the other hand, hard water 
 during steeping causes the formation of insoluble proteine-lime compounds, and thus 
 diminishes the yield of soluble albuminoid matter. A water containing a moderate 
 proportion of lime is decidedly preferable for malting.t 
 
 In the subsequent operations, a soft water is preferable, although a gypsiferous 
 water promotes the clearing of the wort. 
 
 "Water for distilleries should be as pure as possible, and should be at a low tempera- 
 ture in summer. 
 
 Water for starch-works should be especially free from suspended matter, organic 
 excretions, vegetable residues, salts of iron, and algae. 
 
 All these substances may pass through the sieves along with the staruh, remaining 
 in it partially in the centrifugal process, and appear in it when dry. The water must 
 be free from ferments and schizomycetes. The former prevent the starch from de- 
 positing, and throw it into the so-called flowing state. The others form organic acids, 
 such as the lactic and butyric, which cannot be entirely removed, even by the most 
 prolonged washing, and also give the starch a putrid odour. The warmer the 
 
 * Or rather, as far as tan-liquors are concerned, be totally rejected. 
 
 t The largest malthouses in England, e.g., those of Hertford and Stowmarket, have sprung up- 
 in districts supplied with hard water. 
 
SECT, m.] WATER AND ICE. 23! 
 
 weather the more dangerous is the presence of the organisms of putrefaction. Organic 
 matter and ammonia render the water suspicious, and salts of iron are a total bar to 
 its use. 
 
 The water can generally be much improved by the addition of a little milk of lime 
 and warming or filtering. 
 
 For sugar-works, chlorides are less liable to promote treacle than are the sulphates 
 and alkaline carbonates ; especially hurtful are the nitrates, which render six times 
 their own weight of sugar unable to crystallise. The behaviour of the water in 
 steam boilers is also very important at sugar- works, on account of the great demand 
 for steam. 
 
 In paper-mills, the presence of iron is very injurious, on account of the formation 
 of rust-spots ; lime and magnesia weaken the solution of the resin-soap by partial 
 decomposition. 
 
 Water for tanneries should contain no putrescent organic matter, as this causes 
 the leather to decay. Eitner's experiments prove that free carbonic acid and water 
 containing bicarbonates swell the hides ; chlorides do not unite with the hides, and even 
 counteract the swelling effect of acids. Hence sea-water is unfit for tanning. Calcium 
 and magnesium sulphates are especially good for swelling the hides. This explains 
 the advantageous action of a careful addition of sulphuric acid to a water containing 
 an abundance of bicarbonates. 
 
 The finished leathers resulting from these experiments were quite in accordance 
 with their appearance after swelling. The specimen which had been treated with 
 magnesium sulphate had the finest cut, and next came that with sulphuric acid. Samples 
 with distilled water, or with bicarbonates, differed respectively little, that with cal- 
 cium carbonate being the worst. All these leathers were very firm, full, with a com- 
 pact grain, and the cut surface was smooth and shining. Samples from salt and 
 magnesium chloride were thinner than the above, and comparatively soft ; the fibrous 
 texture was finer. 
 
 In the manufacture of glue, it is found that the extraction of the raw materials 
 (parings of hides, &c.) is far more complete with soft than with hard water. A glue 
 boiled with hard water does not re-dissolve clear after being once dried up. 
 
 For bleach- and dye-works, water should be perfectly clear and colourless, containing 
 especially no iron. 
 
 If a water contains so much organic matter as to be distinctly coloured, if used for 
 bleaching wool it occasions stains in the goods. If iron is present, then on treating 
 the wool with soda, ammonia, or lant, the iron is fixed on the fibre in the state of 
 oxide, or if soap is used as an iron-soap. Iron-water in the flot has a very injurious 
 effect upon the tones of the colours, so that it cannot be advantageously used even for 
 dark shades. Iron- waters are not less injurious in other dyeing and printing opera- 
 tions and in bleaching. 
 
 Hard waters do not bleed the dye-wares freely, and often modify the tone of the 
 colours produced. For all bright and light shades they are injurious, though in sad 
 shades or in blacks they economise the dye-ware. But it is easier to render a soft 
 water hard for any particular purpose than to soften a hard water. Hard waters, as a 
 matter of course, decompose soap.* 
 
 Madder and its preparations form an exception to most colouring matters in their 
 behaviour with hard waters. As far back as 1791 J. M. Haussmann observed that in 
 turkey-red dyeing fiery tones can be produced only with calcareous water. According 
 to Kielmeyer, grain-reds and mock-crimsons (peach wood, &c.), whether in cotton or 
 wool, take a bluish tone in hard water, which g'reatly interferes with their brightness. 
 
 * Compare Slater, Manual of Colours and Dye Wares, p. 221. Crosby Lockwood & Co. 
 
232 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 The genuine old madder red and rose as well as the modern alizarine red and rose do 
 not escape the action of calcareous water (?), On the contrary, coralline red, 
 generally so fugitive upon wool or cotton, is not affected by calcareous water, just as 
 coralline reds upon wool resist a frequent soaping much better than do grain (cochineal) 
 reds. The influence of calcium and magnesium carbonate in the water is especially 
 shown when the wet goods are dried in the stove or on the hot-flue. The carbonates 
 remaining along with the water in the wet tissue act upon the red like a feeble alkali, 
 giving it a bluish cast and thereby darkening it. Hence it is prudent to dry such 
 ware spread out as much as possible in a cold room. But the carbonates remain in 
 the air-dried goods and have still the opportunity to act upon the colours on hot press- 
 ing or calandering or passage over the drum. If the dyed woollen goods after washing 
 but before drying are taken a few turns through a water slightly soured with acetic 
 acid, or if (in case of cotton goods) a small quantity of acetic acid or of alum water 
 is added to the dressing, the action of the alkaline earths upon reds will be 
 counteracted. According to the investigations of Rosenstiehl a certain proportion of 
 lime is absolutely necessary for madder, garancine, and alizarine dyeing. The aliza- 
 rine and the purpuririe must encounter in the water of the dye-beck so much neutral 
 calcium carbonate or acetate that there may be formed under all circumstances mono- 
 calcium alizarate or the corresponding purpurine-lime lake ; the latter is not absolutely 
 necessary, but it contributes to the fastness and brightness of the colour produced. In 
 order to render the excess of calcium carbonate in a spring-water harmless in dyeing 
 oxalic acid seems to be the most serviceable agent ; it is used in some works for correct- 
 ing the water, whilst in others acetic or sulphuric acid is employed, though, according 
 to Kielmeyer's observations, with very unsatisfactory results. The oxalic acid added to 
 the flot, even though accurately calculated, strips a part of the mordant from the cotton 
 prior to the formation of the calcium oxalate, thus producing uneven colours and soiled 
 whites. For soap-baths oxalic acid is the best corrective. Here it can be added along 
 with potash to the hot water ; the insoluble calcium oxalate is formed at once before the 
 soap is added, and the latter finds no more lime in the water which could permit of the 
 formation of a lime-soap. If a soap-bath has to be often renewed and used only for a 
 short time, this method of purifying the water is the most suitable. The purifying of 
 soap-becks with potash alone without the additional oxalic acid cannot be recommended, 
 as it is dangerous for the colours. For large soap-becks, for raising-pans which have to 
 be set afresh only once or twice daily, the water is boiled up first with a small portion of 
 the soap ; the lime-soap first formed is carefully skimmed off, and the soap is then added 
 to the water thus purified. 
 
 In cleansing wool and woollen goods lime and magnesia are injurious, not merely by 
 rendering a part of the soap ineffective, but because the lime-soap formed cannot be 
 easily removed from the fibre, and on subsequent treatment with the mordant and the 
 colouring matter it occasions a number of irregularities. In washing wool with soda, 
 ammonia, or lant, lime and magnesia are less injurious, as any carbonates deposited upon 
 the fibre are more easily removed than lime and magnesia soaps. 
 
 The constituents of water have a remarkable influence in the treatment of raw silk. 
 It is universally recognised that the silk thread, as spun by the caterpillar, is coated 
 with a varnish or " gum," which dissolves in boiling soap-lye. During this treatment, 
 according to L. Gabba and O. Textor, the colouring matters of the silk are extracted 
 also. Cocoon silk, on repeated boiling with soap, loses 22*26 per cent, and raw silk 
 20*14 per cent., so that on unwinding the cocoon threads in hot water 2*12 per cent, of 
 organic matter is lost. But these portions give the raw silk its appearance, its colour, 
 and its strength, and hence they should be retained in the raw silk. In order to 
 render the reeling of the cocoons possible, the natural gum should be softened, though 
 not dissolved, as it must cement the single cocoon threads together so as to give 
 
SECT, in.] WATER AND ICE. 233 
 
 strength to the raw silk after hardening. The strength of the silk decreases exactly 
 in proportion to the loss of soluble matter, whilst the elasticity is affected only in a 
 secondary degree. As the cocoons are softened in hot water to facilitate reeling, and 
 are kept floating during this operation for convenience, it appears likely that the com- 
 position of the water must not be without influence upon the character of the silk 
 obtained. 
 
 In fact, comprehensive experiments have shown that silks spun in soft waters were 
 less fine in colour or less strong than those which had been obtained in hard waters. 
 The reason is that the soluble matters which ought to be retained are more readily 
 dissolved by soft than by hard waters, and are thus removed from the silk. 
 
 Investigation has further decided that silks spun out of waters rich in lime and 
 alkali give the best-looking products; therefore the producer of raw silk gives a preference 
 to the use of hard water. But for the silk-manufacturer, and especially for the silk-dyer, 
 the silks spun out of hard water are not the most advantageous, as they always contain 
 lime mechanically enclosed. The lime can be shown by an analysis of the ash the 
 harder the water in which the silk was spun the greater are the quantities of lime found. 
 This inclosed lime cannot be removed on boiling the raw silk preparatory to dyeing. 
 Wherever particles of lime adhere to the fibre the colouring matter of the not will be 
 taken up less perfectly, and the silks will appear stripy a very important defect in 
 unloaded, i.e., honest, silks. For bright shades the dyer will therefore give the 
 preference to silks spun in soft waters. 
 
 Water for Municipal and Domestic Supplies. In the use of soap, whether in the 
 household or in manufactures, the proportion of lime and magnesia in the water is of 
 capital importance. 
 
 It is well known that soap does not give a clear solution in cold water, but is 
 separated into a soluble, more basic portion and a more acid part insoluble even in 
 alcohol. According to Fricke, these parts had the following respective composition in 
 an experiment made with a good curd soap : 
 
 Soap. Insoluble. Soluble. 
 
 Fatty acids . . . 89-55 ... 91-36 ... 86-51 
 
 Soda .... 10-45 8 ' 6 4 X 3'49 
 
 The insoluble part contained chiefly palmitic acid, and the soluble part oleic acid. 
 The insoluble part seems to be perfectly inert, at least in cold water ; the soluble part 
 on agitation in pure water forms a foam whose numberless vesicles during washing take 
 up the dirt and remove it from the articles to be cleansed. This result can occur only when 
 the soap-lye froths, and is possible only when the existing lime and magnesia salts have 
 been eliminated as insoluble, smeary compounds of fatty acids. In the decomposition 
 31 parts of soda and 47 parts of potassa are replaced by 28 parts of lime or 20 parts 
 of magnesia, so that i of hardness destroys about 120 milligrammes of good curd 
 soap, or i litre of a water at 25 hardness 3 grammes of soap ; i cubic metre of the same 
 water consequently destroys 3 kilos, of soap. 
 
 But it is not merely the direct waste of soap which here comes into play ; the lime 
 and magnesia soaps formed obstruct the pores of the skin in washing, and deposit them- 
 selves in the fibres of washed goods, especially woollens, which consequently lose their 
 softness and acquire an offensive smell. A calcareous or magnesian water, therefore, 
 before being used for fulling cloths, wool-scouring, &c., as well as in the laundry, should 
 be heated with the proportionate quantity of soda to 80 or 100 and should then 
 be decanted away irojn the sediment. The same treatment removes the compounds of 
 iron and manganese, which not merely destroy soaps, but occasion most unpleasant 
 stains. 
 
234 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 That vegetables cannot be boiled tender in water containing much lime or magnesia, 
 but remain hard, is a fact which has been known for above a century and which first 
 gave such waters the name of " hard." According to the experiments of Bitthausen, 
 there is formed in peas boiled in hard water a compound of legumin with lime or 
 magnesia which hardens, on boiling, to a horny consistence. Similar unpleasant effects 
 are noticed on boiling other vegetables and meat in hard waters. It is also well known 
 that much better tea and coffee can be prepared with soft than with hard water.* 
 
 Water used for baking should contain no putrescent matters which interfere with 
 the fermentation. The water of a brook near Hanover which had been used for many 
 years in baking yielded a perfectly useless paste as soon as it was polluted by the waste 
 waters of a sugar-works. 
 
 Pettenkofer and Harz suggest the possible contamination of our dwellings by the 
 use of bad water in washing the floors, &c. The same caution must be kept in mind 
 when the streets are sprinkled with polluted waters. 
 
 In the construction of houses the quality of the water used for slacking lime, 
 mixing mortar, and steeping bricks is important. Bricks often display whitish, yellow, 
 green, and even black eruptions. The white efflorescences consist of calcium, magnesiiim, 
 or sodium sulphates, sodium chloride or bicarbonate, which have been originally 
 present in the clay and have been introduced by the water used in building. The 
 green eruptions on light-coloured stones are mostly algae ; black spots such as may be 
 observed on the Berlin Synagogue are fungi which attach themselves only where efflores- 
 cences of calcium carbonate and sulphate appear on the stones. In. rainy weather 
 such of the above salts as are soluble deliquesce, rendering the walls damp and spotty ; 
 in dry weather they effloresce, loosen the plaster by expansion and crystallisation and 
 cause it to peel off. Still more objectionable are calcium and magnesium chlorides, 
 which if once introduced can scarcely ever be removed. The ceilings sooner become 
 grey, as the dust clings more readily, and the wall-papers become spotty. 
 
 The custom of filtering impure turbid water, in the erroneous opinion that clear 
 water is always pure, was known to Pliny. The media used for filtering are wool, 
 sponge, cellulose (Piefke), spongy iron (Bischof), unglazed porcelain (Chamber-land), 
 asbestos, plastic carbon, silicated carbon, and innumerable others. 
 
 As a specimen of a small domestic instrument of this kind the high-pressure filter 
 recently introduced by Glover may be mentioned. The water enters by the cocks 
 A and G (Fig. 222), passes into the ring-shaped space, G, through the filtering 
 material, F, and flows out at D. In order to remove the deposit of mud the water may 
 be caused to flow for a short time in the opposite direction by closing the cocks A and 
 G and opening B, so that the dirt is carried off by lateral openings. In judging filters 
 it must be considered that the organic impurities contained in the water filtered can be 
 diminished only by absorption and oxidation. The absorptive power of filtering 
 materials, with the exception of animal charcoal, is inconsiderable. 
 
 Even this last material does not retain its absorbent powers for ever, and a time 
 comes when it may pollute instead of purifying water passed through it. Oxidation, 
 as it takes place naturally in the earth, is possible only with an abundant access of 
 atmospheric oxygen. But if the filter-bed is constantly covered with water, or if it is 
 closed up, only the oxygen dissolved in the water itself can be transferred to the 
 organic matter of course a limited quantity. 
 
 Hence follows a necessity for the frequent airing and purification of all household 
 filters. If this is neglected the water is not improved by filtration, but deteriorated. 
 Filters containing organic matter, cotton, felt, wool, sponge, &c., cannot be recom- 
 
 * As regards tea, this dictum may be questioned; soft water extracts more readily and 
 abundantly the tannin of the tea, thus rendering the infusion less pleasant and less wholesome. 
 EDITOR. 
 
SECT. III.] 
 
 WATER AND ICE. 
 
 235 
 
 Fig. 222. 
 
 mended, as they promote putrefaction. The recent demand that organic germs should 
 be removed from the water is fulfilled by some ; but their performance is very slight. 
 
 For filtering the water-supply of entire cities large sand-filters are used. Fig. 223 
 shows the section of the filters erected in Dublin in 1869. The bottom of the filters 
 consists of a bed of puddled clay f metre in thickness, a, built in with stones 
 J metre in thickness. The 'filter-materials laid directly upon the clay-bed consist 
 of f metre of coarse, angular 
 stones, b, 15 centimetres of smaller 
 stones, c, the same depth of coarse 
 gravel, d, the same depth of fine 
 sand, e, and f metre (75 centi- 
 metres) of sand, f. To collect the 
 water there are two channels, B, 
 situate half in the bed of clay and 
 half in the stratum of large stones. 
 Each channel is 75 centimetres in 
 width and 60 centimetres in depth. 
 The surface of sand in each metre 
 is 6 1 by 31 metres; the depth of 
 the water is 60 centimetres. 
 
 The speed of filtration varies in 
 the existing sand-filters from i'4 to 
 15 metres per twenty-four hours. 
 
 Each water requires, if it is to be well filtered by a given kind of sand, a determined speed 
 of filtration. Thus, under otherwise similar conditions, 3*5 cubic metres of Thames 
 water may be filtered in twenty-four hours per square metre of filtering surface, but only 
 1-7 cubic metre of Elbe water, as the latter contains much more finely divided dirt. In 
 
 Fig. 223. 
 
 a well-managed filtration the turbid water passes so slowly through the sand that 
 each of the fine particles of dirt, though far smaller than the intervals between 
 the grains of sand, has opportunity to attach itself to one of the grains. Therefore, 
 the finer and more numerous the particles of dirt are, the finer must be the sand 
 and the slower must be the rate of filtration. If this rate is too great, the sus- 
 
236 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. iii. 
 
 pended particles flow simply through between the grains of sand. But if the sand is 
 too fine, the filter-bed may easily become water-tight, whilst if the sand is too coarse 
 slower filtration is to some extent a remedy. The best size of the sand grains is 
 from | to i millimetre, and the sand is the better the more uniform the grains are. 
 A sand containing much finer grains cannot be used, as it is easily rendered too 
 compact by the pressure of the water. 
 
 For the better preservation of the filter it is requisite that the suspended dirt should 
 remain in the upper stratum and not penetrate into the loAver layers. This easily 
 happens at first after cleaning, as the surface of the sand is then very loose. In a newly 
 cleaned filter the head of water should therefore be very small. When once a film has 
 been formed over the surface the pressure may be raised to i metre ; higher pressures 
 easily break up the bed. 
 
 If its performance has become too slow, the filter is allowed to dry, and the upper 
 layer, of about i centimetre in thickness, is taken off and washed. There is often, 
 especially in summer, formed upon the filter a layer scarcely i millimetre in thickness, 
 consisting almost entirely of Diatoniaceae (Pleurosigma, Synedra, &c.), and rendering 
 the cleansing of the filter necessary on account of their impermeability. 
 
 The effects of this sand filtration are confined to a partial oxidation of the dissolved 
 organic matter, and the separation of the suspended matter. The organic germs are 
 especially said to be kept back. According to Koch, filtered water should not contain 
 more than 300 germs per c.c. : 
 
 Day of 
 Examination. 
 1885 June 2 
 
 
 9 
 16 
 
 
 23 
 
 J 
 
 30 
 
 ly 7 
 
 
 14 
 
 
 21 
 
 
 28 
 
 Stralau AVer 
 
 ks. 
 
 Tcgel Work 
 
 i. 
 
 Spree Water. 
 
 Lake Water 
 
 
 Unfiltered. 
 
 Filtered. 
 
 Unfiltered. Filtered. 
 
 5,475 
 
 42 
 
 IlS 
 
 16 
 
 7,980 
 
 22 
 
 117 
 
 39 
 
 6,100 
 
 33 
 
 115 
 
 76 
 
 6,100 
 
 4i 
 
 1,325 
 
 194 
 
 4,400 
 
 53 
 
 880 
 
 44 
 
 3,500 
 
 28 
 
 sample lost ... 
 
 42 
 
 7,200 
 
 200 
 
 1,896 
 
 1 20 
 
 110,740 
 
 ,656 
 
 13:320 
 
 49 
 
 2,640 
 
 54 
 
 1,500 
 
 48 
 
 In filtration through perfectly clean sand the swarms of bacteria are only at first 
 a little checked in their forward movement, but they afterwards become more 
 numerous, so that the filtered water sometimes contains more germs than the un- 
 filtered. The imperfection of the action slowly disappears. Sands not sterilised act 
 better at the very outset, and among such those are preferable which have for some 
 time taken part in the filtration in a large tank. Externally such sand was perceived 
 to be no longer sharp, but smeary to the touch. If examined under the microscope, it 
 was found that the single grains were more or less completely coated with a dirty layer 
 which was readily destroyed by heat, and contained a little ferric oxide along with 
 organic matter. That this coating consisted chiefly of bacteria and their germs was 
 plainly shown on bacteriological examination. If a sample of sand was taken from 
 any of the filters, well rinsed with sterilised water, and the rinsings subsequently 
 examined, bacteria were found in enormous numbers. The entire stratum of sand 
 was infected with them, though their distribution was very unequal, decreasing from 
 the surface rapidly at first, and afterwards more and more slowly. As an example, 
 we may refer to a large sand filter, which had been in use for a year and a half. 
 The thickness of the residual bed of sand was 30 centimetres. On cleansing the filter, 
 there were found, per kilo, of sand : 
 
SECT. III.] 
 
 WATER AND ICE. 
 
 237 
 
 1. From a dirt heap 5028 million germs 
 
 2. From surface of clean filter 734 
 
 3. From 10 centimetres depth below surface . . . 190 
 
 4. From 20 centimetres depth below surface . , .150 
 
 5. From 30 centimetres depth below surface ... 92 
 
 6. From fine gravel below sand 68 
 
 The residue left on the surface of the sand after the filtration of Spree water is, by 
 reason of its peculiar composition, almost exclusively of organic matter, to be regarded 
 as a culture medium in which the introduction of germs keeps up a process of putre- 
 faction, regulated according to the temperature. The first result is a great increase in 
 the micro-organisms. Many of them are endowed with the power of motion ; others 
 with the property of liquefying any gelatinous nutrient matter. They are, there- 
 fore, able to break off their connection with their covering of dirt, and to leave it 
 in great numbers. Nothing further stands in the way of their forward movement. 
 The sterilised sand cannot arrest them ; nothing clings to its smooth grains, and thus 
 we understand the phenomenon, at first so puzzling, that in filtering Spree water for a 
 long time through sterilised sand, we do not find a decrease of micro-organisms. Upon a 
 filter perfectly sterilised by strong heat, and filled up with sterile water, Spree water 
 was poured, and its filtration was commenced after standing for one day. There were 
 found germs capable of development : 
 
 Before After 
 
 Filtration. Filtration. 
 
 2nd day . 13,500 ... 97,9oo 
 
 6th ,, . 13,860 ... 205,000 
 
 loth . 3,120 ... 17,825 
 
 Before Af 
 
 Filtration. Filtration. 
 
 i2th day . 1,320 ... 29,900 
 
 i6th . 1,803 ... 4,928 
 
 22nd . 1,120 ... 2,356 
 
 Results of this kind cannot happen after the sand has become slimy. For as soon 
 as the micro-organisms have left their focus, the covering of dirt, they enter regions 
 which are for them almost impassable, since they present everywhere points of attach- 
 ment. With few exceptions, they cannot penetrate deeply into the sand, and collect 
 in the upper layers in vast multitudes. Hence the question as regards the admissible 
 speed of filtration acquires a new significance ; we must not let the stream become strong 
 enough to wash away any great number of germs from the layers of sand. The question 
 now is, how far we are to take the demands of public health into consideration. If 
 we insist upon the greatest possible freedom from germs the rate of filtration must not 
 exceed 30 millimetres hourly. If we are content with results like those effected at 
 Stralau works, we may admit 60 to 80 millimetres. But to go beyond 100 millimetres 
 would be admissible only under conditions which would be presented by new works 
 constructed with great care. 
 
 However important is the elimination of germs, it must not be forgotten that we 
 are unfortunately not always in a position to distinguish the germs of specific diseases 
 from others which are harmless. When, therefore, no water from unimpeachable 
 springs or deep wells is at hand, it is advisable always to boil water before use, even if 
 it has been filtered. 
 
 Softening Water. The Clarke Process. For softening waters intended for tech- 
 nical purposes the following methods may be adopted. 
 
 On heating water, the calcium and magnesium bicarbonates are decomposed, the 
 so-called half-combined carbonic acid escapes, whilst calcium and magnesium carbonates 
 are precipitated, only about 35 milligrammes calcium and 100 milligrammes magne- 
 sium carbonate remaining in solution. The so-called temporary hardness of the water 
 is thus much reduced. Movement promotes th^ separation. If the water contains 
 iron as ferrous bicarbonate, it is separated out as ferric hydroxide. 
 
 If steam is available, as is generally the case in manufactories, it may be advan- 
 
2 3 8 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 tageously brought into direct contact with the water as in Fig. 224. The steam enters 
 through the pipe e, and the part not condensed escapes by the pipe f . The water 
 entering at the pipe c flows if the cock, b, is properly turned over the plates, d, and 
 escapes, when purified, at g. 
 
 The same result is obtained by the addition of milk of lime : 
 
 H 2 Ca(C0 3 ) 2 + Ca(OH) 2 .. 2 CaCO 3 + 2 H 2 O. 
 
 At the same time the magnesium bicarbonate is decomposed with the separation of 
 magnesium hydroxide. 
 
 A well-water, which had to be used for feeding a steam-boiler, and for brewing, 
 was heated to 40 to 50 by the waste steam of a steam- 
 Iig. 224. engine. It was then mixed in an open cistern, holding 
 
 6 cubic metres, with a quantity of slacked lime (ascer- 
 tained by previous experiments), made up to a stiff paste, 
 the whole thoroughly stirred up and used after the pre- 
 cipitate had settled. The analysis of this water before 
 (I.) and after (II.) the treatment with lime, showed the 
 following composition per litre : 
 
 
 I. 
 
 11. 
 
 Chlorine . 
 
 . 152 
 
 153 milligrammes 
 
 Sulphuric acid . 
 
 . 216 
 
 208 
 
 Nitric acid 
 
 ; 71 
 
 70 
 
 , 
 
 Nitrous acid 
 
 . trace ' ... 
 
 trace 
 
 , 
 
 Ammonia 
 
 slight trace . . . 
 
 o 
 
 , 
 
 Organic matter 
 
 . 51 
 
 28 .., 
 
 , 
 
 Lime 
 
 . 322 
 
 172 
 
 , 
 
 Magnesia . 
 
 . 45 
 
 7 
 
 , 
 
 Precipitable on boiling 
 Lime . . .176 
 
 trace 
 
 Care must be taken that an excess of lime is not 
 introduced, as water so treated forms a bad crock. 
 
 The method of purifying waters with magnesia, as 
 proposed by Bohlig, is expensive, questionable for steam 
 boilers, and for other purposes worthless. 
 
 The action of caustic soda is similar, but the sodium 
 carbonate formed decomposes simultaneously a corre- 
 sponding quantity of the other calcium salts. In most 
 cases the use of sodium carbonate is the more advantageous. Calcium sulphate is decom- 
 posed with sodium carbonate as follows : 
 
 CaS0 4 + Na 2 CO 3 = CaCO 3 + Na 2 SO 4 . 
 
 The reaction with the other calcium and magnesium compounds is similar; these 
 metals are precipitated as carbonates with the simultaneous formation of easily soluble 
 sodium salts. If the water contains a large quantity of bicarbonates and of magnesium 
 compounds, the cistern, A (Fig. 225), made of boiler plate, and holding from 2 to 8 cubic 
 centimetres, is run half full of water, which, if practicable, is previously heated from 
 thirty to forty minutes by the waste steam of the engine. The quantity of slacked lime 
 necessary for the entire precipitation is then added (preferably in the form of a stiff 
 paste), and the weighed quantity of sodium carbonate ; the valve, b, of the Korting 
 blast, B, is then opened, so that the air drawn in at a, ancl escaping from the perforated 
 tube, i, may mix the liquid thoroughly. The rest of the water is run in, and after about 
 five minutes the blast is cut off. In from ten to twenty minutes the water becomes 
 perfectly clear. The clearing is expedited if a portion of the precipitate from former 
 operations is left in the cistern. 
 
 The softened water should turn good red litmus-paper blue in about twenty seconds, 
 
SECT. III.] 
 
 WATER AND ICE. 
 
 239 
 
 and should give only a very slight turbidity with oxalic acid. It is then not merely fit 
 
 for steam purposes, but for washing, cooking, brewing, and other technical uses an 
 
 advantage not shared by other methods. 
 
 According to the process of E. de Haen, water is mixed with the proportions of 
 barium chloride needed for precipitating the sulphuric acid : 
 
 CaSO 4 + Ba01 2 = CaCl 2 + BaSO 4 . 
 
 Milk of lime is then added to dispose of the bicarbonates. The proposal has given 
 satisfaction for the feed-water of 
 
 steam-boilers, as the formation of Fig. 225. 
 
 crock is thus prevented; for other 
 purposes it is not applicable. 
 
 In comparing the cost of these 
 precipitants it must be remembered 
 that 80 parts sulphuric acid (SO 3 ), 
 or 136 parts calcium sulphate re- 
 quire 208 parts barium chloride or 
 1 06 sodium carbonate for decom- 
 position. At equal market prices for 
 both precipitants, barium chloride 
 is therefore twice as expensive as 
 soda. 
 
 Distillation. The removal of ; 
 the mineral and other non-volatile \ 
 impurities of water by distillation 
 
 is especially important for chemical processes and for the water-supply of ships. On 
 the small scale, this is generally effected by means of a copper still, the vapours, 
 as they ascend, being condensed in a worm kept cool by means of water. A violent 
 ebullition of the water is to be avoided, lest particles of water are carried over 
 mechanically and find their way into the receiver. Further, the water which passes 
 over first contains any ammonia which may be present. The distillation must also 
 not be carried to the end, as otherwise the organic matter present and certain salts 
 will be decomposed. In order to obtain water as near as possible of an absolute purity, 
 it is first mixed in a still with potassium permanganate and a little caustic potassa and 
 heated to boiling in a still. As soon as the water boils the fire is reduced, to prevent the 
 liquid which froths much at first from boiling over, and the boiling is then continued 
 hi the ordinary manner. After about ^ of the water has been evaporated, the condensed 
 water obtained is free from all foreign matter, organic or inorganic, if the worm is 
 fitted with an arrangement to keep back water from being carried over mechanically. 
 
 To purify sea-water by distillation, it must be remembered that very little fuel 
 should be used, that the apparatus must take up only a small space, and that the 
 water obtained must be rendered in some measure palatable by the removal of the so- 
 called " still-taste." The ships of the German Navy are provided with stills which 
 can furnish daily from 1*25 to 5 cubic metres of distilled water. As shown in the 
 two sections (Figs. 226 and 227), supposed to be at right angles to each other, the 
 apparatus consists of two cylinders, A and B, 0-4 metre in width. The steam for 
 heating, which is produced in a special boiler, passes through the pipe d, into the net 
 of tubes of the cylinder A, surrounded by the water which is to be distilled. The 
 condensed water collects in the recipient, e, and flows from here, the steam being kept 
 back, into g, from which it is let off by a cock, if it is to be used hot, whilst the rest 
 flows through the tube v, to the refrigerator, o. 
 
 The level of the water to be distilled is observed by a gauge. It is previously 
 heated in the cooling vessel, B, and flows through the tube 1, in such a manner that 
 
240 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT, in, 
 
 the steam formed must first pass over the copper sieve-plate, a, and then impinge on 
 the plate, c, in order to get rid of any sea- water which might be carried over, before it 
 arrives, through the tubem, at the tube-refrigerator, n. The water may be either let 
 off directly, or may pass through a filter filled with animal charcoal. 
 
 The requisite condensing water enters by the tube i, and flows off through k, after 
 the portion required for distillation has been conveyed away. The air which escapes 
 on heating from the condensation water is conveyed, through the pipe t, into the steam- 
 chamber of the distilling apparatus, so that it may dissolve in the water condensed 
 here from the steam, and render it palatable. Through g the steam of the steam- 
 pump is caused to enter. 
 
 Vis. 226. 
 
 Water Mains. Good water mains must be chemically and physically as inactive 
 as possible. They must not impart to the water on its transit any hurtful (poisonous) 
 metals or unpleasant properties (decayed wood), and they should not be attacked and 
 destroyed either by the water, by the moisture of the soil, or by any other external 
 agencies. A low power of conducting heat is also desirable, so that they may resist 
 both the heat in summer and the cold in winter. Water pipes must be perfectly 
 tight, and must be able to withstand both internal and external pressure. 
 
SECT, m.] ARTIFICIAL MINERAL WATERS. 241 
 
 Wooden pipes are apt to give the water aii unpleasant taste, and they are not 
 durable. 
 
 Mains of paper, saturated with coal-tar or asphalt, are said to be durable, but 
 they have not come into extensive use. 
 
 Earthenware pipes may be recommended where there is no danger of shocks or of 
 excessive pressure.* 
 
 Cast-iron mains must be tarred whilst hot, as they may be otherwise much 
 obstructed by rust, or may be corroded. Iron pipes coated with zinc answer well with 
 some waters, but in presence of chlorides they are corroded. Iron mains have also been 
 lined with certain enamels. 
 
 For conveying the water into and within houses tin pipes are very good, but too 
 costly. 
 
 Lead piping is more generally used in houses. It was employed by the ancient 
 Romans, who, however, observed that lead is sometimes attacked by water. 
 
 Lead pipes should be protected from contact with lime and cement, by which they 
 are rapidly destroyed. Water dissolves lead if it contains free carbonic acid or ammonia ; 
 chlorides, nitrates, and organic acids promote the corrosion of lead, but calcium carbonate 
 or dissolved silica prevents the attack. Lead pipes are sometimes attacked by water when 
 first laid down, but there is soon formed an insoluble inner layer which protects the 
 metal from further attack. As a rule the use of lead piping seems free from objections ; 
 the decision when and where they may be used with safety must depend on an analysis 
 of the water, f 
 
 ARTIFICIAL MINERAL WATERS. 
 
 Among the substances used in the production of such liquids, the water itself is of 
 the greatest importance. Those intended for medical use should be prepared from 
 distilled water only. Those which serve merely as beverages may be made from an irre- 
 proachable drinking water. J Certain ignorant or reckless manufacturers use impure well- 
 or river-waters if near at hand. It has been proved that the schizomycetes of Selters- 
 waters (commonly called Seltzer) remain capable of development even after the lapse 
 of seven months. The carbonic acid must be pure. According to the equation : 
 MgC0 3 + H 2 S0 4 = MgS0 4 + H 2 + C0 2 , 84 grammes magnesite and 98 grammes sulphuric 
 acid yield 120 grammes magnesium sulphate, or 246 grammes Epsom salts, and 44 
 grammes or 22-3 litres carbonic acid. The same quantity of carbonic acid is obtained 
 from 100 grammes pure marble or pure chalk, whilst of dolomite there are needed 90 to 
 95 grammes. In the choice of carbonates it must be considered that magnesite yields 
 far the best carbonic acid ; marble sometimes, dolomite often, and chalk always contain 
 organic matter which gives the carbonic acid an unpleasant smell, and which can only 
 with difficulty, if at all, be removed by the use of potassium permanganate and carbon. 
 The development of carbonic acid from magnesite and sulphuric acid is the most regular. 
 Chalk and marble must be finely pulverised and well stirred up if the decomposition by 
 sulphuric acid is to be at all complete. Magnesite only requires a free room of 50 per 
 cent, of the entire capacity of the generator to prevent overflowing, whilst chalk needs 
 fully 75 per cent. 
 
 The sulphuric acid used must be free from arsenic, and must contain neither 
 sulphurous acid nor the nitrogen oxides. 
 
 The manufacture is generally effected by saturating water (mixed with th& 
 
 * Glass mains have been tried experimentally, and may possibly prove successful. 
 
 t Gutta-percha pipes are free from objection from a sanitary point of view, and are less likely 
 to freeze in winter than those of lead or tin. But when alternately wet and dry they gradually 
 lose their cohesion, and, like those cf lead, they are sometimes attacked by rats. 
 
 + Such, e.g., as that of Loch Katrine, or the Clarkised Chiltern Hill water. 
 
 Very bad mineral waters have been exported to India. 
 
 Q 
 
242 CHEMICAL TECHNOLOGY. [SECT. HI. 
 
 necessary ingredients) with carbonic acid. This is done under pressure in appro- 
 priate apparatus, and the mineral water, when ready, is at once filled into bottles 
 which are closed air-tight. The carbonic acid gas is either forced into the water 
 by pumps, or it is generated in closed apparatus and driven in by its own pressure. 
 Latterly liquefied carbonic acid has been used with advantage. 
 
 It must be remembered that all the beverages containing carbonic acid should be 
 kept from contact with lead or copper vessels, unless well tinned, as they will otherwise 
 dissolve considerable quantities of the poisonous metals. 
 
 Ice. Ice, or some form of artificial cold, is indispensable for breweries, parafBne 
 works, for the production of Glauber salts from the mother liquors of littoral salines 
 and Stassfurt salts, and for many other installations. Natural ice is often plentifully 
 stored with bacteria, and artificial ice should therefore be substituted if possible. 
 
 There are two processes change of the condition of aggregation, and expansion of 
 volume by which heat is taken up. Hence we may produce cold in the three follow- 
 ing manners : 
 
 1. By liquefaction of a solid by means of a liquid (solution of salts) or of another 
 solid (salt and snow) that is, by means of so-called freezing mixtures. 
 
 2. By converting a liquid body (ether or ammonia) into a gaseous condition. 
 
 3. By the expansion of compressed air. 
 
 The two latter procedures only can come into question on a large scale, though 
 mixtures of snow with dilute acids may be made to produce intense cold on a small 
 scale. In this manner Faudel obtained a temperature of - 60 with sulphuric acid 
 of 65 per cent, which he had caused to ascend through a cooling-tube within a 
 column of snow and to flow out at the top. 
 
 Evaporation Ice Machines. The-boiling point of liquids depends on the pressure 
 of the atmosphere or gas which rests upon them. If this is reduced the temperature at 
 which the liquid evaporates is reduced also. If no heat is conveyed from without, 
 that needed for, gasification must be taken from the liquid itself, and its temperature 
 must fall the lower the less the pressure and the lower its boiling-point. The following 
 table shows the relations of the bodies which here come into question. 
 
 Pressure in Atmospheres. 
 
 Temperature. 
 -80 . 
 -20 
 - 10 
 O 
 
 + JO 
 + 20 
 + 30 
 
 Carbonic 
 Acid. 
 
 I'D 
 
 Sulphurous 
 Acid. 
 
 Ammonia. 
 
 Methyl- 
 chloride. 
 
 Methyl- 
 ether. 
 
 Ethyl- 
 ether. 
 
 I9-9 
 
 0-6 
 
 1-8 
 
 T2 
 
 1-2 
 
 0-09 
 
 26-8 
 
 I'D 
 
 2-8 
 
 17 
 
 17 
 
 0-15 
 
 35'4 
 
 i'5 
 
 4'2 
 
 2-5 
 
 2'5 
 
 0*24 
 
 46' I 
 
 2-3 
 
 6-0 
 
 3'5 
 
 3'4 
 
 0-38 
 
 58-8 
 
 3'2 
 
 8-4 ... 
 
 4-8 ... 
 
 47 
 
 0-57 
 
 73-8 
 
 4-5 
 
 ii'S 
 
 
 6'3 .- 
 
 0-80 
 
 Hence, the greatest cold is to be produced with liquid carbonic acid ; then follow 
 ammonia, methyl-chloride, and methyl-ether ; next sulphurous acid, whilst ethyl-ether 
 produces cold only under a reduced pressure. 
 
 Still less favourable is water, which at o has a tension corresponding to 4-6 milli- 
 metres of mercury, and can consequently be cooled down to o & only in an almost 
 complete vacuum. Still, of late, large ice machines- h\ve been constructed in which 
 water is frozen by rapid evaporation. To effect this tjie air is drawn off as far as 
 possible from the containing vessels, and the watery vapours formed are absorbed by 
 concentrated sxilphuric acid. 
 
 The machines with liquid ammonia, sulphurous acid, and carbonic acid are the 
 most important. They consist, as it is diagrammatically shown in Fig. 228, mainly of 
 the evaporator, A, in which the liquid concerned vaporises and withdraws the 
 
SECT. III.] 
 
 ARTIFICIAL MINERAL WATERS. 
 
 243 
 
 requisite heat from the solution of magnesium chloride circulating in the pipes. The 
 pump, B, draws the gas, forces it into the cooler, C, in which it is again liquefied, and 
 conveys the heat liberated to the refrigerating water. The cock, D, regulates the 
 reflux to the evaporator, A. 
 
 As an instance may be taken Pictet's machine (Fig. 229), which uses a mixture of 
 sulphurous acid and carbonic acid, as is alleged, in the molecular combination, CSO 4 . 
 Fig. 228. 
 
 The cylinder, a, of the steam- 
 engine, drives directly the forcing- 
 pump. On each of its covers there 
 .are two suction-valves and two pres- 
 sure-valves, d. The valves on both 
 sides are connected with each other 
 by a pipe. Above each of these two 
 connecting-tubes there is a valve, 
 VjVjj, which can be shut perfectly 
 air-tight. The water for the cooling- 
 jacket of the pressure-cylinder and 
 the perforated piston-rod arrives and 
 is carried off by flexible tubes, g. 
 The refrigerator, C, consists of two 
 iron holders, and the worms. The 
 former are set in each other so that 
 they have one side on the bottom 
 in common. The seamless worms 
 of iron, or copper, all run above 
 and below each into a large hori- 
 zontal main, h l and h 2 , which are 
 again connected by two vertical tubes, 
 h 3 and h t . The liquid coming from 
 the condenser is led below into the 
 refrigerator by the tube, r, fills the 
 lower horizontal tube, a part of the 
 vertical, and of the worm, and is 
 again drawn off in a gaseous form 
 through the tube, r, by means of the forcing-pump. The valve V 3 and the entrance 
 cock, V 4 , allow of the whole system being closed air-tight. 
 
 The salt water flowing round the latter is kept in motion by the screw, e. This 
 salt water, which is cooled down by the development of cold which proceeds in the 
 worms, is conveyed by special conductors into the fermenting and storage cellars 
 \(i.e.. supposing the machine is in use in a brewery), and returns to the refrigerator, 
 
244 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 heated several degrees. Iron cells,,/, can be suspended between the worms, in which 
 water is allowed to freeze. In the space between the two holders there is pure water, F, 
 which covers the outer surface of the internal holder partly in the form of ice, G-. This 
 cold pure water serves to circulate in the beer coolers and fermenting vats. 
 
 The condenser, D, likewise consists of an iron receiver and a system of worms. The 
 parallel worms discharge above and below into upright collecting tubes, h 5 and h 6 . The 
 compressed gases enter the condenser through the pipe, r 2 , and are liquefied. The liquid 
 collects at the bottom of the tube, h v and rises up through a narrower tube, r, which 
 extends to the bottom of this large pipe. This pipe conveys the liquid through the 
 regulator, E, to the cooler. The condensing worms are closed perfectly air-tight by 
 the valve V 5 and the cock V 6 . The cooling-water enters the condenser below through 
 a pipe, i, traverses all the rows of worms, and flows off at the top through a perforated 
 collecting-tube, K. 
 
 The regulator is introduced into the tube, which leads the volatile liquid from the 
 condenser to the cooler after it has been liquefied. The bye-cocks, V 7 and V 8 , 
 attached to the main cock, allow the liquid to be introduced into the apparatus and to- 
 draw it out of the machine. 
 
 The latent boiling-heat of the liquids concerned is per kilo. : ammonia, 315 ; methyl- 
 ether, 130 ; sulphurous acid, 94 ; ethyl-ether, 90 ; carbonic acid, 84 heat-units (calories). 
 On account of the different specific heats and densities, the proportionate sizes of the 
 machines are as follows : That of the ammonia-machine (according to Linde) = i ; 
 ethyl-ether, i2'2; sulphurous acid, 2^5 ; methyl-ether 1*5 ; carbonic acid, 0-17. 
 Theoretically, therefore, carbonic acid is the most advantageous. Trustworthy com- 
 parative experiments are still wanting. 
 
 Cold-air machines are to be preferred only where rooms have to be cooled and ven- 
 tilated at the same time. 
 
 SULPHUR. 
 
 Sulphur occurs native in gypsum and in the connected beds of clay and marl, in< 
 the flb'tz and the tertiary formation, more rarely in veins in the crystalline slate and 
 transition formations, occasionally in lignite and coal. It is also found as a sublimation 
 product from volcanoes, as in the Solfatarae of Naples. It is most common in veins 
 and deposits in Sicily, which supplies nearly all Europe with sulphur ; in the Caucasus ; 
 in Egypt, on the coasts of the Red Sea, and especially of the Gulf of Suez ; in the Ionian 
 Islands (especially Corfu), in the Clear or Borax Lake in Nevada ; in Popocatepetl in 
 the Mexican province of Puebla, where above 100 tons of sulphur are collected yearly, 
 and at Krisuvik in Iceland. Sulphur is plentifully found at Swoscowice near Cracow, 
 deposited in the marl. It occurs also on a large scale in New South Wales. Sulphur is 
 deposited from mineral springs, and occurs in combination with metals, as iron, and 
 copper pyrites, galena, blende, &c., also oxidised to sulphuric acid in anhydrite, gypsum, 
 kieserite, heavy-spar, &c. 
 
 Extraction. Volcanic sulphur is obtained, according to the nature and the richness of 
 the minerals either by fusion or distillation. If the raw materials are rich the sulphur is 
 extracted by melting in an iron pan, A (Fig. 230), which is gently heated by a fire on 
 the grate, B. After the sulphur is melted the stony matter is skimmed out with the 
 ladle, (7, and the sulphur is poured into a dish moistened with water or into a sheet 
 iron pan, D. When cold the mass of sulphur is broken up and packed in casks for the 
 market. The stony matter, as well as the poorer sulphur minerals, are melted in 
 heaps or shaft furnaces (Fig. 231), apart of the sulphur serving as fuel. A small 
 quantity of impure sulphur is burnt in the support of this furnace, and the shaft, E, is 
 gradually filled with coarse pieces of the earthy sulphur, which soon take fire on the top 
 and allow the melting sulphur to escape. The openings, /, let in the air necessary 
 
SECT. III.] 
 
 SULPHUR. 
 
 245 
 
 231. 
 
 Fig. 230. 
 
 for the combustion of a part of the sulphur. The melted sulphur which collects at the 
 lower part of the shaft is let off through the channel, </, into wooden or iron vessels. 
 Sulphur can be melted in clamps better than in shaft furnaces. There are no fewer 
 than 630 sulphur mines at 
 present in work in Italy. 
 In many the operation is 
 effected in the most primi- 
 tive manner by melting out 
 a part of the sulphur by 
 means of burning sulphur. 
 This is effected in Sicily 
 with an average loss of 50 
 per cent, of the total sul- 
 phur, and in the Romagna 
 
 with a loss of 43 per cent. 
 Other methods of extrac- 
 tion have only met with a 
 very limited adoption. 
 
 Far better is the distillation process, in which a real distillatory apparatus is now used 
 {Fig. 232). A cast iron-pan, A, is filled with the raw material and closed with an iron 
 cover. The manner of heating and the way which the products of combustion take 
 
 round the pan and the preliminary 
 heater, D, can be perceived from 
 the figure. The vapours of sulphur 
 escape through the iron pipe, ra, 
 into the condenser, , from which 
 the liquid sulphur runs into the 
 vessel, k. . The material, which has 
 been previously warmed in D, is let 
 fall into the pan of the still (which 
 has been emptied in the meantime) 
 by withdrawing a slide at p. 
 
 For extracting the sulphur from 
 Italian ores, Balard recommended 
 
 Fig. 232. 
 
 in 1867 a solution of salt. Dubreuil 
 used a solution of calcium chloride, 
 
 a procedure which had been carried out practically by Ch. Deperais in 1868. For some 
 years sulphur has been eliquated from its ores by means of steam, at 130. According 
 to Gerlach's proposal, which has not been successful, the sulphur ores are heated 
 with the simultaneous introduction of superheated steam. The extraction of the 
 mineral with carbon disulphide has also found a restricted application. 
 
 The Sicilian raw sulphur, as obtained by the fusion-process, had the following com- 
 position : 
 
 i. ii. in. iv. v. 
 
 Sulphur, soluble in C8 2 . 90'! ... 96 - 2 ... 91*3 ... 9O'o ... 887 
 Carbonaceous matter . ro ... o - 5 ... 07 ... ri .. ro 
 
 Sulphur insoluble in CS., 2 - o ... ... i - 5 2 - i ... 17 
 
 Sand .... 2-3 ... 1-5 ... 3-3 ... 2-8 5-5 
 
 Limestone . . 4'i ... i'8 ... 2-5 ... 3 - o ... 2-8 
 Loss . . . o - 5 ... ... 07 ... ro ... 0-3 
 
 Refining. The bottoms of the loaves of raw sulphur contain as much as 25 per 
 cent, of foreign matter. In order to free it from the earthy parts the crude sulphur 
 is refined and comes into the market either as roll sulphur or as flowers of sulphur. 
 
246 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. iii. 
 
 The apparatus for refining sulphur, constructed by Michel, of Marseilles, and im- 
 proved by Lamy, consists of one or of two cast-iron cylinders, B (Fig. 233), which 
 serve instead of a retort, and a large chamber, G, which acts as a receiver. The first 
 cylinder, S, is heated by the fire below. The flame plays round the cylinder and escapes, 
 along with the gases of combustion, through the chimney, E, after having first given off 
 a part of their heat to the pan, 2), through the flues, C. Here the sulphur undergoes a 
 preliminary purification and flows through the pipe, F, into the cylinder, E, which 
 opens into the large vaulted chamber of brick. At one end of this chamber 
 (not shown in the figure) there is a doorway closed inwardly by an iron door coated 
 with lead and secured without by bricks. At the lower part of the chamber there is, 
 in an iron plate, a round hole which can be opened or closed by the rod, H. The 
 
 Fig. 233. 
 
 sulphur flows from here into the pan, L, near which is a rotating vat, M, divided into 
 compartments, into which the sulphur passes in the form of rolls, and is then stored 
 in^. 
 
 If roll sulphur is to be produced, each cylinder is charged with raw sulphur, the 
 covers are luted and one cylinder is heated ; as soon as the distillation is half effected 
 the second cylinder is heated. The combustion gases from both hearths raise the 
 temperature of the pan, Z>, so far that the sulphur melte and is thus purified, by the 
 subsidence of the heavy impurities, by the escape of the moisture present, and by the 
 separation of light matters on the top. As soon as the distillation of the first cylinder 
 is at an end it is charged afresh from the pan, Z), by means of the pipe, F. Each dis- 
 tillation lasts four hours, and 1800 kilos, of sulphur are obtained in twenty-four hours 
 from the two cylinders in six operations. As the temperature in the chamber is always 
 
SECT. III.] 
 
 SULPHUR. 
 
 above 112, the sulphur remains liquid. As soon as the stratum of melted sulphur is 
 deep enough it is drawn off into the small pan, L, and ladled into wooden moulds. 
 
 If flowers of sulphur are to be produced, the temperature in the chamber must not 
 exceed 110, as the sulphur would otherwise melt ; to keep down the heat, only two dis- 
 tillations of 150 kilos, are undertaken in twenty-four hours. As soon as the layer of 
 flowers of sulphur at the bottom of the chamber has reached a certain height the door 
 above mentioned is opened and the flowers of sulphur are shovelled out. 
 
 In Dujardin's refining apparatus the distillation is effected in a lenticular retort, a 
 (Figs. 234, 235, 236), with an annex, b, capable of being closed by the trap, c, in order 
 that no air may enter while the retort is emptied. On the hearth is an oval pan, d, heated by 
 the escaping fire and connected with the retort by the tube, e, which can be closed by the 
 plug, f. This pan holds 600 kilos, of sulphur, which, as soon as melted, is let run with all 
 its impurities into the retort. 
 
 When it is volatilised (in about Fi - 2 34- 
 
 four hours) the trap is closed and [C 
 
 the residue is emptied into g. 
 In general, six distillations are 
 completediri twenty-four hours, 
 using 500 kilos, of fuel. In about 
 five or six days the sulphur is 
 cast into rolls. Only 400 kilos, of 
 raw sulphur are daily distilled 
 i'or the production of flowers 
 of sulphur. The experience 
 of the Wyndt-Aerts works at 
 Merxem, near Antwerp, where 
 such a furnace is in action, 
 shows that the total loss does 
 not exceed 2-23 per cent, and 
 that the residues are quite free 
 from sulphur. This is effected 
 with crude sulphur which con- 
 tains on the average 1*5 per cent, of impurities, so that the true loss is reduced to 
 '73 P er cen t. In the works in which this apparatus is in action 1500 tons of sulphur 
 are distilled yearly. 
 
 Still simpler than the above Belgian apparatus is one used in German refineries, 
 consisting of two cast-iron pans of i metre diameter and height, at the distance of 
 2 metres from each other and connected with each other by a knee-piece. The one 
 pan is fixed over a grate fire and is charged by means of a funnel going down through 
 the knee-piece and descending almost into the melted sulphur, whilst the refuse is 
 removed by a side-tube. The vapours of sulphur as they are driven over condense in 
 the second pan which is bricked round so that the melted sulphur may remain liquid 
 and may be let off by a cock. 
 
 Commercial flower of sulphur always contains sulphurous and sulphuric acids, which 
 may be chiefly removed by washing with water. 
 
 Sulphur from Iron Pyrites (Sulphur Ores), FeS 2 . Iron pyrites may give off 26*65 
 parts of sulphur without being rendered unfit for the manufacture of copperas (ferrous 
 sulphate). But if half the sulphur present in the pyrites were to be expelled by heat 
 it would be necessary to apply a temperature at which the residual iron monosulphide 
 would fuse, and would be absorbed into the fire-clay cylinders and destroy them. It is 
 therefore thought preferable to expel only 13-14 per cent, sulphur by heat when the 
 residue remains pulverulent and does not attack the distillatory vessels. Iron pyrites 
 
248 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 always contains arsenic. According to the analyses of E. Hjelt (1877) Spanish pyrites 
 contain 0-91 per cent. ; Westphalian 0-3 ; Norwegian only traces. 
 
 The pyrites are heated in conical tubes of fire-clay, .1, which, as shown in Fig. 237, 
 are laid over a fire in an inclined position. The lower opening is closed with a sieve- 
 plate of burnt clay, A, which prevents the pyrites from falling out, but allows the 
 melted sulphur to escape either as a liquid or as a vapour. At this end there is an 
 earthen tube, b, through which the sulphur arrives in receiver, C, containing water. 
 The tubes are filled with coarsely pulverised pyrites, closed with fire-clay lids luted on and 
 
 then heated. The raw sulphur 
 
 Fig. 235. found in the receiver is of a 
 
 greenish-grey colour and is 
 purified by re-melting. Such 
 sulphur is met with in com- 
 merce in lumps as melted sul- 
 phur. In order to purify it 
 from the accompanying arsenic 
 sulphide it is redistilled. The 
 residue from this is the so- 
 called horse-sulphur used in 
 veterinary practice. The orange 
 colour of the sulphur obtained 
 from pyrites is owing more 
 frequently to an admixture 
 of thallium than to arsenic. 
 Crookes found in Spanish py- 
 rites-sulphur as much as 0*29 
 per cent, of thallium. 
 Sulphur from Roasting Copper Ores, as 
 a bye-product of the extraction of copper. 
 In the Lower Harz so-called virgin sulphur 
 was formerly obtained in stalactitic pieces 
 from copper pyrites, the sulphur being let 
 drop out at an opening in the side of the 
 roasting-heap. 
 
 Gas-Sulphur, as a bye-product at gas- 
 works. In purifying gas with s Landing's 
 mass the sulphur collects in quantities up 
 to 40 per cent, according to the equation : 
 Fe 2 3 + H 2 S = 2FeO + H 2 + S. The sul- 
 phur is extracted with carbon disulphide, 
 or the mass is roasted in kilns for the 
 manufacture of sulphuric acid. 
 
 Sulphur from Vat Waste. See Alkali 
 Manufacture. 
 
 Sulphur from Sulphurous Acid and Sulphuretted Hydrogen. Dumas in 1830 
 observed that if ^ sulphuretted hydrogen is burnt and the sulphur dioxide produced 
 is passed into a moist chamber along with f sulphuretted hydrogen, almost all the sulphur 
 might be recovered : S0 2 + 2H,S 2H 2 + 38. This reaction, in which nearly half the 
 sulphur is lost by the formation of pentathionic acid, has been often tried in order to 
 recover the sulphur from gypsum, crelestiiie, heavy spar, and the residues of the Leblanc 
 alkali process (according to the method of Schaffner and Helbig). The process is essen- 
 tially as follows : Heavy spar, e.g., is reduced by ignition with carbon to barium sulphide, 
 
 Section across A B. 
 
SULPHUR. 
 
 249 
 
 Fig. 237. 
 
 SECT. III.] 
 
 which is then heated with hydrochloric acid or magnesium chloride in order to obtain on 
 the one hand barium chloride and on the other sulphuretted hydrogen, which is either 
 partially burnt and then converted into sulphur by means of the unburnt sulphuretted 
 hydrogen according to the above reaction, or the sulphuretted hydrogen gas is at once 
 passed into water or a solution of magnesium chloride into which there is passed at the 
 same time sulphur dioxide produced by roasting pyrites. By a similar reaction sulphur 
 is also obtained as an important bye-product in the extraction of potassium salts and 
 iodine from kelp. At Paterson's iodine-works in Glasgow the annual yield of sulphur 
 from kelp is about 100 tons. According to C. Kopp sulphur may be also obtained by 
 the imperfect combustion of sulphuretted hydrogen (H 2 S + O = H 2 O + S). 
 
 Sulphur from Sulphurous Acid and Carbon. If sulphurous acid is passed over ignited 
 coals the latter burn to carbon dioxide, and sulphur is eliminated. In this manner 
 sulphur is obtained at Borbeck on roasting zinc blende. 
 
 Sulphur from Sulphuretted Hydrogen. Sulphuretted hydrogen if passed through 
 tubes at a red-heat is resolved into its con- 
 stituents. It is passed through ferric hy- 
 droxide suspended in water, when the gas is 
 entirely absorbed. The iron sulphide is con- 
 verted into free sulphur and ferric hydroxide 
 if air is forced in. 
 
 Properties. In its ordinary condition 
 sulphur has a peculiar yellowish colour, which 
 becomes darker at 100 and almost disappears 
 at 50 ; it is easy to pulverise ; its spec. gr. is 
 1-98-2-06 ; it melts at i^-iiS'S" to a thin 
 yellow liquid, which becomes thicker and of 
 an orange-colour at 160 ; at 220 it becomes 
 tough and reddish ; between 240 and 260, 
 very tough and reddish-brown ; at 340 it 
 grows more liquid again ; and at 448-4 (Reg- 
 nault), without losing its dark colour, it begins 
 to boil and is converted into dark reddish- 
 brown vapours. If sulphur is heated to 230 
 and is suddenly cooled by plunging into water, 
 it becomes soft and plastic, and in this state 
 it can be used for taking impressions of 
 medals and other engraved work. After 
 
 some days it recovers its original hardness, so that the impressions can be used as 
 moulds for reproducing very sharp copies. If sulphur is heated in contact with air 
 it burns to sulphurous acid. It is insoluble in water, very slightly soluble in absolute 
 alcohol and ether, more readily in carbon disulphide, 100 parts of which at 48-5 dissolve 
 146-21 parts of sulphur. It is also soluble in heated oils, fatty and volatile, and dissolves 
 on boiling in soda and potassa-lye. It is used in the manufactures of gunpowder and 
 matches, for sulphuring hops and wines, for applying to trees as a remedy for the parasitic 
 diseases, for the preparation of sulphurous acid, sulphites and thiosulphites, carbon di- 
 sulphide, vermilion, mosaic gold, and other metallic sulphides, in the manufacture of 
 certain cements, and for vulcanising caoutchouc and gutta-percha. 
 
 Besides Italy, with about 400,000 tons, Spain yields yearly 6000 tons, Austria and 
 Oermany each 900 tons (not including regenerated sulphur), and the rest of Europe 
 900 tons of sulphur. 
 
 Carbon Disulphide, CS 2 . This compound (which was discovered by Lampadius in 
 1796) is obtained by bringing sulphur in contact with ignited carbon, or distilling 
 
250 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT, in 
 
 metallic sulphides (pyrites, blende, &c.) with carbon. The yield, according to W. 
 Stein, is best when the vapour of sulphur is allowed to act upon carbon at a medium 
 grade of redness. 
 
 In the manufacture of carbon disulphide the apparatus of Peroncell is often used 
 (Fig. 238). A clay gas-retort, A, stands on a stone support, fi, and is built into a 
 furnace. On the cover of the cylinder there are two necks, E, into one of which is 
 cemented a porcelain tube which extends almost to the bottom of the cylinder and rests 
 upon a layer of pieces of charcoal with which the bottom is covered and with which 
 it is otherwise filled up. The sulphur is added through this opening, U, fitted with 
 the porcelain tube, and through the other opening charcoal is added from time to time. 
 The fumes of carbon disulphide formed escape through the lateral tube, H, into the 
 stoneware receiver, /, in which a part of the carbon disulphide is condensed and flows 
 through K into the Florentine flask, L, and thence through the bent tube, M, into 
 the jar, 0, from which it can be let off by means of the cock, N. The vapours not 
 liquefied in J pass through the pipe, P, into the cooling-apparatus, T, from which it 
 escapes at R into the receiver , S. 
 
 Notwithstanding the most careful refrigeration, the quantity of disulphide is never 
 
 obtained which the weight of 
 
 Fig. 238. sulphur employed should theo- 
 
 retically yield, not only in con- 
 sequence of the unavoidable 
 loss of a part of the carbon di- 
 sulphide, but probably from the 
 simultaneous formation of car- 
 bon monosulphide (CS, corre- 
 sponding to carbon monoxide), 
 which is formed to some extent 
 along with the disulphide. The 
 product obtained contains 10 to 
 12 per cent, sulphur in solu- 
 tion, in addition to sulphu- 
 retted hydrogen and, doubt- 
 less, some other compounds of 
 carbon, sulphur, and oxygen, 
 
 which give it an exceedingly unpleasant smell. It is purified by rectification, solution of 
 chloride of lime being introduced into the apparatus, which destroys the sulphuretted 
 hydrogen, and the rectification is then begun by passing steam at one atmosphere under- 
 neath the still. According to Braun, pure carbon disulphide may be obtained by 
 repeated distillation over a pure fatty oil. In order to protect carbon disulphide in 
 the refrigerators, &c., from evaporation, it is kept covered with a layer of water of 
 20 to 30 centimetres in depth. 
 
 Properties. When pure, carbon disulphide is a limpid, colourless, motile liquid which 
 refracts light strongly and has an odour somewhat like that of chloroform, and an 
 aromatic flavour. Its spec. gr. = 1-2684. It boils at 46-5 and evaporates quickly 
 at common temperatures. Its ignition point is 170. It does not combine with water, 
 but mixes with it in the proportion of i per cent. It is miscible in all proportions with 
 alcohol, ether, and similar liquids. It dissolves resin, f atty and ethereal oils, caoutchouc, 
 gutta-percha, wax, camphor, sulphur, phosphorus, and iodine, in large quantity. It 
 is very readily inflammable, and burns with a faint blue flame to form sulphurous and 
 carbonic acids (whence its utility in extinguishing burning chimneys and fires in 
 close spaces, such as cellars and magazines). A mixture of its vapour with oxygen or 
 atmospheric air gives a violently explosive gas. A mixture of nitric oxide and vapours 
 
SECT, in.] SULPHUR. 251 
 
 of carbon disulphide give, when ignited, a very intense light, which has been used in 
 photography. 
 
 Up to 1850 the only use of carbon disulphide on the large scale was in vulcanising and 
 dissolving caoutchouc. Latterly it has been employed for extracting fat out of bones 
 which are to be used for the preparation of animal charcoal ; for extracting oils from oil- 
 seeds (palm kernels, olives, rape-seed, linseed, poppy-seed, &c.), for extracting sulphur 
 out of minerals, asphalt from bituminous rock, and recovering oil and fat from matter 
 in which it was formerly lost (such as the " glycerine tar," the glycerine goudroneuse of 
 the French stearine works, where it is found as a bye-product of the saponification with 
 sulphuric acid), from the brown residues of wheel-grease, from saw-dust which has 
 served for filtering oils which have been refined with sulphuric acid ; from the dregs 
 of tallow-melting, the so-called greaves ; for extracting fat from wool and waste used 
 in cleansing machinery the fat thus recovered may be used in soap-boiling ; in the 
 production of potassium ferrocyanide on the Tcherniak and Giintzburg process and 
 of ammonium sulphocyanide ; for purifying raw paraffine by Alcan's process ; in 
 electro-plating a small quantity of carbon disulphide is added to the silver bath to 
 give at once a brilliant surface ; for killing rats and other vermin ; a solution of wax 
 in carbon disulphide is used in preparing wax paper and in coating plaster figures. 
 Konig burns carbon disulphide in an especial lamp for disinfecting, and Dahlen uses 
 it for sulphuring casks. Recently, compounds of the alkali-metals with sulphocarbonic 
 acid, CH 2 S 3 = CS(SH 2 ) 3 , have been successfully used in a watery solution as a remedy 
 for the phylloxera. The salts of xanthogenic acid (ethyl disulphocarbonic acid), a deri- 
 vative of carbon disulphide, have been used by Zoller for preserving articles of food, and 
 by H. Schwarz for producing explosive mixtures. The vapour of carbon disulphide is 
 recommended against the grape-disease. 
 
 Sulphur Chloride (Cl 2 Sj) is a compound used for vulcanising caoutchouc. It is an 
 oily liquid of sp. gr. 1*60 ; is of a brownish colour and has a suffocating smell ; it fumes 
 in the air and boils at 144. In contact with water it is quickly decomposed into 
 sulphurous and hydrochloric acids, sulphuric acid, and sulphur. Sulphur chloride is a 
 good solvent for sulphur ; it converts rape oil into a mass resembling caoutchouc, and 
 linseed oil into a varnish. It is obtained by passing chlorine gas, washed and dried, 
 through melted sulphur heated to 125 to 130. Sulphur chloride is at once formed, 
 and distills over into a cooled receiver, carrying with it vapours of sulphur. It is 
 redistilled to purify it from free sulphur. 
 
 Sulphurous and Sulphuric Acids. Sulphurous acid, S0 2 (more correctly named 
 sulphur dioxide), is obtained by the combustion of sulphur, by roasting metallic sul- 
 phides, or by the reduction of sulphuric acid. 
 
 The furnaces, kilns, or burners are built of bricks (Fig. 239) ; at a height of 80 centi- 
 metres above the floor there is placed a stout iron plate, sloping slightly forwards. Upon 
 this plate rest the side-walls, whilst the back and the top of the furnace are also formed of 
 iron plates. The same applies to the front side of the furnace, in which there are several 
 (three to six)large openings,/*, which are closed with iron plates fitted with wooden handles. 
 Within, upon the iron plate which forms the sole of the furnace, there are three iron 
 rails, placed lengthwise, each 10 centimetres in height, which divide the bottom into three 
 or six compartments, corresponding to the number of the doors. At H, there are air- 
 holes. From the iron plate which forms the top of the furnace there goes off a wide 
 pipe, T, which carries off the gases and vapours formed in the furnace. In starting 
 this furnace the workman places about 50 kilos, of lump sulphur in each compartment, 
 and kindles the surface; the draught through the air-holes, H, is regulated so that 
 the required quantity of sulphur burns to sulphuric acid, but that no sulphur sub- 
 limes. If the furnace is at the same time to furnish the nitrous vapours necessary 
 for the formation of sulphuric acid, there is introduced into each compartment a 
 
252 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 Fig. 239. 
 
 movable furnace on feet, in which is a mixture of soda-saltpetre and sulphuric acid 
 at 1 16 Tw. ( = i -56 spec. gr.). The combustion heat of the sulphur causes hyponitrous 
 
 acid to be evolved f rom this mixture, which es- 
 capes along with the sulphurous acid through 
 the pipe, T. 
 
 However much these furnaces have been 
 improved, they labour under the defect that 
 in them the sulphurous acid is not evolved 
 continuously, but in fits, by which the regu- 
 larity of the process is endangered. It is 
 better to use sulphur furnaces with an un- 
 interrupted working, in which an equal cur- 
 rent of melted sulphur flows down upon the 
 burner-plate, and forms in every part of time 
 the same quantity of sulphurous acid. 
 To every square metre of the floor of the furnace 60 to 70 kilos, of sulphur are allowed 
 in twenty-four hours, and to every too cubic metres of the lead chambers 46 to 50 
 kilos, of sulphur in small works, in larger ones 66 to 100. The sulphur ovens are being 
 gradually superseded by those for pyrites or blende. 
 
 The furnaces for roasting pyrites consisted at first of a shaft without a grate. 
 In the vault there were two openings, the one connected with the chimney and the 
 other with the lead chambers. In the front and the back there were a number of 
 holes which served to admit air and to watch the process. The upper aperture was 
 for the introduction of pyrites, broken to the size of a nut ; the lower was for the 
 removal of burnt ore. 
 
 In the Oker works, in the Harz, similar kilns are in use, according to W. Knocke. 
 For every four kilns there are two nitre-channels, which lie so between the furnace- 
 shafts that the temperature is reached which is needed for decomposition. Figs. 240, 
 Fig. 240. Fig. 241. 
 
 241, 242, 243, give a front and side elevation and the corresponding sections. Two 
 rows of two or four kilns each are in contact with the back wall, a and b are openings 
 for drawing out the burnt ore ; /, openings for introducing the charge (a mixture of 80 
 per cent, iron pyrites and 20 per cent, copper pyrites) 'containing about 50 per cent, 
 sulphur ; c, d, e, i, are openings for stirring up the ore and keeping up the current of 
 air ; g, are the nitre-channels. In the space, h, cast-iron nitre boxes are kept ready 
 filled. In twenty-four hours 2700 kilos, of ore are roasted, and 50 kilos, nitre are 
 consumed. 
 
 When the kilns are new they are heated for some days by a wood fire placed on 
 
SECT. III.] 
 
 SULPHUK. 
 
 the sole of the furnace and gradually strengthened ; roasted ore is then introduced up 
 to 10 centimetres below the door, and upon this ore there is kept up a strong flame fire 
 until the sides of the kiln, and especially the vault, are red hot. Raw ore, in pieces 
 from the size of a walnut to that of a fist, is placed upon the roasted ore to the depth 
 of 9 to 12 centimetres. The raw ore is ignited by the heat of the kiln and the wood 
 fire, and is roasted. The vapours are passed into the open air as long as the wood fire 
 is in existence. When it is consumed and the ore is in full glow, the vapours are 
 conveyed into the chambers. The workmen continue in this manner drawing out as 
 much burnt ore below as they put in raw ore above. The kilns are worked so that each is 
 emptied and refilled three times in twenty-four hours, and attended to three times. Every 
 two hours two kilns are charged afresh and two others are attended to. The attention 
 
 Fig. 242. 
 
 takes place four hours after charging, and consists in breaking up the ore with iron bars, 
 that the air may have proper access. The air required for the oxidation of the sulphur 
 enters chiefly from below, through the roasted ore. If there is any deficiency it is 
 made up by admitting air at the slides in the side doors. The soda-saltpetre is placed 
 in cast-iron boxes, with sulphuric acid, at 30 Tw., and placed in the channels. In 
 the course of four hours they are replaced by fresh nitre boxes, so that each channel is 
 freshly supplied six times in twenty-four hours. In roasting, care must be taken that the 
 fire does not work downwards and so smelt the mass together. The ore must not be 
 placed too closely together, or be broken up too finely. 
 
 Fig. 244. Fig. 245. 
 
 In the sulphuric acid works at Marseilles pyrite kilns with grates are used, arranged 
 as shown in Figs. 244 and 245. They consist of two hearths, A, with grates. Between 
 them is a pan of sandstone or cast-iron for the mixture of nitre and sulphuric acid. 
 The gas of the one hearth, separated by a tongue from the other, that the nitre pan 
 may not be over-heated, meets with the other gases shortly before the exit from the 
 kiln. Slits in the doors admit the air. Each hearth is charged with 150 kilos, of 
 pyrites broken so as to pass a 2 -inch sieve. A furnace with two hearths roasts 2000 
 kilos, pyrites in twenty-four hours. 
 
^54 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 in the Gerstenhb'fer roasting kilns (terrace kilns) the comminuted ore falls through 
 hoppers fitted with grooved rollers xipon earthen bearers, and slips down from one stage 
 to another, being kindled by the ignited sides of the furnace which have been previously 
 heated by fire upon a removable grate, and roasted by the action of the air admitted 
 at the sides. The burnt ore which falls upon the sole of the furnace (which narrows 
 below) is drawn out at a side door. In the roasting space, A (Figs. 246 and 247), there 
 are, besides the three upper distributors of the ore, m, fifteen rows of ore-bearers, n, each 
 alternately of six and seven pieces of Meissen clay (together looin number) ; the bearers 
 with corresponding sections come in contact with projections of the stones in the 
 front and back walls. The roasting-gases from A arrive through the space, e (Fig. 
 248), into the flue-dust chambers, C and E, and thence into the lead-chambers. In 
 
 a vaulted passage, Z>, through 
 
 Fi g- 2 4 6 - Fi S- 2 47. the flue-dust chambers, E, are 
 
 the valves in the air-chest, by 
 means of which is regulated 
 the access of air into the fur- 
 nace through the channel, I, 
 and the opening, a (Figs. 246 
 and 247). The flue-dust 
 settling in B can be removed 
 through openings, g, in the 
 vault. For introducing the 
 ores through the slits, d, the 
 three distributors there serve 
 the shoot-arrangement above. 
 On the platform of the furnace 
 stands a cast-iron chest on feet, 
 9 centimetres broad; its right 
 and left sides are straight, but 
 its front and back are beut in. 
 After it has been set in its 
 place, the masonry of fire-bricks 
 is carried up within the sides 
 as far as 9 centimetres belou- 
 its upper angle, keeping the 
 space for the slits open, and 
 the angle formed on the right 
 of each slit is kept so broken off that a curved cast-iron plate, which conveys the ore to 
 the rollers, is supported both by the wall and on the projections of the chest. To pro- 
 tect the roller-bed from direct contact with the fine mass of the charge, two cast-iron 
 plates are laid over each, resting partly in a niche left in the masonry and partly upon 
 A three-sided prism-shaped piece laid upon the plate. The covers of the slits have two 
 handles ; they prevent the direct fall of the charge into the slits, and cause it to enter 
 the roasting shaft only between the rollers and the guiding plate, thus rendering it 
 possible for it to be introduced always in equal quantity and not beyond a certain 
 limit. The two pieces screwed to the front wall of the chest support bearings for a 
 shaft on which are fixed three endless screws which fit into the teeth of the wheels. 
 
 For starting the furnace, fifteen or sixteen grate-bars, r, are inserted through the 
 middle opening, ", which is then filled up with bricks and clay ; the intervals between 
 the grate-bars are filled up outwardly ; coals are placed upon the grate through h, and 
 kindled by a wood fire from below ; the upper openings, h, are closed tightly with iron 
 plates, but the exit hole, k, is left open. To prevent the ore-bearers from cracking, the 
 furnace is heated to whiteness very gradually, the gaseous products, after the channel, 
 
SECT. III. 
 
 SULPHUK. 
 
 2 55 
 
 Fig. 248. 
 
 g, is closed, being passed, not into the lead-chambers, but through a side-flue into a 
 chimney. The bearers are kept for two days at a white heat, and the rollers are then 
 started, one turn in five minutes. The hoppers have been filled at the beginning of 
 the heating, to prevent the combustion gases from escaping through the slits, d. By 
 the movement of the rollers, the ore-bearers are gradually filled with the charge up to 
 their natural slope, and the firing is continued, until it is observed through c, 6, that 
 about the fourth row of bearers from below is beginning to fill. One grate-bar after 
 another is then drawn out, and the space is closed with bricks and mortar until the 
 opening, i t is entirely blocked. The ash-pit is cleared out, and the valve, m, is opened 
 to admit air through a. The filling with the charge at the above speed of the rollers 
 takes about 6| hours. After the admission of air, the volatile products of roasting are 
 still allowed for a while to escape by the chimney ; afterwards the flue, g, is opened, 
 and the one leading to the chimney is closed. As will be seen from the above description, 
 the ore falls through the slits, d, at first upon the upper bearers, collects there as long 
 as the slope allows, and then all further supplies of material slide down upon the next 
 row of bearers. As to the uniformity of roasting, the Gerstenhofer furnace is 
 much superior to other shaft-fur- 
 naces, and especially to muffle-fur- 
 naces, as it contains an equal 
 amount of the charge in all the 
 horizontal sections at the same time. 
 The ore must be supplied in a suffi- 
 ciently fine form, that the roasting 
 may be expeditious, and that the 
 heat needed for keeping up the pro- 
 cess may be supplied by the oxida- 
 tion of the sulphur. If too much 
 cold air is admitted, the heat moves 
 upwards ; if too little, it goes down- 
 wards. In the former case the fur- 
 nace is too cold, and in the latter 
 too hot. With normal working, 
 almost a white heat is reached in 
 the hottest part ; if any irregularity 
 appears, the air must be partly cut 
 off or the rollers turned more quickly. 
 The Gerstenhofer kiln allows poor 
 ores to be burnt without fuel, at 
 the same time producing rich gas of 
 uniform composition. 
 
 The Hasenclever and Helbig kiln 
 renders it possible to burn smalls 
 
 without an admixture of lump-ore. The ore is introduced through the hopper a 
 (Fig. 249), and when roasted it is removed in proportion as fresh smalls slide down 
 from the hoppers. The air entering the furnace passes upwards over the layers of ore 
 on the lowest four or five plates, becomes heated and mixed with a little sulphurous 
 acid, and leaves the furnace, rising upwards in a flue, becoming heated in contact with 
 the gas-channels, enters the furnace above, and draws downwards when the hot gases 
 leave the furnace in two shafts and enter the lead-chambers. 
 
 The plate-furnace of Maletra has come into extensive use on account of the simpli- 
 city of its construction, joined to the circumstance that it requires no fuel, and burns 
 the ore very completely. This furnace is shown in longitudinal section in Fig. 250. 
 Smalls are made to work down from plate to plate to meet the ascending current of 
 
256 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 gases, and do not slide down spontaneously as in the kilns of Gerstenhofer and 
 Hasencle ver- Helbig. 
 
 It is set in action by the grate, a, and the kiln-door, b, which are bricked up as soon 
 as the furnace is in full heat. The plates, a, b, c, d, e, aiiciy, are charged with smalls 
 through the working doors, h, i, and k, when the ore at once takes fire. The furnace 
 gases sweep, as the figure shows, over all the plates, pass through m into the flue-dust 
 chamber, and through o to the lead-chambers. The ore is removed every two hours 
 from one plate to the next. This furnace is especially adapted for smalls. 
 
 For roasting blende the furnace of Eichhorn and Liebig is suitable. It con- 
 sists of a number of roasting chambers, r (Figs. 251 and 252), with six or more soles, 
 perfectly separate from each other. They are heated from without by fire-gases 
 drawn from a generator, G, and passing through the flues n. For the due distribution 
 of the heat in the long flues the air of combustion, heated in the flues I, is conveyed to 
 the generator-gases at three different places. 
 
 The blende has been previously heated on the top of the furnace by the radiant heat 
 from the masonry, and arrives through the hopper t, on the highest sole of each separate 
 roasting furnace, where it is uniformly spread out. After about six to eight hours 
 it is brought down to the second sole, and after the same length of time to the third. This 
 
 is effected through the breaks, a, in the bottom, which are alternately at the front and 
 the back. Meantime, the upper sole is constantly charged with fresh ore through the 
 hopper. The ore, according to its nature, remains from thirty-six to forty-eight hours 
 in the furnace before it is completely roasted, and leaves the furnace through the vent, 
 k, falling into the cooling space, o. 
 
 In order to obtain complete roasting on the sixth sole, the air which is admitted 
 must be previously well warmed. For this purpose the openings into the furnace are 
 closed as nearly air-tight as possible, so that the roasting air is compelled to take its 
 way through a tube, e, placed under every roasting ohamber ; pas'sing through small 
 ducts left in the sole of the lowest flue (7), it is strongly heated. The access of the air 
 for each chamber can be accurately regulated by a slide at the mouth of the tube, e. The 
 heated air takes its way through the outfall channel, k, over the layers of ore moving 
 in the opposite direction continually meeting charges richer and richer in sulphur, 
 by the oxidation of which it becomes saturated with sulphurous acid, and finally arrives 
 
SECT, in.] 
 
 SULPHUR. 
 
 257 
 
 through the channel, s, at the flue-dust chamber, F, which is common to all the roasting - 
 chambers, from which the roasting gases pass to their destination. 
 
 In such a furnace about 3 tons of blende are roasted in twenty-four hours ; or about 
 333 kilos, per compartment. A charge is drawn every six hours from each com- 
 partment, and the blende remains thirty-six hours in the furnace. In the successive 
 compartments the blende contains the following proportions of sulphur : 
 
 Haw ore 
 Upper sole . 
 Second sole 
 Third sole . 
 Fourth sole 
 Fifth sole . 
 Bottom sole 
 
 31-2 
 
 28-0 
 
 24-3 
 
 16-1 
 
 8-8 
 
 7-8 
 
 0-96 
 
 31-2 
 
 23-8 
 
 227 
 
 16-5 
 
 12-5 
 
 7-8 
 
 0-9 
 
 31-2 
 
 24-3 
 
 197 
 
 12-3 
 
 9'9 
 
 5'4 
 
 1*29 
 
 31-2 
 24-2 
 21-5 
 
 I7-3 
 
 ? 
 
 5-6 
 
 At the Rhenania, near Aachen, the difficulty has been observed, according to Hasen- 
 clever, that the plates of these furnaces have to be often renewed. The mechanical 
 
 Fig, 251. 
 
 Explanation of Terms. 
 Schnitt 1II-IV Section III-IV. 
 
 Fig. 252. 
 
 roasting-furnace of the Vieille Mon- 
 tagne Company is in action at the 
 Rhenania and at Oberhausen. 
 
 This blende-furnace (Figs. 253 and 
 254) consists of several roasting-soles, 
 
 A, one above another, to which there 
 joins up a four-sided roasting-hearth, 
 
 B. The broken ore shot into the 
 hopper, a, is gradually moved down- 
 wards by means of two rollers, and 
 the channels, K, to the upper roasting- 
 sole, in order to be despatched to the 
 lower roasting-plates by the revolving 
 stirring-hooks. The fire-gases from F 
 pass over the hearth, , then through 
 the roasting sides, A, and escape 
 through the dust-chamber, (7, into the 
 
 exit channel S. The arrangement for stirring consists of an axle, b, passing ver- 
 tically through the furnace with cross-rods, e, which carry the stirring-irons, The 
 joint where this axle enters the furnace is packed with asbestos. The axle, b, is 
 in an iron casing, g, to which it is secured in several places. In the interval between 
 
 Explanation of Terms. 
 Schnitt /-//Section I-II. 
 
258 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 g and b cold air ascends from below, thus preventing the too rapid destruction of the 
 casing, g. The toothed stirring-irons, m, are fixed radially to the arms, e, and serve 
 merely to stir up the ore. The smooth stirrers, /, on the other hand, are fixed obliquely 
 to the radial direction of the arm, e, and according to the angle at which they are set, 
 they move the ore either from the middle to the outside, or in the opposite direction. 
 By means of an opening in the roasting-sole, which is introduced either in the middle 
 or at the circumference, according to the position of the hooks, f, the ore, after being 
 thus stirred up, passes down to the next lower floor, where it is again stirred up by the 
 toothed irons, m, and removed by the smooth hooks, f, to the opening for the next lower 
 sole. Lastly, the roasting is completed on the hearth, B. 
 
 The furnaces which have been recently introduced by the Khenania at Stolberg 
 consist of a series of muffles placed above each other and traversed by the fire-gases. 
 The indirect heat suffices for the complete roasting of zinc blende. The ores are 
 finely ground, placed upon the top of the furnace, filled upon the high sole by means 
 of hoppers, and are thence removed by the workmen from muffle to muffle, and at the 
 end of the lowest sole they are completely desulphurised. It requires frequent 
 stirring. The air enters at the working- doors, and is converted into sulphurous acid 
 
 Fig- 253. 
 
 Fig. 254. 
 Schnitt. l-il. 
 
 Explanation of Terms. 
 Schnitt /-//Section I-II. 
 
 in contact with the ig- 
 nited ore. It is carried 
 up in flues opposite to 
 the working-doors and 
 arrives in the lead-cham- 
 bers. By means of these channels the escape of gas is not hindered, and it is possible 
 to convey the products of a number of burners into the same lead-chamber, which is 
 more difficult to effect when hot gases have to be conveyed horizontally. 
 
 In twenty-four hours the furnace, at which two men work in each twelve hours' shift, 
 yields 3000 to 5000 kilos, of roasted blende. The consumption of fuel is at present 980 
 kilos, of Ford coals. The furnaces are worked partly with gas fires and partly with 
 grates. The sulphur in the raw ore was : 
 
 After ist muffle 
 2nd 
 . 3rd 
 
 Finished 
 
 19*2 per cent. 
 . 17-6 
 
 . I2"O 
 
 3'4 
 
 0-6 
 
 26'8 per cent. 
 
 19-1 
 
 II'2 
 I'O2 
 0'35 
 
 26's per cent. 
 
 I5-4 
 9-9 
 
 075 
 075 
 
 The temperature varies according to the proportion of sulphur in the ores, and was 
 in the first muffle 580 to 690 ; in the second and third 750 to 900. In rich ores the 
 middle muffle is hottest ; in poor ores the highest temperature prevails below. 
 
 Pyrites contain almost universally small quantities of foreign matter, which interferes 
 
SECT. III.] 
 
 SULPHUR. 
 
 259 
 
 with the purity of the acid produced. Hence, in commerce, especially in England, a 
 distinction is made between pyrites acid and brimstone acid, the latter being the dearer. 
 It is known that the discovery of selenium is closely connected with the use of pyrites 
 in sulphuric acid works ; it was discovered by Berzelius in 1817 in the mud of the 
 chambers of the works at Gripsholm, in Sweden, where pyrites from Fahlun were burnt 
 for the production of sulphurous acid. In 1862 thallium was discovered by Crookes as 
 accompanying selenium in the flue-dust of pyrites. When blende is burnt, the flue-dust 
 may contain gallium. Tellurium is also found mingled with the roasted gases of certain 
 pyrites. The arsenic of pyrites escapes on roasting as arsenious acid, which accompanies 
 the sulphurous acid into the lead-chambers, and there contaminates the sulphuric acid. 
 If such acid is used in the production of soda, the arsenic passes partly into the hydro- 
 chloric acid and the soda. 
 
 Composition of the Roasting Gases. 480 kilos, of iron sulphide require (n x 32) = 
 352 kilos, or (n x 22-3)- 245*3 cubic metres oxygen, and give (8 x 64) = 512 kilos, or 
 (8 x 22-3) = 178-4 cubic metres of sulphurous acid. We, therefore, do not obtain as 
 on burning sulphur the same volume of sulphurous acid, but from 100 litres oxygen 
 only 72'7 litres sulphurous acid. With blende : 
 
 2ZnS + 30 2 - 2ZnO + 2 SO,, 
 100 litres oxygen yield only 667 litres of sulphurous acid. 
 
 Fig. 255. 
 
 On burning sulphur in atmospheric air, the mixture of gas obtained may theoreti- 
 cally contain 21 volumes per cent, of sulphurous acid, whilst the roasting gases from 
 pyrites can contain at most 15-2 and from blende 14 per cent, sulphurous acid. 
 
 In point of fact, this percentage is not reached, since a part of the sulphurous acid 
 forms always S0 3 (or, owing to atmospheric moisture, H 2 S0 4 ). In burning sulphur this 
 production of sulphuric acid is generally trifling, bxit with pyrites it may amount to 
 20 per cent, of the existing sulphurous acid. If the sulphurous acid is to be used as 
 such, this circumstance involves a considerable loss. 
 
 Liquid Sulphurous Acid. For the production of liquid sulphurous acid the process 
 of Hanisch and Schroder holds good. The roasting gases, &c., pass through the pipe a. 
 (Fig. 255), into the scrubber, b, charged with pieces of coke, over which a rain of cold 
 water trickles down and dissolves the sulphurous acid. The non-dissolved gases, N and 
 O, escape at c. The watery solution of sulphurous acid flows continuously through the 
 pipe d into a series of closed lead pans, e, in which it is heated to a boil. The escaping 
 vapours of sulphurous acid arise through the tube /, at the cooling worm, g, which is 
 surrounded by cold water, and from here through the pipe h into the pan i, into which 
 sulphuric acid is injected to free the sulphurous acid perfectly from moisture. From 
 the pan i, the gases pass through the tube k to the pump, I. The liquid in the lead 
 
2 6o CHEMICAL TECHNOLOGY. [SECT. in. 
 
 pans, e, which still holds small quantities of sulphurous acid in solution, passes for further 
 treatment, through the pipe m, into the recipient, n, in which are placed nets of lead wire, 
 and flows in the form of rain to meet a current of steam, which is introduced by the 
 tube o. The fumes of sulphurous acid thus set free are carried off by the pipe p, opening 
 into /, traverse the refrigerating worm g and the pan *, and unite with the remaining 
 vapours of sulphurous acid in the pump, I. The water liquefied in the worm, g, flows back 
 through p into the recipient, n, and is let off as required through the pipe q. In order 
 to regulate the pressure in the installation, the taffeta bag, r, is introduced into the pipe 
 k, the movement of the pump being regulated by the size of the bag. The gases com- 
 pressed in the pump, I, pass through the pipe s into the refrigerating worm t, and are 
 there liquefied. From the worm t the acid flows into the pan u, from which it is run 
 off into strong bottles, v, fit for transport. In order to carry off the accompanying gases 
 (0 and N), there is connected with the pan u a pipe, w, provided with a valve, by which 
 these gases are let into the scrubber, b. 
 
 This process is in operation, e.g., at the zinc-works of Hamborn near Oberhausen. 
 The sulphurous acid is despatched hence in pan-cans holding 100 hectokilos., or in so- 
 called bombs, containing 5 hectokilos., and is used in manufactories of ice, in sugar- 
 works, and in paper-mills for the production of so-called sulphite stuff. 
 
 The process is worthy of notice, with reference to the utilisation of the sulphurous 
 acid which escapes in melting glass from sulphate : 
 
 Na 2 S0 4 + + Si0 2 = JSa 2 Si0 3 + CO + S0 2 ; 
 in the manufacture of ultramarine, &c. 
 
 Much inferior are the processes of Pictet, who boils sulphur with sulphuric acid, 
 and of Hart, who boils iron pyrites with sulphuric acid. 
 
 Properties. Sulphurous acid is a colourless gas of a pungent odour which can be 
 liquefied by pressure or by strong refrigeration. One litre water at o dissolves 79-8 litres 
 (=229 grammes), at + 10 56*6, and at 20 39'4 litres sulphurous acid. One cubic metre 
 of sulphurous acid at o and 760 millimetres pressure weighs 2 '86 kilos. 
 
 Sulphurous acid is a powerful blood poison. Air containing 0*04 per cent, by 
 volume of S0 2 occasions difficulty of breathing. 
 
 In the presence of water all the higher oxides of nitrogen give off oxygen to 
 sulphurous acid and convert it into sulphuric acid, being at the same time reduced to 
 nitric oxide. Chlorine converts moist sulphurous acid into sulphuric acid. If mixed 
 with sulphuretted hydrogen in presence of water, sulphurous acid deposits sulphur. In 
 contact with zinc there is no escape of hydrogen, but sulphurous acid is converted to 
 hydrosulphurous acid or hyposulphurous acid (H 2 S0 2 ) not to be confounded with the 
 acid formerly called hyposulphurous acid, but now known as the thiosulphuric. 
 
 Applications. Sulphurous acid is used in the production of sulphuric acid, of 
 paper, of the madder preparations of E. Kopp (now almost obsolete) ; for preparing 
 sodium thiosulphate, and for obtaining sulphate from sodium chloride ; for opening up 
 alum shales in the manufacture of alum ; for extracting copper from certain ores ; for 
 dissolving auriferous and argentiferous iron ores; for extracting calcium phosphate 
 from bones 'and minerals ; for preserving fruits, beer, wines, hops, meat, syrups of 
 dextrine, saccharine juices, &c. ; as a disinfectant ; for preparing ice ; for bleaching silk, 
 wool, sponge, feathers, glue, gut strings, isinglass (which are turned yellow by chlorine), 
 baskets, straw-tissues, gum arabic, &c. The bleaching action of sulphurous acid may 
 be reduced to two different causes ; in most cases the colour is merely masked, but in 
 others it is destroyed. The colouring-matters of most red and blue flowers, fruits, &c., 
 form with sulphurous acid colourless combinations, but the colour still exists. A rose 
 bleached by sulphurous acid recovers its original red tone if moistened with dilute 
 sulphuric acid. The colouring matters of yellow flowers are indifferent to sulphurous 
 acid, and are not bleached. Many colours, such as indigo blue, carmine, and the 
 
SECT. HI.] SULPHUB. 261 
 
 natural yellow of silk, are not at first bleached by sulphurous acid, but a subsequent 
 bleaching is effected when the oxygen present is ozonised under the influence of Light, 
 and effects a destruction of the colours. The deoxidising power of sulphurous acid has 
 been used of late for extinguishing fires. 
 
 Sulphurous acid, as furnace smoke and indeed coal-smoke has a destructive action 
 on vegetation. Its continuous escape blights the fields and destroys entire forests ; coni- 
 ferous trees are especially sensitive to sulphurous acid.* 
 
 Calcium Sulphite, CaS0 3 , and calcium bisulphite are obtained by passing the 
 sulphurous acid obtained by burning sulphur or roasting pyrites into towers filled 
 with limestone whilst water trickles down from above, or, better still, by passing 
 sulphurous acid into milk of lime. The acid solution is extensively used for the pro- 
 duction of " sulphite stuff," i.e., vegetable fibre treated with a bisulphite, for the paper 
 manufacturer. 
 
 The uses of sodium bisulphite (leukogene) are much the same as those of the free 
 gaseous sulphurous acid. It bleaches fine woollen and worsted goods in a better manner. 
 
 Sodium Thiosulphate. This compound, Na 2 S 2 3 ,5~E 2 (formerly known as sodium 
 hyposulphite), may be prepared in several ways. Kopp first produced calcium thio- 
 sulphate by passing sulphurous acid over the vat-waste of alkali works, and decomposed 
 the lime salt thus obtained by a solution of sodium sulphate, when gypsum is precipi- 
 tated and sodium thiosulphate remains in solution. 
 
 It has the important property of forming, with silver oxide, a readily soluble double 
 salt (silver sodium thiosulphate, NaAgS 2 3 ), thus readily dissolving insoluble silver com- 
 pounds, such as silver iodide and chloride, whence its application in photography and 
 in the metallurgy of silver. Sodium thiosulphate dissolves iodine in large quantity, 
 whence its application in chlorometry and generally in the iodometric methods. A 
 solution of sodium sulphite mixed with thiosulphate dissolves malachite and azurite in 
 the state of cuprous sodium thiosulphate a property utilised by Stromeyer for the 
 extraction of copper. In sulphuric acid works it is sometimes used to remove arsenic 
 from the chamber acid, being transformed along with arsenious acid into arsenic sulphide 
 and sodium sulphate. It is also used for preparing mercurial and antimonial vermilion, 
 for obtaining aldehyde-green (emeraldine), for dyeing wool with eosine, as well as 
 (Lauth, 1875) for a mordant in dyeing wool a methyl-green. Lead and also copper 
 thiosulphates are successfully used for non-phosphoric matches. 
 
 The determination of free sulphurous acid in presence of sulphides is effected 
 according to the equations : 
 
 1. S0 3 + 2 H 2 O + 2! = H 2 S0 4 + 2lH. 
 
 2. Na 2 S0 3 + H 2 + 2! = Na 2 S0 4 + 2lH. 
 
 3. CaS0 3 + SO, + 3 H 2 + 4 I = CaS0 4 + H,S0 4 + 4lH. 
 There is formed hydriodic acid in quantity equivalent to the iodine used ; the sul- 
 phurous acid becomes sulphuric acid. If the sulphurous acid was free there is produced 
 a corresponding quantity of free sulphuric acid. If at the end of the titration with 
 iodine the total quantity of the free acids is determined alkalimetrically and that of the 
 hydriodic acid is deducted, we obtain the quantity of the free sulphuric acid formed, and, 
 consequently, that of the free sulphurous acid. This process is suitable for the determi- 
 nation of the sulphuric acid of the pyrites furnace gases, if the decolorised solution of 
 iodine resulting from the determination of the sulphurous acid of the gases is titrated with 
 decinormal soda. What more is used than corresponds to the acids formed from SO, 
 and iodine, shows the sulphuric acid present in the furnace gases. 
 
 * The only remedy is to utilise the heat of fuel better, thus reducing the quantity of coal con- 
 sumed. " Smoke consumption " is not of the slightest use in this respect. In manufacturing 
 processes, the sulphurous acid given off may in many cases be absorbed by passing it through lime. 
 
262 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 SULPHURIC ACID. 
 
 Three kinds of sulphuric acid are distinguished in manufactures and in com- 
 merce : 
 
 a. The fuming or Nordhausen sulphuric acid, distilled (formerly) from ferric sul- 
 phate, or obtained by dissolving sulphuric anhydride in ordinary sulphuric acid. 
 
 b. Solid oil of vitriol and sulphuric anhydride. 
 
 c. Ordinary sulphuric acid.* 
 
 Fuming Sulphuric Acid. At a red heat all the sulphates, except those of the alkalies 
 and alkaline earths, are decomposed, giving off vapours of sulphuric acid (or of sul- 
 phurous acid and oxygen). Ferrous sulphate was formerly preferred on account of its 
 cheapness. At a red heat it is decomposed into ferric oxide, sulphuric anhydride, and 
 sulphurous acid : 2FeS0 4 = Fe 2 O 3 + S0 8 + SO 2 . 
 
 Sulphuric anhydride could be obtained in this manner, if it were possible to keep it 
 free from water, on the large scale. Water, however, always remains behind, and there 
 is consequently obtained the so-called fuming acid, a variable mixture of sulphuric anhy- 
 dride (teroxide, S0 3 ) with sulphuric acid (H 2 S0 4 ), or a mixture of sulphuric acid with 
 
 pyrosulphuric acid (H 2 S 2 O.) in vary- 
 
 Kig. 256. ing proportions. In the Bohemian 
 
 vitriol works there is used the very 
 impure copperas (ferrous sulphate) 
 obtained by boiling down the mother 
 liquors, which contain a considerable 
 quantity of ferric sulphate. The 
 decomposition of the anhydrous salt 
 proceeds as follows : 
 
 The preparation of fuming sul- 
 phuric acid from sulphur shales 
 (vitriolic slate) is effected in Bohemia 
 as follows : The shales are allowed to 
 weather by prolonged exposure to the 
 air and are then lixiviated. The 
 pyrites present in the shales is oxid- 
 ised first to ferrous sulphate, and 
 then to ferric sulphate. The lye ob- 
 tained is evaporated to dryness and 
 dehydrated, as far as possible, in 
 pans. The dry, fused saline mass 
 (vitriol stone) is a hard, greenish- 
 yellow mass, which is further heated in a reverberatory in order to convert the 
 remaining ferrous sulphate to ferric sulphate, and is then ignited in the burning 
 stoves (Fig. 2.56). This is a galley furnace, in which there are two ranks of fire- 
 clay flasks, the necks of which are built in such a manner that the mouths of the 
 receivers can be applied and luted on. When the flasks, each of which contains i kilo, 
 of the mass, have been charged, heat is applied. The watery sulphuric acid, con- 
 taining sulphurous acid, is not generally collected. But as soon as white vapours of 
 anhydrous sulphuric acid appear, th# receivers are fixed and luted on and the distilla- 
 tion begins. The process takes from twenty-four to thirty-six hours. The flasks are then 
 
 * This last kind, known on the Continent as English sulphuric acid, is technically spoken of in 
 this country, when undiluted, as oil of vitriol, or double oil of vitriol, D.O.V. 
 
SECT, in.] SULPHURIC ACID. 263 
 
 charged afresh, and the same receivers are applied with the acid which has already 
 passed over. After four repetitions the acid has the proper concentration. The 
 residue is red ferric oxide (colcothar, Paris red). The yield of fuming acid is about 45 
 to 50 per cent, of the weight of the dehydrated vitriol stone. Instead of distilling the 
 vitriol stone, a ferrous sulphate is sometimes used, prepared from colcothar or burnt ore, 
 and sulphuric acid, the iron oxide remaining in the flasks being used again. 
 
 The sodium bisulphate (NaHS0 4 ) remaining as a residue on preparing nitric acid 
 from soda-saltpetre is also used for the manufacture of fuming sulphuric acid. When 
 heated to fusion, this compound gives off water and sodium ; pyrosulphate remains, and 
 on further heating to about 600 the latter is split up into sulphuric anhydride and 
 neutral sulphate : Na 2 S 2 7 = SO 3 + Na 2 S0 4 . The anhydride is passed into sulphuric 
 acid. Wolters recommends for the preparation of the anhydride a mixture of 
 magnesium sulphate and sodium pyrosulphate. Far below a red heat, sulphur teroxide 
 is set free, and there remains a double salt, MgS0 4 + Na 2 S0 4 , which is separated into 
 its constituents in the known manner, and returns to the circuit of the manufacture. 
 
 Properties. Fuming sulphuric acid is a light-brown, thick, oily liquid, of spec. gr. 
 i*86 to 1*89, and consists of a solution of the anhydride in sulphuric acid, from which 
 the anhydride evaporates even at common temperatures, forming white clouds in moist 
 air. In the cold, pyrosulphuric acid separates from it as a crystalline mass, fusible 
 at 35, which, if gently heated, is resolved into sulphuric anhydride and sulphuric acid : 
 
 H 2 S 2 7 = S0 3 + H 2 S0 4 . 
 
 Formerly it was used only for dissolving indigo ( i part indigo is soluble in 4 parts 
 of the fuming acid). Recently it has been used to a larger extent in the treatment of 
 ozokerite and in the production of various tar-colours, e.g., for preparing benzol 
 disulphonic acid, by heating benzol with fuming sulphuric acid in the manufacture of 
 eosine. 
 
 Solid Oil of Vitriol. For some years pyrosulphuric acid, H 2 S 2 O r , has been met with 
 in commerce. It is obtained by dissolving i mol. anhydride in i mol. sulphuric acid, 
 
 Sulphuric anhydride is obtained either by heating ferric sulphate, perfectly dehy- 
 drated, or Wolter's mixture, or by warming strong fuming sulphuric acid; or, 
 according to Winkler, synthetically (S0 2 + O = S0 3 ), by resolving sulphuric acid at a 
 red heat into sulphurous acid, oxygen, and water, the latter being kept back by means 
 of concentrated sulphuric acid, the mixture of sulphurous acid and oxygen being 
 passed over ignited platinised asbestos, where it is again converted into sulphur 
 teroxide. Messel and Squire, of London, use platinised pumice. The real anhydride, 
 S0 3 , is at common temperatures a colourless liquid, which below + 16 solidifies to felted 
 asbestos-like needles, and boils at 46 to 47. The so-called anhydride of commerce, 
 which is sold in sheet-iron boxes containing 60 kilos., consists of 98 per cent, anhydride 
 and 2 per cent. H 2 SO 4 . 
 
 Ordinary Sulphuric Acid. By far the largest quantity of sulphuric acid is prepared 
 by the oxidation of sulphurous acid obtained on the combustion of sulphur, or on 
 roasting pyrites and blende; the oxidation is effected by means of nitric acid. 
 According to the equation, S, + 30 2 + 2H 2 O = 2H 2 S0 4 , 64 kilos, of sulphur require 67 
 cubic metres of oxygen, or 320 cubic metres of atmospheric air, along with 36 kilos. 
 of watery vapour, in order to yield 196 kilos, sulphuric acid. For the production of 
 sulphuric acid the roasting gases must contain to 100 vols. sulphurous acid at least 50 
 vols. oxygen. In fact, an excess of oxygen must be present if the reactions are not to 
 be too slow. With regard to the sulphuric acid already formed, the gases from 
 sulphur when passed into the lead-chambers contain 12 per cent, by volume of 
 sulphurous acid ; if from pyrites, 7 per cent. ; if from blende, 6 to 7 per cent. 
 
 Lead-Chambers. As long as we are compelled, in the manufacture of sulphuric 
 
264 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 acid, to use the requisite substances as gases, and especially to use oxygen in the state 
 of atmospheric air, large chambers are necessary, which must be cheap to construct, 
 air-tight, and must consist of a material not attacked by the nitrous gases and vapours 
 or by sulphuric acid. 
 
 Among the many materials which have been proposed, one only, lead, fulfils most 
 of these demands. In the Fouche-Lepellitier works at Javel, near Paris, a gutta- 
 percha chamber was in use in the years 1860-1870. 
 
 As to the sort of lead which is most suitable for the construction of chambers, it 
 is generally assumed that metals are the less easily attacked by an acid the purer they 
 are. Careful researches, however, proved that lead is attacked by sulphuric acid the 
 more readily the purer it is. On the other hand, according to a communication from 
 J. Glover, in order to test the suitableness of lead for the construction of chambers, 
 sheets of different alloys were placed for no days in a lead-chamber. Pure lead was 
 found to lose 7*5 per cent. Lead alloyed with copper and antimony experienced the 
 following losses : 
 
 Copper. Loss. Antimony. Loss. 
 
 O'l percent. 7'i percent. ... 0*1 percent. 8'i percent. 
 
 0-2 7'i > ' 2 . 9'2 
 
 0-3 7'5 '3 10-9 
 
 0-4 9' 1 '4 > "'6 ii 
 
 0-5 8-5 ... 0-5 11-9 
 
 N. Cookson heated lead with sulphuric acid of different strengths. He found that 
 strong acids at high temperatures attacked antimoniferous lead more than pure lead, 
 but weaker acid at lower temperatures attacked antimoniferous lead less than pure 
 lead. 
 
 It has been repeatedly observed that some coleopterous insects perforate the plates 
 of the chambers. At the Mulden works, wood wasps have made holes in the lead. 
 
 The lead is rolled out in plates o'6 metre in breadth, and of a thickness of 3 to 8 
 millimetres. The chamber consists of two parts : the bottom, which has a plate-like 
 form, and is bent up on all sides to the height of 36 to 54 centimetres ; and the side walls, 
 consisting of one piece, which stand upon the bottom like a bell. Both these parts are 
 made of a great number of sheets soldered together. The chambers are secured in a 
 frame of woodwork, consisting of uprights, horizontal beams, &c. The sides are first 
 covered with lead sheets, which are soldered together at the edges by the autogenous 
 process. After the sides are completed, the bottom and the top are covered with lead 
 plates. On the outside of the chamber several strips of lead, from 18 to 20 centimetres 
 in breadth and 36 centimetres in length, are soldered fast and secured to the woodwork 
 with iron nails. The covering plate is secured, in the same manner, to beams which 
 run across the chamber. 
 
 The bottom of the chamber is always covered with acid ; the lower corners of 
 the side walls dip freely into the liquid, forming a hydraulic joint. Hence, acid can be 
 drawn off at any time, and in any place. In and on the chambers there are arranged 
 man-holes in the sides (for executing repairs), pipes for conveying the gases from the 
 furnaces and steam from the boiler, pipes for carrying off the chamber gases, glass 
 discs for observing the state of the chambers and the progress of the formation of the 
 acid, generally placed in two opposite walls in the direction of the incident light; 
 hydrometers and thermometers, the latter of which are attached to the sides for the 
 estimation of the temperature at different parts of the chamber. In order to take, 
 from time to time, specimens of the acid which is being formed, there are in some 
 works so-called dropping-tables, which, at the height of i metre from the bottom, 
 support a bent plate with a turned-up edge, o - 6 metre in length and 0*5 metre in 
 breadth. The acid which collects upon this plate is conveyed through a lead tube to a 
 
SECT. III.] 
 
 SULPHURIC ACID. 
 
 265 
 
 beaker placed outside the chamber, for the determination of its strength. The 
 chambers are covered in with a roof, which is necessary in Germany, Belgium, and 
 France, whilst in Britain, as the temperature varies much less at different seasons of 
 the year, the chambers commonly stand in the open air. In recent works the chambers 
 are often supported on pillars of masonry, so that the space below is available for the 
 erection of pyrites kilns, &c. 
 
 Arrangements for collecting the Nitrous Vapours. In order to reduce the loss of 
 nitre as far as possible, the nitrous constituents (nitrous and hyponitric acid) are 
 withdrawn from the gases and vapours escaping from the chambers before they can 
 pass out into the air, and are thus made again available for the process of acid forming. 
 This object is effected almost everywhere by means of sulphuric acid in the absorbent 
 coke-tower proposed by Gay-Lussac. This consists of a cylinder of lead about 10 metres 
 high, closed gas-tight above, and standing below, like the chambers, in a lead vessel, 
 filled with acid, so as to form a hydraulic joint (Kg. 257). The inner walls of such 
 
 cylinders are often lined with thin fire- 
 proof stones. The tower is filled with 
 coarse pieces of coke, but sometimes glass 
 balls, pieces of broken drain-pipes, &c., are 
 used. The distribution of the sulphuric 
 acid over the pieces of coke is effected by 
 means of the cistern A, from which a 
 stream of acid flows uninterruptedly into 
 an oscillating trough fixed over a lead- 
 plate with about twenty tubes. From 
 these tubes the acid flows into the tower. 
 For securing a constant outflow of acid 
 the Mariotte bottle is often used, or the 
 apparatus shown in Fig. 258. At the 
 side of the acid cistern, A, is a small lead 
 
 cylinder, a ; the tube b is conical at its mouth and secured acid-tight by means of a 
 leaden plug, m, of suitable shape. This plug is fixed on an iron rod, the part of which 
 below the plug is to guide it in its upward and downward movements and to make it 
 always fall exactly into the opening. In the lead cylinder there hangs a lead jug, fixed 
 to a lever by means of a chain, which at its other end is connected by a short chain 
 with the rod of the lead plug. When the apparatus is to act, the cistern A is filled 
 with acid, and the plug is fixed in the aperture. If the sulphuric acid is to flow into 
 the tower at a uniform pressure the lead jug is drawn up in the cylinder and its chain 
 is secured to the beam, P, which is set horizontally. The plug-rod is now also secured 
 to the beam. If the jug is left to itself the plug is raised, the sulphuric acid flows 
 through the tube b into the lead cylinder, and the jug rises swimming on the acid 
 in proportion as the level of the acid rises. As soon as the jug has been raised 18 to 
 
266 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 20 centimetres the plug sinks and closes the tube b. If the cock, c, in the cylinder is 
 opened the sulphuric acid sinks, and with it the jug ; thereby the plug is lifted, and the 
 level in the lead cylinder is restored by an inflow of sulphuric acid. If the outflow 
 cock, c, is suitably placed, the sulphuric acid flows at a uniform pressure into the 
 coke-tower, supposing that the level of the acid in the cistern A never falls below 
 1 8 centimetres. 
 
 The sulphuric acid is forced up from the monte-jus, D, through the pipe 6, into the 
 cistern A. The gases coming from the lead chambers stream into the coke- tower at 
 H, and pass out again at G, after having lost their nitrous constituents. The sul- 
 phuric acid, charged with these ingredients (nitrose), runs from the dish of the 
 absorption-tower through the pipe k, into the cistern J3, and thence into a monte-jus, 
 which convey it into the denitrifying apparatus. 
 
 In the works of Fikentscher, at Zwickau, the absorption apparatus consists of 
 eight stoneware pipes, set above each other, of o - 8 metre in height and in width; 
 each open above, and provided with a perforated bottom. On each pipe there are 
 three inclined planes of stoneware, on which sulphuric acid of 130 Tw. trickles 
 down as it enters in drops. 
 
 In order to test the remarkable phenomenon that this so-called nitrose of the Gay- 
 Lussac tower contains only nitrous acid, even when the entering gases show consider- 
 able quantities of hyponitric acid, G. Lunge examined the action of coke upon nitric 
 acid. Experiment showed that, in contact with coke, the nitric acid, dissolved in the 
 sulphuric acid, was almost completely reduced to nitrous acid, slowly at common 
 temperatures, but very rapidly al such a temperature as generally prevails in the 
 Gay-Lussac tower. Whether this is immediately effected by the carbon or by its 
 action upon sulphuric acid (with the production of sulphurous acid), or by the joint 
 action of iron sulphide present in the coke, remains undecided. 
 
 The absorptive power of sulphuric acid for nitrous acid differs greatly according to 
 its concentration. Acid of 154 Tw. is able to dissolve more than three times as 
 much nitrous acid as that at 130 Tw. So that, in using the stronger acid, there is 
 the advantage that only one-third of the usual quantity of acid is necessary. Besides, 
 the greater affinity of concentrated acid for the nitrous vapours is a greater guarantee 
 for their complete absorption. 
 
 Denitration of the Nitrose. The acid flowing out of the absorption-tower, the 
 nitrose, is a solution of nitrosulphonic acid, S0 2 .OH.N0 2 , in sulphuric acid. The 
 problem is to decompose this nitrose into the nitrous compounds and into pure sul- 
 phuric acid, using the former again in the chamber process. 
 
 The earlier denitrating appliances all depended on diluting the nitrose with hot 
 water or steam, or with both together. The nitrosulphonic acid of the nitrose is re- 
 solved into sulphurous acid and nitric acid. 
 
 This decomposition can be effected in the stage-apparatus, in Gay-Lussac's denitri- 
 ficator, in the boiling-drum, or in the cascade. 
 
 The stage-apparatus is a small lead chamber, of a few cubic metres capacity, in 
 which five successive lead floors are soldered at different heights. They leave alter- 
 nately, at opposite sides of the chamber, a passage free for the sulphuric gases, which 
 enter beneath the lowest floor, traverse the apparatus in zig-zag, and above the highest 
 stage pass into the lead-chamber through a pipe. The nitrose enters through the 
 cover of the apparatus by a cock, falls upon the highest floor, then upon the second 
 and third, coming in contact with the sulphurous acid all the way, and is denitrated at 
 the foot of the apparatus, so that it may be either drawn off directly or conveyed into 
 the first lead-chamber. 
 
 Gay-Lussac's denitrificator consists of a tower of sheet-lead, into which the furnace 
 gases enter by the pipe, M( Fig. 259), and diffuse themselves under the grating, G, 
 
SECT. III.] 
 
 SULPHURIC ACID. 
 
 267 
 
 Fig. 259. 
 
 Fig. 260. 
 
 Fig. 262. 
 
 upon which rests a bed of coke. The nitrose crosses from the cistern, F, and is distri- 
 buted over the coke, trickling downwards to meet the ascending gases, and passing out 
 denitrised at the bottom of the tower through the tube, t. Both in the stage apparatus 
 and in this tower apparatus steam is introduced, which dis- 
 tinguishes both from the Glover tower. 
 
 The denitrising apparatus devised by J. Glover, of Wallsend, 
 is now almost universally used under the name of the Glover 
 tower. 
 
 In the first place, this tower serves as a concentrating and 
 cooling apparatus, as hot sulphurous acid is conveyed into the 
 tower whilst chamber acid meets the hot gases. Thus the 
 sulphurous acid is cooled and the chamber acid concentrated. 
 The watery vapours evolved pass into the lead chambers, 
 effecting a considerable saving in steam for the working of 
 the chamber. Besides, the Glover tower denitrises the nitrose 
 which is decomposed by the joint action of ttie steam and the 
 sulphurous acid, so that the concentrated sulphuric acid run- 
 ning off' below is denitrised, and the nitric oxide, set 
 free, enters the chamber again, where it again mediates the formation of sulphuric 
 acid. 
 
 In the Glover tower the chief part of the sulphuric acid present in the roasting 
 gases is separated out, so that by this arrangement the performance of the lead-chambers 
 is decidedly augmented. 
 
 Recently the Glover tower has been also used for bringing the nitric acid required 
 
 in the sulphuric acid process into contact 
 without any special apparatus. 
 
 The Glover tower is built of strong lead 
 plates, surrounded with a frame of wood. 
 To protect the lead walls there is a lining of 
 fire-tiles which is stronger in the lower part 
 of the tower than in the upper half. The 
 tower is filled with bricks set like a grating, 
 or with fragments of quartz. At the top 
 of the tower are two cisterns of wood lined 
 with lead, the one containing nitrose and the 
 ether the chamber acid to be concentrated. 
 For the even distribution of each acid there 
 is a small Segner's wheel provided, made of 
 glass, which is caused to rotate by the outflow 
 of the acid which it distributes. It is 
 arranged that both acids meet within the 
 tower and flow out together. The roasting- 
 gases traverse the tower from below upwards 
 and then enter the lead-chamber. 
 
 According to Herreshof , there are erected 
 in the tower (here drawn as greatly short- 
 ened) cross wells, E (Figs. 260, 261, 262), over which large pieces of quartz, G, are 
 laid across and form a vault. Upon these are laid quartz stones, (7, to a certain depth 
 so that they leave a space of 300-400 millim., next to the lead wall of the tower, It, 
 All large gaps on the side of the heaped-up material are filled with smaller pieces 
 of quartz, and around them is laid a thin layer of quartz-sand, which during the building 
 is kept in its place by means of iron plates. The remaining space between the filling 
 
 Fig. 261. 
 
 Explanation of Terms. 
 Schnitt / Section I. 
 Schnitt //Section II. 
 
2 68 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 and the lead wall is filled with rather fine quartz-sand, which completely prevents the 
 acid from touching the lead. Iron plates, a, are secured on the corner pillars, b, so that 
 the lead casing may bear the weight. 
 
 The Glover tower is the simplest and cheapest apparatus for concentrating and 
 denitrification, as in it sulphuric acid can be brought to a strength of 137 or even 
 
 145 Tw. 
 
 The general arrangement of a sulphuric acid works is shown (diagrammatically) in 
 Fig. 263. The sulphurous acid evolved in the furnace, S, from sulphur, pyrites, or 
 blende is let pass through the pipe, r, into the bottom of the denitrising apparatus, G, over 
 
 Fig. 263. 
 
 the contents of which the nitrose and in case nitric acid is not evolved in the furnaces, 
 S, from nitre and sulphuric acid the requisite quantity of nitrie acid trickles down. 
 The concentrated acid flows off below, and is conveyed away if it is not forced up by the 
 monte-jus to the cistern of the Gay-Lussac tower, L. 
 
 The gases pass now, along with the steam entering by the tube v, into the first lead- 
 chamber, A. What is not condensed here passes from the bottom through the tube b, 
 into the upper part of the second lead-chamber, , and then in like manner into the 
 third, C, escaping from here into the Gay-Lussac tower, L, and finally go off at n. The 
 three chambers may be built either separate or together, as the figure shows. The 
 sulphuric acid formed (chamber acid) is led off for further treatment. The nitrose 
 formed in the closed Gay-Lussac tower, Z, flows through o into the monte-jus, D, and 
 thence by means of compressed air (less suitably by means of steam) it is forced 
 through the pipe e into the cistern, /, whence it arrives into the Glover tower, G. 
 
 We must notice Laurent's apparatus for raising sulphuric acid. It consists of a tube 
 of lead, vulcanite, or glass, which branches off directly from the recipient to be emptied, 
 descends more or less deeply, according to the height to which the liquid is to be 
 lifted, and then ascends to the cistern to be fed above. The compressed air is intro- 
 duced at the bottom of the longest part by a very small pipe which ascends high enough 
 to prevent the entrance of the liquid into the apparatus for compressing the air. This 
 arrangement is especially convenient for raising up the acid to the Glover towers. 
 
 Mactear recommends the form shown in Fig. 264. So much air is forced in through 
 
SECT. III.] 
 
 SULPHURIC ACID. 
 
 269 
 
 the pipe, a, thart the mixture of acid with air in the ascending pipe, S, is raised by the 
 column of the affluent acid. The air escapes at v, and the acid flows off at e. If no 
 compressed air is accessible, a Korting suction blast is attached to the tube v, and sucks 
 up the necessary quantity of air through the tube a. If the acid is to be lifted higher, 
 a monte-jus is used and a part of the compressed air is allowed to enter into the tube /S, 
 in order to drive the acid two or three times the height corresponding to the pressure 
 of the compressed air. 
 
 If the liquid has to be taken from a flat cistern, n (Fig. 265), it is let flow into a 
 wide tube, c, closed below, whilst air is driven in through a narrow tube, a ; the mixture 
 of acid and air rises up in the tube e, which is open below. 
 
 The working of a newly installed sulphuric acid plant begins by pouring upon the 
 bottom of the chambers sulphuric acid of spec, 
 gr. 1-45 (90 Tw.) to such a depth that the Fig. 264. 
 
 walls of the chamber may dip into the acid for 
 about 3 centimetres. If the bottom has been 
 soldered to the sides, the depth of the acid must 
 be 12 to 1 8 centimetres. 
 
 After the floor of the chamber is thus 
 covered with acid, the air is expelled from the 
 
 system of chambers by admitting sulphurous f 
 acid from the pyrites furnaces, which will by 
 this time have come into action. Then, ac- 
 cording to the kind of working, either liquid 
 nitric acid is allowed to enter or nitric acid 
 vapour is developed from the nitre pots in the 
 
 sulphur furnaces. At the outset nitre is used in excess (10 to 15 per cent, of the 
 weight of the sulphur), afterwards in the normal proportion of 4 to 6 per cent, as soon 
 as the temperature of the walls is observed to rise, which is generally in about twenty- 
 four hours. When the formation of sulphuric acid has set in, which may be known by 
 the dew of condensed acid on the walls (within) of the lead-chamber and the plugs of 
 the trial-holes, the time has arrived for the admission of steam. 
 
 The chambers are now observed three to four times daily, noting the height of the 
 thermometers and testing the acid formed and the gases passing in and out. 
 
 In general, the proportion of SO 2 in the gases which enter is determined by means 
 of iodine solution, according to Reich. In the summer of 1876 the author repeatedly 
 examined the gases evolved on roasting smalls in a plate furnace. In order to deter- 
 mine the proportion of sulphuric acid vapour and of sulphurous acid, he used in his 
 apparatus for examining smoke gases, petroleum instead of water, the sample of gas 
 being drawn up through a porcelain tube as quickly as possible after measurement into the 
 potassa tube, and after dissolving the acids into pyrogallate to determine the oxygen. 
 In another portion drawn simultaneously S0 2 was determined by the process of Reich. 
 
 A series of experiments, conducted at the works of Meyer and Riemann, near 
 Hanover, July 19, 1876, gave: 
 
 Place of Sample. 
 
 S0 2 by I. 
 
 Total Acids. 
 
 0. 
 
 Plate 2 from below .... 
 
 0-96 
 
 i '4 
 
 18-4 
 
 ,, 4 .... 
 
 1-52 
 
 2'2 
 
 16-6 
 
 ,, 6 .... 
 
 3'8i 
 
 4'6 
 
 12-5 
 
 Collecting pipe 
 
 7'53 
 
 8-6 
 
 7'5 
 
 The gases escaping from the Gay-Lussac contained 0*4 per cent, acid gases and 
 4'4 per cent, oxygen. 
 
 This volumetric process makes no pretensions to great accuracy ; indeed, the real 
 
2 7 o CHEMICAL TECHNOLOGY. [SECT. in. 
 
 proportion of sulphuric acid will be rather greater. It has, however, the advantage 
 that it shows in four or five minutes the total quantity of acids approximately, and the 
 oxygen accurately, to about 0-2 per cent. The apparatus for the determination of 
 S0 2 seems more suitable for checking the work than the method of Reich, as the pro- 
 portion of sulphuric acid often exceeds 2 per cent, by volume. The determination of 
 oxygen in the exit gases deserves attention, as irregularities may thus be quickly and 
 accurately detected. The supply of air to the pyrites furnaces must be so regulated 
 that the gases issuing from the Gay-Lussac contain 3 to 6 per cent, oxygen. 
 
 In the lead-chamber in which the production of sulphuric acid is chiefly effected, 
 a thermometer, hanging at about i^ metre from the ground, should indicate a tempera- 
 ture of 40 to 50. If the chambers grow too hot, less nitre (or nitric acid) is taken ; 
 if they are too cold, more must be added. If an excess of steam is used, there is formed 
 a dilute acid, which takes up nitric and nitrous acids and corrodes the lead ; sulphurous 
 acid also may be taken up. If there is a deficiency of steam, nitrous acid is formed, 
 and leads to the formation of so-called chamber crystals. The strength of the acid 
 formed in the lead-chamber shows whether the influx of steam is normal or abnormal. 
 If the acid taken in the first third of the chamber has a sp. gr. of 1*60 = 120 to 121 
 Tw., the right quantity of steam is being admitted. 
 
 The mud (so-called white lead) collecting in the chambers, which must be removed 
 from time to time, varies greatly in composition, and is formed by the action of the 
 acids upon the lead and its impurities, as well as matter introduced from the furnaces 
 in the shape of flue-dust. It often contains selenium, sometimes thallium and indium. 
 
 Lead-Chamber Process. According to F. Hurter, the following main equations 
 regulate the process : 
 
 S0 2 + H 2 + + N0 2 = H 2 S0 4 + NO, and, 
 S0 2 + H 3 + + N 2 3 = H 2 S0 4 + N 2 3 . 
 
 He shows that the work done in a system of chambers depends essentially on the 
 quantity of nitrogen compounds contained in the gases and on the strength of the acid 
 produced. The work of the succeeding chambers diminishes almost in a geometrical 
 series. The same must be said of the excess of temperature of the chambers over that 
 of their surroundings. The temperature of the first chamber of a system depends on 
 what fraction of the entire system is taken up by its space. 
 
 According to the experiments of Lunge and Naef , in a normal state of the chambers 
 the proportion of sulphurous acid diminishes very rapidly from the entrance to the 
 middle of the first chamber, i.e., from 7 to ry or 1-9 per cent. ; hence here 70 per cent, 
 of the sulphurous acid has already been converted into sulphuric acid; this agrees 
 well with the results of earlier observers, and with Hurter's theory. From the middle 
 to the end of the first chamber, the S0 2 decreases very little, corresponding to a con- 
 version of about 4 per cent, of its initial quantity into sulphuric acid. With the 
 entrance into the second chamber, the reaction is suddenly intensified, and at its middle 
 there is only from 0*2 to 0-4 per cent, sulphurous acid present, so that in this way 20 
 per cent, has been converted into sulphuric acid. From here to the end of the system, 
 on account of the great dilution of the gases, and to reach a practical maximum (it is 
 never absolutely complete), considerable chamber space is still needed. If the supply of 
 nitre-gases is insufficient, the proportion of sulphurous acid decreases less rapidly, and 
 the process goes on more in the second and third chamber. 
 
 Hence it appears that the formation of sulphuric acid goes on in the outset with 
 great energy, that it grows very sluggish at the back of the chamber, and that in the 
 second chamber the reaction is intensified. The only explanation to be found is that 
 in the last part of the first chamber, owing to the dilution of the gases with 90 per 
 cent, nitrogen, the molecules of sulphurous acid do not find sufficient N 2 3 and 0, 
 which are again accumulated in other parts, but that, on passing through the pipe 
 
SECT, in.] SULPHURIC ACID. 271 
 
 leading into the second chamber, an intimate mixture of the gases is effected, so that 
 the molecules of the three active gases are again brought sufficiently close to react 
 upon each other. Hence the best system should be a larger number of smaller 
 chambers. Certainly, doubtless with a regard to the economy of lead and of 
 room, this system has of late been abandoned, and in some works the entire system 
 has been made to consist of a single large chamber. But such attempts cannot have 
 proved successful, as they are very uncommon, and some who had adopted the one- 
 chamber system have gone back to the use of several chambers. It seems that a 
 frequent passage through connection-pipes, and the intermixture of gases thus effected, 
 are advantageous. In the atmosphere of the last chamber, only N 2 3 was found in 
 normal working. 
 
 Formation of Sulphuric Acid in the Lead-Chambers. According to Gr. Lunge, this 
 process depends chiefly on the intermediate formation of nitrosylsulphuric acid. This 
 is formed from sulphur dioxide, oxygen, and nitrous acid : 
 
 2 S0 2 + N 2 3 + 0, + H S = 2 (S0 8 ,OH,ONO), 
 
 and is immediately, in contact with an excess of water, resolved into sulphuric acid and 
 nitrogen trioxide : 
 
 a(SO,,OH,ONO) + H 2 = 2S0 2 (OH) 2 + N,0 8 , 
 
 which with water forms nitrous acid and water, so that the process is repeated. For 
 the front part of the system of chambers we must also consider that here a part of 
 the nitrosylsulphuric acid is denitrised by sulphurous acid : 
 
 2 (S0 2 ,OH,ONO) + S0 2 = 2H 2 = 3SO 4 H 2 + 2 NO, 
 
 and that the nitrogen oxide formed in this manner with oxygen, sulphurous acid, and 
 water forms directly nitrosylsulphuric acid : 
 
 2 S0 2 + 2NO + 3 + H,0 = 2 (S0 2 ,OH,ONO). 
 
 As a secondary reaction the latter can also be formed by the action of nitric acid 
 (whether originally introduced or formed afresh) upon sulphur dioxide : 
 
 S0 2 + N0 2 ,OH = S0 2 ,OH,ONO. 
 
 The direct formation of sulphuric acid from sulphurous acid by the reduction of 
 N0 2 and N 2 8 : SO, + N0 2 + H 2 = S0 4 H 2 + NO ; S0 2 + N 2 3 + H 2 = S0 4 H 2 + 2 NO, 
 certainly takes place to a trifling extent, though latterly this process is taken for the 
 main reaction. Hyponitric acid does not occur in the normal chamber process, and 
 nitric oxide appears only at the beginning, in virtue of a secondary reaction entering 
 then in the direct reaction, of condensation : S0 2 + N0 2 .OH = S0 2 ,OH,ONO. 
 
 Lunge does not view the chamber-process as an alternating reduction and oxidation 
 of the nitrogen oxides, but as a condensation of nitrous acid or nitric oxide with sul- 
 phurous acid and oxygen to nitrosulphuric acid, and a splitting off again of the nitrous 
 acid from the latter by the action of water. 
 
 Under certain circumstances nitrous oxide is known to be formed as a product of 
 the reaction of sulphurous acid and nitrous acid. To this result the " chemical " loss 
 of nitre in the manufacture of sulphuric acid in contradistinction to the mechanical 
 losses by imperfect absorption in the Gay-Lussac tower and the nitrogen in the 
 chamber acid are generally ascribed. 
 
 It cannot be theoretically denied that under very unfavourable circumstances the 
 reduction of nitric oxide may go as far as to free nitrogen, but it has not been demon- 
 strated in practice. It has been shown, firstly by R. Weber, then by Lunge, that the 
 reduction of nitric oxide by sulphurous acid to N 2 occurs only in presence of water, 
 or of sulphuric acid more dilute than that found in the chambers. Hence a formation 
 of N 2 can occur only if an excess of water is present, which is very rarely the case, and 
 with good work the " chemical " loss of nitre is very small, probably not o - 5 per cent. 
 
 Another abnormal reaction leads in practice to far more losses of nitre, namely, 
 the formation of hyponitric acid in the last part of the system of chambers. This 
 
2 7 2 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 causes the appearance of nitric acid in the bottom acid of the last chambers, but 
 not, or very rarely, the nitrose of the Gay-Lussac tower, as it is here reduced by 
 coke, perhaps with the co-operation of the last traces of sulphurous acid. It is said 
 to have been observed in practice that under such circumstances red vapours 
 escape unabsorbed from the Gay-Lussac tower. Lunge has shown that the formation 
 of NO, is quite independent of the quantity of oxygen present, and that it occurs 
 with abnormally low, with normal, and with abnormally high proportions of nitre. 
 The process of the formation of sulphuric acid is then at an end before the gases 
 have left the chambers. In the latter part of the system there is no mist of 
 sulphuric acid, nor does there exist any appreciable quantity of sulphurous acid. The 
 conditions for the normal process, as developed above, are, therefore, here wanting. 
 The nitrous acid, which now meets with no bodies with which it can form permanent 
 combinations, is by degrees dissociated in the large excess of air, and is partially 
 oxidised to N0 2 . The NO 2 comes in reaction with the bottom acid, and yields with it 
 equal molecules of nitrosylsulphuric acid and nitric acid. Another portion of the 
 N0 2 passes with the exit gases into the Gay-Lussac tower, and it was formerly said 
 not to be here absorbed. This has been shown to be utterly erroneous, but it might 
 easily happen that a coke-tower sufficient for ordinary circumstances is insufficient 
 under such circumstances, and that, therefore, some nitric gas escaped into the air. It 
 would be an abnormal condition of the chambers, with an excess of nitre-gases. 
 
 Much worse is the course of the chamber-process, if the nitre is insufficient, whether 
 too little has been used at first, or that, in consequence of the inadequate size of the 
 Gay-Lussac tower, the recovery of the nitrous acid is imperfectly effected. The forma- 
 tion of sulphuric acid is stopped at the back of the system, not, as in the last case, 
 because the sulphurous acid is exhausted, but because there is too much. Now, there- 
 fore, a denitrifi cation of the nitrosylsulphuric acid has to occur at this wrong place : 
 
 2 (S0 2 ,OH,ONO) + S0 2 + 2 H 2 = sS0 4 H 2 + 2 NO, 
 
 and much nitric oxide is formed, the atmosphere of the chambers losing its yellow colour, 
 either partly, or in very bad cases altogether. In all cases the temperature falls below 
 the normal height, i.e., that favourable for the formation of sulphuric acid, and, in spite 
 of the presence of much oxygen, the combination of nitric oxide and sulphurous acid goes 
 on very sluggishly. Water is often present in excess in the air of the chambers, and 
 there is often nothing to prevent the nitric oxide from forming, with the oxygen and the 
 water, nitric acid, which, as the temperature is here much lower, and there is much less 
 sulphurous acid present than in the front part of the chambers, passes unreduced into 
 the bottom acid, and makes the atmosphere of the chambers still poorer. Yet the 
 bottom acid is not " nitrous " in the sense used by manufacturers, since it gives off no 
 red fumes if mixed with hot water, because the nitrosylsulphuric acid is wanting. 
 Also as sulphurous acid predominates, and there is almost no sulphuric acid in the air 
 of the chambers, but only water, the formation of nitrous oxide (N a O) goes on freely. 
 This signifies a total loss of nitre ; and equally lost is the nitric acid contained in the 
 bottom acid if the acid is consumed directly, and the nitric oxide arriving unchanged in 
 the Gay-Lussac tower is lost also. This still encounters oxygen, but not only is its 
 quantity insufficient, but the excess of sulphurous acid acts here at the wrong place as a 
 denitrifier, and can even destroy nitrosylsulphuric acid, if any is present. The nitric 
 oxide escaping from the tower forms red fumes in contact with the air, whilst the " lantern " 
 of the tower is white, as may often be observed. All these facts together lead, not only 
 to great loss of sulphurous acid, and consequently to a poor yield of sulphuric acid, but 
 also to a great loss of nitre, and involves a progressive impoverishment of the chambers 
 in their stock of oxygen transferrers. Hence the well-known phenomenon which has 
 been recently confirmed by Eschellmann, that if we have been too economical of nitre, 
 and the above disease has attacked the chambers, it is necessary to add many times the 
 
SECT, m.] SULPHURIC ACID. 273. 
 
 quantity of nitric acid which has been economised, in order to get them back into a. 
 normal condition. 
 
 It is important that these results take place at the end of the set of chambers. 
 This is the reason why nitric oxide does not enter into the reaction, although, even 
 when the chambers are working badly, there is almost always oxygen enough to con- 
 vert the sulphurous acid into H 2 S0 4 . But in the first place the temperature is too low, 
 probably far below the most favourable point, as the main reaction takes place at the 
 hottest point of the system ; secondly, there is no longer time for the molecules of oxygen 
 distributed in a large volume of nitrogen to meet with the remaining substances in, 
 sufficient quantity ; long before the oxygen is quite exhausted the gaseous mixture- 
 has arrived at the end of the system, and nitric oxide, sulphur dioxide, and oxygen 
 escape together into the outer air, all diffused in a large excess of nitrogen. 
 
 Nothing in the practice of the sulphuric acid manufacture is more distinctly proved 
 than that the process works satisfactorily only in presence of a large excess of oxygen 
 and of nitrous acid, the latter of which is mainly recovered in the Gay-Lussac tower ;. 
 if there is only a slight excess, sulphurous acid always escapes into the air. Even with 
 a large excess of oxygen, a perfect oxidation of the sulphurous acid is impracticable. 
 We seem to have reached the practically best limit when the exit gases contain only 
 0*5 per cent, of the sulphurous acid originally present. We have here to do with one 
 of those reversible reactions whose progress can be tumed in the desired direction by 
 certain external conditions, such as the action of the mass of one of the ingredients, but 
 can seldom be made absolutely complete. With an excess of oxygen and nitrous acid 
 the reactions of condensation predominate 
 
 2 S0 2 -i- N 2 O 3 + 20 + H 2 O = 2 SO 2 .OH.ONO and 
 
 2 S0 2 + 2 NO + 30 + H 2 O = 2 S0 2 .OH.ONO ; 
 
 therefore the conjunction of S0 2 , N 2 3 , and O, characterised as the main reaction of the 
 entire process, and H 2 O to S0 2 .OH.ONO ; but if there is a relative excess of sulphurous 
 acid the reactions of denitration predominate 
 
 2 S0 2 .OH.ONO + S0 2 + 2H 2 = 3H 2 S0 4 + 2 NO, 
 
 by which the chamber crystals of sulphuric acid are again split up into H 2 SO 4 
 and NO. The nitric oxide cannot further enter into reaction at the end of the 
 system, and escapes unutilised, as the Gay-Lussac tower cannot retain it. This in- 
 vertedre action corresponds to that which occurs with an excess of sulphuric acid : 
 SO 4 H 2 . + NOOH = SO 2 .OH.ONO + H 2 0. If water is in excess we have the reaction : 
 S0 2 + OHONO + H 2 = S0 2 (OH), + NOOH. 
 
 In the lead chamber process consequently a relatively large excess of oxygen and 
 nitrous acid is necessary. 
 
 It is now intelligible how to a certain extent, according to practical experience, 
 increased chamber room and an increased supply of nitre compensate each other. If 
 under the other suppositions of the last described progress of a chamber, with an in- 
 sufficient supply of nitre, the chamber room in one case is larger than in another, in the 
 former case more molecules of sulphurous acid will meet with the necessary quantities 
 of oxygen and the oxides of nitrogen than in the latter, because more time is given 
 for intermixture ; hence the excess of the two latter constituents need not be so large. 
 As is well known in practice, the supply of oxygen must be carefully regulated by 
 establishing the correct draught, and modifying it in accordance with any change of the 
 atmospheric conditions. 
 
 In the sulphuric acid manufacture there is little left to be learned from 
 theory. In the utilisation of the sulphur we have arrived nearly, or quite, at the 
 utmost limit fixed by the inversion of the reaction, and the consumption of nitre can 
 scarcely be brought below the small proportion with which the best arranged and best 
 managed establishments are now working. We might perhaps desire to produce con 
 
 s 
 
274 CHEMICAL TECHNOLOGY. [SECT. -in. 
 
 centrated acid at once in the chamber. But this attempt is opposed by theory as well as 
 practice, and the wish is forestalled, since it is found possible by means of the Glover 
 tower, or by utilising heat which would otherwise be lost, to obtain an acid containing 
 80 per cent, of monohydrate. In one direction only does progress seem possible. The 
 chamber process, as now conducted, requires for the production of sulphuric acid a long 
 time and, as a necessary consequence, extensive space.* It does not seem as if a 
 diminution of time and space for the formation of sulphuric acid could be effected by 
 any modifications of the temperature. The process might probably be abridged if a really 
 effective system for the thorough and continuous intermixture of the gases were produced, 
 so that the alternating play of the reactions might be effected at shorter intervals. Still 
 more would this process be abridged if the dilution with nitrogen could be dispensed with 
 by using pure oxygen in place of atmospheric air. Then a higher pressure would be 
 practicable, which would render the reactions quicker and more intense. An easier con- 
 dition would be to occasion a frequent collision of the gases with solid surfaces, whereby 
 the particles which float as mist in the atmosphere of the chamber would soon condense 
 to a fluid and settle to the bottom ; a more rapid removal of the product and the re- 
 action might favour the combination of the other ingredients, and might even promote 
 the intermixture of the gases, f 
 
 Purification of Chamber Acid. The sulphuric acid let off from the great chamber 
 has an average sp. gr. of 1-52 = 104 Tw. or 50 B. This acid may be either used at 
 once for opening up mineral phosphates in manure works, in the manufacture of 
 ammonium sulphate, the manufacture of copperas, &c., or if it has to be carried away 
 it can be evaporated down to the highest grade of concentration, 1-84 sp. gr. = 168 
 Tw. or 66 B. 
 
 Before chamber acid is thus concentrated, certain impurities have to be withdrawn. 
 These accidental impurities are, in addition to traces of lead, copper, iron, lime, 
 alumina, and sometimes selenium and thallium, oxides of nitrogen and arsenic. Nitrous 
 acid may be removed from sulphurous acid by means of oxalic acid, which is decom- 
 posed into carbon dioxide and monoxide : N 2 3 + 3CO = 3C0 2 + 2N. 
 
 The proportion of arsenic in sulphuric acid prepared from Sicilian sulphur is generally 
 slight, but in that from pyrites and blende it is more considerable. For its removal 
 there is used in many works sulphuretted hydrogen gas, which is prepared either from 
 iron sulphide and dilute sulphuric acid (the residual lye being converted into copperas), 
 or according to Binding's proposal, by the action of generator gases upon pyrites at an 
 elevated temperature. According to Hunt's process, sulphuretted hydrogen gas is caused 
 to pass into vessels containing quartz stones, over which the arsenical acid is allowedto flow. 
 The arsenic is thus thrown down as arsenic sulphide, and is separated from the sulphuric 
 acid by means of a sand filter. At Oker, the acid to be purified is let flow into small 
 precipitating pans and diluted down to 88 Tw. (sp. gr. 1-45). The pan is covered 
 with a lead lid with a hydraulic joint, and the acid is heated to 75, when sulphuretted 
 hydrogen is introduced until the acid appears milky from the liberated sulphur The 
 .acid is then clarified by standing for six hours, and is then passed through a small filter 
 consisting of four double-bottomed sieves, between which are layers of asbestos It is 
 received in a cistern and kept for concentration. In the works at Chessy, near Lyons 
 barium sulphide is used for removing arsenic from chamber acid, to which it is added 
 ie proportion of o- 2 to 0-3 per cent. Although a small quantity of acid is thus lost 
 by combining with the barium to form sulphate, this process may be much recommended, 
 ulphuretted hydrogen thus evolved from the barium sulphide is extremely effective. 
 
 * hamber r m P rovid ed cannot well be less than 20 cubic feet per Ib. of 
 
 t It is scarcely necessary to say that of the many proposals for dispensing with the lead- 
 chambers none have proved successful. 
 
SULPHURIC ACID. 
 
 275 
 
 Sodium and barium thiosulphates have also been proposed for removing arsenious acid 
 from the chamber acid. The precipitated arsenic sulphide is worked up as yellow 
 arsenical glass. 
 
 As arsenic is almost exclusively present in sulphuric acid in the state of arsenious 
 acid, it may be removed by the introduction of hydrochloric acid. There is formed 
 arsenious chloride (AsCl 3 ), which boils at a temperature of 134, and can thus be easily 
 removed from sulphuric acid, as the latter does not boil below 325-33o. If thf 
 arsenic occurs as arsenic acid, it must be previously reduced to the arsenious state. 
 This is effected, according to Kupf erschliiger by means of a current of sulphurous acid ; 
 or according to Buchner by heating the chamber acid with a little charcoal, when 
 sulphurous acid is also formed. The arsenious acid when formed is then removed, either 
 by means of sulphuretted hydrogen, or of hydrochloric acid. The lead, indium, and 
 thallium compounds present are removed by means of sulphuretted hydrogen as 
 insoluble sulphides. Iron is found in the form of ferric sulphate in acid prepared from 
 pyrites, especially in such as has been concentrated in the Glover tower. 
 
 Concentration of Sulphuric Acid. When chamber acid is heated it begins to boil 
 .at I30-i35, but the boiling-point continually rises until it reaches 338. This last 
 .acid is the quality which is always obtained on the concentration of chamber acid. It 
 contains 98 per cent. H,S0 4 , and on evaporation at the ordinary atmospheric pressure it- 
 .gives off no more water. 
 
 Chamber acid is concentrated by heating in open lead pans up to 140- 146 Tw. ( = 
 170 sp. gr.), then in vessels 
 of platinum or glass up to 168 
 'Tw. ( = 66 B. or 1*84 sp. gr.). 
 
 Concentration in Leaden 
 Pans. Chamber acid does not 
 begin to attack lead vessels 
 until the concentration exceeds 
 148 Tw., so tha-t it may safely 
 be pushed up to 140- 146 Tw. 
 in leaden pans. According to 
 the experiments of Mallard, 
 sulphuric acid at 140 to 160 
 Tw., if boiling, attacks lead, with the formation of sulphurous acid, lead sulphate, 
 .and sulphur (S0 2 + 2Pb = S + 2PbO). The lead pans are generally, though not univer- 
 sally, heated from below. A pan of this kind is shown in Fig. 266. As a rule several 
 pans are arranged on steps, each successive pan, 40 to 50 centimetres in depth, being fixed 
 from 3 to 7 centimetres lower than the previous one. Above the wall which separates 
 every two pans, small syphons are suspended, the limbs of which stand in small 
 cylindrical vessels. The syphons are always kept full. If they are immersed in the 
 liquid over the partition wall, the acid runs from the one pan into the next lower one. 
 The strength gradually increases in the pan. 
 
 The plates of lead, which are i| centimetre in thickness, rest upon iron plates. 
 From the last lead pan the sulphuric acid passes at once into the concentrating 
 vessels of platinum or glass, in order there to be brought to 168 Tw. 
 
 In the pans of the second kind, the products of combustion sweep over the acid, 
 which is contained in a lead pan in the side of the hearth of a reverberatory. The 
 blackening of the acid thus occasioned is not objectionable if the acid is to be used in 
 the alkali manufacture. At the Rhenania works, near Aachen, there was formerly 
 used for concentrating the chamber acid a reverberatory, with a lead pan, 1-85 metre 
 long, 1*25 metre wide, and o - 26 metre deep, and overhung for 15 centimetres by the 
 fire bridge of masonry. The chamber acid flows laterally into the pan at the height 
 
2?6 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 which is to be its level. At the bottom is a leaden syphon to draw off the concentrated 
 acid. The acid, rendered stronger by the loss of water from its surface, sinks to the 
 bottom and flows off through the syphon. The impurities introduced by the fire-gases 
 float upon the surface. 
 
 In order to concentrate sulphuric acid with indirect steam, the evaporation is effected 
 at Duisburg in wooden cisterns lined with lead, and of the length and breadth of 
 4 metres. On the bottom of each cistern lie two leaden worms, each 45 metres long, 
 0-03 metre inside diameter, and the sides of 0-007 metre in thickness, through which 
 the steam flows whilst the cistern is filled with acid. In order that the condensed 
 water may run off easily from the worms the bottom has the form of a truncated 
 pyramid, and the cistern is in the middle, o'6 metre, and at the sides 0-3 metre deep. 
 Both ends of each worm are connected with the steam boiler and can be shut off with 
 cocks. The steam boiler lies rather lower than the concentrating cisterns, which receive 
 their steam from a pipe running off from the dome of the boiler. The pipes which 
 convey away the steam from the concentration cistern incline towards the steam-space 
 of the boiler, so as to permit a reflux of the condensed steam to the boiler. The cistern is 
 filled with chamber acid of sp. gr. 1*5, and heated until it has risen to 17. The entire 
 contents of the cistern are then transferred to a wooden tank lined with lead. In it 
 lies a worm which the chamber acid must traverse on its way to the concentration 
 cisterns, which are thus always fed with hot concentrated liquid. The pressure of 
 steam in the boiler is three atmospheres, and, in an apparatus of the size given, 5000 
 kilos, of acid of sp. gr. 17 are obtained in twenty-four hours. The consumption of 
 coal is 9 kilos, per 100 kilos, of concentrated acid. The consumption of lead is 2 kilos, 
 per ton of sulphuric acid. It is advisable to place a screen of boards above the 
 concentration cistern, to protect the workmen in case of the bursting of the pipes. 
 Delplace makes the remark that at Stolberg the leaden steam-pipes are attacked at 
 the point where they plunge into the liquid.* The dust which in time attaches itself 
 to the pipes sucks up the acid by capillarity a few centimetres higher than its level in 
 the pan ; this acid is quickly concentrated by the heat and occasions an increased 
 corrosion of the lead. The mischief is prevented by fixing, at the point where the pipe 
 enters the end, a leaden bell of large diameter, opening upwards. Concentration by 
 steam has been of late more common ; no sulphuric acid is volatilised on account of the 
 low temperature, and the process has the advantages of cleanliness, small consumption 
 of fuel, and a decrease of labour. 
 
 The hot gases of the pyrites furnaces are often used for concentrating the chamber 
 icid. To this end leaden pans are fixed upon or behind the furnaces, and the sul- 
 phurous acid is led from the furnaces into a leaden tower filled with hard burned bricks. 
 This arrangement has the defect that, when the pans become leaky, the acid escaping 
 ruins the furnaces. Such accidents, in fact, have frequently happened. 
 
 The concentration of the chamber acid by the hot sulphurous acid of the Glover 
 tower has been already mentioned. 
 
 Completion of Concentration. The acid obtained in the lead pans of a strength of 
 146 Tw. suflices for most purposes. If a more concentrated acid is required 
 (168 Tw.= 1-847 S P- g 1 "-)' ft * s transferred to vessels of glass or platinum. It may be 
 here remarked that the Baume hydrometers used in many works are carelessly con- 
 structed. The point to which the instrument sinks in ordinary (?) sulphuric acid is 
 marked as 66, and the interval between that point and the point for water (o) is 
 divided into 66 parts. Samples of sulphuric acid which marked 67 on this instrument 
 had a sp. gr. of only r8o and i-Si.f 
 
 * This is a very general phenomenon. 
 
 t It must be added that the tables for Baum^'s hydrometer, as given in standard works, differ 
 seriously. In Gmelin's Handbook of Chemistry (Cav. Soc. edition) 46 B. is given as equal 
 
SECT, in.] SULPHURIC ACID. 277 
 
 Concentration in glass vessels is very general. In Britain more than 70 per cent, 
 of all the sulphuric acid is concentrated in glass vessels, the purchase and maintenance of 
 which scarcely amount to half the interest on the cost of a platinum apparatus. 
 Formerly there were used glass retorts of the ordinary shape, fixed to the number 
 of ten in sand-baths in a galley furnace (Fig. 267). The necks have elongations 
 which open into stoneware flasks to condense the escaping vapours. In the works of 
 hance & Co., of Oldbury, the glass vesr3l, B (Fig. 268), 85 centimetres high and 
 
 Fig. 267. 
 
 Fig. 268. 
 
 45 centimetres wide, holds 136 litres, and yields each time 87 litres (= 160 kilos.; of 
 concentrated acid. A is the fire-box, and C the iron sand-bath, which has sand only 
 at its bottom. The gases escape, through /), into the chimney. A glass elbow-tube, E, 
 is in connection with the lead vessel, F, in which the distilled water is condensed. At 
 the end of the process the pipes, E, are removed, and the acid is drawn off with a syphon 
 without disturbing the vessels. During the work the upper part of the glass vessels 
 is protected against chills and currents of air by covers of stoneware or of sheet-iron. 
 
 The glass vessels used in the chemical works at Muehlheim on the Rhine consist of the 
 retort itself in the form of an ovoid body of 70-80 centimetres height and 40-50 centi- 
 metres diameter, and a capital which is like a laboratory retort without bottom. They 
 .are made of white, very thin glass, hold about 300 kilos, of acid, and cost about 38*. Of 
 these retorts thirty -two stand in a row. Each is in an iron vessel filled with sand, into 
 which the retort is embedded to about 10 centimetres from its neck. Each retort has a 
 separate, dii'ect fire, and is separated from the others by an iron screen 15 centimetres 
 in height. The escaping gases from each pass in a common flue to the chimney. In 
 front of the retorts there lies a thin leaden pipe for filling them, and before each single 
 retort there branches off from this leaden pipe a smaller tube, which can be raised and 
 lowered. When the retort is to be filled the lead tube is lowered into the neck and 
 the acid flows in from a leaden pan at a higher level, in which the chamber acid has 
 been previously concentrated. In this manner thirty-two retorts can be filled in half- 
 an-hour. The emptying is effected whilst hot by means of glass syphons, which are 
 " set " by suction from an air-pump. The arm is left loose in the neck of the retort. 
 To prevent glass from coming in contact with glass, there are placed in the neck three 
 or four small lead discs, upon which the arm rests. The arm of each retort enters a 
 common lead tube about 20 centimetres in width, which lies along the retorts and is 
 
 either to 1-468 or to i'456 sp.gr.; in Crookes's Select Methods 46 B. represents I '434. Other 
 varying values are to be found in other works. A further defect in Baume's scale is that its 
 indications cannot be simply recalculated into specific gravities. Hence, it would be well if 
 Continental and American manufacturers would abandon this instrument. 
 
278 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in.. 
 
 Fig. 269. 
 
 connected with the chimney. It carries off the vapours from the evaporation. As some 
 sulphuric acid escapes along with the water, the gases pass first through some coolers, 
 consisting of large lead cylinders tilled with coke and cooled by water. Here the so- 
 called dropping acid is collected. All the retorts are in a building protected from 
 draughts, whilst the fires are in an annex on the outside. In front of each retort 
 there is a small glass window for observing the process and regulating the fire accord- 
 ingly. Boiling begins in one to two hours ; the entire process lasts eight to ten hours. 
 
 The evaporation is continued until the acid 
 becomes colourless a certain sign that it has 
 reached its full strength. 
 
 The platinum stills have a capital either of 
 platinum or lead. The acid which distils over 
 of sp. gr. i -125 to 1-162 is either returned to 
 the lead pans, or concentrated separately for 
 the production of a purer acid, or used as it 
 is. The cooling of the acid concentrated in 
 the platinum still may be effected in several 
 ways, e.g., by the use of the Breant syphon 
 (Fig. 269) of platinum. Its limb, situate 
 
 outside the still, is 5 metres long, and is fitted with a copper tube 15 centimetres 
 in width and 4 metres in length; it is filled with cold water at a, whilst the heated 
 water flows off at b. To increase the surface of the syphon, its main pipe is divided 
 into four narrow tubes. The syphon is set by closing the cock at c, and then pouring 
 in sulphuric acid at the ball valves at d and e to form a tight hydraulic joint ; the' 
 
 Fig. 270. 
 
 Fig. 271. 
 
 Fig. 272. 
 
 \m\sm^ 
 
 cock, c, is opened and the acid flows out. If it were necessary to delay drawing 
 off the acid until cold, time would be lost and the still could not effect a quantity 
 of work commensurate with its high price. 
 
 The arrangement of a platinum still with a platinum capital is shown in Figs. 270, 
 271, 272, and 273. The platinum tube, d, connects the capital, S, with a cooling worm of 
 lead lying in water. The S-tube of platinum, i, with its funnel, has sometimes the 
 shape as in Fig. 270. A cylindrical leaden vessel, g, is provided with an exit tube, h t _ 
 
SECT. III.] 
 
 SULPHURIC ACID. 
 
 and the similar leaden vessel, m, has at its side a slit, so that the tube, h, can move in it up 
 and down when the cylinder, g, is lifted up or let down. A filled leaden syphon connects 
 a- with g. If the cylinder, g, is drawn up as high as it is shown by the dotted lines in 
 Fig. 271, the syphon ceases flowing, but if it is let down the acid of the pan flows 
 through the funnel, i, into the pan, A. Still more simple is the arrangement shown in 
 Fig. 272. A syphon, m, dips in the pan, P, and on the other side into the beaked vessel, 
 n. In proportion as the small cylinder, d, suspended to the chain is raised or lowered, 
 the outflow of the acid is regulated or stopped entirely. Fig. 273 shows the apparatus 
 
 Fig. 273- 
 
 n 
 
 in section at right angles to Fig. 271. In the platinum pan, A, there is a perforated 
 tube, o, of platinum, in which is a float of glass showing the level of the acid in the pan. 
 The long limb of the platinum syphon, d, lies in a wide iron tube supplied with cold 
 water. The syphon, generally of Breant's design, ends in a platinum cock, i. The pan 
 stands on a disc of fire-clay with perforators, into which the flame penetrates and plays 
 round the retort. The specific gravity of the acid which drops off through the pipe of 
 the capital, d (Fig. 271), shows the progress of the work. In the Oker Works on the 
 Harz, a strength of 20 B. here is understood to indicate that the acid in the platinum 
 pan has become 66 B. = 168 Tw., and is fit to be drawn off. It then flows for refrigera- 
 tion through the cooling apparatus, d and h, into the leaden vessel, k, which is 
 surrounded with cold water, from n. The acid when sufficiently cooled is run into the 
 well-known carboys, holding each about 100 kilos., which are placed in wicker baskets 
 packed with straw, and closed by a clay stopper. 
 
 Latterly, platinum apparatus with a leaden capital are coming into use. The 
 apparatus of Johnson, Matthey & Co. (Fig. 274) consists of a platinum body, 
 0*75 metre wide and 0^50 metre in height ; its upper margin, b, is bent over for 
 5 centimetres. This margin bending outwards forms, with channel of platinum resting 
 on the wall built round the platinum body, a hydraulic joint, which is placed for the 
 protection of the platinum in a channel of iron or lead. In this channel, whieh is about 
 15 centimetres wide, there rests the conical capital of strong lead, d, which covers the 
 platinum vessel as with a lid, and on the upper part of which is soldered a low cap, e, 
 with a strongly sloping tube, both of lead. The syphon for drawing off the concen- 
 trated acid is attached to the side of the body at/, the level of the acid provided for, 
 so that when the acid reaches this height it runs off spontaneously. To the leaden cap 
 are soldered the inflow pipe, g, for the acid to be concentrated, and the arrangement, 
 h, for the gauging glass. The pipe sloping down from the cap is connected with 
 the cooling worm, i, in order to carry back to the cooler any vapours which might 
 
280 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 escape. The syphon for drawing off the concentrated acid projects out of k, and is con- 
 nected with the cooling tube, m, i^ metre in length, by means of the ball- joint, I, 
 Hence the acid finally flows through a very efficient pot-cooler, n, which makes it 
 possible to run the acid at once into carboys. To keep the leaden cap cool and prevent 
 it from sinking in on account of the great heat of the boiling acid, it is surrounded with 
 a cylindrical screen, by which the cap itself becomes a kind of evaporating pan, which, 
 
 Fig. 274. 
 
 Fig. 275. 
 
 when kept constantly full of chamber acid, effects the double purpose of cooling and 
 concentration. 
 
 The platinum-lead concentrator of Faure and Kessler aims at high efficiency in the 
 concentration of the acid, combined with a great economy of platinum. It consists of 
 a very large, but shallow, platinum pan, or of several flat pans connected together, and 
 heated from below by a direct fire. The depth of the acid is small. Over the platinum 
 pan is a covering of lead, the outside of which is kept cool by a stream of water. On 
 the inside the acid-vapours ascending from the platinum pans are liquefied, and led 
 
 outwards by a channel. The sulphuric acid 
 flows in a continuous stream from the back 
 to the front, and is drawn off in the ordinary 
 manner by a platinum syphon as acid of 
 1 68 Tw. 
 
 As far back as 1844, Kuhlmann recom- 
 mended the use of a reduced atmospheric 
 pressure. Latterly this procedure has been 
 repeatedly applied. In the arrangement pro- 
 posed by the International Vacuum Ice- 
 Machine Company of Berlin, the pan, S 
 (Fig. 275), made of hard lead, is surrounded 
 with a bad conductor of heat, and fitted with 
 a gauge-glass, C. Into the steam- vessel, E, 
 made of iron or copper plates, there are in- 
 troduced the leaden worms, M, M v traversed by the acid, and resting on the inner 
 supports, N, JV,. The steam for heating enters at a, whilst the steam- water flows off at 
 d. The acid to be concentrated passes through the exchange apparatus, F, through the 
 worm, T (surrounded by steam), of the heater, V, and enters the pan at c. The acid, 
 which has become colder and heavier by the removal of the watery vapours, goes in 
 the direction of the arrows, b, to the heater, E, placed lower than the pan. Here it is 
 
SECT, m.j SULPHURIC ACID. 281 
 
 heated anew, and makes a continual circuit, as in a common water-heating appara- 
 tus. The watery vapour is drawn off at D, and the concentrated acid is let off 
 at J. 
 
 The ordinary sulphur acid of commerce contains 93 to 96 per cent, of the so-called 
 monohydrate, H 2 SO 4 . Exceptionally, a stronger acid of 97 or, at the utmost, 98 per 
 cent, is obtained by further evaporation in glass or platinum vessels ; stronger acid 
 cannot be obtained in this manner, as the monohydrate is dissociated even at a mode- 
 rate temperature, leaving acid of 98 to 98*5 per cent. G. Lunge has observed that, by 
 refrigerating 98 per cent, acid at a little below o, monohydrate can be made to crys- 
 tallise out on an industrial scale, but that the same result can be obtained with acids 
 of 97 or even 96 per cent, by cooling down to - 10, if the occurrence of superfusion is 
 obviated by dropping in a few crystals of the monohydrate. A small quantity of 
 crystals of monohydrate are first prepared by freezing at 10 a 98 per cent, acid 
 (obtained by firing ordinary or fuming acid). A sulphuric acid at 96 to 97 per cent, 
 is next cooled down to at least o, then a few crystals of the monohydrate are thrown 
 in, and the whole is further cooled with stirring until the formation of crystals is com- 
 pleted. The mother liquor is then removed by draining, pressing, &c., not letting the 
 temperature rise above o. 
 
 Of the many modern proposals for manufacturing sulphuric acid in novel manners 
 the following may be mentioned. 
 
 Hahner oxidises sulphurous acid by chlorine in presence of watery vapour : 
 S0 2 + 2 H 2 O + C1 2 = H 2 S0 4 + 2HC1. 
 
 The chlorine is obtained from the hydrochloric acid produced in the alkali manu- 
 facture (Deacon's process). If the sulphuric acid is to serve for the decomposition of 
 common salt it does not need to be purified from hydrochloric acid. Gypsum, 
 CaS0 4 .2H 2 O. has been repeatedly considered as a source of sulphuric acid, and various 
 methods have been proposed to obtain sulphuric acid from gypsum and similar sul- 
 phates, without any such proposal having been carried into successful execution. 
 Tilghman places pieces of gypsum in an upright earthen cylinder lined with magnesite. 
 The charge is then heated to full redness, and the gaseous products of decomposition, 
 O, S0 2 , and H 2 S0 4 , are conveyed through the bottom and the top to the lead chambers. 
 Quicklime is said to be left in the cylinder. Epsomite may be treated in the same 
 manner. 
 
 Seckendorff introduced powdered gypsum and lead chloride into stone tanks along 
 with a large quantity of water heated to 5o-6o. The mixture must be well stirred. 
 Both salts are rapidly decomposed : 
 
 CaS0 4 + PbCl, = CaCl, + PbS0 4 . 
 
 The calcium chloride remains in solution whilst the lead sulphate forms a precipitate, 
 which is filtered off and treated with hydrochloric acid in excess : 
 PbS0 4 + zHCl = PbCl, + H 2 S0 4 . 
 
 The mixture is stirred and heated to 60, when lead chloride collects at the bottom, 
 and the sulphuric acid remains in solution, and is concentrated in the usual manner. 
 The lead chloride serves for the decomposition of fresh quantities of calcium sulphate. 
 If hydrochloric acid is passed over calcium sulphate at a red heat, sulphuric acid escapes 
 and calcium chloride remains : 
 
 CaS0 4 + 2 HC1 = H 2 SO 4 + CaCl 2 . 
 
 According to Scheurer Kestner, if 2 parts calcium sulphate are heated to bright red- 
 ness with i part ferric oxide, all the sulphuric acid is expelled. Sulphuric anhydride 
 escapes first and afterwards sulphurous acid and oxygen. The behaviour of magnesium 
 sulphate is similar. 
 
282 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT, iii. 
 
 PROPERTIES OP SULPHURIC ACID. 
 
 The most highly concentrated sulphuric acid, of the formula H 2 S0 4 , has the sp. gr. 
 1-857 (J. Kolb), 1-854 (Marignac), 1-8384 (Lunge and Naef). When pure it is a 
 perfectly colourless liquid, which, however, is commonly coloured yellowish or brownish, 
 owing to the accidental presence of particles of organic dust. It is thick and oily, 
 destroys many organic bodies with liberation of carbon, does not fume in the air, and is 
 so hygroscopic that it gradually absorbs 15 times its own volume of water. If mixed 
 with water, great quantities of heat are liberated. Of all the volatile acids it has the 
 greatest affinity for bases, and, on heating, it expels all other volatile acids from their 
 salts. But at a red heat sulphuric acid is expelled from its salts (partly decomposed 
 into sulphur dioxide, oxygen, and water) by silicic, boric, or phosphoric acid. The 
 boiling-point of the most concentrated acid is 338. 
 
 Per cent. H 2 S0 4 . 
 
 Specific Gravity. 
 
 Specific Gravity. 
 
 Baum6. 
 
 90 
 
 1-8185 
 
 I '8202 
 
 65-1 
 
 91 
 
 1-8241 
 
 1-8254 
 
 65'4 
 
 92 
 
 I '8294 
 
 I '8306 
 
 65-6 
 
 93 
 
 I ^339 
 
 1-8346 
 
 65-8 
 
 94 
 
 I-8372 
 
 I-8374 
 
 65-9 
 
 95 
 
 I '8390 
 
 I -8397 
 
 66-0 
 
 96 
 
 I '8406 
 
 
 
 97 
 
 1-8410 
 
 
 
 9775 
 
 
 
 1-8468 
 
 66-2 
 
 98 
 
 1-8412 
 
 
 
 99 
 
 I '8403 
 
 
 
 lOO'OO 
 
 1-8384 
 
 
 
 Specific Gravities of Sulphuric Acid, at 15 (KoW). 
 
 Specific 
 Gravity. 
 
 Degrees 
 
 Baume. 
 
 Degrees 
 Twaddell. 
 
 too Parts by Weight correspond 
 to per Cents. 
 
 i Litre contains Kilos, of 
 Pure Acid. 
 
 S0 3 . 
 
 H 2 S0 4 . 
 
 S0 3 . 
 
 H 2 SO 4 . 
 
 OOO 
 
 O 
 
 
 
 07 
 
 0'9 
 
 0-007 
 
 0-009 
 
 '014 
 
 2 
 
 2'8 
 
 2'3 
 
 2'8 
 
 0-023 
 
 0-028 
 
 029 
 
 4 
 
 5'8 
 
 3 '9 
 
 4'8 
 
 0-040 
 
 0-049 
 
 045 
 
 6 
 
 9-0 
 
 5-6 
 
 6-8 
 
 0-059 
 
 0-071 
 
 060 
 
 8 
 
 I2'0 
 
 7-2 
 
 8-8 
 
 0-076 
 
 0-093 
 
 075 
 
 10 
 
 15-0 
 
 8-8 
 
 10-8 
 
 0-095 
 
 0-116 
 
 091 
 
 12 
 
 18-2 
 
 io'6 
 
 13-0 
 
 0-116 
 
 0-142 
 
 108 
 
 14 
 
 21 '6 
 
 12-4 
 
 15-2 
 
 0-137 
 
 0-168 
 
 125 
 
 16 
 
 25 -o 
 
 14-1 
 
 I7-3 
 
 0-159 
 
 0-195 
 
 142 
 
 18 
 
 28-4 
 
 16-0 
 
 19-6 
 
 0-183 
 
 0-224 
 
 162 
 
 20 
 
 32-4 
 
 18-0 
 
 22 '2 
 
 0-209 
 
 0-258 
 
 180 
 
 22 
 
 36-0 
 
 2O '0 
 
 24-5 
 
 0*236 
 
 0-289 
 
 200 
 
 24 
 
 40-0 
 
 22'I 
 
 27-1 
 
 0-265 
 
 0-325 
 
 220 
 
 26 
 
 44 -o 
 
 24-2 
 
 29 '6 
 
 0-295 
 
 0-361 
 
 241 
 
 28 
 
 48-2 
 
 26-3 
 
 32-2 
 
 0-326 
 
 0-400 
 
 26 3 
 
 3 
 
 52-6 
 
 28-3 
 
 347 
 
 o-357 
 
 0-438 
 
 285 
 
 32 
 
 57'0 
 
 30-5 
 
 37'4 
 
 0-392 
 
 0-481 
 
 308 
 
 34 
 
 61-6 
 
 32-8 
 
 40-2 
 
 0-429 
 
 0-526 
 
 332 
 
 36 
 
 66-4 
 
 35'I 
 
 43 '0 
 
 0-468 
 
 0-573 
 
 '357 
 
 38 
 
 7i-4 
 
 37'2 
 
 45'5 
 
 0-505 
 
 0-617 
 
 383 
 
 40 
 
 76-6 
 
 39'5 
 
 48-3 
 
 0-546 
 
 0-668 
 
 410 
 
 42 
 
 82-0 
 
 41-8 
 
 51-2 
 
 0-589 
 
 0-722 
 
 438 
 1-468 
 
 44 
 46 
 
 87-6 
 93 '6 
 
 44'I 
 46-4 
 
 54-o 
 56-9 
 
 0-634 
 0-681 
 
 0777 
 0-835 
 
 Kohlrausch has shown that sulphuric acid has its maximum density below its 
 highest concentration. 
 
 Applications. The applications of sulphuric acid are extremely extensive and mani- 
 fold ; e.g., in the preparation of many acids (nitric, hydrochloric, sulphurous, carbonic, 
 
SECT, in.] POTASSIUM SALTS. 283 
 
 tartaric, citric, stearic, palmitic, and oleic), for producing acid calcium phosphate as a 
 manure for the production of chlorine, of stearine candles (decomposition of lime soaps), 
 of phosphorus (by decomposing bone-earth), for making salt-cake in the alkali-manu- 
 facture, the production of potassium sulphate (from the potassium chloride or 
 carnallite), of ammonium sulphate, alum, iron and copper vitriols, baryta white, 
 hydrogen gas, nitro-glycerine, gun-cotton, picric acid, in separating gold from silver, 
 de-silvering black -coppers, for refining rape oil, petroleum, and paraffine, obtain- 
 ing garancine or other madder products, for producing the sulphonic acids of the 
 tar-colours, for manufacturing glucose, parchment paper, shoe-blacking, as a 
 disinfectant, for desiccating confined air (e.g., for glue), for drying the chlorine obtained 
 in the Deacon process, for cleaning sheet-iron to be tinned, &c. 
 
 POTASSIUM SALTS. 
 
 Potassium is found widely diffused both in the mineral kingdom and in organic 
 nature. The sources of potash available for technical purposes are at present the 
 following : 
 
 / i. Natural salts, carnallite, sylvine, kainite, and schoenite. 
 A. Inorganic I 2. Felspar, and similar rocks. 
 
 sources. j 3. Sea-water, and the mother liquor of salt-works. 
 \ 4. Native saltpetre. 
 , 5. Ash of plants. 
 
 B. Organic 6. Residue from beetroot treacle, 
 sources. "| 7. Seaweeds ; a bye-product of the iodine manufacture. 
 \ 8. The suint from raw wool. 
 
 Of these sources the most important at present are the deposits of alkaline salts. 
 They are supposed to have been formed by the gradual drying up of salt lakes or arms 
 of the sea. Similar phenomena are at present gradually taking place in Central Asia. 
 The more soluble salts, those of potassium and magnesium, would remain in solution 
 longer than sodium chloride, and would thus be in danger of being swept away by 
 intermediate geological changes, inundations, &c. Hence of the many and vast saline 
 beds in the earth, many are totally free from potassium salts, which in North Germany 
 have been accidentally preserved. At Kalucz in Hungary, and on the southern slopes 
 of the Himalaya, similar deposits occur. 
 
 Potassa Salts from the Stassfurt Salt Minerals. I. The very abundant salt-rocks 
 near Stassfurt in Prussia, [and Kalucz in Hungary, chiefly yield carnallite, sylvine 
 (C1K), and kainite, a compound of sulphate of potassa and magnesia with chloride of 
 magnesium. Carnallite, so named in honour of Carnall, a Prussian mining engineer, 
 consists, in 100 parts, leaving the bromide out of the question, of 
 
 Potassium chloride . . . .27 
 Magnesium chloride . . . 34 
 Water 39 
 
 too 
 
 fCl 
 Formula K01 2 ,Mgj T> " + 6H 2 0. This salt is applied in the manufacture of 
 
 a. Potassium chloride. 
 
 |3. sulphate. 
 
 y. carbonate. 
 
 a. Preparation of Potassium Chloride. According to the process originally 
 patented (1861) by Mr. A. Frank, the abraum salts are ignited in a reverberatory 
 furnace, with or without the aid of a current of steam, and next lixiviated with water, 
 the resulting liquor yielding chloride of potassium. The rationale of this process is : 
 I. That the carnallite of the abrauin salts is separated by the action of the water into 
 
284 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 chloride of potassium and chloride of magnesium. 2. The latter salt on being ignited 
 in a current of steam is decomposed into hydrochloric acid, which escapes, and magnesia, 
 which is practically insoluble in water, and which consequently remains. This 
 process is not found to answer well on the large scale, because the abraum salts contain 
 other chlorides, the chloride of sodium and tachydrite, by the presence of which the 
 decomposition of the carnallite is hindered. Dr. Griineberg, therefore, suggested that 
 the abraum salts should be first mechanically purified, that is to say, the different com- 
 ponents of the abraum salts should be separated from each other according to their 
 varying specific gravity, which for 
 
 Carnallite is 1*618 
 
 Chloride of sodium is = 2-200 
 Kieserite is = 2*517 
 
 The abraum salt having been ground to a coarse powder is passed through sieves, 
 And treated as minerals are in metallurgical processes, with the difference that, instead 
 of water, which of course would dissolve the salts, a thoroughly concentrated solution of 
 chloride of magnesium is applied, this solution not acting upon the salts, and being, 
 moreover, obtained as a bye-product in enormously large quantities. The above- 
 mentioned salts settle in layers according to their densities, the carnallite forming the 
 upper, and the kieserite the lowest layer. The carnallite is at once applied to the pre- 
 paration of chloride of potassium ; the middle layer of common salt is so free from other 
 foreign salts as to be fit for domestic use ; the kieserite, after having been washed with 
 cold water to remove any adhering chloride of sodium, is applied to the manufacture of 
 sulphate of potassa, to be presently described. However, the greater number of manu- 
 facturers at Stassfurt prefer another plan, applying the five following operations to 
 the abraum salts as delivered from the salt quarries : i. Lixiviation of the carnallite 
 with a limited quantity of hot water, sufficient to dissolve the chlorides of potassium 
 and magnesium, leaving the bulk of the common salt and magnesium sulphate. 
 2. Crystallising the chloride of potassium by artificially freezing. 3. Evaporating and 
 cooling the mother liquor to produce a second yield of crystallised chloride of potassium. 
 4. Again evaporating and cooling the mother liquor, which yields the double salt of 
 the chlorides of potassium and magnesium, or artificial carnallite, which is next treated 
 in the same manner as the native salt. 5. Washing, drying, and packing the chloride 
 of potassium. 
 
 According to Dupre, ejection apparatus (Fig. 276) are used, so arranged that their 
 
 suction openings, a, are in connection with the 
 
 Fig. 276. space beneath the sieve flooring, s, whilst the 
 
 ejection openings are connected with the space 
 above this flooring. At the same time, the 
 direction of the apparatus is such as to produce 
 an intense circiilation of the liquid and the saline 
 particles. 
 
 The hot solution obtained, of sp. gr. 1-32, is 
 allowed to stand in separate vessels to deposit 
 the suspended particles (of kieserite and clay), 
 and then it is let flow into iron crystallising 
 
 tanks, in which, after cooling for two to three days, a mixture of potassium and sodium 
 chlorides crystallises out. In some works the crude saline solution is diluted with 
 water, whereby the separation of sodium chloride is diminished and a crystallisation 
 of almost pure potassium chloride is effected. In order to obtain the potassium chloride 
 still remaining in the mother liquor, the latter is evaporated down to such a concentra- 
 tion that the potassium chloride separates almost entirely out in the form of carnallite, 
 and only i per cent, is left in solution. The artificial carnallite is dissolved in hot 
 
SECT, m.] POTASSIUM SALTS. 285 
 
 water, and, as it cools, a second crystallisation of potassium chloride is obtained, The 
 potassium chloride obtained from both crystallisations is washed with water at common 
 temperatures to remove magnesium chloride, and in part sodium chloride ; it is dried in 
 a calcining furnace or on kilns heated by steam. The mother liquor from the second 
 crystallisation, and the washings containing potassium, sodium, and magnesium chlorides, 
 are used for dissolving the crude salt. 
 
 The pans for evaporating the mother liquor in the manufacture of potassium 
 chloride have three flame tubes, the middle one, a (Fig. 277), having double the section 
 of the two side tubes, b. The flame strikes first backwards 
 through the middle tube and then forwards through the side 
 tubes. Hitherto the flame tubes were rivetted to both cheeks 
 of the pan, which easily occasioned a strain and a loosening of 
 the joints. For the ready removal of the sodium chloride, 
 which separates out on the evaporation of the mother liquor, 
 the bottom of the pan slopes towards the middle, d, and the 
 lowest point is provided with a helix, s. By its rotation the 
 salt is removed which has been deposited in the lowest part of 
 the pan. 
 
 Of the potassium chloride present in the crude salt, 75 to 
 
 85 per cent, is obtained ; the rest is lost in the various residues. The proportion of 
 potassium chloride in the muddy settlings is sometimes considerable, so that the salt 
 calcined in some works and sold for manure may contain 18 to 24 per cent, potassium 
 chloride. Supposing the loss in the manufacture to be 20 per cent., then 625 kilos, 
 crude salt at 16 percent, are needed for the production of 100 kilos, potassium chloride 
 at 80 per cent. For the daily manipulation of 50 tons raw gait a space of 350 cubic- 
 metres is needed for crystallising, or for a daily turn-over of 3500 tons a total of 
 24,500 cubic metres. 
 
 Of the potassium chloride 80 per cent, is used in the manufacture of potash saltpetre, 
 whilst for the preparation of potash a pure product, as free as possible from sodium 
 chloride, is needed. 
 
 As bye-products, kieserite and sodium sulphate are obtained from the residues. 
 The former is produced in the simplest manner, by dissolving the sodium chloride 
 found, when the sparingly soluble kieserite is split up and deposits as a fine mud ; 
 this takes up water and hardens in a few hours, and is sold in blocks weighing 
 25 kilos. From a part of the kieserite pure magnesium sulphate is obtained by 
 solution and crystallisation. 
 
 The manufacture of Glauber's salt (sodium sulphate) is carried on only in winter. 
 It depends on mutual decomposition of sodium chloride and magnesium sulphate in 
 aqueous solutions at temperatures below o. To this end, the total residue is dissolved 
 in water ; the concentrated lye obtained after it has become clear is exposed in flat 
 exposed wooden troughs to the cold of winter. The crystallisation is often effected in 
 a single night. In this manner about 10,000 tons sulphate are produced yearly. 
 After the introduction of freezing machines the output will be decidedly greater. 
 
 The conversion of potassium chloride into potassium sulphate by Glauber's salt, 
 which has been repeatedly tried, has not been found practicable on the large scale, as 
 the two sulphates have a great tendency to form a double salt. At present large 
 quantities of potassium sulphate are prepared by means of sulphuric acid in a manner 
 quite analogous to the Leblanc soda process and with the same apparatus and furnaces. 
 Griineberg and Schmidtborn allowed a hot solution of potassium chloride and 
 schcenite to crystallise. The result was potassium chloride and carnallite, which are 
 separated by crystallisation. 
 
 Miiller fuses equivalent quantities of potassium chloride, magnesium sulphate, and 
 iron oxide. The potassium sulphate is separated by lixiviation, 
 
2 86 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 Kainite. In the interval between 1878-1880, sixteen processes were patented for the 
 production of potassium magnesium sulphate, of which only three have been worked on 
 the large scale. The United Chemical Works of Leopoldshall work on the Borsche and 
 Briinjes process, the Stassfurt Chemical Works on that of Dupr6 and Hake, and 
 the new Stassfurt Works under the patent of H. Precht. Borsche and Briinjes treat the 
 kainite with a cold saturated solution of kainite at 80 ; on cooling, potassium-mag- 
 nesium sulphate crystallises. Dupr6 and Hake use in a similar manner a con- 
 centrated solution of magnesium sulphate, whilst Precht heats the kainite with water or 
 brine to 120 to 150 under pressure. In this manner 3 tons of coarsely powdered 
 kainite are decomposed in about thirty minutes, the potassium-magnesium sulphate being 
 converted into an exceedingly fine crystalline powder, K 2 S0 4 .2MgSO 4 .H 2 O. For dis- 
 solving there is used a saline solution saturated for sodium chloride, which may contain 
 other of the salts occurring in kainite. The proportions are chosen so that sodium 
 chloride and the new double salt remain undissolved, whilst potassium and magnesium 
 chlorides remain in solution. According to the nature of the saline solution, the 
 decomposition takes place according to one of the two following equations : 
 3 (K 2 S0 4 ,MgS0 4 ,MgCl 2 ,6H 2 0) = 2 (K 2 SO 4 , 2 MgS0 4 ,H O) + 2 KC1 + aMgCl, + xH 2 0, or 
 2 (K 2 S0 4 ,MgS0 4 ,MgCl 2 ,6H 2 0) = K 1 S0 4 , 2 MgS0 4 ,H,0 + 2MgCl a + K 2 S0 4 . 
 
 The transformation ensues according to the former equation if the saline solution 
 contains, along with sodium-chloride potassium, magnesium sulphate and magnesium 
 chloride, but chiefly according to the second, when it consists of a saturated solution of 
 magnesium chloride. Experience in manufacturing has shown that the new salt is 
 precipitated so completely from the decomposition-lye, that this on cooling only allows 
 potassium chloride to separate and does not contain more than 2^4 percent, magnesium 
 sulphate. In contact with cold water it is resolved into schcenite and epsoms. From 
 the hot aqueous solution schcenite crystallises out on cooling, whilst the excess of mag- 
 nesium sulphate remains in solution. If a solution of potassium chloride is taken as a 
 solvent, we find conversion into schoenite and magnesium chloride. 
 
 The potassium-magnesium sulphate, with 50 per cent, potassium sulphate and 3 per 
 cent, chloride, is in great demand both in agriculture and manufactures, and perhaps 
 from this cause its further treatment for pure potassium sulphate is not yet carried 
 out. 
 
 The utilisation of the abundant lyes of potassium chloride is still an unsolved 
 problem. A small portion is evaporated down, and the melted magnesium chloride is 
 sold ; from a larger portion the 0*2 per cent, of bromine present is separated before it 
 is let run into the streams. At present about one-third of the final lye is thus treated 
 with an annual yield of 300 tons. 
 
 Production of Potassium Carbonate. Numerous proposals have been made for the 
 most advantageous conversion of potassium chloride and sulphate into potash. The 
 only process which has been practically carried out is an imitation of the Leblanc soda 
 process, first applied to the production of potash by Griineberg (1861). Large quanti- 
 ties of excellent potash have been made by Forster and Gruneberg, at Kalk, near 
 Cologne, at the Buckau Works, near Magdeburg, and at Stassfurt, on the Leblanc 
 process. Everything is carried on as for soda, save that in the black-ash process high 
 temperatures must be more carefully avoided. If the coal used for reduction is rich 
 in nitrogen, potassium ferrocyanide is produced. On evaporating the carbonated lye 
 to 98 Tw., the ferrocyanide separates out with the undecomposed sulphate still 
 contained in the lyes, and can be extracted from the salt by lixiviation with hot 
 -water ; a second re-crystallisation converts the product into a fine commercial sample. 
 
 The products prepared at Buckau contained (1879) 
 
SECT, in.] POTASSIUM SALTS. 287 
 
 K 2 CO S . . . . . 97 -30 per cent. 
 
 Na,CO 8 0-29 
 
 K 2 S0 4 0-49 
 
 KC1 1-23 
 
 Moisture 0^69 
 
 According to another process, potassium sulphate containing schcenite is ignited 
 with chalk and small coal, and the mass lixiviated with water. Potash dissolves, 
 and calcium sulphide remains, from which the sulphur is recovered according to the 
 processes of Schaffner and Mond. The presence of a certain quantity of schrenite and 
 magnesium sulphate in potassium sulphate which is intended for the manufacture 
 of potash is advantageous, since the crude potash is thus rendered lighter and more 
 porous, and it is consequently easier to lixiviate than crude potash made from a 
 pure potassium sulphate. 
 
 R. Engel mixes a solution of potassium chloride with magnesium carbonate and 
 saturates with carbon dioxide, when the double potassium-magnesium bicarbonate 
 separates out. When separated from the lye of magnesium chloride, this precipitate 
 is heated either alone or along with water, when it is resolved into magnesium 
 carbonate and potassium carbonate 
 
 2 MgKH(C0 3 ) J = 2 MgC0 3 + K 2 C0 3 + H 2 O + C0 3 
 
 The potassium carbonate is extracted in the water. Magnesium carbonate and carbon 
 dioxide go back. The process has recently been given up. 
 
 Experiments to obtain potassium carbonates by the ammonia process have hitherto 
 had little success. 
 
 For the preparation of potassium carbonate, G. Borsche and P. Briinjes introduce 
 carbonic acid and ammonia, or ammonium carbonate, into the solution of a magnesium 
 salt which holds in suspension magnesia or magnesium carbonate, on which the 
 double ammonium-magnesium carbonate (containing all the magnesia in solution) is 
 separated out after some time. This double carbonate is mixed with about an equiva- 
 lent quantity of potassium chloride or sulphate, an excess being of advantage, and with 
 water, in order to bring the above salts into solution. Into this mixture is passed 
 carbonic acid, or carbonic acid and ammonia, when the transformation into potassium 
 magnesium is promoted, though it certainly takes place without the introduction of car- 
 bonic acid and ammonia. This preparation of ammonium-magnesium carbonate, and its 
 transformation into potassium-magnesium carbonate can be combined by introducing, 
 firstly, ammonium carbonate and carbonic acid e.g., into a solution of carnallite, 
 or into a solution of potassium magnesium sulphate, or into suspended magnesia or 
 magnesium carbonate, adding after some time potassium chloride, and then again 
 carbonic acid. They thus obtain crystals of the triclinic system, containing potassium- 
 magnesium carbonate. The potassium-magnesium carbonate is decomposed into 
 potassium carbonate and magnesium carbonate by digestion with water. The mag- 
 nesium carbonate returns to the process. This method is about to be introduced on 
 .a large scale. 
 
 The production of potassium salts from felspar is at present of no importance. . 
 
 In order to obtain salts of potassium from sea-water, especially from the Medi- 
 terranean, the last mother liquors are concentrated by evaporation, and mixed with 
 magnesium chloride, so that carnallite crystallises out.* 
 
 Salts of Potassium from the Ashes of Plants. The residue left from the ignition of 
 the organic matter, or wood, as it is usually termed, of plants contains those mineral 
 substances which the plant has taken from the soil, chiefly potassa, soda, lime, magnesia, 
 small quantities of the protoxides of iron and manganese, combined with phosphoric, 
 sulphuric, silicic, and carbonic acids, and also with the haloids. These combinations are 
 
 * It has been proposed to apply this process to the water of the Dead Sea. 
 
288 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 not, however, the same as those existing in the living plant, because the high temper- 
 ature of the ignition has the effect of changing the affinities. Plants growing near the 
 sea generally contain large quantities of soda, while those inland contain generally 
 more potassa. The quantity of ash varies not only for different kinds of plants, but for 
 various parts of the same plant : very succulent plants and the most succulent parts of 
 others generally yield the largest quantity of ash ; herbs yield more ash than shrubs, 
 shrubs more than trees, and the leaves and bark of the latter more than the wood. It is 
 evident that the inorganic matter, chiefly alkaline salts, being contained in the juice 
 of plants in a soluble state, the quantity must of necessity be greatest in the juicy and 
 succulent parts. 
 
 Dr. Bottger found the ash of beech wood to contain 
 
 21-27 per cent, of soluble salts, 
 7^73 ii of insoluble salts. 
 
 The soluble salts were found to be 
 
 Potassium carbonate . . . 15*40 per cent. 
 
 sulphate .... 2*27 
 Sodium carbonate .... 3-40 
 
 chloride . . 0*20 
 
 2 1 '27 
 
 The value of an ash for the manufacture of potash is chiefly dependent, in the first 
 place, upon the quantity of potassic carbonate it will yield, upon the abundance of the 
 wood or other vegetable product, and the cost of labour. The under-mentioned woods 
 yield on the average, for 1000 parts, the following quantities of potash : 
 
 Pine 0*45 
 
 Poplar 0-75 
 
 Beech 1-45 
 
 Oak 1-53 
 
 Box wood 2*26 
 
 Willow 2*85 
 
 Elm 
 Wheat straw 
 
 3 "90 
 3-90 
 
 Bark from oak-knots . . .4-20 
 Cotton-grass (Eriophorum vayinatuni) 5-00 
 Rushes 5-08 
 
 Vine wood 
 
 5-50 
 
 Beech bark . . . . .6-00 
 
 Dried ferns 6-26 
 
 Stems of maize (Indian corn) . . 17-50 
 
 Bean straw 20 -co 
 
 Sunflower stems . . . . 20-00 
 
 Nettles 25-03 
 
 Vetch straw 27-50 
 
 Thistles 35-37 
 
 Dried wheat plant previous to 
 
 blooming 47-00 
 
 Wormwood 73 "oo 
 
 Fumitory 79-00 
 
 Barley straw 5-80 
 
 According to M. Hoess, 1000 parts of the following kinds of wood yield 
 
 Ash - Potash. Ash , Potash. 
 
 Pine . . . 3-40 ... 0-45 
 
 Beech . . .5-80 ... 1-27 
 
 Ash . . . 12 -20 ... 074 
 
 Oak . . . 13-50 ... 1.50 
 
 Elm . . . 25-50 ... 3-90 
 
 Willow . . .28-0 ... 2-85 
 
 Vine .... 34-0 ... 5-50 
 
 Dried ferns . .36-4 ... 4-25 
 
 Wormwood . .97-4 ... 73-00 
 
 Fumitory . . . 219-0 ... 79-90 
 
 The preparation of potash from vegetable matter is effected in three operations, 
 viz. : 
 
 (a) The lixiviation of the ash. 
 
 (b) The boiling down of the crude liquor. 
 
 (c) The calcination of the crude potash. 
 
 The combustion of the vegetable matter should be so conducted as to prevent its 
 becoming too violent and giving rise to the volatilisation of some of the reduced potassa 
 Mlt; nor should too strong a current of air be admitted, for fear of the ash being 
 mechamcally carried off. A distinction is made abroad no potash from wood or other 
 
SECT, in.] POTASSIUM SALTS. 289 
 
 vegetable matter being produced in the United Kingdom, nor wood used as fuel in 
 sufficient quantities to yield ash. for the preparation of potash between the ash obtained 
 by the combustion of the refuse wood of forests and the ash from wood used as fuel, 
 the former being termed forest- and the latter fuel-ash. As ash from other fuel than 
 wood may be mixed with fuel-ash, a sample may be roughly tested by lixiviation, and 
 the density of the liquor taken by the areometer, the higher the specific gravity the 
 larger the quantity of soluble salts. Formerly the forest-ash was purposely prepared 
 and sold to potash-boilers. There is still known in Eastern Prussia and Sweden a 
 material termed okros or ochras, holding a position intermediate between crude ash and 
 potash. 
 
 (a) The lixiviation of the ash effects the separation of the soluble from the insoluble 
 saline matter, the former amounting to about 25 to 30 per cent, of the entire weight of 
 the ash. The operation is carried on in wooden vessels shaped like an inverted trun- 
 cated cone, and provided with a perforated false bottom, which is covered with straw ; 
 in the real bottom a tap is fixed for removing the liquor. If the lixiviation is system- 
 atically carried on, several of these vessels are placed together, forming what is termed 
 a battery, and under each a tank to receive the liquor. The ash to be lixiviated is first 
 sifted from the coarse particles of charcoal, next put into a small square water-tight 
 wooden box, and thoroughly saturated with water for at least twenty-four hours. By 
 this proceeding the lixiviation is greatly assisted, and the potassium silicate to some 
 extent decomposed by the action of the carbonic acid of the atmosphere. The next step 
 is to transfer the wet ash to the lixiviation vessel, care being taken to press it tightly 
 down on to the false bottom ; cold water is then poured in, until the liquor begins to 
 run off at the taps left open for that purpose. The liquor which runs off, after the 
 water has remained some little time in contact with the ash, is found to contain about 
 30 per cent, of soluble salts, afterwards decreasing to about 10 per cent., when hot water 
 is employed to compete the lixiviation. The insoluble residue left in the lixiviation-tub 
 is of value as a manure, on account of the phosphate of lime it contains, and is also used 
 in making green bottle-glass, and for building up saltpetre-beds. 
 
 (6) Boiling down the liquor. The liquor obtained by lixiviation is of a brown colour, 
 owing to organic matter, humine or ulmine, which the potassium carbonate has dis- 
 solved from the small chips of imperfectly burnt charcoal. The evaporation is carried on 
 in large shallow iron pans, fresh liquor being from time to time added, and the operation 
 continued until a sample of the hot concentrated liquor exhibits on cooling a crystalline 
 solid mass. When this point is reached the fire is gradually extinguished, and as soon 
 as the contents of the pan are sufficiently cold to handle, the solid salt mass is broken 
 up ; its colour is a deep brown. This crude product, containing about 6 per cent, water, 
 is known in the trade as crude, or lump-potash. It is evident that this method of 
 boiling down may cause considerable damage to the iron pans ; therefore in many 
 instances the operation is conducted in a somewhat different manner. The liquid is kept 
 stirred with iron rakes, and the salt, instead of forming a hard solid mass, is obtained 
 as a granular powder, containing upwards of 1 2 per cent, water. Some manufacturers 
 first separate the potassium sulphate, which, being less soluble, crystallises before the 
 carbonate, a deliquescent salt, is separated from the liquor ; in most cases, however, 
 this operation is only carried on where the potassium sulphate is required for alum- 
 making. The pearl-ash or potash of commerce almost invariably contains a large 
 quantity of potassium sulphate. 
 
 (c) In order to expel all the water and to destroy the organic matter, the saline mass 
 is calcined, and as this operation was formerly performed in cast-iron pots, the salt has 
 obtained the name of potash. A calcining furnace, Fig. 278, is now used, distinguished 
 from ordinary reverberatory furnaces by being provided with a double fire-place. These 
 hearths, one of which is exhibited in section at A, Fig. 278, are placed at right angles 
 
290 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. m. 
 
 to each other, and the flame and smoke meeting in the centre of the furnace, pass off 
 at 0, the work-hole, into the chimney. Wood is used as fuel, and as the heating of 
 the furnaces requires a very large quantity, they are only in use when a sufficient 
 supply of crude potash is ready for operating on. The furnace is thoroughly 
 heated in about five to six hours, care being taken to fire gradually, and to bring the 
 interior of the furnace to nearly red heat, so that the vapour due to the combustion of 
 the wood may not condense inside the furnace, but be carried off by the flue. The 
 crude potash, broken up to egg-sized lumps, is next added in such quantities at a time 
 as may suit the size of the calcining hearth ; for instance, if the hearth is fitted to 
 contain 3 cwts., that quantity is divided into three portions and put in at intervals of a 
 few minutes. The first effect of the heat is to expel the water from the potash, the 
 escape of the steam being promoted by stirring the mass with iron rakes. In about an 
 hour all the water is driven off, and the mass takes fire in consequence of the burning 
 of the organic matter, the salt at first being blackened, but gradually becoming 
 white as the carbon burns off. As soon- as this stage is reached, the potash is removed 
 to the cooling-hearth, and, when cold, packed in well-made wooden casks, which, as this 
 salt is very hygroscopic, are rendered as air-tight as possible. The heat of the furnace 
 
 has to be well regulated 
 
 Fig. 278. to prevent the potash 
 
 becoming semi-fused, in 
 which case it would at- 
 tack the siliceous matter 
 of the fire-bricks ; the 
 workmen from time to 
 time take a small sample 
 to test how far the 
 calcination is complete. 
 
 We, in Europe, ob- 
 tain a considerable 
 quantity of potash from 
 the United States and 
 
 Canada, known as American potash, of which there are three kinds, viz. : 
 i. Potash prepared as described. 2. Pearl-ash, or potash, purified by lixiviation, 
 decantation from sediment, boiling down, and the calcination of the salt thus obtained. 
 3. Stone-ash, a mixture of uncalcined potash (potassium carbonate) and caustic potash, 
 obtained by treating the crude potash liquor with caustic lime, and boiling down the 
 mass to dryness; this article has the appearance of the crude caustic soda of this 
 country, but is usually coloured red by oxide of iron ; the lumps, stone-hard, are from 
 6 to 10 centimetres in thickness, and contain upwards of 50 per cent, caustic potash. The 
 under-mentioned analyses exhibit the varying composition of the potash of commerce : 
 Sample i is from Kasan (Russia) ; analyst, M. Herman. 2. Tuscany. 3 and 4 the 
 latter of a reddish colour from North America. 5. Russia. 6. Yosges (France); 
 analyst of 2, 3, 4, 5, and 6, M. Pesier. 7. Helmstedt, in Brunswick; analyst, 
 M. Limpritsch. 8. Russia; analyst, M. Bastelaer. 
 
 Potassium carbonate 
 Sodium 
 
 Potassium sulphate 
 
 chloride 
 
 Water . 
 Insoluble residue . 
 
 The calcined potash varies in colour, being either white, pearl-grey, or tinged with 
 
 I. 
 
 2. 
 
 3- 
 
 4. 
 
 5- 
 
 6. 
 
 7. 
 
 8. 
 
 78-0 .. 
 
 74'i < 
 
 . 71-4 ... 
 
 68-0 . 
 
 69-9 
 
 ... 38-6 , 
 
 .. 49-0 .. 
 
 . 50-84 
 
 .. 
 
 3' .. 
 
 2-3 ... 
 
 5-8 . 
 
 3' 1 
 
 ... 4'2 . 
 
 ,. .. 
 
 . 12-14 
 
 17-0 .. 
 
 13'S - 
 
 . I4'4 
 
 IS'3 
 
 . 14*1 
 
 ... 38-8 ., 
 
 . 40-5 .. 
 
 I7'44 
 
 3'0 ., 
 
 . 0-9 , 
 
 ,. 3-6 ... 
 
 8-1 . 
 
 ,. 2-1 
 
 ... 9'I . 
 
 .. I0'0 .. 
 
 . 5-80 
 
 
 
 .. 7-2 . 
 
 .. 4'5 ... 
 
 . 
 
 .. 8-8 
 
 - 5'3 
 
 .. .. 
 
 . IO-I8 
 
 0'2 .. 
 
 . O'l .. 
 
 . 27 ... 
 
 2-3 -. 
 
 2-3 
 
 .... 3'8 .. 
 
 . .. 
 
 3' 6 
 
SECT, in.] POTASSIUM SALTS. 291 
 
 yellow, red, or blue. The red colour is due to oxide of iron, the blue to the manganates 
 of potash. It is a hard, light, porous, non-crystalline mass, never entirely soluble in water. 
 Formerly, a large quantity of potash was obtained from the residues of wine-making 
 and called vinasse, the semi-liquid left after the alcohol has been distilled from the 
 wine, and containing, among other substances, argol, or crude potassium bitartrate ; it 
 was boiled down, and next calcined, yielding a kilo, of very good potash for every 
 hectolitre of vinasse. The large quantity of potash thus formerly produced may be 
 judged from the fact that nineteen of the wine-producing departments of France, those 
 only where large quantities of wine are converted into alcohol, technically termed trois-six 
 and cinq-huit, yield annually about 9 to 10 million hectolitres of vinasse, at the present 
 time employed for the preparation on a large scale of cream of tartar, glycerine, and 
 tartaric acid. 
 
 5. Salts of Potassium from the Treacle or Molasses of Beet-root Sugar. Of late years, 
 the manufacture of potash salts from the vinasse left after the distillation of fermented 
 beet-root molasses has been added as a new branch of industry by M. Dubrunfaut, and 
 introduced into Germany by M. Varnhagen, in the year 1840, at Mucrena, Prussian 
 Saxony. 
 
 Beet-root, on being subjected to ignition, yields an ash containing a large percentage 
 of potash, a fact first observed in the early part of this century by M. Mathieu de 
 Dombasle, a celebrated French agriculturist, who discovered that 100 kilos, of dried 
 beet-root leaves yield 10-5 kilos, of ash, containing 5*1 kilos, of potash ; but this author's 
 idea that the leaves might be cut off and gathered for the purpose of potash manu- 
 facture proved erroneous, in so far that the growth of the roots was greatly impeded. 
 After the publication of M. Dubrunfaut's researches on this subject, in 1838, the 
 vinasse of the beet-root molasses distillation was evaporated to dryness, next calcined, 
 and the calcined mass refined for the production of potash and other salts of that base, 
 an industry which has obtained a great development, as may be judged from the fact 
 that the quantity of these materials produced on the European continent in 1865 
 amounted to 240,000 cwts. 
 
 The reader who desires details on this subject is referred to the work, On the 
 Manufacture of Beet-Root Sugar in England and Ireland, by Wm. Crookes, F.R.S., 
 <kc., p. 250 et seq. 
 
 The molasses from beet-root sugar consists, previous to fermentation and dis- 
 tillation, of the under-mentioned substances, as recorded by the several analysts whose 
 names are subjoined : 
 
 Brunner. Pricke. Lunge. Heidenpriern. 
 
 Water 15-2 ... iS'o ... 18-5 ... 19-0 197 
 
 Sugar 49-0 ... 48^0 ... 507 ... 46*9 49-8 
 
 Salts and organic substances . 35-8 ... 34^0 ... 30*8 ... 34'! 30*5 
 
 The following analyses by M. Heidenpriern exhibit the average composition of the 
 ashes of molasses : 
 
 I. 2. 3. 
 
 Potassa . . . 5172 ... 47-67 ... 50-38 
 
 Soda .... 8'do ... 1 1 '43 ... 8-29 
 
 Lime .... 5-04 ... 3-60 ... 3-12 
 
 Magnesia . . . o - i8 ... O'lo ... O'i8 
 
 Carbonic acid . . 28-90 ... 27-94 ... 28-70 
 
 The remainder of the 100 parts consists of phosphoric and silicic acids, chlorine, 
 oxide of iron, &c. The quantity of such substances amounts to 10 or 12 per cent. 
 According to Dubrunfaut, the alkalimetrical degree of the ash of beet-root sugar 
 molasses is a constant, as the ash obtained from 100 grammes of molasses neutralises on 
 an average 7 grammes of sulphuric acid (HjS0 4 ). 
 
292 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 The molasses is generally treated in the following manner : It is first diluted with 
 either water or vinasse to 8 or 11 B. = 1*056 or 1-078 sp. gr., and mixed with 0-5 to 
 i '5 per cent, of a pure mineral acid, the object of this addition being not simply the 
 neutralisation of the alkali, but also the conversion of dextrine and such unfermentable 
 sugar into fermentable sugar. Formerly, sulphuric acid was used, but upon the re- 
 commendation of M. Wurtz, hydrochloric acid is now generally employed, the 
 advantage being the formation of readily soluble chlorides, instead of comparatively 
 insoluble alkaline sulphides, by the action of the organic matter present in the molasses. 
 
 The diluted molasses is next mixed with yeast, left to ferment, and the alcohol dis- 
 tilled off; the residue is a liquid of about 4 B. density [=1-027 sp. gr.] containing 
 undecomposed yeast, ammoniacal salts, various organic substances, and all the inorganic 
 salts of the beet-root juice. The potassa is present in this liquid as nitrate chiefly, 
 although by the addition of hydrochloric acid a portion of this salt is decomposed, red 
 nitrous fumes sometimes being seen in the fermentation room. Evrard suggested that 
 the saltpetre should be separated from the beet-root molasses by evaporation, and 
 further purified by the aid of the centrifugal machine. The acidity of the vinasse is 
 neutralised by chalk, and afterwards it is evaporated to dryness in an iron vessel, the 
 total length of which is 20-3 metres, by an average width of 1-6 metre, extended at the 
 top to 2 metres, the depth being 0-34 metre. The vessel is made of stout boiler plate, 
 strengthened by stays and angle irons, and is divided into two divisions, the larger of 
 which has a length of 14-2 metres, and is the real evaporating pan, while the other is 
 used as a calcining furnace, and covered with an arch of fire-bricks o'6 metre high. 
 The fire-place is 1-3 metre wide, and the fire-box has a surface of 3-3 square metres. 
 The evaporation is effected by surface heating, that is to say, the flame and hot gases 
 from the burning fuel after passing across the fire-bridge are conducted over the 
 surface of the vinasse, the calcining pan being nearest to the fire, while the evaporating 
 pan is at its other extremity in contact with the flue or chimney. The vinasse, having 
 been run off from the still, is kept in cisterns, from which it is forced by means of a 
 pump into a reservoir so placed as to admit of the liquid running in a constant stream 
 into the evaporating pan. At a first operation both the evaporating and the 
 calcining pan are filled with vinasse, but afterwards the latter is filled regularly with 
 concentrated thick liquor, which is simply carbonised, only the organic matter being 
 destroyed. 
 
 The daily average of carbonised vinasse is about 5 to 5^ cwts. The composition of 
 that substance may be gleaned from the following approximative analysis : 
 
 Insoluble matter =23-00 per cent. 
 
 Potassium sulphate . . . . =11-07 
 
 chloride . . . . = ir6i 
 
 carbonate . . . . =31-40 
 
 Sodium . . . . = 23-26 
 
 Silica and potassium thiosulphate . . = traces 
 
 100-34 
 
 In Germany the calcined vinasse is generally sold to saltpetre manufacturers, but 
 in Belgium and France this material is calcined, lixiviated, and the salts it contains 
 separately obtained. For this purpose the vinasse is first evaporated to 38 or 40 B. 
 (1-33 to 1-35 sp. gr.), and next carbonised and calcined in a furnace constructed as 
 exhibited in Fig. 279. V is a reservoir containing the concentrated vinasse, which by 
 means of a tube is gradually run into a furnace, of which G is the fire-place, M the 
 calcination space, destined to contain the concentrated or carbonised vinasse, which is 
 evaporated to dryness and calcined in M 1 ; a door is fitted to each compartment, and at 
 P, the end of the furnace opposite to the fire-place. The air required for the caloina- 
 
SECT. III.] 
 
 POTASSIUM SALTS. 
 
 2 93 
 
 tion is admitted partly through the ash-pit, partly through the openings, B, in the 
 brickwork. The thickish liquid vinasse admitted into M 1 is constantly stirred, and, as 
 soon as it is quite dry, it is shovelled across the brickwork bridge, A', into the calcining 
 space, M, care being taken to again fill M' with concentrated vinasse. The organic 
 matter of the saline mass soon takes fire, emitting noxious fumes. The calcination is 
 greatly aided by the access of air at B, and also to some extent by the potassium 
 nitrate present. The temperature has to be regulated to prevent the salts becoming 
 fused and forming a hard compact mass, in which case the potassium sulphate would 
 be reduced to potassium sul- 
 phide, a salt which could not 2 79- 
 be removed. The calcined 
 vinasse, technically termed 
 satin, contains, when removed 
 from the surface, 10 to 25 per 
 cent, of insoluble substances, 
 viz., calcium carbonate and 
 phosphate, more or less char- 
 coal, and, in addition, 3 to 4 
 per cent, moisture ; the re- 
 mainder consists of potassium 
 and sodium carbonates, potas- 
 sium sulphate and chloride, 
 and sometimes cyanide in con- 
 siderable quantity. The relative quantities of potassa and soda are, of course, not at 
 all constant, but vary according to the soil on which the beets have grown ; it has 
 been observed in France that the molasses obtained from beets grown in the Depart- 
 ment Nord are less rich in potassa than those grown in the Departments Oise and 
 Somme. The average composition of the saline is 
 
 7 to 12 per cent, of potassium sulphate. 
 1 8 to 20 of sodium carbonate. 
 17 to 22 of potassium chloride. 
 30 to 35 of carbonate. 
 
 The complete composition of the saline may be gathered from the following tabulated 
 results : 
 
 a. 6. c. d. 
 
 . 22-20 ... 19-82 ... 17-47 ... 13-36 
 
 . 12-95 - 9-88 ... 2-55 ... 3-22 
 
 . 15-80 ... 20-59 ... 18-45 16-62 
 
 0-13 ... 0-15 ... 0-18 ... 0-21 
 
 . 25-52 ... 19-66 ... 19-22 ... 16-54 
 
 . 23-40 ... 29.90 ... 4 2 'i3 5'S 
 
 Water and insoluble matter 
 Potassium sulphate 
 chloride 
 Rubidium ,, 
 Sodium carbonate 
 Potassium 
 
 lOO'OO 
 
 lOO'OO 
 
 lOO'OO 
 
 The method of separating the soluble salts from each other invented by M. Kuhl- 
 mann is generally executed as follows : The saline mass is first broken up and granu- 
 lated by the aid of grooved iron rollers, after which it is placed in lixiviation-tanks, 
 each containing 26-4 cwts., and arranged precisely in the same manner as those in use 
 in soda works. The liquor tapped from the tanks has asp. gr. of 1-229 ( = 2 7 B.); 
 the insoluble residue is used as manure. The liquor having been collected in a large 
 reservoir, capable of containing some 210 hectolitres, is concentrated by waste heat 
 (abgangige warme) to a density of 1*26 ( = 30 B.) ; on cooling, the greater part of the 
 potassium sulphate crystallises, and is removed, care being taken to wash off the 
 adhering mother-liquor. The sulphate thus obtained contains 80 per cent, pure 
 
294 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 potassium sulphate, the rest being carbonate of potassa and organic matter ; this material 
 is converted into potash by Leblanc's process. The liquor at 30 B. is next poured into 
 evaporating- pans, each capable of containing 90 hectolitres, and concentrated by means 
 of heat and a steam pressure of 3 atmospheres ( = 45 Ibs. to the square inch) to a 
 density of 42 B. (= 1*408). By this operation a mixture of sodium carbonate and 
 potassium sulphate is separated, which frequently exhibits 30 alkalimetrical degrees * 
 the liquor is transferred from the evaporating-pans to crystallising vessels, in which it 
 is cooled down to not less than 30. If, by carelessness, the temperature should fall 
 below 30, the potassium chloride crystals become mixed with a layer of sodium car- 
 bonate. The liquor at a temperature of 30, and having a density of 42 B., is again 
 transferred to evaporating-pans each capable of containing 20 hectolitres, and evaporated 
 in winter to a sp. gr. of 1*494 ( = 48 B.), and in summer to a sp. gr. of 1*51 ( = 49 B.). 
 By this operation sodium carbonate separates, the first and purer proportions of which 
 are of 82 alkalimetrical degrees, and the last of 50 only. ' After the separation of the 
 salt, the remaining liquor is poured into small crystallising vessels, each capable of 
 holding 2^ hectolitres, and, having been left standing for some time, yields in each 
 vessel about 130 kilos, of a crystalline salt, mainly composed according to the formula 
 K 2 C0 3 + Na 8 CO 3 + i2H 8 0. The remaining mother-liquor, when evaporated to dry- 
 ness and calcined, yields a semi-refined potash, tinged with red by oxide of iron. This 
 product is again lixiviated with water, and the liquor, having been concentrated to 1*51 
 to 1*525 sp. gr. ( = 49 to 50 B.), deposits a large quantity of potassium sulphate and 
 sodium carbonate. The mother-liquor, having been again evaporated and calcined, 
 yields a potash consisting of 100 parts of 
 
 Potassium carbonate . . . , . 91 -5 
 Sodium .'.... 5*5 
 
 Potassium chloride and sulphate . . ; .- ' 3-0 
 
 The sodium carbonate possessing a strength of 80 to 85 alkalimetrical degrees is 
 refined by being washed with a very concentrated aqueous solution of sodium carbonate, 
 and thus brought to a strength of fully 90 alkalimetrical degrees. 
 
 The sulphate of potassa, chloride of potassium, and the double salt of the two 
 carbonates are purified and re-crystallised. The following analyses exhibit the com- 
 position of refined potash obtained from beet-root sugar molasses : 
 
 a. b. e. 
 
 Potassium carbonate . . . 8873 ... 94*39 ... 89*3 
 
 Sodium 6-44 tracer ... 5-6 
 
 Potassium sulphate . . . 2*27 ... 0-28 ... 2*2 
 
 chloride . . . , *roo ... 2-40 ... 1*5 
 
 iodide . . . o'O2 ... 0*11 ... 
 
 Water 1*39 ... 176 ... 
 
 Insoluble substances .. . 0*12 ... ... 
 
 a and b are from Waghausel in Baden ; c is doubly refined French potash. The 
 
 crude potash from beet-root sugar-works, a product not to be confused with salin, is 
 composed as follows : 
 
 o. b. c . d. e. 
 
 Potassium carbonate . 53*9 ... 79-0 ... y6'oo ... 43-0 .. 32-9 
 
 Sodium . . 23*1 ... 14-3 ... 16-30 ... 17-0 ... 18-5 
 
 Potassium sulphate . . 2^9 ... 3*9 ... 1-19 ... 4-7 ... 14-0 
 
 chloride . . 19-6 ... 5-8 ... 4-16 ... i8'o ... 16*0 
 
 a is a French product ; b, from Valenciennes ; c, from Paris ; d, Belgian ; e, from 
 Magdeburg, Prussia. 
 
SECT, in.] POTASSIUM SALTS. 295 
 
 With recent improvements in the manufacture of beet-sugar the production of the 
 treacle, which is not fit for human consumption, has been much reduced. Con- 
 sequently, less potash is obtained from this source. 
 
 6. Salts of Potassium from Sea-weeds. Potassa salts are obtained in large quantities 
 from various sea-weeds, as a bye-product of the manufacture of bromine and iodine. 
 The three following methods are employed for this purpose : 
 
 (a) The old calcination method, consisting in a complete reduction of the weeds to 
 ash, and the methodical lixiviation of that product, so as to obtain various salts by 
 crystallisation. 
 
 (b) The carbonisation on Stanford's method, consisting in the dry distillation of the 
 weeds to convert them into a carbonaceous mass, afterwards lixiviated, while products 
 are simultaneously obtained the sale of which considerably lessens the cost of the pre- 
 paration of the potassa salts. 
 
 (c) A third mode of treatment, that of Kemp and Wallace, consisting in boiling 
 the weeds with water, evaporating the solution, and carefully incinerating the 
 residue. 
 
 The oldest method is still the most generally employed in France, on the coasts of 
 Brittany and Lower Normandy, especially in the neighbourhood of Brest and Cher- 
 bourg, and in Scotland and Ireland. 
 
 The process is mainly conducted as follows : After drying in the air, the plants 
 are incinerated, the result of which is the formation of a black semi-fused mass, which 
 in France is termed Varech or Vraic, and in England and Scotland is known as kelp. A 
 distinction is made between the kelp obtained by the incineration of the weeds, Fucus 
 s&rratus and Fucus nodosu&, found on rocks near the sea-coast, and the kelp obtained 
 from the plant botanically known as Laminaria digitata, thrown up on the coast during 
 the storms. The latter is richer in potassa salts, but contains much less iodine ; it is 
 found plentifully on the western coasts of Scotland and Ireland, while on the eastern 
 coast of the British Isles the other weed is the chief source of kelp, having an average 
 composition of 
 
 Insoluble matters 57'OOO 
 
 Sodium sulphate io - 2O3 
 
 Potassium chloride .... I3'4?6 
 
 Sodium i6'Oi8 
 
 Iodine o - 6oo 
 
 Other salts ...... 2703 
 
 The best kelp met with in commerce is that from the island of Rathlin, the value 
 at Glasgow amounting to ^7 los. to ;io 105. per ton of 22^ cwts. ; while Galway kelp 
 is valued at only 2 or ^3 per ton, owing to the large quantity of salt it contains. 
 Twenty-two tons of moist sea-weed yield 
 
 Medium kelp i ton 
 
 Potassium chloride 5 to 6 cwts. 
 
 sulphate . . . . 3 cwts. 
 
 The Scotch mode of treating kelp is briefly the following : The material is first 
 broken into small lumps, and put in large iron cauldrons, hot water being added to 
 exhaust all the soluble matter. This operation follows the method of the manufacture 
 of soda from common salt, to be presently considered. The water is first made to act 
 upon nearly exhausted kelp, and at last with quite fresh kelp, until a liquid is pro- 
 duced marking 36 to 40 Tw. = n 8 to 1-20 sp. gr. The insoluble residue contains 
 chiefly silica, sand, calcium and magnesium carbonates, their sulphates and phosphates, 
 
:96 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 and particles of charcoal, and is used for bottle-glass manufacture. The liquor from 
 the kelp is evaporated in large cast-iron semi-globular cauldrons by the direct action 
 of a coal fire, and contains chiefly potassium chloride, a comparatively small quantity of 
 sodium chloride, potassium sulphate and chloride, some sodium carbonate, potassium 
 iodide and sulphide, and potassium and sodium dithionites. The mode of separating these 
 salts from each other is based upon their varying solubility in water, and is therefore 
 conducted by alternate evaporation and cooling. As the potassium sulphate is the 
 least soluble, it falls to the bottom of the cauldron during the first evaporation, and is 
 collected by the workmen by means of perforated ladles, and brought into the trade as 
 plate sulphate. After this salt has been collected the liquid is run into coolers, in 
 which the greater bulk of the potassium chloride crystallises ; the mother-liquor from 
 these crystals is again transferred to the evaporator, and by the continued appli- 
 cation of heat, and consequent concentration, the common salt is separated. It 
 should be borne in mind that common salt is scarcely more soluble in hot than 
 in cold water, while the solubility .of most other salts is greatly increased 
 by a higher temperature ; it is therefore possible to push the evaporation and 
 concentration to the point of incipient precipitation of the potassium chloride, the 
 common salt being then ladled out of the cauldron, and the liquid again run into 
 the coolers in order to obtain another deposit of potassium chloride, always more or 
 less contaminated with common salt. This operation is repeated four times ; the first 
 crop of potassium chloride contains from 86 to 90 per cent, of this salt, the re- 
 mainder is chiefly potassium sulphate ; the second and third crop yield a very pure salt, 
 96 to 98 per cent, of potassium chloride ; the fourth crop contains some sodium 
 sulphate mixed with the potassium chloride. The liquor left after the fourth crystal- 
 lisation having a sp. gr. = i'33 to 1-38 = 66 to 76 Tw., and containing among other 
 compounds sodium sulphate, alkaline sulphides, thiosulphates and carbonates, and 
 iodide of potassium, is not submitted to further evaporation, but, having been 
 poured into shallow vessels placed in the open air, is mixed with dilute sulphuric 
 acid, sulphuretted hydrogen and carbonic acid gases being largely evolved, while, in 
 consequence of the decomposition of the polysulphides and thiosulphates, a thick foam 
 of pure sulphur appears on the surface of the liquid. The sulphur is ladled off, and 
 after having been washed on filters and dried, is sold. Almost as soon as the evolution 
 of gas ceases, there is added to the liquid more sulphuric acid and some manganese, 
 and the mixture treated for the preparation of iodine (quod vide). 
 
 In order to guard against loss of valuable substances by volatilisation during the 
 crude and imperfect mode of incineration, it has been tried to simply carbonise the 
 weeds (Stanford's method). The weeds are first dried and strongly pressed into the 
 shape of peat blocks ; these are submitted to dry distillation in retorts arranged similarly 
 to those in gas-works. The products of the dry distillation collected in the usual 
 manner contain in 100 parts of fresh weed 
 
 68'5 to 72-5 parts of ammoniacal liquor 
 
 4'o tar 
 
 7*0 to 7 '5 carbonised weed or coke-weed 
 2'o to 2'5 illuminating gas 
 
 The coke contains 33 per cent, carbon, the remainder consisting of alkaline and 
 earthy salts ; the volatile products of the distillation are treated for parafime, photogen, 
 acetic acid, and ammoniacal salts, the gas being used for lighting purposes. Although 
 Mr. Stanford's mode of treatment is undoubtedly rational, there are difficulties in its 
 practical execution which have prevented its adoption in Scotland as well as in France. 
 The quantity of potash salts obtained from sea-weeds in the year 1865 amounted, 
 
SECT. III.] 
 
 POTASSIUM SALTS. 
 
 297 
 
 according to M. Joulain, to a total of 2,700,000 kilos., of which the United Kingdom 
 produced 1,200,000 kilos., the remainder being furnished by France. 
 
 Since the production of potassium chloride at Stassf urt and Kalucz has become so 
 extensive, that of potassa salts from sea-weeds is of little consequence. 
 
 7. Salts of Potassium from the Suint of Wool. Raw wool contains about 20 per 
 cent, of suint soluble in cold water. It consists of the potassium compounds of oleic, 
 stearic, and acetic acids with a little valerianic acid and many other organic matters, as 
 well as potassium chloride and sulphate, ammonium compounds, and generally 
 potassium carbonate or some sodium compounds. The portion of raw wool soluble in 
 carbon disulphide consists essentially of cholestearine, and a smaller proportion of iso- 
 cholestearine, partly free, but chiefly combined with fatty acids and a little benzoic acid. 
 The recent researches of Chludinsky show how these substances differ in their pro- 
 portions. He has determined both the moisture, and the quantity of matter soluble 
 in water and in carbon disulphide in average samples of the fleecas of different herds of 
 sheep. 
 
 Race and Characters of Sample. 
 
 Moisture. 
 
 Loss in 
 Water. 
 
 Loss in 
 Carbon Di- 
 sulphide. 
 
 Pure Wool. 
 
 fNegretti ram, from Konska-Wola . 
 
 1 5 '42 
 
 47-28 
 
 21 '6l 
 
 15-69 
 
 H ii i> 
 
 1172 
 
 5473 
 
 I3-33 
 
 2O '22 
 
 Merino -\ Negretti sheep . 
 
 11-81 
 
 44-54 
 
 26-IO 
 
 I7-55 
 
 1 Australian ram ..... 
 
 i3' 2 3 
 
 33'57 
 
 I3-24 
 
 39-96 
 
 iRambouillet ram, from Karlow 
 
 ii '45 
 
 46-95 
 
 I4-83 
 
 26-77 
 
 Southdown, from Poland 
 
 8-18 
 
 62-41 
 
 4-61 
 
 24-30 
 
 Do. from England ...... 
 
 11-90 
 
 39-21 
 
 973 
 
 39T6 
 
 Oxfordshire sheep, from Poland .... 
 
 10-86 
 
 41-27 
 
 4-83 
 
 43 '04 
 
 
 8 '04 
 
 JI-O2 
 
 8-25 
 
 ?2'6q 
 
 
 i?'8i 
 
 J* w** 
 
 2TI4 
 
 " j 
 
 o'Q$ 
 
 O -7 
 
 58-08 
 
 
 J J 
 
 11-87 
 
 2 *t 
 16*10 
 
 s j 
 
 4'QI 
 
 j 
 67*12 
 
 Black wool, from Podolia 
 
 1 1 <_/ 
 
 1 2 '2 J 
 
 5-66 
 
 *T J7* 
 
 1-82 
 
 80-29 
 
 ,, Kijew Government . 
 
 "59 
 
 3-6r 
 
 0-88 
 
 83-92 
 
 ,, Wolhynia Government 
 
 10 - 6o 
 
 6-35 
 
 2'45 
 
 80-60 
 
 White wool, from Radom Government 
 
 10-70 
 
 7-40 
 
 0-65 
 
 81-21 
 
 Maumene and Rogelet took out an English patent for obtaining potash from wool, 
 and showed the first specimens of this new product at the London Exhibition of 1862. 
 The raw wool compressed in casks was extracted with cold water, the liquid obtained, 
 of the sp. gr. i'oi, was concentrated, the brown residue, "potassium suintate," was 
 ignited in retorts to yield lighting-gas, and the residual carbonaceous matter yielded a 
 pure potash on lixiviation. The treatment of suint was introduced into Germany by 
 
 Fig. 280. 
 
 F. Hartmann, and there are now works for this purpose at Doehren, Bremen, &c. 
 In France there are many such establishments at Roubaix, Rheims, EHxeuf , &c. ; and 
 at Liege, Yerviers, and Antwerp in Belgium. The evaporation of the lyes is conducted 
 in Germany and Belgium in reverberatories. At Doehren, the liquors from the 
 ext tion of the wool are pumped into an iron tank A (Fig. 280), where they undergo 
 
SQ 8 CHEMICAL TECHNOLOGY. [SECT. 111. 
 
 a preliminary heating from the combustion of the escaping gases, and are then 
 pumped into the evaporator, E. The condensed residues are next removed into 
 the calcining space, C. As soon as they have been thoroughly dried by the flames 
 coming from the fire-box, x, the fatty matter, dirt, &c., burn, giving off con- 
 siderable heat, so that, by regulating the access of air, it is possible to evaporate 12 
 kilos, of liquid, with i kilo, of coal. The fire-box, the calcining space, and the evaporator 
 are built of fire-proof tiles or stones, and the chimney, n, is constructed of fire-bricks. 
 The crude potash contained 
 
 Soluble salts . ' . .";"' '" 92 '05 per cent. 
 
 Insoluble salts 4'9 2 
 
 Organic matter 3'3 
 
 The soluble salts had the following composition 
 
 Potassium carbonate 85 -34 per cent. 
 
 chloride 6*15 
 
 sulphate 2 '98 
 
 Sodium carbonate . . . . . 5' 2 
 
 A part of the impurities is derived from the river water used for lixiviation. 
 W. Graff, of Lesum, in 1878, worked up the crude potash from six wool washeries to 
 pure potassium carbonate, bicarbonate, chloride, and sulphate. 
 
 We"rotte, of Yerviers, found, in 1873, in two samples of potash from suint 
 
 Potassium carbonate . . 68-50 per cent. ... 64-30 per cent. 
 sulphate . .2-10 ... 2-49 
 
 silicate . . . 8*50 
 chloride . . 12-50 
 Sodium carbonate . . .3-20 
 Water . . ' '-. . . 2-77 
 Insoluble . . . .1-48 
 Loss ..... 0-95 
 
 8-00 
 
 16-88 
 
 3-10 
 
 2-80 
 
 i '55 
 0-88 
 
 Altogether about 1000 tons of potash are obtained from suint every year. 
 
 Pure potassium carbonate as it is met with in laboratories was formerly obtained 
 by igniting tartar, or a mixture of tartar and saltpetre, or by calcining potassium 
 acetate. At present it is produced by the cautious ignition of a mixture of potash 
 saltpetre with an excess of charcoal, by igniting potassium bicarbonate, or by precipi- 
 tating a solution of potassium chloride with ammonium dicarbonate in presence of 
 alcohol. In England potassium carbonate is made industrially for the manufacture of 
 flint-glass, which owes its freedom from colour not merely to the use of lead-glass, but 
 also to the employment of quite pure materials. The pure crystalline potassium 
 carbonate, containing 16 to 18 per cent, of moisture (corresponding approximately to 
 the formula, 4K 2 C0 3 .7H 2 0), is met with in the form of small cubes. The raw material 
 is the American pearl-ash, which is melted in a furnace of the construction of a 
 common side-furnace, with the addition of sawdust in order to convert the potassium 
 hydroxide and sulphide into carbonate. The melted ash is dissolved, the solution let 
 settle, drawn off clear from the sediment, and evaporated down in a reverberatory, 
 when the mass appears as a blackish-grey powder. It is again dissolved, the solution 
 clarified by standing, and evaporated to dryness in a third reverberatory, when the 
 product is white. It is now dissolved for the third time, evaporated until all the 
 potassium sulphate has crystallised out, and the mother-liquor is again evaporated 
 until on cooling it, forms a crystalline mass with the above-named proportion of 
 water. 
 
SUCT. III.] 
 
 POTASSIUM SALTS. 
 
 299 
 
 Table of the Proportion of Potash in Lyes according to Specific Gravity at 15' 
 
 Specific 
 Gravity. 
 
 Baurne. 
 
 Twaddell. 
 
 Per cent. 
 K 3 C0 3 . 
 
 i cubic metre 
 contains 
 kilos, of 
 K 2 C0 3 . 
 
 Specific 
 Gravity. 
 
 Ban me. 
 
 Twaddell. 
 
 Per cent. 
 K 2 CO 3 . 
 
 i cubic metre 
 contains 
 kilos, of 
 K 2 C0 3 . 
 
 I -014 
 
 2 
 
 2-8 
 
 n 
 
 15 
 
 1-241 
 
 28 
 
 48-2 
 
 24-5 
 
 34 
 
 I '029 
 
 4 
 
 5-8 
 
 3-1 
 
 32 
 
 1-263 
 
 30 
 
 52-6 
 
 26-6 
 
 336 
 
 '045 
 
 6 
 
 9-0 
 
 4-9 
 
 51 
 
 1-285 
 
 32 
 
 57'0 
 
 28-5 
 
 366 
 
 060 
 
 8 
 
 12 -O 
 
 6-5 
 
 6 9 
 
 I-308 
 
 34 
 
 6l'6 
 
 37 
 
 402 
 
 075 
 
 10 
 
 IS'O 
 
 8-1 
 
 87 
 
 1-332 
 
 36 
 
 66-4 
 
 327 
 
 436 
 
 091 
 
 12 
 
 I9'2 
 
 9-8 
 
 107 
 
 1-357 
 
 38 
 
 71-4 
 
 34-8 
 
 472 
 
 108 
 
 14 
 
 21 '6 
 
 ii -6 
 
 129 
 
 I-383 
 
 40 
 
 76-6 
 
 37 -o 
 
 SI2 
 
 125 
 
 16 
 
 25-0 
 
 I3-3 
 
 ISO 
 
 1-410 
 
 42 
 
 82-0 
 
 39-3 
 
 554 
 
 142 
 
 18 
 
 28-4 
 
 15-0 
 
 171 
 
 438 
 
 44 
 
 87-6 
 
 41-7 
 
 600 
 
 162 
 
 20 
 
 32-4 
 
 17-0 
 
 198 
 
 468 
 
 46 
 
 93'6 
 
 44 -o 
 
 646 
 
 180 
 
 22 
 
 36-0 
 
 18-8 
 
 222 
 
 498 
 
 48 
 
 99-6 
 
 46-5 
 
 697 
 
 200 
 
 24 
 
 40 - o 
 
 207 
 
 248 
 
 530 
 
 50 
 
 io6 - o 
 
 48-9 
 
 748 
 
 220 
 
 26 
 
 44 -o 
 
 22-5 
 
 275 
 
 563 
 
 52 
 
 II2-O 
 
 SI'S 
 
 802 
 
 Caustic potash (potassium hydrate, KOH) is at present obtained on the large scale. 
 The chief method consists in lixiviating potassium carbonate (as obtained from potassium 
 chloride by the Leblanc process) in the state of crude potash (i.e., mixed with calcium 
 sulphate and hydrate as it comes from the calcining furnace) with water and causticising 
 by treatment with lime. It is more advantageous i.e., an economy of time and 
 materials if the coal added to the mixture of potassium sulphate and limestone is used 
 in a larger proportion, if the smelting is protracted, and if the crude potash obtained is 
 at once lixiviated with water at 50. Thereby the subsequent causticising with lime is 
 avoided. The lye is evaporated to dryness in pans, scooping out the foreign salts as 
 they separate. 
 
 Table of the Specific Gravity of Potash Lye at 15. 
 
 Specific 
 Grevity. 
 
 Baume. 
 
 Twaddell. 
 
 ioo parts 
 contain 
 KOH. 
 
 i cubic metre 
 contains 
 kilos. KOH. 
 
 Specific 
 Gravity. 
 
 Baumd. 
 
 Twaddell. 
 
 ioo parts 
 contain 
 KOH. 
 
 i cubic metre 
 contains 
 kilos. KOH 
 
 014 
 
 2* 
 
 2-8 
 
 17 
 
 17 
 
 I '220 
 
 26 
 
 44-0 
 
 24-2 
 
 295 
 
 029 
 
 4 
 
 5-8 
 
 3'5 
 
 36 
 
 1-241 
 
 28 
 
 48-2 
 
 26'! 
 
 324 
 
 045 
 
 6 
 
 9-0 
 
 5'6 
 
 58 
 
 1-263 
 
 30 
 
 52-6 
 
 28-0 
 
 353 
 
 060 
 
 8 
 
 12 -O 
 
 7-4 
 
 78 
 
 1-285 
 
 32 
 
 57' 
 
 29-8 
 
 385 
 
 075 
 
 10 
 
 IS-0 
 
 9-2 
 
 99 
 
 1-308 
 
 34 
 
 61-6 
 
 31-8 
 
 416 
 
 091 
 
 12 
 
 18-2 
 
 10-9 
 
 119 
 
 I-332 
 
 36 
 
 66-4 
 
 337 
 
 449 
 
 108 
 
 H 
 
 21-6 
 
 12-9 
 
 143 
 
 1-357 
 
 38 
 
 71-4 
 
 35'9 
 
 487 
 
 125 
 
 16 
 
 25-0 
 
 14-8 
 
 167 
 
 I-383 
 
 40 
 
 76-6 
 
 37-8 
 
 522 
 
 142 
 
 18 
 
 28-4 
 
 16-5 
 
 1 88 
 
 I'4IO 
 
 42 
 
 82-0 
 
 39*9 
 
 563 
 
 162 
 
 20 
 
 32-4 
 
 28-6 
 
 216 
 
 I-438 
 
 44 
 
 87-6 
 
 42-1 
 
 605 
 
 180 
 
 22 
 
 36-0 
 
 20-5 
 
 242 
 
 1.468 
 
 46 
 
 93'6 
 
 44-6 
 
 655 
 
 .200 
 
 24 
 
 40-0 
 
 22-4 
 
 269 
 
 1-498 
 
 48 
 
 99-6 
 
 47 'i 
 
 706 
 
 Statistics. The yearly production of potash according to H. Griineberg is 
 
 Wood-ashes. Russia, Canada, U.S. of North America, Hungary, and 
 
 Galicia ............ 20,000 tons 
 
 Beet-sugar ash. France, Belgium, Germany 12,000 
 
 Mineral potash. Germany, France, England 15,000 
 
 Suint. Germany, France, Belgium, Austria 1,000 
 
 48,000 
 
 These conditions differ strikingly from those which existed thirty years ago, when 
 wood-ash was in exclusive use and Russian potash ruled the market. The potash ex- 
 tracted from wood-ashes scarcely amounts to one-half of the total production ; it 
 decreases year by year, and the time when it will disappear from the market seems 
 within measurable distance. It is being superseded by beet potash, which is a bye- 
 product of the beet-sugar manufacture, and hence can be offered at lower prices. Of 
 
3 oo CHEMICAL TECHNOLOGY. [SECT. m. 
 
 greater importance is the manufacture of potash from potassium sulphate, based on the 
 resources of the Stassfurt salt-beds. The centre of production of beet potash is in the 
 north of France, that of mineral potash in Northern Germany, which is now the 
 greatest potash-producing country in the world.* 
 
 Alkalimetry. Commercial potash is commonly a mixture of caustic potash with 
 potassium carbonate and other potassium and sodium salts (as soda itself is a mixture 
 of sodium carbonate with foreign salts, especially sulphate and chloride). In order 
 easily and quickly to ascertain the proportion of pure potassium carbonate in a sample 
 of potash with an accuracy sufficient for technical purposes there are two methods, 
 namely 
 
 (a) To determine the quantity of acid required to neutralise the potassium 
 carbonate ; 
 
 (6) To find the quantity of carbonic acid which can be expelled from potash by the 
 addition of a stronger acid. 
 
 Both methods, of course, are applicable only if besides the alkaline carbonate no 
 other carbonates are present in the potash. All procedures for determining the 
 potassium carbonate in a sample of potash are called potassimetric methods. The 
 methods of testing potash and soda (sodametric) are included under the common name 
 alkalimetric. 
 
 As a normal solution Mohr uses crystalline oxalic acid (CjH 2 4 .2H 2 O= 126) ; 63 
 grammes oxalic acid ( = \ mol.) are dissolved in water and made up exactly to \ litre. 
 To this acid solution there corresponds a second, a solution of caustic potassa (KOH). 
 It is so adjusted that on mixture with an equal volume of the oxalic acid solution the 
 last drop of the potassium solution turns the colour of the litmus solution added from 
 red to blue which can always be effected by a single drop if the solution is free from 
 carbonic acid. For testing alkali -fa mol. in grammes of the anhydrous ignited sample is 
 weighed off, containing, therefore, 6-911 grammes potash or 5-32 soda. As the standard 
 acid contains in 1000 c.c. \ mol. oxalic acid, 100 c.c. of this liquid will saturate 
 exactly ^ mol. of the alkali. The potash along with a solution of litmus is placed 
 in a small boiling flask and a little of the acid is run in, which decomposes the potash 
 with effervescence. The colour passes from blue to violet and the effervescence 
 becomes slighter. The liquid is raised to a boil and more acid is dropped in until the 
 colour becomes a full onion-red. Test acid is then run in excess. The alkali is now 
 super-saturated, and the carbonic acid is expelled by boiling. The point of saturation 
 of the alkali is now overstepped 5 or 6 c.c. A pipette graduated in ^ c .c. is filled 
 up to o with the standard caustic potash, and it is allowed to fall drop by drop into the 
 liquid solution of the sample under examination, keeping it agitated. The colour passes 
 from red to violet and then suddenly into a clear blue. The number of c.c. of the 
 alkaline solution consumed is read off, and deducted from the c.c. of test acid consumed ; 
 the remainder shows pure potassium carbonate 3-45 grammes = ^ mo), potash used, 
 e.g., 36 c.c. of test acid and 3 c.c. of test alkali = 33 c.c. of test acid = 66 per cent, of 
 potassium carbonate (as instead of ^ mol. only -^ mol. was used, whence the c.c. of 
 the acid must be doubled to obtain per cents.). Latterly, instead of litmus, cyanine, 
 fluoresceine, phenolphthaleine, tropaeoleine ooo, and phenacetaline have been proposed 
 for alkalimetric and acidimetric indicators. 
 
 Fresenius and Will decompose potash with sulphuric acid and determine the 
 amount of carbonic acid by the loss of weight. 
 
 Commercial Value. As potash is very hygroscopic, in order to determine its 
 commercial value it is by no means sufficient to state how much potassium carbonate is 
 
 * It must not be forgotten that beet potash can be continually obtained only by either gradually 
 exhausting the soil of a necessary constituent of plant-food, or by continually using potash manure. 
 Hence the beet-potash industry could not exist alone. 
 
SECT, m.] POTASSIUM SALTS. 301 
 
 present ; this statement must be referred to anhydrous potash, and we must know how 
 much water is present. In order to ascertain the quantity of water, a weighed 
 quantity of the sample, e.g., 10 grammes, is heated until all water is expelled, for 
 which five minutes are generally sufficient. The loss of weight expressed in decigrammes 
 shows the amount of water per cent. Of the potash thus dried, 6*23 grammes are 
 weighed out and treated as above. As 6^29 grammes potash and 4*84 grammes soda, if 
 they were pure carbonates, would exactly contain 2 grammes carbonic acid, every 2 centi- 
 grammes of loss signify i per cent, of carbonate. If the loss of weight of the apparatus 
 on testing a potash was 1*64 (= 164 centigrammes) the potash would contain i| = 
 82 per cent, of potassium carbonate. 
 
 According to H. Will and R. Fresenius, the statement of the percentage of potash 
 should refer to the anhydrous condition. This percentage is expressed by the constant 
 numerator of a fraction, whilst the varying proportion of water is shown by a varying 
 denominator. If, e.g., we wish to express that a potash in its anhydrous condition 
 contains 60 per cent, potassium carbonate, we should write -j- 6 ^ ; if the sample absorbed 
 so much moisture that 100 kilos, increased in weight to 105 or 109, we should write 
 TS or TtrV- According to this system, the price of the product would be fixed by the 
 manufacturer in its anhydrous state, and the contents of the article would be designated 
 by a fraction in such a manner that the numerator shows the proportion of potassium 
 carbonate, whilst the denominator 100 shows the absence of water. For instance, 
 potash at T ^ is worth, say, 305. The denominator augmented by the increase of 
 water informs the buyer then how much of the hydrated article should be supplied 
 for the same price. Thus 106 or 109 kilos, of the damp potash ought to be supplied 
 at 305. 
 
 The proportion of soda is generally expressed in " degrees." The French degrees 
 are per cents, of sodium carbonate, whilst the English degrees are sodium oxide (caustic 
 soda, Na 2 0). As sodium carbonate consists of 58-6 parts soda and 41-4 parts carbonic 
 acid in 100 parts, 
 
 80 French = 46-9 English 
 
 86 = 50-5 
 
 96 = 52-8 
 
 G. Lunge (Dingler's Journal) points out that the degrees used in the English soda 
 trade only exceptionally show the percentage "real soda," Na 2 0, as the molecular 
 weight of sodium carbonate is taken at 54 instead of 53. Chemically pure sodium 
 carbonate is consequently made to show 59^26 Na 2 instead of 58*49 per cent, (i.e., 
 077 per cent, too much). In Lancashire they go still further, and put for 53 Na 2 0, 
 54 "real soda," e.g., 51 '6 per cent, instead of 50 per cent. Even with this the trade 
 was not satisfied, for on checking the results of certain Liverpool commercial chemists 
 the returns, especially for caustic soda, were often found 2 to 3 too high. A soda of 
 58, " Liverpool test," corresponds, therefore, not, as it ought, to 99-16 per cent. Na,C0 3 , 
 but to scarcely more than 96 per cent. 
 
 The processes for the determination of alkali given above have grave defec j .o, as 
 they overlook soda contained in samples of potash and treat summarily the quantities of 
 potassium salts. For the technicist they differ considerably in value ; the carbonate is 
 worth more than the chloride and the latter less than the sulphate. A complete 
 analysis is necessary for ascertaining the value of potassium salts. 
 
302 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 COMMON SALT AND SALT WORKS. 
 Occurrence. Common salt, or chloride of sodium, consists of 
 
 Chlorine, Cl . . . . 35*5 ... 60*41 
 Sodium, Na . . . . 23-0 ... 39-59 
 
 58*5 ... loo'oo 
 
 and is found on our globe in the solid state as rock-salt, as well as dissolved in sea- water 
 in enormously large quantities. It occurs as rock-salt in extensive layers, alternating with 
 strata of clay and gypsum, at an average depth of 100 metres. The following are a few 
 of the localities where rock-salt is met with in the tertiary formation : Wieliczka, 
 Poland ; the northern slopes of the Carpathian mountains, and in several districts of 
 Hungary ; in the chalk formation of Cardona, Spain ; in the Eastern Alps, Bavaria, 
 Salzburg, Styria, and the Tyrol. Among the trias formation are the salt deposits of 
 the Teutoburg-wood, Germany, and a great many others, among them the celebrated 
 Stassfurt deposits. In England, rock-salt is found in Cheshire, this county being also 
 plentifully supplied with saline springs, the water of which yields on evaporation an 
 abundance of salt. Petroleum wells are found with salt in many parts of Asiatic 
 Russia, in Syria, Persia, and the slopes of the Himalayas. Salt occurs plentifully in 
 several districts of Africa, America, and other parts of the world, and mixed with clay 
 and marl, forming salt-clay. Salt occurs secondarily by having been dissolved, at a 
 depth varying in Germany from 91 to 555 metres, by water, which carries it again to 
 the surface, there forming salt springs and salt lakes, from which the salt is obtained 
 by evaporation. Among the salt lakes may be noticed the lake near Eisleben, 
 Germany ; the Elton Lake near the Wolga, Russia ; the Dead Sea ; and the Salt Lake of 
 Utah, United States. 
 
 There can be no doubt that the common salt met with in salt springs owes its origin 
 to the solvent action of water upon rock-salt ; and as rock-salt is largely met with in 
 sedimentary geological formations, the prevalence of this formation in Germany has 
 there given rise to a large number of salt springs. Common salt is also found in sea- 
 water, and if obtained by its evaporation is often termed sea-salt ; or if deposited, as is 
 the case in the Polar regions, by intense cold on the surface of ice-fields, it is known as 
 rassol. Common salt is largely obtained as a bye-product of some chemical operations, 
 as in the conversion of sodium-nitrate into potassium-nitrate by the aid of potassium 
 chloride. 
 
 Method of Preparing Common Salt from Sea Water. The constituent salts of 
 sea- water do not differ in any part of the world ; even the difference in quantity is very 
 small, and is generally due to local causes, as the dilution of the sea-water by river- 
 water, melting icebergs, &c. The specific gravity of sea- water, at 17, varies from 
 1-0269 to 1-0289, the specific gravity of the water of the Red Sea being as high as 
 1-0306. One hundred parts of sea- water contain 
 
 Pacific Atlantic German Wo A Con 
 
 Ocean. Ocean. Ocean. sea< 
 
 Sodium chloride . . . 2.5877 ... 27558 ... 2-5513 ... 3-030 
 
 bromide . . 0-0401 ... 0-0326 ... 0-0373 ... 0-064 
 
 Potassium sulphate . . 0-1359 ... 0-1715 ... 0-1529 ... 0-295 
 
 Calcium sulphate . . 0-1622 ... 0-2046 ... 0-1622 ... 0-179 
 
 Magnesium sulphate . . 0-1104 0-0614 ... 0-0706 ... 0-274 
 
 chloride . . 0-4345 ... 0.3260 ... 0-4641 ... 0-404 
 
 Potassium _ _ _ o . 288 
 
 3-4708 ... 3-5519 ... 3-4384 ... 4-534 
 
 The composition of the salt contained in the water of the several seas is shown by 
 the following table : 
 
SECT. III.] 
 
 COMMON SALT AND SALT WORKS. 
 
 33 
 
 
 Caspian 
 Sea. 
 
 Black Sea. 
 
 Baltic.* 
 
 English 
 Channel. 
 Average 
 of 7 locali- 
 ties. 
 
 Mediterra- 
 nean. 
 Average 
 of 3 locali- 
 ties. 
 
 Atlantic 
 Ocean. 
 Average of 
 3 locali- 
 ties. 
 
 Dead Sea. 
 Average of 
 5 locali- 
 ties. 
 
 
 Average quantity of salt 
 
 
 
 
 
 
 
 
 and water 
 
 
 
 
 
 
 
 
 Solid salt 
 
 0-63 
 
 177 
 
 177 
 
 3'3i 
 
 3*37 
 
 3^3 
 
 22-30 
 
 Water .... 
 
 99-37 
 
 98-23 
 
 98-23 
 
 96-69 
 
 96-63 
 
 96-37 
 
 7770 
 
 The dissolved solid matter 
 
 
 
 
 
 
 
 
 consists in 100 parts of 
 
 
 
 
 
 
 
 
 Sodium chloride 
 
 58-25 
 
 79-39 
 
 84-70 
 
 78-04 
 
 77-07 
 
 77-03 
 
 36-S5 
 
 Potassium . . 
 
 I'27 
 
 1-07 
 
 
 
 2-09 
 
 2-48 
 
 3^9 
 
 4-57 
 
 Calcium . 
 
 
 
 
 
 
 0'20 
 
 
 
 
 II-38 
 
 Magnesium 
 
 lO'OO 
 
 7^58 
 
 973 
 
 8-81 
 
 876 
 
 7-86 
 
 45-20 
 
 Sodium and magne- { 
 sium bromides . | 
 
 
 
 0-03 
 
 
 
 0-28 
 
 0-49 
 
 1-30 
 
 0-85 
 
 Calcium sulphate 
 
 778 
 
 0-60 
 
 0-13 
 
 3-82 
 
 276 
 
 4^3 
 
 0'45 
 
 Magnesium ,, 
 
 19-68 
 
 8-32 
 
 4-96 
 
 6-58 
 
 8-34 
 
 5- 2 9 
 
 
 Calcium and magne- ) 
 sium carbonates j 
 
 3 '02 
 
 3-21 
 
 0-48 
 
 0-18 
 
 O'lO 
 
 
 
 
 Nitrogenous and bi- ) 
 
 
 
 
 
 
 
 If\f\ 
 
 tuminous matter J 
 
 
 
 
 
 
 
 MU 
 
 One cubic metre (35*3165 cubic feet) of sea-water contains consequently about 28 
 to 31 kilos, of sodium chloride and 5 to 6 kilos, of potassium chloride. Sodium chloride 
 (common salt) is obtained from sea-water : 
 
 a. By the evaporation of the water by the aid of the sun's heat. 
 
 b. In winter, by freezing. 
 
 c. By artifical evaporation. 
 
 Method of Obtaining Common Salt in Salines. This method of obtaining 
 common salt from sea-water is limited to certain of the coast-lines of Southern Europe, 
 and is never effected beyond 48 N. latitude. The countries best situated for this in- 
 dustry are France, Portugal, Spain, and the coasts of the Mediterranean. The 
 arrangement of the salines, or salt-gardens, is the following : On a level sea-shore is 
 constructed a large reservoir, which, by a short canal, communicates with the sea, care 
 being taken to afford protection against the inroads of high tides. The depth of water 
 in these reservoirs varies from 0*3 metre to 2 metres. The sea-water is kept in the 
 reservoir until the suspended matter has been deposited, and is then conveyed by a 
 wooden channel into smaller reservoirs, from which it is conducted by underground 
 pipes to ditches surrounding the salines, where the salt is separated from the water. 
 The salt is collected, placed in heaps on the narrow strips of land which separate the 
 ditches from each other, and sheltered from rain by a covering of straw. As these 
 heaps are left for some time, the deliquescent magnesium and calcium chlorides are 
 absorbed in the soil ; consequently, the salt is comparatively pure. The mother-liquor 
 is used in the production of potassium chloride, sodium sulphate, and magnesium salts, 
 the process employed being that originally suggested by Professor Balard, and after- 
 wards improved by Merle. 
 
 By Freezing. This process is based upon the fact that when a solution of common 
 salt is cooled to several degrees below the freezing-point, it is split up into pure water, 
 which freezes, and a strong brine. The solution becomes more concentrated by 
 repeated freezing and removal of the ice, until at last a solution is obtained which 
 by a slight evaporation yields a crop of salt. In order to render the product purer, 
 some lime is added to the solution before evaporation to decompose the magnesia 
 salts. 
 
 * According to the experiments of Baron Sass, the water of the Baltic from the Great Sound 
 between the Islands of Oesel and Moon only contains 0*666 per cent, of solid matter, and is of a 
 sp. gr. = 1-00474. 
 
3 o 4 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 By Artificial Evaporation. Common salt evaporated from sea-water by the aid of 
 fuel, or sel ignifere, is chiefly prepared in Normandy, in the following manner : The 
 sand impregnated with salt is employed to saturate the sea-water, which is next 
 evaporated. Very frequently an embankment of sand is thrown up on the shore, so as 
 to be covered at high tides only ; in the interval between two tides a portion of the salt 
 dries with the sand, which in hot summer weather is collected twice or three times 
 daily. The sand is lixiviated in wooden boxes, the bottoms of which are constructed 
 of loose planks covered with layers of straw ; the sand having been put in the boxes, 
 sea-water is allowed to percolate through them till the specific gravity of the water in- 
 creases to i 1 4 or to i 1 7 , the density being observed by means of three wax balls weighted 
 with lead. The salt boilers at Avranchin consider that a solution of brine of ri6 sp. 
 gr. is the most suitable for evaporation. The evaporation is carried on in leaden pans, 
 and during the process the scum is removed and fresh brine added until the salt begins 
 to crystallise out, when again a small quantity of brine is added to produce more scum, 
 which is at once removed, and the evaporation continued to dryness. The salt thus 
 obtained, a finely divided but very impure material, is put into a conical basket sus- 
 pended over the evaporating pan, the object being to remove by the action of the steam 
 the deliquescent calcium and magnesium chlorides. The salt is next transferred to a 
 warehouse, the floor of which is constructed of dry, well-rammed, exhausted sand, and 
 here it is gradually purified by the loss of deliquescent salts, the consequent decrease 
 in weight amounting to 20 to 28 per cent. 700 to 800 litres of brine yield, according 
 to the quantity of salt contained in the sand, 150 to 250 kilos, of salt. A very similar 
 method is in use at Ulverstone, Lancashire. 
 
 At Lymington and in the Isle of Wight, sea-water is concentrated by spontaneous 
 evaporation to one-sixth of its original bulk, the brine being then evaporated by the 
 aid of artificial heat. In the neighbourhood of Liverpool, salt is obtained by employing 
 sea-water in refining crude rock-salt ; in this way at least 2-3 per cent, of common salt 
 results as a bye-product. During a continuation of hot summer weather salt is de- 
 posited from the water of many of the salt lakes in immense quantities, amounting, 
 for instance, at the Elton Lake, Russia, to twenty millions of kilos. 
 
 Rock-salt. This mineral is frequently accompanied by anhydrite, clay, and marl, 
 and is sometimes found in what are termed pockets of irregular shape, interspersed 
 with clay. Again, in some cases saline deposits are separated by layers of marl. 
 With rock-salt other minerals sometimes occur, as, for instance, brongniartine 
 (Na,S0 4 + CaS0 4 ), near Villarubia, in Spain, and the remarkable minerals of the salt 
 deposit near Stassfurt. Above the latter deposit is a layer, 65 metres thick, of bitter, 
 many-coloured, deliquescent salts, consisting of 55 per cent, of carnallite, sylvin, and 
 kainite; 25 per cent, of common salt; 16 per cent, of kieserite ; and 4 per cent, of 
 magnesium chloride. As this saline layer contains 12 per cent, of potassa, it is an 
 important deposit in an industrial sense. 
 
 The composition of rock-salt is as follows': 
 
 I. White rock-salt from Wieliczka ; II. White, and III. Yellow rock-salt from 
 Berchtesgaden ; IV. From Hall in the Tyrol ; V. Detonating salt from Hallstadt ; VI. 
 From Schw'abischhall. 
 
 I. II. in. iv. v. vi. 
 
 Sodium chloride . . loo'oo ... 99-85 ... 99-93 ... 99-43 ... 98-14 ... 99-63 
 Potassium . '.. . ... ... ... ... traces ... 0-09 
 Calcium . . ... traces ... ... 0-25 ... ... 0*28 
 
 Magnesium . . traces ... 0*15 ... 0-07 ... o'i2 , ... 
 
 Calcium sulphate . ... ... 0-20 1-86 
 
 lOO'OO lOO'OO lOO'OO ICO'OO lOO'OO ICO'OO 
 
 The so-called detonating salt, found at Wieliczka in crystalline-granular masses, has 
 
SECT. Ill,] 
 
 COMMON SALT AND SALT WORKS. 
 
 305 
 
 the property when being dissolved in water of giving rise to slight detonations, accom- 
 panied by an evolution of hydrocarbon gas from microscopically small cells, the walls of 
 which, becoming thin when the salt is dissolved in water, give way, and cause the 
 report. If the solution of the salt takes place naturally in the mine, the gas partlv 
 escapes, and partly becomes condensed, forming petroleum, often met with in beds of 
 rock-salt. The minerals of the salt deposit of Stassfurt are, according to MM. Bischof, 
 Reichardt, Zincke, and others, the following : 
 
 
 Chemical Formula. 
 
 In ioo parts are contained : 
 
 Sp. gr. of 
 the com- 
 pound. 
 
 ioo parts of 
 water dissolve 
 at 18 C. 
 
 Synonyms and 
 Observations. 
 
 
 Anhydrite . 
 
 CaS0 4 . 
 
 loo of Sulphate of lime 
 
 2-968 
 
 O'2O 
 
 Karstenite 
 
 
 f 
 
 26 82 Magnesia ] 
 
 
 
 
 Boracite 
 
 B, B 30 C] 2 Mg, 
 
 65^57 Boric acid 
 io~6i Magnesium chlo- F 
 
 2'9 
 
 f Almost ) 
 \ insoluble j 
 
 Stassfurtite 
 
 
 ( 
 
 ride J 
 
 
 
 
 
 ( 
 
 2676 Chloride of potas-K 
 
 
 
 
 Carnallite 
 
 1 KMgCl 3 
 + 6H,0 
 
 sium 
 34-50 Magnesium chlo- 1 
 ride 
 
 1-618 
 
 64*5 
 
 f Contains 
 1 Bromine 
 
 
 ( 
 
 3874 Water 
 
 
 
 
 Red oxide of 
 iron 
 
 Fe 2 s . . 
 
 ioo of Oxide of iron 
 
 3'35 
 
 Insoluble 
 
 
 
 Kieserite 
 
 JMgS0 4 + 
 1 H O* 
 
 87*10 Sulphate of mag- ] 
 nesia 
 
 2-517 
 
 40-9 
 
 Martinsite ? 
 
 
 ^ tlyU* 
 
 1 2 -90 Water j 
 
 
 
 
 
 ( 
 
 45'i8 Sulphate of lime \ 
 
 
 
 
 
 2CaS0 4 
 
 19-93 Sulphate of mag- 
 
 
 ( Is decom- \ 
 
 
 Polyhalite . 
 
 ! MgS0 4 
 1 K 2 S0 4 
 
 nesia 
 28*90 Sulphate of po- f 
 
 2-720 
 
 j posed while 
 j being dis- 
 
 
 
 
 j 2H 2 
 
 tassa 
 
 
 ( solved ) 
 
 
 
 
 5 -99 Water J 
 
 
 
 
 Rock-salt 
 
 NaCl . 
 
 ioo Chloride of sodium 
 
 2 '2OO 
 
 36-2 
 
 
 
 Sylvin . 
 
 | KC1. 
 
 ioo Chloride of potas- 
 sium J 
 
 2-O25 
 
 34'5 
 
 
 
 
 
 2 1 '50 Chloride of cal- 
 
 
 
 
 
 CaCl 2 
 
 cium 
 
 
 
 
 Tachhydrite . 
 
 - 2MgCL, 
 
 36-98 Chloride of mag- 
 
 I-67I 
 
 160-3 
 
 
 
 
 I2H 2 
 
 nesium 
 
 
 
 
 
 
 41 '52 Water 
 
 
 
 
 
 
 36-34 Sulphate of po- > 
 
 
 
 
 Kainite . 
 
 K,S0 4 
 MgS0 4 
 MgC) 2 
 6H 2 O 
 
 tassa 1 
 25-24 Sulphate of mag- 
 nesia 
 1 8 -95 Magnesium chlo- 
 ride 
 
 
 
 
 
 f Contains 
 { Bromine 
 
 
 
 19-47 Water 
 
 
 
 
 
 
 43-18 Sulphate of po- \ 
 
 
 
 
 Schonite or 
 Pikromerite 
 
 K 2 S0 4 
 
 - MgSO 4 
 6H 2 
 
 tassa 
 29-85 Sulphate of mag- - 
 nesia I 
 
 
 
 
 
 
 
 
 
 26-97 Water 
 
 
 
 
 Sylvin is also found in large quantities in the salt deposit near Kalucz, Galicia. 
 
 Mode of Working Bock-salt. Rock-salt, like other minerals and according to its 
 mode of occurence, is either quarried or mined. If it happens, however, that the rock- 
 salt is mixed with other minerals, clay, gypsum, dolomite, &c., a solution in water is 
 effected, which is pumped up from the mine as a concentrated brine. In many 
 instances rock-salt is wrought in extensive and deep mines, as in the celebrated rock- 
 salt mines of Wieliczka. 
 
 * According to Rammelsberg it is probable that kieserite is originally an anhydrous mineral,. 
 a conclusion which seems justified by the variable quantity of water found in different analyses. 
 
 U 
 
3 o6 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 Mode of Working Salt-springs. Natural salt-springs sometimes occur, and these 
 have been imitated artificially by boring to a great depth into layers of earth containing 
 saline deposits. In this manner a brine may be obtained sufficiently concentrated to 
 be at once boiled down. The method of working the natural salt-springs is to form a 
 convenient reservoir from which the saline solution is immediately pumped up for the 
 purpose of being gradated (see p. 168). The solution previous to being boiled down is 
 left to allow the suspended matter to settle. The salt-springs obtained by boring either 
 yield a native brine, or the borings are carried into solid rock-salt and water caused to 
 descend into the salt deposit. This artificial brine is then pumped up, unless there is 
 naturally an artesian formation. The brine previous to further operations is left for 
 some time in reservoirs to deposit suspended insoluble matter. 
 
 These saline solutions are not always free from impurities ; in considering their 
 admixture brines may be divided into two classes; the first containing sulphate of 
 magnesium or sodium, with chloride of magnesium ; the other class embraces brine con- 
 taining the chlorides of calcium and magnesium. If the brine happens to pass through 
 peaty soil or layers of lignite, there often accrues organic matter, humic, crenic, and 
 apocrenic acids. 
 
 Preparation of Common Salt from Brine. This operation is duplex and con- 
 sists in 
 
 a. Concentrating the brine. 
 
 a. By increasing the quantity of salt. 
 /3. By decreasing the quantity of water. 
 
 b. The boiling down of the concentrated brine. 
 
 Concentrating the Brine. Native brines or salt springs seldom contain enough 
 common salt to make it profitable to boil them down at once ; it is consequently 
 necessary to enrich the brine, and this may be done either (a) by dissolving in it rock- 
 salt or crude sea salt, neither being suited for culinary and many other purposes unless 
 refined, or (0) by decreasing the quantity of water without the use of fuel. 
 
 Enriching by Gradation. The enriching or concentration of a brine by decreasing 
 the quantity of water it contains is called a gradation process, and may be proceeded 
 with by freezing off the water in winter time, or more generally by evaporating the 
 water by a true gradation process ; either (a) Gradation by the effect of the sun's rays ; 
 (6) Table gradation ; (c) Roof gradation ; (d) Drop gradation. 
 
 Gradation by means of the sun's rays is obviously the same method of procedure as 
 that described under the treatment of sea-salt. Table gradation has been only experi- 
 mentally tried at Reichenhall, and consists simply in causing the brine to flow slowly 
 from a reservoir down a series of steps, constructed so as to give as much surface as 
 possible, and thus hasten the evaporation. Roof gradation is effected by utilising the 
 roofs of the large tanks containing the brine as evaporation surfaces, by causing the 
 contents of the tanks to flow in a thin but constant stream over the roofs, which, of 
 course, are exposed to the open air. 
 
 Faggot Gradation. This operation, also known as drop gradation, is carried on by 
 means of the following apparatus, termed a gradation house, and consisting of a frame- 
 work of timber, fitted with faggots of the wood of Prunus spinosa, which being thorny, 
 presents a large surface. The entire construction is built over a water-tight wooden 
 tank, which receives the concentrated brine, and frequently the top of the gradation 
 house is provided with a roof. Under the roof and above the faggots a water-tight 
 tank is placed containing the brine to be gradated; this tank is provided with a 
 number of taps, from which the brine trickles into channels provided with holes to 
 admit of the brine falling on the faggots. These taps are placed on both sides of the 
 gradation house, and are generally connected with levers to admit of being readily 
 turned on and off from below. The gradation process is continued until the brine is 
 
SECT, in.] COMMON SALT AND SALT WORKS. 307 
 
 sufficiently concentrated to admit of being further evaporated by the aid of fuel ; 
 the brine may be gradated to contain 26 per cent, of salt, but the operation is rarely 
 carried so far. 
 
 The gradation process not only serves the purpose of concentration, but also that of 
 purifying the brine, as some of the foreign salts are deposited on the faggots ; this de- 
 posit of course varies in composition according to the constituents of the brine, but 
 chiefly consisting of calcium carbonate, with the potassium, sodium, and magnesium 
 sulphates. The deposit has in some instances been used as manure. In the tanks where 
 the gradated brine is collected another slimy deposit is gradually formed, consisting of 
 gypsum and hydrated oxide of iron. As in the present day the brine obtained from 
 bored wells is generally sufficiently concentrated to be at once boiled down, gradation 
 is less frequent, being a very slow process and involving a loss of the salt carried off by 
 the wind. 
 
 Boiling down the Brine. The object is to obtain with the least possible expendi- 
 ture of fuel the largest quantity of pure dry salt. Formerly the evaporation was 
 carried on in large cauldrons, but at the present time evaporating vessels are constructed 
 of well rivetted boiler-plate, the shape being rectangular, the length 10 metres, depth 
 o'6 metre, and width from 4 to 6 metres. These pans are supported by masonry, 
 which also serves to separate the flues. Over the pans a hood is fixed and connected 
 with a tube carried to the outside of the building to afford egress to the steam. The 
 brine, concentrated to contain from 18 to 26 per cent, of salt, is poured into the 
 pans to a depth of 0*3 metre. 
 
 The boiling down process is in many salt works conducted in two different 
 operations : 
 
 a. The evaporation of water to produce a brine saturated at the boiling point. 
 
 b. The boiling down of the saturated brine until the salt crystallises out. 
 
 The boiling down is generally carried on for several weeks, the scum being removed, 
 together with the gypsum and sodium sulphate deposited at the bottom of the pan, with 
 perforated ladles. As soon as a crust of salt is formed on the surface of the liquid, a 
 temperature of 50 is maintained. At this stage the salt is gradually deposited at the 
 bottom of the pan in small crystals, and being removed, is put into conical willow 
 baskets, which are hung on a wooden support over the pan to admit of the mother- 
 liquor being returned to it. Finally, the salt is dried and packed in casks. 
 
 The quantity of mother-liquor collected after boiling for some two or three weeks 
 is, compared with the quantity of brine evaporated, very small ; it was formerly thrown 
 away or used for baths, but is now employed for the preparation of potassium 
 chloride, the sodium and magnesium sulphates, artificial bitter water, and in some in- 
 stances for preparing bromine. It is evident that by the boiling down all the salt 
 contained in the brine is not obtained as dry refined salt, a portion being retained 
 among the early deposit formed at the bottom of the pan, another portion remaining 
 in the mother-liquor, and finally some loss accrues from the nature of the operations, 
 amounting generally from 4 to 9-25 per cent. 
 
 Properties of Common Salt. Sodium chloride crystallises in cubes, the size of 
 the crystals determining the varieties known in the trade as coarse, medium, and 
 fine grained salt, and depending upon the rate of evaporation of the brine, a slow 
 evaporation producing very coarse salt. Perfectly pure common salt is not hygroscopic, 
 but the ordinary salt of commerce contains small quantities of magnesium chloride and 
 calcium. Usually, salt contains from 2*5 to 5-5 per cent, of water, not as a constituent, 
 but as an intermixture ; hence the phenomenon called decrepitation, due to the breaking 
 up of the crystals by the action of the steam when salt is heated. Ignited to a strong 
 red heat sodium chloride fuses, forming an oily liquid, and at a strong white heat 
 is volatilised without decomposition. Common salt is readily soluble in water, and is 
 
3 o8 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 one of the few salts almost equally soluble in cold and in hot water ; 100 parts of water 
 at 12 dissolve 35*91 parts of common salt. 
 
 In order to express the quantity of salt contained in a brine, it is usual to say the 
 brine is of a particular fineness, strength, or percentage ; for instance, a brine at 1 5 
 per cent, contains in 100 parts by weight 15 parts of salt and 85 parts of water. The 
 Grddigkeit or degree of a brine means the quantity of water which holds in solution 
 
 Fig. 281. 
 
 i part by weight of salt; a brine of 15-6 GrddigJceit contains, therefore, i part by 
 weight of common salt in 15-6 parts of water. The poundage (Pfiindiykeit) of a brine 
 indicates in pounds the quantity of salt contained in a cubic foot of brine. The 
 following table shows the percentage of salt contained in brines of the several specific 
 gravities : 
 
 Salt per cent. 
 
 I 
 
 3 
 
 3'5 
 
 4 
 
 4-5 
 
 5 
 
 5-5 
 
 6 
 
 *S 
 
 7 
 
 Sp. gr. 
 
 Salt per cent. 
 
 Sp. gr. 
 
 Salt per cent. 
 
 1-0075 
 
 7'5 
 
 I -0565 
 
 16 
 
 I 0113 
 
 8 
 
 I -0603 
 
 17 
 
 1*0151 
 
 8-5 ... 
 
 1-0641 
 
 18 
 
 0188 
 
 9 
 
 I -0679 
 
 19 
 
 "O226 
 
 9'5 
 
 1-0716 
 
 I9-5 
 
 '0264 
 
 10 
 
 I -0754 
 
 20 
 
 0302 
 
 10-5 
 
 I -0792 
 
 21 
 
 0339 
 
 ii 
 
 I -0829 
 
 22 
 
 0377 
 
 ii'S 
 
 I -0867 
 
 23 
 
 -0415 
 
 12 
 
 1-0905 
 
 24 
 
 I -0452 
 
 13 
 
 I -0980 
 
 25 
 
 I "0490 
 
 14 
 
 I-I055 
 
 26-39 
 
 I -0526 
 
 15 
 
 1-1131 
 
 
 Sp. gr. 
 I'I2O6 
 I-I282 
 
 IT433 
 I-I5IO 
 
 1-1675 
 I-I758 
 I -1840 
 I-I922 
 1-2009 
 I -2043 
 
SECT, in.] SODA. 309 
 
 Uses of Common Salt. It is not necessary to enter into particulars on this subject. 
 Salt is used as a necessary condiment to food ; a man weighing 75 kilos, contains in his 
 body 0-5 kilo, of common salt, and requires annually 7-75 kilos, to maintain this supply. 
 Common salt is used in agriculture, and is as necessary for cattle and horses as for man. 
 It serves industriaDy in the preparation of soda, chlorine, sal-ammoniac, in tanning, in 
 many metallurgical processes, the manufacture of aluminium and sodium. Further, it is 
 employed in the glazing of the coarser kinds of pottery and earthenware, from the fact 
 that when common salt is fused with a clay containing iron, the sodium is oxidised and 
 forms soda, which, combining with the alumina and silica, supplies a glaze, while the 
 iron combining with the chlorine is volatilised. The uses of common salt for the pre- 
 servation of wood, for curing meat, preserving butter, cheese, &c., are too well known 
 to require explanation. Among the salt-producing countries of Europe, England takes 
 the lead, producing annually 32,400,000 cwts., while Germany only produces 10, and 
 Russia 20 million cwts. 
 
 Fig. 281 shows an apparatus used for concentrating brine from salt springs, &c., 
 without the use of artificial heat. It consists of a stout frame work of beams, C, 
 supporting a system, B, of faggots of thorns, &c. At the bottom is a water-tight tank 
 for receiving the brine. 
 
 In countries where a tax upon salt still exists the following substances are officially 
 added to salt used for technical purposes, so as to render it unfit for domestic uses : in 
 alkali works 4 to 1 5 per cent, of soda-ash, 1 2 per cent, of soda crystals, sulphuric acid 
 (about 2 percent, with 3 to 4 parts of water), 10 percent, sodium bicarbonate, ammonia, 
 5 to i6| per cent. Glauber salts. In other chemical and in colour works : anilin colours 
 and decoctions of dyes ; iodine lye, mother-liquors from extract of indigo, 5 per cent, 
 copper chloride, f per cent, red lead, &c., and a variety of other products. 
 
 SODA. 
 
 Soda is either (A) natural soda, or (B) that from plants and sea weeds, or (C) that 
 obtained by chemical processes from the sodium compounds occurring in nature (such 
 as common salt, Glauber salt, soda-saltpetre, cryolite) with the simultaneous production 
 of hydrochloric acid, chloride of lime, sulphur, sal-ammoniac, potassium nitrate, alum, 
 aluminium sulphate, sodium aluminate and thio-sulphate. 
 
 (A) Natural Soda. 
 
 Soda occurs naturally as an ingredient in many mineral springs, it weathers out 
 volcanic rocks, e.g., trass and gneiss, as at Bilinboth, as sodium sesquicarbonate 
 Na s CO 3 + 2NaHC0 3 + 2H 2 O, or as sodium pyrocarbonate, and often exists in solution 
 in the so-called soda-lakes. Such waters exist in Egypt in the western part of 
 the Delta, in Central Africa, in the plains along the Caspian, in California, 
 Mexico, and in some South American States. In the great Hungarian plain crude 
 soda weathers out during the hot season as a saline crust, which is collected for 
 sale. The Egyptian soda is known as Tro-Na, whence the name Natron, still used for 
 soda in Germany. It is exported yearly from Alexandria to the extent of 5 tons. 
 In Columbia soda, called there Urao, is deposited in the hot season at the bottom of a 
 lake in the valley. 
 
 La Lagunitta. In La Plata (province Catamanca) soda is found in great quantities, 
 and is known as Ccollpa. Quite recently an alleged inexhaustible bed of natural soda 
 has been found in Virginia. 
 
 The sodium carbonate of the alkaline lakes is probably formed on the decomposition 
 of common salt by means of calcium or magnesium bicarbonate ; or it may be produced 
 from sodium sulphate which is reduced to sodium sulphide by the action of organic 
 
310 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 matter. The sulphide is then converted into sodium sesquicarbonate by means of car- 
 bonic acid dissolved in the water. 
 
 k 
 
 (B) Soda from Plants. 
 
 As inland plants take up from the alkalies of the soil principally potash, which is 
 found in the ashes of such plants in the state of carbonate, so plants growing on the 
 coast, in the sea itself, or in salt-steppes, contain more or less sodium, combined with 
 sulphuric acid or with organic acids. Such plants, on incineration and lixiviating, yield 
 sodium carbonate. Besides the species of fucus growing in the sea itself, the genera 
 Statice, Chenopodium, Mesembryanthemum, Salsola, Atriplex, Salicornia, &c., serve for 
 the production of soda and in some districts are even cultivated. The plants are 
 mown, the kinds of fucus are collected at ebb-tide and dried on the shore. The plants 
 are then burnt to ashes in pits. The heat is so strong that the ash melts, and on 
 cooling forms a hard, brownish-grey slag-like mass kn'own as crude soda or soda-ash. 
 It contains from 3 to 30 per cent, of sodium carbonate. It is worked up by lixiviating 
 and concentrating the lye. The following kinds are distinguished according to their 
 origin and the manner of their production : 
 
 a. Barilla soda, from Alicante, Malaga, Cartagena, the Canaries, &c. It is obtained 
 from the Barilla (Salsola soda) which is cultivated on the coasts of Spain. It contains 
 from 25 to 30 per cent, of sodium carbonate. 
 
 b. Salicor soda, from Narbonne, obtained by burning Salicornia annua, a plant 
 which is sown and reaped after the seed is ripe ; it yields about 14 per cent, of sodium 
 carbonate. 
 
 c. Blanquette soda, from Aigues-Mortes, from plants grown between Aigues-Mortes 
 and Frontignan, Salicornia Europcea, Salsola kali, Statice limonium, Artiplex portu- 
 lacoides, &c. It contains only from 3 to 8 per cent, of sodium carbonate. 
 
 d. Equal in value to Blanquette soda is Araxes soda, much used in South Russia, 
 and obtained in Armenia in the Schurus direct on the table-lands of the Araxes. 
 
 e. Still poorer is the Varec soda, Tang soda, obtained in Normandy and Brittany 
 from various sea-weeds, especially the goemon, Fucus vesiculosus. 
 
 f. About equal in value to Varec soda is kelp, obtained on the western coasts of the 
 British Islands (Scotland, Ireland, Orkneys), from various kinds of salsola, and sea- 
 weeds (Fucus serratus and F. nodosus, also Laminaria digitata) ; here and there it ia 
 obtained from sea-grass (Zoster a maritima). 
 
 g. Lastly is to be mentioned the soda derived from the beet, which always contains 
 a few per cents, of potassium carbonate. 
 
 (0) Soda obtained by Chemical Means. 
 
 The numerous attempts made at first by French chemists to obtain from common salt 
 a soda equal to barilla in cheapness and quality led to no results, and the large- 
 rewards offered by the Academy of Sciences for the solution of the problem were not 
 claimed. When, in consequence of the revolutionary war the importation of soda and 
 potash was broken off, and when all the potash which France produced was required 
 for the manufacture of saltpetre and gunpowder, the Committee of Public Welfare 
 demanded the most accurate returns concerning all soda manufactories, Leblanc was one 
 of the first manufacturers to obey this call, and he handed over for the public use the 
 principles on which he was on the point of erecting a soda-works. His process was 
 declared the most suitable, and until the recent introduction of the ammonia process it 
 has been in almost exclusive use. 
 
 i. The Leblanc Process. This process consists essentially in the production of 
 sodium sulphate, its fusion with lime and coal, and the purification of the crude soda ;. 
 after this follows the treatment of the residues. 
 
SECT. III.] 
 
 SODA. 
 
 311 
 
 a. The production of sulphate (salt-cake) from common salt is generally effected by 
 means of chamber acid, according to the equation : 
 
 2 NaCl + H 2 S0 4 = Na 2 SO 4 + 2 HC1. 
 
 The decomposition was at first effected in open reverberatories, so that the hydro- 
 chloric acid escaped mixed with the gases of combustion. 
 
 In 1836 Gossage obtained a patent for a closed reverberatory, which during the first 
 part of the decomposition acted as a distilling apparatus, and subsequently, being 
 heated by direct firing, it acted as an open furnace in order to complete the conversion 
 of the salt into salt-cake. By combining this furnace with coke towers as coolers, 
 he succeeded in obtaining in the first section a strong acid fit for the production of 
 chloride of lime, and then a weaker acid. This furnace was decidedly improved by 
 Gamble in 1839 ; at least he seems to have been the first who caused the two portions 
 of the decomposition to take 
 
 place in two distinct com- Fig- 282. 
 
 partments of the furnace 
 G and E (Fig. 28;:)- The 
 principle of this furnace 
 was universally adopted, 
 and for some time the alkali 
 manufacturers made use of 
 a reverberatory which by 
 opening or shutting an 
 aperture could be connected 
 with a kind of muffle, the 
 bottom of which consisted 
 of a strong iron plate. The 
 flame, after heating the re- 
 verberatory, played round 
 the muffle and then up the 
 chimney. The muffle itself 
 
 was connected by M with a condensing apparatus which yielded concentrated hydro- 
 chloric acid. On this principle the salt was let fall upon the cast-iron sole of the plate, 
 G, and the acid, previously heated, is allowed to flow in. A brisk reaction was set 
 up, and half, or nearly f of the acid escaped and could be easily condensed, as it was 
 not mixed with the gases of the fire. The product obtained was a mixture of sodium 
 bisulphate with common salt 
 
 2 NaCl + H 2 S0 4 = NaHS0 4 + NaCl + HC1, 
 
 and was drawn into the reverberatory, E, whilst G received a new charge of s^lt and 
 sulphuric acid. In the reverberatory, which was much hotter than the muffle, the 
 mixture of salt and bisulphate was converted into hydrochloric acid and neutral 
 sulphate : NaHSO 4 + NaCl = Na 2 S0 4 + HC1. 
 
 The hydrochloric acid evolved was difficult to concentrate, as it was mixed with 
 nitrogen, carbon dioxide, and carbon monoxide. In spite of the scrubber, a part of the 
 hydrochloric acid escaped into the air and there were required very large apparatus 
 and especial precautions in order to effect a satisfactory condensation. 
 
 These difficulties are nearly overcome since the salt-cake furnaces have been improved 
 as follows. The new furnace consists of two muffles, one of iron and one of brick. A 
 part of the sole forms a shallow cast-iron basin 2^74 metre in diameter and 0*52 metre in 
 depth ; it stands on a foundation of bricks and is provided with a cast-iron cover, which 
 is likewise a segment of a sphere of 0*30 metres in depth. In this cover there are two 
 apertures closed by doors, the one for introducing the salt, whilst the mixture is conveyed 
 into the brick muffle through the other. The fire is at the side of the cast-iron muffle, 
 
3 I2 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 and its flame acts first upon the cover and then upon the basin. The brick muffle is 
 next to the iron muffle, and is a chamber of 9' 14 metres in length, and 274 metres in 
 width. Beneath its brick sole there is a series of flues ; its upper part consists of a thin 
 vault of brick supporting a second vault, and the flame circulates in the space between 
 both. At one of the sides of the brick muffle is a fire, the flame of which passes first 
 between the two vaults and then through the flues beneath the sole. In this manner 
 the heat passes through the masonry of the vault and the floor to the mixture of bisul- 
 phate and salt in the muffles. 
 
 In working with this apparatus 500 kilos, of salt are placed in the iron muffle, pre- 
 viously heated, and the requisite quantity of acid at sp. gr. 1*7. The mass is 
 stirred up from time to time. It gradually thickens, and in about i^ hour (after f of 
 the hydrochloric acid have escaped) it is so solid that it can be removed into the brick 
 muffle, which is kept at a bright red heat, so that the hydrochloric acid may entirely 
 escape. There is an arrangement for cutting off the connection between the two muffles, 
 so that the gases escaping from either may be received separately. 
 
 Fig. 283. 
 
 The salt-cake furnaces of Jones and Walsh are used for sodium sulphate at Aussig, 
 as well as in Britain, and by Yorster and Griineberg at Cologne for potassium sulphate. 
 Opinions on them differ. 
 
 In the sulphate furnaces of Mactear the salt and sulphuric acid flow uninterruptedly 
 into a pan formed by a ring-shaped prominence in the sole of the furnace. The mass, 
 whilst still thin, flows over into the part of the hearth S (Fig. 283) situate nearest the 
 middle, where the decomposition is carried on about as far as the formation of bisulphate. 
 By the position of the agitator the mass is gradually brought towards the outside and 
 further decomposed, so that the outer part of the hearth plays the part of a calcining 
 furnace. At first Mactear arranged the hearth of the furnace in concentric rings, but 
 he has given up this idea. The removal of the gases of combustion, which are of course 
 mixed with the vapours of sulphuric acid, is effected by a cast-iron pipe on each side 
 of the agitating apparatus. The vault is made to descend, and the entire arrangement 
 is such as may be seen from the illustration (Fig. 283) that the agitating apparatus 
 can suffer little from the heat. The sole of the furnace is lined with fire-clay tiles 
 which have been boiled in tar : for mortar there is used a cement which becomes 
 continually harder by the action of the heat and the sulphate, so that the entire sole 
 bakes together to a solid mass, which effectively resists the action of the charge. The 
 heating is effected as may be convenient, but of course in such a manner that no such 
 flame arises as would choke the condensers. Recently Mactear has made use of four 
 
SECT, in.] SODA. 313 
 
 Wilson gas-generators, between which and the furnace is interposed an iron super- 
 heating apparatus, H. 
 
 The process of producing salt-cake and hydrochloric acid devised by Hargreaves 
 and Robinson has been known since 1872, and is in action on the large scale in a number 
 of English works. It consists in the direct action of sulphurous acid (the gases from 
 roasting pyrites), oxygen (atmospheric), and watery vapour upon sodium chloride 
 S0 2 + O + H 2 O + 2NaCl = Na 2 S0 4 + 2HC1. 
 
 The sodium chloride gives the best results when it is very finely divided before being 
 formed into lumps. It is moistened and dried, when it takes the condition of hard, 
 flat cakes, which are broken into fragments of about 38 millimetres in diameter. By 
 adding a little sulphate to the water the pieces are rendered harder and more suitable. 
 The pieces of salt come upon an iron grating placed near the floor in cylindrical 
 chambers of a fire-proof material. They are there treated at a red heat with a mixture 
 of two vols. of sulphurous acid, two vols. of watery vapour, and so much air that its 
 oxygen may represent one vol. The gaseous mixture enters below the iron grating ; 
 the temperature rises by the heat of the reaction, so that the gaseous hydrochloric acid 
 escapes very hot ; it is drawn into coke towers and there absorbed by water. The process 
 is uninterrupted, and as a rule eight cylinders are used simultaneously. In place of the 
 chambers, a tower is used built of fire-proof stone and provided at bottom with a 
 grating, through which the gases enter. The pieces of salt are introduced from above 
 and the salt-cake as it is formed is withdrawn below. The advantages of the Hargreaves 
 process lie in the dispensing with sodium nitrate, the production of a sulphate of very 
 high grade (free from undecomposed salt), decrease of the escape of gases, continuous 
 development and ready condensation of the hydrochloric acid, reduced loss of sulphur, 
 and consequently greater yield. Its defects are, increased cost of installation, greater 
 consumption of fuel, and increased outlay for labour. 
 
 Hydrochloric Acid. The liquefaction of hydrochloric acid by water is effected the 
 more easily and completely the less the HC1 is mixed with combustion gases, &c., and 
 the lower the temperature of the water ; one gramme of water at the pressure of 760 
 millimetres disssolves 
 
 Temperature. HGJ. 
 
 o ... 0-825 grm. 
 
 4 ... 0-804 
 
 8 ... 0783 
 
 12 ... 0762 
 
 16 ... 0742 
 
 20 ... 0721 
 
 Temperature. HC1. 
 
 24 ... 0-700 grm. 
 
 28 ... 0-682 
 
 32 ... 0-665 
 
 36 ... 0-649 
 
 40 ... 0-633 
 
 44 ... 0-618 
 
 The vapours of hydrochloric acid are passed through a number of earthenware 
 vessels in the opposite direction to the water, so that the solution when nearly saturated 
 comes in contact with the strongest gases ; or the vapours are led through towers 
 built of bricks soaked in tar, or stone plates, the filling of which (coke or stones) is kept 
 constantly moistened with water. 
 
 Properties. Hydrochloric acid forms a colourless liquid, frequently coloured yellow 
 by ferric chloride or organic matter, and having a pungent odour. At 20 water 
 absorbs 475 times its own volume of hydrochloric acid gas; the saturated solution 
 contains 42-85 per cent, of HC1 and its sp. gr.= i'2i. According to J. Thomson 
 (1874), hydrochloric acid probably contains a hydrate of the composition HCl.H a O, 
 which must be regarded as the true molecule of the acid. The following table shows 
 th sp. gr. of hydrochloric acid of different strengths and its percentage of actual 
 acid (at 7): 
 
3*4 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 Specific 
 Gravity. 
 
 Degrees 
 Iiaum. 
 
 Degrees 
 Twaddell. 
 
 Percentage 
 of Acid. 
 
 Specific 
 Gravity. 
 
 Degrees 
 Baumd. 
 
 Degrees 
 Twaddell. 
 
 Percentage 
 of Acid. 
 
 21 
 
 26 
 
 42 
 
 42-85 
 
 I -10 
 
 I4-5 
 
 2O 
 
 2O '2O 
 
 2O 
 
 2 5 
 
 40 
 
 40 '80 
 
 09 
 
 12 
 
 18 
 
 18-18 
 
 19 
 
 24 
 
 38 
 
 38-88 
 
 08 
 
 II 
 
 16 
 
 16-16 
 
 18 
 
 23 
 
 36 
 
 36-36 
 
 07 
 
 IO 
 
 H 
 
 14-14 
 
 17 
 
 22 
 
 34 
 
 34 '34 
 
 06 
 
 9 
 
 12 
 
 I2T2 
 
 16 
 
 21 
 
 32 
 
 32-32 
 
 'OS 
 
 8 
 
 10 
 
 lO'IO 
 
 15 
 
 20 
 
 3 
 
 30-30 
 
 04 
 
 6 
 
 8 
 
 8'08 
 
 14 
 
 !9 
 
 28 
 
 28-28 
 
 03 
 
 5 
 
 6 
 
 6'06 
 
 13 
 
 18 
 
 26 
 
 26-26 
 
 O2 
 
 3 
 
 4 
 
 4-04 
 
 12 
 
 17 
 
 24 
 
 24-24 
 
 oi 
 
 2 
 
 2 
 
 2'O2 
 
 II 
 
 15-5 
 
 22 
 
 21'22 
 
 
 
 
 
 Fig. 284. 
 
 The author remarks in a note that Twaddell's hydrometer scale, used in England, 
 possesses the noteworthy feature that the degrees coincide with tolerable exactness 
 with the percentages of acid. 
 
 Applications. The production of a non-arsenical hydrochloric acid is easily effected 
 by distillation with ferrous chloride, when the arsenic the more readily the greater its 
 strength passes over in the first portions of the distillate. An acid of 30 to 40 per 
 cent, is mixed with a little ferrous chloride, the first 30 per cent, which pass over are set 
 aside as arseniferous, and the 60 per cent, which follow next, and are pure, are collected 
 separately. In this manner an acid of 20 to 30 per cent, is obtained. The process s 
 adapted for the industrial production of a non-arsenical acid, in as far as the crude acid 
 generally containing ferric chloride needs merely to be mixed with a few iron turnings 
 and submitted to fractional distillation. 
 
 Hydrochloric acid is used on a vast scale for the production of chloride of lime, 
 
 potassium chlorate, and other chlorine pre- 
 parations (e.g., chloral hydrate, chloroform, 
 chlorbenzyl, benzotrichloride, methyl chlo- 
 ride) ; it serves also in .the manufacture of 
 sal-ammoniac, antimony chloride, glue, and 
 phosphorus ; in the production of carbon di- 
 oxide (for the mineral water trade) ; in the 
 manufacture of alizarine, resorcine, and* sali- 
 cylic acid ; in the preparation of sodium 
 bicarbonate ; in purifying bone black for 
 
 sugar works ; in bleaching as a substitute for sulphuric acid ; in converting saccharose 
 into a fermentible invert-sugar ; in working up beet treacle into alcohol ; in the produc- 
 tion, of ammonia and methyl chloride from the. dregs of beet treacle : in the metallurgy 
 of copper, nickel, cadmium, zinc, and bismuth ; for dissolving metals (tin), either alone 
 or when mixed with nitric acid as aqua regia ; for purifying ferruginous sands for the 
 glass mamifacture ; for carbonising wool. An important use of hydrochloric acid 
 occurs in the cotton manufacture i.e., for decomposing the lime-soap which is formed 
 when cotton tissues impregnated with fatty matters are bowked with lime. Hydro- 
 chloric acid was formerly sold in glass carboys or stoneware jars (often of more value 
 than their contents). Sometimes it is sent out in casks, lined with a layer of gutta 
 percha i centimetre in thickness. 
 
 For raising hydrochloric acid Kestner uses a stoneware cylinder, #, with cast-iron 
 covers, T (Fig. 284), screwed together with iron rods. The cover, U, is formed of vul- 
 canite, and the valve, V, of caoutchouc. The acid flows in by the tube, g, and is forced 
 out-wards through h ; the compressed air enters at i and escapes during filling by the 
 pipe,.?. An apparatus of this kind, holding 50 litres, lifts hourly 2500 litres of acid to 
 the height of 15 metres. 
 
 Sodium Sulphate, often called simply sulphate. (Na 2 S0 4 .ioH 2 O), is chiefly formed 
 
SECT. III.] 
 
 SODA. 
 
 Fig. 286. 
 
 as an intermediate product by the decomposition of common salt by sulphuric acid in the 
 Leblanc process. It occurs naturally in the minerals thenardite, Na 2 SO 4 , brogniartin 
 or glauberite, Na 2 S0 4 .CaS0 4 , and astrakanite, Na 3 S0 4 .MgSO 4 .4H 2 0, in many mineral 
 waters, in sea-water, and in most lime springs. The sulphate, as it is produced in the 
 alkali works as salt-cake, contains on an average 93 to 97 percent, dry sodium sulphate, 
 and 2 to 3 per cent, sodium chloride. 
 
 Applications. Sulphate is chiefly used in the manufacture of Leblanc soda, ultra- 
 marine, and glass. In the last case only the soda comes in question. It is fused with 
 coal and quartz sand ; by the action of the fuel the sulphuric acid of the sulphate is re- 
 duced to sulphurous acid (Na 2 SO 4 + C = CO + N 2 SO 3 ), which is driven out by the silica, 
 and sodium silicate remains. For use in glass works salt-cake is previously purified 
 from iron by dissolving 
 
 the salt, precipitating Fig. 
 
 the iron oxide by means 
 of lime, evaporating 
 down the clear solution, 
 and drying the product. 
 In the same manner 
 water-glass may be 
 formed from the sul- 
 phate by melting it with 
 sand and carbon, and on 
 the same principle so- 
 dium aluminate is ob- 
 tained from the sulphate 
 along with bauxite or 
 aluminous earth. Con- 
 siderable quantities of 
 sulphate are also used 
 in separating antimony 
 from quartzy ores e.g., 
 at Bouc and Septemes, 
 near Marseilles. Lat- 
 terly, sulphate (freed 
 from any excess of acid) 
 has been used as an 
 adjunct in dyeing, espe- 
 cially for wool. 
 
 b. Conversion ofSul- 
 phate into Crude Soda. 
 The salt-cake is 
 mixed with limestone 
 
 (sometimes hydrated lime) and coal, and the mixture is melted upon the hearth of a 
 reverberatory. The proportions given by Leblanc are : 100 parts salt-cake, 100 carbonate 
 of lime, and 50 coal. In ten different establishments the proportion of limestone used 
 to 100 parts of salt-cake ranges from 90 to 121 parts and the coal from 40 to 75. The 
 lime of the lixiviated and desulphurised vat-waste is sometimes used as a substitute 
 for natural calcium carbonate. In Britain reverberatories with two stages are often 
 used (Fig. 285). The furnace was formerly charged with the materials ground and 
 mixed. Now it is preferred to use them in fragments, in order that the soda " balls " 
 may be sufficiently porous to admit of easy fracture and lixiviation. In Germany the 
 furnaces have sometimes only one hearth (Fig. 286). In others, and in the English 
 
 Fig. 287. 
 
316 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. HI. 
 
 works, the mixture which was prepared by the waste-heat in the upper stage remains 
 only for half an hour on the lower hearth, which is the working-furnace. In German 
 alkali works, the mixture, M, placed in the hot reverberatory, is heated until the mass is 
 in a state of pasty flux, during which it is continually stirred with long iron rabbles, K. 
 Bubbles of carbon monoxide burst out of the mass and burn with a blue flame. 
 When the flames disappear the mass is drawn out of the furnace through the work- 
 ing doors, P, into flat sheet-iron chests on wheels, C, in which it cools. 
 
 As the combustion gases which escape from the hearth of the furnace have a very 
 high temperature, a second hearth is placed behind the ordinary one, which serves for a 
 preliminary heating of the next charge whilst the first charge is being completed. 
 Fig. 287 shows such a furnace, with the two hearths, A and J5, and there is here a 
 third compartment, C, of the form of a pan, in order at the same time to effect the con- 
 centration of the soda-lye by the hot gases as they pass to the chimney, 0. Above this 
 compartment is the pan, D, in which the lye is concentrated before it is led into C. 
 
 The author has examined the temperature of the melted soda and the composition 
 of the gases which are evolved. He found : 10 minutes after charging, a temperatxire 
 
 of 713 ; 20 minutes after, 15-7 per cent, carbon dioxide, 5-3 oxygen, temperature 
 
 40 minutes after, i8'i carbon dioxide, 3*3 oxygen, temperature 779 ; 55 minutes after 
 a temperature of 874 ; 70 minutes after, and shortly before drawing the melt, carbon 
 dioxide 15-8 per cent., oxygen 6.1, and the temperature 532. 150 kilos, salt-cake, 160 
 
 Fig. 288. 
 
 kilos, limestone, and 60 kilos, coal for reduction gave 240 kilos, crude black-ash with 
 a consumption of 96 kilos, of coal. With another quality of coal only 42 kilos, were 
 used for heating, and the carbon dioxide in the gases rose to 28 per cent. 
 
 In the furnace with a rotatory hearth this hearth consists of a cylinder which can 
 be turned on its axle. The mixture of salt-cake, limestone, and coal is placed in the 
 iron cylinder, A (Fig. 288), lined within with fire-stone. Two ribs, B, have been cast 
 upon it, by means of which the cylinder rests upon two pairs of wheels, C. The one 
 pair is provided with an axle, which communicates rotation to the wheels and from 
 them to the cylinder. The fire-gases of the furnace, D, pass through the opening, E, into 
 the cylinder, then through F into the vault, G (for the pans), and through the flue, K, to 
 the chimney. After the interior of the cylinder has been heated to redness the 
 mixture is brought upon a truck, J, and introduced into- the cylinder by a hopper, 7/, 
 which is not permanently connected. After the heat has acted for about 10 minutes 
 upon the contents of the cylinder, the wheels are set in motion, and the cylinder is 
 allowed to make a half-rotation. It is then let stand still for 5 minutes and another 
 half-turn is taken. The operation is continued until the mass is melted, which takes 
 place in about an hour. It is then set in rotation so as to turn once every three minutes. 
 
SECT. III.] 
 
 SODA. 
 
 The progress of the operation is watched from time to time by opening a door placed in 
 the cylinder. When the process is complete the melt is allowed to flow into iron vessels 
 placed below. The openings, B, B, serve for filling and emptying. 
 
 The rotating soda-furnace, or revolver, is an instance of the widely felt need to sub- 
 stitute mechanical appliance for costly manual labour. The idea of producing crude soda 
 in a rotatory apparatus is due to Elliot and Russell. They experimented with several 
 furnaces constructed at the machinery works of Robinson, Cookes, and Co., of St. 
 Helens. The real difficulties were first overcome by J. C. Stephenson, at the works of 
 the Jarrow Chemical Co., of South Shields. The first revolver was supplied to the 
 company by Cookes, of St. Helens, in 1854, but it was not until 1868 that the first 
 larger apparatus was introduced by Gaskell, Deacon, and Co., of Widnes, and by A. G. 
 
 Fig. 289. 
 
 Kurtz, of St. Helens. From that time these apparatus have been introduced into 
 almost all British alkali works. The largest revolver hitherto built has been recently 
 erected by the above-named machinery works of St. Helens for the Widnes Alkali Co., 
 of Widnes. It does the work of 18 hand-furnaces, but only takes up the room of three 
 such. Its daily yield is 80 to 90 tons of black-ash. The fire, F (Fig. 312), covers a space 
 of 5-1 by 3-1 metres, and uses hourly 1-27 tons of coal. The revolver, D, consists of a 
 wrought-iron cylinder, lined with fire-stone, and provided with two bearing rings of 
 steel, which rest upon four small wheels. It is set in motion by two small steam engines 
 mutually connected, the movement being transferred by means of toothed wheels. 
 Above it are the hoppers t, and behind it evaporating pans for utilising the waste 
 heat. 
 
31 g CHEMICAL TECHNOLOGY. [SECT. m. 
 
 Whilst the earlier revolving furnaces of about 5! metres long work up each time 
 4 tons of salt-cake and require 650 kilos, of coal per ton, this furnace requires only 
 500 kilos., and yet the escaping gases suffice to concentrate so much lye of 20 up to 
 50 Tw. that it can supply three special caustic soda pans, representing an economy of 
 fuel of 80 tons weekly. The revolving furnace is 9 metres long, with an inside diameter 
 of 3*4 metres, and has three doors for filling and emptying. It is lined with 16,000 
 ordinary fire-stones and 1 20 weighing each 63 kilos. In seven days 400 tons of salt- 
 cake are worked up to 240 tons of a 60 per cent, caustic soda, with the consumption of 
 200 tons of coal. 
 
 Crude soda (black-ash) has approximately the following composition : 
 
 Sodium carbonate 45 
 
 Calcium sulphide 3 
 
 Caustic lime 10 
 
 Calcium carbonate 5 
 
 Foreign matter 10 
 
 There are sometimes formed in the black-ash crystals of a complex calcium 
 sulphide-alumina-lime silicate, 2CaS.6Ca 3 Si0 5 .Al 3 Si0 5 , as also of the silicate, Ca 3 Si a O 7 
 About 5 per cent, of the sodium forms insoluble compounds. 
 
 Considerable quantities of crude soda, especially in England, are used without fur- 
 ther treatment in soap-making, in bleaching, and in the manufacture of bottle-glass. 
 
 c. Conversion of Crude Soda into Purified Soda, by Lixiviation and Evaporation. 
 Crude soda is resolved by extraction with water into a solution of sodium carbonate and 
 an insoluble residue (tank-waste, vat-waste, soda-waste, and sometimes, erroneously, 
 black-ash !) 
 
 The blocks of English crude soda are in general of a darker colour and richer in coal 
 than those from Continental works. Before lixiviating they are generally exposed to 
 the air for one or two days, in some places ten to twelve days, not merely to let them cool 
 but that they may partially weather, thus rendering the subsequent treatment more 
 easy. As J. Kolb has observed, crude soda during weathering undergoes the following 
 changes : The exposure of crude soda to a perfectly dry air does not, as long as it 
 lasts, notably alter its composition ; if it contains, on being burnt, sodium sulphide, it 
 may be improved to a certain extent, as the sulphate passes into thiosulphate. At 
 100 dry air seems also without action upon crude soda, but as the temperature rises, 
 and especially if it reaches redness, the calcium sulphide is converted into calcium 
 sulphate, which lessens the standard of the soda, since during lixiviation it enters 
 into double decomposition with sodium carbonate, forming sodium sulphate. According 
 to Pelouze, a reduction of the strength is to be seen even between 200 and 300. 
 Hence it is very important to promote cooling of the soda after its removal from the 
 furnace, and to effect this with the exclusion of air in well-fitting trucks. 
 
 If crude soda is exposed to moist air ammonia is evolved in consequence of the de- 
 composition of the sodium cyanide which is always present; the lime passes into 
 hydrate, which expands in volume, and produces clefts in the blocks of soda, which then 
 fall to pieces. The calcium hydrate passes slowly into carbonate, which reduces the 
 proportion of caustic soda in the lye. At the same time the sodium siilphide (the 
 presence of which is always indicated by red spots) is oxidised and becomes sodium 
 thiosulphate. If there were no other reactions the exposure would be advantageous, 
 but any favourable action is neutralised by the oxidation of the calcium sulphide. 
 Moist air, like dry air, can, therefore, act favourably only in case of soda which is 
 not burnt. If the causticity of a well-made crude soda is diminished by exposure, 
 this is effected to the disadvantage of the proportion of alkali, which decreases in the 
 same degree. Hence, the action of air should, generally speaking, continue only long 
 enough for the lime to be partially hydrated, thus greatly facilitating the breaking 
 
SECT. III.] 
 
 SODA. 
 
 3 1 9 
 
 up of the raw soda. The time, according to the moisture of the air and the pro- 
 portion of free lime in the soda, may vary from three to six days. A longer exposure 
 is rarely without injury, and the custom of leaving the balls in the air for sometimes 
 twelve days is to be condemned. 
 
 The oldest method of lixiviation consisted in grinding the crude soda, and stirring 
 up the sifted powder with 4 parts of water. After the undissolved portion had settled 
 the solution was poured off and brought into contact with fresh portions of crude soda, 
 repeating this process three or four times. At the same time fresh water was poured 
 upon the undissolved matter remaining in the first vat, and was gradually transferred 
 from vat to vat. In this manner all the soluble constituents were removed from the 
 crude soda. This method of lixiviation was open to several objections ; the water 
 exerted its solvent power only on stirring, and hence the quantities dissolved were never 
 considerable. It further required much labour, and is, in consequence, no longer in use. 
 
 The method of lixiviation by simple filtration is also not to be recommended, on account 
 of the great labour it requires. It consists in placing the crude soda in sheet-iron tanks 
 provided with perforated false bottoms, and covering it with water. A series of tanks, 
 
 A, , C, D (Fig. 290), 1 1 metre high, r8 metre broad, and 2 metres long, are set close 
 together on a platform of masonry. At metre from the bottom is a perforated false 
 bottom of wood or sheet iron. A wooden main, K, placed above the tanks, and held 
 by the irons, F and F', leads the liquid 
 
 into the tanks though the plugs, t, t', and Fig 290. 
 
 t". In the latter there are fixed below the 
 
 false bottom, the cocks, r, r', r", &c., which 
 
 serve to run off the solution from the 
 
 tanks into the channel, K'. The blocks 
 
 of crude soda broken up into fragments 
 
 of about the size of a head, are laid in the 
 
 false bottom, where they are submitted to 
 
 a repeated process of lixiviation. Suppose 
 
 a system of three tanks, J, B, G, the 
 
 tank A charged with fresh crude soda, B 
 
 with such as has been once lixiviated, and 
 
 C with some that has been twice lixiviated. We let flow into each through the 
 
 channel, K, the last washings of a previous lixiviation. These washings have to 
 
 stand eight hours in each. After the lapse of this time, the lye (which will mark 
 
 about 50 Tw.) is let off through the cock, r, into the channel, K, as also the much 
 
 weaker lyes from B and C, which are mixed in large tanks with the lye from A, and 
 
 reduce its strength to about 40 Tw. Washing-waters are again run in upon A and 
 
 B, and into a fourth tank, Z>, charged with fresh crude soda ; after eight hours the 
 lyes are run into the cistern, which has already received the lyes from the former 
 working, &c. It is thus possible to obtain without interruption a lye of 40 Tw. After 
 the contents of each tank have thus been lixiviated three times, the residues are finally 
 washed with water at 50. The liquid thus obtained serves to lixiviate the soda in 
 the tanks, A, B, and C. 
 
 The lixiviation apparatus introduced by Clement Desormes (Fig. 291) consists of a 
 number of sheet-iron tanks arranged like steps. The number of the tanks is from 
 twelve to fourteen (the figure gives only five, A, B, C, D, E). The upper tank, A, is of 
 cast iron, and is twice the size of the rest. By means of bent iron pipes, which are fixed 
 about 15 centimetres from the bottom, the liquid of each tank can be let off into the 
 next lower one, from A into B, from B into <?, and so further. The lowest tank, E, 
 delivers the liquid into the settling cisterns, F F', of which there are six, and which are 
 connected with each other by pipes fixed about 10 centimetres below the upper margin. 
 
320 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 The crude soda to be lixiviated, finely ground, is placed in sheet iron vessels, e, d, 
 <fcc., perforated like sieves. When the lixiviation is to begin the tanks are filled with 
 hot water, two of the sheet-iron vessels, each charged with 50 kilos, of crude soda, are 
 suspended in the lowest tank, E, by means of a rod thrust through its handles ; after 
 from 25 to 30 minutes they are taken out and transferred to I), whilst two fresh ones 
 are placed in E, &c., so that in eight hours, if we have a set of 14 lixiviation tanks, 
 there are not only in A such soda vessels which have been in all the others, but two,/", 
 have been already taken out of A, and are placed to drain upon h. After thirty 
 minutes the residue from all these vessels is emptied into a truck for removal from the 
 works, whilst e is put to drain in the place of/, d in the place of e, &c., and in E there 
 are placed two newly filled vessels. Whenever two new vessels are thus placed in the 
 
 Fig. 292. 
 
 lowest tank there is run into A about twice as much water as the volume of the soda. 
 The water pushes out the heavier lye at the bottom, which flows through the connect- 
 ing-tube into tank B, and causes the heavier lye to flow over into C, &c., so that 
 at last an almost saturated solution flows from E into the cistern F, where all turbid- 
 ities settle. The temperature in the lixiviating tanks must be kept at from 40 to 
 50, not higher, as the calcium sulphide might undergo a decomposition. The heat is 
 kept up by means of steam pipes, which open into the tanks at about a third of their 
 height. In the settling cistern also the lye is heated by steam to prevent it from 
 
 crystallising. The suspension of the 
 soda in perforated vessels in the 
 lixiviation tanks is the well-known 
 method by which substances to be 
 dissolved or lixiviated are placed at 
 the surface of the solvent, so that 
 the more concentrated solution may 
 not accumulate about the bodies to 
 be dissolved and prevent the action 
 of the solvent, but may flow to the 
 bottom and continually make room 
 for the solvent. If the vessels when 
 
 filled with crude soda are of such a magnitude that they cannot be raised by the work- 
 men, this is effected by means of a set of pulleys. 
 
 Fig. 292 shows two lixiviation tanks of a modified design. Each tank is divided 
 into two compartments by a double vertical partition, which communicate with each 
 other by the openings, a and b. Into the space between the two partitions, the steam- 
 pipes, h, open ; g are the overflows ; the strainers, 12, of sheet iron, are provided at 
 their narrow ends with perforated strips that the rods for lifting them may be thrust 
 through. 
 
SECT, in.] SODA. 321 
 
 According to Diirre, four tanks of wrought or cast iron, of about r6 metre long, 
 i -6 broad, and 1*65 in depth, are placed like terraces. In each of these are put 500 
 kilos, of crude soda, broken into four-inch lumps, with the needful quantity of 
 water. The lixiviation is effected in twelve hours, during which the soda is changed 
 four times, being placed after every three hours in the next higher lixiviating tank, so 
 that in twelve hours the residuum is thrown out from the top tank as exhausted. In 
 the two highest tanks the lixiviation is effected cold, in the third at 44, and in the fourth 
 at 56. From the top tank the lye passes straight into the following one, and from that 
 into a cistern, where it is heated by steam. Whilst in the three upper tanks water is 
 added every three hours, from the lowest tank the lye flows off into a larger cistern at the 
 suitable concentration, 38 Tw. Four such series of tanks with their accessory heating 
 vessels form a system. 
 
 The so-called Shanks more correctly Buff-Dunlop lixiviation apparatus utilises 
 the fact that a solution becomes the heavier the more salts it holds in solution, and 
 that a column of a weak lye may be counterpoised by a shorter column of stronger 
 lye. On this principle the tanks, four to eight in number (Fig. 293), stand side by side 
 horizontally. Water runs through them, and as it passes it lixiviates the soda and 
 becomes denser from tank to 
 
 tank, from the first, which con- Fig. 293. 
 
 tains clear water, to the last, 
 from which saturated soda lye 
 runs off. Although the vats 
 stand in a horizontal plane, 
 the level of the liquids forms 
 steps. Each is provided with 
 a false bottom, F, of perforated 
 sheet metal . From the bottom 
 of each there passes a tube, T, 
 open at both ends, its lower 
 aperture being cut diagonally 
 up to the surface, and supports 
 
 laterally a short tube, t, which, as will be seen from the figure, connects one tube with 
 the next. The main, r, fitted with cocks, supplies each tank with water. Four 
 washings suffice as a rule. One tank contains crude soda which has undergone three 
 lixiviations, and therefore only a small quantity of soluble salts. This vat (I.) 
 contains therefore washing water, which after it has taken up everything soluble 
 from the soda enters tank (II.), which has only been lixiviated twice ; the lye then 
 passes into tank (III.), the contents of which have only been washed once ; and, lastly, 
 into tank (IV.) charged with fresh soda. 
 
 From here the lye travels to the collecting cistern. Tank (I.) is charged with 
 crude soda, and the track of the lye is modified as required by means of the plugs 
 placed in the apertures of the pipes. This arrangement allows the workman to seek 
 out two contiguous vats, and to take the one as the entrance- and the other as the 
 exit-vat. As the vats are alternately filled and emptied, the one which has been 
 last charged contains the richest mass and the most saturated lye, which is densest, 
 and stands lowest ; consequently this vat is the exit-vat for the new series, from 
 which the saturated lye is drawn. On the other hand, the tank in which the 
 mass is most exhausted contains the weakest lye, which has the highest level. This 
 tank serves as the entrance vessel for pure water. As soon the charge in this tank 
 is completely exhausted it is removed and replaced by a new charge ; by opening a 
 series of cocks, this tank is made the exit-tank. At the same time the current of 
 
 x 
 
?22 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 oold water is led into the adjacent vat, &c. The more tanks a series contains the 
 more readily a given quantity of crude soda can be exhausted in a given time. Still 
 there are practical limits which cannot be exceeded, both for the number of the lixivia- 
 tion tanks and for the rapidity of the stream of water. It is sufficient if the lye run- 
 ning off has a sp. gr. of 1-27-1-286, which answers to a proportion of soda of about 
 13-5 per cent, of the weight of the liquid. 
 
 The advantages of this procedure are : (i) The transfer of the crude soda from vat 
 to vat is done away with, as the charge remains in the same vessel until it is exhausted, 
 which represents a considerable economy in labour. (2) The crude soda is always covered 
 by the liquid, so that it never cakes together, as happened in the old process, to the 
 great hindrance of the lixiviation. (3) The ascending current of the liquid carries off 
 the densest part of the solution, so that the lixiviation is effected with less water, in less 
 time, and also more completely than by a descending filtration. (4) The rapidity and the 
 continuity of the operation remove the alkali quickly from the action of the insoluble 
 calcium sulphide, and abridge the duration of the reactions by which soluble sulphides 
 are formed to the disadvantage of the product. (5) The high concentration of the lye 
 abridges the time of evaporation and thus effects an economy of fuel. 
 
 The nature of the lye obtained by the lixiviation of the crude soda and its clarification 
 on standing depends on the quality of the soda, the time of the action of air and water, 
 and the temperature employed. Dry crude soda contains no caustic soda, the presence 
 of which in the lye depends on the action of lime on the sodium carbonate in presence of 
 water. Sodium sulphide occurs only in traces in a normal crude soda, but its quantity 
 in the lye is still more variable than that of caustic soda, and depends on the manner 
 of its lixiviation. It is chiefly monosulphide which is contained in the lye : if a poly- 
 sulphide is present, it is converted into monosulphide by the action of the caustic soda. 
 The quantity of water used in lixiviation has no influence upon the causticity of the lye, 
 whilst the quantity of sodium sulphide increases with the quantity of water, the duration 
 of the digestion, and the increasing temperature and concentration. This is a consequence 
 of the increased solubility of calcium sulphide, which in contact with water is resolved 
 into calcium hydrosulphate and calcium hydroxide ; the former compound yields, with 
 caustic soda, sodium sulphide, and this the more readily the higher the concentration. 
 Sodium carbonate is also decomposed with calcium sulphide, and this the more readily 
 the more dilute the solution, the higher the temperature, and the more prolonged the 
 action. The practical conclusion is that crude soda should be lixiviated rapidly with 
 the smallest quantity of water and at the lowest possible temperature. It would be a 
 great improvement if an apparatus were invented which would lixiviate the soda in 
 a few hours and with so little water as to yield at once a concentrated lye. Such lye 
 would be free from sodium sulphide. 
 
 The lyes may contain iron as sulphide, as carbonate, and as sodium ferro- 
 cyanide. Iron sulphide occurs in solutions of sodium carbonate only if they contain 
 sodium sulphide. The iron sulphide deposits completely from such solutions on prolonged 
 standing. The deposition is not promoted by the addition of sodium bicarbonate, as 
 is erroneously assumed, but by that of dense iron sulphide, which carries down that 
 in solution, or more probably in fine suspension. Iron occurs as carbonate in solutions 
 which have been freed from sodium sulphide by means of a metallic oxide, e.g., zinc 
 oxide, and have been afterwards treated with carbon dioxide. A solution of sodium 
 carbonate containing bicarbonate dissolves iron oxide in considerable quantity. The 
 solution is quite colourless, and does not deposit iron even on long standing. An 
 addition of caustic soda quickly and completely removes iron from such solutions. 
 
 Iron sometimes occurs as ferric acid in melted caustic soda, but only as a result of 
 bad workmanship. Iron sulphide and sodium ferrocyanide are found in crude soda 
 lyes. 
 
SIXT. in.] SODA. 323 
 
 As an example of the composition of a crude lye, the analysis of a lye is quoted 
 obtained from the works of Matthes & Weber at Duisburg. Sp. gr. = 1-25. i litre lye 
 contained 3i3'9 grammes solid salts, consisting of 
 
 Sodium carbonate 71*250 per cent. 
 
 hydrate ...... 24*500 
 
 chloride 1*850 
 
 sulphide 0*102 
 
 thiosulphate ..... 0*369 
 
 sulphide 0*235 
 
 cyanide 0*087 
 
 Alumina ... k .... 1*510 
 
 Silica . . . . . . . 0*186 
 
 Iron . . traces 
 
 Purification and Concentration of the Lye. The lye, when freed by settling from all 
 suspended matter, contains chiefly sodium carbonate and caustic soda, besides common salt 
 and small quantities of other sodium salts. The presence of iron-sodium sulphide in 
 the lye is to be noticed, as it is the cause of the colour of soda-ash. To eliminate these 
 disturbing iron-compounds it is necessary to let the lyes remain for some time in the 
 settlers, when the iron sulphide is deposited. For decomposing the ferrocyanide 
 Hurter and Carey heat the lye in a worm to 180. If a solution of sodium thiosul- 
 phate is heated with potassium ferrocyanide in a closed tube there occurs a peculiar 
 decomposition. A greenish-grey precipitate subsides, having the composition KFeCy 3 . 
 The rest, exactly half the cyanogen, occurs in solution as potassium sulphocyanide. 
 The decomposition takes place according to the following equation : 
 
 K 4 FeCy 6 + 3 Na 2 S 2 3 = KFeCy 8 + 3 KCyS + 3 Na 2 S0 3 . 
 
 But if the solution contains sodium carbonate the ferrocyanogen is completely decom- 
 posed, the iron separating out as ferrous oxide according to the equation : 
 
 Na 4 FeCy 6 + 6Na 2 S 2 3 + 2 Na 2 CO 3 + H 2 O = 6NaCyS + 6Na 2 S0 3 + 2NaHC0 3 + FeO. 
 Further, a part of the cyanogen is split up into ammonia and formic acid, or sodium 
 formiate, so that the equation which most accurately represents the reaction taking 
 place in the lyes is the following : 
 
 Na 4 FeCy 6 + sNa 2 S 2 3 + 2 NaC0 3 + 3H 2 = 
 SNaCyS + 5Na 2 S0 3 + NaCHO 2 + NH 3 + 2 NaHC0 3 + FeO. 
 
 The sulphide can also be removed by oxidation, as it is done in Gossage's process by 
 means of atmospheric air. Pauli promotes the oxidation of the sulphur compounds in 
 the crude soda lye by the addition of a little manganese oxide. Parnell desulphurises 
 by means of zinc or zinc oxide. 
 
 The lye is evaporated to a certain degree of concentration, when from the super- 
 saturated and boiling liquid sodium carbonate is separated as a crystalline powder with 
 i mol. water : Na 2 C0 3 + H 2 0. 
 
 It is fished out in proportion as it separates * during these operations fresh quantities 
 of lye flow in from the more elevated pans, and this is continued for weeks or months 
 as long as a sufficiently pure salt is obtained. At first the quantity of carbonate in the 
 lye greatly preponderates over the quantity of the other constituents above named, 
 but in time the proportion becomes less favourable. Hence the carbonate as it separates 
 out becomes more and more impure, and is accompanied by common salt, and the 
 mother liquor which adheres to the salt contaminates it more and more. The mother 
 liquor ultimately remaining contains chiefly caustic soda and sodium sulphide, an excess 
 of these reduces the solvent power of the lye for salts almost to nil. The soda-salt, 
 fished out and freed as far as possible from the mother liquor by drainage or in a centri- 
 fugal machine, is dried on the hearth of a reverberatory fed with coke, with constant 
 stirring, and calcined, in order to oxidise the sodium sulphide of the adhering mother- 
 liquor and obtain a perfectly white product. This product is soda-ash (calcined soda) 
 
3 24 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 The character of this soda-ash and its percentage of carbonate vary greatly. The 
 different sorts known in commerce are obtained by separating the salt into classes 
 according to the length of the evaporation of the lye. That first obtained is the best 
 quality ; as the evaporation is prolonged it becomes worse, and it is at the option of the 
 manufacturer how many sorts he will produce. A soda containing 90 per cent, of 
 alkaline matter is said to be one of 90 degrees. The rest is sulphate and common salt 
 with a small quantity of sulphite produced during calcining. 
 
 According to K. W. Jurisch, at the works of J. Muspratt, of Widnes, a series of 
 samples of crude soda have been examined i.e., from a revolver furnace in July 1874 
 (I), from a hand-furnace in November 1874 (II), from a revolver furnace in April 
 1876 (III), in the same works, and in February 1876 from a similar furnace in the 
 works of Ch. Tennant at St. Eollox (IV). 
 
 I. II. III. IV. 
 
 Na 2 CO 3 . . . 41*592 ... 41760 ... 46-154 ... 45' 2 8o 
 
 NaCl . . . 1-205 ' 1 '3 86 0-673 X 74 
 
 Na 2 S0 4 . . . 1-213 2 '264 0-353 i'55 
 
 Na 2 SO :i . . . 0-145 - 0-534 
 
 Na 2 S 2 3 . . . ... 0-315 ... 0-593 ... 1-135 
 
 Si0 2 .... 2-375 ... 4-090 ... 2-680 ... 3-120 
 
 A1 2 3 . . . 1*080 ... 1-503 ... 0-785 ... 1-021 
 
 Fe./) 3 . . . 0-877 1*107 1*015 .. 0-724 
 
 CaC0 3 . . . 11-616 ... 6-636 ... 9-686 ... 5-114 
 
 CaO . . . 5-689 ... 5'8i6 ... 1-695 ... 1-328 
 
 CaS . . . 29-783 ... 31*938 33'6i5 30-985 
 
 MgO ... ... 0-303 ... 0-404 ... 0-295 
 
 Coal . . . 4-425 ... 3-260 ... 3-500 ... 7-370 
 
 The proportions of the ingredients used were the following : 
 
 i. n. in. rv. 
 
 Salt cake . . . 100 ... 100 ... 100 ... 100 
 
 Limestone . . . 106 ... 109 ... 78 ... 73 
 
 Coal .... 55 ... 56 ... 47-5 ... 41 
 
 Mactear's lime . ... ... 7-3 .. 7 
 
 During the months of December 1879, January, February, and March, 1880, daily 
 samples were taken of the revolver crude soda-lyes, and the mixture was analysed 
 every week. One litre contained in grammes : 
 
 Mean. Highest. Lowest. 
 
 Total Na.,0 . . 187-980 ... 198-380 ... 168-950 
 
 Na 2 O as Na 2 CO 3 . 147-930 ... i6ri8o ... 131-750 
 
 Na 2 O as NaOH . . 40-050 ... 4774O ... 37-200 
 
 Na 2 CO g . . . 252-910 ... 275-560 ... 225-250 
 
 NaOH . . . 51-680 ... 6r6oo ... 48-000 
 
 NaCl . . . 10-682 ... 15*503 ... 6-274 
 
 Na i SO 4 . . . 2-793 . 3755 - i'944 
 
 Na 2 SO, . . . 0-291 ... 0-543 ... 0-150 
 
 NagSjO, . . . 1-327 ... 2-080 ... 0-980 
 
 Na 2 S .... 4-149 ... 5-043 .... 2-925 
 
 Na 4 FeCy 6 . . . 0-768 ... 1-050 ... 0-510 
 
 Si0 2 ,Al 3 O s ,Fe 2 3 . 4-656 5-630 ... 3-850 
 
 In February there were further taken daily samples of the red liquor (II), of the 
 oxidised red liquor (III), and of the causticised red liquor (IV), and analysed at the end 
 of the month. In comparison with the mean of the February analyses of the revolver 
 crude soda lyes (I), i litre contained in grammes : 
 
SECT. III.] 
 
 
 I. 
 
 Total Na 2 O 
 
 . 191-270 
 
 Na.,0 as Na 2 CO, 
 
 . 149-270 
 
 Na 5 as NaOH . 
 
 42-010 
 
 Na,C0 3 . 
 
 . 255-200 
 
 NaOH 
 
 54-200 
 
 NaCl 
 
 9-719 
 
 NaJ30 4 . 
 
 2953 
 
 Na^O, . 
 
 0-306 
 
 Na,S,0 3 . 
 
 1-437 
 
 Najs" " . 
 
 4-188 
 
 Na 4 FeCy 6 . 
 
 0-710 
 
 Si0 2 , Al 2 0j, Fe,0 3 
 
 5-118 
 
 SODA. 
 
 u. 
 
 189-630 
 
 106-300 
 
 83-330 
 
 181790 
 
 107-520 
 
 26-413 
 
 11-809 
 
 5-603 
 
 6-085 
 
 8-424 
 
 2-280 
 
 6-700 
 
 325 
 
 in. 
 
 158-800 
 81-430 
 77-380 
 
 139-220 
 99-840 
 19-481 
 
 9-143 
 1-1-26 
 9-693 
 1-262 
 1-500 
 4-610 
 
 IV. 
 
 116-850 
 
 14-440 
 
 102-410 
 
 24-690 
 
 132-140 
 
 12-650 
 
 7-204 
 
 2-396 
 
 2-948 
 
 2-507 
 
 0-280 
 
 0-960 
 
 Specific Gravity . 1-279 ... 1-290 ... i'235 ... 1-170 
 
 The red liquor dropping from the revolver salts (II.) is slightly diluted by condensed 
 steam, with which the salts are treated for their better purification. The oxidation 
 of the red liquor was effected by forcing in air with a Korting blast, with the joint use 
 of Weldon mud ; the causticising took place, according to Parnell, at a pressure of 3 
 atmospheres. The analyses confirm the opinion that almost all the impurities of the 
 crude soda-lye pass into the red liquor, so that on oxidation its sodium sulphide is con- 
 verted into sodium dithionate, and on causticising according to Parnell's process the 
 latter is partially reconverted into sodium sulphide and sulphite. The lime also precipi- 
 tates silica, alumina, and iron oxide, apparently also some cyanogen. 
 
 Jurisch further gives the mean (II.), the highest (III.), and the lowest (IV.) values 
 from twenty daily analyses, September 1879, of revolver soda (made by Pechiney's process) 
 by the Runcorn Soap and Alkali Company, referred to 100 parts total soda present as 
 Na 2 C0 3 and NaOH, and for comparison the analysis of a sixteen days' average sample 
 of crude soda-lyes from hand furnaces (Muspratt's works), March 1880 (V.), as also 
 the mean of the January analyses of the revolver. Crude soda-lyes all are given in 
 column (I.) : 
 
 Na 2 O as NaOH 
 NaCl . 
 
 I. 
 21-290 
 c-qiO 
 
 II. 
 13-320 
 
 III. 
 15-160 
 
 IV. 
 
 . 8-500 .. 
 
 V. 
 
 33'57o 
 
 7"27Q 
 
 Na,S0 4 . 
 Na~SO 3 . 
 
 1-720 
 O"l64. 
 
 4-142 
 
 5-400 . 
 
 2-800 
 
 6-042 
 0-383 
 
 Na 2 S 2 3 
 Na.,S . 
 Na'.FeCy, . 
 SiO,, A1 2 3 , Fe 2 3 
 
 . 0-666 ... 
 . 2-053 
 0-358 ... 
 2-373 
 
 1-486 
 1-433 
 
 O'2l6 
 
 1-630 
 1-820 
 0-348 . 
 
 I-20O 
 . 0-930 .. 
 .. 0-174 .. 
 
 1-081 
 
 1-359 
 O-I50 
 2-730 
 
 If the crude soda-lye is at once evaporated to dryness, so that no mother liquor 
 remains, the reverberatory (Fig. 294) is used. A thick layer of the soda-salt is first 
 rammed down upon the sole 
 
 of the furnace to prevent the Fig. 294. 
 
 lye from coming in contact 
 with the bricks. As soon as 
 the furnace has been raised 
 to dull redness by the coke 
 fire burning in A, the lye, 
 which has been concentrated 
 to 55 Tw., is let flow down 
 from the heating pans, D and 
 E, into the furnace. As soon 
 as it touches the hot soda- 
 salt a violent boiling begins ; the mass rises and falls and is easily brought to dryness. 
 The salt is kept in powder by stirring with iron rabbles. As soon as a sufficient 
 
326 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 quantity of salt has been obtained the further flow of the lye is stopped, and the dry 
 salt is drawn out of the furnace. The gases of combustion can be led either into the 
 chimney or underneath the lye-pans, D and E, through the traps, F and G, and the 
 flues, C, C'. 
 
 J. Brown, on analysing the soda ash, obtained by concentrating the crude lye: 
 
 Sodium carbonate 
 hydroxide 
 sulphite 
 thiosulphate 
 sulphide 
 chloride 
 aluminate 
 silicate . 
 
 Insoluble matter 
 
 I. 
 68-907 
 
 I4-433 
 7-018 
 2-231 
 
 i - oi6 
 1-030 
 0-814 
 
 II. 
 
 65-5I3 
 16-072 
 7-812 
 2-134 
 i '542 
 3-862 
 1-232 
 o - 8oo 
 Q'974 
 
 If a reverberatory fire is used, a part of the sulphur dioxide contained in the smoke 
 gases is absorbed by the soda-lye, so that the soda is reduced in value. At the 
 
 Fig. 295. 
 
 Fig. 296. 
 
 Liingenschnilt Longitudinal Section. 
 
 Rhenania works and at Saarau, according to the sugges- 
 tion of Thelen, the evaporation of the soda-lyes is con- 
 ducted in a hemispherical pan of i metre radius and 
 7 metres in depth. In the shaft, W, moved by the helix, 
 E (Figs. 295 and 296), rods, F, are fixed, carrying shovels, 
 G, fixed obliquely. On passing through the lye, they 
 touch the bottom of the pan, push the salt on towards 
 the end, where it is removed by a shovel to be dried 
 in similar drying apparatus. 
 
 For producing soda crystals,* Na 2 C0 3 + ioH 2 (with 
 63 per cent, of water), the soda-ash is dissolved in hot 
 water, clarified by standing, and the liquid is let cool in 
 large iron vessels, when it deposits large crystals. The soda-salt is often dissolved in 
 pans of sheet-iron (Fig. 297), into which a current of steam is passed through the pipe, C. 
 The soda to be dissolved is placed on the sieve-like perforated sheet-iron vessel, D, 
 
 * Sal-soda of American writers. 
 
SECT. III.] 
 
 SODA 
 
 327 
 
 which can be raised or lowered. The pan is filled through the pipe, C, to three-quarters 
 its depth with water, and the vessel. />, containing the soda, is next introduced, whilst 
 steam is blown in through C. As soon as the lye shows a sp. gr. of 50 to 53 Tw. it 
 is run into the sheet-iron crystallisers, which are about 5 metres long, 2 broad, and 
 0-45 metre deep, and which should be placed in a cool, airy place At a medium 
 temperature, the formation of the crystals is complete in about five to six days Alter 
 the mother liquor has been let off through an aperture at the bottom of the crystal- 
 lising vessels it is then worked up to a low-grade soda : * the crystals are removed from 
 the sides and submitted to re-crystallisation. 
 
 For this purpose, the soda-crystals are dissolved in a conical sheet-iron pan, A 
 (Fig. 298), which is directly heated by the flame of the fire, C. By means of the flues, 
 D, the flame plays quite round the pan. The pan is filled with crystals, a little water 
 is introduced through B, and heat is applied. The crystalline water is sufficient to 
 melt the salt. The fire is then withdrawn, the pan is covered with a wooden lid, and 
 the liquid is let settle. When it has become clear, the lye is conveyed by syphons into 
 a cistern, and thence into quadrangular cisterns of sheet-iron of 40 to 50 centimetres in 
 diameter. Here the crystallisation begins, and is completed in about eight days. 
 After the mother liquor has been removed from the crystals, the iron vessels are set 
 
 Fig. 297. 
 
 Fig. 298. 
 
 for a short time in a pan of boiling water, when the crystals are detached from the 
 wall in consequence of beginning to melt, so that on merely inverting the vessels the 
 crystalline mass falls out in a body. After draining, the mass is broken up, dried 
 in a desiccating chamber at 15 to 18, or at once packed in casks to prevent and 
 efflorescence. 
 
 The crystalline state affords a guarantee for purity (supposing that the crystals 
 were not produced from a mixture of sodium carbonate and sulphate, in which case 
 they may contain large proportions of sulphate sometimes up to 50 per cent.). The 
 more general employment of soda-crystals is prevented by their high proportion of water, 
 which increases the freight. 
 
 Melting pans for soda must be constructed of a different kind of iron pan from salt- 
 cake pans. Resistance to acids demands a large proportion of carbon in chemical 
 combination ; whilst resistance to alkalies requires, on the other hand, a high per- 
 centage of graphite and a low percentage of combined carbon. In the former case, 
 
 * So-called "weak ash. 1 ' 
 
328 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 the iron must contain much manganese and little silicon, but in the second case much 
 silicon and as little manganese as possible. From one and the same mixture of irons we 
 may obtain either only good salt-cake pans and bad soda-pans, or bad salt-cake pans 
 and good soda-pans ; or, what most frequently happens, medium salt-cake pans and 
 medium soda-pans. Melting alkalies dissolve the combined carbon with a deep-brown 
 <X)lour, manganese as a manganate, and phosphorus as a phosphate, so that iron is 
 mostly attacked when these substances are present in quantity. Graphite, silicon, 
 and ferrosilicon are very slowly attacked by alkalies. In order to determine 
 the resistence to alkalies of a sample of cast iron, 5*6 grammes of it are heated to 
 quiet fusion with 6*2 grammes caustic soda ; the melt is dissolved in water, and the 
 loss in weight of the iron is determined. For determining the resistance to acids, the 
 sample should be laid in melting acid potassium sulphate ; 5-6 grammes of a salt-cake 
 pan on fusion with 27*2 potassium bisulphate should lose at most 25 per cent. 
 
 Theory of the Formation of Soda. It was formerly assumed, according to the ex- 
 planation of Dumas, that, on calcining a mixture of sulphate, limestone, and coal, the 
 coal, producing carbon monoxide, reduced the sulphate to sodium sulphide, which was 
 then decomposed, with the formation of sodium carbonate and calcium oxysulphide 
 and the escape of a part of the carbon dioxide.* According to the view of Unger, 
 which essentially agrees with that of E. Kopp (1865), after the sodium sulphide has 
 been formed, the calcium carbonate loses carbonic acid, and there remains behind 
 a mixture of caustic lime, sodium sulphate, and carbon, which is transformed into 
 caustic soda and calcium oxysulphide : the soda takes up carbon dioxide, and is con- 
 verted into sodium carbonate. 
 
 The latter view probably approaches nearest the truth ; but it is not necessary to 
 assume the existence of a calcium oxysulphide in order to explain the inaction of cal- 
 cium sulphide with sodium carbonate, since calcium sulphide is almost insoluble in 
 water (i part calcium sulphide requires 12,500 parts water at I2'6 for solution). The 
 excess of lime employed in practice, doubtless favourable for the purity of the product, 
 is sufficiently explained by the circumstance that the lime, as an infusible solid, does 
 not come into full action in the soda-melt, which, though a soft paste, is by no means 
 a liquid. The excess of lime is to be regarded merely as representing the coarser 
 particles which remain inactive. 
 
 During the formation of soda in the furnace the existing carbon becomes carbon 
 dioxide 
 
 5Na 2 S0 4 -I- loC = sNa 2 S + ioC0 2 ; and 
 SNa,S + 7CaCO 3 = 5Na 2 C0 3 + sCaS + 2 CaO + 2 CO r 
 
 However, as during the operation of the formation of soda, and especially towards 
 the end, carbon monoxide is evolved out of the melting mixture and burns with a 
 blue flame, a gaseous development which persists after the melt has been drawn out of 
 the furnace ; this carbon monoxide, though it is a secondary product, must be con- 
 sidered in the equation. The formation of carbon monoxide is of great importance, 
 because its appearance shows when the heat is sufficiently high and the mean reaction 
 is at an end. The researches of Unger place it beyond doubt that in the reduction of 
 sulphate by coal there is a formation of carbon dioxide but not of carbon monoxide. 
 This latter gas, therefore, is not formed during the reduction of the sulphate, but 
 is a result of the action of coal upon the excess of chalk or limestone. The reduc- 
 tion of calcium carbonate by coal does not occur until a far higher temperature is 
 reached than that which effects the reduction of the sulphate ; it follows upon the 
 latter, i.e., the conclusion of the main reaction. In this stage the sodium carbonate 
 is already formed. 
 
 * (a) Na,S0 4 + 4 C = Na.S + 4 CO ; (0) aNa^S + 3 CaC0 8 - zNa^CO, + CaO,2CaS + CO,. 
 
SECT, in.] SODA. 329 
 
 We have therefore to distinguish three stages in the production of soda : at first 
 there is reduction of the sulphate with evolution of carbon dioxide 
 
 Na 2 S0 4 + 20 = Na 2 S + 2 CO,. 
 
 Then follows the double decomposition between the sodium sulphide just produced and 
 the calcium carbonate : Na 2 S + CaCO 3 = Na 2 C0 3 + CaS * then occurs a partial reduction 
 of the excess of calcium carbonate employed bythe carbon(2CaC0 3 + 20 = 2CaO + 4.CO). 
 
 On lixiviation the caustic lime occasions the formation of caustic soda. 
 
 Theory consequently requires only 20 parts of coal to 100 parts sulphate. The 
 customary addition of carbon in excess (40 to 75 per cent.) is advantageous from a two- 
 fold point of view : first, as a substitute for that which has reduced a part of the carbon 
 dioxide to carbon monoxide * secondly, the addition renders it possible to seize the 
 exact moment when the reaction is completed and the melt must be withdrawn from 
 the heat of the furnace, i.e., after the liberation of carbon monoxide has begun and 
 before it has ceased. 
 
 Utilisation of the Leblanc Soda- Residues. As already pointed out, the Leblanc 
 process has furnished (until quite recently) the chief quantity of the soda, caustic 
 soda, and bicarbonate which are consumed. This superiority over all other processes is 
 due in great part to the production of the soda-residues, in as far as they have the property 
 of being easily and completely separated by lixiviation from the alkali contained in the 
 crude soda. At the same time, these residues form the darkest side of this impor- 
 tant branch of chemical industry. The great quantity of sulphur which enters into 
 this process is lost in the residues in such a manner that at the alkali- works of Dieuze, 
 in Lorraine, the sulphur stored up in the solid residues, down to the year 1869, 
 was estimated at the value of 43 million marks, or in round numbers ^2, 300,000. 
 Each ton of alkali yields i| ton of dry residues, and the masses produced in this manner 
 are generally piled up in heaps near the works, forming hills of considerable elevation. 
 These residues, especially in warm weather, evolve sulphuretted hydrogen in serious 
 quantity, which annoys and injures the inhabitants of the district. Moreover, the rain 
 and the surface waters which come in contact with these heaps extract from them a 
 more or less intensely coloured liquid containing calcium sulphide and polysulphide, 
 which poisons the wells and water-courses into which it penetrates. All attempts to 
 recover this sulphur in a simple and cheap manner, and thus to do away with the 
 nuisance and the danger to the public, have until recently proved fruitless. 
 
 The soda-residues (tank-waste or vat-waste) from the " Silesia " works at Saarau 
 have, when dry, according to E. Bichters (1869), the following composition : 
 
 Calcium sulphide . . 37-62 ... 38-04 ... 39*10 ( = 16 to i8%S) 
 
 Iron sulphide . . i'88 ... 175 ... 2'oi 
 
 Calcium thiosulphate . 2-69 ... 3-02 ... 2-35 
 
 carbonate . 23-18 ... 22*24 ... 24*02 
 
 sulphate . . 1*68 ... 1*01 ... 1*38 
 
 sulphite . . 074 ... 0*31 ... 0*63 
 
 Lime (CaO) . . . 6-49 ... 7'oo ... 7^5 
 
 Alumina . . 2'ii ... 2-02 ... 2'oo 
 
 Soda .... 2*52 ... 2*10 ... 1-86 
 
 Silica (combined) . . 4*24 ... 4*03 ... 4*62 
 
 Water .... 2-32 ... 3*29 ... 1-51 
 
 Sand .... 774 ... 6-82 ... 7'2i 
 
 Carbon . . 5-41 ... 6 - oo ... 6*39 
 
 jnesia . . . 0*64 ... 0*51 ... 0-70 
 
 99-26 ... 98-17 ... 101-06 
 
33 o CHEMICAL TECHNOLOGY. 
 
 Chance gives the following analysis, executed in June 1882 : 
 
 [SECT. in. 
 
 
 I 
 
 . 
 
 o 
 
 o 
 O 
 
 i 
 
 
 
 o . 
 
 i 
 
 1 
 
 E* S 
 
 
 4 
 
 8 
 
 -a 
 
 "a 
 
 OQ 
 
 "STS 
 
 -3 $ 
 
 cc . 
 
 2 
 
 
 a 
 
 
 
 
 ~ <u 
 
 <*3 
 
 'o3 
 
 J8.S 
 
 <*3 c 
 
 5 t^-So 
 
 
 8 g 
 
 "s 
 
 11 
 
 || 
 
 <& 
 
 3 
 
 
 3~ 
 
 % 
 
 Works 
 
 , 
 
 <!3 
 
 
 
 
 &g 
 
 A 
 
 1* 
 2 
 
 |S 
 
 "SsJ 
 
 
 ~$ 
 1 
 
 *C 
 
 r 
 
 0) 3 
 
 aSS 
 1 
 
 % 
 
 II 
 
 
 
 H| 
 
 C5g 
 O 
 
 ii 
 
 
 o 
 
 N 
 
 
 
 | 
 
 5 
 
 
 & 
 
 J* 
 
 
 
 Re- 
 volver. 
 
 Re- 
 volver. 
 
 Re- 
 volver. 
 
 Re- 
 volver. 
 
 Hand. 
 
 Re- 
 volver. 
 
 Re- 
 volver. 
 
 Hand. 
 
 Hand. 
 
 Soda mixture 
 
 
 
 
 
 
 
 
 
 
 
 Salt cake . . . 
 
 lOO'OO 
 
 lOO'OO 
 
 lOO'OO 
 
 lOO'OO 
 
 
 
 100*00 
 
 
 
 100-00 
 
 lOO'OO 
 
 lOO'OO 
 
 Limestone . 
 
 86-00 
 
 86-00 
 
 95-0 
 
 105-00 
 
 
 
 loo-oo 
 
 
 
 105-00 
 
 105-00 
 
 105-00 
 
 Coal .... 
 
 40t042 
 
 40-00 
 
 53-0 
 
 33*33 
 
 
 
 57-00 
 
 
 
 57-50 
 
 65*00 
 
 65-00 
 
 Sulphur 
 
 
 
 
 
 
 
 
 
 
 
 Total in waste 
 
 26-33 
 
 24-29 
 
 23-52 
 
 22.66 
 
 2073 
 
 17-94 
 
 18-84 
 
 19-47 
 
 17-22 
 
 18-04 
 
 Recoverable . 
 
 25-28 
 
 23-87 
 
 23-10 
 
 21-30 
 
 19-87 
 
 17-83 
 
 I7-59 
 
 17-17 
 
 I5-59 
 
 16-83 
 
 Per cent. 
 
 96-02 
 
 98-27 
 
 98-21 
 
 94-00 
 
 95-85 
 
 99-39 
 
 93-36 
 
 88-19 
 
 90-53 
 
 93-29 
 
 Soda residues 
 
 
 
 
 
 
 
 
 
 
 
 Sodium carbonate . 
 
 3'i6 
 
 2-57 
 
 
 
 o*45 
 
 
 
 
 
 
 
 3-69 
 
 1*63 
 
 1-97 
 
 Sodium oxide . . 
 
 
 
 
 
 1-47 
 
 
 
 
 
 
 
 I-I7 
 
 
 
 
 Sodium hydrate . 
 
 
 
 
 
 
 
 
 
 
 
 1-88 
 
 
 
 
 
 Calcium carbonate 
 
 zi'ig 
 
 28-10 
 
 20*07 
 
 38-14 
 
 35 '26 
 
 27-92 
 
 28-41 
 
 23-64 
 
 38-8I 
 
 36-92 
 
 Calcium hydrate . 
 
 trace 
 
 
 
 5-92 
 
 7-62 
 
 
 
 8-60 
 
 4-90 
 
 8-89 
 
 9-53 
 
 8-85 
 
 Calcium sulphide 
 
 56-89 
 
 5377 
 
 52-03 
 
 47-97 
 
 44-75 
 
 40-16 
 
 39-62 
 
 38-67 
 
 35-12 
 
 37-90 
 
 Calcium thiosulphate . 
 
 1-07 
 
 
 
 
 
 
 
 
 
 
 
 I-I9 
 
 2-85 
 
 1-49 
 
 0-68 
 
 Calcium sulphite 
 
 trace 
 
 
 
 
 
 
 
 
 
 
 Calcium sulphate 
 
 trace 
 
 
 
 trace 
 
 
 
 376 
 
 
 
 2-13 
 
 0*91 
 
 
 
 O'2O 
 
 Calcium silicate . 
 
 3-53 
 
 1-47 
 
 
 
 
 
 
 
 2-96 
 
 
 
 4-19 
 
 
 
 Carbon 
 
 7 "20 
 
 9-62 
 
 13-69 
 
 0-30 
 
 572 
 
 12-33 
 
 8-03 
 
 5-86 
 
 6-27 
 
 7-04 
 
 Magnesium carbonate . 
 
 
 
 
 
 
 
 
 
 
 
 
 I'35 
 
 0-98 
 
 
 
 Magnesium oxide 
 
 
 
 
 
 0-16 
 
 
 
 0-42 
 
 2-13 
 
 
 
 
 
 
 
 trace 
 
 Alumina 
 
 I -02 
 
 074 
 
 1-98 
 
 
 
 2-45 
 
 2'Ij 
 
 8-62 
 
 I -01 
 
 0-13 
 
 0*34 
 
 Ferric sulphide . 
 
 1-65 
 
 1-16 
 
 1-16 
 
 374 
 
 
 O"29 
 
 O'7O 
 
 2-16 
 
 276 
 
 2-44 
 
 Ferric oxide 
 
 
 
 
 
 
 
 
 
 1-64 
 
 
 
 
 
 
 Silica .... 
 
 
 
 
 
 1-50 
 
 
 
 
 
 
 
 
 
 
 
 I -21 
 
 i-34 
 
 Sand .... 
 
 2-82 
 
 0-89 
 
 2-09 
 
 2-51 
 
 6'oo 
 
 0-66 
 
 3-98 
 
 7-41 
 
 2'6l 
 
 179 
 
 Total . 
 
 98-53 
 
 98-32 
 
 100-51 
 
 10073 
 
 lOO'OO 
 
 99-06 
 
 lOO'IO 
 
 100-56 
 
 99-56 
 
 99-47 
 
 Moisture in fresh water . 
 
 29-20 
 
 29-41 
 
 27-50 
 
 
 
 
 
 
 
 
 
 
 30-40 
 
 29-96 
 
 It was not until 1863 that soda was regularly obtained from vat-waste, i.e., by the 
 process of Guckelberger (improved by L. Mond), of Schaffner (of Aussig), of P. W. 
 Hofmann (of Dieuze), and of Schaffner and Helbig (1878). The earlier processes 
 depend on the conversion of the insoluble calcium sulphides in the waste into soluble 
 compounds by means of oxidation effected by atmospheric oxygen, lixiviation of the 
 oxidised mass, and precipitation of the sulphur present in the lyes (in the form of poly- 
 sulphides and of thiosulphate) by the addition of an acid, hydrochloric acid being always 
 used as a matter of course in actual practice. 
 
 The earliest process of Schaffner consists of the following operations : the 
 production of the sulphur-lye, its decomposition, and the precipitation of the sulphur. 
 
 For obtaining the sulphur-lye, the vat-waste is subjected to an oxidation process in 
 the air by being thrown up in heaps. The heaps heat in time, and the formation of 
 polysulphides, and on further oxidation that of thiosulphates, begins. Practice soon 
 teaches how long a heap should lie. After some weeks the heap has a yellowish-green colour 
 within, and is ready for lixiviation. It is broken up and remains for twenty-four hours 
 exposed to the air, when the oxidation is complete. The lixiviation is effected with cold 
 water, as in the case of crude soda ; so that at the conclusion only concentrated lyes come 
 into play. After this lixiviation process the waste is once more oxidised by placing it 
 in pits i metre in depth and width, made near the lixiviation tanks. This oxidation 
 
SECT, in.] SODA. 331 
 
 in pits is more rapid than the former oxidation. The former lixiviation pro'cess has 
 made the mass more porous, so that the air has better access, and there are formed more 
 thiosulphates along with the polysulphides. Or, instead of putting the residues in 
 these pits, they can be let remain in the lixiviation tanks, and the second oxidation can 
 be accelerated by forcing the gases from a chimney under the double bottom of the 
 lixiviation-tanks. Labour is thus economised, as the filling and emptying the pits is dis- 
 pensed with. This kind of oxidation is very energetic, and in eight to ten hours the mass is 
 again ripe for lixiviation. This oxidation may be repeated from three to ten times, accord- 
 ing to the character of the waste. The furnace gases decompose the calcium sulphide 
 in such a manner that polysulphide and thiosulphate are formed. The gases must not 
 be employed too hot. The lyes from the first oxidation consist chiefly of polysulphides 
 and thiosulphates : in those of the second lixiviation the thiosulphate predominates, 
 and in the third this is still more the case. All the lyes are mixed in a common tank. 
 The product of this operation is therefore a lye of calcium polysulphides with a certain 
 proportion of thiosulphates. 
 
 The decomposition of the lye with hydrochloric acid is effected in closed apparatus 
 of cast-iron or stone. In the decomposition of calcium thiosulphate by hydrochloric 
 acid, sulphurous acid is evolved and sulphur separates out: 
 
 CaS 8 O 3 + 2HC1 = Ca01 2 + SO 2 + S + H 2 O. 
 
 The sulphurous acid further decomposes the polysulphide into calcium thiosulphate 
 with elimination of sulphur : 
 
 2 CaSx + 3 SO 2 = 2CaS,O 3 + Sx. 
 
 By titration the sulphur-lye may be tested for its proportion of polysulphide and 
 thiosulphate, and the waste may be oxidised accordingly. Fig. 299 shows the cast- 
 iron precipitating apparatus as generally introduced. A and B contain the lye to be 
 
 decomposed. By means of a flexible tube attached to I, the lye is directed either 
 through q into A, or through q' into B. Earthen pipes, T, serve for introducing the 
 hydrochloric acid. The tubes, c and d, likewise correspond with the gas apparatus ; c is 
 placed on the cover of A, whilst its long limb opens into the liquid in B ; at d we have 
 the reverse case the short limb is on the cover of B, whilst its long limb plunges into 
 the liquid in A. The cock is closed when the gases have to pass through c into the 
 liquid in B ; the cock b is closed if the gases have to pass through d into the liquid in A. 
 Any superfluous gas escapes through R. After the decomposition steam is blown in 
 through the valves, V and V, in order to expel any residue of sulphurous acid absorbed 
 by the liquid. When the process is at an end, the sulphur flows out, with the chloride 
 of calcium lye, through the aperture, 0. At first the wooden plug is opened, and the 
 
33 2 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 chief part of the calcium chloride lye is allowed to flow out. In order to find whether 
 all the sulphurous acid is expelled, the cock h is opened, and the escape of sulphurous 
 acid, if occurring, is detected by the smell. The cocks//', serve to show whether the 
 apparatus is properly filled with lye, and to judge of the progress of the decomposition. 
 The sulphur obtained is finely granular arid contains a little gypsum ; it flows with the 
 calcium chloride liquor in a channel, g, and from here into a cistern with a double bottom ; 
 the lye flows off and the sulphur is left behind ; it is washed with water, and then under- 
 goes the melting or purifying process. 
 
 The sulphur from the precipitating apparatus is placed in a closed cast-iron pan with 
 so much water that the mass has a pasty composition, and steam is let enter at the 
 pressure of if atmosphere. In this manner the sulphur melts under water, the 
 calcium chloride lye adhering to it is taken up by the water, and the gypsum becomes 
 distributed as a fine crystalline powder. The fused sulphur collects at the lowest part 
 of the pan, and can be run off and cast in moulds. When all the sulphur is removed 
 the gypserous water is let flow off, and sulphur and water are sharply separated from 
 each other by their specific gravities. Along with the sulphur a small quantity 
 of lime is put in the pan to take up any free acid. The excess of lime forms, on 
 melting, calcium sulphide, and if the sulphur is arseniferous the arsenic 
 sulphide dissolves in the calcium sulphide and passes into the supernatant water. On 
 melting under water it is not necessary to carefully wash and dry the sulphur : distilla- 
 tion is dispensed with, and the sulphur is freed from arsenic by one and the same 
 process. The method of smelting with steam pressure has the advantage that the 
 sulphur is only heated enough to become a thin liquid and cannot be overheated, 
 which is important as regards the subsequent casting. 
 
 Fig. 300 shows the melting-pan. A cast-iron cylinder, B, lies in a wrought- 
 iron cylinder, A, the ends of both being screwed together. The apparatus slopes to 
 
 one end, so that the melted sulphur may 
 collect at the lowest part. Into the inner 
 cylinder are put the sulphur, and the need- 
 ful quantity of water, and there is in this 
 cylinder a shaft with ."i/ms turned by means 
 of the toothed wheel, 7\ The sulphur is in- 
 troduced at m. The steam enters at a into the 
 wrought-iron cylinder, surrounding the cast- 
 iron cylinder B, into which it enters at o, 
 and after the fusion is complete it is let 
 escape from the dome, d, provided with a 
 safety-valve, /&*. The melted sulphur is let off 
 at z. In this manner from 50 to 60 per 
 cent, of the sulphur present in the waste is 
 obtained in the state of pure sulphur. To 
 i part sulphur there are used 2 to 2^ per 
 cent, hydrochloric acid. 
 
 Mond's Recovery Process. Guckelberger observed that, by oxidising and lixiviating 
 the vat-wastes, solutions are obtained which contain not merely thiosiilphate, but poly- 
 sulphides in quantity, and which, with acids, give a precipitate of sulphur. Like 
 Schaffner, Guckelberger also found that the waste after being once lixiviated yielded 
 further quantities of lye on repeated oxidation and lixiviation. The experiments were 
 carried on for Guckelberger by L. Mond, who afterwards continued them on his own 
 account, and arrived at the following process : 
 
 The waste remains in the lixiviating vats, the number of which is increased three- 
 fold. The space between the two bottoms is connected by a tube to a blast, the work 
 
 Fig. 300. 
 
?ECT. III.] 
 
 SODA. 
 
 333 
 
 Fig. 301. 
 
 of which can be regulated by a slide in the tube. As soon as the last lye has been 
 drawn off. air is blown in. The waste is heated by reason of the accelerated oxidation 
 up to 94 ; watery vapours escape, and on the surface of the mass there appear white 
 shining spots. From the quantity of the vapours, the number of the spots, and the 
 temperature, it is seen whether the suitable degree of oxidation has been reached. 
 The waste is then covered with water and submitted to a methodical lixiviation. The 
 liquids obtained in the successive lixiviations are collected and conveyed to the precipi- 
 tating apparatus. The precipitation of the sulphur is effected by means of hydrochloric 
 acid in a wooden vessel closed with a cover, in which is a stirring apparatus, an 
 escape-pipe for gases, and an inlet pipe for steam. Hydrochloric acid and sulphur- 
 lye are admitted alternately. The decomposition ensues without any escape of 
 sulphuretted hydrogen or sulphurous acid, if certain proportions are observed which 
 have been ascertained by practice. According to Mond, this is the case when the 
 equivalents of the thiosulphates in the sulphur-lye are to those of the polysulphides 
 as i : 2. He assumes that the decomposition of these compounds of hydrochloric acid 
 is effected almost exclusively according to the following equation 
 
 CaS 2 O 3 + zCaSx + 6HC1 = sCaCl, + 3 H 2 O + xS. 
 
 The temperature of the liquid in the precipitating apparatus should not fall 
 below 40 nor exceed 60. In the former case the precipitated sulphur does not 
 deposit completely, and in the latter there are formed large quantities of gypsum, which 
 mix with the sulphur. The decomposed neutralised lyes are 
 drawn off into settling cisterns. The sulphur collecting at 
 the bottom was formerly washed, dried, and at once melted. 
 
 Schappi gives here the following working directions : - 
 The longer the lye and the oxidised residue are left in 
 contact the more sulphide is dissolved, and the more strongly 
 the mass may be oxidised without danger of having it over- 
 blown. It is best to oxidise as strongly as possible, and to 
 lixiviate as long as possible (two to three hours). The 
 weaker the lye, the richer it is in sulphides ; the stronger, 
 the richer it becomes in hyposulphite. The more we 
 oxidise, therefore, the weaker the solution must be kept. 
 
 Schappi generally works with a solution of 16 Tw. (hot). When he began to work 
 with a solution of 12 Tw. (hot) he could oxidise with a double quantity of air without 
 obtaining an over-blown lye, thus obtaining a better yield of sulphur. With hot water, 
 not only far more sulphide is dissolved in a short time, but, what is more important, 
 the residue is not cooled. Hence the residue after the lye is drawn off oxidises at once 
 well, whilst, otherwise, four to six hours are required before it becomes again sufficiently 
 hot for energetic oxidation. If it is decomposed on the large scale, so that lye and acid 
 mix, with exclusion of air, before entering the decomposer, there is a twofold gain : the 
 loss of sulphuretted hydrogen by imperfect decomposition is unimportant and the 
 decomposer works better. One precaution must be observed : the lye must be kept at 
 between 80 and 90 by means of waste steam, as the sulphur otherwise does not 
 admit of filtration. 
 
 From the decomposer the solution flows through the pipe, / (Fig. 301), upon the 
 filters directly at g, and at i circuitously. Within the decomposer a perforated beam, 
 &, is placed laterally, and is connected by the aperture, c, with the ascending stoneware 
 pipe, e. The lye and the acid flow together (with a hydraulic joint) through the two 
 bent stone-ware pipes, a, mix on the way to e, and discharge into the upper layer of 
 the decomposer, and flow off to the filters, after being completely worked through by 
 the mechanical agitator below in the decomposer. The stone-ware pipe, d, bent at 
 right angles, opens into a channel in the wall of the decomposer. In general it is closed 
 
334 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 with a plug, or with a flexible tube, or a pinch-cock. On setting the decomposer to 
 work, half the contents are run out, d is then opened in order to empty the 
 pipes b and c, so that they may not be stopped by the deposit of sulphur. 
 
 For every residue there is a certain specific gravity to which the sulphur lyes must be 
 brought, and which depends on the time of oxidation, the time of lixiviation, and the 
 volume of air used for oxidation. The longer we oxidise, and the more air we use, the 
 weaker the lye must be kept ; the longer and hotter we lixiviate, the stronger the lye 
 must be, in order to obtain the most advantageous composition. The attempt must be 
 made with very strong oxidation to keep the specific gravity of the lye so low that it is 
 a, little over-blown. 
 
 At St. Salindres, air is blown into the yellow lye of the vat-waste by means of a 
 Korting blast up to the point where on treatment with acid neither H 2 S nor SO 2 is 
 given off, and the decomposition with hydrochloric acid then follows. Much may be 
 here economised, because during the operation of oxidation about one-fourth of the 
 lime, in passing from CaS to CaO, is deposited in a very dense condition, and can be 
 easily filtered off, whilst sulphides are formed richer in sulphur. 
 
 Recovery of Sulphur by P. W. Hofmann. At the works at Dieuze a process was 
 developed between 1864 and 1866 which, in addition to the recovery of the sulphur from 
 vat-waste, aimed at reviving the manganese from the waste of the chlorine stills. The vat- 
 waste had been piled up for more than thirty years. Close to the works flows a streamlet, 
 which afterwards touches the town of Dieuze. This stream takes up all the sulphur 
 compounds flowing from the waste in rainy weather, as well as the acid manganese 
 liquors. The water, for a distance of 6 to 8 kilometres, was coloured black by the 
 precipitate of iron sulphide, and contaminated the air with hydrogen sulphide to such 
 an extent that the authorities threatened to close the works unless the nuisance was 
 promptly removed. 
 
 The experiments made by P. W. Hofmann led finally to the following results : 
 As in the other procedures for the recovery of sulphur, soluble sulphur compounds are 
 first produced by the oxidation of the waste. This oxidation is effected in heaps, which 
 are previously mixed with iron sulphide precipitated from the neutralised manganese 
 liquors. Experiments proved that the addition of iron sulphide promoted the oxidation. 
 The waste, after six or seven days' exposure to the action of the air, was lixiviated, 
 yielding a liquid which was known as eaux jaunes sulfurees. The residues were 
 oxidised twice more and treated with water, the second and third oxidation not requiring 
 more than three days each. The solution thus obtained contains principally calcium 
 thiosulphate, and was called eaux jaunes oxydees. The united liquids from the 
 lixiviations were let flow into a tank made of stone flags, made water-tight at the 
 junctions with asphalt, and let mix with the acid manganese, which had been previously 
 clarified by twenty-four hours' rest in a similar tank. The decomposition of the sulphur- 
 lye is effected at the expense of the free acid existing in the manganese chloride, as 
 well as of the free chlorine and the ferric chloride. The separation of sulphur begins 
 .at once, without the escape of hydrogen sulphide, if the respective proportions of the 
 two " yellow waters " were correct. In order to prevent any such escape the sulphur- 
 lye is led, not at once into the cistern, but into a conical apparatus of sheet-iron. It is 
 provided at half height with two openings, through which pass two tubes, extending 
 down to within a few centimetres of the bottom of the cone. A little higher there are 
 two other openings, through which the liquid can flow off into the cistern. The 
 manganese liquor and the sulphur-lye are let flow in simultaneously through the two 
 tubes, and in such quantity that the efflux openings are kept constantly closed by the 
 inflowing solutions. The first reaction takes place within the cone ; any H 2 S formed 
 collects in its upper part, and is led off through a pipe issuing from the apex of the cone, 
 At the end of which it is burnt. The sulphurous acid formed is carried off by a tube 
 
SECT, in.] SODA. 335 
 
 into a vat filled to two-thirds of its height with eaux jaunes sulfurees and kept in con- 
 stant motion by a mechanical agitator. The S0 2 converts the calcium polysulphides of 
 the eaux jaunes sulphurees into calcium thiosulphate, whilst sulphur is separated. 
 The thiosulphate is decomposed with sodium sulphate and used for preparing sodium 
 thiosulphate. 
 
 The sulphur collecting on the false bottom of the sulphur vessel is washed and dried. 
 The neutral manganese liquors are pumped into underground tanks with puddled clay 
 bottoms, and with sides of bank waste piled up on woodwork. As soon as the liquid 
 is clear, it is drawn into other recipients, in which the last traces of suspended matter 
 quickly settle. The residual mass of iron sulphide is intimately mixed with the vat- 
 waste produced daily, and exposed in heaps to the oxidising action of the air, as already 
 described. The neutral manganese liquors, freed from iron and clarified, are mixed in 
 a special receiver with the yellow sulphur-lye, producing a deposit which contains all 
 the manganese along with a quantity of free sulphur. This precipitate is let settle, 
 the supernatant liquor (calcium chloride) run off upon linen filters, washed with water, 
 and the residual mass dried upon stone flags. 
 
 The dried manganese consists of a mixture of manganic oxide and free sulphur. In 
 order to utilise the latter, the mixture is roasted and the S0 2 is passed into the 
 chambers. The residue consists of mangano-manganic oxide, with 40 to 45 per cent, of 
 manganese sulphate. The latter is dissolved out with water, yielding a mass which 
 consists of pure mangano-manganic oxide, free from iron, and hence fit for use in the 
 glass manufacture, where iron gives a green colour. From the aqueous solution 
 manganese sulphate may easily be obtained by evaporation. It is then mixed with 
 sodium nitrate, and the mixture is heated in the sulphur furnaces with formation of 
 sodium sulphate and manganese nitrate, the latter of which is at once resolved into 
 higher oxides of manganese and hyponitric acid. The hyponitric acid passes into the 
 chambers along with the sulphurous acid, and aids in the conversion of the latter into 
 sulphuric acid. If the ignited mass is lixiviated with water, sodium sulphate dissolves 
 and manganese oxides remain, containing about 55 per cent, of manganese peroxide, 
 and capable of being used in the production of chloride of lime. From the solution of 
 sodium sulphate, Glauber's salts may be obtained by crystallisation, and it is used for 
 the decomposition of the neutral solution of calcium chloride. There is obtained, 
 especially on stirring, a gypsum of fine texture, which may be used in place of china 
 clay in the paper manufacture. 
 
 The more or less profitable application of one or the other process for recovery 
 depends much on the nature of the vat-waste, on the cost of labour, and on the price of 
 sulphur or pyrites. Muddy waste cannot be advantageously oxidised in Mond's process, 
 and oxidation in heaps is here to be preferred. Hofmann's process is somewhat 
 complicated, but the results are said to be satisfactory.* 
 
 The precipitation of sulphur by the processes of Mond and Guckelberger is effected 
 most completely when free sulphurous acid is present in the lye, mixed with hydrochloric 
 acid exactly in such a proportion that in the fresh lye all the sulpho and hydrosulpho 
 compounds are converted into thiosulphates. The thiosulphates, if the process works 
 normally, are exactly converted by a fresh quantity of hydrochloric acid into sul- 
 phurous acid and free sulphur, the former of which serves exclusively for converting 
 the sulphides into thiosulphate. As the liquid which runs off must be neutral, a small 
 quantity of sulphur is always lost in it in the form of dissolved thiosulphate. 
 
 According to Divers, when moist vat- waste is exposed to the air there takes place, 
 first, hydration of the calcium sulphide. The most important of the hydrogenised com- 
 pounds are : calcium hydrosulphide, a colourless crystalline salt, which in the air is 
 quickly decomposed to form calcium hydrate and calcium hydroxy hydrosulphide. 
 * Probably labour is cheap there. It does not appear to have been widely adopted. 
 
33 6 CHEMICAL TECHNOLOGY. [SECT, in 
 
 This latter compound, CaSH.OH. 3 Aq., is deposited from a solution of calcium hydro- 
 sulphide which has been mixed with lime and sugar. The compound is likewise pro- 
 duced if solid calcium hydrate is placed in a solution of calcium hydrosulphate, and if 
 calcium hydrate is treated with sulphuretted hydrogen. In solution the compound is 
 quickly decomposed with separation of calcium hydrate. In a concentrated solution 
 of calcium hydrosulphate the compound is insoluble and is then not decomposed by 
 water. The calcium sulphide in vat-waste passes first into calcium hydroxyhydro- 
 sulphide, and this is the source of calcium hydrosulphate. As the former compound is 
 insoluble with solution of calcium hydrosulphate, only weak solutions are obtained in 
 lixiviating vat-waste. Concentrated lyes of hydrosulphate easily give off hydrogen 
 sulphide and form calcium hydroxyhydrosulphide. The two latter facts have hitherto 
 frustrated all attempts to dissolve out the bulk of the sulphur in vat- waste in an 
 inexpensive manner. 
 
 Divers believes that the best process for extracting the sulphur from vat-waste in 
 the form of hydrogen sulphide is to treat it successively with steam in about four 
 vessels. By gradually oxidising and lixiviating the vat-waste, we obtain a mixture of 
 calcium polysulphide and thiosulphate. A formation of bisulphide was formerly 
 assumed, but now it is found that the products are tetra- and penta-sulphide. Hydra- 
 tion of calcium sulphide precedes all other changes : 
 
 CaS + H 2 O = Ca.SH.OH. Ca.SH.OH + H 2 O = CaO 2 H 2 + H 2 S. 
 
 Ca.SH.OH + H,S = CaS 2 H 2 + H 2 O. 
 
 Wet vat-waste laid in covered heaps contains, in addition to unaltered calcium sul- 
 phide, calcium hydroxyhydrosulphide, calcium hydrate, and free sulphuretted hydrogen. 
 Oxygen during the oxidation of vat-waste acts upon the free sulphuretted hydrogen 
 which is constantly being formed. As has long been known, H 2 S is readily, though 
 slowly, oxidised. The experiments of Divers show that the direct oxidation of calcium 
 hydrosulphate by air is extremely tedious. He therefore concludes that only the free 
 hydrogen sulphide, and not its calcium compounds in vat-waste, is oxidised by the 
 air. Sulphur, if boiled with lime, yields calcium pentasulphide and thiosulphate : 
 
 3 CaO 2 H 2 + 128 = CaS 2 O 3 + 2 Ca 2 S 5 + 3 H 2 0. 
 
 It must be assumed that when the reaction takes place at a boil with ready-formed 
 sulphur it will also take place in the cold with nascent sulphur from the oxidation of 
 vat-waste. The chemistry of the oxidation of vat-waste is thus much simplified. The 
 fixed products of the hydrolysis of calcium sulphide are calcium hydrate and hydrogen 
 sulphide ; the latter is oxidised by the air to free sulphur, whilst pentasulphide and 
 thiosulphate are formed with the hydrate of lime. 
 
 Whilst in the process depending on the oxidation of calcium sulphide only half the 
 sulphur is recovered, the lime and the remaining half of the sulphur forming a vat- 
 waste of the second order, Schaffner and Helbig recover all the lime and all the sulphur 
 in a useful form. Their process for producing sulphur from vat-waste and sulphurous 
 acid with the simultaneous recovery of the earths combined with sulphur as carbonates 
 depends on the use of magnesium chloride for decomposing the calcium sulphide accord- 
 ing to the formula : 
 
 CaS + MgCl 2 = MgS + CaCl 2 , and MgS + 2 H 2 O = Mg(OH) 2 + H 2 S. 
 The calcium carbonate is not decomposed by the magnesium chloride. The magnesium 
 chloride employed is recovered as vat-waste residue ; it consists of the magnesia, the 
 calcium chloride, and the other ingredients which did not enter into reaction after the 
 expulsion of the hydrogen sulphide. This is exposed to the action of C0 2 , when calcium 
 carbonate and magnesium chloride are formed according to the formula : 
 
 MgO + CaCl, + C0 2 = MgCl 2 + CaCO 3 . 
 
 Instead of using magnesium chloride alone, a portion of it may be taken, hydro- 
 chloric acid being alternately or simultaneously introduced, when the liberated 
 
SECT, m.] SODA. 337 
 
 magnesia is dissolved and exerts its action again. Sulphuretted hydrogen is converted 
 by sulphur dioxide into sulphur, according to the formula : 2H 2 S + S0 2 = 38 + 2H 2 O. 
 
 There are here formed, however, not merely sulphur and water, but tetrathionic 
 and pentathionic acid, &c. This injurious bye-reaction is greatly lessened (though 
 not prevented, as the inventors assume) by the use of solutions of calcium and magne- 
 sium chlorides. If there is an excess of one or other of the gases, this has no effect 
 upon the reaction. It is not yet decided what is the part taken by these chlorides in 
 the reaction, but it is certain that one equivalent of calcium or magnesium chloride is 
 required for the total sulphur present. The decomposition of the vat-waste with 
 magnesium chloride is effected in heat in large closed iron vessels, fitted with agita- 
 tors. Either the vat- waste is gradually introduced into the total quantity of magnesium 
 chloride required to fill the generator, or the magnesium chloride is let flow into the 
 entire quantity of vat-waste, or both substances are simultaneously introduced into 
 the vessel in equivalent proportions. The escape of sulphuretted hydrogen is thus pre- 
 vented so that no pressure can arise in the generators and decomposers ; further in the 
 sulphuretted hydrogen decomposers a larger quantity of S0 2 is always kept in store 
 than corresponds to the H^S flowing in from the generators. The silica and alumina 
 in the vat-waste, which, if they remained in the recovered lime, would soon accumulate, 
 so as to render it useless, are removed by elutriation or by passing the residues of 
 decomposition through a fine sieve. The recovery of the magnesium chloride and the 
 lime from the residues thus freed from slags (silica and alumina) is effected by passing 
 into them air containing carbon dioxide (combustion gases). According to Chance, the 
 hydrogen sulphide burns to sulphur dioxide. 
 
 According to a recent proposal of Schaffner, the magnesia may be used for decom- 
 posing the sal-ammoniac lyes of the ammonia soda works. 
 
 According to C. Opl, the sulphur is to be dissolved as calcium hydrosulphate by 
 treating vat-waste with sulphuretted hydrogen. The process is being introduced in 
 the B-henania works, as recently, in consequence of a rise in the price of hydrochloric 
 acid, the recovery of sulphur on Mond's process has become unprofitable. 
 
 Of particular importance is the new process of Chance, which carries out the 
 reaction : H 2 S + = H 2 O + S. The hydrogen sulphide and other gases, chiefly 
 nitrogen, are allowed to mix with an accurately regulated quantity of air in the pro- 
 portion of H 2 S + 0. The gases are burnt beneath the grate of a circular shaft tired 
 with fire-stones. Upon the grate there lies first a layer of brick, and then one 
 of ferric oxide. The latter is heated to dull redness by the reaction itself, and 
 in this state it effects the almost completely smooth combustion of hydrogen 
 sulphide to watery vapour and sulphur vapour. The vapours produced pass first 
 into a small brick chamber and thence into a large chamber. The former soon 
 becomes so hot that the subliming sulphur melts and can be drawn off in this state. 
 But very much sulphur passes in the form of vapour into the large brick chamber, 
 flowers of sulphur condensing at the front and water at the back. As the escaping 
 gases still contain a small quantity of unchanged hydrogen sulphide and also of 
 sulphur dioxide, they are passed through suitable purifiers before escaping into the air. 
 As the success of this process depends in the first place on the exact equivalence of 
 the quantity of oxygen to that of the hydrogen sulphide but the percentage of the 
 latter fluctuates greatly in consequence of the use of impure carbonic acid it is 
 important to obtain the latter of rich and uniform composition. This is effected by 
 utilising the experience obtained in the ammonia-soda process, according to which 
 lime-kiln gases are obtained containing 30 per cent, of carbonic acid. But even with 
 this, in all earlier experiments for decomposing vat-waste, gaseous mixtures were 
 obtained containing very variable quantities of hydrogen sulphide, and, of course, with a 
 very large admixture of foreign gases. Chance has succeeded in greatly reducing these 
 
 T 
 
338 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 mixtures and in producing a fairly constant yield, so that he can now obtain with 
 certainty at pleasure either sulphurous acid or sulphur. He makes use of the long- 
 known reaction, that carbonic acid acts upon calcium sulphide in the presence of 
 water, so that there is at first a production of calcium hydrosulphate 
 
 2 CaS + GO, + H 2 = CaCO, + Ca(SH),. 
 
 An excess of carbonic acid decomposes the hydrosulphate and expels all the sul- 
 phuretted hydrogen : Ca(SH) 2 + C0 2 + H 2 = CaC0 3 + 2H 2 S. 
 
 In the practical execution of the process the vat- waste is made up with water to a 
 thin paste, which is passed through a sieve to remove all coarse parts, and in this state 
 is conveyed into tall cylinders, into which the gases of the lime-kiln are pumped. A 
 battery of seven cylinders, 4^ metres high and i'8 metre in diameter, is sufficient to 
 treat the residue from the weekly working of 300 tons salt-cake. In the first vessel 
 the C0 2 saturates the free lime and then drives out the H 2 S, according to the above 
 equations. The latter, being driven into other vessels, encounters fresh vat-waste and is 
 there absorbed with the formation of calcium hydrosulphate : CaS + H 2 S = Ca(SH) 2 , so 
 that for a time the escaping gases contain mere traces of C0 2 and H S S and consequently 
 may escape into the air, though for safety's sake they are passed through lime or iron- 
 oxide purifiers. In this manner considerable quantities of useless gases are got rid of. 
 In time the sulphuretted hydrogen appears in more than traces. This is detected 
 when in one of the intermediate vessels the gas which escapes on opening a cock can be 
 ignited. The course of the gases is then changed ; the passage from the last receiver 
 into the air is closed and a pipe leading to a gas-holder is opened. Into this the gases 
 are passed as long as they are sufficiently rich in H 2 S. When this ceases the pipe is 
 shut off, and as in the meantime the vat- waste in the first cylinders is fully desulphur- 
 ised, it is taken out and replaced by a fresh charge, so that the process begins again ; 
 the cylinders which were first coming in turn last. The introduction of carbon dioxide 
 is continued until the clear nitrate from the cylinders no longer gives a reaction with a 
 salt of lead. The residue now consists chiefly of calcium carbonate in the form of 
 mud, but containing 2-5 to 3 per cent, of soda in the form of bicarbonate, which is 
 utilised when this mass is used in the decomposition furnace. Another useful appli- 
 cation is that for cement, and in both respects this residue is better than that of the 
 Schaffner-Helbig, process as the following analyses show : 
 
 
 Lime Eesidue. Schafiher- 
 
 Lime Eesidue. 
 
 
 Helbig. 
 
 Chance. 
 
 Calcium carbonate . 
 
 75-62 
 
 7932 
 
 76-48 
 
 71-14 
 
 84-79 
 
 87-16 
 
 86-32 
 
 sulphate 
 chloride 
 
 4-60 
 0.36 
 
 O-25 
 
 4-62 
 0-30 
 
 4-52 
 1-51 
 
 0-36 
 
 0-49 
 
 0-36 
 
 silicate 
 
 
 
 
 
 
 
 
 I '91 
 
 2-30 
 
 2 "35 
 
 Magnesium carbonate 
 Magnesia . 
 
 0'6o 
 2-50 
 
 177 
 1-67 
 
 0-70 
 
 2-85 
 
 3 "20 
 
 
 1-03 
 
 I '07 
 
 Magnesium chloride 
 
 0-88 
 
 078 
 
 1-70 
 
 2-58 
 
 
 
 
 Sodium carbonate . 
 
 
 
 
 
 
 
 
 0'45 
 
 o-S5 
 
 0-63 
 
 sulphate . 
 
 
 
 
 
 
 
 
 
 0-07 
 
 O'2I 
 
 o'O7 
 
 silicate . 
 
 
 
 
 
 
 
 
 
 I'47 
 
 I-42 
 
 I -00 
 
 
 0-96 
 
 0-80 
 
 0-76 
 
 0-94 
 
 I-I9 
 
 I'47 
 
 
 
 FeS 
 
 Fe,O. 
 
 2 "JO 
 
 
 
 
 1-05 
 
 0-71 
 
 0-99 
 
 Coke 
 
 
 372 
 
 34 
 3-00 
 
 I 07 
 
 3-80 
 
 4-06 
 
 2 'O6 
 
 2-98 
 
 n-Xr 
 
 Sand 
 
 
 .- o 
 
 O'3O 
 
 I "12 
 
 
 o 97 
 
 
 
 
 } 4-65 
 
 4-30 
 
 6'oo 
 
 45 
 6-00 j 
 
 o'4S 
 0-58 
 1-31 
 
 0'54 
 0-39 
 I'll 
 
 0-40 
 1-29 
 
 Moisture (to 100) . . 
 Water and loss .... 
 
 Combined silica ... 
 
 
 
 
 
 
 
 
 
 171 
 
 1-89 
 
 172 
 
 SO, 
 S, as sulphide .... 
 
 
 
 
 
 z 
 
 
 0-25 
 0-38 
 
 0-41 
 O-26 
 
 0-25 
 0-36 
 
 S, free 
 
 }. 
 
 0-85 
 
 0-70 
 
 175 { 
 
 o-45 
 0-26 
 
 075 
 
 0'5S 
 0-32 
 0-72 
 
 O-40 
 0-37 
 0-51 
 
 Soda, soluble .... 
 Soda, insoluble . . ... 
 
SECT, in.] SODA. 339 
 
 The water running off from this process is clean enough to flow into any stream ; 
 it is best utilised for making up fresh waste into a paste. It contains grammes per 
 litre: 
 
 Alkalinity, as NaHC0 3 , calculated as Na 2 . . 6 '63 to 8'6l 
 Alkaline earths calculated as CaCO s 1-50 2-16 
 
 Total sulphur o - 22 
 
 Sulphur as sulphates traces 
 
 as thiosulphates 0*05 
 
 as sulphides 
 
 I'll 
 
 O'OI 
 
 0-23 
 
 O'OO 
 
 0-08 
 
 Silica O'oo 
 
 Alumina, ferric oxide ........ traces 
 
 The sulphuretted hydrogen is collected in a gasometer of 15 metres diameter and 
 4'2 metres effective height, containing 850 cubic metres. The water-joint is completely 
 shut off from the air by a layer of coal-tar oil boiling at a very high temperature. The 
 composition of the gases varied, in eight analyses made in four days, only from 32*3 to 
 34-0 H 2 S and i'io to 2'o CO, (using lime-kiln gases of 27*0 to 29*1 per cent. CO 2 ). 
 
 The gas burns at once if lighted. The heat is sufficient to work the Glover tower, 
 and to concentrate acid set in lead pans on or around the furnace. The chamber 
 room is the same as the pyrites furnaces, and the consumption of nitre ranges from 
 i 'i 5 to i '44 per cent, on the acid produced, calculated as S0 3 . 
 
 In working for several months a complete set of chambers in this manner, 90 per 
 cent, of the sulphur found analytically in the vat- waste had been recovered ; 8 percent, 
 were lost as iron sulphide, as S0 2 and H 2 S in the main separation, in consequence of 
 accidental leakages, &c. ; 5 per cent, remained in the coarser parts sifted out, which 
 will be utilised by improved arrangements. 
 
 Of the H 2 S taken from the gasometer, 98 to 99 per cent, were recovered as sul- 
 phuric acid. The acid is perfectly free from arsenic, contains a mere trace of iron, and 
 is nearly colourless. From November 1877 * March 3, 1888, more than 3000 tons 
 of vat-waste were worked up, and about 40 tons S0 3 were produced weekly. 
 
 The expense of the process is very small. The outlay for the installation is only one- 
 half of that for the Schaffner-Helbig process. The cost of labour for the entire process 
 is smaller than that for breaking up pyrites, serving the pyrites furnaces, and carrying off 
 the burnt ores. No fuel is required, except that for raising the steam used in pumping 
 the lime-kiln gases. An alkali manufacturer who makes either caustic alkali or 
 chloride of lime requires for each of these operations more quicklime than that corre- 
 sponding to the quantity of kiln-gases required for treating the vat-waste. Brock (of 
 the firm of Sullivan & Co.) estimates the total cost of the sulphur at id. per unit i.e., 
 about 8s. 6d. per 21 cwt. or 1067 kilos. 
 
 The economy of Chance's process can best be appreciated if we realise that at 
 present 300,000 tons of pyrites are used annually in England in the Leblanc process, 
 and that their sulphur has till lately passed into the unendurable mounds of vat- waste. 
 If, in future, as Chance hopes, the pyrites sulphur may be obtained gratis from the 
 mining companies, and if the vat-waste were worked upon the Chance process, there 
 would be obtained in England yearly 300,000 tons of sulphur, of which 30,000 to 
 40,000 would be used in this country, and the rest would be available for exportation. 
 It is to be remarked that, in 1887, 312,446 tons were exported from Sicily, of which 
 88,593 tons went to America. 
 
 The Ammonia-soda Process. If ammonium bicarbonate in a concentrated solu- 
 tion is brought in contact with saturated brine, or preferably if the brine is mixed 
 with finely powdered ammonium bicarbonate, the less soluble sodium bicarbonate 
 separates as a crystalline powder, and the supernatant liquid is a watery solution of 
 ammonium chloride : 2NaCl 4- 2NH 4 .H.C0 3 = 2 NaHC0 3 -t- 2 NH 4 C1. 
 
 As sodium bicarbonate passes into sodium carbonate at dull redness : 
 2 NaHCO, = Na,CO, + H,O + CO,, 
 
340 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 we have here the foundation of a process for the manufacture of soda, where, of course, 
 the ammonia required for precipitating fresh quantities of common salt must be re- 
 covered by means of lime or magnesia : 
 
 2 NH 4 C1 + Ca(OH) 8 = 2 NH 3 + CaCl 2 + 2H 2 0. 
 
 Dyar and Hemming carried out the industrial production of soda from common 
 salt and ammonium bicarbonate in England as early as 1838. The next process, of 
 Schloesing and Holland, for which they took out a British patent in 1855, contained 
 certain improvements, but it was essentially similar to the process above described. 
 Schloesing used for the manufacture strong brine, which was saturated with ammonia 
 and carbon dioxide. Ammonia and carbonic acid were let act upon the brine; the 
 separation of the precipitated bicarbonate from the liquid was effected by means of a 
 centrifugal machine. If the soda is to be perfectly pure, the salt is washed in the 
 centrifugal machine with a solution of bicarbonate. The calcination of the bicarbonate 
 and the consequent conversion into soda are effected in a cylinder of sheet-iron. 
 The carbon dioxide is collected as it escapes. The manufactory of Schloesing and 
 Holland, at Puteaux, near Paris, ran from 1855 to 1857, and yielded 25 tons of 
 ammonia soda monthly. 
 
 After the ammonia-soda process had been attempted with more or less success by 
 Gerstenhoefer of Freiberg, Honigmann of Aachen, and many others, E. Solvay of 
 Brussels introduced it in his works at Couillet in Belgium, and subsequently at 
 Varangeville-Dombasle, near Nancy. 
 
 The conversion of sodium chloride into bicarbonate is effected in three connected 
 pieces of apparatus, the first serving to prepare the concentrated brine, the second for 
 saturating the solution with ammonia, and the third for decomposing the ammoniacal 
 liquid by means of carbon dioxide. The apparatus in which the brine is saturated with 
 ammonia is a cistern of tin-plate, or of wood lined with lead, taller than it is wide. It 
 has a perforated false bottom, beneath which the ammoniacal gas enters, which is divided 
 by the holes into many separate bubbles, and is easily absorbed by the brine. The 
 liquid increases considerably in volume, whilst its density falls from 37-6 Tw. to 18 
 to 21 Tw. As considerable heat is liberated on the absorption of the ammonia, the 
 saturated solution is first passed into a vessel, where it is cooled by a stream of cold 
 water flowing in a worm, and then into the absorber, in which it is decomposed by 
 carbonic acid. This gas may be produced in any convenient manner. 
 
 As an absorber there is used a cylinder as shown in section in Fig. 302. In this 
 cylinder, a, lie a number of finely perforated plates, b, of the shape of the segment of a 
 globe. Fig. 303 is such a plate seen from above. In a there are also a number of 
 plates, c, with one hole or a few holes, which give passage to the gas and the saturated 
 solution, without allowing the freshly entering liquid to mix with that at the bottom, 
 which is nearly saturated. In the margin of the perforated plates there are teeth, z, 
 cut out so that the liquid and the gas may pass through when the apertures are partly 
 choked. The absorber is always kept nearly full of liquid whilst carbon dioxide is 
 forced in from below through the pipe d. By this means the gas is not only kept in 
 very intimate contact with a liquid moving in the opposite direction, but it also exerts, 
 in consequence of its expansion, a considerable mechanical power, and consumes thereby 
 such a quantity of heat that the heating of the liquid is prevented (as would otherwise 
 be the case on the absorption of carbonic acid by the ammonia), and which could not be 
 otherwise easily avoided. The liquid enters through a pipe, e, at about half the height 
 of the cylinder, into which it flows out of a trough, so that its level is kept uniform, 
 about 3 metres from the upper end of the cylinder. The trough is closed, and is con- 
 nected with the upper end of the cylinder by a tube, which maintains an equal pressure 
 in both. One trough can supply several absorbers. In this manner the liquid is 
 reserved only in the upper half ; it sinks down very slowly, and is soon saturated 
 
SECT. III.] 
 
 SODA. 
 
 Fig. 304. 
 
 with carbonic acid suited for taking up all the ammoniacal gas which the gas may bring 
 with it from the lower part of the absorber. The absorbers must be so high that at 
 least half the carbonic acid entering from below is absorbed, and, at the same time, all 
 the ammonia contained in the liquid may be converted into bicarbonate. A height of 
 ii to 1 6 metres, when the gas must be forced in at a pressure of i| to 2 atmospheres, 
 gives the best results. It is well not to let the gas enter in an uninterrupted current, 
 as an irregular motion 
 prevents the bicarbonate 
 separated out from at- 
 taching itself to any one 
 place. The liquid satu- 
 rated with carbonic acid 
 is best allowed to run 
 out in portions every 
 three minutes ; the sus- 
 pended bicarbonate is 
 collected in a vacuum 
 filter and washed in a 
 very small quantity of 
 water. In a cylinder, 
 g (Figs. 304 and 305), 
 there are at suitable 
 distances from each 
 other a number of round 
 plates, A, with openings 
 at the centre and at the 
 circumference. A shaft, 
 i, passes through the 
 cover in the bottom of 
 the cylinder and carries 
 arms, k, with scraping 
 knives, I, which push 
 the mass lying on the 
 plates alternately to- 
 wards the circumference 
 of one plate and towards 
 the middle of the fol- 
 lowing, so that it gra- 
 dually passes from the 
 top plate to the bottom 
 of the cylinder. The 
 plates are hollow, and 
 can be heated by the in- 
 troduction of steam or 
 hot gases of any origin 
 
 from the pipe ra. The Fig. 302. Fig. 303- Fig. 305. 
 
 bicarbonate is intro- 
 duced by means of an apparatus, n, which resembles the body of a grinding-mill, with 
 arms, o, which move slowly. It is always kept full, so that the carbonic acid may not 
 escape here. The dried mass arrives at the bottom of the cylinder in a finely ground 
 state, fit for packing. The gases expelled on drying escape by a tube, r, in the cover. 
 If hollow plates are not used the hot gas may be passed directly through the cylinder. 
 
 | 
 
 Fig. 302. 
 
342 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. III. 
 
 Fig. 307. 
 
 Another drying apparatus suitable for the production of soda consists of an iron pan, s 
 (Fig. 306), closed with a cover, through which passes a vertical shaft in a stuffing-box. 
 The shaft carries arms with scrapers, which stir up the bicarbonate introduced, whilst 
 the pan is raised to a suitable temperature by the fire placed below. 
 
 The gas expelled in both these apparatus is carried by an air-pump into a washing 
 apparatus, in which all the ammonia is retained. If soda has been made, the carbonic 
 acid expelled is returned to the absorbers. From the ammonium chloride ammonia is 
 regenerated by lime. 
 
 According to H. Schreib, in the present way of working not more than 60 per cent, of 
 the sodium chloride used is converted into bicarbonate. The ammonia present in excess 
 in the ammoniacal lime on saturation with carbonic acid does not, after its conversion into 
 ammonium bicarbonate, enter into the desired reaction with the sodium chloride, but 
 subsides as ammonium bicarbonate. To effect a better utilisation both of the salt and 
 of the apparatus, sodium chloride in a solid form is introduced into the ammoniacal 
 brine used in the ammonia-soda process,, during its saturation with carbonic acid in the 
 carbonisation apparatus. In proportion as sodium bicarbonate is deposited, sodium 
 chloride is dissolved, and this is converted into sodium bicarbonate by the ammonium 
 bicarbonate formed in the solution, richer in salts by the continuous passage of the 
 
 carbonic acid. In this manner it is said that about 80 
 per cent, of the salt is converted into sodium bicarbonate. 
 For introducing the salt the pan, A, containing the 
 ammoniacal brine (Fig. 307) is connected with the brine 
 pan, B, by the pipes d and b. If solid salt is to be intro- 
 duced the cock c is closed and air is forced in through 
 the pipe a, so that all liquid is forced out of the pan, B. 
 If the cock e is also closed we may, after the com- 
 pressed air has been let out through the pipe b, introduce 
 solid salt into B through the man-hole, o. The man- 
 hole is then closed, and the connection of A and B is re- 
 established by opening the cocks. The passage of the 
 air containing carbonic acid promotes the circulation 
 both in A and B, The sodium bicarbonate thus obtained 
 is separated from the liquid in the ordinary manner and 
 converted into soda, whilst the filtrate, which chiefly 
 contains ammonium and sodium chloride (if solid salt is present), is saturated with 
 ammonium carbonate up to 20 to 25 per cent. Sodium chloride passes into solution and 
 ammonium chloride separates out. The reaction is assisted by agitation and strong 
 cooling. After the end of the action the solid sal-ammoniac is filtered out. The filtrate, 
 which contains 20 to 25 per cent, ammonium carbonate, 24 per cent, sodium chloride, 
 and 9 per cent, ammonium chloride, is treated with carbon dioxide in the apparatus, 
 A, and returns to the circuit of the manufacture. There is then again formation 
 of sodium bicarbonate and the above-mentioned lye of sodium chloride and ammonium 
 chloride, which is anew treated with common salt and ammonium carbonate. From the 
 sal-ammonium obtained, ammonium carbonate is prepared by treatment with ground 
 calcium carbonate, and as such it is introduced into the apparatus, A. 
 
 Weldon attempts to combine the ammonia-soda and the Leblanc process by 
 saturating a saturated solution of salt-cake with ammonia and then with carbonic acid, 
 whilst solid salt-cake is further added. 
 
 According to G. Carey and F. Hurter, for the same purpose a saturated solution of 
 salt-cake at 50 to 60 is freed from iron, lime, and free sulphuric acid by a certain 
 quantity of soda. The filtered solution is let cool down to 38 and treated with am- 
 monia, 24 to 25 parts qf which come to 100 parts of salt-cake. The temperature of 
 
SECT, in.] SODAi 343 
 
 the solution must never fall below 32, as otherwise sodium sulphate crystallises out; 
 and never rise above 38, as otherwise the pressure required for completing the reaction 
 would be inconveniently high. So much carbonic acid is then introduced that am- 
 monium carbonate is formed. It is convenient to pass in carbonic acid as soon as the 
 liquid is ammoniacal, as sodium sulphate is more soluble in solutions of ammonium 
 carbonate than in ammonia. As soon as ammonium monocarbonate is formed, it is 
 necessary, in order to complete the reaction, to introduce carbonic acid under pressure. 
 When sodium bicarbonate separates out the solution is let cool. The bicarbonate 
 is washed and freed from the mother liquor by pressure. From the residual solution, 
 which contains ammonium sulphate and carbonate and sodium sulphate, the ammonia is 
 recovered by suitable means. 
 
 Whether the proposal of the Croix Company to use trimethylamine instead of am- 
 monia in the production of alkaline carbonates can be used to advantage appears 
 doubtful. 
 
 Hasenclever (1880) gives a comparative table of the cost of the two processes, 
 which shows a balance in favour of the ammonia method to which must be added on 
 both sides repairs, lighting, salaries, general expenses, &c. If we disregard the bye- 
 products, ammonia soda is cheaper than Leblanc soda, and the first cost of the installa- 
 tion and the outlay for repairs are lower. On the other hand, the Leblanc process gives 
 a greater scope in sales, if sulphuric acid and salt-cake happen to be in better demand 
 than soda, or if chloride of lime and sulphur are more marketable than hydrochloric 
 acid ; whilst the ammonia-soda process does not furnish any intermediate products. 
 Most German establishments work with rock-salt ; if cheap brine is accessible, the 
 ammonia soda is in a better position, except the price of fuel at the spot in question if 
 too high. 
 
 Cryolite Soda. Soda is obtained from cryolite, which is opened up by heating 
 with lime - 
 
 Na 6 Al 2 F 12 + 6CaO = 6CaF 2 + Na 6 Al 2 6 . 
 
 The latter compound is soluble in water when alumina is deposited, and is utilised 
 in the state of alum; whilst soda remains in solution. In 1867 five German alkali 
 works consumed 7500 tons cryolite, and produced from it 5500 tons of soda-ash. The 
 Pennsylvania Salt-manufacturing Company consumes yearly in its works at Natrona, 
 near Pittsburg (1876), 1800 tons of cryolite. More and more accessible sources of 
 cryolite are greatly to be desired. 
 
 Soda from Sodium Sulphide. If moist carbonic acid is passed over sodium sul- 
 phide (obtained by igniting salt-cake with ground coke), sodium carbonate is formed 
 with the liberation of H 2 S 
 
 Na 2 S + C0 2 + H 2 = H 2 S + Na 2 COy 
 The process is not likely to survive. 
 
 Caustic Soda. Since the year 1851 caustic soda has become an article of com- 
 merce, either as a very strong lye or more frequently as fused hydrate (caustic soda), and 
 it is manufactured on a large scale. It is often still prepared by treating dilute solutions 
 of crude soda (black-ash) with caustic lime: Na 2 C0 3 + Ca(OH) 2 = CaCO 3 + 2NaOH. 
 The calcium carbonate formed in quantity in this process is mixed with gypsum, and 
 serves for the production of writing- or marking-chalk. In order to economise the fuel 
 for evaporating such dilute solutions the process of Dale is sometimes imitated, who 
 used the dilute lye to feed his steam-boilers and thus brought it up to sp. gr. 1-24 
 to 1-25. The lye is then further concentrated in cast-iron pans up to sp. gr. 1-9, at 
 which strength it solidifies on cooling. 
 
 G. Lunge sought to determine the limits of the conversion of sodium carbonate 
 into sodium hydroxide by treatment with lime. At the common atmospheric pressure 
 the experiments gave the following numbers : 
 
344 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 After causticising in the state of 
 
 Before causticising. NaOH per 100 parts Soda. 
 
 Per cent. Na 2 COj. Specific Gravity. I. II. 
 
 2 ... I -022 at 15 ... 99-4 parts ... 99-3 parts 
 
 5 ... 1-052 ... 99 'o 99 '2 
 
 10 ... i '107 ... 97 '2 . 97 '4 
 
 12 ... 1-127 ... 96-8 ... 96-2 
 
 14 ... 1-150 ... 94 '5 95 '4 
 
 16 ... 1-169 at 30 ... 937 n 94'O 
 
 20 ... 1-215 907 9i 'o 
 
 Corresponding experiments, conducted under pressure at 148 to 153, gave 
 
 Before causticising. After causticising there are out of 
 
 ioo parts Soda as NaOH. 
 Per cent. NajjCO,. Specific Gravity. I. II. 
 
 10 ... 1-107 at 15 ... 97-06 parts ... 97-5 parts 
 
 12 . I-I27 ... 96-35 96-8 
 
 14 ... I'i5 .1 95'6 ... 96-6 
 
 16 ... 1-169 at 30 ... 95'4 i, .- 94'8 
 
 20 ... 1-215 "... 91 '66 ... 91-61 
 
 Hence the application of high pressures in causticising offers no perceptible 
 advantage. A more thorough agitation than now commonly takes place is to be 
 recommended. 
 
 The use of lime for converting soda into caustic has been abandoned in many estab- 
 lishments, and caustic soda is at once produced in the process of manufacture. This is 
 effected by somewhat increasing the quantity of coal added to the mixture of salt-cake 
 and limestone, and lixiviating the ball-soda at once with water at 50. After the lye has 
 been let settle it is quickly concentrated to sp. gr. 1-5, when sodium carbonate, sulphate, 
 and chloride sink to the bottom, and the liquid takes a brick-red colour (red liquor), 
 derived from a peculiar compound of sodium and iron sulphides. The lye is then heated 
 in large cast-iron pans, and from 3 to 4 kilos, of soda-saltpetre are added for every 
 ioo kilos, of caustic soda to be produced. As the water escapes, the soda-saltpetre 
 reacts upon the sodium sulphide and the sodium cyanide, which is always present, and 
 there is a plentiful evolution of ammonia and nitrogen. A part of this ammonia is due 
 to the decomposition of the cyanides, whilst another and larger portion is a consequence 
 of the oxidation of the sulphides, when water is decomposed, and the hydrogen reduces 
 the nitric acid to ammonia. When the evaporated mass reaches dull redness, finely 
 divided graphite is seen on its surface. 
 
 For the oxidation of sulphides in the production of caustic soda G-. Lunge gives the 
 following advice, based upon comprehensive experiments. All sodium sulphide is first 
 oxidised to thiosulphate by atmospheric oxygen. Even if this process were not less 
 costly than nitre, it would be preferable, as the iron of the vessels would be less 
 attacked. Thiosulphate is oxydised by the air only at high temperatures, and slowly, 
 since it is first split up into sodium sulphide and sodium sulphite. The oxidation is 
 therefore hastened by adding nitre. It is useless to do this at temperatures at which 
 the thiosulphate has not been decomposed ; the practical rule would be to begin the 
 addition of nitre as soon as, on further raising the temperature, a reaction for Na,S 
 appears, and then to add gradually small quantities, thus preventing the nitre from 
 coming in direct contact with the iron, and preventing waste of the former and injury 
 to the latter. This method seems to present other advantages. The addition of nitre 
 must cease as soon as neither sodium sulphide nor thiosulphite is present, which occurs 
 at about 300 to 360. In this manner we reach the most favourable result the forma- 
 tion of ammonia as the main reaction. Theoretically it would be the more advantageous, 
 as the ammonia might be recovered a result which should not be pronounced cb priori 
 impossible; but there is little immediate prospect of an economical solution of the 
 problem. "We have, then, all the sulphur as sulphite, or a little of it as sulphate ; 
 
SECT. III.] 
 
 SODA. 
 
 345 
 
 by fishing out the salts, a part of the sulphite can be removed along with the 
 sulphate ; the main bulk, however, must be oxidised during fusion, preferably not by 
 nitre, which would chiefly be decomposed into nitrogen, but by forcing in a current 
 of air. 
 
 The following analyses are obtained from some works in which ball-soda lye, previously 
 desulphurised by means of air, is agitated during causticising by means of a current of 
 air. I. is desulphurised crude lye; crystallises at 20*5; becomes clear at 24; sp. gr. 
 at 24, 1-302 ; boils at 120. II. Lye I. diluted and causticised; liquid clear, except a 
 small residue of iron oxide; sp. gr. at 20, 1*1338 ; boiling-point, 110. III. Lye II., 
 concentrated to 45, before the addition of nitre; clear, except an unimportant grey 
 residue; sp. gr. at 20, 1*301 ; boiling-point, 120. IV. Lye III., evaporated after the 
 addition of nitre, and clarified, ready for the melting-pan; sp. gr. at 18*5, 1-5417; 
 boiling-point, 150. V. Salt fished out during evaporation of III.; greyish- white, 
 uniform, soluble in water ; all but o* i per cent, of residue (chiefly ferric oxide) soluble. 
 VI. Salt deposited on standing from IV. in settling cistern. About a quarter of the 
 whole was removed as a liquid ; there remained a dirty mass, which was mixed up. 
 
 
 
 Causticised with a Current, of Air. 
 
 I. 
 
 Crude Lye. 
 
 II. 
 
 Caustic Lye. 
 
 III. 
 
 Evaporated 
 before adding 
 Nitre. 
 
 IV. 
 Melting Lye. 
 
 V. 
 
 Fishing 
 Salts. 
 
 VI. 
 
 Clarifying 
 Salts. 
 
 Grammes per Litre. 
 
 Grammes per Kilo. 
 
 NaOH ^ 
 Na 2 CO, 
 
 Na^S . 
 
 52-0 
 
 295 "4 
 
 
 
 57 
 
 4'5 
 3*i 
 
 trace 
 94i*3 
 
 IO2'5 
 33-9 
 O 
 2- 9 
 
 2*5 
 1*4 
 
 trace 
 991-6 
 
 267-1 
 77-2 
 O 
 
 7*i 
 
 6-7 
 3*6 
 
 trace 
 939 '3 
 
 75*-6 
 34*1 
 
 
 
 io - 6 
 5-6 
 
 2*5 
 
 io'6 
 47 
 
 722-0 
 
 26IT 
 
 365-6 
 
 
 5-6 
 4*1 
 38-9 
 5*2 
 
 I'O 
 
 o 
 
 318-5 
 
 28 3 -9 
 241'! 
 O 
 
 6-0 
 71-1 
 92-1 
 4*4 
 
 
 6-2 
 
 
 
 295-2 
 
 Na 2 S 2 O s 
 Na 2 8O 8 
 Na 2 S0 4 
 
 NaUl . 
 
 NaN0 2 
 Insoluble 
 Na 4 FeCy, 
 Water 
 
 Total . 
 
 1302-0 
 
 II33-8 
 
 1301-0 
 
 IS4I7 
 
 lOOO'O 
 
 lOOO'O 
 
 Deacon and Hurter for decomposing sodium sulphide pass a weak electric current 
 through the lye. The sulphur is deposited at the anode, which is kept clean by 
 brushing ; at the kathode there is formed a corresponding quantity of sodium hydrate. 
 Stronger currents (30 to 50 amp. per square metre of electro) convert the sulphide 
 at once into sulphate. To avoid polarisation they use alternating currents or movable 
 electrodes. 
 
 Caustic soda produced in England (1875) contained 
 
 70 per cent. 
 89-600 
 2-481 
 3-9I9 
 3*4I9 
 0*025 
 0-304 
 trace 
 
 So-called 60 per cent. 
 
 Sodium hydrate . 
 
 
 . 75-246 
 
 
 carbonate 
 
 
 2-536 
 
 
 chloride . 
 
 
 . 17-400 
 
 
 sulphate . 
 
 
 4-398 
 
 
 sulphite . 
 
 
 0-027 
 
 
 silicate . 
 
 
 . 0-297 
 
 aluminate 
 
 
 . trace 
 
 99-904 
 
 99748 
 
 Caustic soda has its chief uses in the soap manufacture, in obtaining and purifying 
 the products of the dry distillation of lignite, peat, &c., for the purpose of obtaining 
 paraffine, solar oil, and phenol ; for purifying petroleum, for preparing soluble sodium 
 
346 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. iii. 
 
 silicate (soluble glass) ; and of late in considerable quantities in the production of wood- 
 cellulose of alizarine, resorcine, &c. 
 
 The subjoined table shows the actual caustic soda contained in lyes of different 
 specific gravities at 15 : 
 
 Specific Gravity. 
 
 Banine". 
 
 Twaddell. 
 
 Per cent. 
 NaOg. 
 
 Per cent. 
 NaOH. 
 
 i cubic metre contains kilos. 
 
 Na 2 0. 
 
 NaOH. 
 
 007 
 
 I 
 
 1*4 
 
 0-47 
 
 0-61 
 
 4 
 
 6 
 
 029 
 
 4 
 
 5-8 
 
 2'IO 
 
 2-71 
 
 22 
 
 28 
 
 045 
 
 6 
 
 9-0 
 
 3-IO 
 
 4-00 
 
 32 
 
 42 
 
 060 
 
 8 
 
 I2'O 
 
 4'10 
 
 5 '29 
 
 43 
 
 56 
 
 075 
 
 10 
 
 IS'O 
 
 5-08 
 
 6-55 
 
 55 
 
 70 
 
 091 
 
 12 
 
 18-2 
 
 6 -20 
 
 8-00 
 
 68 
 
 87 
 
 108 
 
 14 
 
 21*6 
 
 7-30 
 
 9-42 
 
 81 
 
 104 
 
 125 
 
 16 
 
 25-0 
 
 8-50 
 
 10-97 
 
 96 
 
 123 
 
 142 
 
 18 
 
 28-4 
 
 9-80 
 
 12-64 
 
 112 
 
 144 
 
 I-l62 
 
 20 
 
 32-4 
 
 11-14 
 
 H'37 
 
 129 
 
 167 
 
 1-180 
 
 22 
 
 36-0 
 
 - 12-33 
 
 IS'PI 
 
 146 
 
 188 
 
 I"20O 
 
 24 
 
 40 'o 
 
 1370 
 
 17-67 
 
 164 
 
 212 
 
 I'22O 
 
 26 
 
 44 -o 
 
 iS'iS 
 
 I9-58 
 
 185 
 
 239 
 
 1-241 
 
 28 
 
 48-2 
 
 1676 
 
 2 1 '42 
 
 208 
 
 266 
 
 I-263 
 
 30 
 
 52-6 
 
 18-35 
 
 23-67 
 
 232 
 
 299 
 
 I-285 
 
 3 2 
 
 57-o 
 
 20 -oo 
 
 25-80 
 
 257 
 
 332 
 
 I-308 
 
 34 
 
 61-6 
 
 21-55 
 
 27-80 
 
 282 
 
 364 
 
 I-332 
 
 36 
 
 66-4 
 
 23-20 
 
 29-93 
 
 309 
 
 399 
 
 i '357 
 
 38 
 
 7I-4 
 
 25-17 
 
 32H7 
 
 342 
 
 441 
 
 1-383 
 
 40 
 
 76-6 
 
 27-10 
 
 34-96 
 
 375 
 
 483 
 
 1-410 
 
 42 
 
 82-0 
 
 29-05 
 
 37-47 
 
 410 
 
 528 
 
 1-438 
 
 44 
 
 87-6 
 
 31-00 
 
 39-99 
 
 446 
 
 575 
 
 1-468 
 
 46 
 
 93 '6 
 
 33-20 
 
 42-83 
 
 487 
 
 629 
 
 1-498 
 
 48 
 
 99-6 
 
 3570 
 
 46-15 
 
 535 
 
 691 
 
 i -530 ' 
 
 50 
 
 106-0 
 
 38-00 
 
 49-02 
 
 58i 
 
 750 
 
 Sodium Bicarbonate.* NaHC0 3 is obtained by passing washed carbon dioxide 
 through a solution of sodium carbonate. If the solution is concentrated, the bicarbonate 
 separates out as a crystalline powder ; if it is dilute, large crystals are obtained. As 
 carbonic acid is absorbed slowly by the solution, it is more advantageous to let it act upon 
 crystallised or partly effloresced sodium carbonate. An intimate mixture is made of i 
 part crystallised sodium carbonate and 4 parts of the effloresced salt or a mixtui*e of 
 equal weights of both, and it is saturated either with the carbonic acid of fermentation 
 or with that obtained on burning lime. Where carbonic acid issues from the earth the 
 process is greatly simplified. The bicarbonate of the ammonia-soda process generally 
 contains ammonia. 
 
 In the production of sodium bicarbonate from ordinary soda crystals (dekahydrated) 
 the product retains all the impurities of this material ; hence Carey took the mono- 
 hydrate as a starting-point. H. Gaskell and F. Hurter, of Widnes, went further, and 
 converted the anhydrous neutral sodium carbonate into bicarbonate by simultaneous 
 treatment with watery vapour and carbonic acid. 
 
 Sodium bicarbonate crystallises in monoklinic tables ; it has a faintly alkaline reac- 
 tion, and on exposure to 70 or in solution on boiling it loses half its carbonic acid 
 and returns to monocarbonate. In dry air it is gradually converted into sesqui- 
 carbonate; 100 parts water dissolve at o 6*0 parts, and at 15 8-85 parts of sodium 
 bicarbonate. It is used for developing carbonic acid in the manufacture of effervescing 
 drinks, in the preparation of unfermented bread (with hydrochloric acid, or acid calcium 
 phosphate), for precipitating alumina from the solution of sodium aluminate (in the 
 cryolite and bauxite industries), and in the preparation of baths for gilding and 
 platinising. It has of late been proposed for ungumming silk and scouring wool, as it 
 attacks the fibres less than soap or ammonia. 
 
 * Hydrocarbonate, carbonate of soda of pharmacy and cookery. 
 
SECT, in.] CHLORINE, CHLORIDE OF LIME, AND CHLORATES. 
 
 347 
 
 CHLORINE, CHLORIDE OF LIME, AND CHLORATES. 
 
 For obtaining chlorine, pyrolusite (manganese peroxide) is heated along with hydro- 
 chloric acid : MnO 2 + 4.HC1 = MnCl 3 + 2H 2 4- C1 2 . As developers there are used large 
 stone-ware vessels, A (Fig. 308), fitted with a wide opening, a, for filling and emptying 
 and with narrower tubulures, b, in which the delivery pipes are inserted. Heat is 
 applied by means of steam. To this end, several such vessels are set in a chest, B, of 
 wood or masonry, with a wooden lid, so that only the necks and the delivery-pipes pro- 
 ject outside. The joints of the chest are carefully closed with clay or felt at r, in order 
 to prevent the loss of the steam which is led into the chest from the boiler. The lye 
 of manganese chloride is let out at c. On the large scale a trough is used, made up of 
 plates of sandstone cemented together or hollowed out of a block of sandstone and 
 saturated with hot tar. 
 
 If a mixture of manganese peroxide, salt, and sulphuric acid is used 
 
 2 NaCl + Mn0 2 + 2 H 2 SO 4 = Na 2 SO 4 + MnS0 4 + 2 H 2 + C1 2 , 
 a strong heat is needed. A pan is used, the lower part of which, b (Fig. 309), is made 
 of cast iron and the upper part, d, of lead ; both parts are secured together at a. 
 
 At the Josephsthal paper works there is used a stout cast-iron pan, A (Fig. 310), 
 its outflow pipe, D, being closed with a wooden plug luted in with clay. The lead 
 
 Fig. 309, 
 
 Fig. 308. 
 
 cylinder, B, which is screwed on, and the lid of which, C, carries the delivery-pipe, gives 
 room for the materials to swell up. The production of chlorine takes place in A ; the 
 iron is but little attacked as long as an excess of manganese is present. When the 
 pan is eaten through, a new one is quickly and inexpensively substituted. The lead 
 cylinder is made very stout at the lower part, where it is most likely to be attacked. 
 The upper part, which does not come in contact with the liquor, soon becomes coated 
 with a dense layer of lead chloride, and is then no longer attacked. The spent liquor 
 is run off at D, and the vessel is then well rinsed out with water. 
 
 For work on the large scale the recovery of the manganese is important. 
 
 Dunlop's process, which came into use at the St. Rollox works at Glasgow, is based 
 upon the fact, first observed by Forchhammer, that carbonate of manganese, when heated 
 to 260, is converted into peroxide of manganese ; that is, the carbonic acid is driven 
 off, and the compound, 2MnO 3 + MnO, obtained. The process consists in the following 
 operations : 
 
 i. Conversion of the manganese chloride into manganese carbonate. 
 
348 CHEMICAL TECHNOLOGY. [SECT. HI. 
 
 2. Conversion of the carbonate into peroxide of manganese. 
 
 To the chlorine preparation residues, when they have become clear, either chalk or 
 milk of lime is added to neutralise the excess of acid and precipitate the oxide of iron. 
 This precipitate having settled, the clear liquid, a rather pure solution of manganous 
 chloride, is poured into shallow troughs and intimately mixed with finely powdered 
 chalk. The magma thus formed is transferred for further decomposition to a large 
 cast-iron trough, 27 metres long by 3 metres wide. Parallel to the length of this 
 vessel, a stout wrought-iron axle is carried, to which are fitted cast-iron branches 
 serving as stirrers. The axle passing through stuffing boxes at each end of the trough 
 gears with a motive power, whereby the stirrers are caused to keep the chalk constantly 
 suspended in the manganese solution. High-pressure steam is conveyed into the trough 
 and aids decomposition. The manganese carbonate obtained is freed from calcium 
 chloride by washing, and, having been well drained, is calcined in a peculiarly con- 
 structed furnace, in which the carbonate is first dried on a higher stage, and then 
 transferred to a lower and hotter stage, where oxidation is commenced. The oxidation 
 is completed at the lowest stage of the furnace, to which plenty of air is admitted. 
 The fire-place is constructed to admit of the regulation of the heat with great nicety, 
 because too high a temperature would cause the formation of protosesquioxide, and too 
 low a temperature would leave the carbonate undecomposed. 
 
 Gatty 's Process. In this process the residues are converted into manganese nitrate, 
 which is next decomposed by heat. The residues are evaporated to the consistency of 
 a syrup, and mixed with sodium nitrate : 
 
 To 76 kilos, of manganese chloride ) 
 
 and to 95 kilos, of manganese sulphate \ Io6 kllos ' of sodlum mtrate are taken ' 
 The mixture is dried, and then heated to a dull red heat in an iron retort, the fumes of 
 nitric acid given off being used in the manufacture of sulphuric acid. The residue in 
 the retort consists, according to the salt of manganese employed, of manganese 
 peroxide, and sodium chloride or sodium sulphate ; it may be lixiviated with water to 
 obtain the manganese peroxide in a pure state if sodium sulphate is present. 
 
 The process of P. W. Hofmann has been described under the methods for the 
 recovery of vat- waste. 
 
 Fr. Kuhlmann proposes to transfer the oxygen of the air at once to the manganous 
 oxide. By heating manganese nitrate to 200 there are formed manganese peroxide 
 and hyponitric acid. The escaping gases, mixed with air, are conveyed into recently 
 precipitated manganous hydroxide, when a fresh quantity of manganese nitrate is 
 formed 
 
 Mn(OH) 2 + 2 N0 2 + O = Mn(N0 3 ), + H 2 O, 
 which, when heated, furnishes anew manganese peroxide and hyponitric acid. 
 
 Weldon's Process. Mr. Walter Weldon's process is performed by means of an 
 apparatus comprising five vessels arranged at successive elevations, so that, after having 
 been pumped up to the highest of them, the liquor operated upon can afterwards 
 descend to all the others by its own gravity. The lowest of these vessels is a well, 
 which is furnished with a mechanical agitator. The slightly acid chloride of man- 
 ganese liquor with which the process commences runs from the stills in which it is 
 produced into this well, and is there treated with finely divided calcium carbonate, the 
 action of which is facilitated by energetic agitation. When the neutralisation of 
 the free acid which is at first contained in this liquor and the decomposition of 
 the iron and aluminium sesquichloride, which are also at first contained in it, 
 are completed, the liquor is pumped up into settling tanks, placed nearly at the 
 top of the apparatus, and known as the " chloride of manganese settlers." It 
 now consists of a quite neutral mixed solution of manganese chloride and calcium 
 chloride, containing in suspension considerable quantities of calcium sulphate, and small 
 
SECT, in.] CHLORINE, CHLORIDE OF LIME, AND CHLORATES. 349 
 
 quantities of ferric oxide and alumina. These solid matters rapidly deposit in the 
 chloride of manganese settlers, leaving the bulk of the liquor perfectly bright and 
 clear, and of a faint rose colour. The next step is to run off the clear portion of the con- 
 tents of the settlers into a vessel immediately below, called the oxidiser. This is usually 
 a cylindrical iron vessel about 12 feet in diameter, and about 22 feet deep. Two pipes 
 go down nearly to the bottom of the oxidiser a large one for conveying a blast of air 
 from a blowing engine, and a smaller one for the injection of steam. The latter is for 
 the purpose of raising the temperature of the contents of the oxidiser when necessary ; 
 for sometimes the chloride of manganese liquor reaches the oxidiser sufficiently hot 
 between 130 and 160 or 170 F. Immediately above the oxidiser is a reservoir 
 containing milk of lime. The oxidiser having received a charge of clear liquor from 
 the settlers, and this liquor having been heated up to the proper point if it was not 
 already hot enough, blowing is begun, and milk of lime is then run into the oxidiser 
 as rapidly as possible, until the nitrate from a sample taken at a tap placed nearly at 
 the bottom of the oxidiser ceases to give a manganese reaction with solution of bleach- 
 ing-powder. A certain quantity of milk of lime is then added, and the blowing 
 continued until peroxidation ceases to advance. That point is usually attained when 
 from about 80 to 85 per cent, of the manganese present has become converted into 
 peroxide. The contents of the oxidiser are now a thin black mud, consisting of 
 solution of calcium chloride containing in suspension about 2 Ibs. of manganese 
 peroxide per cubic foot, these 2 Ibs. of manganese peroxide being combined with 
 varying quantities of manganous oxide and lime. This thin mud is now run off 
 from the oxidiser into one or other of a range of settling tanks or " mud settlers," 
 placed below it, and is there left at rest until it has settled as far as it will, usually 
 until about one-half of its volume has become clear. The clear part is then decanted, 
 and the remainder, containing about 4 Ibs. of manganese peroxide per cubic foot, is 
 then ready to be used in the stills. There it reacts upon hydrochloric acid, liberating 
 chlorine, with reproduction of exactly such a residual solution as was commenced with. 
 With that solution the round of operations is begun again ; and so on, time after time, 
 indefinitely. 
 
 The extraordinary simplicity of the Weldon process ensures it the preference as 
 against other methods aiming at the same object, and it is almost universally em- 
 ployed. According to Jetzler, the manganous hydroxide, after being washed in the air, 
 is partly oxidised and then exposed to a current of hot air whilst suspended in the lime- 
 lye. In this manner a more rapid and complete oxidation is effected and a dry 
 manganese peroxide is obtained. 
 
 According to the more recent proposals of Weldon, the lyes of manganese chloride 
 are evaporated and treated either separately or along with solid calcium, or magnesium 
 chloride, or with magnesium or manganese manganite obtained in a former operation 
 in a cylindrical retort, heated from without, and so arranged that at one end the 
 powder is regularly and continuously introduced, whilst the solid product of the 
 reaction is taken out at the other. The retort, E (Figs. 311 and 312), maybe made of 
 fire-clay, or of cast iron, or of both materials. It seems best to construct the retort 
 of fire-clay for the chief part of its length, and only to make the part where the 
 charge is introduced of cast iron for a short extent. The outer cylinder, (7, can be 
 made of wrought iron with a fire-clay lining. The whole rests and turns on the 
 friction rollers, D. Through the pipes F, heating-gas enters from a generator into 
 the annular combustion chamber, X, and the air necessary for combustion through the 
 apertures, e. The heating-gas arrives in the immovable pipe, J, which is connected by 
 the ring-shaped conduit, a, with the tubes F. Air enters through the tube K into 
 the interior of the retort. E, and hereby the solid product of the reaction, manganese 
 and magnesium manganite, is emptied. This evacuation is facilitated by wings placed 
 
35 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 spirally, fixed on the axle, n. The gases, charged with the chlorine generated, escape 
 through the tube, N which also serves for charging the retort. The axles, n and o, 
 may be either immovable, or may turn in the opposite direction to the retort, E. 
 The products of combustion issue from the ring-shaped combustion chamber, JT, 
 through the apertures, H, into the fixed smoke chamber, P. The manganite obtained 
 is treated with hydrochloric acid for the production of chlorine ; the lyes are evaporated 
 dow-n and mixed with a portion of the manganite ; they are again conveyed into the 
 
 -Fig. 311. 
 
 Fig. 312. 
 
 decomposition chamber, E. The hydrochloric acid is thus almost completely converted 
 into chlorine. Working results on this modification have not yet been made known. 
 
 For the utilisation of the chlorine residues, Schaffner, of Aussig, precipitates the 
 manganous chloride with lime, dries the precipitate, and calcines it in a reverbera- 
 tory furnace, obtaining protosesquioxide of manganese, employed with iron ore in 
 the blast furnace. The solution of calcium chloride simultaneously obtained is 
 precipitated by sulphuric acid, yielding the material known as annaline ; that is to 
 say, the gypsum used in paper manufacture. In the process of soda-making from 
 sodium and iron sulphides, as suggested by Malcherbe and improved upon by Kopp, 
 for the oxides and carbonate of iron, the corresponding manganese compounds may 
 be substituted. Carbonate of manganese may be used to convert sodium sulphide 
 into soda, and may also serve for the preparation of permanganates. A. Leykauf 
 suggests that the residues of chlorine manufacture should be employed to form a 
 violet-coloured paint, known as Nuremberg-violet, a compound of ammonia, oxide of 
 manganese, and phosphoric acid. In England the residues are frequently employed 
 in the purification of coal-gas and as disinfectants.* 
 
 Of the processes for obtaining chlorine without manganese, the most important is 
 that of Deacon, in which hydrochloric vapours are oxidised by atmospheric oxygen ; 
 
 Deacon and Hurter found that the decomposition of hydrochloric acid by oxygen 
 takes place at a much lower temperature if the gaseous mixture, instead of simply 
 passing through ignited tubes or over porous substances, is led over heated salts of 
 copper, lead (except the sulphate), or compounds of manganese. The most efficacious 
 are the compounds of copper ; so that, if a mixture of hydrochloric acid with an excess 
 of atmospheric air is passed over porous bodies, soaked in solution of copper sulphate 
 and heated to 360 to 400, all the hydrochloric acid is burnt to chlorine and water. 
 In this reaction, which begins at 260, the copper sulphate remains unchanged unless the 
 temperature is raised too high. Not until about 425 are formation and volatilisation 
 of copper chloride perceptible. The power of resistance as well as the efficacy of 
 the copper sulphate can be intensified by joining with it certain salts which are in 
 
 * Chlorine residues, as long as they were procurable, were an excellent agent for the precipitation 
 and purification of sewage. See Slater, Sewage Treatment, p. 102. 
 
SECT, in.] CHLORINE, CHLORIDE OF LIME, AND CHLORATES. 351 
 
 themselves without action upon the gaseous mixture, e.g., potassium or sodium 
 sulphate. Numerous experiments showed the conditions for the decomposition 
 between air and hydrochloric acid in presence of copper sulphate. 
 
 1. The quantity of the hydrochloric acid decomposed by i mol. copper sulphate in 
 gaseous mixture of similar composition and at the same temperature depends upon how 
 often the gaseous molecules pass through the sphere of activity of the copper sulphate. 
 
 2. For all velocities of the gases in transit the opportunity for efficacy is the same 
 for long tubes of the same section in one and the same time. 
 
 3. In long tubes of different section the opportunities for action are alike when the 
 speeds of the currents are inversely as the squares of the diameters of the tubes. 
 
 4. In porous masses the efficacy increases directly as the rapidity. 
 
 5. Circumstances being otherwise equal, the quantity of the hydrochloric acid de- 
 composed varies with the square root of the number expressing the proportion between 
 hydrochloric acid and oxygen. 
 
 6. At very high temperatures a little copper chloride is formed, but its quantity is 
 in no proportion to the quantity of chlorine formed. 
 
 7. The efficacy of the copper salt extends to gaseous molecules not in contact with 
 the salt ; the decomposition of the hydrochloric acid takes place under circumstances in 
 which no material exchange can take place between the copper salt on the one hand 
 and the hydrochloric acid and air on the other. 
 
 In the technical execution of the Deacon process the hydrochloric acid is either 
 prepared from sodium chloride and sulphuric acid in an ordinary salt-cake furnace or it 
 is liberated from aqueous acid already obtained. On a small scale the latter is pre- 
 ferable, as in this manner it is always practicable to produce a current of hydrochloric 
 acid of uniform strength, whilst the evolution of hydrochloric acid from the sulphate 
 furnaces is very rapid at first and then becomes very slow. On the large scale this 
 defect may be avoided by having several salt-cake furnaces in serial action, so that 
 when the evolution declines in one the activity of the next begins. The gas obtained 
 in either manner is immediately mixed with a quantity of air which contains more 
 oxygen than suffices to convert all the hydrochloric acid into chlorine, and is passed 
 through heated U-shaped tubes of cast iron, which supply the temperature required 
 for the process. The composition of the gaseous mixture can be checked at any time 
 by means of a small air-pump, which at every stroke of the piston forces a certain 
 volume of the gas through a standard soda-lye coloured with litmus. The succeeding 
 decomposition furnace consists of a cast-iron chest in which are chambers, each 
 provided in its lower part with a grating, or false bottom. Upon this stand in the first 
 chamber, and also in the second, upright drain-pipes which have been steeped in a hot 
 concentrated solution of 2 mols. copper sulphate and 3 mols. sodium sulphate and 
 dried. The other chambers are filled with fragments of brick or clay balls which have 
 been treated in the same manner. The entire furnace is enclosed with an air-jacket and 
 this again with a jacket of masonry traversed by fire-flues, serving to keep back a 
 part of the radiant heat from being lost. Another part is restored in the process 
 itself by the combustion of the hydrochloric acid. The pipes serve to prevent any 
 obstruction of the apparatus by ferric oxide or chloride. It has been observed that, 
 especially when an iron apparatus is used for producing and conducting hydrochloric 
 acid, the acid always carries with it ferric chloride, from which it cannot be freed 
 before it enters the decomposition furnace. In this it deposits the iron upon the copper 
 sulphate, either as chloride, or, if the formation of chlorine has already set in, as 
 pulverulent ferric oxide. This iron dust falls out of the drain-pipes through the 
 grating into the space below, where it is easily removed. Deacon has recently 
 removed the partition walls from the decomposition furnace. 
 
 After the gaseous mixture has passed through the decomposition furnace, it consists 
 
352 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 of chlorine, nitrogen, water, excess of oxygen, and unburnt hydrochloric acid. The 
 latter is eliminated as the gases (the temperature of which has been previously 
 reduced by means of cold air) are passed through a scrubber charged with dilute 
 hydrochloric acid and water. The gas is then freed from the accompanying water by 
 a tower charged with calcium chloride, or preferably a coke-tower in which sulphuric 
 acid trickles down, and it is then ready for use in the chloride of lime chambers. Of 
 course the drying arrangement is superfluous if an aqueous liquid is to be saturated 
 with chlorine, as in the preparation of potassium chlorate. For the latter purpose, 
 Kunheim uses the chlorine obtained by Deacon's method. The chlorine is so completely 
 absorbed by the milk of lime in its passage that mere traces are present in the escaping 
 air. The draught in the entire plant is effected by any suction apparatus placed beyond 
 the chloride of lime chambers. 
 
 Of other methods for producing chlorine, the following deserve notice : 
 
 1. MacDougal, Rawson, and Shanks's process, consisting in the decomposition of 
 calcium chromate by hydrochloric acid, the result being the formation of chromium 
 and calcium chlorides, and the evolution of free chlorine 
 
 2 CaCr0 4 + i6HCl = Cr 2 Cl 6 + zCaCL, + 3 H 2 + 6C1. 
 
 158 parts of chromic acid yield 106 parts of chlorine. The chloride of chromium is 
 again precipitated with carbonate of lime, and by ignition converted into chromate of 
 lime. Only three-eighths of the chlorine contained in the hydrochloric acid is given up, 
 while manganese yields one-half. 
 
 2. Yogel's method of decomposing chloride of copper by heat. 3 mols. of chloride 
 yield i mol. of chlorine ; according to Laurens the process is 
 
 2 CuCl 2 = 01, + Cu 2 Cl 2 . 
 
 The chloride in the crystalline state is mixed with half its weight of sand, and heated in 
 earthenware retorts to 200 to 300, yielding chlorine gas, while the remaining proto- 
 chloride of copper is re-converted into perchloride by the action of hydrochloric acid. 
 Mallet has constructed a peculiar rotating apparatus for the decomposition of this salt, 
 the same apparatus serving to prepare oxygen. 100 kilos, of cupric chloride yield 6 to 
 7 cubic metres of chlorine gas. 
 
 3. Peligot's method. When 3 parts of bichromate of potassa and 4 parts of con- 
 centrated hydrochloric acid are gently heated, the fluid yields, on cooling, crystals of 
 bichromate of chloride of potassium, KCl,Cr0 3 ; at 100 this salt yields chlorine. 
 
 The production of chlorine from calcium and magnesium chlorides appears especially 
 important, as, if this end is reached, the Leblanc process will probably be entirely super- 
 seded by the ammonia-soda process. Among the many attempts, those of Solvay and 
 Pechiney demand especial attention. 
 
 Solvay ignites the residues of calcium chloride with clay. From the mass the 
 carbonic acid is expelled by an addition of hydrochloric acid, and the organic matter is 
 destroyed by heating in the air. To prevent the mass from caking together in the 
 furnace there is added to the mixture of calcium chloride with silica or clay a sufficient 
 quantity of the residues of former decompositions or of brickbats. It appears that sand 
 is not adapted for the process, but a kind of infusorial earth, known in Belgium as 
 " ergeron." Before entering the apparatus the air is passed through vessels containing 
 pieces of caustic soda, so as to take up carbonic acid and moisture. The decomposi- 
 tion apparatus is made of iron, coated with a mixture of clay, soda, and nitrifiable 
 matters. 
 
 The chlorine prepared in this manner is strongly diluted with air and nitrogen. To 
 make it fit for the production of chloride of lime, the pulverulent slacked lime is spread 
 out in layers of suitable thickness upon a bed of porous mineral matters e.g., gravel, 
 flints, sand, or asbestos cloth. The layers of lime are laid methodically, as is done 
 with the masses for purifying coal tar. The chambers may be arranged in series, but 
 
SECT, in,] CHLORINE, CHLORIDE OF LIME, AND CHLORATES. 353 
 
 in any case they must be placed so that the chloriferous mixture of gases may encounter 
 the layer of lime in its whole thickness, and pass through from above downwards. Each 
 of the six lead chambers, B (Figs. 313, 314), connected by the reverser, ^l,and arranged 
 in a circle, is provided with two false bottoms, upon which is laid first asbestos cloth 
 on a bed of gravel, and then the lime. The chloriferous gases enter the reverser, A. 
 and pass from there through a pipe, C, into the upper part of the chamber B which 
 has been longest in use. 
 
 They pass downwards, Fig. 313. Fig. 314. 
 
 first through the upper 
 and then the lower layer 
 of lime, and return 
 through D to the re- 
 verser, passing thence to 
 the upper part of the 
 next chamber B, which 
 they traverse in the 
 same manner, and so on 
 until they arrive at the 
 chamber with the most 
 recent charge of lime. 
 Five chambers B are 
 always in use, as the 
 sixth is disconnected for 
 emptying and refilling 
 as soon as its contents 
 are sufficiently strong. 
 
 The process of Wei- 
 don and Pechiney has 
 been at work for a year 
 
 at Salindres, and promises to be of importance for the utilisation of magnesium 
 chloride. 
 
 The solution is evaporated until it corresponds to the formula MgCl 2 .6H 2 O, and then 
 mixed with i'3 equivalent of MgOfor the formation of oxychloride. For mixing there 
 is used a revolving pan, A (Figs. 315 and 316), turning on rollers, a. Movement is 
 taken from the driving belt, B, by means of the toothed wheel, c ; the agitators, (7, Z>, E, 
 are driven in the same manner. The magnesia is introduced into the pan containing 
 the concentrated magnesium chloride, with constant stirring. The oxychloride is 
 formed with liberation of heat, and congeals to hard masses, broken into lumps by the 
 stirrers. 
 
 It has the following composition : 
 
 MgCl 2 . 
 MgO . 
 H 2 . 
 
 Impurities 
 
 35 -oo ; Cl = 26 1 6 per cent. 
 19-84 
 41-16 
 4-00 
 
 It is broken up and sifted. What passes through a sieve with meshes of 5 mm. is 
 returned to the magnesium chloride for the further preparation of oxychloride. The 
 granular oxychloride is dried. The temperature must not exceed 300. At Salindres, 
 Pechiney uses for a drying chamber a channel of masonry. The oxychloride is placed in 
 seven layers, each of 5 to 6 cm. in thickness, upon small trucks, which are drawn through 
 the heating channel as in Figs. 317 and 318. To keep out the external air on the admission 
 of a truck, the door, a, is opened, the truck is pushed into the chamber A, and the door, 
 a, is again closed. The slides, c and d, are then raised and the entire train of trucks drawn 
 
354 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 Fig- 315 
 
 forwards in the channel by the contrivance, G, so that the first truck partly enters the 
 chamber J3, and can be entirely drawn into it by the hook, Z>. It can be removed after 
 
 lowering the slide, d, 
 and opening the door. 
 The gases at 300 enter 
 at M, and leave the 
 channel through the 
 pipe, N. 
 
 ! Hf V&. The measuring ap- 
 
 paratus, A, of the filling 
 arrangement (Fig. 319) 
 is divided into seven 
 compartments corre- 
 sponding to the basins 
 on the trucks. Each 
 compartment can be 
 closed below by a door, 
 a. By turning the 
 wheels, (7, all these doors 
 may be simultaneously 
 opened or closed. Below 
 the measuring apparatus 
 is a hopper, D, mov- 
 able on wheels and also 
 divided into seven com- 
 partments contracted 
 below. Underneath, on 
 
 Fig. 316, 
 
 Fig. 317. 
 
 the height of the drying channel, there is a movable frame, 
 E, to receive any empty truck. In Fig. 319 the frames 
 and trucks are shown in a position ready to be loaded. 
 Before the truck is brought into this position there are 
 placed between each two basins two short iron partitions, 
 d, which determine the thickness of the layer of oxychloride. 
 The partitions are secured by the screws, n, the heads of 
 which press against the cross rails, o, which form a part of 
 
 Fig. 318. 
 
 the partitions. To the movable frame there are fixed below two rails, R, upon which 
 the truck moves. The rails are fixed to the levers, F, so that the truck can be raised 
 
SECT, in.] CHLORINE, CHLORIDE OF LIME, AND CHLORATES. 355 
 
 towards the top of the frame by turning the screw, M, which is in connection with 
 
 the great lever, G ; when the partitions have been introduced the frame is turned by 
 
 means of a toothed wheel with a crank, which 
 
 is only shown in dotted lines in the figure; 
 
 the hopper is moved above it ; the measuring 
 
 apparatus is filled, and the contents are then 
 
 emptied into compartments of the truck by 
 
 turning the wheel, C. The frame is then turned, 
 
 the partitions removed, and the truck moved 
 
 into the drying stove. 
 
 The oxy chloride loses up to 65 per cent, of 
 water and 5 to 8 per cent, of the chlorine in 
 the state of hydrochloric acid ; 100 parts oxy- 
 chloride of the above composition yield 73*36 
 per cent, of residue of the following composi- 
 tion : 
 
 MgCl 2 . 
 MgO . 
 H,0 . 
 
 Impurities 
 
 44-45; 01 = 33 -30 per cent. 
 28-36 
 21-62 
 5 '47 
 
 The decomposition of the oxychloride is 
 effected in chambers, which are heated by gas 
 generator fires. Each of the narrow work- 
 chambers, A (Figs. 320 and 321), opens upward 
 into the combustion chamber, B, and is fitted 
 with an inspection slit, q. The movable re- 
 generator turner, D, consists of cast-iron tubes divided into three compartments 
 i, o, u. When the valve, N, is opened (Fig. 322), heating gas passes through the pipes, 
 V and C (connected at JF), into the compartments, o, to arrive by way of the pipe, d, in 
 the combustion-chamber, B. The air needed for burning this heating-gas enters at 
 the bottom of the compartments, i and u; rises in them upwards and issues from their 
 
 Fig. 320. 
 
 FIG. 321. 
 
 upper end through the broad, flat pipe, T, into the combustion chamber, B. The com- 
 bustion gases go downwards through the working-chambers, A, then through the 
 -channels a and z and round the iron pipes, D, in order finally to escape, through Q 
 
556 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 FIG. 322. 
 
 and P, into the channel G. For the easy connection of the burner with the pipe P, the 
 piece, Q, can be raised or lowered by the lever, S. When the burner is in the position 
 with respect to the furnace (properly speaking) which is shown in Fig. 321 the rails 
 upon the block-truck, K, are fixed to other rails (of which one is shown at r, Fig. 321), 
 in such a manner that the burner can be pushed over upon these other rails and be 
 carried upon them to another block-truck opposite the next furnace. Whilst, 
 therefore, in one furnace a solid substance giving off chlorine is being heated in 
 a current of air, the movable regenerative burner can be used for heating the work- 
 chambers of another similar furnace. As soon as these work-chambers are hot enough, 
 the valve, N, is closed, the pipe Q is lowered and the block-truck, J, upon which the 
 entire regenerative burner rests, is drawn away from the furnace until the wheels of 
 the burner are opposite the rails. The openings for introducing the gases into the 
 
 work-rooms must be closed by the door E, 
 and the openings for removing the products 
 of combustion from the working-chambers 
 by the doors F. The doors E and F, 
 when in the closed position, are pressed 
 tightly by screws. The work-chambers, A, 
 are now charged with magnesium oxy- 
 chloride in small pieces by a tilting-truck, 
 which, after being loaded, has been brought 
 into the proper position upon the cover of 
 the furnace. After the lid has been re- 
 moved a hopper is placed over the opening 
 H, and the oxychloride is shot into the 
 
 hopper, so that it falls into the work-chamber A. The cover of the openings H 
 is then quickly put on again, and air is admitted through several openings (not 
 shown in Fig. 321) in the door E to A. The oxychloride is quickly heated by 
 taking up a part of the heat previously stored up in the walls of the chambers, and 
 there escapes from these chambers a mixture of gases and vapours containing chlorine 
 and hydrochloric acid. This mixture goes from A through the channels a into 
 the space between the masonry of the furnace and the door F, then through the 
 channel I (Fig. 322) and the pipes, m, to corresponding arrangements for utilising the 
 chlorine. When the decomposition of the oxychloride is sufficiently advanced, the access 
 of air to the work-chambers is cut off; the door F is opened, and the residual oxide 
 contained in the chambers A is taken out. The cover of the opening H is again put 
 
 Fig. 323. 
 
 Fig. 324. 
 
 325- 
 
 Fig. 326. 
 
 in its place, and after opening the door E, the movable generative burner is brought 
 back to the position shown in Fig. 321 when the work-rooms of the furnace (strictly 
 so called) are again heated for the next operation. 
 
 A refrigerator is connected with the decomposition apparatus. It consists of a stone 
 tower filled with glass tubes, through which cold water flows down. The glass 
 tubes (Figs. 323 to 328) project with their ends from the sides of the tower. On one 
 side, A, each tube is connected by a caoutchouc pipe with the main, w, which is supplied 
 with water from the hollow column, JV(Fig. 323). On the other side, C, the water 
 flows through flexible pieces, s, into channels, m, from which it is carried off through 
 
SECT, in.] CHLORINE, CHLORIDE OF LIME, AND CHLORATES. 357 
 
 the hollow column, M (Fig. 223). That the glass tubes, c, may be less likely to break, 
 they are kept always filled with water. As the acid liquid condensing on the surface 
 of the tubes flows to the end, A, the joints here must be well closed. For this purpose 
 there is on the end of the glass tube a short caoutchouc tube, i, with a flange (Figs. 
 325 and 326), which is firmly pressed against the stone by the tube-shaped part of the 
 stuffing-box, n. The stuffing-boxes are drawn on by screws, which pass through the 
 ring-shaped flanges, and catch in threads cut in the rail, R. The gases or vapours to 
 be cooled are most conveniently introduced at P, near the cover of the tower, and escape 
 
 Fig 327. 
 
 Fig. 328. 
 
 near the bottom, on the opposite side. The 
 liquid condensed in the tower runs out through 
 the opening S. 
 
 The mixture of nitrogen, superfluous air, 
 chlorine, and hydrochloric acid is let out of the 
 decomposition apparatus through this tube- 
 cooler by means of two gasometer bells dipping 
 into a solution of calcium chloride and moving 
 
 alternately up and down, then through a number of sandstone vessels, and lastly 
 through a scrubber. The hydrochloric acid in the gases is thus completely condensed, 
 and a mixture of chlorine and air is carried on. The hydrochloric acid from the 
 various condensers is mixed and marks on the average 17 Tw. 
 
 Of 100 parts of the chlorine of a charge, 15 parts remain in the residues, 45-23 are 
 evolved as free chlorine, and 3977 parts form hydrochloric acid. As about 7 parts are 
 lost in drying, the original 100 parts of chlorine are distributed as follows : 
 
 Loss in drying 
 Left in residues 
 Free chlorine 
 Chlorine as HC1 
 
 6 '60 per cent. 
 14-00 ,, 
 42-25 
 37-15 
 
 As a further loss of 5 per cent, is admitted the result is 
 
 Loss | on drying ' 
 ss l general . 
 01 returned f residues . 
 to process { as HC1 . 
 Free chlorine obtained 
 
 '. 5 -co} 11 ' 27 P ercent - 
 
 13-30] 
 
 35 '29 > 
 
 40-14 
 
 To obtain 40*14 free chlorine there must be produced 100 -48-59 = 51-51 parts of 
 chlorine. 
 
 The yield will probably be increased by improvements e.g., by heating more 
 strongly. The residue, after the decomposition in the furnace, is placed in vessels 
 cooled by water and provided with agitators. 
 
 The refrigeration is quickly effected. The mass is then sifted ; about pass through 
 the sieve, being almost completely decomposed and containing scarcely 4 per cent, of 
 chlorine. The part remaining on the sieve, about ^ of the mass, is still solid oxychloride, 
 slightly decomposed. The chlorine is about 40 per cent. This part of the residue is 
 
558 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 at once returned to the furnace, whilst the magnesia (at Salindres) is dissolved in 
 hydrochloric acid, and is again submitted to the process. 
 
 At Salindres there are at work (December 1887) two fires with eight chambers each. 
 A thousand kilos, of chlorine ought to be produced in twenty-four hours, but the present 
 yield is 720 to 760 kilos. The author states that at Stassfurt 200,000 tons of mag- 
 nesium chloride yearly are allowed to flow into the river, so that a ton of chlorine 
 ought to be produced decidedly cheaper at Stassfurt than it is now in England. 
 
 Properties and Uses of Chlorine. At the ordinary temperature and pressure of the 
 atmosphere chlorine is a greenish-yellow gas, its sp. gr. = 1*33 ; it possesses a pecu- 
 liarly disagreeable, irritating 'odour, and is soluble in water, i volume absorbing 
 2 '5 volumes of gas, forming the well-known aqua chlorii, or acidum muriaticum 
 oxygenatum aqua solutum of the pharmaceutists, and the chlorine water of the scientific 
 chemist. The bleaching property of chlorine gas, shared also by its solution, is due 
 to the great affinity of chlorine for hydrogen, so that the chlorine, while seizing upon 
 the hydrogen of the organic body, in most instances causes the simultaneous decom- 
 position of water, and by the formation "of ozone destroys the organic colouring matter, 
 hydrochloric acid being formed at the same time, a fact requiring attention in the 
 use of chlorine as a bleaching agent. When linen, or rather flax, raw cotton, and paper 
 pulp are bleached by chlorine, the fibre, really cellulose, is not acted upon, but only the 
 colouring matter is oxidised by the ozone formed. Chlorine cannot be used to bleach 
 animal matters, or such as contain nitrogen, these becoming yellow by its action. 
 Chlorine is not suited for transport either as gas or in aqueous solution, therefore one 
 of its combinations with oxygen and a base, viz., a hypochlorite, is used. Hydrated 
 oxide of calcium or slaked lime is the chief constituent of bleaching-powder. Usually 
 the alkali manufacturers prepare bleaching-powder. 
 
 Chloride of Lime. In the production of chloride of lime the chlorine passes from the 
 generator through the tube, M, Fig. 329, into a room constructed of large blocks and 
 
 slabs of sandstone joined by 
 means of asphalt cement, or 
 a mixture of coal-tar and 
 fire-clay. Sometimes the 
 room is built of bricks laid 
 in a similar cement, the 
 interior being lined with 
 asphalt ; leaden chambers 
 also are used for this pur- 
 pose. The room is fitted 
 with several shelves upon 
 which slaked lime is placed 
 in layers of 3 to 4 inches 
 
 and more in thickness. The chlorine gas is readily absorbed, heat being evolved. Care 
 is to be taken that the temperature does not exceed 25, because then calcium chlorate 
 is formed ; this is prevented by admitting the gas slowly. As soon as the absorption 
 ceases, the bleaching-powder is removed with rakes from the shelves, and fresh lime 
 introduced. Frequently the chloride of lime is somewhat diluted by an admixture of 
 slaked lime. 
 
 Chloride of lime, on a system involving the use of several chambers, has been 
 successfully manufactured at the Lari alkali works at Petrowitz for eighteen months. 
 According to L. Jahne, the system consists of a lead chamber, 2 metres in height, 
 divided by cross walls into four completely distinct compartments. The chlorine is 
 supplied from three sandstone generators, placed at a suitable distance, having a 
 
Fig. 330- 
 
 D - 
 1 
 
 c 
 
 t 
 
 A 
 
 *' 
 
 SECT, in.] CHLORINE, CHLORIDE OF LIME, AND CHLORATES. 359 
 
 common delivery-pipe, and which are charged and emptied at equal intervals of time, 
 so that a uniform current of chlorine is always supplied to the chambers. Each of 
 the four chambers, A to D (Fig. 330), has at that corner of the top which is nearest to 
 the middle of the system, a pipe for the removal of the chlorine, and at the angle 
 diagonally opposite a longer escape-tube. In each chamber there is also, besides the 
 working door and the opening at the bottom for withdrawing the finished product, a 
 bell for observing the gases, a thermometer, and an opening for 
 taking samples. The ends of the eight entrance and exit tubes 
 and the chlorine main, open into a reversal apparatus, and there 
 are arranged accordingly three chief exit-pipes which open 
 through a lead main into the chimney. The connection of 
 the ends of the various tubes is effected by placing a leaden 
 ball over each two ends, so that the chlorine main in the 
 middle is connected with the entrance-pipe of A, the exit- 
 pipe of A with the entrance-pipe of 7>', the exit of B with the entrance (7, &c. 
 
 Liquid Chloride of Lime. When it is desired to prepare a solution of chloride of 
 lime, the apparatus shown in Fig. 331 is employed. Two or four earthenware vessels, 
 A, about 2 hectolitres capacity, are placed in the leaden trough, B, the bottom of which 
 .is protected by a cast-iron plate and a stoneware slab, F, from the direct action of 
 the fire at D. B represents a concentrated solution of calcium chloride serving the 
 purpose of a bath, such a solution boiling at i79'5. By the syphon funnel, K, the 
 hydrochloric acid is poured into A. I is a perforated cistern filled with manganese. 
 S is the leaden gas tube. The chlorine, being first washed in R, passes through n into 
 T, filled with pieces of manganese, to decompose any vapours of hydrochloric acid 
 carried over, and, lastly, the chlorine passing through m reaches the absorption vessel, 
 S. This vessel is a lead-lined 
 
 wooden cask, fitted with an 1'ig- 33 * 
 
 axle bearing spokes to which 
 are fastened gutta-percha floats. 
 The bearings andplummer-blocks 
 of the axle are made of guaiacum 
 wood and ebonite. The axle, o, 
 gears with a suitable motive 
 power, the purpose being to keep 
 the milk of lime in continuous 
 motion while the gas is being 
 admitted. 
 
 The chlorine gas enters above 
 the level of the fluid, which is 
 kept constantly stirred, to assist 
 
 in the absorption. From the vessel wherein the absorption takes place a small tube 
 leads into another vessel filled with water to a depth of 1 8 to 24 centimetres ; a tube 
 fitted to this vessel leads into the open air to convey away any unabsorbed chlorine. 
 As in the preparation of solid chloride of lime, it is here necessary to guard against an 
 increase in temperature and also saturation ; Schlieper has proved that too concentrated 
 solutions evolve oxygen, while too dilute solutions yield calcium chlorate. 
 
 Numerous researches have been published on the Formation of Chloride of Lime. In 
 the chlorination of lime the presence of water is of capital importance, though there exist 
 the most contradictory views. Graham, and subsequently Frike and Reimer, main- 
 tained that an anhydrous calcium hydrate was incapable of chlorination. Gopner thinks 
 an excess of 8 per cent, the most favourable, but by no means sufficient (?). Richters 
 
360 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 and Junker recommend an excess of water of i to 2 per cent. Davis recommends 3 
 
 to 4 per cent. Kopfer obtained chloride of lime on chlorinising lime imperfectly 
 
 slaked. Lunge and Schappi show that imperfectly slaked lime may be chloridised, 
 
 and that only ^ mol. water of hydration may be communicated to the chloride of 
 
 lime, according to which the great absorption of chlorine is intelligible 
 
 2 Ca(OH) 2 + 2 C1 2 = 2 CaOCl s .H 2 O + H S 0; and 
 
 CaO + H 2 O = Ca(OH) 2 . 
 
 It has not been found possible to chlorinate a perfectly anhydrous caustic lime, which 
 goes against Gopner's formula. Chloride of lime containing 42 to 43 per cent, of 
 effective (bleaching) chlorine can be easily obtained ; thus any formula which regards 
 such proportions as exceptional becomes untenable. The strongest chloride of lime is 
 prepared with dry chlorine and a hydrate of lime containing 2 to 4 per cent, excess of 
 water. If the chlorine is imperfectly dried, an excess of i to 2 per cent, is most 
 favourable. The formation of calcium chloride is unimportant. 
 
 Scheurer-Kestner gives the highest temperature in normal working as 55, Hurter 
 as 40, Gmelin as 18, and Bobierre as 50. On using moist chlorine, Schappi obtained 
 at 
 
 Temperature. Effective Chlorine. 
 
 -17 ... 2-30 
 
 O ... 19-88 
 
 7 33-24 
 
 21 - 35-50 
 
 21 ... 39-50 
 
 30 ... 40-10 
 
 40 ... 41-18 
 
 45 ... 40-50 
 
 So ... 41-52 
 
 60 ... 39-40 
 
 90 ... 4-26 
 
 Hence it is an error to suppose that hydrate of lime cannot absorb chlorine at o, 
 as, after two hours' action, a 20 per cent, chloride was produced, and a weak sample was 
 even obtained below o. With dry chlorine the most favourable temperature is 10 
 to 16 ; with moist chlorine, 20 to 60, though the action is best between 40 and 45. 
 The residue obtained on dissolving chloride of lime in water consists chiefly of calcium 
 hydroxide, as appears from the following analysis of a good sample : 
 
 CaO . . . 39-89 
 
 Bleach do. . . 43-13 
 
 ClasCaCl 2 . . 0-29 
 
 H 2 . . . 17-00 
 
 C0 a 0-42 
 
 100-73 
 
 H.,0 . 82-65 
 
 CaCO 3 . . .0-95 
 
 CaCl 2 . . .0-44 
 
 Ca(OH) 2 . .6-80 
 
 H 2 (free) . .9-82 
 
 1 00-66 
 
 The latest experiments by Lunge confirm the formula CaOCl 2 for chloride of lime. 
 
 The bleaching salts obtained from the bivalent metals, calcium, strontium, and prob- 
 ably barium, have probably the nature of double salts of the formula C1...R...OC1, in 
 which all the chlorine can be directly replaced by carbonic acid. 
 
 Properties of Chloride of Lime. Chloride of lime is a white powder, the bleach- 
 ing constituents of which dissolve in about 10 parts of water, whilst the excess of 
 lime is undissolved. The bleaching action is manifested only on the addition of an 
 acid. 
 
 The loss of value of chloride of lime on preservation in casks at temperatures from 
 5 to 17 was examined by J. Pattinson. Three sorts of chloride of lime had on 
 January 29, 1885 (I.), and, after being kept for a year in casks, on January 5, 1886 
 (II.), the following respective compositions : 
 
SECT, in.] CHLORINE, CHLORIDE OF LIME, AND CHLORATES. 361 
 
 
 A 
 
 
 B 
 
 
 C 
 
 
 
 I. 
 
 II. 
 
 I. 
 
 II. 
 
 I. 
 
 II. 
 
 Effective chlorine 
 
 37 -oo 
 
 33-o 
 
 38-30 
 
 35-10 
 
 36-00 
 
 39-20 
 
 01 as chloride 
 
 o-35 
 
 2-41 
 
 0-59 
 
 2-42 
 
 0-32 
 
 1-97 
 
 Cl as chlorate 
 
 0-25 
 
 
 
 0'08 
 
 
 
 0-26 
 
 
 Lime . 
 
 44 '49 
 
 43'57 
 
 43-34 
 
 42-64 
 
 44 '66 
 
 43-65 
 
 Magnesia . 
 
 0-40 
 
 o-34 
 
 0-31 
 
 0-36 
 
 o-43 
 
 0-38 
 
 Ferric oxide 
 
 0-05 
 
 0*05 
 
 O'O4 
 
 0-04 
 
 0'02 
 
 O'O2 
 
 Alumina 
 
 0'43 
 
 o-35 
 
 O'4I 
 
 0-36 
 
 0-33 
 
 0'35 
 
 Manganic oxide 
 
 trace 
 
 trace 
 
 trace 
 
 trace 
 
 trace 
 
 trace 
 
 CO, . 
 
 0-13 
 
 0-80 
 
 0-30 
 
 1-48 
 
 0-48 
 
 i'34 
 
 Silicates 
 
 0-40 
 
 0-50 
 
 0-30 
 
 0-04 
 
 0-50 
 
 0-50 
 
 Water 
 
 i6'45 
 
 18-15 
 
 16-33 
 
 17-20 
 
 17-00 
 
 18-89 
 
 Total chlorine 
 
 37-60 
 
 36-24 
 
 38-97 
 
 37-52 
 
 36-58 
 
 34-87 
 
 Chlorametry, As only the chlorine which exists in chloride of lime in the form of 
 CaOCl 2 comes into play in its applications, such quantity determines its value. 
 
 Gay-Lussac makes use of the oxidising action of chloride of lime upon arsenious 
 acid, a volume of dry chlorine gas dissolved in water being employed. The solution of 
 chlorine is poured into a graduated tube divided into 100 parts, each of these divisions 
 corresponding to one-hundredth of chlorine. A solution of arsenious acid in dilute 
 hydrochloric acid is also prepared, the strength of the solution being such that equal 
 bulks of the two liquids suffer mutual decomposition : 
 Arsenious acid, As 2 O 3 ,' 
 
 yield 
 
 J Arsenic acid, As 2 5 , 
 
 (Hydrochloric acid, 4C1H. 
 
 Water, 2H 2 O, 
 Chlorine, 2C1 2 , 
 
 Water is decomposed ; its oxygen combines with the arsenious acid, forming arsenic 
 acid, while the hydrogen combines with the chlorine. Usually i litre of dry chlorine 
 gas is dissolved in i litre of distilled water. The normal solution of arsenious acid 
 is so prepared that it is entirely decomposed by the chlorine water to arsenic acid. 
 The test is carried out as follows : Take 10 grammes of the sample, and triturate with 
 distilled water, adding sufficient of the latter to make up a litre. Next take, by 
 means of a graduated pipette, 10 c.c. of the arsenious acid solution, and pour it into a 
 beaker, adding a drop of indigo solution to impart a faint colour ; next add, by means 
 of a burette, sufficient of the bleaching-powder solution to cause the colour nearly to 
 disappear, then add more of the indigo solution, and again bleaching-powder solution, 
 until the fluid becomes quite colourless. The normal arsenious acid solution is pre- 
 pared by dissolving 4-4 grammes of this acid in 32 grammes of hydrochloric acid, the 
 liquid to be di'ubed to i litre. If 10 grammes of bleaching-powder contain i litre of 
 chlorine gas, it is of 100 strength. 
 
 Penot's Test. Penot has modified Gay-Lussac's method in the following particulars : 
 For the arsenious acid solution he substitutes sodium arsenite, and for the indigo 
 solution a colourless iodised paper, which is turned blue by the smallest quantity of 
 free acid. The paper is prepared in the following manner: i gramme of iodine, 
 7 grammes sodium carbonate, 3 grammes of starch, and litre of water are mixed. 
 When the solution becomes colourless, it is diluted to litre ; in this fluid white 
 paper is soaked. The arsenical fluid is prepared by dissolving 4-44 grammes of arsenious 
 acid, and 13 grammes of crystallised sodium carbonate in i litre of water. This solution 
 is poured, by means of a burette, into the solution of the chloride of lime intended to 
 be tested (10 grammes of the sample to i litre), the completion of the reaction being 
 known by the paper remaining uncoloured. Mohr, again, has modified this process, 
 not, however, in very essential particulars. 
 
 Wagner's Method. This test, discovered in 1859, is the so-called iodometrical 
 method, and is based upon the fact that a solution of chloride of lime separates the 
 
3 6 2 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 iodine from a weak (i to 10) and slightly acidified potassium iodide solution, the 
 iodine being quantitatively estimated by means of sodium thiosulphate : 
 
 x ( Sodium iodide, alSTal, 
 
 Iodine, 2!, I .j d I g odium tetrathionate, Na 2 S 4 O 6 , 
 
 Sodium thiosulphate, 2Na 2 S 2 3 + 5H 2 0,j * | Water, 5H O. 
 
 The test is thus executed: 100 c.c. = i gramme of bleaching-powder solution, 
 obtained by dissolving 10 grammes of chloride of lime in i litre of water, are mixed 
 with 25 c.c. of solution of iodide of potassium acidified with dilute hydrochloric acid. 
 The ensuing clear, deep brown coloured solution is treated with sodium thiosulphate 
 solution until quite colourless. The sodium thiosulphate solution is composed of 24*8 
 grammes of that salt to i litre of water; i c.c. of this solution neutralises 0*0127 
 gramme of iodine and 0-00355 g ramme of chlorine. 
 
 G. Lunge's method for determining the bleaching chlorine in chloride of lime 
 depends on the observation that hypochlorous acid if mixed with hydrogen peroxide 
 immediately gives up its active oxygen, as does the hydrogen peroxide itself, so that 
 we obtain a double quantity of oxygen. A turbid solution of chloride of lime is 
 obtained in the ordinary manner with 10 grammes of the sample to 250 c.c. of water. 
 5 c.c. of the solution ( = 0*2 gramme chloride of lime) are drawn off with a pipette, 
 and this is let flow into the external space of the decomposition bottle of the nitro- 
 meter. Into the interior tube there is poured an excess of hydrogen peroxide ; for 
 this purpose 2 c.c. of the commercial article are sufficient. The quantity need not 
 be accurately measured, and the proportion of actual hydrogen ' peroxide does not 
 need to be determined as long as it is in excess. The little bottle is then fixed upon 
 the caoutchouc stopper, grasping it by the neck, so as to avoid warming it ; the cock of 
 the nitrometer is then turned so as to connect the little bottle with the measuring 
 tube, the mercury in which has been previously fixed at o. The bottle is inclined so 
 that the liquids mix ; it is shaken for a few moments, the mercury in both tubes is 
 placed at the same level, and the result is read off. If 0*2 gramme chloride has 
 been used, each c.c. of gas at o and at a pressure of 760 mm. represents 5 French 
 degrees or 1-632 per cent, of efficient chlorine. If we dissolve 7*917 grammes 
 chloride of lime in 250 c.c., and use for each test 5 c.c. of the solution, i c.c. of gas 
 represents 2 per cent, chlorine. 
 
 The determination of bleaching chlorine i.e., of free HOC1 or NaOCl, is also 
 effected by titration with sodium arsenite. According to Penot, it is not usual to 
 titrate back with solution of iodine, but to ascertain the end of the reaction by 
 spotting. Here all the HOC1 and NaOCl are converted into NaCl ; it is therefore 
 quite unnecessary to resort to other reducing agents, such as zinc powder, &c. We 
 have in the sodium arseniate now present an indicator for the next operation, which 
 even surpasses potassium chromate. 
 
 For determining the total chlorine present as hypochlorite and chloride, a part of 
 the liquid obtained in the last operation is titrated with decinormal silver nitrate until 
 the reddish-brown colour of silver arseniate appears. 
 
 For determining the chlorate another portion of the liquid obtained in the former 
 operation (which contains no hypochlorite, but all the chlorate) is boiled in the valve flask 
 with a strong solution of ferrous sulphate, the value of which with permanganate has 
 been accurately ascertained, and, after cooling, it is titrated back with permanganate. 
 
 Chlorometric Degrees. In Germany, Britain, Russia, and America the strength of 
 chloride of lime is expressed in degrees, which give the percentage of effective chlorine ; 
 in France (and in some German works) the degrees represent the number of litres 
 chlorine gas, at o and at a pressure of 760 mm., which can be liberated from i kilo, of 
 the sample in question. The following table gives the chlorometric degrees for France 
 and for Britain and Germany : 
 
SECT, in.] CHLORINE, CHLORIDE OF LIME, AND CHLORATES. 363 
 
 French 
 Degrees. 
 
 65 
 
 70 
 
 75 
 So 
 
 85 
 90 
 
 English and German 
 Degrees. 
 20*65 
 22-24 
 23-83 
 25-42 
 27-01 
 28-60 
 
 French 
 
 Degrees. 
 
 100 
 
 105 
 110 
 
 115 
 
 1 20 
 
 125 
 
 English and German 
 
 Degrees. 
 
 31-80 
 
 33 '36 
 
 34-95 
 
 38-I3 
 3972 
 
 The percentage may be calculated from the French degrees by multiplying the 
 latter with 0-318 (i litre chlorine gas weighs 3*18 grammes). 
 
 Chloride of Alkali. A solution of hypochlorite of potassa is known in commerce 
 under the name of Eau de Javette, while the corresponding soda solution is known as 
 JSau de Labarraque ; these solutions are prepared by passing chlorine gas into a 
 solution of either caustic (i) or carbonated (2) alkali 
 
 (i) 2 NaOH + 01, = NaOCl + NaCl + H 3 O; 
 (a) 2 Na 2 C0 3 + 01, + H 2 O = NaOCl + NaCl + 2NaHC0 3 ; 
 or by exhausting bleaching powder with water, and precipitating the solution with 
 sodium sulphate or carbonate solution, calcium sulphate or carbonate being thrown 
 down, while the hypochlorite and chloride of the alkali remain in solution. 
 
 Aluminium hypochlorite, or Wilson's bleaching liquor, is obtained by mixing 
 chloride of lime solution with aluminium sulphate; it acts by evolving oxygen, 
 leaving aluminium chloride in solution. Hypochlorite of magnesia (Ramsay's or 
 Crouvelle's bleaching liquor) is obtained by adding magnesium sulphate to a solution 
 of bleaching powder ; the result is the formation of a very energetic bleaching com- 
 pound, which, especially for the purpose of bleaching finely woven fabrics, as muslins, <fec., 
 is preferable to chloride of lime on account of the absence of caustic lime. Varren- 
 trapp's bleaching salt, or zinc hypochlorite, is another energetic bleaching compound 
 obtained by treating a solution of chloride of lime with zinc sulphate, the result being 
 the precipitation of calcium sulphate, while zinc hypochlorite remains in solution ; 
 zinc chloride may be employed, but, of course, the solution then retains calcium 
 chloride. Hypochlorite of baryta is sometimes used, hypochlorous acid being obtained 
 by the addition of very dilute sulphuric acid. 
 
 Potassium Chlorate (Chlorate of Potassa). This salt (KC10 3 ) consists, in 100 parts, 
 of 38-5 of potassa and 61-5 of chloric acid; its crystals are rhombic and tabular in 
 form. It formerly was prepared by passing chlorine gas into a concentrated solution 
 of potassium carbonate, the result being the formation of potassium chlorate and 
 chloride. As the chlorate is the less soluble it crystallises first, while by evaporation 
 the mother liquor yields potassium chloride. The chlorate is then washed with 
 cold water, and purified by recrystallisation. 100 kilos, of potassium carbonate 
 yield in this manner 9 to 10 kilos, of the chlorate. At the present day, however, 
 potassium chlorate is prepared by a method, a suggestion of the late Dr. Graham. 
 Chlorine is caused to act at a high temperature upon milk of lime, with the result of 
 the formation of calcium chlorate and chloride, the calcium chlorate being after- 
 wards decomposed by potassium chloride. The method by which potassium chlorate 
 is prepared on the large scale according to this plan is the following : i moL of 
 potassium chloride and 6 mols. of hydrate of lime, having been mixed with water, 
 are submitted to the action of chlorine gas; the solution yields on evaporation 
 crystallised potassium chlorate, while calcium chloride remains. 
 
 According to Lange there are used for saturating the milk of lime two mutually 
 connected cylinders lined with lead, and provided with agitators (compare Fig. 331). 
 Both are connected with each other and with the chlorine generator in such a manner 
 that the contents of the one approach saturation, whilst the chlorine left unabsorbed in 
 the other is taken up by fresh milk of lime. As soon as complete saturation is reached 
 
364 CHEMICAL TECHNOLOGY. [SECT. ui. 
 
 in the first cylinder fresh milk of lime is substituted for the contents, and the current 
 of chlorine is turned so that it first enters the second cylinder. The lye of calcium 
 chloride and chlorate obtained has a rose-red colour, which some chemists refer to 
 permanganic acid, and others to ferric acid, as it appears when manganese has 
 been used. The colour is the sign of perfect saturation even where the chlorine (as at 
 Kunheim's works at Berlin) is obtained by the Deacon process. The red liquid after 
 settling is mixed with potassium chloride, concentrated down to sp. gr. 1-28, and let 
 crystallise. The mother liquor from the first crop of crystals is again concentrated to 
 sp. gr. i '3 5, when a second, though smaller, crop of potassium chlorate is obtained. 
 About 1 2 per cent, of the chlorate remains in the mother liquor, which consequently 
 has to be worked up for chlorine. The crystals obtained contain calcium chloride 
 and iron as impurities. To remove these the crude chlorate is dissolved in the smallest 
 possible quantity of hot water; to 10 hectolitres of the liquid there are added 2^ kilos, 
 of soda, and the solution after settling is let crystallise. For the formation of chlorate 
 a small excess of chlorine is necessary, but a special application of heat is not needed, 
 as the heat developed during reaction is sufficient. 
 
 Calcium chlorate is also formed by evaporating a solution of chloride of lime to 
 dryness, and is then converted into the potassium salt by adding potassium carbonate 
 or chloride. Old chloride of lime, which has partly lost its bleaching power, contains 
 calcium chlorate, and may be used in the manufacture of potassium chlorate. 
 
 According to Muspratt, a solution of chlorine in milk of magnesia is evaporated 
 down to 6o-98 Tw., so that, on cooling, a portion of magnesium chloride crystallises 
 out. This lye is decomposed by the addition of potassium carbonate with formation of 
 potassium chlorate and magnesium chloride. The bulk of the former crystallises out. 
 The mother liquor still retains 5 to 10 per cent, of the potassium chlorate, which is not 
 worth extraction. This lye is now further treated with hydrochloric acid and steam. 
 The potassium chlorate is then decomposed into potassium chloride, with liberation 
 of chlorine, which is absorbed by means of magnesia or lime. The solution, 
 which contains hydrochloric acid in excess, is neutralised with magnesium carbon- 
 ate, and forms then a solution of magnesium chloride, with a very slight impurity 
 of potassium chloride, and in Germany would have very little value. But as 
 the yield is larger than with the lime process, the magnesia process deserves more 
 attention. 
 
 Properties. Potassium chlorate crystallises in leaflets of a nacreous lustre, perma- 
 nent in the air, which dissolve in 16 parts of water at 15, in 8 parts of water at 
 35, and in r6 part of water at 100. If heated they give off oxygen, and if rubbed 
 together with combustible matter they explode most violently. One kilo, potassium 
 chlorate, if strongly ignited, or if heated with 0^5 kilo, pyrolusite or i kilo, ferric 
 oxide, yields 391 grammes or 274 litres oxygen. It is extensively vised in pyrotechny, 
 in percussion caps, &c., as a constituent of the white gunpowder of Augendre and other 
 explosives, for preparing permanganates, as an oxidising agent in tissue-printing e.g., 
 in the production of aniline-blacks, and recently to a large extent in obtaining violet 
 colours from dtmethylaniline. In the production of aniline-blacks a few per cents, of 
 potassium chlorate are added to the colour, and, after printing, the black is fixed by 
 steam at 3-4 atmospheres. At this temperature the chlorate in contact with the 
 organic matter is decomposed, when there occurs an oxidation, and sometimes a 
 destruction, of the colouring matter, though generally the colour is rendered brighter 
 and more beautiful. In the alizarine works in the transformation of sulphanthra- 
 quinonic acid into sodium alizarate, potassium chlorate is added to the melt to prevent 
 the reduction of the alizarine. 
 
 Potassium Perchlorate (KC10 4 ). This salt is sometimes used in pyrotechnics as a 
 substitute for the more dangerous chlorate, It is obtained by cautiously heating the 
 
SECT. IIL] BROMINE. 365 
 
 chlorate until the mass becomes pasty. It is separate from the potassium chloride 
 formed simultaneously by recrystallisation from hot water. 
 
 BKOMINE. 
 
 Bromine is found in sea-water, which contains about 0*06 gramme per litre. The 
 mother liquor of many brine-springs e.g., those of Schoenebeck (near Magdeburg), 
 those of the basins of the Ohio and the Kanawha, especially at Mason City, Pomeroy, 
 and Parkersburg, at Alleghany and Monongahala, in Western Pennsylvannia, as well 
 as the mother liquors from working the salts of Stassfurt and Leopoldshall, are so rich 
 in bromine that its extraction is remunerative. In order to prevent admixtures of 
 chlorine, the mother liquor of sp. gr. i'32, containing 0*15 to 0^35 per cent, bromine, 
 is mixed with dilute sulphuric acid, when hydrobromic and hydrochloric acids are 
 liberated; the mixture is heated to 120, thus separating the volatile hydrochloric 
 acid from the less volatile hydrobromic acid which remains in the liquid. On cooling, 
 sulphates separate out. The acid liquor, separated from the crystals, is distilled with 
 manganese peroxide and sulphuric acid. As a receiver are used two WoulfFs bottles, 
 the first of which is empty, whilst the second contains soda-lye. In the first are 
 condensed water, some bromine, bromoform, bromine chloride, and carbon bromide, 
 whilst the bromine vapours pass into the second bottle, and dissolve there as sodium 
 bromide and brornate. The lye is evaporated to dryness, the residue ignited (to convert 
 the bromate into bromide) and distilled with sulphuric acid and pyrolusite, thus 
 yielding pure bromine, which is best collected and preserved under concentrated 
 sulphuric acid. 
 
 According to the process of A. Frank, the distillation of the bromine mother 
 liquors with pyrolusite and sulphuric acid is effected at Stassfurt in large cubical stone 
 vessels containing 3 cubic metres, and braced together with iron bars. At some 
 distance from the ground there is introduced a perforated plate of the same stone upon 
 which the pyrolusite is laid in pieces of the size of a nut. This vat is covered with a 
 plate of the same material, which is lifted by means of a rope, with a counterpoise 
 passing over a pulley. In this plate there is a stoneware pipe for the admission of 
 steam ; it is provided with a man-hole and an opening for introducing the bromine- 
 lye and the dilute sulphuric acid. There is another aperture for the escape of 
 bromine vapours. The stones after a time allow the solution of manganese chloride 
 to ooze through, and have to be coated with tar. This introduces a new defect : 
 the hydrocarbons of the tar are converted into bromine substitution-compounds, 
 and thus considerable quantities of bromine are lost, and the product is rendered 
 impure. The loss at every new tarring is estimated at 50 kilos, of bromine. A 
 kind of stone has since been discovered at Porta, Westphalia, which does not require 
 this costly preparation, and can be used at once. 
 
 The bromine-lyes are placed in a large cistern situate above the distilling vessels, in 
 which they can be warmed by a steam-pipe. Not all kinds of manganese are fit for 
 this use, that of a medium hardness being the most suitable. The rest of the charge, 
 both the bromine-lye and the acid, is run in through one of the small apertures in 
 the stone lid, which is then immediately closed with a clay ball held down with iron 
 weights. As soon as the apparatus is duly closed, steam is allowed to enter, when 
 abundant vapours of bromine escape through the leaden pipe fitted in the second 
 aperture of the stone plate. This lead pipe leads to a cooling worm of stoneware, sur- 
 rounded by cold water, in which the bromine is condensed. The lower end of the 
 worm opens into the middle tubulure of a large three-necked Woulff's bottle, in which 
 bromine and bromine water collect. In one of the lateral tubulures there is a movable 
 glass syphon, by means of which the bromine water can be drawn off into stoneware 
 
3 66 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. m. 
 
 jugs. In the other tubulure there is a bent glass tube, which passes down to the bottom 
 of a conical iron vessel which widens upwards, and which is filled with water and 
 iron borings. The vapours of bromine which have escaped condensation in the 
 bottle combine with the iron. The impure iron bromide thus obtained, as well as the 
 bromine water drawn off, are returned to the distilling apparatus for the next 
 operation. 
 
 In the distillation there escapes at first scarcely anything but bromine ; towards 
 the end of the operation there appears bromine chloride, and, ultimately, when there 
 is no more bromine present, pure chlorine passes over. These three stages of the 
 operation can be easily distinguished by the colour of the gas in the glass receivers. 
 In regular work the process is continued only to the first appearance of bromine 
 chloride. An operation which takes two hours yields from 2 to z\ kilos, of bromine. 
 
 In this process for obtaining bromine the apparatus must be emptied after each 
 operation and residues, still containing bromine and chlorine, contaminated with salts 
 of manganese, <fec., must be run off. Instead of the single distillatory vessels charged 
 with bromine-lye, Frank employs a series of stills placed like stairs, and directly above 
 each other, B (Fig. 332), connected by pipes and cocks. Into the uppermost of these 
 
 vessels the lye, serving for the 
 Fig- 33 2 - production of bromine, enters 
 
 t - ,1 v I, ,' through the pipe, b, whilst 
 
 into the lowest there passes a 
 current of chlorine and steam, 
 which is evolved in separate 
 generators, either by the in- 
 troduction of steam into the 
 chlorine generator, D, or by 
 conveying the two conjointly 
 by means of pipes or by draw- 
 ing the chlorine by means of 
 the current of steam. They 
 are mixed and distributed in 
 
 the bromine-lye. The chlorine and steam entering the lowest vessel liberate the 
 bromine from its compounds, and drive it, partly as pure bromine, partly as bromine 
 chloride, and mixed with some free chlorine, into the next higher still, containing 
 fresher lye, and so on through the entire column. Both the free chlorine and the 
 chlorine in the bromine chloride, in as far as it is present, are absorbed, and in decom- 
 posing the bromine compounds present in the lyes and at the end of the column there 
 escape merely vapours of bromine (nearly pure) and steam to the condensers. The 
 number of the stills depends on their size and on the quantity and the strength of the lye 
 to be operated upon. As soon as the lowest still is sufficiently driven off, its contents pass 
 into the dechlorinising vessel, C, which is at a lower level, and is connected by means 
 of pipes and cocks. In this process the mother liquor is of course free from the salts 
 -of manganese, &c., which interfere with the treatment of the residues from the 
 ordinary process. 
 
 In the apparatus used at the United Chemical Works of Leopoldshall the bromine- 
 lye flows through the tube, a, fitted with a hydraulic joint into a drum, 6, of fire-clay 
 or sandstone extending transversely through the entire width of the tower, which is 
 provided on each side with a row of openings directed obliquely downwards. Below 
 this drum there is a horizontal sandstone plate, e, well cemented into its place, in 
 which are cemented conically shaped earthern pipes, cut off obliquely below and 
 provided with a slit above (Figs. 333 and 334). They are fixed with the oblique point 
 downwards, whilst the upper part is free and projects to the same height above the plate. 
 
SECT. 
 
 III.] 
 
 BROMINE. 
 
 367 
 
 These pipes are so fixed that each stream of liquid issuing from the openings of the 
 drum, b, falls in the place between two ranks of the tubes. The lye distributes itself 
 equally above the plates, flows through the slits of the tubes and out at their points in 
 fine streams upon the balls, which fill the tower nearly to the top. The vapours given 
 off are led through the tube o of the stoneware worm, placed in the cooler, p, and the 
 liquefied bromine collects in the bottle, q. In the recipient, B, there lie four sandstone 
 
 Fig. 333- 
 
 Fig- 334- 
 
 plates, 5, above each other, joining close up to three of the walls, but leaving a small 
 interval against tne fourth wall. The intervals are alternately on two opposite sides, 
 and each plate is provided with a row of fine holes. In the middle of the apparatus 
 there is a short sandstone pipe which can be connected above with the steam pipe, and 
 which penetrates all the sandstone plates. It is placed close up to another short sand- 
 stone pipe, r, which lies on the bottom and extends straight through the apparatus, and 
 is bored longitudinally, and is also fitted with lateral openings arranged at regular 
 intervals. The lye trickling through the tower, A, collects beneath the sieve-like false 
 bottom, c, arrives from here through the tube z in the apparatus, B, and flows zig- 
 zag downwards over all the plates in the direction indicated by the arrows, in order to 
 pass from the bottom through the ascending pipe, i, into the exit channel, k. The 
 apparatus is constantly kept full of liquid to the point of the tube z. At the same 
 time steam is led in through the pipe g, and keeps the lye constantly boiling. The 
 vapours rise chiefly through the holes of the plates, s, and thus compel the lye to take 
 its way over the plates through the slits. By this apparatus the lye is completely freed 
 from small adhering traces of free chlorine and bromine. The vapours collect in the 
 upper part of the apparatus, mix there with the chlorine arriving from the washing 
 apparatus, Z>, through the tube I (shown in the figure by dotted lines), rise through 
 the tube z (which offers a sufficient transverse section), back into the tower, A, which 
 they traverse from below upwards. Into the vessel, n, there plunges a stoneware pipe, 
 d, suspended by a strap to the rod, t, so as to admit of turning. Above the entrance 
 of the tube x lies a perforated false floor, and upon it a charge of iron filings. These 
 are covered with a second false bottom, upon which a slight current of water is passed 
 
368 CHEMICAL TECHNOLOGY, [SECT, in 
 
 through the pipe/. The vapours not condensed in the cooler, p, pass from below into 
 the moistened iron turnings ; all the chlorine and bromine are absorbed, and the lye 
 dropping off flows continually through the tube v, into the receiver, w, whilst air and 
 watery vapour escape freely from the top of the tube d. For the production of the 
 uniform current of chlorine which is necessary, the tubing, ra, connected with the 
 chlorine generator is bent at right angles. At its lowest point, a glass tube, h, pro- 
 vided with a tubulure, is inserted, so that the small quantity of condensed water which 
 nere collects escapes through the flexible pipe, u, connected with the tubulure into the 
 washing apparatus, D. 
 
 Crude bromine when obtained by the earlier process always contains chlorine, 
 even when, as it is done at Stassfurt, the WoulfFs bottle is slightly warmed towards 
 the end of the operation, so as to drive the volatile bromine chloride into the iron 
 borings. It must therefore be submitted to rectification. This takes place in glass 
 retorts containing about 15 litres each, the necks of which are cemented into glass 
 receivers, surrounded with cold water. Each retort is placed in a small special sand 
 bath, so that if a retort bursts the damage may be as limited as possible. Only a 
 small watery fraction contains chlorine ; it is removed and returned to the stone vats. 
 
 At Stassfurt bromine is sent off in strong glass bottles with ground stoppers. The 
 stoppers are covered over with melted shellac, then luted with clay and tied with 
 parchment paper. Four or twelve such bottles are packed in a box. Stassfurt and 
 Leopoldshall furnish yearly about 300 tons of bromine, and North America about 200 
 tons.* 
 
 Properties and Applications of Bromine. Bromine as a liquid appears in mass of a 
 dark reddish brown, but in thin layers of a hyacinth red. Its odour is strong, and 
 resembles that of chlorine. Bromine is rather freely soluble in water but more 
 readily soluble in solution of potassium bromide, in hydrobromic acid, and in hydro- 
 chloric acid in the last-mentioned liquid 13 per cent. The aqueous solution is 
 reddish brown, and on exposure to light it is decomposed, like chlorine water, with the 
 liberation of oxygen and the formation of hydrobromic acid. At 15 100 parts of 
 bromine water contain 3*226 parts of bromine. With water, bromine forms at o a 
 solid, crystalline hydrate. Bromine dissolves readily in ether, alcohol, -chloroform, and 
 hydrogen sulphide. In aqueous sulphurous acid it dissolves, forming hydrobromic 
 acid; it boils at 63 and is converted into dark-red vapour. At 7-2 bromine forms 
 a reddish-brown crystalline mass. With colouring- matters bromine behaves like 
 chlorine. It turns organic matters brown. Like iodine, potassium bromide, ammo- 
 nium and cadmium bromide, and potassium hypobromate, it is used in photography 
 and pharmacy. In the form of bromethyl, bromamyl, and brommethyl, it serves in 
 the production of certain coal-tar colours, e.g., Hofmann's blue. Since 1874 bromine 
 is used in the production of cosine (tetrabromfluoresceine). It is also used as a dis- 
 infectant. Cinnabar, blende, and copper pyrites are decomposed and dissolved by 
 bromine. 
 
 IODINE. 
 
 Iodine was discovered in 1811 by Courtois in a lye obtained from sea-weeds. The 
 first iodine manufactory was set up by Tissier, at Cherbourg, in 1824. It occurs in 
 sea-water and is taken up by marine plants. In the crude nitre of South America it 
 is found in large quantity, and in smaller proportions in some brine springs. The pre- 
 sence of iodine in the phosphorites of Amberg in Bavaria and of Diez (on the Lahn), as 
 also in the French departments of Lot and of Tarn and Garonne, may possibly become 
 
 * This latter quantity could be indefinitely increased if the demand were greater, which would 
 be the case if better means of transport could be adopted. Shippers fear it, and the freight is 
 consequently high. 
 
SECT, in.] IODINE. 369 
 
 of commercial importance. Kuhlmann of Lille obtains iodine as a lye-product in pre- 
 paring superphosphate from French phosphorites, which in 1000 kilos, contain ^ kilo, 
 of iodine. The chief seat of the iodine manufacture is at Glasgow, where there are 
 twelve works. There are two in Ireland, and ten to twelve in the Department of 
 Finisterre in France, arid also in Asturias. At Tarapaca in Peru, and Antofagasta in 
 Bolivia, iodine is obtained in very considerable quantities from the mother-liquors of the 
 nitre works. 
 
 In order to obtain iodine from sea-weeds, the latter are first converted into kelp, 
 that is to say, they are incinerated, the product broken to pieces and lixiviated with 
 water, leaving an insoluble residue of 30 to 40 per cent., and yielding to the liquid 60 
 to 70 per cent. This solution, having a sp. gr. of i'i8 to 1*20, contains chlorides, 
 sulphates, and carbonates of alkalies, potassium sulphide, chloride, and iodide, and hypo- 
 sulphites of alkalies ; by evaporating and cooling the liquor, the potassium sulphate 
 and potassium and sodium chlorides are removed. To the remaining mother-liquor, 
 previously poured into shallow open vessels, dilute sulphuric acid is added, the result 
 being, that while a strong evolution of gases, sulphuretted hydrogen, and carbonic acid 
 takes place, there is formed a thick scum and a deposit of sulphur at the bottom 
 of the vessel ; the sulphur when washed and dried is sold. When the evolution of gas 
 has completely ceased, more sulphuric acid is added, and, according to Wollaston's 
 method, the required quantity 
 
 of manganese ; this mixture is l %' 335- 
 
 poured into a large leaden dis- 
 tilling apparatus, C, Fig. 335. 
 By this means the iodine is set 
 free, carried over in the state of 
 vapour to the receivers, B, B', B", 
 and condensed as a solid crystal- 
 line mass. In Paterson's large 
 iodine works at Glasgow this 
 operation is carried on in a cast- 
 iron hemispherical vessel of 1*3 
 metre diameter, the cover being 
 
 a leaden dome, to which are fitted two earthenware still heads, connected by means 
 of porcelain tubing with two earthenware receivers, Fig. 335, each consisting of 4 to 5 
 parts. At Cherbourg, iodine is obtained, according to Barruel's plan, by passing 
 chlorine gas into the mother-liquor ; by this plan the iodine is separated from the 
 iodide of magnesium, the latter taking up chlorine instead 
 
 (MgI 2 + 01, = Mg01 2 + I,). 
 
 A more recent method, by which all the iodine present in the mother-liquor is obtained, 
 consists in distilling the liquor with chloride of iron 
 
 ( 2 NaI + Fe a Cl 6 = 2! + 2NaCl + 2 FeCl 2 ). 
 
 As iodine is only very slightly soluble in water, i part of iodine requiring 5524 parts 
 of water at 10 to 12 for its solution, that is, i grain of iodine to 12 ounces of water, 
 it is carried over with the steam and deposited at the bottom of the receiver in the 
 form of a black powder. When iodine is prepared by the aid of chlorine, the quantity 
 of gas should be exactly sufficient to decompose the iodide of magnesium, for if the 
 quantity of chlorine be too small no iodine is separated ; and if too large, chloride of 
 iodine is formed and free bromine, both of which, being volatile, escape. The iodine 
 when removed from the receivers is drained on porous bricks or tiles, and dried between 
 folds of blotting-paper. It need hardly be said that the iodine should not come in 
 contact with a metallic surface. The iodine thus obtained has to be purified by sub- 
 limation, an operation carried on in the apparatus represented in Fig. 336, consisting 
 
 2 A 
 
37 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 Fig. 336. 
 
 of stoneware retorts, C C, placed in the sand-bath, B, heated as shown in the woodcut. 
 Each of these retorts is filled with upwards of 40 Ibs. of crude iodine, and entirely 
 
 surrounded by sand in order to prevent the 
 sublimation of any iodine in the necks of 
 the retorts. These are then connected with 
 the receiver or condenser, E, R, in which 
 the crystalline iodine is deposited, the tubes, 
 a b, a b, being for the purpose of carrying off 
 the watery vapour, i ton of kelp yields on 
 an average 4-07 kilos, of iodine. 
 
 Allary and Pellieux evaporate the sea- 
 weed lyes after separating the potassium 
 chloride and sulphate and roast the residue 
 to oxidise the sulphur compounds. The 
 .residue is lixiviated, the solution evapo- 
 rated, pulverised and extracted with alcohol. 
 The alcohol is distilled off and the residue, consisting of potassium and sodium iodide 
 in a saturated solution, is mixed with a quantity of potassium carbonate equivalent to 
 the sodium iodide present, and treated with carbon dioxide. There are formed potas- 
 sium iodide and sodium carbonate which is converted into bicarbonate and deposited. 
 The residual solution of potassium iodide is neutralised with hydrochloric acid and 
 recrystallised from alcohol in order to eliminate traces of potassium chloride. 
 
 Vitali saturates the sea- weeds with a solution of potash so that on incineration no 
 iodine may be lost. The ash is heated to redness with potassium dichromate. The 
 yield is said to be much greater than after treatment with chlorine. 
 
 The process of Stanford is carried out on the large scale by the British Sea- weed 
 Company, at Dalmuir, near Glasgow. 
 
 To prevent losses Pellieux lets the fresh weeds ferment before incineration in shaft 
 furnaces. 
 
 The crude nitre of Chili and Bolivia contains 0-059 to 0-175 P er cent, iodine in the 
 state of sodium iodate, besides traces of sodium and magnesium iodide. The mother- 
 liquors from refining the crude nitre and converting it into potash saltpetre are treated 
 for iodine by passing in a current of S0 2 until the iodine begins to redissolve. Latterly 
 nitrous acid is preferred to sulphurous. The iodine liberated is dried and refined by 
 sublimation. The iodine present as iodides is precipitated by means of chlorine. 
 One litre of the mother-liquors from refining nitre contains 2-3 to 4-8 grammes iodine. 
 At Peruana in Tarapaca the concentrated lyes of sodium saltpetre have the fol- 
 lowing composition : 
 
 Sodium nitrate 28 
 
 chloride n 
 
 ,, sulphate . . . 3 
 
 Magnesium sulphate .... 3 
 
 Sodium iodate 22 
 
 Water 33 
 
 The quantity of the solution of sodium bisulphite necessary for precipitation 
 depends on the proportion of iodine present. The two liquids are mixed by means of 
 a mechanical agitator, when the iodine falls to the bottom of the vat as a black mud. 
 Flakes of iodine, which rise to the surface, are skimmed off with wooden ladles and 
 put in settling vats. The mother-liquor thus chiefly freed from iodine is run off into 
 a deep receiver, and is first treated for nitrate. It is afterwards again treated 
 
SECT, m.] NITRIC ACID AND NITRATES. 371 
 
 for iodine. The iodine mud deposited at the bottom of the precipitating vat is re- 
 peatedly washed with clean water, filtered and converted by means of a filter-press 
 into blocks of 0*2 metre in thickness. This crude iodine contains 80-85 P er cent - 
 pure iodine, 510 per cent, of fixed matter, and 5-10 per cent, of water. It is distilled 
 in an iron retort, connected with eight stone- ware receivers, each 0-9 metre long and 075 
 metre in diameter. The last is closed with a wooden cover, luted on with clay, as are 
 all the joints of the apparatus. The sublimed iodine is packed in small pitched kegs. 
 
 Iodine has recently been brought into commerce in the form of copper iodide, 
 obtained by treating the lyes with a mixture of sodium bisulphite and copper 
 sulphate. 
 
 Properties and Uses. Iodine (1=127; S P- gr- = 4'94) is a black-grey coloured 
 crystalline substance, with a metallic appearance not unlike graphite. On being 
 heated iodine is converted into vapours which, according to Stas, when concentrated 
 exhibit a blue colour, and a violet in a more dilute state. Iodine fuses at 115, 
 and boils above 200. It is somewhat soluble in water, readily so in alcohol, ether, 
 hydriodic acid, potassium iodide solution, carbon disulphide, chloroform, benzol, 
 aqueous solution of sulphurous acid, and solution of sodium thiosulphate. A solution 
 of iodine imparts a violet colour to starch. Adulteration of iodine with either pul- 
 verised charcoal or graphite may be at once detected by treating a sample with alcohol 
 or a solution of sodium thiosulphate, in each of which the iodine, if pure, ought to 
 dissolve completely, leaving no residue on sublimation. Sometimes the weight of 
 iodine is fraudulently increased by the addition of water. Iodine is largely used in 
 photography in the form of potassium iodide; for the preparation of other iodine 
 compounds, for instance, mercury iodide ; also in the preparation of some of the tar 
 colours, iodine violet, iodine green, and cyanine blue, the latter a compound of iodine 
 and lepidin, a volatile base. The total production of iodine in Europe and Chili 
 amounted in 1869 to 3453 cwts., more than half, or 1829 cwts., being produced in 
 Scotland and Ireland. At the present day the production of iodine at the South 
 American nitre works is estimated at 300 tons yearly. Scotland and Ireland now 
 produce 130 tons, and France 50 tons. 
 
 Iodine is also used in the production of eosine, blue shade (tetraiodofluoresceine). 
 According to the analysis of Wanklyn (1872) the iodine of commerce contains 
 
 Good. Inferior. 
 
 Iodine . . . 88'6i ... 76-21 
 
 Chlorine . . . 0-52 ... o - 88 
 
 Ash .... 072 ... I'll 
 
 Water .... 10-15 * 21-80 
 
 lOO'OO lOO'OO 
 
 NITRIC ACID AND NITRATES. 
 
 Soda Saltpetre. This salt, NaNO 3 , known as cubic nitre, Chilian and Peruvian 
 saltpetre, is found in the middle regions of the rainless district of the west coast (costa 
 seca) of South America, most abundantly between 19 and 24 S. Lat. The chief 
 localities are in the southern extremity of Peru, in the province Tarapaca, on the 
 barren coasts of Bolivia, and the desert of Atacama. It is found in beds (caliche or tierra 
 salitrosa) of to i| metre in thickness, extending for more than 240 kilometres to the 
 neighbourhood of Copiapo in the north of Chili. The beds are covered with clay, and 
 consist almost entirely of clean, dry, hard salt, and have apparently been formed from 
 sea-weed. 
 
 The superjacent rock (lostra) is from J to 2 metres thick, and consists chiefly of 
 a hard conglomerate of sand, felspar, porphyry, and other minerals. The composition 
 
37 2 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 of the caliche varies. It contains from 48 to 75 per cent, sodium nitrate, 20 to 40 per 
 cent, sodium chloride, and undetermined quantities of sodium sulphate, calcium sul- 
 phate, potassium nitrate and iodate, magnesium chloride, as well as insoluble matter, 
 and organic substances including guano. It is broken up in a disintegrator, and 
 placed in dissolving pans. Some of the works operate in open, quadrangular cisterns ; 
 those better arranged use closed, egg-shaped pans, provided with two movable covers, 
 the one for introducing the caliche and the other for taking out the spent mineral. 
 The mass rests upon a perforated false bottom at about one-quarter the height of the 
 pan, and which consists of four pieces movable on hinges. The pans are filled up to the top 
 with comminuted caliche, mother- liquor is run in to half height, and heat is applied by 
 means of steam. In i^ to 2 J hours the lye is sufficiently saturated with nitre, and is run 
 off into settling vats. After standing for some hours, the clear lye is let flow into flat 
 crystallisers. The residue in the pan is removed. The crystals formed, after the 
 mother-liquor has drained off, are spread out in layers of 0-3 to 0*5 metres in thick- 
 ness upon a large floor (Cencha) exposed to currents of air, and dried by frequent 
 turning. 
 
 /Sodium Nitrate. This salt, also known as cubical saltpetre, Chili- saltpetre, nitrate 
 of soda, NaN0 3 , containing in 100 parts 36*47 soda, and 63*53 P ar> ts nitric acid, is 
 found native in the district of Atacama and Tarapaca, near the port of Iquique, in Peru. 
 The deposit chiefly consists of the pure, dry, hard salt, and is close to the surface of the 
 soil. It is also found in other parts of Peru mixed with sand, in some places close to 
 the surface of the soil, in others at a depth of 2'6 metres. Valparaiso being the great 
 exportation depot for Peru, Bolivia, and Chili, both surface and deep soil salts are 
 met with in the trade of that important port. The unrefined Chili saltpetre is crys- 
 talline, brown or yellow, and somewhat moist; but the salt sent to the European 
 markets is commonly semi-refined by being dissolved in water and evaporated to dry- 
 ness. The composition of a sample in 100 parts is : 
 
 Sodium nitrate 94*03 
 
 Sodium nitrite o - 3i 
 
 Sodium chloride . . 1-52 
 
 Potassium chloride 0*64 
 
 Sodium sulphate 0*92 
 
 Sodium iodide 0^29 
 
 Magnesium chloride 0^93 
 
 Boric acid traces 
 
 Water 1-96 
 
 lOO'OO 
 
 Being deliquescent the salt is not employed in the manufacture of gunpowder, but 
 may be used for blasting powder. It is largely used for the preparation of sulphuric 
 and nitric acids ; for purifying caustic soda ; for making chlorine in the manufacture 
 of bleaching powders ; for the preparation of sodium arseniate ; in the curing of meat ; 
 in glass-making in the preparation of red lead ; in large quantities in the conversion of 
 crude pig-iron into steel, by Hargreave's and by Heaton's processes ; for preparing 
 potassium nitrate ; and for the preparation of artificial manures and composts, it being 
 also used unmixed as a manure for grain crops. 
 
 It may be seen from the analysis of nitrate of soda quoted above that that salt 
 contains a small quantity of iodine, which at Tarapaca is extracted from the mother- 
 liquor remaining from the re-crystallisation. According to M. L. Krafft the iodine 
 amounts to 0-59 gramme in i kilo, of crude nitrate ; 40 kilos, of iodine being prepared 
 per day. M. Nollner thinks that the formation of the nitre deposits in Chili and 
 other parts of South America has taken place under the influence of marine plants 
 containing iodine. In order to give some idea of the large and increasing exportation 
 
SECT, in.] NITRIC ACID AND NITRATES. 373 
 
 of Chili saltpetre, we quote from the published statistics, that in 1830, 18,700 cwts., 
 and in 1869, 2,965,000 cwts., were shipped.* 
 
 Potassium Saltpetre. (KN0 3 = 101-2. In 100 parts, 46-5 parts potassa, and 53-5 
 parts nitric acid.) This salt is to some extent a native as well as a chemical product. 
 The well-known flocculent substance often observable on walls, especially those of 
 stables, is composed in a great measure of nitrates ; a similar phenomenon is seen in 
 subterranean excavations, and even in many localities the surface of the soil is covered 
 with an efflorescent saline deposit, consisting largely of potassium nitrate. These 
 deposits are most common in Spain, Hungary, Egypt, Hindostan, on the banks of the 
 Ganges, in Ceylon, and in some parts of South America, as at Tacunga in the State of 
 Ecuador ; while in Chili and Peru nitrate of soda, so-called Chili saltpetre, is found 
 in very large quantities under a layer of clay as above-mentioned. 
 
 Occurrence of Native Saltpetre. Although native saltpetre is met with under a 
 variety of conditions, they all agree in this particular, that the salt is formed under the 
 influence of organic matter. As already stated, the salt covers the soil, forming an 
 efflorescence, which increases in abundance, and which if removed has its place supplied 
 in a short time. In this manner saltpetre, or nitre as it is sometimes called, is obtained 
 from the slimy mud deposited by the inundations of the Ganges,! and in Spain from the 
 lixiviation of the soil, which can be afterwards devoted to the raising of corn, or arranged 
 in saltpetre beds for the regular production of the salt. The chief and main condition 
 of the formation of saltpetre, which succeeds equally in open fields exposed to strong 
 sunlight, under the shade of trees in forests, or in caverns, is the presence of organic 
 matter viz., humus inducing the nitre formation by its slow combustion ; the col- 
 lateral conditions are dry air, little or no rain, and the presence in the soil of a 
 weathered crystalline rock containing felspar, the potassa of which favours the forma- 
 tion of the nitrate of that base. All the known localities where the formation of nitre 
 takes place naturally, including the soil of Tacunga, formed by the weathering of 
 trachyte and tufstone, are provided with felspar. The nitric acid is due to the slow 
 combustion of nitrogenous organic matter present in the humus, it having been proved 
 that the nitric acid constantly formed in the air in enormously large quantities by the 
 action of electricity and ozone, as evidenced by the investigations of MM. Boussingault, 
 Millon, Zabelin, Schonbein, Froehde, Bottger, and Meissner, has nothing what- 
 ever to do with the formation of nitre in the soil ; a fact also supported by Dr. 
 Goppelsroder's discovery of the presence of a small quantity of nitrous acid in native 
 saltpetres. 
 
 Mode of Obtaining Saltpetre. The mode of obtaining saltpetre in the countries 
 where it is naturally formed is very simple, consisting in a process of lixiviation with 
 water, to which frequently some potash is added for the purpose of decomposing the 
 nitrate of lime occurring among the salts of the soil, the solution being evaporated to 
 crystallisation. Soils yielding saltpetre are termed Gay earth or Gay saltpetre. The 
 process by which nitrate of potassa is naturally formed is imitated in the artificial 
 heaps known as saltpetre plantations, formerly far more general than at the present 
 time, it having been found that the importation of Indian saltpetre, and the manu- 
 facture of potassium nitrate by conversion from sodium nitrate, are cheaper sources. 
 Thus, saltpetre beds are to be met with only under peculiar conditions, as, for instance, 
 in Sweden, where all landed proprietors are required to pay a portion of their taxes in 
 saltpetre. 
 
 The mode of making these plantations may be briefly described as follows: 
 Materials containing much carbonate of lime for instance, marl, old building rubbish, 
 
 * The exports from Chili to Europe were, in 1882, 410,000 tons, and in 1883, 530,000 tons, 
 f The mud of the Ganges contains, after exposure, 8-3 per cent, of potassium nitrate and 3 per 
 cent, calcium nitrate. The yearly export of saltpetre from India is 25,000 tons. 
 
374 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 ashes, road scrapings, stable refuse, or mud from canals is mixed with nitrogenous 
 animal matter, all kinds of refuse, and frequently with such vegetable substances as 
 naturally contain nitrate of potassa, such as the leaves and stems of the potato, the 
 leaves of the beet, sunflower plants, nettles, &c. These materials are arranged in heaps 
 of a pyramidal shape to a height of 2 to 2 J metres, care being taken to make the bottom 
 impervious to water by a well puddled layer of clay, the heap being in all directions 
 exposed to the action of the atmosphere, the circulation of which is promoted through 
 the heap by layers of straw. The heap is protected from rain by a roof, and at least 
 once a week watered with lant (stale urine). The formation of saltpetre of course 
 requires a considerable length of time, but when, taught by experience, the workmen 
 suppose a heap ripe, the watering is discontinued, the salt containing saltpetre soon 
 after efflorescing over the surface of the heap to 6 to 10 centimetres in thickness ; this 
 layer is scraped off, and the operation repeated from time to time until the heap 
 becomes decayed and has to be entirely removed. In Switzerland saltpetre is artifi- 
 cially made by many of the farmers, simply by causing the urine of the cattle, while in 
 stable in the winter time, to be absorbed by a calcareous soil purposely placed under 
 the loose flooring of the stables, which are chiefly built on the slope of the mountains, 
 so that only the door is level with the earth outside, the rest of the building hanging 
 over the slope, and being supported by stout wooden poles ; thus a space is obtained, 
 which, freely admitting air, is filled with marl or other suitable material. After two 
 or three years this material is removed, lixiviated with water, mixed with caustic lime 
 and wood ash, and boiled down. The liquor having been sufficiently evaporated, is 
 decanted from the sediment and left for crystallisation ; the quantity of saltpetre vary- 
 ing from 50 to 200 Ibs. for each stable.* 
 
 Treatment of the Ripe Saltpetre Earth. The crude salt from the heaps is converted 
 into potassium nitrate by the following processes: a. The earth is lixiviated with 
 water, this operation being known as the preparation of raw lye. b. The raw lye is 
 broken, that is to say, it is mixed with a solution of a potash salt in order to convert 
 the magnesium and calcium nitrates present into potassium nitrate. c. Evapora- 
 tion of this liquor to obtain crude crystallised saltpetre, d. Refining the crude salt- 
 petre. 
 
 Preparation of Raw Lye. The ripe earth is lixiviated to obtain all the valuable 
 soluble matter, it being expedient to use as little water as possible in order to save fuel 
 in the subsequent evaporation, for which the liquor is ready when it contains from 12 
 to 13 per cent, of soluble salts. 
 
 Breaking ^vp the Raw Lye. The raw lye, sometimes known as soil water, contains 
 the nitrates of lime, magnesia, potassa, soda, the chlorides of calcium, magnesium, and 
 potassium ; also ammoniacal salts and organic matter of vegetable as well as of animal 
 origin. In order to convert the magnesium and calcium nitrates into potassium nitrate, 
 the raw lye is broken up as it is termed, that is to say, there is added to it a solution 
 of i part potassium carbonate in 2 parts water 
 
 Calcium nitrate, Ca(N"0 3 ) 8 
 Magnesium nitrate, Mg(N0 3 ) 
 Potassium carbonate, 2K 2 CO, 
 
 [Potassium nitrate, 4.KN0 3 . 
 yield \ Calcium carbonate, CaCO 3 . 
 
 (Magnesium carbonate, MgCO 3 . 
 
 The calcium and magnesium chlorides are also decomposed, being converted into 
 carbonates, while potassium chloride is formed. The addition of the solution of 
 potassa to the raw lye is continued as long as a precipitate is formed ; in order, how- 
 ever, to have some approximative idea of the quantity of potassium carbonate which may 
 be required a test experiment is made with litre of the raw lye. 
 
 Sometimes potassium sulphate is used instead of the carbonate, but in that case the 
 magnesia salts of the raw lye have first to be decomposed by milk of lime, an operation 
 * In London 100 tons of saltpetre were obtained in a similar manner in 1873. 
 
SECT, in.] NITKIC ACID AND NITRATES. 375 
 
 which has to be followed by the evaporation of the fluid. If, after this, potassium 
 sulphate is added, calcium sulphate is precipitated 
 
 [Ca(N0 3 ) 2 + K 2 S0 4 - 2 KN0 3 + CaSOj. 
 
 When potassium chloride is used for the decomposition of raw lye, the salts of magnesia 
 are first removed by the addition of milk of lime ; and the clear supernatant fluid 
 having been decanted from the sediment, there is added a mixture of equal molecules 
 of potassium chloride and sodium sulphate, the result being the formation of gypsum, 
 while the sodium nitrate generated exchanges with the potassium chloride, carrying 
 over to the latter the nitric acid, and taking up the chlorine to form common salt. 
 
 Boiling down the Raw Lye. The clarified raw lye decanted from the precipitate 
 of the earthy carbonates consists of a solution in which there are present the potassium 
 and sodium chlorides, potassium nitrate, ammonium carbonate, excess of potassium 
 carbonate, and colouring matter. The boiling 
 
 down of this liquid is effected in copper cauldrons, Fl - 337- 
 
 Fig. 337, so set in the furnace as to admit of the 
 circulation of the hot air and smoke from the fire- 
 place, passing by c c below the heating pan, and 
 thence by g into the chimney. In some works 
 this waste heat is utilised in drying the saltpetre 
 flour. As the bulk of the fluid in the cauldron 
 decreases by evaporation, fresh lye enters by 
 means of a pipe and tap from the pan, D. About 
 the third day the alkaline chlorides begin to be 
 deposited, and the workmen have then to take 
 great care to prevent these salts from becoming 
 
 what is technically termed burnt, which might give rise to serious explosions, and for 
 this purpose the liquid is stirred with stout wooden poles. After each stirring the 
 loose saline matter is removed from the boiling liquid by means of perforated copper 
 ladles. However, as a hard deposit is always formed, a peculiar arrangement exhibited 
 in Fig. 337, consisting of a shallow vessel, m, suspended by a chain, h, and weighted 
 with a piece of stone, is lowered into the middle of the cauldron to about 6 centi- 
 metres from the bottom, the object being to catch the solid particles, which would, 
 when aggregating, form an incrustation, previously to their reaching the bottom of 
 the vessel ; and as no ebullition takes place at m, the particles once deposited remain 
 there, and can be readily removed by raising the dish out of the cauldron, and empty- 
 ing it into a box placed over the cauldron, the bottom of the box being perforated to 
 admit of any liquor which may have been raised with the solid salt to return again to 
 the cauldron. The deposit thus removed consists chiefly of gypsum and carbonate 0? 
 lime. 
 
 When a portion of the impurities contained in the boiling liquid have been removed, 
 the raw lye still frequently contains some sodium chloride, as this salt is not, as is 
 the case with nitre, more soluble in boiling than in cold water. The abundant crystal- 
 lisation of the saltpetre is a sign that the lye has been sufficiently evaporated ; in 
 order, however, to prove this, a small sample is taken, and if on cooling the nitre 
 crystallises so that the greater part of the sample becomes a solid mass, the liquid is 
 run into tanks and left for 5 or 6 hours, during which time impurities are deposited, 
 and the liquid rendered quite clear. As soon as the temperature of the liquid has 
 fallen to 60, it is poured into copper crystallisation vessels ; after a lapse of 24 hours 
 the crystallisation is complete, and the mother-liquor being separated from the salt is 
 employed in a subsequent operation. 
 
 Refining the Crude Saltpetre. The crude saltpetre is yellow-coloured, and contains 
 on an average some 20 per cent, of impurities, consisting of deliquescent chlorides, 
 
376 CHEMICAL TECHNOLOGY. [SECT. HI. 
 
 earthy salts, and water. The object to be attained by the refining is the removal of 
 these substances. At the present day a large portion of the refined saltpetre met with 
 in commerce is obtained by the refining of the crude saltpetre imported from India. 
 It may be noted that this importation is steadily increasing, there being, in 1860, 
 16,460,300 kilos., and in 1868, 33,062,000 kilos, of the salt brought to England; and, 
 indeed, the production of saltpetre from natural sources in Europe is now limited to 
 very few and unimportant localities. 
 
 The method of refining saltpetre is based upon the fact that potassium nitrate 
 is far more soluble in hot water than are the sodium and potassium chlorides. 600 
 litres of water are poured into a large cauldron, and 24 cwts. of the crude saltpetre are 
 added at a gradually increasing temperature ; as soon as the solution boils, 36 cwts. 
 more crude saltpetre are added. Supposing the crude nitre to contain 20 per cent, of 
 alkaline chlorides, the whole of the nitre will be dissolved in this quantity of water, 
 while a portion of the chlorides will remain undissolved even at the boiling-point. 
 The non- dissolved salt is removed by a perforated ladle, and the scum rising to the 
 surface of the boiling liquid by the aid of a flat strainer. The organic matter present 
 in the solution is removed by the aid of a solution of glue from 20 to 50 grammes of 
 glue dissolved in 2 litres of water are taken for each hundredweight of saltpetre. In 
 order that the saltpetre may crystallise, the quantity of water is increased to 1000 
 litres, and as soon as this water is added the organic matter entangled in the glue rises 
 as a scum to the surface and is removed. The operation having progressed so far, and 
 the liquid being rendered quite clear, it is kept at a temperature of 88 for about twelve 
 hours, and then carefully ladled into copper crystallising vessels, constructed with 
 the bottom a little higher at one end than at the other. The solution would yield on 
 cooling large crystals of saltpetre, but this is purposely prevented by keeping the liquid 
 in motion by means of stirrers, so as to produce the so-called flour of saltpetre, which 
 is really the salt in a finely divided state. This is next transferred to wooden boxes, 
 termed wash- vessels, 10 feet long by 4 feet wide, provided with a double bottom, the 
 inner one being perforated ; between the two bottoms holes are bored through the 
 sides of the vessel, and when not required plugged with wooden pegs. Over the flour 
 of saltpetre contained in these wooden troughs, 60 Ibs. of a very concentrated solution 
 of pure potassium nitrate are poured, and allowed to remain for two to three hours, 
 the plugs being left in the holes. The plugs are then removed, the liquor run off, the 
 holes again plugged, and the operation twice repeated, first with a fresh 60 Ibs., and 
 next with 24 Ibs. of the solution of potassium nitrate, followed in each case by an equal 
 quantity of cold water. The liquors which are run off in these operations are of course 
 collected, the first being added to the crude saltpetre solution, while the latter, being 
 solutions of nearly pure nitre, are again employed. The saltpetre is next dried at a 
 gentle heat in a shallow vessel, sifted, and packed in casks. 
 
 Preparation of Potassium Nitrate from Chili Saltpetre. During the last twenty 
 years the preparation of potassium nitrate from Chili saltpetre has become an im- 
 portant branch of manufacturing industry. The product obtained by any of the 
 following processes is called " converted saltpetre," to distinguish it from the preceding 
 preparation. The method of procedure may be one of the following : 
 
 I. The sodium nitrate is decomposed by means of potassium chloride 
 roo kilos, of sodium nitrate "I . JIIQ'I kilos, potassium nitrate. 
 8 7 - 9 kilos, of potassium chloride / ^ \ 68*8 kilos, common salt. 
 
 MM. Longchamp, Anthon, and Kuhlmann first suggested this mode of preparation, 
 which is now generally used on the large scale, as the decomposition of both salts is 
 very complete, and as the common salt as well as the saltpetre can be utilised. The 
 potassium chloride is obtained by the decomposition of carnallite, or by means already 
 mentioned. 
 
SECT, in.] NITKIC ACID AND NITRATES. 377 
 
 Equivalent quantities of sodium nitrate and of chloride of potassium are dissolved 
 in water contained in a cauldron of some 4000 litres cubic capacity. As the nitrate of 
 soda of commerce (Chili saltpetre) does not, as regards purity, vary very much from 
 96 per cent., some 7 cwts. are usually taken, while of the chloride of potassium, which 
 varies in purity from 60 to 90 per cent., a quantity is taken corresponding, as regards 
 the amount of pure chloride, to the quantity of sodium nitrate. The chloride of potas- 
 sium is first dissolved, the hot solution being brought to a sp. gr. = 1*2 to 1*21 next 
 the sodium nitrate is added, and the liquid brought, while constantly heated, to a 
 sp. gr. = i'5- The sodium chloride continuously deposited is removed by perforated 
 ladles, and placed on a sloping plank so that the mother-liquor may flow back into the 
 cauldron, care being taken to wash this salt afterwards, so as to remove all potassium 
 nitrate, the washings being poured back into the cauldron. When the liquid in the 
 cauldron has been brought to 1*5 sp. gr. an aqueous solution of potassium nitrate at 
 15, with a sp. gr. = 1*144, contains 21*074 per cent, of that salt the fire is ex- 
 tinguished, the liquid left to clear, the common salt still present carrying down 
 all impurities, and when clear it is ladled into very shallow crystallising vessels, 
 where the crystallisation is finished in twenty-four hours. The mother-liquor having 
 been run off, the crystals are thoroughly drained and covered with water, which 
 is left in contact with the salt for some seven to eight hours, and then run off; this 
 operation is repeated during the next day ; the mother-liquor and washings are poured 
 back into the cauldron at a subsequent operation. 
 
 2. Sodium nitrate is first converted into sodium chloride by means of barium 
 chloride, barium nitrate being formed, and in its turn converted into potassium 
 nitrate by the aid of potassium sulphate : 
 
 a. 85 kilos, of sodium nitrate ) . , , (130*5 kilos, barium nitrate. 
 122 kilos, of barium chloride J 1 5 8' 5 kilos, of common salt. 
 
 /3. 130*5 kilos, of barium nitrate] 87*2 kilos, of potassium sulphate, 
 require for conversion intof or 
 
 potassium nitrate I 69*2 kilos, of potassium carbonate. 
 
 When potassium sulphate is used, permanent-white, baryta-white, or barium sul- 
 phate is obtained as a by-product, while if potassium carbonate is used, barium car- 
 bonate remains, and of course may be readily re-converted into barium chloride. 
 In order to estimate the advantages of either process, the following points must be 
 kept in view : a. Taking into consideration that it is profitable to convert native 
 barium carbonate into barium chloride for instance, by exposing witherite to the 
 hydrochloric acid fumes produced in alkali works by the decomposition of salt and to 
 precipitate an aqueous solution with dilute sulphuric acid to obtain permanent-white, 
 it may be inferred that it will also pay to obtain it as a by-product. 6. Notwith- 
 standing the complication of this process, it is advantageous as producing a far purer 
 potassium nitrate. 
 
 3. Sodium nitrate is converted by means of potash into the nitrate of that base, 
 pure soda being obtained as a by-product : 
 
 85 kilos. Chili saltpetre 1 . , , f 101*2 kilos, of potassium nitrate. 
 
 69*2 kilos, potassium carbonate/ \53 kilos, of soda (calcined). 
 
 This mode of manufacturing saltpetre was first introduced into Germany 
 during the Crimean War (1854-55) by M. Wollner, of Cologne, who established 
 large works to prepare saltpetre in this way, and very soon after, during the con- 
 tinuance of the war, five other manufactories of potash saltpetre had been established 
 on this method. In 1862 the production amounted to 7,500,000 Ibs. of potash salt- 
 petre, the potassium carbonate required being obtained from beet-root molasses, the 
 soda resulting as a by-product being even superior to that produced by Leblanc's 
 process. 
 
37 8 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 According to M. Lunge's description, this process, first suggested by MM. Land- 
 mann and Gentele, afterwards modified by M. Schnitzer, and practically applied by 
 M. Nollner, is carried on in Lancashire in the following manner : There is added 
 to a caustic potash lye of 1-5 sp. gr., containing about 50 per cent, of dry caustic 
 potassa, an equivalent quantity of sodium nitrate, and the whole, after a short time, 
 is crystallised. The potassium nitrate having been separated from the mother-liquor, 
 that fluid, the density of which has been greatly decreased by the reaction, is by evapo- 
 ration again brought to its former density, and yields on cooling another crop of 
 crystals of potash-saltpetre. Usually there then only remains a solution containing 
 caustic soda with saline impurities ; sometimes, however, a third crop of crystals is 
 obtained. The deposit during the evaporation is chiefly sodium carbonate derived 
 from the sodium chloride contained in the potassium chloride from which the caustic 
 potassa is made, this chloride being also converted into carbonate. The small quantities 
 of undecomposed potassium and sodium chlorides and calcium sulphate are retained 
 in the mother-liquor, which is evaporated to dryness and ignited, yielding a dry caustic 
 soda of a bluish-colour. The crystallised potassium nitrate is noAv carefully refined to 
 remove all impurities to about 0*1 per cent, of sodium chloride, converted into 
 saltpetre-flour, and treated as already described. Notwithstanding that the various 
 operations have been carried on in iron vessels, the salt does not contain any of this 
 metal, nor is the colour in any way affected . The flour is dried in a room 2 metres 
 wide by 5 metres in length, built of brick- work, similarly to the chloride of lime rooms, 
 and having a pointed arched roof 2 metres in height. The saltpetre-flour is spread on 
 a wooden floor, under which extends a series of hot-air pipes, keeping the temperature 
 at 70, and very rapidly effecting the drying. 
 
 Testing the Saltpetre. If, when perfectly pure, saltpetre is carefully fused and 
 allowed to cool, it becomes a white mass, exhibiting a coarsely radiated fracture ; even 
 so small a quantity as ^th of sodium chloride causes the fracture to appear some- 
 what granular ; with T Vth the centre is not at all radiated, and is less transparent ; 
 and with -^th the radiation is only slightly perceptible at the edges of the fracture. 
 Sodium nitrate has the same effect. This method of testing the purity of nitre, due to 
 M. Schwartz, is employed in Sweden, where every landowner pays a portion of his 
 taxes in saltpetre of a specified degree of purity. A great number of methods of 
 testing saltpetre have been suggested by various authors for the purposes of the manu- 
 facture of gunpowder, not, however, in sufficiently general use to interest the reader. 
 Werther's test for chlorine and sulphuric acid is by solutions of the barium and silver 
 nitrates ; the silver solution is such that each division of the burette corresponds to 
 0*004 grammes of chlorine, and the baryta solution to 0*002 gramme of sulphuric 
 acid. According to Reich's plan, 0-5 gramme of dried and pulverised saltpetre is 
 ignited to a dull red heat, with from 4 to 6 times its weight of pulverised quartz ; the 
 nitric acid is expelled, the loss of weight consequently indicating the quantity, the 
 sulphates and chlorides not being decomposed at a dull red heat. If the loss = d, we 
 have 1*874 d potassium nitrate, or 1*574 d sodium nitrate. 
 
 Another method, due to Dr. A. Wagner, is based upon the fact that when salt- 
 petre, or any other nitrate, is ignited, access of air being excluded, with an excess 
 of chromic oxide and sodium carbonate, the nitric acid oxidises the chromic oxide 
 according to the formula Cr 2 3 + NO. = 2Cr0 3 + N0 2 . 76*4 parts, by weight, of 
 chromic oxide are oxidised to chromic acid by 54 parts of nitric acid, or i of 
 chromic oxide by 07068 of nitric acid. The operation is performed by taking from 0.3 
 to 0*4 gramme of the nitrate, mixing it intimately with 3 grammes of chromic oxide 
 and i gramme of sodium carbonate, introducing this mixture into a hard German glass 
 combustion-tube, one end of which is drawn out, and a vulcanised india-rubber tube 
 attached to it, which is made to dip for about a quarter of an inch into water, while to 
 
SECT. III.] 
 
 NITRIC ACID. 
 
 379 
 
 the other open end, by means of a cork and glass tube bent at right angles, an ap- 
 paratus is fitted for the evolution of carbonic acid gas, which is made to pass through 
 the tube before igniting it, and kept passing through all the time until the tube is 
 quite cool again after ignition. The contents of the tube are placed in warm water, 
 and after filtration the chromic acid is estimated by Rose's method. This process of 
 estimating nitric acid has been found to yield very accurate results. 
 
 Uses of Saltpetre. This salt is employed for many purposes, the most important 
 being (i) The manufacture of gunpowder. (2) The manufacture of sulphuric and 
 nitric acids. (3) Glass-making, to refine the metal as it is termed. (4) As oxidant 
 and flux in many metallurgical operations. By the ignition of i part of nitre and 2 of 
 argol, in some cases refined argol (cream of tartar), black flux is formed consisting of 
 an intimate mixture of potassium carbonate and finely divided charcoal. The ignition 
 of equal parts of saltpetre and cream of tartar gives white flux, consisting of a mixture 
 of potassium carbonate and undecomposed saltpetre; both these mixtures are often 
 used. Black flux may also be made by intimately mixing potassium carbonate with 
 lamp-black and white flux. (5) When mixed with common salt and sugar in the 
 salting and curing of meat. (6) For preparing fluxing and detonating powders. 
 Baume's fluxing powder is a mixture bf 3 parts of nitre, i of pulverised sulphur, and 
 i of sawdust from resinous wood; if some of this mixture be placed with a small 
 copper or silver coin in a nutshell and ignited, the coin is melted in consequence of 
 the formation of a readily fusible metallic sulphide, while the nutshell is not injured. 
 Detonating powder is a mixture of 3 parts saltpetre, 2 potassium carbonate, and i pul- 
 verised sulphur ; this powder when placed on a piece of sheet-iron, and heated over a 
 lamp, will explode with a loud report, yielding a large volume of gas : 
 
 Saltpetre, 6KN0 3 , \ 
 
 Potassium carbonate, 2K 2 C0 3 , [ 
 Sulphur, 58. J 
 
 Nitrogen, 6N. 
 Carbonic acid, 2C0 2 . 
 Potassium sulphate, 5K 2 S0 4 . 
 
 (7) For manure in agriculture, 
 the preparation of Heaton steel. 
 
 (8) In many pharmaceutical preparations. (9) For 
 
 NITEIC ACID. 
 
 Methods of Manufacturing Nitric Acid. This acid (NH0 3 ) is generally manufac- 
 tured by decomposing nitrate of soda by sulphuric acid, and condensing the vapours set 
 free. It is obtained on the large scale by placing in a cast-iron vessel, A, Fig. 338, the 
 nitrate to be operated upon, to which is added by means of a funnel strong sulphuric 
 
 Fig- 338- 
 
 acid. The lid is replaced, and the vessel connected by means of the clay-lined tube, B, 
 with the glass tube, C, dipping into the large stoneware flask, D, which serves the purpose 
 
380 CHEMICAL TECHNOLOGY. [SECT. HI. 
 
 of a receiver. This flask is connected by means of a tube, a, to a similar vessel, ZX, 
 and that to a third vessel, J)", and so on, in order to completely condense the vapours 
 which might have escaped through the first, second, and third vessels. The iron 
 vessel, A, is heated by means of the fire placed in the hearth, F, the smoke and hot 
 gases being carried off by G H. At the outset of the operation the damper, d, is so 
 regulated as to shut off the lower channel, and cause the smoke and hot gases to pass 
 through E, heating the vessels Z>, D' ', and D", this precaution being required to prevent 
 their cracking by the hot acid vapours entering from A. As soon, however, as the 
 distillation has fairly commenced, the damper is altered to shut off E, and pass the hot 
 air and gases through G. The nitric acid condensed in the first receiver is sufficiently 
 strong for immediate use, but to facilitate the condensation some water has been 
 poured through the openings, b r b", into the other receivers, the acid from which is 
 weaker and known in the trade as aquafortis. 
 
 Very frequently the distillation of nitric acid is conducted in a series of glass retorts 
 placed on a sand-bath ; there are generally two rows of retorts, the heating apparatus 
 being a galley oven. If the acid is to be pure, the first condensations are collected in 
 separate receivers, as the acid first condensed contains hydrochloric acid due to the 
 chlorides contained in the nitrates under operation. 
 
 The proportion of materials employed is 
 
 30 kilos, of potassium nitrate to 29 kilos, of strong sulphuric acid ; or, 
 17 sodium nitrate to 14/5 
 
 The sodium bisulphate which remains may either be used for the preparation of 
 fuming sulphuric acid, or may be mixed with common salt, and ignited, to produce 
 hydrochloric acid and neutral sodium sulphate, available in the preparation of sodium 
 carbonate. 
 
 The nitric acid (NHO g ) resulting from the above operation is a colourless, trans- 
 parent fluid, having a sp. gr. of 1*55, and boiling at 80. When diluted with water 
 the boiling-point is higher. An acid containing 100 parts (NHO 3 ) and 50 parts of 
 water boils at 129, but if the dilution with water is carried further the boiling-point 
 is again lowered ; consequently when such an acid is heated above 100 the result is 
 that at first water with only a trace of acid distils over, and if the process be continued 
 the boiling-point gradually increases until it reaches 130, when there distils over what 
 is termed double aquafortis, sp. gr. = i'35 to 1*45, ordinary or single aquafortis 
 having a sp. gr. = rig to 1*25. Nitric acid, when in contact with air, emits fumes, 
 owing to the absorption of water from the atmosphere. 
 
 Bleaching Nitric Acid. The stronger acid manufactured as described is usually 
 of a yellow colour, due to the presence of hyponitric acid. If a colourless acid is 
 desired, the crude acid must be submitted to a bleaching operation, conducted as 
 follows: The coloured acid is poured into large glass vessels placed in a water- 
 bath, heated to 80 to 90, and left in these vessels as long as any coloured vapours are 
 given off. The escaping hyponitric acid is carried by means of glass or glazed earthen- 
 ware tubes either into a sulphuric acid chamber and there utilised, or into the flue of a 
 chimney, and thus into the air. Any hydrochloric acid present in the nitric acid is 
 also carried off as chlorine. In order to remove any sulphuric acid it is necessary to 
 distil the nitric acid over pure barium nitrate, while the last traces of hydrochloric 
 acid can be removed by distillation over pure silver nitrate. 
 
 Condensation of the Nitric Acid. More recently improvements have been made in 
 the manufacture of nitric acid, bearing especially upon the possibility of omitting the 
 bleaching process, and a better mode of condensing the vapours of the acid. The first 
 point is supplied by an arrangement introduced in the manufactory of M. Cheve, in 
 Paris. Every practical chemist knows that the red vapours appear only at the outset 
 and towards the end of the distillation of the nitric acid, and it is therefore only 
 
SECT, in.] NITRIC ACID. 381 
 
 required to distil fractionally to obtain on the one hand a red-coloured acid, the acidum 
 nitroso-nitricum or acidum nitrictim fumans fortissime of the pharmaceutists, and on 
 the other a colourless acid, which can be forthwith delivered to the consumer. In 
 order to practically effect the fractional distillation, a tap of porcelain or hard-fired 
 stoneware, constructed as exhibited in Fig. 339, 
 
 is fixed by means of A, in communication with Fig. 339. 
 
 the iron distilling vessel, while the tubes B and 
 ' are connected with two different receivers. 
 The tap is bored in such a manner, that at 
 pleasure either the communication between A 
 and E\ or the communication between A and 
 B, can be established. By proper management, 
 therefore, it is possible to separate the red- 
 coloured acid entirely and without any additional expense, from the colourless 
 acid.* 
 
 For preparing a chemically pure nitric acid it is best to distil the tetra-hydrated 
 acid (sp. gr. i - 42. 84 Tw.) in glass vessels and receive the product which goes 
 over separately as long as it occasions a turbidity with a solution of silver nitrate. 
 The receiver is then changed and the rest of the acid distilled off down to a small 
 residue. At some works a purified nitre is used for obtaining nitric acid free from 
 chlorine. 
 
 Instead of the apparatus figured, horizontal cylinders of cast iron are employed as 
 stills, fixed so that they are uniformly encompassed by the hot gases. The acid going 
 over last should be collected separately as the iron is attacked when the cylinder has 
 cooled down. The two ends of the cylinder are not exposed to the fire and are best 
 closed with plates of sandstone, cemented in with a mixture of iron filings, sal 
 ammoniac, sulphur and vinegar. This cement dries quickly and resists the action of 
 heat and acid. The front plate has in its upper half an opening for introducing the 
 nitre. This opening can be closed by a stone plug, luted in with .clay. In this plug 
 there is a small hole through which the sulphuric acid is introduced. The gases which 
 escape are collected in the usual way by passage through a scrubber. The proportion 
 of sulphuric acid to nitre is not uniform. Some makers use to i mol. nitre if mol. 
 sulphuric acid, in which case the bisulphate formed so reduces the melting-point of the 
 residue of sulphate that it may be run out at the end of the operation. 
 
 The strength of the sulphuric acid depends on that of the nitric acid to be pro- 
 duced. In most cases an acid is taken of 171 8 sp. gr. (= 143 Tw.) The mixture 
 froths then least, so that the retorts or cylinders can be filled up rather high. The 
 mean strength of the nitric acid thus obtained ranges from 1*38 to 1*41 sp. gr. (76 to 
 82 Tw.). For nitric acid at 1-50 to 1-52 sp. gr. dried nitre is employed and sulphuric 
 acid of sp. gr. 1-85 (= 170 Tw.). 
 
 The bisulphate remaining serves either for producing fuming sulphuric acid and 
 anhydride or it is ignited with common salt to yield salt-cake and hydrochloric 
 acid. 
 
 Nitric acid may be produced by the action of manganous chloride upon sodium 
 nitrate. If a mixture of both salts is heated to 230 there are evolved nitrous fumes 
 (N0 2 -f O), and there remains a manganese oxide (Mn 5 8 = 2MnO + 3Mn0 3 ) which may 
 serve for the production of chlorine. 
 
 * Coloured nitric acids are sometimes decolorised by the addition of a small quantity of lead 
 peroxide, which gives off oxygen to the lower nitrogen oxides, and is at the same time converted 
 into lead nitrate, which is almost insoluble in nitric acid. A so-called " single aquafortis " supplied 
 to dyers has to be very carefully purified from sulphuric acid and the lower nitrogen oxides, bat 
 may contain a certain proportion of hydrochloric acid or of ammonium chloride. 
 
382 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 Fig. 340. 
 
 If the mixture of N0 2 and is passed into a condensation apparatus along with 
 water it is converted into nitric acid, the excess of the hyponitric acid being resolved 
 into nitric acid and nitric oxide. If the air in the apparatus is sufficient to convert the 
 
 entire nitric oxide into nitric acid the process is repeated. 
 From numerous experiments in clay retorts, conducted 
 by Kuhlmann, he found on this process 100 parts nitre 
 yielded a mean of 125 to 126 nitric acid at 60 Tw., the 
 yield in the ordinary process being 127-128 per cent. 
 A similar result was obtained with chlorides, especially 
 calcium and magnesium chlorides. The sulphates also, 
 even those which are very permanent and do not in any 
 wise play the part of an acid, effect the decomposition 
 of the alkaline nitrates. 
 
 For obtaining nitric acid by the oxidation and con- 
 densation of the lower oxides of nitrogen, Rohrmann 
 (Fig. 340) uses an earthen condensing columm. The 
 lower part, A, contains a perforated inverted beaker, a. 
 At the foot is the efflux pipe, C, and on the other side 
 the outflow, D, which receives the junction-pipe, E t 
 through which is led nitric oxide gas obtained in any 
 manner. To the pipe, E, is affixed the piece, F, through 
 which there enters a pipe, G, which at its upper end 
 receives the blast, H, for the introduction of steam and 
 
 air. Above the beaker, A, rise the beakers, E, in the form of a column. They have a 
 large aperture, 7, at the bottom, with a thickened margin at the under side. Over 
 the opening, J, is the inverted beaker, S, the side of which is perforated like a sieve. 
 In the earthen pipe-connections placed between the several columns, there is intro- 
 duced a lantern provided with glass discs. The openings for the access of air in the 
 blast can be altered. 
 
 The Densities of Nitric Acid. According to J. Kolb, the connection between the 
 sp. gr. of nitric acid and its per centage of concentrated acid is as follows : 
 
 ioo parts contain 
 
 Density. 
 
 ioo parts contain 
 
 Density. 
 
 NH0 3 . 
 
 NA- 
 
 Ato. 
 
 At i S C. 
 
 NHO 3 . 
 
 N 2 5 - 
 
 Ato. 
 
 At 15 C. 
 
 IOO '00 
 
 8571 
 
 I'S59 
 
 I-530 
 
 50-99 
 
 43-70 
 
 I-34I 
 
 323 
 
 97-00 
 
 83-14 
 
 I-548 
 
 1-520 
 
 45'OQ 
 
 38-57 
 
 300 
 
 284 
 
 94'DO 
 
 80-57 
 
 1-537 
 
 1-509 
 
 40-OO 
 
 34-28 
 
 267 
 
 251 
 
 92-00 
 
 78-85 
 
 1-529 
 
 I-503 
 
 33-86 
 
 29-02 
 
 226 
 
 211 
 
 9I-OO 
 
 78-00 
 
 1-526 
 
 1-499 
 
 30-00 
 
 2571 
 
 2OO 
 
 I8 S 
 
 9O-OO 
 
 77-15 
 
 I-522 
 
 1-495 
 
 2571 
 
 22-04 
 
 171 
 
 157 
 
 85-00 
 
 72-86 
 
 I-503 
 
 1-478 
 
 23-00 
 
 1971 
 
 153 
 
 138 
 
 80 -oo 
 
 68-57 
 
 1-484 
 
 1-460 
 
 20-00 
 
 17-14 
 
 132 
 
 I2O 
 
 75-00 
 
 64-28 
 
 I-465 
 
 1-442 
 
 15-00 
 
 12-85 
 
 099 
 
 089 
 
 69-96 
 
 60 -oo 
 
 1-444 
 
 I-423 
 
 11-41 
 
 977 
 
 1-075 
 
 I-067 
 
 65-07 
 
 5577 
 
 1-420 
 
 1*400 
 
 4-00 
 
 3-42 
 
 I-O26 
 
 I'022 
 
 60'00 
 
 51-43 
 
 1-393 
 
 1-374 
 
 2'OO 
 
 1-71 
 
 I-OI3 
 
 I'OIO 
 
 55-00 
 
 47-I4 
 
 1-365 
 
 1-346 
 
 
 
 
 
 The following table exhibits comparative data of density and degrees according to 
 
SECT. III.] 
 
 NITRIC ACID. 
 
 383 
 
 Degrees according 
 to Beaum^. 
 
 Density. 
 
 100 parts contain at o 
 
 ioo parts contain at 15 C. 
 
 NH0 3 . 
 
 N 2 5 . 
 
 NH0 3 . 
 
 N 2 5 - 
 
 6 
 
 044 
 
 67 
 
 57 
 
 7-6 
 
 6-5 
 
 7 
 
 052 
 
 8-0 
 
 6-9 
 
 9'0 
 
 77 
 
 9 
 
 067 
 
 IO'2 
 
 87 
 
 II'4 
 
 9'8 
 
 10 
 
 075 
 
 II'4 
 
 9-8 
 
 127 
 
 io'9 
 
 15 
 
 116 
 
 17-6 
 
 iS'i 
 
 19-4 
 
 16-6 
 
 20 
 
 161 
 
 24 '2 
 
 207 
 
 26-3 
 
 22'5 
 
 25 
 
 2IO 
 
 3i '4 
 
 26-9 
 
 33-8 
 
 28-9 
 
 30 
 
 26l 
 
 39-1 
 
 33 '5 
 
 4i-5 
 
 35-6 
 
 35 
 
 321 
 
 48-0 
 
 41-1 
 
 507 
 
 43'5 
 
 40 
 
 384 
 
 58-4 
 
 50*0 
 
 617 
 
 52-9 
 
 45 
 
 "454 
 
 72-2 
 
 61-9 
 
 78-4 
 
 72 '2 
 
 46 
 
 470 
 
 76-1 
 
 65-2 
 
 83-0 
 
 7I-I 
 
 47 
 
 485 
 
 80-2 
 
 687 
 
 87-1 - 
 
 747 
 
 47 B. correspond to 96 Twaddell. 
 46 92 
 
 45 
 
 43 
 42 
 
 38 
 
 84 
 80 
 70 
 
 34 B. correspond to 60 Twaddell. 
 
 29 , 50 
 
 25 
 20 
 14 
 
 7 
 
 40 
 30 
 20 
 
 Nitric acid of i -52 sp. gr. boils at 86 
 ,, 1-50 99 
 
 i '45 ii5 
 
 i '42 123 
 
 1-40 119 
 
 Nitric acid of i'35 sp. gr. boils at 117 
 
 ,i i'3 "3 
 
 1-20 108 
 
 ,, I 'IS n 104 
 
 Fuming nitric acid is generally now obtained by mixing in a retort ioo parts of nitre 
 with 3-5 parts of starch and adding ioo parts of sulphuric acid at sp. gr. 1*85. The 
 retort should only be filled to one-third. 
 
 Fuming nitric acid or even nitric acid of sp. gr. 1*26, if it comes in contact 
 with dry packing materials, may give rise to fires. Straw, or the like, should there- 
 fore be previously steeped in a solution (saturated in the cold) of Glauber's salt, 
 Epsoms i.e., magnesium sulphate, &c. 
 
 Technical Applications of Nitric Acid. The technical application of nitric acid is 
 based on its property of oxidation when in contact with certain substances, the acid split- 
 ting up into nitrogen dioxide, hyponitric acid and ozone, the latter forming with the 
 body which caused the decomposition of the acid either an oxide or a peculiar com- 
 pound, while the hyponitric acid, when organic substances are present capable of 
 combining with it, forms the nitro-compounds, nitrobenzole, nitronaphthaline, nitro- 
 glycerine, nitromannite, nitrocellulose, or gun-cotton, &c. A large number of metals 
 are soluble in moderately concentrated nitric acid, but the strongest acid fails to act 
 upon iron and lead. Proteine compounds, albumen, the skin of the hands, silk, horn, 
 feathers, &c., are stained yellow by nitric acid, hence the use of this acid in dyeing 
 silk. If the acid is in contact with these substances for any length of time, they are 
 completely decomposed, and partly converted into picric acid. Starch, cellulose, and 
 sugar, are converted by the action of nitric acid into oxalic acid ; but very dilute nitric 
 acid converts starch into dextrine, and concentrated acid into xyloidine. Owing to the 
 property nitric acid possesses of destroying certain pigments for instance, indigo it 
 is sometimes employed in calico printing to produce a yellow pattern on an indigo 
 ground. This acid is also used in dyeing woollen materials ; in hat-making, to prepare 
 a mercurial solution used in dressing felt hats ; in the manufacture of sulphuric acid ; 
 in the preparation of lacquers ; in the preparation of nitrate of iron, a mordant used in 
 dyeing silk and cotton black ; for preparing picric acid from carbolic acid, and naphtha- 
 line-yellow from naphthaline; in the manufacture of nitrobenzol, nitrotoluol, and 
 
384 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 phthalic acid ; and for the preparation of nitrate of silver, arsenic acid, fulminating 
 mercury, nitroglycerine, dynamite, &c. 
 
 It serves further, under the name fiouille, for producing a compound of iron 
 fraudulently used for " loading " or " weighting " black silks in the process of dyeing, 
 of which ten tons are consumed daily in Lyons. 
 
 EXPLOSIVES. 
 
 Gunpowder. The substance known as gunpowder, or simply as powder, is a more 
 or less finely granulated mechanical mixture of saltpetre, sulphur, and charcoal, the 
 quantities of these materials being properly denned. It ignites at 300, also when 
 touched with a red-hot or burning body, or under certain conditions by friction or a 
 sudden blow. Powder under these conditions burns off rapidly but not instantaneously, 
 yielding as the products of its combustion nitrogen, carbonic acid, or carbonic oxide, 
 while there remains a solid substance consisting of a mixture of potassium sulphate and 
 carbonate. When the powder is ignited in a closed vessel, the sudden evolution of the 
 large volume of gases causes a pressure almost impossible to be withstood ; and even in 
 guns and large ordnance, in which one side of the vessel is formed by the yielding shot, 
 the metal forming the other sides must possess great strength and elasticity. In guns 
 and artillery the pressure only lasts as long as the ball is inside the gun, therefore the 
 slower the combustion of the powder through its entire mass, the lower is the velo- 
 city of the projectile. 
 
 Manufacture of Gunpowder. It is essential that the materials employed in the 
 manufacture of powder should be very pure ; the saltpetre should not contain any 
 chlorides ; the sulphur should be free from sulphurous acid, hence not flowers of sul- 
 phur but refined roll sulphur is used ; and lastly the charcoal requires very great 
 attention. The wood from which it is intended to prepare a charcoal for gunpowder 
 should be such as yields the least possible quantity of ash, while the charcoal should be 
 soft, like that used in pharmacy. The stems of the hemp and flax plants, especially the 
 former, yield excellent charcoal, but in consequence of the limited supply, the wood of 
 the wild plum tree (Prunus padus) is largely used in Germany, France, and Belgium ; 
 and in England the lime, willow, poplar, horse-chestnut, hazel, cherry, alder, and 
 other light white woods are employed for this purpose. All these varieties yield on 
 being carbonised effected in various ways, in retorts similar to those used in gas-works, 
 in pits dug in the earth, or by the aid of superheated steam, the wood being placed in 
 boilers, &c. from 35 to 40 per cent, charcoal. The temperature during the progess 
 of carbonisation being kept as low as possible, there is obtained a very soft reddish- 
 brown charcoal, known as charbon roux. The charcoal prepared in cylindrically shaped 
 retorts is very inappropiately designated distilled charcoal. 
 
 Mechanical Operations of Powder Manufacture. These operations include : 
 
 I. The pulverising of the ingredients. 2. The intimate mixing of these substances 
 3. The moistening of the mixture. 4. The caking or pressing. 5. The granulation 
 and sorting of the grain, as it is termed. 6. Surfacing the powder. 7. Drying. 
 8. Sifting from the dust. 
 
 Pulverising the Ingredients. This operation can be performed in three different 
 ways : 
 
 a By means of revolving drums. 
 
 b. By mill stones ; or 
 
 c. In stamping-mills. 
 
 a. The pulverisation by means of revolving drums is an invention due to the French 
 Revolution, and has the advantages of being very effective, rapid in execution, and of 
 preventing the flying about of the ingredients in a fine dust. The drums are made of 
 
SECT, in.] EXPLOSIVES. 385 
 
 wood, lined with stout leather, and provided with a series of projections. The substance 
 to be pulverised is put into the drum with a number of bronze balls of about ^ inch 
 diameter, their action aided by that of the projections, when the drum is turned on its 
 horizontal axis at a moderate speed, soon effecting a reduction to a fine powder. The 
 charcoal and sulphur are separately pulverised ; the saltpetre being obtained as a flour. 
 (See Saltpetre.) 
 
 b. Grinding by the aid of mill-stones. Two heavy vertical stones, similar to those 
 in 066 for crushing linseed, revolve on a fixed horizontal stone. This contrivance is the 
 most frequently used. 
 
 c. Stampers are now employed only in small powder-mills. Frequently 10 to 12 
 stamps made of hard wood are placed in a row, each stamp being fitted with a bronze 
 shoe, the entire weight being about i cwt. The stamps are moved by machinery, and 
 make from 40 to 60 beats a minute. The materials to be pulverised are placed in 
 mortar-shaped cavities in a solid block of oak wood, each cavity containing 16 to 20 Ibs. 
 In Switzerland hammers instead of the stampers are employed. 
 
 Mixing the Ingredients. The mixing is performed by the aid of drums similar in 
 size and shape to those used in the pulverisation, but made of stout leather instead of 
 wood. The mixing of 100 kilos, of the ingredients, aided by the action of 150 bronze 
 balls, takes fully three hours, the drum making ten revolutions a minute. It is usual 
 to moisten the materials with i to 2 per cent, of water, supplied by fine jets regulated 
 by taps. 
 
 When stampers and mill-work are employed, the sulphur and charcoal are first 
 separately pulverised by 1000 blows, and saltpetre having been mixed with these 
 ingredients in the proper proportion, the machinery is again set in motion, and at first, 
 after every 2000 blows, and then after every 4000 blows, the contents of the stamp- 
 holes are removed from the one to the other, this operation being repeated some six or 
 eight times. Where drums are used for the mixing operation, the moistening takes 
 place after the mixture has been removed to a wooden trough, where 8 to 10 per cent, 
 of its weight of water is added, care being taken to stir with a wooden spatula. 
 
 Caking or Pressing the Powder. This operation, which in stamping-mills is the 
 last of a continuous series, is separately performed where other machinery is employed. 
 In the French and German powder-mills, the compression is effected in a rolling-mill, 
 the rollers having a diameter of o'6 metre. The lower roller is made of wood, the upper 
 of bronze ; between the two an endless piece of stout linen is arranged, and upon this 
 the moist powder is placed. The cakes are i to 2 centimetres in thickness with the 
 hardness and very much the appearance of clay-slate. 
 
 The operation of pressing is of great importance ; the stronger the pressure the 
 greater the quantity of active material present in a given bulk, and hence the larger 
 the volume of gas given off by the ignition of the powder. In many English powder- 
 mills the pressing is effected by very powerful hydraulic machines, because, within 
 certain limits, the more the materials are pressed, the more slowly the powder burns 
 when finished, while the temperature of ignition being lower, the expansion of the 
 gases is less. If the powder were finished either without having undergone any pressure 
 at all, or with only a slight pressure, it would act as a detonating-powder, the decom- 
 position being instantaneous throughout its entire mass. 
 
 Granulation of the Cake, and Sorting the Powder. The conversion of the cake into 
 granules is effected 
 
 1. By means of sieves. 
 
 2. By means of peculiarly constructed rollers, Congreve's method ; or 
 
 3. According to Champy's method. 
 
 The granulation of gunpowder by the aid of sieves is carried on in the following 
 manner : The sieves consist of a circular wooden frame, across which a piece of parch- 
 
 2 B 
 
3 86 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 ment is stretched perforated with holes ; the sieves are named according to their 
 uses, and by the size of these holes ; that employed for breaking up the cake having 
 larger holes, and bearing a name different from the sieves used to produce the granules 
 this sieve again being distinguished from that employed for sorting the powder into 
 the variously sized grains as commercially known. The sieves are provided with a 
 so-called rummer, a lens-shaped disc made of hard wood, guaiacum, box, or oak-wood, 
 motion being imparted to the sieves by hand if they are small, or by suitably arranged 
 machinery if they are large, in which case Lefebvre's granulating-machine fitted with 
 ight sieves in an octagonal wooden frame is generally employed. 
 
 Congreve's granulating-machine consists of three pairs of brass rollers, 0^65 metre 
 in diameter, provided with diamond-shaped projections 2 millimetres high, the projec- 
 tions of the upper rollers being coarser than those of the others. The broken-up cake 
 is conveyed to the upper rollers by means of an endless canvas sheet. The mode of 
 feeding this sheet is somewhat peculiar and ingenious : the loose bottom of a square 
 box filled with coarsely pounded cake is made to rise slowly upwards, and discharge the 
 ake uniformly upon the sheet through an opening in the side of the box. ,The cake 
 while passing through the rollers is granulated, and then showered upon two sets of 
 wire-gauze sieves to which a to-and-fro motion is imparted. Below these sieves again 
 is a frame containing wire-gauze, the meshes of which are too small to admit of the 
 passage of ordnance powder, while the dust and cartridge-powder readily fall through 
 upon another wire-gauze, the meshes of which retain the rifle-powder but let the dust 
 pass. The quantity of dust made by tbe Congreve machine is very small, owing to 
 the fact that the rollers do not crush but break the cake. Champy's method, by which 
 & very round-grained powder is obtained, is performed in the following manner : 
 Through the hollow axis of a wooden drum a copper tube, perforated with very small 
 holes, is carried, and from these holes water sprouts in a fine spray upon the broken-up 
 powder-cake placed in the drum, to which a comparatively rapid motion is imparted. 
 Each drop of water forms the nucleus of a grain of powder, which is constantly in- 
 creasing in size by being turned round in the midst of a mass of damp powder-cake ; 
 the rotation of the drum is discontinued as soon as the grain has attained a sufficient 
 size. The powder thus obtained is almost perfectly globular, but not of the same size ; 
 the sorting is effected by means of sieves, the over-sized grains being returned to the 
 drum, as well as the under-sized grains, which become the nuclei of proper-sized grain. 
 According to the Berne method, round-grained powder is prepared by causing the 
 -angular-shaped powder to be rotated in stout linen-bags ; but by this plan much dust 
 is formed. 
 
 Polishing the Granulated Powder. The aim of this operation is to impart symmetry 
 to the grain, and to separate all the dust. It is performed in drums similar to those 
 described above ; 5 cwts. of the powder is polished at a time, the drums rotating slowly 
 for a few hours. 
 
 In some countries the polishing is effected by placing the powder in casks internally 
 provided with quadrangular rods. In Holland, Dr. Wagner states that some black- 
 lead is added to the powder during this operation to prevent ignition, but this is not 
 generally done. Highly-polished powder does not readily attract moisture, and is to 
 be preferred in a very damp climate. 
 
 Drying the Powder. It is clear that this operation requires very great care in 
 more than one respect. In small powder-works the powder is sometimes dried by 
 exposure to the heat of the sun, being spread out on canvas sheets stretched in wooden 
 frames ; or the drying-room is heated by a stove. In large powder-mills other methods 
 of drying the powder are general. 
 
 The quality of the powder very much depends on the care bestowed upon the 
 drying. A too rapid drying entails the following disadvantages : a. The powder may 
 
SECT, in.] EXPLOSIVES. 387 
 
 be very wet and not polished ; coarse ordnance and ordinary military powder is never 
 polished, and hence blackens the hands ; while, although the water is driven off, the 
 nitre is carried to the surface of the grain, which thereby cakes together, b. By the 
 too rapid evaporation of the water, channels and cracks are made in the grain, impair- 
 ing its density, increasing its bulk, and rendering it more hygroscopic, c. Lastly, 
 rapid drying entails a large amount of dust. For these reasons gunpowder, before 
 being placed in the drying-rooms, is exposed for some time to a gentle heat in a well- 
 ventilated room, the heat from a waste steam-pipe being sufficient. 
 
 Sifting the Dust from the Powder. Having been dried, the powder is sometimes 
 glazed, as it is termed ; that is to say, again polished in the manner above described ; 
 but generally this second polishing is dispensed with, and the dry powder cleansed 
 from the dust which adheres to it, by being placed in bags, made of a peculiar kind of 
 woollen fabric, and arranged in frame-work to which a to-and-fro motion is given by 
 machinery, the fine dust passing between the threads of the fabric into a box. The 
 loss thus occasioned amounts on an average to 0*143 P er cen ^-j the dust consisting 
 chiefly of charcoal. 
 
 Properties of Gunpowder. Good powder is recognised by the following properties : 
 i. Its colour should be slate-black; when blue-black it indicates that the powder 
 contains too much charcoal, while a deep black colour shows the powder to be damp. 
 If the charcoal employed was the so-called charbon roux, the colour of the powder will 
 be a brown-black. 2. It should not be too much polished so as to shine like burnished 
 black-lead. Small shining specks indicate that the saltpetre has crystallised on the 
 surface. 3. The grains should be uniform in size, unless, of course, two differently 
 sized powders have been mixed. 4. The grain should crack uniformly when strongly 
 pressed, it should withstand pressure between the fingers, and should not be readily 
 crushed to powder when pressed between the hands. 5. When pulverised the mass 
 should feel soft ; hard sharp specks show that the sulphur has not been well pulverised. 
 
 6. Powder should not blacken the back of the hands or a sheet of white paper when 
 gently rubbed. If it does so, there is either powder-dust or too much moisture. 
 
 7. When a small heap of powder is ignited on paper the combustion should be rapid, 
 completely consuming the powder and not setting fire to the paper. If black specks 
 remain, the powder either contains too much charcoal, or it is an indication that that 
 substance has been badly incorporated with the rest of the materials. Yellow streaks 
 left after the ignition show the same defects for the sulphur. If no grains of powder 
 remain, it is a proof that the powder was not well mixed ; when any remaining grains 
 of powder cannot be separately ignited, the saltpetre used was impure. If the powder 
 on being ignited sets fire to the paper, it is a proof that it is either damp or of very 
 inferior quality. 
 
 Gunpowder can absorb more than 14 per cent, of moisture from the air ; if the 
 quantity of water thus taken up is not above 5 per cent., the powder, on being gently 
 dried, reassumes its former activity ; but if the quantity of water absorbed exceeds 
 that amount, the gunpowder will not burn off rapidly, and when dried the single grains 
 become covered with an efflorescence of saltpetre, of course impairing the com- 
 position and active qualities of the powder. Even what is termed dry powder contains 
 at least 2 per cent, of hygroscopic moisture. Powder can be exploded by a heavy 
 blow as well as by an increase of temperature, and as regards its explosion by a blow, 
 very much depends upon the material upon which it is placed and with which the 
 blow is imparted. The following list exhibits in decreasing order the materials between 
 which a blow most readily ignites powder : Iron and iron, iron and brass, brass and 
 brass, lead and lead, lead and wood, copper and copper, copper and bronze. For this 
 reason gunpowder magazines are provided with doors turning upon bronze and copper 
 hinges, the locks also being of copper. When dry powder is rapidly heated to above 
 
3 SS CHEMICAL TECHNOLOGY. [SECT. ra. 
 
 300 it explodes. Even if only a very small portion of the powder is thus rapidly 
 elevated in temperature, the entire quantity, be it large or small, is exploded ; hence 
 a very small quantity touched by a red-hot or burning body is sufficient to effect an 
 explosion. It is generally held that the charcoal is first ignited, and that it spreads 
 the ignition to the other materials. Although Mr. Hoarder found by experiment that 
 powder does not ignite when touched with a red-hot platinum wire while under the 
 receiver of an air-pump, Professors v. Schrotter and Abel proved that gunpowder so 
 placed ignited rapidly when heated by a spirit-lamp. 
 
 Composition of Gunpowder. Gunpowder consists very nearly of 2 molecules of 
 saltpetre, i molecule of sulphur, and 3 of charcoal. Accordingly 100 parts of powder 
 
 contain 
 
 Saltpetre 74*84 
 
 Sulphur 11-84 
 
 Charcoal (No. I.) 13 -32 
 
 The above figures approximately express the composition of the best kinds of sport- 
 ing and rifle-powder. Ordinary powders, such as blasting-powder, consists of nearly 
 equal molecules of potassium nitrate and sulphur, with 6 molecules of charcoal. 
 Accordingly 100 parts contain 
 
 Saltpetre * "... 66-03 
 
 Sulphur 10*45 
 
 Charcoal (No. II.) 23-52 
 
 Products of the Combustion of Powder. Drs. Bunsen and Schischkoff found the 
 composition of a sporting and rifle-powder to be, in 100 parts, as follows : 
 
 Saltpetre 78'99 
 
 Sulphur .' 9-84 
 
 Carbon . 7-69 
 
 Charcoal, Hydrogen . .0-41 
 
 consisting of Oxygen . 3-07 
 
 .Ash traces 
 
 The residue of this powder after combustion was found to consist of 
 Potassium sulphate . . . . . .56-62 
 
 carbonate ...... 27-02 
 
 hyposulphite 7-57 
 
 ,, sulphuret . . . , . . 1-06 
 
 Hydrated potassium oxide (caustic potassa) . . 1-26 
 Potassium sulphocyanide . . . . . o'86 
 
 Saltpetre 5-19 
 
 Carbon . . . . . . . ' . . 0*97 
 
 Ammonium carbonate \ 
 
 Sulphur [ traces 
 
 100-55 
 
 It appears from this analysis that the residue left after ignition of the gunpowder 
 consists essentially of potassium sulphate and carbonate, and not, as has been formerly 
 stated, of potassium sulphide. The composition of the smoke of the powder was 
 ascertained to be 
 
 Potassium sulphate 64-29 
 
 carbonate 23-48 
 
 hyposulphite 4-90 
 
 sulphide . 
 
 Caustic potassa 1-23 
 
 Potassium sulphocyanide 0-55 
 
 Saltpetre . . 2-48 
 
 Carbon (charcoal) . . . . . . .1-86 
 
 Ammonium sesquicarbonate 0*11 
 
 Sulphur ....... 
 
SECT. III.] 
 
 EXPLOSIVES. 
 
 389 
 
 From these figures it is clear that the smoke of gunpowder consists essentially of 
 the same substances as the residue from the combustion, the only difference being that 
 the sulphur and potassium nitrate of the powder have been more completely converted 
 into potassium sulphate, while, instead of the potassium sulphide, ammonium car- 
 bonate makes its appearance. 100 parts by volume of the gaseous products of the 
 combustion were found to consist of 
 
 Carbonic acid . . 
 
 Nitrogen 
 
 Carbon monoxide 
 
 Hydrogen . 
 
 Sulphuretted hydrogen 
 
 Oxygen 
 
 Nitrous oxide 
 
 52-67 
 
 41-12 
 
 3'88 
 
 I '21 
 
 0-60 
 
 The solid residues of combustion formed during the generation of the gases were 
 
 found to be 
 
 Potassium sulphate 62*10 
 
 carbonate ....... 18*58 
 
 hyposulphite 4 '80 
 
 sulphide ....... 3-13 
 
 sulphocyanide 0*45 
 
 nitrate 5 '47 
 
 Charcoal 1*07 
 
 Sulphur . . 0*20 
 
 Ammonium sesquicarbonate . . 4-20 
 
 The decomposition of powder by its ignition may be represented by the following 
 f ormulse : 
 
 Grm. 
 'K 2 SO 4 0-422 
 
 i gramme. 
 >of powder 
 
 
 
 K 2 CO, . 
 
 . . 
 
 0-126 
 
 
 
 K 2 S 2 0, . 
 
 . 
 
 0-032 
 
 
 
 Kesidue 
 0-680 " 
 
 K 2 S 
 KCNS . 
 KNO, . 
 
 1 ; 
 
 0*021 
 0-OO3 
 0-037 
 
 
 
 
 C 
 
 . . 
 
 0-007 
 
 Saltpetre 
 
 0789) 
 
 
 s 
 
 
 O'OOI 
 
 Sulphur 
 Charcoal 
 
 ;;^ yields after 
 H 0*004 combustion " 
 
 
 (NH 4 ) 2 CO, + 2(NH 4 HCO S ) 
 Grm. 
 
 fN ... 0-0990 = 
 
 0*028 
 c.c. 
 
 79-40 
 
 
 (o 0-030' 
 
 GfclSCS I f^f^ 
 
 . O'2OIO = 
 
 10171 
 
 
 
 01IA. -^ U 
 
 . O-OO9O = 
 
 7-49 
 
 
 
 34 |H 
 
 . O-OOO2 = 
 
 2*34 
 
 
 
 SH. 
 
 . O'OOlS = 
 
 1*16 
 
 
 0*994 | Q * 
 
 . 0-OOI4 = 
 
 1*00 
 
 193-10 
 
 The proportions of the mixtures used in different countries for military powder are : 
 
 Saltpetre 
 Sulphur . 
 Charcoal 
 
 Germany. 
 74 
 . 10 
 16 
 
 Russia. 
 
 75 
 10 
 
 Britain. 
 
 75 
 IO 
 
 15 
 
 France. 
 74 
 I0i 
 
 I Si 
 
 Since the American civil war compressed gunpowder has been introduced, especially 
 the so-called "prismatic powder." It is merely ordinary powder, which has been 
 compressed in hexagonal moulds. The pressed grain has the shape of a smooth hexa- 
 gonal prism (Fig. 341) perforated by six tubes. When ignited, the grain burns both 
 from without and from within, in consequence of the tubes. Yet it burns more slowly 
 than finely granulated powder, and imparts a greater force to the projectile. 
 
39<> 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 Fig. 341. 
 
 Testing Gunpowder. In order to determine the strength or projectile force of gun- 
 powder, and to ascertain which sample is dependent for equality of composition on the 
 mechanical treatment the powder has undergone, the following apparatus are used : 
 Test mortar, rod testing machine, lever testing machine, ballistic pendulum, and chrono- 
 scope. The first of these contrivances is a piece of heavy ordnance, charged with 92 
 
 grammes of powder, and a ball weighing 29-4 kilos., the 
 mortar being placed at an angle of 45. The bore of the 
 mortar is 191 millimetres in diameter by 239 in depth. 
 Powder of good quality should propel the ball a distance of 
 225 metres, and frequently the ball is carried a distance of 
 250 to 260 metres. The rod gunpowder testing apparatus 
 consists of a mortar placed vertically, and which, when 
 charged with 22 to 25 grammes of powder, lifts a weight 
 of 8 Ibs., made to move between toothed rods ; by the 
 height this weight is raised, springs attached to the weight 
 
 fastening in the notches of the rods and holding it, the quality of the powder is 
 judged. 
 
 Pyrotechnics. Chemical Principles of Pyrotechny. Under the name of fireworks we 
 include certain mixtures of combustible substances employed as signals, as destructive 
 agents (for instance, congreve rockets), and for purposes of display. 
 
 The various forms are, according to the end in view, so contrived as to burn off 
 either rapidly or slowly, and with more or less emission of gaseous matter, heat, and 
 light. These mixtures are mainly distinguished as heat-producing, ignition com- 
 municators (technically termed a fuse), and light-producing. The principle of the 
 rational manufacture of fireworks, applying the word in its extended sense, is that 
 neither any excess of the combustible nor of the combustion promoting and supporting 
 agents should be employed, and that unavoidable accessory materials, viz., such as are 
 intended only to keep the essential ingredients in a certain required shape, the paper 
 casings, &c., be in precisely the quantity required. The best proportions of the com- 
 bustible and combustion-supporting substances can be readily ascertained by theoretical 
 calculations; for instance, it will be evident that a mixture of 2 equivalents of salt- 
 petre and i equivalent of sulphur (i), or a mixture of 2 equivalents of saltpetre and 
 3 equivalents of sulphur (2), is in each instance wrong ; in the latter, too much of the 
 combustible body is used ; and in the former case, too much of the supporter of com- 
 bustion is employed 
 
 (1) S can take up from 2KNO 3 at most 30 ; consequently, 30 remain inactive. 
 
 (2) 38 and 2KNO 3 yield either K 2 S and 2S0 3 , or a mixture of K 2 SO 4 , K 2 S, and 
 
 S0 2 , in each case some sulphur remaining unburnt. 
 
 We have to bear in mind, however, that it is not always possible to elucidate theo- 
 retically the decomposition of firework mixtures, as the affinity of the substances which 
 react upon each other is not well known, and depends on accessory conditions and com- 
 paratively unknown influences. It will require a more advanced knowledge of the 
 products of the decomposition of the different substances and their specific heat before 
 we can predict with some degree of certainty the best mixtures. As regards the 
 existing mixtures, they are the result of a lengthy series of experiments, really made 
 by rule of thumb, though with a certain correspondence with the best composition 
 theory can give, that is to say, many of these mixtures have been somewhat modified 
 and improved by modern science. 
 
 The More Commonly Used Firework Mixtures. These mixtures consist mainly of 
 saltpetre, sulphur, and charcoal, either in the same proportions as those in use for gun- 
 powder, or with an excess of sulphur and charcoal. Some mixtures contain, instead of 
 saltpetre, potassium chlorate and other salts, not always essential to the combustion, but 
 
SECT, in.] EXPLOSIVES. 391 
 
 intended either to intensify the light evolved or impart to it a distinctive colour, as in 
 signals and Bengal lights. 
 
 Gunpowder is used in fireworks when it is desired that there should be projectile 
 force. A slower combustion of the powder is obtained partly by the use of so-called 
 meal powder, that is, pulverised, not granulated powder, partly by compressing the 
 mixture. If, however, it is intended to produce loud reports, granulated powder 
 is used. 
 
 Saltpetre and Sulphur Mixture. This consists of 2 molecules (75 parts by weight) 
 of saltpetre, and i molecule (25 parts by weight) of sulphur, and is used as the chief 
 constituent of such firework mixtures as are intended to burn off slowly and evolve a 
 strong light. However, this mixture is not used by itself, for two reasons, viz., it does 
 not develop a sufficient degree of heat to support its continued combustion, and it does 
 not possess a sufficient projectile force, being capable of producing in the best possible 
 condition of complete ignition only i molecule of sulphurous acid 
 
 2 KN0 3 + S = K 2 SO 4 + S0 2 + N; 
 
 that is to say, i part by bulk of this mixture only yields 7 '28 volumes of gas. For 
 these reasons the saltpetre-sulphur mixture is employed with charcoal or floury gun- 
 powder. 
 
 Grey-coloured Mixture. Such a mixture, sanctioned by long use, is that known as 
 grey-coloured mixture, consisting of 93*46 per cent, of saltpetre-sulphur and 6-54 of 
 floury gunpowder. This mixture is the chief constituent of other compounds intended 
 to burn slowly, emitting at the same time a brilliant light, owing to the fact that the 
 potassium sulphate formed by the combustion acts similarly to a solid brought to an 
 incandescent state. All mixtures intended to emit light, including coloured lights, are 
 prepared upon the same principle, that the salt which is to give colour shall be non- 
 volatile at the temperature of combustion. 
 
 Potassium Chlorate Mixtures ; Friction Mixtures ; Percussion Powders. This salt, 
 KC10 3 , when in presence of combustible substances, gives off its oxygen to the latter 
 more readily, rapidly, and completely than saltpetre ; accordingly, this salt is used in 
 all mixtures in which it is desired to combine rapid ignition with combustion. Formerly 
 a mixture of 80 parts by weight of potassium chlorate and 20 parts of sulphur was 
 added to intensify and quicken the combustion of mixtures consisting of more slowly 
 burning salts. A mixture of sulphur, charcoal, and potassium chlorate constitutes an 
 active percussion powder. A mixture of equal parts by weight of black antimony 
 sulphide and potassium chlorate is used for the purpose of discharging ordnance 
 by means of a percussion tube put in the touch-hole of the gun. Sir William 
 Armstrong uses for this purpose a mixture of amorphous phosphorus and potassium 
 chlorate. 
 
 Mixture for Igniting the Cartridges of Needle-guns. This mixture consists either 
 of potassium chlorate and black antimony sulphide, or a compound containing mercury 
 fulminate. The following is a good preparation : 16 parts of potassium chlorate, 
 8 of black antimony sulphide, 4 of flour of sulphur, and i of charcoal powder are 
 moistened with either gum or sugar-water, and about 5 drops of nitric acid added. 
 A small quantity, technically known as the pill, is placed in the cartridge and ignited 
 by the friction produced by the sudden passage of the steel needle through it. In this 
 country either the above or a mixture of amorphous phosphorus and potassium 
 chlorate is used. Leaving the silver and mercury fulminates out of the question, 
 the explosive bodies and their applicability to warlike purposes and military pyro- 
 techny have not been sufficiently investigated. Nitromannite or fulminating mannite, 
 the alkaline picrates, and nitroglycerine, of which we shall presently treat more fully, 
 especially deserve notice. M. Dessignolles, who suggests that, instead of saltpetre, 
 potassium picrate should be used in the manufacture of gunpowder, states that quite 
 
392 CHEMICAL TECHNOLOGY. [SECT. ra. 
 
 different products are formed by the ignition of potassium picrate, when effected in 
 the open air (a, or under pressure (6) : 
 
 a. 2 C 6 H 2 K(N0 2 ) 3 = K 2 C0 3 + 5 C + 3 N + NO + N0 2 + 4 C0 2 + CHN. 
 
 Potassium picrate. 
 
 b. 2 C 6 H,K(N0 2 ) 3 = K 2 C0 3 + 6C + sN + sCO 2 + 2 H 2 + O. 
 
 Potassium picrate. 
 
 Fulminating aniline, diazobenzol chromate, obtained by the action of nitrous acid 
 upon aniline, and the precipitation of the product by the aid of a hydrochloric acid 
 solution of potassium bichromate, is, according to MM. Caro and Griess, an efficient 
 substitute for fulminating mercury. 
 
 Heat-producing Mixtures. These consist chiefly of floury gunpowder and grey mix- 
 ture, to which are added certain organic substances, as pitch, resin, tar, igniting readily, 
 but consumed more slowly than any firework. The heat generated by the combustion 
 of fireworks is much higher than is required to ignite wood, but not of sufficient 
 duration to cause the thorough burning of the wood ; hence the addition of tar, &c. 
 
 Coloured Fires. The salts employed to produce coloured flames are barium, stron- 
 tium, and sodium nitrates, and the ammoniacal copper sulphate. The so-called cold 
 fuse mixture, composed of grey mixture, flour gunpowder, and antimony sulphide, 
 moistened with brandy and then mixed, produces a white flame. The mixtures 
 for coloured fires used in artillery laboratories are the undermentioned, calculated for 
 100 parts of each mixture : 
 
 a. b. c. d. e. 
 
 Green. Red. Yellow. Blue. White. 
 
 1. Potassium chlorate .... 327 ... 297 ... ... 54-5 ... 
 
 2. Sulphur 9-8 ... 17-2 ... 23-6 ... ... 20 
 
 3. Charcoal 5-2 ... 17 ... 3-8 ... i8'i ... 
 
 4. Barium nitrate 52-3 ... ... ... ... 
 
 5. Strontium ... 457 ... ... ... 
 
 6. Sodium ... ... 9-3 ... ... 
 
 7. Ammoniacal copper sulphate . . ... ... ... 27-4 ... 
 
 8. Saltpetre ... ... 62'8 ... ... 60 
 
 9. Black antimony sulphide . . . ... 57 ... ... ... e 
 IO. Flour gunpowder . . . . ... ... ... ... ft 
 
 It is hardly necessary to mention that great care is required in mixing these materials, 
 and that each ingredient ought be pulverised separately. 
 
 According to M. Uhden, a beautiful white flame edged with blue is obtained by the 
 ignition of the following mixture : 20 parts of saltpetre, 5 of sulphur, 4 of sulphuret 
 of cadmium, and i of charcoal. Thallium chloride with other ingredients yields a 
 beautiful green flame. Magnesium was used during the Abyssinian war in various 
 ways when a brilliant light was required. The chlorates of the alkaline earths and 
 sodium chlorate would be preferable, were it not for the expense, and for the facts 
 that these salts are rather hygroscopic and liable to spontaneous combustion. The 
 barium and strontium carbonates are sometimes used instead of the nitrate. Ac- 
 cording to MM. Dessignolles and Castelhaz, most brilliant coloured flames are obtained 
 with ammonium picrate in the following proportions : 
 
 Yellow f Ammoniur a picrate . . 50 
 
 (Ferrous . N . 50 
 
 Green I Ammonium . . 48 
 
 ( Barium nitrate . . S 2 
 
 j^ e( j | Ammonium picrate . . 54 
 
 1 Strontium nitrate . . .46 
 
 More Recent Explosives. Dessignolles proposes to substitute potassium picrate for 
 
SECT, in.] EXPLOSIVES. 393 
 
 saltpetre in the manufacture of gunpowder. The fearful power of picrate powder, 
 which is also known as Bobosuf powder, Dessignolles powder, and Fontaine powder, is 
 fully known. Mellinite consists essentially of picric acid. Nitromannite, 
 
 C 6 H 8 N 6 18 - C 6 H 8 (O.N0 2 ) 6 , 
 
 is formed on dissolving mannite in fuming nitric acid, and separates out on the addition 
 of concentrated sulphuric acid. It crystallises from boiling alcohol in fine silky 
 needles, which, if heated to 120, burn with detonation, and explode violently if struck. 
 Nitromannite has been substituted for fulminating mercury as a material for per- 
 cussion caps. It is said to undergo decomposition on long keeping. Nitrised cane- 
 sugar has been in transient use as an explosive agent under the name Vixorite. 
 Fulminating aniline (diazobenzol chromate), made by the action of nitrous acid upon 
 aniline and precipitating the product with potassium dichromate, has also been pro- 
 posed as a substitute for mercury fulminate. Hellhoffite is a solution of nitrobenzol 
 in nitric acid.* 
 
 Nitroglycerine (nitroleum, pyroglycerine, glyceryl trinitrate, or glono'ine). This sub- 
 stance was discovered in 1847 by Dr. A. Sobrero, while a student in the laboratory of 
 Professor Pelouze, at Paris. Since the year 1862, M. Alfred Nobel, a Swede, has manu- 
 factured this liquid on the large scale. The formula of nitroglycerine is C 3 H 5 N 3 O 9 or 
 
 C 1 IT 1 * C H 
 
 /xrr 5 \ \3> consequently, it consists of glycerine, Vj 5 1 , in which 3 atoms of H 
 
 \*Wj/r "-3) 
 
 have been replaced by 3 atoms of NO 2 . 100 parts of nitroglycerine yield on combustion 
 
 Water 20 'O parts 
 
 Carbonic acid . . . . 58*0 
 
 Oxygen 35,, 
 
 Nitrogen i8'5 
 
 lOO'O 
 
 As the specific gravity of nitroglycerine is i'6, i part by bulk will yield on com- 
 
 bustion 
 
 Aqueous vapour . . .' -554 volumes 
 Carbonic acid .... 469 
 
 Oxygen 39 
 
 Nitrogen 236 
 
 1298 
 
 According to experiments made in Belgium, the combustion of nitroglycerine does 
 not yield free oxygen, but a large quantity of nitrous oxide ; hence, the following 
 equation will give some idea of the mode of explosion : 
 
 /Carbonic acid, 6CO r 
 2 molecules of ) _ J Water, 5H 2 O. 
 Nitroglycerine, C S H S N S OJ ~ j Nitrous oxide, N 2 O. 
 V Nitrogen, N 4 . 
 
 M. Nobel states that the heat set free by explosion causes the gases to expand to eight 
 times their bulk ; accordingly, i volume of nitroglycerine will yield 10,384 volumes of 
 .gas, while one part by bulk of powder only yields 800 volumes of gas ; the explosive 
 force of nitroglycerine is, therefore, to that of powder 
 
 By volume as 13 : i, 
 By weight as 8 : I. 
 
 In order to prepare nitroglycerine, very strong nitric acid, density 95 to 98 Tw. = 
 1-476 to i -49 sp. gr., is mixed with twice its weight of concentrated sulphuric acid, 
 3300 grammes of this mixture, thoroughly cooled, are poured either into a glass 
 
 * Compare Eissler, Handbook of Modern Explosives. London : Lockwood & Son. 
 
394 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 flask or into a glazed earthenware jar, placed in a pan of cold water, and there is 
 next gradually added 500 grammes of concentrated and purified glycerine, having a 
 density at least of 49 to 51 Tw. = sp. gr. 1-246 to 1-256, care being taken to stir 
 constantly. According to Dr. E. Kopp's recipe (1868) the acid mixture should consist 
 of 3 parts of sulphuric acid at 153 Tw. = 1-767 sp. gr., and i part of fuming nitric acid. 
 To 350 grammes of glycerine 2800 grammes of the acid mixture are added ; and in per- 
 forming this operation care should be taken to avoid any perceptible heating for fear 
 of converting by a violent reaction the glycerine into oxalic acid. The mixture is now 
 left to stand for five or ten minutes, and afterwards poured into five or six times its 
 bulk of very cold water, to which a rotatory motion has been imparted. The newly 
 formed nitroglycerine sinks to the bottom of the vessel as a heavy oily liquid, 
 which is washed by decantation ; but if not intended for transport and experience 
 has proved the transport of nitroglycerine to be highly dangerous the washing may be 
 dispensed with, as neither any adhering acid nor water impairs the explosive properties. 
 Nitroglycerine is now generally made on the spot in America and elsewhere by those 
 whom experience in mining, quarrying, and engineering matters has taught the real 
 value of this very powerful agent. 
 
 Nitroglycerine is an oily fluid of a yellow or brown colour, heavier than and 
 insoluble in water, soluble in alcohol, ether, and other fluids ; when exposed to con- 
 tinuous cold, not of great intensity, it becomes solidified, forming long needle-shaped 
 crystals. The best means of exploding nitroglycerine is a well-directed blow, neither 
 a spark nor a lighted body will cause the ignition, which even with a thin layer 
 takes place with difficulty, only part being consumed. A glass bottle filled with 
 nitroglycerine may be smashed to pieces without causing the contents to explode. 
 Nitroglycerine may even be gently heated and volatilised without decomposition or 
 combustion, provided violent boiling is carefully prevented. When a drop of nitro- 
 glycerine is caused to fall on a moderately hot piece of cast-iron the liquid is quietly 
 volatilised ; if the iron is red-hot the liquid burns off instantaneously, just as a grain 
 of powder would do under the same conditions ; if, however, the iron is at that heat 
 which will cause the immediate boiling of the nitroglycerine, it explodes with great 
 force. Nitroglycerine, especially if sour and impure, is liable to spontaneous decom- 
 position, which, accompanied by the formation of gas and of oxalic acid, may have 
 been the proximate cause of some of the dreadful explosions of this substance, it being 
 surmised that the pressure exerted by the generated gases upon the fluid in hermeti- 
 cally closed vessels had something to do with the occurrences. On this account M. K. 
 last advises that vessels containing nitroglycerine should be only loosely stoppered, or 
 if being transported provided with safety-valves. Nobel secures nitroglycerine from 
 explosion by dissolving it in pure wood-spirit, from which it may be again separated 
 by the addition of a large quantity of water. Mr. Seeley on this score observes that : 
 i. The wood -spirit is expensive, and lost in the large quantity of water required for 
 precipitating the nitroglycerine; 2. Wood-spirit, being volatile, may evaporate, and 
 leave the nitroglycerine unprotected ; 3. There is a chance of chemical action between 
 these bodies ; 4. The vapour of wood-spirit is very volatile, and forms with air an 
 explosive mixture. Many suggestions have been made as to rendering nitroglycerine 
 safe to warehouse ; among them may be noted the mixing with pulverised glass in a 
 manner similar to Gale's process for gunpowder. Wurtz recommends the mixture 
 of nitroglycerine with equally dense solutions of either zinc, calcium, or magnesium 
 nitrates, so as to form an emulsion, the nitroglycerine being recovered simply by the 
 addition of water. The taste of nitroglycerine is sweet, but at the same time burning 
 and aromatic ; it is a violent poison even in small doses, and its vapour is of course equally 
 virulent, hence great care is required in working with this substance in localities where, 
 as in mines and pits, the supply of fresh air is limited. Instead of manufacturing 
 
SECT, in.] EXPLOSIVES. 395 
 
 nitroglycerine in works specially arranged for that purpose, and transporting this 
 dangerous compound, it is better, as advised by and executed under the direction of 
 Dr. E. Kopp, at the Saverne quarries, to have the quantity required for daily use 
 prepared on the spot by intelligent workmen. Notwithstanding the very serious 
 accidents which have been caused by the explosions of nitroglycerine in this country 
 as well as abroad, and the consequent prohibition of its use, there is no reason why this 
 powerful agent should not be employed according to Kopp's suggestion. Instead of the 
 acid mixture used in the preparation of nitroglycerine, M. Nobel suggests the follow- 
 ing: In 3^ parts of strong sulphuric acid of 1-83 sp. gr. is dissolved i part of 
 saltpetre, and the fluid cooled down ; the result is the separation of a salt consisting 
 of one molecule of potassa, 4 molecules of sulphuric acid, and 6 molecules of water, 
 and which at 32 F. is altogether eliminated from the fluid, leaving an acid which, by 
 the gradual addition of glycerine, is converted into glonoine, afterwards separated by 
 water, as already described. 
 
 Nobefs Dynamite. Under the name of dynamite, Nobel, in 1867, brought out a new 
 explosive compound, consisting of 75 parts of nitroglycerine absorbed by 25 parts of any 
 porous inert matter, as finely divided charcoal, silica. As evidenced by the experiments 
 of Bolley and Kuiidt, dynamite has the advantage over nitroglycerine of not being 
 exploded even by the most violent percussion, therefore requiring a peculiarly arranged 
 cartridge. The explosion is attended with such force that large blocks of ice are shat- 
 tered to atoms. Dynamite burns off quietly in open air, or even when loosely packed, 
 the combustion being accompanied by an evolution of some nitrous acid ; but when 
 dynamite is exploded there are generated only carbonic acid, nitrogen, and aqueous 
 vapour, no smoke being formed, and only a white ash left. Dynamite is not affected 
 by damp, and undoubtedly offers great advantages as regards its use in mining, 
 quarrying, and similar operations, for although the price exceeds four times that of 
 powder dynamite performs eight times as much work with less danger and less labour 
 in boring blast holes. The dynamite is placed in cartridges of thick paper, and 
 ignited by means of a fusee, which passes through the sand serving the purpose of a 
 wad. Dynamite can be transported without danger of explosion. Dittmar's dualine is 
 a mixture of nitroglycerine with sawdust or wood-pulp as used in paper mills, both 
 previously treated with nitric and sulphuric acids. 
 
 The annual production of dynamite in Europe is now 7000 tons. 
 
 Lithofracteur, Dualine, Colonia-powder, Fulminatine, Sebastine, Serranine, Atlas 
 powder, Yulcan powder, Neptune powder, and Forcite are all mixtures containing nitro- 
 glycerine. 
 
 The gelatine dynamites, which are obtained by dissolving 7 to 8 per cent, of 
 collodion cotton in nitroglycerine, form a solid gelatinous mass, blasting gelatine. It 
 combines the shattering power of nitroglycerine with a more or less decided propelling 
 action, and will doubtless before long supersede dynamite.* 
 
 Gun-Cotton. If cotton is treated with a mixture of nitric acid and sulphuric 
 acid there is formed, according to the proportions and the conditions of action, either 
 gun-cotton or collodion-cotton, bodies which differ considerably in their properties. 
 
 Gun-cotton (pyroxiline, fulmicoton) was simultaneously discovered by SchOnbein 
 and Bottger. The raw material is cotton, generally the waste of spun cotton freed 
 from all impurities, mechanical and chemical. After being thoroughly torn up and 
 loosened by machinery and dried, it is ready for nitrising. 
 
 For this purpose there are used i part nitric acid at 1*516 sp. gr. and 3 parts 
 
 * The employment of nitroglycerine and its mixtures for criminal purposes is a fatal objection 
 to Kopp's suggestion. These substances should be manufactured only in works carefully con- 
 structed and guarded, and should be supplied only to responsible persons. 
 
39 6 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 sulphuric acid at 1*842 sp. gr. ; the acids are poured into a large cylindrical vessel 
 of cast-iron, in which revolves an iron shaft fitted with arms driven by conical 
 wheels. After the acids are mixed they are let off into cast-iron vessels, which 
 stand lower, and are closed with covers. Each vessel has a conical bottom with 
 a cock for letting off, from which a branch leads to a common cast-iron main leading 
 to the nitrising room. Here there are thick brick walls in which there is a special 
 cavity for each vessel (at Waltham Abbey a long open channel), in which cold water is 
 constantly flowing. In these cavities there are placed quadrangular cast-iron nitrising 
 vessels, which have a grate at their back part. The quantity of acid used is always 
 twenty times greater than is necessary about 20 kilos. Into each there is put a 
 small quantity of cotton, about ^ kilo. ; it is stirred about with an iron fork, and when 
 nitrised it is hard on the grating. As the cotton, in spite of being pressed, has either 
 consumed or absorbed eleven times its weight of acid, about an equal quantity of fresh 
 acid is added to the vessel. After twenty charges the entire acid mixture will thus 
 have been renewed. The cotton requires a very careful treatment, so as not to obtain 
 portions which have entirely or partially escaped the action of the acid. For this 
 purpose the nitrised cotton is placed in small stoneware pots, set in a cistern constantly 
 traversed by cold water. Here it remains for some time to cool. 
 
 At Waltham Abbey the nitrised cotton is whizzed. It is then placed in a large 
 tank of water with a dash-wheel, and is whizzed again. It is then transferred to other 
 washing tanks, each time with fresh water gently heated by steam pipes, to which soda 
 and elutriated chalk are sometimes added to remove the last traces of acid. The 
 cotton is next transferred to a hollander, as they are used in paper-mills, where it is 
 converted into a uniform paste amidst continual washing. Every four hours the water 
 is run off and fresh water is run on. After from twenty-four to thirty-six hours 01 
 upwards of such washing a sample of the lot (potcher) is tested for its explosion point. 
 If satisfactory, it is once more whizzed and stored for use. 
 
 Properties of Gun-cotton. In its outward appearance gun-cotton does not differ 
 from ordinary cotton, neither is any difference perceptible by microscopic investigation. 
 It is insoluble in water, alcohol, and acetic acid, difficultly soluble in pure ether, but 
 readily soluble in ether which contains alcohol, and in acetic ether. Gun-cotton is 
 liable to spontaneous decomposition, which may even induce its spontaneous com- 
 bustion j this decomposition is attended with the evolution of aqueous vapour and of 
 nitrous acid fumes, the remaining substance containing formic acid. As regards the 
 temperature at which gun-cotton ignites statements differ ; it has in some instances 
 been dried at 90 to 100 without any dangerous consequences, while it has been 
 found to ignite at 43. Instances are on record of serious explosions of gun-cotton 
 having taken place under conditions which leave no doubt that the greatest care is 
 required in handling and warehousing this substance ; for instance, a small magazine, 
 filled with gun-cotton, situated in the Bois de Vincennes, Paris, was exploded by the 
 sun's rays ; and at Faversham the Le Bouchet drying rooms, which could not possibly 
 be heated above 45 to 50, exploded with great violence.* Gun-cotton explodes by 
 percussion, leaving no residue after its ignition. Good gun-cotton may be burned oft 
 
 * The extraordinary statements just given are to be explained by the presence of impurities. If 
 the least trace of acid remains the gun-cotton will sooner or later explode spontaneously, even at 
 common temperatures. Or if fatty matter or other impurities are left adhering to the fibre, bye- 
 products are formed which lead to decomposition. The behaviour of gun-cotton when heated 
 depends on the gradual or sudden rise of temperature. In the former case the gun-cotton ignites 
 at a lower point. Cold gun-cotton burns harmlessly if a light is applied to it, but if it has been 
 gradually heated it explodes as if it had been fired by a detonator. The fearful explosion at 
 Stowmarket in 1871 was traced to the malicious addition of acid to some of the finished and dried 
 discs in the magazine. 
 
SECT. HI.] 
 
 EXPLOSIVES. 
 
 397 
 
 Fig. 342. 
 
 when placed on dry gunpowder without igniting the latter. It is very hygroscopic, but 
 may be kept for a length of time under water without affecting its explosive properties. 
 
 Gun-cotton is generally regarded as trinitro-cellulose, C 6 H 7 (N0 2 ) 3 O 5 , but according 
 to Eder it is cellulose hexanitrate, C 13 H 14 O 4 (N0 3 ) 6 ; collodion cotton is mainly the 
 tetranitro-cellulose, C 12 H 16 O 6 (NO 3 ) 4 . 
 
 The apparatus of Hess for determining the chemical stability of explosives, especially 
 gun-cotton and nitroglycerine, is shown in Fig. 342. The samples, p, of the explosives 
 are placed in vessels of badly conductive mate- 
 rials in a heating chest, W, with double sides, 
 the intermediate space being filled with water. 
 In the samples is placed a thermometer, t, which 
 passes through the chest. The temperature of 
 the heating-room, which can be kept at a suit- 
 able point by the burner, S, can be read off on 
 the thermometer, t ; the thermo-regulator, R, 
 serves to keep the internal temperature at 70. 
 The overstepping of the temperature of t in 
 the explosives, if found by regular observation, 
 is the consequence of a decomposition, the pro- 
 gress of which is to be regularly followed. 
 Samples of 100 grammes will suffice. In order 
 to make the observation without danger it may 
 be watched from a distance by means of a tele- 
 scope. The samples, as is, shown in the middle 
 vessel, p, may be placed in a perforated capsule 
 provided with a cover, and suspended by a 
 
 flange. It can be raised or lowered into cold water by means of a cord, S, passing 
 over pulleys. 
 
 The examination of gun-cotton is effected by Alberts as follows : the samples are 
 dried for two hours at 40, then rubbed through a fine sieve of brass wire. An 
 average sample of 10 grammes is then taken and dried in the exsiccator until its 
 weight is constant. The requisite quantity of gun-cotton (about 0*48 gramme), is 
 weighed into a small flask, provided with a glass stopper, and holding about 10 c.c. 
 After the nitrometer (holding 140 c.c.) is prepared as usual, about 5 c.c. pure con- 
 centrated sulphuric acid is poured into the flask, the gun-cotton is stirred up in it with 
 a platinum wire, the contents of the flask are emptied as completely as possible into 
 the funnel of the nitrometer, and without loss of time it is drawn into the measuring 
 tube by turning the three-way cock. By repeatedly rinsing out the flask, each time with 
 3 c.c. of concentrated sulphuric acid, always stirring with the platinum wire, all the 
 rest of the substance is brought into the funnel and thence into the measuring-tube. 
 Lastly, the funnel and the wire are rinsed with sulphuric acid which is also conveyed 
 into the measuring-tube. The three-way cock is closed and the work is complete as 
 usual by shaking.* 
 
 * The ordinary way to analyse samples of gun-cotton is to dry a quantity until the weight is 
 constant, and then to weigh 100 grains into a small light flask closed with a stopper, or into a 
 roomy test-tube with a well-fitting cork, an excess of a mixture of 18 parts anhydrous ether and 
 3 parts anhydrous alcohol is poured upon the gun-cotton, the stopper is inserted and the flask is 
 let stand for 15 minutes, with occasional shaking. The liquid is then poured off and the sample 
 rinsed with a little more of the same mixture. The residue of gun-cotton is allowed to evaporate 
 under the air-pump. If any loss of weight is formed the deficiency is due to a lower compound of 
 cellulose, which has been dissolved out. The remaining quantity is again treated in the same 
 manner with acetic ether, which dissolves the true gun-cotton. If any matter remains undissolved 
 it is cotton fibre which has escaped the action of the acids. 
 
398 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 Gun-cotton has been used with success for filtering strong acids, &c., and if steeped 
 in potassium permanganate as an application to wounds which have become offensive. 
 
 Collodion Cotton. Maynard used the solution of gun-cotton in alcohol and ether as 
 an adhesive, and gave it the name of collodion. If it is poured in a thin film upon the 
 skin there is formed on the evaporation of the ether an impervious and adherent layer. 
 It is used in surgery instead of court-plaster for closing up incised wounds, and for the 
 production of photographs on glass (so-called collodion process). Legray produces by 
 the following process a collodion cotton perfectly soluble in ether : 80 grammes of 
 dried and pulverised potassium nitrate are mixed with 120 grammes of concentrated 
 sulphuric acid, and 4 grammes of cotton are thoroughly immersed by the aid of a 
 glass rod or porcelain spatula in the pulpy acid mass, which is stirred about for a few 
 minutes ; next the vessel containing acid and cotton is placed in a large quantity of 
 water, and the converted cotton washed until all the acid is eliminated, when it is 
 dried. Soluble cotton may be made with sodium nitrate, 1 7 parts ; sulphuric acid, 
 sp. gr. = i-8o, 33 parts; cotton, ^ part. -The converted cotton is soluble in acetic 
 ether, acetate of methyl oxide, wood-spirit, and aceton ; the usual solvent is a 
 mixture of 18 parts of ether and 3 parts of alcohol. 
 
 Collodion cotton has recently been used in the manufacture of celluloid, a substance 
 which is not explosive, but highly inflammable. 
 
 Fulminating Mercury. The compound known as fulminating mercury is a com- 
 bination of f ulminic acid, an acid unknown in a free state, and of oxide of mercury ; its 
 formula may be written C 2 Hg 2 N 2 O 2 . In 100 parts it consists of 77*06 of peroxide of 
 mercury and 23-94 of fulminic acid. According to the late Dr. Gerhardt's view, this 
 body is a nitre-compound which may be regarded as cyan-methyl, the hydrogen of the 
 methyl of which has been replaced by hyponitric acid and mercury ; the formula is then : 
 
 CJ -v^M 2 tCN. This substance was first discovered by Mr. Howard, and was known, until 
 
 Liebig gave the clue to its nature, as Howard's detonating powder. It is prepared 
 on a large scale in the following manner : First, 2 Ibs. of mercury arc dissolved, 
 by the aid of a gentle heat, in 10 Ibs. nitric acid (<sp. gr. 1*33), and 10 Ibs. more 
 of nitric acid are then added. The resulting fluid is poured into six tubulated 
 retorts, and to the contents of each retort is added 10 litres of alcohol (sp. gr. 0-833). 
 If the ingredients are mixed by measure instead of weight, for every volume of mercury 
 there is taken 7^ volumes of nitric acid, and 10 volumes of alcohol. After a few 
 minutes a strong evolution of gas takes place, and at the same .time a white precipitate, 
 the fulminate of mercury, is formed. The retorts are fitted with tubulated receivers, 
 from which glass tubes carry off the very poisonous gas and fumes, either to a flue or 
 directly to the outside of the shed in which the operation is performed. The pre- 
 cipitate is collected on filters, and washed with cold water to eliminate the free acid. 
 The fulminate is next dried, filtered, and all being placed on plates of copper or earthen- 
 ware, heated by steam to less than 100. 100 parts of mercury yield in practice from 
 118 to 128 parts of fulminate, while, according to theory, 142 should be obtained. 
 The dried fulminate is, with cautious manipulation, divided into small portions, kept 
 separately in a paper bag. The fulminate thus prepared is a crystalline white-coloured 
 substance, which, by being heated to 1 86, or by a smart blow, explodes with a loud 
 report. When placed on iron and struck with an iron instrument, the detonation is 
 much increased. This substance also explodes by contact with concentrated sulphuric 
 acid. When mixed with 30 per cent, of its weight of water, the crystalline fulminate 
 may be rubbed to powder with a wooden pestle on a marble slab. The manufacture 
 of this substance on a large scale requires peculiar arrangements, into the particulars 
 of which we cannot here enter. 
 
 Percussion-Caps. The fulminate of mercury is chiefly used for filling percussion- 
 
SECT. III.] 
 
 AMMONIA. 
 
 399 
 
 caps. For this purpose 100 parts of the fulminate are rubbed to powder with 30 parts 
 of water, 50 to 62*5 parts of saltpetre, and 29 of sulphur. This mixture is dried 
 sufficiently to admit of being granulated, after which it is forced, by means of machinery, 
 into the copper caps, and simultaneously covered with either a layer of varnish or tin- 
 foil, to protect it from damp. Tin-foil being more expensive is not used for military 
 gun-caps. The best varnish for the purpose is a solution of mastic in oil of turpentine. 
 The caps are finally dried by a gentle heat, and packed in boxes. One kilogramme of 
 mercury converted into fulminate suffices for the filling of 40,000 gun-caps of the 
 larger or military size, and for 57,600 caps of the size used by sportsmen. 
 
 AMMONIA. 
 
 The ammonia and the ammoniacal salts employed in the arts are chiefly obtained 
 by the dry distillation of coal. Comparatively small quantities are obtained as bye- 
 products in the manufactures of animal charcoal and of the f errocyanides ; also from 
 stale urine, faecal waters, from beet-treacle, and from the action of superheated steam 
 upon certain cyanides. 
 
 Ammonia, NH 3 , consists of i volume of nitrogen and 3 volumes of hydrogen, con- 
 densing to 2 volumes of ammonia gas, a colourless gas of a peculiar and well-known 
 odour and sharp biting taste. At 15 water absorbs 727, and at o 1050, times its 
 own bulk of this gas, the solution being known as liquid ammonia, or spirit of sal- 
 ammoniac, the sp. gr. of which is 0-824 ( = 31-3 per cent. NH 3 ). Usually, however, a 
 weaker and more stable liquid ammonia is prepared for pharmaceutical and technical 
 purposes, having a sp. gr. = 0-960 (= 9-75 per cent. NH 3 ). The following table 
 shows the specific gravity of liquid ammonia, and the percentage of ammonia con- 
 tained : 
 
 Specific 
 
 Per 
 
 Specific 
 
 Per 
 
 Specific 
 
 Per 
 
 Specific 
 
 Per 
 
 Specific 
 
 Per 
 
 Specific 
 
 Per 
 
 gravity 
 
 cent. 
 
 gravity 
 
 cent. 
 
 gravity 
 
 cent. 
 
 gravity 
 
 cent. 
 
 gravity 
 
 cent. 
 
 gravity 
 
 cent. 
 
 at 14. 
 
 NH 3 . 
 
 at 14. 
 
 NH 3 . 
 
 at 14. 
 
 NH S . 
 
 at 14. 
 
 NH 3 . 
 
 at 14. 
 
 NH S . 
 
 at 14. 
 
 NH S . 
 
 0-8844 
 
 36-0 
 
 0-8976 
 
 30-0 
 
 0-9133 
 
 24-0 
 
 0-9314 
 
 l8'0 
 
 0-9520 
 
 12 "O 
 
 0-9749 
 
 6-0 
 
 0-8864 
 
 35 '0 
 
 o 9001 
 
 29-0 
 
 0-9162 
 
 23-0 
 
 0-9347 
 
 17-0 
 
 0-9556 
 
 II'O 
 
 0-9790 
 
 .S'O 
 
 0-8885 
 
 34 'o 
 
 0-9026 
 
 28-0 
 
 0-9191 
 
 22 -O 
 
 0-9380 
 
 16-0 
 
 0-9593 
 
 IO'O 
 
 0-9831 
 
 4-0 
 
 0-8907 
 
 33 P o 
 
 0-9052 
 
 27-0 
 
 0-9221 
 
 21 -O 
 
 0-9414 
 
 15-0 
 
 0-9631 
 
 9'0 
 
 0-9873 
 
 3-0 
 
 0-8929 
 
 32-0 
 
 0-9078 
 
 26*0 
 
 0*9251 
 
 2O "O 
 
 0-9449 
 
 14-0 
 
 0-9670 
 
 8-0 
 
 0-9915 
 
 2'O 
 
 0-8953 
 
 31-0 
 
 0-9106 
 
 25-0 
 
 0-9283 
 
 ig-O 
 
 0-9484 
 
 13-0 
 
 0-9709 
 
 7-0 
 
 0-9959 
 
 I'D 
 
 Ammoniacal gas is abundantly soluble in alcohol. It has numerous technical 
 applications, e.g., in extracting the colouring matters of orchilla-weeds, in the produc- 
 tion of ammoniacal cochineal, as an addition in the manufacture of snuff, in purifying 
 coal-gas from carbonic acid and carbon disulphide, in saponifying fats and oik, in the 
 manufacture of ferrocyanides along with carbon disulphide, for dissolving silver (silver 
 chloride) from its ores, in bleach-works, in the manufacture of lakes and colours, and in 
 the production of indigo. 
 
 In Java (at the suggestion of Sasser) ammonia has been added to the fermenting 
 mass of indigo and the colour is thus rendered purer. 
 
 The uses of ammonia in the ammonia-soda process and in the artificial production 
 of ice are of great importance. 
 
 Preparation of Liquid Ammonia. By decomposing with caustic lime either ammo- 
 nium chloride or sulphate, ammoniacal gas is set free, and can be absorbed by water, 
 care being taken that the lime is in excess. When ammonium carbonate is prepared 
 on the large scale by the sublimation of a mixture of chalk and sal-ammoniac, a 
 large quantity of ammoniacal gas, 14 parts for each 100 parts of ammonium car- 
 bonate, is obtained and may be utilised. Wagner has been the first to observe that 
 the technical preparation of liquid ammonia might be combined with the preparation 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 of baryta-white by precipitating a solution of ammonium sulphate with caustic baryta 
 water ; the clear supernatant liquor will be a solution of caustic ammonia. 
 
 According to Isambert, the reaction taking place during the production of ammonia, 
 CaO + 2NH 4 C1 = CaCl 2 + 2NH 3 + H 2 0, involves a consumption of 10,900 calories. At 
 common temperatures, even in a vacuum, the ammonia escapes from the mixture because 
 there is formed the molecular compound CaCl 2 .2NH 3 , which gives off ammonia only at 
 1 80 to 200. Baryta and strontia drive off ammonia from ammonium chloride at 
 1 80 to 200, whilst it is liberated by litharge at common temperatures. 
 
 Inorganic Sources of Ammonia. i. Native ammonium carbonate, met with in large 
 quantities in the guano deposits of South America, was imported into Germany as a 
 commercial article in 1848. On being analysed this substance was found to consist of 
 Ammonia, 20*44; carbonic acid, 54*35; water, 21*54; and insoluble matter, 21*54 
 parts. It is, therefore, an ammonium bicarbonate, (NH 4 )HCO 3 . 
 
 2. The preparation in Tuscany of native ammonium sulphate as a bye-product of 
 
 Fig- 343- 
 
 the preparation of boracic acid has recently become important. The suffioni contain, 
 in addition to boracic acid, potassium, sodium, ammonium, rubidium, &c., sulphates ; 
 and that the quantity of these substances is by no means small may be inferred from 
 Travale's researches, from which it appears that four suffioni yielded within twenty- 
 four hours 5000 kilos, of saline matter, consisting of 150 kilos, of boracic acid, 1500 
 kilos, of ammonium sulphate, 1750 kilos, of magnesium sulphate, 750 kilos, of the 
 ferrous and manganous sulphates, &c. The ammonia is probably due to the decom- 
 position of nitrogenous organic matter, occurring largely in the Tuscan mountains, the 
 soil near the lagoons being impregnated with ammonium sulphate. In combination 
 with the sodium, magnesium, and iron sulphates, ammonium sulphate forms the 
 mineral Boussingaultite, discovered by Bechi. 
 
 3. The ammoniacal salts due to volcanic action are of little or no value to industry. 
 Mascagnin, ammonium sulphate, is met with on Vesuvius and Etna; sal-ammoniac is 
 
SECT, in.] AMMONIA. 40I 
 
 sometimes also found on Etna, as in the years 1635 and 1669, in such large quantities 
 as to become temporarily an article of commerce at Catania and Messina. 
 
 Attempts to convert atmospheric nitrogen into ammonia have led hitherto to no 
 practical results, 
 
 Organic Sources of Ammonia. Industrially speaking, the organic sources of 
 ammonia are far more important than the inorganic. Coal takes here the first place. 
 In the production of coal-gas and of coke, it yields up its nitrogen as ammonia, which 
 is obtained as gas liquor. 
 
 The ammonia of the gas-water may be utilised in various ways. Where fuel is 
 cheap, and crude ammonium sulphate or crude sal-ammoniac a marketable article, the 
 gas-water may be at once neutralised by an acid, and the liquid thus obtained evapo- 
 rated. This is done in a sal-ammoniac factory at Liverpool, where, during the colder 
 season of the year, 300 cwts. weekly of this salt are prepared. Generally, however, 
 the gas-water is submitted to a process of distillation, and the ammonia evolved 
 converted into sulphate, as in Mallet's apparatus, or into sal-ammoniac, as in Rose's 
 apparatus. 
 
 Mallet's Apparatus, This apparatus, in use in many of the large gas-works, is 
 shown in vertical section in Fig. 343. The plan of action is to force steam into large 
 vessels filled with gas-water, the effect being the volatilisation of the ammonium 
 carbonate. Sometimes lime is added. The volatilised ammonia of course if lime is 
 added caustic ammonia is evolved is next conveyed into an acid liquor, and thus con- 
 verted into ammonium sulphate. The apparatus consists of two cylindrical boiler- 
 plate vessels, A and E. A is heated directly by the fire, and is provided with a leaden 
 tube, c, dipping into the liquid contained in , this vessel being placed to catch the 
 waste heat from the fire, b and e are man-holes ; a and a 1 stirrers. By means of 
 the tube, d, the fluid from B can be run off into A . Gas-water is poured into both 
 vessels and lime added ; ammonia is set free, while calcium carbonate and sulphide 
 are formed, and of course remain in the vessels after the volatilisation of the ammonia. 
 The vessel, B, is also filled with ammoniacal water, and when the operation is in pro- 
 gress this water, already warmed, is run by the aid of the tube, h, from D into B. E is 
 a gas-water tank, from which B is filled by means of g. The ammonia set free in A is, 
 with the steam, conveyed by the pipe, c, into B, thence through c', into the wash- vessel, 
 O, and thence again through c", into the first condenser, D. The partially condensed 
 vapour now passes into the condensing vessel, F, the worm of which is surrounded by 
 cold water. The dilute ammonia is collected in G, and forced by means of the pump, 
 R, into (7, whence it is occasionally syphoned into either A or B. The non-condensed 
 ammoniacal gas is carried from G, through a series of Woulfe's bottles, the first bottle, 
 H, containing olive oil for the purpose of absorbing any hydrocarbons mixed with the 
 gas ; the bottle, J, contains caustic soda lye, in order to purify the ammonia and retain 
 impurities ; the bottle, K, is half -filled with distilled water. The ammoniacal gas having 
 passed through K, is conveyed to the large lead -lined wooden tank, Z, filled with dilute 
 sulphuric acid if it is intended to prepare ammonium sulphate, or with water for making 
 liquid ammonia. The vessel, Z, is placed in a tank of water ; i is a small pipe for intro- 
 ducing acid ; while the tube leading to M serves to carry off any unabsorbed ammonia, 
 M being also filled with acid. 
 
 Lungds Apparatus. This apparatus, also intended for the utilisation of gas-water, 
 is shown in Fig. 344 ; a, is the boiler ; h the gas tube connected with the worm, c, 
 which is placed in a tank, d, filled with gas liquor, run into a by means of the tube, e. 
 The tube, /, is so fitted to a as to admit of discharging the waste liquor readily, b re- 
 presents a stirrer fitted to the boiler by a stuffing box, and being intended to rake up 
 the lime and prevent it getting caked to the bottom of a / h v a tube intended for run- 
 ning gas-liquor into d, from a tank placed at a higher level ; i, a tube provided with a 
 
 2 C 
 
402 CHEMICAL TECHNOLOGY. [SECT, m 
 
 tap and fitted to the cover of d, to convey any gas or vapours from d into the worm. 
 k represents a wash vessel, sometimes filled simply with water, at others with milk 
 of lime. The gas and vapours having passed through k, are conveyed to the absorp- 
 tion vessel, I. The tube, m, through which the gas passes, is funnel-shaped, and oppo- 
 site to the mouth of the funnel, at the bottom of the tank, a thick disc of lead is fixed 
 because at this spot the action of the gas would soon wear away the leaden lining 
 
 Fig. 344- 
 
 of the vessel. o is a smaller wooden tank, also lead-lined, into which sulphuric 
 acid is poured, and whence it runs into I through the stoneware syphon, p. Any 
 vapours given off are caught by the hood, r, and thence conveyed by a tube into the 
 chimney. The saline matter deposited in I is removed by a leaden pail, as shown 
 in the cut ; when this pail is filled it is drawn up by means of the chain and pulley 
 aided by the counter-weight, t. The salt (ammonium sulphate) is placed in the 
 basket, u, from which the mother -liquor adhering to the salt drains again into the 
 tank, I. Evaporation is therefore unnecessary with this apparatus. 
 
 According to Kunheim, the presence of ammonium sulphide is especially, trouble- 
 some in working up as gliquors. To remove it, and at the same time to utilise all 
 the sulphur, a powerful but greatly subdivided stream of common air is allowed to 
 act upon the cold gas liquor. The ammonium sulphide is then split up into sul- 
 phuretted hydrogen and ammonia. The former, along with the excess of air,"is passed 
 through finely divided feirichy dioxide and thus absorbed. The hydroxide is sus- 
 pended in a dilute solution of an alkaline earth. 
 
 Among the recent; apparatus for distillation the following deserve notice. 
 
 The apparatus of H. Griineberg consists of a still, A (Fig. 345 and 346), a rectifier, 
 B, a condensing apparatus, C, connected with an absorption vessel, Z>, and a hydraulic 
 joint, E. The vertical cylindrical pan, A, has an internal concentric compartment, a, 
 which passes through the lower part of the. pan and is prolonged below. It is closed 
 with a vaulted bottom, which latter has an exit cock, /, serving to remove the im- 
 purities of the lime (introduced through the pipe, e, into' the cylinder, a), as well as to 
 run off the calcium sulphate formed. In the compartment, a, the tube, b, is suspended 
 concentrically down to the cylindrical affix. This tube, 6, is closed below and fitted 
 with small outflow tubes, , but above it is connected with the main pan, A, by means 
 of the collar, c, with its series of perforations at d. In the above-mentioned cylindrical 
 
SECT. III.] 
 
 AMMONIA. 
 
 appendage there is a small stirring apparatus, s, serving to keep the lime introduced 
 through e in close contact with the liquid descending from the internal tube, b, through 
 the tubes, t, and freed from volatile ammoniacal compounds. The pan, h, has an exit 
 pipe, h, hydraulically cut off from the cylindrical vessel, i, outside the apparatus. It has 
 also an exit-cock, g, for complete emptying. Upon the pan, A, there is fixed a rectifier 
 of ordinary construction, or in its place a scrubber filled with coke. It is connected with 
 the refrigerator, C, by the tube, k. The refrigerator is fed from the cistern, R. The 
 pipe, I, serves to convey away the water which has been warmed in C to the rectifier. 
 
 Fig. 345 and 346. 
 
 The crude gas-liquor flows from F into the cooler, C, and hence, by means of the 
 tube, I, through the rectifier, B, into the descending tube of the still-pan, A. At the 
 bottom of the piece, a, of this pan it meets, whilst flowing down through the pipes, t, 
 with the milk of lime which is there present. It is there decomposed, a reaction which is 
 assisted by the occasional movement of the agitator, s. The liquid, which now 
 contains free ammonia, rises up in the cylinder, a, and flows over at its upper margin 
 into the main pan, A. From this it is carried off by the tube, h, at the bottom, after 
 the ammonia has been expelled. The vapours evolved in A pass through the apertures, 
 d, into the rectifier, and from here either into the cooler, (7, which at the same 
 time separates the gases and the vapours from each other, or, if it is desired to obtain 
 ammonium sulphate, into a lead vessel full of sulphuric acid. In the former case the 
 
404 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 ammoniacal liquor condensed in C flows through the tube, m, into the vessel, E (cut 
 off by a hydraulic joint), and flows from there through n; the tube, o, conveys the 
 nncondensed vapours into the cistern, D, lined with lead and filled with sulphuric 
 acid, and from there the gases not absorbed are conveyed into the furnace by the 
 tube, p. 
 
 Recently the column, B (Fig. 347), has been connected with a regulator. R. This 
 is an ascending pipe enclosed in a cooling cylinder. It renders it possible to carry off 
 the vapours entering the cooling worm, Z), as concentrated (as rich in ammonia), as it 
 may be desired by simply regulating the temperature of the refrigerating cylinder, 
 which receives a constant inflow and outflow of cooling water. The more plentiful this 
 flow and consequently the colder the cylinder, R, the richer are the ammoniacal vapours 
 issuing from the tube, k. To prevent the injurious 
 cooling of the lime vessel and of the steam pipes 
 leading to it, and to supply it with more heat, 
 this lime vessel, C, is connected with the still-pan, 
 A, and the steam pipes are carried up within the 
 
 Fig- 347- 
 
 ing. 348. 
 
 Fag. 349. 
 
 spaces A and G. This is done in order to keep these parts of the apparatus as hot as 
 possible, and thus accelerate the operation as well as to convey hot vapours into the 
 acid, and thus prevent any further evaporation of the saline lye. 
 
 H. Griineberg and E. Blum further recommend, the application of a so-called 
 stairs column for gas liquor. The liquid enters above at a (Figs. 348 and 349), into 
 the upper column, which it traverses in the opposite direction to the ascending vapours, 
 so that the ammonia is expelled. From the lower column, b, the water flows through 
 the pipe, c, to the lime-vessel, d, where the combined ammonia is set free by the action 
 of milk of lime. The liquid thus treated passes through the pipe, e, to the mud bag,/, 
 and flows over upon the steps of the column to the outfall, g. Inversely the steam serving 
 
SECT. III.] 
 
 AMMONIA. 
 
 405 
 
 350. 
 
 in the distillation enters the perforated worm-tube, underneath the stair column, ascends 
 high up the column, being guided by the concentric partitions, */ passes through the 
 pipe, k, into I, which compel the steam to traverse the liquid in the lime pan, and then 
 ascends through m to the upper column, which it leaves at n, in admixture with the 
 ammoniacal vapours. Thus, the expelled water which contains only a part of the 
 ammonia liberated by the lime, comes, on the stair column, in intimate contact with the 
 fresh steam. 
 
 The apparatus of J. Gareis, designed for small gasworks, contains the liquid to be 
 distilled in the two vessels, A and C (Fig. 350), whilst B contains also an addition of 
 milk of lime, admitted from the cistern, D. The boiler, A, is heated by direct fire 
 in the grate, b, and the smoke, &c., escapes 
 through the flue, n, into the chimney. The 
 gases and vapours evolving from the liquid 
 in A, traverse the liquid mixed with milk 
 of lime in B, in the direction of the arrows, 
 heat it to a boil, and pass them in the 
 same manner through the fresh gas liquor 
 in the cistern, C, finally arriving through 
 h in the condensers, when all the ammonia 
 has been expelled by prolonged boiling 
 from the liquor in B ; this pan is emptied 
 by opening the cock, i, and after closing 
 it again the cock, k, is opened, when the 
 liquid in brushes from below into A. The 
 liquid here rises up, flows over the upper 
 edge of A, and falls into B. When this 
 has received the requisite quantity of 
 liquid the cock, k, is closed, and by opening 
 the cock, I, so much milk of lime is trans- 
 ferred from D to B as is sufficient for 
 liberating the combined ammonia. The 
 receiver, (7, is then again filled with fresh 
 gas liquor from a cistern fixed at a higher 
 level. C is advantageously filled slowly, 
 say in four hours ; to this end the gas 
 liquor, entering at , runs slowly through 
 
 the warmer, V, and arrives in the receiver, C. By removing the cover, o, the pan, A, 
 may be cleaned out as required. For cleaning B, there are several small man-holes, 
 p. The smallest size of the apparatus works up i cubic metre of gas liquor in twenty- 
 four hours, and uses 50 kilos, of waste coke. 
 
 Ammonia from Lant or Stale Urine. An adult man produces daily on an average 
 30 grammes urea, representing a yearly yield of 24*2 kilos, ammonium sulphate. Lant, 
 or .stale urine, is a very important source of ammonia. Whenever nitrogenous organic 
 bodies are decaying, ammonia is always formed ; when the organic substance is a 
 proteine compound, there is formed ammonium carbonate as well as sulphide ; but 
 when the organic substance contains no sulphur, only ammonium carbonate is formed, 
 as is the case with the urea, CH 4 N 2 O, contained in urine, the urea by taking up the 
 elements of the water being converted into ammonium carbonate. Lant is frequently 
 employed without further preparation for various purposes, on account of the ammo- 
 nium carbonate it contains, as, for instance, in washing wool and removing the fat 
 from flannel and other woollen fabrics.* 
 
 * Practical dyers maintain that lant leaves the wool in a better condition for dyeing than pure 
 ammonia or soap, and gives it a more kindly " handle." 
 
406 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. m. 
 
 The apparatus exhibited in Fig. 351, contrived by Figuera, and until lately in 
 operation at a large establishment for the utilisation of the contents of the latrines and 
 cloacae of Paris, consists of a steam-boiler, W, the steam generated in which is con- 
 veyed to two large iron cylinders filled with lant. The ammonium carbonate expelled 
 is, with the steam, condensed in a leaden worm ; the cooled liquid is conveyed to a 
 tank filled with acid, and thus converted into ammonium sulphate. The arrange- 
 ment of the apparatus is as follows : The wooden vessel, A, contains some 250 hecto- 
 litres of lant. and is filled by means of the tube, h. C and (7 are two cylindrical sheet- 
 iron vessels of 100 hectolitres capacity ; P and P' are similar vessels, the use of which 
 will be presently explained. At the commencement of the operation the boiler, W, is 
 filled with about 130 hectolitres of exhausted lant, taken from the vessels C and C'. 
 The lant in A, warm in consequence of having served for condensation, is conveyed to 
 C by a tube, and thence by the tube, h", to C', cold lant being poured into A. The 
 boiler, W, is fitted with three tubes, viz., T, the steam pipe, m, a safety tube, brought 
 to within a few centimetres from the bottom of the boiler, and carried above the roof 
 of the shed, and n a smaller safety tube ; V is a tube fitted with a stopcock. The 
 steam evolved in W is carried by T into C", evolving from the liquid therein the am- 
 
 monium carbonate it holds in solution. The carbonate, with the steam, passes through 
 t into the vessel, P, which serves to retain any liquid carried over from C'. The car- 
 bonate of ammonia vapour now passes from P through the tube, T', to C, and taking 
 up in that vessel more ammonium carbonate, is conveyed through the tube, T', into P' 
 (which again serves the purpose of P), and thence through T" into the leaden worm of 
 the condensing apparatus. The condensed liquor, a more or less concentrated solution 
 of ammonium carbonate, is run through t" into S, a wooden vessel, lead lined, and filled 
 with a sufficient quantity of sulphuric acid to saturate the ammonium carbonate. The 
 whole operation lasts about twelve hours ; after this time the waste liquid in the boiler 
 is run off by opening the stopcock, F, and the operation again repeated. On an average 
 the lant operated upon at Bondy, near Paris, yields per cubic metre from 9 to 12 kilos, 
 of ammonium sulphate, and at each operation 200 kilos, of that salt are obtained by 
 the working of one of the apparatus just described. It is stated that, from the 800,000 
 cubic metres of urine yearly run waste in Paris alone, there could be obtained, by 
 proper treatment, 700,000 to 800,000 kilos, of ammonium sulphate. 
 
 Ammonia from Bones. By the destructive distillation of animal substances, such as 
 bones, hoofs of horses, refuse horn, skins, hides, decayed meat, &c., there is obtained a 
 series of products, among which ammonium carbonate prevails, with cyanogen com- 
 pounds, ammonium sulphide, and tarry matter a very complex liquid containing 
 
SECT. III.] 
 
 AMMONIA 
 
 407 
 
 pyrrol, bases of the ethylainme series, pyridin, C 5 H 5 N, picolin, C 6 H 7 N, lutidin, C,H N, 
 and collidin, 8 H U N. The organic matter of these substances contains from 12 to 18 
 per cent, nitrogen ; the organic matter of bones contains 18 per cent, of nitrogen, and, 
 as the organic matter amounts to about one-third of the weight of the bones, these 
 contain about 6 per cent, of nitrogen. Buffalo horn contains 17, waste woollen fabrics 
 10, and old leather 6"j per cent, of nitrogen. 
 
 It is evident that the quantity of ammonia in the products of the dry distillation 
 of animal substances depends upon the kind and condition of these materials, and upon 
 the temperature at which the operation takes place. The ammonium carbonate is 
 obtained in the condensers as a solid saline mass, the crude hartshorn, or sal cornu cervi, 
 or in solution (so called spiritus cornu cervi), floating on the surface of the tar. At the 
 present time the manufacture of ammonia and its salts from the products of the dry 
 distillation of animal substances is a matter of but limited industrial importance, owing 
 to the extended coal-gas manufacture. Indeed, dry distillation is now only carried on 
 for the purpose of obtaining animal charcoal, and the occurrence of ammoniacal pro- 
 ducts is rather considered as a necessary but unavoidable evil. A large quantity of 
 animal matter is used for the manufacture of phosphorus and of prussiates, and in 
 these operations the manufacture of ammoniacal salts is either left altogether out of 
 the question or effected only on a limited scale. 
 
 Ammonia from Beet-Sugar. When the beet-root juice is boiled, ammonia is evolved 
 in large quantities, and may be utilised in the preparation of ammonium sulphate. 
 The ammonia yielded by the juice is the product of the decomposition of the aspartic 
 acid and betain present in the roots. According to Renard, a beet-root sugar manu- 
 factory which yearly consumes 200,000 cvvts. of beets might thus obtain 887 cvvts. of 
 ammonium sulphate. 
 
 Technically Important Ammoniacal Salts. Sal-ammoniac, ammonium chloride, 
 NH 4 C1, consists 100 parts of 
 
 Ammonia, 3 1 '83 ) f Ammonium, 33 75 
 
 Hydrochloric acid, 68*22) (Chlorine, 66 '25 
 
 From the thirteenth to the middle of the eighteenth century this salt was imported 
 into Europe exclusively from Egypt, where it was obtained by the combustion of 
 camel's dung. The camel feeds almost exclusively upon'- plants containing salts, and 
 the./sal-ammoniac is sometimes found ready formed in the animal's stomach. The sal- 
 ammoniac having t sublimed 
 
 with the soot from the com- Fig. 
 
 bustion of the dung, was col- 
 lected and refined by a second 
 sublimation. 
 
 In localities where dung is 
 used as fuel, it has been tried 
 to obtain sal-ammoniac by 
 combustion with common salt. 
 The first sal-ammoniac manu- 
 factory in Germany was estab- 
 lished by Gravenhorst 
 Brothers, at Brunswick, in 
 1759. We have already seen 
 how crude sal-ammoniac may be prepared from gas-water or by other means. The 
 salt, no matter whence derived, is purified by sublimation in cast-iron cauldrons, 
 W > Fi g- 35 2, Uned with fire-clay. As soon as the crude sal-ammoniac is put into these 
 vessels and tightly rammed, heat is applied, at first gently, so as to drive off any 
 
4 o8 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 353- 
 
 moisture. This effected, iron lids, F, G, H, are luted to the cauldrons ; the lids can be 
 readily moved by means of the pulleys and chains provided with counter-weights, 
 B, C, D. Instead of iron covers lead hoods sometimes are employed, the opening of 
 which is temporarily closed with an iron disc. The hoods or covers are always securely 
 fastened to the cauldrons, to prevent them being forced off by the pressure of the 
 vapours. The temperature has to be regulated during the process with great nicety, 
 for too low a degree of heat yields a loose salt, and with too high a degree of heat the 
 organic matter present in the crude sal-ammoniac is liable to give off' empyreumatic 
 matter, spoiling the appearance of the sublimed salt and interfering with its good 
 quality. Experience has proved that it is expedient to have the sublimation vessels 
 of rather large size, zj to 3 metres interior diameter. When the sublimed sal- 
 ammoniac cake has attained a thickness of 6 to 12 centimetres the operation is discon- 
 tinued and the cake removed. The furnace is provided with an oven for drying the 
 sal-ammoniac, this oven being shut with a door, E, movable by means of a chain 
 running over a pulley, and aided by a counterpoise. At the present day sal-ammoniac 
 is often sublimed in earthenware vessels or large glass flasks, the crude salt being first 
 mixed with 20 to 30 per cent, of its weight of powdered animal charcoal, then dried 
 over a good fire, and next put into the stoneware sublimation vessels, B and M, Fig. 
 353, placed in two rows over the fire-place, G. Each of these vessels is 50 centimetres in 
 
 height ; the openings are surrounded 
 by an iron plate properly fitted to the 
 neck and provided with a flange upon 
 which rest the earthenware vessels 
 wherein the sublimed sal-ammoniac is 
 condensed. When glass flasks are used, 
 the height of these vessels is 60 centi- 
 metres by 30 centimetres diameter. 
 Sixteen of these flasks, each charged 
 with 9 kilos, of the mixture of sal- 
 ammoniac and charcoal, are placed 
 upon a furnace in cast-iron pots, which 
 are filled with sand. The cover is in this case a leaden plate. The sublimation is care- 
 fully conducted, and goes on slowly, lasting about twelve to sixteen hours. After this 
 time, the leaden plates are removed, bungs or plugs of cotton-wool inserted, and the 
 flasks allowed to cool very gradually, for as the salt expands on cooling the glass 
 vessels may be broken. The cake of sal-ammoniac when quite cool is scraped clean 
 with a knife, and afterwards presents a perfectly crystalline appearance. When it 
 is desired to obtain the salt free from iron, the crude salt should be mixed, before 
 sublimation, with about 5 per cent, of superphosphate of lime, or with 3 per cent, of 
 ammonium phosphate ; by this addition any iron chloride is decomposed and left in the 
 retort as phosphate. The sal-ammoniac of commerce is met with either in a crystal- 
 line state or as a compact fibrous sublimed material ; in the latter case the cakes or 
 discs have a meniscus shape, weigh abroad from 5 to 10, but in England usually about 
 50 kilos., and exhibit the appearance of having been formed in layers. Crystalline 
 sal-ammoniac is obtained by adding to previously re-crystallised sal-ammoniac a 
 boiling hot and saturated solution of the same salt, so as to form a thickish magma, 
 which is next placed in moulds similar in shape to those in use for making loaf-sugar ; 
 after draining, the loaf of sal-ammoniac is removed, dried, and packed in paper ready 
 for sale. Besides the use made of sal-ammoniac in chemical laboratories, by pharma- 
 ceutists and veterinary surgeons, it is industrially in demand for tinning, zincing, and 
 soldering, in calico-printing and dyeing, in the manufacture of paints and pigments, in 
 the preparation of platinum, snuff, and very largely in the preparation of a mastic 
 
S-ECT. in.] AMMONIA. 409 
 
 i part of sal-ammoniac, 2 of sulphur, and 50 of iron filings used in joining steam- 
 pipes, the sockets and spigots of iron gas- and water-pipes, &c. Sal-ammoniac is also 
 employed in the preparation of pure ammonia liquida and ammoniacal salts. 
 
 Ammonium Sulphate. It has been already mentioned that ammonium sulphate, 
 (NH 4 ) 2 S0 4 , is met with native in small quantities in the mineral known as mascagnin, 
 in larger quantities in the boracic acid of Tuscany, while it is also found in Boussin- 
 gaultite. 
 
 The modes of preparing this salt from the ammoniacal water of gas-works, lant, the 
 products of the dry distillation of bones, by the aid of sulphuric acid, or by double 
 decomposition by means of gypsum or iron sulphate, have been already given. The 
 concentration of the weak solution by evaporation yields the crystalline salt, which, 
 however, when obtained from liquors containing tarry matters is usually of a deep 
 brown colour, and has therefore to be purified by being dissolved in hot water, filtered 
 through animal charcoal, and then re-crystallised, the best plan being to evaporate the 
 solution rapidly, and remove the salt gradually by means of perforated ladles. The 
 salt is then drained by being placed in baskets, and next quickly dried on heated fire- 
 clay slabs, in which operation any particles of tar are decomposed. Sulphite of 
 ammonia obtained by saturating ammonium carbonate solution with sulphurous acid 
 gas is, when exposed to air, gradually converted into sulphate. Ammonium sulphate 
 is, industrially speaking, far the most important of the ammonia salts, because besides 
 being very largely used in artificial manure mixtures, and by itself for the same 
 purpose, it is extensively employed in alum-making, and is the starting-point of the 
 preparation of ammonium chloride, ammonium carbonate, liquid ammonia, and other 
 similar products. 
 
 Ammonium Carbonate, as met with in commerce, was formerly supposed to be am- 
 monium sesquicarbonate, but the investigation of H. "Vogler, in 1878, showed that it is 
 approximately a mixture of ammonium bicarbonate and carbaminate. 
 
 The salt used in pharmacy and industry under this name is in reality ammonium 
 sesquicarbonate, and composed according to the formula 
 
 (NH 4 ) 4 3 8 , or 2 ([NH 4 ] 2 C0 3 ) + CO 2 . 
 
 It is obtained either directly from the products of the distillation of bones, or by sub- 
 liming a mixture of chalk and sal-ammoniac. 
 
 Among the products of the dry distillation of bones is found a solid sublimate, 
 essentially impure ammonium carbonate, purified by sublimation. For pharmaceutical 
 use ammonium carbonate is prepared by submitting a mixture of either ammonium 
 chloride or sulphate with chalk 4 parts of the ammonia salt, 4 of chalk, and i of 
 charcoal powder to a low red heat. The product is a perfectly pure white salt ; 
 during the operation a large quantity of ammoniacal gas is evolved, which is either 
 absorbed by water or by coke moistened with sulphuric acid. Kunheim decomposes 
 the sal-ammoniac by subliming it with barium carbonate, barium chloride being 
 obtained as a bye-product. When freshly prepared, ammonium carbonate is a trans- 
 parent crystalline mass, which, while absorbing water from the atmosphere, and 
 evolving ammonia, is superficially converted into ammonium bicarbonate (ammonium 
 
 "VTTT , 
 
 hydrocarbonate, jr 4 [ C0 3 ). Owing to the penetrating odour emitted by this salt, 
 
 it is known as smelling salts. Impure ammonium carbonate is also used for cleaning 
 woollen and other fabrics, for the removal of grease from cloth, and further, for the 
 production of the orchil pigments. Pure ammonium carbonate, besides its use in 
 pharmacy, is an ingredient of baking and yeast powders. 
 
 Ammonium Nitrate. This salt, (NH 4 )N0 3 , is prepared by the double decomposition 
 of solutions of ammonium sulphate and potassium nitrate. The potassium sulphate 
 is first separated, and the solution of ammonium nitrate having been concentrated by 
 
4 jo CHEMICAL TECHNOLOGY. L SEGT - m - 
 
 evaporation is left to crystallise, its crystalline form being similar to that of saltpetre, 
 When dissolved in water this salt produces cold, and is therefore used in freezing 
 mixtures ; while the fact that when strongly heated it is converted into nitrous oxide 
 and steam (N 3 + 2H 2 0) might perhaps render it of use in the preparation of a 
 blasting powder. 
 
 The manurial value of ammoniacal salts is, according to C. 0. Harz, higher than it 
 is commonly assumed. Barley, rice, clover, peas, flourish better with ammoniacal 
 manures than with nitre. The behaviour of maize and oats is the reverse ; wheat and 
 barley take an intermediate position, wheat inclining more to ammonia. 
 
 PHOSPHORUS. 
 
 Phosphorus is widely distributed in nature as phosphates. The most important 
 phosphatic mineral is Apatite, Ca 3 Cl (P0 4 ) 3 , which as Phosphorite and Staffelite forms 
 massive deposits ; less abundant are Vivianite, Fe 3 (P0 4 ) a .8H 3 ; Turquoise, 
 
 A1 2 P0 4 (OH) 3 H 2 0, 
 
 and pyromorphite, Pb 5 Cl(P0 4 ) 3 . Phosphorus is a frequent constituent of iron ores 
 and a very important ingredient of agricultural soils, being necessary for all culti- 
 vated plants. Phosphorus is also an indispensable constituent of the animal body 
 e.g., of the brain ; the bones consist chiefly of calcium phosphate. 
 
 Preparation of Phosphorus. Bone-ash is now the only material used by phosphorus 
 makers, as the commercial preparation of phosphorus has not succeeded by using either 
 apatite and other varieties of pure phosphorite which contain about 18-6 per cent, of 
 phosphorus as well as sombrerite (a mineral met with on the American island of 
 Sombrero), consisting of calcium phosphate and carbonate, and imported into England 
 for the manufacture of superphosphates ; or the Navassa guano, also imported from 
 the United States, containing, according to Ulex's researches, one-third of its weight 
 of phosphoric acid ; or iron phosphate, as proposed by Minary and Soudray, by dis- 
 tilling that substance with previously well-ignited coke-powder. 
 
 Bones, as used by the manufacturers, contain : 
 
 In dry state, but not ignited, from n to 12*0 per cent, of phosphorus. 
 As bone-black 16 to i8'o 
 
 As bone-ash (white burnt bones) 20 to 25 -5 
 
 The composition of bone-ash is exhibited by the following results of analysis : 
 
 i. a. 
 
 Calcium carbonate ..... 10^07 ... 9*42 
 
 Magnesium phosphate . . . . 2-98 ... 2*15 
 
 Tricalcium phosphate . . . . 83 '07 ... 84*39 
 
 Calcium fluoride ..... 3-88 ... 4^05 
 
 The bone-ash is decomposed by means of sulphuric acid, according to a plan first 
 suggested by Nicolas and Pelletier : 
 
 a. Bone-ash, Ca 3 (P0 4 ) 2 } . , , ( Acid calcium phosphate, CaH 4 (P0 4 ) z 
 
 Sulphuric acid, 2H a S0 4 J (Calcium sulphate, 2CaS0 4 . 
 
 The acid calcium phosphate is heated with charcoal, and converted by loss of water 
 into calcium metaphosphate : 
 
 Acid calcium Calcium 
 phosphate. metaphosphate. 
 
 Calcium metaphosphate yields, when ignited to a white heat with charcoal, two- 
 thirds of its weight of phosphorus, while one-third remains in the residue 
 
SECT, in.] PHOSPHORUS. 411 
 
 ~ , . , , ,-rt^. x . ( Tribasic calcium phosphate, Ca_(PO,) g 
 
 c. Calcium metaphosphate, 3Ca(PO 3 U lrl ! . . s\ 4/2 
 
 i ,-N y ielcl 1 Carbonic oxide, i oCO 
 
 Charcoal, loC ' 1-. i l 
 
 "Phosphorus, 4P. 
 
 The ordinary mode of preparing phosphorus includes the following operations : 
 In some instances the preparation of phosphorus is cotemporary with other busi- 
 nesses, viz., glue-boiling, the preparation of sal-ammoniac, yellow prussiate of potash, 
 ifec., but generally in England the phosphorus makers do not even burn the bones to 
 ashes, but purchase bone-ash and occasionally apatite ; this salt, however, is very diffi- 
 cult to treat with sulphuric acid, and is also objected to on account of its hardness, for 
 it has to be ground to a very fine powder. English makers only carry out these 
 four processes : 
 
 i. Burning the bones and grinding the bone-ash to powder. 
 
 2 Decomposition of the bone-ash by sulphuric acid, and evaporation of the acid 
 phosphate previously mixed with charcoal. 
 
 3. The distillation of the phosphorus. 
 
 4. The refining and preservation of the phosphorus. 
 
 Burning of the Bones to Ash. i. The bones to be used for phosphorus making are 
 obtained either from bone-boilers or from the waste bone-black of sugar-refiners. The 
 aim of the ignition of the bones is the complete destruction of the organic matter. 
 The operation is conducted in a kiln very similar to those in use for burning lime. 
 A layer of brushwood having been put at the bottom of the kiln, bones form the next 
 stratum, and so on alternately. The wood having been lighted, the combustion of the 
 bones ensues. In order to carry off" the fumes, the smell of which is very offensive, a hood 
 made of boiler-plate is placed on the kiln, and either connected with a tall chimney, or 
 the smoke and gases are conducted into the fire of the kiln and burnt. The white 
 burnt bones are withdrawn through an opening reserved in the wall on purpose, the 
 kiln being kept continuously in operation, as is the case with some lime-kilns. 
 
 100 kilos, of fresh bones yield from 50 to 55 kilos, of white burnt bone-ash, which 
 is converted into a coarse powder by means of machinery. 
 
 Decomposition of the Bone-ash l>y Sulphuric Acid. 2. 100 kilos, of the bone-ash, of 
 which about 80 per cent, is tribasic phosphate, require for decomposition : 
 10673 kilos, sulphuric acid of 1-52 specific gravity. 
 85-68 17 
 
 73 '63 .. 1<8 o 
 
 Payen advises that for 100 kilos, of bone-ash 100 parts of sulphuric acid at 50 per 
 cent, or 1-52 sp. gr. be taken. The operation of mixing the acid and bone-ash is 
 effected in lead-lined wooden tanks, or in wooden tubs internally coated with pitch or 
 coal-tar asphalte. The liquor decanted from the precipitate has a sp. gr. of 1*05 to 
 1-07 = 12 to 14 Tw. The sediment is lixiviated with water, and the liquor obtained 
 ( = 6 to 8 Tw.) evaporated with the first liquor in leaden pans. A second lixiviation 
 of the sediment yields a fluid which is used instead of water for the purpose of diluting 
 the oil of vitriol. The evaporation in the leaden pans (these are smaller, but otherwise 
 similar in construction to those used for evaporating sulphuric acid) is continued until 
 the fluid has attained a sp. gr. of i'45 = 84Tw., when it is mixed with charcoal- 
 powder, or rather granulated charcoal, of the size of small peas, in the proportion of 20 
 to 25 parts of charcoal to 100 of liquor, and quickly dried after having been put into 
 cast-iron pots placed on a furnace. 
 
 The dry mass consists of phosphate of lime, carbon, and water, to an amount of 
 5 to 6 per cent. At the commencement of the manufacture of phosphorus the idea 
 prevailed that in the preceding preparation the phosphoric acid was present in the free 
 -tate, while the lime had combined with sulphuric acid ; but Fourcroy and Vauquelin 
 tinding that the tribasic calcium phosphate as met with in bone-ash (Ca 3 (P0 4 ) 2 ) was, by 
 
4t2 CHEMICAL TECHNOLOGY. [SECT. ra. 
 
 the action of the sulphuric acid, converted into acid calcium phosphate (CaH 4 (PO 4 ) 2 ), 
 supposed that more sulphuric acid was required, an opinion opposed by Javal, who 
 proved that when pure phosphoric acid is intimately mixed with carbon, it yields only 
 a small quantity of phosphorus, because the acid is volatilised at a temperature lower 
 than that required for its decomposition, or rather reduction by carbon. Owing to 
 the presence of water in the mixture, there is given off during the distillation in addi- 
 tion to oxide of carbon, hydrogen carbide and phosphide. 
 
 Distillation of Phosphorus. 3. The mixture of acid calcium phosphate and char- 
 coal is distilled in fire-clay retorts similar in shape to those used for distilling Nbrd- 
 hausen sulphuric acid, while the furnace in which these retorts are placed is also 
 similar in construction and holds twelve retorts on each side. The body of the retorts 
 is placed on the side of the fire, while the neck passes through an opening in the wall 
 of the furnace, that portion of the wall being only lightly bricked up, as the retorts, 
 after the distillation is finished and the furnace cooled, have to be removed, in order 
 to clear out the residue and introduce fresh mixture. Between each pair of retorts is 
 left a space of some 1 2 to 15 centimetres, in order to afford room for the passage of the 
 flame. As already mentioned, the heat causes the acid calcium phosphate, (CaH 4 (P0 4 ) s ), 
 to be converted into calcium metaphosphate, (Ca(P0 3 ) 2 ), which, with increased heat, 
 gives off two-thirds of its phosphorus, there being left in the retorts one-third in the 
 shape of calcium triphosphate, (Ca 3 (P0 4 ) 2 ). The receivers used in Germany are con- 
 structed in the following manner : The material is clay, glazed. The receiver consists 
 of two parts, one of which is a cylindrical vessel open at the top, into which the other 
 part fits, and is fixed by means of a rim which is prolonged so as to form a neck, 
 between which and the first part is inserted a tube fitted on the neck of the retort, 
 while the other end of this tube dips for about 10 centimetres into the receiver, the 
 latter being filled with water. Into each retort 6 to 9 kilos, of the mixture intended 
 to be operated upon are introduced ; the retorts are then placed in the furnace and the 
 brickwork is restored. This having been done, the fire is kindled and kept up very 
 gently for some time in order to dry the fire-clay used in joining the bricks. The 
 receivers are filled with water and fitted to the retorts. In each receiver a small iron 
 spoon is placed fastened to an iron wire which serves as a stem. After six to eight 
 hours' firing the heat has been so much increased as to cause the expulsion of any 
 moisture left in the material placed in the retorts, while quantities of hydrocarbon gase? 
 and oxide of carbon are formed and expelled with the sulphurous acid. Subsequently 
 other gases are given off, and because they contain some hydrogen phosphide are 
 spontaneously inflammable. As soon as this phenomenon is observed, the joints of the 
 receivers and apparatus connecting it with the retort are luted with clay, care being 
 taken to leave, by the insertion of an iron wire, a small opening for the escape of the 
 gases, which are as speedily as possible removed by well-arranged ventilators from the 
 building in which the furnace is placed. The appearance of amorphous phosphorus at 
 the small opening indicates the commencement of the distillation. The spoon is then 
 placed in the receiver in such a direction that any phosphorus coming over may collect 
 in it. During the progress of the operation, and as long as any phosphorus distils 
 over, the evolution of combustible gases continues, and consequently a small blue- 
 coloured flame is observed at the opening in the lute. The water in the receivers is 
 kept cool during the operation. After forty-six hours, with a greatly increased firing, 
 a full white-heat is reached, and the quantity of phosphorus coming over has decreased 
 so much as to make a continuation of the ignition process wasteful. The receivers 
 are therefore disconnected from the retorts, and the crude phosphorus, a mixture of 
 phosphorus, phosphorus silicide and carbide, amorphous phosphorus, and other allotropic 
 modifications of this element, is poured into a tub containing water. The furnace 
 having become cool is broken up and the retorts are removed, the contents taken out 
 
CECT. III.] 
 
 PHOSPHOKUS. 
 
 413 
 
 with an iron spatula, and the retorts replaced after having been re-filled with fresh 
 mixture. 100 kilos, of the mixture yield about 14-5 kilos, of crude and 12-6 kilos, of 
 refined phosphorus. As to Wohler's method of preparing phosphorus by the ignition 
 of a mixture of charcoal, sand, and bone-ash, the process is not well adapted for 
 practical use, because it requires a very high temperature, which would melt, or nearly 
 so, and at any rate soften, the retorts. Moreover, the proposed mixture contains only 
 one-third the quantity of phosphoric acid met with in the mixture now in general 
 use. 
 
 Refining and Purifying the Phosphorus. 4. As already stated, the crude phos- 
 phorus is contaminated with carbon, silicon, red and black phosphorus, and various 
 other impurities, which in former days were eliminated by forcing the phosphorus 
 through the pores of stout wash-leather by means of a machine exhibited in Fig. 354, 
 C representing a tightly tied piece of wash-leather containing the crude phosphorus, 
 
 Fig. 354- 
 
 Fig. 355- 
 
 G 
 
 Fig. 356. 
 
 the bag being placed on a perforated copper support, situated in a vessel filled with 
 water at 50 to 60. As soon as the phosphorus is molten, there is placed on the 
 wash-leather a wooden plate, D D, which by the aid of the mechanical arrangement E, 
 and the lever, G G, can be forced downwards so as to cause the fluid phosphorus to 
 pass through the pores of the leather, the impurities being retained. More recently 
 French manufacturers have introduced another system of purifying phosphorus, viz. : 
 . By filtration through coarsely powdered charcoal, which is placed in a layer of 6 to 
 10 centimetres on a perforated plate of the vessel, A, Fig. 355, two-thirds filled with 
 water, kept by means of the water-bath, B, at a temperature of 60. The molten 
 phosphorus placed on A passes through the layer of charcoal, and is thereby purified. 
 It flows through the open tap, (7, and the tube, E (Fig. 356), being collected in the 
 vessel, F, filled with water, maintained by means of the water-bath, 6f, at a tempera- 
 ture sufficiently high to render the phosphorus fluid, so that it may, when aided by 
 hydraulic pressure, pass through the perforated bottom, II, and the wash-leather 
 spread over it. The filtered phosphorus may be run off by means of the tap, J. 
 
 According to another process of purification (6), porous, unglazed porcelain or 
 earthenware plates are fixed in an iron cylinder connected with a steam-boiler. The 
 steam yielded by the latter forces the molten phosphorus previously mixed with char- 
 coal powder for the purpose of preventing the pores of the plates becoming choked 
 through the earthenware plates. The charcoal containing some phosphorus is used in 
 the distillation of the phosphorus. This method of purification yields from 100 kilos. 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. HI. 
 
 of crude, 95 kilos, of refined, phosphorus. In Germany crude phosphorus is purified 
 by distillation, this operation being carried on in iron retorts of a peculiar make, and 
 shaped like the glass retorts used in chemical laboratories. The neck of these retorts 
 dips for a depth of 15 to 20 millimetres in water contained in a basin filled to the 
 rim, so that any phosphorus which is discharged into this water causes it to over- 
 flow. The crude phosphorus having been fused under water is next mixed with 12 
 to 1 5 per cent, of its weight of moist sand, and this mixture is placed in the retorts 
 in quantities of 5 to 6 kilos., the object of the mixing with sand being to prevent 
 the phosphorus becoming ignited during the filling of the retorts. Crude anhydrous 
 phosphorus yields by this process of distillation about 90 per cent, of the refined 
 product. In a phosphorus manufactory at Paris the crude phosphorus is purified by 
 chemical means viz., by mixing with TOO kilos, of the crude substance 3-5 kilos, of 
 sulphuric acid and the same quantity of bichromate of potash ; a slight effervescence 
 ensues, but the result is that the phosphorus is rendered very pure, and may, after 
 washing with water, be at once cast in the shape of sticks. The yield of refined phos- 
 phorus by this process is 96 per cent. 
 
 Moulding the Refined Phosphorus. It has long been the custom to mould phos- 
 phorus into the shape of sticks formed by the aid of a glass tube open at both ends, 
 one of these being placed in molten phosphorus covered by a stratum of warm water. 
 The liquid phosphorus is sucked by the operator into the tube until it is quite filled. 
 The lower opening of the tube being kept under water is closed by the finger of the 
 operator ; the tube is instantly transferred to a vessel filled with very cold water, bv 
 which the phosphorus is solidified. It is removed from the glass tube by pushing it 
 out with a glass rod or iron wire while being held under water. Instead of suction by 
 the mouth, a caoutchouc bag similar to that used in volumetric analysis for the purpose 
 of sucking liquids into pipettes may be employed. In the French phosphorus works 
 the glass tubes are fitted at the top with an iron suction tube provided with a stop- 
 cock. The operator, who has from one to two thousand of these tubes at his disposal, 
 sucks, either by mouth or with a caoutchouc bag, the molten phosphorus into the glass 
 tube, and having turned off the stop-cock, rapidly transfers the tube to a vessel filled 
 with cold water. When all the tubes are filled the phosphorus is removed by opening 
 
 the stop-cock and pushing the stick out 
 
 Fig 357. by the aid of a wire. A clever work- 
 
 man may mould in this way 2 cwts. of 
 phosphorus daily. 
 
 Another mode of performing the 
 moulding has been introduced by Seu- 
 bert. The apparatus contrived by him 
 for this purpose is exhibited in Fig. 357, 
 and consists of a copper boiler fitted 
 on a furnace ; to the flat bottom of 
 this boiler is fastened by hard solder 
 an open copper trough communicating 
 with the water-tank, C. In the boiler 
 is fitted a copper funnel, A, provided 
 with a horizontal tube, B. This portion 
 of the apparatus is intended for the 
 reception of the phosphorus, of which 
 
 it will hold 8 to 10 kilos. At the end of the horizontal tube is placed a stop-cock, B, 
 while the portion of the projecting mouth of the tube beyond the cock is widened 
 out and fitted by means of bolts and nuts, with a flange-like copper plate, into which 
 are inserted two glass tubes, a a. Into the copper trough is let a wooden partition, 
 
SECT, m.] PHOSPHORUS. 415 
 
 c c, which serves the purpose as well of supporting the glass tubes as of preventing the 
 communication of the hot water in the boiler and a portion of the trough with the 
 cold water of the tank and the portion of trough nearest to it. The vessel A having 
 been filled with refined phosphorus, the water in D is gently warmed so as to cause the 
 fusion of the phosphorus. As the warm water reaches to the partition, c c, it is clear 
 that on opening and closing the tap B, some phosphorus will pass through and flow 
 out of the tubes a a, but that remaining in these tubes will solidify, and on opening 
 the tap B again the soh'd sticks of phosphorus may be removed from the glass tubes 
 by taking hold of the piece of projecting phosphorus, the phosphorus being imme- 
 diately immersed under water in the tank C, and kept there protected from the 
 action of the light. While, according to Seubert, it would be possible for a workman 
 to mould in an hour's time 30 to 40 kilos, of phosphorus, Fleck has found that, under 
 the most favourable conditions of temperature, it takes six hours to mould 50 kilos, 
 of phosphorus. If it is desired to prepare granulated phosphorus with this apparatus, 
 a stratum of 6 to 8 centimetres thickness of hot water is so carefully poured on cold 
 water as not to mix ; next the tap, B, is opened sufficiently to cause the phosphorus 
 to form drops, which, immediately on falling into the cold water, becomes a hard solid 
 mass. For practical purposes granulated phosphorus is preferable to the moulded 
 sticks. The phosphorus is stored either in strong sheet-iron tanks or in wooden boxes 
 lined with thinner (tinned) sheet-iron, these vessels being capable of holding 6 cwts. 
 of phosphorus covered with a stratum of water fully 3 centimetres deep. When large 
 quantities, say, from i to 5 cwts., of phosphorus have to be sent off, it is usually 
 packed in water in small wine casks, and the casks having been tightly closed, are 
 coated externally with molted pitch, then rolled through chaff, and lastly covered with 
 stout canvas sewed tightly round the cask. Another method of packing phosphorus 
 consists in placing it in well-made water-tight sheet-iron or tinned iron canisters, such 
 as are largely used in London for the purpose more particularly of conveying oil 
 paints, and which are closed by soldering on a lid very securely. In some cases these 
 canisters are packed in wooden boxes to the number of six or twelve, according to size 
 and weight. 
 
 The process for obtaining phosphorus proposed by Fleck depends on the solubility 
 of calcium phosphate in hydrochloric acid and its separation as acid calcium phosphate 
 on evaporating down the solution in stoneware vessels. According to theory 156 
 parts calcium triphosphate Ca 3 (P0 4 ) 2 require 73 parts anhydroiis hydrochloric acid, 
 yielding in parts calcium chloride, 100 parts acid calcium phosphate, and 18 parts of 
 water. On igniting 100 parts acid calcium phosphate and 20 parts carbon there are 
 formed 21-3 parts phosphorus, 5*2 parts calcium triphosphate, and 46*7 parts carbon 
 monoxide. If the residual mixture of calcium triphosphate and carbon is incinerated 
 and again treated with hydrochloric acid, calcium phosphate is again obtained from the 
 solution on evaporation and so on. It is thus possible to extract in this manner all 
 the phosphorus from the bones if the acid is free from sulphuric acid. The bones, 
 cleansed, broken up and freed from fat, are treated with dilute hydrochloric acid at 
 10 Tw. The bones are then laid in hydrochloric acid at 5 Tw., in which they are left 
 until completely softened ; this second liquid serves instead of water for mixing the 
 acid for the lixiviation of fresh bones. When the first liquid, a solution of acid 
 calcium phosphate and calcium chloride, marks 24 Tw., it is placed in the evaporating 
 vessels. 
 
 In the choice of these vessels lies one of the difficulties of the Fleck process, as 
 hydrochloric solutions cannot be evaporated in leaden vessels, but require the use of 
 stoneware vessels, not easy to be procured. The lye crystallises when it reaches 50 Tw. 
 The crystalline paste is pressed and mixed with one-fourth its weight of charcoal powder 
 in an earthen pan at 100 and rubbed through a copper sieve. The crude phosphorus 
 
416 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 obtained is refined and moulded as usual. The residue of calcium phosphate and 
 carbon is incinerated and lixiviated with strong hydrochloric acid. The bones which 
 have been freed from calcium phosphate are worked up for glue. 
 
 Properties of Phosphorus. When perfectly pure and kept under distilled water, 
 which previously to being employed for this purpose has been by boiling deprived of 
 the air it held in solution, and has been cooled either under a layer of oil or in well- 
 stoppered bottles, and in perfect darkness, phosphorus is a colourless and transparent 
 substance ; but usually it has a white-yellow colour and waxy appearance. Its sp. gr. 
 is = i"3 to i '84. When the temperature of the air is not too low this element is as 
 soft as wax, but becomes brittle in cold weather. Phosphorus cannot be pulverised ; 
 is tough ; but when molten in a bottle under warm water and shaken until the fluid 
 is quite cold the substance is thereby reduced to a finely divided state ; instead of 
 water it is better to use either alcohol, urine, or a weak aqueous solution of urea. 
 Phosphorus fuses at 44 to 45, and remains, especially if kept under an alkaline 
 solution, fluid for a considerable time though cooled far below its melting-point, but 
 solidifies suddenly when touched by a solid body. At 290 phosphorus boils, and it 
 evaporates sensibly at the ordinary temperature of the air. By slow oxidation (fumes 
 of phosphorus are given off at the ordinary temperature of the air) there is formed not 
 only phosphorus acid but nitrate of ammonia and antozone. Phosphorus is in the 
 state of vapour slightly soluble in water. The solid element itself is slightly soluble 
 in alcohol and ether, also in linseed oil and oil of turpentine, the best solvents being 
 sulphide of carbon, chloride of sulphur, and chloride of phosphorus. At 75 phos- 
 phorus ignites in contact with air, and in order to ignite it by friction this temperature 
 has to be reached. Amorphous or red phosphorus requires a very high temperature 
 (300) for ignition. Commercial phosphorus usually contains some impurities, such as 
 sulphur, arsenic, and sometimes traces of calcium, due to the lime of the bone-ash used 
 in the preparation. Beside being used in chemistry, phosphorus is chiefly employed in 
 the making of matches ; also for what is termed liquid fire (a solution of phosphorus 
 in sulphide of carbon), for the preparation of tar colours, and for hardening some 
 copper alloys. 
 
 Amorphous or Red Phosphorus. Dr. Schrotter, of Vienna, discovered in 1848 that 
 the property possessed by ordinary phosphorus (first noticed in 1844 by E. Kopp) of 
 
 becoming coloured red by the action of light, was 
 
 Fl '-- 358. d ue to the formation of an allotropic modification, 
 
 which has been since termed red or amorphous 
 phosphorus. This is best prepared by heating 
 ordinary phosphorus, with exclusion of air and 
 water, in a closed vessel and under pressure, to 
 250 for a length of time. On the large scale this 
 operation is conducted in an apparatus invented 
 by A. Albright, of Birmingham. In Fig. 358, 
 g represents a glass or porcelain vessel, filled for 
 five-sixths of its capacity with pieces of phosphorus 
 to be heated to 230 to 250. The vessel, /, is 
 placed in a sand-bath, b, heated by the fire. To 
 the vessel, g, is fitted an air-tight lid, into which 
 is fastened the bent tube, i, provided with a tap, 
 k, and dipping into the vessel, n, which is filled 
 with water, or preferably with mercury covered 
 with a layer of water. The tap, k, is left open at the commencement of the operation 
 for securing the escape of the air contained in g, and as soon as no more air escapes 
 the tap is closed, and the heat increased so as to convert the ordinary into amorphous 
 
SECT, in.] MATCHES: PRODUCTION OF FIRE. 417 
 
 phosphorus. The time required for the operation depends upon conditions which 
 can be met only by experience. After the thorough cooling of the apparatus, the 
 vessel, g, is opened, and the red phosphorus removed. It is then placed under water 
 and crushed to a pulp in order to remove any unconverted ordinary phosphorus. 
 Carbon disulphide might be used for this purpose, but the danger of ignition (by 
 accident) of the solution of ordinary phosphorus thus obtained is prohibitive. Nickles 
 proposes to separate ordinary from amorphous phosphorus by shaking up the mixture of 
 amorphous and ordinary phosphorus with a fluid, the specific gravity of which is less 
 than that of amorphous phosphorus (2*1), and greater than that of ordinary phos- 
 phorus (i'84). A solution of calcium chloride at 66 to 71 Tw. can be used for this 
 purpose ; the ordinary phosphorus floats in this fluid and can then be readily taken 
 up by carbon disulphide, while the operation can be carried on in a closed vessel. 
 When very large quantities of amorphous phosphorus have to be purified it is best 
 to follow Coignet's plan, consisting in treating the boiling mixture of the two varieties 
 of phosphorus with caustic soda solution, whereby the ordinary phosphorus is con- 
 verted into phosphuretted hydrogen gas, and sodium hypophosphite formed, the 
 remaining amorphous phosphorus being purified by washing with water. R. Bottger 
 suggests the use of a solution of copper sulphate, which with ordinary phosphorus 
 forms copper phosphide. 
 
 Properties of Amorphous Phosphorus. This substance occurs either in powder of a 
 red or scarlet colour or in lumps of a red-brown hue ; fracture conchoidal, sometimes 
 with an iron-black hue; sp. gr. = 2'i. Amorphous phosphorus is not soluble in 
 carbon disulphide or other solvents of ordinary phosphorus. It is unaltered by 
 exposure to air ; and when heated to 290 is re-converted into ordinary phosphorus. 
 When mixed and rubbed with dry potassium bichromate, red phosphorus does not 
 explode, and when mixed with nitre it does not burn off by friction, but only by 
 application of heat, and then noiselessly. It explodes, however, when mixed with 
 potassium chlorate. With lead peroxide, amorphous phosphorus ignites by friction 
 with a slight explosion, but when heat is also applied a violent explosion ensues. 
 
 Owing to its properties and behaviour with several oxides, its non- volatility 
 and non-poisonous properties, as well as on account of its less ready ignition, 
 amorphous phosphorus is an excellent material for the making of matches ; but 
 amorphous phosphorus is not in general use for this purpose. It is, however, used for 
 preparing phosphorus iodide, which serves for the preparation of iodides of amyl. 
 ethyl, and methyl, used in the manufacture of cyanin, ethyl violet, and other coal-tar 
 colours. Sir William Armstrong's explosive mixture for shells contains amorphous 
 phosphorus and potassium chlorate. From 66,000 cwts. of bones there are annually 
 prepared in Europe some 5500 cwts. of phosphorus. 
 
 The production of phosphorus in 1 880 was approximately as follows : 
 
 England (Albright & Wilson at Oldbury, near Birmingham) 1750 tons 
 France (Coignet Freres, at Lyons) . . . . . 1500 ,, 
 Philadelphia 18 
 
 There is a phosphorus factory in Sweden, but its output is not known. The yearly 
 consumption of phosphorus in Germany is estimated at 1200 tons. 
 
 MATCHES: PRODUCTION OF FIRE. 
 
 In the year 1823, Dobereiner, at Jena, discovered that finely divided spongy 
 platinum has the property of igniting a mixture of atmospheric air and hydrogen gas, 
 and he contrived the so-called Dobereiner hydrogen lamp, which has been, and is still 
 occasionally, employed to procure fire and light. About the same period there was 
 invented a kind of phosphorus match of the following arrangement : Equal parts of 
 
 2 D 
 
4 i 8 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 sulphur nnd phosphorus were cautiously fused in a glass tube ; after the fusion was 
 completed the tube was tightly corked. If it were desired to obtain fire, a thin splint 
 of wood was immersed in this mixture, and some of it having been fixed to the wood, the 
 latter on being brought into the air became ignited by the combustion of the mixed 
 substances, which took fire spontaneously in the air. It is evident that this rather 
 clumsy contrivance never became general. Of far more importance as suited for 
 practical purposes were the chemical matches or dip splints, first manufactured at 
 Vienna, as early as 1812. These splints were tipped with sulphur covered with a 
 mixture of potassium chlorate and sugar, to which for the purpose of imparting colour 
 was added some vermilion, while a little glue gave a pasty and adhesive consistency. 
 By touching this composition with concentrated sulphuric acid ignition ensued ; 
 the acid was kept in a small glass or leaden bottle into which some asbestos had been 
 inserted, which acted as a sponge for the acid. The only friction matches known up 
 to the year 1844 were discovered and made by M. Chancel, assistant to the well-known 
 Professor Theiiard of Paris, 1805. The " Promethean s," first made in England in or 
 about the year 1830, were contrived on the same principle, viz., the ignition, by friction 
 between two hard substances, of a mixture of potassium chlorate and sugar fixed to a 
 kind of paper cigarette, which contained also a small glass globule filled with sulphuric 
 acid ; however, the high price of this kind of match prevented its general use. Under 
 the name of " Congreves" the first real friction matches were made in 1832. On the 
 sulphur-tipped splints was glued a small quantity of a mixture of one part of potas- 
 sium chlorate and two parts of black antimony sulphide, to which some gum or glue 
 was added. By strongly rubbing this composition between two pieces of sand-paper 
 the mixture became ignited, but frequently also, on becoming detached from the wooden 
 splint, flew about in all directions without igniting the sulphur or the wood. It is not well 
 known who was the first to substitute phosphorus for antimony sulphide ; but accord- 
 ing to Nickles, phosphorus matches were already used in Paris as early as 1805, while 
 in 1809 Derepas proposed to mix magnesia with phosphorus in order to lessen its great 
 inflammability when in a finely divided state. Derosne (i Si 6) appears to have been the 
 first who made phosphorus friction matches at Paris. However, it was not before the 
 middle of 1833 that phosphorus matches became more generally known, when 
 Preshel, at Vienna (a city famous for the match and fusee industry), made not 
 only phosphorus matches, but also fusees and German tinder slips tipped with the 
 phosphorus composition. About the same period F. Moldenhauer, at Darmstadt, made 
 phosphorus lucifer matches. The South Germans attribute to Kammerer the invention 
 of phosphorus lucifer matches, while in England, according to the opinion of the late 
 celebrated Faraday, John Walker, of Stockton, Durham, was the inventor of lucifer 
 matches, or at least the first maker. The older kind of matches, although very com- 
 bustible, ignited with a rather sharp report, owing to the presence of chlorate of potash 
 in the mixture, while, moreover, the too ready ignition by concussion rendered the 
 carriage of these matches so unsafe that in Germany the transport, as well as the 
 manufacture, became prohibited. In the year 1835 Trevany substituted a mixture 
 of red lead and manganese for a portion of the chlorate of potash, thereby greatly 
 improving the composition. In 1837 Preshel altogether discarded this salt, substituting 
 peroxide of lead, or, as Bottger advised, either a mixture of red lead and potassium 
 nitrate, or of lead peroxide and nitrate. From this period the manufacture of matches 
 became an extensive industry, greatly aided by the manufacture of phosphorus on 
 the large scale. 
 
 In the course of time other improvements were made, as, for instance, the substitu- 
 tion for sulphur of wooden splints, thoroughly dried and soaked in wax, paraffine, or 
 stearic acid, and the coating of the composition with a varnish to protect it from the 
 action of moisture, while, at the same time, the appearance of the matches was 
 
SECT, in.] MATCHES: PRODUCTION OF FIRE. 419 
 
 rendered more ornamental. At the present day matches are the product of an industry 
 which cannot possibly be much more improved in a technical point of view, besides 
 being, as regards price, within the reach of all. 
 
 However useful phosphorus lucifer matches may be, it is a great drawback to their 
 utility that the combustible composition is a poisonous mixture ; while, moreover, the 
 workpeople engaged in that department of the lucifer-match making in which the 
 phosphorus is handled are often affected by a peculiar kind of caries of the jawbones, 
 the real cause of which is the more difficult to ascertain as the workpeople engaged in 
 the manufacture of phosphorus, and exposed to its vapours to such an extent as to 
 render their breath luminous in the dark, are not similarly affected. The discovery of 
 the red or amorphous phosphorus, which is neither poisonous nor very inflammable, 
 affords a happy substitute for the ordinary phosphorus, but the former is by no means 
 generally used in the preparation of matches. 
 
 Manufacture of Lucifer Matches. The operations required are : 
 
 1. The preparing of the splints of wood. 
 
 2. The mixing of the combustible composition. 
 
 3. The dipping, drying, and packing of the matches. 
 
 i. The Preparation of the Wooden Splints. Generally white woods are used for 
 this purpose, such as white fir, pine, aspen, more rarely fir (Fohrenholz), some- 
 times beech, lime-tree, birch, willow, poplar, and cedar. The shape of the splints 
 is usually square in section, but abroad the splints are sometimes cylindrical. 
 The square splints are readily made by hand, simply by splitting up a block of 
 wood of the length required for the splint. A cutting tool, a large knife, similar 
 to that which is sometimes used by chaff-cutters, is very frequently used for the 
 purpose of cutting the wooden splints, while a contrivance similar to that in use 
 for propelling the hay or straw forward is also employed, being so arranged as, after 
 every cutting stroke, to propel the wood the length required for a splint. More 
 generally the operation of splitting the block of wood parallel to its fibres and next 
 cutting off the splints to the required length is effected by machinery, consisting of fixed 
 knives, against which the wood is moved with sufficient force to split it up into splints, 
 which are next cut to the required length. Instead of splitting the wood by these 
 means, the splints are now in Germany always made by a kind of plane, invented by 
 S. Romer, of Vienna, by which the wood is cut into circular splints. The cutter of 
 this plane differs from that of the ordinary carpenter's plane in possessing, instead of 
 the cutting edge, a slight bend, in which three to five holes have been bored in such a 
 manner that one of the edges of these holes is sharpened ; in practice, three holes are 
 preferred. When this plane is forced against a lath of wood, placed edgeway, the 
 cutting tool penetrates into the wood, splitting it up into as many small sticks or 
 splints as the cutter contains holes. When a number of thin splints have been cut 
 from the lath, it is again planed true with an ordinary plane and then the operation 
 repeated. The dividing of the thin sticks into splints of the required length is effected 
 by a tool consisting of a narrow trough about 6 centimetres wide and provided with a 
 slit in which works a knife fastened to a lever. A clever workman can prepare 400,000 
 to 450,000 splints daily. In the south-west of Germany a plane for cutting wooden 
 splints, the invention of Anthon, at Darmstadt, and similar in action and construction 
 to that above mentioned, is in general use ; but throughout an extensive portion of the 
 empire the manufacture of the splints has become a separate trade, often carried on in 
 woods and forests, the splints being sold to the lucifer-match makers in bundles ready 
 for dipping. 
 
 Instead of making the splints by hand, they are occasionally made by a machine, 
 such as that of Pelletier, at Paris (1820), having on a bench a plane 36 centimetres 
 long by 9 wide, made to move backwards and forwards, while a piece of wood is placed 
 
420 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 so that it is caught by the fore-cutter, which consists of a steel knife provided with 
 twenty-four teeth sharpened like little knives, the second cutter removing the small 
 laths from the plank of wood. Cochot's machine (1830) consists of a large iron wheel 
 i metre in diameter, on the periphery of which are fixed thirty woodn blocks length- 
 ways of the size of the splints. When the wheel is turned round, the blocks of wood 
 are caught by the knives fastened to a small cylinder, and the wood is split up into 
 splints, which are removed from the block by another knife. Jeunot's machine, 
 patented in 1840 in France, is of a similar construction. Neukrantz, at Berlin (1845), 
 contrived a tool based upon the principle of the hand-plane, the wood intended to be 
 cut being moved against a fixed steel cutter, which produced sixteen to twenty splints 
 at a movement. Krutzsch, at Wlinschendorf, Saxony, has improved upon this plan 
 (1848) by perforating a steel plate with about 400 holes placed as near together as 
 possible ; the edges of these holes having been sharpened, a block of wood is forced in 
 the direction of its fibres against the plate and thus divided into splints. A piece of 
 wood 3 centimetres in thickness and width by i metre in length yields 400 lengths, 
 each of which can be cut up into fifteen" splints ; 6000 of the latter are made in two 
 minutes. Of the several tools and machines contrived for the purpose of cutting 
 splints and the number of these contrivances is very large we quote the following of 
 German origin. The machine invented by C. Leitherer, at Bamberg (1851), consists 
 of what might be termed a kind of guillotine, viz., a box at the bottom of which is 
 placed the wood to be formed into splints, the fibre of the wood being vertical. In 
 front of this box is placed a framework, in which a heavy block, provided with four 
 cutters, each terminated by eight to ten narrow tubes (somewhat similar to cork- 
 borers), can be made to move rapidly, so as to give forty-five strokes a minute, the 
 wooden block intended to be cut into splints being made to move under the cutting 
 tool after each stroke. Wrana's machine is in principle the same as that of Neukrantz, 
 but has been greatly improved, the plane not being fixed, but supported by a piece of 
 wood. Long's machine, again, consists of a series of cylinders, between which the 
 block of wood is placed, while knives are so arranged as to cut the block into splints 
 while the wood moves on by the motion imparted to the cylinders. 
 
 3,. The Preparation of the Combustible Composition is carried on in the following 
 manner : The glue, or gum, or any other similar substance is first dissolved in a 
 small quantity of water to the consistency of a thin syrup, with which, having been 
 heated to 50, the phosphorus is incorporated by gradually adding it and keeping the 
 mixture stirred so as to form an emulsion, to which are next added the other ingre- 
 dients after having been pulverised. In order to obtain a good composition, it is 
 essential that there should be neither too much nor too little phosphorus, for an excess 
 of phosphorus will not only tend to increase unnecessarily the price of the composition, 
 but it has also the effect of rendering it unfit for igniting the sulphur and stearin 
 wherewith the matches are tipped, because the phosphoric acid generated by the com- 
 bustion of the phosphorus is deposited as an enamel-like mass, which prevents further 
 combustion. It appears that the best proportion is from one-tenth to one-twelfth of 
 phosphorus. 
 
 A much smaller quantity of phosphorus is required if this element is first dissolved 
 in carbon disulphide and the solution added to the other constituent of the composi- 
 tion ; the carbon disulphide while rapidly volatilising leaves the phosphorus in a very 
 finely divided state. As phosphorus is very readily soluble in sulphide of carbon, and 
 as the latter is moderately cheap, the method has the advantage that the mixing of 
 the materials can take place without the application of heat. It is, however, evident 
 that the greatest care is required in manipulating such a liquid as sulphide of carbon, 
 and far more when phosphorus is dissolved therein. C. Puscher suggested (1860) the 
 use of phosphorus sulphide, P X S, instead of pure phosphorus in the composition for 
 
SECT. III.] 
 
 MATCHES: PRODUCTION OF FIKE. 
 
 421 
 
 matches. He prepared a composition containing 3^5 per cent, of this sulphuret, and 
 obtained excellent matches. 
 
 Among the metallic oxides which are employed in the mixture, preference is given 
 either to a mixture of lead peroxide and potassium nitrate, or to a mixture of the 
 former with lead nitrate obtained by treating red lead with a small quantity of nitric 
 acid and leaving this mixture for a period of several weeks to dry. Glue, gum, and 
 dextrine are used as excipients ; the first, however, is objectionable because it carbon- 
 ises and prevents the combustion. Perhaps a dilute collodion solution or a mixture of 
 sandarac or similar resin, with benzole, might be used as an excipient instead of the gum. 
 
 The mixtures actually used in the trade are kept secret, but the following recipes 
 may give some idea of the composition : 
 
 Phosphorus . , . 
 Gum Senegal . . 
 Lamp-black , . 
 
 Red lead . . . 
 Nitric acid, sp. gr. i '384 
 
 Phosphorus . . . 
 
 Glue .. . . . 
 Lead peroxide 
 
 Potassium nitrate . 
 
 Phosphorus . 
 Gum Senegal . 
 Lead peroxide 
 Fine sand and smalt 
 
 I -5 parts 
 
 II. 
 
 8'O part? 
 21 'O 
 
 24 '4 
 24 - o ,, 
 
 A mixture of lead ni- 
 trate and peroxide, 
 technically known as 
 oxidised red lead. 
 
 Dissolved in the required 
 quantity of carbon di- 
 snlphide. 
 
 111. 
 
 3 'o parts 
 3-0 
 
 2'0 
 2'O 
 
 No doubt there is room for great improvements in these compositions. 
 
 3. Dipping and Drying the Splints. In order to fix the sulphur and combustible 
 composition to one end of the splints, it is clear that these should not touch each other, 
 but be so arranged as to leave an intermediate space. A contrivance is employed, 
 consisting of small planks, 0*3 metre long by 10 centimetres wide, the surface being 
 provided with narrow grooves placed both together, and just large enough each to 
 hold a single splint, Fig. 359. The splints are one by one placed in the grooves, an 
 operation usually performed by girls. One plank having been filled another is placed 
 
 Fig. 359- 
 
 Fig. 360. 
 
 Fig. 361. 
 
 on the top of it. The surface of the plank on one side is provided with a piece of 
 coarse flannel, while the other side is grooved for holding splints. Each of the planks 
 has at the end a round hole, through which pass iron rods, Figs. 360 and 361, in the 
 
422 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. 
 
 top of which a screw thread is cut, so that as soon as some twenty to twenty-five 
 planks have been filled with splints and placed one upon another, they are fastened so 
 as to form a framework. A clever hand can fill during ten hours fifteen to twenty-five 
 of these frames, each containing 2500 splints. Attempts have lately been made to per- 
 form this work by machinery, and the machine constructed by 0. Walsh, at Paris 
 (1861), enables a lad to frame 500,000 to 600,000 splints in ten hours. 
 
 The sulphur intended for dipping the splints is kept in a molten state over a mode- 
 rate fire in a shallow rectangular trough, in the middle of which a stone is placed as 
 precisely level as possible. The quantity of sulphur is so regulated that it covers the 
 stone to a depth of i centimetre. In the operation of dipping, the ends of the splints 
 are made to just touch the stone and immediately removed, care being taken to cause,, 
 by shaking the frame, any superfluous sulphur to flow into the trough again. 
 
 In the dipping apparatus of Roller the mixture is in the cast-iron pan, a (Figs. 362, 
 363, and 364). In its middle there is a dipping plate, b, in two ribs, c, upon which the 
 ignition mass is spread in the usual manner. Into this stratum of uniform, thick- 
 ness the woods, previously fixed in the frame, z, are dipped with the end to be coated. 
 In order to dip all the splints equally deep, even if they have been laid unevenly, the 
 
 Fig. 362. 
 
 Fig. 363- 
 
 press plate,/, is held by its handle, g, and rolled over the filled frame. The weight off 
 pushes down any splints which stand up above the level and presses all down to the 
 planed surface of the dipping plate, b. For guiding the press plate, /, there serve the 
 two counter-guides, h, which turn on the pivot, i, and the joint, k, in a curve approaching 
 to a cycloid. 
 
 When at rest the press plate, /, stands perpendicularly behind the dipping table, 
 whilst the counter-guides, h, come in contact with the angles, m, the press plate,/, turns 
 on the connecting bolt, /, and the pieces, n, are supported against the side of the pan. 
 The hollow space, o, of the dipping pan, closed below by the foot, serves for warming the 
 ignition mass, if needful, by hot water, steam, or hot air. The funnel, p, serves for 
 introducing hot water or letting off that which has become cold through the cock, r. 
 
 Inodorous matches, when dry, are coated with a coloured solution of resin, or some- 
 times finally with collodion. Phosphorus is recovered from matches which adhere 
 together by boiling in water. 
 
 Matches with Amorphous Phosphorus. This variety of match was invented in 1848 
 by Bottger, at Frankfort, and was prepared industrially by Furth, at Schiittenhofen ; 
 Lundstrom, at Jonkoping (Sweden) ; Coignet, at Paris "(under the name of Allumettes 
 hygieniques et de surete au phosphore amorphe) ; De Villiers and Dalernagne, Paris 
 (under the name of Allumettes androgynes) ; also by Fcirster and Wara. These matches 
 are of two kinds : (a) Those which are free from phosphorus, the amorphous phosphorus 
 being incorporated with the sand-paper ; (0) Those which are free from phosphorus 
 both in the match and on the sand-paper. 
 
SECT, m.] MATCHES: PRODUCTION OF FIKE. 423 
 
 To the matches of the first category belong : (i) Matches the composition of which 
 is free from phosphorus, consisting simply of a pasty mass, the main constituents of which 
 are antimony sulphide and potassium chlorate. (2) The amorphous phosphorus, mixed 
 with some very fine sand or other substance promoting friction, is, with glue, put on to 
 the box in which the matches are contained ; or, as is the case with the androgynes, at 
 the other end of the splint. The friction surface on the boxes consists of a mixture of 
 9 parts of amorphous phosphorus, 7 parts of pulverised pyrites, 3 parts of glass, and 
 i part of glue. The matches ignite readily by friction on the surface containing this 
 composition, but do not ignite when rubbed on any other rough surface. These so- 
 called safety matches are largely manufactured at Jonkoping, under the Swedish name 
 of Sakerhets-Tdndstickur (security fire matches). Jettel (1870) uses for the friction 
 surface a compound consisting of equal parts of amorphous phosphorus, pyrites, and 
 black antimony sulphide; for coating on the two sides of 1000 small boxes, each con- 
 taining fifty matches, about 80 grammes of this mixture are required. It need 
 hardly be mentioned that in England safety matches are largely made and of excellent 
 quality. 
 
 B. Forster and F. Wara, at Vienna, have introduced a " non-poisonous " match. 
 The amorphous phosphorus is mixed up with the combustible composition in the 
 usual way, so that these matches ignite readily by being rubbed on any rough surface, 
 but the ignition is accompanied by noise, owing to the potassium chlorate contained in 
 the mass. 
 
 As regards the matches belonging to the second category viz., such as neither 
 contain phosphorus nor require a phosphorus-containing surface, we may give the 
 analysis, by Wiederhold, of the composition of those made by Kummer and Glinther, at 
 Konigswalde, near Annaberg, in Saxony : 
 
 Potassium chlorate 8 parts 
 
 Black antimony sulphide . . . . 8 
 
 Oxidised red lead 8 
 
 Gum Senegal I 
 
 Oxidised red lead is a variable mixture of lead peroxide, nitrate, and undecomposed 
 red lead. Wiederhold, at Cassel, suggested (1861) the following ignition mixture : 
 
 Potassium chlorate 7 '8 parts 
 
 Lead hyposulphite 2'6 
 
 Gum arabic i 'o 
 
 This is the best anti-phosphorus mixture. Jettel, at Gleiwitz, gives the following 
 mixtures free from phosphorus : 
 
 a. 6. e. d. 
 
 Potassium chlorate . . . 4*0 ... 7*0 ... 3*00 ... 8*0 
 
 Sulphur I'O ... i'o ... ... 
 
 Potassium bichromate . . .0*4 ... 2*0 ... ... 0*5 
 
 Antimony sulphide ... ... ... ... 8'Q 
 
 Sulphur auratum, SbS 3 (Stibium } 
 
 sulphuratum aurantiacum) - ... ... 0*25 
 (Antirnonium sulphuratum, B.P.)J 
 
 Lead nitrate .... ... 2*0 ... ... 
 
 While R. Peltzer has called attention to the applicability of copper-sodium hypo- 
 sulphite for the preparation of a phosphorus-free ignition mass, Fleck* has also 
 remarked the use which might be made of sodium in this respect. 
 
 Wax or Vesta Matches. Instead of the phosphorus composition being fixed to a 
 wooden splint, in the wax matches (allumettes bougies) it is attached to a thin taper 
 made of a few cotton threads (four to six) immersed in a molten mixture of 2 parts of 
 
 * Jahreslericht der Chem. Techndogie (Dr. Wagner), 1868, p. 220. 
 
424 CHEMICAL TECHNOLOGY. [SECT. HI. 
 
 stearine and i part of wax or paraffine. The tapers, while this mixture is hot, are 
 drawn through a hole perforated in an iron plate, the opening of which corresponds to 
 the desired thickness of the taper. The taper is next cut, by means of machinery, into 
 suitable lengths ; afterwards the phosphorus composition is affixed and the vestas put 
 into boxes. 
 
 Zulzer's machine for cutting the tapers and for making them into matches has the 
 following arrangement: The wicks, having been rolled on a drum, are forced between 
 two cylinders, which impart the fatty composition, and next the tapers are carried by 
 the machinery across grooves in planks to holes in a movable vertical iron plate, 
 which is connected with a cutting apparatus intended to divide the tapers into suitable 
 lengths. As the cutters are placed at the entrance of the holes, the tapers, after 
 having been separated from the main wicks, are left dangling in those holes, and, by a 
 mechanical contrivance, the plate containing the holes is lifted sufficiently to bring 
 another row of holes level with the wick-producing apparatus. When a plate has 
 been thus filled with tapers it is removed, another put in its place, and the ends of the 
 tapers immediately immersed in the phosphorus composition, and next placed in a 
 drying room. Marseilles is the great centre of the wax-match industry, while Austria 
 stands next. 
 
 PHOSPHATES, MANURES. 
 
 Since Liebig demonstrated the importance of phosphoric acid, of nitrogen (as 
 nitric acid and ammonia), and of potash as plant-food, so-called artificial manures have 
 come more and more into use in agriculture. 
 
 Poudrette. Repeated attempts have been made to bring the contents of cess- 
 pools, <fcc., into a portable condition. But as the cesspools contain in the mean 96 per 
 cent, of water and only 0-35 per cent, of nitrogen, with 0*2 per cent, of phosphoric 
 acid, the attempt seems vain. However, a manure obtained by precipitating sewage 
 contains, according to Tidy, 3 per cent, ammonia and 5 per cent, tricalcium phosphate 
 derived exclusively from the sewage. So that irrigation is not the only method of 
 utilising human excreta, though in dry, hot climates it may be the best.* 
 
 Guano. On certain islands off the Peruvian coast the droppings of sea-fowl had 
 accumulated to a depth of 60 metres. In 1853 the quantity of these deposits was 
 estimated at 1 2 million tons, but they are now nearly exhausted. 
 Guano contains : 
 
 i. n. in. 
 
 Sal-ammoniac 2*25 ... 6*500 ... 4-2 
 
 Ammonium urate . . . . 12*20 ... 3*244 ... 9 - o 
 
 oxalate .... 1773 I3'35i io'6 
 
 phosphate . . . 6-90 ... 6*250 ... 6 - o 
 
 carbonate . . . 0*80 ... ... 
 
 bromate .... 1*06 ... 
 
 magnesium phosphate .11-63 4 ''96 ... 2 '6 
 
 Sodium phosphate .... ... 5*291 ... 
 
 Calcium phosphate .... 20*16 ... 9'94O ... 14*3 
 
 oxalate 1*30 ... 16*360 ... 7-0 
 
 carbonate .... 1*65 ... ... 
 
 Sodium chloride .... 0*40 ... 0*100 ... 
 
 Potassium sulphate .... 4*00 ... 4*227 ... 5*5 
 
 Sodium sulphate .... 4*92 ... 1*119 3'8 
 
 Waxy matter 0*75 ... 0*600 
 
 Sand and clay 1*68 ... 5*904 ... 4*7 
 
 Water 4'3"0 
 
 Organic matter 8*26J *" 22*718 
 
 ICO'OO lOO'OOO ICO'O 
 
 Compare Slater, Sewage Treatment, 1888. 
 
SECT, in.] PHOSPHATES, MANURES. 425 
 
 A more recent analysis gave : 
 
 Per cent. 
 
 Ca 3 P 2 O g 31759 P./) s =i5-552percent. 
 
 Mg 2 P 2 7 .... 1-568 
 
 MgS0 4 0-838 
 
 CaSO 4 ........ IQ.-II3 
 
 CaCO, 1-612 
 
 NaCl 7-238 
 
 Fe 2 3 , Al./) 3 .... 0-598 
 Insoluble .... 3-840 
 
 Water 16-175 
 
 C 5 H 3 (NH 4 )N 4 8 . . . 3-122 
 NH 4 N0 3 .... 1-499 
 (NH 4 ). 2 C0 3 .... 2-823 
 
 Organic matter . . . 13-815 = 2-513 N = 3'O52 NH 3 
 
 100-000 = 5-075 total N = 6-i63 NH 3 
 
 Guano from Mejillones contains about 70 per cent, tricalcium phosphate and only 
 o'3 to o'8 per cent, nitrogen. Guano from the Aves Islands, on the coast of Venezuela, 
 contains 45 to 50 per cent, of phosphate and 0-3 to 0*4 per cent, nitrogen. Guano 
 from Sydney Island contains 34 per cent, phosphoric acid and 0-28 per cent, 
 nitrogen; that from Cape Verde, n per cent, phosphoric acid and 0-3 nitrogen. 
 
 Guano is used powdered and sifted, but generally rendered soluble by admixture 
 with sulphuric acid (chamber acid) to get the phosphoric acid into solution. The 
 pasty mass solidifies on cooling from the formation of gypsum, and is therefore again 
 pulverised and sifted. 
 
 Bone Meal. The bones are deprived of fatty matter and ground finely. Various 
 samples of bone meal had the following compositions : 
 
 I. n. in. 
 
 Bone earth 63-3 ... 60-7 ... 47-7 
 
 (Containing phosphoric acid) . . 25-5 ... 25-4 ... 2o - o 
 
 Organic matter 29-7 ... 31-8 ... 42-5 
 
 Nitrogen 3-9 3-5 ... 4-7 
 
 Water 3-9 5-0 ... 7-4 
 
 Sand 3-1 ... 2-5 ... 2-4 
 
 Precipitated Tricalcium Phosphate can scarcely be produced to advantage at the 
 present prices for hydrochloric acid. 
 
 Superphosphate. To render soluble the phosphoric acid present in natural phos- 
 phates, they are mixed with sulphuric acid 
 
 Ca 3 (P0 4 ) 2 + 2 H 2 S0 4 = 2 CaS0 4 + CaH 4 (P0 4 ) 3 . 
 
 Monocalcium phosphate is freely soluble in water, whilst tricalcium phosphate, 
 Ca 3 P 2 8 , is sparingly soluble. 
 
 The most important materials for the manufacture of superphosphate are the 
 phosphorites. That occurring in large masses in Estremadura is nearly pure phos- 
 phate, but large quantities are met with in commerce which contain only 60 per cent, 
 along with considerable quantities of silica and calcium chloride, f Of less value are the 
 staffelites from the valley of the Lahn. 
 
 The Canadian phosphorite contains : 
 
 Tricalcium phosphate 91-20 
 
 Calcium fluoride 7-60 
 
 chloride 0-78 
 
 Sand 0-90 
 
 100-58 
 
 * Compare Griffith : Treatise on Manures, p. 146. 
 f And occasionally calcium fluorides. 
 
426 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 South Carolina phosphate contains : 
 
 Moisture 779 
 
 Organic matter 4-60 
 
 Silica io - 35 
 
 Calcium carbonate . . . . . . 8*20 
 
 Tricalcium phosphate 6i'89 
 
 Earthy and alkaline salts 7-17 
 
 1 00 'GO 
 
 Coprolites, the fossil excrements of saurians, are found in the lias at Norfolk, 
 Suffolk, Cambridgeshire, &c., in England, and near Helmstadt, in Germany. 
 A sample of Cambridge coprolites contained : 
 
 Moisture O'I2 
 
 Organic matter and combined water . . . 5-61 
 
 Silica O'i8 
 
 Carbon dioxide 6-50 
 
 Phosphoric acid 30-2 1 
 
 Lime ......... 49*01 
 
 Fluorine 3-08 
 
 Alkaline salts 5-29 
 
 100-00 
 
 In general the proportion of phosphate in coprolites varies from 15 to 70 per cent.,* 
 so that they must be examined before being used for superphosphate. The spent 
 animal charcoal from sugar works is of less value. 
 
 The materials are finely ground and mixed with the requisite quantity of sulphuric 
 acid in pits provided with agitators. The mixture Is rendered dry by the combination 
 of the calcium sulphate with water (CaSO 4 .2H 2 0), and is then broken up. 
 
 Double superphosphate is made by separating the gypsum from the soluble phos- 
 phate, when the solution of the latter is evaporated. 
 
 The so-called reversion of superphosphates (i.e., their return to an insoluble form) 
 is occasioned partly by the formation or presence of aluminium or ferric phosphates, 
 and partly by the action of calcium carbonate. Superphosphates made from the Lahn 
 phosphorites are peculiarly liable to this change.! 
 
 From a double superphosphate, I., the quantities given under II. were dissolved 
 out by lixiviation with small quantities of water in a filter, and those under III. by 
 immediate treatment with much water. 
 
 i. n. in. 
 
 PA 49'9Q ... 47'20 ... 45-80 
 
 S0 3 . . . . I'2O ... I '2O ... I -2O 
 
 SiO 2 . . . 0-50 ... ... 
 
 CaO . . . 17-24 ... 15-20 ... 1470 
 
 MgO . . . 1-15 ... 1-12 ... i-ri 
 
 Fe,0, . . . 2-87 ... 1-32 ... 0-66 
 
 A1 2 S . . .1-38 ... 1-33 ... 1-38 
 
 Na,jO . . . 0*40 ... 0*40 ... 0*40 
 
 Water . . . 23-52 ... ... 
 
 Organic . . 1-53 
 
 An immediate great dilution dissolves out 1-4 per cent, less phosphoric acid than 
 does gradual lixiviation. 
 
 * Fragments of wood have been found among coprolites as rich in phosphoric acid as the 
 animal remains. 
 
 t The author thinks that the preference given to soluble phosphates is an error which has cost 
 Germany 200,000,000 marks. Foreign phosphorites have been imported and the Lahn phosphorites 
 exported at very low prices. 
 
SECT, in.] BORIC ACID AND BOKAX. 427 
 
 As nitrogenous manures, in addition to guano and bone-dust, there are ammonium 
 sulphate, nitre, dried blood, horn-dust, and shoddy. Of sources of potash the chief are 
 kainite and potassium chloride. 
 
 For determining nitrogen in ammonium sulphate the ammonia is driven off into 
 normal acid by boiling with soda-lye. Saltpetres are examined by means of the nitro- 
 meter. Organic nitrogen and total nitrogen in mixed manures are best determined by 
 the Kjeldahl process. The sample is boiled with strong sulphuric acid, to which phenol 
 is added if a nitrate is present. All the nitrogen is thus converted into ammonia, 
 which is distilled off. 
 
 For determining the soluble phosphoric acid the following procedure was agreed 
 upon at a meeting of agricultural chemists held on November 30, 1885 : 
 
 Five grammes of the sample are rubbed up with the strong citrate solution and 
 gradually washed into a ^-litre flask. The mixture is filled up to the mark with the 
 dilute solution of citrate, let stand for eighteen hours at the temperature of the room 
 with frequent shaking, and filtered. 50 c.c. of the filtrate are mixed with so much 
 molybdenum solution that not less than i c.c. of the solution may come to each milli- 
 gramme P 2 O 5 , and so much strong ammonium nitrate (see below) is added as is equal 
 to a quarter the volume of the mixture. After standing twenty minutes in the water- 
 bath and subsequent cooling, the liquid is filtered, the precipitate washed with dilute 
 ammonium nitrate (see below), and rinsed back into the beaker with ammonia at 2^5 per 
 cent, through the perforated filter. The filter is well washed, and to the ammoniacal 
 solution magnesia mixture is added drop by drop, with constant stirring. The whole 
 is filtered after one hour, the precipitate is washed with ammonia at 2 per cent., dried, 
 and ignited. 
 
 Preparation of the Solutions. (i) Strong solution of citrate. 150 grammes citric acid 
 are put in a i -litre bottle, dissolved in water, and neutralised with ammonia. To the solu- 
 tion are added 10 grammes citric acid, and the liquid is filled up to the mark with water. 
 
 (2) Dilute solution of citrate, i volume of the foregoing strong solution is mixed 
 with 4 volumes water. 
 
 (3) Strong solution ammonium nitrate. 750 grammes ammonium nitrate are dis- 
 solved in water, and the solution is diluted to i litre. 
 
 (4) Dilute ammonium nitrate. 100 grammes ammonium nitrate are dissolved in 
 water, and the solution is made up to i litre. 
 
 (5) Molybdic solution. 150 grammes ammonium molybdate are dissolved in water, 
 the solution is diluted to i litre, and poured into i litre nitric acid of sp. gr. 1-2. 
 
 (6) Magnesia mixture, no grammes pure crystalline magnesium chloride and 140 
 grammes ammonium chloride are dissolved in 700 c.c. liquid ammonia (at 8 per cent, 
 actual ammonia) and 1300 c.c. of water. 
 
 BORIC ACID AND BOEAX. 
 
 Boric acid occurs native as sassoline, H 3 B0 3 ; in 100 parts- 
 Anhydrous boric acid, B 2 O S . . . .56*45 
 Water 43'55 
 
 lOO'OO 
 
 and further in the following minerals : 
 
 Boracite, or magnesium borate and chloride with 62 '5 per cent, boric acid 
 
 Rhodicite, or calcium borate . . . ,, 30 to 45 
 
 Hayescine, tiza, or calcium borate . . ,, 30 to 44 
 
 Hydroboracite . . . . . 47 
 
 Tincal or borax, sodium borate . . 36*53 
 
 Datholite, or boro-silicate . . . . ,, 18 
 
 Botryolite 2O'35 
 
 Axiiiite ,, 2 to 6'6 
 
 Tourmaline 2 to 1 1 '8 
 
428 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 Boric acid is found also in small quantities in many mineral waters and in sea- 
 water. Larderellite, or ammonium borate, and lagonite, or iron borate, are both 
 found in very small quantities in Tuscany, and are interesting to mineralogists only. 
 
 Boric acid is found as sassolin in many volcanic regions, mixed with sulphur, in 
 the hot springs of Sasso, in Tuscany, and also between Volterra and Massa Maritima 
 in the clefts and rents of volcanic formation of rock. H offer and Mascagui (1776) 
 first mentioned the occurrence of boric acid in the waters subjected, in the clefts 
 of the rock, to the sulphurous exhalations. The little pools formed in these clefts 
 are variously known as fumacchi, fumarole, soffioni, and mofetti. The boric acid 
 deposits in some cases cover an extent of six miles. Since 1818 artificial soffioni have 
 been constructed, and the benefit derived by the country from the introduction of the 
 industry is immense. The first artificial lake was situated near Monte Cerboli, and the 
 product was for some time known as larderellite, from the owner's name, Larderel. The 
 production from these works alone amounted in 1839 to 7 X 7>333 kilos., and in 1867 to 
 2,350,000 kilos. The increase has been greatest since 1854, owing to the energy with 
 which Gazzeri and Durval entered upon the construction of the artificial soffioni. 
 
 The soil of the natural lakes, or beds of the natural soffioni, are of a slimy for- 
 mation, and have a peculiar seething movement due to the escape of the sulphurous 
 vapours from the fumaroles or vents. According to Payen, this vapour or steam may 
 be considered as condensible and as non-condensible, the former containing, besides 
 water, calcium, magnesium, and ammonium sulphate, iron chloride, hydrochloric acid, 
 organic substances, a fishy-smelling oil, clay, sand, and a small quantity of boric acid. 
 The non-condensed vapour consisted of 
 
 Carbonic acid ..... 0-5730 
 
 Nitrogen . '. . . . . 0-3480 
 
 Ox} ? gen 0-0657 
 
 Sulphuretted hydrogen . . . 0-0133 
 
 Payen is of opinion that the vapours contain no boric acid, while C. Schmidt 
 thinks otherwise, as the vapours, when condensed without contact with the water of 
 the soffioni, yield boric acid. The condensed vapours contain 0*1 per cent, boric 
 acid. 
 
 Theory of the Formation of the Native Boric Acid. Dumas and Payen founded a,n 
 explanation of the formation of volcanic boric acid upon the hypothesis that 
 there exists in the interior of the volcano or beneath the under-crust of the 
 earth a layer of boron sulphide (B 2 S 3 ), which under the action of the mineral waters 
 becomes converted into boric acid and sulphuretted hydrogen. P. Bolley gives the 
 action as similar to that occurring in the formation of sal-ammoniac, a very common 
 mineral in volcanic regions. Professor Becchi, of Florence, found boron nitride (BN) 
 in one of the under-strata, from which he prepared artificially, by means of steam, 
 ammonia and boric acid. Also "VVarington (1854) and Popp (1870) attributed the 
 appearance of boric acid and ammonia in volcanoes to the decomposition of boron 
 nitride by evaporation. Recently (1862) Becchi has obtained boric acid by the de- 
 composition of calcium borate in a stream of superheated steam. 
 
 TJie Production of Boric Acid. The most general method of obtaining boric acid 
 is by the evaporation of the water of the natural or artificial soffioni. The water is 
 either naturally or artificially introduced into the natural fumaroles, as these sometimes 
 do not re-supply themselves with sufficient rapidity. As soon as the water has absorbed 
 a considerable quantity of the vapours it is removed and placed in a large mason-work 
 cistern ; this cistern is imbedded in the soil near the fumaroles, and the natural heat 
 is sufficient to cause evaporation. The vapours are condensed in a wooden chimney 
 The separated impurities, gypsum, &c., remain in the cistern. As soon as the solution 
 is of a sp. gr. = 1-07 ro8 at 80, it is poured into leaden crystallising vessels, where 
 
SECT. III.] 
 
 BOEIC ACID AND BORAX. 
 
 429 
 
 the boric acid crystallises out. The mother liquor is evaporated to dryness. It 
 should be remembered that the entire operation is conducted with the assistance of the 
 natural heat of fumaroles only. Occasionally the boric acid is only present in the 
 natural waters to 0*002 of a part ; and in these cases fuel must be used in the evapo- 
 ration, which therefore entails the expense of carriage, as fuel is very scarce near the 
 soffioni. Charcoal is generally used. But by this means an acid is obtained, containing 
 about 70 to 80 per cent, hydrated boric acid, with 10 per cent, impurities. Clouet 
 removes the impurities by treatment with 5 per cent, of ordinary hydrochloric acid. 
 Boric acid for pharmaceutical purposes may be prepar/ed by dissolving i part of borax 
 in 4 parts of boiling water, and decomposing the solution with one-third part of 
 sulphuric, or better with one-half part of hydrochloric acid of 1*2 sp. gr. The acid 
 separates on cooling, and can be purified by crystallisation. 
 
 In 100 parts of commercial boric acid from Tuscany, H. Yohl (1866) found : 
 
 Boric acid . 
 
 45 '1996 
 
 ... 47-6320 ... 
 
 48-2357 
 
 ... 45-2487 
 
 ... 48-1314 
 
 Water of crystallisation 
 
 . 34-8916 
 
 ... 35-6983 ... 
 
 37-2127 
 
 ... 34-9010 
 
 ... 38-0610 
 
 Water .... 
 
 4-5019 
 
 ... 2-5860 ... 
 
 I -0237 
 
 ... 4-4990 
 
 ... 1-5240 
 
 Sulphuric acid 
 
 9-6I3S 
 
 ... 7-9096 ... 
 
 8-4423 
 
 - 9-5833 
 
 ... 7-8161 
 
 Silicic acid 
 
 . O'8l2I 
 
 1-2840 ... 
 
 0-6000 
 
 0-2134 
 
 0-0861 
 
 Sand .... 
 
 . 0-2991 
 
 0-5000 ... 
 
 0-1000 
 
 ... 0-7722 
 
 ... 0-4154 
 
 Iron oxide 
 
 . 0-1266 
 
 0-1631 ... 
 
 O-O92O 
 
 0-1030 
 
 0-0431 
 
 Manganous oxide . . 
 
 . 0*0031 
 
 traces ... 
 
 traces 
 
 traces 
 
 traces 
 
 Alumina . . . 
 
 . 0-5786 
 
 0-0802 ... 
 
 0-0504 
 
 0-1359 
 
 ... 0-1736 
 
 Lime .... 
 
 . 0-0109 
 
 ... 0-3055 ... 
 
 0-1578 
 
 traces 
 
 traces 
 
 Magnesia . . 
 
 . 0-6080 
 
 traces 
 
 traces 
 
 traces 
 
 traces 
 
 Potash .... 
 
 
 O "2 "- "i, I 
 
 0-1:178 
 
 0*6140 
 
 OMTIyl 
 
 Ammonia 
 
 . 2-9891 
 
 ... W *33 * ... 
 ... 3-5I65 ... 
 
 w j i / *-* 
 3-5i 6 9 
 
 ... 3-7659 
 
 <j i\ i ^q. 
 3-0890 
 
 Soda .... 
 
 . 0-0029 
 
 traces ... 
 
 traces 
 
 traces 
 
 traces 
 
 Sodium chloride 
 
 . O-IOI2 
 
 ... 0-0595 ... 
 
 0-0401 
 
 0-1671 
 
 0-0321 
 
 Organic substances and loss 
 
 . 0-0918 
 
 O'OIOI 
 
 O'OIOI 
 
 
 
 0-0449 
 
 lOO'COOO 
 
 Properties and Uses of Boric Acid. Pure boric acid crystallises in mother-of- 
 pearl-like leaves, which at 100 C. lose half their water of crystallisation without 
 melting, the other half being driven off at a red-heat. After cooling, the anhydrous 
 acid appears as a hard, transparent, brittle glass of 1-83 sp. gr. i part boric acid 
 dissolves in 25*6 parts water at 15 C., and in 2-9 parts at 100 C. At 8 a saturated 
 solution has a sp. gr. of 1*014. I* imparts a green colour to the flame of the spirit- 
 lasip. In a chemical point of view it is similar to silicic acid. Boric acid is largely 
 used in the preparation of borax for glazing porcelain, and, mixed in a weak aqueous 
 solution with sulphuric acid, in the preparation of the wicks of stearine and paraffine 
 candles. It is also used for colouring gold, for decorating iron and steel, in the 
 preparation of flint-glass, and artificial precious stones. In 1859 boric acid was 
 used in the preparation of hydrated oxide of chromium, known under the name of 
 Pannetier's green, Vert-Guignet, &c. 
 
 Borax. Borax, or sodium biborate, when anhydrous according to the formula 
 Na 2 B 4 7 , contains in i oo parts : 
 
 Anhydrous boric acid (B 2 0. t ) 
 
 69-05 
 30-95 
 
 It is found native in Alpine lakes, on the snow-capped mountains of India, China, 
 Persia, in Ceylon, and Great Thibet. It is found in large quantity at Potosi in 
 Bolivia, where the Borax Lake, according to Moore's analysis (1870), contains in i litre 
 
43 o CHEMICAL TECHNOLOGY. [SECT. in. 
 
 of its water (sp. gr. = 1-027) 3'9^ grammes of borax. Pyramid Lake, Humboldt Co., 
 Nevada, yields also large quantities. By the heat of the sun the water of the borax 
 lakes is evaporated, and the borax crystallises out and is gathered and brought into 
 commerce under the name of tincal. It appears in small six-sided crystals, more or 
 less smooth. The Clear Lake in California, to the north of San Francisco, yields daily 
 2000 kilos, of borax. 
 
 Formerly tincal was purified by washing in water containing soda, to free the 
 borax from adhering fatty substances which combine with the soda to form an almost 
 insoluble soap. After the borax has been well washed, it is dissolved in boiling water ; 
 for each 100 parts of refined salts there are added 12 parts of sodium carbonate. The 
 solution is next filtered, and then evaporated to 26 to 30 Tw. It is now placed in 
 wooden crystallising vessels lined with lead, where it is necessary to allow the fluid to 
 cool gradually. Another method is to place the tincal in cold water, and to stir in 
 i per cent, of caustic lime. The fatty substances are thus removed, combining with 
 the lime to form an insoluble calcium soap. 2 per cent, of calcium chloride is added to 
 the fluid, which is next evaporated, and set- aside to crystallise. Clouet recommends the 
 powdering of the tincal, which is next mixed with 10 per cent, sodium nitrate, and 
 calcined in a cast-iron pan, the fatty substances being thus destroyed. The calcined 
 mass is dissolved in water, and the solution evaporated to crystallisation. 
 
 Borax from Boric Acid. In 1818 the manufacture of borax from boric acid 
 was commenced, and since that time borax has sunk to three-fourths it former price. 
 Both according to the proportion of water and the crystalline form, there may be con- 
 sidered two varieties of borax (i) the ordinary or prismatic borax; (2) octahedral 
 borax. The prismatic borax (Na 2 B 4 7 + ioH 2 0) contains in 100 parts : 
 
 Boric acid . ... ' 36-6 
 
 Soda . . . . i6 - 2 
 
 Water of crystallisation . . . . . 47-2 
 
 ICO'O 
 
 The octahedral borax (Na 2 B 4 7 + 5H 2 0) contains in 100 parts : 
 
 Boric acid) 
 
 Soda } ..... ' 
 
 Water . ....... 30-64 
 
 Prismatic borax is manufactured in the following manner : There are dissolved in a 
 lead-lined vessel, A, Fig. 365, 26 cwts. of crystallised sodium carbonate in about 1500 
 litres of water, heated, by means of steam, to the boiling-point. The boiler, C, is for 
 the purpose only of generating steam, which is passed by the pipe, c, and the rose, m, 
 into A. By means of the large taps, b and r, the fluid may be removed from A. 
 Through the tube, a, the substances thrown down from the solution can be removed. 
 Boric acid is added in quantities of 8 to 10 Ibs. after the solution has been heated to 
 the boiling-point. Besides carbonic acid a small quantity of ammonium carbonate is 
 developed, and passes by o into the vessel D, containing dilute sulphuric acid, by which 
 it is absorbed. To saturate the solution of 26 cwts. of soda, 24 cwts. of crude boric 
 acid are necessary. The boiling saturated solution marks 32 to 33 Tw., and has a 
 temperature of 104. If the solution is too strong, water is added ; if too weak, a small 
 quantity of crude borax, to bring it to 32 Tw. The solution is allowed to stand in A 
 until all insoluble substances are deposited. The clear lye is conducted by means of 
 the tap, r, into the crystallising vessels, P, P, the mud or deposit being received into K. 
 The crystallising vessels are of wood lined with lead. The crystallisation is complete 
 in two to three days, and the mother liquor is drawn off into the vessel H. The 
 
SECT. III.] 
 
 BORIC ACID AND BOKAX. 
 
 431 
 
 crystals are placed to drain on the inclined plane, M. The mother liquor is retained for 
 the solution of a fresh quantity of soda. After three or four operations, the mother 
 liquor contains sufficient sodium sulphate to admit of profitable crystallisation ; and the 
 lye is allowed to cool at 30. As the solubility of sodium sulphate has reached the 
 
 Fig. 366. 
 
 maximum at a temperature of 33, it is clear that the crystallisation of the sulphate 
 commences at the completion of that of the borax. After the crystallisation of the 
 sodium sulphate, the mother liquor is evaporated to dryness, and the saline residue is 
 sold to the glass-manufacturer. 
 
 Purifying the Borax. The cnide borax to be purified is placed in a lead -lined 
 wooden cistern, A, Fig. 366, heated by steam. The borax is suspended in a wire sieve 
 immediately under the surface of the 
 water with which A is filled. To 100 
 parts of borax, 5 parts of crystallised 
 sodium carbonate are added, and the liquid 
 is strengthened from time to time till it 
 marks 33'8 T\v. When the solution has 
 settled it is removed by the tap to the 
 cooler, B. To prevent loss of lye, the 
 floor under B is stippled with waterproof 
 cement, and sloped towards a gutter. 
 The crystallising vessel is of thick timbers, 
 H, F, H, lined stoutly with lead ; this 
 
 vessel is filled with lye to within an inch 
 of the edge, the cover being then placed on. 
 when removed, is found covered with small crystals, the larger crystals falling to the 
 bottom of the vessel. To hasten the cooling, spaces are left in the timbers, F ; but the 
 crystallisation is not effected under sixteen to twenty-eight days. After this time the 
 lye still has a temperature of .27 to 28 C. When quite cool the foreign substances 
 separate from the borax. The vessel, B, contains the large borax crystals from which the 
 adhering mother liquor is separated by a sponge. If the crystals are not thus carefully 
 treated, they split into thin leaves ; for this reason also the cooling should be gradual. 
 The crystals are dried on a wooden table, finally sorted, and packed. 
 
 The steam condenses on the cover, which, 
 
432 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 In England borax is prepared from boric acid in the following manner : The 
 crude boric acid is mixed with half its weight of calcined soda and submitted to the 
 action of heat in a muffle-oven. The ammonia, which as sulphate is an important 
 constituent of crude boric acid, is, with carbonic acid, given off during the process, 
 and passes through a tube to a condensing chamber. The melted mass is removed, and 
 lixiviated in an iron pan ; the suspended matter is allowed to settle, and the clear liquor 
 is put to cool into smaller vessels, in which beautiful crystals form. It has already been 
 mentioned that this manufacture had its origin in France, where sulphuric vapours 
 were employed. A mixture of calcined Glauber salts and boric acid were placed in a 
 retort and subjected to distillation, the residue on lixiviation and crystallisation yielding 
 borax. Kohnke substitutes caustic soda for the sodium carbonate, the borax crystal- 
 lising from a very alkaline solution. 
 
 Recently borax has been obtained from native calcium borate, tiza, ulexite, frank- 
 landite, or borocalcite (formula, according to Wohler, Na 2 B 4 7 + 2CaB 4 7 + i8H 2 ; or 
 according to more recent determinations, NaCaB 5 O 9 .8H 2 0), which occurs in large 
 quantities in California and Nevada, in Greece and Nova Scotia, at Tarapaca in Peru, 
 and in Western Africa. Treatment with sulphuric acid gives only unsatisfactory 
 results, and hydrochloric acid is therefore employed. The acid is poured upon the 
 mineral to two-thirds of its weight with twice the quantity of water, and the whole 
 heated to the boiling-point, and allowed to digest. The heat must be maintained 
 to the completion of the digestion, and the water lost by evaporation re-supplied. The 
 clear liquor is then decanted, and, on cooling, the boracic acid crystallises out, the 
 mother liquor retaining sodium or calcium chloride with a slight excess of hydro- 
 chloric acid. Stassfurt boracite, or stassfurtite, is also becoming largely used in the 
 preparation of borax. 
 
 Prismatic borax is colourless, and forms transparent crystals of 175 sp. gr., 
 soluble in 1 2 parts cold and 2 parts boiling water, the solution having a weak alkaline 
 reaction upon test-paper, although borax is an acid salt. By exposure to the air it 
 loses water. At a moderate heat it separates into a spongy mass known as calcined 
 borax, and at a red heat assumes a glassy appearance ; in this condition it is used 
 as a blowpipe flux. 
 
 Octahedral Borax. Octahedral borax (Na,B 4 7 + 5H 2 0) is prepared in the following 
 manner : Prismatic borax is dissolved in boiling water till the solution marks 49 Tw. 
 = 1*260 sp. gr. This solution is then allowed to cool very slowly. When the 
 temperature has fallen to 79 C., the octahedral crystals begin to form, the formation 
 continuing till the temperature reaches 56. After this the mother lye yields only 
 prismatic crystals. Unless great care be taken, a mixed crystallisation results. 
 Buran recommends the preparation of octahedral borax by evaporating a borax solution 
 to 53 Tw. = i'282 sp. gr., when it is removed to a crystallising vessel. When 10 cwts. 
 of borax are operated upon, the process will take six days to complete. The prismatic 
 and octahedral salt crystallise in distinct layers that can be separated mechanically. 
 Indian borax and Chinese half-refined borax sometimes contain octahedral crystals. 
 Octahedral borax is known in French commerce under the names of calcined borax, 
 jewellers' borax, surface borax, &c. It is distinguished from prismatic borax by its 
 crystalline form and the proportion of water contained, by its sp. gr. = i'Si, and its 
 greater hardness. While the prismatic borax remains unaffected in transparency by 
 exposure to air, the octahedral borax rapidly becomes opaque, and, absorbing five 
 equivalents of water, is converted into the prismatic salt. 
 
 Uses of Borax. The uses of borax are very numerous. Molten borax has the 
 property, at high temperatures, of fluxing metallic oxides, vitrefying with them into 
 coloured transparent glasses ; for instance, with cobaltous oxide a blue glass is formed, 
 and with chromic oxide a green glass. This property is of great utility in chemical 
 
SECT, in.] BORIC ACID AND BORAX. 433 
 
 analysis, as the various metallic oxides may be thus distinguished in the blowpipe 
 flame. It is also used for soldering metals ; and is a constituent of Strass, used 
 in glass manufacture and enamelling. It is used extensively in glazing the finer 
 kinds of earthenware, and for separating metals from their ores. Borax forms 
 with shellac in proportion of i part to 5 a peculiar varnish, soluble in water, 
 and used when mixed with aniline black to stiffen felt hats. With casein it gives a 
 fluid resembling a solution of gum-arabic, for which it is often substituted. Borax 
 is made into a soap for washing purposes, into a solution for cleansing the hair, and it 
 is also used in various cosmetics, &c. It is largely employed to fix mineral mordants. 
 According to Clouet, a mixture of boric acid and potassium or sodium nitrate is in 
 many cases a better flux than borax. He recommends 100 parts boric acid and 100 
 parts of the nitrate to be placed in an enamelled iron kettle with 10 per cent, water 
 and heated till fluid. When cooled, flat white crystals are formed; those made with 
 potassium nitrate can be used for crystal-glass manufacture, and those with sodium 
 nitrate for enamelling. Chromium borate is known in commerce as Vert-Guignet or 
 Pannetier's green. Borax sold in powder under fanciful names is often adulterated 
 with soda ash, common salt, and even with quicklime. 
 
 The Chilian borosodium calcite has the following composition : 
 
 I. II. III. IV. 
 
 Water .... 27-33 I3'8 ... 40'9 ... 31 '50 
 
 Lime .... 17-44 ... J 5'4 8 '3 8 ... I2 '34 
 
 Salt 7-19 ... 31-6 ... 14-20 ... 3-80 
 
 Insoluble . . . 10-69 ... 10-3 ... 1*04 ... 0*21 
 
 Sulphuric acid . . 12*60 ... 9'4 ... 1*20 ... trace 
 
 Boric acid . . . 22-55 J 9'6 ... 22-32 ... 47'52 
 
 Soda .... 2-33 ... ... 3-96 ... 1-63 
 
 According to the proposal of Lunge, the borate ground a,nd elutriated is mixed with 
 two-thirds its weight of common hydrochloric acid and double the quantity of water, heat 
 being applied until the decomposition is complete. It is now allowed to settle, and the 
 clear hot liquor is drawn off with a syphon. On cooling, the boric acid crystallises out 
 almost entirely, whilst sodium and calcium chloride remain in solution with the excess of 
 hydrochloric acid. The proportion of two-thirds refers to the average composition 
 of the mineral, and must be arranged according to each sample. The crystals of boric 
 acid are drained, pressed, or whizzed, washed in cold water, whizzed again, and obtained 
 almost absolutely pure, so that on treatment with soda they yield pure borax on the first 
 crystallisation. 
 
 The bulk of the borax consumed in Germany is prepared from boronite-calcite. 
 The manufacture consists of four processes : 
 
 1 . Boiling the calcium borate with soda. 
 
 2. Working up the residues. 
 
 3. Fine crystallisation. 
 
 4. Working up the lyes. 
 
 The first process is conducted in large pans fitted with powerful agitators, and 
 heated by the direct introduction of steam. 2500 kilos, of the lime salt are stirred up 
 with four to five times its quantity of water, and the soda is gradually introduced 
 when the mixture boils. The soda should be in slight excess. A mixture of soda ash 
 and bicarbonate is preferred. The boiling is completed in three to four hours. 
 
 As the neutral borate contains only 4 molecules of crystalline water, the formation 
 of this salt is a serious loss. The contrary condition is also to be avoided. If there is 
 no excess of soda the crystallisation is sluggish. After the whole has settled, the clear 
 supernatant lye is run off and the mud is passed through a filter-press. The lye is 
 kept to crystallise in iron, four-sided cisterns, holding 1000 to 1500 litres. It must 
 have, on the average, a strength of 49-5g Tw. 
 
434 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 In three or four days the crude borax has separated out in thick crystalline 
 crusts on the sides and bottoms of the cisterns. The average pure sodium biborate 
 (Na 2 B 4 7 + ioH 2 0), contained in these crude crystals is 40 to 50 per cent., the 
 residue being sodium sulphate and chloride. The lyes can be used for boiling several 
 times in succession, but if they become too concentrated it is better to evaporate them 
 down. The first crystallisation obtained on evaporation contains borax enough to 
 be added to the crude borax for further treatment. 
 
 The filter press turns out the mud from the boiling in solid cakes, which still 
 contain a quantity of mother liquor. They are lixiviated with hot water ; the lye is 
 concentrated and added to the crude borax. 
 
 The next stage is the fine crystallisation conducted in large four-sided iron cisterns 
 holding 8-10 cubic metres. They are enclosed with an outer coating of wood, the 
 space between the wood and the iron being packed with sawdust, peat, &c., to prevent 
 sudden changes of temperature. 
 
 The crude borax is dissolved in as much pure water as to yield a solution which 
 boiling marks 50 Tw. The so-called fine lye can be repeatedly used for dissolving fresh 
 quantities of crude borax, but the solutions must be made stronger each time, as the 
 sp. gr. is raised by the sodium sulphate, &c. 
 
 Care must be taken not to make the solutions too strong. From such lyes 
 octahedral borax crystallises out containing only 5 mols. water of crystallisation, which 
 involves considerable loss, as the prismatic borax the commercial quality crystallises 
 with 10 molecules of H S 0. 
 
 To remove iron and traces of organic matter a small quantity of sodium hypochlorite 
 is added, until the lye is colourless in water and gives no reaction with potassium 
 ferrocyanide. The hot lye is run into the crystallisation-cisterns, which must be quite 
 full and carefully covered, to prevent too rapid cooling. In ten to fourteen days, 
 according to the weather and the season, the temperature will have fallen to 33, and 
 the crystallisation of the borax will be completed. At 33 the sodium sulphate begins 
 to crystallise, and the lye must be let off. 
 
 The crystalline crusts are rinsed with pure cold water to remove drops of mother 
 liquor, and are then detached by striking the outsides with a hammer. The borax is 
 finally dried in baskets, in a drying-chamber at 30 for twenty-four hours, and any dirt 
 adhering to the under side of the crystals is removed. 
 
 The lyes from the coarse and the fine crystallisations must not be too often used for 
 repeated boilings, as they would become too rich in sodium sulphate and chloride. 
 Hence large evaporating pans are provided to receive them. In winter after being 
 concentrated they are received into crystallising vats set in the open air, when sodium 
 sulphate crystallises out in quantity. In summer the sulphate and the common salt 
 have to be boiled out, which involves a loss of borax. 
 
 In order to recover the borax (about 10 per cent.) which attaches itself to the 
 sodium sulphate, it is heated very gently until the latter salt melts in its own water of 
 crystallisation. The melted sulphate is then run off, and the borax which has remained 
 undissolved remains in hard pieces, which may be added to the fine crystallisation. 
 
 Diamond-Boron or Adamantine. Wohler and H. Deville in 1857 were the first to 
 notice that boron occurs, similarly to carbon in two allotropic conditions, namely, 
 crystalline* and amorphous. Diamond boron is prepared, in two ways, either by the 
 reduction of calcined borax with aluminium 
 
 Boric acid, B,CU . }ds f Alumina,. A1.0,, ' 
 Aluminium, 2A1) * (Boron, 2B; 
 
 or by converting amorphous boron into crystalline. The latter method gives the 
 
 * Graphitic boron is by a later discovery of Wohler's (1867) resolved into boron-aluminium j 
 formula, AlBj. 
 
SECT, in.] SALTS OF ALUMINIUM. , 435 
 
 better result. 100 grammes of anhydrous boric acid are mixed with 60 grammes of 
 sodium in a small iron crucible heated to a red heat. To this mixture 40 to 50 grammes 
 of common salt are added, and the crucible is luted clown. As soon as the reaction is 
 finished, the mass, consisting of amorphous boron with boric acid, borax, and common. 
 salt intermingled, is stirred into water acidified with hydrochloric acid. The boron is 
 filtered out, washed with a weak solution of hydrochloric acid, and placed upon a 
 porous stone to dry at the ordinary temperature. Molten iron, it is well known, 
 converts amorphous carbon into crystalline graphitic carbon, and aluminium exercises 
 a similar action upon boron. The crystalline boron is prepared in the following manner : 
 A small crucible is filled with amorphous boron, in the centre of which a small bar of 
 aluminium, weighing 4 to 6 grammes is placed. The crucible is submitted to a tempera- 
 ture sufiicient to melt nickel for one-and-a-half to two hours. After cooling, the 
 aluminium will be found covered with beautiful crystals of boron. The diamond 
 boron is easily separated from, the graphitoid. The former is a transparent tetragonal 
 crystal, of a garnet -red or honey -yellow colour, or, if perfectly pure, colourless. It is 
 very brittle, hard, and lustrous; it will scratch rubies easily. This discovery may 
 in time be of great technical importance. 
 
 SALTS OF ALUMINIUM. 
 
 Alum. Alum is a saline substance, consisting of aluminium sulphate, potassium, or 
 ammonium sulphate, and water of crystallisation. It occurs native as potash alum and 
 as ammonia alum, being, in fact, a double salt, consisting of either aluminium sulphate 
 and potassium sulphate, or aluminium sulphate and ammonium sulphate. The alum 
 
 known as potash alum, 2 1 4SO 4 + 24H 2 0, is found in alum-shale. But all natural 
 
 K 2 j 
 
 alums are more of mineralogical than of technical interest, the alums of commerce being 
 always artificially prepared. We shall, therefore, pass on to the consideration of the 
 latter. 
 
 Material of Alum Manufacture. The manufacture of alum is based on the 
 formation of aluminium sulphate and sodium aluminate from the various alum ores. 
 These ores or earths, necessitating different methods of treatment, may be divided into 
 four groups, viz. : 
 
 1. Those which contain alumina, potassa, and sulphuric acid in such proportions 
 that the addition of an alkaline salt is not requisite. To this group belong alum-stone 
 and several varieties of alum-shale. 
 
 2. Those in which the aluminium sulphate is alone present, necessitating the 
 addition of alkali salts in large quantities. To this group belong the alum-shale and 
 alum-earths found in the brown-coal formation. 
 
 3. Those in which alumina only is contained, and to which both sulphuric acid and 
 alkali salts must be added. To this group belong (a) clay, (b) cryolite, (c) bauxite, 
 alumina terhydrate (Gibbsite), (d) refuse slack. 
 
 4. To the fourth group belong those materials, such as felspar, containing alumina 
 and potash in sufficient quantity, but needing the addition of sulphuric acid. 
 
 Preparation of Alum from Alum-stone (ist Group}. Alum-stone or alunite occurs 
 only in volcanic regions, and is the product of the action of the sulphurous 
 vapours upon substances rich in felspar. It is found at Tolfa, near Civita Vecchia, and 
 in large quantities at Muszag, in Hungary. The crystallised alum-stone consists 
 of potassium and aluminium sulphates with aluminium hydroxide, according to 
 Mitscherlich K 2 S0 4 + A1 2 (S0 4 ) 3 + 2 (A1 2 O 33 H 2 O). 
 
 Alum-stone loses its water at a red heat, the product of the calcination being 
 oifluenced by water, while unburnt alum-stone is not. At a strong red heat the 
 
43 6 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 aluminium sulphate separates into alumina, sulphurous acid, and oxygen, and the 
 potassium sulphate is also decomposed. The mineral is calcined in lime-kilns in the 
 ordinary manner or in reverberatories. The calcined alum-stone is lixiviated with 
 boiling water, the supernatant liquor decanted, and the alum crystallised out. Roman, 
 rock, or roche alum is prepared in a similar manner, the red colour being due to 
 peroxide of iron.* Latterly, the calcined stone is lixiviated with dilute sulphuric acid 
 instead of water. 
 
 Preparation of Alum from Alum-Shale and Alum-Earths (2nd Group}. This 
 mode of preparation yields the greatest amount of alum with as much facility as does 
 alum-stone. 
 
 Alum-Shale. Alum-shale or schist is a sulphurous iron pyrites found under beds of 
 clay in Upper Bavaria, in Prussia, near Dlisseldorf, Saxony, Bohemia, Belgium, 
 Hurlet and Campsie, near Glasgow, &c. Only very inferior kinds require an addition 
 of alkali salts. 
 
 Alum-Earths. Alum-earth is more qr less a mixture of weathered iron pyrites with 
 various bituminous matters. The sulphur is present partly in a free state, partly as iron 
 and vitriol pyrites ; the iron is present partly as sulphide, partly as iron humate. 
 
 Preparation of Alum. The preparation of the alum may be considered in the 
 following six operations : 
 
 1. Roasting the Alum-Earth. The roasting of the alum-earth is the easiest of the 
 operations. The greater part of the alum manufactured is produced by precipitating 
 aluminium sulphate with a solution of alkali salts. It is not always necessary that the 
 schist should be burnt to concentrate the aluminium sulphate, a lengthy weathering 
 being sufficient. The action may be explained as follows : By the weathering, 
 the iron bisulphide absorbs oxygen, to form iron sulphate, which separates into 
 protoxide of iron and sulphuric acid, the latter acting upon the alumina forming an 
 equivalent quantity of aluminium sulphate. Or by roasting, the bisulphide is decom- 
 posed to monosulphide and sulphur, which, with the sulphur of the alum-earth, gives 
 rise to sulphurous acid, and this acting upon the alumina produces aluminium sulphate 
 and sulphite. The roasting or calcination, however, should not take place with earths 
 that have been subjected to less than a year's weathering, as there is found to be in 
 practice a loss of one-sixth of the aluminium sulphate. 
 
 2. Lixiviation. The lixiviation of the calcined alum earths is effected in a lixivia- 
 tion cistern in which the earth is placed. These tanks stand in rows of five, the best 
 arrangement being to build them on a slope near the calcination heaps. Each 
 vessel has a length of 6 to 7 metres, is 5 metres broad, and about 1-3 metre in height. 
 They are three-parts filled with the burnt earth, and completely with water ; the 
 lixivium flows from the highest tank to the lowest. If the lye is not of ri6 sp. gr. 
 fresh shale is added. 
 
 3. Evaporation of the Lye. The concentration of the raw lye by evaporation is 
 accomplished in leaden pans. These, however, deteriorate, crack, are easily melted, 
 
 * The composition of Roman alunite, according to C. Schwarz, is- 
 Silica 13*40 per cent. 
 
 Alumina . . . . 35'5o 
 Potassa . . . . 1 2 - 50 
 Sulphuric acid . . . 30-00 
 Ferric oxide .... 0^05 
 
 Water 8-50 
 
 The alunite is most advantageous if roasted at 500, and extracted with sulphuric acid at from 
 1*297 to I '530 sp. gr. Roman alum crystallises in cubes. If such alum is dissolved in water and 
 the liquid is heated to 100, basic alum is deposited and the mother liquor yields on evaporation 
 octahedral crystals. Common alum can be converted into the cubic kind by digesting with 
 aluminium hydroxide at 40. 
 
SECT, m.] SALTS OF ALUMINIUM. 437 
 
 and their place is now generally supplied by cisterns of masonry. But most to be 
 preferred is Bleibtreu's method of heating with gas, introduced in the alum works on 
 the banks of the Rhine. The treatment of the raw lye while being concentrated 
 depends upon its condition and upon the ferrous sulphate it contains. As ferrous sul- 
 phate is commonly present in large quantities in the raw lye or liquor, many of the 
 German alum works are also vitriol works. When, however, the quantity of ferrous 
 sulphate is too small to admit of being advantageously treated for the preparation of 
 copperas, the liquor is at once evaporated until it has attained a sp. gr. of 1*40. During 
 the ebullition basic iron sulphate is deposited, the liquor becomes of yellow-red colour, 
 assumes a somewhat slimy condition, and has to be rendered clear before alum is 
 obtained from it. This clearing is effected by pouring the liquor into large wooden 
 water-tight tanks ; the liquor having deposited, the suspended matter is tapped or 
 syphoned off from the sediment, and transferred to the precipitation tanks. 
 
 4. Alum-flour. The precipitation of flour of alum is effected, in case it is desired tc 
 make potash-alum by the addition to the liquor of a potash salt, or of an ammonia 
 salt if it is desired to make ammonia-alum. The solution of the alkaline salt is called 
 the precipitant ; by the combination of the aluminium sulphate contained in the 
 liquor with the precipitant alum is formed, and deposited as a solid salt, care being 
 taken to prevent the formation of large crystals by keeping the liquid stirred. By 
 this means the alum is deposited as a crystalline powder or so-called flour of alum, 
 which by being washed with cold water can be freed from any adhering mother 
 liquor. The precipitation was formerly effected by the addition of wood-ash lye or 
 lant ; at the present day potassium chloride obtained either from kelp, carnallite, or 
 beet- root molasses, and potassium sulphate derived from the decomposition of kainite, 
 are employed for this purpose. Potassium chloride is useful only when the 
 solution contains large quantities of ferrous sulphate, which, being converted into 
 ferric chloride, forms potassium sulphate. Potash can only be used when the lye contains 
 enough free sulphuric acid to combine with the salt ; for otherwise a portion of the 
 aluminium sulphate would become precipitated as insoluble alumina. The ammonia 
 salt made use of is generally ammonium sulphate ; 100 parts of aluminium sulphate 
 require for precipitation 
 
 Potassium chloride . . . . . 43'S parts 
 
 sulphate 50^9 
 
 Ammonium sulphate 47*8 
 
 The liquor covering the alum-flour is somewhat of a green colour, and contains little 
 alum, but chiefly ferroso-ferric chloride, iron and magnesium sulphates, or magnesium 
 chloride, dependent upon whether the precipitation was effected by sulphates or 
 by chlorides. This liquor is used for making impure alum, ferrous sulphate, or is 
 employed in the preparation of ammonium sulphate. 
 
 5. Washing and Re-crystallisation. The floury alum is generally washed in the 
 hydro-extractor or centrifugal machine and the liquor obtained again used for pre- 
 paring alum. The washed floury alum is (6) converted into large crystals by re-crystal- 
 lisation, the alum at the same time being purified. For this purpose the alum-flour 
 is dissolved in 40 per cent, of its weight of boiling water, the operation being carried 
 on in wooden lead-lined tanks. The hot solution is run into crystallising vessels, 
 where the crystallisation is finished, according to the temperature of the air, in eight to 
 ten days. From this operation hardly any mother liquor remains, the vessel being 
 almost entirely filled with alum crystals. 
 
 Preparation- of Alum from Clay (yd Group). The manufacture of alum and of 
 aluminium sulphate from such materials as contain only alumina, to which consequently 
 sulphuric acid and alkaline salts have to be added, has come largely into practice in 
 
43 8 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 England. The materials employed are : (a) clay, (b) cryolite, (c) bauxite, (d) blast- 
 furnace slag. 
 
 (a) Preparation of Alum from Clay. The clay to be employed for this purpose 
 should be as free as possible from calcium and iron carbonates. It is first gently 
 heated in contact with air, partly with the view of dehydration, partly for the 
 purpose of converting any iron into oxide, and lastly to render the clay more readily 
 soluble in acids. By dehydration the clay becomes porous and fit to take up 
 sulphuric acid by capillarity. The gently ignited and powdered clay is gradually put 
 into sulphuric acid of 140 Tw. ( = 1-52 sp. gr.) contained in a leaden pan, and heated 
 nearly to the boiling-point. The mass effervesces and becomes thick, and is next 
 transferred to iron tanks, where it solidifies. It is afterwards lixiviated with water, or, 
 better, with the liquor obtained by washing the alum-flour. The lixivium, having become 
 clear by standing, is syphoned off from the sediment, and boiled with a sufficient 
 quantity of potassium bisulphate or ammonium sulphate from gas liquor. The hot 
 solution is transferred to a shallow leaden pan, and kept stirred for the purpose of 
 converting the alum on separating into flour. The flour is washed, dried, and is then, 
 converted into large crystals as described above. The product known in the trade as 
 alum-cake is the result of the action of sulphuric acid upon clay ; it is met with in a 
 pulverised state, is used more especially in the manufacture of inferior kinds of paper, in 
 dyeing, and as a precipitant for sewage, and contains from 13 to 17 per cent, of alumina. 
 
 (b) Preparation of Alum from Cryolite. Since the year 1857 alum and aluminium 
 sulphate have been prepared, along with soda, from the mineral known as cryolite or 
 Greenland spar, A1 2 F 6 + 6NaF 2 , and consisting in i oo parts of 
 
 Fluorine .';''. ,. . . . . 54*5 
 Aluminium ; . ' , : . . . . . 13*0 
 Sodium ' . . . . u . . 3 2 '5 
 
 The following are the methods employed for this purpose : 
 
 (a) Decomposition of Cryolite by Ignition with Calcium Carbonate according to 
 Thomsen's Method. i molecule of cryolite is ignited with 6 molecules of calcium car- 
 bonate, carbonic acid escapes, and soluble sodium aluminate and insoluble calcium 
 fluoride are formed Al 2 F 6 .6NaF + 6 CaC0 3 = Al 2 (ONa) 6 + 6CaF 2 + 6C0 2 . From 
 the ignited mass the sodium aluminate is obtained by lixiviation with water, and into 
 the solution carbonic acid gas is passed. The result is the precipitation of hydrated 
 gelatinous alumina and sodium carbonate, which remains in solution. If it be desired 
 to obtain the alumina as an earthy compact precipitate, sodium bicarbonate is used as 
 a precipitant instead of carbonic acid. While the clear liquor is boiled down for the 
 purpose of obtaining sodium carbonate, the precipitated alumina is dissolved in dilute 
 sulphuric acid ; this solution is evaporated for the purpose of obtaining aluminium 
 sulphate (so-called concentrated alum), or the solution, after having been treated with a 
 potassa or ammonia salt, is converted into alum. 100 Ibs. of cryolite yield 33 Ibs. of 
 alumina, which require 90 Ibs. of sulphuric acid to yield a neutral solution ; 100 Ibs. of 
 cryolite will therefore yield 305 Ibs. of alum, and may give in addition 
 
 Calcined soda 75-0 Ibs., or 
 
 Crystallised sodium carbonate . . . 203x3 or 
 
 Caustic soda 44-0 or 
 
 Sodium bicarbonate . . . . .119-5,, 
 
 (j3) Decomposition of Cryolite urith Caustic Lime by the Wet Way (Sauerwein's Method). 
 Yery finely ground cryolite is boiled with water and lime, the purer the better, and 
 as free from iron as possible, in a leaden pan. The result is the formation of a solution 
 of sodium aluminate and insoluble calcium fluoride 
 
 Al,Fl 4 ,6NaFl + 6CaO = Al 2 (ONa) 6 + 6CaFl,. 
 
SECT, m.] SALTS OF ALUMINIUM. 439 
 
 When the calcium fluoride has been deposited, the clear liquid is decanted, and the 
 sediment washed, the first wash-water being added to the decanted liquor, and the 
 second and third wash-waters being used instead of pure water at a subsequent 
 operation. In order to separate the alumina from the solution, of sodium aluminate, 
 there is added to the liquid, while being continuously stirred, very finely pulverised 
 cryolite in excess, the result of the decomposition being exhibited by the following 
 formula Al 2 (ONa) 6 + Al 2 Ka G F in - 2A1 2 3 + i2NaF. When no more caustic soda can 
 be detected in the liquid a small quantity of which should, after filtration, yield, 
 upon the addition of a solution of sal-ammoniac and application of heat, a pre- 
 cipitate of alumina it is left to stand for the purpose of becoming clear. The 
 clarified solution of sodium fluoride is then drawn off, and the alumina treated as 
 above described. The solution of sodium fluoride having been boiled with caustic lime 
 yields a caustic soda solution which, having been decanted from the sediment of calcium 
 fluoride, is evaporated to dryness. The calcium fluoride obtained as a bye-product 
 of the cryolite industry is now used in glass-making. 
 
 (y) The decomposition of cryolite by sulphuric acid yields sodium sulphate, con- 
 vertible into carbonate .by Leblanc's process, and aluminium sulphate free from iron- 
 238 parts of cryolite require for decomposition 240 parts of anhydrous or 321 parts of 
 ordinary sulphuric acid. The resulting compounds are aluminium sulphate, sodium 
 sulphate, and hydrofluoric acid : Al 2 Na F l2 + 6H 2 S0 4 = Al 2 (S0 4 ) 3 3Na 2 SO 4 + 1 2HF. This 
 method of decomposing cryolite is, however, by no means to be recommended, as, 
 owing to the liberation of hydrofluoric acid, peculiarly constructed apparatus are 
 required ; while the sodium sulphate has to be converted into sodium carbonate. 
 Persoz suggests that cryolite should be treated in platinum vessels with three times its 
 weight of strong sulphuric acid, to be recovered with the hydrofluoric acid by distil- 
 lation. The solid residue should be treated with cold water in order to dissolve the/ 
 larger part of the sodium bisulphate contained in the saline mass, from which the 
 anhydrous aluminium sulphate is extracted with boiling water, and converted by the 
 addition of potassium or ammonium sulphate into alum free from iron. The solution of 
 sodium bisulphate, having been evaporated to dryness, is employed for the preparation 
 of fuming sulphuric acid, Glauber's salt remaining as a residue. 
 
 (c) Preparation of Alum from Bauxite. In some parts of Soiithern France, in 
 Calabria, near Belfast, Ireland, and other parts of Europe, a mineral occurs consisting 
 essentially (60 per cent.) of hydrated alumina of greater or less purity, termed bauxite, 
 from the fact of having been first found in the commune of Baux, in France. In order 
 to prepare alum and aluminium sulphate from this mineral, it is first disintegrated by 
 being ignited with sodium carbonate, or with a mixture of sodium sulphate and 
 charcoal ; in each instance the lixiviatioii of the ignited mass yields sodium aluminate, 
 from which, by processes already described under Cryolite, alum, or aluminium sulphate 
 and soda are prepared. 
 
 (d) Preparation of Alum from Blast-Furnace Slag. J.Lurmann recommends that the 
 slag should be decomposed by means of hydrochloric acid. From the resulting solution 
 of aluminium chloride * the alumina is precipitated by calcium carbonate, any dis- 
 solved silica being precipitated at the same time. The alumina is dissolved in 
 sulphuric acid, leaving the silica; 100 kilos, of slag containing 25 per cent, of 
 alumina yield 180 kilos, of alum and 31 kilos, of silica. 
 
 Alum from Felspar (qth Group}. The manufacture of alum from minerals (for 
 instance, felspar) containing alumina and potassa is not of any industrial importance. 
 
 * Crude aluminium chloride is used as a disinfectant under the name of chloralum, and as a 
 precipitant for sewage. Compare Slater's Sewage Treatment. 
 
440 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 Properties of Alum. Potash-alum, K 3 J4S0 4 + 24H,0, orK 2 S0 4 + A1,(SO<), 
 consists in 100 parts of 
 
 Potassa 9*95 
 
 Alumina 10-83 
 
 Sulphuric acid 337 * 
 
 Water 45'S 1 ' 
 
 It crystallises readily in regular octahedra, loses at 60 18 mols. of water, and fuses at 
 92 in its water of crystallisation, yielding a colourless fluid which retains its state of 
 aggregation for some time after cooling before it solidifies into a crystalline mass. At 
 a temperature a little below red heat alum loses all its water, becoming converted into 
 burnt-alum, alumen ustum, a white, porous, readily friable mass. "When ignited 
 with carbonaceous matter, air being excluded, potash-alum forms a pyrophoric 
 
 compound. 
 
 100 parts of water at o dissolve 3-9 parts of potash-alum 
 20 15-8 
 
 i 40 31'2 r , 
 
 loo 360-0 
 
 The solution of alum in water (the salt is insoluble in alcohol) has an astringent, 
 sweet taste, and possesses an acid reaction so strong that when alum is heated with 
 common salt hydrochloric acid is evolved; while a concentrated solution of alum 
 destroys the blue colour of many not of all artificial ultramarines. 
 
 Ammonia Alum. This salt, 
 
 ' or ( NH 4)* S 4 + A1 2 (S0 4 ) 3 + 2 4 H 2 0, 
 consists in 100 parts of : 
 
 Ammonia ...... 3-89 
 
 Alumina ...... 11-90 
 
 Sulphuric acid ..... 35' 10 
 
 Water . 48-11 
 
 lOO'OO 
 
 Ammonia-alum is now far more extensively manufactured than potash-alum. 
 When ammonia-alum is strongly heated, ammonium sulphate, water, and sulphuric 
 acid are driven off, and alumina remains. 
 
 loo parts of water at o dissolve 5-22 parts of ammonia-alum 
 ii 20 i3"C5 ,i 
 
 4 27-27 
 
 I0 ii 421-90 ii M 
 
 Soda-Alum. The formula of this salt is 
 
 + 2 4 H 2 0, or Na,S0 4 + A1 2 (S0 4 ) 3 + 2 4 H,O, 
 containing in 100 parts 
 
 Soda 6-8 
 
 Alumina n-2 
 
 Sulphuric acid 34-9 
 
 Water 47-1 
 
 lOO'O 
 
 It is as readily prepared from aluminium sulphate and sodium sulphate as the 
 alums already mentioned, but its solubility prevents the separation from the mother 
 
 * Manmene questions the existence of 45-51 per cent, of water in alum. 
 
SECT, in.] SALTS OF ALUMINIUM. 441 
 
 liquor, while its solution when boiled loses the property of crystallising. As iron 
 cannot be removed from this salt by re-crystallisation, the materials it is obtained from 
 should be free from that metal. The solutions should be mixed cold, and gently 
 evaporated at a temperature not exceeding 60. 
 
 Neutral or cubical alum (K 2 S0 4 + A1 2 3 , 2 S0 3 ) is obtained either by adding to an 
 alum solution so much potassium or sodium carbonate as will begin to separate the 
 alumina, or a solution of alum is treated with gelatinous alumina. By boiling 1 2 parts 
 of alum and i part of slaked lime in water, the same salt is obtained. This neutral 
 salt is often preferred in dyeing and calico printing, as it does not affect certain 
 colours. When ammonia-alum is similarly treated, it also yields a neutral alum. 
 Blesser (a) and Schmidt (b) found the following to be the composition of cubical alum 
 in 100 parts : 
 
 () W 
 
 Sulphuric acid 34'52 ... 33'95 
 
 Alumina ir86 ... 11-48 
 
 Potassa 9-44 ... 9-04 
 
 Water 45-27 ... 45-61 
 
 101-09 loo-oS 
 
 Insoluble or basic alum, A1 2 K 2 .2S0 4 , is obtained by boiling a solution of alum with 
 hydrate of alumina ; it is a white, insoluble powder, and as regards its composition 
 similar to alum-stone. Basic alum is soluble in acetic acid. 
 
 Aluminium Sulphate. The active principle of alum is evidently the aluminium 
 sulphate, not the potassium and ammonium sulphates, the object of the preparation of 
 the double salt being simply the obtaining of a definite compound, which, while it 
 readily crystallises, can be obtained in a pure state, especially free from iron, a very 
 injurious ingredient in alum used in dyeing and calico-printing.* However, at the 
 present day, with improved methods of manufacture, aluminium sulphate is largely 
 prepared, and of excellent quality. It is often sold under the name of concentrated 
 alum or cake alum, as it occurs in the trade as square cakes. It is white, somewhat 
 transparent, and may be cut with a knife ; is readily soluble in water, contains always 
 free sulphuric acid, and also to some extent potassa- and soda-alum. 
 
 In the pure state this salt has the formula A1 3 (S0 4 ) 3 + i8H 2 O, and contains in 100 
 parts alumina, iS'yS; sulphuric acid, 38'27 ; water, 42^95; total, 100. That the 
 composition of this salt as met with in commerce varies greatly may be inferred 
 from the following results of Varrentrapp's analyses of different samples of this 
 salt: 
 
 i. 2. 3- 4. 
 
 Alumina . . . 15*3 ... I2'5 ... 15'! ... 13-0 
 Sulphuric acid . . 38-0 -~ 30-6 ... 38x3 ... 34*0 
 
 According to the formula, the quantify of sulphuric acid in these samples should have 
 been 
 
 I- 2. 3. 4- 
 
 35'8 . 29-2 43'3 3o-5 
 
 The quantity of water even varies between 56 and 48 per cent, for different parts 
 of the same cake. "Weygand found a sample of this salt prepared at Schwemsal to 
 contain alumina, I5'57; sulphuric acid, 38'i3; oxide of iron, i'i5; potassa, 0*62; 
 water, 45*79 parts. The aluminium sulphate prepared from cryolite at Harburg con- 
 tains about 5 per cent, of sodium sulphate. The results obtained in the analyses by 
 H. Fleck of various samples of cake-alum are 
 
 * An almost infinitesimal trace of iron renders alum unfit for dyeing alazarine reds or roses. 
 
44 2 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 Aluminium sulphate . . . 47'35 ... 5o'8o ... 51-63 
 Sodium ... 4-35 ... 1-24 ... 077 
 
 Free sulphuric acid . . . 073 ... 0-27 
 
 Water 47'37 47'47 46'94 
 
 99-80 ... 9978 ... 99-34 
 
 Cake-alum is prepared either from clay, cryolite, or bauxite, by methods already 
 described. When clay is employed, the iron has to be removed from the dilute solution 
 of the aluminium sulphate by precipitation as Berlin blue by means of potassium 
 ferrocyanide. When cryolite is used, the alumina, separated from the solution of 
 sodium aluminate by carbonic acid or powdered cryolite, is put into sulphuric acid, 
 contained in a wooden lead-lined tank, and heated to 80 to 90, the addition of the 
 alumina to the acid being continued until solution ceases to take place. The solution 
 having been clarified by standing for some time is next evaporated in a copper vessel 
 until the salt fuses ; it is then cast into moulds. With due care aluminium sulphate 
 may be used in dyeing and calico-printing, but it cannot be altogether substituted for 
 alum, owing to its variable composition. 
 
 Aluminium hydrochlorate, formerly known as muriate of alumina, may be prepared 
 in an impure state by the process of Georges Fournier, who lixiviates pyritic alum shales, 
 previously well weathered, allows ferrous sulphate to crystallise but and adds to the 
 residual lye of aluminium sulphate containing iron sulphate, sodium chloride. At tem- 
 peratures of i or 2 sodium sulphate crystallises out and is drained by whizzing. 
 The mother liquor is aluminium hydrochlorate. 
 
 Slater dissolves in crude hydrochloric acid a mineral found in the North of Ireland 
 which differs from bauxite by containing 3 instead of 2 mols. of combined water 
 and by being easily soluble in hydrochloric acid. Both these forms of aluminium 
 hydrochlorate are well adapted for the treatment of sewage and refuse waters -by 
 precipitation. 
 
 Sodium Aluminate. Sodium aluminate is now prepared on the large scale, as it 
 has been found to be a useful form of soluble alumina, especially in dyeing and calico- 
 printing. The preparation of this compound is based upon the solubility of alumi- 
 nium hydroxide in caustic potassa- or soda-lye, and the ready decomposition of the 
 solution by carbonic and acetic acids, sodium bicarbonate and sodium acetate, sal- 
 ammoniac, &c. 
 
 Sodium aluminate was first brought under the notice of dyers by Macquer and 
 Hausmann in 1819, but owing to the preparation being too expensive it did not come 
 into industrial application until comparatively recently. We have already described 
 the mode of manufacturing sodium aluminate from cryolite ; but in Germany the 
 chief seat of the cryolite industry this salt is not made on the large scale ; in France 
 it is manufactured by Merle & Co.. at Alais, and in England at the Washington 
 Chemical Works. In France bauxite, containing 60 to 75 per cent, of alumina and 
 from 12 to 20 per cent, of oxide of iron, is the raw material, and is treated with sodium 
 hydroxide or carbonate. If caustic soda is used, the pulverised mineral is boiled with a 
 solution of the alkali ; while if the carbonate is employed, the mixture is ignited in a 
 reverberatory furnace. In either case sodium aluminate is produced, dissolved in the 
 case of ignition, the semi-fused mass is lixiviated with water and evaporated to 
 dryness. The salt met with in commerce is a white powder with a green-yellow hue, 
 dry to the touch, and consisting of 
 
 Alumina . _ . . . . . .48 
 
 Soda ........ 44 
 
 Sodium chloride and sulphate . .8 
 
SECT, in.] , SALTS OF ALUMINIUM. 443 
 
 Al ) 
 The formula, ^ 2 j- 6 , would require 
 
 Alumina ... . . . 5279 
 
 Soda 47'2i 
 
 Sodium aluminate is equally soluble in cold and hot water. Exposed to air it 
 absorbs moisture and carbonic acid, and consequently on being dissolved in water the 
 salt so changed yields a turbid solution, owing to alumina being suspended. The aqueous 
 solution of this salt -is not stronger than 14 to 18 Tw. = 1*07 to 1^09 sp. gr. 
 According to Le Chatelier, Deville, and Jacquemart, aluminium sulphate is the starting- 
 point of the preparation of sodium aluminate by precipitating from the sulphate 
 the alumina, and re-dissolving the latter in caustic soda-lye. Sodium aluminate is 
 largely used in the preparation of an opaque, milky-looking glass, or semi-porcelain. 
 Sodium aluminate is a bye-product of Balara's method of soda manufacture from 
 bauxite, Glauber's salt, and coal ; this bye-product, or rather product of the second 
 stage of the process, is decomposed by carbonic acid into sodium carbonate and alumina, 
 which is thrown down. The Pennsylvania Salt Manufacturing Company at Natrona, 
 near Pittsburg, manufacture large quantities of sodium aluminate, which is used in 
 soap-boiling under the name of natrona refined saponifier.* 
 
 Aluminium Hydrate, A1 2 (OH) 6 , is obtained by adding to sodium aluminate cream 
 of lime, when insoluble calcium aluminate separates out 
 
 Al 2 (ONa) 6 + 3Ca(OH) 2 = 6Na(OH) + Ca 3 Al 2 6 . 
 
 After washing, the precipitate is dissolved in hydrochloric acid, and the solution 
 decomposed with a fresh quantity of calcium aluminate, when aluminium hydroxide is 
 deposited, which is washed and dried 
 
 Ca 3 Al 2 6 + I2HC1 = 3CaCl 2 + A1 2 C1 6 + 6H 2 0. 
 A1 2 C1 6 + Ca 3 Al s 6 + 6H 2 = -sCaCl, + 2A1 S (OH) 6 . 
 
 Aluminium hydrate is obtained also on precipitating a solution of sodium with 
 carbonic acid, sodium bicarbonate, or sal-ammoniac, or by precipitating a solution of 
 alum with sodium carbonate. 
 
 Aluminium hypochlorite has been proposed for bleaching ; aluminium sulphite for 
 disinfection and for preserving articles of animal food ; and aluminium oxalate for pre- 
 serving articles of marble, dolomite, &c. Aluminium chloride, free from iron, &c., was 
 proposed some time ago as a disinfectant, under the name of chloralum, but at present 
 it is used for " carbonising " wool. Aluminium acetate is used in dyeing f (see Mordants). 
 A very questionable aluminium carbonate has been proposed for sanitary purposes. 
 Applications of Alum and Aluminium Salts. Owing to the great affinity of the 
 alumina contained in alum for textile fibres, especially wool and cotton, alum is largely 
 used as a mordant in dyeing, except when the tar colours are employed. Again, owing 
 to the affinity of alumina for many pigments, alum is employed in the preparation of the 
 lake colours, combinations of active colouring principles with alumina. It is also used 
 in the melting of tallow ; for hardening gypsum ; it is found in the preparation used 
 for sizing hand-made paper, the alum in this case forming with the glue or size an 
 insoluble compound. Alum with resin is employed for the same purpose in machine- 
 made paper, an aluminium pinate being formed. It is very largely used for the 
 preparation of aluminium acetate, and with common salt in the tawing of leather. 
 Alum is employed in clarifying turbid fluids, more especially water ; in this case the 
 
 * Sodium aluminate is nsed by Maxwell Lyte for the treatment of soda by precipitation, for 
 which purpose it is very suitable. 
 
 t Aluminium acetate, for the production of alizarine roses and reds in dyeing and tissue-printing, 
 is being to some extent superseded by aluminium sulphocyanide (rhodanide). Compare Hummel, 
 Dyeing of Textile Fabrics, p. 172. Aluminium nitrate is also occasionally used as a mordant. 
 
444 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 alum takes up the alumina suspended in the water, and, forming an insoluble (basic) 
 alum, carries down organic and other suspended impurities. A boiling solution of 
 alum, common salt, and potassium nitrate is used by jewellers for the purpose of 
 colouring gold that is to say, to produce a film of pure gold on the alloy, the copper 
 of which is dissolved by the boiling solution. Sodium aluminate is used in dyeing and 
 calico-printing ; further, for the preparation of lake colours, the induration of stone, 
 and the manufacture of artificial stone, and for the saponifi cation of fats in the stearine 
 candle manufacture, an alumina soap being first formed, which is decomposed by acetic 
 acid into aluminium acetate and free fatty acid. 
 
 ULTRAMARINE. 
 
 Ultramarine is a splendid blue colour, formerly obtained in small quantities from 
 lazulite. Its analysis led to the production of artificial ultramarine an invention 
 ascribed by the French to Guimet, but by. the Germans to C. Gmelin. 
 
 Raw Materials. These are i. Aluminium silicate as free as possible from iron, a 
 good china clay, the kaolin of Cornwall being esteemed the best; 2. Calcined sodium 
 sulphate ; 3. Calcined soda ; 4. Sodium sulphide, as a bye-product of the manufacture ; 
 5. Sulphur; 6. Pulverised charcoal, or pit-coal. 
 
 Porcelain, or china clay, is generally used, or a white clay, the composition of 
 which is nearly the same. Small quantities of lime and magnesia have no injurious 
 effect, but the oxide of iron should not exceed i per cent. The composition of the 
 clay should approach as nearly as possible to the formula H 2 Al,Si 2 8 ; the silica may be 
 combined or partly free. The clay is washed with water and treated in the same 
 manner as for making porcelain; ib is next dried, ignited, and ground to a very 
 fine powder. The sodium sulphate should not contain any free acid, lead, or iron. If 
 the sulphate does not possess the requisite qualities, it is dissolved in water, milk of 
 lime being added to neutralise the acid and to precipitate oxide of iron. The clear 
 solution is left to crystallise, and the crystals are ignited in a reverberatory furnace 
 and then pulverised. The clear solution is in some cases evaporated to dryness and 
 ignited in iron vessels. Barium, but not potassium, salts form ultramarine.* The 
 calcined soda is obtained from the alkali works, and should contain at least 90 per cent, 
 of sodium carbonate ; it is also finely pulverised. Very recently caustic soda has been 
 substituted in some ultramarine works. Sodium sulphide (Na 2 S) is usually a bye-pro- 
 duct of the process of making ultramarine, and is obtained either in solution or as a 
 dry powder. The sulphur is used very finely pulverised. The carbonaceous matter 
 employed is also in a very fine powder. Its use was introduced by Leykauf for the 
 purpose of deoxidation. In order to have the carbon in as finely divided a state as 
 possible it is ground to a pulp with water under granite stones ; the pulp is lixiviated, 
 and the fine powder obtained dried and passed through a sieve ; in some cases resin 
 and pitch are employed. For ultramarines which must not have their colour discharged 
 by alum, pure silica, either as fine glass, sand, or pulverised quartz, is used. Several 
 substances are used to reduce the depth of colour of ultramarine viz., gypsum, barium, 
 sulphate, baryta white, and flour ; the last is employed in making up washing blue. 
 
 Manufacture of Ultramarine. The methods of ultramarine preparation may be 
 classified, according to the crude materials employed, as the three following : 
 (a) Preparation of sulphate, or Glauber's salt, ultramarine. 
 (6) ,, soda-ultramarine, 
 
 (c) ,, ,, silica-ultramarine. 
 
 (a) Preparation of Sufyhate- Ultramarine. This ultramarine is prepared according 
 
 * See Chemical News, vol. xxiii. pp. 119, 142, 204. 
 
SECT, in.] ULTRAMARINE. 445 
 
 to the Nuremberg process from kaolin, sodium sulphate, and charcoal ; the preparation 
 consisting in two distinct stages, viz. : 
 
 (a) Preparation of green ultramarine. 
 (/3) Conversion of green into blue ultramarine. 
 
 (a) Preparation of Green Ultramarine. In order to obtain a most intimate mixture 
 of the dry and finely pulverised materials, small quantities are weighed off, mixed in 
 wooden troughs by means of shovels, and several times passed through sieves. If 
 solutions of Glauber's salt, soda, and sodium sulphide are used instead of powders 
 the kaolin is mixed with these solutions, and the whole evaporated to dryness, gently 
 ignited in a reverberatory furnace, and then pulverised and sifted. The quantities of 
 the crude materials vary, but the following conditions have to be complied with : 
 i. Soda, whether sulphate or caustic, must be present in such quantity that it can 
 saturate half of the silica of the clay (kaolin). 2. There must be sufficient soda 
 remaining to form with the sulphur a certain quantity of sodium polysulphide. 
 3. There ought to remain enough sulphur and sodium to form another sodium sul- 
 phide (Na 2 S) after deducting from the whole mixture as much green ultramarine as, 
 according to its composition as proved by recent analysis, the silica and alumina 
 present are capable of forming. The following figures will give an idea of the pro- 
 portions : 
 
 I. n. 
 
 Kaolin (dried) .... 100 ... 100 
 Calcined Glauber's salt . . 83-100 ... 41 
 
 Calcined soda .... ... 41 
 Carbon (char- or pit-coal) . . 17 ... 17 
 
 Sulphur ... 13 
 
 For 100 parts of calcined soda So parts of calcined Glauber's salt, and for 100 parts of 
 the latter 60 of dry sodium sulphide, are taken. 
 
 It is usual to have a large quantity of this mixture prepared for use. If this 
 mixture is ignited without access of air, a white mass is obtained, which, having been 
 treated with water, is a light, somewhat flocculent, white substance, to which Ritter 
 has given the name of white ultramarine. It becomes green by exposure to air, and 
 blue by being calcined in contact with air. The mixture is well rammed into fire-clay 
 crucibles, placed in furnaces similar in construction to those used for burning porcelain, 
 being raised to, and maintained at, a high temperature with a very limited supply of air. 
 This operation lasts from seven to ten hours, and is completed at a bright white heat. 
 The furnace is closed and slowly cooled; on removing the crucibles, the contents appear as 
 a semi-fused grey- or yellow-green mass, which is repeatedly treated with water. The 
 ultramarine thus obtained is in porous lumps, which are pulverised into an impalpable 
 powder ; this is washed, dried, and again ground, then sifted, and finally packed in 
 boxes or casks, and sent into the market as green ultramarine, consisting, according to 
 Stolzel's analysis (1855), in 100 parts, of 
 
 Alumina 3O - n 
 
 Iron 0'49 (ferric oxide, 07) 
 
 Calcium 0-45 
 
 Sodium 19-09 (soda, 2573) 
 
 Silica 37"46 
 
 Sulphuric acid 076 
 
 Sulphur 6 - o8 
 
 . , . Chlorine 0-37 
 
 Magnesia, potassa, phosphoric acid . traces 
 
 94-81 
 Oxygen ... . . . 5'i9 
 
446 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 Green ultramarine is a pigment of comparatively inferior value, owing to its being 
 less brilliant than the green copper pigments. 
 
 (/3) Conversion of Green into Blue Ultramarine. This operation may be variously 
 effected, generally by roasting the green ultramarine and sulphur at a low temperature 
 with access of air, so as to form sulphurous acid, while a portion of the sodium is 
 oxidised into soluble sulphate and afterwards washed out ; but the sulphur originally 
 present in the green ultramarine remains combined with a smaller quantity of sodium. 
 The roasting may be variously carried out, but very frequently the apparatus consists 
 of a fixed iron cylinder similar to a gas-retort, provided with a stirring apparatus, by 
 means of which the mixture of green ultramarine and sulphur (25 to 30 Ibs. of the 
 former to i Ib. of sulphur) is submitted equally to the source of heat. The addition of 
 sulphur is repeated until the desired blue colour is produced ; but in some works this 
 calcination is interrupted by repeated lixiviation, the object being to produce a superior 
 article. Muffle-ovens and a kind of reverberatory oven are also used for this operation. 
 The sulphurous acid, which is evolved in large quantities, is now generally employed in 
 making sulphuric acid, sometimes a co-product of ultramarine manufacture, and used 
 for the preparation of the sodium sulphate required. The ultramarine, when quite 
 blue, is pulverised, lixiviated, dried, and finally separated into various qualities known 
 in the trade as No. oo, i, 2, 3, &c. 
 
 (b) Preparation of Soda-Ultramarine. As manufactured in France, Belgium, and 
 some parts of Germany, this ultramarine is either pure soda-ultramarine or a mixture 
 of soda- and sulphate-ultramarine. The materials and proportions are 
 
 i. II. m. 
 
 Kaolin 100 ... ioo ... 100 
 
 Sulphate .... ... 41 
 
 Soda . . . . . ioo ... 41 ... 90 
 
 Carbon (char- or pit-coal) . 12 ... 17 ... 6 
 
 Sulphur .... 60 ... 13 ... ioo 
 
 Kosin ..... ... ... 6 
 
 The ignition takes place either in crucibles, or, better, in a reverberatory furnace ; 
 the result is the formation of a brittle and porous green substance, which absorbs 
 oxygen very rapidly, so that, during the cooling of the mass in the oven, the greater 
 part is converted into blue ultramarine.* The complete conversion, after the addition 
 of sulphur, is obtained by heating to redness in large muffles, the bottoms of which 
 consist of plates of fire-clay and the lids of iron, the product being distinguished from 
 the foregoing by a greater depth and beauty of colour. By increasing, within certain 
 limits, the quantities of soda and sulphur, the formation of blue ultramarine may be 
 at once obtained, the product containing 10 to 12 per cent, of sulphur. 
 
 (c) Preparation of Silica- Ultramarine. Silica-ultramarine is really soda-ultramarine 
 in the preparation of \vhich silica to the amount of 5 to 10 per cent, of the weight of 
 the kaolin is added. The calcination at once yields blue ultramarine, and further 
 treatment with sulphur is therefore unnecessary. 
 
 This ultramarine is not acted upon by a solution of alum, and may be recognised 
 by its peculiar red hue, the intensity of which is increased by an increase of silica. 
 Notwithstanding the superiority of the ultramarine obtained by this process, its pre- 
 paration is disadvantageous owing to the tendency of the mixture of crude materials to 
 fuse during ignition. 
 
 The composition of the two chief kinds of ultramarine with a reddish blue (I.) and 
 a pure blue tone (II.) appears from the following analysis by B. Hofmann : 
 
 * Ultramarine green cannot be obtained by this process. 
 
SECT. nr. ULTRAMARINE, 447 
 
 i. n. 
 
 Clay residues 3-61 ... 2-11 
 
 Silica . . . . . . 4077 ... 3777 
 
 Alumina 2374 ... 29-54 
 
 Potassa . . 0-83 ... 1-38 
 
 Soda ...... 18-54 ... 21-61 
 
 Sulphur . . . . . . 13-58 ... 7-87 
 
 101-07 100.28 
 
 Siliceous blues from the Hirschberg works (I. to IV.) and from the Marienberg 
 works (V. and VI.) had, according to Guckelberger's analysis, the following composi- 
 tions : 
 
 I. II. III. IV. V. VI. 
 
 Si . . 19-2 ... 19-0 ... 19-0 ... 19-3 ... 19-3 ... 19-0 
 
 Al . . i2'6 ... 12-7 ... 13-0 ... 12-5 ... i2'8 ... 13-0 
 
 Na . 16-5 ... 16-8 ... 16-5 ... 16-8 ... i6'i ... 15-9 
 
 S . . 14-2 ... 14-0 ... 13-8 ... 13-9 ... 14-0 ... 14-0 
 
 O 37'5 37'5 - 377 - 37'5 - 37'8 ... 38-1 
 
 Since 1873 the Nuremberg Ultramarine Works produces violet and red ultra- 
 marine. These kinds are obtained by treating blue, green, or white ultramarine, at 
 a high temperature and with access of air, with acids or salts which give off acids if 
 strongly heated. A violet is first formed, and on heating more strongly a red. Violet 
 ultramarine can also be obtained by hydroxylating the blue and the green kinds. 
 
 Constitution of Ultramarine. The cause of the blue colour of ultramarine has been 
 the subject of repeated investigation. In 1758, Marggraf refuted the view then pre- 
 valent that lazulite contained copper, which was the cause of its colour. As he 
 detected the presence of iron he thought this metal must be the colouring principle. 
 Guy ton de Morveau ascribed the colour to iron sulphide. 
 
 As according to Guckelberger there are in the colour almost exactly Na 2 CaSi 2 , the 
 charge must contain Si 2 Na 4 . On exposure to the action of S0 2 at a suitable tempera- 
 ture, without escape of oxygen, there is formed from Na 3 + 2S0 2 = S 4- Na a S0 4 i.e., the 
 nascent sulphur fills up the vacancy formed by the exit of Na 2 ; we may, therefore, 
 obtain from Si 2 Al 2 Na 4 O 9 , the compound Si,Al 2 Na,S0 9 i.e., ultramarine blue. Hence 
 there is no Na 2 S in the compound, and if on the action of aqueous acids H 2 S, or 
 along with it S0 2 , is obtained and free sulphur is separated out, this ensues because 
 the constituents of water combine with the nascent sulphur. The composition 
 of ultramarine green agrees with the formula Si 6 Al c N"a 8 S 2 24 . Under the influence 
 of heat the 5 mols. Na 2 S0 4 of the charge are converted by carbon into 5Na 2 S0 3 . 
 With the increase of temperature 4 mols. Na 2 S0 3 are resolved into 3Na 2 S0 4 + Na 2 S. 
 The fifth mol. may for the first be considered as unaltered. The regenerated 
 sulphate (3 mols.) is again reduced by carbon to 3Na 2 S0 3 , which along with the 
 still existing mol. Na 2 SO 3 undergo the well-known change on heating, so that in a 
 certain stage there are present 3Na 2 S0 4 and 2Na 2 S. On increase of temperature 
 the Si0 2 enters into reaction, and by the aid of carbon it withdraws Na 2 from 
 sodium sulphate. There is formed Si 6 Al 6 Na 6 24 , an unsaturated nucleus with two 
 free affinities. The escaping S0 3 acts upon the existing 2Na 2 S ; there are formed 
 sulphate and 2NaS, which satisfy the free affinities of the nucleus. 
 
 In the blue strata the same process goes on at first, but the S0 2 escaping from the 
 green acts by removing sodium, so that sulphur must be found in the crude green 
 and |- in the crude sulphur, as experiment has shown sulphur escapes partly as SO 2 
 and partly free. The compound examined by Silber is, according to Guckelberger, 
 to be considered as Si 6 Al 6 Na 4 (OH) 2 23 . If we suppose in this compound HO 
 replaced by the equivalent NaS, the simplest expression for ultramarine blue will be= 
 
44 S CHEMICAL TECHNOLOGY. [SECT. in. 
 
 Si 6 Al 6 Na 4 (NaS) 2 23 . The siliceous colour, Si 6 Al c Na 4 (NaS) 2 + S 2 , contains the sulphur, 
 either as NaS S, or we have S S , instead of A1 2 3 . 
 
 Properties of Ultramarine. Artificial ultramarine is an impalpable powder of a fine 
 blue colour, entirely insoluble in water, and, when washed with distilled water, leaving 
 no residue on evaporation of the filtrate. It is not acted upon by alkalies, but is highly 
 sensitive to the action of even very dilute acids and acid salts, sulphuretted hydrogen 
 being evolved and the colour discharged. Native ultramarine obtained from lapis lazuli 
 is not thus decomposed by weak acid solution. There sometimes accidentally occurs in 
 soda furnaces a more or less blue ultramarine which exhibits the same resistance to acids. 
 That kind of ultramarine commercially termed acid proof is manufactured with the 
 addition of silica, as described, but it really only resists the action of alum-salts. Ultra- 
 marine is now largely used for the purposes to which smalt, litmus, and Berlin blue 
 were applied that is to say, ultramarine is employed as a paint, as a pigment in stereo- 
 chromy, for paper-hangings, calico-printing with albumen as fixing material, for colour- 
 ing printing-ink, for the bluing of linen and cotton fabrics, paper, stearine- and paraffine- 
 candles, and lump-sugar. For 1000 cwts. of sugar 2\ Ibs. of the pigment are employed, 
 a quantity so small as to be perfectly innocuous ; further, ultramarine does not contain 
 anything injurious to health. Green ultramarine is a dull-coloured powder used by 
 wall-paper stainers, and is sometimes mixed with indigo-carmine and a yellow pigment 
 to improve the colour. 
 
 Adulterations of ultramarine with Berlin blue, smalt, and other blue pigments do 
 not now occur, as ultramarine is a cheaper material ; but to obtain lighter tints, 
 ultramarine is sometimes mixed with chalk, kaolin, alabaster, and chiefly with barium 
 sulphate. 
 
 COMPOUNDS OF TIN AND ANTIMONY. 
 
 Mosaic Gold (Aurum Musivum). The substance known under this name is in 
 reality a bisulphide of tin (SnS 2 ), prepared in the following manner : 4 parts of pure 
 tin, with 2 of mercury, are amalgamated by the aid of a gentle heat, and introduced 
 wich z\ parts of sulphur and 2 of sal-ammoniac into a flask, and heated on a sand-bath, 
 at first gently, and then gradually increasing to a full red heat. First the sal-ammoniac 
 volatilises, and next mercury in the shape of cinnabar mixed with a trace of the sulphide 
 of tin ; while there is left the preparation known as mosaic gold, forming the upper layer 
 of the remaining contents of the flask, the lower portion being of badly coloured sul- 
 phide. The rationale of the formation of this peculiar coloured sulphide that is, 
 peculiar as regards its physical appearance is not quite clearly explained ; the compound, 
 moreover, may be prepared without mercury. When properly prepared, it appears as a 
 golden-coloured metallic substance, greasy to the touch, and soluble in the alkaline sul- 
 phurets. It is chiefly used for imitating gilding on painted surfaces, but its employment 
 is very much restricted from the fact that the bronze-colours give a more satisfactory 
 result. Indeed, in the English market mosaic gold is almost obsolete. 
 
 Tin Crystals (solid) (Stannous Chloride, SnCl 2 .2H 2 0). By the name of tin-salt the 
 trade understands chloride of tin (SnCl 2 ), but the commercial article, being prepared by 
 dissolving granulated tin in hydrochloric acid and evaporating the solution, is really 
 SnCl 2 +2H 2 0. According to H. Nollner, hydrochloric acid gas should be caused to 
 act on granulated tin placed in earthenware receivers, and the concentrated tin-salt 
 solution thus obtained evaporated in block-tin vessels. The salt occurs in the trade in 
 colourless, transparent, diliquescent crystals, of course very soluble in water. The 
 aqueous solution, unless acidulated with more hydrochloric or tartaric acid, soon depo- 
 sits a basic salt. Tin-salt is used chiefly in dyeing and calico-printing.* 
 
 * Copper vessels may be used for dissolving tin in hydrochloric acid, as whilst any tin remains 
 undissolved the copper is not attacked. Stannous chloride is also used in the liquid state as single 
 
SECT, in.] COMPOUNDS OF ANTIMONY. 449 
 
 Tin Chloride, Stannic Chloride (SnCl 4 5H 2 0) is obtained by dissolving stannic oxide 
 in hydrochloric acid. If it be desired to obtain the solid stannic chloride, the solution 
 is mixed with clean sand or infusorial earth, dried and distilled in a current of super- 
 heated steam.* 
 
 The so-called " nitrate of tin " is made by dissolving grain bar tin (not granulated) 
 in single aquafortis, which must be absolutely free from sulphuric acid or the lower 
 oxides of nitrogen, though it may contain a proportion of hydrochloric acid. The 
 operation must be conducted very carefully, the temperature must not be allowed to rise, 
 and no red fumes must be given off. This mordant, which is of a peculiar reddish 
 yellow colour, served in grounding cochineal scarlets, is now consequently nearly fallen 
 into disuse. 
 
 Pink Salt, SnCl 4 + 2NH 4 C1, is used in tissue-printing, though less in Britain than 
 on the Continent. A concentrated solution of this salt is not affected by boiling, but if 
 diluted it deposits all its stannic oxide upon the fibre. Its neutral character is its great 
 recommendation . 
 
 Stannate of Soda, preparing salt (Na 2 Sn0 3 ). This salt is now very largely used in 
 dyeing as well as in calico-printing, and is prepared in various ways, sometimes by 
 fusing tin-ores with caustic soda and lixiviating the molten mass with water; or, 
 according to Brown, by boiling soda lye with metallic tin and litharge, the effect 
 being the formation of sodium stannate and metallic lead. Hiiffely somewhat 
 modifies this process by digesting litharge with soda lye at 22 per cent, in a metallic 
 vessel. Into the solution of sodium plumbate thus obtained, granulated tin is placed 
 and heat applied. Sometimes a sodium stannite is used, made by dissolving tin- 
 salt in an excess of caustic soda, but this preparation is unstable and does not answer 
 well in dyeing and printing ; it is only extemporaneously used on a limited scale by 
 small dyers."}" 
 
 COMPOUNDS OF ANTIMONY. 
 
 Antimony Oxide. This substance (Sb 3 3 ), obtained by calcining antimony sul- 
 phide, or by the precipitation of a solution of antimony chloride with a solution 
 of sodium carbonate, finally washing and drying the precipitate, has of late been used 
 as a substitute for white-lead, but it does not cover so well and is more expensive, though 
 it is not affected by sulphuretted hydrogen. As this oxide takes up oxygen in the 
 presence of alkalies, and is converted into antimonic acid (Sb 2 5 ), it has been lately 
 proposed for use in the preparation of aniline red and for the conversion of nitrobenzol 
 into aniline ; also for the preparation of calcium iodide by keeping antimonic oxide 
 suspended in milk of lime, and adding iodine as long as the latter is taken up. 
 
 Black Antimony Sulphide. This compound (Sb 3 S 3 )' obtained by liquation, occurs 
 in commerce in the conical shape it has assumed while cooling ; its colour is like that of 
 graphite, but it has a stronger metallic lustre, is of a deeper black colour, a fibrous, 
 crystalline structure, and very brittle ; it usually contains iron, lead, copper, and arsenic, 
 and is employed for separating gold from silver, in veterinary surgery , pyrotechny, and in 
 
 and double muriates, differing merely in their concentration ; single muriates vary from 40 to 60 
 Tw. and double muriates from 70 to 120. The former contain i to 2 oz. metallic tin in the 
 pound, and the double kind from z\ to 5 oz. All forms of stannous chloride are used as mordants. 
 See Slater : Manual of Colours and Dye Wares. 
 
 * The various liquids used by dyers and printers under the names of solution, composition, &c., 
 are made by dissolving metallic tin in mixtures of hydrochloric acid and nitric acid, differing 
 greatly in strength and proportions, and with or without the addition of alkaline chlorides. Oxalic 
 acid or tartaric acid is often added to the finished solution. 
 
 t The author states that " some years ago the use of a double sodium salt of arsenic and stannic 
 acids was introduced among English dyers." The use of this dangerous preparation, though 
 not prohibited by law, is condemned by the best authorities as affording no advantages com- 
 mensurate with its poisonous properties. 
 
 ?. F 
 
45 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. iii. 
 
 the preparation of the percussion pellets used in the cartridges of the now celebrated 
 Prussian needle-gun. 
 
 Neapolitan Yellow. This pigment, used as an oil paint and in glass and porcelain 
 staining, is of an orange-yellow colour, and very permanent. It is lead antimo- 
 iiiate, and is prepai-ed as follows : i part of potassium antimonio-tartrate (tartar 
 emetic), 2 parts of lead nitrate, and 4 parts of common salt, are fused at a moderate 
 red heat, and kept at that temperature for two hours. The molten mass is put after 
 cooling into water and becomes disintegrated, the salt dissolving and the pigment 
 precipitating. When required for staining glass or porcelain it is mixed with a lead- 
 glass. It has recently been prepared by roasting a mixture of antimonious acid 
 and litharge. 
 
 Antimony Cinnabar. Antimony oxysulphide (Sb.-SgO^, is a compound in colour 
 similar to vermilion, and is obtained by causing sodium or calcium dithionite to act 
 upon antimonious chloride in water, and boiling this mixture, a precipitate being 
 readily deposited ; it is a soft, velvety powder, unaltered by the action of air and light, 
 and suited for either oil- or water-colour. This substance may be prepared on a large 
 scale by the following process : (i) Black antimony sulphide is calcined in a current 
 of air and steam, antimonic oxide being formed as well as sulphurous acid, which may 
 be employed for the preparation of calcium dithionite from soda waste ; the antimonic 
 oxide is next dissolved in crude hydrochloric acid. (2) Large wooden tubs which 
 admit of being internally heated by steam, are for |ths of their capacity filled with the 
 solution of calcium dithionite, and the solution of antimonious chloride is gradually 
 added, the liquid being stirred and heated to about 60 ; the reaction soon ensues, and 
 the precipitate having subsided, is thoroughly washed and dried at a temperature not 
 exceding 50. There are prepared, on a large scale, by operative pharmaceutical and 
 manufacturing chemists, numerous varieties of antimoiiial preparations, among which 
 are several sulphides and one oxysulphide, different from the preparation here 
 mentioned. 
 
 Antimony Pentasulphide, Sb 2 S 3 , is obtained by decomposing sodium sulphanti- 
 moniate with hydrochloric acid. It is used for vulcanising caoutchouc, for which 
 purpose sodium thiosulphate is added. 
 
 COMPOUNDS OF ARSENIC. 
 
 Arsenic Acid, according to Schoop, is obtained on the large scale in the following 
 manner. The plant shown (Fig. 367) in plan in ^ v of its natural size, consists of the 
 
 Fig- 367- 
 
 generators, A, the absorbent vessels, B, a neutralising pan, 0, and an evaporating pan, D. 
 Six generators, A, are connected in a suitable manner with five receivers, v. ~R *k 
 
 From the 
 
SECT. III.] 
 
 COMPOUNDS OF ARSENIC. 
 
 last receiver the tube, r, leads to the condensing pots, B. After the gases have passed 
 through these vessels, they enter the chimney through the tube, z. Shortly before this 
 exit, there is a glass tube inserted for observing the colour of the gases. Each 
 generator consists of an earthen vessel, A (Fig. 368 in ^ natural size), which has three 
 apertures provided with hydraulic joints. The middle, largest aperture serves to 
 admit a cylindrical stoneware piece, R. This piece is perforated like a sieve in its lower 
 half. The arsenical powder is introduced through a smaller opening, o, in the cover, 
 whilst the third smaller opening receives the escape-pipe, n. The entire stoneware 
 vessel stands in a wooden vat, Jf, and can be surrounded with water, the temperature 
 of which can be regul ated at pleasure by meansof the steam- or water-pipes, w and d. 
 The exit pipe, n, opens into an earthen vessel, which has essentially the same form as 
 that shown in the conde nsing-vessel, B (Fig. 369, in -^ of its natural size), but having 
 three openings instead of two. The five receivers, r, are connected below with the 
 
 Fig. 370 
 
 generators in such a manner that the fumes of a generators have to traverse two to 
 three receivers before arriving at the real condensation -pots, B. This arrangement is 
 to prevent loss in case the contents of any generator boil over. The condensing pots 
 B (Figs. 369 and 370), have two large apertures for the gas-entrance- and exit-pipes, 
 as well as a small hole, i, for supplying water or dilute nitric acid. Near the bottom 
 there is a smaller opening, x, provided with a stoneware cock for letting off nitric acid. 
 The number of the pots is at least 60, to avoid imperfect condensation. In proportion 
 as the contents of the pots nearest the generators, A, reacn the necessary concentration 
 {sp. gr. 1-32 to i'35), they are drawn off and replaced by a similar quantity of 
 liquid from the next pot, further from the generators. Whilst water is put into the 
 pot nearest the chimney, nitric acid of sp. gr. 1*34 is drawn off from the first 
 condensing-pot. Into each generator there are poured 180 kilos, nitric acid of sp. gr. 
 1 '35 to i '4> and 150 kilos, powdered arsenic (so-called white arsenic) are then added. 
 Whilst pure nitric acid has an oxidising action only at high temperatures, crude nitric 
 acid begins to act at common temperatures. The chief reaction sets in at 65 and is 
 most violent at 70, declining afterwards. Hence, at the outset but little arsenic is 
 added ; the water-bath is then heated to 70 by turning in steam, and the remainder of 
 the arsenic is added in small portions. The reaction lasts about sixty hours. At last 
 the heat is raised and the end of the process is ascertained by sampling. A small 
 sample is heated in a porcelain capsule with a little arsenic, over a spirit or gas flame, 
 and if only traces of nitrous fumes escape the operation is broken off. The mass is 
 allowed to cool a little, and it is then drawn with syphons out of the generators, A, into 
 the neutralising pan, C. If the mixture from all the six generators contains any free 
 nitric acid, arsenic is added, and if it contains an excess of arsenious acid, nitric acid is 
 
452 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 added. In either case heat is applied until the escape of gases entirely ceases. The 
 concentration of the arsenic acid is carried to 195 Tw. A continual oversight of the 
 generators is necessary to prevent rising over. If the evolution of gases is very 
 violent, cold water is run from the pipe, w, into the vat, If, and it is not heated again 
 until the contents are quiet. In general the temperature does not fluctuate much, as 
 the escape of gas absorbs the more heat the more rapid it becomes. Arsenic must 
 never be added in large quantities at once. As much air enters through the loose 
 cover as is needed to oxidise the nitrogen oxides. If the glass tube, g (Fig. 367), has 
 a yellow colour near the chimney, there is either too little air in the pots, B, or the 
 reaction in A is too violent. With careful watching, 75 per cent, of the nitric acid 
 may be recovered. 
 
 Besides serving for the production of magenta (a process now generally superseded), 
 sodium arseniate is used as a mordant in tissue printing and in turkey-red dyeing. It 
 is now being superseded in the latter industry by sodium phosphate. 
 
 Arsenic acid is tested by dissolving an average sample in a solution of sodium bicar- 
 bonate and titrating with solution of iodine. It has been already stated how arsenic 
 acid is tested for free nitric acid or arsenious acid. The commercial product is gener- 
 ally valued according to its sp. gr. 
 
 COMPOUNDS OF GOLD, SILVER, AND MERCURY. 
 
 Cassius's Purple, Gold Purple. The preparation which bears this name was dis- 
 covered by Dr. Cassius, at Ley den, in the year 1663. It is prepared by adding to a 
 solution of gold chloride a certain quantity of tin sesquichloride. Dr. Bolley prescribes 
 the following process : First, 107 parts of the double tin and ammonium chloride 
 are digested with pure metallic tin until the metal is quite dissolved ; 18 parts of 
 water are then added, and the liquid mixed with the gold solution previously diluted 
 with 36 parts of water. The result is the throwing down of a purple or black coloured 
 precipitate, about the chemical constitution of which nothing is certainly known. 
 Well-prepared Cassius's purple should contain 39*68 per cent, of gold. 
 
 Salts of Gold. The double salts of gold and sodium chloride (AuCl 3 ,NaCl + 2H 8 0), 
 and the corresponding potassium salt (2Au01 3 ,KCl + 5H 2 0), are employed in photo- 
 graphy and medicine. 
 
 Salts of Silver, Silver Nitrate, Lunar Caustic. This salt (AgN0 3 ) is now pre- 
 pared on the large scale by dissolving silver containing copper in nitric acid, evapo- 
 rating the solution to dryness, and igniting the residue until all the copper nitrate is 
 decomposed. The residue is next exhausted with pure water, the solution filtered and 
 left to crystallise. For medical purposes the crystals are fused, and, while liquid, 
 poured into moulds to form small round sticks. The most extensive use of silver 
 nitrate obtains in photography, a re-crystallised neutral and pure salt being preferred. 
 Under the name of Sel Clement, there is now in use in photography a mixture of fused 
 silver, sodium and magnesium nitrates, recommended as preferable to silver nitrate 
 alone. It is stated that the consumption of this salt for photographic purposes 
 amounted, in 1870, to 1400 cwts. for Germany, France, England, and the United 
 States ; the money value of this quantity being estimated at ^630,000. 
 
 Marking Ink. A large quantity of silver nitrate is also used for the purpose of 
 making indelible ink for marking linen. This ink often consists of two different fluids, 
 one a solution of pyrogallic acid in a mixture of water and alcohol, being intended to 
 moisten the linen previous to writing ; the other, or writing fluid, consisting of a solu- 
 tion of ammoniacal nitrate of silver thickened with gum. More recently aniline black 
 has been applied in the marking of linen.* 
 
 * The number of marking-inks is now almost endless, and many of them corrode linen. 
 
SECT, in,] COMPOUNDS OF MERCURY. 453 
 
 Mercurial Compounds. The more important mercurial compounds which are manu- 
 factured on the large scale are the following : 
 
 Mercuric Oxide, HgO, is prepared by cautiously heating a mixture of mercuric 
 nitrate with mercury. It is sometimes applied to the iron hulls of steamers to prevent 
 the attachment of mollusca, &c. 
 
 Mercuric Chloride. The substance commonly known as corrosive sublimate is the 
 perchloride of mercury, HgCl 2 , molecular weight =135, consisting, in 100 parts, of 
 73'8 parts of mercury and z6'z parts of chlorine. It is prepared either by sublima- 
 tion from a mixture of mercuric sulphate and common salt, or by dissolving the 
 same oxide in hydrochloric acid, and also by boiling a solution of magnesium chloride 
 with the peroxide (MgCl 2 -1- HgO = HgCl 2 + MgO). When sublimed, this salt forms a 
 white crystalline mass, which fuses at 260, boils at 290, is soluble in 13-5 parts 
 of water at 20, and in r85 parts of the same liquid at 100. It is more readily 
 dissolved by alcohol, i part of the salt requiring only 2-3 parts of cold and i'i8 parts 
 of boiling alcohol. Mercuric chloride has been industrially employed as a preservative 
 for timber by Kyan, and is used in the manufacture of aniline-red, in dyeing 
 and calico-printing, in etching on steel-plates, and for the preparation of other 
 mercurial salts. Lately, the use of the double salt, HgCl 2 ,2KCl, obtained by boiling 
 potassium chloride with mercury peroxide, has been suggested as a preservative 
 for timber. It should be borne in mind that this preparation of mercury is extremely 
 poisonous and easily absorbed by the skin of the hands. 
 
 Cinnabar or Vermilion. Under this name is designated the mercuric sulphide, 
 HgS, which occurs native in crystalline or compact red-coloured masses, and was known 
 in Pliny's time by the term minium.* The use of mercuric chloride in the manufac- 
 ture of aniline red, and in dyeing and printing, has practically ceased. The cinnabar, 
 or vermilion of commerce, used as a pigment, is always artificially prepared either by the 
 dry or wet way. By the former process 540 parts of mercury and 75 of sulphur are very 
 intimately mixed. The ensuing black-coloured powder is introduced into iron vessels, and 
 exposed to a moderate heat so as to cause the fusion of the mass, which, after cooling, is 
 broken up and then introduced into earthenware and loosely closed vessels, heated on a 
 sand-bath. The sublimed mass is of a cochineal-red colour, exhibits a fibrous fracture, 
 and yields when pulverised a scarlet powder, which is the more beautiful the purer the 
 materials used in its preparation and the greater the care taken to avoid an excess of 
 sulphur. Some chemists allege that a greatly improved vermilion is obtained if i part 
 of antimony sulphide is added to the mixture of sulphur and mercury previously to 
 the sublimation, and the sublimed and pulverised mass placed in a dark room for 
 several months and treated with either dilute nitric acid or caustic potassa. Accord- 
 ing to Liebig, vermilion is obtained in the wet process by treating the white 
 precipitate of the Pharmacopoeia, or hydrargyrum amidato bichloratwm, with a solu- 
 tion of sulphur in ammonium sulphide. Hofmann considers white precipitate to be 
 ammonium chloride, in the ammonium of which 2 equivalents of mercury have 
 
 ,TT 
 
 taken the place of 2 equivalents of hydrogen; formula NJ-rA Other chemists, 
 
 *"& 
 
 again, hold different views as to the constitution of this body, which has been used 
 in medicine since, if not before, the time of Paracelsus. Vermilion is generally 
 obtained by precipitating a solution of corrosive sublimate in ammonia with a 
 solution of sulphur in ammonium sulphide; or, according to Martius, by agi- 
 tating, in a suitable vessel, i part of sulphur of mercury, and 2 to 3 of a con- 
 centrated solution of liver of sulphur. According to Brunner's method, by which 
 decidedly the finest vermilion is obtained, 114 parts by weight of sulphur and 300 
 
 * Bed lead, afterwards called minium, was, as far as it appears, unknown to the ancients, being 
 first prepared by the Arabs and Saracens. 
 
454 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 parts by weight of mercury are mixed, with the addition of a small quantity of caustic 
 potassa solution, and incorporated by being shaken by machinery. The resulting 
 black compound is next treated with a solution of 75 parts caustic potassa in 400 parts 
 of water, and heated on a water-bath to 45. The mixture assumes a scarlet-colour 
 after a few hours, and as soon as this is apparent the semi-liquid mass is poured into 
 cold water, next collected on niters, washed, and dried. The vermilion of commerce 
 is often adulterated with red lead, iron peroxide, chrome lead, and, more frequently, 
 with from 15 to 20 per cent, of gypsum. These adulterations are, however, readily 
 detected, as they are left behind when the vermilion is sublimed. Red lead, one of 
 the most usual adulterations of vermilion, can be readily detected either by treating a 
 small quantity of the suspected sample with nitric acid, when, in consequence of the 
 formation of puce-coloured lead peroxide, the mass assumes a brown colour, or by 
 the addition of hydrochloric acid, when chlorine is given off. Pure cinnabar is com- 
 pletely and readily soluble in hydrosulphuret of sodium sulphide (NaSH). 
 
 Red lead, or antimonial cinnabar, is sometimes passed off as vermilion by steeping 
 it in a solution of eosine. If such a sample is digested in alcohol, the cosine is dissolved 
 away, and the red lead, &c., is revealed. 
 
 COMPOUNDS OF COPPEE. 
 
 Copper Sulphate, Blue Vitriol, Blue Stone. This salt is met with naturally in 
 kidney-shaped masses, or as an outer covering of minerals containing copper, as 
 well as in solution, as referred to under Cementation-copper. Copper sulphate, blue- 
 or Cyprus-vitriol crystallises in the shape of triclinohedrical blue-coloured crystals, 
 soluble in two parts of hot and four of cold water, and insoluble in alcohol. 100 parts 
 of the salt contain 
 
 Sulphuric acid . . . 32-14 
 Oxide of copper . . .3179 
 
 Water 36-07 
 
 Formula CuS0 4 + sH 2 0. 
 
 Preparation of Blue Vitriol. Pure copper sulphate is obtained by heating metallic 
 copper with concentrated sulphuric acid ; the metal is oxidised by a portion of the 
 oxygen of the acid, while sulphurous acid escapes : 
 
 (Cu + 2 H 2 S0 4 = CuS0 4 + 2 H 2 + SO,). 
 
 If the metal is previously converted into copper oxide by exposure to a red heat, 
 only half the quantity of sulphuric acid is required. Copper sulphate is manu- 
 factured on a large scale by any of the following processes ; i. By the evaporation of 
 cementation water until crystallisation is attained. 2. By heating sheets of copper in 
 a reverberatory furnace to the boiling-point of sulphur ; a quantity of that element 
 being then thrown in, and the flues and other openings closed, the effect is the forma- 
 tion of copper sulphide (Cu 2 S), which is converted by a comparatively low heat and 
 the action of the oxygen of the air into sulphate (Cu 2 S + 50 = CuS0 4 + CuO). The 
 mass is next placed in a suitable vessel, and as much sulphuric acid is added to it as 
 is sufficient to saturate the oxide of copper. The clear solution, having been decanted 
 from the insoluble residue, is set aside for crystallisation. 3. By treating the crude 
 copper obtained by smelting the ores, and containing about 60 per cent, of metal, 
 with sulphuric acid. The resulting solution is evaporated in leaden vessels, and the 
 clear liquid left to crystallise in copper pans. From the mother liquor of the crystals- 
 metallic copper is precipitated by means of iron, because the presence of a large- 
 quantity of iron sulphate renders this mother liquor unfit for the further making 
 of blue vitriol. This method of obtaining copper sulphate is the least expensive,. 
 
SECT, m.] COMPOUNDS OF COPPER. 455 
 
 but the salt is not quite pure, containing, according to M. Herter s analysis of Mans- 
 feld blue vitriol, about 3 per cent, of iron sulphate, and 0*083 per cent, of metallic 
 nickel. Very frequently the scraps and refuse of copper-smithies, copper-scale, and 
 other residues of that metal, are used in preparing copper sulphate. 4. At Mar- 
 seilles, malachite is dissolved in sulphuric acid to obtain blue vitriol. 5. In Norway, 
 iron pyrites containing copper are roasted and treated with water, the copper con- 
 tained being precipitated with sulphuretted hydrogen, and the copper sulphide, 
 when dry, converted into sulphate by exposure to a gentle heat. 6. Large quantities 
 of copper sulphate are obtained as a bye-product of silver-refining (especially when 
 silver is treated for the purpose of extracting the gold it contains), by boiling usually 
 silver coins, chiefly Mexican and Peruvian dollars with strong sulphuric acid ; silver 
 sulphate and, as the coins contain some copper, the sulphate of that metal, are 
 formed, while the gold is left as an insoluble substance. The silver is reduced to the 
 metallic state (Ag 2 S0 4 + Cu = CuS0 4 + 2 Ag) by means of sheets of copper placed in the 
 acid solution, which is previously diluted, and which, after having been decanted from 
 the sediment of spongy metallic silver, yields on evaporation a very pure copper sul- 
 phate. 7. Copper sulphate is also obtained as a bye-product of the hydrometallur- 
 gical process of extracting silver, or Ziervogel's process. In order to separate the iron 
 sulphate from the crude blue vitriol, as obtained at copper-smelting works from 
 various cupriferous refuse, the crude salt is roasted so as to bring about a partial de- 
 composition. By this means the irons ulphate is decomposed, and the oxide of that 
 metal formed is insoluble in water. The saline mass is dissolved in water, and the 
 clear solution, decanted from the sediment, evaporated to crystallisation. According 
 to Bacco's plan, the crude blue-vitriol is dissolved in water, and copper carbonate 
 added to the solution, to cause the precipitation as oxide of all the iron present, while 
 an equivalent quantity of copper oxide is dissolved and converted into sulphate. 
 The purified copper sulphate solution having been filtered is evaporated and left to 
 crystallise. 
 
 Double Vitriol. Under the name of double vitriol, a mixture of the copper and 
 iron sulphates crystallised together, and sometimes containing white vitriol, is met 
 with on the Continent. The Salzburg vitriol, known by the brand of a double eagle, 
 contains about 76 per cent., the Admont 83 per cent., and the double Admont 80 per 
 cent, of ferrous sulphate. Of later years, however, these vitriols have been less in 
 demand. 
 
 Applications of Blue Vitriol. As the base of the pigments obtainable from copper, 
 the sulphate is very frequently used, and should be pure, or at least free from iron 
 and zinc sulphates. Blue vitriol also serves for the manufacture of copper acetate, 
 for bronzing iron, for bringing out the colour of alloys of gold. It is used in 
 dyeing and printing in various ways, for gal vano- plastic purposes, and during the last 
 twenty years large quantities of this salt have been sent to Mexico and Peru to be 
 applied in the American amalgamation-process of extracting silver. 
 
 Copper Pigments. (Brunswick Green, Bremen Blue or Green, Casselmanris Green, 
 Scheele's Green, Oil Blue, Schweinfurt Green, Verdigris.). Brunswick Green. Under 
 this name several compounds of copper are applied as oil-paints. The pigment now 
 chiefly in use bearing this name is basic copper carbonate (CuC0 3 + CuH 2 O 2 ), an 
 imitation of mountain- or mineral-green, and obtained from either finely pulverised 
 malachite or the sediment often met with in cupriferous cementation liquids. Bruns- 
 wick green is prepared on a large scale by the decomposition of ferrous sulphate 
 by means of either sodium or calcium carbonate, and in other cases by the 
 decomposition of copper chloride by means of a carbonated alkali. The ensuing 
 precipitate is washed with boiling water, and afterwards mixed with a smaller or larger 
 quantity of barium sulphate, zinc- white, or gypsum, and frequently with Schweinfurt 
 
456 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 green (copper aceto-arsenite) in order to obtain the desired hue. Another variety of 
 Brunswick green, rarely met with in the present day, appears to be a kind of artificially 
 prepared atacamite, a copper oxychloride, the formula of which is, according to Eitt- 
 hausen, CuCl 2 .3Cu(HO) 2 . 
 
 Bremen Blue or Bremen Green. These substances are essentially hydrated copper 
 oxide, and are met with as a very bright spongy blue mass with a greenish hue. The 
 value is greater according to the finer blue colour and loose spongy texture. When used 
 with water, gum, or glue, this pigment yields a bright blue colour, hence its first name ; 
 but when it is mixed with linseed oil, the blue colour turns within twenty-four hours to 
 green, in consequence of the saponification of the copper oxide, which becomes oleate, 
 palmitate, and linoleate of that base. Bremen green occurs in various hues, obtained 
 by mixing the precipitate with well-cleansed gypsum. At the present time the pig- 
 ment is generally obtained from copper oxychloride (CuCl 2 3CuO + 4.H 2 0). This pre- 
 paration may be made in various ways, provided care be taken that the light green 
 paste technically known as oxide contains no cuprous chloride (CuCl 2 ). Gentele's 
 method is as follows : 
 
 i. 1 1 2 '5 kilos, of common salt, and in kilos, of copper sulphate, both free from 
 iron, are ground together with sufficient water to promote reaction. 2. 112*5 kilos, of 
 old copper sheeting is cut into pieces a square inch in size, and placed with water 
 acidulated with sulphuric acid in rotating casks so as to remove all rust, oxide, and 
 oxychloride from this metal, which is next washed with water. 3. The clean metal thus 
 obtained is next placed in what are known as oxidisation-closets and covered for a thick- 
 ness of half an inch with the paste mentioned above. A mutual action, aided by that of 
 the atmosphere, is set up, the result being that the copper chloride first takes up copper, 
 becoming cuprous chloride ; this in its turn takes up oxygen from the atmosphere 
 and water, and thus becomes converted into the green-coloured insoluble hydrated copper 
 oxide, the action being greatly aided by the turning over of the mass with a copper 
 spade every two or three days. As the treatment of cuprous chloride with alkalies 
 or alkaline earths gives rise to the separation of red or yellow coloured suboxide, 
 the mass should not, on being tested and previous to further operations, yield 
 even the faintest indication of the presence of suboxide, since the slightest trace 
 would spoil the hue of the pigment to be obtained ; consequently, in some works 
 the pasty mass is left for years before it is used for further operations. The action is 
 accelerated by causing the mass to become dry before turning it over with a spade, the 
 consequence being that the air gets thorough access, and a complete oxidation is 
 obtained in from three to five months' time. The mass is then cleaned with the 
 smallest possible quantity of water, and is thus separated from the non-oxidised metallic 
 copper. 4. To about 6 gallons of this cleaned material are added 6 kilos, of hydrochloric 
 acid, and this mixture is allowed to stand for about two days. 5. Into a tank or tub 
 the blue tub are poured 1 5 gallons of clear colourless potassa lye. This having been 
 done, the acid mixture is first diluted with 6 more gallons of .water, and then, as 
 rapidly and expeditiously as possible, poured into the blue tub, the mixture being 
 continuously stirred. The result of this last operation is that the previously basic 
 copper compound, converted by HC1 into neutral cupric chloride, is, when brought 
 in contact with the potassa, converted into blue-coloured copper oxyhydrate or 
 Bremen blue, while potassium chloride is also formed. 6. After the mass has 
 become pasty, it is left to stand for a couple of days, and then thoroughly washed by 
 decantation to remove the potassium chloride. The cupric oxyhydrate is then put 
 on cloth filters, kept moist, and exposed to the air for some time. It is next dried at a 
 temperature of from 30 to 35, since at a higher temperature the hydrate of the oxide by 
 losing its water becomes blackish-brown coloured. It is clear that Bremen blue can be 
 differently obtained, but these differences of preparation do not bear so much upon the 
 
SECT, m.] COMPOUNDS OF COPPER. 457 
 
 precipitation of the hydrated oxide as upon the means of obtaining copper chloride ; 
 these means may of course be varied in many ways ; for instance, by causing a mixture 
 of common salt, dilute sulphuric acid, and copper scraps to act upon each other, the mass 
 being afterwards exposed to the action of the air ; by the action of hydrochloric acid 
 upon copper and its oxide ; or by partly decomposing neutral copper nitrate by means 
 of sodium carbonate. In this case a precipitate of copper carbonate is formed, which 
 while giving off its carbonic acid, becomes converted into a basic copper nitrate 
 (CuN 3 6 + CuH 8 Oj), deposited as a heavy green powder. A solution of zinc-oxide of 
 potassa (solution of zinc- white in caustic potassa) is next added, the result being the 
 formation of a deep blue pigment, very spongy and very covering (a technical term in 
 use by painters), consisting of copper zincate with a small quantity of basic copper 
 nitrate. A magnesia Bremen blue is obtained by the precipitation of a solution of 
 the magnesium and copper sulphates, to which some cream of tartar is added by means 
 of potassa, care being taken to pour the saline solution into the alkaline, and to keep 
 an excess of the latter. 
 
 Casselmann's Green. Dr. Casselmann discovered this pigment, a beautiful green 
 free from arsenic. It is prepared by mixing together boiling solutions of copper 
 sulphate and an alkaline acetate ; the resulting precipitate is a basic salt of 
 copper (CuS0 4 + 3CuH 2 2 + 4H 2 0). After drying, this salt is, next to Schweinfurt 
 green, the finest of all colours obtained from copper, and being free from arsenic, is 
 highly commendable, though poisonous, like most preparations of copper, especially 
 the acetates. 
 
 Mineral Green and Blue. This pigment, also known as Scheele's green, is not so 
 frequently used now as formerly. It is essentially a mixture of hydrated copper 
 oxide and arsenite, and does not cover very well. It is prepared by dissolving i kilo, 
 of pure copper sulphate in 12 litres of water, to which is added, with constant 
 stirring, a solution of 350 grammes of arsenious acid and i kilo, of purified potash 
 (carbonate) in 8 litres of water. The resulting grass-green coloured precipitate 
 is washed with boiling water and dried. Another pigment, sometimes known as 
 mineral green, is obtained from malachite, or basic hydrated copper oxide. By the 
 term mineral blue is generally understood a kind of Berlin blue, rendered less deep 
 coloured by the addition of pipe-clay or other white-coloured powders, but the terms 
 also applies to a pigment formerly obtained by grinding and washing the purest pieces 
 of copper lazulite, a mineral (2CuCO s + CuH 2 2 ) found in the Tyrol and near Lyons. 
 This pigment is artificially obtained in France, Holland, and Belgium, by precipitating 
 a solution of copper nitrate with caustic lime or caustic potassa, and afterwards mix- 
 ing the previously washed precipitate with chalk, gypsum, or heavy spar. The pig- 
 ment is sent into the trade for use chiefly as a water-colour. Under the name of lime 
 blue a similar preparation occurs in quadrangular lumps, obtained by precipitating a 
 solution of 100 parts of copper sulphate and 12^ parts of sal-ammoniac with a milk of 
 lime containing 30 parts of caustic lime. The precipitate is a mixture of hydrated 
 copper oxide and calcium sulphate, according to the formula, 2CaS0 4 .2H 2 O + 3CuOH r 
 This pigment exhibits a purer tint than Bremen blue, but though it covers pretty well 
 as a water-colour, it is almost useless as an oil-colour. 
 
 Oil Blue. A pigment which, when ground with oils and varnishes, yields a beau- 
 tiful violet-blue, and is essentially composed of copper sulphide, (CuS), there being 
 employed in its manufacture either the native mineral, known as cupreous indigo, or an 
 artificially prepared sulphide, obtained by fusing finely divided metallic copper with 
 hepar sulphuris, a mixture of several potassium sulphides. The fused mass is 
 treated with water, and the copper sulphide remains in small blue-coloured crystals, 
 which, after drying, are pulverised and mixed with oil. 
 
 Schweinfurt Green or Emerald Green. This pigment is by far the most beautiful, but 
 
458 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 also the most poisonous, of all green-coloured copper pigments. In Germany this 
 substance is known under a number of aliases derived from the peculiar depth of hue 
 as modified in various manufactories by means of barium sulphate, lead sulphate, and 
 chrome-yellow. The constitution and mode of preparation of this pigment remained, 
 at least on the Continent, a trade secret, until the researches of MM. Braconnot and 
 Liebig made the particulars known. According to Ehrmann, pure emerald or Schwein- 
 furt green is a copper aceto-arsenite, Cu(C,H 3 O 2 ) 2 .3Cu(As0 2 ) 2 ; in 100 parts oxide 
 of copper, 31*29 ; arsenious acid, 58'65 ; acetic acid, io - o6. Wagner states that 
 this formula is only empirical, because a portion of the copper is present as suboxide, 
 and a portion of the arsenic as arsenic acid. 
 
 According to Ehrmann's statement, this pigment is prepared by first separately 
 dissolving equal parts by weight of arsenious acid and neutral copper acetate in 
 boiling water, and next mixing these solutions while boiling. There is immediately 
 formed a flocculent olive-green coloured precipitate of copper arsenite, while the 
 supernatant liquid contains free acetic acid. After a while the precipitate becomes 
 gradually crystalline, at the same time forming a beautifully green pigment, which is 
 separated from the liquid by filtration, and after washing and carefully drying is 
 ready for use. The mode of preparing this pigment on a large scale was originally 
 devised by Braconnot, as follows: 15 kilos, of copper sulphate are dissolved in the 
 smallest possible quantity of boiling water and mixed with a boiling and concen- 
 trated solution of sodium or potassium arsenite, so prepared as to contain 20 kilos, of 
 arsenious acid. There is immediately formed a dirty greenish-coloured precipitate, 
 which is converted into Schweinf urt green by the addition of some 1 5 litres of concen- 
 trated wood vinegar. This having been done, the precipitate is immediately filtered 
 off and washed. It thus appears that the preparation of this pigment aims first at 
 the least expensive preparation of neutral copper arsenite, which is next converted 
 into aceto-arsenite by digesting the precipitate with acetic acid. The pigment is 
 available as a water- and an oil-colour, but does not cover very well in oil, although it 
 dries rapidly. The colour cannot be used for mural painting, as the lime absorbs the 
 acetic acid, leaving a yellowish-green copper arsenite. The Schweinfurt green consists 
 of microscopically small crystals ; if these crystals are pulverised, the colour, previously 
 grass-green, becomes paler. Air and light do not affect this pigment, which is insoluble 
 in water, but becoming, when boiled with it for a length of time, brown-coloured, 
 probably in consequence of the loss of some acetic acid. It is a well-known fact that 
 paper-hangings containing this pigment, and pasted on damp walls, cause the inmates 
 of the rooms to suffer from headaches, due in all likelihood to volatile arsenical 
 emanations, among which is hydrogen arsenide. The use of this pigment is very 
 limited. 
 
 Copper Stannate. This preparation, also known as Gentele's green, is obtained by 
 precipitating a solution of copper sulphate with sodium stannate, washing and drying 
 the precipitate, which forms a beautifully green copper pigment, innocuous, at least as 
 compared with the foregoing. 
 
 Verdigris. Under this name we meet in commerce with a neutral and a basic 
 copper acetate ; the one, a crystalline substance, is Cu(C 2 H 3 2 ) 2 .H 2 O, a salt formerly 
 only prepared in Holland, and designated as " distilled verdigris," in order to mislead 
 as to its mode of manufacture. 
 
 The basic salt, blue verdigris, is chiefly prepared at and near Montpellier, by em- 
 ploying the marc of grapes, the skin and stems of the bunches after the juice has 
 been squeezed out, which readily forms acetic acid by fermentation. Into the marc 
 are placed sheets of copper previously moistened with a solution of copper acetate. 
 The metal becomes coated with a layer of verdigris, which is removed by scraping. It 
 is next kneaded with water, after which the paste is put into leathern bags and pressed,. 
 
SECT, in.] COMPOUNDS OF ZINC AND CADMIUM. 459 
 
 so as to obtain rectangular cakes. The metal is again treated in the same manner until 
 it is entirely converted into basic verdigris, having a blue colour, and known as French 
 verdigris. Formula Cu(C 2 H s O 2 ) 2 .Cu(OH) 2 .5H 2 O. A green-coloured verdigris is 
 obtained at Grenoble and elsewhere by submitting sheets of copper to the action 
 of vapours of vinegar, or by placing the metal between pieces of coarse flannel, 
 soaked with that liquid in a warm place. The formula of the substance thus pro- 
 duced is Cu(C 2 H 3 O 2 ) 2 . 2 Cu(OH) 2 . 
 
 Neutral copper acetate first made by the Saracens in Southern Spain, and since the 
 middle of the fifteenth century by the Dutch, is now obtained either by i. Dis- 
 solving the basic salt in acetic acid. 2. Or by the double decomposition of copper 
 sulphate and lead acetate : CuSO 4 + Pb(C 2 H 3 2 ) 2 = PbS0 4 + Cu(C 2 H 3 2 ) 2 . 
 
 By the first method the basic acetate is dissolved in 4 parts of acetum destillatum 
 (purified vinegar) or in wood vinegar, the liquid being placed in a copper cauldron and 
 heat applied. The clear liquid is decanted, and then evaporated in copper pans until a 
 saline crust makes its appearance, when the fluid is transferred to wooden vessels pro- 
 vided with thin laths serving as a solid nucleus for the crystals. According to the second 
 plan, the solutions of the two salts are mixed, the liquid decanted from the sediment of 
 lead sulphate, and next evaporated, after the addition of some acetic acid, until a crust 
 of the salt is formed. Instead of lead acetate, the calcium and barium acetates are now 
 used. The neutral copper acetate is met with in commerce in " bunches" (grappes), 
 consisting of deep green-coloured, non-transparent crystals, soluble in 13-4 parts of cold, 
 in 5 parts of hot water, and in 14 parts of boiling alcohol. This salt, like the basic ace- 
 tates, is highly poisonous. 
 
 Applications of Verdigris. Both basic and neutral are employed as oil- and water- 
 colours. In Eussia, verdigris, mixed with white : lead, is frequently used as an oil 
 paint, the result being the formation of copper carbonate and basic lead acetate. 
 The former of these substances yields with the undecomposed white-lead a bright blue 
 colour, which, after painting, turns to a peculiarly fine green, the usual colour of the 
 iron roofs of the houses in Russia, more especially in Moscow and the interior of 
 the country. In Holland the same mixture is frequently applied as a paint to out- 
 door woodwork, of which it is an excellent preservative. Verdigris is sometimes 
 further applied in the preparation of other copper colours for instance, Schwein- 
 furt green ; also in dyeing and calico-printing, though less commonly than formerly ; 
 in gilding (see Gold). The neutral salt was formerly used in the preparation of acetic 
 acid. 
 
 Egyptian Slue, a blue pigment known to the Egyptians from time immemorial, 
 and lately rediscovered, is obtained by fritting a mixture of sand (free from iron) 70 
 parts, copper oxide 15 parts, chalk 25 parts, and sodium carbonate 6 parts.* 
 
 COMPOUNDS OF ZINC AND CADMIUM. 
 
 Zinc- white. Under this name there has during the last fourteen years been 
 brought into the market anhydrous white zinc oxide, applied instead of white-lead 
 as a pigment. Zinc-white is prepared for this purpose by oxidising metallic zinc in 
 fireclay retorts, placed to the number of 8 to 1 8 in a reverberatory furnace. As 
 soon as these retorts are at a bright white-heat, cakes of zinc are placed in them, and 
 the vapours of the metal on leaving the retort are brought into contact with a current of 
 air heated to 300 ; oxidation results, and the oxide, a very loose, snow-white, flocculent 
 material, is carried by the current of hot air into condensing chambers, and gradually 
 
 * Concerning these preparations and pigments, the reader may consult, A. H. Church, Chemistry 
 of Paints and Painting, London, Seeley & Co.; and Gentele, Lehrbuch der Farbenfabrikation, Bruns- 
 wick, Vieweg & Son. 
 
460 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 4 
 
 deposited. The oxide thus prepared is immediately fit for use ; it is of a pure white colour, 
 and very light. Zinc- white is also prepared by exposing metallic zinc to the action of 
 superheated steam, hydrogen being at the same time evolved, and used for illuminating 
 purposes, as at Narbonne, St. Chinian, Ceret, and a few other places, where it is known 
 as platinum-gas, because the flame is used for imparting a white heat to small coils of 
 platinum wire, thus producing a very steady and highly pleasant light. As regards 
 the use of zinc- white as a pigment, it is rather more expensive than white-lead, yet 
 according to some it is a better covering material in the surface proportion of 10 to 13, 
 that is to say, 13 parts by weight of zinc- white cover as much space as 10 of white-lead : 
 moreover, zinc- white is i-.ot affected by sulphuretted hydrogen. Like white-lead, this 
 compound may be mixed with other pigments. By mixing Rinmann's green with 
 it a green colour may be obtained ; blue with ultramarine ; lemon-yellow with cadmium 
 orange- yellow (cadmium sulphide). 
 
 A zinc carbonate has been proposed as a pigment ; it is prepared by precipitating 
 solution of zinc sulphate with ammonium carbonate. 
 
 Zinc-white is often prepared directly from its ores ; the roasted ores are heated upon 
 the grate of a furnace and when fully ignited submitted to a current of air passed 
 underneath the grate. The escaping vapours are again strongly heated along with 
 a current of air and condensed in lead chambers. Schnabel digests zinc dust with 
 ammonium carbonate in leaden vessels. The great advantage of zinc-white is that it is 
 not blackened by sulphur-gases, and that it is less injurious to workmen than white 
 lead. 
 
 White Vitriol, Zinc Sulphate. Zinc- vitriol (ZnS0 4 + 7 H 2 O), zinc sulphate or 
 white vitriol, is found as a native mineral, as a product of the oxidation of zinc blende; 
 it is also prepared by dissolving zinc in dilute sulphuric acid, and by roasting native 
 zinc sulphide. This vitriol occurs in white agglomerated crystals and in small acicular- 
 shaped crystals, as purified zinc sulphate ; it is used as a " dryer " in oil paints and 
 varnishes ; as a mordant in dyeing ; for disinfecting purposes, and sometimes as a source 
 of oxygen, since, on being submitted to a red heat, it gives off sulphurous acid and 
 oxygen, zinc oxide remaining. 
 
 Zinc Cnromate. This preparation, obtained by precipitating a solution of zinc sul- 
 phate with potassium bichromate, is a very fine yellow-coloured powder, used now and 
 then in pigment printing, because it is soluble in ammonia, and thrown down again as 
 a powder insoluble in water when that menstruum is volatilised. A basic zinc 
 chromate is used as a pigment in the paint trade. 
 
 Zinc Chloride. This compound of zinc, ZnCl,, is obtained either by dissolving 
 zinc in hydrochloric acid, or more cheaply by causing the hydrochloric acid gas given 
 off in manufacturing soda to act upon native zinc sulphide. By this action sul- 
 phuretted hydrogen is formed, which can be burned to produce sulphurous acid for the 
 sulphuric acid chambers. The solution of zinc chloride thus obtained is evaporated to 
 the consistency of a syrup. 
 
 Anhydrous zinc chloride is obtained by heating an intimate mixture of dried 
 zinc sulphate and sodium chloride; zinc chloride is formed which sublimes, and 
 sodium sulphate which is left behind (ZnSO 4 + 2NaCl = Na 2 S0 4 + ZnCl,). This anhy- 
 drous chloride may be sometimes advantageously used instead of strong sulphuric acid, 
 for instance, in rape and colza oil refining, and perhaps, although it would be more 
 expensive and less manageable, in the manufacture of garancine from madder. This 
 chloride has of late been employed instead of sulphuric acid in the manufacture of stearic 
 acid, and in the preparations of ether and parchment paper. Zinc chloride in a 
 strong and crude solution is largely and very successfully used for preserving timber ; 
 in paper-making for the decomposition of bleaching powder, for bleaching the half -stuff 
 and rags, and also in sizing paper. The disinfectants sold as Sir William Burnett's 
 
SECT, in.] COMPOUNDS OF LEAD. 461 
 
 Fluid and Drew's Disinfectant are solutions of zinc chloride. The salt used in 
 soldering iron, zinc, pewter, &c., is a compound of zinc and ammonium chlorides 
 (2NH 4 C1 + ZnCl 2 ) ; its solution is obtained by dissolving 3 parts by weight of zinc in 
 strong hydrochloric acid, and adding after the solution is complete an equal weight 
 of sal-ammoniac. Zinc oxy chloride, obtained by mixing zinc oxide with a concen- 
 trated solution of zinc chloride, or with solutions of iron or manganese chlorides, 
 has been recently proposed by M. Sorel as a plastic mass suited for stopping hollow 
 teeth. 
 
 Cadmium Yellow (Jaune brilliant ; CdS). This pigment is prepared by the action of 
 sulphuretted hydrogen upon soluble cadmium salts ; a little free acid should be present. 
 The hotter and more concentrated the solution, the more the product inclines to a red. 
 
 COMPOUNDS OF LEAD. 
 
 Lead Oxide, PbO, is used in used in the arts as massicot or as litharge. 
 
 Massicot. Massicot, or yellow lead oxide, occurs as a yellow or ruddy-coloured 
 powder, obtained either by heating lead carbonate or nitrate, or by calcining metallic 
 lead on the hearth of a reverberatory furnace. Before lead chromate was known, 
 massicot was used as a yellow pigment. At a red heat this substance fuses and becomes 
 glassy. In most instances it is not a pure lead oxide, but is mixed with lead silicate, 
 the fact being that lead oxide at a red heat strongly attacks any material containing 
 silica, dissolving the silica and combining with it. 
 
 Litharge. Litharge is a fused crystalline lead oxide, and is obtained as a bye- 
 product of the separation of silver from lead in the process described under Silver. 
 Litharge always contains a larger or smaller quantity of copper oxide, antimony oxide, 
 traces of silver oxide, and, according to Dr. Wittstein, metallic lead, varying in 
 quantity from 1*25 to 3*10 per cent. The copper oxide can be removed by digesting 
 the litharge with a cold solution of ammonium carbonate. Litharge absorbs 
 carbonic acid from the atmosphere, combines at a higher temperature with silica, 
 forming with it a readily fusible glass, is soluble in acetic and nitric, and also 
 in very dilute hydrochloric acids, and is equally soluble in boiling solutions of caustic 
 potassa and soda. It is insoluble in ammonium carbonate and in the potassium and 
 sodium carbonates. Litharge is largely used, entering into various compounds for 
 glass, so-called crystal-glass, flint-glass, strass for imitating jewels, for glazing pottery 
 and earthenware, as a flux in glass and porcelain staining, for the preparation of 
 boiled linseed and poppy-seed oil, for the preparations of lead plaster, putty, minium, 
 red-lead, and lead acetate. A solution of lead oxide in caustic soda lye is employed in 
 the preparation of sodium stannate ; this solution is also used for imparting to combs 
 and other toilet articles made of horn the appearance of tortoiseshell or of buffalo-horn. 
 A very dilute solution is used as a hair-dye, and in metallochromy to produce iridescent 
 colours on brass and bronze. 
 
 Minium. Red Lead. Red lead is a combination of lead oxide with peroxide, 
 the formula being Pb 2 4 . Red lead of excellent quality is largely manufactured near 
 Newcastle-on-Tyne, by carefully heating lead oxide in a reverberatory furnace expressly 
 built for that purpose, the access of air being limited so as to prevent the fusion of a por- 
 tion of the oxide to litharge which cannot then be converted into minium. Sometimes 
 metallic lead is oxidised in a reverberatory furnace, the process, as, for instance, at 
 Shrewsbury, being so arranged that at the hotter places of the furnace massicot, and at 
 the cooler red lead, is produced. The finest coloured minium, or Paris-red, is obtained 
 from lead carbonate by the same method. According to Burton's plan, lead sulphate 
 is heated with Chili saltpetre, and after the mass has been exhausted with water the 
 red-lead is left, while sodium sulphate and nitrite are dissolved. Red lead is used 
 
462 CHEMICAL TECHNOLOGY. [SECT. m. 
 
 for a variety of purposes, many similar to the applications of lead oxide. Besides 
 being applied as a cement, when mixed with linseed-oil and mastic, for the flanges 
 of steam-pipes, it chiefly enters the market as a pigment, being for that purpose 
 either mixed with water or with linseed-oil, in both instances covering extremely 
 well. 
 
 Lead Peroxide. When red-lead is treated with moderately strong nitric acid, 
 there are formed lead nitrate and peroxide of that metal, Pb0 2 , a brown-coloured 
 powder largely used in the composition of the phosphorus mixtm^e for lucifer matches. 
 The mixture known in lucifer match works as oxidised minium, is a dried composition, 
 consisting of lead nitrate, lead peroxide, and undecomposed red-lead, and obtained 
 by drying a magma of minium and nitric acid. 
 
 White-lead, basic lead carbonate, 2PbCO 3 .Pb(OH) 2 , or rather hydrate carbonate, is 
 commercially known as of the Dutch, French, or English manufacture, according to 
 the method employed. The Dutch process for making white- lead is founded on the 
 fact that when metallic lead comes in contact with the vapours of acetic acid, car- 
 bonic acid, and oxygen, at a sufficiently high temperature, the metal is converted 
 into basic lead carbonate. It is quite evident from this brief statement that the chief 
 conditions being fulfilled, the methods of operation may be more or less varied. In 
 Holland, Belgium, and some parts of Germany, the lead as pure as possible and 
 free from silver, which, even in small quantities greatly impairs the good colour of the 
 white-lead is cast into thin strips, which are wound in a spiral P, Fig. 371, in coarse 
 earthenware pots, A (Fig. 371). Common vinegar, C, is poured into the lower part of 
 
 these pots, some beer-yeast being added. The lead is supported and placed on a perforated 
 piece of wood, B, so as to prevent direct contact with the vinegar. After this the pots are 
 covered with leaden plates and buried (see Fig. 372) in amass of horse-dung or spent-tan 
 and dung. The fermentation of the dung causes the requisite increase of temperature, 
 and the vinegar evaporating, aided by the oxygen of the air, converts the lead into basic 
 acetate, which, in its turn, is converted into basic lead carbonate by the carbonic acid 
 resulting from the fermenting manure. This rather clumsy process has given place 
 in Germany to the chamber method, consisting essentially in the following arrange- 
 ment. Instead of the pots being made the receptacles for the lead, the strips of that 
 metal are bent and suspended on a series of laths run lengthwise through the chamber, 
 on the floor of which is placed a layer of spent tan, marc of grapes, or other ferment- 
 able material, saturated with vinegar. An improvement upon this arrangement is to 
 have the chamber constructed with a double flooring, one water-tight, the other a 
 light planking perforated so as to admit of the vapours of vinegar being carried into 
 the compartment. The action upon the lead is in each case the same ; it is converted 
 chiefly into white-lead, and this crude product is purified from any adhering lead 
 acetate by washing with water before being brought into the market. There is still in 
 use in this country a modification of the method practised by the Dutch, who, by-the- 
 by v are not the inventors of white lead manufacture, the true origin being Moorish, 
 
SECT, in.] COMPOUNDS OF LEAD. 463 
 
 the trade being successfully carried on by these semi-savages* in Southern Spain, whence 
 the Dutch brought over the art in the sixteenth century to Holland. The modification 
 consists in the following arrangement : Granulated lead is first moistened with about 
 I '5 per cent, of vinegar, the metal being previously placed on hurdles in a wooden box, 
 the interior of which is heated by means of steam to 35, some steam being introduced 
 to keep the lead moist. If care is taken to supply carbonic acid, after from ten to 
 fourteen days the operation is finished, and the product having been lixiviated with 
 water and dried, is ready for use. 
 
 English Method of Manufacturing White Lead. According to this plan the metal is 
 melted in a large iron cauldron, and then made to flow on the hearth of a reverberatory 
 furnace, so as to convert the lead, by proper access of air, into litharge, which is 
 obtained in a very finely divided state by a peculiar arrangement of the furnace. The 
 hearth is constructed with a gutter, into which the fusing mass flows, and the sides 
 or walls of the gutter are perforated to admit of the passage of the molten litharge, 
 while the heavier metal sinks to the bottom. The litharge is next mixed with -^^ 
 of its weight of a solution of lead acetate, and then placed in a series of closed 
 troughs communicating with each other and admitting of the passage of a current of 
 impure carbonic acid, obtained by the combustion of coke in a furnace provided with a 
 blast to give an impulse to the gas. The litharge is continually stirred by machinery 
 to accelerate the absorption of the carbonic acid gas. White lead made by this process 
 covers very well, and is preferred to that prepared by the wet method. We may 
 mention in passing that it is the custom in this country to bring white lead into the 
 market ground with linseed oil to a thick paste, packed in strong oaken kegs or in iron 
 canisters. 
 
 French Method of Preparing White Lead. This method, invented by MM. Thenard 
 the elder, and Hoard, is not only generally adopted in France but in all countries where 
 it is desired to carry out a really sound and rational plan of white lead manufacture. 
 The method is as follows : Litharge is dissolved in acetic acid to obtain a solution of 
 basic lead acetate Pb(C 2 H 3 0) 2 2 + Pb(OH 2 ), and through the solution a current 
 of carbonic acid gas is passed. Two molecules of oxide of lead are converted into 
 white lead, while neutral lead acetate remains. Litharge is again added to the solu- 
 tion of this salt, and, by digestion, more lead subacetate is obtained, which is applied 
 as just described. 
 
 Apparatus used in White Lead Manufacture at Clichy. The machinery and contri- 
 vances at Clichy, near Paris, for effecting the method just explained, are exhibited in 
 Fig- 373- In the tub, A, the litharge is dissolved in acetic acid. B C is a stirrer, moved 
 by means of the shaft shown in the engraving, bearing at the top a pulley for the 
 strap. The solution of basic lead acetate can be run off through the tap into the 
 vessel, E, made of copper and tinned inside, the object being to let the impurities the 
 solution might contain subside. From E the fluid is led into the decomposition vessel 
 constructed with 800 tubes, which pass from the top to a depth of 32 centimetres beneath 
 the level of the fluid. These tubes are in communication with the main pipe, gg, which 
 also communicates with the washing apparatus, P, answering the purpose of purifier for 
 the carbonic acid gas generated in the small lime-kiln, GT, by the ignition of a mixture of 
 parts by bulk of chalk and i part by bulk of coke with sufficient access of air. The 
 decomposition of the basic lead acetate being finished in from twelve to fourteen 
 hours, the supernatant liquor, neutral lead acetate, is run off into the vessel, i, and 
 the semi-fluid magma of white-lead passes into 0. The pump, R, serves to again convey 
 the neutral acetate to the tank, A, and the operation is re-commenced. The white lead 
 in O is well washed the first wash-water being conveyed back to the tank, A, and 
 
 * How the builders of the Alhambra and the inventors of the rotation of crops can be called 
 -" semi-savages," is an unsolved problem. EDITOR. 
 
464 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 after drying is ready for use. In order to obtain the carbonic acid cheaply, it has been 
 proposed to ignite a mixture of chalk or limestone, charcoal, and peroxide of manga- 
 nese (CaC0 3 + C + 3MnO 2 = Mn 3 O 4 + CaO + 2CO 2 .) Where admissible, the carbonic 
 acid resulting from the fermentation of beer-wort, or of distillery- wash, may be applied. 
 
 Fig- 373- 
 
 Natural sources of carbonic acid sometimes occur in the neighbourhood of active or 
 extinct volcanoes ; and near Brohl, close to the Laacher Sea in Rhenish Prussia, a 
 locality well-known to tourists, a very plentiful and continuous supply of carbonic 
 acid is naturally obtained and actually applied for the purpose under consideration. 
 
 Among the very various suggestions for improved methods of making white lead, 
 and for which an enormous number of patents have been taken out, especially in this 
 country and in the United States, we briefly mention the following : Button and 
 Dyer first slightly moisten litharge with water, next mix it with a small quantity of a 
 solution of lead acetate, place the mixture in a stone trough, agitating and passing 
 hot carbonic acid over it. Pallu (1859) causes finely-divided lead to be thrown with 
 great force, by means of a centrifugal machine, on an inclined plane, care being taken 
 to moisten th# lead with acetic acid. After the lapse of an hour, the finely divided 
 lead is converted into acetate and carbonate. A solution of lead acetate is then 
 poured over the mass, and the lead acetate it contains is dissolved, while the white 
 lead is carried into a tank, and there forms a deposit. Griineberg (1860) prepares 
 white lead by submitting granulated lead to the simultaneous action of air, acetic and 
 carbonic acid, aided by the rapid motion of the metal. From private information 
 obtained from the largest wholesale house in London dealing in white lead, whose con- 
 nections and trade relations embrace literally the whole world, we have learned that 
 not loooth part of the lead, as it is technically termed, of good and saleable quality 
 met with in the trade, is made by these new processes, since the products of most of 
 them are deficient in some respect or other. 
 
 Theory of Preparing White Lead. Leaving out of the question the prepai'ation of 
 white lead from lead sulphate, the preparation of the pigment as regards all the other 
 methods is dependent upon : 
 
 1 . The formation of basic lead acetate ; 
 
 2. The decomposition of that compound into neutral lead acetate and white lead. 
 Viewing white lead for this purpose simply as a lead carbonate, although we shall 
 presently see that the white lead of commerce is not so simply constituted, the forma 
 tion may be illustrated by the following formulae : 
 
IECT. in.] COMPOUNDS OF LEAD. 
 
 Acetic acid. Basic lead acetate. 
 
 , + 200, + 2 PbC0 3 
 
 Basic lead acetate. Lead car- Neutral lead 
 
 bonate. acetate. 
 
 It is therefore evident that a comparatively very small quantity of lead acetate can 
 produce a large quantity of white lead, and the manufacture of that material would be 
 endless but for the fact that white lead retains some neutral lead acetate, and that 
 the loss of acetic acid cannot be practically avoided. 
 
 Properties of White Lead. When unadulterated and well-made, white lead is an 
 exquisitely fine white coloured powder, devoid of taste and smell. The white lead of 
 commerce exhibits, according to the mode of preparation, different features ; one pre- 
 paration is met with in flakes, having been obtained by the corrosion of thin strips of 
 lead placed in pots. The lead known as Krems lead is pure white lead made up into 
 cakes by means of gum-water. 
 
 The variety of white lead known as pearl white is blued with either a small quantity 
 of indigo or Berlin blue. The white lead of commerce has frequently been made the 
 object of chemical analysis, especially by Dr. G. J. Mulder and M. Griineberg. The 
 results of the analyses of the undermentioned samples prove the correctness of the 
 formula given above. The numbers refer to : i. Krems white lead. 2. Precipitated 
 by the Clichy method and manufactured at Magdeburg. 3. From the Harz. 4. An- 
 other sample from Krems. 5. A sample from a chemical laboratory by imitating 
 the Dutch method on a limited scale. 6, 7. Samples from Klagenfurt, Carynthia. 
 . English lead manufactured according to the Dutch method. 
 
 i. 2. 3. 4. 5. 6. 7. 8. 
 
 Oxide of lead . 8377 ... 85-93 ... 86-40 ... 86-25 8 4'4 2 8672 ... 86-5 ... 86-51 
 
 Carbonic acid . 15-06 ... 11-89 H'53 "'37 I4'45 H'28 ... 11-3 ... 11-26 
 
 Water . . 1*01 ... 2*01 ... 2*13 ... 2-21 ... 1-36 ... 2-00 ... 2*2 ... 2-23 
 
 It is certain that the covering properties of white lead are dependent upon its state 
 of aggregation, because a loose crystalline white lead does not cover nearly as well as 
 the perfectly amorphous lead prepared by the old Dutch method. It appears that the 
 covering power increases with the amount of hydrated lead oxide. This is proved 
 by the fact that those who merely choose white lead by its covering power are often 
 misled, a fact lately tested by the editor of this work, by giving to a workman, 
 thoroughly acquainted with white lead as commercially met with, a mixture of 
 carefully prepared and dried hydrated lead oxide, to which white precipitate, 
 bismuth subnitrate, and bismuth carbonate had been added. The man, after testing 
 a series of samples of purposely adulterated white lead, all of which he detected 
 as adulterated, was unable to speak with certainty of the above mixture, which 
 he took for pure lead. 
 
 Adulteration of White Lead. It has been, and is still, to some extent, the cus- 
 tom in manufactories to add to white lead a certain quantity of barium sulphate 
 either native or artificially prepared. Lead is often mixed with lead sulphate, 
 chalk, barium carbonate, barium sulphate, and pipe-clay; but these adulterations 
 are most common in the retail trade. None of these substances ought to be 
 present ; they possess no covering power and needlessly absorb oil. Pure white lead 
 ought to be perfectly soluble in very dilute nitric acid, and in the resulting clear 
 solution caustic potassa should not produce a precipitate. A residue insoluble 
 in the dilute nitric acid indicates the presence of gypsum, heavy-spar, or lead 
 
 2 G 
 
466 CHEMICAL TECHNOLOGY. [SECT. HI. 
 
 sulphate. The lead sulphate may be recognised by reducing the lead with the 
 blowpipe. Barium sulphate can be made evident by ignition with charcoal in 
 the blowpipe flame, treating the residue with dilute hydrochloric acid, and adding 
 a solution of gypsum, which again yields a precipitate of barium sulphate. Gypsum 
 does not yield an insoluble precipitate with dilute nitric acid, but does so with a 
 solution of ammonium oxalate. According to Dr. Stein, the most simple method 
 of estimating quantitatively a mixture of white lead and barium sulphate, is to 
 heat the weighed sample in a piece of combustion-tube, and to collect the carbonic 
 acid in a Liebig's potassa-bulb, a chloride of calcium-tube being fastened by a per- 
 forated cork to the combustion-tube to absorb the moisture. The quantity of 
 carbonic acid given off stands in direct proportion to the quantity of lead carbonate 
 present. Pure white lead of good quality gives off about 14-5 per cent, of the 
 gas, and, according to Dr. Stein's researches, the undermentioned series of mix- 
 tures gave off the quantities of carbonic acid indicated : 
 
 33*3 parts of white lead and 66 '6 parts of heavy-spar lost by ignition 4*5-5 per cent. 
 66-6 33-3 6-5-7 
 
 80-0 20-0 13-0 
 
 50-0 50-0 10-10-4 
 
 Applications of White Lead. The extensive applications of this material as a con- 
 stituent of paints, " to give body," as the term runs, and as putty, and for various 
 chemical operations are well known. It has been experimentally proved by Dr. G. J. 
 Mulder in his treatise On the Chemistry of Drying Oils and the Practical Applica- 
 tions to be drawn therefrom, that the quantity of white lead used in proportion to 
 linseed oil for painting purposes is far too great, being on an average from 2 50 to 280 
 parts of white lead to 100 parts of oil, while the author found that 52 parts of un- 
 adulterated white lead, or 44 parts of oxide of lead (PbO) to 100 parts of raw or 
 boiled linseed oil are amply sufficient quantities. White lead, however useful, is very 
 sensitive to the action of sulphuretted hydrogen, by which it is blackened and dis- 
 coloured, causing not only all the white paint to be spoiled, but also all pigments and 
 paints of which white lead is a constituent, as may be seen to a very large extent every 
 summer at Amsterdam, where sulphuretted hydrogen is abundantly given off from 
 the stagnant canals. The action, however, of the sea air in autumn has the effect of 
 somewhat restoring the blackened and discoloured painted surfaces to their primitive 
 hue. Thenard suggested that pictures which had become blackened should be 
 cleaned by means of hydrogen peroxide, the oxygen of which present as ozone converts 
 the blackened lead colours into white lead sulphate. 
 
 In this country it has become an almost universal custom to sell white lead ready 
 ground with linseed oil into a thick paste. This practice certainly saves painters a 
 great deal of trouble, but is also pregnant with the difficulty of detecting adulteration, 
 while there is a chance of an inferior oil, rosin oil, being added. The oil almost 
 entirely prevents the action of any acid upon the paste ; even if very strong nitric 
 acid be taken, and heat applied, the decomposition and disintegration are very slow 
 and incomplete, and, besides, owing to the insolubility of lead nitrate in nitric acid, 
 the action of strong nitric acid upon oil thus mixed gives rise to a variety of com- 
 pounds, which interfere with the usual modes of testing the white lead. To remove 
 the oil in order to test white lead, the best plan is to thoroughly incorporate some 
 of the sample with a mixture of chloroform and strong alcohol in equal parts, 
 and to wash the mass by decantation or on a filter with a fluid composed of 2 parts 
 of chloroform and i of strong alcohol. The quantity of the oil may then be ascer- 
 tained by the evaporation of this solvent. After washing once or twice with boiling 
 
SECT. ni.] COMPOUNDS OF MANGANESE AND CHEOMIUM. 467 
 
 alcohol and then drying, the white lead can be readily tested by any of the known 
 methods. 
 
 The proposed electrolytic method of producing white lead seems not to promise 
 good results. 
 
 White Lead from Chloride of Lead. M. Tourmentin prepares white lead from basic 
 lead chloride, obtained by the action of common salt upon litharge, by mixing that 
 compound with water, passing through it a current of carbonic acid, and next boiling 
 the fluid in a leaden-pan with powdered chalk until a test sample, when filtered, does 
 not become blackened by the addition of ammonium sulphide. The white lead thus 
 formed is freed from salt by washing with water. 
 
 Basic Lead Chloride as a /Substitute for White Lead. Mr. Pattinson, of the 
 Felling Chemical Works, near Newcastle-on-Tyne, has proposed that, instead of white 
 lead, a basic lead chloride (oxychloride) should be used, and he prepares that sub- 
 stance by adding to a hot solution of lead chloride (PbCl 2 ), containing from 400 
 to 500 grammes of the salt to the cubic foot, an equal bulk of saturated lime-water. 
 This addition causes the throwing down of the compound (PbCl 2 + PbH 2 2 ), which, 
 after having been collected on a filter and washed, is dried and used as a pigment. 
 The lead chloride is obtained directly from galena, which is decomposed in leaden 
 vessels with strong hydrochloric acid. The sulphuretted hydrogen thus formed is 
 carried by suitable tubing to a burner in the sulphuric acid chamber, the resulting 
 sulphurous acid from the combustion being used for the production of sulphuric 
 acid. Pattinson's white lead is not so white as ordinary white lead, its colour 
 verging to yellow, but this is 110 objection where white lead is to be used with other 
 paints, and the less so as Pattinson's oxychloride of lead covers well. 
 
 Lead Sulphate (PbS0 4 ), obtained as a bye-product in the preparation of aluminium 
 acetate from alum and sugar of lead, or in obtaining acetic acid by the action of 
 sulphuric acid upon lead acetate, or in a very impure state as a deposit in the lead 
 chambers of sulphuric acid works, is a difficult bye-product to utilise. It cannot be 
 easily reduced to metallic lead, and its low covering power prevents its use as a 
 pigment. It may be used in the manufacture of lead chromate (which see). 
 
 Cassel Yellow and Turner's Yellow. If i part of ammonium chloride is melted with 
 10 parts lead oxide there is produced a yellow foliaceous crystalline mass, which, when 
 finely ground and elutriated, is sold as Cassel yellow. Its composition is said to be 
 PbCl 2 ,7PbO. If lead oxide is treated with solution of sodium chloride, a white lead 
 oxychloride is produced, which, after melting, is known as Turner's yellow. Its 
 formula is PbCl 2 ,5PbO. Both these preparations have been superseded by chrome 
 yellow. 
 
 COMPOUNDS OF MANGANESE AND CHROMIUM. 
 
 Manganese. Of all the ores of manganese met with in various degrees of oxidation, 
 only the peroxide, mineralogically known as pyrolusite, polianite, and technically as 
 glass-makers' soap, is industrially of much importance. When perfectly pure this 
 mineral consists of 63-64 per cent, of manganese, and 36-36 per cent, of oxygen, 
 its formula being Mn0 8 ; but the ore, as met with in commerce, frequently contains 
 baryta, silica, and water, and sometimes oxides of iron, nickel, cobalt, and lower oxides 
 of manganese viz., Braunite, Mn 2 3 ; Manganite, Mn,O s ,H 2 O; Hausmannite, Mn 3 4 ; 
 and various other minerals, as potassa compounds, lime, &c. In Germany the ore is 
 purified by most ingeniously contrived machinery, which might be very advanta- 
 geously applied to a great many other metallic ores and phosphatic minerals. Manganese 
 is industrially employed in making oxygen, the preparation of bromine and iodine, 
 glass-making, colouring enamels, for producing mottled soaps, in puddling iron, and 
 in dyeing and calico-printing, for preparing potassium permanganate ; but the largest 
 
468 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 consumers are the manufacturers of chlorine. The bulk of the manganese of commerce 
 is derived from Germany, which supplies about 700,000 cwts. to Europe annually. It 
 is found also very largely and of excellent quality in Spain, as well as in Italy, Greece, 
 Turkey, Sweden, and British India. 
 
 Testing the Quality of Manganese. The value of manganese for technical purposes 
 depends i. On the quantity of oxygen it is capable of yielding, or the quantity of 
 chlorine it will evolve, not taking into account the of the MnO. 2. On the nature 
 and quantity of the substances soluble in acids, such as the calcium and barium car- 
 bonates and ferrous oxide, which, not yielding chlorine, saturate a certain quantity of 
 hydrochloric acid. But even if these impurities are absent, it may happen that, of two 
 samples of manganese, one requires more acid than the other to evolve the same bulk 
 of chlorine gas, as, for instance, when one of the samples contains in addition to 
 manganese peroxide (MnO.,) also the sesquioxide (Mn 2 3 ), especially if the latter is 
 present as hydrate. 3. On the quantity of water, which may amount even to 
 15 per cent. 
 
 According to the experiments of Fresenius, the most suitable temperature for 
 drying a weighed sample of manganese, in order to estimate the water it contains, is 
 1 20, no water of hydratation being expelled at that heat ; but for commercial analysis 
 the drying of a sample at 100 is quite sufficient, provided it be kept at that heat for 
 some hours consecutively. Among the many methods proposed for testing manganese, 
 that originally invented by Thompson and Berthier, and improved upon by Will and 
 Fresenius, is based on the fact that a molecule of manganese peroxide treated with sul- 
 phuric acid is capable of converting, by the given off, i moL of oxalic acid into 
 2 mols. of COj. 
 
 From the weight of C0 8 evolved the quantity of manganese peroxide actually 
 present in the sample is calculated.* 
 
 Potassium Permanganate. This salt (KMnOJ, used for disinfecting, bleaching, 
 and other oxidising purposes, and constantly employed in chemical laboratories, 
 owes its efficiency to the fact that, in contact with dilute sulphuric acid, it yields 
 manganous oxide and oxygen (Mn 2 O 7 = 2MnO + 50). The potassium permanganate is 
 for technical purposes prepared in the following manner : 500 kilos, of caustic potassa 
 solution at 84 Tw. (= 1-44 sp. gr.) are added to 105 kilos, of potassium chlorate, and 
 the mixture evaporated to dryness, there being gradually added 180 kilos, of powdered 
 manganese, and the heating continued to the fusion of the mass, which is stirred until 
 cold. The powder thus obtained is heated in small iron crucibles to a red heat, and 
 when semi-fluid is cooled ; the mass is next broken up and put into a large cauldron 
 filled with hot water, and left standing for about an hour. The clear liquid having 
 been decanted from the sediment, hydrated manganese peroxide, is evaporated to 
 crystallisation ; 180 kilos, of manganese yield 98 to 100 kilos, of crystallised permanga- 
 nate. Approximately the process may be elucidated as follows : 
 
 (a) By the fusion of the potassium manganate and potassium chloride 
 6Mn0 3 + 2 KC10 3 + i 2 KOH = 6K,MnO 4 + 2 KC1 + 6H,0. 
 
 (6) During the solution of the fused mass in water, the potassium manganate is 
 converted into potassium hydrate, hydrated manganese peroxide, and potassium per- 
 manganate, 3K,MnO 4 + 6H,O = 4KOH + 2 KMn0 4 + MnO, + 4H 2 O. Consequently 
 one-third of the manganic acid is lost by the formation of manganese peroxide. 
 This also occurs when, according to M. Tessie du Motay's plan, the conversion of 
 potassium manganate into permanganic acid is effected by magnesium sulphate 
 3 K,Mn0 4 + 2MgSO 4 = 2KMnO 4 + Mn0 2 + 2 K,SO 4 + 2 MgO. Dr. Staedeler therefore 
 suggests that the potassium manganate should be converted into permanganate by 
 chlorine, according to the formula 2K 2 Mn0 4 + Cl = KC1 2 + 2KMn0 4 . For disinfecting 
 * See Select Methods in Chemical Analysis, by W. Crookes, F.R.S. 
 
SECT, in.] COMPOUNDS OF CHROMIUM. 469 
 
 purposes a mixed sodium and v potassium permanganate, or even the latter alone, is 
 usual ; the well-known Condy's fluid is a solution of this salt in water. Kuhne's dis- 
 infectant is a mixture of sodium permanganate and ferric sulphate. Potassium per- 
 manganate is used to some extent in dyeing, and for staining wood.* 
 
 The Berlin Joint-Stock Chemical Company produces permanganates by the electro- 
 lysis of a manganate. 
 
 Ohromates. The yellow, neutral salt, K,Cr0 4 , is prepared by heating chrome 
 iron ore, previously pulverised and elutriated, with potassium carbonate and nitrate 
 on the hearth of a reverberatory furnace. The oxygen of the saltpetre causes the 
 higher oxidation of the ferrous oxide and chromium sesquioxide, the latter being 
 converted into chromic acid. The thoroughly sintered, not molten, mass is, after 
 cooling, again ground up and lixiviated with boiling water, and also boiled for a time 
 to extract the neutral potassium chromate. Wood vinegar is added to the solu- 
 tion to precipitate the alumina and silica, after which the clear liquid is evaporated, 
 until a film of saline material begins to form, when it is left to crystallise. The 
 crystals take a column-like form, and are of a lemon-yellow colour, readily soluble 
 in water, but insoluble in alcohol, and having a great tendency to become converted 
 into potassium bichromate or red chromate. This conversion of the neutral salt into 
 the bi- or acid- salt is at once effected by the addition to its solution of sulphuric or 
 nitric acid preferably the latter, on account of the formation of potassium nitrate, 
 which may be either sold or used in the manufacture of the neutral chromate. 
 
 The potassium dichromate or acid chromate, K 2 Cr 2 7 , crystallises in anhydrous, 
 aurora-red coloured triclinohedric prismatic crystals, soluble in 10 parts of water. 
 This solution is highly caustic and poisonous. When heated to redness the salt gives 
 off oxygen, leaving chromium oxide and neutral potassium chromate in the retort. 
 
 Jacquelain proposes that the chrome-iron should be mixed with chalk and the 
 mixture heated and frequently stirred, then cooled, pulverised, and put into water, 
 with the addition of enough sulphuric acid to produce a weak reaction, the result 
 being the formation, first of calcium chromate, which, by the addition of the acid, 
 becomes the bichromate of that base. The ferrous sulphate present in this solution 
 is precipitated by means of chalk. In order to convert the calcium bichromate into 
 the corresponding potassium salt, it is only necessary to add a solution of potassium 
 carbonate, the result being of course the precipitation of calcium carbonate and the 
 exchange of the chromic acid from the lime to the potassa. According to Tilghman's 
 process chrome-iron ore is mixed with 2 parts of lime, 2 of potassium sulphate and 
 heated for eighteen to twenty hours in a reverberatory furnace. The same inventor 
 suggests the heating of chrome-iron ore with powdered felspar and lime. Mr. 
 Swindells ignites chrome ore with equal parts of either sodium or potassium chloride 
 to the highest possible white heat, at the same time exposing the mixture to a con- 
 stant current of superheated steam, the formation of sodium or potassium chromate 
 resulting. The most important improvement in the preparation of potassium chro- 
 mate is the substitution of potash for saltpetre and the use of a furnace so constructed 
 \s to admit of the proper access of air to the strongly heated mass, the oxygen of the 
 air being made to oxidise the chromic oxide to chromic acid. Another improvement 
 is, that in using lime instead of alkali, the oxidation of the chromic oxide is greatly 
 accelerated, by reason that when lime is employed instead of potassa the heated 
 materials do not become semi-fused or pasty, but, remaining pulverulent, admit of 
 the readier access of air, as well as preventing the sinking, on account of higher 
 specific gravity, of a portion of the chrome ore to the bottom of the hearth, and there 
 becoming withdrawn from the action of the heat. 
 
 * Latterly sodium permanganate has been prepared and used at great expense for deodorising 
 the Thames. 
 
470 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 Applications of the Potassium Chromates. Before the year 1820 the salts spoken of 
 were only used for the preparation of chrome-yellow ; their preparation was then very 
 expensive, viz., the calcination of the chrome-iron ore with potassium nitrate only. 
 At this date M. Koachlin discovered the applicability of potassium dichromate to the 
 obtaining of what is technically termed " discharge " for Turkey red a madder 
 colour a discovery soon followed by others bearing upon the useful applications 
 of this salt, among which are the formation of chrome-yellow and chrome-orange in 
 calico-printing, chrome-black in dyeing, the oxidation of catechu and Berlin blue, the 
 discharge of indigo blue, the bleaching of palm oil and other fatty substances, the pre- 
 paration of mixtures for the heads of lucifer matches, the preparation of mercurous 
 chromate and chromic oxide as green-coloured pigments in glass- and china-painting, 
 and for the preparation of Guignet's Green, a peculiar hydrated chromium oxide, 
 Cr a O 3 2H 2 0, obtained by heating i part of potassium bichromate and 3 parts of crys- 
 tallised boric acid, and used as a pigment in calico-printing. As might be expected, 
 all these discoveries gave a strong impulse to the manufacture of the potassium 
 chromates, which have recently found still further useful applications in the obtaining 
 of colours from coal-tar i.e., aniline violet, aniline green, and alizarine, in the manu- 
 facture of chlorine gas, in defuseling brandy and other spirits, and in the purification 
 of wood-vinegar made from the crude pyroligneous acid. 
 
 According to M. J. Persoz, there exist, America excepted, only six manufactories 
 of the potassium chromates viz., two in Scotland, one in France, one at Trjbndhem, 
 Norway, and one at Kazan, near the Oural, Russia ; the total production of these works 
 amounted in 1869 to 60,000 cwts.* 
 
 Sodium Chromate (Na 2 Cr0 4 ). Walberg mixes 6 parts finely-ground chrome ore 
 (containing 44 per cent. Cr 8 3 ), 3 parts soda-ash (containing 92 per cent, sodium 
 carbonate), and 3 parts chalk in a reverberatory in the oxidising flame ; the charge of 
 the furnace being i ton. The hot mass is lixiviated with water, forming a lye of 
 84 Tw. It is then boiled down in an iron pan to 104 Tw., and poured into tanks 
 lined with lead. When cold, there are formed acicular yellow crystals of 
 
 Na 2 Cr0 4 .ioH s O. 
 
 They are drained in a centrifugal machine, placed in a drying-chamber, at a heat not 
 exceeding 30, and well ventilated. Here they effloresce, and are converted into a 
 yellow anhydrous powder. 
 
 Sodium chromate so prepared has the composition 
 
 Na.jCr0 4 96-60 
 
 Sodium sulphate . . . . 0^92 
 
 Insoluble residue . . . . 0^40 
 
 Water 1-28 
 
 99 '20. 
 
 For producing sodium dichromate, Chrystal ignites chrome ore with lime and soda, 
 lixiviates, decomposes the neutral chromate with an acid, and evaporates to crystallisa- 
 tion. Ammonium chromates may be obtained from the sodium salts by double decom- 
 position. 
 
 Chromic Acid, Cr0 8 , is obtained by decomposing potassium dichromate with sulphuric 
 acid. It is used in galvanic batteries in place of nitric acid. 
 
 Chrome-Yellow, Lead Chromate (PbCrO 4 ), is not to be confounded with yellow 
 chrome, the neutral potassium chromate. There are in technical use three different 
 compounds of lead and chromic acid viz., neutral lead chromate or chrome-yellow, 
 basic chromate or chrome-red, and a mixture of these two salts constituting chrome- 
 orange. The first of these substances is obtained by two methods: (i) By the 
 
 * There is also a manufactory of the chromates at Sowerby Bridge, near Halifax. 
 
SECT. HI.] COMPOUNDS OF CHROMIUM. 471 
 
 precipitation of a solution of potassium chromate with a solution of lead acetate ; or 
 (2) by the use of lead sulphate or chloride. According to the first plan, the operation 
 begins with the preparation of a solution of lead, for which purpose granulated 
 lead is put into wooden tubs placed one above the other, and the taps each tub is 
 provided with being turned off, vinegar is poured into the upper tub. In about ten 
 minutes the tap at the bottom of the tub is opened, and the contents let into the 
 second tub. The operation is repeated with all the tubs, four to eight in number, the 
 object simply being to moisten the lead thoroughly with the vinegar, so as to cause 
 rapid oxidation on its subsequent exposure to air. The metal soon becomes coated 
 with a bluish-white coloured film, and when this is apparent, vinegar is again poured 
 into the topmost tub and left for about an hour, after which it is run off into the 
 second tub, and the operation continued until there is obtained a saturated solution of 
 basic lead acetate. To prepare chrome-yellow enough vinegar is added to obtain an 
 acid reaction, and the fluid left to deposit any suspended sediment. At the same time, 
 in another tub, a solution of 25 kilos, of potassium bichromate in 500 litres of water is 
 kept in readiness. The clear lead solution is next poured into the bichromate solution 
 as long as any precipitate ensues. This precipitate is well washed, and usually mixed 
 with gypsum, or barium sulphate, to obtain the lighter chrome colours ; finally it is 
 dried. According to Liebig, chrome-yellow is obtained from lead sulphate, an almost 
 useless bye-product from calico-printing and dye-works, by digesting it with a warm 
 solution of neutral potassium chromate. The depth of colour of the ensuing yellow pig- 
 ment depends upon the quantity of lead sulphate which is converted into lead chromate. 
 The white lead deposit from the sulphuric acid chambers is too impure for this use. 
 
 Dr. Habich states that there exist two binary compounds of lead chromate and 
 sulphate, the formula of which are : PbS0 4 + PbCr0 4 and 2PbS0 4 + PbCr0 4 . The 
 former is obtained when a solution of potassium bichromate, previously mixed with 
 enough sulphuric acid to cause its dissociation, is precipitated with a solution of lead; 
 while the second compound is formed if the quantity of sulphuric acid is doubled. 
 When dry it has a bright, sulphur-yellow colour with a fiery fracture. According to 
 M. Anthon a beautiful chrome-yellow is obtained by the digestion of 100 parts of 
 freshly precipitated lead chloride with 47 parts of potassium bichromate. 
 
 Chrome-Red. The basic lead chromate, known as chrome-red and Austrian cin- 
 nabar, PbCr0 4 + PbH 2 2 ,* is a red-coloured pigment much in demand, and obtained 
 from the yellow or neutral lead chromate, either by boiling it with a caustic potassa 
 solution, or by fusing it with potassium nitrate, the effect being that half of the 
 chromic acid is withdrawn from the neutral chromate. Liebig and Wb'hler state that 
 chrome-red is best obtained by fusing together, at a very low red-heat, equal parts of 
 potassium and sodium nitrates, gradually pouring into the fused salt small quantities 
 of chemically pure yellow lead chromate. After cooling, the insoluble chrome-red is 
 well washed and dried. It is then a magnificently coloured cinnabar-like crystalline 
 powder. Dulong prepares chrome-red by precipitating a solution of lead acetate with 
 a solution of potassium chromate to which caustic potassa has been added. The 
 various shades and qualities of chrome-red, from the deepest vermilion to the palest 
 red, are due to the difference in size of the constituent crystalline particles. This 
 fact is proved by experiment, for when several samples are uniformly ground to a fine 
 powder the result is the production of a uniformly deep-coloured hue. In pre- 
 paring chrome-red of a deep colour, everything which might interfere with or injure 
 the crystallisation has to be avoided. The pigments commercially known as the 
 chrome-orange colours are mixtures, in varying proportions, of the basic and neutral 
 
 * According to Dr. Duflos (see Handbuch der AngewandtenPharmaceutisch-Technisch Chemischen 
 Analyse. &c., Breslau, 1871, p. 293) the formula of this substance is, 2PbO,CrO,p and the dried salt 
 does not contain any water as a component part. 
 
472 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 lead chromates, and are usually made by boiling chrome-yellow with milk of lime. 
 M. Anthon recommends for the preparation of a good chrome-orange the treatment of 
 loo parts of chrome-yellow with 55 parts of potassium chromate and 12 to 18 parts of 
 caustic lime made into milk of lime. 
 
 Chromic Oxide or Chrome-Green. This substance, Cr 2 3 , is used in glass- and 
 porcelain-staining as a couleur grand feu, that is to say, it stands the most intense heat, 
 provided no reducing materials are allowed to affect it. It is commercially known 
 under the name of chrome-green as an indelible pigment for printing, being especially 
 employed for bank-notes. It is prepared in various ways, the finest being obtained by 
 heating mercurous chromate, but this method is far too expensive to admit of any 
 extensive application. Lassaigne heats equal molecules of sulphur and yellow potas- 
 sium chromate, and exhausts the mixture with water, leaving the insoluble green 
 sesquioxide behind. Wohler prefers to mix the yellow potassium chromate with 
 sal-ammoniac, to heat that mixture, and afterwards treat it with water, leaving the 
 insoluble chrome-green as a fine powder. 
 
 Among other methods of preparing the anhydrous sesquioxide is the heating of an 
 intimate mixture of potassium bichromate and charcoal. The hydrated chromium 
 oxide, according to the formula Cr 4 H 6 9 , is met with in the trade under a variety 
 of names, and often contains boric or phosphoric acids, not, however, as an essential 
 constituent (see Schiitzenberger's formula for Guignet's green), but as a remnant 
 of imperfect preparation. This hydrated oxide, the preparation of which so as to 
 ensure a good colour is rather a difficult matter, requiring very careful manipulation, 
 is known as emerald green, Pannetier green, Matthieu-Plessy green, and Arnaudon 
 green. The pigment is used as an artist's colour and in calico-printing as a substitute 
 for Schweinfurt green, but is very expensive. 
 
 Guignet's green is best obtained by melting together potassium dichromate and 
 crystalline boric acid at a red heat. The melted mass is lixiviated with hot water, 
 and the residue finely ground. 
 
 In an English manufactory 8 parts of boric acid and 3 parts potassium dichromate 
 are finely pulverised, well mixed, and heated for four hours to dull redness in a reverbe- 
 ratory. The burnt mass must have a peculiar green tone, which can be recognised only 
 by long experience. In any case the mass must have no (or but few) yellow or brown 
 rusty spots ; if these are abundant the entire melt is worthless. Such spots may arise 
 from different causes, the most common of which is a dirty furnace, or too high a tempera- 
 ture. The mass, a mixture of calcium borate and chromic oxide, is washed to remove 
 the former. The waters from the two first washings are kept apart for the recovery of 
 the boric acid. The third is kept to be used for the first washing of a fresh melt, and 
 the further waters are allowed to collect in a cistern, where they deposit any oxide which 
 may have been carried over. The washing lasts six days. The mass is then ground in a 
 wet mill, and washed again, being mixed up with water, and boiled four or five times in 
 the course of the day, each time with fresh water. Heat is applied by blowing in 
 steam. The mass is pressed, yielding a product which, at 100, contains 33 per cent, 
 of solid matter, and after ignition 26 per cent. 
 
 Chromic Hydrate, either alone, or in combination with boric, phosphoric, or arsenic 
 acid, is a fine green pigment, used under the names of Mittler green, emerald green, 
 Pannetier green, Arnaudon green, Schnitz green, and Matthieu-Plessy green.* It is 
 prepared, according to Kothe, by treating 10 grammes potassium dichromate with a 
 solution of 1 2 grammes sugar in i oo c.c. of water, adding 30 c.c. phosphoric acid of sp. gr. 
 1-3, and the solution of 10 grammes barium chloride, and boiling for some time. 
 
 Dingler's Green is a mixture of chromium and calcium phosphates. 
 
 There is lamentable confusion in the momenclature of pigments. 
 
SECT, in.] COMPOUNDS OF IRON. 473 
 
 Casali Green is obtained by igniting i part potassium dichromate and 3 parts gypsum 
 and boiling the mass in very dilute hydrochloric acid. 
 
 Chrome Alum. This salt, K . r [ 4$O 4 + 24H 2 0, is obtained in rather large quan- 
 
 iv 2 j 
 
 tities as a bye-product of the manufacture of aniline- violet, aniline-green, and anthracene- 
 red. It is a deep violet-coloured octahedrically crystallised substance, now used to 
 some extent as a mordant in dyeing, for rendering gum and glue insoluble, for water- 
 proofing woollen fabrics, and for the preparation of potassium chromate. 
 
 Chromium Chloride. This compound, Cr 2 Cl 6 , best prepared by the decomposition 
 of chromium sulphide by means of chlorine, constitutes a crystalline violet-coloured mica- 
 like material, employed in the manufacture of coloured paper and paper-hangings. 
 
 Basic Ferric Chromate, Fe 2 (Cr 4 ) 3 , has been recommended by Kletzinsky by the 
 name of siderine yellow as a water- and oil-colour, drying very quickly. It is obtained 
 by heating a solution of potassium dichromate mixed with neutral ferric chloride. It 
 forms a fiery red precipitate, which is carefully washed and dried. 
 
 IKON COMPOUNDS, INCLUDING FERROCYANOGEN. 
 
 Copperas or Green Vitriol. The substance called copperas and green vitriol, 
 ferrous sulphate (FeSO 4 + 7H 2 0), is met with in trade in the form of greenish- 
 coloured crystals possessed of an inky astringent taste ; on exposure to dry air the 
 crystals effloresce, and are gradually converted into a yellowish powder basic ferric 
 sulphate. 100 parts of the chemically pure crystallised salt consist of 
 
 2 6' 10 parts of ferrous oxide. 
 
 29^90 sulphuric acid. 
 
 44 - oo water. 
 
 Preparation of Green Vitriol as a Eye-product in Alum Works. Since the minerals 
 ordinarily used in the manufacture of alum the alum schists generally contain iron 
 pyrites (FeS 2 ), either as such or already partly converted into a basic sulphate of the 
 peroxide (which on being treated along with the alum shale, becomes by weathering 
 and roasting converted into iron protosulphate and peroxide), green vitriol is frequently 
 a bye-product of alum manufacture, and is obtained by evaporating the mother liquor 
 containing iron, and leaving it to crystallise. In some localities, as, for instance, at 
 Goslar (Prussia), on the Hartz mountains, the liquor obtained by the lixiviation of 
 the iron-containing minerals alluded to is first evaporated for the separation of the 
 green vitriol, then a potassium or ammonium salt is added to the remaining acid 
 liquid to obtain alum. 
 
 Preparation of Green Vitriol in Beds. The material sometimes rather largely found 
 in coal pits, and called brasses (iron pyrites), is collected and placed in layers over a 
 somewhat excavated surface, which has been rendered impervious to water by puddling 
 with clay, and made to incline slightly in one direction, where water-tight tanks stand, 
 into which scraps of old iron are placed with the view of saturating any free acid ; the 
 pyrites, placed on these beds to a thickness varying from i^.to 3^ or 4 feet, is slowly 
 oxidised by atmospheric agency, and the falling rain carries into the tanks a more or 
 less strong solution of copperas, which, when sufficiently concentrated, is slowly 
 evaporated, some scrap-iron being placed in the evaporating-pans. 
 
 Green Vitriol from the Residues of Pyrites Distillation. In countries where iron 
 pyrites abounds, and fuel and labour are sufficiently cheap to make the distillation of 
 sulphur from pyrites a profitable business, the residues are utilised in green vitriol 
 making, a salt which thus made must, of necessity, contain a good deal of impurity. 
 
 Green Vitriol from Metallic Iron and Sulphuric Acid. The brown sulphuric acid or 
 chamber acid, also such waste sulphuric acid liquids as are obtained in the oil and 
 
474 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. III. 
 
 petroleum refining, are sometimes used as solvents for scrap-iron for the preparation 
 of green vitriol, which may also be made by boiling the finely pulverised puddling and 
 iron refining slags with sulphuric acid. 
 
 Green Vitriol from, Spathic Iron Ore. In localities where spathic iron (ferrous car- 
 bonate, FeCO 3 ) occurs in a pure state, that mineral may be usefully applied to the 
 preparation of green vitriol by treatment with sulphuric acid, and evaporating the 
 solution thus obtained. The ferrous sulphate, prepared on the large scale, is often, 
 met with crystallised round a small thin stick of wood, which is hung up in the solu- 
 tion to promote crystallisation ; sometimes, at least abroad, a so-called black vitriol is 
 met with, which is simply green copperas superficially coloured black by means of 
 some astringent decoction, such as nut galls. 
 
 Uses of Green Vitriol. This substance is employed as a disinfectant, as a mordant 
 in dyeing and calico printing for various black and brown shades, for the preparation 
 of ink, the deoxidation of indigo in the so-called cold vat used for cotton dyeing in 
 gas purifying, in the precipitation of gold from its solutions, in the preparation of 
 Prussian blue, in the manufacture of fuming (Nordhausen) sulphuric acid, in the 
 treatment of sewage, and for a host of other purposes. 
 
 Iron Minium is a dark red-brown pigment, consisting chiefly of ferric oxide. It is 
 obtained by roasting, sorting, and grinding burnt pyrites. 
 
 Potassium Ferrocyanide. The yellow-coloured salt, generally known as yellow 
 prussiate of potassa (potassium ferrocyanide, K 4 FeCy 6 + 3H 2 0), is, in a technical point 
 of view, a very important substance. It crystallises in large lemon-coloured prismatic 
 crystals, which are not affected by exposure to air, are not poisonous, and possess a 
 sweetish bitter taste. This salt is soluble in 4 parts of cold and 2 of boiling water, 
 but is insoluble in alcohol; in 100 parts there are 
 
 37 '03 Potassium 
 
 1 7 '04 Carbon ) .-, 
 
 \ Cyanogen. 
 19-89 Nitrogen j ' 
 
 13-25 Iron 
 1279 Water 
 
 At 100 the water is driven off. The salt is prepared on a large scale by igniting 
 such carbon as contains nitrogen to a red heat with potassium carbonate in closed vessels. 
 The quantities of the materials may be varied, the relative proportions being given by 
 some makers as 100 parts of potassium carbonate to 75 of the nitrogenous carbon, or, 
 according to Runge, 100 parts of potassium carbonate, 400 of torrified horn, and 10 parts 
 of iron filings. The nitrogenous materials used are horns, hoofs, blood, wool-dust, 
 cuttings of hides, and leather. 
 
 The fusion of these ingredients is carried on either in closed iron vessels of a 
 
 Fig- 374- 
 
 Fig- 375- 
 
 peculiar shape, or in a reverberatory furnace. The iron-vessel, a, termed a muffle, 
 (Fig. 374), is egg- or pear-shaped, having a diameter of 1-2 metre, a width of 0*8 metre, 
 
SECT, in.] COMPOUNDS OF IRON. 475 
 
 and varying from 12 to 15 centimetres in thickness, with a short, wide neck in front. 
 As shown in the woodcut, the iron vessel is placed in the furnace in such a manner as 
 to be exposed to the action of the flame and hot gases on all sides, being supported 
 at the back by a projection about 27 centimetres long, and resting at g on the brick- 
 work, leaving space sufficient for the gases generated in the interior to pass off by c 
 into the chimney-flues ; m is an iron cover which is closed during the operation of melt- 
 ing, g being an opening in the front wall of the furnace, through which the ingredients 
 are put into the iron vessel, and the molten mass taken out. The shallow pan, i, on 
 the top of the furnace, is intended for the evaporation of the liquor obtained by treating 
 the molten mass with water. The use of the iron vessel, however, is attended with the 
 serious drawback that the iron is eaten into holes in a comparatively short space of time ; 
 and, though this action is greatest on the lower part of the vessel, and it may there- 
 fore be turned bottom upwards, and the holes stopped with fire-clay, the vessel has 
 soon to be replaced by another. It is on this account, and also owing to the fact that 
 a larger quantity of raw material can be operated upon at once, that instead of the 
 apparatus described above, there has come into general use a reverberatory furnace, 
 ^ig- 375> arranged with a shallow cast-iron pan, a, from i to i'8 metre in diameter, 
 with a rim about i decimetre high ; b is the fire-place ; g, the bridge ; c, a flue leading 
 to the chimney, e. Sometimes the hot air is applied to the heating of evaporating pans, 
 being carried under them before entering the chimney. The result of the ignition is 
 the formation of a black mass, technically called the metal, yielding the liquor from which 
 the crude salt crystallises. The salt is purified by re-crystallisation, while the black 
 residue is employed as a manure and for decolorising paraffine, &c. 
 
 The theory of the formation of the potassium ferrocyanide is as follows : The car- 
 bonate and potassium sulphate, the nitrogenous coal and the iron reacting upon each 
 other, give rise to the formation first of potassium sulphide, which in its turn converts 
 the iron into sulphide, while the nitrogen contained in the charcoal unites, under the 
 influence of potassium, with the cyanogen of the carbon, which again in its turn com- 
 bines with the potassium, giving rise to the formation of potassium cyanide. When 
 the fused mass is treated with water, potassium cyanide and sulphide of iron decompose 
 each other, the result being the formation of potassium ferrocyanide and sulphide, 
 the last-named salt remaining in the mother liquor. M. E. Meyer states (1868) that 
 it is more advantageous to employ, instead of the iron sulphide, the carbonate of 
 that metal, for the purpose of converting cyanogen into ferrocyanogen, because the 
 potassium ferrocyanide crystallises far more completely and freely from solutions not 
 containing any potassium sulphide. Liebig has since proved that the fused mass only 
 contains potassium cyanide and metallic iron, and not any potassium ferrocyanide, 
 which is only formed by treating the molten mass with water, or more slowly by its 
 exposure to moist air. Among the materials frequently added to the fusing mass 
 are scraps of metal, the refuse of leather, dried blood and other dry animal offal, 
 because the ammonia evolved by their decomposition in the presence of ari alkali aids 
 the formation of potassium cyanide. According to M. P. Havrez, the crude suint 
 obtained from wool is an excellent material for the preparation of potassium ferro- 
 cyanide, since 100 kilos, of the suint contain about 40 kilos, of potassium carbonate, 
 from i to 2 kilos, of potassium cyanide, and about 50 kilos, of combustible hydro- 
 carbons, the heating value of which is at least equal to that of 40 kilos, of coal. 
 
 Attempts have been made to obtain the potassium cyanide on a large scale, by caus- 
 ing a current of ammoniacal gas to pass through and over potassium carbonate heated 
 to redness ; and also to obtain potassium cyanide from, or by aid of, the nitrogen of 
 the atmosphere. This process was tried nearly forty years ago at Bramwell's works 
 iiear Newcastle-on-Tyne, but was found to be a failure commercially.* As it has 
 
 * Compare Richardson and Watts' Chemical Technology. 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. in. 
 
 been proved by experiment that baryta, far more readily than potassa, converts 
 carbon and nitrogen into cyanogen, forming barium cyanide at a lower temperature, 
 baryta might perhaps be substituted for potassa, but as yet this plan is not carried 
 out commercially. According to Gelis (1861), the yellow prussiate may be prepared 
 by the mutual reaction of carbon sulphide and ammonium sulphide, the resulting 
 sulphocarbonate being converted into potassium sulphocyanide by means of potassium 
 sulphuret, by which reaction ammonium sulphide and sulphuretted hydrogen are vola- 
 tilised. The potassium sulphocyanide is next converted into ferrocyanide by being 
 heated with metallic iron to redness, iron sulphide being at the same time formed. 
 It is evident that this process could not be carried out commercially. Mr. H. Fleck 
 described, in 1863, a plan for preparing the ferrocyanide by the action of a mixture 
 of ammonium sulphate, sulphur and carbon, upon fusing potassium sulphide, which 
 thus becomes potassium sulphocyanide, one-half of the nitrogen of the ammonium 
 sulphate remaining in the fused metal as cyanogen, while the other half escapes 
 as ammonium sulphide, which is again converted into ammonium sulphate. The 
 potassium sulphocyanide produced is treated with metallic iron at a red-heat, and 
 thus potassium cyanide and iron sulphide are produced. This process is also too 
 cumbrous and expensive on a large scale. 
 
 Applications of the Yellow Prussiate. This salt is employed in the manufacture of 
 the ferricyanide or red prussiate, in the preparation of Berlin blue, and of potassium 
 cyanide (the impure salt as met with in commerce), in dyeing and calico-printing for 
 the production of blue and brown -red colours, for the purpose of surface-hardening 
 small iron articles, as an ingredient of white gunpowder, and for use in chemical 
 laboratories. 
 
 Great loss is experienced in the manufacture of ferrocyanide because the nitro- 
 genous organic matter floats and burns upon the surface of the melting potash, whilst 
 the nitrogenous gases only pass through a thin layer of potash, so 
 that a part escapes without being utilised. To prevent this the 
 
 N potash is melted in the pan E (Fig. 376), 2 metres high, and 0*6 
 
 metre wide, and the nitrogenous bodies are pressed down to the 
 bottom by a plunger, n. This plunger consists of a strong bor- 
 dered plate of metal with several perforations, its rod, d, being 
 raised and lowered by means of a counterpoise. In working, 300 
 kilos, of potash are melted in the cylinder, the plunger is raised, 
 and the nitrogenous matters are introduced through b. The mass 
 is forced to the bottom by lowering the plunger. The intro- 
 duction of the nitrogenous matter continues until all is melted 
 up. The heat is then raised for a short time ; the melt is drawn 
 off at e into a truck, and a new charge is introduced. The 
 ammonia in the vapours is condensed in a scrubber. 
 
 For obtaining ferrocyanide from Laming's mass, Kunheim 
 dissolves out the ammonia with water and the free sulphur with 
 carbon disulphide. It is then mixed with dry lime. The dry 
 mixture is then either heated from 40 to 100 in a closed vessel, 
 with constant stirring to expel any undissolved ammonia, the 
 escaping vapours being passed through a scrubber, and the mass 
 then submitted to methodical lixiviation with water, or the lixiviation is applied first, 
 yielding an ammoniacal lye of calcium ferrocyanide. This lye is carefully neutralised and 
 heated to the boiling point, when a sparingly soluble compound is deposited, calcium- 
 ammonium ferrocyanide. It is treated with lime in closed vessels ; the compound is 
 decomposed ; the escaping ammonia is secured in the usual manner, and a pure lye of 
 calcium ferrocyanide is obtained. It is utilised as Prussian blue by treatment with 
 
 Fig. 376. 
 
SECT, in.] COMPOUNDS OF IKON. 477 
 
 ferrous salts and subsequent evaporation. If potassium ferrocyanide is to be produced, 
 calcium -potassium ferrocyanide is first formed by evaporating and adding so much 
 potassium chloride as is sufficient for forming CaK 2 FeCy 6 . The double cyanide sepa- 
 rates out, is filtered off, washed, and boiled with potassium carbonate, which converts it 
 into potassium ferrocyanide. 
 
 Potassium Ferricyanide. The red prussiate of potassa, properly potassium ferri- 
 cyanide, or Gmelin's salt, K g FeCy, is prepared on a large scale and extensively used 
 in dyeing and calico-printing. This salt crystallises in prismatically shaped ruby -red- 
 coloured, anhydrous crystals, which consist in 100 parts of 
 
 35-58 Potassium 
 
 21 '61 Carbon ) -, 
 
 , [ Cyanogen 
 
 25-54 Nitrogen ) ' 
 
 17-29 Iron. 
 
 It is prepared by submitting either the solution of the yellow prussiate or that salt in 
 powder to the action of chlorine gas until a sample, when heated, yields no precipitate 
 with a solution of a ferric salt. When the dry and pulverised yellow prussiate is 
 acted upon by chlorine gas, the salt is frequently placed in casks, closed so as only to 
 leave a small outlet, while the vessel can be made, by means of machinery, to turn 
 slowly on its axis, so as to bring all the particles of the salt into contact with the 
 chlorine. Sometimes, again, the pulverised yellow prussiate is placed on trays in a 
 chamber, into the top of which chlorine gas is admitted ; when no more chlorine is 
 absorbed the newly formed salt is, if a solution of the yellow prussiate has been 
 operated upon, evaporated to dryness, or in the case where the dry powder of 
 the salt has been taken, the newly formed salt is dissolved in the smallest possible 
 quantity of water, and the solution left to crystallise, the mother liquor containing 
 potassium chloride. This reaction is represented by 
 
 K 4 FeCy 6 + 01 = KOI + K 3 FeCy 6 . 
 Yellow prussiate. Red prussiate. 
 
 The powdered red prussiate is of an orange-yellow colour. According to M. E. 
 Reichardt (1869), bromine may be successfully employed instead of chlorine for the 
 preparation of this salt, which is chiefly used for dyeing woollen fabrics blue, and, with 
 solutions of caustic soda or potassa, for the Mercerising process of cotton. 
 
 Potassium Cyanide, KCy. This salt is obtained in an impure state Liebig's or 
 crude potassium cyanide by the fusion of the yellow potassium prussiate in a porce- 
 lain crucible, continued as long as nitrogen escapes. Iron carbide sinks to the bottom 
 of the crucible, while the crude cyanide is poured off in a state of fusion 
 
 (K 4 FeCy 6 = 4KCy + FeC 2 + 2 N). 
 
 According to Liebig's plan, the potassium cyanide is prepared by fusing i mol. of 
 potassium ferrocyanide with i mol. of potassium carbonate; by this method 
 10 parts of the ferrocyanide yield 8'8 potassium cyanide, mixed with 2' 2 parts 
 potassium cyanate. For all technical and industrial purposes it is far cheaper to use 
 cyan-salt, a mixture of the potassium and sodium cyanides, prepared by fusing 
 together 8 parts of previously dried (anhydrous) potassium ferrocyanide and 2 parts 
 of sodium carbonate. As this mixture fuses readily, the iron carbide easily sepa- 
 rates ; moreover, the salt thus obtained is less liable to decomposition on exposure to 
 air, and its preparation requires less heat. The industrial applications of the crude 
 potassium cyanide, or of the cyan-salt, are the following : In the process of electro- 
 gilding, for the preparation of Grenat soluble, potassium isopurpurate, from picric acid, 
 and in the reduction of metals. It has been mentioned, while treating of the blast- 
 furnace process, that potassium cyanide is formed during the reduction of iron. 
 
 Prussian Blue. This substance, so named when it was accidentally discovered at 
 
478 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 Berlin, in 1710, by Diesbach, is chemically an iron ferrocyanide, more correctly ferrous- 
 ferric cyanide. A distinct variety of this substance is known as Paris blue. Three 
 different kinds of Berlin blue are known, viz., neutral, basic, and a mixture of the two, 
 differing in composition and prepared by different processes. 
 
 (a) Neutral Berlin blue, also known as Paris blue, is obtained by pouring a solution 
 of yellow prussiate into a solution of iron chloride, or into a solution of a peroxide 
 salt of iron ; the result is the formation of a large quantity of a magnificently blue- 
 coloured precipitate, very difficult to wash out, and always retaining a certain quantity 
 of the yellow prussiate, which cannot be removed by washing. 
 
 (6) Basic Berlin blue is obtained by precipitating a solution of yellow prussiate 
 with a solution of a ferrous salt (green copperas), the result being at first the forma- 
 tion of a white precipitate of ferrous cyanide, which, either by exposure to air, or by 
 the action of oxidising substances, becomes blue ; because a portion of the iron is 
 oxidised and another portion takes up the cyanogen thus liberated, converting some of 
 the ferrous cyanide into the corresponding ferric salt, which in its turn combines with 
 the unattacked protocyanide to form Berlin blue, with which, however, some ferric oxide 
 remains mixed. It is stated that basic Berlin blue is distinguished from neutral Berlin 
 blue by being soluble in water ; but this solubility is due to the presence of some of the 
 yellow prussiate, and is not a property inherent in the basic Berlin blue in a pure state. 
 
 (c) As the materials employed on a large scale are neither pure ferrous nor pure 
 ferric salts, but a peroxide containing protosalt of iron, the precipitate obtained 
 consists at first of a mixture of neutral Berlin blue with more or less of the white 
 ferrous cyanide, which afterwards becomes basic Berlin blue ; accordingly the Berlin 
 blue of commerce is a variable mixture of neutral and basic Berlin blues. The iron 
 salt employed is green copperas (ferrous salt), which of course should not contain 
 any appreciable amount of copper, the salts of this metal, as is well-known, yielding 
 with yellow ferrocyanide a chocolate-brown coloured precipitate. 
 
 Old Method of Preparing Prussian Blue. Ferrous sulphate and alum are dis- 
 solved together in boiling rain- or river- water ; the fluid, while yet hot, is decanted 
 from any sediment and forthwith poured into a hot aqueous solution of ferrocyanide, 
 care being taken to stir the mixture, and to add the copperas and alum solution as 
 long as any precipitate is formed. The liquor is run off, and the precipitate washed 
 with fresh water, until all the potassium sulphate is removed ; after which the preci- 
 pitate is drained on filters made of coarse canvas. This having been accomplished, the 
 substance is suspended in water in a boiler, and, while being heated to the boiling- 
 point, nitric acid is added ; after a few minutes' boiling, the contents of the boiler are 
 poured into a large wooden tub or cask, and strong sulphuric acid is added. The 
 solution is now allowed to stand for some time, during which the blue colour fully 
 develops. The Berlin blue is then thoroughly washed with water, drained on coarse 
 canvas filters, next dried, pressed, and cut into cakes ; finally it is dried in rooms heated 
 to 80. As Berlin blue, when once quite dry, is reduced to powder with great diffi- 
 culty, and cannot be brought to the state of fine division as when first precipitated, it 
 is also sent into the market in the state of paste. The alumina derived from the alum 
 is so intimately mixed with the blue that the bulk of the mass is thereby increased 
 without any very perceptible decrease in the intensity of the colour. If the quantity 
 of alumina is very much increased, the colour, of course, becomes much lighter, and 
 this variety of Berlin bluo is then known as mineral blue ; a name also given to a pre- 
 paration of copper obtained either from the native hydrated copper carbonate, or artifi- 
 cially prepared by precipitating copper nitrate or chloride by means of lime and chalk.* 
 
 * The presence of alumina is essentially an adulteration which may be detected by comparison 
 with a genuine sample and observing how much of any inert white powder may be added to the 
 latter to bring it down to the same shade as the former. 
 
SECT. HI.] COMPOUNDS OF IRON. 479 
 
 Recent Methods of Preparing Berlin Blue. Among the improvements made more 
 recently, we may briefly notice the following : i. The mixing of the solutions of 
 copperas and alum with that of yellow prussiate is effected as above described, but great 
 care is taken to prevent any oxidation of the white precipitate, which is converted into 
 an intense blue by being treated with nitro-hydrochloric acid, the chlorine evolved 
 serving as an oxidising agent. The remaining operations, viz., washing, drying, &c., 
 are performed as in the former methods. 2. Ferric chloride solution is employed for 
 the purpose of converting the white precipitate into blue, while the ferrous chloride 
 thus formed serves at a subsequent operation instead of ferrous sulphate. 3. In 
 some cases manganic chloride (Mn,01 6 ), is applied ; likewise a solution of chromic 
 acid, a mixture of potassium dichromate and sulphuric acid ; but it is self-evident that 
 the application of any of these improvements is dependent, as regards success in a 
 commercial point of view, upon local conditions, and upon the possibility of advan- 
 tageously obtaining the various ingredients. 
 
 Turnbull's Blue. By mixing together a solution of red prussiate and of ferrous 
 sulphate in such proportions as to prevent the entire saturation of the former salt, 
 there is obtained a blue-coloured precipitate, known in commerce as Turnbull's blue, 
 consisting of Fe s FejCy l8 , but also containing some chemically combined ferrocyanide. 
 
 Berlin Blue as a Bye-Product of the Manufactures of Coal- Gas and Animal Charcoal. 
 MM. Mallett and Gautier-Bouchard have proved experimentally that Berlin blue mav 
 be obtained as a bye-product of coal-gas manufacture from the ammoniacal liquor, from 
 the spent lime of the purifiers, and from Laming's purifying mixture. The spent 
 lime contains, in addition to the calcium and ammonium cyanides, a good deal of free 
 ammonia, mechanically absorbed in the moist lime. Free ammonia is first removed by 
 forcing steam through the lime, and collecting the ammoniacal gas in dilute sulphuric 
 acid. The lime is next washed with water, and the liquor obtained, containing the 
 cyanogen compounds, is employed for the manufacture of Berlin blue. According to 
 M. KrafFt's experiments, 1000 kilos, of spent gas-lime yield, when treated as described, 
 from 12 to 15 kilos, of Berlin blue, and from 15 to 20 kilos, of ammonium sulphate. 
 Mr. Phipson states that i ton of Newcastle gas-coal yields a quantity of cyanogen 
 which corresponds to from 5 to 8 Ibs. of Berlin blue. The manufacture of animal 
 charcoal also yields, if desired, Berlin blue as a bye-product. 
 
 Soluble Berlin Blue. As ordinary Berlin blue is quite insoluble in water, and the 
 basic variety is only soluble in the presence of potassium ferrocyanide, these pigments are 
 only fit for use as paints, and the discovery of the solubility of pure Berlin blue in oxalic 
 acid is of some importance, for thereby its employment as a water-colour becomes 
 possible. This soluble blue is obtained by digesting the Berlin blue of commerce for one 
 to two days, with either strong hydrochloric acid or with strong sulphuric acid, which 
 latter, after having been mixed with the Berlin blue previously pulverised, is diluted 
 with its own bulk of water. The acid is next decanted from the sediment of blue, and 
 the latter thoroughly washed and dried, and then dissolved in oxalic acid, the best pro- 
 portions being 8 parts of Berlin blue, treated as just mentioned, i part of oxalic acid, 
 and 256 of water. According to other directions, Berlin blue readily soluble in water 
 can be obtained i. By the precipitation of ferrous iodide with yellow potassium 
 prussiate, care being taken to keep the latter in excess. 2. By mixing a solution of 
 ferric chloride in alcoholic ether (tinctura ferrichlorati cetherea, Ph. Huss.) with an 
 aqueous solution of ferrocyanide. 
 
 Pure Berlin blue is of a very deep blue colour, with a cupreous gloss ; it is insoluble 
 in water and alcohol, is decomposed by alkalies, concentrated acids, and by heat. The 
 lighter and more spongy it is, the better is its quality ; it is employed as a pigment and 
 in dyeing and calico-printing, but in case of silks and woollens, pigment-printing 
 excepted, it is obtained on the tissues by a circuitous process. The Berlin blue of 
 
4 8o CHEMICAL TECHNOLOGY. [SECT. ni. 
 
 commerce is frequently adulterated with alumina, pipe-clay, kaolin, magnesia, heavy- 
 spar, and, according to Pohl, even with starch-paste coloured blue by means of tincture 
 cf iodine. 
 
 CONSPECTUS OF INORGANIC PIGMENTS. 
 
 Whites. 
 
 Bismuth white, pearl white, Spanish white (bismuth oxychloride). 
 China clay, kaolin. 
 
 Hamburg white, Dutch white, Venice white, Tyrol white (white lead with heavy- 
 spar). 
 
 Lithophan (BaS0 4 + ZnS). 
 
 Permanent white, new white, mineral white, blanc fixe (BaS0 4 ). 
 Pattinson's white lead (basic lead chloride). 
 Satin white (lime, ZnO and a little indigo). 
 Vienna white, Vienna lime, Bologna- lime (prepared chalk). 
 White lead, Krems white, pearl white, silver white (lead carbonates). 
 White lead substitute : Antimony oxide. 
 Zinc carbonate. 
 
 Zincoh'th, Griffith's snow white (zinc sulphide and barium sulphate). 
 Zinc white, snow white (zinc oxide). 
 
 Beds. 
 
 Antimonial vermilion. 
 Bloodstone (Fe 2 3 ). 
 Chrome red, chrome garnet, chrome vermilion, chrome carmine, chrome orange 
 
 (basic lead chromate). 
 
 Colcothar, Paris red, English red, polishing red, iron minium (Fe 2 3 ). 
 Gold purple, Cassius' purple. 
 
 Mineral lake, pink colour (glass flux coloured with tin chromate). 
 Minium, orange minium, Paris red, gold cinnabar, Saturn cinnabar, mineral 
 
 orange (Pb 3 4 ). 
 
 Ochre, terra di sienna, Naples red, red bole, ruddle (ferruginous clays). 
 Realgar (As 2 S 2 ). 
 Umber (clayey-brown iron ore). 
 Umber, Colognese (lignite). 
 Vermilion, cinnabar, Chinese red (HgS). 
 
 Yellows. 
 
 Cadmium yellow (CdS). Jaune Brillant. 
 Cassel yellow, Turner's yellow (lead oxychloride). 
 Chrome yellow, Paris yellow, Leipsic yellow, Hamburg yellow, crown yellosv (lend 
 
 chromate). 
 Cobalt yellow. 
 Litharge, massicot. 
 Mosaic gold (SnS f ). 
 Naples yellow (lead antimoniate). 
 
 Ochre, gold ochre, Chinese yellow, Lemnian earth (clay containing ferric hydrate). 
 Orpiment (As 2 S 3 ). 
 Siderine yellow (iron phosphate). 
 Ultramarine yellow, barium yellow (BaCr0 4 ). 
 Zinc yellow (zinc chromate). 
 
SECT, in.] THERMO-CHEMISTRY. 481 
 
 Greens. 
 
 Brunswick green, mountain green (chiefly copper carbonate). 
 
 Bremen green (copper hydrate). 
 
 Casali green (chromic oxide). 
 
 Chrome green, emerald green, Guignet's green, Victoria green (chromic oxide). 
 
 Dingler's green (chromium phosphate). 
 
 Gentele's green (copper stannate). 
 
 Green cinnabar, Naples green (chrome yellow and Prussian blue). 
 
 Malachite, copper green, mountain green (copper carbonate). 
 
 Mittler green, emerald green, Pannetier's green, Arnaudon's green, Schnitzer green, 
 
 Matthieu Plessy's green (chiefly chromium hydrate). 
 Rinmann's green, cobalt green, Saxon green, Gellert's green, Scheele's green r 
 
 Swedish green (copper arsenite). 
 Schweinfurt green, Mitis green, Neuwied green, Leipsic green, Vienna green^ 
 
 imperial green, royal green, Bale green, Kirschberg green (copper aceto-arsenite). 
 Ultramarine green. 
 Verdigris (copper acetate). 
 Zinc green (zinc yellow and Prussian blue). 
 
 Blues. 
 
 Azurite, mountain blue, copper lazulite. 
 Bremen blue (copper hydrate). 
 
 Berlin blue, Turnbull's blue, Erlangen blue, Hamburg blue, Milori blue. 
 Cerulean blue (cobaltous-stannic oxide). 
 Chrome chloride (violet). 
 
 Cobalt blue, cobalt ultramarine, Leyden blue (alumina cobaltate). 
 Egyptian blue (copper glass). 
 Mineral blue (Prussian blue mixed with clay). 
 Oil blue, copper indigo (copper sulphide). 
 Smalts, kind's blue (cobalt-glass). 
 Ultramarine. 
 
 THERMO-OHEMISTRY. 
 
 Thermo- chemistry, the doctrine of the heat-processes in chemical combinations and 
 decompositions, does not yet by any means sufiice to explain all the various transforma- 
 tions and reactions in chemical manufactures. It yields, however, already a basis for 
 the greater or less probability of the practicability of certain chemical reactions, as in 
 general those compounds are most easily produced which originate with the liberation 
 of heat, whilst those which involve the absorption of heat are generally much more 
 difficult to effect. There are, indeed, many exceptions. Thus, in the formation of 
 ammonia in an aqueous solution from 14 kilos. N, 3 kilos. H, and much water : 
 
 N + H s + aq = NH 3 .aq 
 
 20,400 calories (heat-units) are set free, and yet the reaction is so far practically 
 impossible. 
 
 Thermo-chemistry is very important for determining the consumption of heat in 
 the chemical arts, as we can can only decide whether it is possible to economise fuel by 
 improvements in a smelting-furnace, a decomposition-pan, or a distilling apparatus, 
 if we first know the actual minimum heat needed in the process in question. If 
 further experience enables us to estimate the size of cooling-surfaces, the quantity of 
 coob'ng-water, or of ice in obtaining hydrochloric or nitric acid, for regulating certain 
 processes in colour-works, in the fermentation trades, &c., errors are often committed 
 
 2 H 
 
482 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 in this respect, as the plant is often erected too large and consequently too costly 
 or, what is generally still worse, much too small. The right proportions of size can only 
 be determined in advance if we know the quantity of heat which must be produced or 
 removed. Many a plant must be altered at a great expense, or even done away with, 
 because it has been carried out on a basis of assumption, not of calculation. Such 
 calculations unfortunately can only be effected in part, as many of the necessary data 
 are still wanting. 
 
 As a unit we generally take the quantity of heat needed to raise the unit weight 
 of water from p to i. In chemistry there is generally employed as a unit of weight 
 i gramme, and the unit of heat is known as a calorie. Berthelot proposes a unit 
 1000 times greater. Ostwald, in accordance with the proposal of Schuller and 
 "Wartha, takes as the unit K, i.e., that quantity of heat which i gramme water loses 
 between the boiling-point and the freezing-point. It is 100 tunes as great as the 
 specific heat of water between 15 and 18. With regard to the variable specific heat 
 of water, K is ioo'6 cal. We may generally put i cal. (Berthelot's) = 10 K = 1000 col. 
 For technical uses it is preferable to use the kilo, as the unit of weight ; whether we 
 in addition take the specific heat of water at o or at 18 is seldom of moment in the 
 calculations which here come into question, though the latter value is preferable since the 
 determinations are generally effected at 15 to 18. As, in using the cal., decimal places 
 are almost always reached, and with K very frequently, the different units are best 
 given up, calculating, in round numbers, by the heat-unit as that quantity of heat 
 which raises i kilo, of water from o to i (or from 17 to 18). As then all the 
 calculations are carried out with kilo.-molecular weights, but with cal. for gramme- 
 molecular weights, the numbers in both cases are equal. 
 
 According to the general equation of the mechanical theory of heat, dQ = dTJ + dW, 
 in which dQ, is the heat which enters or passes out, dU signifying the change in the 
 internal energy, and dW the external work ; in considerable changes of space the 
 mechanical work is to be considered. When gas is evolved the pressure of the air i 
 to be overcome. At 760 mm. of the barometer the pressure of the atmosphere upon 
 each square centimetre of surface 76 x 13-6 = 1033*6 grammes, that is, 10,336 kilos, on 
 i square metre. As 425 kilogrammetres are the mechanical heat equivalent to the expan- 
 sion of i cubic metre, 10,336 : 425 = 24*3 heat-units. As the kilo.-molecular weight of 
 all gases = 22*3 cubic metres, in the development of i kilo.-molecular of a gas at o, 
 22-3 x 24-3 = 542 units of heat are consumed, but at t 542 (i + 0*00367 t) heat-units. 
 In the development of oxygen, 2KC10 2 = 2KC1 + 20 2 , there are required (if the oxygen 
 in the apparatus is cooled down to o) to overcome the pressure of the atmosphere for 
 the 3 x 32 = 96 kilos., or 3 x 22*3 = 66*9 cubic metres oxygen, 3 x 542 = 1626 heat-units ; 
 if the gas escapes at 20, 1745 heat -units are required. 
 
 This heat is of course liberated again if the gases are absorbed, as in the oxidation 
 of Weldon mud, the production of chloride of lime, &c. 
 
 In degasifying coals in the generator, there are required to overcome the pressure 
 for each kilo, of coal corresponding to 0*3 cubic metre of gas, if it leaves the generator 
 at 600, o'3 x 24-3 x (i + 0-00367) = 24 heat-units. 
 
 In converting coke into carbon monoxide there is also an increase of volume as 
 C, + 0, = 200, and C + H,O = CO + H s . 
 
 Let us take as an instance the compounds of chlorine. In the combination of 
 i kilo. Hwith 35-5 kilos. 01, to form 36*5 kilos. HCl r there are liberated, according to 
 Thomsen, 22,000 heat-units ; in the formation of solid sodium chloride from 23 kilos, 
 sodium and 35*5 kilos, chlorine gas, 97,700 heat-units ; in the formation of sodium 
 hydroxide from 23 kilos, sodium, i kilo, hydrogen, and 16 kilos, oxygen, 101,900 heat- 
 units, whilst the reaction Na 2 + = Na 2 furnishes 80,400 heat-units. 
 
SECT, in.] THERMO-CHEMISTRY, 483 
 
 The attempt to decompose sodium chloride by oxygen 
 
 2 NaCl + O = Na 2 + 01, 
 
 195,400 + 80,400 = - 1 15, ooo heat-units, 
 
 appears futile from the enormous requirement of heat-units. The decomposition 
 of sodium chloride by watery vapour 
 
 NaCi + H 2 = NaOH + HC1 
 
 97,700 57,000 + 101,900 + 22,000 = 30,800 heat-units, 
 would require only 30,800 heat-units, but so far it is impracticable. 
 
 General attention is now turned to the production of chlorine from magnesium 
 chloride by ignition in a current of air 
 
 MgCl 2 + = MgO + 01 
 
 -151,000 + 144,000 = - 7000 heat- units. 
 
 But if we assume that there is first formed from the moist magnesium chloride, 
 magnesium hydrate, the formation heat of which = 149,000 heat-units, only 2000 
 heat-units are required. Pechiney uses oxychloride. As according to Andre a fused 
 mixture of MgO + Mg01 2 gives 15,400 heat-units, but MgCl 2 .6H 2 O + MgO - 600 heat- 
 units, it may be in part understood why Pechiney's mixture in its production must not 
 be heated above 300. 
 
 If hydrochloric acid is to be obtained from magnesium chloride 
 
 Mg01 2 + H 2 O = MgO + 2 HC1 
 
 151,000 57,000 -*- 144,000 + 44,000 = 20,000 heat-units, 
 there are required 20,000 heat-units. Hence this process as regards its demand for 
 heat is less favourable than the production of chlorine, because the formation-heat of 
 watery vapour is greater than that of hydrochloric acid. The case is still more 
 unfavourable if we set out from crystalline magnesium chloride, since in the formation 
 of MgCl 2 .6H 2 O from Mg01 2 , 33,000 heat-units are liberated, and must be again supplied 
 during the decomposition. The evolution of hydrochloric acid on heating hydrated 
 magnesium chloride has not hitherto been explained solely on thermo-chemical 
 procedures. 
 
 The oxidation of hydrochloric acid by atmospheric oxygen according to Deacon's 
 .process seems simple 
 
 2 HC1 + O = H 2 O + C1 2 
 44,000 + 57,000 13,000 heat-units. 
 
 If the sides are properly isolated this temperature suffices to keep the clay at the 
 "temperature required without any especial heating of the mixture of hydrochloric 
 acid and air. The size of the subsequent cooling-apparatus depends on the composition 
 and the temperature of the gaseous mixture. 
 
 That chlorine water readily passes into hydrochloric acid may be understood from 
 its great solution heat in presence of much water 
 
 H 2 O + C1 2 = 2H01.aq + O 
 68,400 + 78,600 = 10,200 heat-units. 
 
 In order to render the demand for heat in the Pechiney decomposition furnace more 
 intelligible, let it be supposed that the composition of the mixture decomposed at 1000 is: 
 
 MgCl 2 47-5 per cent. 
 
 Mg ...... 30-0 
 
 H 2 ..... 22-5 
 
 Let half the chlorine escape as HC1 ; 200 kilos, of the mass would then yield 
 
 Cl 35-5 kilos. 
 
 HC1 ..... ., 36-5 ,, 
 
 H.,O (vapour) . . . . 36*0 
 
 MgO loo-o 
 
 208 'o 
 
484 CHEMICAL TECHNOLOGY. [SECT. in. 
 
 In addition, 8 kilos, of oxygen have been consumed from 200 cubic metres of 
 atmospheric air introduced. To heat them to 1000 there will be required : 
 200 x 0*31 x 1000 = 62000 heat-units. 
 
 The 100 kilos, magnesia : too x 0*244 x 1000 = 24400 heat-units. 
 
 The chlorine 35*5 x 0-12 x 1000 = 4260 heat-units. 
 
 The HC1 : 36-5 x 0-19 x 1000 = 6935 heat-units. 
 
 The water : 36 [620 + (900-0-48)] = 37*872 heat-units. 
 
 For the evolution of 35-5 kilos, chlorine from magnesium chloride, there are re- 
 quired 3500, and for hydrochloric acid 10,000 heat-units. Hence results the following 
 distribution of heat for each 35-5 kilos, of chlorine : 
 
 Chemical work . . . . . . . 13-500 heat-units. 
 
 Heating air . . . . . 62*000 
 
 Magnesia 24*400 
 
 Watery vapour 37 '900 
 
 Chlorine and hydrochloric acid . .11 '200 
 
 149-000 
 
 In addition come the losses of conduction and radiation from the masonry. As nearly 
 half the consumption of heat goes to heating the air, the regulation of the access of air 
 is very important. It may be recommended to warm the air before its admission by 
 means of the gases escaping, on the same principle as in the hot blast in iron-smelting. 
 At the same time, the refrigerating apparatus would be relieved which has now to over- 
 come 62,000 + 37,900 + 1 1,200 =11 1,100 heat-units. 
 In working up calcium chloride, there result 
 
 CaCl z + O = CaO + 01, 
 
 170,230 + 131,360 = 38,870 heat-units, and 
 CaCl 2 + H 2 O = CaO + 2 HC1 
 
 170,230 57,000 + 131,360 -r 44,000 = 51,870 heat-units. 
 Hence, as regards the heat needed for its decomposition, calcium chloride is less 
 advantageous than magnesium chloride. 
 
 In obtaining hydrochloric acid from sodium chloride and sulphuric acid, there is first 
 formed bisulphate : 
 
 NaCl + H 2 S0 4 = NaHSO 4 + HOI 
 
 97,700 - 192,900 + 267,800 + 22,000 = - 800 heat-units. 
 
 The demand for heat is therefore almost nil. In the formation of monosulphate : 
 2 NaCl + H 2 S0 4 = Na 2 S0 4 + 2 HC1 
 
 195,400 - 192,900 + 328,500 + 44,000 = - 15,800 heat-units. 
 Hence the mixture must be heated to complete the reaction, as experience shows. 
 To calculate the heat required by a salt-cake furnace, let us suppose that the 98- 
 
 kilos. sulphuric acid required to decompose 117 kilos, sodium chloride contain 30 kilos, 
 of water, and that the hydrochloric acid escapes as a mean at 400, the watery vapour 
 at 500, whilst the sulphate is heated to 600. 
 
 If the specific heat of the salt-cake is assumed at 0*232, there are required to heat 
 the 142 kilos, of salt-cake 142 x 0-232 x 600= 19,766 heat-units. The specific heat of 
 hydrochloric acid is, on the average, 0-19, therefore 73 x 0-19 x 400 = 5,548 heat-units. 
 To convert water of 17 into steam at 500 there are required 812 heat-units i.e., for 
 30 kilos. 24,360 heat-units. 
 
 If we consider the draught of the chimney, &c., there may be reckoned in round 
 numbers 500 heat-units for the work performed by the hydrochloric acid generated. 
 
SECT, m.] THERMOCHEMISTRY. 485 
 
 Hence 
 
 Heating sulphate 19,766 heat-units. 
 
 hydrochloric acid 5,54$ ,, 
 
 watery vapour 24,360 
 
 Chemical work 15,800 
 
 Mechanical work 500 
 
 Together about 66,000 
 
 In the condensation of the hydrochloric acid, there have to be removed by refri- 
 geration : 
 
 Watery vapour 24,360 heat- units. 
 
 HC1 specific heat 5,548 ,, 
 
 HC1 solution heat 15,000 ,, 
 
 45,000 
 
 It is here supposed that the watery vapour is condensed, but not the fire-gases. 
 
 These figures merely show in what manner such calculations may be conducted on 
 analytical data. 
 
 In accordance with the easy execution of the oxidation of Weldon mud, it is con- 
 ducted with a development of heat, as the formation of the manganous hydrate yields 
 94,770, and that of the hydrated peroxide 116,2 80 heat-units. 
 
 The decomposition of the latter with strong hydrochloric acid gives 
 Mn0 3 H 2 + 4 H01.aq. = MnCl 2 .aq. + 01, + 3H 3 O 
 
 116,300 148,000 + 128,000 + 205,200 = 68,900 heat-units. 
 
 As soon as the mixture is raised to the temperature of the reaction the liberation of 
 Cl goes on readily. 
 
 The thermic relations of the manufacture of chloride of lime have not been deter- 
 mined, though it is known that in the formation of potassium hypochlorite in an 
 aqueous solution 24,600 heat- units are liberated according to the reaction 
 2KOH.aq. + 01, = KCl.aq. + KOCLaq. 
 
 In the formation of potassium chlorate in an aqueous solution there are liberated : 
 
 6KOH.aq. + 3Cl 2 .aq. = sKCl.aq. + KC10 3 .aq. 
 
 that is, 97,900 heat-units, a renewed proof that the reactions which give most heat are 
 not always most easy to conduct. 
 
 The following works may be consulted : J. Thomsen, Thermochem. Untersvxhungen 
 {Leipzig, 1882 to 1888). Berthelot, Essai de mecanique chimique (Paris, Dunod, 1879). 
 Al. Naumann, Handbuch der Thermochemie (Brunswick, 1882). Horstmann, Theoretische 
 Chemie. W. Ostwald, Verwatidtschafts Lehre (Leipzig, 1887). 
 
SECTION IV. 
 THE ORGANIC CHEMICAL MANUFACTURES. 
 
 ALCOHOLS AND ETHERS. 
 
 Methylic AlcoJwL CH 3 .OH, a liquid boiling at 65-5 to 66, is formed on the dry 
 
 distillation of wood. Leaf-bearing trees yield it in larger proportion than the conifers. 
 
 For the distillation there are commonly used horizontal iron retorts, heated in the 
 
 same manner as gas retorts, though in general not above 500. Occasionally, large 
 
 upright retorts are 
 
 Fig. 377. used, or, in France, 
 
 cylinders of sheet-iron 
 ( Fi g- 377)- Such a 
 cylinder, A, has in its 
 upper half an opening 
 o, to which a connect- 
 ing-piece is screwed 
 on. Upon the cylin- 
 der is laid the cover, 
 which is screwed fast 
 as soon as the cylinder 
 has been filled with 
 wood. The cylinder 
 itself is lowered by 
 means of the crane, 
 D, into a cylindrical 
 furnace, , closed 
 above with the stone 
 cover, E. The pro- 
 ducts given off on the application of heat pass through the pipe, b (Fig. 378),which is con- 
 nected with the cylinder and bent in a zigzag manner, through the refrigerating appa- 
 ratus c, set in the support d, to which cold water is conveyed through /, whilst the 
 heated water escapes at k. Acetic acid, tar, and wood-spirit are liquified, and flow 
 into the vat #, in which the tar is chiefly deposited. The lighter liquids run through 
 m to the second vat, h. The combustible gases escape through the pipe i, into the 
 open air, or into the furnace, though their value as fuel is but small. In large works 
 there are used, instead of the wooden vats, cisterns of cement or masonry sunk into the 
 ground, each being connected with the next following by a pipe at its upper end. The 
 bulk of the tar collects in the first cistern, whilst the wood-vinegar, freed from the tar, 
 which is merely mechanically suspended, flows into the last cistern. Wood-gas works, 
 of course, produce wood-vinegar as a bye-product. 
 
 The watery liquid separated from the tar contains methylic alcohol, acetone, acetic 
 acid, &c., and is distilled. Crude wood-spirit first passes over and then acetic acid, which 
 
SECT. IV.] 
 
 ALCOHOLS AND ETHERS. 
 
 487 
 
 The wood-spirit is purified by rectification in the column 
 
 is neutralised with lime, 
 apparatus. 
 
 In order to remove the last portion of acetone, the purified wood-spirit is treated 
 with chlorine and rectified again. Oak- 
 wood yields on distillation i per cent, of 
 wood-spirit. 
 
 The proportion of methyl alcohol in 
 commercial wood-spirit is ascertained by 
 converting it into methyl iodide by phos- 
 phorus di-iodide (PI 2 ) ; 5 c.c. of absolute 
 methyl alcohol yield 7*19 c.c. methyl iodide. 
 
 Uses. Crude wood-spirit is used for 
 denaturising spirits ; pure methyl alcohol 
 is used in the manufacture of coal-tar 
 colours and in ice-machines, after con- 
 version into ether. 
 
 Ethyl Alcohol (ordinary alcohol), 
 C 2 H 5 .OH. The production of alcohol by 
 fermentation will be described below. It 
 is obtained in the anhydrous state by 
 distillation over quicklime. Pure alcohol 
 boils at 78. 
 
 The determination of the percentage composition of samples of alcohol is effected 
 by means of the sp. gr. For technical purposes hydrometers are used. Hitherto the 
 hydrometers or areometers of Tralles and Richter have been most in use. That of 
 Stoppani agrees with the latter. Both are percentage hydrometers i.e., they show 
 by the number down to which they sink how much pure alcohol is contained in the 
 liquid in question. The difference between the two instruments is that the hydro- 
 meter of Tralles indicates percentages by volume, and that of Richter percentages by 
 weight. As the graduation of the Richter hydrometer proceeds from inaccurate 
 assumptions that of Tralles is to be preferred.* The hydrometer of Tralles has been 
 until quite lately the legally recognised instrument in Germany for determining per- 
 centages of alcohol, though one which gives percentages by weight has now been intro- 
 duced in its place. 
 
 Spirits intended for technical purposes are exempted from duty if they are dena- 
 turised by any one of a variety of methods which the manufacturer may select. The 
 most suitable of all these agents is " Dippel's animal oil." The alcohol tables of 
 O. Hehner, which give the proportion of alcohol for different sp. gr. at 15 '5, are here 
 given as far as they are important in analysis and the arts. 
 
 In England the hydrometer of Sykes is in official use. 
 
488 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. rv. 
 
 Specific Gravity 
 = 15-5 
 
 Absolute Alcohol. 
 
 Specific Gravity 
 = i5*5- 
 
 Absolute Alcohol. 
 
 Specific Gravity 
 = 15-5- 
 
 Absolute AlcohoL 
 
 Weight. 
 
 Volume. 
 
 Weight. 
 
 Volume. 
 
 Weight. 
 
 Volume. 
 
 Per Cent 
 
 Per Cent. 
 
 Per Cent. 
 
 Per Cent. 
 
 Per Cent. 
 
 Per Cent 
 
 I-OOOO 
 
 O'OO 
 
 O'OO 
 
 0-9878 
 
 7-40 
 
 9'2I 
 
 0-9758 
 
 I6-62 
 
 20-43 
 
 0-9998 
 
 o-n 
 
 0-13 
 
 6 
 
 7'53 
 
 9-37 
 
 6 
 
 1677 
 
 20 '6 1 
 
 6 
 
 O'2I 
 
 0.26 
 
 4 
 
 7-67 
 
 9'54 
 
 4 
 
 16-92 
 
 20 '80 
 
 4 
 
 0-32 
 
 0-40 
 
 2 
 
 7'8o 
 
 9-70 
 
 2 
 
 17-08 
 
 20-99 
 
 2 
 
 O'42 
 
 0'S3 
 
 
 
 7'93 
 
 9-86 
 
 O 
 
 17-25 
 
 21-19 
 
 
 
 o-53 
 
 0-66 
 
 
 
 
 
 
 
 0-9988 
 
 0-63 
 
 079 
 
 0-9868 
 
 6 
 
 8-07 
 8-21 
 
 10-03 
 10-21 
 
 0-97 4 8 
 
 6 
 
 17-42 
 17-58 
 
 21-39 
 21-59 
 
 6 
 4 
 
 074 
 0-84 
 
 0-93 
 I -06 
 
 4 
 
 2 
 
 8-36 
 8-50 
 
 IO-38 
 10-56 
 
 4 - 
 
 2 
 
 1775 
 17-92 
 
 21-79 
 21-99 
 
 2 
 
 
 '95 
 i -06 
 
 1-19 
 
 i'34 
 
 O 
 
 8-64 
 
 1073 
 
 O 
 
 18-08 i 
 
 22-18 
 
 0-9978 
 
 rig 
 
 1-49 
 
 0-9858 
 
 879 
 
 IO-9I 
 
 0-9738 
 
 18-23 
 
 22-36 
 
 6 
 
 1-31 
 
 l-6 5 
 
 6 
 
 8-93 
 
 II -08 
 
 6 
 
 18-38 
 
 22-55 
 
 4 
 
 1-44 
 
 1-81 
 
 4 
 
 9-07 
 
 11-26 
 
 4 
 
 18-54 
 
 2273 
 
 2 
 
 1-56 
 
 1-96 
 
 2 
 
 9-21 
 
 11-44 
 
 2 
 
 18-69 
 
 22-92 
 
 
 
 1-69 
 
 2-12 
 
 
 
 9-36 
 
 11-61 
 
 O 
 
 18-85 
 
 23-10 
 
 O.9968 
 
 1-81 
 
 2'27 
 
 0-9848 
 
 9*50 
 
 1179 
 
 0-9728 
 
 19-00 
 
 23-28 
 
 6 
 
 1-94 
 
 2'43 
 
 6 
 
 9-64 
 
 11*96 
 
 6 
 
 19-17 
 
 23-48 
 
 4 
 
 2-06 
 
 2-58 
 
 4 
 
 979 
 
 12-13 
 
 4 
 
 I9-33 
 
 23-68 
 
 2 
 
 2-17 
 
 272 
 
 2 
 
 9-93 
 
 12-31 
 
 2 
 
 19-50 
 
 23-88 
 
 O 
 
 2-28 
 
 2-86 
 
 
 
 10-08 
 
 12-49 
 
 O 
 
 19-67 
 
 24-08 
 
 0-9958 
 
 2-39 
 
 3-00 
 
 0-9838 
 
 10-23 
 
 12-68 
 
 0-9718 
 
 19-83 
 
 24-28 
 
 6 
 
 2-50 
 
 3-I4 
 
 6 
 
 10-38 
 
 12-87 
 
 6 
 
 20 -oo 
 
 24-48 
 
 4 
 
 2'6l 
 
 3-28 
 
 4 
 
 10-54 
 
 13-05 
 
 4 
 
 20-17 
 
 24-68 
 
 2 
 
 272 
 
 3 '42 
 
 2 
 
 10.69 
 
 13-24 
 
 2 
 
 20-33 
 
 24-88 
 
 O 
 
 2-83 
 
 3'5S 
 
 O 
 
 10-85 
 
 3'43 
 
 O 
 
 20-50 
 
 25-07 
 
 0-9948 
 
 2-94 
 
 3-69 
 
 0-9828 
 
 II'OO 
 
 13-62 
 
 0-9708 
 
 20-67 
 
 25-27 
 
 6 
 
 3-06 
 
 3-83 
 
 6 
 
 11-15 
 
 13-81 
 
 6 
 
 20-83 
 
 25-47 
 
 4 
 
 3-i8 
 
 3-98 
 
 4 
 
 11-31 
 
 I3-99 
 
 4 
 
 21*00 
 
 25-67 
 
 2 
 
 3-29 
 
 4-12 
 
 2 
 
 11-46 
 
 14-18 
 
 2 
 
 21*15 
 
 25-86 
 
 O 
 
 3 '4i 
 
 4-27 
 
 O 
 
 11-62 
 
 1437 
 
 O 
 
 21-31 
 
 26-04 
 
 0-9938 
 
 3'53 
 
 4-42 
 
 0-9818 
 
 1177 
 
 14-56 
 
 0-9698 
 
 21-46 
 
 26-22 
 
 6 
 
 3-65 
 
 4'56 
 
 6 
 
 11-92 
 
 I4-74 
 
 6 
 
 21-62 
 
 26-40 
 
 4 
 
 376 
 
 47i 
 
 4 
 
 12-08 
 
 I4-93 
 
 4 
 
 2177 
 
 26-58 
 
 2 
 
 3'88 
 
 4-85 
 
 2 
 
 12-23 
 
 15-12 
 
 2 
 
 21-92 
 
 26-77 
 
 
 
 4'OO 
 
 S'oo 
 
 O 
 
 12-38 
 
 15-30 
 
 O 
 
 22-08 
 
 26-95 
 
 O-9928 
 
 4-12 
 
 5-i6 
 
 0-9808 
 
 12-54 
 
 15-49 
 
 0-9688 
 
 22-23 
 
 27-I3 
 
 6 
 
 4-25 
 
 5-32 
 
 6 
 
 12-69 
 
 15-68 
 
 6 
 
 22-38 
 
 27-31 
 
 4 
 
 4'37 
 
 5 '47 
 
 4 
 
 12-85 
 
 15-86 
 
 4 
 
 22-54 
 
 27-49 
 
 2 
 
 4-50 
 
 5-63 
 
 2 
 
 13-00 
 
 16-05 
 
 2 
 
 22-69 
 
 27-68 
 
 O 
 
 4-62 
 
 578 
 
 O 
 
 I3'i5 
 
 16-24 
 
 O 
 
 22-85 
 
 27-86 
 
 0-9918 
 
 475 
 
 5 "94 
 
 0-9798 
 
 13-31 
 
 I6'43 
 
 0-9678 
 
 23-00 
 
 28-04 
 
 6 
 
 4-87 
 
 6-10 
 
 6 
 
 13-46 
 
 16-61 
 
 6 
 
 23-15 
 
 28-22 
 
 4 
 
 5-00 
 
 6-24 
 
 4 
 
 13-62 
 
 16-80 
 
 4 
 
 23-31 
 
 28-41 
 
 2 
 
 5'i2 
 
 6-40 
 
 2 
 
 1377 
 
 16-98 
 
 2 
 
 23-46 
 
 28-59 
 
 O 
 
 5-2S 
 
 6'5S 
 
 O 
 
 13-92 
 
 17-17 
 
 O 
 
 23-62 
 
 2877 
 
 0-9908 
 
 5'37 
 
 6-71 
 
 0.9788 
 
 14-09 
 
 1737 
 
 0-9668 
 
 2377 
 
 28*95 
 
 6 
 
 5-|o 
 
 6-86 
 
 6 
 
 14-27 
 
 I7-59 
 
 6 
 
 23*92 
 
 29*13 
 
 4 
 
 5-62 
 
 7-01 
 
 4 
 
 HHS 
 
 17-81 
 
 4 
 
 24-08 
 
 29*31 
 
 2 
 
 575 
 
 7-17 
 
 2 
 
 14-64 
 
 18-03 
 
 2 
 
 24-23 
 
 29-49 
 
 
 
 5-87 
 
 7'32 
 
 O 
 
 14-82 
 
 18-25 
 
 O 
 
 24-38 
 
 29-67 
 
 0-9898 
 
 6-00 
 
 7-48 
 
 0-9778 
 
 15-00 
 
 18-48 
 
 0-84I8 
 
 82-62 
 
 87-61 
 
 6 
 
 6-14 
 
 7-66 
 
 6 
 
 I5-I7 
 
 18-68 
 
 6 
 
 82-69 
 
 87-67 
 
 4 
 
 6-28 
 
 7-83 
 
 4 
 
 I5-33 
 
 18-88 
 
 4 
 
 82-77 
 
 8773 
 
 2 
 
 6'43 
 
 8-01 
 
 2 
 
 I5-50 
 
 19-08 
 
 2 
 
 82-85 
 
 8779 
 
 O 
 
 6-57 
 
 8-18 
 
 O 
 
 15-67 
 
 19-28 
 
 O 
 
 82-92 
 
 87-85 
 
 0-9888 
 
 671 
 
 8-36 
 
 0-9768 
 
 15-83 
 
 19-49 
 
 0-8408 
 
 83-00 
 
 87-91 
 
 6 
 
 6-86 
 
 8'54 
 
 6 
 
 16-00 
 
 19-68 
 
 6 
 
 83-08 
 
 87-97 
 
 4 
 
 7-00 
 
 872 
 
 4 
 
 16-15 
 
 19-87 
 
 4 
 
 83-15 
 
 88-03 
 
 2 
 
 7-13 
 
 8-88 
 
 2 
 
 16-31 
 
 20 -06 
 
 2 
 
 83-23 
 
 88-09 
 
 O 
 
 7-27 
 
 9-04 
 
 O 
 
 16 46 
 
 2O-24 
 
 
 
 83-31 
 
 88-16 
 
SECT. IV.] 
 
 ALCOHOL. 
 
 489 
 
 Specific Gravity 
 = 15-5. 
 
 Absolute Alcohol. 
 
 pecific Gravity 
 = 15-5. 
 
 Absolute Alcohol. 
 
 pecific Gravity 
 = iS'S . 
 
 Absolute Alcohol. 
 
 Weight. \ 
 
 Volume. 
 
 Weight. 
 
 Volume. 
 
 Weight. 
 
 Volume. 
 
 Per Cent. 1 
 
 Per Cent. 
 
 Per Cent. 
 
 Per Cent. 
 
 Per Cent. 
 
 Per Cent. 
 
 0-8398 
 
 83-38 
 
 88-22 
 
 0-8278 
 
 88-04 
 
 91-81 
 
 0-8158 
 
 92-52 
 
 95-08 
 
 6 
 
 83-46 
 
 88-28 
 
 6 
 
 88-12 
 
 91-87 
 
 6 
 
 92-59 
 
 95-13 
 
 4 
 
 83-54 
 
 88-34 
 
 4 
 
 88-20 
 
 9I-93 
 
 4 
 
 92-67 
 
 95-I9 
 
 2 
 
 83-62 
 
 88-40 
 
 2 
 
 88-28 
 
 91-99 
 
 2 
 
 92-74 
 
 95-24 
 
 O 
 
 83-69 
 
 88-46 
 
 
 
 88-36 
 
 92-05 
 
 
 
 92-81 
 
 95-29 
 
 0-8388 
 
 8377 
 
 88-52 
 
 0-8268 
 
 88-44 
 
 92-12 
 
 0-8148 
 
 92-89 
 
 9",35 
 
 6 
 
 83-85 
 
 88-58 
 
 6 
 
 88-52 
 
 02-lS 
 
 6 
 
 92-96 
 
 9 "40 
 
 4 
 
 83-92 
 
 88-64 
 
 4 
 
 88-60 
 
 92-24 
 
 4 
 
 93 -4 
 
 95-45 
 
 2 
 
 84-00 
 
 88-70 
 
 2 
 
 88-68 
 
 92-30 
 
 2 
 
 93-11 
 
 95'SO 
 
 
 
 84-08 
 
 8876 
 
 
 
 88-76 
 
 92-36 
 
 O 
 
 93-18 
 
 95-55 
 
 0-8378 
 
 84-16 
 
 88-83 
 
 0-8258 
 
 88-84 
 
 92-42 
 
 0-8138 
 
 93-26 
 
 95-61 
 
 6 
 
 84-24 
 
 88-89 
 
 6 
 
 88-92 
 
 92-48 
 
 6 
 
 93-33 
 
 95'66 
 
 4 
 
 84-32 
 
 88-95 
 
 4 
 
 89-00 
 
 92-54 
 
 4 
 
 93HI 
 
 9571 
 
 2 
 
 84-40 
 
 89-01 
 
 2 
 
 89-08 
 
 92-60 
 
 2 
 
 93H8 
 
 95-76 
 
 O 
 
 84-48 
 
 89-08 
 
 O 
 
 89-16 
 
 92-66 
 
 O 
 
 93-55 
 
 95-82 
 
 0-8368 
 
 84-56 
 
 89-14 
 
 0-8248 
 
 89-23 
 
 9271 
 
 0-8I28 
 
 93-63 
 
 95-87 
 
 6 
 
 84-64 
 
 89-20 
 
 6 
 
 89-31 
 
 9277 
 
 6 
 
 9370 
 
 95'92 
 
 4 
 
 84-72 
 
 89-27 
 
 4 
 
 89-38 
 
 92-83 
 
 4 
 
 93-78 
 
 95^7 
 
 2 
 
 84^80 
 
 89-33 
 
 2 
 
 89-46 
 
 92-89 
 
 2 
 
 93-85 
 
 96-03 
 
 
 
 84-88 
 
 89-39 
 
 
 
 89-54 
 
 92-94 
 
 O 
 
 93-92 
 
 96-08 
 
 0-8358 
 
 84-96 
 
 89-46 
 
 0-8238 
 
 89-62 
 
 93-00 
 
 0-8118 
 
 94-00 
 
 96-13 
 
 6 
 
 85-04 
 
 89-52 
 
 6 
 
 89-69 
 
 93-06 
 
 6 
 
 94-07 
 
 96-18 
 
 4 
 
 85-12 
 
 89-58 
 
 4 
 
 8977 
 
 93-11 
 
 4 
 
 94-14 
 
 96-22 
 
 2 
 
 85-I9 
 
 89-64 
 
 2 
 
 89-85 
 
 93-I7 
 
 2 
 
 94-21 
 
 96-27 
 
 
 
 85-27 
 
 8970 
 
 O 
 
 89-92 
 
 93-23 
 
 O 
 
 94-28 
 
 96-32 
 
 0-8348 
 
 85-35 
 
 89-75 
 
 0-8228 
 
 90-00 
 
 93-29 
 
 0-8108 
 
 94'34 
 
 96-36 
 
 6 
 
 85-42 
 
 89-81 
 
 6 
 
 90-07 
 
 93-34 
 
 6 
 
 94-4I 
 
 96-41 
 
 4 
 
 85-50 
 
 89-87 
 
 4 
 
 90-14 
 
 9339 
 
 4 
 
 94-48 
 
 96-46 
 
 2 
 
 85-58 
 
 89-93 
 
 2 
 
 90-21 
 
 93-44 
 
 2 
 
 94-55 
 
 96-50 
 
 O 
 
 85-65 
 
 86-99 
 
 O 
 
 90-29 
 
 93*49 
 
 O 
 
 94-62 
 
 96-55 
 
 0-8338 
 
 85-73 
 
 90-05 
 
 0-82I8 
 
 90-36 
 
 93-54 
 
 0-8098 
 
 94-69 
 
 96-60 
 
 6 
 
 85-81 
 
 90-11 
 
 6 
 
 90-43 
 
 93^9 
 
 6 
 
 94-76 
 
 96-64 
 
 4 
 
 85-88 
 
 90-17 
 
 4 
 
 90-50 
 
 93^4 
 
 4 
 
 94-83 
 
 96-69 
 
 2 
 
 85-96 
 
 90-23 
 
 2 
 
 90-57 
 
 9370 
 
 2 
 
 9490 
 
 96-74 
 
 O 
 
 86-04 
 
 90-29 
 
 O 
 
 90-64 
 
 9375 
 
 O 
 
 94-97 
 
 96-78 
 
 0-8328 
 
 86-12 
 
 SO'35 
 
 0-8208 
 
 9071 
 
 93-80 
 
 0-8088 
 
 95-04 
 
 96-83 
 
 6 
 
 86-19 
 
 90-40 
 
 6 
 
 90-79 
 
 93-85 
 
 6 
 
 95.11 
 
 96-88 
 
 4 
 
 86-27 
 
 90-46 
 
 4 
 
 90-86 
 
 93-90 
 
 4 
 
 95-18 
 
 96-93 
 
 2 
 
 86-35 
 
 90-52 
 
 2 
 
 90-93 
 
 93-95 
 
 2 
 
 95-25 
 
 96-98 
 
 O 
 
 86-42 
 
 90-58 
 
 O 
 
 91-00 
 
 94-00 
 
 O 
 
 95-32 
 
 97-02 
 
 0-83I8 
 
 86-50 
 
 90-64 
 
 0-8I98 
 
 91-07 
 
 94-05 
 
 0-8078 
 
 95'39 
 
 97-07 
 
 6 
 
 86-58 
 
 90-70 
 
 6 
 
 91-14 
 
 94-10 
 
 6 
 
 95'46 
 
 97-12 
 
 4 
 
 86-65 
 
 90-76 
 
 4 
 
 91-21 
 
 94-I5 
 
 4 
 
 95-54 
 
 97-17 
 
 2 
 
 8673 
 
 90-82 
 
 2 
 
 91-29 
 
 94-21 
 
 2 
 
 95-61 
 
 97-22 
 
 O 
 
 86-81 
 
 90-88 
 
 O 
 
 91-36 
 
 94-26 
 
 O 
 
 95-68 
 
 97-27 
 
 0-8308 
 
 86-88 
 
 90-93 
 
 0-8188 
 
 91-43 
 
 94-3I 
 
 0-8068 
 
 9575 
 
 97*32 
 
 6 
 
 86-96 
 
 90-99 
 
 6 
 
 91-50 
 
 94-36 
 
 6 
 
 95-82 
 
 97-37 
 
 4 
 
 87-04 
 
 91-05 
 
 4 
 
 91-57 
 
 94-41 
 
 4 
 
 95-89 
 
 97-4 
 
 2 
 
 87-12 
 
 91-11 
 
 2 
 
 91-64 
 
 94-46 
 
 2 
 
 95-96 
 
 97-46 
 
 
 
 87-19 
 
 91-17 
 
 O 
 
 91-71 
 
 94-5I 
 
 
 
 96-03 
 
 97'5* 
 
 0-8298 
 
 87-27 
 
 91-23 
 
 0-8I78 
 
 91-79 
 
 94-56 
 
 0-8058 
 
 96-10 
 
 97-55 
 
 6 
 
 8735 
 
 91-28 
 
 6 
 
 91-86 
 
 94-61 
 
 6 
 
 96-16 
 
 97-60 
 
 4 
 
 87-42 
 
 9I-34 
 
 4 
 
 9I-93 
 
 94-66 
 
 4 
 
 96-23 
 
 97-64 
 
 2 
 
 87-50 
 
 91-40 
 
 2 
 
 92-00 
 
 947i 
 
 2 
 
 96-30 
 
 97-68 
 
 O 
 
 87-58 
 
 91-46 
 
 
 
 92-07 
 
 94-76 
 
 O 
 
 96-37 
 
 9773 
 
 0-8288 
 
 87-65 
 
 91-52 
 
 0-8168 
 
 92-15 
 
 94-82 
 
 0-8048 
 
 96-43 
 
 9777 
 
 6 
 
 8773 
 
 9i'57 
 
 6 
 
 92-22 
 
 94-87 
 
 6 
 
 96-50 
 
 97-8i 
 
 4 
 
 87-81 
 
 91-63 
 
 4 
 
 92-30 
 
 94-92 
 
 4 
 
 96-57 
 
 97-86 
 
 2 
 
 87-88 
 
 91-69 
 
 2 
 
 92-37 
 
 94-98 
 
 2 
 
 96-63 
 
 97-90 
 
 
 
 8796 
 
 9175 
 
 O 
 
 92-44 
 
 95-03 
 
 
 
 96-70 
 
 97-94 
 
49 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. iv. 
 
 Specific Gravity 
 = i5-5 
 
 Absolute Alcohol. 
 
 Specific Gravity 
 = iS-5 
 
 Absolute Alcohol. 
 
 Specific Gravity 
 = iS-5. 
 
 Absolute Alcohol. 
 
 Weight. 
 
 Volume. 
 
 Weight. 
 
 Volume. 
 
 Weight. 
 
 Volume. 
 
 Per Cent. 
 
 Per Cent. 
 
 Per Cent. 
 
 Per Cent. 
 
 Per Cent. 
 
 Per Cent. 
 
 0-8038 
 
 9676 
 
 97-98 
 
 0-8002 
 
 97-96 
 
 98-76 
 
 0-7968 
 
 99-03 
 
 99'39 
 
 6 
 
 96-83 
 
 98-03 
 
 
 
 98-03 
 
 98-80 
 
 6 
 
 99-10 
 
 99-43 
 
 4 
 2 
 
 96*90 
 96-96 
 
 98-07 
 98 II 
 
 0-7998 
 
 6 
 
 98-09 
 98-16 
 
 98-83 
 98-87 
 
 4 
 
 2 
 
 99-16 
 99-23 
 
 99-47 
 99-5I 
 
 O 
 
 97*03 
 
 98-16 
 
 4 
 
 98-22 
 
 98-91 
 
 O 
 
 99-29 
 
 99-55 
 
 0-8028 
 
 97-10 
 
 98-20 
 
 2 
 
 98-28 
 
 98-94 
 
 0.7958 
 
 99-36 
 
 99-59 
 
 6 
 
 97-16 
 
 98-24 
 
 
 
 98-34 
 
 98-98 
 
 6 
 
 99-42 
 
 99-63 
 
 4 
 
 2 
 
 
 97-23 
 97 '30 
 97-37 
 
 98-29 
 98-33 
 98-37 
 
 0-7988 
 
 6 
 4 
 
 98-41 
 98-47 
 98-53 
 
 99-02 
 
 99-05 
 99-09 
 
 4 
 
 2 
 O 
 
 99-48 
 
 99-55 
 99-61 
 
 99-67 
 9971 
 99-75 
 
 0-8018 
 
 97-43 
 
 98-42 
 
 2 
 
 98-59 
 
 99-I3 
 
 0-7948 
 
 99-68 
 
 99-80 
 
 6 
 
 97-50 
 
 98-46 
 
 O 
 
 98-66 
 
 99-16 
 
 6 
 
 9974 
 
 99-84 
 
 4 
 
 2 
 O 
 
 97-57 
 97-63 
 97-70 
 
 98-50 
 98-54 
 98-59 
 
 07978 
 
 6 
 
 4 
 
 9872 
 98-78 
 98-84 
 
 99-20 
 99-24 
 99-27 
 
 4 
 
 2 
 
 
 99-81 
 99-87 
 99-94 
 
 99-88 
 99-92 
 99-96 
 
 0-8008 
 
 97-76 
 
 98-63 
 
 2 
 
 98-91 
 
 99-3I 
 
 0-7938 
 
 lOO'OO 
 
 lOO'OO 
 
 6 
 
 97-83 
 
 98-67 
 
 O 
 
 98-97 
 
 99-35 
 
 
 
 
 4 
 
 97-90 
 
 9871 
 
 
 
 
 
 
 
 Chloroform, CHC1 3 , a colourless liquid, boiling at 61, is obtained by distilling 
 alcohol with chloride of lime. For this purpose there are used iron vessels, of about 
 i '4 metres in height and 2 metres in diameter. They are fitted with a mechanical 
 agitator, a pipe for introducing steam and one for water, and a manhole for filling in 
 the chloride of lime. At the upper margin of the generator there is placed a per- 
 forated lead tube (the holes towards the cylinder), which is connected with the water- 
 supply. A pipe of 75 mm. inside diameter, with a strong decline, leads to the con- 
 denser. It is best to use 4 parts chloride of lime of 103 to 108 (higher and 
 lower qualities are less suitable), 3 parts alcohol at 96 Tralles in 13 parts of water, 
 so that we have 16 parts of liquid to 4 parts of solid matter. For a daily output of 
 115 kilos, of chloroform, each of the four generators must have a charge of 400 kilos. 
 chloride of lime, 300 kilos, alcohol, and 1300 kilos, of water. The alcohol is first in- 
 troduced, then water enough to make up 1600 litres of liquid, next the agitator is set 
 in action, and the 400 kilos, of chloride of lime are added. The apparatus is then 
 closed air-tight, and the mixture is heated by means of steam. As soon as the ther- 
 mometer reaches 40 the steam is shut off. The agitator is worked until the thermometer 
 reaches 45, when it is disconnected. The temperature still rises slowly, and the re- 
 action reaches its height at about 60. In very hot weather the temperature rises 
 much higher, and in that case cold water is let flow over the apparatus. Between the 
 receiver and the refrigerator there is a glass-tube introduced in the connecting-pipe. 
 As soon as the reaction is in progress, a fine rain of chloroform, alcohol, and water is 
 seen to drive through this tube. As the air which issues from the apparatus is 
 saturated with the vapour of chloroform, it is caused, before escaping, to pass through 
 a washing bottle filled with water. This violent " blowing" lasts about a minute, when 
 the chloroform begins to flow. As soon as about 30 kilos, have been distilled off from 
 each apparatus the agitator is again set in motion. When the chloroform no longer 
 separates as a heavy layer in the distillate, the tin vessels which serve as receivers are 
 charged. The distillate which next follows consists of alcohol saturated with chloro- 
 form, and it is collected as long as chloroform separates out after shaking with water. 
 As soon as the distillate becomes clear after shaking, the efflux cocks are closed, and 
 the distillate runs into the pressure-vessels. The agitator is kept in motion to prevent 
 the solid matter from settling, and the distillation is kept up until the distillate marks 
 only 3 Tralles. The lime liquor is then let off through a hole near the bottom. In 
 
SECT, iv.] ORGANIC ACIDS. 491 
 
 each pressure-vessel there are now contained 500-600 litres of very dilute alcohol. 
 Before a new operation is commenced, it is calculated accurately how much alcohol is 
 present and how much liquid. If there are between 270 and 300 kilos, of alcohol in the 
 pressure-vessel it is only made up to 300 kilos. The quantity of liquid still required 
 is calculated and run into the generator, whilst the chloride of lime is stirred up. 
 When this has been done the generators are closed air-tight, and the contents of the 
 pressure-vessels are forced into them. The turbid alcoholic chloroform which distils 
 over first on washing after rectification is collected separately and washed again. 
 
 According to Giinther, the carbonic acid formed from the oxidation of the alcohol 
 initiates the production of chloroform by setting free hypochlorous acid : 
 
 1. CaO 2 01 2 4 C0 2 + H O -= 2HOC1 + CaCO 3 . 
 
 2. C,H 6 + HOC1 = C 2 H 4 4 HC1 + H 2 0. 
 
 3. HC1 + HOC1 = 2 C1 + H 2 O. 
 
 4. C,H 4 4 6C1 = CC1 3 COH 4 3HC1. 
 
 5. CC1 3 COH + Ca0 2 H 2 = 2 CHC1 3 + Ca(HCOO) 2 . 
 
 In the production of iodoform, CHI 3 , the same author recommends mixing alcohol 
 containing 20 to 25 parts of aldehyde with 10 parts solution of soda and then to intro- 
 duce iodine. The mixture is allowed to stand at the common temperature with occa- 
 sional stirring until the separation of iodoform has begun ; perhaps it is advantageous 
 to add here a little sodium iodide at the outset. The formation of iodoform is 
 explained by the following formulae : 
 
 1. Na 2 CO g + 2 I+ H 2 O = HOI 4 Nal + NaHC0 3 . 
 
 2. C,H 6 + HOI = C 2 H 4 O + HI + H 2 0. 
 
 3. HI + HOI = 2! + H 3 O. 
 
 4. C 3 H 4 + 61 + 3 HOI = CI 3 (COH) + 61 4- 3H,0. 
 
 5. CI S (COH) 4 NaHC0 3 = CHI 3 4 NaHCOO 4 C0 2 . 
 
 Chloral hydrate, C 2 HC1 3 O.H 2 O, is obtained by passing chlorine into alcohol. If 
 heated with potassa-lye it yields pure chloroform : 
 
 C 2 HC1 3 4 KOH = CHC1 3 4 KCH0 2 . 
 
 Ether (C 2 H.O) boils at 35'5. It is obtained by distilling alcohol with sulphuric acid : 
 C 2 H 5 OH 4 H 2 S0 4 = C 2 H 5 .HS0 4 4 H 2 0, and 
 C,H S HS0 4 4 C 2 H 5 OH = (C 2 H.) 2 O 4 H 2 SO 4 . 
 
 As the sulphuric acid is constantly re-constituted, whilst ether and water distil off, 
 alcohol is let constantly flow in as fast as it is decomposed. 
 
 ORGANIC ACIDS. 
 
 Among the organic acids which are not obtained from tar the following are 
 technically the most important. 
 
 Acetic Acid. H.C 2 H 3 O 2 is formed by the oxidation of ethyl-alcohol by atmospheric 
 oxygen. Aldehyde is first formed, and on taking up one atom oxygen it becomes acetic 
 acid 
 
 C 3 H 6 O 4 O = C 2 H 4 4 H 2 O; C 2 H 4 O 4 O = C 2 H 4 O,; or 
 
 CH 3 .CH 2 OH 4 O a = CH 3 .COOH 4 H 2 O. 
 
 46 kilos, ethyl-alcohol consequently require 32 kilos, or 22*3 cubic metres of oxygen 
 ( = 107 cubic metres of atmospheric air) in order to yield 60 kilos, of pure acetic acid 
 
 The following kinds of vinegar are distinguished by their origin : 
 
 1. Wine vinegar, containing in addition to acetic acid, almost all the constituents 
 of wine e.g., tartaric acid, succinic acid, glycerine, and certain others which give it an 
 agreeable aroma. 
 
 2. Spirit vinegar, which generally consists of a mixture of acetic acid and water 
 with small quantities of aldehyde and acetic ether. 
 
492 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 3. Fruit vinegars, obtained from cyder and perry or direct from apples, contain, 
 along with acetic acid, malic acid (and have the aroma of ripe apples). 
 
 4. Beer, malt, or grain vinegar, made from unhopped beer- worts (or sometimes, 
 under the name of alegar, from spoiled beer). It contains, along with acetic acid and 
 small quantities of aldehyde, extractive matter, phosphates, nitrogenous matter and 
 dextrine (which may be the cause of its want of aroma). 
 
 5. Sugar vinegar, made from solutions of cane-sugar or cane-treacle. It is probable 
 that with the addition of the proper vinous ferments a true wine vinegar might be 
 obtained from this source. Vinegar is also made from sugar-beets. 
 
 6. Vinegar is also obtained from pyroligneous acid, after elimination of the tarry 
 matters, and acetose. 
 
 The Older Method of Vinegar Making. As regards the so-called old method of 
 vinegar making it is without doubt an imitation of the spontaneous souring of beer, 
 wine, and fermented liquors generally, and under conditions which are conducive to the 
 improvement of the product ; such conditions are a suitable temperature, intimate 
 contact of the souring liquor with air, and a so-called acetification inducing ferment. 
 This method is very generally employed for making wine vinegar French vinegar as it 
 is termed in England but may of course be used for malt or fruit vinegar making as 
 well. Generally a '" souring " vessel or " mother " vessel made of oak wood is employed ; 
 this vat is first, when newly made, thoroughly scalded with boiling water, and when 
 thereby the extractive matter of the wood is exhausted the vessel is filled with boiling 
 vinegar ; when the wood is soaked with vinegar there is poured into the vessel one 
 hectolitre of wine, and after eight days again 10 litres of wine are added, and this 
 operation continued weekly until the vessel is filled for two-thirds of its cubic capacity. 
 About fourteen days after the last addition of the wine the whole of the contents will 
 have become converted into vinegar. Half this quantity is withdrawn from the souring 
 vessel and carried to the store ; to the remainder more wine is added, and the prepar- 
 ation of vinegar proceeded with uninterruptedly by the operation described. A 
 souring vessel may continue to serve its purpose for six years, and often longer, but 
 generally at the end of this time there is collected in the vessel so large a quantity of 
 yeast sediment, argol, stone, and other matter, as to render the thorough cleansing of 
 the vessel necessary ; after this operation it is again fit for further use. Although it 
 might appear that in this process of acetification there is no great contact of air, and 
 the fluid is apparently quite at rest, there is a constant change of the particles of the 
 surface of the fluid, owing to the fact that every drop of vinegar formed sinks to 
 the bottom of the vessel, or at least below the surface, owing to its increased specific 
 gravity ; while as regards the air, that portion of it from which the oxygen has been 
 absorbed by becoming specifically lighter (0.9 sp. gr.) has a tendency to rise upwards, 
 and to be replaced by heavier air (ro sp. gr.) ; thus a constant circulation of air is 
 provided. 
 
 Quick Vinegar Making. The so-called quick vinegar process, founded on an older 
 method of vinegar preparation suggested by Boerhaave in 1720, was first introduced 
 by Schutzenbach in 1823. The chief principle of this method consists in causing the 
 fluid, generally brandy, to be converted into vinegar by ultimate contact with the 
 atmosphere at the requisite temperature ; or, in other words, the oxidation of the alcohol 
 to acetic acid is effected in the shortest time and with the least possible loss. The 
 intimate contact of the fluid with the air is effected by : i. Increasing the quantity of 
 air admitted by means of a continual current of air, made to meet the drops of the 
 fluid intended to be converted into vinegar, in the opposite direction to that in which 
 these drops fall downwards. 2. By causing the liquid to be operated upon to trickle 
 down drop by drop. A peculiarly constructed vessel is required for this operation ; 
 according to the strength of vinegar desired to be made two or four of these vessels 
 
SECT. IV.J 
 
 ORGANIC ACIDS. 
 
 493 
 
 Fig. 379- 
 
 are employed, these constituting a group, or battery as it is termed. A sectional view 
 of such a vessel is exhibited in Fig. 379 ; it is made of stout oaken staves, the vat being 
 from 2 to 4 metres in height, and from i to 1*3 in 
 width ; at a height of from 20 to 30 centimetres 
 from the bottom of the vessel are bored, at equal 
 distances from each other, six holes air-holes of 
 about 3 centimetres in diameter, so cut that the 
 inner mouth of the hole is situated a little deeper 
 than the outer ; that is to say, the holes are bored 
 towards the bottom in a slightly sloping direction. 
 About one-third of a metre above the real lower 
 bottom a false bottom is placed, similar in con- 
 struction to a sieve, and at a height of a centi- 
 metre above the air-holes ; upon the false bottom 
 is a layer of beech-wood shavings extending up- 
 wards to about from 15 to 20 centimetres below 
 the upper edge of the vat. The false bottom is 
 sometimes constructed of laths of wood, forming a 
 kind of gridiron-like network. Before their appli- 
 cation the wood shavings are thoroughly washed 
 with hot water and afterwards dried. The tub 
 
 is then nearly filled with the dry wood shavings, which are next " soured." For this 
 purpose warm vinegar is poured over them, and allowed to remain in contact with the 
 wood for twenty-four hours, so as to cause the acetic acid to soak into the wood. At 
 from 1 8 to 24 centimetres below the upper edge of the vat is fixed a perforated wooden 
 disc, the holes of which are as large as a goose-quill, and are bored from 3 to 5 centi- 
 metres apart from each other. In order that the liquid intended to be converted into 
 acetic acid may trickle slowly, and in fine spray as it were, over the wood shavings 
 or thin chips of wood, through the holes, strings of twine or loosely spun cotton yarn 
 are passed so as to penetrate downwards for a length of 3 centimetres, while at the 
 top a knot is tied which prevents the strings slipping through the holes ; by the action 
 of the liquid, dilute spirits of wine usually, which is poured into the vessel, the twine 
 becomes more or less swollen, and thereby obstructs the passage of the fluid so as to 
 divide it into constantly trickling drops. The sieve bottom is fitted with from five to 
 eight larger holes, each about 3 to 6 centimetres wide, which by means of glass tubes, 
 each of from 10 to 15 centimetres in length, inserted and firmly fastened therein, act as 
 draught tubes, so placed that no liquid can pass through them. The vat is covered at 
 the top with a tightly-fitting wooden lid, in the centre of which a circular hole is cut, 
 which serves as well for the purpose of pouring the liquid into the vessel as for the 
 outlet of the air which enters the vessel from below. In consequence of the absorp- 
 tion of the oxygen so much heat is generated in the interior of the vessel that the air 
 streams strongly upwards, causing fresh air to enter by the lower air-holes. 
 
 After the vinegar tub has been soured the fluid to be converted into vinegar 
 generally brandy, more rarely malt liquor or wine is poured in ; the fluid flowing off 
 from the first vessel is poured into the second, and if the original liquid did not con- 
 tain more than from 3 to 4 per cent, of alcohol, the fluid which runs off from the second 
 vessel will be completely converted into good vinegar. The vinegar collects between 
 the true and false bottoms. As will be seen from the woodcut the vinegar cannot flow 
 out until its level is equal to that of the mouth of the glass tube. In consequence of 
 this arrangement a layer of about 1 6 to 20 centimetres in depth of warm vinegar assists 
 in the acetification by the evolution of acid vapours which ascends into the fluid above. 
 The tube must dip into the lower part of the fluid in the interior of the tub, as it is 
 
494 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. iv. 
 
 Fig. 380. 
 
 there that the specifically heavier vinegar collects. The arrangement will be readily 
 understood from Fig. 380 ; c p is the perforated bottom, just below which is situated 
 
 the wooden tap /z, fastened to the bent 
 glass tube, m m, the free open . end of 
 which touches the bottom of the tub. 
 
 Recently (1868) Singer's vinegar 
 generator has been introduced. It con- 
 sists of a number of vessels, one placed 
 above the other, and so connected to- 
 gether by wooden tubes that the liquid 
 intended to be converted into vinegar 
 trickles drop by drop from the one 
 vessel into another ; in each tube is cut 
 a longitudinal slit, through which air 
 freely circulates ; the apparatus is placed 
 
 in a suitably constructed shed, wherein a convenient temperature is kept up and from 
 which draught is excluded. By means of this apparatus the loss of alcohol experienced 
 in the use of the vats above mentioned is prevented. Singer's apparatus is fully de- 
 scribed in the Jahresbericht der Chem. Technologic, 1868, p. 580. 
 
 The composition of the fluid to be acetified varies very much ; one of the mixtures 
 very generally used is made up of 20 litres of brandy of 50 per cent. Tralles, 40 
 litres of vinegar, and 120 litres of water, to which is first added a liquid, made by 
 soaking a mixture of bran and rye meal in water in order to promote the formation of 
 the vinegar fungus (Mycoderma aceti). The room in which the vats are placed should 
 be heated to 20 to 24 ; the temperature in the vats rises to 36 and more ; consequently 
 the alcohol, aldehyde, and acetic acid are volatilised, and this loss may amount to about 
 one-tenth. Taking this loss into account we may assume that i hectolitre of brandy at 
 50 per cent. Tralles ( = 42 per cent, according to weight) yields by weight 
 
 13-0 hectolitres of vinegar of 3 per cent, acetic acid. 
 9-9 4 
 
 7-9 
 6-6 
 5-6 
 4'9 
 4 '4 
 3'9 
 
 9 
 10 
 
 When required for transport it is, of course, most advantageous to prepare very 
 strong vinegar which (at the place where it is to be consumed) can be diluted with the 
 requisite quantity of water. 
 
 In this process it is very essential that the shavings should be uniformly moistened. 
 Rose therefore omits the strings, and places over the bottom a rocking^trough, which 
 pours out the liquid alternately on each side of the false bottom. The distribution may 
 be better effected by means of Segner's wheel. 
 
 In the process of Michaelis acetification is effected in rotating tubs. 
 
 Pasteur has referred the formation of vinegar from alcohol to the action of bacteria, 
 and in 1862 described a physiological process for the manufacture. A fungus (Myco- 
 derma aceti} is the agent. This fungus is first propagated in a fluid, consisting of water and 
 2 per cent, of alcohol with i per cent, of vinegar and a small quantity of potassium, calcium, 
 and magnesium phosphate. The small plant soon spreads itself over the entire surface 
 of the fluid, without leaving the smallest space uncovered. At the same time the alcohol 
 is acetified. As soon as half the alcohol is converted into vinegar, small quantities 
 of wine or alcohol mixed with beer are added daily. When the acetification becomes 
 
SECT. IV.] 
 
 ORGANIC ACIDS. 
 
 495 
 
 weaker, the complete conversion of the free alcohol still present in the fluid is allowed 
 to take place. The vinegar is then drawn off and the plant again employed in the 
 same apparatus. Vinegar prepared by this method possesses much of the aroma 
 characteristic of wine vinegar. An essential condition to the rapid formation of vinegar 
 by this method is a strong development of the plant. A vessel with i square metre of 
 surface, and capable of containing 50 to TOO litres of fluid, yields daily 5 to 6 litres of 
 vinegar. The vessels are circular or rectangular wooden tanks, with but a slight depth, 
 and covered with lids. At the ends are bored two small openings for the entrance of 
 the air. Two tubes of gutta-percha, pierced laterally with small holes, are carried down 
 to the bottom of the tank, and used to pour alcohol into the tank without opening the 
 lid. The tank which Pasteur employed had a surface of i square metre and a depth of 
 20 centimetres. He found phosphates and ammonia necessary for the growth of the 
 plant. When wine or malt liquor, &c., is employed, these substances are present therein 
 in sufficient quantity ; but when only alcohol is used, ammonium sulphate, potassium 
 phosphate, and magnesia are added in such quantity that the fluid contains j-f7^oTr tn f 
 this saline mixture, to which also some vinegar is added. It has been long known that 
 the addition of bread, flour, malt, and raisins to alcoholic fluids about to be acetified 
 greatly promotes the formation of vinegar, as these substances contain the requisite 
 organic and inorganic food suited for the propagation of the vinegar fungus. 
 
 According to this method a manufactory for wine vinegar was established in 
 Orleans in 1871, and in 1879 E. Wurm erected similar works at Breslau. He used 
 large wooden vats, charged with 200 litres of the vinegar mixture, consisting of water, 
 alcohol, and acetic acid, along with the nutritive salts recommended by Pasteur ; i.e., 
 potassium phosphate, o - oi per cent.; calcium phosphate, o'oi per cent.; magnesium 
 phosphate, o'oi per cent.; ammonium phosphate, o - o2 per cent. The vats are closely 
 covered with wooden lids. Air is admitted through small holes at the sides. The 
 fungus is sown by means of a small, thin wooden spatula. The main conditions 
 are : a pure ferment, uniform temperature of 30, and a regulated inflow of alcohol. 
 This process has not become more widely used, as its production was not sufficiently 
 abundant. 
 
 Vinegar by means of Platinum Black. Dobereiner was the first who pointed out 
 that, with the aid of platinum black, alcoholic vapours could be acetified in a very short 
 time ; and to this process the following 
 apparatus is especially adapted. Fig. 381 
 shows a small glass house, in the interior 
 of which are seen a number of compart- 
 ments. The shelves forming these com- 
 partments support a number of porcelain 
 capsules. The alcohol to be acetified is 
 poured into these capsules, in each of 
 which is placed a tripod, also of porcelain, 
 supporting a watch-glass containing pla- 
 tinum black, or spongy platinum. In the 
 roof and at the bottom of the apparatus 
 are ventilators, so constructed as to admit 
 of regulating access of air. By means of 
 a small steam pipe the interior of the 
 house is heated to 33. By this means 
 the alcohol is gently evaporated, and 
 
 coming into contact with the platinum black or sponge, is acetified. So long as the 
 ventilation is maintained, the platinum black retains its property of oxidising the 
 alcohol. With an apparatus of 40 cubic metres capacity and with 1 7 kiloa. of platinum 
 
 Fig. 381. 
 
49 6 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 black, 150 litres of alcohol can daily be converted into pure vinegar. If it be desired to 
 prepare the vinegar without any loss of alcohol, it becomes necessary to pass the outgoing 
 air through a condenser in order to collect the vapours of alcohol and acetic acid 
 which otherwise would be carried off. 
 
 Properties and Examination of Vinegar, Acetometry. The value of a vinegar is 
 dependent upon its flavour and upon its strength, or upon the quantity of acetic acid it 
 contains. According to its containing more or less acetic acid the vinegar tastes more 
 or less sour. The colour varies with the fluid from which the vinegar has been pre- 
 pared ; wine vinegar is of a yellow or red-yellow colour, fruit vinegar exhibits a golden 
 colour, brandy vinegar is colourless, but as a rule the latter is coloured with caramel 
 in imitation of wine vinegar. Freshly made vinegar contains, besides small quantities 
 of unconverted alcohol, some aldehyde, which always occurs largely in vinegar not 
 properly prepared. Recently it has become customary to add a small quantity of gly- 
 cerine to the prepared vinegar. 
 
 The quantity of acetic acid contained in a vinegar depends upon the alcoholic con- 
 tents of the fluid to be acetified, and also upon the more or less perfect conversion of 
 the alcohol into acetic acid. Malt vinegar contains from 2 to 5 per cent., brandy vinegar 
 from 3 to 6 per cent., wine vinegar from 6 to 8 per cent, of acetic acid. The sp. gr. of 
 various kinds of vinegars differs from I'oio to 1*030; the more alcohol a vinegar 
 contains the lighter is it, the more extractive matter the heavier. 
 
 Acetometry. Commercial vinegar varies greatly as regards the quantity of acetic 
 acid it contains. The sp. gr. of a commercial vinegar is no certain indication of the 
 quantity of acetic acid, owing to the fact that the vinegar nearly always contains foreign 
 matters. The testing of the strength can therefore only be accurately effected by 
 means of saturating it with an alkali. According to the ordinary method, first intro- 
 duced for this purpose by Otto, ammonia is added to the vinegar to be tested until the 
 previously added tincture of litmus becomes again blue ; although this method is not 
 absolutely correct owing to the fact that the neutral alkaline acetates exhibit an 
 alkaline reaction this does not much impair the correctness of this process. Otto's 
 acetometer is a glass tube sealed at one end, 36 centimetres long by 1*5 wide, whereon 
 is engraved a double scale of divisions, one of these towards the bottom of the tube 
 serving for measuring the vinegar coloured by litmus, while the upper scale is intended 
 for measuring the test liquor. "When it is intended to apply the test with this 
 measuring tube, a certain quantity (indicated by the divided scale) of litmus tincture is 
 first poured into the tube, next vinegar is added in sufficient quantity to fill the tube 
 up to the second division ; afterwards so much of the test-liquor is added as to restore 
 again the blue colour of the litmus. 
 
 A very useful apparatus for determining the value of vinegar and essence of 
 vinegar has been proposed by Hartmann and Hauer, of Hanover. A box contains a 
 bottle of normal potassa-lye, a bottle of an indicator, a small pipette, a cylinder with a 
 back of milk-glass (Fig. 382), and a mixing vessel for 50 and 80 per cent, essence of 
 vinegar and glacial acetic acid at 100 per cent. 
 
 The method of using the apparatus is as follows : The cylinder (Fig. 383) is twice 
 well rinsed out with the vinegar to be tested, shaking it well, and expelling the last 
 drops by a centrifugal movement. The sample is poured in until the surface of the 
 liquid stands a little above the zero-point, and so much liquid is removed with the 
 pipette that the top line, o o (Fig. 384) of the liquid, coincides with the zero mark. 
 To this end, the pipette, which must be previously shaken out several times before use, 
 is plunged with its point into the liquid. Its upper opening is then closed with the 
 moistened fore-finger, and raised up until the point is just above the mouth of the 
 cylinder. If too much liquid was taken out, so much is let flow back by gently raising 
 the fore-finger until the zero-point is reached. "When this is done, 2 drops of the 
 
SECT. IV.] 
 
 ORGANIC ACIDS. 
 
 497 
 
 Fig. 383. 
 
 Fig. 384 
 
 indicated liquid are added, and the normal lye is cautiously run in until the red clouds 
 in the cylinder disappear more slowly. The lye is then added, drop by drop, until the 
 vinegar is completely saturated. As soon 
 as the entire liquid remains red, after 
 careful agitation, the operation is at an 
 end. The cylinder is set on a horizontal 
 surface, let stand for a minute, and the 
 degrees consumed are read off, which in- 
 dicate how many per cents, of absolute 
 acetic acid (C,H 4 2 ) are contained in. 
 
 Testing Vinegar -Essence. This may be 
 effected on the principle just laid down. 
 
 Wood Vinegar. After the dry distil- 
 lation of wood a portion of the carbonised 
 matter remains in the retorts as charcoal, 
 while the remainder of the constituents 
 of the wood are eliminated partly in the 
 state of gases and vapours, such as car- 
 bonic oxide, carbonic acid, hydrogen, light 
 and heavy carburetted hydrogens partly 
 in the shape of a condensed matter, consisting of a thick, brown, oily fluid floating upon 
 a stratum of a watery liquor. The latter, wood vinegar, consists essentially of impure 
 acetic acid, some propionic and butyric acids, small quantities of oxyphenic acid, 
 creosote, and an alcoholic wood spirit, a mixture of methylic alcohol, aceton, and methyl 
 acetate, the brown, tiiickish fluid substance known as wood tar, consisting of a 
 number of both fluid and solid bodies, paraffin, napthalin, creosote, benzol, toluol, <fec. 
 A well-conducted distillation will yield as much as from 7 to 8 per cent, of the weight of 
 the wood of acetic acid. According to the researches of H. Yohl, peat can be employed 
 in the preparation of wood vinegar and of wood spirit. 10 cwts. of peat yield 3 kilos, 
 of acetic acid and 1-45 kilos, of wood spirit. 
 
 Raw wood vinegar contains in solution a not inconsiderable quantity of resin, and 
 also small quantities of phenol and guaiacol ; all these bodies impart a more or 
 less brown colour and empyreumatic odour and flavour, and they also render it a 
 valuable antiseptic. Where the principal aim is to obtain wood vinegar, an iron 
 retort, somewhat similar to a gas retort, is employed for the distillation of the wood. 
 In large factories, instead of the wooden receivers, large stone or brickwork cisterns are 
 employed, generally several of such tanks being used, the largest quantity of tar being 
 condensed in the first cistern, while the wood vinegar, mechanically freed from the tar 
 and floating on its surface, finds its way into a second cistern. Pettenkofer's patent 
 wood-gas generators produce a not inconsiderable quantity of wood vinegar. 
 
 Purifying Wood Vinegar. Raw wood vinegar is a clear dark brown fluid, having a 
 tarry taste and smoky odour. It is employed in small quantities in the preservation 
 of meat, also for the preservation of wood, ropes, &c. ; but by far the largest quantity 
 is employed in the manufacture of the various acetates used in dyeing and calico 
 printing, chiefly as crude iron acetate and crude aluminium acetate. It is also used 
 in the preparation of concentrated acetic acid for industrial purposes ; that is, for the 
 production of aniline from nitro-benzol, and of sugar of lead (lead acetate). Lastly, 
 it is largely used in the preparation of table vinegar, an operation economical only 
 where, as in England, there is a high duty on alcoholic fluids. 
 
 Among the means of purifying crude wood vinegar, the most simple leaving out 
 of the question the filtration of the crude liquor over coarsely granulated wood charcoal 
 as recommended by E. Assmus is distillation, an operation usually carried on in a still 
 
 2 I 
 
49 8 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 made of copper fitted with a copper condensing apparatus. At first a yellow fluid 
 comes over raw wood spirit, from which the wood spirit of commerce is prepared and 
 next the distillate becomes richer in acetic acid. 
 
 The principal methods at present employed for the purification of wood vinegar 
 may be considered as falling under either of two classes : 
 
 a. The first includes the purifying of wood vinegar without saturation with a base ; 
 while 
 
 b. The second includes those methods in which the wood vinegar is purified by- 
 conversion into an acetate, the acetic acid being next separated by distillation with an 
 acid possessing greater affinity for the base. 
 
 To the first class belongs Stoltze's method, consisting in first obtaining by distillation 
 10 per cent, of a liquid which is employed for the preparation of wood spirit; 80 per 
 cent, of the liquid is next distilled off, and the empyreumatic substances contained are 
 destroyed by the action of either ozone or chlorine. The purification of the crude 
 wood vinegar by the second method is more generally in use among manufacturers, 
 the inventor of the system being Mollerat. The crude wood vinegar is first saturated 
 with lime, and the solution next precipitated with Glauber's salt to obtain sodium 
 acetate ; this salt is purified by crystallisation, and when in a dry state is so far heated 
 that the empyreumatic matter it is mixed with becomes carbonised, and is thus 
 rendered insoluble ; the sodium acetate is then extracted with water, and the acetic 
 acid separated from it by distilling the previously crystallised and dried salt with 
 sulphuric acid. Instead of sodium acetate, the calcium acetate is frequently employed 
 in the preparation of acetic acid from crude wood vinegar, the latter being saturated 
 with lime, and the salt formed evaporated to dryness. The dry salt is roasted am! 
 treated similarly to the sodium acetate to calcine any empyreumatic products. The 
 acid is employed in the distillation is, according to the method invented by C. Yolckel, 
 hydrochloric acid. The distillation can be effected in a retort with a helm of copper 
 and a condenser of lead, tin, or silver. To 100 parts of acetate of lime 90 to 95 
 parts of hydrochloric acid at ri6 sp. gr. are used. When hydrochloric acid is used in 
 this preparation, instead of sulphuric acid, any contamination of the crude calcium 
 acetate with empyreumatic or tarry matter does not affect the purity of the acetic acid 
 which is obtained, provided the crude acetate be first so well dried as to be free from 
 all other volatile substances ; when sulphuric acid is used for this purpose, the result 
 is that an acetic acid is obtained, which contains not only a large quantity of 
 sulphurous acid, but also offensive volatile compounds, due to the decomposition (by the 
 sulphuric acid) of empyreumatic resins and tarry matter present in the crude calcium 
 acetate. 
 
 For the preparation of acetic anhydride 250 kilos, of sodium acetate, previously 
 dried to a dust, are placed in a double kettle fitted with an agitator. The temperature 
 in the kettle is raised to 140, and a strong current of chloro-carbonic oxide is 
 introduced. The oil which distills over must be carefully condensed, as it has a very 
 irritating effect on the mucous membranes. The crude product (150 kilos.) is 
 submitted to fractional distillation, and 100 kilos, of fairly true anhydride may thus be 
 obtained. The temperature of 140 must not be exceeded, as otherwise acetose is 
 formed in considerable quantities, and can scarcely be completely separated from the 
 anhydride. 
 
 Formic Acid, HCHO 2 , a natural secretion of ants [and many other insects, e.g., larva* 
 of Cerura vinula, Gychrus rostratus, &c.] is obtained by heating oxalic acid with 
 glycerine. 
 
 According to Lorin, we mix at 108 equal equivalents of oxalic acid and gly- 
 cerine in small properties, allowing the escape of gas to come to an end after 
 ach addition. At first more water is liberated than corresponds to the carbon 
 
SECT. IV.] 
 
 ORGANIC ACIDS. 
 
 499 
 
 dioxide evolved, and the water split off on etherification ; the oxalic acid at first 
 yields up simply its water of crystallisation. Subsequently the production of water 
 and formic acid ceases almost entirely, though much carbon dioxide is still liberated, and 
 ultimately the water which has escaped is exactly equal to the crystalline water and 
 that formed by etherification, since about 91 per cent, of the formic acid are com- 
 bined with glycerine. The same phenomena occur on further additions: the oxalic 
 acid expels a part of the combined formic acid ; the newly-formed formic acid escapes 
 in part, and is partly taken up by the glycerine. At the third addition the glycerine 
 is almost completely saturated, and 43 grammes of formic acid have been liberated. At 
 the fourth addition there is formed from i equiv. of oxalic acid exactly i equiv. formic 
 acid and the crystalline water. The synthetic production of formic acid by the action 
 of moist carbon monoxide upon soda-lime at about 200 deserves attention. 
 
 Butyric acid, H.C 4 H 7 O,, is 'obtained by the fermentation of a solution of sugar 
 mixed with putrid cheese. Fitz dissolves 180 grammes sugar in 6 litres water, adds o'l 
 gramme potassium phosphate, 0*02 magnesium sulphate, i gramme ammonium chloride, 
 and 70 grammes calcium carbonate, heats to 110, lets cool, and sows with a pure 
 culture of Bacillus butylicus. He thus obtains 42 grammes pure butyric acid. Stinde 
 recommends 50 kilos, carobs (Ceratonia siliqua) crushed up to a thin paste with water 
 at 28, adds after four or five days 12 kilos, of elutriated chalk, and lets the whole 
 ferment, which in summer is completed in six weeks. The thick pasty mass is then 
 etherified in a copper still by a mixture of 18 kilos, sulphuric acid and 30 kilos, alcohol 
 at 95 per cent. 
 
 Butyric ether is used in perfumery as rum or cognac ether. 
 
 Valerianic acid, H.C 5 H g O 2 , is chiefly obtained by heating amylic alcohol with potas- 
 sium dichromate and sulphuric acid. Its ethylic and amylic ethers are extensively used 
 as fruit ethers (oil of apples). 
 
 Oxalic Acid., H 8 .C 2 O 4 , a constituent of many plants (oxalis), is now almost ex- 
 clusively obtained by melting sawdust with caustic potassa. Mixtures of potassa and 
 soda give a smaller yield. 
 
 Thorn added 50 parts of sawdust to 100 parts hydrated alkali in the state of a lye 
 of 98 Tw., and then heated it in a layer of i centimetre in thickness with frequent 
 stirring. He obtained the following yields : 
 
 Proportion of KHO to NaHO. 
 
 Temperature. 
 
 Oxalic acid. 
 
 
 
 Per cent. 
 
 O-IOO 
 
 2OO-22O 
 
 33T4 
 
 10-90 
 
 230 
 
 S8-36 
 
 20-80 
 
 24O-25O 
 
 74*76 
 
 30-70 
 
 240 250 
 
 7677 
 
 40-60 
 
 240 250 
 
 80-57 
 
 60-40 
 
 240 250 
 
 80-08 
 
 80-20 
 
 245 
 
 81-24 
 
 IOO-O 
 
 
 81-23 
 
 In experiments with different woods it was observed that soft woods proved to be 
 the best material. On heating 50 parts of wood with 40 parts KOH and 60 NaOH, in 
 thin layers, there was obtained : 
 
 Kind of Wood. 
 
 Moisture. 
 
 .Oxalic acid. 
 
 Oxalic acid calculated in 
 wood dried at 100. 
 
 
 Per cent. 
 
 Per cent. 
 
 Per cent. 
 
 Pine 
 
 15-0 
 
 8o-s 
 
 94-70 
 
 Fir . 
 
 I5-0 
 
 80-5 
 
 94-70 
 
 Poplar 
 
 I4'0 
 
 80-1 
 
 93-14 
 
 Beech 
 
 8-6 
 
 79"o 
 
 86-43 
 
 Oak. 
 
 6-5 
 
 75-1 
 
 83-42 
 
5 oo CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 The melt is lixiviated with water, the solution is boiled with milk of lime, and the 
 calcium oxalate is decomposed with sulphuric acid. If a mixture of soda and potassa 
 is used for melting, the lye is concentrated to 66 Tw., when the sodium oxalate crys- 
 tallises out and is freed from the mother liquor in a filter-press or a centrifugal. The 
 sodium oxalate is dissolved in boiling water and the liquid is boiled with milk of lime 
 for some hours. It is advantageous to use the solution very dilute, as otherwise the 
 decomposition takes place very slowly. When a filtered specimen no longer gives the 
 reaction of oxalic acid the lye is drawn off, the precipitate is washed with hot water 
 and filtered. The lye is used again. An excess of sulphuric acid is required for the 
 decomposition of the calcium oxalate, according to Chandelon, 3 mols. sulphuric acid 
 to i mol. calcium oxalate. The salt is stirred up with water to a thin paste, and the 
 requisite quantity of sulphuric acid (at 22 to 30 Tw.) is stirred in. It is then heated 
 for some hours, after the addition of water, and filtered off from the calcium sulphate. 
 The solution, which along with oxalic acid contains sulphuric acid and gypsum, is con- 
 centrated to 22 Tw. Gypsum separates out on standing, and after its removal the 
 liquor is further concentrated to 50 Tw. On cooling, oxalic acid separates out in long 
 crystals, and is purified by recrystallisation. The sulphuric acid can also be used 
 again. 
 
 According to Merz, by quickly heating sodium formiate with the utmost possible 
 exclusion of air to above 400, a saline mass is formed, which contains along with car- 
 bonate 70 per cent, and more of oxalate. At lower temperatures more carbonate is 
 formed. Potassium formiate behaves in a similar manner ; calcium, barium, and 
 magnesium formiates yield merely carbonates. It is, perhaps, possible that the 
 synthetic formation of sodium formiate by means of carbon monoxide and its conver- 
 sion into oxalate may prove a more advantageous method for the production of oxalic 
 acid than the reaction of caustic potassa upon sawdust.* 
 
 Oxalic acid is used for bleaching straw, as a discharge in tissue printing, and in 
 certain mordants used in woollen and silk dyeing. Its most important salts are the 
 acid potassium and antimony oxalate, now used in tissue printing instead of tartar 
 emetic. 
 
 Lactic Acid, H.C 2 H 5 3 , is obtained by the fermentation of sugar with cheese, or 
 preferably, according to Kiliani, by heating inverted sugar with soda lye. Antimony 
 lactate serves as a mordant in dyeing in place of tartar-emetic. 
 
 Tartaric Acid, H 2 .C 4 H 4 6 . Only the dextro-rotary tartaric acid is of technical im- 
 portance. It is contained in grape juice and is deposited during fermentation as 
 so-called tartar, or argol, which consists chiefly of potassium bitartrate. According 
 to Kurtz, 500 to 700 kilos, of crude argol are heated to boiling in a wooden vat by the 
 introduction of steam. Half the tartaric acid is then precipitated by the addition of 
 powdered chalk. Less than the theoretical quantity of chalk must be used (18-8 
 potassium bitartrate require 5 parts of chalk), as the crude argol rarely contains more 
 than 80 per cent, of acid potassium tartrate, and besides on complete neutralisation the 
 magnesia, alumina, and iron oxide would be also precipitated. With tartars and argols, 
 which are very rich in such impurities, it is advisable at the beginning of the operation 
 to add 12 to 25 kilos, hydrochloric acid, and not to neutralise completely, as otherwise 
 during the crystallisation of the tartaric acid the presence of alum, magnesium sulphate, 
 &c., would cause much annoyance. 
 
 To convert the neutral potassium tartrate into the calcium salt, Kurtz recommends 
 gypsum when cheaper than calcium chloride. 8'6 parts of gypsum equal 5 parts of 
 chalk. The gypsum may be added before or during the neutralisation with chalk, and 
 an excess does no harm. As the calcium tartrate obtained from the lyes is very pure, 
 pure gypsum is used for working it up for potassium tartrate. The reaction of the 
 calcium sulphate with neutral potassium tartrate is slow, and requires several hours. 
 * It was formerly obtained by the action of nitric acid on sugar. 
 
SECT, iv.] ORGANIC ACIDS. 501 
 
 As soon as acetic acid occasions no precipitate in a cooled and filtered specimen, the 
 reaction is at an end. The contents of the vat are allowed to cool down to 50, and 
 are let off into another vat intended for the deposition of the calcium tartrate, passing 
 through a sieve in order to keep back chips of wood, grape stalks, &c., usually present 
 in crude argols. In three to four hours the calcium tartrate is deposited, and the lye 
 is drawn off with a syphon. It is rich in potassium sulphate. When the lime salt 
 has been washed three times it is sufficiently clear for further treatment. 
 
 In working up wine-lyes the alcohol present is first distilled off; then about 2500 
 kilos, are placed in a vat holding from 100 to 150 hectolitres, which is almost filled with 
 water. About 50 kilos, of crude hydrochloric acid are added, and the whole is heated 
 almost to boiling whilst stirring. The contents are then allowed to settle, and the clear 
 liquid is drawn off through syphons into a second vat, in which it is nearly neutralised with 
 powdered chalk whilst being constantly stirred. All the tartaric acid is precipitated by 
 the calcium chloride which is formed. The liquid is drawn off into a third vat, where 
 the calcium tartrate is deposited and washed. The muddy sediment of the first vat is 
 pressed to recover any tartaric acid present, and the residue can be worked up for 
 Frankfort black. 
 
 The process of Dieter has also proved successful. It consists in heating the crude 
 tartar, or the dried, or the freshly pressed and liquid lyes, to 140 170, which 
 is effected by steam at a pressure of 3 to 7 atmospheres, in closed pans ; or by boiling 
 under pressure, and by dry roasting with superheated steam. The impure product is 
 easily lixiviated, and the tartaric acid solution is separated out by means of filter-presses. 
 The calcium tartrate is decomposed by sulphuric acid. More than the theoretical 
 quantity of sulphuric acid must be used (which would be 4*9 parts to 9^4 calcium 
 tartrate), as fine crystals of tartaric acid can be obtained only from solutions containing 
 strong mineral acids. The presence of small quantities of calcium tartrate or 
 potassium sulphate (resulting from imperfect washing of the calcium tartrate) greatly 
 disturbs the crystallisation. The lime-salt is mixed with the sulphuric acid, the 
 needful amount of water is added to obtain a paste which admits of stirring, and it it 
 heated by means of steam to 75 with agitation. As soon as the sulphuric acid is in a 
 certain excess (which is judged by the bulk of the precipitate produced by a filtered 
 specimen with calcium chloride), the tartaric acid is separated from the gypsum by 
 filtration, and is boiled down in leaden pans by means of a steam worm of lead, when 
 a little gypsum separates out. As the lye becomes more concentrated the heat must 
 not be allowed to exceed 70 75, as otherwise the tartaric acid will be turned brown 
 by the sulphuric acid. At the concentration of 72 Tw. the lye is run into wooden 
 tanks lined with lead, or large earthenware pans, and allowed to crystallise. The mother 
 liquors are evaporated down three times, taking each time a crop of crystals. The 
 fourth mother liquor is treated as a raw material. The crystals are whizzed,* redissolved, 
 and decolorised with bone-black ; the solution is filtered, mixed with a little sulphuric 
 acid, evaporated down to 72 Tw., and again run into the crystallisers. The acid, 
 which is now finely crystallised, is whizzed and dried. 
 
 In some works the evaporation of the tartaric solutions is very successfully carried 
 on in lead vacuum pans. 
 
 The yearly production of tartaric acid is, in hectokilos. : 
 
 Germany 8000 
 
 Austria-Hungary 5000 
 
 France 3000 
 
 Italy ......... 2000 
 
 Spain 500 
 
 Britain 13,000 
 
 United States 12,000 
 
 amounting in value to 16-20 million marks. 
 
 * The ordinary technical expression for treatment in a centrifugal machine. 
 
S oa CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 Tartaric acid is used in large quantities as a discharge in tissue printing, as a 
 mordant in dyeing (in the state of acid potassium tartrate), in the preparation of 
 baking-powders, effervescing drinks, &c. 
 
 Citric Acid, H 3 .C 6 H 5 7 , is especially present in the juice of lemons and limes (6 to 7 
 per cent.), and of currants. To obtain it, limejuice is precipitated with milk of lime, 
 the calcium citrate is decomposed with sulphuric acid, and the solution of citric acid is 
 evaporated down. Citric acid is used as a discharge in tissue printing and in the 
 manufacture of lemonades. 
 
 Benzole Acid, H.C r H 4 0,, is prepared for medicinal uses from the gum-resin benzoin. 
 For technical purposes it is obtained from hippuric acid or from naphthalene or 
 toluene. In its preparation from hippuric acid, which on boiling with dilute acids or 
 on putrefaction is split up into benzoic acid and glycocol, the urine of horses or cows 
 is either boiled for a long time with hydrochloric acid or it is allowed to putrefy, pre- 
 cipitated with milk of lime, filtered, the filtrate is concentrated, and the benzoic acid is 
 thrown down by hydrochloric acid. For purification it is dissolved in weak milk of 
 lime with a little chloride of lime, reprecipitated by hydrochloric acid and recrys- 
 tallised. The acid thus obtained has a slightly urinous odour. 
 
 For obtaining benzoic acid from the phthalic acid produced by the oxidation of 
 naphthalene, its calcium salt is heated to 33o-35o : 
 
 2CaC 8 H 4 4 + Ca(OH) a = Ca(C T H 5 O a ), + aCaCO,. 
 
 According to Laurent, the ammonium compound of phthalic acid by dry distillation 
 is converted into phthalimide, and this again by distillation with slaked lime into 
 benzonitril ; 
 
 C 8 H 5 O a N + Ca(OH), - C,H 4 N + 2 CaCO, + H,O. 
 
 On boiling with caustic soda lye, benzonitril is converted into sodium benzoate, whilst 
 ammonia is liberated : 
 
 C r H 5 N + NaHO + H 2 O = NaC,H 5 O a + NH 3 . 
 
 Sodium Benzoate. Toluene is converted into benzylchloride, C 7 H ? C1, by treat- 
 ment with chlorine, and this compound, if heated with water under pressure or boiled 
 with dilute nitric acid, passes into benzoic acid. G. Lunge boils 100 parts benzyl- 
 chloride with 300 parts nitric acid at 60 Tw. and 200 parts of water for ten hours, 
 with a reflux condenser. Benzoic acid melts at 121 and boils at 249. 
 
 Tannin, C 14 H 10 9 , is found chiefly in nut-galls and also in sumac. It is obtained by 
 extracting powdered nut-galls with ether. A mixture commonly employed consists of 
 30 parts ether, 4 parts water, and i part alcohol. The acid obtained by evaporation 
 may be purified from the accompanying gallic acid by solution in lime and precipitation 
 with solid sodium chloride, or by repeated solution in water and treatment with 
 animal charcoa 
 
 Tannin serves for clarifying wines (rarely beers), but chiefly as a mordant in dyeing, 
 for the production of ink and of pyrogallol, and in medicine. 
 
 TREATMENT OF COAL-TAR. 
 
 The so-called aromatic compounds are almost entirely obtained from coal-tar. 
 Most tar is obtained in the manufacture of coal-gas, and a smaller quantity from coke- 
 burning. The composition of the tar depends on the quality of the coal, but still more 
 on the temperature employed. 
 
 According to Wright, the specific gravity of tar is the higher the stronger the heat 
 which has been employed. Five tars obtained from the same coals, but at an increasing 
 temperature, yielded : 
 
SECT. IV.] 
 
 TREATMENT OF COAL-TAR. 
 
 503 
 
 I. 
 
 II. 
 
 in. 
 
 IV. 
 
 V. 
 
 I -086 
 
 I'IO2 
 
 1-140 ... 
 
 1-154 
 
 1-206 
 
 I -2O 
 
 ... 1-03 
 
 1-04 
 
 1-05 
 
 ... 0-38 
 
 9-I7 
 
 ... 9-05 
 
 - 373 - 
 
 3-45 
 
 ... 0-99 
 
 lO'SO 
 
 ... 7'46 
 
 ... 4-47 
 
 2-59 
 
 ... 0-57 
 
 26-45 
 
 - 25-83 
 
 ... 27-29 ... 
 
 27-33 
 
 ... 19-44 
 
 20-32 
 
 ft J 5'57 
 
 ... 18-13 ... 
 
 13-77 
 
 ... 12-28 
 
 28-89 
 
 ... 36-80 
 
 ... 41-80 ... 
 
 47-67 
 
 ... 64-08 
 
 Specific gravity of tar 
 
 Ammonia liquor 
 
 Crude naphtha 
 
 Light oils 
 
 Creosote oils 
 
 Anthracene oils 
 
 Pitch . . .'"'". 
 
 The quantity of crude naphtha (benzol, &c.) of the light oils and the phenols de- 
 creases rapidly with the rise of temperature. Tar from the Berlin gasworks contains 
 
 in 100 parts : 
 
 Benzol and Toluol o - 8 
 
 Other clear oils O"6 
 
 Phenol 0-2 
 
 Naphthaline 3*7 
 
 Anthracene (pure) o'2 
 
 Heavy oils 24*0 
 
 Pitch for asphalt and briquettes, &c. . . 55*0 
 
 For the distillation of tar, Lunge recommends the still intended for 25 tons of tar, 
 of which Fig. 385 shows Fi 
 
 the section, on the line E 
 F of the ground - plan ; 
 Fig. 386 a section through 
 D C' of Fig. 385 ; Fig. 387 
 a section through the body 
 of the still itself along A B 
 of Fig. 385. The body is 
 3 metres in width and 3^ 
 metres high without the 
 capital, and is constructed 
 of boiler-plates 10 mm. in 
 thickness. A concavity of 
 the bottom corresponds ap- 
 proximately to the con- 
 vexity of the cover. The 
 body may have a very slight 
 slope towards the side of 
 the outflow cock, a, which, 
 however, must be placed as 
 close as possible to the 
 bottom or even in its flat 
 part. 
 
 The fire-box, b, is ac- 
 cessible from without by 
 the door, c, which must be 
 placed on the side opposite 
 to the exit-cock for the 
 pitch. In the drawing is 
 shown the arrangement of 
 one of the largest English 
 manufactories, in which the 
 wall underneath the fire- 
 doors is closed in front, and 
 the ashpits are all connected through the opening, d, with a large vaulted channel, e, 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. rv. 
 
 Fig. 386. 
 
 which runs underneath the entire series of stills, and which is accessible only at 
 both ends. This affords complete security against the danger of fire, in case 
 the tar in the stills should boil over, fill the receivers, and flow away from the 
 
 latter. 
 
 The flame strikes over the fire-bridge, /, and beneath the vault, g. The latter is 
 struck as a tun-vault from the circular wall, k, upon which the still rests, and com- 
 pletely protects its bottom from the pointed flame. The space between g and the 
 bottom of the still is merely an air-bath, the temperature of which is kept high by the 
 
 flame playing underneath ^, but 
 can never become excessive. In 
 g so much heat is stored up that 
 towards the end of the distillation 
 there is no need to fire up. The 
 weight of the still-body, resting 
 upon the ring-wall, Jc, makes the 
 latter a safe bed for the protective 
 vault, which is quite independent 
 of the masonry of the fire-box, 
 and can be repaired without in- 
 terfering with the work. The 
 flame passes through the four 
 flues, h, into two vertical chan- 
 nels, i, to arrive at the cylindrical 
 jacket-wall of the still. The mas- 
 sive pillar, i', between the chan- 
 nels, i, is continued some distance 
 above. In it there lies, protected 
 from the fire, but kept warm by 
 the channels, i and p, running 
 close alongside, the pipe which 
 connects the exit-cock with the 
 body of the still. The pillar, i, 
 compels the flame to divide into 
 a left and a right stream, which 
 pass round the lowest part of the 
 still-body in the ring- channels, I, 
 are hindered from uniting in 
 front by the pillar i", pass through 
 the flues, m, into the upper ring- 
 channel, n, pass again backwards, 
 and open through o into the per- 
 pendicular shafts, p, which are 
 connected with the main smoke- 
 flue, q. The shafts, p, are inter- 
 rupted at suitable places by slides, 
 by means of which a uniform 
 heat can be kept up on both sides of the still-body. Above the fire flues the body 
 is protected against the radiant heat with a wall, 0*22 metre in thickness; 
 this is carried up above the cover, and preferably above the ascending part, t, of the 
 capital. A protection of this kind is the more necessary when, as it is to be recom- 
 mended, the stills are quite in the open air, or merely covered with a slight roof of 
 corrugated iron. Any explosions or fires are then much less destructive than when 
 
SECT, iv.] TREATMENT OF COAL-TAR. 505 
 
 the stills are fixed in a massive building. When the stills are uncovered, the masonry 
 should be coated with melted pitch as a protection against the rain. 
 
 The charging is effected by means of the cast-iron pipe, r, closed with a slide cock or 
 otherwise, and about 0*15 metre in width, so as not to take too much time in filling the 
 still. If the tar is not pumped in, but let flow down from a tank at a higher level, 
 there is provided a filling-hole, which is afterwards closed with a conical iron plug or a 
 screw. There is also an air-hole through which the height of the liquid can be gauged ; 
 preferable to both is an overflow cock, s, of 25 millimetres in width. Through this 
 there escapes at first air ; if tar flows the feeding is stopped and * is closed. 
 
 The vapours are led through the cast iron capital, t, which tapers from 0*3 to 0*15 
 metre, and is then prolonged into an iron-pipe of the same width, leading to the cooler. 
 Sometimes there is placed at the base of the capital in the inside a channel which 
 leads the liquids condensing in the ascending part of the capital direct to the outside, so 
 that they may not drop back into the still, and occasion frothing. This arrange- 
 ment is scarcely necessary if the ascending part of the capital is covered with poor 
 conductors of heat. Sometimes a steam-pipe is made to open into the capital to 
 remove any obstruction. But with a capital of the above width and with a slight fall 
 such stoppages cannot happen. 
 
 Each still has a man-hole. This is shown at u, as in a steam boiler, and is 
 closed by a lid pressed down by a screw handle. It is tightened either by a border 
 of fatty clay or a ring of asbestos paper. In some places the cover of the man- 
 hole acts as a safety-valve. It consists then of an iron plate lying loosely upon 
 a corresponding short tube, the connecting joints being connected with some cement 
 which does not set too hard. If the pressure in the still rises too high the cover 
 of the man-hole is thrown off before injury can be done. In default of such an 
 arrangement a real safety valve should be provided, as is here shown at w, though many 
 stills are left without such an arrangement. It is very convenient to attach a lateral 
 pipe leading away from the capital, with a safety valve opening downwards, so that in 
 case of boiling over the tar may be led to a place protected from fire. The insertion 
 of a thermometer, v, is to be recommended. It is inclosed in an iron tube filled with 
 iron filings and mercury and reaching down to half the depth of the still. 
 
 In the figure there is seen a system of tubes, x y z, for introducing steam into the 
 still. This is generally effected merely by cross tubes with apertures in their arms for 
 the escape of the steam. Here the full arrangement is shown as designed by Trewly 
 and Fenner. The steam is led in by a pipe 25 millimeteres in width, with a cock, x, 
 which gives off in the inside three descending pipes, y z y. Of these y is connected 
 with the ring-tube, y', which lies at the lowest part of the still, and z is in connection 
 with a system of branch tubes, z, which cover the entire bottom of the still. Both 
 from y and from z' there branch off a great number of open, slightly curved exit tubes 
 with tapering mouths. The steam streaming in through this apparatus is divided into 
 very many slender jets, which sweep over all parts of the still-bottom, prevent it from 
 being overheated, and carry along the vapours of the heavy hydrocarbons. In conse- 
 quence of the great surface of the distribution tubes the steam becomes superheated 
 before escaping, and there is no need for a special superheater. 
 
 Another still, for a charge of 25 tons, has the dimensions given in Fig. 388. The 
 vaulted bottom is rivetted together out of 1 2 plates fixed star-shaped, which are united 
 at their inner ends by a round plate. A German establishment has larger stills, of 4 
 metres diameter and 4 metres in height from the lower angle of the bottom to the 
 upper angle of the cover, and are fitted for the distillation of 35 tons of tar. The 
 bottom of the still either lies in the open fire or is protected by a grating, which 
 is always to be recommended where thick tars are worked, which readily form a 
 deposit of coke on the bottom and allow the plates to become red hot. The cooling 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. iv. 
 
 worms have an inside width of at least 13 centimetres and an incline of 2 per cent, in 
 a length of 48 metres. The trough for receiving the cooling worm is 5! metres long, 
 1-53 metre wide, and 1-23 metre deep. The longitudinal tubes lie no metre apart, 
 measured from middle to middle, and the cross tubes are 476 metres apart, so that the 
 total surface traversed by the tar is about 20 square metres, whilst the largest section of 
 
 Fig- 388. 
 
 --W8S- 
 
 the still is io| square metres. The cooling worm is of wrought iron, and only that part 
 which stands up out of the water and is connected with the beak of the still is of cast- 
 iron, as a wrought iron piece is very quickly destroyed at the point where the surfaces of 
 air and water come in contact. In order to keep the cooling-worm clean, a steam pipe 
 is attached at the point where the beak and the worm meet, and steam is blown in in 
 case napthaline begins to be deposited. But if this crystallisation of napthaline in 
 the cooling- worm has made too much progress the cooling- water has to be heated by 
 blowing in steam, so as to melt the deposit and open the way of issue for the distillate. 
 The stills are filled either by means of a pump or a montejus, in both of which cases 
 the error of having too narrow tubes must be avoided. For tar the pipes should never 
 be below 130 millimetres inside diameter, and for creosote and anthracene oils not less 
 than 80. In filling the still with tar the inflow-pipe must project with its mouth 
 beyond the side of the still, thus preventing the tar from running down the sides, as 
 the plates at this spot are quickly corroded by the sulphur-compounds of the ammonia- 
 water and the tar. Many tars are characterised by an abnormal proportion of carbon, 
 which on distiDing attaches itself to the bottom, and sometimes produces a considerable 
 deposit of coke, even after a single operation, so that the distillation cannot be 
 completed without considerable danger. It is hence advisable, before purchasing, to 
 distil not merely a small quantity of the tar, but to shake out and wash a small average 
 sample with benzol, and to dry and weigh the residue. 42 Westphalian, Ehenish, and 
 North German tars gave proportions of carbon from 7 to 33 per cent. The latter 
 
 percentage was found in the tar of a large, well-arranged gas works on the Rhine, 
 ,.,,,. ' 
 
 which had in consequence great difficulty in the disposal of its tar. In order to distil 
 such tars without injury to the still bottom this carbon should be kept in suspension 
 either by blowing in super-heated steam, or by means of an agitator. By means of the 
 latter expedient it was found possible to effect 15 distillations, each of 25 tons in 
 succession, and to interrupt the work then merely to ascertain the general state of the 
 still. The bottoms, even after such a number of operations, were almost free from coke, 
 and since the introduction of the agitators the consumption of coal had considerably 
 diminished. The only disadvantage lay in the polishing off the rivet-heads in the 
 
SECT, iv.] TREATMENT OF COAL-TAR. 507 
 
 bottom, and wearing out the chains of the agitator, so that after six months it was 
 necessary to re-rivet the bottom and to renew the chain. The bottoms of the stills 
 were uninjured, although they had no protective vaults, and the wearing of the rivet- 
 heads is avoided if they are counter-sunk. It was only possible to distil highly 
 carboniferous tars by means of agitators, and to work upon hard pitch, which was 
 softened by the addition of tar-oils of low value. 
 
 The cooler for pitch is best made of masonry, and not of iron, as the latter material 
 cools too unequally, and renders a frequent cleansing of the cooler needful. After 
 cleaning out with a pick-axe it is recommended to admit steam as dry as possible. 
 
 The distillation must be conducted very cautiously at first, as the tar is apt to boil 
 over as long as any ammonia water is present. According to the indications of the 
 thermometer in the still the following fractions are separated : 
 
 1. First runnings . . . up to 105 or 1 10 
 
 2. Light oils up to 210 
 
 3. Carbolic oils (for phenol and naphthaline), up to 240 
 
 4. Heavy oils . . . . . . up to 270 
 
 5. Anthracene oils above 270 
 
 Towards the end of the distillation the condensing water must be kept warm to 
 prevent the distillate from solidfying in the cooling pipes and causing an obstruction. 
 Steam is often introduced into the still for the same reason, sometimes being previously 
 super-heated. Lunge obtained as an average : 
 
 First runnings ..... 2*4 to 3*5 per cent. 
 
 Light oils 6'0 to 67 
 
 Heavy oils 30-4 
 
 Hard pitch 55-0 
 
 According to Haussermann a tar of German origin gave : 
 
 fractions. 
 
 Light oil 5-0 to 8-0 per cent. 
 
 Heavy oil 25*0 to 30^0 
 
 Anthracene oils 8 g o to io - o 
 
 Pitch 50*0 to 55-0 
 
 final Products. 
 
 Benzol 0*6 per cent. 
 
 Toluol 0*4 
 
 Higher homologues o'5 
 
 Pure naphthaline .... 8'O to 12*0 
 
 Phenol S'o to 6'o 
 
 Anthracene 0*25 to 0*3 
 
 The value of the pitch depends on its proportion of oils, determined by dissolving 
 the sample in benzol, filtering, washing the residue (in benzol), and evaporating the 
 benzol, when the weight of the carbon present is ascertained at the same time. Another 
 method, chiefly followed at briquette works, for determining the quality of soft pitch, 
 consists in keeping a fragment of the sample of about 100 millimetres in length and 10 
 millimetres in thickness, in hot water at 60 for two minutes. The piece must admit of 
 being bent without cracking. For harder sorts a temperature of 70 is used. It serves 
 for the manufacture of " coal-blocks," as an addition to asphalt, to lacquers, for roofing, 
 papers, &c. 
 
 The treatment of the heavy oil for naphthaline is generally not remunerative. It is 
 therefore used for saturating wood, for softening hard pitch, as a tar varnish, for 
 producing blacking, for lighting, or it is burnt like tar. The light oil, the carbolic 
 oil, and the anthracene oil, are worked up specially. 
 
5 o8 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. rv. 
 
 The light oil (crude naphtha) is first treated with strong sulphuric acid, and then 
 with soda-lye, in order to remove the pyrogenous resins, defines, &c. Lunge mixes 100 
 kilos, of naphtha with 12 kilos, sulphuric acid for ten to fifteen minutes, and lets the 
 mixture settle over night. The naphtha is then separated from the acid (the utilisation 
 of which has not yet been effected), washed repeatedly with water, treated with soda-lye 
 of sp. gr. 1*1, washed again, and then distilled. The crude benzol obtained up to 110 
 is farther purified. 
 
 According to Lunge, Fig. 389 shows an apparatus used in English manufactories. 
 The still, a, is heated by the steam-pipe, d, which is continued in a spiral, b, of lead or 
 wrought-iron, with the pipe, g, for carrying off the condensed water. The direct intro- 
 duction of steam is effected by the cock, e, and the cross of perforated tubes, f ; h is the 
 feed-pipe, i the outlet-cock, k the capital. In order to carry away the steam the cock, 
 It is opened, and the steam rushes first into the spirit-catcher, v (which should never 
 
 Fig. 389- 
 
 be wanting), and into the cooling-pipe, w, a lead tube of 35 mm. inside diameter, the 
 end of which, at u, returns into the space where the receivers are placed. The cooling- 
 vat is fed at x with cold water, which runs off hot at y. But if the vapours are to be 
 purified, the cock, I, is closed and m is opened. The vapours then pass into the 
 condenser, n, the lower drum of which is connected with the upper by about fifty 
 copper tubes only 10 mm. wide. The condensed oil runs through the hydraulic 
 joint, r, back into the still. 
 
 Heat is applied at first by the closed steam-pipe, b, and afterwards by the intro- 
 duction of steam through the pipe,y. In order to separate the benzol, which passes 
 over first as free as possible from toluol, the vapours arriving through h are com- 
 pelled to flow into n by closing the cock, I, and opening m, whilst the water of o is 
 heated to a sufficient temperature by means of the steam-cock, s. For so-called Qo-per 
 cent, benzol the water is kept at 60, for 5o-per cent, benzol at 70 or 80 ; but these 
 numbers cannot be absolutely fixed, and must be determined for every apparatus. The 
 
SECT. IV.] 
 
 TREATMENT OF COAL-TAB. 
 
 59 
 
 temperature in o is kept as constant as possible. What condenses in n flows back 
 through r to the still a ; it is chiefly toluol, containing little benzol. What is not 
 liquified in m i.e., vapours of benzol containing little toluol passes into the main 
 steam-pipe, thence into the cooling-worm, w, and the benzol condensed there flows 
 through u into the receiver. 
 
 After some time scarcely anything comes from u, and now, in order to obtain 
 weaker benzoles, the temperature in o must be raised. In general, even if it is desired 
 to produce pure toluol, it is possible to work with water in o, which, however, must be 
 heated to a boil. Water can the more readily be used if the intention is to obtain 
 benzol at 30 or 40 per cent., as is generally the case. In most distilleries it is not 
 sought to effect any further separation into pure hydrocarbons, and hence purification 
 is not carried any further. If nothing more runs from the worm, w, the condenser, n, 
 is thrown out of action by closing the cock, m, and opening I. All the vapours pass 
 now directly to w, and are there condensed, so that there is again an abundant distil- 
 late. By degrees this again grows less, and when little or nothing more is obtained 
 the indirect steam from e is shut off, and by opening d, direct, steam is allowed to issue 
 from the apertures of the cross-tube,/, and we have then, even with steam of only 
 2^ to 3 atmospheres, a plentiful distillation of xyloles and trimethyl benzoles, which 
 mixtures are either used as solvent naphtha and burning naphtha, or are further worked 
 up for xylol, &c. 
 
 The distillation-apparatus of Coupier, very extensively employed, consists (Fig. 390) 
 of the body, B, into which are introduced the benzoles to be submitted to fractional 
 distillation. The still is heated by steam admitted by the pipe, C. The vapours given 
 off from the boiling liquid arrive in the column, N, which acts as a dephlegmater, where 
 the first fractiona- 
 
 tion occurs. The Fig. 390. 
 
 most volatile con- 
 stituents of the 
 vapours, not con- 
 densed in N, ar- 
 rive in the appara- 
 tus, Z>, filled with 
 solution of calcium 
 chloride, which is 
 raised by the 
 steam-pipe, m, to 
 a certain tempera- 
 ture, ascertained 
 by the thermo- 
 meter, t. The 
 steam of the heat- 
 ing-pipe escapes 
 through P. If 
 pure benzol (ben- 
 zene) is to be obtained, the solution of calcium chloride is heated to 80. The 
 vapours arriving at G are a mixture of benzol, toluol, &c. As the temperature of G is 
 not above 80, the vapours of toluol or other homologues, such as xylol, condense there, 
 whilst the vapours not condensable in G pass on to the recipients H, J, K, depositing 
 there the last traces of the less volatile hydrocarbons, and are finally condensed in the 
 refrigerator, L (fed with cold water), and are received in the flask, M. The liquids 
 condensed in G, ff, J, and K pass back into the column, N. As the receiver, (2, contains 
 the heaviest products, they must be conveyed to the lowest part of Jf t whilst the 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. IY. 
 
 products of condensation from K are passed into the upper part of the column. If it 
 be desired to obtain, not benzol but toluol, the temperature of the calcium chloride 
 apparatus must be raised to 108 to 109. 
 
 For obtaining pure benzene a column apparatus is used, such as is employed in 
 rectifying spirits. 
 
 In English commerce the following ultimate products of the light oils and the first 
 runnings are distinguished, to which Lunge (according to his own analysis of the 
 products which he has himself obtained), appends the results of fractionation in volume 
 percentages : 
 
 Commercial names. 
 
 Boils at 
 
 88 
 
 93 ! 100 
 
 IIO 
 
 120 
 
 130 
 
 138 
 
 149 
 
 1 60 
 
 171 
 
 90 p.c. Benzol . 
 
 82 
 
 30 
 
 65 
 
 90 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 50 p.c. Benzol . 
 
 88 
 
 
 
 13 
 
 54 
 
 74 
 
 90 
 
 
 
 
 
 
 
 
 
 
 
 Toluol 
 
 I OO 
 
 
 
 
 
 S6 
 
 90 
 
 
 
 
 
 
 
 
 
 
 
 Carbonating ) 
 naphtha j 
 
 108 
 
 
 
 
 
 
 
 i 
 
 35 
 
 7i 
 
 84 
 
 97 
 
 
 
 
 
 Solvent naphtha. 
 
 110 
 
 
 
 
 
 
 
 
 
 17 
 
 57 
 
 7i 
 
 90 
 
 
 
 
 
 Lamp naphtha . 
 
 138 
 
 
 
 
 
 
 
 
 
 
 
 
 30 
 
 7i-5 
 
 89 
 
 Fig. 
 
 Bannow's boiling vessel (Fig. 391) for determining the boiling point of ' benzol 
 consists of a globular body holding 200 c.c. and made of sheet platinum, silver, or 
 copper of 0*7 mm. in thickness. The diameter is about 73 mm. The body consists 
 
 of two parts, which are held together by four screw 
 clamps, the joint being made good with a washer 
 of pasteboard, slightly moistened or oiled, i mm. 
 in thickness. The upper part carries a short piece 
 25 mm. in length and 20 in width to receive the 
 boiling tube. The glass boiling-tube of 12 to 14 
 mm. outside diameter and 100 mm. in length is 
 expanded globularly in the middle ; the side-piece 
 is melted on at about 10 mm. above the globe, 
 almost at right angles, and so as not to encroach 
 upon the clear internal width of the tube. The 
 body stands upon a plate of asbestos, with a circular 
 aperture of 30 mm. in diameter ; the stove is pro- 
 vided at 10 mm. from its top edge with four round 
 openings for letting out the products of combus- 
 tion. The source of heat is a plain Bunsen burner 
 with an aperture of 7 mm. in diameter ; the flame 
 must burn a pure blue at every position of the 
 cock. The Liebig's condenser to be used is ^ 
 metre in length, and is inclined so that the out- 
 flow is 100 mm. lower than the influx. The ther- 
 mometer has a scale which can be displaced by a 
 screw, and must be made of thin glass ; the out- 
 side diameter must not be more than half the 
 inside diameter of the boiling tube. It is so placed 
 that the bulb shall be in the middle of the globe 
 of the boiling tube. The charge consists of 1 10 c.c. ; 
 
 the first 3 c.c. passing over are to be rejected. The distillation is so regulated that 
 5 c.c. pass over per minute (2 drops per second); it is continued until the graduated 
 receiver is filled up to the mark 100 c.c. A correction for the height of the baro- 
 meter is not applied, but before every experiment the thermometer is adjusted to 
 the boiling point of a standard specimen by means of the movable scale. This is 
 
SECT, iv.] TREATMENT OF COAL-TAR. 511 
 
 done at the moment when 60 c.c. of the 100 c.c. of the type specimen have distilled 
 over. 
 
 On shaking up with sulphuric acid of sp. gr. 1*845 the benzol must not be 
 discoloured at all and the acid not immediately. In ten minutes it may turn slightly 
 yellow. If poured into nitric acid at 72 Tw. no white vapours must be produced, and 
 on shaking the benzol must not be coloured. On prolonged standing the nitric acid 
 turns slightly reddish; afterwards it becomes colourless and the redness passes to 
 the benzol. 
 
 Benzene. The pure substance C 6 H 6 boils at 80 and solidifies at o sp. gr. at o* = 
 0-8991 ; at 15 = o'884i. It is slightly soluble in water, easily soluble in alcohol, ether 
 and methyl-alcohol. Common coal-tar benzol contains generally thiophene, C 4 H 4 S, 
 and carbon disulphide. 
 
 Toluol (called toluene when absolutely pure) a benzyl-benzol C 7 H 8 or 6 H 5 .CH 8 , 
 boils at 1 10 ; its sp. gr. at 15* = 0-872. It is also obtained from wood-tar. 
 
 Xylol or dimethyl-benzol from coal tar C 8 H 10 = C 6 H 4 (CH S ), boils at 138 to 140. 
 
 The light oil, containing some benzol, much toluol and its higher homologues, 
 phenoles, naphthaline and liquid oils is rectified. The fraction up to 120 is added to 
 the corresponding fraction of the first runnings (of the main distillate up to 150). The 
 fraction from 150 to 190 is purified with acid and alkaline lye, and is then taken to a 
 second rectification. The residue (above 190) goes to the heavy oils. The second 
 rectification of the chemically purified fraction 120 to 190 gives : 
 
 (a) Product up to 120 contains benzol and toluol, and comes to the corresponding 
 product from the first runnings. 
 
 (b) Product from 120 to 127 gives benzene No. i. for taking out spots. 
 
 (c) Product from 127 to 140 gives benzene No. 2. 
 
 (d) Product from 140 to 150 gives benzene No. 3. 
 
 (e) Residue comes to the heavy oil. 
 
 For obtaining phenol it is advantageous not to work up all the light oil, but to 
 take the portion which passes over last, the so-called carbol-oil, which has in general 
 the sp. gr. 0-99 to 1-005. It is treated with soda lye, which dissolves the phenoles, 
 (tar-acids), whilst the oil not soluble in soda is worked up for naphthaline. The solution 
 of sodium carbolate is decomposed by the addition of sulphuric acid, or, better, by passing 
 into it carbonic acid. 
 
 The crude carbolic acid thus obtained contains only about 50 per cent, phenol with 
 water, creosotes, naphthaline, &c. It is purified by redistillation, and the part passing 
 over between 175 to 200 is set in a cool place to crystallise. Or the crude carbolic 
 acid is treated with i per cent, potassium dichromate and the quantity of sulphuric acid 
 at 1*845 sp. gr. necessary for its decomposition, stirring constantly. This is done in a 
 fiat vessel, so that the carbolic acid may present the greatest possible surface to the air ; 
 the sulphuric acid is added first, and then the solution of the dichromate, and the whole 
 is stirred for some hours, being placed if possible in a place exposed to the sun. The con- 
 tents of the flat pan are then drawn off into a deep glass jar, allowed to settle, and the oil 
 is drawn off and distilled between 1 70 to 198, whilst the first runnings of this distillation 
 are added to the next distillation of crude oil, and the residue in the still is again distilled 
 with the crude tar. The fraction passing over between 170 and 198 is again treated 
 in a flat vessel with i per cent, potassium dichromate, and a corresponding quantity of 
 trong sulphuric acid, stirred for some hours, drawn off from the dregs and distilled in 
 a small column apparatus. The distillate is collected in small half -litre bottles until the 
 contents of the still begin to become thick, which is found by stirring with an iron rod. 
 The bottles are at once well closed, and let stand to crystallise, the oil is poured off from 
 the crystals, which are melted in the water bath, and collected in dry litre glass 
 bottles. 
 
5 12 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. iv. 
 
 Phenol (carbolic acid), C 6 H 5 OH, melts at 42 and boils at 182. It dissolves in 20 
 parts of water, but at any proportion in alcohol, ether and benzene. Phenol is poisonous, 
 but it is a good disinfectant. The cause of its turning red has not been ascertained 
 with certainty. 
 
 The quantitative determination of phenol is effected volumetrically with bromine. 
 It is used in preparing colours, explosives (picrates) and as a disinfectant. 
 
 Cresol, or the cresylic acid of coal-tar, C 7 H 8 O or C 6 H 4 .CH 3 OH, boils at 190 to 203, 
 and is a variable mixture of metacresol, orthocresol, and paracresol. 
 
 The oil drawn off from sodium carbolate is first re-distilled, and then set in a cold 
 place, the naphthaline which crystallises out is pressed and once more distilled. This 
 distilled naphthaline, in order to remove the pyrogenous resins, is melted in a double iron 
 pan lined with lead, along with i per cent, of sulphuric acid at 156 Tw., and stirred 
 for some hours. After prolonged settling, the sulphuric acid is separated from the 
 naphthaline and the latter is sublimed in an upright still over an open fire. Into the 
 naphthaline there opens a pipe for the direct admission of steam, and in the capital of 
 the still a pipe which introduces steam from a fine aperture. As soon as the ther- 
 mometer plunging into the naphthaline marks 160, dry steam is let in very gently 
 from both pipes. The beak of the still opens into the sublimation building, consisting 
 of an antechamber and a main chamber 1 2 metres long, 3 metres high, and 2 metres 
 in breadth. The liquid naphthaline passing over collects in the antechamber, which is 
 3 metres in length. 
 
 According to another communication there is used a subliming chamber, A (Fig. 392), 
 5 metres long and 3 metres wide. The wrought-iron pan, B, 3 metres long and i metre 
 
 broad, is built in so over 
 
 392- the grated arch, C, that 
 
 the fire-gases from the 
 heating-room pass back- 
 wards through D, below 
 the grated arch, rise up 
 in the flues, E E, leading 
 round the subliming 
 pan, B, and escape at 
 the chimney. The door, 
 F, which turns on an 
 axle, G, is luted up 
 with clay during the sub- 
 limation. Two wooden 
 covers, H, coated with 
 sheet-iron placed above 
 
 the pan, rest upon iron clasps which are secured in the two side walls, cutting off the 
 door, F. These two doors act like the dephlegmators in distillation, as vapours of the 
 heavier, less volatile tar oils, carried along by the vapours of the naphthaline condense 
 here on their surfaces and flow back into the pan. The wooden door, J, also lined 
 with sheet-iron, can be removed on cleaning the naphthaline out of the chamber. To 
 the iron air-pipe, L, 8 centimetres in thickness, there hangs the dish, M, which serves 
 to catch the water condensed in the air-pipe. The pan is filled with crude naphthaline 
 and from 3 to 4 per cent, of slaked lime is added ; the doors are then luted up with 
 clay, and at first a strong fire is kept up, but as soon as the sublimation begins it is 
 kept very slight and uniform. In the door, F, there is a small hole so that the depth 
 and the quality of the naphthaline remaining in the pan can be tested with an iron rod. 
 The hole, of course, is closed with a cork. In two-and-a-half to three days, if the heat 
 has been maintained all day, the pan will be empty down to 6 to 8 centimetres. It is 
 
SECT, iv.] TREATMENT OF COAL-TAR. 513 
 
 now frequently tested with the iron rod, and when it is seen that the naphthaline no 
 longer congeals upon the iron the heating is stopped, because merely heavy tar oils 
 remain in the pan. The pan is then emptied, charged afresh, and the sublimation is 
 continued. When two or three pans have thus been worked off the sublimed naph- 
 thaline is cleared out of the chamber. It is melted in an open cast-iron pan with an 
 emptying spout, and mixed with a 20 per cent, lye at 27 Tw., the lye is let off and 
 there is added to the liquid naphthaline 6 per cent, of sulphuric acid at 156 Tw., 
 and a little pyrolusite. After stirring diligently for fifteen or thirty minutes, according 
 to the size of the pan, the naphthaline is allowed to settle, and in an hour the acid is 
 drawn off. The naphthaline is then twice washed with hot water to remove any 
 traces of acid, and once more sublimed. 
 
 Naphthaline, C 10 H 8 , forms thin, white, rhombic leaflets of a peculiar odour some- 
 what like that of storax, and of a burning taste. After fusion and solidification it appears 
 as dazzling white crystalline masses of sp. gr. ri5i. It melts at 79 and boils at 
 216 to 218. It is insoluble in cold water, very slightly soluble in hot water, easily 
 soluble in boiling alcohol, benzol, in the volatile and the fatty oils, and in acetic acid. 
 
 Anthracene oil when cold forms a greenish-yellow mass, of a buttery consistence, 
 consisting, besides oils of high boiling points, of naphthaline, methylnaphthaline, anthra- 
 cene, phenanthrene, acenaphthine, diphenyl, methylanthracene, pyrene, chrysene, retene, 
 fluorene, acridine, &c. The anthracene oil is let cool, when crude anthracene crystal- 
 lises out and is separated from the oils in a filter-press. This 28 per cent, crude 
 anthracene is dissolved by heat (in a double pan, arranged for steam-heating and water- 
 cooling and fitted with an agitator) in 120 per cent, creosote oil, from which the 
 phenols have been removed by treatment with soda-lye. This creosote oil, boiling at 
 220 to 320 is very suitable for removing paraffine from anthracene. The solution of 
 paraffine is stirred until cold with water refrigeration and is then forced through a 
 filter-press. The product so obtained contains 36 to 40 per cent, of actual anthracene. 
 If it has to be brought to a higher grade this can be effected by a repeated washing in 
 tar oils, but in this manner much anthracene is dissolved. A pure product is obtained 
 by distilling the 36 per cent, anthracene with caustic potassa at 30 per cent. The 
 anthracene is distilled in horizontal cylinders of wrought-iron or cast-iron, 1-2 metre 
 in diameter, 2*2 metres long, and containing about 26 hectolitres. The fire-gases pass 
 through two channels at the bottom of the cylinder, which is protected against the 
 direct action of the flame by fire-proof plates, and pass then along its sides. The 
 distillate runs through an air-cooler into iron pans, in which the anthracene (now 48 
 per cent.) crystallises. The residue in the cylinder, containing carbazol and potassa, as 
 it is spontaneously inflammable in contact with air, is immediately after distillation 
 drawn off into iron chests, allowed to cool and burnt on an open grate in a furnace for 
 crude potash. Here a flue-dust chamber must be arranged between the chimney and the 
 exit channel in order not to let the fine dust of potash escape into the air. The loss of 
 anthracene in this purification with caustic potassa is, in good kinds, 2 per cent., but 
 in inferior sorts as much as 12 per cent. If a high-grade anthracene is required, this 
 anthracene distilled over potassa can be easily brought up to 70 per cent, by dissolving 
 it in 140 per cent, of heavy benzol, boiling at 140 to 170, stirring till cold, pressing 
 and recovering the heavy benzol which adheres to it by heating with indirect steam. 
 The total loss in heavy benzol in large works, properly arranged, is z\ per cent. 
 Instead of heavy benzol, creosote oil washed in soda lye may be used, and after 
 hydraulic pressure the residual creosote oil may be removed by direct steam entering 
 through a perforated false bottom. After the anthracene has been washed the heavy 
 benzol contains large quantities of phenanthrene and heavy oils, as well as of dissolved 
 anthracene, from which the benzol is separated by direct and indirect steam. The 
 crude phenanthrene and the oils running off on hydraulic pressure contain up to 8 per 
 
 2 K 
 
5 i 4 CHEMICAL TECHNOLOGY. [SECT iv. 
 
 cent, of anthracene. From phenanthrene it is extracted by adding to the distilled 
 anthracene, during the purification with benzine, about 20 per cent, of phenanthrene. 
 From the press-oils the anthracene may be advantageously recovered by fractional 
 crystallisation during the winter. 
 
 Anthracene, C 14 H 10 , melts at 210 to 213, and boils at 360. It is insoluble in water, 
 slightly soluble in alcohol, ether, and benzol, but more freely in toluol* 
 
 Organic Colouring Matters. Up to the middle of the present century, organic 
 colouring matters were obtained solely from plants and from a few animals (cochineal, 
 &c.) With the discovery of aniline violet in 1856 by Perkins, tar-colours were added 
 to those from natural sources. These artificial products have superseded to some 
 extent several of the natural colours, alizarine, the colouring principle of madder, being 
 now almost exclusively obtained from coal-tar. 
 
 Red Colours. Madder. Madder is the root of the Rubia tinctorum, a perennial 
 plant cultivated in Southern, Central, and Western Europe ; while in the Levant the 
 R. peregrina, and in the East Indies and Japan the R. mungista (mungeet), are partly 
 cultivated, partly met with in the wild state. According to researches made in 
 England, the dye imported under the name of mungeet from India is not the root, 
 but the reedy stem of a species of Rubia, and as a dye it is inferior. The native 
 country of the madder plant is the Caucasus. All these plants are perennial. The 
 root varies in length from 10 to 25 centimetres ; it is not much gnarled, and is gene- 
 rally a little thicker than the quill of a pen. Externally the root is covered with 
 a brown bark ; internally it exhibits a yellow red colour. Madder is met with in the 
 trade as the root (technically ratine, if European), and in powder exhibiting a red- 
 yellow colour-, and possessing a peculiar odour. Avignon madder, however, has hardly 
 any smell ; but the odour is particularly marked in Zeeland, or so-called Holland, 
 madder. The powdered madder is always kept in strong oaken casks, so as to 
 exclude air and light. The best kind of madder is that grown in the Levant (Smyrna 
 and Cyprus), and met with in the trade under the name of lizari or alizari, in 
 roots, which are usually rather thicker than the roots of the European varieties, owing 
 partly to the fact that the Levant madder is generally of four to five years' growth, 
 while in Europe the roots are of two to three years' growth only. Dutch madder, 
 chiefly grown in the province of Zeeland, is met with decorticated (robe), the outer bark 
 and sometimes the splint bark having been removed. The well-dried roots are 
 broken up by means of wooden stampers moved by machinery, to reduce the bark and 
 splint bark to powder, while the very hard internal portion of the root is left untouched, 
 this being separated from the powder by means of sieves. The powder is put into 
 casks and termed beroofde. During the last ten or twelve years the old madder sheds 
 (meestoven) in Zeeland have been superseded by large manufactories, in which the 
 madder root is treated as it is in the Vaucluse (France), and ground up entirely, so- 
 that the former distinct qualities of madder are no longer met with. When the 
 whole root is pulverised the madder is termed onberoofde, non robe. Besides the Dutch 
 madder, that from Alsace and from the "Vaucluse, Avignon, occurs very largely in the 
 trade. What is known as mull madder is the refuse and dust from the floors of the 
 works, and is the worst quality. In addition to colouring matter, madder contains a 
 large quantity of sugar, of which W. Stein (1869) found as much as 8 per cent. While 
 it was formerly considered that madder contained no less than five different colouring 
 substances, it appears from recent researches that this root in the fresh state only con- 
 tains two pigments, viz., ruberythrinic acid (formerly termed xanthin) and purpurine. 
 According to Dr. Rochleder, the former of these is converted under the influence of 
 
 * For further particulars on the primary coal-tar products the reader may consult G. Lunge, 
 Coal-Tar and Ammonia, Gurney & Jackson, London; and Anthracene, its Properties, &c,, by 
 G. Auerbach, edited by W. Crookes, F.R.S., &c. : Longmans, London. 
 
SECT, iv.] TREATMENT OF COAL-TAR. 51$ 
 
 a peculiar nitrogenous substance present in the madder root into alizarine the 
 essential colouring matter of madder and into sugar : 
 
 C^H^ + 2 H 2 = C M H,0 4 + 20^0 P 
 
 Ruberythrinic Alizarine. Sugar, 
 
 acid. 
 
 According to the researches of Graebe and Liebermann, alizarine is a derivative 
 from anthracen, C 14 H 10 , the formula of the former being C 14 H 8 O 4 . As elsewhere mentioned 
 the same chemists have succeeded in converting anthracen into alizarine (169). 
 Alizarine is yellow, but becomes red under the influence of alkalies and alkaline earths. 
 Madder contains a red pigment, purpurine, or rubiacine, C 14 H g 5 , which by itself, as 
 well as in combination with alizarine, yields a good dye.* 
 
 Madder Lake. We understand by this term a combination of alizarine and pur- 
 purine (the colouring matter of madder) with basic aluminium salts. Madder lake is 
 prepared by first washing madder with water, distilled, or at least free from lime salts, 
 next exhausting the dye-stuff" with a solution of alum, the liquor thus obtained being 
 precipitated with sodium carbonate or borax. The bulky precipitate, having been 
 collected on a filter, is thoroughly washed and dried. 
 
 Flowers of Madder. The preparation made from madder on the large scale, and 
 known in the trade as flowers of madder (fleur de garance), is obtained from the 
 pulverised madder by steeping it in water, inducing fermentation of the sugar con- 
 tained in it, and next thoroughly washing the residue, first with warm, next with 
 cold water. The residue, after subjection to hydraulic pressure to remove the- 
 water, is dried at a gentle heat, and having been pulverised again, is used in the 
 same manner as madder for dyeing purposes. The operation of dyeing with 
 the flowers of madder requires a less elevated temperature of the contents 
 of the dye-beck. It would appear that by the preparation of the flowers of madder 
 the pectine substances of the root are eliminated, which otherwise become insoluble 
 during the operation of dyeing. 
 
 Azak. When flowers of madder are treated with boiling methylic alcohol (wood- 
 spirit), the solution obtained filtered, and water added to the filtrate, a copious yellow 
 precipitate is obtained, which having been washed with water and dried constitutes the 
 material known as azale (from azala, Arabian for madder), which has been suggested for 
 use as a dye material in France. Probably this substance is crude alizarine ; as obtained 
 from madder or garancine, it is sometimes met with in the trade under the name of 
 Pincoffine, having been first discovered and prepared by Mr. PincofFs at Manchester. 
 
 Garancine. This preparation of madder contains the colouring principles of the root 
 in a more concentrated, pure, and more readily exhaustible state. In order to pre- 
 pare garancine, madder (generally this term is given to the pulverised root) is first 
 moistened uniformly with water, and next there is added part of sulphuric acid 
 diluted with i part of water. This mixture is heated by means of steam to about 100 
 for one hour, and the magma then thoroughly washed with water for the purpose of 
 eliminating all the acid. This having been done, the garancine is submitted to hydraulic 
 pressure for the purpose of getting rid of the greater part of the water, after which the 
 material is dried and lastly ground to a very fine powder. By the action of the sulphuric 
 acid some of the substances contained in madder, and more or less interfering with its 
 application as a dye, are eliminated in the washing of the garancine, while the colouring 
 matter remains mixed with the partly carbonised organic substances. As regards its 
 tinctorial value i part of garancine may be taken as equal to 3 to 4 parts of madder. 
 
 Garanceux. As madder when employed in dyeing does not become quite exhausted, 
 the fluids of the dye-beck are strained from the solid residue, and this is treated with half 
 * Mungistine, C 16 H S 6 , is found in madder from India (rnunjeet), and dyes like alizarine. 
 
5i6 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 of its weight of sulphuric acid. The mass is next treated as has been described under 
 garancine, and constitutes after drying what is known as garanceux, being used generally 
 for the production of what are termed sad colours (black, deep brown, lilac). As a 
 matter of course garanceux is of less tinctorial value than garancine. 
 
 Colorine. The substance met with in commerce under the name of colorine is the 
 dry alcoholic extract of garancine, and consists essentially of alizarine, purpurine, fatty 
 matter, and other substances soluble in alcohol present in garancine. E. Kopp com- 
 menced some years since to exhaust madder with an aqueous solution of sulphurous 
 acid, thereby obtaining the pigments of madder in a (for technical purposes) pure con- 
 dition. These preparations, which are already extensively used, are distinguished as : 
 Green alizarine (Alizarine verte), which from Alsace madder is obtained to an amount 
 of about 3 per cent., containing with the alizarine a green resinous material ; yellow 
 alizarine (Alizarine jaune), the former substance without the resinous material, this 
 having been "eliminated by suitable solvents, as purpurine and flowers of madder. 
 The tinctorial value of purpurine amounts to 10 times and that of the green and 
 yellow alizarine to 32 to 36 times that of madder. Madder of good quality yields on 
 the large scale * 
 
 Purpurine . . . . . . 1-15 per cent. 
 
 Green alizarine 2*50 
 
 Yellow alizarine 0-32 
 
 Flowers of madder . . . . 39*00 
 
 Safflower. The drug to which this name is given consists of the dried petals of the 
 flowers of the Carthamus tinctorius, a thistle-like plant belonging to the family of the 
 Synantherece, a native of India, and cultivated in Egypt, the southern parts of Europe, 
 and also to some extent in parts of Germany. Saffiower contains a red matter, 
 carthamine, insoluble in water, and also a yellow substance soluble in that liquid. 
 The quality of this drug is better according to its greater purity from mechanical 
 admixtures, such as seeds, leaves of the plant, &c. Carthamine, C 14 H 16 O 7 , or Rouge vegetal, 
 is prepared in the following manner : The safflower is exhausted with a very weak 
 solution of sodium carbonate, and in this fluid strips of cotton-wool are dipped, after 
 which the strips are immersed in vinegar or very dilute sulphuric acid for the purpose 
 of neutralising the alkali. The red-dyed cotton strips are next washed in a weak 
 solution of sodium carbonate, and the solution thus obtained is precipitated with an 
 acid; the carthamine thrown down is first carefully washed, and next placed on 
 porcelain plates for the purpose of becoming dry. Carthamine when seen in thin films 
 exhibits a gold-green hue, while when seen against the light the colour is red. When 
 carthamine has been repeatedly dissolved and precipitated it is termed safflower- 
 carmine. Mixed with French chalk (a magnesium silicate), carthamine is used as a 
 face powder. Safflower is used for dyeing silk, but the red colour imparted is, although 
 brilliant, very fugitive. 
 
 Carthamine is used for red tape, as the exact shade preferred by consumers has 
 not been obtained from coal-tar colours. 
 
 Cochineal, or Cochenille. This substance is the female insect of the Coccus cacti 
 found on several species of cacti, more especially on the Nopal plant and the Cactus 
 opuntia. This insect and the plants it feeds on are purposely cultivated in Mexico, 
 Central America, Java, Algeria, the Cape, &c. The male insect, of no value as a dye 
 material, is winged, the female wingless. The female insects are collected twice a year 
 after they have been fecundated and have laid eggs for the reproduction of young, and 
 are killed either by the aid of the vapours of boiling water or more usually by the heat 
 of a baker's oven. Two varieties of cochineal are known in commerce, viz., the fine 
 cochineal or mestica, chiefly gathered in the district of Mestek, a province of Honduras, 
 on the Nopal plants there cultivated ; and the wild cochineal, gathered from cactus 
 
 * Since the introduction of artificial alizarine the cultivation of madder has been almost 
 abandoned. 
 
SECT, iv.] TREATMENT OF COAL-TAR. 517 
 
 plants which grow in the wild state. This latter variety is of inferior quality. 
 Cochineal appears as small deep brown-red grains, at the lower and rather flattened 
 side of which the structure of the insects is somewhat discernible. Sometimes the 
 dried insect is covered with a white dust, but frequently the material is met with 
 exhibiting a glossy appearance and black colour. The white dust, very frequently 
 fraudulently imparted by placing the grain with French chalk or white-lead in a bag, 
 is, according to the results of microscopical investigation, the excrement of the insect, 
 exhibiting when seen under the microscope the shape of curved cylinders of very 
 uniform diameter and a white colour. Cochineal contains a peculiar kind of acid 
 carminic acid which, by the action of very dilute sulphuric acid and other reagents, is 
 split up into carmine-red (carmine) also present in the insect, together with the acid 
 and into dextrose 
 
 Carminic Carmine- Dextrose. 
 
 acid. red. 
 
 What is commonly termed carmine is prepared by exhausting the cochineal with 
 boiling water ; to the decanted clear fluid alum is added, after which it is allowed to 
 settle. By another method carmine is prepared by exhausting the pulverised cochinea 
 with a solution of sodium carbonate ; white of egg is next added to this solution for the 
 purpose of clarifying it, and afterwards the solution is precipitated with an acid. In 
 either case the washed precipitate is next diied at 30. So prepared, a finer and better 
 kind of carmine is obtained, but the common carmine carmine lake and round lake is 
 prepared by treating an aluminous solution of cochineal with sodium carbonate ; the 
 larger the quantity of alumina contained in these preparations, the coarser the quality. 
 
 Lac Dye. This dye-stuff is obtained from a resinous substance, stick or grain lac, 
 or gum resin, and is derived from a variety of the cochineal insect in the following 
 manner : The Coccus laccce, a native of India, pierces the branches of certain kinds of 
 fig-trees, from which a milky juice exudes, which, while becoming inspissated, encloses 
 the insects, and at last forms a hard resinous mass tinged with the dye-stuff contained 
 in the insects. This pigment is extracted from the resinous matter by means of a 
 solution of sodium carbonate, and the solution obtained is precipitated by alum solution. 
 The lac dye is not very different from cochineal. 
 
 Lac shades are somewhat more permanent than those obtained from cochineal, as 
 the carminic acid is accompanied by resinous matter. 
 
 Tyrian Purple. The secretion of the purple snail, which on exposure to sunlight 
 forms the " purple " of antiquity, is not now an article of commerce. 
 
 Weed Colours. By orchil, or archil and cudbear (called persio on the Continent), 
 we designate red dyes which are met with in commerce in pasty masses. Orchil is 
 prepared from several kinds of sea-weed, Roccella tinctoria,R.fuciformis,R. Montagnei, 
 Usnea barbata, Usnea florida, Lecanora parella, Unceolaria scruposa, Ramalina calicaris, 
 Gyrophora pustulata, and others, which having been well dried, are first ground to a 
 very fine powder. This is mixed with ammonia and left to enter into putrefactive 
 fermentation. The ammonium carbonate* acting upon the peculiar acids lecanoric, 
 alpha- and beta-orcellic, erythrinic, gyrophoric, evernic, usninic, &c. contained 
 in these sea-weeds, converts these non-nitrogenous substances into orcine, C 7 H 8 0,, 
 this reaction being accompanied by the elimination of water, and usually also 
 with the elimination of carbonic acid. By taking up nitrogen and oxygen orcine 
 is converted into orceine, C 7 H 7 NO,, constituting the essential colouring matter of 
 orchil. This substance appears as a red paste, exhaling a peculiar violet odour 
 (viola odorata) and having an alkaline taste. Before the coal-tar colours were 
 discovered this dye material was prepared chiefly in England and France from 
 
 * Stale urine, or '/, was formerly used instead of solution of ammonia. 
 
S t8 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 weeds collected on the Pyrenees, or imported from the Canary Islands, or from 
 Lima and Valparaiso. Cudbear, or red-indigo, is much the same kind of product 
 as orchil, from which it differs mainly in being freed from all excess of ammonia 
 and from moisture, and in being reduced to a fine powder; it was formerly 
 prepared in Scotland from sea-weeds found on the coast. At a later period it was 
 made in large quantity in Germany, in France, and in England. Persio was a red 
 yiolet powder. Some ten years ago two preparations of orchil were brought into 
 commerce under the names of orchil carmine and orchil purple (pourpre Francois). 
 -These substances contained the orchil dyes in a very pure condition. Since the tar- 
 colours have made their appearance the dyes obtained from the sea-weeds, very 
 beautiful but very perishable colours, have in a great measure become obsolete". 
 
 Less Important Red Dyes. Among the less important red dyes and colouring 
 matters are the alkanet root (Anchusa tinctoria) ; dragon's blood, a red-coloured resin 
 from Dracaena draco ; harmala red from the seeds of the Peganum harmala, a plant 
 growing in the Steppes of Russia ; chica red, or carajura, from the leaves of the 
 Bignonia chica, a tree growing in "Venezuela ; purple-carmine, or murexide, obtained 
 from uric acid by treating it with oxidising substances (nitric acid for instance) and 
 next with ammonia. 
 
 Murexide produces reds and purples equal to the aniline dyes, but it is more 
 expensive, and the supply of those guanos which are rich in uric acid is falling off. 
 
 lied Woods. There are two distinct classes of red woods used by dyers and printers, 
 by the manufacturers of red inks and of certain pigments. On the one hand are the 
 soft woods, all produced by different species of the genus Caesalpinia. The principal 
 kinds are Pernambuco wood, Brazil wood, peach wood, Lima wood, Nicaragua wood, 
 Santa Martha wood, Brazilette and Sapan wood. All these except the last are 
 produced in Central and South America. Sapan is a product of India and Siam. 
 The colouring matter of these woods, Brasiline, (C 22 H 18 7 according to Kopp, but 
 to Liebermann C 16 H 14 5 ), crystallises in small colourless needles, but the watery 
 solution, on exposure to the air, and especially on boiling or in presence of alkalies, 
 turns crimson. 
 
 In dyeing, a very fine but fugitive red colour is obtained from the red woods. 
 
 The red woods are extensively used for the production of red inks. For this 
 purpose there are taken 250 grammes red wood, 30 grammes alum, 30 grammes tartar, 
 and 2 litres water, and the decoction is boiled down to 2 litres. The liquid is filtered ; 
 and for those who like a perfectly limpid ink it is now ready for use. Those who 
 prefer inks which may clog in the pen and dry slowly add 30 grammes gum-arabic and 
 30 grammes sugar-candy. A finer and more permanent ink is obtained by dissolving 
 2 decigrammes carmine in 15 grammes liquid ammonia. At present red inks are 
 made simply with solution of magenta to which a little alum has been added, or by 
 dissolving aurine (rosolic acid) in sodium carbonate, or simply with eosine alone. Eosine 
 ink is made by dissolving i part eosine in 150 to 200 parts boiling water. Yiolet 
 aniline ink is obtained by dissolving i part soluble aniline violet blue in about 300 
 parts of water. 
 
 Brasilein, C 16 H 12 5 , an oxidation product of brasiline, forms small dark crystals with 
 a greyish metallic lustre, which dissolve in hot water with a bright rose colour and an 
 orange fluorescence. 
 
 The second class of red woods, the hard woods, comprise barwood, camwood, 
 ganders or santalwood and calliatura wood. The colouring matter of these woods 
 is very sparingly soluble in water and is accompanied with a yellow principle, so that 
 they dye tones more inclining to a scarlet. Barwood and camwood are obtained 
 from Africa, and are both said to be the product of Baphia nitida, though the colouring 
 matter of camwood is found in practice to be the more soluble. They contain 23 per 
 
83CT. iv.] TREATMENT OF COAL-TAR. 519 
 
 cent, of colouring matter. In like manner santalwood and calliatura are alleged to be 
 identical, the tone of the colour being modified, perhaps by difference of soil. Both 
 are obtained from India. Their colouring principle, santaline, contains C 17 H 16 6 . 
 
 The dyewoods of whatever colour are met with in commerce in four different 
 states; in chips, in raspings, in liquid extracts, or in solid or paste extracts. These 
 different preparations are used according to the texture of the materials to be dyed or 
 printed. 
 
 Most woods require after chipping or rasping to lie exposed to the air for some 
 time, and to expedite the process they are sprinkled with water. This addition is 
 carried to such a height that it becomes a fraud.* 
 
 The liquid extracts of the woods are often found to contain treacle (beet), dextrine, 
 sodium sulphate, and extracts of materials of little tinctorial value, such as of chestnut, 
 and quebracho. Extract of sumac is rarely added. 
 
 The proportion of the ash found in an extract is no better guide to its quality than 
 is the specific gravity. 
 
 For detecting and determining treacle, starch, sugar, and dextrine, L. Brueh 
 proceeds as follows : from i to 5 grammes of the extract dried at 100 are treated 
 with absolute alcohol until the alcoholic solution no longer gives colour reactions. The 
 sugar and the dextrine remain in the residue along with other colouring matters. 
 
 Blue Colouring Matters. Indigo. Indigo is the chief blue dye. Although known 
 to the Romans and Greeks, who used it for painting purposes, it was not employed 
 as a dyestuff in Europe until about the middle of the sixteenth century. Indigo is a 
 substance which is widely dispersed in the vegetable kingdom. It is found in large 
 quantity in the leaves of several species of the anil plants, Indigofera, belonging to 
 the family of the Papilionacece. Indigo is also obtained from woad, Isatis tinctoria, 
 JYerium tinctorium, Marsdenia tinctoria, Polygonum tinctorium, Asclepias tingens, &c. 
 The indigo is not met with in the plants ready formed, but is generated when the 
 freshly-pressed juice of the plant is exposed to the action of the atmosphere. 
 
 According to the results of a series of experiments, it appears that in the living 
 plant the colourless pigment is present in combination with a base, lime or an alkali. 
 Dr. Schunck states that the indigo plant contains a material which he has termed 
 indican, which either by fermentation or by the action of strong acids is converted 
 into indigo blue and a peculiar kind of sugar, indigo glycine, according to the following 
 formula 
 
 C^NA, + 4 H 2 - flja^O,,* 6C^y 
 Indican. Indigo blue. Indigo glycine. 
 
 The indigo of commerce is prepared from the indigo plants in the East and West 
 Indies, Southern and Central America, Egypt, and other parts. In Hindostan indigo 
 is prepared from the Nerium tinctorium. The following five varieties of the indigo 
 plant are more particularly employed for the preparation of this dye material : 
 Indigofera tinctoria, I. anil, I. disperma , I. pseudotinctoria, and /. argentea. The 
 plant requires a warm climate and a soil so situated that it is not liable to become 
 inundated. When the plants have grown to maturity they are cut down with a sickle 
 close to the soil and transferred to the factory, where the indigo is extracted from the 
 plant by the following process : The factory is fitted with large water tanks, filtering 
 apparatus, presses, a cauldron, drying-room, and, lastly, with fifteen to twenty tanks 
 t>f brickwork laid in hydraulic cement and plastered inside with the same material. 
 Into these tanks the branches, twigs, and the leaves are placed, and water is run in, 
 care being taken to force the green plants down under the water by the aid of stout 
 .wooden balks wedged tight against the sides of the tanks. At the usual high tempera- 
 * Compare Slater, Manual of Colours : Lockwood & Son, London. 
 
5 20 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 ture of the air in the tropical regions fermentation soon sets in, and the liquid con- 
 tained in the tanks assumes a bright straw-yellow or golden-yellow colour, a large 
 quantity of gas is evolved, and after a lapse of nine to fourteen hours, the liquid, 
 having become of a deeper yellow hue, or almost the colour of sherry wine, is run from 
 the fermenting tanks into a very large tank of similar construction, into which, when 
 as full as may be judged convenient, a number of workmen enter, provided with long 
 bamboo poles, and commence stirring the fluid vigorously for the purpose of exposing 
 it as much as possible to the action of the air. During this operation, continued for 
 some two or three hours, the colour of the liquid gradually changes to pale green, and 
 the indigo may then be seen suspended in the liquid in very small flocks. The liquid 
 is then left to stand, and the suspended matter gradually subsiding, the water is 
 gradually run off by the aid of taps or plugs fitted into the tank at different heights. 
 At last the somewhat thick, yet fluid, precipitate of indigo is run into a cauldron, 
 where it is boiled for about twenty minutes in order to prevent it fermenting a 
 second time, for by this second fermentation it would be rendered useless. The 
 magma is left in the cauldron over night and the boiling resumed next day, and then 
 continued for three to four hours, after which the indigo is run on to large filters, con- 
 sisting first of a layer of bamboo, next mats, and on these stout canvas, all placed in 
 a large masonry tank. Upon the canvas is left a thick, very deep blue, nearly black 
 paste, which is thence taken and put into small wooden boxes, perforated with holes 
 and lined with canvas ; a piece of canvas is put on the top of the paste, and next a 
 piece of plank is fitted closely into the box. So arranged, a number of these are 
 placed under a screw-press for the purpose of eliminating, by a gradually increased 
 pressure, the greater portion of the water, and thus solidifying the pasty material. On 
 being removed from these boxes the cakes of indigo are transferred to the drying-room, 
 and there, daylight and direct sunlight being carefully excluded, gently dried by the 
 aid, in some cases, of artificial heat. In order to prevent the cracking of the cakes, 
 the drying has to be effected very gently, and lasts usually for some four to six days. 
 The dried cakes of indigo are next packed in stout wooden boxes and then sent into 
 the market. The exhausted plants are used for a manure, for although the boughs on 
 being planted in the soil would again grow, they would not yield either in quality or 
 quantity enough indigo to pay the expenses of culture. 1000 parts cf fluid from the 
 fermenting tanks yield 0*5 to 0*75 parts of indigo. 
 
 Properties of Indigo. The indigo met with in commerce exhibits a deep blue colour, 
 dull earthy fracture, and when rubbed with a hard substance (the better kinds of 
 indigo even when rubbed with the nail of the thumb) give a glossy purplish-red 
 streak. In addition to a larger or smaller quantity of mineral substances, indigo 
 contains a glue-like substance, or indigo glue ; a brown substance, indigo brown ; a red 
 pigment, indigo red ; and the indigo blue, or indigotine, C l6 H 10 N 2 2 , the peculiar dye 
 material for which the drug is valued. The quantity of indigo blue contained in the 
 several kinds of indigo of commerce varies from 20 to 75 and 80 percent., and averages 
 from 40 to 50 per cent. Indigo may be purified according to Dumas' process by 
 digestion in aniline, whereby the indigo-red and indigo-brown pigments are dissolved 
 and eliminated. According to Dr. V. Warther,* Venetian turpentine, boiling parafline, 
 spermaceti, stearic acid, and chloroform, are, at high temperatures, solvents for indigo 
 blue.f 
 
 Testing Indigo. The quality of indigo is ascertained by its deep blue colour and 
 lightness.:}: G. Leuchs found that in forty-nine samples of this material the best con- 
 tained 60-5 per cent., the worst 24 per cent, of indigotine, the specific gravity of the 
 
 * See Chemical News, vol. xxiii. p. 252. 
 
 t See also CJiemical News, vol. xxv. p. 58, " On the Solubility of Indigo (Indigotine) in Phenic 
 Acid." 
 
 i See Chemical News, vol. xxiv. p. 313. 
 
SECT, iv.] TREATMENT OF COAL-TAR. 521 
 
 former being low and of the latter high. Indigo should float on water, and when of 
 good quality it should not, on being broken to pieces, deposit at the bottom of the 
 vessel filled with water in which it is contained a sandy or earthy sediment. On 
 being ignited, indigo should leave only a comparatively small quantity of ash. 
 When suddenly heated, indigo should give off a purplish-coloured vapour, sublimed 
 indigotine, and the drug should be perfectly soluble in fuming sulphuric acid, 
 yielding a deep blue fluid. That kind of indigo which on being rubbed with a 
 hard body exhibits a reddish coppery hue is termed coppery-tinged indigo, indigo 
 cuivre. In order to test indigo more accurately, a weighed portion is dried at 
 1 00 for the purpose of ascertaining the quantity of hygroscopic water contained, 
 which should not exceed from 3 to 7 per cent. Next the dried indigo is 
 ignited for the purpose of ascertaining the quantity of ash it yields. For good 
 qualities of the drug this amounts to 7 to 9*5 per cent. Numerous methods have been 
 proposed by practical dyers as well as by scientific men for the purpose of ascertaining 
 the value of indigo ; that is to say, the quantity of indigotine it contains. Some of 
 these processes are either too tedious, and cause great loss of time, or are not sufficiently 
 exact. A commercial sample of indigo may be treated first with water, next with 
 weak acids, then with alkaline solutions and alcohol, and the ash and hygroscopic 
 water having been estimated, the residue of the different operations will be the indigo- 
 tine, the process being based upon the insolubility of the latter in the different solvents 
 used for the removal of the impurities met with in the sample under examination. 
 Mittenzwei proposes to reduce the indigo by means of an alkali and solution of ferrous 
 sulphate, to pour over the surface of the liquid a layer of petroleum oil for the purpose of 
 excluding air, to take by the aid of a curved pipette a known bulk of the indigo-con- 
 taining fluid, and to introduce this fluid at once into a test-jar placed over mercury, 
 and containing a known and accurately measured bulk of pure oxygen. As i gramme 
 of white indigotine (soluble) requires for its conversion into blue (insoluble) indigotine 
 45 c.c. of oxygen, the quantity of gas absorbed gives the quantity of indigotine. This 
 method yields very correct results, but requires an experienced manipulator. 
 
 For the spectroscopic examination of indigo, Wolff treats 0*5 grammes of the 
 sample to be examined with 5 c.c. of concentrated sulphuric acid, effects its complete 
 solution by shaking up and digestion, and dilutes to i litre. The light is measured 
 in a stratum of i centimetre in thickness. 
 
 Indigo Blue. This substance, also known as indigotine, may be obtained from the 
 indigo of commerce, either by carefully conducted sublimation, or, as already stated, by 
 treating indigo with lime, ferrous sulphate, and water. The formula of indigo blue 
 is C 16 H 10 N 2 2 . When indigo blue, in the presence of alkaline substances, is brought 
 into contact with bodies which readily absorb oxygen for instance, with ferrous 
 sulphate, sulphites, &c. there is formed, with simultaneous decomposition of water, 
 white indigo, or reduced indigo, C 16 H 12 N 2 2 . The use of indigo as a dye material is in 
 great measure based upon this reduction. By the action of oxidising substances, such 
 as permanganic acid, chlorine, chromic acid, a mixture of so-called red prussiate of 
 potash (potassium ferricyanide) with potash, soda, oxide of copper, <fec., indigo blue 
 is converted into isatine, C 16 H, N 2 4 . Indigo blue dissolves in concentrated sulphuric 
 acid, but becomes thereby radically changed, and cannot be brought back to its primitive 
 state, forming as it does with the acid a chemical compound sulphindigotic acid, or, 
 as it is termed by dyers, sulphate of indigo. When this acid solution is treated with 
 potassium carbonate there is formed indigo extract, soluble indigo, a deep blue precipi- 
 tate soluble in 140 parts of cold water. This indigo extract is used as a water-colour 
 pigment ; while, mixed with some starch and a little gum- water, it is formed into balls 
 or other suitable shapes and used as washing-blue, ultramarine being also employed for 
 the same purpose. 
 
522 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 The present yield of indigo is 4450 tons yearly : 
 
 Bengal, Oude, Madras . . . . 3500 
 
 Java 300 
 
 Guatemala, &c 55 
 
 Artificial Indigo, though of very high theoretical^ interest, is not technically im- 
 portant, and modifications in the culture and treatment of the indigo-plant are in 
 progress, which are likely to improve the yield, both in quantity and quality, thus 
 reducing the probability of the success of any artificial substitute. It may be men- 
 tioned that natural indigo is a product of fermentation, set up by a specific bacillus. 
 Micro-organisms play important parts also, both for good and evil, in dyeing with indigo. 
 
 Logwood, or Campeachy. This dye material is the wood, freed from bark and splint, 
 of the logwood tree, Hcematoxylon campechianum, a native of Central America, and 
 cultivated in several of the West Indian Islands. The colouring matter contained in 
 this wood is called hsematoxyline, C, 6 H 14 6 , a pale yellow, transparent, aciculated 
 crystalline body. By itself it is not a pigment, but is a colourable material, which 
 becomes coloured when brought into contact with strong alkalies, more especially with 
 ammonia and the oxygen of the air. The solution of hsematoxyline in water is quite 
 colourless, but becomes at once purple-red by the smallest addition of ammonia. The 
 colouring matter thus formed is termed hsemateine. Logwood is used for the purpose 
 of dyeing blue and black. Extract of logwood is very frequently prepared. As 
 with other similar extracts, it should be made in vacuum pans withdrawn from the 
 oxidising action of the air, because the hsematoxyline contained in logwood becomes 
 thereby altered. The makers of the extracts of dyewoods invariably use vacuum 
 apparatus. 
 
 Instead of extract of logwood, there has been used since 1 880 a preparation known 
 as " hematine," which is probably impure hsematoxyline. 1 5 parts of hematine are 
 reputed equal to 100 parts of the best logwood. It gives faster and brighter 
 shades. 
 
 Litmus is used for giving a blue tint to lime and white-wash. It is obtained from 
 the same lichens as archil and cudbear. The difference in the preparation is that the 
 fermentation and oxidation have been carried further, and that the red colouring- 
 matter, ortine, has been transformed into the blue compound azolitmine 
 
 C 7 H 8 2 + NH 3 + 2 2 - C 7 H 7 N0 4 + 2^0. 
 
 The fermented mass is mixed with chalk and gypsum, and brought into commerce 
 moulded into small cubes. 
 
 The bezettes or turnesol rags, obtained in the South of France from the juice of 
 Croton tinctorium, contain a different colouring-matter. They are turned purple-red 
 or dark-green by ammonia. They are used in Holland for colouring cheese, confec- 
 tionery, liqueurs, &c. 
 
 Yellow Colouring Matters. Fustic (Cuba-wood or old fustic) is the wood of a 
 species of mulberry (Morus tinctoria or Madura aurantiaca}. It is chiefly imported 
 from Cuba and Hayti. The heart-wood, which alone is used, is of a yellow colour, here 
 and there verging to orange. The colour is due to a colourless crystalline compound, 
 morine, C 12 H 8 0., which is found in the wood in combination with lime and a peculiar 
 tannic acid, named morinetannic acid (or Maclurine), C 13 H 10 O 6 , which is found deposited 
 in the wood, sometimes in considerable quantities. Morine takes a yellow colour on 
 exposure to air, or on contact with alkalies. Maclurine, if treated with caustic potassa, 
 is split up into phloroglucine and protocatechutic acid. 
 
 . Fustic is used for dyeing yellows and blacks, where it serves to correct the blue 
 tone of logwood. It is extensively used as a liquid extract and also as a paste. 
 
 Young Fustic (Zante Fustic, Fustet, or Fiset) is a greenish-yellow wood, striped 
 
SECT, iv.] TREATMENT OF COAL-TAR. 523 
 
 with brown, obtained from Rhus cotinus, a shrub growing wild in the South of Europe, 
 and sometimes named Venetian sumac. Its colouring-matter, fustine, or fisetine, 
 
 C 23 H 10 3 (OH) 6 , 
 is a bright, but rather fugitive dye. It is chiefly used by some woollen-dyers. 
 
 Annatto (Annotto, Arnatto, or Orleans) is a yellowish-red colouring matter, 
 formerly much used in silk-dyeing, but now employed only in the manufacture of 
 varnishes and in colouring butter.* 
 
 It is sold as a stiff paste, and is obtained from the fruit of Bixa Orellana, a shrub 
 native in South America, and cultivated at Cayenne, in the Antilles, and in India. It 
 contains two colouring matters bixine, a yellow ; and orelline, a red (C 5 H 6 O 4 ). 
 
 Berries (Persian berries, French, Avignon, or Turkey berries) are the fruit of 
 Rhamnus infectorius, R. saxatilis, and R. amygdalinus, species of buckthorn. They are 
 met with large and full, of an olive-yellow colour, and also smaller, wrinkled and dark- 
 brown. The former kind are collected before full ripeness, whilst the latter are left to 
 dry on the trees. They contain a fine golden-yellow colour, chrysorhamnine, which Bolley 
 regards as identical with quercetine, and an olive-yellow colouring matter, xantho- 
 rhamnine. They are extensively used in calico-printing, chiefly in the form of extract, 
 in staining paper, and in the manufacture of yellow lake. 
 
 Turmeric is the dried root of Curcuma longa and 0. rotunda, plants cultivated 
 chiefly in Bengal. The roots, which vary in thickness from that of a quill to a diameter 
 of inch, are wrinkled, and have ring-like swellings at short intervals. They contain 
 ii to 12 per cent, of curcumine (C 8 H 10 2 ), a yellow tinctorial principle. 
 
 Weld or Wold; a plant sometimes erroneously confounded with woad, was 
 formerly much used for dyeing moderately fast yellows on silk and cotton with sodium 
 aluminate. Its colouring principle is luteoline. 
 
 Quercitron (commonly named " bark " by the dyers) is the rind of Quercus infectoria, 
 & species of oak growing in North America. There are two varieties, obtained re- 
 spectively from Philadelphia and Baltimore, the former being superior. It contains a 
 jellow colouring matter, quercitrine C 3S H 80 O 17 , and tannic acid. On treatment with 
 dilute acids, quercitrine splits up into isodulcite (a sugar of the formula C 6 H 10 5 ) and 
 quercetine, C 27 H 18 Oj.,, a bright yellow powder sold as flavine. Quercitron, both in sub- 
 stance, as extract, and as flavine, is more extensively used than any other yellow dye. 
 
 Among other yellow dye-wares we may mention Serratula, tinctoria, dyers' broom 
 (Genista tinctoria) ; wongshy, the seed pods of Gardenia Jlorida ; puree or Indian yellow, 
 a colour consisting of magnesium euxanthate and free euxanthon, and obtained from 
 the urine of cows fed upon the leaves of the mango. The vegetable yellow colours 
 have been almost entirely superseded by chrysoidine, tropaeoline, picric acid, Victoria 
 yellow, and other coal-tar colours. 
 
 Brown, Green, and Black Colours. Brown colours were formerly obtained from 
 mixtures of reds, yellows, and blues, or of yellows and reds with blacks. Browns are 
 often dyed with catechu and other tanniferous extracts, in conjunction with oxidising 
 agents, such as potassium dichromate, ammonium vanadate, &c. They are also 
 ; obtained with the so-called " patent colours " (Cachou de Laval) invented by Croissant 
 and Bretonniere. 
 
 Black is obtained with ferrous-ferric oxide in conjunction with solutions of tannin 
 or gallic acid, with decoction of logwood and potassium chromate, or, in printing, with 
 aniline black. 
 
 Greens were obtained with mixtures of yellows and blues, or with Chinese green 
 (Laokao) from RJiamnus cMorophorus and R. utilis, and with sap or bladder green from 
 
 * For this latter purpose it is utterly improper, as it is made up with stale urine and swarms 
 with bacteria, some of which may be morbific. 
 
524 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 the berries of the buckthorn (Rhamnus catharticus). The use of green vegetable colours 
 has been much interfered with by the introduction of methyl-green, malachite green, &c. 
 
 Ordinary writing ink consists essentially of ferric and ferrous tannates and gallates, 
 held in suspension by means of gum-arabic.* 
 
 A good black ink may be obtained by extracting i kilo, pulverised gall-nuts and 150 
 grammes logwood, with 5 litres hot water, dissolving at the same time 600 grammes gum 
 in 2 1 litres water and | kilo, copperas in 4 kilos, of water. The tannic extract and 
 the solutions of gum and copperas are then poured together, and a few drops of oil of 
 cloves or gualtheria are added and water enough to make up 16 litres. 
 
 Tannin Ink is obtained by dissolving 1 2 grammes tannin, 40 grammes copperas, and 
 50 grammes gum in i litre of boiling distilled water. Iron inks, beside attacking the 
 steel pens, have the defect that the writing in time turns yellow. Hence the proposal 
 to use ammonium vanadate instead of iron salts deserves notice. 
 
 Ink from 1000 parts decoction of logw.ood (i part wood to water) and i part yellow 
 (neutral) potassium chromate, with the addition of a trace of mercuric chloride, is at 
 once cheap, permanent, and beautiful ; the colour is a compound of haemateine and 
 chromium oxide. 
 
 To obtain the so-called alizarine ink, 42 parts galls and 3 parts madder are extracted 
 with water, so as to make up 120 parts of liquid, to which are added 1*2 part indigo 
 sulphate, 5*2 parts copperas, and 2 parts iron pyrolignite solution. 
 
 The reddish-blue ink from Rouen (encre rouennaise), extensively used in France, con- 
 sists of a decoction of 750 grammes logwood, 35 grammes alum, and 31 grammes gum 
 in 5 to 6 litres water. Coupier's induline ink is simply a solution of induline in 50 parts 
 of water. 
 
 Copying inks are merely strong common inks with a large addition of gum and 
 sugar or glycerine. Inks are prevented from turning mouldy by the addition of a little 
 quinine sulphate, salicylic acid, or phenol. 
 
 TAR COLOURS. 
 
 Repeated attempts have been made to arrange the colouring matters obtained from 
 coal-tar in natural groups. 
 R. Nietzki distinguishes : 
 
 1. Nitro compounds. 
 
 2. Azo colouring matters. 
 
 3. Triphenyl methan colouring matters. 
 
 4. Indamines and indophenoles. 
 
 5. Saffranines and their allies. 
 
 6. Aniline black. 
 
 7. Indulines and nigrosines. 
 
 8. Quinoline and acridine colouring matters. 
 
 9. Anthraquinone colouring matters. 
 
 The nitro-compounds contain the group NO,, e.g., picric acid, binitrocresol. 
 
 The azo-colours contain the groups - N = N - . The entrance of the azo-group into 
 a hydrocarbon or into a compound similar in its behaviour (e.g., anisol, phenetol) pro- 
 duces in the first place certain coloured compounds which are not true colouring 
 matters, as they do not unite with the animal fibre. This affinity to the fibre is 
 obtained only by the introduction of certain groups, which give the azo-compounds 
 acid or basic properties. On the other hand, the intensity of the colouring matter is 
 generally heightened and the tone is essentially modified. 
 
 * Hence has been derived the custom of adding gums or sugars to all inks, even such as are 
 true solutions and do not require to be suspended. 
 
SECT, iv.] TAR COLOURS. 525 
 
 In colouring matters which, besides the benzene group, possess no higher hydrocarbon 
 residue, the colours represented are merely yellow, orange, and brown. Only by intro- 
 ducing the naphthaline residue there are obtained reds, and by its repeated introduction 
 violets and blues. The introduction of groups which are in themselves indifferent (e.g., 
 the methoxyl groups OCH 3 ) may produce a striking modification of the colouration. 
 The relative position of the groups is also important. Thus the compound 
 
 
 
 HO 
 
 has, e.g., a red colour if the benzene nucleus, the meta position, is occupied, but a blue 
 if the para position is taken. 
 
 The azo-dyes in technical uses are mostly sulph-acids and behave as acid colours. 
 There are employed in their production the sulph-acid of the diazo-compounds or of 
 the phenoles. In some cases the previously formed azo-compound is converted into a 
 sulph-acid by treatment with sulphuric acid. 
 
 The triphenylmethan colouring matters contain, according to Nietzki, the group 
 
 ^\/ \|/ 
 
 C NH or C which is to be regarded as the chromogen of the compound. If 
 the salts of the nitrogenous triphenylmethan colours are decomposed by alkalies there 
 occurs an addition of water, and there are formed amide-derivatives of triphenylcarbinol 
 
 which contain the group C The ring-shaped combination has therefore become 
 
 OH. 
 
 open. These carbinol derivatives are generally regarded as the bases of the colouring- 
 matters and the latter as salts of the former. But in truth both possess a distinct con- 
 stitution, and in consequence quite distinct properties. The carbinol compounds are 
 perfectly colourless, whilst their salts, or more correctly those of their anhydrides, are 
 powerful dyes. The conversion of the carbinol compounds into colouring matters is 
 not effected as easily as the formation of salts from bases and acids, but requires in 
 many cases a prolonged action, which often seems to follow after the mere formation 
 of a salt. Tetramethyldiamidotriphenylcarbinol (the colourless base of malachite 
 green) dissolves first in dilute acids to a colourless liquid. On heating, or on prolonged 
 standing, it becomes intensely green, all the triphenylmethan colouring matters be- 
 longing here are para-derivatives i.e., they contain the nitrogenous or oxygenous groups 
 in the para-position to the methan carbon. Here belong the true aniline colours, such 
 as malachite green. 
 
 Indamines and Indophenoles are formed when paradiamines or para-amidophenoles 
 are oxidised in presence of rnonamines or phenoles. Indamines are formed by oxidation 
 in a neutral, and indophenoles in an acid liquid. Indophenoles form colouring matters 
 in the free state, and their salts are colourless ; in indamines the reverse holds good. 
 Both are readily decomposed by an excess of acid with the formation of quinones. 
 Their constitutional formulae are probably 
 
 Indamine. Indophenol. 
 
 HN-C 6 H 4 ^; HN-C 6 H 4 
 
 Saffranines contain four atoms of nitrogen in their molecule, two of which are in the 
 fcrm of amido groups. Four atoms of hydrogen may be replaced by alcohol radicles, 
 
526 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. iv. 
 
 and two by acid radicles e.g., of acetyl. They may also be converted into diazo- 
 compounds, in which generally one, but sometimes two, amido groups may be converted 
 into diazo groups. 
 
 In all these substitutions the strongly basic nitrogenous group which serves for I 
 the formation of the monobasic salts is not attacked. The acetyl derivations of 
 saffranine still form salts, and the primary diazo-compounds have a strongly bibasic 
 character, and contain, therefore, an acid molecule which is not linked to the diazo- 
 group. 
 
 The formation of saffranine from paradiamidodiphenylamine, with a simultaneous 
 oxidation with monamines, lets us conclude that in it two benzene nuclei are connected by 
 an atom of nitrogen, that both the amido groups belong to this benzene nucleus, and 
 are in the para-position as regards the atom of nitrogen which connects them. 
 
 The saffranines are therefore closely related to the indamines, and are formed 
 from the latter when heated with monamines in an aqueous solution, whilst hydrogen 
 is being split off, and, if no oxidising agent is present, effects a partial i eduction of the 
 indamine. The amidised indamines (e.g., toluylene blue) are converted directly on heat- 
 ing with partial reduction into colouring matters resembling saffranine. Their 
 ordinary production depends on the oxidation of one mol. of a paradiamine with two 
 mols. of a monamine. 
 
 The mono-acid salts of the saffranines are generally red, but the introduction of 
 alcohol radicles into the amidic groups modifies the colours towards a violet. The 
 introduction of methoxyl and ethoxyl groups into the benzene nuclei changes the tone 
 of the colours in the direction of yellow. Upon animal fibres and upon cotton 
 mordanted with tannin the saffranines take very readily, producing the colour of their 
 mono-acid salts. 
 
 The formula for aniline black is not yet decided. 
 
 Among the indulines and nigrosines are included a series of colouring matters formed 
 by the action of certain nitro- and azo-compounds upon aromatic amines and having all 
 blue-grey or black-blue colours. On heating amido-azo-benzol with aniline hydro- 
 chlorate to 1 60, ammonia is eliminated, and there is formed a violet colour, C 18 H 15 N 9 
 (azo-diphenyl blue), which may be regarded as the first link of the induline series. 
 
 Flavaniline is ranked among the quinidine colours. For anthracene colours, see 
 below. 
 
 Schultzand Julius arrange the 2 74 most important colouring matters as follows : 
 i. Nitroso colours e.g., naphthol green B (a 
 ferrous sodium, salt of nitroso-/3-naphthol 
 monosulphuric acid) 
 
 2. Nitro colours e.g., picric acid 
 
 3. Azoxy colours e.g., sun yellow (Jaune soleil), maize,] 
 acid curcumine (a sodium salt of azoxystilbene-' 
 disulphonic acid) 
 
 (a 
 
 
 f SO,NaNa0 3 S * 
 
 
 ol 
 
 ~ C 10 H 5 
 
 1 1 
 
 " C 10 H 6 
 
 
 
 I NO Fe ONJ 
 
 
 i 
 
 OH 
 
 i 
 
 ONH 4 
 
 2 
 "4' 
 
 -Krr\ 3 ', Flavaurin = C 6 H J 
 
 2 
 
 [6 
 
 NO, 
 
 NO; 
 
 x 
 
 NO* I 
 
 "4" 
 
 S0 3 NH 
 
 4. Azo colours e.g., 
 
 Aniline yellow, amidoazo- 
 benzol hydrochlorate 
 
 Fast yellow B, acid yellow\ 
 B, the sodium salt of I _ 
 amido azotoluol-disulph- 1 
 acid . 
 
 
 CH[i]C 6 H 3 
 
 CH[i]C 6 H 3 {[' 
 NH n .HCl 
 
 2 lSO.Na 
 
 rf2lCH 
 J SOjNa* 
 H 1 ]^ = N[i]C 6 H, 
 
 O,Na 
 
SECT. IV.] 
 
 TAR COLOURS. 
 
 5. Hydrazon colours e.g.', phenanthrene red, the] 
 sodium salt of a-naphthyl-a-sulphacid azo- } 
 
 527 
 [ 4 -CN-NH-C l0 H 6 -S0 3 Na 
 
 phenanthreno quinone 
 
 J C g H 4 ON NH C 1 
 
 6. Diphenyl methan colours ; only auramine' 
 
 (hydrochlorate of imidote tramethyldiamido 
 diphenyl-methan) . . . . . 
 
 7. Triphenyl methan colouring mat-^ /[i]C 6 HJ4]N(CH 3 ) a 
 
 ters e.g., fast green (the sodium I = H0 _ ~ I [i]C 6 H 4 [4]N(CH 3 ) x 
 
 salt of tetramethyl-diphenyl- [ ' IfilC H rN^"^" 2 ^6^4 S0 3 Na 
 
 pseudo-rosanilinesulpho acid) ' 
 
 [i]C 6 H 4 [ 4 ]N(CH 3 ) 2 
 =NH +H 2 
 
 [i]C 6 H 4 [ 4 ]N(CH 3 ),H01 
 
 CH 2 C 6 H 4 S0 3 Na 
 
 8. Anthracene colours e.g., alizarine (a-/3-dioxy- ^ 
 
 anthraquinone) . . . . . J ~ 6 
 
 9. Indophenoles e.g., indophenol, dimethyl-amido-a- ) _^ JC HMO 
 
 naphtho-quinone anilide ..... J 
 
 10. Oxazines e.g., new blue (naphthylene blue R in 
 crystals); fast cotton blue = dimethyl-phenyl-a- 
 ammonium-/3-oxynaphthoxazine . . . 
 
 ii. Thionine colours, Lauth's violet, thionine hydro- 
 chlorate . .... 
 
 12. Eurhodines e.g., neutral violet,] 
 
 dimethyl-diamephenazineh = (CH 3 ) 2 N[4]C 6 H 3 
 hydrochlorate . . J 
 
 13. Saffranines e.g., Magdala s 
 
 red, naphthaline red, 
 naphthaline rose, naph- 
 thaline scarlet, Soudan I = HC=HC[5J 
 red, rosa-naphthylamine 
 (diamidonaphthylnaph- 
 thazonium chloride) 
 
 []C' H [/3] 
 
 -N r " 6 f 2 
 
 N(CH S ),01 
 
 C 6 H 3 [ 4 ]NH,.HCl 
 
 HC=HC[6]) 
 
 =HC[ 5 ] 
 H 8 Nt 4 ] 
 
 a 
 l 
 
 [4]CH= 
 
 Cl 
 
 [i] /[ 2 ]CH=CH 
 
 PA] i 
 
 [4] l[ 3 ]CH=CH 
 NH S 
 
 14. Indulines and nigrosiues e.g., fast blue 
 
 -^r ,' 
 
 ' 
 
 CO 
 
 15. Artificial indigo 
 
 1 6. Quinoline and acridine colours e.g., 
 flavaniline (hydrochlorate of para- 
 amido phenyl and lepidine 
 
 CO 
 
 = C fi H 4 
 
 CH 3 
 
 [i]C=CH 
 
 [ 2 ]N=C[ 4 ]C 6 H 4 [i]NH 2 .HCl 
 
 In research, or for instruction in organic chemistry, such an arrangement is doubt- 
 less preferable, but in technology it seems more important to follow the process of 
 manufacture. 
 
528 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 i. BENZOL COLOURS. 
 
 Commercial benzol contains, besides benzene (true benzol), toluol (C 6 Hj.CH 3 ), xylol 
 C 6 H 4 (CH 3 ) 2 , and cumol C 6 H 3 (CH 3 ) 3 . 
 
 Nitrobenzol. On the nitration of benzol there is formed nitrobenzol : 
 
 C 6 H 6 + HN0 3 = C 6 H 5 .N0 2 + H,0. 
 On nitrating toluol, 
 
 C G H 5 .CH 3 + HNO 3 = C 6 H,.NO.CH 3 = H 2 0, 
 
 there are produced three isomcric nitrotoluols, chiefly orthonitrotoluol (boiling point 
 22 3)> with small quantities of meianitrotoluol. 
 
 The technical nitrobenzol is therefore a mixture of nitrobenzol and nitrotoluol along 
 with nitroxylol. For its production there is run into the benzol, in a cast-iron 
 vessel fitted with an agitator, a mixture of two parts strong nitric acid and sulphuric 
 acid. It must be refrigerated at first, which is effected by letting water flow over the 
 vessel ; after a few hours the temperature is gradually let rise to 60-80. When 
 the reaction is completed the two liquids are allowed to separate, and the nitro- 
 benzol is purified by washing it with water. 100 kilos, benzol yield 135 to 140 kilos, 
 nitrobenzol. 
 
 There are three nitrobenzols, corresponding to the different benzols: i. Light 
 nitrobenzol, boiling between 205 and 210. It forms the artificial oil of bitter almonds 
 (not to be confounded with the benzaldehyd, C 6 H 5 .COH, prepared from toluol), or 
 mirbane oil (essence de mirbane), sp. gr. = i'2O. It is used in quantity in perfumery 
 and in soap-making, and also in the sophistication of wines. 2. Heavy nitro-benzol, 
 distilling between 210 and 220, sp. gr. = 1-19. Its peculiar odour prevents its use 
 in perfumery. From this kind the " aniline for reds" is obtained. 3. Very heavy 
 nitrobenzol, distilling between 222 and 235, sp. gr. = 1*167. Its odour is unpleasant. 
 
 Aniline. By amidising nitrobenzol there is obtained crude aniline, aniline oil, the 
 initial point for obtaining the aniline colours. It is substantially a mixture of aniline 
 (amidobenzol) (C 6 H 5 NH 2 ) and toluidene amidotoluol (C 6 H 4 NH 2 .CH 3 ). It is known in 
 the trade as aniline oil. Pure aniline and pure toluidene alone, form colours only under 
 certain conditions. 
 
 Aniline was discovered at Dahme, in Saxony, by Dr. Unverdorben, in 1826, among 
 the products of the dry distillation of indigo, and in 1833 Runge, at Oranienburg, near 
 Berlin, discovered its presence in coal-tar. Runge also discovered that aniline yielded, 
 when brought into contact with a solution of hypochlorite of lime (bleaching powder), 
 a beautiful violet colour; hence the name kyanol (blue colouring oil). Fritzsche of 
 St. Petersburg, 1841, thoroughly investigated the substance obtained by Dr. Unver- 
 dorben from indigo, ascertained its composition, and called it aniline, from anil, the 
 Portuguese name for indigo. In the year 1842 Zinin found that when nitrobenzol 
 was treated with sulphuretted hydrogen there was formed a base which he termed 
 benzidam. The further researches of O. L. Erdmann and Dr. A. W. Hoffmann brought 
 the fact to light that Dr. Unverdorben's crystalline, kyanol, benzidam, and aniline were 
 the same substance, to which the aniline was then finally given. We owe to the ex- 
 tensive researches of Dr. A. W. Hoffmann our present knowledge of aniline and its 
 compounds. 
 
 Coal-tar contains 0-3 to 0-5 per cent, of aniline, but its extraction from tar is 
 attended with so many difficulties that it is preferred to prepare aniline from nitro- 
 benzol by a reaction discovered by Zinin that is to say, to bring nitrobenzol into con- 
 tact with reducing agents : i molecule of nitrobenzol, C 6 H 5 N 2 = 123, yields i molecule 
 of aniline, C 6 H 7 lSr = 93. * n practice it is assumed that 100 parts of nitrobenzol yield 
 100 parts of aniline. 
 
SECT. IV.] 
 
 BENZOL COLOURS. 
 
 5=9 
 
 Fig- 393- 
 
 Although sulphuretted hydrogen completely reduces nitrobenzol to aniline, the 
 trade working on a large scale prefers to follow Bechamp's method, the treatment of 
 nitrobenzol with iron-filings and acetic acid. The apparatus in use for carrying out 
 this operation was devised by Nicholson, and is exhibited in Fig. 393. It consists 
 essentially of a cast-iron cylinder, A, 
 of 10 hectolitres (220 gallons) cubic 
 capacity. A stout iron tube is fitted 
 to this vessel, reaching nearly to the 
 bottom of the cylinder. The upper 
 part of this tube is connected with 
 the machinery, G, while the surface 
 of the tube is fitted with steel pro- 
 jections. The tube serves to admit 
 steam, besides acting as a stirring 
 apparatus. Sometimes, instead of 
 this tube, a solid iron axle is em- 
 ployed, and in this case there is a 
 separate steam -pipe, D. Through 
 the opening at K the materials for 
 making aniline are put into the ap- 
 paratus, while the volatile products 
 are carried off through E. H serves 
 for emptying and cleaning the ap- 
 paratus. The S-shaped tube con- 
 nected with the vessel, J3, acts as 
 a safety-valve. When it is intended 
 to work with this apparatus there is first poured into it through K TO kilos, of 
 acetic acid at 8 B. ( = sp. gr. ro6o), previously diluted with six times the weight of 
 water ; next there are added 30 kilos, of iron-filings or cast-iron borings, and 125 kilos, 
 of nitrobenzol, and immediately after the stirring apparatus is set in motion. The 
 reaction ensues directly, and is attended by a considerable evolution of heat and of 
 vapours. Gradually more iron is added until the quantity amounts to 180 kilos. The 
 escaping vapours are condensed in F, and the liquid collected in R is from time to time 
 poured back into the cylinder. A . The reduction is finished after a few hours. The 
 resulting thick magma exhibits a reddish-brown colour, and consists essentially of 
 hydrated oxide of iron, aniline, acetate of aniline, acetate of iron, and excess of iron. 
 Leaving the acetic acid out of the question, the process may be elucidated by the fol- 
 lowing formula : 
 
 C 6 H 5 N0 2 + H 2 + Fe 2 = C 6 H 7 N + Fe 2 O 3 . 
 
 Nitro-benzol. Aniline. Ferric 
 
 oxide. 
 
 This magma is either first mixed with lime or is put into cast-iron cylinders shaped 
 like gas-retorts, and submitted to distillation, the source of heat being either an open 
 fire or steam. The product of this operation, consisting of aceton, acetaniline, aniline, 
 nitrobenzol, &c., is rectified by a second distillation, care being taken to collect separately 
 the product which comes over between 115 and 1 90 ; but a product which comes over at 
 between 210 and 220 is very suitable for the preparation of aniline blue. The aniline 
 oil thus obtained is a somewhat brown-coloured liquid, heavier than water, and pure 
 enough for the preparation of the aniline colours. According to Brinmeyer, acetic acid 
 is not necessary, and a very good result may be obtained by mixing nitrobenzol with 
 60 parts of pulverised iron with acidified water (2 to 2-5 per cent, of hydrochloric acid 
 
 2 L 
 
530 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 upon the weight of nitrobenzol), and leaving this mixture to stand in a retort for some 
 three days before distilling off the aniline oil. In the aniline oilworks of Coblentz Freres, 
 at Paris, nitrobenzol is reduced by the aid of iron-filings, a portion of which have been 
 coated with copper by being immersed in a solution of the sulphate. 
 
 The composition of the aniline oil essentially a mixture of aniline, toluidine, and 
 pseudo-toluidine depends upon the nature of the benzol and nitrobenzol used for 
 its preparation. The aniline oil boiling between 180 and 195 (sp. gr. - 1-014 to 
 1-021 = 2 to 3B.) is prepared from nitrobenzols which boil between 210 and 220, 
 and the aniline it yields is chiefly used for aniline red ; while for aniline blue a very 
 heavy nitrobenzol is employed, and for aniline violet a nitrobenzol which boils at 210 
 to 225. The following table exhibits the boiling-points of the substances which have 
 been mentioned : 
 
 Benzol .... 80 
 
 Toluol 1 08 
 
 Nitro-benzol . . .213 
 
 Nitro-toluol . . . 225 
 Aniline .... 182 
 Toluidine 108 
 
 As regards the annual production of aniline oil, it is now (1871) 3,500,000 Ibs., 
 of which 2,000,000 Ibs. are consumed in Germany, and the remainder in Switzerland, 
 England, and France. 
 
 The so-called pure aniline, which has been produced on the large scale since 1870, 
 has at 15 the sp. gr. 1-0245. 1^ contains very small quantities of toluidine (not above 
 i per cent.), and forms a clear solution in dilute acids. Its chief use is in the manufacture 
 of aniline blue, of methyl aniline and diphenyl amine. It is also used in printing for 
 the production of aniline black. 
 
 Toluidine corresponds in purity to the aniline described above. It contains a predo- 
 minating quantity of ortho- or of para-toluidine according to the manner of its prepara- 
 tion. The largest quantity of aniline oil is that " for red," a mixture of aniline with the 
 two toluidines and a little xylidine, which distils over within a range of 10-12, and has 
 the sp. gr. 1-004-1*006. It consists approximately of 20 percent, aniline, 40 percent, 
 toluidine, and 40 ortho- toluidine. Besides aniline for reds there is produced a much 
 smaller quantity of aniline for saffranine, which contains a large relative proportion of 
 aniline, namely, 35 per cent. Its sp. gr. is i-oio, and it distils over at 185-190. It 
 has a similar composition to the so-called echappes from the manufacture of magenta, 
 which, indeed, are often used for obtaining saffranine. 
 
 The most important of the aniline colours are the following : Aniline red (magenta), 
 called on the Continent and in America by the misleading name of fuchsine, and for- 
 merly by the still worse names of azaline and harmaline, belongs to the derivatives of 
 triphenyl methan, C 19 H 16 , or of tolyldiphenyl methan, C 20 H 18 . 
 
 CUT O TT n~LT 
 
 -.xi, i\Ji.n-.*\-jtt.~ 
 
 65 1643 
 
 r~\ TT 1 /~H TT 
 
 ^n oSr 5 ^Mmr 8 
 
 Vy-Xl, V_/.,_Ll, 
 
 H (H (H 
 
 Methan. Triphenyl methan. Tolyldiphenyl methan. 
 
 If in triphenyl methan hydrogen is replaced by NH 2 , and again by CH 3 ,C 6 H 5 , &c., 
 there are formed leuko-bases, which form with acids colourless salts, but on oxidation 
 pass into colour-bases, yielding coloured salts e.g. : 
 
 (C 6 H 4 .NH, (C 6 H 4 .NH 2 (C 6 H 4 .NH, 
 
 0JCJL.NH, r jC 6 H 4 .NH 2 + HC1 = C C P H 4 .NH; + H.O 
 
 ' C 6 H 4 .NH f '] C 6 H 4 .NH; loj^NRHCl 
 
 in IOH 
 
 Paraleukaniline. Pararosaniline. Its hydrochlorate. 
 
 Magenta is a mixture of pararosaniline and rosaniline hydrochlorate or acetate, rarely 
 
SECT. IV.] 
 
 BENZOL COLOURS. 
 
 nitrate or sulphate, the rosaniline being derived from tolyldiphenyl methan e.g., as 
 hydrochlorate, C 19 H, 6 N 3 C10 4 and C W H^N,C1O 4 . 
 
 ,C B H 4 .NH, (C 6 H,.CH,NH, 
 
 C C 6 H 4 .NH, andCj< 
 
 (C,,H 4 .^H:HC1 
 
 Salt of rosaniline, with 3 mols. of acid, have an insignificant yellow colour, and are 
 decomposed by water into monacid salts, 2 mols. acid being liberated. By the action 
 of nitrous acid upon the salts of rosaniline there are formed diazo-rosaniline salts, 
 which on boiling in water yield rosolic acids. 
 
 Aniline red is produced from aniline oil by treatment with various oxidising agents 
 e.g., with stannic chloride (Yerguin), carbon perchloride (Hofmann and Nathan- 
 son), mercuric nitrate (Gerber-Keller), mercuric chloride (Schnitzer), nitric acid 
 (Lauth and Depouilly), antimonic acid (Medlock, Girard, and De Laire), nitrobenzol 
 and iiitrotoluol (Coupier). From 100 parts of aniline there are obtained 25 to 30 
 parts of crystalline magenta. 
 
 Arsenic Acid Process. If a mixture of the cliacid arseniates of aniline 
 
 /OH (OH 
 
 AsO - OH of o- and ^-toluidine AsO \ OH 
 
 (ONH 3 .C 6 H 5 (O.NH 3 .C 7 H 7 
 
 is heated to 180-190, the acid is reduced, and there is formed a mass of a cantharides 
 green colour, containing the magenta bases : pararosaniline, methyl-pararosaniline, 
 and probably climethyl-pararosaniline ; the phosphine bases : chrysaniline and methyl- 
 chrysaniline ; and the induline bases : melaniline and mauvaniline, in the state of 
 arsenites and arseniates. The formation of pararosaniline is effected by oxidising out 
 the hydrogen atoms from a mixture of i mol. paratoluidine and 2 mols. aniline accord- 
 ing to the following equation : 
 
 (C 6 H 4 .NH 2 (C 6 H 4 .NH, 
 
 TT n T 
 
 4 2 H.C 6 H 4 .NH 2 + 3 = 2 H 2 + O 
 
 The formation of methyl-pararosaniline (rosaniline), and of dimethyl-pararosaiiiline 
 ^rosotoluidine), ensues from corresponding mixtures of bases. 
 
 The melting-pot used in the arsenic process (Fig. 394), i metre high, consists, 
 according to Schoop, of cast-iron ; the cover can be raised by means of a pulley. The 
 exit-pipe for the distillate is screwed to 
 one side. The contents of the melting- 
 pot are kept in motion during the process 
 by means of an agitator. A smaller 
 opening serves for taking out specimens 
 of the melt. Th pan is built up in such ^ 
 a manner that the flame gases stream 
 through a perforated arch against the 
 bottom of the pan, and thence pass up 
 uniformly along its sides, and are finally 
 led through a ring-shaped channel to the 
 chimney. 
 
 The following is the composition of two approved aniline oils for reds :- 
 
 Aniline . 
 
 Orthotoluidine 
 
 Paratoluidine 
 
 A. 
 22'0 
 
 58-4 
 
 68-4 
 
 Sp. gr. i -0020 
 
 I'OOOO 
 
532 CHEMICAL TECHNOLOGY. [SECT, iv, 
 
 The pan is charged with 700 kilos, arsenic acid at 195 Tw. 300 kilos, recovered 
 arsenic acid of the same strength, 300 kilos, aniline for reds, and 200 kilos, of distillate 
 from former charges. If the pan is cold the mixture coagulates to a thick jelly. 
 Generally, the pan is so warm from former operations that the mixture remains liquid. 
 The fire is kindled at 6 A.M., so that the distillation begins at t or 2 P.M. After 
 twenty hours (when 20 to 25 jugs of distillate have been collected) the fire is raised 
 until 20 litres distil over hourly. After 400 litres in all have passed over, the melt 
 will have become thick. Samples are now taken frequently, and the melt is broken up 
 as soon as it becomes pasty. The cover is quickly drawn up and the contents are baled 
 out upon sheet-iron trays by means of copper scoops. The melting takes thirty- six 
 hours. As soon as the melt becomes pasty the fire is only kept up faintly, as the 
 heat of the pan is sufficient to complete the reaction. Only prolonged experience 
 enables the operator to judge when the melting should be stopped. If the melt is too 
 thin the yield will be low ; if it has become too thick it is a hard task to dig it out of 
 the pan with chisels. During baling out, the copper scoops are frequently plunged 
 into cold water to prevent the melt from adhering. The workman protects himself 
 during baling out against the dense aniline vapours by a sponge moistened with acetic 
 acid and fixed over the mouth and nostrils. The operator is also changed every two or 
 three minutes. The melt when cold is broken up into pieces the size of a fist. The 
 average weight is 88'6 kilos. The fracture of the melt is conchoidal, it is brittle, and 
 has a golden lustre. The distillate is collected in a large parting funnel, and there are 
 added to it 100 kilos, of salt. The oil then rises readily to the surface; the solution 
 is drawn off and diazotised after the proportion of aniline present has been ascertained, 
 precipitated with a solution of naphthol and worked up for naphthol orange. The 
 stratum of oil is rectified in a still and used for future melts. The distillates from the 
 red oils A and B contain respectively : 
 
 A. B. 
 
 Aniline . . . 29 per cent. ... 21 per cent. 
 
 Orthotoluidine . .71 ,, ... 79 
 Paratoluidine , 
 
 Sp. gr. at 18 1-0076 1*0057 
 
 The distillates may be worked up more advantageously for safranine (see below). 
 On an average a melt yields 220 kilos, of distillate. 
 
 The melt is now ground up wet to a fine mud, for which two hours are generally 
 required. The mud is let off into a monte-jus and passed through a filter-press. 
 Whilst the filtrate is concentrated in an iron pan, to recover the arsenic acid, the press- 
 cakes are stirred up with lukewarm water and filtered again. The filtrate now 
 obtained is used in grinding up the next melt. As a matter of course the melt is 
 ground up in small lots of about 100 kilos, each. The crude melt after being thus 
 treated is a greenish-yellow powder, which is twice subjected to a lixiviation with 
 boiling water in the extraction pan (Figs. 395 and 396). Whilst the melt was formerly 
 baled in open vessels by means of steam, and afterwards in closed horizontal cylinders, 
 which allowed of extraction at a slight pressure, upright lixiviators are now preferred. 
 
 This vessel consists of a cast-iron foot-piece with an opening for introducing the 
 pulverised melt, and can be closed with the lid D running upon rails. On the semi- 
 globular bottom of this foot-piece there are three inlets for steam, e, of 37 mm. 
 diameter, arranged symmetrically and fed from the common steam pipe, d. A little 
 higher is the inlet for water, w, and at the lowest point the outflow, a. The cover, D, 
 which closes the circular feeding-hole is secured with screws, and is provided Avith a 
 stuffing box, which serves for the axle of the agitator, R, which is occasionally moved 
 by hand. Above the foot-piece rises the upper cylindrical part of the apparatus, 
 
SECT. IV.] 
 
 BENZOL COLOUKS. 
 
 533 
 
 Fig. 395- 
 
 Fig. 396. 
 
 riveted together with boiler plates, which is closed above with a slightly arched cover. 
 At about three-quarter height of the entire apparatus is a small escape-cock which 
 shows the height to which 
 the pan is filled with water. 
 In addition there is a mano- 
 meter attached to the cover, 
 to indicate the pressure within. 
 The upper portion of boiler 
 plate is screwed down to the 
 foot-piece. The entire appa- 
 ratus, which is i metre in 
 diameter and 4^ metres in 
 height, rests by means of its 
 lower hemispherical part upon 
 a solid frame of wood. At 
 three-quarters height the ap- 
 paratus passes through a second 
 frame to prevent vibration. 
 
 For continuous working two such extractors are conveniently placed side by side. 
 It is convenient to divide the crude melt into 10 equal parts. Each part i.e., 88'6 kilos. 
 is ground up separately, and the lixiviated powder is placed in the extractor. The 
 cover is closed, and water is run in till it runs out at the upper cock. This cock is 
 then closed and steam is turned in. The quantity of liquid is about 3600 litres. When 
 the water boils the supply of steam is so regulated that the manometer shows i \ to 2 
 atmospheres. After four hours (altogether) the decoction is passed through the filter- 
 press, and the filtrate is run into a large cistern. The residue is now placed in the 
 second extraction pan, and again treated with 3600 litres in the same manner. This 
 second liquor is now transferred to the first apparatus, which has been already charged 
 with a fresh portion of melt, so that the fresh melt is always extracted with the second 
 extract of the former charge. The doubly extracted residue, a powder resembling 
 humus, forms a part of the poisonous, useless magenta residues. 
 
 The colour liquor of one decoction (about 3600 litres) deposits a little impurity on 
 standing for half-an-hour. It is let off into an apparatus placed below, and whilst 
 still hot is stirred up with 200 kilos, of rock-salt. The colouring matter is now- 
 converted into a hydrochlorate, and is very completely deposited owing to the presence 
 of salt. The liquid drawn off after two days is collected in a large cistern, and the 
 colouring matter remaining is precipitated from time to time by means of a little milk 
 of lime ; it is filtered off and worked up separately. The lye now obtained, containing 
 much arsenious acid, should be completely precipitated with lime to remove the arsenic. 
 This is, unfortunately, often not done at all, or at least very imperfectly, so that the 
 poisonous waters enter the rivers and occasion extraordinary pollution. The lime to 
 be obtained in this manner is of considerable bulk, and forms the second and larger 
 portion of the poisonous residues. 
 
 The crude magenta after being salted out has to be purified. Along with several 
 rosanilines chrysaniline, mauvaniline, violaniline it contains further constituents not 
 yet understood. The separation of these ingredients depends on a systematic fractional 
 precipitation. The crude magenta from two extractions ( = \ of a melt) is dissolved in 
 a wooden vat in 1000 litres of water boiled by steam. To the boiling water there are 
 added gradually 40 litres of a solution obtained by dissolving 40 kilos, soda-ash in 100 
 litres water. A part of the colouring matter separates out as a green or golden 
 shining resin on the sides of the vat and on the surface of the liquid. The resin is 
 skimmed off, and the liquid is rapidly poured through a coarse sieve into a wooden butt. 
 
534 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 To the filtrate there are added 2 litres hydrochloric acid to prevent the separation of 
 chrysaniline, and to delay the crystallisation of the magenta. There is laid upon 
 the surface of the liquid a cover with a number of wooden rods, by which means the 
 cooling takes place more slowly. When the lid is taken off after the lapse of two days- 
 it is found covered with a layer of fine crystals. The lye is run into a cistern, and the 
 crystals adhering to the sides and the bottom are allowed to drop off. These crystals are 
 let dry first in the air, and then in a drying-room at 40. In this manner 20 kilos, of 
 magenta crystals are obtained, while about 4 kilos, of magenta remain in the mother 
 liquor, and the weight of the resin eliminated is 15 to 1 6 kilos. The mother liquor 
 from the crystallisation is precipitated with soda-lye, and the coloured base deposited 
 as a brownish-red mud after about 40 kilos, (calculated on the dry matter) have 
 accumulated, is dissolved in hydrochloric acid. This solution is treated exactly as in 
 the purification of the crude magenta liquor ; i.e., about ^ of the colouring matter is- 
 separated out as resin by the addition of soda-lye ; the filtrate on cooling yields a crop 
 of magenta crystals. In this mother liquor there remains very much chrysaniline 
 along with a smaller portion of magenta. By precipitation with soda-lye, filtering and 
 concentrating the base with acetic acid, we obtain cinnamon brown. 
 
 The resin separated on purifying the crude magenta (resin I.) is dissolved in hydro- 
 chloric acid. On boiling the acid liquor a little resin separates out, chiefly mauvaniline. 
 By the cautious addition of soda-solution a portion of colouring matter is separated out,, 
 and the mother liquor (after filtration and cooling) yields a further quantity of 
 magenta. The mother liquor from this crystallisation is mixed with the resin I. 
 Resin II., obtained on purifying resin I., is dissolved in hydrochloric acid, and the acid' 
 liquor is boiled, when some mauvaniline again separates out and is removed. The hot 
 solution is mixed with salt, when cerise is precipitated. It is filtered, and the coloured 
 base, after washing, is neutralised with hydrochloric acid and concentrated by steam in 
 iron pans. It is then the cerise of commerce. 
 
 In the filtrate from the precipitate of cerise the magenta remaining in solution is 
 precipitated by soda-lye, and the base obtained is mixed with the resin II. remaining 
 from resin I. The more or less complete separation of the bye-products depends on the 
 demands of the market. The required tones of magenta, cerise, cinnamon brown, 
 maroon, &c., are prepared by mixing suitable products. Mauvaniline (along with 
 violaniline) is an almost worthless product, and is very seldom made soluble by treat- 
 ment with fuming sulphuric acid, but is more frequently neglected. 
 
 In order to test a magenta for the presence of chrysaniline a portion is dissolved in. 
 hot water. A little hydrochloric acid is added and zinc dust in small portions until 
 the red colour has disappeared. The reduction is promoted by heat. Magenta free 
 from chrysaniline dissolves to a clear, colourless liquid, whilst the presence of 
 chrysaniline gives a more or less distinct yellowness. 
 
 The arsenic process is said, as compared with the nitrobenzol process to have the- 
 advantage that the quantity of bye-products is considerable enough to render it more 
 profitable. In the meantime the nitrobenzol process yields a very fine maroon, fully 
 equal to that obtained by the arsenical process. Except for the production of acid 
 magenta, that obtained according to the above described process is only suitable for 
 nferior rosaniline blues of a reddish cast. Neither cotton blue nor Nicholson blue 
 can be obtained from it in a satisfactory manner. 
 
 Coupler's process for magentas, which has been carried on for years at the colour- 
 works at Hoechst on the Main, at the Berlin Joint Stock Aniline Co., and elsewhere, 
 avoids the use of arsenic acid, and is founded on the oxidising action of nitrobenzol 
 containing nitrotoluol upon aniline oil in presence of iron and hydrochloric acid. An 
 enamelled pan, fitted with an agitator and an outflow pipe, is charged with 38 kilos, 
 aniline oil, 17 to 20 kilos, nitrobenzol, 18 to 22 kilos, hydrochloric acid, and 2 to 2^ kilos.. 
 
SECT, iv.] BENZOL COLOURS. 555 
 
 iron turnings. The pan is heated to 180, with stirring, for four to five hours. The crude 
 melt, scooped out upon sheet-iron trays with iron ladles, still contains 25 per cent, of 
 aniline. It is dissolved in water, the rosaniline is separated with common salt, and 
 the unconverted aniline is distilled off from the lye after the addition of lime. The 
 formation of this rosaniline (Briining's red, Coupier red, nitrobenzol red) may be 
 represented by the following equation : 
 
 2 C 7 H 7 .NH 2 + C 8 H 6 .NO, = C 20 H 19 N 3 + 2 H 2 0. 
 
 Lange observes that in the nitrobenzol magenta process the nitro compounds have 
 merely an oxidising action, or if they contain methyl groups they participate in the 
 formation of rosaniline in so far only as they furnish the atom of carbon necessary for 
 the production of carbinol. 
 
 The salts of rosaniline have mostly in reflected light the green metallic lustre 
 of the elytra of certain beetles (Cetoniadce, <fec.), whilst by transmitted light they 
 appear red. The hydrochlorate was formerly called fuchsine, the acetate roseine, and 
 the nitrate azaleine. The salt obtained by the action of mercuric nitrate was called 
 rubine. Their solutions in water have the splendid shade well known as magenta.* 
 
 Its tinctorial power is very great ; t kilo, of magenta suffices for 200 kilos, of wool. 
 Aniline tannate is sparingly soluble in water.f 
 
 Rosaniline is the basis of most of the other aniline colours ; thus blue and violet 
 colouring matters (alkylised rosanilines) may be produced from the rosanilines by 
 partially or entirely replacing the amidohydrogen atoms by alcohol radicles. More 
 recently, however, some of these alkylised rosanilines are preferably obtained by intro- 
 ducing the alkyl (e.g., methylaniline), not into the pre-formed rosaniline, but into the 
 aniline and toluidine, which is then submitted to oxidation for obtaining alkylised 
 rosaniline. 
 
 Acid magenta, Rubine S, or acid rubine, consist of mixtures of the sodium or 
 ammonium salts of the pararosaniline and rosaniline trisulpho acids ; according to 
 
 (C 6 H 3 .NH,.S0 3 Na (C 6 H 2 .CH 3 .NH 2 .S0 3 Na 
 
 HO.CJC 6 H 3 .NH^S0 3 Na and HO.c|C 6 H 2 .CH 3 .NH 2 .SO 3 Na 
 
 C 6 H 3 .NH 2 .S0 3 Na tC 6 H 2 .CH 3 .NH 2 .S0 3 Na 
 
 It is obtained by heating magenta with fuming sulphuric acid to 168 to 170, 
 pouring into much water, supersaturating with milk of lime, and treating the solution 
 with soda after removing the gypsum. The sodium salt obtained on evaporation is 
 readily soluble in water, and, unlike ordinary magenta, dyes in a strongly acid bath. 
 
 Aniline Slue. If rosaniline is heated with about 10 parts of aniline and a little 
 benzoic acid (the action of which is not yet understood) to the boiling point, ammonia 
 escapes, and the excess of aniline distils over 
 
 C 20 H 10 N 3 4- 3 C 6 H 5 .NH 2 = C 20 H 19 (C 6 H 5 ) 3 N 3 + 3 NH 3 . 
 
 The residue is neutralised with hydrochloric acid; triphenylrosaniline hydro- 
 chlorate is insoluble in water (though the excess of aniline dissolves as hydrochlorate), 
 but more readily soluble in spirit (spirit blues). 
 
 If, in like manner, aniline is allowed to act upon a mixture of pararosaniline and 
 rosaniline, we obtain a mixture of the hydrochlorates, sulphates or acetates of triphenyl- 
 rosaniline and triphenylpararosaniline occurring under the trade names of aniline 
 spirit blue, gentian blue, opal blue, and light blue 
 
 * Magenta is soluble in acetic acid, in alcohol, in glycerine, and in solutions of alkaline 
 bicarbonates. By acids the colour is turned more on the blue side, but is apt to be dulled and 
 impoverished. 
 
 t Magenta, like many other coal-tar colours, is apt to be sophisticated with sugar and dextrine. 
 
536 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 (C 6 H 4 .NH.C 6 H 5 (C 6 H 3 .CH 3 .NH.C 6 H 5 
 
 C C 6 H 4 .NH.C 6 H 5 and C C 6 H 4 .NH.C 6 H 5 
 (C 6 H 4 .N.C 6 H..HC1 IC 6 H 4 .N.C 6 H 5 .HC1 
 
 To render aniline blue soluble in water it is treated with concentrated sulphuric 
 acid. The mixture of sodium salts, of triphenylrosaniline, monosulpho acid, and 
 triphenylpararosaniline monosulpho acid, occurs in trade under the names of Nicholson 
 blue, alkali blue, and soluble aniline blue. If it contains also disulpho acids we have 
 water blue, China blue, and marine blue. If aniline is heated to 250 with aniline 
 hydrochlorate we obtain diphenylamine hydrochlorate (C 6 H 5 ) 2 NH.HC1. The diphenyla- 
 mine on heating with oxalic acid to i2o-i3O yields triphenylpararosaniline 
 3 (C 6 H 5 ) 2 NH + H,C 2 4 = C 19 H 14 (C e H 5 ) 3 N 3 + CO + 3 N f O. 
 
 The hydrochlorate is sold as spirit-diphenylamine blue, or Bavarian blue, and is 
 distinguished from aniline blue merely by the absence of triphenylrosaniline. When 
 rendered soluble by treatment with concentrated sulphuric acid the sodium salts are 
 sold as alkali blue D, and Bavarian blue D S F. 
 
 According to De Laire andGirard (1866), the mixture of aniline and aniline hydro- 
 chlorate is heated in an enamelled cast-iron autoclave for twenty-four hours, at a 
 pressure of 3 to 4 atmospheres and a temperature of 250. From time to time the 
 ammonia collecting in the autoclave must be expelled by opening a cock, as otherwise 
 the reaction might be reversed, and the yield of diphenylamine might be decreased. 
 In this manner the yield of diphenylamine is 50 per cent, of the weight of the aniline 
 used. The mass taken out of the autoclave is treated with strong hydrochloric acid 
 in order to separate the unchanged aniline from the diphenylamine. From six to ten 
 volumes of water are now added, which occasions a dissociation of the diphenylamine 
 salt into base and acid. The base liberated collects on the surface of the liquid as an 
 oily layer, which, when cold, is taken off, pressed, and distilled. It forms a solid, 
 crystalline, yellowish-white mass, which melts at 5o-55 and distils at 310. By 
 sulphurising the diphenylamine or its alkylised products, they obtain the mono- and 
 disulpho-acids, which, after treatment with oxidising agents, can be at once used in 
 dyeing and printing for the production of blacks and violets. 
 
 For producing alkylised diphenylamine various methods may be adopted e.g., 
 (a) the action of methyl-chloride or nitrate at a temperature below 100 ; (b) the action 
 of methyl-aniline upon aniline hydrochlorate ; (c) the action of methyl-alcohol upon 
 anhydrous diphenylamine hydrochlorate ; (d) the action of the nascent chlorides of the 
 alcohol radicles, i.e., by treating diphenylamine with a mixture of hydrochloric acid and 
 methyl-alcohol, when the most important of these bases, methyl-diphenylamine : 
 
 (C 6 H 5 ) 2 NH + C 2 H 8 C1 = (C 6 H 5 ) 2 CH 3 N.HC1, 
 
 is formed. The latter base is obtained by heating 100 kilos, diphenylamine, 68 kilos, 
 hydrochloric acid of sp. gr. 1-2, and 24 kilos, methyl-alcohol, in an enamelled cast-iron 
 autoclave for eight to ten hours in the oil bath at 200 to 350 and bringing the mass in 
 contact with hot caustic soda-lye. The crude base separates out and is purified by 
 distillation. It boils at 282 to 286 ; its salts are decomposed by water. If heated to 
 110 to 120 along with oxalic acid, it becomes a blue. In a quite analogous manner 
 the bases ethyl-, amyl-, and benzyl-diphenylamine may be obtained, which all yield blue 
 colouring matters on treatment with oxidising agents. 
 
 For obtaining diphenylamine blue, soluble in water, one part of one of the sulpho- 
 acids of diphenylamine is heated in an autoclave with two parts of oxalic acid, at a 
 temperature not exceeding 130. After heating from eighteen to twenty hours the mass 
 is let cool, treated with boiling water, saturated with ammonia, filtered ; the colouring 
 matter is precipitated with sulphuric acid, washed with acidulated water, and finally 
 converted into the salt desired, with ammonia, soda, or lime. The blue solution is 
 
SECT, iv.] BENZOL COLOURS. 537 
 
 evaporated to dryness and the residue is pulverised. For silk there is used the ammo- 
 nium salt, for wool the sodium salt, and for cotton the calcium salt. 
 
 Aniline Violet. If rosaline is heated in an alcoholic solution with methyl chloride or 
 iodide, or ethyl bromide, we obtain the methyl and ethyl derivatives of rosaniline, 
 the hydrochlorates, hydriodates, or acetates of which are known as Ilofmann's violet, 
 iodine violet, dahlia, primula, red violet, violet 7?., &c. The blue violet hydrochlorate of 
 triethylrosaniline corresponds to the formula 
 
 (C 6 H 3 .CH 3 .NH.C 2 H 5 
 C {C.H 4 .NH.C,H. 
 
 (C 6 H 4 .NH.C 2 H 5 C1 
 
 Methyl Violet or Paris Violet is substantially the hydrochlorate of pentamethylpara- 
 rosaniline 
 
 (C 6 H 4 .N(CH 3 ), 
 C C 6 H 4 .N(CH 3 ) 2 
 
 IC 6 H 4 .N(CH 3 )HC1 
 
 and is formed by oxidising dimethylaniline with copper chloride, which is first mixed 
 with much sodium chloride, then with dimethylanine and acetic acid and dried at 50. 
 The bulk of the sodium chloride is removed by means of a little water, the residue is 
 removed with water, the copper is precipitated by hydrogen sulphide, the colouring 
 matter is precipitated with much salt, and purified by re-crystallisation. According to 
 the statement of the Baden Aniline Works, methyl violet is obtained as follows : Into 
 100 kilos of dimethylaniline 1 8 or 20 kilos, of chlorocarbonic oxide are introduced at 
 20, and after standing for twenty-four hours, 50 more kilos, of dimethylaniline and 30 
 kilos, of powdered zinc chloride. Then, whilst constantly stirring at 40 to 50 chloro- 
 carbonic oxide is introduced until there is an increase of 20 kilos, in weight. The reaction 
 is completed by heating for six hours to 50. From the melt obtained the colouring base 
 is extracted in the usual manner by supersaturation with soda lye and distillation with 
 steam, and this base is again converted into a sulphate. From the hot solution of the 
 latter the finely crystalline hydrochlorate of methyl violet may be obtained by an 
 addition of common salt. The same method is taken in obtaining the corresponding 
 violet colours from diethylaniline and methylethylaniline. 
 
 A. W. Hofmann gives the following equations for the formation of the colouring 
 matter obtained by the action of phosgene upon dimethyl aniline 
 
 C 6 H 6 N(CH 3 ) 2 4 COC1 2 = C 6 H 4 N(CH 3 ) 2 COC1 + HC1. 
 
 C 6 H 4 N(CH 3 ) 2 COC1 + C 6 H 5 N(CH 3 ) 2 = [C 6 H 4 N(CH 3 ) 2 ] 2 CO + HC1. 
 [C 6 H 4 N(CH 3 ) 2 ] 2 CO + COC1 2 = [C 6 H 4 N(CH 3 ) 2 ] 2 CC1 2 + CO,. 
 [C 6 H 4 N(CH 3 ) 2 ] 2 CC1 2 + C 6 H 5 N(CH 3 ) 2 = [C 6 H 4 N(CH 3 ) 2 ] 3 CC1 + HCL 
 The hexamethylpararosaniline is sold as a hydrochlorate under the names crystal 
 violet, or violet 6B. 
 
 Methyl violet is soluble in water ; it dyes silk, wool, and cotton prepared with 
 tannin and tartar emetic. 
 
 If methyl chloride is heated in an alcoholic solution with benzyl chloride, 
 
 C 6 H 5 .CH 2 C1, 
 
 and soda, a part of the methyl groups are replaced by benzyl and the tone of the colour 
 is turned more to a blue. The hydrochlorate of pentamethylbenzylpararosaniline : 
 
 C 6 H 4 .N(CH 3 ) 2 
 
 C 
 
 C 6 H 4 .N(CH 3 ) 2 
 
 (C 6 H 4 .N.CH 3 .C 6 H 5 .CH 2 C1 
 is an article of commerce, under the names Methyl violet 6B, or Benzyl violet. 
 
 Aniline Green. The chlormethylhexamethylpararosaniUne hydrochlorate is now very 
 generally preferred to the chlormethylhexamethylrosaniline hydrochlorate, obtained 
 
53 8 CHEMICAL TECHNOLOGY [SECT. iv. 
 
 by the action of methyl chloride or iodide upon rosaniline, the double zinc chlorides of 
 which are met with under the names, iodine-green, night-green, or Metternich green* 
 The double zinc chlorides of the former compound are sold as methyl green, Paris green,, 
 or light green. The compositions of both are shown by the formula 
 
 (C 6 H 4 .N(CH 3 ) 2 (C 6 H 3 .CH 3 .N(CH 3 ) 2 
 
 C C 6 H 4 .N(CH 3 ),.CH 3 C1 C C 6 H 4 .N(CH 3 ),CH 3 C1 
 
 iC 6 H 4 .N(CH 3 ) 2 Cl + ZnCl 2 (C 6 H 4 .N(CH 3 ) 2 C1 + Zn01 2 
 
 Methyl green. Iodine green. 
 
 Both dissolve in water, with a blueish-green colour. 
 
 The double zinc chloride of bromethylhexamethylpararosaniline, which is sold as. 
 ethyl green, is obtained by the action of bromethyl upom methyl violet. ^ 
 
 The bluish-green sodium salt of tetramethyldibenzylpseudorosaniline disulpiio- 
 acid is known as fast green. The respective compositions of the two coloxirs are 
 
 (C 6 H 4 .N(CH 3 ) 2 (C 6 H 4 .N(CH 3 ) 2 
 
 C \ C 6 H 4 .N(CH 3 ) 2 .C 2 H 5 Br HO.C C 6 H 4 .N(CH 3 ) 2 
 tC 6 H 4 .N(CH 3 ) 2 Cl + ZnCl 2 (C 6 H 4 .N(CH 2 .C 6 H 4 .S0 3 Na) 2 
 
 Ethyl green. Fast green. 
 
 Aniline yellow, along with some other colours prepared from aniline, is discussed 1 
 among the azo-colours. 
 
 Flavaniline, obtained by heating acetanilide with zinc chloride, is 110 longer an article 
 of commerce. It is included as is also the chrysaline or phosphine obtained as 
 bye-products of the manufacture of magenta, among the quinoline and acridine 
 colours. 
 
 Aniline Black is an intense aniline green, produced by the slow oxidation of 
 aniline. It is almost exclusively produced upon the fibre, and more generally in 
 printing than in dyeing, in the strict sense of the word. A black dye which can be 
 obtained in trade and can be conveniently applied both in dyeing and printing does not 
 hitherto exist. The formation of aniline black, however obtained, seems to take place as 
 follows : 
 
 nC 6 H 5 .NH 2 = n(C 6 H 5 N) + nH 2 
 Aniline. Aniline black. 
 
 According to R. Kayser, aniline black has the formula C 12 H 10 2 ; according to 
 Goppelsroder, C 24 H 20 N 4 ; according to Metzki, C 30 H 25 N 5 ; and according to Liechti, 
 C 18 H 15 N 3 .HC1. 
 
 The formation of aniline black by the action of oxidising agents upon aniline oil is 
 said to have been observed by Fritsche as early as 1843.* 
 
 As oxidising agents for obtaining aniline black there are used potassium chlorate 
 and copper chlorate, ammonium ferrocyanide, potassium chromate, and latterly, above 
 all others, ammonium vanadate. One part of the vanadium preparation, in presence of 
 the requisite quantity of potassium chlorate, can convert 1000 parts of aniline hydro- 
 chlorate into black. The use of aniline black is confined almost exclusively to cotton 
 printing and dyeing. For woollen dyeing it would be requisite to bring it 
 into a soluble state after the manner of indigo, which has not hitherto been found 
 practicable. 
 
 Aniline black has now for some years been used as a marking ink for linen, under 
 the name jetoline. 
 
 Along with magenta there figure, as representatives of the different classes of 
 triphenylmethan colours, 
 
 * The practical discovery of the colour was made by J. Lightfoot in 1863. 
 
SECT, iv.] BENZOL COLOURS. 539 
 
 Malachite Green> Rosolic Acid, and Fluoresceine 
 
 n. (CJL.OH / C 6 H 3- OH 
 
 0- 
 
 C 6 H 4 .N(CH 3 ) 2 C C 6 H 4 .OH 
 
 (c 6 H 4 o 
 
 o 
 
 Malachite green Pararosolic acid. Fluoresceine. 
 
 as Hydrochlorate. 
 
 Benzaldehyd Green or Malachite Green. This compound was at first obtained 
 on Dobner's process by the action of benzotrichloride upon dimethylaniline and zinc 
 chloride, but it is now prepared universally by the oxidation of the tetramethyl- 
 diamidotriphenylmethan obtained from benzaldehyde with dimethylaniline. 
 
 Oil of bitter almonds, or benzaldehyde, is now chiefly obtained by introducing 
 chlorine into toluol, and boiling the benzyl chloride thus produced, C 6 H S .CH 2 C1, with 
 copper nitrate and water, or by boiling the benzyl chloride, C 6 H S .CHC1 2 (obtained on 
 passing chlorine into boiling toluol), along with milk of lime. Benzotrichloride, 
 C 6 H 5 .CC1 3 , is obtained by the prolonged treatment of toluol with chlorine. 
 
 Dimethylaniline is obtained by heating aniline and soda-lye to 100 and gradually 
 introducing chlormethyl, the pressure not being allowed to rise above 6 atmospheres 
 
 C 6 H 5 .NH 2 + 2 CH 3 C1 + 2 NaOH = C G H 5 .N(CH 3 ) 2 + 2 KaCl-H 2 0. 
 Or aniline is heated under pressure with methyl alcohol and hydrochloric acid. 
 According to O. Miihlhauser, there are placed in an enamelled cast-iron autoclave 
 60 kilos, aniline oil (for blues), 45 kilos, wood spirit, and finally 18 kilos, hydrochloric 
 acid at 32 Tw. When the apparatus is charged, the entrance is tightly closed, and 
 heat is applied by means of an open coke-fire. 
 
 On commencing the reaction at a moderate heat, the pressure in the autoclave 
 quickly rises to 25-28 atmospheres, at which it is kept for four to five hours. At the end 
 of this time the methylation of the aniline is complete, and the autoclave may be 
 let cool. After the lapse of twelve hours the apparatus is still warm and the pressure 
 slight. The contents are brought to the ordinary pressure of the atmosphere by 
 gradually and cautiously raising the filling cover, when a current of methyl chloride 
 escapes. The cover is then unscrewed, and in its place a pipe is introduced for the oil 
 to be forced out. This pipe, which can be screwed in tightly, and which reaches 
 to the bottom of the autoclave, is twofold, and allows on one side admission for 
 compressed air, and on the other an exit for the contents. The warm liquid mass 
 is forced into a wooden tank lined with lead. For decomposing the hydrochlorate and 
 separating the oil, a milk of lime is added, which is prepared the previous day from the 
 lime of 20 kilos, of marble ; agitation is kept up during its introduction. The contents 
 of two autoclaves are rendered alkaline in this manner, run into the still, and the 
 cistern is washed out with water. The still is closed, and the oil is expelled by 
 heating over an open fire and the introduction of steam. After heating for two hours 
 the water in the still boils, escapes and is condensed in the refrigerator along with oils 
 which have been carried over. As soon as the distillation of water begins, a current of 
 steam is allowed to enter, and the distillation with the aid of steam is kept up briskly. 
 After the lapse of about five hours the distillation is complete and all the oil has passed 
 over. The operation is then brought to an end by shutting off the steam. The residue in 
 the still is treated as waste ; a cock at the bottom allows it to be run off into the drain. 
 
 For the separation of oil and water a peculiar receiver is used a combination of 
 the parting funnel and the Florentine flask. The distillate, which enters the refri- 
 gerator in a stream of the thickness of a finger, passes into this receiver, and is separated 
 there into an upper layer of oil and a lower stratum of water. As soon as the level of 
 liquid in the receiver has reached the height of the outflow opening, the water is run off 
 
540 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 through a tube, which reaches nearly to the bottom of the receiver. In this manner a 
 preliminary separation of the bulk of the water from the oil is effected. At the end of 
 the distillation a complete separation of oil and water is effected by opening a cock 
 fixed at the lowest part of the bottom. The oil is placed in an iron cylinder along 
 with dry salt in order to remove the last traces of water. 
 
 According to Miihlhauser, the manufacture of malachite green resolves itself into 
 four separate stages i. The production of a pure, dry leuko-base ; 2. The oxidation of 
 this base into green, and obtaining it in a solid form; 3. The purification of the 
 green colouring matter, and the production of the green base ; 4. The production of 
 green crystals. To these processes there correspond four independent systems of 
 apparatus in addition to an apparatus for working up the residues. For a daily out- 
 put of 70 kilos, there are required : 
 
 An installation for obtaining the leuko-base, consisting of three cast-iron double 
 pans ; connection of the outside pan to the water and steam mains ; connection of the 
 cover, fitted with a man-hole and pressure-gauge, with the air-piping from the still, 
 and capable of being heated by direct and indirect steam, as also a worm cooler, and 
 a drying-pan placed beneath the still. 
 
 A system of vats for oxidising the leuko-base and obtaining the green in a solid 
 state, consisting of an elevated vat for dissolving the leuko-base ; three oxidation butts 
 fitted with agitators ; the precipitating vats corresponding to these three oxidising vats, 
 and placed below them, with box filters for previous and subsequent filtration. 
 
 The purifying system consists of a horizontal pan provided with an agitator, and 
 containing 3500 litres. This pan has an elevated dome with a man-hole. A second 
 opening of equal size is situate close to the bottom, and serves for emptying the pan, 
 which has a slight incline. This pan is in connection with the water and steam 
 mains, and also with a pressure-filter, a cast-iron chest, the inside bottom of which can 
 be unscrewed. This chest is divided into two compartments by a strong cotton cloth 
 in such a manner that the liquid streaming in from below under pressure allows only 
 dissolved substances to flow into the second compartment, but retains the solids. The 
 filtrate escapes through a side aperture in the chest, and flows through a pipe into the 
 precipitating vats, with three filter-chests placed below. 
 
 The system of crystallisation consists of a vat for dissolving the bases, of the 
 capacity of 2000 litres, and six crystallising vats, each of the same size, and provided 
 with round floating covers in several compartments. 
 
 For producing the leuko-base there are placed in the double pan, provided with an 
 agitator, 100 kilos, of dimethylaniline and 40 kilos, of benzaldehyde. The mass is kept 
 in agitation, and there are added within two hours 40 kilos, of anhydrous zinc chloride 
 in powder. The pan is closed, and it is heated to 60 the first day, to 80 the second, 
 and to 100 on the third, the water in the outside kettle being brought to a boil. After 
 thus working for three days the condensation is completed, and the leukobase can be 
 separated from the excess of dimethylaniline. A pressure-pipe is placed in the pan, 
 and the contents, yet hot, are forced into the still. 
 
 The mass in the still is exposed to the action of direct steam, which carries along 
 with it the oil ; the steam and oil are liquefied in the refrigerator and collected in a 
 receiver. The distillation is continued until clean water passes over. By opening the 
 outlet-cock in the vaulted bottom, the contents are entirely discharged into a copper 
 pan placed below, and there allowed to cool. The liquid solution of zinc chloride is 
 separated from the supernatant solid base by means of syphons, washing lastly with 
 cold water. The solid base remaining in the copper pan is melted by admitting steam 
 into the outer pan, and dried by agitation, which takes about twelve hours. The dry 
 liquid base is placed upon zinc plates in such a manner that every plate receives a 
 nett weight of 33 kilos. ; any residue is weighed into the next operation. The yield 
 
SECT, iv.] BENZOL COLOURS. 54 t 
 
 from 100 parts dimethylaniline, 40 benzaldehyde, and 40 solid zinc chloride is about 
 123 parts. 
 
 In order to remove the base from the zinc plates, one plate with its 33 kilos, is 
 placed in a small wooden vat holding 400 litres. The plate is laid upside down upon 
 a steam-worm in the vat provided with many apertures ; steam is turned on, and the 
 base is melted off the plate. When this is done the plate is removed ; about 200 litres 
 water are run into the vat and heated to a boil, so that the base melts. To the boiling 
 mixture are added 25 kilos, hydrochloric acid at 32 Tw., a quantity which suffices for 
 complete solution. If, on pouring a sample into water, there still remains a white 
 milky turbidity of basic salt, a little more acid is added, until all the test shows 
 complete solution i.e., a sample poured into water remains clear, and all the leuco- 
 base is converted into a bi-acid salt. The clear solution is run into a vat placed 
 below, containing 1000 litres water, and is mixed with 31 kilos, of acetic acid of 
 40 per cent., with thorough agitation. For obtaining the lead peroxide there are used 
 67 kilos, litharge, 125 kilos, acetic acid at 40 per cent., and 81 kilos, chloride of lime. 
 The dark-brown paste produced is placed in a cask, and made up to a nett weight of 
 1 68 kilos, by the addition of water. The whole is then divided into three small tubs, 
 so that in each tub there are exactly 56 kilos, of paste, corresponding to 33 kilos, of 
 leucobase. 
 
 For producing the green there is placed in each of the vats its portion of peroxide 
 paste, which is thoroughly mixed up in five to ten minutes by means of the agitator. 
 The solution is then a deep green. 
 
 In order to precipitate the paste in the small dissolving-vat placed above the 
 oxidation- vats, 72 kilos, sodium sulphate are dissolved in 200 litres of water, and made 
 up to a volume of 300 litres. Immediately after the oxidation 100 litres of the solution 
 of sulphate are let run into each of the three oxidising vats with vigorous stirring. The 
 sodium sulphate precipitates all the lead as a sulphate. It is allowed to settle for twelve 
 hours, and filtered the next day into the precipitating- vats through a chest lined with felt. 
 
 For precipitating the colouring matter, the green is first converted into the 
 sparingly soluble double zinc salt. As this double zinc chloride is sparingly soluble 
 even in a dilute solution of zinc chloride, it is mixed with an excess of zinc chloride, and 
 then completely salted out with common salt. Into each vat there are stirred in, first, 
 20 kilos, of zinc chloride, and the double zinc salt is completely salted out by adding 
 175 kilos, of common salt, which is also stirred in. The precipitation is complete as soon 
 as a drop of the liquid applied with a glass rod to a slip of filter-paper no longer shows 
 a coloured margin. All three vats are treated in the same manner ; allowed to stand for 
 twelve hours, and finally passed through a chest-filter. The residue is drained, and 
 consists of a moist mixture of double zinc salt, resin, and excess of salt. 
 
 To separate the double zinc salt from the accompanying matters the mass is stirred 
 up with hot water in a large horizontal boiling-pan. For this purpose it is conveyed 
 into 2400 litres of hot water, keeping the agitator in action, boiled for ten minutes, and 
 about 500 litres of cold water are run in to separate out the resin, which at the high 
 temperature had dissolved along with the green. The pan is closed and left at rest for 
 ten minutes. The resin has in the meantime been chiefly deposited and may be filtered 
 off, forcing the liquid through a filter press by means of compressed air. The filtrate 
 runs into a wooden vat, where it is let cool down to 40, and is then precipitated by 
 stirring in 100 kilos, ammonia. 
 
 If the temperature is attended to, we thus reach the precipitation of the base in a 
 melted state, without including the zinc hydroxide, which is completely dissolved. The 
 )iquor is filtered into an iron cistern and passed on to the ammonia still; the greyish- 
 white base is packed in bags and drained in the centrifugal. The yield of moist base 
 is 82 kilos. 
 
542 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. rr. 
 
 Leuko- 
 base. 
 
 HC1 at 32 
 Tw. 
 
 Acetic 
 Acid 40 
 per cent. 
 
 PbO 
 
 Acetic 
 Acid 40 
 per cent. 
 
 Chloride 
 of lime. 
 
 Salt 
 cake. 
 
 NaCl 
 
 ZnClii 
 
 Ammonia. 
 
 Yield of 
 moist 
 base. 
 
 3><33 
 
 3x25 
 
 3X31 
 
 67 
 
 125 
 
 81 
 
 72 
 
 3X175 
 
 3X20 
 
 I GO 
 
 84.0 
 
 3><33 
 
 3X25 
 
 3X31 
 
 67 
 
 "5 
 
 81 
 
 72 
 
 3X175 
 
 3 x 20 
 
 100 
 
 85.0 
 
 3><33 
 
 3X25 
 
 2x31 
 
 6 7 
 
 125 
 
 81 
 
 72 
 
 3X175 
 
 3x20 
 
 IOO 
 
 82.5 
 
 Along with the green base there is obtained the insoluble residue of double zinc 
 chloride. 
 
 For crystallising we dissolve in a wooden vat holding 2000 litres 120 kilos, of oxalic 
 acid in 1200 litres of water, promoting solution by heating to a boil ; 100 kilos, of base 
 are then added, which dissolves in the oxalic acid. The volume of the liquid is made 
 up to 1800 litres, and it is filtered into a tall, slightly conical cask, holding 2000 litres. 
 Into the liquid, which has a temperature of 80, there are stirred 30 kilos, of ammonia 
 at 20 per cent, in a thin stream, and the surface is covered with boards cut to fit, 
 which float upon the liquid and are adapted to the circular form of the cask. 
 
 The separation of the crystals ensues, chiefly not at the bottom, but on the sides 
 and on the lid. The crystallisation is broken off as soon as the temperature within the 
 cask has fallen to 18. If it were allowed to cool down lower, ammonium oxalate would 
 separate out and would contaminate the green in a very unpleasant manner. In order 
 to separate the crystals from the mother liquor the floating boards are removed and a 
 spigot at the bottom is withdrawn. The crystals are left in a felt filter through which 
 the liquid has to pass. 
 
 The crystals are first taken away from the bottom, and those on the sides are scraped 
 down. The crystals from the sides and the cover are mixed on a filter, and those from 
 the bottom are kept separate. After drainage on the filters the crystals are packed in 
 woollen bags and drained in centrifugals. The size of the crystals depends on the 
 position of the crystallising vats, and the thickness of the wood-work. The vats should 
 be set in places free from agitations or shocks, such as might be produced from steam 
 engines, pumps, &c., and must be on the firm ground. 
 
 The thickness of the wood must not be excessive. If such is the case the crystals 
 are too large and are open to all the defects of large crystals. The crystals after being 
 whizzed are finally uniformly distributed over a fine sieve to prevent them from ad- 
 hering together, and are dried at 5o-6o in a drying stove. The yield is 70 kilos. 
 
 As bye-products are obtained, during the condensation, the oil driven off and a lye 
 containing zinc chloride ; from the oxidation, a mixture of lead sulphate and a little 
 colouring matter ; on dissolving the crude colouring matter, the double salt of zinc 
 containing resin and adhering colouring matter ; on precipitating the base from the 
 solution of the double chloride, a lye containing ammonia ; lastly, from the crystallisation, 
 a mother liquor from which oxalic acid and a quantity of good base may be recovered. 
 
 About 70 kilos, of " driven-off oil," the yield of 10 lots, are once more distilled with 
 direct steam, separated from water in a cylindrical pan, and dried with anhydrous 
 sodium chloride. The dimethylaniline thus obtained is used in a fresh condensation. 
 
 The solution of zinc chloride drawn off from the leuko-base is filtered, and after it 
 has been brought up to 50 per cent. ZnCl 2 by the addition of solid zinc chloride, it 
 serves for salting out the green. 
 
 The lead residues from ten lots are boiled up in a tub with 2000 litres of water, 
 allowed to settle and filtered when cold. The saline matter liquor is separated by 
 filtration. The double salt remaining on the filter is worked up for green crystals with 
 a succeeding lot. The lead sulphate, after again boiling up with water to which a 
 little sulphuric acid has been added, is filtered and dried, and is used as such. 
 
SECT, iv 1 BENZOL COLOURS. 543 
 
 200 kilos, of moist double zinc chloride residues are stirred into 2000 litres of boiling 
 \vaier and mixed with 20 kilos, of hydrochloric acid. After boiling for 30 minutes it 
 is let settle and filtered into a vat below. From the filtrate the base is separated out 
 with soda. The residue in the boiling vat, consisting of resin and residues of salt, is 
 thrown away. The base separated out by soda is worked up for liquid green or so-called 
 'marine Hue. 
 
 The lye containing ammonia is treated for ammonia. 
 
 The mother-liquor separated from the crystals is heated to 80 in a vat and mixed 
 with soda-lye until it has a slight alkaline reaction. The green base separates as a 
 dense resin, which incloses but little oxalates. It is allowed to cool, and filtered. 'The 
 filtrate (sodium oxalate) is mixed with calcium chloride and worked up for calcium 
 oxalate, which is filtered, and after again being boiled in water, and being passed 
 through the filter press, it goes back into work for the recovery of oxalic acid. The 
 resinous base from the mother liquor is boiled out with water, and after separation from 
 the washing water it is converted into green or navy blue. 
 
 Production of Liquid Colour. The base from the mother liquor, or that from 
 working of the double zinc residues, is first mixed with an equal weight of the strongest 
 hydrochloric acid and heated on the water bath in an enamelled pan. The melt 
 obtained is baled into water at 50, with stirring. Resinous products separate and the 
 .green remains in solution. After standing for about a day it is filtered into a tub, in 
 which the base is precipated by ammonia with the aid of heat. The base thus purified 
 serves for the production of colours. 
 
 Liquid Green. 50 kilos, of the base just mentioned are dissolved in 40 kilos, of 
 hydrochloric acid and 150 litres water, allowed to cool, and filtered. The filtrate is 
 slightly acidified, if necessary, and made up with distilled water to the tone of a green 
 solution obtained with 20 grammes crystal green in 80 grammes water. This solution 
 is sold as liquid green. 
 
 For so-called "navy blue" 50 kilos, of base are dissolved in 40 kilos, of hydro- 
 chloric acid and 150 litres of water, and filtered when cold. The filtrate is again 
 heated, and mixed with 22^ kilos, violet 36, which is sprinkled in while stirring, and 
 dissolved. The solution is made up with distilled water to 250 litres and filtered when 
 cold. It is sold under the names liquid indigo blue (!), navy blue, cotton blue, &c. 
 
 Malachite green is sold as oxalate, 2C 23 H 24 N 2 .3C 2 H 2 4 , or as the double zinc 
 chloride, 3C 23 H 24 N 2 .HC1 + 2 ZnCl 2 + 2 H 2 O, by the names malachite green, bitter almond 
 green, Victoria green, fast green and solid green. It is soluble in water with a bluish- 
 green colour. 
 
 Helvetia green, formed by sulphurising malachite green, has disappeared from the 
 market. 
 
 For obtaining brilliant green, emerald green, new Victoria green, the procedure is very 
 similar to that for malachite green. 60 kilos, of diethylaniline are heated with 22 
 kilos, of benzaldehyde and 32 kilos, of dry oxalic acid. The leukobase is dissolved in 
 Tiydrochloric acid, acetic acid is added, and it is oxidized with a paste of lead peroxide. 
 After throwing down the lead as sulphate, it is filtered, and the green is obtained from 
 the filtrate in the form of a zinc double salt. It is extracted with ammonia in a large 
 boiling-pan, and from this solution the base is precipitated with ammonia. Into the 
 enamelled pan, set in a water bath, there are put 120 kilos, sulphuric acid and 280 
 litres of water, and 100 kilos, of base are stirred into the warm mixture. After the 
 base is entirely dissolved the contents of the pan are cooled down to 20, and 130 kilos, 
 ammonia are let run in, in a thin stream and with constant stirring. The solution i 
 heated to 55-6o until there is a slight separation of green, which may be easily seen if 
 a, drop is placed upon a piece of white filter-paper. As soon as a separation appears 
 it is allowed to settle and filtered through felt into a second pan, in which the filtrate is 
 
544 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 rapidly heated to 85-9O. The colouring matter separates out in crystals of a metallic 
 lustre. They are placed on a filter, drained, and freed from mother liquor by vfhhzirg 
 in the centrifugal. The yield is 94 kilos. 
 
 The colouring matter consists of the tetraethyldiparaamidotriphenylcarbinol sul- 
 phate (rarely the oxalate) : 
 
 ( C 6 H 5 
 
 C C 6 H 4 .N(C 2 H 6 ) 2 
 
 (C 6 H 4 .N(C 2 H 5 ).S0 4 H 
 
 The hydrochlorate of tetramethyldiamidodichlorotriphenylcarbinol is sold as 
 Victoria green 3 B : 
 
 (C 6 H 3 C1 2 
 C 6 H 4 .N(CH,) f 
 
 IC 6 H 4 .N(CH 3 ) 2 C1 
 
 All these colouring matters dye silk,- wool, and cottons, mordanted with tannin and 
 tartar-emetic, a green. But brilliant green has a yellower and Victoria green a more 
 blue tone than malachite green. In wool-dyeing acid green is chiefly used. 
 
 Acid green and light green SF is the sodium salt of diethyldibenzyldiamidotriphenyl 
 carbinoltrisulpho acid : 
 
 ( C 6 H 4 .S0 3 Na 
 
 HO.C J C 6 H 4 .KC 2 H 5 .CH 2 .C 6 H 4 .S0 3 Na 
 (C 6 H 4 .N.C 2 H 5 .CH,C 6 H 4 .S0 3 Na 
 
 According to Miihlhauser the formation of the leuko-base of acid green is effected by 
 the condensation of i mol. benzaldehyde and 2 mols. ethylbenzylaniline by anhydrous 
 oxalic acid according to the equation : 
 
 H. ( H .C 6 H,KC 2 H,CH 2 .C 6 H 5 _ ^ + fo^^^OH..^ 
 
 [H.C 6 H 4 .N.C 2 H 5 .CH 2 .C H. 1 C^ 6 H 4 .N.C,H 5 .CH,.C 6 H 6 
 
 By sulphurising the leuko-base thus formed with fuming sulphuric acid there 
 is obtained a mixture of the di- and tri-sulpho acids of diethyldibenzyltriphenyl- 
 methan : 
 
 C 37 H 38 N 2 + 2 S0 4 H a = C 37 H 36 (S0 3 H) 2 N 2 + 2 H 2 O 
 C 37 H 38 N a + 3 S0 4 H 2 = C 37 H 35 (S0 3 H) 3 N 2 + 3 H 2 0. 
 
 The oxidation of the acid effected with lead peroxide leads to a green colouring 
 matter according to the equation : 
 
 C 37 H 36 (S0 3 H),N 2 + PbO, = C 37 H 34 (S0 3 ) 2 PbN 2 + H 2 0, 
 which is converted into a sodium salt. 
 
 For producing the leuko-base there are introduced 21 kilos, benzaldehyde and 80 
 kilos, benzylethylaniline into an enamelled double pan fitted with an agitator and 
 connected with the steam and water-pipes. To the mixture, which is kept in motion, 
 there are added 34 kilos, of well-dried and finely sifted oxalic acid. This addition is 
 made in successive portions within an hour. When the mixture is complete the pan 
 is closed, the water in the jacket is brought to 60, a temperature which is maintained 
 for one day. The two following days the heat is kept at 80, and on the fourth day it 
 is maintained at 100. By keeping the given temperature for these times, and 
 agitating continually, the reaction is kept up very regularly. At the end of the 
 fourth day the leuko-base is obtained as a soft green paste, still containing benzoic acid 
 and benzaldehyde. The cover of the manhole is removed and the hot paste is neu- 
 tralised by agitation with soda-lye. About 100 kilos, of lye at 62 Tw. are needed. 
 
 The man-hole is closed, the pressure-pipe fixed in its place, and the contents of the 
 pan are entirely forced over into the still, where the excess of benzaldehyde is com- 
 pletely removed from the leuko-base by distillation in a current of steam. When this 
 
SECT, iv.] BENZOL COLOURS. 545 
 
 has been effected the still is closed and the contents are heated to a boil with indirect 
 steam. Direct steam is then turned into the boiling mass, which carries with it the 
 benzaldehyde which has escaped the reaction. The distillation is kept up until only 
 clean water passes over, thus showing that the benzaldehyde has been completely 
 separated from the base. The wide cock at the bottom of the pan allows it to be 
 emptied into a double pan placed below. When cold the faintly alkaline lye is 
 drawn off with a syphon from the solidified leuko-base, which is then again washed 
 with water. The liquor and the washings are worked up as sodium oxalate. 
 
 The base remaining in the copper pan is melted and heated for about a day, stirring 
 until it is completely dry. When cold the base is broken out of the double pan, 
 and divided as finely as possible by beating with a wooden mallet. The yield is 93 kilos. 
 The condition for producing a good base is pure material pure benzaldehyde, pure benzol- 
 ethyl aniline, and perfectly dry oxalic acid. 
 
 For sulphurising, 200 kilos, of a 20 per cent, fuming sulphuric acid are placed in a 
 pan, fitted up in the same manner as for obtaining the leuko-base. There are then 
 added, with constant stirring, 50 kilos, of the pulverised leuko-base, not letting the 
 temperature rise above 45, which is effected by a rapid current of water through the 
 jacket. The base soon dissolves in the acid, with an escape of sulphurous and carbonic 
 acids. After the introduction of the leuko-base the pan is heated to 8o-85, neither 
 higher nor lower. 
 
 Specimens taken out of the pan, which may be drawn after two hours of action, are 
 covered with distilled water in a test-tube, and mixed with ammonia in excess, and show 
 the progress and the end of the sulphurising. As soon as such a specimen, after the 
 addition of the ammonia, no longer appears turbid, it is tested in the dye-house against 
 the standard sample, and the process is stopped or continued according as the right tone 
 has been reached or not. 
 
 The perfectly sulphurised mass is let cool, and the next day it is forced over into a 
 vat with 1000 litres water. To separate the sulphuric acid it is mixed with milk of 
 lime prepared from 150 kilos, of lime until the reaction is slightly alkaline. The mass 
 is heated with direct steam to the boiling-point. To separate out the gypsum in a 
 crystalline state, about 500 litres of cold water are added with agitation, bringing the 
 temperature to 6o-65 & . The whole contents are let off into the montejus and filtered 
 through a filter-press. The filtrate is run into a large iron tank containing a copper 
 steam-worm. The cakes remaining in the press are thrown each time into the lime-cask, 
 and after all the residues have been united they are boiled up with 1000 litres of water, 
 and further treated as above. The final residue is thrown away ; the filtrates, united, 
 are evaporated down to 1200 litres, and filtered through an open filter into the oxidation- 
 vat set below, where the liquid is cooled to i9-2o. 
 
 For obtaining the lead peroxide needful for oxidation 22 kilos, of litharge are dis- 
 solved in 40 kilos, of acetic acid at 40 per cent, and i oo litres of water in a wooden vat, 
 with agitation, and the introduction of steam. The lead acetate thus obtained is mixed 
 with a finely strained paste of chloride of lime (obtained from 27 kilos, chloride of lime 
 and 54 litres water) until all the lead acetate has been converted into peroxide. The 
 end of the reaction is known as follows : A drop of the lead solution placed with a glass 
 rod upon a slip of filter-paper gives a brown spot of peroxide with a moist colourless spot 
 around it. If this colourless zone is turned yellow on applying to it a drop of a clear 
 solution of chloride of lime, more chloride of lime must be added. 
 
 The lead peroxide is allowed to settle, and the weak acetic solution is poured through 
 a filter. After twice boiling up in water and letting settle, the dark-brown mud is placed 
 on a filter ; the paste, when well washed, is put in a small tared tub, and the whole is 
 made up with water to a net weight of 56 kilos. 
 
 For producing acid green the oxidation is conducted below 20, the agitator is set in 
 
 2 M 
 
546 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 rapid action, and the mass is acidified with 10 kilos, sulphuric acid at 158 Tw. The 
 lead peroxide is added to the liquid, which is in rapid motion. The colourless solution 
 becomes a deep green, acid green being formed. 
 
 After stirring for ten minutes, all the lead and lime are removed from the solution 
 by scattering in about 25 kilos, of soda. The addition of soda must cease as soon as a 
 specimen, after nitration and dilution with water, no longer gives a precipitate on the 
 further addition of soda. It is then heated to 70, the mass is run off into the 
 montejus and forced through a filter-press with double filter-cloths. The filtrate is 
 passed into an iron cistern fitted with a steam -worm. The green solution .is concentrated 
 to about 600 litres and run into the copper stirring-pans placed below, fitted with 
 mechanical scrapers. Here it is evaporated down to dryness, and the residue is exposed 
 for two to three days on zinc plates in the drying-room. 
 
 The dried green is ground in a ball-mill (such as used for grinding indigo), and is 
 sent out as a dark green powder. It is also sold in a liquid state liquid acid green 
 in 10 or 20 per cent, solutions. The yield is 85^5 kilos. 
 
 Resorcine, C 6 H 4 (OH)j, is obtained by melting sodium benzoldisulphate with sodium 
 hydrate. 
 
 Into a double pan fitted with an agitator are put 300 kilos, sulphuric acid at 158 
 Tw. and 60 kilos, of benzol free from thiophene. The pan is then connected with a reflux- 
 condenser. The reaction is set up by constant stirring, supported by the introduction 
 of steam into the jacket, so that the tube connecting the pan and the condenser is but 
 slightly warm to the hand. The vapours of benzol are liquified and flow back. After 
 continuous mixing for about ten hours at a moderate heat the reaction is completed with 
 the formation of benzolmonosulpho acid, C 6 H 5 .SOj.OH. This acid, dissolved in an 
 excess of sulphuric acid, is put the next day into a pan fixed in an oil-bath (provided 
 with an agitator and connected with a leaden ascending condenser), in order to be 
 converted into the disulpho acid. For this purpose the mass is mixed with 85 kilos, of 
 salt-cake, ground and well dried ; the agitator is set in motion, and the oil-bath is heated 
 to 240. After heating for four hours, the contents of the pan take a temperature of 
 225. This heat is kept up for about eight hours, whilst the agitator is in constant 
 action. During the first half of the time benzol distils over and is collected in a re- 
 ceiver, whilst sulphurous acid escapes. 
 
 The next day the contents of the pan, which are still moderately warm, are mixed 
 with 1500 litres of water in a wooden vat holding 3000 litres, and limed out with milk 
 of lime made from 200 kilos, of lime, and passed through a sieve. The boiling faintly 
 alkaline mass is chilled with 800 litres of cold water to form gypsum. The contents of 
 the vat are run off into a montejus and forced through the filter-press. The filtrate is led 
 into a large evaporating trough. The press-cakes are again boiled up with about 1500 
 litres of water, and separated from gypsum after the vat has been filled with water. The 
 combined filtrates are concentrated to 2000 litres, and the solution is then run off into 
 the conversion tanks. An addition of 6 to 10 kilos, of soda is sufficient to precipitate 
 all the lime. The liquor let off into a montejus is separated from calcium carbonate 
 by means of the filter-press. The filtrate is evaporated in two stirring-pans until the 
 scrapers stop from the toughness of the mass. The moist salt is put in flat double 
 pans and dried, constantly stirring with an iron rod, to a powder, which is then ground 
 and sifted. The yield is 200 kilos, sodium benzoldisulphate, C 6 H 4 (S0 3 .Na) 2 . The 
 following conspectus shows the limit values for so-called " return oil," and yield in 
 two lots : 
 
 Sulphuric acid: Benzol. Salt-cake. Lime. Soda, Return Oil Yield, 
 
 300 ... 60 ... 85 .... 200 ... 6'5 ... 14 ... ISO 
 
 300 ... 60 ... 85 ... 210 ... 9'0 ... 8 ... 200 
 
 There are put 250 kilos, solid caustic soda into an open melting-pan over an open 
 
SECT, iv.] BENZOL COLOUES. 547 
 
 fire, provided with an agitator, and to effect a more rapid solution there are added 10 
 kilos, of water. The formation of a scum on the top shows that the caustic is not hot 
 enough to take up the salts to be added without solidifying. It is therefore heated 
 until both the scum and the crusts adhering to the sides are perfectly liquified. If a 
 piece of the salt thrown in melts quickly with a hissing sound the temperature is high 
 enough. The agitator is set in motion, and in a short time 125 kilos, of the dry salt 
 are thrown in, but so that the contents do not boil over, which is regulated by stopping 
 or turning the agitator. The introduction of the salt takes thirty minutes. The 
 .mass begins to froth as water escapes ; gradually it becomes more quiet, turns oily, and 
 retains a white foam. In time it becomes yellow, and then brown, and spirts violently. 
 When the brown mass no longer works it is ready, and the hot mass is baled out with 
 iron ladles upon iron sheets, where it cools. The process may be explained by the 
 following equation 
 
 C 6 H 4 (S0 3 Na) 2 + 4 NaOH = C G H 4 (ONa) 2 + 2 Na 2 S0 3 + 2H 2 O 
 
 The melt, broken up, is thrown into a large stone trough containing 500 litres of 
 water. 9 to 10 carboys of strong hydrochloric acid expel all the sulphurous acid, and 
 produce a moderately acid solution of resorcine. So much acid is added as to turn a 
 ,piece of blue litmus paper slightly red. 
 
 The liquid, run off into an iron receiver lined with lead, is pressed over by opening an 
 air-cock into a horizontal mixing-pan provided with an agitator. In this apparatus 
 the solution containing resorcine is extracted four times, each time with 100 litres of 
 purified amylic alcohol. The solution and the amylic alcohol are mixed for half-an- 
 hour, and the liquid is then syphoned into the elevated pointed cylinder. After 
 ettling for an hour the salt solution is run back into the mixer, and the deep brown 
 alcohol charged with resorcine is let into the amyl-cistern. After this extraction has 
 <been repeated four times the salt solution is exhausted, and the fourth extract is 
 scarcely coloured. The combined extracts, after standing for twelve hours and 
 separation from the adhering saline solution, are run off into the still. 
 
 The amylic solution of resorcine is heated by indirect steam to about 100. As 
 soon as this temperature is reached direct steam is allowed to enter, which carries 
 away the amylic alcohol, and leaves the resorcine behind in the pan. When only water 
 issues from the condenser the distillation is stopped, and the solution of resorcine is 
 run out into an enamelled iron pan. The water is evaporated off, which takes twelve 
 Ihours. The resorcine has now to be purified. 
 
 The purification is effected by distillation in a vacuum. For this purpose the liquid 
 contents of the double pan (about 30 kilos.) are baled into a copper pan provided with 
 a thermometer, and closed. A copper Liebig's condenser connected with the cover 
 conveys the distillate into a copper receiver with an exit cock, which is again connected 
 with the suction pump. At first some water and phenol pass over from the heated 
 mass, and escape on opening the cock of the receiver. At about 190 the cock is 
 closed, and the pressure of the air is reduced to 630 millimetres. On raising the heat 
 the resorcine begins to boil and passes over into the receiver. Here caution is needed 
 on account of a possible stoppage of the cooler, which, however, may be overcome by 
 letting only a moderate stream of water into the cooling tube, or interrupting it for a 
 time entirely. The liquid resorcine collecting in the receiver is run in known 
 quantities into moulds of tinned copper, and thus the commercial product is obtained 
 of 20 to 23 kilos, of pure resorcine from 125 kilos, of benzol disulphate. 
 
 Fluoresceine Colouring Matters. The halogenous and nitro-halogenous derivations 
 of fluoresceine are colouring matters highly valued as eosines ('Ear, morning redness), 
 .surpassing all other colours in lustre and fire. The most important are : 
 
 i. Tet/rabrom fliwresceine, the sodium and ammonium salts of which are met with in 
 trade as eosine, eosine B, soluble cosine, &c., in the form of red and reddish-brown 
 
548 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 powders. It is obtained by bromising fluoresceirie in alcohol or in water. The garnet- 
 red crystals of tetrabrom fluoresceine sodium (Eosine A extra) are used in silk-dyeing, 
 whilst the first-named eosine brands serve especially also in colouring paper and in the 
 manufacture of lakes. 
 
 2. Dibromfluoresceine occurs in trade as a sodium salt, more or less mixed with 
 tetrabrom fluoresceine under the name of Eosine orange. 
 
 3. Ethyltetrabromfluoresceine is obtained as a potassium salt in red crystals with a 
 green surface lustre. It is known by the trade names primrose, spirit eosine, ethyl- 
 eosine, eosine S., rose J. B. a 1'alcool, &c. It is obtained by bromising fluoresceine in 
 hot alcohol, when alkylising and bromising are effected simultaneously. It is used to 
 some extent in silk-dyeing. 
 
 4. Dibromdinitrofluoresceine is prepared ou the large scale by bromising dinitro- 
 fluoresceine in an alcoholic solution, or by nitrising tetrabrom fluoresceine in glacial 
 acetic acid, or by nitrising bibromeosine in a water solution. It is sold under the 
 names: eosine scarlet, eosine B.N., safrosine, lutecienne, daphnine, rose des Alpes, 
 in the state of alkaline salts. The sodium and potassium salts appear black, and the 
 Ammonium salt red. These salts meet with but slight application in dyeing, but the 
 ammonium salt and the neutral sodium salt, which when evaporated down in thin 
 layers has a greenish colour, are exported to China to a considerable extent. 
 
 5. Tetraiodofluoresceine is obtained by iodising fluoresceine in an aqueous solution. 
 Its alkaline salts are of a brown red, but the ammonium salt is of a light brick 
 red. These salts are used in silk and cotton dyeing and paper-staining, under the 
 names erythrosine, eosine J, pyrosirie B, iodeosine B, dianthine B, rose B a I'eau, 
 soluble primrose, eosine bleudtre. 
 
 6. Di-iodo fluoresceine, is also found mixed with tetraiodofluoresceine in the state of 
 an alkaline salt, as erythrosine G, dianthine G, iodeosine G, &c. 
 
 (C 6 H 3 .OH (C 6 HBr 2 .ONa (C 6 HBr 2 .OC,H 5 
 
 c o I o Jo 
 
 U j C 6 H 3 .OH ' C 6 HBr r ONa J | C fi HBr,.OK 
 
 lan.co.o la,H,.co.o 
 
 lC 6 H 4 .CO.O 
 
 Fluoresceine. Eosine. Primrose. 
 
 (C 6 HBr(N0 2 ).OK fC 6 HL.ONa 
 
 iJ oJ 
 
 ]C 6 HBr(N0 2 ).OK U )C 6 HL.ONa 
 
 lC^.CO.0 Ic.H.CO.O 
 
 C 6 H 2 I.OK 
 
 
 
 C 6 H S I.OK 
 IC 6 H 4 .CO.O 
 
 Eosine scarlet. Erythrosine. Erythrosine G. 
 
 Fluoresceine is obtained, according to Miihlhauser, by melting 2 5 kilos, of resorcine 
 in a pan placed in an oil bath at 160, and stirring in 17^ kilos, of phthalic anhy- 
 dride. The reaction begins as soon as the liquid has been heated for about ninety 
 minutes to 180. During the reaction, which lasts forty minutes, the mass must not be 
 stirred, as it would otherwise flow over. The mass thickens to a paste, and it is then 
 stirred from time to time by means of an iron rod until it is perfectly dry, which is 
 effected in twenty-four to thirty hours' heating to 200 to 205. The end of the reaction 
 is observed by the brittleness of a small lump of fluoresceine when struck with the 
 hammer. 
 
 The main points to be observed in melting are purs materials and the maintenance- 
 of a temperature of 180 during the reaction. If the mass rises during the reaction, 
 and there is danger of an overflow, the temperature is reduced by blowing in air with 
 bellows. The yield of crude fluoresceine is 37^ kilos. 
 
 The crude fluoresceine is dissolved by boiling with 500 litres of water and 50 kilos, 
 of soda-lye at 62 Tw., and the liquid is made up to 1000 litres. After filtration 
 into a vat fixed below, the reddish-yellow filtrate is precipitated with 90 kilos, of 
 
SECT, iv.] BENZOL COLOURS. 549 
 
 hydrochloric acid. The fluoresceine goes down, and the fluorescent colour liquor is 
 poured off. By again boiling up the sediment in 500 litres of water we obtain a red- 
 dish yellow turbid liquid, from which the fluoresceine is generally completely pre- 
 cipitated by the addition of a little hydrochloric acid. It is allowed to settle, the solution 
 is decanted off, all the fluoresceine is collected upon a filter, drained, and dried. 
 
 The drying is effected in shallow enamelled capsules, the flat bottom of which is 
 about 80 square centimetres ; four such capsules are placed on a water- bath, and are 
 then exposed to a temperature not exceeding 98. At this temperature the moist 
 fluoresceine, which has been spread in a layer of about 5 millimetres in thickness, 
 quickly dries to a fine powder, which is then sifted. The yield is 36 kilos. ; 
 
 Resorcine. Phthalic Acid. ZnCl a . Crude Melt. Lye, 6a Tw. Hydrochloric Acid. 
 
 25 ... 17 ... 8 ... 45 ... 60 ... loo 
 
 For obtaining tetrabrom fluoresceine in an aqueous solution, 60 kilos, of soda-lye at 
 62 Tw. are mixed in a jacketed cast-iron pan with 150 litres of water. Then, whilst 
 the lye is being stirred, 32 kilos, of bromine are run in direct from the bottles by means 
 of a syphon. 
 
 Then is formed a mixture of NaBr, NaBr0 8 , and NaBrO ; the last compound is 
 converted into NaBr by boiling for half an hour. The decomposition of the sodium 
 hypobromite is necessary, as otherwise a yellow product would be formed on decom- 
 posing with hydrochloric acid. 
 
 Meanwhile, in an adjacent steam-pan, 10 kilos, of fluoresceine have been dissolved 
 in 25 kilos, lye at 62 Tw. and 150 litres of water by boiling for thirty minutes. Both 
 solutions are run off into a vat as soon as cold, well stirred up, and precipitated by 
 the immediate addition of 140 kilos, crude hydrochloric acid, with thorough agitation. 
 Yellow bromeosine separates out. It is heated to boiling by direct steam, and as soon 
 as it boils the vat is filled up with water, allowed to settle, the sediment boiled up 
 twice in the same manner with fresh water, and lastly filtered. The eosic acid, thus 
 entirely freed from mineral acids, is dried upon plates, as described under fluoresceine 
 The yield of tetrabromfluoresceine is 30 kilos. : 
 
 Fluoresceine. Soda-lye, 62 Tw. Bromine. Soda-lye at 62 Tw. Hydrochloric Acid. 
 
 16 ... 25 ... 32 ... 60 ... 140 
 
 Two such lots i.e., 60 kilos. of eosic acid are made soluble by means of alcoholic soda 
 in order to obtain eosine B, and allowed to crystallise from the solution. 
 
 In order to render the eosic acid soluble, we must first ascertain by a trial what 
 quantity of soda is necessary for the formation of the neutral eosine salt. For this 
 purpose we take an average sample of 50 grammes eosic acid, mix it in a litre flask 
 with 175 grammes of alcohol at 96, and heat to boiling. In the meantime a portion of 
 the soda-lye, to be used on the large scale (i part sodium hydroxide and 2 parts water 
 = 72 Tw.), and about 40 grammes, are placed in a dropping-bottle. 
 
 This bottle with the soda weighs (say) 134*7 grammes. Soda is then let flow in, 
 drop by drop, to the boiling alcoholic solution of eosine. As the soda is added there 
 is formed the red acid salt of eosine, which subsides. This sparingly soluble salt serves 
 as an indicator, for we continue dropping in the soda, keeping up a moderate heat 
 and shaking the flask, until the acid salt dissolves, passing into the neutral salt. The 
 addition of lye must cease as soon as the last granule of eosine sodium has disappeared. 
 The liquid appears now of a yellowish-red, but if an excess of soda has been used it 
 looks blackish-red. Whether the right quantity of soda has been used may be known 
 not merely from the disappearance of the acid salt, but by dipping a glass rod into the 
 solution and letting it dry in the air. If it is then dipped into distilled water, the 
 adhering eosine will dissolve clear if sufficient soda has been added, but if the quantity 
 has been deficient there is formed a cloud round the end of the rod. 
 
 A correctly neutralised sample when dropped into a glass of water gives a yellowish- 
 
550 CHEMICAL TECHNOLOGY. [SECT, iv, 
 
 green dichroism ; a solution supersaturated with alkali gives a dirty green colour with 
 a brownish-green dichroism. If the eosine solution is poured into a capsule the margin 
 should look yellowish-red and not brown. In the latter case too much alkali has been 
 added. If the contents of the capsule are allowed to crystallise overnight, there must 
 be no acid salt at the bottom of the cake. On weighing the dropping-flask it cauie 
 to 1 14*46 grammes, consequently 20*24 grammes soda had been used to saturate 50 
 grammes eosic acid. This number is used in calculating the quantity of soda to be em- 
 ployed on the large scale. 
 
 Sixty kilos, of eosic acid are placed in a copper pan on the water-bath, and 210 
 kilos, of alcohol are added i.e., the quantity which is necessary to keep in solution the 
 salt formed on neutralising the eosic acid with soda. For this purpose there are 
 required 3^ times the quantity of alcohol referred to the weight of the free eosic 
 acid. It is convenient to put the alcohol first in the copper pan, and then to stir in 
 the eosine, which is otherwise apt to adhere to the bottom and is difficult to remove. 
 The water-bath is heated to boiling and the contents of the pan to 60. When this 
 temperature has been reached we run in (20^4 x 60) : 50 = 24^ kilos, soda-lye during 
 ten minutes, stirring constantly. The free acid dissolves, after having formed the 
 acid saltj The solution is run into three wooden casks, holding each 120 litres. On the 
 surface of the liquid there are laid thick wooden lids, which dip i to 2 centimetres into 
 the alcohol, so as to give the greatest possible space for crystallisation and at the same 
 time to decrease the proportion of the crystals forming at the bottom. The crystals- 
 deposited on the cover and the sides are always a finer and better-looking article than 
 those attached to the bottom. 
 
 After standing two or three clays in a cool place the crystallisation is complete. The 
 cover is raised, the mother liquor run off, and the crystals from the cover and sides are 
 put upon the filter, as are those also from the bottom separately. Cakes of crystals 
 are detached from the wood with a knife. The crystals, when they have been drained, 
 are dried on frames at 60 in the drying-room, which takes three days. When dry the 
 crystals are ground. The brownish-red powder is sold as eosine B : 
 
 Eosine. Alcohol. Soda. Eosine B. 
 
 60 ... 210 ... 24-5 ... 57-5 
 
 The mother liquor obtained on the crystallisation of eosine B is distilled, and yields 
 alcohol at 96 per cent., the colouring matter remaining in solution being disregarded. 
 
 The bromising of fluoresceine in an alcoholic solution is effected in three enamelled 
 pans. Each pan is charged with 10 kilos, fluoresceine and 80 kilos, of alcohol at 96. 
 The bromising is effected by letting 24 of bromine flow in a slow stream and with 
 constant stirring from a bottle fitted with a cock, the exit pipe of which plunges a 
 little into the alcohol. This operation lasts fifteen minutes ; when it is completed the 
 mixture is well stirred and covered up. It is set aside four days, but is well stirred up 
 three times each day, thus effecting a complete separation of the eosic acid. In bromising 
 we remark that when half the bromine has been added, the liquor, which was at 
 first a reddish-brown, has changed to a blackish -bro wn ; there is first formed the 
 dibromide of fluoresceine, which is readily soluble in alcohol. On the further addition 
 of bromine the tetrabromide is deposited as a brick-red mass. After standing for four 
 days the alcohol is drawn off with a syphon, and the red. deposit is twice washed with 
 alcohol. For this purpose 40 kilos, of alcohol are placed in each pan ; it is well stirred 
 up, let stand for one day, and the washing alcohol is then drawn off. A second washing 
 is executed in the same manner. The red deposit at the bottom of the pan is collected 
 upon filters of felt, drained, and pressed. The comminuted press-cakes are dried upon 
 cotton cloths spread out on frames in the drying-room, which lasts two days. The yield, 
 of eosic acid is 50 kilos. 
 

 Fluoresceine. 
 
 AlcohoL 
 
 
 30 
 
 240 
 
 Washing Alcohol. 
 
 Yield of Eosic Acid. 
 
 Soda. 
 
 240 
 
 50 
 
 20 
 
 SECT, iv.] BENZOL COLOURS. 551 
 
 The conversion of tetrabromfluoresceine into eosine A extra is effected by crystalli- 
 sation according to the method above mentioned. The crystals are not broken, but 
 merely crushed with a piece of wood to fragments of the size of a nut, and they are 
 despatched in this state. The yield is 50 kilos. 
 
 Bromine. 
 72 
 
 Alcohol. Eosine A extra. 
 
 175 - So 
 
 For obtaining eosine B with a red surface, 30 kilos, of tetrabrom fluoresceine, 
 obtained by the alcohol process and finely sifted, are used. The eosine is made soluble 
 in an upright wooden box, which can be tightly closed with a door. In this box are 
 inserted thirty frames, arranged like drawers, each 3 centimetres in height, and with 
 linen bottoms of 6 square metres in surface, at intervals of 3 centimetres, so that one 
 frame is exactly upon the other. The available linen surface extended in the box is 
 about 1 8 square metres. Upon each frame there is spread as uniformly as possible 
 about i kilo, of eosic acid, and after all the frames have been inserted the box is 
 closed. The box is connected with an apparatus for generating ammonia, consisting 
 of a still and two gas-desiccators. The ammonia is conducted into the bottom of the 
 box, it traverses the entire layer of eosine from below upwards, and is very eagerly 
 absorbed by the free eosic acid, in accordance with the equation : 
 C 2o H 8 Br 4 5 + 2 NH 3 = C 2o H 6 Br 4 O s .(NH 4 ) 2 . 
 
 In about two hours all the eosic acid is converted into the neutral ammonium salt. 
 If a fragment taken out of one of the frames dissolves in distilled water without 
 turbidity, the process is broken off. The slight excess of ammonia escapes into the 
 chimney through an iron tube fixed above the box : 
 
 Eosic acid. Sal-ammoniac. Lime. Eosine B. 
 
 30-0 . 15-0 ... 30 31-8 
 
 Utilisation of the Residues. The alcohol which has been used for bromising in ono 
 process is poured into an enamelled pan. It contains free eosic acid, resin, hydrogen 
 bromide, and a little bromethyl. In order to separate the eosine from the alcohol, water 
 is run into the liquid in a thin stream and with constant agitation, about equal to one- 
 third of the volume of the alcoholic solution. If more water is added, the resin is sepa- 
 rated out along with the eosine, which has to be avoided. The free eosine subsides to the 
 bottom. After completely settling, the watery alcohol is drawn off. The deposit put on 
 the filter is twice washed with water. If on the second washing the eosine remains sus- 
 pended for a long time, it is a sign that all the acid is washed out, for in acid water the 
 subsidence is more rapid and without turbidity. If the residue, thus filtered and freed 
 from acid, is sandy, it is, after draining, put through the filter-press and dried ; if it is 
 resinous, it must be washed with alcohol to take up the resin. The residuary eosine 
 thus obtained is collected until about 60 kilos, have accumulated. Such residues are 
 then, according to their purity, washed once or twice with alcohol. To each kilo, of 
 eosine residues, we add 2 kilos, of alcohol. The eosine in washing must be ground into 
 the alcohol, if this is neglected and the whole mass is added at once, it clots together 
 and is very difficult to wash. 
 
 The eosine after being thus washed is now fairly pure, and is filtered, pressed, and 
 dried. By crystallisation it is made to yield a fine, pure colouring matter. The 
 necessary quantity of soda for solution is determined, and the product is crystallised 
 from alcohol as described above. Many impurities pass into the alcohol. The crystals 
 are dissolved in water, precipitated with hydrochloric acid, filtered, dried and re- 
 crystallised, and then generally yield a product equal in its properties to eosine B. 
 
 On working up the alcoholic bromine lye we obtain eosine B, dilute bromising 
 
552 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 alcohol, washing alcohol, and mother liquors from the first and second crystallisation. 
 All the alcoholic liquids are collected and redistilled. 
 
 The mother liquors obtained from the crystallisation of " Eosine A extra " are 
 separated from alcohol in the distillatory apparatus, and the residue is dried. Here 
 also about 60 kilos, of residues are allowed to accumulate, dissolved in water, and the 
 eosine is precipitated with hydrochloric acid. The further treatment of the dried eosic 
 acid is effected by washing and recrystallisation with alcoholic soda in the manner 
 described above. 
 
 The subjoined table (p. 553) collates the conversion of fluoresceine to eosine and 
 the treatment of the alcoholic residues. 
 
 For the production of dibromfluoresceine 10 kilos, of fluoresceine are suspended 
 in 80 kilos, of alcohol at 96, and treated with 12 kilos, of bromine as above described. 
 The fluoresceine passes into solution with the formation of dibromide. When cold 
 the dibromfluoresceine is precipitated with 100 litres water and the diluted alcohol is 
 drawn off. The dibromfluoresceine, separated out as a resin, after washing with water, 
 is dissolved in a cask in 200 litres of water and 20 kilos, lye at 62 Tw.,ancl when cold 
 it is precipitated with 40 kilos, of hydrochloric acid. It is obtained as a pulverulent 
 precipitate, which is freed from acid, filtered, and dried. The yield is 15-4 kilos. 
 
 Eosine Orange. A laboratory experiment shows the quantity of lye necessary for 
 dissolving. To the dibromeosine suspended in 150 litres of hot distilled water there is 
 added the quantity of lye determined by experiment, and the mixture is evaporated to 
 a paste. It is then completely dried on sheet metal in the drying-room. The yield is 
 17 kilos. 
 
 To obtain ethyltetrabromfluoresceine, 80 kilos, of alcohol at 96, and 20 kilos, of 
 fluoresceine are placed in a jacketed and enamelled autoclave, agitating all the time. 
 The autoclave, which is fitted with an enamelled mechanical agitator and an ascending 
 leaden cohobater, is closed and heated. Steam is let enter the jacket until the alcohol 
 boils. Meantime, 13 kilos, bromine are weighed into a glass bottle provided with acock, 
 and the bottle is placed upon the elevated refrigerating tub. When the alcohol boils 
 the cock of the bottle is opened and the bromine is allowed to flow down through a glass 
 tube dipping but little into the apparatus, which is connected with the outside air 
 merely by the leaden worm. In this manner four bottles of bromine of 13 kilos, each 
 are successively run in during 50 minutes. The autoclave is then closed as tightly as 
 possible and heated at the pressure of i atmosphere ; the steam is then shut off, and the 
 mass is left at this pressure for three hours, allowing steam to enter the jacket from 
 time to time. When completely cold the autoclave is opened by raising the lid. The 
 alcohol is drawn off, and the residue at the bottom is placed upon an asbestos filter. 
 
 The eosine thus obtained has in this state a black, a greenish-black, or a brown 
 colour. By hot bromising we obtain a mixture consisting chiefly of ethyltetrabrom- 
 fluoresceine and a little tetrabromfluoresceine. A bye-product is the bromising alcohol 
 containing ethyl and vinyl bromide which is used for eosine B, and alcohol at 96. 
 
 The eosic acid, after draining on the asbestos filter, is pressed and washed with 100 
 kilos, of spirit in an enamelled pan, distributed in the alcohol with a wooden stirrer, 
 allowed to subside, filtered, and pressed. The filtration residue is again washed with 
 about 100 litres of water. The moist, brown, eosine mass is filtered, pressed, and dried 
 on frames in the drying- room. The yield is 27 kilos, of, eosic acid. 
 
 Spirit Eosine. To isolate eosic acid and to render it alcoholic it is crystallised from 
 an alcoholic solution of potassa. The eosine soluble in water remains dissolved in the 
 mother liquor, whilst the spirit-eosine crystallises from the 36 per cent, alcohol. 
 
 In order to ascertain the quantity of potassa lye which will be necessary for neutralis- 
 ing the acid, 50 grammes of eosic acid are weighed out, suspended in a glass flask in a 
 mixture of 125 grammes water and 75 grammes alcohol, and heated to boiling. To 
 
SECT. IV.] 
 
 BENZOL COLOURS. 
 
 553 
 
 0) g 
 
 v s 
 
 *r? w 
 
 c i! 
 
 yj r^ 
 
 o 
 
 1 s 
 
 H 
 
 
 n 
 
 pq 
 
 0) (V 
 
 d> 
 
 .a .a 
 
 .a 
 
 
 
 CO 
 
 o 
 
 W M 
 
 
 n-iw'-s a 
 
 ^ T5 
 
 11:21 j s s 
 
 SSJiS S3 
 
 a-s-lg, ~ 5 ft 
 
 41 O 3 43 
 
 !|1|^ 
 
 "" oo oo 
 
 
 o o o 
 
 a- 
 
 bCN_o to C^.ij bCC**,^ 
 
 
 
 C . C fl-fl C _ 
 
 G - S 
 
 ~ -r a> '3 T5 'S <-% o 
 
 ^-i O y H-Oy ^COy 
 
 S'S 8 
 
 w ^5 
 
 |1| ||| ||| 
 
 C^ O *^ 
 
 ^^ ft 
 
 "3 3l 
 
 r "3 
 
 ^ 3 "3 
 
 "So 
 
 OH <J O 
 
 <j o 
 
 o o> *3 
 
 4 p. 
 
 a 
 
 w g 
 
 
 
 P H S 
 
 
 Cr 1 o C7* 
 
 
 ?H H fc^ 
 
 
 0} w i^> O ^ 
 
 
 r" ft S ^^ .5* 
 
 
 1*' I II 
 
 " 
 
 ** ' " A T T3 .3 *r * " ' ^^5 * 
 
 -i--o ^2-s 
 
 ^ M p.2 * & W ^ 
 -S -72 S: ' ' * 43 rrt hH 
 
 - ^R * s CD 2 
 
 3 llaP g g^^^ 
 ^j ' ' | '-ell 125 
 
 11111 . f fill 
 ? "- ' sll| 
 
 ~ -So ft 84 * 
 
 "5 
 
 ? = s ^zr~ 
 * ^ w ^ ^^ ^s 
 
 
 "B y 3 s^^ ^ 
 
 
 
 
 1 ill 1 s i 
 
 - ^___j w ^ | 2 
 
 
 06?, to S '5 
 
 
 n -w C ? 
 
 
 . * s 5 |S 5Jr d 
 
 
 , llo . ^_ , s~ 
 
 
 
 
 O p^^*H 
 
 
 S 2 o-z ^ -a 
 
 
 O w w ^2 O i" 1 
 
 
 *' 5 ^ a *S *- "* * 
 
 
 "^ r^ to | ^ "w ^ 
 <3 <-> O 
 
 
 1 IT' ! Ill 
 
 
 ** & 1 <u T? 3 S ^ 
 ^ -a <3 M it 
 
 "Si <_ o f 
 
 
 
 
 oS. g -3 
 
 
 'S-^-J -f . 1 
 
 
 2.3 ^ 
 
 
 '3 I '3 bO 
 
 
 .a 
 
 
 '3 o S 
 
 
 o ^ t^. 
 
 
 W <J ^ 
 
 
554 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 the boiling mass is added lye from a weighed dropping-bottle until all red powder has 
 disappeared, and merely minute shining green crystals are to be seen at the bottom of 
 the flask. From the number of grammes of potassa lye consumed (i part KHO and 2 
 parts H,0), the quantity of lye is calculated which will be required for neutralising the 
 entire lot. 
 
 For converting the ethyl eosic acid into the potassium salt, there are placed in an 
 enamelled and jacketed pan (with a reflux cooler), z\ parts water and i^ part alcohol, 
 calculated for the weight of the eosine to be operated upon. The eosine is stirred into 
 the cold alcohol 36 per cent., the pan is closed and heated to boiling. To the boiling 
 mass there is allowed to enter in a thin stream the calculated quantity of potassa- 
 lye, previously heated to 80, with agitation, which is continued for fifteen minutes 
 after the introduction of the lye. The cold apparatus is opened after the lapse of three 
 days ; the mother liquor is drawn from the crystals ; the latter are placed on a filter and 
 freed by pressure from the mother liquor ; the cakes are once more washed in hot water, 
 filtered, pressed again, and dried on enamelled plates. The yield is 25-3 kilos, of spirit 
 eosine. 
 
 In working up the residues, the bromising alcohol is run into an enamelled pan, 
 mixed with half its volume of cold water, which is caused to run in as a thin stream and 
 with agitation. Tetrabromfluoresceine separates out as a red powder. It is allowed to 
 subside, the eosine is washed out perfectly with water, filtered, pressed, and dried. 
 The further process is conducted as in the case of the residues of eosine A, by washing 
 with alcohol, and twice recrystallising the sodium salt from alcohol. 
 
 The mother liquor separated from the crystals is allowed to stand about eight days, 
 when about 2 kilos, of crystals separate out, which are worked up with the following lot. 
 The mother liquor (now drawn off for the second time) is separated from alcohol in the 
 still. Moderately pure eosic acid may be obtained by precipitating the residues from this 
 apparatus (previously dissolved in water) with hydrochloric acid. It is filtered, washed, 
 and pressed, the cakes are dried, and can then be worked up like the eosine A 
 residues. 
 
 The working up of the alkaline and acid alcohols by distillation depends upon their 
 reaction. Those of an acid character (the bromising and washing alcohols) are neu- 
 tralised with milk of lime in a montejus lined with lead, and are then forced into 
 the so-called column apparatus and rectified. The alkaline or neutral alcohols, those 
 from the mother liquors and those which have been merely diluted with water are 
 rectified per se, and worked up for alcohol at 96 or 97. The residue in the still, 
 obtained by working up the acid alcohols, is let off into an autoclave, and when suitably 
 diluted with water forced through a filter-press. The filtrate is worked up for bromine. 
 The contents of the filter-press and the impure coloured liquors obtained in working up 
 the alkaline alcohols go to waste. 
 
 Dinitrodibromfluoresceine. In bromising dinitrofluoresceine in an alcoholic solu- 
 tion (nitro-bromising of fluoresceine in alcohol) there are placed in five enamelled pans 
 60 kilos, of alcohol at 96 with 7 kilos, of fine fluoresceine, keeping up agitation. To 
 the fluoresceine, which is kept divided by agitation, we add gradually 7 kilos, nitric 
 acid at 72 Tw., and immediately afterwards 7*25 kilos, of bromine, which is drawn 
 directly out of the bottles by means of a syphon. Dibromdinitrofluoresceine, which is 
 sparingly soluble in alcohol, separates out. The pans are allowed to stand undisturbed 
 to the next day. The black liquid is drawn off, and the precipitate is washed once with 
 30 kilos, of alcohol. The precipitates placed on the filter, after draining, are boiled up in 
 a tub with water, allowed to settle, decanted, and this treatment is repeated until the 
 boiling water begins to be faintly coloured. When this is the case all the acid is 
 washed away. The fine paste is spread out in a thin layer on enamelled dishes on the 
 water-bath and dried. The yield of sifted produce is 63 kilos. : 
 
SECT, iv.] BENZOL COLOUES. 555 
 
 Dibromdinitro- 
 Fluoresceine. Alcohol. Nitric acid. Bromine. Washing alcohol.. ftuoresceiue.. 
 
 35 - 300 ... 35 - 36-25 ... 150 ... 63-0 
 
 For nitrising in glacial acetic acid, 30 kilos, of bromeosine are introduced into an 
 enamelled pan on the water-bath, which, according as a more or less fine product is 
 desired, is taken either from a spirit-bromised or a water-bromised sort. To the brom- 
 eosine are added 25 kilos, of glacial acetic acid, and the whole is stirred up to a uniform 
 paste, with which 4 kilos, of soda- saltpetre are incorporated by diligent stirring. The 
 pan is then covered and the water-bath is raised to a boil. The reaction begins about 
 7o-8o, whilst small quantities of nitrous acid and a little glacial acetic acid escape. A 
 uniform temperature is kept up by frequent stirring. After heating for six to eight 
 hours, the red mass has turned to a flesh colour, and the reaction is at an end. The 
 course of the reaction is followed by sampling, and it is brought to an end when a sample 
 dissolved in ammonia and compared with a type-sample produces at once a blue colour 
 upon a slip of filter-paper. 
 
 The mass, after cooling, is boiled up in a wooden vat with 500 litres of water. 
 After boiling for about ten minutes it is allowed to settle and the liquor is pressed off. 
 The residue at the bottom is deacidified in the usual manner. The fine flesh-coloured 
 paste is spread in thin layers upon enamelled capsules and dried. Yield, 29^ kilos. 
 
 For nitrising in wateiy solution, 10 kilos, of fluoresceine are dissolved in a double 
 pan in 200 litres of water and 13 kilos, of lye at 62 Tw. In an adjoining double pan 
 there are dissolved 12 kilos, of bromine in a mixture of 20 kilos, of lye at 62 Tw. and 
 50 kilos, of water. This liquor is used for decomposing sodium hypobromite. When 
 completely cold, the fluoresceine solution and the bromine solution are run into an 
 enamelled pan set in a water-bath, and are further mixed, with constant stirring, with 
 60 kilos, sulphuric acid at 72 Tw. Yellow bromeosine separates out. 30 kilos, of 
 nitric acid at 72 Tw. are run in, stirring constantly. The admixture of the acids 
 must be effected with refrigeration ; but as soon as all the ingredients are together the 
 water-bath is heated to boiling. The heating lasts five to six hours, with occasional 
 stirring. The reddish-yellow eosine is then converted into the flesh-coloured nitrobrom- 
 eosine. The product, mixed with water in a cask and freed from acid by repeated 
 decantations, is finally filtered and dried on the water-bath in thin layers. The yield 
 is 19^ kilos.: Fluoresceine, 10 ; soda. 13; bromine, 12; soda at 62 Tw., 20; sul- 
 phuric acid at 72 Tw., 60 ; nitric acid at 72 Tw., 30. 
 
 The dibromdinitrofluoresceine is rendered soluble either by passing over it gaseous 
 ammonia when dried and finely sifted, or as above described, or by adding a solution 
 of potash to the eosine paste stirred up in hot water. The first method yields the 
 ammonium salt, the second that of sodium, and the third that of potassium. 
 
 The ammonium salt of nitrobromfluoresceine is produced in the same manner as 
 the ammonium salt of tetrabromfluoresceine, namely, by conducting dry ammonia 
 over the free acid in an ammonia-chest. There are used 30 kilos, eosic acid obtained 
 by either of the two first methods above described. The yield is 31*9 kilos. As very 
 pure products are obtained by bromising in alcohol or glacial acetic acid it is recom- 
 mended to employ here the ammonia method. 
 
 For obtaining the sodium salt, 30 kilos, of eosic acid are diffused in 200 litres oi 
 water in an enamelled double pan, and heated to 90. To this liquid, which is kept 
 uniform by agitation, there is added soda-lye, which is run in from a vessel with a cock 
 The addition of soda is stopped before complete neutralisation. This incomplete 
 saturation is in order to separate the pure eosine from the impure colouring matters 
 formed during nitrising, which would ultimately dissolve in the soda with the formation 
 of salts, but which remain undissolved as long as the soda added is insufficient. The 
 progress of the solution of the free acids is observed by means of a slip of filter-paper, 
 
S5 6 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 and soda-lye is added, until a drop of the solution taken out with a glass rod and let 
 fall upon a slip of filter-paper held aslant does not give a pure, uniform spot, but 
 shows a small quantity of a solid powdery residue at the point of contact. On the 
 quantity of this residue depends the purity of the product. The saturation may, 
 however, be carried rather far. The deep-red liquid, containing little sediment, is 
 allowed to settle in a tall cask, drawn off after standing for two days, and evaporated 
 clown in a drying-pan. The yield is 29! kilos, of scarlet. 
 
 The potassium salt is obtained with potassium-lye exactly as above described. The 
 potash must be cautiously added to the hot cosine liquid in small portions. The 
 further conduct of the operation and the testing are effected as with the sodium salt. 
 The yield is 30 kilos. 
 
 Tetraiodofluoresceine. Erythrosine B. The iodising of the fluoresceine is effected 
 in the same manner as the bromising, only with the difference that no mineral acid, 
 but acetic acid, is used for setting up the reaction, as it can dissolve iodine, and hence 
 allows it to react in a finer state of division. 
 
 In an enamelled double pan of 100 litres capacity there are dissolved 6 kilos. 
 fluoresceine in a hot mixture of 8 kilos, soda-lye at 62 Tw. and 60 litres of water. In a 
 similar pan of equal size there are dissolved 24 kilos, of iodine (not sublimed) in 27 to 28 
 kilos, of soda-lye at 62 Tw. and 60 litres of water. The liquid, which is at first brown, 
 and afterwards colourless, is boiled, and is then run off into a wooden vat of 600 litres 
 capacity (set in a low place), as is also the solution of fluoresceine. After the mixture 
 has been thoroughly stirred 25 kilos, of glacial acetic acid are run out of a stone- 
 ware vessel, in a stream of about the thickness of a finger, into the alkaline mixture, 
 with vigorous stirring. Fluoresceine and iodine are separated out in a state of the 
 finest division, and substitution takes place. When all the glacial acetic acid has been 
 added the iodine is boiled, neutralised with 1 7 kilos, of lye, and a mixture of 2 5 litres 
 water and 25 kilos, hydrochloric acid is added within the lapse of three minutes. The 
 vat is then filled up with water, boiled, and allowed to settle. The hot iodine solution 
 is separated after about an hour from the red precipitate of tetraiodo fluoresceine by 
 decantation into a wooden vat. The deposit is placed upon an alkaline filter, drained, 
 returned to the cask, and boiled up once more there with about 300 litres of water and 
 10 kilos, hydrochloric acid. This decantation and boiling are repeated once more, but 
 without the hydrochloric acid. The free iodeosic acid is placed on a filter, allowed 
 to drain thoroughly, the brick-red paste is spread out thinly upon enamelled drying 
 capsules placed on the water-bath, and dried. The red powder is then sifted. The 
 yield is 1 5 kilos. 
 
 For obtaining the ammonium salt the sifted iodeosine is placed upon frames and 
 exposed to the action of ammonia in a chest as above described. The excess of 
 ammonia is cut off as soon as a sample appears completely soluble. The yield is 15-3 
 kilos, erythrosine B. 
 
 Bi-iodoftuoresceine. Erythrosine G. The less iodised product, consisting chiefly of 
 bi-iodo fluoresceine, is obtained if we use only 16 kilos, iodine instead of 24, proceeding 
 otherwise exactly as above. 
 
 Fluoresceine, 6 ; lye, 8; iodine, 16; lye, 20; acetic acid, 20; lye, 17; hydrochloric 
 acid I., 25 kilos.; hydrochloric acid II., 10 ; yield, 12-9; sal-ammoniac, 8; CaO, 16; 
 erythrosine G, 13-2. 
 
 By methylating the eosine the potassium salt of tetrabromfluoresceinemethylether 
 is obtained, and is sold as erythrine, spirit-eosine. 
 
 Phloxine P is the potassium salt of tetrabromdichlorfluoresceine, which is obtained 
 by the action of bromine upon dichlorfluoresceine. By methylating phloxine we obtain 
 cyanosine, and cyanosine B is formed by ethylating tetrabromtetrachlorfluoresceine, 
 whilst phloxine T is produced by bromising tetrachlorfluoresceine in an alcoholic 
 
SECT, iv.] BENZOL COLOURS. 557 
 
 solution. Ease Bengale is formed by the action of iodine upon dichlorfluoresceine, and 
 Rose Bengale B by iodising tetrachlorfluoresceine, e.g. : 
 
 C 
 
 C.HBr..O.CH, /CJHI..OK ,C.HBr..OK 
 
 o jo ! o 
 
 C 6 HBr 2 .OK U C 6 HI 2 .OK V C 6 HBr 2 .OK 
 
 Cyanosine. Rose Bengale. Rose Bengale B. 
 
 Sesorcine Blue, Lacmoid, is formed by heating resorcine with sodium nitrite. By 
 the action of nitrous acid upon resorcine there is produced dinitroresorcine, or solid 
 Green, C 6 H 4 (N"0 2 ) 2 or C 6 H 2 (O.NOH) 3 , which dyes a green on tissues mordanted with 
 iron. 
 
 With tetramethyldiamidobenzophenon chloride resorcine gives resorcine violet, which 
 is not met with in commerce. 
 
 Auramines. The simplest members of this series are pure yellow colouring matters, 
 which are formed from the tetra-alkylised diamidobenzophenones (or their haloid deri- 
 vatives) by the action of ammonia upon the methan residue. From these dyes there 
 are prepared phenyl-, tolyl-, naphthyl-auramines of redder or browner tones by heating 
 with aniline, its homologues and its derivatives (substituted in the benzol nucleus), 
 naphthylamine, &c., with the elimination of ammonia. These same substituted 
 auramines are obtained by the immediate action of the amines concerned upon the 
 above-named ketone bases and their haloid derivatives. If tetramethyldiamidobenzo- 
 phenone and tetraethyldiamidobenzophenone are used, practically useful results have 
 been obtained hitherto with ammonia, aniline, para- and orthotoluidine, metaxylidine 
 and phenylenediamine, cumidine, a and /3 naphthylamine. 
 
 Free ammonia does not act upon the ketone bases, but upon their haloid derivatives. 
 If, e.g., the product obtained by treating tetramethyldiamidobenzophenone with phos- 
 phorus chloride in presence of an indifferent solvent is mixed with concentrated 
 ammonia, with good refrigeration, a yellow colour at once appears, and after some time 
 auramine separates out in a crystalline form. More advantageous is the direct action 
 of the ketone bases, which, on heating with ammonium chloride, acetate, tartrate, 
 benzoate, or sulphocyanide, especially with the aid of zinc chloride or other dehydrating 
 agents, can be easily converted into auramines. 
 
 There is put into an enamelled pan provided with an oil or air bath, and previously 
 heated to about 200 e.g., an intimate mixture of 25 kilos, tetramethyldiamidobenzo- 
 phenone (obtained by saturating dimethylaniline with COC1 2 ) 25 kilos, sal-ammoniac, 
 and 25 kilos, zinc chloride. The mixture gradually melts down and takes a deep yellow 
 colour. To promote the fusion of the mass it is thoroughly stirred from time to 
 time. If the temperature within the melt is about 150 to 160, the colouring matter is 
 formed in from three to five hours. The end of the reaction is recognised when a sample 
 of the melt dissolves almost completely in hot water. The cold, solid mass is broken up, 
 and first treated with cold water acidified slightly by hydrochloric acid, so as to remove 
 the bulk of the excess of sal-ammoniac and zinc chloride. The residue is then 
 exhausted with hot water, and the extract, previously filtered from any unattacked 
 ketone base, is precipitated with sodium chloride. The crystalline precipitate can then 
 be easily rendered perfectly pure by re-crystallisation from water. The colouring 
 matter is the hydrochlorate of imidotetramethyldiamidodiphenylmethan 
 
 (C 6 H 4 .N(CH 3 ) 2 
 C-NH + H S O. 
 
 C 6 H 4 .N(CH 3 ),HC1 
 
 The hydrochlorate, sulphate, and acetate are relatively easily soluble in water, less 
 easily the double zinc chlorides, whilst the hydriodic and hydrosulphocyanic salts 
 
558 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 dissolve with difficulty, or scarcely in the cold. The watery and alcoholic solutions are 
 not fluorescent. On the addition of mineral acids there is at first no change ; but on 
 prolonged standing, or more rapidly when heated, there then occurs decolorisation, whilst 
 the ketone-base is re-formed and ammonia is split off. Alkaline reducing agents e.g., 
 sodium amalgam slowly decolorise the alcoholic solution in the cold. On the addition 
 of water there separates out a colourless crystalline reduction product. The acetic 
 solution is scarcely coloured, but on heating it at once takes a deep blue colour. This 
 process depends on splitting up the reduction product into ammonia and tetramethyl- 
 diamidobenzhydrol. On heating the auramine with aniline to the boiling-point of the 
 latter, ammonia is evolved, and the mixture contains the orange-yellow dye plienyl- 
 auramine. 
 
 Nitrosodimethylaniline, C 6 H 4 .NO.N(CH 3 ) 2 , a very important material for the 
 preparation of many colouring matters, is obtained by dissolving 2 parts dimethyl- 
 aniline in 5 parts strong hydrochloric acid and 10 parts of water, and adding the 
 required quantity of sodium nitrite. Nitrosodimethylaniline separates out. 
 
 This salt yields with metaphenylenediamine the hydrochlorate of dimethyl- 
 diamidophenazine, called neutral violet; with metatoluylenediamine it forms the 
 hydrochlorate of dimethyldiamidotoluphenazine, neutral red. 
 
 Both are spoken of as eurhodines. 
 
 Indophenol, 
 
 N (C 6 H 4 .N.(CH 3 ) 3 , 
 1CH0 
 
 10 
 
 is formed by the action of nitrosodimethylaniline upon a-naphthol, or by the oxidation 
 of amidomethylaniline and a-naphthol. It is insoluble in water. 
 
 New Blue, Naphthylenene Blue B, Cotton Blue R, Fast Blue for Cotton, the 
 chloride of dimethylphenylammonium-/3-naphthoxazine, 
 
 is formed from nitrosodimethylaniline-/3-naphthol. It is easily soluble in water, with 
 a violet-blue colour. 
 
 The similar colouring matter, Muscarine, is formed from nitrosodimethylaniline 
 hydrochlorate with a-dioxynaphthaline, and with a-naphthylamine it yields Nile Blue. 
 
 Gallocyanine (Solid Violet], the chloride of dimethylphenylammoniumdioxyphene- 
 oxazine carbonic acid, is formed from nitrosodomethylaniline with gallic acid. It is 
 insoluble in water, whilst the colouring matter, Prune, obtained in a similar manner 
 from gallic methyl ether, is easily soluble. 
 
 Methylene Blue is the hydrochlorate or zinc double chloride of tetrarnethylthionine. 
 According to Caro, dimethylaniline is converted by sodium nitrite into nitrosodimethyl- 
 aniline, reduced by hydrogen sulphide to amidodimethylaniline, which is finally 
 oxidised by ferric chloride. Or it may be first oxidised and then treated with ferric 
 chloride. The colouring matter is precipitated from the splendid blue solution with 
 common salt and zinc chloride. Or nitrosodimethylaniline is dissolved in sulphuric acid, 
 of sp. gr. 1-40, converted by zinc sulphide into the leuko-base of methylene-blue, which 
 is then oxidised (Ethylene Blue}. 
 
 Methylene Blue is characterised by its fine blue tone, slightly verging on green, 
 and its fastness against soap and light. It dissolves readily in water, dyes cotton with- 
 out a mordant, and is distinguished from aniline blues by the odour of dimethylaniline 
 which it evolves if boiled with caustic alkali. 
 
 The manufacture of methylene blue includes, according to Miihlhausen i, the 
 production of the solution of nitrosodimethylaniline; 2. the sulphurising; 3, the 
 oxidation ; 4, the precipitation ; and lastly, the filtration. 
 
 For obtaining the solution of nitrosodimethylaniline there is prepared a solution 
 
SECT, iv.] BENZOL COLOURS. 559 
 
 of dimethylaniline hydrochlorate and a solution of sodium nitrite. Into each of three 
 vats there are poured 1200 litres of water. To this is added a mixture, previously 
 prepared, of 10 kilos, dimethylaniline and i carboy of hydrochloric acid at 30 Tw., 
 which are best mixed in an enamelled vessel, stirring the dimethylaniline into the 
 hydrochloric acid, which has been previously diluted with about 50 litres of water. 
 
 For preparing the nitrite solution there is put into each nitrite vessel correspond- 
 ing to the three colour vats 6'6 kilos, of sodium nitrite (at 98 per cent.) and about 150 
 kilos, of water. After about twelve hours the cocks of the nitrite vessels are opened, 
 and the solution is run during two hours through a leaden funnel-tube, which reaches 
 to the bottom of the colour vats. The temperature of the solution before nitroising is 
 from 8 to 9, but afterwards from 10 to 12. In summer or winter the temperature 
 is regulated with ice or steam. Constant agitation is kept up during the nitroising, 
 and afterwards 2 carboys of hydrochloric acid are added to each vat. 
 
 The object of the sulphurising is to expel the excess of nitrous acid, to reduce the 
 nitroso-compound to an amine, and to saturate the liquid with hydrogen sulphide. 
 The development of the sulphuretted hydrogen is effected with quite fresh moist soda- 
 mud (i.e., vat- waste). A pail filled with soda-mud has the net weight of 35 kilos. 
 The contents of two such pails suffice to expel the nitrous acid of all the three vats. 
 Into each vat there is put by means of a shovel ^ pailful. A yellowish-green froth 
 appears, and on adding another J, orange vapours of nitrous acid are expelled by the 
 sulphuretted hydrogen, which dissolves in the water. These operations require constant 
 stirring, and last about five minutes. The liquid then smells of sulphuretted hydrogen. 
 
 Previous to reduction we then add to each vat two more carboys of hydrochloric 
 acid, and then begin to introduce the vat- waste. Each vat receives at intervals of i J 
 to 2 hours four or five pails of the vat-waste. On adding each pail (which takes about 
 two minutes) the agitator is set in action in order to distribute the mud equally at 
 the bottom of the vats. Caution is here needed, as the mass easily overflows, which 
 may be prevented by stopping the agitator in time. After the mud has been thrown 
 in, the agitator is stopped, so that the development of the sulphuretted hydrogen 
 may proceed quietly and slowly, and it may have full opportunity for dissolving, but 
 little for escaping. The reduction is generally complete by the introduction of the 
 fourth pail. A strip of filter-paper dipped in the liquid should no longer show the 
 characteristic nitrose margin. As the liquid remains standing over night, half or one 
 pail is added for subsequent development, according as the reduction and saturation 
 have made more or less progress. 
 
 After adding the soda-mud the solution becomes a milky white, and contains 
 chiefly amidodimethyline hydrochlorate and small quantities of a sulphuretted base, 
 which both yield the blue colouring matter, also milk of sulphur and the residue of the 
 mud, along with some sulphide not attacked, and which may subsequently cause irre- 
 gularities in the production of the colouring matter. The calcium chloride formed 
 does not come into consideration. 
 
 During the sulphurising the liquor undergoes a series of changes in colour, which 
 prove that not merely diamine but colouring matter is formed, which is partly 
 reduced to methylene white, and partly converted into methylene red by being more 
 highly sulphured. The following table shows the observations made during such a 
 reduction : 
 
5 6 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. iv. 
 
 Number 
 of Pails. 
 
 Heat after 
 adding 
 Mud. 
 
 Time. 
 
 Reaction on Filter-paper. 
 
 Appearance of Liquor. 
 
 I* 
 
 1 6 
 
 9.20 a.m. 
 
 Pure yellow 
 
 Brownish-yellow 
 
 
 
 10.15 
 
 Yellow, orange 
 
 Black-green 
 
 
 
 10.30 
 
 Yellow, orange, red 
 
 Black 
 
 2 
 
 174 
 
 11.5 
 
 
 Black-brown 
 
 
 
 11.25 
 
 Yellow, red, blue 
 
 Black 
 
 
 
 "45 
 
 Yellow, red, very strong 
 
 Deep black 
 
 3 
 
 19 
 
 12.0 noon 
 
 
 Chocolate 
 
 
 
 12.30 p.m. 
 
 Yellow, blue and red 
 
 Blue 
 
 4 
 
 20 
 
 1.50 
 
 
 Very blue 
 
 5t 
 
 21 
 
 2.50 
 
 
 Red 
 
 
 
 4.0 
 
 
 Colourless 
 
 The oxidation is effected by the addition of ferric chloride, of sp. gr. i'i6 to 1*17, 
 which corresponds to 20-21 per cent. Fe a Cl 6 , to the sulphured liquid. Ferric chloride 
 is added until the smell of sulphuretted hydrogen has entirely disappeared and a slight 
 excess of iron chloride is present. For the oxidation, four carboys of ferric chloride, 
 containing each 70 kilos, of the above-mentioned sp. gr., are nearly always sufficient. 
 
 Whether enough has been added can be judged at once by the eye. The oxidised 
 liquor must appear of a deep blue ; if it is reddish-blue the oxidation is not quite 
 sufficient. 
 
 It sometimes happens that the oxidised liquid, after standing for some time, again 
 evolves sulphuretted hydrogen ; in this case also a little more ferric chloride is to be 
 added. These accidents are due either to an irregular introduction of the mud or to 
 imperfect stirring. 
 
 The tests for ascertaining whether a vat has received enough ferric chloride are the 
 following : A sample precipitated with common salt and a little zinc chloride is placed 
 upon a slip of filter-paper, and the opposite margin is touched with a solution of 
 potassium f errocyanide ; if a faint blue spot appears where the two liquids meet, 
 sufficient ferric chloride has been added. If, on the contrary, a slip of filter-paper 
 dipped in the colour-liquor becomes darker if touched with ferric chloride, more ferric 
 chloride must be added to the bulk. 
 
 "When the solutions are perfectly oxidised, the colouring matter is salted out. 
 
 For precipitation 180 kilos, of rock-salt are stirred into each vat, and as this 
 effects only a partial precipitation, there are further added to each 2 5 kilos, zinc chloride 
 at sp. gr. 1-5. 
 
 In order to ascertain whether the colouring matter is completely precipitated, a slip 
 of filter-paper is dipped into the liquid and examined by reflected light; if all the 
 colour has been deposited we see blue flocks on a red ground. If the ground is 
 blue or blueish-red, more salt and zinc chloride must be added. As soon as the test 
 indicates complete precipitation, the liquid is at once filtered through a double woollen 
 filter laid over a tub. 
 
 The filtration is effected with constant agitation, and takes two to three hours. 
 The crude colour is on the filter, and the red liquid is caught in the tub below. In 
 the upper colour-vat there is still a residue. It is baled into a wooden trough and 
 elutriated with water until it no longer gives off any colour. The watery extract is 
 placed along with the crude colour in the extraction cask ; the residue is thrown away. 
 The crude colour is turned over with a wooden shovel to promote drainage and is then 
 ready for extraction. 
 
 The crude colour consists of methylene blue, a residue of mud, sulphur, and dregs of 
 salt tinged with blue. 
 
 Initial temperature, 14. 
 
 t The fifth pail was not entirely added. 
 
SECT, iv.] BENZOL COLOURS. 561 
 
 The red filtrate is worked up for a zinc colour ; 36 kilos, of zinc powder are stirred 
 up to a paste with a little water, to each vat there are allowed, therefore, 12 kilos, 
 of zinc. The paste is put in with iron spoons ; a spoonful being briskly stirred into 
 each vat every ten minutes. The liquid foams ; streams of sulphuretted hydrogen 
 escape. Zinc is thus added until the liquor becomes colourless. There is now added to 
 each vat, stirring vigorously, a carboy, equal to 70 kilos, ferric chloride, which gives a deep 
 blue solution, from which the colouring matter is at once deposited on account of the 
 salt and zinc chloride present. The contents of the vats, after being well stirred up, 
 are filtered. The liquid flows away and a zinc colour remains on the filter. 
 
 In order to work up the crude colour, the dissolving cask is filled up with water 
 and heated with steam to 24. Into the water, which is mixed with 18 kilos, ferric 
 chloride, is poured the crude colour from six vats ; it is stirred up until the water is per- 
 fectly saturated with colouring matter and adhering salts, allowed to settle, and the 
 better to clear the liquid a few handfuls of salt are strewn upon the surface of the 
 solution. After twelve hours' rest the coloured liquid is drawn off by means of a 
 syphon into another tub fixed below. On filtering the solution it is well to let the first 
 turbid portions of the filtrate run upon a second filter, also placed over the lower vat, 
 and as soon as the solution is clear it is passed through another filter. The filtrate is 
 now completely salted out with 200 kilos, of clean salt and 30 kilos, zinc chloride. As 
 soon as perfect precipitation has been effected it is filtered at once through a filter below, 
 passing previously through a fine sieve to keep back any coarse particles of rock salt. The 
 colouring matter is then well drained. 
 
 The extraction-tub is then again filled with water, heated to 24, and mixed with 18 
 kilos, of ferric chloride. The residue left on the filter is stirred in, and the contents are 
 further treated as in extract No. i . In the third extraction there are only added 
 9 kilos, ferric chloride, proceeding otherwise as before. As all the salts are dissolved 
 out, this extract yields the finest, strongest, and purest colour. There is, especially in 
 this colour, no more methylene red. Sometimes it may be necessary to make four 
 extracts, but in general three suffice. The residue on the filter and in the cask is 
 placed in the boiling vat, where it is opened up with hydrochloric acid. 
 
 The boiling vat is half filled with water ; the contents, well stirred up, are mixed with 
 15 kilos, hydrochloric acid and heated to boiling. The liquid, deep blue at first, becomes 
 pale blue and even colourless, and nitrous acid escapes. As soon as the mass boils, 30 
 kilos, of ferric chloride are added and filtered at once into a tub below. The purpose 
 of the boiling is the reduction of the methylene blue attached to finely divided sulphur. 
 The filtrate is re-oxidised within the lower cask with 8 kilos, ferric chloride, and then 
 salted out with 150 kilos, rock-salt and 30 kilos, solution of zinc chloride. If the residue 
 in the boiling-vat is not yet entirely opened up (rarely the case), a further extraction 
 is made, the vat being only one-quarter filled with water. 
 
 The zinc colour from the six additional casks is placed in the boiling-vat and there 
 stirred up with cold water. The liquid is then allowed to settle for twelve hours and 
 filtered into a tank below. The filtrate is mixed with 10 kilos, ferric chloride, 150 kilos, 
 rock-salt, 30 kilos, solution of zinc chloride, and filtered. The residue on the filter is 
 returned to the vat. The vat is now filled one-quarter with water and heated as above, 
 but only with 40 kilos, salt and 6 kilos, solution zinc chloride. The second extract of 
 zinc colour is generally omitted, working so that when the boiling colour from the raw 
 colour vat arrives in the boiling tank the first extract of the zinc colour is just 
 finished. 
 
 According to the working up of the crude colouring matters we have three sorts 
 of extract : pure colour, zinc colour, and boiling colour on the filter. After each 
 filtration the colour on the filter is scraped up and drained in a pointed woollen bag 
 filter; when the last saline liquor runs off. The colours then are mixed in a cask, 
 
 2 K 
 
562 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. iv. 
 
 and for mixing, water is added until it begins to dissolve colour also, and not- 
 merely salts i.e., until a slip of paper moistened with the solution is coloured faintly 
 blue. The paste, allowed to stand for some hours, is passed through bag niters, 
 wrapped in strong cotton cloths and pressed under a screw-press. The press cakes so 
 obtained are dried on zinc plates, cut up with wooden spatulse, and dried in a drying- 
 room at 60. 
 
 Instead of mixing the three grades of colour, they may all be worked up separately. 
 The pure colour is then the finest and strongest, and the boiling colour the weakest. If 
 these colours are mixed up with water, the pure colour is blue and the zinc colour and 
 boiling colour grey. Similar is the behaviour of the pressed and dried colours. The 
 yield for every vat is 5 to 6 kilos. The colour when ground is a bronze powder. The 
 following table gives a view of the numbers given above : 
 
 
 Oil. 
 
 HC1 
 
 NaNOg 
 
 Na or N 
 Waste. 
 
 Fe 2 Cl & 
 
 Rock 
 
 Salt. 
 
 ZnCl 2 
 
 ine 
 Powder. 
 
 Sodium 
 Chlo- 
 ride. 
 
 Yield. 
 
 Crude colour . 
 Pure colour A I. 
 
 30 
 
 1050 
 
 19-8 
 
 500 
 
 1050 
 18 
 
 540 
 
 75 
 30 
 
 36 
 
 2OO 
 
 
 
 AH. . 
 
 
 
 
 
 
 
 
 
 18 
 
 
 
 30 
 
 
 
 2OO 
 
 
 
 A III. 
 
 
 
 
 
 
 
 
 
 9 
 
 
 
 3 
 
 
 
 2OO 
 
 
 
 Boiling colour A I. 
 
 
 
 15 
 
 
 
 
 
 38 
 
 
 
 30 
 
 
 
 150 
 
 
 
 Zinc colour 
 
 
 
 
 
 
 
 
 10 
 
 
 
 30 
 
 
 
 5P 
 
 
 
 Finished product . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 36 
 
 
 60 
 
 2115 
 
 39-6 
 
 IOOO 
 
 2193 
 
 1 080 
 
 300 
 
 72 
 
 900 
 
 36 
 
 The Zinc Sulphide Process. If sulphuretted hydrogen is passed into sulphuric 
 acid at 72-98 Tw., sulphur separates out and the sulphuric acid is reduced to 
 sulphurous acid : H 2 S0 4 + SH 2 = SO 2 + S + aH 2 0. 
 
 The sulphurous acid again is at once decomposed in contact with H 2 S with further 
 liberation of sulphur : S0 2 + 2H 2 S - 2H 2 + 38. 
 
 If this liberation of sulphur takes place in presence of nitrosodimethylaniline 
 sulphate it is converted into a colourless sulphur base, which, when oxidised, yields a 
 blue dye-stuff. For nitrising the following plant is required: 3 enamelled iron pans, 
 each holding 400 litres, fitted with agitators and cooling jackets ; 3 sulphuring pans, 
 each containing 1500 litres, with cooling jackets; escapes for sulphuretted hydrogen 
 gas ; pressure gauge and cover fitted with a man-hole (the agitator and the pan are lined 
 with lead); a settling beck with a box-filter, and below it an oxidation vat; finally, a 
 purifying system consisting of a redissolving vat and a precipitating tank with a box; 
 filter. 
 
 The materials needed are : methylaniline, sodium chloride, zinc chloride, of qualities 
 as above mentioned ; sulphuric acid, both of 40 and of 130 Tw. ; the former is obtained 
 by mixing 23 kilos, sulphuric acid and 50 kilos, water; the latter from 150 kilos, 
 sulphuric acid and 22^ kilos, water. The zinc sulphide must be pure, dry, and finely 
 sifted. 
 
 The production of the crude colour comprises: i, nitrising; 2, sulphuring; 3, 
 clearing ; and 4, oxidation. 
 
 Into each nitroso-pan there are stirred 10 kilos, methyl-aniline and 75 kilos, of the 
 weak sulphuric acid ; the mixture is cooled down to 6 to 8 with ice, and a solution of 
 6\ kilos. NaN0 2 in 30 kilos, water is run in from a bottle fitted with a cock, and' 
 with constant agitation, the temperature not being allowed to rise above 12. When 
 this operation is at an end the mass is mixed with 175 kilos, of the stronger sulphuric- 
 acid, keeping the temperature at 12. The contents of the pans charged in this 
 manner are now forced up by means of compressed air into the sulphurising pans. 
 
SECT, iv.] BENZOL COLOUES. 563 
 
 The mass is sulphurised by introducing dry zinc sulphide, ground to an impalpable 
 powder, in lots of 100 kilos., and with continual stirring, keeping the temperature at 20 
 to 25. After entering the zinc sulphide the pan is closed, and the contents are digested 
 at 35 to 40, until the reaction is completed. This is indicated by the decolorising 
 of the solution, which has been in succession light green, blue, dark blue, and finally 
 red. All the contents of the pans are forced into the settling beck, which holds 3000 
 litres of water, and after being well mixed up they are left to settle for twelve hours. 
 The sulphur is then filtered off, the liquid is boiled again with 5 kilos, of sulphuric acid 
 and 1000 litres water, allowed to subside, and filtered. The united filtrates are oxidised 
 as above described with 5 carboys of ferric chloride, the colouring matter is precipitated 
 with common salt, and filtered. 
 
 This colour is purified by redissolving and treating as already described. The blue 
 produced in this manner has a considerably higher tinctorial power than the product 
 obtained by the former process. 
 
 Lauth's Violet (Thionine) is similar in composition to methylene blue : 
 
 C 6 H 3 .NH 2 (C 6 H 3 .N(CH 3 ) 2 
 
 1ST- S NJ S 
 
 C 6 H 3 .NH.HC1 (C 6 H 3 (CH 3 )C1 
 
 Lauth's violet. Methylene blue. 
 
 It is obtained by oxidising paraphenylondiamine in an acid solution containing 
 hydrogen sulphide. 
 
 Bernthsen heats 10 parts diphenylamine with 4 parts sulphur in a cohobater to 
 250 to 300 for two hours, or until the end of the reaction is indicated by cessation of 
 the development of sulphuretted hydrogen. The crude thiodiphenylamine is purified by 
 distillation and repeatedly recrystallising from alcohol the light-yellow distillate which 
 solidifies in crystals. For nitrising it is introduced with good cooling and agitation by 
 degrees into 5 parts of nitric acid at 72 Tw. The pasty mixture is then put in much 
 cold water, and the nitro-compound, which separates out as a light-yellow powder, is 
 filtered and washed. It is sparingly soluble in alcohol and benzol, more readily in 
 glacial acetic acid. Instead of free nitric acid the well-known nitrising mixtures can 
 be used. For reducing this nitrised thiodiphenylamine the usual reducing agents may 
 be taken e.g., stannous chloride, iron, tin, or zinc, with hydrochloric acid, &c. If 
 tin and hydrochloric acid are used, the mixture proceeds very quickly with the applica- 
 tion of heat, the nitro-compound dissolves, and there is formed a colourless solution, 
 from which, after tin has been removed by H 2 S or zinc, a double zinc chloride is to be 
 obtained by evaporating the hydrochlorate of the leuko-base. This leuko-base is 
 characterised by the reaction that on saturation with ammonia it is on contact with, 
 an oxidising agent at once resolved into a violet colouring matter. 
 
 The oxidation of the above-mentioned reduction-product can be conveniently effected' 
 with the colourless solution freed from tin by means of zinc. On the introduction of 
 ferric chloride in slight excess there appears at once an intense violet precipitation 
 of the sulphuretted colouring matter, which, if necessary, can be completed by the 
 addition of common salt. After filtering off the precipitate it may be further puri- 
 fied by recrystallisation from boiling water. The colour may also be obtained 
 perfectly pure, and in the form of fine crystalline needles, if the concentrated aqueous 
 solution is precipitated by the addition of hydrochloric acid. When dry the colour- 
 ing matter is a green crystalline powder of a metallic lustre, soluble in concentrated 
 sulphuric acid with a green colour, which, as Avater is added, becomes first blue and 
 then violet. The colouring base, when set at liberty by alkalies, is red, and dissolves 
 in ether with a yellowish-red colour. If heated in a dry state, the colour is decom- 
 posed with liberation of sulphuretted hydrogen. The watery solution has an intense 
 violet colour, and is quickly decolorised by reducing agents, such as zinc-powder, tin, 
 
564 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 and hydrochloric acid, solution of hydrosulphite, &c. Oxidising agents quickly restore 
 the colour. The dye-stuff fixes itself directly upon animal fibre, and is peculiarly suit- 
 able for dyeing animalised or tanned cottons. 
 
 By the introduction of alcohol radicles into the molecule there are formed colouring 
 matters of violet-blue to bluish-green tones. 
 
 Induline, Nigrosine, Azodiphenyl Blue, Violinaniline, Couplers Blue, Fast Blue, 
 Printing Blue, Acetine Blue may be best obtained by heating amidoazobenzol with 
 aniline hydrochlorate : 
 
 C 6 H 5 .NH, + C 6 H 6 .N.NC 6 H 4 .NH f = NH 3 + C 18 H 15 N 3 
 Aniline. Amidoazobenzol. Induline. 
 
 Induline is converted into a more valuable colouring matter if it is again treated 
 with aniline salts in presence of aniline. For this purpose we heat in an enamelled 
 cast-iron pan 100 kilos, induline hydrochlorate (azodiphenyl blue), 45 kilos, aniline hydro- 
 chlorate, and 200 kilos, of aniline to 1 60 to 170 for twenty- four hours. The thick melt, 
 when cool, is mixed with 500 litres of alcohol. Fine brass-coloured crystals of the new 
 colouring matter separate out, which are collected on a filter, purified by washing with 
 alcohol, and dried. To effect the formation of induline and its transformation in one and 
 the same operation, we mix in an enamelled pan 100 kilos, diazoamidobenzol with 130 
 kilos, of aniline hydrochlorate and 300 kilos, pure aniline. The molecular transforma- 
 tion of the diazoamido compound is effected by standing for twenty-four hours, or more 
 rapidly by heating to 40 or 50, and it is then heated for four to five hours to 1 10 . The 
 melt is now of a deep violet colour, and still contains traces of amidoazobenzol. It is ad- 
 vantageous, though not strictly necessary, to add 65 more kilos, of aniline hydrochlorate, 
 and then to heat for twenty-four hours to 160 to 170. The blue thus obtained is then 
 converted into a sulpho-aoid by heating with 3 parts sulphuric acid of sp. gr. 1-840 to 
 110 for six hours. The sulpho-acid is then converted into the sodium salt which 
 forms the commercial product. This new colouring matter, C 36 H 27 N 8 HC1, induline 
 6B, formed from induline with liberation of ammonia, is distinguished from the well- 
 known colour by its complete insolubility in alcohol and its pure greenish-blue tone, 
 which does not vary in artificial light. The indulines are distinguished by fastness. 
 
 Sajfranine (Aniline Hose) is a mixture of tolusaffranines and phenotolusaffranines. 
 The colouring matter, which dissolves in water with a red colour, is formed by the 
 oxidation of i mol. each of aniline, orthotoluidine, and paratoluylendiamine. 
 
 Phenosaffranine, H 2 N.C 6 H 3 .N 2 .C 6 H 4 .C 6 H 4 .NH 2 .C1 (Saffranine B extra), is formed 
 by oxidising paraphenylendiamine with 2 mols. aniline. It forms green crystals, 
 which dissolve in water with a red colour. 
 
 Neutral Blue is formed from nitrosodimethylaniline with phenylnaphthylamine, 
 and Bale Blue, from nitrosodimethylaniline with ditolylnaphthylendiamine. 
 
 Girofle is obtained from nitrosodimethylaniline hydrochlorate and a mixture of 
 meta- and para-xylidine hydrochlorate. 
 
 Aurantia (Imperial Yellow), the ammonium salt of hexanitrodiphenylamine, 
 
 N[C 6 H 2 (N0 2 ) 3 ] 2 .NH 4 , 
 is formed on treating diphenylamine with nitric acid. 
 
 2. Phenol Colouring Matters. Phenol serves for the production (besides the azo- 
 dyes) of the following colours : 
 
 Picric Acid (Trinitrophenol), C 6 H 2 (N0 2 ) 3 OH, is formed by the action of nitric acid 
 upon phenol, or by treating crystallised sodium phenol sulphonate with nitric acid. It 
 crystallises in yellow leaflets, sparingly soluble in cold water, but readily in alcohol and 
 in hot water. It melts at 122, and deflagrates if rapidly heated. It is used in dyeing 
 yellows, and in the form of a picrate with aniline green (iodine green), and with indigo 
 or Prussian blue for obtaining green, upon silk or wool.* 
 
 * It does not bear soaping. 
 
SECT, iv.] PHENOL COLOURS. 565 
 
 It has happened that instead of the free acid its sodium salt has been sold under the 
 names of picric acid and aniline yellow, and has given rise to very serious accidents in 
 consequence of its explosive character. 
 
 In France large quantities of picric acid are regularly made, not for dyeing, but 
 for producing picrate powder. If treated with potassium cyanide, picric acid yields 
 isopurpuric acid (C 8 H 5 N 5 6 ), whilst trinitrocresolic acid yields cresylpurpuric acid 
 (C 9 H 7 !N" 5 6 ), the potassium and ammonium salts of which are known as garnet brown. 
 As garnet brown explodes with great violence on sh'ght friction, it is generally sold as 
 a paste. To prevent the paste from drying up it is mixed with a little glycerine.* 
 
 Phenyl Brown(Phenicine,Rotheine) was obtained by Roth in 1865, and is sometimes 
 used in silk and woollen dyeing. It is formed by treating phenol with a mixture of 
 sulphuric and nitric acids. Phenyl brown is an amorphous powder a mixture of two 
 colouring matters, the one yellow (according to Bolley dinitrophenol, C 6 H 4 (N0 2 ) 2 0), 
 and a blackish-brown compound allied to the humoids. Phenyl brown is no longer met 
 with in commerce. 
 
 Flavaurine (New Yellow), the ammonium salt of dinitrophenolparasulpho-acid, 
 C 6 H 8 (NO a ) 2 .S0 3 NH 4 , is obtained by treating niononitrophenolparasulpho-acid with 
 nitric acid. 
 
 Victoria Yellow (Saffron substitute, Victoria Orange, Aniline Orange) is a mixture of 
 the potassium and ammonium salts of dinitro-, ortho-, and para-cresol, 
 
 C 6 H 2 .CH 3 (N0 2 ) 2 OK, 
 
 obtained by treating ortho- and para-cresolsulpho-acid or diazotoluol with nitric acid. 
 It has been recently proved that this dye-stuff is poisonous. Hence it cannot be used 
 for colouring articles of food, &c., as a substitute for saffron. f 
 
 (C 6 H 4 .OH) 
 
 Aurine C-jCJHLOHf is obtained by heating i part phenol with 0*5 part sulphuric 
 IC 6 H 4 J 
 
 acid (at sp. gr. i'S4) and o - 6 to 0*7 part oxalic acid, to 120 to 130. The yield is 60 
 to 70 per cent. It may also be produced by heating a mixture of i mol. phenol, 2 
 mols. cresol, 3 niols. sulphuric acid and pulverised arsenic acid to 120. On lixiviating 
 the mass with water, aurine remains as a resinous mass of a metallic green colour, 
 yielding a yellowish-red powder. Commercial aurine, also called rosolic acid, contains, 
 besides aurine, oxidised aurine, methylaurine, pseudorosolic acid, &c. It is soluble in 
 water and insoluble in alcohol. 
 
 Coralline (Peonine, Aurine fi) is obtained by treating aurine with ammonia, and is 
 probably rosaniline rosolate. 
 
 Azuline (Azurine, Rosolic Blue] impure triphenylpararosaniline hydrochlorate, is 
 obtained by heating rosolic acid with aniline. 
 
 Here also belongs the substance first isolated by Reichenbach from beech wood tar 
 under the name of pittacal. It is now found to consist of the deep-blue salts of 
 eupittonic acid, C 25 H 26 9 = C 19 H 8 (O.CH 3 ) 6 3 . 
 
 Quinoline, C 9 H 7 N, a constituent of coal-tar, formerly obtained by distilling 
 cinchonine with sodium hydrate, is now obtained from phenol synthetically. Skraup 
 heats i -4 kilo, of ortho-, meta-, or para-nitrophenol with 2'i kilos, of one of the three 
 amidophenoles, 6 kilos, glycerine at sp. gr. 1-26, and 5 kilos, sulphuric acid of sp. gr. 
 1*845, ^ I 3 ^ r 4 c - When the reaction is complete, the volatile impurities are 
 distilled off in a current of steam, the mass is neutralised with soda, the volatile 
 orthoquinoline is distilled off in a current of steam, and the other compounds are 
 precipitated with soda. 
 
 According to the statement of the works formerly Meister, Lucius and Bruning, 
 
 * Garnet brown is scarcely ever used in dyeing. 
 
 t In England saffron is rarely used as a colour for food, except in Cornwall. 
 
566 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 the orthonitrobenzylidenacetone obtained from benzylidenacetone by nitrising passes 
 into methylquinoline or quinaldine on treatment with reducing agents : 
 C 6 H 4 .N0 2 .CH.CO.CH 3 + 3 H 2 = C 6 H 4 .C 3 H 2 .CH 3 .N + 3 H 2 0. 
 
 For the reduction of orthonitrobenzylidenacetone, stannous chloride and hydro- 
 chloric acid are the most suitable. For 20 parts orthonitrobenzylidenacetone, there are 
 used 75 parts stannous chloride and 75 parts hydrochloric acid (of sp. gr. 1*2) diluted 
 with the same quantity of water. The formation of methylquinoline is effected with a 
 strong liberation of heat. The mass is then mixed with hydrate of lime in excess, and 
 the new base is distilled off in a current of steam. Methylquinoline, which may be used 
 in the preparation of the azo-dyes, boils about 240, and yields very finely crystalline 
 salts. It is also formed from aniline and aldehyde : 
 
 C 6 H 7 N + 2 C 2 H 4 O = C 10 H t N + 2 H 2 O + H s . 
 
 According to Dobner and Miller the reaction of the aldehydes with aniline ensues 
 always on the same principle as with acetaldehyde, 2 mols. aldehyde reacting with 
 i mol. aniline so that 2 mols. water and one mol. hydrogen are split off. 
 
 Acetaldehyde . . 2 C 2 H 4 + C 6 H 7 N = C 10 H 9 N + 2H 2 + H 2 
 Propionaldehyde . 2C 3 H 6 O + C 6 H 7 N = C,,H IS N + 2H 2 + H 2 
 Normal Butylaldehyde 2C 4 H 8 + C 6 H 7 N = C, 4 H 17 N + 2H 2 + H 3 
 Isovaleraldehyde . 2C 6 H 10 *. C 6 H 7 N = C 16 H 21 N + 2 H 2 + H 3 
 (Enanthaldehyde . 2C 7 H 14 + C 6 H 7 N = C 20 H 29 N + 2H 2 O + H 2 
 
 The most important quinoline colours are 
 
 Quinoline Green, the hydrochlorate of tetramethyldiamidodiphenylquinolyl carbinol 
 obtained from quinoline and tetramethyldiamidobenzophenonchloride is not now an 
 article of commerce. 
 
 Quinoline Blue, Cyanine, is obtained from the product of the reaction of amyliodide, 
 quinoline, and methylquinoline. 
 
 Quinoline Red is produced if benzotrichloride is heated with quinaldine and 
 isoquinoline in presence of zinc chloride. In preparing quinoline red from benzotri- 
 chloride and the quinoline of coal-tar, not more than, at the outside, one molecule of 
 quinoline can thus be converted into colouring matters. According to the experiments 
 of A. W. Hof mann in preparing quinoline red the simultaneous presence of isoquinoline 
 and quinaldine is requisite. If a mixture of i moL isoquinoline and i mol. quinaldine is 
 heated in presence of zinc chloride and benzotrichloride the colour is formed at 120, 
 and the yield is much larger. The analysis of the colouring matter leads to the formula 
 C 26 H 1S N 2 C1, the exact formula which might be expected on the assumption that in 
 its formation i mol. quinoline, i mol. quinaldine, and i mol. benzotrichloride are 
 condensed, whilst 2 mols. hydrochloric acid are split off, as in the formation of 
 malachite green. 
 
 C 8 H U N + C 8 H U N + C 7 H 5 C1 3 = C a TL K TS,Cl + 2 HC1 
 Dimethylaniline. Dimethylaniline. Benzotrichloride. Malachite green. 
 
 C,H 7 N + C 10 H 9 N + C 7 H 5 C1 3 = C 26 H 19 N 2 C1 + 2 HC1 
 
 Chinolin. Chinaldin. Chinolinroth. 
 
 ( CH C H N~i 
 Quinoline Yellow, C ' In jj nr^f)}'* 8 ^ orme< ^ on heating quinaldine with phthalic 
 
 anhydride and zinc chloride. In order to render it soluble in water it is converted into 
 a sulpho-acid by treatment with concentrated sulphuric acid, and this again is trans- 
 formed into the sodium salt. 
 
 Perhaps as important as the quinoline colouring matters are the quinoline nostrums 
 such as antipyrine and thalline.* 
 
 * Of these substances, antipyrine is the only one which has not since been found to be 
 injurious. 
 
SECT, iv.] NAPHTHALINE COLOUES. 567 
 
 Salicylic Acid, C 6 H 4 .OH.CO.OH, formerly obtained from oil of winter-green and other 
 vegetable matters, is now produced synthetically from phenol. 
 
 According to Kolbe's directions, phenol is evaporated to dryness with the 
 quantity of soda-lye needed to form phenol sodium, C 6 H 5 ONa in an iron retort 
 and heated to 180. Carbon dioxide is then introduced until no more phenol distils 
 over on slowly heating at from 226 to 250 : 
 
 2 C 6 H 5 ONa + CO S = C G H 5 OH + C G H 4 .ONa,COONa. 
 
 The sodium salicylate obtained is dissolved in water, acidified with hydrochloric 
 acid, the salicylic acid liberated is separated from the lime and purified. 
 
 According to the works, formerly Hofmann and Schotensack, phenol and soda- 
 3ye are heated in a double pan provided with an agitator in proportion of 3 to 4 
 mols. evaporated to dust-dryness, phosgene gas is introduced, beginning at 140, and 
 the temperature is gradually raised to 200. As soon as the phenol is distilled off to go 
 per cent, of its calculated quantity the operation is stopped, the dusty residue of basic 
 sodium salicylate is dissolved in water, and crude salicylic acid is precipitated by means 
 of carbonic acid, the last portion of phenol having first been driven off by a current of 
 steam after the addition of i mol. hydrochloric acid to i mol. salicylic acid. 
 
 At Schering's works, 50 kilos, diphenyl-carbonate and 54 kilos, phenol-sodium are 
 heated in a pan provided with an agitator at from 160 to 1 70 for six hours. From the 
 product the salicylic acid is separated in the known manner. The reaction takes place 
 according to the equation 
 OC 6 H 5 .CO.OC 6 H 5 + 2 C 6 H 5 ONa = C 6 H 4 .ONa.COO.Na + C 6 H.OC 6 H 5 + C 6 H 5 OH. 
 
 Schroeder finds that sodium salicylate is formed according to the equation 
 
 C 6 H s ONa + Na 3 C0 3 + CO = C 6 H 4 .ONa.CO,Na + NaCHO s , 
 
 if carbon monoxide is passed over a mixture of sodium phenylate and sodium carbonate 
 at 200. 
 
 Among the colours obtained from salicylic acid the most important are 
 
 Salicyl Yellow, the mono-bromsalicylic acid or its sodium salt, 
 
 C 6 H,.Br.NO s .OH.COOH, or C 6 H,Br.NO s .ONa.COONa. 
 This compound, like Salicyl Orange, C 6 H.Br.(NOj).,ONa.COONa, is no longer in use. 
 
 Salicylic acid is much used for the preservation of articles of food, as an addition 
 to beer, wine, tfcc., it is generally considered objectionable.* 
 
 3. Naphthaline Dye-stuffs. Naphthaline, C 10 H S , forms with chlorine addition and 
 substitution products e.g. Naphthaline tetrachlomde, C 10 H 8 C1 4 , by heating naphthaline 
 with chlorine gas, which is converted into phthalic acid by means of nitric acid. With 
 naphthaline there arc formed only substitution products e.g., C 10 H 7 Br. Nitric acid 
 forms in the first place a-nitroiiaphthalme, C 1(> H r N0 2 , which is converted by reducing 
 
 /TVTTT P*TT 
 
 .agents into a-naphthylamine, C 10 H 7 NH 2 , or C 6 H 4 1 QJT Q jj 
 
 According to Witt, naphthaline used for the production of a-naphthylamine must 
 have the following properties : the melting point must be exactly 79, the boiling point 
 216 to 217. A little cylinder cast of the product to be tested, exposed to the free air 
 on a plate of glass, should entirely evaporate in a few days without residue and remain 
 white to the last ; i gramme of the naphthaline heated in a test-tube with pure coii- 
 -centrated sulphuric acid at from 170 to 200 must not colour the acid red, but at 
 the outside only grey. 
 
 The agitator used in nitrising consists of four to six wings placed obliquely at an 
 angle of 45. The cast-iron apparatus, provided with a cooling- jacket, is fitted with a 
 lid (left out in Fig. 397), the one half of which may be thrown open, whilst the other 
 has a wide pipe serving for the escape of the gases formed. The lower part of this 
 
 * Its use is prohibited in France. 
 
568 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. iv. 
 
 Wasserzufluss 
 
 Explanation of Terms. 
 Wassennfluss . . Entrance for water. 
 Wasserobfluss . . Escape for water. 
 
 pipe is provided with a steam jacket, so that any naphthaline which congeals in the 
 pipe and causes an obstruction may be melted out from time to time. 
 
 The agitator is set in slow action and effects a gentle but complete intermixture 
 
 of the ingredients. The apparatus 
 
 Fig- 397 is charged with 2 50 kilos, naphtha- 
 
 line, 200 kilos, nitric acid (72 Tw.), 
 and 200 kilos, sulphuric acid (sp. gr. 
 1-84), and for dilution 600 kilos, of 
 the spent acid from a former opera- 
 tion. After adding the acid the 
 agitator is put in action, and the 
 introduction of the finely ground 
 naphthaline is commenced. The 
 naphthaline is at once attacked 
 by the acid, the temperature rises, 
 but it is kept from 45 to 50 by 
 regulating the introduction of the 
 material and by letting water flow 
 in the cooling-jacket. At this tem- 
 perature the nitrising proceeds 
 quietly, and for the quantities given 
 it is completed in a day. The con- 
 tents are then run out at a cock into a cistern lined with lead. On cooling, the 
 naphthaline is deposited on the surface in the form of a cake, so that the subnatant 
 acid may be kept clear. The cake of nitro-naphthaline is freed from acid by boiling 
 with water in leaded troughs, and finally granulated by an influx of cold water 
 with continual stirring. 
 
 If nitro-naphthaline is melted or the water-bath is mixed with 10 per cent, of 
 cumol or solvent naphtha, we obtain an oil which remains fluid for a long time, and 
 can be filtered and dried perfectly by means of calcium chloride. The clear mixture 
 is left to itself, when it gradually congeals to a heap of very fine crystals. If the 
 crystalline cake thus obtained is placed under a hydraulic press the solvent which 
 had been added flows off along with a part of the nitro-naphthaline, and may be 
 separated by distillation in a current of steam, and recovered. The press cake consists 
 of fine yellow crystals of nitro-naphthaline, which readily crumble to a light crystalline 
 meal. 
 
 The reduction of nitro-naphthaline is effected with iron and hydrochloric acid, 
 exactly as in the preparation of aniline ; 600 kilos, of air-dried naphthaline, 800 kilos. 
 of iron borings, and 40 kilos, of hydrochloric acid are used. The iron and the acid 
 are mixed with the addition of some water and heated, and soon after the naphthaline 
 is added in portions through a feeding-socket, which can be. closed by a block of wood. 
 The agitator is kept in constant motion. The reaction is rather violent. The addition 
 of the nitro-compound must be so regulated that the entire apparatus is warm to the 
 touch, corresponding to an internal heat of 50. 
 
 When the addition of the nitro-naphthaline is completed the apparatus is kept in 
 action for six to eight hours, the right temperature being maintained by admitting steam 
 through the hollow shaft. 
 
 Towards the end of the process samples are drawn from time to time and tested for 
 their proportion of nitro-i aphthaline by distillation and dissolving the distillate in 
 hydrochloric acid. 
 
 As soon as the reaction is complete, milk of lime is added (50 kilos, are sufficient 
 for the quantities above given), and after thorough stirring the mass is removed 
 
SECT. IV.] 
 
 NAPHTHALINE COLOURS. 
 
 569 
 
 from the apparatus. Witt assumes that the ferrous chloride is the real reducing 
 agent, and that, during the reduction, it is converted into one of the basic chlorides, 
 perhaps Fe,C] 4 O. In this case the reduction would be expressed by the equation 
 
 2 4 FeCl 2 + 4C 10 H.NO, + 4 H 5 - i 2 Fe 2 01 4 + 4C 10 H 7 NH 2 . 
 
 The basic chloride formed is in turn attacked by the excess of iron, or reduced to 
 ferrous chloride, which exerts a new or reducing action upon nitre-naphthaline 
 i2Fe 3 Cl 4 + 9 Fe - sFe 3 4 + 2 4 FeCl 2 . 
 
 For the distillation of naphthaline there are used the so-called stage-retorts 
 (Figs. 398 and 399), into which the masses to be sublimed are inserted in flat sheet- 
 iron boxes. The retorts 
 
 are well heated, and in Fi %- 39& 
 
 order to convey away "i? 
 
 quickly the vapours of \v MfiVi mmium IB i mmaaan- ^ mm, J 
 
 naphthylamine steam is 
 blown in. from above, 
 and the steam-pipe can 
 easily be superheated by 
 the fire gases. The cast- 
 iron cooling-pipes con- 
 nected with the retorts 
 lie in troughs, in which 
 the condensing water is 
 kept at 60, so that the 
 pipes may not be blocked 
 up by solidifying naph- 
 thylamine. The naph- 
 thylamine mixed with 
 some water distils over 
 as a blackish oil, and 
 solidifies in the receivers 
 to a crystalline mass. For conversion 
 into the commercial product it may 
 require to be rectified. 
 
 ft-Waphthylamine, 
 
 |CH.C.NH 2 
 'ICH.CH "' 
 
 is obtained by heating 10 kilos. /3- 
 naphthol, 4 kilos, caustic soda, and 4 
 kilos, sal-ammoniac in an autoclave at 
 from 150 to 1 60 for 60 to 70 hours, 
 or /3-naphthol sodium with sal-ammo- 
 niac. It melts at 112 and boils at 
 294, whilst a-naphthylamine melts at 
 50 and boils at 300. 
 
 a-Amidoazonaphthaline, 
 N.C 10 H 6 .NH 2 , 
 
 is produced when a solution of 13 
 parts a-naphthylamine is mixed with 
 a solution of 3 parts potassium nitrate and 2 parts caustic potassa. Amidoazonaph- 
 thaline separates out. 
 
 a-Naphthylamine yields with concentrated sulphuric acid a mixture of two amido- 
 naplithaline-sulplw- acids, which are converted by nitrous acid into diazonaphthaline- 
 
 Explanation of Terms. 
 Abzug der Feuergase . . Outlet for combustible gases. 
 
 Fig. 399- 
 
 an. 
 
570 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 sulpho-acids, C 10 H 6 .N 2 .S0 3 . With fuming sulphuric acid a-naphthylamine yields 
 
 , 
 
 <i-na2}Jithylamine, a-sulpho-acid, or naphthionic acid C G H 4 lp ^rv fr PTT- 
 
 Naphthaline heated with concentrated sulphuric acid gives a mixture of a- and /3- 
 monosulpho-acid, C 10 H.S0 3 H. The lime salt of ^-naphthaline sulpho-acid is much less 
 soluble than that of a-naphthaline sulpho-acid ; hence the acids are generally separated 
 as lime salts. 
 
 O OTT 
 
 a-Naphthol, C 6 H 4 -^pW pir , is formed from a-naphthylamine and nitrous acid, but 
 
 is most commonly prepared by melting a-naphthaline sulpho-acid with caustic soda. 
 
 f '"FT o OTT ) 
 For the production of /3-naphthol, C 6 H 4 / pTr'pVr r, 2 parts of caustic soda are 
 
 melted with a little water and i part of /3-sodium naphthaline sulphate is added, the 
 temperature being slowly raised to 300, The melt is dissolved in water, decomposed 
 with hydrochloric acid, and the /3-naphthol, which separates out, is purified by dis- 
 tillation. 
 
 If treated with sulphuric acid both the naphthols yield various naphthol-sulpho- 
 acids. Of special importance is the /3-n.aphtholmonosulpho-acid (Bayer), Schaffer's 
 /3-naphtholmonosulpho-acid S, and the two /3-naphtboldisulpho-acids, E, and G. 
 
 Phthalic Acid, C G H 4 .(COOH) 2 , is obtained by heating i part naphthalinetetrachloride 
 with 5 to 6 parts of nitric acid. Phthalic anhydride, C 6 H 4 (CO),0, is obtained by sub- 
 limation. 
 
 Naphthaline Red (Magdcda Red, Soudan Red, A/rvhthaline Scarlet], the cliamido- 
 naphthylnaphthazionium chloride, C 30 H 21 N 4 C1, is obtained by heating a-amidoazonaphtha- 
 line with a-naphthylamine. 
 
 According to Witt, 23-1 kilos, of naphthylendiamine hydrochlorate, 28-6 kilos, of 
 a-naphthylamine, and 59^4 kilos, of amidoazonaphthaline are melted together and heated 
 at from 130 to 140, until the original violet, the colour of the mixture, has changed 
 to a pure red and no longer increases in intensity.* 
 
 Martius's Yellow (Novhthol Jelloio, Manchester Yellow) is ammonium-, sodium-, or 
 
 calcium-salt of dinitro-a-naphthoi, C 6 H 4 j^^'^ * 
 
 tc.isro 2 .CH. 
 
 It is prepared by treating a-napthylamine, a-naphtholsulpho-acid, or naphthionic acid 
 with nitric acid. 
 
 According to Wickelhaus and Darmstadter, dinitronaphthol is obtained by sulphuris- 
 ing naphthaline ; the /3-acid, which is formed along with the a-acid, is removed as a 
 calcium salt, and the former is converted into a-naphthol by melting with caustic 
 potassa, C 10 H 7 S0 2 OK + K.OH = C 10 H 7 .OH + K,S0 3 , and then nitrising the naphthol. 
 
 Martius's yellow dyes wool and silk in all tones, from the lightest yellow to a full 
 gold, without a mordant ; i kilo, of the dry calcium or sodium compound is sufficient 
 to dye 200 kilos, of wool a fine yellow. A chief property of the Martius's yellow is that 
 it bears steaming, whilst picric acid is volatilised along with the watery vapours. It is 
 often used for modifying red and gold-yellow tar colours. 
 
 Naphthol Yellow S, Acid Yellow /S, the sodium salt of dinitro-a-naphtholsulpho acid 
 is obtained by treating a-naphtholtrisulpho-acid with nitric acid. 
 
 Brilliant Yellow is the sodium salt of dinitro-a-naphtholmonosulpho-acid, which is 
 formed by treating a-naphtholdisulpho-acid with nitric acid. 
 
 Sun Gold, the sodium salt of tetranitro-a-naphthol, C 10 H 3 (N0 2 ) 4 ON"a, no longer 
 occurs in trade. 
 
 * It is more permanent than magenta, saffranine, and the eosines, and is characterised by its 
 strong fluorescence. 
 
SECT, iv.] ANTHRACENE COLOURS. 571 
 
 Naphthol Green B is the ferrous-soda compound of nitroso-/3-naphtholmono-sulpho- 
 
 fS0 3 Na 2 3 S] 
 acid, C 10 H 5 JO 1 C 10 H 5 , is obtained by treating the /3-naphtholmonosulpho-acid S. 
 
 (NO re ON] 
 
 with nitrous acid. 
 
 Phenanthrene Red, the sodium salt of a-naphthyl-a-sulpho-acid osazonphenanthren- 
 quinone, C fi H 4 .CN.CH.C 10 H 6 .S0 3 Na, is obtained from naphthylhydrazinsulpho-acid and 
 phenanthrenquinone. The azo-colours, capable of being obtained from naphthaline and 
 naphthol, are especially numerous. 
 
 4. Anthracene Colours.* The most important of the anthracene compounds are 
 the alizarines. 
 
 Alizarine, a-/3-dioxyanthraquinone, C U H 8 4 or C G H 4 (CO) 2 C 6 H 2 (OH) 2 . The anthra- 
 quinone obtained according to the original process of Graebe and Liebermann was con- 
 verted by bromising into bibromanthraquinone, C 14 H 6 Br0 2 , and the latter again was 
 transformed into alizarine potassium (or sodium) by heating with caustic alkali to 180 to 
 200. From the alizarine potassium the alizarine was separated by hydrochloric acid. 
 
 C ]4 H 6 Br 2 2 + 4 KOH = C 14 H 6 K 2 4 + 2BrK + 2 H 2 
 
 Bibrorn-Anthraquinone. Alizarine potassium. 
 
 C 14 H G K 2 4 + 2 HC1 = C 14 H 8 4 + 2KC1 
 Alizarine potassium. Alizarine. 
 
 According to the process now generally in use, alizarine is obtained from anthra- 
 quinone by treating one part with 4 to 5 parts sulphuric acid of sp. gr. 1-84 at a tem- 
 perature of from 270 to 290. It is first converted into aiithraquinonedisulpho acid, 
 C 14 H G 2 (HS0 3 ) 2 ; this acid is neutralised with calcium carbonate, the liquid is filtered 
 off from the gypsum, and sodium carbonate is added until all the lime is precipitated. 
 The clear liquid is evaporated to dryness, and the saline mass obtained is converted 
 into alizarine sodium by heating with caustic soda at from 250 to 270 ; from the melt 
 thus obtained the alizarine is precipitated with acid. 
 
 In converting sublimed anthracene into anthraquinone : 
 
 _ C 14 H 10 + K 2 Cr 2 7 + 4 H 2 S0 4 = C U H 8 O 2 + K 2 Cr 2 (S0 4 ) 4 + 5H 2 0: 
 the required quantity of potassium clichromate is first ascertained by a preliminary ex- 
 periment. The proper quantity of potassium dichromate is placed in a wooden tank 
 lined with lead (fitted with an agitator and holding 3 cubic metres) along with 1500 
 litres of water which are heated to a boil by admitting steam, the steam is shut off, 100 
 kilos, powdered anthracene are gradually added, and whilst stirring gently for nine 
 hours the requisite quantity of dilute sulphuric acid (sp. gr. i'24) is run in. 
 When the reaction is at an end the solution of chrome alum is drawn off in order 
 to convert the chromic oxide (which has been precipitated by lime) into chromate again. 
 The anthraquinone is washed, dried, dissolved in sulphuric acid at 100, and when cold 
 precipitated by the addition of water. 
 
 In preparing the anthraquinone sulpho-acids ordinary sulphuric acid was used at 
 first. But in order to convert the anthraquinone into a sulpho-acid it was necessary to 
 heat to a very high temperature, which involved much loss. At present it is found pre- 
 ferable to use sulphuric acid containing a proportion of sulphuric anhydride. The 
 anthraquinone is mixed with the calculated quantity of sulphuric acid and heated to a 
 higher or lower temperature according as the intention is to produce the mono- or the 
 disulpho-acid. In preparing the disulpho-acid, all the anthraquinone is dissolved, 
 heating until a sample if poured into water dissolves completely, whilst in preparing 
 the mono-acid a portion of the anthraquinone remained undissolved. As far back as 
 1871 it was known that only the sodium anthraquinone monosulpho-salt yielded 
 
 * Compare AuerbacKs Anthracen, edited by W. Crookes, F.R.S. London : Longmans. 
 
572 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 pure alizarine, and the endeavour then was to obtain as pure a raonosulphate as possible 
 for obtaining the " blue cast." In the sulphurising process it was not practicable to 
 obtain the monosulpho-acid directly, and the makers were therefore obliged to separate 
 it out from a mixture of the different sulpho-acids. The sulpho-acid obtained at a high 
 temperature was neutralised with lime, and the calcium salt formed was converted into 
 sodium salt by means of sodium carbonate. On evaporating down the solutions of these 
 sodium compounds, white crusts were soon separated out, which, on fusion with alkali, 
 gave a very blue alizarine and proved to be the anthraquinone monosulpho-salt of 
 sodium. This fractional crystallisation required much time, and it was therefore an im- 
 provement when it was found that from a mixture of the mono- and the disulpho-acid 
 the former could be precipitated first by alkali. It became necessary merely to par- 
 tially neutralise the acids with caustic soda in order to obtain a precipitate of the mono- 
 sulpho-salt. This salt was filtered and the filtrate was worked up for alizarine of a 
 " yellow tone." 
 
 In melting the anthraquinone sulpho-salts with caustic soda the alkali takes the 
 place of the sulphuric residue in anthraquinone, and there is formed sodium alizarate. 
 Alizarine is formed only out of anthraquinone sulpho-acid. If the alkali were to act 
 upon this acid in such manner that merely the sulphuric residue would be substituted 
 by NaOH, a compound would be formed containing one atom oxygen less than does 
 alizarine: C 14 H 7 .S0 3 Na0 2 + NaOH = C 14 H 7 Na0.0 2 + NaHS0 3 . 
 
 This compound is monoxyanthraquinone. If alkali acts upon this compound again 
 it has an oxidising action ; one atom hydrogen is replaced by hydroxyl, hydrogen escapes, 
 and alizarine is formed : C 14 H 7 (O.Na)0 2 + NaOH = C 14 H 6 (NaO) 2 O 2 + H 2 . 
 
 In the action of alkali upon disulpho-acids, at first the true sulphuric acid residues 
 are replaced by hydroxyls and there are formed compounds isomeric but not 
 identical with alizarine. On further action of the melting alkali one more atom 
 hydrogen is replaced by hydroxyl, and there are formed colouring matters containing 
 more oxygen than the alizarine i.e., the purpurines. 
 
 Under certain circumstances, however, alizarine is also formed from the disulpho- 
 acid, but only in small quantity. To prevent the reducing action of the hydrogen, 
 substance is added which gives off oxygen and oxidises the nascent hydrogen to 
 water. The most suitable substance is potassium chlorate. 
 
 The melting process has undergone important changes and has reached a 
 degree of perfection which leaves little room for improvements. The yield of colouring 
 matter has risen from 30 or 40 to 95 to 98 per cent, of the amount theoretically possible. 
 
 The form of the autoclaves can be varied at pleasure, but the plates must be strong 
 enough to bear a pressure of 15 to 20 atmospheres, and the arms of the agitator must 
 pass very close over the edge of the vessel so as to prevent the melt from being 
 deposited. The safety-valve is connected with a covered vessel, so that if it is 
 opened the melt is not scattered about. Whether heat is applied in an oil-bath or an 
 air-bath is indifferent, but the latter has the advantage that the temperature can 
 be better regulated and that there is no risk of fire. In the air-bath the tempera- 
 ture can be kept perfectly constant for days, and the entire melt may be finished in 
 thirty-six to forty-eight hours. The autoclave is charged with concentrated soda-lye, 
 the sodium sulphate and the potassium chlorate are added, the autoclave is closed, the 
 agitator set in motion, and the contents heated to 180 to 210. In a relatively 
 short time the operation is at an end ; the melt is forced through a pipe into a vessel of 
 water by means of the pressure in the autoclave. By boiling the violet solution of the 
 melt in water and decomposing the alkaline solution with an acid, the colouring matters 
 are obtained in the state of yellow or orange flocks, which are passed through filter- 
 presses, freed by means of water from sodium chloride or sulphate, and finally made 
 up into pastes of any required strength by adding the calculated quantity of water. 
 
SECT, iv.] ANTHRACENE COLOURS. 573 
 
 Alizarine VI., or alizarine I., or the a-/3-dioxyanthraquinone, forms an ochre yellow 
 paste. Alizarine GI .; Alizarine FA. ; Flavopurpurine, oxyanthraflavic acid, 
 
 C 14 H 8 5 or 
 
 which is prepared by melting a-anthraquinone disulpho acid soda with caustic soda 
 and potassium chlorate, as well as Alizarine G.D., or Alizarine R.F. isopurpurine 
 anthrapurpurine, oxyiscanthraflavic acid, 
 
 C 14 H 8 5 or 
 
 are obtained in the same manner from /9-anthraqunionesulpho acid sodium form 
 brownish-yellow pastes and dye red shades on cotton mordanted with alumina. 
 
 Purpurine, trioxyanthraquinone, obtained by the oxidation of alizarine, is C U H 8 0. or 
 C 6 H 4 (CO) 2 C 6 H(OH) 3 . 
 
 A lizarine Orange, Alizarine N, /3-monontroalizarine : 
 
 iCO) (OH 
 C 14 H : NO fi or C 6 H C 6 H OH 
 
 'CO) [NO, 
 
 was first used by Strobel, who formed it by the action of nitrous vapours upon cotton 
 pieces previously printed with alizarine. Subsequently the Baden Aniline Company have 
 supplied this colour, made according to Caro's patent. It is obtained by exposing 
 alizarine spread out in thin layers to the action of nitrous vapours in closed 
 chambers, or by passing nitrous acid into a solution of alizarine in nitro benzol. It 
 crystallises in orange-red leaflets with a green reflection, and melts at 230. 
 
 Alizarine Carmine (Alizarine WS), the sodium salt of alizarine monosulpho acid, 
 C 14 H 7 4 .SO 3 Na, is obtained by treating alizarine with concentrated sulphuric acid. 
 
 The aluminium salt dyes woollens without a mordant, as do also some other salts. 
 It is better, however, to mordant the wool and dye up with the sodium salt along with 
 tartar. In this manner different tones of colour can be obtained from the same dye- 
 ware by using various mordants. The scarlets, of course, cannot rival those obtained 
 with cochineal, eosine, &c., in brightness, and are also not cheaper, in spite of the low 
 price of artificial alizarine, but they surpass all others in their resistance to light and 
 air. Flannels dyed with alizarine carmine come up bright after every washing, and 
 are not discoloured by the action of perspiration, as are goods dyed with cochineal. 
 They may also be exposed without injury to their beauty to the sun and the weather, 
 an advantage not shared by the other tar-colours. When resistance to light is essen- 
 tial, as for carpets, curtains, army cloths, &c., this colour deserves especial attention. 
 
 Alizarine blue, C 17 H 8 N0 4 or 
 
 rOH 
 
 OH 
 
 N.CH 
 
 CH.CH 
 
 is formed on heating with glycerine and sulphuric acid 
 
 C 14 H 7 4 (N0 2 ) + C 3 H 8 3 - C 17 H 9 N0 4 + 3 H 2 + O r 
 
 Alizarine blue is met with in the form of a thin brownish- violet paste, containing 
 i o per cent, of colour. The colour is almost insoluble in water ; in benzol and alcohol 
 it dissolves with difficulty with a red colour. From its benzol solution alizarine blue is 
 obtained in violet-blue needles of a metallic lustre, fusible at 270. It forms a red 
 solution with concentrated sulphuric acid. If this solution is heated for some time 
 and then diluted with water, a blueish sediment is deposited having the same properties 
 as a dye-ware as the original alizarine blue. The colour is soluble in a solution of 
 sodium bisulphite. The alizarine blue S thus obtained contains to one mol. blue, two 
 mols. sodium bisulphite C n H 9 N0 4 . 2NaHS0 3 . 
 
574 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 In dilute alkalis the dye- ware dissolves with a blue or a greenish-blue 
 colour. After some time, especially in presence of an excess of alkali, it is re-depo- 
 sited as an insoluble salt. "With calcium, strontium, and barium salts, and with those 
 of iron, it forms greenish-blue lakes ; with alumina violet blues ; with chromic oxide 
 violets, and with tin red violets. Alizarine blue may be reduced, like indigo, in an 
 alkaline solution. With zinc-powder, hyposulphurous acid, or grape-sugar, there is- 
 formed in presence of alkali a yellowish-brown solution, from which the colouring matter 
 on exposure to the air is precipitated with a fine blue colour. Unmordanted tissues, if 
 steeped in an alizarine blue vat and then exposed to the air, are dyed a good blue. The 
 vat itself is red, with a blue scum. After airing, the dyed goods are taken through a 
 cold chloride of lime bath or through a solution of potassium, chromate mixed with 
 lime. Alizarine blue has not come into general use since the indulines can also be used 
 in the form of a vat. 
 
 5. Azo dyes contain the group N = N . If they contain this group twice they 
 are named tetrazo dyes. They are mostly yellow to orange, more rarely red. Among 
 the great number of these dye-stuffs the following may be mentioned : 
 
 Aniline Yellow (Spirit yellow), amidoazobenzol C 12 H 12 N 3 C1 or C 6 H 4 {^'?-?? }i s 
 
 '-.N.N.CgH.j ) 
 
 formed by heating diamidoazobenzol with aniline hydrochlorate. Steel blue crystals 
 which dissolve in water with a yellow colour and on treatment with fuming sulphuric- 
 acid, yield sodium amidoazobenzclclisulphate, C 12 H 9 N 3 (S0 3 Na) 3 . 
 
 Acid Yellow or Fast Yellow. Fast yellow R, Acid yellow R, Yellow W, the sodium 
 salt of amidoazotoluoldisulpho acid, C 14 H 13 ISr 3 (S0 3 lS'a) 2 , is obtained by treating amido- 
 azotoluol hydrochlorate with fuming sulphuric acid. 
 
 Bismarck Brown (Phenylen Brown, Gold Brown, Aniline Brown, Leather Brown 
 
 Cinnamon Brown, C 12 H 15 N.C1 2 or Ce^ljq-.N.C H tNH 2 ' 2HCI )' is obtained when 
 dinitrobenzol is amidised with tin and hydrochloric acid and then treated with solution 
 of sodium nitrite. The diazo compound of aniline, if conjugated with naphthol or 
 naphtholsulphuric acid : 
 
 Soudan I, C 6 H 5 .N.KC 10 H 6 [/3]OH 
 
 Tropaolin oooo, C 6 H 5 .KN.C 10 H 5 
 Cochineal scarlet G, C 6 H 5 .N.N.C 10 H 5 { g 
 Crocein orange : Ponceau G B, 
 Orange G, C 6 H 5 .N.N.C 10 I 
 
 Ponceau 2 G, C 6 H 5 .N.N.( 
 
 Diamidoazobenzol with 2 mols. sodium nitrite can be converted into a tetrazo compound,, 
 which may unite with 2 mols. naphthylaminesulpho acid, a-naphtholsulpho acid, or 
 /3-naphtholdisulpho acid R, to form azo dyes, which are valuable, as they dye unmor- 
 danted cotton directly in a soap-beck. 
 
 ^ For instance, 2-12 kilos, pure diamidoazobenzol are dissolved in 5 kilos, hydrochloric 
 acid of 30 Tw. and 100 litres water, and converted into the tetrazo compound by the 
 addition of a solution of 1-38 kilo, sodium nitrite in 20 litres water. The latter is then 
 run into a solution of 6| kilos, sodium a-naphthylamine sulphate and ij kilo, soda 
 in 200 litres of water, stirring constantly. After standing for twelve hours, the pro- 
 duct of the reaction is dissolved by boiling in water ; the colour is salted out, pressed,, 
 and dried. It dyes cotton in an alkaline soap-beck a reddish- violet. If in the above 
 
SECT, iv.] AZO DYES. 575 
 
 mentioned instance the sodium a-naphthylarnine sulphate is substituted by 5 kilos, 
 sodium a-naphtholmono sulphate there is formed a sparingly soluble dye-stuff, which 
 works on unmordantecl cotton with a violet colour. 
 
 Azo dyes form the diazo compounds of cliamidodiphenyl ketones, CO(C 6 H 4 .lSrH 2 ) 2 . 
 According to Wichelhaus, the amicloketon is obtained from, the salts of rosaniline and' 
 pararosaniline, commonly known as magenta, by simply boiling with hydrochloric acid. 
 If this process is continued for some days in a cohobator, replacing the acid which has 
 evaporated, there are obtained from 100 parts of magenta 30 parts amicloketon, with, 
 corresponding quantities of aniline or toluidine. The rest of the magenta is un- 
 changed, and may be again applied in a similar manner. 
 
 In order to separate the amidoketone from the mixture the solution is rendered' 
 alkaline, the aniline or toluidine is driven out by a current of steam, and the residual 
 bases are dissolved in dilute sulphuric acid, taking care that the solution is perfectly 
 neutral. On evaporation the formation of a crystalline scum shows the condition in> 
 which the sulphate of the amidoketone crystallises out, the rosaniline or pararosaniline 
 sulphate remaining in solution. 
 
 For the production of dye-stuffs, we may either use the amidoketon itself, forming 
 the tetrazo compound by the action of sodium nitrite upon the chloride of this base 
 (with refrigeration), and bringing this then in contact with phenole bases or their 
 sulpho acids. The combination leads if we, e.g., use resorcine and afterwards salt- 
 out with sodium chloride to a dye-stuff of the formula 
 
 CO(C B H 4 N 2 ) 2 .(C 6 H 3 .(ONa) 2 ) 3 . 
 
 It dyes an intense yellow on unmordanted cotton in a neutral watery solution. 
 
 By combining the tetrazo compound of the amidoketon with the sodium salt of naph- 
 thionic acid, a dye-ware is produced of the formula CO.(C 6 H 4 N 2 ) 2 (C 10 H 5 (NH 2 )S0 3 N"a) 2> 
 which dyes unmordanted cotton red in a watery solution. Phenol and its homologues, 
 dimethylaniline, other phenols, and aromatic bases, as well as the sulpho acids of these 
 compounds, unite to form dye-wares with the above-mentioned tetrazo compound. 
 
 Benzopurpurine 4 B -j /ar 3 v K s f rme( l from orthotolidine 
 
 ICH, 
 
 and 2 mols. naphthionic acid. According to the Berlin Joint-Stock Aniline Com- 
 pany, the tetrazo compounds of tolidine formed by the alkaline reduction of ortho- 
 or paranitrotolual, or a mixture of both (i.e., the technical nitrotoluol), form, with 
 a- and /S^naphthylamine and their mono- and disulpho acids, fine dye-stuffs, partly- 
 soluble in spirit and partly in water, which dye unmordanted cottons in a soap-beck a. 
 series of tones, from a deep yellowish-red to a bluish-red, and are distinguished from 
 the corresponding benzidine colours by their superior fastness against light and acids. 
 
 Whilst the red dye-ware known by the name Congo, obtained from tetrazodiphenyl 
 with a-naphthionic acid, is turned brown or black by the slightest trace of acetic acid,, 
 the corresponding product from ditetrazoditolyl is not nearly so sensitive to dilute acids 
 and is much faster towards light. 
 
 A still greater difference between the benzidine and the tolidine dye-wares appears 
 in conjunction with /3-naphthylaminesulpho acids, whether they are obtained by directly 
 sulphurising /3-naphthylamine or by heating Schaffer's /3-naphtholsulpho acid with 
 ammonia. In both cases tetrazodiphenyl forms with them colouring matters, which 
 are insoluble even in boiling water, and in this state cannot be fixed upon cotton, being 
 therefore technically worthless. On the other hand, tetrazoditolyl forms in conjunc- 
 tion with these sulpho acids dyes soluble in water, which are very valuable from their 
 
576 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 fastness against strong acetic acid, and even against dilute mineral acids, as well as by 
 their brilliance. 
 
 For the production of these dye-stuffs, aqueous solutions of the tetraditolyl salts 
 are run into the mono- and disulpho-acicls of a- and /3-naphthylamine, finely divided 
 in water, and the free mineral acids present are neutralised by salts of the organic 
 acids, e.g., sodium acetate. The spirit-dyes thus formed are converted into water- 
 dyes by treatment with fuming sulphuric acid, and have now a great resemblance to 
 the dyes at once obtained in a form soluble in water. For instance, 150 kilos, 
 of toluidine sulphate (diamidoditolyl) obtained from technical nitrotoluol are finely 
 divided in water, mixed with 50 kilos, of hydrochloric acid at 32 Tw. and 22*2 
 kilos, sodium nitrite, dissolved in 10 litres of water, are slowly run into the 
 solution, which is cooled with ice. In this manner is formed tetrazoditolyl chloride. 
 This solution is then added to an aqueous solution of 58 kilos, of a- and j3-naphthyla- 
 mine hydrochlorate ; the free mineral acid is neutralised with sodium acetate, and the 
 mixture is allowed to stand for 24 hours. The dark brown or bright red precipitate 
 is filtered off and dried, previous to its conversion into its sulpho acids. Further, 50 kilos, 
 of the dry dye- ware, soluble in spirit, are gradually added, at 15, to 150 kilos, or 
 fuming sulphuric acid containing 20 per cent, anhydride, with constant stirring, and 
 the deep blue melt obtained is allowed to stand at common temperatures until the 
 sulphurising is complete. It is then poured into water, and the sulpho acid formed 
 is converted into its soda-salt. 
 
 According to another procedure, the tetrazoditolyl chloride is added to 73 kilos. 01 
 naphthionic acid, i.e., sparingly soluble a-naphthylaminesulpho acid ; the free mineral 
 acid is saturated by the addition of sodium acetate, and the mixture is allowed to stand 
 for several days with frequent stirring. There is formed a reddish-brown slimy precipi- 
 tate, which is converted into its soda-salt by heating and neutralising with soda. On 
 cooling, the dye-stuff is deposited, almost quantitatively, as an orange-red powder, which 
 dyes unmordanted cottons a deep bluish-red. 
 
 A scarlet dye-ware, fast against acids and more beautiful than the colours above- 
 named, is obtained from /3-naphthylaminesulpho acid, formed by heating Schaffer's 
 /3-naphtholsulpho acid with ammonia. After an excess of soda has been added to the 
 aqueous solution of 80 kilos, of sodium /3-naphthylaminesulphate, tetrazoditolylchloride 
 is run into it slowly, stirring the mixture and keeping it cool with ice. There is 
 formed a brownish-red precipitate, which redissolves completely after standing for 
 twelve hours. If brine is added to this solution, a red slimy precipitate is obtained, 
 which becomes crystalline on heating, and is the sodium salt of the above-named dye- 
 ware. 
 
 Sodium paranitrotolulsulphate in a watery solution, if heated with soda-lye, be- 
 comes, according to Leonhardt, a condensation product, soluble in water. It can be 
 used as a yellow on woollens, and by reduction it is converted into an amidosulpho 
 acid ; 50 kilos, of sodium paranitrotoluolsulpho salt are dissolved in 700 litres of 
 water and digested with 30 kilos, of soda-lye at 72 Tw. The colour of the liquid 
 passes to an intense yellowish, red. The condensation product formed can be precipi- 
 tated by the addition of brine. 
 
 Either the boiling liquid is mixed with zinc powder until it is colourless, filtered whilst 
 hot, and the new acid is precipitated with hydrochloric acid, or it is strongly acidified and 
 reduced with tin or stannous chloride until a specimen of the liquid, after being ren- 
 dered alkaline, shows but a faint colour. In either case the acid liberated is purified 
 by dissolving in soda and precipitation with acid, and forms then a yellowish-white 
 powder, quite insoluble in water. The barium salt may be obtained in shining nacreous 
 leaflets by precipitating the concentrated aqueous solution with common salt. 
 
 The new amidosulpho acid is characterised by the fact that its sparingly soluble 
 
SECT, iv.] AZO COLOURING MATTERS. 57 7 
 
 diazo-derivative, in combination with aromatic amines and phenoles or their sulpha 
 salts, forms with the carbon acids yellow, red, brown, and blue dye-stuffs, which give 
 fast colours on vegetable fibres without a mordant. Red and brown-red colours are 
 thus obtained with resorcine, resorcylic acid, orcine, methylaniline, dimethylaniline, 
 diphenylamine, phenylendiamine, /3-naphthylamine, and its sulpho acids, a-naphthyl- 
 aminesulpho acid. 
 
 20 kilos, of the sodium salt of the new acid are dissolved in soda and diazotised with 
 7 kilos, nitrite and 25 kilos, hydrochloric acid. The liquid thus obtained is added 
 to a solution of 15 kilos. /3-naphthylamine in 12 kilos, hydrochloric acid and 500 litres 
 water. The free colouring acid separates out ; it is filtered, washed, and converted 
 into its sodium salt. 
 
 Or we diazotise 20 kilos, of the sodium salt of the amidosulpho acid into the above 
 manner, and pour the solution of the diazo compound to a solution of 28 kilos, of the 
 sodium salt of the /3-naphthylaniinesulpho acid (obtained from /3-naphthol-/3-sulpho 
 acid), to which the necessary quantity of sodium acetate has been added to saturate the 
 free mineral acid. The free colouring acid is salted out, washed, and converted into its 
 sodium salt. 
 
 Or we diazotise 20 kilos, of the acid as above, and pour the solution into a solution 
 of 19 kilos, diphenylamine in 30 litres of spirit. After standing for a time, the free 
 colouring acid separates out in an insoluble state. It is filtered, washed, and converted 
 into its soluble sodium salt. 
 
 The following dyes are obtained with i mol. diamidostilbenedisulpho acid : With 
 2 mols. phenol, brilliant yellow ; with 2 mols. /3-naphthylamine, Hessian purple N ; with 
 2 mols. naphthionic acid, Hessian purple P ; with 2 mols. /3-naphthylaminemonosulpho 
 acid, Hessian purple D; with 2 mols. salicylic acid, Hessian yellow; with i mol. 
 a-naphthylamine and i mol. /3-naphthol, Hessian violet. By ethylating brilliant yellow 
 there is formed Chrysophanine : 
 
 Brilliant yellow. Hessian purple N. 
 
 fCHC e H 
 
 6 3 (KN.C 6 H 4 .OC 2 H 5 
 N.N.C 6 H 4 .00 S H 5 
 
 KN.CJI 
 
 (OH 
 
 MCOONa 
 rCOONa 
 
 N N H 
 
 3 1 OH 
 
 3 
 
 Chrysophenine. Hessian yellow. 
 
 For the production of Croceine scarlet 50 kilos, of amidoazobenzolmonosulpho acid 
 are diazotised with hydrochloric acid and sodium nitrite. The diazobenzolsulphuric 
 acid is introduced into a solution of 75 kilos. /3-naphthol-a-sulpho acid in 500 litres 
 water and 140 kilos, of 10 per cent, ammonia : 
 
 ,SO P NH 4 fONa 
 
 H 
 
 If instead of the sulpho acid free amidoazobenzol is used, the colouring matter has a 
 yellower tone. The homologues of amidoazobenzol yield bluish red dyes, diazobenzol 
 and its homologues reddish yellow ones, a-diazonaphthaline a blue-red dye and /3- 
 diazonaphthaline a brick-red colouring matter. 
 
 Biebrich scarlet is formed by the action of diazoazobenzol upon /3-naphthol ; the 
 commercial product consists of the sodium salts of the mono- and di-sulpho acid. 
 
 2 o 
 
578 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 From a-naphthylamine and naphthol or the naphtholsulpho acids there are ob- 
 tained : 
 
 Soudan brown, C 10 H 7 [a]N.N.C l0 H 6 [a]OH 
 
 Buffalo rubine, 
 
 New coccine E, C l0 H 7 [a]N.y.C l0 H 4 g . 
 
 
 scarlet S.. 
 1 
 
 Fast red B, Bordeaux B, C 10 H 7 [a]KN.C 10 H 4 
 
 Carmine naphtha, 10 H 7 [/3]N.N.C 10 H 6 [/3]OH 
 
 _ /S0 3 Na 
 Orange I., tropseolme ooo Nt. i, C 6 H 4 j-^- jq- @ JT r -JQTT is obtained from sulphanilic 
 
 and acid a-naphthol, the similarly composed Orange II., tropceoline ooo No. 2, chrys- 
 aurine, gold orange from sulphanilic acid, and /3-naphthol. Orange III., methyl orange, 
 
 tropceoline D, helianthine, C 6 H 4 |_... A. ~ . . , is obtained from sulphanilic acid 
 
 and dimethylaniline. 
 
 Double brilliant scarlet G is obtained from the diazo compound of yS-naphthyl- 
 amine-monosulpho acid and ^-naphthol; it dyes wool a yellowish red in an acid 
 flot, If instead of /3-naphthol there is used a-naphtholmonosulpho acid we obtain double 
 
 ..G..H. R \r a -,^-r -^ n TT ffalOH i i j t -i i. ' -j i_ i 
 
 1 10 6 1 [P\N .N.C 10 H 6 \ [ -L n , which dyes wool a scarlet in an acid beck. 
 
 i I ct lOvJoJN l 
 
 1_ J o -* 
 
 Woollen black, C 6 H. j AT * f S0 3 Na CH ) . 
 
 1 i]N.N.C 6 H 3 J >r xr rj TJ XTJT | C 6 H 4 , a blue-black azo-dye is ob- 
 
 tained by combining paratolyl-/3-naphthylamine with the diazo compound of azobenozol- 
 disulpho acid. The paratolyl-j8-naphthylamine is dissolved in 20 parts of alcohol and 
 mixed with an equivalent quantity of hydrochloric acid at 31 Tw. An equivalent 
 amount of diazoazobenzoldisulpho acid is introduced, when the free acid of the dye- 
 stuff is formed. The latter is salted out with sodium chloride, filtered, and washed 
 until the washings run off colourless. The residue is then taken up in soda-lye, the 
 solution is filtered, and the colouring matter is salted out, when it separates in fine 
 crystalline leaflets. It is filtered, pressed, and dried. In an acid beck it dyes woollens 
 a blue-black. 
 
 Congo, I C 6 H 4 .N.N.C 10 H 5 jgQ-5,- L is one of the numerous benzidineazo dyes. It 
 
 is prepared from benzidine and naphthionic acid, and is by no means permanent. 
 
 (NH a 
 ( C 6 H 4 .N.KC 6 H 3 { so ^ a 
 
 Congo G It, j r -,~~ ,, is a red colouring matter obtained from 
 
 lC 6 H 4 .N.N,3C 10 H 6 H 
 
 benzidine, amidobenzolsulpho acid, and naphthionsulphuric acid. 
 
 For the preparation of mixed azo-dyes, which take upon unmordanted vegetable 
 fibre at once in a soap beck, the German patent 40,954 gives thirty prescriptions, of 
 which the following are specimens : 
 
 i. In order to convert benzidine into the chloride of the tetrazo compound 18-4 
 kilos, of benzidine are dissolved in 600 litres water which contain 55 kilos, hydrochloric 
 acid at 32 and diazotised with 14 kilos, of sodium nitrite. The solution of the tetrazo 
 compound, made up to 1000 litres, is run, with thorough agitation, into a solution 
 of 20 kilos, of sodium meta-amidobenzol sulphate and 40 kilos, sodium acetate made up 
 
SECT, iv.] ORGANIC COLOURING MATTERS. 579 
 
 to 500 litres. After acting for one hour the formation of the intermediate pro- 
 duct (an orange-yellow insoluble precipitate) is completed. It is then introduced 
 into a solution of 35 kilos, sodium a-naphthylamine sulphate and 20 kilos, soda in 
 500 litres water. After thorough stirring it is let stand for some time, boiled up, 
 filtered, and salted out, yielding a product which dyes cotton a yellowish red in a soap 
 beck. 
 
 2. If the intermediate product obtained as according to i (from tetrazodiphenyl 
 and meta-amidobenzolsulphuric acid) is mixed, instead of with the quantity of naphthi- 
 onic salt above given, with a solution of 26 kilos, of sodium a-naphthol monosulphate, a 
 colouring matter is obtained which dyes cotton a reddish violet. 
 
 3. If, instead of the naphthionic salt in i, there are used 37 kilos, sodium ^-naphthol 
 disulphate (R salt), there is obtained a product which dyes cotton a violet-red in an 
 alkaline soap beck. 
 
 4. The combination of tetrazodiphenyl with para-amidobenzolsulphuric acid is 
 effected similarly to that with the isomeric meta-amidobenzolsulpho acid. In the 
 preparation of the intermediate product from the /3-acid there is used the same quantity 
 of benzidine, hydrochloric acid, and sodium nitrite for producing tetrazophenyl, and the 
 latter is made to act upon a solution of 30 kilos, sodium para-amidobenzol sulphate 
 (sulphanilate). The intermediate product is redder than that from the isomeric meta- 
 amidobenzolsulpho acid. For obtaining the dye the intermediate product is made to 
 act upon a solution of 35 kilos, sodium /3-naphthylamine sulphate in 20 kilos, soda and 
 500 litres water. The product dyes a brownish orange. 
 
 5. If the intermediate product obtained with the proportionate quantities given in 
 4 is allowed to react on a solution of 14 kilos, phenol in 14 grammes soda-lye at 
 72 Tw. and 20 kilos, of sodium carbonate, there is formed a yellow dye. 
 
 6. A yellow dye is also obtained if the phenol given in 5 is replaced by 1 5 kilos, 
 salicylic acid. 
 
 Other Organic Colouring Matters. Gallic acid is used for obtaining various 
 colouring matters, such as gallocyanine, galleine, ceruleine, and galloflavine. 
 fO.B,.OH.O 
 
 TT OH O> * s ^ orme( ^ by the action of phthalic anhydride 
 
 lcX- c -0 
 
 upon pyrogallol in the same manner as phthalic anhydride combines with resorcine 
 to form fluoresceine. 
 
 For its preparation Baeyer heats one part phthalic anhydride with two parts of 
 pyrogallol to 190 to 200 for some hours, until the melt becomes thick. The cold 
 melt is dissolved in alcohol, precipitated with water, and the separated galleine is purified 
 Toy repeated solution and precipitation. In practice he does not set out with pyro- 
 gallol, but heats a mixture of gallic acid and phthalic anhydride to 190 to 200. At 
 this temperature gallic acid is resolved into pyrogallol and carbonic acid ; the latter 
 escapes and the former combines with phthalic anhydride to form galleine. The 
 -colouring matter is also known as alizarine violet or anthracene violet. 
 
 Ceruleine, C 20 H g 6 , is obtained by dissolving galleine in concentrated sulphuric 
 acid and heating to 190 to 200. Galleine loses i molecule water and yields the dye in 
 question, which is also known as alizarine green and anthracene green. 
 
 Ceruleine is closely connected with phenylanthracene, and passes into this hydro- 
 carbon if distilled over zinc powder. Ceruleine forms when dry a bluish-black 
 shining mass. It dissolves with difficulty in the ordinary solvents with a dirty 
 green colour, but with a fine green colour in the alkalies. With the alkaline 
 bisulphites ceruleine forms double compounds soluble in water. 
 
580 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 Of these two colours ceruleine is by far the more important. The brownish-red 
 shades of galleine can be obtained quite as easily, though finer and faster, with alizarine, 
 but the rich olive tones of ceruleine have become quite indispensable to the tissue- 
 printer from their fastness against light and soap, as well as by the ease and 
 certainty of their application. Both galleine and ceruleine, like gallocyanine, are most 
 readily fixed by means of the salts of chrome. The soluble bisulphite compound of 
 ceruleine is less frequently used than the paste, to which bisulphite is added, thus 
 producing the soluble double compound in the printing colour itself. 
 
 Gattqflavim, C 13 H 6 9 , is formed by the oxidation of gallic acid in an alkaline solution 
 by means of atmospheric air. 
 
 The Baden Aniline Company dissolve 5 parts gallic acid in 80 parts alcohol at 
 96 Tralles and 100 parts of water. The solution after cooling down to 5 to 10 is 
 slowly mixed with 17 parts of potassa-lye at 49 Tw., stirring thoroughly, and is 
 exposed to the action of the atmosphere at a temperature not exceeding 10. For 
 this purpose either a strong current of air is passed through the alkaline solution, 
 or it is exposed to the air in thin layers, a constant renewal of the surface being effected 
 by means of suitable apparatus. The progress of the oxidation is recognised by the 
 increasing olive or greenish-brown colour and by the deposition of a crystalline precipi- 
 tate, the potassium salt of the new tinctorial acid. To watch the operation there is 
 taken a sample from time to time ; it is filtered and the filtrate is shaken with 
 air, observing if after a time there appears a precipitate of the potassium salt insoluble 
 in dilute hydrochloric acid. If no further separation of crystals takes place the 
 process is interrupted to prevent a further oxidation and destruction of the colouring 
 matter which has been formed. The crystalline paste is quickly filtered, pressed, and 
 dissolved in warm water. The solution is slightly supersaturated at about 50 with 
 hydrochloric or sulphuric acid and boiled until the colouring matter separates out 
 in a heap of shining light yellowish-green crystals, which are separated from the 
 reddish-brown solution by filtration. After washing with water at a hand-heat the 
 product is ready for dyeing or printing. 
 
 Styrogallol. Cinnamic and gallic acids unite in presence of a dehydrating agent 
 according to the equation : 
 
 C 6 H 6 .CH : CH.COOH + 6 H,(OH) 8 COOH = C 16 H 10 O 5 + 2 H,O. 
 
 Under the same conditions tannin (digallic acid) forms the same condensation 
 product. 
 
 10 parts (i molecule) cinnamic acid and 17 parts of gallic acid are heated for 
 two or three hours to 55 with 150 parts of concentrated sulphuric acid. The melt 
 is poured into an excess of cold water, when styrogallol separates as a pale green 
 powder, consisting of microscopical needles. Like nitroalizarine, it gives with mordants 
 tones ranging from yellow to blackish. The colours bear soaping. Styrogallol can 
 be converted into a soluble sulpho acid by treatment with fuming sulphuric acid. In 
 this state it dyes wool a light yellow. 
 
 Tartrazine. The sodium salt of disulphodiphenylhydrazindioxytartaric acid is 
 obtained by the action of phenylhydrazinmonosulpho acid from diazoamidobenzol 
 upon dioxitartaric acid. 
 
 Ten parts of sodium dioxytartrate are diffused in 30 parts of water and mixed 
 with 35 parts hydrochloric acid at 30 Tw. To the clear solution thus obtained there 
 is added a solution of 12 '8 parts phenylhydrazin hydrochlorate in 100 parts of water 
 and gently heated. A yellow voluminous precipitate is formed, and after standing 
 twelve hours it is collected on a filter and dried. The light yellow colouring matter 
 when cold is filtered, pressed, and dried ; it is readily soluble in water, insoluble in 
 alcohol, and gives a pure yellow, fast to light on animal fibres. 
 
SECT. IV.] 
 
 ORGANIC COLOURING MATTERS. 
 
 In a corresponding manner isatine yellow is obtained by the action of phenylhydra- 
 zinparasulpho acid. 
 
 Canarine (persulphocyanogen), C 6 N 4 2 H 4 S 5 , is.form.ed from potassium sulphocyanide 
 by oxidation. 
 
 Three kilos, of sulphocyanide are dissolved in 6 litres of hot water in an earthen 
 vessel; 300 grammes potassium chlorate are added and 2^4 kilos, hydrochloric acid 
 are stirred in. The mixture is gently heated, if necessary, until the reaction which sets 
 in after a few minutes has almost entirely subsided. The vessel is then set in cold 
 water, and rz kilo, potassium chlorate and 3-6 kilos, hydrochloric acid are gradually 
 added in small lots. The temperature of the mixture must be kept at about 80. The 
 orange -coloured precipitate formed is washed by decantation three times with hot water, 
 collected 011 a linen strainer, washed until neutral, and dried. 
 
 For purification this crude product is heated to solution with an equal weight of 
 potassium hydrate and 20 parts of distilled water until dissolved. The dark-red solution 
 is filtered through wool, and when it is cooled down to 40 it is mixed with 20 parts 
 ethyl alcohol at 90 per cent., and the whole is set aside for twenty-four hours. The 
 reddish- orange, granular crystalline precipitate of the potash compound of the colouring 
 matter is filtered, pressed, and dried ; the filtrate, after the alcohol has been distilled 
 off, is melted down for potassium ferrocyanide. In order to separate the colouring 
 matter from the potassium compound it is dissolved in 10 parts of water and the solu- 
 tion is mixed with hydrochloric acid enough to precipitate the colouring matter ; the 
 brown precipitate formed is washed, filtered, and dried. 
 
 The aqueous solutions of canarine-alkaline salts dye cotton, without mordants, shades 
 of maize, yellow, and orange. The colours bear soaping and light. For making up 
 the dye beck, one part canarine, one part potassium hydrate, and 400 parts water are 
 heated to boiling, and one part curd soap is added, or two parts canarine potassium are 
 dissolved in 400 parts water and the part of soap is added. 
 
 Goppelsroeder obtains persulphocyanogen by the electrolysis of an aqueous solution 
 of potassium sulphocyanide as an orange-yellow deposit at the positive pole. He has 
 also formed and fixed canarine simultaneously by electrolysis upon vegetable and animal 
 fibres. 
 
 Murexide, C 8 H 4 (NH 4 )N 5 6 , has been already mentioned. 
 
 Lampblack (soot) is obtained by the imperfect combustion of resin, gas-tar, oils, &c. 
 The furnaces consist of one or two slightly ascending combustion shafts, A (Fig. 400 
 .and 401), in which the solids to be burnt are thrown in in front, whilst tar and oils are 
 
 Fig. 400. 
 
 . 401. 
 
 Explanation of Term. 
 Schnitt x-y . . Section x-y. 
 
 passed in through iron pipes from the vessels, a. The smoke fumes pass from there 
 into the first massive cooling chamber, , through b into the long chamber, C, extend- 
 ing above it, then into the tower, Z>, divided by a partition into two perpendicular 
 
582 CHEMICAL TECHNOLOGY. [SECT. iv. 
 
 compartments, and finally through a regulating chimney into the air outside. A coarse 
 cloth, stretched across the half of the tower, serves to keep back the hist residues of 
 soot. 
 
 The materials are ignited every Tuesday morning, and the combustion is kept up 
 until Saturday evening, with cessations only from 9 or TO P.M. to 4 or 5 A.M. On 
 Sunday the furnaces cool, and on Monday they are emptied. From 100 parts of tar 
 the yield of lampblack is 25 parts, and from 100 parts of dregs of resin 20 parts. 
 
 Finer blacks are obtained by burning mineral oils in lamps ; the flame strikes upon 
 cold surfaces, on which the liberated carbon is deposited as lampblack. 
 
 Lampblack is used in the production of printing-inks, Indian inks, and as an admix- 
 ture to some painters' colours.* 
 
 EXAMINATION OF COLOURING MATTERS.! 
 
 The first point to be ascertained is whether a sample be it a dry powder, a paste, or a 
 liquid is a unitary, homogeneous substance or a mixture. To this end, Slater f places a 
 drop of the solution upon a piece of filter-paper. . 
 
 If the colour is homogeneous, the spot produced will be alike throughout. If the 
 colour is a mixture there are seen rings of different colours. 
 
 Goppelsroeder about the same time applied the same principle in a manner which 
 is often more convenient. He suspends slips of filter-paper so as to dip into the 
 solution of the dye-stuff. If we have to do with a mixture, the different colours will 
 ascend to different heights on the slip, forming a succession of bands. 
 
 If time is not a pressing object, a portion of the colour may be dissolved, and 
 swatches of woollen and silken tissues may be dyed successively until the bath is ex- 
 hausted, noting the order of the swatches. If the colour is homogeneous, the first and 
 the last swatch will display exactly the same tone, but, if it is a mixture, a difference 
 will be observed, some one of the ingredients combining more readily with the fibre 
 than the others. 
 
 In the case of the azo dyes, we may utilise their property of dissolving in 
 sulphuric acid with different colours. Pure, clean, concentrated sulphuric acid is 
 placed in a white porcelain capsule a few fine granules of the dye are sprinkled upon 
 the acid, and the tones of colour which they produce are observed. Mixtures may 
 thus often be detected, especially as the reaction is very sensitive. 
 
 Besides the joint presence of different colours, mineral impurities are often found, 
 such as potassium and sodium carbonates, common salt, sodium and magnesium sulphates, 
 and dextrine. These substances are not always due to intentional fraud, but are re- 
 sidues of matters used in the process of manufacture and not fully removed. Common 
 salt is found in almost every soluble colouring matter which is not capable of crystalli- 
 sation. A small part of the dye is ignited and chlorine is tested for. Sodium sulphate 
 is chiefly found in the azo dyes. The dye is dissolved in water, salted out with chemi- 
 cally pure sodium chloride, and sulphuric acid is sought for in the filtrate in the ordinary 
 manner. Magnesium sulphate is rarely used in place of Glauber's salt. Alkaline car- 
 bonates may be used in case of the phthaleines. Dextrine is recognised by the smell 
 which it gives off on dissolving the dye in water, and which resembles that of bugs. Or 
 the colouring matter may be extracted with concentrated alcohol, which leaves dextrine- 
 undissolved. 
 
 * On the coal-tar colours the reader may compare The Chemistry of the Coal-tar Colours, by 
 Benedikt and Knecht. London : G. Bell & Sons. 
 
 t Section added by the Editor. J Manual of Colours and Dye-wares. 
 
 Capittar Analyse und Hire Amcendungen : Mulhouse, Wenz & Peters. 
 
SECT, iv.] EXAMINATION OF COLOURING MATTERS. 583 
 
 In carrying out the systematic examination of colouring matters, we mix a mode- 
 rately concentrated solution of the dye with solution of tannin (25 parts tannin, 25 
 sodium acetate, and 250 water). An excess of tannin is to be avoided (since the 
 precipitate is often soluble in excess), and the liquid is then heated, as certain sul- 
 phonised derivatives of triphenylmethane form precipitates which redissolve at higher 
 temperatures. In the presence of a basic colouring matter the filtrate should be nearly 
 colourless after the addition of the solution of tannin. 
 
 We reduce the basic dye-wares with zinc-powder and hydrochloric acid ; after filtra- 
 tion, we saturate with sodium acetate, since an excess of hydrochloric acid may form 
 acid salts from the basic colours after re-oxidation, having different colours from those 
 of the neutral salts. In reducing Bismarck brown and chrysoidine, there are formed 
 di- and tri-amines, which are easily oxidised in contact with the air, and take a brownish- 
 red colour. It is therefore necessary, especially in the case of the brown and the 
 yellow basic colours, to compare the colour of the reduced and the re-oxidised dye-stuff 
 with that of the original solution. After the reduced solution has been dropped upon 
 filter-paper, it is advantageous to assist the oxidation by heating it slightly over a 
 flame. Certain dye-stuffs become oxidised with such rapidity that the original colour 
 reappears during filtration. 
 
 Acid Colouring Matters. The reduction of the non-fluorescent yellow, orange, pon- 
 ceau, and claret dye-wares must be effected with great caution. It is best to reduce with 
 zinc powder and hydrochloric acid and neutralise with sodium acetate, since the nitro 
 groups which may be present in the sample would not be reduced quickly enough if 
 ammonia or acetic acid were used. It is prudent to compare the reduced and re- 
 oxidised solution with the original solution of the colouring matter, since in the reduc- 
 tion of the nitro or azo colours there are formed diamines or amido phenoles, which 
 on oxidation produce dirty-yellow or brown tones. To this section (azo dye- wares) 
 belongs likewise erythrosine, for in its reduction iodine is liberated with re-formation 
 of fluoresceine. All colours not mentioned may be reduced with zinc powder and acetic 
 acid or ammonia. In the reduction of the acid dyes the solution, as soon as the zinc 
 powder has been added to it, should be rendered colourless, or should at most have 
 merely a faint yellowish or reddish tint. The nitrofluoresceine derivatives and the 
 azo dyes may be easily recognised if they are burnt. There are formed upon the sheet 
 platinum " Pharaoh's serpents," especially on working with a large quantity say 0*5 
 gramme. In order to detect the nitro groups in the light-yellow colouring matters it is 
 necessary, before ignition, to mix them (e.g., picric acid) with a little soda. 
 
 It is very difficult to reduce " alizarine S " completely ; it is placed in the last 
 column of Table B., under the heading " The colour of the ammoniacal solution re- 
 appears." But if the reduction is carried too far the original colour does not re- 
 appear. 
 
 All the sulphonised amido-azo and tetrazo colouring matters are almost decolorised 
 if they are reduced with zinc-powder and ammonia, without heat. After filtration 
 the solution is a pale yellow, and if it is poured upon filter-paper and heated it causes 
 yellow spots. The azo colours produce no spots, or, at most, show a dirty brown. 
 The reactions with barium or calcium chloride must be tried with a concentrated 
 solution of the colouring matters. As sodium sulphate is contained in most azo 
 colours, turbidity cannot be reckoned as a reaction. The sulphuric acid test must be 
 carried out as directed above. 
 
584 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. iv. 
 
 Artificial Colours Soluble in Water. 
 The aqueous solution is mixed with solution of tannin. 
 
 A. There is formed a Precipitate. 
 Basic Colouring Matters. 
 
 The aqueous solution is reduced with zinc-powder and hydrochloric acid, neutralised, 
 and placed upon filter-paper. 
 
 The original colour returns. 
 
 Original colour 
 does not 
 return. 
 
 Bed. 
 
 Yellow and 
 Orange. 
 
 Green. 
 
 Blue. 
 
 Violet. 
 
 Magenta 
 
 Toluylen red 
 (Cassella) 
 Safranine 
 
 Phosphine 
 Flavaniline 
 
 Malachite 
 green 
 Brilliant green 
 
 Methyl green 
 
 Methylene 
 blue 
 New blue 
 (Cassella) 
 Muscarine 
 (Durand and 
 Huguenin) 
 
 Methyl violet 
 
 Hofmann's 
 violet 
 Mauveine 
 
 Amethyst blue 
 Crystal violet 
 
 Chrysoidine 
 Bismarck brown 
 Auramine 
 
 Victoria blue 
 
 B. No Precipitate is formed. 
 Acid Colours. 
 
 The aqueous solution is reduced with zinc-powder and hydrochloric acid (or with 
 zinc-powder and ammonia). 
 
 Solution decolorised. 
 
 The colour changes to 
 a brownish red. The 
 ammoniacal solution 
 takes its original 
 colour on the filter. 
 
 Original colour 
 reappears. 
 
 Original colour does not 
 reappear. 
 
 Aqueous solution acidi- 
 fied with HC1 and treated 
 with ether. 
 
 Colouring matters heated on 
 platinum foil. 
 
 Ether dissolves the 
 colour and the 
 aqueous solution 
 is nearly colourless. 
 
 Ether re- 
 mains colour- 
 less. 
 
 Deflagrates 
 without 
 coloured 
 fumes. 
 
 Burns slowly with 
 coloured vapours, or de- 
 flagrates slightly with 
 coloured fumes. 
 
 Alizarine S. 
 Alizarine blue S. 
 Ceruleine S. 
 
 Phthaleines. 
 
 Sulphonised 
 derivatives o1 
 Rosaniline. 
 
 Nitro colours 
 (Nitro- 
 phenoles). 
 
 Heat an unmordanted 
 swatch of cotton with 
 aqueous solution. 
 
 Dye bears 
 hot soap. 
 
 Dye does 
 not bear hot 
 soap. 
 
 Benzidine 
 azo dyes. 
 
 s Azo dyes. 
 
SECT. IV.] 
 
 EXAMINATION OF COLOURING MATTERS. 
 
 55 
 
 Solid or Pasty Colours, Insoluble in Water. 
 The dye-wares are treated with water and a few drops of soda-lye at 5 per cent. 
 
 The dye-wares dissolve. 
 
 The dye does not dissolve. 
 
 The alkaline solution is filtered, zinc- 
 powder is added, heated, and put 
 on filter-paper. 
 
 The colouring matters are heated with alcohol 
 at 70 per cent, and dissolve, except indigo. 
 
 Colour of alkaline 
 solution returns. 
 
 Colour does not re- 
 turn in the same tone, 
 or original colour is 
 not changed. 
 
 Alcoholic solution not 
 fluorescent. 
 
 Alcoholic solution 
 fluorescent. 
 
 Soda-lye at 33 per cent, is added. 
 
 Ceruleine. 
 Galleine. 
 Gallocyanine. 
 Galloflavine. 
 
 Canarine. 
 Alizarine. 
 Anthrapurpurine. 
 Flavopurpurine. 
 Nitroalizarine. 
 Alizarine brown. 
 Alizarine blue. 
 Chrysamine. 
 Solid green. 
 (Dinitroresorcine. ) 
 
 Colour 
 changes to 
 red-brown. 
 
 No change 
 of colour. 
 
 Fluoresence 
 disappears. 
 
 Fluoresence 
 does not 
 disappear. 
 
 Induline. 
 Nigrosine. 
 Rosaniline 
 blue. 
 Diphenyl- 
 amine blue. 
 
 Indophenol. 
 
 Magdala 
 red. 
 
 Primrose 
 Cyanosine. 
 
 Basic Colouring Matters. 
 
 Reds : Watery solution bluish red : yellow-brown with 
 HC1 and strong sulphuric acid. Sodium acetate restores 
 original colour. Zinc-dust decolorises watery solution ; 
 colour does not return. Strong sulphuric acid dissolves it 
 with a yellow-brown. Solid colour green, of metallic lustre Magenta, Rubine. 
 
 Solution reddish blue; ammonia throws down flocks 
 which dissolve in ether with greenish-yellow fluorescence. 
 HC1 turns it blue ; sulphuric acid, brownish green ; on 
 addition of water, colour turns blue, violet, and lastly red 
 
 Alcohol added to the original colour gives orange 
 fluorescence. Zinc-powder decolorises solution. Colour 
 returns on exposure to air. Sulphuric acid makes it green ; 
 on dilution with water, passes to blue, violet and red 
 
 Yellows: Easily soluble in water. With alkalies, a 
 yellow flocky precipitate (brown if impure) ; soluble in ether 
 with fine yellow colour and strong green fluorescence 
 
 With alkalies, yellowish- white milky precipitate ; soluble 
 in ether without colour, and splendid blue fluorescence . 
 
 Greens : Easily soluble in water with strong green 
 colour. Alkalies give a rose-coloured or grey precipitate ; 
 acids turn it yellow. Sulphuric acid, yellow ; green on 
 dilution with H 2 O . . . . . . .' 
 
 Soluble in water with a more yellowish-green colour ; 
 ammonia gives no precipitate, or a very slight one. Solu- 
 tion of colour in sulphuric acid does not turn green as 
 quickly when diluted with water as does malachite green . 
 
 Soluble in water with a blue or greenjsh-blue colour. 
 With acids, yellow. Alkalies discharge, but give no preci- 
 pitate ; swatch dyed with this colour turns violet at 100. 
 Sulphuric acid, yellow ; on dilution, green 
 
 Violets : Easily soluble in water. Alkalies give a violet 
 
 Neutral Red. 
 
 Safranine. 
 
 Phosphine (ChrysaniUne). 
 
 Flavaniline. 
 
 Malachite Green. 
 Brilliant Green. 
 Methyl Green. 
 
586 
 
 CHEMICAL TECHNOLOGY, 
 
 [SECT. iv. 
 
 brown solution precipitate, sulphuric acid a yellow, on 
 dilution with water violet blue ..... 
 
 Sparingly soluble in cold water ; HC1 turns solution blue ; 
 alkalies throw down brown flocks ; sulphuric acid turns it 
 a dirty violet ., ... , . . . '.- 
 
 Not very soluble in water ; alkalies give a violet precipi- 
 tate, sulphuric acid turns colour to grey ; on slow dilution 
 with water turns sky-blue, violet- blue, and reddish violet . 
 
 Soluble in water with red-violet colour. Carmine-red 
 fluorescence on adding alcohol. Sulphuric acid, fine green, 
 on dilution becoming blue and then violet 
 
 Soluble in water with very pure tone ; HC1 turns it 
 orange ; soda-lye, a violet-brown precipitate. Strong sul- 
 phuric acid, an orange colour, which does -not disappear on 
 adding 10 parts of water. Base dissolves in ether with a 
 yellow colour ........ 
 
 Blues : Easily soluble in water ; HC1 gives the solution 
 a greenish cast. Strong soda-lye, a violet-black precipitate. 
 The colour contains zinc. A 7 per cent, solution of chloride 
 of lime destroys the colour only after the lapse of some 
 hours. Sulphuric acid gives a grass-green 
 
 The watery solution is bluish violet. Strong sulphuric 
 acid gives a green colour which turns blue and violet on 
 dilution. Soda-lye gives a black-brown precipitate. On re- 
 duction with Zn and acetic acid, appears first a green colour. 
 Colouring matter a fine powder which causes sneezing 
 
 There has latterly been sold as " bleu nouveau " a dye 
 the solution of which is violet when hot but green when 
 cold. Alkalies give a red-brown precipitate ; HC1 a slight 
 blue precipitate. Sulphuric acid gives a violet-red colour, 
 turning violet on dilution ; probably a mixture. 
 
 Sparingly soluble in cold water, with a violet colour. 
 Tannin gives an indigo-blue precipitate. Sulphuric acid 
 dissolves it bluish green, blue on dilution and then violet ; 
 then is formed a precipitate, soluble in much water ; soda- 
 lye gives a red-brown precipitate ..... 
 
 Soluble, with a yellow colour. Alkalies give a white 
 milky precipitate. Precipitate soluble in ether without 
 fluorescence. The yellow solution of the dye gradually 
 loses its colour; if boiled with dilute sulphuric acid it 
 becomes colourless. A transient yellow colour on reduc- 
 tion with zinc-powder and acetic acid .... 
 
 Dyes wool orange-yellow ; watery solution of the dye 
 congeals (not always) to a blood-red gelatinous mass. 
 Sulphuric acid dissolves it with a brown-yellow 
 
 Dyes wool a brown-orange ; sulphuric acid, a brown ; 
 does not gelatinise on cooling . ..... 
 
 Moderately soiuble in water. Yellow brown with acids ; 
 alkalies give a brown-red precipitate ; zinc and acetic acid 
 decolorise solution permanently. Sulphuric acid gives a 
 red-brown, turning green-blue on dilution 
 
 Methyl FioZei(Hofmann's). 
 Neutral Violet. 
 Mauveine (Rosolane). 
 Amethyst (Giroflee). 
 
 Crystal Violet. 
 Methylene Blue. 
 New Blue B and D. 
 
 Muscarine(Dur8iiid & Co.) 
 
 Auramine. 
 
 Chrysoidine. 
 
 Vesuvine (Bismarck 
 brown). 
 
 Victoria Blue. 
 
SECT. IV.] 
 
 EXAMINATION OF COLOURING MATTERS. 
 
 Acid Colouring Matters. Phthaleines. 
 
 The aqueous solution is pure red with a yellowish-green 
 fluorescence, becoming stronger the more the solution is 
 diluted. Acids throw down orange flocks, soluble in 
 ether with a yellow colour. Strong sulphuric acid dissolves 
 it with a yellow colour ; on heating the solution, white 
 fumes of hydrobromic acid escape. With the addition of 
 manganese peroxide, an escape of bromine 
 
 Watery solution more bluish than that of eosine, and 
 but slightly fluorescent. Acids give a yellow-brown pre- 
 cipitation, which dissolves in ether with a yellow colour. 
 Dissolves in strong sulphuric acid with a golden yellow ; on 
 heating, the same phenomena as with eosine. Ammoniacal 
 solution reduced with zinc-powder quickly recovers its 
 colour in the air. If heated on platinum foil, brisk com- 
 bustion with formation of " Pharaoh's serpents " . 
 
 Watery solution bluish red with slight greenish 
 fluorescence. With HC1, a flesh-coloured precipitate which 
 dissolves in ether with a brownish-yellow colour. Sulphuric 
 acid changes the colour to a golden yellow, and on heating 
 this solution hydrogen bromide escapes, or free Br on 
 addition of MnO 2 ....... 
 
 The watery solution is dark bluish red, not fluorescent. 
 HC1 gives a scarlet precipitate, soluble in ether with an 
 orange-yellow colour. The reduced solution is but little 
 oxidised in the air. Dissolves in sulphuric acid with an 
 orange, and, on heating, iodine deposits on the sides of the 
 vessel . . . . . . . . . 
 
 Solution brownish yellow with strong green fluorescence 
 which disappears on adding HC1 with formation of a yellow 
 precipitate . . . . . . * . 
 
 Solution eosine red. HC1 gives a yellow precipitate. 
 Strong sulphuric acid gives a yellow precipitate from which 
 neither iodine nor bromine is separated. The watery 
 solution smells of phenol . . 
 
 Eosine. 
 
 Safrosine Scarlet. 
 
 Phloxine. 
 
 Bengal Rose. 
 
 Uranine, Chrysoline, 
 
 Coralline, Aurine. 
 
 Sulphonised Rosaniline Derivatives. 
 
 The watery solution is bluish red, colour disappears 
 on heating with soda-lye and reappears on adding acetic 
 acid. Sulphuric acid turns it yellow, red on dilution . Acid Magenta. 
 
 Easily soluble in water with slight greenish colour. On 
 the addition of a little acid the colour darkens, but turns 
 
 yellow with acid in excess. Alkalies discharge the colour Helvetia Green. 
 
 Alkalies discharge almost entirely. Wool takes up the 
 colour from an ammoniacal solution. The dyed wool turns 
 deep blue if washed in dilute acid ..... Nicholson Blue. 
 
 Easily soluble in water. Wool dyes only in an 
 acidified solution. Alkalies do not precipitate the aqueous 
 solution. Commonly sold in the state of fragments of a 
 metallic lustre ... . . China Blue. 
 
588 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT 
 
 IV. 
 
 Watery solution violet. Ammonia discharges it com- 
 pletely without giving a precipitate. Sulphuric acid turns 
 it orange ; on dilution with water, turns green, blue, and 
 at last violet . . . 
 
 Soluble in water with a colour varying from blue-grey 
 to red-grey. HOI gives a reddish blue. Alkalies, red or 
 violet. Dilute nitric acid, no change even on heating 
 
 Nitro Colouring Matters. 
 
 Soluble with greenish-yellow colour ; solution tastes 
 bitter. Alkalies turn it a dark yellow ; no precipitate on 
 adding a yellow to this solution. Colouring matter deflag- 
 rates only if mixed with soda . .... . . 
 
 Dissolves with gold-yellow colour. HC1 gives a yellowish- 
 white precipitate solution in ether . .... 
 
 Soluble with gold-yellow colour. HC1 gives no precipi- 
 tate. It does not colour ether ..... 
 
 Concentrated aqueous solution red ; yellow if dilute ; 
 sulphuric acid gives no coloration. Acids turn it 
 yellowish milky ; excess of alkalies, a dark-red precipitate. 
 Generally sold as an ammonium salt .... 
 
 Benzidine-Azo Colouring Matters. 
 
 Watery solutions red ; trace of HC1 turns it blue. 
 Strong sulphuric acid turns it a slate-blue, and there is no 
 change on diluting with water ..... 
 
 Watery solution orange red. Strong sulphuric acid or 
 HC1 gives a brown precipitate in a concentrated solution ; 
 brown solution on diluting ... ... 
 
 Soluble with blue-violet colour ; with alkalies, a red 
 solution. Strong sulphuric acid gives it a violet colour. 
 HC1 a violet precipitate in strong solution 
 
 Solution blue-red. HC1 and sulphuric acid, an orange 
 precipitate. Iodine sublimes on heating this colour 
 
 Azo Colours. Yellow-Orange. 
 
 Sulphuric acid gives a yellow colour, turning to brown- 
 red and then to orange on dilution. Watery solution 
 yellow. Barium chloride gives a precipitate, but not cal- 
 cium chloride ......... 
 
 Sulphuric acid turns it violet, red- violet on dilution with 
 immediate formation of a slate-green precipitate. Watery 
 solution yellow ; colouring matter separates out in crystals 
 on cooling. Barium and calcium chlorides produce precipi- 
 tates 
 
 Watery solution orange ; turns violet with HC1. The 
 reduced ammoniacal solution is yellow. Sulphuric acid 
 turns it violet-red, changing to magenta-red on dilution. 
 Sparingly soluble precipitate with barium chloride ; no pre- 
 cipitate with calcium chloride ..... 
 
 Acid Violet. 
 
 Induline, Nigrosine. 
 
 Picric Acid. 
 
 Martins Yellow. 
 
 Naphthol Yellow 
 
 Aurantia. 
 
 Congo Red. 
 
 Benzo Purpurine 
 
 Azo Blue. 
 
 Erythrosine. 
 
 Fast Yellow. 
 
 Diphenylamine Yellow* 
 
 Azqflavine. 
 
SECT. IV.] 
 
 EXAMINATION OF COLOURING MATTERS. 
 
 589 
 
 Sulphuric acid colours it yellow, carmine-red on dilution. 
 Watery solution yellow. Colour crystallises out on cooling 
 in yellow scales. Dilute acids precipitate red-violet scales Methyl Orange. 
 
 Sulphuric acid changes colour to a bluish green, passing 
 on dilution into a violet and depositing a slate-blue pre- 
 cipitate. Watery solution yellow ; colouring matter crystal- 
 lises out on cooling. Barium chloride gives a yellow pre- 
 cipitate which crystallises out from the dilute solution in 
 the form of scales . . . . 
 
 Sulphuric acid turns it a yellow-green, which on dilution 
 becomes violet with a grey precipitate. Watery solution 
 yellow ; colouring matter crystallises out on cooling.Calcium 
 chloride gives an orange precipitate, which on heating turns 
 red and crystallises ........ 
 
 Sulphuric acid gives a carmine colour, which turns 
 yellow on dilution. Watery solution is yellow and often 
 turbid. With an alcoholic solution of soda the colour is 
 red to violet. " Pharaoh's serpents " are formed on ignition 
 
 Sulphuric acid turns it deep orange ; no change on 
 dilution. Watery solution is orange. With calcium 
 chloride, a finely crystalline salt . ... 
 
 Sulphuric acid dissolves it orange-brown ; no change 
 on dilution. Watery solution yellow ; on adding a trace of 
 HC1 the original solution crystallises out in yellow scales. 
 If more hydrochloric acid is added the crystals appear as 
 grey needles ......... 
 
 Sulphuric acid, a carmine solution ; on dilution, an 
 orange precipitate. Watery solution red-orange. Calcium 
 chloride gives a yellow precipitate, which crystallises in red 
 needles on adding an excess of boiling water. Barium 
 chloride yields a sparingly soluble crystalline precipitate . 
 
 Dissolves violet in sulphuric acid ; on dilution, brown 
 precipitate and orange solution. Watery solution orange- 
 red, and carmine-red on adding soda-lye . . ... 
 
 Watery solution orange. Hot solution deposits a yellow 
 precipitate on cooling. Sulphuric acid dissolves it yellow. 
 Barium chloride gives a gold-yellow precipitate. Calcium 
 chloride, no reaction ... ... 
 
 Dissolves of a dirty violet in sulphuric acid, passing into 
 magenta-red on dilution. Watery solution orange. Barium 
 chloride gives a sparingly soluble precipitate . 
 
 Bordeaux Reds. 
 
 The strong hot watery solution becomes gelatinous on 
 cooling. Acids precipitate red-brown flocks. Sulphuric 
 acid dissolves it with a green, which on dilution becomes 
 violet-blue and deposits after some time a dirty-brown 
 precipitate . Biebrich Scarlet. 
 
 Calcium chloride throws down a red flocky precipitate 
 which on boiling becomes crystalline and brown-red. 
 
 Yellow N (Poirrier), 
 
 Luteoline. 
 
 Oitronine (Curcumine). 
 Orange G, 
 
 Tropaoline 0. 
 Orange II. 
 
 Orange I. (Tropceoline 
 000.) 
 
 Tartrazine. 
 
 Metanile Yettow. 
 
59 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. iv. 
 
 Sulphuric acid changes the colour to an indigo-blue, which 
 on dilution becomes first violet and then red. The re- 
 duced ammonical solution of the colouring matter turns 
 yellow in the air . . 
 
 The hot aqueous solution gelatinises on cooling and 
 forms bronzy crystals. Dissolves with a violet colour in 
 sulphuric acid ; a brown precipitate on adding water 
 
 The hot concentrated aqueous solution of the colouring 
 matter on admixture with manganese sulphate deposits, 
 on cooling, long silky crystals of the manganese salt. 
 Sulphuric acid produces a blue colour ; wool is dyed a 
 scarlet-red. The ammoniacal solution if reduced no longer 
 becomes yellow on filter-paper . . . . 
 
 Watery solution a fine red ; cosine red in sulphuric 
 acid. Barium chloride gives an almost insoluble precipi- 
 tate ; calcium chloride gives a precipitate gradually 
 
 Watery solution a fine red. Ammonia turns it a red- 
 brown ; sulphuric acid, a magenta-red, turning to a pure 
 red on dilution. Barium chloride gives a brown precipitate, 
 soluble with difficulty. Calcium chloride gradually gives a 
 red precipitate . . . . . . . ... . 
 
 Solution dark brownish red, as also the dyed wool. 
 Sulphuric acid dissolves it violet, red on dilution. The 
 strong watery solution on the addition of a few drops of 
 strong soda-lye deposits the sodium salt in the form of 
 brown shining scales , . . . . . 
 
 Watery solution red to claret ; barium chloride gives 
 a sparingly soluble precipitate ; that with calcium chloride 
 is easily soluble of a brown-red colour. Sulphuric acid 
 dissolves it indigo-blue, red on dilution .... 
 
 The reactions are the same as those of croceine scarlet. 
 The watery solution mixed with ammonia gives a dark 
 violet-red colour. The ammoniacal solution when reduced 
 is re-oxidised again to a yellow on filter-paper . 
 
 Anthracene Derivatives. 
 
 The watery solution is brownish yellow. With HC1, 
 pure yellow; the ammoniacal solution, magenta-red ; soda-lye 
 gives a violet colour in the strong solution of the colouring 
 matter; red precipitate with calcium chloride; dissolves 
 of a golden yellow in sulphuric acid ; becomes straw colour 
 on solution. Eeduced with difficulty .... 
 
 Watery solution olive-brown, ammoniacal solution 
 green. Brown-red solution, obtained by reduction with 
 zinc and ammonia ; is very quickly oxidised in the air, with 
 formation of a green precipitate .... 
 
 Watery solution a brownish-red, becoming green with 
 soda-lye, and greenish blue with ammonia ; HC1 gives an 
 orange-yellow solution. The solution reduced with 
 ammonia and zinc becomes a brown-red and is easily 
 oxidised in the air. The watery solution must be prepared 
 cold 
 
 Croceine Scarlet. 
 
 Xylidine Ponceau. 
 
 Croceine Scarlet JJB. 
 Ponceau R, $R and G. 
 
 Coccine, Coccinine. 
 
 Rocceline. 
 
 Bordeaux G and R. 
 Ponceau S. 
 
 Alizarine S. 
 
 Coeruleine S. 
 
 Alizarine Blue S. 
 
SECT. IV.] 
 
 EXAMINATION OF COLOURING MATTERS. 
 
 Colouring Matters Insoluble in Water. 
 i. Solution in soda-lye is violet ; in sulphuric acid, blue. 
 
 The colour takes on tissues mordanted with tannin. Met 
 with as a paste or a powder . ... 
 
 Solution in strong soda-lye, indigo-blue ; violet-red on 
 dilution ; in sulphuric acid orange. Met with as a paste 
 
 Soluble in soda-lye with a green colour ; in sulphuric 
 acid, the same. Met with as a paste . . . . . 
 
 Soluble in soda-lye with a dirty yellow ; reduces very 
 badly. Soluble in sulphuric acid with a yellow colour. 
 Met with as a straw-colour paste ..... 
 
 2. Insoluble in sulphuric acid; dissolves in soda-lye 
 with a yellow colour. Dyes unmordanted cotton a fast 
 yellow in a soap-bath. An orange powder 
 
 Soluble in soda- lye with a violet-blue colour; the 
 alkaline solution mixed with a little zinc-powder turns red 
 without heating ; the paste is orange .... 
 
 Solution in soda-lye a magenta-red. Reaction and 
 appearance like alizarine. The above three colouring 
 matters occur mixed, forming the different brands of 
 commercial alizarine ....... 
 
 Solution in soda-lye orange ; in sulphuric acid, 
 magenta-red, giving a brown precipitate on dilution. 
 Dyes cotton at once and forms yellowish, brown paste 
 
 Solution in soda-lye is red ; if reduced with zinc-powder 
 it produces deep indigo-blue spots on filter-paper. Forms 
 a yellow paste * ' . 
 
 Solution in soda- lye orange-brown ; if reduced, produces 
 on filter-paper dark, dirty-brown spots. Dissolves in 
 sulphuric acid with a brownish red . . . 
 
 Soluble with difficulty in soda-lye with a green colour ; 
 the reduced solution produces deep-blue spots on filter- 
 paper ; a deep-blue paste . . . . . 
 
 3. The alcoholic solution is blue-grey or red-grey. A 
 small quantity of the dry substance heated with a 5 per 
 cent, soda-lye and then extracted with benzene yields a 
 colourless or slightly yellowish solution having a deep 
 reddish-brown fluorescence ...... 
 
 Alcoholic solution deep blue, greenish on adding HC1 ; 
 turns brown with soda-lye. No fluorescence with benzol. 
 Dissolves reddish brown in sulphuric acid 
 
 4. Alcoholic solution turns brown-red if mixed with HOI. 
 
 5. Alcoholic solution bluish red with intense, splendid 
 vermilion fluorescence 
 
 6. Bluish red alcoholic solution, with greenish-yellow 
 fluorescence, disappearing on addition of HOI. Colour turns 
 yellow .......... 
 
 Blue-red alcoholic solution has a brick-red fluorescence, 
 disappearing on adding HC1. Colour turns orange . 
 
 7. Pulverised substance, insoluble in alcohol; reduced 
 with zinc and ammonia, gives a yellow liquid, which produces 
 spots on filter-paper . ..... 
 
 Gallocya-nine. 
 
 Galleine. 
 
 Ceruleine. 
 
 Galloflavine. 
 
 Canarine. 
 
 Alizarine. 
 
 Anthra- 
 purine. 
 
 and Flavo-pier- 
 
 Chrysamine. 
 
 Nitro-alizarine. 
 
 Alizarine Maroon. 
 
 Alizarine Blue. 
 
 Induline, Nigrosine. 
 
 Diphenylamine Blue. 
 Indophenol. 
 
 Magdala Red. 
 
 Primrose. 
 
 Cyanosine. 
 
 Indigo . 
 
SECTION V. 
 GLASS, EARTHENWARE, CEMENT AND MORTAR. 
 
 GLASS MANUFACTURE. 
 
 THE manufacture of glass is exceedingly ancient. As the Temple of Belus in Egypt, 
 the age of which is estimated at 12,000 years, was constructed of bricks covered with 
 a glaze, the production of glass cannot be very much less ancient. The composition 
 of certain specimens of glass from Autun, traceable to the second century is, according 
 to Peligot : 
 
 SiO 2 .... 
 
 667 
 
 ... 66-0 ... 
 
 67-4 
 
 ... 70-9 ., 
 
 . 69-4 ., 
 
 69-4 
 
 CaO .... 
 
 5-8 
 
 ... 7-2 ... 
 
 27 
 
 ... 7-9 -, 
 
 6-4 .. 
 
 ,. 7'i 
 
 A1 2 O S , Fe 2 3 , Mn 2 O, . 
 
 2-8 
 
 ... 3-0 ... 
 
 5'4 
 
 ... 4'5 
 
 . 2-9 ., 
 
 ,. 2-8 
 
 Na 2 0, K,0 
 
 247 
 
 ... 23-8 .. 
 
 24-5 
 
 ... 167 .. 
 
 . 21-3 . 
 
 .. 207 
 
 Composition of Glass. If we leave out of consideration the glasses soluble in water 
 and varying in composition between R 2 0.2Si0 2 and R 2 0.4Si0 2 , glass may be regarded 
 as a mixture of silicates obtained by fusion, liquid at high temperatures, becoming 
 pasty as it cools, and finally congealing to a hard, amorphous, and generally 
 transparent mass. The condition is that, besides the compounds of silica (in part re- 
 placeable by boric acid) with potassium or sodium, there must be simultaneously present 
 silicates of metals of the calcium, magnesium, or iron group, in order to render the 
 alkaline silicate as far as possible capable of resisting atmospheric and chemical 
 influences. As the lime and lead silicates are chiefly selected to this end, with other 
 metals in case of coloured glass, we can distinguish mainly the following groups : 
 
 (i) Alkaline silicates or soluble glass ; (2) Soda-lime silicates or soda glass ; (3) potash 
 lime silicates or potash glass ; (4) Alkali-lead silicates or lead glass ; (5) coloured glass. 
 
 If we take the constituents of glass as anhydrides, the simplest formula for soda- 
 glass is cNa 2 0.2/Ca0.2;SiOj ; in potash glass Na is replaced by K, and in lead glass 
 Pb is substituted for Ca. 
 
 Dumas was of opinion that glass has quite as definite a composition as certain 
 minerals, or is at least a mixture of definite silicates ; the glasses which he examined 
 gave the proportion of saturation Na 2 O.Ca0.4SiO 2 . This formula would indicate for 
 soda glasses the composition Si0 2 67*0 per cent., Na 2 iy'3 per cent., and CaO 15*7 per 
 cent. ; for potash glasses 6i'6 per cent. Si0 2 , 24-1 per cent. K 2 0, and 14*3 per cent. CaO, 
 If we compare the composition of good glasses met with in commerce we find that the 
 latter contain much more silica. But since Berthier has shown that an increase of silica 
 renders glass less fusible and harder, whilst lime gives it the power of resisting certain 
 chemical influences, Benrath regards as " glass " also silicates whose saturation answers 
 to the general formula R0.2Si0 2 . He points out that the most favourable composition 
 for all purposes of the glass manufacture excepting optical glasses falls between the 
 boundaries Na 2 O.Ca0.6SiO 2 and 5Na 2 0.7Ca0.36SiO,, where, of course, Na may be 
 replaced by K and Ca by Pb. Hence would follow the subjoined compositions : 
 
SECT. V.] 
 
 GLASS MANUFACTURE. 
 
 593 
 
 
 
 SiO, 
 
 Na-jO. 
 
 K,0. 
 
 CaO. 
 
 PbO. 
 
 K,O.CaO.6Si0 2 . 
 
 70-6 
 
 
 
 18-4 
 
 II'O 
 
 _ 
 
 Na. 2 O.Ca0.6SiO 2 . 
 
 75-3 
 
 13-0 
 
 
 
 117 
 
 
 
 EgO.PbO.6SiO., . 
 
 
 
 
 I3-9 
 
 
 32-9 
 
 5K 2 O.7Ca0.36Si0 2 
 
 71-5 
 
 
 
 15-6 
 
 12*9 
 
 
 SNajO. 7CaO. 36SiO 2 
 
 75-5 
 
 10-8 
 
 
 137 
 
 
 
 5K 2 0.7Pb0.36SiO 2 
 
 51-6 
 
 
 
 11 '2 
 
 
 37'2 
 
 Composition of Soda Glass. 
 
 
 
 Si0 2 . 
 
 Na 2 O. 
 
 K 2 0. 
 
 CaO. 
 
 MgO. 
 
 Pe 2 3 . 
 
 A1,0 S . 
 
 MnO. 
 
 Sb0 8 . 
 
 Window glass, Saarbruck . 
 
 71-27 
 
 12-50 
 
 
 
 H'lS 
 
 
 
 1-44 
 
 -^ _ 
 
 ' 
 
 
 
 O'2I 
 
 Witten 
 
 72-25 
 
 13-02 
 
 
 
 13-40 
 
 
 
 v~ 
 
 1-23 
 
 
 
 O'I2 
 
 Stollberg . 
 
 72-42 
 
 12-71 
 
 
 
 13-81 
 
 
 
 0-93 
 
 
 
 0*14 
 
 Flask, from Stender, Hanover . 
 
 7379 
 
 I3-94 
 
 0-60 
 
 8-61 
 
 O'I2 
 
 0-68 
 
 0-58 
 
 0*32 
 
 
 
 Mirror glass, Miinsterbusch 
 
 72-31 
 
 11-42 
 
 
 
 14-96 
 
 
 
 
 0.81 
 
 
 
 - 
 
 Window glass, from 
 
 72-80 
 
 12-30 
 
 
 
 14-10 
 
 
 
 073 
 
 
 
 
 
 Combustion-tube, Warm- ) 
 brunn, Quilitz & Co. j 
 
 74-06 
 
 11-46 
 
 3-92 
 
 971 
 
 
 
 0-98 
 
 
 
 
 
 White medicine bottles, | 
 Rhenish Works 
 
 72-07 
 
 18-45 
 
 
 
 8-96 
 
 
 
 o-54 
 
 
 
 
 
 White vessel, from Zwiesel 
 
 78-39 
 
 13-91 
 
 
 
 7-10 
 
 
 
 O'2I | O.24 
 
 0-15 
 
 
 
 Cast mirror glass, Dorpat . 
 
 74 'OS 
 
 10-95 
 
 
 
 12-96 
 
 
 
 I-8 7 
 
 
 
 
 
 Beaker glass, St. Petersburg 
 
 74-66 
 
 10-36 
 
 4'32 
 
 9T3 
 
 
 
 078 
 
 
 
 
 
 Russian semi-white vessel glass 
 
 74-00 
 
 17.44 
 
 
 7-35 
 
 
 
 O'2I 
 
 0'2O 
 
 0-8o 
 
 
 
 ii 
 
 69-99 
 
 17-96 
 
 
 
 9-90 
 
 
 
 0-39 
 
 I'll 
 
 0-65 
 
 
 
 Venetian window glass 
 
 68-60 
 
 8-10 
 
 6-90 
 
 11-90 
 
 2*IO 
 
 I'20 
 
 0-30 
 
 
 
 
 
 White glass, Bagneaux, Nemours 
 
 72-00 
 
 17-00 
 
 
 
 6-40 
 
 
 
 I'lO 
 
 2 '60 
 
 
 
 
 
 French medicine bottles . 
 
 62-00 
 
 16-40 
 
 
 
 15-60 
 
 2 -2O 
 
 O-7O 
 
 2-40 
 
 
 
 
 
 French crown glass,) 
 for lighthouses ) 
 
 72-10 
 
 I2-OO 
 
 
 
 1570 
 
 
 
 trace 
 
 trace 
 
 
 
 
 
 English mirror glass, St. Helens 
 
 77-36 
 
 13-06 
 
 3-02 
 
 5-3I 
 
 
 
 0-92 
 
 trace 
 
 
 
 
 
 Do., Thames Co., London . 
 
 78-69 
 
 11-63 
 
 i'34 
 
 6'io 
 
 
 
 trace 
 
 2-68 
 
 
 
 
 
 Do., London & Manchester Co. . 
 
 77-91 
 
 12-36 
 
 173 
 
 4-85 
 
 
 
 ^ 
 
 3-60 
 
 trace 
 
 
 
 Window glass, Charleroi, ) 
 Belgium j 
 
 74-82 
 
 13-01 
 
 
 
 ll'2l 
 
 
 
 i 
 1-03 
 
 
 
 trace 
 
 American pressed glass . 
 
 75-00 
 
 18-62 
 
 
 
 5-i8 
 
 0-52 
 
 0-19 
 
 O'll 
 
 0-38 
 
 
 
 Potash Glass. 
 
 
 ^ift 
 
 Kn 
 
 
 Port 
 
 MffO 
 
 
 Al.,0, 
 
 MnO 
 
 
 
 
 
 
 
 
 
 
 White glass, Venice . 
 
 68-60 
 
 6-90 
 
 8-10 
 
 11*00 
 
 2'IO 
 
 0-20 
 
 I '20 
 
 O'lO 
 
 Bohemia 
 
 7170 
 
 12-70 
 
 2-50 
 
 10*30 
 
 
 
 0-30 
 
 0*40 
 
 O'20 
 
 Bohemian tubing . 
 
 74-40 
 
 18-50 
 
 
 
 7-20 
 
 
 
 
 
 O*IO 
 
 
 
 i) 
 
 73-I3 
 
 11-49 
 
 3-07 
 
 10-43 
 
 O-26 
 
 0-13 
 
 0-30 
 
 0-46 
 
 it 
 
 7f60 
 
 ii-oo 
 
 
 10*00 
 
 2-30 
 
 3-90 
 
 2*20 
 
 0'20 
 
 mirror 
 
 67-70 
 
 21 'GO 
 
 
 
 9-90 
 
 
 
 
 
 1*40 
 
 
 
 average glass 
 
 76-00 
 
 I5-OO 
 
 
 
 8-00 
 
 
 
 
 
 1*00 
 
 
 
 Wine glass, Nortjo, Finland . . 
 
 74-37 
 
 I2-7I 
 
 3-42 
 
 9*02 
 
 
 
 O 
 
 71 
 
 
 
 
 62*29 
 
 21*12 
 
 6*78 
 
 6-;o 
 
 
 
 3 
 
 25 
 
 Mi 
 
 Russian beer glass .... 
 
 73'90 
 
 12-55 
 
 6*90 
 
 5-65 
 
 
 
 
 
 90 
 
 
 
 2 P 
 
594 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. v. 
 
 
 Si0 2 . 
 
 K 2 O. 
 
 Na 2 0. 
 
 CaO. 
 
 PbO. 
 
 FeoO, 
 
 Al 
 
 MnO. 
 
 
 
 
 
 
 
 r eV3. 
 
 2 3- 
 
 
 Crystal glass, Boneche 
 
 56-00 
 
 6-60 
 
 
 
 
 
 34-40 
 
 _^_ 
 
 I'OO 
 
 
 
 from London for) 
 chemical apparatus} * 
 
 59-20 
 
 9-00 
 
 
 
 
 
 28-20 
 
 0-40 
 
 . " 
 
 I'O 
 
 from Newcastle . 
 
 5IHO 
 
 9-40 
 
 
 
 
 
 37-40 
 
 2'OO 
 
 
 
 from Baccarat . 
 
 5I-IO 
 
 7'6o 
 
 170 
 
 
 
 38-30 
 
 I-30 
 
 
 
 French lamp glass . . . 
 
 48-10 
 
 12-50 
 
 
 
 o'6o 
 
 38-00 
 
 0-50 
 
 
 
 
 
 Flint glass, Guinaud . . . 
 
 42-50 
 
 11-70 
 
 
 
 0-50 
 
 43-50 
 
 
 
 i.8J 
 
 As 2 5 
 
 trace 
 
 Waldsteien, Vienna . 
 
 75-24 
 
 12-51 
 
 
 
 1-48 
 
 10-48 
 
 trace 
 
 trace 
 
 
 
 French pressed glass . 
 
 50-18 
 
 IJ'62 
 
 
 
 
 
 38-11 
 
 trace 
 
 0-14 
 
 trace 
 
 English . 
 
 61-27 
 
 7-07 
 
 7'55 
 
 1-05 
 
 22-36 
 
 
 
 0-86 
 
 
 
 Schott made a number of experiments, giving glasses of the following com- 
 positions : 
 
 - 
 
 I. 
 
 II. 
 
 ill. 
 
 IV. 
 
 V. 
 
 VI. 
 
 VII. 
 
 VIII. 
 
 
 MoL 
 
 p.c. 
 
 Mol. 
 
 p.c. 
 
 Mol. 
 
 p.c. 
 
 Mol. 
 
 p.c. 
 
 Mol. 
 
 p.c. 
 
 Mol. 
 
 p.c. 
 
 Mol. 
 
 p.c. 
 
 Mol. 
 
 p.c. 
 
 Si0 2 . 
 
 2 
 
 5 '4 
 
 3 
 
 60-4 
 
 4 
 
 67-0 
 
 5 
 
 71-8 
 
 6 
 
 75'3 
 
 3 
 
 50-0 
 
 4 
 
 S7'i 
 
 5 
 
 62-4 
 
 CaO . 
 
 I 
 
 23.6 
 
 i 
 
 18-8 
 
 I 
 
 15-6 
 
 i 
 
 13-4 
 
 I 
 
 117 
 
 i 
 
 l.S-6 
 
 i 
 
 i.V.S 
 
 I 
 
 12-6 
 
 Na 2 . 
 
 I 
 
 26-0 
 
 i 
 
 20-8 
 
 I 
 
 I7-4 
 
 i 
 
 14-8 
 
 I 
 
 13-0 
 
 2 
 
 34 '4 
 
 2 
 
 29-6 
 
 2 
 
 26-0 
 
 The glass I. was completely devitrefied on slow cooling ; II. chiefly, and III. (which 
 answers to the formula of Dumas) but little ; IV., which corresponds to the formula 
 Na 8 O.CaO.5SiO r was very good. Sample V. could be melted only with great difficulty; 
 VI. was half devitrified ; VII. and VIII. were apparently good, but would have been 
 too little resistant. Schott believes that no single unitary formula can be proposed 
 for all glasses in common use. Window glass may answer to the above formula, 
 Na 2 O.CaO.5SiO, ; mirror glass must contain more silica, but less lime; and glass for 
 vessels, bottles, &c., more lime. 
 
 R. Weber gives the following analyses of good glasses : 
 
 8i0 2 . 
 
 Alj,O s . 
 
 CaO. 
 
 MgO. 
 
 PbO. 
 
 K 2 O. 
 
 Na.,0. 
 
 In all. 
 
 Si0 2 -CaO-Na 2 O. 
 
 71-23 
 
 170 
 
 16-39 
 
 O'20 
 
 
 
 
 
 1078 
 
 IOO-30 
 
 4-0-1-0-60 
 
 71-03 
 
 2-98 
 
 15-62 
 
 0-15 
 
 
 
 
 
 10-76 
 
 100-54 
 
 4-2-1-0-60 
 
 71-92 
 
 0-85 
 
 I3-65 
 
 0-16 
 
 
 
 
 
 13-42 
 
 lOO'OO 
 
 4-8-1-0-88 
 
 73-35 
 
 073 
 
 11-91 
 
 071 
 
 
 
 
 
 13-12 
 
 loo-oo 
 
 5-3-1-0-90 
 
 72-68 
 
 I -06 
 
 12-76 
 
 0*26 
 
 
 
 
 
 13-24 
 
 100 -OO 
 
 5-2-1-0-90 
 
 72-66 
 
 0-95 
 
 15-20 
 
 0-25 
 
 
 
 
 
 10-94 
 
 lOO'OO 
 
 4-4-1-0-60 
 
 70-58 
 
 I -01 
 
 16-07 
 
 0-80 
 
 
 
 
 
 1177 
 
 99-23 
 
 3-8-I-O-6O 
 
 74-58 
 
 23 
 
 S'57 
 
 0-14 
 
 0'34 
 
 17-90 
 
 
 
 99-76 
 
 I2-5-I-2-00 
 
 75-81 
 
 oi 
 
 7-38 
 
 O'lO 
 
 
 
 11-39 
 
 4-84 
 
 100-53 
 
 9-6-1-1-50 
 
 72-13 
 
 41 
 
 11-51 
 
 
 
 
 
 5'66 
 
 10*06 
 
 10077 
 
 5'8-J-I-OO 
 
 75-23 
 
 12 
 
 8 'oo 
 
 0-03 
 
 
 
 6-38 
 
 8-84 
 
 1 00 '60 
 
 8-8-I-I-50 
 
 70-07 
 
 02 
 
 12-13 
 
 0-32 
 
 
 
 I5-03 
 
 2-00 
 
 100-57 
 
 5-2-I-0-85 
 
 5370 
 
 12 
 
 0*17 
 
 
 
 37-02 
 
 7-36 
 
 O7O 
 
 100-07 
 
 5-3-I-0-50 
 
 5370 
 
 07 
 
 o'59 
 
 
 
 34-9I 
 
 9'12 
 
 0-30 
 
 99-69 
 
 5-3-1-0-60 
 
 52-41 
 
 0-96 
 
 077 
 
 
 
 35-24 
 
 10-37 
 
 0'08 
 
 99-83 
 
 5-1-1-0-64 
 
 45-24 
 
 0-82 
 
 0-36 
 
 
 
 47-06 
 
 6-80 
 
 
 
 100-28 
 
 3-5-1-0-33 
 
 Glass when in a state of full fusion dissolves metals (gold, copper, silver, lead), oxides 
 (SnO,, Cr 2 3 , A1 2 3 , Fe 3 O 4 , Mn 3 4 ,SiO,, CaO), and salts (calcium phosphate, aluminium 
 fluoride, sodium sulphate), and if quickly cooled forms a homogeneous, amorphous mass. 
 If cooled slowly a part of the dissolved matter separates out either in crystals or in an 
 amorphous state. Even the excess of alkali seems to be merely in a state of solution. 
 Glass melted with alkali corresponds to the same saturation ; it dissolves at high 
 temperatures up to 84 per cent, of silica in excess, which on slow cooling separates out 
 
SECT. T J GLASS MANUFACTURE. 595 
 
 Calcium in glass can be substituted by a series of other elements. Thus on melting 
 together 
 
 I. IL 
 
 Sand .... 250 ... 250 
 
 Sodium carbonate . . 100 ... 100 
 
 Magnesia .... 50 ... 50 
 
 Calcium carbonate . . ... 60 
 
 Pelouze obtained the following glasses : 
 
 SiO 2 . . . 68-9 ... 657 
 
 Na.,0 .... 16-2 ... 15-0 
 
 MgO .... 14-9 ... 12-0 
 
 CaO .... ... 7'3 
 
 Specific gravity . 2-47 ... 2-54 
 
 These glasses are very fusible and readily become devitrified, especially II. 
 
 Whilst compounds of barium and strontium have often been added to mixtures for 
 
 glass, Benrath has shown that apparently the alkali can be replaced by baryta, as the 
 
 following analyses of three specimens of glass show, of which III. had been prepared at 
 
 St. Gobin, according to Peligot : 
 
 i. n. in. 
 
 SiO 2 . . . 44-93 ... 54-69 ... 46-5 
 
 CaO . . . 6-61 ... 17-06 ... 6-3 
 
 BaO . . . 44-98 ... 24-51 ... 47-2 
 
 Al 2 3 .Fe 2 O s . .3-48 374 
 
 But these glasses, scarcely corresponding to the saturation R0.2Si0 2 , are rapidly attacked 
 even by dilute mineral acids, and are consequently quite useless. The following glass, 
 (I.) was good ; its composition approximates to the equivalent proportion : 
 
 Na 2 O.CaO.BaO.9SiO g . 
 
 I. n. 
 
 Si0 2 65-14 ... 74-19 
 
 Nap . . . 9-37 ... 17-02 
 
 CaO .... 5-29 ... 2-88 
 
 PbO ... 0-86 
 
 BaO 17-18 ... 5-16 
 
 Al 2 O t .Fe 2 O s . . . 2-57 ... 0-58 
 
 S0 3 .... 0-45 ... 0-28 
 
 II. is the analysis of a good English compressed glass, of the sp. gr. 2-524. A 
 good barium lead glass is made at Mastricht with witherite, corresponding to the 
 formula 4K 2 0.2Ba0.3Ca0.3Pb0.36SiO,, and is mentioned by Benrath in support of 
 his formula. 
 
 We may notice the attempts of Lamy to introduce thallium into glass. From 
 300 parts sand, 400 thallium carbonate and 100 parts potassium carbonate or 300 
 sand, 200 red lead, and 335 thallium carbonate, he obtained an easily fusible, quite 
 homogeneous glass of sp. gr. 4.235, and with an index of refraction for the yellow ray of 
 1*71 ; finally he succeeded in obtaining a glass of sp. gr. 5*625 and a refractive index of 
 1-965. 
 
 On the other hand, calcium may be in part replaced by zinc ; a very good glass for 
 optical purposes by Maes, of Clichy, has the following composition : 
 
 Alkali and 
 
 Si0 2 . ZnO. PbO. Fejj0 3 and A1 Z S . CaO. As. Boric acid. 
 
 56-61 ... I3'5o ... 4'io ... 0-40 ... 070 ... trace ... 24-69 
 
 Bottle glass, prepared from very impure materials, can only approximately 
 correspond to the normal formula, on account of its high percentage of ferric oxide and 
 
596 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. v. 
 
 alumina, as it appears from the composition of good bottles. If the proportion of 
 alumina, lime, and alkali exceeds a certain limit the glass becomes less capable of resist- 
 ing water and acids, and is consequently useless. The following analyses of bottles 
 which have proved bad in practice show that the proportion of the ingredients of 
 glass cannot be made to vary very widely : 
 
 Analysis of Bottles. 
 
 
 Si0 2 . 
 
 Na 2 O. 
 
 K 2 0. 
 
 CaO. 
 
 MsrO 
 
 rip o 
 
 Al O 
 
 MnO. 
 
 SO.. 
 
 
 
 
 
 
 ^Wi 
 
 * e 2 u 3- 
 
 Ai 2*-'3' 
 
 
 
 Good wine bottles, Souvigny . 
 
 6o'00 
 
 3'IO 
 
 
 
 22-30 
 
 
 
 4'OO 
 
 8-00 
 
 I '20 
 
 
 
 St. Etienne . 
 
 60*40 
 
 3-20 
 
 BaO 
 0-90 
 
 20-70 
 
 0-60 
 
 3^0 
 
 10-40 
 
 
 
 
 
 Epinac 
 
 59-60 
 
 3-20 
 
 
 
 18-00 
 
 7-00 
 
 4-40 
 
 6-80 
 
 o'40 
 
 PA 
 
 0-40 
 
 Good Champagne bottle . 
 
 58-40 
 
 9-90 
 
 I -80 
 
 1 8 -60 
 
 
 
 8-90 
 
 2'IO 
 
 
 
 
 
 Bottle glass, Follembray . 
 
 61-35 
 
 2'8o 
 
 2'OI 
 
 24-66 
 
 
 
 5'5I 
 
 3-67 
 
 
 
 
 
 Montplaisir . 
 
 66*04 
 
 2-83 
 
 2-82 
 
 22-88 
 
 
 
 278 
 
 2-65 
 
 
 
 
 
 French bottle, attacked by wine 
 
 52-40 
 
 
 
 4-40 
 
 32-10 
 
 
 
 6 -00 
 
 S'lO 
 
 
 
 
 
 English do., do. ... 
 
 49-00 
 
 7-25 
 
 2'OO 
 
 2475 
 
 2'OO 
 
 lO'OO 
 
 4-10 
 
 trace 
 
 
 
 Good English wine bottle . 
 
 59-00 
 
 lO'OO 
 
 I-70 
 
 19-90 
 
 0-50 
 
 7-00 
 
 i -20 
 
 
 
 
 
 Do. at Paris Exhibition . 
 
 53-25 
 
 4-25 
 
 
 
 25-5 
 
 2-OO 
 
 i 
 
 ;-o 
 
 
 _ 
 
 Swedish bottle, ineted with) 
 fluor-spar J 
 
 55-20 
 
 6-99 
 
 2-8 5 
 
 15-40 
 
 I -08 
 
 3-6o 
 
 >. 
 
 II'OO 
 
 279 
 
 ^ 
 
 F 
 1-75 
 
 Bottle from Siemens, Dresden . 
 
 63-91 
 
 7-05 
 
 
 
 14-52 
 
 
 
 
 ^^- 
 
 13-97 
 
 
 o-55 
 
 Water bottle, bad 
 
 69-55 
 
 13-61 
 
 O'4I 
 
 15-09 
 
 0-42 
 
 o-33 
 
 0-42 
 
 
 
 
 Do., attacked by water 
 
 70-12 
 
 13-01 
 
 0-42 
 
 14-94 
 
 0-38 
 
 o-39 
 
 X 
 
 0-37 
 
 -s 
 
 
 
 
 
 Do., corroded . . . 
 
 72-63 
 
 14-86 
 
 
 
 9-92 
 
 
 
 1 
 
 2 
 
 07 
 
 
 
 trace 
 
 Dull window pane . . 
 
 69-37 
 
 2I'II 
 
 
 
 7^4 
 
 
 
 I 
 
 55 
 
 
 
 0*40 
 
 Opaque glass 
 
 73^4 
 
 I6-54 
 
 
 
 7-85 
 
 
 
 I 
 
 59 
 
 
 
 0-38 
 
 Opalescent mirror glass 
 
 7370 
 
 I7-I8 
 
 
 
 6-53 
 
 
 
 I 
 
 89 
 
 
 
 070 
 
 Spotty window glass 
 
 66-47 
 
 5-6i 
 
 18-79 
 
 5'6o 
 
 
 
 3 
 
 10 
 
 
 
 
 
 Lime-Alumina Glass. Pelouze has attempted the production of an alumina-glass 
 without arriving at results of importance. Korschelt recommends the production of a 
 white glass from alumina, silica, and lime. As raw materials he takes the kaolin of 
 Meissen (consisting of 77 per cent, silica, 18 per cent, alumina, and 5 per cent, water) 
 along with a calc-spar free from iron burnt lime. Quartz is added only if the kaolin 
 does not contain sufficient silica. The mixture is regulated so that it consists of 55-67 
 silica, 10-18 alumina, and 15-35 lime. A mixture of 100 parts Meissen kaolin and 41 
 parts burnt lime would, e.g., contain 55-2 per cent, silica, 14-2 alumina, and 30*6 per 
 cent. lime. The lime of the mixture can be partially or entirely substituted by baryta 
 or magnesia. Magnesia makes the mixture less fusible but permits of the use of 
 magnesian limestones, dolomite, &c. 
 
 Phosphatic Glass, obtained from fused calcium phosphate, is recommended for vessels 
 which have to come in contact with hydrogen fluoride. 
 
 Solubility of Glass. Whilst Boyle (1664) and Margraf were of opinion that 
 earth could be produced from pure water by continued distillation, Kunkel (1744) 
 and Scheele and Lavoisier (1770) were aware that glass is more or less dissolved 
 by water. Glasses rich in alkali become damp on exposure to the air, gradually lose 
 their lustre, become semi-transparent, and have sometimes an iridescent surface. 
 The same phenomena occur if glass has been placed for a long time in water or 
 moist earth: the water extracts the alkalies, the surface loses its compactness and 
 exfoliates. According to Hausmann, a glass thus decomposed had the following com- 
 position : 
 
SECT, v.] GLASS MANUFACTURE. 597 
 
 SiO* A1 2 3 . CaO. MgO. FeO. Na 2 0. K,O. Hj.0. 
 
 Undecomposed part 59-2 ... 5-6 ... 7*0 ... 1*0 ... 2*5 ... 217 ... 3*0 ... 
 
 Decomposed surface 48-8 ... 3-4 ... 11-3 ... 6*8 ... 11-3 ... ... ... iy* 
 
 The decomposition by water increases rapidly with the rise of temperature. Griffith 
 found that on slow ebullition water extracted from flint glass 7 per cent. ; the solution 
 contained no lead. 
 
 According to Pelouze two samples of glass of the following compositions : 
 
 L II. 
 
 SiO, . . . . . 72-1 ... 77-3 
 
 CaO .... 15-5 ... 6*4 
 
 Na/) .... 12-4 ... 16-3 
 
 when powdered and boiled in water, lost, I., 10 per cent.; and II., 32 per cent. The 
 solution contained basic silicate and always a little sulphate. Powdered glass on 
 exposure to the air slowly absorbs carbon dioxide and at once exerts an alkaline 
 reaction with litmus paper. Benrath digested 16 parts powdered glass for three days 
 and obtained in the solution 0*193 parts of the following composition : 
 
 Si0 2 . CaO. Na.jO. A1 Z O 3 . SO S . Ca 2 . 
 
 Glass used . 76*27 ... 6*09 ... 16*38 ... 0*63 ... trace 
 Kesidue . 28*43 47'39 O'i8 ... 24*00 
 
 Here a strongly basic alkaline silicate had been extracted. When Daubree treated 
 glass with superheated steam under pressure it was completely resolved into silica, 
 Wollastonite (CaSi0 3 ), and alkaline silicate. 
 
 Emmerling shows that the loss of weight of a glass vessel by the action of liquids 
 depends on the time of boiling, the size of the surface wetted, its condition, the 
 composition and the concentration of the solution. The speed of evaporation is not 
 essential. The composition of the glasses examined was 
 
 a. &. c. d. 
 
 Si0 2 . . . 73*79 ... 72*69 ... 74*14 ... 79*57 
 
 A1 2 $ . . 0*58 ... 0*63 ... 1*15 ... 0*35 
 
 Fe 2 0, . . 0*68 ... 0*97 ... 0*68 ... 0*24 
 
 MnO . . . 0*32 ... 0-54 ... 0*49 
 
 CaO . . . 8*61 ... 9*20 ... 6*94 ... 7*18 
 
 MgO . . . 0*12 ... 0*34 ... 0*24 ... 0*18 
 
 Na,O . . 13-94 ... 12*83 ... 15*07 ... 3*45 
 
 K^O . . . 0-60 ... 1*77 ... 0*60 ... 8*04 
 
 98-64 98-97 99*31 99*01 
 
 In experiments with glass flasks containing 600 to 700 c.c. of the first sort of glass, 
 using 400 c.c. of the liquid in question and replacing the water lost by evaporation, 
 there was found on boiling with pure water in the first hour a decrease of weight 
 of 3*9 milligrammes; in the second, 2*7 milligrammes, and during the following twenty- 
 eight hours losses of 2*5 to 1*5 milligramme. Hydrochloric acid at 1 1 per cent, dissolved 
 in the first hour 4-2 and 5*3 milligrammes ; in the following only 0*9. Hydrochloric acid 
 of 0*2 to 3 per cent, dissolved scarcely anything. The action increases thus both with 
 greater dilution and with greater concentration ; 0*008 per cent, nitric acid counteracts 
 the solvent power of water ; i per cent, dissolved 3 milligrammes. Sulphuric acid from 
 0*25 to 25 per cent, dissolves hourly about 3*8 milligrammes, and i per cent, oxalic 
 acid dissolves o'i and 0*2 milligramme. Alkaline liquids attack glass especially 
 readily. 
 
 From these researches it appears that in accurate work no new glass vessels should 
 be used, that liquids should be boiled in them for as short a time as possible. Alkaline 
 solutions, even if dilute, should not be heated in glass vessels. 
 
598 CHEMICAL TECHNOLOGY. [SECT. v. 
 
 Kreusler calls attention to analytical errors which may be occasioned by the 
 alkaline reaction of glass. In order to determine the behaviour of different sorts of 
 glass with water, glass tubes were fixed in the necks of small boiling-flasks containing 
 about 50 c.c. of water in such a manner that on boiling they might act as reflux 
 condensers. The contents of the flasks were then titrated and the result calculated for 
 nitrogen (in determinations of ammonia), and in caustic alkali. For 1000 square 
 centimetres of surface attacked the result was hourly, if calculated for the first 
 two to three hours : 
 
 Thuringian glass, I . 24/0 
 
 ,, 2 . 3-2 
 
 Bohemian combustion tube 0*3 
 
 Fusible potash glass 0*5 
 
 calculated in milligrammes nitrogen. On the basis of the entire duration of the 
 experiment the loss was reduced in the first two cases respectively to 9-5 and 2*04 
 milligrammes nitrogen. With the other two kinds of glass the result was not altered. 
 According to the experiments of Stass, glasses rich in silica and free from alumina 
 stand best. A glass of the following composition totally resisted the attacks of acids 
 and dilute alkalies : 
 
 Si0 4 . K S 0. NU..O. CaO. 
 
 77 - o ... 77 ... 5' io*3 
 
 Weber and Wiebe show that glass intended for the manufacture of thermometers 
 should contain as alkali only soda, or only potash. To test the resistance of glass 
 Weber exposes the articles to the fumes of hydrochloric acid. Good glasses when 
 dried should show no coating. 
 
 Devitrification. As far back as 1727 Reaumur observed that glass exposed for 
 some time to a temperature at which it softens but does not melt becomes dull, opaque, 
 and of a milky white. Opinions still differ on the cause of this phenomenon. Dumas 
 and Peligot hold that definite silicates crystallise out of the glass, leaving the rest as a 
 kind of mother liquor. Glasses rich in silica are most easily devitrified. 
 
 Coloured Glasses. Combustion tubes used in organic analysis sometimes take a 
 fine red colour. If glass is coated with a mixture of copper oxide and some adhesive 
 matter, and ignited, it takes up copper, but remains colourless. On heating in hydrogen 
 or any other reducing glass it becomes a fine red. More beautiful is the " copper 
 ruby " obtained by fusion. If glass is melted with i per cent, copper oxide, on adding 
 2 per cent, of tin or i| per cent, forge-scales, there is obtained a glass which is colour- 
 less or merely greenish, but if it is heated to the point of softening it suddenly takes 
 an intense red, the well-known colour of old church windows. Copper ruby contains 
 0*42 to o'66 of metallic copper. If the proportion is increased glass takes up 6-75 
 per cent, copper as a maximum and then becomes opaque. 
 
 Hematinon. This is a glass resembling that found in the Pompeiian excavations, 
 and mentioned by Pliny. It posesses a beautiful red colour, between that of vermilion 
 and of minium, is opaque, harder than ordinary glass, bears a high polish, and has 
 a sp. gr. = 3-5. The colour is lost by melting, and by no addition can be recovered. 
 The glass contains no tin or cupreous oxide as a colouring matter. Von Pettenkofer 
 assimilated to this glass by melting together silica, lime, burnt magnesia, litharge 
 soda, copper-hammerings, and smithy scales. A part of the silica in the mixture is 
 decomposed by means of boric acid, and a mass is obtained which, when ground and 
 polished, exhibits a dark red colour of great beauty. Pettenkofer gave to this glass 
 the term astralite, from the beautiful shotte- colour of blue or dichromatic tint shim- 
 mering throughout the mass. 
 
 By a somewhat similar process we obtain Aventurine. 
 
 Aventurine Glass. Aventurine or avanturin glass was formerly made only in the 
 
SECT, v.] GLASS MANUFACTURE. 599 
 
 Island of Murano, near Venice, but is now prepared throughout Germany, Italy, 
 Austria, and France. It is a brown glass mass in which crystalline spangles of metallic 
 copper according to Wohler (of cuprous oxide according to Von Pettenkofer) appear 
 dispersed. Fremy and Clemandot have produced a glass similar to aventurine glass, 
 and which consisted of 300 parts glass, 40 parts cuprous oxide, and 80 parts 
 copper scale. The Bavarian and Bohemian glass houses produce an aventurine glass 
 rivalling the original. Von Pettenkofer has prepared aventurine glass direct from hema- 
 tinon by mixing sufficient iron-filings with the molten mass to reduce about half the 
 copper contained. Pettenkofer surmises, and with good reason, that aventurine glass 
 is a mixture of green cuprous oxide glass with red crystals of cuprous silicate, these 
 complementary colours giving the brown tint. This glass is also well imitated by 
 melting a mixture of equal parts of ferrous and cuprous oxides with a glass mass. 
 The cuprous oxide appears after a long annealing as a separate crystalline red 
 combination, while the ferrous oxide is lost in the green colour it imparts to the glass. 
 Pelouze found that by freely adding potassium chromate to the glass materials 
 spangles of chromium oxide were separated. He termed this glass chrome-aventurine ; 
 it has been employed by A. Wachter in the glazing of porcelain. 
 
 The production of gold ruby glass was known to Neri (1612) but it was first brought 
 under full control by Kunckel. According to the researches of Miiller and Knapp, 
 glass dissolves only a small proportion of metallic gold ; 20 milligrammes of gold are 
 sufficient to give a uniformly fine colour to i kilo, of lead glass ; other glasses are less 
 readily treated. If the glass is cooled quickly, the metallic gold is like copper in a 
 colourless state, and on reheating changes into the coloured variety. 
 
 Glass with a mixture of fine silver oxide or silver chloride, coated over with 
 clay and water and heated in a muffle, takes a fine yellow colour. According to 
 Bontemps this sometimes takes place in the cold. Metallic silver dissolves in glass, 
 which takes yellow or orange shades. From 8 to 92 milligrammes metallic silver ore, 
 metallic lead, and antimony oxide do not impart any colour to glass. 
 
 Ferric oxide, known commercially as blood-stone, ochre, or red chalk, is also used to 
 impart a red colour. Yellow and topaz-yellow are obtained by means of potassium 
 antimoniate or glass of antimony, silver chloride, silver borate, and by silver sulphide. 
 Uranium oxide imparts a green-yellow. Blue is obtained from cobalt oxide, more 
 seldom by means of copper oxide. Green results from the addition of chromium 
 oxide, copper oxide, and ferrous oxide. Violet is obtained from manganese oxide 
 (braunite) and saltpetre ; black, from a mixture of ferrous oxide, copper oxide, braunite, 
 and cobaltous oxide. A beautiful black results from iridium sesquioxide. 
 
 Alkaline poly sulphides turn glass a fine red. Glass coloured yellow with sulphur is 
 especially adapted for windows, glass shades, &c., for protecting sensitive objects from 
 light. Pelouze considers that the reason why many glasses turn yellow on prolonged 
 exposure to light is that sulphates present are reduced to sulphides. He observes that 
 selenium gives glass an orange-red colour. Uranium gives glass a green or a yellow 
 colour. It is, like sulphur, often used where the chemically active rays of light are to 
 be excluded. Reference is made to the fluorescent properties of light-green uranium 
 glass. As fluorescent substances convert the chemical light-waves into the luminous, it 
 is very probable that the utility of uranium glass depends not upon the optical characters 
 of yellow colours, but upon their transforming power. 
 
 Venetian mosaic glasses have been examined by H. Schwartz. Their composition 
 was 
 
6oo 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. v. 
 
 
 A 
 
 
 
 a 
 
 
 
 
 
 
 
 , 
 
 
 Jl 
 
 g 
 
 "a 
 
 o 
 
 3 
 
 1 
 
 
 
 t 
 
 I 
 
 
 
 p 
 
 
 
 1 
 
 fi 
 
 
 
 i 
 
 i 
 
 1 
 
 
 
 & 
 
 E 
 o 
 
 m 
 
 ' 
 
 3 
 P< 
 
 6" 
 
 Si0 2 
 
 Sb 2 5 
 
 5174 
 7-9I 
 
 48-80 
 13-47 
 
 46-95 
 1-42 
 
 52-68 
 
 62-48 
 
 58-00 
 S'47 
 
 29-20 
 4-00 
 
 57'20 
 3-55 
 
 52-08 
 3-I5 
 
 52^0 
 
 52-20 
 
 As 2 0. 
 
 
 
 9-96 
 
 7-84 
 
 
 
 2-33 
 
 i;95 
 
 0-66 
 
 4^9 
 
 2-35 
 
 0-56 
 
 PbO 
 
 I9-94 
 
 9-99 
 
 18-98 
 
 16-52 
 
 9-86 
 
 674 
 
 
 5'95 
 
 9'53 
 
 4-04 
 
 5 '37 
 
 Cu 2 O 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 2-25 
 
 O'22 
 
 
 
 
 
 CuO 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 (2-51) 
 
 
 
 O'lO 
 
 0-31 
 
 CoO 
 
 
 
 
 
 
 
 
 
 O'2O 
 
 
 
 
 
 0-51 
 
 0-09 
 
 0-15 
 
 0-36 
 
 Fe,0, 
 
 0-70 
 
 0-70 
 
 0-63 
 
 0-30 
 
 I'49 
 
 0-60 
 
 2-02 
 
 0-90 
 
 0-76 
 
 I -60 
 
 1-55 
 
 MnO 
 
 0-42 
 
 
 
 
 
 
 
 
 
 
 
 
 
 4'49 
 
 
 
 
 
 
 
 Mn 2 0, 
 
 
 
 
 
 0-15 
 
 0-15 
 
 
 
 trace 
 
 2-91 
 
 (5-02) 
 
 5-28 
 
 11-50 
 
 1 1 '45 
 
 CaO 
 
 4-42 
 
 11-85 
 
 3-80 
 
 4-50 
 
 2-99 
 
 5-20 
 
 1-50 
 
 7-64 
 
 
 7-61 
 
 7-30 
 
 MgO 
 
 0-91 
 
 1-45 
 
 1-40 
 
 0-81 
 
 
 
 0-38 
 
 0-36 
 
 I-J2 
 
 0-86 
 
 0-86 
 
 1-98 
 
 Ka.,0 
 
 2-26 
 
 
 9-99 
 
 IOT5 
 
 7-85 
 
 9-96 
 
 1-41 
 
 5-26 
 
 9'59 
 
 1-41 
 
 4-90 
 
 Na.0 
 
 I2-83 
 
 13-12 
 
 5-43 
 
 4-69 
 
 1375 
 
 9-29 
 
 
 9-39 
 
 8-57 
 
 11-89 
 
 8-54 
 
 Au 
 
 
 
 
 
 trace 
 
 
 
 
 
 O'lO 
 
 
 
 
 
 
 
 
 
 Bo 2 a and loss 
 
 
 
 
 
 1-29 
 
 2-40 
 
 
 
 i-93 
 
 
 
 
 
 
 
 
 
 
 
 
 101-13 
 
 100-52 
 
 lOO'OO 
 
 lOO'OO 
 
 98-82 
 
 lOO'OO 
 
 90-90 
 
 98-92 
 
 99-39 
 
 99-17 
 
 100-41 
 
 Physical Properties of Glass. Glass is so completely impervious that according to 
 Quincke no ponderable quantities of carbon dioxide or of hydrogen escape through it 
 even in 17 years and at pressures ranging from 40 to 126 atmospheres. The sp. 
 gr. of alkali lime-glasses varies from 2-4 to 2-6; that of alkali-lead glasses from 3-0 
 to 3'8, and that of thallium glasses may reach 5-625. The sp. gr. is increased by 
 cooling. Thus, according to Eiche flint glass after cooling has a sp. gr. of 3-610. 
 The linear expansion of glass on heating from o to 100 is 0-0007 to 0-0009. 
 
 The power of glass to refract light seems to decrease where the proportion of silica 
 and alumina is high, and to increase very considerably with a rising percentage of lead. 
 
 Glass is a bad conductor of heat and electricity, though glasses which are rich in 
 alkali, and consequently hygroscopic, are not good insulators. A glass from Glasgow, 
 distinguished for its insulating power, has the following composition : 
 
 Si0 2 . K 2 0. Na 2 O. PbO. CaO. MgO. Fe s 3 . 
 
 58-45 ... 9-24 ... 374 ... 28-02 ... ox>6 ... 0-05 ... 0-47 
 
 In consequence of its low conductivity for heat, glass breaks readily if suddenly 
 cooled or heated, especially if it has been imperfectly annealed. If too suddenly 
 cooled the external layers contract whilst the internal mass is still hot and soft, so 
 that on further refrigeration a tension occurs which shatters the glass on the slightest 
 contact, and sometimes apparently even without any external cause. This is the case 
 with the so-called glass tears and with Bolognese phials, small flasks which have been 
 cooled rapidly and which burst if scratched with a grain of sand. 
 
 Glass is flexible only in fine threads, so that it can even be felted. In larger pieces 
 it is always brittle. The statement that glass becomes flexible by prolonged burial in 
 the earth and resumes its brittleness on exposure to the air seems incredible. Glass 
 is tolerably resistant to steady pressure. Glass tubes bear an internal pressure of 120 
 kilos, per square centimetre. The resistance of glass globes is somewhat less. 
 According to other experiments the crushing strain of flint-glass is 1700 kilos, and 
 the resistance to rupture 180 kilos; that of bottle-glass is 200 kilos. A small glass 
 of i millimetre thickness of glass resisted, according to Cailletet, an external pressure 
 of 460 atmospheres, but burst with an internal pressure of 140 atmospheres. 
 
 Raw Materials used in Glass Making. These are : i. Silica, viz., quartz, for very 
 pure glass ; for other kinds sand of varying quality, or pulverised flint stones. For very 
 pure glass the silica ought to be free, or very nearly so, from iron ; in some cases the 
 
SECT, v.] GLASS MANUFACTURE. 601 
 
 ferric oxide adhering to the quartz or mixed with the sand is removed by hydro- 
 chloric acid; while the sand is always first ignited, and in some instances previously 
 washed, to remove clay, marl, humus, &c. Ordinary glass is made with coarser 
 materials ; the sand is not required to be so pure, as when it contains lime, chalk, or 
 clay, it renders the mass more fusible. 
 
 2. Boric acid is sometimes used as a substitute for a portion of the silica. It 
 increases the fusibility of the glass, imparts to it a high polish, and prevents devitrifi- 
 cation. It is employed as borax or as boro-calcite, a native boric acid. 
 
 3. Potassa and soda are used in a variety of forms, the former chiefly as potash 
 (potassium carbonate), or partly lixiviated wood-ash. 
 
 Not so large a quantity of soda is required as of potash; 10 parts of sodium 
 carbonate correspond to 13 parts of potassium carbonate. Recently the soda has been 
 used in the form of Glauber's salt ; in this case, so much carbon is added to the siliceous 
 earth and Glauber's salt as will reduce the sulphuric acid of fehe sodium sulphate to 
 sulphurous acid, and the carbon to carbon monoxide. The silicic acid then easily 
 decomposes the sulphurous acid of the sulphite. To 100 parts of Glauber's salt 
 (anhydrous) 8 to 9 parts of coal are measured. An excess of carbon is detrimental, 
 as a large quantity of sodium sulphide is formed, which imparts a brown tint to 
 the glass. 
 
 4. The lime used in glass-manufacture must be free from iron. It is generally 
 employed as marble or chalk, either raw or burnt. To 100 parts by weight of sand, 
 20 parts by weight of lime are added. In the Bohemian manufacture the lime is 
 employed as neutral calcium silicate, Wollastonite, Si0 3 Ca. Instead of lime, strontia 
 and baryta can be used, the former as strontianite (SrCo 3 ), the latter as witherite 
 (BaC0 3 ). Fluor-spar (CaFl 2 ) and sodium aluminate were at one time used in making 
 milky or semi-opaque glass. 
 
 5. Lead oxide is employed in most cases in the form of minium or peroxide, 
 giving up some of its oxygen to form a lower oxide, and purifying the glass. The 
 lead gives the glass a higher specific gravity, greater brittleness, transparency, and 
 polish. It must be free from copper and tin oxides, the former imparting a green 
 colour, and the latter an opacity to the glass. White-lead is as efficacious as red-lead, 
 provided no heavy -spar be present. 
 
 6. Zinc oxide is always added as zinc- white. When the colour is not of importance, 
 zinc-blende with sand and Glauber's salts may be used. 
 
 7. Bismuth oxide is only added in small quantities in the preparation of glass for 
 optical instruments. Bismuth may be employed either as oxide or nitrate. 
 
 The natural silicates are only employed alone in the manufacture of bottle-glass; 
 some of the preceding additions are requisite in clear glass manufacture. 
 
 Bleaching. Coloured glass as it occurs in the first processes of manufacture may have 
 the colour disguised by mechanical mixture with white glass, or the colour may be 
 discharged by chemical agents. Such agents are usually braunite, arsenious acid, 
 saltpetre, and minium or red-lead. 
 
 i. Braunite Mn0 2 , has long been used as material for glass-clearing. This oxide 
 of manganese is, however, used only in small quantities ; too much imparts a violet or 
 amethyst-red colour to the glass ; while an excessive amount renders the glass dark- 
 coloured and opaque. The violet-coloured glass is generally prepared with manganese 
 silicate by the addition of braunite to colourless glass. The action of braunite in 
 clearing glass or rendering it colourless has been variously explained. It may be 
 considered that there arises in the molten glass the colours complementary to white, 
 that is, the green from iron silicate and the violet from manganese silicate. This 
 view is supported by the experiments of Kb'rner, who obtained a colourless glass 
 from a mixture of red and violet glasses; and further by those of Luckow, who 
 
602 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. v. 
 
 obtained a colourless glass by the melting together of a glass strongly tinted red 
 by manganous oxide with copper oxide. The glass-blowers of the Bavarian Forest 
 assert that a rose-red quartz there found is equalled by no other quartz in the 
 production of the best crystal or clear glass. Von Fuchs says that this quartz 
 contains i to 1*5 per cent, of titanium oxide, which, similarly to Braunite, effects 
 the chromatic neutralisation. Kohn employs for this purpose nickel or antimony 
 oxide. Zinc oxide has lately been employed to remove or mask the green colour of glass, 
 also imparting a higher polish. 2. Arsenious acid effects the removal of colour by 
 chemical means only from glass containing carbon or iron silicate : in glass containing 
 carbon 
 
 Arsenious acid, As 2 3 
 
 Carbon 30 
 
 in glass containing ferrous oxide : 
 Ferrous oxide, 6FeO 
 Arsenious acid, As 2 3 
 
 give 
 
 give 
 
 j Arsenic, As 2 , 
 (Carbon monoxide, 3CO; 
 
 ( Ferric oxide, 3Fe s O 3 , 
 
 (Arsenic, As 2 . 
 
 The arsenious acid is reduced by the carbon and ferrous oxide at a dull red heat, 
 while the arsenic is volatilised. 
 
 3. Saltpetre is added chiefly as Chili-saltpetre or sodium nitrate. In the manu- 
 facture of lead-glass (flint-glass) lead nitrate is substituted for the sodium nitrate. 
 Barium nitrate has recently been employed to discharge the colour of glass; its 
 action is similar to that of arsenious acid. 
 
 4. That minium serves to render glass colourless has already been noted. 
 Chambland states that glass may be whitened by forcing through it while molten a 
 stream of air. 
 
 Utilisation of Refuse Glass. The materials of glass manufacture are never melted 
 alone, but always with nearly the third part of prepared or finished glass. For this 
 purpose, pieces of broken glass, flaw glass, the hearth droppings, and the glass remain- 
 ing adherent to the blowers' pipes may be utilised serving a purpose in the manufac- 
 ture of glass similar to the rags in paper-making. Thus there is only a very small loss 
 of materials. At each re-melting, however, a portion of the alkali of the fragmentary 
 glass is volatilised, and must be replaced by the addition of an alkaline salt. 
 
 A proportion of old broken glass, known in the trade as " cullet," is added to tfie 
 materials for glass-making, sometimes to the extent of one-third. 
 
 Melting Vessels. The vessels in which the glass is melted are placed immediately upon 
 Fig. 402. Fig. 403. Fig. 404. 
 
 Fig. 405. 
 
 the hearth, and are made of difficultly-fusible clay and powdered old broken melting-pots. 
 They are usually 0-6 metre in height, the walls being 9 to 12 centimetres thick. They 
 
SECT. V.] 
 
 GLASS MANUFACTURE. 
 
 603 
 
 are dried in a temperature of 12 to 15, and then placed in a chamber heated to 30 to 
 40. After remaining about a month, the vessel is put into the tempering or annealing 
 oven, heated to 50 ; it is next removed to the ordinary melting-oven, and gradually 
 heated to the melting-point of glass, at which it remains for three to four hours. When 
 a new pot is first used for glass-melting, the alkaline constituents of the glass act upon 
 the clay, forming a rich clay glaze or glass, which, if allowed to mix with the ordinary 
 glass, would be highly detrimental. Consequently broken glass and refuse are first 
 melted in the vessel, and the glaze imparted, termed technically the lining, is a sufficient 
 protection to the glass in after-practice. The shape of the melting vessels varies. For 
 melting with wood or gas the conical form, Fig. 402, is employed. When coal is used 
 as fuel, the vessel takes the covered form, Fig. 403. Fig. 404 represents a rather 
 peculiar form ; the glass coristi tuents are melted in A, the clear molten glass passing by 
 the aperture in the central wall into B. The glass in B is thus always free from glass-gall 
 or impurities, which remain behind in A. In the manufacture of looking-glasses, large 
 quadrangular vessels, Fig. 405, are employed for refining purposes. 
 
 The Glass-furnace. The glass-ovens are respectively: i. The melting-oven. 2. 
 The tempering- or annealing-ovens, used in the after-manufacture. The melting-oven 
 can only be made of fire-proof clay. It is built of a mixture of white clay and burnt 
 clay of the same kind. Ordinary mortar and cements are useless for this purpose, on 
 account of their fusibility; therefore the same clay as is used for building is also 
 used for binding. The oven must be built on dry ground ; if built on damp ground 
 it is difficult to maintain the lower parts at a constant heat, requiring a larger supply 
 of fuel. The arch is closed with a single piece of fire-proof clay, weighing 800 to 
 1000 cwts. After building, the oven is dried for four to six months at a temperature 
 
 Fig. 406. 
 
 of 12 to 15. A low fire is then lighted, and the temperature gradually increased for 
 about a month until the oven is fit for actual work. The arch is further covered 
 with massive backstones, and these again are covered to a thickness of 5 to 6 inches 
 with a lime-mortar. When much in use, and if not built of very good clay, an oven will 
 not remain in working order for longer than i^ to if year ; but if fire-clay is used, and 
 only easily-fusible lead-glass is manufactured, the oven may last for four to five years. 
 The oven contains six or eight to ten melting-pots, which must all be raised to the 
 same temperature. Further, the melting-pot is placed over half the fire-room. The 
 annexed woodcut, Fig. 406, is a ground plan of a complete oven. Fig. 407 is a sec- 
 
604 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT, v 
 
 tion showing the melting-ovens and work-holes ; Fig. 408 a vertical section through 
 the length of the oven ; Fig. 409 a vertical section of the breadth. In the ground 
 plan, Fig. 406, o o is the flue ; c c c are the melting-pots ; n n, pots containing glass 
 in another stage of preparation ; d d d, the work-holes ; b b, the banks ; i i, warm- 
 Fig. 407. 
 
 ing and cooling ovens ; h h, tempering ovens ; e e, the breast-walls ; ff, the splint 
 walls ; 1 1 are small hearths to increase the heat in the tempering-oven when 
 repaired. In Fig. 407 I is the flue ; y y are blocks of stone bearing the wooden 
 frame-work, z z, on which the wood used as fuel is placed to dry. Fig. 408 shows 
 the bank, ff, on which the melting-pots, h h h, stand ; over these pots are the work- 
 
 holes ; n n are the side chambers. In Fig. 409, b b is the key-stone ; c d are the banks ; 
 g the flue, although in most glass-ovens there are no flues. The flame from the fuel 
 burning in both grates, m m, Fig. 408, after heating the melting-oven, passes by the 
 tempering-rooms, and finally to the chimney-stalk. 
 
 Siemens' gas-oven has lately found extensive use. At the Paris International 
 Exhibition of 1867 this oven obtained the gold medal. It consists of two parts, the 
 generator, Fig. 410, and the melting-oven, Fig. 411. These parts are separate, and 
 can be 30 or more metres from each other, being connected by a large gas-pipe. The 
 fuel, brown coal, turf, stone coal, or wood, is placed in a generator at A, Fig. 410, 
 and falls on the sloping grid, 0. The gas, a mixture of carbonic oxide and nitrogen, 
 ascends at a temperature of 150 to 200, and flows out of the generator by a large 
 
SECT. V.J 
 
 GLASS MANUFACTURE. 
 
 605 
 
 pipe, F, 4 to 5 metres in height, and is conveyed thence by a horizontal pipe to the 
 melting oven. The upper chambers of the melting-oven are similar to those of the 
 usual ovens. P P are the melting-pots. The gas first passes into the first system 
 
 Fig. 409. 
 
 of regenerators, the stones of 
 which are raised to a red 
 heat, and passes thence to 
 the melting-room, where it 
 meets with air heated in like 
 manner. The products of 
 combustion then pass to the 
 second regenerating system, 
 the stones of which are cold 
 until heated by the passing 
 gases. The waste gas is finally 
 conducted to the chimney- 
 stalk. When stone-coal is 
 used in the generator, lead- 
 glass may be melted in the 
 oven in open vessels without 
 reduction. The saving of fuel 
 in comparison with the old 
 system is about 30 to 50 
 per cent. 
 
 For manufacturing bot- 
 tles, &c., on the large scale, 
 the continuous glass-melting 
 tank of Siemens (Figs. 74 
 to 76, pp. 67, 68) has proved 
 satisfactory. The mixture, 
 as it is introduced at c, 
 sinks to the bottom as it 
 melts, and thereby drives 
 upwards another portion of 
 glass, which has become 
 stiffer by cooling at the 
 bottom and in consequence 
 specifically lighter. This 
 portion, again, after being 
 exposed for a time to the 
 heat of the surface and 
 thoroughly fused, becomes 
 specifically heavier than 
 the subjacent masses, and 
 must consequently descend. 
 This behaviour of the glass, 
 determined by the differ- 
 ences in specific gravity, 
 in conjunction with the hy- 
 drostatic pressure exerted 
 
 by the glass-makers standing on the stage, M, occasions an undulatory movement of 
 the glass towards the work-places in the direction of the arrows. This ascending 
 and descending movement and continuous progress cause the glass to be thoroughly 
 
 Fig. 411. 
 Section I.-II. 
 
6o6 
 
 CHEMICAL TECHNOLOGY. 
 
 melted through, so that the particles of glass are thoroughly purified if they come to 
 be worked. As the floating fenders dip rather deep into the mass, the glass must 
 sink almost to the bottom, and consequently devitrification is avoided. The generator- 
 gases and the air issue separately through the channels, y and I, the flame strikes across 
 through the furnace, the products of combustion escape through the opposite channels 
 to the heat accumulators, R, and arrive in the chimney through the channels, x. By 
 this arrangement of the channels, g and I, the glass in the free space of the tank before 
 the fenders receives the greatest heat. 
 
 The tank-furnaces, Figs. 410 and 411, which F. Siemens uses in the glass-works 
 at Neusattel-Ellbogen, approximate to the ordinary glass-furnace for melting-pots, 
 as it can be used for the most different kinds of glass. The tank is divided into 
 four compartments by bridges placed crossways. The raw materials, introduced 
 separately, are mixed at G, and from here passed into the furnace through the 
 apertures, n. The regenerators, JR, forming the base of the furnace, 2 metres 
 broad and 2^75 long (between which is the access- vault, T), are connected by the 
 channels, s, with the lateral channels, &\ from which gas and air arrive into the furnace 
 through the channels, g and L The round tank is divided into four compartments 
 for four different kinds of glass, by the bridges, z, which intersect each other at right 
 angles. 
 
 The refrigerations of these bridges run into the common ventilating chimney, V, 
 which is carried through the vault of the furnace. Its lower part is divided by an 
 iron cross, about i metre high, in such a manner that the ventilation of each bridge is 
 kept apart from the others to above the level of the glass. This is to prevent mutual 
 
 Fig. 412. 
 
 Section A. B. 
 
 <... 
 
 v "i"- 1 :^-'^^:^'^--: .^ 
 
 Explanation of Term. 
 Einlegtbiikne .... Introductory Stage. 
 
 disturbance in the aeration of the several bridges. The s bottom and the side walls of 
 the tank are provided with air -refrigerators, e, which open into the four small chimneys, 
 f, in such a manner that, in case of accident, one compartment may not affect the 
 others. The air-channels of the bridges are separated by large stones of correspond- 
 ing shape, which rest upon a number of small pillars. 
 
 Before each of the 28 work-places, a, there floats in the half -melted mass a refining- 
 boat, which renders continuous working possible. Every working place is occupied by 
 
SECT. V.] 
 
 GLASS MANUFACTURE. 
 
 607 
 
 a workman and an assistant, so that the work is carried on in twenty working hours 
 daily in two 1 2-hour shifts. Each work-place produces hourly 50 bottles. 
 
 Latterly, F. Siemens proceeds on the supposition that large spaces are necessary 
 for producing a great heat. Hence he has built a tank-furnace which, as shown in 
 Figs. 412-414, has a very lofty vault. 
 
 The furnace of Boetius is most widely used in Germany next to that of Siemens. 
 
 Glass-melting. At the temperature of a glass furnace, 1200 to 1250, the melted 
 glass is a thin liquid, like a thick solution of sugar. This condition is very important 
 for the purification of the glass, since all substances which cannot dissolve in the mass 
 separate out, either on the surface or at the bottom. In this state, further, glass can 
 be cast. At a red heat glass becomes very extensible and flexible, conditions on which 
 the mechanical treatment of glass depends. Two pieces of red-hot glass can be made 
 to unite by being simply pressed together. In spinning glass the material is brought 
 to its utmost degree of extensibility, so that it can be manipulated upon a wheel. 
 The glass thread of Brunfaut's, at Vienna, which is now used for producing wadding, 
 feathers, veils, nets, &e., has, according to the measurements of Fr. Kick, a diameter of 
 o'oo6 to o'oi2 millimetre. It is, therefore, rather finer than the single cocoon thread. 
 
 Not until the furnace has reached its highest temperature is the cullet and then the 
 mixture put into the crucibles, an operation performed in three or four lots. 
 
 Fig. 413- 
 
 Section C. D. 
 
 Melting the Glass Material. When the temperature of the melting-oven has reached 
 the required degree, the material first frits together and is then melted. The oven 
 must be heated equably throughout At the melting-point the siliceous earth combines 
 with the potash, soda, lime, alumina, lead oxide, &c., to form glass. The substances 
 not taken up form a scum, known as glass-gall, upon the molten glass, which is removed 
 by the aid of iron shovels. This scum is generally composed of sodium sulphate and 
 chlorides of the alkalies. The progress of the melting process is from time to time 
 ascertained by removing a sample of the glass by the help of an iron rod terminating in 
 a flat disc in fact, a large flat spoon. 
 
 Clear-melting. When the mass is well molten it is "cleared" that is, maintained 
 for some time at such a temperature that the glass remains in a thinly fluid condition. 
 During this period the uncombined substances settle to the bottom of the melting vessel, 
 the air-bubbles disappear, and the glass-gall still remaining is volatilised or separated. 
 At the commencement of the melting the disengagement of the gases from the molten 
 
6o8 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. v. 
 
 mass causes an advantageous agitation, by which the several constituents of unequal 
 specific weight and different composition become well mixed. After the disengagement 
 of the gases the lower part of the melting vessel is at a lower temperature than 
 the upper part ; consequently the molten glass is well stirred with the iron ladles or 
 
 Fig. 414. 
 Section E. F. 
 
 " poles." Lastly, a piece of either arsenious acid, damp wood, raw turnip, or any 
 other water -containing substance, is introduced to the bottom of the vessel on an 
 iron rod, the end in view being the violent agitation of the molten glass by the steam 
 evolved. 
 
 If the mixture consists of soda, calcium carbonate and silica, the process is 
 
 NaC0 
 
 = Na 2 Ca(Si0 3 ) 2 + 2C0 2 . 
 
 But if salt-cake is employed 
 
 2Na 2 S0 4 + C + 2SiO 2 = 2Na 2 Si0 3 + C0 2 + 2S0 2 . 
 
 In the course of melting the sodium silicate is transformed with the calcium carbonate 
 and the silica as follows : N a;! SiO 3 + CaC0 3 + Si0 2 = Na 2 Ca(Si0 3 ) 2 + C0 3 . 
 
 Cold-stoking. After the completion of the clearing follows the cold-stoking that is, 
 the lowering the temperature of the oven till the glass attains a tough fluid consistency 
 requisite before it can be blown. The glass remains at this temperature, 700 to 800 
 C., during the rest of the manufacture. 
 
 The length of the several processes is as follows : 
 
 Melting 
 Clearing 
 Blowing 
 
 10 to 12 hours. 
 4 to 6 
 
 IO tO 12 ,. 
 
 so that five to six meltings can be effected in a week. 
 
 Defects in Glass. It is extremely difficult to prepare glass perfectly free from 
 blemish. The principal defects are streaking, threading, running unequally, or 
 
SECT, v.] GLASS MANUFACTURE. 609, 
 
 dropping, stoning, blistering, and knotting. Streaking follows from heating the glass 
 unequally, another consequence of which is the threading or the formation of the strise, 
 by glazing, into coloured threads, generally green. By dropping is understood the 
 lumps or globules formed in the glass by the glazing of the clay cover of the melting 
 vessel, and its combination with the volatilised alkalies, the crude glass thus formed on 
 the cover dropping into the molten glass contained in the vessel. Blistering is a common 
 result of the imperfect clearing of the glass from air bubbles. Lastly, knotting, another 
 common defect, results from uncombined grains of sand taken up in the glass ; the 
 small particles of the oven and melting vessel detached during the melting similarly 
 giving rise to stoning. Other defects, such as the imperfect combination of the mate- 
 rials, arising from carelessness or inability of the workman, need not here be noticed. 
 
 Various Kinds of Glass. Glass is divided according to its composition or method 
 of manufacture into 
 
 I. Glass free from Lead. 
 
 A. Plate glass, a. Window glass : 
 
 a. Boiled glass. 
 /3. Crown glass. 
 b. Plate glass : 
 
 a. Blown plate glass. 
 /3. Cast plate glass. 
 
 B. Bottle glass. 
 
 a. Ordinary bottle glass. 
 
 b. Medicine and perfumery glass. 
 
 c. Glass for goblets, drinking glasses. &c. 
 
 d. Water pipes and gas tubes. 
 
 e. Retort glass. 
 
 C. Pressed or stamped glass. 
 
 D. Water glass. 
 
 II. Glass containing Lead (Flint Glass). 
 
 A. Crystal glass. 
 
 B. Glass for optical purposes. 
 
 C. Enamel. 
 
 D. Strass. 
 
 III. Coloured and Stained Glass. 
 
 Plate and Window Glass. Glass melted in muffles or vessels is manufactured as- 
 plate glass or as crown glass. Plate glass, as its name implies, is formed in large or 
 small plates ; window glass is generally either ordinary bottle glass or a finer glass of a 
 whiter colour. Recently, thick has taken the place of thin glass for windows, but the 
 colour is hereby considerably increased. That window glass should be prepared cheaply 
 is an essential point ; consequently crude materials are employed crude potash and 
 soda, wood ash, salt cake, ordinary sand, and broken glass from the warehouses, 
 &c. Plate or window glass is generally composed of 100 parts sand, 30 to 40 parts 
 crude calcined soda, 30 to 40 parts calcium carbonate. Instead of the soda may 
 be substituted an equivalent quantity of salt cake. Benrath (1869) found in 
 several kinds of plate glass the following constituents : 
 
 Silicic acid . . . 7071 .. 71*56 ... 73'ii 
 
 Soda i3'35 I2 '97 13*00 
 
 Lime 13-58 ... 13-27 ... 13-24 
 
 Alumina and ferric oxide . . 1*92 ... 1*29 ... 0*83 
 
 99-56 ... 99'O9 100-18 
 
 2 Q 
 
6io 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. v. 
 
 Tools. The tools ordinarily used by the glassblower in the preparation of plate and 
 crown glass are the following : 
 
 The pipe or blow-tube, Fig. 415, is an iron pipe 1*5 to i - 8 metre in length, 3 
 to 5 centimetres thick, and i centimetre interior diameter, a is the mouth-piece, made 
 
 Fig. 415. 
 
 3ig. 416. 
 
 fig. 417. 
 
 
 Fig. 418. 
 
 Fig. 4 1 9. 
 
 so as to turn easily between the lips, c is a hollow handle from 0-3 to 0-5 metre in 
 length. 6 is the part attached to the glass. 
 
 The handle or hand irons are rods i to i "3 metre in length, used to transport 
 the hot vessels, &c. The marbel, Figs. 416 and 417, is a piece of wood with semi- 
 globular indentations, which serve as matrices for the glass to be taken up on the 
 blower's pipe. The whip, Fig. 41 8, is a block of wood, hollowed so as to form a long neck 
 to the soft semi-molten glass ; it is also used to remove the glass from the pipe. 
 Fig. 419 is the shears used for trimming the molten glass, and to cut openings during 
 the blowing of various articles. 
 
 Window glass is manufactured as crown glass or as rolled glass. 
 
 Crown Glass. Crown glass is the oldest kind of window glass. It is formed in the 
 manufacture as a disc of glass, generally of about 6 inches in radius from the periphery 
 to the centre knot left by the glassblower's pipe, technically termed the bull's-eye. 
 The largest discs are scarcely 64 to 66 inches, from which a square plate of 22 inches 
 only can be cut, the bull's-eye interfering with the cutting of a larger size. In the 
 preparation of this glass three workmen are employed ; the first takes so much molten 
 glass on the end of a pipe as will serve for a single disc, and passes pipe and glass to the 
 second workman, the blower. He blows the glass into a large globe or ball, which, 
 when finished, he hands to a third workman, the finisher, who opens the globe and 
 forms the sheet or pane. The labour is divided in detail in the following manner : 
 The first workman receives the warm pipe, thrusts it into the vessel of molten glass, and 
 turns it steadily round until he has collected upon the end a knob of glass of sufficient 
 size. The weight of this knob is generally 10 to 14 Ibs. The first workman by means 
 of the marbel imparts somewhat of a spherical form to the solid glass ball, which is 
 now taken in hand by the blower, who by turning and shifting the glass about, at the 
 same time blowing through the tube, perfects the hollow spheroid. The glass has by 
 this time cooled considerably, and with the pipe is therefore returned to the oven, the 
 tube of the pipe being fastened in a fork or hook in the ceiling of the oven. As the 
 globe of glass is gradually heated the weight of the rod causes it to flatten out, and it is 
 removed by the finisher as a disc of nearly molten glass. He places the tube in the 
 cavity of the whip, and by a series of dexterous movements perfects the shape, enlarges 
 the disc if required, or in some cases makes a larger disc by removing the partially 
 
:SECT. V.] 
 
 GLASS MANUFACTURE. 
 
 611 
 
 flattened sphere from the oven, opening the bottom with a maul or iron rod, and causing 
 the glass to take the form of a disc by means of the centrifugal force resulting from 
 a rapid rotary motion of the rod. Finally, the discs are separated from the pipe by the 
 help of a drop of cold water, and are next placed in an annealing oven, to the number 
 of 150 to 200, to cool. The finished plates are cut to the required size ; the centres or 
 bull's-eyes serve for the making of strass and for other purposes. 
 
 Sheet Glass, or Cylinder Glass. Rolled or sheet glass is made by cutting a glass 
 cylinder or roll throughout its length, and beating or rolling it out flat on a table. It 
 is for this reason termed sheet glass. Usually this sheet glass is used for ground glass, 
 and is further separated into ordinary sheet or roll glass and fine sheet glass, the latter 
 having larger dimensions. 
 
 The preparation of sheet glass is one of the most difficult processes of glass manu- 
 facture ; it may be considered as consisting of two operations 
 
 1 . The blowing of the roll, or cylinder ; and 
 
 2. The flattening. 
 
 After the molten glass has cleared, and attained the barely fluid consistency before 
 mentioned, the workman inserts his pipe into the mass, and by turning manages to 
 accumulate on it a globe of 
 glass, during the time blowing 
 into the tube to keep it clear 
 of the molten glass. The 
 glass now takes the form , 
 Fig. 420. By continued mani- 
 pulation in the marbel, and 
 by blowing, the enlarged forms, 
 b and c, and finally d, are 
 obtained. The glass has by 
 this time cooled, and is taken 
 to the oven to be re-heated. 
 When this is effected, the work- 
 man, by means of his tools, 
 by a continued rotation of 
 glass, and by blowing, brings 
 the globe to the shape repre- 
 sented by /. He then opens 
 out the bottom of this form 
 with a maul-stick, and obtains 
 the cylinder e, which is sepa- 
 rated from the pipe by drop- 
 ping a little cold water upon 
 the neck, o, joining the two. 
 The removal of this neck is 
 next effected by means of a 
 red-hot iron rod, which also 
 serves to open the cylinder 
 throughout its length as shown 
 by A. 
 
 After a great number of these cylinders have been blown, the operation being 
 generally continued for three days, the opening into plates is commenced. The cylinders 
 are placed in an oven termed the plate-oven, shown in ground plan in Fig. 421, con- 
 sisting of two chambers, one the heating room, C, and the other the tempering or 
 
612 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. v. 
 
 annealing room, D. in the passage B, the heated glass rolls or cylinders, a a a, are 
 suspended upon two iron rods, where they are maintained at a certain heat. The most 
 important part of the plate-oven is the platten, C, made of a well-rammed fire-clay. 
 A similar plate, D, is placed in the annealing room. When sufficiently heated, the 
 cylinders are brought to the flattening table, c, Fig. 422, where they are speedily opened 
 
 Fig. 421. 
 
 Fig. 422. 
 
 out m the manner shown in the woodcut. A workman stationed at d, Fig. 421, receives 
 the Hat panes of glass, and leans them against the iron bars, s s, in the annealing room, 
 whence; having gradually cooled during four or five days, tney are removed to be sorted 
 and packed. 
 
 Plate Glass. Plate glass is either blown or cast. The manufacture is very similar 
 to that of table glass just described. The materials are in great part the same as those 
 employed in the manufacture of fine white glass. This branch of glass manufacture is 
 most strikingly illustrative of the rapid growth of the industry during the last ten or 
 twenty years. Formerly plate glass was esteemed an article of luxury, whereas now 
 it is that most generally used for workshop windows, carriages, showrooms, &c., and 
 for windows of private residences. It far surpasses in transparency and elegance the 
 small panes formerly used. By the Glass Jury of the International Exhibition of 
 Paris of 1867, it was surmised that before ten years had elapsed plate glass would be 
 that most generally in the market. The blowing of plate glass is effected with the 
 same tools as the blowing of table glass ; and the cylinder is obtained in a similar 
 manner. The lump of glass taken by the blower on his pipe from the melting vessel 
 weighs about 45 Ibs., from which a plate of 1-5 metre in length and i to n metre 
 breadth by i to n centimetre thickness is obtained. But the chief method of 
 making plate glass is by casting. Cast plate glass is always made from pure materials, 
 and may be considered as a sodium-calcium glass free from lead. Potassium-calcium 
 glass is far more expensive, being almost a colourless glass. In England, Belgium, 
 and Germany the raw materials used in manufacturing cast plate glass are sand, 
 limestone, and soda, or salt cake. 
 
 Benrath (1869) found in English (a) and in German () plate glass: 
 
 Silica . 
 
 Soda 
 
 Lime .... 
 Alumina and oxide of iron 
 
 Sp. gi. 
 
 76-300 
 
 16-550 
 
 6-500 
 
 0-650 
 
 1 00 -000 
 
 2-448 
 
 78750 
 
 13-000 
 6-500 
 1-750 
 
 lOO'OOO 
 
 2-456 
 
SECT, v.] GLASS MANUFACTURE. 613 
 
 The following description of casting the plates is mainly founded upon the method 
 pursued at St. Gobain and Ravenhead. The manufacture is included in 
 
 1. The melting and clearing. 
 
 2. The casting and cooling. 
 
 3. The polishing ; including 
 a. The rough polishing. 
 
 /3. The fine polishing. 
 
 y. Finishing. 
 
 The Melting and Clearing. The melting and clearing vessels are of very different 
 form and size. The first is a conical vessel surmounted by a cupola having three 
 apertures, making an angle of 120 with each other. The clearing pans are small, 
 wide, and low vessels. These vessels are never in the same oven. After the materials 
 are melted, which is effected in sixteen to eighteen hours, the molten mass is poured into 
 the clearing vessels. The impurities are then removed with a large copper ladle, this 
 process occupying about six hours. During the clearing the excess of soda is volatilised. 
 When the glass is sufficiently cleared the casting commences. The vessel containing 
 the molten glass is taken up by a crane and swung to the casting table, this table 
 or mould being on a level with the 
 
 cooling or annealing oven. The casting Fig. 423. 
 
 table consists of a large polished metal 
 plate, Fig. 423, in the French works of 
 copper or bronze, 4 metres long, 2*25 
 metres wide, and 1 1 to 1 8 centimetres 
 thick. The plate at St. Gobain weighs 
 55,000 Ibs. and cost 100,000 francs 
 {^4000). In England the plates are 
 of cast-iron, 25 centimetres thick, 5 
 metres in length, and 2 '8 metres wide. 
 In order that the glass plate shall be 
 of equal thickness, a bronze or cast- 
 iron roller passes over the surface on 
 guides of the thickness required. The 
 metal plate is first warmed to prevent 
 the sudden cooling of the glass. The operation of casting includes 
 
 a. The conveyance of the pan to the table. 
 
 b. The cleansing of the plate and the pan. 
 
 c. The casting and conveyance of the plate to the annealing room. 
 
 The cooling room has two fire-places and three glass tables. The temperature is at 
 first that of the glass plate introduced. So soon as three plates are placed in the oven, 
 all the openings are closed, and the glass left for a day to cool. The cooled glass 
 plate is taken out of the annealing oven to the cutting room, laid on a cloth-covered 
 table, and cut to size with a diamond. 
 
 Polishing. The glass plate is cut into tablets. The under side of the plate, where 
 it has been in contact with the table, is smooth, while the upper surface is wavy, and 
 requires to be polished. This is effected by fastening the plate or tablet to a bench 
 with plaster-of-Paris, and grinding the upper surface smooth with some sharp powder ; 
 or another plate is caused by machinery to move above the former in such a manner 
 that the surfaces of both are ground smooth. The ground plates are then removed 
 to the polishing table, where a similar process is gone through, but with a finer 
 powder. Finally, when placed upon the finishing table, only the finest powder and 
 leathern pads are employed. By grinding and polishing, the glass sometimes loses half 
 
614 CHEMICAL TECHNOLOGY. [SECT. v. 
 
 its weight in thickness. Suppose a plate-glass manufactory to produce 400,000 square 
 feet of glass annually, there will be with this amount of glass, weighing about 16,000 
 cwts., a loss of 8000 cwts., corresponding to 2700 cwts. of calcined soda, and a money 
 value of more than ^1000. 
 
 /Silvering. After polishing, each glass tablet intended to make a looking-glass is 
 silvered, or, more correctly, coated on one side with an amalgam of tin. In the 
 preparation of this amalgam tinfoil is used, but it must be beaten from the finest tin, 
 and possess a surface similar to that of polished silver. The art of silvering is simple, 
 and merely requires dexterity. The glass plate having been thoroughly cleansed from 
 all grease and dirt with putty powder and wood ash, the workman proceeds to lay a 
 sheet of tinfoil smoothly upon the table, carefully pressing out with a cloth dabber all 
 wrinkles and places likely to form air bubbles. He spreads over it a quantity of 
 mercury, taking care that all parts are equally covered, and then the glass plate is 
 pushed gently on to the surface, commencing at one edge. A glass plate of 30 to 40 
 square feet requires 150 to 200 Ibs. of mercury, although the amalgam is not so 
 thick as a sheet of the finest paper. The glass is allowed to remain for twenty-four 
 hours. It is then removed to a wooden incline similar to a reading desk to allow of 
 the excess of mercury draining off. As the amalgam gradually sets, the incline is 
 increased till finally the plate reaches the perpendicular, when the process is finished, 
 and the mirror removed to the store room. 
 
 Silvering by Precipitation. The former method of coating the glass with tin- 
 amalgam obtains its name of silvering by analogy only : the true process of silvering i& 
 the following, patented in 1844 by Mr. Drayton: 32 grammes of silver nitrate are 
 dissolved in 64 grammes of water and 16 grammes of liquid ammonia, adding to the 
 filtered solution 108 grammes of spirits of wine of 0*842 sp. gr., and 20 to 30 drops of oil 
 of cassia. Call this fluid No. i. Another fluid (No. 2) is prepared by mixing i volume 
 of oil of cloves with 3 volumes of spirits of wine. The workman places the glass plate 
 upon a table, carefully levels it, and floods it to a depth of 0*5 to i centimetre with 
 fluid No. i . He then precipitates the silver by adding 6 to 1 2 drops at a time of fluid 
 No. 2 until the whole of the surface is covered. For every square foot of glass 9 deci- 
 grammes of silver nitrate are required. Liebig recommends an ammoniacal solution 
 of fused silver nitrate to which 450 c.c. of soda-lye of 1*035 sp. gr. are added. 
 The precipitate thrown down is dissolved by means of ammonia, the volume being 
 increased to 1450 c.c., and by water to 1500 c.c. This fluid is mixed shortly before 
 application with one-sixth to one-eighth of its volume of solution of sugar of milk, 
 containing 10 parts by weight to i of sugar of milk. The glass is flooded with this 
 fluid to about half an inch in depth ; reduction soon sets in, and the glass becomes 
 thickly coated, i square metre of glass plate requires 2*210 grammes of silver. The 
 plate is then dried, cleaned, and polished. Lowe employs silver nitrate, starch-sugar, 
 and potash A. Martin, silver nitrate, ammonia, and tartaric acid. 
 
 Platinising. According to the researches of Dode, platinum may be used for coat- 
 ing plate-glass. In France, Creswell and Tavernier have already brought platinised 
 mirrors before the public. Hitherto platinum had been used in ornamenting porcelain, 
 and the glass plates are prepared in a similar manner, the metal being burnt in, as it 
 is termed. The platinum is precipitated from its chloride by oil of lavender, the 
 chloride being spread equally over the glass with a fine-haired paint-brush. The 
 plate is then placed in a muffle. Cheapness is a prominent feature of this process ; 
 as by it all faulty glasses can be very easily repaired, those by the old methods being 
 thrown aside as useless. In Paris the lids of boxes and fancy articles are largely 
 manufactured from platinised glass. 
 
 For gilding glass there is employed a dilute solution of sodium aurate, which is 
 reduced by means of a saturated solution of ethylene in alcohol. 
 
SECT. V.] 
 
 GLASS MANUFACTURE. 
 
 Bottle Glass. Bottle glass includes all kinds of glass made into vessels for holding 
 fluids. It is made from common green glass, from fine white glass, and from crystal 
 glass. Medicine bottles, &c., are made from common green glass ; tumblers, or drinking 
 glasses, from fine white glass ; and crystal glass is employed for the same articles, but 
 selling at a higher price. 
 
 The materials for ordinary bottle glass are sand, potash or soda, basalt, &c. For 
 medicine glass the materials must be free from iron, and still purer for articles of 
 white glass. In the manufacture of bottle glass no considerable amount of care is 
 required, the desiderata being strength and sufficient resistance to the action of 
 ordinary acids. The processes of melting and annealing are conducted in the ordinary 
 manner. The analyses of several glasses gave the following results : 
 
 Silicic acid 
 
 Potash 
 
 Soda 
 
 Lime . . 
 
 Alumina . 
 
 Iron oxide ; 
 
 Manganese oxide 
 
 7471 
 
 1574 
 877 
 0'43) 
 0-14 [ 
 
 0'2I ) 
 lOO'OO 
 
 2-47 
 
 74-66 
 
 4-32 
 
 1 1 -01 
 
 9-I3 
 
 lOO'OO 
 
 2-48 
 
 75 "94 
 
 1 00 'GO 
 
 2-47 
 
 74-37 
 12-48 
 
 3 '42 
 9-02 
 
 071 
 
 lOO'OO 
 
 2-30 
 
 74-26 
 
 14-06 
 
 8-60 
 
 2-52 
 
 0-38 
 
 0-18 
 
 100 -oo 
 2-40 
 
 The details of the several processes of bottle glass manufacture are, after the 
 making of the rough shape out of the tough fluid glass, so various that only single 
 examples can be given. We will select the ordinary wine bottle. The glass blower, 
 taking some molten glass on his pipe, turns and moulds it into the shape of a, Fig. 424. 
 By continued blowing the enlarged form, b, is obtained; this form, still more enlarged, 
 as at c, is placed in the mould, d. The workman now blows sharply into the incipient 
 bottle, the glass filling out the mould and producing the sharp curve of the shoulder of 
 the wine bottle. The rod or puntili, e, is now introduced, and a firm footing given by 
 pressing in the bottom of the bottle. While the blower prepares a new bottle, the 
 assistant places that already formed in the annealing oven. In the making of flasks 
 
 Fig. 425- 
 
 Fig. 426. 
 
 and retorts the flask tongs, Fig. 425, are employed, the neck being allowed to remain 
 straight, as at a, Fig. 426, to form a flask, or bent, as at b, to make a retort. The 
 manufacture of a beaker will be readily understood from Figs. 427 and 428, A, B t C, 
 being the method of producing a globular body, and a, 6, c, a beaker with nearly per- 
 pendicular sides. Glass-tubing is drawn out as shown at Fig. 429. Glass rods are 
 similarly made, but without blowing. 
 
6i6 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. v. 
 
 Pressed and Cast Glass. Pressed or cast glass comprises the many cheap glass 
 ornaments, and indeed, ornamental glass-work of all kinds, now so general. The tall, 
 narrow-mouthed chimney ornaments are thus made by being blown into engraved brass 
 moulds, instead of into plain moulds as in the case of the bottle. Cup-shaped articles 
 
 Fig. 428. 
 
 Fig. 428. 
 
 Fig. 429. 
 
 are made with molten glass pressed between a concave and convex surface, the surplus 
 glass escaping at some point purposely arranged. As a rule, the objects taken from 
 the moulds require but little polishing. 
 
 Hardened Glass. The invention of hardened glass by De la Bastie (1875) excited 
 a greater sensation than do most novelties, but the sanguine hopes entertained of its 
 usefulness have not been fulfilled. The process consists essentially in a rapid, uniform 
 cooling of the glass when in a soft state after it has been already blown or otherwise 
 shaped. By this means it acquires such a physical character that it withstands blows or 
 other external attacks better than ordinary glass which has been cooled slowly in the 
 usual manner. Besides the oil-baths used by De la Bastie must be noticed the 
 process of hardening with cold, solid objects, e.g., plates of clay, proposed by Fr. Siemens. 
 
 The glasses to be hardened, after they have been heated to softness, are subjected to 
 a sudden chill, which may be effected by very various means. In consequence of the 
 rapid cessation of the state of softness there sets in a state of molecular tension to 
 which the hardened glass is indebted for its peculiar properties. The glass to be 
 hardened must be well melted and clarified, and should contain neither unmelted 
 quartz grains nor glass gall. Articles of badly clarified, streaky glass generally burst 
 in the hardening bath. The external form and the thickness of the vessels have a 
 great influence upon the results. Vessels with thick sides have to be hardened in very 
 thick baths, and the chilling must not be too sudden. The temperature which must 
 be given to the objects is that at which the glass softens, and they are plunged into 
 the bath either directly after being blown or after being re-heated. At the first 
 introduction of the process it was supposed that the chemical composition of the 
 hardening bath was a point of importance, only certain oils and fats being suitable and 
 elementary substances being excluded. It was soon found that the physical properties 
 only of the hardening baths were of importance. One and the same quality of glass 
 can be tempered equally well in different baths, but the temperature must be higher 
 or lower according to their conductivity. Baths which conduct heat well require a 
 higher temperature than those which have a low conductive power, if the chilling 
 effect is to be alike in both. The first group of substances selected for tempering 
 baths comprise liquids and solids which are liquefied at the required temperature, e.g.. 
 
SECT, v.] GLASS MANUFACTUKE. 617 
 
 mixtures of fats, oils, glycerine, paraffine, hydrocarbons, saline solutions, and easily 
 fusible alloys. Pure water is excluded. Glasses which have been hardened in an oil 
 bath at 70 burst if plunged into water of the same temperature. Baths composed of 
 fats have proved most satisfactory, the better, in general, the longer they have been in use. 
 
 The objections to fat baths are their costliness, their combustibility and the fact that 
 their temperature is continually raised by the introduction of hot objects. 
 
 In the case of solid bodies the hardening is effected simultaneously with shaping. 
 In liquid baths the softened objects, especially plates, lose their shape more or less. 
 For the goodness of hard glass it is important that both the heating and the chilling 
 are effected with the utmost possible rapidity. It is also important that the glass 
 should be heated to the highest point at which it can be lifted out of the furnace. 
 
 A hardened glass plate of 16 centimetres in length, 12 centimetres in breadth, and 
 5 millimetres in thickness bore the fall of a weight of 200 grammes from the height of 
 4 metres. A similar plate of common glass was broken by a weight of 100 grammes 
 falling a height of 30 to 40 centimetres. Hardened glass also bears pressure to about 
 four times the extent of common glass. But the same tension which gives to hardened 
 glass its elasticity and solidity is the cause of explosive disruptions if suddenly liberated 
 at any one point. Articles which are exposed to shocks or blows on their sides or 
 corners should not be hardened e.g., plates, beakers, capsules, &c. A hardened glass 
 plate which bears the fall of considerable weights if struck in the middle breaks easily 
 by a blow on its edges, especially from a narrow instrument. In common glass only a 
 few splinters may be broken off, so that the vessel may still be fit for use, whilst 
 hardened glass is completely shattered. Hence the process cannot be recommended 
 for bottles, drinking glasses, &c. : whilst window panes or plates, which are mostly ex- 
 posed to blows on the surface, where they are most resistant, are much better fitted 
 for hardening. The great objection to hardened glass is that there is no means of 
 distinguishing good from bad articles until they come into actual use. Hence the 
 original confidence of the public has been succeeded by justifiable distrust. For 
 laboratory apparatus hardened glass is quite unfit, and for domestic purposes it is at 
 least very doubtful. Hence it has almost entirely disappeared from commerce. 
 
 Soluble Glass, Water Glass. By water glass is understood a soluble alkaline silicate. 
 Its preparation is effected by melting sand with much alkali, the result being a fluid 
 substance, first observed by "Van Helmont in 1640. 
 
 It was made by Glauber in 1648 from potash and silica, and by him termed fluid 
 silica. Von Fuchs, in 1825, obtained what is now known as water glass by treating 
 silicic acid with an alkali, the result being soluble in water, but not affected by atmo- 
 spheric changes. 
 
 The various kinds of water glass are known as 
 
 Potash water glass. 
 Soda ,, 
 
 Double 
 Fixing 
 
 Potash water glass is obtained by the melting together of pulverised quartz or 
 purified quartz sand 45 parts, potash 30 parts, powdered wood charcoal 3 parts, the 
 molten mass being dissolved by means of boiling in water. The solution contains 
 much potassium sulphide, which is removed by boiling with copper oxide. The 
 addition of carbon assists in reducing part of the carbonic acid to carbonic oxide, 
 which disappears during the melting. Soda water glass is prepared with pulverised 
 quartz 5 parts, calcined soda 23 parts, carbon 3 parts ; or, according to Buchner, 
 with pulverised quartz 100 parts, calcined Glauber's salts 60 parts, and carbon 15 to 
 20 parts. Double water glass (potash and soda water glass) is prepared, according to 
 Doebereiner, by melting together quartz powder 152 parts, calcined soda 54 parts, 
 
618 CHEMICAL TECHNOLOGY. [SECT. v. 
 
 potash 70 parts ; according to Yon Fuchs, from pulverised quartz 100 parts, purified 
 potash 28 parts, calcined soda 22 parts, powdered wood charcoal 6 parts. It is 
 further obtained by melting potassium and sodium tartrate, 
 
 4 H 4 6 + 4 H 2 0, 
 
 with quartz ; from equal molecules of potassium and sodium nitrate and quartz ; from 
 purified tartar and sodium nitrate and quartz. It is more fusible than the foregoing. 
 For technical purposes a mixture of 
 
 3 volumes of concentrated potash water glass solution, 
 2 soda 
 
 is employed. By the name of fixing water glass, Yon Fuchs designates a mixture of 
 silica well saturated with potash water glass and a sodium silicate, obtained by melting 
 together 3 parts of calcined soda with 2 parts of pulverised quartz. It is used to fix 
 or render the colours permanent in stereochromy. 
 
 The kind known commercially as prepared water glass is obtained by boiling the 
 powdered water glass with water ; and the solution, as found in the market, is known 
 as of 33 and 66, the difference being that the first 100 parts by weight contain 33 
 parts by weight of solid water glass and 67 parts by weight of water. It therefore 
 follows that in solutions of 40 and 66, the water is proportioned as 60 and 34 parts 
 respectively. Acids, with the exception of carbonic acid, decompose water glass solu- 
 tions, separating the silica as a gelatinous substance ; it should, therefore, be kept in 
 vessels well protected from volatile acids. 
 
 Water glass is an important product in industry. It is used to render wood, linen, 
 and paper non-inflammable. The water glass of 33 is first mixed with double 
 its weight of rain-water, and is then treated with some fire-proof colouring 
 matter, as clay, chalk, fluor-spar, felspar, &c. The material to be rendered unin- 
 flammable is painted with the solution, and again with another coat after the first has 
 remained twenty-four hours to dry. Wood is thus preserved from being worm- 
 eaten, from incrustation of fungi, &c. Another industrial application of water 
 glass is as a cement ; in this it is equal to glue, and, indeed, is known as " mineral 
 glue." Chalk mixed with water glass forms a very compact mass, drying as hard as 
 marble; no chemical change is hereby effected; there is no conversion to calcium 
 silicate or potassium carbonate ; the hardening is entirely the result of adhesion. 
 Calcium phosphate treated with water glass acts similarly. Zinc-white and magnesia 
 lose none of their useful properties when mixed with water glass. Another im- 
 portant application of water glass is in the painting of stone and concrete walls, 
 and in the preparation of artificial stone. The latter, first made by Ransome, is 
 daily meeting with more extended application in England, India, and America. It 
 is prepared by mixing sand with sodium silicate to a plastic mass, which is pressed 
 into the required shape, and then placed in a solution of calcium chloride. By 
 this means calcium silicate is formed, and cements the grains of sand together, while 
 the sodium chloride is removed by repeated washings. As cement for stone, glass, 
 and porcelain, water glass is especially useful. It is also employed in the preparation 
 of xyloplastic casts, made of wood rendered pulpy by treatment with hydrochloric acid, 
 and afterwards impregnated with water glass. 
 
 Stereochromy. An interesting and important application of water glass is in the new 
 art of mural and monumental painting, termed by Yon Fuchs Stereochromy (a-repeos, 
 solid, and xP w M a > colour). In this method of painting the water glass forms the 
 foundation or binding material of the colour. There is first to be considered the 
 mortar or cement ground upon which the painting is to be executed. This ground 
 has to receive an under- and an over-ground. It is essential, of course, that the 
 fundamental groundwork should be of a stone or cement possessing every requisite 
 
SECT, v.] GLASS MANUFACTURE. 619 
 
 for durability. The next, or under-ground, is made with lime-mortar, and is allowed 
 to remain for some time to harden. When well dried, the water glass solution 
 is applied, and allowed to soak well into the interstices of the mortar. After the 
 under-ground has been thus prepared, the over-ground, or that to receive the painting, 
 is laid on. This consists of similar constituents to the under-ground, with the 
 exception that a good sharp sand is used, and the mixture treated with a thin lye 
 of calcium carbonate. This over-ground of fine cement being nicely levelled, and 
 having dried, it is thoroughly impregnated with water glass. When this is dry, the 
 painting is executed in water-colours. Nothing further is necessary than to fix these 
 colours, which is effected by a treatment with a fixing water glass. The colours 
 employed are : Zinc-white, chrome-green, chrome-oxide, cobalt-green, chrome-red 
 (basic lead chromate), zinc-yellow, iron oxide, cadmium sulphide, ultramarine, 
 ochre, &c. Vermilion is not employed, as it changes colour in fixing, turning to a 
 brown. Cobalt-ultramarine, on the contrary, brightens on the application of the fixing 
 solution, and is, therefore, a very effective colour. As a decorative art stereochromy 
 will doubtless attain great importance, the paintings being unaffected by rain, smoke, or 
 change of temperature. 
 
 Crystal Glass. Crystal glass includes all potash glass containing lead. Crystal 
 glass was first prepared in England. There are a few difficulties in manufacturing this 
 glass. The smoke from an anthracite coal fire is injurious to the pure colour of the 
 glass, so that the melting-pot is provided with a cover ; but this addition has the dis- 
 advantage that the temperature necessary to melt the glass cannot easily be ascertained. 
 A larger proportion of alkali must therefore be added, which deteriorates the 
 quality of the glass, rendering it liable to after-change. To prevent this as much as 
 possible, lead oxide is used to make the glass more easily fusible, and by this means a 
 beautifully clear, transparent glass results. The following table will give some idea of 
 the proportions of the materials : 
 
 Sand 300 
 
 Potash . . . . ..'*. . too 
 
 Broken glass . . 300 
 
 Minium . . ... 200 
 
 Arsenious acid 0-60 
 
 Manganese sesquioxide 0*45 
 
 The following mixture is used in the glass houses of Edinburgh and Leith : 
 
 Sand 300 
 
 Potash 100 
 
 Minium 150 
 
 Lead-glaze 50 
 
 and a small quantity of manganese sesquioxide (braunite) or arsenious acid. 
 
 To render the glass fluid, saltpetre is sometimes added, but in moderate quantities. 
 Dumas recommends sand 300, minium 200, dry potash 95 to 100. On the supposition 
 that there is no loss during melting, the mixtures contain : 
 
 Silica 57-4 57 
 
 Lead oxide 36*3 ... 36 
 
 Potash 6-3 ... 7 
 
 The whole melting process is concluded in twelve to sixteen hours. The glass is 
 treated in a manner similar to that already described, but is more easily worked. 
 Benrath (a) and Faraday (/3) found crystal glass by analysis to consist of : 
 
620 CHEMICAL TECHNOLOGY. [SECT. v. 
 
 j8. 
 
 Silicic acid SO'iS ... 51 '93 
 
 Oxide of lead 38-11 ... 33'28 
 
 Potash ii*6i ... i3'67 
 
 Alumina, &c. 0^04 
 
 99 '94 98-88 
 According to Benrath, normal crystal glass has the formula K 10 Pb 7 Si 36 84 (i.e., 
 
 Polishing. Crystal glass is either cast in brass moulds or is ground. Its hardness 
 admits of its taking a better polish than other glasses. The grinding wheel is of 
 cast-iron ; above the periphery is fixed a vessel containing water and fine washed sand, 
 which constantly drops upon the wheel, assisting in the cutting. The polishing wheel is 
 of wood, well served with pumice-powder and water. 
 
 Optical Glass. The preparation of good optical glass, especially of large dimensions, 
 is a matter of much difficulty. Transparency, hardness, a high refractive power with 
 perfect achromatism are all required, and must be obtained at the outlay of any amount 
 of labour. The glass must also be entirely homogeneous, else the light is not refracted 
 regularly; threads and streaks (striae) are the results of inequality, and it naturally 
 follows that, if these appear to the unassisted eye, they will seriously affect delicate 
 observations when high magnifying powers are used, as in telescopes and microscopes. 
 It is an error, however, to suppose that these irregularities arise from impurities ; they 
 are rather due to interruptions in heating and cooling, or to unequally heating and 
 cooling during manufacture. This must especially be evident in the case of waviness or 
 an undulating structure of the glass. Crown glass, free from lead, is not so liable 
 to faults as flint glass ; both these are employed for optical purposes. 
 
 The Rev. Mr. Harcourt's experimental researches as to the best optical glass, com- 
 municated to the British Association, at the recent meeting at Edinburgh, by Professor 
 Stokes, show fully what has been accomplished in preparing glass of this order. 
 Mr. Harcourt's researches were chiefly carried on with phosphates, combined in many 
 <jases with fluorides, and sometimes with tungstates, molybdates, and titanates, owing 
 to the difficult fusibility and pasty consistency of silicate glasses. The experiments 
 included glasses containing potassium, sodium, lithium, barium, strontium, calcium, 
 aluminium, manganese, magnesium, zinc, cadmium, lead, tin, nickel, chromium, lead, 
 thallium, bismuth, antimony, tungsten, molybdenum, titanium, vanadium, phosphorus, 
 fluorine, boron, and sulphur. The molybdic glasses first prepared were of a somewhat 
 deep colour, deteriorating with age ; but at length molybdic glass was obtained free 
 from colour, and permanent. Titanic acid gave results much superior to those obtained 
 with molybdic. Glass made with lead terborate agreed in dispersive power with 
 flint glass ; while a prism of this glass extends the red and blue ends of the spectrum 
 equally with a prism of one part by volume of flint glass with two of crown glass. Not- 
 withstanding the great difficulties arising from striae, Mr. Harcourt finally succeeded in 
 preparing discs of lead terborate and of titanic glass, 3 inches in diameter, almost 
 homogeneous. 
 
 It is well known that flint and crown glass form an achromatic combination. Hint 
 glass is very easily rendered fluid, conducing to the formation of striae. A variation of 
 the proportions of the constituent materials, though not producing effects visible to the 
 eye alone, will strongly striate the glass, rendering it unfit for optical purposes. The 
 constituents must be equally distributed throughout, and this is a great difficulty. The 
 oxide of lead, being of so much greater weight, sinks to the bottom, while the lighter 
 constituents float at the upper part of the melting vessel. Usually this is so much the 
 case that glasses of different specific gravities are obtained from the upper and lower 
 parts of the melting-pot. 
 
SECT. V.] 
 
 GLASS MANUFACTURE 
 
 621 
 
 Bontemps manufactures flint glass in the following manner -A glass mass is pre- 
 pared of 
 
 White sand . . . .... , IOO kilos. 
 
 Minium . . . . Io6 
 
 Potassium carbonate ..... 4 , 
 
 and placed over an anthracite or stone-coal fire in a small melting oven shown in Fig. 
 430 in vertical, and in Fig. 431 in horizontal section. The oven contains only one 
 
 Fig. 430. 
 
 Fig. 431. 
 
 covered melting vessel, B, standing on the bank, A 
 a a are the grate bars ; c an iron rake, enclosed in 
 a fire-clay cylinder, d, and resting upon the roller, 
 /. After about fourteen hours the mass becomes 
 equally fluid ; and a red-hot rake is introduced into 
 the vessel, by which the several layers of material 
 are intimately mixed. In about five minutes the 
 mass is sufficiently stirred ; the iron rod is then 
 removed, the clay cy Under remaining. This stir- 
 ring is effected several times without removing the clay cylinder ; and the glass is then 
 ready for blowing or casting. But for optical purposes it is, after the removal of the 
 clay cylinder, allowed to cool gradually during eight days in an annealing oven. The 
 most perfect pieces of glass are then cut from the interior of the mass. According to 
 Dumas's analysis of a sample obtained from Guinand, flint glass consists of 
 
 Silica . . . . . ' . ' " . . 
 
 Lead oxide 
 
 Lime . 
 
 Potash 
 
 Alumina, iron oxide, and manganese protoxide 
 
 42'S 
 43'5 
 
 o'S 
 117 
 
 1-8 
 
 lOO'O 
 
 The second kind of optical glass, crown glass free from lead, contains, according 
 to Bontemps: Sand, 120; potash, 35; soda, 20; chalk, 15; and arsenious acid, 
 i part. 
 
 The best optical glass now known is that used by Zeiss of Jena for the object-glasses 
 of his microscopes. 
 
 Strass. The imitation of precious stones is an interesting feature of glass manu- 
 facture, and in Egypt and Greece it was an art that attained to great perfection. All 
 precious stones, with the solitary exception of the opal, can be imitated artificially. The 
 chief constituent of these artificial gems is strass, or, as it was termed by Fontanier, 
 Mayence base ; and in France artificial gems are mostly known as Pierres de Strass. This 
 base is colourless, and may be considered as a borosilicate of the alkalies containing 
 lead oxide, this being in larger proportion than in flint glass. 
 
 Donault-Wieland found colourless strass by analysis to consist of : 
 
622 CHEMICAL TECHNOLOGY. [SECT. 
 
 Silica . 38-1 
 
 Alumina i'o 
 
 Lead oxide 53'o 
 
 Potash 7 -9 
 
 Borax 
 
 traces 
 
 Arsenious acidj 
 
 This analysis gives the formula (3K 2 0,6Si0 2 ) 4 3(3PbO,6Si0 2 ). 
 
 The various gems are imitated by the addition of colouring oxides, the whole of the 
 materials being ground to a fine powder, intimately mixed, and melted at a strong heat. 
 The imitation of the topaz is obtained by taking strass, 1000; antimony, 40; and 
 Cassius's purple, i part. The topaz can also be imitated with strass, 1000 ; iron 
 oxide, i part. The imitation ruby is obtained with i part of the topaz paste 
 and 8 parts of strass, the whole being melted together for thirty hours. A ruby of 
 less beauty is obtained with strass, 1000 ; manganese dioxide, 5 parts. A good emerald 
 can be prepared from strass, 1000 ; copper oxide, 8; chromium oxide, o - 2 part. The 
 sapphire is obtained from strass, 1000 ; pure cobalt oxide, 15 parts. The amethyst from 
 strass, 1000; manganese dioxide, 8; cobalt oxide, 5; Cassius's purple, 0-2. The 
 beryl or aqua, marina is imitated by strass, 1000 ; glass of antimony, 7 ; cobalt oxide, 
 0*4. The carbuncle by strass, 1000 ; glass of antimony, 500 ; purple of Cassius, 4; 
 manganese dioxide, 4 parts. Sufficient attention has not been paid to the mode in 
 which the colouring is effected by the metallic oxides ; nor have experiments been tried 
 with any definite result as to the employment of tungstic acid, molybdic acid, titanic 
 acid, chromic acid, and chromic oxide, &c. 
 
 Genuine rubies and sapphires, crystals of alumina with all the characteristics 
 chemical and optical of the natural stones have now been obtained artificially, though 
 of small size.* 
 
 Coloured Glass and Glass Staining. Coloured glass may be considered in two classes 
 that coloured as a whole, and that only partially coloured. The latter is prepared 
 with such metallic oxides as will impart to the glass very intense colour ; for instance, 
 cuprous oxide, cobalt, gold, and manganese oxides. This kind of glass is termed super- 
 fine, and is prepared in the following manner : Two melting vessels are placed in the 
 oven ; one contains a lead glass, the other the coloured glass. We will take as an 
 example glass coloured red with cuprous oxide, which if further oxidised imparts a 
 green colour to the glass. The glass blower dips his pipe first into the red glass ; and 
 collects a sufficient quantity to blow ; then he dips this into the white glass, and pro- 
 ceeds to form a cylinder or roll, as in the making of table glass. Superfine glass is 
 known as " outside " and " double," or " double layer." In the first case the workman 
 takes a lump of white glass upon his pipe and covers it with the coloured glass ; or, 
 in the second case, he takes up only a small quantity of white glass, then sufficient of 
 the coloured glass, and again more white glass. Red glass may be obtained with either 
 Cassius's purple, cuprous oxide, or iron oxide as the colouring ingredient. Cassius's 
 purple is used chiefly for ruby-red glass. It was long thought that ruby-coloured 
 glass could not be obtained with any other preparation than Cassius's purple, but 
 twenty-five years ago Fuss showed that gold chloride was effectual. If glass con- 
 taining salts of gold or cuprous oxide is cooled suddenly, the colour disappears ; 
 then if again gently warmed, not quite to softness, the colour suddenly reappears 
 in full splendour. This phenomenon occurs equally in atmospheres of oxygen, 
 hydrogen, and carbonic acid. In the preparation of cuprous oxide glass, lead glass 
 'is taken as a basis, to which 3 per cent, of the cuprous oxide is added. The 
 
 * In the artificial sapphire the blue colour has been obtained, in the absence of cobalt, by a 
 compound of chromium not yet examined. 
 
SECT, v.] GLASS MANUFACTURE. 623 
 
 drawback to the employment of the protoxide is the readiness with which it becomes 
 oxide, thus imparting a green colour to the glass. To prevent this change, iron filings, 
 rust, or tartar is added, or the glass is stirred with green wood. Copper glass, as 
 has just been said, is colourless on cooling, regaining its colour during the process of 
 annealing. Iron oxide, known commercially as blood-stone, ochre, or red chalk, is 
 also used to impart a red colour. Yellow and topaz-yellow are obtained by 
 means of potassium antimoniate or glass of antimony, silver chloride, borate, and 
 sulphide. Uranium oxide imparts a green-yellow. Blue is obtained from cobalt 
 oxide, more seldom by means of copper oxide. Green results from the addition of 
 chrome-oxide, copper oxide, and ferrous oxide. "Violet is obtained from manganese 
 oxide (braunite) and saltpetre ; black, from a mixture of ferrous oxide, copper 
 oxide, braunite, and cobalt oxide. A beautiful black results from iridium sesqui- 
 oxide. 
 
 For the production of Satin Glass, vessels blown of coloured glass are further blown 
 within a metal mould so as to display in a kind of relief depressed stripes, rows of 
 small depressions. Then comes a layer of colourless crystal glass above the coloured 
 glass. It attaches itself to the smooth, level parts, but it does not penetrate into the 
 depressions, which remain filled with air. When the vessel is completed, fitted with 
 handles, feet, &c., and has been cooled down, the outer surface receives a matt polish 
 which gives it a satin-like appearance. The favourite colours for this style are reseda 
 green, heliotrope violet, garnet red, and jonquil yellow. 
 
 Painting on Glass. The delineation of figures and scriptural events in coloured 
 glass dates from a very remote period. At first the work was merely mosaic, pieces of 
 coloured glass being inserted in leaden framework. Glass painting was known in 
 Germany in the Middle Ages, and soon extended throughout Europe. In the thirteenth 
 century, when Gothic architecture became prevalent, glass painting also became more 
 general, as until then the heavy, round-arched windows were too small to admit of 
 ornament. But it was not until the fifteenth century that the heavy outlined figures were 
 discarded for the more mingled colours of heraldic device, as seen in the churches of 
 Sebaldus and Lorenz, of Nuremburg, in the productions of the celebrated Hirschvogel 
 family. This style lasted till the sixteenth century, when the glassmaker tried the effect 
 of pigments upon glass. Since that time the art has gradually developed, the improve- 
 ment at first being most manifest in France and the Netherlands. 
 
 The nature of glass painting or staining is in principle the following : When 
 coloured glass, rendered easily fusible by the metallic oxide it contains, is finely pulver- 
 ised, and laid upon a plain glass surface and heated, it forms a skin, or " flash," as it is 
 termed, this skin or layer of glass being said to be " flashed on." It is evident that 
 very brilliant effects may thus be obtained. The near surface of the glass receives the 
 strong shades and colours, the other or distant surface the lighter tints. White was 
 not employed in the older glass paintings, but is now used in the flesh-tints, pure white 
 effects, &e. Tin oxide and potassium antimoniate yield a good white. For yellow, 
 Naples-yellow, or antimony-yellow, or a mixture of the iron, tin, and antimony oxides, 
 or of antimonic acid and iron oxide, of silver and antimony sulphides, or silver 
 chloride is used ; for red, iron oxide, purple of Cassius, and a mixture of gold oxide, 
 tin oxide, and silver chloride ; for the brown, manganese oxide, yellow ochre, umber, 
 and iron chromate ; for black, iridium, platinum, cobalt, and manganese oxides ; for 
 blue, cobalt oxide, or potassium-cobalt nitrate; for green, chromium and copper 
 oxides. Two kinds of colours are distinguished, the hard and the soft. The soft 
 are called varnish colours, are very easily melted, forming a kind of glaze upon the 
 glass. These colours are placed upon the outer surface. The hard or decided tints are 
 semi-opaque, and are placed upon the inner surface of the glass. The binding fluid 
 or vehicle is a mixture of silica, minium, and borax, with which the colour, being pre- 
 
624 CHEMICAL TECHNOLOGY. [SECT. v. 
 
 viously ground to a fine powder, is intimately mixed. This mixture is painted on the- 
 glass with a pencil, and the glass plate is afterwards fired in a muffle. Volatile oils have 
 recently been employed as vehicles viz., oil of turpentine, lavender, bergamot, and 
 cloves. The burning-in, or firing, the colours was formerly effected by placing the 
 glass tablet with dried and pulverised lime in an iron pan raised to a red heat. But 
 recently the muffle oven has been employed. The bottom of the muffle is covered to a 
 depth of one inch with dry powdered lime, upon which the plate of glass is laid, and 
 again a layer of lime. The oven is then raised equally to a dark-red heat. After six 
 to seven hours the fire is gradually withdrawn, and the oven allowed to cool. The glass 
 is taken out, cleansed with warm water, and dried. 
 
 Enamel, Bone Glass, Alabaster Glass. By enamel is understood in glass manufac- 
 ture a coloured or colourless glass mass rendered opaque by the addition of oxide of tin. 
 It was formerly prepared in the following manner : An alloy of 15 to 1 8 parts tin and 
 100 parts lead was oxidised by heat in a stream of air, the oxide pulverised and washed. 
 The mixture of the oxides was then fritted with the glass. An enamel-like appearance 
 is imparted to glass by arsenious acid, silver chloride, calcium phosphate, cryolite, 
 fluor-spar, sodium aluminate, and precipitated barium sulphate. Bone glass, so called, 
 is a milk-white, semi-opaque glass, containing calcium phosphate in the shape of 
 white bone-ash, sombrerite, or phosphorite. It is employed for lamp globes and shades, 
 thermometer scales, &c. It is made by adding to white glass about 10 to 20 per cent. 
 of white bone-ash, or a corresponding quantity of mineral phosphate. After melting, 
 the glass is generally clear and transparent, becoming milk-white and opaque during the 
 process of blowing. The colour is finally developed during annealing. 
 
 A glass resembling bone glass, but opaque and of as uperior lustre, is the alabaster or 
 opal glass, sometimes known as rice glass. It is merely a preliminary stage in the 
 formation of glass, very rich in silica and imperfectly fused. Its opacity is derived from 
 undissolved particles. The same mixture is used for alabaster glass as for crystal glass ; 
 as soon as it is melted it is baled out and chilled. When the next lot is melted the 
 chilled mass is put upon it and worked up together at the lowest possible temperature. 
 The undissolved particles of the melt which cause the turbidity should be only micro 
 scopic, and be neither distinctly perceptible grains nor bubbles. This is the great diffi- 
 culty in the manufacture of alabaster glass, since the impurities as a rule do not dis- 
 appear until the mass has been thoroughly melted and clarified. Alabaster glass is 
 identical with Reaumur's procelain. 
 
 Cryolite Glass (hot cast porcelain) is obtained, according to Williams, by melting a 
 mixture of 
 
 Silica .' 67-19 
 
 Cryolite 23-84 
 
 Zinc oxide . 8-97 
 
 An Austrian cryolite glass, according to Weinreb, contained 
 
 Silica 78-00 
 
 Alumina 3-12 
 
 Ferric oxide trace 
 
 Manganous oxide trace 
 
 Lime 3-87 
 
 Soda 9-46 
 
 Potassa .......... 4-35 
 
 Fluorine . -377 
 
 Ice Glass. Ice glass is made by plunging the mass of glass attached to the end 
 of the blower's pipe, still at a glowing red heat, into hot water, in which the 
 glass is opened and blown out. It then resembles a mass of thawed ice, with a 
 beautifully pellucid appearance. It is also known as crackle glass ; in France, as 
 
SECT, v.] GLASS MANUFACTURE. 625 
 
 verre craquele. Agate glass is obtained by melting together the waste pieces of 
 coloured glass. 
 
 Hematinone and Aventurine have already been described. 
 
 Muslin Glass is plate glass ornamented with designs in dead white. One method 
 of producing this effect consists in flashing over the surface a thin layer of plumbiferous 
 crystal glass. The other method depends on coating the glass with a coating of enamel. 
 The mixture of the Belgian enamel is 100 parts sand, no red lead, no parts of cullet 
 (from crystal glass), 35 borax (anhydrous), and 25 parts tin oxide. 
 
 Glass relief. Glass relief is obtained by enclosing a body of well-burnt unglazed 
 white clay, moulded to the required form between layers of lead-glass, the result being 
 similar in appearance to an article in matted silver. Gold matte is imitated by employing 
 a yellow glass. This branch of their art has been known to the Bohemian glass 
 manufacturers for upwards of eighty years. 
 
 Iridescent Glass. Since 1872 articles of glass have been made with rainbow coloured 
 iridescence. Such glass was first obtained by Brianchon by coating the objects (i.e,, 
 paper-weights, &c.,) with a flux of auriferous bismuth oxide, so thin that it is almost imper- 
 ceptible by transmitted light, but in reflected light shows the colours of the spectrum. 
 Whether the observation of Fremy and Clemandot that glass can be made iridescent by 
 treatment with hydrochloric acid under pressure can be applied in practice is still 
 undecided. 
 
 Filligree or Reticulated Glass. By fibre or filligree glass is understood that kind of 
 glass work formed of variously coloured or white opaque glass threads, these threads 
 being sometimes as fine as a single hair. They are generally drawn from tubes or 
 sticks of glass of various colours, heated to redness, and formed into sticks, tubes, or 
 spirals. Two of these tubes are taken, placed together, and blown out into a vessel 
 of the required form,which is characterised by the conformation of the glass threads in 
 the stick. From the spiral network thus formed this kind of glass is sometimes termed 
 reticulated. 
 
 Millifiore Work. Millifiore work is a peculiar form of mosaic glass work, in prepa- 
 ration similar to that of Petinet glass. Small filligree canes of different coloured glass 
 are placed side by side to form a thick cord or column, the cross section of which appears 
 of a particoloured grain. These cords or columns can be twisted to almost any required 
 form, or when heated and drawn out the glass threads of various colours of which it is 
 composed form a single thread of very varied hue and great beauty. These threads 
 again can be worked into ornaments, or formed into lumps or balls. The best kind of 
 millifiore work are the paper-weights, often sold at fancy bazaars as Bohemian glass 
 weights these are merely lumps or rolls of the many coloured glass thread placed 
 together, heated, and finally coated with a film of clear white glass by being for a few 
 moments held in the white glass melting-pot. 
 
 Glass Pearls. There are two kinds of artificial or glass pearls, namely, solid or 
 massive pearls and blown pearls. The first are known as Venetian pearls, and those made 
 in Venice are preferred, the export from this city in 1868 representing a money value 
 of 7,755,000 francs. The manufacture is chiefly carried on in the Island of Murano. 
 The pearls are made from small glass tubes, either white or coloured. Oxide of tin is 
 employed in the preparation as well as the various metallic oxides for imparting the 
 desired colours. 
 
 Solid Pearls. The glass tubes are cut into small pieces or cylinders. The sharp 
 edges of these cylinders are removed by placing them in an iron vessel brought to 
 a red heat, the beads being constantly stirred with an iron spoon. Previous to this 
 operation the interior or hollows of the beads are filled with powdered charcoal. 
 They are then well washed, dried, and packed. By another mode of preparation, 
 the pieces of glass tubing are placed in a revolving vessel similar to a coffee roaster. 
 
 2 B 
 
6 2 6 CHEMICAL TECHNOLOGY. [SECT. v. 
 
 The finished pearls are generally strung, the charcoal being placed in the interior or 
 tube to prevent its closing. 
 
 Blown Pearls. The preparation of blown pearls is quite a distinct manufacture. 
 They resemble the real pearl in form, colour, and surface. Jaquin, a French 
 paternoster or rosary maker, in the year 1656, remarked that when whitings (Cyprinus 
 alburnua, ablettes) were washed with water, a residue remained consisting of a beautiful 
 pearly substance. This was the foundation of the manufacture of the artificial pearl. 
 Jaquin scaled the fish, mixed the scales with water, and obtained the celebrated 
 " Oriented pearl-essence," or " Essence d'Orient," a substance identical with Guanin. 
 A small bead of gypsum or other hardening paste is coated with this mixture, dried, 
 and dipped into molten glass, a thin film of which adheres. 
 
 The pearl is sometimes round, sometimes pear-shaped, or flat. Another method of 
 preparing the pearls is by means of beads blown from glass tubes of various thicknesses. 
 These beads or small bulbs are then filled with pearl essence. To prepare this essence, 
 say a quantity of 120 grammes, 4000 fish are necessary ; thus a pound of pearl essence 
 requires from 18,000 to 20,000 fish for its preparation. The scales are allowed to stand 
 about an hour in water to permit the slimy matter adhering to them to settle ; they 
 are rubbed down in a mortar with fresh water, and strained through a linen cloth. 
 Thus prepared the paste is ready for insertion in the glass beads, a little ammonia 
 being added to prevent decay. 
 
 Into the red pearls, which are to imitate coral, and into the yellow ones there are 
 blown suitable colours ground up with gum arabic, and into the marcasite or mirror 
 pearls there is introduced an easily fusible metallic alloy. 
 
 According to Heckert (Pefcersdorf ) a pearl mosaic with perforated pearls is made by 
 executing the pearl mosaic in the first place as a kind of embroidery ; the front of the 
 pearls is then attached by means of cement or enamel to the objects to be decorated. 
 If a cement is used the tissue and the threads of the embroidery are burnt away after 
 it has hardened. If enamel is used it is melted together with the pearls. The effect 
 is very fine. 
 
 Glass Etching. Etching in glass was discovered in 1670 by Schwankhardt. If 
 powdered fluor-spar is covered with strong sulphuric acid, hydrofluoric acid is given off 
 on the application of heat, which acts upon the silica of the glass so as to form silicon 
 fluoride, which escapes, and water. At the parts acted upon the other constituents of 
 the glass remain as a loose powder, which can easily be removed. The idea of etching 
 upon glass plate designs suitable for printing came from Hann, of Warsaw (1829). 
 More recently, Bottger and Bromeis, with Auer, of Vienna, have improved the pro- 
 cesses. The etching-ground used for engraving on metallic surfaces would not in this 
 case give favourable results. Pul recommends a molten mixture of i part asphalt and 
 i part colophonium, with as much oil of turpentine as will bring the mass to the 
 consistency of a syrup. Etched glass plates have been used by B&ttger and Bromeis 
 to print from instead of steel and copper. In the press the glass plate is backed by a 
 cast-iron plate. The process, however, has not been practically successful ; it is better 
 suited to the production of bank-notes, &c., than engravings, the resulting etchings 
 being hard in tone. But for purposes of decoration, etched glass is largely used. By 
 the method of Tessie du Motay and Marechal of Metz, a bath is made of 250 grammes 
 of hydrofluoride or fluoride of potassium, i litre of water, and 250 grammes of ordinary 
 hydrochloric acid. Kessler employs a solution of fluoride of ammonium. 
 
 Etching for decorative purposes is likewise effected with hydrofluoric acid. 
 According to Tessie du Motay, the acid is best produced in a bath of 250 grammes 
 double hydrogen potassium fluoride, i litre water, and 250 grammes ordinary hydro- 
 chloric acid. For matte etching and writing on glass, Kessler recommends a solution of 
 ammonium fluoride, which is found serviceable for marking bottles, cylinders, tubes, &c. 
 
SECT. v.J GLASS MANUFACTURE. 627 
 
 For matte etching on glass Reinitzer uses solutions of acid alkaline fluorides. In 
 order that the matte may come up in different tones, where it is desired to obtain the 
 darkest possible tone by reflected light, the practice in the National Glass Painting and 
 Etching Establishment at Budapest is to etch the same spot twice in succession. A 
 single etching gives a lighter tone, and for still lighter tones the surface which has been 
 etched is cleared, once to nine times, with dilute liquid hydrofluoric acid. In this 
 manner they obtain at Budapest eleven gradations. If such an etched plate is 
 examined under a moderate microscopic power, we see a very uniform arrangement of 
 depressions and elevations of a crystalline form. At the margin of the matte surface 
 these crystals are more thinly scattered 
 
 and better developed, so that their form Fi S- 43 2 - 
 
 can be distinctly recognised. Fig. 432 
 shows the margin of such an etching 
 from the Budapest establishment mag- 
 nified 450 diameters. The predominant 
 crystals are hexagonal, and quite agree 
 with those of sodium silicofluoride. 
 Besides there are long crystals, very 
 similar to those of calcium silicofluoride. 
 That the crystalline figures are elevated 
 we may readily learn by the phenomena 
 apparent on raising or lowering the 
 tube of the microscope. It may be seen 
 still more plainly if we rub the matte 
 plate over with indian ink and then 
 wipe it superficially with elder pith. 
 All the parts between the crystals will 
 
 then appear dark under the microscope, while the crystals themselves are colourless. 
 If a plate of potash glass is etched matte there will appear the tesseral crystals of potas- 
 sium silicofluoride, and in this manner potash and soda glasses might be respectively 
 distinguished. 
 
 The etchings are the most delicate in presence of potassium salts. If ammonium 
 salts are used the solution should be saturated ; less concentrated for sodium salts and 
 more dilute for potassium salts. In all processes for rapid etching ammonium fluoride 
 is in use, and we may easily see that a concentrated solution of ammonium fluoride, 
 acidified with hydrofluoric acid, produces a fine matte in a few seconds. 
 
 As regards the proportions of the ingredients in the mixing baths, we can lay down 
 definite formula only if the glass is identical in composition. In practice it is sufficient 
 to set out with an approximate formula for glass e.g., R 2 Si 3 O 7 , when R is a monova- 
 lent metal. The reaction then ensues according to the equation : 
 
 R 2 Si 3 7 + 4F 2 HNa + loFH = SiF 6 R 2 + 2 SiF 6 Na 2 + 6H 2 O. 
 
 Hence it appears that for the complete utilisation of the sodium fluoride there must 
 be present a considerable quantity of free hydrofluoric acid. But as this hydro- 
 fluoric acid may easily prove injurious, it is better to use some other acid to saturate 
 the bases. 
 
 Acetic acid is the most suitable, as it does not decompose the acid fluorides and 
 liberate hydrofluoric acid. The process then takes place according to the equation : 
 R 2 Si 3 7 + 9 F 2 HNa + 5C 2 H 4 O 2 = SiF 6 R 2 + 2 SiF 6 Na 2 + 5 C 2 H 3 2 Na + 7 H 2 0. 
 
 We see that free hydrofluoric can never occur in this process, and further, that 
 the solubility of the silico fluoride is diminished by the sodium acetate which is formed. 
 From the last equation we see that the proportion of sodium fluoride to acetic acid is 
 93 : 5> r approximately 9:5. On the basis of the second reaction we should have 
 
628 CHEMICAL TECHNOLOGY. [SECT. v. 
 
 the following composition : 30 parts hydrofluoric acid (50 percent.), 17 sodium acetate 
 and soda-ash, 9 or 23-4 soda crystals. 
 
 Matte etching with gaseous hydrofluoric acid yields very unequal results. It is unfit 
 for surfaces, and can serve only for line-drawings. 
 
 Sand-Blast Machine. C. Tilghman, in working glass, uses a current of sand pro- 
 jected forcibly against the surface of the object to be etched. The sand derives its 
 velocity from air or steam. Whilst brittle bodies are attacked by the current of sand, 
 elastic bodies are able to resist it, and hence stencil-plates of caoutchouc can be 
 applied to the object. The parts left uncovered are ground by the sand, thus forming 
 a design. 
 
 EARTHENWAEE OR CERAMIC MANUFACTURE. 
 
 Weathering. In consequence of the reactions between the solid crust of the earth 
 and the atmosphere the masses of rock are gradually destroyed and broken up. The 
 causes of this weathering are partly mechanical, partly chemical. Among the former 
 are changes of temperature, especially frost, the mechanical power of falling water 
 (rain, streams, &c.) ; the chemical includes the action of atmospheric oxygen, of carbonic 
 acid, and of water. 
 
 The water absorbed by rocks becomes, in consequence of the formation of ice during 
 the cold season, a powerful agent for the disaggregation of the superficial strata. Of 
 more importance are the chemical changes in rocks ; oxygen converts sulphides into 
 sulphates and ferrous into ferric compounds. Water forms, with numerous substances, 
 hydrates and silicates, with an accompanying increase of volume, and converts 
 anhydrite into gypsum. By the prolonged action of water even the more permanent 
 minerals, such as felspar, are decomposed and their ingredients are rendered soluble. 
 Carbonic acid in watery solution dissolves the carbonates present in rocks (iron-spar, 
 limestone, dolomite, &c.) and phosphates (apatite, phosphorite).* 
 
 The final result of weathering is always mechanical comminution and chemical 
 decomposition in such a manner that a portion of the constituents is dissolved in 
 water. The residue either remains in heaps at the place where it was formed, or it is 
 conveyed away and subjected to a process of elutriation by the action of water, the 
 coarser and heavier matter being separated from the finer and lighter. 
 
 Clays and their Application. Felspar. To the most important alumina combinations 
 found native belongs felspar. This mineral is one of the chief members of the class 
 
 containing gneiss, granite, and porphyry. Potash-felspar, j?,^ |0 8 , with 65-4 parts of 
 
 silica, 1 8 alumina, and 16*6 potash, is also known as orthoclase or adularia; when 
 sodium takes the place of potassium, the felspar albite is formed. According to 
 Mitscherlich some felspars contain 0*4 to 2*25 per cent of barium. When felspar is 
 under the influence of water and carbonic acid with changes of temperature, it loses its 
 potassium silicate, which being washed out, the potash is taken up by plants, and will 
 perhaps account for some portion of the potash always present in their ash ; some of 
 the silicate is acted upon by carbonic acid, by which the silicic acid is separated and 
 soluble potassium carbonate formed. In following this decomposition to a conclusion, 
 we may surmise that the silicic acid thus set free becomes a constituent of the opal and 
 chalcedony spar. All clays are essentially aluminium silicate ; and, in many instances, 
 as in Devonshire and Cornwall, the change from felspar of the fine white granite to 
 clay by disintegration is very perceptible. By washing this clay to free it from quartz 
 and mica a fine white clay is obtained, known as kaolin or porcelain clay. Again, by 
 
 * Biological agents take a part in the work which is not yet fully recognised ; lichens secrete 
 oxalic acid and corrode the rocks upon which they grow, and microscopic plants exert a more 
 varied and profound influence. 
 
SECT, v.] EARTHENWARE OR CERAMIC MANUFACTURE. 
 
 washing with potash lye, whereby the free silica is taken up, there is obtained, in most 
 cases, a fine plastic mass, consisting of i mol. of alumina, i mol. of silica, and 2 mols. 
 of water. The quantity of free silicic acid varies between i and 14 per cent. 
 The weathering of the felspar may be formulated thus 
 
 i mol. felspar, Si 3 8 KAl, or 
 
 gives, under the influence of water, 
 
 i mol. porcelain clay, 2SiO 4 HAl, and 
 
 i acid potassium silicate, 
 
 the latter forming a soluble combination similar to water-glass. Porcelain clay occurs 
 in the following localities: i. Bavaria: Aschaffenburg, Stollberg, Diendorf, Obereds- 
 dorf . 2. Prussia : Mori and Trotha, near Halle (material for Berlin porcelain manu- 
 facture decomposed or disintegrated porphyry). 3. Saxony: near Schneeberg and 
 Misnia. The first is a weathered granite ; the latter, porphyry. 4. Eastern Hungary ; 
 Brenditz in Moravia; near Carlsbad, Bohemia; Primdorf in Hungary. 5. France; 
 St. Yrieux, near Limoges. 6. England : St. Austell, in Cornwall. Weathered granite : 
 a mixture of orthoclase and quartz. It is found chiefly on Tregoning Hill, near Hel- 
 ston. 7. China. It naturally follows that the clay should contain foreign substances; 
 and it is from the quality and quantity of these substances that the several varieties of 
 clay are obtained, of course with due reference to the chief constituents silicic acid 
 and alumina. The purer clays contain generally the following foreign substances : 
 Sand, partly as quartz sand, as potassium silicate, and partly as particles or fragments 
 of undecomposed minerals ; baryta combinations ; magnesium carbonate ; calcium 
 carbonate ; ferric oxide ; sulphur pyrites ; and organic matter. 
 
 In the examination of clays, Seger treats the sample with concentrated sulphuric 
 acid. The clayey matter is decomposed, while quartz and felspar remain untouched. 
 The kaolins named below have the following composition : 
 
 
 B 
 
 B . 
 
 a . 
 
 - 
 
 a 
 
 a 
 
 B . 
 
 3 
 
 
 fj 
 
 
 .! 
 
 5s 
 
 43 
 
 *l 
 
 *l 
 
 53* 
 
 Components. 
 
 .g-S 
 
 "3 
 
 SB 
 
 2 
 
 IN 
 
 II 
 
 
 || 
 
 
 
 M 
 
 M 
 
 
 W 
 
 M 
 
 M M 
 
 M* 
 
 
 
 
 88-26 
 
 87-41 
 
 QO*2Q 
 
 96-55 
 
 74*09 
 
 78-5I 
 
 6377 
 
 54-92 
 
 
 3-08 
 
 6'4O 
 
 4-08 
 
 
 17*21 
 
 20*QO 
 
 
 
 
 8-66 
 
 6'IQ 
 
 5*63 
 
 j.jr 
 
 870 
 
 O'W 
 
 O"73 
 
 21-56 
 
 Composition of the Clay 
 
 
 
 
 
 
 
 
 
 Silica 
 
 45-36 
 
 4476 
 
 45-98 
 
 45-36 
 
 45*63 
 
 45-00 
 
 45-30 
 
 4? "40 
 
 Alumina . 
 
 39-58 
 
 39-65 
 
 
 3971 
 
 38-08 
 
 39-32 
 
 37-15 
 
 37-35 
 
 
 0*92 
 
 0*72 
 
 0-73 
 
 I'I3 
 
 0-88 
 
 75 
 
 I'29 
 
 1-07 
 
 Magnesia 
 
 0'2O 
 
 0-34 
 
 0-45 
 
 
 0-66 
 
 0-28 
 
 0-78 
 
 073 
 
 Potassa . 
 
 O'2I 
 
 O'O2 
 
 0-99 
 
 1-24 
 
 1-84 
 
 o'53 
 
 2 'O2 
 
 2 '57 
 
 Water . 
 
 I4-O2 
 
 14-07 
 
 13-28 
 
 I3-32 
 
 I3-32 
 
 14-20 
 
 I3-U 
 
 1274 
 
 Technical Qualities of Clays, For the technical application of the clays the im- 
 portant qualities are colour, plasticity, and hardening well under heat. 
 
 Colour. Naturally clays are white, yellow, blue, or green. Pure clay is white ; 
 coloured clays are the result of several admixtures. White clay contains but a small 
 quantity of ferrous oxide, and becomes after burning yellow or red ; these colours origi- 
 nating from the organic substances disappear on their being volatilised after many 
 firings. The coloured clays change their colour during firing, becoming red or red- 
 yellow. Fine clays are prepared only from those becoming white by continued 
 burning. 
 
 Plasticity. The clay should absorb water readily, forming a tenacious mass, capable 
 of taking sharp and clear impressions. It is evident that the plasticity of the clays 
 
630 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. v. 
 
 depends in a great measure on their composition. Sand is the constituent most 
 prejudicial to plasticity, lime less so, and oxide of iron least of all. Clay pos- 
 sessing a high degree of plasticity is said to be fat or long, and when in the opposite 
 condition lean, thin, or short. All shrunk clays, that is, all clays decreased in volume 
 by burning, are said to be either drawn or burst. The amount of shrinkage depends 
 of course upon the quantity of water the clay contains ; the same kind of clay does 
 not always exhibit the same shrinkage. Fat clays shrink more than short clays. 
 The diminution in surface by shrinkage varies between 14 and 31 per cent, the 
 capacity or solid contents between 20 and 43 per cent. Clay may be burnt so hard 
 as to give sparks when struck with steel ; but its property to form a plastic mass 
 with water is then wholly lost. Pure clay (aluminium silicate) is by itself infusible, 
 but by mixture with lime, ferric oxide, and other bases, it becomes more or less easily 
 fusible. According to the experiments of E. Bichters (1868) the refractory qualities 
 of clay are least influenced by magnesia, more so by lime, still more by oxide of iron, 
 and most by potash. Fusible clay obviously is not adapted to the manufacture of 
 porcelain or such ware as is likely to be exposed to a high temperature. A fusible and 
 a refractory clay, when heated together, combine into a mass that does not cleave to the 
 tongue. By the manufacture of clay ware, then, is understood the binding of certain 
 clays together by means of a suitable flux. 
 
 Kinds of Clay. The clays employed in ceramic manufacture are 
 
 1. Refractory clays; as porcelain and plastic clays. 
 
 2. Fusible clays ; as potter's clay. 
 
 3. Limey clays ; as marl, loam. 
 
 4. Ochre clays ; as ruddle, ochre. 
 
 Of these porcelain clay is the most important ; it is of various colours, very tena- 
 cious, plastic to a high degree, burns white, and is not fusible in a porcelain-oven fire. 
 It is ordinarily found in the tertiary formation, almost always accompanied by other 
 kinds of clay, by quartz-sand, and by brown coal. For practical purposes it is 
 important to know that clays of the same strata and of the same pit often differ 
 largely in their refractory property. This knowledge is not only the result of experi- 
 ence, but of a lengthy series of experiments made by C. Bischof , Otto, and Th. Bichters. 
 The strata near Klingenberg-on-the-Maine, at Coblenz, Cologne, Laiitersheim, and 
 Vallendar-on-the-Rhine, Weisbach in Baden, Bunzlau in Silesia, Schwarzenfeld near 
 Schwandorf, and Kemnath in Bavaria, in the province of Hessen, in Saxony, in 
 Belgium, near Dreux in France, and Devonshire and Stourbridge in this country, are 
 all celebrated for this clay. 
 
 As plastic clays may be mentioned the white clays of Ebernhahn (i), Baumbach (2), 
 Bendorf (3), Lammersbach (4), and Hohr (5), all from the so-called Kannenbackerland, 
 Germany ; as well as a lean (6) and a fat (7) white clay of French origin. 
 
 Constituents. 
 
 i. 
 
 2. 
 
 3- 
 
 4- 
 
 5- 
 
 6. 
 
 7- 
 
 Clay substance .... 
 
 
 
 
 
 
 
 
 Quartz . 
 
 
 
 3y 7 1 
 
 
 54 73 
 
 44 03 
 
 7 1 54 
 
 Feldspar residues 
 
 ^4 3 
 
 4"7C 
 
 
 57 X 5 
 
 3 1 4 2 
 
 4 1 77 
 
 5 2 77 
 
 2 5 97 
 
 Components of Clay substance 
 Silica . 
 
 /J 
 
 3 
 
 J 4 
 
 o5 
 
 3-5 
 
 
 2 49 
 
 Alumina 
 
 
 47 44 
 
 47 44 
 
 47 39 
 
 47 45 
 
 ti'StS 
 
 45 '99 
 
 ~Q.~O 
 
 4575 
 
 Ferric oxide 
 
 
 37 2I 
 
 T &% 
 
 35 74 
 
 36 40 
 
 37 
 
 30 oo 
 
 3577 
 
 Lime 
 
 1 o9 
 
 
 i 94 
 
 i 5 2 
 
 i 41 
 
 2 44 
 
 2 94 
 
 Magnesia . 
 
 
 
 ^cc 
 
 
 
 
 
 Potassa 
 
 73 
 
 o 79 
 
 i -^r- 
 
 0-51 
 
 o 71 
 
 A -<~lS 
 
 1-19 
 
 
 Loss on ignition 
 
 6 47 
 
 4 22 
 
 3 o5 
 
 3 '9 
 
 
 2-36 
 
 1-24 
 
 
 
 y y 
 
 9 5 2 
 
 9 9 2 
 
 
 
 13 70 
 
SECT, v.] EARTHENWARE OR CERAMIC MANUFACTURE. 631 
 
 The chemical composition does not enable us. to judge of the sharply-marked 
 differences in the degree of plasticity, which is very low in kaolins even when the 
 proportion of pure, hydrated aluminium silicate is high. Hence the property of 
 plasticity does not belong to any peculiar chemical compound, but seems to fluctuate in 
 clays of similar chemical composition, according to degree of mechanical subdivision 
 and to the molecular arrangement. Possibly the degree of plasticity may be determined 
 by the structure of the rocks from which the clay has originated. 
 
 The following analyses show the composition of certain fire-clays (refractory 
 clays) : 
 
 i. 2. 3- 4. 5- 
 
 Silica . . . 47-50 ... 4579 ... 53-00 ... 63-30 ... 55-50 
 
 Alumina . . 34-37 ... 28*10 ... 27-00 ... 23-30 ... 2775 
 
 Lime . . . 0-50 ... 2-00 ... 1*25 ... 073 .... 0*67 
 
 Magnesia . . i-oo ... ... ... ... 075 
 
 Ferric oxide . 1-24 ... 6-55 ... 175 ... 1-80 ... 2-01 
 
 Water. . . i-oo ... 16-50 . ... 10-30 ... 10-53 
 
 i. Almerode in Kurhessen (crucible). 2. Schildorf near Passau (graphite crucible). 
 3. Einberg near Coburg (porcelain capsule). 4. Stourbridge. 5. Newcastle (fire- 
 brick). 
 
 The composition of the Stourbridge fire-clay will be seen from the following 
 analyses by Sir F. A. Abel, F.R.S., Chemist to the War Department : 
 
 Sample. Silica. Alumina. Ferric oxide. Alkalies, Waste, Ac. 
 
 1 . . . 66-47 26-26 ... 6*63 ... 0-64 
 
 2 ... 65-65 ... 26-59 ... 571 ... 2*05 
 
 3 65-50 ... 27-35 . 5'40 ... 175 
 
 4 . . . 67.00 ... 25-80 ... 4-90 ... 2-30 
 
 5 . . 63-42 ... 31-20 ... 470 ..., , o - 68 
 
 6 ... 65-08 ... 27-39 .- 3'98 ... 3'SS 
 
 7 ... 65-21 27-82 ... 3-41 3-56 
 
 8 . . .58-48 3578 ... 3-02 2-72 
 
 9 ... 63-40 ... 3170 ... 3-00 ... 1-90 
 
 The sample No. 9 containing only such a small quantity of iron, is much superior 
 to No. i, whose refractory properties may be doubted. The clay is dug from pits 
 varying from 120 to 570 feet in depth. It is generally found below three workable 
 conl measures, between marl or rock and an inferior clay. The seam averages 3 feet 
 in thickness, and never exceeds 5 feet, while the middle of the seam contains the clay 
 selected for crucibles, &c. Pot-clay or crucible-clay only occurs in small quantities, and 
 costs at the pit-mouth 553. a ton, ordinary fire-clay only realising los. a ton. 
 
 Potter's Clay. Ordinary potter's clay also possesses most of the properties of plastic 
 clay; many varieties form with water a similarly tenacious mass. But potter's clay is 
 highly coloured, retaining the colour after burning. It effervesces on the application 
 of hydrochloric acid and forms the transition to marl. It follows from its containing 
 large proportions of lime and oxide of iron that it is fusible, and melts according to 
 the quantity of these constituents at a higher or lower temperature into a dark coloured, 
 slag-like mass. It is found in the last formation, or entirely on the surface of the 
 earth, and sometimes in the tertiary formation. It contains among other foreign 
 substances organic matter, iron and other pyrites, gypsum, &c. 
 
 fullers Earth is a soft, friable mass, formed by the weathering of diorite. In 
 water it falls to a powder, not forming a plastic pulp. It is used for removing grease- 
 spots from paper, &c., and was formerly employed in fulling cloth, whence its name. 
 It is also used in paper-making, and as an addition to ultramarine. It contains 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. v. 
 
 a small proportion of alkali, but its detergent action depends on its mechanical 
 texture.* 
 
 Marl. Marl is a mechanical mixture of clay and calcium carbonate, containing 
 sand (sand-marl) and other constituents; that containing lime is called lime-marl; 
 that clay, clay-marl. In water it falls to powder, and forms a non-adhesive, pasty 
 mass. With acids it effervesces, whereby more than half the weight is lost. It melts 
 easily. It is found in the lias and chalk formation. Its chief application is to the 
 improvement of land. 
 
 Loam,. Loam may be considered as the result of the mixture of clay with sand. 
 It is a clay more or less mixed with quartz-sand and iron-ochre, also with lime, when it 
 assumes a yellow or brown colour, changing on burning to a red. It forms with water 
 a slightly plastic mass, and is not very refractory. It is found always on the surface 
 of the earth, and known as common clay, employed in the manufacture of bricks, coarse 
 pottery, &c.f 
 
 Two brick-clays, belonging to the cretaceous formation, near Hanover, had the 
 following composition when dried at 120 
 
 
 Stocken. 
 
 Lindener Hill. 
 
 
 Total. 
 
 Insoluble in H 2 S0 4 . 
 
 Total. 
 
 Insoluble in H a SO 4 . 
 
 Si0 2 
 A1 2 S 
 
 54 '01 
 27-98 
 
 18-81 
 0-68 
 
 59-91 
 17-96 
 
 37'i7 
 1-79 
 
 Fe 2 0, 
 
 2'IO 
 
 trace 
 
 1-09 
 
 trace 
 
 CaO 
 
 2-85 
 
 
 
 8-21 
 
 trace 
 
 MgO 
 
 0-65 
 
 
 
 0-41 
 
 
 
 Alkalies 
 
 0-68 
 
 
 
 0-41 
 
 
 
 C0 2 
 
 1-94 
 
 
 
 6-02 
 
 
 
 SO, 
 H,0 
 
 0-56 
 9-03 
 
 = 
 
 0-46 
 5' 6 4 
 
 
 
 
 99-80 
 
 19-69 
 
 lOO'II 
 
 39-30 
 
 If, according to Seger's proposal, we consider the part soluble in sulphuric acid as 
 the true clay substance, and consider that for each i part alumina 3-51 silica belong to 
 the felspar, we have the composition 
 
 Components. 
 
 Stocken. 
 
 Lindener Hill. 
 
 Quartz 
 
 16*42 
 
 zo'QO 
 
 
 3 '27 
 
 8'4O 
 
 
 80-31 
 
 u iyj 
 DO "7O 
 
 Components of Actual Clay 
 Si0 2 
 
 AvS-j 
 
 37 "21 
 
 Al,0 3 
 Fe,O. . 
 
 33 '99 
 
 2 '6 1 
 
 26-46 
 1*77 
 
 CaO 
 MgO 
 
 3-55 
 0*80 
 
 1 3 '43 
 0*67 
 
 Alkalies 
 CO, . 
 
 0-84 
 
 0-67 
 
 Q'8? 
 
 SO. . 
 
 0*70 
 
 O'73 
 
 H,O . 
 
 ii "26 
 
 Q'23 
 
 
 
 
 As further calcium carbonate and sulphate do not belong to the true clay, and as 
 the former has an influence on the burning, they are to be mentioned separately : 
 
 * It is found near Beigate (Connonger's Farm), in Surrey ; near Maidstone, in Kent ; Woburn, 
 in Bedfordshire ; Old Town, near Bath ; and in the north-east of Ireland. 
 
 f In horticultural works the word loam is used in a totally different sense to signify the mass 
 resulting from the decomposition of grass sods, pared off from the ground and laid up in heaps. 
 
SECT, v.] EARTHENWARE OR CERAMIC MANUFACTURE. 
 
 Components. 
 
 Stocken. 
 
 Lindener Hill. 
 
 Quartz 
 
 
 
 
 
 16-42 
 
 30-90 
 
 Felspar remains 
 
 
 
 
 
 3' 2 7 
 
 8-40 
 
 Calcium carbonate . 
 
 
 
 
 
 4-45 
 
 14-10 
 
 sulphate . 
 
 
 
 
 
 0'95 
 
 0-82 
 
 Actual clay 
 
 
 
 
 
 74-9I 
 
 46-78 
 
 Components of Actual Clc 
 
 w 
 
 
 
 
 
 
 SiO 2 . 
 
 . 
 
 
 
 
 
 46-96 
 
 48-83 
 
 ALjOg . 
 
 . 
 
 
 
 
 
 36-42 
 
 34-81 
 
 Fe 2 t . 
 
 . 
 
 
 
 
 
 2-80 
 
 2'37 
 
 MgO . 
 
 . 
 
 
 
 
 
 0-87 
 
 0-89 
 
 Alkalies 
 
 . 
 
 
 
 
 
 0-91 
 
 0-89 
 
 H,0 . 
 
 
 
 
 
 
 12-04 
 
 I2'2I 
 
 Certain clays contain also manganese, cobalt, barium, titanium, vanadium, moly- 
 bdenum, gold, and cerium. 
 
 Behaviour of Clays in Working. Clays lose their water partly on drying, when they 
 undergo a linear shrinkage of 11-5 per cent., and partly at a higher temperature. 
 On losing this water of hydration at a red heat clay loses permanently its plasticity 
 and forms a stony, very porous, and friable mass. At higher temperatures: it becomes 
 denser, harder, sonorous, but still has an earthy fracture. The silica expels the car- 
 bonic acid, chlorine, and sulphuric acid, forming silicates with the alkalies, lime, 
 magnesia, and ferric oxide. These silicates form with the aluminium silicate double 
 silicates, which are easily fusible. The clay sinters more and more, and finally melts. 
 Though the specific gravity of the clayey substance rises at a dull red heat from 2-47 
 to 2*70, and then falls at a white heat to 2-48, the density of the entire bricks increases 
 with the rise of temperature by the loss of the pores. According to Karmarsch, newly 
 moulded bricks of 262 millimetres long, 130 broad, and 51 millimetres thick, shrink 
 per cent. : 
 
 
 Length. 
 
 Breadth. 
 
 Thickness. 
 
 
 On drying 
 ,, drying and slight burning . 
 burning to clinkers . 
 
 7-25 
 8-50 
 
 "75 
 
 1075 
 13-00 
 23-00 
 
 975 
 1475 
 1975 
 
 Aron observed a linear shrinkage of from 0-3 to 4*1 per cent, at redness, and of 12 to 
 8 per cent, at whiteness. The less the bricks shrink the coarser the grains of sand 
 which they contain. 
 
 Experiments by Daube show how much the porosity and the resistance of bricks 
 moulded from the same clay depend on the temperature. The results are given in the 
 following table : 
 
 
 Slightly 
 
 Medium 
 
 Hard 
 
 
 
 burnt. 
 
 burnt. 
 
 burnt. 
 
 
 Moisture taken up on dipping in water, per cent. . . 
 
 16-2 
 18-0 
 
 16-5 
 19-3 
 
 16-4 
 19*0 
 
 1-6 
 2-6 
 
 
 O'7 
 
 0*2 
 
 0*15 
 
 0*09 
 
 
 8-5 
 
 8-0 
 
 7 '4 
 
 2-5 
 
 Do. in nitric acid 
 Increase of weight in sulphuric acid by formation of CaSO 4 
 
 S'o 
 
 1*2 
 
 4'9 
 
 I'2 
 
 4-0 
 0-9 
 
 0-6 
 0-8 
 
 After treatment with HC1 the light- and medium-burnt bricks had strong fissures ; 
 those hard burnt only fine fissures, and the clinkers none at all. 
 
 The presence of calcium carbonate in fragments or coarse grains is very injurious 
 in fire-clays. According to Seger clays are, indeed, used containing as much as 
 
634 CHEMICAL TECHNOLOGY. [SECT. v. 
 
 30 per cent, of calcium carbonate, but such clays, especially if lightly burnt, have a 
 great tendency to weather. This explains why the clays which burn red and which 
 contain little or no calcium carbonate are preferred for roofing tiles, whilst the 
 calcareous clays which burn yellow have been found quite useless. Calcareous clays 
 are, indeed, easier to work, but as they lose in burning not merely water but carbon 
 dioxide, they yield porous bricks. The temperature at which the pores are closed and 
 a dense, porcelain-like mass is produced, lies very near to that at which the mass melts 
 to a slag, and great experience is necessary to prevent the bricks from slagging. 
 Hence, in burning such clays it is necessary to avoid a strong heat. The bricks in 
 consequence retain their porosity and absorb water eagerly. A really weather-proof 
 brick cannot be obtained from clays which contain upwards of 10 to 15 percent, calcium 
 carbonate. 
 
 Changes of Colour in Burning. Considerable importance often attaches to the 
 property of calcium carbonate to give a yellow or yellowish-green colour on burning to 
 the common ferruginous clays. Whilst pure clay burns white it is turned a red by 
 ferric oxide, the darker as the heat applied is stronger. If the heat is still raised 
 the colour becomes greenish, and finally black, according to Kemole, by the partial 
 formation of ferrous oxide. If the ferruginous clay contains at the same time calcium 
 carbonate it will be red, if slightly burnt, flesh-coloured, whitish to dark yellow at 
 incipient sintering, owing to the formation of a yellowish basic silicate of lime and 
 ferric oxide, and green to black on full nitrification. According to Seger this yellow 
 colour appears distinctly if to every per cent, of ferric oxide the clay contains at least 
 3 to 3 per cent, calcium carbonate. The yellow colour appears at a lower temperature 
 and is lighter the more the proportion of calcium carbonate exceeds this minimum, 
 appearing at a higher temperature and verging more upon a yellowish-red or yellowish- 
 brown on approaching the proportion above given. If the amount of lime is still 
 lower it merely reduces the red without producing a yellow. 
 
 Efflorescences. After a time bricks, especially if lightly burnt, often show whitish, 
 yellow, green, and even black eruptions. White eruptions generally consist of magne- 
 sium, calcium, and sodium sulphates, sodium chloride or bicarbonate, which are either 
 present in the clay or have been introduced by the water, the mortar, or the cement. 
 
 Green eruptions upon light-coloured bricks in moist places consist chiefly of algae, 
 or they may be due to the presence of chrome. Facing-bricks made of the lignitic 
 clays near Wittenberg, displayed, sometimes on their entire surfaces, sometimes only 
 in spots, especially at the corners, a very intense golden-yellow colour, which if 
 examined with a lens was found to consist of mammillary protuberances, in part of a 
 bright grass-green or yellowish-green. Some such bricks contained o'i 6 per cent, of 
 soluble salts, consisting of : 
 
 Potassa 19-82 
 
 Soda 3-17 
 
 Lime ...... 3*24 
 
 Magnesia 3*34 
 
 Alumina and ferric oxide . . 077 
 Vanadic acid . . . .29-43 
 
 Molybdic acid . . ; . 1-12 
 Sulphuric acid . . . .15-70 
 Silica ...... 2-07 
 
 Chlorine 2-63 
 
 Water 18-25 
 
 Insoluble matter . . . 0-46 
 
 These coloured eruptions consisted, therefore, chiefly of potassium vanadate, the 
 yellow colour of which is partially modified to green and blue by molybdic acid. 
 Reducing combustion gases and high temperatures make the vanadium compounds 
 insoluble. 
 
 Black spots are due chiefly to fungi, which attach themselves where calcium car- 
 bonate and sulphate effloresce out of the brickwork. 
 
 In addition to the composition of the clay and the temperature of the kilns, the 
 nature of the combustion gases has an influence upon the colour of the bricks. 
 
SECT, v.] EARTHENWARE OR CERAMIC MANUFACTURE. 635 
 
 Seger showed that the dark-red colour of the surface of yellow bricks is occasioned 
 by the absorption of sulphuric acid from the sulphur of the fuel. The moisture 
 precipitated from the combustion-gases of the Berlin Porcelain Works contained per 
 litre : 
 
 Wood furnace. Gas furnace. 
 
 Hydrochloric acid 39 ... 114 
 
 Sulphuric acid 153 ... 384 
 
 Phosphoric acid 73 
 
 Ferric oxide and alumina 8 ... 17 
 
 Lime II ... 39 
 
 Magnesia 8 ... 18 
 
 Potassa) _ 37 
 Soda ) ' 106 
 
 Ammonium chloride ....... ... 47 
 
 At higher temperatures, and on exposure to the action of reducing gases, the sul- 
 phuric acid is expelled and the normal colour restored. A yellow brick which had 
 been ignited to redness was uniformly yellow within, but was dark-red on those parts 
 of the surface which had been most exposed to the combustion-gases. The red colour 
 had only penetrated into the brick to the depth of 2 to 3 millimetres. A comparative 
 analysis of the red (I.) and the yellow (II.) parts showed : 
 
 i. n. 
 
 Silica 53-96 57-55 
 
 Alumina . . . 10-29 11-98 
 
 Ferric oxide . . . . . . . 6-25 ... 10-05 
 
 Magnesia . . .176 ... 1-51 
 
 Lime . . . 16*70 ... 17*85 
 
 Sulphuric acid ino ... o - 88 
 
 Some red colorations seem to be due to volatile compounds of iron. 
 
 The action of the other constituents of the combustion-gases upon the colour of 
 clays has been examined by Seger. 
 
 Clays containing iron and lime, and burning yellow if the combustion-gases con- 
 tain an excess of oxygen, are turned at a red heat a dirty red colour, then flesh colour, and 
 at full redness yellow with a brownish cast. Reducing -gases (hydrogen, hydrocarbons, 
 carbon-moncxides) effect a blackening which, on access of air, gives place to redness. 
 After a preceding reduction, the colours produced by the action of oxygen are lighter, 
 and incline more to a whitish or yellowish-green than if there had been no previous 
 reduction. An occasionally reducing flame in the furnace contributes to develop the 
 light colour of the calcareous clays. Ferruginous clays free from lime turn to a pure 
 red in an excess of oxygen, this the more decidedly the higher the temperature. 
 Reducing-gases change this red colour to a velvet black by the reduction of the ferric 
 oxide to ferrous oxide and metallic iron. If such black bricks are ignited in the air 
 the red colour returns, but not so finely as with an exclusively oxidising flame, so that 
 here to obtain pure colours the action of reducing-gases must be avoided. Clays free 
 from lime and poor in iron, and turning white or yellow, are also blackened by the 
 action of reducing-gases. The clay of Greppin, on exposure to pure hydrogen, after 
 ignition to dull redness, became a light ash grey, and contained 1*69 per cent, ferric 
 oxide and i-oi per cent, ferrous oxide, after prolonged heating to bright redness it 
 was a dark ash grey, and contained r8i per cent, ferric oxide and 0-34 metallic iron. 
 This grey colour very quickly disappears again on the admission of air, but the original 
 colours return, only in a much fainter degree. The flesh colour which characterises the 
 lower temperatures is converted into a whitish yellow, whilst at stronger heats there 
 appears a pure yellow. Clays poor in iron, which burn white in an excess of oxygen, are 
 turned light grey by reducing-gases, and on ignition in the air they become white again. 
 
 Infusibility, C. Bischof and Seger have made comprehensive experiments on the 
 
6 3 6 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. v. 
 
 influence of the composition of a clay upon its behaviour at high temperatures. 
 Bischof holds that the fusion of clays consists in the formation of double silicates and 
 aluminium silicates on the one hand, and a silicate on the other which may have for 
 its base either magnesia, lime or iron, potassa or soda. Pure aluminium silicate is 
 infusible in our ordinary fires, especially if it contains alumina in excess. If one of 
 the above-mentioned bases is present, its fusibility increases with the quantity of the 
 base. If we calculate from the complete analysis of a clay how much alumina comes to 
 one equivalent of fluxing agent, and how much silica comes to one equivalent alumina, 
 the quotient obtained by dividing the latter value by the former will be proportional to 
 the infusibility. On the other hand, Seger maintains that if it were possible to infer 
 the fusibility of a clay from its composition, this could be practicable only if it could be 
 brought into a chemically homogeneous mass. 
 
 For the experimental determination of the behaviour of a clay under heat, specimens 
 must be ignited. For this purpose Seger recommends the 
 Deville furnace, Fig. 433. In it there is laid a thick wrought- 
 iron plate B, beneath the hollow fire-clay cylinder A , which is 
 surrounded with a sheet-iron screen. The cylinder, 1 1 centi- 
 metres in width and 20 centimetres in height, is continued by 
 a fire-clay cap C, likewise enclosed in iron. The plate B is 
 perforated in three concentric rings, with apertures of 5 to 6 
 millimetres in width, a. In the middle is a large hole, b, of 
 30 millimetres in width. The lower part of the sheet-iron 
 screen is closed below with a round iron plate, D, which can 
 be luted on air-tight with clay. The air forced in through 
 the pipe, c, enters the fire-box through the holes, a a, whilst 
 the wider aperture, 6, serves to receive the support of the 
 crucible, which for this purpose has a plug-like elongation 
 
 below, fitting into b. The same aperture serves to clean out the furnace after use. 
 On the support stands a crucible of 40 millimetres outside diameter and 45 millimetres 
 height, also centred with a small plug at the bottom. This crucible receives the 
 samples of clays to be tested, together with the normal clays, made up in the form 
 of small tetrahedral or prismatic pieces. The crucible, its support, and the cylinder 
 are all made of a mixture of equal parts of Zettlitz kaolin and Neuroda slaty clay. Along 
 with the cones a piece of platinum wire is placed in the crucible. Some burning charcoal 
 is placed in the furnace and retort-graphite from the gasworks, which is preferable to 
 coke on account of its small yield of ashes. Air is forced in at c until the melting- 
 point of platinum is reached. The appearances presented by the clays are then 
 examined, and their position with respect to the normal samples is determined. 
 
 As a scale, Bischof uses a series of neutral clays, the slatey clay of Saarau, the kaolin 
 of Zettlitz, the clays of Stroud-Maiseroul, Mulheim, Griinstadt, Oberkaufungen, and 
 Niederpleis. A further normal point is the fusion of platinum to boiling. The standard 
 clays of the quality used by Bischof cannot be obtained by purchase. The fusion of. 
 platinum gives no certain indication, for platinum, like iron, can under certain circum- 
 stances absorb carbon from the combustion-gases and thus alter its melting-point. 
 Seger, on the other hand, has prepared tetrahedra of definite composition, which are 
 to be obtained at any time from the Royal Porcelain Works at Charlottenburg. 
 
 The Production of Earthenware. The assertion of the Chinese that they had 
 invented porcelain 3000 years ago is scarcely accurate. It is first mentioned in the 
 ninth century under the name Yao. A century later they learnt the use of a blue colour 
 underneath the glaze. This improvement appeared of such importance that porcelain 
 so adorned was reserved for the exclusive use of the Emperor. No one was allowed to 
 buy such porcelain articles, or even to look at them ! In the thirteenth century 
 
SECT, v.] EARTHENWARE OR CERAMIC MANUFACTURE. 637 
 
 porcelain vessels were first decorated with turquoise, yellow, and violet, on coloured 
 grounds, and even with painted designs. Under the Emperor Ching-hoa (1465-1488) 
 a method was discovered of decorating glazed porcelain vessels with coloured designs, 
 often with splendid paintings, in which a green colour predominated. In the fifteenth 
 period, down to 1726, a purple-red pigment was introduced. But towards the end of 
 this period the keramic art of China began to decline. Their material is still, however, 
 excellent in quality, though the Japanese have outstripped them in the decoration of 
 their earthenware. Satsuma, especially, produces splendid vases. 
 
 Classification of Earthenware. Clay ware is generally separated into dense and 
 porous ware. The dense ware is so strongly heated that half its mass is lost ; its 
 fracture is glazed and conchoidal ; it is translucent and compact, being impenetrable to 
 water ; and it gives a spark when struck with steel. Porous clay ware is, in the mass, 
 not glazed, its fracture open and earthy ; and, when not superficially glazed, water freely 
 percolates through it. It also clings to the tongue. The burnt mass, whether dense or 
 porous ware, either remains rough or is glazed. 
 
 The following are the essential varieties of clay ware : 
 
 I. Dense Clay Ware, A. Hard porcelain. The mass equal throughout ; not in- 
 dented with a knife ; fine-grained, translucent, sonorous, and white. Fracture, fine- 
 grained, and conchoidal. Sp. gr. = 2 '07 to 2-49. It may be considered as composed 
 of two substances namely, a natural clay or true kaolin, infusible, and preserving 
 its whiteness imder a strong heat ; and a flux consisting of silica and lime, or felspar 
 with or without gypsum, chalk, and quartz. The glazing is essentially due to this flux, 
 and not to lead or tin oxide. It is characteristic of the manufacture of hard porce- 
 lain that the burnings are concluded in one operation. 
 
 B. Soft or tender porcelain. The mass more easily fluid than hard porcelain. Two- 
 kinds are known : 
 
 a. French porcelain, a glass-like mass, essentially a potassuim-aluminium silicate, 
 prepared with the addition of clay, therefore erroneously termed a clay ware, and 
 containing lead similarly to crystal glass. 
 
 ft. English soft porcelain. The mass similar to kaolin, plastic, remaining white 
 when burnt (pipe-clay). It is made with a vitreous grit, consisting of gypsum, Cornish 
 stone (weathered pegmatite), bone-ash (essentially calcium phosphate), in very varied 
 proportions. The glaze is obtained by pulverised Cornish stone, chalk, powdered fire- 
 clay, and borax, mostly with, seldom without, the addition of lead oxide. The glazing, 
 is a second process. 
 
 C. Statue porcelain, or biscuit ware : 
 a. Genuine and unglazed porcelain. 
 
 ft. Parisian porcelain, or parian. Unglazed statue porcelain is similar to English 
 porcelain. 
 
 y. Carrara, less translucent than parian, and sometimes of a whiter colour. 
 
 D. Stone ware. Dense, sonorous, fine-grained, homogeneous, only slightly, if at all, 
 translucent, white or coloured. 
 
 a. Glazed porcelain stoneware. Plastic, remaining white after burning, slightly 
 refractory with the addition of kaolin and fire-clay ; a felspar as flux ; the glaze con- 
 tains borax and lead oxide. 
 
 ft. White or coloured unglazed stoneware. Wedgwood ware. 
 
 y. Common stoneware (salt-glazed). No fluxing material is employed, but the 
 firing is increased. Glazed with siliceous soda-alum. 
 
 II. Porous Clay Ware. A. Fine Fayence with transparent glaze. The body 
 earthy, clinging to the tongue, non-transparent, sometimes sonorous ; the glaze con- 
 taining lead, borax, felspar, &c. 
 
 B. Fayence, with non-transparent glaze. The body of a yellow burnt potter's clay 
 
638 CHEMICAL TECHNOLOGY. [SECT. v. 
 
 or clay-marl, with non-transparent white or coloured glaze or enamel, containing tin. 
 To this class belongs majolica, delft ware, &c. 
 
 C. Ordinary potter's ware. The body of ordinary potter's clay, or clay-marl, red, 
 coloured, soft, and porous. Mostly glazed with lead, the glaze being always non-trans- 
 parent. According to the colour of the glaze, the ware is distinguished as white and 
 brown. 
 
 D. Plate, terra-cotta, fire-clay ware, tubes, ornaments, vases, &c. The body earthy ; 
 mostly more or less unequal ; always coloured, porous, easily fluid, and slightly 
 sonorous. Is not usually glazed. 
 
 I. Hard Porcelain. Grinding and Mixing the Material. Hard porcelain is composed 
 of a mixture of colourless porcelain clays with felspar as a flux, which sometimes is com- 
 posed of quartz, chalk, or gypsum. The porcelain clay, in itself infusible, and becoming 
 in the fire only an earthy, opaque mass, when intimately mixed with the flux material, 
 melts easily at a higher temperature than that of the glass oven. The materials of 
 porcelain manufacture are not found native in such a condition that they may at 
 once be employed ; they must be ground to a fine powder, and this washed to separate 
 the foreign substances. Pure kaolin, however, is not utilisable in porcelain manufac- 
 ture, as it becomes much decreased in volume on the application of heat. It is there- 
 fore mixed with fine washed quartz sand, although this addition somewhat impairs the 
 plasticity. This mass on treatment with fire would be porous, and felspar is added 
 to close the pores and to form a binding glass. The proportions in Berlin 
 porcelain, according to G. Kolbe(i863), are66'6 parts silica, 28*0 parts clay, 0*70 part 
 ferrous oxide, o'6 part magnesia, and 0*3 part lime. 
 
 Proportions of the material as employed at a. Nymphenburg ; /3. Vienna ; 
 y. Meissen : 
 
 a. Kaolin from Passau 65 
 
 Sand therewith .....4 
 
 Quartz '-. J X. .V- l i* *" 2I 
 
 Gypsum * 5 
 
 Broken biscuit ware 5 
 
 b. Kaolin from Zedlitz 34 
 
 Kaolin from Passau 25 
 
 Kaolin from Unghvar 6 
 
 Quartz 14 
 
 Felspar 6 
 
 Broken ware 3 
 
 e. Kaolin from Aue 18 
 
 Kaolin from Sosa 18 
 
 Kaolin from Seilitz . 36 
 
 Felspar . . . ' . . . 26 
 
 Broken ware 2 
 
 The mixture of the materials in the required proportion takes place in large vats, 
 whence the thin pulp is pumped and forced through sieves into another vessel. 
 
 Drying the Mass. After the water is removed from the sediment at the bottom of 
 the vat or tank, the clay appears as a slime, which has to be dried to the required con- 
 sistency. The drying or evaporation of the water is effected in wide wooden tanks 
 exposed to a strong current of air. This is a very general method of drying the mass, 
 but can only be employed during the summer months on account of the dampness of 
 our climate. It is not, therefore, sufficiently extensive for large manufacturers, and 
 consequently other means of drying are resorted to usually by means of absorption, 
 the mass being laid on a porous layer of burnt lime, gypsum, &c. Drying by means of 
 gypsum is expensive, as it soon becomes hardened, and has to be removed. The mass 
 can also be dried by means of air pressure, being in this case placed in flat porous boxes, 
 
SECT, v.] EARTHENWARE OR CERAMIC MANUFACTURE. 639 
 
 under which a vacuum chamber is situated. Talbot's apparatus is formed on this prin- 
 ciple. In Grouvelle and Honore's system of drying, the water is first partially removed, 
 by means of draining over gypsum, and the mass is then put into firm hempen sacks, 
 which are subjected to pressure in a screw or lever press. Pressed clay has greater 
 plasticity than that dried by artificial heat ; but the method is expensive, as the sacks 
 soon require replenishing, being speedily worn out by the constant pressure. 
 
 Kneading the Dried Mass. When the mass is dried by pressure or by absorption, 
 the water in all cases is not equally expelled, and there are also air-bubbles which must 
 be removed. This is done by kneading and treading the mass with the feet and hands, 
 and by this means also the plasticity of the mass is improved. Another method of 
 improving the plasticity is by allowing the moist clay to stand till it becomes putrid. 
 Stagnant water is often employed. Brongniart explained the action of this rotting, as 
 it is termed, to be that gases were formed in the body of the clay, and that by the con- 
 tinuous movement caused in their endeavour to escape, the finest particles of the 
 materials were intimately mixed. Salvetat gives the following hypothesis : By the 
 rotting there is formed in the mass a large quantity of sulphuretted hydrogen gas. 
 This gas effects the reduction of the alkaline sulphides to calcium sulphides under 
 the influence of the organic substances, the calcium sulphide being set free, a similar 
 action taking place with the carbonic acid in contact with the air. The bleaching of 
 the mass on exposure to the air is due to the oxidation of the black iron sulphide 
 to iron sulphate, which is removed by washing. The decomposition of the felspar 
 constituents may also ensue from the long-continued action of the water. Ac- 
 cording to E. von Sommaruga, of Vienna, the existing sulphates are decomposed by 
 the air into sulphuretted hydrogen and carbonates, and these being removed with the 
 water, the refractory nature of the clay is improved. 
 
 The Moulding. The kneading and rotting accomplished, the porcelain mass is taken 
 to another room to be moulded. This is effected either on a potter's wheel or in a mould. 
 The Potter's Wheel. The potter's wheel consists of a vertical iron axis, on which a 
 horizontal solid wheel is fixed, and caused to revolve by the feet or by steam-power, 
 the motion in the latter case being regulated by the feet. A lump of clay is laid 
 upon the wheel, the thumb being placed in the centre of the lump and pressed down- 
 wards ; a hollow is thus formed, which is widened, or the walls continued vertically 
 according to the shape of the vessel to be made. The constant revolution of the wheel 
 easily allows the moulder to obtain a perfectly cylindrical form. By thus humouring 
 the clay, elongating the vessel, again depressing it, widening it, and by continued 
 manipulation in this manner, the most exquisite shapes are produced. To form the 
 ridges or sharp edges of the vessel a small piece of iron, a strip of horn or wood, 
 termed a bridge, is used. The perfectly formed vessel is cut away from the wheel by 
 .a piece of brass wire. 
 
 Moulding in Plaster of Paris Forms. A mould is first taken from the pattern or 
 original object, which may be of clay, wax, gypsum, or metal. The moulding is 
 performed with dry material, with clay of the consistency of dough, or with fluid clay. 
 The moulds must possess a certain amount of elasticity, and be porous in order to 
 absorb the moisture expressed. For these reasons plaster of Paris is generally used. 
 The mould is taken from the original article in parts, which are trimmed to fit together 
 accurately ; into each part is then pressed sufficient clay to fill the indentations of the 
 pattern, more clay being added till a proper thickness is obtained. The parts are then 
 fitted together, and the moulds left for some time. This method of moulding is some- 
 times called presswork, and is adapted to all kinds of pottery not of circular form. 
 Plates, cups, and dishes are also made in a similar manner. A leaf of clay is rolled 
 out and pressed between flat moulds. Sometimes, instead of rolling, the clay is beaten 
 out with a wooden hammer covered with leather. 
 
640 CHEMICAL TECHNOLOGY. [SECT. v. 
 
 Casting. Moulding porcelain articles out of thin pulpy clay is one of the most 
 ingenious arts of the potter. The fluid clay is poured into porous moulds, which 
 absorb a portion of the water, thereby reducing the pulp to a certain consistency. 
 The interior pulp remaining fluid is now poured out, and the cast or coating of clay 
 adhering to the mould allowed to harden. When sufficiently hard the vessel is taken 
 to the lathe to be finished, or if not of circular form, to the finishing room, where with 
 sharp tools any required pattern is cut, or handles, spouts, &c., which have been made 
 in separate moulds, attached. 
 
 Preparation of Porcelain Articles without Moulds. The finest porcelain is finished 
 by hand, as machinery or moulds could not give sufficient sharpness to the beautiful 
 flowers and figures sculptured on vases, &c. The flowers, &c., are first prepared in 
 moulds, are then attached to the body of the article, and finally are finished off with 
 edged tools. The stalks of the flowers are sometimes formed on wire ; and the leaf in 
 first roughly constructed in the palm of the hand, the furrowing and veining being 
 done afterwards. The texture of drapery is imitated by means of a piece of tulle, 
 which is laid on the clay, and allowed to dry. During the burning the tulle is con- 
 sumed, leaving the pattern on the porcelain. 
 
 Drying the Porcelain. After the porcelain ware is formed it is dried for some 
 time at the ordinary temperature. This is continued till the clay contains no moisture, 
 that is, until its weight is tolerably constant. During this drying the clay is said to 
 be in the green state, and possesses a greater tenacity than it has in any of the former 
 processes. 
 
 Glazing. Only very few articles of porcelain ware, generally statues or figures, 
 remain unglazed ; these are termed biscuit ware. All other articles are glazed. The 
 glazings employed are of four kinds : (i) Earth or clay glazings are transparent, and 
 formed by melted silica, alumina, and alkalies; they easily become fluid, and melt 
 about the temperature at which the vessels are baked. This kind of glazing is used 
 for hard porcelain. (2) Lead glazes are transparent glazes containing lead ; most of 
 these melt at the temperature at which the articles are burnt. (3) Enamel glazes are 
 partly white, partly coloured opaque glasses containing tin oxide besides lead oxide. 
 This kind of glaze is easily melted, and serves to cover the unequal colour of the under 
 mass. (4) Lustres are mostly earth and alkali glazes. This class includes the 
 ordinary salt-glazed ware, as well as glazes containing metallic oxides used to imitate 
 gold and silver surfaces for ornament merely. 
 
 Porcelain Glaze. We will here, however, concern ourselves only with porcelain 
 glaze. It is necessary that this glaze should melt readily at the temperature at which 
 the article is fired ; that it should be colourless and opaque ; that it should fire 
 sufficiently hard to withstand pressure, grinding, and ordinary cutting. The glaze is 
 added to the porcelain mass with a flux, so that the melting may be readily effected. 
 At Meissen the glaze used contains 
 
 Quartz . . 37-0 
 
 Kaolin from Seilitz 37-0 
 
 Lime from Pirna 17-5 
 
 Broken porcelain 8 -5 
 
 In the Berlin porcelain manufacture the following glaze is employed : 
 
 Kaolin, from Morle, near Halle 31 
 
 Quartz-sand 43 
 
 Gypsum ... 14 
 
 Broken porcelain . . 12 
 
 100 
 
SECT, v.] EARTHENWARE OR CERAMIC MANUFACTURE. 641 
 
 Applying the Glaze. The glaze can be put on in four ways: (i) By immersion. 
 (2) By dusting. (3) By watering. (4) By volatilisation. The glaze is either mixed 
 with the ingredients, or applied superficially by one of the preceding methods. 
 
 Immersion. Glazing by immersion is employed in the case of porcelain, the finer 
 fayence ware, and sometimes for stoneware. It requires some degree of porosity in 
 order that the glazing paste may be absorbed. The glazing materials are mixed with 
 water to form a thin pulp. The articles previous to their immersion are slightly baked 
 to prevent the clay being softened and running fluid in contact with the water of the 
 glaze. The articles are dipped into the glaze, which they readily absorb, a coating or 
 thin layer of glaze remaining on their surface when they are removed from the bath. 
 The glaze is removed from the bottom of the article immediately in contact with the 
 substance on which it stands to prevent its sticking. 
 
 Dusting. Glazing by dusting is a surface method, and only used for costly ware. 
 The freshly formed and still damp ware is dusted with lead glaze or minium, a layer 
 being left on the surface. The powders employed chiefly contain lead oxide, which 
 combines with the silica and alumina of the clay mass during the firing to form a glaze. 
 Recently finely pulverised zinc blende and Glauber's salt have been employed. 
 
 Watering. Watering is a method of glazing employed for non-porous articles, such 
 as English porcelain, ordinary pottery ware, and some kinds of fayence ware. Glaze 
 of the proper consistence is poured over the articles, the interior sometimes being left 
 covered with a white glaze, while the outside is again coated with a coloured glaze, as 
 is seen in common brown-ware. 
 
 By Volatilisation or Smearing. Glazing by volatilisation is effected by conveying 
 into the oven a salt or metallic vapour which shall form with the silica of the mass an 
 efficient glaze. The most general method is applied to ware not requiring to be baked 
 in fire-clay vessels. Common salt is placed in the oven with green wood for fuel to 
 form an aqueous smoke. This, the salt, heated to redness, receives, and is decom- 
 posed into hydrochloric acid and soda, the vapours of which fill the oven. The inside 
 and the outside of the vessel submitted to this process are thus simultaneously glazed. 
 Fine stoneware baked in fire-clay vessels may be glazed by the ignition of a mixture 
 of potash, plumbago, and common salt. During the baking or firing lead chloride is 
 formed, which combines with the silica of the clay to form a thin glass. This method 
 of glazing is in England termed salting, boric acid being employed. 
 
 Lustres and Flowing Colours. A method of glazing by volatilisation, known as 
 glazing with flowing colours, is employed for porcelain. It essentially consists in the 
 ignition of a mixture of calcium chloride, lead chloride, and clay, placed in a small 
 vessel in the firing capsule or firing chamber, and to which some metallic oxide is 
 added, as cobalt oxide. The oxide is converted into chloride, and combines with the 
 constituents of the article. 
 
 The Capsule, or Sagger. Porcelain ware and superfine earthenware are not exposed, 
 while burning, to the free action of the flame, as various impurities, such as ashes and 
 smoke, would deteriorate the beauty. They are therefore enclosed in fire-clay vessels, 
 termed in France gazettes, in Germany Jcapseln, and in England saggers. These 
 saggers are manufactured of the best fire-clay, with which is mixed a cement made 
 from broken saggers. First into each sagger is put a perfectly true disc of the same 
 material, and upon this the porcelain ware is placed, three knobs or small props pro- 
 jecting from the disc, and keeping the article from contact with a large surface to 
 which the glaze would cause it to adhere. 
 
 The Porcelain Kiln. Fig. 434 is a vertical section of the porcelain kiln, Fig. 435 
 the elevation. The kiln is essentially a reverberatory furnace with three stages and 
 five fire-rooms supplied with wood fires. The kiln may be considered as a tall cylinder, 
 surmounted by a cone, in the apex of which is the chimney opening, the flat vaults by 
 
 2 s 
 
642 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. 
 
 v. 
 
 which it is divided being pierced to allow of communication. Both the stages L and L' 
 serve for the "strong firing" of porcelain. The upper stage, L", termed variously the 
 howell, crown, or cowl, serves for the " raw burning." At the bottom of both the lower 
 stages are built the fire-places, f, leading by g into the kiln. G is the ash-pit, T the 
 opening to the ash-pit closed during the burning ; o is an opening through which fuel 
 is introduced ; c c are the openings, admitting of the circulation of the hot gases. P is 
 
 Fig. 434- 
 
 Fig. 435- 
 
 the door by which the kiln is entered. The kilns are gradually heated first to 
 a glowing heat and then to a strong red heat. At this stage the openings are closed, 
 and the kiln raised to a stronger heat, at which it is allowed to remain for a short 
 time. This intense burning lasts about seventeen to eighteen hours ; the kiln is then 
 opened, and allowed to cool gradually for from three to four days. 
 
 Emptying the Kiln and Sorting the Ware, After the kiln is cooled, the saggers 
 containing the ware are removed, and the ware taken out. It is then separated into 
 four kinds : (a) Superfine, containing no blemish ware; (b) Medium, the ware slightly 
 inferior in glaze, &c. ; (c) The chipped and imperfectly glazed ware ; (d) Waste, or ware 
 so distorted or cracked as to be useless. 
 
 Faulty Ware. The chief faults are : Cracking from the porcelain not being 
 sufficiently plastic, from drying unequally, and from unequal heating. Partial fusing 
 from a too strong heat. Air-bubbles causing lumps to appear on the surface of the 
 ware through the expansion of the air by heat. Spotting, from fragments of the 
 sagger fusing and falling in upon the ware. Yellow- colouring, from smoke having 
 entered the sagger. The chief faults in the glaze are : Blowing, the result of the 
 development of gas by the reaction of the constituents of the glaze upon each other ; 
 also resulting from too strong a firing. Shelling, or the exfoliating of the glaze. 
 
SECT, v.] EARTHENWARE OR CERAMIC MANUFACTURE. 
 
 643 
 
 Porcelain Painting. Porcelain painting is really a branch of glass painting, the 
 colours being glass colours, which when burnt in become durable and bright. The 
 colours employed, technically termed muffle colours, are 
 
 Iron oxide, for red, brown, violet, yellow, and sepia. 
 
 Chromium oxide, for green. 
 
 Cobalt oxide and potassium-cobalt-nitrite, for blue and black. 
 
 Uranium oxide, for orange and black. 
 
 Manganese oxide, for violet, brown, and black. 
 
 Iridium oxide, for black. 
 
 Titanium oxide, for yellow. 
 
 Antimony oxide, for yellow. 
 
 Copper oxide (and cuprous oxide), for green and red. 
 
 Iron chromate, for brown. 
 
 Lead ,, for yellow. 
 
 Barium ,, for yellow. 
 
 Silver chloride, for red. 
 
 Platinum. ,, for platinising. 
 
 Purple of Cassius, for purple and rose-red. 
 
 These colour's are mixed with a fluxing material, so that by the melting a silicate or 
 borate may be formed, yielding a good glaze. Therefore the cobalt oxide . and the 
 copper oxide must first be mixed with silicic acid and boric acid, oxide of antimony 
 with lead oxide, &c., to form a blue, green, or yellow colour, because there are few 
 metallic oxides yielding these colours that are not affected injuriously by heat or are by 
 themselves sufficiently easily fluid. The burning in of the colours is effected in a 
 muffle, Fig. 436, the opening o serving as a communnication with the interior, by 
 which the degree of heat may be 
 ascertained ; the opening m serves 
 for the escape of the vapours of the 
 essential oils (oil of turpentine, oil 
 of lavender, <tec.), with which the 
 enamel colours are sometimes ground 
 up. Fig. 437 shows the method of 
 heating the muffle. The heating is 
 commenced at a low temperature 
 and is gradually increased to a red 
 heat. From time to time the muffle 
 is opened till the colours begin to 
 disappear ; then the muffle is care- 
 fully closed, raised to a blight red 
 heat, and finally allowed to cool as 
 slowly as possible. 
 
 Ornamenting the Porcelain. The gold employed for decorating the porcelain is 
 dissolved in aqua regia, and precipitated with either iron sulphate, bismuth nitrate, 
 or by means of oxalic acid. In its application the gold must be intimately mixed 
 with a flux, generally mercurous nitrate. Shell gold is employed, also gold-beaters' 
 refuse. The article to be gilt must be thoroughly freed from grease, else the gold 
 will not adhere. The gold powder, finely ground up with sugar or honey, or some 
 such soluble substance, is applied with a pencil brush. The burning in is effected in a 
 muffle. The gold is not melted during the burning, but becomes firmly set upon 
 the article by means of the flux. After burning the gold does not at once appear bright, 
 but requires burnishing with an agate tooL 
 
 Bright Gilding, Bright gilding differs from the foregoing in requiring no after 
 
 437- 
 
 Fig. 436. 
 
644 CHEMICAL TECHNOLOGY. [SECT. v. 
 
 polishing or burnishing. It is effected by burning in a mixture of gold sulphide or 
 fulminating gold in balsam of sulphur. When an article is gilded with precipitated 
 metallic gold or a bright gold preparation, the gilding is secure from injury by handling 
 or scratching with the finger-nail, &c. 
 
 Silvering and Platinising. Silvering and platinising are usually only in slight 
 requisition. Metallic silver is thrown down from its solution by means of copper or 
 zinc ; the platinum is precipitated from its neutral chloride by means of boiling with 
 potash and sugar. The tarnishing of silver on porcelain by sulphuretted hydrogen 
 may, according to Rousseau, be prevented by placing, before burning, a thin layer of 
 gold upon the part silvered ; the result then is a white layer of gold-silver. The 
 silver and platinum are mixed with basic bismuth nitrate, painted on and burnt in, and 
 afterwards burnished. 
 
 Lithophanie. Transparent porcelain is used in the art of lithophanie, or making 
 transparencies. A thin and unglazed porcelain plate is pressed into a flat gypsum 
 mould bearing the pattern in high relief. The figures by transmitted light appear in 
 delicately rounded tones of light and shade. The applications of this art to the 
 manufacture of lamp shades, window ornaments, &c., are too well known to need remark 
 here. 
 
 Very similar to lithophanies are the articles of porcelain and fayence now pro- 
 duced under the names Email ombrant, or Email de Rubelles, or lithoponies. They are, 
 however, as regards the pressing, the very opposite to lithophanies, since in Email 
 ombrant the darkest parts must be most depressed and therefore the thinnest, and the 
 picture is seen not by transmitted but by reflected light. In these objects depressions 
 are produced by means of moulds, and are then filled up with a semi-transparent and 
 coloured mass of glaze, when the deepest parts take up thicker strata of glazing, and 
 appear darker than the more elevated parts. 
 
 II. Tender Porcelain. French Fritte Porcelain. Tender or fritte porcelain is dis- 
 tinguished in commerce as of two manufactures, French and English. The French 
 manufacture, in 1695, was first carried on at St. Cloud, near Paris, by Morin, who 
 employed a glassy mass, without the addition of kaolin, but containing lead, somewhat 
 similar to crystal glass. It can, therefore, hardly be considered a porcelain, strictly 
 so called, until melted with lime and alumina. Thus fritte porcelain is composed of 
 (i) A glass mass or fritte, obtained from silica and alkalies. (2) Marl, as a clay con- 
 stituent ; chalk, as a lime constituent. The proportions of these constituents are 
 
 Fritte 75-75 
 
 Marl 17 ... 8 
 
 Chalk 8 ... 17 
 
 The fritte is mixed with the chalk and marl to form a thin pulp, which is allowed 
 to remain for a month to dry, and then again pulverised. When required quickly, 
 plasticity is obtained by adding soap- or lime-water. Fritte porcelain is burnt in saggers, 
 generally before glazing. During the burning this kind of porcelain softens more than 
 the hard, and requires supporting on every side. It is for this reason generally baked 
 in fire-clay moulds. The ordinary oven is employed. The glaze for tender porcelain 
 is a kind of crystal glass containing lead. This glaze is poured over the articles, as 
 they are non-absorbent on immersion. French porcelain is similar to cryolite glass or 
 hot-cast porcelain. ^ 
 
 English Fritte Porcelain. English tender porcelain consists of a plastic clay, so- 
 called china clay or Cornish stone, a weathered pegmatite, with fire-clay and bone-ash. 
 The addition of the latter is due to Mr. Spade, in 1802 ; recently calcium phosphate, 
 as apatite, phosphorite, staffelite, or sombrerite, has been substituted. The glaze 
 is composed of Cornish stone, chalk, fire-brick, borax, and lead oxide. The article 
 must be baked before glazing, as the glaze is so much more easily fusible than 
 
SECT, v.] EARTHENWARE OR CERAMIC MANUFACTURE. 645 
 
 the body of the article ; and in this second firing lies the difference between the 
 manufacture of tender and of hard porcelain. In hard porcelain the melting-point of 
 the glaze and the body are the same. English porcelain is far less solid and more 
 liable to crack than the hard ; upon the other hand, English porcelain is the more 
 plastic, and can be produced at a lower temperature in saggers of inferior fire- 
 resisting qualities, consequently at a less expense. The burning takes place in a stage 
 oven with anthracite coals, the articles being placed in saggers. The glaze is applied 
 by immersion. Recently boric acid has been largely employed in glazing English 
 porcelain. 
 
 Parian and Carrara. Parian is an unglazed statue-porcelain, similar to English 
 porcelain, but more difficultly fusible, containing less flux and more silica. The colour 
 is a very slight yellow ; the surface is wax-like. Parian was first prepared by Cope- 
 land, in 1848, although the idea was not new, as before this time Kiihn, of Meissen, 
 had prepared statues and medallions of porcelain in imitation of marble. The compo- 
 sition of Parian is very variable; some on being tested yield calcium phosphate, 
 others barium silicate, and again some contain only kaolin and felspar. 
 
 Carrara, so named in imitation of the marble produced from Carrara in Tuscany, 
 is intermediate to Parian and stoneware, is less transparent than Parian, and sometimes 
 whiter in colour. 
 
 III. Stoneware. Stoneware differs entirely from porcelain. It is dense, sonorous, 
 fine-grained ; does not cling to the tongue ; it is semi-fused and opaque. Even fine 
 white stoneware is different from porcelain in transparency, being entirely opaque, 
 although in some other respects similar. Stoneware is distinguished 
 
 1. As porcelain glazed. 
 
 2. As Avhite or coloured unglazed. 
 
 3. As common stoneware, salt-glazed. 
 
 The fine white stoneware is made from a plastic clay, burning white, and not very 
 refractory. To the clay is added kaolin and fire-clay with a felspar mineral, generally 
 Cornish stone, as a flux. The glaze contains lead oxide and borax, and is transparent. 
 The flux is used, in the making of stoneware, much more freely than in porcelain, in 
 the proportion of more than half the weight of the mass. It follows that stoneware can 
 be burnt at a lower temperature than porcelain. The articles are fashioned out of the 
 plastic clay in the same manner as porcelain. Fine stoneware is used as a cheap sub- 
 stitute for porcelain, it being much more easily burnt. 
 
 White or coloured unglazed stoneware, or Wedgwood ware, is made from a plastic 
 slightly refractory clay, kaolin, fire-clay, and Cornish stone, the latter in the proportion 
 of half the weight of the whole. It is more easily fusible than porcelain, requiring a 
 lower temperature in burning. The coloured stoneware is of the same composition as 
 the white, the colouring being only superficial. Frequently other coloured clays are 
 used for ornaments in relief. Coloured Wedgwood ware is known as Egyptian, 
 bamboo, fine salt ware, fine biscuit, &c. 
 
 Common stoneware differs from the preceding in containing no flux, the clay being 
 semi-fused by the continued action of the fire. To the clay is added fine sand, or 
 pulverised fragments of stoneware. Chemical and pharmaceutical utensils, acid 
 tanks, &c., are made of this ware, it being strong and durable. The colour is 
 generally grey. 
 
 Stoneware Ovens. The ovens for burning stoneware are so constructed that the 
 articles can either lie down or be placed vertically. Fig. 438 is the vertical section of 
 such an oven through the line AB in Fig. 439. Fig. 440 is a section through the 
 line CD seen from B. Fig. 441 is a section through CD seen from A. Fig. 439 is 
 the plan on the line EF, Fig. 438. a a is the arch or vault of the oven, built of 
 clay ; J, the vessel-chamber ; c, the fire-room ; d, the fire-bars ; e, the stoke-hole ; f t 
 
646 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. v. 
 
 the ash-pit ; y, an air-draught ; i i, a pierced wall ; k, a pierced back- wall, through 
 which the flame and hot gases escape into o, serving as a flue. Anthracite is used as 
 
 Fig. 438 
 
 Fig. 439- 
 
 Fig. 440. 
 
 Fig. 441. 
 
 fuel. Another form of oven in which mineral-water bottles are burnt is shown in 
 Fig. 442. It is constructed on an easy slope ; at the lowest part is the fire-room, A. 
 In the middle of the burning-room is the pierced wall, C, technically termed the 
 
SECT, v.] EARTHENWARE OR CERAMIC MANUFACTURE. 647 
 
 window, through which the hot gases and flame escape into D. The vault and walls, 
 B and E, are of broken earthenware, bound with mortar. A chimney is unnecessary, 
 the gases escaping through the pierced wall, E, into the air. The burning usually takes 
 about eight days. The high temperature at which common stoneware is burnt, and 
 the nature of its components, render glazing unnecessary ; but generally a gkze is 
 obtained with the help of common salt 
 
 placed in the oven during burning. After *S- 44 2 - 
 
 the placing of the salt the openings of the 
 oven are closed for some time, and then 
 a second quantity of salt is introduced. 
 The silica, with the assistance of the 
 steam, decomposes the salt into hydro- 
 chloric acid and soda, with which it com- 
 bines. Thus there is formed on the surface 
 of the ware a glaze of sodium and alu- 
 minium silicate. The salt will take up more than 50 per cent, silica, according to 
 Leykauf's experiments; therefore, the more silica the better glaze. An oven of 
 moderate size will require 80 to 100 Ibs. of salt ; the purity of the salt is not a 
 subject of much consideration. The glaze is colourless, and the vessel appears the 
 colour of the clay. Stoneware that is unequally coloured, one part brown, the other 
 grey, has been brought to that state by escape of hydrocarbons into the burning-room. 
 
 Lacquered Ware. Lacquered ware, known as Terralite and Siderolite ware, is 
 manufactured in Northern Bohemia by the firm of Villeroy & Boch, of Mettlach, and is 
 an intermediate ware to fine and common stoneware. It has no glaze, but a strong 
 surface colour of varnish or lacquer. Candlesticks, bowls, flower-vases, jugs, flower- 
 pots, baskets, butter-dishes, fruit-dishes, &c., are formed from this ware, and baked in 
 saggers in the usual manner. Great care and attention are required in burning 
 the ware. The colour or bronze is mixed with varnish, thinned with turpentine or 
 linseed-oil, and applied with a pencil. The ware is then placed in a slow oven ; the 
 ethereal oils volatilise, and the bronze colour becomes fixed to the surface of the ware. 
 
 IV. Fayence. Fayence ware (English fine stoneware) derives its name from 
 the town of Faenza, in Central Italy, where the ware was skilfully made. In 
 the ninth century the Spanish Moors manufactured fayence in the Island of Majorca, 
 whence the present majolica, the slight alteration in the manner of spelling being 
 accounted for by Dante, in his " Tra isola di Capri e Majolica" on the ground that 
 the older Tuscan writers spell the name of the island " Majolica." The industry 
 developed from the thirteenth to the fifteenth century ; from that to the seventeenth 
 it culminated, and then commenced to decline. In the middle of the sixteenth century 
 Bernard Palissy introduced the ware known as Palissy-fayence into France. Palissy's 
 celebrated pieces rustiques consist of ware ornamented with fish, fruit, vegetables, &c., 
 naturally coloured in enamel. The body of porous fayence ware is earthy, and 
 clings to the tongue. It is opaque, with more or less plasticity, and little or no 
 sonorosity. It consists generally of plastic clay, or a mixture of this with common 
 potter's clay. It differs from clay ware in the employment of finer material, mani- 
 pulated with greater care. Fine white fayence is distinct from common enamelled 
 fayence. Fine fayence (semi-porcelain) consists of a plastic clay with pulverised 
 quartz or fire-bricks, with kaolin or pegmatite and felspar minerals. It remains 
 white after burning, and is coated with a transparent glaze. The fayence wares of 
 different countries differ greatly ; some are easily fusible, others again are burnt at a 
 high temperature. The composition of the glaze is therefore very varied. Common 
 lime fayence is a mixure of potter's or plastic clay, marl (clay with calcium carbonate), 
 or quartz and quartz-sand. It is characterised by containing 15 to 25 per cent, of 
 
648 CHEMICAL TECHNOLOGY. [SECT. v. 
 
 lime, which, at the low temperature at which common fayence is burnt, only loses a 
 portion of its carbonic acid. The common fayence ware is thus easily distinguished 
 from other wares by its property of effervescing when an acid is poured into a vessel 
 made of this ware. Its fracture is earthy ; the colour, consequent upon its containing 
 2 to 4 per cent, of iron oxide, is a decided yellow, so that an opaque glaze is employed. 
 The glaze or enamel contains usually tin and lead oxides, alkalies, and quartz. 
 The more iron oxide and lime contained in the mass, the lower the temperature 
 required for burning. Fayence, like porcelain, is twice burnt, first without, and secondly 
 with, the glaze. It is burnt in saggers ; the ware is placed in the saggers, and these 
 are piled one upon the other in the furnace, with a layer of fat clay between each pair 
 The articles stand in the saggers upon small tripods, in order to expose as small a con- 
 tact surface as possible. The hard -burnt ware has next to be glazed. A thin pulp 
 with water is made of the materials of the glaze placed in a cistern into which the 
 articles are dipped. The glaze usually consists of felspar (Cornish stone), fire-clay, 
 heavy spar, sand, borax and boric acid, crystal glass, soda and sodium nitrate, white- 
 lead, minium, and smalt. The composition of this glaze is ordinarily very complicated, 
 but the essential constituents are silica, boric acid, alumina, lead oxide, and alkali. 
 Recently the Peruvian mineral, so-called tiza (sodium and calcium borate), has been em- 
 ployed. The addition of lead serves to render the glaze easily fusible, while the felspar 
 imparts the softness characteristic of a lead-alkali glaze. 
 
 Ornamenting Fayence. Fayence is ornamented by i. Painting; 2. Casting; 
 3. Printing ; 4. Lustring. Painting is usually done with the brush, partly under, and 
 partly upon, the glaze. The glazing oven not attaining so high a temperature as the 
 porcelain oven, the colours are not affected by the heat. The colours used are 
 chromium, cobalt, iron, antimony oxides, &c. The rose- and purple-red colours are 
 obtained from gold preparations. The pink colour, carnation pink, was discovered 
 in this country, and is a stannic chromate. To make this colour 
 
 Stannic acid 100 
 
 Chalk 34 
 
 Potassium chromate .......... 3-4 
 
 Silica 5 
 
 Alumina i 
 
 are well mixed and allowed to stand for some hours in a strong heat. The mass 
 appears as a dirty rose- red colour, attaining its full brilliancy when washed with 
 water acidulated with hydrochloric acid. The casting consists in the fayence vessel 
 receiving a surface layer of coloured clay in any required part, independently of the 
 colours of the mass. These coloured clays or clay-washes are made of the ordinary 
 fat clays d metallic oxides. The printing is accomplished with the aid of thin 
 tissue-paper, upon which the pattern is first printed from a copper plate, and after- 
 wards transferred to the ware. For black, a mixture of forge-scale, manganese, 
 and cobalt oxide or chrome-black is employed ; for blue, cobalt oxide mixed with, 
 for bright blue, fire-brick, and for less intense colours, heavy-spar, both of course 
 being pulverised. This mixture is burnt, the frit ground, and mixed with a flux 
 of equal parts of flint-glass and fire-clay. Copper plates, in which the pattern is 
 deeply cut, are charged with colour mixed with linseed-oil ; a transfer is then taken 
 on the fine " pottery tissue" paper, and laid on the ware. By means of a rubber 
 the colour is caused to leave the paper, which has been previously moistened with 
 water, and adhere to the ware. The paper is then washed off, and the article taken 
 to the kiln. 
 
 Flowing Colours, Flowing colours are nmch employed in ornamenting fayence. 
 The common fayence or delft ware is coloured blue in this manner by means of cobalt 
 oxide mixed with the glaze. When the vessels are taken to the burning-kiln, a 
 
SECT, v.] EARTHENWARE OR CERAMIC MANUFACTURE. 649 
 
 mixture of calcium chloride, lead chloride, and clay is also introduced on a small 
 plate. The cobalt oxide is converted into a chloride by combining with the 
 volatilised materials, and in turn combines with components of the material of the 
 vessel. By this means the articles obtain an apparent transparency somewhat similar 
 to that characteristic of porcelain. 
 
 Lustres. Some kinds of ware have a second coating a metallic lustre or glaze 
 given to them after burning. Gold Lustre : The different kinds of gold lustre are 
 very similar and need not be detailed. They are essentially composed of fulminating 
 gold and balsam of sulphur, the latter prepared by heating linseed-oil and sulphur 
 together. Platinum Lustre : This is obtained by mixing anhydrous platinum chloride 
 with lavender-oil or balsam of sulphur; also by the well-known precipitation of 
 platinum with sal-ammoniac. Silver Lustre is either a yellow lustre or a cantharidine 
 lustre, so called from its similarity in appearance to the wing-cases of the Spanish fly 
 (Cantharis vesicatoria). Salvetat believes that silver chloride may be employed as a 
 yellow lustre, similarly to gold preparations. The cantharidine lustre is generally a 
 yellow lustre, the difference being that it is only used for white grounds, while the 
 former is employed for blue grounds, on which it appears slightly tinged with green. 
 Copper lustre is both red and yellow ; it is used for Spanish fayence and majolica 
 wares. It is chiefly formed by a copper silicate. Lead oxide, or lead lustre, is merely 
 a lead glaze. Silver chloride, mixed with lead lustre, is reduced, the result being a 
 deposit of a gold-yellow or a silver-white colour, according to the proportion of silver. 
 
 Etruscan Vases. The vases of the old Romans were a kind of fayence ware, con- 
 taining iron, and formed of a clay decomposed by quartz, only slightly burnt, some- 
 times unglazed, sometimes coated with an easily fusible glaze. These vases and 
 articles are celebrated more for their beauty of form than for any peculiarity in com- 
 position, which is very analogous to the well-known delf ware of which our table- 
 services are made. 
 
 Clay Pipes. In the manufacture of clay pipes there is employed the beautifully 
 white pipe-clay, containing neither iron, nor sand, nor carbonate of lime. The clay, if 
 pure, always burns white : but occasionally, when a yellow colour appears, the clay is 
 burned for a longer time, whereby the iron oxide colouring the clay is removed. 
 The pipes are formed in a mould similar in shape to the pipe. A roll of clay is taken, 
 and carefully spread out to the length of the pipe. The mould is constructed in two 
 parts, hinged together like a meerschaum pipe-case, and is generally of iron. The 
 roll of clay is placed on the lower half of the mould, and the upper half is then pressed 
 or screwed down. A wire is then pushed up the entire length of the stem. The pipe 
 is then taken out of the mould, and set aside to dry. It is afterwards taken to the 
 oven, where about a gross of pipes are introduced into each sagger. The saggers are 
 long clay tubes. Sometimes the pipes are burnt without saggers. To prevent the 
 pipe adhering to the lips on account of the porosity of the clay, the end put to the 
 mouth is rubbed with a mixture of soap, wax, and lime-water. 
 
 Water Coolers. The Spanish water-cooling vessels, or alcarrazas, are made of a 
 porous, unglazed earthenware. The constant evaporation of the water exuding to the 
 outer surface of the vessel causes the water to be kept cool in the hottest climates. 
 The vessels are only slightly burnt. According to Sallior, water can be cooled 15 in 
 an alcarraza, while Sevres ware only permits of the cooling of its contents in a 
 similar manner some 2 or 3. These vessels are known in France as hydrocera/mes. 
 In this country Egyptian wine and butter coolers are very common, while in Egypt, 
 Spain, Turkey, the Indies, and Americas they are really necessaries. In Bengal these 
 coolers are made from the mud of the Ganges. In the Levant they are termed baldaques ; 
 in Syria and Egypt collies or giillies, while in many places they are also known as 
 gargoulettes. 
 
650 CHEMICAL TECHNOLOGY. [SECT. v. 
 
 V. Common Pottery. To distinguish between the different kinds of this ware 
 is extremely difficult. The manufacture is entirely distinct from the preceding. 
 For the so-called white pottery, used for culinary purposes, ordinary potter's clay is 
 employed, and for brown ware a moderately refractory clay. The natural clays are, as 
 a rule, too fat to be used without the addition of some other material, generally sand ; 
 besides sand, fire-brick, chalk, charmotte, and anthracite coal-ash are employed. The 
 vessels are formed upon a potter's wheel, air-dried, and then glazed. The employment 
 of a lead glaze was but a short time ago unknown in the glazing of this kind of ware. 
 Ordinarily the mass is white or yellow, sometimes brown-red ; the glaze being 
 transparent, the colour of the body or mass is always visible. Partly because the 
 ware is very easily fusible, and partly because a low heat is used in the burning, the 
 glaze must also be very easily fusible. For this reason a lead glaze, forming an 
 aluminium and lead glass is very applicable, and is employed mixed with loam (clay 
 and sand). The materials are ground and very intimately mixed in a hand-mill. The 
 lead used is generally a lead-glance. During the burning the lead-glance is roasted, 
 and the sulphur is driven off as sulphurous acid. The lead oxide combines with 
 the silica and alumina of the loam, or mixture of sand and clay, to form aluminium 
 and lead silicate. 
 
 The glazing of the air-dried ware can be performed in three ways : either by 
 immersion, by sprinkling, or by dusting. By immersion the workman's hands come 
 into contact with the lead-containing glaze, with detriment both to his health and the 
 adhering of the glaze if his hands should be greasy. This method is not therefore 
 often employed. Sprinkling is generally adopted. In dusting, the ware is first im- 
 mersed in a pulp of fat clay, and then, while still damp, dusted with the finely 
 pulverised glaze. The danger of this process is the inhaling of the fine particles of 
 glaze floating in the air of the work-room. When the lead oxide is properly pro- 
 portioned to the silica of the clay or loam, the resulting lead-glass is not affected by 
 ordinary organic acids. But if the lead oxide is not well combined with the silica, 
 it will be dissolved by boiling vinegar. The experiments of Buchner, A. Vogel, 
 Erlenmeyer, and others have shown that the insolubility of lead-glaze is not so great 
 as has been supposed, very dilute vinegar in some cases being sufficient to effect a 
 solution. The use of vessels thus glazed may therefore have no little influence upon 
 the health of a family, and it becomes necessary to consider if there is not some sub- 
 stitute. All injury likely to accrue from the use of this glaze would be removed if 
 the potter would but reburn imperfect ware, or employ ovens of the best construc- 
 tion ; but this is not always the case. Recently the preparation of a glaze free from 
 lead has been attempted, by employing water-glass, or a mixture therewith of calcium 
 borate. 
 
 Burning. The glazed vessels are next taken to the oven. This is generally a 
 reverberatory furnace, 2% to 2f metres in height, and 7 to 10 metres in length. At 
 one end is the fire-grate, and at the other the chimney. The vessels are burnt with- 
 out saggers, and are exposed to the full influence of the flame. The fire is at first 
 kept low for eleven to twelve hours, and then maintained strongly for four to five 
 hours. The vessels can be removed from the oven about eighteen to twenty-four 
 hours after being burnt. 
 
 VI. Brick and Tile Making. The bricks of modern times are very distinct from 
 the unburnt, air-dried clay lumps ; although these are still in use in some districts. 
 
 Terra-cotta. The term terra-cotta ware generally includes the burnt, unglazed 
 yellow or red clay ware, and also tiles, employed in building and architectural orna- 
 mentation. The preparation of this ware is almost entirely mechanical, and does not 
 call for any further elucidation in this work than will be found in the following pages 
 descriptive of the class of manufacture to which it belongs. 
 
SECT, v.] EARTHENWARE OR CERAMIC MANUFACTURE. 651 
 
 Brick Material. Various clays are used in brick-making. Usually those only are 
 selected that will form a brick capable of bearing a considerable strain. In the burning 
 a test-brick is employed, which is removed from time to time to see the progress of the 
 fire, to prevent the over-burning of the bricks, or the lowering of the fire till the 
 bricks are sufficiently burnt ; but this brick must not be confounded with another 
 test-brick for the following purpose. A brick is made of any new clay to be tested. 
 and is set apart in an active kiln, being burnt at the same temperature as the bricks of 
 this kiln afterwards sent into the trade. By the qualities of this test-brick the nature 
 and worth of the new clay is judged. A batch of bricks should be composed of clays 
 that may all be burnt at the same temperature, else very unequal results will follow ; 
 some bricks will be under-burnt and some over-burnt, while only those bricks to the 
 clay of which the temperature is adapted will be of use commercially. A brick-clay 
 containing much calcium carbonate can be burnt at a very low temperature, and in- 
 deed bricks so composed are very solid, and have great durability. Brick-clays often 
 contain felspar, mica, ferric hydrate, and phosphate, besides organic matter. When 
 these are not in large quantities their presence is not detrimental. Mica and felspar 
 with iron oxide act as fluxes, and in moderate quantities are useful rather than per- 
 nicious. Flint stones, large pieces of calcium carbonate and gypsum, interfere with 
 the easy utilisation of brick-clays. Sulphur pyrites render clays unsuited to the 
 manufacture of bricks, as the iron sulphide remaining in the brick after burning 
 oxidises in the air to sulphate, which in a short time weathers out and renders 
 the brick brittle. In the Netherlands, in the Thames near London, on the banks 
 of the Ganges and Nile, in the muds of rivers, and in nearly all clays exposed 
 to the ebb and flow of water, is found an admirable material for brick-making. Since 
 1852 a mixture of lime, river-sand, and water has been extensively used as a brick 
 material, and for other building purposes. 
 
 Preparation of the Clays. The excavating of the clay for making bricks is carried 
 on in the summer or spring. The clay is placed in not too high a layer, and allowed to 
 weather. It is very advantageous if, during the weathering, a frost sets in. The 
 clay is allowed to remain thus exposed to atmospheric influence until it becomes boggy 
 or marshy. In this condition it is brought to a tank dug in the ground, 4 metres long, 
 2 metres broad, and 1*3 metre in depth, where it is mixed with about as much water 
 as will stand to a height of 6 centimetres in the tank. So soon as the clay is thoroughly 
 saturated it is treadled that is, the brick-maker fastens boards or wooden shoes to 
 his feet, and carefully treads over the clay, picking out all the flints, &c., which resist 
 the passage of his foot to the bottom of the layer. This process is repeated two or three 
 times. Sand is then added to the clay. If the clay is fat the mixture is proceeded 
 with ; but if it is a poor clay it is advantageous to wash out a portion of the sand. 
 This may be effected in two ways. The ground-tank just described may be flooded 
 with water, and the sand allowed to settle to the bottom ; or the mixed sand and clay 
 is placed in a large wooden tub, with a hole in the side near the bottom stopped with 
 a plug. When the water has thoroughly impregnated the clay it is let off, carrying 
 part of the sand with it. Or the clay is stirred with the water to a thin pulp, and 
 allowed to run out of the wooden cistern into a ground-tank, where, with the water, 
 the sand settles to the bottom. London clay, being mostly alluvial, has to be very 
 carefully treated to free it from flint stones, &c. ; it is afterwards mixed with ash or 
 sand. 
 
 The " treading " of the clay is at the present time performed in mills, termed 
 " pug" mills and "washers." At the International Exhibition (1871) several machines 
 were exhibited for performing the whole process of brick-making continuously. Among 
 these was the three-process brick-making machine of Messrs. Clayton, Son, & Hewlett, 
 of the Atlas Works, and combining at one operation crushing, pugging, and brick- 
 
652 CHEMICAL TECHNOLOGY. [SECT. v. 
 
 making. The rough clay is thrown into the hopper of the machine ; in this hopper 
 revolves a shaft, upon which are keyed several small knives to cut up the clay pre- 
 viously to its being crushed. It next passes through a pair of crushing rollers, and these 
 effectually reduce any stones or hard lumps of clay which may enter. The clay, thus 
 partially prepared, next passes into a horizontal pugging or mixing cylinder situated 
 beneath, where it is mixed by the pug-knives fixed upon the central shaft. The knives 
 force the clay towards the further end of the cylinder, where it is received by rollers 
 and forced through the dies, forming a smooth bar of clay of the width and depth of a 
 brick. This bar is cut into the required lengths by wires. The machine is capable of 
 producing 20,000 to 30,000 bricks per diem, and is, perhaps, the best of its class. 
 Mr. Rawden has constructed a machine in which no rollers or crushers are employed, 
 the clay being turned out as wet and as soft as in hand-moulding. One horse-power will 
 pug the clay and mould from 12,000 to 15,000 bricks per day. It consists of a square 
 pug-mill, through which runs a vertical shaft bearing pug-knives. On the top of this 
 shaft, above its bearing, is attached the horse-pole, which gives motion to the whole 
 machine. Upon the lower end of the shaft, which passes through the bottom of the 
 pug-mill, is a wheel having two cams, on which two rocking-arms work. One arm 
 presses the soft clay through a grating into a six-brick sanded mould, and the other 
 arm is connected to a slide for pushing the empty sanded moulds under the grate, the 
 empty mould at the same time pushing the full one out. Among the best continental 
 machines are those of Henschel of Cassel, and of Karrens. 
 
 The moulding of bricks and tiles is effected partly by hand, but chiefly by machinery. 
 The burning is effected either in kilns or in specially constructed furnaces. They are 
 either open or closed, or arranged for continuous work, and burn either wood, peat, 
 lignite, coal, or gas. 
 
 The brick furnaces with unintermittent action are coming more into use. The first 
 step in this direction was the furnace of Hoffmann and Licht. It consists of a circular 
 channel, which is accessible from without in its various parts, and closed at as many 
 parts, against a central chimney. Hoffmann's ring furnace is usually a smooth 
 building, 3-4 metres in height, and flat above. The chimney rises generally in the 
 middle of the masonry, but it may be placed externally. The whole is covered with a 
 slight roof for protection against the weather. The furnace itself may be round, oval, 
 oblong, three- or four-sided, or even of horse-shoe shape. 
 
 The space for burning is a vaulted continuous channel, returning into itself. This 
 endless channel has in its top a number of openings, equally distributed, the heating- 
 holes. There are also a number of doorways, which pass through the outer wall. In 
 the inner and hinder wall of the burning space there are an equal number of smoke- 
 flues. A movable partition, filling up the entire cross-section of the burning space, can 
 be introduced into the endless channel, so that at its right hand in front there is always 
 a doorway, and at its left, behind, a smoke-flue. Latterly, instead of this, iron 
 slide-paper has been used, which is torn by means of a cord when the fire is to 
 advance into a chamber. All the outer doors and flues can be closed so tightly that, 
 if one of them is opened, the others may be considered as non-existent. 
 
 The smoke-flues open into the smoke-chamber, which is a connecting link between 
 the burning space and the chimney, and may either lie on the horizontal plane of the 
 burning-space by which it is surrounded and protected, or it can be placed below, 
 above, or outside the furnace. 
 
 Of the following figures, 445 shows a vertical section ; 446 in its upper half a view 
 from above, and in its lower half the ground plan of a circular ring furnace, in which the 
 movable partition is introduced from above through slits in the vault of the furnace ; 
 443 is a small ground plan ; 444 shows the manner in which the smoke-flues are closed 
 air-tight. If we suppose the section of the furnace closed at one point by the intro- 
 
SECT, v.] EARTHENWARE OR CERAMIC MANUFACTURE. 
 
 65S 
 
 duction of this movable partition ; if we suppose this entrance doorway and the 
 adjoining smoke-flue opened, but all the other entrance doorways of the outer wall and 
 all the other smoke exits of the back wall are closed, the air passes through the open 
 door into the burning spaces, traverses it through its entire length, as far as the other 
 side of the movable partition, passes here through the open flue to the smoke-chamber,, 
 and thence to the chimney. 
 
 Fig. 444. 
 
 Fig. 443. 
 
 Explanation of Terms. 
 
 Schieber 
 
 Raiichsammler 
 
 Ofencanal 
 
 Slide. 
 
 Smoke-collector. 
 
 Kiln-channel. 
 
 Raiichsammler Smoke-collector. 
 
 Glocke Bell. 
 Fuchs ockr Rauch- 
 
 canal Smoke-cUaunel. 
 
 Fig. 445- 
 
 When the bricks which are nearest the open outer door are cooled down in such a 
 manner that they are fit for removal, their place is taken by fresh, unburnt bricks. 
 The closure of the furnace is then effected at the next door on the right hand, and 
 behind the raw bricks which have just been put in. This door is then opened and the 
 former one is closed ; in like manner the next flue is opened and the former one closed, 
 and the fire is advanced forwards by the length of the compartment. By continually 
 repeating this process the fire makes the entire circuit of the furnace. Burnt bricks 
 are simultaneously taken out and raw ones put in without interruption. If we pass 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. v. 
 
 round the furnace, setting out from the movable partition in the opposite direction to 
 the advancing combustion -gases, we have the furnace-channel on our light. We first 
 
 pass bricks which have only 
 
 Fig. 446. just been put in and are there- 
 
 fore still cool ; then to others 
 which are gradually warmer and 
 warmer, until in the middle 
 of the circuit we meet the 
 full fire. Beyond that point 
 we meet with bricks which are 
 still strongly heated and then 
 successively with such as are 
 cooler and cooler, and at the 
 first open door we find such as 
 are quite cold and are being 
 carted away. At the next 
 open doors the men are en- 
 gaged in charging the furnace 
 with raw (technically green) 
 bricks. 
 
 According to the author's 
 experiments the charge for the 
 fourteen chambers of a ring 
 furnace requires seven to eight 
 days for thorough burning. 
 The highest temperature was 
 I0 57? whilst the gases escaped 
 at 1 08 and 172. The diagram, 
 
 Fig- 447> shows the rise and fall of the temperature. The proportion of carbon dioxide 
 in the gases taken at the bottom is essentially larger than under the vault, and carbon 
 monoxide is found only when the gases are taken direct from the coals introduced. In 
 
 Fig. 447. 
 
 Explanation of Terms. 
 
 Jtauchsammler 
 Ofencanal 
 
 Smoke- collector. 
 Kiln-chaimei. 
 
 Einfftxen Dorro^^mcj^ Breynen iMkuhten, ^aszittm 
 
 '0 tO 9^ ' 8 1 6 
 
 nTTTiji IHiHIII'lllllllliiiililDll III Illlttttttltttttt^^^ 
 
 COO ::::::::::: :::::::::;:--- - j, 
 
 x ' -* 5 ^ r 2 1 14 / N '' " 
 
 Miii![inilllMllll!in!M!llt!tlllllMMlllllMllllMMI'lilli!!llllll 
 
 144444444 144 1 1 HI HI ilrrnt fn 1 1 1 1 1 1 II 1 1 1 1 1 [1 1 1 1 11 
 
 |||ij||(fjPpp||||^^ 
 
 3. 
 
 Explanation of Terms. 
 
 Einsetzen 
 V or war men 
 Brennen 
 
 Putting in. 
 Preliminary heating. 
 Burning. 
 
 AbMhlen 
 Auaziehen 
 Tag 
 
 S. 
 
 Cooling off. 
 Taking' out. 
 Day. 
 
 ring-furnaces a reducing fire can scarcely occur even 'transiently, thus obviating the 
 discoloration produced by sulphuretted coal. But, generally, facing-bricks of a good 
 colour are more difficult to produce in ring-furnaces than in common furnaces. The 
 quantity of coal consumed depends on the quality of the clay. From 242 to 360 bricks 
 
SECT. v.J EARTHENWARE OR CERAMIC MANUFACTURE. 
 
 655 
 
 take T cubic metre of furnace space. Ring-furnaces may be used for brick-making 
 either on the small or the large scale. 
 
 Bock has recently devised a channel furnace in which the green bricks, &c., are 
 brought on trucks, meeting the furnace-gases up to the fire, where they are fully burnt, 
 and as they pass onwards they give off their heat to the furnace-gases. The propulsion 
 of the trucks often involves difficulties. 
 
 Fig. 448. 
 
 Gas-firing. In Escherich's ring-furnace the gas produced in the generators, G, 
 issues from the flues, v, into the pipes, d, built of hollow stones, and issues from 
 numerous lateral openings 5 to 20 millimetres in width, where it forms flames of 3 to 
 20 centimetres in length, at right angles to the direction of the draught (Figs. 448 and 
 449). By this distribution of the gas the bricks themselves are not touched by the 
 flame, and the composition of the gases in the entire cross-section of the burning 
 channel is uniform, so that the production of pure colours is relatively easy. If a 
 reducing flame is required the access of air is moderated by means of the smoke-valve. 
 
 Fig. 449. 
 
 SchnittHI. 
 
 Section I. -II. 
 
 As the entrance of the gas and the exit of the smoke are remote from each other, it is 
 possible to use the ring-channel simultaneously for gas and smoke, by connecting the 
 alternating trap on the one hand with the generators, G, and on the other with the 
 chimney, E. The tar deposited from the gas collects in the receivers, T. Numerous 
 cross-channels, w, connect the ring-channel with the furnace-chambers. The burning 
 channel is itself divided into four compartments by the three bells, V, the first of 
 which is in direct connection with the chambers i to 4, the second with chambers 
 5 to 8, and the third with chambers 13 to 1 6. By raising and lowering the bells the 
 
6 5 6 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. v. 
 
 connections between i and 2, i and 3, 4 and 3, &c., can be opened or closed at pleasure. 
 By a suitable placing of the alternating apparatus each division of the ring-channel 
 can be connected either with the generator or the chimney. The same flues and bells 
 which effect the introduction and distribution of the gas in the various chambers serve 
 to carry off the smoke. Lastly must be mentioned the smoke flue, /S, and the view- 
 holes, s, introduced between every two rows of pipes. 
 
 Mendheim, of Munich (German patent 22,086), effects a uniform distribution of 
 temperature by causing the generator-gas of each chamber to enter the channel b 
 through the valves (Figs. 450-452), a, and to pass from here by means of the branch 
 
 Fig. 450. 
 achrifff. .VI; 
 
 Fig. 451. 
 
 
 
 D 
 
 
 3(2 
 
 
 
 Dy. p 
 
 D 
 
 a 
 
 
 
 D 
 
 
 
 
 n , 
 
 
 3 
 
 D 
 
 
 a 
 
 
 
 n 
 
 
 
 
 a 
 
 
 a ad n D 
 
 da 
 
 
 
 a 
 
 
 
 
 ah 
 
 
 ML 
 
 n 
 
 8 c<z 
 
 n 
 
 a 
 
 =^ 
 
 Section VI. 
 
 Section I. 
 
 flues c, underneath the sole of the furnace. Here a part of it passes through the 
 openings d, into the space filled with bricks, after heated air has passed beneath the 
 sole from the flues z, and has formed flame, which then streams from below upwards ; 
 another part of the gas arises behind the fire-bridges. Here the gas comes together 
 with the hot air issuing from the flues z, in order to be conducted through the charge 
 
 Fig. 452. 
 
 Section II. Section III. Section IV. 
 
 from above downwards. The entire escape of the flame from the heated chamber takes 
 place through the openings h, so that both the fire coming from the fire-bridges and 
 that from the sole of the furnace pass unitedly through h, and the channels i, v, w, and 
 the plate-valve, e, into the channel /, of the next chamber and its ramifications, z. 
 This furnace is found to work well. 
 
 Kilns. If peat or wood is used as fuel the bricks to be burnt are piled up in a heap 
 much in the same manner as they would be placed in a furnace ; several fire-flues are 
 left in the mass, and the entire mound, which may contain 50,000 bricks, is covered 
 with a thin coating of clay and protected on the windward side with movable screens 
 
SECT, v.] EARTHENWARE OR CERAMIC MANUFACTURE. 657 
 
 of straw. The fire is inserted in the flues which have been left ; the gases sweep through 
 the mass of bricks and escape at the top. If coal is used as fuel the flues are made 
 narrower than for peat. Upon every layer of bricks is laid a stratum of small coal, 
 then another layer of bricks, then more coal, &c. The kiln is covered with clay, in 
 which air-holes are left to regulate the burning. The coal placed in the flues is kindled, 
 and the fire gradually extends through the kiln. 
 
 Clinkers are bricks burnt until they are half vitrified. 
 
 Roofing-tiles. For tiles a better clay is required than that for bricks, and it must 
 be more carefully prepared. Tiles are generally burnt along with bricks, occupying 
 the upper portion of the kilns. If it is desired to produce tiles of a grey cast, twigs of 
 alder, with their leaves green and moist, are placed in the kiln at its greatest heat, 
 and the air-holes are closed. The smoke thus produced deposits carbon in the porous 
 tiles, and perhaps reduces part of the iron to the ferroso-ferric state. 
 
 Flooring-tiles. The manufacture of flooring-tiles agrees mainly with that of 
 roofing-tiles. They are four- or six-sided, and are used for paving kitchens, fore- 
 courts, cellars, &c.* 
 
 Ballast consists of clay or arable soil not moulded into any definite forms, but lightly 
 burnt in the state of irregular fragments. The fuel is partly coal of the worst sort 
 obtainable, and partly the contents of the dust-bins, i.e., a mixture of cinders with very 
 promiscuous animal and vegetable matter. The smell given off is most disgusting, as 
 the process is little more than a semi-destructive distillation. This ballast is used for 
 making poor roads, garden walks, &c., and it is converted into an inferior sort of brick 
 by grinding to powder, mixing with water, and moulding under powerful pressure. The 
 use of such bricks is one cause of the very perishable character of the houses run up by 
 building speculators. 
 
 An important point for determining the value of bricks, at least in extreme climates, 
 is their resistance to frost. A clay gave at different temperatures : 
 
 Porosity. Disruptive Force. 
 
 Per cent. Kilos, per square centimetre. 
 
 700 ... H'23 ... 16-5 
 
 800 ... IO'56 ... 22-4 
 
 850 ... IO'22 ... 25'2 
 
 900 9-53 ... 30-5 
 
 960 ... 8 - i6 ... 44-2 
 
 1050 ... 2-n ... 59-5 
 
 Some samples which had been burnt at 800 to 850 were frost-proof, whilst 
 facing-bricks of the same material, and burnt at the same heat, were destroyed when they 
 had taken up moisture and were then exposed to frost. Bricks with a porous surface 
 seem to resist better than such as have a very compact and especially a glazed surface. 
 According to Braun, a brick is frost-proof if its cohesive force per square centimetre is 
 greater than the expansive force which the water absorbed by i square centimetre 
 exerts in freezing. It would be desirable to saturate a brick thoroughly with water and 
 then to expose it repeatedly to a temperature of 15. 
 
 The so-called light bricks, which float upon water, were known to antiquity. These 
 bricks are mentioned by Posidonius and Strabo, whilst Yitruvius and the elder Pliny 
 speak of them as very important. The infusorial earth (Kieselguhr) obtained at 
 Oberohe, in Hanover, is at present often used for the production of such bricks. 
 Kieselguhr is also found in Skye and other islands on the west coast of Scotland. 
 
 Fire-bricks. These bricks (known in Germany as Scharmotte-bricks and in 
 France as Chamottes) are used in the erection of fire-places, furnaces, flues, &c., where 
 
 * These flooring-tiles, called in Germany " Fleissen," must not be confounded with the glazed 
 and coloured tiles used by the ancient Komans, and now revived as a material for hearths and for 
 paving churches, entrance-halls, &c. 
 
 2 T 
 
658 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. v. 
 
 common bricks would melt. They are made of a clay rich in silica and alumina, but 
 as far as possible free from lime, alkali, and ferrous oxide. To increase its infusibility 
 and secure it from shrinkage and cracking, it is mixed with clay which has been 
 already burnt, sand, coke, graphite, &c. In the manufacture of fire-bricks it must be 
 considered that there are two agencies which imperil their duration a high temperature 
 in itself, and then the simultaneous attack of matter which may act as a flux, such as flue- 
 dust, alkaline vapours, melting alkalies, and metallic oxides. In addition, fire-bricks must 
 resist great alternations of temperature and be firm enough to bear a strong pressure. 
 
 Particular notice must be taken of the action of slags, &c., upon the resistance of 
 clays to fire. Basic slags attack quartz-stones, whilst acid slags have no such action. 
 Coke burnt in generators yielded 11*9 per cent, of ash of the following composition : 
 
 
 Ai 
 
 ih. 
 
 
 
 Soluble in 
 Water. 
 
 Total. 
 
 Slag. 
 
 SiO, 
 ALO. 
 
 
 
 47 '9 1 
 
 2O "1 7 
 
 62-95 
 2<C'23 
 
 Fe'CL 
 
 
 I2"l6 
 
 
 FeO 
 
 
 
 3-T2 
 
 Mn s O. ..... 
 MnO 
 
 
 
 0-38 
 
 O'28 
 
 CaO .... 
 
 MgO . . 
 Na.,0 
 
 O'24 
 O'4I 
 O'2O 
 
 I- 4 I 
 I '22 
 2 '6O 
 
 O'46 
 0-92 
 0-82 
 
 K,6 
 SO, 
 
 0-26 
 0-84 
 
 3 '34 
 
 O-82 
 
 3-5I 
 
 P.O. 
 
 
 
 O'CC 
 
 Fe .... 
 
 
 
 o'o9 
 
 FeS 
 
 
 
 0*04 
 
 
 
 
 
 
 i'95 
 
 lOO'OI 
 
 99-97 
 
 The watery extract is a basic mixture of sulphates ; the residual silicate corresponds 
 with the formula 2RSiO s .5Al 2 Si s O 7 .2SiO,. 
 
 The analysis of the difficultly fusible blackish slag flowing off leads to the formula 
 2B,Si0 3 .3AljSi 3 9 .2SiO,. It contains no globules of metallic iron. Hence in the 
 generator a part of the iron from the ash has been reduced to metal, the calcium and 
 magnesium sulphates have been volatilised or dissipated, and the alkalies have been con- 
 verted into slags. The Scharmotte bricks, containing 88*9 per cent, of silica, were but 
 slightly attacked by this acid slag. 
 
 The worst enemies of basic bricks are the oxides of iron, whence, in using the earthy 
 bases for fire-bricks, the utmost possible freedom from iron should be aimed at ; silicic 
 and phosphoric acids and manganese oxides are not so destructive. 
 
 From the fire-proof mass there are made not alone bricks, but linings for furnaces 
 in circular segments, plates, saggers for porcelain, stone-ware muffles for burning in 
 the colours for porcelain vessels, and apparatus for chemical works, dye-houses, and 
 paper manufactories (chlorine stills), capsules, dehydrating plates, cocks, gas-retorts, <fec. 
 Some analyses of fire-bricks gave the following results : 
 
 
 
 i 
 
 3 
 
 3 
 
 4 
 
 5 
 
 Silica .... 
 
 
 00. T 
 
 CO..., 
 
 
 
 Alumina .... 
 
 
 
 so 43 
 
 09 3 
 
 77 *> 
 
 Lime .... 
 
 
 5 
 
 
 2 9 5 
 
 
 Magnesia 
 
 0*66 
 
 
 3 4 
 
 
 n 
 
 Ferric oxide .... 
 
 2-88 
 
 fi'T 
 
 
 
 
 Potassa 
 
 T 'O2 
 
 
 5 
 
 
 3 
 
 Soda 
 
 
 
 
 
 
 
 u O l 
 
 
 
 
 
 
 
 
 
 
 
 
 lOO-SS 
 
 99 -9 
 
 100-23 
 
 ioo-8 
 
 997 
 
SECT, v.] MORTARS, ETC. 659 
 
 No. i was clay from Dowlais; 2, bricks from copper furnaces in Wales; 3, in 
 Pembroke; 4, for blast-furnaces ; 5, for reverberatories. 
 
 The Dinas bricks made from the Dinas rock in the Yale of Neath in Glamorgan, 
 consist of almost pure quartz sand and i per cent, of lime. They bear the highest 
 temperatures occurring in metallurgical work without melting or shrinking too much, 
 and are, hence, invaluable for steel furnaces, all kinds of reverberatories, glass ovens, 
 porcelain ovens, &c. Yery similar is ganister, a compact, siliceous stone, which, 
 when ground and mixed with clay, serves for lining Bessemer converters, puddling 
 furnaces, &c. 
 
 Wasum shows that good bricks may be obtained at a white heat from dolomite and 
 limestone, but not from magnesite. The addition of 5 per cent, of clay yields better 
 bricks without rendering them much less fire-proof. The higher the temperature at 
 which the bricks are burnt the more durable they become. In the construction of 
 furnaces for burning such bricks it is important to arrange the flues so that 
 the temperature may be equal throughout. Dolomite and limestone bricks, if 
 not too much contaminated with matters which increase fusibility, shrink at the 
 strongest white heat only about 2*4 per cent. ; bricks made of strongly burnt magnesia 
 shrink only 4 per cent. All substances which decrease the resistance of basic bricks to 
 fire increase their shrinkage. Bricks of limestone and dolomite are equally attacked 
 by the slags formed in iron-smelting, while magnesia bricks are more resistant. The 
 best material for basic bricks is magnesia burnt at the utmost white heat. 
 
 Clay pipes may serve either for water-mains or for drain-pipes. Both are made 
 by means of a mould and stamp. 
 
 Crucibles. For crucibles it is necessary that materials shall be used that will with- 
 stand the highest temperature. Good crucibles do not crack on being rapidly cooled, 
 and they must also withstand the action of the fluxes that may result from the smelting 
 of metals. The most common crucibles are the Hessian, the graphite or plumbago, and 
 the English. The Hessian crucible is made of i part clay (of 71 parts silica, 25 parts 
 alumina, and 4 oxide of iron) and one-half to one-third the weight of quartz sand. 
 They are refractory, remain unaltered by variations in temperature, but are unsuited to 
 some chemical operations on account of coarseness of grain and porosity. If containing 
 too large a proportion of silica, they become perforated by lead oxide, alkalies, &c. 
 Graphite or plumbago crucibles are made from i part of refractory clay and 3 to 4 
 parts graphite. The Patent Plumbago Crucible Company, of Battersea, as well as the 
 Nuremberg manufacturers, employ Ceylon graphite and fire-clay. Graphite crucibles 
 will bear the highest temperature, and they can be made to almost any required size. 
 English crucibles are made from 2 parts of Stourbridge clay and i part of coke. Crucibles 
 containing coke exert a reducing action when heated in contact with metallic oxides, and 
 are therefore unfitted to the smelting of metals. Recently lime and chalk crucibles have 
 been employed for this purpose. Caron has used magnesia crucibles in the smelting of 
 iron and steel. Gaudin employs an equal mixture of bauxite or cryolite and magnesia. 
 Yery similar are the bauxite crucibles of Audouin. 
 
 MORTARS, ETO. 
 
 The substances used for the production of mortars are either sufficiently comminuted 
 by the action of water (lime), or they are ground up by mechanical means. They are 
 divided into 
 
 A. Such as set only in the air. 
 
 1 . Gypsum must be mechanically pulverised, and sets by combining with water. 
 
 2. Lime when moistened with water crumbles to a powdery hydroxide, and 
 hardens with sand by the formation of a silicate (ordinary mortar). 
 
 B. Such as set either in the air or under water (hydraulic cements). 
 
660 CHEMICAL TECHNOLOGY. [SECT. v. 
 
 3. Hydraulic Limes, obtained by burning limestones containing more or less clay 
 and silica, and fall to powder on slacking with water. 
 
 4. Roman Cements, formed from clayey calcareous marls by burning below the limit 
 of sintering. They do not slack when moistened with water, but have to be pulverised 
 mechanically. 
 
 5. Portland Cements are obtained from calcareous marls, or from artificial mix- 
 tures of lime and clay heated to sintering and then grinding to a fine powder. They 
 contain to i part of SiO,, A1 2 O 3 , Fe 2 3 , r8 to 2-2 of lime, and their specific gravity w 
 
 above 3. 
 
 6. Hydraulic admixtures are natural or artificial substances which do not harden 
 alone, but only in conjunction with caustic lime, e.g., puzzuolane, blast-furnace slags, 
 and trass obtained from volcanic tufa. 
 
 7. Puzzuolane Cements are obtained by a very intimate mixture of pulverulent cal- 
 cium hydroxide with trass, &c. 
 
 8. Mixed Cements, made by adding other matters to prepared cements. 
 
 Gypsum. Gypsum is a hydrated catcium sulphate of the formula CaS0 4 + 2H 8 0. 
 100 parts contain 
 
 Lime . . . 32*56 
 
 Sulphur . . 1 8 -60) 
 
 - Sulphuric acid . 46x1 
 Oxygen . . 27-91! 
 
 Water . . . 20-93 
 
 It belongs to the commonly occurring class of minerals, and is found alone or with 
 anhydrite (karsenite, CaS0 4 ) in strata chiefly of the tertiary formation. The following 
 kinds are distinguished : (i) Gypsum spar, foliated gypsum, glass stone, isinglass stone, 
 or selenite, possessing a very perfect cleavage, and allowing fine laminae to be sepa- 
 rated ; (2) Fibrous gypsum, or satin spar ; (3) Froth-stone, a scaly crystalline gypsum ; 
 (4) Granular gypsum, or alabaster, of coarse or fine-grained texture ; (5) Gypsum stone, 
 plaster stone, or heavy stone, a laminated gypsum ; (6) Earthy gypsum, or plaster 
 earth. 
 
 Nature of Gypsum. Gypsum is soluble in 445 parts of water at 14 C., and in 420 
 parts at 2O'5 C. ; the solubility is increased by the addition of sal-ammoniac. Its be- 
 haviour under the influence of heat is important. Graham states that gypsum placed 
 in a vacuum over sulphuric acid, and heated to 100 C., loses its water, forming the com- 
 bination CaS0 4 + H 2 O, with 12-8 per cent, water. According to Zeidler, the statement 
 that this combination does not harden with water is incorrect. By heating to 90 for 
 some time 15 per cent, of the water may be expelled ; at 170, according to the experi- 
 ments of Zeidler, all the water will be given off. But of more importance are the ex- 
 periments not carried on in vacua. In the air gypsum begins to lose its water at 100, 
 and the loss is not complete under 132. Gypsum from which all the water has been 
 removed is termed burnt gypsum, or spar-lime ; it has the property of re-forming with 
 water the same hydrate, thus becoming hardened. Advantage is taken of this property 
 in the application of gypsum as a mortar. According to Zeidler, gypsum as technically 
 employed in stucco-work, &c., is not anhydrous, but contains 5-27 per cent, water. If 
 gypsum is " over burnt," that is, heated above 204", it loses the property of hardening 
 with water, probably owing to the fact of its being converted into anhydrite, which 
 does not re-combine with water. 
 
 The water of crystallisation of the gypsum is saline, and consequently can be re- 
 moved by the addition of salts ; this probably accounts for the hardening of unburnt 
 gypsum when treated with a dilute solution of potassium sulphate or carbonate, 
 &c. The hardening in this follows more quickly than with burnt gypsum and pure 
 water. With potassium sulphate a double salt is formed according to the formula 
 
SECT. V.] 
 
 MORTARS, ETC. 
 
 661 
 
 K,S0 4 + CaS0 4 + H 2 ; gypsum and potassium bitartrate give rise to tartar and crys- 
 talline gypsum. Potassium chlorate and nitrate, as well as sodium salts, do not effect 
 the hardening of powdered gypsum. Gypsum thus hardened, if re-powdered and again 
 treated with potassium sulphate or carbonate solution, hardens once more. Technical 
 use is made of this property in re-hardening old or in hardening gypsum not sufficiently 
 burnt, by employing instead of water a solution of potassium carbonate. 
 
 The Burning of Gypsum. Gypsum is burnt to effect the removal of the water. 
 Lately many improvements have been made in the methods of burning, it having been 
 found that the good qualities of the gypsum mainly depend upon the preparation. There 
 is, however, a choice in the stone to be burnt, the heavier and denser varieties of gypsum 
 yielding the best commercial article. 
 
 Payen, by experimenting with large quantities of gypsum, obtained the following 
 results : (a) The lowest temperature at which gypsum can be burnt \vith advan- 
 tage is 80 C., a long time even then being required. (6) A temperature of 110 to 
 120 yields the best technical preparation, (c) In order that the burning may take 
 place equally, the gypsum should be first reduced to powder or small pieces. The aim, 
 of course, is in all cases to obtain a small homogeneous product rather than a large 
 quantity unequally burnt. Small quantities of gypsum may be burnt in an iron vessel 
 over a coal fire ; the operation should be continued till no aqueous vapour is condensed 
 on a cold glass plate. 
 
 Kilns, or Burning Ovens. In large quantities gypsum is burnt in an oven or kiln, 
 the one necessary precaution being to avoid arranging the layers of gypsum with such 
 fuel as will reduce the gypsum to calcium sulphide (CaS0 4 + 40 = CaS + 4CO). 
 
 A very simple and very general construction of kiln is shown in Fig. 453. It con- 
 sists of walls of strong masonry, A, spanned by a flat arch, ventilated at a a a. In this 
 room is placed the gypsum only, the fire being lighted in a series of small chambers in 
 the lower part of the room : brushwood is the best fuel. & is a door, through which the 
 material is introduced. The oven (Fig. 454) used by M. Scangatty is very similar. 
 
 The inner room is divided unequally by an arch, P, about one foot from the floor ; into 
 the upper part the gypsum is introduced through the door, G. The under part or fire- 
 room is in connection with a flue, E, of a furnace, A A, the flames from which, driven 
 by the draught from the gallery, (7, are carried through X to play upon the arch, P, the 
 hot air and gases passing through c c c into the upper room. The aqueous vapour 
 escapes through H. 
 
662 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. v. 
 
 Lately Dumesnil's oven, shown in plan at Fig. 455, and in section Fig. 456, has been 
 much employed. It somewhat resembles Scanegatty's oven in construction, and 
 consists of an under fire-room and an upper room or oven, in which the gypsum is 
 burnt. The fire-room contains an ash-pit, A, with a door, B, a grate or grid, C, and the 
 hearth, D. A draught, H, assists the combustion. The hot air and gases pass by the 
 flues, E, to the chamber, F. The walls of the oven, J, K, L, are of solid masonry. I is 
 a vault, furnished with a staircase, g h, to facilitate access to the furnace. P, the 
 chimney, is of iron plate, with a clack, Q, which can be regulated by the chain U U. 
 O O are ventilating pipes. In the wall of the burning-room are two openings one, M, 
 through which admittance to the interior is gained to place the lower layers of 
 gypsum ; the other, N, for the upper layers of gypsum : both are closed by doors of iron 
 plate. An equal heat is necessary in the burning-room, and is maintained by the 
 peculiar arrangement of the chamber F. This chamber, closed at the top by the cap, 
 
 Fig. 456. 
 
 Fig. 455- 
 
 G, is provided with twelve openings, each 07 metre high, the chamber itself being 
 i metre in diameter. The channels thus commenced by the openings in F are continued 
 to the walls of the room by the arrangement of large blocks of gypsum. The layers 
 of gypsum, R, S, T, are placed crosswise alternately with intermediate layers, so as to 
 facilitate the draught in every possible way. The firing is continued gently for four 
 hours, then strengthened for eight hours, when all the openings are closed, and 5 to 
 6 cubic metres of coarse gypsum powder spread equally over the top of the burning 
 gypsum. By this means the quantity of burnt gypsum is increased without a further 
 expenditure of fuel. After standing twelve hours in the oven to cool the whole 
 contents are removed. 
 
 Grinding the Gypsum. After the burning the gypsum is to a certain extent in 
 powder, but if not sufficiently even it has to be ground. The usual modes of grinding are 
 in a stamp or roller mill. After grinding, the gypsum is sifted, and placed in some 
 position where damp cannot affect it. Sometimes the grinding and sifting are 
 conducted in one apparatus ; generally the mill and sieves are separate. 
 
 Uses of Gypsum. Gypsum is employed industrially in very many ways. It is 
 sometimes used unburnt in building ; it is then difficult to manipulate with water, but 
 becomes plastic by continued moistening. The heavy and strong fine-grained gypsum, 
 especially the white powdered gypsum, is used in building for decorative purposes. 
 From the alabaster of Voltena, Florence vases of great beauty were fabricated ; the 
 same material is used for making Roman pearls. The clear varieties of gypsum are 
 used in the manufacture of cheap jewellery, being ground and polished. The fibrous 
 gypsum is sometimes used for writing sand, as a substitute for pounce, &c. Fine 
 
SECT, v.] MORTARS, ETC. 663 
 
 gypsum powder is an ingredient of porcelain manufacture. Unburnt gypsum finds, 
 further application in the conversion of ammonium carbonate into sulphate. Gypsum 
 contains 46-5 per cent, sulphuric acid and i8'6 per cent, sulphur. It is largely 
 employed in agriculture as a manure, both burnt and unburnt. It is generally 
 agreed that the favourable action of the gypsum upon vegetation is due to the 
 absorbed ammonia which is again yielded up. 
 
 Putridity gives rise to the formation of carbonic acid, which combines with the 
 lime of the gypsum, leaving calcium carbonate and ammonium sulphate. This explana- 
 tion of the efficacy of gypsum-manuring, as it is termed, is, however, insufficient. 
 The investigations of Mayer have shown that in clayey soils the iron oxide, &c., 
 affords larger and better combinations with ammonia than gypsum. The quantity 
 of gypsum used is generally about 5 cwts. to the acre, containing and realising at the 
 most 2 '7 cwts. of ammonium carbonate. Mayer's researches, however, show that in 
 an acre of 
 
 Field land . . . 227 cwts. 
 
 Chalky soil . . . 158 
 
 of ammonia were contained. According to Liebig's late researches (1863) it appears 
 that the gypsum gives up to the earth a portion of its lime in exchange for magnesia 
 and potash. But it must be borne in mind that pulverised gypsum, as well as 
 unburnt gypsum, when brought into contact with a solution of potash, sets into a 
 difficultly soluble mass. We must, then, wait for an adequate theory until the several 
 reactions have been more closely studied.* 
 
 Gypsum Casts. The employment of gypsum in casting, and in all cases where 
 impressions are required, is very extensive. A thin paste of i part gypsum and 2^ 
 parts water is made : this paste hardens by standing, forming CaS0 4 + 2H 2 O. The 
 hardening of good, well-burnt gypsum is effected in one or two minutes, and more 
 quickly in a moderate heat. Models are made in this substance for galvano-plastic 
 purposes, for metallic castings, and for ground works in porcelain manufacture. The 
 object from which the cast is to be taken is first well oiled, to prevent the adhesion of 
 the gypsum. Where greater hardness is required a small quantity of lime is added ; 
 this addition gives a very marble-like appearance, and the mixture is much employed 
 in architecture, being then known as gypsum-marble or stucco. The gypsum is 
 generally mixed with lime-water, to which sometimes a solution of zinc sulphate is 
 added. After drying, the surface is rubbed down with pumice-stone, coloured to 
 represent marble and polished with Tripoli and olive-oil. Artificial scaliogla work is 
 largely composed of gypsum. Gypsum is also much employed in the manufacture of 
 paper. 
 
 Hardening of Gypsum. There are several methods of hardening gypsum. One of 
 the oldest consists in mixing the burnt gypsum with lime-water or a solution of gum- 
 arabic. Another, yielding very good results, is to mix the gypsum with a solution of 
 20 ounces of alum in 6 pounds of water ; this plaster hardens completely in fifteen 
 to thirty minutes, and is largely used under the name of marble cement. Parian cement 
 is gypsum hardened by means of borax, i part of borax being dissolved in 9 parts of 
 water, and the gypsum treated with the solution. Still better results are obtained by 
 the addition to this solution of i part of cream of tartar. 
 
 The hardening of gypsum with a water-glass solution is found difficult, and no 
 better results are obtained than with ordinsny gypsum. Fissot obtains artificial stone 
 from gypsum by burning and immersion in water, fii-st for half a minute, after which 
 
 * The use of gypsum in manures has proved less satisfactory in Britain than on the Continent. 
 It plays- no small part in the sophistication of articles of consumption, such as flour, wines, sweet- 
 meats, &c. Its chief locality in Britain is in the neighbourhood of Newark-upon-Trent. 
 
664 CHEMICAL TECHNOLOGY. [SECT. v. 
 
 it is exposed to the air, and again for two to three minutes, when the block appears 
 as a hardened stone. It would seem from this method that the augmentation in 
 hardness is due to a new crystallisation. Hardened gypsum, treated with stearic acid 
 or with paraffine, and polished, much resembles meerschaum : the resemblance may 
 be increased by a colouring solution of gamboge and dragon's blood, to impart a faint 
 red-yellow tint. The cheap artificial meerschaum pipes are manufactured by this 
 method. 
 
 Scott's " gypsum cement " or " selinitic mortar " was made by the action of the 
 fumes of burning sulphur upon ignited lime. Schott has since pointed out that it can 
 be more simply obtained by igniting quicklime with burnt calcium sulphate. 
 
 Tripolite is merely gypsum with impurities of sand, calcium, and magnesium 
 carbonate, and burnt with o'i of its weight of coal or coke. 
 
 Lime. Lime, calcium oxide (CaO = 56), in its combination with carbonic acid as 
 calcium carbonate (CaC0 3 ), is a substance of very frequent occurrence. It is a con- 
 stituent of bone, of the shells of the mollusca, and is found most extensively in the 
 mineral kingdom as marble, limestone, coral, Iceland spar, arragonite, chalk, &c. Its 
 technical applications are as marble in building, in the manufacture of artificial mineral 
 waters, as Iceland spar for optical purposes, as chalk in colours and drawing materials, 
 in the manufacture of soda, in the preparation of hydraulic mortars, building and 
 plastering materials, &c. Limestone, Alpen lime, lias lime, Jura lime, &c., is, when 
 mixed with clay, iron, and other metallic oxides, used as a colour. Lithographic stone 
 is a yellow-white limestone, employed, as its name implies, in lithography. Chalk or 
 earthy calcium carbonate occurs in strata in North Germany, Denmark, France, and 
 England. To this class belongs marl-limestone, distinguished by containing clay. 
 With sodium carbonate, calcium carbonate forms Gay-Lussite (CaC0 3 + Na 2 C0 3 ) ; with 
 barium carbonate, baryto-calcite (BaC0 3 + BaC0 3 ) ; and with magnesium carbonate, 
 bitter-spar or dolomite (CaC0 3 + 3MgC0 3 ), the latter occurring with 3 mols. of 
 magnesium carbonate to i mol. of lime. 
 
 Properties. Calcium carbonate is not soluble in pure water ; but if the water should 
 hold carbonic acid in solution, bicarbonate is formed. When this solution, by means 
 of evaporation, loses half its carbonic acid, an insoluble carbonate is formed. In this 
 manner are naturally formed stalactites and stalagmites. The deposit of calc-sinter upon 
 objects deposited in caverns, in limestone-rock, &c., is thus explained. When calcium 
 carbonate is ignited to whiteness in a porcelain crucible, the carbonic acid is disengaged, 
 and there remains calcium oxide (CaO) or caustic lime. TOO parts of calcium car- 
 bonate yield 56 parts of burnt lime. The volume of the lime undergoes no diminution 
 by burning. Burnt lime is the form under which lime most commonly appears in the 
 market. Calcium carbonate, heated in a closed porcelain tube, melts, and forms a crys- 
 talline mass, a carbonate, afterwards unalterable. 
 
 Lime-Burning. The burning of lime is effected 
 
 In kilns, 
 
 In field-ovens, and 
 In lime- ovens. 
 
 Lime-burning in kilns is accomplished in the following manner : The limestone, 
 unless it has previously been broken into small pieces, is heaped up into cairns similar 
 to the heaps of wood to be converted into charcoal. The kiln is then covered with earth 
 or turf, and the fire so placed that the larger pieces of lime in the interior of the heap 
 are burnt. The regulating of the draught, the kindling, the covering, and the cooling 
 are on the same principle as that followed by the charcoal-burner in the conversion of 
 wood into charcoal by combustion. According to P. Loss, a kiln of this kind, 4-5 metres 
 in height, contains 35-5 cubic metres of lime as well as 2'6 cubic metres of lime-dust. 
 In the field-ovens the burning is similarly conducted, but sometimes on a larger scale, 
 
SECT. V.] 
 
 MORTARS, ETC. 
 
 665 
 
 the kilns being always temporary. It is easy to see that the burning in this manner 
 is only of slight technical importance ; besides the great waste, only a small quantity 
 could be produced at an operation. Therefore, permanent ovens are employed. These 
 are divided into 
 
 a. Those kilns in which the burning is interrupted, or occasionally employed (the 
 
 occasional kiln). 
 
 b. Those kilns in which the burning is continuous (the continuous kiln). 
 
 In the occasional kiln, after the burning is finished, the kiln is cooled, and the lime 
 then removed. In the continuous kiln, on the contrary, the calcination is continuous, 
 the kiln never being allowed to cool. It is so constructed that the burnt lime can 
 be removed and fresh limestone introduced, without in the least interrupting the 
 process. The continuous kiln has many recommendations among them that of effecting 
 a saving in fuel. In a small way, where, as a rule, burning cannot be constantly carried 
 on, the small occasional kiln is of course to be preferred. 
 
 Occasional or Periodic Kilns. The occasional or periodic kiln with interrupted burn- 
 ings sometimes have, and sometimes have not, a grated furnace. Figs. 457 and 458 
 
 Fig. 458. 
 
 Fig- 457- 
 
 show two lime-kilns of the ordinary construction without grated furnaces. They are 
 built either on the slope of a hill or on the slope of the limestone quarry itself. As a rule, 
 the kilns are built near one another, so that one wall serves for two kilns. The height 
 of the vault varies from 1-3 to r6 metre, and it is generally built of the largest lime- 
 stones, while the smaller stones and lime-dust are placed in the interior of the kiln. 
 Through the furnace doors, easily combustible fuel, such as brushwood, light timber, 
 shavings, &c., is introduced. The mass becomes gradually heated, the larger stones 
 crack and break up, and the whole mass sinks together. As the firing is increased the 
 lime becomes of a brighter colour and the flames free from smoke. As soon as the lime 
 immediately under the stones on the top of the kiln is at a white heat the burning 
 is complete. The mass by this time will have sunk one-sixth. A burning generally 
 occupies thirty-six to forty-eight hours. An occasional kiln with a grated furnace 
 effects a quicker and more complete combustion of the fuel ; but they are open to the 
 objection that the consumption is greater. On the other hand, the kilns without a grated 
 furnace are less perfectly heated. A kiln much used in Hanover is shown in Fig. 459, 
 and in plan in Fig. 460 ; Fig. 461 shows the under part of the kiln in vertical section. 
 The lower room serves for the calcination of the lime ; over this is a vaulted chamber 
 3-12 metre in diameter and u feet in height, e e e e, Figs. 460 and 461, are four 
 stoke-holes for the introduction of fuel, stone-coal, brown-coal, breeze, &c. B is the 
 approach by which the limestone is introduced into the furnace; d the door by which 
 entrance is obtained to remove the burnt lime. Both these openings are closed during 
 
666 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. v. 
 
 the actual burning, a is an approach to the " upper jacket," as the upper chamber ia 
 termed. This opening is necessary as a draught to assist the flame and hot gases in 
 their escape from the top of the kiln ; it also causes a more intense flame in other parts 
 of the kiln. Figs. 460 and 461 show how the limestone is kept clear of the hearths. 
 
 A piece of wood is placed ver- 
 
 Fig. 459. tically in the centre of the 
 
 I oven to direct the flames up- 
 
 wards when the fire is lighted. 
 During the first six hours the 
 fire is weak ; then a stronger 
 fire is obtained until the yellow 
 lime-flames spring from the 
 openings in the vault, and the 
 oven is in a clear glow. 
 
 The Continuous Kilns. 
 The construction of the kilns 
 for continuous burning is some- 
 what different to that of the 
 preceding. They are of two 
 kinds. In one the fuel and 
 the Jimestone are placed in 
 alternate layers ; in the other 
 
 kind, the fuel and the limestone are not in contact, there being furnaces for the 
 former and separate chambers for the latter. In either, fresh limestone is added in 
 proportion as the burnt stone is removed from the bottom of the kiln. 
 
 Fig. 460. 
 
 Fig. 461. 
 
 At Rudersdorf, near Berlin, a very efficient kiln is employed, shown in section in 
 Fig. 462. The lining wall of the shaft, d, is built of fire-brick; the counter wall, e, is 
 separated from the lining wall by a chamber filled with ashes, building refuse, &c. 
 The outer wall, B J3, is not an essential portion of the kiln ; it serves merely as a jacket 
 for the retention of the heat, while the galleries, H and F, can be used as drying-rooms 
 for wood, fuel, &c. During the process, the under part, B, of the shaft is filled with 
 prepared lime, which is removed by the draught-hole, a, in the sole of the shaft. For 
 the purpose of hastening the descent of the burnt lime, the sides of the lower part 
 
SECT, v.] MORTARS, ETC. 667 
 
 of the shaft are sloped towards the draught-holes. The shaft is usually 14*123 metrea 
 in height. About 4 metres above the sole of tha shaft is situated the fire-room, h. 
 Three to five fire-rooms are in action in a single shaft. The fuel is wood or turf, i is 
 the ash-pit, whence the ashes fall into E. The flame enters the shaft through the 
 opening, 6, at the end of the fire-room. The freshly burnt lime is received in F. K K 
 is a draught gallery communicating with H. The kilns are locally known as three-, 
 four-, or five-fired kilns, according to the number of fire-rooms. Should the kiln not 
 have been in use for some time, the firing is commenced by adding fuel, such as wood, 
 turf, &c., to the limestone in the shaft. When the shaft is thoroughly warmed and a 
 good draught obtained, lime only is introduced into the shaft. The shaft is entirely 
 filled with limestone, and sometimes the limestone accumulates upon the mouth or top 
 of the kiln to a height of 1-3 metre. 
 
 Kilns far Burning Lime and Bricks. When the locality is favourable, the kilns 
 are arranged to burn both lime and bricks at the same time. The annular' kiln of 
 Hoffmann and Licht, described under Brick-making, is the most suitable for this double 
 purpose. 
 
 Properties of Lime. The quality of the burnt lime is greatly influenced by the 
 constitution of the limestone burnt. When the limestone consists chiefly of pure 
 carbonate of lime, the resulting lime is what is termed a " fat " lime. On the other 
 hand, if the limestone is of similar composition to dolomite (Ca00 3 + MgC0 3 ), containing 
 magnesia, the resulting lime forms a short, thin " milk " with water, and istermed " poor." 
 With 10 per cent, of magnesia the lime is noticeably poor, and with 25 to 30 per cent, 
 almost useless. The lime on being taken from the kiln is by no means found to be 
 burnt equally. Some pieces that have almost escaped the fire are merely superficially 
 burnt, and contain a kernel of unburnt limestone. Other pieces exposed to the full 
 heat of the kiln are ' ' over-burnt." The " over-burning " of the lime is either due to 
 the forming of " half-burnt " lime (CaC0 3 + CaH 2 2 ) by a strong and sudden ignition ; 
 or by means of the high temperature the small quantity of silica and alumina contained 
 in the limestone become sintered over the surface, and the lime is thus prevented by a 
 coating of silicate from combining with the water to form a cream. 
 
 Slacking Lime. Burnt lime moistened with water slacks with great violence, 100 
 parts by weight of lime requiring only 32 parts water, or 3 vols. of lime to i vol. 
 water, to obtain by the combination a temperature of 150. The result of the slacking 
 is a soft, white powder, lime-meal or powdered lime, hydrated calcium oxide (CaH 2 Oj), 
 which in volume exceeds three times that of the lime slaked. If less water is 
 added than is requisite for the formation of the hydrate, a sandy powder is obtained 
 of little value technically. It is therefore very disadvantageous to place lime in 
 baskets in damp situations. For technical application to building purposes, after the 
 lime has been slaked with one-third of its weight of water, an equal quantity of water 
 is added to the mass to form a thin cream. Slaked lime retains its water of forma- 
 tion with such obstinacy that at a temperature of 250 to 300 no loss of weight 
 occurs. The hydrate forms a thin cream with water, and from this cream by further dilu- 
 tion lime-water or milk of lime is obtained. If the lime-water be filtered, there results 
 a saturated solution of hydrate of lime, containing i part hydrate to 778 parts water. 
 
 The temperature required for burning lime has been determined by Le Chatelier. 
 The tension of dissociation of calcium carbonate is 
 
 Temperature. Pressure, millimetres. 
 
 547 ... 27 
 
 625 ... 56 
 
 740 ... 255 
 
 810 ... 678 
 
 812 ... 763 
 
 865 ... 1333 
 
668 CHEMICAL TECHNOLOGY. [SECT. v. 
 
 Although the dissociation temperature at 812 is equal to the pressure of the atmo- 
 sphere, a heat of 925 is needed for the complete expulsion of the carbon dioxide. 
 
 Mortar. Mortar is a mixture of sand with cream of lime, used in building as a 
 binding material. The ordinary mortar sets or hardens only in the air ; hydraulic mortar 
 sets under water. 
 
 A. Common Mortar. When slaked lime is exposed to the atmosphere it absorbs 
 carbonic acid, and the mass becomes much shrunken and cracked. The carbonate 
 thus formed, on becoming perfectly dry, attains the hardness of marble. Such a 
 material, with certain modifications, is consequently admirably adapted as a cement 
 to bind together bricks, blocks of stone, &c., in building. But as the contraction or 
 shrinkage would give rise to great unevenness in the construction of walls, it becomes 
 necessary to add sand or some similar substance to the lime-cream. This addition gives 
 a body to the mortar, which combines with the bricks into one coherent mass. Common 
 mortar is ordinarily made with slaked lime, an intimate mixture with sand and water 
 being formed. Angular or sharp sand is preferred to smooth, round sand, as making 
 a more tenacious mortar. Round-grained sand yields a very brittle mortar. The 
 proportion of sand to the lime is a matter immediately affecting the quality and hard- 
 ness of the mortar. In practice, i cubic metre of stiff lime-cream requires 3 to 4 cubic 
 metres of sand ; but poor lime containing magnesia will only admit of i to 2\ cubic 
 metres of sand. When mortar is employed in brick -laying, the surface of the brick is 
 moistened, the mortar laid between each brick, and left to dry. When dry it is often 
 harder than the brick itself.* 
 
 Hardening of Mortar. Mortar sets or hardens very quickly. After a day it will 
 attain a firmness that will last for centuries. The drying out of the water from the 
 mortar is not the sole cause of its hardening, as may be very easily ascertained by 
 drying the mortar in a water-bath or over the spirit-lamp ; the result is not a stone- 
 like, but a friable, non-coherent mess. Fuchs accounts for the hardening of mortar by 
 supposing the formation of a basic calcium carbonate (CaC0 3 + CaH 8 O 2 ), a combination 
 which has not been known to suffer conversion into ordinary carbonate of lime (CaC0 8 ). 
 Recent researches have shown this supposition to be erroneous, as it does not agree 
 with the results of analyses, which have yielded a quantity of carbonic acid incom- 
 patible with the existence of a neutral carbonate ; 20 and even 70 per cent, of carbonic 
 acid have been found. The experiments of Alexander Petzholdt, A. von Schrotter, 
 and others have proved that there is an increase of soluble silica. The conversion 
 of quartz -sand into soluble silica under the influence of hydrate of lime is not, how- 
 ever, a reaction at all explanatory of the hardening of mortar, as washed chalk instead 
 of silica forms an equally hard mass. W, Wolters gives the formation of silicate of 
 lime as accounting for the hardening of mortar. It is not seldom in the analysis of 
 old mortar from the interior of walls that caustic alkalies are found. 
 
 B. Hydraulic Mortar. Limestone containing more than 10 per cent, silica possesses, 
 when burnt and made into a mortar, the peculiar property of hardening under water. 
 Lime burnt from such limestone is termed hydraulic lime, and the mortar hydraulic 
 mortar. 
 
 When unburnt, hydraulic lime is a mixture of calcium carbonate with silica or a 
 silicate, generally aluminium silicate, the latter being insoluble in hydrochloric acid. 
 During the burning, the hydraulic lime suffers a change similar to that taking place 
 when a silicate insoluble in acid is precipitated, during the application of heat, with an 
 
 * The durability of the old Roman masonry was in a great degree owing to the fact that they 
 slacked their lime in small quantities as it was needed, mixed it with clean, sharp sand, and used 
 it whilst still warm. The wretched character of the work done by modern building speculators is 
 owing, on the contrary, to the fact that they slack a large quantity at once of the worst lime pro- 
 curable, and let it lie sometimes for weeks before use. Instead of sand they sometimes take 
 sifted garden and field soil, containing abundance of decaying organic matter. 
 
SECT, v.] MORTAKS, ETC. 669 
 
 alkaline carbonate. After burning, the lime is to a great extent soluble in hydrochloric 
 acid, and has lost some of its carbonic acid. Yon Fuchs, Feichtinger, Harms, Heldt, 
 W. Michaelis, and A. von Kripp's experiments have proved that the silica of 
 hydraulic lime is precipitated in a gelatinous condition, and that constituents such as 
 alumina and iron oxide are of influence only when, under ignition, they have formed a 
 chemical combination with the silica. 
 Hydraulic mortars are made 
 
 1. With a thin cream of lime and water to which sand is added ; or with 
 
 2. A mixture of ordinary air-mortar with water and cement. 
 
 During the slacking of the hydraulic lime water is absorbed, but without any con- 
 siderable evolution of heat or increase in volume. Hydraulic mortar is employed in the 
 same manner as ordinary mortar the lime-cream must be freshly made, and the brick 
 or masonry work moistened. The mortar should be placed thickly between each layer 
 of bricks, in order to afford a good firm bed and allow for shrinkage. 
 
 Hydraulic limes form a transition from ordinary lime to Roman cement. 
 
 Roman cement is obtained by burning calcareous clays above a sintering-heat and 
 grinding the product. The powder, which is usually of a reddish brown, yields a 
 hydraulic mortar which sets more rapidly than Portland cement, but does not attain 
 the same firmness if magnesia is present. 
 
 Michaelis found by the analysis of various Roman cements 
 
 I. 2. 3. 4 . 
 
 Lime . . 58-38 ... 55-50 ... 47-83 ... 58-88 
 
 Magnesia . 5*00 ... 173 ... 24*26 ... 2-25 
 
 Silicic acid . 28-83 25*00 ... 5-80 ... 23-66 
 
 Alumina . 6-40 ... 6-96 ... 1-50 ... 7-24 
 
 Iron oxide . 4-80 ... 9-63 ... 20*80 ... 7-97 
 
 The analyses are from cements free from water and carbonic acid. No. i is Roman 
 cement from Riidersdorf limestone ; 2. From limestone from the Isle of Sheppy, yellow- 
 brown in colour, coarse, and hard ; 3. From limestone forming the under bed of the 
 lead ores at Tarnowitz, of a blue-grey colour, firm, and of a crystalline appearance ; 4. 
 From Hausbergen limestone. 
 
 Portland cement, the best of all the mortars, is distinguished by the high tempera- 
 ture, reaching white heat, used in its preparation. 
 
 Portland cement, so named from the resemblance it bears when set to Portland 
 stone, is a scaly crystalline powder of grey colour, and was first prepared by Mr. Joseph 
 Aspdin, of Leeds, in 1824. According to his letters patent, he prepared his cement 
 in the following manner : A large quantity of limestone was taken and pulverised 
 or the dust or pulverised limestone used to mend the roads was employed. This 
 material was dried and burnt in a lime-kiln. An equal quantity by weight of clay 
 was added to the burnt lime, and thoroughly kneaded with water to a plastic mass. 
 This was afterwards dried, broken in pieces, and burnt in a lime-kiln to remove all 
 the carbonic acid. The mass, thus transformed to a fine powder, is ready for the 
 market. It is known in commerce as a grey, or green-grey, sandy powder. 
 But Pasley must be considered the true founder of artificial cement manufacture in 
 England. He, in 1826, obtained a cement by the burning of river mud from the 
 Medway, impregnated with the salts from sea-water, with limestone or chalk. The 
 mud from the Medway is probably the best adapted for the manufacture of Portland 
 cement, on account of the sodium salts it contains ; and from this supposition there seems 
 good ground for Pettenkofer's recommendation that various marls, burnt after lixivia- 
 tion with a solution of common salt, should be tried. At the present time the mud from 
 the mouths and delta formations of several large rivers is employed in the preparation 
 of this cement. 
 
670 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. v. 
 
 The manufacture of Portland cements usually follows this mode. The raw mate- 
 rials, limestone and clay or mud in equal quantities, are intimately mixed, the mixture 
 dried in the air, and then burnt in a shaft-oven. The shaft-oven is generally 14 to 30 
 metres in height, with a width of 2-3 to 4 metres. At a height of i to 1-3 metre 
 from the ground is a strong grating, through which the lumps of limestone mostly 
 fall, those remaining being afterwards broken by the heat. The oven is so arranged 
 that a layer of fuel and a layer of cement stone alternate. Coke is generally chosen 
 as fuel, being found by experience best adapted for the purpose. After the mass 
 has been submitted to a red heat for one hour, it assumes a yellow-brown colour, and 
 at a higher temperature becomes a dark brown. Gradually the lime becomes 
 causticised, and enters more and more into chemical combination with the silicates. 
 At a white heat the mass becomes grey in colour, with a streak here and there of 
 green. If during the operation these colours are shown at the several stages, the 
 resulting cement will be good and set hard. If the heating is continued, the cement 
 will assume a blue-grey colour, and become quite useless. If removed at the first 
 stage the mass yields a yellow-brown light powder ; at the second, a grey sharp 
 powder, tinged with green. Beyond this stage the powder is blue-grey, or grey- white, 
 clear and sharp, and very similar to glass-powder. The more lime the mixture con- 
 tains, or, it might be said, the more basic the mixture, the more durable is the cement, 
 and the less it falls to pieces in burning. A mixture in which clay predominates is 
 always more or less a weaker cement, falling to pieces readily, or, technically, not 
 binding well. According to Michaelis, the addition of lime or alkalies prevents the 
 cement separating, and renders it more binding ; but in practice this addition would 
 not be sufficiently economical. The more intimately the clay and lime are mixed, 
 the larger the amount of lime that may be incorporated. From the moment of 
 stiffening till the final hardening, the cement, if set in the air, experiences no 
 
 change ; but if in water, there is at first a small loss 
 of the more soluble constituents the alkalies. 
 
 Portland cement mixed with water to a paste 
 stiffens in a few minutes, and after the lapse of a 
 day sets tolerably hard. After a month the cement 
 sets into a substance so hard and firm that it emits 
 a sound when struck by a hard body. It is ad- 
 mirably adapted, when mixed with sand or gypsutn, 
 for being cast into various architectural ornaments, 
 and, indeed, has from this property been termed 
 artificial stone. Lately Griineberg has made crys- 
 tallising vessels of this cement, and Posch employs 
 it in constructing reservoirs for hot fluids. 
 
 Portland cement is considered by military en- 
 gineers the best material to oppose to the projectiles 
 used in modern warfare. 
 
 It has been very successfully burnt in the stage- 
 furnace of Dietzsch (Fig. 463). The raw materials, 
 artificially dried, are introduced through a hopper, 
 E, into the preliminary warming-chamber, A. It 
 slips down over the arched connecting-shoot, B, and 
 is shovelled from the working-door, F, into the 
 melting-space, C. Any clinkers which have become welded to the sides of the furnace 
 are removed through the opening, G, so that they fall into the cooling-room, D. 100 
 parts of cement require in this furnace only 9 to 19 parts of coal, as against 6-23 parts 
 in a ring-furnace, and 20 to 28 parts in a shaft-furnace. 
 
 Fig- 463- 
 
SECT. V.] 
 
 MORTARS, ETC. 
 
 671 
 
 These varying statements may be in part explained by the difference in the fuel 
 and by the more or less careful superintendence of the work. If, e.g., Meyer found 
 in the combustion -gases of a ring-furnace only 3-2 to 7-6 per cent, carbon dioxide, as 
 against 2 to 11-9 per cent, in the gases of the stage-furnace (where we have also to 
 take into account that a considerable part is derived from the decomposition of the 
 lime in the raw material), this proves that there is a great waste of fuel. If only half as 
 much carbonic acid were introduced, we should have a much greater heat, more rapid 
 burning, and less loss of heat at the chimney. These differences seem in part to be ex- 
 plained by the different nature of the mass itself. At least Dietzsch observed that in 
 his furnace two masses used 15-9 to 19 kilos, of coal and a third only 9. As the 
 chemical processes in burning (decomposition of OaCO s into CaO + C0 2 , formation of 
 silicates and aluminates) do not explain so great a difference, the reason probably is 
 that one mass requires a higher temperature than the other, and that for its produc- 
 tion especially if the supply of air is unsuitable a disproportionate quantity of coal 
 is needed. 
 
 M. W. Michaelis gives the following analyses of Portland cements, the samples 
 being free from water and carbonic acid : 
 
 
 
 
 
 
 
 g 
 
 
 g 
 
 
 
 
 
 
 
 
 
 
 
 9- 
 
 Lime . 
 Silicic acid 
 Alumina 
 Iron oxide 
 Magnesia 
 Potash 
 
 59-06 
 24-07 
 6-92 
 
 3-4I 
 0-82 
 O'73 1 
 
 62-81 
 23-22 
 5-27 
 
 2'OO 
 I-I4 
 
 6I-9I 
 24-I9 
 7'66 
 2'54 
 I-I5 
 fo'77 
 
 60-33 
 25-98 
 7-04 
 2-46 
 0-23 
 O'Q4. 
 
 61-64 
 23-00 
 6-17 
 2-13 
 
 6174 
 25-63 
 6-17 
 
 o-45 
 2-24 
 0*60 
 
 55^ 
 22^2 
 
 8-00 
 5-46 
 077 
 
 T'TS 
 
 57-83 
 23-81 
 
 9-38 
 S -22 
 
 i-35 
 
 O'CQ 
 
 55-28 
 22-86 
 
 9-03 
 
 6-14 
 1-64 
 
 0*77 
 
 
 0-871 
 
 1-27 
 
 1 n'/ift 
 
 O"3O 
 
 
 0*40 
 
 I '7O 
 
 O*7T 
 
 
 Calcium sulphate . 
 Clay I 
 
 2-8 5 
 I "4.7 
 
 I-30 
 2't.A 
 
 I "32 
 
 I'52 
 
 I "O4 
 
 i'53 
 
 1-28 
 
 1-64 
 
 T'I2 
 
 i-75 
 
 2 '27 
 
 I'll 
 
 3-20 
 i'o8 
 
 Sand] ' 
 
 
 
 
 
 
 
 
 
 
 No. i is Portland cement from White & Brothers, analysed by Michaelis. No. 2 
 is Stettin cement, analysed by Michaelis. Nos. 3 and 4 are Wildauer cements. No. 
 5, known as Star cement, and No. 6, another Stettin cement, by the same analyst. 
 No. 7, English cement, and No. 8, cement from works near Bonn, were both analysed 
 by Hopfgartner. No. 9 is a strong and porous cement, analysed by Feichtinger. 
 
 Boehme gives the analysis of ten samples, which are of little value, as they do not 
 give the locality or the name of the maker. 
 
 Hardening of Hydraulic Mortars. The hardening of hydraulic mortars has often 
 been the subject of investigation. Two views may be taken : first, the mere setting, 
 the congealing of the mass from a fluid state to a moderate degree of hardness ; and 
 then the hardening to a stony state. The knowledge we possess of the setting of these 
 mortars is chiefly due to the experiments of Yon Fuchs, Von Pettenkofer, Winkler, 
 Feichtinger, Heldt, Lieven, Schulat-Schenko, Ad. Remete, Heereen, W. Michaelis, and 
 Von Schoenaich-Carolath. The cements when thus considered are best divided in two 
 classes : The first class, of which Roman cement is the type, embraces the mixture of 
 caustic lime with puzzuolane, pulverised tile, and brick, and such hydraulic mortar as 
 is obtained by burning hydraulic lime and marl. All the cements contain caustic lime 
 unacted upon. The second class comprehends Portland cements, containing no fresh 
 caustic lime. M. Von Fuchs has explained the chemical actions taking place during 
 the hardening of Roman cements as being principally the combination of the lime with 
 silicic acid, the combination giving rise to the peculiar property of hydraulic mortars. 
 He draws this conclusion partly from the fact that from all hydraulic mortars the 
 silica can be thrown down as an insoluble gelatinous mass by the action of 
 carbonic acid. 
 
 A similar gelatinous mass results from the combination of silicic acid and lime. 
 
672 CHEMICAL TECHNOLOGY. [SECT. v. 
 
 Silicates do not yield gelatinous silica when treated with hydrochloric acid alone, but 
 attain this property when subjected for a length of time to the influence of lime under 
 water ; the water also dissolves out the alkalies. Kuhlmann, who has long been employed 
 in the study of the chemistry of hydraulic cements and artificial stones, states that 
 lime can be rendered hydraulic by the intimate mixture of 10 to 12 per cent, of an 
 alkaline silicate, or by treatment with a water-glass solution. Collecting the results of 
 these experiments, the setting of Roman cements appears due to the combination of 
 acid silicates or silica with burnt lime, forming a hydrated calcium silicate intermixed 
 with the alumina and iron oxide. 
 
 The hardening of Portland cements has been investigated by Winkler and Feich- 
 tinger. According to the former, the chemical action, which is effected under the co- 
 operation of the water, consists in the separation of the silicates into free lime and 
 combinations between the silica and the calcium, the alumina and the calcium. The 
 separated lime combines with the carbonic acid in the air to form calcium carbonate. 
 The hardened Portland cement contains the same combinations as hardened Roman 
 cement ; these combinations are formed, however, under the influence of water on opposed 
 conditions. From the results of Winkler's experiments, it would appear that the silicic 
 acid in the Portland cements can be replaced by alumina and iron oxide. Alumina 
 does not affect the hardness, but may lessen the capability of the cement to withstand 
 the action of carbonic acid. During the hardening the influence of the water separates 
 the lime, till finally the combinations Ca 3 Si 3 9 and CaAl 2 O 4 remain, the latter being 
 gradually decomposed by carbonic acid, remaining, however, as long as there is any 
 hydrate of lime in the cement. G. Feichtinger maintains a theory differing from that 
 of Winkler. His experiments lead him to the opinion that in all hydraulic mortars 
 the hardening depends upon the chemical combination between lime and the silica, and 
 between lime and the silicates contained in the cement. In all hydraulic cements free 
 lime is contained ; and upon this fact we may base the following experiments. When 
 Portland cement is brought to a paste with a concentrated solution of ammonium 
 carbonate, and stirred for a long time, no hardening is traced, the greater part of the lime 
 forming calcium carbonate. Then let the excess of ammonium carbonate be washed 
 away, the cement dried, and made into a mortar with pure water. This mortar will 
 not harden unless some calcium hydroxide be added, when it hardens similarly to fresh 
 mortar. The same result may be obtained by substituting a stream of carbonic acid 
 gas for the ammonium carbonate ; by this means 27 per cent, of calcium carbonate may 
 be obtained. Consequently the views of Winkler must be regarded as the most correct. 
 These experiments also show that in Portland cements silicates or free silica are con- 
 tained; that, further, free lime does and must exist. Portland cement will not take a 
 glaze, and can only be so far affected by burning as to cause the sintering of the clay 
 contained in the cement. 
 
 Erdmenger ascribes the setting of cement chiefly to the formation of a crystalline 
 lime hydrate. This hypothesis agrees ill with the experiments of Ostwald, who found 
 the composition of three cements from Riga (I. to III.) and two from Stettin (IV. and 
 V.) to be as follows : 
 
 I. ii. in. iv. v. 
 
 CaO . . . 72-10 ... 65-42 ... 61-92 ... 65-05 ... 60-52 
 
 MgO . . . 3-27 ... 3-89 ... 4-03 ... 3-04 ... 3-02 
 
 A1 2 S . . 6-66 ... 7-52 ... 7-97 ... 8-09 ... 7-57 
 
 FeA . . 1-99 ... 2-15 ... 2-71 ... 3-25 ... 4-48 
 
 Si 2 10-38 ' 1476 ... 16-75 1 7'4 20 '7 2 
 
 Alkalies . . 0*85 ... o - 86 ... 1-25 ... 0-92 ... ro2 
 
 SO, . . . 0-42 ... 0-52 ... 0-42 ... 0-30 ... 0-37 
 
 CO, . . . 1-64 ... 2-19 ... 2-42 ... 0-83 ... 0-52 
 
 C 0-36 ... 0-50 ... 0-47 ... 0-67 ... 0-53 
 
 HO . . . 2-56 ... 2-32 ... 2-24 ... ro6 ... 1-22 
 
SECT, v.] MORTARS, ETC. 673.. 
 
 In connection with these analyses, Ostwald determined the heat of setting : 
 
 Time. I. II. III. IV. V. 
 
 2 hours . . 20-53 ... 20-47 9'94 -- 34'Oi ... 7-53 
 
 6 37'05 -. 29-57 ... 12-23 35'46 ... 10-09 
 
 I day .. . 41-35 ... 3978 ... 15-32 ... 38-39 ... 18-79 
 
 4 days . . 46-16 ... ... 29-72 ... ... 
 
 5 ,, 47'*7 - ... 32-10 ... 
 
 6 57'96 44'34 33'5 6 ... 
 
 7 65-63 ... 51-55 ... 40-26 ... 
 
 Thus the development of heat was at first very rapid ; after six hours more than 
 half the total heat has been liberated. Afterwards the liberation of heat becomes 
 slower and slower, and after thirty days it is as good as imperceptible. We must note 
 the striking increase of the liberation of heat on the fifth, sixth, and seventh day. At 
 this time there evidently begins a new epoch in the chemical process of hardening, which 
 involves a renewed development of heat. The more quickly a cement sets, the greater 
 is its " setting-heat." According to Berthelot i gramme lime in slacking evolves 268 
 heat-units. If we calculate from the analyses how much free lime is contained in the 
 cements, the existing carbonic acid being assumed as combining first with the alkalies 
 and then with the lime, and the water being supposed to combine with the lime to a 
 hydrate, we may determine what quantity of heat would be developed by the action of 
 the water if the lime were free and became hydrated. The calculation is carried out 
 in the following table : 
 
 I. II. III. IV. V. 
 
 Hydration heat of lime . i68 - 8 ... 150*0 ... 136-6 ... 162-4 *55'4 
 Setting heat of cement . 70-2 ... 66'2 ... 45-4 ... 52-8 ... 42-3 
 
 The specimens IV. and V. have not been examined to the end, but they have plainly 
 already given off the chief portion of their combining heat, which is in all cases much 
 smaller than the hydration heat of the lime regarded as uncombined. Hence, the 
 assumption that no chemical interaction takes place between the lime and the clay 
 during the formation of Portland cement is not tenable. On the contrary, there occurs 
 a very important reaction, during which a quantity of heat is set free. The so-called 
 physical theory of the formation of cement must be considered as refuted, and the 
 chemical theory alone must be accepted as in harmony with facts. The objection might 
 of course be raised that chemical processes take place during the setting, to which 
 the difference observed might be ascribed. But such processes, like the formation of 
 zeolitic silicates, aluminium hydrates, &c., all evolve heat and therefore tend to lessen 
 the difference. That such difference is still so great proves the importance of the 
 chemical processes during burning. 
 
 Le Ohatelier ascribes the most important part in the setting of hydraulic mortars 
 to the crystallisation of dissolved matters of the combination CaO.Si0 2 .3H 2 O (the 
 composition of which is deduced, not from analyses, but from the crystalline compound, 
 BaO.Si0 2 .6H 2 O), which is resolved by water into free lime and an acid silicate, 2Si0 2 .CaO, 
 and by carbon dioxide and water into silica and a calcium carbonate. But the former 
 decomposition ceases when the water contains 0*052 gramme lime per litre. The 
 formation of this silicate during the setting ensues either by the union of the two con- 
 stituents or by the decomposition of silicates richer in lime, or perhaps by the mere 
 hydration of the anhydrous compound. The above-named combinations of lime with 
 ferric oxide or alumina, which can exist in water in presence of an excess of lime, are 
 decomposed by an excess of water ; but the decomposition ceases with a proportion of 
 lime of 0-225 gramme or of o - 6 gramme per litre at 15. Ferric oxide and alumina 
 are essential in burning, for the better combination of the lime with the silica. 
 
 Further experiments are necessary for the full elucidation of the question. 
 
 Testing Cement. In examining cements it is necessary to have in view the mixture 
 
 2 U 
 
674 CHEMICAL TECHNOLOGY. [SECT. v. 
 
 of cement with ground slags, now unfortunately in extensive practice. According 
 to Fresenius. a genuine cement should show (a) a specific gravity of at least 3*125, 
 certainly not less than 3'! ; (b) a loss on ignition of between 0-34 and 2*59 per cent., cer- 
 tainly not higher; (c)an alkalinity in the watery solution of o'5 gramme, corresponding 
 to 4 6-35 c.c. of decinormal acid ; (d) a consumption of normal acid on the direct treat- 
 ment of i gramme ground cement between i8'8o and 21-67 c.c., certainly not much 
 lower; (e) a consumption of permanganate solution by i gramme cement equal to 
 between 079 and 2*80 milligrammes potassium permanganate, not more. 
 
 Hydraulic Admixtures. Trass or tarass is a kind of trachytic tufa found in con- 
 siderable quantities in the Brohl- and Nettethall, near Andernach.* It contains 
 magnetic iron in small quantities, and also titanic iron. 
 
 Soluble in Insoluble in 
 
 Hydrochloric Acid. Hydrochloric Acid. 
 
 Silica . . . . 11-50 37'44 
 
 Lime .... 3-16 ... 2-25 
 
 Magnesia . . . 2*15 ... 0*27 
 
 Potash . . . 0-29 ... 0-08 
 
 Soda . . , . 2-44 ... ri2 
 
 Alumina. -. . . 1770 ... 1^25 
 
 Iron oxide . . . ii'ij ... 075 
 
 Water .... 7-65 
 
 56-86 ... 
 
 This cement has been employed for 300 years as a hydraulic mortar, and is one of 
 the most important of its class. 
 
 Puzzolana is another tertiary earth, occurring chiefly at Puzzuoli, near Naples, as 
 a loose, grey, or yellow-brown mass, of partly a fine-grained and partly an earthy 
 iracture. It contains in 100 parts: 
 
 Silicic acid 44 '5 
 
 Alumina iS'o 
 
 Lime 8 4 8 
 
 Magnesia 47 
 
 Iron oxide 12 x> 
 
 Potash ) 
 
 Soda ) 
 
 Water 9-2 
 
 997 
 
 The oxide of iron contains small quantities of titanium. More lime must be 
 added to form a hydraulic mortar. The masonry of the light-room of the Eddystone 
 Lighthouse is cemented with a hydraulic mortar formed from equal parts of pulverised 
 puzzolana and slaked lime. 
 
 Santorin derives its name from the Greek island of Santorin, where it was first 
 found. It is, similarly to trass, a volcanic formation, and, according to G. Feichtinger 
 (1870), consists of a mixture of cement and sand, the latter containing large quantities 
 of pumice-stone. It is not largely employed as a cement, on account of the difficulty 
 of separating the true cement from the accompanying sand. 
 
 Puzzolane Cements. Under this name, or that of Victoria " cement," there are 
 sold mixtures of finely ground slag and of lime slacked to a powder. This mixture, if 
 kept sufficiently moist, sets slowly and becomes moderately hard. Frost has a destructive 
 action upon recent slag cement structures, so that they are not admissible below o. For 
 the first fortnight such structures should be kept uniformly moist. It is better suited 
 for constructions under water. A further bad property of slag cements is their 
 tendency to crack, which can be combated only by grinding the slags less finely. A 
 * It is also found at Ardwick, near Manchester. ^EDITOR.] 
 
SECT, v.] MORTARS, ETC. 675 
 
 pure slag cement cannot oppose any satisfactory resistance to external mechanical 
 action. In all probability it will not acquire importance for constructions in the air 
 which are exposed to wear and tear. Its low initial hardness which it shares with 
 all puzzolanes, natural or artificial is another defect. 
 
 Concrete. The mention of concrete, so largely used in England, where a good 
 weathering mortar is required, must be included in that of cements. Concrete is a 
 mixture of ordinary mortar with stones, grit, broken brick, tiles, &c. To the concrete 
 is generally added lime, and then the whole mixed with two or three times the 
 quantity of fine sand. Pasely tells us that a better product may be obtained with i 
 part of freshly burnt lime, in pieces not larger than the fist, 3^ parts of sharp river- 
 sand, and i -5 part of water, the whole being well mixed. The bricklayer prefers to 
 mix the dry materials and then add water, the concrete in this manner taking a longer 
 time to harden, and admitting of greater care being taken to fill all interstices. The 
 several uses of concrete are too well known to need mention. The employment of un- 
 slaked lime in the preparation of concrete was first introduced by Mr. Smirke, of 
 London, to whom also its employment as a foundation to brickwork is mainly due. 
 
 Mixed Cements. We have already mentioned that for some years a number of 
 manufacturers and dealers have begun adding ground slags to the finished cement, 
 under pretence of improving it. A good Portland cement cannot be improved by such 
 additions. The admixture of slag with Portland cement, like that of heavy spar and 
 gypsum to painters' colours, is therefore a fraud on the purchaser, and consequently to 
 be condemned. 
 
SECTION VI. 
 ARTICLES OF FOOD AND CONSUMPTION. 
 
 STARCH AND DEXTRINE. 
 
 THE starch granule is an organised tissue, consisting essentially of starch with water, 
 a little sugar, dextrine, &c. Its composition corresponds to the formula C 6 H 10 O 5 , or, 
 according to Mylius, C 24 H 40 20 , or according to Nageli, C 36 H 62 31 . According to Dafert, 
 starch consists of bodies which are not mutually homogeneous (starch-cellulose, granu- 
 lose, dextrine), a little sugar, proteine compounds, amides, fat, and ash. He therefore 
 considers it idle to discuss the formula of starch, since it is a mere mixture. 
 
 The starch granule consists of numerous layers, which generally contain the 
 more water the further we proceed inwards. The innermost part is generally a 
 hollow, filled with air, around which the layers seem to be arranged. As a rule, the 
 thickest parts of all the layers are turned in the same direction. If they are equally 
 thick in all directions, the granules are globular ; if they are thicker in the equatorial 
 zone, the granule has a lenticular shape. On microscopic examination the limits of the 
 layers appear as lines, more or less distinct, running round the central cavity. Its 
 specific gravity = i'53- Iodine water colours starch blue, and the starch iodide formed 
 has, according to Bondonneau, the formula (C 6 H 10 O 5 ) 3 I, or according to Mylius, 
 
 (c 24 H 40 o 20 i) 4 m. 
 
 Payen gives the largest dimension of the granules as o'ooi millimetre; from his 
 researches we gain also the following examples : 
 
 Starch granules from hard potatoes 
 
 ordinary potatoes 
 Maranta indica 
 beans . 
 sago palm 
 Iceland moss 
 peas 
 
 wheat . . 
 Indian corn . 
 
 185 
 140 
 140 
 
 74 
 70 
 67 
 5 
 So 
 So 
 
 Fig. 464 shows, according to Schleiden, granules of potato starch, and Fig. 465 of 
 wheat starch. The potato has a larger granule, and sometimes gives a finer powder 
 than wheat. 
 
 Nature of Starch. Ordinary starch contains in its dry state nearly 18 per cent, 
 water, and in this state has a tendency to form itself into globules ; it has been proved 
 that, exposed to a damp atmosphere, it absorbs 33*5 per cent, water. Starch is insoluble 
 in cold water, alcohol, ether, and oil. At a temperature of 160 starch yields dextrine. 
 Starch mixed with twelve to fifteen times its quantity of warm water at a temperature 
 of 55 varies little in substance ; at a temperature of 55 to 58 it begins to change, the 
 higher temperature making the fluid thicker. Lippmann says that potato starch is 
 affected at 62*5, wheat starch at 67-5. When boiled the granules burst and form 
 
SECT. VI.] 
 
 STARCH AND DEXTRINE. 
 
 677 
 
 .a gelatinous mass, which, largely diluted with water, can be made of a consistence to be 
 filtered through paper, and, when allowed to cool, sets in a jelly. A stiffer paste, 
 according to J. Wiesner (1868), is made from Indian corn than from the potato or 
 
 Fig. 464. 
 
 Fig. 465. 
 
 wheat. The longer the starch is boiled the stiffer the paste becomes, i part of starch 
 separating in 50 parts water, and, upon cooling, setting into paste of a blue or violet 
 hue. 
 
 Alkalies and dilute acids, with lime, tend to re-form the granules ; when boiled 
 with 2 per mille of oxalic acid, starch loses its consistence, becoming thin, and 
 changing into a soluble substance called dextrine. Starch treated with almost 
 any dilute acid, or with diastase obtained from an infusion of malt, at the proper 
 temperature is converted into dextrine, forming a liquid which after a few hours ; 
 standing can be made into sugar. Starch is soluble in the cold in concentrated 
 nitric acid ; water dropped into this solution precipitates the granules as an explosive 
 combination. Under the name of xylodine, or white gunpowder, this combination has 
 lately been employed for pyrotechnical experiments. By boiling starch with con- 
 centrated nitric acid, a formation of oxalic acid is obtained, evolving nitrous 
 vapours. Starch paste, upon exposure to the atmosphere, becomes sour, forming 
 lactic acid. 
 
 In the determination of starch in raw materials, it must be considered that for the 
 textile arts and for domestic uses only the actual starch must be considered, and 
 sugar, if present, must be estimated separately. For brewery purposes the sugar is 
 determined along with the starch. For the spirit manufacture it must be remembered 
 that the sugar present is destroyed by the high pressure, whilst other substances are 
 converted into carbohydrates capable of fermentation. 
 
 For the two former purposes, according to Reinke, 3 grammes of the sample, 
 ground as finely as possible, are heated to boiling with 50 c.c. of water, cooled down to 
 62*5, and mixed with 0^05 gramme of diastase prepared according to Lintner. Saccha- 
 rification is allowed to proceed for an hour at the same temperature. The mixture 
 is then diluted with water, cooled, and made up to 250 c.c. 200 c.c. are then inverted 
 with 15 c.c. hydrochloric acid (of sp. gr. i'i25) at a boiling heat for two and a half 
 hours in an Erlenmeyer flask with a reflux condenser, almost entirely neutralised 
 with soda-lye, made up to 500 c.c., and 25 c.c. are taken for reduction with Fehling's 
 solution. The dextrose is calculated from the reduced copper according to Allihn's 
 tables, i oo dextrose = 90 starch. 
 
 For distillery purposes 3 grammes of the finely ground sample are stirred up with 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 25 c.c. of lactic acid at i per cent, and 30 c.c. of water heated for two and a half hours in 
 Soxhlet's autoclave at a pressure of 3^ atmospheres, then mixed with 50 c.c. hot water, 
 when cold made up to 250 c.c., and filtered ; 200 c.c. of the nitrate are inverted as above 
 and used for the determination of dextrose. 
 
 Sources of Starch. But few vegetables yield starch in large quantities ; the potato 
 yields 20 per cent. ; wheat, 55 to 65 per cent. ; rice, 70 to 73 per cent. ; and the roots of 
 Jatropha Manihot and Maranta arundinacea, palm pith, and the Canna coccinea, similar 
 quantities. In Germany starch is prepared only from potatoes, rice, and wheat, the 
 latter yielding a greater quantity of gum, and potato starch being thinner and not so 
 gelatinous. 
 
 Starch from Potatoes. Potatoes form an important material in the manufacture 
 of starch ; their constitution is as follows : 
 
 Water . 
 Albumen 
 Fatty matter 
 Cellulose 
 Salts . 
 Starch . 
 
 Newly dug 
 Potatoes. 
 
 2-3 
 
 0'2 
 
 0'4 
 
 I'O 
 
 21 'O 
 
 Potatoes 
 dried at 100 
 
 9-6 
 0-8 
 17 
 4'i 
 83-8 
 
 They contain 28 per cent, dry substance, or 23 per cent, insoluble substance, and 
 7 7 per cent. sap. The starch found in potatoes is of cellular construction ; the cell 
 walls require breaking up to fit it for manufacture. Fig. 466 shows, according to 
 Schleiden, a fine specimen of a healthy potato under the microscope. On the outside of 
 the potato a layer of flat, pressed, brown cells are found, sometimes appearing in a 
 patch, a, forming the outer skin of the potato, and covering the cells, b, which some- 
 
 Fig. 467. 
 
 times contain a finer grain, but mostly a clear fluid. These cells become wider as 
 they near the interior of the potato. The series of cells c enclose the inner cells, d, 
 the pith of the potato. When the potato is dried, the cells separate from each other, 
 as in Fig. 467, a specimen of a mealy potato. The starch granules swell in each 
 cell, the cells uniting in reticulated streaks. 
 
 The process of manufacturing starch consists in 
 
 i . Triturating the fresh potato. 
 
 2 Washing the starch granules from the pulp. 
 
 3. Purifying and drying the starch. 
 
SECT, vi.] STARCH AND DEXTRINE. 679- 
 
 The potatoes are placed in a grinding cylinder, which formerly consisted of wood, 
 with iron plate rollers placed half-way in water to cleanse the pulverised potato pulp. 
 Of late grinding cylinders with saw-teeth are used (Thierry's machine). The saw- 
 blades have short teeth, lacerating the cells to obtain the starch granules, which mere 
 gentle washing and grinding would not effect ; the cylinder revolves 600 to 700 times 
 a minute. One cylinder, with knives 0*50 metre in length and saw-blades of 0*40 metre, 
 can grind fourteen to fifteen batches in an hour to a pulp, which is afterwards sub- 
 mitted to the process of washing. A cylindrical metal sieve is generally used for 
 separating the starch granules from the potato pulp ; it contains a pair of brushes 
 slowly rotating, whilst water is supplied to the sieve to wash the pulp, which is ground 
 to a consistence that will admit of its readily flowing off, in order that fresh pulp may 
 be received on the sieve. The starch granules are suspended in the water strained off, 
 and finally settle to the bottom as a soft white powder. Laine's uninterrupted cleans- 
 ing sieve is now generally used ; it consists of a series of wire-work frames placed over 
 a trough. The potato pulp flows from the grinding cylinder to a space under the 
 cleansing sieve, from thence over two gratings, where the pulp is cleansed by a stream 
 of water playing all over it, the granules settling down at the bottom of the trough. 
 The granules are then crushed between steel rollers to separate the starch from the 
 fibre. 80 to 100 cwts. potatoes can be thus prepared in a day. From the above 
 method of preparing starch from the potato we gain the general principles of such 
 operations. The structure of the potato is shown to be partly chemical, partly 
 mechanical, and by destroying the latter we gain starch, which is separated after the 
 potato pulp has been standing eight days, when it becomes a white pasty mass contain- 
 ing starch. This is placed in a coarse sieve, which retains a greater part of the* fibre, 
 another finer hair sieve being used to receive the starch and finer fibre, separated from 
 each other by means of a cleansing apparatus, which washes the fibre away, leaving the 
 starch granules and sugar behind. 
 
 Drying the Potato Starch. The result of the washing is a milk-like fluid, which 
 settles at the bottom of the trough as starch ; it is then mixed with fresh water and 
 allowed to solidify into a hard substance, which is cut into pieces, poured upon a linen 
 cloth, placed on a hurdle, with a plaster-of -Paris vessel, or a vessel containing gypsum, 
 underneath, to dry the starch. After being filtered and left to stand for twenty-four 
 hours, the starch dries to the thickness of 2 decimetres upon the gypsum. Of late the 
 water has been removed by a centrifugal machine. The moist starch contains 33 per 
 cent, water, and is called fresh starch. The average temperature of the drying-rooms 
 is not over 60. When the starch is dried it is broken into pieces by iron rollers. The 
 stalk or whole starch is made by boiling to a thick paste, which is forced by machinery 
 through a small opening into a trough, where it dries in a kind of mould. 
 
 Preparation of Wheat Starch. According to M. O. Dempwolf (1869), the un- 
 prepared wheat contains : 
 
 Water . . . . . . 10-51 
 
 Ash 1-50 
 
 Gum 14-35 
 
 Starch 65-40 
 
 Fatty and woody fibre . . . 8-24 
 
 From the constituent parts of wheat it is seen that 
 
 Starch 
 
 Gum 
 
 Husk 
 
 > are insoluble in water. 
 
 Salts 
 
 Albumen 
 
 Dextrine 
 
 h are soluble. 
 
68o 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 The first three are insoluble, the gum, however, being gradually dissolved by the 
 lactic acid developed from the seed, while the starch and husk remain unattacked. 
 There are two methods of preparing wheat starch viz. : 
 
 A. By fermentation (old method) of the 
 
 a. Ungroundj 
 , n f , [ Wheat. 
 ft. Ground J 
 
 B. New mode of treatment without fermentation. 
 The old method consists of the following operations : 
 
 1 . Fermenting the wheat. 
 
 2. Washing the starch from the mass. 
 
 3. Washing and cleansing the starch. 
 
 4. Drying the starch. 
 
 The whole wheat is soaked in water until soft. The seed is separated from the 
 husk either by treading in sacks in a flat tub of water, or by being placed under 
 rollers, and the pulp thinned with water .to a milky fluid, in which a greater part of 
 the starch and gum are found. After standing a day this fluid turns acid ; a part of 
 the gum becomes dissolved by the action of the lactic and acetic acids, and is taken away 
 and replaced by fresh water, the same process being gone through until the fermenta- 
 tion ceases, when the starch is washed with water and dried. In the fermenting tub 
 it forms with the water a thin, sour pulp. The time varies according to the tempera- 
 ture ; all the gum is not separated until about twelve to thirty days. The sour 
 water contains acetic acid, lactic acid, butyric acid, succinic acid, ammoniacal salts, and 
 the mineral constituents of the wheat. The mass is then placed in a sack and trodden, 
 the milky fluid being allowed to escape, leaving the husk and refuse gum behind. The 
 milky fluid containing starch is strained through a fine hair sieve and washed with 
 water. Another method is that of placing the milky fluid in a tub and allowing it 
 to settle. The first layer of the sediment is fine starch, next a mixture of starch, husk, 
 and gum, the last layer containing but little starch. In the preparation a little 
 ultramarine blue is added during the cleansing process. Of late the centrifugal 
 machine has been used for the purpose of drying the starch. 
 
 Preparing Wheat Starch without Fermenting. According to E. Martin's treatment, 
 wheat flour is mixed with water to a paste, 100 parts flour to 40 parts water; the 
 paste remains half to two hours to affect the gum, and is then washed in a fine wire 
 sieve placed over a tub. The starch is found at the bottom of the tub mixed with 
 water, and is placed in a warm spot to ferment slightly. It is dried in a mass, and 
 goes through similar processes to the other starch, being made into stalk and powder 
 starch, and sold in packets. 
 
 TOO parts of wheat flour yield 25 per cent, of gum (gluten, gluten granule), with 33 
 per cent, of water ; the fresh gluten is mixed with a double weight of flour, the paste 
 rolled into long strips, and ground into granules which become dry at 30 to 40, and 
 are afterwards sifted. The consumption of this granular gum is extensive, it being 
 employed for food (with ordinary flour as macaroni), art purposes, and manufactures. 
 
 Constituents and Uses of Commercial Starch. According to M. J. Wolff, the 
 constituents of commercial starch are as follows : 
 
 
 
 
 
 
 
 
 
 
 
 3- 
 
 4- 
 
 5- 
 
 
 Water .... 
 Gum .... 
 Fibre 
 Ash .... 
 
 I7-83 
 0-48 
 
 15-38 
 
 0-50 
 
 OM 
 
 14-52 
 
 O'lO 
 
 1-44 
 
 o'O3 
 
 17-44 
 
 traces 
 
 I '20 
 
 14-20 
 
 1-84 
 3-77 
 
 rvCC 
 
 17-49 
 4-96 
 2-47 
 
 I - 2O 
 
 Staxch .... 
 
 81-48 
 
 u 3J 
 
 83-59 
 
 83-91 
 
 8I-32 
 
 79-63 
 
 7379 
 
 
 lOO'OO 
 
 lOO'OO 
 
 lOO'OO 
 
 100 '00 
 
 lOO'OO 
 
 lOC'OO 
 
SECT. VI.] 
 
 STARCH AND DEXTRINE, 
 
 68 1 
 
 No. i was the finest white patent starch in stalks, of a bright and crystalline appear- 
 ance, made from pure potato starch ; No. 2, the finest blue patent starch, potato starch 
 coloured with ultramarine ; No. 3, pure wheat powder; No. 4, fine wheat starch in pieces ; 
 No. 5, medium fine wheat starch in yellowish- white pieces ; No. 6, ordinary wheat starch 
 in greyish-yellow coarse pieces, that upon microscopic examination appear as a mixture of 
 potato and wheat starch. Starch is used for stiffening domestic articles in washing, for 
 stiffening paper, and extensively in the linen and cotton manufacture, in gum, syrups, 
 sago, vermicelli, &c. It is also a basis from which we can obtain sugar. Potato starch 
 is preferred for domestic washing, but where great stiffness is requisite, wheat starch 
 is used, as in book-binding, &c. In wheat starch, the paste is formed of closely united 
 gelatinous particles, which are more widely disseminated in potato starch, the latter 
 being transparent and more suitable for stiffening fine linen, ironing smoother, and 
 not sticking. Wheat starch will keep fresh upon exposure to the atmosphere longer 
 than potato starch, the latter turning sour after a day's standing. 
 
 According to C. Wiesner (1868), maize starch possesses the highest, wheat the next, 
 and potato starch the most inferior stiffening qualities. Maize and wheat are 
 considered the best for forming a smooth, equal paste. Sugar can be prepared from 
 starch by means of the active principle of malt diastase. From this sugar, again, 
 brandy and spirits can be distilled. According to the researches of Liidersdorff : 
 100 pounds of potato starch need 2 5 '5 pounds of dry malt, and 
 100 wheat 90*5 
 
 to effect the full conversion of the starch into sugar. 
 
 Rice Starch, Maize Starch, Chestnut Starch, Cassava Starch, Arrowroot. Rice 
 starch is largely manufactured in England, France, and Belgium. To extract the gum, 
 rice is placed in a bath of weak soda solution 287 grammes of caustic soda to the hecto- 
 litre. After standing twenty-four hours, the rice grain becomes softened, and is then 
 washed, ground between rollers or millstones, and placed on a sieve with brushes to 
 retain the husk or bran. The water strained off contains the starch, which is washed, 
 dried, and manufactured into the form required. The gum-containing alkaline lye being 
 neutralised with sulphuric acid is fit for inferior uses. J. & J. Colman's rice starch 
 manufacture employs 1000 workpeople, and the result of their manipulation is used as 
 the customary washing starch, the stiffer and brighter starch for ball dresses, window 
 hangings, and for the size in paper manufacture. 
 
 Rice Starch. Mack treats rice in a steeping-vat with double sides (Fig. 468). 
 Atmospheric air rushes in from all sides 
 in such quantities that the mass is kept in 
 a state of motion like ebullition. The 
 rice is heaped up on the perforated false 
 bottom, p, whilst the space, B, under the 
 false bottom, and the free space above the 
 rice are filled with the dilute soda-lye. 
 The air is introduced under pressure 
 through the tube, r, into the receptacle, 
 jR. from which it passes through many 
 narrow pipes, t, into the space, jB, and 
 then through the false bottom, p, into the 
 rice. The floor, a, is raised towards the 
 centre, so that the liquid can be let off 
 afterwards through the cock, h, when the rice is left half dry on the floor, p. 
 
 Maize Starch. Maize is softened, ground, pressed, ground again, and finally treated 
 with caustic alkalies. This treatment is important, as it is necessary to remove oil, 
 mineral matter, and the nitrogenous compounds which enclose the starch. Rice starch is 
 
 r: 
 
682 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 separated into three qualities by a process of elutriatioii, which contain, according to 
 Archbold : 
 
 I. u. in. 
 
 98-5 ... 92-88 ... 90-33 
 2-38 4-25 
 
 0-3 ... 0-60 ... 0-65 
 
 1-2 ... 4-14 ... 477 
 
 Starch . 
 
 Gluten and cellulose 
 
 Ash 
 
 Water . 
 
 Fig. 470. 
 
 According to Tschirch, maize flour contains starch granules of two distinct forms 
 
 more or less angu- 
 lar, almost isodia- 
 metric, and poly- 
 hedral granules 
 often adhering to- 
 gether in groups 
 of nearly the same 
 size (Fig. 469) ; 
 and rounded 
 grains, varying 
 much more in size 
 (Fig. 469, m). 
 
 The starch 
 granules of rice 
 are almost exclu- 
 sively angular (tri-, 
 quadra-, pent-, or 
 hexangular). 
 Large or conglo- 
 merated masses are often found (Fig. 
 470). There are found in rice flour, 
 though less commonly in starch, frag- 
 ments of such conglomerates (Fig. 47 1 ). 
 The sharpness of the angles is the most 
 prominent characteristic of rice starch. 
 According to Tschirch, the largest 
 granules do not exceed 8-5 micromillim., 
 and the smallest have a size of 4*5 to 
 6 micromillim. 
 
 In France the horse-chestnut is used 
 for the manufacture of starch. Chest- 
 nuts produce a starch possessing the 
 evenness of potato starch with the 
 
 stiflhess of wheat starch. 100 parts of the fresh bitter chestnut give 19 to 20 per 
 cent, dry starch. 
 
 Arrowroot is obtained from the Maranta arundinacea and M. indica, cultivated 
 in the West Indies ; it is very like potato starch, and is prepared in a similar 
 manner. Cassava starch is made from the root of Jatropha Manihot, or Manihot 
 utittissima, and M. aipin, largely cultivated in South America, the West Indies, and 
 the Brazils. 
 
 Cassava is used as an article of consumption both in Europe and the Tropics. The 
 root of the manioc is thoroughly purified from its poisonous juice, being coarsely ground 
 to allow the sap to escape, and roasted in an earthenware vessel, the cassava forming 
 into granules on the sides of the vessel (Cassava sago, or Tapioka), the prussic acid 
 
SECT. VI.] 
 
 STARCH AND DEXTRINE. 
 
 683 
 
 contained in the root becoming volatilised. From arrowroot and the analogous roots 
 containing a poisonous juice, arrowroot derives its name, having been used by the 
 Indians as a poison for the tips of their arrows. Its components, according to Benzon, 
 in 100 parts, are: Volatile 
 
 oil, 0-07 part ; starch, 26 parts, Fig ^ lt 
 
 89 per cent, of the starch being 
 obtained in a powder, while 
 the remainder is extracted 
 from the parenchyma by boil- 
 ing water ; albumen, 1-58 part ; 
 gum, o'6 part ; calcium chlor- 
 ide, 0*25 ; insoluble fibrin, 6 
 parts; and water, 65-5 parts. 
 It is known in commerce in 
 several varieties viz., Port- 
 land arrowroot, Arum vulgare ; 
 East India arrowroot, Curcuma 
 angustifolia ; Brazilian arrow- 
 root, Jatropha Manihot ; Eng- 
 lish arrowroot, from the starch 
 of the potato ; Tahiti arrow- 
 root, Tacca oceanica. 
 
 Sago. Sago is made from the soft central portion of the stem of the palm, Sagus 
 Rumphii. According to J. Wiesner, the Guadaloupe sago is prepared from Raphia 
 farinifera, and an East Indian variety from Caryota urens. The stem is torn to fila- 
 ments and elutriated on a sieve with water. The starch obtained is then washed, dried, 
 and sifted into a copper plate, where it remains a hard granular substance. A greater 
 part of the common sago is manufactured from potato starch, coloured with oxide of iron 
 or burnt sugar. 
 
 Dextrine. Dextrine, gommeline, moist gum, starch gum, or Alsace gum, isomeric 
 with gum arabic, and expressed by the formula C 6 H 10 O 5 , is formed by boiling starch 
 with a small quantity of almost any dilute acid, which thins its consistence, and con- 
 verts it into a soluble substance similar to gum arabic. It is soluble in cold water, 
 insoluble in absolute alcohol, but slightly soluble in weak spirits of wine. Dextrine 
 derives its name from dexter, the right, from the action of this substance on polarised 
 light, twisting the plane of polarisation towards the right hand. Dextrine in grape 
 sugar is converted into dextrose by the action of dilute acids. Dextrine solution does 
 not ferment with yeast ; but a little yeast mixed with a large quantity of gelatinous 
 starch, at a temperature of 160, quickly liquefies it, dextrine being produced, the 
 greater part of which, if allowed to stand, becomes converted into grape sugar. From 
 this decomposed dextrine a cheap and largely employed substitute for gum arabic is 
 obtained. The components of this decomposed dextrine, according to the analyses of 
 R. Forster (1868), are: 
 
 
 i. 
 
 2. 
 
 3- 
 
 4- 
 
 5- 
 
 6. 
 
 
 Dextrine. 
 
 Opaque 
 Starch. 
 
 Dark 
 Dextrine. 
 
 Gommeline. 
 
 Old 
 Dextrine. 
 
 Bright 
 Starch. 
 
 
 Dextrine .... 
 
 72-45 
 
 70-43 
 
 63-60 
 
 59-71 
 
 49-78 
 
 5 '34 
 
 Sugar .... 
 Insoluble substances 
 
 877 
 13'H 
 
 1-92 
 19-97 
 
 7-67 
 I4-5 
 
 576 
 20-64 
 
 1-42 
 30-80 
 
 0-24 
 86-47 
 
 Water .... 
 
 5-64 
 
 7'68 
 
 14-23 
 
 13-89 
 
 18-00 
 
 7-95 
 
 
 lOO'OO 
 
 lOO'OO 
 
 lOO'OO 
 
 lOO'OO 
 
 100.00 
 
 lOO'OO 
 
684 CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 Potato starch is preferable to wheat starch for the manufacture of this material, not 
 only on account of its cheapness, but for its greater purity at an equivalent price. 
 Dextrine is prepared by 
 
 a. Gently roasting. 
 
 b. Carefully treating with nitric acid. 
 
 c. Boiling with dilute sulphuric acid. 
 
 d. Treating with malt extract (diastase). 
 
 Preparing dextrine by means of gentle heat is an easy operation. The starch is 
 roasted until it becomes brown-yellow in colour, in a large copper or iron plate 
 cylinder, similar to a coffee- drum, situated on one side of the oven. Dextrine is 
 formed at a temperature of 225 to 260. According to Heuze, the following is a 
 better method : 2 kilos, of nitric acid, of i "4 specific gravity, with 300 litres of water, 
 are mixed with 1000 kilos. (=20 cwts.) of starch, and boiled to form a mass, which, 
 when exposed to the air, becomes dry. It is sometimes effected at 80, but it becomes 
 a paste at 100 to 110. The starch changes into dextrine in an hour or an hour and 
 a half at the most ; it is white and soluble in water. Sulphuric, hydrochloric, and 
 acetic acids will produce dextrine ; and by the addition of water to dextrine, dextrine 
 syrup, or gum syrup, is obtained. 
 
 Dr. Vogel gives a simple experiment to illustrate the action of dilute sulphuric 
 acid upon starch. Nearly all kinds of writing-paper are so very largely sized with 
 starch, that if figures or letters are traced on the paper with very dilute sulphuric 
 acid, and then dried, the application of iodine in a dilute solution will impart a blue 
 tinge to that portion of the paper not affected by the acid, the characters remaining white. 
 
 Dextrine is extensively used instead of gum arabic in printing wall-papers, for 
 stiffening and glazing cards and paper, for lip-glue, surgical purposes, wines, and in the 
 fine arts it is applied in many ways. 
 
 SUGAR. 
 
 Those carbohydrates which are comprised under the name of sugar are divided into 
 two great groups : those which, disregarding crystalline water, have the composition 
 C 6 H 12 6 ; and those which correspond to the formula C 12 H 22 O U . 
 
 I. The former group includes, chiefly, dextrose (which, when it occurs naturally, 
 should be known as grape sugar, starch sugar, &c.), levulose (fruit sugar), arabinose, 
 cerasinose, lactose (galactose), sorbine, eucalyne, inosite, dambose, mannitose, and 
 others. 
 
 II. To the group C 12 H 22 O n there belong saccharose (cane sugar and beet sugar), treha- 
 lose (mycose), melezitose, melitose (raffinose), maltose, galactose (or lactose, milk sugar). 
 
 The sugars of the latter group, on treatment with dilute acids, undergo inversion, 
 i.e., take up the elements of water, and are converted to equal quantities of sugars of 
 Oroup I., one of which is always dextrose : 
 
 C 12 H 22 U + H 20 = C G H 12 6 + C 6 H 12 6 
 
 Saccharose + water = dextrose + levulose. 
 
 Trehalose + = + dextrose. 
 
 Melitose + = + eucalyn. 
 
 Maltose + = + dextrose. 
 
 Galactose + = ^+ lactose. 
 
 The sugars of technical importance are dextrose, inverted sugar (dextrose and 
 levulose), maltose, and saccharose. 
 
 Grape Sugar. Grape sugar (potato sugar, starch sugar, glucose, or dextrose) is a 
 sugar crystallisable with difficulty, occurring in a non-crystallised state as levulose or 
 chylariose (yv\apiov, syrup) in many sweet fruits, in the vegetable kingdom, and it 
 
SECT, vi.] < SUGAK. 685. 
 
 forms the solid crystalline portion of honey. It may be obtained by any of the follow- 
 ing processes : 
 
 a. By the conversion of starch, dextrine, cane sugar, or some gums, by means of 
 
 dilute acids or diastase. 
 
 b. By treating cellulose and similar vegetable matter with dilute acids. 
 
 c. By decomposing organic substances, such as amygdalin, salicin, ploridzin, 
 
 populin, quercitrin, gallo-tannic acid, &c., which by treatment with dilute- 
 acids or synaptase (emulsin) are separated into grape sugar and other 
 substances. 
 Grape sugar is found in the various fruits in the following quantities : * 
 
 
 Per cent. 
 
 
 I'Vf 
 
 Apricot 
 
 I -80 
 
 Plum 
 
 2'12 
 
 Raspberry 
 
 4-00 
 
 Blackberry . 
 
 4-44 
 
 Strawberry 
 
 573 
 
 Bilberry 
 
 . . . 578 
 
 Currant 
 
 6-10 
 
 Plum (sweet) . 
 
 ... . 6-26 
 
 Gooseberry 
 
 7T5 
 
 Cranberry 
 
 7 '45 (according to Fresenius) 
 
 Pear 
 
 8 -02 to 10-8 (E. Wolff) 
 
 Apple 
 
 8-37 (Freserius) 
 
 
 7-28 to 8-04 (E. Wolff) 
 
 Sour cherry 
 
 . .. . 877 
 
 Mulberry 
 
 9-19 
 
 Sweet cherry . 
 
 . 1079 
 
 Grape 
 
 . 14-93 
 
 Grape sugar, C 6 H 12 6 H 2 0, crystallises from its aqueous solution in granular, hemi- 
 spherical, warty masses. It is less easily soluble in water than cane sugar, and requires 
 1 1 of its own weight of cold water, while in boiling water it is soluble in all propor- 
 tions, forming a syrup possessing but poor sweetening qualities. There are required 
 z\ times more grape sugar than cane sugar to sweeten the same volume of water. At 
 120 grape sugar loses its water, and has the formula C 6 H 12 O 6 . At 140 it is converted 1 
 into caramel. Heated with caustic alkalies, melassic acid is formed, together with 
 humus-like substances. Treated with sulphuric acid, grape sugar forms sulpho-saccharic 
 acid ; and with common salt, a soluble compound of sweetish saline taste. With caustic 
 potash in excess, a grape-sugar solution, when heated to the boiling-point, reduces the 
 hydrate of copper oxide to suboxide, silver oxide to metallic silver, and gold chloride to 
 metallic gold. A mixture of potassium ferricyanide and potash with the aid of heat 
 decomposes grape sugar, and discharges the original yellow colour of the fluid. Under 
 the influence of a ferment grape sugar suffers many changes, the product varying with 
 the ferment and method of treatment employed. Beer yeast decomposes grape sugar 
 into alcohol and carbonic acid. 
 
 100 kilos, of grape sugar give : 
 
 Alcohol ..... 51 'it 
 Carbonic acid . . . . 48^89 
 
 There are also found, under certain conditions of temperature and concentration, 
 the homologues of alcohol viz., propylic alcohol, butylic alcohol, and amylic alcohol ; 
 and under all conditions glycerine and small quantities of succinic and lactic acids. 
 When fermentation is effected in the presence of alkaline reagents, lactic acid is 
 
 * The sweetness of a fruit does not depend simply on the quantity of sugar. The proportion 
 and the kind of acid, and the presence or absence of gum, have to be considered. [EDITOR. ] 
 
686 CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 formed without any disengagement of gas. Ordinarily the formation of lactic acid is 
 merely a stage in the process of conversion, the lactic acid decomposing into butyric 
 and acetic acids, with development of hydrogen. Under certain conditions mannite 
 may be prepared from grape sugar ; several other gum-like substances may also be 
 obtained. If to a grape-sugar solution a small quantity of caseine and calcium carbon- 
 ate be added, and the mixture submitted to a temperature of 90, calcium butyrate 
 will be thrown down after fermentation, carbonic and hydrogen gases being continu- 
 ously evolved. 
 
 Preparation of Grape Sugar. Grape sugar may be prepared from 
 
 a. Grapes. 
 
 b. Starch. 
 
 c. Wood and similar vegetable substances. 
 
 When grape sugar is prepared from the grape, the juice of the Avhite grape is 
 preferred, and set aside to clear. The cleared must is heated to the boiling-point 
 with pieces of marble, chalk (not with burnt lime), or witherite (barium carbonate), 
 to neutralise a portion of the tartaric acid. It is then allowed to stand for twenty- 
 four hours, and during this time the insoluble salts of lime are deposited. The must 
 is now cleared with ox blood, in the proportion of 2 to 3 litres of blood to 100 litres 
 of must, and next evaporated to 41 Tw. After remaining a short time in a tub to 
 clear, the impurities are removed, and the must again evaporated this time to 57 Tw. 
 By these means a syrup is produced, from which the grape sugar can be immediately 
 obtained. The syrup is concentrated by boiling, and run into crystallising vessels, 
 where after three to four weeks the sugar crystallises out ; it is separated from the 
 non-crystallised chylariose in a centrifugal machine. For experimental purposes the 
 crystals may be separated by placing the concentrated syrup on a heated porcelain or 
 .glass plate. 
 
 1000 parts by weight of grapes give : 
 
 Must .... 800 
 
 Syrup .... 200 
 
 Raw grape sugar . . 140 
 
 Pure grape sugar . . 60-70 
 
 The preparation of grape sugar from starch is an important branch of the sugar- 
 'boiler's art. Dilute sulphuric acid and the f ecula of potato starch are the active agents. 
 The principal processes are the following : 
 
 a. The Soiling of the Starch-meal with Dilute Sulphuric Acid is effected on a small 
 scale in leaden pans, but in an extensive preparation iron pans are employed. The 
 -requisite quantity of water is first heated to the boiling-point, and to this is added the 
 sulphuric acid diluted with 3 parts by weight of water. The starch is also previously 
 brought, by the addition of water, to a milky consistency. The liquids so prepared 
 are mixed, and the boiling continued until all the starch is converted into sugar. An 
 intermediate stage, not usually noticed by the manufacturer, is the conversion of the 
 starch into dextrine, which in its turn suffers conversion into grape sugar. The entire 
 conversion of the dextrine into grape sugar cannot be ascertained with certainty by 
 the iodine test, as sometimes a purple-red tint is produced, while in others there is no 
 change. The most reliable test is that with alcohol, founded on the known insolu- 
 bility of dextrine in an alcoholic menstruum. To i part of the solution to be tested 
 there are added 6 parts of absolute alcohol : if no precipitate is thrown down there is 
 no dextrine remaining, and the conversion has been entire. The proportions of the 
 materials are generally to 100 kilos, of starch-meal 2 kilos, of ordinary sulphuric acid 
 of 130 Tw. and 300 to 400 litres of water. 
 
 The conversion of the starch into grape sugar is hastened by the addition of a small 
 quantity of nitric acid. 
 
SECT, vi.] SUGAR. 687 
 
 b. The /Separation of the Sulphuric Acid from the Sugar Solution is a most important 
 operation, for the colour, purity, and flavour all depend upon success in this stage 
 of the process. The acid is neutralised by baryta or by lime, with either of which 
 it forms a precipitate, deposited at the bottom of the neutralisation vessels, and 
 leaving a clear supernatant syrup. The baryta can be employed as carbonate 
 (witherite), and is without doubt the better neutralising agent, barium sulphate 
 being very insoluble. Lime, although ordinarily used, forms with the sulphuric acid 
 a sulphate (gypsum) that is not perfectly insoluble in water. It can be employed 
 either as marble, chalk, or caustic lime. The neutralisation is completed in the 
 boiling-pan while the sugar solution is still hot. For every kilo, of sulphuric acid 
 so much pulverised marble is required as the varying strength of the acid may demand. 
 After the addition of the marble powder, and when the effervescence has subsided, the 
 liquid must be tested with litmus-paper, or, better, with tincture of litmus ; if the 
 sugar solution be neutralised when at 41 Tw. density, the following evaporation will 
 concentrate even the smallest quantity of sulphuric acid which may have remained, 
 and render another neutralisation necessary. To ensure perfect neutralisation it is 
 useful to add an excess of barium carbonate in the proportion of 250 to 500 grammes 
 to every 10 kilos, of sulphuric acid. 
 
 c. Evaporating and Purifying the Sugar Solution. This part of the process is 
 accomplished first in a copper pan over a slow fire, or, better, by heating with steam. 
 The impurities separate and are absorbed in the scum, which is removed by means of 
 ladles. The evaporation is continued until the syrup marks 21 to 2 3 Tw., when it is passed 
 through a filter, generally of animal charcoal. It is then removed to a large reservoir, 
 and, if a granular sugar be desired, evaporated to 71 to 73 Tw. in flat pans, from which 
 it is taken to be placed in the crystallising vessels. These vessels are provided at the 
 bottom with twelve to twenty-four holes, into which wooden plugs are fitted, by re- 
 moving which, when the sugar has crystallised, the molasses are removed. The crystals 
 are dried, sifted, and either pressed into sugar-loaf forms or packed in casks. The 
 crystallisation is effected in eight to ten days. 
 
 The manufacture of grape sugar from wood and similar vegetable substances is only 
 of value in relation to the production of spirits, and recently as a bye-process of the 
 manufacture of paper from wood. 
 
 Composition of Starch Sugar. The composition of starch sugar as it occurs in 
 commerce is very varied. During inferior seasons the marketable starch sugar may 
 contain 50 per cent, sugar, 32*5 per cent, foreign substances, and 17-5 per cent, water. 
 G. Schwaendler found by the analysis of various samples of the year's (1870) sugar the 
 following percentages : 
 
 I. 2. 3- 4- 5- 
 
 Grape sugar . . 67*5 ... 64*0 ... 67*2 ... 75'8 ... 62*2 
 
 Dextrine . . . g~o ... 17-4 ... 9-1 ... 9-0 ... 8'8 
 
 Water . . . 19-5 ... 11-5 ... 20-0 ... 13-1 ... 24-6 
 
 Foreign substances . 4-0 ... 7-1 ... 37 ... 2*1 ... 4*4 
 
 lOO'O ... lOO'O ... lOO'O ... lOO'O ... lOO'O 
 
 Uses of Grape Sugar. The sugar prepared from starch, in addition to the sugar 
 yielded really by the grape, is largely employed in wine making and in the brewing of 
 beer. In the latter case the grape sugar is prepared by means of diastase. That its 
 use is extensive may be gathered from the fact that to 3 cwt. of malt i cwt. of potato 
 sugar is employed. It is also employed instead of honey in confectionery, for colour- 
 ing liquors and vinegars brown, in rum and cognac, beer and wines. In the latter 
 cases it is known as sucre-couleur, being then a grape sugar that has been re- 
 melted, sometimes with the addition of sodium carbonate or caustic soda to deepen the 
 colour. 
 
688 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 Grape sugar made from maize in America is used in the manufacture of spurious 
 honey.* 
 
 Steiner examined four kinds of starch sugar ; Wagner analysed a French crystal 
 syrup (V.) and a solid grape sugar (VI.) : 
 
 
 
 I. 
 
 H. 
 
 III. 
 
 IV. 
 
 V. 
 
 VI. 
 
 Water .... 
 Ash 
 
 1 5 '50 
 0*30 
 
 6-00 
 2-50 
 
 1 3 '30 
 0-40 
 
 7 -60 
 
 I -10 
 
 12-15 
 
 I5-I8 
 
 Dextrose . 
 Maltose . 
 Dextrine . 
 Carbohydrates 
 Proteines . 
 Acid = SO S 
 
 45 '40 
 28-00 
 9-30 
 1-50 
 traces 
 0-08 
 
 26-50 
 40-30 
 15-90 
 7-00 
 i -80 
 0-03 
 
 76-00 
 S'oo 
 
 5-30 
 
 O'2O 
 O-05 
 
 42-60 
 39-80 
 8-90 
 
 64 
 
 21 
 
 64-66 
 18-22 
 
 Sample I., from a German factory, is white and soft ; the other samples are from 
 English factories, No. II. being obtained by treating maize with sulphuric acid under 
 high pressure, and is tough like IV. ; III. is solid. 
 
 Neubauer examined in 1875 a number of German starch sugars, and found on an 
 
 average : 
 
 Fermentable sugar . . . . 61-08 
 
 Non -fermentable matter . . . 20-54 
 
 Ash, chiefly gypsum . . . 0*34 
 
 Water 18-04 
 
 Sieben, in 1884, found the following composition of syrupy starch sugar : 
 
 Dextrose 
 
 Maltose 
 
 Dextrine 
 
 Water 
 
 Ash 
 
 21-70 
 15-80 
 41-96 
 
 2O-IO 
 
 0-30 
 
 German starch sugars are generally obtained from potato starch. 
 The product obtained in the United States from maize starch treated with sul- 
 phuric acid (rarely oxalic acid) has the following composition : 
 
 Dextrose 
 
 Maltose 
 
 Dextrine 
 
 Water 
 
 Ash 
 
 Syrup. 
 
 34-30 to 42'8o 
 o-oo ,, 19-30 
 
 29-80 45-30 
 
 14-20 ,, 22'6O 
 
 0-32 ix>6 
 
 Solid Sugar. 
 72-00 to 73 -40 
 
 O.OO 3-60 
 
 4-20 9-10 
 14-00 17-60 
 
 o'34 0-75 
 
 Inverted sugar has been latterly used to some extent in the manufacture of cham- 
 pagne, in Gallicising wines, in confectionery, &c. It is obtained by inverting solutions 
 of cane sugar with carbon dioxide. It is a mixture (or a compound) of dextrose and 
 levulose. 
 
 Maltose. The sugar obtained by the reaction of extract of malt upon starch 
 paste forms a mass consisting of fine crystalline needles, soluble in water, of a faintly 
 sweetish taste, and convertible into dextrose by boiling with dilute sulphuric or hydro- 
 chloric acid. In a solution of neutral copper acetate, acidulated with acetic acid, 
 dextrose reduces red cuprous oxide on heating, whilst maltose does not. Maltose is 
 directly and completely fermentable without previous conversion into dextrose. 
 
 According to Schulze, 100 parts of anhydrous maltose have the same reductive 
 power as 66-67 parts dextrose. The air-dry substance contains 5 per cent, crystalline 
 water. Its composition corresponds to the formula C 12 H 22 O n .H 2 0. If dried at 10 
 
 * It would be well if the name grape sugar were reserved exclusively for the natural product, 
 and if the factitious varieties were known as starch sugar. [EDITOE.] 
 
SECT, vi.] SUGAR. 689 
 
 in a current of air, it has the same composition as cane sugar. According to Meissl, 
 the specific rotatory power of maltose becomes smaller with increasing concentration 
 and rising temperature, and, as seen by the sodium light, in a solution containing 
 P per cent, of anhydrous maltose at T, it may be expressed by 
 [a]D = i4'375 ~ 0-01837? - 0-095!. 
 
 The rotatory power of freshly prepared solutions is less by 15 or 20 per cent, than 
 that of such as have stood for some time. It melts below 100. Anhydrous dextrose 
 crystallises in the form of needles and columns, which melt at 146. 
 
 According to Soxhlet, for obtaining maltose 2 kilos, of potato starch are made into 
 paste with 9 litres water on the water-bath. After the paste has cooled down to 60 to 
 65, an infusion of 120 to 140 grammes of air-dried malt, prepared at 40, is stirred into 
 the paste, and is kept at that temperature for an hour. It is then heated to a boil, 
 and filtered whilst hot, and evaporated to a syrup in flat dishes. This syrup is then 
 repeatedly boiled by portions with alcohol at 90 per cent. After a portion has 
 thus been extracted once or twice, it is lixiviated with absolute alcohol. The 
 matter thus obtained is evaporated to a syrup, and let stand -in thin layers to 
 crystallise. 
 
 Dubrunfaut attempted to produce maltose for breweries, distilleries, &c., by sacchari- 
 fying maize, potatoes, &c., with extract of malt. The patent was sold for ^10,000, 
 but it has not proved successful in practice. 
 
 Cane Sugar (saccharose) is found in the sugar-cane, in maize, in the sap of several 
 species of maple and of the birch, in the beet, the carrot, in madder-root, in pumpkins, 
 melons, bananas, pineapples, and in several species of palm. 
 
 The Sugar-came. The sugar-cane, Saccharum qfficinarum, is a plant of the grass 
 tribe ; its stalk is round, knotted, and hollow, and the exterior of a greenish yellow 
 or blue, with sometimes violet streaks. It grows from 2-6 to 6-6 metres high, and from 
 4 to 6 centimetres in thickness ; the interior is cellular. The leaves grow to a length 
 of i'6 to 2 metres, and are ribbed. The plant is grown from seed, and also cultivated 
 from cuttings. 
 
 A hectare of land yields raw sugar : 
 
 By 15 Months' Cultivation. In i Year. 
 
 From Martinique . . . 2500 kilos. ... 2000 kilos. 
 
 Guadaloupe . . . 3000 ... 2400 
 
 Mauritius . . . 5000 ... 4000 
 
 Brazil .... 7500 ... 6000 
 
 Components of the Sugar-cane. The sugar-cane yields the largest amount of sugar, 
 generally 90 per cent, juice, containing, according to Peligot, 18 to 20 parts crystallised 
 sugar. The components of sugar-cane, according to the analyses of Peligot, Dupuy, and 
 leery, are as follows : Martinique (a) ; Guadaloupe (b) ; Mauritius (c). 
 
 () (&) () 
 
 P<ligot. Dupuy. leery. 
 
 Sugar . . . 18-0 ... 17 '8 . 20*0 
 
 Water . . . 72'! ... 72-0 ... 69-0 
 
 Cellulose ... 9-9 ... 9'8 ... io-o 
 
 Salts ... 0-4 ... 0-71-2 
 
 From 1 8 per cent, sugar found in the sugar-cane, as a rule not more than 8 per cent, 
 crystallised sugar can be realised. The loss may be accounted for thus : 90 per cent, 
 juice is expressed from the cane, from which only about 50 to 60 per cent, can be 
 clarified from the straw, &c. ; a fifth part is exhausted by refining ; and finally two-thirds 
 of the sugar is obtained by boiling, while the rest goes to the molasses. The 18 per 
 cent, sugar may be realised in the following manner : 
 
 2 X 
 
690 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT, vi. 
 
 In the refuse sometimes remains 
 By skimming .... 
 In the molasses 
 As raw sugar .... 
 
 6'o per cent. 
 
 6-5 
 18-0 
 
 Preparing the Raw Sugar from the Sugar-cane. The preparation of raw sugar 
 from the sugar-cane consists in first expressing, and then cleansing and boiling the 
 juice. 
 
 1. Expressing the Juice. The sugar-canes are crushed in a press consisting of three 
 hollow cast-iron rollers, a b c, Fig. 472, placed horizontally in a cast-iron frame. By 
 means of the screws, i i, the approximate distance of the rollers is adjusted. One 
 
 roller is half as large 
 
 Fig. 472. as the others, and 
 
 is moved by three 
 cogged wheels fitted 
 on to the axis of the 
 rollers. The sugar- 
 canes are transferred 
 from the slate gutter, 
 d d, to the rollers, 
 a c, which press them 
 a little, and from 
 thence they are car- 
 ried over the arched 
 plate, n, to the roll- 
 ers, c b. The pressed 
 sugar-canes fall over 
 the gutter, f, the 
 
 expressed juice collecting in g g, and running off through h. The middle roller is 
 termed the king roller ; the side cylinders are individually the side roller and macasse. 
 Latterly the diffusion-process has been introduced in the cane-sugar works, to the 
 great improvement of the yield.* 
 
 2. Refining and Boiling the Juice. The expressed juice is removed to the boiling 
 house, which is fitted with five iron or copper vessels. To 15,000 litres of expressed 
 juice 5 to 9 litres of milk of lime are added. The lime neutralises the malic and 
 other vegetable acids, and upon boiling forms, with the albumen and the other con- 
 stituents of the juice, a thick green scum, which being removed the juice is allowed 
 to remain in two of the pans to evaporate. A fresh scum is formed on the first pan, 
 which returns after a second or third time of removal. A juice as it issues from 
 the press is received into the first pan, in which, by slow boiling, it becomes a thick 
 froth, changing by rapid boiling to a clear colourless fluid ; in the third and fourth 
 pans the liquid becomes gradually purer, until in the fifth it crystallises. The finger 
 is dipped into the boiled juice to test its consistence, and by the length of the 
 pendant drop, which ought to be about 3 centimetres, the thickness is ascertained. 
 The boiled juice is placed in a large open wooden vessel of about 16 centimetres 
 capacity, and termed the cooler, where, after standing twenty-four hours, the sugar 
 crystallises, the cooler being provided with a double perforated bottom to allow the 
 molasses to escape, leaving the crystals behind. After standing five or six weeks, the 
 molasses dries into a mass commonly known as moist, raw, or Muscovado sugar. 
 The molasses passes into a cistern placed underneath the cooler, capable of con- 
 
 * If the further improvements devised by Prof. Galloway are introduced, the sugar-cane need 
 fear no competition in a fair market. 
 
SECT, vi.] SUGAR. 691 
 
 taining 15,000 to 20,000 litres of juice, and after standing fourteen days is ready for 
 the market. In the French and English colonies sugar is exported in chests covered 
 with fire-clay under the name of chest or tub sugar. 
 
 Varieties of Sugar. European commerce deals with the following kinds of raw 
 sugar : 
 
 1. West Indian Cuba, San Domingo or Haiti, Jamaica, Porto Rico, Martinique, 
 Guadaloupe, St. Oroix, St. Thomas, Havanna. 
 
 2. American Rio Janeiro, Bahia, Surinam, Pernambuco. 
 
 3. East Indian Java, Manilla, Bengal, Mauritius, Bourbon, Cochin China, Siam, 
 Canton. 
 
 Of late there has been a distinction between sugar cultivated by slave and that by 
 free labour : the latter comes from Jamaica, Barbadoes, Demerara, Antigua, Trinidad, 
 Dominica ; the former from Cuba, Havanna, Brazil, St. Croix, and Porto Rico. 
 
 The mode of manufacture varies according to the nature of the foreign substances 
 that always form part of the constituents of sugar, such as water, fibre, gluten, sand 
 or earth, soluble mineral salts, acetic and other acids, all of which must be destroyed 
 before the sugar can be refined. According to Renner we have in the following sugars 
 from : 
 
 Java. Havanna. Surinam. In Sugar Candy. 
 
 Kaw sugar . . 98*6 83*1 ... 97*0 87*3 ... 92*3 85-4 ... 99-6 
 
 Slime sugar . . 5-5 0*3 ... 37 0*9 ... 4*4 i'6 ... o'i 
 
 Water . . . 6'i 0*3 ... 3-5 0-9 ... 6-3 3-6 ... 0-2 
 
 Ash .... 2'i 0*2 ... i '4 O'O ... 2'o i '2 ... o'i 
 
 Molasses. The production of molasses is due to the long-continued heating of the 
 cane juice, but the quality varies according to the nature and culture of the sugar- 
 canes, the heat of the season, &c. By chemical treatment molasses appears as a con- 
 centrated watery solution of crystallised sugar, slime sugar, with a small admixture 
 of caramel and mineral salts. It is a dull red-brown sweet fluid used principally in the 
 colonies for the manufacture of rum ; it is soon converted to spirit, and then quickly 
 becomes acetated. Renner gives the constituents of molasses as : 
 
 Raw sugar ..... 32*97 436 
 
 Slime sugar .... 4*30 ... 7*38 
 
 Water ..... 1371 ... 16*25 
 
 Ash ...... 3-35 ... 378 
 
 Caramel, gum, &c. . . . 45 '65 ... 3 2 ' 22 
 
 Refining the Sugar. Sugar refining consists in 
 
 1. Dissolving and Refining. The raw sugar is dissolved in water, and during the 
 process of evaporation the apparatus is connected by a gutter to a reservoir, into which 
 the sugar flows. It is then submitted to a straining apparatus, which retains the 
 several impurities. The refined fluid is then heated in a copper pan, termed the 
 melting pan, the water adding 30 per cent, to the weight of the sugar, and is after- 
 wards placed in the refining pan, a vessel constructed with a double bottom. For the 
 purpose of clearing, a mixture of albumen is added in the shape of serum of blood, or 
 white of egg, with lime-water and sulphuric acid, an addition afterwards being made of 
 3 to 4 per cent, animal charcoal and \ to 2 per cent, blood, and the whole heated to 
 the boiling-point. The albumen coagulates and forms a fibrous scum, containing aU 
 the impurities. 
 
 2. Taylor's filtering apparatus is now much used for filtering the sugar, charcoal 
 being employed as the purifying agent. 
 
 3. The boiling of the clear sugar in pans placed over a vacuum apparatus resembles 
 
699 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 the previous boiling, with the exception that the fluid is rendered purer, 10 to 12 per 
 cent, water remaining. 
 
 4. Cooling and Crystallising. When the sugar begins to crystallise on the surface of 
 the vacuum pan, generally at 80, the temperature is lowered to about 50, as too great 
 heat at this stage of the process exercises an injurious effect upon the sugar, which now 
 forms an amorphous mass, and is drained, washed with clean syrup, and prepared for 
 ordinary loaf sugar. Sugar- candy is the result of slow crystallisation, the crystals by 
 this means acquiring a larger size and more regular form. 
 
 5. The shaping of the crystallised mass into the form of a sugar-loaf is accomplished 
 by evaporating the sugar and placing it in earthen conical moulds to solidify at a 
 temperature of 25 to 30. After standing ten minutes the sugar sets into form. 
 
 6. Drying the Sugar. After standing twelve hours a green-coloured syrup is 
 obtained from the crystalline mass, which is removed, and the crystals submitted to a 
 centrifugal process of drying, then placed in a drying-stove at a temperature of 25, 
 which is gradually increased to 50. By thus refining the raw sugar, the ordinary 
 loaf sugar is obtained. 
 
 Beet Sugar. Most of the sugar consumed on the European continent is obtained 
 from a species of beet. 
 
 Species of Beet. The vegetable known as beet-root is a lai'ge fleshy root of a plant 
 of the species Beta maritima, largely cultivated in France, Belgium, Germany, and 
 Portugal for the production of sugar. There are several varieties of the two species, 
 the white beet being preferred on account of its yielding more sugar, and also for its 
 purity of colour, the red beet being chiefly cultivated for culinary purposes. There 
 is also the field beet, commonly known as the mangold wurzel, which was first used 
 as provender for cattle about the end of the last century. The sugar beet has, in 
 course of cultivation, been improved by many new methods of manuring, &c., until it 
 yields 13 and sometimes 14 per cent, of sugar. In Germany the following varieties 
 of beets are principally cultivated : 
 
 i . Quedlinburg beet, a slender rose-coloured root, and very sweet ; it is matured 
 fourteen days before any other kind. 2. Silesian beet is pear-shaped, with bright 
 green ribbed leaves : it is known as the green-ribbed beet, and does not produce so 
 much sugar as the former. 3. Siberian beet is pear-shaped, with white-green ribbed 
 leaves, and is known as the white-ribbed beet. It does not yield so well as the 
 Silesian beet, although of a greater weight. 4. The French, or Belgian beet, 
 has small leaves and a slender and spiral root, yielding sugar. 5. The Imperial 
 beet is slender and pear-shaped, yielding much sugar. The king beet is a biennial : 
 in the first year the root is merely developed, in the second it bears seed. 
 
 The following is a list of the countries where the beet is cultivated for sugar : 
 
 In 
 
 According to 
 
 Beets 
 gathered 
 in ewts. 
 
 The Manufacture 
 of Suitable Beets 
 in cwts. 
 
 Into Sugar 
 in pounds. 
 
 
 Krause 
 Burger 
 Neumann 
 Liidersdorff 
 Thaer 
 Stolzel 
 
 Dumas 
 Boussingault 
 
 104145 
 169193 
 112145 
 146 
 1 80 
 I2Ol6o 
 
 /I93 
 (124 
 149 
 
 88123 
 143164 
 95123 
 I2 4 
 
 153 ^ 
 102136 
 
 168 
 105 
 127 
 
 770 1084 
 1256 1560 
 8361160 
 1088 
 1336 
 8961196 
 
 1476" 
 924 
 1116 
 
 
 
 Prussia 
 
 Baden 
 
 France : 
 Northern Departments) 
 Other } 
 France 
 
 In general 140 to 160 cwts. are cultivated, cut, and cleaned per acre, there being 
 4 Magdeburg acres to i hectare, which usually yield sufficient roots for three days' 
 work. 
 
SECT. VI.] 
 
 SUGAR. 
 
 11-3 
 0-8 
 
 i '5 
 OT 
 
 37 
 
 Chemical Constituents of the Beet. The flesh of the beet consists of a quantity of 
 small cells containing a clear, colourless fluid. The constituents of the sugar-beet, 
 according to chemical analyses, are 
 
 Water . . 827 
 
 Sugar . . . 
 
 Cellulose 
 
 Albumen, caseine, and other bodies 
 
 Fatty matter .... 
 
 Organic substances, citric acid, pectin and pectic 1 
 acid, asparagin, aspartic acid, and betain, a sub- 
 stance having, according to M. Scheibler, the 
 formula C 15 H 33 N 3 O (i 
 
 Organic salts, calcium, potassium, and sodium, oxal- 
 ate and pectate . . . . 
 
 Inorganic salts, potassium nitrate and sulphate, 
 calcium and magnesium phosphate . . . / 
 
 Near Magdeburg, where the beet is extensively cultivated, the general results 
 give 
 
 The greatest sugar production, as 13 '3 per cent. 
 That from inferior beets, as .9-2 ,, 
 The average beet yielding . .11*2 
 
 The components of the beet vary according to the time of the year; at some 
 periods it contains more water than at others, from 82 to 84 per cent, being the 
 average. In the autumn it does not contain slime sugar ; in February and March the 
 components intermingle, and some decrease nearly 2 per cent., as shown by the following 
 analyses : 
 
 October. 
 3 -49 per cent. 
 82-06 
 
 Woody fibre and pectin 
 
 Water . 
 
 Sugar . 
 
 Slime sugar . . *i<vj 
 
 Mineral salts . . - 
 
 Organic acid and extractives 
 
 o'oo 
 
 075 
 1-30 
 
 February. 
 
 2*52 per cent. 
 84*36 
 io'6o , 
 
 0-65 
 
 0-63 
 
 1-24 
 
 lOO'OO 
 
 \2\ cwts. of beet yield on an average i cwt. of raw sugar. 
 
 Saccharimetry. For obtaining an average sample a piece is either dug out or rasped 
 out from each root. The 
 rasping machine of Bothmer **B ! 473- 
 
 consists of a double case, A 
 (Figs. 473, 474, and 475), 
 screwed to a block and en- 
 closing the rasping disc, C. 
 The roof-shaped friction- 
 surfaces of this disc are 
 fitted with a rasp lift, and 
 their outer edge is toothed 
 like a saw. The disc fixed 
 on the axle, D, makes 1000 
 revolutions per minute, and 
 can turn either to the right 
 or to the left. The beets, JR, 
 are thrust through the 
 
 opening, E, by means of a wooden handle, H, shown in section in Fig. 474. It is 
 provided with four iron points, s, to hold fast the beets, which are then pressed against 
 
$94 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 Fig. 476. 
 
 the rasper, which cuts them up lengthwise and tears them to a pulp. This pulp falls 
 into a collecting-box, J, set below. The pulp thus obtained is covered with alcohol, 
 which is then filtered off, or it is lixiviated in an extraction apparatus. 
 
 Stockbridge recommends a lixiviation apparatus, the cylinder of which, A (Fig. 476), 
 is a glass tube somewhat contracted below, 32 centimetres long and 36 centimetres 
 wide. Through its lower aperture, closed with a caoutchouc stopper, there passes a 
 tube, B, ground off obliquely, 28 centimetres long and o'8 wide, connecting the ex- 
 traction cylinder with the flask, E, containing 250 c.c., and traversing its caoutchouc 
 plug. The annular space between the tube, B, and the cylinder, A, is intended to 
 
 receive the beet-pulp, and holds about 100 c.c. The 
 tube, B, has an aperture, a, just above the caoutchouc 
 plug, and round it at this point is wrapped a piece 
 of wire gauze, so that when there is liquid in the 
 pulp it can run off clear and without difficulty into the 
 flask. The upper end of the cylinder is closed with a 
 caoutchouc stopper, through which passes the pipe of the 
 reflux condenser, c. When the contents of the flask 
 are boiled, the vapours pass through the ascending 
 tube, B, into the cylinder, A, and the contents are heated 
 almost to the boiling-point of alcohol, whilst the alcohol 
 is partly liquefied, saturates the beet-paste, and returns 
 partly through the aperture, a, into the flask, E. The 
 alcoholic vapour condensed in A passes into the cooler, 
 C, where it is liquefied, and drops back into the ap- 
 paratus. In order to effect a sudden and complete 
 saturation of the beet-pulp, the apparatus, D and F, is 
 secured to the lower end of the cooling tube by means 
 of a caoutchouc stopper. This apparatus is a tube, 2 '5 
 centimetres wide and 7*5 centimetres long, closed below, 
 and having above two holes, ft, through which the vapours 
 arrive in the cooling tube. The -alcohol liquefied in the 
 cooler is thus not permitted to drop upon the contents 
 of the extractor, A, but it is compelled to collect in D. 
 Through the bottom of D there passes a tube, c, bent 
 above like a syphon nearly to the bottom of the vessel, 
 whereby, as soon as alcohol enough to cover the bend of 
 the tube has collected in the vessel, the syphon begins to 
 work, and all the alcohol which has collected is poured 
 upon the beet-pulp. Thus the entire surface is covered ; 
 the saccharine juice is rapidly displaced, and flows through 
 the wire-gauze and the hole in the inner tube into the 
 flask. This process repeats itself hourly, from twelve to 
 thirty times, according to the intensity of the heat. 
 
 For the determination of the sugar, about 80 grammes of beet-pulp are placed in 
 the extraction tube by means of the funnel, g ; about 140 c.c. of alcohol at 95 per cent. 
 are poured into the flask, the sand-bath is heated, and the pulp is satisfactorily lixiviated 
 in about an hour and a half. The flask, which contains the total sugar of the sample, is re- 
 moved from the extractor ; its contents are placed in a 200 c.c. flask, rinsed with alcohol, 
 and 5 per cent, basic lead acetate is added. The flask is now filled with 95 per cent, alcohol 
 up to the mark ; the liquid is filtered and polarised in the ordinary manner. 
 
 Extraction of Sugar from the Root. The preparation of sugar from the beet consists 
 in the following operations : 
 
SECT, vi.] SUGAR. 
 
 1. Washing and cleansing the beet. 
 
 2. Separating the juice from the root. 
 
 a. The root is ground to a pulp and subjected to hydraulic pressure. 
 
 ft. The juice is extracted from the pulp by means of a centrifugal machine. 
 
 y. According to Schiitzenbach, after maceration the juice is separated from 
 
 the pulp by water. 
 8. The root is cut into thin slices and placed in a vessel (diffusion apparatus). 
 
 with water at a certain temperature. 
 
 3. Refining the juice with lime, and removing the lime with carbonic acid. 
 
 4. Filtering the juice through charcoal. 
 
 5. Boiling the refined juice for crystallisation. 
 
 6. The manufacture of raw and refined sugar. 
 
 a. Raw or moist sugar. 
 /3. Refined or loaf sugar. 
 
 1. Washing and Cleansing the Beet. The beet when newly dug requires washing 
 and cleansing, which takes 10 and sometimes 20 per cent, from the weight of the root. 
 Champonnois's washing machine is, perhaps, the most successful. It consists of re- 
 volving drums of open iron- or wood -work, placed in a trough supplied with water, the 
 drums making 8 to 40 revolutions in a minute. The beets, cleansed from all impuri- 
 ties, and washed, are cut and submitted to elutriation on a sieve. From 1000 to 1 200 cwts. 
 beets can be prepared per day of twenty hours with 2 -horse power ; the length of the 
 washing-drum being from 3-1 to 4 metres with a diameter of i metre, the drum making 
 from 30 to 40 revolutions per minute. 
 
 2. Separating the Juice from the Root. There are two methods of effecting this : 
 the first by grinding the root to a pulp, and then removing the juice by 
 
 a. Pressing. 
 
 /3. Centrifugal force. 
 
 y. Maceration. 
 
 The sugar in the beet-root is contained in the cells, which are easily opened, but 
 require a moderate pressure to extract the juice containing the sugar. A hand- 
 grinding machine is sometimes found sufficient for this purpose; but Thierry's 
 crushing machine, shown in the following illustration (Fig. 477), is generally used. 
 
 Fig. 477. 
 
 The grinding cylinder (Fig. 478) is 0-5 to o - 6 metre in length, and o'8 to ro metre 
 in diameter, the periphery being set with 250 saw-blades, i (Fig. 477) is a funnel 
 to admit water ; i the trough into which the roots are placed ; m the cistern to 
 
6 9 6 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 receive the pulp. The motive power gears with a and s ; and the motion of the 
 axis of a is by means of the pinion, 6, communicated to the eccentric, d, and friction 
 
 roller, e, thence by the arm, g, and con- 
 Fig. 478. necting-rod, h, to the plunger, f, which 
 
 presses the roots against the edges of the 
 saw-blades concealed by the case, u, the 
 pressure being regulated by the weight, 
 k. The cylinder revolves 1000 to 1200 
 times a minute, reducing from 800 to 
 1000 cwts. of beets to pulp in twenty 
 hours. The water from t is necessary, 
 that the pulp may be ground to a finer 
 consistence. 
 
 The juice is obtained by pressing the 
 
 pulp by means of a stone or iron roller through a series of linen cloths. But in 
 the French manufactories the hydraulic or Bramah press is most generally adopted. 
 The pulp is placed in sacks or bags between iron plates, and subjected to a pressure of 
 500 to 600 Ibs. The expressed juice flows from the bed-plate into a pipe, which con- 
 ducts it to a receptacle. 100 cwts. of beet, with a pressed residue of 18 per cent., yield 
 82 per cent, good juice. 
 
 The production of juice from the pulp by pressure is effected either by the 
 hydraulic press, the roller press, or the filter press. But pressure, the centrifugal 
 process, and maceration have been almost entirely superseded in Germany by diffusion, 
 which is a modification of maceration depending upon dialysis. 
 
 The roots are cut up into slices of about i millimetre in thickness, and digested with 
 pure water at 50 in closed iron cylinders. The sugary juice passes through the walls 
 of the cells and mixes with the water, whilst water enters the cells, and certain non- 
 saccharine substances remain behind. Hence the sugary solution is tolerably pure. 
 
 The vessels used for diffusion are mostly upright iron cylinders, with flat or arched 
 bottoms, having a large opening, capable of being tightly closed, for receiving 
 
 Fig. 479. 
 
 the slices. A number of such diffusers connected together is called a battery. In 
 order to keep the contents at the required temperature of 50, there is in each 
 diffuser a copper worm lying at the bottom heated by steam. The vessels are con- 
 
SECT, vi.] SUGAR. 697 
 
 nected in such a manner by means of pipes that the same portion of liquid can be 
 driven through the entire battery. The driving power is the hydrostatic pressure of a 
 cistern placed 6 to 9 metres high. 
 
 A diffusion-battery, with 10 vessels and juice-heaters, is shown in ground plan, 
 
 Fig. 480. 
 
 Fig. 481. 
 
 Fig. 479; in longitudinal section, Fig. 480; and in cross section, Fig. 481. From 
 the bottom of each diffuser, / to X, passes the outflow pipe 5, and opens into the lower 
 part of the juice-heater, where it is divided into the seven heating-pipes. At the 
 head-end of each juice- 
 heater is a tube, bent at 
 right angles, the overflower, 
 a, Fig. 481, which connects 
 the juice-heater with the 
 next following diffuser. At 
 the bend the overflower has 
 a horizontal valve, /. The 
 form of the overflower ap- 
 pears from the ground plan, 
 Fig. 479. Its entrance into 
 the neck of the diffusers is 
 shown in Fig. 481. 
 
 The connection of the 
 opposite vessels, V and F7, 
 as well as X and 7, is 
 effected so that the juice- 
 heater is to the right of the 
 diffuser, V. The overflow 
 pipe branching off from this 
 is considerably prolonged, 
 and makes three bends at 
 
 right angles before it opens into the vessel VI. The valve, 7, of the overflower lies 
 exactly in front of diffuser VI. In the same manner X is connected with 7. The 
 juice-heater stands on the right of X ; the prolonged overflow pipe makes three 
 knee-shaped bends before it enters the neck of diffuser 7. The valve of the diffuser 
 
698 CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 lies straight before the neck of I. Close below the overflow-pipe is the water-pipe, 6, and 
 the pipe leading to the purifying pans, both in the same plane. To render both visible 
 in Fig. 480, the water-pipe is drawn as if broken away in some places. The water- 
 piping lies nearest the diffusers ; it begins at /, and arrives there from an elevated 
 cistern. It passes along the diffusers / to V, turns round, passes along VI to X, and 
 ends at diffuser X. The purifying pan-pipe begins near the juice-heater of vessel /, 
 passes from 7 to V, turns round, goes from VI to X, and is here prolonged to the 
 purifying pan by a piece not shown in the drawing. The water-main has in front of 
 every diffuser an upright valve, II, by means of which it is possible to establish or 
 interrupt the connection with each diffuser. To effect the connection, a short piece of 
 piping branches off from the main and passes into the limb of the knee-shaped over- 
 flower, which enters the diffusion vessel. 
 
 In a similar manner, the piping to the purifying pans is connected with each vessel, 
 but with the difference that, while these are connected with the lower part of the diffusers, 
 the water-main is connected with the upper part, as the movement of the juices has to 
 take place in such a manner that the water enters above and displaces the juice below, 
 causes it to pass through the next juice-heater, and passes it then either to the next 
 following vessel or to the purifying pan. 
 
 For carrying off the water from the slicings, there are used the two pipes, d (Fig. 
 479), at the front of the juice-heaters. One of these lies in front of / to V, beginning 
 at I and ending near V, in an open channel, d f . The second pipe begins near X and 
 ends near VI, in the same channel (Figs. 480 and 481). The pipes for the slicing 
 water are connected with the lower end of the juice-heaters by short pipes, which can 
 be closed tightly by the valves 4. The juice-heaters are heated by the steam which 
 enters their jackets from above at 7. 
 
 The upper man-holes of the diffusers are easily accessible from the platform, e, which 
 runs along both series ; a second, supported by the cross-beams, f, is between the two 
 series of diffusers rather lower than e, so as to give access to the valves i, 2, 3. A 
 third, g, is fixed below the valves 4. From here the exhausted slicings are removed 
 by a mechanical arrangement. For this purpose there is in the middle a sunk channel, 
 h, at the bottom of which an endless web moves in the direction of the arrows. It is 
 wrapped round the tension rollers, i i', of which i is put in motion by a driving band 
 at the side. The slicings drawn out of the man-holes fall at first upon the platform, g, 
 and are swept into the channel, h, where they are carried along by the endless web, 
 and on arriving at the roller, i, they fall upon a movement, I, in order to be taken up 
 by the little boxes, n, and conveyed further. 
 
 Diffusion apparatus in which the slicings are carried along continuously to meet the 
 water or the juice have not yet met with approval. 
 
 The advantages of the diffusion process are : (i) The production of a purer juice, 
 more easily worked ; (2) a better cattle food ; (3) diffusion allows of a more complete 
 extraction of the sugar than any other method ; (4) considerable economy of mechani- 
 cal power; (5) the press-cloths are dispensed with ; (6) labour is economised ; (7) the 
 juice is more concentrated ; (8) the cost of the installation is much reduced. 
 
 Composition and Treatment of the Juice. The juice, after being expressed from the 
 pulp, if allowed to remain exposed to the action of the air, throws down a dark flaky 
 precipitate. The more free acids the juice contains the lighter will be the colour of the 
 precipitate, and the juice will appear of a brown-red. The juice is not only a solution 
 of sugar, but contains the soluble constituents of the beet, in which nitrogenous and 
 mineral substances are very prominent. Sugar under fermentation forms lactic acid 
 and other products ; but it is separated from all the impurities and refined into 
 crystals. The usual method of refining is to boil the juice rapidly in copper refining 
 vessels constructed with double bottoms. The rapid boiling separates the coagulated 
 
SECT. VI,] 
 
 SUGAR. 
 
 699 
 
 juice, whilst the free acid is neutralised by the introduction of dilute milk of lime. 
 The lime also serves to separate the nitrogenous substances of the juice, and enters 
 into a combination with a small portion of the sugar, forming a sugar-lime or 
 calcium saccharate. Lime, too, throws down from their salts iron protoxide and 
 magnesia, while potash and soda are set free. The quantity of lime added depends 
 upon the condition of the root. As a rule, to 100 Ibs. of juice i to 2 Ibs. of lime are 
 added, or to 2 cwts. of roots i Ib. of lime. The insoluble combinations of lime are sepa- 
 rated from the juice as a slime by filtering in a filtering-press. 
 
 3. De-liming or Saturating the Juice with Carbonic Acid. The clear juice is by no 
 means a pure sugar solution, but contains besides free sugar, sugar-lime, free potash, 
 and soda, sometimes ammonia, and a small quantity of nitrogenous organic substances, 
 decomposed by the free alkalies, ammonia being largely developed by their evapora- 
 tion. The juice also contains various organic acids (as aspartic acid) and alkaline salts 
 (as potassium sulphate and nitrate). The decomposition of the sugar-lime effects the 
 removal of the extraneous substances from the juice. The physical method of puri- 
 fying the juice is by filtering it through animal charcoal, while the chemical method 
 is effected by means of carbonic acid. The use of carbonic acid was first recom- 
 mended by Barruel, of Paris, in 1811, and later by Kuhlmann, Schatten, and 
 Michaelis. The latter obtained the gas from the action of sulphuric acid upon chalk, 
 or, better, upon magnesite ; the former employed the gas resulting from the combus- 
 tion of charcoal or coke. Lately, Ozouf has prepared carbonic gas by heating sodium 
 bi-carbonate. In the German manufactories the decomposition of the sugar-lime 
 is effected in a Kleeberger's pan (Fig. 482). This apparatus consists of a cast-iron 
 cistern, B t to contain the juice. The carbonic acid, having been washed in pure 
 
 Fig. 482. 
 
 Fig. 483. 
 
 water, is admitted by the pipe, m, which dips nearly to the bottom of the vessel, B, 
 and is divided internally by a partition for the better dissemination of the gas. The 
 unabsorbed gas collects in B over the juice, whence it passes through the opening, p, 
 into the upper chamber, A. When the juice sinks through p into B, the^gas there 
 collected passes through A into w, and is thence re-conducted to the reservoir. When 
 the juice is sufficiently cleared, the carbonic acid cock, o, is turned off, and the juice 
 allowed to flow into a reservoir through q, where the carbonate of lime settles. The 
 clear juice is then fit for crystallisation. The man-hole, e, is provided for the cleansing 
 of the apparatus from separated calcium carbonate. The juice to be de-limed is supplied 
 to the cistern, B, by means of the pipe, s, and the gutter, t. 
 
 Other Methods of De-liming the Juice. Instead of employing carbonic acid or 
 animal charcoal, the lime of the sugar-lime may be removed by the addition of a sub- 
 stance or an acid, which forms with it an insoluble body, but does not affect the sugar. 
 
700 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT, vi 
 
 Oxalic acid is suitable for this purpose, calcium oxalate being insoluble in the sugar 
 solution, but the acid is very expensive, and, besides, the precipitate is too fine, passing 
 through the filter. Phosphoric acid is used for the purpose, calcium phosphate separat- 
 ing into flakes, which can be easily removed by filtering through a thin layer of char- 
 coal. Any free phosphoric acid is converted into ammonium phosphate, neutralising 
 the alkali, while the excess of ammonia is volatilised on the application of heat to 
 the juice. Oleic, stearic, and hydrated silicic acids, and casein, similarly throw down 
 precipitates. Acar uses pectic acid, which forms with the lime an insoluble pectate. 
 Morgenstern has found a magnesium sulphate prepared from the Stassfurt kieserite 
 successful in removing part of the impurities as well as a portion of the colouring 
 matter. Frickenhaus tried hydrofluoric acid. In 1811, Proust recommended calcium 
 sulphite ; and in 1829 Dubrunfaut took out a patent for the employment of sulphur- 
 ous acid. Melsens, of Brussels, in 1849, employed hyposulphurous acid, which at 
 100 separates the lime and most of the protein substances, and disguises for a time 
 the colouring matter; the colour, however, returns on exposure to air, and remains 
 permanent. 
 
 Purifying with Baryta. About fifteen years ago, Dubrunfaut and De Massy 
 patented a method of purifying the juice by means of caustic baryta, which forms with 
 cane sugar at the boiling-point the insoluble saccharate, C 12 H 22 O n .BaO ; in practice, 
 sufficient caustic baryta is added to throw down all the sugar. The sugar-baryta is 
 thus separated from the supernatant fluid, in which all the foreign substances remain 
 suspended ; and is next treated with carbonic acid to form barium carbonate and set 
 the sugar free. The solution is then filtered and some gypsum added, which gives rise 
 to the double decomposition of the barium carbonate into sulphate, and of the gypsum 
 into calcium carbonate. 
 
 The purification of the juices by means of electricity does not seem to have a 
 future. 
 
 Filtration through Animal Charcoal. The purpose of filtration is to remove a part of 
 the non-saccharine constituents of the juice. Bone-black was first introduced into the 
 
 beet-sugar manufacture by Derosne in 
 1812. Subsequently, Schatten ob- 
 served that it removed, not merely 
 colouring matters, but lime and salts 
 
 Dumont's filter. Pajot des 
 Charmes employed animal charcoal in 
 1822, but Dumont was perhaps the 
 first to make its use successful by 
 means of a filter still bearing his name, 
 shown in vertical section in Fig. 484 
 and in plan in Fig. 485. The juice is 
 supplied to the filter, .4, from the cistern, 
 D, the supply being regulated by the 
 ball-cock, d e. The pieces of charcoal 
 in A rest upon the sieve, b b, the per- 
 colating juice being received into the 
 cistern, and removed by the tap, o. 
 C is a man-hole for the cleansing of the 
 apparatus. 
 
 Instead of this filter there have 
 been lately used sheet-iron cylinders, 
 
 5 or 6 metres in height, filled with granulated bone-black. When its purifying power 
 is exhausted it is lixiviated with pure water, so as to recover the sugar. 
 
 Fig. 484. 
 
SECT. VI.] 
 
 SUGAR 
 
 701 
 
 To revivify spent charcoal it is covered with warm water and allowed to ferment, 
 washed, and ignited with exclusion of air. 
 
 In Fichet's furnace the gas-fire, with the coal-shaft, a (Figs. 485 and 486), and 
 
 Fig. 485. 
 
 Fig. 486. 
 
 grating, b, is supplied with fuel from above. The gene- 
 rator gases pass through the channel d into the channel 
 E, with numerous burner slits in its top, which can be 
 enlarged or contracted by means of a common slide; 
 the slide is formed of a plate of fire-stone, the position 
 of which regulates the access of the combustion gases 
 in the entire length of the channel E. When this has 
 been once arranged there is nothing more to be done 
 
 but to keep up the same heat. The air serving for combustion enters at G, but is pre- 
 viously warmed at the tubes, J, which are surrounded for this purpose with an 
 iron screen, S. It effects the greatest development of heat at F ; therefore here small 
 especial protective walls are constructed for the lateral ignition spaces. The fire gases 
 do not pass in a straight current to the chimney, but the draughts are so arranged that 
 the action upon the charcoal takes place in several distinct spaces, called zones. The 
 charcoal passes through the grating, R, then through the drying zone, D, then through the 
 preparatory zone, JS, then through the ignition zone, A, and lastly through the cooling 
 zone, (7. The combustion gases go upwards in the middle and give off their heat laterally 
 to the walls or screen of the ignition-room, are then turned downwards by the cover, Q, 
 and pass, as shown by the arrows, up again through K and H, and through the 
 internal ignition spaces formed of inverted funnels placed one over the other, carry with 
 them the ignition products issuing from the intervals of the funnels, and pass then down- 
 wards to the space J3, where they give a preliminary warming to the charcoal intended 
 for ultimate ignition, and escape finally by the chimney, 0. It is easily seen that the 
 combustion gases, on their arrival in the zone, B, have already given off a great part of 
 their heat, and that the temperature in B will be lower than in A , so that the heat is well 
 
702 CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 utilised and the coal is heated by degrees. Above B is the drying zone, D, which forms 
 the upper part of the column, and where the charcoal is kept loose by the inverted chan- 
 nels by which it is traversed, whilst the air which rises through S and M and is heated 
 to 60 to 70, passes through these hollow spaces, D, and dries the charcoal. This is then 
 piled up upon the grate, R, in heaps of 2 metres and upwards in height, and falls 
 slowly into the space beneath as it is drawn away below. The ignition columns are 
 formed of funnels placed upon each other and held in their places by supports and 
 bolts. The charcoal is now between the slanting sides of these funnels and the wall, H, 
 and forms around each a free inclined plane, whilst it is heated in a thin layer from 
 within and without, and gives off on its surface its gases to the passing fire gases. As 
 often as charcoal is drawn away below, it falls downwards in the entire column, 
 when the grains roll over each other, renewing the free surface and promoting the 
 escape of gases. The cooling tubes, J, have ribbed or undulated surfaces, which pro- 
 mote the escape of heat to the air passing upwards. The hot air passes partly through 
 G to the burner, partly ascends through M, effects the desiccation in D, and escapes 
 through a pipe which surrounds the chimney, 0, so that its heat serves to increase the 
 draught. Suitable slides allow of a right distribution of the ascending current. The 
 removal of the charcoal below is effected by a box, holding about 13 litres and closed 
 by slides moved by levers. Each movement of the levers delivers 13 litres of charcoal 
 into the truck below and fills the box for the next delivery. The workman has merely 
 every twenty minutes to pull the levers at each column and to push away the truck which 
 receives the carbon from three or four columns. As the heating seldom requires addi- 
 tional fuel, the manual labour is reduced to a very small quantity, and the correct igni- 
 tion, which is regulated by the burner-register, is quite independent of the workman. 
 The right temperature cannot be exceeded, and a delay in emptying has no bad con- 
 sequences, since then the charcoal merely remains rather longer at a dull red heat, 
 which occasions no injury. If two or three lots are withdrawn rapidly in succession it 
 is of no consequence. If the work is partly at a stand the register in the two flues 
 at E is closed to one-tenth, so that the heat in the furnace is kept up without any 
 important consumption of fuel. 
 
 Sulphurous acid is often used for saturation, in order to be able to substitute filter- 
 presses or gravel filters for the more expensive animal charcoal filters. Possibly animal 
 charcoal may be ultimately dispensed with in obtaining raw sugars. 
 
 From the thin juice the water is withdrawn after filtration by two processes, known 
 as evaporation and boiling down. The work differs according to the intended product, 
 and is in this respect divided into three kinds 
 
 (1) Haw sugar work ; 
 
 (2) Refinery work, which is the yield of a refined product from the raw sugar ; 
 
 (3) Melis work, which is a combination of (i) and (2), and aims at yielding a sugar 
 fit for consumption directly from beet- juice. 
 
 Evaporation Pans. The pans generally in use for evaporating the juice to crystallisa- 
 tion are made sufficiently strong to withstand high steam and atmospheric pressure. 
 The processes of evaporation are 
 
 I. Under the usual air-pressure : 
 
 a. In pans suspended over an open fire ; 
 
 b. With high steam pressure ; 
 
 c. By hot air. 
 
 II. By diminished air-pressure or vacuum pans, the vacuum being produced : 
 
 a. By the air-pump ; 
 
 b. On the principle of the Torricelli vacuum ; 
 
 c. By means of steam and condensation ; 
 
 d. By combining the methods a and b. 
 
CECT. Vi.j 
 
 SUGAR. 
 
 703 
 
 The pans are constructed to prevent the boiling over of the juice. One of the bad 
 effects of an open fire is the danger of over-heating, or burning as it is called, which 
 deteriorates the quality of the sugar solution in various ways, forming caramel. 
 
 Evaporation in open pans has been entirely abandoned in Germany. The evapora- 
 tion apparatus devised by Robert and Tischbein has introduced a new principle into the 
 chemical arts, which comes widely into play where evaporation is necessary. The 
 steam occasioned by evaporation in the first pan was led into a second, where it also 
 raised the temperature. This was called the " double effect " system, or, where three 
 vessels were used in connection, the " triple effect." 
 
 Vacuum Pans. An improved evaporation apparatus was invented by Howard, in 
 1812, in which the juice was placed in chambers of rarefied air, or vacuum pans. 
 The lowest boiling point of the clear juice in the vacuum pans is 46'! C. ; the usual 
 
 Fig. 487. 
 
 temperature at which the sugar is boiled is 65-5 to 71-1 C. ; at a higher temperature 
 the juice loses its power of crystallisation, and forms caramel. The vacuum may be 
 considered as two distinct apparatus: (i) The boiling pan; (2) the apparatus for 
 exhausting the air and condensing the steam from the juice. 
 
 In France, Derosne's apparatus is extensively used; but that which we shall 
 describe meets with general approval in Germany, and has the advantages of being 
 simpler in construction and less costly to work. Fig. 487 is a perspective view, and 
 Fig. 488 a section of this form of evaporating pan. The boiling pan, , consists of 
 two air-tight hemispheres, surrounded by a funnel connected by the tube, I, with the 
 cendenser, A. The apparatus is supplied with steam by r s, the steam circulating in 
 the boiling pan by means of the pipes, g (Fig. 488). By opening the lever valves,/, 
 
74 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. TI. 
 
 the juice can be run by means of the pipe, o, into the pan, p. When the pan, after 
 continued boiling, requires to be re-filled, the pipes, I and w, are connected to an air- 
 pump. The manometer, h, shows the state of the air-pressure, which can be regulated 
 by opening the pipes connected to the vacuum chamber. By means of the gauge- 
 cylinder, G, the quantity of syrup in the boiling pan can be ascertained, the gauge- 
 cylinder being connected to the boiling pan by the pipes, a and i, and the height 
 read off from the gauge-tube, n. For the purpose of ascertaining its consistency, 
 the syrup can be removed from the gauge-cylinder by means of either of the three 
 pipes, bed. By u steam can be admitted to the boiling pan and condenser, e is 
 generally of stout glass, through which the state of the juice can be observed, g is 
 the grease-cock, butter or Sostman's parafiine being generally used to prevent the 
 adhesion of the scum to the working parts of the pan, the taps, &c. f is the man-hole. 
 The condenser consists of the jacket, B, arranged to prevent the mixing of the juice 
 with the water used for condensation, x is the gauge. The pipe, m, conveying water 
 to the condenser, terminates in a rose, z is a thermometer, showing the interior 
 temperature of the boiling pan. 
 
 Fig. 488. 
 
 The air-pump being set in operation, the tube, c, is opened, and the gauge-cylinder 
 filled by the juice rising from q. By closing m and opening z, the juice is admitted 
 to the boiling pan. When this is half full, the steam pipe, s, is opened, the steam 
 quickly heating the contents of the pan to the boiling-point. The condenser is then 
 placed in working ; by opening the pipe I, the steam of the juice passes into the con- 
 denser, where it is speedily condensed, passing with the water through /3. Trappe's 
 arrangement is sometimes found useful in working the Torricelli vacuum. The con- 
 denser is 10*6 to ii metres above the pan ; from it reaches a pipe to a water reservoir 
 beneath, the height of the water in this pipe indicating the degree of rarefaction in 
 the pan. 
 
 The construction of vacuum apparatus has been lately much improved. 
 
 In the apparatus of Wellner and Jelinek, with horizontal heating pipes, the bottom 
 (Figs. 489 and 490) is formed by two sides converging obliquely. In order to open 
 and shut the evacuation valves, c, at pleasure, they should be connected with the 
 arrangement shown in the drawing. This consists of an angle-lever, f } turning on the 
 bolt, f y With one of its arms, f v the valve, c, is connected in such a manner that 
 
SECT. 
 
 VI.] 
 
 SUGAR. 
 
 705 
 
 it can turn on d, whilst the second arm,y" 2 , leans against the lower end of a projection 
 of the sledge, g. The sledge slides in a smaller tail-shaped groove, h, of the guiding- 
 piece, i, and can be raised or lowered by turning the screw, j. If the screw is raised 
 the valve opens in consequence of its weight and the pressure of the liquid, so that the 
 contents can flow out. By screwing down g, the lever, f, is turned, and the valve is 
 shut. The figure represents for every valve, c, a special screw, j, with its accompany- 
 ing sliding-piece, g. 
 But the arrangement 
 can be so made that, 
 instead of the bolt, 
 f 3 , a shaft is intro- 
 duced, having as 
 many arms, f v as 
 there are valves, and 
 which can be turned 
 by a single arm, / 2 . 
 The heating steam 
 circulates from the 
 boxes, k, through the 
 vertical tubes, I. 
 There is also a longi- 
 tudinal channel in 
 the bottom, capable 
 of being heated. As 
 a sign of the sufficient 
 concentration of the 
 boiled juice several 
 tests are in use. The 
 determination of the specific 
 gravity is not decisive. We 
 may say in general that the 
 boiling down may be carried 
 from 7 2 to 76 Tw. (taken hot). 
 Among the empirical tests 
 may be mentioned the thread 
 test. A drop of the liquid is 
 taken up between the thumb 
 and the forefinger, and the 
 concentration is judged by 
 the length to which a thread 
 can be drawn out and the 
 manner in which it breaks. 
 If the juice is not sufficiently 
 boiled the thread soon breaks. 
 On further evaporation, it can 
 be drawn out as far as the 
 separation of the fingers will 
 allow. If the thread tears 
 
 about mid-length, and the upper part contracts into the shape of a hook, it is 
 considered that the concentration is sufficient. This is the " hook test." The 
 " blow test " consists in taking a little of the boiling liquid in a flat scum-spoon, 
 and blowing against it, when bubbles are formed on the far side, the size and irides- 
 
 2 Y 
 
 Fig. 490. 
 
706 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 cence of which show what degree of concentration has been reached. In inferior 
 liquids, crystallisation takes place, not in the cooler, but in the vacuum-pan. 
 
 If the liquid is boiled " blank," it is a hot saturated solution of saccharose. If 
 boiled " to crystal," it is a mixture of crystals of saccharose with the saturated solution. 
 There are, besides, the same non-saccharose matters as in the thick juice. The water 
 ranges from 6 to 14 per cent., and the sugar from 68 to 90. The mass may then be 
 treated either for raw sugar or for consumption sugar (so called). 
 
 If the mass has been boiled blank, the crystallisation must be managed so as to 
 give the largest yield of well-developed crystals. Coarse crystals can be more rapidly 
 and thoroughly freed from treacle than the smaller crystals, and give the product a 
 better appearance. The more concentrated the solution, and the more rapidly it has 
 been cooled, the smaller are the crystals. In order that the crystallisation may pro- 
 ceed slowly, the room where the crystallisers are set (the filling-room) is heated to 
 3o-35. The crystallisers hold from i to 20 hectolitres. Beneath the spout through 
 which the mass passes from the vacuum -to the filling -room there is a flat dish, the so- 
 called cooler, in which it is allowed to remain until it has grown tough from the forma- 
 tion of crystals. It is then poured into the crystallising vessels or forms. 
 
 If the mass has been boiled "to crystal," the mass is filled direct from the vacuum 
 into the forms at a temperature of 5O-6o. 
 
 When the crystallisation is finished, the next step is to separate the crystals (first 
 product) from the syrup. This is generally effected in a centrifugal. The most im- 
 portant part of the instrument is a drum, open above (a, Fig. 491), of a fine metallic 
 
 tissue, strengthened externally by iron bands. 
 It is made to revolve in a cast-iron frame, b, 
 at a speed of 1000 to 1500 rotations per minute. 
 To this end the iron axle, e, contains at its upper 
 end a conical friction wheel, c, covered with 
 leather, and turned by another conical wheel, d. 
 The inner part of the drum is contracted by a 
 sheet-iron cone, g, by which the sugar to be 
 dried is brought more to the margin of the 
 drum, and room is obtained for three heavy 
 pieces, which serve to maintain the equilibrium 
 of the drum in its rapid rotation. According 
 to the nature of the mass, from 30 to 50 kilos. 
 are put into the centrifugal ; the mass rises up 
 on the sides, and the syrup issues through the 
 meshes of the wire gauze, whilst dry sugar 
 remains behind. 
 
 The syrup remaining from the coarse sugar 
 is boiled in the vacuum pan, and worked up 
 to a filling mass, from which a second product 
 
 and a syrup from the second product are obtained. The latter, on repeated boiling, yields 
 a third product, and the syrup of the latter again yields a fourth product, and, as a final 
 residue, treacle. The second product is mostly sold mixed with the first. The third 
 and fourth are thrown into the thick juice to improve its quality. 
 
 Consumption Sugar. Raw sugar from the beet, known as consumption sugar, is 
 distinguished from that of the caiie by containing substances of a disagreeable smell and 
 taste.* 
 
 * It must be remarked that even the most carefully refined beet sugars possess a remnant of 
 this taste, which can be detected by experienced sugar buyers, and much more readily by bees, 
 which reject beet sugar if cane sugar is at hand. It may be added that raw beet sugar is some- 
 
vi.] SUGAR. 707 
 
 "Consumption sugar" is met with in commerce in three forms (i) As crystal 
 sugar (something like the form in which cane sugar was produced by Finzel's process) ; 
 (2) as juice-melis (with its modifications, cube sugar and pile) ; and (3) as farin. The 
 iirst kind consists of distinct, isolated crystals ; melis is a heap of agglomerated crystals, 
 which either takes the form of the crystallising vessels, or is broken into lumps or into 
 fragments as pile ; farin is sugar ground to a fine meal, the crystalline appearance being 
 intentionally destroyed. 
 
 For the production of crystal sugar the clear liquor is boiled slowly and continu- 
 ously in the vacuum pans, with a reduction of temperature towards the end, so as to 
 produce distinct crystals. The contents of the vacuum pan are washed into the centri- 
 fugal with syrup. Some of the syrup adheres to the crystals after whizzing, and has 
 to be removed by washing the crystals, the so-called " covering." 
 
 " Covering" is resorted to in obtaining all the finer sorts of raw sugar, and is either 
 water covering, syrup covering, steam covering, or steam-vapour covering. Water cover- 
 ing is effected by spirting water into the revolving drum, which dilutes and washes away 
 the syrup, but involves a considerable loss of sugar, and has therefore been mostly given 
 up. Washing the crystals with a clear, saturated solution of sugar is in very general use, 
 both in the centrifugal and in the moulds. The liquid thrown out is added to the thick 
 juice. Steam washing is effected by admitting steam at a low tension, which condenses 
 to drops, and acts in the same manner as water. The steam-vapour covering consists in 
 admitting into the drum a mixture of steam and air cooled down to 50. 
 
 Melis is the commonest kind of consumption sugar, and is obtained either directly 
 from the juice or by adding sugar to the concentrated syrup. The quality of the melis 
 depends upon the proportion and the purity of the sugar thrown in. If much is added, 
 and if sufficient animal charcoal is used, it cannot be sharply distinguished from refined 
 sugar. As it retains a slight yellowish tone, it is got up with ultramarine, which 
 masks the natural tone and gives the product a bluish-white reflection. 
 
 The forms or moulds hold from 1 5 to 1 7 kilos, of filling weight, and yield loaves of from 
 10 to 12 kilos, in weight. These moulds are of sheet-iron, lined with enamel. The point 
 after filling is turned downwards, and a tube is attached, through which the syrup runs off. 
 Melis is sold as cube sugar and as pile. To produce the former the mass is run 
 into plates and converted into cakes of equal size. Pile is a coarse melis, produced in 
 Austria for the Italian market. 
 
 Farin is a ground consumption sugar, made up of products which would be 
 unsaleable in their original form. 
 
 Sugar-candy. The large, hard crystals formed during the various stages of sugar 
 manufacture are known as sugar-candy. The commercial article is generally obtained 
 from cane sugar, the crystals of beet-root sugar being too long and flat. The amount 
 of sugar-candy made from beet sugar does not exceed 20 per cent, of the entire produc- 
 tion. The sugar selected for candy is mixed with 3 to 4 per cent, of animal charcoal, 
 then cleared with white of egg, and filtered. It is next boiled in a copper or 
 enamelled-iron pan over an open fire, whence it is conveyed to a crystallising vessel, 
 the sides of which are perforated with a series of holes, in eight or ten concentric rings, 
 the distance between each hole laterally being less than that between each ring. 
 Through these holes the candy crystallises, the size of the holes being adjusted 
 to the consistency of the boiled sugar by means of a paste made of fine clay, 
 ashes, and ox blood. The temperature of the drying-room is maintained at 75 for six 
 days, when it is reduced to 45 or 50, and in eight to ten days the crystallisation is 
 complete. During the crystallisation the candy must not be moved or shaken, or the 
 
 times coloured with a coal-tar yellow dye, and is then exported to England for sale as " Demerara." 
 This is done with the double purpose of obtaining an illicit profit, and of injuring the reputation of 
 cane sugars. [EDITOR.] 
 
708 CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 air allowed to affect it. Upon the completion of the crystallisation, the candy is found 
 covered with a mixture of syrup and small crystals ; these are removed by filling the 
 crystallising vessels with weak lime-water. The rinsing water must be lukewarm, as 
 cold water cracks the crystals, and hot water makes them blind, as it is technically 
 termed. The crystallising vessel, when emptied of the rinsing water, is soaked to remove 
 all saccharine matter, and, if this be not effected with hot water, a smooth stone is used 
 to knock away the adhering crystals. After standing a day to dry, the sugar-candy is 
 ready for the market. It is commercially known as of three kinds the finest, re- 
 fined white, has a large colourless crystal ; yellow candy, a straw-coloured crystal ; and 
 brown candy is similar in colour to ordinary moist sugar. In some parts of France a 
 dark candy is manufactured under the name of Sucre de Boerhave. Inferior cane 
 sugar is employed for the brown, boiled sugar for the yellow, and refined sugar for 
 the white candy. Sugar-candy is extensively used, the white principally in preparing 
 " liqueur," a solution of candy in wine or cognac ; also in the champagne manufacture, 
 and in all cases where a clear sweetening solution is required in large quantities. The 
 yellow candy is used for sweetening tea and coffee in restaurants, and enters largely 
 into the recipes of the pharmaceutist for affections of the throat and chest, as well as 
 for making syrups intended as vehicles for nauseous medicines. 
 
 Beet Treacle. The last residual syrup contains on an average in 100 parts 
 
 Sugar . - v "'. 50 
 Non-sugar . . 30 
 
 Water . . ,.- 20 
 
 Of the 30 parts which are not sugar, 10 parts consist of mineral matter, chiefly 
 potassium salts (always including nitrate) ; the remaining 20 parts comprise oxalic 
 acid and betain combined with inorganic bases, nitrogenous matter, derivatives and 
 decomposition products of albumen, protoplasm, cellular tissue, &c. In consequence 
 of the offensive taste and smell of beet treacle it is rarely admissible as an article of 
 human consumption. 
 
 In making up this treacle, the chief processes are the osmose, the treatment with 
 lime and spirit, or water, and the strontia process. 
 
 The osmose process depends on diffusion through parchment-paper, and is of 
 importance, as the treacle contains a number of constituents which differ greatly in 
 diffusive power. The saline matters diffuse very rapidly, the saccharose more slowly, 
 and the other matters with great difficulty or not at all. But the difference in the 
 rate of diffusion is not sufficient for a direct method of separation. At the commence- 
 ment of the process large quantities of the salts pass through the parchment-paper and 
 little saccharose. Afterwards the proportions are inverted. The osmotic process is 
 therefore interrupted when a part of the salt has been removed, so that a part of the 
 saccharose crystallises out on evaporation, and the treacle whizzed out from the sugar 
 crystals has nearly the same composition as ordinary treacle. This second treacle 
 is again freed from salts osmotically, until there finally remains a treacle so con- 
 taminated with colloid matters as not to admit of further treatment. The yellowish- 
 brown osmotic water contains all the diffused bodies, salts, and varying quantities of 
 sugar. It is used in irrigating meadows (for which the presence of sugar renders 
 it questionably suitable). The process requires little initial outlay. One quire of 
 parchment-paper serves for 540 kilos, of syrup. 
 
 Elution. This process, devised by Scheibler in 1865, depends on the formation of 
 a tribasic calcium saccharate and its lixiviation with alcohol at 30 per cent., in which 
 the chief part of the non-sugar dissolves, whilst a fairly pure saccharate remains. The 
 difficulty of obtaining a dry compound of treacle and lime was overcome by Seyferth, 
 who takes a concentrated treacle at 80 Tw. and mixes it with freshly burnt 
 lime in fine powder. One mol. of saccharose in the treacle requires 3 to 4 mols. 
 
SECT, vi.] SUGAR. 709 
 
 quicklime. The lime treacle, after lixiviation with alcohol, is freed from alcohol by 
 means of steam, and then converted into a sugary milk of lime, which is pumped into 
 large cisterns and run into separating pans. The elution-lye is worked up for alcohol. 
 Elution yields about 80 per cent, of the saccharose present in the treacle in the state of 
 a saccharate. 
 
 Substitution and Separation. As elution and similar processes consume much 
 alcohol, Steffen obtained by his process a tolerably pure calcium saccharate from 
 water. 
 
 The treacle to be worked up daily is placed in tanks capable of containing water 
 equal in weight to ten times the mass, and mixed with cream of lime at 54 Tw. The 
 dilution with water is so managed that the solution gives a precipitate on heating to 
 100. To the diluted treacle so much lime is added as can dissolve in the liquid i.e., 
 about 28 parts of pure lime to 100 parts of sugar in the solution. The cisterns, each 
 of which has a capacity of 20 cubic metres for the reception of 10 tons of treacle, are 
 fitted with agitators. When the lime has been dissolved for eight hours, the lye is 
 heated to i jo, in closed boilers, by means of steam, so that the insoluble sugar-lime 
 separates out, when the entire contents of the boilers are forced through filter-presses, 
 which are so arranged that the cakes can be lixiviated with water at 110. The cakes 
 are then wrapped in press-cloths of ticking, placed in a hydraulic press, and submitted 
 to a pressure of 100-150 atmospheres. During filtration the lye must not cool down 
 below 1 00, and hence the filter- presses are heated with steam before the admission 
 of the liquid. 
 
 The mother liquor running from the presses is allowed to cool, and a quantity of 
 sugar, corresponding to the sugar-lime which has been precipitated again, is added in the 
 state of a saccharated cream of lime. The mother liquor so treated is stirred for three 
 hours at the common temperature until the liquid is saturated with lime. The mother 
 liquor is then, by means of substitution, equal in percentages of sugar and lime to the 
 original lye. The mother liquor is then heated in the boilers, when, on the application 
 of heat, sugar-lime again separates out, or is filtered out and pressed. The quantity of 
 sugar contained therein is equal to the total sugar which has been substituted. Sub- 
 stitution and precipitation are repeated with the same mother liquor twenty to 
 twenty-five times, until it can be no longer treated, owing to the accumulation of salts 
 arid non-saccharine matter. The sugar-lime obtained is made up in water into a liquid 
 of 14 Tw., and is then further treated like beet- juice. 
 
 For the separation process, the treacles, syrups, &c., are diluted with cold water in 
 a cistern fitted with an agitator. The temperature of the solution must not exceed 
 35 Tw., and its concentration must correspond to 6' 12 per cent, of sugar. A certain 
 quantity of this cold solution is run into a vessel fitted with an agitator, and to 
 every 100 parts of sugar there are added, by means of a measuring cylinder, 50-100 
 parts of ground lime. The whole is then pumped into the so-called lixiviation filter- 
 presses in order to remove any excess of undissolved lime. For 100 parts of sugar in 
 solution for medium qualities of lime, and at temperatures below 35, 65 parts of lime 
 are mostly sufficient to separate the sugar. When the lime has been stirred in for a 
 short time the sugar is deposited. The paste is pumped into a second group of lixiviation 
 filter-presses, which separate the sugar-lime from the liquid. This liquid, which 
 contains but little sugar, and almost all the non-sugar, is either run off as a waste 
 liquor or the same process is repeated a second time. To remove the liquid still 
 adhering to the sugar-lime, it is purified with cold water in the filter-presses. The 
 sugar-lime cakes are taken out of the press, ground up in a wet mill with beet-juice 
 and solutions of sugar or water, and the sugar then separated from the lime. 
 
 Fig. 492 may serve to elucidate the entire process. Into the so-called cool- 
 masher, A y which serves for forming and precipitating the sugar-lime, the treacle from 
 
710 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 the measuring vessel is put, whilst the washing liquor of the sugar-lime presses flows 
 in from the cistern, C. The lime, which has passed through a wire sieve with 2000 
 meshes per square centimetre, passes through the measuring vessel, D, generally made 
 as a drum with four wings, so that the space between the wings contains 4 kilos, of 
 
 lime dust. 
 
 Fig. 492. 
 
 Fig. 493- 
 
 Fig. 494. 
 
 The cooling-masher shown in 
 Figs. 493 and 494, is one-fiftieth of 
 its real size, consists of a cylinder, 
 with the tubes, r, inserted, which 
 are surrounded by cold water in 
 the direction from a towards 5. The 
 shaft, c, in the interior wide tube, 
 carries the wings, d, and the mixing 
 screw, e. The treacle is run in by the 
 tube /, the lime by the tube g, the 
 water, or the washings, by the pieces, 
 k, into the worms, I. These are pro- 
 vided with fine apertures, from which 
 the liquid passes down. The lime 
 treacle formed is let off by the valve, 
 in. The apparatus is fitted with 
 man-holes, n ; eye-glasses, o ; ther- 
 mometers, t; air-pipe, q ; short pieces,. 
 s, for cleaning the eye-glasses ; and 
 a trial-cock, s. The treacle, as al- 
 ready mentioned, is diluted with 
 water so as to form 25 hectolitres 
 of liquor, containing about 7 per 
 cent, of sugar. It is then cooled 
 as far as possible by letting in the 
 
 cooling water and putting the agitating screw, e, in action. The lime-dust is then 
 gradually added. The cooling water, six times the weight of the treacle, enters 
 at 8 and escapes at 12. The entire contents of the cooling-masher are forced 
 through the filter-presses, E, by a pump at P. From these there first flows off a lye 
 which contains scarcely any sugar (polarising only 0-5 to o - 6), and is, therefore, at once? 
 
SECT. VI.] 
 
 SUOAR. 
 
 711 
 
 allowed to flow off. As the saccharate has a granular crystalline texture, it can be 
 washed in the same presses with cold water, in which it is almost insoluble. 
 
 The washings are also allowed to flow away, but that finally obtained is used to 
 dilute the treacle, and it is for the present collected in the cisterns, F. The saccharate 
 from the filter-presses is a white, sandy mass, and it is converted in the sugar-lime mill, 
 G, into sugary milk of lime, and forced by the montejus, JOT, into the cistern, J, where 
 it stands ready for further use. 
 
 The sugar-lime mill is shown in Figs. 495, 496, and 497 at one-fiftieth of its actual 
 size. The spiral, a, which lies below the filter presses, moves the sugar-lime into the 
 body, b, which lies above the guiding piece. If a diluting liquid is used, it enters 
 ate. The guiding-piece is constructed after the manner of coffee-mills. A conical toothed 
 
 Fig. 495. 
 
 Fig. 496. 
 
 disc, d, is fixed on a vertical shaft, e, the track of which can be raised by the lever, g, so 
 that the teeth of the disc, d, can be set exactly opposite those of the edge, h. The 
 ground product falls into the horizontal mash- drum, i ; is here well worked through, and 
 is drawn off at k as ready milk of lime. If only so much treacle is worked up that the 
 lime in the saccharine milk of lime can be entirely used for separation in the sugar 
 vats, the saccharate is immediately mixed with beet-juice in the mill. But if the lime 
 would be too much, a part of it has first to be removed. It is mashed, therefore, in 
 the mill with the thin juice, or with the juice of the first saturation. The excess of 
 lime, two thirds of that originally combined with the sugar, is separated out in filter- 
 presses, and the solution, which now contains 25 to 30 of lime to 100 of sugar, is then 
 passed on to saturation. 
 
 The Strontia Process. Dubrunfaut proposed, as far back as 1849, ^ separate sugar 
 out of treacle by means of strontia or baryta, and in 1863 Stammer showed that, on 
 woi-king up treacle by means of strontia, a much purer product was obtained than with 
 lime. He considered the process as impracticable on account of the difficulty of pro- 
 curing strontia. Meantime the Dessau sugar refinery used strontianite with success, 
 though the details of the process were unknown. The process has recently been 
 developed by Scheibler. 
 
 The treacle is intimately mixed with a hot saturated solution of strontia ; the mixture 
 passes through a cooling apparatus a,nd arrives at the crystallisers, where, after the 
 addition, if necessary, of a little strontium non-saccharate to induce crystallisation, it 
 congeals completely to mono-strontium sugar, C 13 H, 2 O u Sr0.5H 2 O. The congealed 
 mass is then again liquefied by agitation and passed through the filter-presses, when it 
 is resolved into A, non-strontium sugar, and B, sacchariferous lye. 
 
 The worked, white saccharate cakes, A, from the filter-presses are mashed up with 
 
7i2 CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 water or beet-juice, and saturated with water only so far that there remains an 
 alkalinity of 0^04 or o - o6 SrO. The precipitated strontium carbonate is then sepa- 
 rated from the solution of sugar by filter-presses ; the white mud of SrC0 3 is made up 
 into bricks for the oven, whilst the filtered sugar-juice undergoes a second saturation 
 in order to be entirely freed from SrO. It is boiled up and filtered again in order to 
 separate the white SrC0 3 mud from the pure solution of sugar. The press mud goes 
 to the brick-pressing machine, whilst the thin juice obtained is worked up after fil 
 tration to filling mass in the ordinary manner, or prior to filtration it is mixed with 
 separated and saturated thin juice, in order to be worked up together. 
 
 The above-mentioned saccharine-lye, JB, is mixed up with the required quantity of 
 caustic strontia, and boiled ; the sugar is separated out as bi-strontium sugar in the 
 form of a dense precipitate, which rapidly subsides. The precipitate and the lye are 
 most easily separated from each other by settling ; the former serves at once for 
 mixing with treacle in order to form mono-saccharate, whilst the latter is passed into 
 special large cisterns, in which it cools and deposits the excess of the dissolved strontium 
 salt, Sr(OH) 2 .8H 2 0, in the form of yellow crystals. After standing for two or 
 three days, the yellow salt is separated from the lye ; the salt is again used for forming 
 mono-saccharate or bi-strontium sugar, whilst the brown lye, free from sugar, is saturated 
 with carbonic acid in presence of an alkaline carbonate, and all the strontia is thrown 
 down as a strontium carbonate. The brown product thus obtained goes to the brick- 
 pressing machine, and the final lye (containing no sugar) is used as a manure. Caustic 
 strontia is obtained by igniting strontium carbonate. Both the commercial strontia 
 and that recovered by the above process are dried, pressed into bricks, and, after 
 thorough drying, ignited in the furnace. 
 
 Palm Sugar, Maple Sugar, and Sorghum Sugar are of no importance so far as 
 Europe is concerned. There are produced yearly about 12,000 tons of palm sugar, 
 2 500 tons of maple sugar (in the United States and the Dominion), and 3000 tons of 
 Sorghum sugar. The cane and the beet yield each from two to two and a half million 
 tons. 
 
 FERMENTATION ARTS. 
 
 Fermentation and Yeast. Fermentation is a term applied to the peculiar changes 
 of complex organic substances of the amylaceous and saccharine type under the influence 
 of certain putrescible nitrogenous substances or ferments. The decomposition of fer- 
 mentable organic bodies by a ferment effects the separation of their constituents into 
 two or more combinations, as when by a yeast-ferment dextrose and levulose are 
 converted into alcohol, its homologues, and carbonic and succinic acids ; or the molecules 
 of the original substance are re-grouped, as in the conversion of sugar of milk into 
 lactic acid during lactic-acid fermentation ; finally, the elements of the organic sub- 
 stance may enter into combination with the oxygen of the atmosphere either to form 
 new organic combinations, or to separate into its inorganic constituents carbonic acid, 
 carburetted hydrogen, &c. This latter decomposition is termed mouldering when a 
 residue rich in carbon (humus) remains, but when only the mineral constituents 
 remain, decay is said to have been reached. These terms are thus defined more by 
 custom or usage than by direct etymology dictionaries hardly distinguish between 
 them, but the difference is known to all. If large quantities of water be present both 
 these processes are resolved into putrefaction, in which chiefly gases carbonic acid, 
 ammonia, sulphuretted hydrogen and water are disengaged. But fermentation 
 always results in the remaining or the formation of other organic compounds, and the 
 variety of fermentation set up mostly depends on the state of decomposition of the 
 azotised matter employed as a ferment. The most important ferment is undoubtedly 
 yeast, but the ferment may be either an organic substance (yeast) or a protein body in 
 
SECT, vi.] FERMENTATION ARTS. 713 
 
 a putrescent state it is always a nitrogenised body. In a technological work the 
 varieties of fermentation may be classed as 
 
 1. Vinous or alcoholic fermentation, including the changes observed during the 
 
 processes of wine making, beer brewing, and the production of alcoholic 
 liquors or spirits. 
 
 2. Lactic-acid fermentation, taking place during the souring of milk; and at a 
 
 higher temperature changing to 
 
 3. Butyric-acid fermentation. 
 
 To these fermentations may be added 
 
 4. Putrescence, noticeable only in technological chemistry as a stage to be most 
 
 carefully avoided. 
 
 Vinous Fermentation. Vinous or alcoholic fermentation is the result of the decom- 
 position of saccharine matter, dextrose or glucose, levulose or chylariose, and lactose 
 into several products, principally alcohol and carbonic acid. According to the recent 
 researches of Lermer and Von Liebig (1870), dextrine in the presence of sugar is con- 
 verted into equal parts of alcohol and carbonic acid. 
 
 Dextrose, according to the equation C 6 H 1S 6 = 2C 2 H 6 + zCO,, yields 5 1 i per 
 cent, alcohol and 48 - p carbonic acid, saccharine, and maltose 
 
 C U H M U + H,0 = 4 C,H 6 + 4 C0 2 . 
 In the latter process 132,000 heat-units are liberated, or 720 per kilo, of alcohol. 
 
 Recently Pasteur has shown that lactic acid does not result from alcoholic fermen- 
 tation, but that succinic acid is a constant product of this fermentation in quantities 
 never less than o'6 to 0*7 per cent, of the weight of the sugar employed. Glycerine is 
 another constant production to the extent of 3 per cent, of the sugar; this substance 
 occurs in all wines. The 5 to 6 per cent, of substances remaining may therefore be 
 thus divided : 
 
 Succinic acid .... o'6 to 0*7 
 
 Glycerine . . . . :.. 3^2 to y6 
 
 Carbonic acid .... o'6 to 0*7 
 
 Cellulose, fatty substances, &c. j'2 to i'5 
 
 5-6 to 6-5 
 
 Yeast. The nature of alcoholic fermentation was first investigated by Cagniard- 
 Latour, while our present knowledge is due chiefly to the researches of A. de Bary, 
 J.Wiesner, Hoffman, Bail, Berkley, Pasteur, Hallier, Bechamp, and Leriner. Yeast on 
 being introduced into a fermentable fluid rapidly throws out fermenting arms, as it 
 were, until the fluid is covered with a superficial ferment, termed in German the 
 Oberhefe, while at the bottom of the vessel a viscid sediment is deposited, known in 
 German as the Unterhefe. The oberhefe, or superficial ferment, is employed as barm 
 by the baker, for the purpose of leavening his bread ; while the unterhefe, or sedi- 
 mentary ferment, is that employed in the fermentation of wines and of Bavarian beers ; 
 these beers differ from the general beers of England, France, and Germany in not 
 souring by exposure to air, this quality being due to the peculiarity in the process of 
 fermentation, Untergaehrung, or fermenting from below, during which the gluten, the 
 substance absorbing the oxygen of the air, is removed. In the distillation of brandy, 
 the yeast employed is a mixture of barm and bottom yeast, as the terms run in this 
 country. Fresh yeast appears as a grey-yellow or red froth of strong odour, and with 
 an acid reaction. Under the microscope the two kinds of yeast are easily distinguished. 
 The superficial yeast or barm consists of globular or ellipsoidal cells of equal size, and 
 about o-o i millimetre diameter. They float in the fluid partly alone, partly in groups. 
 The walls of the cells are so transparent that the inner cells can be seen through the 
 upper. In the centre of each cell appears a dark speck or grain, the protoplasma, 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 Fig. 498. 
 
 sometimes consisting of more than i grain. The bottom yeast, or sedimentary ferment, 
 also consists of cells, but these do not cling together so tenaciously as the cells of the 
 barm, and are generally isolated, while the adhesion is merely mechanical between those 
 that do cling together, a slight concussion being sufficient to effect their separation. 
 Sometimes a large cell of the bottom yeast contains two, three, or even four smaller 
 cells, the dimensions of these cells varying greatly, and not being nearly so constant as 
 in the cells of the barm. 
 
 E. C. Hansen distinguishes six kinds of yeast ; the more important are Saccharomyces 
 .cerevisice /., the ordinary beer ferment. It is a powerful form of a top yeast. The 
 cells (Fig. 498) are greyish, both by reflected and by transmitted light, and more or less 
 
 globular. The size of the cells varies from 
 2\ to 6 micromillimetres. There are generally 
 found in each mother cell one to four, or very 
 exceptionally, five cells (49 8, 6). The cell walls 
 of the spaces are generally more distinct 
 than in the other kinds. Fig. 498, c, shows 
 cells with undeveloped askospores. Fig. 498, 
 a, is a peculiar form of development which 
 often occurs. The cells are divided by par- 
 tition walls into several parts, each of which 
 can send out growths. 
 
 Saccharomyces pastorianus 1. is a yeast 
 which Hansen has often collected in the air 
 
 of a brewery at Copenhagen. If cultivated in wort it occasions bottom fermentation. The 
 askospores (Fig. 499) have in general the diameter of 1-5 to 3-5 micromillimetres. 
 There are commonly one to four askospores in each cell, but sometimes as many as 
 ten (Fig. 499, 6). 
 
 Saccharomyces ellipsoideus I. (Fig. 500) was collected in the Vosges on ripe grapes. 
 It is the ordinary ferment of wines. 
 
 Fig. 499. 
 
 An important step in the fermentation industries is' the obtaining and utilisation of 
 pure cultures by Hansen. 
 
 The moist chamber used is shown in section on a reduced scale, Fig. 501. The 
 cultivation is carried on on the lower side, 6, of the covering glass, a : c is the side of the 
 chamber and c? is a stratum of water at the bottom to prevent desiccation. All these 
 objects must be passed through a gas or spirit flame, or, preferably, wrapped in several 
 
SECT. vi. j FERMENTATION ARTS. 715 
 
 folds of filter-paper and sterilised by two hours' exposure to the temperature of 150 in 
 an oven. The upper edge of the sides must be covered with vaseline. A water bath 
 heated to 3O-35 is kept ready ; also a stand upon which is set a Chamber-land flask (Fig. 
 502). Two such flasks are required, each holding about 30 c.c., half full of nutrient 
 gelatine. Their outer surfaces are passed through the flame, and 
 they are then set under a bell till they are wanted for use. They 
 are fitted with ground-glass caps drawn out to a slender tube, 
 which is filled with sterilised cotton. A 5 per cent, solution of 
 gelatine in clear hopped wort is taken as nutrient solution. 
 
 For the propagation of pure cultures, the flasks which contain 
 the nutrient gelatine are cautiously heated until their contents 
 are liquid, when they are placed in the water-bath. For pure 
 cultivations young cells are taken in vigorous vegetation. A small 
 number of them are diluted in the flask with sterilised water 
 until it becomes slightly dull ; the flask is shaken in order that 
 the cells may be uniformly distributed ; a few drops are taken 
 out with a glass rod and examined under the microscope. A low 
 power is used, so as to just distinguish the cells from other small 
 accompanying bodies. The purpose of this first microscopic ex- 
 amination is to estimate the quantity of cells in the mixture. After it has been well 
 shaken up, an ignited platinum wire is dipped into the liquid and quickly inserted into 
 one of the flasks containing nutrient gelatine. The temperature of the gelatine must 
 not exceed 35 ; it is sufficient, if kept liquid, and the microscopic examination shows 
 that the mixture is rich in cells, for the platinum wire to be plunged in only to the 
 depth of 2 millimetres ; in the opposite case it is plunged in more deeply. 
 
 For greater safety two preparations are made; if both give the same result, 
 it may be assumed that the cells are uniformly distributed, and that average speci- 
 mens have been obtained. It must next be determined whether the gelatine has 
 received a sufficient number of cells or not. If a considerable error is committed in 
 this respect all further work is in vain. In order that the cells may be so distributed 
 in the gelatine that pure colonies may be obtained with certainty, the colonies which are 
 afterwards formed must have room enough not to intermingle with each other. Such 
 drops, in shape and size as are to be afterwards used, are placed upon an ordinary glass 
 slip, or, preferably, on a slip where a number of squares have been marked with a diamond. 
 The squares give a guide for the microscopic examination. If it appears that too few or 
 too many cells have been sown, more cells must be added in the first case, and in the latter 
 more gelatine, all being calculated beforehand. If we find that the mixture contains 
 twice as many cells as was intended, the right point is reached by adding as much 
 more gelatine as is already present. A corresponding portion must be at once placed upon 
 the glass covers, which are immediately covered with a little glass bell. As a matter of 
 course, the gelatines must be kept liquid in the water bath ; the cells must be distributed 
 by shaking, avoiding the formation of foam. At the ordinary temperature of a room 
 the gelatines coagulate in a quarter of an hour. As soon as the gelatine is coagulated, 
 the covering glass is fixed to the ring in such a manner that the cultivation is down- 
 wards. By a cautious pressure on those points of the glass which touch the ring the 
 chamber is quite shut off from the outer air. When the chambers are in order they are 
 examined with a low power. It must be ascertained whether the spots of vegetation 
 are pure i.e., whether each proceeds from a single cell. The operations up to this 
 point engage an investigator of some experience for three hours. The moist chambers 
 are then placed in a thermostat at 24-25. If there is a microscope in reserve, a 
 chamber may be secured to its stage in such a manner that the cell in question can be 
 accurately seen and its development followed step by step. Spots of vegetation, visible 
 
7 i6 CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 to the naked eye, develop in two or three days. In the Saccharomycetes the vegeta- 
 tive spots have the appearance of minute pin-heads and a pale yellowish-grey colour ; 
 the surface may be either dull or slightly shining : the margin, under a low power, 
 appears sharply bounded or uneven. The colonies of Mycoderma vini and M. cerivisice 
 and some kindred species are of a pale grey, with a dead surface, spread out like a film 
 and hollowed like a capsule. As long as they are covered with gelatine they resemble 
 the spots of the Saccharomycetes. In the gelatine film of a single covering glass sixty 
 spots of vegetation may be developed. When the pure cultivations are transferred to 
 the nutritive liquid the air must be pure and calm, and the apparatus must be 
 thoroughly sterilised. A pair of small forceps and platinum wires, which have been 
 passed through the flame, must be at hand, and a sufficient number of small bells with 
 their glass plates. For culture in a nutrient liquid, Pasteur's two-necked flask is 
 generally used (| litre, Fig. 503) and hopped sterilised wort. The thin tube is closed 
 at its end with an asbestos plug ; to the straight tube is attached a piece of flexible 
 
 tubing closed with a glass stopper. If a pure culture 
 Fig- 53- of a single species is desired, four or five of such flasks 
 
 are needed. This number is to enable the observer to 
 compare the vegetations developed in the flasks and 
 ascertain whether he has obtained a growth of the cells 
 which have been sown. It may accidentally occur that 
 one of the flasks has been infected by a foreign organism, 
 or no vegetation at all may be developed e.g., if the 
 platinum wire was too hot. The chambers are examined 
 with the microscope ; the vegetations, the origin of 
 which has been ascertained, are scrutinised so that we 
 may be sure that the colonies arise each from a single 
 cell. The boundaries of the selected colonies are marked 
 out with a fine brush and a little white colour. A 
 covering glass is then lifted off its ring, and turned up- 
 side down, so that the spots are upwards and placed, if possible, on a dark back- 
 ground, that they may be seen more distinctly. By means of a forceps we lift up a 
 platinum thread, and, after drawing it rapidly through a gas or spirit flame, the 
 selected spots are touched with it. If several specimens are to be taken from the 
 covering glass, it must of course be covered each time with a small bell. The operator, 
 with his left hand, removes the flexible tube of the Pasteur flask, and brings at the 
 same moment, with the other hand, the infected platinum wire to the opening of the 
 tube, into which it is let fall. The tube is now inclined so far that the liquid does 
 not run out, and at the same time it is passed through the fire and again covered 
 with the caoutchouc tube. The flasks are placed in a heat of 25-28. In the course 
 of one or two days there is a Avell-marked development. If every foreign infection has 
 been avoided on transferring the cells to the flasks, each flask contains a pure cultiva- 
 tion. A specimen is taken from each with due precautions and examined with the 
 microscope. 
 
 In order to obtain larger quantities of pure yeast, the receiver, C (Fig. 504), fitted 
 with a safety valve, <?, and a pressure gauge, r, is filled with air to a pressure of 3 to 
 4 atmospheres by means of the air-pump, t u, and the pipe s. The wort cylinder, 
 A, provided with a trial cock,y*, is sterilised with steam under pressure, when the air 
 escapes through the tube, b, and air is admitted in its place through the cock g, and 
 the cotton filter, d. The wort is conveyed in a boiling condition into the cylinder from 
 the main pipe of the boiling-house. Cooling is effected by water trickling out of the 
 ring, e ; the air needed for aeration is let pass through the filter d. The fermentation 
 cylinder, B, is sterilised in the same manner as the wort cylinder. It has a similar 
 
SECT. VI.] 
 
 FERMENTATION ARTS. 
 
 717 
 
 Fig. 504. 
 
 filter, k ; a glass tube, o, in order to observe the level of the liquid ; a tube, i h, for the 
 escape of carbonic acid ; an agitator, 
 k, in order to mix the yeast with 
 the liquid ; a small tube, I, for introdu- 
 cing pure yeast and for taking small 
 samples. 
 
 The yeast is added only once, and 
 the apparatus then works for a year, 
 or longer if required. The outflow 
 cock, m, is so arranged that the liquid 
 itself effects the purification, and no 
 infection from without can take place, 
 but high tension must always be kept 
 up. The wort is passed into the fer- 
 mentation cylinder through the piping, 
 a n, which connects both cylinders. 
 As soon as it comes near the yeast 
 tube, I, the pipe is closed until the yeast is added ; it is then filled up to the mark in the 
 upper part of the glass tube; it is stirred, and 220 litres of sterilised wort are thus 
 brought into fermentation with absolutely pure yeast. In about ten days the beer 
 is drawn off through the cock m. During tapping, air is let enter through the 
 filter h. As soon as any mud appears the running is stopped, wort is added, stirred 
 up, and 27 litres are taken out of this mixture of wort and yeast. Wort is added 
 afresh, stirred again, and 27 litres are taken of this last mixture. The measures 
 are shown by a graduation on the glass tube, o. In the 54 litres taken out there 
 is yeast enough to set 8 hectolitres of wort in fermentation ; the yeast remaining in 
 the cylinder is enough to bring again 220 litres into fermentation, and so it goes on 
 continuously. 
 
 Nageli and Low (1878) found in the bottom yeast of beer (with nearly 8 per cent, 
 of nitrogen) 
 
 Cellulose and vegetable mucus . . . : .- 37 per cent. 
 
 Proteines : . Common albumen . i .: 36 
 1). Gluten casein albumen . . 9 
 
 Peptones (precipitable by basic lead acetate) . 2 
 
 Fat '5 
 
 Ash 7 
 
 Extractive matter, &c 4 
 
 Top yeast contains 2*5 per cent, and bottom yeast up to 7 per cent, of ash. The 
 proportion of sulphur averages 0*5 to o'8 per cent. The ash of the yeast consists 
 chiefly of potassa, phosphoric acid, silica, and magnesia. 
 
 Physiologists are not agreed as to the part played by yeast in alcoholic fermenta- 
 tion. If the yeast is to act upon another substance, there must be interpenetration. 
 As the yeast is enclosed in a cell-membrane, the substances upon which the yeast is to 
 act must penetrate this membrane, i.e., must be capable of diffusion. Hence malt is 
 required in the mashing process in order to split up the starch into maltose and 
 dextrine, the former of which is able to penetrate through the cellular membranes of 
 the yeast. It is not sufficient for a complete conversion of the maltose into alcohol to 
 carry out the process of saccharification, namely, at a suitable temperature. For a good 
 fermentation, such as is required in the distilling business, the subsequent action of 
 diastase is needed, whereby the dextrine, which is not diffusible, is gradually converted 
 into maltose, and penetrates into the yeast cell. The thinner the membrane the better 
 the diffusion. Old yeast is harder to nourish than young yeast, as in the former the 
 membrane is thicker. The albuminoids are converted by the action of the peptase of 
 
7I g CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 the malt into soluble and diffusible peptones, and in this state they pass into the yeast 
 cell. There they become insoluble and are reconverted into albumens. The case is 
 similar with the maltose, which is formed from the starch in the mashing process. A 
 small part of it is precipitated as cellulose within the yeast cells ; but in great part it is 
 split up into alcohol and carbon dioxide, which do not form constituents of the starch. 
 A vigorous, healthy yeast prolongs its life even if it receives no fresh nutriment. This 
 vegetation of the yeast without nutrition is called the self -fermentation of the yeast. 
 We have, therefore, to distinguish two stages in the development of yeast i.e., (i) the 
 reception of nutriment and their use in the production of new cells ; (2) the katagenesis, 
 in which the substance of the yeast cell is decomposed. 
 
 Conditions of Alcoholic or Vinous Fermentation. The conditions of alcoholic 
 fermentation are the general conditions of the vegetation of the yeast plant, with the 
 distinction that by vinous fermentation the largest amount of alcohol is obtained. The 
 following conditions must be f ulBlled when alcoholic fermentation is the desideratum : 
 
 1. An Aqueous Solution of Sugar, in the proportion of i part of sugar to 4 to 10 
 parts of water. The sugar can be employed as grape sugar, dextrose, or levulose, which 
 is always capable of fermentation ; or an unfermentable sugar, cane sugar, or sugar of 
 milk, may be converted by means of an acid or suitable agent into fermentable sugar. 
 However gradual the process may seem, cane sugar is always converted into grape 
 sugar before fermentation sets in. 
 
 2. The Presence of Yeast or Spawn. In the first case, i part of yeast to 5 parts 
 of sugar is sufficient to effect a strong fermentation. If spawn only is present, there 
 must also be present substances upon which the spawn may feed or develop protein 
 substances, phosphoric acid, humus, and alkalies. If no ferment exists, the only other 
 condition under which fermentation is effected is by exposure to 
 
 3. The Atmosphere, which introduces the before-mentioned ferment and furnishes life. 
 
 4. A known Temperature, the limits of which are 5 and 30 C. As a rule, vinous 
 fermentation is effected between 9 and 25. The lower the temperature the longer 
 the time required for the fermentation to subside, and conversely. At 30, and at 
 higher temperatures, the vinous fermentation easily goes over into butyric-acid 
 fermentation. The making of wines is based on a practical acquaintance with alcoholic 
 fermentation ; but in this case only a portion of the sugar of the must goes over into 
 alcohol and carbonic acid. The alcohol remains, while the greater part of the carbonic 
 acid escapes. 
 
 Yeast, like all plants, requires for its development and increase the co-operation of 
 atmospheric oxygen ; in the absence of free oxygen yeast cannot grow in a nutritive 
 solution. The assertion of Pasteur, that yeast can obtain the oxygen needed for its 
 increase from oxygenous compounds (e.g., from sugar), is disputed. Under suitable 
 conditions yeast grows without setting up fermentation, and, on the other hand, it is 
 established that fermentation occurs without the growth of yeast. The growth of 
 yeast and fermentation are, therefore, not inseparable. The production of the " seed 
 yeast " must ensue with abundant access of air, but the process of fermentation goes 
 on with the completest possible exclusion of air. 
 
 Pressed Yeast (Dry Yeast). Yeast may be made in various ways. At Schiedam 
 (Holland) it is made of excellent quality by a mode which is to a certain extent a trade 
 secret, and differs materially from the following process : A mash is made in the 
 ordinary manner of i part of bruised barley malt with 3 parts of bruised rye, the 
 mash being cooled with the fluid portion of the wash. To 100 kilos, of the bruised 
 grain is added 0-5 kilo, of sodium carbonate and 0-35 kilo, of sulphuric acid diluted 
 with water ; these ingredients having been added to the mash, it is brought to fermenta- 
 tion by the aid of yeast. The newly formed yeast is removed from the strongly 
 fermenting fluid by the aid of perforated ladles ; it is then strained through a linen 
 cloth or fine sieve, and poured into cold water, wherein it is allowed to form a sediment. 
 
SECT. vi. J WINE MAKING. 719 
 
 The sediment thus produced is collected after the supernatant water has been run off, 
 is placed in a stout canvas bag under a press, and formed into a stiff clayey dough, to 
 which usually 4 to 10 (sometimes as much as 24) per cent, of dry potato starch is 
 added. Sometimes the water is removed from the yeast by placing that substance 
 upon slabs made of gypsum or other absorbent materials, care being taken to keep the 
 yeast in a cool place ; by the use of the hydro-extractor expressly arranged as regards 
 its construction for this purpose yeast may be very rapidly rendered dry. As regards 
 the use of the sodium carbonate, it appears to assist in the separation of the glutinous 
 constituents of the cereals ; the action of the sulphuric acid is partly similar, and it also 
 prevents the formation of lactic acid, which, if formed, causes a loss of both starch and 
 spirit ; the sulphuric acid also accelerates the separation of the yeast. According to 
 communications by some of the most eminent distillers at Schiedam to Dr. G. J. 
 Mulder, neither soda nor sulphuric acid is used at Schiedam in the preparation of 
 what the trade terms dry or German yeast, some of which is imported into this 
 country from Hamburg. Assuming the researches of Pasteur and others on fermenta- 
 tion to be correct, these observations are of great value in reference to the manufacture 
 of yeast. It is found that the yeast sporulse become properly developed when they are 
 placed in a fluid which, instead of containing protein compounds, consists of aqueous 
 saline solutions mixed with a sugar solution, such as, for instance, ammonium 
 tartrate, potassium and magnesium phosphate, and gypsum. It would hence appear 
 that under such conditions yeast cells take up the material for the propagation 
 of new cells, partly from inorganic substances, partly from organic, viz., the decom- 
 posing sugar which yields carbonic acid : in this respect the yeast cells agree, then, 
 with higher organised plants. As regards the quantity of yeast obtainable from a 
 given weight of materials, it may be stated that from 100 kilos, of rye, including the 
 bruised malt, about 15 to 16 kilos, of dry yeast can be obtained. As the quantity of 
 real yeast or of the nitrogenous matter for sale present in the ready prepared dry 
 yeast amounts at the most to 20 per cent., the nutritive value of the wash obtained 
 after the distilling off of the spirits from the fermented liquid is but little impaired. 
 
 In testing yeast a portion is placed in solution of sugar, and the carbon dioxide 
 formed is determined gravimetrically or volumetrically. 
 
 The industries based on alcoholic fermentation are 
 
 1. The production of wine. The alcohol is not separated from the fermented 
 liquid. If the fermentation is suppressed, a portion of the carbon dioxide formed 
 remains in solution and escapes with effervescence on the removal of the pressure 
 {champagnes). 
 
 2. Brewing, in which the substance forming alcohol is chiefly starch. A part of 
 it is changed into non-fermentible dextrine, but the greater part into maltose, which 
 is decomposed on fermentation. A small part of the sugar serves to keep up a 
 secondary fermentation, which is retarded as much as possible by a reduction of 
 temperature, whilst the gradual escape of carbon dioxide contributes to the preservation 
 of the beer. Here also, as in the case of wine, the alcohol is not separated from the 
 fermented liquid. 
 
 3. Whilst, in brewing, a part only of the starch used as a raw material is converted 
 into maltose, and is only by degrees transformed into alcohol and carbon dioxide, the 
 object in a distillery is to obtain from the given material (starch or sugar) in a minimum 
 of time a maximum of alcohol, which is separated from the fermented liquid by 
 distillation. The secondary fermentation is conducted so that the yeast destroys itself. 
 
 WINE MAKING. 
 
 By the name of wine is generally distinguished an alcoholic fluid prepared with- 
 out distillation by the fermentation of grape-juice. In the widest meaning of the term 
 is included the result of the vinous fermentation of all natural juices. 
 
7 20 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 The Vine and its Cultivation. The vine, Vitis vinifera, is generally cultivated in 
 Europe at a temperature of 50, while the best and ripest drinking wines are obtained 
 from grapes grown at a temperature of 51 to 52. It requires an average tempe- 
 rature of 10 to 11, and an average summer temperature of 18 to 20 ; but it is the 
 summer's sun that forms the sugar. A climate with severe winters and hot summers 
 is therefore as favourable to the cultivation of the grape as a temperate climate. 
 England, with a mean average annual temperature of 11, is consequently very 
 unsuited to the growth of the vine. The weather has the greatest influence upon 
 the vine : during the growth rain is required, but during the ripening only the sun's 
 rays should reach the grape. The soil is not so much a matter of consequence if a 
 quantity of potash be present ; but a warm, loose soil is the best. 
 
 Volcanic soils, rich in potash, such as those of the banks of the Rhine, of the Greek 
 islands, and of Southern Italy, are most suitable for the vine. The wines produced at 
 high latitudes on the continent of Europe, e.g., at Grlinberg, in Silesia, are of a very 
 low character. 
 
 Besides serving for the production of" wine, grapes are used for immediate consump- 
 tion, and also dried in the state of raisins. They are also employed in the preparation 
 of (genuine) grape sugar, and in the manufacture of cognac, wine- vinegar, &c. An oil 
 is obtained from the seeds, and the lyes are the principal raw material for the manu- 
 facture of tartar and tartaric acid. 
 
 Vintage. The sugar is found at an early stage of the growth of the grape. When 
 unripe the grape contains malic, citric, and tartaric acids, potassium and calcium bitar- 
 trate, organic salts in smaller proportions, and a little colouring and extractive matter. 
 Successive analyses have been made of the grape during its period of growth by C. 
 Neubauer from samples obtained from the Neroberg, near Wiesbaden (i86S), and have 
 given the following results : 
 
 July 27th . 
 
 August Qth . 
 
 I ;th . 
 
 28th . 
 
 September 7th . 
 
 1 7th . 
 
 28th . 
 
 October 5th . 
 
 ,, I2th . 
 
 22nd 
 
 O'6 percent. sugar and 27 per cent, free acid 
 
 0-9 
 
 2-3 
 
 8-2 
 
 11-9 
 
 18-4 
 
 17-5 
 16-9 
 18-6 
 17-9 
 
 2'9 
 
 2-8 
 i-9 
 
 I '2 
 
 0-8 
 0-8 
 0-9 
 0-9 
 
 It appears that the riper the grape the more sugar it contains, and it produces a 
 wine richer in alcohol, so that the grapes are never gathered until perfectly ripe. The 
 grapes of the white vine are of a brown-yellow when ready for gathering for wine, and 
 the red and blue grape must be extremely dark before the seed will separate from the 
 fleshy part of the grape sufficiently for wine-making purposes. 
 
 The grapes are sometimes plucked, and sometimes left on the stalk. The separation 
 of the grape from the stalk is effected either by hand or by the aid of a hurdle, the 
 openings between the bars of which are only sufficiently wide to admit the passage of 
 the grape, or by a wooden or brass trellis-work, or finally with a large wooden fork 0*5 
 to 0*6 metre in length. The stalk contains much tannic acid, and it is therefore 
 necessary that all the grapes should be thoroughly separated before pressure ; but in 
 some cases, when the grape contains too little of this acid, a few stalks are purposely 
 allowed to remain. 
 
 The Pressing of the Grapes. After the grapes are stripped from the stalks, they are 
 placed in a vat and stamped with a wooden maul or pestle to express the juice. They are 
 generally allowed to remain for some time, and afterwards submitted to a second bruis- 
 
SECT. VI.] 
 
 WINE MAKING. 
 
 721 
 
 ing, the maceration being for the purpose of softening the skins and fleshy part of the 
 grape. The whole of the juice and grape-skins, or marc, is then put into a butt with 
 perforated sides, through which the must trickles into the fermentation vat beneath. 
 If a white wine is being operated upon, to prevent it becoming stringy, as the term 
 runs, from an insufficient supply of tannic acid, small quantities of stalks are added 
 from time to time. This addition renders the wine more easily clarified by the addition 
 of white of egg or isinglass in a subsequent stage of the process. While the wine is in 
 the vat, the fermentation is allowed to proceed, and the slight acidity generated reacts 
 upon the colouring matter and aromatic constituents of the grape, these being taken 
 up in the alcohol set free. 
 
 The wine-presses are of very various construction. The most general is the beam- 
 press, roughly constructed with a pole 12 to 16 metres in length, and four to six oaken 
 cross-beams. These presses have considerable power, but they are tedious to work, and 
 soon get dirty. The lever-press is more efficacious, and is made in many forms, the 
 pressure being mostly from below. The hurdle- or sledge-press is of the rudest kind, 
 consisting merely of hurdles and rough heavy stones. The best presses are the screw- 
 presses made of wood or cast-iron. 100 parts of grapes yield 60 to 70 parts of must. 
 The ripest grapes yield the first juice in the press ; the results of stronger pressure are 
 more acid. The result of the first pressure is termed the wine or the first wine ; then 
 comes the press-wines ; and finally the after-win.es. The residue or marc is sometimes 
 treated with water to obtain an inferior wine. 
 
 The Centrifugal Machine. In 1862 Steinbeis, of Stuttgart, with the co-operation 
 of Reihlen, endeavoured to express the juice of the grape with the aid of the 
 centrifugal machine instead of the press. They were enabled in ten minutes to ex- 
 press the juice perfectly from 100 to 120 Ibs. of grapes, including the time required 
 to fill and empty the machine. In 1869, Ballard and A lean obtained equally 
 successful results, some of which were made comparative with those obtained by a 
 good press : 
 
 Must 
 Residue 
 
 Loss 
 
 Centrifugal Machine. 
 . 79'Hi 
 . 20-214 
 . 0-645 
 
 Press. 
 77-086 
 18-601 
 
 4-3I3 
 
 lOO'OOO 
 
 Fig- 55- 
 
 Ferret fixes in a vat six pillars, each of which has six hooks pointing downwards 
 (Fig. 505) at 25 centimetres apart. Six hurdles made of ribs 
 placed 6 to 8 centimetres from each other are then put in the 
 vat in such a manner that as it is filled they may rise only so 
 far as the hooks of the pillars allow, thus preventing the skins, 
 stalks, &c., from ascending. Upon the upper hurdle is laid a 
 thin layer of straw in order to prevent any berries which may 
 be carried up by the motion of fermentation from ascending to 
 the top. When the wine is drawn off, the hurdles, with the 
 dregs, &c., between them, sink to the bottom. The process 
 deserves attention. 
 
 The Chemical Constituents of the Must. Besides the stalk 
 of the grape, there are the outside skin, the hull, the seeds, and 
 the juice. Of the composition of all these substances, with the 
 
 exception of the grape-juice, our knowledge is very deficient. J ^^ - ^ 
 
 Besides cellulose, the stalks contain much tannic acid, and an acid very sour to the 
 taste. The hull of th.3 grape contains the colouring matter and a small quantity of 
 tannic acid. The seed contains a peculiar acid, oenanthic acid, and an ether, bearing 
 the same name, to which the bouquet of the wine is due. 
 
 2 z 
 
722 CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 The Sugar of the Grape. The wine grape contains more sugar than any other kind 
 of grape. The quantity of sugar a mixture of dextrose and levulose is seldom less 
 than 12 per cent., while it is sometimes as much as 26 to 30 per cent. The proportion 
 of acid to sugar is in good years and in a good grape, according to Fresenius, i : 29 ; in 
 average years and cases, i : 16 ; and when the proportion is only i : 10 the grapes are 
 useless for the production of wine. The proportion between the acid and sugar in wine- 
 must from the same kind of grape for different years is, according to this eminent 
 
 chemist 
 
 In a very inferior year, 1847, as i : 12 
 In a better year, 1854, as i : 16 
 
 In a good year, 1848, as I : 24 
 
 During the fermentation of the must, potassium bitartrate is deposited, and from 
 this source most of the tartar of commerce is obtained. This salt is insoluble in dilute 
 alcohol ; consequently, as the sugar changes into alcohol it is thrown down. It is from 
 the fact of containing tartaric acid, which, by combining to form an insoluble salt, is 
 thus prevented exerting an unfavourable influence on the wine, that grapes possess so 
 much more the property of making a good wine than do other fruits. The malic and 
 citric acids contained in currants and gooseberries cannot be withdrawn in this manner. 
 Hence the addition of sugar to wines made from these fruits to veil the acidity the 
 addition, however, giving rise to the danger of a second fermentation, and consequent 
 acidity. According to Al. Classen, i kilo, of ripe grapes gave (in 1868) 577 to 688 
 grammes of juice ; and i litre of juice contained 
 
 Water 860 to 830 grammes 
 
 Sugar (dextrose and levulose) . . 150 300 
 Pectin, gums, extractive matter,) 
 
 protein substances, organic [ 30 20 
 
 acids, and mineral matters . I 
 
 1040 to 1 1 50 
 1000 parts of juice of ripe (Rhine, 1868) grapes contained 
 
 I. 2. 3. 
 
 Solid matter .... 164*4 l &9'7 204-6 
 
 Sugar . ... 149*9 ... 162-4 ... 174-0 
 
 Free acid . . . . .7-2 ... 6'8 ... 4-8 
 
 Ash 27 ... 3-0 ... 4-0 
 
 In too parts of the ash were contained 
 
 I. 2. 3. 
 
 Phosphoric acid . . . 16*6 ... i6'i ... 14-0 
 Potash . . ... . 64-2 ... 66-3 ... 71-4 
 
 Magnesia ..... 47 ... 2'8 ... 2'6 
 
 C. Neubauer (1868) analysed two kinds of grapes, and found 
 
 Neroberger Steinberger 
 
 (Large Grapes). (Selected Grapes). 
 
 Sugar 18-06 ... 24-24 
 
 Free acid 0*42 ... 0*43 
 
 Albuminous substances . . . 0*22 ... 0*18 
 
 Mineral constituents (potash, phos- ) 
 
 phoricacid, &c.) . . . ]" ' 47 
 
 Combined organic acids and extract- 1 
 ive matter j 
 
 Total of soluble constituents . . 23-28 ... 29*22 
 
 Water 7672 ... 70-78 
 
 lOO'OO ICO'OO 
 
SECT, vi.] WINE MAKING. 723 
 
 The Fermentation of the Grape-juice. The fermentation of the grape-juice is 
 spontaneous that is, it is consequent upon the exposure of the grape- juice to the 
 atmosphere, without the addition of yeast. The albuminous matter of the must forms, 
 under the influence of the atmospheric spawn, or yeast germ, the well-known fungus 
 Penicillium glaucum, or yeast cells. The fermentation begins at a temperature of 10 
 to 15, and is effected more or less rapidly according to the temperature. Too low a 
 temperature will retard the progress of fermentation, as also will the addition of sul- 
 phurous acid ; the same effect is obtained by the addition of other sulphur compounds, 
 as, for instance, the essential oil of mustard, which contains allyl sulphocyanide. 
 The must is left in open vats. Bubbles of carbonic acid soon appear, scum collects 
 upon the surface of the juice, and an alcoholic odour pervades the wine at this stage. 
 About the seventh day the fermentation commences to decrease, and about the tenth 
 or fourteenth day the fluid begins to clear, no more carbonic acid or scum appearing. 
 The yeast cells formed are carefully removed from the bottom of the vessel, and the 
 wine run into casks, where it undergoes a slight after-fermentation. If there be much 
 sugar contained in the grape, and a small quantity of azotised matter, the resulting 
 wine will be sweet ; but if the proportion of sugar be small and albumen large, a dry 
 wine is the result. 
 
 Drawing-off and Cashing the Wine. After the principal fermentation, the greater 
 part of the sugar of the must is found to be separated into alcohol and carbonic acid. 
 There is still likely to arise, unless the temperature be considerably decreased, a fresh 
 fermentation, known as the after-fermentation. Should this after-fermentation continue 
 too long, vinegar is formed, and to prevent this the wine, after the disappearance of the 
 bubbles of carbonic acid upon the conclusion of the principal fermentation, is at once 
 " spigotted off" from the lees into casks, the object being to cut off communication with 
 the atmosphere as much as possible. The casks are nearly filled, and are bunged loosely, 
 being filled completely a day or two after. Wines casked in December will often con- 
 tinue fermenting till February or March. Strong wines rich in alcohol can be kept in 
 cask until they have become quite clear ; but weak wines must be soon bottled, as the 
 oxygen of the air is liable to convert the hydrate of the oxide of ethyl, or alcohol, into 
 tri oxide of acetyl, or vinegar. 
 
 Constituents of Wine. Constituents that were not found in the must are character- 
 istic of the wine ; the chief of these is alcohol. Succinic acid and glycerine, the constant 
 products along with alcohol and carbonic acid of vinous fermentation, are also to be found. 
 A " dry " wine, such as the French and Rhenish wines, is one in which all the sugar 
 has been decomposed ; a " sweet" wine, on the other hand, is one in which some sugar 
 has remained undecomposed, either from an insufficiency of albuminous matter to nourish 
 the yeast cells, or from the checking of the fermentation by exposure to a low tempera- 
 ture. A very sweet and thickly fluid wine is termed a "liqueur." The difference in 
 colour is due to three substances a blue colouring matter, a brown colouring matter, 
 and tartaric acid. The brown colouring matter is present in all light or white wines, 
 while the blue colouring matter, found in the skins of purple or black grapes, becomes 
 in the wine a red colour, the change arising from the contact with the tartaric acid. 
 Wines of the first year after growth are termed new or " green " wines. The average 
 composition of wines, in 1000 parts, is the following : 
 
724 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 900-891 
 80-70 
 
 20-30 
 
 Fig. 506. 
 
 Water . . . ..... 
 
 Alcohol* ... .... 
 
 Homologues of alcohol (propylic, butylic alcohol)* 
 
 Ethers (acetic, osnanthic)* 
 
 Essential oils . . . ..<< 
 
 Grape sugar (dextrose and levulose) . ...;_ .... 
 
 Glycerine* . . . . . . . ,..;.,,.' 
 
 Gums . . . . . - . . . , " . ., 
 
 Pectin . *' r ."'''' I" .... . . ' " 
 
 Colouring and fatty substances . . .' ' . ' 
 Protein bodies ' >. '* '. ' . ' ... . 
 
 Carbonic acid* . ;.'.,i , .. . . ..-:.'/ 
 
 Tartaric and racemic acids . '.>'.. . ..',/.. .j 
 
 Malic acid .....'.. 
 
 Tannic acid . " '. " ." . . ., 
 Acetic acid* . ' '. " ' . . . '. .' . 
 Lactic acid (?) * . - 1 '. : . 
 Succinic acid* ,.:>i-v- '..' '.-.. . , 
 Inorganic salts . . ; . ' 
 Those substances marked (*) are formed during the principal fermentation. 
 
 The quantity of alcohol contained in a wine is due partly to the quantity of sugar 
 
 and partly to the quantity of albuminous matter con- 
 tained in the must. It is chiefly ethylic or ordinary 
 alcohol. The specific weight of the wine gives only 
 approximately the alcoholic contents. A better 
 method of estimation is by means of an alcoholometer. 
 Of these instruments, Geissler's vaporimeter is, per- 
 haps, one of the best, in which the pressure exerted 
 by the vapour of the wine upon a column of mercury 
 gives a measure of the alcohol contained. The vapour 
 of absolute alcohol at a temperature of 78'3 exerts 
 a tension equal to that exerted by aqueous vapour at 
 1 00. It is therefore only necessary to ascertain the 
 height of the column of mercury and the temperature 
 to arrive at the quantity of alcohol. The apparatus 
 is shown in Fig. 506, and consists essentially of four 
 parts viz., (i) A brass vessel, A, half filled with 
 water, heated by means of the lamp to the boiling- 
 point ; (2) A bent glass tube, B, to which a wooden 
 scale is fixed ; (3) A cylindrical glass vessel, 0, filled 
 with mercury and the wine to be tested ; (4) A 
 cylinder of sheet-brass, in the upper part of which a 
 thermometer, T, is fixed. The glass vessel, 0, is 
 filled with mercury to the mark, a, and then com- 
 pletely filled with the liquid to be tested. The boiling- 
 vessel is now affixed, the brass cylinder drawn over 
 the mercury tube, and the thermometer inserted. 
 Heat is applied, and the water raised to the boiling- 
 point ; the steam ascends into the brass cylinder, and 
 heats the wine and mercury to the boiling-point of 
 water. The wine expands, and is partly vaporised, 
 forcing the mercury up the arm, B, which has been 
 previously graduated by experiments with fluids of 
 known alcoholic contents ; the mercury of course 
 rises the higher the more .alcohol there is contained in the wine. The variable consti- 
 
SECT. VI .] 
 
 WINE MAKING. 
 
 725 
 
 tuents of the wine, the extractive matter, &c., do not influence the result. The 
 carbonic acid must have been removed previously by filtering the wine through freshly 
 burnt lime. Equally good, if not better, results are, however, to be obtained by the 
 distillation test, effected by distilling 10 c.c. of the wine, and adding to the distillate 
 sufficient water to make a total of 10 c.c., the specific weight of the fluid giving the 
 alcoholic contents of the wine. The alcoholometer most generally employed is the 
 ebuMioacope of Tabarie (Fig. 507). With the barometer at 760 mm. water boils 
 
 Fig. 508. 
 
 at + 1 00, and alcohol at + 78'3 C. The nearer, therefore, the boiling-point of the 
 fluid tested approaches 7 8 '3, the greater the alcoholic contents. The wine is poured 
 into the vessel (7, and the cover, E II, replaced. The fluid is heated by means of the 
 lamp, L, and the steam ascends round the thermometer, t t', the height of the mercury 
 of which, when the fluid boils, varies inversely as the alcoholic contents of the wines 
 tested. The vessel M M' is filled with cold water, to hasten the condensation of the 
 vapours. If the boiling-point of pure water be taken at 99-4 C., the following boiling- 
 points show the quantity of alcohol contained : 
 
 96-4 C. 3 per cent, alcohol 
 
 95'3 , 4 
 
 94'3 
 
 927 
 91-9 
 
 91-1 C. 9 per cent, alcohol 
 
 9O'2 , 1O i, 
 
 11 >< 
 
 12 
 
 , 13 
 14 
 
 >4 
 
 Latterly, the ebullioscope of Malligand and Vidal has come into use in France and 
 Germany. It consists of a brass vessel, F (Fig. 508), of the form of a truncated cone, 
 and is connected at its bottom with a vessel, bent in the shape of a ring. A lid, 
 which can be screwed on, and which is provided with two apertures, closes the vessel 
 
726 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 ^perfectly air-tight. One of the apertures receives the refrigerator, 7?, and the 
 other the thermometer, T. The thermometer is horizontal, and is provided with a 
 scale, upon which the vol. percentages of alcohol are shown, from o to 25. The 
 boiler is first filled with water, which is heated to boiling by the spirit-lamp, L, and 
 the thermometer is read off. Boiling-point answers to the nul of the alcoholic scale. 
 The vessel is then filled with the wine in question up to a ring in the inside, and 
 its proportion of alcohol is found by heating to the boiling-point. Wines very rich 
 in alcohol are first diluted with an equal volume of water before being submitted to 
 the experiment. 
 
 Amagat's ebullioscope (Fig. 509), in order to compensate for the height of the baro- 
 meter, has, in addition to the wine-boiler, A, a similar boiler, 7?, for water. The pipes 
 leading to the funnels, C and D, are surrounded by the coolers, R. 
 When the instrument is to be used, 50 c.c. of the wine in question 
 are introduced into A through the funnel C, and 15 c.c. water into 
 B through D, and it is heated to a boil by means of the spirit-lamp, 
 L. The thermometer F shows the boiling-point of water, accord- 
 ing to which the scale G is fixed by means of the handle, k, so that 
 the result can be read off on the thermometer E. 
 
 Red French wines contain 9 to 14 percentage by volume of 
 alcohol; Burgundy, 9, 10, and n percent.; Bordeaux, 10, u, and 
 1 2 per cent. Other French wines contain 8 to i o per cent. ; the 
 wines of the Palatinate, 7 to 9*5 per cent. ; Hungarian wines, 9 to 
 ii per cent. Champagne contains 9 to 12 per cent.; Xeres, 
 17 per cent.; Madeira, 17 to 23-7 per cent. Acids exist in all 
 wines, and are generally carbonic, succinic, tartaric, malic, and 
 acetic acids ; these acids are found partly free, partly combined as 
 salts ; tartaric acid, for instance, as cremor tartari, potassium bitar- 
 trate, and other acid tartrates. Faure found an essential gum, 
 which he termed oenanthin, and which, with glycerine first shown 
 by Pasteur in 1859 to be a normal constituent of wine helps to 
 give a certain consistency to the wine. Pohl found (1863) in 
 Austrian wines 2'6 per cent, glycerine. As wine ages the glycerine disappears. The 
 colouring matter of wine is of interest in the case of red wines only, as the yellow-brown 
 colour of some wines is undoubtedly due to oxidised extractive matter. The colouring 
 matter of red wines has received from Mulder and Maumene the name of renocyanine, 
 while it is commonly termed wine-blue; it is a blue substance similar to litmus, pos- 
 sessing the property of turning red in the presence of acids. It is insoluble in water, 
 alcohol, ether, olive oil, and oil of turpentine ; but soluble in alcohol containing small 
 quantities of tartaric or acetic acid. With a trace of acetic acid the solution is practi- 
 cally blue, turning red upon the addition of more acid ; neutralised with alkalies, the 
 solution remains blue. On the evaporation of a wine to dryness the extractive matter 
 remains, consisting of a mixture of non-volatile acids, the salts of organic and inorganic 
 acids, with cenanthin, colouring matter, sugar, protein substances, and extractive 
 matter, the nature of which is unknown. The quantity of extractive matter differs 
 greatly, varying with the kind of wine and the degree of fermentation of the sugar. 
 Fresenius found in Rhine wines a maximum of io - 6 and a minimum of 4' 2 per cent, 
 of extractives; Fischern, in the wines of the Palatinate, from io'7 to 1*9 per cent. ; in 
 Bohemian wines, 2*26; in Austrian, 2-64; in Hungarian, 2-62 per cent. The mineral 
 constituents of wines exist in but small quantities as an average in old Madeira, 
 0-25 per cent.; in old Rhine wines, 0-12 per cent.; and in old ports, 0-235 per cent. 
 Van Gockom, Veltmann, and Mosmann found in 1000 parts of wine 
 
SECT. VI.l 
 
 WINE MAKING. 
 
 727 
 
 Madeira . 
 Teneriffe . 
 Khine wine 
 Port 
 
 2-55 parts of ash 
 
 2-91 
 
 i '93 i, 
 
 2'35 
 
 Pohl estimated the following number of parts ash in 100 parts of wine: 
 
 Bohemian 
 Croatian . 
 Carniola . 
 Lower Austrian 
 
 1-97 part 
 1-68 
 1-81 
 2'oo parts 
 
 Slavonian . 
 Styrian 
 Tyrol 
 Hungarian 
 
 1-91 part 
 
 1-63 ,, 
 
 1-84 
 i -80 
 
 The ash contains potash, lime, magnesia, soda, sulphuric acid, and phosphoric acid. 
 
 The ffandtuorterbuch der Reinen und Angewandten Chemie (Bd. ix. Seite 676) gives 
 the following analyses of wine-ash, the first four being by Crasso, and the fifth by 
 Boussingault : 
 
 Ash of Wine. 
 
 i. 
 
 2. 
 
 3- 
 
 4- 
 
 5- 
 
 Ash (per cent) .... 
 
 0-26 
 
 0-34 
 
 0'4I 
 
 0'29 
 
 0-18 
 
 
 6?-!; 
 
 6vo 
 
 71"? 
 
 62'O 
 
 A.1'1 
 
 Soda 
 Lime 
 Magnesia 
 Iron oxide 
 Manganese oxide 
 Phosphoric acid 
 Sulphuric acid 
 
 0'3 
 5*2 
 3 '3 
 07 
 0-8 
 
 IS'5 
 5 '2 
 
 2'O 
 
 0-4 
 
 3'4 
 47 
 0-4 
 07 
 16-8 
 5 '5 
 
 2*1 
 
 I '2 
 
 3'4 
 4'0 
 O'l 
 O'l 
 I4-I 
 
 3'6 
 
 I "2 
 
 2'6 
 
 5'i 
 4-0 
 0-4 
 0-3 
 17-0 
 
 4 '9 
 
 2 '2 
 
 4'9 
 9'2 
 
 22'I 
 
 5'3 
 O'l 
 
 Potassium chloride 
 Carbonic acid 
 
 i'5 
 
 2'I 
 
 I'O 
 
 i '5 
 
 I3-3 
 
 
 IdO'O 
 
 100 'O 
 
 ICO'O 
 
 IdO'O 
 
 lOO'O 
 
 For the determination of glycerine in sweet wines 50 c.c. of the sample are mixed 
 in a capacious flask with 10 grammes sand and slaked lime in powder and heated on 
 the water bath until no more lime is dissolved, all the sugar is converted into sugar- 
 lime, and the mass, after prolonged heating, has still a caustic smell. 100 c.c. of alcohol 
 at 96 per cent, are gradually added, the whole is well shaken, the precipitate is allowed 
 to settle, the largest part of it is decanted or passed through a flannel filter, the residue 
 is twice washed with alcohol (filtered), the precipitate is rinsed upon the filter, drained, 
 washed again if the filtrate is slightly yellowish, the alcohol is expelled from the filtrate, 
 and the residue is treated like the first evaporation residue of a common wine. 
 
 Concerning the odoriferous constituents of wine, which often determine its value, 
 nothing trustworthy is yet known. That compound which gives wine its peculiar 
 odour is a mixture of renanthic ether with alcohol. But, according to an investigation 
 of Neubauer's, cenanthic ether is a compound of different substances, of which the most 
 important are caprylic and capric ethers, and is a product of the fermentation of the 
 must. The bouquet (German : Blume) is probably a mixture of ethers formed during 
 fermentation, but which, on account of their extremely minute quantity, have not been 
 distinguished and insulated. 
 
 Neubauer justly says in his Chemie des Weines : " Everything which art has yet 
 -done to imitate the aroma of wine, in spite of the enticing names by which it is 
 advertised, is a miserable sham [elendes Machwerk]. Our chemical knowledge of the 
 bouquet is extremely trifling, and science, with her present resources, is impotent as 
 against the genii of wine." 
 
 The Diseases of Wine. Wines are subject to various causes of deterioration, termed 
 maladies, distempers, or diseases. That most commonly occurring is ropiness or 
 viscidity, the cause of which was for a long time unknown. Fra^ois showed that it 
 
728 CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 was due to the decomposition of the glucose into azotised matter and mannite, and at 
 the same time indicated the proper remedy the addition of tannic acid. He employs 
 15 grammes of tannin to 230 litres of wine. This is well mixed with the wine, which is 
 allowed to stand for a few days. At the end of this time the tannin will have separated 
 the azotised matter, and the wine may be bottled off. 
 
 The souring of wine is due to the conversion of the alcohol into acetic acid, caused, 
 according to Pasteur, by the formation of the vinegar plant, or Mycoderma aceti, which 
 he found in all sour wines. This disease is very common, and may result from too 
 small a proportion of alcohol, too high a temperature of the cellars, or exposure to 
 the atmosphere. The wine, if too far soured, is fit only for making vinegar ; but 
 slight cases can be remedied by an addition of sugar. The formation of vinegar may 
 be somewhat delayed by impregnating the wine with sulphurous acid. In some 
 cases the acetic acid may, by the addition of tartaric acid, be removed as acetic ether ; 
 but the acetic acid can never be neutralised with alkalies, as the salts formed are 
 very easily soluble. 
 
 The bittering of wine, or its acquirement of a bitter flavour, is due to another 
 cause, the formation of a bitter substance, which develops as the wine ages, or at too 
 high a temperature. Maumene suggests as a remedy the addition of slaked lime in 
 the proportion of 0-25 to 0-50 gramme per litre. Bittering is due also to the formation 
 of brown aldehyde resin. Mould in wines appears as a white vegetable (fungus) film 
 covering the surface, and arises from an insufficiency of alcohol ; consequently, weak 
 wines are more subject to this malady. The film of mould should be removed and the 
 wine used as soon as possible, for wine affected with this disease soon turns sour. The 
 decaying of a wine is due to the dissipation of the alcohol and the decomposition of 
 the acids of the wine ; the wine obtains an astringent taste and a dim, thick colour, 
 finally turning sour. The potassium bitartrate is converted into potassium carbonate, 
 affecting the colouring matter, and tannic acid, which pass over into humus substances. 
 At the commencement of this decomposition a remedy may be found in the addition of 
 a small quantity of sulphuric ether. Caskiness, or the taste of the cask, due to an 
 essential oil formed in casks that have long stood empty, is best removed by the 
 addition to the wine of a small quantity of olive oil, and agitation ; the olive oil 
 absorbs the essential oil, and brings it to the surface of the wine, whence the oily 
 matter may be skimmed, or the wine may be filtered through freshly burnt 
 charcoal. All casks and vessels that have stood long empty should be well steamed 
 before use. 
 
 Pasteuring. Pasteuring, a term which usage has substituted for pasteurisation, 
 or the conservation and artificial ageing of wines, according to Pasteur's method, is 
 a great improvement in the general treatment of wines to ensure their keeping. It 
 consists essentially in heating the wine to 60 C., and for this purpose the apparatus 
 designed by Rossignol is best suited. A metal cask, T (Fig. 510), contains at the 
 bottom a copper vessel, (7, with a trumpet-shaped cover extending in the open tube, c, 
 above the top of the vessel T ; t is a thermometer. Water is poured into the vessel, 
 C, until the tube c is three parts full. The wine is placed in the metal cask, T, and, 
 by means of the tap, r, and the tube/, run off into the cask f, when sufficiently 
 heated. The water in the copper vessel, C, is employed to prevent the direct heating, 
 by the flame, of the vessel containing the wine, and the consequent burning of any 
 insoluble matter settling to the bottom of the vessel. Fig. 511 shows in detail the 
 manner of fastening the vessels together. A copper ring, a, encircles the vessel T, and 
 beds with the walls of this vessel into the india-rubber band, d, into which it is pressed 
 by the tightening of the bolts, e, binding the ring of angle-iron and lower iron ring, 6, 
 together. The joint is thus rendered water-tight. The vessel T is not quite filled 
 with wine, to allow for expansion under heat , by this means the wine is exposed to a 
 
WINE MAKING. 
 
 729 
 
 known quantity of air. Wine should not be artificially aged in contact with air, as 
 Pasteur has proved that such processes deteriorate the colour and the flavour of the 
 wine ; and in ordinary cases, where part of the process of ageing consists in heating 
 the wines for a short time in an open vessel with a full exposure to air, the wine 
 acquires a peculiar boiled flavour, goilt de cuit, easily recognisable by the connoisseur. 
 By Pasteur's method, however, neither the flavour nor the colour of the wine is deterio- 
 rated ; indeed, the latter is improved by the expulsion of the carbonic acid. 
 
 Pasteur has shown that most of the diseases of wine (acetification, ropiness, 
 bitterness, and decay or decomposition) are due to the growth of different fer- 
 ments, consisting of minute vegetable cells, always existing in wines, and becoming 
 active and destructive under certain conditions, such as change of temperature and 
 oxidation. He recommends * that these plants or fungi should be kitted, as 
 the best means of ensuring the keeping of the wine, and the particular modus 
 operandi selected is essentially the following, differing considerably from the fore- 
 going method. The bottles are quite filled, the wine touching the cork, which is 
 inserted with such a degree of firmness that the wine in expanding may force tho 
 
 Fig. 510. 
 
 Fig. 512. 
 
 Ffg. 511. 
 
 cork out a little, but not so much as to admit air into the bottle. The bottles are 
 then placed in a chamber heated to 45 to 100, where they remain for an hour or two, 
 after which they are removed, set aside to cool, and the cork driven in. By this means 
 the life or active principle of the fungi is destroyed, while the wine acquires an 
 increased bouquet, is of a more beautiful colour, and, in fact, is to a considerable extent 
 aged. Both new and old wines can be thus treated. 
 
 For heating wine in its own casks, Ballo proposes an apparatus, the hygrothermant. 
 The liquid, heated in the spiral, ascends through the tube, a (Fig. 512), into the cask, 
 and cold wine enters in its place through b. The circulation begins with the smallest 
 difference in temperature between a and b, and lasts to the boiling-point. The 
 apparatus depends on the principle of heating by hot water. The novelty here is that 
 the cold- and hot-water pipes, on their exit from the source of heat, unite to a single 
 tube in which the two opposite currents are separated by a thin metal partition. The 
 form of the pipe is shown in Fig. 513. 
 
 * Comptes-Rendus. May I, 29; August 14, 1865. 
 
73 o CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 Clearing or Fining the Wine. Most wines are self -clearing, the ferment settling to 
 the bottom of the cask, and leaving the wine clear and pure. This applies chiefly to 
 dry wines, which have less sugar than sweet wines. The sweet wines are generally 
 more thickly fluid on account of the quantity of sugar they contain, and consequently 
 more frequently need clearing. Fining, as it sometimes called, or clearing, consists in 
 adding to the muddy wine some albuminous or similar substance that will mix with 
 the suspended matter and carry it to the bottom or bring it to the surface of the wine. 
 The substances most generally employed are white of egg, ox-blood, and milk, or 
 mixtures of these substances. " Plastering," or the addition of gypsum to the must, is 
 said to improve the colour of red wines, and, by taking up water, it increases the relative 
 proportion of alcohol, which retards the fermentation, and thus gives more time for the 
 extraction of colouring matter. It converts the soluble potassium salts into insoluble 
 lime salts and potassium sulphate. As the plastered wine contains potassium sulphate 
 in quantity and remains saturated with gypsum, wine thus treated has probably un- 
 pleasant and injurious effects on the human organism ; the addition of gypsum to wine 
 is to be unconditionally condemned. 
 
 Hugounenq recommends, instead of gypsum, an addition of calcium diphosphate as a 
 clarifying and preservative agent. " Phosphatage " is said to have all the good effects 
 of plastering without increasing the proportion of sulphates and diminishing that of 
 phosphates. 
 
 Residues from the Production of Wine. The waste of wine making consists of the 
 stems, husks, and seeds of the grapes, as well as of the fermentary sediment and tartar. 
 Both descriptions of waste find numerous applications. The lees left from the pressing 
 of the wine contain a not unimportant quantity of must, which (i) is employed in 
 preparing an inferior wine ; (2) in the making of an inferior brandy ; (3) in the pre- 
 paration of verdigris (see page 458) ; (4) in vinegar making, and for promoting the 
 formation of vinegar from saccharine or alcoholic fluids. (5) In wine-making countries 
 the lees are much employed as fodder for horses, mules, and sheep; while (6) the 
 residue of the after-pressing or final pressing is used as manure. (7) The grape seed 
 yields an oil in quantities of 10 to u per cent., or (8) tannic acid in large quantities. 
 The oil can be extracted by pressure or by treatment with benzole, or with carbon 
 disulphide. The tannin obtained can be employed for the preservation of hides, &c. 
 (9) Potash is prepared from the calcined lees. (10) The stalks and seeds when calcined 
 are employed in the preparation of a black colouring material (vine black), (n) The 
 ferment and stalks are in some wine-producing countries, besides being employed in 
 the preparation of tartar and potash, also used in the distillation of a peculiarly rich 
 brandy, in which an oil is found possessing highly the flavour of cognac, and known in 
 commerce as wine oil, cognac oil, huile de marc. (12) Crude tartar is found with 
 calcium tartrate, colouring matter, and yeast, forming a more or less thick crust on the 
 walls of the wine cask or in the crust deposited in the wine, but not firmly attached to 
 the vessel, and is the chief source of the pharmaceutical potassium bitartrate (C 4 H 5 KO 6 ) 
 and tartaric acid. 
 
 Effervescing Wines. Effervescing wines have been known for many centuries. 
 Some of Rembrandt's paintings exhibit, among the accessories, a champagne glass with 
 effervescing wine. And from Yirgil 
 
 " Ille impiger hausit, 
 Spumantem pateram " 
 
 it would appear that this description of wine was known to the Romans. In 1870 
 there were in Germany fifty producers of effervescing wines, with a production of 2^ 
 to 3 1 millions of bottles, i| million of which were exported. In France the pro- 
 duction amounts yearly to 16 to 18 millions of bottles. 
 
 All wines are capable of being produced as effervescing wines if bottled before the 
 
SECT, vi.] WINE MAKING. 731 
 
 fermentation is over. By bottling at this period the carbonic acid is retained in the 
 wine, and, when the bottle is opened, the disengagement of the gas causes the appear- 
 ance of effervescence. In this country the effervescing wine most generally known is 
 champagne ; but hocks, Moselles, and even red wines are very admirable when thus 
 treated. If the wine contains much sugar, the fermentation is arrested in the bottle 
 before all the sugar is consumed, producing a sweet effervescing wine. On the other 
 hand, if the sugar is all exhausted in producing the carbonic acid, the result is a dry 
 effervescing wine. These wines are very agreeable to the palate, and may be supposed 
 to assist the digestion of the food with which they are taken ; but, when new, they 
 are dangerous, as being likely to communicate their state of change to the contents 
 of the stomach, interfering seriously with digestion, and producing what is well known 
 as " acidity." Dry effervescing wines are less likely to disagree than sweet wines of 
 this class containing much sugar and fermentable matter. The connoisseur places 
 great reliance in his judgment of a champagne upon the loudness, or rather sharpness, 
 of the report when the cork is drawn, and upon the " bead " or bubble formed on the 
 side of the glass by the carbonic acid gas. These effects are not proportionate, for 
 while a loud report results from an extended fermentation, a good bead may 
 be obtained with a very weak fermentation. The gas in a bottle of champagne 
 exerts a pressure of some 5 atmospheres, and it will at once be evident that if 
 the bottle be made a little smaller, reducing the space between the cork and the 
 wine only one-twentieth, a considerable increase in loudness of the report will 
 ensue. 
 
 The process of manufacturing effervescing wines is in general the following : The 
 best grapes are used for this purpose ; for champagne, the black grape, called by the 
 French noirien, is employed. The juice is expressed from the grape as soon after 
 gathering as possible, in order to prevent the colouring matter of the skin affecting the 
 wine ; while the fruit is pressed as quickly and as lightly as possible. The juice from 
 the second and third pressings is reserved for inferior, or red-tinted effervescing wines. 
 The expressed juice is immediately poured into tuns or vats, where it is left to stand 
 for twenty-four to thirty-six hours. In this time any earthy matter or vegetable im- 
 purities will have settled, and the juice is ready to be transferred to the fermenting 
 vats, where it remains for about fifteen days. It is then put into casks, which are 
 securely bunged ; sometimes brandy is added in the proportion of one bottle to one 
 hundred bottles of juice or must. Towards the end of December the wine is fined 
 with isinglass, and a second time in the ensuing February. About the beginning of 
 April the clear wine is fit for bottling. It now contains, if a good wine, 16 to 18 
 grammes of sugar, u to 12 per cent, of the volume of alcohol per bottle, and an 
 equivalent to 3 to 5 grammes of sulphuric acid in free acids. 
 
 Great care is necessary in the manufacture of champagne bottles ; they must be 
 free from flaws, and made of pure materials. Generally each bottle is from 850 to 900 
 grammes in weight, and equal in thickness throughout. Formerly the flawed bottles 
 amounted to 15 to 25 per cent., but recent improvements in manufacture have reduced 
 the percentage to 10. Before the wine is introduced, the bottle is rinsed with a liqueur 
 of white sugar-candy 150 kilos., wine 125 litres, and cognac 10 litres, the liqueur being 
 .allowed to remain in the bottle : according to F. Mohr, the cane sugar of the liqueur 
 becomes converted into grape sugar in the champagne. It is doubtful whether glycerine 
 might not be advantageously substituted for a portion of the sugar of the liqueur. 
 The liqueur employed varies with the flavour of the wine : port, Madeira, essence of 
 muscatels, cherry water, &c., are used, but rarely unmixed with some other favourite 
 solution of the manufacturer, as, for instance, water 60 litres, saturated solution of 
 alum 20 litres, tartaric acid solution 40 litres, tannin solution 80 litres. About 2 litres 
 of this mixture would in practice be added to a butt of wine. The bottles are filled by 
 
73 2 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 women, the proportion of liqueur introduced being about 15 to 16 per cent, of the 
 wine. A space of about 2 to 3 inches is left between the wine and the cork, which, 
 after being thoroughly moistened, is next inserted by a machine. The bottle is then 
 passed to a man, termed in the French establishments the maillocher, who drives the 
 cork home with a mallet. Another process, now generally effected by the aid of a 
 machine, is the "wiring" or securing the cork with wire or string. The bottles are 
 now conveyed to a cellar, where they are laid in horizontal racks against the wall. 
 In about eight or ten days a deposit, termed " griffe," is formed, and shows that the 
 time has arrived for the wine to be transferred to the cellar where it is to remain 
 until sold to the merchant. The deposit is allowed to form during the summer, and in 
 the ensuing winter means are taken for its removal. The bottles are well shaken, and 
 placed with their mouths downwards, to cause the deposit to settle on the cork. The 
 cork being removed, the sediment falls out, when more liquor is added, and the bottle 
 re-corked and again wired. The bottle is now laid upon its side at an angle of about 
 20, and in about eight to ten days the inclination is gradually increased until the 
 vertical position is attained, when, by a dexterous movement of the cork, the gas is 
 permitted to force out the remaining sediment. This process is repeated as many 
 times as may be necessary, until the wine is perfectly clear. Wine thus prepared, 
 generally known as sparkling wine, inn mousseux, is ready for the consumer at the end 
 of from eighteen to thirty months, the time varying with the temperature of the season. 
 One of the greatest causes of loss is the bursting of the bottles, sometimes as much as 
 30 per cent, of the wine being wasted. This in some measure accounts for the dearness 
 of these wines. 
 
 By the analysis of several sparkling wines (1867 and 1870) the following results 
 were obtained : 
 
 
 
 
 
 
 
 
 
 *' 
 
 ' 
 
 3- 
 
 
 
 
 
 Per mille. 
 V3OO 
 
 Per mille. 
 e-qoo 
 
 Per mille. 
 7-^00 
 
 Per mille. 
 7-800 
 
 Per mille. 
 6"2OO 
 
 Per mille. 
 6*500 
 
 
 Per cent. 
 
 Per cent. 
 
 Per cent. 
 
 Per cent. 
 
 Per cent. 
 
 Per cent. 
 
 Alcohol 
 
 Sugar . . . .:.:,.! 
 Extractive matter .... 
 Specific gravity .... 
 
 8-400 
 8-200 
 1 1 -600 
 1-036 
 
 9-500 
 4-300 
 7-500 
 1-029 
 
 8-500 
 6-900 
 9-800 
 1-039 
 
 8*400 
 9'100 
 I2'OOO 
 1-046 
 
 9'8oo 
 7-500 
 1 1 -600 
 1-039 
 
 8-400 
 5-400 
 15-200 
 1-041 
 
 No. i came from Chalons; Nos. 2, 3 and 4 from Wiirtzburg, 2 being for export to 
 India ; 3 being the manufacture of J. Oppmann, and 4 of Silligmiiller, both well-known 
 German firms. No. 5 came from Sotaine & Co., of Rheiins, and 6 from a well-known 
 Rhenish firm, glycerine being substituted for a portion of the sugar. 
 
 Improving Wine Musts and Artificial Wines. The worth or character of a wine is 
 determined by its aroma and the amount of alcohol and free acid contained decreasing 
 with an increase of the latter, and increasing with increase of the former. The pro- 
 portion between the chief constituents of the grape-juice, sugar, acid, and water, is 
 nearly equal in all good wines, and this proportion is never accidental, but always 
 belongs to a good wine. The grapes not fitted for making good wines are treated in 
 two ways : either the expressed juice is allowed to ferment as it is, in which case an 
 inferior wine is obtained ; or, by the study of chemical analyses of good wines, the in- 
 complete constituents are supplied, and others injurious to the wine removed, to make 
 the must of that quality which will yield a good wine. The following are the best 
 methods of improving the must : 
 
 1. The addition of sugar to wine poor in this constituent, and the neutralisation of 
 an excess of acid by means of pulverised marble (Chaptal's method). 
 
 2. The addition of sugar and water to must poor in sugar and rich in acid (Gall's 
 method). 
 
SECT, vi.] WINE MAKING. 733 
 
 3. Repeatedly fermenting the husks with sugar-water (Petiot's method). 
 
 4. Removing the water by means of freezing, or by treatment with gypsum. 
 
 5. Removing the acid by means of a chemical reaction. 
 
 6. Addition of alcohol to poor wines. 
 
 7. Treating the prepared wine with glycerine (Scheele's method). 
 
 The addition of sugar to must poor in this constituent is the oldest method of im- 
 provement, and appears to have been known to the Greeks and Romans. At that time 
 cane sugar was unknown, honey being used for sweetening purposes, which, being 
 added to the wine, gave it a peculiar flavour, and rendered it thick. In years when 
 honey was scarce, we are informed that the wine was inferior. Chaptal, in 1800, wrote 
 a work on the cultivation of the grape, in which he gives a recipe for adding sugar to 
 an inferior must, to render the wine equal to that of better years, the acid being 
 neutralised with pieces of marble. In Burgundies, Chaptal's method is not much 
 required to be used, as these wines rarely contain more than 6 parts per 1000 of free 
 acid. The amount of pulverised marble (calcium carbonate) required to neutralise 
 60 parts of free acid is, as a rule, 50 parts ; and the amount of sugar to be added, 
 when the acid is in excess, is 100 parts for each 50 parts of alcohol required after 
 fermentation, it being found that 15 per cent, of sugar in the must produces 7-5 per 
 cent, of alcohol in the prepared wine. Thus, should it be desired to heighten the 
 alcoholic contents from 7*5 to 10 per cent., 50 kilos, of sugar are added to every 
 1000 kilos, of must. 
 
 The cause generally of the poorness of the must in sugar is a wet or cloudy season, 
 during which there has been but little warmth from the sun to ripen the grapes. 
 Most German wines show, besides a lack of sugar, a superabundance of malic and 
 tartaric acids ; and while the addition of a sugar solution increases the alcoholic con- 
 tents, it does not remove these acids, which impart a flavour to the wine and lessen 
 its worth. The addition of saccharine solution does not, as might be expected, enfeeble 
 the bouquet of the wine if pure starch sugar, containing no dextrine, be employed. 
 The use of impure starch sugar causes a quantity of unfermented matter to remain in 
 the wine, imparting to it a tendency to decay. Gall's method is found to be economical, 
 as a flavouring material can be added to very inferior must. According to Gall, a 
 normal must should consist of 
 
 Sugar . . . . . . 24*0 per cent. 
 
 Free acid . . . . . o'6 
 
 Water 75-4 
 
 100 X> 
 
 1000 kilos, of such a must contain, therefore, 240 kilos, of sugar, 6 kilos, of free acid, 
 and 754 litres of water. If, by analysis, the must to be improved yields only 167 per 
 cent, sugar and o'8 per cent, acid, there are to be added 153 kilos, of sugar and 180 
 kilos, or litres of water, by which addition 1333 kilos, of normal must are obtained, 
 corresponding to an increase in quantity of 33 per cent. ; while in some years, when 
 the acid contents are as much as 12 to 14 per cent., the increase in quantity rises to 
 100 to 115 per cent., but seldom more. 
 
 Petiot based his method on the fact that, according to the usual process of pre- 
 paring the must, the colouring arid bouquet constituents remaining in the marc are 
 sufficient to give the flavour and odour of wine to a lixivium of sugar-water. This 
 method may therefore very justly be considered as yielding a wine without the aid of 
 grape-juice. To the marc left after the expressure of the grape-juice cold water is 
 added, equal in quantity to the must removed : in this water the marc is allowed to 
 macerate for two to three days. The water takes up the various soluble constituents 
 of the marc; after the time specified the liquor is removed, and the amount of sugar 
 
734 CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 and acid it contains ascertained. There is usually only 2 to 3 per cent, of sugar ; con- 
 sequently, an addition of 17 to 1 8 per cent, must be made ; and if there should be too- 
 little acid, tartaric acid must be added to approximate to the acid contents of a normal 
 must. The artificial must, as it may be considered, is then put into the fermenting 
 vat, while the marc is again treated in a similar manner, a longer immersion being this 
 time required. The resulting wines are darker in colour than wines prepared from the 
 natural must, in consequence of a larger proportion of tannin. The flavouring of these 
 wines is a matter of experience, and does not fall under any chemical consideration. 
 
 Freezing is employed in the improvement of wine, for the purpose of reducing the 
 aqueous contents. According to the experiments of Vergnette-Lamotte and Bous- 
 singault, the effect of cold upon wine is of a very complicated nature. By cooling the 
 wine at a temperature of o'6 there first occurs the precipitation of those substances 
 that are insoluble at this temperature. These consist of cream of tartar, colouring 
 matter, and nitrogenous substances, and a fluid possessing the property of becoming 
 solid at 6. When these substances are removed the wine becomes more ardent, richer 
 in alcohol, and its peculiar merit is that it is not liable to after-fermentation, and can 
 be kept in vats and half-empty casks. The removal of the acid from wine is effected 
 best by means of calcium carbonate (pulverised marble, chalk), sugar of lime, or neutral 
 potassium tartrate. An addition of calcium carbonate to the must, or to the wine, is 
 not detrimental, in so far that the wine retains none, or a very small quantity, of the 
 lime-salt. Calcium carbonate will not be of service in the case of so-called acid fermen- 
 tation, as calcium acetate will then be formed, and the wine is no longer worthy the 
 name. Liebig recommends the use of neutral potassium tartrate for this purpose, as 
 potassium bitartrate is formed, which settles as an insoluble salt on the sides of the 
 vessel or bottle. The use of this neutralising agent has the merit, moreover, of not 
 injuring the flavour and odour of the wine. Sugar of lime can be employed in the 
 case of wines not containing acetic acid. To prepare the sugar of lime, slaked lime is 
 diluted with ten times the quantity of water, to form a thin cream. This cream is 
 thinned with sufficient water to obtain a milk of lime, in which sugar-candy is dissolved. 
 The solution is left to stand, and the clear supernatant liquor a solution of sugar of 
 lime decanted to mix with the wine as required. When the wine is treated with the 
 sugar of lime solution, the lime forms with the acid of the wine an insoluble salt, which 
 is precipitated, while the sugar remains in the wine. 
 
 Another addition to wine, hardly bearing upon its improvement, but effected as a 
 means for its preservation during removal or exportation, is that known in France as 
 the vinage, a certain quantity of brandy being mixed with the prepared wine. When 
 the wine is to be exported from France, the law permits the addition of 5 litres of 
 brandy to each hectolitre of wine, provided the alcoholic contents after the addition do 
 not exceed 21 per cent. But experiments have proved that the wine delivered to 
 private consumers does not on the average contain more than 10 to n per cent, of 
 alcohol, while the wine delivered to retail firms averages 16 to 17, and to wholesale 
 firms 22 to 24 per cent. To prevent this fraudulent proceeding, the operation of 
 vinage is permitted only in the Departments of the Pyrenees-Orientales, Aude, Herault, 
 Garde, Bouches-du-Rhone, and Var, immediately under the inspection of the Com- 
 missioners appointed to this duty. In 1865 Scheele introduced his method of improv- 
 ing wine by the addition of glycerine, the addition being made after the first fermenta- 
 tion has subsided. The limits of the addition lie between i to 3 litres of glycerine to 
 I hectolitre of wine. But the expense will not permit of extended operations. 
 
 It is to be remarked that if a must is sweetened with starch sugar, a substance 
 (dextrine) is introduced which is absent in natural wines [and which probably prevents 
 the formation of a fine aroma, doubtless the reason why malt vinegars are deficient in 
 the odour and flavour of wine, fruit, and cane-sugar vinegar]. 
 
SECT. vi.J BEER BREWING. 735 
 
 Cider. A must obtained from apples contained before and after filtration ia 
 100 c.c. 
 
 Must (Filtered). Cider. 
 
 Alcohol .... ... 5 -800 centimetres 
 
 Extract .... 16-250 ... 2-360 grammes 
 
 Ash .... 0-350 ... o '310 gramme 
 
 Malic acid . . . 0-330 ... o'3io ,, 
 
 Acetic acid ... ... 0*080 
 
 Sugar .... 12-500 ... 0-750 
 
 Pectin .... 0-620 ... trace 
 
 Lime .... 0*025 0-024 
 
 Magnesia . . . 0*018 ... 0*018 
 
 Potassa .... 0*106 ... 0-105 > 
 
 Phosphoric acid . . 0-024 ... 0-022 
 
 Sulphuric acid . . 0*009 0*680 (?) 
 
 Glycerine ... ... 0*680 
 
 Tartaric and citric acids were absent. Hence cider is distinguished from grape wine 
 merely by the complete absence of tartaric acid and the corresponding larger pro- 
 portion of lime. The same feature distinguishes gooseberry, currant (Ribes), and other 
 fruit wines. If a moderate proportion of tartaric acid is added to cider the product 
 cannot be distinguished from wine. 
 
 APPENDIX. A. Kommir finds that an active ellipsoidal ferment, if introduced into grapes when 
 crushed at temperatures below 2i-22, multiplies more rapidly than the spores of the ferments found 
 on the skins of the grapes. If a small quantity of an ellipsoidal ferment is added to grapes at 
 temperatures above 2i-22, the ferment added develops along with the natural ferment, and modi- 
 fies the bouquet of the wine. K. Martinand has made an experimentum crwis which seems to con- 
 firm the author's theory. He divided the grapes of one and the same vine into five lots, and added 
 to each lot a different ferment to (i) that of a must of cherries in full fermentation ; (2) of Beau- 
 jolais ; (3) of Burgundy ; (4) of champagne ; (5) of Bordeaux. All these wines presented distinct 
 flavours. Chemical News, vol. Ixi. p. 277. 
 
 BEER BREWING. 
 
 By beer, in the ordinary meaning of the word, we understand a spirituous liquor 
 still in the state of secondary fermentation, obtained from germinating amylaceous 
 seeds, chiefly barley (or wheat, latterly also rice), and hops, water, and yeast, by fermen- 
 tation, but without distillation. According to the views of the German Brewers 
 Association and the International Medical Congress at Brussels (1874), with which the 
 conclusions of the Imperial Sanitary Department coincide, only liquors brewed from 
 cereals and hops, fermented, but still in a state of secondary fermentation, have a right 
 to be regarded as beer. 
 
 Materials far Beer Brewing. The materials of beer brewing are: (i) Grain, or 
 amylaceous substances ; (2) hops ; (3) a ferment ; (4) water. 
 
 The Grain. The grain selected for this purpose is generally barley, as containing 
 the proportion of sugar and starch best adapted to form alcohol. Many substitutes 
 have been suggested, but with less success. In Bavaria, the large double barley 
 (Hordeum distichon) is preferred. According to Lermer, 100 parts of dried barley 
 contain 
 
 Starch 68-43 
 
 Protein substances 16-25 
 
 Dextrine 6-63 
 
 Fat 3-08 
 
 Cellulose 7-10 
 
 Ash and other constituents . . . . 3*51 
 
 The ash of barley contains in 100 parts 
 
736 CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 Potash 17 
 
 Phosphoric acid 30 
 
 Silicic ac'd 33 
 
 Magnesia . . 7 
 
 Lime 3 
 
 with other constituents. Potatoes, rice, maize, glycerine, and potato or starch sugar 
 are employed in some modern breweries. 
 
 A good barley for brewing should be rich in starch, so that, when malted and con- 
 verted into wort, it may give the highest proportion of extract. It must have a 
 thorough germinating capacity, swell uniformly, and grow uniformly and rapidly if it 
 has to produce a good, sound malt. The starch of the barleycorn should dissolve 
 uniformly and rapidly ; it must be free from mould and bacteria, perfectly inodorous, 
 and in the subsequent operations it must communicate to the wort and the beer no 
 substances of a bad smell or taste. The nitrogen must not exceed a certain limit. 
 Marcker found in the highest quality of barley from the Saale an amount of proteine not 
 exceeding 9 or 9^ per cent. 100 barley grains weigh from 3 to 5-26 grammes. The 
 best barley contains 6| per cent, of husk ; other qualities up to 24/2 per cent. 
 
 Barley for distilling must have coats of a very uniform thickness. It should have 
 a high percentage of proteine, which is converted into diastase, capable of transforming 
 starch into maltose and dextrine. 
 
 For judging the quality of a barley for brewing a high germinating power is required. 
 A good barley should have a germinating power of from 88 to 90 per cent. The barley 
 should also grow uniformly. The weight of the grains and their degree of clearness 
 should also be regarded. A germinating bed is prepared as follows : Fine sand, which 
 has been previously ignited, is laid upon a plate so high as to touch the upper margin 
 of the cavity of the plate. So much water is added that the sand on shaking moves 
 loosely. So much more sand is then sifted evenly over the surface as to stiffen the whole. 
 The sand is then smoothed off level with the edge of the plate, and, after sowing, it is 
 covered with a second plate. 
 
 Hops. The hop (Humulus lupulus) is a disecious plant of the natural order of 
 Urticacece, the female flowers of which, or catkins, are used for flavouring beer. The 
 catkins, or strobils, are composed of a number of bracts or scales, which are green, 
 afterwards changing to a pale yellow. At the base of each flower is seated the pistil 
 containing the seed, while surrounding the pistil are a number of little grains, embedded 
 in a yellow powder, the farina, containing the active property of the hop, essentially 
 lupuline, the grains being termed lupulinic grains. This yellow pulverulent substance 
 contains an essential oil, tannic acid, and mineral constituents. The essential oil, the 
 flavouring principle of the hops, is found, in air-dried hops, to the amount of o - 8 per 
 cent. ; it is yellow-coloured, with an acrid taste, without narcotic effect, of a sp. gr. 
 = 0-908, turning litmus-paper red. It requires more than 600 times its weight of 
 water to effect a solution. It is free from sulphur, and belongs to the group of essential 
 oils characterised by the formula C 5 H 8 , and can become oxidised under contact with 
 the air into valerianic acid (C 5 H 10 O,,), this oxidation being the cause of the peculiar 
 cheesy odour of old hops ; it is a mixture of a hydrocarbon, C 5 H 8 , isomeric with the 
 oils of turpentine and rosemary, with an oil containing oxygen, C 10 H 18 0, having the 
 property of oxidation alluded to. Tannic acid is found in the several kinds of hops, in 
 quantities varying from 2 to 5 per cent., and is an important constituent, as it pre- 
 cipitates the albuminous matter of the barley and serves to clear the liquor. It gives 
 with the per-salts of iron a green precipitate ; treated with acids and synaptase, it does 
 not separate into gallic acid and sugar ; and by dry distillation it does not give any 
 pyrogallic acid. The hop resin is the important constituent of the hops, and contains 
 the bitter principle or lupuline. It is difficultly soluble in water, especially in pure 
 
SECT. vi.'J BEER BREWING. 737 
 
 water, and when the lupuline or essential oil is absent. But water containing tannic 
 acid, gums, and sugar dissolves a considerable quantity of the resin, especially when the 
 essential oil is present. It is intensely bitter in taste, and becomes foliated when 
 exposed to the atmosphere. Hop resin and the essential oil are not identical ; the 
 former is soluble in ether, the latter is not. In the course of long exposure it becomes 
 insoluble. The gum and extractive colouring matter are of little use. The mineral 
 constituents of hops dried at 100 are 9 to 10 per cent, ash, 15 per cent, phosphoric 
 acid, 17 per cent, potash, &c. 
 
 Quality of the Hops. The quality of the beer is almost proportionate to the quality 
 of the hops. A rich soil is required for the growth of the hop-plant, well exposed to 
 the influence of the sun's rays, and protected from easterly winds, which are highly 
 detrimental. The hops must on no account be gathered until the seed is perfectly ripe, 
 as it is only then that the bitter principle is fully developed. The ripeness of the hops- 
 can be ascertained by rubbing them between the fingers ; if an oily matter remains, 
 with a strong odour, they are fit for gathering. When gathered, the next most impor- 
 tant operation is the drying, which is effected in kilns or stoves, at a temperature of 40, 
 with a good ventilation. When sufficiently dried, the small stem attached to the 
 flower snaps readily. The temperature must be carefully regulated : not permitted ta 
 range so high as to run the risk of burning the hops, nor allowed to fall so low that 
 the hops may afterwards become mouldy from under-drying. When dried, the hops 
 are carefully packed, the finer kinds being put into canvas pockets, and the inferior 
 into hop-bags of a coarser texture. The bags are then subjected to slight pressure in 
 a hydraulic or screw press, to render them more impervious to air. To preserve the 
 hops they are sometimes sulphured, that is, subjected to the action of vapours of 
 burning sulphur, i to 2 Ibs. of sulphur being employed to i cwt. of hops. Old hops- 
 are sometimes treated in this manner, to impart the colour and appearance of freshly 
 dried hops, but the fraud can be detected by the odour. A good method of testing 
 for sulphur in hops is as follows : A sample of the hops is placed in a sulphuretted 
 hydrogen apparatus, with some zinc and hydrochloric acid ; the disengaged gas is passed 
 through a solution of acetate of lead. If the hops contain sulphurous acid, sulphu- 
 retted hydrogen will be disengaged (S0 2 + 2H 2 = SH 2 + 2H 2 0), and lead sulphide will be 
 thrown down from the lead solution. Another, and still better, method is to receive 
 the disengaged gas in a solution of sodium nitroprusside, to which a few drops of 
 potash-lye have been added ; the slightest trace of sulphuretted hydrogen imparts a 
 beautiful purple-red colour to the solution. 
 
 Substitutes for Hops. Attempts have been made to substitute quassia, walnut leaves, 
 wormwood, gentian, extract of aloes, colchicum, and picric acid for the hop. None of 
 these substances are efficient substitutes for the hop, though they impart a strong, bitter 
 flavour. Three of them may be considered as poisonous. There was no foundation 
 for the report that the seeds of a species of strychnos (and even ready prepared 
 strychnine) were used in brewing bitter ales. 
 
 The water used in steeping the barley, extracting the malt, and mashing has a 
 great influence upon the quality of the beer. A pure, soft water, or, at the most, one 
 very slightly hard, is best suited for the purposes of the brewer. 
 
 Water contaminated with decomposing organic matter is especially objectionable. 
 Such substances cling to the barley, continue to decompose on the softening floor, 
 occasion mouldiness and putridity, and, under some circumstances, interfere with 
 the fermentation of the wort obtained from such malt. Tannic, crenic, and apocrenic 
 acids have an injurious action ; hence water from woodlands, and that of rivers which 
 receive the waste of tanneries, are to be used, if at all, with caution. Beer made with 
 water containing animal impurities Avill not keep. The entrance of the waste waters 
 of the brewery is often manifested by disturbance in the process of fermentation. 
 
 3 A 
 
738 CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 Lintner points out that the water used for softening the barley and filling the casks 
 should contain little organic matter, and especially no ferment organisms. As regards 
 the primary decomposition products, ammonia and nitrous acid, Lintner remarks that 
 as we justly view with suspicion water containing such impurities, and reject it for 
 dietetic use, so also in malting and brewing it should be used only in extreme cases and 
 with great caution. A malting-house which used such water for softening had always 
 to contend with mouldiness in the malt, which disappeared as soon as it was found 
 possible to get a better supply of water. "Water containing calcium carbonate is good 
 for malting ; calcium and magnesium chlorides, gypsum, and iron are injurious. 
 The brewing of beer may be considered to consist of the following operations : 
 
 (1) The malting. 
 
 (2) The mashing. 
 
 (3) The fermentation of the beer- worts and the fining, ripening, and preserva- 
 
 tion of the beer. 
 
 i. The Malting. Malting is the process during which the grain barley is 
 germinated, by means of steeping in water until it swells and becomes soft. The non- 
 germinated grain possesses only in a very small degree the property of changing its 
 starch into sugar (dextrose) ; this property is very fully developed during the germina- 
 tion, so much so that it would be an easy matter to distinguish between the germinated 
 and non -germinated seed by the degree of this property alone. As has been already 
 stated, barley is the grain preferred, on account of its forming sugar in larger 
 quantities than any other kind of grain. The germination of the seed takes place in 
 three well-marked periods. In the first, the seed is enveloped in an outer organ, 
 which becomes exhausted and withered. In the second, the growth of the germ is 
 shown by the swelling at the end by which it was attached to the stalk ; and in the 
 third period, the little plumule, or acrospire, which would form the stem of the new 
 plant, is put forth. The germinating seed is similar to an egg, with its white, yolk, 
 and embryo ; the shell corresponds with the outer or hard coating of the seed ; the 
 white and yolk of the egg appear as the albumen, or meal of the grain ; while the 
 embryo of the egg has its analogue in the germ of the grain. A remarkable change 
 takes place during germination ; the glutinous constituent has passed from the body 
 of the grain to the radicula, or rootlet, which has grown to nearly the length of the 
 grain, while about one-half of the starch has been converted into sugar. This conver- 
 sion is the aim of the malting, as by this means the sugar can be readily dissolved. 
 The grain is supposed to have been sufficiently treated when the plumule, or acrospire, 
 has attained a length equal to two-thirds of the entire length of the grain. The 
 operation of germination is the same with all kinds of grain employed in brewing. 
 The conditions of success are the saturation of the grain with moisture, and a 
 temperature of not higher than 40 nor lower than 4, with access of air and exclusion 
 of light. 
 
 (a) The Softening or Soaking of the Grain is accomplished in large cisterns of wood, 
 sandstone, or cement, half filled with water. The grain is poured into the water, and, 
 after the lapse of an hour or so, sinks to the bottom of the tank, only the inferior and 
 diseased seed remaining on the surface, to be removed with wooden shovels, and 
 thrown aside for use as fodder for horses, cattle, &c. The steep water receives the 
 soluble constituents of the husk of the seed, and becomes of a brown colour and 
 peculiar flavour, with a decided inclination to lactic, butyric, and succinic acid 
 fermentation. The duration of the softening varies according to the age of the grain, 
 the temperature of the water, &c. A young, fresh grain requires forty-eight to seventy- 
 two hours' soaking, while an older grain, containing more gluten, is not thoroughly 
 softened under six to seven days. Grains of equal age and constitution must be soaked 
 together, to obtain an equally softened product. After sufficient soaking, the grain 
 
.SECT, vi.] BEER BREWING. 739 
 
 is allowed to drain for eight to ten hours, then taken out and thrown into heaps 
 on the floor of the malt-house. The sufficiency of the soaking is ascertained (i) 
 By pressing the grain between the finger and thumb-nail, when, if sufficiently 
 moistened, the germ, or embryo, will be projected. (2) The husk is easily destroyed 
 by pressure between the fingers. (3) When crushed with a piece of wood the grain 
 yields a floury mass. The grain when softened has a peculiar aroma, resembling 
 that of apples. The quantity of water usually absorbed by the barley amounts to 
 40 to 50 per cent, of its weight, while the grain correspondingly increases in volume 
 1 8 to 24 per cent. During this absorption the grain loses 1*04 to 2 per cent, of 
 its own weight in solid matter. Lermer states, that in fresh steep water he has 
 found succinic acid in the proportion of 30 grammes to i bushel of grain soaked . 
 
 (b) The Germination of Softened Grain. As soon as the grain is thoroughly 
 saturated with moisture, the conversion of the starch into sugar commences. 
 When germination has proceeded far enough it must be stopped, as about this time 
 the formation of sugar has reached a maximum. The softened barley is, as before 
 stated, transferred to the floor of the malting-room, where it is " couched," or placed 
 in a layer of 4 to 5 inches in thickness. Here the germination proceeds till the 
 plumules have attained the desired length. The temperature rises some 6 to 10 
 on account of the heat developed during germination, and consequently much of the 
 moisture is dissipated. The chief art of the maltster consists in stopping the ger- 
 mination at that point when the plumules and roots commence to draw upon the 
 constituents of the grain. The duration of the germination varies, during the 
 warmer months of the year, from seven to ten days, while towards autumn the 
 process will not be completed under ten to sixteen days, but the average duration 
 is eight days. The grain, during germination, loses about 2 per cent, of its weight, 
 probably by the oxidation of the carbon to carbonic acid by the oxygen of the air. 
 
 (c) The Drying of the Germinated Grain. The grain is now removed to the drying 
 floor (Welkboden}, where it is exposed to the air in layers 3 to 5 centimetres in depth, and 
 turned about with rakes six to seven times daily. When the malt becomes dry it is 
 cleared from the rootlets, some of which drop off by themselves, while others have to 
 be removed by winnowing. Malt must be dried for the making of most kinds of beer, 
 and has to undergp a roasting process before quite fitted for use. This drying or 
 roasting is effected in a malt kiln or cylinder heated by flues to the boiling-point of 
 water. During the roasting the malt acquires a darker colour, due to the conversion 
 of the remainder of the starch into sugar. The equality of the temperature is of the 
 utmost importance, so that one part of the malt may not be more strongly heated than 
 .another. Before the malt is submitted to this operation, however, it is first heated to 
 30 or 40. By this means some of the starch is converted into gluten, and forms a 
 coating to the grain impervious to water, the malt being in this stage known as "bright" 
 malt from its smooth, glossy appearance. 
 
 The malt kilns consist essentially of the drying plates upon which the malt is laid, 
 .and the heating flues. The plates used to be of stone or sheet-iron, but modern 
 brewers employ wire-wove frames, placed one above the other, so that the hot air from 
 the flues beneath may ascend through the interstices. The flues are generally of 
 sheet-iron for the better conduction of heat to the surrounding atmosphere. Coke is 
 used as fuel on account of the absence of smoke, as with coal or wood, in the event of 
 a leakage in the flues, considerable damage would be done to the malt. 
 
 The malt is not all dried at the same heat (50 to 100 C.), but is distinguished 
 as pale, amber, brown, or black malt, according to the degree of heat to which it has 
 been exposed. Pale malt results from heating to 33 to 38 ; amber, from a tem- 
 perature of 49 to 52 ; and brown from the rather high temperature of 65-5 to 76-5. 
 Black malt, commonly called patent malt, is prepared by roasting in cylinders, like 
 
74 o CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 coffee cylinders, at a temperature of 163 to 220. These darker malts are used in 
 
 England for colouring porters and stouts. 
 
 100 parts of barley give 92 parts of air-dried malt. The loss of 8 parts may be thus 
 
 accounted for : 
 
 In the steep- water i'S 
 
 During malting 3' 
 
 During germination 3' 
 
 Other losses '5 
 
 Total loss . . 8-0 
 
 The moisture in air-dried malt amounts to 12 to 15*2 per cent., and is expelled 
 during the kiln drying. According to C. John (1869), 100 parts of dried barley give 
 
 I. II. 
 
 Malt ... . 83-09 85-88 
 
 Plumules . . . 3-56 ... 3-09 
 
 Eadicules (rootlets) . 4-99 ... 4-65 
 
 Fermentary products .- 8-36 ... 6-38 
 
 The change undergone during the drying or roasting of the malt is shown in the 
 following table, the result of Oudeman's analyses : 
 
 Air-dried Malt. Kiln-dried Malt. Strongly Dried Malt 
 
 Products of roasting . o'o ... 7'8 ... I4'O 
 
 Dextrine . . 8'O ... 6'6 ... IO'2 
 
 Starch .... 58-1 ... 58^6 ... 47'6 
 
 Sugar 0-5 ... 07 ... 0-9 
 
 Cellulose . . . 14-4 ... io - 8 ... 11-5 
 
 Albuminous matter . iy6 ... 10-4 ... io'5 
 
 Fat .... 2-2 ... 2-4 ... 2'6 
 
 Ash .... 3-2 ... 27 ... 27 
 
 The amount of sugar is undoubtedly increased during the process ; and the dextrine 
 appears to increase with decrease of starch, and vice versd. The conversion of starch 
 into dextrine and sugar is effected, as far as is known, by the agency of diastase. 
 Dubrunfaut has (1868) shown that malt presents another sukstance similar in its 
 effect to diastase, and which he termed maltin. This principle is found to be much 
 more active than diastase, so that with the same quantity of maltin which a known 
 quantity of malt contains, ten times as much beer can be obtained as when diastase 
 only is employed. Dubrunfaut has also found a second but less active substance. Its 
 behaviour with respect to the decomposition of starch is similar to that of diastase ; 
 malt contains i| per cent., while only i per cent, of maltin is found. The treatment 
 with alcohol necessary to obtain diastase destroys the maltin. Dubrunfaut believes 
 diastase to be only a less active modification of these new substances. 
 
 The author is of opinion that the building in which the process of germination is 
 conducted may have its windows advantageously constructed of violet glass. 
 
 The combustion value of i kilo, of starch is = 4200 heat-units. For 100 kilos, of 
 dry malt there will be evolved during the process of germination 6"j x 4200= 28,100 
 heat-units. 
 
 Pneumatic Malting. In order to remove the carbon dioxide, which interferes with 
 germination, and to prevent an excessive rise of temperature, so-called pneumatic malt- 
 ing has been devised. Galland, e.g., in his pneumatic maltings keeps the air moist 
 by means of a tower (Fig. 5 14), which contains coke resting on the gratings, b and c. 
 The air, previously heated, enters through the pipe a, ascends to meet the descending 
 water through the bed of coke, and passes through C into the recipients, A and E, 
 which contain the barley. The requisite water is let into the cistern, w, through a 
 
SECT. 
 
 VI.] 
 
 BEER BREWING. 
 
 74i 
 
 Fig. 514. 
 
 Fig. SIS- 
 
 cock, J, flows through the overflow, y, to the sprinkling apparatus, r, and then down- 
 wards. In order to use the water over again, it is lifted by the pump, //, below the 
 filter, k, through which it rises to the cistern, 10. In the softening-beck, A , there is a 
 perforated false bottom, d. The 
 barley to be malted is softened 
 in this beck for forty-eight to 
 sixty hours in water. When 
 the water is removed the grain 
 soon begins to sprout. Contrary 
 to the present process, it is left 
 undisturbed for two or three 
 days, the softening-beck being 
 meantime kept closed with a 
 plate. In order to remove the 
 heat which is evolved, fresh air 
 is conveyed to the barley through 
 the pipe B, which escapes through 
 the pipe D. The sprouted grain 
 falls through the hopper, t, and 
 the aperture, o, into the drum, 
 E (Fig. 515). This, consists of 
 a sheet-iron cylinder, closed at 
 both ends. The partition, s, is 
 provided with openings, d, with 
 which are connected the channels 
 , made of sieve-plate. The air 
 entering at / arrives from the 
 ante-chamber, N, in the channels 
 JE, traverses the barley, and is 
 
 drawn off by the intermediate sieve -tube, and the main, S. The drum is continually 
 turning on the rollers, G. The movement can be effected in various manners e.g., as 
 in Fig. 515, by an endless screw, V, which plays into a circuit of cogs. During the first 
 four days after introduction into the drum, E, fresh, moist air is continually supplied 
 to the barley from the coke-tower through the pipe P. As soon as the germination 
 is retarded, there is supplied for two days a suitable mixture of fresh, moist, and 
 warm air, the latter coming from a hot-air chamber through an opening in the tubing, 
 P. Then dry air at 50 is allowed to enter, and the temperature is gradually raised 
 until the malt is ready. 
 
 In Leicht's malt kiln (Fig. 516) the combustion gaees pass from the fire a, through 
 the flues b, beneath the preliminary air-heaters, to the flues c, in which case the 
 movable dampers A, B, and D are closed, whilst E is open ; from the flue c, the fire- 
 gases pass through the iron flues d, to the common duct, e, and if the damper F is 
 closed and G is open, through the flue f, to the vapour chimney h. Inversely, the 
 combustion-gases from the fire a l take their way through the flues b v c v whilst the 
 dampers A , B, and E are closed, and D is open, to d v e ; and, further, if G is closed 
 and F open, to 6 P and then to the vapour chimney h v in the direction indicated by 
 the dotted arrows. By alternately opening and closing the dampers A, D, and B, E, the 
 combustion-gases can be led from the fires, a or a v directly into the chimney above, 
 whereby the roasting of the malt on each floor is assisted. Further, the escaping 
 gases can be led either to h or h v by opening and shutting dampers F and G, in 
 order to promote the draught in the required direction, according as the drying is 
 conducted on H or H r In practice this is done alternately day by day, one flue being 
 
742 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 used for drying and one for roasting. If H is used for drying, the fire a and the^ 
 preliminary heating chamber are active, and the draught is accelerated by the heated 
 
 chimney h, whereby the 
 temperature on the floor 
 II remains moderate even 
 with the strongest fire, 
 whilst the radiant heat is 
 given off in the flues d for 
 roasting on the floor H v 
 
 If the temperature on 
 the floor 7/ x is not sufficient 
 for roasting, the fire a l is 
 used in assistance, with the 
 open dampers B and E, so 
 that the fire gases may pass 
 directly into the flues d. 
 
 In a trial-malting all 
 the samples of barley are 
 steeped, malted, and dried: 
 under identical conditions. 
 The barley, freed as far as 
 possible from stones, the 
 seeds of weeds, oats, &c. r 
 is weighed, washed till the 
 water runs off clean, and 
 then steeped in a cylin- 
 drical glass with an equal weight of water. After some hours the floating grains are 
 taken off, air-dried, and weighed. The steeping water is changed every twenty- 
 four hours, at a maximum temperature of 15 in the room, and is replaced by an equal 
 quantity of water. After the barley has reached the right degree of softness it is 
 spread on a horse-hair sieve in a layer 6 to 8 centimetres in height. Each sieve is laid 
 over a flat vessel containing water, and covered with a wet cloth. In these experi- 
 mental maltings on the small scale it is necessary to free the barley from dust before 
 steeping, rubbing the grains cautiously in water with the fingers or on a cloth, as 
 otherwise mouldiness would set in. The malt is then weighed and spread on a small 
 square drying-floor heated with gas, where it remains twenty -four hours. The drying 
 takes twenty-four hours at a maximum temperature of 36 ; the heat is gradually 
 raised, and the malt is finally roasted at 80 for five hours. 
 
 
 . 
 
 
 
 
 si 
 
 
 
 ji 
 
 ^ 
 
 
 
 S 
 
 "o fi 
 
 'o 
 
 bD 
 
 a 
 
 s 
 
 03 
 
 
 O^ 
 
 3 
 
 o 
 
 
 M 
 
 sj 
 
 2 a? 
 
 la 
 
 1 
 
 3 
 
 a 
 
 be 
 
 88? 
 
 *" S *-* 
 
 a 
 
 1g S g 
 
 Origin. 
 
 'Z 
 
 ^2 
 
 Jfl 
 
 S 
 
 
 2-S 
 
 "rfPP 
 
 \S ("(. 
 
 .g-3 
 
 M I-.J 
 
 
 2 
 
 QJ i 
 
 r^ *-* 
 
 
 o 
 
 'S'S 
 
 ^ >- 
 
 5 ^ 
 
 ^ ^j 
 
 ** C ^ 
 
 
 
 
 
 o 
 
 
 
 
 
 
 
 
 b 
 
 p 
 
 2 3 
 
 " i 
 
 ,2<! 
 
 
 
 H 
 
 
 
 1 
 H 
 
 I 
 O 
 
 Q) .^3 
 
 rt ^* 
 
 If 
 
 'o 
 
 ^ O 
 
 SS3 
 
 
 p. c. 
 
 mgrm. 
 
 p. c. 
 
 hours. 
 
 days. 
 
 hours. 
 
 p. c. 
 
 p. c. 
 
 p. e. 
 
 p. c. 
 
 Hungary . 
 
 85-87 
 
 37^4 
 
 073 
 
 75 
 
 II 'OO. 
 
 41 
 
 148-1 
 
 83-2 
 
 5'79' 
 
 91-27 
 
 Slavonia . . . 
 
 87-03 
 
 38-02 
 
 0-44 
 
 92 
 
 9-40' 
 
 34 
 
 153-1 
 
 84-4 
 
 6-55 
 
 90-62 
 
 Regensburg 
 
 84-65 
 
 41-17 
 
 1-28 
 
 79 
 
 8-90 
 
 47 
 
 157-3 
 
 81-0 
 
 4-80 
 
 91-09 
 
 Bohemia . 
 
 86-31 
 
 44-50 
 
 0-82 
 
 74 
 
 8-90 
 
 38 
 
 
 83-3 
 
 5 '40 
 
 91-30 
 
 Franconia 
 
 82-35 
 
 47-40 
 
 1-40 
 
 95 
 
 10-25 
 
 57 
 
 146-4 
 
 78-5 
 
 4-72 
 
 90-82 
 
 Saale 
 
 86-56 
 
 43-60 
 
 0-56 
 
 73 
 
 933 
 
 48 
 
 153-7 
 
 83-3 
 
 5 '42 
 
 9I'OI 
 
 Moravia . 
 
 86-70 
 
 38;6 5 
 
 1-34 
 
 94 
 
 9-25 
 
 46 
 
 158-2 
 
 80-8 
 
 5'7 
 
 89-17 
 
 Sweden . 
 
 81-69 
 
 
 1-14 
 
 92 
 
 11-05 
 
 92 
 
 152-9 
 
 79-6 
 
 
 92-86 
 
SECT. VI.] 
 
 BEEE BREWING. 
 
 743 
 
 The nitrogen of the barleys and the malts obtained, with the constituents of the ash, 
 amounted to 
 
 
 Barleys. 
 
 
 i. 
 
 2. 
 
 3- 
 
 4- 
 
 5- 
 
 6. 
 
 7- 
 
 8. 
 
 N 
 
 1-809 
 2-690 
 
 0-599 
 I -010 
 
 0-056 
 0-009 
 
 I-629 
 2-64O 
 0-67I 
 0-790 
 
 0-059 
 0-013 
 
 1*877 
 2-850 
 0-656 
 I-078 
 
 0-065 
 
 0-016 
 
 I*809 
 2*570 
 0-65I 
 0-923 
 0*082 
 0-062 
 0-23I 
 O-OI5 
 0-3I5 
 
 1-859 
 2-810 
 0-826 
 0798 
 0-147 
 0-059 
 0*229 
 O-O07 
 0-608 
 
 1-696 
 2-860 
 
 0*579 
 0-8I7 
 
 0-037 
 
 0*216 
 0*013 
 0-528 
 
 1750 
 2-650 
 0-645 
 0-804 
 
 0-640 
 O-009 
 
 1-605 
 2-630 
 0-711 
 0-767 
 0-107 
 0-067 
 0-224 
 0-003 
 0-592 
 
 Ash .... 
 
 Si0 2 
 
 P,0 e 
 
 SO, . 
 
 CaO .... 
 
 MgO 
 
 Fe,0 3 
 K 2 
 
 N . 
 Ash 
 Si0 2 
 PA 
 SO 3 
 CaO 
 MgO 
 Fe 2 8 
 K 2 O 
 
 Malts. 
 
 1-625 
 2*480 
 0-598 
 0-929 
 0*029 
 O-O9I 
 0-253 
 O'O22 
 0-468 
 
 ir6oo 
 2-390 
 0-711 
 0-868 
 0-054 
 0-072 
 0-266 
 0*018 
 0-363 
 
 1-857 
 2-440 
 0-677 
 0-904 
 0*012 
 0-087 
 0-236 
 0-019 
 0-470 
 
 1-798 
 2-300 
 0^644 
 0-708 
 O-O29 
 0-077 
 O-2I9 
 O-OI4 
 0-367 
 
 1729 
 2-420 
 0-725 
 0-779 
 0-012 
 0-084 
 0-239 
 0-017 
 0-385 
 
 1*568 
 2-350 
 0-556 
 0-784 
 
 0-019 
 
 0*096 
 
 0*239 
 
 0*011 
 
 0-417 
 
 1733 
 2*320 
 0*770 
 0-830 
 0-03I 
 0-085 
 0-2.19 
 0-015 
 
 I-4I3 
 2-310 
 0-651 
 0-693 
 0-058 
 0-082 
 O'2I2 
 O-OI5 
 0-407 
 
 It is seen how different is the loss in the several constituents of barley on malting. 
 One part of the loss is due to the .steeping water, which has a lixiviating action. 
 Another part consists of the matters removed in the germs. Though the Munich 
 water used in the experiments was not very hard, it did not extract any lime, but yielded 
 some to the grain. 
 
 Balke examined several specimens of barley of the season 1883, and of the malts 
 obtained from them. He obtained in percentages 
 
 
 Barley. 
 
 Dry Substance. 
 
 
 Origin. 
 
 Dry 
 
 Substance. 
 
 Starch 
 Value. 
 
 Proteine 
 NX 6-25. 
 
 Ash. 
 
 P 2 5 in 
 
 Ash. 
 
 Germ-power. 
 
 
 
 
 
 
 Per cent. 
 
 Per cent. 
 
 Moravia, I. 
 
 84-84 
 
 64-8 
 
 8-89 
 
 2-77 
 
 31-82 
 
 98-0 
 
 Moravia, II. 
 
 85-82 
 
 69-2 
 
 9-68 
 
 2-76 
 
 35-I4 
 
 95-0 
 
 Silesia 
 
 85-I9 
 
 6 3 -2 
 
 10-71 
 
 3'02 
 
 20-54 
 
 84-0 
 
 Magdeburg 
 
 8477 
 
 68-9 
 
 1077 
 
 2-56 
 
 37-19 
 
 96-0 
 
 Stumsdorff 
 
 8775 
 
 71-4 
 
 10-07 
 
 3-08 
 
 2875 
 
 95-8 
 
 Coethen 
 
 84-84 
 
 69-9 
 
 10-16 
 
 2*58 
 
 37-80 
 
 97-5 
 
 
 Malt. 
 
 Dry Substance. 
 
 Extract. 
 
 Origin. 
 
 Dry 
 
 Substance. 
 
 Extract. 
 
 Proteine 
 NX 6-25. 
 
 Ash. 
 
 P 2 5 in 
 Ash. 
 
 Maltose. 
 
 Maltose : 
 Non-mal- 
 tose=i. 
 
 Moravia, I. .91*18 
 Moravia, II. . 92*22 
 Silesia . . 89*35 
 
 75-54 
 73-68 
 75-26 
 
 II79 
 9-40 
 
 8-53 
 
 2-65 
 2-8 S 
 2-48 
 
 38-50 
 32-I8 
 37'35 
 
 Per cent. 
 69-50 
 72-30 
 6872 
 
 0-46 
 0-39 
 0-45 
 
 Magdeburg 
 Stumsdorff 
 
 89-34 
 93-30 
 
 72-90 
 76-19 
 
 10-44 
 10-25 
 
 2*39 
 2-39 
 
 40-00 
 
 7271 
 70-23 
 
 0-38 
 0-31 
 
 Coethen . 
 
 93-20 
 
 74-93 
 
 9-94 
 
 2-49 
 
 
 70-63 
 
 0-31 
 
 The proportion of soluble nitrogenous constituents of different malts in per- 
 centages of the dry matter amounted, according to Salamon (1886), to 
 
744 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 Origin. 
 
 Total 
 Nitrogen. 
 
 Albuminoid 
 Nitrogen. 
 
 Peptonic 
 Nitrogen. 
 
 Amidic 
 
 Nitrogen. 
 
 Unknown 
 
 Nitrogen. 
 
 England, good . 
 
 0-6148 
 
 O-I2OO 
 
 0-0340 
 
 0-4090 
 
 0*05490 
 
 England, ordinary 
 
 0-6167 
 
 0-I44I 
 
 0-0074 
 
 0-3804 
 
 0-08490 
 
 Scotland . 
 
 0-5404 
 
 0*0514 
 
 0-0149 
 
 0*4025 
 
 0*07160 
 
 France 
 
 07147 
 
 I -0470 
 
 0*0624 
 
 0*5000 
 
 0*07476 
 
 Denmark . . 
 
 0-7111 
 
 0-1393 
 
 0-0634 
 
 0*5084 
 
 
 Moravia 
 
 0-6159 
 
 0-1435 
 
 0-0438 
 
 0-4286 
 
 
 Or in percentages of total nitrogen 
 
 England, I 
 England, II 
 
 I9-5I 
 2V^6 
 
 5'53 
 
 I - 2O 
 
 66-02 
 6 1 -68 
 
 8-94 
 1-7-76 
 
 Scotland 
 France 
 Denmark 
 Moravia 
 
 9-5I 
 14-64 
 
 I9'59 
 23-30 
 
 275 
 873 
 8-91 
 7*11 
 
 76-33 
 69-95 
 71-50 
 
 69-59 
 
 11*41 
 6-68 
 
 According to Lintner and Aubry, good malt should yield an extract of at least 7 1 
 per cent, of its dry substance. In the extract there should be 64 to 69 per cent, 
 maltose, and hence the proportion of maltose to non-maltose in the extract should be 
 as i : 0*45 to i : 0*55. If the proportion is higher, say i : 0*30, the beers ferment 
 too strongly and bear little head ; if it is lower, as i : 0*60, there is too little maltose in 
 the wort, and the fermentation is feeble. These proportions are doubtless correct 
 for the full-bodied Bavarian beers, but in malts for the light and vinous North German 
 beers the most favourable proportions of maltose to non-maltose in the extract are 
 1 : '35 to i : 0*47, the maltose in the extract being 68-75 per cent. Practice shows 
 that such malts yield normal worts, fine fermentations, and beers of a good flavour. 
 A further character which Lintner and Aubry demand in a good malt has been fully 
 confirmed i.e.) a good malt should be completely saccharified in twenty minutes, if 
 mashed at 70. 
 
 The object of the malting process is to form a non-organised ferment, diastase, at the 
 expense of the nitrogenous constituents of the barley. This starch, in the subsequent 
 mashing process, splits up the starch into maltose and dextrine. According to 
 Zulkowsky (1878), the mean composition of a purified diastase obtained from barley 
 malt is 
 
 Carbon 45 "57 
 
 Hydrogen 6*49 
 
 Nitrogen 5*14 
 
 Ash 3-16 
 
 Oxygen and sulphur 37*64 
 
 A second non-organised ferment, generated during the malting process, is peptase, 
 which during mashing converts the protein compounds into peptones and para-peptones. 
 A part of the constituents of the gluten, the parenchyma in which the starch granules 
 are embedded, is rendered soluble or much loosened. The starch is so modified that 
 it is turned into paste at a lower temperature. 
 
 The Production of the Wort. In Bavaria, the Schenk, or pot beer, is brewed in the 
 winter, and the Lager, or store beer, in the summer. The winter beer is brewed during 
 October to April, when the highest range of the thermometer is 12 to 13. A part of 
 the beer by a short storing is set aside for winter consumption, while the remainder is 
 used during the summer months. 
 
 i volume of malt gives on an average 2-5 to 2*6 volumes of winter beer. 
 i ,, ,, 2'oto2'i summer beer. 
 
 2. Preparation of the Wort. Under this head is included the preparation from 
 
SECT, vi.] BEER BREWING. 745 
 
 malt of the wort a saccharine fluid containing dextrine and the flavouring with 
 hops. The general method of preparation is in three operations 
 
 a. The bruising of the malt. 
 
 b. The mashing. 
 
 c. The boiling and flavouring of the wort with hops. 
 
 a. The Bruising of the Malt. Beer- wort, or the wort, as it is generally termed, is 
 obtained by means of the extraction of the bruised malt with water. To the end that 
 all the active principles may be extracted from the malt, it must be bruised or ground 
 to a fine meal. The obtaining of a clear liquor, after the extraction, is effected by means 
 of nitration. The grinding is ordinarily performed in a malt mill, a machine with 
 rollers being preferred, as affording a more equable product. 
 
 b. Mashing. The mashing is a most important operation, on success in which 
 depend many of the good qualities of the beer. It is during this operation that not 
 only are the sugar and dextrine already existing in the malt set free, but the uncon- 
 verted starch, by the aid of diastase, water, and a favourable temperature, suffers 
 conversion into sugar and dextrine. Lermer found, in the best cases of mashing, that 
 only half the starch was converted into a corresponding quantity of sugar. The opera- 
 tion is very variously performed, but generally may be considered as effected by either 
 of two methods : 
 
 (1) The Decoction Method. After the infusion has been made the mash is brought 
 
 to the boiling-point, and 
 
 (a) A portion of the water evaporated to form a thick mass (thick mash 
 
 boiling). At a subsequent stage, only a portion of the mash 
 
 having been thus treated, the remainder of the mash is added ; 
 
 and 
 (/3) The whole of the mash is heated to the boiling-point (clear mash 
 
 boiling). The hops are added during the clear mash boiling. 
 
 (2) The Infusion Method, according to which the mash is prepared at a certain 
 
 degree of heat, but never attains the boiling-point. The crushed malt is 
 thrown into hot water (first cast) in the mash tun, and when the mash has 
 reached a certain saccharine condition, a further addition of water is made 
 (second and third cast). The infusion method is much employed in North 
 Germany, Prance, England, Austria, and Bavaria. 
 
 The mashing vessels are either round tubs or wooden cisterns with a double 
 bottom, the upper being perforated, and about an inch above the true bottom. Between 
 the bottoms is a tap through which the wort is drawn off. In large breweries these 
 bottoms are of metal instead of wood. The hot water is supplied from the bottom 
 and not from the top of the vessel. Under the mashing vessel is situated a large 
 reservoir, either of stone, cement, wood, or masonry, and destined to receive the 
 fluid run off from the mash. The continuous stirring of the contents of the mash- 
 tun or tub is effected either by hand or machinery driven by water or steam 
 power. 
 
 (i) Decoction Method. The general description of the mashing process having been 
 given, we now pass on to the particular method of preparing the wort by decoction. 
 The infusion takes place in the mash-tun, in which the required quantity of water is 
 placed, and the malt to be mashed shaken in. The quantity of water employed in 
 making the infusion is generally in the proportion of 202 volumes of water to 100 
 volumes of malt, both at the ordinary temperature. After the bruised malt has been 
 well stirred in the water, the whole is allowed to stand for six to eight hours. During 
 this tune the necessary quantity of water is heated to the boiling-point in the copper. 
 The quantity of water used to prepare an estimated quantity of beer is termed the 
 
74 6 CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 " cast," and the quantity of malt the " yield." In Bavaria the quantity of beer 
 prepared from a denned quantity of malt is as follows : 
 
 (2O2'3 volumes of Schenk beer. 
 100 volumes of malt yield | ^^ >? ^ Lager beer> 
 
 In order to produce this quantity of beer an equivalent quantity of water must of 
 course be employed, so that, in a Bavarian brewery, to 100 volumes of malt there are 
 taken of water 
 
 Schenk Beer. Lager Beer. 
 
 For infusion . . . : 202-3 vols. ... 202*3 vols. 
 
 For mashing . . . 170*0 ,, ... 130*0 
 
 372-3 . 3323 
 
 These proportions vary according to the quality of the grain, the state of the weather, 
 the length of time of keeping, &c. 
 
 The various modifications of the decoction method are (a) The Bavarian or Munich 
 method ; (/3) The Augsburg-Nuremberg,, or Swabian method, sometimes termed " sedi- 
 ment brewing " (Satz brauen). 
 
 (a) Thick Mash Soiling. According to the Munich method (thick mash boiling) the 
 cast of water is divided into three portions, two of which are poured into the mash-tun 
 to form a paste with the bruised malt. After this mash has stood for two to four 
 hours, the remaining third of the water, which during this time has been heated to the 
 boiling-point in the copper, is added, the whole of the mash attaining thereby a tem- 
 perature of 30 to 40. Then follows the first thick mash boiling for this purpose the 
 brewer draws the mashed grain to one side of the tun, and removes a portion to the 
 copper, where for schenk beer it is boiled for thirty minutes, and for summer beer for 
 seventy-five minutes. The quantity of mash boiled at each operation is generally 
 about half the cast. The boiling mass is returned to the mash-tun. Then follows the 
 second thick mash boiling, which for schenk beer lasts seventy-five minutes, and for 
 summer beer an hour. By means of the first boiled mash the contents of the mash- 
 tun are raised to a temperature of 48 to 50, and by the second addition to 60 to 
 62. After the finishing of the second mashing the clear mashing begins ; that is, the 
 thinly fluid part of the mash is placed in the copper and boiled for about fifteen 
 minutes, and is then returned to the mash-tun. The temperature of the mash is now 
 72 to 75, and is most suited for the formation of sugar. The mash remains in the 
 covered tun i^ to 2 hours. During this time, and as soon as the clear mash has been 
 removed from the copper, the latter is refilled with a sufficient quantity of water for the 
 purposes of brewing small beer. When the sugar has been properly formed and dis- 
 solved in the wort, the latter is removed from the mash-tun to the fermenting vessels. 
 The remaining mash is then treated with hot water to yield small beer, i bushel of 
 malt yielding 35 to 50 quarts of this beer. The residue of the small beer is again 
 treated with water, the resulting infusion being employed in vinegar making. The 
 residue from this process is used as fodder for cattle. 
 
 The thick mash boiling is by no means a rational method, as the separation of the 
 mash and the several removals are unnecessary labour, and do not contribute so much 
 to the complete extraction of the malt as is generally supposed ; the high temperature 
 renders a portion of the diastase ineffective, while much of the starch remains uncon- 
 verted into dextrine and dextrose. 
 
 All who have tried to reduce the brewing process to simple methods based upon 
 sound chemical and physical principles declaim against the process of thick mash 
 boiling, stating and with good reason, proved by experiments that the advantages 
 of this method are absurdly overrated ; and that, in order to lessen the bad effects of 
 this method as much as possible, it should be replaced by a method of hot mashing 
 viz., at a temperature of from 60 to 65. 
 
SECT, vi.] BEER BREWING. 747 
 
 (/3) Augsburg Method. Distinct from the foregoing mash methods is the so-called 
 " sediment brewing " used in many Swabian and Franconian breweries. It essentially 
 consists in treating the bruised malt with cold and then with hot water, to obtain a 
 saccharine wort. The bruised malt is mixed with cold water in the mash-tun in the 
 proportion of 7 Bavarian bushels to 30 to 35 eimers (each = 68*41 litres) of water. 
 After standing for four hours, two-thirds of the fluid is drawn off. During this time 
 a quantity of water (48 eimers to 7 bushels of bruised malt) is brought to the boiling- 
 point in the copper ; a portion of this water is now added to the contents of the mash- 
 tun, which thus attains a temperature of 50 to 52, while the liquor or weak wort 
 drawn off' from the mash-tun is poured along with the rest of the water in the copper. 
 The liquor that has been drawn off contains albumen, diastase, dextrine, and dextrose. 
 The mash is allowed to stand for a quarter of an hour in the tun, when the fluid is- 
 entirely drawn off, transferred to the copper, and heated to the boiling-point. This i& 
 termed the " first mash." While this is going on, enough fluid will have drained from 
 the malt in the mash-tun to fill the space between the double bottoms of the tun ; this- 
 fluid is at once removed to the cooling vessels. The fluid heated in the copper is now 
 returned to the mash-tun, the entire contents of which attain a temperature of 72 to- 
 75. This "second mash" is, after an hour's interval, followed by a "third mash." 
 The wort is then run into the cooling vessels. 
 
 (2) Infusion Method. The infusion method is distinguished from the decoction 
 method by a slight difference in the procedure, the bruised malt being treated with 
 water at a temperature of 70 to 75, but without any portion of the mash being 
 boiled. The method is that usually employed in this country, North America, France,. 
 Belgium, and North Germany. 
 
 The water intended to be used for the mashing process is, according to the initial 
 temperature of the water the brewer has at hand, heated, either wholly or in part, in 
 the copper, the temperature being raised in winter to 75, in summer to from 50 to 60. 
 The necessary quantity is first poured into the mash-tun, the bruised malt being next 
 added, and the mixture made up so as to form a moderately thin paste. Water is 
 heated to the boiling-point in the copper in order to proceed further with the mashing 
 process. As soon as a sufficient quantity of water boils it is usually by means of 
 properly constructed pipes allowed to run into the mash-tun, wherein it is consider- 
 ably cooled owing to the colder liquor present in that vessel ; the increase of temperature 
 of the contents of the tun to 75 (the most suitable for saccharification) is gradually 
 made in order to prevent the formation of starch paste, whereby the formation of 
 diastase would be interfered with. Since the conversion of amylum (starch) into dex- 
 trine and dextrose proceeds gradually only, it is clear that the contents of the mash- 
 tun should be kept at the temperature suitable for that process ; while, however, on 
 the other hand, care has to be taken to prevent the mash becoming sour by the for- 
 mation of lactic (probably also propionic) acid. 
 
 The progress of the formation of dextrine and dextrose is best ascertained by the 
 help of an aqueous solution of iodine, or preferably of iodine dissolved in iodide of 
 potassium, in the proportion of i - o gramme of iodine and ro of iodide of potassium to 
 100 c.c. of water ; this solution will at first give with a sample of the mash a dark blue 
 coloration, next a wine red, and finally, when only dextrine and dextrose are present, 
 no coloration at all. The addition of 2 or 3 drops of the clear wort to a small 
 quantity of this iodine solution is sufficient for testing. When the mash has been 
 kept for about one hour's time at the temperature most suitable for the saccharification, 
 the wort is run either into a large reservoir, or into a vessel kept expressly for this 
 purpose, or, lastly, at once into the copper ; a fresh quantity of water is then 
 poured into the tun, and the contents of the tun are allowed to remain for half to 
 one hour at a temperature of 75. It is of course quite evident that the infusion 
 
74 8 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vr. 
 
 method may be varied as regards the quantity of water and repeated number of 
 infusions ; but in order to brew a beer of a certain and fixed brand it is requisite 
 that the degree of concentration of the wort be always the same. For the purpose of 
 ascertaining the degree of concentration, Balling's saccharometer is generally employed, 
 which instrument, when put into sugar solutions, indicates the percentage of sugar 
 they contain. Balling has shown that solutions of dry extract of malt have the 
 same specific weight as cane-sugar solutions of equal percentage. For use in a brewery 
 the saccharometer need only be graduated for solutions varying between 20 and 30 per 
 cent. 
 
 Extractives of the Wort. The quantity of extract which a wort should contain 
 depends, of course, upon the quality of the beer which the brewer desires to make, and 
 differs according to the nature of the beer, whether it shall be thick, heavy (rich in ex- 
 tract), or strong (of great alcoholic strength). The quantity of malt extract varies in dif- 
 ferent beers from 4 to 1 5 per cent., that of the alcohol from 2 to 8 per cent, i per cent, of 
 sugar in the wort yields after fermentation o - 5 per cent, of alcohol. To produce a beer 
 containing 5 per cent, of alcohol and 7 per cent, of malt extract, the wort should, before 
 fermentation, mark the degree on the saccharometer corresponding to 17 per cent. A 
 
 beer of 3-5 per cent. 
 
 Fig. 517. of alcohol and 5-5 
 
 per cent, of malt ex- 
 tract will result from 
 a wort containing 
 12-5 per cent, of 
 sugar. 
 
 c. Boiling the 
 Wort. The prepared 
 but not yet boiled 
 wort contains dex- 
 trose, dextrine, some 
 unconverted starch, 
 protein substances, 
 extractive matter, 
 and organic salts. 
 The colour of the 
 wort is a brown or 
 yellow-brown, accord- 
 ing to the variation 
 of colour of the malt 
 fxom which it has 
 been obtained. The 
 odour is agreeable 
 and the taste sweet. 
 The wort exhibits an 
 acid reaction to test- 
 paper, owing to the 
 presence in that fluid 
 of small quantities of 
 free phosphoric, lac- 
 tic, and probably other acids ; but in case the wort has by accident become sour, or if 
 wort is made purposely from already exhausted grain which has become sour, this 
 reaction is far stronger, and may be ascertained by the odour, owing to the formation 
 of volatile acids, among which butyric, and in the latter case lactic and propionic acids, 
 
SECT. VI.] 
 
 BEER BREWING. 
 
 749 
 
 are present in large quantity. The boiling of the wort aims at its concentration, and 
 also at the extraction of the bitter principle of the hops ; further, also, for the purpose 
 of coagulating and precipitating a portion of the albuminous substances by the aid of 
 the tannic acid contained in the hops. This latter reaction renders the wort clear. 
 In many breweries gypsum is added to the boiling wort to reduce the whole of the 
 nitrogenous substances. The boiling is generally effected in copper cauldrons (tech- 
 nically, also simply, " the copper "), set in masonry over a fire-grate. The fire is very 
 carefully disposed, to prevent the burning of the wort, as the pans are exposed to the 
 direct action of the flame. The manner of hopping (as it is termed) that is to say, 
 the mode of adding the hops to the wort varies in different breweries, and depends, as 
 regards quantity, also upon the quality (strength) of the hops, the larger or smaller 
 amount of extract contained or desired to be retained in the beer, and last, but not 
 least, the mode of preservation and length of time it is intended to keep the beer. 
 
 Figs. 517 and 518 show the ground plan and section of the mashing-house in the 
 Bavarian State Brewery in Weihenstephan. The bruised malt is mixed with water in the 
 beck, B, which is fitted with an agitator. A part of the mixture is allowed to flow down, 
 through the pipe (7, into the pan, M. Here it is boiled with agitation ; the hot mass 
 flowing off is then brought 
 back through the tube, n, 
 by means of the centri- 
 fugal pump, P, into 7> ; 
 it is well mixed, another 
 portion boiled in the pan, 
 M, so that, when it has 
 been pumped back into B , 
 the temperature desired 
 for converting the starch 
 into maltose and dextrine 
 (68 to 70) is reached. 
 When the formation of 
 sugar is completed the 
 mixture is brought into 
 the clearing tank, L, pro- 
 vided with a perforated 
 false bottom, in which 
 the grain remains whilst 
 the wort flows through 
 the tubes, o, into a com- 
 mon channel, and thence 
 to the wort-pan, W, in 
 which a steam pan is 
 laid. Here it is boiled 
 up with hops. The watery 
 vapours escape through 
 the pipes a. The wort 
 flows through a strainer, 
 and is pumped into the 
 cooling-becks, K. 
 
 Lintner prefers the Bavarian to every other method of decoction, with two thick 
 mashes and a clearing mash. 
 
 A pan-mashing adopted in the brewery at Niirtingen, with steam washing, deserves 
 more general attention. The mashing-pan, M (Fig. 519), is fitted in the ordinary 
 
75 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 manner with a thermometer, safety-valve, pressure-gauge, inlets for cold and hot 
 water, double globular bottom, and cocks for the admission of steam. The prepara- 
 tory mashing apparatus, v, is connected by the pipe, ra, with the chest for bruised 
 malt. A mashing machine with a double movement effects the regulation of the tem- 
 
 perature. The waste steam escapes through d to a preliminary water heater. The mash 
 and clearing beck, L, contains a combined machine for stirring up and throwing out the 
 grains, and is connected with the wort-pump, p. The wort-pan, W, is arranged like 
 the mashing-pan, and in its jacket there is a glass introduced to show the level of the 
 wort. All the vessels are made of sheet-iron, jacketed, and with double bottoms. The 
 hop-pan, H, is connected with the circular pump, P. 
 
 Adding the Hops. To make winter beer, which in Germany, as a rule, is consumed 
 in four to six weeks after brewing, old hops (viz., one year old) are added in the 
 proportion of 2 to 3 Ibs. to a Bavarian bushel of malt (2^22 hectolitres). For 
 summer beer, to be consumed in May and June, 4 to 5 Ibs. of new hops are added 
 to the bushel of dried malt ; while for the beer for September and October consump- 
 tion, 6 to 7 Ibs. of new hops are employed with each bushel of malt. Among the 
 constituents of hops which are active in the process of brewing, we may mention in the 
 first place the bitter ingredient it contains (not correctly known, notwithstanding 
 recent research), and which imparts to beer its bitter taste and narcotic property ; 
 further, the tannic acid, which combines, during the boiling of the wort, with a portion 
 of such of its protein compounds as are not rendered insoluble by the boiling alone, and 
 form together a precipitate, rendering the wort previously turbid quite clear, and 
 also regulating the first and second (so-called after-) fermentation. The essential oil 
 and resin met with in hops act to a certain extent as retarding the fermentation, and 
 thxis prevent the wort becoming converted into a sour liquid. The inorganic 
 constituents of hops do not appear at least cannot be directly proved to be of 
 much consequence. As regards the degree of concentration to be given to the wort 
 by the process of boiling, it should be observed that the degree of concentration as 
 ascertainable by the saccharometer should remain from o - 5 to i saccharometrical 
 percentage under the degree of concentration which the wort should indicate at the 
 beginning of the fermentation, because, while cooling, the wort gains in concen- 
 tration just the percentage alluded to. The separation of the coagulated albumen 
 does not take place until the temperature of the wort has reached 90; and the quan- 
 tity separated is greater from wort prepared by the infusion method than from that 
 
SECT. VI.] 
 
 BEER BREWING. 
 
 7S 1 
 
 prepared by the decoction method. As soon as, in a sample of the boiling wort taken 
 from the pan and poured into a large test-glass, the suspended flocculent matter 
 settles rapidly to the bottom of the glass, the boiling can be discontinued, the wort 
 being then ready ; but, in the infusion method, the boiling is continued for the purpose 
 of further concentrating the liquor, and for this purpose it may even last for from five 
 to eight hours. If the boiling only aims at the coagulation of the albuminous 
 compounds, one hour in winter, and three-quarters of an hour in summer, is quite 
 sufficient. As regards the hops, it is best to add them in a somewhat cut-up state, 
 and not before the greater part of the albuminous compounds have been, as far as 
 possible, precipitated by a good boiling of the wort. In order to extract the hops, 
 the wort is either passed through a basket or through any suitably constructed per- 
 forated vessel retaining the hops, this vessel being placed in communication with the 
 coolers ; or the hops are boiled along with the wort ; or, again, several portions of the 
 wort are boiled successively along with the same quantity of wort ; and lastly, even with 
 the weakest wort or after- run. 
 
 Cooling the Wort. The cooling of the wort to the degree necessary for the com- 
 mencement of the fermentation is effected in large wooden, stone, or iron cisterns. As 
 at a temperature of 25 to 30 C. the wort has a great tendency to set up lactic- 
 acid fermentation, the cooling has to be very rapid in order that the temperature 
 of the liquid may be soon much below 25 to 30, and thus any danger of souring 
 prevented. 
 
 The cooling of the wort is an operation which is performed in well-constructed 
 buildings well ventilated in all directions and protected from rain, in which buildings 
 the coolers are placed. Owing to improvements in the modes of cooling, it is now 
 possible even to brew beer in localities (as, for instance, Montpellier and Marseilles, 
 Barcelona and Naples) where formerly, on account of the prevailing high temperature 
 during the greater portion of the year, brewing could not take place at all ; while also, 
 for the same reason, in various countries (America, United States, especially) excellent 
 lager beer is brewed. The cooling vessels are generally only 6 to 8 inches deep, of 
 wood, iron, or copper, and are placed in an airy situation near or immediately under 
 the roof of the brewery. Metallic vessels are of course more effectual in cooling the 
 wort in a short time than wooden ones ; they are also more cleanly, and less liable to 
 get out of order. In some breweries where a constant stream of cold water is avail- 
 able, the coolers are placed therein ; but this is of course a matter entirely depending 
 on the locality of the brewery. Without doubt the surest means of cooling the wort 
 rapidly is by employing ice, either in blocks in the wort or in pans placed in the cooling- 
 tuns. But, for economic reasons, this plan is not generally available. The temperature 
 to which the wort is to be cooled is that best suited to fermentation, the next process 
 to which the wort is subjected. The following are the temperatures at which fermen- 
 tation most readily sets in, depending upon the temperature of the locality and upon 
 the kind of fermentation : 
 
 Temperature of the 
 Locality where the Fer- 
 mentation takes place. 
 
 Temperature of the Wort. 
 
 In Sedimentary 
 Fermentation. 
 
 In Superficial 
 Fermentation. 
 
 6 to 7 
 
 12 
 
 15 
 
 7 8 
 
 II 
 
 14 
 
 8 9 
 
 IO 
 
 13 
 
 9 ii I0 
 
 9 
 
 12 
 
 IO 12 
 
 7 to 8 
 
 12 tO 11 
 
 The concentration of the boiled and hopped wort is expressed in degrees per cent, of 
 the saccharometer. 
 
75 2 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 Fig. 520. 
 
 The old cooling process has the defect that the wort is exposed for a long time to 
 impure air, so that the benefit of pure air is rendered doubtful. In order to prevent 
 the contamination of the wort with schizomycetes during cooling, the improved cooler 
 (Figs. 520 and 521) has been used with success at the Carlsberg Brewery. The boiling 
 vat runs through the pipe, M, into a large cistern of galvanised iron capable of holding 
 
 100 hectolitres. It has a roof- 
 shaped cover, B, which can be 
 raised and lowered, and closes the 
 cistern by means of a water- joint. 
 Through an opening in the middle 
 of the cover there moves the axle 
 of a screw, D ; there are at the 
 side of the cover two openings 
 for the escape of steam, E, F, in 
 which there are short tubes filled 
 with cotton. There is also in the 
 cover a tube, G, through which 
 sterilised air can be introduced 
 into the space about the wort, 
 when the latter, after cooling, is 
 allowed to stream down into the 
 fermenting cellar, thus prevent- 
 ing the entrance of impure air. 
 Into the lowest part of the cis- 
 tern underneath the screw there 
 
 opens a tube, H, with numerous small apertures ; through these sterilised air is intro- 
 duced, ascending through the wort in bubbles, and supplying it with oxygen. In the 
 middle of the cistern lies a system of cylindrical tubes through which flows cold water 
 to cool the wort. In the bottom there is an outflow for the wort, N, another, 0, 
 for droppings, and a third, P, for the deposited sediment and for the water required 
 for rinsing and cleansing the apparatus. 
 Lastly, there is a thermometer which 
 shows the temperature of the wort in a 
 man-hole, H. The air which is pumped 
 into the cistern and rises through the 
 wort has been previously freed from all 
 organisms and germs by means of a 
 cotton filter, and is consequently sterile. 
 As soon as the wort has risen above 
 the entrance places of the air, its access 
 is permitted, and the wort remains in 
 continual contact with the air until it 
 is cooled down to a suitable tempera- 
 ture, or, in summer, so far that the 
 cooling can be completed by means of 
 ice. The stay of the wort in the appa- 
 ratus does not require more time than 
 its exposure in the cooling-becks. 
 When all the wort is run into the 
 cistern the water is allowed to flow through the cooling-worm, and the screw is set in 
 action until the required temperature has been reached. The wort is left to stand quietly 
 xintil the sediment has been deposited, and it can be conveyed into the fermenting cellar. 
 
SECT. VI.] 
 
 BEER BREWING. 
 
 753 
 
 By means of two apparatus and mashings, each of 100 hectolitres, wort was cooled 
 down daily at Alt-Carlsberg. 
 
 The point to which the wort must be cooled depends on the temperature of the 
 cellar and the kind of fermentation. The following temperatures have been found 
 most satisfactory in practice : 
 
 Temperature of Cellar. 
 
 Temperature of Wort. 
 
 Bottom Fermentation. 
 
 Top Fermentation. 
 
 6 to 7 
 
 8 9 
 
 10 12 
 
 12 
 IO 
 
 7 to 8 
 
 15 
 13 
 11 to 12 
 
 According to J. Gschwandler's researches (1868), the under-mentioned Bavarian 
 beer-worts had the following composition : 
 
 Beer-wort. 
 
 Decoction. 
 
 Bock. 
 
 Sedimentary 
 Method. 
 
 Infusion. 
 
 Sugar . . . . ,. .. . 
 
 4-850 
 
 7-100 
 
 4 '3 70 
 
 5-260 
 
 
 6^240 
 
 8'6oo 
 
 7'6io 
 
 6 "680 
 
 Nitrogenous substances 
 
 0790 
 
 i '350 
 
 
 
 Other constituents 
 
 0-410 
 
 0-630 
 
 0-950 
 
 0-700 
 
 Specific weight . 
 
 I-05O 
 
 1-073 
 
 1-052 
 
 1-051 
 
 Extract (direct estimation) 
 ,, (according to Balling) 
 
 1 1 '870 
 I2'29O 
 
 17-050 
 1 7 '680 
 
 1 1 -980 
 12-930 
 
 1 1 '940 
 12*640 
 
 While the wort remains in the cooler a yellow-grey or brown sediment is deposited, 
 consisting of a compound of coagulated albumen with the tannic acid of the hops, 
 and some starch similarly combined. This sediment, during the first cooling, is formed 
 in quantities varying from 3 to 4 per cent, of the quantity of the cooled wort ; the 
 sediment, when washed and dried, amounts to 0*5 per cent, of the quantity of malt 
 employed. 
 
 3. The, Fermentation of the Beer-wort. The wort, when cool, is run into the 
 fermenting tanks, where fermentation sets in either spontaneously or is induced by 
 the addition of yeast. The first kind spontaneous fermentation begins as soon 
 as the wort, having been cooled down to the temperature most suitable for fermenta- 
 tion, is left to itself, and this fermentation is induced by the sporules of yeast 
 (ferment cells) always present in all fermenting localities, which, meeting with the 
 wort, find in that liquid the proper conditions for their growth. This kind of 
 spontaneous fermentation is applied usefully in the brewing of the Belgian beers 
 known as Faro and Lambick, which are rich in lactic acid. Usually, however, yeast 
 is added to the wort, and there is avoided the dangerous first stage of spontaneous 
 fermentation, for by the addition of the yeast a regular and rapid fermentation is set 
 up, but yet so regulated that the yeast only gradually converts the dextrose into 
 alcohol and carbonic acid. 
 
 The results of the researches made by Yon Lermer and Liebig (1870) are of great 
 importance for a rational basis of the brewer's business. According to these savants, 
 an addition of sugar to a solution of dextrine, to which previously beer-yeast has been 
 added, causes a large quantity of the dextrine to be converted into alcohol and carbonic 
 acid, just as if the dextrine were sugar. 
 
 The higher the temperature of the wort and of the locality, the smaller the quantity 
 of yeast required. A yeast formed by a violent fermentation and at a high temperature 
 has more active qualities than yeast formed at a lower temperature and by a longer 
 fermentation. The first spreads itself rapidly over the surface of the fluid, and is 
 termed superficial yeast (Oberhefe) ; while the second sinks to the bottom of the vessel, 
 and there continues its action; this is termed sedimentary or bottom yeast (Unterhe/e). 
 
754 CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 The fermentations resulting from these two yeasts are respectively termed super- 
 ficial fermentation (Obergahrung) and sedimentary fermentation ( Untergahrung). The 
 latter fermentation is induced in worts that are intended to yield beers of great 
 durability, such as the Bavarian beers. The superficial fermentation is induced in 
 such beers as are intended to be soon drunk. Where fermentation is induced in a 
 wort at a low temperature and with deposit only (bottom-yeast), the so-called surface 
 fermentation that is to say, a vinous fermentation whereby yeast is carried to the 
 surface of the fermenting fluid is employed chiefly for such kinds of worts as are 
 intended to produce a beer which is not required to be kept for any length of time, 
 but rapidly consumed after having been brewed. The wort is in this instance generally 
 rich in sugar (glucose) ; and while only a portion of this sugar is converted into 
 alcohol (sweet beer being formed), the formation of a small quantity of alcohol (the 
 wort being only lightly hopped) contributes largely to the preservation of this kind 
 of beer. Surface fermentation is also induced in such kinds of worts as are either 
 very concentrated or contain substances which to some extent retard, or might even 
 altogether impede, fermentation ; as, for instance, the empyreumatic substances pre- 
 sent in a very highly roasted malt or a large quantity of hops, these conditions 
 obtaining in the brewing of porter, stout, and, as regards hops, of bitter ale. Worts 
 of this description come comparatively very difficultly into fermentation. Fermenta- 
 tion, no matter whether surface or sedimentary (the yeast is in this case slowly 
 deposited as a sediment on the bottom of the vessel), exhibits the three following 
 phases viz. : 
 
 1. The chief fermentation, beginning soon after the addition of the yeast, 
 characterised by tho decomposition of the glucose, by the formation of new yeast, and 
 by an increase of temperature. 
 
 2. The after-fermentation, during which decomposition of glucose continues 
 slowly, while the formation of new yeast cells does not ensue so energetically as in 
 the first phase, the suspended particles of yeast settling down, and the beer becoming 
 clear. 
 
 3. The quiet or imperceptible fermentation, taking place when the after-fermentation 
 is finished, is characterised by a further decomposition of glucose, while the formation of 
 yeast is not perceptible to any extent. 
 
 Sedimentary fermentation. Sedimentary fermentation is employed in the brewing 
 of the Bavarian schenk and lager beers, taking place in large fermentation vats con- 
 taining 1000 to 2000 litres of wort. Recently, upon the suggestion of G. Sedlmayr, 
 these vessels have been constructed of glass. The addition of yeast may be effected in 
 two different ways : yeast may be either added to the wort, or a small portion of the 
 wort is first separately brought into a state of fermentation, and next added to the 
 bulk of the liquid. In the first case dry y easting, as it is termed the yeast is placed 
 in a small tub and wort poured over it, and, these substances having been well mixed, 
 the whole of the contents of the vessel are thrown into the fermentation vats, and 
 there worked about by the aid of a stirring pole. According to the second method 
 wet y easting or yeast carrying 6 to 8 maas* of yeast are added to 100 maas of 
 wort, and well mixed with about 3 eimers of wort, the mixture being allowed to 
 stand for four to five hours. After fermentation has set in, the fermenting liquid is 
 mixed with the wort in the fermentation tank. Tho yeast intended to be used for 
 this purpose should be obtained from a former and normal fermentation ; it should 
 not be too old, should possess a pure odour (not be foul) and a thick consistency, and 
 be frothy. 
 
 After the wort has been mixed with the yeast the following phenomena are ex- 
 hibited: After ten to twelve hours the decomposition of the dextrose becomes 
 * The Bavarian maas is equivalent to 1-25 English quart. 
 
SECT, vi.] BEER BREWING. 755 
 
 apparent by the evolution of bubbles of carbonic acid gas, which forms a wreath of 
 white froth at the edge of the vessel. In another twelve hours larger quantities of a 
 more consistent froth are formed, causing the surface of the liquid to exhibit a very 
 peculiar appearance, which might be compared to that of irregular masses of broken- 
 up rocks ; at the same time a more vivid evolution of carbonic acid takes place, and 
 becomes perceptible by the smell. The German term for this phase of the fermenta- 
 tion, das Bier steht im Krdusen, can hardly be expressed in English, but the meaning 
 is the fermentation is in full force ; these phenomena continue, with a regularly 
 proceeding fermentation, in full activity for from two to four days, and then gradually 
 subside, there remaining on the surface of the liquid a somewhat brown-coloured film 
 of froth, much contracted, and chiefly consisting of the resinous and oily constituents 
 of hops. 
 
 The yeast formed is only to a very small extent present on the surface of the 
 liquid, as, in the case of sedimentary fermentation, the carbonic acid evolved cannot 
 carry the isolated yeast-cells to the surface. The temperature of the fermenting 
 liquid increases at the beginning of the fermentation, so that the liquid becomes 
 several degrees warmer than the air of the locality where the fermenting vats are 
 placed. By the fermentation the wort loses the greater portion of its dextrose, about 
 half of which is evolved in the shape of carbonic acid, while the remainder is con- 
 verted into alcohol ; further, a portion of the albuminous substances dissolved in the 
 wort is rendered insoluble, and deposited in the shape of yeast. On being tested 
 with the saccharometer, the liquid for reasons just explained exhibits after fer- 
 mentation a less degree of strength than before. The difference in percentage 
 shown by the saccharometer before and after fermentation is in direct proportion 
 to the quantity of dextrose decomposed, and provides a means of ascertaining the 
 course of the progress of the fermentation. If this difference be made the numerator 
 of a fraction, the denominator of which is the percentage indicated by the sac- 
 charometer before fermentation, the value of the fraction will increase proportionately 
 with the completeness or efficacy of the fermentation ; if, for instance, a wort 
 before fermentation marks a saccharometrical percentage of 11*5, and afterwards 
 gives 5 per cent., the difference (6*5 divided by 11*5) gives the co-efficient 
 0-565; that is, of 100 parts of malt extract 56-5 per cent, are decomposed during 
 .fermentation. 
 
 After-fermentation in the Casks. After the chief fermentation is completed, which 
 'for summer or lager beer requires nine to ten days, and for winter or schenk beer 
 seven to eight days, the young or green beer is put into barrels, after having become 
 quite clear by the separation of the yeast. Before the beer is vatted the scum 
 present on its surface is removed. The yeast, settling to the bottom of the vat in 
 which the fermentation took place, consists of three layers, the middle being the 
 best yeast ; the lowest, decomposed yeast and foreign matter, is mixed with the yeast 
 of the upper layer, and if not otherwise saleable is sometimes employed in the 
 distilleries of malt spirits. The middle layer serves for further fermenting opera- 
 tions. In breweries where pure water (the reader should bear in mind that Bavaria 
 is alluded to) is not to be had, this yeast is occasionally obtained fresh from other 
 breweries. It is usual to fill casks or vats with winter beer at once quite full; but 
 . as regards summer beer several brewings are mixed in smaller vats in order to obtain 
 a uniformly coloured mixture. The barrels are usually coated with pitch on the 
 inside, the aim being to prevent the beer soaking into the wood, and thus giving rise, 
 when the cask is emptied, to the formation of acetic acid. For the after-fermentation, 
 the beer is placed in stone cellars, which should be kept at the lowest temperature 
 practicable, so as to cause the after-fermentation to proceed as slowly as possible, and 
 thus admit of the beer being kept until the brewing season opens. 
 
756 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 In all parts of Germany, but mostly so in Bavaria, great attention is paid to the 
 construction of the cellars : these cellars are often excavated in rocks, and sometimes 
 ice-pits are placed in the cellars to keep them very cool. The after-fermentation of 
 the beer sets in when it is vatted, the moment of the beginning of this process partly 
 depending on the condition of the beer when vatted and partly upon the temperature 
 of the cellar. The after-fermentation, which becomes manifest by the appearance of a 
 bright white-coloured foam at the bung-hole, may set in immediately after the vatting 
 of the beer, or may only become perceptible some eight days after. Should the beer 
 happen not to exhibit any sign of incipient after-fermentation, green, young, or new 
 beer is added for the purpose of inducing this process. When the after-fermentation 
 is finished, the bungs of the casks or tuns are not tightly fastened, and the beer is left 
 in this condition (in the cellars, of course) during the summer months. About a fort- 
 night before the beer in the casks is intended to be tapped, the bungs are tightly 
 closed in order to cause as much carbonic acid to accumulate in the fluid as will occasion 
 the beer to foam on being tapped ; but if beer happens to be vatted in very green 
 condition, the bung-hole should not remain- closed for so long a period, because then so 
 violent a fermentation may set in that, on tapping the cask, its contents become too 
 much agitated, and thereby a very turbid beer (full of yeast) is served to the customers. 
 Sometimes the addition of liqueur (a solution of white sugar) is resorted to for the 
 purpose of setting up a strong fermentation in very old beer. According to J. 
 Gschwandler (1868), beer obtained by the processes alluded to has the following 
 composition : 
 
 Beer. 
 
 Decoction. 
 
 Bock. 
 
 Sedimentary 
 Method. 
 
 Infusion. 
 
 Alcohol 
 
 2 -8 10 
 
 3-380 
 
 2-940 
 
 3'ISO 
 
 Sugar .... 
 
 1-580 
 
 2-320 
 
 1-460 
 
 i '330 
 
 Dextrine 
 
 4-610 
 
 6-910 
 
 4-770 
 
 4-800 
 
 Nitrogenous substances 
 
 0-380 
 
 0740 
 
 
 
 Other constituents 
 
 0-380 
 
 0-400 
 
 0-890 
 
 0-550 
 
 Sp. gr. of solution of extract 
 
 I -022 
 
 1-042 
 
 1-028 
 
 1-026 
 
 Extract (direct estimation) . 
 (according to Balling) 
 
 6-570 
 6-950 
 
 9-980 
 10-380 
 
 6-230 
 7'I2O 
 
 6-130 
 6-680 
 
 Surface Fermentation. Surface fermentation is that induced in the worts intended 
 for the brewing of the bottled beers of North Germany, Bohemia, Alsace, England, 
 and Belgium. Beer obtained by this process of fermentation is not so lasting as that 
 prepared by the sedimentary fermentation process. This difference is due to the fact 
 that the surface fermentation goes on at a higher temperature, proceeds more rapidly,, 
 while the elimination of the nitrogenous compounds is also less complete. The reason 
 why this process is preferred to the sedimentary fermentation process is that brewing 
 by the application of the last process is so greatly dependent upon a low temperature 
 that this mode of brewing cannot be continued throughout the whole year, while, as 
 regards the other process, it may be continuously carried on, and the stock of beer kept 
 ready for use can thus be considerably decreased. Surface fermentation, however, i& 
 the only plan for preparing briskly foaming and strong beers. Porter, stout, and ale 
 could be brewed as well by the sedimentary method although in the English climate 
 this process would be more difficult to conduct successfully but the main reason why 
 the surface fermentation is employed for English malt liquors is that this method, by 
 the great saving of time, is cheaper. The phenomena of the surface fermentation are 
 similar to those of the sedimentary, with the exception that the progress is by far more 
 violent, the froth surging more to the surface of the wort. The yeast is employed in 
 the same manner. An ingenious contrivance is adopted in the London breweries for 
 the purpose of carrying off the yeast from the beer after it has undergone the process- 
 of fermentation. The wort is placed in large hogsheads, or rounds, the tops of 
 
SECT. 7i.] BEER BREWING. 757 
 
 which are fitted with wooden troughs. Into these troughs the yeast runs as it 
 rises, and is carried away. The beer now becomes clear, and is pumped into the 
 stone vats. 
 
 Steam Brewing. The extensive application of steam to the manufacture of beet- 
 root sugar and alcoholic spirits has given rise to many suggestions for the substitution 
 of heating by steam for direct firing in brewing. The heating is effected by a system 
 of tubes similar to that described in the preparation of beet-root sugar (see p. 705). 
 In brewing, however, though much would be gained by uniformly heating the worts, 
 and by reducing the chances of burning, there would not ensue any great economising 
 of fuel, though much labour might be saved. Steam could not be employed directly 
 without a series of tubes, as the condensation would cause a great dilution of the 
 mash. 
 
 Constituents of Beer. The constituents of a normal beer prepared from malt and 
 hops (not from substitutes) are: Alcohol, carbonic acid, undecomposed dextrose, 
 dextrine, constituents of the hops (oil and bitter substance, no tannic acid), protein 
 substances, a small quantity of fat, some glycerine, and the inorganic matter of the 
 barley and hops. The acid reaction which a normal beer exhibits after the carbonic 
 acid has been expelled from it by boiling is due to succinic and lactic acids, with 
 traces of acetic acid, and perhaps propionic acid. The sum of all the constituents of a 
 beer after the abstraction of the water is termed the total contents ; the sum of the 
 non-volatile constituents, the extractive contents. Beer rich in malt extract is termed 
 rich, fat, or full-bodied beer ; and that which is poor in extract, but contains much 
 alcohol, the wort having been rich in sugar which has all been converted, is termed a 
 dry beer. 
 
 The proportion of alcohol in beer can be estimated by distillation and the testing 
 of the distillate with an alcoholometer, or by means of an ebullioscope, or with the help 
 of a vaporimeter (see Wine-testing, pp. 724-5-6). The following table shows the 
 average weight per cent, of the alcoholic contents of several beers : 
 
 Per cent. 
 
 Wiirtzburg lager beer (1870) 4 4 o-4'3 
 
 schenk beer 3 '3-4 '2 
 
 Stuttgardt lager beer (1865) 4*1 
 
 Culmbach lager beer (1865) 4-$ 
 
 Coburg lager beer 4*4 
 
 Munich lager beer . . 4'3~5*l 
 
 ,, schenk beer 3-8-4 - o 
 
 Bock (Munich, 1870) . 4 '3-4 *8 
 
 Porter (Barclay, Perkins & Co., London, 1862) . . 5'5-7'Q 
 
 Strasburg beer (1870) 4*21 
 
 Vienna beer (1870) . 4'i 
 
 Rice beer of the " Rhenish Brewery " in Mentz . . 3*6 
 
 The quantity of carbonic acid in beer varies between o'i to 0*2 per cent. Accord- 
 ing to C. Prandtl (1868), dextrose is found in beer in quantities varying from o'2 to 
 i '9 per cent. The quantity of dextrine, according to Gschwandler's analyses, varies 
 from 4' 6 to 4*8 per cent. The proportion of sugar to dextrine is never constant. The 
 occurrence of protein substances in beer has not been sufficiently investigated to warrant 
 an exact conclusion. It may be said that, on an average, malt extract contains 7 per cent, 
 protein substances, from which Mulder deduces that i litre of beer should contain 5*6 
 per cent, albuminous substances. A. Yogel (1859) found that i Bavarian maas 
 (= i~o6g litre) of beer on an average contained i to 1*2 gramme nitrogen ; and Feich- 
 tinger (1864) obtained from i Bavarian maas of several Munich beers between 0*467 
 and 1-248 gramme nitrogen. Succinic acid, acetic acid, and lactic acid occur in Belgian 
 and Saxony beers in large quantities. Tannic acid occurs in Bavarian beers only in 
 small quantity. The inorganic constituents of beer have received great attention. 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. 
 
 Martius obtained from 1000 parts of Bavarian lager beer 2-8 to 3-16 parts ash, con- 
 taining one-third potash, one-third phosphoric acid, and one-third magnesia, lime, and 
 silica. J. Gschwandler and C. Prandtl (1868) found an average extractive contents in. 
 100 parts of 
 
 Schenk beer (Munich) . . . 
 Lager beer (Munich) . . . . 
 Schenk beer (Wiirtzburg) 
 Lager beer (Wiirtzburg) . 
 
 Bock (Munich) 
 
 Salvator (Munich) 
 
 Rhenish rice beer 
 
 Porter (Barclay, Perkins & Co., London) 
 Scotch (Edinburgh) . 
 
 Parts. 
 
 S'5-6-0 
 
 6-r 
 
 4-6 
 
 4 '4 
 
 S'6-9'8 
 9-0-9-4 
 
 7'3 
 
 5-6-6-9 
 lO'O-II'O 
 
 Burton ale 14-0-19-29 
 
 100 parts of extractive matter contain^ according to A. Vogel (1865), 3-2 to 3-5 parts 
 of ash ; 100 parts of ash contain 28 to 30 parts phosphoric acid, i litre of beer contains 
 0-57 to 0-93 gramme of phosphoric acid. 
 
 Lermer (1866) subjected several Munich beers to analysis, with the following 
 results : 
 
 
 T * 
 
 
 
 
 
 
 
 
 
 2 - 
 
 
 
 
 
 
 Specific gravity . 
 
 i -02467 
 
 1-0141 
 
 1-01288 
 
 I -O2 
 
 i -02678 
 
 i -03327 
 
 1-017 
 
 
 Per cent. 
 
 Per cent. 
 
 Per cent. 
 
 Per cent. 
 
 Per cent. 
 
 Per cent. 
 
 Per cent. 
 
 Extractive matter 
 
 773 
 
 4 "93 
 
 4'37 
 
 4'55 
 
 8-50 
 
 9^3 
 
 5 '92 
 
 Alcohol 
 
 5-08 
 
 3'88 
 
 3'SI 
 
 4-41 
 
 5 '23 
 
 4 '49 
 
 3-00 
 
 Inorganic constituents 
 
 0-28 
 
 0-23 
 
 0-15 
 
 o-iS 
 
 
 
 
 Nitrogen 
 
 
 
 
 
 
 
 
 In 100 parts extract 
 
 11-15 
 
 871 
 
 12-19 
 
 8-85 
 
 
 
 6-99 
 
 
 In loo parts beer 
 
 0-87 
 
 0-43 
 
 0'53 
 
 0-39 
 
 
 
 0-67 
 
 
 The analysis of the ash of five of these beers gave- 
 
 
 
 2. 
 
 3 
 
 
 
 
 
 
 J' 
 
 4- 
 
 s 
 
 Potash . 
 
 29'3I 
 
 33-25 
 
 24-88 
 
 34-68 
 
 29-32 
 
 Soda 
 
 1-97 
 
 0-45 
 
 20-23 
 
 4-19 
 
 O'll 
 
 Sodium chloride 
 
 4-61 
 
 6'oo 
 
 6-56 
 
 5-06 
 
 6-00 
 
 Lime 
 
 2-34 
 
 2-98 
 
 2- 5 8 
 
 3-14 
 
 6'2I 
 
 Magnesia 
 
 11-87 
 
 8-43 
 
 0-34 
 
 777 
 
 775 
 
 Iron oxide 
 
 I'OI 
 
 O'll 
 
 0-47 
 
 0-52 
 
 0-84 
 
 Phosphoric acid 
 
 34-i8 
 
 32-05 
 
 26-57 
 
 29-85 
 
 29-28 
 
 Sulphuric acid 
 
 1-29 
 
 271 
 
 6-05 
 
 5-16 
 
 4-84 
 
 Silicic acid . 
 
 12-43 
 
 14-12 
 
 770 
 
 2-86 
 
 S-oi 
 
 Sand 
 
 0-83 
 
 0-67 
 
 2-30 
 
 5-20 
 
 6-27 
 
 Carbon ..... ; 
 
 O'4Q 
 
 0-81 
 
 0-40 
 
 0-65 
 
 0-28 
 
 
 v +f~y 
 
 
 
 
 
 
 100-33 
 
 101-47 
 
 98-03 
 
 99-08 
 
 98-91 
 
 The high importance of beer, both as regards its value as a nutriment and the- 
 enormous trade done in this article, has given rise to attempts to find proper and 
 suitable means for testing that liquid in respect of its quality and purity. 
 
 Beer-testing .The experiments proposed for ascertaining the strength as well as 
 freedom from adulteration of beer are termed beer-testing; it is desirable that these 
 operations should be easily executed and yield sufficiently trustworthy results. The 
 strength of the beer is judged according to the quantity of alcohol, extract, and 
 
 * i. Bock beer. 2. Summer beer. 3. White beer. 4. White Bock beer (superficially fer- 
 mented, obtained by surface fermentation from malted wheat). 5. Another sample of Bock beer.. 
 6. Salvator beer. 7. Winter beer. 
 
SECT, vi.] BEER BREWING. 759 
 
 carbonic acid it contains ; it is evident, however, that the real constituents of the 
 extract viz., the therein contained quantities of dextrine, hop constituents, the 
 bye-products of alcoholic fermentation, such as, for instance, succinic acid and 
 glycerine, not to mention such substances as glucose and glycerine purposely added 
 to the wort as substitutes for malt largely influence the quality of any kind of beer, 
 and therefore ought to be determined when any rigorously exact analysis of that 
 liquid is wanted. 
 
 Beer-testing is effected partly by ascertaining certain physical qualities of the beer, 
 partly by chemical means. To the former belong its flavour, odour, colour,* con- 
 sistency, transparency, specific gravity, refractive power to light, &c. By chemical 
 analysis we ascertain and determine the immediate constituents viz., carbonic acid, 
 alcohol, extractives, and water. The carbonic acid contained in the beer is first 
 eliminated either by repeatedly pouring a quantity of beer from one tumbler or beaker- 
 glass into another, care being taken to let the beer fall from some height, or is 
 removed by shaking the liquid up in a bottle and pouring it out of the same and into 
 it again. The gas having been driven off, the specific gravity of the beer is taken 
 by means of the hydrometer or saccharometer ; the beer is next boiled down to half 
 its original bulk ; next there is added to it as much water (best distilled) as is required 
 to restore the liquid to its original bulk, and of this liquid the specific gravity is again 
 determined ; this will be found greater than that previously obtained. The difference 
 between the two determinations gives the amount of alcohol contained in the beer. 
 
 Sailing's Saccharometrical Beer-test. Since, by fermentation, 100 parts of malt ex- 
 tract yield 50 parts alcohol, twice the quantity of alcohol found will indicate the 
 quantity of malt extract necessary for its formation. This quantity of malt extract 
 added to that still existing in the beer indicates the whole of the malt extract existing 
 in the wort before fermentation. 
 
 The specific gravity of the beer-wort becomes lower by fermentation, partly because 
 the specifically lighter alcohol is formed, partly by the loss of some of the extractive 
 matter, and partly also by the loss of the substances taken up in the yeast. This 
 decrease of the specific gravity, or attenuation, as it is termed, can be estimated either 
 directly by weighing, or by means of the saccharometer. The degree marked by the 
 saccharometer in a beer freed from carbonic acid we will call m ; the malt extract of 
 the wort, p. Subtracting m from p, the difference (p-m) gives the apparent 
 attenuation, which is the greater the more thorough the fermentation. The quantity 
 of alcohol in a beer varies in direct proportion with the apparent attenuation. The 
 empirical alcohol factor, a, by which the apparent attenuation must be multiplied to 
 obtain the alcoholic contents of the beer = A in weight per cent, [(p m)a A], be- 
 comes the greater the higher the original degree of concentration of the wort. For 
 worts between 6 to 30 per cent, of extractive matter, this factor varies from 0-4879 to 
 0-4588. The alcohol factor can be found by the following equation, when the apparent 
 attenuation (p-m) and the alcoholic contents of the wort (A) are known; then 
 
 With the help of the alcohol factor, a, the alcoholic contents in weight 
 
 per cent, can be calculated. A quantity of beer being boiled to volatilise the alcohol, 
 and the residue having been diluted with water to the original bulk or weight, if a 
 weighed quantity were operated with, the specific gravity gives the quantity of 
 extractive matter contained in the beer, which Balling terms n. The difference be- 
 tween the extractive matter contained in the wort (p) and that of the beer (n), or 
 
 * Very recently, C. Leyser has invented a colorimeter with which, by means of a normal 
 solution of iodine (12-7 grammes iodine to a litre) after having brought the beers to an equal colora- 
 tion with water, he estimates the relative degree of the original colour. The invention is -fully 
 described in the Jahresberichte der Chem. Technologic for 1869, p. 467. 
 
 _/ A \ 
 
 \p-mj' 
 
760 CHEMICAL TECHNOLOGY. |_ SECT - VI - 
 
 (p ri), gives the actual attenuation, which, multiplied by the alcohol factor for the 
 actual attenuation (b), likewise gives the quantity of alcohol contained in the beer 
 expressed in percentage by weight. The alcohol factor for the actaal attenuation 
 
 / A \ 
 is 6 = ( _ ). Subtracting from the apparent attenuation (p - m) the actual (p-ri), 
 
 the difference (d) in the attenuations is obtained d = (p-m) - (p -n) ; or d = m n. 
 d is known when the extractive matter contained in the beer (?i) and the saccharo- 
 inetrical percentage (m) of the beer free from carbonic acid are known; d is the 
 greater the more alcohol the beer contains. The alcohol factor multiplied by the 
 difference in attenuation gives the percentage (A) of alcohol, from which the alcohol 
 factor for the difference in attenuation can be obtained by the following equation: 
 A 
 
 c = . It averages 2 -24. Finally, with the help of c, the difference in attenuation 
 
 (p-m) 
 
 of the alcoholic contents of a beer can b.e calculated approximative^, even when the 
 quantity of extractive matter of malt contained in the wort is not known. The apparent 
 divided by the actual attenuation gives a quotient (d), which is the ratio of the 
 
 p m, 
 attenuations, d = - , and can be calculated with the help of the alcohol factor for 
 
 the apparent attenuation (a) and of the original extractive contents of the wort (p\. 
 First (a) is obtained by the division of the alcohol factor for the actual attenuation 
 by the corresponding attenuation quotient or ratio. Assuming the alcohol factor for 
 the difference in attenuation to be 2-24, and next doubling the approximative alcoholic 
 contents thus obtained, we arrive at the quantity of the extractive matter of the wort 
 from which the alcohol was formed. Adding to this the extract yet met with in the 
 beer, the sum thus found expresses the approximate percentage of the extractive con- 
 tents of the wort. When (p) has thus been approximately obtained, Balling's tables 
 give the corresponding attenuation quotient q, reckoning all decimals above 0*5 as 
 units, and neglecting those under 0-5. If only the original concentration of the 
 wort (p) is to be calculated, the percentage of the alcohol of the beer may be 
 obtained from the equation to the actual attenuation A = (p n)b. If the degree 
 after fermentation is 975 or (16-29 6-54), the saccharometrical percentage (see 
 
 9'75 
 
 PP- 748, 759) = =0-542. 
 
 16-29 
 
 THE MANUFACTURE OF SPIRITS. 
 
 The industrial production of alcohol has in most countries a different basis and 
 signification, different raw materials, different purposes, and different fiscal regulations 
 and circumstances, all of which have a great influence on the conditions of manufacture. 
 If an alcoholic fluid is submitted to distillation, alcohol and water pass over, whilst 
 the non-volatile constituents of the liquid remain behind in a more concentrated 
 form. 
 
 Properties of Alcohol. The formula of alcohol (as a chemically pure substance) is 
 
 C 1 IT i 
 C,H 6 O,or * jj}0- I* is a colourless, thin, very mobile fluid of 0-792 sp. gr., boiling 
 
 a* 78'3, while water boils under the same atmospheric pressure at 100 ; thus there is 
 afforded a means of ascertaining, by the boiling-point of an alcoholic fluid, the quantity 
 of alcohol contained. Between o and 78-3 (its boiling-point) alcohol expands 0-0936 
 of its volume, while the co-efficient of expansion of water between the same degrees is 
 0-0278. The expansion of alcohol is thus 3^ times greater than that of water; and 
 this fact is made available in alcoholimetry. The tension of the vapour of alcohol 
 
SECT, vi.] THE MANUFACTURE OF SPIRITS. 761 
 
 at 78-3 is equal to an atmosphere, while water must be raised to a temperature of 100 
 to obtain the same pressure. Thus, the variation in height of a column of mercury 
 subjected to the pressure of these vapours may be made a measure of the quantity of 
 alcohol contained in a fluid. On this principle the vaporimeter (see p. 724) is con- 
 structed. Alcohol is readily inflammable, and burns with a pale blue flame without 
 giving off soot. Its heat of combustion corresponds to 7183 units of heat. It eagerly 
 absorbs water, and upon this property is based its use for the preservation of articles 
 of food, cherries and other fruit, and also anatomical preparations. It mixes with 
 water in all proportions, whereby a decrease of bulk of the mixture and increase of 
 specific gravity is observed 
 
 5 3 '9 volumes of alcohol, with 
 
 49*8 water, form a mixture, not of 
 
 103*7, but of 100 volumes. 
 
 Alcohol is a solvent for resins (upon which property is based its application to the 
 manufacture of varnishes, cements, and pharmaceutical preparations), and also a 
 solvent of many essential oils. These solutions are employed either as perfumes, such 
 tis eau de Cologne, or as liqueurs, cordials, and aqua vitse, or as spirits for burning in 
 lamps, as, for instance, the mixture of oil of turpentine and alcohol, so-called fluid gas ; 
 jilcohol also dissolves carbonic acid gas, a property made available in the making of 
 effervescing wines. 
 
 By the influence of certain oxidising agents, alcohol is converted first into aldehyde 
 and next into acetic acid, as illustrated in the so-called quick vinegar making process. 
 Alcohol does not dissolve common salt, and upon this property Fuchs's test is based. 
 
 By the action of most of the stronger acids, aided by heat, alcohol is converted into 
 what are termed ethers ; as regards the action of sulphuric acid upon alcohol, it 
 depends upon the relative quantities and degree of concentration of these liquids 
 whether sulphovinic acid, ether, or bicarburetted hydrogen gas be formed. Hydro- 
 chloric acid forms, with alcohol, ethyl chloride or hydrochloric ether. Butyric and 
 oxalic acids form ethers directly when heated along with alcohol ; but most of the 
 other organic acids require the aid of sulphuric or hydrochloric acid for this purpose. 
 Alcohol is the intoxicating principle of all spirituous liquors. 
 
 Eaw Materials. Alcohol is always the product of vinous fermentation. The 
 manufacture of spirits therefore includes three principal operations : 
 
 1. The preparation of a saccharine fluid. 
 
 2. The fermentation of this fluid. 
 
 3. Separation of the alcohol by distillation. 
 
 All saccharine fluids, therefore, or those substances which yield alcohol by fermen- 
 tation, can be employed in the manufacture of spirit ; and all materials so employed 
 contain already either completely formed alcohol, or cane sugar and dextrose, or, finally, 
 substances which by the influence of diastase or dilute acids are converted into dextrose. 
 Such substances are starch, inuline, lichenine, pectin compounds, and cellulose. The 
 raw materials of spirit manufacture may be generally classed in the three following 
 groups : 
 
 ist Group. Fluids in which the alcohol is already present, requiring only distilla- 
 tion to effect its separation. Such fluids are wine, beer, and cider. 
 
 2nd Group. Substances, either solid or liquid, which contain sugar, which may be 
 either cane sugar, or dextrose and levulose, or sugar of milk. In this group are 
 included the sugar-cane, beet-root, carrot, maize stalk, the Chinese sugar-cane (sorghum), 
 some kinds of fruit viz., apples, cherries, figs some berries (grapes, mountain ash 
 berries, &c.), the melon and gourd, some fruits of the cactus tribe, the molasses of cane 
 
7 6 2 CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 and of beet-root sugar manufacture, the marc of grapes and refuse grain of beer 
 making, honey, and milk. 
 
 yd Group. All substances which originally contain neither alcohol nor sugar, but 
 the constituents of which may be converted into sugar and dextrose. Such are starch, 
 inuline, lichenine, pectin compounds, and cellulose, chiefly found in 
 
 (a) Roots and bulbs : Potatoes, dahlia roots, &c. 
 
 (b) Cereals : Rye, wheat, barley, oats, maize, and rice. 
 
 (c) Leguminous and other seeds : Buck- wheat, millet, black or negro millet, peas, 
 
 lentils, beans, vetch, chestnut, horse-chestnut, oak leaves, &c. 
 
 (d) Substances containing cellulose : Sawdust, paper, straw, hay, leaves, osiers, 
 
 moss. 
 
 In the future a 
 
 ajtk Group may be added, which will embrace all substances which probably 
 may enter into the synthetic preparation of alcohol, and thus form what might be 
 called a mineral spirit. Berthelot in 1855 proved that alcohol can be formed from 
 olefiant gas and water (C 2 H 4 + H 2 = C 2 H 6 0). Olefiant gas, when agitated for a 
 length of time with concentrated sulphuric acid, gives rise to the formation of sulpho- 
 vinic acid: and from this liquid, after having been diluted with water, a dilute 
 alcohol can be distilled. This experiment has as yet only a scientific interest ; the 
 process has been tried on the large scale in France, but failed to be commercially 
 available. 
 
 For the conversion of the starch of potatoes, &c., into maltose, diastase is employed. 
 The production of malt for the distiller differs little from that of a malt for brewing. 
 For the purpose of distilling, it is necessary to produce a malt which is able to split up 
 a maximum of starch into maltose and dextrine. It is, therefore, the object of the 
 distillery maltster to produce a maximum of diastase in the sprouting barley and to 
 bring it into a state of efficacy. 
 
 Saccharification. As has been explained above, when starch is split up by the 
 action of diastase at temperatures below 75, there are formed diastase and dextrine ; 
 this process is saccharification. By the action of dilute sulphuric acid upon starch at 
 higher temperatures there is formed, along with dextrine, chiefly dextrose, and also- 
 small quantities of maltose. By the prolonged action of sulphuric acid much though 
 not all of the dextrine changes into dextrose. The dextrine which is formed from 
 starch by the action of diastase may be regarded as non-fermentable in the short time- 
 allowed for the alcoholic fermentation in distilleries, and yet during the fermentation 
 it is converted into a fermentable sugar as appears from the experiments of 
 Delbruck and Marcker by the subsequent action of the residual diastase. When, 
 therefore, the fermentable maltose has been used up by the yeast, the residual diastase 
 converts the dextrine into maltose. For the exhaustion of the fermentable material 
 it is therefore necessary to retain diastase in the mash for alcoholic fermentation. 
 The secondary action of the diastase is disturbed by too high a temperature and by 
 lactic acid in the fermenting mash. 
 
 Mashing Process. The mashing process was formerly carried on in distilleries in 
 the same manner as in breweries. The new methods are based upon the use of steam 
 under pressure, and have been developed in different directions by Hollefreund, Bohm, 
 and Henze. 
 
 All these new mashing processes aim at a simplification of the operations, a better 
 utilisation of the raw materials, perfection and certainty in execution, or (like the 
 apparatus of Henze) simplification in the saccharification. The apparatus of Holle- 
 freund consists of a horizontal vessel resembling a steam boiler, and for a fermenting 
 space of 4000 litres it must have a capacity of 6000 litres. The potatoes 3000 kilos. 
 for the above capacity are introduced through a man-hole, and heated by direct steam 
 
SECT. VI.] 
 
 THE MANUFACTURE OF SPIRITS. 
 
 Fig. 522. 
 
 after the apparatus has been closed, until the temperature reaches 137 to 143, which 
 answers to a pressure of 2 to 2\ atmospheres. An agitator, consisting of knives placed 
 spirally around a shaft, is set in action to comminute the potatoes. The steam is then 
 blown oft' by opening a valve, and the temperature is let sink to about 160, a degree, 
 however, which would still destroy the diastase in the malt which is now added. An 
 artificial refrigeration is therefore needed. As soon as the pressure in the mashing - 
 pan has fallen to i atmosphere the valve is closed, and an air-pump connected with 
 the apparatus is set in action which causes the contents to boil and water to evaporate. 
 By a powerful air-pump it is possible in fifteen minutes to reduce the temperature 
 from 1 06 to 65. The rarefaction of the air serves to suck the bruised malt into 
 the apparatus and effect saccharification in a very short time. 
 
 Bohm's apparatus consists of a pan in which the potatoes are steamed. The 
 apparatus works without an air-pump, and effects refrigeration by a combined agitat- 
 ing and cooling arrangement. The agitator consists of flat cylindrical vessels of sheet- 
 iron, fitted 011 their surfaces with knife-like projections, in order to comminute the 
 potatoes. The sheet-iron cylinders are fixed 011 a hollow axle in such a manner that 
 the cooling wnter passes through the cylinders and escapes through a double tube in 
 the hollow axle. The apparatxis is cooled from without by sprinkling with cold 
 water. 
 
 Both apparatus require a great mechanical power, and have been almost completely 
 superseded by that of Hen/e, a cylinder of strong boiler-plating, provided with a 
 manometer and a safety-valve. It is filled with 
 potatoes through a man-hole in the cover ; 
 steam is introduced through pipes, one of 
 which opens underneath the cover, and the 
 others in the lower conical part, until all the 
 air has been expelled through the open safety- 
 valve, which is then closed, and a pressure of 
 2 to 3 atmos. is given. After the steaming 
 process, the lower valve is opened, so that the 
 potatoes are forced out in a state of fine 
 division. They then arrive in a preliminary 
 mashing-tub, cooled by means of water ; they 
 meet here with the needful supply of malt, and 
 are easily liquefied. Greatly to be recommended 
 is the method of admitting steam introduced at 
 Biesdorf, which sets the mass in rotatory move- 
 ment. In order that the steam may move 
 spirally upwards, the inlet-pipe, c (Fig. 522), is 
 turned upwards. 
 
 According to the experiments of Maercker 
 and Delbriick on the action of the modern 
 steaming apparatus, the starch of the fresh 
 potato floats in a watery liquid, as shown in 
 the section (Fig. 523) of a potato magnified 
 400 times. The intercellular substance, con- 
 sisting of matters resembling pectine, which connects the several cells, is insoluble in 
 cold water, but is readily converted into soluble substances in boiling water under pres- 
 sure. Fig. 524 shows the cells of a potato steamed at 3 atmospheres ; the starch 
 granules are completely swelled, and the intercellular matter is perfectly dissolved ; the 
 cells still hang together, but they are easily separated if they have not all burst. 
 
 The further continuation of this part of the subject would be superfluous where, as 
 
764 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 in Britain, the distiller does not operate upon roots, but upon either grain or saccharine 
 matter. 
 
 Fig 523- 
 
 Figr. 524. 
 
 Preparation of a Vinous Mash. Vinous Mash from Cereals. Grain brandy (corn 
 brandy) may be prepared from either wheat, rye, or barley. Generally more than one 
 kind of grain is xised, because experience has proved that a larger quantity of alcohol is 
 obtained when two kinds of grain for instance, wheat and barley, rye and barley are 
 mixed. A mixture of rye with wheat or barley malt, or wheat with barley malt, is very 
 generally used, at least abroad. To i part of malt from 2 to 3 parts of non-malted gram 
 are usually taken. Either, as is done in England, wort is made, the gram being first 
 malted, next mashed, and the wort drawn off, or the mixture of malt or unmalted gram is 
 allowed to ferment together. The latter method is more usual in Germany, and will be 
 that described here. In Russia and Sweden brandy is prepared without malting ; by 
 properly mashing rye-meal a reaction ensues between its constituents, the effect of 
 which is the same as if it had been acted upon by diastase of malt 
 
 The preparation of a mash from grain may be considered as consisting of the follow- 
 ing four operations : 
 
 (1) The Bruising. The materials, malted as well as unmalted grain, are first 
 bruised. As it is not essential in the manufacture of spirits that a clear wort should 
 be prepared, the grain may be broken up very small, whereby the formation of sugar 
 is rendered more complete. Green malt is now generally considered preferable by many 
 distillers. 
 
 (2) The Mixing with Water. Making of Mash. This operation is almost identical 
 with that of the mashing of the brewer ; the only distinction being that the distiller 
 aims at the entire conversion of the starch into glucose, while the brewer does not re- 
 quire this, as he also wants some dextrine. The complete saccharification, and next 
 the complete conversion of the glucose into alcohol during fermentation, are possible 
 only with a certain degree of dilution of the mash. The quantity of water to be 
 mixed with the grain must not be reduced too much, because that would involve a loss 
 of spirits. 
 
 (3) The Cooling of the Mash. When the saccharification is complete, the mash 
 should be rapidly brought to the temperature suitable for fermentation by being 
 placed in cooling vessels, just as is done with the wort in brewing, by being placed in 
 an apparatus termed a refrigerator, or by the application of ice or cold water. The 
 temperature to which the mash has to be cooled varies according to the locality and 
 the duration of the fermentation, but it averages 23 C. When sufficiently cooled the 
 liquid is placed in the fermenting vats. 
 
 (4) The Fermentation of the Mash. The fermentation vat is generally made of wood, 
 
SECT. VI.] 
 
 THE MANUFACTURE OF SPIRITS. 
 
 765 
 
 though sometimes stone is used. The first possesses the property of retaining the heat 
 for a longer time, and, for the same reason, large vessels are preferred. The capacity 
 seldom exceeds 4000 litres. Either beer yeast in its fluid condition or dry yeast is used 
 to set up fermentation. The latter is mixed with warm water before being added to the 
 contents of the fermentation tanks. Of the fluid beer yeast there are usually taken 
 to 1000 litres of mash 8 to 10 litres ; while for 3000 litres of mash 15 to 20 litres of 
 yeast are a sufficient quantity. Of the dry yeast, f kilo, is employed to 1000 litres 
 of mash, or i kilo, of yeast to 3000 litres of mash. In large distilleries artificial 
 yeast is sometimes employed, as beer yeast of the requisite quality cannot always be 
 procured at a remunerative price. The mode of adding the yeast is the same as that 
 employed in breweries. After standing for from three to five hours the temperature of 
 the mash will have increased to from 30 to 32. Carbonic acid is then given off, and 
 the heavier substances settle to the bottom of the tank. This continues for about 
 four days, when the clear fluid may be considered ready for further operations. 
 
 The yield of alcohol is better if the temperature is reduced to 2 7- 28. It 
 is therefore prudent to sus- 
 pend in the cooling-beck a Fi - 5 2 5- 
 copper refrigerating worm tra- 
 versed by cold water, as shown 
 
 in Fig- 5 2 5- 
 
 An apparatus for cooling 
 introduced by Eckert is shown 
 in Fig. 526. The agitators, 
 formed as U -tubes, can be 
 
 easily taken to pieces. In the front sides of the vat, A, is fixed the shaft a, 
 upon which are arranged within the vat a number of hollow rings, b. At the ends 
 
 Fig. 526. 
 
 of the shaft a there is fixed a rather longer ring, c, provided with a screw thread. 
 Upon this thread two female screws, c v are cut, so as to hold the rings, 6, fast 
 together. Each of the rings, b, has two radial perforations, in which threads are 
 cut, and in which a number of U -tubes, d, are screwed, and connected by concentric 
 rings in such a manner that the ends of each tube, d, open into two rings, 6, lying side 
 by side. Thus all the rings and tubes form with the shaft a system which can be set 
 in motion. This system of pipes effects an energetic mixture of the mass in the vat 
 by means of its curvature. In order to effect an afflux and reflux of the water for 
 cooling, a pipe, g or h, is pushed upon the shaft a, over the rings, c. This pipe is 
 closed by the stuffing-boxes, e. Both tubes, g and h, are fitted with short pieces, 
 I or m, of which the former effects the influx of the cooling water and the latter its 
 outflow. 
 
766 CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 Spirits from /Sugar Waste. In India the scum from the boiled sugar, the molasses, 
 <fec., are brought to fermentation and the fermented fluid distilled. The product is in 
 the English colonies known as Sum, in Madagascar and Mauritius as Guildine. The 
 peculiar aroma of rum is contained in the portion which first distils over. By the 
 fermentation and distillation of the scum from the boiling of the sugar-cane juice, a 
 coarse, sour, dark brown or black-coloured, acrid-tasting brandy is obtained ; it is 
 known as Negro rum. In England and Germany rum is frequently made from the 
 diluted molasses of the sugar refineries fermented with yeast, the fermented fluid being 
 distilled after about three or four days' fermentation. The aroma peculiar to rum is 
 obtained by the addition of some pelargonic ether or essence of pine-apple. Beet-root 
 molasses is also largely used for the purpose of obtaining spirits. By itself the beet- 
 root sugar molasses is difficult to ferment, but if the alkalinity of this material is 
 first neutralised by the addition of some sulphuric acid, and the material next boiled 
 with a further addition of acid for the purpose of converting into inverted sugar the 
 cane sugar it yet may happen to contain, the fermentation may be readily set up and 
 regularly proceed. 100 kilos, of molasses yield on an average 40 litres of spirit. The 
 very objectionable odour of this spirit is due to fusel oil, which contains small quanti- 
 ties of propylic, butylic, and amylic alcohol, pelargonic acid, and caprylic acid, while 
 later researches have added to this list cenanthic, caproic, and valerianic acids. The 
 residue left in the retort is used for the preparation of potassa (see page 291). The 
 addition of sulphuric acid has not only the effect of converting the cane sugar into 
 an easily fermentable sugar, but also prevents the setting up of lactic-acid fer- 
 mentation. 
 
 Spirits from Wine and Lees. The distillation of spirits from wine is chiefly carried 
 on in France, Spain, and Portugal. The yearly production of spirits from wine or 
 French brandy (alcool de vin) in France alone amounts to 450,000 hectolitres of 85 
 per cent, and 400,000 hectolitres of 60 per cent. The quality of the spirit is indirectly 
 affected by the degree of ripeness of the grapes, and directly by the care bestowed 
 upon the fermentation and distillation, by the more or less intimate mixture of the 
 volatile principles of the wine with the alcohol, and by the age of the wine. Old wine 
 yields a spirit of better quality than new wine. The freshly distilled brandy is colour- 
 less, and remains so even when bottled ; but since the spirit is kept in oaken casks it 
 extracts therefrom some colouring and extractive matter. The best kinds of brandy 
 are distilled in the Departement de Charente, and the brand known in commerce as 
 Cognac (name of a town) is the most valued. From the marc and wine-lees spirit is 
 also distilled. By the distillation of spirits from wine a residue is left in the retort 
 (the vinasse) which contains a large quantity of glycerine, which may thus be obtained 
 as a bye-product. 
 
 Since the invasion of the phylloxera the amount of spirit distilled from Avine has 
 sunk to about 15,000 hectolitres (1885). 
 
 Fermentation. The addition of yeast to the cooled mash in the fermenting vat 
 takes place in the same manner as with malt. To 100 kilos, of mash are added i to 
 2 litres of beer-yeast, or f to i kilo, of dry yeast. The potato mash contains, besides 
 the husks of malt and grain, some finely divided cellular tissue ; these substances during 
 fermentation are carried to the surface of the mash and form a scum, the appearance 
 and behaviour of which give an opportunity of judging the progress of the fermenta- 
 tion. The fermentation is said to be regular or irregular ; the former begins some 
 four to six hours after the yeast has been added, and proceeds in a regular manner, 
 the end depending upon the quantity of yeast added and upon the temperature. The 
 progress is quiet, not violent, the scum which appears on the surface sinking or being 
 drawn to one side of the vat and thrown up at the opposite side, while bubbles of air 
 or gas appear and burst on the surface, much as bakers' dough heaves under the 
 
SECT, vi.] THE MANUFACTURE OF SPIRITS. 767 
 
 influence of the ferment. Irregular fermentation is so far opposed to the former that 
 the surface of the mash is only partly covered with froth, which remains in one 
 position, and does not move of itself. The result of such a fermentation is generally 
 defective, the reason being the incomplete saccharification of the mash, the addition of 
 too small a quantity of yeast, or, finally, working at too low a temperature. After 
 about sixty to seventy hours with a regular fermentation, the mash is ready for distil- 
 lation. Recently, large quantities of spirits have been prepared from maize and also 
 from rice. 
 
 Distillation. The fermented mash (as obtained from potatoes) is a mixture of non- 
 volatile and volatile substances. To the first belongs the fibre, malt husks, inorganic 
 salts, protein substances, undecomposed and decomposed yeast, succinic acid, lactic 
 acid, glycerine, <fec. ; to the volatile, the alcohol, fusel oil, water, and small quantities 
 of acetic acid. The volatile constituents of the mash, the products of the fermenta- 
 tion, are separated from the non- volatile by distillation, during which the volatile 
 constituents are converted into vapour, afterwards cooled and condensed in another 
 vessel. When a vinous mash is heated to the boiling-point, vapours are generated 
 which consist essentially of alcohol and water ; by condensing these vapours there is 
 obtained a mixture of alcohol and water. 
 
 Water boils at+ 100, barometer 760 mm. 
 Alcohol + 78-3, 
 
 Thus it might be thought that, while the boiling-point of water is 21-7 higher 
 than that of alcohol, it would follow that, when a vinous mash is heated to 80, only 
 the alcohol would be converted into vapour, the water remaining behind. But this is 
 not the case, for under all circumstances the boiling-point of a mixture of alcohol and 
 water is higher than that of pure alcohol alone, and the vapour formed consists of both 
 alcohol and water. The reason is partly due to the affinity of alcohol for water, partly 
 also to the fact that water evaporates at a lower temperature than its boiling-point ; 
 the former (affinity) retains alcohol and prevents its escape at proper boiling-point 
 (78'3) in the shape of vapour. If the mixture of alcohol and water be heated to its 
 boiling-point (suppose 90), much more alcohol will be converted into vapour, because 
 its boiling-point is lower, while of water only just so much is evaporated as would be 
 the case were it when pure to be heated to this temperature, while simultaneously a 
 current of air is passed through it, because the vapours of alcohol evolved from the 
 mixture act exactly in the same manner as would a current of air carried through the 
 mixture of alcohol and water, the former substance taking up just as much water as 
 will be volatilised at the boiling-point of the mixed liquids. As the quantity of vapour 
 evolved from a liquid bears a direct relation to the temperature of that liquid, the 
 quantity of aqueous vapours in the mixture of vapours will increase according to the 
 increase of temperature, until at last, as soon as the boiling-point rises to that of water 
 (100), no more alcohol will be present in the vapours which are given off. At the 
 commencement of the distillation the vapour given off contains much alcohol and very 
 little water ; presently more water comes over, and finally only water. It is therefore 
 quite evident that we cannot by distillation separate alcohol at once from the rest of 
 the volatile constituents of a vinous mash liquor. By interrupting the distillation at 
 the proper time, there is obtained in the distillate all the alcohol contained in the 
 mash, along with a certain quantity of water, while the residue of the distillation will 
 not contain any trace even of alcohol. The liquor obtained by the first distillation is 
 generally very weak alcohol, and requires further rectification, as it is termed, to 
 increase tho proportion of alcohol. This rectification (another process of distillation) 
 may be continued till the alcohol contains only a small quantity of water, which can 
 only be eliminated by the aid of such substances as have a greater affinity for water 
 than the alcohol, which retains that liquid very tenaciously. Anhydrous, or absolute 
 
768 CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 alcohol, can only be obtained by treating highly rectified alcohol with some substances 
 which have a great affinity for water, such as caustic lime, fused calcium chloride, 
 <fec. ; but really absolute alcohol is never used on the large scale in industry. The first 
 portions of liquid obtained by the distillation of vinous mash are rich in alcohol, and are 
 termed fore-run or first-run, while the last portions of the fluid yet containing alcohol 
 are termed after-run. A doubly rectified alcohol contains 50 per cent, pure spirit ; but 
 by means of rectification alone a stronger alcohol than of 95 per cent, cannot be 
 obtained. The residue of the distillation is called fluid-wash. 
 
 Apparatus for Distillation. A distilling apparatus as usually employed consists in 
 its simplest form of four parts namely, the still or retort, the head or cap of the 
 still, the cooling apparatus, and the receiver. 
 
 The still or retort is generally constructed of sheet-copper more rarely, of iron 
 boiler-plates. The shape of the vessel varies, but is generally a somewhat flattened 
 cylinder, provided with a round opening of 12 to 14 inches diameter, fitted with a 
 collar about i inch in height forming the neck, on which the cap or head is placed. 
 The bottom of the still is either somewhat bulged inwards at the centre or is quite 
 flat. The residue of the distillation is removed through a waste-pipe fitted with a 
 stop-cock attached to the bottom of the vessel. From the cap or head a pipe conveys 
 the volatilised alcohol to the receiver, while jutting obliquely from the top of the still 
 is a pipe for the introduction of the mash. The head carries the vapours from the 
 still into the cooling or condensing apparatus ; although a simple tube might answer 
 this purpose, it is preferred to make the head of the stills large and wide, not only for 
 the purpose of separating any particles of mash which might happen to be carried oft" 
 with the vapours of the boiling liquid, but also to obtain a distillate richer in alcohol, 
 because an increased surface is favourable to the cooling of the vapours, whereby 
 the aqueous vapour is first condensed ; moreover, large heads are advantageous, lest 
 by a rapid evolution of vapours the mash might boil up (priming) ; roomy space in 
 the head then prevents the liquid passing over into the worm. Since the volume of 
 the vapours decreases during the condensation, a somewhat conically shaped head would 
 be the best form for this portion of the apparatus. The cooling apparatus is not 
 simply destined to convert the vapours carried into it from the head into liquid, but it 
 is also required that this liquid be so far cooled down as to prevent at least as much 
 as possible the evaporation of the distillate ; the condensing apparatus should not 
 be too roomy ; that is to say, there should not be too much space for the vapours, 
 because this would cause air to enter the cooling apparatus, and this air, while mixing 
 with the vapours of alcohol, carries off along with it some of this fluid, thereby causing 
 a loss of the fluid. It is also requisite that the cooling apparatus be strongly made, 
 yet at the same time so constructed as to admit of being readily taken down for 
 cleansing purposes and easily fitted up again ; usually the cooling apparatus techni- 
 cally termed worm consists of a series of spirally bent tubes made either of block 
 tin or copper, seldom of lead ; this apparatus is placed in a large wooden or metal vat 
 containing cold water, or as in the more recently constructed distilling apparatus, cold 
 vinous mash, which is thus made warm previous to being transferred into the still, 
 whereby, of course, a saving of fuel is effected. 
 
 The principal improved apparatus which we shall describe are those of Pistorius, 
 Gall, Schwarz, Siemens, and Cellier-Blumenthal. 
 
 Pistorius's Apparatus. Pistorius first introduced in Germany a distilling apparatus 
 fitted with two stills ingeniously connected with rectificators and dephlegmators. 
 When a distilling apparatus is required which not only extracts all the alcohol from 
 the mash, but also produces the alcohol in' a very pure and concentrated state, per- 
 forming this work with the least possible expenditure of fuel and labour, Pistorius's 
 apparatus answers the purpose admirably. A and B, Fig. 527, represent the two stills. 
 
SECT. VI.] 
 
 THE MANUFACTURE OF SPIRITS. 
 
 769 
 
 A is the main still, which is either placed on a furnace and heated directly by fire or 
 by means of steam. Heating by steam-pipes instead of direct firing possesses many 
 advantages. The second still, B, is placed at a somewhat higher level than the first, 
 and when not heated by steam-pipes is situated on the flue of the furnace fire of the 
 first still. The main still, A, is fitted with a large helm, D, fastened on the still with 
 bolts and nuts, p is a tube projecting from the helm and provided with a safety-valve 
 which opens inwards, in order to give access to air as soon as a vacuum ensues in the 
 interior of the apparatus towards the end of the distillation in consequence of the con- 
 densation of the vapours. There is also connected with this tube, p, a small condenser 
 q, as in Dorn's apparatus, from which samples showing the progress of the distillation 
 may be taken. In both stills stirring apparatus, m and n, are fitted to prevent 
 the mash from burning. By the tube x the vapour of the " low wine " is admitted 
 to the second still, the mash-still. From the helm, F, of the mash-still a curved pipe, 
 s, conveys the vapour to the mash fore-warmer, which, as in Dorn's apparatus, is 
 
 Fig. 527. 
 
 divided into two parts, the upper, E, containing the mash, the lower, g (the "low wine" 
 cis-tern), the vapour ascending along the narrow passage, V, to the rectification 
 apparatus, H. Frequently the vapour is conveyed to a third still before entering #/ 
 this still is not shown in the drawing. The rectification apparatus, ff, consists of two 
 or three conically shaped vessels, made of sheet-copper and connected together, and is 
 provided with a cistern filled with water, W ' ; it is connected with the condenser, R, by 
 the tube C. The tube x conveys cold water to the rectification apparatus, and the 
 short tube, y, does so to the fore-warmer. The pump, P, is employed to pump the 
 mash from the cistern, Z, to the fore-warmer; thence it is carried to the second still, 
 and thence again to the first still. When both stills and the fore-warmer are filled 
 with mash, the fire is lighted under the first still. The steam or vapour from the 
 inash in A passes to the mash in B, which is thereby heated to the boiling-point. The 
 still B serves, therefore, the purpose of a rectificator. When the distillation has begun, 
 the vessel, W, on the rectificator is filled with cold water, which is re-supplied when it 
 has become warmed by the passing vapours. As soon as the steam reaches the upper 
 
 3 c 
 
770 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. TO. 
 
 rectificator, the real distillation commences. The condensed fluid drops into a cistern 
 in which a hydrometer is placed. 
 
 Gall's Apparatus. In most apparatus for distilling from a vinous mash the distil- 
 late becomes gradually weaker and is not throughout of the same strength. Gall and 
 Marienbad have endeavoured to avoid this defect in their apparatus, Fig. 528, 
 so as to obtain a more uniform product during each distillation. Two stills are placed 
 in a suitable manner in a steam-boiler and the stills are connected with the separator 
 (low wine cistern). B B are the stills ; C is a boiler with flues, * i. The stills, in order 
 to prevent them cooling, are fixed into the boiler. D is a third still placed on, not in, 
 the boiler ; E is the low wine cistern ; F and G two dephlegmators or separators ; A 
 is a condenser with a worm, H. The mash is put first into the still D by means of the 
 tube a a, this still serving as a fore-warmer and rectificator. From this still both the 
 
 Fig. 528. 
 
 stills B B are filled. From the boiler a current of steam is conveyed through the bent 
 tube, b, into the three-way cock, c, whence the steam is either passed into one or both 
 the stills B B, or is conveyed upwards by the tube b to the vessel destined to steam the 
 potatoes. The vapour from one or both of the stills B B proceeds to the still Z>, and 
 thence into the low wine cistern, E, and passing through the dephlegmators, F and G, 
 finally enters into the condenser. The peculiarity of Gall's apparatus consists in that 
 by the peculiar arrangement of tubes and stop-cocks, each of the two stills may at will 
 be brought into action, it being possible to turn the s,team at pleasure into the right- 
 hand still, and next into the left-hand still, or vice versa. Each still may be also dis- 
 connected, the wash therefrom discharged, and the still re-filled without in the least 
 interrupting the working of the other apparatus of the portions ; the distillation can 
 therefore proceed uninterruptedly, one part of the apparatus being filled while the 
 other is at work. 
 
SECT. VI.] 
 
 THE MANUFACTURE OF SPIRITS. 
 
 771 
 
 Schwarz's Apparatus. Schwarz's apparatus is in very general use in the south-west 
 of Germany. It consists, Fig. 529, of the steam boiler, D ; two mash-stills, A and B ; 
 the fore-warmer, C ; the " low wine " cistern, or receiver, E ; the rectificators, H and 
 F ; and the condenser, G. M is a, reservoir for cold, N one for hot water. The steam 
 generated in the boiler, Z>, passes through the pipe, g, into the under compartment, A, 
 of the double still, and through the mash contained there becoming mixed with vapours 
 of alcohol, it arrives in the helm z, and further makes its way by means of the tube u 
 into the upper part of the double still; thence, after a double rectification, it is conveyed 
 by means of the tube t to the fore- warmer, G ; the upper part of this vessel, pro- 
 vided with the tubes a a a, acts as a dephlegmator or separator, the condensed fluid 
 flowing into E. The steam which arrives from the upper part of the still passes 
 through E, and thence, by way of the tubes a a, into the helm and the tube n, which 
 latter is surrounded with the vessel H, kept cold by means of cold water ; the dephleg- 
 mation continues here. From H the steam passes through V to F, an apparatus cor- 
 
 Fig. 529- 
 
 responding to the fore-warmer, C, but of smaller dimensions, because here the 
 quantity of vapour has become greatly reduced while it has become richer in alcohol. 
 The dephlegmator tubes are here surrounded by cold water, not by cold mash, the 
 former liquid being constantly renewed so as to keep cold. The steam or vapour 
 collected in the helm b is sufliciently laden with alcohol to admit of being at once 
 conveyed to the condenser, G, the condensed distillate flowing out at i. The vinous 
 mash is first poured into the fore-warmer, (7, wherein it is occasionally stirred by the 
 arms, d d, and crank, d, so as to keep it uniformly mixed and heated. When the mash 
 has become warm it is conveyed into the upper compartment of the double still by the 
 pipe e, and into the lower compartment through the open valve ; this compartment 
 also serves as cistern for the phlegma from all other parts of the apparatus ; the fluid 
 flows backwards from the compartments h and I of the rectificators, H and F, by way 
 of the tubes m' and n, into the low wine cistern, E, thence into the upper compart- 
 
772 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 ment of the double still, where it mixes with the mash. As soon as the mash has given 
 up all its alcohol, which can be ascertained by testing the inflammability of the vapour 
 issuing from the test stop-cock, o, the residue is removed by opening the tap, p. By 
 means of the tubes q q q, the rectificators and condensing apparatus are supplied with 
 cold water. The warm water from the condenser is conveyed by the tube r into the 
 boiler. By means of fi, the steam can be admitted to the potato vessel, and by S into 
 the reservoir, N, when it is desired to heat the water it contains to the boiling-point. 
 Schwarz's apparatus possesses the advantage of being easily taken to pieces and 
 cleansed. But, on the contrary, among its disadvantages are the following : The con- 
 struction of the mash-warmers is not quite suited for the purpose, while also the 
 condensed liquid in E is not brought sufficiently into contact with the hot steam to 
 effect a thorough distillation or rectification. The steam passes so quickly through 
 the liquid that it is only very imperfectly deprived of its water (dephlegmated) when 
 it reaches the dephlegmation apparatus, where it will consequently be but imperfectly 
 rectified, while the vertical steam-pipes offer too few points of contact, and allow 
 much steam to pass off without being fully condensed ; while even the partly con- 
 densed vesicular steam is carried off along with the steam escaping condensation. The 
 condenser itself is imperfect, being constructed of a number of vertical pipes, through 
 which the condensed liquid rapidly falls without becoming quite cold, and in order to 
 
 obtain a sufficient condensation an 
 immense quantity of cold water has to 
 be used. 
 
 /Siemens's Apparatus. Among the 
 apparatus capable of producing a large 
 quantity of spirits at a small cost is 
 that of Siemens. This apparatus is 
 much used in the distillation of brandy. 
 It consists, Fig. 530, of two mash-stills 
 set in a boiler, and capable of being 
 alternately used (by means of the three 
 cocks, a, b, and c), in the same manner 
 as in Gall's apparatus, while the fore-warmer and dephlegmator is constructed accord- 
 ing to Siemens's plan L is the boiler; P one of the mash-retorts; K is the low wine 
 receiver; R the fore- warmer; A, a reservoir in which the condensed water intended 
 as feed water of the boiler is collected ; is the dephlegmator ; B a reservoir for the 
 
SECT. 7i.] THE MANUFACTURE OF SPIRITS. 773 
 
 vapours condensed in C. From the dephlegmator the vapour passes to a condenser not 
 shown in the engraving. This apparatus is constructed of such dimensions that it can 
 perform the work about to be mentioned. The boiler has to steam about 5000 kilos, 
 of potatoes in four lots, during from forty to forty-five minutes each, and should thus 
 lie capable of yielding in three hours the fifth part of the weight of the potatoes, = 1000 
 kilos., or in one hour 333 kilos, of steam, which renders necessary a steam-generating 
 surface of about 1 1 square metres. But since the distillation requires steam also, this 
 generating surface has to be increased by about 20 per cent., and should consequently 
 be 13-5 to 14 square metres. The size of the mash-stills should be sufficiently large 
 to contain with ease 500 litres when properly filled because, as already stated, the fluid 
 from A is not returned to the still, but to the steam-boiler, the stills being set into the 
 last-named vessel not becoming externally cooled, whereby the quantity of water carried 
 along with the vapours of spirit is compensated for. 
 
 The mash-warmer consists of a cylindrical portion, i i, the lower part of which 
 has an indentation, c. In the cylinder is placed a narrower portion, o o, of the real 
 mash-containing vessel fitted with the heating tube,/w. The upper part of the fore- 
 warmer is fitted to the lower part by means of the flange, h h. r is a stirring apparatus, 
 which is frequently set in operation during the process of distillation. The vapours 
 from the second still are carried into the depression, c, under the fore-warmer, which, 
 in order that the vapours may come into contact with the phlegma, is covered with a 
 sieve. The vapours surround the under part of the mash reservoir and enter into the 
 tube /, through which they pass to the lower cylinder of the dephlegmator. The con- 
 densed water of the dephlegmator is conducted into the reservoir, A. The upper and 
 under part of the fore-warmer are made of cast-iron, but the interior bottom and 
 heating surfaces are made of copper. This kind of fore-warmer has the advantage of 
 uniformly distributing the heat, while it can be easily cleansed. The dephlegmator, C, 
 is so contrived that the rectified vapour can be conveyed to the condenser by two separate 
 pipes placed in an opposite direction to each other, and are joined again in close 
 proximity to the condenser. The remainder of the details will be seen on studying the 
 drawing. 
 
 Continuous Distilling Apparatus. Among the distilling apparatus intended for the 
 distillation of wine (not of mash), and so constructed as to be fit for continuous 
 working, we must not neglect to mention the apparatus of Cellier-Blumenthal, as 
 improved by Derosne, and represented in Fig. 531. This apparatus consists of two 
 stills, A and A' ; the first rectificator, B ; the second rectificator, C ; the wine warmer 
 and dephlegmator, D ; the condenser, F ; the regulator, E ; a contrivance for regulating 
 the flow of the fluid wine from the cistern, G. The still A, which, as well as the still 
 A', is filled with wine, acts as a steam boiler. The low wine vapours evolved come, when 
 they have arrived in the rectificators, in contact with an uninterrupted stream of wine, 
 whereby dephlegmation is effected ; the vapour thus enriched in alcohol becomes still 
 stronger in the vessel Z), and thence arrives at the cooling apparatus, F. In order that 
 a real rectification should take place in the rectificators, the stream of wine should be 
 heated to a certain temperature, which is imparted to it by the heating of the condenser 
 water. The steam from the still A' is carried by means of the pipe Z to the bottom of 
 the still A. Both stills are heated by the fire of the same furnace. By means of the 
 tube B' the liquid contained in the still A can be run into the still A'. The first 
 rectificator, , contains a number of semicircular discs of unequal size, placed one 
 above the other, and which are so fastened to a vertical centre rod that they can be 
 easily removed and cleansed. The larger discs, perforated in the manner of sieves, are 
 placed with their concave surfaces upwards. In consequence of this arrangement the 
 vapours ascending from the stills meet with large surfaces moistened with wine, which, 
 moreover, trickles downwards in the manner of a cascade from the discs, and comes, 
 
774 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 therefore, into very intimate contact with the vapours. The second rectificator, C, ia 
 fitted with six compartments; in the centre of each of the partition walls (iron or 
 copper plates) a hole is cut, and over this hole, by means of a vertical bar, is fastened 
 an inverted cup, which nearly reaches to the bottom of the compartment wherein it is 
 placed. As a portion of the vapours are condensed in these compartments the vapours 
 
 are necessarily forced 
 
 Fig- S3 1 - through a layer of low wine, 
 
 and have to overcome a 
 pressure of a column of 
 liquid 2 centimetres high. 
 The fore-warmer and de- 
 phlegmator, Z>, is a hori- 
 zontal cylinder made of 
 copper fitted with a worm, 
 the convolutions of which 
 are placed vertically. The 
 tube M commxmicates with 
 this worm, the other end 
 of which passes to 0. A 
 phlegma collects in the con- 
 volutions of this tube, which 
 is richer in alcohol in the 
 foremost windings and 
 weaker in those more re- 
 mote : this fluid, collecting 
 in the lower part of the 
 spirals, may be drawn off by 
 means of small tubes, thence 
 to be transferred, at the 
 operator's pleasure, either 
 all or in part, by the aid 
 of another tube and stop- 
 cocks, to the tube 0, or 
 into the rectificator. By 
 means of the tube L the 
 previously warmed wine of 
 the clephlegmator can be 
 run into the rectificator. 
 The condenser, F, is a cylin- 
 drical vessel closed on all 
 sides, and containing a 
 worm communicating with 
 the tube 0. The other end 
 of the condensing tube car- 
 ries the distillate away. 
 On the top of this portion of the apparatus the tube K is placed, by means of which 
 wine is run into the dephlegmator. The cold wine flows into the cooling vessel by 
 the tube /. When it is desired to work with this apparatus, the first thing to be 
 done is the filling of the vessels A and A' with wine. The stop-cock, U, is then opened, 
 whereby the tube J, the condenser, F, and the dephlegmator are filled with wine. The 
 wine in the still A' is next heated to the boiling-point ; the steam enters the tube Z 
 and is condensed in A until the wine here is heated to the boiling-point by the combined 
 
SECT, vi.] THE MANUFACTURE OF SPIRITS. 775 
 
 effect of the steam and the hot gases circulating in the flue. The low wine vapour then 
 passes to the rectificator, B, and thence into the worm of the dephlegmator, D, where 
 the greater portion of it is condensed, the phlegma flowing backwards into the rectifi- 
 cator. As soon as the fore- warmer is so far heated that the hand cannot be kept in the 
 hot wine, the stop-cock of the vessel E is opened, and the distillation commences. The 
 wine which is conveyed by the tube J into the cooling vessel, F, soon begins to become 
 hot, and is then conveyed to the fore-warmer, where its temperature becomes nearly as 
 high as the boiling- point ; by means of the tube L this fluid is conveyed into the recti- 
 ficator, , and thence into the still A. 
 
 As soon as the wine in the still A' contains no more alcohol, the stop-cock fitted to 
 the lower part of the vessel is opened, and the vinasse run off at R, the still being re- 
 supplied by opening the stop-cock B'. The vapour proceeds in the same way, but in a 
 reversed direction ; when the vapour has been condensed in F it is first collected, as 
 alcohol, in the small vessel, N, provided with an areometer, and thence conveyed to the 
 cistern, H. The strength of the alcohol obtained by means of this apparatus increases 
 with an increase of the number of coils of the condenser placed in the dephleg- 
 mator and connected with the rectificator. Practical experience decides, according to 
 the alcoholic strength of the wines to be distilled, and the quantity of pure alcohol 
 desired in the distillate, the opening or shutting of the various stop-cocks of this 
 apparatus. Derosne's apparatus may be readily made continuous ; for this purpose it 
 is only necessary to fill the reservoir, condensing apparatus, and rectificator with cold 
 water, while the lower portion of the tube L is closed. 
 
 Among the recent continuous action apparatus is that of R. Ilge. It consists (Fig. 
 532) of the steam regulator, ABC, the mash-column, D, the vinasse regulator, E, 
 the rectifier, F, and the dephlegmator, G. The apparatus is chiefly constructed of 
 cast-iron only the cocks, the steam damper, C, and the support of the float in the 
 vinasse regulator are of brass, the float and the tubes are of copper, and certain rods 
 are of wrought iron. The function of the steam regulator is to reduce to a normal 
 pressure the boiler-steam, which enters through the cock, d, and the engine-steam, 
 introduced through the pipe, b. The body of the still, A, is filled with water up to 
 the short tube, c, which is pressed up by the steam entering by d through the tube e 
 to the float, B. The float, by means of its guide-rod, communicates its movement 
 downwards to the plunger of C. The case of C contains, as shown in the drawing, 
 two mutually superimposed expansions, f and g, each with a short pipe. Four slits in 
 the hollow piston connect, according to the movement of the float, the interior of the 
 piston either with the expansion f or with g, or with neither of the two. As long 
 as the float does not rise, the slits convey the entire steam of the boiler from f . The rise 
 of the float cuts off the steam more and more, and as, at the same time, the escaping 
 steam from the engine streams in through b, the case may occur that the slits are 
 exactly covered by the intervals between the two expansions, or extend beyond the 
 expansion g, and let the superfluous steam escape into the open air. In any case the 
 piston will place itself so that the pressure of the steam is equal to the column of 
 water raised. In order that the steam boiler is not filled with water above L, a tube, 
 h, is inserted through which the steam presses the water up and down without itself 
 escaping. In the mash-column, D, the boiling mash forms a continuous, unbroken 
 column of liquid. From the cock a' the regulated steam enters through the short 
 piece, k, into the space between the vessel 1, and the lowest cy Under, m, passes through 
 the vinasse downwards, and streams, equally distributed, in an upper direction into the 
 mash. Ribs are cast on the lower surface of the bottom m, and through their inter- 
 vals the steam enters the mash in the same direction as the mash. Hereby the liquid is 
 kept in a rotatory movement, and as it arrives at the bottom n with a movement in the 
 opposite direction, a thorough interpenetration of steam and mash is effected. Tho 
 
77 6 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 ascending vapours collect on the superjacent floor, o, and are led back into the mash by 
 the ribs, but with a rotation to the left, while a rotation to the right was produced by 
 the floor n. The upward passage of the vapours takes the same form ; at the floor 
 in the mash is turned to the right, and every floor o to the left. A plentiful distilla- 
 
 . 532. 
 
 Explanation of Terms. 
 
 Nach H 1 .... Across Section H I. 
 Nach K L . . . . Across Section K L. 
 Nach M N . . . Across Section M N. 
 
 tion takes place by both currents, and also a dephlegmation on the upper floors, where 
 the vapours meet with the cold mash flowing in by the tube p. In the elevation only 
 two ribs are shown, but on the ground floor we see the whole arrangement of the ribs, 
 
SECT. VI.] 
 
 THE MANUTACTURE OF SPIRITS. 
 
 777 
 
 Fig. 533- 
 
 seen from below. It appears from the drawing how the floors n are mounted on a 
 wrought-iron rod by means of sheaths, and how the floors n are arranged between 
 two cylinders, m. As the mash-column, D, during working, is filled with mash above 
 its highest floor, o, the vinasse, which had entered into the vinasse regulator, E, 
 through the square channel, q, has risen to the same height in the latter, though less 
 high than in D, as here the mash is specifically lighter than the vinasse. The float in 
 E communicates its upward movement by means of a rod to the vinasse cock, r, and 
 emits through the latter as much vinasse as mash enters through the pipe p. The 
 development of steam from the overheated vinasse (which is perceptible in large works) 
 is rendered innocuous by the floors s, which expedite the vapours upwards, and at the 
 same time present by their conical sections sufficient room for the ascending and de- 
 scending vinasse. The floor t, resting on four feet, keeps off the vapours from the float. 
 The ascending vapours come in intimate contact with the liquid dripping down 
 from the dephlegmator, G. The rectifier, F, and the dephlegmator, G, have four-sided 
 sections. F is filled with porcelain 
 balls from the grate up to its upper 
 edge. G contains a number of copper 
 tubes laid almost horizontally in rows, 
 among which the cooling water flows 
 upwards from row to row by means 
 of the two water-covers, u. To each 
 copper tube there are soldered slips 
 of sheet-copper, 30 millimetres in 
 length, 6 millimetres in breadth, and 
 painted below, at intervals of 25 milli- 
 metres from each other, as shown in 
 the lowest tube in the figure. The 
 alcoholic vapours rising out of the 
 mash pass through the grate, through 
 the intervals of the porcelain balls, 
 through the intervals of the cooling- 
 tubes, and ultimately through the 
 short tube, v, to the spirit-cooler. 
 Each drop which is formed on the 
 cooling-tubes runs to the next copper 
 slip, falls off from its point to the next 
 tube below, and arrives ultimately at 
 the upper layer of balls, which are 
 uniformly wetted by all the descending 
 drops as they trickle downwards from 
 ball to ball. Rectification takes place 
 on the balls and on the moistened 
 surfaces of the pipes and the slips. 
 
 In the distilling and rectifying ap- 
 paratus of Siemens Brothers & Co. 
 the principal parts are : The pre- 
 iminary heater, A, the mash-column, 
 B, and the rectifier, C (Figs. 533 to 
 
 536), formed of cast-iron pieces, held together by the long bolts, m, and with 
 joints rendered air-tight by means of varnished pasteboard. In working, the cham- 
 bers b of the preliminary-heater, A, and a part of the support, c, are full of hot 
 vinasse ; the chambers a and the remaining part of c are f nil of cold mash, which 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 is to be deprived of its spirit, which obtains a preliminary heating by withdrawing 
 a large share of heat from the adjacent boiling vinasse before passing into the de- 
 alcoholising column, B. Accordingly, the mash, which is pumped up at d into the 
 preliminary heater, traverses in succession the compartments, a, of the band, D (Fig. 
 534), falls down into the piece, c, underneath, and passes through a wide opening 
 into the central tube, D, in which it rises upwards and pours at f into the mash- 
 column, B. 
 
 This column, B, consists of a number of pieces, with central tube open at both ends 
 and ring-shaped perforated bottoms (Fig. 535). The space beneath this bottom serves 
 for collecting and receiving the vapours rising from the liquid below, whilst the space 
 above the bottom serves to receive the liquid which has to give up its alcohol. In every 
 one of these nested pieces the liquid to be deprived of its alcohol, in passing through the 
 apparatus, can only flow round in one direction, and not quite round, because a perpen- 
 dicular rib hinders the annular connection of the liquid, whilst a lower opening makes 
 a connection with the liquid in the next lower compartment. In consequence of this 
 arrangement of the column, the mass is so thoroughly de-alcoholised that the heat can 
 be used over again, and the removal of the alcohol effected at the cost of relatively very 
 little heat. 
 
 Fig. 534- 
 
 frische Maische 
 heisse Schlempe 
 
 che 
 Jaische. 
 
 btisseSchltmpt. 
 
 Fresh mash. 
 Hot vinasse. 
 
 Explanation of Terms. 
 
 Dampfe 
 Maische 
 
 Vapours. 
 Mash. 
 
 Wosser . . Water. 
 hochgrtidige Alkoholddmpfe : 
 
 Strong alcoholic vapours. 
 schwoche Alkoholddmpfe . 
 Weak alcoholic vapours. 
 
 From the lowest part of the column, B, the mash, perfectly freed from spirit, passes 
 as vinasse into the preliminary heater, traverses the chambers b, giving off a consider- 
 able quantity of heat to the cold mash in the interposed mash-chambers, a, and flows 
 off continuously at K from the vinasse outflow pipe, I. The chambers, a and b, of the 
 preliminary heater having sloping bottoms, both mash and vinasse flow downwards ; 
 hence no deposits can be formed in the chambers. Grains, &c., pass into the piece, c, 
 which keeps them back, and is removed every two or three months. The apparatus, 
 when working, is full of mash up to the gauge-glass, n. 
 
 The alcoholic vapours liberated from the mash ascend into the rectifier, c. It con- 
 sists of a number of cast-iron pieces, put together so as to form a way for the vapours 
 rising from the mash-column, B, and partly serve to receive the cooling- water, which 
 deprives the vapours of their excess of heat and facilitates the process of rectification. 
 
SECT, vi.] THE. MANUFACTURE .OF SPIRITS. 779 
 
 The vapours pass at F into ; the : spirit-cooler for condensation, whilst the phlegni 
 formed in the rectifier collects on the floors of the chambers, and, if it is not re- 
 evaporated by the process of rectification, flows back into the mash-column by an in- 
 ternal tube. 
 
 The cooling- water takes its way into the rectifier at i, and flows off at h. It is 
 convenient to let this cooling-water first act on the spirit-cooler, so that it enters the 
 cooler, S, at s, and then flows through the tube t into the rectifier at i. 
 
 The sensitive indicator, T, gives an easy and certain indication whether the mash is 
 perfectly de-alcoholised .or not. It must be considered that spirit, distilled in cast-iron 
 apparatus, often gets a bad smell and taste, by taking up hydrocarbons and sulphuretted 
 hydrogen. 
 
 Purification of the 'Crude Spirit (De-fuseling). In working up crude spirits there 
 are obtained two products, which contain the impurities. Some of the ethers thus formed 
 exhibit a highly agreeable odour, and are therefore used in perfumery, and for the 
 flavouring of sweetmeats, bon-bons, &c. 
 
 As for many of the applications of potato-spirit the fusel oil is a disadvantage, 
 the spirit has to be submitted to an operation of rectification, whereby the fusel 
 oil is got rid of. The suggestions which have been made for this purpose refer 
 either to the destruction of the fusel oil by oxidation or the action of chlorine, or of the 
 masking of the oil and its conversion into less disagreeable compounds ; partly also to 
 a real removal of the fusel oil from the spirit. When the fusel oil containing spirit is 
 rectified over chloride of lime (bleaching- powder), potassium permanganate, <fec., valeri- 
 anate of fusel ether is formed. But since the action of these reagents is not limited to 
 the amylic alcohol, but extends to the ethylic, it is very difficult to adjust the quan- 
 tity of these reagents so that only the amylic alcohol be acted upon. If the spirits 
 from which the fusel oil is to be removed are treated with a mixture of sulphuric acid 
 and vinegar, there is formed, besides some acetic ether, amyl acetate, of a pleasant 
 fruity flavour. Hydrochloric and nitric acids, also used to remove fusel oil, act 
 in a somewhat similar manner. The most approved method of removing the fusel oil 
 is by means of well-burnt charcoal (vegetable charcoal, or 
 bone-black), which, when brought into contact with the 
 crude spirit, absorbs the fusel oil mechanically. By the 
 aid of charcoal, spirits and brandy (when not obtained from 
 wine) are purified either in the state of vapour, or by 
 digestion with the charcoal, and filtration at the ordinary 
 temperature of the air ; rectification at boiling temperature 
 over charcoal is altogether unsuitable, owing to the fact that 
 the fusel oil absorbed by the charcoal is again readily dis- 
 solved at that temperature. The charcoal to be employed 
 is granulated and passed through a sieve, in order to remove 
 adhering dust. The granulated charcoal is placed in a 
 copper cylinder, fitted at the top and bottom with a per- 
 forated plate or disc. This cylinder is connected with the 
 distilling apparatus between the dephlegmator and recti- 
 
 ficator in such a manner that the vapours pass through the charcoal. To 100 litres of 
 brandy to be purified, 3 to 5 litres of granulated charcoal are generally required ; this 
 can be again employed after having been re-burnt at a bright red heat. Falkmann's 
 apparatus consists of a helm-shaped vessel, A (Fig. 537), in which the perforated dia- 
 phragms, b b b, are placed ; upon each diaphragm a layer of charcoal, surmounted with 
 a cover, c, is placed. The apparatus is closed with a hollow cover containing a layer of 
 charcoal, d d. The vessel, 2, is surrounded by a cooling apparatus, which in the cut is 
 represented by the cold-water tubes,///, and the hot- water (which becomes hot by 
 
780 CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 the passage of alcoholic vapours through A) tubes, e e e e; these serve the purpose cf 
 regulating the temperature of the layers of charcoal. 
 
 100 litres of Cognac distilled from wine contained, according to Morin (1887) 
 
 Aldehyde ; trace 
 
 Ethylic alcohol 50*837 
 
 Propylic alcohol (normal) 27*170 
 
 Isobutylic alcohol . . . . i.' . . 6*520 
 
 Amylic alcohol . . . . . . 190*210 
 
 Furfurol bases . . . . - . . . . 2*190 
 
 Oil of wine ./. ; . . . 7*610 
 
 Acetic acid trace 
 
 Butyric acid trace 
 
 Isobutylglycol . .' . . . . . . 2*190 
 
 Glycerine . ....... 4*380 
 
 Butylic alcohol is absent. The presence of furf urol can be directly shown by adding 
 aniline to the Cognac. It is noteworthy that wine contains amylic alcohol. 
 
 Brockhaus has examined by experiments upon himself the action of the most im- 
 portant impurities of potato-spirit : aldehyde, paraldehyde, acetal, propylic-isobutylic 
 and amylic alcohol. 10 drops of aldehyde in 100 grammes of water had a repulsive, 
 and violently burning taste ; there was a sensation of burning on the tongue 
 and in the throat, a repulsive after-taste, not to be removed by frequent draughts 
 of water, cough, feeling of suffocation, nausea, pain in the stomach, heat in the head, and 
 palpitation of the heart. These symptoms passed away in about an hour. The effects 
 of 10 drops of aldehyde in wine were rather less unpleasant. From the experiments 
 with amylic alcohol and other constituents of fusel the inference seems justified that 
 the impurities of ordinary spirits play a leading part in the development of drunkard's 
 diseases. 
 
 Rabuteau (1878) found on analysing i litre potato-fusel 
 
 c.c. 
 
 Isopropylic alcohol . 1 50 
 
 Primary propylic alcohol 30 
 
 Butylic alcohol, ordinary 50 
 
 normal 65 
 
 Secondary amylic alcohol (methyl propyl carbinol) . . 60 
 
 Ordinary amylic alcohol (isobutyl carbinol) . . . 275 
 
 Products boiling above 132, containing amylic alcohol . 170 
 
 Water 125 
 
 Yield of Alcohol. The quantity of alcohol obtainable from any given substance 
 not only depends on the relative quantity of the alcohol-forming constituents (starch, 
 dextrose, or cane sugar) of the raw material applied for the purpose of distillation, 
 but very largely also on the more or less suitable mode of conducting all the opera- 
 tions of the spirit distillation (mashing, fermentation), in properly constructed 
 apparatus. Leaving out of the question the small quantities of glycerine and succinic 
 acid formed by vinous fermentation, chemistry teaches that 
 
 100 parts of starch yield 56*78 of alcohol 
 
 100 cane sugar 53'8o 
 loo dextrose 51*01 
 
 Experience shows that the yield of alcohol is in practice less than it should be, 
 premising that every mol. of starch or sugar yields 2 mols. of alcohol ; 100 parts of 
 cane sugar do not yield in practice the quantity of alcohol above indicated, viz., 53*8 
 parts, but only 51*1. 
 
SECT, vi.] FLOUR AND BREAD. 781 
 
 loo kilos, of barley give 44-64 litres of corn brandy at 50 Tralles 
 loo barley malt 54-96 
 
 100 wheat 49-22 M |f 
 
 100 !7 e it 45'So 
 
 loo potatoes 18-32 potato spirit 
 
 6 litres (quart or maas) of brandy, from the metrical hundredweight (hectolitre, <fcc.), 
 is reckoned to yield 6 x 50 = 300 per cent, alcohol ; 7 litres, consequently, 350 ; 8 litres, 
 400. 8 litres at 48 per cent. Tralles = 384 per cent, alcohol. The number of litres of 
 brandy or spirit multiplied by the alcohol in percentage according to Tralles therefore 
 yield 
 
 I metrical cwt. of barley 44 '64 x 50=2232 per cent, alcohol 
 
 i barley malt 54-96x50=2748 
 
 I wheat 49-22x50=2461 
 
 I rye 45*80x50=2290 
 
 i potatoes 18-32x50= 916 
 
 FLOUR AND BREAD. 
 
 Modes of Bread Making. The preparation of bread aims at the production in the 
 flour obtained by grinding up the cereals of such a chemical and physical condition as 
 will tend to render it most readily masticated by the teeth, and, after having been duly 
 mixed with saliva in the mouth, digested by the juices of the stomach. When flour 
 is mixed with water so as to form a dough, and this mixture dried at the ordinary 
 temperature of the atmosphere, a kind of cake is obtained which contains the starch 
 unaltered and in an insoluble state, so that this kind of cake is very difficult to digest, 
 while, moreover, its taste is so unpleasant as to create no appetite. Again, if the cake 
 is dried at the boiling-point of water, it becomes like a dried starch-paste, which is also 
 very difficult to digest. When this temperature only acts upon the surface of such dough, 
 and does not penetrate into the interior, the resulting cake will be a mixture somewhat 
 similar to ship's biscuit, which may always be considered as a strongly dried dough, 
 and, although it may be preserved for almost any length of time, it is far less digestible 
 than bread. The object of the baking process is to impart to the dough so high a degree 
 of heat as to render the starch soluble, while it is further desired to form a light spongy 
 mass, instead of a brittle or watery paste ; the heat should be strong enough to torrify 
 and roast the outer surface of the bread mass to such an extent as to form a deeply 
 coloured crust, whereby not only the taste of the bread is greatly improved, but it can 
 also be kept in good condition for some time. The usual means of rendering dough 
 spongy is by vinous fermentation set up by the addition of a ferment, this being either 
 leaven or yeast; a small portion of the starch of the flour is thus converted into 
 glucose, which is then decomposed, yielding alcohol and carbonic acid gas ; the latter 
 is prevented from escaping by the toughness of the dough, which is thereby rendered 
 spongy. 
 
 The alcohol is of no consequence whatever. White bread is prepared with 
 wheaten flour and yeast ; rye meal, or a mixture of rye meal and wheaten flour, 
 with leaven, yields " black" or rye bread. Heeren found that flour in the state 
 in which it is usually applied for bread baking contains an average of 13 per cent, 
 moisture. 
 
 The Details of Bread Baking. The raw materials in the preparation of bread are 
 flour, water, and a ferment ; salt, spices, &c., are also used. The composition of the 
 most important kinds of flour and meals is as follows : 
 
CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 Water . 
 
 Albumen . . 
 
 Vegetable glue 
 
 Casein . 
 
 Fibrin . 
 
 Gluten . 
 
 Sugar 
 
 Gum . . 
 
 Fat 
 
 Starch . 
 
 Sand 
 
 15:54 
 i'34 
 176 
 o'37 
 5-19 
 3 'So 
 2-33 
 6-25 
 1-07 
 
 63-64 
 
 b. 
 
 14-60 
 i-56 
 2-92 
 0-90 
 7-36 
 
 4*10 
 i -80 
 
 64-28 
 
 c. 
 
 14-00 
 i -20 
 3-60 
 
 i '34 
 
 8-24 
 
 3 '04 
 6-33 
 
 2-23 
 
 53T5 
 6-85 
 
 d. 
 
 11.70 
 1-24 
 
 3-25 
 
 0-15 
 
 14-84 
 
 2-19 
 
 2-81 
 
 5-67 
 
 58-I3 
 
 a. Wheat flour. 6. Kye meal. c. Barley meal. d. Oatmeal. 
 
 In addition to these kinds of meal, those derived from Zea-Ma'is (Indian corn), beans, 
 
 &c., are occasionally employed for making bread. 
 The principal phases of the preparation are : 
 
 The Mixing of the Dough. The mixing of the flour with water is the first mani- 
 pulation of the baking process. The object of this operation is first to render dextrine 
 and sugar (owing to the action of the gluten upon the starch, the quantity of sugar 
 becomes increased while the mixing process is going on) and some albuminous sub- 
 stances soluble, and next to mix the solution thus formed thoroughly with the 
 starch and gluten of the flour, and to soak and somewhat dissociate these substances ; 
 dry yeast or leaven is at the same time admitted to the bread mass, the former ferment 
 being used when it is intended to make white, the latter when black bread is desired to 
 be made. 
 
 By sour dough or leaven is understood that portion of the already fermenting 
 dough which is set apart and kept for the next baking operation ; it consists of a 
 mixture of flour and water, in which a portion of the starch is converted, partly 
 into sugar, which is again changed by vinous fermentation, and acetic acid, but 
 chiefly into lactic acid, by a process of fermentation, set up by the peculiar conversion 
 into active ferments of the protein compounds of the flour itself. Leaven, therefore, 
 acts as a fermentation-producing substance in a fresh batch of dough, its action being 
 similar to that of yeast, or of already fermenting wort when added to a freshly made 
 wort. After a length of time the leaven becomes putrid and unfit for use as a fer- 
 ment. As regards the quantity of leaven to be used with the dough nothing definite 
 can be said, since it depends as much on the degree of sourness of the leaven as on the 
 quality of the bread intended to be made ; usually, 4 parts of leaven are added to 100 
 parts of flour, or to 80 parts of bread 3 parts of leaven. In the case of white bread, 100 
 parts of flour require 2 parts of dry yeast. The mixing of the flour is effected with 
 lukewarm water, at a temperature of from 21 to 37. 
 
 Kneading. The thin dough obtained from flour, water, and ferment is dredged 
 over with dry flour, and placed in a warm situation for a time, generally during the 
 night. Fermentation is thus set up by the action of the ferment upon the dextrose 
 of the dough, the carbonic acid developed rendering the dough spongy. The sponge 
 thus prepared is next mixed with more flour, to bring it to the consistency required 
 for the baking, this operation being known as the kneading of the sponge. The 
 method usually employed in these operations is that one-third of the total quantity 
 of flour required for a batch is mixed first with water and ferment, and when this 
 mass has come into full fermentation, the two other thirds of flour are kneaded up 
 along with the sponge, sufficient water being added to form a normal dough. After 
 the kneading operation the dough is again dredged over with some dry flour, and left 
 in a warm situation for the purpose of becoming thoroughly spongy ; for this con- 
 tinued fermentation only about half the time is required for the first-mentioned 
 
SECT. VI.] 
 
 FLOUR AND BREAD. 
 
 783 
 
 fermentation. In most bakeries, however, this second fermentation is not proceeded 
 with, but the dough is, immediately after having been kneaded, cut up and shaped 
 into loaves. 
 
 By means of the kneading the dough becomes squeezed together, and has, there- 
 fore, again to be left in a warm situation for further fermentation, during which it 
 heaves up and increases to double its size. The bulk of the dough increases twofold. 
 When rye bread is made, the dough is frequently moistened on its external surface 
 with lukewarm water, applied by the aid of a brush, in order to prevent cracks in the 
 outer coating of the dough by the evaporation of the water ; just before putting the 
 loaves into the oven this brushing over with water is repeated. The water softens the 
 outer surface of the dough, and dissolves some of the dextrine it contains, which sub- 
 stance, after the evaporation of the water from the surface, remains as a glaze upon 
 this kind of bread. When the loaves have risen sufficiently and exhale a peculiar 
 vinovis odour, it is time to commence the baking process. Since the bread loses consider- 
 ably in weight during the baking, the baker must proportion so much dough to each 
 loaf before baking as will yield the legal weight of the baked bread. The weight of 
 dough to be proportioned to a loaf of a certain fixed weight varies according to the 
 size of the loaf ; but increases comparatively with decrease therein. The dough 
 generally loses in baking about 25 per cent, of its weight. The smaller the loaf, the more 
 crust in proportion to crumb; and since the crust contains less moisture, and consequently 
 weighs less than the crumb, the loss of weight is proportionately greater in a small than 
 in a large loaf. 
 
 The use of machinery in kneading dough is gradually extending, and it will doubt- 
 less become general wherever bread is prepared on the large scale. 
 
 Baking. The conversion of the fermented dough into bread is- effected by baking 
 in ovens, the common kind of which consists of a round or oval hearth, covered with a 
 
 Fig- 538. 
 
 Explanation of Terms. 
 
 Schnitt 1U-IV. . . . Section ITI.-IV. 
 Schnitt I-IL . . . Section I.-II. 
 
 Explanation of Terms. 
 Schnitt V-VI. . . Section V.-VI. 
 Schnitt VII-VIII. . Section VII.-VIII. 
 
 vault. Far more advantageous are the ovens heated from below, which allow of un- 
 interrupted work with a smaller consumption of fuel and greater cleanliness. In 
 Seidel's oven, e.g., the baking-room, A (Figs. 538 to 540), rests on stones forming 
 
784 CHEMICAL TECHNOLOGY. [SECT, vi 
 
 parallel channels, whilst the actual hearth is kept at some distance from the side by 
 cubic stones, so as to form the hollow space, w. On both sides of the baking-space, 
 A, the flues z are formed, through which the air heated by the fire-gases passing in 
 the flues i rise up and enter the baking-space, A. The sole of the space c is provided 
 with an opening on both sides, which can be closed by means of the dampers moved 
 by the hand-levers, h, and through which the heat, when the firing is completed, can 
 be passed directly into w or A. To the flues i, underneath which there crosses a 
 cleansing flue, x, there are joined the flues c, which rise up at the rear- wall of the 
 baking-space, and extend to the flues a, with the openings for cleansing, y. Tho 
 flues c and a are so arranged that the heat in each two flues i and c passes forwards 
 in each one of the flues a, turns round backwards in the second of the flues a, as 
 shown by arrows on the left hand of Fig. 540, in order to escape into a general flue, n, 
 opening into the chimney, S. From the water-pan, e, a pipe, d, leads to the steam 
 generator, /. The pipe g conveys the steam into the baking-space, A, whilst the 
 steam-escape, o, which vents into the flue n, is regulated by cross-valves and a draught 
 arrangement, b. 
 
 The temperature of the furnace suitable for baking is 200 to 225. Before the 
 loaves are introduced into the oven their surface is brushed over with water in order 
 to prevent the crust from bursting in consequence of the too rapid action of a high 
 temperature. The watery vapours with which the oven is gradually filled are neces 
 sary in order to convert the starch into dextrine on the surface of the bread, and thus 
 obtain a smooth crust. The time required for baking depends on the size, the shape, 
 and the kind of the loaves. Black bread requires a longer time than white. 
 
 Substitutes for Yeast in Baking. We have seen from the preceding details that the 
 preparation of bread is essentially based upon the fact that by the act of fermentation 
 the gluten of the flour forms a kind of cellular tissue by which the escape of the 
 carbonic acid is prevented, and the bread thus rendered porous and spongy, whereby 
 its digestibility is increased. This quality of the bread is obtained at the cost of a 
 portion of the starch of the flour, which is first converted into starch-sugar, and then 
 by means of fermentation into alcohol and carbonic acid gas ; to the expansion of the 
 latter the bread owes its spongy texture. Many attempts have been made for the 
 purpose of effecting the " raising " of the bread, as it is termed, without the use of a 
 ferment, by introducing into the dough some gas- or vapour -producing substance, 
 which would have the same mechanical effect at least as the carbonic acid derived from 
 the fermentation. Although the problem of preparing bread of good quality without 
 the aid of fermentation cannot be said to be quite settled, many proposals have been 
 made in this direction, and some of these deserve notice ; we therefore quote the most 
 important. When ammonium sesquicarbonate (the so-called sal cornu cervi of 
 pharmacy) is added in small quantity to the dough, it will cause the raising of the 
 same, partly because some acid is always present in the dough, whereby the salt is 
 decomposed and carbonic acid set free, partly because by the heat of the oven the salt 
 is volatilised, and, by assuming the state of vapour, causes the expansion and consequent 
 sponginess of the dough. Liebig recommends the addition of sodium bicarbonate and 
 hydrochloric acid to the dough, the carbonic acid being evolved according to the 
 formula NaHCO 3 -f HC1 = NaCl + H 2 O + C0 2 , with the formation of common salt, 
 which remains in the dough. The proportions are as follows : To 100 kilos, of meal 
 for making black bread i kilo, of sodium bicarbonate is taken, and 4^25 kilos, of hydro- 
 chloric acid of 1*063 8 P- g r - ( = 9'5 B. = 13 per cent. C1H), yielding 175 to 2 kilos, of 
 common salt; the quantity of water to be added amounts to from 79 to 80 litres. 
 From this mixture is obtained 150 kilos, of bread. The proportion of the sodium bi- 
 carbonate to the hydrochloric acid is so arranged that 5 grammes of the former are fully 
 saturated by 33 c.c. of the latter, leaving in the bread a faintly acid reaction. The 
 
SECT, vi.] FLOUR AND BREAD. 785 
 
 substance known and sold as Horsford's yeast powder, also recommended by Liebig, is 
 preferable and more readily employed. This powder consists of two separate prepara- 
 tions, viz., the acid powder (acid calcium phosphate with acid magnesium phosphate), 
 the other the alkaline powder (a mixture of 500 grammes of sodium bicarbonate and 
 443 grammes of potassium chloride). To 100 kilos, of flour, 2'6 kilos, of the acid powder 
 and i '6 kilo, of the alkali powder are added. During the kneading the following 
 changes occur : The sodium bicarbonate and potassium chloride are first converted 
 into sodium chloride and potassium bicarbonate, the latter salt being in its turn 
 decomposed by the acid phosphate, whereby carbonic acid is set free. By the use of 
 this baking powder it is possible to make flour into bread within two hours' time, 
 while, moreover, 100 pounds of flour yield 10 to 12 per cent, more bread than with 
 the best method of baking in the usual way. The plan of incorporating pure 
 carbonic acid gas with the dough has been frequently taken up, and successful work 
 has been done in this direction, but the process has its opponents as well as its 
 defenders. 
 
 Yield and Composition of Bread. Flour from various kinds of grain contains 
 in its ordinary air-dry condition from 12 to 1 6 per cent, of water ; by its conversion 
 into bread the flour takes up much more water. 100 Ibs. of fine wheaten flour 
 combine with 50 Ibs. of water, and give 150 Ibs. of bread. The composition of the 
 flour and of the bread is, therefore, as follows : 
 
 Wheaten Flour. Wheaten Bread. 
 
 Dry Flour 84 ... 84 
 
 Water originally contained in the flour 16 ... 16 
 
 Water added for making the dough . ... 50 
 
 100 ... 150 
 
 According to Heeren, 100 Ibs. of wheaten flour yield at least 125 to 126 Ibs. 
 of bread; 100 Ibs. of rye meal, 131 Ibs. of bread. Fresh wheaten bread contains 
 9 per cent, of soluble starch and dextrin, 40 per cent, of unchanged starch, 6'5 
 per cent, of protein compounds, and from 40 to 45 per cent, of water. As is generally 
 known, newly baked bread possesses a peculiar softness, and is at the same time tough 
 and does not crumble readily : after one or more days' keeping, the bread loses this 
 softness, becomes dry, crumbles readily, and is then called stale or old bread ; it is 
 usually supposed that this change is due to a loss of water, but, according to the 
 researches of Boussingault, stale bread contains as much water as fresh bread ; the 
 alteration is solely due to a different molecular condition of the bread. 
 
 Impurities and Adulterations of Bread. When the flour intended for the pre- 
 paration of bread is more or less decayed, the gluten it contains is thereby altered ; 
 the carbonic acid evolved during the fermentation of the bread does not render 
 the dough spongy, but it becomes, owing to the altered state of the gluten, a 
 more or less slimy mass, which yields a tough and far less white-coloured bread ; in 
 order to counteract this defect, and to impart a good appearance to the bread made 
 from flour which has been damaged by damp, or by having been too closely con- 
 fined in casks and thereby heated, the bakers in Belgium and Northern France 
 add to the dough a small quantity of copper sulphate, y-^^jj to -goooo > ^ e ^ ase 
 of this salt combines with the gluten, forming therewith an insoluble compound, 
 thus rendering the dough tough and white, and capable of taking a large quantity of 
 water. In order to detect the copper sulphate in the bread, a portion of the bread 
 to be operated upon is first dried, then ignited, and the copper separated from the ash 
 by gently washing away the lighter particles, leaving the metallic copper in the shape 
 of small shining spangles. 
 
 In England alum was at one time very generally added to flour and' bread. But 
 
 3D 
 
786 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. 
 
 VI. 
 
 this fraud, which was always illegal, has been practically suppressed since the appoint- 
 ment of public analysts. In Germany the addition of copper sulphate and of alum is- 
 forbidden by the authorities. 
 
 MILK, BUTTER, CHEESE. 
 
 Milk. Cows' milk contains, according to the race of the animals, the kind of 
 feeding, &c : 
 
 Per cent. 
 
 Total solids 6-8-17-1 
 
 Fat i-4-7'2 
 
 Albuminates 2 '2- 6 '2 
 
 Sugar . . . s . . . . I '0-5 '2 
 Salts 0-1-17 
 
 A verage samples of total milk taken morning, noon, and evening in three different 
 cow-houses contained, according to ThOrner, 1885 : 
 
 Time of Milking. 
 
 Spec. Grav.- 
 
 Cream. 
 
 Fat. 
 
 Total Solids. 
 
 Ash. 
 
 Entire Milk. 
 
 Skim Milk. 
 
 I. 
 
 
 
 Vol. per cent. 
 
 Per cent. 
 
 Per cent. 
 
 Per cent. 
 
 Morning 
 
 I '0306 
 
 I-0325 
 
 7-0 
 
 2-460 
 
 lO'So 
 
 0-57 
 
 Noon .... 
 
 I -0304 
 
 I '0320 
 
 9-0 
 
 3-460 
 
 1 2 '2O 
 
 0-58 
 
 Evening . . . 
 
 1-0311 
 
 I -0332 
 
 S-o 
 
 2-940 
 
 11-50 
 
 0-60 
 
 II. 
 
 
 
 
 
 
 
 Morning 
 
 1-0314 
 
 I -0329 
 
 6-5 
 
 2-620 
 
 "'37 
 
 0-65 
 
 Noon .... 
 
 1-0309 
 
 I -0339 
 
 9-8 
 
 3 '470 
 
 12-09 
 
 0-68 
 
 Evening . . . 
 
 I -0303 
 
 1-0317 
 
 8-0 
 
 3-230 
 
 H'74 
 
 075 
 
 III. 
 
 
 
 
 
 
 
 Morning 
 
 I -0294 
 
 I -0324 
 
 I HO 
 
 3-470 
 
 1 1 -80 
 
 074 
 
 Noon .... 
 
 I '0289 
 
 I -0326 
 
 11 '5 
 
 4-004 
 
 12-15 
 
 0-66 
 
 Evening 
 
 I "0302 
 
 I -0324 
 
 13-5 
 
 4-6^0 
 
 12-91 
 
 0-65 
 
 Lot I. consisted of the milk of twenty- five cows, each fed daily with 10 to 12^ 
 kilos, brewery grains, i kilo, of a cattle-food (containing 14 per cent, protein and 38- 
 per cent, of non -nitrogenous extractive) and green food, with hay and straw as- 
 required. 
 
 Lot. II. comprised the milk of thirty-two cows, fed on 80 litres rye-vinasses and 
 6 kilos, of hay. 
 
 Lot III. was obtained from twelve cows, half pasturage and half stall-fed. The 
 latter consisted of red clover with Italian rye-grass and 0*25 kilo, of cotton-seed cake- 
 and i kilo, of crushed rye. 
 
 The composition is hence very variable.* 
 
 If we subtract the fat from the dry substance we obtain a figure which varies but 
 little. 
 
 Milk is a mixture of several insoluble, very minutely divided, emulsified substances,, 
 suspended in a watery liquid. The specific gravity of milk varies from 1-030 to 1*045^ 
 Under the microscope it becomes evident that the white colour of milk is due to the 
 so-called milk globules small globular bodies of a yellow colour, with a more deeply 
 coloured circumference, and exhibiting a pearly gloss. It was formerly believed that 
 these globules consisted of an exterior envelope filled with butter, but the recent 
 researches of Drs. Von Baumhauer and F. Knapp have proved these opinions to- 
 be eironeous. When milk is left standing these globules rise to the surface and form 
 cream, below which remains a blue transparent fluid containing the sugar of milk, 
 salts, and caseine, the latter in the form of caseine-soda. When milk is kept for some 
 
 * Compare Wanklyn's treatise on the Analysis of Milk. London: Kegan Paul, Trench, 
 Trubner & Co. 
 
SECT, vi.] MILK, BUTTER, CHEESE. 787 
 
 time, a portion of the lactose (sugar of milk) is decomposed and converted into lactic 
 acid by the aid of the caseine, which acts as a ferment. In its turn the lactic acid 
 decomposes the caseine-soda, whereby the caseine is set free and separated as an 
 insoluble substance; this action takes place in the coagulation of milk. The whole 
 of the lactose or sugar of milk becomes converted into lactic acid by long keeping. 
 
 Lactic acid (C 3 H 6 2 ) is also formed by the fermentation of starch, cane sugar, and 
 glucose, under the influence of caseine and a ferment. This acid is met with in 
 sauerkraut (a favourite dish of the Germans, being a well-preserved mixture of white 
 and savoy cabbages cut into shreds, and packed in casks along with salt, coarse pepper, 
 and some water) and in other pickles, in beer, and in nearly all animal liquids. Lactic 
 acid is also present in some of the fluids of the tan-yard tanks; in the sour water 
 of starch works where starch is prepared by the old methods ; in the bran baths of 
 dye works ; and is constantly met with in the residual liquids of corn spirit distilla- 
 tion. When lactic acid is heated with sulphuric acid and peroxide of manganese, 
 aldehyde is formed, which is used in the preparation of aniline green and of hydrate of 
 chloral. 
 
 The coagulation of fresh milk is effected by the use of rennet, which is prepared 
 from the stomach of a calf, well washed and stretched out on a wooden frame, then 
 dried either in the sun or near a fire. The substance thus prepared was formerly soaked 
 in vinegar, but experience has proved this to be unnecessary. When required, a small 
 piece is cut off and steeped in warm water, and the liquid added to the milk, previously 
 heated to from 30 to 35. The milk is hereby coagulated, even in large quantity, in about 
 two hours; i part of rennet is sufficient for the purpose of coagulating 1800 parts of 
 milk. The mode of action of rennet is not well understood, but it does not consist, as 
 was formerly believed, in the instantaneous conversion of a portion of the lactose 
 present in milk into lactic acid, since experiments have shown that rennet coagulates 
 milk which exhibits an alkaline reaction. 
 
 Whey. By the term whey is understood the fluid in which the coagulated caseine 
 of milk floats, and which may be obtained either by decantation or filtration. The 
 whey of sour milk contains very little lactose and a large quantity of lactic acid (sour 
 whey) ; while sweet whey, obtained by coagulating milk with rennet, contains all the 
 lactose. Sweet whey containing 3 to 4 per mille of a proteine compound (termed lacto- 
 proteine by Millon and Commaille) is evaporated to some extent in Switzerland, with 
 the view of obtaining the sugar of milk in a crystalline state. The substance thus 
 obtained is purified by recrystallisation. 
 
 Lactose (Sugar of Milk), C 12 H 22 O n + H.,0, does not possess a very sweet taste, and 
 feels sandy in the mouth. It is soluble in 6 parts of cold and 2 parts of hot water. 
 It is not capable of alcoholic, but only of lactic acid fermentation. By the action of 
 dilute acids sugar of milk is converted into galactose, a kind of sugar similar to grape 
 sugar, and is then capable of alcoholic fermentation. Industrially, sugar of milk is 
 sometimes employed for the purpose of reducing a silver solution to the metallic state, 
 as in the case of looking-glass making. 100 parts of the commercial sugar of milk 
 from Switzerland (a), and from Giesmannsdorf in Silesia (b), were found to consist 
 
 ( 1 868) of: 
 
 a. b. 
 
 Salts . . . . . . 0-03 ... 0-16 
 
 Insoluble matter . . . 0*03 ... 0^05 
 
 Foreign organic substances . 1*14 ... 1*29 
 
 Sugar of milk .... 98-80 ... 98*50 
 
 Uses 0/J/t7&. Milk is used as food and for the preparation of butter and cheese, 
 for clarifying wine in order to render it less deep-coloured and, if turbid, quite clear. 
 
788 CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 More recently milk has been largely sold in the so-called condensed state, by which is 
 understood milk evaporated in vacua, after the addition of sugar, to the consistency of 
 thick honey. This mode of preserving milk was first employed by the Anglo-Swiss 
 Condensed Milk Company at Cham, Canton Zug, Switzerland, and is now carried on 
 in various parts of the Continent and in the United States, and also in England, in 
 Surrey and Buckinghamshire. 
 
 The average composition of condensed milk, according to Soxhlet, is 
 
 i. ii. 
 
 Water 26-88 ... 2470 
 
 Salts ;. 2-26 ... 2- ii 
 
 Fat 8-67 ... 6-02 
 
 Albumen iro; ... 977 
 
 Sugar . . . ... 51-12 ... 57-40 
 
 Kefyr is obtained by a peculiar fermentation of cows' milk set up by certain fungi. 
 The fermentation of mares' milk yields koumiss. Three samples of koumiss had the 
 
 following composition : 
 
 I ii. in. 
 
 Water . . . . . 91-87 ... 92-38 ... 92-42 
 
 Alcohol , . . . 3-29 ... 3-26 ... 3-29 
 
 Fat 1-17 ... 1-14 ... i -20 
 
 Caseine . .., . . o - 8o ... 0-85 ... 0-79 
 
 Albumen .... 0-15 ... 0-32 ... 0-32 
 
 Lacto-proteine and peptone . 1-04 ... 0-59 ... 0-76 
 
 Lactic acid .... 0-96 ... 1-03 ... i'oo 
 
 Sugar 0-39 ... 0*09 
 
 Ash, soluble . . . . o'io ... O'i2 ... 0-12 
 
 insoluble . . . 0-23 ... O"22 ... 0-23 
 
 Butter. This substance is prepared as follows : Milk of good quality is placed in 
 a, rather cool cellar or other locality for the purpose of causing the cream to separate. 
 The cream is poured into a clean stoneware or glass vessel kept for the purpose, and 
 left until by constant stirring it has become thick and sour ; it is then put into a 
 churn, by the action of which the solid fat globules are separated from the thick fluid 
 in which the caseine with a small quantity of butter remains suspended. Butter, being 
 specifically lighter than water, should, it might be thought, separate very readily from 
 a liquid which contains in solution various substances which are heavier ; but the fact 
 is that caseine renders the separation of butter from cream difficult even when the 
 cream is sweet and not thick ; when, on the other hand, milk coagulates before the 
 cream is separated, the butter is lost. Two methods have been devised for the purpose 
 of obtaining all the butter contained in milk. Gussander, a Swedish agriculturist, has 
 proposed that the separation of cream should be rendered more rapid, and always com- 
 pleted before the milk becomes sour, while Trommer prevents the souring of the milk 
 by the addition of some soda. 
 
 The liquid from which the butter is separated is known as churn-milk or butter- 
 milk; it contains 0-24 per cent, butter, 3-82 per cent, casein, 90-80 per cent, water, 
 5*14 per cent, sugar of milk and salts. Lactic acid is present in the water. 18 parts 
 of milk yield on an average i part of butter, which in fresh condition consists of 
 
 I. II. Ill IV. 
 
 Butter fat . . . 94-4 ... 93-0 ... 87-5 ... 7^5 
 
 Caseine, sugar of milk) 1>o 
 Extractive matter ) 
 
 Water .... 5-3 ... 67 . ll'S ... 21-2 
 
 Owing to the presence of water and caseine, butter after some time becomes rancid. 
 It is salted in order to prevent this rancidity as much as possible, the salt being 
 thoroughly mixed with the butter by kneading. To i kilo, of butter 30 grammes of 
 
SECT, vi.] MILK, BUTTER, CHEESE. 
 
 789 
 
 salt are required. According to Dr. Wagner, butter in England is salted with a 
 mixture of 4 parts of common salt, i part of saltpetre, and.i part of sugar. In Scot- 
 land, France, and Southern and Western Germany, butter is not salted at all, and is 
 therefore only made and sold in comparatively small quantities at a time. Salt butter 
 is termed in Scotland pounded butter. 
 
 By melting butter until the first turbid liquid has become clear and oily, water and 
 caseine are eliminated, and, settling to the bottom of the vessel, the supernatant fat 
 may be put into another vessel, and will, after cooling, keep sweet without salt for any 
 length of time. Butter is often artificially coloured by the aid of either annatto, 
 turmeric, or infusion of calendula flowers. 
 
 Chemical Nature of Butter. Butter consists of a mixture of neutral fats (glycerides) 
 which on being saponified yield several fatty acids, among which the non-volatile 
 are Palmitinic acid (C 16 H 32 2 ) and butyroleic acid (CjjH^O,). The volatile are- 
 Butyric acid* (C 4 H 8 2 ), capronic acid (C 6 H 12 2 ), caprylic acid (C 8 H 18 2 ), and caprinic 
 acid (C 10 H 20 2 ). The last four constitute in the shape of glycerides the butyrin or 
 special fat of butter, and impart to that substance its peculiar odour and flavour. 
 
 Schmitt examined two samples of cow-butter with the following results : 
 
 i. II. 
 
 Melting-point 36*5 ... 36*5 
 
 Fat 86-250 ... 86-50 
 
 Water 9-800 ... 10-54 
 
 Caseine 2-225 J '4 2 
 
 Ash o-ioo ... 0-85 
 
 Solid fatty acids, insoluble in water . 88*570 ... 89-15 
 
 Volatile acids, soluble in water . . 4-452 ... 4-45 
 
 Melting-point of solid fatty acids . . 39 '8 ... 40*0 
 
 Composition of Butter Fats : 
 
 Butyrine [C S H 5 (O.C 4 H,0) S ] .... 5 per cent. 
 Oleine [C S H 5 (O.C I8 R S 0) 3 ] . . . . 60 
 Margarine (tristearine and tripalmitine) . 35 
 
 Rancid butter contains free butyric acid, O'O2 gramme of which per kilo, is suffi- 
 cient to spoil the taste. 
 
 Artificial Butter (Margarine and Oleomargarine) is now manufactured on the large 
 scale. At first the process consisted in softening tallow by a gentle heat and freeing it 
 by pressure from the excess of stearine, thus producing a softer mixture of oleine and 
 palmitine. Such mixtures were formerly called margarine, under which name and 
 that of " oleomargarine " artificial butter is now legally sold, according to the law for 
 the prevention of fraud. The want of the smell and taste of genuine butter is in part 
 overcome by a treatment similar to that which true butter undergoes in churning. 
 
 This manufacture was first established by Mege-Mouries at Vincennes in 1869. 
 The tallow, washed in water and comminuted, is cautiously melted. The clear, yellow 
 liquid deposits on standing all membranes, &c. The liquid is let off into large wooden 
 cisterns and conveyed into a room of the temperature of 20, where it cools slowly. In 
 from twelve to twenty-four hours sufficient stearine has separated out in a granular- 
 crystalline form ; the cisterns are removed to the press-room, where at an air tempera- 
 ture of 30 the soft fatty masses, wrapped in press-cloths, are exposed to a gradually 
 increasing pressure. The liquid oily fat drains off; the press-cakes consist of white 
 stearine, which is used in the manufacture of soap and of candles. The expressed oil, 
 consisting of a hot saturated solution of stearine and palmitine in oleine, is cooled 
 
 * This acid is formed, not only by the saponification of butter, but is also met with in secreted 
 perspiration and the juices of the stomach, and results from the fermentation and decay of sugar 
 (in weak solutions), starch, fibrine, caseine, &c. 
 
790 CHEMICAL TECHNOLOGY. [SECT. vi. 
 
 down to 20, and then worked up in butter kegs with sour milk and a little of the 
 colouring matter of annatto. After ten to fifteen minutes the mixture becomes rmiform, 
 and is emptied out through an opening in the bottom into a vessel, where it is stirred 
 up with powdered ice in order to prevent the fat from separating out in a granular form. 
 In from two to three hours the mass is taken out and divided on tables with slightly 
 sloping tops, so that the ice may melt away. Lastly, the butter is salted by working 
 in 2 to 3 per cent, of common salt. Or to 200 kilos, of solid fat there is added the 
 stomach of a sheep or a swine finely mixed up and so much calcium phosphate and 
 hydrochloric acid as to form an artificial gastric juice, and heated to 2o-5o. In an 
 hour there rises to the surface a yellow liquid of a butter-like smell. This is drawn 
 off and mixed with per cent, common salt at 45, which eliminates a small 
 quantity of a ferment. When clear the mass is allowed to crystallise at 25, the 
 liquid part is pressed out and mixed in the butter keg with 12 to 20 per cent, of 
 sugar, to which yrJW sodium bicarbonate has been added. After churning for half an 
 hour it is allowed to cool and solidify.; all the milk is pressed out of the mass by 
 passing it under rollers, and it is moulded for sale. As a matter of course, artificial 
 butter should be sold only as such. When carefully prepared it is less liable to turn 
 rancid in hot climates than is natural butter. 
 
 Cheese. Cheese is prepared from caseine. It is made either from skimmed or un- 
 skimmed milk. In the former case a lean, dry cheese is obtained ; in the latter a fat 
 cheese, such as Cheshire, Cheddar, American, and the bulk of Holland cheeses. Lean 
 cheese is made in Germany by pouring the skimmed and already sour milk upon a 
 cloth, through the pores of which the whey passes, while the caseine remains on its 
 surface as a pasty mass, which is put by hand into the cheese-moulds, these being next 
 exposed to air. 
 
 Fat cheese is made of sweet milk just drawn from the cows, the milk being coagu- 
 lated by rennet after having been heated to 30 to 40. The gelatinous mass thus 
 obtained is broken up and pressed by hand, and the whey gradually removed by the 
 aid of wooden ladles. The caseine, having been freed from whey, is next well kneaded 
 with some common salt, and then put into wooden moulds with two or three small 
 holes at the bottom for the purpose of allowing the whey to flow off when the cheese 
 is pressed. - The newly made cheese is usually dipped every alternate day in warmed 
 whey, next wiped dry, put into the mould again, and pressed. When the crust has 
 sufficiently formed and the cheese become so hard as to admit of being handled, some 
 salt is rubbed into its surface, and it is then placed in a cool well-aired room upon a 
 shelf to dry and become, as it is termed, ripe. The vesicular appearance of some kinds 
 of cheese (the Gruyere cheese exhibits this in a high degree) is indirectly due to the 
 incomplete removal of the whey, the sugar contained becoming, during the ripening, 
 converted into alcohol and carbonic acid, which by its expansion while escaping pro- 
 duces the vesicular texture. Dutch cheese does not exhibit this appearance, on account 
 of being strongly pressed and containing much salt, by which the fermentation of 
 the sugar of milk in the cheese is prevented. The quality of the cheese depends to 
 some extent npon the temperature of the room in which it ripens. At Allgiiu i cwt. 
 of Swiss cheese of the first quality is produced from 600 litres of milk, while for the 
 second quality 720 to 750 litres of milk are taken for the same weight. The theory of 
 cheese formation is not well known, but it appears that fermentation plays an impor- 
 tant part in it. W. Hallier has proved that freshly made cheese is filled with ferment 
 nuclei (Kemhefe). 
 
 Cheese cannot be formed without this ferment, and by the addition of suitable 
 ferments the duration of the cheese-ripening process and the quality of the cheese may 
 be to some extent regulated at will. By exposure to air cheese undergoes changes 
 which may be best observed in skimmed-milk cheese. When new or young its colour 
 is white. By being kept so that it does not dry, it turns yellow and often 
 
SECT. VI.] 
 
 MILK, BUTTER, CHEESE. 
 
 791 
 
 becomes transparent, waxy and then exhibits the peculiar odour of cheese. When 
 cheese gets very old it becomes a soft and pasty mass, this change commencing at the 
 outside and progressing towards the interior. The waxiness of cheese is due to an 
 evolution of either ammonia or acid. Mild cheese usually exhibits an acid reaction, 
 while strong cheese is ammoniacal. Chemically speaking, skirnmed-milk cheese is a 
 compound of caseine with ammonia or ammonia bases amylamine, for instance. The 
 so-called dry cheeses, green Swiss cheese, contain an infusion of herbs, Melilotus, &c., 
 with volatile fatty acids, valerianic, capric, and caproic acids, and indifferent substances, 
 leucin, &c. The composition of sweet milk cheese (a) and of sour skim- milk cheese (b) 
 is exhibited by the following table : 
 
 a. b. 
 
 Water 36^0 ... 44-0 
 
 Caseine 29-0 ... 45-0 
 
 Fatty matter 30-5 ... 6 - o 
 
 Ash . . . . ' . ' . , c 4-5 ... 5-0 
 
 ICO'O ... lOO'O 
 
 The results of the researches of Payen on cheese are quoted below in 100 parts for 
 the following kinds: (i) Brie, (2) Camembert, (3) Roquefort, (4) Double cream, 
 (5) Old Neufchatel, (6) New Neufchatel, (7) Cheshire, (8) Gruyere, (9) Ordinary 
 Dutch, (10) Parmesan. 
 
 
 
 
 I. 
 
 
 
 
 i. 
 
 2. 
 
 3- 
 
 4- 
 
 5- 
 
 Water . 
 
 45 '20 
 
 5I-90 
 
 34'50 
 
 9'50 
 
 34'50 
 
 Nitrogenous matter 
 
 18-50 
 
 I8-90 
 
 26-50 
 
 18-40 
 
 13-00 
 
 Nitrogen 
 
 2-93 
 
 3-00 
 
 4'2I 
 
 2-92 
 
 3'3i 
 
 Fatty matters 
 
 2570 
 
 21-00 
 
 30-10 
 
 59 '90 
 
 41-90 
 
 Salts . 
 
 5 '60 
 
 470 
 
 5'oo 
 
 6-50 
 
 3-60 
 
 Non-nitrogenous organic ) 
 matter and loss } ' 
 
 5'oo 
 
 4 '50 
 
 3-90 
 
 570 
 
 7-00 
 
 
 
 
 ir. 
 
 
 
 
 6. 
 
 7- 
 
 8. 
 
 9- 
 
 IO. 
 
 Water . 
 
 T.6 60 
 
 JC'OO 
 
 
 
 
 Nitrogenous matter . 
 
 8-00 
 
 26-00 
 
 31'50 
 
 29-40 
 
 44-10 
 
 Nitrogen 
 
 1-27 
 
 4-13 
 
 5 'oo 
 
 4-80 
 
 7-00 
 
 Fatty matters .... 
 
 4070 
 
 26-30 
 
 24-00 
 
 27-50 
 
 r6'oo 
 
 Salts 
 
 0-50 
 
 4-20 
 
 3-00 
 
 0-90 
 
 570 
 
 Non-nitrogenous organic \ 
 matter and loss } * 
 
 14-20 
 
 7-60 
 
 1-50 
 
 6-10 
 
 6-60 
 
 The varieties mentioned under I. exhibit an alkaline reaction, and contain, with, 
 ammonia, cryptogamic plants, or, as it is termed, are mouldy. The varieties under II., 
 so-called boiled, strongly pressed, and salted cheese, exhibit an acid reaction, as also 
 does freshly prepared caseine. A portion of the fat contained in the cheese is even 
 from the first decomposed into glycerine and fatty acids. 
 
 Emmenthaler (a) and Backstein (b) cheese are composed, according to Lindt's 
 researches (1868), as follows: 
 
 
 
 
 If 
 
 
 
 
 
 
 
 Water 
 
 77-4 
 
 367 
 
 45'2 
 
 35-8 
 
 Fatty matters 
 Caseine 
 Salts 
 
 2 
 30-6 
 
 28-5 
 3'5 
 
 30-5 
 
 29-0 
 3'8 
 
 28-2 
 23-2 
 3'4 
 
 37'4 
 24-4 
 2-4 
 
 
 lOO'O 
 
 lOO'O 
 
 lOO'O 
 
 lOO'O 
 
792 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vi. 
 
 The results of E. Hornig's recent analyses (1869) of different kinds of cheese 
 are : 
 
 
 
 
 
 
 
 6 
 
 , 
 
 g 
 
 
 
 
 2> 
 
 
 
 
 
 
 
 Water . 
 
 38-66 
 
 56-60 
 
 51-21 
 
 57-64 
 
 36-72 
 
 34-08 
 
 59-28 
 
 49'34 
 
 Fatty matters 
 
 20-14 
 
 17-05 
 
 9-16 
 
 20-31 
 
 33'69 
 
 28-04 
 
 10-44 
 
 20-63 
 
 Caseine . 
 
 34-90 
 
 1876 
 
 33-60 
 
 18-51 
 
 25-67 
 
 23-28 
 
 24-09 
 
 24-26 
 
 Salts 
 
 6-17 
 
 678 
 
 6-01 
 
 3-51 
 
 37i 
 
 5-58 
 
 6-17 
 
 5'4S 
 
 Loss 
 
 0-13 
 
 0-8 1 
 
 O'O2 
 
 0-04 
 
 0-71 
 
 0'02 
 
 0'O2 
 
 0-32 
 
 
 lOO'OO 
 
 lOO'OO 
 
 lOO'OO 
 
 lOO'OO 
 
 lOO'OO 
 
 lOO'OO 
 
 IOO-OO 
 
 lOO'OO 
 
 No. i was Dutch cheese ; 2 and 3, Ramadoux cheese, made in Bavaria ; 4, Neuf- 
 chatel cheese ; 5, Gorgonzola cheese ; 6, Bringen or Liptau cheese, from the Zyps 
 Comitat, Hungary ; 7, Schwarzenberg cheese ; 8, Limburg cheese, made in the environs 
 of Dolnain-Limburg, in Belgium. 
 
 Every rennet contains, according to Benecke, the hay bacillus, Bacillus subtilis, 
 which is also present in ripening cheese. There is also a bacterium, which splits off 
 butyric acid from the albuminoids, and this, if it is formed in unusual quantities, gives 
 the cheese a bad flavour. 
 
 Loose, fat cheese is digested in from four to ten hours ; lean cheese is more difficult 
 of digestion. 
 
 Freshly made caseine mixed with lime is used as a kind of cement. Caseine is also 
 used in calico-printing as a mordant, under the name of " lactarine " ; and a solution of 
 caseine in borax is used instead of glue. In tho seeds of the leguminous plants, peas, 
 beans, lentils, &c., a nitrogenous substance is met with which is soluble in water and 
 precipitable therefrom by weak acids ; this material is very similar to caseine, and, 
 according to M. J. Itiers's accounts, in China peas and beans are boiled with water 
 and strained, and to the liquid thus obtained some solution of gypsum is added, 
 whereby the vegetable caseine (legumine) is coagulated, and the coagulum thus 
 obtained is treated as that of milk, obtained by the addition of rennet to the latter. 
 The mass so obtained gradually becomes like cheese in all respects. 
 
 MEAT. 
 
 What is commonly known as meat is the muscular substance of the slaughtered 
 animals, together with more or less fat and bone. 
 
 Muscular tissue is histologically composed of a variety of complex tissues and fluids, 
 the basis of which is animal fibre or fibrin, an organised proteine compound. The 
 muscular fibre held together by cellular tissue forms the muscle, fat being deposited 
 in the cellular tissue and in cells peculiarly constructed for that purpose. Blood- 
 vessels, lymph-vessels, nerves, and other organised tissues are dispersed through the 
 muscles, and serve a variety of physiological purposes. The muscular tissue is im- 
 pregnated with a proteine fluid in which a variety of other substances are met with, 
 as kreatinin, hypoxanthin, kreatin, inosite or muscular sugar, lactic acid, inosinic acid, 
 extractive matter, and inorganic salts among these being potassium chloride and 
 magnesium phosphate. 
 
 Constituents of Meat. The average results of a great number of researches recently 
 made on the large scale concerning the quantity of water contained in the meat of 
 fattened or half- or non-fattened animals are the following : 
 
 In the non-fattened meat 
 half -fattened meat 
 fully fattened meat 
 fat meat 
 
 Lamb. 
 62 
 
 49 
 
 Sheep. 
 58 
 5 
 40 
 33 
 
 Bullock. 
 
 54 
 46 
 
 Pi?. 
 
 56 
 
 39 
 
SECT, vi.] MEAT. 793 
 
 Hence it appears that with an increase of fat the quantity of water present in meat 
 decreases, a portion being replaced by fat. Well-fed and fattened meat contains for 
 equal weights about 40 per cent, more dry animal matter than non-fattened meat, while 
 in highly fattened meat it may amount to 60 per cent. 
 
 The difference in nutritive value of the meat of well-fattened bullocks as compared 
 with that of non-fattened is exhibited in the following percentage results obtained by 
 Breunlin : 
 
 Fattened. Non-fattened. 
 
 Water ,* ; , . . . . 38-97 ... 59-68 
 
 Ash ~. , . . . . 1-51 ... 1-44 
 
 Fat 23-87 ... 8-07 
 
 Muscle '.'".". . . 35-65 ... 30-81 
 
 lOO'OO ... lOO'OO 
 
 1000 grammes contain 
 
 Muscular Meat. Fat. Ash. Water. 
 
 Meat from fattened bullocks . 356 ... 239 ... 15 ... 390 
 Meat from non-fattened bullocks . 308 ... 81 ... 14 ... 597 
 
 Difference .... +48 ... +158 ... +i ... -207 
 
 Consequently, the meat of fattened bullocks contains in 1000 parts 207 more of solid 
 nutritive matter than the meat of the same in unfattened condition. 
 
 The Cooking of Meat. Meat is either roasted or boiled. By boiling, meat is very 
 essentially altered in composition according to the time it is boiled, and the quantity 
 of water used to bcil it in. The fluid in which meat has been boiled contains 
 soluble alkaline phosphates, salts of lactic and inosinic acids, magnesium phosphate, 
 and a trace of calcium phosphate. In order to be of the highest nutritive value, 
 meat should retain all its soluble constituents; hence, boiled meat loses much in 
 nutritive power. The albumen contained in meat is lost by boiling according to the 
 usual plan. Meat intended to be boiled should be immersed in boiling water to 
 which some salt has been added, the meat being put in while the water boils violently, 
 whereby so great a heat is at once imparted to the outer portions of the meat as 
 to coagulate the albumen, which then acts as an impermeable layer, retaining the juices 
 in the meat. Liebig's directions for making good broth are the following : Lean 
 meat is minced, mixed with distilled water, to which a few drops of hydrochloric acid 
 and common salt are added. After having been digested in the cold for about an hour, 
 the liquid is strained through a sieve, and upon the residue some distilled water is 
 again poured so as to extract all soluble matter. In this way an excellent and highly 
 nutritive cold solution of extract of meat is obtained ; this may be drunk without 
 being heated, and contains albumen in solution, which is coagulated by heating. 100 
 parts of beef yield an extract containing 2*95 parts of albumen and 3*05 parts of other 
 constituents of meat not coagulable by heat. Chevreul obtained from 500 grammes of 
 beef containing 77 per cent, water, 27*25 grammes of extract, in which were 3^25 grammes 
 fat; deducting these, there remain 4-8 per cent, extract. The bulk of this fluid extract 
 was i '2 5 litre, the weight 1004-09 grammes, and it contained 
 
 Water 
 
 Organic matter f Soluble in alcohol 
 1 Insoluble in alcohol 
 
 . 991-30 
 0-44 
 3-12 
 8-67 
 
 
 
 
 
 1004-09 
 
 Broth made from beef contains only 3 parts of meat substance, inclusive of glue 
 and fat. 
 
794 CHEMICAL TECHNOLOGY. [SECT, vi. 
 
 Under the best conditions, i kilo, of beef yields 
 
 ... (Coagulated albumen . . 29-5 
 Soluble in cold water . . 60 j ... & . . .. 
 
 I Albumen in solution . . 30-5 
 
 . (Glue-yielding substance . 6~o 
 
 Insoluble m cold water . . ^{y.^,^ _ _ ; ^ 
 
 Fat 20 
 
 Water 75 
 
 The Soiling of Meat. We have already stated that the meat intended to be boiled 
 should be immersed in boiling water and the fluid kept boiling for a few minutes, so 
 much cold water being next added as will reduce the temperature of the liquid to 70 
 or 74. At that heat the liquid should be kept for some hours to produce a very 
 savoury, sweet, succulent piece of boiled meat. If, however, it is desired to make a 
 strong broth, lean meat is first minced, next well exhausted with cold water, and then 
 slowly heated best on a water bath and just allowed to come to the boil over a slow 
 fire. The liquid is strained from the solid meat, and the latter put into a clean cloth 
 and well pressed. The residue is fit only for the making of manure. The broth may 
 be coloured with caramel if desired. Broth so made contains all the soluble consti- 
 tuents of meat, and exhibits an acid reaction owing to the free lactic and inosinic 
 acids. Broth does not owe its good properties to the gelatine it contains, this sub- 
 stance being present in very small quantities, while the so-called bouillon tablettes 
 obtained from bones are altogether unfit for food. These tablettes should not be con- 
 fused with solid-meat extract cakes of Russian make, which contain, according to 
 Reichardt (1869) 
 
 Water driven off at 1 00 15*13 per cent. 
 
 Ash 475 
 
 Fat o'22 ,, 
 
 Nitrogen 10*57 ,, 
 
 Substance soluble in alcohol at 80 per cent. . 38 '09 
 
 When broth is boiled for a long time it becomes deep-coloured and assumes the 
 very agreeable flavour of roast meat. Evaporated upon a water-bath it yields a pasty, 
 deep brown-coloured mass, 18-27 grammes of which yield, with i Ib. of hot water and 
 the addition of some salt, a very strong and excellent soup. 32 Ibs. of bones, with the 
 adhering scraps of lean meat, yield i Ib. of this extract. Extract of meat, as gen- 
 erally met with, is now made in South America by several firms, at Fray-Bentos, 
 Uruguay, Gualeguaychu (Entre Rios). i kilo, of this extract contains all the soluble 
 portion of 34 kilos, of meat without bones, or 45 kilos, of average butchers' meat. 
 Australian extract of beef (the American extract is of mutton and beef mixed, manu- 
 factured by R. Tooth) is largely imported into Europe. The chief test for the purity 
 of the extract of meat is its solubility in alcohol at 80 per cent., next the quantity of 
 moisture it contains, and the absence of albumen and fat. At least 60 per cent, of the 
 extract should be soluble in alcohol. The quantity of water amounts to about 16 per 
 cent., the nitrogen to 10 per cent., and the ash to 18 to 22 per cent., consisting essen- 
 tially of calcium and magnesium phosphates, and chlorides of the alkalies, among which 
 potassium chloride predominates. 
 
 Preservation of Meat. Among the many methods employed for the preservation of 
 meat, that by complete exclusion of air ranks foremost. Appert's plan of packing 
 meat in tin canisters, from which the air is completely exhausted, is generally the 
 following : The meat, or very concentrated soups, game, &c., is put into tin canisters, 
 which are thoroughly filled. A lid is then soldered on, in which a small hole is made 
 for the purpose of entirely filling any interstices with gravy. This having been done, 
 the small hole is soldered over, after which the canisters are placed in a cauldron filled 
 
-SECT, vi.] . MEAT. 795 
 
 with brine and boiled therein for a half to four hours, according to the size of the 
 canisters. When any of them is not well soldered, there will issue from the leakage 
 smaller or larger vesicles of air and vapour, and where such is the case hot solder is 
 applied on the spot. By this boiling the albuminous substances are coagulated and 
 converted into a less readily putrescible modification. The oxygen of the air contained 
 in the canisters is partly converted into carbonic acid, partly deozonised, and thus ren- 
 dered ineffective for the production of putrescence. After having been submitted to 
 the action of boiling heat for some time, the canisters are placed in a room heated to 30, 
 and left there in order to test whether putrefaction can set in, manifested by the bulging 
 outward of the top cover, which, if the operation has been thoroughly successful, is 
 usually somewhat concave in consequence of a vacuum having been formed inside the 
 tin. After having been thus tested for several days, the canisters may be considered 
 sound, and will keep for an indefinite period. Dr. Redwood's method of preserving 
 meat under a layer of paraffin, and Shaler's plan of preserving meat in dry carbonic 
 acid gas at o, are in principle the same as Appert's method. 
 
 Preservation of Meat by Withdrawal of Water. Meat may be preserved by drying 
 it or salting it, both methods being based upon the withdrawing of the water. Al- 
 though drying is the best method of preserving meat, it is an operation attended 
 with very great difficulty. The natives of North and South America cure meat by 
 cutting it into thin strips, removing the fat, and rubbing Indian-corn meal on the 
 surface. Thus prepared, the meat is exposed to the heat of the sun, and dries rapidly 
 forming a flexible, non-putrescent mass, which in North America is termed Pemmican, 
 in South America Tassajo, and in South Africa Biltongue. 100 parts of beef, which 
 is, after drying, rolled up so as to form a compact mass, yield 26 parts of tassajo. 
 The drying of meat is in Europe never effected on a large scale, partly on account of 
 the low temperature, partly on account of the necessity of cutting the meat into pieces, 
 rendering it in many instances unfit for culinary purposes. 
 
 Many preparations of flour and meat extract have been introduced at different 
 times under the name of meat biscuit, first made in 1850 by Gail Bordon at Galveston, 
 Texas, U.S., and greatly improved upon by C. Thiel at Darmstadt. The latter minces 
 fresh lean meat, next exhausts it with water, and uses the liquid obtained for mixing 
 with the flour instead of water. The large biscuit manufacturing firms in England, 
 especially Huntley & Palmer at Reading, prepare patent meat biscuits or wafers, made 
 with Liebig's extract of meat and Hassall's flour of meat. On the Continent, E. 
 Jacobsen at Berlin prepares a similar biscuit, more especially with the view of pre- 
 paring soup. To the mixtures of animal and vegetable matter prepared so as to be 
 suitable for keeping for a length of time belong the pea-sausages, first made by 
 Griineberg at Berlin, and largely used as an excellent food for the German armies 
 during the Franco-Prussian war. 
 
 /Salting Meat. This method of preserving meat, based upon the principle of 
 withdrawing water, has been used from time immemorial. The salt, while penetrating 
 into the meat and thereby hardening it, displaces the water and aids the preservation 
 of the substance. The freshly slaughtered meat is first rubbed with coarse salt, and 
 then left in a cask with salt for some days. It is next pressed and put into another 
 cask, the wood of which has been previously soaked with brine. Some salt is then 
 added, and lastly the brine, which had been obtained by pressing the meat, is poured 
 over it, and the lid of the cask put on. Frequently some potassium nitrate and sugar 
 are added, as well on account of the antiseptic property of these substances as for impart- 
 ing a bright red colour to the meat. 
 
 Salt, however, not only withdraws water from the meat, but also, as has been proved 
 :.by Dr. Liebig's researches, some of the very best and essential portion of the juices of 
 
796 CHEMICAL TECHNOLOGY. [ 8E cT. vi. 
 
 the meat, including albumen, lactic and phosphoric acids, magnesia, potash, kreatin, 
 and kreatinin. Hence it is clear that unless these substances are in some way or other 
 added to the salted meat, its use as food for a lengthened period cannot fail to become 
 injurious to the system, and it is surmised that scurvy is due to this condition of salt 
 meat. Liebig has suggested that meat, instead of being treated with dry salt, should 
 be salted with a strong brine made up of common salt, Chili saltpetre, potassium 
 chloride, and extract of meat. The salt to be used for making this brine should be 
 previously purified by the application of a solution of sodium phosphate, whereby lime 
 and magnesia are precipitated. Cirio's method of meat preservation, which was ex- 
 hibited in 1867 at the Paris Exhibition, consists in placing the meat in vacuo and then 
 forcing brine into it. By this process the nutritive value of meat is much impaired, 
 owing to the loss of the juices. 
 
 Smoking or Curing Meat. The ratioiiale of this process and the preservative action 
 of the smoke have not been scientifically elucidated. In the first place, the heat of the 
 smoke dries the meat, while, further, smoke contains a creosote, which, according to 
 the more recent researches of Hlasiwetz, -Gorup-Besanez, Marasse, and others, essen- 
 tially consists of a mixture of C 7 H 8 2 , C 8 H 10 2 , and C 9 H 12 Oj. This creosote possesses 
 the property of coagulating the albuminous substances of meat, and once coagulated, 
 and thereby rendered insoluble, these substances are not capable of decay, or only so 
 after a very great lapse of time. Smoke, moreover, contains some pyroligneous acid 
 and other creosote-like substances (oxyphenic and carbolic acids), which undoubtedly 
 play some part in the preservative action. 
 
 Vinegar is an excellent preservative of meat, especially in hot summer weather. 
 Abroad, meat is frequently put into a clean linen cloth which is thoroughly soaked 
 with vinegar, some salt also being sprinkled on the cloth. Meat kept for a few days 
 in this manner is very tender and readily digested. It is very probable that vinegar 
 might be advantageously employed on the large scale for the preservation of meat, 
 together with complete exclusion of air. In order to prevent the vinegar extracting 
 the juices of the meat, the latter should be exposed to the action of the vapours of 
 strong vinegar. 
 
 Lamy more recently, and Bracoimot, Robert, and De Dombasle nearly half a cen- 
 tury ago, proposed to preserve meat by the aid of sulphurous acid gas, pieces of meat 
 weighing from 2 to 3 kilos, being exposed to the action of this gas for ten minutes, 
 while larger pieces, of 10 kilos, or more, are exposed to the action of the gas for twenty to 
 twenty-five minutes. After having been exposed to fresh air for some minutes for the 
 purpose of getting rid of the excess of the gas, the meat is coated, with a brush, with a 
 solution of albumen in a decoction of marsh-mallow root to which some molasses have 
 been added. Very recently meat has been preserved by first drying it in a current of 
 hot air and next coating it with a film of caoutchouc or gutta-percha, by immersing 
 the meat in a solution of these substances in chloroform or sulphide of carbon. It is 
 very generally known that a temperature below freezing-point is a most perfect pro- 
 tection against decay of animal matter ; hence ice is largely used for the preservation 
 of fish in summer time. Meat, as well as game and poultry, are best preserved in hot 
 weather in ice-pits. In no country in the world is so much use made of this mode 
 of preserving meat and vegetables as in Russia, where the very severe winter is 
 turned to good account for preserving all kinds of animal food ; in fact, oxen, sheep, 
 hogs, deer, and all kinds of game and poultry are brought to market in a frozen 
 condition, and may be kept so for any length of time -without impairing the good- 
 ness or taste after cooking. At St. Petersburg large stores of frozen animal food 
 and game brought from distances of hundreds of miles are kept throughout the 
 winter. At the Dornburg, near Hadamar (Province of Nassau, Prussia), a natural 
 permanent ice store exists, wherein perishable food is kept stored in large quantity. 
 
SECT, vi.] NUTRITION. 797 
 
 The artificial production of ice by means of Carre's machine is employed in New 
 South Wales for the freezing of meat, which is next packed in ice ready for trans- 
 port. 
 
 It must be added that the process of smoking meat has some resemblance to a 
 tanning process, whereby its digestibility is naturally diminished. On the other hand, 
 the digestibility of meat can be improved by rubbing it with the juice of Carica 
 papaya.* 
 
 NUTRITION. 
 
 The blood circulating in the living animal body consists of a clear liquid, containing 
 substances capable of forming albumen and fibrine, and numerous microscopic corpuscles, 
 especially haemoglobin. This haemoglobin takes up in the lungs the oxygen of the 
 inhaled air, and assumes in consequence a bright red colour. The bright red arterial 
 blood gives off this oxygen whilst circulating through the body, and the haemoglobin 
 of the blood-corpuscles absorbs carbon dioxide in its place, which the venous blood, 
 rendered thereby darker, exchanges again for oxygen in the lungs. A man inhales 
 at every breath about 0*5 litre of air, and consumes daily 750 grammes oxygen, giving 
 off 320 grammes watery vapour and 900 grammes carbon dioxide. 
 
 The food is moistened in the mouth by the saliva secreted by three glands, which 
 converts starch into dextrine and sugar. The food encounters in the stomach the 
 strongly acid gastric juice containing free hydrochloric acid and pepsine. This agent 
 prepares the proteine matters in the food for reception into the blood. In the bowels 
 the digestion is completed by the alkaline pancreatic secretion and the gall, when the 
 substances suitable for the formation of blood are taken up by the lymphatic vessels 
 and conveyed into the veins. 
 
 By the inspiration of oxygen the parts of the body are oxydised and conveyed away 
 by the blood, the carbon dioxide being eliminated in the lungs, and the urea, CO(NH !! ),, 
 formed from the proteine substances, in the kidneys. These losses must be com- 
 pensated by the blood, to which fresh matter must be conveyed by taking food. 
 
 Nutrition has therefore two distinct tasks to fulfil viz., (i) the formation and 
 preservation of the body; (2) supply and utilisation of energy for the power of the 
 entire body and its organs i.e., the production of heat, mechanical work, and elec- 
 tricity. The first duty is chiefly assigned to the albuminoids ; in the production of 
 power all the organic matters are concerned according to the sum of the tension forces 
 contained in them and liberated by the metabolism in the body. The non-nitrogenous 
 substances, which only play a subordinate part in building up the organs, but possess 
 the greatest sum of available tension, are chiefly concerned in the production of vis 
 viva, the chief representative of which is animal heat. 
 
 If a strong man, previously well fed, entirely abstains from food for twenty-four 
 hours, he consumes muscle corresponding to the expenditure of 8-024 grammes of nitro- 
 gen, 3*65 grammes carbon in the liquid excretions, 180-5 grammes carbon in respira- 
 tion, 507 grammes albumen, and 198'! grammes of fat. With a diet entirely free from 
 nitrogen, consisting of 150 grammes of fat, 300 grammes starch, and 100 grammes 
 sugar (together = 254-68 grammes carbon), there were eliminated in the liquid excreta 
 8' 1 6 grammes nitrogen and 3*6 1 grammes carbon ; in the solid excretions 18*79 grammes 
 and in respiration 200-50 grammes carbon, so that the body had lost 51*8 grammes 
 albumen, but gained 81-5 grammes fat. On a purely animal diet, nitrogen is retained in 
 the body, and the amount of fat is reduced. A perfect equilibrium between the intake 
 and the outlay in the body of a vigorous man (during muscular rest) is obtained 
 by- 
 
 * This process is applicable only if the meat is to be immediately consumed. [EDITOR.] 
 
793 CHEMICAL TECHNOLOGY. 
 
 Albumen (with 15-5 grammes N.) .... 100 grammes 
 
 Fat .......... 100 ,, 
 
 Starch and sugar 240 ,, 
 
 Water, drunk, and contained in the solids . . 2535 ,, 
 
 Salts 25 ,, 
 
 [SECT, 
 
 These quantities correspond to 250 grammes meat, 400 grammes bread, 70 grammes sugar r 
 100 grammes fat, 10 grammes salt, and 2100 grammes water. A man on a mixed diet 
 uses, therefore, 49 grammes albumen and 43 grammes fat more than a similarly hungry 
 man not doing work which promotes digestion. With severe muscular work a man 
 needs very little more albumen, but considerably larger quantities of fat and carbo- 
 hydrates, than when at rest. This extra consumption of albumen and fat for the 
 work of digestion must be considered in deciding on the value of nutriment. Th& 
 greater tension-power a certain weight of nourishment introduces which becomes free- 
 and available in the organism the higher is its food value. 
 
 If we estimate, in animal foods, 100 grammes albumen at 65 pfennige,* 100 grammes- 
 fat at 20 pfennige, and in vegetable foods 100 grammes albumen at 15, fat at 4-5, and 
 non-nitrogenous extract at 2*5 pfennige, we have the following values : 
 
 
 Chemical Composition in per cent. 
 
 T.-1 . 
 
 i Kilo, has 
 
 
 
 
 
 e 
 
 
 
 3 
 
 ~ 
 
 Vegetable Foods. 
 
 tS 
 
 "o 
 
 e 
 
 .. 
 
 *" 
 
 s 
 
 
 
 
 
 
 a>"3'" 
 
 o 
 
 
 i 
 
 Album 
 
 n 
 
 H 
 
 K 
 
 S 
 
 ^O 
 
 * 
 
 S 
 
 "S g 
 
 
 13-38 
 
 Q'o6 
 
 I "42 
 
 -..-, 
 
 0-6"? 
 
 0-08 
 
 -J-j'2 
 
 "6 
 
 coarse .... 
 
 15-02 
 
 9-18 
 
 1-63 
 
 69-86 
 
 0-62 
 
 1-69 
 
 37 '9 
 
 24 
 
 
 14-41 
 
 6 "94 
 
 O'tJI 
 
 77'6i 
 
 0-08 
 
 o'4t; 
 
 7O'O 
 
 80 
 
 
 4"? '26 
 
 6*12 
 
 O'QT 
 
 46*6'* 
 
 O'i7 
 
 i '80 
 
 21 -3 
 
 20 
 
 Fine wheat bread .... 
 
 26-39 
 
 8-62 
 
 0*60 
 
 62-98 
 
 0-41 
 
 i-oo 
 
 28-9 
 
 48 
 
 
 I4'5O 
 
 2VOO 
 
 2"OO 
 
 53-50 
 
 4 '"JO 
 
 2'tJO 
 
 48-7 
 
 JQ 
 
 
 QI'22 
 
 O*7Q 
 
 0*26 
 
 6'OQ 
 
 0-86 
 
 O'7Q 
 
 2-8 
 
 j-i 
 
 Cauliflower . . 
 
 
 2-89 
 
 0-16 
 
 3-02 
 
 0-80 
 
 0-79 
 
 5-2 
 
 320 
 
 
 7577 
 
 1-79 
 
 0-16 
 
 20-56 
 
 075 
 
 0-97 
 
 7-5 
 
 6 
 
 
 Animal Foods. 
 
 Chemical Composition in per cents. 
 
 i Kilo, has 
 
 C 
 
 "3 
 
 'O . s 
 
 1.S 
 1-tt 
 
 <"" 
 
 "8 
 
 fi 
 
 e > 
 
 f|| 
 ;: t< 'a 
 
 !S 
 
 o S 
 Ko 
 
 05 
 
 j3 
 
 *i& 
 
 ill 
 
 ill 
 
 ?5 
 
 a <= 
 fc 
 
 Market Price, 
 Pfennige. 
 
 
 73-48 
 65-11 
 71-66 
 71-41 
 71-17 
 4871 
 73-82 
 
 73-13 
 47-12 
 51-77 
 42-79 
 49-93 
 72-46 
 88-00 
 
 I2-OO 
 
 36-00 
 
 19-17 
 17-94 
 18-14 
 14-65 
 17-94 
 15-98 
 23-54 
 
 22*19 
 
 18-97 
 
 22-30 
 11-69 
 
 11-81 
 
 11-36 
 
 3 "20 
 
 0-50 
 23-00 
 
 5-86 
 
 15-55 
 7-18 
 
 12-64 
 
 8-38 
 34-62 
 1-19 
 1-77 
 16-67 
 
 2'2I 
 39-6I 
 II-48 
 I3-40 
 4'OO 
 
 86-00 
 37-00 
 
 O'll 
 0-62 
 
 0-32 
 0-47 
 
 0-47 
 1-39 
 
 2-25 
 25-09 
 
 1-73 
 4"OO 
 0-50 
 
 1-38 
 0-78 
 3-02 
 0-98 
 2-04 
 0*69 
 1-07 
 I-52 
 I7-24 
 23-72 
 
 3-66 
 1-69 
 1-05 
 i -80 
 
 I -00 
 
 4-00 
 
 I36-3 
 I43-9 
 I32-3 
 I20-5 
 
 I33-4 
 I72-I 
 
 I43-4 
 147-8 
 156-6 
 
 I49-3 
 I55-2 
 76-4 
 
 1 06 '6 
 33-6 
 176-9 
 
 223-5 
 
 1 60 
 144 
 86 
 
 IOO 
 
 5o 
 300 
 
 221 
 6OO 
 105 
 
 465 
 360 
 60 
 2OO-24O 
 
 15 
 
 200-240 
 I 50-200 
 
 2nd quality .... 
 3rd quality .... 
 
 
 Hain (pig) . .... 
 
 Fieldfares 
 Herring ...... 
 
 Frankfurt sausage .... 
 
 
 Milk 
 Butter 
 
 Cheese 
 
 loo pfennige = 
 
SECT, vi.] NUTRITION. 799 
 
 According to this table the fattest kinds of meat are most to be recommended ; 
 game and poultry are very costly ; fish cheap in proportion to nutritive value. 
 Sausage and smoked meats are dearer than fresh meat. Milk and cheese are 
 cheap. 
 
 Legumens are cheap in proportion to nutritive value. Wheat and rye are cheaper 
 than rice ; vegetables (cauliflower, carrots, &c.) the most costly. Meat, eggs, and milk 
 are most completely utilised ; vegetables much less thoroughly, as from 20 to 40 per cent, 
 are excreted undigested. A powerful body can scarcely be built up and maintained 
 on a purely vegetable diet. The small capacity for work of persons so fed is known. 
 
SECTION VII. 
 CHEMICAL TECHNOLOGY OF FIBRES. 
 
 WOOL. 
 
 Origin and Properties of Wool. Wool is distinguished from hair chiefly by the 
 three following properties : it is finer ; it is not straight, but curled ; while it generally 
 contains less pigment, and hence is white in colour. The quality of wool improves 
 with the increase of these three characteristics. Wool, like hair, exhibits an organised 
 structure, consisting histologically of an epithelium, of a rind, and of a pith or 
 marrow. The epithelium of wool consists of small thin plates which overlap each 
 other like the tiles on a roof ; in this manner the cuticular plates give to the sur- 
 face a squamose appearance, which may be coarsely represented as the appearance 
 exhibited by a fir-cone. Fig. 542 exhibits a piece of wool of an ordinary 
 sheep; while Fig. 541, magnified to the same number of diameters, exhibits a 
 Fig. 541. Fig. 542. 
 
 Fig. 543- 
 
 piece of the very finest Saxony wool, thus showing the great difference of fine- 
 ness of these two sorts of wool. The grooves on the surface of the wool are 
 the cause of its rawness to the touch, and from the existence of these grooves 
 wool admits of being felted. When the fibres which exhibit this texture are 
 pressed together with a kind of kneading motion, and at the same time softened 
 by the action of steam, they join to each other in the direction of the scales on 
 
SECT. VII.] 
 
 WOOL. 
 
 801 
 
 their surface and, becoming entangled, form a firm, dense texture, which is termed 
 felt. 
 
 Coarser wools have also longitudinal grooves, as shown in Fig. 543. 
 
 The varieties of wool obtained from animals other than sheep are : 
 
 (a) Cashmere wool ; the fine downy hair of the Cashmere goats inhabiting the 
 eastern slopes of the Himalaya, from 14,000 to 18,000 feet above sea level. The colour is 
 white-grey or brown. In the state in which it is sent to Europe it is largely mixed 
 with coarse hair, so that, after sorting and cleansing, 100 kilos, of the raw material yield 
 only 20 kilos, of fine hair. 
 
 (b) Vienna wool ; the very slightly curly hair of the llama or vicuna goat 
 (Auchenia vicuna), a native of the high mountains of Peru, Chili, and Mexico. This 
 kind of wool, or rather woolly hair, was formerly more used than now for weaving 
 fine tissues. Sometimes a mixture of ordinary wool and the finest hair of hares and 
 rabbits is substituted for this wool. What is now termed viguna or vicuna wool in 
 the trade is a tissue made of a mixture of wool and cotton. 
 
 Fig- 544- 
 
 Fig- 545- 
 
 J 
 
 (c) Alpaca wool, or pacos hair ; the long, sleek, white, black, or brown hair of tht, 
 alpagua or alpaco (pako), a kind of goat which dwells in Peru. This kind of woolly 
 hair has great similarity with the vicuna wool, but is not quite so fine.* 
 
 (d) Mohair, or so-called camel's wool ; the long, slightly curly, silky hair of the 
 angora goat (Capra angorensis), a native of Asia Minor. This substance is spun and 
 woven into non-fulled tissues (camlet or plush), and is also mixed up with the half-silk 
 tissues of which it forms the woof or weft. 
 
 Chemical Composition of Wool. Purified and cleansed wool consists chiefly of an 
 albumenoid sulphur-containing substance termed keratin (horny matter), but, as met 
 with on the animals, wool contains much dirt, dust, and suint. The labours of Faist, 
 Reich, Ulbricht, Hartmann, Marcker, and E. Schulze have greatly increased our 
 knowledge of this substance. 
 
 The following results are those obtained by Faist when analysing various kinds of 
 
 merino wool : 
 
 * The microscopical texture and properties of this kind of hair have been investigated and are 
 described in Wiesner's work, Einleitung in die technische Mikroslcopie. Vienna, 1867, pp. 172 
 ? seq. 
 
302 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vn. 
 
 
 i. 
 
 2. 
 
 
 a. 
 
 b. 
 
 c. 
 
 d. 
 
 e. 
 
 /. 
 
 Mineral matter 
 
 6-3 
 
 16-8 
 
 0-94 
 
 i'3 
 
 I'O 
 
 I '2 
 
 Suint and fatty matter 
 
 44 '3 
 
 447 
 
 21'00 
 
 40-0 
 
 27*0 
 
 16-6 
 
 Pure wool 
 
 38-0 
 
 28-5 
 
 72-00 
 
 56-0 
 
 64-8 
 
 777 
 
 Moisture . . . . 
 
 11-4 
 
 7-0 
 
 6-06 
 
 27 
 
 7-2 
 
 3'5 
 
 
 lOO'O 
 
 lOO'O 
 
 lOO'OO 
 
 lOO'O 
 
 lOO'O 
 
 lOO'O 
 
 Percentage of pure | 
 air-dry wool ) 
 
 49 "4 
 
 35-5 
 
 78-06 
 
 58-7 
 
 72 x> 
 
 82-2 
 1 
 
 i . Raw wool, air-dried. (a) Hohenheim wool, with a small quantity of readily soluble 
 suint. (6) Hohenheim wool (the name of a large agricultural establishment and agrono- 
 mical school near Stuttgart, Wurtemburg), containing a large quantity of glutinous 
 suint. 2. Washed wool, air-dry.* (c) Hohenheim wool. (d) Same variety, with 
 difficultly soluble suint. (e) Hungarian wool, very soft. (/) Wiirtemburg wool, 
 less soft. 
 
 While making researches on wool, Eisner of Gronow estimated the loss which wool 
 experiences when treated with sulphide of carbon for the elimination of the suint. 
 The results were 
 
 Washed merino wool * . . . . . 15 to 70 per cent. 
 Unwashed wool (laine en suint, raw wool) . 50 to 80 
 Long carded wool 18 ,, 
 
 Suint is a mixture of secreted and accidental substances, dust, &c. When raw wool 
 is macerated for some time in warm water, there results a turbid liquid which contains 
 
 suspended as well as dissolved matters. 
 
 Fig. 546. The dry substance of the aqueous extract 
 
 of suint consists, according to Marcker 
 and Schulze (1869), of 
 
 T. 2. 3. 4. 
 
 Organic matter . 58-92 6i'86 59-12 60*47 
 Mineral matter . 41-08 38-14 40-88 39-53 
 
 i and 2 relate to wool of mountain sheep. 
 3 and 4 to full-bred Eambouillet sheep. 
 
 The soluble portion contains the potash 
 salt of a fatty acid (potassium suintate}. 
 The fatty acids contained in suint are, 
 according to Reich and Ulbricht, mixtures 
 of oleic and stearic acids, probably also 
 palmitic acid and a small quantity of 
 valerianic acid, with potash in such quan- 
 tity, that more recently this material 
 has been employed for obtaining there- 
 from potassium carbonate and potassium 
 chloride. 100 kilos, of raw wool may 
 yield from 7 to 9 kilos, of potash (see 
 p. 283). 
 
 Artificial Wool is formed by tearing up woollen rags, and is used in very con- 
 siderable quantities both along with, and instead of, fresh wool. The trade dis- 
 
 * Washed on the sheep while alive, an operation performed by the farmers, and to be distin- 
 guished from the washing wool undergoes during manufacture. 
 
 W = Wool. 
 B = Cotton. 
 L = Linen. 
 S = Silk. 
 J = Juie. 
 
SECT, vii.] SILK. 803 
 
 tinguishes shoddy, the artificial wools obtained by tearing up into a fibrous state 
 all sorts of fabrics known as " softs " i.e., blankets, flannels, old stockings, &c. 
 Mungo is obtained by grinding up the " hard " rags from milled cloths. Fig. 546 
 shows the mixed fibres obtained by tearing up cloth.* 
 
 SILK. 
 
 Silk is at once distinguished from cotton, flax, hemp, and wool by being 
 naturally produced as a very long and continuous thread, whereby the operation of 
 spinning is dispensed with ; but in its stead the operation known as silk-throwing is 
 required, by which several of the natural fibres of the silk are twisted into one in order 
 to obtain a stouter yarn. 
 
 Silk is the produce of the silkworm (Bombyx mori), an insect which undergoes four 
 metamorphoses. The worm is produced, in the spring, from the egg, or ovule. It 
 casts its skin from three to four times, and finally spins a thread, produced, or rather 
 secreted, by two glands placed near the head, from small apertures, in which is gluti- 
 nous fluid, which immediately coagulates under contact with air. Thus, what is 
 termed a cocoon is formed, which serves as a shelter for the pupa against injury and 
 cold. The thread is double, but is united in one by a peculiar kind of glue termed 
 sericin, which is laid as a kind of varnish over the whole surface of the thread, of 
 the weight of which it forms about 35 per cent. After a period of from fifteen to twenty- 
 one days, the pupa is metamorphosed into a butterfly, which, in order to leave its 
 prison, softens a portion of the cocoon with a juice which it secretes, and then per- 
 forates the softened part. For the purpose, however, of producing silk, the pupa is 
 not allowed to develop so far, but is killed (excepting in a number of cocoons intended 
 for the full development of the moths, so that they may produce eggs), and the 
 thread of the cocoon is carefully wound on a reel. 
 
 Sericiculture. Varieties of Silkworms. The Bombyx mori is the main supplier of 
 silk. Its food is the leaves of the white mulberry tree, Morus alba. There are, 
 however, other silk-producing insects, among which the following are to be 
 noticed : 
 
 (a) Bombyx cynthia, largely cultivated by the natives of the north-east portion of the 
 interior of Bengal and also by the Japanese. The former call this worm A rrindy-arria, 
 the latter Yama-ma'i. This worm feeds on rice leaves, and on Ricinus communis. The silk 
 obtained from this insect, although less brilliant than that which the ordinary silkworm 
 yields, is very useful, as being durable and strong. This worm will feed on other leaves, 
 such as that of the weavers' thistle, Dipsacus fullonum, wild chicory, Chicoriv/m intibiis, 
 and the leaves of the Ailanthus glandulosa. The results of acclimatising this insect in 
 France and Germany have been satisfactory. 
 
 (&) Bombyx pernyi is a native of Mongolia and China ; it feeds on oak-leaves. 
 Some years ago these worms were introduced into France, and have been fed and 
 reared successfully upon European oak-leaves. 
 
 (c) Bombyx mylitta, or Tussa worm, is a native of the colder parts of Hindostan 
 and of the slopes of the Himalaya. Its silk is an important article of commerce in 
 Bengal. This insect feeds on oak and other leaves, casts its skin five times, and yields 
 large cocoons. The fibre of this kind of silk is from six to seven times stouter than 
 the silk of the ordinary worm, but unfortunately the Tussa worm only lives in its 
 free natural state, and when captive does not produce silk. The following silk- 
 producing varieties belong to North America: (d) Bombyx polyphemus ; on oak and 
 
 * For full information on wool from an industrial point of view, the reader may compare The, 
 Structure of the Wool Fibre in its delation to tlie Use of Wool for Technical Purposes, by Dr. F. H. 
 Bowman, F.L.S., &c. Manchester : Palmer and Howe. [EDITOR.] 
 
804 CHEMICAL TECHNOLOGY. [SECT. vn. 
 
 poplar trees, (e) B. cecropia ; on elm, whitethorn, and wild mulberry trees. (/) S. 
 platensis ; on a kind of mimosa, Mimosa platensis. (g) B. leuca, which deserves f urther 
 attention. 
 
 We quote the following account of the culture and rearing of silkworms : (i) The 
 mulberry tree. The leaves of the variety known as the white mulberry tree, from 
 the fact that its fruit is yellow or light red in colour, is the most suitable food for this 
 insect, but its cultivation belongs to horticultural pursuits, and we cannot enter upon 
 the subject here. (2) The production of the eggs or ova of the silkworm is effected in 
 the following manner : The largest and finest cocoons, and such as have a fine 
 thread, are selected and preserved ; usually the cocoon of the female insect is more 
 oval than that of the male, which is more pointed at the ends and is somewhat 
 depressed in the centre. Although these characteristics do not apply in all cases, 
 sericiculturists become sufficiently adepts in this matter to be able to select a 
 sufficient number of cocoons of each sex. 100 to 120 pairs of well-formed cocoons 
 yield 30 grammes of eggs, about 50,000 in number, from which, however, only 
 70 to 75 per cent, of worms are obtained. The cocoons selected for breeding 
 purposes are allowed to remain on a table covered with a white cotton cloth. 
 After some twelve days the moths make their appearance, and, having paired, 
 the females, after a lapse of some forty hours, lay from 300 to 400 eggs. (3) The 
 eggs are properly protected from cold in winter and remain in the buildings 
 called magnaneries, being placed in a uniform layer on a cotton cloth stretched on 
 a wooden frame. The eggs are covered with sheets of white paper, perforated with 
 small holes. Upon the sheets of paper mulberry leaves, at first cut up so as to form 
 a kind of chaff, are placed. In France a contrivance known as a couveuse, that is 
 to say, an oven, in which a suitable temperature is kept up is now generally used 
 for the purpose of breeding the worms, which are best hatched from the eggs at a 
 temperature of 30, provided moisture is also present. The young brood, on leaving 
 the eggs, creep through the holes in the paper, and seeking daylight (there is always 
 free access of light in magnaneries) begin at once to feed on the mulberry leaves. 
 (4) The rearing of the worms requires care and attention. They are best placed 
 on paper laid on wooden frames. The worms grow rapidly, and are very voracious. 
 They cast their skins four times, and after from thirty to thirty- two days begin to spin the 
 cocoons. (5) When the period of spinning approaches, the worms are placed in small, 
 somewhat conical wicker-work baskets, in which they are comfortably located. The 
 first thread spun, or rather an entangled flocky mass, is afterwards separately collected 
 and kept as floss silk. The insect discharges, before beginning to spin further, first 
 a solid substance, white or green in colour, and consisting, according to Peligot, chiefly 
 of uric acid ; next a clear, watery, very alkaline liquid, which contains 1-5 per cent, of 
 potassium carbonate, this curious discharge amounting to from 15 to 20 per cent, of the 
 weight of the worm. The formation of the cocoon is finished in about five days, but 
 the cocoons are not collected for the purpose of reeling the silk until after seven or 
 eight days, so as to make sure that all the worms have spun. 
 
 As far as the chemical composition of silk is concerned, we have to distinguish 
 between the fibre and its envelope. The fibre consists, for about half its weight, of 
 fibroin, a substance which, according to Stadeler's researches, is nearly related to 
 horny matter and mucus, and is identical with these as regards chemical compo- 
 sition. The formula of silk fibroin is C 15 H 23 N 5 6 . The gum-like envelope of the 
 silk fibre, which has been termed by Cramer and Stadeler silk glue or sericin, is 
 partly soluble in water and readily so in soap-suds and other alkaline fluids. The 
 formula of sericin is Ci 5 H 25 N" 5 8 . P. Bolley's researches have proved that in the silk- 
 producing and secreting glands of the worm only glutinous, semi-liquid fibroin 
 occurs, which, on coming into contact with air, is acted upon by the oxygen, and 
 
SECT, vii.] SILK. 805 
 
 then converted into seriein. Haw silk leaves, on ignition, a small quantity of ash ; 
 Guinon found in Piedmontese raw silk, dried at 100, 0-64 per cent, of ash, consisting 
 of 0-526 lime and o'ii8 alumina and oxide of iron. Dr. J. G. Mulder found in 100 
 parts of raw silk 
 
 Yellow Silk from White Silk from the 
 Naples. Levant (Almasin Silk). 
 
 Fibroin 53-40 .. 54 - o 
 
 Glue-yielding matter . . . . 2070 ... 19-1 
 
 Wax, resin, and fatty matter . . 1*50 ... 1-4 
 
 Colouring matter . . . . 0-05 ... 
 
 Albumen ....... 24-40 ... 25-5 
 
 (6) Killing the Pupa in the Cocoon. The pupa remains in the cocoon for from fif- 
 teen to twenty days, and is then metamorphosed into a butterfly, which will perforate 
 the cocoon, and thus obtain an exit. It is clear, however, that the cocoon not intended 
 for breeding purposes should not be kept so long, because by the perforation of the cocoon 
 the silk is spoiled, or at least greatly deteriorated. Therefore the pupae in the cocoons 
 are either killed by the application of oven-heat or of steam. 
 
 Manipulation of the Silk. Six different operations are required to render raw silk fit 
 for use as an article of commerce and suitable for weaving, &c. These operations are : 
 
 1 i) The Sorting of the Cocoons, an operation which requires great care and greater expe- 
 rience, its aim being (a) the separation of yellow from white cocoons ; (/3) the elimina- 
 tion of all damaged cocoons as only fit for yielding floret silk ; the damage may arise in 
 various ways, as, for instance, by mouldiness, injury by other insects, and, lastly, foul- 
 ing of the pupa, as well as perforation by the moth ; (7) selection of the cocoons 
 according to varying fineness of thread and uniformity of the silk. 
 
 (2) Winding the Silk on the Reel is the first operation with the cocoon. By this the 
 threads of silk which the insect has wound up into a kind of ball are unwound and 
 brought into the shape of a skein or strand. 
 
 As the single fibre of silk is far too thin to be manipulated, the operator usually 
 takes from 3 to 10 or even 20, making them unite by the operation of reeling. This 
 is not by any means so readily performed as might be imagined, because it is difficult 
 to find the end of the thread, whilst the surface of the cocoon is varnished with a 
 gum-like mass, which glues the fibres together. Partly by the aid of hot water and 
 partly by dexterity these difficulties are overcome, and by good management a thread 
 of from 250 to 900 metres length may be obtained from each cocoon, each yielding 
 from 0-16 to 0*20, at the very utmost 0-25 gramme, of raw silk, i kilo, of raw silk 
 requires from 10 to 12 kilos, of cocoons. The silk thus obtained is termed raw silk, 
 which should be quite uniform as regards thickness and strength of fibre. That por- 
 tion the interior and a portion of the outer layer of the cocoon which does not 
 admit of being reeled off is employed for making floret silk, by operations similar to 
 those in use for wool and cotton viz., cleansing, disentangling, combing, carding, and 
 spinning, to produce a silk yarn. 
 
 (3) The Throwing of Silk. As the thread obtained by reeling is too fine for use, 
 either for weaving, knitting, sewing, &c., it is usual to unite several threads of silk by 
 means very similar to those used in rope- making, an operation termed throwing, known 
 as twisting when the thread of raw silk is simply rotated on its axis so as to make it 
 stronger. The following are the chief varieties of thrown silk : (a) Organzine, used as 
 chain for woven silk fabrics, is prepared from the best raw silk. The threads of from 3 to 
 8 cocoons are united, being first strongly twisted and next thrown, after which two of 
 such threads are twisted together, (b) Trame used for woof or weft, and for silk cord, 
 is made from inferior cocoons. Single-threaded trame consists of one single twisted 
 raw silk thread made up of the united threads of from 3 to 1 2 cocoons. The double- 
 threaded trame consists of two threads twisted to the left, but less strongly than in 
 
806 CHEMICAL TECHNOLOGY. [SECT. vii. 
 
 organzine. There are also three-threaded trame, &c. Trame is softer and smoother 
 than organzine, and therefore fills better than round threads in weaving, (c) Marabou 
 silk is stiffly thrown and similar to whipcord ; it is made from three threads of the 
 whitest raw silk and thrown in the trame fashion ; is dyed without being previously 
 scoured (boiling the gum out in this instance), and is again thrown after dyeing. 
 (d) Foil silk is a simple raw silk thread, twisted, and chiefly used as a basis for gold and 
 silver wire, such as is worn on military uniforms. Sewing silk is obtained from some 
 3 to 22 cocoon threads being twisted together. There are several other varieties of 
 silk thread used for crochet, knitting, &c. 
 
 (4) Conditioning or Testing of Silk. The fineness of raw as well as of thrown silk 
 is expressed by stating how many yards or metres length of the fibre are contained in 
 a certain weight. The unit abroad is 400 ells or 475 metres. When the expression 
 is used, that such silk is at 10 grains, it is understood that 475 metres length of that 
 particular silk weighs 10 grains; a silk at 20 grains has the same length but double the 
 weight, and consequently that silk is only. half <is fine as the former. 
 
 Raw, as well as thrown silk, contains a large quantity of hygroscopic water, the 
 quantity of which cannot be judged by the external appearance of the material. The 
 silk usually met with in commerce contains from 10 to 18 per cent, of hygroscopic water ; 
 and silk may occasionally contain even 30 per cent, without appearing to be moist. 
 As silk is a very expensive material and often sold by weight, it is clear that this 
 property of taking up water is too important to be left unnoticed ; and for that reason 
 silk is conditioned as it is called, that is, the quantity of water it contains is duly 
 ascertained. 
 
 (5) Scouring or Boiling the Gum out of Silk. Excepting a few instances, such a& 
 for example, in the weaving of fine silken sieve cloths, and for crape and gauze fabrics, 
 raw silk has to be deprived of its envelope, the gummy matter already mentioned,, 
 in order to give softness, suppleness, gloss, and especially also to render the silk fit for 
 being dyed. 
 
 The operation of scouring is comprised in the following manipulations : 
 
 (1) Removing the gum. 
 
 (2) Boiling. 
 
 (3) Colouring. 
 
 The taking out of the gum is performed in the following manner : Olive oil soap 
 is first dissolved in hot water and into this solution at 85 the skeins of silk are 
 placed hung on sticks. The skeins are moved about in this bath until all the gum has 
 been uniformly taken out. The silk is next wrung out, rinsed in fresh water and then 
 dried. Silk may by this process lose from 12 to 25 per cent, in weight, according to the 
 quality of the raw silk and the quantity of soap employed. The scoured silk is ready 
 for dyeing with dark colours, but if required to be dyed with bright colours it has to be 
 first boiled. To this end it is put into coarse canvas bags, each containing from 12 to- 
 1 6 kilos, of silk, and in these sacks the silk is placed in a soap bath and boiled for i 
 hours : the silk is next rinsed in water, wrung out, and dried. The operation of rosing 
 or colouring aims at imparting to the silk a slight tint in order to enhance its beauty. 
 The trade distinguishes various hues of white silk, such as Chinese white, azure white, 
 pearl white, &c. The first of these hues, a somewhat ruddy tint, is obtained by rinsing 
 the silk in soap- water, to which some annatto has been added. The bluish hues are 
 produced by indigo solutions. The bleaching of scoured silk is effected by the aid of 
 sulphurous acid, the fibre either being placed in a room where this gas is evolved from 
 burning sulphur, or by treating the silk with an aqueous solution of the acid. As silk 
 loses a great deal in weight as well as in body by the scouring, which is, however r 
 required, because raw silk does not permit of being dyed, it has become the practice to 
 produce a material called souple, obtained by treating the raw silk with boiling water 
 
SECT, vii.] SILK. 807 
 
 in which only a small quantity of soap, i kilo, to 25 kilos, of silk, is dissolved. Instead 
 of this soap solution, an acidified (with dilute sulphuric acid) solution of magnesium 
 or sodium sulphate is sometimes used. The silk loses by this process only from 4 to 10 
 per cent, in weight. In order to bleach raw silk without depriving it of its natural 
 rigidity, the skeins are digested at a temperature of from 20 to 30 with a mixture of 
 alcohol and hydrochloric acid ; this liquor becomes green in colour, and the deeper 
 the hue the whiter the silk. The silk is rinsed in water, and having been dried will 
 be found to have lost only about 2*91 per cent, in weight. The alcohol used in thi 
 process may be readily recovered by neutralising the acid with chalk and subsequent 
 distillation. 
 
 Means of Distinguishing Silk from Wool and from Vegetable Fibres. Owing to 
 the manufacture of mixed fabrics, it has become a necessity to be enabled to detect and 
 distinguish silk from woollen as well as from cotton and linen fibres. Microscopical 
 investigation aided by chemical tests is resorted to for this purpose. 
 
 The animal fibres (silk, wool, and alpaca) are at once distinguished from the 
 vegetable (flax, hemp, cotton), by the fact that the former are soluble in caustic potash 
 and the latter not. The animal fibres on being singed give off a smell of burnt 
 feathers, and when ignited in the flame of a candle are almost immediately extinguished, 
 a carbonaceous residue being left. Cotton and linen fibres continue to burn, do not 
 give off the smell of burnt feathers, and do not leave a carbonaceous mass when 
 extinguished. Wool and silk are coloured yellow by nitric acid (i'2 to 1-3 sp. gr.), 
 cotton and linen not so. Nitrate of protoxide of mercury colours animal fibres 
 intensely red, and upon the addition of a soluble alkaline sulphuret this colouration 
 becomes black. Linen, or flax, and cotton are not at all acted upon by this reagent. 
 An aqueous solution of picric acid dyes wool and silk intensely yellow, but not so 
 vegetable fibres. The colourless liquid obtained (according to Liebermann) by boiling 
 a solution of magenta with caustic potash does not impart to a mixed fabric of wool 
 and cotton any colour at all ; but when the fabric is thoroughly washed in water, the 
 woollen fibre becomes intensely red-coloured, while the cotton fibre remains colourless. 
 A solution of ammoniacal oxide of copper in excess of ammonia dissolves, first silk, 
 next cotton, but not wool. When wool and floret silk are mixed the latter may be 
 dissolved by successive treatment with nitric acid and ammonia, while wool is left. 
 A solution of oxide of lead in caustic potash or soda may serve to distinguish wool 
 from silk, owing to the fact that, in consequence of the former containing sulphur and 
 the latter not, the mixture, when wool is present, becomes black. Sodium nitro- 
 prusside is undoubtedly the most delicate test for distinguishing between silk and wool 
 in solution in caustic alkali, because, owing to the sulphur of the wool, this reagent 
 produces in the solution a violet colouration. 
 
 By the aid of the microscope, cotton, wool, and silk are readily distinguished from 
 each other. As for cotton, it is fully described on pp. 802, 813, 815, and its micro- 
 scopical appearance illustrated by woodcuts, as also are silk and woollen fibres. Of 
 the latter we may now state that, whereas cotton fibre consists of only one cell, wool 
 (as also hair and alpaca) is made up of numerous juxtaposed cells ; the silk fibre being 
 similar to the secreted matter of spiders and various kinds of caterpillars. The silk fibre 
 (Fig. 547) is smooth, cylindrical, devoid of structure, not hollow inside, and equally 
 broad. The surface is glossy and irregularities are but seldom seen on it. If it 
 is desired to detect in a woven fabric the genuineness of the silk, it is best to cut a 
 sample to pieces, place it under water under the object-glass of a microscope magni- 
 fying from 120 to 200 times, covering it with a thin piece of glass. The round, glazed, 
 equally proportioned silk fibre, Fig. 547, is easily distinguished from the unequal and 
 scaled wool fibre (TFin Fig. 548), and from the flat band -like and spiral cotton fibre 
 (B Fig. 549). Under the microscope also the admixture of inferior with superior fibres 
 
8o8 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vii. 
 
 of silk can be easily detected. A small microscope known as a " linen prover " is sold 
 for these examinations.* 
 
 Fig. 548. Fig. 549. 
 
 Fig. 547- 
 
 Silk. 
 
 Cotton. 
 
 VEGETABLE FIBEES. 
 
 Fig. 550. 
 
 Vegetable fibre, essentially cellulose, C 6 H I0 0., forms the texture of plants. With 
 incrustations it forms woody fibre ; in long threads or tufts it appears as flax, hemp, 
 
 cotton, &c., which constitutes the impor- 
 tant groups of vegetable fibres, and serves 
 for the production of tissues, paper, and 
 gun-cotton. 
 
 Flax. The flax used in spinning is the 
 fibre of the flax plant, Linum usitatis- 
 simum, a plant of the class Pentandrise, 
 order Pentagynise, in the system of Lin- 
 naeus, and the type of the order Linnacese 
 in the natural system of Botany. The 
 flax is gathered, tied in bunches, and dried 
 in the fields. After drying the plant is 
 combed with an iron or flax comb, to 
 separate the seeds, and is then bound in 
 thick bunches. The flax fibre used in 
 linen fabrication lies under the bark of 
 
 Bruckstelle. ljIJ)Wk\ \ the plant, and is surrounded by a gummy 
 
 mbstance, or pectose according to J. Kolb, 
 which must be removed by chemical or 
 mechanical means to fit the fibre for in- 
 dustrial purposes. This is done by " soft- 
 ening " or " rottening," by which, according to Kolb, pectin-fermentation is set up, and 
 
 Flax. 
 Druclcstelle = Place of pressure. 
 
 For further particulars on silk Dr. Bowman's work may be consulted ; and for an account of 
 the so called wild silks see Handbook of the Collection of the Wild Silks of India, by Thomas Wardle 
 (Her Majesty's Stationery Office.) [EDITOR.] 
 
SECT, vii.] VEGETABLE FIBRES. 809 
 
 the pectin converted into pectic acid. The flax is kept under water until the impurities 
 float on the surface, leaving the fibre intact ; this is the soaking method. Another 
 method, dew-softening, as it is termed, consists in spreading out the flax in layers 
 to the influence of the atmosphere, water being occasionally thrown over the flax. 
 Both these methods are unsound, as the flax is liable to become rotten, while the 
 impurities are not thoroughly removed. 
 
 Hot-water Cleansing. -After many experiments with different chemical substances, 
 an alkaline bath and dilute sulphuric acid have been found the best agents to effect the 
 separation. The flax is placed in large vessels of water heated by steam from 25 to 30 ; 
 after standing from sixty to ninety hours the operation is complete. This mode of treat- 
 ment, aided by an alkaline or acid solution, yields the best results, the value of the 
 process being (i) That the construction of the fibre is equally affected, rendering the 
 article better suited for manufacture. (2) That the fibre does not lose weight as in the 
 other methods, where 10 per cent, is sometimes lost. (3) That there is a considerable 
 saving in expense. 
 
 The retted flax, as it is technically termed, consists of cellulose and pectic acid. The 
 next process is termsd scutching, and includes the separating of the fibre from the 
 woody structure of the stem. The machine for this purpose consists of two parts ; the 
 upper of wood, in the form of two splints, working on hinges. Wooden knives 
 are placed under the splints, and are arranged to act upon the fibre by pressure upon 
 a handle. 
 
 Beating or Batting the Flax. Scutching consists of two operations bruising the 
 flax and beating away the woody parts from the fibre. For the latter operation the 
 Belgian batting-hammer is generally used. It is a deeply grooved wooden block, 
 furnished with a long curved handle. The sheaf of flax is laid on the ground, untied, 
 and spread out, and is beaten with the hammer by the workman. If the flax is not 
 sufficiently loosened by batting, it is submitted to the swinging-block, having a cut 
 at three-fourths of its height serving to hold about a handful of flax. This flax is then 
 beaten with the scutch-blade, a piece of hard, tough wood, generally walnut-wood. 
 Instead of the swinging-block a grinding-knife is sometimes used on an iron block. 
 The knife is formed of a thin blade, and a heavy wooden handle. A bunch of flax is 
 held in the left hand, at an angle for the easy use of knife with which the flax is 
 beaten. Notwithstanding these clarifying processes the bark still adheres to the flax, 
 which has to undergo a further operation, that of combing. 
 
 Combing the Flax. The combing or hackling of the flax removes all the material 
 detrimental to the ultimate spinning of the fibres, and also equalises their length, 
 rendering them smooth and parallel. The combs are made of zinc or steel, and are of 
 varying degrees of fineness, the process commencing with a coarse comb and finishing 
 with a fine one. 
 
 Tow, or Tangled Fibre. However carefully the operation of scutching may be per- 
 formed, there is always a certain amount of waste resulting from the entanglement of 
 the fibre, and this waste is termed scutching-tow or codilla. It is used in the manu- 
 facture of ropes, and for similar inferior purposes. The flax fibre, before it is fitted 
 for spinning, has to be boiled in an alkaline lye, to remove the dirt and grease. 
 
 100 kilos, of cleansed flax weigh after 
 
 Bruising . . . . . 45 to 48 kilos. 
 Scutching . . . . 15 25 
 Combing .... 10 ,, 
 
 Flax Spinning. The spinning of the combed flax into yarn is effected by hand and 
 by machinery. The combed flax is first placed in bands of equal thickness, and then 
 stretched. The hand spinning-wheel is universally known. The mechanical spinning 
 consists in (i) Placing the fibres in a parallel series of equal thickness and length 
 
8ro 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vii. 
 
 throughout. (2) These bands are stretched, the finer the fabric to be woven the 
 greater being the stretching required. (3) By further stretching and twisting cord is 
 spun. (4) The fine cord is still further stretched and twisted. Tow, or codilla, is spun 
 similarly to the flax, being previously combed and placed in bands of equal length. 
 Flax yarn is either used unbleached or is bleached before spinning. Linen thread is 
 obtained by twisting sevei'al cords together. 
 
 Weaving the Linen Threads. By weaving the cords parallel to each other, chain 
 cords are spun. Webbing, wrappers, and thick fabrics are made in this way. 
 
 Linen. Linen is produced by weaving the twisted cord. The selvage is made by 
 the return of the shuttle on each side of the fabric. For coloured fabrics coloured 
 threads are used instead of white, only more shuttles are required, one shuttle to each 
 colour. Linen damask, as well as drill, is woven in various patterns, the difference 
 being that the woof forms the pattern on drill, while chain-cord is used for that of 
 damask. Batiste is a fine linen cloth, slightly thinner than cambric. 
 
 Hemp. Hemp (Cannabis sativa) is ohiefly cultivated for the fibre of its inner bark. 
 This fibre, although rough, is very hard and firm, and better adapted for the manu- 
 
 Fig- 552- 
 
 Hemp. 
 
 Hemp, when spun. 
 
 553- 
 
 facture of sail-cloth, canvas, rigging, &c., than any other. 
 Its uses for inferior domestic purposes are manifold. 
 The working of the hemp stalk accords essentially with 
 that of flax, being steeped in water, dried and crushed in 
 a hemp mill. By the old method the husk is crushed 
 under a large stone cone moving in a circular course 
 around a vertical axis. The construction of the new 
 hemp mill is more advantageous. The hemp is purified 
 by winnowing and afterwards combing. It is difficult to 
 spin on account of its length, and is woven in two or 
 three parts. Of late various foreign fibres have been 
 used as substitutes, principally the following : 
 
 a. Stalk Fibre. 
 
 (i) Chinese Grass (Chinagras, Tschuma),ei fibre from 
 Urtica s. Boehmeria nivea and heterophylla, which is cul- 
 tivated in China and the East Indies, Mexico, the Valley 
 of the Mississippi, Cuba, the Wolga Plains in Russia, the 
 South of France, and in Algiers. The Chinese method of treating the fibre is 
 
 Chinese Grass, Tschuma. 
 
SECT. VII.] 
 
 VEGETABLE FIBRES. 
 
 811 
 
 remarkable. The fibre is not spun, but cut into appropriately small pieces, these 
 being placed end to end, and rolled by the hand until joined together. The fibre is 
 thus rolled quite smooth and does not require pressing. It forms a beautiful texture 
 of singular brightness, called grass linen, or China grass cloth. The raw material is 
 of a green or brown colour, but when bleached, can be dyed any colour. 
 
 (2) The Great Nettle (Fig. 554), Urticas. dio'ica. The interior fibrous pith supplies 
 the material for nettle cloth and muslin. 
 
 Fig- 554- 
 
 II 
 
 Nettle Fibre. 
 
 (3) Ramie Hemp, from Urtica s. Boehmeria utilis, is of the nettle species, and a 
 native of Borneo, Java, Sumatra, and other islands of the Indian Archipelago. Of late 
 various experiments as to its mode of manufacture have been tried in Germany. It is 
 from one to two metres in length, of a delicate golden white, and not so bright and stiff 
 as flax. 
 
 (4) Rhea Grass, Urtica s. Rhea tenacissima, is a native of the East Indies, of little 
 value for manufacture. 
 
 (5) Jute (paut hemp) is obtained from a lime tree, a native of the East Indies and 
 China, Corchorus caf>sularis, G. textilis, G. olitorius, C. siliquosus (Figs. 555, 556). The 
 fibre for spinning is brown, and in England is used for sackcloth and coarse packing 
 thread. It is not a material adapted for purposes of nautical application, as it has not 
 sufficient firmness to withstand water. 
 
 Queensland Hemp, the bast-fibre of various species of sida, belonging to the family 
 of the Malvaceae. 
 
 (6) Bombay Hemp, from Hibiscm cannabinus. The woody fibre of this plant is 
 roasted and separated by means of beating. In England it is used for cordage, 
 rigging, &c. 
 
 (7) Sun Hemp, Japan, or East Indian Hemp, from Crotolaria juncea, resembles 
 other hemp in the length and firmness of its fibre. 
 
 p. Leaf Fibre. 
 
 (8) New Zealand Flaxes (Phormium tenax), Fig. 557, are employed in their native 
 country for articles of domestic use. The leaf is straight, the fibre tough, and of a 
 
&12 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. VH. 
 
 shining white. The prepared material is similar to ordinary hemp in roughness and 
 stiffness. 
 
 Fig. 555- 
 
 Fig. 556. 
 
 Jute. 
 
 557- 
 
 (9) Aloe Hemp (Agave Americana, A. vivipara, A. 
 foetida, &c.) is a native of Peru, India, the Antilles, 
 and Mexico, where the leaf, which is generally a 
 yellow-white, is cultivated for its fibre, and used for 
 rope-making. 
 
 (10) Manilla Hemp (Feather Fibre) is a native of 
 India and many islands of the Malay Archipelago, and 
 comes from Musa textilis, M. troylodytarum, and M. 
 paradisiaca. It is commercially known as a yellow- 
 white or brown-yellow fibre, and is from 1*3 to 2*2 
 metres long. The inside bark is stripped off from the 
 bottom upwards, refined, and combed. The white kind 
 is silky and bright, and is used in the manufacture o.f 
 damask furniture and various fancy articles. 
 
 (n) Ananas Hemp comes from the West Indies, 
 Central and South America, where the common 
 ananas is cultivated, Ananassa sativa s. Bromelia 
 ananas, as welt as other species. It is rather inferior 
 to some fibres for spinning. 
 
 (12) Pikaba Hemp is from the leaf of the Attalia 
 funifera, a Brazilian, palm. It is used in rope-making. 
 
 (13) Cocoa-nut Fibre is a reddish-brown fibrous material, in which the cocoa-nut 
 shell (Cocos nucifera) is enveloped. It is very strong and elastic, and is used for 
 matting, ropes, hurdles, &c. 
 
 Cotton. Cotton surrounds the fruit of a shrubby plant of the species Gossypium, cul- 
 tivated in the tropics and the Southern States of America for manufacturing purposes. 
 
 Phormium Tenax. 
 
SECT. VII.] 
 
 VEGETABLE FIBRES. 
 
 The fruit consists of a cup-shaped calyx, enclosed in a three-cleft exterior calyx, bearing 
 
 a soft white down. Another species, Gossypium religiosum, bears a yellow down, used 
 
 by the Chinese in manufacture. The down is kept separate from the seed when 
 
 packed for travelling, to prevent its becoming oily 
 
 and unfit for use. While in a raw state, it is 
 
 subjected to an operation termed ginning in a 
 
 saw-gin, to separate the wool from the seed. 
 
 Whitney's saw-gin consists of from 1 8 to 20 circular 
 
 saw-blades, revolving on a horizontal axis about 
 
 100 'times a minute. The teeth of these saws 
 
 project through a grating, seize the wool and pull 
 
 it through, the bars of the grating being too 
 
 narrow to admit the seed. Twenty saw-blades will 
 
 clean 400 Ibs., and 80 saw-blades, worked by 
 
 2-horse power, 500 Ibs., raw cotton per day. Of 
 
 late the carding cylinder is sometimes used 
 
 instead of the saw-gin. In America oil is largely 
 
 extracted from the seed, 30 Ibs. yielding about 
 
 i Ib. of oil. The seed is also used for manure. 
 Species of Cotton. The quality of cotton is 
 
 decided by its smoothness, and distinguished by 
 
 the country from which it is imported. The various 
 
 kinds are : North American : Sea Island, or Long 
 
 Georgia, Orleans, Upland, Louisiana, Alabama, 
 
 Tennessee, Georgia, Virginia. South American : 
 
 Fernambuco, Bahia. Columbian and Peruvian. 
 
 Barthelemy. East Indian : Dhollerah, Surat, Manilla, Madras, Bengal. Levant : 
 
 Macedonian, Smyrna. Egpytian : Mako or Jumel. Australian : Queensland. Euro- 
 pean : Spanish and Sicilian. 
 
 /Substitutes for Cotton. Substitutes for cotton are found in the black poplar 
 (Populus ncgrra)andthe aspen (P. tremula) ; the fibres of the latter are not so elastic as 
 some of the substitutes discovered. The rush (Juncus effusus], the German tamarisk, 
 and the thistle (Ayrostis), the Salix pentandra, the Zostera marina,, and the flax tree, 
 supply material for manufacture. Some twenty years ago Chevalier Claussen 
 endeavoured to open the filaments of flax by chemical action by steeping the fibres in 
 a bath of t part sulphuric acid to 200 parts water, and then dipping it into a weak 
 solution of carbonate of soda. By this process the flax is changed into a downy mass 
 resembling cotton in lightness ; but the method was not successful, as the firmness of 
 the fibre was injured, and its value deteriorated in other ways. 
 
 Detecting Cotton in Linen Fabrics. There is a great difficulty in detecting cotton 
 in linen fabrics when the fibres are closely interwoven. The old method of testing the 
 presence of cotton in linen was by placing it under a powerful microscope, but chemical 
 analysis presents more reliable methods. The following tests, recommended by Kindt 
 and Lehnert, prove the existence of cotton in linen by absorption. The linen con- 
 taining cotton fibre is placed in a bath of sulphuric acid of 1-83 sp.gr. for from i to i| 
 minutes. The cotton fibre is immediately absorbed, the sulphuric acid acting upon it 
 more quickly than upon the linen ; the fabric upon being dried has a curled or 
 shrivelled appearance. Other fibres sheep's wool, silk, and flax are now treated 
 chemically, and their smoothness and glossiness, which are found to be the greatest 
 preservatives against decay, are attributable to chemical agency. The colour test of 
 Eisner is useful, but not always successful, on account of the transition of the delicate 
 colours being so instantaneous as to make it difficult to form a decision. As a colour 
 
 Cotton, spun. Cottoii, unspun. 
 
 West Indian : Domingo, Bahama, 
 
CHEMICAL TECHNOLOGY. [SECT, vn 
 
 test there may be taken half an ounce of the root Rubia tinctorum, i.e., madder, macerated 
 for twenty-four hours in 6 ounces of alcohol at 94 per cent. When filtered, the tincture 
 appears a clear brown-yellow. Pure linen fabrics immersed in it become a dull 
 orange red, and pure cotton yellow ; the flax fibre will assume a yellow red, and the 
 cotton a bright yellow, the fabric appearing not uniform in colour but streaky. When 
 the fabric becomes so unequally streaked as to make it difficult to discern whether it be 
 linen or cotton, the following test will prove decisive : Place the streaky fabric in a 
 solution of spirits of wine, and then in a weak solution of aniline red, by which it 
 becomes coloured, and finally let it remain from one to three minutes in a weak solution 
 of sal ammoniac; the colour of the cotton fibre will be dissipated and the linen will 
 become a beautiful rose red. From Eisner's first test for change of colour the method 
 of previously colouring the linen fabric was established. Cochineal was selected for 
 this purpose, and the linen placed in a weak solution, chloride of lime being used to 
 prevent the colour in the linen running, while the cotton contained in the fabric 
 changes colour immediately. Frankenstein's oil test for uncoloured fabrics can be 
 recommended for its simplicity and excellence. The fabric is dipped in olive or rape- 
 seed oil ; it quickly becomes soaked through, and the surplus oil is removed by blotting- 
 paper, the linen fibre becoming transparent, leaving the cotton opaque. When an 
 unbleached fabric is tested in this manner it appears shining at first, but becomes 
 dimmer in the parts where the cotton is present. A truer method of testing, however, 
 is given by the magnifying glass. Bottger gives a test with potash. The linen fabric 
 is immersed in a concentrated solution of potash ; in about two minutes it becomes a 
 deep yellow, the cotton fibre assuming a light yellow. 
 
 Stockhardt gives a spirit test. Linen fabrics are placed in layers with lighted 
 brandy ; the linen fibre extinguishes the flame, while the cotton acts as a wick, absorb- 
 ing the spirit. This experiment can be successfully used with coloured materials, 
 with the exception of those coloured with chrome yellow, lead chromate. The 
 singeing test requires the most delicate treatment. The fibre is placed in a glass 
 vessel over the flame of the spirit-lamp until it becomes a light yellow ; then by 
 microscopic examination the cotton fibres will be found curled up, while the flax fibres 
 are distended and clearly separated from each other. Hemp and flax act in the same 
 manner, but do not separate so much. Nitric acid can be so applied as to leave the 
 flax fibre unchanged in colour, while the hemp immediately becomes a pale yellow, and 
 the New Zealand flaxes, Phormium tenax, a blood red. The admixture of cotton in 
 linen fabrics is detected by the following test, the discovery of 0. Zimmermann : 
 Place the fabric in a mixture of 2 parts saltpetre and 3 parts sulphuric acid for from 
 eight to ten minutes, then wash, dry and treat with alcohol containing ether. The cotton 
 so treated is soluble as collodion, the linen fibre is not. 
 
 Separation of Animal and Vegetable Fibres by Means of Singeing. The mixture is 
 placed near a bright flame to singe until the hair is consumed, leaving a black ashy 
 mass in the same proportion as the fibre, if it be mixed with sheep's wool. 
 
 Animals and flaxen fibres are separated by boiling in potash, which loosens the 
 filaments of wool or silk, leaving the cotton and linen fibres unaltered. Pohl gives us 
 the following test : Place the fibres in a solution of picric acid for one minute ; then 
 carefully wash ; the wool or silk filaments will have turned yellow, the cotton or flax 
 fibre remaining white ; this can be applied to mixed fabrics. The most certain method 
 is examination under the microscope, where the linen fibre appears in a cylindrical forn? 
 and never flat ; it is not stiff or twisted, and is chiefly characterised by the narrow- 
 ness of its inner tube. Hemp is similar to flax fibre, being easily broken ; its ends 
 branch out stiffly, and its tube is open. The fibres in cotton fabrics are long, of a close 
 'thin texture, like a twisted band. Sheep's wool under the microscope appears thicker 
 
SECT, vii.] BLEACHING. 815 
 
 than the other filaments, having a perfectly circular stalk with tile-shaped scales. The 
 silken fibre, Fig. 559, is a slender column, smooth on the exterior and easily dis- 
 tinguishable from wool, Fig. 561 representing a mixed silken and woollen fabric, as it 
 appears under a low power. Wool and cotton, Fig. 560, are also easily distinguished 
 from one another.* 
 
 Fig. 560. 
 
 Fig- 559- ^ i **** 
 
 Adulteration of Cotton Fabrics. No other name can be given to the dressing 
 cottons with salts of magnesium, china clay, &c., to an extent sometimes exceeding 
 50 per cent. This practice is carried to such a length that the finished goods are 
 sometimes sold for a lower price than the same weight of raw cotton. f 
 
 BLEACHING. 
 
 The operation of bleaching aims at more or less perfectly whitening or decolourising 
 the yarns spun from flax, hemp, jute, cotton, or the textile fabrics woven from the 
 same. Vegetable fibre resists the action of most chemical agents in use in bleach- 
 ing, while the foreign or incrustating or colouring matters, occurring chiefly on the 
 surface of the fibre, are rendered soluble or completely destroyed. The bleaching of 
 the fabrics and fibres which, such as linen or cotton tissues, consist mainly of cellulose, 
 is based on this principle. The method of bleaching wool and silk differs from that of 
 the vegetable fibres, inasmuch as the chemicals used for the latter would exert upon 
 the former a solvent action, not only as regards the impurities, but the substance 
 itself. 
 
 Grass Bleach. The agent in natural or grass bleaching is apparently ozone, or 
 doubtless more accurately hydrogen peroxide. In this process the formation of ozone 
 is due to the decomposition of water in consequence of the action of light. 
 
 Chlorine Bleach. Schiitzenberger regards chloride of lime as an oxidising agent, 
 and not as a source of chlorine. Without the co-operation of an acid it is split up 
 into calcium chloride and oxygen (CaOCl 2 = CaCl 2 + 0), which latter destroys the 
 colouring matter. Witz remarks hereby that the slightest trace of carbonic acid 
 
 * For further information the reader is referred to The Structure of the Cotton Fibre in its 
 Relation to Technical Application, by Dr. F. H. Bowman, F.L.S., F.C.S., &c. Manchester: Palmer 
 & Howe. 
 
 t See Sizing and Mildew in Cotton Goods, by G. E. Davis, C. Dreyfus, and P. Holland ; Man- 
 chester : Palmer & Howe ; and The Sizing of Cotton Goods, by W. Thompson ; Manchester : 
 J. Heywood. It must not be forgotten that the sizing and dressing of cottons in England is not 
 carried to the same extent as the " loading " and " weighting " silks on the Continent a fraud the 
 more reprehensible as the genuine article is so much more expensive than cotton. [EDITOR.] 
 
8x6 CHEMICAL TECHNOLOGY. [SECT. vn. 
 
 makes the chloride of lime much more efficacious. Without the presence of carbonic 
 acid in the atmosphere, chloride of lime is inactive in certain bleaching processes. 
 Whilst the hypochlorous acid gives off oxygen there is hydrochloric acid formed, which 
 in turn reacts upon the chloride of lime, and so continuously increases its action, which 
 would end in complete combustion of the organic matter. A. Girard ascribes the 
 destructive effects of chloride of lime to the formation of hydrochloric acid, which 
 remains free in spite of the presence of CaC0 3 and CaOCl 2 , hydrating the cellulose 
 and converting it into brittle cellulose. Witz shows that ozone produces the same 
 modifications of cellulose as does chloride of lime ; in this case hydratising acids are 
 not present, and consequently Girard's suppositions cannot hold good. 
 
 Witz warns us against baths of chloride of lime which are too strong or too pro- 
 longed, and which, if applied unequally and under the influence of air and light, have 
 inevitably a destructive action. In practice a strength of 07 Tw. should not be 
 exceeded. Hunter shows that chloride of lime is cheaper than permanganic acid and 
 similar oxidising agents. 
 
 In order to strengthen the action of solutions of chloride of lime, G. Lunge recom- 
 mends the addition of acetic or of formic acid. The price of the acid need 
 scarcely be considered, as only a small quantity is required. There first result from 
 acetic acid and chloride of lime free hypochlorous acid and calcium acetate ; during 
 the action the former gives up oxygen, and is converted into hydrochloric acid, which, 
 in conjunction with the calcium acetate, is at once transformed into calcium chloride 
 and free acetic acid ; the latter acts anew upon chloride of lime : 
 
 (1) 2 CaOCl 2 + 2C 2 H 4 O 3 = Ca(C 2 H 3 2 ) 2 + CaCl 2 + 2 HOC1, 
 
 (2) 2HOC1 = 2HC1 + O 2 , 
 
 (3) Ca(C 2 H 3 2 ) 3 + 2HC1 - CaCl, + 2C 2 H 4 2 . 
 
 The hydrochloric acid produced according to equation (2) is never present in a free 
 state, as it at once reacts upon calcium acetate as in equation (3). This is very 
 important, as hydrochloric acid attacks the fibres on prolonged contact, whilst acetic 
 acid is perfectly harmless. As no insoluble calcium salts are present, the treatment 
 with acids after bleaching is dispensed with ; this not merely economises acid and the 
 trouble of the subsequent washing, but it obviates the danger especially in the case 
 of thick goods of any traces of acid being left adhering to the fibre. Such traces 
 become concentrated on drying, and attack the fibre, besides being injurious in 
 various dyeing operations. The acid can be applied in various ways e.g., by 
 adding a small quantity to the solution of chloride of lime at the outset, and at the 
 end of the ordinary treatment with chloride of lime ; by passing the goods (prior to 
 washing) through water containing a very small trace of acetic acid ; or by placing them 
 iu water very slightly acidulated with acetic acid, and gradually running in the solution 
 of chloride of lime with constant agitation. If the goods to be bleached retain a little 
 alkali from the previous bowking, or if the water is very hard, or if the solution of 
 chloride of lime contains appreciable traces of caustic lime, important quantities of 
 acetic acid would be required to neutralise the bases before hypochlorous acid can be 
 set free. In such cases acetic acid can be economised by using a portion of sulphuric 
 or hydrochloric acid in its place, taking care, however, that no free mineral acid is 
 present, but merely acetic acid. This is easily reached in practice by keeping the 
 reaction very faintly acid to litmus-paper. 
 
 According to Lunge the removal of the last traces of the bleaching agents from 
 fibrous goods may be effected by means of hydrogen peroxide. On bleaching with 
 chloride of lime the hydrogen peroxide gives off its active oxygen along with that of 
 the hypochlorous acid, whereby the latter (or its salts) is destroyed. Hydrogen 
 peroxide can also be used as " antichlore " in bleaching vegetable fibre or paper stuff in 
 
SECT, vn.] BLEACHING. 817 
 
 order to increase the durability of the bleached goods, and to remove the smell of 
 bleach without the disadvantages of other " antichlores." 
 
 Sulphurous acid bleaches by masking the colouring-matter, and in few cases only 
 by its destruction. The colouring matters of many blue and red flowers, fruits, &c., 
 form colourless combinations with sulphurous acid ; but the colour is merely concealed, 
 not destroyed ; dilute acids, nitrous vapours diluted with air, chlorine, bromine and 
 iodine, and the mere action of heat, destroy the bleached sulphurous compounds, and the 
 original colour re-appears. The colouring-matters of yellow flowers are not bleached 
 by sulphurous acid. The same is the case with the green of plants (chlorophyll). Many 
 dyed tissues, such as indigo blue and carmine, are at first not affected by sulphurous 
 acid, but bleaching ultimately takes place, the colouring matters being oxidised under 
 the influence of light. Bleaching with sulphurous acid, as it is industrially carried out, 
 is not a, fast, but merely a fugitive process, which disguises the colours to the eye. On 
 mere exposure to the air, the sulphurous acid gradually disappears from the bleached 
 goods, especially after previous friction, so that many bleached tissues resume their 
 original colour spontaneously. Lunge recommends the removal of the fixed sulphurous 
 acid by a weak solution of hydrogen peroxide. 
 
 For bleaching, the goods are suspended in the sulphuring chamber on rods in a moist 
 state as they come from the centrifugal machine after washing. They are covered 
 with a layer of thick cloth, which is removed from time to time. After filling the 
 sulphur chamber (stove) the necessary quantity of sulphur is placed in an iron pot in 
 one corner, set fire to, and the chamber is tightly closed. The sulphur burns as long 
 as there is sufficient oxygen present in the chamber and the sulphurous acid condenses 
 upon the moist fibre. According to Moyret sulphurous acid acts only at the moment 
 of condensation, and he compares it with the action of an acid in the nascent state, and 
 he describes the alleged inertness of sulphurous acid in solution to the absence of this 
 circumstance. According to Lauber gaseous sulphurous acid owes its stronger action 
 merely to the circumstance that in the gaseous condition it comes in contact with the 
 slightly moistened fibre in a very concentrated state, whilst the solution of sulphurous 
 acid finds its limit at the point of saturation.* 
 
 According to the desired purity of the whites the goods are left in the stove for 
 twelve, twenty-four, and even more hours. The cover of cloth serves to prevent any 
 drops of sulphuric acid formed on the roof of the stove from falling upon the goods and 
 destroying them at the point of contact. When the process is completed the air of 
 the stove is forced into the chimney of the works by means of a blast, and the goods 
 are freed from sulphur by taking them through dilute hydrochloric acid at a hand 
 heat. Any yellow spots which have been formed by a condensation of sulphur dis- 
 appear, and the white comes up. Sometimes the stoving is twice repeated if 
 a particularly good white (so-called double-stove white) is required. The goods may 
 also be treated with a solution of soda, in which case sodium bisulphite is formed on 
 the fibre ; this process is especially used for straw. Sodium bisulphite is used on the 
 large scale for bleaching loose wool ; the wool is steeped for some hours in the solution 
 of sodium bisulphite, and then taken through hydrochloric acid at a hand heat. 
 
 Cotton is bleached by steeping in boiling water, which removes all soluble matter. 
 It is then boiled in a solution of soda. After the dressing and grease have thus been 
 removed the cotton is treated with a weak caustic soda-lye, which dissolves away 
 certain resinous matters. The goods are then placed in a clear solution of chloride of 
 lime, which is heated by the admission of steam, and they are then rinsed by a passage 
 
 * Sodium bisulphite, known in commerce as leucogene, has some advantages over the fumes of 
 burning brimstone. Its action is more regular and it does not injure the health of the workmen. 
 Liquid sulphurous acid at about 14 Tw. bleaches silk and wool better than the fumes of burning 
 brimstone. [EDITOR.] 
 
 3 
 
8i3 CHEMICAL TECHNOLOGY. [SECT. vn. 
 
 through dilute sours (sulphuric and hydrochloric). The acid is finally removed by an 
 alkaline bath. 
 
 According to H. Koechlin the raw cotton cloth is saturated with alkali and then 
 steamed. The alkali can be used either as caustic, or carbonate, or as soap. The dura- 
 tion of the action of the steam varies according to the concentration of the solution and 
 the pressure of the steam from a few seconds to several hours. As in the ordinary 
 bleaching process, this treatment is preceded by an acid bath and a passage through 
 the solution of a hypochlorite. The cotton, in the state of yarn or cloth, is washed 
 and taken through a bath of dilute hydrochloric and sulphuric acid at roi33 sp. gr. 
 It is then allowed to lie wet for one hour and taken through the solution of hypo- 
 chlorite preferably sodium hypochlorite at roo66. The cotton is then allowed to lie 
 in heaps for an hour, washed, and passed through soda-lye at 1-0704 sp. gr. It is then 
 steamed for an hour, washed, again taken through a bath of sodium hypochlorite of 
 the above strength, left in heaps for an hour, washed, taken again through a bath of the 
 strength given, again washed and dried. 
 
 The bleaching process of J. Thompson is carried out as follows by the firm of Mather 
 and Platt, of Manchester. For removing the dressing the pieces are first taken, spread 
 out, through a solution of soda, for which purpose there is used the washing machine 
 commonly employed in bleach works. They are then laid in basket trucks, simply 
 folded backwards and forwards. These trucks are made of a sheet-iron texture, 
 covered with zinc ; they can convey a ton weight of pieces, and run upon rails laid on 
 the floor of the works. The trucks when full are at once run into the new Mather work- 
 ing-pan. This pan is a horizontal cylinder closed at its front by a door, which can be 
 lifted, within which the rails are continued and which has room for two trucks one behind 
 the other. The door hangs from a chain which is conveyed over pulleys to the back of 
 the cylinder and is there joined to a piston to be moved by steam or water-pressure. 
 On admitting the pressure-liquid into its cylinder the door is quickly raised. The 
 steam-tight closure of the door is effected not by means of screw-bolts, &c., but the frame 
 of the door is made wedge-shaped below and the front margin of the boiler is hollowed 
 accordingly, so that the door is tightly closed by its own weight. These arrangements 
 promote speed in loading and unloading. After two trucks full of pieces moistened with 
 the solution of soda have been introduced, steam is turned in at the pressure of 
 I atmo. To protect the pieces from the injurious action of dry heat, they are continually 
 moistened with a weak solution of soda, or with caustic lye at 2 per cent. This pro- 
 cess is effected by means of a pump which constantly sucks up the liquid from the 
 lowest part of the pan and then squirts it out over the trucks by means of a perforated 
 tube. Instead of the soda-solution hot water is then conveyed into the pan and the 
 goods are washed in the same manner. They are then run out of the cylinder, 
 which immediately receives a fresh charge in the same manner, so that 6 tons of cloth 
 can be prepared daily for bleaching. The trucks with the cloth thus freed from dres- 
 sing are run to the bleaching machine, into which the pieces are at once transferred, so 
 that there is no interruption in the process. 
 
 The continuous bleaching machine of the same firm is an essential requisite for the 
 proper working of the Thompson bleaching process, since by its means the repeated 
 saturation of the tissues with the bleach liquor, the subsequent treatment with gaseous 
 carbonic acid, and the repeated washing, are rendered possible in one passage, whether 
 the pieces are spread out at full width or folded into a cord, in which latter case 
 several such cords can be treated side by side. The pieces move at the rate of about 
 60 metres per minute. The cloth passes first into the washing beck, II (Fig. 562), 
 with hob or cold water, and after being nipped between two rollers it arrives at beck C, 
 containing the bleaching liquid (mostly a solution of chloride of lime at 0*4 per cent.). 
 After leaving the nipping-rollers of the beck, (7, the pieces pass into the carbonic acid 
 
SECT. VII.] 
 
 BLEACHING. 
 
 819 
 
 chamber, K. This is a simple sheet-iron chest with guide-rollers for the pieces, and pro- 
 vided at the slits left for the entrance and exit of the pieces with slips of caoutchouc, 
 which apply themselves to the cloth and prevent the escape of the gas. The carbonic acid 
 is introduced by a pipe at the bottom of the chest, 
 and a simple arrangement indicates the level of the 
 <*as in the chamber, K. At one of the sides there 
 is a gas-pipe connected above and below with the 
 interior of the chamber. In the gas-pipe a thin 
 parti-coloured glass bulb, filled with air, indicates 
 the level of the carbonic acid. The carbonic acid, 
 being of a higher specific gravity, keeps the glass 
 bulb suspended at a height corresponding with its 
 own level in the chamber. After the treatment of 
 the pieces with carbonic acid there follows a wash- 
 ing with water and a o.i per cent, solution of 
 soda in the several vats W v JF 2 and W 3 , then a 
 passage in a hot solution in S, and repeated washing. 
 The beating of the pieces in the washing becks is 
 effected by means of the rollers to ; the washing 
 water is conveyed upon the cloth between the nip- 
 ping-rollers through the spirting tube s. The 
 goods, conveyed for a little into the open air, 
 arrive for a renewed similar treatment, are washed 
 in the vat JF, with weak hydrochloric acid, then 
 with water, then with soda-solution and again with 
 water, and are finally conveyed to an ordinary 
 washing machine for the final washing. 
 
 The advantages of the Mather-Thompson pro- 
 -cess (with the employment of the plant just de- 
 scribed) lie chiefly in the economy of time and 
 washing water. As two pieces can be taken 
 through the apparatus side by side, from 4500 to 
 5000 kilos., or 36,000 to 40,000 metres, of goods 
 can be bleached in a day of ten working hours. 
 But if we also include the time needed for steam- 
 ing, it appears that from 2000 to 5000 kilos, 
 (according to the size of the plant) can be com- 
 pletely bleached in eighteen to twenty hours. 
 
 The process above described is used for cloth 
 which is to be sold white. But if it is desired to 
 produce good whites for printing the pieces are 
 first taken, not through soda-lye, but through hot 
 sours. The steaming is effected in the same manner, 
 only to 2000 kilos, of cotton there are added 10 kilos, 
 of resin, previously saponified. The chlorinising is 
 effected in the manner above described. 
 
 Latterly a bath of weak hydrochloric acid has 
 been substituted for the carbonic acid treatment. 
 For bleaching on the large scale this process seems 
 likely to supersede all others. 
 
 Bleaching with chlorine produced electrolytically has been repeatedly attempted 
 but hitherto without noteworthy results. 
 
820 CHEMICAL TECHNOLOGY. [SECT. vii. 
 
 In bleaching linens, according to Kolb it is necessary to remove two substances, 
 pectic acid and a grey substance formed during the rotting of the flax. This is effected 
 either by the grass bleach or by treatment with chloride of lime. The grey matter is 
 oxidised and the pectic acid is removed in a soluble form. 
 
 According to Cross, jute may be easily bleached by treatment with the permanga- 
 nates and subsequent washing with dilute acids or by means of hydrogen peroxide, but 
 these two processes are too expensive. 
 
 Cross washes the cloth with a solution of soluble glass, borax, or soda, at 70 to 
 80, and then takes it through a solution of sodium hypochlorite, containing 07 
 to i per cent, effective chlorine, corresponding to 2 per cent, chloride of lime. A 
 slight excess of soda completely prevents the formation of chlorinised products from 
 the fibre. After a thorough rinsing the goods are passed into cold, dilute hydro- 
 chloric acid, containing a small quantity of sulphurous acid in order to remove salts 
 of iron and basic compounds which might subsequently, in contact with oxidising 
 agents, discolour the fibre. If thus treated the jute has a pale cream colour and a 
 soft, shining appearance. If it is to be dyed it may, after a thorough rinsing, be at 
 once transferred to the dye beck. If intended for printing the pieces are first placed 
 in a bath of sodium bisulphite, containing from i to 2 per cent, of sulphurous acid. 
 Here they remain two or three hours and are then dried on steam cylinders. 
 Sulphurous acid escapes and the goods when dry are uniformly saturated with sodium 
 sulphite, which subsequently prevents the oxidising and destructive action of steaming 
 upon the fibre, without interfering with the development of the printed colours. The 
 whiteness of the goods is farther improved by the treatment with sodium bisulphite. 
 
 If an attempt be made to bleach jute with chloride of lime in the same manner 
 as cotton or linen, a chlorinised compound is formed which is easily recognised by 
 the magenta-red colour which it assumes if moistened with sodium sulphite. If 
 such a tissue were afterwards steamed hydrochloric acid would be set free by the 
 decomposition of the chlorine compounds, a dark brown colour would appear and the 
 tissue would crumble away. Sometimes these changes appear only after the cloth has 
 come into use, which increases the common prejudice against jute. This fibre 
 is further oxidised by hypochlorites to form derivatives which produce insoluble lime 
 compounds. These are deposited on the fibre, so that the common bleaching process 
 converts jute into a rough, brittle, ill-smelling product of low quality. 
 
 The first step in bleaching silks is the ungumming. Silk goods which are to- 
 remain white are stoved. To mask the yellow tint which remains it receives a slight 
 red tint by means of a solution of annatto in soap-lye, or a blue reflection with aniline 
 blue. Latterly silks are bleached with hydrogen peroxide. 
 
 Wool bleaching begins with scouring effected by treatment with stale urine (lant) 
 or with a soap-bath. The bleaching itself is performed with sulphurous acid in the 
 stove, more rarely with sodium bisulphite (leucogene). 
 
 Wool intended to be bleached with hydrogen peroxide must be washed clean. If 
 the commercial peroxide is diluted with 10 parts of water the wool should be treated. 
 in the bleaching-bath for from thirty to forty minutes. The wool must have sufficient 
 room in the vat to be turned readily, as this expedites the bleaching. If the hydrogen- 
 peroxide is diluted with 1 5 parts of water the wool must be allowed to steep for an hour 
 after it has been taken out of the bleach-bath ; the action continues as long as the. 
 wool is moist. Hence it should not be dried too rapidly, and if possible it should be 
 dried in the open air with exposure to the sun. If a very dilute peroxide has been 
 used a very small quantity of extract of indigo which is necessary for the production 
 of a pure white may be added at once to the bath, and if a more concentrated peroxide 
 bleach is used, the blue tone must be given in a special bath. With strong yellow 
 wools it is well to add to the bath a few drops of dissolved methyl violet. 
 
SECT, vii.] DYEING AND TISSUE-PRINTING. 821 
 
 DYEING AND TISSUE-PRINTING. 
 
 Textile fibres are capable of taking up colouring-matters and certain constituents of 
 mordants from solutions and of retaining them. The combination, however, is often 
 so unstable that it is easily destroyed by repeated treatment with solvents, especially 
 with the aid of heat. Thus, a fibre dyed with indigo sulphate, or with Prussian blue 
 dissolved in oxalic acid, can be decolorised by continual washing. The fibre is, therefore, 
 truly dyed only when the dissolved colouring-matter forms with the fibre, and mostly 
 with the co-operation of a third substance, a mordant, an insoluble compound which 
 cannot be removed by the application of a solvent. According to Knecht's recent 
 investigations, wool forms with colouring-matters actual chemical compounds. The 
 colour thus produced is called fast when it resists the weather, light, soap-lye, dilute 
 alkalies, and very dilute acids. A colour which is destroyed under such circumstances 
 is called fugitive.* 
 
 The combination of the fibre with the colouring matter necessary for dyeing may 
 be effected (i) by removing the solvent. Thus, copper oxide dissolved in ammonia can 
 be fixed upon the fibre by the mere evaporation of the ammonia. The precipitation of 
 carthamine from an alkaline solution by means of an acid and the precipitation of many 
 tar-colours soluble in spirit by the addition of water, likewise belong here. An in- 
 soluble combination can also be produced (2) by oxidation, the colouring-matter, 
 previously soluble, being rendered insoluble by taking up oxygen. Here belong besides 
 ferrous and manganous sulphate which form insoluble hydrates on oxidation, the 
 tanniferous substances which at the same time contain a colouring-matter, such as 
 quercitron bark, sumach, fustic, fustet, &c. If we saturate cloth with the watery or 
 alkaline extract of these substances and expose it to the air, the colouring-matter is 
 turned brown and ceases to be soluble in water, possibly in consequence of the form- 
 ation of substances resembling phlobaphene. A similar change is effected more 
 quickly if tissues saturated in this manner are treated with oxidising agents, such as 
 potassium chlorate, chromic acid (alkaline bichromates), or vanadium compounds. An 
 instance of this kind is black-dyeing by means of logwood and potassium chromate, 
 where the haematoxyline of the wood is oxidised to haemateine, and the chromic acid 
 is reduced to a chromium sesquioxide. Similar is blue-dyeing with indigo in the vat 
 and the production of aniline black. Often (3) the insoluble compound is produced by 
 double decomposition e.g., blue by a soluble ferrocyanide and ferric oxide, yellow by 
 potassium chromate and a soluble salt of lead. This method of fixation is applicable 
 only with mineral colours. The most important method of fixing colours is (4) by 
 means of mordants. 
 
 Bancroft divided the colouring-matters into substantive and adjective ; the former 
 are those which pass into an insoluble state upon the fibre without the intervention of 
 a mordant, as all the mineral colouring-matters, indigo, turmeric, annatto, safflower, 
 and most of the coal-tar colours. By adjective colours he means those which require 
 some mediating agent in order to become insoluble upon the fibre. These mediating 
 substances are the mordants in question. But such mordants have not merely the 
 function of effecting the combination of the colouring-matter with the fibre. They 
 serve in certain cases for effecting such a change in tissues already saturated with 
 earthy or metallic salts that the parts upon which they have been placed appear 
 colourless when lifted out of the flot. Such mordants are called discharges. They 
 include the phosphoric, tartaric, oxalic, and arsenious acids. Here also belong the 
 resists used in tissue printing. Mordants are often used to modify the tone of colours 
 which have already been produced, rendering them brighter and purer, an effect which 
 is known as raising (Fr. aviviren ; Ger. schoenen). 
 
 * Compare Leo Vignon, Chem. News, vol. Ixiii. pp. 153, 177 & 285. [EDITOB.] 
 
822 CHEMICAL TECHNOLOGY. [SECT. vn. 
 
 Among the most important mordants are the salts corresponding to the sesquioxides- 
 of the general formula, R 2 3 , especially the salts of aluminium, iron, and chrome. 
 Here it is important to present solutions of the salts to the fibre in a form such that. 
 they can easily and completely pervade it with the co-operation of the fibre itself 
 and to deposit upon the fibre either the oxides or very basic salts. The insoluble com- 
 pounds of aluminium, iron, chrome, &c., deposited in, upon, or between the several 
 fibres and tufts of fibre form the mordant in the stricter sense of the word. They 
 combine with the colouring matters either chemically, or in the opinion of some,. 
 mechanically only, and thus effect the colouration of the fibre, which would otherwise 
 be impracticable. The compounds of antimony are also important. 
 
 The chief organic mordants are turkey-red oil (alizarine oil), tannin (especially for 
 fixing the madder colours, cochineal, and the aniline dyes upon cotton and linen), 
 albumen, gluten, caseine, glue, glycerine (sometimes a solution of arsenious acid in 
 glycerine), and fatty oils. The cloth to be dyed is taken through these mordants 
 which are again fixed according to th.eir nature, either by airing, by the dunging 
 process, by the bran bath, or by soaping, and the tissues are then introduced into the 
 solution of colouring-matter. 
 
 Alumina mordants were used by the ancients, and are still employed on all kinds of 
 fibres. Aluminium sulphate, Al 2 (S0 4 ) 3 .i8H s O, is decomposed, according to the re- 
 searches of Liechti and Suida, by soda or sodium bicarbonate : 
 
 A1 2 (S0 4 ) 3 + Na 2 C0 3 + H 2 = A1 2 (S0 4 ) 2 (OH) J + Na,SO 4 + C0 2 , 
 A1 2 (S0 4 ) 3 + 6NaHC0 3 = A1 4 (S0 4 ) 3 (OH) 6 + 3 Na 2 S0 4 + 3 CO r 
 A1 2 (S0 4 ) 3 + 4 NaHC0 3 = A1 2 S0 4 (OH) 4 + 2 Na 2 SO 4 
 
 The more basic the compound the more alumina is deposited upon the fibre. 
 Similar is the behaviour of aluminium acetate, whilst aluminium chloride and aluminium 
 sulphocyanide behave less favourably. Thus, in order e.g., to mordant cotton it is- 
 saturated with a solution of 2 kilos, aluminium sulphate and 0-32 kilo, sodium car- 
 bonate in 10 litres of water, diluted if requisite to 1-05 sp. gr., the excess is removed 
 from the cotton by pressure, dried, passed for five or ten minutes through liquid 
 ammonia (0-5 per cent.), washed and dyed. Instead of ammonia there may be used 
 solutions of sodium arseiiiate or phosphate, soaps, or turkey-red oil. 
 
 Aluminium acetates and sulphacetates are especially used in calico-printing. The- 
 solutions are thickened with flour, starch, or dextrine, printed upon cotton cloth and 
 dried. Too high a temperature during dyeing must be carefully avoided, especially 
 with mordants which are very readily decomposed (basic salts), as the results will 
 otherwise be uneven and poor. The object is reached by the use of hot plates, hot 
 air, &c., in place of rollers heated by steam. If too strong a heat is employed the- 
 mordant fixed upon the fibre is deprived of its water of hydration, or undergoes some- 
 physical change by which it is rendered incapable of taking up colouring-matter. 
 When this occurs the printed mordant is said to have been burnt. 
 
 Upon printing and dyeing follows ageing, which consists in exposing the printed 
 goods in a more or less open state to an atmosphere at a suitable temperature and 
 degree of moisture. This treatment is rendered continuous by means of the ageing 
 apparatus, a large chamber heated to from 32 to 38, whilst at the same time steam is- 
 admitted until the moistened bulb of the thermometer stands at from 4 to 6 lower. 
 The printed pieces are slowly passed over and under a set of rollers fixed at the top andi 
 bottom of the chamber, so that they remain exposed to the moist, warm atmosphere for 
 from twenty to thirty minutes. During this process the starch, or other thickener, is- 
 more or less softened by the moisture and the mordant penetrates more completely into> 
 the fibre. Quantities of acetic acid are expelled and an insoluble basic salt is fixed 
 upon the cotton. Immediately after leaving the chamber the pieces are rolled up 
 
SECT, vii.] DYEING AND TISSUE- PRINTING. 823 
 
 loosely and left lying to complete the ageing, for twenty-four to forty-eight hours, in a 
 room in which the dry-bulb thermometer indicates 32, and the wet-bulb 28. 
 
 The next treatment is the so-called " dunging " (Fr. bousage, Ger. Jcuhkothen), in 
 which the pieces, spread out, are drawn for two minutes through hot solutions of one 
 or more of the following substances : cow-dung, sodium arseniate, phosphate or silicate, 
 calcium carbonate, &c. 
 
 The purpose of dunging is three-fold. Firstly, to retain that part of the mordant 
 which was not affected during ageing more completely upon the fibre ; secondly, to 
 protect the unprinted and consequently unmordanted parts of the tissue from the 
 mordants, so that they may not be stained by mordant rubbed off from the printed 
 parts; and, lastly, to remove the thickeners. The last purpose is effected more 
 completely if the dunging is repeated, the pieces being folded up in the form of cords 
 and passed between rollers. The most effective process for removing the thickenings, 
 is to place the pieces for one to two hours in a bran-bath, the diastase of which 
 quickly converts the insoluble starch into soluble glucose. After thorough washing 
 the printed and mordanted cloth is ready for dyeing. 
 
 Aluminium acetates (red liquor) are very generally used in many steam colours in 
 calico printing e.g., in the so-called alizarine steam reds. In the colour or thickened 
 mixture for printing the aluminium acetate is merely mechanically mixed with the 
 alizarine or other colouring-matter ; when the printed cloth is exposed to steam decom- 
 position of the mordant takes place, its combination with the colouring-matter and 
 the fixation of the coloured compound upon the fibre also occurring simultaneously. 
 
 Experiment shows that pure aluminium acetate does not give such full, rich colours 
 as do double compounds, especially A1 2 S0 4 (C 2 H 3 O 2 ) 3 OH. Aluminium acetates are 
 also used in turkey-red dyeing. For wool dyeing aluminium acetate is unsuitable. 
 Wolf recommends solution of ammonium carbonate for fixing aluminium mordants 
 upon cotton. The use of this agent has the advantage that pure aluminium hydrate, 
 only a small part of which is combined with carbonic acid, is deposited upon the fibre, 
 whilst if we use the ordinary dung-substitutes (substances other than cow-dung used in 
 the dunging process) we obtain basic phosphates, arseniates, &c., the acids of which 
 are much less readily expelled by alizarine or other dye-wares of an acid character ; 
 that is, they dye up more slowly. 
 
 According to experiments the ammonium carbonate exerts a favourable action 
 especially in the case of mordants containing sulphocyanides, and it is altogether 
 preferable to the use of silicates and ammonia, and equal to sodium phosphate and 
 arseniate. In comparison with the former it has the advantage of producing brighter 
 shades. Ammonium carbonate, other points being equal, is preferable to the arseniate 
 on account of the poisonous character of the latter. 
 
 Iron Mordants. The use of ferrous sulphate (copperas) as a mordant, though still 
 considerable, has been reduced by the introduction of the chrome compounds ; the 
 ferrous acetate (black liquor, pyrolignite of iron) is more important, as it serves for 
 blacks, purples, and chocolates ; it should be as free as possible from ferric salts. 
 
 Iron pyrolignite is especially used for dyeing silks black and for the fraudulent 
 process of " loading " or " weighting." The silk is steeped at 4O-5o in a solution 
 of tannin, especially extract of chestnut, then treated with iron pyrolignite of 1*06 
 to 1*07 and exposed to the air. This treatment is repeated from twice to fifteen times, 
 and the weight of the silk is increased from 30 to 400 per cent.* 
 
 * To counteract the rusty brown tone apt to be thus produced, the silks, after an iron bath 
 (rouille) are taken through a solution of potassium ferrocyanide, which produces a deposit of 
 Prussian blue on the fibre. It must be remembered that by the weighting-process silks are not 
 merely rendered liable to a slow decay (eremacausis), but they become capable of spontaneous 
 (so-called) combustion. 
 
824 CHEMICAL TECHNOLOGY. [SECT. vn. 
 
 Ferric sulphate, Fe 2 (S0 4 ) 3 , erroneously called nitrate of iron, as it is obtained by 
 oxidising copperas with nitric acid, is largely used in silk dyeing, especially in the state 
 of the basic compound : 1 2FeS0 4 + 3H 2 SO 4 + 4HN0 3 = 3Fe 4 S0 4 ) 5 (OH 2 ) + 2H 2 O + 4^0. 
 
 In mordanting raw silk it is, according to Hummel, first treated in a solution of 
 sodium carbonate at 40 to 50, and then worked for half an hour to one hour in a cold 
 solution of the mordant at 14 Tw. The silk is then taken out, well washed, and left 
 to steep for thirty minutes in a solution of sodium carbonate at from 40 to 50. It is 
 well washed. These different treatments are repeated three to four times if fraud is 
 intended. 
 
 In mordanting boiled silks they are soaked for half to one hour in a cold solution 
 of basic ferric sulphate at 48 Tw., the excess of liquid is removed by pressing, and 
 the silk is well washed, first in cold and then in lukewarm water. This treatment is 
 repeated seven or eight times, and the silk is then put into an old soap-beck at 100, 
 or in a bath of panama-bark, to which have been added 2 per cent, of soda-crystals, and 
 oleicacid soap equal to about 12 per cent, of the weight of the silk. It is again washed 
 in water when the mordanting process is completed. Both the iron- and the soap- 
 beck remain continuously in use, care being taken to keep up the proper concentration 
 in the former by the addition of fresh mordant, and to boil up a fresh quantity of soap 
 in the latter before mordanting so that the iron-soap which has been formed during 
 former operations may rise to the surface and be skimmed off. 
 
 In raw silks where a relatively weak solution of ferric sulphate is used, the gummy 
 matter of the silk occasions decomposition and precipitates a quantity of an insoluble 
 basic salt during dipping. The washing in water and the rinsing in solution of 
 sodium carbonate complete the decomposition and remove the acid salts which have 
 been liberated. In silk which has been boiled off the liquid is simply absorbed by the 
 fibre whilst being dipped into the concentrated solution of the mordant. The use of 
 water containing calcium bicarbonate is advantageous for washing, as it promotes tho 
 decomposition of the mordants which have been absorbed. Boiling in soap lye is 
 necessary to complete the decomposition of the mordants, and the temperature of 100 
 then applied modifies the precipitated ferric sulphate so that it is less easily dissolved 
 in the following baths. 
 
 Silk is destroyed by oxidation if it is allowed to lie in the air after saturation with 
 ferric oxide. 
 
 Ferric nitrosulphates, so-called nitrates of iron, e.g. 
 
 6FeS0 4 + 8HN0 3 = 3^e 2 (S0 4 ) 2 (NO g ) 2 + 2 NO + 4 H 2 
 i 2 FeS0 4 + ioHN0 3 = 3Fe 4 (SO 4 ) 4 (N0 3 ) 2 (OH) 2 + 4 NO + 2H 2 O, 
 
 are used chiefly for blacks on cotton. Pure ferric nitrate, ferric acetate, and iron-alum 
 are little used. 
 
 Nickel mordants, according to Leichti, may be recommended for producing fast 
 colours in light shades. For dyeing the nickel-ammonium chloride, and for printing the 
 nickel nitro-acetate, are to be recommended. 
 
 Chrome mordants are of comparatively recent origin. According to Liechti, the 
 quantity of the chromium oxide deposited upon the fibre in mordanting, drying, and 
 ageing increases with the neutralisation, as with the aluminium mordants ; in mor- 
 dants of the same acid, of the same degree of neutralisation but different production, 
 the presence of foreign salts has an unfavourable influence. Alkaline sulphates espe- 
 cially, under circumstances otherwise the same, decrease the quantity of the chromium 
 oxide retained by the fibre, and must be considered as agents which retard dissocia- 
 tion. The fixation of the acetates and mixed acetates during drying, &c., is, with the 
 exception of those mordants which incline to spontaneous decomposition, to be referred 
 alone to the decomposing influence of the fibre, as in the absence of the fibre insoluble 
 basic salts are not obtained by the evaporation of acetic acid. The strongly basic 
 
SECT, vii.] DYEING AND TISSUE-PRINTING. 825 
 
 sulphates, Cr 2 (S0 4 ) 2 (OH) 2 , Cr(SO) 4 (OH) 6 , Cr 2 S0 4 (OH) 4 , &c., yield the largest quantity 
 of chromium oxide to the fibre, but never in so large a proportion as in the case of 
 certain aluminium products. Kopp recommends chromium fluoride. 
 
 Chromium chlorate is recommended by Lauber, and H. Koechlin proposes a mix- 
 ture of 1 6 parts solution of chromium acetate at 24 T\v., 48 parts water, 32 parts soda- 
 lye at 66 Tw., and i part glycerine. After mordanting, the goods are allowed to dry 
 for some hours and are then washed. The more caustic the solution of chrome the better 
 it acts ; if the proportion of soda-lye is insufficient, little or no chromic oxide is depos- 
 ited on the fibre. On the other hand, if the causticity is excessive the fibre contracts 
 strongly. According to Schmidt, this phenomenon always takes place, and in modera- 
 tion it is not unwelcome, since it strengthens the fibre by mercerisation. Alkaline 
 chrome mordants must be used with care, as they may produce sores. If cotton yarns 
 are mordanted by hand, caoutchouc gloves should be used. Instead of fixing chromium 
 oxide by letting the cloth lie for some time rolled up, the same end is reached in a very 
 short time by steaming. Knecht shows that the quantity of chrome deposited upon 
 wool varies with the concentration of the solution. If we take the quantity of chrome 
 precipitated upon the fibre as a measure for the efficiency of the mordant, chromic 
 acid is by far the best chrome mordant for wool. Next in value follows potassium 
 dichromate along with sulphuric acid, then the dichromate alone, and, lastly, neutral 
 potassium chrom^te. 
 
 Tin Mordants.* Stannous chloride, SnCl 2 2H 2 0, called salts of tin or tin crystals, 
 is still extensively used in printing, both as a solid and in solution. Generally the 
 stannous salts are more serviceable for woollens and the stannic salts for cotton goods. 
 Sometimes stannous chloride is added to the dye-bath towards the end of the dyeing 
 process, in order to heighten the shade. Stannic chloride, and less frequently " pink 
 salt," SnCl 4 (NH 4 Cl) 2 , as well as sodium stannate, have a number of applications. 
 
 Manganese Mordants (MnCl 2 and KMn0 4 ) and lead mordants are little used, the 
 affinity of lead for the fibre being feeble. Copper mordants, especially the nitrates, 
 Cu(N0 3 ) 2 , are sometimes used on account of their oxidising action e.g., in catechu 
 colours. 
 
 Antimony Mordants were first recommended by Brooks, in order to combine tannin 
 at once with colouring matter and with a metallic oxide, which he effected with tartar 
 emetic, K.SbO.C 4 H 4 6 . The action of all antimonial mordants depends on the fact 
 that antimony oxide deposits on the fibre as an antimonial lake in conjunction with 
 tannin, thus fixing the colour upon the fibre. 
 
 On account of the high price of tartar emetic, potassium-antimony oxalate has 
 latterly come into use. Koehler recommends antimony oxide in an alkaline solution of 
 glycerine as a mordant for cotton dyeing. Antimonious chloride and antimony lac- 
 tate have been recommended. Of more importance is the antimony sodium fluoride, 
 SbNaF 4 , and especially ammonium antimony fluoride sulphate, SbF 3 (NH 4 ) 2 S0 4 . 
 
 Tannin Mordants. For colours of a basic character, such as magenta, malachite 
 green, &c., tannin plays the part of a mordant, just as does alumina for alizarine, as it 
 combines with the colourless base contained in these colouring-matters and produces an 
 insoluble lake. During the precipitation of a basic colouring-matter from its solution 
 by means of tannin, the acid previously combined with the colour base is liberated. 
 J. Koechlin has remarked that the addition to the mixture of an alkali like sodium 
 carbonate makes the precipitation easier and more complete. For the production of a 
 tannin lake it is, according to Hummel, not necessary that the tannic acid should be 
 
 * The importance of the tin mordants has greatly declined since the introduction of the coal- 
 tar colours. So long as scarlets, crimsons, and other bright colours had to be obtained from 
 cochineal, lac and the woods, compounds of tin were used in a multitude of modifications, and 
 much skill and nicety were needed in their preparation. [EDITOR.] 
 
826 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vii. 
 
 in a free state. Insoluble metallic tannates have as great, if not a greater, affinity for 
 basic colouring-matter. The presence of the metallic oxido facilitates the decomposi- 
 tion, because it neutralises a part of the liberated acid of the colouring-matter, and 
 there is probably formed an insoluble bibasic compound (antimony and colour-base 
 tannate). But the use of insoluble metallic salts prevents the lake formed upon the 
 fibre from re-dissolving, either on account of an excess of tannin or of colouring 
 matter. An excess of tannin yields soluble compounds with basic colouring-matters, 
 so that the exact amount of tannin needful must first be deposited upon the fibre and 
 then the colouring-matter. 
 
 Tannin forms insoluble compounds with alumina and the iron, tin, and antimony 
 oxides. These bases act as mordants for colouring-matters of an acid character, 
 whether they occur as hydrates or in combination with tannic acid or other acids, 
 such as the phosphoric, arsenic acids, &c. They have still the power to attract such 
 colouring-matters, and to form with them coloured lakes. For this reason tannin is 
 often used as a precipitant or fixing agent for aluminous, tin, or iron mordants. 
 
 The tannin compounds obtained with the iron mordants have a bluish black colour, 
 of sufficient intensity to serve as a grey or even as a black dye. In this respect tannin 
 may be regarded as a coloming-matter in the same manner as alizarine. In many 
 cases the blue-black iron tannate serves merely to darken certain colours, which is 
 effected by means of preparations specially applied. In such cases the iron tannate 
 acts at once as a mordant and a ground colour. 
 
 Cotton is worked, or steeped in a solution of tannin, and the excess of liquid is 
 removed by draining or nipping, sometimes followed by drying. In padding, the 
 cotton is saturated with the solution for a few seconds, and is then wrung out and 
 dried. In this case the solution employed must contain at least ten times as much 
 tannin as the former process, if it is to be equally effective. ' 
 
 If textile fabrics soaked in oil especially castor-oil or olive-oil are exposed to the 
 air, the oil is partially decomposed, and the free fatty acid forms insoluble soaps with 
 the aluminous mordants. Especially important is the turkey-red oil obtained by 
 treating these oils with sulphuric acid, on the composition of which there is still a 
 variety of opinions. Its chief constituent is probably (according to Benedikt) sul- 
 phoricinoleic acid, C^Hj^.OSOjH. It is used in turkey-red dyeing, and in fixing 
 aniline colours upon the fibre. 
 
 The rancid smell of tissues mordanted with oil is unpleasant. 
 
 Albumen and casein (dissolved in ammonia or borax) and gelatine are used in tissue 
 printing. 
 
 Apparatus. Of the recent apparatus used in dye-works the following may be 
 mentioned : 
 
 Colour -pans for Laboratories are heated by steam, according to Dawson's design. 
 In a strong cast-iron tray, M (Figs. 563 and 564), fixed in a frame so as to admit of 
 
 Fig. 
 
 Fig. 564. 
 
 turning, the cast-iron pans, D, are fixed steam-tight by means of screws. The pans, Z>, 
 receive water used for a water-bath, or preferably in its place glycerine, into which the 
 
SECT. VII.] 
 
 DYEING AND TISSUE-PRINTING. 
 
 827 
 
 Fig. 565. 
 
 copper dye-pan, E, is fitted and secured by the brass ring, A', and the caoutchouc rings, r. 
 The lower ring prevents the escape of annoying vapour? from the liquid bath. Into the 
 tray, M, steam of about 4 centimetres is admitted at one side through the revolving 
 plug, whilst the condensed water escapes from the lowest point of the tray by a 
 vertical channel. Handles, H, allow 
 the entire series of pans to be emptied 
 by turning the tray, M. To prevent 
 felting, loose wool and cotton are 
 exposed to the rotating liquid in a 
 compressed state. 
 
 For bleaching and dyeing cops 
 0. Fisher recommends a centrifugal 
 
 O 
 
 machine. Into the internal sieve, A 
 (Figs. 565 and 566), there extend 
 the two tubes, Z>, fed in common by 
 one conductor, and both having a 
 slit, through which the liquid issues 
 uniformly, in its entire height. In 
 order to cleanse the slits there are 
 small slides, m, fixed to the rods, E, 
 and dirt may thereby be expelled 
 from the machine even while it is 
 at work. The tubes, I), are also 
 closed below with nuts provided with 
 holes, so that dirt cannot accumulate 
 or can be easily removed by un- 
 screwing the nuts. 
 
 For the uniform saturation of 
 the yarns with dye liquor, mordants, 
 or dressing, &c., there are used, 
 especially in indigo and turkey-red 
 dyeing, so-called passing-machines, 
 
 Fig. 567. 
 
 Fig. 566. 
 
 the general arrangement of which is shown in Fig. 567. First the roller A, fixed 
 perpendicularly on the axle //, is pushed up to roller B, so that a workman can easily 
 hang the yarns over A and B. The nipping roller, C, fixed on the weighted lever, Z>, 
 
8 2 8 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vn. 
 
 presses against the roller, B, the lever, E, which stands above the roller, J3, falls down 
 into the position shown, and draws the yarns into the bath in the cistern, F ; so that 
 when the roller, B, is turned, they are carried along through the beck. After a 
 certain time the yarns are stretched, the axle, H, being brought back by the weight, 
 C ; the roller, (7, and the lever, //, return to their original position, and the axle, H, 
 revolves, whereby the yarns are wrung out. The axle, //, then in turning back wrings 
 the yarns again, the roller, B, makes a rotation, and the axle, H, wrings the yarns 
 again by moving forwards. This is twice repeated, so that the parts which lie over 
 the rollers may be uniformly wrung out. The weight, G, is then lifted off, and the 
 machine stands still to allow the dyed hanks to be taken off, and fresh ones to be put 
 in their place. The introduction of these various movements is effected by curved 
 discs from the shaft, M. 
 
 The machine for dyeing piece-goods and yarns, made by the Zittau Machine Works, 
 consists of a trough for the flot (Figs. 568-571), over which there are several reels, B, 
 movable alternately from the r.ight to the left, and reversely over the entire length of 
 the trough, or a portion of it, and keeping all the time in rotation. By this slow to 
 and fro and alternately turning movement of the reels the pieces to be dyed are moved 
 
 Fig. 568. 
 
 in such a manner that the pieces are always conveyed from one half of the trough to 
 the other in quite even folds, and are thus brought in uniform contact with the dye 
 liquor, and it is rendered possible to dye up any given quantity of goods at once in one 
 and the same flot, or in several flots in succession. Fig. 568 shows the machine in 
 elevation, and Fig. 569 gives a side view, with a smooth drum, and with an undivided 
 trough as used for dyeing piece-goods, spread out. Fig. 570 shows the elevation, and 
 Fig. 571 the side view of the machine, with two compartments provided with reels, and 
 with a trough divided into two compartments in length and four in breadth, as applied 
 for yarns in warps (French, chaines ; German, Ketten], and for pieces folded up. In 
 both cases the reels are placed capable of rotation on rolling trucks, b, which run on 
 horizontal rails, J), fixed to the supports, C, C ir The movement of these trucks to and 
 
SECT. VII.] 
 
 DYEING AND TISSUE-PRINTING. 
 
 829 
 
 fro, and the alterna tin rotatory movement of the reels, B, is effected by the endless 
 band, S" S", which in turn is moved by the screw wheels, V, V,,, or the band discs, 
 g' g", fixed on the shafts of the screw wheels. The screw-wheel shafts, V, V, are 
 connected by the wheels, R / B. /; , with a corresponding number of teeth, according as 
 the open band, ?', or the cross band, r", runs upon the middle disc, c, whilst each 
 
 Fig- 57i- 
 
 time the other band runs upon one of the discs d. The change effected thereby is 
 that the rail, K, is pushed to the left or to the right by the impact of the truck, b. 
 
 In Sulzer's yarn-dyeing machine the yarns are exposed to a current of hot 
 air alternately in a freely suspended and in a horizontal position, and arrive pro- 
 gressively at higher temperatures as 
 the dyeing proceeds. The hanks of 
 yarn are suspended on rods at e, 
 which, as appears from Fig. 572, 
 are laid in endless chains moving 
 backwards and forwards. Similar 
 is the yarn-dyeing machine con- 
 structed by the Hartmann Machine 
 Works at Chemnitz. The difference 
 between the Sulzer and the Hart- 
 mann machine lies in the manage- 
 ment of the chains and the arrange- 
 ment of the system of hot-air pipes. 
 The temperature of the current of 
 air, which is 60 above, falls to 30 
 at the exit from the machine. A 
 drying machine 5 metres in length, 
 3 1 metres wide, and 4 metres high, 
 dries in eleven hours 1300 to 1400 
 kilos, of yarn, and requires about 
 4 horse-power. 
 
 Dyeing Woollens. Wool is dyed 
 either loose or spun into yarns, or 
 
 after weaving as cloth. As in M ^ I \ ( 
 
 working up the wool a certain part 
 is always lost in the mechanical operations, piece-dyeing is the most advantageous.* 
 
 Blue Dyeing. The imparting of a blue colour to wool is one of the most important 
 
 * On the other hand, it is the most difficult. Any unevenness in dyed wool or yarn is lost after- 
 wards, but a spot on a woven piece is a permanent defect. If the colour to be produced is 
 required to be fast, the cloths are often prepared by boiling in solutions of alum and tartar, of 
 copperas and tartar, or of tartar and stannic chloride, or pink salt. All processes which involve the 
 use of tartar (argol) are expensive, and it is therefore dispensed with whenever possible. [EDITOE.] 
 
830 CHEMICAL TECHNOLOGY. [SECT. vn. 
 
 operations of dyeing woollen goods. It is frequently effected with indigo, which 
 produces the most beautiful and fast colours ; but indigo is used only for the better 
 and heavier kinds of woollen fabrics ; lighter tissues merinos, for instance are often 
 dyed with Prussian blue (not a fast colour), while common woollen goods, flannels, <fec., 
 if dyed blue at all, are dyed with logwood and blue vitriol (copper sulphate). In 
 order to ascertain whether a woollen tissue has been dyed with indigo, Prussian blue, 
 or copper salts, the following tests may be employed. Woollen tissue dyed with 
 indigo does not change its colour by being boiled with caustic potash, or by being 
 moistened with concentrated sulphuric acid. When Prussian blue is the dye used, 
 the tissue becomes red-coloured by being boiled with caustic potash, and becomes 
 discoloured by being moistened with strong sulphuric acid. Woollen goods dyed with 
 logwood and copper salts are reddened by being moistened with dilute sulphuric acid, 
 and, on being incinerated, the tissue leaves an ash containing copper. 
 
 Indigo Blue. Woollen goods are most frequently dyed blue with indigo by means 
 of a solution of white indigo (reduced indigo) in an alkaline fluid, the goods being 
 blued by exposure to air that is to say, by the oxidation of the indigo taken up by 
 the fibre, the dye becoming simultaneously fixed. The principle of this mode of dyeing 
 with indigo (technically known as blue vat) may be elucidated by the following 
 formula : C 16 H 12 N 2 0, + = C 16 H 10 N 2 2 + H 2 0. 
 
 Blue Vats. The greatest consumption of indigo is in forming the blue vats, in 
 which woollen or cotton goods, more rarely linen, are dyed by simply immersing them 
 in the solution of white indigo. The same vats are not equally adapted for wool and 
 calico, there being, as will be seen in the following details, a wide difference in their 
 composition. According to the general accounts, the lime and copperas vat (see below) 
 is not well adapted for woollen goods; still, in the most recently published French 
 treatise on woollen dyeing there is no mention made of any other kind of vat ; the 
 following proportions and directions being given for setting a vat for dark blue : 
 1 200 gallons of water; 34 Ibs. of quicklime; 22 Ibs. of green copperas; 12 Ibs. of 
 ground indigo ; 4 quarts of caustic potash solution at 34 = sp. gr. i'288. The indigo 
 is ground very fine by trituration in properly constructed mills, this being a point of 
 the utmost importance. In the above recipe the potash is mixed with 5 gallons of 
 water in an iron pan, and the indigo added. The mixture is gradually heated to 
 ebullition and kept boiling for two hours with uninterrupted stirring ; this softens and 
 prepares the indigo for dissolving. The lime is well slacked so as to be very fine, and is 
 next passed through a sieve in the state of milk of lime. It is then mixed with the 
 indigo and potash ; the copperas (ferrous sulphate), previously dissolved, is added to 
 the vat and well stirred ; then the mixture of lime, potash, and indigo is poured in, 
 and the whole well stirred for half an hour. If the proportions are well kept, the vat 
 will be fit for working in twelve hours ; if, however, it looks blue under the scum, it is 
 a sign that the indigo is not wholly dissolved, and more lime and copperas should be 
 added, and the vat left undisturbed for another twelve hours. The vat is worked at a 
 temperature of 70 to 80 F. This is the ordinary composition of a vat for dyeing 
 cotton, but is not, at least in England, in use for dyeing woollen goods. 
 
 The usual blue vats for wool contain neither copperas nor lime, or but a small 
 quantity of the latter ; as, for instance Water, 500 gallons ; indigo, 20 Ibs. ; potash 
 (carbonate, pearl-ash), 30 Ibs. ; bran, 9 Ibs. ; madder, 9 Ibs. The water is heated to 
 just below its boiling-point ; the potash, bran, and madder are first put into the vat, a 
 well-made wooden tub of convenient size, and then the indigo, previously very finely 
 ground. Cold water is added so as to reduce the temperature to 90 F., and that 
 temperature is maintained constant by means of a steam-pipe. The ingredients are 
 well stirred every twelve hours. The vat is generally ready for use in forty-eight hours 
 after setting. This vat does not work longer than about a month, and is somewhat 
 
SECT, vii.] DYEING AND TISSUE-PRINTING. 831 
 
 expensive on account of the potash. Another the so-called German vat is much 
 more manageable, and may be worked for two years without emptying, being freshened 
 up as required. It is composed of the following ingredients : 2000 gallons of water 
 are heated to 130 1\, and there are added 20 Ibs. of crystals of soda (common 
 carbonate); z\ pecks of bran; and 12 Ibs. of indigo, the mixture being well stirred. 
 In twelve hours fermentation sets in ; bubbles of gas rise ; the liquid has a sweet smell, 
 and has assumed a green colour ; 2 Ibs. of slaked lime are now added and well stirred, 
 the vat is again heated and covered up for twelve hours, when a similar quantity of 
 bran, indigo, and soda, with some lime, is added. In about forty-eight hours the vat 
 may be worked ; but as the reducing powers of the bran are somewhat feeble, an 
 addition of 6 Ibs. of molasses is made. If the fermentation becomes too active, it is 
 repressed by the addition of lime ; if too sluggish, it is stimulated by the addition of 
 bran and molasses. Like all the other blue vats for wool, it is worked hot. Another 
 kind of vat may be called the woad vat, because a considerable quantity of woad is added 
 to it, and also madder, which in this case acts simply by reason of the saccharine matter 
 it contains. The proportions are : Pulverised indigo, i Ib. ; madder, 4 Ibs. ; slaked 
 lime, 7 Ibs., boiled together with water and poured upon the woad in the vat. After 
 a few hours fermentation sets in, and fresh indigo is added according to the depth of 
 colour required to be dyed. The pastel vat is set with a variety of woad which grows 
 in France, and which is richer in colouring matter than the common woad. It is 
 possible that the colouring matter of the pastel adds to the effect ; but it is more likely 
 that, while it furnishes fermentiscible matters useful in promoting the solution of 
 indigo, it is added as a remnant of ancient usage. Before indigo became again known 
 in Europe (the dye was known to the Greeks and Romans) in the seventeenth century, 
 woad was the general blue dye material. The method of dyeing the woollen fibre and 
 fabrics is very simple. The wool, thoroughly wetted out, is suspended on frames, and 
 dipped in the vat for an hour and a half or two hours, being agitated all the time to 
 insure regularity of colouring. The pieces are then removed, washed in water, and 
 treated with weak hydrochloric or sulphuric acid to remove the alkali retained. As 
 regards blue vat for cotton dyeing, in some exceptional cases, when thick and heavy 
 goods have to be dyed, the so-called German vat is used ; but generally all calicoes are 
 dyed blue by means of the cold lime and copperas vat. The materials used are lime, 
 ferrous sulphate, ground indigo, and water. The chemical action consists, in the 
 first instance, in the formation of calcium sulphate and ferrous oxide; the latter 
 substance, having a considerable affinity for oxygen, removes an atom of it from the 
 blue indigo, converting it into white, which dissolves in the excess of lime, and is 
 ready for dyeing. The proportions are as follows: 900 gallons of water, 60 Ibs. 
 of green copperas, 36 Ibs. of ground indigo, and 80 to 90 Ibs. of slaked lime. These 
 are stirred up together every half-hour for three or four hours, then left twelve 
 hours to settle, well raked up again, and as soon as the vat has subsided it is ready 
 for dyeing. 
 
 The urine vat is set up by dissolving indigo in stale urine (lant). The indigo is 
 reduced by the organic matters of the putrescent urine, and the indigo- white thus 
 obtained dissolves in the ammonium carbonate produced at the same time. This vat 
 is difficult to manage, and is rarely used either for wool or cotton. 
 
 The hydrosulphurous vat (of Schutzenberger) is set up by bringing a concentrated 
 solution of sodium bisulphite in contact with zinc powder. The zinc dissolves without 
 any escape of hydrogen, and a hyposulphite is formed: S0 2 + Zn = ZnSO 2 . The zinc 
 oxide is eliminated by an addition of milk of lime. This liquid is filtered with exclusion 
 of air and mixed with ground indigo and soda or hydrate of lime, when a solution of 
 indigo-white is quickly obtained. This vat is suitable either for animal or vegetable 
 fibres, and is less liable to " diseases " than the fermentation vats. 
 
832 CHEMICAL TECHNOLOGY. [SECT. vir. 
 
 The arsenical or orpiment vat is more used in tissue-printing than in dyeing blue on 
 woollens. It is set by dissolving orpiment (As s S 3 } and indigo in potassa-lye, and the 
 solution is thickened with gum and printed. 
 
 In the tin vat, indigo is brought in contact with a solution of stannous oxide in 
 caustic potassa, or caustic soda is boiled with indigo and metallic tin. There is a 
 formation of indigo-white and an alkaline stannate. This vat is chiefly used in 
 tissue-printing. 
 
 Saxony Blue. As already stated, indigo dissolves in concentrated sulphuric acid, 
 forming (because it is not a solution in the ordinary sense of the word) sulphindigotic 
 acid, which is employed in dyeing wool in the following manner : First, i part of in- 
 digo is treated with 4 to 5 parts of fuming sulphuric acid ; next, this solution is poured 
 into a vessel containing water ; and into this mixture flock wool is immersed for twenty- 
 four hours. After this time the wool is removed from the vessel and drained, and 
 transferred to a cauldron filled with water, to which has been added either carbonate 
 of ammonia, or of soda, or of potash, and boiled for some time. The solution thus 
 obtained, technically known as extract of indigo or as indigo carmine, is used for dyeing 
 wool which has been previously mordanted with alum. There is formed on the wool 
 aluminium sulphindigotate. 
 
 Recovery of Indigofrom Rags. In order to recover the indigo from scraps and rags 
 of woollen and other fabrics dyed indigo blue, the materials are treated with dilute sul- 
 phuric acid, which is heated to 100. The wool is dissolved, while the indigo is left as 
 an insoluble sediment. Military uniforms yield from 2 to 3 per cent, of indigo. The 
 acid solution is next neutralised with chalk, and a calcium sulphate is obtained 
 which, owing to the nitrogenous matter intermingled, may be usefully employed as a 
 manure. 
 
 Berlin Blue, Royal Blue.* Wool is dyed with the so-called Prussian blue (iron 
 ferrocyanide) by two methods, one of which consists in saturating the wool with a 
 solution of a ferric salt (generally the persulphate, or preferably the pernitrate), after 
 which the wool is passed through a solution of potassium ferrocyanide in water, 
 acidulated with sulphuric acid. The other process, producing the so-called Bleu 
 de France, is based upon the decomposing action which the atmosphere exerts on the 
 ferro- and ferricyanhydric acids. The goods are immersed in a solution of either the 
 ferro- (yellow) or ferri- (ruby-red) potassium cyanide (commonly called yellow or red 
 prussiate) in water, to which are added sulphuric acid and alum. Afterwards the 
 goods are aged, or exposed to the air in rooms in which steam is simultaneously ad- 
 mitted to elevate the temperature and assist the action of the oxygen of the air. The 
 result is that the ferro- or ferricyanhydric acid is decomposed, hydrocyanic acid being 
 evolved, while there is deposited on the fibres of the woven fabric iron ferrocyanide, 
 Prussian or Berlin blue. MeitzendorfF has proposed a method of dyeing this blue by 
 which a colour is produced very similar to that obtained by the so-called Saxony 
 blue. He prepares a solution containing potassium ferrocyanide, stannic chloride 
 (SnCl 4 ), tartaric and oxalic acids ; this solution is heated, and the wool kept therein for 
 some time. The oxalic acid dissolves the Prussian blue, which of course can only act 
 
 * This colour is called in Germany " kali blue," which is confusing, as the name " alkali blue " 
 is there given to Nicholson blue. The first method given above for producing Berlin blue on wool 
 is not satisfactory. The best royal blue, on 36 Ibs. wool, is obtained as follows : Mix 4 Ibs. 
 potassium ferrocyanide and 6 Ibs. oxalic acid ; dissolve, enter wool at ico F. , and work well for 
 two hours, raising heat gradually to 180 F. ; take out, and cool. Cool liquor with 2 pails cold 
 water ; add 21 Ibs. alum, and work for half an hour. Add f pint " yellow spirit," and work for one 
 hour, raising heat to 180 F., at which heat work for an hour and a quarter longer. Take out, and 
 add i to 2 pints nitrate of iron, according to shade required. Enter wool, and give five or six 
 turns. Take out, cool, and wash very well. This is an expensive colour, and is generally super- 
 seded by aniline blues. [EDITOK.] 
 
SECT, vii.] DYEING AND TISSUE-PRINTING. 833 
 
 as a dye when dissolved, any of it left undissolved being lost. The tartaric acid 
 increases the brilliancy of the colour. 
 
 Logwood and Copperas Blues. For this purpose logwood is boiled in the dye-beck 
 with water, and to the decoction are added alum, cream of tartar, and copper 
 sulphate. The wool is boiled in this fluid, and is next cleared by being boiled in a fluid 
 containing logwood, tin salt (stannous chloride), alum, and cream of tartar. The 
 goods dyed in this manner do not, as is the case with the indigo goods, become white 
 by wear. Instead of logwood, archil and cudbear are frequently used for so-called 
 half-fast colours. 
 
 In dyeing blues on wool with coal-tar colours the chief dyes employed are Nicholson 
 blue and methylene blue ; blue-blacks are obtained with the indulines. 
 
 For dyeing with indophenol wool, silk, or cotton mordanted for turkey-red, the 
 following mixture is prepared : 10 litres acetic acid, 10 litres tin acetate, 2 kilos, indo- 
 phenol, 5 litres calcium acetate at 27 Tw., and i litre black liquor at 14 Tw. The 
 whole is heated to effect reduction, and poured into 500 litres of water. The pieces are 
 worked in this flot at 60 for two hours, washed and oxidised with bichromate. If the 
 wool has been slightly chlorised, it dyes up more readily and gives a deeper blue, which 
 .bears soaping at a boil much better. According to Rosenstiehl's proposal the wool may 
 be dyed in an alkaline bath. It is plunged at 50 for two minutes into i litre water, 
 200 grammes soda crystals, 25 grammes indophenol, and the same weight of glucose; 
 it is then exposed to the air for some minutes, and the blue is fully developed by 
 chroming. 
 
 For dyeing with alizarine blue (S), which in many cases threatens to supersede 
 indigo, the wool is mordanted with chrome by boiling with 3 kilos, potassium bichro- 
 mate and 2 \ kilos, argol to 100 kilos, wool. For light shades it is sufficient to boil for 
 one hour with 2 per cent, potassium bichromate and i per cent, argol. If the 
 water contains lime it must be corrected with acetic acid. The wool is well turned in 
 the dye-beck until the liquid is clear. The process must be continued at a boil until 
 the colour, which at first appeared reddish, takes a pure blue tone. 
 
 Dyeing Yellows. On the Continent, weld, which has become quite obsolete for 
 dyeing yellow on wool in the United Kingdom, having been entirely superseded by 
 quercitron bark, is still used for producing a yellow dye, on account of the fact that 
 weld, when brought into contact with an alkali, becomes less red-coloured than do the 
 other yellow dyes. 
 
 In dyeing with weld its colouring-matter is extracted by water, and the decoction 
 added to the goods intended to be dyed. With alum it dyes a very fine clear yellow, 
 tolerably permanent in soap, but not resisting air and light. Weld has not more than 
 one-fourth the tinctorial power of quercitron bark, and on this account, as well as ou 
 that of its great bulk relative to its weight, it is not used in this country. Fustic, 
 yellow-wood, is very extensively employed in dyeing, and is the most suitable yellow 
 matter for working with other colours in compound shades. With aluminous mordants 
 it gives yellow of an orange shade; with iron mordants it gives drabs, greys, and 
 olives. As a yellow colouring-matter it is considered to be weight for weight of far less 
 power than quercitron bark, while it is also inferior in purity of colour ; but as fustic 
 withstands the action of acids and acid salts better than bark, it is used in greens, 
 bkcks, and mixed colours where yellow is required. Young or French fustic (also 
 known as Venice sumac or f ustet) is used for imparting yellow to merinos. A golden 
 yellow is produced upon wool with either picric acid or Manchester yellow. 
 
 Martius's yellow, Victoria orange, aurantia, chrysoidine, tropaeoline, &c., have to a 
 great extent superseded the vegetable yellows. 
 
 Eed Dyeing. Cochineal and lac are the chief colouring matters used for giving wools 
 a red or scarlet colour. The goods are prepared by boiling in a bath of cochineal, tartar, 
 
 3 G 
 
834 CHEMICAL TECHNOLOGY. [SECT, vii, 
 
 and tin crystals or scarlet spirit, and finished with cochineal and scarlet finishing spirit, 
 a stannous chloride to which much oxalic acid has been added.* For crimsons a part or 
 the whole of the cochineal used must be previously prepared with ammonia. The 
 water used should be pure and soft, and especially free from even the least trace of iron. 
 
 Faster, though less brilliant, reds are obtained with madder, or latterly with aliza- 
 rine. The goods are prepared by boiling with alum and tartar, and then dyed with 
 alizarine. 
 
 The redder azo-colours have very much interfered with the use of cochineal. 
 
 Roccelline, a colour obtained bydiazotising naphthylaminesulpho acid and conjugat- 
 ing with -naphthol, has to a great extent displaced orchil, and in some cases it is even 
 used in place of cochineal and madder. It is very extensively employed for silk-dyeing, 
 which is done in a curdled soap-beck, the colour being afterwards raised with sulphuric 
 acid. For wool-dyeing Roussel acidifies the beck slightly with hydrochloric acid, heats to 
 50, and lets the wool steep for from fifteen to thirty minutes. The roccelline is gradually 
 added, and the temperature is then gradually raised to 90, at which point it is allowed 
 to remain for half an hour. By the addition of chrysoine a colour is obtained which 
 may be substituted for madder-reds. Other tones are produced by mixtures of roccelline 
 with extract of indigo, chrysoine orange, naphthol yellow, &c. The extract of indigo 
 is added towards the end of the process, along with sulphuric acid and Glauber's salt. 
 These colours prove, on exposure to air, almost as fast as cochineal, and more permanent 
 than orchil. Their tone is also unaffected by acids and alkalies. The production of 
 roccelline shades is cheaper by 80 per cent, than those produced with cochineal, and by 
 40 per cent, than those obtained with orchil. 
 
 Green Dyeing. Green dyes are usually obtained by combining blue ana yellow, 
 "Wool is first dyed blue, and, having then been mordanted with cream of tartar and 
 alum, is dyed with fustic, or, on the Continent, with weld. The green cloth used for 
 covering billiard-tables and other furniture is dyed in the following manner : A weak 
 decoction of fustic is prepared, and into this some Saxony blue is poured, while there 
 is next added alum and cream of tartar. The woollen fabric is immersed in the bath 
 and boiled for two hours. It is next thoroughly washed and brightened by being 
 again immersed in a dye-beck filled with a fresh fustic decoction, to which a smaller 
 quantity of Saxony blue has been added. All kinds of woollen tissues, worsted, half- 
 wool, alpacas, delaines, &c., may be dyed green by means of lo-kao (Chinese green) and 
 iodine green. 
 
 Among the green tar colours those most commonly used are methyl green, malachite 
 green, and iodine green. As methyl green is transformed at high temperatures into a 
 violet colour, hot rollers cannot be used in finishing goods dyed with this colouring 
 matter. Malachite green and analogous tar colours are often used along with picric acid. 
 Mixed colours, singularly spoken of in France and Germany as modes, are obtained by~ 
 mixtures of greens with cochineal, fustet, madder, &c. 
 
 Slack Dyeing. Excepting only aniline black, all black dyes may be considered as com- 
 binations of iron or chrome with tannic or gallic acid ; but the best and fastest blacks on 
 broadcloth are such as have as a first dye either madder or indigo. The woollen goods- 
 are mordanted with ferrous sulphate (green copperas) and dyed by immersion in a 
 decoction of logwood, galls, sumac, &c. The so-called Sedan black (this town is cele- 
 brated for its cloth manufacture) is produced by dyeing the cloth blue with woad, 
 when, after careful washing, it is placed in a dye-beck containing water, sumac, and 
 logwood, and is boiled for some three hours, after which copperas in a solution of 
 known strength is added. This operation is repeated until the cloth has assumed 
 an intensely black colour. Half -fast black colours are produced on cloth by dyeing 
 
 * The composition of the bath requires to be varied according as the wool is hard or soft ; some 
 dyers use a stannic chloride. [EDITOR.] 
 
SECT, vii.] DYEING AND TISSUE-PRINTING. 835 
 
 them blue with Prussian blue, after Avhich the operation just described is gone through. 
 Common black is produced by dyeing with logwood, sumac, some fustic, and a mixture 
 of green and blue vitriol. Chromium black, invented by Leykauf at Nuremberg, is 
 obtained in the following manner : The cloth is mordanted with a solution of 
 potassium bichromate and cream of tartar, after which it is dyed in a decoction of log- 
 wood. The so-called iron pyrolignite (crude iron acetate prepared from scraps of 
 old iron and crude acetic acid) is now very generally used as a mordant instead of the 
 green copperas. This acetate, also known as black or iron liquor, is prepared on the 
 large scale and sold as a liquid at a sp. gr. of 1*09 to 1-14. 
 
 Vienna black, used in the cloth works in the Department Isere, is obtained as 
 follows : For one piece of cloth weighing 30 kilos, there are boiled in the dye-pan 
 6 kilos, logwood and i kilo, fustic for thirty minutes ; 2 kilos, gall-nuts are added, and as 
 much sumac, and it is again boiled for half an hour. The cloth is then entered and 
 turned for half an hour, taken out, and aired. 2 kilos, of copperas are dissolved in the 
 beck, and the cloth is again entered and worked for one hour, without coming to a 
 boil. It is again taken out, i kilo, of copperas is added, and the cloth is re-entered and 
 again treated as above. Finally, it is Avashed in a fulling mill. 
 
 Very similar is the Bedarieux black produced upon woollens in a boiling bath of 
 logwood (3 kilos, to 15 kilos, cloth), 0*5 kilo, fustic, and 3 kilos, sumac, with the 
 addition of 0^75 kilo, copperas. 
 
 Geneva black is obtained with logwood and fustic, with copperas and bluestone 
 along with a little argol. 
 
 Tours black is got up with logwood, sumac, copperas, and a little verdigris. The 
 cloth is entered five times in the dye-bath and aired between each operation, whence 
 it is called noir d, cinqfeux. 
 
 Nenuphar black is obtained by boiling wool with the roots of the white water-lily, 
 logwood, and a little sulphuric acid, and dyeing up, after airing, with copperas or black 
 liquor. 
 
 Vanadium black on wool is an aniline black obtained in a not of 1000 water, 80 
 salt of aniline, 40 potassium chlorate, 5 hydrochloric acid, and o - i ammonium vanadate. 
 That cloth dyed black is especially liable to become rotten is due on the one hand to 
 the oxidising action of the iron mordants, and on the other to the circumstance that 
 when the dyer has failed in producing the right shade on a piece of cloth it is dyed black, 
 and has of course been enfeebled by the extra boilings, &c., which it has undergone. 
 
 Silk-dyeing. Silk is usually dyed in skeins, either in the crude state (souple) or 
 after it has been ungummed. It is then scoured, bleached, and sulphured ; the latter only 
 when the silk is to be dyed with very bright colours and delicate light hues. Silk is 
 chiefly dyed in cold dye solutions. It is dyed black by any of the following processes : 
 
 1 . Logwood and iron mordant ; 
 
 2. Logwood and potassium bichromate ; 
 
 3. Galls and other substances containing tannic acid with iron salts as mordant ; 
 
 4. With aniline black, according to the recipes of Persoz, jun., and others, by 
 
 the use of copper chromate and aniline oxalate. 
 
 The first and second are simply known as ordinary blacks, while the third is known 
 as fast black. The ordinary black is obtained by simply mordanting the silk with 
 iron nitrate, and then dyeing it in a decoction of logwood. This cheap dye is more 
 particularly applied to light silken fabrics. The colour is reddened even by weak acids, 
 such as lemon and orange and other fruit juices. The fast black is far more expensive, 
 but it is not affected by weak acids, while it affords the additional advantage of largely 
 increasing the weight of the silk (in the raw state, as well as in spun yarn, silk is sold 
 and bought by weight), as this textile fibre absorbs from 60 to 80, and even 100 per cent, 
 of its own weight, and silk used for shoe-laces even 225 per cent, of the dye material. 
 When desired, the silk-dyer has, for 100 Ibs. of raw silk delivered to him, to return from 
 
3 6 CHEMICAL TECHNOLOGY. [SECT. vu. 
 
 160 to 180 or 250 Ibs. of dyed material, the increase being obtained by " weighting." 
 In England nut-galls imported from the Levant are employed to dye silk black. 
 Although the increase in weight of the silk by black dyeing is advantageous to 
 the dealers, the depositing of so much foreign matter in the fibre of the silk, not 
 only injures its wearing qualities, but also gives rise to the disagreeableness of the 
 dye coming off while the material is being worn. Microscopic research has proved 
 that the dye adheres very loosely to the silk. The process of dyeing silk black with 
 galls is very simple. The fibre is first steeped in a solution, or rather infusio- 
 decoction, of galls, technically known as " galling," after which the silk is placed in 
 a solution of iron nitrate. This black is sometimes dyed on silk previously dyed 
 with Prussian blue, but far more frequently a bluish shade is given to black by first 
 dyeing the silk with logwood, copperas, and some copper sulphate. 
 
 As regards the weighting of the silk, it is essentially due to the fact that silk, as 
 an animal product, has the property of combining with tannic acid and thereby becoming 
 heavier. The larger, therefore, the quantity of tannic acid contained in the dye-bath, 
 or the oftener the galling of the silk is repeated, the heavier, within certain limits, will 
 the fibre become. It is not quite indifferent whether a ferric or ferrous salt of iron bo 
 employed, the former being preferable. The previously galled silk becomes, when 
 passed through a solution of ferric salt, at once coloured black ; but when it is 
 passed through a solution of a ferrous salt, the silk becomes at first coloured only 
 black-violet, and gradually deep black by exposure to air. Although in every case the 
 result is the same, the use of a ferric salt is advantageous, and becomes necessary 
 with a small quantity of tannic acid, while for a heavy weighting of the silk the ferrous 
 salt of iron only can be employed. It is stated that the dyeing of silk with aniline 
 black by means of copper chromate and aniline oxalate yields excellent results. 
 
 For some years silks have also been dyed with an aniline black got up with ammo- 
 nium vanadate. 
 
 Blue Dyeing. Silk is dyed blue either with indigo, Berlin blue, logwood, or 
 aniline blues. The indigo vat has not been much used for imparting a blue colour to 
 silk since the discovery of fixing Prussian blue upon silk ; and if indigo is used at all it 
 is as indigo extract, or the so-called distilled blue purified sulphindigotic acid. In 
 order to dye silk with Prussian blue, it is first immersed in a solution of iron 
 nitrate. This salt is generally in use in England, while in Fi-ance iron persulphate 
 made by dissolving green copperas in nitric acid is employed, and known under the 
 name of Raymond's solution, the blue produced being termed Raymond's blue ; 
 Napoleon blue is produced by the addition of a tin salt to the iron bath, followed by 
 treatment with a solution of potassium ferrocyanide acidulated with sulphuric acid. 
 The latter blue, more brilliant than the former, is usually preferred in England, a 
 tin salt being invariably added to the iron mordant. The mordanted silk is next passed 
 through a boiling soap solution, then washed, and next steeped in a solution of 
 potassium ferro-cyanide acidulated with hydrochloric acid. The brilliancy of the dyed 
 silk is greatly enhanced by passing it through water containing ammonia. Dyeing silk 
 with aniline or naphthaline blue is a very simple process, it being only necessary to put 
 the silk into a solution of the dyes, the solvent being alcohol or wood-spirit, or, in the 
 case of soluble aniline blue, water. The silk is left in the solution until it has assumed 
 the desired hue. 
 
 Until very recently silks were dyed red with safflower (carthamine), cochineal, 
 and orchil. Now magenta, coralline, safFranine, eosine, and Magdala red are employed.* 
 Violets are still dyed on silk with orchil, which is being gradually superseded by 
 methyl and benzyl violet. 
 
 * None of these tar colours surpass, even if they equal, carthamine in beauty. No true rose 
 can be dyed with magenta. The finest reds on silk are now produced with the cosines. [EDITOR,] 
 
SECT, vii.] DYEING AND TISSUE-PRINTING. 837 
 
 Yellow Dyes. Yellow is produced upon silk by first mordanting with alum and 
 dyeing in a decoction of weld, to which, if it be desired to impart an orange hue, some 
 annatto is added, or, preferably, Manchester yellow. By cautious treatment with nitric 
 acid, silk may be dyed yellow, some xanthroproteic acid being formed, while, without 
 any mordant, picric acid produces a bright lemon-yellow on silk, the colour becoming 
 deeper by treatment with alkalies. The production of picric acid upon silk by the action 
 of nitric acid is not now in use.* 
 
 Green Dyes. Silks are now dyed green almost exclusively with methyl green and 
 malachite green. 
 
 Cotton- dyeing. Cotton is dyed either as yarn or woven fabric, but more generally 
 as yarn. Cotton is far more difficult to dye than wool, and requires, especially for 
 obtaining fast colours, stronger mordants. Blue is produced upon cotton (which, when 
 woven, is termed calico) by means of the copperas vat (see Indigo) ; further, by Berlin or 
 Prussian blue, logwood, and green copperas; and, finally, by being passed through 
 a solution of copper oxide in ammonia, the fibre, yarn, or tissue after drying ex- 
 hibiting a beautiful bright blue colour. Yellow is produced with Persian berries, 
 weld, fustic, quercitron, annatto, iron acetate, technically known as black liquor 
 (nankeen), and chrome-yellow. Green is obtained by the copperas vat followed by 
 dyeing with fustic. Brown is produced with a salt of iron and with quercitron or 
 madder, or simply by means of hydrated manganese oxide. Black is either a fast 
 aniline black, or is produced by dyeing blue by the aid of the copperas vat, next 
 mordanting with iron acetate, and then dyeing in a bath consisting of galls and 
 logwood. The majority of the aniline colours can be fixed upon cotton only by the- 
 aid of a specific mordant a solution of tannin in alcohol ; or the fibre of cotton is first 
 animalised, as it is termed that is to say, impregnated with either albumen or casein r 
 the fibre being thus to a certain extent made similar to that of wool or silk, and ren- 
 dered absorbent of aniline dyes. Cotton may be mordanted with Gallipoli oil or for 
 certain dyes with soft soap. 
 
 A very important observation has been made by Witz, Cross, and Schmidt, that 
 cotton oxidised by chloride of lime, chloric acid, &c., readily takes up colouring-matters. 
 The bath employed is a solution of potassium chlorate, saturated at common tempera- 
 tures, and containing to i mol. KC10 3 less than i mol. HC1, but more than -J mol. 
 and o-oi gramme vanadium per litre in the state of chloride. The cotton, whether 
 loose, as yarn or as cloth, and whether crude or scoured, is steeped in the solution and 
 then wrung out, or, after insertion in the liquid, it is quickly exposed to a heat of 60, 
 until the formation of chlorous acid is indicated by vapours or by the appearance of a 
 yellow colour. Or there is used as an oxidising bath a solution of potassium dichromate, 
 saturated at common temperatures, and acidulated with i to 2 mols. hydrochloric acid 
 or sulphuric acid to i mol. K,Cr z O 7 . The cotton is steeped in this liquid for thirty- 
 minutes. If it is desired to increase the action, the liquid may be slightly heated, or 
 the effect may be reduced by the addition of water. In every case the cotton is thoroughly 
 washed after oxidation, and it is then ready for dyeing. 
 
 According to a process given by the Baden Aniline Company, cotton (loose, in yarn, 
 or cloth) is placed in a bath of from 30 to 40 grammes turkey-red oil (sulphoricinate) per 
 litre, whizzed, and dried at from 50 to 60. As a chrome mordant there is used a basic 
 chromium chloride, obtained by dissolving precipitated chromium hydrate in an insuffi- 
 cient quantity of hydrochloric acid. The oiled cotton is soaked in such chromium 
 chloride at 14 Tw. for from two to three hours, turned out, and washed. To remove all 
 mineral acids, it is taken through sodium acetate at 5 grammes per litre and washed 
 again. The goods are then ready to be dyed. Calcareous water must be neutralised or 
 
 * Picric acid cannot be used for dyeing handkerchiefs or other articles which have to be washed, 
 as the colour is discharged. [EDITOR.] 
 
838 CHEMICAL TECHNOLOGY. [SECT. vn. 
 
 acidified to prevent the formation of an insoluble lime-lake of alizarine blue or ceruleine. 
 Light shades require 3 per cent, of alizarine blue (S) or ceruleine, and dark shades 
 require 6 per cent. The flot is heated slowly and gradually ; cotton-wool is kept in it 
 for two hours at from 70 or 80, whilst yarn and cloth are boiled for an hour. After 
 dyeing, the steaming follows, at once in the case of loose cotton, but after a repeated 
 oiling in the case of yarn or cloth. The process is concluded by washing and soaping. 
 Alizarine red and orange can be dyed under the same conditions in the chrome bath. 
 
 C. Koechlin mordants the cotton in a bath containing to 100 kilos, of goods 10 to 
 1 2 kilos, of tin crystals, 5-3 kilos, of stannic chloride at 1 1 5 Tw. ( = 3 litres), and 2^ kilos, 
 sulphuric acid at 154 Tw., together with water enough to wet the cotton thoroughly. 
 The hanks, after being wrung out, are left lying over-night, washed well, and then 
 taken through a bath of from 40 to 50 grammes of soda-crystals per litre at 4Q C . The 
 cotton, when washed, is ready for chroming. It is worked for an hour at 80 in 
 a beck of from 40 to 50 grammes chrome alum per litre. Probably the use of 
 basic chrome salts, as Cr 4 (S0 4 ) 3 (OH) 6 , would be better. H. Koechlin uses chromium 
 acetate. 
 
 The solid violet obtained by H. Koechlin by the action of nitrosodimethylaniline 
 upon gallic acid, after it has been rendered soluble with sodium bisulphate, can be at 
 at once dyed upon cotton mordanted with chrome, and yields fine violet-blue tones, 
 which approach aniline violet in brightness, but are distinguished by their far greater 
 fastness. If solid violefc is dyed along with yellows, such as bark or berries, &c., we 
 obtain deep blues, resembling indigo. According to the tone desired, the bath is made 
 up with from 10 to 1 5 per cent, of solid violet (calculated on the weight of the cotton) and 
 from 6 to 1 2 per cent, extract of bark at 14 Tw., with the addition of from i to 2 per cent, 
 tannin and from o'i to 0*2 per cent, methylene blue. Piece goods may be dyed in this 
 flot in a jigger. They are entered at the common temperature, which is then gradually 
 and regularly raised in an hour and a half to 70, at which temperature it is allowed to 
 remain from a quarter to half an hour. The bath is completely exhausted, and the 
 pieces are then washed and dried. If they are steamed, the colour not merely becomes 
 much deeper, but also much faster. The colour also yields better if the alkaline chrome 
 bath is applied to pieces which have been prepared in a bath of tin chloride (i litre SnCl 4 
 at 1 1 4 to 1 6 litres water). The blue thus obtained bears soaping, exposure to light and 
 dilute acids, and, if it is not as fast as vat blue against alkaline carbonates, it has the 
 advantage of not smearing off. The fibre is dyed through and through, whilst indigo 
 is deposited more on the surface, and therefore rubs off on repeated washing and the 
 accompanying friction. A further advantage of the fast blues obtained with solid 
 violet is the ease with which their tone can be modified at pleasure from the purest 
 violet to the greenest blue by merely changing the proportions of violet and bark- 
 liquor, whilst indigo does not admit of such modulations. 
 
 Turkey Red. Of the three similar processes, that with turkey-red oil is the most 
 important. The bleached and dyed cotton is saturated by steeping or padding with a 
 solution of from 10 to 15 kilos, of saturated turkey-red oil (50 per cent.) to 100 litres 
 water. The excess is drained off and the cotton is dried. It is steamed for from sixty 
 to ninety minutes, and then worked for from two to four hours at a hand-heat in red 
 liquor or in a solution of basic aluminium sulphate, Al 2 (S0 4 ) a (OH) 2 , at 7 Tw. 
 
 After mordanting, the excess of the aluminium salt is removed in a centrifugal, and 
 the cotton is dried and washed in cold water, or first treated for half an hour at from 40 
 to 50 in a chalk bath containing from 20 to 30 grammes ground chalk per litre. Alkaline 
 fixing agents, such as ammonia and sodium carbonate, must be avoided, as they would 
 strip off a part of the oil preparation. Then follows dyeing, with from 15 to 20 per cent, 
 of alizarine ( 10 per cent, strength), with the addition of i per cent, of its weight of chalk 
 or calcium acetate. The cotton is dyed in the cold for half an hour to secure a level 
 colour, and the temperature is then gradually raised in the course of an hour to 70% 
 
SECT, vii.] DYEING AND TISSUE-FEINTING. 839 
 
 and the dyeing is continued at this temperature till the bath is exhausted. The cotton 
 is next thoroughly washed, avoiding very calcareous water, the excess of liquid is 
 removed with the centrifugal, and the cotton pressed and dried. 
 
 The dyed and dried cotton is again saturated with a dilute solution of neutralised 
 turkey-red oil (from 50 to 60 grammes to the litre), and dried. This second preparation 
 may also take place after the mordanting, in which case the oil is fixed upon the 
 fibre by a second treatment with a weak solution of basic aluminium sulphate. The 
 dried cotton is again steamed for an hour as before, and raised with soap and 
 stannous chloride. 
 
 Aniline-Mack Dyeing. In the old process, chiefly used in printing, the black is 
 developed in the so-called oxidation-rooms, i.e., chambers in which the goods printed 
 with the black colour, after being quickly dried in a drying chest, are hung up to 
 oxidise. This hanging process is suitable only for the development of patterns, but not 
 for giving calicoes a uniform black ground, since, wherever the tissue is not exposed to 
 the air in a uniform tension, lighter stripes remain, which cannot be removed by any 
 subsequent treatment. Wherever a black ground is required, it has been found 
 advisable to develop the black in a steam chest, in which the mordanted pieces are 
 oxidised merely by steaming, without the intervention of drying. This steam aniline 
 black, however, does not equal the blacks produced by oxidation in the air in respect to 
 beauty and purity of colour. 
 
 The third process, now very generally used for cotton yarns, both in hanks and in 
 warps, depends on the use of a metallic salt, generally potassium chromate, to effect 
 the oxidation in the formation of aniline black. But this process is not suitable for 
 producing blacks on piece goods, for not only is it very difficult to obtain a uniform dye 
 in this manner, but this aniline black smears off, as it is not perfectly attached to the 
 fibre. Hence it follows that the black produced by oxidation, as it does not smear off 
 at all, surpasses every other aniline black in quality. 
 
 As far as piece-dyeing is concerned, the original process has been very widely 
 resumed, but the drying and oxidation processes take place in a long chest in which the 
 tissue, saturated with the mordant, is passed slowly up and down, stretched out equally. 
 The interior of the apparatus is kept at a temperature of from 44 to 50 by means of hot- 
 air pipes, and the vapours and gases given off are drawn away uniformly the entire 
 length of the chest. The drying and oxidation of the mordant take place in the front 
 of the chest, and fresh air of about 25 streams constantly from below into this part of 
 the chest and between the tissues. As soon as the goods thus dried and oxidised 
 arrive at the back part of the apparatus, which is completely closed, they begin to 
 show colour. At the end of the chest there are placed between the folds of the tissues, 
 some water-troughs, to ensure a moist atmosphere, which is essential for the pro- 
 duction of a good black. 
 
 Linens are dyed like cottons, but the process is more difficult, as the affinity of the 
 linen fibre for colouring-matters is still feebler than that of the cotton fibre. 
 
 Tissue-printing. The most important part of tissue-printing is cotton- or calico- 
 printing. It depends on the same principles as dyeing, but it has much greater difficul- 
 ties to encounter, partly because only certain given spots have to take up the colours 
 with well-defined outlines, whilst other parts remain colourless or have to be deprived 
 of colour, and partly, again, because several colours have to be produced in juxtaposition. 
 There is further required a pleasing, tasteful, and artistic arrangement of the colours. 
 The colours applied in tissue-printing may be divided into two main classes those in 
 which the colours are at once placed directly upon the cloth by means of engraved 
 rollers or plates (application colours), and those which are obtained by the immersion 
 of the tissue in a dye bath (generally called pan or madder colours). To the former 
 belong the iron colours, Prussian blue, madder lake, indigo, cochineal, and most of tho 
 -coal-tar colours. In the second class fall madder and alizarine, cochineal, logwood, 
 
840 CHEMICAL TECHNOLOGY. [SECT, vm 
 
 weld, sumac, &c. If steam is used to fix the colours upon the tissue, we have the steam 
 styles. If the colours are of an inorganic nature (ultramarine) or lakes (madder lake),, 
 which are fixed mechanically i.e., by the help of albumen, caseine, gluten, or oil 
 varnish we have the pigment style. The pan colours are more generally applied in 
 calico-printing. The tissue is passed into the dye pan as if it was to be dyed of one- 
 colour, but by various means the colour is only attached locally. 
 
 If the colouring-matter requires a mordant for its fixation, this is often printed on 
 alone, and, after dyeing, there is thus obtained a coloured design upon a white ground. 
 If, e.g., the cloth is printed with thickened red liquor and dyed up in the madder (ali- 
 zarine) beck, the mordanted parts only are dyed red, &c. In this manner are obtained 
 the so-called madder styles. Or the parts which are to remain white are printed with 
 a resist, i.e., a preparation which hinders the colouring-matter from attaching itself to 
 such parts. Thus in the case of indigo we use as resists copper acetate or sulphate ; 
 if cloth thus printed is passed into the indigo vat, the ground is dyed blue whilst the- 
 design remains white. 
 
 There is often added to a resist a mordant for some other colour, so that the places 
 which remain white in the vat may take up some other colour in a dye beck, which 
 acts merely on the resisted or the reserved parts. Here belongs the so-called lapis 
 style. 
 
 The cloth may also be uniformly mordanted or dyed, and then the mordant or the 
 colour is removed in parts. The agents employed are called discharges (Fr. erilevages t 
 Ger. Aetzbeizen}. If the cloth is first uniformly treated with a mordant and then 
 printed with a discharge (e.g., citric or tartaric acid), which dissolves the alumina or 
 the iron oxide of the mordant, then on dyeing we obtain a white design on a coloured 
 ground. A similar result is obtained by printing a suitable discharge on dyed cloth. 
 Such are either oxidising agents (like chloride of lime and chromic acid) or reducing 
 agents (like salt of tin or ferrous sulphate). 
 
 Here may be mentioned a curious application of photography to tissue-printing. 
 The cloth to be printed is padded with a preparation sensitive to light, then covered 
 with a thick black paper in which the pattern is cut out, and exposed to the sun, 
 when the parts not protected are coloured. The matter susceptible to light is then 
 removed. 
 
 The above-mentioned processes can be almost indefinitely modified for the produc- 
 tion of certain designs. Thus, if a cloth has been printed with mordants and dyed, the 
 mordanted parts appear coloured upon a white ground. Upon this ground other 
 mordants or colours may be blocked in. Colours which have been already produced 
 may be modified by printing upon them other mordants or colouring-matters, thus 
 producing conversion colours (couleurs de covnersiori). 
 
 The pieces which are to be printed are singed, bleached, and calendered by a passage 
 between rollers to press the threads of the tissue smooth, so as to give the cloth a per- 
 fectly even surface to which the mordants and colours may be applied uniformly. 
 The cloth is then printed. 
 
 Thickenings* In order to give the colours or mordants used in printing, either by 
 block or cylinder, a sufficient consistency, they are mixed with what are technically 
 known as thickenings. As such are used Gums Senegal and tragacanth, leiocome, 
 British gum, dextrine, salep, flour, gluten, pipe-clay with gum, glue, and size, lead 
 sulphate, sugar, molasses, glycerine, starch, sometimes zinc chloride and nitrate. 
 
 * If the intensity of the colour produced by means of a mordant is inversely as the quantity 
 of the solids which the mordant requires for the thickening, the reason lies in the property of 
 solids to form with a portion of the mordant, a compound upon which the tissue has no action, 
 and, partly, also because a colour which contains less solid matter in a given volume, when dyeing, 
 undergoes a kind of fading which is far greater than when the thickening predominates. [EDITOR.] 
 
SECT, vii.] DYEING AND TISSUE-PRINTING. 841 
 
 The purity of the colours and the distinctness of the outlines depend on the right 
 selection of the thickeners. Not every substance which has the property of rendering 
 liquids glutinous can be thus used. Thus, sugar is generally excluded in consequence of 
 its tendency to deprive the mordants of their affinity for the fibre. In the selection of 
 a thickener for any particular case the colour-mixer has to be guided by the following 
 considerations : 
 
 1. He must attend to the temperature necessary for thickening a colour; if, e.g., a 
 colour is apt to be decomposed in heat, flour and starch are not admissible, since these 
 substances thicken only when mixed hot. 
 
 2. The reaction of the colour or mordant is important. If it is very acid, 
 flour, starch, and dextrine are excluded, since these substances are liquefied by the 
 action of the acids, and form products which have often an injurious action upon the 
 colours. If the reaction is alkaline, the question is does it contain earths or metallic 
 oxides : in the former case all thickeners which are coagulated by alkalies, such as flour 
 and starch, are excluded, but gums and dextrine are admissible; in the second 
 case no thickener which forms insoluble compounds with metallic oxides must be 
 admitted. 
 
 3. All decompositions between constituents of the colour or the mordant and those 
 of the thickener must be avoided ; thus, basic lead acetate precipitates most of the 
 thickeners above mentioned with the exception of sugar. Ferric salts are coagulated 
 by gums tragacanth and Senegal, and must therefore be thickened with starch or 
 dextrine. Stannic chloride and iron tannate are not coagulated by gum Senegal, 
 but by all other thickeners. 
 
 4. The consistency of the colour is to be regarded, as the speed with which it dries 
 may have a great influence upon the intensity of the colour as it appears on the 
 calico. Thus, iron and aluminium mordants (which are distinguished for drying 
 rapidly) do not give such full colours if thickened with gum as if starch had been 
 used. 
 
 5. The intensity of the colour to be produced is often important. A mordant 
 thickened with tragacanth or starch paste yields stronger tones than if gum Senegal or 
 dextrine had been used. 
 
 6. The colour of the thickener is unimportant only if the colour printed upon the 
 tissue can bear cleansing and the removal of the thickener without injury. If, in print- 
 ing woollens witn rose or blue, two colours which do not bear washing well, they are 
 thickened with dextrine, the former would take a brownish and the latter a greenish 
 tone. Upon calico, on the contrary, both colours can be safely thickened with 
 dextrine, as in this case a thorough washing is practicable. 
 
 7. The ease with which a thickener can be removed from the cloth is often 
 decisive. Even a colourless thickener may, in proportion as more or less of it is left 
 upon the tissue, have an injurious effect upon the colour, and give the cloth properties 
 which impair its value. 
 
 8. The degree of contraction to which the tissue is exposed by some thickeners is 
 important, especially if several colours have to be printed on in succession. If a very 
 thick solution of gum is printed upon cloth, it contracts in drying and causes the cloth 
 to shrink unequally, producing unevennesses, which render the subsequent accurate 
 application of other colours impossible. To avoid this evil there is used a mixture of 
 thickeners, which counteract, or at least reduce, this shrinkage. Thus, the solution of 
 gum is sometimes mixed up with pipe-clay, lead sulphate, or glycerine, which effects a 
 mechanical division of the gummy mass. 
 
 9. The succession in which the colours are applied after each other, or upon each 
 other, is important, for, if we merely regard the mordant, the design may easily suffer 
 by the mutual action of the thickeners upon each other and by their colours. The 
 
842 CHEMICAL TECHNOLOGY. [SECT. vn. 
 
 colour to be printed on first is generally the darkest, and is thickened with starch, 
 whilst the next is thickened with gum. In fine cylinder work with three colours, the 
 first is thickened with dextrine, the second with starch, and the third with gum 
 Senegal. 
 
 10. The manner of producing a design is also important. If it is very delicate, 
 starch and flour are inadmissible. Thin colours must be used for shallow engraving. 
 
 Madder Style. Calico-printing in the dye beck (otherwise called dyeing upon mor- 
 dants) is effected by printing the cloth with mordants > and, after fixing and .drying 
 them, dyeing up with madder, alizarine, or other colouring-matters, when only the 
 mordanted parts become dyed, whilst the ground remains white, or takes up merely 
 so little colour that it may be completely removed by a soap or a bran bath, or by a 
 slight chlorising. 
 
 Madder printing is effected as follows : 
 
 (a) The mordant is printed on with the cylinder machine. If flowers have to be 
 produced in which red, brown, and black occur, the mordants are put on simultaneously 
 with three cylinders with the one, red liquor thickened with flour or starch ; with the 
 second, a mixture of red liquor and black liquor ; and with the third, black liquor (an 
 iron mordant). The following may serve as specimens of the composition of the 
 mordants: For red liquor, 188 litres water, 50 kilos, alum, 5 kilos. soda, and 38 kilos, 
 sugar of lead ; the mordant decanted off from the lead sulphate marks 16 to 16-5 Tw. 
 To "sighten" the mordant i.e., to show where it has been applied i litre of this 
 liquid let down to 675 Tw., 120 grammes starch, and a little red-wood or logwood 
 liquor are taken. According to another formula, we take, to 100 litres water, 35^- 
 kilos, alum, 24^ kilos, sugar of lead, 4 kilos, soda crystals, and 2 kilos, common salt. 
 The liquid decanted off from the sediment is mixed with 45 litres zinc nitrate at i'ii 
 sp. gr., thickened by boiling with z\ kilos, starch, and sightened with 100 grammes 
 neutral extract indigo dissolved in vinegar. For the black mordant, take, to i litre 
 ferrous chloride at 9 Tw., 130 grammes starch and 130 grammes wheat flour. The 
 colour, mixed by boiling and stirring, is intimately incorporated with 15 grammes 
 olive oil. 
 
 Printing on the mordants is not always merely the first step. Frequently, if it is 
 intended to produce a full and a light red along with brown and black, red liquor of the 
 proper concentration is first printed on by two cylinders, then air-dried, dunged, and 
 dyed up in the madder beck. The black liquor and the mixture of red and black 
 liquors for browns are blocked in by hand, aired, dunged, and dyed up in a beck of 
 madder and sumach. 
 
 (6) Drying and Ageing. If the cloth were dried in the air just as printed, the 
 mordant would in many cases spread and spoil the outlines of the pattern. Hence it 
 is important that the pieces, when dry, should hang for at least thirty-six hours in a 
 heated chamber, that the mordants may be fixed insolubly upon the fibre. 
 
 (c) The dunging process serves not merely to effect a more intimate combination of 
 the base of the mordants with the fibre, but to remove a part of the thickening and 
 the sightening colour, as well as any uncombined parts of the mordant. 
 
 (d) The dyeing in the madder or the alizarine beck is effected either in a single process 
 or in two operations. For dyeing in a single operation the beck is filled with water. As 
 soon as the temperature has reached 35-45, the madder is introduced, and the pieces are 
 run over the reel in the beck, which is kept in constant motion during the dyeing. 
 The temperature of the beck is slowly raised so as to reach 50 in half an hour, and 
 after another hour 70, at which the beck is kept for another half an hour, and is then 
 gradually raised to a boil. When the dyeing is completed the pieces are wound off 
 the reel, and washed. Light shades are generally dyed only once ; for full shades, 
 especially for red grounds, the dyeing is performed twice. For the success of the 
 
ECT. VH.] DYEING AND TISSUE-PRINTING. 843 
 
 process, it is necessary that the mordants should be thoroughly saturated with colouring- 
 matter. This is especially the case for colours which have to be raised or taken through 
 flots of other colouring-matters. If, e.g., it were intended to print upon the white 
 ground of the cloth, after maddering, red or black liquors, and then dye them up in the 
 -quercitron bark beck, the first mordants, if not fully saturated with the madder colour, 
 would take up a yellow colouring-matter, and thus convert the red into an orange and 
 the violet into a grey olive-green.* That a mordant is not saturated with colouring- 
 matter is known because during dyeing the not becomes clear and exhausted, 
 and the different tones are not sharply distinguished. Until they have taken up 
 their maximum of colour they seem almost alike. The want of colouring matter is 
 detected too late when the dyed pieces lose their colour in bleaching. A certain sign 
 of unsaturated mordants is a change of colour when the goods are passed into a bark 
 beck. 
 
 Among the ordinary colouring-matters fixed by means of alum and iron mordants, 
 that of madder has the greatest affinity for the bases, and cannot be eliminated by any 
 other colouring-matter. Hence every change of colour in a beck other than one of 
 madder is a certain sign of incomplete saturation. 
 
 In dyeing mixed colours with madder and other dye-wares whose affinity for the 
 mordants is not equal, care must be taken that no more madder is used than is exactly 
 .needed, unless the dyeing is effected in two separate operations. 
 
 Witz utilises oxycellulose for calico-printing by means of the chlorates. Chloric 
 acid can be substituted for the hypochlorites if it is brought into contact with the fibre 
 under such circumstances that it is resolved into oxygen and unstable oxides of 
 chlorine under the influence of the reagents which it meets. Vanadium salts decompose 
 chloric acid most easily and rapidly. A saturated solution of potassium chlorate mixed 
 with rather less hydrochloric acid than the quantity required to set free the chloric 
 .acid, thickened with gum tragacanth and with 10 milligrammes vanadium per litre, is 
 printed on the cloth. On drying at a temperature of from 50 to 60, the formation of 
 oxycellulose takes place. The quantity of chlorate and of vanadium may be reduced 
 according to the temperature and the duration of the reaction. Steaming is less ad- 
 vantageous than hot air. Quick, sharp drying evolves a strong odour of chlorine, and 
 leads to energetic oxidation, which, however, is not attended with any notable injury 
 to the fibre. For printing, composition " doctors " are preferable to those of steel. 
 Though the chief action of the chloric acid takes place during drying in the hot air, 
 yet, in order to prevent injury from the acid vapours, the pieces must hang for some 
 hours in a warm room, which must be well ventilated. Or the cloth is padded with 
 a 10 per cent, solution of potassium bichromate, and dried. A starch paste contain- 
 ing 15 per cent, of oxalic acid is then printed on at a hand-heat. The goods are 
 dried, washed, taken through weak sours, and washed again. On dyting in a cold 
 beck of methylene blue, the design comes up in ten minutes as a deep blue on a pale 
 blue field. 
 
 By " padding on mordants " is understood a process by means of which the cloth 
 is saturated with a mordant over its entire breadth, in order either to apply different 
 colours to it topically, or to dye it entirely, forming a coloured ground upon which 
 -coloured designs may be produced by printing on mordants and dyeing them on white 
 designs by printing on discharges. 
 
 The machine used in this operation consists essentially of two brass cylinders 
 wrapped round with thick layers of a cotton tissue, and a colour trough placed beneath. 
 The piece to be padded passes first into the trough, where it is saturated with the 
 mordant, and then between the rollers, which are pressed together by a weighted 
 
 * English calico-printers unfortunately speak of madder violet as "purple," which leads to 
 eome confusion. [EDITOR.] 
 
8 4 4 CHEMICAL TECHNOLOGY. [SECT. VIL 
 
 lever, which promotes the absorption of the mordant into the cloth, and at the same 
 time removes the superfluous liquid. The pieces are generally passed twice through, 
 the pressure being stronger the second time. Red liquor, black liquor, and mixtures 
 of both can be applied by means of the machine with great uniformity. In 
 order that in drying the padded pieces there may not take place any accumu- 
 lation of the mordant, which would occasion spots in dyeing, the pieces are either 
 stretched out horizontally or they are passed on guide-rollers through drying-stoves. 
 The dried goods are washed, dunged, printed with the colour, washed, and raised if 
 necessary. This process is especially suitable for inorganic colours in buff, Prussian 
 blue, manganese or bistre brown, chrome yellow, and chrome green. 
 
 Printing with Resists. Sometimes there are applied to the cloth, at places which 
 are to remain white, certain substances which prevent dyeing. Such substances are 
 known as resists. In most cases a resist serves to prevent the absorption of indigo- 
 in the vat at the reserved places. In tissue-printing there are four different kinds of 
 resists the fatty, the white, the coloured, and the so-called lapis. 
 
 Fatty Resists are used chiefly in silk-printing, sometimes in woollen-printing, but 
 rarely on calico. They consist generally of wax or ceresine, or a mixture of resin and 
 tallow, or resin and paraffine, sometimes of an emulsion of tallow, palm oil, and gum 
 mucilage. Now and then fatty resists are used on cottons. If, e.g., a red or violet 
 pattern has been printed upon a white ground, dyed, and raised, and it is intended to 
 produce also a lighter purple colour on the ground, the pattern is provided with a 
 fatty resist, and the pieces are taken through a dilute iron mordant, proceeding 
 exactly as in the madder style. As the designs are covered, the colours reappear, 
 after the second raising, with their original shade. 
 
 White Resists. A very common constituent of white reserves is a copper salt, blue- 
 stone, or verdigris, which is thickened with pipe-clay and gum. On dyeing up in the 
 vat, its alkali decomposes the salt of copper, forming at once insoluble indigo-blue from 
 the dissolved indigo-white. 
 
 Coloured Resists not merely prevent the indigo-blue from being deposited on the 
 reserved parts, but also produce other colours in these reserved places. In this 
 manner buff and chrome-yellow designs can be obtained on a blue ground. 
 
 Lapis Style. This manner of printing consists in a combination of the madder 
 style and of indigo-vat colours. The mordants intended for the madder colours are 
 mixed with the resists, printed, dyed in the vat to the shade intended, and then dyed 
 in the madder or in the bark beck, and the whites are cleared. The lapis style 
 yields not only very fast, but very manifold, products, in consequence of the numerous 
 modifications which it admits of, and it is hence extensively used. It derives its name 
 from a certain resemblance of the patterns thus obtained upon a blue ground to- 
 lapis lazuli. The white resists in this style have not merely to protect certain parts 
 from the action of the vat, but to keep them unmordanted, so as to consume as little 
 colour as possible in the madder beck. In this case mercuric chloride is preferred to- 
 copper sulphate. 
 
 Two kinds of white resists are used in the lapis style. The one kind acts like the 
 ordinary resist containing copper oxide i.e., it covers, without exerting any action 
 upon, the mordants beneath, so that it may be safely printed over mordants for dark 
 or light reds without interfering with their subsequent action. The other kind 5 
 renders the mordant ineffective. To this latter kind belongs a resist made up of i| 
 kilo, sodium arseniate, i kilo, gum Senegal, 2 kilos, pipe-clay, and 4 litres water, with 
 which are incorporated by boiling 500 grammes olive oil and 375 grammes mercuric 
 chloride. The arsenic acid forms, with the ferric oxide and the alumina of the mor- 
 dants afterwards printed on, insoluble arseniates which have no affinity for the fibre. 
 A resist of the first kind is composed of a mixture of 0*5 kilo, gum Senegal, i 
 
SECT, vii.] DYEING AND TISSUE-FEINTING. 845 
 
 pipe-clay, 180 grammes olive oil, and 2 litres water, to which 180 grammes mercuric 
 chloride are added. 
 
 Discharges are to effect the local removal of the mordant printed upon the cloth by 
 means of thickened acids. On dyeing there is obtained a white design on a coloured 
 ground. Or an acid, by itself, or mixed with a mordant, is printed upon the cloth, 
 upon which a dark mordant is then padded and the piece is dyed. The parts printed 
 with the acid remain white, forming white designs on a coloured ground. 
 
 The acids used as discharges act upon the metallic oxides in the mordants and form 
 with them soluble salts, liberating the fibre from the mordant. The common mineral 
 acids (sulphuric, nitric, and hydrochloric) are otherwise suitable for this purpose, but 
 they are apt to weaken the fibre, whence organic acids (such as malic, citric, and 
 tartaric) are preferred, as they do not tender the fibre and have little action upon the 
 doctors and the rollers. Phosphoric and arsenic acid at sp. gr. 1*85 may be used 
 instead of tartaric acid, as can also hydrofluosilicic acid. Instead of i kilo, tartaric 
 acid there may be used from 1*25 to 1*5 kilo, of liquid phosphoric or arsenic acid. The 
 latter has the grave defect that it attacks the hands of the workmen, destroys the finger 
 nails, and is highly poisonous. Oxalic acid is commonly used in the proportion of 
 from 12 to 15 per cent, to tartaric acid. It has the property very important for the 
 preparation of steam colours of dissolving alumina and ferric oxide in the cold and 
 of re-depositing them at higher temperatures in an insoluble condition. 
 
 Stannic chloride may also be used in place of tartaric acid : 1 1 parts of the com- 
 mercial salt, as free as possible from acid, serve instead of 10 parts of tartaric acid. 
 Stannic chloride (with which lime is mixed, the quantity depending on the proportion 
 of acid) acts by liberating chlorine, forming calcium chloride, and separating tin 
 hydroxide. If an iron mordant has to be removed, stannous chloride is to be used, 
 which dissolves tho iron mordants in virtue of its reducing power, whilst stannous 
 oxide is converted into stannic oxide, which partly remains on the fibre. Hence, in 
 using tin salts as a discharge, it must be remembered that a tin mordant takes the 
 place of an iron mordant, and the colour produced in the dye beck will be modified 
 accordingly. 
 
 Discharges are thickened with gum Senegal and pipe-clay in order to obtain well- 
 defined outlines ; for heavy designs, dextrine may be used. 
 
 Discharges are often combined with ordinary mordants. Thus, if it is intended to 
 produce a red-and-white design upon a purple ground, the calico is padded with weak 
 black liquor, and, when dry, red mordant mixed with citric acid is printed on. The 
 iron mordant is thus removed at these places, and an aluminium mordant is sub- 
 stituted. A discharge is printed at the places which are to remain white, and the cloth 
 is cleansed with milk of lime, dunged, dyed in the madder beck, and raised. 
 
 China-blue Style. This style (otherwise known as Fayence blue) was often used 
 for producing blue designs on a white ground. The process is very old, and has been 
 used in India for centuries. It is a topical style, which can be effected only with 
 indigo. Its peculiarity is that the indigo is applied in the insoluble state, dissolved, 
 and then fixed on the fibre. 
 
 A very intimate mixture of finely ground indigo and copperas is printed upon a 
 white ground, and it is then dissolved and reduced by alternate treatment with lime- 
 water and solution of copperas. The indigo penetrates, as indigo-white lime, into the 
 fibre, and in contact with the air the indigo-white is oxidised to indigo-blue, rendered 
 insoluble, and thus fixed upon the fibre. To improve the action, orpiment is commonly 
 added, which acts similarly to copperas and prevents higher oxidation. 
 
 Pencil blue is distinguished from china blue as follows : In the latter, indigo-blue 
 is printed upon the fibre, and is then converted into indigo-white, whilst in pencil blues 
 an indigo- white, already prepared, is printed upon it. To obtain mere concentrated solu- 
 
846 CHEMICAL TECHNOLOGY. [SECT, viu 
 
 tions, orpiment is used, which reduces indigo-blue just as copperas does. The arsenical 
 or orpiment vat gives a very intense colour, which is thickened with gum, and applied to 
 the tissue by means of small pencils, whence the name pencil blue. Instead of the 
 or orpiment vat the tin-crystal vat may be vised for the production of a pencil blue. 
 
 The discharge style aims at the local removal of a colour already printed on by 
 means of oxidising agents, whilst the discharge mordants act, not upon the colouring 
 matter, but upon the mordant ; either removing it, or cancelling its character as a 
 mordant. 
 
 As a discharge for indigo there is used chromic acid or ferric chloride, or a 
 mixture of potassium ferricyanide with soda ; for madder, chlorine is used. 
 
 To produce a white design on a blue ground, according to Koechlin's process, potas- 
 sium chromate is used, which, when decomposed by oxalic or tartaric acid, decolorises 
 the indigo-blue by supplying oxygen, and converts it into soluble isatine, whilst the 
 chromic acid is reduced to chromium sesquioxide. Instead of chromic acid, Mercer 
 proposes to destroy the indigo with a mixture of potassium ferricyanide with concen- 
 trated caustic soda (Mercer's liquid). To this end the cloth dyed blue in the vat is 
 saturated with a solution of ferricyanide, and caustic soda thickened with starch gum 
 is printed on. The alkali converts the ferricyanide into ferrocyanide, and the indigo- 
 blue is transformed into isatine by the oxygen liberated. 
 
 In order to obtain a white design upon a turkey-red ground, the property of chloride 
 of lime is utilised, not to destroy the colouring-matters by itself, but to act only in 
 proportion as chlorine is evolved by the action of acids. For this purpose the parts 
 to be discharged are printed with an acid mordant and taken through chloride of lime. 
 
 The discharges are put together in such a manner as to constitute the mordant 
 for subsequently dyeing the discharged spots ; they may also contain colours to dye 
 the decolorised parts. For white there is printed on an acid mixture of tartaric 
 and oxalic acid and lime-juice thickened with gum and pipe-clay; for yellow, a 
 similar mixture containing lead nitrate and sightened with a little potassium chromate. 
 The calico printed with the discharge passes into the chloride of lime liquor, contained 
 in a wooden cistern lined with sheet-lead. On leaving this cistern the cloth passes 
 between a pair of rollers, when it is suspended in flowing water, rinsed, and dried. If 
 the discharge contain lead nitrate to produce white on a red ground, the pieces are 
 reeled through a solution of potassium chromate, and, after rinsing, they are raised by 
 a passage in dilute hydrochloric acid. 
 
 According to Steinbach, the solution of chloride of lime is printed on with the 
 cylinder and the cloth is dried on steam drums, when the chloride of lime is converted 
 into calcium chloride and chlorate, the latter giving off oxygen at elevated temperatures 
 and destroying the alizarine. This process has the defect that the reds and the roses 
 are turned distinctly brown. 
 
 For printing aniline blacks on dyed cottons the aniline-black colour is made up with 
 i^- kilo, potassium chlorate dissolved in 40 litres of water ; then there are added 4 litres 
 solution of potassium ferrocyanide (28 : 100) and 2*6 kilos, aniline hydrochlorate pre- 
 viously mixed with the quantity of aniline oil needed for complete neutralisation. The 
 bleached goods are taken through this liquid, dried, oxidised in the steaming-machine 
 so that they issue dark green ; then they are taken through a chrome bath at 80 (i litre 
 water to 10 grammes potassium dichromate, 5 grammes soda, and 5 grammes sodium 
 chloride), washed, and printed on as a discharge. For whites : 10 kilos, calcined starch 
 with 6 litres water and 16 kilos, calcium acetate (24 Tw.), boiled; then there are 
 added 5 kilos, sodium acetate and 5 kilos, sodium-lye at 30 Tw. For yellows: 
 10 kilos, chrome yellow (paste), 6 kilos, albumen water, 2 kilos, sodium acetate, 
 o'3 kilo, soda-lye at 30 Tw. For reds: 16 kilos, cinnabar, 2 kilos, glycerine, 2 kilos. 
 water, 2 kilos, sodium acetate, 8 kilos, albumen water. 
 
SECT, vii.] DYEING AND TISSUE-PRINTING. 847 
 
 Steam Colours. For a long time there were known only two methods of fixing 
 colouring -matter on the fibre i.e., either the printing matter was printed on, which, like 
 indigo in the china-blue and pencil-blue styles, had been made soluble and was again sepa- 
 rated on the fibre as insoluble indigo-blue ; or, recourse was had to discharges, to discharge 
 mordants, to resist, and discharge styles, upon which the various styles are founded 
 which have been described in the previous sections. Not until 1 740 was the attempt 
 made to print on the colouring-matters themselves, and to obtain colours which were 
 afterwards known as application colours. They did not, however, bear washing, and had 
 so little fastness that their general introduction was attended with great difficulty. 
 Gradually it has been found practicable to fix them by steaming, and thus create the 
 steam style, which now plays so important a part in tissue-printing. 
 
 The colours almost exclusively used as steam colours require the co-operation of a 
 mordant. Some of them are thickened, printed upon the mordanted cloth, and then 
 steamed. In other steam colours the colouring-matters and mordants are printed 
 together, but they are always added to a body which holds the lake in solution or hinders 
 the combination of the colouring-matter and the mordant to a lake until the operation 
 of steaming. To the latter class of bodies belongs stannic chloride, which is resolved 
 by watery vapours into hydrochloric acid (which is either volatilised or neutralised), 
 and into stannic oxide, which is deposited on the fibre. Aluminium chloride acts in the 
 same manner. Acetic acid is also used in the production of steam colours, and in con- 
 siderable quantity since the introduction of artificial alizarine. Acetic acid is added 
 to the mass in order to keep the colouring-matter in solution until the cloth is 
 steamed. .Recently copper chromate is often used, and proves to be an excellent oxid- 
 ising agent. The steaming is generally effected under tension in the apparatus of 
 Mather & Platt. 
 
 Steam blue is obtained by printing a solution of potassium ferrocyanide and 
 tartaric acid with small quantities of sulphuric acid, thickened with starch, drying, 
 airing, and steaming for half an hour; there is formed hydroferrocyanic acid, which is 
 decomposed at high temperatures, yielding Prussian blue, which is deposited upon the 
 cotton fibre. 
 
 Steam colours may also be obtained from reduced indigo when the indigo-white 
 is precipitated by hydrochloric acid from the copperas vat and mixed with magnesia 
 or with magnesium sulphate with an addition of alkali. A good blue may be ob- 
 tained with 5 kilos, precipitated indigo, 5 litres of gum water, and o - 6 kilo, of mag- 
 nesia. 
 
 Steam green is produced by mixing blue with a salt of lead, printing on the 
 mixture, and dyeing up the cloth after washing and steaming in a beck of potassium 
 chromate. 
 
 Steam reds are at present obtained with artificial alizarine. 
 
 Schlieper and Baum propose a very curious process of indigo printing. The first 
 step is the careful grinding of an indigo mixture of 25 kilos, indigo, 100 litres water, 
 50 litres soda-lye at 1-35 sp. gr., and 58-33 kilos, of solid caustic soda. The colours 
 consist of 
 
 Dark Blue. Medium. Light. 
 
 British gum .... 3-00 ... 3' 3' 
 
 Maize starch . . . . 1-50 ... i'5o ... i'SO 
 
 Water 375 375 - 375 
 
 Soda-lye (sp. gr. i -35) . . 16-00 ... 28-00 ... 40-00 
 
 Indigo mixture . . . 30-00 ... iS'oo ... 6'oo 
 
 Dark blue contains 55-5 grammes indigo per kilo, of colour, medium blue 33^3 
 grammes, and light blue in grammes. These colours are printed on the tissue, which 
 has been padded with a solution of i kilo, glucose in 4 litres water and then well 
 Iried. After printing, the goods are rapidly dried at from 60" to 70 and then taken 
 
848 CHEMICAL TECHNOLOGY. [SECT. vii. 
 
 through a small steam chest for from fifteen to twenty seconds, so that the indigo is 
 reduced. They are then passed through cold water for two minutes. 
 
 Precipitated sulphur is the only good resist under the new steam blue, 150 grammes 
 sulphur to I litre of thickening resists even the darkest blue. A yellow resist consists 
 of 220 grammes cadmium chloride, 140 grammes precipitated sulphur, and i litre 
 thickening. 
 
 A red resist consists of red liquor, salt of tin, calcined starch, and 150 grammes 
 sulphur per litre; buff and similar colours have from 130 to 140 grammes sulphur 
 to i litre thickening. 
 
 For a light blue, soda-lye of sp. gr. 1*35 thickened with British gum and starch is 
 printed on cloth which has been saturated with glucose, steamed for fifteen seconds, dried, 
 and the indigo colour padded on with the cylinder. The glucose undergoes a decom- 
 position under the action of the caustic soda, so that the colour is only developed up to 
 a light blue. Yery fine designs can be produced in indigo-discharge colours on grounds 
 dyed in turkey red or prepared with turkey-red mordant. 
 
 For a turkey-red mordant 40 kilos, of dry aluminium hydrate is heated for three 
 hours with 64 litres soda-lye at 60 Tw. It is made up with water to 300 litres, neu- 
 tralised with 8 litres hydrochloric acid at sp. gr. 1-15, and water added to make up a 
 volume of 620 litres. 
 
 A mordant for padding is obtained by diluting 4 litres of the above mixture with 
 i litre of water. The cloth padded in this liquid is dried on the drum, when it turns 
 yellow, but on hanging in an oxidation chamber the original colour returns. The 
 pieces are left till the following day, taken through cold water in a cistern fitted with 
 rollers, washed well, and lastly passed through a chalk beck at a hand-heat in order 
 to convert the sodium bi- or tri-aluminate into calcium aluminate. The mordant, 
 now ready for dyeing, bears sulphuric sours at n'5 Tw. without losing much of 
 its efficacy, and the red thus produced behaves similarly. The production of the 
 indigo-discharge styles is founded upon this property. The tissue thus mordanted, 
 whether dyed or not, is prepared in glucose, and the indigo colour is then printed 
 on. The pieces are then steamed, washed, aged for a few .minutes in the air, passed 
 through sulphuric sours at ii'5 Tw. for from ten to twenty seconds, washed, taken 
 through weak soda, and washed again. The discharged turkey-red pieces are 
 .soaped at a boil. The alizarine present below the indigo is dissolved, and the blue 
 appears. 
 
 In order to obtain white upon turkey red and indigo-blue the dark indigo colour 
 and a strong soda-lye are printed on, proceeding otherwise as indicated above. Or 
 strong soda-lye may be printed on the turkey-red mordant, steamed to destroy the 
 glucose, dried, and the indigo colour printed on. A light blue appears when the 
 indigo is superimposed on the whites. 
 
 Goppelsroder proposes to produce patterns in indigo and turkey -red by means of 
 electrolysis. 
 
 In order to utilise the mordanting action of metallic sulphides in steam colours, 
 Schmid thickens those metallic salts whose sulphides can be precipitated by means 
 of sodium hyposulphite (thiosulphate) along with the latter salt and the colouring 
 matter, and prints them. On steaming, an insoluble sulphide is precipitated, and along 
 with it the colouring matter. In this manner there may be fixed in one operation the 
 cadmium, lead and copper sulphides, methylene blue, malachite green, dimethylaniline 
 violet, &c. The tones obtained correspond to those of the sulphides and the colouring 
 matters employed. Thus, cadmium sulphide with methylene blue forms a green ; with 
 aniline green, a yellowish green ; &c. These colours bear soaping fairly well. A bright 
 yellowish steam green is, e.g., obtained with 950 grammes tragacanth mucilage (200 
 grammes per litre), 200 grammes crystalline cadmium nitrate, 30 grammes crystal 
 
SECT. VIL] DYEING AND TISSUE-PRINTING. 849 
 
 lised sodium thiosulphate, 20 grammes malachite green, 10 grammes acetic acid at 
 10 Tw., and 150 c.c. water. 
 
 Along with the steam styles rank the processes used, both in printing and dyeing, 
 to produce a metallic appearance on tissues. This operation is called coppering. The 
 cloth is covered with an exceedingly thin layer of metallic sulphide, when the colour 
 comes up in thin layers, resembling the elytra of certain beetles. 
 
 According to Barlow's process, the pieces are steeped in a solution of copper acetate 
 or nitrate, or corresponding salts of lead, or bismuth, pressed, washed, and then 
 steamed for five to thirty minutes, hydrogen sulphide being mixed with the steam. 
 After steaming, the goods are washed and dried. 
 
 Topical or application colours include such as are fully formed when printed, and 
 are freed from the thickenings and acid salts by washings, so that the colours appear 
 intimately combined with the fibre. Some such colours (I.) are applied in solution and 
 gradually pass into the insoluble state upon the fibre, and thus become combined with 
 it and rendered able to resist washing. Others (II.) indeed, the most are printed 
 in the insoluble state, and are thickened with plastic substances, by means of which 
 they adhere to the fibre. The chief difficulty in producing such colours consists in find- 
 ing thickeners which give the colours the violet lustre, and which best resist water. 
 
 Examples of Class I. (" Spirit Colours "). According to Schmid, we obtain, e.g., a 
 fine soap-fast chrome yellow by printing 250 grammes tragacanth water (200 grammes 
 per litre), 250 grammes lead nitrate, 5 50 grammes barium chromate, and 50 grammes 
 water, and subsequent steaming. Red and rose are obtained from red wood and a 
 mixture of stannic and stannous oxides. The red wood (generally sapan) is used 
 either as a decoction or as a solution of the solid extract, to which a preparation 
 of tin. is added, or a lake is made of the red wood and dissolved in stannous chloride. 
 The oxide of tin, separated from the tin compound, deposits on the fibre and gradually 
 takes up the colouring matter. 
 
 Madder lakes are also often used for obtaining such colours. 
 
 A topical black is often obtained from a decoction of logwood and galls, thickened, 
 and mixed with an iron mordant. 
 
 The second group of these colours (pigment style) includes those which are applied 
 in an insoluble state ground up with albumen or with an oil varnish. Such colouring 
 matters are ultramarine, umber, chrome yellows, Guignet's green, vermilion, shearings 
 from dyed woollen cloth, metallic powders, &c. As examples may be mentioned ultra- 
 marine and gold and silver printing. 
 
 In the use of ultramarine in printing, the earliest agent at once for fixing and 
 for thickening was albumen, often mixed with gum Senegal, both from economical 
 reasons and that the mixture may print more easily. Some printers fix ultramarine 
 simply by a passage through boiling water, and thus obtain purer, but less saturated, 
 colours than by steaming. But fixation by steam is necessary if other pigments, such 
 as Schweinfurt green or violet lakes, are to be fixed along with the ultramarine. 
 Chrome orange and chrome green require peculiar care, as all substances must be 
 avoided which tend to convert copper or lead into sulphides. Colours containing oils 
 are to be rejected, as well as acids and acidifiable substances which may decompose the 
 albumen and evolve from it hydrogen sulphide. 
 
 For printing with gold and silver, isinglass is dissolved in water and brandy ; on the 
 other hand, powdered mastic is dissolved in alcohol, and the two are mixed. Red bole, 
 previously ground up with brandy, is stirred into the mixture, which then serves as a 
 ground for gold. For silver, pipe-clay is used instead of bole, and the mixture is printed 
 in the ordinary manner. Immediately after printing, leaf gold or silver is applied to 
 the printed parts, which are then pressed down with cotton. When dry, the superfluous 
 
 3 H 
 
850 CHEMICAL TECHNOLOGY. [SECT. vn. 
 
 metal is removed with a brush. In order to print with a metallic powder, such powder 
 is stirred into the above-mentioned mixture instead of the bole or pipe-clay. Or the 
 requisite parts of the design are moistened with a solution of gold, which is then con- 
 verted into the reguline state by means of reducing agents. 
 
 Printing with Coal-tar Colours. These colours may be printed and fixed upon 
 cotton tissues in several manners. Either (i) the thickened mordant is printed on, fixed 
 by drying and airing or by steaming, and afterwards dyed in a beck of the colouring 
 matter, when the colour attaches itself only to the mordanted places. If it is desired 
 to keep the ground clean, the mordant is padded on locally. Or (2) the mordant is mixed 
 with the dye, thickened, printed, dried, and steamed. After printing, the pieces are 
 washed and dried. 
 
 The substances used as mordants are numerous albumen (egg or blood), preparations 
 of gluten, caseine dissolved in caustic alkali or in acetic acid, gelatine or tannate of 
 gelatine, tannin, fatty oils and preparations of oils (sulpholeic acid, sulphopalmitic and 
 sulphoglyceric acids), and certain gum-resins, e.g., shellac dissolved in borax. 
 
 In aniline printing by means of gluten, the gluten of wheat is left to itself until it 
 becomes slimy. It is then saturated with sodium carbonate and thus rendered in- 
 soluble, washed, redissolved in caustic soda at sp. gr. ro8, and the solution is diluted. 
 When the cloth has been printed or padded with this liquid and dried, it is steamed and 
 rinsed. The solution of the aniline colour is then used as a dye beck through which 
 the pieces are taken. Or the colour is printed upon the cloth prepared as before, which 
 is then steamed again. 
 
 According to certain colour manufacturers (not named), levulates of the colouring 
 bases or mixtures of levulic acid with the colouring matters may be used for printing. 
 Such mixtures are obtained by grinding in a wet mill levulic acid with the colouring 
 base (dry, or preferably rather moist) until a complete mixture is obtained. Thus the 
 goods may be printed with the following mixture : 
 
 183 parts printing blue (induline) as a 25 per cent, paste 
 500 ., levulic acid 
 40 ., emulsion of oil 
 630 ,, acetic-starch thickening 
 100 tragacanth tannin (50 parts tragacanth mucilage and 50 parts 
 
 tannin), 
 developing the colour by steaming the printed cloth. 
 
 " Levuline " blue is obtained by adding i part moist induline base to 3 parts levulic 
 acid and mixing intimately. 
 
 According to Botsch, the Congo colours are prepared for printing as follows : 
 
 Benzoazurine Steam Blue. 
 
 Water 750 parts 
 
 Wheat starch 100 
 
 Benzoazurine G- ) 50 
 
 Water . . j 250 
 
 Chrysamine Steam Yellow. 
 
 Water 750 parts 
 
 Wheat starch . 100 
 
 Chrysamine ) 50 
 
 Water / 250 
 
 These colours are printed on prepared cloth, yielding respectively blue or yellow, or 
 by a mixture of the true indigo-blue to olive according to the proportions ; a very nice 
 blue may be produced by adding Victoria blue B or Nicholson blue 6B. The goods 
 
SECT, vii.] DYEING AND TISSUE-PRINTING. 851 
 
 are steamed, according to shade, from thirty minutes to an hour. These colours are all 
 fast, especially if chrysamine predominates. They may also be used for wool. The 
 stilbene dyes (Leonhardt & Co.) may be used in the same manner. 
 
 In fixing by means of chrome, the following, e.g., colour may be used for blue : 
 
 Indophenol 2000 grammes 
 
 Acetic acid (8*25 Tw.) 10 litres 
 
 Tin acetate (31 Tw.) 10 
 
 Gum 8000 grammes 
 
 'The mixture is boiled and stirred for half an hour. After printing, the goods are aged 
 for twenty-four hours, steamed fortwe minutes, preferably in Mather & Platt's apparatus, 
 chromed at 50 for two minutes in a beck of 10 grammes potassium dichromate per 
 litre water, lastly washed and soaped. Indophenol is less advantageous than the two 
 following colours. 
 
 If gallocyanine (from gallic acid) is used, excellent results are obtained with the 
 following mixture : 
 
 Wheat starch 150 grammes 
 
 Gallocyanine paste (commercial) . . i litre 
 
 Tragacanth mucilage . . . . 075 litre 
 
 Acetic acid (i o Tw.) 0-25 
 
 Turkey-red oil 0*25 
 
 Boil, stir till cold, and add ^ litre chrome acetate at 50 Tw. and 60 grammes potassium 
 ferrocyanide. The colour is printed, steamed, and treated as usual. 
 
 For alizarine blue there are used 120 grammes of a solution containing too grammes 
 starch per litre of water, 15 to 20 grammes alizarine blue S, and 30 to 40 grammes 
 .solution of chromium acetate (14 Tw.). In place of starch, tragacanth or gum may be 
 used as a thickener. The printed pieces may be steamed without pressure for ten to 
 twenty minutes, when the blue is found fully developed and the pieces are washed, 
 soaped, and dried. The steaming may be effected in two or three minutes in the 
 continuous apparatus. If the bisulphite compound of alizarine blue is used, the colour 
 in the beck is completely used up. The colour produced resists light, soap, and chlorine, 
 and is in this respect faster than indigo. Soluble alizarine blue has, in point of fact, 
 superseded both indigo and ultramarine in a variety of applications. 
 
 Propiolic acid is now little applied. 
 
 Auramine is printed with tannin and tartaric acid upon vegetable fibre ; the colour 
 is very fine. 
 
 Printing with aniline black has been previously mentioned. 
 
 Attempts have been made, especially by T. Holliday & Sons, to produce azo colours 
 directly upon the fibre, and these experiments have been attended with encouraging 
 results. 
 
 Finishing. After printing, the goods are finished i.e., taken through starch becks 
 to give the cloth more firmness, dried, folded, and pressed. In finishing furniture 
 prints, white wax or paraffine is added to the solution of starch. In order to give 
 printed muslins the admired velvety feel, there is added to the starch, whilst boiling in 
 water, a small quantity of spermaceti, paraffine, or stearic acid. 
 
 Linen-printing is confined to the production of vat-blue cloths with light blue or 
 white designs, 
 
 In woollen and worsted printing, topical styles are in use, and the colours are fixed 
 by steaming.* 
 
 For producing a discharge blue upon azo colours, the woollen tissue is first dyed 
 
 * Space does not allow a description of the methods used for printing mixed cotton and woollen 
 goods. 
 
852 CHEMICAL TECHNOLOGY. [SECT. vn. 
 
 with ponceau or any desired azo colour. A mixture of solid violet, indophenol, arid an 
 alkaline reducing agent is then printed and steamed ; the azo colour undergoes the 
 characteristic splitting up on reduction, whilst the blue colouring matters, reduced 
 to leuko compounds, penetrate into the fibre, and, on subsequent exposure to the air, 
 reproduce an insoluble fast blue on a red ground. The following is the composition of 
 the colour : 
 
 Indophenol in powder 4 kilos. 
 
 Tin pulp 10 litres 
 
 Thick dextrine water (2^ kilos, per litre) . . .14 
 
 Water 6 
 
 Soda crystals 4 
 
 Solid violet, B.S 10 
 
 Glycerine 5 
 
 The mixture is heated to 60 for half an hour until completely reduced, which is 
 shown by the yellowish colour of the mixture. It is then printed, steamed, and fully 
 developed by ageing. 
 
 The processes of silk-printing are generally the same as those of cotton -printing, 
 but greater care has to be taken to keep the whites clear. Either topical colours are 
 applied and fixed by steaming, or various mordants are printed and dyed in the beck 
 as in the madder style. 
 
 A peculiar style of silk-printing is founded on the property of nitric acid to colour 
 silks and woollens a permanent yellow, to destroy most colours, but to act upon fats 
 and resins only after some time. This kind of printing is called mandarining. In 
 order to effect a yellow discharge on vat-blue grounds, the silks are printed with a 
 resist of resin and fat, steeped for two to three minutes in an acid flot of i part water 
 and 2 parts nitric acid at 50, and placed in running water. After this operation the 
 silk is boiled off in a soap bath mixed with potash. The parts which have not been 
 resisted are of a fine yellow. 
 
 Examination of Dyed and Printed Textiles. In order to test the fastness of the 
 dye, the sample is first rubbed upon white paper, which must not be stained in the 
 slightest. To pure water it must give off no colour. To ascertain the effect of heat, a 
 swatch is laid between white papers and smoothed with a flat iron. To find the action, 
 of light, the swatch is covered with a piece of black pasteboard, or of sheet metal in 
 which two round holes have been cut, and thus exposed to the sun or to an electric light. 
 
 Colours which appear unchanged after they have been steeped in 10 per cent, 
 solutions of sulphuric acid, caustic soda, and ammonia may be pronounced fast. Fast 
 colours should not be altered by boiling for half an hour in a i per cent, solution of 
 soap. 
 
 Whether, in the production of printed calicoes, the colour has been generated within 
 the fibre, or whether it has been applied pre-formedand fastened by means of albumen, 
 or whether both these procedures have come into play, can best be determined by 
 means of the microscope. 
 
 If the tissue is teased out with a needle so far that the individual fibrillse are 
 isolated, these latter appear uniformly coloured and translucent if the materials 
 forming the colour have been applied in a dissolved state. In many colouring matters 
 there appears a granular texture, the characteristic form of the fibre is unchanged, and 
 the colouring matter appears everywhere uniformly deposited within it. In the 
 albumen processes the fibre is not dyed, but at numerous points there appear single 
 coloured rays of coagulated albumen adhering externally. Here and there such may 
 be seen detached from the fibre in consequence of the maceration. 
 
 Lenz, Martin, Hummel, and Lepetit have given instructions for detecting the 
 colouring matters on the fibre. (See page 854, et. seq.} The following reagents are 
 
BECT. vii.] DYEING AND TISSUE-PRINTING. 853 
 
 employed: Sulphuric acid 154 Tw., hydrochloric acid 32 Tw., soda-lye at 10 per 
 cent., the strongest ammonia, and equal parts of concentrated hydrochloric acid and 
 stannous chloride (pp. 854-861). 
 
 For further information on the tinctorial industries, the reader is referred to : 
 A Practical Handbook of Dyeing and Calico-printing. By William Crookes, F.R.S. London : 
 Longmans, Green & Co. Dyeing and Calico-printing. By the late Dr. F. Crace-Calvert, F.K.S. 
 Edited by Dr. J. Stenhouse, F.R.S., and C. E. Groves, F.C.S. (London and Berlin.) Manchester : 
 Palmer & Howe. Dyeing and Tissue-printing. By W. Crookes, F.R.S. London : G. Bell & Sons. 
 The Dyeing of Textile Fabrics. By J. J. Hummel, F.C.S. London: Cassell & Co. (Limited.) 
 Dyeing : comprising tJie Dyeing and Bleaching of Wool, Silk, Cotton, <&c. By Antonio Sansone. 
 London: Hamilton, Adams & Co.; Manchester: A. Heywood & Son. The Printing of Cotton 
 Fabrics. By Antonio Sansone. London : Hamilton, Adams & Co. ; Manchester : A. Heywood & 
 Son. Chemistry of the Coal-tar Colours. By Dr. R. Benedikt and Dr. E. Knecht. London : G. Bell 
 & Sons. Anthracene : its Constitution, Properties, Manufacture, and Derivatives, with their Applica- 
 tions in Dyeing and Printing. By G. Auerbach. Edited by W. Crookes, F.R.S., &c. London : 
 Longmans, Green & Co. Manual of Colours and Dyewares. By J. W. Slater. London : Crosby 
 Lockwood, & Co. Dictionary of Calico-printing and Dyeing. By C. O'Neill. London : Simpkin, 
 Marshall & Co. 
 
 PAPER MANUFACTURE. 
 
 History of Paper. Paper is in reality a thin felt of vegetable fibres, mechanically 
 and chemically clarified, crushed, and torn into a pulp suspended in water. This pulp 
 is spread equally in thin layers, drained, pressed, and dried into the compact substance 
 we call paper. 
 
 Materials of Paper Manufacture. The chief materials of paper manufacture are 
 the waste rags from flax, hemp, silk, wool, and cotton. The linen rags are mostly in 
 request for making the best and most durable white writing and printing paper. Silk 
 and woollen rags are unfit for this purpose, as the bleaching material will not act upon 
 animal substances. Cotton in a raw state requires less preparation than hemp. Bags 
 are classed under different denominations fines, seconds, and thirds, the latter com- 
 prising fustians, corduroys, stamps, or prints, as they are technically termed. The 
 waste refuse from the wadding machine used in cotton spinning is employed for 
 scribbling paper. Bibulous papers, such as blotting and filter papers, are made from 
 woollen rags, on account of their open texture ; cotton rags, also, make a spongier, 
 looser paper when unmixed with linen. 
 
 Substitute for Rags. The consumption of paper in Europe has more than doubled 
 within the last fifty years, and, owing to the insufficient supply of rags, substitutes had 
 to be found in straw and wood. The Chinese first used vegetable pulp for paper 
 manufacture. The inner bark of the bamboo is particularly celebrated as affording a 
 paper yielding the most delicate impressions from copper-plate, and this paper was 
 originally called India-proof. The Chinese also use the bark of the mulberry and elm 
 trees, hemp, rice-straw, and wheat. Among the straw species appears the maize 
 (Indian corn), from the fibre of which a paper is made that for purity and whiteness 
 cannot be equalled. Also the Andropogon glycichylum, or Sorghum saccJiaratum, a 
 native of North America, is used. In fact, nearly every species of tough fibrous 
 vegetable, and even animal, substance has been tried ; but of these straw has been 
 most successfully applied, in combination with linen and cotton rags, when the silica 
 contained in the straw is destroyed by means of a strong alkali. If the straw is not 
 properly prepared the paper will be brittle and unfit for use. The use of straw is not 
 very extensive, owing to the extra expense of preparation, and its waste under the 
 process. 
 
 Esparto grass (the fibre of the Macrochloa tenacissvma) and certain soft woods are 
 very extensively used. 
 
 Straw, chopped up, is boiled with soda-lye in a revolving boiler, and is then washed 
 
854 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vii.. 
 Red Colouring- 
 
 Colouring Matter. 
 
 HC1. 
 
 H,SO*. 
 
 . 
 
 NaOH. 
 
 Orseilline B B. 
 
 Fibre violet-black, then 
 
 Fibre black-blue ; liquid 
 
 Fibre violet ; liquid 
 
 (Bayer & Co.) 
 
 black ; liquid faint in- 
 
 indigo, reddish violet 
 
 reddish violet. 
 
 
 digo. 
 
 with water 
 
 
 Congo red 
 
 Dilute HC1 : Fibre blue- 
 
 Fibre blue-black ; dis- 
 
 Fibre scarcely 
 
 (Berlin Aniline Co.) 
 
 black. 
 
 solves dark blue on 
 
 changed. 
 
 
 Strong HC1 : Liquid 
 
 stirring. 
 
 
 
 colourless 
 
 
 
 Benzopurpurine I-B. 
 
 Dilute : Fibre red -brown ; 
 
 Fibre black-blue ; liquid 
 
 No action. 
 
 
 liquid colourless. 
 
 do., on dilution red- 
 
 
 
 Strong: Fibre dark 
 
 black. 
 
 
 
 brown. 
 
 
 
 Benzopurpurine II-B. 
 
 Dilute : Fibre blue-black ; 
 
 Fibre black-blue ; liquid 
 
 No action. 
 
 
 liquid colourless. 
 
 dark blue, blue on dilu- 
 
 
 
 
 tion. 
 
 
 Delta purpurine G. 
 
 Dilute : Fibre brown-red ; 
 
 Fibre blue-black ; liquid 
 
 No action. 
 
 
 liquid colourless. 
 
 dark blue, on dilution 
 
 
 
 Strong : Fibre greenish 
 
 grey, then red-brown. 
 
 
 
 black. 
 
 
 
 Delta purpurine 56. 
 
 Dilute: Fibre red-brown. 
 
 Fibre dark brownish 
 
 No action. 
 
 
 Strong : Fibre olive- 
 
 olive; liquid dirty green, 
 
 
 
 black. 
 
 turning reddish on 
 
 
 
 
 dilution. 
 
 
 Brilliant Congo. 
 
 Dilute : Fibie red-brown ; 
 
 Fibre blue-black ; liquid 
 
 No action. 
 
 
 liquid colourless. 
 
 blue, on dilution purple- 
 
 
 
 Strong : Fibre reddish 
 
 violet. 
 
 
 
 black- violet. 
 
 
 
 Direct red. 
 
 Dilute : Fibre black- 
 
 Fibre black-blue ; liquid 
 
 Fibre darker and 
 
 
 violet. 
 
 black-violet, grey-blue 
 
 rather bluer ; 
 
 
 Strong : Fibre blue ; liquid 
 
 on dilution. 
 
 liquid faint brown- 
 
 
 colourless. 
 
 
 red. 
 
 Naphthylene red. 
 
 Fibre dark black-green. 
 
 Fibre and liquid blue- 
 
 Scarcely any action. 
 
 
 
 black. 
 
 
 Eosazurine B. 
 
 Dilute: Fibre dark purple- 
 
 Fibre and liquid dark 
 
 No action. 
 
 
 red. 
 
 blue, on dilution red- 
 
 
 
 Strong : Olive-green. 
 
 dish, and then greenish. 
 
 
 Congo-Corinth. 
 
 Fibre black. 
 
 Fibre black ; liquid dark 
 
 Fibre redder ; liquid! 
 
 
 
 blue, blue on dilution. 
 
 colourless ; wash- 
 
 
 
 
 ing restores ori- 
 
 
 
 
 ginal colour. 
 
 Hessian purple N. 
 
 Dilute : Fibre black ; 
 
 Fibre black ; liquid blue, 
 
 No action. 
 
 
 liquid colourless. 
 
 on dilution grey-blue. 
 
 
 Hessian purple B. 
 
 Strong: Fibre dark grey, 
 
 Fibre grey-black ; liquid 
 
 No action ; liquid 
 
 
 nearly black. 
 
 faint blue. 
 
 faint rose. 
 
 Azarine S. 
 
 Fibre gradually dark 
 
 Fibre darker ; liquid fine 
 
 Fibre more blue ; 
 
 
 brown-red ; liquid 
 
 red ; on dilution both 
 
 liquid bright 
 
 
 scarcely coloured. On 
 
 yellow. 
 
 cherry-red. 
 
 
 dilution colour of fibre 
 
 
 
 
 restored. 
 
 
 
 Azoeosine. 
 
 Fibre deep red-violet ; 
 
 As with HC1. 
 
 Fibre dirty orange. 
 
 
 liquid scarcely lilac. 
 
 
 
 
 Water restores colour. 
 
 
 
 Carmosine. 
 
 Dilute : no action. 
 
 Fibre violet-black ; li- 
 
 Fibre rather browner; : 
 
 
 Strong : Fibre deep red- 
 
 quid the same. 
 
 liquid light rose. 
 
 
 violet ; liquid faint 
 
 
 
 
 lilac. Washing restores 
 
 
 
 
 original colour. 
 
 
 
 * All the colours unattacked by NaOHT 
 
SECT. VII.] 
 
 Matters. 
 
 DYEING AND TISSUE-PRINTING. 
 
 855 
 
 NH 3 . 
 
 SnCl 2 +HCl. 
 
 Alcohol. 
 
 Other Reactions and Remarks. 
 
 Like NaOH. 
 
 Fibre decol. slowly 
 
 No action. 
 
 UNO, : Violet spot, disappears 
 
 
 in cold, quickly 
 
 
 on washing. 
 
 
 boiling. 
 
 
 
 No action. 
 
 Fibre blue-black, 
 
 No action. 
 
 HNO, : Blue-black spot ; red 
 
 
 then blue, then 
 
 
 restored by NH S . 
 
 
 grey, then dis- 
 
 
 HN0 2 : Fibre red-brown, 
 
 
 charged. 
 
 
 colour not restored by NH, ; 
 
 
 
 
 liquid becomes bluish red. 
 
 No action. 
 
 Fibre brown-red, 
 
 Traces of colour 
 
 HNO 2 : Fibre brown-black, 
 
 
 then rose, then 
 
 extracted. 
 
 Picric acid: Fibre red-brown.* 
 
 
 discharged. 
 
 
 
 No action. 
 
 Fibre blue- black, 
 
 No action. 
 
 HN0 2 : Fibre-violet black, then 
 
 
 then pale grey, 
 
 
 more violet. 
 
 
 then discharged. 
 
 
 Picric acid : Fibre dark brown 
 
 No action. 
 
 Fibre dark brown. 
 
 No action. 
 
 HNO 2 : Fibre violet-black ; 
 
 
 then lighter, then 
 
 
 violet red with NH S . 
 
 
 rose, lastly dis- 
 
 
 Picric acid : Fibre brown-red. 
 
 
 charged. 
 
 
 
 No action. 
 
 Fibre cinnamon 
 
 A little colour ex- 
 
 
 
 brown, then slowly 
 
 tracted. 
 
 
 
 discharged. 
 
 
 
 No action. 
 
 Fibre red- brown, 
 
 Trace of colour 
 
 HN0 2 : Fibre black; with 
 
 
 then discharged. 
 
 extracted. 
 
 NH, black-violet. 
 
 
 
 
 Picric acid : Fibre brownish. 
 
 Fibre fiery red ; 
 
 Discharged. 
 
 No action. 
 
 HN0 2 : Fibre red-brown ; not 
 
 liquid scarce 
 
 
 
 changed by NH 3 . 
 
 reddish. 
 
 
 
 Picric acid : A brown spot. 
 
 Extracts dye slightly 
 
 Fibre black, then 
 
 Liquid faint rose. 
 
 HN0 3 : Blue spot with green 
 
 that change of 
 
 grey, then dis- 
 
 
 margin. 
 
 colour. 
 
 charged. 
 
 
 HNO 2 : Fibre yellow-brown ; 
 
 
 
 
 NaOH turns the washed 
 
 
 
 
 fibre dark brown ; liquid 
 
 
 
 
 light brown. 
 
 No action. 
 
 Fibre deep purple- 
 
 Some colour ex- 
 
 HNO 2 : Dark yellow-grey,red- 
 
 
 red, then discharged. 
 
 tracted, red. 
 
 brown on washing, and 
 
 
 
 
 touching with NH g . 
 
 Fibre redder ; liquid 
 
 Fibre black, then 
 
 Liquid scarcely rose- 
 
 HNO 2 : Fibre black-blue ; 
 
 pale rose. 
 
 blue-grey, and 
 discharged. 
 
 coloured. 
 
 turns dark magenta-red 
 on touching with NH 3 . 
 
 No action. 
 
 Fibre black, then 
 
 Liquid scarce 
 
 HN0 2 : Fibre violet-black; 
 
 
 colourless. 
 
 coloured. 
 
 dark red-brown with NH r 
 
 
 
 
 Picric acid : Fibre brown. 
 
 Liquid pale rose. 
 
 Fibre reddish grey, 
 then colourless. 
 
 No action. 
 
 HNO 2 : Fibre dark violet ; with 
 NH S red-brown. 
 
 Like NaOH, but 
 fainter. 
 
 Fibre yellow on boil- 
 ing ; liquid yellow. 
 
 Liquid scarce rose. 
 
 Smells of alizarine oil ; ash 
 contains tin. 
 
 
 
 
 HNOj : No action. 
 
 
 
 
 HN0 3 : Orange spots. If NH 3 is 
 
 
 
 
 addedtothe yellow li quor with 
 
 
 
 
 SnCl, and HC1, turns violet. 
 
 Fibre scarlet ; liquid 
 scarcely coloured. 
 
 Very slight action in 
 cold ; on heating 
 
 No action. 
 
 HNO S : Brown spot, removed 
 by washing. 
 
 
 fibre colourless, 
 
 
 
 Fibre unchanged ; 
 liquid rose. 
 
 liquid colourless. 
 Slight action in cold, 
 discharged on 
 
 No action. 
 
 HNO S : Violet-brown spot, 
 removed by washing. 
 
 
 boiling. 
 
 
 
 are strongly attacked by hot soap-lye. 
 
856 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vii. 
 
 Colouring Matters. 
 
 HC1. 
 
 H 2 S0 4 . 
 
 NaOH. 
 
 Rhodamine. 
 
 Fibre dirty brick-red ; 
 
 As with HC1. 
 
 Fibre rather darker 
 
 
 liquid colourless. Fibre 
 
 
 and. bluer ; liquid 
 
 
 restored by washing. 
 
 
 colourless. 
 
 Primuline red. 
 
 Fibre dark red-brown ; 
 
 Fibre black-violet ; liquid 
 
 Fibre dirty red- 
 
 
 liquid faint red-brown. 
 
 dirty do., red on dilu- 
 
 brown. 
 
 
 
 tion. 
 
 
 Alizarine S. 
 
 Fibre orange; liquid 
 
 Fibre orange-brown ; 
 
 Fibre and liquid 
 
 
 light orange. 
 
 liquid orange, yellow 
 
 violet. 
 
 
 
 on dilution. 
 
 
 Alizarine S. (purple 
 
 Fibre brownish yellow ; 
 
 Fibre brown ; liquid 
 
 Fibre and liquid 
 
 shade with bi- 
 
 liquid yellow. 
 
 brown-red, yellow on 
 
 violet. 
 
 chromate). 
 
 
 dilution. 
 
 
 Yellow Colouring 
 
 Quinoline yellow. 
 
 Fibre yellow ; liquid 
 
 As with HC1. . 
 
 Fibre deeper yellow, 
 
 
 colourless, colour re- 
 
 
 then discharged, 
 
 
 stored by water. 
 
 
 restored by H 2 O. 
 
 Auramine. 
 
 Fibre nearly discharged ; 
 
 Fibre discharged ; liquid 
 
 Fibre and liquid 
 
 
 liquid colourless, yel- 
 
 colourless. 
 
 colourless, yellow 
 
 
 low partly restored by 
 
 
 colour partly 
 
 
 dilution. 
 
 
 restored by H 2 0. 
 
 Chrysamine. 
 
 Dilute : Fibre pale yel- 
 
 Fibre magenta -red: 
 
 Fibre dark orange ; 
 
 
 low. 
 
 liquid red-violet. 
 
 liquid scarcely 
 
 
 Cone. : Fibre red-brown ; 
 
 
 coloured. 
 
 
 liquid rose yellowed on 
 
 
 
 
 dilution. 
 
 
 
 Chrysophenine. 
 
 Dilute : No action. 
 
 Fibre brown, then deep 
 
 Fibre unchanged ; 
 
 
 Con. : Fibre black-violet 
 
 violet ; blue on dilution. 
 
 liquid scarcely 
 
 
 liquid scarcely coloured. 
 
 
 yellowish. 
 
 Hessian yellow. 
 
 Dilute : Fibre paler. 
 
 Fibre deep violet ; liquid 
 
 Fibre dark red ; 
 
 
 Con. : Fibre black-blue ; 
 
 red violet. 
 
 liquid light rose. 
 
 
 liquid violet. 
 
 
 
 Brilliant yellow. 
 
 Dilute : No action. 
 
 Fibre black-violet ; liquid 
 
 Fibre cherry-red ; 
 
 
 Cone.: Fibre dark yellow; 
 
 violet. 
 
 liquid scarcely rose. 
 
 
 liquid nearly colourless. 
 
 
 
 Curcumine. 
 
 Dilute : No action. 
 
 Fibre black-violet ; liquid 
 
 As in brilliant yellow. 
 
 
 Cone. : Fibre dark violet ; 
 
 fine violet ; blue on 
 
 
 
 liquid nearly colourless. 
 
 dilution. 
 
 
 Ta*irazine. 
 
 Fibre more orange ; liquid 
 
 Same as HC1. 
 
 Fibre more orange ; 
 
 
 yellow. 
 
 
 liquid orange- 
 
 
 
 
 yellow. 
 
 Citronine. 
 
 Fibre deep violet-red ; 
 
 Fibre deep-violet ; liquid 
 
 Fibre dirty green- 
 
 
 liquid magenta on dilu- 
 
 violet. 
 
 yellow ; liquid 
 
 
 tion. 
 
 
 colourless, yellow 
 
 
 
 
 with water. 
 
 Primuline yellow. 
 
 No perceptible action. 
 
 Fibre first brighter and 
 
 Fibre brighter and 
 
 
 
 deeper, then pale 
 
 more orange ; liquid 
 
 
 
 yellow. 
 
 colourless. 
 
 Toluylen orange G. 
 
 Dilute : No action. 
 
 Fibre magenta-red ; liquid 
 
 Fibre light orange- 
 
 
 Cone. : Fibre violet ; 
 
 not much reddened. 
 
 red ; liquid scarcely 
 
 
 liquid reddish, on dilu- 
 
 
 coloured. 
 
 
 tion colour restored. 
 
 
 
 Toluylen orange R. 
 
 Dilute : Fibre more rose. 
 
 Fibre yellowish ; liquid 
 
 Fibre more orange ; 
 
 
 Cone. : Fibre paler liquid 
 
 yellow. 
 
 liquid colourless. 
 
 
 yellow ; on dilution 
 
 
 
 
 rose. 
 
 
 
 Primuline orange. 
 
 Fibre and liquid reddish 
 
 Fibre orange brown ; 
 
 Fibre darkred-brown ; 
 
 
 brown. 
 
 liquid deep red. 
 
 liquid nearly colour- 
 
 
 
 
 less. 
 
 Oriol. 
 
 Dilute : No action 
 
 As with HC1. 
 
 Fibre orange-red ; 
 
 
 Cone. : Fibre dark red ; 
 
 
 liquid colourless. 
 
 
 liquid light red, yel- 
 
 
 
 
 low on dilution. 
 
 
 
SECT. VII.] 
 
 DYEING AND TISSUE-PRINTING.* 
 
 857 
 
 NH 3 . 
 
 SnCl 2 +HCl. 
 
 Alcohol. 
 
 Other Reactions and Remarks. 
 
 Fibre as with NaOH ; 
 liquid rose, fluores- 
 cent. 
 
 No action. 
 
 No action in cold ; 
 fibre dirty brown 
 in heat ; liquid 
 faint rose. 
 Fibre slowly becomes 
 light reddish brown. 
 
 Slightly fluorescent 
 extract. 
 
 No action. 
 
 HNO 2 : No action. 
 NH0 3 ; orange spot removed 
 by washing ; bears hot soap- 
 lye well. 
 HN0 2 : No action. 
 
 Fibre fine deep red ; 
 liquid colourless. 
 
 No action. 
 
 Fibre gradually 
 orange ; liquid 
 yellow. 
 No action in cold, 
 red brown on 
 
 No action. 
 No action. 
 
 Yellow colour of SnCl 2 solu- 
 tion turns violet with NaOH, 
 
 HNO, : Orange spot. 
 
 
 heating. 
 
 
 
 Matters. 
 
 Scarce any action. 
 
 In cold no action ; 
 
 No action. 
 
 3NO S : Deep yellow spot. 
 
 
 liquid yellow on 
 
 
 
 heating. 
 
 
 
 Fibre paler ; liquid 
 
 Slowly discharged 
 
 No action. 
 
 HN0 3 : White spot ; turning 
 
 colourless. 
 
 in cold, quickly on 
 
 
 orange in the middle. 
 
 
 heating. 
 
 
 
 Fibre bright orange ; 
 liquid colourless. 
 
 Fibre dirty yellow, 
 slowly discharged. 
 
 No action. 
 
 HN0 8 : Brown spot, turning 
 reddish grey 
 
 No action. 
 
 Fibre brownish 
 
 No action. 
 
 HNO, : No action. 
 
 
 yellow, then col- 
 
 HNO, : Violet spot. 
 
 
 ourless. 
 
 
 Fibre dark orange ; 
 
 Fibre pale yellow, No action. 
 
 
 liquid faint orange. 
 
 then decolorised. 
 
 
 ..... 
 
 
 
 
 Iff 
 
 As with NaOH. 
 
 Fibre dirty yellow, 
 
 No action. 
 
 ':. ' V 
 
 
 quickly discharged. 
 
 
 t i 
 
 ! 
 
 As in brilliant yellow. 
 
 Fibre brownish yel- 
 
 No action. 
 
 
 
 low, then dis- 
 
 
 
 
 charged. 
 
 
 
 As with NaOH, but 
 
 Discharged on heat- 
 
 No action. , 
 
 HNO, : No action. 
 
 fainter. 
 
 ing. 
 
 
 
 Fibre unchanged ; 
 liquid colourless. 
 
 Fibre yellowish 
 brown, discharged 
 
 Slowly extracted. 
 
 HNO, : Violet red spot, then 
 red in the middle, violet on 
 
 
 on heating ; liquid 
 
 
 margin 
 
 
 yellowish. 
 
 
 
 No action. 
 
 Faint action. 
 
 No action. 
 
 HN0 2 : Fibre deep orange; 
 
 
 
 
 with NH S , orange-brown ; 
 
 
 
 
 red with -naphthol. 
 
 No action. 
 
 Fibre more rose, dis- 
 charged on boiling ; 
 
 No action. 
 
 HN0 2 : Fibre grey ; with 
 NH S , turns dirty yellow. 
 
 
 liquid colourless. 
 
 
 
 No action. 
 
 Fibre first rose, 
 slowly discharged 
 on boiling. 
 
 No action. 
 
 HN0 2 : Fibre lilac-grey ; 
 more reddish with NH,. 
 HNO S : Red violet spot turn- 
 
 
 
 
 ing grey. 
 
 No action. 
 
 Fibre orange-brown, 
 
 Slight extraction. 
 
 HNOg : Red-brown spot. 
 
 
 then colourless. 
 
 
 
 Fibre orange ; liquid 
 nearly colourless. 
 
 Fibre faint yellow, 
 by degrees dis- 
 charged ; liquid 
 
 No action. 
 
 HN0 2 : No action. 
 HN0 8 : Faint orange spots, 
 fast to light. 
 
 
 colourless. 
 
 
 . .> 
 
8 5 8 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vii. 
 
 Colouring Matter. 
 
 HC1. 
 
 H 2 S0 4 . 
 
 NaOH. 
 
 Croceine orange. 
 
 Fibre reddish brown ; 
 liquid rose. 
 
 Fibre darker ; liquid 
 orange ; fibre colour re- 
 
 Fibre orange-brown ; 
 liquid nearly col- 
 
 
 
 stored on washing. 
 
 ourless. 
 
 Anthracene (derived 
 from a vegetable 
 
 Fibre rather greener ; 
 liquid also. Fibre and 
 
 As with HCL 
 
 Colour deeper yellow; 
 liquid pale yellow. 
 
 colour). 
 
 liquid colourless on 
 
 
 
 
 watering. 
 
 
 
 Xanthaurine (derived 
 
 Like anthracene. 
 
 Like anthracene. 
 
 Like anthracene. 
 
 from vegetable 
 
 
 
 
 colour). 
 
 
 
 
 Galloflavine (yarn 
 dyed with alum 
 
 Fibre darker ; liquid yel- 
 low ; both nearly colour- 
 
 As with HCL 
 
 Fibre more orange; 
 liquid yellow. 
 
 tartar and SnCl z ). 
 
 less on dilution. 
 
 
 
 Green Colouring 
 
 Kesorcin green. 
 
 Fibre yellow-grey ; liquid 
 
 Fibre and liquid ; brown 
 
 Fibre darker ; liquid 
 
 
 orange-red. 
 
 no change on dilution. 
 
 colourless. 
 
 Blue Colouring 
 
 Victoria blue. 
 
 Fibre blue-black ; liquid 
 
 As with HC1. 
 
 Fibre dark red ; 
 
 
 reddish ; on dilution 
 
 
 liquid colourless. 
 
 
 fibre green, then blue. 
 
 
 
 Azo blue. 
 
 Dilute : No action. 
 
 Fibre blue-black ; liquid 
 
 Fibre cherry-red ; 
 
 
 Cone. : Fibre black- 
 
 blue. 
 
 liquid faint rose. 
 
 
 blue ; liquid colourless. 
 
 
 
 Benzoazurine. 
 
 Fibre blue-black ; liquid 
 
 Fibre black-blue ; liquid 
 
 Fibre dark crim- 
 
 
 colourless. 
 
 greenish blue. 
 
 son ; liquid rose. 
 
 Basle blue. 
 
 Fibre dark grey ; liquid 
 
 Fibre blue-black, then 
 
 Fibre darker. 
 
 
 yellow ; fibre blue on 
 
 green, then yellow; li- 
 
 
 
 washing. 
 
 quid yellow. With water 
 
 
 
 
 both blue. 
 
 
 New blue. 
 
 Fibre reddish violet. 
 
 Fibre dark grey ; liquid 
 
 Fibre violet-brown ; 
 
 
 
 grey. 
 
 liquid pale rose. 
 
 Nile blue. 
 
 Fibre green, then orange ; 
 
 Fibre and liquid brown- 
 
 Fibre red; liquid rose. 
 
 
 liquid orange. 
 
 red ; on dilution yellow, 
 
 
 
 
 green, and then blue. 
 
 
 Naphthylene blue G. 
 
 Fibre brown-violet ; liquid 
 
 Fibre black-brown ; liquid 
 
 Fibre brown ; liquid 
 
 
 brown-orange. 
 
 dark brown, on dilu- 
 
 orange-brown. 
 
 
 
 tion dirty blue. 
 
 
 Violet Colouring 
 
 Fast violet. 
 
 Fibre dark blue-black ; 
 
 Fibre black ; liquid grey- 
 
 Fibre black-blue ; 
 
 
 liquid faint bluish. 
 
 blue ; on dilution green- 
 
 liquid pale violet. 
 
 
 
 ish, then red; fibre 
 
 
 
 
 violet. 
 
 
 Azo violet. 
 
 Dilute : Fibre blue. 
 
 Fibre dark blue ; liquid 
 
 Fibre crimson ; liquid 
 
 
 Cone. : Fibre black-blue ; 
 
 blue-green. 
 
 colourless. 
 
 
 liquid colourless. 
 
 
 
 Hessian violet. 
 
 Fibre dark blue; liquid 
 
 Fibre dark violet-blue ; 
 
 Fibre redder ; liquid 
 
 
 nearly colourless. 
 
 liquid black-blue, on 
 
 colourless. 
 
 
 
 dilution blue- violet. 
 
 
SECT. VII.] 
 
 DYEING AND TISSUE-PRINTING. 
 
 859 
 
 NH,. 
 
 SnCl.+HCl. 
 
 Alcohol. 
 
 Other Reactions and Remarks. 
 
 No action. 
 
 Little action in cold ; 
 quickly discharged 
 
 No action, or faint 
 orange tint. 
 
 HNO, : Black-blue spots. 
 
 
 on boiling. 
 
 
 
 Fibre unchanged ; 
 liquid scarcely 
 
 Fibre and liquid 
 rather paler ; no 
 
 No action. 
 
 HN0 3 : Brown spot, lighter in 
 middle. 
 
 yellow. 
 
 discharge on boil- 
 
 
 Fe 2 Cl s : Fibre and liquid olive- 
 
 
 ing. 
 
 
 green. 
 
 
 
 
 Alum does not give the fluor- 
 
 
 
 
 escence of fustic. 
 
 Like anthracene. 
 
 Like anthracene. 
 
 Like anthracene. 
 
 (Anthracene and xanthaurine 
 
 
 
 
 both from Persian berries ? 
 
 Fibre darker and 
 
 No particular action. 
 
 
 Heated with Fe 2 Cl 6 : Fibre 
 
 more olive ; liquid 
 
 
 
 dirty olive. 
 
 almost colourless. 
 
 
 
 
 Matters. 
 
 No action. 
 
 Slight discharge; 
 
 No action. 
 
 HNO 3 ; Yellow-brown spot. 
 
 
 liquid brownish. 
 
 
 Ash contains iron. 
 
 Matters. 
 
 Fibre black-blue ; 
 
 Fibre darker in cold, 
 
 Slight extraction in 
 
 HN0 3 : Black spot, turning 
 
 liquid colourless. 
 
 green-blue on boil- 
 
 colci, abundant on 
 
 red-brown ; turned brown- 
 
 
 ing ; liquid green 
 
 boiling. 
 
 yellow by NH 3 ; latter colour 
 
 
 in heat, light blue 
 
 
 permanent on washing. 
 
 
 when cold. 
 
 
 
 Fibre violet-red ; 
 
 Fibre black-blue, 
 
 No action. 
 
 Picric acid : Colour blackish 
 
 liquid rose. 
 
 then slow dis- 
 
 
 brown. 
 
 
 charge. 
 
 
 
 Fibre deep violet ; 
 
 Slow discharge. 
 
 No action. 
 
 Liquid turned deep blue by 
 
 liquid cherry-red. 
 
 
 
 boiling with soap-lye. 
 
 No action. 
 
 No action. 
 
 Liquid very faint 
 
 HNO S : Black spot. 
 
 
 
 blue. 
 
 
 As NaOH. 
 
 Fibre green, then 
 
 Liquid faint blue. 
 
 
 
 colourless ; liquid 
 
 
 
 
 colourless, blue on 
 
 
 
 
 exposure to air. 
 
 
 
 Fibre violet. 
 
 Fibre green, then 
 
 Liquid faint blue. 
 
 HNO f : Yellow spot, green 
 
 
 colourless ; liquid 
 
 
 in middle. 
 
 
 colourless, blue on 
 
 
 
 
 exposure. 
 
 
 
 Fibre brown-violet ; 
 
 Fibre and liquid col- 
 
 Liquid very faint 
 
 Vapour of HC1 turns the 
 
 liquid light red. 
 
 ourless. 
 
 violet. 
 
 blue to chocolate-brown 
 
 
 
 
 (colour better for printing 
 
 
 
 
 than dyeing). 
 
 Matters. 
 
 Fibre unaltered ; 
 
 Fibre discharged, 
 
 Liquid scarcely 
 
 HN0 3 : Blue-black spots. 
 
 liquid very pale 
 
 quickly on boiling. 
 
 violet. 
 
 
 violet. 
 
 
 
 
 Fibre dark violet ; 
 liquid a faint 
 
 Discharged slowly. 
 
 No action. 
 
 Picric acid: Fibre black; 
 turns blue with dilute acetic 
 
 magenta. 
 
 
 
 acid. 
 
 No particular action. 
 
 Fibre blue, dis- 
 charged by pro- 
 
 No action. 
 
 HN0 2 : Dirty violet-grey ; 
 turned dirty red by NaOH. 
 
 
 longed boiling. 
 
 
 HNO 8 : Large spot with pale 
 
 
 
 
 blue margin. 
 
86o 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vii. 
 
 
 i 
 
 
 Colouring Matter. 
 
 HCl. 
 
 H 2 SO V 
 
 NaOH. 
 
 Heliotrope. 
 
 Dilute : Fibre dark violet. 
 
 Fibre black-blue; liquid 
 
 Fibre dark crimson ; 
 
 
 Cone. : Fibre black- 
 
 blue. 
 
 liquid colourless. 
 
 
 blue ; liquid light blue, 
 
 
 
 
 violet on dilution. 
 
 
 
 Acid violet 7B. 
 
 Fibre green ; liquid yel- 
 
 Fibre blackish, then 
 
 Fibre discharged ; 
 
 
 lowish brown, green- 
 
 brown and brown-red ; 
 
 liquid colourless. 
 
 
 blue on dilution. 
 
 liquid brown-red, on 
 
 
 
 
 dilution green-blue. 
 
 
 Gallocyanine. 
 
 Fibre and liquid violet. 
 
 Fibre dark blue-black ; 
 
 Fibre black-violet ; 
 
 
 
 liquid intense Prussian 
 
 liquid dirty purple. 
 
 
 
 blue, light magenta on 
 
 
 
 
 dilution. 
 
 
 Muscarine. 
 
 Fibre blue-black ; liquid 
 
 Fibre green-black ; liquid 
 
 Fibre brownish black; 
 
 
 dirty blue. 
 
 greenish, on dilution 
 
 liquid nearly col- 
 
 
 
 dirty violet. 
 
 ourless. 
 
 Brown Colouring 
 
 Benzo brown. 
 
 Dilute : Fibre reddish 
 
 Fibre and liquid black- 
 
 No action. 
 
 
 brown. 
 
 brown. 
 
 
 
 Cone. : Darker ; liquid 
 
 
 
 
 purple-red. 
 
 
 
 Anthracene brown. 
 
 Fibre paler and yellower ; 
 
 Fibre paler and redder ; 
 
 Fibre black ; liquid 
 
 
 liquid brown-yellow. 
 
 liquid chestnut, yellow 
 
 grey. 
 
 
 
 on dilution. 
 
 
 Fast brown KG. 
 
 Fibre dark violet-red ; 
 
 As with HCl. 
 
 Fibre bright crimson ; 
 
 
 liquid violet, colour 
 
 
 liquid cherry-red. 
 
 
 restored on dilution. 
 
 
 
 Black Colouring 
 
 Cachou de Laval. 
 
 Fibre little changed ; li- 
 
 Fibre rather yellower, 
 
 No action. 
 
 
 quid faint grey. 
 
 especially after wash- 
 
 
 
 
 ing. 
 
 
 Alizarine black. 
 
 Fibre unchanged ; liquid 
 
 Fibre and liquid as with 
 
 Fibre unchanged ; 
 
 
 faint greenish blue. 
 
 HCl. 
 
 liquid faint blue. 
 
 Brilliant black. 
 
 Fibre unchanged ; liquid 
 
 
 Fibre more greenish, 
 
 
 faint violet-red. 
 
 
 liquid violet-black. 
 
 Naphthol black. 
 
 Fibre unchanged ; liquid 
 
 Fibre unchanged ; liquid 
 
 Fibre unchanged ; 
 
 
 reddish. 
 
 olive-green. 
 
 liquid scarcely red- 
 
 
 
 
 dish. 
 
 Eesorcin Mask. 
 
 Fibre yellow-grey ; liquid 
 
 Fibre and liquid brown. 
 
 Fibre unchanged ; 
 
 
 orange-brown. 
 
 
 liquid very faint 
 
 
 
 
 green. 
 
 Wool black. 
 
 Fibre unchanged ; liquid 
 
 As with HCl. 
 
 No action in cold ; 
 
 
 light blue, rose on dilu- 
 
 
 on boiling, fibre 
 
 
 tion. 
 
 
 and liquid violet. 
 
 with hot water, the mass being then comminuted in a stuff-mill and bleached with 
 chloride of lime whilst still hot. According to the statement of Lahkusse, 200 kilos, 
 straw, 26 kilos, caustic soda, and 10 kilos, chloride of lime are required for the produc- 
 tion of 100 kilos, of bleached, air-dried straw-stuff. 
 
 The root-cuttings of jute are also used in the manufacture of paper, as also the waste 
 from rope-making, which serves for an inferior paper for envelopes. 
 
 Mechanical wood-stuff was first obtained by F. G. Keller, in 1840, by grinding wood 
 
SECT. VII.] 
 
 DYEING AND TISSUE-PRINTING. 
 
 861 
 
 NH 3 . 
 
 SnCla+IICl. 
 
 Alcohol. 
 
 Other Reactions and Remarks. 
 
 No particular action. 
 
 Fibre dark grey, 
 
 No action. 
 
 HNCX : Fibre green-grey, 
 
 
 then discharged. 
 
 
 orange brown on washing 
 
 
 
 
 and treatment with NH 3 ; 
 
 
 
 
 liquid faint brown. 
 
 
 
 
 Picric acid : Dark brown. 
 
 Like NaOH. 
 
 Fibre green ; liquid 
 
 Liquid scarcely 
 
 HN0 2 : No action. 
 
 
 blue-green ; both 
 
 violet. 
 
 HN0 3 : Olive, then dirty yel- 
 
 
 blue on dilution. 
 
 
 low ; washing does not re- 
 
 
 
 
 store colour. 
 
 Like NaOH, but 
 
 Fibre turns yellowish 
 
 No action. 
 
 HN0 2 : Fibre dirty violet- 
 
 fainter. 
 
 grey ; liquid colour- 
 
 
 grey; liquid blue-green, 
 
 
 less. 
 
 
 green, and then yellow. 
 
 Fibre violet-blue ; 
 
 Fibre blackish, blue 
 
 No action. 
 
 HN0 3 : Black spots. 
 
 liquid scarcely 
 
 on heating, then 
 
 
 (Probably formed by action 
 
 violet. 
 
 green and yellow- 
 
 
 of a nitroso compound upon 
 
 
 ish grey. 
 
 
 a dioxynaphthaline). 
 
 Matters. 
 
 No action. 
 
 Colour yellower and 
 lighter ; liquid 
 brown- yellow. 
 
 Extracts traces of 
 of colour. 
 
 Resists light badly. 
 
 Fibre brown-grey ; 
 liquid nearly 
 colourless. 
 As with NaOH. 
 
 Fibre brown-yellow ; 
 liquid the same. 
 
 Darker at first, then 
 discharged. 
 
 Extracts traces of 
 colour. 
 
 No action. 
 
 HN0 3 : Black spot. 
 
 HN0 3 : Black spot, turning 
 light red-brown. 
 
 Matters. 
 
 No action. 
 No action. 
 
 Fibre more reddish 
 or brownish. 
 
 On boiling, brownish. 
 
 No action. 
 No action. 
 
 Goods are rarely dyed with 
 cachou de Laval alone. 
 When topped with other 
 colours, it is difficult to 
 detect. 
 HN0 3 : A dark olive spot. 
 
 Fibre unchanged ; 
 liquid violet-black. 
 
 No action. 
 No action. 
 
 Fibre dark garnet on 
 boiling ; liquid 
 colourless. 
 On boiling, fibre 
 light green, blue 
 on washing. 
 Fibre and liquid 
 light brown. 
 
 No action. 
 No action. 
 No action. 
 
 HN0 3 : Dark red-brown spot. 
 
 HNO S : A brown spot. (A 
 mixture of various colours.) 
 
 HN0 3 : Yellowish brown spot. 
 Ash contains iron. 
 
 No action. 
 
 Fibre discharged. 
 
 No action. 
 
 HN0 3 : Light red-brown spot. 
 
 under millstones. This article only obtained industrial importance in 1846, by the 
 introduction of suitable machinery for its comminution and sorting, which rendered 
 possible the production of a uniform quality on the large scale. Ground wood serves 
 for the production of inferior papers, as its fibre is too short for strong papers and 
 not susceptible of felting. Hence it serves more for filling up than as a substitute for 
 rags. The resin present resists the action even of a strong bleach. Paper from ground 
 wood (mechanical wood-stuff) readily turns yellow. 
 
862 CHEMICAL TECHNOLOGY. [SECT. vn. 
 
 Much more important is the chemical production of cellulose, for which the wood 
 of coniferous trees is chiefly used. The stems, freed from bark, branches, &c., are cut 
 tip and boiled from two to three hours in wrought-iron vessels in caustic soda-lye of 
 sp. gr. 1*085 under a pressure of from 6 to 10 atmospheres. The whole is then run oft 
 into cisterns, where the brown lye escapes at the bottom. The soda is recovered by 
 evaporating down the liquid and igniting the residue. The fibrous mass is lixiviated 
 with water and washed clean. The oil of turpentine evolved is sometimes collected 
 in suitable refrigerators. The recovery of vanilline, the presence of which is detected 
 by the odour, has been attempted unsuccessfully. The bleaching is effected in the 
 hollander. 
 
 From a calculation given by the author, it appears that, at German prices, I ton 
 of wood cellulose costs only 240 marks, whilst the same weight of esparto cellulose costs 
 305-6 marks. 
 
 Sulphurous acid is also used in the production of cellulose. The comminuted wood 
 is treated under pressure with an acid solution of calcium sulphite obtained by placing 
 pieces of calcium carbonate in a tower and passing over them water from above and 
 sulphurous acid from below. The wood, cut up and freed from bark, is steamed in a 
 boiler lined with lead, into which the acid solution of calcium sulphite is introduced. 
 The whole is heated first to 108 and then gradually raised to 118. If a sample of 
 the liquid is mixed with ammonia the residual calcium sulphite falls to the bottom, but 
 the salts formed during the working of the process are not precipitated. The propor- 
 tion of the effective solution can easily be determined from the precipitate. If the 
 precipitate is only about $ of the volume of the sample, the time for boiling off the 
 sulphurous acid is arrived. The temperature and the pressure sink simultaneously. 
 If the precipitate in the test-glass is only ^V in bulk, the process is completely at an 
 end and the solution must be quickly run off. A higher temperature would hasten 
 the process, but would require a higher pressure, and the cellulose obtained would be 
 inferior in both quality and quantity. 
 
 The chemical process which takes place during boiling is, according to Mitscherlich, 
 as follows : The sulphurous acid is oxidised to sulphuric acid by a part of the oxygen of 
 the organic matter, and this acid under normal conditions combines with the bases, 
 which were previously combined with the sulphurous acid. If the process is mis- 
 managed, free acid is formed in the solution. At the same time tannic acid is formed 
 from the incrusting substances. For the right management of the process a main 
 condition is that the sulphurous solution must be free from polythionates, as the 
 operation miscarries in presence of the latter. At the same time the temperature in- 
 creases rapidly, and samples drawn show an anomalous decrease of sulphurous acid. 
 The polythionic acids generally appear in consequence of the presence of free fumes of 
 sulphuric acid during the roasting process To avoid this, care must be taken that the 
 sulphurous acid is free from sulphuric acid or its salts. 
 
 Ekman boils with a solution of magnesium sulphite produced by exposing calcined 
 magnesia in towers to the action of sulphurous acid and of water. He boils, e.g., 
 esparto grass (freed from roots, &c.) with a solution of 1-4 per cent, magnesia and 
 4-5 per cent, sulphurous acid. After the pressure has gradually been raised to 575-6 
 atmos., and is kept at this point for from two to four hours, fibres are obtained which, 
 after being well washed, are at once fit for common printing paper, and for better 
 sorts after bleaching with chloride of lime. 
 
 An experiment made at Bergvik gave the following results : Of the 4395 kilos, of 
 deal planks used there appeared by the removal of branches a loss of 260 kilos. ; by 
 cutting, sorting, and dusting, &c., of 565 kilos., or a total loss of 825 kilos. The 
 remaining 3570 kilos, were placed in four boilers, and yielded, after washing in common 
 
SECT. VII.] 
 
 PAPER MANUFACTURE. 
 
 863 
 
 hollanders, 2875 kilos, of stuff, equivalent to 1437 kilos, of dry stuff, or 32^68 per cent, 
 of the crude wood, which contained 21 per cent, of moisture. 
 
 In comparing the results of the various sulphite processes, the test for lignose with 
 aniline sulphate is not trustworthy. It is better to treat the products with chlorine, 
 after which the lignose substance is turned a magenta colour by sodium sulphite. 
 The remaining lignose may be quantitatively determined by boiling with potassa-lye. 
 According to Christy, in Ekman's process the incrustations are completely dissolved, so 
 that the washed stuff gives no colour with aniline sulphates, and dissolves in sulphuric 
 acid almost entirely without 
 a dark coloration. Fig. 573 ** 573- 
 
 shows the fibres of the white 
 pine (tanne) in a longitudinal 
 section, and Fig. 574 in a 
 cross section as it appears 
 under the microscope after 
 treatment by Ekman's process. 
 Fig. 575 shows the fibres 
 (strongly attacked) of linen 
 (L) and cotton (B) rag papers. 
 Fig. 576 shews ground wood 
 from conifers, with the cells and pith radii, which are here easily recognised, whilst in 
 
 Fig- 575- Fig- 576. 
 
 Fig- 574- 
 
 chemical cellulose (Fig. 577) they are not easily recognised. Fig. 578 represents 
 straw-stuff, with its cells, 0, very distinct from those of esparto. 
 
 In examining wood and other fibrous vegetable matter, H. Miiller boils 5 grammes 
 of the sample five times, using each time 100 c.c. of water. He dries and weighs them, 
 and then treats them in a lixiviating apparatus with a mixture of alcohol and benzene, to 
 dissolve fat, wax, resin, &c. Colouring matter and pectosic substances are removed 
 by repeated boiling with dilute ammonia. For obtaining the cellulose in a state of 
 purity the sample is covered with 100 c.c. water in a wide-necked stoppered glass, and 
 then, according to the nature of the sample, there are added from 5 to 10 c.c. of a solu- 
 tion of bromine containing 2 c.c. bromine in 500 c.c. water. The yellow colour of the 
 liquid disappears gradually on treating the purer bast-fibres, such as flax or hemp, but 
 
86 4 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vn. 
 
 in a few minutes in straw-stuffs or woods. When the colour has disappeared a fresh 
 quantity of the bromine solution is added, and so on, until at last a point is reached 
 when the absorption becomes so sluggish that the liquid remains yellow even after the 
 lapse of from twelve to twenty-four hours, and the presence of free bromine can be 
 
 Fig. 577- 
 
 Fig. 578. 
 
 detected. The mass, when freed from the liquid by nitration, is washed Avith water, and 
 heated almost to a boil with 500 c.c. of water, to which 2 c.c. of liquid ammonia have 
 been added. All crude vegetable fibres and woods, without exception, if thus treated, take 
 a more or less intense deep brown colour, as does also the liquid. The filtered and 
 washed mass is returned to the stoppered glass, again covered with water, and solution 
 of bromine is again added. The first addition of bromine is generally easily absorbed, 
 and the dark colour becomes lighter. The purer fibres, to which only quantities of 
 5 c.c. are added in the second treatment, soon become colourless, and if further 
 quantities of bromine are added, they remain unabsorbed for days. On the other 
 hand, lignified tissues, after the above-mentioned treatment with ammonia, absorb 
 bromine with undiminished readiness, and we may continue adding quantities of 10 c.c. 
 of the bromine solution until the absorption comes to an end. When this point is 
 reached the treatment with dilute ammonia is repeated. With the purer fibres this 
 second treatment is usually sufficient, but more strongly lignified tissues require a third 
 and sometimes a fourth treatment with bromine in gradually reduced quantities. After 
 drying and weighing the cellulose, the quantity of the soluble modification of cellulose 
 can be approximately determined by the loss on boiling four or five times, each time 
 with a solution of I part crystallised sodium carbonate in 100 parts of water. Such 
 soluble cellulose is probably in most cases wasted in the technical treatment of fibrous 
 materials. 
 
 The nitrogenous material derived from the protoplasmic contents of the cells, which. 
 are partly soluble and partly insoluble, are small in quantity, and their presence has no 
 technical importance. 
 
 In many raw materials an important part of the cellulose occurs in the state of 
 worthless tissues, and it is then important to know its proportion. As this is not 
 practicable chemically, it has to be reached by mechanical means. An approximate 
 separation may be reached by stirring up the cellulose with an abundance of water, 
 and pouring it upon a straining-cloth, stretched over a funnel, repeating this treatment 
 
SECT. VII.] 
 
 PAPER MANUFACTURE. 
 
 865 
 
 as long as the water runs through turbid. In this manner the following figures were 
 obtained : 
 
 Woods. 
 
 Water. 
 
 Watery 
 Extract. 
 
 Resin. 
 
 Cellulose. 
 
 [ncrusttng 
 Matter. 
 
 Birch 
 
 12*48 
 
 2-6"; 
 
 I -JA 
 
 et'C-? 
 
 28-91 
 
 
 I2'^7 
 
 2 M.T 
 
 
 33 3^ 
 
 
 Oak 
 
 I7-J2 
 
 I2'2O 
 
 O'QI 
 
 43 47 
 
 J9 J 4 
 
 Alder 
 
 IO"7O 
 
 2*48 
 
 0*87 
 
 
 
 Lime 
 
 lO'IO 
 
 V(6 
 
 3"Q1 
 
 54 2 
 
 3 1 33 
 
 Chestnut 
 Fir 
 
 12-03 
 12-87 
 
 SHI 
 4*O? 
 
 I'lO 
 
 1-6^ 
 
 52-64 
 
 C3'?7 
 
 28-82 
 28-18 
 
 Poplar ...... 
 
 I2'IO 
 
 2 -88 
 
 I "37 
 
 
 20 "88 
 
 Pine 
 Willow 
 
 I3-87 
 
 11-66 
 
 1-26 
 2-65 
 
 0-97 
 1-23 
 
 56-99 
 5572 
 
 26-91 
 28-74 
 
 According to F. Schulze, i part of the dried and pulverised material is extracted 
 first with water, then with alcohol and ether, and after it has been well dried it is 
 treated for from twelve to fourteen days, at a temperature not exceeding 15, with 0*8 
 part potassium chlorate and 12 parts nitric acid of sp. gr. no. After the lapse of this 
 time it is diluted with water, filtered, and washed, first with cold and then with hot 
 water. The contents of the filter are rinsed into a beaker and digested for three- 
 quarters of an hour with weak ammonia (i part to 50 water) at about 60. The mass 
 is then washed with cold ammonia until the filtrate runs through colourless. It is then 
 successively and completely washed with cold and hot water, with alcohol and ether. 
 If we disregard a small trace of nitrogen, the cellulose so obtained is chemically pure. 
 
 K wood is treated with soda-lye at elevated temperatures and high pressure, a 
 relatively large part of the cellulose is dissolved and wasted. 
 
 As a reagent for wood Friesner recommends phloroglucine. If a paper contains 
 ground wood-stuff it turns violet red, if first moistened with HC1 and then with 
 phloroglucine. When lignose is mixed with cellulose the test is uncertain, and a 
 miscroscopic examination is required. 
 
 Mineral Additions to Rags. A moderate addition of a mineral body to the paper 
 material whitens the whole, and for inferior or ordinary paper it is successfully 
 employed. It is unfit for very thin paper, making it shiny and brittle. A profitable 
 addition of mineral matter is from 5 to 10 per cent, of the weight of paper, a greater 
 addition making the paper dull, brittle, and hairy to write upon. The usual mineral 
 mixtures in frequent use at the present day are clay free from sand, china clay, or 
 kaolin. Annaline pearl-hardening, in the form of a pulp resembling clay, is most 
 preferred, being not so expensive. In 1850 it was favourably received, under the 
 names of fixed white, raw white, patent white, or permanent white. 15 kilos, of the 
 paste with i oo kilos, of paper pulp are generally employed. 
 
 Precipitated barium sulphate has been latterly much used in paper-making, as have 
 also finely -ground bauxite and precipitated magnesia. 
 
 Manufacture of Paper by Hand. The old method of making paper by hand was 
 from the pulp of waste paper placed in a mould of the required size ; but this method, 
 although still used for writing paper, was found to restrict the size of the sheets, and 
 different methods were tried with varied success, until a machine was invented which, 
 without the aid of moulds, manufactured the paper in any length. 
 
 Cutting and Cleaning the Rags. The Cutting and Sorting of the Rags. The first 
 operation is performed by two machines, called the half-hollander and the whole- 
 hollander. The rags are next treated chemically with potash to rot them. By the 
 old method, rags were cut into pieces about four inches square, by being drawn across 
 a sharp knife fixed upon a table. Machinery has superseded this arrangement, and 
 various cutting machines have been invented, among which we may mention that of 
 
 3 i 
 
866 CHEMICAL TECHNOLOGY. [SECT. vii. 
 
 Davey, in which a horizontal knife revolves around a fixed cylinder cutting the 
 rags into strips. Bennet's cutting machine consists of two knives radiating from a 
 wheel, and bearing against another knife. Some machines are constructed with a 
 quantity of circular sharp-edged steel plates, like the machine of Uffenheiruer, of 
 Vienna. After cutting, the rags are cleansed from dust and other impurities by the 
 Willow machine. The best kind of sifting machine is in the form of a drum with the- 
 upper part covered with a wire grating. The rags are put in by a side door, which 
 acts, as the drum revolves, as a refuse door, casting off the sand and impurities, 
 leaving the rags winnowed. They are next boiled in an alkaline lye, or solution 
 of 4 to 10 Ibs. of sodium carbonate, with one-third of quicklime to 100 of the- 
 material. The rags are placed in large cylinders slowly revolving, and causing them 
 to be constantly turned over. Into these cylinders a jet of chlorine water, with a 
 pressure of 30 Ibs. to the square inch, is directed. H. Volter patented in 1859 a hori- 
 zontal steam cylinder, which receives the steam from a tubular guide-cock provided to 
 the boiler, an inner cylinder revolving to- move the rags. The distant end of the boiler 
 and the tubular cylinder draws up, and the mass is easily poured into the washing 
 machine when in a fluid state (Silberman's Washing Hollander). Although partly 
 cleansed by the above method, the rags still require further boiling. 
 
 The Separation of the Rags for Half-stuff and the Whole-stuff. The machine used in- 
 separating and rending the rags are : 
 
 1 . The German stamping machine. 
 
 2. The rag mill (rolling hollander). 
 
 (a) The half-hollander. 
 (/3) The whole-hollander. 
 
 Formerly the rags were rotted before crushing, being placed in a stone trough, 
 where in two or three days they became heated, and developed a strong amnioniacal 
 odour. When the surface was covered with a mould, the rags were sufficiently decayed 
 for the purpose of manufacture. They were then taken out in a brown mass, those 
 remaining behind as sediment being used for coarse paper. The present method of 
 boiling the rags with alkalies is preferable, giving the paper greater firmness. 
 
 Stamp Machine. The German stamp machine is at the present time only to be 
 found in smaller manufactories. It is of the nature of a hammer. Six or eight stamp 
 rods are fixed into a strong oak beam, and work intermittently with a set below. 
 Through an opening provided with a fine sieve the water is conveyed away. As the 
 hammers rise and fall, the stamp holes serve for a water conduit. Three to five 
 hammers work in each hole. The rags are mixed with sufficient water to form a pulp, 
 and remain in the machine twelve to twenty hours. 
 
 The hollander has a cylinder set with blades or knives and kept in rapid rotation. 
 Below this is the so-called ground-work fitted with similar blades. After the chest 
 has received the necessary quantity of water the rags, &c., are thrown in. The roller 
 is set in motion with a speed of from 100 to 150 rotations per minute. The blades 
 strike into the liquid and draw the rags into the space between the circumference of the- 
 roller and those of the ground-work the two sets of knives acting like the blades of 
 scissors and finally eject the mass in a state of fine division over the steep slope of the 
 cran. 
 
 Bleaching the Pulp. After this the mass is placed in another machine, the whole- 
 hollander, and bleached by a solution of chloride of lime, chlorine water, chlorine 
 gas, or other bleaching agent. The lime is retained in the machine until the rag& 
 are sufficiently bleached ; the pulp is then let down into long slate cisterns to steep- 
 before placing in the beating machine. 
 
 When bleached by chloride of lime, i to 2 kilos, are applied to 100 kilos, of pulp- 
 
SECT, vii.] PAPER MANUFACTURE. 867 
 
 When greater smoothness is required, a little hydrochloric or sulphuric acid is added, 
 although care must be taken in its use, for applied too largely it destroys the fibre. 
 Orioli employs aluminium hypochlorite, known by the name of "Wilson's bleaching 
 preparation, aluminium chloride being obtained on the one hand, while, on the other, 
 all the bleaching effects arise from the delivery of ozonised oxygen, 
 
 A1 2 C1 6 3 = 3 + A1 2 C1 6 . 
 
 Varrentrapp's zinc hypochlorite, under the name of Varrentrapp's bleaching-powder, 
 is worthy of notice as being extensively used. In this powder, chloride of lime, 
 decomposed with zinc vitriol, or, better, with zinc chloride, is employed. When bleached 
 by zinc chloride, the mineral acid decomposes the chloride of lime, therefore no 
 risk is incurred by the fibre. 
 
 Antichlore. When the bleach retains chlorine, it is washed in soda, potash, or anti- 
 chlore, to neutralise the adhering hydrochloric acid, which merely washing in water 
 would not effect. The chief constituents of antichlore are sodium sulphite, tin chloride, 
 and sodium hyposulphite. A mol. of sodium sulphite (Na 2 S0 3 + 7H 2 O) removes i mol. 
 of chlorine (C1 2 ), whilst hydrochloric acid and sodium sulphate are formed. A 
 mixture of sodium sulphite with sodium carbonate is employed to neutralise the 
 hydrochloric acid. The sodium sulphate and sodium chloride a*>e removed by 
 washing. Calcium sulphite is greatly approved, and is considered to be as effective 
 as antichlore, when applied as the corresponding sodium salt. A mol. of tin-salt 
 (SnCl 2 + 2H 2 0) is taken up by a mol. of chlorine (C1 ), by which tin chloride (SnCl 4 ) 
 arises. After the working is completed, so much sodium carbonate is added as 
 is required to saturate the hydrochloric acid. A mol. of sodium thiosulphate 
 (Na 2 S 2 3 + 5H 2 O), absorbs 4 mols. of chlorine, whilst sodium sulphate, hydrochloric 
 and sulphuric acids are formed. 
 
 Blueing. Notwithstanding careful chemical bleaching, the pulp has still a yellow 
 tinge, and requires a colouring matter which is generally introduced in the process 
 of beating. The blues commonly used are ultramarine, Paris blue, indigo, aniline 
 blue, and oxide of cobalt. With 100 kilos, of the dry paper stuff, o'5 to 1*5 kilo, of 
 ultramarine are mixed, according to the strength of the colour required. 
 
 Sizing. The pulp requires sizing to preserve the colour. It is guided, as it issues 
 from the hollander, through a tub of size, and afterwards carried over skeleton drums, 
 containing revolving fans to dry it as it passes ; heated cylinders are also used for drying. 
 Starch is used to give a thicker consistence to the size, which is generally made from 
 the best glue, resin being added in quantities never exceeding 3 kilos, per 100 kilos, 
 of the pulp, to impart the desired amount of stiffness. 
 
 a. Hand-made Paper. Straining the Paper Sheets. There are three ways of 
 straining or filtering the pulp : First, by straining through a brass sieve with fine 
 slits to allow the pulp to pass, and retaining all lumps and knots. Secondly, by 
 pressure ; and, thirdly, by evaporation. In the first operation the sheet is formed by 
 a mould of the size required being dipped into a tub of pulp previously strained. The 
 pulp becomes extended to a thin layer and the water filters off. The tub is either 
 round or of a quadrangular shape made of wood, lined with lead. A broad board 
 running across the tub is called the bridge, and a smaller one under the large one the 
 little bridge. The large bridge has a pointed support, technically termed the donkey, 
 for the form or frame to lean against. 
 
 The sifting machine, technically termed the knotter, used in the manufacture of 
 hand-paper, consists of an upright cylindrical sieve, in which an inner cylinder revolves. 
 As the whole-stuff is taken from the tub, the remainder becomes massed together, and 
 steam or other pressure is employed to force the pulp through the sieve and cylinder, 
 the latter retaining the lumps and knots. The paper forms, upon which the whole- 
 
868 CHEMICAL TECHNOLOGY. [SECT. vn. 
 
 stuff is placed, are constructed with brass wires to allow the water to drain off, 
 retaining the pulp. There are two kinds of forms : 
 
 (1) The Ribbed Form. A square or oblong frame of oak or mahogany with parallel 
 brass wires and cross wires at intervals to steady them. Lined paper is made on this 
 form, and is not much glazed on account of the time and expense, being reckoned an 
 inferior paper. 
 
 (2) The Vellum Form. A frame of fine brass wire-work. Vellum paper is made 
 on this form, and has a delicate even surface ; it can be made to present any degree of 
 glossiness, by pressing and satining. When held to the light it appears uniform, not 
 possessing bright and opaque lines as in the former paper. 
 
 A ribbed form similar to the vellum form is employed in the manufacture of paper 
 distinguished by trade marks, coats of arms, &c., the impress of the wire forming what 
 is termed the water-mark ; bank-notes are made separately in a mould in this way. 
 The edge of the form makes the edge of the paper, forms being used according to the 
 size required; also the quantity of the whole-stuff varies in accordance with the 
 required thickness of the sheets. Felt is extensively used in the manufacture of paper ; 
 it is unlike the ordinary felt for hats, being a coarser, looser, white woollen fabric, more 
 suitable for rolling. 
 
 The work of the pulp-tub is divided into two parts, the squaring and the scooping ; 
 the latter is the placing of the pulp in the mould, the former the placing of the sheets 
 between felt. The tub is stirred occasionally with a pointed stick, technically termed 
 the scoop stick. The pulp is taken out on the form in a sloping position, shaken a 
 little to aid cohesion, and finally placed on the small bridge. The next sheet is placed 
 on the large bridge. The form is laid in a sloping position against the donkey-rest to 
 drain, and the paper finally placed on the felt to dry a little, the empty form returning 
 to the tub. The first paper sheet is covered with felt, on which the next is placed ; 
 the average number of sheets manufactured exceeding 5000 a day. 
 
 Pressing the Paper. As soon as there is a sufficient number of sheets, they are 
 made into a thick bale and placed under the press, the number of sheets comprising 
 a bale being generally 181. Three bales, 181 x3 = 543 sheets; twenty quires = 480 
 sheets sized, and 500 unsized. Pressing gives firmness and glossiness, and by continued 
 pressing exceeding smoothness is obtained. 
 
 Drying the Paper. The process of pressing has not quite removed the water from 
 the paper, which has to be dried in an airy chamber, the sheets being placed separately, 
 or two to five together as required. An expert workman can place from 800 to 900 
 layers of two to five sheets each in a day, as well as hang and dry the sheets and 
 take them off the cord. 
 
 Sizing the Paper. Paper is not durable unless it is sized, and is only used for 
 filtering, packing, .printing, or scribbling papers. Sizing gives the paper substance by 
 filling the pores, and making it firmer, stifier, and harder. Ordinary size dissolved in 
 water will not always prove effective, and it is necessary to add a solution of an 
 aluminium salt, such as that of alum, aluminium sulphate, or aluminium chloride, to 
 prevent decay. Without chemical preparation the sheets are rendered sticky and have 
 to be sized separately, but with the above addition from 80 to 100 sheets can be success- 
 fully sized by hand ; a good workman can size from 40,000 to 50,000 sheets in twelve 
 hours. The sheets must not be dried too quickly after sizing. 
 
 Preparing the Paper. After the sized paper is pressed and dried, it requires further 
 preparation to make it fit for use. The first process consists in the finishing or 
 trimming to remove all the little specks and blemishes, and to smooth the sheets. 
 The finished sheets are counted and placed together, the workman by continued 
 practice counting 8000 to 15,000 sheets as he places them, and separating them into 
 whole and half quires, twenty-four sheets of sized and twenty-five sheets of unsized 
 
SECT, vii.] PAPER MANUFACTURE. 869 
 
 paper making a quire ; the upper and under quire of each ream being placed on an 
 extra sheet, known as outsides. The even and glazed surface is mostly obtained by 
 hot-pressing, when every sized sheet is interposed between two unsized sheets ; this is 
 called interchanging. The preparation of the various kinds of paper is now accom- 
 plished, with the exception of the finest letter paper, which requires an extra process 
 to give it a final gloss, by pressing between the rollers of the satining machine. The 
 different varieties of paper are classed under three denominations : 
 
 The Different Kinds of Paper. A. Writing and drawing paper, the smaller kinds 
 of copy paper, deed paper, the finer post and letter paper, and vellum letter paper. 
 
 B. Printing paper for books, as distinguished from copy printing, deed printing, 
 post and vellum printing, note and copper-plate paper. Silk papers for fancy pur- 
 poses ornamented with gold or silver, and printed from engraved copper plates. 
 
 C. The looser textured papers, such as unsized parcel paper ; the better kinds are 
 filter* and blotting-papers. Packing-paper is half-sized, and is met with as a yellow 
 straw paper, blue sugar paper, and pin and needle papers. 
 
 /3. Machine Paper. Manufacture. Manufacturing paper by hand requires much 
 time and labour, and machinery is found to be quite as efficient. Endless paper of 
 any breadth can be made by machinery with the same amount of strength and 
 firmness as hand paper. The straight form and the vibrating machine are used for 
 finer paper. 
 
 It is requisite that the machine should : 
 
 (1) Make the pulp of a suitable consistence by diluting it with water. 
 
 (2) Purify the whole-stuff from knots. 
 
 (3) When free from knots work the material by means of regulators, delivering the 
 stuff from the form, and producing by the uniform flow of the pulp a smooth paper 
 leaf of the breadth required. 
 
 (4) Be so regulated that the stream of whole-stuff may form a sharply turned leaf. 
 
 (5) Free the paper leaf from water, so that it only requires drying in an airy cham- 
 ber and pressing. 
 
 (6) Remove the water, steam cylinders being principally used. 
 The finished paper is cut into sheets by the paper-cutting machine. 
 
 After the whole-stuff is thinned to a consistence easily moved by water, it flows to 
 the knotter, placed in a perforated cylinder of sheet brass, which is supplied with an 
 interior mechanism revolving with greater velocity. One of the best knotting machines 
 is Manuhardt and Steiner's, of Munich. After the whole-stuff is purified by the 
 knotting machine it passes out, and the whole-stuff reservoir is supplied anew. In 
 course of time the consistence becomes altered, sometimes producing a thicker sheet 
 than required. This variation is obviated by the regulator, an essential in the paper 
 manufactory. 
 
 Hartig classifies papers as blotting-paper (unsized), printing-paper (sized with 
 resin), draught-paper, letter-paper, paper for account books and legal documents, and 
 covering paper, all the three better kinds being sized with a mixture of glue and resin- 
 size, and lastly parchment paper. 
 
 For testing the strength of papers apparatus have been devised by Heuer, Rausch, 
 and Wendler. Papers are also arranged in seven classes, according to their resistance 
 to rubbing and crumbling. The position of a paper in this series is ascertained by 
 certain manipulations, which can only be learned by practice. 
 
 Paper-Cutting Machine. When finished by the machine, the paper is cut off into 
 long lengths and rolled by hand for the manufacturers of drawing- and wall-papers, 
 
 * Filter paper should be free from soluble matter and from earthy, alkaline, or metallic 
 compounds, being as near as possible chemically pure cellulose. The finest qualities are made in 
 Sweden and in Germany. [EDITOR.] 
 
8;o CHEMICAL TECHNOLOGY. [SECT. vn. 
 
 scene-painters, &c. Attached to a large wheel is a knife, whose regular strokes cut paper 
 into the size required. The clipping machine is used for cutting the edges of books, 
 y. Pasteboard, &c. Making Pasteboard. Pasteboard is made in three ways : 
 
 (1) By placing the pulp in a form form-board. 
 
 (2) By placing several damp sheets to form a thick card elastic pasteboard. 
 
 (3) By pasting together the finished paper sheets sized pasteboard. 
 
 (1) Form-board is an inferior kind employed for ordinary purposes of packing, 
 bookbinding, &c. It is made from waste paper, refuse rags, and the coarser parts of 
 the pulp. Clay or chalk is sometimes present to 25 per cent, of the weight of this 
 pasteboard. It is made in a coarse ribbed form, goes through the same process of 
 knotting as the paper sheet, and is dried and pressed under a roller. 
 
 (2) Elastic pasteboard is of better material and presents a smoother surface ; 
 six to twelve sheets of paper previously damped are placed together, and pressed into 
 one compact sheet. A separate and harder kind of pasteboard is the thick elastic 
 board used for binding books. The inner layer is made of coarser stuff, sawdust, &c. 
 
 (3) Sized pasteboard, or cardboard, is made of two to fifteen sheets of sized paper, 
 pressed, and satined. There are varieties of this cardboard, such as Bristol-board, 
 and London-board, the former being extensively used for water-colour drawing, 
 mounting-board, ornamental board, &c. 
 
 Papier-Mache is used for fancy articles, such as the covers for albums, inkstands, 
 blotting-books, paper-knives, &c., as well as for the cells of galvanic batteries. It is 
 obtained from old paper made into a pulp with a solution of lime, and gum or starch, 
 pressed into the form, required, coated with linseed oil, baked at a high temperature, 
 and finally varnished. The pulp is sometimes mixed with clay, sand, chalk, &c., and 
 other kinds are made of a paste of pulp and lime, and used for ornamenting wood, 
 inlaying, &c. 
 
 Coloured Paper. The papers made from coloured rags are the brown packing-paper 
 and coarse coloured papers, such as sugar- and pin-paper. To 50 kilos, of dry pulp 
 coloured pin-paper requires the several undermentioned substances : 
 
 12 '05 kilos. Lead acetate 
 Yellow | o -45 Potassium bichromate 
 
 Blue 
 
 Green 
 
 r 
 1 1-- 
 
 5 
 '05 
 j'oo 
 [05 
 
 Violet 1-05 
 
 Eose 6-00 
 
 Buff 
 
 3-00 
 3-00 
 
 Iron sulphate 
 
 Potassium f errocj-anide 
 
 Blue 
 
 Yellow 
 
 Extract of logwood 
 
 Extract of Brazil wood 
 
 Oil of vitriol 
 
 Chloride of lime 
 
 Ultramarine and aniline blue are also used in colouring the paper. In variegated 
 papers, chemical, mineral, and vegetable colourings are used according to the 
 required colours. Body colours are rendered fluid by a solution of gum arabic or 
 alum in the size, which can be applied by a brush or sponge when only one side is 
 to be coloured. Variegated and tapestry papers are an important part of the 
 manufacture. 
 
 In the manufacture of coloured papers there are used solutions of mineral or 
 organic colours, prepared according to the rules of dyeing, and fine earthy colours 
 are stirred up with starch-paste or with solutions of gum, dextrine, or glue mixed 
 with alum. If only one side of the paper is to be coloured, the colour is applied 
 with a brush or sponge. Otherwise the sheets are taken at once through the liquid. 
 In the manufacture of paper-hangings the processes are similar to those employed 
 in calico-printing. This manufacture is now very important. 
 
SECT. VII.] 
 
 PAPEE MANUFACTURE. 
 
 871 
 
 Graphite paper, used for packing up needles, and other small and fine articles of 
 iron or steel, with a view of preventing rusting, is prepared by hand with an addition, 
 of finely powdered graphite. 
 
 Parchment Paper. Parchment, although made of animal membranes, is often con- 
 founded with vegetable parchment (phy toper gamenf). The latter is made of unsized 
 paper treated with a solution of chloride of zinc or sulphuric acid : i kilo, of 
 concentrated sulphuric acid and 125 grammes of water, in which the paper is immersed 
 so as to equally affect both sides. The length of time differs according to the quality 
 of the paper, the thicker or firmer paper taking a longer time to saturate ; soft paper 
 will take five to ten seconds. It is then placed in a weak solution of sal ammoniac, 
 rinsed in water till no trace of the acid remains, and then dried. When these opera- 
 tions are effected mechanically, a steam machine first pulls the endless paper through 
 a vat of sulphuric acid, then through water, sal ammoniac, and again water, the 
 paper passing on over cloth rollers to dry, and finally over polished rollers to press and 
 glaze the surface. 
 
 In Fritsch's machine for parchmentising paper, the paper travels from the cylinder 
 A (embraced by the beak, a, Fig. 579, to regulate its tension), over the roller, B, into 
 
 Fig- 579- 
 
 the trough, K, filled with sulphuric acid, in which 
 it is supported by a glass roller, C, and between 
 the two glass rods, D, to the first press, _", in 
 which the superfluous acid is squeezed out. The 
 rollers of this press are laid obliquely, so that the 
 acid pressed out may quickly flow back into the trough, K, without flowing along the 
 paper. From E the paper passes into a chest, k, filled with water, and fixed in the large 
 tank, /r, in order to wash off the acid adhering to the paper. The water remains in 
 k until it marks about 30 Tw., and is then let off to recover the acid, whilst its place 
 is taken by fresh water. The paper is passed over a row of wooden rollers, b, and is 
 rinsed from above and below with fresh water from the spirting tubes, s, in order to 
 arrive after the expander, e, at the second press, E z , when the dilute acid or the gela- 
 tinous coating is pressed out. The paper next passes through the^trough, K v filled with 
 an alkaline bath, in order to neutralise any adhering acid, and for its second and third 
 washings respectively to the trough, .A" 2 , with the spirting tubes, t, and the trough, K# 
 with the spirting tubes, u. After a passage through the third press, E v the paper is 
 passed upon the drying cylinder, F, heated by steam, round which it is held by an 
 endless felt, d. Above the drying cylinders are placed the smoothing rollers, H, H^ 
 the upper one of which, H v is" heated to prevent sweating and the formation of rust- 
 stains. The finished parchment paper is then rolled up. For the press rollers, E^ E 3 , 
 
872 CHEMICAL TECHNOLOGY. [SECT. vn. 
 
 and J2 3 , there are used so-called anti-deflection rollers, which are coated with a layer of 
 caoutchouc. The presses are set in action by expansible band discs. 
 
 If dipped in water parchment paper becomes soft and limp without losing its firm- 
 ness. It is permeable for liquids only by dialysis. It is not attacked by boiling, and 
 does not putrefy. From its valuable properties parchment paper is suitable for a 
 variety of purposes, especially as a material for deeds, official documents, &c., and 
 indeed for all writings the preservation of which is important. In comparison with 
 ordinary parchment it is much less liable to be destroyed by insects. It is used in 
 bookbinders' work, and as a substitute for leather e.g., the so-called " sweat-leathers " 
 in hats and caps. It is used instead of animal bladder for covering glasses of pre- 
 served fruits, and for connecting the joints of distillatory, &c., apparatus. It may be 
 cemented together by means of cellulose dissolved in cupric ammonia. According to 
 Ludicke in the conversion of paper into parchment paper the thickness of the paper 
 decreases from 35 to 37 per cent. Its density increases from 32 to 42 per cent, and 
 it increases in firmness 3*8 to 4^5 fold. 
 
SECTION VIII. 
 
 MISCELLANEOUS ORGANO-CHEMICAL ARTS AND 
 MANUFACTURES. 
 
 TANNING. 
 
 THE operation by which the skins of various animals, more especially those of 
 the larger mammalia, are converted into leather is called tanning. By leather 
 we understand a substance, tough, flexible, not harsh ; further, distinguished by re- 
 sisting putrefaction and by not yielding any glue when boiled in water, as is the case 
 with tanned hide, sole leather, and the so-called red-tanned leather, or only after a 
 very continued boiling, as with tawed skins of calves, sheep, or goats. Whatever the 
 differences which obtain in the practical processes for carrying out the conversion, the 
 physical principle involved is the same in all. Knapp's general definition of leather is 
 that it is skin, in which by some means or other the agglutination of the fibres after 
 drying has been prevented. 
 
 To a comparatively very recent period tanning was conducted on an empirical basis ; 
 it is only by a more accurate knowledge of the histological structure of the skin and 
 of the tannin-containing materials that the real nature of the process has become 
 known ; this knowledge being due chiefly to the researches of F. Knapp and Rollet. 
 
 That which is converted into leather is, however, not the skin or hide, but really 
 what is known anatomically as the corium, that is to say, the inner portion of the 
 skins, from which by mechanical (cutting and scraping) as well as by chemical means 
 (action of lime) the other integuments have been removed. In its most general sense 
 tanning should (i) effect the prevention of putrefaction; (2) render the dry skin a 
 supple, fibrous, tough, non-transparent substance, and not horny as would be the case 
 were the skin simply dried. A well-tanned skin or hide possessing these properties 
 is termed " well finished." The specific process of tanning is of course preceded by 
 some preliminary operations, the aim of which is to " dress " the skins or hides that 
 is, in scientific terms, to free the corium more or less perfectly from all other 
 integuments. Tanning in the more restricted sense of the word may be effected by a 
 great many organic and inorganic substances ; but in practice on the large scale there 
 are employed : 
 
 (1) The tannins of the vegetable kingdom. 
 
 (2) Alum and sodium chloride used in tawing or white tanning. 
 
 (3) Oils and fats oil tawing. 
 
 Anatomy of Animal Skin. Leaving the hair out of the question, the skin of tho 
 mammalia consists of several layers. The uppermost of these in which the hair is 
 growing, the epidermis, is very thin, semi-transparent, and consists of cells which 
 contain nuclei. This epidermis is covered by a more or less horny layer not possessing 
 any vital properties, which gradually wears off, and is as gradually replaced by the 
 stratum Malpighii, or Malpighian net, a structure consisting of cells containing fluid 
 
874 CHEMICAL TECHNOLOGY. [SECT. vm. 
 
 and nuclei. It is this layer in which the nerves and finer blood vessels are embedded, 
 together with the glands which provide the perspiration. In the tan-yards this layer 
 is known as the bloom side, or hair side of the skin or hide. The real corium or derma, 
 situated under the layer just mentioned, does not consist of cells, but is of a fibrous 
 texture, and is that portion of the skin which after tanning constitutes the leather ; 
 in the living animal it is separated from the muscles by a more or less strongly 
 developed fat-bearing tissue, the so-called pannicuhis adiposus, which is, however, 
 removed in the dressing, the side of the skin or hide to which it was attached being 
 termed the flesh side. All the histological constituents of skin or hide possess the 
 property of swelling up when put into hot water, and of becoming after more or less 
 protracted boiling converted into glue, more slowly when the skin is taken from old, 
 more rapidly when from young animals. By the action of acetic acid the fibrous 
 tissue of the skin is converted into a jelly-like transparent mass, in which the fibres 
 are not only not destroyed, but are present with their peculiar structure. Alkaline lyes 
 dissolve this tissue but very slowly ; while lime- and baryta-water have no other effect 
 on it than simply dissolving therefrom the cellular binding tissue which permeates it, 
 and which is an albumen compound also acted upon by dilute acids. 
 
 The various operations of tanning, more particularly the preliminary operations of 
 steeping and dressing, are based upon the behaviour of the different histological 
 elements of the skin and hide with alkaline and acid fluids ; but the real process of 
 tanning is based upon the behaviour of the corium with totally different re-agents. 
 This latter substance has the property of combining with tannic acid, several metallic 
 oxides viz., alumina and the iron and chromium oxides oxidised fatty matter, 
 the insoluble metallic soaps (compounds of fatty acids viz., stearic, palmitic, &c. 
 with lead oxide, &c.), picric acid, pinic acid (present in rosin), and other organic 
 substances, somewhat in the same way as animal and vegetable fibres combine with 
 dyes and pigments. In the most extended sense of the word all these substances are 
 tanning agents, because they possess the property of being precipitated on and in the 
 fibres of the corium, so that when the latter is dried the agglutination of the fibres is 
 prevented, and the natural suppleness and softness of the skin preserved. But in the 
 case of the application of alumina compounds, the softness is only imparted to the 
 tanned skins by the operations of currying and dressing. 
 
 Red or Bark Tanning. This branch of industry concerns itself with the conversion 
 of hides into ordinary leather by the use of tannins. 
 
 The tanniferous vegetable matters employed contain as their essential principle 
 tannin which varies in different plants, but which has always an astringent taste and 
 an acid reaction ; it gives a black or green coloration with ferric salts, precipitates 
 solutions of glue and of cinchonine, and converts hides into leather. Etti distin- 
 guishes quercitannic acid : C ly H 16 8 ; the first anhydride or phlobaphen : C 34 H 3o O ir ; 
 the second anhydride C 3l H 28 1G ; the third anhydride or Oser's " oak red " : 
 C 34 H, 6 ]5 ; and the fourth anhydride or Lowe's oak-red : C 34 H 24 O I4 . He considers 
 this tannic acid to be a threefold methylated gallylgallic acid. According to Bottinger 
 the tannin of oak-bark is C l9 H 16 O 10 , but that of oak-wood C^H^O^ and the tannin of 
 hemlock-bark C 20 H 1S 10 . Concerning the tannin of nut-galls, it is converted by acids 
 and by fermentation into gallic acid, which is not suitable for the production of leather. 
 Phlobaphen is apparently as important in tanning as tannic acid itself. Every tannin 
 is quickly destroyed by alkaline liquids (lime water, potassa, or ammonia) with access 
 of air, brown humoid products being formed. 
 
 Oak Bark. This substance is for the tanner the most important of all tannin- 
 containing materials, and cannot be replaced by any other. It is the inner bark of 
 several kinds of oak, Quercus robur, Q. pedunculata, &c., and is stripped from the trees 
 and branches when these have attained an age of from nine to fifteen years, the bark 
 
.SECT, vm.] TANNING. 875 
 
 when cut into splints being termed tan. According to E. Wolff, the quantity of 
 tannin contained in oak-bark is as follows : 
 
 Tannic acid. Age of the trees. 
 
 In the crude bark covered with the rind io-S6 per cent. ... 41 to 53 
 inside layer of the old bark . 14*43 41 to 53 
 
 inside of the bark . ... 13-23 
 
 crude bark and inside of bark . 1 1 -69 
 
 inside layer and inside of bark . 13-92 
 
 inside of bark .... I3'95 
 
 ., .... 15-83 
 
 4i to 53 
 4i to 53 
 4i to 53 
 14 to 15 
 2 to 7 
 
 According to Buclmer's researches (1867) the quantity of tannic acid contained in 
 the best kinds of oak bark does not exceed 6 or 7 per cent. The fir bark (produce of 
 Pinus sylvestris) is one of the best tanning materials, and is frequently used for sole 
 leather ; this bark is stripped off the trees immediately after they have been cut down 
 for timber. While J. Feser found from 5 to 15 per cent, of tannin in this bark, 
 Dr. Wagner found only 7-3 per cent. In the United States the bark of the Abies 
 canadensis is used ; and an extract is in the trade which, according to Nessler's 
 researches (1867), contains 14-3 per cent, of tannic acid. The extract is imported 
 into this country under the erroneous appellation of hemlock extract. The bark 
 of the elm with 3 to 4 per cent, tannin, the bark of the horse-chestnut with about 
 2 per cent, tannin, and beech tree bark with also about 2 per cent, tannin, are all 
 employed for tanning purposes. The younger branches and twigs of the willow 
 trees yield a bark (3 to 5 per cent, tannin) which is especially suited for certain 
 kinds of glove leather ; while another kind of willow bark is used for the tanning of 
 Russia leather. 
 
 In Australia the barks of several species of Acacia (wattle-barks) are used. The 
 most important species are, Acacia calamifolia, A. pycnantha and A. decurrens. 
 A. pycantha may contain upwards of 40 per cent, of tannin. 
 
 Sumac. This substance is, next to oak bark, one of the most important tanning 
 materials ; it is the product the leaves and stems of a shrub, the so-called tanner's 
 sumac (Rhus coriaria and R. typhina), which grows wild in Southern Europe and the 
 Levant, and is cultivated in North America and Algeria. The shoots from the roots 
 -are collected and planted in June, and after some three years' growth, the shrubs are 
 large enough to admit of the branches and leaves being gathered. The young branches 
 and twigs are cut off, and after drying in the sun, the leaves are beaten off with sticks 
 or clubs and next crushed under mill-stones, sifted, and packed into sac.ks, and thus 
 sent into the market. The sumac of commerce is a coarse powder, exhibiting a yellow 
 or blue-green colour, and containing 12 to 16*5 per cent, of tannic acid. By keeping, 
 the tannic acid of sumac is converted into secondary products, owing to a spontaneous 
 fermentation. Sumac also contains a yellow dye-stuff which seems to be identical with 
 quercitrin. With sumac should not be confused another material of the same name, 
 but distinguished as Italian or Venetian sumac, and derived from the Rhus cotinus, 
 also yielding fustet or yellow dye-wood.* Italian sumac is the pulverised bark of the 
 young twigs and leaves of this plant, which under the name of ruga grows in Southern 
 Europe and also near Vienna ; where it is largely used for tanning purposes, being more 
 particularly employed for preparing goat- and sheep-skins. 
 
 Dividivi.The material designated by this name is the seed capsule of some trees 
 found native in Central America, and belonging to the Ccesalpiniacice ; these seed 
 capsules are about 6 centimetres long, are bent as an S, have a brown-red colour, and 
 contain olive-green coloured, egg-shaped, polished seeds. In 1 768 the Spaniards brought 
 
 * This substance is sometimes erroneously confounded with true fustic, the wood of Morut 
 tinctoria. [EDITOK.] 
 
876 CHEMICAL TECHNOLOGY. [SECT. vm. 
 
 this material to Europe, where it is used for tanning purposes on account of the 
 tannin contained in the epidermis of the capsules (more correctly siliquce, or pods). 
 The quantity of tannin was found by Miiller to be 49 per cent., by Fleck 32-4 
 per cent., while Dr. Wagner found from 19 to 267 per cent. Dividivi is rather an 
 expensive tanning material, but is much used for dyeing purposes. Among the 
 tannin-containing substances which are occasionally imported from abroad may be 
 mentioned the bablah, the produce of the Acacia bablah and allied species. This 
 material contains, according to Fleck, 20-5 per cent tannin, while Dr. Wagner found 
 14*5 per cent. Algarobilla, the seed capsules of the Prosopis pallida, a native of 
 Chili, has been also occasionally employed as tanning material in this country. 
 Myrobalans, the fruit of Terminalia chebula and of some allied species, are largely im- 
 ported from Bombay, and are used to a limited extent as a source of tannin, in which 
 they are much richer than is sumac. 
 
 Nut Galls. We understand by this name an excrescence formed on the leaves of 
 the Quercus infectoria by the puncture of the female insect of the Cynips gallce tinc- 
 torice, or oak wasp, effected in the leaves and young twigs in order to deposit its eggs ; 
 the juices of the tree collect round the egg, and on hardening form the nut-gall. This 
 material is best collected before the young insect has become fully developed, because 
 then the gall contains the largest quantity of tannic acid. In the market three 
 varieties are met with, termed black, green, and white galls. The black and green 
 variety have been gathered before the insect became fully developed inside the nut ; 
 these galls therefore do not exhibit outwardly any hole or opening, but on breaking 
 the gall there will be observed in the centre a small cavity surrounded by a light brown 
 friable substance, which contains the larva of the insect. Galls are generally spherical, 
 but exhibit small irregularities of surface, and are of a black-green or grey colour. 
 The white galls are gathered after the insect is fully developed, and has escaped by per- 
 forating the tissue of the gall. This variety is more spongy, and its colour is a red-brown 
 or brown-yellow. Galls of good quality are obtained only from warmer countries, for 
 although galls are formed in our climate upon oak leaves, the quantity of tannin 
 contained amounts to only 3 to 5 per cent. Fehling found in Aleppo galls from 
 60 to 66 per cent, of tannic acid, while Fleck found 58*71 per cent, of this acid, and 
 5'9 per cent, gallic acid. 
 
 Valonia Nuts. These are the dried immature acorn cups of two species of oak, 
 Quercus cegilops and Valonia camata, both being employed in tannin as well as the 
 valonia nuts produced by the puncture of the Cynips quercus calycis. The quantity of 
 tannic acid met with in these substances averages from 40 to 45 per cent. In the so- 
 called valonia flour, obtained by grinding the acorns belonging to this class, Dr. Wagner 
 found from 19 to 27 per cent, of tannin. The acorn cups are imported under the name 
 of drillot, and according to Rothe these contain from 43 to 45 per cent, of tannin. 
 
 Chinese Galls. Under this name has been known in the trade since 1847, an( * 
 imported from Japan, China, and Nepaul, the excrescence upon a kind of sumac, Rhus 
 javanica and R. semialata, produced by the puncture of the Aphis sinensis. This gall- 
 nut is rather oblong or bean-shaped, with an irregular surface covered with a yellow- 
 grey felt; the length varies from 3 to 10 centimetres, and the thickness from 1-5 to 
 4 centimetres; the texture is horny; the quantity of tannin varies from 60 to 70 
 per cent. 
 
 Cutch. The substances long known in medicine under the name of catechu and 
 kino have been for the last fifty years also employed as tannin materials. They are 
 vegetable extracts, that known as cutch (trade term) being obtained by exhausting 
 with boiling water the pith of the wood of the Acacia catechu, a tree met with in 
 different parts of the tropical regions of Asia. The liquor obtained by boiling the 
 pith-wood in water is inspissated, and on cooling forms a solid mass, which is brought 
 
SECT, viii.] TANNING. 877 
 
 into commerce in various shapes and named after the port of shipment. Bombay 
 cutch is met with in the shape of large square blocks, through and round which the 
 leaves of a kind of palm-tree are placed. The colour of the fracture of this substance 
 is a brown-black with a fatty gloss ; externally the mass is dull and friable. Bengal 
 cutch is prepared from the nuts of the Areca catechu, and occurs in commerce as large, 
 irregularly shaped cakes, externally brown, internally more yellow-coloured. Gambir 
 is a variety of cutch prepared in Sumatra, Singapore, and Malacca, and especially in 
 the Island of Eiouw, from the leaves and stems of the Uncaria gambir. The dry 
 extract occurs in commerce in small cubical blocks, which are light, of a cinnamon- 
 colour, and very friable, the fracture being earthy. All these substances contain about 
 40 to 50 per cent, of a peculiar kind of tannic acid or catechu-tannic acid, the formula 
 of which, according to J. Lowe, is C 15 H 14 6 , as well as a peculiar acid, catechueic acid, 
 C 16 H U 6 , not of much use in the tanning process. 
 
 Kino. This drug is very similar to catechu, and is said to be the extract prepared 
 from various plants viz. : 
 
 African kino from Pterocarpus erinaceus. 
 
 East Indian kino from Pterocarpus marsupium. 
 
 East Indian kino, according to others, from . . Butea frondosa. 
 
 West Indian kino from ...... C.uccolaba uvifera. 
 
 Australian kino from Eucalyptus resinifera. 
 
 Kino is met with in small, angular, brittle, brown-red to black-coloured masses, 
 the powder of which is always brown-red. It is soluble in hot water and alcohol, 
 yielding a blood-red solution of an astringent and sweet taste. Kino contains from 
 30 to 40 per cent, of a tannic acid similar to that contained in cutch; both of these 
 materials are especially useful in so-called quick tanning. 
 
 Estimation of the Value of the Tanning Materials. The value of all the tanning 
 materials entirely depends upon the quantity of tannic acid they contain. The latter 
 is soluble in water, and more or less completely precipitated from that solution by 
 various re-agents, such as glue and animal skin, copper acetate, iron acetate, 
 cinchonine and quinine, while a solution of potassium permanganate completely 
 destroys the tannic acid. Upon these properties the following properties have been 
 based for the approximative estimation of the quantity of tannic acid present in various 
 tanning materials : 
 
 1. Precipitation by glue or skin : 
 
 (a) Weighing of the skin before and after immersion in the liquor containing tannin, the 
 
 increase of weight giving the quantity of tannic acid (DAVY). 
 (6) Precipitation with gelatine solution of known strength (FEHLING). 
 
 (c) Titration by means of aluminated solution of glue (G. MCLLER). 
 
 (d) First discover the specific gravity of the tannin solution by means of an areometer, 
 
 next remove the tannin by skin, and then again take specific gravity of liquid, the 
 decrease being proportionate to the quantity of tannin in the original liquor (C. 
 HAMMER). 
 
 2. Precipitation of tannin by copper acetate, and estimation of the relation between tannin 
 
 and copper oxide in the precipitate : 
 
 (a) Volumetrically (H. FLECK) ; or 
 
 (b) By the gravimetrical method (E. WOLFF). 
 
 3. Volumetrical estimation of tannin by iron acetate (R. HANDTKE). 
 
 4. Oxidation of tannic acid by potassium permanganate (LoWENTHAL). 
 
 5. Precipitation of tannin by means of cinchonin, the solution of which is tinged red by means 
 
 of magenta, i gramme of quercitannic acid requires 07315 gramme cinchonine, 
 equal to 4'523 grammes of crystallised neutral sulphate of cinchonin (R. WAGNER). 
 
 The subjoined table shows the composition of several tanning wares : 
 
878 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. viii.. 
 
 
 _ H 
 
 tc 
 
 
 3.5 
 
 <*~~3 
 c -*- 
 
 
 
 
 
 
 * 
 
 
 * 
 
 "5 <" 
 
 6C x 
 C *"" 
 
 fcc'TS ^- 
 
 s S, a 
 
 
 
 
 *" rt 
 
 c S 
 
 *5 "-^ 
 
 "S ai "^ 
 
 3-2 S 
 
 
 . - 
 
 "*? il 
 
 
 
 
 o e = S 
 
 
 
 
 
 
 
 
 1 
 
 * 
 
 
 H !l 
 
 2 ^^ 
 
 Dark pine bark, Carinthia 
 
 22-34 
 
 12-19 
 
 10-15 
 
 5^3 
 
 0*5I5 2 
 
 ,, Thuringen 
 
 30-56 
 
 14-30 
 
 16-26 
 
 IO-24 
 
 0*6298 
 
 Light Swiss do. . 
 
 3I-58 
 
 14-82 
 
 1676 
 
 II-S9 
 
 0-7094 
 
 Nearly white pine bark from) 
 Bohemia . . j 
 
 26-72 
 
 I4-74 
 
 10-98 
 
 8-31 
 
 07586 
 
 Oak bark, Rhine . 
 
 I7-02 
 
 6'43 
 
 10-59 
 
 7-46 
 
 0-7044 
 
 Hungary 
 
 I7'I2 
 
 8-66 
 
 8-46 
 
 6-05 
 
 0-7151 
 
 ,, Sweden 
 
 22 'O8 
 
 10-30 
 
 1178 
 
 874 
 
 0-7420 
 
 Saarlohe 
 
 23-32 
 
 IO'I2 
 
 13-20 
 
 9'97 
 
 07553 
 
 Quebracho wood (red) 
 
 22-46 
 
 I'90 
 
 20-48 
 
 18*30 
 
 0-8935 
 
 (white) 
 
 27-32 
 
 2-44 
 
 24-88 
 
 21-03 
 
 0-8452 
 
 
 38*40 
 
 lO'OO 
 
 28 40 
 
 28-81 
 
 I '0144 
 
 
 J T^ 
 
 
 26 'AA 
 
 26-87 
 
 I "0162 
 
 
 41 "2O 
 
 2VQ2 
 
 mv T-T- 
 I7-28 
 
 16*89 
 
 0*077/1 
 
 
 T^ 
 
 17'SO 
 
 
 6'QO 
 
 w y / / T- 
 
 
 
 * / ** 
 
 J 
 
 V y*J 
 
 
 The Hides. The skins of almost all quadrupeds might be converted into leather by 
 tanning ; but the tanner chiefly prepares his leather from the hides of cattle, occasion- 
 ally from those of horses and asses, as well as of pigs. The quality of the hides not 
 only depends upon the kind of animal, but also upon its fodder and mode of living. 
 The hides of wild cattle yield a more compact and stronger leather than those of 
 our domesticated beasts; among these the stall-fed have better hides than the meadow- 
 fed or grazing cattle. The thickness of the hide varies considerably on different parts 
 of the body, the thickest part being near the head and the middle of the back, while at 
 the belly the hide is thinnest. These differences are less conspicuous in sheep, goats,. 
 and calves. As regards sheep, it would appear that their skin is generally thinnest 
 where their wool is longest. 
 
 The hides of bulls and oxen yield the best and stoutest leather for soles. In the 
 raw untanned state, and with the hair still on, the hides are termed " green " or 
 " fresh." Fresh or green hides are supplied to the tanners by the butchers, or are 
 imported either dry or salted. A hide weighing in the fresh state from 25 to 30 kilos, 
 loses by drying more than half its weight. South America (Bahia, Buenos Ayres, &c.y 
 exports a large quantity of hides, both dry as well as salted, and cured by smoking. 
 The hides of cows yield generally an inferior grained leather ; but South American 
 cow hides may be worked for light sole leather. Calves' hides, again, are thinner, but 
 when well tanned, curried, and dressed, yield a very soft and supple upper leather for 
 boots and shoes. Horse hides are only tanned for saddlery purposes, while sheep- and 
 goat-skins and the skins of lambs are tanned or more generally tawed for the 
 purpose of making wash-leather, morocco, glove-leather, bookbinders' leather. Pigs' 
 hides and seals' skins are tanned for saddlery purposes.* 
 
 The Several Operations. The several operations of the oak bark tanning process 
 may be reduced to three, viz. : A. The cleansing and dressing of the hide on the hair 
 and flesh side ; in other terms, the separation of the corium from the other integu- 
 ments. B. The true tanning. C. The currying and dressing operation, by which the 
 tanned hide becomes a saleable article. These three operations are again subdivided as- 
 follows : > 
 
 A. The cleansing of the hide : 
 
 (1) Steeping and macerating the hide. (3) Dressing the hair side. 
 
 (2) Dressing the flesh side. (4) The swelling of the cleansed hide. 
 
 * The hide of the porpoise yields an excellent leather for stout boots. [EDITOR.] 
 
SECT, viii.] TANNING. 879 
 
 B. The tanning of the cleansed hide, performed either by placing it in tanks or pits 
 with oak bark and water, or in a liquor of these previously prepared, or by the so-called 
 quick method. 
 
 C. The dressing and currying of the tanned hides, by which is understood all the 
 operations which tend to improve the compactness of texture, or give a better grain 
 and better appearance to the leather, together with softness, toughness, suppleness, and 
 colour. 
 
 A. Cleansing the Hides. This operation includes : (i) The steeping or macerating 
 of the hide in water for the purpose of rendering the texture uniformly soft and 
 so supple that it may be bent without danger of cracking, while, on the other hand, 
 steeping also effects a cleansing of the hide by removing from it blood and dirt. The 
 fresh hides of recently slaughtered animals require a maceration in water for some 
 two or three days, but dried, cured, or salted hides have to be left macerating for 
 some eigLt to ten days. This operation should, if possible, be carried on in a stream 
 of water ; but if there is no such convenience, then the hides are placed in large tanks ; 
 in either case the hides are taken out twice daily and put back into the water 
 again. When the hides have become quite soft, they are (2) cleansed or dressed on. 
 the flesh side by being placed with the hair side downwards on a " tree," a stout semi- 
 circular plank, one end of which is placed on the ground while the other is supported 
 by a trestle, so that the plank is in a sloping position. The workman has a so-called 
 dressing-knife, a tool to which handles are fastened, and which is bent so as to form a. 
 slight curve ; with this knife he shaves, or, as it were, planes off, from the hide all fatty 
 tissue and integuments which are situated between the hide and the muscles. At the 
 same time the water is squeezed out of the hide to some extent. After a preliminary 
 or first dressing, the hides are again placed for twenty -four hours in water; the 
 dressing and planing is then quite finished, and the hides having been well washed, are 
 left to drain on the tree ready for removing the hair. In some instances the hides are 
 washed by the aid of " possing-sticks," and " fulled " by means of machinery, by which 
 the operation is greatly shortened, so much so, that two to three days suffice, instead 
 of, as is usual by the aid of manual labour, eight to ten days. (3) This operation aims 
 at the removal from the corium of the epidermis and hair-containing integuments. As 
 the hair and integuments connected therewith are very firmly attached to the corium, 
 the removal can only be safely proceeded with, so as to leave the corium uninjured, 
 by the employment of a menstruum, which more or less dissolves and causes the 
 epidermis to swell up. For this purpose the hides are usually placed in lime-pits, the 
 effect of the lime being the partial dissociation (in an anatomical sense) of the 
 epidermis, so that it and the hairs may be readily removed by mechanical means. 
 
 The effect is usually obtained by (a) Sweating ; (6) Liming ; (c) Application of rusma 
 or compounds of calcium sulphide. 
 
 (a) A semi-putrefactive fermentation called sweating is employed in the case of 
 thick hides, such as serve for sole leather, which are not placed in lime owing to the 
 fact that it cannot be completely removed, and would render the leather brittle. The 
 operation of sweating consists in placing the hides one upon the other, the flesh side 
 turned inward, some salt or crude wood vinegar having been first rubbed in, in a tank, 
 or box, which can be closed, so that the heat generated by the fermentation which sets 
 in may be confined as much as possible to aid the action. As soon as the evolution of 
 ammonia is perceptible, the hides are ready for the removal of the hair, which is 
 shaved off, together with the epidermis, by the aid of the dressing-knife. Instead of 
 causing the sweating to be done by fermentation, the hides are sometimes hung on laths 
 in rooms either heated by means of steam or by fire. A temperature of from 30 to 50 
 should be kept up, together with a good current of steam, by which the epidermis is 
 thoroughly softened. In order to prevent any injury to the corium, the hides are 
 
88o CHEMICAL TECHNOLOGY. [SECT. vm. 
 
 sometimes submitted to what may be termed a cold sweating process, consisting 
 essentially in placing the hides in water-tight tanks, in which there is a constant 
 current of fresh water, the temperature being kept at from 6 to 12. The hides thus 
 submitted to a constantly moist atmosphere become, after from six to twelve days, with- 
 out any perceptible putrefaction, fitted for the removal of the epidermis and hair. 
 
 (5) The liming of the hides not only prepares them for the removal of the hair, but 
 also saponifies the fatty matter ; and though the lime soap thus formed is insoluble in 
 water, it is removed by subsequent mechanical and chemical operations. The operation 
 of liming is carried on in pits, into which, along with milk of lime, the hides are placed 
 so as to be quite covered. Usually several (three to five) pits are in use at once, each 
 of which contains a different quantity of lime. That the milk of lime should be fre- 
 quently stirred in these pits is of course evident. The hides remain in the lime-pits for 
 from three to four weeks. 
 
 (c) The very thin skins of the smaller animals will neither sustain sweating nor 
 liming, and are therefore treated with rusma, a salve-like mixture of orpiment i part, 
 with 2 to 3 parts slaked lime. By the rubbing in of this mixture on the hair side of 
 the skins, the hairs are so softened as to make their removal an easy matter. Bottger 
 states that calcium hydrosulphuret has the same effect ; hence the lime of the purifiers 
 of the gas-works have been of late years frequently employed for treating hides as 
 well as skins, with the additional advantage of yielding a better leather. 
 
 Stripping off the Hair. As soon as the hides are sufficiently prepared to admit of 
 the removal of the hair and epidermis, they are stretched out on the tree and the 
 integuments peeled off by the aid of the blunt dressing-knife. In order to give to the 
 dressing-knife a better grip, the workman strews some fine sand on the hide, and if he 
 has to deal with very heavy and thick hides, uses a large and rather sharp knife. 
 When the hair and the epidermis have been removed, the hides are again washed and 
 macerated in water, and after this dressed ; that is to say, reduced as much as possible 
 to an equal thickness, while the waste tail, leg, and head-pieces are cut off, and the 
 hide planed, thereby losing some 10 to 12 per cent, in weight. 
 
 Swelling the Hides. The aim of this operation is to remove the lime, and also to 
 render the corium more capable of readily absorbing the tan materials. This end is 
 attained by placing the hides in a so-called sour bath, made of refuse malt and bran, 
 which by acid fermentation yields as active principles propionic, lactic, and butyric 
 acids. 
 
 The lime is removed from the dressed hides when placed in this acid liquid, and 
 the lime-soap present becoming decomposed, the fatty acids set free float on the 
 surface of the liquid. The soluble lime salts are completely removed from the hides 
 by a subsequent thorough washing with water. The thickness of the hides is doubled 
 by the swelling action of the acid liquid, aided by the mechanical action of the carbonic 
 acid evolved from the calcium carbonate deposited within the fibres of the hides ; while 
 the butyric acid fermentation distends the fibres of the hides by the gases thereby 
 evolved. When the hides have not been treated with lime but have been submitted 
 to a " sweating," they do not require the acid bath, but are simply placed in water for 
 the purpose of swelling them. Yet the sour bath is preferable owing to its more 
 regular action. 
 
 Instead of using the preceding mixture for the purpose of removing the lime and 
 of swelling the hides, they are often placed in acid tan. liquor (red tan liquor) that 
 is to say, a liquor containing exhausted oak bark solution which has served for 
 tanning. This liquor appears to contain also large quantities of lactic and butyric 
 acids. The dressed hides are first placed in a diluted red liquor, and then in a 
 stronger liquor, this operation taking some twelve to fourteen days. Macbride and 
 Seguin have proposed to substitute very dilute sulphuric acid (i in 1500), but although 
 
SECT, viii.] TANNING. 88 1 
 
 by the use of this acid the operation of swelling is rendered far more rapid, the 
 quality of the leather is impaired. Phosphates and animal excreta which contain a 
 large quantity of uric acid, such as that of dogs and of pigeons, have been, and in 
 many cases are still, used for the purpose of swelling hides, especially skins of sheep, 
 calves, and goats. 
 
 B. The Tanning. The main object of the operations just described is first to obtain 
 the corium as much as possible separated from the other integuments and textures be- 
 longing to the skin, and next to render the corium as much as possible permeable by 
 the liquor in which the vegetable matter containing tannin is dissolved. In practice 
 it is taken for granted that a dry hide gains one-third in weight by being converted 
 into leather, consequently it absorbs that proportion of tannin. 
 
 The impregnation of the fibres of the hide or skin with tannin is effected by two 
 different methods, viz. : 
 
 (1) By placing the hides between layers of oak bark chips in a tank, so-called tan- 
 
 ning in the bark ; or 
 
 (2) By immersing the hides, first in a dilute, and then in a concentrated aqueous 
 
 infusion of oak bark. 
 
 (i) Tanning in Bark. This mode of tanning is at the present time confined to 
 heavy hides intended for sole leather. The tanks in which this operation is carried 
 on are made of wood, either oak or fir, are of course watertight, and are usually sunk 
 into the soil. Brick cisterns lined with cement are occasionally used, but are objec- 
 tionable, at least when newly built, on account of the deteriorating action of the 
 lime and cement upon the oak bark. In some parts of Germany tanks constructed 
 of slabs of slate or sandstone are used. Each tank has sufficient capacity to contain from 
 50 to 60 hides. On the bottom of the tank is first placed a layer of exhausted (spent) 
 tan, and upon this a layer of some 3 centimetres in thickness of fresh bark, then a 
 hide with the hair side downwards, again a fresh layer of oak bark, and again a hide, 
 alternately until the tank is nearly filled, care being taken to put some more bark on 
 the thickest part of the hides, and to fill not only all interstices with bark, but to put 
 on the top a layer of some 30 centimetres thickness of spent tan. Water is next 
 poured into the tank until it stands a few centimetres above the topmost hide ; this 
 having been done, a lid in England loose planks is placed on the tank, the contents 
 of which are left undisturbed for some time. When Valonia flour is employed with 
 the oak bark only half the quantity of the latter is necessary. 
 
 The hides are left in " the first bark" for from eight to ten weeks, the period being a 
 little shortened if Valonia flour is also used. Before all the tannin has been absorbed, 
 and as a consequence the formation of volatile and odorous acids (valerianic, butyric, 
 <fec.) has commenced, the hides are transferred to another tank, and again placed be- 
 tween alternate layers of fresh bark, the only difference in the arrangement being that 
 the hides which were first placed on the top are now laid at the bottom of the tank. 
 The hides are now left for three or four months, so as to thoroughly absorb the tannin. 
 They are next placed for some four or five months in another tank which contains less 
 bark. In the case of very heavy and thick hides the process is repeated four or five 
 and even six times. The quantity of bark required for obtaining thoroughly well- 
 tanned leather depends partly on the quality of the bark and somewhat on the condi- 
 tion of the hides. Usually the tanners reckon that the quantity of bark required 
 amounts to from four to six times the weight of the dry hides ; and taking the weight 
 of these at an average of 20 kilos there will be required : 
 
 For the first tank 40 kilos, of bark 
 second 35 
 
 third 30 
 
 105 
 
832 CHEMICAL TECHNOLOGY. [SECT. vm. 
 
 A dried and well-tanned hide weighs about 22 kilos., or from 10 to 12 per cent, 
 more than the dry raw hide. A thoroughly tanned hide exhibits, when cut with a 
 sharp knife, a uniform texture, free from fleshy or horny portions, while the grain on 
 the hair side should not, on being bent, slowly exhibit signs of cracking. 
 
 (2) Tanning in Liquor. The thinner hides, and indeed most skins (when tanned, 
 as distinguished from tawing), are placed in infusions of the tannin-containing mate- 
 rial. There are various methods in use for this operation, which is based mainly upon 
 a thorough uniform swelling of the hides, so that when these are placed in weak 
 liquors the tannin may penetrate readily and uniformly. The hides are, in fact, very 
 gradually tanned. When taken from the liquor the fluid is forced by mechanical 
 means out of the hides before they are placed in a stronger liquor, which is obtained 
 by exhausting the tanning materials by the aid of cold water. The thinner kinds of 
 hides are thoroughly tanned in from seven to eight, the heavier hides in from eleven to 
 thirteen weeks. 
 
 Quick Tanning. Many methods some quite impracticable, and most of them 
 thoroughly irrational have been proposed- for converting hides into leather in a very 
 short time. Of these different methods we briefly mention the following : (i) The 
 hide is simply placed in an infusion of the tannin-containing material Macbride's 
 process, improved by Seguin (1792). Application of hydrostatic pressure to force the 
 liquor through the hides, kept from contact with each other by a stout woollen 
 tissue. (2) Circulation of the fluid containing tannin, several tanks being connected 
 together by means of pipes, and the liquor being forced through the tanks by means 
 of pumps (Ogereau, Sterlingue, and Turnbull's methods). (3) The hides are sewn 
 together so as to form sacks, which are filled with oak bark chips and water, and then 
 placed in an aqueous solution of cutch, to which, in order to increase its specific 
 gravity, coarse molasses is added Turnbull's method by increased endosmose. At 
 the time this mode of proceeding was brought forward, the diffusion of liquids 
 by dialysis (discovered by Graham in 1861) was unknown. (4) Motion of the hides 
 in the tannin-containing liquids, the hides being placed in a cylinder constructed of 
 wooden laths, so as to leave open spaces between them. This cylinder is immersed 
 horizontally in the liquid to a greater or less depth, so that in every revolution the 
 hides are alternately in and out of the liquid Brown, Squire, and C. Knoderer's 
 methods. (5) Application of mechanical pressure to the hides, which having been 
 from time to time removed from the tanning tanks, are placed upon perforated planks, 
 and either pressed under a heavy roller or are placed in a press Jones, Nossiter, Cox, 
 and Herapath's method. (6) Application of hydrostatic pressure for the purpose of 
 causing the tan-liquor to penetrate the hides, which are sewn together so as to form 
 bags, which, having been filled with oak bark liquor, are placed in suitably constructed 
 vessels, so that hydraulic pressure may be applied without fear of bursting the bags ; or 
 the hides are fastened by means of screws and bolts, placed on a framework which is 
 immersed in a well-constructed cistern filled with tan-liquor, hydraulic pressure being 
 applied Drake, Chaplin, and Sautelet's methods. (7) Snyder's method of punctation, 
 consisting in perforating the hide over its whole surface, the punctation being effected 
 by sharp needles, so as to constitute artificial pores. The experiments of Knapp have 
 proved the thorough irrationality of this plan, it having been found that the hide is so 
 permeable to tannin-liquor that a piece of calf-skin, when placed iji a solution of tannin 
 of the consistency of syrup, is thoroughly well tanned in about an hour's time. 
 (8) Application of a vacuum by placing the hides in a vessel from which the air may be 
 withdrawn by the aid of air-pumps ; tan liquor having been forced into the vessel, the 
 air is re-admitted and again withdrawn Knowly and Knewsbury's plan. Knoderer 
 has recently found that by a judicious combination of the vacuum method, followed by 
 motion and fulling of the hides in the tan-liquor, the operation of tanning is much 
 
viii.] TANNING. 
 
 883 
 
 shortened. The reader should bear in mind that the methods here alluded to are not 
 now in general use. 
 
 Dressing or Currying the Leather. When the hides have been converted into 
 leather by the processes described, they are not by any means fit for use nor ready 
 for sale as a finished material, but require to be dressed, or, as it technically termed, 
 curried, an operation not necessarily performed by the tanner at least, not in 
 England and France. The several operations are not similar for all kinds of leather, 
 but depend to some extent upon the use to which it is intended to be put. For in- 
 stance, sole leather is submitted simply to a process the object of which is to render 
 it sufficiently stiff and compact, so as not to alter its shape by wear. 
 
 Sole Leather. The dressing or currying of this kind of leather consists mainly in 
 submitting it to a mechanical operation of hammering, by which the material is 
 rendered more compact. As soon, therefore, as the hides are taken from the tanning 
 tanks, the adhering spent tan is brushed off with a broom, after which the hide is dried 
 in a cool place, and when dry is laid flat upon a polished stone slab, and then beaten 
 with wooden or iron hammers, an operation in large establishments performed by 
 .hammers moved by machinery. 
 
 Upper Leather. The dressing of this kind of leather, chiefly used by saddlers and 
 boot and shoe makers, is a far more complicated process, and depends in a great mea- 
 sure on the use for which the leather is intended. 
 
 The Paring. The first of these operations is the paring or whitening, which 
 means the cutting away, by the aid of a tanner's shaving-knife, of all portions of 
 the hide which are too thick, so that the whole hide may be made of uniform 
 thickness. This operation is carried on upon the tanner's " wooden leg," the hide 
 being placed with the hair-side downwards. When goat, lamb, sheep, or calf- 
 skins are to be pared, they are placed upon a polished slab of marble, and, having 
 been well-stretched, the raw or projecting parts are cut off with the tanner's shaving- 
 knife. 
 
 The Scraping or Smoothing. The aim of this operation is similar to that of the 
 former, and more particularly is employed in the case of leather intended for making 
 gloves. The leather is first dried and next fixed on the " perching-stick," one end of 
 the skin remaining free, the other being taken hold of by the operator with a pair of 
 forceps. The skin having been stretched, the perching-knife, a highly polished some- 
 what convex steel disc of from 1 8 to 30 centimetres diameter, and provided in the centre 
 with an opening fitted with a piece of leather serving as a handle, is brought into use, 
 the portions of the skin which require to be pared off being usually indicated by being 
 rubbed over with chalk. 
 
 Graining the Leather. As in consequence of the drying of the leather the grain 
 has become flat, smooth, and unequal, it is raised by an operation performed by means 
 of the pommel, also termed the graining- or crimping-board, a piece of hard wood 
 30 centimetres in length by 10 to 12 centimetres breadth, flat and smooth on the top, 
 but on the opposite side, in the direction of the length, somewhat curved, so that it is 
 thickest in the middle, this part being provided with parallel notches, which are 
 occasionally sharpened by means of a file ; a leather strap is fastened to the top as a 
 handle. The leather to be grained, having been placed on the dressing-table, is 
 fastened to the edge of the wooden board by means of iron clamps, and those portions 
 of the leather, the grain of which has to be raised, having been somewhat bent, are 
 rubbed with the pommel so as to render the grain uniformly visible. 
 
 Polishing with Pumice-Stone. Such kinds of leather as require no grain (for 
 instance, the leather used in carding machines) after having been pared, are moistened 
 and then rubbed over on both sides with pumice-stone, being thus rendered smooth. 
 
 Raising the Grain Slightly with Pommels of Cork. Leathers which require a higher 
 
884 CHEMICAL TECHNOLOGY. [SECT. vin. 
 
 gloss, such as the coloured leathers, are treated with a pommel made of cork, by which 
 they are made to assume a velvety appearance. 
 
 Smoothing with the Tawers Softening Iron. If a still higher gloss is required, 
 the leather is first smoothed, or rather ironed, with iron or copper " sleekers," and 
 next polished with glass sleekers, a stout cylindrical piece of glass, 0-3 metre in length 
 by 10 centimetres diameter, the leather being placed on a tanner's wooden-leg. 
 
 Rolling. Leather intended for saddles, in order to impart to it the appearance 
 natural to hog's leather, is passed through rollers, the surfaces of which are provided 
 with blunt points, which, being forced into the leather, give to it the desired 
 appearance. 
 
 Finishing Off, In order to remove from the leather any creases and other in- 
 equalities of surface, it is damped, and then smoothed with a flattening-iron, or, if the 
 skins are thin, with a piece of horn provided with blunt teeth. 
 
 Greasing. When the upper leather is required to be very supple and soft, it is 
 greased ; that is to say, it is rubbed with a mixture of fish-oil and tallow, or better, 
 with the peculiarly modified fish-oil which has been used in " chamoising," having been 
 recovered by the aid of a solution of potash from the chamois leather skins. The hides 
 to be greased are first moistened, and having been rubbed with the greasy matter, are 
 dried in heated rooms, so that the hides, by actually combining with the fatty 
 matters, become, as it were, tanned and tawed at the same time. The greasing is there- 
 fore not simply an operation of dressing, but in reality a second tanning (technically 
 tawing) process. 
 
 The black colour usually seen on the surface of leather required for saddlery and 
 boot-making is imparted to the hides by rubbing them with a fresh solution of oak 
 bark and then sponging them over with a solution of copperas to which some blue 
 vitriol has been added ; the hides are then again dressed, and lastly rubbed with a 
 paste made of fish-oil, tallow, lamp-black, yellow wax, soap, and copperas, the object of 
 this operation being to protect the leather from the injurious effects of the shoe- 
 blacking, which usually contains sulphuric acid.* Finally, the leather is painted or 
 brushed over with a mixed tallow and glue solution, and then, having been polished 
 again with glass, is ready for sale. In order to keep leather supple and soft, it is besfc 
 to rub it with a mixture of fish-oil and lard. 
 
 Yufts, Jufts, or Jufti, Russia Leather. Under the name of yufts is understood a 
 peculiar kind of leather, usually of a red or black colour, which is very water-tight and 
 strong. This kind of leather was formerly made exclusively in Russia, whence it was 
 obtained in large quantity, the name being derived from the Russian Jufti, signifying a 
 pair, and apparently due to the fact that, in tanning, the hides are sewed together in pairs. 
 The hides usually prepared for Russia leather are those of young cattle ; sometimes, how- 
 ever, the hides of horses and the skins of sheep, goats, and calves are employed. The 
 operations for preparing yufts are: (i) The cleansing of the hides, performed in the 
 usual manner with lime. (2) The swelling of the hides in an acid bath prepared with 
 malt, exhausted tan-liquor, or with kaschka (excreta of dogs rubbed up with water). 
 (3) The tanning, not performed with oak bark, but with the barks of various kinds of- 
 willows, fir and birch bark being also used. The dressed hides are first placed for 
 some days in partly exhausted bark, and are then put into the tanning tanks along 
 with bark (as above described), or are sometimes placed in a warm infusion of the 
 tannin -containing materials. The tanning continues for five or six weeks. (4) The 
 tanned hides are placed on the planing-block for the purpose of draining, and are next 
 impregnated with diggut or elachert, oil of birch, obtained by a process of dry distil- 
 lation from birch wood . This oil contains creosote, phenol (of a peculiar kind accord- 
 ing to Louginine), and paraffine. It is rubbed into the hides on the flesh side, and 
 
 * For a shoe-blacking without acid see Chemical News, vol. xxir. p. 120. 
 
SECT. vni.J TANNING. 885 
 
 when thoroughly impregnated they are stretched until they become soft and supple. 
 The hides are next rubbed on the hair side with a solution of alum, and then grained 
 and dried. The dry hides are dyed in pairs, sewn together so as to form a sack, into 
 which a decoction of dye material is poured. When a red colour is desired, the dye is 
 prepared from sandal-wood and Pernambuco-wood extracted with lime-water, to which 
 some potash or soda is added. In more recent methods the hides are dyed by being 
 brushed over five or six times with the dye material. The dry leather is finally dressed 
 by the mechanical operations previously described. The use of yufts for bookbinding 
 and other purposes is well known. Owing to the empyreumatic oil with which this 
 kind of leather is impregnated insects do not attack it. 
 
 Morocco Leather. By morocco leather is understood a kind of leather which, when 
 genuine, is obtained from goat- or kid-skins, and is very soft, elastic, highly coloured, 
 and not lacquered. We distinguish between genuine morocco and the imitation 
 obtained by the splitting of calf, sheep, and other skins, as chiefly employed in book- 
 binding. 
 
 The preparing of morocco leather is undoubtedly one of the many industrial 
 discoveries of the Saracens ; even at the present day a great deal of morocco leather 
 is made by their descendants in Northern Africa and the Levant. The preparation 
 of good morocco leather requires very great care, especially as regards the 
 preliminary operations. The skins are deprived of the hair by the aid of lime and 
 sweating. The tanning material in general use is sumac, the skins being sewn up so 
 as to form sacks into which water is poured together with pulverised sumac ; by this 
 mode of employing the tanning matter the operation is finished in three days. Calf 
 and sheep skin are very generally tanned in England by the same method. The 
 dyeing of morocco leather is not performed in the Oriental countries ; the dry tanned 
 skins are exported under the name of Meschin leather (cuir en croutes) to be dyed and 
 dressed in Europe. 
 
 Dressing Morocco Leather. The skins are dyed and next dressed. The dyeing is 
 performed (a) by means of the dye- vat (for genuine morocco), or (/3) with the 
 brush (for imitation morocco), (a) The operation of dyeing with the vat is performed 
 in a small trough large enough to hold one skin, and filled with dye-li nior at 60 from 
 a larger tank. The workman pours in no more of the dye material than can be con- 
 veniently absorbed by the skin, which is continually moved to and fro. The dyed 
 skins are layed out flat, and from two to four dozen placed one upon the other. The 
 dyeing operation is repeated several (three to five) times, care being taken to turn the 
 heap over so that the undermost skin is placed on the top of the heap previous to 
 beginning the dyeing operation again. The dyed skins are washed in water and next 
 dressed. () The imitation morocco is dyed by the dye-liquor being uniformly brushed 
 over the skins ; these having been first stretched on a table, the dye-liquor is 
 brushed over more than once so as to produce a uniform hue. The effect of the 
 dyeing is greatly enhanced by the dressing of the skins and the fine grain given to 
 them. The dyed skins are first rubbed on the hair-side with linseed oil applied by 
 means of a piece of flannel. The calendering or glazing by machinery is the next, 
 operation, after which the peculiar appearance of the surface is imparted by means of 
 strong pressure or so-called platting. Yellow skins are not glazed, because their colour 
 would thereby become a brown. The aniline colours are now largely employed in 
 dyeing skins. 
 
 Cordwain, Cordovan Leather. This differs from morocco only by being prepared 
 from heavy skins, and by retaining its natural grain or not being platted. It is usually 
 met with dyed red, yellow, or black. 
 
 Lacquered Leather. This kind of leather, now largely used by coachbuilders and 
 for making shoes, boots, helmets and other military accoutrements, is an invention of 
 
886 CHEMICAL TECHNOLOGY. [SECT, vin^ 
 
 the present time, its great merit being its property of resisting water, and in being; 
 supple and soft, while the lacquer, if well laid on, should not crack nor peel off. Only 
 black lacquered leather is generally met with. On the tanned, rarely tawed, hide, which 
 has not been greased, is very uniformly laid a varnish, which is thick arid tough while 
 cold, but thinly fluid when warm ; this having been done, the hide is placed in a brick- 
 built stove kept at 50, where the varnish dries after having become so fluid as to- 
 run uniformly over the surface of the leather, which is placed quite horizontally. The 
 coloured lacquers are generally more thinly fluid and are dried at a lower temperature. 
 The hides chiefly used for lacquering are cow-hides ; or a thin hide is obtained by 
 splitting thick hides and lacquering them. 
 
 The leather in use by pianoforte-makers for covering the hammers is prepared by a 
 process usually kept a trade secret. This kind of leather requires to be soft and very 
 elastic. All that is known about the process of preparing this material is that ifc is 
 obtained by tanning and tawing (chamoising) combined ; the hair having been removed,, 
 but not the epidermis, the hide is first fulled in oil, then washed in lye, bleached in the 
 sun, and next tanned in a tepid oak bark infusion. Danish leather is prepared by 
 tanning sheep-, goat-, kid-, and lamb-skins with willow bark ; such leather being 
 chiefly used for gloves. It is distinguished by its strength, suppleness, and bright 
 colour. 
 
 Alum Tanning Taiving. Alum-tanning makes use especially of aluminous 
 salts for converting hides into a white or light-coloured leather. It has three varieties : 
 
 (1) Ordinary tawing, in which thin hides, such as those of sheep and goats, are 
 
 worked lip with a mixture of alum and common salt without the use of oil. 
 
 (2) Hungarian tawing, in which the hides of oxen, buffaloes, horses, &c., are worked 
 
 up without a previous treatment with lime and then saturated with oil. Closely 
 connected with this process is the preparation of Klemm's fat-leather. 
 
 (3) French or Erlangen tawing, for obtaining glove-leather from the skins of kids, 
 
 young calves, lambs, rarely of chamois. 
 
 (4) Preparation of leather with insoluble soaps and its tanning with compounds of 
 
 iron or of chrome (Knapp's Leather). 
 
 (i) Common Tawing. The tawer obtains sheep-skin, or occasionally goat-skin, 
 either with the wool off or " in the wool," as the term runs, in the latter case greater 
 care being required, because the value of the wool, which, by careful working may be 
 obtained in good condition, refunds a considerable portion of the expense of the 
 operation by its sale. The various operations of tawing are in a certain measure 
 similar to those of tanning. 
 
 The steeping and planing is carried on as in the tanning process. The workman 
 places ten skins on the planing-tree, and dresses each skin with the dressing-knife on 
 the hair as well as on the flesh side; next, the wool or hair is shaved off after the 
 skins have been first treated with the lime; but when "in the wool " the skins are 
 cleansed with thin lime-water, which is laid on the flesh side of the skin by a brush 
 made of cow's hair, so that the wool is not brought into contact with lime. The wool 
 is removed, not by a planing-iron, but by means of a piece of wood somewhat sharpened. 
 The wool having been removed, the skins are brushed over with a mixture of equal 
 parts of lime and sifted ashes ; next the head and leg strips of the skin are turned 
 inside. Each skin is then folded together and beaten, in order to prevent the wool 
 being touched by the lime. The skins are left in this condition for eight to ten days 
 until the wool is loosened. The skins are next thoroughly washed on the flesh side as 
 well as on the wool side in order to remove the lime and dirt ; tliis having been done 
 the wool is partly pulled off by the hands, partly removed by a blunt tool. The skins 
 thus deprived of wool are placed in the lime-pit and further treated as just described. 
 In order to remove the paste adhering to the skins they are, on being removed, placed. 
 
SECT, viii.] TANNING. ' 887 
 
 in a tank, where, owing to the quantity of animal matter dissolved in the water, a 
 fermentation has arisen accompanied by an evolution of ammonia. By the action of 
 this alkali a large portion of the fatty matter contained in the skins is removed. After 
 being taken from the lime-pit the skins are placed on the dresser's block, and some 
 parts, such as the ears, skin of tail, portion of top part of chest, are cut off and thrown 
 aside for the glue-boiler. The skins are put over-night to soak in water, and then 
 again placed on the dressing-block in order to be planed with a blunt iron on both sides 
 of the skin ; this operation is repeated after the skins have been placed in a tank 
 containing water, and while there thoroughly beaten with a heavy wooden " possing- 
 stick " in order to remove lime. In the subsequent planing the lime and lime-soap are 
 forced out, and any wool that has remained shaved off. In order to dissolve the last 
 traces of lime the skins are placed in an acid-tank containing bran and water, in which 
 by fermentation lactic and acetic acid have been formed. These acids convert the 
 lime of the skins into soluble salts, while the process causes the swelling of the skins, 
 which thus become better adapted to absorb the tanning material. The skins remain 
 in the sour-tank for two to three days. The tanning material consists for i dicker 
 (10 skins), of an alum lye, containing 0^75 kilo, of alum, and 0*30 kilo, of common salt 
 dissolved in 22*5 litres of boiling water, i litre of this liquid is poured into a trough, 
 and having become tepid, each skin is separately thoroughly washed with and soaked 
 in it, and then put aside without being wrung out, the skins being placed one upon the 
 other so as to form a heap. After lying thus for two or three days, the skins are 
 wrung out and hung up to dry slowly by exposure to air. 
 
 As regards the theory of the action of the alum lye in the^tawing operation, it was 
 formerly believed that only the aluminium chloride formed by double decomposition 
 between the constituents of the common salt and the aluminium sulphate of the alum 
 (the alkaline sulphates being considered useless) was active, and that a basic alu- 
 minium chloride (aluminium oxychloride) combined with the skin, there being left in 
 solution aluminium chloride. It was also known that aluminium acetate, if used 
 instead of alum lye, was quite as active and yielded excellent results. The experiments 
 made by Dr. Knapp, sen., with alum, aluminium acetate, and aluminium chloride 
 have proved that 110 decomposition ensues when the aluminium salt is taken up by the 
 skin, the quantity taken up being for the undermentioned salts as follows : 
 
 Of alum 8'Spercont. 
 
 Of aluminium sulphate . . . . . 27^9 
 
 Of aluminium chloride 2 7'3 > 
 
 Of aluminium acetate . . 2 3'3 
 
 The aluminium salts do not, however, combine with skin under all conditions in the 
 same quantity as just mentioned, as experience proves that the skins absorb more when 
 placed in concentrated than when in dilute solutions. As regards the part played by 
 the common salt in the preparation of the alum lye, the salt is not there simply to bring 
 about the conversion of the aluminium sulphate into aluminium chloride (recent 
 experiments made by Knapp in 1866 have proved that by employing i mol. of potash 
 alum and 3 mols. of common salt, = 37 per cent., no mutual decomposition ensues), but 
 the salt is in this process active by itself, partly aiding dialytically the action of the 
 alum, partly owing to its property possessed also by alcohol of withdrawing from 
 animal tissues the water they contain sufficiently to prevent the fibres from becoming 
 glued together by the drying of the substance, thus promoting the formation of leather. 
 The dry and tawed skins will be found to have become shrunken and stiff, having lost 
 much of their suppleness and flexibility. In order to remedy these defects the skins 
 previously damped with water are submitted to a mechanical operation, being placed 
 on the convex side of a curved iron, and stretched by being drawn between this fixed 
 iron and a movable steel plate, which is fitted closely upon the other. After having 
 
888 CHEMICAL TECHNOLOGY. [SECT. vm. 
 
 been thus softened, the skins are stretched on a frame for some time to become dry. 
 When dry they are ready for sale, the leather thus obtained being largely used under 
 the name of white skins for the lining of boots and shoes. 
 
 (2) Hungarian Tawing Process. This process is distinguished from that just 
 described, inasmuch as the heavy hides of oxen, buffaloes, cows, horses, &c., are made 
 into leather for saddlery and other purposes, while sometimes also the skins of wild 
 boars and of other animals are thus tawed for making flail strings. The raw hides are 
 first soaked in water to remove blood and impurities. Next the hair is shaved off by 
 means of a sharp knife. This operation performed, the hides are put into an alum 
 lye, which for a hide weighing 25 kilos., consists of 3 kilos, of alum, 3 of common salt, 
 and 20 litres of hot water. This liquor when tepid is poured into an elliptical tub in 
 which the hide is placed. 
 
 One of the workmen then jumps into the tub and by moving the hide about with 
 his feet soaks it thoroughly with the liquor, in which it is then left for at least eight 
 days, the operation of treading with the feet being repeated. The hide is now taken 
 from the tub and hung up to dry, and when dry is stretched and " fatted " in by the 
 following method : The hide is warmed by being held over a charcoal fire, and when 
 warm is rubbed on the hair as well as on the flesh side with molten tallow, of which 
 some 3 kilos, are used for every hide. "When thirty hides have been thus treated, 
 they are one by one again held and moved to and fro over the fire, and next hung 
 up in the open air to dry. The tallow partly combines with the hide. 
 
 The hides thus prepared are converted into a leather of excellent quality, especially 
 suited for the harness of horses and saddlery work of a more common kind, in which, 
 as in that used for artillery horses, great strength is required. This leather is cheap 
 on account of its being prepared in a short time. 
 
 (3) Glove Leather. The so-called Erlanger, or French tawing process, is employed 
 only for the production of the glace, or kid leather, used for making gloves and ball- 
 room shoes. The hair side of the skins intended to be converted into this leather is 
 left unchanged, while as regards wash-leather gloves which are treated (tanned) with 
 fish-oil the hair side is cut off. The skins intended to be converted into kid leather 
 are treated with extraordinary care, and thus acquire in a very high degree all the 
 good quality of alum-tanned (or rather tawed) leather. As these skins are often 
 intended to remain white or are dyed with delicate colours, the greatest care is taken 
 to prevent any injury, as, for instance, contact with oak wood or with iron while wet. 
 
 Two kinds of skins are employed for conversion into the better varieties of kid 
 leather ; one of these, the moie expensive, being the skins of young goats, fed solely 
 with milk, the other being lambskin. Each of these skins yields on an average two 
 pairs of gloves. The leather of which ladies' ball-room shoes are made is obtained 
 from the hides of young calves (so-called calf kid). The preliminary operations of 
 preparing this leather are exactly similar to those already described for the ordinary 
 white leather ; but the tawing operations are quite different, the skins being put into 
 a peculiar mixture, by which they are not only tawed, but simultaneously impregnated 
 with a sufficient quantity of oil to render them soft and give suppleness. The mixture 
 consists of a paste composed of wheaten flour, yolks of eggs, alum, common salt, and 
 water. The flour, by the gluten it contains, aids the absorption of the alumina com- 
 pound, and thus assists the real tawing. The starch does not enter into the composition 
 of the skins, while the yolk of eggs acts by the oil it naturally contains in the state of 
 emulsion, this oil giving to the kid leather that suppleness and softness which is so 
 much esteemed in gloves. It appears that emulsions made with almond oil (the so- 
 called sweet oil of almonds a fixed oil), olive oil, fish oil, and even paraffine may be 
 advantageously substituted for yolk of eggs. The skins are thoroughly soaked and 
 kneaded in this mixture, to which, in France, there is sometimes added from 2 to 3 per 
 
SECT, vni.] TANNING. 889 
 
 cent, of carbolic acid for the purpose of preventing the too strong heating of the 
 skins when impregnated with the mixture and packed in heaps. The skins are 
 next stretched by hand and dried as rapidly as possible by exposure to air. Having 
 been damped, a dozen of the skins are placed between linen cloths and trodden upon to 
 render them soft. After this they are, one by one, planed, dried, and again planed. 
 Either by rubbing with a heavy polished glass disc or by the appreteur, simultaneously 
 with the application of some white of egg, or a solution of gum, or of fine soap, a 
 gloss is given to the skins, the hair side of which is the right side or dyed side. The 
 dyes are applied either by immersion or by brushing over the leather; the latter, or 
 English method of dyeing skins, is more ordinarily practised. 
 
 According to Knapp's researches very good white kid leather is obtained by tawing 
 the epidermis (bloss) from lamb- or goat-skins in a saturated solution of stearic acid in 
 alcohol. The leather thus obtained is very soft, has a whiter colour than ordinary 
 glace leather, and a beautiful gloss. 
 
 (4) Knapp's Leather. The preparation of leather with the aid of insoluble soaps, 
 introduced by Knapp, would appear to have become of some importance. The pro- 
 perty possessed by oxide of iron of acting as a tanning material has been known for 
 along time, and in 1855 Mr. Belford took out a patent in this country for a mineral 
 tan method, in which oxide of iron was used ; but good leather did not result. The 
 hides do not become really tanned by being immersed in solutions of such metallic 
 salts as those of the ferrous and ferric oxides, and zinc and chromium oxides ; for 
 though the acidity of these solutions is reduced to a minimum without producing 
 a permanent precipitate, and thereby the deleterious action of the acid upon the fibres 
 of the hides decreased, and though a certain combination of the oxide and fibres takes 
 place, no real leather is formed because the substance when finished is not fitted for 
 contact with water, for then the so-called tanning is washed out. Knapp's process also 
 is not really a tanning but a tawing operation, by which the skins are alternately 
 immersed in a solution containing from 3 to 5 per cent, of soft soap, and then in a saline 
 solution of oxide of iron, or of chromium, containing 5 per cent, of the salt, from which 
 an insoluble metallic soap is precipitated and impregnated with the fibres. After this 
 operation has been several times repeated the hides or skins are washed in water and 
 dried. Although the exterior colour of good sound leather may be imitated, the real 
 qualities of leather are wanting. Knapp's process is not in use or is so entirely 
 modified by substituting alum for metallic oxides that the skins are tawed by a 
 combination of the preceding tawing processes and the oil-tawing process now to be 
 described. 
 
 Iron-tanning is hitherto without practical importance and Heinzerling's chrome 
 tanning is, in the opinion of the author, perfectly worthless. 
 
 Electrical Tanning. The novel process of electrical tanning, patented by MM. Worms 
 and Bale, and worked in this country by the British Tanning Company, Limited, makes 
 use of ordinary tan-liquors, but the tannin is made to act upon the hides by means of an 
 electrical current. At a demonstration of the process which took place in May, 1 890, 
 at Eothsay Street, Bermondsey, the visitors were first shown a drum containing tan 
 liquor of the required strength, into which a pack of Australian salted hides, unhaired 
 and cleaned in the ordinary way, were put. The drums employed are 1 1 feet 6 inches 
 in diameter by 8 feet wide, and contain an electrode running round the interior of one 
 end or head, from which the current passes through the liquor to a similar conductor 
 in the other head. 
 
 The drum was set in motion, and a current of 10 amperes passed through the 
 Hquor. The action of the current which is applied is partly to promote diffusion and 
 partly to electrolyse the liquor, both these effects, aided by the rotation of the drum, are 
 no doubt the explanation of the remarkable saving of time effected by this process, it 
 
890 CHEMICAL TECHNOLOGY. [SECT. vin. 
 
 being possible thus to tan skins and hides in from 24 to 144 hours, against from four to 
 fifteen months by the old process of steeping in pits. A drum was opened which had 
 been running for a little over five days, sections of the hides (salted Australian) were 
 cut and examined by tanners present, and found to be thoroughly tanned. The visitors- 
 then inspected the drying sheds and shops above, where leather was seen in all stages, 
 rolled for sole leather, curried, &c.,also some hides prepared for machine belting, of which, 
 according to some tests shown us by Mr. Conrad Falkenstein, manager at Rothsav 
 Street, the tensile strength before breaking, taking the average from a number of 
 samples, was equivalent to 4305 Ibs. per square inch for the electrically tanned leather,, 
 against 3570 to 3800 for leather tanned by the ordinary process. The leather is now- 
 being sold in the market, and is steadily taking its place in every branch of the trade. 
 
 Oil-Tawing and Wash-leather Process, By this name is understood a peculiar 
 process by which the skins and hides of various animals, such as harts, deer, sheep, 
 calves, oxen (for the white leather for military use as belts, &c.), are converted into so- 
 called oil- or wash-leather. The tanning material is oil, fat, tallow, or fish oil, to 
 which there has been recently added from 4 to 7 per cent, of carbolic acid. The leather 
 thus obtained is chiefly used for making military breeches, socks, vests, gloves, braces, 
 belts, and surgical appliances, a not inconsiderable quantity being also used, owing to its- 
 softness, for washing glass and porcelain. On this account wash-leather is also largely 
 used by gold- and silversmiths for polishing trinkets with rouge (very carefully pre- 
 pared oxide of iron). The upper or exterior layer of the corium, which owing to its 
 greater compactness does not possess the ductility and suppleness of the lower or 
 interior layer, is in the skins intended to be converted into wash-leather entirely cut 
 away, so that no hair and flesh side are taken into consideration. The cutting away 
 of this layer greatly promotes the absorption of the oil, which by the joint action of 
 air and heat yields a product which is a dry compound of fibre and oil, in which the 
 latter physically has disappeared, inasmuch as the leather is not impervious to water. 
 Wash-leather differs in this respect from oil or fat leather ; still, on immersion in, 
 water, the skin does not glue together and shrink. Thin skins, such as those of 
 goats and lambs, are not deprived of their hair side, because it would render them too 
 thin for use. 
 
 The skins intended to be made into wash-leather are, as regards the first stage of 
 the operation, treated exactly as described for the skins treated with alum, the only 
 difference being that the hair is removed together with the hair side portion of the 
 skins, which are next placed in a bran bath in order to remove the lime. After this 
 the skins are stretched and conveyed to the fulling machine in order to become 
 saturated with oil, for which purpose the skins are first laid on a table or bench and 
 are rubbed with oil, the hair side being placed uppermost. This having been done 
 they are made into clouts and placed under the stampers of a machine so as to 
 thoroughly impregnate them with oil. From time to time the skins are taken from 
 the trough and exposed to the air, then again rubbed with oil and put under the 
 stampers until enough oil has been absorbed. By the repeated exposure to air the 
 skins become dry, and oil (fish oil is chiefly used) absorbed ; the exposure to air 
 is continued until the surface of the skins appears quite dry. When the skins have 
 an odour somewhat similar to that of horse-radish, and have lost their fleshy odour,, 
 they have absorbed a sufficient quantity of oil, while a portion of the oil has been 
 somewhat changed and has entered into combination with the fibre, another portion 
 only mechanically adhering to the pores of the skins. The next operation therefore 
 aims at rendering the process of the combination of the oil with the skins more rapid 
 by bringing about a fermentation attended with an elevation of temperature ; this is 
 effected by placing the skins in a warm room, heaping them together, and covering 
 them with canvas to keep in the heat which is generated, care being taken to air the 
 
SECT, viii.] TANNING. S 9 i 
 
 heap from time to time in order to prevent overheating and consequent deterioration 
 of the skins. This operation of airing the skins is repeated until by the spontaneous 
 heating they have acquired a yellow colour and the workmen know by experience that 
 the oxidation of the oil is finished. A portion of the oil (estimated at about 50 per 
 cent, of the quantity originally employed) is left in the skins in uncombined state, and 
 is removed by washing with a tepid solution of potash. From this liquor there 
 separates on being left at rest a portion of fat termed degras, and which, as already 
 mentioned, is employed for the dressing of tanned hides. The skins having been thus 
 deprived of the excess of oil are wrung out, dried, and next dressed, in order to restore 
 to them their softness and suppleness partly lost in the drying. Cordovan or Turkey 
 leather, is oil-tawed without the hair side having been first removed, while the flesh 
 side is blackened in the usual way. This kind of leather is chiefly used for ladies' 
 boots and shoes. According to Knapp, skins from which the hair has been first 
 removed may be tawed by treating them alternately with a solution of soap and dilute 
 acids, so that the fatty acids are precipitated into the fibre. After the tawing the 
 skins thus treated should be thoroughly washed in water to remove all acid. As 
 regards the constitution of the leather, commonly known as wash-leather, tawed with 
 oil, nothing is definitely known, but it would appear that this process of tawing has 
 some analogy to the process of imparting oil to calico intended for Turkey-red dying. 
 
 Parchment. The substance known as parchment is not really leather, because its 
 fibres are neither tanned nor tawed, as proved by the fact that boiling water readily 
 converts parchment into a superior kind of glue similar to isinglass, of course too 
 expensive for joiners' use. Parchment is essentially the well-cleansed and carefully 
 dried skins of hares, rabbits, and especially of calves and sheep. 
 
 Ordinary parchment is prepared from sheepskins, but the variety known as 
 vellum, Velin or Parchemin vierge, is far finer, and is made from the skins of young 
 calves, goats, and stillborn lambs. According to the use intended to be made of 
 parchment, so is its preparation modified. The skins are first soaked in water and 
 then placed in the lime-pits. Sheepskins are cleansed by working with cream of lime 
 in order to preserve the wool. When the hair has been removed the skins are washed, 
 being placed on the dresser's block, and usually also planed with a sharp knife to 
 remove the superfluous fleshy parts. This having been done, each skin is separately 
 stretched in a frame, in a manner very similar to that in use for so-called Berlin-wool 
 work, the skins being held in position by means of strings, and dried by exposure in 
 the open air. Parchment intended for drum skins (from calves' skins), for kettle- 
 drums (from asses' skins), does not require any further operation. If intended for 
 bookbinding the parchment is treated as described, but after drying it is planed with 
 a tool the cutting edge of which is somewhat bent in order to impart a rough surface, 
 whereby the parchment is rendered capable of being written on and dyed. If 
 the parchment be intended as it was frequently before the invention of metallic 
 paper for memoranda written with lead pencils, to be wiped out if desired with a 
 wet sponge, it is after planing painted over with a thin white lead paint, for which 
 a mixture of glue water with baryta or zinc white is often substituted. The vellum 
 of this country is generally obtained from sheepskins, which are split into two 
 sheets by means of cutting-tools. Parchment, after having been dried on the frames, 
 is dusted over with chalk and rubbed with pumice-stone. The sieves used in powder 
 mills for granulating the powder are made of parchment obtained from hogs' skins. 
 
 Shagreen. Genuine Oriental shagreen (saghir, sagri, sagre) is a variety of tawed 
 parchment, one side of Avhich is covered with small hard grains. This material is 
 manufactured in Persia, at Astrakan, in Turkey, and in Roumania, from certain por- 
 tions of the skins and hides of wild asses, horses, and other animals. The hides are 
 soaked in water until the epidermis can be removed easily together with the hairs by 
 
892 CHEMICAL TECHNOLOGY. [SECT. vm. 
 
 the aid of a dressing-knife ; next, the hides are again placed in water so as to swell the 
 material sufficiently to admit of cleansing it, and cutting away on both flesh and hair 
 side all superfluous material, so as to leave only the corium, which then has the 
 appearance of a fresh bladder. In order to produce on skins thus prepared a grained 
 surface, they are put into frames, as described under Parchment, while on the hair 
 side, allabuta, the hard black seed of the Chenopodium album is stamped in, either by 
 the feet or forced in by pressure. When the skins are dry they are removed from the 
 frame, the seed shaken off, and the skins thoroughly planed with a sharp dressing- 
 knife, then put again into water, tawed, and finally dyed. The tawing is effected by 
 the aid either of alum or of oak bark. The dye of shagreen is generally green, and is 
 due to salts of copper. After dyeing the skins are soaked in mutton tallow. 
 
 Fish skin, or fish shagreen, is obtained from various kinds of sharks (Squalus 
 canicula, /S. catulus, S. centrina) and other fishes of the same class. The skin of these 
 animals is not covered with scales, but with more or less projecting hard points. The 
 skins having been removed from the fish are stretched in frames and simply dried, 
 being then sent to the market. Formerly sharks' skin was in some countries used by 
 joiners instead of sand- and glass-paper for preparing wood. The skins deprived of 
 the projections are dyed and used for covering small boxes, tubes of small tele- 
 scopes, &c.* 
 
 GLUE, SIZE, GELATINE. 
 
 General Observations. The organisms of all animals, but more especially of the 
 higher classes, contain tissues which are insoluble in cold as well as in hot water, but 
 which by continued boiling become dissolved, and yield on evaporation of the solution 
 a glutinous gelatinising mass, which, by further drying, exhibits, according to the 
 degree of purity of the material, a more or less transparent and brittle substance, 
 which in its pure state is devoid of colour as well as of smell, becoming swollen in cold 
 water and dissolved by boiling in that liquid. This substance i.e., the product of the 
 conversion of the so-called glue- or gelatine-yielding tissues, is what is known in the 
 trade as glue, and is largely used by carpenters, joiners, &c., for joining wood. It is 
 also largely used for sizing paper, for clarifying various liquids beer and wine, for 
 instance and as a cement. Among the glue-yielding tissues the following are the 
 most important : Cellular tissue, the corium, tendons or sinews, the middle mem- 
 brane of the vasa lymphatica and veins, the osseine or organic matter of bones, 
 hartshorn, cartilage, the air bladders of many kinds of fish, &c. Chemically, we 
 distinguish between glutin, that is to say, glue derived from skins, bones, <fcc., and 
 chondrin, which has been obtained from cartilage. From a technical point of view 
 this distinction is hardly required, as the cartilaginous matter is as much as possible 
 eliminated from other glue-making materials, because experience has shown that glutin 
 has a much greater power of adhesion than chondrin. The latter, however, is largely 
 used as size in this country. 
 
 As already observed, the glue or gelatine-yielding tissues yield on being dissolved 
 a gelatinising mass, the aqueous solution of which does not, however, possess to any 
 great extent a glueing property, which is only imparted to the gelatine by a process of 
 drying. In considering, therefore, the process of glue-boiling, we have to distinguish 
 the animal matter capable of yielding glue, the gelatinous mass obtained therefrom, 
 and the glue obtained by drying the latter. The temperature required for producing 
 gelatine differs according to the different animal tissues employed ; the consistency of 
 the gelatine obtained from equally strong solutions varies with the age of the tissues 
 operated upon. 
 
 * The reader may further consult Leather Manufacture, by A. Watt (London : Crosby Look- 
 wood & Co.) ; Text-Book of Tanning, by H. K. Procter (London : C. & F. N. Spon). 
 
SECT, viii.] GLUE, SIZE, GELATINE. 893 
 
 Glue readily dissolves by boiling in water, forming on cooling a gelatinous mass, 
 even if the quantity of glue is only i per cent. Repeated boiling and cooling a 
 glue solution causes it to lose the quality of gelatinising, and the same effect is produced 
 by acetic and dilute nitric acids. Solutions of alum precipitate glue solutions only after 
 the addition of potash or soda, the precipitate consisting of glue mixed with basic 
 aluminium sulphate. Glue enters with tannic acid into a combination of constant 
 composition ; hence glue or gelatine may be used for the estimation of tannin in 
 vegetable matter. 
 
 Three different kinds of glue are distinguished by the manufacturers, viz. : 
 
 (a) So-called skin-glue, or leather-glue, prepared from refuse hides, skins 
 
 tendons, <fec. 
 
 (6) The glue obtained from bones. 
 (c) The glue obtained from fish-bladders, termed isinglass. 
 
 Very recently glue from vegetable gluten and so-called albumen glue have been 
 prepared. 
 
 Leather Glue. This substance is prepared from a large variety of animal refuse, the 
 chief sources being the following : Refuse from tanyards, tawing and leather- dressing 
 works, old gloves, rabbit and hare skins (the hair having been used by hatmakers), 
 skins of cats and dogs, ox feet, parchment cuttings, surons (skins which have served 
 the purpose of carrying drugs, especially from America), sinews, gut, leather cuttings 
 (leather tanned with oak bark cannot be readily converted into glue). The glue-boiler 
 on an average obtains from the various materials about 25 per cent, of glue, preference 
 being given to the refuse of tawing operations and kid leather making, because these 
 materials are ready for boiling without requiring any previous treatment. Glue-boiling 
 involves the following operations : 
 
 (1) Treating the glue-yielding materials with lime. 
 
 (2) Boiling these materials. 
 
 (3) Forming the gelatine. 
 
 (4) Drying the gelatine so as to form glue. 
 
 (i) Treating with Lime. The aim of this operation is the cleansing of the refuse and 
 the prevention of putrefaction. It is effected by placing the cuttings in tanks or lime- 
 pits and pouring in a thin milk of lime. The materials, while the milk of lime is 
 frequently renewed, are thoroughly mixed with the lime-liquid and left for fifteen to 
 twenty days in the pits. By the action of the lime any blood and flesh is dissolved 
 and the fatty matter saponified. In order to remove the excess of lime, the materials 
 are placed either in nets or willow baskets, and these are immersed in a brook or 
 river, where a continuous stream of fresh water removes the greater part of the 
 lime in a few days. The washed material is next exposed in the yard to the action of 
 the air in order that it may become dry, as well as form a carbonate of any lime 
 still present in the materials. When the materials are dry they are packed and 
 sent off to the glue-boilers, who, previous to proceeding with the boiling operation, 
 macerate the materials again in a weak milk of lime, the maceration being followed by 
 washing. 
 
 Fleck states that a weak alkaline lye (5 kilos, of soda ash and 7-5 kilos, of 
 quicklime to 750 to 1000 kilos, of glue-yielding material) is preferable to the use of 
 milk of lime. When the glue-boiling and tanning operations are executed on the 
 same premises, the lime-treated glue materials are put for a few hours into old oak 
 bark liquor, the acids (lactic, butyric, and propionic acids) of which remove the lime, 
 while the animal matter is at the same time superficially tanned. This glue tannate 
 rises during the boiling as scum to the surface, and assists in rendering the glue liquor 
 clear. According to Dullo, the Cologne glue a very pale and strong glue is obtained 
 
CHEMICAL TECHNOLOGY. [SECT, vm, 
 
 from offal, which, after liming, has been treated with a solution of chloride of lime 
 {calcium hypochlorite), and thereby bleached. 
 
 Boiling the Materials. This operation is carried on either in the ordinary manner 
 of boiling anything with water, or by so-called fractionated boiling, or finally by the 
 application of steam. As the conversion of the glue-yielding materials into glue 
 takes place slowly and gradually under the influence of the boiling- water, it is clear 
 that the method of boiling cannot be without influence upon the glue ultimately 
 produced. The first portions of gelatine which are formed remain in contact with a 
 boiling-hot mass, and are thereby further changed so as to lose the capability of 
 gelatinising, while the glue at last obtained exhibits a dark colour, and is often not so 
 strong, although it is generally believed that deep-coloured glue is of a better quality. 
 A rational mode of glue-boiling would involve the gradual removal of the solution 
 obtained, while of course fresh water would have to be supplied to replace the liquor 
 drawn off. The older method of glue-boiling consists in simply placing the materials 
 with water in a cauldron, care being taken to prevent burning by placing them 
 on a stout wire gauze or tying them in a net and suspending it in the boiling liquid. 
 Soft water yields a better result than hard. Gradually the materials become dissolved, 
 and the scum which is formed is taken from the surface with a large ladle. The 
 refuse of glue of former operations is added to the boiling liquid, and the operation 
 continued until the liquid is of the required strength, which is tested by pouring into 
 a broken egg-shell a small portion of the liquor, and by placing the partly -filled shell 
 in ice-cold water. If the solution gelatinises after a while, forming a hard and rather 
 stiff gelatine, the liquor is run off by means of a tap, filtered through a layer of straw 
 placed in a basket, and conveyed to a wooien lead-lined cistern, externally covered 
 with mats or straw, or some bad conductor of heat. In some works the liquor is 
 decanted into a deep but narrow boiler, the furnace of which is so arranged as to 
 impart heat to the top of the vessel only. This vessel, as well as the cistern, is heated 
 previously to the liquor being poured in. The liquor is clarified by stirring into it a 
 small quantity of very finely-pulverised alum, 0*07 to 0*15 per cent., into the liquid. 
 After this the liquid is left to stand all night. The alum precipitates any lime 
 remaining as calcium sulphate, and also some organic matter which renders the liquid 
 turbid. Alum, though it prevents the putrefaction of the glue while drying, impairs 
 its strength. The lime might better be precipitated by oxalic acid, and the organic 
 matter removed by adding to the boiling mass some astringent matter, such as oak 
 bark decoction or hops, so that during the boiling the organic impurities could be taken 
 away as scum. 
 
 Fractionated Boiling. By this operation only a comparatively small quantity of 
 water is added to the animal matter intended to be converted into glue. When the 
 water is fairly boiling the cauldron is covered with a well-fitting lid, and the steam 
 being kept in as much as possible, is allowed to act upon the materials so as to convert 
 them into glue. When, after continued boiling for about two hours, the water has 
 taken up sufficient gelatine, the liquor is run off and fresh water poured on the 
 materials. This operation is repeated until the decoction no longer gelatinises, the 
 last liquor being kept instead of water for use for a following operation. The liquors 
 tjius obtained, excepting the last, are either mixed or each is treated separately. The 
 glue yielded by the first decoction is stronger than that yielded by the subsequent 
 liquors. By this method of boiling the saturated liquor does not remain exposed to 
 the action of heat and water too long, and consequently a better article is produced. 
 In some instances the materials intended to be converted into glue are boiled in a 
 vessel similar in construction to those in use in bleaching-works and in paper-mills, 
 arranged in the folio-wing manner. At some distance from the bottom a perforated 
 false bottom is placed, in the centre of which is fixed a wide tube which reaches to 
 
SECT, vin.] GLUE, SIZE, GELATINE. 895 
 
 about two-thirds of the height of the cauldron. The materials intended to be converted 
 into glue are placed upon the perforated bottom, and water under it ; as soon as the 
 water boils, the steam produced, not being able to escape rapidly and readily through 
 the materials, exerts a pressure upon the liquid, and forces it through the tube, the 
 consequence being a constant stream of boiling liquid falls upon the glue materials, 
 which are rapidly dissolved. 
 
 A more rational mode of conducting this operation consists in employing high- 
 pressure steam, admitted into the mass of the animal materials to be converted into 
 .glue. In this manner a very concentrated solution of glue is obtained in a short 
 time. In England steam is generally employed, but on the Continent its use is the 
 exception. It has been said that it is advantageous to allow the animal offal intended 
 for glue to become somewhat decomposed, and then to disinfect it with chlorine or 
 sulphurous acid before boiling it for glue, because by this mode of treatment a brighter 
 glue is obtained. We are unable to say whether this opinion is correct. 
 
 Moulding. As soon as the glue solution has, by standing in the tanks into which 
 it had been transferred from the boilers, become quite clear and somewhat cooled, the 
 liquid is poured into moulds, and when solidified the jelly is cut into cakes of the 
 shape and size met with in the trade. 
 
 The moulds, into which the glue solution is poured through a strainer made of 
 rnotal gauze, are of wood, and generally a little wider at the top than at the bottom, 
 so as to admit of an easy removal of the solid material. At the bottom of the moulds 
 a series of grooves are cut at such a distance from each other as agrees with the size 
 of the intended glue-cakes. Before the liquid is poured into the moulds, these are 
 thoroughly washed, and either allowed to remain damp, or if dried, are oiled, so as to 
 prevent the solidifying gelatine adhering to the wood. Recently moulds made of 
 sheet-iron and zinc have been introduced. The moulds are filled with the lukewarm 
 glue solution, and when the glue is sufficiently hard it is gently loosened from the 
 sides with a sharp tool, and the mould having been turned over on a wooden or stone 
 table, previously damped, is lifted off the block of gelatine, which is next cut into 
 cakes or slabs. The cutting-tool is simply a piano-wire, or more frequently a series 
 of these stretched in a frame at sufficient distance from each other to make the cakes 
 of the desired thickness, the frame being placed on small wheels so as to be easily 
 moved. Glue is met with in the trade as a gelatinous mass, or is sold in casks under 
 the name of size. It is said that the process of drying impairs the good qualities of 
 the glue. 
 
 Drying the Glue. This operation is performed by placing the gelatine cakes on 
 nets made of twine stretched in frames, and exposed in a dry airy place to the action 
 of the sun. The drying is one of the most difficult operations of the glue-making 
 process, because the temperature of the air and its hygrometric condition exert a 
 great influence on the product, especially during the first few days.* The glue will not 
 bear a temperature above 20, because at a higher temperature it becomes again fluid, 
 and as a matter of course flows through the meshes of the net and adheres to the 
 twine so strongly as to require the nets to be put into hot water for the removal of 
 the mass. Air too dry causes an irregularity in the drying of the glue, and as a 
 consequence the cakes become bent and cracked ; while frost causes disintegration, so 
 as to necessitate a re-melting of the glue : hence it follows that drying in the open air 
 can only be effected in the spring and autumn. Although the glue^boilers have tried 
 to dry glue by artificial heat, this plan has not been generally introduced owing to the 
 fact that a slight excess of heat causes the melting of the gelatine, the more readily 
 when ventilation is neglected. Drying-rooms, as recently constructed, are large-sized 
 
 * It is very generally considered that the occurrence of a thunderstorm during the process 
 -of drying renders it necessary to remelt the product. [EoiTOE.] 
 
896 CHEMICAL TECHNOLOGY. [SECT. vm. 
 
 sheds fitted with the required frame-work for receiving the gelatine cakes, and heated 
 by steam-pipes placed on the floor near the latter. The walls are provided with 
 openings which can be closed by means of valves, while there are ventilators in the 
 roof arranged to obtain a proper circulation of air. As the gelatine placed nearest to 
 the floor of the room becomes most quickly dry, it is, with the frames upon which it 
 placed, removed after eighteen to twenty-four hours to a higher part of the drying- 
 room, which is not heated at all if the outer air has a temperature of from 15 to 20. 
 The drying-shed, or room, is by preference built so as to face the north. When the glue 
 has been thus dried as much as possible, it is generally quickly dried in a stove in order 
 to impart hardness. It is next polished by being immersed in hot water, and cleaned 
 with a brush, and again dried. 
 
 Bone-Glue. The organic matter contained in bones, forming nearly one-third part 
 (32-17 per cent.) of their weight, consists of a material which, after the bones have 
 been treated with hydrochloric acid, is very readily converted into glue by the action 
 of high-pressure steam. The preparation of glue from bones by the action of hydro- 
 chloric acid is the usual mode of proceeding, and the operation is advantageously 
 combined with the making of sal ammoniac and phosphorus. 
 
 The preparation of glue from bones includes the following operations : 
 
 (1) Boiling out the Grease. The bones are put into water and boiled in a cauldron, 
 the fat floating to the surface. Frequently, in order to save fuel, the bones are put into 
 an iron wire basket, which is removed after the boiling has been continued for some 
 time, the bones thrown out and fresh ones put in, the boiling being continued until a 
 thick gelatinous liquor is obtained. The fat or grease is removed from the surface 
 of the liquid by means of ladles. The gelatinous mass obtained by this process is 
 either used as a manure or is given to cattle as fodder ! In some works bones have 
 been exhausted with carbon disulphicle for the purpose of extracting the grease. 
 
 (2) Treating the Bones with Hydrochloric Acid. The bones, having been drained, 
 are placed in baskets, and in these are immersed in tanks to more than half their height, 
 the tanks being filled with hydrochloric acid at 9'6 Tw. (=1-05 sp. gr. = 10-6 per cent. 
 C1H) : 10 kilos, of bones require 40 litres of acid. The bones are kept in this liquor 
 until they become quite soft and transparent. They are next drained, and then, with 
 the baskets, immersed in a stream or brook with a good supply of running water to 
 wash out the greater portion of the acid,* which is fully neutralised by placing the 
 bones in lime-water, again followed by washing with fresh water, the bones being then 
 ready for boiling. Gerland has suggested the use of sulphurous instead of hydrochloric 
 acid. 
 
 (3) Conversion of the Organic Matter into Glue. The cartilaginous substance having 
 been either partly or completely dried is put into a cylindrical vessel containing a false 
 perforated bottom, and between that and the real bottom a pipe or tube. To the top 
 of the vessel a lid is fitted, provided with an opening for a steam-pipe leading from a 
 small boiler. Shortly after the admission of the steam a concentrated glue solution 
 begins to run off from the pipe at the bottom of the cylinder ; this solution is usually 
 so concentrated as to admit of being at once run into the moulds, and, after having 
 become solid, is treated as before described. After a few hcurs a weak liquid makes 
 its appearance, and as soon as this happens the cylindrical vessel is opened, the glue 
 mass removed with the weak liquid to a copper and boiled, care being taken to stir the 
 magma constantly. As soon as the glue is dissolved the liquor is poured into moulds. 
 Glue obtained from bones exhibits a milky appearance, due to the presence of a small 
 quantity of calcium phosphate retained in the substance. Sometimes there is purposely 
 
 * This method of washing pollutes the streams, and is no longer permissible where due 
 sanitary inspection is enforced. [EDITOR ] 
 
SECT, viii.] GLUE, SIZE, GELATINE. 897 
 
 added more or less baryta-white, zinc-white, white-lead, chalk, or pipe-clay. The glue 
 obtained from bones is sold under the name of patent glue. 
 
 Liquid Glue. When glue is dissolved in its own weight of water and a small 
 quantity of nitric acid added to the solution, it loses the property of gelatinising, while 
 the adhesive property of the glue is not impaired. Dumoulin prefers to dissolve 
 i kilo, of Cologne glue in i litre of boiling water, and to add to the solutiou o'2 kilo, 
 of nitric acid at 62 Tw. = 1-31 sp. gr. After the evolution of the nitrous acid fumes 
 has subsided the fluid is cooled. A better liquid glue is obtained by dissolving good 
 gelatine or glue of superior quality in strong vinegar or moderately strong acetic 
 acid, to which some pulverised alum and one-fourth of its bulk of alcohol are added, 
 the solution being aided by a water-bath. The action of the acetic acid is the same as 
 that of the nitric acid. According to Knaffl, a very excellent liquid glue is obtained 
 by heating for some 10 to 12 hours upon a water-bath, a mixture of 3 parts of glue 
 in 8 parts of water, to which are added 0*5 part of hydrochloric acid, and 0-75 parb 
 of zinc sulphate, the temperature of the mixture being kept below 85. This kind 
 of liquid glue keeps for a very long time and is largely used for joining wood, horn, and 
 mother-of-pearl. This glue is employed by the makers of artificial pearls. 
 
 Tests of Quality of Glue. Although the quality of glue is best ascertained by 
 practical use, some of the physical qualities and the external appearance of glue may 
 be mentioned as indicating a superior article. Glue of good quality should exhibit a 
 bright brown or brown -yellow colour, should be free from specks, glossy, perfectly 
 clear, brittle, and hard, should not become damp by exposure to air ; when being bent 
 it should snap or break sharply, the fracture presenting a glassy, shining appearance. 
 When placed in cold water glue should not even after remaining forty-eight hours in this 
 fluid swell up and increase in bulk nor dissolve. A splintery fracture of glue indicates 
 that it has not been well boiled. The adhesive property of glue is often increased by 
 adding certain pulverulent earthy substances. This addition is regularly the case with 
 Russian glue. Among the substances employed are white lead, lead sulphate, zinc 
 white, baryta white, and even lead chromate. As different kinds of glue may agree 
 in their external aspect and yet vary as regards their adhesive power, methods of 
 testing glue have been proposed, some of which are based upon the chemical, others 
 upon the physical, properties of this substance. 
 
 Chemical tests are less decisive than mechanical trials. Lipowitz dissolves 5 parts 
 of the glue in so much hot water that the weight of the solution makes up 50 parts 
 and allows the solution to stand for twelve hours at a temperature of 18, in order to 
 gelatinise. On the top of an open glass of uniform width, he lays a slip of tin plate, 
 through the middle of which passes a perpendicular wire, a cup-shaped piece of tin with 
 its convex side outwards being soldered to its lower end. The wire with the cup 
 weighs 5 grammes and moves freely in the tin plate. To the top of the perpendi- 
 cular wire is fixed a funnel which also weighs 5 grammes and into which there may be 
 poured fine shot up to the weight of 50 grammes. According to the greater aptitude 
 of the glue to form a solid jelly the apparatus must be the more heavily weighted in 
 order to sink into the jelly, whence the tenacity of the glue may be approximately 
 calculated. 
 
 Karmarsch simply glues two pieces of wood together and determines the weight re- 
 quired to break them asunder. Weidenbusch saturates rods of plaster of Paris with 
 glue and breaks them. Bauschinger glues two pieces of red beech-wood together in 
 such a manner that their fibres run parallel and that each projects one centimetre 
 beyond the other, the glued surface being 10x10=100 square centimetres. When 
 thoroughly dry these pieces are fixed in Werder's testing machine in such a manner that 
 its steel cheeks catch in the retreating angles formed by the projecting parts of the 
 pieces of wood, just at the beginning of the glued joint. On seeking to move these 
 
 3 L 
 
898 CHEMICAL TECHNOLOGY. [SECT. vin.. 
 
 angles towards each other by a measured and gradually increasing force, the glued 
 surfaces of the pieces of wood were at last pushed over each other and in this manner the 
 resistance to a lateral pressure was measured in kilos, and square centigrammes. 
 
 Horn determined the resistance of common glue to a tearing force as 9-6 kilos., that 
 of Cologne glue as io - 6, and that of gelatine as 31-5 kilos. 
 
 Kissling found in glue 12-3 to 18 per cent, of water, 1-4 to 5-1 per cent, of ash,, 
 o to o'S per cent, of a volatile acid, and o to 40 per cent, of matter insoluble in water.. 
 
 SIZES. 
 
 Coarse glues are used in finishing, and to some extent in dyeing, textile goods, in 
 order to increase their body, stiffness and gloss. The kinds occurring in commerce are 
 bone-size and glue-size. 
 
 The best bone- size is made from the " sloughs " of the horns of oxen. Of these- 
 4 cwts. are boiled for ten hours. The liquid is strained, and then are added, with' 
 vigorous stirring, alum 3 Ibs., and zinc sulphate 2 Ibs., both in fine powder. The 
 solution is received in shallow tubs and allowed to cool. The yield from the above- 
 proportions is 10 cwt. It keeps for eighteen months. 
 
 It is pale, clear, and semi-transparent. Its adhesive power is less than that of 
 the glue size made from the clippings of hides. 
 
 Glue size is a dark brown, stiff semi-solid mass of great tenacity. It is frequently 
 contaminated with the exuviae of the larvae of blow-flies, which adhere to the goods and 
 render them unsightly. Hence glue size should be preferably made in winter, and be 
 kept in cold, dark, but draughty places. 
 
 Isinglass, fish Glue. The substance met in commerce under the name of 
 Isinglass is, if genuine, the dried interior pulpy vesicular membrane of the air- 
 bladder of certain kinds of fish belonging to the order of the cartilaginous ganoids, 
 and more especially of the common sturgeon (Accipenser sturio) ; the huso, or grand 
 sturgeon (.4. huso); the A. Giildenstaedti and A. stellatus. The bladders of these and 
 of kindred species of fish, plentifully met with in the Caspian Sea and the estuaries of 
 the rivers running into it, are cut open, cleansed, stretched, and dried by exposure to 
 sunlight, and when sufficiently dry to admit of being handled without fear of tearing 
 the outer muscular membrane, which does not yield any glue on being boiled, is torn 
 off, while the interior membrane is moulded in various ways (as in rings, lyre-shaped, 
 or folded as leaves of paper), and bleached by sulphurous acid, then thoroughly dried, 
 by exposure to sunlight. 
 
 According to the countries from which it is sent into the trade, isinglass is 
 distinguished as Russian (the best kind being obtained from Astrakan); North 
 America (from (Jadus melucius) ; East Indian (from Polynemus plebejus), met with 
 in leaves, also in small sacks, and in the entire bladder ; Hudson's Bay isinglass 
 (derived from sturgeons) ; Brazilian is probably obtained from various kinds of 
 Silurus and Pimeladus. This isinglass is met with in commerce in hollow tubes, in 
 lumps, and in discs. German isinglass is prepared at Hamburg from the air-bladder 
 of the common sturgeon. In Roumania and Servia the skin and intestines (not the 
 liver) of cartilaginous fishes are boiled into a stiff jelly, which, having been cut into- 
 thin slices, is di'ied and sent into the market as isinglass. As regards the use of 
 this material, we have to distinguish between fish glue and isinglass. The former, if 
 properly prepared, is not at all distinguishable from ordinary glue as obtained from 
 bones or other animal refuse ; but isinglass is not glue, and is only converted into it 
 by boiling. It consists of fibres or threads, which when placed in water are somewhat 
 dissolved, but retain their organised structure ; this being especially of importance for 
 the use of this substance in clarifying wine, beer, and similar fluids, as the fibres 
 
SECT, viii.] BONES. 899 
 
 constitute as it were a close network, which readily takes up the turbidity produced by 
 small particles. The presence of tannin in liquids which are intended to be clarified 
 by the use of isinglass is advantageous, inasmuch as it promotes the contraction of the 
 isinglass fibres, whereby the suspended particles present in the fluid to be clarified are 
 retained; so that in truth the clarifying by isinglass is a kind of filtration, which 
 cannot be performed either by glue or by a hot saturated solution of isinglass. For 
 isinglass, in all other instances, such as the dressing of woven silk fabrics, the pre- 
 paration of so-called court-plaster and cements, there may be substituted good gelatine. 
 Under the name of Ichthyocollefranqaise, Rohart some years ago introduced a substitute 
 for isinglass, a compound said to be obtained from fibrin of blood and tannin. 
 
 Substitutes Jor Glue. Recently three substitutes for glue have been introduced, 
 viz. : (i) Gluten glue (colle gluten). (2) Albumen glue (colle vegetale ou albu- 
 minoide). (3) Casein glue (colle caseine). The first is a mixture of gluten and 
 fermented flour. It is a very sour mixture, endowed with but very slight adhe- 
 sive power. Albumen glue is partially decayed gluten, the substance largely 
 obtained in the manufacture of starch from wheaten flour thoroughly washed with 
 water, and then exposed to a temperature of from 15 to 20, at which it begins 
 to ferment and become partly fluid, or more correctly soft, so as to admit of 
 being poured into moulds, which are placed in a room heated to 25 or 30 for from 
 twenty-four to forty -eight hours. The surface having become dry enough to admit 
 of the cakes being handled, they are taken from the moulds and further dried by 
 being placed either on canvas or on wire gauze. After four or five days the cakes are 
 quite dry and fit for being kept in a dry place for any length of time. A solution of 
 this substance in twice its weight of water constitutes a normal solution, which may 
 be used for the following purposes : Glueing wood, cementing glass, porcelain, 
 earthenware, mother-of-pearl, for pasting leather, paper, and cardboard ; it may fur- 
 ther serve as weaver's glue, and as dressing for silk and other woven fabrics ; also for 
 a mordant instead of albumen in dyeing and printing various fabrics ; and lastly, for 
 clarifying liquids. Casein glue is prepared by dissolving casein in a strong solution of 
 borax. The thick fluid thus obtained has great adhesive powers, and may be advan- 
 tageously employed by joiners and bookbinders.* "What is known as elastic glue is a 
 preparation of glue and glycerine, by the addition of which glue may be rendered 
 permanently elastic and soft. It is prepared in the following manner: Glue is 
 melted in water, by the aid of a water-bath, into a very thick paste, to which 
 glycerine is added in the same quantity by weight as that of the dry glue. The 
 mixture is thoroughly stirred, and then further heated, in order to evaporate the 
 excess of water. The mass is then cast on a marble slab, and after cooling, serves 
 for the purpose of making printer's inking rollers, elastic figures, galvano-plastic 
 moulds, &c. 
 
 BONES. 
 
 The bones of animals serve for obtaining phosphorus, as already described, for bone- 
 meal and animal charcoal, bone-black or spodium. 
 
 For extracting fat, the bones are either boiled in water or steamed. A great part 
 of the fat separates out, but at the same time a part of the cartilage is dissolved as 
 glue, so that the mammal value of the bones is reduced. The fat extracted by 
 boiling is the best ; that obtained by steaming is inferior ; whilst the fat extracted 
 by benzene has the lowest value, since soaps prepared from such fat retain the mouldy 
 smell of the bones. 
 
 * Skimmed milk, as free from fatty matter as possible, is coagulated by means of weak acetic 
 acid. The curd is well washed, pressed and dissolved, either, as above said, in a concentrated 
 solution of borax, or in sodium silicate (so-called water-glass). The liquid is very useful in getting 
 up ornamental articles, artificial flowers &c. [BDITOB.] 
 
900 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. viii. 
 
 Fig. 5 So. 
 
 As only from 3 to 4 per cent, of fat are obtained by boiling, but from 5 to 6 by the 
 
 benzene process, and as in this latter case there is no loss of glue i.e., of nitrogen 
 
 the extraction by means of benzene is coming more and more into use. 
 
 According to Biittner, the recipient, A (Fig. 580), is filled with bones ; then steam is 
 let into the jacket, Ic, and the pipes, e, through the cock, c, whereby the moist air formed 
 
 by heating the bones is sucked out by the 
 steam-blast, y, at o. The cock, q, is then 
 opened into the pipe, n, the cock, d, to the pipe 
 i, the cock, d, to the pipe, u, and the residual 
 air from the pan, A, and from the bones is 
 sucked by the water-blast, x, until the air in A 
 is sufficiently exhausted, when the cock, g, is 
 closed again. On opening the cock, g, the 
 benzene in the space, t, of the receiver, J3, rises 
 -up in the pipe, f t penetrates into the worm, v 
 (perforated below), falls in the form of rain 
 upon hot, dry bones free from air, and pene- 
 trates into them until they are saturated. The 
 rest of the solvent is let through the pipe,/,, 
 into the receiver, 0, and is there evaporated. 
 The vapours of the solvent are now drawn by 
 the aid of the water-blast, x, from above down- 
 wards through the pan, A, the pipe, n, the cocks, 
 q and d, and the pipe, i, liquefied on their way from x to the receiver, It, by the water 
 of the water-blast, and collected along with the water in the space, r, of the receiver, 
 B. The water flows off chiefly by the pipe, I, whilst the pure benzene flows to the 
 space, t, in order, after the air-pressure, to rise into the worm, v, and the receiver, 0. 
 When the extraction of the fat is at an end, the solvent is driven out by admitting 
 steam into k in the manner described above, and collected in the space, t, of the 
 receiver, B, in order to be used again. An expansion of air is now produced in the 
 space, V, below the bottom, ^Y, by opening the cock, q, to the pipe, m, by means of 
 the water-blast, x, the fat on the filtering stratum of the bottom is sucked through, and 
 the pure fat is let off at b. 
 
 In order to extract the glue from the bones, water is let in through the cock, a, 
 and the worm, v, and steamed till the glue is dissolved. The cock, q, is opened into the 
 pipe, m and i } cock, d, steam-blast, x, and cock, d, opened to u, and the steam is let off 
 through u. 
 
 There thus arises a strong current of vapours from above downwards through 
 the pan, A, which forcibly sweeps the dissolved glue downwards through A, and 
 through the filtering-bed, where it is freed from dirt and particles of bone. When this 
 has been repeated a few times, the bones are freed from gelatine, and the concentration 
 of the glue and the simultaneous drying of the bones may begin in the pan, A. For 
 this purpose the space, k, is heated by steam under pressure, so that the glue in V 
 begins to boil. Lest the temperature in A should rise too high, the water-blast, x, 
 and the steam-blast, y, are set in action, so that these two apparatus draw away the 
 water evaporating from the glue and the bones through the cocks, iv^ and q, and the pipes, 
 n and m, at o, the glue is sufficiently thickened. ThJ glue is then run off, and the 
 bones are heated and dried for a short time until the last remnant of moisture is 
 expelled. 
 
 Bone-black (Animal Charcoal). The carbonisation of the bones is so conducted that 
 the volatile products are either burnt or condensed. In the latter case the broken-up 
 bones are put into iron retorts similar to those used for coal-gas manufacture, and the 
 
SECT. VIII.] 
 
 BONES. 
 
 901 
 
 volatne products are collected in suitable condensing apparatus, while the gas after having 
 baen purified, is sometimes led into a gas-holder and used for illuminating purposes, 
 or when not purified is burnt under the retorts. According, however, to the experience 
 obtained in Germany, bone-black thus made has a lower decolorising power than when 
 the bones are ignited in iron pots, the volatile products being burnt at the same time. 
 In Germany, therefore, the older plan of carbonisation in pots is usually resorted to. 
 In England and Scotland, and also in Holland, Belgium, and France, retorts are 
 generally used for this purpose. The carbonisation in pots is carried on in the fol- 
 lowing manner : Cast-iron pots are filled with broken-up bones placed one on the top 
 of the other, the edges of the mouths of the pots being luted with clay. The pots are 
 placed on the hearth of a kind of reverberatory furnace. After awhile the vapours 
 which are forced through the lute become ignited, thereby enveloping the pots in a 
 sheet of flame, so that the carbonisation goes on without requiring the firing of the 
 furnace to be kept up. When the flame subsides the carbonisation is complete. The 
 yield of animal charcoal amounts by this method of procedure to 55 to 60 per cent., the 
 carbonaceous matter being, however, mixed with about ten times its weight of mineral 
 matter, as may be inferred from the following results of analysis of a dried 
 sample of bone-black, which in 100 parts was found to consist of: Carbonaceous 
 matter, 10; calcium phosphate, 84; calcium carbonate, 6 parts. By exposure to air 
 bone-black absorbs from 7 to 10 per cent, of moisture. The carbonised bones are broken 
 up and granulated by machinery , the formation of dust having to be avoided as much as 
 possible because it has very little value. 
 
 Zwillinger carbonises bones with superheated steam in a large iron receiver, A 
 (Fig. 581), coated with an insulating 
 
 mass, and secures at the same time the Fig. 581. 
 
 bye-products. Superheated steam is 
 introduced at the pipe, b. The vapours 
 given off escape through the refrige- 
 rating room, D, to the iron washing- 
 ivcssels, E, and the gas-purifier, F. 
 
 Properties of Bone-black. As far 
 back as the year 1811, Figuier dis- 
 covered that bone-black possesses the 
 property of withdrawing organic and 
 inorganic substances viz., lime and 
 potash from solutions. It appears that 
 this property is duo to surface attrac- 
 tion (capillary action), although bone- 
 black is also capable of decomposing 
 
 chemical compounds. Owing to the fact that bone-black can absorb inorganic matter, 
 ifc is largely used for the purpose of withdrawing lime and saline matter from saccharine 
 fluids in beet-root sugar works. According to Anthon, the property of bone-black to 
 withdraw lime from solutions is partly due to the fact that carbonic acid is condensed 
 in the pores of this substance. 
 
 By treating bone-black with hydrochloric acid, and thus dissolving the mineral 
 matter it contains, the residue, after having been well washed with water, dried, and 
 re-ignited in a closed crucible, has lost in a very great measure its property of with- 
 drawing from solutions and retaining within its pores inorganic matter. When acid 
 liquids are to be decolorised by bone-black, it should always be employed after having 
 been treated with hydrochloric acid. Shoe-blacking manufacturers employ in their 
 trade a large quantity of bone-black. 
 
 Testing Bone-black. The greater the decolorising power of charcoal the better its 
 
9 02 CHEMICAL TECHNOLOGY. [SECT. vm. 
 
 quality, though it appears that the decolorising power is not proportionate to the 
 power of withdrawing lime and saline matters from solutions. In order to ascertain 
 the decolorising power of any sample of bone-black, its quality in this respect is com- 
 pared with that of another of known strength. Payen proposes to take equal bulks of 
 water coloured with caramel, to treat these with equal weights of animal charcoal, and 
 to filter these mixtures ; the charcoal which yields the clearest liquid being the best. 
 Bussy obtained the following results by the estimation of the relative decolorising 
 power of equal quantities by weight of different kinds of charcoal : 
 
 Ordinary bone black i 'o 
 
 Bone-black treated with hydrochloric acid . . . . i '6 
 
 and afterwards ignited with potassium carbonate 20 x> 
 
 Blood ignited with potassium carbonate .... 20-0 
 
 calcium carbonate 20 'o 
 
 Glue ignited with potassium carbonate 1 5 *5 
 
 Brimmeyr's experiments on the decolorising properties of bone-black led to the 
 following results : (i) The capability of absorption of this substance does not depend 
 upon the mechanical structure of the bone-black, but upon the quantity of pure carbon 
 it contains. (2) The quantities of matter absorbed by bone-black of various kinds are 
 when reduced to pure carbon really equivalent, and are probably independent 
 of the varying chemical nature of the soluble absorbed substance. (3) Bone-black 
 saturated with any substance retains its absorptive power for other materials of 
 a different chemical nature. (4) Bone-black acts the quicker and better the less its 
 capillary structure has been interfered with either by mechanical or chemical means 
 (action of hydrochloric acid). Schultz's results of experiments agree with those 
 just quoted. The specifically lightest bone-black which contains the largest amount of 
 carbon is the most strongly decolorising material. As regards the sugar (especially 
 beet- root) manufacture, the power of bone-black to withdraw lime from a solution 
 comes also into consideration ; this lime-absorbing capability is estimated by directly 
 testing the quantity of lime which a given sample of charcoal can take up. 
 
 Revivification (Re-burning) of Charcoal. After having served the purpose of deco- 
 lorising and absorbing lime for some time in the process of sugar refining, the bone- 
 black becomes, as it is termed, foul and requires to be revived, for which purpose it is 
 either first thoroughly washed with hot water or sometimes left to enter into a state 
 of fermentation, or treated with steam, and finally always re-ignited. The more usual 
 plan is to wash the bone-black, while still in the filters, with hot water, so as to remove 
 all soluble matter, the material being next re-ignited. In this manner bone-black 
 may be restored for use from twenty to twenty -five times. This mode of reviving labours 
 under the disadvantage that during the ignition the organic matter (absorbed im- 
 purities) is not quite destroyed, and by choking the pores of the bone-black impairs 
 its decolorising power. It is therefore preferable to cause the bone-black to ferment, 
 to treat it next with dilute hydrochloric acid, wash it well, and lastly ignite it. The 
 quantity of hydrochloric acid employed for this purpose in sugar-producing works is 
 very large. 
 
 Substitutes for Bone-black. Among the substances which have been tried as substi- 
 tutes for the use of bone-black, carbonised bituminous shale takes the first place. This 
 material (the coke of the Boghead coal is an excellent example) absorbs colouring 
 matter, but does not touch the lime. Moreover it often happens that the coke is 
 rendered unfit for this use by the presence of a considerable amount of iron mono- 
 sulphide. The coke of sea-weed is perhaps a more suitable material.* 
 
 * A variety of artificial carbons have been prepared by charring mixtures of organic and 
 inorganic matter, but none of them have come into general use. [EDITOB.] 
 
:SECT - vm -] FATS. go3 
 
 FATS. 
 
 Fats are neutral substances of animal or vegetable origin which leave upon paper 
 transparent spot which does not disappear on prolonged exposure to the air. They 
 cannot be volatilised without decomposition their specific gravity is less than that of 
 water, in which they are insoluble, but they dissolve in ether, carbon disulphide, or 
 benzene. Almost all fats, in contradistinction to wax, are triglycerides i.e., compounds 
 of glycerine, C 3 H.(OH) 3 , with fatty acids. Berthelot has, e.g., obtained factitious 
 tripaimitine from palmitic acid and glycerine : 
 
 C 3 H 5 (OH) 3 + 3 H.C 16 H 31 2 = C 3 H 5 (C 1G H 31 2 ) 3 + 3 H.O, 
 and in like manner trioleine from oleic acid : 
 
 C 3 H 5 (OH) 3 + 3 H.C 18 H 33 2 = C 3 H 6 (C 18 H 33 2 ) 3 + 3 H 2 0. 
 ,tmg the drying oils aside there are two homologous series of fatty acids : 
 The first series has the general formula C n H 2n O,. 
 
 Formic acid CH. O 
 
 Acetic acid C,H 4 O 2 
 
 Propionic acid C H 
 
 Butyric acid C 4 HgI 
 
 Valerianic acid . C H O 
 
 .... v/ 5 n, Uj 
 
 Capronic acid C.H,./)., 
 
 (Enanthylic acid C 7 H ]o 
 
 Caprylicacid C^A 
 
 Pelargonic acid 9 H I8 2 
 
 Capricacid C^H^O, 
 
 Laurie acid C, 2 H 24 O 2 
 
 Myristicacid O u H' 8 O t 
 
 Palmitic acid C, 6 H K O Z 
 
 Stearicacid C 18 H 36 O 2 
 
 Arachicacid C, H 40 0. 2 
 
 Behenic acid C 2 ,H 44 2 
 
 Ceroticacid C 27 H M t 
 
 Melissic acid C^H^Og 
 
 'The second series has the general formula C n H 2n - aO,-. 
 
 Acrylic acid C 3 H 4 2 
 
 Crotonic acid C 4 H B 2 
 
 Angelicic acid C S H 8 O 2 
 
 Pyroterebic acid C 8 H )0 0, 
 
 Cyminic acid Cu^aA 
 
 Hypoparic aoid C 16 H S0 2 
 
 Oleicacid C 1S H 34 0., 
 
 Doeglic acid . . . . \ . . C,,,!!,, X) 2 
 
 Erucic acid C^H^O.,, 
 
 The most important of these acids are stearic acid, fusible at 69.2 under a reduced \ 
 ,'pressure, and volatile in superheated steam without decomposition : it is readily soluble / 
 in alcohol and ether, and insoluble in water. Palmitic acid melts at 62. Chevreul's 
 margaric acid is a mixture of 10 parts stearic acid and 90 parts palmitic acid. Oleic 
 acid is a colourless oily liquid which congeals at 4 and melts again at 44. Nitrous 
 acid converts it into its isomere, elai'dic acid, which melts at 44. 
 
 Most fats consist chiefly of tripaimitine, tristearine and trioleine. Tripaimitine, 
 generally called simply palmitine, melts at 60 and congeals at 46 ; it is the chief 
 constituent of palm-oil. Tristearine (stearine) C 3 H.(C 18 H 35 2 ) 3 melts at 6 3 , and if 
 heated to 65 it solidifies at 61 and melts at 66 ; if it is superheated for a length of 
 time its melting-point sinks to 55. Trioleine (oleine), the chief constituent of the 
 liquid fats, solidifies at 5, and is converted by nitrous acid into elai'dine fusible at 
 3 6. If heated with water under a high pressure the triglycerides are split up into 
 glycerine and fatty acid : 
 
 C 3 H 5 (C 18 H 35 2 )3 + 3H 2 = C 3 H 5 (OH) 3 + 3 H.C 18 I! 35 0,. 
 
904 CHEMICAL TECHNOLOGY. [SECT. vm. 
 
 The chief animal fats are, with the exception of butter, suets (beef and mutton) and 
 hog's lard. Tallow is obtained by rendering (i.e., melting out) the fat which collects 
 in the intestinal cavity of oxen or sheep. The hardness of tallow depends on the species 
 of animal from which it is obtained, and on the food which it has consumed. Dry 
 fodder produces the hardest tallow, while the softest is obtained from animals fed on 
 the waste grain from breweries and distilleries. Russian tallow is far harder than the 
 German quality, since in Russia cattle subsist on dry fodder for more than eight months 
 in the year. Tallow generally melts at 35-37. It contains 75 percent, hard fat 
 (tristearine and tripalmitine), the remainder is trioleine. 
 
 Goose-grease, which is a valued food-fat in Germany, is or was chiefly burnt in 
 lamps in Russia. In Britain it is of little importance. 
 
 Fish-oil, seal-oil, obtained from the blubber of several varieties of Mammalia 
 inhabiting the seas, especially of the colder regions of the globe, and belonging 'to the 
 Cetacea and Phocena, varies somewhat in its properties, according to the mode of pre- 
 paration and the animal from which it has been derived. The specific gravity of this 
 oil is 0*927 at 20; when cooled to o it' deposits solid fat; it is readily soluble in 
 alcohol, and consists of oleine, stearine, and small quantities of the glycerides of 
 valerianic and similar fatty acids. Fish-oil, besides being an important material in 
 soap-making, is also used in tanning, tawing, and leather- dressing operations. 
 
 Vegetable fats either become rancid on exposure to the air, and acid from the forma- 
 tion of free fatty acid, though they do not solidify, the non-drying oils ; or they are 
 converted into a solid mass by taking up oxygen, drying oils. 
 
 The most important non-drying oils from a technical point of view are : Palm-oil, 
 of vegetable origin, met with in the fruit of a palm-tree, Avoira dais or Elais guinensis; 
 according to others, however, this oil is derived from the Cocos butyracea, C. nucifera, 
 and Areca oleracea, trees growing wild, and also cultivated in Guinea and Guiana. The 
 colour of this oil is a red-yellow, its consistency that of butter, while it possesses a 
 strong but by no means disagreeable odour, similar somewhat to that of orris root. 
 When fresh, this oil melts at 27, but by becoming rancid as it is termed that is, by 
 its decomposition into glycerine and free fatty acids its melting point rises to 3 1 and 
 even to 36. It is chiefly composed of palmitine mixed with a small quantity of oleine. 
 Palmitine, formerly confused with margarine, is saponified by the alkalies and converted 
 into potassium or sodium palmitate, while glycerine is set free : 
 
 Palmitine (tripalmitine), ,^ -/ ^ [0 3 | (Glycerine, 3 TT 5 }^3' 
 
 Potassium hydroxide, ?KOH f = | -r, , * , (CLH,.0)~ 
 
 / /. ' r Potassium palmitate, -; i l6 3l y - 0. 
 
 (caustic potassa) ) ( ' *\ Kf 
 
 Palmitic acid is very similar to, and has often been confused with, stearic acid ; the 
 former is in a pure state a solid white crystalline mass, which fuses at 62. Palm-oil 
 often contains one-third of its weight of this acid in free state, and the quantity- 
 increases with the age of the oil. The red-yellow pigment of the palm-oil not being 
 destroyed by its saponification, the soap made from this oil is of yellow colour, but if, pre- 
 vious to saponification, the oil is submitted to a bleaching process, that is to say, the pig- 
 ment destroyed by chemical agents, such as the joint action of potassium bichromate and 
 sulphuric acid, the oil becomes nearly white, and yields, on being saponified, a white soap. 
 
 Palm-oil has latterly come into use in the so-called white baths in turkey- red 
 dyeing [EDITOR]. Sometimes a cask of palm-oil arrives in England without having 
 become rancid. Could this result be regularly secured palm-oil would doubtless 
 supersede " margarine." 
 
 The illipe, or bassia-oil, very similar to palm-oil, is obtained by pressure from the- 
 seeds of the Bassia latifolia, a tree growing on the slopes of the Himalaya. At first 
 the colour of this oil is yellow, but by exposure to sunlight it becomes white. Its 
 
SECT, viii.] FATS. 9 o 5 
 
 odour is not very strong, but rather pleasant. At the ordinary temperature of the air 
 this oil has the consistency of butter ; its sp. gr. is = 0-958 ; its melting-point from 27 
 to 30. It is somewhat soluble in alcohol, readily in ether, and easily saponified by 
 potassa and soda. In its saponification, oleic acid and two solid acids with a variable 
 melting-point are formed. The galam butter produced by the Bassia lutyracea, a tree 
 met with in the interior of Africa, is sometimes confounded with palm-oil, to which it 
 is very similar, but of a deeper red colour. Galam butter fuses at 20 or 21, and is 
 in its properties very much like palm-oil. Carapa oil and vateria tallow belong to the 
 same class of fatty substances ; the first, the product of the kernel of a species of 
 Persoonia, a palm-tree met with in Bengal and Coromandel, is a bright yellow-coloured 
 material, which at 18 separates into an oil and a solid fafc, known as pine-tallow, 
 Malabar tallow, and obtained from the fruits of the Vateria indica, is a white-yellow 
 wax-like tallow, melting at 35. Mafurra tallow is obtained by boiling ia water the 
 seeds or kernels of the mafurra tree found in Mozambique ; this seed, very rarely 
 seen in Europe, is of the size of small cacao beans. Mafurra seed also occurs in 
 Madagascar and Isle de Reunion. The fat obtained from this seed has a yellow 
 colour, the smell of cacao butter, and melts more readily than tallow. The fat of the 
 seeds of the Brindonia indica, employed at Goa, instead of butter, also for medicinal 
 purposes, and for use in lamps, is nearly white, melts at 40, and is insoluble in cold, 
 but somewhat soluble in boiling alcohol. Cocoa-nut oil, obtained from the kernels of 
 the cocoa-nut (Cocos nucifera, C. butyracea), is largely used in the tropics, where the 
 tree abounds. This oil is imported into Europe, and is also obtained here by pressing 
 and by treating the kernels of the imported nuts with carbon disulphide. It is white, 
 has the consistency of lard, but possesses a disagreeable odour and a somewhat foliated 
 texture ; its melting-point is 22. Chemically considered this fat consists of a peculiar 
 substance termed cocinin, with small quantities of oleine ; by saponification the former 
 yields glycerine and cocinic acid (cocoa-stearic acid), C 13 H 26 2 . W. Wicke obtained in 
 1860, 6 1 '5 7 per cent of fat from the kernels. During the last twenty years cocoa-nut 
 oil has been largely used for soap-boiling, because it is an excellent material for the 
 preparation of so-called filling soaps.* 
 
 Olive oil is obtained from the fruit of the olive tree, Olea europea, belonging to the 
 natural order of the Jasminece, and largely cultivated in the whole of Southern Europe 
 and the coastlands of North Africa. 
 
 In order to obtain an oil of good quality it is essential that the olives should be 
 gathered when they are fully ripe, which happens in the months of November and 
 December. Unripe olives yield an oil having a harsh bitter taste, while, again, over- 
 ripe fruit yields a thick oil, readily becoming rancid. The method of oil extraction 
 from olives as carried on in Southern France is the following : The ripe olives are first 
 reduced to pulp in a mill ; this pulp is put into sacks made of strong canvas, or, better, 
 of horsehair, and submitted to pressure. The first portion of oil thus obtained is the 
 best and is known as virgin oil, or huile merge. In order to eliminate all the oil as 
 much as possible, the cake, after the first pressing, is treated with boiling water and 
 again pressed. The oil thus obtained possesses a fine yellow colour, but is more liable 
 to become rancid than the virgin oil. Notwithstanding the second pressure the cake 
 retains enough oil to make it worth while to submit it to further operation. Some 
 kinds of olive oil obtained by the second pressing are employed, under the name of 
 Gallipoli oil, in dyeing Turkey-red. This oil has an acid reaction consequent upon its 
 containing free fatty acids, is turbid, rancid, and possessed of the property of forming 
 with carbonates of alkalies a kind of emulsion, which in dyeing is known as the white 
 
 * Cocoa-nut oil has recently been used for preparing an artificial butter which approaches cow- 
 butter more closely than any other substitute. The rancidity and offensive odour are removed by 
 treatment with alcohol and filtration over bone-black. [EoiTOE.] 
 
.906 CHEMICAL TECHNOLOGY. [SECT. vm. 
 
 bath. The olive oil used for the purpose of greasing wool in spinning is known as 
 lampant oil. Under the name of Huile d'enfer is understood the olive oil deposited in 
 the tanks where the water used for adding to the olives about to be pressed is kept ; 
 it is used in the manufacture of soap. During the last few years it has become the 
 custom to exhaust the olives with carbon disulphide instead of pressing them. 
 
 Rape-oil and Colza-oil (formerly much used for burning in lamps) are obtained from 
 the seeds of various kinds of Brassica, which are, in fact, merely varieties of Brassica 
 campestris. The oils differ very little. 
 
 Beech oil, from the seeds of the beech (Fagus sylvatica\ is used for food. 
 
 Sesame oil is obtained in India, Brazil, Greece, &c., from the seeds of Sesamum 
 orientate and S. indicum. It much resembles olive oil, and is used for the sophistica- 
 tion of the latter. . 
 
 Earth-nut oil is obtained from Arachis hypogcea in India and South America and 
 much resembles oil of sesame. 
 
 The chief drying oils are : Hemp-oil, obtained from the hemp-seed (Cannabis 
 sativa), containing about 25 per cent, of "oil, chiefly used for making black, green, or 
 soft soap. When fresh pressed, hemp-oil possesses a bright green colour, which in 
 time becomes a brown-yellow.* Linseed oil, like the former a so-called drying oil, is 
 obtained from the well-known linseed (Linum usitatissimum), containing about 22 per 
 cent, of this oil, the sp. gr. of which is at 12 = 0*9395. This oil consists chiefly of a 
 peculiar glyceride which, on being saponified, yields a fatty acid different from oleic 
 acid ; moreover, linseed oil contains some palmitine.t 
 
 Nut oil, from the nuts of Juglans regia, and poppy oil, from the seeds of Papaver 
 somniferum, are used in oil-painting and also as articles of food. 
 
 Cotton oil is now obtained in vast quantities from the seeds of the cotton shrub, and 
 being a bye-product, formerly wasted, it is sold at a low price. It consists of 60 per 
 cent, linoleic acid and 40 per cent, oleic acid. It is used as an article of food, either 
 alone or in admixture with oleic acid. It appears to be perfectly wholesome. 
 
 The Waxes, with the exception of Japan wax, are not glycerides. The most im- 
 portant are 
 
 Beeswax, collected by the honey-bee, Apis inelliftca, and obtained by melting out 
 the combs with warm water. It is yellow, seldom reddish, and may be bleached by 
 exposure to air and light. Yellow wax melts at from 61 to 63 ; bleached white wax 
 at 70. It is used for the production of tapers, candles, &c., and for smoothing thread, &c. 
 
 White wax is often adulterated with stearine, paraffine, or ozokerite. John 
 first observed that wax is a mixture of these substances; the one, cerotic acid, 
 C 27 H 54 2 , is soluble in boiling alcohol ; the other, myricine, is sparingly soluble in 
 alcohol, and consists, according to Brodie, of the meh'ssyl-ester of palmitic acid, 
 C 46 H 9 ,0 2 = C 16 H 31 (C 30 H 61 )0 2 . The difference in the melting-point of different sorts of 
 wax is due to the different proportions of the two constituents. 
 
 Chinese wax is now imported from China in quantity, and is derived from the wax 
 plant-louse, Coccus ceriferus, which deposits it upon the trees especially Rhus succe- 
 danea. It much resembles spermaceti in appearance, being snow-white, crystalline, 
 brittle and fibrous, and fusible at 82. On dry distillation it yields cerotic acid and 
 cerotine, a body resembling paraffine. According to Brodie, Chinese wax is the ceryl- 
 ster of cerotic acid, C 54 H 108 2 , or C 2r H 53 (C 2J H 55 )0 2 , 
 
 Andaquies wax is produced by an insect found on the Orinoco and the Amazon. It 
 melts at 77, has the sp. gr. 0*917, and seems to have the same composition as beeswax. 
 
 * Hempseed oil contains 70 per cent, linoleic acid, 15 per cent, linolenic acid, and 15 per cent, 
 oleic acid. [EDITOE.] 
 
 t Linseed oil contains linolenic acid, isolinolenic acid and linoleic acid. Oleic acid is almost 
 entirely absent. [EDITOR.] 
 
.SECT, viii.] FATS. 907 
 
 The chief vegetable waxes are : 
 
 Japan wax, from Rhus vernicifera and R. succedanea, is met with in commerce 
 in round discs, soft and brittle ; it melts at 42 ; dissolves in boiling alcohol, and 
 consists chiefly of tripalmitine. 
 
 Carnauba wax is imported from Rio de Janiero, and forms a coating on the leaves 
 of a kind of palm-tree, Copernicia cerifera, or Corypha cerifera. It consists essentially 
 of palmitic melissylester ; it melts at from 82 to 83-5, and on account of its high 
 melting point it serves to make more fusible fats, as also paraffine and ceresine (mineral 
 wax), fit for the manufacture of candles. Of late it has been used in the soap manufacture. 
 Stuercke has isolated from it a hydrocarbon melting at 59, three alcohols, and three 
 acids, an alcohol C 26 H 53 .CH 9 OH, melting at 76, also myricyl alcohol C 29 H 59 .CH 2 OH, 
 melting at 85-5, from which there was obtained melissic acid, C 29 H 50 .COOH, melting at 
 90, and a bi-acid alcohol C 23 H 4S (CH 2 .OH) 2 , having a melting-point about 103-5; 
 from this alcohol there was obtained the acid C 23 H 4G (C0 2 H) 2 melting at 102-5. An 
 acid, C 23 H, ? .COOH, melting at 72-5, isomeric with lignoceric acid; then an acid, 
 C 2(i H 53 .COOH melting at 79, identical or isomeric with cerotic acid ; lastly, an acid 
 C 19 H 3s .CH 2 OH.COOH, an oxy-acid or its lactone, C 19 H 38 CH 2 .O.CO, melting at 103-5; 
 from this there was obtained the acid, C 19 H 38 (COOH) 2 , melting at 90. 
 
 Palm wax, from the bark of Ceroxylon andicola, a palm growing in the upper regions 
 of the Andes, is obtained by scraping and boiling with water. It melts at from 83 to 
 86, and is perhaps identical with Carnauba wax. 
 
 Myrtle Wax is obtained in some of the more southern American States on boiling 
 the fruits of Myristica cerifera with water. It melts at 45. 
 
 Ucuhula Wax, obtained in the Brazilian province of Para from Myristica surinam- 
 ensis, is olive-green, a,nd melts at 40. It is used for candles. 
 
 Lubricants. The various substances used for lubricating machinery have the object 
 of diminishing friction, so as to economise motive power and diminish the wear and 
 tear of the parts which come in contact. Such mixtures must neither contain nor 
 form any acid capable of corroding metals, nor must they thicken in the air as do the 
 drying oils, linseed and hemp-seed oil. 
 
 The lubricants chiefly in use have been olive and rape oil, often mixed with 
 mineral oils ; also other vegetable and animal fats, sometimes with the addition of 
 graphite, &c., also resin oils and paraffines. The heavier mineral oils are now more and 
 more coming into use as lubricants. 
 
 The American mineral oils used for this purpose are known as globe oil, Vulcan 
 oil, topaz oil, star oil, &c. Valvoline is obtained from Hamburg; whilst in South 
 Germany we more commonly meet with the thick-flowing Smaragd oil, dark 
 brown, with a green fluorescence; opal, which is thin and yellow; and ruby oil, 
 -which is semi-solid at low temperatures. The Russian petroleum workings supply 
 caucasine, &c. 
 
 A lubricant reduces friction merely by forming a layer between the moving sur- 
 faces and preventing their actual contact. The friction becomes less the more easily 
 the molecules. of the lubricant move upon each other. If the pressure is very strong, 
 & highly fluid oil is driven out, and if the rotation is very rapid it may be thrown 
 out centrifugally, so that the metallic surfaces come into immediate contact. Hence 
 for strong pressures there is required a thick oil of little fluidity, and for light pres- 
 sures a thin and very fluid oil. The oil must therefore be selected with due regard to 
 the weight of the machinery, to its speed of rotation, and to the prevailing tempera- 
 ture. No one lubricating oil is equally well adapted for all purposes. 
 
 The examination of lubricants must include the detection and determination of 
 any free acid, and the determination of the coefficient of friction for different pressures 
 and temperatures. 
 
908 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. vin. 
 
 Fig. 582. 
 
 A 
 
 In order to ascertain the fluidity of an oil at different temperatures, the author 
 uses the apparatus, Fig. 582. The outflow of the copper cylinder, A, consists of a fine 
 platinum tube, 1*2 mm. in width and 5 mm. in length, enclosed in a thicker copper 
 tube, a. The latter expands at its top like a funnel, and can be closed by the cone, c, 
 the handle of which works up or down in a guide-frame, secured to the vessel. 
 The inner vessel is connected by three slips of sheet-metal, e, to the external 
 vessel, B, which rests on three feet, n centimetres high and not shown in the 
 figure. In use, the vessel, A, is filled up to a mark with 65 c.c. of 
 the oil in question, the vessel, B, is filled with cold or warm 
 water, and the oil is stirred with a sensitive thermometer, until 
 both it and the water outside are at the desired temperature. A 
 bottle holding 50 c.c., with a narrow neck, is placed between 
 the efflux opening, the stopper, c, is raised, and the time required 
 for 50 c.c. to flow into the bottle is carefully noted. The end of 
 the tube projecting out of the vessel, B, is expanded, whence its 
 cylindrical portion, which determines the speed of flowing, has 
 the same temperature as the liquid used for the experiment. 
 
 Varnishes. By varnish we understand a liquid of an oily or 
 resinous nature employed for coating various objects, the thin film 
 becoming dry and hard, thus protecting the object on which it is 
 laid from the action of air and water, and at the same time im- 
 parting a glossy and shining surface. 
 
 Linseed Oil Varnishes. Oil varnishes are usually prepared from linseed oil, but 
 sometimes, especially for artist's purposes, poppy seed and walnut oil (so-called 
 drying oils) are used. Linseed oil (raw) becomes slowly converted by the action 
 of the air into a tough, elastic, semi-transparent mass ; but this property is possessed 
 in a far higher degree by the so-called boiled oil that is to say, an oil which 
 has been brought by the action of heat and of oxidising materials into a state 
 of greater activity, in fact, into a state of incipient slow oxidation, the result 
 of which is the formation of the substance termed by Dr. G. J. Mulder* linoxine, 
 which in many of its properties corresponds to caoutchouc. The drying of oil 
 varnishes is not therefore due to evaporation (leaving, as is the case with alcohol 
 varnishes, a coherent film of resin), but to the oxidising action of the oxygen of the 
 air, whereby a coherent film of linoxine is formed. Linseed oil (raw) is converted into 
 so-called boiled oil by boiling with litharge, zinc oxide, and manganese peroxide, which 
 act upon the elaine, palmitine, and myristine of the linseed oil. The greater part of 
 the linseed and other drying oils is linoleirie, 3(C., 2 H 27 3 ).C 6 H.0 3 , which by slow oxida- 
 tion becomes linoxine = C,,H.,,O ,, by the action of alkalies converted into linoxic acid, 
 
 OJ j II 7 / 
 
 HO.C 32 O 25 O 9 . It is certainly preferable to carry this operation into effect upon the 
 water bath, or at least in vessels provided with steam jackets. The oxides are employed 
 in coarse powders, which are suspended in a linen bag in the oil. In practice, i part 
 of zinc oxide or litharge is taken to 16 parts of raw oil; and of the manganese 
 i part to 10 of oil; the oxides become partially dissolved in the oil, while they aid 
 in converting the palmitine, &c. (not linoleine), into plaster (lead or zinc soap). 
 Boiled linseed oil usually contains from 2-5 to 3 per cent, of litharge dissolved. 
 Neither the addition of zinc sulphate, nor such absurdly added substances as 
 onions, bread crust, or beetroot, have any result whatever. Linseed oil intended to 
 be mixed with zinc white should not be boiled with litharge, but with manganese 
 peroxide. The lower the temperature at which linseed oil is boiled the brighter 
 its colour. Mulder found that when raw linseed oil, especially if old, was kept for from 
 
 * This author published some rears ago in the Dutch language a highly interesting and valuable 
 work practically as well as scientifically on the drying oils. 
 
SECT, viii.] FATS. 909 
 
 twelve to eighteen hours at a temperature of 100, it acquired the property of boiled 
 oil. Sometimes, after boiling, linseed oil is bleached by exposing it in shallow trays 
 
 10 centimetres deep, best made of sheet lead, covered with sheets of glass, to the 
 action of strong summer sunlight. Liebig's recipe for making a bright varnish 
 is the following : To 10 kilos, of raw linseed oil are added 300 grammes of finely 
 pulverised litharge, after which there is added a solution of 600 grammes of 
 lead acetate. The mixture is vigorously stirred, and, after the subsidence of the 
 materials, the clear varnish is ready for use. Manganese borate is, according 
 to Barruel and Jean, an excellent so-called siccative (dryer) when added to raw 
 linseed oil, i part to 100 of oil. Mulder's experiments confirm this statement in 
 every respect. 
 
 Varnish for Paper Hangings. The varnish used for fixing gold or shearings of 
 dyed wool upon paper-hangings, &c., is a solution of linseed oil and lead plaster in oil 
 of turpentine. The mixture is obtained by first saponifying linseed oil with caustic 
 alkali and precipitating the aqueous solution of this soap with a solution of lead acetate. 
 The lead soap thus obtained is next dissolved in oil of turpentine. 
 
 Printing Ink. This is, when genuine and when prepared from good linseed or 
 Avalnut oil, anhydride of linoleic acid, C 32 H 27 O 3 , mixed with very finely divided lamp- 
 black, and obtained by heating raw linseed oil for several hours, at a high tempera- 
 ture (from 315 to 360), whereby the fatty constituents glycerine, palmitine, &c. are 
 volatilised. Usually the oil is heated in vessels directly exposed to the action of fire, 
 and as the colour of the ink is black, a deep colour from the residue of the heating of the 
 
 011 is not of much consequence. In order to render printing ink more rapidly drying, 
 some manganese borate may be heated with it at 315 for some hours. The quantity 
 of fine lamp-black (best re-ignited in close vessels, or exhausted with boiling alcohol) 
 usually added to printing ink, amounts to about 16 per cent. Soap is necessary to be 
 added in order to prevent smearing and assist in obtaining sharpness of impression. 
 Coloured printing inks are obtained by adding to boiled oil red or blue or other 
 pigments ; for red, vermilion is used. The ink used in lithography and copper-plate 
 printing is made thicker, a better black being added. 
 
 The varnish for lithographic ink has to be thicker than that for book- work. Copper- 
 plate ink is a mixture of thick varnish with Frankfurt black. Instead of linseed or 
 nut-oil, bankul-oil (from Aleurites triloba) has been proposed for the preparation of 
 printing ink. 
 
 Fat Varnishes. The so-called fat or oil varnishes are solutions of resins in boiled 
 linseed oil mixed with oil of turpentine, benzol, or benzoline. Amber, copal, anime, 
 gum dammar, and asphalte, are among the more ordinary resins employed for this 
 purpose, the varnishes being made by melting, with the aid of gentle heat, the amber, 
 copal, &c., to which, while liquid, boiling linseed oil is added. The cauldron in which 
 this operation takes place should be only two-thirds filled ; and the mixture of oil and 
 resin kept boiling for ten minutes. The cauldron having been removed from the fire 
 its contents are allowed to cool down to 140, when the oil of turpentine is added. 
 The quantities by weight are 10 parts copal or amber, 20 to 30 boiled linseed oil, 25 to 
 30 oil of turpentine. Black asphalte varnish is obtained in a similar manner by 
 treating 3 parts of asphalte, 4 of boiled linseed oil, and 15 to 18 parts of oil of turpen- 
 tine. Dark coloured amber varnish is not prepared from amber, but from the residue 
 (amber colophonium) of the distillation of the empyreumatic oil of amber arid succinic 
 acid left in the still from the preparation of succinic acid. These varnishes are the 
 most durable, but they dry slowly, and are more or less coloured. 
 
 Spirit Varnish. The so-called spirit varnishes are solutions of certain resins vis., 
 sandarac, mastic, gumlac (shellac), anime in alcohol, aceton, wood spirit, benzoline, or 
 carbon disulphide. Good spirit varnish ought to dry rapidly, give a glossy surface, 
 
910 CHEMICAL TECHNOLOGY. [SECT, vm, 
 
 adhere strongly, and be neither brittle nor viscous. As shellac is frequently employed, 
 the name of lac varnish is sometimes given to these varnishes. The spirit, usually 
 methylated spirit, ought to be strong, about 92 per cent. The solution of the resins 
 is promoted by the addition of one-third of their weight of coarsely powdered glass for 
 the purpose of preventing the resinous matter caking together, and being thus to some 
 extent withdrawn from the solvent action of the alcohol. In order to render the- 
 coating remaining from the evaporation of the spirit less brittle, Venice turpentine is- 
 usually added. Sandarac varnish is obtained by dissolving 10 parts of sandarac- 
 and i of Venice turpentine in 30 of spirit. Shellac varnish, more durable than the 
 former, is obtained by dissolving i part of shellac in 3 to 5 of spirits. French polish is a 
 solution of shellac in a large quantity of spirits, and when this polish is to be applied to 
 white wood, the varnish is bleached by filtration over animal charcoal. Copal varnish, 
 far superior to the foregoing, is made by first melting the resin at as gentle a heat as- 
 possible so as to prevent the coloration of the substance, which is next pulverised,, 
 mixed with sand, treated with strong alcohol on a water bath, and filtered. A solution 
 of turpentine or elemi resin is added to render the varnish softer. Colourless copal 
 varnish is obtained by pouring over 6 kilos, of previously pulverised and molten copal,, 
 contained in a vessel which may be closed, 6 kilos, of alcohol at 98 per cent., 4 kilos, of 
 oil of turpentine, and i kilo, of ether ; the vessel containing this mixture having been 
 closed is gently heated. The solution is clarified by decantation. 
 
 Lacquers. These are used chiefly for the purpose of coating instruments, and" 
 other objects of brass and coloured metallic alloys, so as to prevent the action of the 
 atmosphere. Such varnishes are used for imparting a gold-colour to base metals ; for 
 this purpose alcoholic tinctures of gamboge and dragon's blood, or magenta, picric 
 acid, Martius yellow, and coralline, are separately prepared and added, in quantities 
 found by trial, to a varnish consisting of 2 parts of seed lac, 4 of sandarac, 4 of elemi, 
 and 40 of alcohol. 
 
 Turpentine Oil Varnishes. These are prepared in the same manner as the pre- 
 ceding. They dry more slowly, but are less brittle and more durable. Common 
 turpentine oil varnish is obtained by dissolving ordinary resin in oil of turpentine ;. 
 but this varnish is liable to crack. Copal is either dissolved in oil of turpentine 
 without or after having been melted ; in the latter case the varnish being coloured. 
 When non-melted copal is used it is broken into small lumps, and is suspended in a. 
 stout canvas bag over the surface of the oil of turpentine contained in a glass flask, 
 and placed on a sand bath, the vapours arising from the oil of turpentine gradually 
 dissolving the copal. Dammar gum resin varnish, made with oil of turpentine, is 
 prepared by drying the resin at a gentle heat and dissolving it in from three to four times 
 its weight of oil of turpentine. This varnish, though colourless, is not very durable. 
 Green turpentine oil varnish is prepared by dissolving sandarac or mastic in con- 
 centrated caustic potash solution, diluting with water, and precipitating with acetate 
 of copper, the dried precipitate being dissolved in oil of turpentine. 
 
 Polishing the Dried Varnish. In order to increase the gloss of varnished surfaces 
 especially on metallic objects and coaches, carriages and woodwork in theatres, concert- 
 rooms, halls, &c., the dry surface is first rubbed over with soft felt, on which some very 
 fine pumice-powder is laid, and is next polished with very soft woollen tissue on which 
 some oil and rotten-stone is placed, the oil being rubbed off with starch-powder. 
 Instead of varnishes, solutions of collodion (fulminating cotton in alcohol and ether), 
 and solutions of water-glass are sometimes used ; while Puscher recommends a solution 
 of shellac in ammonia, largely used by hatters. 
 
 Pettenkofer's Process for Restoring Pictures. In order to remove the cracks often 
 observed in old pictures, Von Pettenkofer has suggested exposure to the vapour of 
 alcohol at the ordinary temperature of the air, the picture being placed in an air-tight- 
 
SECT. VIII.] SOAP. 9II 
 
 box, at the bottom of which is a tray containing alcohol. This method has been tried, 
 but not only has it failed in many cases, but some pictures have been completely spoiled. 
 According to Dr. G. J. Mulder's researches, the only effective preservative of pictures 
 is complete exclusion of air. He suggests that pictures should be well varnished on 
 the painted side as well as on the back, and next hermetically covered with well-fitting 
 sheets of polished glass on the front, and some substance on the back impermeable to 
 air. The real cause of the ultimate destruction of pictures as well as of paint is the 
 gradual, but continuous, yet slow, oxidation of the linoxine, resulting in the crumbling 
 to powder of the pulverulent matter pigments used as colours. It may not here be 
 out of place to state that one of the best solvents of linoxine (dried paint) is a mixture- 
 of alcohol and chloroform, which may be advantageously used to remove stains of paint r 
 and also of waggon and carriage grease from silk and woollen tissues. 
 
 Linseed oil varnish mixed with white lead, litharge, or red lead, or with a mixture 
 of 10 parts litharge and 90 parts elutriated chalk is used for cementing articles of glass- 
 or porcelain. Instead of the chalk, there may be taken lime slacked to a powder, and 
 instead of litharge zinc white. 
 
 As a cement for steam-pipes, &c., Stephenson uses a mixture of 2 parts litharge,, 
 i part lime slacked to a powder, and i part sand, the whole intimately mixed with hot 
 linseed oil varnish. If alum soap (obtained by precipitating solution of alum with soda- 
 soap) is dissolved in hot linseed oil, we obtain a mixture suitable for cementing stones. 
 Common glaziers' putty is made by grinding up chalk with boiled linseed oil. If the 
 oil has not been boiled it sets very slowly. Glycerine putty, a mixture of glycerine- 
 with litharge, is excellent for joining iron to iron, stone to stone, and iron to stone. 
 The best proportions are 50 grammes litharge to 5 c.c. glycerine. 
 
 Iron putty consists of ferric oxide ground up with boiled linseed oil ; it resists acids- 
 well* 
 
 SOAP. 
 
 Soap, in the common acceptation of the word, is the product of the action of caustic 
 alkalies upon fats, and consists essentially of potassium or sodium stearate, palmitate,. 
 or oleate. Though soap was known in the pre-historic ages, its manufacture was not 
 properly conducted until Chevreul ascertained the nature of fats and the principles of 
 saponification, and until the soda industry was developed. 
 
 The raw materials for soap are of two kinds, the natural fats or the fatty acids and 
 the lye, an aqueous solution of caustic potash or soda. 
 
 The soap-boiler now rarely prepares caustic lye for his own use. He generally finds 
 it more convenient to buy solid caustic soda and potash from the alkali manufacturers. 
 Usually three different kinds of lye are prepared and kept, viz. : (i) Strong lye, 18 to- 
 20 percent, of alkali; (2) Middling strong lye, 8 to 10 percent, of alkali ; and (3) Weak 
 lye, containing only i to 4 per cent, of alkali. This weak liquor is commonly used 
 instead of water for lixiviating a new soda-ash and lime mixture. The sodium-aluminate 
 obtained by the decomposition of cryolite is used in the United States under the name 
 Natrona refined saponifier, for soap manufacturing purposes. Sodium sulphide may 
 also be used instead of caustic alkali. 
 
 Theory of Saponification. Before Chevreul published his researches, it was supposed 
 that fats and oils possessed the property of combining with alkalies. Chevreul found, 
 however, that fats separated from their state of combination as soaps possessed 
 properties differing from those existing before they were saponified, the fact being 
 that the substances we are acquainted with as oils or fats are compounds of peculiar 
 acids, stearic, palmitic, margaric, oleic, all non-volatile substances ; while certain fats 
 which give off a peculiar odour contain, in addition to these acids, volatile fatty acids, 
 
 * On cements the reader may compare Spon's " Encyclopaedia of Industrial Arts," pp. 623, et seq. 
 
 [EDITOR] 
 
912 CHEMICAL TECHNOLOGY. [SECT. vm. 
 
 as butyric, capric, capronic, valerianic, <fec. The volatile acids in the ordinary oils 
 and fats are combined with a sweet material, discovered by Scheele, and known under 
 the name of glycerine. 
 
 According to Berthelot's researches, it is held that all the oils and fats which are 
 used in soap-making are ethers of glycerine, C 3 H 8 O 3 , that substance being viewed as a 
 
 C H ~1 
 
 trivalent alcohol, 3 5 VO 3 . Palmitine, for instance, the main constituent of palm-oil, 
 
 H-aJ 
 
 is glyceryl-tripalmitate, or tripalmitine, that is to say, glycerine in which three atoms 
 
 C H "I 
 
 of hydrogen are replaced by the radical of palmitic acid, 3 s l0 3 . Stearine (tri- 
 
 3^16^31^' ) 
 
 stearine) and oleine (trioleine) have an analogous constitution. When the fats, take 
 
 palm-oil for instance, are saponified with caustic alkalies, say caustic soda, the fat 
 
 that is, in chemical parlance, the ether is decomposed into alcohol, i.e., glycerine, 
 and soda palmitate, i.e., soap, according to the following equation : 
 
 Tripalmitine ^4r 
 
 ^3 ,6 H 3l 
 
 and caustic soda, 3lS"aOH, 
 
 s ( 
 
 Glycerine, 
 
 and soap, or sodium palmitate, 3 \ W 6 32 I O. 
 
 v. ( JN a j 
 
 The glycerine formed during the process of saponification remains, after the separa- 
 tion of the soap, dissolved in the mother liquor from which it is prepared. It is clear 
 that such fats as palm- and cocoa-nut oil, which in their ordinary state contain fatty 
 acids, are more readily saponified than the perfectly neutral fats, viz., olive-oil and 
 tallow ; while the oleic acid derived from the stearine candle manufactories is readily 
 saponified by carbonated alkalies. This operation applies to colophonium (resin), 
 which consists essentially of a peculiar acid, pinic acid, but in these instances no real 
 saponification takes place, inasmuch as no glycerine is formed. The decomposition of 
 a fat by an alkali does not take place suddenly and throughout the whole of the fat 
 at once, in the manner of inorganic salts, but passes through several stages, the first 
 being the formation of an emulsion of lye and fat ; next fat acids and fat acid salts are 
 formed, retaining the rest of the fatty matter in suspension ; gradually the free fatty 
 matter is saponified, and the fat acid salts are converted into neutral salts, or, in other 
 words, soap. 
 
 When caustic potassa is used, soft soaps are produced, while the hard soaps result 
 from the use of caustic soda. We distinguish soaps 
 
 (a) As hard soaps or soda soaps ; 
 () As soft soaps or potassa soaps. 
 
 According to the fatty substances used in soap-boiling, soaps are distinguished as 
 tallow, oil, palm-oil, oleic acid, cocoa-nut, fish-oil, and resin soaps, &c. Technically, 
 hard soaps may be divided into : 
 
 (1) Grain soap ; 
 
 (2) Smooth soap; 
 
 (3) Filled soap. 
 
 (1) Grain soap takes its name from the fact that the finished soap when being salted 
 out from solution separates from the spent lye in the state of semi-solid, rounded lumps 
 or grains, which solidify to a uniform mass free from bubbles. It is the only pure soap, 
 being freed by the salting out from glycerine, superfluous lye, excess of water, or other 
 impurities. The majority of soap-boilers no longer make this kind. 
 
 (2) Smooth soap is made by what is called polishing the grain soap. If such soap is 
 boiled in the pan with water or weak lye it takes up a proportion of water, and loses 
 the power of marbling. It is distinguished from grain soap merely by its larger 
 proportion of water. 
 
 (3) Filled soaps are now unfortunately the commonest. They are 30 imperfectly 
 
SECT. VIII.] SOAP. 9 ! 3 
 
 salted out that the entire contents of the pan remain together and are sold as soap. 
 On cooling, the whole solidifies, and does not betray its proportion of water. 
 
 This property of appearing dry and hard, along with a heavy percentage of water, 
 is a peculiarity of cocoa-nut oil soaps, which communicate the same property to tallow 
 and palm-oil soaps. A yield of 200 to 300 kilos, soap from 100 kilos, fat is nothing 
 uncommon, especially if water-glass is used. 
 
 The mixture of oil 100 kilos., resin 70 to 80 kilos., water-glass 300 kilos., talc 100 
 to 150 kilos., and soda-lye at 56 Tw. 240 kilos., gives a yield of 800 kilos, of a product 
 which sells as soap. 
 
 Chief Varieties of Soap. The German tallow soap or curd soap is essentially a 
 mixture of sodium stearate and palmitate, and it is commonly prepared indirectly 
 by first saponifying tallow with caustic potassa, and next converting, by means of 
 common salt, the potassium stearate and palmitate into the corresponding sodium com- 
 pound. 
 
 The soap-boiling pan employed is somewhat conical in shape. It is made of cast- 
 iron, and provided at the top with a high lintel or bulwark to prevent any fluid boiling 
 over. Supposing it to be intended to convert 10 cwts. of tallow into soap : Into the 
 cauldron is first poured about 500 litres of strong lye at 20 per cent. ( = i - 226 sp. gr.) ; 
 next the tallow is added, and a wooden or iron lid having been fitted to the cauldron, 
 the fire is kindled. When ebullition sets in, it is kept up, with occasional stirring of 
 the contents of the cauldron, for five consecutive hours. The materials in the cauldron 
 are converted into soap-glue, as it is termed, a gelatinous mass, which, if the operation 
 has been well conducted, ought not, upon the addition of fresh lye, to become thin, 
 while it also should not flow in drops, but similarly to treacle from a spatula. The 
 production of this substance is promoted by adding oil of tallow to the lye gradually and 
 in small portions at a time. 
 
 Mege-Mouries recommends either yolks of eggs, bile,* or albuminous compounds. 
 As proved by the researches of F. Knapp, it is always advantageous to first convert 
 the fat, with the requisite quantity of lye, into an emulsion, and to leave the lye either 
 not heated at all or only to 50 in contact with the fat, so as to saponify first slowly in 
 the cold and to finish off Avith ebullition. When caustic soda-lye is used it is of a density 
 of from 14 to 17 Tw. (=1-072 to ro88 sp. gr.). When the saponification is complete 
 the operation of fitting or parting is proceeded with, and consists in adding from 12 to 
 1 6 Ibs. of salt to 100 of tallow. The soap is kept boiling until the soap-glue has become 
 a greyish mass, from which the mother liquor or under-lye readily separates, the latter 
 being let off by a tap ; or, if no tap is fitted to the cauldron, the soap is gradually 
 ladled over into the cooling tank. The addition of salt not only aims at the separation 
 of the soap from the lye, but also at the partial conversion of the potassp. into soda- 
 soap. If the soap-glue has been removed, it is again put into the cauldron, and there 
 is added a moderately strong lye, and heat again applied. The soap again becomes 
 quite fluid, but consists chiefly of soda-soap glue. The ebullition is kept up, and 
 during its continuance fresh lye and salt are added alternately. By continued boiling 
 the soapy mass becomes more and more concentrated ; as soon as the foaming ceases, 
 and the whole mass is in a steady ebullition, it is again ladled over into the cooling- 
 tank, or the mother liquo'r is tapped off. The object to be gained by this second 
 boiling is the conversion of the material into a uniform mass free from air-bubbles ; 
 this object is promoted by beating with iron rods. The hot soap is next placed in a 
 wooden box, so constructed that it can be taken to pieces; upon the bottom of this box, 
 which is perforated, a piece of cloth is stretched, so as to allow of any adhering lye 
 running off. When the soap is cool the box is taken to pieces, the soap cut into bars, and 
 
 * Ox-gall is the finest soap known for cleansing dyed goods, especially silks. Its synthetic pro- 
 duction without the unpleasant smell would be a most valuable invention. [EDITOE.] 
 
9 14 CHEMICAL TECHNOLOGY. [SECT. viir. 
 
 these are placed in a cool, dry room. The cutting of the soap into bars is now effected 
 by machinery ; formerly it was performed by hand with a peculiar tool, a copper-wire 
 with suitable handles, such as cheesemongers sometimes use. 10 cwts. of tallow yield 
 on an average i6| cwts. of soap, which by drying loses some 10 per cent. As it is 
 impossible, even with repeated applications of salt, to convert potassa-soap completely 
 into soda-soap, the German curd-soap, or Kernseife, is always mixed with a considerable 
 quantity of potassa-soap, to which it owes its peculiar softness. According to the 
 researches of Dr. A. C. Oudemans (1869), only half the potassa is converted into soda- 
 soap. 
 
 Olive Oil Soap. This kind of soap, also known as Marseilles, Venetian, or Castilian 
 soap, is chiefly prepared in the southern parts of Europe. The olive oil is frequently 
 mixed with other kinds of oil, such as linseed, poppy seed, cotton-seed oil, &c. Two 
 kinds of lye are employed in the preparation of this soap ; the first lye is only a caustic 
 soda solution, and used for fitting or preparatory boiling ; the other lye is mixed with 
 common salt, and intended to effect the separation of the soap. The preparatory 
 boiling aims at the formation of an emulsion or the production of an etat globulaire, 
 whereby the contact of oil and alkali is greatly promoted, and a real soap-glue 
 ultimately results. In order to remove the water from this material as much as 
 possible, a lye containing common salt is employed, and lastly by a third boiling the 
 saponification is rendered complete. By the use of the lye containing common salt it 
 is possible to keep the soap-glue in such a condition that it can take up alkali without 
 combining with the water. The preparatory boiling, or fitting, is carried on in large 
 copper vessels, capable of containing 250 cwts., the caustic soda employed for this 
 purpose having a strength of from 8'2 to 12*5 Tw.(= i - o4i to 1*064 S P- g r -)- The lye 
 is brought to ebullition first, and the oil to be saponified is next added, care being taken 
 to stir the mixture in order to promote the reaction. Gradually the mass becomes thick, 
 and as soon as black vapours arise, due to the decomposition of a small quantity of the 
 soap-glue by coming in contact with the very hot copper, there is added the stronger lye 
 of 30 Tw. (1-157 sp. gr.). If it is intended to produce a blue- white soap, some sulphate 
 of iron is added. As soon as the mass has become sufficiently thick, the soda-lye, 
 mixed with salt, is added. After some hours the soap entirely separates from the 
 mother liquor, which is then run off, and fresh lye added, also containing common salt. 
 The final boiling is then proceeded with, the lye having a strength of from 30 to 45 Tw. 
 The ebullition is continued gently until the alkali is exhausted, when the mother liquor 
 is again run off, and fresh lye mixed with common salt again added ; this operation is 
 repeated some four to six times, when the soap is at last quite ready. This stage is 
 indicated by the absence of all smell of oil and the peculiar grain of the mass, which 
 is left to cool; but if sulphate of iron has been added, it is necessary to stir the 
 soap continuously until nearly cold, in order to produce the mottled appearance due to- 
 the formation of iron sulphide from the sulphate by the action of the sodium sulphide 
 of the soda-lye. Mottled soap is produced in England by adding a concentrated 
 solution of crude caustic soda, containing sodium sulphide, to the liquid soap, pre- 
 viously being impregnated with iron sulphate. When nearly cold the soap is placed 
 in wooden boxes and left to completely solidify. After from ten to twelve days it is- 
 ready for being cut into bars. 64 litres of oil =58 to 60 kilos., yield from 90 to 95 
 kilos, of soap. White-oil soap is prepared in a similar manner, but purer materials 
 are employed. A good sample of Marseilles mottled soap should contain 
 
 I. n. 
 
 Fat acids 63 ... 62 
 
 Alkali 13 ,.. ii 
 
 24 ... 27 
 
 100 100 
 
SECT, viii.] SOAP. 9I5 
 
 Oleic Acid Soap is obtained from crude oleic acid, a bye-product of stearine candle 
 manufacture. The oleic acid produced by the distillation process is less suitable for 
 soap-making purposes. Oleic acid is saponified simply by being mixed with a strong 
 solution of sodium carbonate, or by the application of caustic soda. In the use of the 
 sodium carbonate, however, there is the disadvantage of the effervescence due to the 
 evolution of carbonic acid, and consequent boiling over or spilling of the materials. 
 Pitman uses the sodium carbonate in a dry state. Heat is best applied by Morfit's 
 arrangement, in which steam is passed through a system of pipes moved by machinery 
 and acting as stirrers. Resin is sometimes added. As soon as the mass has acquired 
 sufficient consistency, and the effervescence ceases, the soap is put into moulds to cool 
 and solidify. When caustic soda is used,half the lye (sp.gr. 1-15 to 1-20 = 30-4 to 4oTw.) 
 is first poured into the cauldron and brought to ebullition, next the oleic acid is added, 
 and as soon as the soap-glue is formed, the other half of the lye is put in, and the 
 ebullition continued until the soap is formed. The separation from the mother liquor 
 is greatly promoted by the addition of some salt. The soap is poured into moulds to 
 cool and solidify. In order to impart greater hardness to the soap, from 5 to 8 per cent, 
 of tallow is added to the oleic acid. 100 kilos, of oleic acid yield from 150 to 160 kilos, 
 of soap, which, when well made, consists of 
 
 Fat acids t ....... 66 
 
 Soila 13 
 
 Water 21 
 
 Resin-Tallow Soaps. Colophonium and ordinary fir-tree resin combine at boiling 
 heat mere readily with alkalies than do fats and oils ; but the compounds obtained bv 
 treating resin alone with alkalies are not soaps in a chemical sense, nor have they the 
 appearance or properties of soap. When tallow is saponified along with a portion of resin, 
 a true soap is obtained. In England resin-tallow soap is manufactured very largely 
 by first preparing a tallow-soap, and when this is ready adding to it from 50 to 
 60 per cent, of the best resin, previously broken into small lumps. The mass is 
 thoroughly stirred, and after the resin has been incorporated with the tallow, the 
 mother liquor or under-lye is run off, and the soap-making finished by boiling with a 
 quantity of fresh lye at from i o to 1 3 Tw. The insoluble alumina and iron soaps having 
 been removed as scum from the top of the liquid, the hot soap is poured into moulds 
 made of wood or sheet-iron ; sometimes palm-oil is added in order to improve the 
 colour of the soap. Usually, palm oil is not saponified alone, but is added to tallow ; 
 by treating a mixture of 2 parts of tallow and 3 parts of palm oil with potassa or 
 soda-lye in the ordinary manner, and by mixing this soap with a resin soap prepared 
 from i part of resin and a proper quantity of potassa-lye, the German palm-oil soap is 
 obtained. 
 
 Cocoa-nut Oil Soap. The manufacture of cocoa-nut oil soap resembles that of the 
 other kinds of soap. With a weak lye cocoa-nut oil does not form the emulsion common 
 to other soaps, but swims on the surface as a clear fat ; when, by boiling, the lye has 
 reached a proper consistence, the oil suddenly saponifies. A strong soda-lye is used in 
 the preparation of this kind of soap. Cocoa-nut oil in saponifying does not separate from 
 the under-lye ; therefore potash-lye is never employed. To prevent the separation of the 
 soap from the mixing, the quantity of caustic-lye used must be accurately measured. 
 Pure cocoa-nut oil soap hardens quickly. It is white, like alabaster, shiny, soft, and easily 
 lathered ; it has, however, a peculiarly unpleasant smell, which cannot be entirely 
 masked by any perfume. Cocoa-nut oil is seldom used alone, but usually as an addition 
 to palm oil and tallow. This kind of soap can be made without boiling, by merely 
 heating it to 80, by means of steam, to melt the fats, a strong soda-lye being added, 
 
9i6 CHEMICAL TECHNOLOGY. [SECT. vin. 
 
 and the mixture quickly stirred. This is known as the " cold method," and soap can 
 be thus prepared in large quantities in a short time, and is generally hard and dry. 
 When exposed to the air for a month or so, the soap loses considerably in weight, and 
 becomes effloresced superficially. B. linger (1869) prepares a soap in the following 
 manner : He saponifies palm-oil with soda-lye and salt as usual. The product is 
 sodium palmitate. At the same time cocoa-nut oil is saponified by means of carbonated 
 and caustic soda-lye ; this is added to the palm-oil soap, and they are boiled. As a 
 rule, there are taken 2 parts of palm-oil to i part of cocoa-nut oil ; and to 100 parts 
 of the latter are added i4'3 parts of caustic soda (Na 2 0) and 12 '8 parts of sodium 
 carbonate. According to Unger's experiments, this soap contains 5 mols. sodium 
 palmitate, i mol. sodium carbonate, and x mol. water. The " marbling " or " mottling " 
 is effected in the following manner : Colouring matters, oxide of iron, brown-red, 
 Frankfort-black, are mixed with a small portion of soap ; this is poured into the 
 rest of the soap, with which it forms layers of unequal thickness. The entire mass is 
 now stirred, and by this means a marbled or grained appearance imparted. 
 
 Soft-Soap. As before mentioned, potash forms with fats and oils only a soft-soap, 
 which does not dry when exposed to the air, but on the contrary absorbs water, 
 remaining constantly like a jelly. As a rule, these so-called soaps are impure 
 solutions of potassium oleate in an excess of potash-lye, mixed with the glycerine 
 separated in the saponification. Soft-soaps can be prepared only with potash-lyes, 
 although in practice i part of soda-lye is substituted for a part of the potash to assist 
 in somewhat hardening the soap. There is no separation of the soap from the under- 
 lye, which contains all the impurities ; consequently these are disseminated in the soap. 
 
 In consequence of the solubility and cleansing properties of soft-soap, its use is 
 preferred to that of soda-soap in the manufacture of cloth and woollen articles. It 
 will have been seen that the difference in manufacturing hard- and soft-soaps 
 consists in employing potash-lye for the latter, and soda for the former. Wood- ash 
 is not used in preparing the potash-lye, but always pure potash ; the preparation 
 follows the usual method with caustic lime. The fats used are mixtures of the 
 vegetable and animal oils, as the fish-oil known as " Southern," with rape, hemp, and 
 linseed oils. The particular oil used varies according to the time of the year and 
 market price : in winter the soft oils are employed ; in summer the firmer oils. 
 Soft-soap is generally used for fulling and scouring ; but abroad it is sometimes used 
 for washing linen, to which it imparts a most disagreeable fishy odour, hardly concealed 
 by any amount of perfume. The best soft-soap is made from hemp-seed oil, this oil 
 imparting a green tinge, which, however, can be imitated by adding indigo to inferior 
 soaps. Summer soap, as it is termed, contains, owing to the fat employed, more 
 potassium palmitate in proportion to oleate than the winter soap. Sometimes saponifi- 
 cation is effected with a mixture of hemp- and palm-oil or tallow, of train oil and 
 tallow, &c, 
 
 The boiling of the soft-soap commences with a strong lye containing from 8 to 10 
 per cent, potash, by which an emulsion is formed. The scum is dashed about with a 
 stick, the beating-stick, and by this means all the alkali is taken up. A fresh 
 lye is then added, and the boiling continued, until the soap upon cooling stiffens 
 into a clear tough mass. When the soap contains too much caustic alkali, which 
 can be ascertained by the taste, more oil is added. The clear-boiling now commences, 
 during which the excess of water is removed. To avoid lengthy evaporation a 
 concentrated lye is employed, and the soap, instead of bubbling up, has its surface 
 covered with blisters as large as the hand ; these blisters are termed leaves. When 
 the boiling is finished ascertained by placing some of the soap to cool on a glass 
 plate, from which, if firm, it can be separated the soap is cooled, and stored in 
 barrels. 
 
SECT. VIII.] SOAP. 
 
 917 
 
 Soft-soap will take up a considerable quantity of water-glass solution without 
 alteration. Recently, for fulling, there has been added to the soft-soap a solution 
 of potassium sulphate, or a mixture of alum and common salt, and also potato 
 starch. 
 
 Various other /Soaps. Another soap is prepared from hog's-lard, and when 
 scented with oil of almonds or essence of mirbane (nitrobenzol) is sold as almond- 
 soap, and as a cosmetic. A soap is made from the grease of sheep's- wool. The so-called 
 bone-soap is nothing more than a mixture of the usual hard or cocoa-nut oil soap 
 with the jelly from bones. The bones are first treated with muriatic acid to separate 
 the calcium phosphate. A variety of bone-soap is the Liverpool common soap. 
 Flint-soap is an oil- or tallow-soap with which siliceous earth is mixed. When 
 powdered pumice-stone is substituted for the siliceous earth, the soap is called pumice- 
 soap. In America as well as in England a water-glass solution is substituted for the 
 siliceous earth, although according to Seeber the result is not so efficacious. Cocoa- 
 nut oil soap, however, containing 24 per cent, of sodium silicate and 50 per cent, water, is 
 very firm. In the United States water-glass is added to the soap when, still hot from 
 the boiling-pan, it is poured into the moulds. The water-glass solution is of a density 
 = 60 Tw. (=1-31 sp. gr.) ; the proportion of soap is 60 per cent. This kind of 
 water-glass soap generally sets hard. Recently cryolite and sodium aluminate have 
 been employed. 
 
 Toilet-soaps. On account of the reduction in the duty toilet soaps are now very 
 largely in demand. They are generally made by re-melting and perfuming common 
 soap. English toilet soap is considered the best, as that of France and Germany being 
 perfumed while cold is not so uniform a product. 
 
 There are three modes of preparing toilet soap, viz. : 
 
 (1) By re-melting raw soap ; 
 
 (2) By the cold perfuming of odourless soap ; 
 
 (3) By direct preparation. 
 
 (i) In the method of re-melting, good raw soap is scraped into a boiling-pan, and 
 after melting and skimming the perfume is added. The soap is then cast in moulds 
 of the required form. (2) In the method of perfuming in the cold, odourless soap is 
 cut into fine shreds by a machine ; the perfume is then added, and the soap is passed 
 between rollers, the sheets or bars thus formed being cut into tablets. Struve, of 
 Leipsic, has invented a machine by means of which soap is stamped into the shape 
 required. (3) The direct preparation of toilet-soap consists in colouring and scenting 
 pure white common soap without an intervening cooling. The colouring materials 
 are f or re d, cinnabar, coralline, and magenta; the violet tar-colours for violet; for 
 blue, ultramarine; for brown, a solution of raw sugar or caramel. Windsor soap 
 is prepared in the following manner: 40 Ibs. of mutton tallow and from 15 to 
 20 Ibs. of olive oil are mixed with soda-lye marking 19, making a soap of 15; 
 finally, with lye marking 20, when the soap is of the consistency of marrow. The 
 excess of lye is then neutralised. When the soap is set it is allowed to stand from six 
 to eight hours, and during this time most of the under-lye separates. It is then 
 placed in a flat form, and pressed until no fluid exudes. It is scented with cumin 
 oil, bergamot, oil of lavender, oil of thyme, &c. Rose soap, savon & la rose, is manu- 
 factured by melting the ingredients of three parts of oil-soap with two parts of tallow- 
 soap and sometimes water ; the perfume is attar of roses, oil of roses, or gilliflower 
 water, the colouring-matter being generally cinnabar. Shaving-soap must not contain 
 free alkalies. It is sometimes prepared by boiling fat acids with a mixture of potassium 
 and sodium carbonates. Lather-soaps have in equal volume only half the substance of 
 the other soaps. Palm- or olive-oil soap is melted with an addition of one-third to one- 
 ei^hth the volume of water, and the mass stirred until it has increased to double the 
 
CHEMICAL TECHNOLOGY. [SECT. via. 
 
 volume. It is then placed in a mould. It should be remarked that the oil-soaps, and 
 not tallow-soaps, are the true formatives of the lather-soaps. 
 
 Transparent Soap. Ordinary dry tallow-soap is cut into splinters, and heated with 
 an equal weight of alcohol, in which the soap dissolves. The mixture is allowed to 
 cool ; therewith all impurities are thrown down, and the clear fluid is placed in the 
 moulds, where it has to remain from three to four weeks to harden. Tincture of cochineal 
 and aniline red are employed for colouring transparent soaps, and also Martius's yellow. 
 The perfume is chiefly oil of cinnamon, sometimes oil of thyme, oil of marjoram, and 
 sassafras oil. Glycerine-soap is prepared from an alcoholic solution of ordinary soap, 
 to which glycerine is added. Or 5 cwts. of soap with an equal quantity of glycerine 
 are heated by steam in a copper vessel. The mixture is placed in moulds, and 
 allowed to set in the usual manner. A solution of soap in an excess of glycerine 
 (35 : 3) forms fluid glycerine-soap, which is of a clear honey consistency. Both 
 varieties are perfumed with essential oils. 
 
 Uses of Soap. Soap is used for cleansing purposes in washing, in bleaching cloth 
 and woollen materials ; for the preparation of lithographic inks, &c. The cleansing 
 properties of soap are due to the alkalies it contains. The alkali, although combined 
 with the fat acids, loses none of these properties, which are, in fact, included in the 
 combination of the alkali with the fatty substances of the dirt to be removed. The 
 explanation of the action chemically, according to Chevreul, is the following : The 
 neutral salts formed by the alkalies and the fat acids, stearates, palmitates, and oleates 
 are decomposed by the water, whereby insoluble double fat acid salts are separated, 
 while the alkali is set free. By means of the free alkali the impurities clinging to the 
 materials are removed, and taken up by the fat acid salts, the suspended dirt being thus 
 contained in the lather.* 
 
 Soap Tests. The greater the quantity of fat acids combined in the soap, the 
 higher is its value. A normal soap, besides alkaline fat acids, should only contain 
 free water, the quantity of which gives a means of estimating the value of the soap. 
 It is in the power of the soap-maker to manufacture 300 parts of a good hard soap 
 out of 100 parts of fat. When too small a quantity of water is contained the soap 
 becomes too hard, and much labour is lost in obtaining a lather. If, on the other 
 hand, water is held in too large a quantity there is a great loss of material. The 
 degree of hardness of the soap forms, therefore, another means of estimating its value. 
 Many soaps contain 2 to 3 per cent, glycerine. But the proportion of water and the 
 hardness of a soap are not the only means of estimation, there still remains the 
 estimation of the neutral fat, acid, alkalies, the free alkali, common salt, or unsaponified 
 fat in the residue left after the drying of the soap. According to W. Stein, the 
 presence of free alkali may be ascertained by means of calomel, or according to 
 Naschold, by mercurous nitrate. Uncombined fat retards the formation of a lather, 
 and after a time imparts to the soap a rancid odour. But the worth of a soap can 
 only be accurately ascertained by means of chemical analysis. 
 
 The table by Dr. Leeds (p. 919) gives a method for the examination of soaps. 
 
 Insoluble Soaps. All soaps which have not a base of potassa or soda are insoluble 
 in water. Calcium-soap plays an important part in the manufacture of stearine 
 candles. It is obtained either by saponifying fat with calcium hydrate or by 
 decomposing a soluble soap with a soluble salt of lime. It is constantly formed if we 
 attempt to dissolve soap in hard water. Magnesium-soap is not readily formed in a 
 direct manner, but it may be formed indirectly by dissolving common soap in sea 
 water. Aluminium-soap is one of the most important of the insoluble soaps. 
 Alumina does not saponify fats, but alumyiium-soap is obtained by means of a sodium 
 
 * Soaps used for cleansing wool and woollen goods should always have a basis of potash, to 
 the exclusion of soda. [EDITOR.] 
 
SECT. VIII.] 
 
 SOAP. 
 
 919 
 
 
 
 " ' 02~ 
 
 J 
 
 j, 'O ,, ^, 
 
 
 
 j 
 
 Ci Q^ r*4 ^ 
 
 r^3 ^ 
 
 
 
 
 3 
 
 ~ 3 tl d n*'s 
 
 ( ^ *O 
 
 ^ .S " * "S /u O2 ' . 
 
 
 
 3 
 
 r^ 3^CSrC"rC.Sfcj 
 
 ^ W W 
 
 ^ pcT'o P^M "*"* 3 "^ S CD 
 
 
 
 "o 
 
 'S'S'o^ ,^6002 u 'fl <S 
 
 a r] JQ 
 
 r ;"SP3tiDg r c" Ha3a3 - tj 
 
 
 
 02 
 
 
 
 
 
 
 .S 
 
 ^|iiS^f5^ 
 
 2'g.S 
 
 BS^^II^^aa 
 
 
 
 i 
 
 tn 
 
 2 
 
 CO Qi "^ M" SH 
 
 In ^ 
 
 
 
 
 be 
 
 
 
 S 5 s" 1 ^ ^^^ 
 
 oToT 
 
 
 
 
 fa 
 1 
 
 M 
 
 | 
 
 |t O ^> r>. fu TJ 
 3 X "C <B J3 fl 
 
 a-^'S 
 
 Sr3 o 
 02 CQ 
 
 
 
 
 oT <u 
 
 -4-> 
 
 rQ 
 
 ^3 J3 O* W 
 
 ^H 
 
 
 c3 c3 
 
 O 
 
 3 
 
 o 
 
 
 t; 
 
 a 
 
 o 
 
 
 "3 
 
 ^^ 
 
 a 
 
 
 tn o 
 
 03 ^ 
 
 ,a 
 *> 
 
 "o 
 
 3 
 
 3* 
 
 I 
 
 s 
 
 o 
 ^o 
 
 o.-e 
 
 pfcS 
 
 ^ 3 
 
 
 
 s 
 
 
 02 > 
 
 CO ^< 
 
 ^5 "g _ "3 m cS 
 
 oT^. 
 
 i 
 
 is 
 
 ,jg 
 
 if OH 
 
 $5 w 
 
 
 - 'C 
 
 O) __. 
 
 tn 
 O 
 
 | 
 
 *J 
 
 O"o 
 
 ^||| '5 
 
 01 o _j 
 
 ^O 
 
 -4-3 
 
 ^3 
 
 r5 C3 
 
 ^^ ^fH 
 
 rH fl *02 "-+J P 
 
 tn O cd 
 
 o ^J 
 
 | 
 
 S 
 
 oH 
 
 tS*-2 
 
 H 
 
 
 
 EH 
 
 H 
 
 CQ 
 
 .2 
 
 rfl ri 
 
 5, 
 
 
 
 
 ^ 
 
 ** d> 
 
 "*-* ^ pW 03 
 
 O 
 
 
 
 
 <13 O 
 
 9) T3 
 
 cT'fe <n rt "^ 
 
 U 
 
 
 B 
 
 02 
 -4J 
 
 rg S 
 
 "c'> 
 
 r^ ^"cs g ^ 
 
 oT 
 
 
 I 
 t 
 
 S3 
 
 3 
 
 11 
 
 M 
 
 t-< -*H 
 
 j'llis] 
 
 ^IHll 
 
 IB 
 | 
 
 4J 
 
 
 BQ 
 
 i 
 
 02 
 
 
 
 H 
 
 
 
 o 
 
 8 
 O 
 
 
 
 
 
 02 
 
 tn 
 
 H 
 O 
 
 M 
 
 i 
 
 b 
 
 ti 
 
 
 
 due consists of soap and mineral c 
 
 Q, combined alkali), glycerine, and 
 phenol-phthaleine, and titrate, if 
 1. The consumption of the latter 
 id as NaOH. Add water in large 
 mpose with excess of normal sul- 
 
 consists of fatty acids and reszw. 
 t 1 10, and weigh. Dissolve a part 
 c.c. of strong alcohol, add phenol- 
 leine, and saponify with soda in 
 excess. Boil, let cool, make up to 
 .c. with ether, decompose with 
 nitrate in fine powder, shake for 
 inutes, and let settle. 
 
 Jll^.a sJ!S'8'8)5 &5 1^1 
 
 o 
 
 a) ^ <o 2 
 
 S 
 
 'tn 
 
 i-i tn ,y 43 o 
 
 03 * O J3 
 
 M a 
 
 "co ^ a5 ^ co ^ 
 
 o 
 
 j 
 
 M^.SrS -'3J 
 
 |.alf 
 
 tn -*J 
 
 flifll 
 iPlll 
 
 02 
 
 
 T3 m &- 1 CO oC co 
 
 *'" H fl} ^ f G b- 
 
 P^ 
 
 
 O O 02 PH cj 
 
 
 
 
 
 
 
 P-l 
 
 
 
 4-3 ^ tn j3 ^ 
 
 tlliil 
 
 jiiii 
 
 fcc 
 
 C 
 '> O 
 
 g -g 
 
 *-< Co 
 
 *3 t. 
 
 _O 
 
 8 ,1<i| ||.S IX^ 
 
 iFl|H|.-s^fi 
 
 ^ ej * * is i ^ *a -2 g i & j 
 
 .P 
 
 
 10 S fl "^ d 1 
 
 "^ 'd w ^ ^ 
 
 S c3 
 
 5 ri " -^ ^ fl"S^^^ ^^d ** 
 
 V 
 
 
 tn 'O .rj .,, ^H c 
 
 BQ O w iS H 
 
 ^3 g 
 
 o g Q 5^ ^2ScSoc3c8 
 
 ^ 
 
 
 _fl <J +J $ J3 
 
 fl rt ^ "^ fe 
 
 ^ 
 
 1 t 
 
 
 
 & "it 'S * 
 
 C^ i-H ^ d 
 
 
 
 
 
 ^i is !! 
 
 1 ^ J .^ 
 
 a> 
 
 rf3-w 3 
 
 ^ O fl O 
 
 
 
 Q CO 02 ^ 02 [-; 
 
 Ol r^ .rt 
 
 o 'S 
 
 ^ '-'^^'g: <D ^^ 
 
 
 
 .S to o ^ y a 
 "o ** 
 
 02 
 
 jlltl 
 
 OH 
 S * 
 
 H 
 
 l ill! fill 
 
 
 1 *JI5| t|.S-l| 
 
920 CHEMICAL TECHNOLOGY. [SECT. vm. 
 
 or potassium aluminate. Jarry proposes to protect wood from moisture by saturation 
 with aluminium oleate. Textile goods are often rendered waterproof by successive 
 treatment with aluminium acetate and soap-lye, a process which results in the forma- 
 tion of an aluminous soap. In raising the colours of tissues mordanted with aluminium 
 salts and afterwards dyed or printed with a solution of soap, there is formed aluminium 
 oleate which is sometimes used as a size in the manufacture of paper. Lieber recom- 
 mends aluminium palmitate. 
 
 Manganese-soap is obtained by decomposing manganese sulphate with common soap 
 or by dissolving manganese carbonate in oleic acid. It is used as a siccative. 
 
 Zinc-soap, formed by double decomposition or by saponifying zinc oxide with olive 
 oil with the aid of heat, is a yellowish- white mass. If obtained by the first method it 
 quickly dries to a friable mass ; if produced by the second method it has the con- 
 sistence of a plaster. Zinc-soap is also formed when zinc white is used as an oil 
 colour. Lead-soap may be formed by double decomposition or by saponifying litharge 
 or white-lead with olive oil. It is a yellowish-white mass and is present in lead 
 varnishes. Tin-soap formed by double decomposition is produced when tissues are 
 raised by soaping after being mordanted with salts of tin. Copper-soap, obtained by 
 double decomposition is a green, dry mass which becomes brittle. It is sparingly 
 soluble in alcohol, more readily in ether or oils, and it can also be prepared by boiling 
 copper carbonate in oleic acid. A mixed copper and iron soap, obtained by precipitating 
 with soap a mixed solution of copper and iron, if ground up with litharge varnish and 
 wax, serves to produce a permanent green bronze on plaster figures. 
 
 Mercury or quicksilver soap is prepared from mercuric chloride and soap ; it is 
 white, but turns grey on exposure to air and light. Silver, gold, and platinum soaps 
 are severally prepared by double decomposition, but they are of little use. Gold soap is 
 employed in gilding porcelain, and silver soap for darkening the hair. 
 
 Washing Powders, Extracts of Soap, Soap Powders, Washing Sugars, Soap Ash, Sapona- 
 ceous, &c., are mixtures used both in manufactures and for domestic purposes. They 
 vary greatly in their composition and their value. One of the commonest kinds is 
 made by allowing soda crystals to melt in their own water of crystallisation, often with 
 the addition of a small quantity of water to compensate for that which escapes during 
 the process. Some palm oil, ground yellow resin, or ordinary soap, is incorporated with 
 the mixture, and the whole is then poured out into large, shallow trays of sheet iron, 
 in which it is diligently stirred during cooling, so that it solidifies not into crystals or 
 coherent masses, but into a rough powder, having the appearance of coarse sugar. The 
 supposed advantage of these preparations is that they dissolve more readily than soap 
 and soda crystals. Some varieties are coloured with a little turmeric, and others with 
 artificial ultramarine. 
 
 In the lower qualities, a considerable quantity of sodium sulphate (Glauber's salt) 
 is melted down along with the soda crystals. It cannot be detected by the appearance 
 of the sample. 
 
 Soap-pastes, or washing-pastes, consist of soda-lyo with which farinaceous matter 
 has been incorporated. [EDITOR.] 
 
 Adulteration of Soaps. In the manufacture of soap integrity is nearly beaten out 
 of the market. The principal adulterant is water, which, by various artifices, is incor- 
 porated with the soap to an alarming extent. (See p. 913.) The other adulterants 
 are silica, alumina, water-glass, or talc. Caustic alkali, though a necessary ingredient 
 of the soap, becomes hurtful if present in excess, or if it has not been duly saponified. 
 Unsaponified fats may also prove injurious in certain manufacturing processes. 
 [EDITOR.] 
 
 The reader may compare " The Art of Soap-making," by Alexander Watt. London Crosby 
 Lockwood & Son. "A Treatise on the Manufacture of Soap and Candles," by W. L. Carpenter. 
 
SECT. VIII ] 
 
 STEARINE AND GLYCERINE. 
 
 921 
 
 London : C. & F. N. Spon. " Soap and Candles," by R. S. Cristiani, Philadelphia and London. 
 " Manufacture of Soap," by fl. Dussance, Philadelphia and London. " Soaps," by C. Morfit, New 
 York. [EDITOR.] 
 
 STEAEINE AND GLYCERINE. 
 
 The preparation of the fatty acids can be effected by saponification with lime, 
 with sulphuric acid, with water and high pressure, and with superheated steam and 
 subsequent distillation. 
 
 Saponification with Caustic Lime. The fat used is tallow (beef or mutton) or palm 
 oil. Mutton tallow contains large quantities of solid fatty acids and is easier to work, 
 but beef tallow is cheaper. The tallow imported from Russia is generally a mixture of 
 beef and mutton tallow. Since palm-oil has been introduced in quantity and at a low 
 price, it is used in many manufactories of stearine candles. 
 
 The fat is first melted in wooden vats lined with lead, the charge being 500 kilos, 
 of tallow and 800 litres of water, heated by steam through a pipe, the end of which 
 lies on the bottom, coiled in a spiral. After the fat is melted there are gradually added 
 with constant stirring, 600 litres milk of lime, containing 70 kilos, of burnt lime 
 ( = 14 per cent, of the weight of the fat). After heating for from six to eight hours the 
 formation of the lime-soap is completed. From the hard crumbly lime-soap the 
 yellowish glycerine water (at 5*50 to 8-25 Tw.) u drawn off and worked up by concen- 
 tration and distillation. According to theory, on the assumption that in neutral fats 
 i mol. glycerine exists, combined with 3 mols. fatty acid, only 87 quick-lime should be 
 required to 100 parts of fat. Still 14 per cent, were used at first, as it was found that 
 an excess facilitates saponification, though it subsequently occasions a corresponding 
 increase in the outlay for sulphuric acid. 
 
 The lime-soap is now decomposed by means of sulphuric 
 acid, of which 137 kilos, are used to 500 kilos, fat and 70 kilos. 
 lime. The sulphuric acid is diluted with water to 17 Tw. 
 (containing in this state 30 per cent. H a S0 4 ) placed in a 
 decomposition-vat along with the lime-soap, heated by the intro- 
 duction of steam and stirred for three hours. After the fatty 
 acids are separated, the steam is shut off and the liquid is allowed 
 to settle. The fatty acids collect on the surface and a great 
 part of the calcium sulphate subsides to the bottom. The fatty 
 acids are run off or skimmed off into a vat lined with lead, and 
 in order to remove the residues of lime and gypsum they are 
 washed first with dilute sulphuric acid of 1*089 sp. gr. under the 
 action of steam and then with water. 500 kilos, tallow yield 
 from 460 to 488 kilos, of fatty acids, or 74 per cent. The yield 
 depends on the kind, the purity, and the treatment of the 
 tallow. 100 parts of the fatty acids yielded from 43*3 to 48^4 
 parts of solid fatty acid, in the mean 45-9 part of a mixture of 
 stearic and palmitic acid. 
 
 After the fatty acids have been freed as completely as pos- 
 sible from lime, gypsum, and sulphuric acid by repeated wash- 
 ings with water, they are kept for some time in a state of 
 fusion to let the last traces of water escape. They are then allowed to congeal or 
 crystallise, and the part which has not solidified consisting chiefly of oleic acid is 
 pressed either in hydraulic presses or filter-presses, first in the cold and then in heat. 
 The congelation is effected in moulds of tin plate, which, like chocolate moulds, are 
 wider at the edge than at the bottom and hold about 2 kilos, of fatty acid. 
 
 The moulds are filled as follows : The melted acids are conveyed by means of a 
 
 Fig. 583- 
 
922 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. viu. 
 
 pump and the pipe, B, into a wooden funnel, A, which is placed over the entire 
 length of a wooden scaffold on which the moulds are set above each other as shown in 
 Fig. 583. Each mould has a spout at its upper edge ; the fat then flows down through 
 the spout into the next mould, and so on until all the moulds are filled. The supply 
 is then cut off by closing the leaden spouts, J' 7 through which the fat flows out of the 
 funnel into the highest mould by means of wooden plugs. The fatty acids are left 
 in the moulds to crystallise slowly, which requires twelve hours in winter, but twenty- 
 four in summer. The slower the crystallisation and the better the crystals are 
 developed the more easily and completely the liquid portions may be removed by 
 expression. 
 
 According to A. Kind the cooling should be effected slowly and as it may be 
 required in order to obtain a well-crystallised mass. By sudden cooling there is 
 obtained a mass from which the solid fatty acids can only be 
 separated with difficulty. The cylinder used, a (Figs. 584 and 585), 
 is turned smooth within ; it is closed at both ends by the covers 
 b and c, and is provided externally with ribs, n, set against each 
 other which when the cylinder, a, is introduced into an exterior 
 cylinder, w, coated with a non-conductive mass, join up to the 
 corresponding ribs of the latter. There is thus formed a cooling- 
 room serving for the admission of cold water and alternately 
 
 Fig- 585- 
 
 Fig. 584. 
 
 rS^wZ^M^ 
 
 Explanation of Term. 
 Kiihlwasser Water for refrigeration. 
 
 interrupted by partitions above and below, so that the cold water entering below at e 
 is compelled to pass up and down round the cylinder in the direction of the arrow, 
 finally leaving the apparatus of the pipe, f. For the oleine to be refrigerated there is 
 in the cylinder, a, a narrow, annular space formed by the cylinder, v, placed con- 
 centrically to a, and set in slow movement with its axle, h. Around its circumference 
 there are placed ribs which, as the axle revolves, brush slightly against the inside of 
 the cylinder, a. These ribs may either be straight or have the form of a rapid screw 
 thread. The oleine entering through the pipe, o, into the cover, b, is, on turning the 
 axle, h, moved slowly in the opposite direction to the cooling water and is forced 
 though the tube, t, to a store-tank. 
 
 Another apparatus for continuous working has been devised by Messener. 
 
 Petit uses a drum, A (Fig. 586), consisting of two cast-iron plates, which are held 
 together by bolts and kept between two cylindrical sheet iron walls. Within the 
 drum is cold water coming from a refrigerating machine which flows through the pipe, 
 C) and a hollow arm, D, to the drum, and flows away through another arm. The drum 
 
.SECT. VIII.] 
 
 STEARINE AND GLYCERINE. 
 
 9 2 3 
 
 is moved by means of a circle of teeth from a shaft, E ; this shaft drives a pump, P, 
 
 by means of an eccentric. The pump sucks the congealed mass out of the receiver, F, 
 
 and forces it to the filter-press. The external 
 
 jacket of the drum as it revolves takes up a 
 
 thin layer of liquid from the trough, f, to 
 
 which the oleine flows through the cock, g ; 
 
 as the drum revolves this film of liquid congeals 
 
 and is finally stripped off at h by a scraper, 
 
 and falls into the recipient, F, which is also 
 
 cooled by cold water. Hence the mass arrives 
 
 at a Farinaux filter-press. 
 
 The separation of the solid and the liquid 
 fatty acids is effected by cold pressing followed 
 by hot pressing. For the former the moulds 
 are thrown upon the press-cloth, a coarse, 
 sack-like tissue of especially strong tough wool ; 
 the yellowish-brown cakes of fat are emptied 
 into it, the press-sacks then filled are arranged 
 between iron and zinc plates upon the table of 
 a common hydraulic press and submitted to a pressure of 200,000 kilos. The oleic 
 acid flowing off is received in collecting funnels placed below the table. It is used 
 in the soap manufacture, for greasing wool, and recently as oleic ether mixed 
 with clay forming an excellent oil for rendering leather supple. When the cold 
 press no longer yields any oleic acid, hot pressing follows. Fig. 587 shows the 
 
 Fig. 587- 
 
 most important parts of a horizontal hot press, in which the press-bags and the 
 intermediate plates are upright for the better escape of the oleic acid. The water 
 used for pressing arrives through the pipe, R, into the press-cylinder, C, in which it 
 acts upon the great piston, jT, which presses the bags on the horizontal tables. The 
 akes of fat from the cold press are broken up, placed in horsehair bags (called in 
 
924 CHEMICAL TECHNOLOGY. [SECT. vm. 
 
 French works etreindilles) and interstratified with the press-plates. These plates are 
 of cast-iron and made hollow, so that they may be heated by the introduction of steam 
 which arrives by the pipe, V, and the flexible tubes, a. In using the press the plates, 
 P, and the sacks are arranged alternately and as soon as the table is full the steam- 
 pipe, V, is opened to heat the plates. The access of steam is so regulated that the 
 temperature first rises to 70, then falls so low that it does not reach the melting- 
 points of palmitic and stearic acid, but keeps the oleic acid liquid enough to flow off 
 with ease. For this purpose a temperature of 40, or even of 35, is most suitable. 
 At the same time the piston of the press is allowed to act. When oleic acid no- 
 longer flows off, the hard, solid fatty mass is taken out. It is contaminated with a 
 little organic matter and ferric oxide only at the places where it has come in contact 
 with the apparatus, and it is exposed to the light for some days. It is next, at some 
 works, sorted into three or four qualities, according to its degree of purity. Besides the 
 oleic acid obtained on hot pressing there crystallise out on cooling not inconsiderable 
 quantities of palmitic acid, which is added in the next operation to the mixture of 
 liquid and solid fatty acids. According to Girard there is sometimes placed over the 
 press-cylinder, C, a manometer, M, connected with an electric signal apparatus which 
 shows the workmen when the required pressure has been reached. Latterly the filter- 
 press is coming more and more into use in the stearine industry. 
 
 The various sorts of solid, fatty acids obtained by hot pressure are next refined. 
 To effect this the acids are melted by steam in very dilute sulphuric acid (475 Tw.) in 
 washing becks lined with lead. This process is then repeated two or three times until 
 all the sulphuric acid is washed away. It is then kept for some time in a state of 
 fusion, to eliminate traces of water, and is finally poured into moulds. The washing; 
 water must be quite free from lime ; if this is not the case the lime must be precipi- 
 tated by oxalic or stearic acid. The fatty acid obtained is cast in tin moulds and 
 supplied to candle-makers in the state of flat cakes. 
 
 Saponlfication with a Reduced Proportion of Lime and the Use of High Pressure. 
 Milly observed that the quantity of lime required for saponification could be reduced 
 from 14 per cent, of the weight of the tallow, not merely to 8, but to 4 or even to 
 2 per cent., if the mixture of lime water and fat is exposed to a higher temperature 
 than has been customary. 
 
 He placed in a closed boiler 2300 kilos, of tallow and 20 hektolitres of lime milk, 
 containing 50 kilos, of lime (2 per cent.), or 69 kilos. ( = 3 per cent.), and caused 
 steam of 182 (= a pressure of 10 atmospheres), to act upon the mixture so that the 
 temperature within the boiler was 172. After seven hours the saponification was 
 complete. In the boiler there was a watery solution of glycerine and a mass of fatty 
 acids, among which were distributed small quantities of lime-soap. The boiler was 
 emptied and charged again, so that 6900 kiios. of tallow could be worked up in 
 twenty-four hours. This procedure is advantageous, as the quantity of sulphuric 
 acid required to decompose the lime-soap is much reduced. The Milly process is 
 introduced in the great candle-works at Vienna, in the " Apollo candle-works " 
 on the Schottenfelde in Vienna and Penzing, in Sarg's works at Liesing, and in those 
 of Himmelbaur at Stockerau. Sarg, of Liesing, saponifies with 3 per cent, lime 
 and a pressure of 10 atmospheres, obtaining 95 per cent, fatty acids, and 30 per cent, 
 glycerine water at from 6*75 to 8-25 Tw. The fatty acids after cold and hot pressure yield 
 25 percent, stearic acid and 35 per cent. " returns" i.e., fatty acids which are pressed 
 along with the total yield, which is finally 45 per cent, stearic acid and 50 per cent, oleic- 
 acid. The glycerine water is evaporated and after repeated distillation yields 5 to 6 per 
 cent, glycerine. 
 
 The apparatus constructed by Leon Droux, fitted with an agitator for saponifying 
 fats under pressure, deserves notice. (Fig. 588.) The cylinder is of copper, an 1 is. 
 
SECT. VIII.]' 
 
 STEARINE AND GLYCERINE. 
 
 925 
 
 generally 8 metres in length by 1-05 to no in diameter, the shaft fixed in the longitu- 
 dinal axis of the cylinder is 50 mm. in diameter, and is fitted with copper arms for 
 stirring ; it revolves thirty times in the minute. For saponifying 3000 kilos, of fat 
 there are used 80 kilos, of lime. The yield is 2800 kilos, fatty acids and 240 kilos, 
 glycerine at 46 T\v. The increase of weight is due to the water taken up in the 
 formation of glycerine. After the saponification is completed the contents of the boiler 
 are run into a settling beck. The glycerine water obtained has the sp. gr. of 7 Tw. 
 The decomposition of the lime-soap by sulphuric acid is made easier by its fluid state. 
 The new apparatus has also been adopted in works where the distillation process is 
 applied. In the latter the saponification with sulphuric acid is discarded and the fatty 
 acid obtained is saponified in Droux's apparatus with slight acidification. Latterly its 
 shape has been made globular instead of cylindrical. The axle of the agitator is 
 horizontal ; the apparatus is heated by direct steam distributer. Below, at the side of 
 the apparatus are two trial-cocks, and above these is a man-hole for charging the 
 apparatus. Each operation takes six or seven hours and the apparatus is kept for 
 
 Fig. 588. 
 
 five or six hours at a pressure of 7 or 8 atmospheres. When the process is at an 
 end the contents of the tube are run off through a pipe opening into the apparatus 
 below, by simply turning a cock. The product is then treated in the manner already 
 described. The advantages of this new construction are said to be the greater strength 
 of the globular vessels, the shortening the shaft and the decrease of condensation by 
 surface cooling, as a globe has the largest capacity with the smallest surface. 
 
 In explaining this kind of saponification Payen holds that lime in its action upon 
 tristearine, tripalmitine, and trioleine gives the impulse to a molecular movement 
 which is completed by the water at a temperature of 172. Pelouze had observed that 
 lime-soap, obtained by precipitating an aqueous solution of calcium chloride with an aque- 
 ous solution of common soap with an equal quantity of water and then put in a digester 
 with olive oil, saponifies the oil, at a temperature of from 155 to 165, setting glycerine 
 at liberty. From this and from other experiments he concluded that in Milly's saponi- 
 fication with a small percentage of lime, the process consists of several stages in which 
 there is first formed a basic or neutral soap which is finally converted into an acid soap. 
 But if we consider that Milly in his saponification with 2 per cent, of lime employs 
 a temperature of 182 (corresponding to a pressure of 10 atmospheres), and that Wright 
 and Fouche effected an almost complete decomposition of the fats at the same tempera- 
 ture with water alone and that Cloez effected a complete saponification of the fats at 
 200 with water, it seems simplest to assume that in this case water is the decomposing 
 
926 CHEMICAL TECHNOLOGY. [SECT. vra. 
 
 element, and that the presence of 2 per cent, lime merely promotes and simplifies the- 
 saponification by cancelling a counter-affinity. The same result is attained still better 
 by a small quantity of alkali. 
 
 Saponification by Means of Sulphuric Acid and Subsequent Distillation by Means- 
 of Steam. It was known to Achard, in the year 1777, that the neutral fats are 
 decomposed by concentrated sulphuric acid in a manner similar to the decomposition 
 effected by caustic alkalies. This fact was again brought for ward in 1821 by Caventon,. 
 and in 1824 by Chevreul, but was not scientifically investigated until 1836 by Fremy, 
 and not industrially applied until the year 1841, when Dubrunfaut introduced the 
 distillation of the fatty acids on the large scale. The crude fatty matter usually 
 submitted to this process of saponification is of the kind that cannot be saponified by 
 the lime process by reason of its impurities ; thus, for instance, palm and cocoa-nut oil, 
 bone and marrow fat, fat of slaughter-houses, kitchen-stuff, the products of the 
 decomposition, by means of sulphuric acid, of the soap- water obtained from wool- 
 spinning and cloth-making works, residues -of the refining of fish and other oils, residues 
 of tallow-melting, &c. 
 
 This process of saponification by means of sulphuric acid as carried on in the large 
 establishment for stearine candle-making of Leroy and Durand, at Gentilly, near Paris, 
 consists of three operations, viz. : 
 
 (a) Saponification with sulphuric acid ; 
 
 (/3) Decomposition of the products of saponification ; 
 
 (y) Distillation of the fatty acids. 
 
 (a) In order to eliminate the greatest impurities first, the crude fatty matters are 
 molten and kept in the liquid state for some time, so that the coarser impurities may 
 subside. The fatty matters are then transferred to a kind of boiler made of iron boiler- 
 plates lined inside with lead, and fitted with a stirring apparatus and a steam-jacket, 
 connected by means of pipes with a steam-boiler, so that the apparatus may be heated. 
 Into this vessel sulphuric acid at 153*4 Tw. = r8 sp. gr. is poured, the quantity of this 
 fluid being regulated according to the nature of the fatty matters operated upon. 
 Kitchen-stuff, fat from slaughter-houses, and the like require 12 per cent, of their 
 weight of acid ; palm oil requires from 6 to 9 per cent, according to quality. The fatty 
 substances having been put into the vessel, the stirring apparatus is set in motion, and 
 the steam turned on for the purpose of supplying heat to the vessel. The temperature 
 to which the vessel is heated varies, being 177 in Price's Works, Battersea, while at 
 Gentilly the heat is seldom higher than from 110 to 115. During the operation the 
 mass foams, becomes brown, and evolves sulphurous acid, partly due to the action of a 
 portion of the concentrated sulphuric acid upon the glycerine, partly to its action upon 
 the impurities present among the fatty matters. The neutral fat is converted into a 
 mixture of sulpho-fatty acids and sulpho-glyceric acid. The saponification is complete 
 after some fifteen to twenty hours' application of heat. According to De Milly's new 
 process (1867) the tallow is heated to 120, along with 6 per cent, of sulphuric acid, 
 and the action of the latter is limited to two or three minutes ; it is thereby possible to 
 obtain 80 per cent, of the solid fatty acids in a condition at once fit for making candles 
 without re-distillation, only 20 per cent, having to be distilled. 
 
 (|3) Decomposition of the products of the sulphuric acid saponification. The mass is 
 left to cool for three or four hours and is next transferred to large wooden tanks lined 
 with lead, and previously one-third filled with water. At the bottom of these tanks 
 steam pipes are fitted, by means of which the fluid contents of the vessel are soon 
 heated to 100. The sulphuric acid and the fatty acids are dissociated, and these 
 bodies, partly combined with a larger quantity of hydrogen and oxygen than was 
 present in the fatty acids from which they were formed, partly also in an unaltered 
 condition, are found floating on the surface. After having been repeatedly triturated 
 
SECT. VIII.] 
 
 STEARINE AND GLYCERINE. 
 
 927 
 
 with boiling water, the fatty acids are tapped or poured over into a vessel filled with 
 water heated to from 40 to 50, for the purpose of allowing the impurities to become 
 deposited. The clarified fatty acids are next heated in a vessel placed on an open fire 
 in order to evaporate all the water, after which they are submitted to distillation. 
 
 (y) The distillation requires several precautions. Distillation with an open fire 
 would convert the fatty acids into oil, gas-tar, and a carbonaceous residue, if the heat 
 were sufficiently high. But when the temperature is properly regulated, the fatty 
 acids are protected from the direct action of the fire. Air should be completely excluded 
 from the distilling apparatus. With these precautions the fatty acids distil over with- 
 out undergoing any essential alteration. These conditions are complied with by the use 
 of superheated steam at a temperature of from 250 to 350. The fatty acids are placed 
 in a capacious retort with which there is connected on the one hand a pipe for admit- 
 ting the superheated steam, and on the other an ordinary condenser. Fig. 589 shows 
 
 Fig. 589. 
 
 the arrangement of the distilling apparatus, the flame plays round the spiral coils and 
 escapes through the chimney, C. The spiral begins at M, passes through the fire-box, 
 comes out in front at T, enters again at T', and opens at last into the retort, T". The 
 latter, which projects out of the fire is of copper or cast-iron ; from the upper part of 
 this retort there passes the tube, U, which is continued as an iron cooling-worm lying 
 in an iron tank full of water. This pipe conveys the fatty acids into the receiver, 
 K, whilst the gaseous products escape through the tube, K r When the apparatus is to 
 be set in action, the spiral is first heated and the retort, Z>, is run three-quarters full 
 of the melted fat through the pipe, V ; steam is turned in at 300. The air is then 
 completely expelled and distillation soon begins in consequence of the high temperature, 
 which does not fall below 200 in the retort. The fatty acids collecting in the receiver, 
 K, are not identical at all times of the distillation. 
 
 When the several fatty acids are fractionally collected from the beginning to the 
 end of the distillation their melting points are : 
 
 From Palm Oil. 
 
 ist product . . 54'5 
 
 2nd . . 52 'o 
 
 3rd . . 48x3 
 
 4th . . 46-0 
 
 5th . . 44 'o 
 
 6th . . 41 'O 
 
 7th . . 39-5 
 
 From Kitchen-stuff 
 
 and Bone Fat. 
 
 44-0 
 
 41-0 
 
 41'0 
 
 42-5 
 44-0 
 
 45 o 
 41-0 
 
028 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. viii. 
 
 The water condensed with the fatty acids runs off from the receiver through a tap. 
 At the beginning of the operation the water constitutes half the produce ; towards the 
 end only about one-third. With a retort capable of containing 1000 to noo kilos, of 
 material the distillation takes some twelve hours. The end of the operation is indicated 
 by the coming over of coloured products. There remains in the retort a black tarry matter 
 the quantity of which amounts in the case of palm-oil distillation to from 2 to 5 per cent., 
 and for kitchen-stuff to from 5 to 7 per cent. This residue is not removed after each 
 distillation but left in the retort until it has accumulated to such an extent as to render 
 its removal necessary. The first products of the distillation of palm oil saponified by 
 means of fatty acids are so solid, that by pressure they do not yield any fluid acid, and 
 are at once fit for the manufacture of candles. The products which come over after- 
 wards are further purified by hydraulic pressure, re-melting, and washing with water. 
 The substance obtained by pressure, more or less pure oleic acid, is only used for 
 soap-making in this country, although abroad it is burnt in some kind of lamps. The 
 oleic acid obtained by this process is essentially different from that obtained by the 
 lime saponification process. The quantities of fatty acids obtained by this process of 
 saponification are the following : 
 
 from suint .... 
 olive oil residues. 
 palm oil . 
 
 fat from slaughter-houses 
 oleic acid 
 
 47 to 55 P er cent. 
 47 to 50 ,, 
 75 to 80 
 60 to 66 
 25 to 30 
 
 The boiler recommended by Julian and Blumsky for distilling fatty acids has two 
 domes, B (Figs. 590 and 591), connected with corresponding coolers. The two end 
 
 plates give exit to a num- 
 
 Fig. 590. Fij-. 591. ber of tubes, Z>, connected 
 
 by intermediate pieces. 
 The steam which has been 
 superheated in an especial 
 arrangement enters 
 through the pipe, E, passes 
 through the tubes, D and 
 d, and the two tubes, e, 
 connected with the sieve- 
 tubes, n, into the liquid. 
 The mixture of fatty acids 
 is filled in through the 
 man-hole, C, to the 
 height of the cock, /. The apparatus is then heated until drops appear at the 
 cooling-tubes ; the cock F is closed, G is opened, and superheated steam is allowed to 
 enter through E. It passes through the pipe, Z>, and escapes at the cock, G. In this 
 manner the entrance of steam-water into the boiler is avoided, which would interfere 
 with the distillation. As soon as the temperature of the charge has risen so high thai 
 no more liquefaction takes place at Z>, and the steam in consequence escapes tolerably 
 dry, the cock F is gradually opened to allow the dry steam to pass through the tube, e, 
 to the sieve-tubes, n. The cock G is then closed and N the distillation is continued b) 
 the double action of the superheater-tubes, Z>, and the sieve-tubes, n, until the distillate 
 appears coloured, when the operation is stopped. Two hours after the distillation is at 
 an end the residues may be let off through the cock H into a closed receiver ; but if 
 they are to be collected in an open cistern from five to six hours should elapse after the 
 conclusion of the distillation. 
 
SECT, viii.] STEABINE AND GLYCERINE. 929 
 
 Zinc chloride, which in many respects (see p. 460) is similar in its action to 
 sulphuric acid, has been proposed as a substitute for the latter. For countries into 
 which sulphuric acid has to be imported zinc chloride might be of greater advantage, 
 being capable of recovery and less dangerous and difficult in transport. When, 
 according to the researches of L. Kraft and Tessie du Motay, a neutral fat is heated 
 with anhydrous zinc chloride, a complete incorporation of these substances takes 
 place between 150 and 200; and by continuing the heating for some time, and 
 washing the materials with warm water, or better with water acidulated with hydro- 
 chloric acid, there is obtained a fatty matter, which, on being submitted to distillation, 
 yields the corresponding fatty acid, while only a small quantity of acroleine is formed. 
 The zinc chloride, becoming soluble in the water used for washing, may be recovered 
 by evaporating the fluid. The yield of fatty acids by this process is the same as that 
 obtained by the use of sulphuric acid, while the fatty acids also agree as to their physical 
 properties. The quantity of zinc chloride required amounts to from 8 to 1 2 per cent. 
 of the fat. 
 
 Saponification with Water and High Pressure. Some sixteen years ago another 
 agent, capable of bringing about, in a manner similar to alkalies and acids, the disso- 
 ciation of fatty matters into glycerine and fatty acids, was introduced, this agent being 
 simply superheated steam at high pressure : 
 
 + 3H.O = 
 
 Tripalmitine. Water. Glycerine. Palmitic acid. 
 
 The idea of submitting fatty matters to a similar method of treatment is not a 
 new one, for in the researches of Appert (1823) and Manicler (1826) some hints are 
 given on the decomposition of fats by means of superheated water ; but the aim of 
 these technologists was different, for in their experiments they employed steam to 
 separate the tallow from the cellular tissue it is contained in, and for that purpose a 
 temperature of from 1 15 to 121 was quite sufficient, while at a temperature of 180 and 
 a pressure of from 10 to 15 atmospheres (=150 Ibs. to 225 Ibs. pressure to the square 
 inch) water can exert a far more energetic action upon the neutral fats, dissociating them 
 and thus setting free their constituents. The knowledge of this interesting fact is due 
 to the researches of Tilghman and Berthelot, who almost simultaneously made this 
 discovery in the year 1854, while shortly after Melsens, at Brussels, obtained the same 
 result. As regards the industrial application of this discovery, Tilghman and Melsens 
 made further researches ; their modes of operating are very similar. 
 
 Tilghman adds to the neutral fat about to be decomposed one-third to one-half of 
 its bulk of water, and pours this mixture into a sufficiently strong vessel in which the 
 fluids can be submitted to the action of a temperature nearly as high as the 
 melting-point of lead, 320. This vessel is so arranged that during the operation it 
 can be closed so as to prevent on the one hand the evaporation of water, and, on the 
 other, admit of a sufficiently strong pressure. The process is carried on continuously by 
 causing the fluids to circulate through a tube heated to the required temperature. 
 Melsens uses a Papin's digester, in which the fat to be decomposed is heated to 180 to 
 200, with from 10 to 20 per cent, water, to which from i to 10 per cent, of sulphuric acid 
 has been added. Wright's and Fouche's apparatus consists of two hermetically closed 
 copper vessels placed one above the other and connected together by means of two 
 tubes, one of which reaches nearly to the bottom of the lower vessel, and ends in the 
 upper one just above the bottom. 
 
 The apparatus of Tilghman, shown in section in Fig. 592, consists of a boiler, A, in 
 which the fat previously freed from impurities is brought in contact with hot water, 
 and is thus converted into a kind of emulsion. The piston, B perforated like a sieve, 
 
93 
 
 CHEMICAL TECHNOLOGY. 
 
 vni. 
 
 which is moved quickly up and down in the vessel, A, effects an intimate mixture of 
 the fat and the water. The forcing pump, C, drives the mixture through a long 
 wrought-iron tube, D, which, as it appears in the figure, makes several bends in the 
 furnace, E, and is heated by the fire, F, up to the melting point of lead. On issuing 
 from the heating-tubes the mixture, the fat of which has been already split up into 
 glycerine and fatty acids, passes through the worm, G, in which its temperature is 
 reduced to 100. It then escapes through //"and falls into a suitable receiver. The 
 valve placed at If is loaded in such a manner that when the heating-tubes have the 
 proper temperature and the forcing-pump is not in action, it cannot be opened by the 
 pressure within ; consequently when the pump drives nothing into the apparatus, 
 nothing can escape from it, if the temperature is not too high. When the forcing 
 pump is at work and drives the mixture through the apparatus, the valve, ff, opens and 
 
 a corresponding quan- 
 
 Fi S- 592. tity O f tne mixture 
 
 escapes at G. The 
 hot mixture of fatty 
 acid and solution of 
 glycerine is sepai-ated 
 by settling, the fatty 
 acid is washed with 
 water, the solution of 
 glycerine is concen- 
 trated and purified 
 in the usual manner. 
 A treatment for ten 
 minutes is generally 
 sufficient for the com- 
 plete decomposition 
 of the fats. A simi- 
 lar apparatus has 
 been designed by 
 Hugues. 
 
 The process of Melsens consists in treating the fat in a Papin digester at from 180 
 to 200, with from 10 to 20 per cent, of water, to which from i to 10 per cent, of 
 sulphuric acid has been added. The apparatus is a long horizontal boiler, in which 
 the mixture of the water and the fat is effected in a small, second kettle, which is placed 
 in connection with the former, filled with steam, which is then allowed to escape into 
 the air, and the rest is condensed. The vacuum formed in the small boiler draws, on 
 opening a cock, water and fat from the large, lower boiler. If a connection is then 
 again effected between the upper parts of both boilers, the liquid mixture is violently 
 forced into the lower boiler. 
 
 According to Marix the decomposition of fats by water can be effected at pressures 
 of from 3 to 5 atmos., if a little magnesium carbonate and chalk are added. 
 Violette and Buisine have recourse to ammonia. 
 
 Manufacture of Fatty Acids by Means of Superheated Steam and Subsequent 
 Distillation. Allied to the process just described is the operation carried on by the 
 well-known Price's Candle Company. Limited, at -Battersea. Gay-Lussac and 
 Dubrunfaut had already tried to apply to industrial purposes the fact that neutral 
 fats are dissociated by distillation, yielding fatty acids ; but notwithstanding that these 
 savants employed steam, the results obtained did not answer the expectation, because a 
 portion of the fatty matter was decomposed, yielding acroleine and leaving a 
 carbonaceous residue. Wilson and G\vynne were more successful with their experi- 
 
SECT. VIII. I 
 
 STEARINE AND GLYCERINE. 
 
 merits, and by using a distilling apparatus similar to that described on p. 503, they 
 obtained by means of superheated steam the complete dissociation of the neutral fats 
 into fatty acids and glycerine; while by closely watching and regulating the tem- 
 perature, they could not only completely saponify the neutral fats, but also distil the 
 fatty acids and glycerine over without undergoing any decomposition. 
 
 The retorts have a cubic capacity of 60 hectolitres, and are heated by direct fire to 
 a temperature of from 290 to 315. A malleable iron steam-pipe conveys steani at a 
 temperature of 315 into the molten fatty matter. The admission of steam is con- 
 tinued for from twenty-four to thirty-six hours according to the kind of fat. The 
 .saponification proceeds regularly and the products distil over and are collected at the 
 lower aperture of the cooling apparatus. The fatty acids are at once fit for candle- 
 making purposes, while the glycerine is purified by a subsequent distillation with 
 steam. As already mentioned, the proper temperature has to be scrupulously main- 
 tained, for if the temperature falls below 310, the saponification proceeds very slowly ; 
 but if the temperature rises much above that degree, a portion of the fatty substance 
 is decomposed and acroleine is formed in large quantity. 
 
 H. Heckel describes a simple apparatus for the purpose. 
 
 According to Korschelt the decomposition is much facilitated if the fat is finely 
 divided before exposure to the steam. The fat is heated for this purpose in a receiver, 
 A (Figs. 593 and 594), to 100 and passes thence into a wrought-iron pipe, a, with 
 
 Fig- 593- 
 
 Fig. 594- 
 
 many curves which lies in the metal bath, B. The latter consists of a strong iron 
 vessel in which lead and an alloy of lead and tin (preferably an alloy melting at 290 
 of 100 parts lead with 6 or 7 tin) is kept in a molten state. The oil issues from thij 
 bath at about 300 and arrives in the tower, C, in which the decomposition is effected. 
 The tower is built of cast-iron plates surrounded with masonry, but with an isulating 
 stratum of air between, and is filled with balls of burnt clay, &c., lying on gratings, e. 
 The hot oil is forced upwards through a pipe, a, which ascends in the middle of the 
 tower and flows through the descending end of this tube upon a distributor, n. 
 From this the oil pours over the clay balls and flows down among them, coming 
 thereby in intimate contact with superheated steam introduced into the tower through 
 the pipe, c, and rising upwards. The glycerides are thus split up into free fatty acids 
 and glycerine, and these products of decomposition pass along with the steam through 
 exit tube, d, to a suitable refrigerator. Into the tube, c, conveying the superheated 
 steam a box, /, is inserted in which are fixed two or more tubes, g, open above and 
 
932 
 
 CHEMICAL TECHNOLOGY. 
 
 [SECT. viii. 
 
 closed below ; one of these is filled with lead (melting point 334) ; the second with an 
 alloy of 100 parts lead with 6 parts tin (melting point 289) and a third with zinc 
 (melting-point 412), so that the observation of these tubes renders it possible to 
 estimate the temperature of the steam entering the tower. A similar arrangement, h, 
 is introduced into the oil-pipe, a. The inflow of the oil is so regulated that little or 
 none arrives at the bottom of the tower undecomposed. The oil which collects there is 
 conveyed away by the pipe, i, passes through the worm, s, into the condenser, m, and 
 runs away into a receiver. If fats are used which are solid at common temperatures 
 a little steam is allowed to enter through the tube, i, or the condensing water is raised 
 to the required temperature in some other way. 
 
 For some years the process proposed by Bock has been in use for the saponification 
 of fats. He treats the fat with sulphuric acid at a moderate temperature and without 
 distillation. By this treatment the albuminous membranes in which the fat globules 
 are enclosed and which make up i-o to 1*5 per cent, of the fat are destroyed and the 
 fat may be decomposed by simply boiling with water in open vessels. According to 
 Birnbaum the mixture of fatty acids thus obtained contains 99^53 per cent, fatty acid 
 without a trace of glycerine. Hartl, of Vienna, carries out this process in an im- 
 proved form. 
 
 Conversion of Okie Acid into Palmitic Acid. Tallow generally yields about 50 per 
 cent, of oleic acid which scarcely fetches half the price of the solid acids. The con- 
 version of oleic acid into solid palmitic acid which was formerly carried out by Cramer 
 and then on the large scale by Radisson, of Marseilles, is based upon the reaction 
 discovered in 1841 by Varrentrapp of an excess of caustic potassa upon oleic acid, 
 the latter being split up into palmitic acid, acetic acid and hydrogen according to 
 the equation, C 12 H 34 O 2 + 2 KOH = C 16 H 31 K0 2 + C 2 H 3 K0 2 + H 2 . 
 
 On the large scale the re-action is effected in cast-iron cylinders with covers of 
 sheet-iron, three metres in diameter (Fig. 595). Into these are pumped about 1-5 ton 
 of oleic acid and 2^5 ton potassa lye of 80 Tw., and heated by a fire placed at such a 
 
 distance as to prevent overheating. The steam given 
 off at first escapes through the man-hole m in the 
 cover. When the soap becomes dry the man-hole is 
 covered and the escaping gases are conveyed through 
 the pipe z to the condensing tower and then to a 
 gas-holder. The temperature of the mass is slowly 
 raised to 290. An agitator keeps the mixture in 
 constant movement. At 290 the escape of hydrogen 
 begins after the soap is melted. When the tempera- 
 ture reaches 320 the escaping gases have a peculiar 
 smell. The operation must then be at once ended, 
 as otherwise decomposition would ensue. Steam and 
 water are therefore let into the cylinder, and at the 
 same time a trap at the bottom is opened through 
 
 which the potassium palmitate falls into water, where it is boiled by means of steam 
 with a certain quantity of water. On settling, the product separates into two layers, 
 the upper of neutral potassium palmitate, and the lower of potassa-lye at about 27 Tw. 
 Potassium palmitate is decomposed by sulphuric acid in another vessel, yielding a pale- 
 brown palmitic acid which on cooling forms large tabular crystals. After crystallisation 
 it is perfectly white, burns with a luminous smokeless flame, and is equal to the best 
 quality of stearic acid. If mixed with common stearic acid it loses the tendency to 
 crystallise and has a translucency which is much esteemed in the candle trade. An 
 attempt has been made to decompose the palmitate by boiling with milk of lime in 
 order to recover the potassa. But it is necessary to work with a solution at 8'5 Tw., 
 and the expense of concentration to 80 T\v. is far from insignificant. 
 
 Fig. 595- 
 
SECT, vin.] STEARINE AND GLYCERINE. 933 
 
 By this process oleic acids from the most different sources may be converted into 
 solid acids excepting that from mare's fat and from the suint of wool. Oleic acid pre- 
 pared by Bock's process gave the best yield i.e., 94 to 95 per cent, palmitic acid. The 
 cost of the conversion amounts at Marseilles to 31-15 francs for 100 kilos, of white 
 palmitic acid. 
 
 The substition of soda for potassa in this process presented at first some difficulties, 
 since sodium oleate is relatively difficultly fusible and is a bad conductor of heat, so that 
 a uniform temperature of the melted salt could not be obtained even by the use of an 
 agitator. Radisson found, however, that this defect might be removed by adding a cer- 
 tain quantity of paraffine to the mixture of soda-lye and oleic acid. The paraffine effects 
 a perfect liquefaction of the mass and prevents the sodium palmitate from being heated 
 above its decomposition point. The small quantity of paraffine volatilised in the opera- 
 tion is received in a condenser. The escaping hydrogen is so rich in hydrocarbon that 
 it is a good gas for lighting. After the end of the operation the mass is treated with 
 water as usual and separates into three layers, paraffine at the top, sodium palmitate in 
 the middle, and soda-lye, containing some sodium acetate, at the bottom. The paraffine 
 and the soda-lye are used for succeeding operations, whilst the sodium palmitate is 
 decomposed by sulphuric acid. The conversion is so complete that the loss does not 
 exceed i per cent. 
 
 C H ( OH \ 
 
 Glycerine. Glycerine, C 3 H 8 3 (a triatomic alcohol, H 5 }0 3 , or C 3 H 5 JOHJ, is 
 
 present in the shape of glycerides in combination with solid and fluid fatty acid to an 
 amount of 8 to 9 per cent., and may be separated by treatment with bases (potash, 
 soda, lime, baryta, lead oxide), or with acids (sulphuric acid), and certain chlorides 
 (e.g., zinc), also by means of superheated steam, or very hot water without the formation 
 of steam, in closed vessels. Glycerine is also formed as a constant product by the 
 alcoholic fermentation of dextrose, levulose, and lactose. According to Pasteur's 
 researches, the quantity of glycerine thus formed amounts to about 3 per cent, of 
 the weight of the sugar. Glycerine was first discovered by Scheele whilst engaged in 
 preparing lead plaster. Industrially, glycerine has been used for only twenty-five 
 years, in consequence of the large quantity of glycerine now obtained as a bye-product in 
 the manufacture of soap as well as of stearine candles. The vinasse of the potato, 
 and molasses from beet-root sugar distillation, and likewise the residue of the distilla- 
 tion of wine, vinasse proper, as carried on in the South of France, contain large 
 quantities of glycerine. 
 
 As regards the preparation of glycerine on the large scale, it is mainly a question 
 of purification of the glycerine obtained in the industrial preparation of the stearic 
 acid from neutral fats above described. When the lime saponification process is used, 
 the glycerine remains dissolved in the water after the separation of the insoluble lime- 
 soap. The dissolved lime having been eliminated by either sulphuric or preferably 
 oxalic acid, the evaporation of the liquid to the consistency of a syrup will yield a 
 glycerine pure enough for many technical purposes. When the decomposition, or rather 
 dissociation, of the neutral fats is effected by means of superheated steam, the glycerine 
 and fatty acids are both obtained in a pure state, provided the heat be kept 
 at or below 310, because otherwise a portion of the glycerine is decomposed vith 
 evolution of vapours of acroleine. The fact that, when fats are saponified with sul- 
 phuric acid, the sulphoglyceric acid in aqueous solution yields readily by evaporar.ior 
 glycerine and sulphuric acid, may be applied for the preparation of glycerine. The 
 soapboiler's mother liquor, now the most important source of crude glycerine, may be 
 made available for its production, according to Reynold's patent, in the following 
 manner : The mother liquor is first concentrated by evaporation ; the saline matter 
 which is thereby gradually separated being removed from time to time. When the 
 
934 CHEMICAL TECHNOLOGY. [SECT, vin 
 
 fluid is sufficiently concentrated ascertained by the boiling point having risen to- 
 il 6 it is transferred to a still, and the glycerine distilled off by means of superheated 
 steam carried into the still. The distillate is next concentrated and brought to the 
 consistency of a syrup in a vacuum pan. 
 
 The boiling-point of glycerine is 290. The glycerine, freed from colouring matters, 
 if necessary by means of animal charcoal, cannot be brought to the necessary concen- 
 tration in open vessels without becoming coloured. It is therefore allowed to flow into a 
 vacuum pan, in which it is concentrated in the absence of air. Frequently, however, a 
 re-heating with animal charcoal and a filtration are needed. Dynamite works require 
 a glycerine free from chlorine ; for this purpose it is purified with silver nitrate. 
 
 The distillation of glycerine for its purification, as indicated by Wilson and Payne 
 in 1855, forms a great advance in the manufacture. 
 
 The glycerine, after being entirely, or almost entirely, freed from fatty acids, is 
 distilled with superheated steam in the absence of air, when the steam also serves tO' 
 expel volatile impurities. A current of steam at from 100 to 110 is then passed for 
 several hours, by means of a perforated tube, through glycerine, which has been pre- 
 viously brought at the lowest possible temperature to sp. gr. 1*15, until the products 
 passing over have no longer an acid reaction. It is then heated (while still introducing 
 superheated steam) to from 170 to 180, but not above 200. If necessary, it may be- 
 rectified in the same manner. It is important that glycerine should be separated from the 
 accompanying water by fractionated refrigeration, to a degree sufficient for all technical 
 purposes. By distillation with heated steam there is obtained, not an aqueous solution 
 of glycerine, but, if the vapours are passed into a series of refrigerators surrounded 
 with bad conductors of heat, in the first, a glycerine which is nearly anhydrous, in the 
 following, water, containing little glycerine, and in the last, water which has scarcely 
 a sweet taste. These liquids are used for diluting glycerine which is to be refined 
 
 Pure glycerine has the sp. gr. i - 2653 ; it takes fire if heated to 150, and burns 
 with a blue, faintly luminous flame ; it burns also with a wick. The freezing of 
 glycerine was observed by W. Crookes, of London, in 1867, by Sarg, of Vienna, and 
 by Woehler, of Gottingen. 
 
 Among the many applications of glycerine are the following : For keeping clay 
 moist for modelling purposes ; for preventing mustard from drying up ; for keeping 
 snuff damp ; preserving fruit ; sweetening liqueurs ; and for the same purpose for 
 wine, beer, and malt extracts. Glycerine is also useful as a lubricating material for 
 some kinds of machinery, more especially watch and chronometer works, because it is 
 not altered by contact with air, does not become thick at a low temperature, and does 
 not attack such metals as copper, brass, &c. Glycerine is used in the making of copy- 
 ing inks, and of a great many cosmetics. In order to render printing ink soluble in 
 water its insolubility is, however, its greatest advantage it has been proposed to use 
 glycerine for its preparation instead of linseed oil. Glycerine is an excellent solvent 
 for many substances, including the tar-colours (aniline blue, cyanine, aniline violet) and 
 alizarine.* In order to render paper soft and pliable glycerine is added to the pulp. 
 To the quantity of pulp required for making 100 kilos, of dry paper, 5 kilos, of glyce- 
 rine, sp. gr. i*i8, are sufficient. It is not out of place here to mention the following 
 useful weavers' glue or dressing, composed of Dextrine, 5 parts ; glycerine, 1 2 parts ; 
 ammonium sulphate, i part; and water, 30 parts. By the use of this mixture 
 the weaving of muslins need not be as was formerly the case carried on in damp, 
 darkened cellars, but may be performed in well- aired and well-lighted rooms. It is 
 said that leather driving-belts, made as usual of weakly tanned leather, when kept in 
 
 * In dyeing with colouring matters of great tinctorial power, such as many coal-tar colours, 
 glycerine is an excellent addition to the dye-beck. It prevents " flurry," i.e., the formation of a 
 coloured froth or scum on the surface, which is a frequent cause of unevenness. [EoiTOK.] 
 
SECT, viii.] ESSENTIAL OILS AND RESINS. 935 
 
 glycerine for twenty-four hours, are not so liable to fray. A glycerine solution is now 
 largely used instead of water for the purpose of tilling gas-meters, as such a solution 
 does not freeze in winter nor evaporate in summer. Santi uses glycerine for the com- 
 passes on board screw-steamers, in order to protect the inner compass-box against the 
 vibrations caused by the motion of the propeller. It is impossible to enter here 
 into minute details on the use of glycerine. Suffice it to observe further, that it is 
 employed for preserving anatomical preparations, for rendering wooden casks imper- 
 vious to petroleum and other oils ; for the preparation of artificial oil of mustard or 
 sulpho-cyan-allyl, made by treating glycerine with phosphorus iodide, whereby allyl 
 iodide is formed, which on being dissolved in alcohol, and next distilled with potas- 
 sium sulphocyanide, yields sulpho-cyan-allyl. When glycerine is treated with very con- 
 centrated nitric acid or with a mixture of strong sulphuric and nitric acids, it is converted 
 into nitro-glycerine (trinitrine or glyceral nitrate) (see p. 393), largely used for various 
 purposes, the preparation of clualine and dynamite, &c. A mixture of finely powdered 
 litharge and very concentrated glycerine, made into a paste, forms a rapidly hardening 
 cement, especially useful as a cover for the corks or bungs of vessels containing such 
 fluids as benzol, essential oils, benzoline, petroleum, &c., the cement being impermeable 
 to these liquids. 
 
 When used for sweetening wines or liqueurs, it is sold under the incorrect name 
 of saccharine, and its application is known as " scheelising." 
 
 ESSENTIAL OILS AND KESINS. 
 
 These substances almost all occur naturally. To the essential oils most plants 
 owe their odour and flowers their perfume. The essential oil in plants is met with 
 enclosed in cells; hence, after bruising a plant, or the parts containing the 
 essential oil, the peculiar odour is more perceptible; for instance, by gently rub- 
 bing between the fingers the leaves of some kinds of geraniums, melissa, lemon 
 plant, &c. Essential oils do not impart to the fingers a fatty, but a rather rough, 
 harsh feeling. A large number of essential oils possess the property of precipitating 
 silver from its ammoniacal solution in a metallic state ; hence the use of essential oils 
 in silvering glass (see p. 614). 
 
 Preparation of Essential Oils. These oils are chiefly obtained by submitting parts 
 of plants, previously ground to a coarse powder, to distillation with water. Although 
 the boiling point of these oils is generally much higher than that of water, the oils are 
 mechanically carried over in a minute state of division with the aqueous vapour. When 
 oils the boiling point of which is very high, have to be extracted, some common salt is 
 added to the Avater to heighten its boiling-point. In order to separate the oil from the 
 water, there is employed a peculiarly shaped vessel, called a Florentine flask. In this 
 way the essential oils of aniseed, chamomile, lavender, peppermint, cloves, cinnamon, &c., 
 are obtained, while the most common essential oil viz., that of turpentine is obtained 
 by the distillation of Venice turpentine with water. 
 
 Preparation of Essential Oils by Pressure. The essential oils largely met with en- 
 closed in the cells of the skin of lemons, oranges, bergamots, and, in fact, all the fruits 
 belonging to the Citrus genus, are obtained by pressing the rinds of these fruits. 
 Although the greater number of the essential oils occur ready formed in various 
 parts of the plants, some of these oils are the result of the action of water as, for 
 instance, the essential oil of bitter almonds, which is formed by the action of water 
 upon amygdalin under the influence of a peculiar albuminous compound called 
 synaptase or emulsin ; the essential oil of mustard seed is formed in a similar manner, 
 bnt may be artificially prepared by distilling a mixture of propyl iodide and potassium 
 cyanide, &c. 
 
936 CHEMICAL TECHNOLOGY. [SECT. vin. 
 
 Extraction of Essential Oils by Means of Fatty Oils. Some of the essential oils, 
 more especially those present in flowers, are so sparingly distributed, that they can 
 only be obtained by digesting the fresh flowers with pure olive oil or with cotton- 
 wool soaked in sweet olive oil, the fresh flowers being placed in alternate layers be- 
 tween the cotton saturated with oil ; in some cases pure lard is employed. The 
 essential oils may be recovered from the sweet oils by agitation with strong and 
 highly rectified alcohol. The essential oils of jasmine, sweet violets, hyacinths, &c., 
 are obtained in this manner. 
 
 Properties and Uses of Essential Oils. These oils are more or less soluble in 
 water, and the solutions are known in pharmacy as distilled waters. The essential 
 oils are soluble in alcohol in proportion to the amount of oxygen they contain. 
 Upon this property is based the use of these oils in perfumery and for the preparation 
 of liqueurs (cordials). 
 
 Perfumery. This branch of industry provides us with scented waters (esprits eaux 
 de senteur), odoriferous extracts (extraits a odeurs), perfumed fats, pomatums, oils, &c. 
 Scented waters are really alcoholic solutions of one or more essential oils. The 
 alcohol used for this purpose requires to be very pure and perfectly free from fusel oil 
 or other impurity. The oils are dissolved in the alcohol, and in order to blend the 
 mixture and render it mellow, it is kept for several months in a bottle before being 
 sold. The old process of distillation is very properly discarded, because, owing to 
 the high boiling point of the oils, a portion was left in the still, while the scented 
 waters thus prepared were inferior in quality. Eau de Mills, Fleurs is prepared by 
 dissolving in 9 litres of alcohol, 60 grammes of balsam of Peru, 120 grammes of oil of 
 bergamot, 60 grammes of oil of cloves, 1 5 grammes of neroli oil (oil of orange-flowers, 
 a very expensive oil), 15 grammes of oil of thyme, adding to the mixture 4 litres of 
 orange-blossom water, and 120 grammes of tincture of musk, obtained by digesting 1 5 to 
 25 grammes of civet and 75 grammes of musk with 2 litres of alcohol. Eaude Cologne 
 is obtained by dissolving in 6 litres of alcohol 32 grammes of essential oil of orange- 
 peel and equal quantities of oil of bergamot, lemon, essence de limette, essence de petit 
 grains, 16 grammes essence de cedro, and equal quantities of essence de cedrat and essence 
 de Portugal; further. 8 grammes of neroli oil and 4 grammes of rosemary. The per- 
 fumed extracts are generally obtained by the exhaustion, by means of alcohol, of the 
 scented fats and oils prepared from flowers as before described. 
 
 Artificial Perfumes. Doebereiner first suggested the use of artificial perfumes ; 
 among these are an alcoholic solution of amyl acetate as pear oil, amyl valerate as apple 
 oil, amyl butyrate as pineapple oil, ethyl pelargonate as quince oil, ethyl suberate as 
 essence of mulberries, while nitrobenzol mixed with nitrotoluol (commercial nitrobenzol) 
 is termed artificial oil of almonds, and, when very coarse, is sold as essence de mirbane, 
 chiefly used for the preparation of aniline. The perfumed fats (pomatums) of better 
 quality are generally prepared from an infusion of the flowers with oil or fat at a tem- 
 perature of 65, or by a process of digestion in the cold by placing the flowers in layers 
 between pure lard or cotton-wool soaked in very pure olive oil ; enfteurage is the 
 name given to this operation. The ordinary pomatums are made simply of lard or 
 marrow-fat coloured with turmeric, annatto, or alkanet root, and perfumed with a few 
 drops of some essential oil.* 
 
 Preparation of Cm-dials. The aim of the preparation of liqueurs (cordials) is to 
 render brandy a more agreeable beverage by the addition of sugar, glycerine, and 
 aromatic substances. A distinction is made between the finer liqueurs \rosoglio} and 
 
 * The reader may here consult Piesse's " Art of Perfumery." 5th edit. London : Piesse & 
 Lubin. It is not demonstrated that the artificial perfumes made according to Doebereiner's 
 process agree in their physiological action with the natural products which they simulate. 
 [EDITOR.] 
 
SECT. VIII.] 
 
 ESSENTIAL OILS AND RESINS. 
 
 937 
 
 ordinary cordials (aqua vitce) according to the quality of the materials employed for 
 the purpose. When a sufficiently large quantity of sugar is used to render the 
 liqueurs thickly fluid they are designated cremes, while those made with the juices of 
 fruit obtained by pressure, sugar and alcohol are called ratafia. These liqueurs are not 
 prepared to any great extent in this country ; but in France, Italy, Austria, and 
 especially in Holland, the preparation is on a large scale. 
 
 The basis of all liqueurs is a very highly rectified and pure alcohol. The vegetable 
 materials used in the liqueurs may be classified under three heads : In the first place, 
 such vegetable substances as contain essential oils and are used for that reason only, 
 caraway, aniseed, juniper- berries, mint, lemon-peel, orange-blossom, and bitter almonds. 
 These substances, previously bruised or cut up, are digested with alcohol, the mixture 
 being next distilled, or, as is more generally the case, alcoholic solutions of the essential 
 oils are employed and the preparation performed in the cold. To the second class 
 belong such vegetable substances as are used for the sake of their essential oil and 
 for their aromatic bitter substances, chiefly roots, such as sweet calamus, gentian, 
 ginger, orange-peel, unripe bitter Cura9oa apples (a peculiar kind of orange), worm- 
 wood, cloves, cinnamon, vanilla (the pod of an orchidaceous plant originally brought 
 from Mexico). These substances having been bruised are digested with alcohol 
 either at the ordinary temperature of the air or at 50 or 60, the result being the 
 formation of what is termed a tincture. To the third class belong fruits, such as 
 cherries, pineapples, strawberries, raspberries, the juice of which is obtained by pres- 
 sure, passed through a sieve, and mixed with alcohol and sugar or syrup, viz., a 
 solution of 4 Ibs. of refined loaf-sugar in 4 litres of water. The liqueurs generally 
 contain from 46 to 50 per cent, of alcohol. It is customary to colour the liqueurs 
 red with santal-wood, cochineal, aniline red, or with the Coccus polonicus, as in the 
 case with the celebrated Alkermes de Firense, a liqueur made at Florence ; yellow 
 with saffron, turmeric, or marigold flowers (Calendula) ; green by mixing yellow and 
 blue ; blue, with tincture of indigo ; violet, with aniline violet ; while in many cases 
 caramel is used to impart a brown colour. The so-called cremes contain for every 
 litre of liquid about i Ib. of sugar or a corresponding quantity of glycerine. As an 
 instance of the composition of a liqueur, Maraschino 
 consists of 4 litres of raspberry water, 175 litres 
 orange-blossom water, 1-5 litres kirschwasser (a 
 Swiss preparation from cherries fermented and 
 distilled a strong, spirituous liquid which con- 
 tains hydrocyanic acid), 18 Ibs. of sugar, and 9 litres 
 of alcohol at from 89 to 90 per cent. Liqueurs 
 are very similar to cremes, but contain less sugar. 
 English bitter contains 5 parts of flavedo corticum 
 aurantiorum (outer rind of dried orange peel), 6 
 parts of cinchona bark, 6 parts of gentian, 8 parts 
 of Carduus benedictus, 8 parts of centaury, 8 parts 
 of wormwood, 4 of orris root digested with 54 litres 
 of alcohol at 50 per cent., while after filtration 
 i-2 Ibs. of sugar are added. Cherry ratafia: 
 20 litres of cherry juice, 20 litres of alcohol at 
 85 per cent., 30 Ibs. sugar, and usually 4 to 8 litres 
 of bitter almond water. Peppermint : 2-5 litres 
 of essential oil of peppermint dissolved in i litre of 
 
 alcohol at 80 per cent. ; this solution is poured into 54 litres of alcohol at 20 per cent., 
 sweetened with 60 Ibs. of sugar previously dissolved in 26 litres of water, and , 
 with either tincture of indigo or turmeric. 
 
 Fig. 596. 
 
 
 
 
 c 
 
 -~.= 
 
 'V. 
 
 -*~ -~-~ 
 
 a 
 
 
 
938 CHEMICAL TECHNOLOGY. [SECT. vm. 
 
 In Miirrle's apparatus for the extraction of ethereal oils (Fig. 596) there is suspended 
 a copper boiler, .4, in the round iron furnace, 0. Steam enters through the tube, E, 
 into the receiver, B, on the perforated bottom of which, s, the plants are laid, and it 
 escapes then with the ethereal oil through the pipe, b, into the worm, C. The dis- 
 tillate collects first in the Florentine receiver, D, where the ethereal oil separates out at 
 the top whilst the water, being heavier, flows back through the bent tube-funnel into the 
 boiler, A, to be evaporated anew. The distillation is continued until the water escaping 
 from the worm is scentless. When the distillation is at an end the capital is detached 
 and raised by means of the tackle, K, when the receiver, B, can be lifted off the two 
 handles, b, b. The perforated bottom is taken out downwards and the residue is then 
 thrown away. The charging can also be executed rapidly, the upper aperture being 
 closed by the accompanying screw lid and B being inserted, in which position it stands 
 on its three feet, f. When B is filled the perforated bottom is introduced, the whole 
 is inverted and replaced upon the boiler, A. By providing a second receiver, B, of 
 the same size, the working power of the apparatus can be increased, as one receiver is 
 at work whilst the other is being emptied and filled again. The catch-pan, E, prevents 
 any extractive matter from falling down into the boiler, A, burning and spoiling the 
 odour of the essential oil. 
 
 In the process of enfleurage it has lately been proposed to use chlormethyl instead 
 of fatty oils. 
 
 The artificial essences simulating the odour of certain natural perfumes may be 
 legitimately used in cosmetics, &c., but it is at least doubtful whether their physiolo- 
 gical action is identical with that of the natural products which they imitate. Hence 
 their use in the production of liqueurs is questionable. 
 
 Resins. By the action of the oxygen of the air most of the essential oils are 
 gradually thickened, and at length converted into a substance termed resin. Resins- 
 are frequently met with in the vegetable kingdom ; in some instances, as with 
 coniferous trees, resin flows spontaneously from the wood in combination with an 
 essential oil, so-called Venice turpentine, which hardens by exposure to air. Some 
 resins are extracted from vegetable matter by means of alcohol, this solution being 
 either precipitated with water or evaporated to dryness. Resins are either soft, and 
 are then termed balsams, chiefly solutions of resin in essential oils, or hard. To the 
 former belong Venice turpentine, Canada balsam, balsam of Peru, copaiva balsam, &c. ; 
 to the latter, amber (a fossil resin), anime, copal, gum dammar, mastic, shellac, asphalte. 
 The gum resins are obtained from incisions made in certain kinds of plants, the milky 
 juice of which hardens by exposure to air; these substances are partly soluble in 
 water, and yield with it in many instances an emulsion ; for instance, asafcetida, gum 
 gutti, &c. Many gum resins possess a very strong odour and contain essential oils. 
 Although it is customary to treat of caoutchouc and gutta-percha under the head of 
 resins, these substances are not related to resins at all, but belong to a separate class 
 of bodies, among which, according to Dr. G. J. Mulder's researches, the so-called drying 
 oils must be enumerated. 
 
 Sealing- Wax. Sealing-wax of modern time (for mediaeval sealing-wax was really 
 a mixture of wax with Venice turpentine and colouring matter) is prepared from 
 shellac, to which some turpentine is added in order to promote fusibility and prevent 
 brittleness. Red sealing-wax and bright coloured wax are made of a very pale, some- 
 times even purposely bleached, shellac, while black and dark coloured sealing-wax are 
 made of more deeply coloured shellac. In addition to shellac and turpentine, sealing- 
 wax contains earthy matter, added not only for the purpose of increasing the weight, 
 but also for preventing the too rapid fusion of the mass ; chalk, magnesia, plaster of 
 Paris, zinc-white, barium sulphate, kaolin, and finely divided silica, are employed for this 
 purpose. Red sealing-wax is prepared by melting together in an iron pan placed on a 
 
SECT. VIII.] 
 
 ESSENTIAL OILS AND RESINS. 
 
 939 
 
 charcoal fire 4 parts of shellac, i part of Venice turpentine, and 3 parts of cinnabar 
 (vermilion), care being taken to stir the mixture constantly. Ordinary red sealing- 
 wax is often composed of 
 
 
 
 
 
 
 
 
 
 
 3- 
 
 4- 
 
 5- 
 
 Shellac 
 
 550 
 
 620 
 
 550 
 
 7OO 
 
 600 
 
 Venice turpentine 
 
 740 
 
 680 
 
 6OO 
 
 540 
 
 600 
 
 Chalk or magnesia 
 
 300 
 
 200 
 
 
 
 
 
 
 Gypsum or zinc-white 
 
 200 
 
 
 
 
 
 
 
 
 
 Baryta white 
 
 
 
 IOO 
 
 380 
 
 300 
 
 300 
 
 Vermilion 
 
 130 
 
 22O 
 
 340 
 
 300 
 
 300 
 
 Oil of turpentine 
 
 
 
 
 
 
 2O 
 
 25 
 
 The cooled but still soft mass is either rolled on a slab of marble and shaped into 
 sticks, or the fluid mass is run into brass moulds. Perfumed sealing-wax contains 
 either benzoin resin, storax, or balsam of Peru. The various colours are imparted by 
 cobalt ultramarine (cobalt blue), lead chromate, bone-black, &c. Marbled sealing- 
 wax is made by mixing variously coloured sealing-waxes together. Inferior kinds of 
 sealing-wax parcel-wax are coloured with red oxide of iron, while instead of shellac 
 ordinary resin is used with gypsum or chalk. New Zealand resin, the produce of the 
 Xanthorrhcta hastilis, is now frequently used instead of shellac. 
 
 Asphalte. This material, sometimes known as bitumen, is a black, glossy, brittle 
 resin, probably formed by the gradual oxidation of petroleum oil ; it occurs very 
 largely on the island of Trinidad, on the northern coast of S. America, at the mouth of 
 the Orinoco, on the water of the Dead Sea (anciently Lacus Asphaltites), and in some 
 other localities viz., France, Seyssel, Department de 1'Ain, a limestone containing 
 1 8 per cent, of asphalte. By boiling this limestone, previously broken up into small 
 lumps, with water, there is obtained an asphalte, 7 parts of which are mixed with 90 
 parts of native asphalte limestone. The materials are ground up together and are 
 employed for paving purposes, being compressed with heavy and highly heated irons. 
 Asphalte is also found at Yal de Travers, Switzerland ; Limmer, Hanover ; Lobsann, 
 Lower Alsace; and in the Northern Tyrol. Asphalte, or bitumen, is somewhat 
 soluble in alcohol, readily so in Persian naphtha, oil of turpentine, benzene, and 
 benzoline. It is used in varnish making (iron varnish), in engraving copper and steel, 
 as an etching ground, and as an oil paint. Asphalte mixed with sand, lime, or lime- 
 stone, is largely used for paving purposes, being durable and somewhat elastic ; it is 
 employed for this purpose either in a pasty or semi-fused state, or in powder. Instead 
 of native asphalte, Busse's terresin, a mixture of coal-tar, lime, and sulphur is some- 
 times used, as well as coal-tar asphalte, obtained from gas works. The residue of the 
 distillation of coal-tar is often employed instead of asphalte, and pebbles mingled with 
 coal-tar are now used to form excellent footpaths in some parts of the metropolis. 
 
 Tubes of paper, saturated with asphalte, are often used for water-, gas-, and drain- 
 pipes. Sheets of strong paper and pieces of woven cloths steeped in asphalte are used 
 
 for roofing. 
 
 Caoutchouc. Elastic gum, or india-rubber, is derived from the milky juice of a 
 series of plants, occurring also in opium ; but the commercial article is obtained from 
 the milky juice of various trees belonging to the natural orders of the Urticece, 
 EuphorUacece, Apocynece. Among the trees which yield caoutchouc in large quantity 
 are the Siphonia cahucu, in South America, and the East Indian species, Urceola elastica; 
 Ficus elastica, F. religiosa, F. indica, also yield caoutchouc. It is obtained by making 
 incisions in the tree and collecting the exuding juice in vessels of dried clay. The 
 juice is solidified by the application of fire or by exposure to the sun's rays ; the variety 
 known as lard gum is usually dried by exposure to the sun. Perfectly pure caoutchouc 
 is a white and in thin sheets semi-transparent, substance ; its texture is not fibrous ; 
 
940 CHEMICAL TECHNOLOGY. [SECT. VIH. 
 
 it is perfectly elastic, becoming turbid and fibrous when strongly stretched. Excessive 
 cold renders it hard but not brittle. The specific gravity of caoutchouc is 0*925. 
 Although hot water and steam render caoutchouc soft, it is not further acted upon by 
 them. It is insoluble in alcohol, not acted upon by dilute acids or strong alkalies, 
 while for a very long time it resists the action of chlorine. Strong sulphuric and 
 nitric acids decompose india-rubber, and when red fuming nitric acid is employed a 
 violent combustion ensues. If strongly stretched india-rubber is placed in cold 
 water for a few minutes it temporarily loses its elasticity, which it regains by being 
 immersed for a few minutes in water at 45. By exposure to a gentle heat caoutchouc 
 becomes supple, and finally melts at 200, with partial decomposition, forming a viscous 
 mass which does not again become solid on cooling. When caoutchouc is ignited in 
 contact with air it burns with a sooty flame. Of all substances with which we are 
 acquainted none would be better suited to gas manufacture than caoutchouc, which, 
 according to experiments made many years ago at Utrecht, yields at red heat rather 
 more than 30,000 cubic feet of gas to the ton, the gas being quite free from sulphur 
 and ammonia compounds, and its illuminating power very superior to that of the best 
 oil gas. Unfortunately caoutchouc is much too high priced for this application. 
 Caoutchouc may be kneaded with sulphur and other substances by the aid of heat, 
 becoming converted into what is known as vulcanised india-rubber, vulcanite, ebonite, 
 &c. When caoutchouc is submitted to dry distillation, at much below red heat, it 
 yields only oily fluids, consisting of carbon and hydrogen (caoutchen, heveen, &c.), 
 which are par excellence solvents for caoutchouc. Caoutchouc itself contains only 
 carbon and hydrogen, its formula being C 4 H 7 (in 100 parts: 87*5 carbon and 12-5 
 hydrogen) ; probably, however, caoutchouc is a more complex mixture of various 
 hydrocarbons. 
 
 Solvents of Caoutchouc. India-rubber is soluble in ether containing no alcohol, in the 
 oils(empyreumatic)of caoutchouc, in Persian naphtha, oil of turpentine, carbon disulphide, 
 and in chloroform. Industrially the ethereal solution of caoutchouc is useless, because 
 it contains hardly more than a trace of that substance. As regards oil of turpentine, 
 it dissolves caoutchouc only when the oil is very pure and with the application of heat ; 
 the ordinary oil of turpentine of commerce causes india-rubber to swell rather than to 
 become dissolved. In order to prevent the viscosity of the india-rubber when 
 evaporated from this solution, i part of caoutchouc is worked up with u parts of 
 turpentine into a thin paste, to which is added part of a hot and concentrated 
 solution of potassium sulphide (K 2 S 5 ) in water ; the yellow liquid formed leaves the 
 caoutchouc perfectly elastic and without any viscosity. The solutions of caoutchouc 
 in coal-tar naphtha and benzoline are most suited to unite pieces of caoutchouc, but the 
 odour of the solvents is perceptible for a long time. As chloroform is too expensive 
 for common use, carbon disulphide is the most usual and also the best solvent for 
 caoutchouc. This solution, owing to the volatility of the menstruum, soon dries, leav- 
 ing the caoutchouc in its natural state. When alcohol is mixed with carbon disulphide, 
 the latter no longer dissolves the caoutchouc, but simply softens it and renders it capable 
 of being more readily vulcanised. Alcohol precipitates solutions of caoutchouc and 
 gutta-percha. 
 
 The great diversity of the sorts of caoutchouc, according to Hoehnel, is not merely 
 external, but extends to their essential properties, and is due both to the different 
 methods of preparation and to the fact that the commercial article is derived from 
 upwards of fifty plants, belonging to different families. 
 
 The methods of preparing caoutchouc from the milky juice are as follows : (i) The 
 juice is poured upon a mould in thin layers, and these layers are gradually dried in hot 
 smoke. More than one hundred layers are thus often produced. (2) The milky juice is 
 conveyed directly from the tree to small pits made in the soil. The soil acts as a filter ; 
 
SECT, viii.] ESSENTIAL OILS AND RESINS. 941 
 
 the watery part of the milk filters off or partly evaporates, whilst the caoutchouc remains 
 behind. This method is very crude, and can be applied only in the dry season. (3) The 
 milky juice is mixed with a little water and allowed to stand for some days to coagulate. 
 The mass thus separated out is freed from excess of water by kneading and pressing, and 
 then dried in the sun or in smoke. (4) The milky juice is mixed with a solution of 
 salt or of alum, with an acid, or with the extract of certain plants, whereon it quickly 
 curdles ; the clot is then pressed and dried. (5) The milky juice is mixed with 4 to 8 
 parts of water, when the caoutchouc comes to the surface like a thick cream, which is 
 collected, repeatedly washed, and dried either in smoke or very slowly in the air. 
 (6) The milky juice is simply allowed to dry in shallow vessels. (7) The milky juice 
 is concentrated, and is caused to flow down upon the arm of the collector, where it 
 quickly dries, and is rolled off in the form of a ring. (8) Or the concentrated juice 
 flows down upon the stem or drops to the ground, where it is collected and moulded into 
 balls. 
 
 The most valuable kinds known in commerce, the " Para," are obtained by the first 
 process. The same method is in use in Columbia. Para caoutchouc consists of strata 
 generally less than ^ mm. in thickness, white or dark grey, and it appears separated by 
 sharp black lines where it has been exposed to smoke ; the finer and the more equal 
 these layers are which may be seen on section the better is the sample. Inclosed air- 
 bubbles signify an inferior quality. As soon as there are seen layers from i to 2 centi- 
 metres in thickness, white, and full of bubbles, we have a second-rate Para. The second 
 process is in use in Columbia, Central America, and occasionally, along with other 
 methods, in Africa and Southern Asia; it yields a watery, contaminated, inferior 
 product. The processes (3) and (4) yield an article rich in water, often containing un- 
 coagulated milky juice. Those kinds are especially bad which have been coagulated by 
 the addition of foreign matter, salts, &c. Coagulation is practised in the north of 
 South America, in Central America, West Africa, India, and the Sunda Islands. 
 These kinds are often dried too rapidly, and have therefore a black surface, smelling of 
 smoke and sometimes are even burnt. If the drying is too rapid, the surface remains 
 smeary. Such sorts are named resinous, and are often found in Indian, "West African, 
 and Central American lots. It must not be forgotten that South Asiatic samples 
 are often artificially contaminated with resins or vegetable extracts. Such resinous 
 sorts are in very low estimation. Recent samples of qualities obtained by coagulation 
 show on section a homogeneous grey rind, a few millimetres in thickness, and a thick, 
 white, violet, yellow, or flesh-coloured nucleus, which is quite soft and often contains 
 water or milky juice. The sorts obtained by coagulation are poor in fragments of wood 
 and bark, which occur most abundantly in sorts prepared by methods (7) or (8). 
 Process (5) is used in some parts of Central America, and yields a good quality. Pro- 
 cess (6) gives a similar product, highly esteemed, and imported from the Gaboon and 
 
 from India. 
 
 Preparation and Use of India-rubier. India-rubber is used to clean paper, to rub 
 out black-lead pencil marks, for making waterproof fabrics (macintosh), rubber sponge, 
 tubing, elastic webs, lutes, &c.* 
 
 Vulcanised Caoutchouc. When caoutchouc is immersed for seme time in molten 
 sulphur it absorbs the latter, and becomes converted into a yellow, very elastic mass. 
 The most valuable property of vulcanised india-rubber is its elasticity even at low 
 temperatures ; ordinary india-rubber hardens at 3. Vulcanised india-rubber is in- 
 soluble in the solvents of caoutchouc. It resists compression to a very great extent ; hence 
 its use instead of steel springs on tramcars. According to the old method, caoutchouc 
 
 * The most important of all the uses of caoutchouc at present is in the insulation of electric 
 wires and cables. It is the preferable ingredient in all cases when the conduction traverses a dry 
 medium, such as air, dry earth, the interior of houses, &c. [EDITOR.] 
 
94 2 CHEMICAL TECHNOLOGY. [SECT. vin. 
 
 was vulcanised by being placed for some ten to fifteen minutes in thin plates in 
 molten sulphur heated to 120, the weight of the caoutchouc increasing 10 to 15 per 
 cent. The material was subsequently mechanically treated by pressure, and then 
 heated to 150. In order to prevent efflorescence of the sulphur, caoutchouc is 
 sometimes heated to 120, and then kneaded by the aid of powerful machinery, with 
 either kermes (Sb 2 S) or a mixture of sulphur and arsenic sulphide. At the present 
 day Parkes's method is generally adopted : the caoutchouc is simply immersed in a 
 mixture of 40 parts of carbon disulphide and i part of sulphur chloride ; it is 
 next placed in a room heated to 21, and when all the carbon disulphide has been 
 volatilised, the process is in so far complete that it is only requisite to boil the 
 material in a solution of 500 grammes of caustic potassa to 10 litres of water, the 
 vulcanised caoutchouc being next washed to remove excess of alkali. In 1870 
 Humphrey introduced the use of petroleum ether (benzoline) instead of carbon disul- 
 phide, as the former fluid dissolves sulphur chloride readily. H. Gaultier de Claubry 
 (1860) vulcanised caoutchouc by the aid of bleaching-powder and flowers of sulphur. 
 This mixture produces sulphur chloride, and the caoutchouc treated by it contains 
 some calcium chloride. Neither this process nor that of Gerard the use of a solution 
 of potassium pentasulphide of 40 to 49 Tw., aided by a temperature of 150, and a 
 pressure of 5 atmos. or 75 Ibs. to the square inch are practically available on the 
 large scale. Articles of vulcanised india-rubber are made of ordinary caoutchouc 
 and then vulcanised. The uses of vulcanised india-rubber are so many and so gene- 
 rally known that it is hardly necessary to enumerate them. 
 
 In 1852 Goodyear discovered a process by which caoutchouc is rendered hard 
 and wood-like, being then termed vulcanite or ebonite. This substance exhibits a 
 black or brown colour, and is largely used for making combs, imitation jet ornaments, 
 stethescopes, and a variety of articles. The preparation of ebonite differs from that 
 of vulcanite only in the introduction of a larger amount of sulphur (30 to 60 per 
 cent.), at a higher temperature, with the addition of other substances shellac, gutta- 
 percha, asphalte, chalk, barium sulphate, pipe-clay, zinc, antimony, or copper sulphides, 
 &c. Ebonite is capable of taking a high polish ; it does not, as is the case with horn, 
 become rough when cleaned with hot water ; and it is to some extent elastic. 
 
 For articles which require elasticity, such as artificial whalebone, walking-sticks, 
 &c.,less sulphur is used than for those which require rigidity, such as rulers, discs for 
 frictional electric machines, &c. The hardness required cannot be obtained with less 
 than 20 per cent., but quantities above 35 per cent, are useless, on account of the 
 increasing brittleness. After the caoutchouc, sulphur, and the other ingredients have 
 been duly mixed together, and the articles are moulded into the required shapes 
 the actual combination is effected by means of steam. The articles, placed on small 
 trucks, are run upon rails into a strong cylindrical boiler, which is then tightly closed 
 Steam is then admitted at a pressure not exceeding 4^ atmos. The introduction 
 of the steam must be regulated in such a manner that the internal temperature 
 gradually rises to 135. From this moment a very uniform temperature must be 
 maintained. A few degrees too high would burn the contents of the boiler ; and a few 
 degrees too low, or a fluctuation in the temperature, would render the whole work 
 nugatory. Vulcanite mixed with sand, emery, &c., sometimes serves for the produc- 
 tion of artificial grindstones whetstones for sharpening scythes, sickles, and other 
 agricultural implements. Vulcanite expands very considerably in heat, about three 
 times as much as zinc. 
 
 The yield of caoutchouc in 1882 was 20,000 tons. 
 
 Gutta-percha. Plastic gum, gutta- or getah-percha, gettannia gum, taban gum, is a 
 substance in many respects similar to caoutchouc; it is the inspissated juice of the 
 Isonandra gutta, a tree growing in Malacca, Borneo, Singapore, Java, Madura, and 
 adjacent countries. 
 
SECT. VJIL] ESSENTIAL OILS AND RESINS. 943 
 
 Gutta-percha was at first obtained by felling the trees and collecting the exuding 
 juice, either in suitable vessels or in shallow pits dug in the soil, or in baskets made 
 from banyan leaves, the juice being left to coagulate under the action of the sun. 
 More recently the practice has been to make deep incisions in the trees, and to collect 
 the exuding juice. The lumps of solid gutta-percha thus obtained are united by 
 softening in hot water and by pressure. The raw gutta-percha of commerce is a dry, 
 red, or marbled mass, not unlike leather cuttings which have been pressed together ; 
 the raw material contains as impurities some sand, small pieces of wood and bark, and 
 sometimes other inspissated vegetable juices of less value than gutta-percha. The name 
 gutta-percha means, in fact, Sumatra gum, this island being known in Malay language as 
 Pulo-percha. When perfectly pure, gutta-percha is quite white, its ordinary brown 
 colour being due to an acid insoluble in water, which is present, partly free, partly as 
 insoluble salts (of magnesia, ammonia, potash, and manganese protoxide), of apocrenic 
 acid ; but in addition there is a small quantity of organic colouring matter. Gutta- 
 percha is a mixture of several oxygen-containing resins, which appear to be the products 
 of the oxidation of a hydrocarbon, the formula of which is C 20 H 60 . Payen found in 
 gutta-percha the following substances : 75 to 80 per cent, of pure gutta-percha, 14 to 
 21 per cent, of a white crystalline resin termed alban, and from 4 to 6 per cent, of an 
 amorphous yellow resin named fluavil. Previously to being used, gutta-percha is 
 cleansed from dirt by a mechanical process of kneading in warm water, being then 
 usually rolled into thick plates or sheets. The purified material exhibits a chocolate- 
 brown colour, and is not transparent unless first reduced to sheets as thin as paper, when 
 the gutta-percha is equal to horn in transparency. At the ordinary temperature of the 
 air gutta-percha is very tough, stiff, not very elastic nor ductile. Every square inch 
 of a strap of gutta-percha, if of good quality and as homogeneous as possible, can 
 sustain a strain of 1872 kilos, without breaking. Its sp. gr. = 0-979. At 50 it 
 becomes soft, and at 70 to 80 it is so soft as to be very readily moulded, while two 
 pieces pressed together at this temperature become perfectly joined. By the aid of 
 heat, gutta-percha can be rolled into sheets, drawn into thread, and kneaded into a 
 homogeneous mass with caoutchouc. 
 
 Solvents of Gutta-percha. Gutta-percha is insoluble in water, alcohol, dilute acids, 
 and alkalies ; it is soluble in warm oil of turpentine, carbon disulphide, chloroform, 
 coal-tar oil, caoutchouc oil, and in the somewhat similar oil obtained by the dry distilla- 
 tion of gutta-percha. Ether and some of the essential oils render gutta-percha pasty. 
 As already stated, this substance becomes soft in hot water, absorbing a small quantity, 
 which is only very slowly driven off. Dry gutta-percha is a very good insulating 
 material for electricity. 
 
 Uses of Gutta-percha. The natural properties of this substance indicate its use as a 
 substitute for leather, papier-mache, cardboard, wood, millboard, paper, metal, &c., in 
 all cases not exposed to the action of heat, and where a substance is desired resisting 
 water, alcohol, dilute acids, and alkalies. The raw material, previously to being moulded 
 into shape, is purified, and kneaded by means of powerful machinery and with the 
 assistance of hot water (some soda or bleaching-powder solution being added), the aim 
 being the removal of such impurities as are only mechanically mixed with the gutta- 
 percha, as well as the removal of some of the colouring matter, while a more homoge- 
 neous mass is produced. The purified substance is next submitted to the action of 
 kneading machinery similar to that in use for working up caoutchouc, while it is rolled 
 out intopl ates of some 3 centimetres in thickness. Gutta-percha is moulded into tubes 
 by the aid of machinery such as are employed for making lead and block-tin tubing. 
 Many objects are made from gutta-percha by pressing it while soft into wooden or 
 metal moulds. By the use of a solution of gutta-percha in benzol, it may be glued to 
 leather and similar substances. It is almost impossible to enumerate the various uses 
 of gutta-percha. It is employed for straps for machinery instead of leather, tubes for 
 
94 4 CHEMICAL TECHNOLOGY. [SECT. vin. 
 
 conveying water, pumps, pails, surgical instruments, ornamental objects of various 
 kinds, for covering telegraph wires, &c.* Unlike pure caoutchouc, gutta-percha becomes 
 gradually deteriorated by exposure to the atmosphere, so that ultimately it can be even 
 readily ground to powder .t 
 
 Mixture of Gutta-percha and Caoutchouc. Frequently a mixture of i part of 
 gutta-percha and 2 parts of caoutchouc is employed. Articles made of this compound 
 possess the properties of both substances, and may be vulcanised equally as well as 
 gutta-percha alone. A mixture of equal parts of caoutchouc, gutta-percha, and sulphur, 
 heated for several hours to 120, obtains properties similar to those of bone and horn. 
 Sometimes gypsum, resin, and lead compounds are added to this mixture, which is then 
 used for making knife-hafts, buttons, &C.J 
 
 Balata. Since 1857 a product has become known which is intermediate in its 
 properties between caoutchouc and gutta-percha, and finds similar industrial applica- 
 tions. Balata is obtained from the inspissated milky juice of the so-called bully-tree 
 (Sapota Muelleri), a sapotaceous tree growing throughout Guiana. It is chiefly used 
 for driving-bands, for soles and heels, and in dentistry. 
 
 Celluloid. This name is applied to a mixture of nitro-cellulose and camphor. It 
 has the advantage over vulcanite that it can be obtained in various colours, but it has 
 the defect of being exceedingly combustible. 
 
 PRESERVATION OF WOOD. 
 
 On the Durability of Wood in General. The durability of wood i.e., its power of 
 resisting the destructive influences of wind and weather varies greatly, and depends 
 as much upon the particular kind of wood and the influences to which it is exposed as 
 upon the origin of the wood (timber), its age at the time of felling, and other condi- 
 tions. Beech wood and oak placed permanently under water may last for centuries. 
 Alder wood is very lasting and substantial under water, as also is fir, though in a dry 
 situation alder quickly perishes. Taking into consideration the different kinds and 
 varying properties of wood and the different uses to which it is applied, we have to 
 consider, as regards its durability, the following particulars : 
 
 1 . Whether it is more liable to decay by exposure to open air or when placed in 
 
 damp situations. 
 
 2. Whether, when left dry, it is more or less attacked by the ravages of insects 
 
 which, while in the state of larvae, live and thrive in and on wood. 
 Pure woody fibre by itself is only very slightly affected by the destructive influences 
 of wind and weather. When we observe that wood decays, that decay arises from the 
 presence of substances in the wood which are foreign to the woody fibre but are pre- 
 sent in the juices of the wood while growing, and consist chiefly of albuminous matter, 
 which, when beginning to decay, also causes the destruction of the other constituents of 
 the wood. But these changes occur in various kinds of wood only after a shorter or 
 
 * The last-mentioned purpose is now by far the most important. Like caoutchouc, gutta- 
 percha is a very bad conductor of electricity, and is therefore invaluable for insulating wires which 
 are conveying electric currents, especially if they have to be laid under water. If constantly wet 
 it lasts a long time, but if alternately wet and dry it is inferior to caoutchouc. [EDITOR.] 
 
 f The supply of gutta-percha has been imperilled by incautiously felling the trees. Without 
 diligent planting and strict preservation, the Isonandra gutta will -soon be extirpated. [EDITOR.] 
 
 J It was at first expected that gutta-percha, on account of its lightness, its freedom from brittle- 
 ness, and its resistance to acids, would be of great use in chemical, dye, and print works, &c. , for 
 funnels, jugs, measures, &c. It was soon, however, found that such vessels, though apparently not 
 attacked save by concentrated sulphuric acid, became gradually disintegrated on continual use, and 
 crumbled away. This process is much retarded, though not prevented, if the vessels are always 
 plunged into cold water immediately after being used. [EDITOR." 1 
 
SECT, viii.] PRESERVATION OF WOOD. 945. 
 
 longer lapse of time. Indeed, wood may in some instances last for several centuries and 
 remain thoroughly sound ; thus, the roof of Westminster Hall was built about A.D. 1090. 
 Since resinous woods resist the action of damp and moisture for a long time, they 
 generally last a considerable time ; next in respect of durability follow such kinds of 
 wood as are very hard and compact, and contain at the same time some substance 
 which like tannic acid to some extent counteracts decay. The behaviour of the 
 several woods under water differs greatly. Some woods are after a time converted into 
 a pulpy mass. Others e.g., teak contain caoutchouc, and are very permanent. 
 
 Insects chiefly attack dry wood only. Splint wood is more liable to such attack than 
 hard wood ; while splint of oak wood is rather readily attacked by insects, the hard 
 wood (inner or fully developed wood) is seldom so affected. Elm, aspen, and all 
 resinous woods are very seldom attacked by insects. Young wood which is full of sap 
 and left with the bark on soon becomes quite worm-eaten, especially so the alder, birch, 
 willow, and beech. The longer or shorter duration of wood depends more or less upon 
 the following circumstances : 
 
 (a) The conditions of growth. Wood from cold climates is generally more durable than 
 that grown in warm climes. A poor soil produces, as a rule, a more durable and compact 
 wood than does a soil rich in humus, and therefore containing also much moisture. 
 
 (b) The conditions in which the wood is placed greatly influence its duration. The 
 warmer and moister the climate the more rapidly decomposition sets in ; while a dry, 
 cold climate materially aids the preservation of wood. 
 
 (c) The time of felling is of importance ; wood cut down in winter is considered more 
 durable than that felled in summer, as in the former season it contains much less 
 sap. In many countries the forest laws enjoin the felling of trees only between 
 November 15 and February 15. 
 
 Wood employed for building purposes in the country, and not exposed to either heat 
 or moisture, is only likely to suffer from the ravages of insects ; but if it is placed so- 
 that no draught of fresh air can reach it to prevent accumulation of products of decom- 
 position, decay soon sets in, and the decomposing albuminous substances acting upon 
 the fibre cause it to lose its tenacity and become a friable mass. Under the influence 
 of moisture, fungi are developed upon the surface of the wood. These fungi are 
 severally known as the " house fungi " (Thetephora, domestica and Boletus destructor) 
 and the clinging fungus (Cerulius vastator). They spread over the wood in a manner 
 very similar to the growth of common fungi on soil. Their growth is greatly aided by 
 moisture and by exclusion of light and fresh air. A chemical means of preventing 
 such growths is found in the application to the wood of iron acetate, prepared from 
 wood vinegar. Wood is often more injuriously affected when exposed to sea water, 
 when it is attacked by a peculiar kind of mollusc known as the bore-worm (Teredo 
 navalis}. This creature is armed with a horned beak capable of piercing the hardest 
 wood to a depth of 36 centimetres. These pests originally belonged to, and abound 
 in great numbers in, the seas under the tropical clime, but they are also met with on 
 the coasts of Holland and England. 
 
 Preservation of Wood in Particular. The means usually adopted to prevent the 
 destruction of wood by decay are the following : 
 
 1. The elimination, as much as possible, of the water from the wood previously to 
 
 its being employed. 
 
 2. The elimination of the constituents of the sap. 
 
 3. By keeping up a good circulation of air near the wood so as to prevent its suffo- 
 
 cation, as it is termed. 
 
 4. By chemical alteration of the constituents of the sap. 
 
 5. By the gradual mineralisation of the wood, and thus the elimination of the organic 
 
 matter. 
 
 30 
 
946 CHEMICAL TECHNOLOGY. [SECT. vin. 
 
 1 . Drying Wood. Thoroughly dried wood remains for a long time unaltered while 
 in a dry situation, more especially so when dried by so strong a heat that it becomes 
 browned. When timber has to be put into a damp situation, it should, after having 
 been well dried, be first coated with a suitable substance to prevent the moisture 
 penetrating into the wood. This purpose is attained by coating the wood with linseed 
 oil, so-called Stockholm tar, coal-tar creosote, and other hydrocarbons. Hutin and 
 Boutigny adopt the following method to prevent the absorption of moisture by wood 
 that is put hito the ground : The portion of the post or wood to be buried is first 
 immersed in a vessel containing benzol, petroleum, photogen, &c., and when taken out 
 is ignited and thus charred. When extinguished, the wood is put to a depth of from 
 3 to 6 centimetres into a mixture of pitch, tar, and asphalte, and next the entire piece 
 of wood is thoroughly painted over with tar. 
 
 2. Elimination of the Constituents of the Sap. The constituents of the sap are 
 the chief cause of the decomposition of wood, and they should consequently be removed ; 
 many plans are adopted. The constituents, of the sap can be eliminated from the felled 
 tree by three methods : 
 
 (1) By treatment with cold water, with which the wood must be thoroughly saturated 
 to dissolve the constituents of the sap, which are removed when the wood is exposed 
 to a stream of water. It is evident that with large timber a long time is necessary to 
 ensure perfect saturation. 
 
 (2) By employing boiling water the sap is removed much more quickly and efficiently. 
 The pieces of wood are placed in an iron vessel with water, and boiled. Large pieces of 
 timber cannot be treated in this manner, but are immersed in a cistern in which the 
 fluid is heated by means of steam. According to the thickness of the wood, the boiling 
 occupies some six to twelve hours. 
 
 (3) By treatment with steam (steaming of wood) the most effectual method of re- 
 moving the constituents of the sap, the hygroscopicity of the wood thus treated being 
 rendered much less, while the wood is far more fitted to resist the effects of weather. 
 The apparatus employed in carrying out the method consists of a boiler for the genera- 
 tion of steam, and a cistern or steam chamber for the reception of the wood, this 
 chamber being constructed of masonry and cement, of boiler-plate, or being simply a 
 large and very wide iron pipe. In most cases a jet of steam is conveyed from the 
 boiler to the steam chamber, where it penetrates the wood, and dissolves out the 
 constituents of the sap, which, on being condensed, is allowed to run off. In the case 
 of oak this fluid is of a black-brown colour ; with mahogany, a brown-red ; with 
 linden wood, a red-yellow ; with cherry-tree wood, a red ; &c. The operation is 
 finished when the outflowing water is no longer coloured. The steamed wood is dried 
 in the air or in a drying- room ; it loses from 5 to 10 per cent, in weight by the process, 
 and becomes of a much darker colour. The steam is sometimes worked at a temperature 
 of above 100, but generally the contents of the steam chamber are maintained at from 
 60 to 70. Towards the end of the operation some oil of coal-tar is introduced into the 
 boiler, and is consequently carried over with the steam, impregnating the wood. 
 
 The removal of the sap can also be effected to some extent by means of mechanical 
 pressure between a pair of iron rollers, which are gradually brought more closely 
 together. Another method is by means of air pressure. Barlow employs for this 
 purpose a metal case in which the wood is enclosed, and to one end of which an air 
 pump is attached. Air being forced into the tube or case, the sap flows away at the 
 end opposite to which the pump is attached. But both these methods are costly, and 
 are not applicable in all cases. 
 
 3. Air Drains. The construction of air drains or passages around woodwork to be 
 preserved is, where the method is applicable, a great aid to the preservation of the 
 wood. The consideration of the best means of effecting ventilation in this respect is 
 
SECT, viii.] PRESERVATION OF WOOD. 947 
 
 not a matter with which we can deal in this work. It is sufficient to say that, in 
 many instances, the air channels are connected on the one hand with the open air, and 
 on the other with the chimney. 
 
 4. Chemical Alteration oj the Constituents of the Sap. One of the most usual and 
 most effective means of preventing the decomposition of wood is by producing a chemical 
 change in the constituents of the sap, so that fermentation can no longer be set up. 
 To this class belongs the well-known plan of protecting woodwork that is to be exposed 
 to the action of the moisture of the earth by charring the wood, either by fire or by 
 treatment with concentrated sulphuric acid, so that the wood is coated to a certain 
 depth with a layer of charcoal, the charcoal acting as an antiseptic. The charring or 
 carbonisation of the wood can be effected either with the help of a gas flame or the 
 flame from a coal fire. The apparatus of De Lapparent, invented for this purpose, 
 became very generally employed in 1866 at the dockyards of Cherbourg, Pola, and 
 Dantzic. According to another method, the wood is impregnated throughout its whole 
 mass with some substance that either enters into combination with the constituents of 
 the sap, or so alters their properties as to prevent the setting up of decomposition. 
 To this class belong the four following methods, these being the only ones that have 
 met with any more extensive use. 
 
 (i) Kyan's preserving fluid is a solution of mercuric chloride of various degrees 
 of concentration. In England a solution of i kilo, of corrosive sublimate in 80 to 100 
 litres of water is generally employed for railway sleepers. The timber is laid in a 
 water-tight wooden trough containing the solution, where, according to its size, it 
 remains a longer or shorter time. In Baden the wood remains in the kyanising 
 solution, when it is to be impregnated to a depth of 
 
 82 mm. 
 
 85 to 150 
 150 to 180 
 1 80 to 240 
 240 to 300 
 
 for 4 clays, 
 7 i, 
 
 10 
 
 18 
 
 the solution consisting of i kilo, of sublimate to 200 litres of water. The prepared 
 wood is washed with water, rubbed dry, and then placed in sheds free from exposure 
 to rain and strong sunlight. The principal action of the mercuric chloride is to 
 convert the albumen of the sap into an insoluble combination, capable of withstanding 
 decomposition, while the bichloride becomes gradually reduced to mercurous chloride 
 (calomel). A great objection to this method is the danger to which the carpenter 
 or joiner who may afterwards shape the wood is exposed, the free chemicals acting 
 upon his system through his hands, nostrils, and mouth. In England, wood to be 
 varnished is seldom kyanised. 
 
 Erdmann remarks upon this plan of preserving wood that the interior of the log is 
 still left in its original condition. To answer this objection the kyanising has been 
 made more effective by placing the wood in a water-tight trough with the solution 
 of sublimate, and, by a great pressure of air, thoroughly impregnating the wood. 
 Kyanising by this method becomes, however, as expensive as any other impregnation 
 method. Recently there has been substituted for the pure mercuric chloride a double 
 salt of the formula HgCl.. + 2KC1, obtained by decomposing a solution of carnallite 
 with mercuric oxide. 
 
 (2) Burnett's (1840) patent fluid consists of i kilo, of zinc chloride dissolved in 
 go litres of water. Wood treated with Burnett's fluid has been buried in the earth for 
 five years without undergoing any change, while unprepared wood buried for the same 
 length of time has been totally destroyed. Zinc chloride has been much used in 
 Germany as an impregnating material. Besides this salt, copper sulphate and zinc 
 ace tate zinc pyrolignite (Scheden's method) have been employed. The action of 
 
948 CHEMICAL TECHNOLOGY. [SECT. vin. 
 
 the copper and zinc salts may be explained by considering that the metallic oxides 
 of the basic salt formed during seasoning separate, and combine with the colouring 
 matter, tannic acid, resin, &c., of the wood to form an insoluble compound. 
 
 (3) Bethell's (1838) patented method consists in treatment under strong pressure 
 with a mixture of tar, oil of tar, and carbolic acid, this mixture being known, com- 
 mercially by the name of gallotin. In and near London wood thus treated has 
 remained eleven years in the earth without undergoing change ; other pieces of timber 
 so treated were subjected to the action of the sea for four years ; and were still in good 
 condition. Yohl employs for preservation peat and brown coal creosote; Leuchs uses 
 paraffine. Such agents, however, render wood treated with them highly inflammable. 
 
 (4) Payne's method. This includes two patents, the first having been taken out in 
 1841. Both are based on the impregnation of the wood first with one salt, and next 
 with another salt, which is capable of producing with the former a precipitate insoluble 
 in water and in the sap of the tree. The first solution is usually one of iron sulphate 
 or of alum ; then follows a solution of calcium chloride or of soda. The wood to be 
 impregnated is placed in a vessel from which the air is exhausted, the first solution 
 being then admitted, and pressure subsequently applied. The first solution being 
 removed, the second is admitted, and pressure again applied. It is necessary to dry the 
 wood partially between the two impregnations. Payne's method, much used in England, 
 possesses, moreover, the advantage of rendering the wood somewhat uninflammable. 
 The same effect results with the methods of Buchner and Von Eichthal, who im- 
 pregnate the wood with a solution of iron sulphate, and then with a water-glass 
 solution, whereby the pores of the wood are filled with ferrous silicate. Ransome 
 attains the same end by an impregnation with a water-glass solution and subsequent 
 treatment with an acid. It is found that the treatment of wood according to the 
 above methods is generally attended with good results. A method of impregnation 
 with materials forming insoluble soaps, aluminium, and copper oleates, or those of other 
 metals patented in 1862, has given some moderate results on the small scale. 
 
 5. Mineralising Wood. When the terms mineralised, petrified, metallised, or in- 
 crusted are applied to wood, they mean that the wood has undergone impregnation 
 with an inorganic substance, which has so filled the pores of the wood that it may 
 be said to partake of the characteristics of a mineral substance. Suppose that 
 the wood has become impregnated with iron sulphate and then exposed to the 
 rain, the sulphate will be gradually dissolved out, in time leaving only a basic sulphate. 
 By the researches of Striitzki (1834), of Apelt in Jena, and of Kuhlmann (1859), the 
 influence of iron oxide upon wood fibre has been rendered very clear. Wood im- 
 pregnated with basic iron sulphate ceases to be wood after some time. 
 
 .Boucherie's Method of Impregnation. This method consists in the impregnation 
 of the wood with the necessary substance, in a manner similar to the natural filling of 
 the pores with sap ; that is to say, the solution is introduced into the tree from its 
 roots, and is thus made to take the place of the sap in all parts of the timber. When 
 the tree is felled, the root end is placed in a solution of the salt (copper sulphate, 
 iron acetate) and allowed to remain for some days ; at the end of the required time 
 the wood will have become completely impregnated with the salt. Occasionally this 
 method is employed in colouring woods, colouring matter being used instead of, or as 
 well as, the salt. The linden, beech, willow, elm, alder, and pear tree can be treated 
 in this manner. The fir, oak, ash, poplar, and cherry tree do not, however, absorb 
 the impregnating fluid sufficiently. 
 
APPENDIX. 
 USEFUL TABLES. 
 
 THERMOMETRIC SCALES. 
 
 IN this work temperatures, almost without exception, are given on the Centigrade 
 scale, which takes the boiling-point of water at the ordinary atmospheric pressure at 
 100, and its freezing-point at o. Where any other scale is used it is specially 
 mentioned. The following rules will be useful for manufacturers who prefer to make 
 use of the thermometer of Fahrenheit, or that of Reaumur. 
 
 To convert, degrees Centigrade into degrees Fahrenheit 
 
 If the temperature is above the freezing-point of water (o C.), multiply by 9, 
 divide by 5, and add 32 to the quotient. 
 
 If the temperature be below o 0., but above - 18 C., multiply by 9, divide by 5, 
 and subtract the result from 32. 
 
 If below 1 8 C., multiply by 9, divide by 5, and subtract 32 from the result. 
 
 To convert degrees Fahrenheit into degrees Centigrade : 
 
 If above 32 F., subtract 32, multiply by 5, and divide by 9. 
 
 If below 32 F., but above o F., subtract the temperature from 32, multiply by 5, 
 and divide by 9. 
 
 If below o F., add the temperature to 32, multiply by 5, and divide by 9. 
 
 The conversion of Reaumur's scale in which the boiling-point of water is taken as 
 80, and vice versa is effected in the same manner ; the number 4 being used instead 
 of 5 as a multiplier or divisor. 
 
 HYDROMETER TABLES. 
 
 For determining the specific gravity of liquids heavier than water the scale of 
 Twaddell has been generally used. 
 
 for its conversion into direct specific gravity : 
 
 Multiply by 5, and add i to the product. 
 
 For converting specific gravity into Twaddell : 
 
 Subtract i and divide by 5. 
 
 The degree Tw. of any liquid shows its weight per gallon in pounds, if we prefix i 
 and insert the decimal point before the last figure. Thus, hydrochloric acid = 32 Tw. ; 
 its weight, therefore, is 13-2 Ibs. per gallon. 
 
 Some manufacturers, especially in the Liverpool district, use a hydrometer which 
 shows direct specific gravity if we place i before its first figure. Thus a sample of 
 hydrochloric acid of 32 Tw. will be on this scale 160. 
 
 The scale of Baum6 bears no simple relation to direct specific gravity; con- 
 sequently its conversion into degrees Tw., and into direct specific gravity, can only be 
 effected by means of tables, as follows : 
 
95 
 
 APPENDIX. 
 
 Degrees 
 Baume'. 
 
 Specific 
 Gravity. 
 
 Degrees 
 Baume". 
 
 Specific 
 Gravity. 
 
 Degrees 
 Baum6. 
 
 Specific 
 Gravity. 
 
 Degrees 
 Baume. 
 
 Specific 
 Gravity. 
 
 
 
 I'OOO 
 
 2O 
 
 I'I52 
 
 40 
 
 i '357 
 
 60 
 
 1-652 
 
 I 
 
 1-007 
 
 21 
 
 1-160 
 
 41 
 
 1-369 
 
 61 
 
 1-670 
 
 2 
 
 I.OI3 
 
 22 
 
 1-169 
 
 42 
 
 1-382 
 
 62 
 
 1-689 
 
 3 
 
 I'O2O 
 
 23 
 
 1-178 
 
 43 
 
 i '395 
 
 63 
 
 1-708 
 
 4 
 
 1-027 
 
 24 
 
 1-188 
 
 44 
 
 1-407 
 
 64 
 
 1727 
 
 5 
 
 1-034 
 
 25 
 
 1-197 
 
 45 
 
 1-421 
 
 65 
 
 1747 
 
 6 
 
 I-O4I 
 
 26 
 
 i -206 
 
 46 
 
 i '434 
 
 66 
 
 1767 
 
 7 
 
 1*048 
 
 27 
 
 i -216 
 
 47 
 
 1-448 
 
 67 
 
 1788 
 
 8 
 
 1-056 
 
 28 
 
 1-226 
 
 48 
 
 1-462 
 
 68 
 
 1-809 
 
 9 
 
 1-063 
 
 29 
 
 1-236 
 
 49 
 
 1-476 
 
 69 
 
 1-831 
 
 10 
 
 I-070 
 
 30 
 
 1-246 
 
 50 
 
 1-490 
 
 70 
 
 1-854 
 
 II 
 
 I-078 
 
 31 
 
 1-256 
 
 5i 
 
 I-505 
 
 7i 
 
 8 77 
 
 12 
 
 I -086 
 
 32 
 
 1-267 
 
 52 
 
 1-520 
 
 72 
 
 -900 
 
 13 
 
 1-094 
 
 33 
 
 1-277 
 
 53 
 
 '535 
 
 73 
 
 924 
 
 14 
 
 I'lOI 
 
 34 
 
 1-288 
 
 54 
 
 551 
 
 74 
 
 '949 
 
 15 
 
 1-109 
 
 35 
 
 1-299 
 
 55 
 
 567 
 
 75 
 
 '974 
 
 16 
 
 1-118 
 
 36 
 
 1-310 
 
 56 
 
 583 
 
 76 
 
 2-OOO 
 
 17 
 
 1-126 
 
 37 
 
 1-322 
 
 57 
 
 600 
 
 
 
 18 
 
 i '134 
 
 38 
 
 i '333 
 
 58 
 
 617 
 
 
 
 19 
 
 I'i43 
 
 39 
 
 i "345 
 
 59 
 
 634 
 
 
 
 For liquids lighter than water no determination can be effected with Twaddell's 
 hydrometer. The scales used are those of Beck, Cartier, or Baume's light instru- 
 ment. 
 
 Deg. 
 
 Beck. 
 
 Cartier. 
 
 Baume". 
 
 Deg. 
 
 Beck. 
 
 Cartier. 
 
 Baume. 
 
 a. 
 
 6. 
 
 a. 
 
 4. 
 
 70 
 
 0-7083 
 
 
 
 
 35 
 
 0*8292 
 
 0-840 
 
 0-845 
 
 0-849 
 
 6 9 
 
 0-7112 
 
 
 
 
 34 
 
 0-8333 
 
 0-845 
 
 0-850 
 
 0-854 
 
 68 
 
 07142 
 
 
 
 
 33 
 
 0-8374 
 
 0-851 
 
 0-855 
 
 0-859 
 
 67 
 
 07173 
 
 
 
 
 3 2 
 
 0-8415 
 
 0-856 
 
 n-86 1 
 
 0-864 
 
 66 
 
 0-7203 
 
 
 
 
 3 1 
 
 0-8457 
 
 0-862 
 
 0-866 
 
 0-869 
 
 65 
 
 0-7234 
 
 
 
 
 30 
 
 0-8500 
 
 0-867 
 
 0-872 
 
 0-875 
 
 64 
 
 0-7265 
 
 
 
 
 29 
 
 0-8542 
 
 0-872 
 
 0-878 
 
 0-88 1 
 
 63 
 
 0-7296 
 
 
 
 
 28 
 
 0-8585 
 
 0-879 
 
 0-883 
 
 0-886 
 
 62 
 
 07328 
 
 
 
 
 27 
 
 0-8629 
 
 0-885 
 
 0-889 
 
 0-892 
 
 61 
 
 07359 
 
 
 
 
 26 
 
 0-8673 
 
 0-891 
 
 0-895 
 
 0-897 
 
 60 
 
 0-7391 
 
 ... 
 
 ... 
 
 0744 
 
 25 
 
 0-8717 
 
 0-897 
 
 0-901 
 
 0-903 
 
 59 
 
 0-7423 
 
 
 
 
 24 
 
 0-8762 
 
 0-903 
 
 0-907 
 
 0-909 
 
 58 
 
 0-7456 
 
 
 
 
 23 
 
 0-8808 
 
 0-909 
 
 0-914 
 
 0-915 
 
 57 
 
 0-7489 
 
 
 
 
 22 
 
 0-8854 
 
 0-916 
 
 0-921 
 
 0*921 
 
 56 
 
 0-7522 
 
 
 
 
 21 
 
 0*8900 
 
 0*922 
 
 0-927 
 
 0-927 
 
 55 
 
 07556 
 
 
 .. 
 
 0763 
 
 20 
 
 0-8947 
 
 0-929 
 
 o-934 
 
 o-933 
 
 54 
 
 07589 
 
 
 
 
 19 
 
 0-8994 
 
 0-935 
 
 0-941 
 
 0-939 
 
 53 
 
 0-7623 
 
 
 
 
 18 
 
 0-9042 
 
 0-942 
 
 0-948 
 
 0-946 
 
 52 
 
 0-7658 
 
 
 
 
 17 
 
 0-9090 
 
 0-949 
 
 o-955 
 
 0-952 
 
 Si 
 
 0-7692 
 
 
 
 
 16 
 
 0-9139 
 
 0-956 
 
 0-962 
 
 o-959 
 
 5 
 
 07727 
 
 ... 
 
 ... 
 
 0-784 
 
 15 
 
 0-9189 
 
 0-963 
 
 0*969 
 
 0-965 
 
 49 
 
 0-7763 
 
 
 
 0-780 
 
 14 
 
 0-9239 
 
 0-970 
 
 o'976 
 
 0-972 
 
 48 
 
 0-7799 
 
 
 
 0-792 
 
 13 
 
 0*9289 
 
 0-977 
 
 ... 
 
 o-979 
 
 47 
 
 0-7834 
 
 
 
 0-795 
 
 12 
 
 0-9340 
 
 0-985 
 
 ... 
 
 0-986 
 
 46 
 
 0-7871 
 
 ... 
 
 
 0-799 
 
 II 
 
 0-9392 
 
 0-992 
 
 
 0-992 
 
 45 
 
 0-7907 
 
 
 
 0-803 
 
 IO 
 
 0-9444 
 
 I'OOO 
 
 ... 
 
 I'OOO 
 
 44 
 
 0-7944 
 
 0-794 
 
 
 0-807 
 
 9 
 
 0-9497 
 
 
 
 
 43 
 
 0-7981 
 
 0-799 
 
 ... 
 
 0-8II 
 
 8 
 
 0-9550 
 
 
 
 
 42 
 
 0-8618 
 
 0-804 
 
 
 0-816 
 
 7 
 
 0*9604 
 
 
 
 
 41 
 
 0-8061 
 
 0-809 
 
 
 0-820 
 
 6 
 
 0-9659 
 
 
 
 
 40 
 
 0-8095 
 
 0-814 
 
 
 0-824 
 
 5 
 
 0-9714. 
 
 
 
 
 39 
 
 0-8133 
 
 0-819 
 
 O - 824 
 
 0-829 
 
 4 
 
 0-9770 
 
 
 
 
 38 
 
 0-8173 
 
 0-825 
 
 0-829 
 
 0-834 
 
 3 
 
 0-9826 
 
 
 
 
 37 
 
 0-8212 
 
 0-830 
 
 0-834 
 
 0-839 
 
 2 
 
 0-9883 
 
 
 
 
 36 
 
 0-8252 
 
 0-835 
 
 0-839 
 
 0-844 
 
 I 
 
 0-9941 
 
 
 
 
APPENDIX. 
 
 The following scale is very often used for alcohol : 
 
 Gay-Lussac's Alcoholometer (Alcoornetre) at 15. 
 
 95* 
 
 Degree. 
 
 Sp. Gr. 
 
 Degree. 
 
 Sp. Gr. 
 
 Degree. 
 
 Sp. Gr. 
 
 Degree. 
 
 Sp. Gr. 
 
 IOO 
 
 0795 
 
 75 
 
 0-879 
 
 50 
 
 0-936 
 
 25 
 
 0-971 
 
 99 
 
 O'Soo 
 
 74 
 
 0-881 
 
 49 
 
 0-938 
 
 24 
 
 0-972 
 
 98 
 
 0-805 
 
 73 
 
 0-884 
 
 48 
 
 0-940 
 
 23 
 
 0-973 
 
 97 
 
 0-810 
 
 72 
 
 0-886 
 
 47 
 
 0-941 
 
 22 
 
 0-974 
 
 9 6 
 
 0-814 
 
 7i 
 
 0-888 
 
 46 
 
 0'943 
 
 21 
 
 0-975 
 
 95 
 
 0-818 
 
 70 
 
 0-891 
 
 45 
 
 0-945 
 
 20 
 
 0-976 
 
 94 
 
 0-822 
 
 69 
 
 0-893 
 
 44 
 
 0-946 
 
 19 
 
 0-977 
 
 93 
 
 0-826 
 
 68 
 
 0-896 
 
 43 
 
 0-948 
 
 18 
 
 0-978 
 
 92 
 
 0-829 
 
 67 
 
 0-899 
 
 42 
 
 0-949 
 
 17 
 
 0-979 
 
 9i 
 
 0-832 
 
 66 
 
 0-902 
 
 4i 
 
 0-951 
 
 16 
 
 0-980 
 
 90 
 
 0-835 
 
 65 
 
 0-904 
 
 40 
 
 0-953 
 
 15 
 
 0-981 
 
 89 
 
 0-838 
 
 64 
 
 0*906 
 
 39 
 
 0-954 
 
 14 
 
 0-982 
 
 88 
 
 0-842 
 
 63 
 
 0-909 
 
 38 
 
 0-956 
 
 13 
 
 0-983 
 
 87 
 
 0-845 
 
 62 
 
 0-911 
 
 37 
 
 0-957 
 
 12 
 
 0-984 
 
 86 
 
 0-848 
 
 61 
 
 0-913 
 
 36 
 
 0-959 
 
 II 
 
 0-986 
 
 85 
 
 0-851 
 
 60 
 
 0-915 
 
 35 
 
 0-960 
 
 IO 
 
 0-987 
 
 84 
 
 0-854 
 
 59 
 
 0-918 
 
 34 
 
 0-962 
 
 9 
 
 0-988 
 
 83 
 
 0-857 
 
 58 
 
 0-920 
 
 33 
 
 0-963 
 
 8 
 
 0-989 
 
 82 
 
 0-860 
 
 57 
 
 0-922 
 
 32 
 
 0-964 
 
 7 
 
 0-990 
 
 81 
 
 0-863 
 
 56 
 
 0-924 
 
 3i 
 
 0-965 
 
 6 
 
 0-992 
 
 80 
 
 0-865 
 
 55 
 
 0-926 
 
 30 
 
 0-966 
 
 5 
 
 0-993 
 
 79 
 
 0-868 
 
 54 
 
 0-928 
 
 29 
 
 0-967 
 
 4 
 
 0-994 
 
 78 
 
 0-871 
 
 53 
 
 0-930 
 
 28 
 
 0-968 
 
 3 
 
 0-996 
 
 77 
 
 0-874 
 
 52 
 
 0-932 
 
 27 
 
 0-969 
 
 2 
 
 0-997 
 
 76 
 
 0-876 
 
 5i 
 
 0-934 
 
 26 
 
 0-970 
 
 I 
 
 0-999 
 
 The weights and measures used in this book are given on the metric system. Their 
 value in comparison with English weights and measures is as follows : 
 
 1 5 '4384 grains 
 1-5438 grain 
 
 0-1543 ,, 
 
 0-0154 
 
 o-ooooi 
 I kilogramme, generally abridged kilo. = 2*2054 Ibs. avoirdupois 
 
 = 2-6803 Ibs. troy 
 
 100 kilos, or metric quintal = 220-5486^8. 
 jooo kilos, or metric ton = 2205-486 Ibs. 
 
 i gramme 
 
 i decigramme 
 
 i centigramme = 
 
 i milligramme 
 
 i micro-milligramme = 
 
 MEASURES OF CAPACITY. 
 
 i cubic centimetre (generally written c.c.) = i5'43 8 395 fluid grains (water) 
 1000 c.c. = i litre = 1760773 imperial pint; or, =0-2200967 imperial gallon 
 i cubic metre = 1-308 cubic yard; or, = 35'3 I 7 l cubia feet 
 i gallon of water (= 277-274 cubic inches) weighs 10 Ibs. 
 224 gallons = i ton 
 
 i cubic inch of water = 252-45 grains 
 mercury = 34 2 5' 2 5 
 
APPENDIX. 
 
 i metre 
 
 i millimetre = 
 
 i centimetre = 
 
 i decimetre = 
 
 i inch 
 
 i foot = 
 
 I yard = 
 
 i mile (1760 yards) = 
 
 1000 metres = 
 
 MEASURES OF LENGTH. 
 
 = 39-37079 inches = 3*2808992 feet = 1*093633 yard 
 
 = 0*03937 inch 
 
 = 0-393708 
 
 = 3'93779 inches 
 
 = 2-539954 centimetres 
 
 = 3-0479449 decimetres 
 
 0-91438348 metre 
 
 1609-3149 metres 
 
 i kilometre 
 
INDEX. 
 
 ABEL, F. A., analyses of fire-clay, 631 
 Abraum salts, 284 
 Acetic acid, 491 
 Acetometry, 496 
 Acid, acetic, 491 
 
 arsenic, 206, 450 
 process, 531 
 arsenious, 205 
 benzoic, 502 
 boric, 427 
 
 formation and production of, 428 
 butyric, 499 
 carbonic determinations, 48 
 
 in beer, quantity, 757 
 chromic, 470 
 citric, 502 
 
 colouring matters, 583, 587 
 colours, 584 
 crude carbolic, 511 
 formic, 498 
 hydrochloric, 313 
 
 treatment of bones with, 896 
 lactic, 500 
 nitric, 371, 379 
 
 applications, 383 
 densities, 382 
 oleic, conversion into palmitic acid 932 
 
 soap, 915 
 oxalic, 499 
 phthalic, 570 
 picric, 564 
 
 purification of chamber, 274 
 salicylic, 567 
 sulphuric, 262, 271, 282 
 concentration of, 275 
 green vitriol from, 473 
 sulphurous and sulphuretted hydrogen, sul- 
 phur from, 248 
 liquid, 259 
 tartaric, 500 
 valerianic, 499 
 Acids, fatty, boiler for distilling, 928 
 
 manufacture of, 930 
 organic, 491 
 
 sulphuric and sulphurous, 251 
 Adamantine, 434 
 Agate glass, 625 
 
 Ageing printed and dyed goods, 822 
 Air drains for preserving wood, 946 
 gas, 80 
 heating, 115 
 thermometers, 4 
 Alabaster glass, 624 
 
 Alberts' examination of gun-cotton, 397 
 Alcohol, properties of, 760 
 
 tables, 487 
 
 Alcoholic or vinous fermentation, 718 
 Alcoholometer, 951 
 
 Alcohols and ethers, 487 
 Alizarine, 573 
 
 blue, 851 
 
 Alkali, chloride of, 363 
 Alkalimetry, 300 
 
 Allary and Pellieux, obtaining iodine from sea- 
 weed, 370 
 Alloys, brass, 167 
 
 of aluminium, 223 
 
 of antimony, 205 
 
 of copper, 1 66 
 
 of gold, 195 
 
 of lead, 174 
 
 of silver, 187 
 
 Almaden mercury works, 208 
 Almond soap, 917 
 Aloe hemp, 812 
 Alpaca wool, 80 1 
 Alum, 435, 440, 443 
 
 chrome, 473 
 
 earths, 436 
 
 flour, 437 
 
 from alum shale and alum earths, 436 
 
 from alum stone, 435 
 
 from azolite, 438 
 
 from bauxite, 439 
 
 from blast-furnace slag, 439 
 
 from clay, 437 
 
 from felspar, 439 
 
 shale, 436 
 
 tanning, 886 
 
 works, green vitriol as a bye-product, 473 
 Aluminate of soda, 442 
 Aluminium, 221 
 
 acetates for calico-printing, 822 
 
 alloys, 223 
 
 bronzes, 223 
 
 hydrate, 443 
 
 properties of, 223 
 
 salts, 435, 443 
 
 soap, 918 
 
 sulphate, 441 
 
 Amagat's ebullioscope, 726 
 Amalgamation of silver, 175 
 Amalgam copper, 168 
 American grape sugar, 688 
 
 mineral oils, 907 
 
 America, North and South, oil springs, Si 
 Ammonia, 399 
 
 alum, 440 
 
 from beet sugar, 407 
 
 from bones, 406 
 
 from lant, 405 
 
 inorganic sources of, 400 
 
 in purified gas, determination, 78 
 
 organic sources of, 401 
 
 soda process, 339 
 Ammoniacal purifying, 76 
 
954 
 
 INDEX. 
 
 Ammoniacal salts, important, 407 
 Ammonium carbonate and nitrate, 409 
 
 sulphate, 409 
 
 Amorphous or red phosphorus, 416 
 Analyses of crude iron, 124 
 
 of fire-clay, 631 
 
 of purified gas, 39 
 
 of soda-lyes, 324 
 
 of soda residues, 329 
 
 of Upper Silesian coals, 26 
 
 of wine ash, 727 
 Analysis of beer, 758 
 
 of bottles, 596 
 
 of colourless strass, 622 
 
 of gas, complete, 78 
 
 of glass, 619 
 
 of Gleiwitz coke, 125 
 
 of sparkling wine, 732 
 Ananas hemp, 812 
 Anatomy of animal skin, 873 
 Andaquies wax, 906 
 Aniline, 528 
 
 black, 538 
 
 for cotton, 839 
 
 blue, 535 
 
 green, 537 
 
 oil, composition of, 530 
 
 red, 530 
 
 violet, 537 
 
 yellow, 538 
 Animal charcoal, filtration of beet-root juices 
 
 through, 700 
 
 manufacture, Berlin blue as a bye-pro- 
 duct, 479 
 
 fats, 904 
 Annatto, 523 
 Anthon, M., Longchamp, M., and Kuhlmann, M., 
 
 preparation of potassium nitrate, 376 
 Anthracene, 514 
 
 colours, 571 
 
 derivatives, 590 
 Anthracite, 25 
 Antichlore, 867 
 Antimony, 202 
 
 and tin compounds, 448 
 
 cinnabar, 450 
 
 compounds, 449 
 
 extraction of, 203 
 
 mordants, 825 
 
 oxide, 449 
 
 pentasulphide, 450 
 
 properties of, 204 
 
 Apel, W., apparatus for gas analysis, 50 
 Apparatus used in dyeworks, 826 
 Appolt Bros., coke-oven, 28 
 Arc light, estimating, 105 
 Arrowroot, 68 1 
 Arsenic, 205, 450 
 
 acid, 206, 450 
 
 process, 531 
 Arsenious acid, 205 
 Art-bronze, 167 
 Artificial colours, 584 
 
 Arts and manufactures, organo-chemical, 873 
 Asia, oil-wells in, 81 
 Aspdin, J., Portland cement, 669 
 Asphalte, 939 
 Assay of antimony ores, 205 
 
 of silver, 187 
 
 of tin ores, 200 
 Atakamite, 150 
 
 Atmospheric moisture, decomposition of, 1 19 
 Augustin's process for silver extraction, 177 
 Auramine printing, 851 
 
 Auramines, 557 
 
 Aurantia, 564 
 
 Aurine, 565 
 
 Australia, oil-wells, 81 
 
 Austria, method of obtaining wood-tar, 15 
 
 oil-wells in, 81 
 Aventurine glass, 598 
 Azele, 515 
 Azo colouring matters, 577 
 
 colours, 525, 588 
 
 direct production of, 851 
 
 dyes, 574 
 
 mixed, German patent, 578 
 Azuline, 565 
 Azurite, 150 
 
 BADEN ANILINE COMPANY, cotton dyeing, 837 
 Baking bread, 783 
 
 water for, 234 
 
 Balard's method for extracting sulphur, 245 
 Balata, 944 
 
 Balke, examination of barley, 743 
 Balling's saccharometrical beer test, 759 
 Bannow's boiling vessel, 510 
 Bar iron, 127, 131 
 Bark tanning, 874, 88 1 
 Barlow, process in printing, 849 
 Bartoli, A., and Papasogli, G., experiments on 
 
 coal, 19 
 
 Baryta, purifying juice of beet-root with, 700 
 Basic colouring matters, 585 
 
 ferric chromate, 473 
 
 hearth smelting, 140 
 
 lead chloride as a substitute for white lead, 
 
 467 
 Baum and Schlieper, process for indigo-printing, 
 
 847 
 
 Baume, M., densities of nitric acid, 383 
 Bauxite, alum from, 439 
 Bean ore, 1 14 
 
 Bedarieux black for wool, 835 
 Beech oil, 906 
 Beer, analysis of, 758 
 
 brewing, 735 
 
 cellars, construction of, 736 
 
 constituents, 757 
 
 quantity of carbonic acid in, 757 
 
 testing, 758 
 
 wort, fermentation of, 753 
 Beeswax, 906 
 Beet sugar, 692 
 
 ammonia from, 407 
 
 treacle, 708 
 
 Belgian system for zinc distillation, 212 
 Bell-metal, 166 
 Benrath, M., analysis of glass, 619 
 
 analysis of plate-glass, 612 
 Benzene, 511 
 Benzoic acid, 502 
 Benzol colours, 528 
 Berlin blue, 478 
 
 for wool, 832 
 Bernthsen violet, 563 
 Berries, various, used for dyeing, 523 
 Berthelot's researches on fats, 903 
 
 on soap, 912 
 Bessemer converter, copper ores worked in, 156 
 
 steel, 133 
 
 Bethell's method of preserving wood, 948 
 Biebrich scarlet, 577 
 Bismarck brown, 574 
 Bismuth, 201 
 
 ores, treatment, 202 
 
 properties of, 202 
 
INDEX. 
 
 955 
 
 Bismuth, uses, 202 
 Bittering wine, 728 
 Black, aniline, 538 
 
 antimony sulphides, 449 
 
 colours, 523 
 
 dye for cotton, 839 
 
 dyeing wool, 834 
 
 silk dyeing, 835 
 
 topical, 849 
 
 woollen, 578 
 
 Bias and Miest, working up zinc blende, 216 
 Blast furnace heat, conditions of, 117 
 
 furnaces, 114 
 
 Bleach and dye works, water for, 231 
 Bleaching, 815 
 
 glass, 601 
 
 machine, continuous, 818 
 Blende furnace for roasting, 256 
 
 process for working up, 216 
 Blister copper, 155 
 Blue alizarine, 573, 851 
 
 and green mineral, 457 
 
 aniline, 535 
 
 Bremen, 456 
 
 colouring matters, 519 
 
 Egyptian, 459 
 
 fayence, 845 
 
 green, 481 
 
 indigo, 521 
 
 methylene, 558 
 
 neutral, 564 
 
 new, 558 
 
 oil, 457 
 
 Paris or neutral Berlin, 478 
 pencil, 845 
 Prussian, 477 
 quinoline, 566 
 silk dyeing, 836 
 steam, 847 
 stone, 454 
 
 vats for woollen, 830 
 vitriol, 454 
 woollen dyeing, 829 
 Blues, siliceous, 447 
 Blum, E., and Griineberg, H., stairs column for 
 
 gas liquor, 404 
 Blumsky and Julian, boiler for distilling fatty 
 
 acids, 928 
 Bock, M., brick furnace, 655 
 
 saponiflcation of fats, 932 
 Boetius, gas firing of, 42 
 Boghead coal, 25 
 
 Bohemia, method of obtaining wood tar, 15 
 Bohm's mashing apparatus, 763 
 Boiler, roller, 85 
 
 steam, duty of, 59 
 
 size of grate, 58 
 waggon, 84 
 
 Boiling-point, determination, 3 
 Bombay hemp, 811 
 Bone black, 900 
 glass, 624 
 glue, 896 
 meal, 424 
 soap, 917 
 Bones, 899 
 
 ammonia from, 406 
 
 Bontemps, manufacture of flint glass, 621 
 Booth, furnace for melting alloys, 195 
 Borax, 427, 429 
 
 from boric acid, 430 
 octahedral, 432 
 prismatic, 430 
 purifying, 431 
 
 Borax, uses of, 433 
 Bordeaux reds, 589 
 Boric acid and borax, 427 
 
 formation and production of, 428 
 Botsch, Congo colours, 850 
 Bottle glass, 595, 615 
 Bottles, manufacture, 605 
 Boucherie's method of preserving wood, 948 
 Bovey coal, 19 
 Bradford oil, 82 
 Brass, 167 
 Bread and flour, 781 
 
 impurities and adulterations, 785 
 
 making and baking, modes and details, 781 
 
 yield and composition, 785 
 Bremen blue or green, 456 
 Breweries, water for, 230 
 Brewing, 753 
 Brick and tile making, 650 
 
 furnaces, 652 
 
 kilns, 656 
 
 Bricks, green eruptions, 634 
 Brine, common salt from, 306 
 Briquettes, block coal, 35 
 Brockhaus, M., experiment with potato spirit, 
 
 780 
 Bromine, 365 
 
 properties and applications of, 368 
 Bronze, art, 167 
 
 cobalt, 147 
 
 colours, 168 
 
 phosphor, 167 
 Bronzes, aluminium, 223 
 Brown, J., analysis of soda-lyes, 326 
 
 coal, 19, 92 
 
 green and black colours, 523 
 
 phenyl, 565 
 
 Biichner's researches on barks for tanning, 875 
 Buff-Dunlop, lixiviation apparatus, 321 
 Bunsen, electrolytically prepared magnesium, 224 
 
 photometer, 95 
 
 Burnett's preserving fluid for wood, 947 
 Burning clays, change of colour, 634 
 Butter, 788 
 
 artificial, 789 
 Butyric acid, 499 
 
 CADMIUM, 217 
 
 alloys, 218 
 
 and zinc compounds, 459 
 
 detection of, 218 
 
 yellow, 461 
 Calcium soap, 918 
 
 sulphite, 261 
 Calico-printing, 843 
 Canada, oil-springs, 81 
 Canarine, 581 
 Candles, lighting with, 98 
 Cane sugar, 689 
 Caoutchouc, 939 
 
 and gutta-percha, mixture of, 944 
 Capacity, measures of, 952 
 Carbolic acid, crude, 511 
 Carbonate of potassium, production of, 286 
 
 of soda, 346 
 Carbon dioxide, determination, 78 
 
 disulphide, 249 
 
 properties of, 250 
 
 gasification of, 43 
 
 in iron, determining, 124 
 
 sulphur from sulphurous acid and, 249 
 Carbonic acid, determinations, 48 
 
 in beer, quantity, 757 
 Carbonisation steel, 142 
 
956 
 
 INDEX. 
 
 Carmine alizarine, 573 
 
 Carnauba wax, 907 
 
 Carnot, A., researches on the quality of coal, 24 
 
 Carrara porcelain, 645 
 
 Carthamine, 516 
 
 Casali green, 473 
 
 Cashmere wool, 80 1 
 
 Casks, after-fermentation of beer in, 755 
 
 Cassava starch, 68 1 
 
 Casselmann's green, 457 
 
 Cassel yellow, 467 
 
 Cassius's purple, 452 
 
 Castner, reduction of sodium, 219 
 
 Cast steel, 142 
 
 Caustic, lunar, 452 
 
 potash, 299 
 Ceollpa soda, 309 
 Celluloid, 944 
 
 Cellulose, chemical production, 862 
 Cement, copper, composition of, 158 
 
 Portland, 669 
 
 steel, 142 
 
 testing, 673 
 Cements, mixed, 675 
 Centrifugal A for sugar, 706 
 
 machine, 721 
 
 Ceramic manufacture, 628 
 Cereals, vinous mash from, 764 
 Ceruleine, 579 
 Chalkosine, 150 
 
 Champagne bottles, manufacture of, 731 
 Chance, analysis of soda residues, 330 
 
 recovery of sulphur, 337 
 Chapman, E. T., and Wanklyn, J. A., examination 
 
 of water, 228 
 Charcoal, manufacture of wood, 12 
 
 moulded, 35 
 
 ovens, 14 
 Cheese, 790 
 
 Chemical alteration in the constituents of the 
 sap in preserving wood, 947 
 
 composition of silk, 804 
 of wool, 801 
 
 constituents of beet, 693 
 of must, 721 
 
 examination of bar iron, 131 
 
 means, soda obtained by, 310 
 
 nature of butter, 789 
 
 principles of pyrotechny, 390 
 
 production of cellulose, 862 
 
 purification of kerosene, 85 
 
 works of Leopoldshall, apparatus for distill- 
 ing bromine, 366 
 ChemicaSy pure gold, 195 
 
 pure silver, 186 
 Chestnut starch, 681 
 Chevreul's researches on soap, 911 
 China blue style, 845 
 Chinese galls, 876 
 
 grass, use of, 810 
 
 wax, 906 
 
 Chloral hydrate, 491 
 Chlorates, 347 
 Chloride of alkali, 363 
 
 of lime, 347, 358 
 liquid, 359 
 properties, and loss of value, 360 
 
 of mercury, 453 
 
 of potassium, preparation of, 283 
 
 of sulphur, 251 
 
 of tin, 449 
 
 of zinc, 460 
 Chlorination, 192 
 Chlorine, 347 
 
 Chlorine, bleach, 815 
 
 properties and uses, 358 
 Chloroform, 490 
 Chlorometric degrees, 362 
 Chlorometry, 361 
 
 Christy, chemical production of cellulose, 863 
 Chromate of zinc, 460 
 Chromates, 469 
 Chrome alum, 473 
 
 green, 472 
 
 mordants, 824 
 
 red, 471 
 
 yellow, 470 
 Chromic acid, 470 
 
 hydrate, 472 
 Chromium chloride, 473 
 
 compounds, 469 
 Cider, 735 
 Cinnabar antimony, 450 
 
 or vermilion, 453 
 Cinnamon brown, 574 
 Citric acid, 502 
 
 Clarke, process for softening water, 237 
 Glaus, ammoniacal purifying, 76 
 Clay, alum from, 437 
 
 pipes, 649 
 
 ware, varieties of, 637 
 Clays and their application, 628 
 
 behaviour of, in working, 633 
 
 change of colour in burning, 634 
 
 plastic, 630 
 
 various kinds, 630 
 
 Clichy, apparatus for preparing white lead, 463 
 Coal, 23 
 
 analyses of, 26 
 
 block, 35 
 
 boghead, 25 
 
 brown and Bovey, 19, 92 
 
 coking of small, 27 
 
 combustion value of, 24 
 
 fields of the world, 24 
 
 formation and location, 23 
 
 gas, desulphurising, 76 
 heating with, 65 
 
 manufacture, Berlin blue as a bye-pro- 
 duct, 479 
 
 products of degasification, 36 
 
 researches on the quality, 24 
 
 tar colours, printing, 850 
 
 treatment, 502 
 Cobalt, 145 
 
 bronze, 147 
 
 colours, 145 
 
 green, 146 
 
 pure protoxide of, 147 
 
 speiss, 146 
 
 ultramarine, 146 
 
 yellow, 147 
 Cochineal, 516 
 Cocoa-nut fibre, 812 
 
 oil soap, 915 
 Cocoons, sorting, 805 
 Creruleum, 146 
 Cognac, analysis, 780 
 
 Cohn, H., quantity of light for reading, 104 
 Coke generator, 41 
 
 Gleiwitz, analysis of, 1 25 
 
 object of making, 26 
 
 oven of Appolt Bros., 28 
 
 ovens at Pluto Mine, 32 
 closed, 27 
 
 to gasify, 41 
 Coking in heaps, 26 
 
 of small coal, 27 
 
INDEX. 
 
 957 
 
 Collodion cotton, 398 
 Colorimeter for beer, 759 
 Colorimetric test for kerosene, 86 
 Colorine, 576 
 Coloured fires, 392 
 
 glasses, 598, 622 
 
 resists, 844 
 
 Colouring matters, examination, 582 
 fiuoresceine, 547 
 insoluble in water, 591 
 on the fibre, detection of, 852 
 organic, 514, 579 
 phenol, 564 
 
 Colour-pans for laboratories, 826 
 Colours, anthracene, 571 
 
 artificial, acid, &c., 584 
 
 azo, direct production of, 851 
 
 benzol, 528 
 
 coal-tar, printing with, 850 
 
 Congo, 850 
 
 naphthaline, 567 
 
 phenol, 564 
 
 steam, 847 
 
 topical, 849 
 
 weed, 517 
 Colza oil, 906 
 Combustion, 35 
 Concrete, 675 
 Congo colours, 850 
 
 red, 575 
 
 Congreve's granulating machine, 386 
 Copper, 150 
 
 alloys, 166 
 
 amalgam, 168 
 
 blister, 155 
 
 cement, 158 
 
 compounds, 454 
 
 matte, roasting, 152 
 
 ores, sulphur from roasting, 248 
 
 worked in Bessemer converter. 156 
 
 pigments, 455 
 
 production in the dry way, 151 
 in the wet way, 157 
 
 properties of, 165 
 
 refining, 153, 161 
 
 in the United States, 155 
 
 slate, 150 
 
 smelting, English system, 154 
 
 stannate, 458 
 
 sulphate, 454 
 Copperas, 473 
 
 and logwood blues for wool, 833 
 Coprolites, 426 
 Coralline, 565 
 Cordials, preparation, 936 
 Cordwain leather, 885 
 
 Cork, use of, for raising the grain of leather, 883 
 Cotton, bleaching, 817 
 
 detection in linen fabrics, 813 
 
 dyeing, 837 
 
 fabrics, adulteration, 815 
 
 oil, 906 
 
 species and substitutes, 812 
 Coupler, distillation apparatus, 509 
 
 process for magentas, 534 
 Cowles Bros., process for aluminium, 222 
 Crackle glass, 624 
 Cresol, 512 
 Crookes, W., freezing of glycerine, 934 
 
 gold extraction process, 190 
 
 Odling, W., and Tidy, C. M., examination 
 of water, 228 
 
 treating refractory gold ores, &c., 191 
 Cross, bleaching jute, 820 
 
 Cross, Witz, and Schmidt, cotton dyeing, 837 
 Crown glass, 610 
 Crucibles, manufacture, 659 
 Cryolite, alum from, 438 
 
 decomposition of, 438 
 
 glass, 624 
 
 soda, 343 
 Crystal glass, 619 
 Cupellation, 187 
 Cupola furnace, 151 
 Curd soap, 913 
 Currying leather, 883 
 Cutch, 876 
 
 Cyanide of potassium, 477 
 Cylinder glass, 611 
 
 DAMASCUS steel, 144 
 
 Deacon and Hurter, caustic soda, 345 
 
 process for obtaining chlorine, 350 
 Degasified wood, 12 
 Degasifying, 35, 36 
 Dempwolf , M. 0. , preparation of wheat starch, 
 
 679 
 
 Descotils, method of extracting platinum, 197 
 Desilvering work-lead by electricity, 185 
 Desormes, C., lixiviation apparatus, 319 
 Deville, H., and Wohler, M., observations on. 
 
 adamantine, 434 
 Dextrine, 677, 683 
 Diamond-boron, 434 
 Didier and Hasse, furnaces, 73 
 Dieter, M., working up wine-lyes, 501 
 Dingler's green, 472 
 Dinitrodibromfluoresceine, 554 
 Discharges used in printing, 845 
 Distillation of spirits, 767 
 Distilleries, water for, 230 
 Disulphide of carbon, 249 
 properties of, 250 
 Dividivi, 875 
 
 Dobereiner, production of fire, 417 
 Domestic and municipal supplies, water for, 233 
 Dotsch, process for copper, 158 
 Dougal, boiler furnace grate, 61 
 Drayton's process for silvering plate glass, 614 
 Droux, L., saponification, 924 
 Drummond light, 104 
 
 Dujardin's refining apparatus for sulphur, 247 
 Dumas, M. , composition of crystal glass, 619 
 
 experiments on glass, 592 
 " Dunging" printed and dyed goods, 823 
 Dunlop, process for obtaining chlorine, 347 
 Dupre, ejection apparatus, 284 
 Diirre, lixiviation apparatus, 321 
 Dyar and Hemming, soda-ammonia process, 340 
 Dye and bleach works, water for, 231 
 
 stuffs, naphthaline, 567 
 
 works, apparatus used, 826 
 Dyeing and tissue-printing, 821 
 
 cotton, 837 
 
 linen, 839 
 
 silk, 835 
 
 wool black, 834 
 blue, 829 
 green, 834 
 red, 833 
 yellows, 833 
 
 woollens, 829 
 Dynamite, 395 
 
 EAKTHENWAKE manufacture, 628 
 
 production of, 636 
 
 stoves, 62 
 Earth-nut oil, 906 
 
95* 
 
 INDEX. 
 
 Ebullioscope, 725 
 
 Edinburgh and Leith, composition of crystal 
 
 glass in, 619 
 Egyptian blue, 459 
 Eichhorn and Liebig, furnace for roasting 
 
 blende, 256 
 
 Ekman, chemical production of cellulose, 862 
 Electrical tanning, 889 
 Electricity, desilvering work-lead by, 185 
 
 obtaining and refining copper by, 161 
 
 production of zinc by, 214 
 Electric lighting, 105 
 
 production of lead, 172 
 
 thermometers, 5 
 
 Electrolysis, use in tissue-printing, 848 
 Electrolytic extraction of antimony, 204 
 Electro-plating, 188 
 Eliquation, 153 
 Emerald green, 457, 543 
 Enamel, 624 
 Enargite, 150 
 Enfleurage, 938 
 English apparatus for tar distillation, 508 
 
 borax, 432 
 
 fritte porcelain, 644 
 
 method of manufacturing white lead, 463 
 of obtaining zinc, 214 
 
 process for the production of lead, 169 
 
 system of copper smelting, 1 54 
 Envelopes, inferior paper for, 860 
 Eosine, 551 
 Erythrosine, 556 
 Escherich's ring furnace, 655 
 Essen, generator gas made at, 47 
 Essential oils, 935 
 Etching glass, 626 
 Ether, 491 
 
 Ethers and alcohols, 487 
 Ethyl alcohol, 487 
 Etruscan vases, 649 
 
 Europe, various oil wells and springs, 8l 
 Explosives, 384 
 
 FAHL ores, 150 
 
 Fahnehjelm's " globe light," 103 
 
 Fahrenheit's thermometer, 2 
 
 Faist, analysis of merino wool, 801 
 
 Faraday, M., analysis of glass, 619 
 
 Farin, 707 
 
 Fats, 903 
 
 animal, 904 
 Fat varnishes, 909 
 Fatty resists, 844 
 Faure and Kessler, platinum lead concentrator, 
 
 280 
 Fayence blue, 845 
 
 ware, 647 
 
 Feichtinger and Winkler, Portland cement, 672 
 Felspar, 628 
 
 alum from, 439 
 Fermentation, 712, 718 
 
 of spirits, 766 
 
 Ferric chromate, basic, 473 
 Ferricyanide of potassium, 477 
 Ferrocyanide of potassium, 474 
 Feser, J., researches on barks for tannin, 875 
 Filigree glass, 625 
 Filters, 234 
 Fire bricks, 657 
 
 clays, 631 
 Fires, domestic and industrial, combustion in, 50 
 
 for house heating, 61 
 
 Firework mixtures more commonly used, 390 
 Firing, steam boiler, 58 
 
 Fisher, 0., bleaching and dyeing machine, 827 
 Fish glue, 898 
 
 oil, 904 
 
 Flach's proposal for extracting silver, 180 
 Flashing-point of oils, determination, 86 
 Flavaniline, 526, 538 
 Flavaurine, 565 
 Flax, spinning, 809 
 
 use and treatment, 808 
 Flaxes. New Zealand, 811 
 Fletcher, grate for boiler furnace, 60 
 Flint glass, 621 
 
 soap, 917 
 
 Flooring tiles, 657 
 Flour and bread, 781 
 Flowers of madder, 515 
 Flue dust, lead, 172 
 Fluoresceine, 539 
 
 colouring matters, 547 
 Food, articles of, 676 
 Foods, value of certain, 799 
 Formic acid, 498 
 Forster, B., and Wara, F. A., " non-poisonous " 
 
 match, 423 
 Frank, A., distillation of bromine, 365 
 
 preparation of potassium chloride, 283 
 Franklinite, 114 
 French berries, 523 
 
 method of preparing white lead, 463 
 Fresenius, K., and Will, commercial value of 
 
 potash, 301 
 
 Friesner, reagent for wood, 865 
 Fritsch's machine for parchmentising paper, 871 
 Fuel and its treatment, I 
 Fuels, behaviour when heated, 35 
 
 determination of the value, 6 
 Fuller's earth, 631 
 Furnace, blast, 1 14 
 
 cupola, 151 
 
 for melting gold and silver alloys, 195 
 
 puddling, 130 
 
 reverberatory, 126 
 
 smelting, 117, 154, 169 
 
 soda, rotating, 317 
 Furnaces, brick, 652 
 
 for mercury in America, 208 
 
 for the production of lighting gas, 73 
 
 salt cake, 311 
 
 sulphate, 312 
 Fustic, 522 
 
 GALLEINE, 579 
 
 Gallocyanine, 558 
 
 Galloflavine, 580 
 
 Gall's apparatus for distillation, 770 
 
 Galls, Chinese, 876 
 
 Galvanic gilding, 197 
 
 Garancine, 515 
 
 Gareis, J., apparatus for small gas works, 405 
 
 Gas, air, 80 
 
 analyses of purified, 39 
 
 analysis, 50 
 
 burners, materials and construction, 101 
 
 fires, 41 
 
 firing, 66 
 
 for bricks, 655 
 
 in metallurgy, &c., 71 
 
 of Boetius, 42 
 
 for lighting, production, 72 
 
 formation in the generator, 66 
 
 generator, 41 
 
 lighting, 71, 101 
 
 liquor, stairs column for, 404 
 
INDEX. 
 
 959 
 
 Gas manufacture, boghead coal as fuel in, 25 
 
 natural, 82 
 
 composition from various sources, 82 
 
 oil, 80 
 
 oven for glass, 604 
 
 peat, 79 
 
 purification, 75 
 
 resin, 79 
 
 sulphur, 248 
 
 to preserve samples, 56 
 
 wood, 79 
 
 works, small apparatus for, 405 
 Oases, composition of the roasting, 259 
 
 generator, composition of, 70 
 Gasifying, 35 
 
 Gatty's process for obtaining chlorine, 348 
 Gay-Lussac, alcoholometer, 951 
 
 assay of silver, 187 
 
 denitrificator, 266 
 
 method of chlorometry, 361 
 
 tower, 271 
 Gelatine, 892 
 Generator gas, 41 
 Geneva black for wool, 835 
 German borax, 433 
 
 silver, 168 
 
 starch sugar, analysis, 688 
 
 stoves, 62 
 
 Germany, oil wells in, 81 
 Gerstenhofer, roasting kilns for sulphuric acid, 
 
 254 
 
 Gilding, 196 
 
 Gillard's " platinum gas," 103. 
 Girofle", 564 
 Glass, agate, 625 
 
 alabaster, 624 
 
 analyses, 594, 619 
 
 aventurine, 598 
 
 blowers' tools, 610, 615 
 
 bone, 624 
 
 cryolite, 624 
 
 defects in, 608 
 
 denitrification, 598 
 
 etching, 626 
 
 filigree, 625 
 
 flint, 621 
 
 furnace, 603 
 
 hardened, 616 
 
 ice, 624 
 
 iridescent, 625 
 
 lime, alumina, 596 
 
 making, raw materials used in, 600 
 
 manufacture, 592 
 
 melting, 607 
 furnace, 68 
 vessels for, 602 
 
 muslin, 625 
 
 optical, 620 
 
 painting, 623 
 
 pearls, 625 
 
 phosphatic, 596 
 
 physical properties, 600 
 
 polishing, 620 
 
 potash, 593 
 
 pressed and cast, 616 
 
 refuse, utilisation of, 602 
 
 relief, 625 
 
 satin, 623 
 
 soda, 593 
 
 solubility of, 596 
 
 soluble, 617 
 
 staining, 622 
 
 various kinds, 609 
 Glasses, coloured, 598, 622 
 
 Glasses, Venetian mosaic, composition, 600 
 
 Glauber's salt, manufacture of, 285 
 
 Glaze, porcelain, 640 
 
 Glove leather, 888 
 
 Glover tower, 267 
 
 Gluckelberger, precipitation of sulphur, 335 
 
 Glue, drying, 895 
 
 substitutes, 899 
 
 tests of quality, 897 
 
 water for the manufacture of, 231 
 Glycerine, 921, 933 
 
 in sweet wines, determination, 727 
 Gold, 188 
 
 alloys, 195 
 
 and silver printing, 849 
 
 production in 1884 : 186 
 
 chemically pure, 195 
 
 deposits, 189 
 
 extraction, 189 
 
 mosaic, 448 
 
 ore, &c., process for treating refractory, 191 
 
 proof, 195 
 
 properties of, 195 
 
 purple, 452 
 
 ruby glass, 599 
 
 salts of, 452 
 
 separation of, 194 
 
 silver, and mercury compounds, 452 
 
 soap, 919 
 
 Goodyear, M. , caoutchouc, 943 
 Goose greast, 904 
 
 Goppelsroder, use of electrolysis in tissue-print- 
 ing, 848 
 
 Gossage, closed reverberatory, 311 
 Grain soap, 912 
 Graining leather, 883 
 Grains used for beer, 735 
 Grape-juice fermentation, 723 
 
 sugar, 684, 722 
 Grapes, pressing, 720 
 Grass bleach, 815 
 
 Chinese, 810 
 Grate, chain, 60 
 
 shape of, for boiler furnace, 60 
 Grates, oblique, 60 
 
 polygon, 60 
 Green, aniline, 537 
 
 Bremen, 456 
 
 Casali, 473 
 
 Casselmann's, 457 
 
 cobalt, 146 
 
 colours, 523 
 
 converted into blue ultramarine, 446 
 
 Dingler's, 472 
 
 dyeing wool, 834 
 
 emerald, 457, 543 
 
 eruptions on bricks, 634 
 
 Guignet's, 472 
 
 liquid, 543 
 
 malachite, 539 
 
 quinoline, 566 
 
 Scheele's, 457 
 
 silk dyes, 837 
 
 steam, 847 
 
 ultramarine, preparation, 445 
 
 vitriol, 473 
 Greens, blues, 481 
 
 Griineberg, H., and Blum, E., stairs column for 
 gas liquor, 404 
 
 ammonia apparatus, 402 
 Gruner, L., technical value of a coal, 26 
 Gschwandler, J., composition of certain beer, 
 
 756 
 Guano, 424 
 
g6o 
 
 INDEX. 
 
 Guignet's green, 472 
 Gum, boiling out of silk, 806 
 Gun-cotton, 395 
 metal, 167 
 powder, 384 
 
 composition and products of combus- 
 tion, 388 
 properties, 387 
 Gutta-percha, 942 
 
 and caoutchouc, mixture of, 944 
 Gypsum, 660 
 uses, 663 
 
 HALSKE AND SIEMENS, measuring electric light, 
 
 105 
 
 Hanover, oil wells in, 81 
 Hansen, E. C., yeast, 714 
 Harcourt, M., experiments on optical glass, 
 
 620 
 
 Hard soap, 912 
 Hartmann, M., and Hauer, M., apparatus for 
 
 determining the value of vinegar, 496 
 Hasenclever and Helbig, kiln, 255 
 Hasse and Didier, furnaces, 73 
 Hauer, M., and Hartmann, M., apparatus for 
 
 determining the value of vinegar, 496 
 Heat, diffusion of, 5 
 Heating arrangements, 50 
 
 with coal gas, 65 
 
 with hot air, 63, 65 
 
 with open fires, 61 
 Hehner, O., alcohol tables, 487 
 Helbig and Hasenclever, kiln, 255 
 Heinatinon, 598 
 
 Hemming and Dyar, soda-ammonia process, 340 
 Hemp, 810 
 
 various kinds, 81 1 
 Henze's mashing apparatus, 763 
 Hess, apparatus for determining the stability of 
 
 explosives, 397 
 
 Heupel, gas firing for lignite, 66 
 Hides for tanning, treatment, 878 
 History of lighting gas, 7 1 
 Hoffmann and Licht, brick furnace, 652 
 Hoffmann, G., combination of coke-ovens with 
 Siemens' heat reservoirs, 30 
 
 P. W., recovery of sulphur, 334 
 Hollefreund, M., mashing apparatus, 762 
 Holliday, T., & Sons, direct production of azo 
 
 colours, 851 
 Hops, 736 
 
 adding to beer, 750 
 
 substitutes for, 737 
 Hornig's researches on cheese, 792 
 Hot-air heating, 63, 65 
 
 oven, 22 
 
 House heating, 61 
 
 Hubner's method of preparing paraffine, 92 
 Hummel, Lepetit, Lenz, and Martin, detection of 
 
 colouring matters on the fibre, 852 
 Hungarian tawing, 888 
 Hurter and Deacon, caustic soda, 345 
 
 process for obtaining chlorine, 350 
 Hydraulic admixtures, 674 
 
 mortar, 668, 671 
 Hydrochloric acid, 313 
 
 treatment of bones with, 896 
 Hydrogen, amalgamation for gold, 191 
 
 sulphuretted, and sulphurous acid, sulphur 
 
 from, 248 
 sulphur from, 249 
 Hydrometer tables, 949 
 Hydrometers, various, 487 
 Hygrothermant, 729 
 
 ICE and water, 226 
 
 glass, 624 
 
 machines, evaporation, 242 
 
 manufacture, 242 
 Idria mercury works, 207 
 
 Ilge, K., continuous distillation apparatus, 775. 
 Indamines, 525 
 India-rubber, 941 
 Indigo, 519, 522 
 
 blue, 521 
 
 dyeing woollen, 830 
 
 printing, 847 
 Indophenol, 558 
 Induline, 526, 564 
 
 Industries based on alcoholic fermentation, 719 
 Ink, marking, 452 
 
 printing, 909 
 Inks, writing, 524 
 
 Inorganic pigments, conspectus of, 480 
 Iodine, 368 
 
 properties and uses, 371 
 Iron, 113 
 
 and steel, castings, 143 
 examination of, 124 
 
 compounds, 473 
 
 crude, 114, 123 
 
 melting-heat, 119 
 
 determining, silicon and sulphur, 124 
 total carbon in, 124 
 
 founding, 125 
 
 metallic, green vitriol from, 473 
 
 minium, 474 
 
 mordants, 823 
 
 ore, spathic, green vitriol from, 474 
 
 oxide, purifying gas with, 76 
 
 putty, 911 
 
 pyrites, sulphur from, 247 
 
 refining, 129 
 
 spar, 113 
 
 wrought or bar, 127, 131 
 Ironstone, magnetic and red, 113 
 Isambert, M., reaction during the production of 
 
 ammonia, 400 
 Isinglass, 898 
 Italian kiln, 13 
 
 ores, extracting sulphur from, 245 
 
 JACQUELAIN, analysis of anthracite, 25 
 
 Japan wax, 907 
 
 Jensen, E., analyses of ash of Upper Silesian 
 coals, 26 
 
 Jetoline, 538 
 
 Josephsthal paper works, apparatus for obtain- 
 ing chlorine, 347 
 
 Juices of beet-root, treatment, 695 
 
 Julian and Blumsky, boiler for distilling fatty 
 acids, 928 
 
 Julius and Schultz, arrangement of most im- 
 portant tar-colours, 525 
 
 Jurisch, analyses of soda-lyes, 325 
 
 Jute, 811 
 
 bleaching, 820 
 
 KAINITE, 286 
 
 Kaolins, composition of, 629 
 
 Karmarsch, assay of silver alloys, 187 
 
 Kefyr, 788 - 
 
 Keith's process for refining lead by electrolysis, 
 
 173 
 Keller, F. G., mechanical wood-stuff for paper, 
 
 860 
 
 Kerosene, chemical purification of, 85 
 Kessler and Faure, platinum lead concentrator, 
 
 280 
 
 ' 
 
INJ3EX. 
 
 961 
 
 Kiln, porcelain, 641 
 Kilns, 12, 14 
 
 brick, 656 
 
 for gypsum, 66 1 
 
 various, for lime, 665 
 Kind, A., saponification, 922 
 King's yellow, 206 
 Kino, 877 
 
 Kjeldahl's process for determining nitrogen, 7 
 Klonne and Liegel, furnaces for lighting gas, 73 
 Knapp, F., researches on soap-making, 913 
 Knapp's leather, 889 
 Knox, furnace for mercury, 209 
 Koechlin, C. , cotton mordant, 838 
 
 H., cotton bleaching, 818 
 Kolb, bleaching linen, 820 
 
 J., densities of nitric acid, 382 
 Korschelt, manufacture of fatty acids, 931 
 Kosmann, production of zinc, 215 
 Kreusler, analytical errors from the alkaline re- 
 action of glass, 598 
 Krigar furnaces, 125 
 Kroncke, process for silver, 176 
 Kuhlmann, M., Longchamp, M., and Anthon, M., 
 
 preparation of potassium nitrate, 376 
 Kurtz, converting neutral potassium tartrate into 
 
 the calcium salt, 500 
 Kyan's preserving fluid for wood, 947 
 
 LAC dye, 517 
 Lacmoid, 557 
 Lacquered leather, 885 
 
 ware, 647 
 Lacquers, 910 
 Lactic acid, 500 
 Lactose, 787 
 Lampblack, 581 
 Lamps, lighting with, 98 
 
 oil used for, 99 
 
 various forms of, 99 
 Lant, ammonia from, 405 
 Lapis styles, 844 
 Lather soaps, 917 
 Laurent's apparatus for raising sulphuric acid, 
 
 268 
 
 Lauth's violet, 563 
 
 Le Chatelier, setting of hydraulic mortars, 673 
 Lead, 169 
 
 alloys, 174 
 
 chambers, 263, 270 
 
 formation of sulphuric acid in, 271 
 
 chloride, white lead from, 467 
 
 chromate, 470 
 
 compounds, 461 
 
 ore washings at Alternau, 170 
 
 oxide, 461 
 
 peroxide, 462 
 
 production, 174 
 
 by electricity, 172 
 
 properties of, 173 
 
 red, 461 
 
 smelting furnace, 169 
 
 sulphate, 467 
 
 white, 463 
 Leather dressing, 883 
 
 finishing and greasing, 884 
 
 glue, 893 
 
 various kinds, 883 
 Leblanc, process for obtaining soda, 310, 329 
 
 soda residues, utilisation of, 329 
 Lebon's " thermo lamp," 79 
 Leeds, examination of soap, 918 
 Leicht's malt kiln, 741 
 Length, measures of, 952 
 
 Lenz, Martin, Hummel, and Lepetit, detection of 
 
 colouring matters on the fibre, 852 
 Lepetit, Lenz, Martin, and Hummel, detection of 
 
 colouring matters on the fibre, 852 
 Leroy and Durand, saponification at candle 
 
 works, 926 
 L6trange, L., production of zinc by electricity, 
 
 214 
 
 Leuko-base, production of, 540, 544 
 " Levuline " blue, 850 
 Leyser, 0., colorimeter for beer, 759 
 Licht and Hoffmann, brick furnace, 652 
 Liebig, researches on preserving meat, 795 
 
 and Eichhorn furnace for roasting blende, 
 
 256 
 M., and Von Lerrner, M., researches on 
 
 brewing, 753 
 
 Liegel and Klonne, furnaces for lighting gas, 73 
 Light, intensity of, 107 
 production of, 94 
 units, 96 
 Lighting gas, 71 
 
 checking the process of manufacture, 
 
 78 
 
 with candles, 98 
 with lamps, 98 
 Lignite, 19 
 
 gas-firing for, 66 
 
 Lignites, average composition, 20 
 Lime, 664 
 
 alumina glass, 596 
 burning, 665 
 chloride of, 347, 358 
 liquid, 359 
 
 properties, and loss of value, 360 
 Limonite, 114 
 
 Lindt's researches on cheese, 791 
 Linen, 810 
 
 bleaching, 820 
 dyeing, 839 
 
 fabrics, detection of cotton in, 813 
 printing, 851 
 Linseed-oil varnish, 908 
 Liquid glue, 897 
 
 Liquids lighter than water, scales for, 950 
 Liquor, tanning, 882 
 Litharge, 461 
 Lithophanie, 644 
 Litmus, 522 
 Lixiviation, 318, 436 
 Loam, 632 
 Logwood, 522 
 
 and copperas blues for wool, 833 
 Longchamp, M., Anthon, M., and Kuhlmann, M., 
 
 preparation of potassium nitrate, 376 
 Longden, J. N., and Morgan, W. P., dry amal- 
 gamation process for gold, 191 
 Low and Niigeli, yeast, 717 
 Lubricants, 907 
 Lubricator for the cocks of apparatus for gas 
 
 analysis, 55 
 
 Lucifer matches, manufacture of, 4|9 
 Ludicke, experiment on parchmentiskig paper, 
 
 872 
 
 Lunar caustic, 452 
 Lunge's ammonia apparatus, 401 
 Lunge, Or., caustic soda, 343 
 
 commercial value of potash, 301 
 
 distillation of tar, 503 
 
 formation of sulphuric acid in the leac 
 
 chambers, 271 
 
 manufacture of saltpetre, 378 
 method of chlorometry, 362 
 removal of bleaching agents, 816 
 
962 
 
 INDEX. 
 
 Lye, evaporation of the, 436 
 
 soda, purification and concentration of, 323 
 treatment of raw, 374 
 
 MABEEEY, volatilisation of aluminium, 222 
 
 Macco's heater, 117 
 
 MacDougal, Eawson, and Shanks, process for 
 
 producing chlorine, 352 
 Machine for bleaching and dyeing, 828 
 
 paper manufacture, 869 
 
 sand-blast, 628 
 Mactear, manufacture of sodium, 220 
 
 sulphate furnaces, 312 
 Madder, 514 
 
 lake, 514 
 
 printing, 842 
 Magenta, 530 
 
 purification, 533 
 Magnesium, 224 
 
 soap, 918 
 
 uses of, 225 
 
 Magnetic ironstone, 113 
 Maize starch, 68 1 
 Malachite, 150 
 
 green, 539 
 
 Maletra, plate furnace, 255 
 Mallet's ammonia apparatus, 401 
 Malligand and Vidal's ebullioscope, 725 
 Malt kilns, 739 
 Malting, 738 
 Maltose, 688 
 Manganese, 145, 467 
 
 mordants, 825 
 
 soap, 919 
 
 Manilla hemp, 812 
 Manufacture of oil, 84 
 
 of paper, 853 
 Manures, phosphates, 424 
 Margarine, 789 
 Marl, 632 
 
 Martin, E. , preparation of wheat starch, 680 
 Martin, Hummel, Lenz, and Lepetit, detection of 
 
 colouring matters on the fibre, 852 
 Martius's yellow, 570 
 Massicot, 461 
 Matches, 417 
 
 inodorous, 422 
 
 various kinds of early, 418 
 Mather Thompson, bleaching process, 819 
 Meat, 792 
 
 cooking, 793 
 
 curing, 796 
 
 various methods of preservation, 794 
 Mechernich, treatment of lead ores, 171 
 Meissl, M., maltose, 689 
 Melis, 707 
 
 Melting vessels, 602 
 
 Mendheim, M., gas furnace for bricks, 656 
 Mercurial compounds, 453 
 
 fumes, condensing, 207 
 Mercuric chloride, 453 
 
 oxide, 453 
 Mercury, 207 
 
 fulminating, 398 
 
 gold, and silver compounds, 452 
 
 properties of, 211 
 
 soap, 919 
 
 uses and detection, 212 
 Merino wool, analysis, 80 1 
 Metallic iron, green vitriol from, 473 
 Metallurgical operations, application of water 
 
 gas in, 49 
 Metallurgy, 108 
 
 of nickel, 148 
 Metals, hardness of, 1 1 1 
 
 Metals, pliancy of, 112 
 
 properties of, 1 10 
 Methylene blue, 558 
 Methylic alcohol, 486 
 Methyl violet, 537 
 
 Miest and Bias, working up zinc blende, 216 
 Milk, 786 
 
 Millifiore work, 625 
 "Milling" gold, 191 
 Milly, saponification, 924 
 Mineral additions to rags in paper-making, 86$ 
 
 green and blue, 457 
 
 oil, 80 
 
 waters, artificial, 241 
 Mineralising wood, 948 
 Minium, 461 
 Mitscherlich, chemical production of cellulose, 
 
 862 
 
 Mohair, 80 1 
 Molasses, 691 
 Molloy, hydrogen amalgamation process for gold, 
 
 191 
 
 Mond, L., process for obtaining pure nickel, 149 
 for obtaining soda from vat waste, 332 
 Mordants, various, for dyeing, 822 
 Morgan, W. P., and Longden, J. N., dry amal- 
 gamation process for gold, 191 
 Morin, M., analysis of cognac from wine, 780 
 Morocco leather, 885 
 Mortars, &c., manufacture, 659 
 
 various, 668 
 Mosaic gold, 448 
 Mottled soap, 914 
 
 Miihlhauser, manufacture of malachite green, 
 540 
 
 production of leuko-base, 544 
 Mulder's researches on picture restoring, 911 
 Miiller, H., examination of wood and other 
 
 fibrous vegetable matter, 863 
 Mungo, 803 
 
 Munich generator furnace, 68 
 Municipal and domestic supplies, water for, 233 
 Miirile's apparatus for extracting ethereal oils, 
 
 938 
 
 Muslin glass, 625 
 
 Must, chemical constituents of, 721 
 Myrtle wax, 907 
 
 NAGELI AND Low, yeast, 717 
 Naphthaline, 513 
 
 distillation, 569 
 
 dye-stuffs, 567 
 Neapolitan yellow, 450 
 Nenuphar black for wool, 835 
 Nessler's researches on barks for tanning, 875 
 Nettle, the great, use of, 811 
 Neubauer, C., analyses of grapes, 722 
 Nickel, 147 
 
 mordants, 824 
 
 obtaining pure, 149 
 
 ores from New Caledonia, 149 
 
 properties of, 149 
 
 wet process for, 148 
 Nitrate of ammonia, 409 
 
 of potash, preparation of, 376 
 
 of silver, 452 
 
 of soda, 372 
 Nitrates, 371 
 Nitric acid, 371 
 
 applications of, 383 
 densities, 382 
 Nitro-benzol, 258 
 Nitro colouring matters, 588 
 Nitro-compounds, 525 
 Nitrogen, determination, 7, 427 
 
INDEX. 
 
 9 6 3 
 
 Nitroglycerine, 393 
 
 Nitrose, denitration of, 266 
 
 Nitrosodimethylaniline, 558 
 
 Nitrous vapours, arrangements for collecting, 
 
 265 
 Nobel, M., dynamite, 395 
 
 nitroglycerine, 393 
 " Non-poisonous" match, 423 
 Nut galls, 876 
 
 oil, 906 
 
 Nuts, valonia, 876 
 Nutrition, 797 
 
 OAK bark for tanning, 874 
 
 Octahedral borax, 432 
 
 Odling, W., Crookes, W., and Tidy, C. M., ex- 
 
 amination of water, 228 
 Oil blue, 457 
 
 from Bradford, 82 
 
 gas, 80 
 
 mineral, 80 
 
 of vitriol, solid, 263 
 
 tawing, 890 
 
 wells and springs, 81 
 Oils, crude, rectification of, 91 
 
 drying, 906 
 
 essential, and resins, 935 
 
 ethereal, extracting, 938 
 
 various, 904 
 
 manufacture, 84 
 Oleic acid, conversion into palmitic acid, 932 
 
 soap, 915 
 
 Oleomargarine, 789 
 Olive oil, 905 
 
 soap, 914 
 
 Opl, C. , recovery of sulphur, 337 
 Optical glass, 620 
 Orange alizarine, 573 
 Ore, bean, 114 
 
 processes of reduction, 118 
 
 tile, 150 
 Ores, assay of tin, 200 
 
 copper, 150 
 
 gold, &c., process for treating refractory, 
 191 
 
 treatment, 108 
 Organic acids, 491 
 
 colouring matters, 514, 579 
 Organo-chemical arts and manufactures, 873 
 Orpiment, 206 
 Oven-coking, 27 
 Ovens, stoneware, 645 
 
 variou, 21 
 Oxalic acid, 499 
 Oxidation of silver, 188 
 Oxide of antimony, 449 
 
 of iron, purifying with, 76 
 
 of lead, 461 
 
 of mercury, 453 
 
 " PADDING on mordants," 843 
 Painting or staining glass, 623 
 
 porcelain, 643 
 Palm oil, 904 
 
 soap, 917 
 
 wax, 907 
 
 Pans, vacuum, for beet-juice, 703 
 Papasogli, G., and Bartoli, A., experiments on 
 
 coal, 19 
 Paper, different kinds of, 869 
 
 hand-made, 865, 867 
 
 hanging varnish, 909 
 
 history and materials used, 853 
 
 mills, water for, 23 1 
 
 sheets, straining, 867 
 
 Paper, various substances used in making, 853 
 
 Papier-mache, 870 
 
 " Para " caoutchouc, 941 
 
 Paraffine, applications, 93 
 
 discovery and use, 87 
 
 manufacture, 87 
 
 purified, 93 
 
 refining crude, 91 
 
 yield of, from various raw materials, 92 
 
 and solar oil industry, 87 
 Parchment, 891 
 
 paper, 871 
 
 Parian porcelain, 645 
 Paring leather, 883 
 Paris blue, 478 
 
 violet, 537 
 
 Parkes, process for extracting silver, 1 80 
 Pasley, Portland cement, 669 
 Pasteboard making, 870 
 Pasteur, M., fermentation, 713 
 
 formation of vinegar from alcohol, 494 
 Pasteuring, 728 
 Patio, process for silver, 175 
 Pattinson, process for extracting silver, 179 
 Payen's experiments with gypsum, 66 1 
 
 researches on cheese, 791 
 
 saponification, 925 
 
 Payne's method of preserving wood, 948 
 Pearls, glass, 625 
 Peat, 18 
 
 gas, 79 
 
 sampling, 7 
 
 Pechiney, production of chlorine, 352 
 Peligot's method for obtaining chlorine, 352 
 Pellieux and Allary, obtaining iodine from sea- 
 weed, 370 
 
 Pelouze, experiments on glass, 595, 597 
 Penot's test f or chlorometry, 361 
 Percussion-caps, 398 
 Perfumery, 936 
 Permanganate of potash, 468 
 Peroncell's apparatus for the manufacture of di- 
 
 sulphide of carbon, 250 
 Peroxide of lead, 462 
 Persian berries, 523 
 Petit, apparatus for saponification, 922 
 Petroleum, origin of, 81 
 Phenol, 512 
 
 colouring matters, 564 
 Phenosaffranine, 564 
 Phenyl brown, 565 
 Phloxine, 556 
 Phosphates, manures, 424 
 Phosphatic glass, 596 
 Phosphor bronze, 167 
 Phosphorus, 410 
 
 in iron, determining, 124 
 
 manufacture, 411 
 
 match, 417 
 
 purification, 413 
 Photogene, 94 
 Photometers, various, 96 
 Photometry, 95 
 Phthaleines, 587 
 Phthalic acid, 570 
 Physical properties of glass, 600 
 Picric acid, 564 
 Pictet's ice machine, 243 
 Picture restoring, 910 
 Pikaba hemp, 812 
 Pink salt, 449 
 
 Pistorius's apparatus for distillation, 768 
 Pitch, value of, 507 
 Plants, salts of potassium from the ashes of, 287 
 
 soda from, 310 
 
964 
 
 INDEX. 
 
 Plate furnace of Maletra, 255 
 
 glass, 609, 612 
 Platinum, 197 
 
 black, vinegar by means of, 495 
 
 extraction from its ores, 197 
 
 lead concentrator, 280 
 
 light unit, 97 
 
 properties, 198 
 
 soap, 919 
 
 stills, 278 
 
 Platinising plate glass, 614 
 Plattner, extraction of gold, 192 
 Pluto Mine, arrangement of coke-ovens, 32 
 Pneumatic malting, 740 
 Poling, 159 
 
 Polishing leather with pumice-stone, 883 
 Polygon grate, 60 
 Porcelain glaze, 640 
 
 hard, manufacture of, 638 
 
 kiln, 641 
 
 ornamenting, 643 
 
 tender, manufacture, 644 
 Portland cement, 669 
 Potash, caustic, 299 
 
 commercial value, 300 
 
 glass, 593 
 
 Potassa and cobalt, nitrate of protoxide of, 147 
 Potassium and sodium, 218 
 
 carbonate, production of, 286 
 
 chlorate, 363 
 
 chloride, preparation of, 283 
 
 chromates, 470 
 
 cyanide, 477 
 
 ferricyanide, 477 
 
 ferrocyanide, 474 
 
 nitrate from Chili saltpetre, 376 
 
 perchlorate, 364 
 
 permanganate, 468 
 
 preparation of, 220 
 
 price of, 221 
 
 saltpetre, 373 
 
 salts, 283 
 
 from sea-weeds, 295 
 from suint of wool, 297 
 from the ashes of plants, 287 
 from the treacle of beet-root sugar, 291 
 Potatoes, starch from, 678 
 Potato spirit, experiment, 780 
 Potter's clay, 631 
 
 wheel, 639 
 
 Pottery, common, 650 
 Poudrette, 424 
 Price's Candle Company, manufacture of fatty 
 
 acids, 930 
 Printing ink, 909 
 
 linen, 185 
 
 silk, 852 
 
 tissue, 821, 839 
 
 with coal-tar colours, 850 
 
 with gold and silver, 849 
 
 with resists, 844 
 Protoxide of cobalt, pure, 147 
 Prussian blue, 477 
 
 preparing, 478 
 Prussiate, yellow, 476 
 Puddled steel, 133 
 Puddling, 129 
 
 furnace, 130 
 Pulp-bleaching 866 
 
 bluing and sizing, 867 
 Pumice soap, 917 
 Purple, 452 
 
 Tyrian, 517 
 Purpurine, 573 
 Puzzolane cements, 674 
 
 Pyrites distillation, green vitriol from the resi- 
 dues, 473 
 Pyrogene, 94 
 Pyrotechnics, 390 
 
 QuBRCiTKON, 523 
 Quinoline, 565 
 
 EABUTEAU, M., analysis of potato fusel, 780 
 Rags, mineral, additions to, 865 
 
 recovery of indigo from, 832 
 
 substitutes for, in paper-making, 853 
 
 treatment of, 865 
 Ramie hemp, 811 
 Rawson, Shanks, and MacDougal, process for 
 
 producing chlorine, 352 
 Realgar, 206 
 Red aniline, 530 
 Red dyes, less important, 518 
 
 colours, 514 
 
 copper ore, 1 50 
 
 dyeing wool, 833 
 
 ironstone, 113 
 
 lead, 461 
 
 or bark tanning, 874 
 
 phosphorus, 416 
 
 quinoline, 566 
 
 silk dyeing, 836 
 
 woods, 518 
 Reds, Bordeaux, 589 
 
 steam, 847 
 
 whites, yellows, 480 
 Regulus, crude, 156 
 Resin gas, 79 
 
 tallow soap, 915 
 Resins, 938 
 
 Resists, various, for printing 844 
 Resorcine, 546 
 
 blue, 557 
 
 Retorts for charring wood, 15 
 Retted flax, 809 
 Rhea grass, 811 
 Rice glass, 624 
 
 starch, 68 1 
 
 Richters, E., analyses of soda, residues, 329 
 Richter's hydrometer, 487 
 Rinmann's or cobalt green, 146 
 Rock salt, 304 
 
 mode of working, 305 
 Roller boiler, 85 
 Rolling leather, 884 
 Roofing-tiles, 657 
 
 Rope-making waste, use in paper making, 860 
 Rosaniline, 535 
 
 derivatives, sulphonised, 587 
 Rose soap, 917 
 Royal blue for wool, 832 
 Run steel, 143 
 Rusma, 206 
 Russia leather, 884 
 
 oil springs, 81 
 
 process for obtaining wood tar, 1 5 
 
 use of platinum in, 198 
 Russian stoves, 62 
 
 SACCHAKIFIC^TION, 762 
 
 Saccharimetry, 693 
 
 Saccharometrical beer test, 759 
 
 Safflower, 516 
 
 Saffranines, 525, 564 
 
 Sagger, 641 
 
 Sago, 683 
 
 Sal ammoniac, 407 
 
 Salicylic acid, 567 
 
 Salines, common salt in, 303 
 
INDEX. 
 
 965 
 
 Salt cake furnaces, 311 
 
 common, from brine, 306 
 from sea water, 302 
 in salines, 303 
 properties of, 307 
 uses, 309 
 lixiviation, 177 
 pink, 449 
 rock, 304 
 
 springs, mode of working, 306 
 works and common salt, 302 
 Saltpetre earth, treatment of ripe, 374 
 mode of obtaining, 373 
 native, 373 
 refining crude, 375 
 soda, 371 
 testing, 378 
 uses, 379 
 
 Salts of aluminium, 435, 443 
 of gold, 452 
 of potassium, 283 
 
 from sea-weeds, 295 
 from suint of wool, 297 
 from the ashes of plants, 287 
 from the treacle of beet-root sugar, 291 
 Sand blast machine, 628 
 
 filters, 235 
 
 Saponification theory, 911 
 various methods of, 924 
 with caustic lime, 921 
 Sarg, freezing, of glycerine, 934 
 Satin glass, 623 
 Sauerwein's method for the decomposition of 
 
 cryolite, 438 
 
 Saxony blue for wool, 832 
 Scales, thermometric, 949 
 Scarlet, biebrich, 577 
 
 double brilliant, 578 
 Schaffner, process for obtaining soda from vat 
 
 waste, 330, 337 
 
 " Schafhautel's mixture," use of, 131 
 Scheele's green, 457 
 Scheibler, M., elution, 708 
 Scheurer-Kestner, combustion value of coal, 24 
 Schilling, N. H., Munich generator furnace, 68 
 Schmidt, Cross, and Witz, cotton dyeing, 837 
 
 tissue-printing, 848 
 
 Schwackhofer, combustion value of coal, 24 
 Schoop's apparatus for the manufacture of 
 
 arsenic acid, 450 
 Schott's experiments on the composition of glass, 
 
 594 
 
 Schreib, H., soda-ammonia process, 342 
 Schlieper and Baum, process for indigo printing, 
 
 847 
 
 Schultz and Julius, arrangement of most im- 
 portant tar colours, 526 
 
 tube drying oven of , 21 
 Schulze, F., extraction of cellulose, 865 
 
 M., maltose, 688 
 Schwarten kiln, 13 
 
 Schwarz's apparatus for distillation, 771 
 Schweinfurt green, 457 
 Scraping or smoothing leather, 883 
 Sealing-wax, 938 
 
 Sea-water, common salt from, 302 
 Sea-weeds, iodine from, 369 
 
 potassium salts from, 295 
 Seger, M., experiments on clays, 635 
 Senff, determination of different kinds of wood 
 
 on distillation, 17 
 Sericiculture, 803 
 Sesame oil, 906 
 Shagreen, 891 
 Shanks' lixiviation apparatus, 321 
 
 Shanks, MacDougal, and Rawson, process for 
 
 producing chlorine, 352 
 Shaving-soap, 917 
 Sheer steel, 142 
 Sheet glass, 61 1 
 Shoddy, 803 
 
 Shot, manufacture of small, 173 
 Sicilian raw sulphur, composition, 245 
 Siemens and Halske, measuring electric light, 
 
 105 
 working up zinc blende, 216 
 
 apparatus for distillation, 772, 777 
 
 C. W., electric pyrometer, 5 
 
 formation of gas in the generator, 66 
 
 F., gas burner, 101 
 generator, 42 
 
 gas oven for glass, 604 
 
 glass-melting furnace, 68 
 
 heat reservoirs combined with coke ovens, 30 
 Siemens-Martin process for steel, 138 
 Silica, ultramarine, 446 
 Siliceous blues, 447 
 Silicon in iron, determining, 124 
 Silk, 803 
 
 bleaching, 820 
 
 dyeing, 835 
 
 from wool and vegetable fibres, distinguish- 
 ing, 807 
 
 manipulation of, 805 
 
 printing, 852 
 Silkworm, varieties, 803 
 Silver, 174 
 
 alloys, 187 
 
 amalgamation of, 175 
 
 and gold, printing, 849 
 
 production in 1884 : 186 
 
 assay, 187 
 
 chemically pure, 186 
 
 extraction, 174 
 
 by solution and precipitation, 176 
 in the dry way, 178 
 
 fine, burning, 185 
 
 German, 168 
 
 gold, and mercury compounds, 452 
 
 nitrate, 452 
 
 oxidation of, 188 
 
 purification, 185 
 
 soap, 919 
 Silvering, 187 
 
 plate glass, 614 
 Singeing, use of, for detecting cotton in linen, 
 
 814 
 
 Sizes, 898 
 
 Slag, alum from blast furnace, 439 
 Slags, 109, 122, 138 
 
 melting, heat of, 119 
 Slavonian kiln, 13 
 Skin, animal, anatomy of, 873 
 Smalts, 146 
 Smelting, 108, 117, 140, 154 
 
 copper, 154 
 
 treatment of nickel before, 147 
 Smoke consumption, 61 
 
 formation, 50 
 
 gases, 57 
 Soap, 911 
 
 ash, 919 
 Soap, examination, 918 
 
 extracts and powders, 919 
 
 pastes, 919 
 
 transparent, 918 
 
 uses and tests, 918 
 
 varieties of, 913, 917 
 Soaps, adulteration, 919 
 
 insoluble, 918 
 
INDEX. 
 
 Soda, 309 
 
 alum, 440 
 
 ammonia process, 339 
 
 caustic, 343 
 
 crude, conversion into purified, 318 
 conversion of sulphate into, 315 
 
 cryolite, 343 
 
 crystals producing, 326 
 
 from plants, 310 
 
 from sodium sulphide, 343 
 
 from vat waste, 330 
 
 furnace, rotating, 317 
 
 glass, 593 
 
 lye, purification and concentration of, 323 
 
 lyes, analyses of, 324 
 
 obtained by chemical means, 310 
 
 residues, analyses of, 329 
 utilisation of, 329 
 
 saltpetre, 371 
 
 stannates, 449 
 
 theory of the formation of, 328 
 
 ultramarine, 446 
 Sodium aluminates, 442 
 
 amalgam for gold extraction, 190 
 
 and potassium, 218 
 
 benzoate, 502 
 
 bicarbonate, 346 
 
 chromate, 470 
 
 manufacture of, 218 
 
 nitrate, 372 
 
 salt, 555 
 
 sulphate, 314 
 
 thiosulphate, 261 
 Soft soap, 912, 916 
 Solar oil, 94 
 Sole leather, 883 
 Solvay, E., soda-ammonia process, 340 
 
 production of chlorine, 352 
 Soot, 581 
 
 " Souring " of kerosene, 85 
 Souring wine, 728 
 Soxhlet, M., maltose, 689 
 Specific heats of metals, 1 1 1 
 Speiss, 145 
 Spirit, eosine, 552 
 
 purification of crude, 779 
 Spirits, from sugar waste, 766 
 
 from wine and lees, 766 
 
 manufacture of, 760 
 
 varnish, 909 
 
 Spring and well water, 227 
 Springs of mineral oil, 81 
 Stamp machine, 866 
 Stannate of soda, 449 
 Stannic chloride, 449 
 Starch, 676 
 
 sugar, composition, 687 
 
 works, water for, 230 
 Stas's experiments on glass, 598 
 Steam boiler, duty of, 59 
 firing, 58 
 
 boilers, water for, 229 
 
 brewing, 757 
 
 colours, 847 
 
 heating, 65 
 
 oven, 21 
 
 Steam pipe cement, 911 
 Stearine, 921 
 
 Stedman's retort furnace for lighting gas, 73 
 Steel, 132 
 
 and iron castings, 143 
 examination of, 124 
 
 basic process, 136 
 
 Bessemer, 133 
 
 carbonisation, 142 
 
 Steel, cast, 142 
 
 cement, 142 
 
 Damascus, 144 
 
 engravings, 144 
 
 properties of, 143 
 
 puddled, 133 
 
 rough or natural, 133 
 
 run, 143 
 
 sheer, 142 
 Steeling, 143 
 
 Stenhouse, Dr., composition of boghead coal, 25 
 Stereochromy, 618 
 Stills, platinum, 278 
 Stockb ridge, M., beet sugar, 694 
 Stoltze's method of preparing wood vinegar, 498 
 Stones, imitation of precious, 621 
 Stoneware, manufacture, 645 
 Stove heating for houses, 61 
 
 Russian, 62 
 
 tile, 63 
 Stoves, earthenware, 62 
 
 in Germany, 62 
 Strass, 621 
 
 Strontia process for beet treacle, 711 
 Style, china blue, 845 
 
 lapis, 844 
 
 madder, 842 
 Styrogallol, 580 
 Sugar, 684 
 
 candy, 707 
 
 consumption, 706 
 
 extraction from beet-root, 694 
 
 of the grape, 722 
 
 salts of potassium from treacle of beet-Toot, 
 291 
 
 varieties of, 691 
 
 works, water for, 231 
 Sugars, various, 712 
 
 washing, 919 
 Suint, 802 
 Sulphate, conversion into crude soda, 315 
 
 furnaces, 312 
 
 of ammonia, 409 
 
 of copper, 454 
 
 of lead, 467 
 
 of zinc, 460 
 
 sodium, 314 
 Sulphide of soda, soda from, 343 
 
 of zinc, process for benzol colours, 562 
 Sulphides, tellurides, gold ores, &c., process for 
 
 treating refractory, 191 
 Sulphite of calcium, 261 
 Sulphur, 244 
 
 chloride, 251 
 
 determination of, 78 
 
 extraction, 245 
 
 from iron pyrites, 247 
 
 from roasting copper ores, 248 
 
 from sulphuretted hydrogen, 249 
 
 from sulphurous acid and carbon, 249 
 
 from sulphurous acid and sulphuretted hy- 
 drogen, 248 
 
 from vat waste, 248 
 
 gas, 248 
 
 in iron, determining, 124 
 Sulphur, properties of, 249 
 
 recovery of, "334, 337 
 
 refining, 245 
 
 Sulphuric acid, 262, 271, 282 
 concentration, 275 
 green vitriol from, 473 
 Sulphurous acid, liquid, 259 
 
 and sulphuric acids, 251 
 Sulzbach, coke-ovens used at, 28 
 Sulzer's yarn-dyeing machine, 829 
 
INDEX. 
 
 967 
 
 Sumac, 875 
 Sun gold, 570 
 
 hemp, Sir 
 
 Superphosphate, 425 
 Sutton, F., examination of water, 228 
 Swedish fining for iron, 129 
 
 " thermo-kettles," 16 
 Sykes's hydrometer, 487 
 
 TABAKils, M., ebullioscope, 725 
 Tables, useful, 949 
 Tanneries, water for, 231 
 Tanning, 873, 88 1 
 
 alum, 886 
 
 by electricity, 889 
 
 in bark, 88 1 
 
 in liquor, 882 
 
 materials, estimation of the value of, 877 
 
 wares, composition of several, 878 
 Tannin, 502 
 
 ink, 524 
 
 mordants, 825 
 Tar colours, 524 
 
 arrangement of , 526 
 
 condensation of vapours, 88 
 
 distillation, 90, 503 
 
 firing, 73 
 
 mode of operating with, 89 
 
 of paraffine, preparation, 87 
 
 properties of, 89 
 
 retort from brown coal, 93 
 
 treatment of the products of distillation, 90 
 Tartaric acid, 500 
 Tartrazine, 580 
 Tawer's softening iron, smoothing leather with, 
 
 884 
 
 Tawing, 886, 890 
 
 Temperatures, high determination of, 4 
 Textiles, examination of dyed and printed, 852 
 Thermo-chemistry, 481 
 "Thermo-kettles," 16 
 " Thermo-lamp," 79 
 Thermometers, various, 2, 5 
 Thermometric scales, 949 
 Thermometry, 2 
 
 Thickenings, importance in tissue-printing, 840 
 Thomas and Gilchrist, basic process for steel, 136 
 Thompson, J., bleaching cotton, 818 : > 
 
 Thomson's method for the decomposition of 
 
 cryolite, 438 
 
 Tidy, C. M., Odling, W., and Crookes, W., exami- 
 nation of water, 228 
 Tile and brick-making, 650 
 Tile ore, 150 
 
 stove, 63 
 
 Tilghman, saponification, 929 
 Tin, 199 
 
 and antimony compounds, 448 
 
 chloride, 449 
 
 crystals, 448 
 
 mordants, 825 
 
 ores, assay of, 200 
 
 properties of, 200 
 
 uses of, 200 
 Tinning, 201 
 
 Tissue-printing, 821, 839 
 Toilet soaps, 917 
 Toluidine, 530 
 Topical colours, 849 
 Tours black for wool, 835 
 Tow, 809 
 Treacle of beet-root sugar, salts of potassium 
 
 from, 291 
 
 Tube drying oven, 21 
 Turkey berries, 523 
 
 Turkey red for cotton, 838 
 
 oil mordant, 822 
 Turmeric, 523 
 Turnbull's blue, 479 
 Turner's yellow, 467 
 Turpentine-oil varnish, 910 
 Tyrian purple, 517 
 
 UCUHUBA wax, 907 
 
 Uhden, M., coloured fires, 392 
 
 Ultramarine, 444 
 
 adulterations, 448 
 
 cobalt, 146 
 
 constitution, 447 
 linger, B., soap-making, 916 
 Upper leather, 883 
 
 VALEBIANIC acid, 499 
 
 Valonia nuts, 876 
 
 Vanadium black for wool, 835 
 
 Varnishes, 908 
 
 Varnish polishing, 910 
 
 Vats, blue, for woollens, 830 
 
 Vat waste, soda from, 330 
 
 Vegetable fibres, 808 
 
 Velin, 891 
 
 Venetian mosaic glasses, 599 
 
 Verdigris, 458 
 
 Vermilion or cinnabar, 453 
 
 Victoria cement, 674 
 
 green, 543 
 
 yellow, 565 
 Vicuna wool, 80 1 
 
 Vidal and Malligand's ebullioscope, 725 
 Vienna black for wool, 835 
 Vine cultivation, 720 
 Vinegar essence, 497 
 
 methods of making, &c., 491 
 Vinous fermentation, 713, 718 
 
 mash, 764 
 Vintage, 720 
 Violet, aniline, 537 
 
 solid, 558 
 Violets, 563 
 
 Violle, determination of melting-points, 4 
 Vitriol, blue, 454 
 
 green, 473 
 
 solid oil of, 263 
 
 white, 460 
 
 Vogel's method for producing chlorine, 352 
 Volatilisation of aluminium, 222 
 Volhard, precipitating silver, 187 
 Von Lermer, M., and Liebig, M., researches on 
 
 brewing, 753 
 
 Von Welsbach, A., gas burner, 103 
 " Vulcanol," 94 
 
 WAGGON boiler, 84 
 
 Wagner, A., method of chlorometry, 361 
 
 researches on barks for tannin, 875 
 
 testing saltpetre, 378 
 
 Wanklyn, J. A., and Chapman, E. T., examina- 
 tion of water, 228 
 Wara, F., and Forster, B., a "non-poisonous" 
 
 match, 423 
 Wash-leather, 890 
 Washing powders, 919 
 
 sugars, 919 
 
 Water, and high pressure, use of, for saponifi- 
 cation, 929 
 
 and ice, 226 
 
 colouring matters insoluble in, 591 
 
 colours soluble and insoluble in, 584 
 
 composition of, 226 
 
 coolers, 649 
 
INDEX. 
 
 Water, distillation, 239 
 
 examination of, 228 
 
 for bleach and dye works, 231 
 
 for breweries, 230 
 
 for distilleries, 230 
 
 for municipal and domestic supplies, 233 
 
 for paper mills, 231 
 
 for starch works, 230 
 
 for steam boilers, 229 
 
 for sugar works, 231 
 
 for tanneries, 231 
 
 for the manufacture of glue, 231 
 
 gas, 45, 48 
 
 manufacture, 46 
 
 glass, 617 
 
 heating, 65 
 
 mains, 240 
 
 purification, 229 
 
 scales for liquids lighter than, 950 
 
 softening, 237 
 
 used for baking, 234 
 
 well and spring, 227 
 Waters, artificial mineral, 241 
 Wax matches, 423 
 Waxes, 906 
 
 Weber, K., analyses of glass, 594 
 Weber and Wiebe, experiments on glass, 598 
 Weed colours, 517 
 Weld and wold, 523 
 Welding, 113, 132 
 
 Weldon, W., process for obtaining chlorine, 348 
 Weldon and Pechiney, production of chlorine, 
 
 353 
 
 Well and spring water, 227 
 Wheat starch, preparation, 679 
 Whey, 787 
 White lead, 462 
 
 from chloride of lead, 467 
 
 oil soap, 914 
 
 resists, 844 
 
 vitriol, 460 
 
 Whites, reds, yellows, 480 
 Whitwell's air heater, 117 
 Wiesner, J., sags, 683 
 Will, H., and Fresenius, R., commercial value of 
 
 potash, 301 
 
 Wilson's bleaching liquor, 363 
 Window glass, 609 
 Windsor soap, 917 
 Wine, casking, 723 
 
 clearing or fining, 730 
 
 constituents, 724 
 
 diseases of, 727 
 
 lyes, working up, 501 
 
 making, 719 
 
 musts, improving, 732 
 Wines, and lees, spirits from, 766 
 
 artificial, 732 
 
 effervescing, 730 
 
 Winkler and Feichtinger, Portland cement, 672 
 Witz, calico printing, 843 
 
 Cross, and Schmidt, cotton dyeing, 837 
 Woehler, freezing of glycerine, 934 
 
 process for determining total carbon in 
 iron, 124 
 
 M., and Deville, H., observations on adaman- 
 tine, 434 
 Wollner, M., manufacture of saltpetre, 377 
 
 Wolff, J., commercial starch, 680 
 Wood, ii 
 
 charcoal, manufacture, 12 
 
 composition of air-dried, 12 
 
 examination of, 863 
 
 gas, 79 
 
 preservation of, 944 
 
 products of degasification, 36 
 
 stuff for paper-making, 860 
 
 tar, 15 
 
 vinegar, 497 
 Wood's metal, 218 
 Woods, red, 518 
 Wool, artificial, 802 
 
 bleaching, 820 
 
 chemical composition, 801 
 
 distinguishing silk from, 807 
 
 origin and properties of, 800 
 
 suint of, salts of potassium from, 297 
 
 varieties, 80 1 
 Woollen black, 578 
 
 printing, 851 
 Woollens, dyeing, 829 
 Wootz, 133 
 Work-lead, 172 
 
 desilvering, by electricity, 185 
 Wort, cooling, 751 
 
 extractives of, 748 
 
 production of, 744 
 Wrought iron, 127, 131 
 
 XYLOL, 511 
 
 YEAST, 713, 718 
 
 substitutes for, in baking, 784 
 Yellow, aniline, 538, 574 
 
 cadmium, 461 
 
 Cassel and Turner's, 467 
 
 cobalt, 147 
 
 colouring matters, 522 
 
 Martius's, 570 
 
 Neapolitan, 450 
 
 prussiate, 476 
 
 quinoline, 566 
 
 salicyl, 567 
 
 silk, dyeing, 837 
 
 Victoria, 565 
 Yellows, dyeing wool, 833 
 
 whites, reds, 480 
 Young fustic, 522 
 
 ZEISS of Jena's optical glass, 621 
 Ziervogel's process for extracting silver, 178 
 Zinc, 212 
 
 and cadmium compounds, 459 
 
 blende, working up, 216 
 
 chloride, 460 
 
 chromate, 460 
 
 distillation, 212 
 
 English method of obtaining, 214 
 
 production by electricity, 214 
 
 properties of, 216 
 
 soap, 919 
 
 sulphate, 460 
 
 sulphide process for benzol colours, 562 
 
 uses of, 217 
 
 white, 459 
 Zulzer's machine for making wax matches, 424 
 
 PRINTED BY BALLANTYNE, HANSON AND CO. 
 LONDON AND EDINBURGH 
 
YD 07579 
 
 
 UNIVERSITY OF CALIFORNIA LIBRARY