Class \0SH5 Book__ 2M^ Gsi}yn§\tW^ CfOPJfRICHT DEPOStn CELLULOSE, CELLULOSE PRODUCTS, AND RUBBER SUBSTITUTES. CELLULOSE, CELLULOSE PRODUCTS, AND ARTIFICIAL RUBBER, COMPRISING THE PKEPABATION OF CEIiLULOSE FROM WOOD AND STRAW ; MANXTFACTTTBE OF PARCHMENT ; METHODS OF OBTAINING SUGAR AND ALCOHOL, AND OXALIC ACID ; PRODUCTION OF VISCOSE AND VISCOID, NITRO-CELLULOSES, AND CELLULOSE ESTERS, ARTIFICIAL SILK, CELLULOID, RUBBER SUBSTITUTES, OIL-RUBBER, AND PACTIS. BY DR. JOSEPH BERSCH. AUTHORIZED TRANSLATION FROM THE GERMAN, BY WILLIAM T. BRANNT, EDITOR OP "THE TECHNO-CHEMICAL RECEIPT BOOK." I L-LUSXRA-TED BV RO RTY-O M E EN <3 RAN/I N <3S. PHILADELPHIA : HENRY CAREY BAIRD & CO., industriaii publishers, booksellers, and importers, 810 Walnut Street. LONDON : KEGAN PAUL, TKENCH, TRUBNER & CO., Ltd., DRYDia^ HOUSE, 43, GERRARD STREET, SOHO. 1904 LIBRARY nf CONGRESS Two Cooles Rereived JUL 14 1904 Cooyrlgrht Entry PYB COPYKIGHT, BY HENRY CAREY BAIRD & CO. 1904. Printed by the WICKERSHAM PRINTING CO. 53 and 55 North Queen St., Lancaster, Pa., U. S. A. PEEFACE. Among the raw materials which nature has placed at our dis- posal for industrial purposes, Cellulose has from time immem- orial occupied a prominent position, having from prehistoric days, continuously served for the production of tissues, and been, even for thousands of years, employed as a basis for the execu- tion of writings. By the development of the science of chem- istry, we have become acquainted with a large number of com- pounds, which have to be considered as derivatives of Cellulose, and we have learned of processes for the separation of this important body, in a pure form, from wood and straw. The nitro-compounds, which can be prepared from Cellulose, form the starting point for all the explosive bodies in use at the present time; and the nitro-celluloses themselves have led to the invention of processes for the production of so-called artificial silk and of celluloid. The discovery of the peculiar compound, to which the term viscose has been applied, was the initiatory step towards the preparation of a series of bodies of technical importance — solutions of cellulose having created the basis for the preparation of lustra-cellulose, etc. The branches of in- dustry thereby called into existence have in a comparatively short time developed into noteworthy manufactures, and scarcely a month passes by, without our becoming acquainted with new applications of the compounds derived from Cellulose. It would appear that the problem of the production of fer- mentable sugar, and thence of that of alcohol, ether, acetic acid, etc., from Cellulose or wood, has at present more closely ap- proached its final solution than it had, even a few years since; and by the perfection of methods for this purpose a radical revo- lution in certain industries may eventually be looked for. In consideration of the far-reaching importance to the indus- tries of Cellulose and the products capable of being prepared (v) VI PREFACE. from the latter, the author has endeavored to bring together in a comprehensive manner everything that has up to the present time become known on this subject, and it is hoped, that he has produced a work which gives clear explanations of all questions pertaining to Cellulose and the products obtainable from it, and which will serve as a hand-book for all who may be profession- ally interested — from the forester to the manufacturer of arti- ficial silk, lustra-cellulose and celluloid. By reason of their extensive use for insulating purposes for electric lines, etc. , substances which are available as substitutes for rubber have acquired great industrial importance, and a comprehensive description of their preparation is also here given, and it is believed may serve to arouse the interest of a large body of manufacturers. Dr. J. Bersch. CONTENTS. I. Cellulose. PAGE Distribution of cellulose throughout nature; Structure of plants; Change of cellulose vessels into wood vessels ....... 1 Occurrence of cellulose; Occurrence of cellulose in the animal and veg- etable kingdoms; Cellulose formerly at our disposal; Straw as a mater- ial for cellulose; Deficiencies of pulp and paper from straw ... 2 Employment of wood for the preparation of cellulose, a modern achieve- ment; Chemical nature of wood; Encrusting substance of wood; Cotton. 3 Fruit of the cotton plant, described and illustrated; Appearance of the cotton fibre 4 Cotton fibres, described and illustrated; Determination of the value of a variety of cotton; Short-staple and long-staple cotton .... 5 Chemical composition of cotton; Otlier fibre-producing plants and natural sources of cellulose-fibres; Preparation of chemically pure cellulose from cotton; Properties of cellulose; Formula of cellulose ... 6 Percentage composition of cellr' ?e; Transformation of substances in the living plant-organism; Conversion of cellulose into soluble substances; Digestibility of cellulose by carnivorous animals and human beings . 7 Solubility of cellulose; Solvents for cellulose; Behavior of cellulose to- wards acids; Effect of water upon cellulose ...... 8 Hydrocellulose and its composition; Mode of manufacture on a large scale of hydrocellulose .......... 9 R. Sthamer's process for the preparation of larger quantities of hydro- cellulose . . . . . . . . . . . .10 Preparation of hydrocellulose with the use of hydrochlof-ic acid; Behavior of cellulose towards acids . . . . . . . . .11 Upon what the various processes for the preparation of alcohol from cel- lulose or wood are based; Action of sulphuric acid upon cellulose; Formation of amyloid .......... 12 Action of hydrochloric acid and of sulphurous acid; Action of organic acids; Chemical changes effected by nitric acid; Effect of the acid sulphites of the alkalies and alkaline earths ...... 13 Combinations formed by cellulose with organic acids; Behavior of cellu- lose towards alkalies; Action of caustic alkalies; Mercerization and its invention by John Mercer; Conversion of cellulose into oxalic acid . 14 (Vii) Vlll CONTENTS. PAGE Behavior of cellulose at an increased temperature; Destructive distillation of cellulose and products formed thereby; Cellulose the basis-material of a large series of combinations of great technical importance . . 15 Industrial uses of cellulose; Vegetable parchment; Cellulose sulphocar- bonate or viscose; Nitro-celluloses ....... 16 Artificial silk; Celluloid; Conversion of cellulose into fermentable sugar; Production of cellulose; Former sources of cellulose . . . . 17 Plants utilized for the production of- cellulose; Constitution of paper; First experiments for the purpose of obtaining cellulose from straw . 18 Experiments for the purpose of obtaining cellulose from wood, and final success in this respect .......... 19 Invention of a processs for the solution and destruction of the lignin or encrusting substance of wood; Substances used for this purpose; Ex- periments for the production of textile threads from cellulose; Phases of the historical development of the production of cellulose from wood. 20 Possibility of obtaining cellulose from wood in the form of textile fibres. 21 II. Wood-stuff or Mechanical Woob-Pulp. Definition of the term wood-stuff or mechanical wood-pulp; Chief use of wood-stuff; Origin of the fundamental idea of the process of wood grinding; First patents granted for the process ..... 22 Execution of Voelter's process of wood grinding; Wood for grinding; Most suitable varieties of wood ........ 23 Preparation of the wood to be ground; Machine for cutting away the bark, described and illustrated ........ 24 Machines for the removal of the knots, described and illustrated . . 25 Spliting machine, described and illustrated ...... 26 Wood-grinding machines; Essential parts of every kind of machine for grinding wood ........... 27 Voelter's grinding machine, described and illustrated . , ... 28 A. Oser's grinding machine, described and illustrated . . . .30 Freitag's grinding machine, described and illustrated . . . - 31 Abadie's grinding machine, described and illustrated . . . .32 Liebrecht's grinding machine ......... 33 Use of hydraulic pressure for pressing the wood against the grindstone; Water used for grinding; Filtration of the water used for grinding . 34 Sorting the ground mass; Sorters for sorting the wood-stuff; Voith's shaking sieves, described and illustrated ...... 35 Mode of operation of the shaking sieve; Use of cylinder sieves . . 36 The refiner, described and illustrated ....... 37 Use of corrugated rolls for the reduction of particles of wood . . .38 Recovery of the finest particles of pulp ....... 39 Dehydration of the pulp; The board-machine; Mode of obtaining thor- oughly dried pulp 40 CONTENTS. IX PAGE Pulp for transporting long distances; Drying apparatus; Arrangement of the apparatus for drying pulp ........ 41 Properties of wood-pulp; CI. Winkler's experiments; Change of color of pulp 42 Bleaching agents for pulp; Bleaching by means of sulphurous acid; Pulp from steamed wood; Quantities of substances which pass into solution by steaming different kinds of wood . . . . . . . . 43 Combinations formed in steaming wood; Apparatus for steaming wood; Production of pulp from steamed wood . .■ .. . . .44 Microscopical examination of steamed wood; Preparation of mechanical wood-pulp by the crushing process; Chopping machines, described and illustrated ............ 45 Reduction of the small pieces of wood in a stamping mill; Usual mode of working the mass obtained from steamed wood . . . ... 47 Difference between ground wood and the original material . . .48 III. Preparation of Cellulose from Wood. ( Wood-Celltjlose, Cellulose IN THE Technical Sense of the Word, Chemical Wood-Pulp. ) Constitution of paper; Principal point in the preparation of cellulose from wood 50 Principal processes employed for the preparation of wood-cellulose; Bachet and Machard's method ........ 51 Preparation of cellulose by means of soda; First step in the manufacture; Disintegration of the encrusting substance ...... 52, Substitution of sodium sulphite for a portion of the caustic soda; Boiling the chips of wood . . 53 Sinclair's boiler, described and illustrated 54 lingerer's boiling process ......... 55 Keegan's process ........... 56 Use of a battery for lixiviation; Contrivances for washing cellulose. . 57 Preparation of cellulose by means of sodium sulphite; Further working of the washed cellulose ......... 58 Consumption of wood and chemicals; Yield of finished cellulose from various kinds of wood; Preparation of cellulose with the assistance of sulphites (sulphite-cellulose according to Mitscherlich's process); Im- portance of an abundance of water; Quantity of water required . . 59 Preparation of the wood; Freeing the trunks from bark; Reduction of the wood; Woods most suitable for the preparation of sulphite cellulose . 60 Operations into which the preparation of cellulose by the sulphite process may be divided; Preparation of the sulphite solution according to Mitscherlich's process 61 Limestone for the preparation of the lye; Preparation of the sulphurous acid; Tests as to whether combustion of the sulphur is complete . . 62 The absorbing tower and its arrangement, described and illustrated . . 63 X CONTENTS. PAGE Arrangement of a plant .......... 65 Lye reservoirs; Causes of irregularities in the operation, and their remedies ............ 66 Boiling the wood with the lye; Boiler for this purpose, described and illustrated; Brick work for lining the boiler, described and illustrated. 67 Mode of heating the mass in the boiler; Proportion between wood and lye ............. 68 Test for ascertaining how much effective calcium bisulphite is still present. 69 Recovery of sulphurous acid; Washing the cellulose. . . . .70 Freeing the cellulose from admixtures; Arrangement of a stamping mill for this purpose ........... 71 Defects of cellulose and their remedies; Cause of yellowish or brownish color; Occurrence of white pieces not converted into fibre; Occurrence of black particles and of larger brown bundles of fibre . . . .72 Change in color of the cellulose during washing; Preparation of cellulose with the assistance of the electric current — Kellner's process . . 73 Apparatus used for this purpose, described and illustrated . . .74 Advantages of the electrical process; Preparation of cellulose from straw; Preparatory operations. ......... 7-5 Cutting and winnowing the straw; Further working of the winnowed straw; Boilers for working the straw ....... 76 Bleaching the cellulose; Yield of cellulose; Various plants which are utilized for the preparation of cellulose . . . . . .77 Utilization of jute bagging; Mode of working jute; Utilization of exhausted lyes and their neutralization ........ 78 Recovery of soda; Discharge of lyes into running water when working with the sulphite process; Dilution of the lyes . . . . .79 Neutralization of the lyes; A. Frank's process; Utilization of sulphite lyes in tanning ............ 80 IV. Vegetable Parchment. Change in unsized paper when subjected to the action of sulphuric acid; Chemical composition of vegetable parchment; Explanation of the parchmentizing action of sulphuric acid ...... 82 Nature of the paper to be parchmentized; Paper suitable for parchmentiz- ing; Preparation of parchment of greater thickness . . . .83 Sulphuric acid used for parchmentizing; Use of so-called chamber acid . 84 Time required for parchmentizing; Parchmentizing apparatus . . .85 Removal of the last traces of acid adhering to the paper; Drying the fin- ished parchment; Recovery of the sulphuric acid . . . . .86 Properties of parchment; Table showing the changes paper undergoes by parchmentizing ........... 87 Preparation of parchment of special thickness; Rendering parchment paper flexible .88 CONTENTS. XI PAGE Coloring parchment'[paper; Preparation of chrome glue for joining to- gether parchment paper ^2 .-...•••• 89 Applications of vegetable parchment; Vulcanized cellulose (vulcanized fibre) , and its preparation; Process according to the patent specification. 90 Forms in which vulcanized fibre is found in commerce . . . • 91 V. Production op Sugar and AlcohoI/ from WooD-CEiiLULOSE. First experiments for the conversion of cellulose into sugar . . .93 Older methods; Zetterlund's process 94 Bachet and Machard's process ........ 95 Other methods for the production of alcohol from wood; Failure of an ex- periment for the production of alcohol from beech; Nature of the wood to be worked . . . . . . • . . . . .96 Varieties of wood suitable for the production of alcohol; Apparatus to be used and mode of procedure in general ...... 97 More modern methods for the production of alcohol from wood; Cutting up the wood; Conversion of the cellulose into sugar; Boiling under pressure ............ 98 Apparatus used for boiling; Tests as regards the time required for obtain- ing the largest possible quantity of sugar ...... 99 Removal of the hydrochloric acid; Neutralization of the sugar solution . 100 Fermentation of the sugar solution; Distillation of the fermented fluid . 101 Value of alcohol obtained from wood; Classen's process for the production of directly fermentable sugar from wood ...... 102 A noteworthy process also patented by Classen. . . . . .104 Main point of the process ...... ... 105 Disintegration of the wood by means of chlorine or hypochlorides; An- other process patented by Classen. ....... 106 Modification of Classen' s process ........ 107 VI. Preparation of Oxalic Acid from Wood-Cellulose. Materials from which the largest^yields of oxalic acid are obtained; Suita- bility of wood for the preparation of oxalic acid ..... 108 Mode of formation of oxalic acid; Thorn's investigations; Yield of oxalic acid from sawdust . . . . . . • • • .109 Table showing yield of oxalic acid under different conditions; Changes taking place in sawdust by treating it with mixtures of caustic alkalies. 110 Best proportions between caustic soda and caustic potash; Advantage of heating the mixture of sawdust and caustic alkalies in a thin layer . Ill Prevention of the turbulent reaction during fusion; Capitaines and Hert- lings's process 112 Xll CONTENTS. PAGE Preparation of oxalic acid on a large scale; Preparation of the mixed lyes; Melting apparatus . . . . . . . • • • .113 Mode of heating; Contrivance for turning the mass while being heated . 114 Working up the melt; Utilization of the mother-lye 115 Mode of obtaining pure oxalic acid from the crude sodium oxalate . .116 Production of pure oxalic acid; Pans used for this purpose . . . 117 Production of an almost chemically pure product 118 VII. Viscose and Viscoid. Invention of these products, in 1892, by Brown, Beadle and Cross; Main point of the invention; Regulation of the progress of the conversion of viscose into viscoid .......... 119 Raw material for the preparation of viscose solution; Preparation of vis- cose for experimental purposes, and for working on a small scale. . 120 Preparation of viscose on a large scale; Material for this purpose . . 121 Comminution of the cellulose, and apparatus used; Quantitative propor- tions between cellulose and caustic soda; Recognition of the commence- ment of the formation of soda-cellulose. . . . . . .122 Methods used in practice for the preparation of soda-cellulose. . . 123 Soda-cellulose; Main point in the manufacture of soda-cellulose; Storing of soda-cellulose ........... 124 Injurious changes in soda-cellulose; Advantages of storing this material in an ice-house. . . . . . . . . . . .125 Products formed by the decomposition of soda-cellulose; Preparation of viscose; Properties of carbon disulphide ...... 126 Apparatus for the preparation of larger quantities of viscose; Proportion between soda-lye and carbon disulphide; Nature of cellulose sulphocar- bonate 127 Recovery of carbon disulphide; Preparation of viscose solution . .128 Storing viscose; Vessels used for this purpose; Stability of viscose; Best temperature for preserving viscose . . . . . . .129 Shipping of viscose; Properties of viscose solutions; Recognition of the commencement of the decomposition of a viscose solution; Changes taking place in viscose solution ........ 130 Influence of temperature upon the decomposition of viscose . . . 131 Conversion of viscose into viscoid; Chief uses of viscose; Preparation of thicker plates from viscoid ........ 132 Behavior of viscose towards metallic salts; Magnesium-viscose. . . 133 Proportional quantities of bodies added to soda-viscose for the purpose of obtaining other varieties of viscose; Preparation of viscose according to Cross 134 Preparation of viscose according to Seidel 135 Transparent plates from viscose 136 Mode of giving a loosely- woven, thin tissue the appearance of a close and firm fabric . . . . . . . . . . . . 137 CONTENTS, Xlll PAGE Preparation of chemically-pure cellulose sulphocarbonate (viscose); Uses of viscose; Incorporation of pulverulent substances . -a^^ • • 138 Use of viscose in the manufacture of paper; Ammonium viscose . . 139 Advantages of the use of ammonium or magnesium viscose; Application of viscose as a size to wi'apping paper; Table showing how the qualities of the papers are effected by the addition of viscose .... 140 Viscose in the manufacture of wall paper; Advantage of its use in the manufacture of flock paper; Coating of ordinary wall paper with viscose; Imitations of leather and velvet hangings 141 Viscose in cloth printing; White design upon a colored ground . . 142 Printing color prepared with viscose; Viscose solution for marking fabrics in mills, and as a substitute for ink for marking household linen, etc.; Viscose as a size or dressing. ........ 143 Simplest mode of sizing; Addition of loading agents to the viscose; Im- parting smoothness and lustre to the tissue treated with viscose . . 144 Preparation of leather-like bodies by means of viscose; Constitution of leather; Main point in the production of a satisfactory imitation of leather 145 Fabrics to be used and working them up into leather-like masses; Viscose solution for impregnating the tissues ....... 146 First step in the operation; Coloring imitations of leather; Vat for the viscose solution; Passing the fabric through the viscose solution . . 147 Conversion of the viscose into viscoid; Protection of the workmen from the gases evolved; Recovery of the carbon disulphide; Finishing and drying the fabrics. . . . . . • • • • .148 Working thick fabrics; Condition of the impregnated fabrics; Properties of the impregnated fabrics ......... 149 Uses of fabrics impregnated with cellulose; Impregnation of ordinary pasteboard with viscose solution ........ 150 Uses of such pasteboard; Felt-plates impregnated with viscose solution, and their use ........... 151 Viscose in the manufacture of artificial flowers; Mode of application; Pure viscose for especially delicate flowers ....... 152 Viscose in photography; Preparation of films from viscose . . . 153 Viscoid masses; Preparation of homogeneous viscose masses free from bubbles 154 Working of pure viscoid; Incorporation of foreign bodies with the viscose; Materials for the preparation of white masses; Masses of a pure, milk- white color and of comparatively slight specific gravity . . .155 Experiment on a small scale in mixing filling substances with viscose . 156 Properties of a viscoid mass of the proper quality; Preparation of larger quantities of viscoid masses; Mixing or kneading machine . . . 157 Shape of a kneading and mixing paddle, described and illustrated ; Mode of working the viscose solution in the mixing machine. . . . 158 Moulding the viscoid mass, and moulds used for the purpose; Moulding solid and hollow articles; Finishing and painting the articles . . 159 Xiv CONTENTS. PAGE Viscoid masses with cellulose or mechanical wood pulp as filling sub- stances and their various applications 160 VIIL Nitbo-Celi.txlose (Gtjn-Cotton, Pyroxylin). Combinations formed by bringing pure cellulose in contact with nitric acid; Two distinctly marked groups of combinations; Discovery of the combinations formed by the action of nitric acid upon cellulose; Former opinions regarding the formation and composition of the combinations. 161 Modern views i-egarding the composition of gun-cotton; Formation of nitro-cellulose . . . . . • . . . . .162 Preparation of nitro-cellulose in explosive as well as soluble form; Investi- gations by G. Lunge and E. Weintraub 163 Effect of the presence of a very large quantity of sulphuric acid; Use of a nitrating fluid containing but a small quantity of sulphuric acid; Time required for the completion of the process of nitration .... 164 Loss in cellulose when working with a nitrating fluid heated to different degrees of temperature; Change in the structure of the nitro-cellulose; Action of nitro-cellulose towards polarized light 16& Main objects to be attained in practice in the preparation of nitro- cellulose; Products which come chiefly into question for practical pur- poses ............. 166- Modes of calculating the nitrogen in nitro-cellulose adopted by the French chemists and by the English and German chemists; G. Lunge and J. Bebie's investigations; Table showing the relation between the modes of determination adopted by the French and German chemists . . 167 Table showing the influence exerted by the content of water in the acid mixture upon the process of nitration ....... 168 Typical soluble nitro-cellulose — the actual collodion-cotton; Solubility of nitro-celluloses 169^ Table showing the efiect of higher tempei-atures such as are used in the preparation of collodion-cottons . . . . . . . .170 General use of a mixture of nitric and sulphuric acids for the preparation of collodion-cotton; Figures obtained with the use of 1 nitric acid to 3 sulphuric acid ........... 171 Nitrating fluids used in the experiments; Table showing the final results of further experiments. ......... 172 Importance of paying attention to the content of water in the nitrating fluid; Experiments in this direction ....... 173- Analyses of various nitro-celluloses; Preparation of gun-cotton; First requisite for the production of gun-cotton ; Purification of raw cotton . 174 Acid used for nitration; Use of mixtures of concentrated nitric and sul- phuric acids; Former mode of nitration; Strength of nitric acid for very explosive products and for readily soluble products . . . . 175 CONTENTS. XV PAGE Sulphuric acid for nitration; Storage of the acids; Stoneware vessels forlj:^ nitrating purposes; Constitution of the nitrating fluid .... 176 Proportions of acids for explosive gun-cotton and for soluble gun-cotton or collodion-cotton; Condition of the nitrating fluid; Importance of the constancy of the composition of the acid mixture . • • . . 177 Regeneration of the nitrating fluids; Use of fuming sulphuric acid; Execu- tion of nitration 178 Nitrating apparatus, described and illustrated. . • . . . 179 Proportion between acid and cotton; Time required for nitration; Use of a centrifugal apparatus for effecting nitration » , , , * 181 Washing the gun-cotton; Ignition of gun-cotton when introduced into the washing tank; Construction of the wash-tank ..... 183 Changes in gun-cotton ; Measures to insure the removal of the acid, and comminution of the gun-cotton for this purpose; Apparatus used . . 184 Separation of the comminuted gun-cotton from the water , , . 185 Drying the gun-cotton; Drying upon frames covered with linen; Gutt- mann's plan of drying gun-cotton; Mode of heating the drying room . 186 Hygroscopicity of dry gun-cotton; Mode of packing gun-cotton; Explosive gun-cotton, and mode of compressing it 187 Compression of gun-cotton for loading torpedoes; Increasing the stability of the nitro -cellulose; Manifestation of changes in the product . . 188 A. Luck and C. F. Gross's process for increasing the stability of nitro- cellulose; O. E. Schulz's process for this purpose . .... 189 Soluble gun-cotton or collodion-cotton; Great importance of collodion- cotton for the preparation of threads ....... 190 Influence of the duration of the action of the acid mixture upon the cot- ton; Temperature to be used for nitration; Connection between the solu- bility of nitro-celluloses and the content of nitrogen in the products . 191 Characteristics of properly prepared collodion-cotton; Disintegration of the nitro-combination; Collodion-cotton from fine tissue-paper , . 192 Collodion; Collodion for photographic purposes; Material best adapted for the preparation of collodion ........ 193 Composition of nitro-celluloses; Cellulose hexanitrate; Cellulose tetra- nitrate ............. 194 Cellulose trinitrate; Cellulose dinitrate; Behavior in drying of a solution of dinitro-cellulose in ether-alcohol; Effect of an admixture of dinitro- cellulose upon collodion . ... ... ... 195 Neutralization of the collodion-cotton; Preparation of the solution; Influ- ence of the physical condition of collodion-cotton upon its solubility; Mode of keeping collodion-solution . . . . . , .196 Elastic masses from nitro-cellulose (artificial rubber); Production of masses from nitro-cellulose possessing considerable elasticity; Fluids which may be used for this purpose 197 Mechanical manipulation of the mass; Most suitable solvent; Recovery of the volatile solvent; Further manipulation of the mass. . • . 198 Nature of the masses finally obtained; Mixing the masses with indifferent bodies; Inflammability of the masses and mode of reducing it . . 199 Xvi CONTENTS. PAGE Cellulose esters; Cellulose acetic ester 200 Composition of cellulose tetra-acetate, and its indifFerence towards the action of chemicals .......... 201 Applications of cellulose acetic ester; Preparation of an acetyl derivative of cellulose according to L. Lederer ....... 202 Cellulose butyric ester; Other similar combinations; "Solid spirit;" Mode of bringing alcohol into a solid form ....... 203 IX. Artificial Silk. Source of natural silk; Composition of raw silk; Scouring or boiling raw silk ; ; ; ; 205 Appearance of silk under the microscope; Early efforts to produce artifi- cial silk; Varieties of artificial silk 206 Historical development of the artificial -si Ik industry; Credit due to M. de Chardonnet; Du Vivier's and Lehner's processes; A. Millar's method; Hummel's process .......... 207 Cadoret's method; Diiference between the methods according to which textile threads are prepared from pure cellulose and from nitro-cellu- lose; Invention of Dr. Hermann Pauldy; Process proposed by Langhaus. 208 Cheapness and safety of the preparation of silk-like threads from viscose solution; Chardonnet artificial silk; Chardonnet's original patent for preparing textile threads 209 Details of the practical application of Chardonnet's process; Nitration of the cotton 210 Nitrating vessels; Time required for nitration ...... 211 Physical behavior of the nitrated cotton; Physical examination of the nitrated cotton; Results of Chardonnet' s comparative experiments . 212 Eemoval of acid from the cotton; Washing the nitrated cotton; Prepara- tion of the collodion solution ........ 213 Solvent used; Time required for solution; Filtering the solution and filter for the purpose 214 Storing the solution; Spinning the collodion; Disposition of the spinning apparatus; Mode of making the glass spinners 215 Arrangement of the spinners; Reeling up the threads; Removal of the vapors of alcohol and ether from the spinning room .... 216 Chardonnet's spinning apparatus, described and illustrated . . . 217 Condensing vessels; Throwing or twisting the individual threads; Inflam- mability of artificial silk; Denitration ....... 219 Mode of effecting denitration; Composition of denitrating fluids; Use of ammonium sulphide for the purpose, and its preparation; Recognition of the correct composition of the denitrating fluid .... 220 Bleaching the silk; Preparation of colored artificial silk; Direct coloring of the silk while in the course of preparation; Mixture of the coloring matter with the collodion . . . . . . . • . 221 CONTENTS. XVll PAGE Dyeing the finished silk; Du Vivier's artificial silk .... 222 Method of nitration by means of dry saltpetre and sulphuric acid; Solvent for the nitro-cellulose .......... 223 Lehner's artificial silk; Solvent for the nitro-cellulose; Modification of Lehner's process ........... 224 Denitration of artificial silk; H. Richter's investigations regarding this subject; Pith of Richter's method; Cuprous chloride for denitration . 225 Special advantage claimed for Richter's process; Recovery of the nitrogen compounds; Recovery of the oxy-salts 226 A. Peit's method for the preparation of artificial silk; Drawbacks of the process of producing artificial silk from nitro-cellulose; Spontaneous ignition of nitro-cellulose ......... 227 X. Cellulose Threads (Cellulose Artificial Silk and Lustra- Cellulose). Methods for the conversion of cellulose into a solution from which artificial textile threads may be produced; Advantages of the process; Use of cuprammonium as solvent for cellulose ..... 229 Dr. Pauly's artificial silk; Operation for the production of the thread; Purification of the cotton ......... 230 Dissolving the cotton in cuprammonium; Apparatus for the purpose . 231 Judging the progress of solution by samples ...... 232 Filtration of the solution and filter used for the purpose .... 233 Spinning the solution; Construction of the contrivance in which the formation of threads is effected; Arrangement of the spinners; Col- lector for the threads .......... 234 Washing the threads; Further manipulation of the threads by mechani- cal means; Properties of cellulose artificial silk ..... 235 E. Bronnert's process for the preparation of textile threads; Conversion of cellulose into soda-cellulose; Use of the substances according to molecular weights .......... 236 Preparation of cuprammonium; Removing the turbidity of the solution; Filtering the solution .......... 237 Conversion of cupric hydroxide into cuprammonium, and apparatus employed ............ 238 Preparation of cuprammonium solution according to the process of E. Bronnert, M. Fremery and J. Urban 239 Recovery of the copper; Various methods for this purpose . . . 240 Artificial silk according to M. Fremery and J. Urban; Manner of drying the thread ; Phases in the drying process 242 Composition of the fluid used for the decomposition of the cellulose solu- tion; Explanation of the effect of concentrated sulphuric acid . . 243 Artificial horse hair, its production and uses ...... 244 XV 111 CONTENTS. XL Textile Threads prom Viscose (Threads from Lustra-Celllulose). Coagulation of viscose solution; Simplicity of the process of obtaining pure cellulose from viscose; Experiments in making textile threads from viscose. ............ 246 Properties of viscose threads; Cost of producing threads from viscose . 247 Preparation of perfectly clear viscose solution, and apparatus employed . 248 Filtering the solution, and filter used; Spinning apparatus . . . 249 Treatment of the threads emerging from the spinning apparatus . . 250 Importance of using viscose solution of the same temperature . . . 251 Kegulation of heat; Preparation of textile threads according to Stearn.; Preparation of long, narrow strips for taking pictures for the cinemato- graph 252 Millai-'s artificial silk (gelatine silk) . . . . . . .253 Deprivinggelatine threads of their brittleness; General properties of textile threads produced by artificial means; Lustre of artificial silk; Effect of water on artificial threads 254 Facts to be taken into consideration in dyeing threads of artificial silk; Microscopical examination of artificial textile threads; Difference be- tween natural and artificial silks ........ 255 Table showing diameters of various kinds of silks; Optical phenomena ex- hibited by natural and artificial silks; Tenacity of artificial silk as com- pared with natural silk 256 Dr. Hassack's investigations; Moisture and hygroscopic! ty of artificial silks; Specific gravity of artificial silks 257 Elasticity and tenacity of artificial silk; Eesults of tests .... 258 Behavior of artificial silk in a chemical respect; Principal difference be- tween the various kinds of artificial silk 259 Microscopical examination of artificial silk with the use of reagents. . 260 Distinction between cellulose and nitro-cellulose silks .... 261 XII. Celluloid. Invention of celluloid by Hyatt, of Newark, N. J. ; Properties of cellu- loid; Nature of celluloid 263 Methods for the preparation of celluloid; Value of the separate methods . 264 Classification of the methods used for the manufacture of celluloid; Prep- aration of the collodion-cotton 265 Material used according to the original statements by Hyatt; Preparation of celluloid according to Hyatt 266 Preparation of celluloid according to Tribouillet and Besancele . . 268 Preparation of celluloid with alcoholic camphor solution .... 269 Preparation of celluloid according to Magnus 270 Mode of preparing the solution of dry collodion-cotton; Preparation of CONTENTS. XIX PAGE celluloid with recovery of the solvent; Description of a process which can be practically applied ......... 271 Manner of testing freshly-prepared collodion-cotton; Requisites of collod- ion-cotton which is to be dissolved ....... 272 Drying the collodion-cotton; Apparatus in which the solution of collod- ion-cotton and camphor is effected, and manner of working with it; Solvent to be used .......... 273 Advantages of anhydrous ether as a solvent; Recovery of the ether evaporating from the fluid celluloid mass ...... 274 Apparatus for preparing the solution ; Trays for solidifying the solution, described and illustrated ......... 275 Apparatus for condensing the ether-vapors, described and illustrated . 276 Removing the finished celluloid from the trays ..... 278 Drying chamber; Heating celluloid to be rolled ..... 279 Properties of celluloid; Nature of celluloid at the ordinary temperature . 280 Mode of rendering celluloid plastic by heating; Spontaneous decomposi- tion of celluloid; Inflammability of celluloid. ..... 281 Behavior of celluloid towards solvents; Physical properties of celluloid; Example of the great tenacity and elasticity of celluloid . . . 282 Working celluloid; Mechanical manipulation of celluloid; Rolling cellu- loid 283 •Coloring celluloid; Employment of tar colors for this purpose; Coloring transparent celluloid articles; Production of articles from the colored material ............ 284 Production of certain color effects; Red and scarlet ..... 285 Blue; Indigo-blue; Berlin-blue; Violet; Brown; Gray; Black . . . 286 Printing on celluloid; Preparation of a celluloid-plate for printing; Pro- cess for providing celluloid articles with colored pictures . . . 287 Transferring pictures to celluloid; Mode of protecting the pictures . . 288 Printing on celluloid in the same manner as pictures, in many colors, are produced on paper; Preparation of gutta-percha printing blocks; Cellu- loid with filling masses. ......... 289 Milk-white bodies; Imitation of white marble; Materials used; Celluloid masses of light weight .......... 290 Methods for combining the pulverulent filling substance with the cellu- loid; Coloring filled celluloid masses; Imitation, of ivory . . . 291 Imitation of tortoise-shell ......... 292 Moulding celluloid articles; Heating apparatus for the purpose, described and illustrated ........... 293 Manufacture of celluloid tubes; Joining two pieces of celluloid. . . 294 Shaping celluloid by pressing; Imitations of corals; Manufacture of combs; Cliches from celluloid ........ 295 Method of making a plaster of Paris cast; Celluloid stamps . . . 296 Collars and cuffs from celluloid; White masses for this purpose; Making the mould; Cleaning celluloid collars and cuffs ..... 297 -Celluloid for dentists' use . . . 298 XX CONTENTS. PAGE Coloring celluloid with cinnabar; Mode of making the plates; Temijera- ture to which the celluloid has to be heated 299 Objects of art from celluloid; Metals used for incrustations; Finishing the incrusted plate; Bending incrusted plates 300 Celluloid mosaics; Imitation of lapis lazuli^ and of variegated marble; Pro- duction of mosaics; Execution of the design 301 Celluloid lacquer; Use of celluloid lacquer for coating maps, copper and steel engravings and drawings ........ 302 Protecting metals from rust; Basis-material of all celluloid lacquers; Names under which celluloid lacquers are brought into commerce . . . 303 Preparation of an excellent celluloid lacquer 304 Effects produced with colored celluloid lacquers; Conservation of metals by means of celluloid lacquer; Special importance of a coating of cellu- loid lacquer for metallic articles which come in contact with sea water. 305 Protection of iron vessels from the action of sea water; Celluloid masses without an addition of camphor; Use of naphthaline .... 306 Substitutes for camphor proposed by Zuhl and Eisemann, and by J. E. Goldsmith 307 XIII. Rtxbbek Compounds. Definition of rubber compounds; Principal substances used as additions to rubber 309 Advantages of coal-tar pitch; Plastite masses, and their nature . . 310 Composition of plastite masses, and their preparation; Elastic rubber masses ............. 311 Balenite, its composition and preparation; Uses of balenite; Rubber- leather; Properties and preparation of rubber-leather . . . .312 Cost of producing i-ubber-leather; Marine glue, and definition of this term. 313 Mode of applying marine glue; Preparation of a lacquer from marine glue. 314 XIV. RtTBBER Substitutes. Increasing demand for rubber; Groups of rubber substitutes; Steenstrup's method for -the preparation of a rubber substitute 315 Importance of actual rubber substitutes, and their preparation by the treatment of oils; Oil-rubber; Drying and non-drying oils; First step in the manufacture of oil-rubber . . . . . . . 316 Heating the oil;^Test as to whether the oil has been suflSciently heated; Cooling the oil . . . . . . . . . . .317 Oxidation of the oil with nitric acid; Nature of the oil-rubber obtained . 318 Restoring old oil-rubber; Uses of oil-rubber; Manufacture on a large scale of oil-rubber by means of thick oil ..... . 319 Apparatus for oxidizing the oil, described and illustrated . . . 320 CONTENTS. XXI PAGE Time required for thickening the oil; Working the thick oil . . . 321 Use of oil-rubber for securing large panes of glass in frames; Factis masses, and their nature ......... 322 Sulphured oils (brown and black factis) and their preparation . . 323 Substances which may be added to oil-rubber; Vulcanized oil, and its preparation ............ 324 White factis; R. Henriquez's investigations ...... 325 Oils used for the production of factis, and quantities of disulphur dichlor- ide required for their manipulation ....... 326 Vessels for the oxidation of the oils; Boilers for the preparation of factis. 327 Mode of mixing factis with genuine rubber; Sulphuretted hydro-cellulose as rubber substitute, and its preparation according to Sthamer . . 328 Preparation of disulphur dichloride, and apparatus used, described and illustrated 329 Preparation of pure disulphur dichloride for experimental purposes . 330 Necessity of exercising care in handling disulphur dichloride . . . 331 Index 333 CELLULOSE, CELLULOSE PRODUCTS, AND RUBBER SUBSTITUTES. I. CELLULOSE. The substance to which the term cellulose has been applied is very widely distributed throughout nature, it forming the structural basis of all vegetable organisms. All plants, from the unicellular bacterium up to the mam- moth conifers of California, are built up of cells, the en- velopes or walls of which consist, in every case, of one and the same body, namely, cellulose. In the higher plants the individual contiguous cells coalesce in such a way that, in certain places, their walls are broken up, tubular struct- ures — the so-called vessels — which frequently attain extra- ordinary lengths, being thereby formed. There are vessels which extend from the roots to the tops of gigantic trees, and, as above stated, have been formed by the coalescence of individual cells of a more or less globular form. While in many plants the cells, as well as the vessels formed from them, always remain soft, in others combina- tions are deposited in them by which the cellulose is •changed in a characteristic manner, the walls of the vessels frequently acquiring considerable firmness ; and the cellu- lose vessels are changed to wood-vessels. In herbaceous plants such a transformation does not take place, and hence they have to be sharply distinguished from the 2 CELLULOSE, AND CELLULOSE PRODUCTS. < wood-forming plants, and the process of the formation of wood will have to be more closely discussed. OCCURRENCE OF CELLULOSE. While formerly the opinion prevailed that cellulose oc- curs exclusively in the vegetable organism, more recent investigations have also shown its presence, though to a limited extent, in the animal kingdom, its occurrence in many Tunicata having been definitely established, and it has also been found in insects and other articulates. Its occurrence in the skins of snakes has not been finally proved. It is also claimed that cellulose is formed in the human organism during certain morbid processes (tubercu- losis). However, such occurrences are of minor importance, all the cellulose made use of being exclusively derived from plants. Formerly we had to content ourselves with such quantities of cellulose as were in a quite pure state at our disposal in the form of vegetable wool and the fibres of textile plants, but the demand for cellulose having ac- quired colossal dimensions by reason of the enormous in- crease in the consumption of paper, efforts had to be made to open up other sources of it. Attention was first directed towards straw as a material for the preparation of cellulose, because it was supposed that its vessels having been only slightly, or not at all, converted into wood, the cellulose could without much difficulty be obtained in a sufficiently pure state. However, it was left out of consideration that the stalks of grasses, which in a dry state form the material termed straw, contain consider- able quantities of silica and, in many cases, are provided with what may be called a siliceous armor. This fact frustrated for a long time every attempt to prepare from straw cellulose which might at least be available for the manufacture of paper. Although successful processes for the treatment of straw for paper-making were finally intro- duced, the pulp obtained as well as the papers manufac- CELLULOSE. 6 tured from it, showed so many defects that this mode of obtaining cellulose was soon again abandoned. The employment of wood for the successful preparation of cellulose in a pure state, and in any quantities desired, is an achievement of modern times, no attempt having been formerly made to utilize this material for the purpose. Chemically, wood is nothing but cellulose which has under- gone certain changes. Originally, every kind of wood is cellulose, and in genuine woody plants there is always found around the stalk a growing annular layer which, in accordance with its nature, has to be designated as cellu- lose. This annular layer, to which the term liber has been applied, is formed anew in every period of vegetation, and in the next and succeeding periods of vegetation it is grad- ually transformed into wood. This transformation is efifected by various bodies, known by the general term of encrusting substances, becoming im- bedded in the cellulose mass. By this encrustation the originally thin walls of the vessels of which the liber con- sists, become thicker, more solid, acquire a dark coloration, and are finally transformed into wood-vessels of consider- able strength and tenacity, extraordinarily great in some varieties of wood. The encrusting substances of the wood possess the prop- erty of being destroyed or dissolved by various chemicals, while the cellulose is not at all, or but slightly, attacked by them. Hence by one or the other of the processes to be fully described later on, a cellulose is obtained which, when sufficient care has been taken in purifying it, may be called chemically pure, i. e., free from all foreign bodies. COTTON. Cellulose as found in nature is never chemically pure, it containing in addition a series of other combinations. In its purest state it occurs in the vegetable structures known as hair or wool. As a rule, each hair consists of a mem- CELLULOSK, AND CELLULOSE PRODUCTS. Fig. 1. branous cell, frequently of considerable length, the wall of which is formed of cellulose, admixed, however, with certain salts, nitrogenous combinations, and, in some cases, with coloring matter. Cotton is, unquestionably, the most important of all the vegetable wools. It is the product of several species of the genus Gossypium of the Natural Order Malvacex or Mallows. The cotton plant has from time immemorial been cultivated in tropical countries. The cotton is found in the fruit of the plant, and actually is the hairs or fibres growing around the seed and attached to it. This attachment of the hairs or fibres to the seed is typical of the genus. The fruit. Fig. 1, known as boll, consists of a capsule or pod divided by mem- branes into three or five cells. It bursts at the time of maturity and the hairs or fibres protrude from it in the form of a compact ball of a white or yellow color. The seeds are the size of a pea and the cotton fibres are separated from them by means of special mechanical con- trivances. Viewed under the microscope, the cotton fibre appears as a hollow cylinder, one end of which is pointed and closed, while the other end, by means of which it was attached to the seed, is irregularly torn. Cotton is the more highly valued the thin- ner the individual fibres are, the more uniformly smooth they appear under the microscope, and the more closely their form approaches that of a cylinder. Fig. 2 shows cotton fibres highly magnified. As will be seen from the illustration, the individual fibres are more or less strongly twisted and smooth, but with the use of a very high magnifying power they appear obliquely striate. Fruit of the Cotton Plant. CELLULOSE. O The length of the cotton fibre varies between 0.391 and 1.575 inches, and its diameter between 0.0004 and 0.0016 inch. In fine qualities of cotton the cavity or lumen of the fibre is quite narrow, while in coarser varieties it is three or four times the size of the cell-wall ; in unripe fibres it is sometimes entirely wanting. Like the striation. of the fibre, its cuticle can be plainly recognized only with a very high magnifying power. Fig. 2. Cotton Fibres. Ff cotton filaments ; d, places of twist ; g C, granulated cuticle ; I, cavity or lumen ; Q, cross sections. The value of a variety of cotton is determined by two factors, namely, the length and diameter of the individual fibres ; the longer the fibres are and at the same time the smaller their diameter is, the more valuable the cotton. Cotton with fibres less than 0.984 inch long is called short- staple as distinguished from long-staple, the fibres of which may reach a length of up to 2.362 inches. With regard to the diameter of the fibres, eight different grades of fineness are distinguished in commerce, the limits of diameter for the respective classes being from 0.0004 to 0.0016 inch. 6 CELLULOSE, AND CELLULOSE PRODUCTS. According to numerous analyses, the chemical composi- tion of cotton is as follows : Cellulose 87 to 91 per cent., water 5.2 to 8.0 per cent., fat and wax 0.4 to 0.5 per cent., nitrogenous bodies (remains of protoplasm) 0.5 to 0.7 per cent., ash 0.1 to 0.13 per cent. In addition to cotton, there are numerous other plants producing fibres consisting largely of cellulose, and which are also used as textile fibres. Among them may be men- tioned the fibres of the various species of Bomhax or wool tree, and of the different varieties of Asclepias, but they are far behind cotton in technical importance. Other natural sources of cellulose-fibres are the bast of a large number of plants, and finally the fibres obtained by a special process (retting) from the stalks and leaves of many plants. As the most important of these may be mentioned : flax, hemp, various kinds of nettle, jute, aloe, Manila hemp, New Zealand flax, etc. For the purpose of preparing from cotton a cellulose which may be considered chemically pure, white cotton is first for some time extracted with ether to dissolve the entire quantity of fat and wax present. It is then repeatedly boiled with soda lye, which, however, should not be too concentrated, whereby the nitrogenous combinations are brought into solution. Very dilute hy- drochloric acid is then poured over the cotton and the whole gently heated, the operation being continued for some time. Finally the cotton is treated with water till the last traces of acid have disappeared. When incinerated, cotton, which has been sufiiciently purified, should leave no residue. PROPERTIES OF CELLULOSE. Cellulose, purified in the manner given above, remains unchanged as regards its structure, chemicals when used in sufficiently dilute state having no effect upon it. The elementary analysis of cellulose leads to the formula C12H20O10. However, this formula actually expresses CELLULOSE. 7 only its elementary composition, and the actual formula would probably correspond to quite considerable multiples of the numbers above mentioned. As regards the percentage composition, cellulose agrees with a very large number of other bodies which frequently occur in plants. Thus, it has, for instance, the same com- position as starch, gum, gum-like substances, dextrin, etc. These bodies form a large group of isomeric combinations, they having the same percentage composition, but exhibit- ing different physical and chemical properties. There can be no doubt that in the living plant-organism these bodies may constantly be transformed one into the other, incontestable proof of this fact being furnished by the bulbs and tubers of many plants. In the cells of such bulbs and tubers large quantities of starch are stored up, but as the development of the plant progresses, the quan- tity of starch decreases more and more, it being largely transformed into cellulose, gum, etc. Since cellulose may be converted into soluble combinations by the acids formed in plants, it would not seem improbable that, in the higher plants, the chemical process takes place in such a way that a very large number of non-nitrogenous compounds occur- ring in plants may be directly or indirectly formed from these combinations. It would also seem very probable that the acids and fer- ments, which appear during the digestion of nutriment in the stomach, possess the property of transforming cellulose into soluble combinations, because many animals can digest considerable quantities of cellulose, it forming a very im- portant fodder for them. While formerly the opinion pre- vailed that cellulose is absolutely indigestible for carniv- orous animals and human beings, recent researches have shown such not to be the case and that the human stomach is, after all, capable of digesting quite remarkable quanti- ties of it. 8 CELLULOSE, AND CELLULOSE PRODUCTS. SOLUBILITY OF CELLULOSE. Cellulose is insoluble in ordinary solvents, such as water, alcohol, ether, etc., and, without undergoing a change, actually dissolves only in amraoniacal solution of cupric oxide. When brought in contact with such a solution, the fibres first swell up very much, and solution is then grad- ually effected. On mixing the solution with alcohol or sugar solution, or neutralizing it with an acid, the cellulose is precipitated in colorless flakes, retaining, however, its original chemical properties. Formerly no other solvent for cellulose than ammoniacal solution of cupric oxide was known, but towards the end of the 19th century a body also capable of dissolving it was found in the alkaline sulphocarbonates. Solutions of cellu- lose prepared according to this method exhibit peculiar properties which will without doubt insure their extensive application in various branches of industry. As an exam- ple may here be mentioned that textile threads may be pre- pared from such a cellulose solution. The behavior of cellulose towards the action of chemical agents is of great importance since a series of combinations of considerable industrial interest may thus be formed. BEHAVIOR OP CELLULOSE TOWARDS WATER. At the ordinary temperature water has no effect what- ever upon cellulose. In boiled water pure cellulose may be kept for any length of time without suffering any change. If, however, moist cellulose be exposed to the air, the com- mencement of a change will in a short time be observed, the originally white mass turning gray, becoming constantly darker and finally acquiring the appearance of the black- brown mould found in the rotten core of trees. A micro- scopical examination of such altered cellulose shows it to contain innumerable bacteria which, in appearance, closely resemble those found in wood mould. This destructive process in cellulose is very probably similar to that which CELLULOSE. 9 takes place in the decay of wood, if not entirely identical with it. That cellulose belongs to the readily changeable com- binations is shown by the fact that at a higher temperature it is noticeably affected by water. By boiling pure cellu- lose with distilled water, for some time in an open vessel under the ordinary pressure, a portion of it is converted into sugar. In water in which pure filter-paper has been boiled, the presence of sugar can be distinctly established. The action of water upon cellulose is, however, consider- ably enhanced by boiling for a certain length of time under increased pressure. With a pressure of 5 to 6 atmospheres the cellulose is very noticeably attacked, and the higher the pressure becomes the more energetically the water acts upon the cellulose ; with a pressure of 20 atmospheres the cellulose becomes completely hydrated and is changed to hydrocellulose. However, at this pressure not only hydration of the cellu- lose takes place, but there appear also other products re- sembling those which are obtained in abundance in the destructive distillation of wood, especially in the first stages of it ; the presence of considerable quantities of formic and acetic acids having been established in water wdtli which cellulose had been treated. In addition, dextrin-like bodies are also formed. HYDEOCELLULOSE. The combination of cellulose with water, called hydro- cellulose, has the composition C12II22O11. Hence it differs from ordinary cellulose which has the composition C12H20O10 ill containing one more equivalent of water. For the preparation of pure hydrocellulose use is made of the energetic action of highly dilute acids upon cellulose even when brought in contact with them at a lower tem- perature. On a large scale the mode of manufacture is as follows : Mix 3 parts of concentrated sulphuric or hydro- 10 CELLULOSE, AND CELLULOSE PRODUCTS. chloric acid with 97 parts of water, and immerse in the fluid purified cotton — entirely free from fat — until it is completely saturated, which will be the case in at the utmost three to four minutes. The cotton is then taken from the mixture and freed as quickly as possible from adhering fluid, this being best effected by means of a centrifugal apparatus. It is then spread out in a thin layer and allowed to dry completely in the air. The air-dry mass is finally placed in stoneware vessels and heated for three to ten hours at a temperature which should not be below 104° F., and not exceed 158° F.; the higher the temperature the less time is required for heating. The hydrocellulose is then washed with water till the last traces of acid have been removed, and is finally completely dried in the air. Hydrocellulose has the appearance of the cotton from which it has been prepared, but can be readily rubbed to a very fine powder. It is manufactured on a large scale be- cause it possesses the property, when converted into gun- cotton, of yielding a product which can be more readily exploded by percussion than ordinary gun-cotton, and it is, therefore, preferably used for the preparation of detonating fuses for military purposes. For the preparation of larger quantities of hydrocellulose, R. Sthamer uses the following process : Chlorine is con- ducted into glacial acetic acid until the latter is perceptibly colored yellow. It is then heated to between 140° and 158° F., and dry cellulose separated into fibres is intro- duced while the mass is constantly stirred. The cellulose in a short time swells up very much, so that the mass can scarcely be stirred, hence three to five parts by weight of acetic acid should be used to one part by weight of cellu- lose. The mass at first increases constantly in volume, but after some time it sinks down, and is finally transformed into a thin paste which is washed with water and dried. Care must be taken not to allow the temperature to rise CELLULOSE. 11 above 158° F., as otherwise oxidizing processes may take place in the mass, and the hydrocellulose would not exhibit a pure white, but a brownish color. In place of glacial acetic acid, hydrochloric acid, which is cheaper, may also be used for the preparation of hydro- cellulose, the process, according to Sthamer being as fol- lows : Bring into a vessel provided with a steam jacket and a stirring apparatus, 200 lbs. of cellulose in fibres and add, with constant stirring, 1600 to 2000 lbs. of crude hydro- chloric acid of 21° Be., keeping the temperature at 158° F. A small quantity of finely pulverized potassium chlorate — about 0.5 to 0.8 oz. at a time — is from time to time added to the mass. When in the course of about 1^ hours a total quantity of 2 lbs. of potassium chlorate has been added, the formation of hydrocellulose may be considered finished, the end of the reaction being recognized by the uniformly pasty nature of the mass. The hydrochloric acid is whirled out by means of a centrifugal apparatus, and may be used for the next operation. The hydrocellulose is then washed and dried. The time required for finishing the process de- pends largely on the nature of the cellulose used, a fine- fibered material requiring less time than one with close and tough fibres. Hydrocellulose prepared with the use of potassium chlorate is said to be distinguished by very great chemical indifference towards acids and lyes, and its use for the manufacture of articles which come in (Contact with them is especially recommended by Sthamer. BEHAVIOR OF CELLULOSE TOWARDS ACIDS. While in the presence of even small quantities of acid, especially of strong inorganic acids, the action of water upon cellulose is very much enhanced, the acids them- selves do not enter into combination with the pjoducts formed. Hence it may be supposed that by the action of the acids upon the cellulose certain combinations are 12 CELLULOSE, AND CELLULOSE PRODUCTS. formed which, however, are again immediately decomposed SO tliat the liberated acid can act upon a fresh quantity of cellulose. If this supposition is correct, the phenomenon of the mere presence of minute quantities of acid being suflBcient to change an almost unlimited quantity of cellu- lose is readily explained. The behavior of cellulose towards acids varies according to the kind of acid, its concentration, and duration, of its action. Highly diluted sulphuric acid has no effect what- ever, even if left for a long time in contact with cellulose, but when boiled with it for some time, the cellulose is partly transformed into fermentable sugar. Upon this be- havior are based various processes for the preparation of alcohol from cellulose or wood. The fluid obtained by boiling cellulose with dilute sulphuric acid is neutralized with lime and brought into alcoholic fermentation with yeast. The process has the appearance of being a very simple and obvious method of manufacturing alcohol, nev- ertheless in practice a number of difficulties are encoun- tered, so that hitherto very little use has been made of this property of cellulose. When cellulose, best in the form of unsized paper, is for a few seconds immersed in concentrated sulphuric acid, and the acid is then quickly removed by washing in a large quantity of water, it undergoes a profound physical change. The paper by this treatment acquires great strength, and in appearance resembles parchment. By treating paper Avith concentrated solution of zinc chloride, a product resembling parchment is also obtained. Cellulose is completely dissolved if allowed to remain for some time in contact with cold concentrated sulphuric acid. If, in a short time after solution is complete, the fluid be diluted with water, a colorless body having the composition of cellulose is separated and which, from its resemblance to starch, has been termed amyloid. If solution of cellulose in concentrated sulphuric acid be CELLULOSE. 13 allowed to stand for some time, the cellulose is completely converted into dextrin. However, when boiled with concentrated sulphuric acid, cellulose is entirely decomposed, and by reason of its car- bonization imparts to the fluid a deep black color. The sulphuric acid is also decomposed, as shown by the develop- ment of sulphur dioxide from the hot fluid. Generally speaking, the action of hydrochloric acid upon cellulose is similar to that of sulphuric acid, its effect, how- ever, being less energetic, and in boiling cellulose with it no carbonization takes place. Sulphurous acid acts quite energetically, especially with the use of higher pressure, and converts cellulose partially into fermentable sugar. By organic acids, such as tartaric, citric and acetic acids, cellulose is but slightly attacked, they acting somewhat more energetically when in a concentrated state; oxalic acid produces the most vigorous effect. Nitric acid effects profound chemical changes in cellulose, the nature of the products formed depending on the con- centration of the acid used and the duration of its action. Cellulose esters or cellulose nitrates or nitro-cellulose are formed, a group of combinations which are especially dis- tinguished by their power of exploding with great force and dissolving in various bodies. However, notwithstand- ing the profound chemical change, nitrated cellulose ex- hibits no difference in its physical structure. Under the microscope it presents the same appearance as non-nitrated cotton, but differs from it essentially in its behavior towards polarized light. The acid sulphites of the alkalies and alkaline earths attack cellulose only to a very limited extent, but they act all the more vigorously upon the encrusting substance of the wood. The same is the case with free chlorine, and the action of the sulphites and of chlorine (the latter in the electro-chemical process) is made use of in the preparation of cellulose from wood. 14 CELLULOSE, AND CELLULOSE PRODUCTS. Cellulose also forms with a number of organic acids, such as acetic acid, butyric acid, etc., combinations which possess the characters of esters. These combinations, which have only recently been discovered and investigated, show prop- erties which lead to the expectation that they may also be of industrial importance, though at present they only have been experimented with on a small scale. BEHAVIOR OF CELLULOSE TOWARDS ALKALIES. The caustic alkalies — caustic potash and caustic soda — when allowed to act for a short time produce a favorable change in cellulose, the fibres becoming more compact and solid, so that fibres, especially those of cotton thus treated, can be more readily dyed and acquire a more beautiful color than the ordinary material. When concentrated solutions of caustic alkali — caustic potash or caustic soda — are for a short time allowed to act upon cellulose (cotton) the fibres undergo a peculiar change. Fibres thus treated, when viewed under the microscope, appear very much swollen, their cross sections are much enlarged and nearly circular, and the cavity in the interior is so much smaller that it can scarcely be recognized ; the twist of the fibre is also considerably increased. By this treatment the fibres become also more solid and firmer and in dyeing behave differently from ordinary ma- terials. With the use of the same dyeing liquor they ac- quire a much fuller tone of color, and the same result is obtained with smaller quantities of coloring matter than otherwise would be possible. This peculiar behavior of the cotton fibre was discovered by John Mercer and introduced by him in the practice of cotton dyeing. The term mercerization has been applied to the process, and it is much used at the present time. By treating cellulose with highly-concentrated solution of caustic alkalies it is largely converted into oxalic acid. By treating cellulose with a suitable quantity of caustic CELLULOSE. 15 soda and then adding to the mass a certain quantity of car- bon disulphide, a thickly-fluid solution is obtained which is distinguished by an extraordinary adhesive power. By heating, the solution is again decomposed, whereby the car- bon disulphide is volatilized and the cellulose passes again into an insoluble form. BEHAVIOR OP CELLULOSE AT AN INCREASED TEMPERATURE. Cellulose exposed in a close vessel to a higher tempera- ture commences to decompose at about 302° F., and when the temperature is constantly increased there remains fin- ally a lustrous black coal. By this heating, or destructive distillation as it is called, various products, partially gase- ous, partially fluid or solid, are formed. The gaseous pro- ducts form to upwards of 30 per cent, of the weight of the cellulose, and consist chiefly of varying quantities of car- bonic acid and carbonic oxide. The fluid products separate in two layers, one of them being of an aqueous nature and amounting to about 40 per cent, of the weight of the cellu- lose, while the other represents a thick, viscous mass — the so-called wood tar — of a dark brown, nearly black, color, which amounts to from 4 to 6 per cent, of the weight of the cellulose. The aqueous fluid, the so-called wood vinegar, contains, besides water, considerable quantities of acetic acid, acetone, methyl alcohol, small quantities of butyric acid and other combinations. The wood tar consists of a large series of hydrocarbons which are partially fluid or of an oil-like nature, while other constituents, to which belongs parafline, are at the ordinary temperature solid and crystalline. It will be seen from the brief explanations given above of the behavior of cellulose towards the action of chemicals and of the effect of higher temperatures upon it, that it forms the basis-material of a large series of combinations of great technical importance. In the forms in which it is yielded by the so-called textile plants, it constitutes the 16 CELLULOSE, AND CELLULOSE PRODUCTS. chief material of the textile industry and partially supplies the material for the manufacture of paper, though for the latter purpose the artificial product furnishes an exceed- ingly valuable substitute. Cellulose is further used in the manufacture of most of the blasting materials and explosive bodies, for the preparation of viscose, celluloid and several other substances, and it maj'', therefore, be properly called one of the most important raw materials of the textile and chemical industries. INDUSTRIAL USES OF CELLULOSE. Cellulose and its derivatives are used for many purposes, and the object of the enumeration here given is simply to show in a comprehensive manner the great importance of these bodies for the various industries. Pure cellulose as at present prepared from wood is most extensively employed in the manufacture of paper and con- siderable quantities of it are also used for the manufacture of fire-proof paste-board for roofing (carton pierre), for the preparation of plastic masses, and as an excellent filter material. The term vegetable parchment has been applied to cellulose in the form of paper which has been changed by subjecting it for a short time to the action of concentrated sulphuric acid. On account of its strength it is used for book bind- ings, as well as a dialyzer in various chemical industries, for instance, in the manufacture of sugar. CeUulose sulphocarbonate or viscose is used as a sizing material for dressing tissues, as a thickening substance in calico-printing and for the preparation of textile threads. In the course of time, it very likely will also be applied to other purposes. Solutions of pure cellulose in cuprammon- ium are at present used in a similar manner to viscose for the production of textile threads. To the important derivatives of cellulose belong the com- binations to which the general term of nitrocelluloses has CELLULOSE. 17 been applied. Some of these combinations are distin- guished by great explosive power and are extensively used for the preparation of blasting agents, while others, which are soluble in certain fluids, form with them the so-called collodion which is used in surgery and photography and, in modern times, also for the preparation of textile threads to which the term artificial silk has been applied. The peculiar substance formed by bringing together nitrocellulose wath certain hydrocarbons and known as celluloid has found many applications in the industries and arts. The general suggestions which have here been made as to the utilization of cellulose and its derivatives suffice to prove that they belong to the most important bodies avail- able to the industries. The conversion of cellulose into fermentable sugar, and of the latter into alcohol, being actually possible, it is not unlikely that some time or another in the future a process will be perfected by means of which the production of alcohol from cellulose, relatively wood, will be more profitable than from plants containing starch. Since alco- hol itself forms the initial material for the preparation of many other chemical products, such as ether, vinegar, etc., a new field for the utilization of cellulose would be opened and the import of the invention of a suitable process for the production of alcohol from wood can scarcely be esti- mated. Present experiences in this line, though encour- aging, are not sufficiently perfected for their application on a large scale. However, it maj^ be fairly asserted that the rational preparation of alcohol from wood is only a ques- tion of time. PRODUCTION OF CELLULOSP:. Up to modern times — about the first half of the nine- teenth century — no other sources for cellulose than certain parts of plants were known, fn warmer countries where 2 18 CELLULOSE, AND CELLULOSE PKODUCTS. the cotton plant thrives, the hair which grows around the seed and which consists almost of pure cellulose, formed the material for the preparation of textile threads. In coun- tries having a colder climate, flax, as well as hemp, has from time immemorial been the principal source of cellu- lose fibres. In addition to the plants mentioned above, a number of others were to a more limited extent utilized in other parts of the globe for the production of cellulose. However, the use of such plants was merely local, while that of cotton, flax and hemp was universal. Since communication with cotton-producing countries has been greatly facilitated, this material has been gen- erally adopted in Europe and has in many cases displaced flax for the production of textile fibres. Paper consists of cellulose fibres felted together in a peculiar manner, and formerly linen rags were exclusively used for its manufacture. In consequence of the enormous increase in the consumption of paper the price of rags ad- vanced constantly, and it became necessary for the paper manufacturer to find other sources of cellulose suitable for his purposes. It had for a long time been known that unlimited quantities of cellulose were available in the higher plants, the larger part of their tissues consisting of it. However, this cellulose occurs in such a form that no means were known by which it could be separated in a suitable shape for the manufacture of paper. The first experiments made in this direction were for the purpose of obtaining the cellulose contained in the straw of the various kinds of grain. The results of these experi- ments were, however, satisfactory only in so far that a material was obtained which at the best was only suitable as an addition to the cellulose mass prepared from rags. When used by itself for the manufacture of paper, the re- sulting product was of a very inferior quality as to appear- CELLULOSE. 19 ance and solidity. A substance suitable for the manufacture of paper was obtained from maize straw and yielded some- what better results, Alois Auer, formerly director of the Austrian government printing-office at Vienna, deserving special credit for his efforts in this respect. As might be expected, many experiments were made for the purpose of obtaining the cellulose contained in wood, but none of them was successful because no means were known to bring into solution the encrusting substance by which the individual vascular bundles are cemented together. However, the production from wood of a material which would at least serve as a partial substitute for cellulose, in the manufacture of paper was finally successfully accom- plished, though the paper made from it was inferior in quality to the product from pure cellulose. This substitute consisted of wood reduced to a more or less fine condition by mechanical means. The reduction was effected by means of grindstones, and large works for the manufacture of this material w^ere established. How- ever, this wood pulp prepared by mechanical processes was nothing but wood, and could only be mixed in certain pro- portions with the pulp prepared from rags, and the result- ing paper was of an inferior quality. It was brittle and its color was not pure, and by exposure to light soon turned brownish. It constituted, however, a valuable material for newspapers and other printed matter intended for tem- porary purposes. In the manufacture of paper, wood-pulp prepared by mechanical means is at present onlj'^ used for very ordinary grades ; it is, however, extensively used in the manufacture of paste-board. By the efforts of chemists a process was finally found by means of which it was rendered possible to prepare from wood pute cellulose of such a quality as to be suitable for the better grades of paper, and from this period on' dates a great revolution ia the manufacture of paper. 20 CELLULOSE, AND CELLULOSE PRODUCTS. A process was discovered by which the complete solution and destruction of the lignin or encrusting substance of the wood is made possible, so that the individual vascular bundles are deprived of their coherence and fall apart, and after removing the solvent and bleaching, appear as pure cellulose. Thus far only two groups of bodies are known which may be used for the destruction of the encrusting substance, namely, the caustic alkalies, alkaline sulphites, and chlorine, and one or the other group of these combinations is em- ployed in every process, no matter under what name it may be known, for the preparation of cellulose. To judge from the present state of the industry, the ques- tion as regards the preparation from wood of cellulose suit- able for the manufacture of paper would, therefore, appear to be solved. However, there remains the solution of a no less important problem, namely, the production from wood of cellulose of such a quality as to render it suitable for the preparation of textile threads. Many experiments have been made in this direction, but without entirely satis- factory results, it having thus far been only possible to make cellulose threads a few millimeters long, while fibres of considerably greater length are required for textile purposes. There can scarcely be any doubt that this question will also be solved in the course of time, and we will then have in wood-cellulose a material available for the manufacture of paper, as well as for weaving tissues, and which will to a considerable extent be detrimental to the cultivation ot cotton and flax. With reference to what has been said above, two phases of the historical development of the production of cellulose from wood will have to be kept in view, the one in which the efforts were directed towards the preparation by mechanical processes of a material suitable for the manu- facture of paper, and the other, in which the efforts led to CELLULOSE. 21 the production of pure cellulose from wood. According to the nature of the chemicals used, the manufacture of cellu- lose may be divided into that of soda-cellulose, sulphite- cellulose and electro-chemical-cellulose. As has been previously mentioned, the problem of pro- ducing textile threads from wood has thus far not been satisfactorily solved, though such threads are at the present time made in a roundabout way from cellulose. As this subject will be fully discussed later on, it need here be only briefly referred to. From wood, pure cellulose can only be obtained in the form of short fibres, but fluids are known in which the cellulose dissolves without undergoing a change as regards its physical and chemical properties. These solutions can be converted into very long and ex- tremely thin threads, from which the cellulose can be sep- arated so that it retains all its original properties. Threads thus produced may be spun into yarn like other textile fibres and from such yarn fabrics can be made which do not differ from other cellulose tissues, except that they present a more beautiful appearance as regards smoothness and lustre. It will thus be seen that, even at the present time, cellulose from wood may actually be obtained — though in an indirect way — in the form of textile fibres. II. WOOD-STUFF, OR MECHANICAL WOOD-PULP. The term wood-stuff or mechanical wood-pulp, is applied to wood converted by purely mechanical means into a fine- fibred mass, which by itself may serve for the production of coarser grades of paste-board, as well as for the manu- facture of various articles. Its chief use, however, is as an addition to paper stock for the manufacture of inferior grades of paper. Although wood-stuff, if properly pre- pared, is sufficiently fine-fibred to be made into paper in the paper machine, it is not used by itself for this purpose, because such paper possesses the disagreeable property of becoming darker, and acquiring in a short time a brown coloration when stored exposed to the light. The cause of this phenomenon is found in the fact that the wood-stuff still contains nearly the entire quantity of encrusting sub- stance, lignin, etc., originally present in the wood, these substances being subject to great changes. Hence, in the course of time efforts were made to remove these substances from the wood, so that only pure cellulose remains behind, which, as it does not show the above-mentioned defects, can be used by itself for the manufacture of paper. The process of grinding wood has been known for a com- paratively long time. The fundamental idea originated with F. G. Keller, of Hainichen, Saxony, and was so far perfected by him in conjunction with Heinrich Voelter^ of Heidenheim, Wurtemberg, that as early as 1846, the first patents for wood-grinding processes were granted. In the second half of the 19th century, wood-grinding processes were introduced in all countries abounding in varieties of (22) WOOD-STUFF, OR MECHANICAL WOOD-PULP. 23 wood suitable for the purpose, and the bulk of paste-board, as well as that of ordinary newspaper, is made from ground wood. Voelter's process of wood grinding is executed as follows : Suitably prepared blocks of wood are pressed against a rapidly revolving grindstone which is kept constantly wet by water. By the grindstone the wood is reduced to a mixture of fine fibres, larger shreds, quite large shavings, and water. This mixture is first caused to press against a quite coarse wire screen which retams the coarser shavings and splinters. From this screen the mass is led through a series of cylindrical screens covered with wire gauze increas- ing in fineness, so that from the last screen a thin paste consisting of the finest wood fibre and water runs off. The separation of the wood fibres from the water is effected in various ways, it being frequently accomplished by allowing the paste to flow over an endless fine-meshed metallic cloth. The water runs off through the meshes while the fibres in the form of a delicate pulp remain upon the cloth, and may be still further freed from water by rolls. In this case, the pulp is very frequently conducted at once to the rolls of the paper machine where it is converted into sheets of fixed size. According to another method, the pulp is allowed to drain off in large boxes and is then freed from water by pressing. WOOD FOR GRINDING. Although every kind of wood may be ground, the differ- ent varieties are by no means alike suitable for the pur- poses for which the pulp is to be used. Of the European varieties of wood, asp, linden, fir, pine and birch are espe- cially well adapted for the purpose, while beech is less suitable. In America the soft white wood of the tulip tree (Liriodendron tulipifera) commonly called poplar, as well as the wood of spruce and pine, is used in large quantities for mechanical wood-pulp. 24 CELLULOSE, AND CELLULOSE PRODUCTS. The soft white woods of the asp and linden yield a beauti- ful white pulp, which, however, does not act to advantage in the paper-stuff, paper prepared with such pulp turning out soft and spongy. The pulp from pine or fir, to be sure, is not quite so white, but can be worked into firm, smooth paper. Before being subjected to the grinding process the wood must be carefully examined and prepared. Decayed or rotten wood should be absolutely rejected since the resulting pulp would have a brownish color, and when allowed to lie for some time in a moist state would become mouldy throughout. Hence only sound, clean wood should be worked. PREPARATION OF THE WOOD TO BE GROUND. The preparation of the wood for the grinding process is effected by means of special machinery. The blocks of Fig. 4. wood are first submitted to a machine, which is a sort of revolving plane, and cuts away the bark. Such a machine WOOD-STUFF, OR MECHANICAL WOOD-PULP. 25 is^shown in front and side views in Figs. 3 and 4. As will be seen from Fig. 3, three knives are fixed to the rapidly revolving drum. By conducting the blocks of wood against these knives, the bark is cut away, care being taken to see that it is completely removed, otherwise the pulp will in- evitably show dark spots. Since knotty wood cannot be properly ground, the knots Fig. 5. have to be removed, various kinds of machinery being used for this purpose. A machine of simple construction is shown in Fig. 5, the removal of the knots being effected by means of a rapidly revolving auger. Another machine for the purpose, Fig. 6, is furnished with a spoon-shaped 26 CELLULOSE, AND CELLULOSE PRODUCTS. auger, which is set in rapid motion by the bevel gear, Fig. 7. The blocks of wood thus prepared are cut by means of a circular saw into pieces of such a length that they can be laid in the individual pockets of the grinding apparatus. Each block is finally split into at least two pieces by means Fig. 6. Fig. 7. of a splitting machine, Fig. 8. The chief object of this splitting is not so much to chop up the wood as to give an opportunity for examining it inside, since many blocks ap- pearing perfectly sound from the outside may be rotten at the core, and hence of no use for the preparation of pulp. When the wood has been thus freed from bark and knots, and on splitting been found to be sound throughout, it is ready for the grinding machine. WOOD-STUFF, OR MECHANICAL WOOD-PULP. 27 WOOD-GRINDING MACHINES. Every kind of machine for grinding wood consists of a grindstone, generally of fine-grained sandstone, which re- volves with great velocity around its axis, and against the surface of which the wood is pressed, the latter being kept constantly wet with water. The wood is placed so that its vascular bundles lie parallel to the surface of the grind- stone. The latter in revolving tears from the wood indi- FiG. 8. vidual vascular bundles, as well as entire groups of them, and not seldom even larger splinters. The mass torn loose is carried by the water into a vat, in which the revolving stone is placed, and from there to the sorting contrivances, by which the different-sized particles of wood are separated one from the other. 28 CELLULOSE, AND CELLULOSE PRODUCTS. The oldest of these machines is that constructed by Voelter, and it has proved so satisfactory that up to the present time it has undergone but slight modifications, its main features remaining the same. In Voelter's, as well as in other machines built in imita- tion of it, the grindstone is fixed to a horizontal shaft, but in some more modern constructions, to a vertical shaft. However, a horizontal position of the shaft is considered more suitable by all who have had the opportunity to test the capacity of the different machines. voelter's grinding machine. Voelter's grinding machine, Fig. 9, consists of a frame having two strong, cast-iron sides firmly bolted together and supporting the bearings of the grindstone. One side of the frame is so arranged that the sheet-iron jacket can be re- moved so as to allow of the grindstone being readily ex- changed without the necessity of taking the entire machine apart. Between the two sides, fixed to their surfaces, are pockets or boxes, in which the wood to be ground is placed. The blocks of wood are pressed against the grindstone by a spur gearing, uniform pressure being kept up by means of a tight endless chain. The arrangement of this mechan- ism is such that when one pocket becomes disengaged, the others receive a somewhat stronger pressure, the uniform running of the machine being thus constantly maintained, and one or two pockets may be refilled without stopping the machine. The grindstone is somewhat wider than the blocks of wood to be ground, and is furnished with a mechanical contrivance by means of which, while it revolves, it can alternately be shifted towards the right and the left. The effect of this arrangement is that not only the stone wears more uniformly, but its disintegrating action upon the wood is also increased. The pockets in which the wood is placed have the form of truncated pyramids. Each pocket WOOD-STUFF, OR MECHANICAL WOOD-PULP. 29 is provided with a strong, cast-iron cover which is pressed down by the racks connected with the spur wheels, the latter being constantly drawn down by the endless chain. When a pocket has been filled with wood, the cover is placed in position and, by engaging the spur wheel, is firmly pressed upon the wood, and the latter is then sub- mitted to the grinding action of the stone. Each pocket is Fig. 9. furnished with a pipe through which an abundance of water is constantly conducted over the wood and the stone. The fragments of wood detached by the stone, being imme- diately washed away, fall to the bottom of the vat, and are carried to the sorting screens. As the water is generally introduced in fine jets under high pressure, the detached particles of wood are sure to be washed away by the force 30 CELLULOSE, AND CELLULOSE PRODUCTS. thus brought to bear upon them, and there is no danger of the machine becoming clogged by splinters. There are numerous constructions of machines in which the grindstones are placed vertically, but in principle they do not differ from Voelter's machine. Some of them, how- ever, show certain improvements as regards the mode of pressing the blocks of wood against the grindstone. Fig. 10. A. Oser's machine, Fig. 10, is so arranged that a constant and adjustable pressure upon the blocks of wood by the endless chain is produced by means of a movable crank, a, which receives its impulse from the shaft of the stone, further by the spring-connecting rod, h, the contrivance for engaging the binding attachment, c, and the connecting gear, which is set in motion by the wheels, d e and / g. WOOD-STUFF, OR MECHANICAL WOOD-PULP. 31 Fig. 11 shows Voith's wood-grindiner machine, which differs but little from the one described above. freitag's grinding machine. This is an original construction of a grinding machine with stones fixed to a perpendicular shaft. Four or five Fig. 11. grindstones, each having a diameter of only about 20 inches, are used, and their bearings are so arranged that the surfaces of all the stones can be adjusted at exactly the same height. The wood to be ground, in the form of a long block. Fig. 12, is laid upon the stones, pressed against them 32 CELLULOSE, AND CELLULOSE PRODUCTS. by means of an iron plate, and, during the process of grind- ing, is to a fixed extent moved to and fro. This grinding Fig. 12. apparatus is said to furnish especially long fibres which is certainly of great advantage for the quality of the pulp. abadie's grinding machine. Of an entirely different construction are the wood-grind- ing machines in which one of the circular surfaces of the stone is used as the grind- ^^*^- 1^- ing plane, as is the case in the machine constructed by August Abadie. This machine, Figs. 13 and 14, is furnished with four press-pockets, h, the pis- tons of which are loaded with the weights, k. The load may be increased by tlie use of the connecting gears fixed above k, which serve also for raising the press-pockets when they are to be refilled. In the spaces i between the press-pockets, weights of iron, stone or wood are to be placed, their object being immediately to grind up the wood-stuff detached by the grindstone. This specification, however, has yet to be proved by direct experiments. It is a matter of experience that the wood-stuff detached WOOD-STUFF, OR MECHANICAL WOOD-PULP. 33 Fro. 14. from the blocks of wood in one press-pocket, should as rapidly as possible be withdrawn from the further action of the machine, since the fibres, when dragged again into another pocket and there again exposed to the action of the grindstone, are too much reduced or what is technically called dead-ground. This contingency need not be feared in Abadie's machine, since the water is supplied from the centre of the machine so that it is forced outward by centrifugal force and immediately carries away all the particles of wood lying in its course. The indi- vidual pockets or presses are fixed in a frame g, and the latter is pressed firmly against the grindstone by three per- pendicular screws /, and ac- curately centered by three horizontal screws. In addition to the construc- tions above described, there are a few other wood -grinding machines in which the stone is fixed to a vertical shaft, so that its entire surface may be set with press-pockets. In an ap- paratus of this kind, con- structed by Liebrecht, eight grinding pockets in all are used, and the wood is pressed against the grindstone by hydraulic pressure. Such a machine, of course, can in the same time work up a larger quantity of wood than one with only four or five grinding pockets, but it must also be borne in mind that the con- sumption of power is correspondingly greater and that the grindstone is subject to much greater wear. 3 34 CELLULOSE, AND CELLULOSE PRODUCTS. Regarding the use of hydraulic pressure for pressing the wood against the grindstone, Liebrecht's construction in this respect must be acknowledged as a very ingenious one. However, the apparatus becomes, thereby, more expensive and more complicated, two factors which are not in favor of a machine on which heavy demands are made. In construction, Voelter's wood-grinding machine is more simple than any other apparatus for the same pur- pose, and the unexpected giving-away of any important part can scarcely happen ; furthermore, the grindstone can be readily removed and in a short time replaced by another one. With this machine, as shown by practical experience, operations can be carried on for a long time without having to stop work for more extensive repairs. WATER USED FOR GRINDING. Regarding the water which during the grinding opera- tion has to be constantl}'' conducted upon the grinding sur- face, it may be mentioned that it should be perfectly clear and free from suspended solid bodies — especially sand or clay. Such bodies would, of course, adhere to the pulp and affect its purity, this being especially the case with par- ticles of clay contained in the water used. Pulp from a variety of wood which otherwise would yield a nearly white product, acquires by a content of clay — according to the color of the latter — a yellow or gray appearance. Hence, when in the locality where a grinding plant is to be established, perfectly clear water, free from sand or clay, is not available, it would seem advisable to pass the water required for grinding through a filter which retains the suspended solid bodies. In order to economize, in this case, with filtered water, the water running off" from the sorting screens is not allowed to flow away, but is collected in a basin and pumped into a reservoir placed at a higher level, from which it is reconducted to the grinding apparatus. WOOD-STUFF, OR MECHANICAL WOOD-PULP. 35 SORTING THE GROUND MASS. The operation subsequent to the grinding process consists in separathig the different-sized particles detached by the grindstone from the blocks of wood. The general term sorters is applied to the various contrivances used for the purpose. Before commencing the actual sorting operation, the fluid coming from the grinding apparatus is passed through the so-called splinter-catcher. The latter consists of a larger vessel in which sits a cylinder with slit sides, or covered with a wire screen. The cylinder revolves slowly around its axis and frequently is also kept in an oscillating motion. The particles of wood, which are small enough to pass through the slits or meshes of the cylinder, are carried, together with the water, to the sorters, whilst the coarser splinters collect in the box of the splinter-catcher, to be further reduced in special mills. The sorters, which serve for sorting the wood-stuff, re- semble in the main other appliances used for similar pur- poses. They consist either of a series of sieves of gradually increasing fineness which are kept in a shaking motion, or of revolving cylinders covered with wire sieves. In place of revolving cylinders, hexagonal prisms covered with wire sieves are also used. Voith's shaking sieves are shown in Figs. 15 and 16. The sifting frames consist of sheet iron, the ends being turned up. Each frame rests upon four steel springs, d — d, e — e and / — -/, and is connected with a spring-connecting rod, g h i. The cranked axle lies in k I, its crank-pins being placed one against the other at an angle of 120°, whereby, in connection with the fly-wheel, a quite uniform running of the machine is attained. The sieves are kept in a very rapid jerking or shaking motion — 400 to 500 motions per minute. By the use of springs, as applied in the above-described machine, the otherwise great wear and tear of the machine is reduced 36 CELLULOSE, AND CELLULOSE PRODUCTS. and the very loud noise made by the shaking sieves is con- siderably modified. The mode of operation of the shaking sieve is a very simple one : The mass, consisting of particles of wood and water which comes from the splinter-catcher, falls upon the Fig. 15. uppermost sieve. Water and all particles of wood smaller than the meshes fall through the sieve, whilst the coarser particles slide down over it and collect in a receptacle. The same process is repeated in the succeeding sieves, and a pulp of delicate particles of wood and water runs finally from the lowest and finest-meshed sieve into the settling vat. Fig. 16. ;^gjA With the use of cylinder-sieves the same process takes place in a revolving cylinder, in which the mass coming from the splinter-catcher is freed from the coarser particles, then passes to the succeeding narrower-meshed cylinder- sieve, and so on. Instead of arranging three or more WOOD-STUFF, OR MECHANICAL WOOD-PULP. 37 cylinder-sieves one after the other the sieves may also be fixed one inside the other so that they revolve towards each other in opposite directions, the second revolving in an opposite direction to the first outermost, and the third again in the same direction as the outermost. The mass coming from the splinter- catcher passes into a trough into which the outermost sieve dips, and being carried along by it, reaches the second sieve, and from this finally the innermost one. The particles of the ground wood which have passed through the sieve with the narrowest meshes are considered of sufficient fineness not to require further manipulation. Hence this pulp is directly conducted to the settling vats, the dehydrating apparatus or the board machines. The particles of wood which are not sufficiently ground have to be further reduced, the simplest manner of accom- plishing this being by means of mill-stones of ordinary con- struction. However, special mills which are better adapted for this purpose have also been constructed. Such a mill, known as a refiner, is shown in Figs. 17 and 18. This mill differs from the ordinary constructions in being furnished with two stationary millstones placed in a verti- cal position, between which revolves a runner dressed on both sides. Since this stone possesses two grinding planes, the same performance can be attained with one stone of small diameter as with much larger stones in an ordinary mill. In the illustrations, A, B, represent the three stones, the middle stone B being fixed by means of a box-screw to the shaft D. The stones A and C sit upon the carriage F F, and are firmly fixed to it by the screws u and u. Z is a jacket enclosing the stones, and the carriage F F, together with the stones, can be shifted in it. The shifting of the stones for the purpose of regulating the distance between them is effected by means of the wheel J. Both stones are simultaneously shifted upon the support Z, the shaft H being furnished with a left and right thread. S represents 38 CELLULOSE, AND CELLULOSE PRODUCTS. the contrivance for the introduction of the wood. It is fixed to the jacket Z by means of the iron supports r r, and terminates in two outlets t t. /S* is a gutter also furnished with two outlets, so that the wood to be ground reaches the grinding surface by means of t i, the channels W W, and the two exterior sides of the stones, the latter receiving it only upon the lower halves of their circumferences. The wood remains between the stones only long enough to be Fig. 17. reduced to a degree of fineness corresponding to the distance between the stones, when it falls down on its own account. In place of the refiner, finely corrugated rolls may be used for the reduction of the particles of wood. They re- volve with difierent velocities whereby the wood is at the same time torn and crushed. The wood thus reduced is, for the sake of precaution, passed through a fine-meshed sieve in order to retain coarser particles which may have escaped the action of the mill, and finally reaches the con- WOOD-STUFF, OR MECHANICAL WOOD-PULP. 39 trivances for the separation of the pulp from the water. These contrivances consist of revolving cylinders covered with fine gauze-wire sieves so that the water, but not the pulp, can pass through. By this means, the pulp, to be sure, loses considerable water, but is not sufficiently freed from it, the use of special apparatuses being required for Fig. 18. the complete removal of the water as far as it is at all pos- sible. The water running off from the dehydrating cylinders always carries with it a certain quantity of the finest par- ticles of the pulp which is sought to be recovered in various ways, sieves of the finest gauze wire being most frequently 40 CELLULOSE, AND CELLULOSE PRODUCTS. used for the purpose. The water flows over the sieve while the air is exhausted underneath it. The water penetrates through the meshes while the pulp remains upon the sieve, and is removed from it by a scraper. DEHYDRATION OF THE PULP. The removal of water, as far as possible, from the pulp is an important operation, especially if the pulp is to be shipped, because the smaller the content of water the less the expense for freight will be. If the pulp is to be used in the establishment itself in which it is prepared, thorough dehydration is of course not required, it being only necessary to free it from water sufficiently to allow of the preparation of boards, in which state it is further worked, the finished boards being finally completely dried. The board machine consists in the main of an endless cloth 10 to 13 feet long which is stretched tight over rolls so as to present a perfectly level surface. Over this cloth, several wooden rolls lie loose in crotches, their object being to distribute uniformly the quite thinly-fluid pulp taken up by the endless cloth and, at the same time, to somewhat squeeze it out by their weight. By this means quite a tenacious paste is obtained on the portion of the endless cloth opposite to where the pulp enters. This paste is then pressed more vigorously between two iron rolls so that it forms a quite firm, coherent mass. This is allowed to wind several times round a roll and the hollow cylinder thus formed is cut through, all the sheets thus produced being of the same size. Sheets of any desired length may also be formed upon an endless cloth which takes up the pulp. If, however, in place of sheets thoroughly dried, or more correctly, thoroughly dehydrated, pulp is to be pro- duced, the pulp is allowed to flow over a cylinder covered with wire cloth, both ends of which are rendered as tight as possible by rubber, and under which vigorous rarefaction of air is maintained. The pulp flowing upon the slowly WOOD-STUFF, OR MECHANICAL WOOD-PULP. 41 revolving sieve is much dehydrated by the air-pressure and is removed in the form of a coherent mass. It is then again vigorously pressed between rolls and finally divided by smooth rolls into small pieces which are immediately packed. If, however, the pulp is to be freed as much as possible from water as would seem necessary for transporting it long distances, filter-presses are used, a quite powerful hydro- static pressure being produced by means of an accumulator. In the chambers of the press, sheets quite dry to the touch are thus obtained, which can be readily packed and trans- ported long distances. The only drawback as regards the use of filtering-presses is that a plant working on a larger scale would require a number of them to work up rapidly all the raw material furnished by the grinding machine. DRYING APPARATUS. The preparation of perfectly dry pulp has recently been successfully accomplished without too large an expenditure^ by the use of apparatus which in its construction closely resembles the contrivances employed in sugar houses and breweries for drying beet slices and grains. They are so arranged that the substance to be dried moves in a direc- tion opposite to that of a hot air current, so that drying is effected by a counter-current. The substance to be dried is first met by the hot air-current while it still contains all the water, and though it becomes highly heated, it loses but little water by evaporation, the latter process, however, proceeding very rapidly as the heated mass advances. The apparatuses used for drying pulp are generally so arranged that the crumbled pulp previously freed as much as possible from water by mechanical means, is carried a,long with a certain velocity upon endless wire cloth, while underneath the latter a hot air-current passes in an opposite direction. The velocity of the movement of the pulp upon the cloth is fixed by the temperature, and the latter has to 42 CELLULOSE, AND CELLULOSE PRODUCTS. be carefully regulated. By the use of such an apparatus the pulp may be only partially or completely dried, as may be desired. The apparatus is furnished with automatic charging and discharging contrivances. PROPERTIES OF WOOD-PULP. With the exception of pulp completely freed from water by artificial drying — and this exception applies only to material dried shortly after its preparation — its color under- goes a considerable change, which, of course, is also trans- mitted to the paper prepared from it. Experiments made by CI. Winkler with pulp from different varieties of wood which was exposed to the action of the air at a temperature of between 30° and 50° F., gave the following results : COLOR OF PUXP. From When freshly prepared After several weeks. Pine pale yellow pale yellow Fir yellow yellow Scotch fir greenish-white dirty reddish Larch pale yellow pale yellow Aspen yellowish-white yellowish-white Linden gray-white gray-white Maple yellowish-white yellowish-white Beech pea yellow superficially reddish Birch yellowish-white flesh color Alder deep yellow brick-red The change of color appears first upon the surface of the moist pulp, spreading from there to the interior, and is, without doubt, a process of oxidation. Since pure cellulose does not exhibit this change of color, it can only be caused by a chemical change of the lignin and eventually of the very small quantity of protein substances. The content of rosin in the conifers appears to exert but little influence as regards the change of color, as will he seen from the be- havior of the pulp prepared from them. The change in color of the pulp being very annoying as regards the paper made from the material, experiments WOOD-STUFF, OR MECHANICAL WOOD-PULP. 43 have been made to overcome this defect by bleaching. Of all the bleaching agents experimented with, sulphurous acid, produced by burning sulphur, is the only one which has proved of value in practice. The simplest mode of application is to conduct sulphurous acid into an air-tight box which is filled with broken pulp containing 60 per cent, of water. The gas is absorbed with avidity by the water, and the entire mass is in a short time saturated with it. Pulp thus bleached should not be allowed to lie too long, since it has been shown that after some time it con- tains sulphuric, in place of sulphurous, acid. When the pulp is dried in the air, the sulphuric acid acquires a cer- tain concentration and has a browning effect upon the pulp. Hence the bleached mass should immediately be worked further. The effect of the sulphurous acid appears to be that, on the one hand, it arrests the oxidizing action of the air, and, on the other, that it enters with the coloring matter con- tained in the pulp into a colorless combination, which, however, is in the course of time again decomposed, the sulphurous acid being again liberated and slowly oxidized to sulphuric acid. PULP FROM STEAMED WOOD. When treated with water under high pressure and at a high temperature even pure cellulose is chemically changed and converted into hydrocellulose. Wood, when treated in a similar manner, undergoes, however, more far-reaching changes, the lignin contained in it being very likely most eflPected, because by the treatment with high-pressure steam the fibres are considerably loosened, and there is no diffi- culty whatever in preparing from such wood a pulp which is distinguished by particularly long fibres. The quantities of substances which pass into solution by steaming vary according to the variety of wood. In steam- ing beech 26.75 per cent, passes into solution, 11.19 per 44 CELLULOSE, AND CELLULOSE PRODUCTS. cent, of this being sugar and substances resembling sugar. Steamed pine showed a loss in weignt of 19.17 per cent., 9.07 per cent, of this being sugar and substances alhed to it. The latter probably consist chiefly of dextrin-like bodies, since the wood extract yields with alcohol very heavy precipitates. However, in addition to the bodies mentioned above, there are formed in steaming wood, combinations like those appearing in abundance at the commencement of the de- structive distillation of wood. In w^ater in which wood has been steamed are found considerable quantities of acetic and formic acids. When resinous woods are subjected to steaming, considerable quantities of volatile oil escape with the aqueous vapor when the pressure in the vessel used for steaming is interrupted. By steaming the wood acquires a more or less dark leather to liver-brown color, and the fibres are very much loosened. By reason of this brown coloration of the wood, the pulp prepared from it cannot be used as an addition in the manufacture of white paper. It is, how^ever, very suit- able for the production of stout wrapping paper, because it has very long fibres, which, in making it into paper, felt together, the resulting product being very durable and flexible. In its construction the apparatus used for steaming wood resembles a cylindrical steam boiler, both upright and hori- zontal types being used. It is advisable to line the walls of iron boilers with copper, they being in the course of time strongly attacked b}'^ the organic acids formed from the wood. The production of pulp from steamed wood may be efi"ected in various ways. When working with the ordi- nary grinding apparatus, the wood is prepared in exactly the same manner as the ordinary material, i. e., it is freed from bark, the knots are cut out, and the blocks are finally cut into lengths to fit the pockets of the machine. WOOD-STUFF, OR MECHANICAL WOOD-PULP.' 45 and split. The blocks are then brought into the boiler and for 8 to 12 hours treated with steam of 4 to 6 atmospheres. The higher the tension of the steam and the longer the wood is exposed to it, the more energetic its action upon the encrusting substance and the darker the color of the wood will be. On subjecting steamed wood to a microscopical examina- tion, it will be found that the greater portion of the en- crusting substance has disappeared and that the vascular bundles consisting of cellulose are quite uncovered. By long-continued steaming under high pressure, it might be possible to bring all the encrusting substance into solution, and thus obtain a product which does not essentially differ from pure cellulose. However, in practice, this process cannot be profitably applied because, on the one hand, by long-continued steaming under high pressure, a portion of the cellulose itself is hydrolized, causing a considerable re- duction in the yield, and on the other, the cost of produc- tion is much increased. Hence steaming is continued only long enough for the wood to acquire a sufficient degree of softness, when it is submitted to the grinding machine. In grinding steamed wood much less power is required than in working the raw material, which is readily ex- plained by the breaking-up of the coherence of the vascular bundles by steaming. PREPARATION OF MECHANICAL WOOD-PULP BY THE CRUSHING PROCESS. A process — called by the inventor the crushing process — for the preparation of pulp from steamed wood without the necessity of grinding, has been invented by Rasch-Kirchner of Frankfort-on-the-Main. The steamed wood to be worked is first converted into small pieces by means of a chopping machine of original construction, the arrangement of which is shown in Figs. 19, 20, and 21. In a strong iron frame, K, rests in the 46 CELLULOSE, AND CELLULOSE PRODUCTS. bearing, L, the shaft, A, which carries a heavy disk-knife, M. The latter in revolving passes the box, D, and by- means of the knife, p, cuts the wood only lengthways into shavings of fixed size, or lengthways as well as crossways, if the cross-slitters, o, are at the same time applied. The construction of the machine is such as to allow of its being set so that the wood can be cut up in different ways. The wood may be placed in an oblique position and the cross- FiG. 19. sections thus obtained can readily be reduced to pieces. By placing the wood so that it is worked perpendicularly to its length and bringing the knives which serve for the production of cross-slits into activity, shavings If inches wide and long and from 0.11 to 0.19 inch thick may be obtained. The small pieces of wood coming from the machine are then still further reduced by mechanical means, they being WOOD-STUFF, OR MECHANICAL WOOD-PULP. 47 first subjected to the action of a stamping mill in which they are reduced to such a degree that they can be trans- ferred to the hollander, a machine used in paper mills for the disintegration of paper-stuff. In this apparatus the mass may be worked till it has become sufficiently uniform for the direct preparation of boards in the board machine. If, however, loose pulp is to be.pioduced, the sorters em- FiG. 20. vvAiJ5,^i,i^ii.\-J^\^s\^-^^-vciiii£s\bv^S>x.^\v\-a ployed for ground wood have to be used in order to sepa- rate the coarser particles from the finer fibres. However, the course most generally pursued in working the mass obtained from steamed wood, is to manufacture from it at once brown boards or stout wrapping paper. A pulp with longer fibres being more readily obtained from steamed wood than from wood not steamed, boards and paper made from it possess greater strength, the boards being especially suitable for roofing purposes. Roofs cov- 48 CELLULOSE, AND CELLULOSE PRODUCTS. ered with such boards properly impregnated with coal-tar possess great capability of resisting the action of the weather, being perfectly indifferent to water as well as to changes in temperature. Numerous attempts have been made to bleach the pulp from steamed wood, but thus far without satisfactory re- sults, no effect worth speaking of being produced on it even by the most powerful bleaching agents. It is very likely Fig. 21. that the coloring bodies formed in steaming wood belong to the group of combinations to which the term humus bodies has been applied. They are distinguished by a very dark brown to black color which it is impossible to lighten up by any bleaching agent. Physically, ground wood actually differs from, the orig- inal material only in that the individual vascular bundles -appear to be quite completely separated one from the other. WOOD-STUFF, OR MECHANICAL WOOD-PULP. 49 However, the individual vessels adhering together are still firmly connected by the encrusting substance — the lignin — this fact being shown by storing the pulp for some time exposed to the light, it acquiring in a short time a quite strong brownish coloration. This coloration also appears in the paper-mass to which the pulp has been added. Paper thus prepared turns perceptibly brown when for a few weeks exposed to the light, and at the same time be- comes brittle. The manufacture of paper which could lay claim to durability for a longer time would therefore ap- pear impossible with the use of larger quantities of mechan- ical wood-pulp, it being possible only when pure cellulose, the great stability of which has previously been referred to, is employed. 4 III. PREPARATION OF CELLULOSE FROM WOOD. (WOOD-CELLULOSE, CELLULOSE IN THE TECHNICAL SENSE 0^ THE WORD, CHEMICAL WOOD-PULP.) Paper consists of cellulose fibres felted together in a pe- culiar manner so that the individual fibres can no longer be distinguished. The cellulose which was formerly ex- clusively used for the manufacture of paper consisted of waste of linen and cotton fabrics, and other vegetable fibrous substances. By reason of the constant increase in the consumption of paper, the price of this waste, technically called rags, rose steadil}^ so that the efforts of chemists were for a long time directed towards finding a substitute for rags in another vegetable substance. After many ex- periments, the results of which, however, were not veiy satisfactory, a process was finally discovered which allowed of the separation of cellulose from certain varieties of wood in such a form as to render it suitable for use in the manu- factur^e of paper. The production of cellulose from wood has now become a highly developed industry, and every 3'ear the quantity of raw material worked up becomes larger. In the preparation of cellulose from wood, the principal point is the removal of the substances which incrust the cellulose, and to convert tlie latter into actual wood sub- stance, as well as to obtain it in a pure form. It is, how- ever, also of importance that the individual fibres should be of a certain length to allow of them being properly felted together into paper, and the solution of this demand (50) CELLULOSE FROM WOOD, OK CHEMICAL WOOD-PULP. 51 presented for a long time many difficulties which, however, finally were successfully overcome. There are quite a number of methods by which wood cellulose may be prepared, but only three of them — namely, the soda process, the sulphite process and the electric pro- cess — have at present been firmly established in practice. The sulphite process, while it yields the same favorable re- sults, is far more simple in execution than the soda process, and is more and more replacing the latter, many wood- cellulose plants at present working exclusively with it. Since the encrusting substance of the wood may also be destroyed by acids, a series of processes have from time to time been introduced, the object of which is to eff'ect the disintegration of the wood-fibre by their use, concentrated nitric acid, as well as aqua regia — a mixture of nitric and hydrochloric acids — having been employed for the purpose. However, independent of the great expense connected with them, these processes have the further disadvantage that it seems next to impossible to keep the operating vessels tight, in consequence of which products of decomposition of nitric acid escape into the work-room, rendering the air of the latter very injurious to the health of the workmen. For these reasons, this method of preparing cellulose has been entirel}'^ abandoned. It may, however, be mentioned that one acid process by which the disintegration of the wood is effected with hydrochloric acid, would seem to be available, since it yields a very valuable by-product. BACHET AND MACHARD's METHOD. According to this method thin slices of fir are subjected to hot treatment with hydrochloric acid. Four thousand eight hundred pounds of fir in thin slices are brought into a wooden vessel and after pouring over them 2000 gallons of water and 1760 lbs. of hydrochloric acid, the fluid is brought to boiling by the introduction of steam, boiling being continued for 12 hours. The fluid is then drawn off 52 CELLULOSE, AND CELLULOSE PRODUCTS. and neutralized with calcium carbonate. It now represents a dilute solution of grape sugar which can be brought by yeast into vinous fermentation, and by distillation yields a considerable quantity of alcohol. The residue consisting of cellulose is washed with water . until all the acid is re- moved, crushed under millstones and disintegrated in the hollander. Since by this process a considerable portion of the cost of manufacture is covered by the alcohol gained as a by-product, it would appear to be of importance for the practice. To judge, however, from its present state, this method has many inherent defects which prevent its gen- eral introduction. If, however, these defects can be over- come, it might prove of importance for the manufacture of cellulose. Later on more modern processes for obtaining alcohol from wood will be referred to. PREPARATION OF CELLULOSE BY MEANS OF SODA. This method of preparing cellulose is an American in- vention — poplar, pine, spruce, and occasionally birch, being used for the purpose. Poplar is especially distinguished from other woods in yielding very long-fibered cellulose. This process which may be called the American wood-pulp system can also be profitably applied to the conifers indig- enous to Europe. The first step in the manufacture is, in all cases, the mechanical preparation of the wood to be worked. This consists in carefully freeing the wood, cut up into short blocks from the bark, cutting out the knots by special machinery and reducing the blocks to chips about | inch long, ^ inch wide, and 0.19 to 0.31 inch thick. All the mechanical operations : Freeing from bark, cutting out knots, etc., are carried out by special machines. The disintegration of the encrusting substance of the wood is effected by means of caustic soda lye. The state- ments regarding the quantities of soda lye — relatively of caustic soda — required for working 220 lbs. of wood vary CELLULOSE FROM WOOD, OR CHEMICAL WOOD-PULP. 58 very much, but the quantity of caustic soda obtained from 48.4 lbs. of carbonate of soda is said to be sufficient in all cases. By the action of the caustic soda, the encrusting substance of the wood is destroyed and the resins are saponified. When the process of disintegration is finished, the fluid is discharged and evaporated in iron pans to dry- ness. The residue is heated in a reverberatory furnace whereby the acids fixed to the soda are destroyed, carbonate of soda remaining finally behind. This carbonate of soda is again converted into caustic soda, so that for the next operation only a sufficient quantity of fresh caustic soda to replace that unavoidably lost in the wash waters is required. Sodium sulphite having the same destructive effect upon the encrusting substance as caustic soda, it is frequently substituted for a portion of the latter. This is effected by evaporating the lye which has once been used for boiling the wood, together with sodium sulphate, which is quite cheap, and heating the residue. By the carbonization of the organic combinations contained in the salt-mass, the sodium sulphate is reduced to sodium sulphite and a fluid is obtained which, when again made caustic, contains, in addition to caustic soda, a certain quantity of sodium sulphite. To free the chips of wood from the encrusting substance by boiling them with soda lye in open vessels, would re- quire so much time as to make the process scarcely avail- able for practical purposes. If, however, the lye is allowed to act under increased pressure upon the wood, disintegra- tion will be accomplished in a comparatively shorter time and with greater rapidity, the greater the pressure is and the higher the temperature prevailing in the apparatus. In practice a pressure from 6 to 14 atmospheres is used, though one from 10 to 11 atmospheres is most frequently employed. 54 CELLULOSE, AND CELLULOSE PRODUCTS. Fig. 22. SINCLAIR S BOILER. From what has been said above, the construction of the boiling apparatus must be such as to be capable of resisting the high pressure prevailing in its interior, as its explosion might cause terrible accidents. Since, considering the size of the boilers, even if constructed of the best quality of steel, it is difficult to keep them tight under the high pres- sure, of, say 14 atmospheres, prevailing in them, an ingen- ious contrivance to de- crease the pressure is made use of in Sinclair's boiler, the actual boiler being- enclosed by another boiler also made of steel. In the inner boiler in which the soda lye acts upon the wood, prevails a pressure of 14 atmospheres, while in the space between the' inner and outer boilers circulates steam of 6 at- mospheres, and hence the pressure upon the wall of the inner boiler is reduced to 8 atmospheres. The arrangement of Sinclair's boiler is shown in Fig. 22. The vertical boiler con- sists of a cylindrical vessel A tapering above and be- low. In this vessel stands a second one B, of the same form, which, however, is constructed of thin sheet iron, and its surface is perforated with holes. Its diameter is such that the walls of B are at a distance of 1.18 to 1.57 inch from A. B is the portion of the apparatus which serves for the reception of the wood. The boiler is charged through CELLULOSE PROM WOOD, OR CHEMICAL WOOD-PULP. 55 the aperture C, and after the operation is finished, the fluid is discharged through the pipe Oi. The vessel G serves as a storage reservoir for soda lye and is so arranged as to allow of the introduction of lye into the boiler during the operation without a decrease in the pressure taking place. When lye is to be introduced, the lower cock h is first opened, and then the upper one h^. The same pressure then prevails in the vessel G as in the boiler and lye may run into the latter. The entire apparatus is heated by an open fire from the fire-place F. The lower portion of the boiler is protected by brickwork to prevent its coming in direct contact with the flame. The flames pass upwards through special flues which are so arranged that the flames come on every side in contact with the boiler. UNGERER's boiling PROCESS. In some systems of boiling wood an entire battery of boiling vessels, one connected with the other, is used in- stead of a single boiler. When the boilers have been filled with wood, soda lye is introduced into the first one, and allowed to act upon the wood for some time, for instance, one hour. Fresh lye is then introduced into the first boiler in such a way that the fluid contained in it is forced into the second boiler. In about one hour fresh lye is again brought into the first boiler, the lye contained in the second boiler being forced into the third one, and so on. Hence the wood is constantly treated with fresh lye, and disinte- gration is effected more completely and in a shorter time than when the wood is always boiled with the same quan- tity of lye. The system sketched above has been intro- duced by lingerer. In its arrangement the apparatus closely resembles the difl"usion apparatuses used in sugar houses and in factories for the preparation of dye extracts. It seems probable that by this method the object of the dis- integration of the wood might be accomplished with cer- tainty and in the shortest time. 5q cellulose, and cellulose products. keegan's process. This process for the disintegration of the wood b}^ means of caustic soda, differs essentially from the methods in which the wood is heated under high pressure with soda lye. The process in its distinctive features consists in that the wood is brought into a vessel from which the air is ex- hausted. The cold soda lye is then introduced and the pressure upon the fluid raised to 3| atmospheres. When it is supposed that the wood is completely saturated with soda lye, the lye not absorbed is allowed to run off and the vessel is heated to 302° F. The quantity of soda lye absorbed by the vessels of the wood suffices to bring into solution all the encrusting substances, and one great ad- vantage of this process is that the wood treated with lye need only be washed with a small quantity of water in order to regain from it the greater portion of the soda. Hence only a comparatively small quantity of fluid has to be evaporated, thus saving considerable in operating ex- penses, since the great consumption of fuel conditional to the evaporation of a large quantity of lye is one of the drawbacks of the process of producing cellulose by means of caustic soda. The mass of wood boiled according to one of the methods above described, consists of cellulose, the interspaces of which are filled with the fluid which has been formed from the soda lye and the substances absorbed by it. The next problem is to obtain this fluid as completely as possible, so that the soda contained in it may again be brought into use. However, so as not to use too much fuel for evaporat- ing the lye, the recovery of the soda should at the same time be effected in such a manner that as little fluid as possible is obtained. In order to attain this object as com- pletely as possible, the system of gradual lixiviation em- ployed everywhere in chemical establishments when a solid body has to be entirely freed from adhering fluid, is made use of in cellulose plants. CELLULOSE PROM WOOD, OR CHEMICAL WOOD-PULP. Oi In working according to this method a battery has to be used in which lixiviation is effected by means of a current. The distinctive features of such an apparatus are as follows : A number of vessels — ten to twelve — are connected one with the other in such a way that when the level of the fluid in the first vessel reaches a certain height, the fluid running off rises from the bottom through a pipe and can flow into the next vessel. When these vessels are filled with the mass coming from the boiler and water is poured into the first vessel, it will in a short time become mixed with the fluid contained in the mass of wood. By now allowing more water to run into the vessel, the fluid con- tained in it is forced into the next vessel where it becomes more enriched with soda. Now, with the use of twelve lixiviating vessels, the mass in the first vessel will have been twelve times in contact with water at the time when the last vessel has just been filled. When water is then again poured into the first vessel, a corresponding quantity of fluid will run off from the twelfth vessel. This fluid is a very saturated soda solution, and the quantity of soda contained in it corresponds with that present in the fluid discharged from the boiler. The mass of cellulose in the first vessel is now completely washed and can be immedi- ately bubjected to further working by mechanical means. While the first vessel is being emptied, the course of the supply ot water is so changed that the second vessel of the battery becomes the first and in this manner lixiviation is systematically continued. A number of contrivances, such as counter-current wash- ing machines, wash-drums, etc., have been introduced for washing cellulose, which do good service provided they fulfill the object of lixiviating the cellulose mass in the most complete manner, and with the smallest possible con- sumption of water. 58 CELLULOSE, AND CELLULOSE PRODUCTS. PREPARATION OF CELLULOSE BY MEANS OF SODIUM SULPHITE. It has been previously mentioned that in preparing cellulose with caustic soda a portion of the latter may be replaced by sodium sulphate. This salt, to be sure, does not take part in the process, but when the used lyes are evaporated and the residue is heated, it is converted into sodium sulphite, which, like caustic soda, has a destructive effect upon the encrusting substance of the wood. Hence, in the course of the operation, before evaporating the used lyes, it is only necessary to add to them a determined quantity of sodium sulphate in order to obtain by the re- generation of the salt, the corresponding quantity of sodium sulphite. The highly evaporated lyes are mixed with limestone and coal-dust, and after drying, melted in a reverberatory furnace, whereby caustic soda and sodium sulphite are obtained. After washing the salts with water, they are dissolved and used for boiling. For every J 00 parts of dry substance of the lye used, 100 parts of lime- stone and 25 parts of coal-dust are used. The further working of the washed cellulose is effected by purely mechanical means. As a rule, the pieces of cellulose, which still retain largely the form of the frag- ments of wood originally used, are ground in a mill with water to a paste. This paste is mixed with a large quan- tity of water and made homogeneous in the hollander. If to be used in the manufacture of finer qualities of paper it is also bleached with chlorine. The value of cellulose is the greater the longer its individual fibres are, because long fibres felt more completely together than short ones, the resulting paper being much stronger. However, generally speaking, finer qualities of paper are not made from wood cellulose alone, the pulp for them consisting, as a rule, of cellulose prepared from rags mixed with a certain per- centage of wood-cellulose. CELLULOSE FROM WOOD, OR CHEMICAL WOOD-PULP. 59 The statements regarding the consumption of wood and chemicals in the different factories vary so much as to ren- der it difficult to give a correct idea of it. Moreover, the yield of cellulose appears to be essentially effected by the content of water in the wood to be worked. The content of water in thoroughly air-dry wood is about 20 per cent., while in many varieties of wood, when freshly cut, it may amount to twice as much, and for that reason the yield of cellulose will turn out quite different from that calculated from the weight of the wood. The nature of the wood to be worked is also of great influence upon the yield of fin- ished cellulose, as shown by the following figures given by Reid : Variety of wood. Cellulose in per cent. Length of fibre. Beech 38.5 short Birch 42.0 short Hemlock spruce 37.5 long Poplar 41.7 medium Pine 39.0 long Fir 38.0 long. PREPARATION OF CELLULOSE WITH THE ASSISTANCE OF SUL- PHITES, (sulphite-cellulose ACCORDING TO mitscherlich's process). Solutions of acid sulphites possess, similar to caustic alka- lies and their combinations with sulphur, the property of dissolving and destroying the encrusting substance of wood. The process of preparing cellulose in this manner is the in- vention of the German chemist Mitscherlich, all other sul- phite processes being more or less suitable modifications of it. In establishing a sulphite-cellulose plant it is of the utmost importance that an abundance of water should be available, and besides the conditions must be such that the waste liquor can be discharged into a water-conrSe of consid- erable size. For the manufacture of 4,400 lbs. of air-dry cellulose about 15,000 gallons of water are required, and the waste liquor of the plant must be diluted to such an 60 CELLULOSE, AND CELLULOSE PRODUCTS. extent as not to be detrimental to the existence of animals in the streams into which it is discharged, since otherwise the unavoidable consequence would be that the plant would constantly have to pay large amounts for damages to the proprietors of the fishing rights in the respective streams, and might even be forced entirely to suspend operations. The wood has to be prepared with special care and should be used as soon as possible after having been cut down. In case wood which has been cut for some time is to be worked, it should previously be for a few days placed in water. Since there is a difference in the behavior of the various kinds of wood toward the sulphites, only one special variety should at one operation be worked. The trunks to be used must be carefully freed from bark and bast, and adhering dirt is to be removed, so that only perfectly clean wood is brought into the saw-mill. In the latter, the trunks are cut by circular saws into blocks about 16 inches long, and the knots cut out by a suitable machine. Finally the blocks are cut up into thin discs not more than 1 inch thick, which are again inspected, pieces with knots in them being rejected. In preparing the wood in the manner above described there will naturally be con- siderable waste, and besides a large quantity of sawdust. The latter, to be sure, can be worked together with the discs, but readily causes annoyance and trouble by obstruct- ing pipes, etc. Hence, in many plants the practice of cutting the blocks into discs has been entirely abandoned, the blocks being converted by a machine resembling a planing machine, into thin boards 0.27 to 0.29 inch thick, an essential advantage of this procedure being that the longitudinal fibres of the wood are preserved and cellulose of greater length can be obtained. Pine is considered the best material for the preparation of sulphite cellulose, and next to it, fir is most highly valued. Scotch fir, to be sure, is also suitable for the pur- CELLULOSE PROM WOOD, OR CHEMICAL WOOD-PULP. 61 pose, but only the sap-wood should be used, the heart yielding cellulose of a dark color. Other varieties of wood, including deciduous trees, may also be used, but the cellu- lose obtained from them is not as strong as that from coni- fers, and the yield of finished cellulose is small. The preparation of cellulose by the sulphite process may be divided into three principal operations : I. Preparation of the sulphite solution. II. Boiling the prepared wood with the solution. III. Treatment of the cellulose mass obtained. PREPARATION OP THE SULPHITE SOLUTION. According to Mitscherlich's process, the incrusting sub- stance of the wood is dissolved by the use of solution of calcium bisulphite, obtained by treating calcium carbonate with sulphurous acid. The operation is carried out as fol- lows : Sulphurous acid in gaseous form is conducted into a vessel filled with porous limestone, water being at the same time allowed to flow over the limestone. From the limestone, from which the carbonic acid has been expelled, neutral calcium sulphite is first formed. However, since sulphurous acid is present in excess, it ascends in the ves- sel, dissolves in the water trickling down and flows back over the neutral calcium sulphite, which, as it dissolves with greater difficulty than the limestone, has settled upon the latter. Calcium bisulphite, which dissolves with ease, is now formed, and the resulting solution of this salt runs off into a collecting reservoir. In cellulose plants this solution is briefly called lye, and by this term it will be referred to throughout the succeeding pages. Very large quantities of lye being required in a cellulose plant, the apparatus for its preparation must be of ade- quate size. In reference to this, Mitscherlich, who has worked out to the smallest details the entire operation of this process, makes the following important statements: 62 CELLULOSE, AND CELLULOSE PRODUCTS. The limestone serving for the preparation of the lye should be as pure as possible, so that not too much niud is formed by foreign substances (magnesia or organic sub- stance) contained in it. It should further be very porous and at the same time firm, so as not to be crushed by the weight of the layer over it, which might cause troublesome obstructions in the apparatus. A material which can be recommended for the purpose is solid tufaceous limestone in pieces about the size of the fist, which are piled up to the height of 39.37 inches in the tower-like structure in which the lye is prepared. To prevent the pieces of limestone from packing too closely together and crumbling in falling down the entire height of the tower, the latter is filled to a certain depth, and a fresh charge equal in size to the orig- inal one is introduced from the top of the tower w^hen the layer of limestone has sunk to a certain depth. * The sulphurous acid required for the preparation of the lye is obtained by burning sulphur or, if cheaper, pyrites. Sulphur-burning is an operation requiring careful regula- tion, so that combustion is complete and no unburnt sul- phur reaches the absorbing tower. One of the best tests in this respect is the color of the flame, which should be pure blue. The appearance of a yellow, dark flame is an indi- cation of an insufficient admission of oxygen, the conse- quence of which is generally an evaporation of unburnt sulphur which may damage the pipes and become very troublesome. Incomplete combustion of the sulphur may be due to an inadequate supply of air to the furnace itself, but it may also be caused by the current of gas ascending in the absorbing tower not being strong enough, and hence the entire apparatus needs careful watching. In order to have, in addition to the appearance of the flame, a means of testing whether sulphur in the form of vapor is carried along with the sulphurous acid, a wide glass tube, /, Fig. ,28, is inserted in the pipe through which the sulphurous acid is conducted, a portion of the latter passing through CELLULOSE FROM WOOD, OR CHEMICAL WOOD-PULP. (')3 the glass tube, and the appearance of a 3'ellow tinge in the latter is an indication of a content of unburnt sulphur in the gas. The arrangement of the absorbing tower in which the formation of the lye takes place is shown in Figs. 24 and 25. The pipe through which the sulphurous acid is conducted from the furnace k should rise at least two- thirds the height of the tower, then turn downward at a right angle and enter the tower from below. The ascending portion a of this pipe is constructed of iron, while the descending portion b consists generally of tile-pipe. The nearly horizontal portion of the pipe through which the gas enters the tower must by all means consist of tile-pipe. The diameter of the pipe should be such that the gases are not exposed to considerable friction and may sufficientl}' cool off before entering the tower. The absorbing tower is 105 feet high and about 5 feet square. It is constructed of wood, very resinous wood, for instance, Scotch fir or pitch pine, being used. Larch being expensive is more seldom employed. The walls of the tower must be thick, the lower portion being made 3.15 inches, the centre portion 2.36 inches and the upper portion 1.57 inches thick. The separate i)arts of wood are held together by stout iron hoops secured by screws, they, as well as the screws, being carefully coated witb tnr. Joints be- tween the })arts of wood are stufted with tcnv and coated with tar. The lower poiiion of the tower is furnished with a grate h of oak beams, which must be strong enough to support the load of the layei- of limestone placed upon it. Between the grate beams are openings 2.5)5 inches wide through which the gases ascend and the lye runs flown. The upper faces of the beams are 2. 1^5 inches wide, but the lower ones only 1.96 inches. Two oak beams are also placed in the tower 64 CELLULOSE, AND CELLULOSE PKODUCTS. 3i feet above the grate for tl,e purpose of partially relieving lit Boards placed horizontally are secured by Fi(i. 25. means of stout wooden pvgs to the walls of the tower at CELLULOSE PROM WOOD, OR CHEMICAL WOOD-PULP. 65 distances of 3^ feet one above the other. These boards slope inward, so that the fluid dripping down upon them is conducted towards the interior of the tower and the walls of the latter are not moistened. Figs. 26 and 27 show on an enlarged scale the shape of these boards and the manner of fastening them. Large as such a tower is, it is scarcely of sufficient size to prepare in it the lye required for one boiler. In order to carry on operations without interruption and to be able occasionally to clean a tower which has been in use for a Fig. 26. Fig. 27. longer time, it would seem to be advisable to build four towers, erecting one on each corner of a square, and placing the stairs, water pipe and hoist for the limestone in the square. Reservoirs for the reception of the lye which is discharged through a lead pipe from the tower are located alongside the latter. The lead pipe is placed slightly above the bottom of the tower and is bent at a very obtuse angle like a siphon, thus forming a hydraulic joint which allows of the lye running ofl^, but prevents the escape of gas from the tower. The lye first passes through the lead pipe into a barrel open at the top and divided into two compartments by a partition reaching half-way up. The greater portion of the mud carried along by the fluid settles on the bottom 5 66 CELLULOSE, AND CELLULOSE PRODUCTS. of the barrel. From the bottom of this barrel the fluid passes through a lead pipe into an<^t]ier barrel filled with small pieces of limestone in which the small quantity of free sulphurous acid, which ma}' still be contained in the lye, is fixed. After passing through this barrel, the lye runs into the actual lye-reservoirs. Large, prismatic, wooden boxes, 16J feet wide, 10 feet deep and 23 feet long, serve for lye reservoirs, at least two of which should be provided for every boiler. The lye con- tained in one of these reservoirs being just sufficient for one boiling, the two reservoirs are connected by a wooden pipe so arranged that the connection can be cut off for the pur- pose of cleaning one reservoir while the latter is being filled. The conduits leading from the reservoirs to the boiler are also constructed of tarred wood, this material being more capable of resisting the action of the lye than all others, even not excepting lead. In preparing the lye care must be taken that the sulphur- ous acid obtained by combustion reaches the tower entirely cooled oflP. When the odor of sulphurous acid commences to be perceptible at the upper aperture of the tower, water is introduced from the reservoir m placed at a higher level, and the supply is so regulated that the odor of sulphurous acid can just be noticed, the object in view, namely, to ob- tain a lye as concentrated as possible being in this manner most assuredly attained. In case an irregularity should occur in the course of the operation, it is either due to the sulphurous acid carrying along with it vapors of sulphur, or the supply of water is too small, so that the neutral cal- cium sulphite formed upon the pieces of limestone cannot be converted into the readily-soluble acid combination, or, finally, it may be caused by the current " gas being ob- structed in the tower. In this case a remedy must at once be applied and an effort be made to overcome the disturb- ance by a stronger supply of water kept up for some time. CELLULOSE FROM WOOD, OR CHEMICAL WOOD-PULP. 67 BOILING THE WOOD WITH THE LYE, The object of this operation is to bring into solution the encrusting substance and convert the wood into cellulose. For this purpose a large iron vessel or boiler of cylindrical shape, Figs. 28 and 29, is used, which is furnished with four manholes, two on top and two on the bottom. All the fixtures for the introduction of lye, steam, etc., are placed on the lids of the manholes, because they can be more readily kept tight there than in an}' other place. To pre- vent the lye from coming in direct contact with the iron, the latter being strongly attacked by it, the interior surface of the boiler is first coated with a mixture of pitch and common tar, the proportions of the mixture being such Fig. 28. that, when heated the coat is quite thinly-fluid^ but very sticky at the ordinary temperature. Upon this coat is laid a thin layer of sheet-lead, at least 0.07 inch thick, and rubbed down smoothly so that the interior surface of the boiler appears to be lined with lead. The portions of the boiler which have to be moved — the lids of the manholes, etc. — are prov' i with a double protecting covering of thicker sheet J. The interior space of the boiler is lined with brick k. as shown in Fig. 30. The brick used for the pur' should not be porous but of a porcelain-like riaturr Phe lower portion of the interior surface of the 68 CELLULOSE, AND CELLULOSE PRODUCTS. boiler is furDished with a double-brick lining, that in the upper portion being single. For the sake of a close joint, the bricks are grooved and tongued and the spaces between them filled with cement. Lining has to be done with the Fig. 29. Fig. 30. greatest care, and when testing the boiler in the cold up to six atmospheres no exudation of fluid should anywhere be perceptible. Heating of the mass in the boiler is effected by four sys- tems oi heating pipes — see Fig. 28, below to the left. The heating pipes are made of hard lead — an alloy of lead and antimony — and they have comparatively thick walls — 3.15 to 3.18 inches. For a boiler 39 feet long and 13 feet in diameter, the pipes of each heating system must have a length of 656 feet, hence a total length of 2,624 feet is re- quired. The heating pipes are connected with the steam pipes and, on the places where they branch off from the latter, are provided with valves which prevent the lye from running into the boiler in case one of the pipes becomes defective. The proportion between wood and lye is as follows : The Ij'^e should have a concentration of 7° B^., and for every 70.62 cubic feet of boiler space 35.31 cubic feet of pine wood, together with the sawdust belonging to it, are used. CELLULOSE FROM WOOD, OR CHEMICAL WOOD-PULP. 69 If weaker lyes are employed, the quantity of wood has to be correspondingly decreased ; thus, for instance, with lye of 6°, one-seventh less the quantity of wood is taken. The wood and sawdust are as uniformly as possible distributed in the boiler, the latter being filled one-quarter full of wood, and the sawdust is distributed in piles upon the wood. When the boiler has been filled with wood, the lids of the manholes are placed in position and their joints luted with a thick cellulose paste. The safety-valve is then re- lieved and the valves on the lower portion of the boiler are slightly opened. Steam is then introduced into the boiler in such a way that a very slight jet of it passes out of the lower valves, the object of this operation being to moisten the wood uniformly and to expel the air from its pores. In working dry wood, the steam is allowed to pass through the boiler up to ten hours, but for wood freshly cut and containing even considerable moisture, a much shorter time is required. When, after steaming is finished, the cold lye is allowed to run into the boiler, the steam in the pores of the wood is condensed and the lye penetrates quickly into the interior of the blocks of wood. Immediately after the introduction of steam has been interrupted and the valves have been closed, the valve con- necting the boiler with the lye reservoir is opened, and in consequence of the vacuum thus created in the boiler the lye runs rapidly into the latter. Steam is now continuously introduced through the system of heating pipes, so that the contents of the boiler are as rapidly as possible brought to a temperature of 230° F., this temperature being main- tained as uniformly as possible for twelve hours, when it is gradually raised to 242.6° F. When the temperature has reached 230° F. a series of tests are made to see how much effective calcium bisulphite is still present. The test is executed as follows : A glass tube about 7| inches long is suspended to a vertical stand which is furnished with marks indicating |, f^, 3V of the 70 CELLULOSE, AND CELLULOSE PRODUCTS. volume content of the glass tube. Ammonia is now intro- duced into the glass tube up to the gV mark, and the tube is then almost entirely filled with hot lye drawn from the boiler. The glass tube is then closed and ammonia and lye mixed by vigorous shaking. The glass tube is then sus- pended to the stand and in a few minutes a precipitate is formed, the semi-fixed sulphurous acid being neutralized b}' the ammonia, while calcium sulphite, which is soluble with difficulty, is separated as a precipitate. From the precipi- tate the proportion of the effective solution can be readily determined. When the precipitate is only equal to one- sixteenth of the length of the glass tube, boiling is nearly complete. When the precipitate is only equal to one- thirty-second, heating is immediately interrupted and the boiler emptied. A very rapid decrease in the precipitate towards the end of boiling is an indication of detrimental processes taking place in the boiler. When the lye in con- sequence of having been improperly prepared contains poly- thionic acids, a modification of the process in the boiler takes place, the calcium sulphite being then decomposed and calcium sulphate (gypsum) and sulphur are separated upon the wood. The wood remains brown and hard, and is not completely converted into cellulose. When the operation is properly conducted, boiling is finished in from 36 to 48 hours. For the purpose of regaining the sulphurous acid, an abundance of which is still contained in the lye after the operation, the lye is allowed to enter a lead coil which lies in a cooling vat and terminates in one of the towers. In the lead coil the water which is saturated with sulphurous acid is condensed and collected by itself, while the sulphur- ous acid passes into the tower, to be again used for the preparation of lye. WASHING THE CELLULOSE. When boiling has been finished, the contents of the CELLULOSE FROM WOOD, OR CHEMICAL WOOD-PULP. 71 boiler are emptied into a receptacle underneath the boiler, and after the cellulose-mass has settled to the bottom, the supernatant fluid is discharged into a watercourse, provided it is in a highly diluted state. If this, however, is not the case, the fluid has to be mixed with a quantity of milk of lime sufficient for the conversion of the calcium bisulphite and the free sulphurous acid still contained in it, into cal- cium sulphite, which settles on the bottom of the receptacle and may be again converted into calcium bisulphite by the introduction of sulphurous acid into the water poured over it. When the boiler has been emptied it is rinsed out with water, and before starting a fresh operation, it is advisable to subject it to a thorough examination and to knock off with a wooden mallet any gypsum which may have de- posited on the brick work. The cellulose-mass coming from the boiler contains cer- tain quantities of finely divided gypsum, fragments of neutral calcium sulphite, and besides is saturated with lye. To free it from these admixtures it is subjected to the action of a stamping mill, the operation being assisted by large quantities of water. The cellulose-mass is directly con- veyed by a transporting contrivance from the boiler to a funnel from which it falls into the stamping trough, in which, mixed with the proper quantity of water, it is sub- jected to the action of the stamps. The latter are so set that they cannot fall entirely to the bottom of the trough, crushing the mass being thus prevented. From the stamp- ing mill the pasty mass runs off through broad gutters which are provided with sand-catchers for keeping back sand, grains of gypsum, etc., the particles floating on the top being retained by a cleaner placed over the fluid. From the gutters the pulp reaches an inclined cylinder covered with a wire sieve. The water runs off through the meshes of the sieve, while the cellulose in the form of crumbs leaves the cylinder at the lower end and is quite completely freed from moisture by rolls. 72 CELLULOSE, AND CELLULOSE PRODUCTS. DEFECTS OF CELLULOSE AND THEIR REMOVAL. Owing to deviations from the proper process of working, the finished cellulose may show various defects which may partially be remedied. According to Mitscherlich the most important defects are as follows : The cellulose instead of being pure white shows a yellow- ish or brownish color. The cause of this phenomenon is due to the fact that towards the end of boiling the required quantity of sodium bisulphite was no longer present. Such cellulose can be made quite white by bleaching with chlorine. Some white pieces not converted into fibre may occur in the otherwise uniform mass, which is an indication of too much wood having been brought into the boiler. Such cellulose may very well be used for the manufacture of firm and strong paper, but must first be carefully rolled. How- ever, such cellulose is less suitable for bleaching. The occurrence of black particles in the mass is gen- erally due to insufiicient cleaning of the wood before it is cut up, and is caused b}' rotten pieces of bark which have been left on the wood. The black spots may also be due to particles of the belts, this being a defect which cannot be removed. Some kinds of cellulose contain small, soft bundles of fibre of a brownish color which may have been caused by the respective particles having become too hot in the boiler, or by incompletely freeing the wood from bast. These defects, as a rule, disappear completely by subjecting the cellulose to bleaching with chlorine. The occurrence of larger brown bundles of fibre of con- siderable firmness is mostly due to a gross error committed in boiling, or to the fact that some of the stamps of the stamping-mill have come too near to the trough. With the use of the proper quantity of water and a right width of the slits in the splinter-catcher, these pieces should have been retained during washing. With the microscope small, lustrous crystals may some- CELLULOSE FROM WOOD, OR CHEMICAL WOOD-PULP. 73 times be noticed in the cellulose, this being proof of an in- sufficient quantity of water having been used in washing. If the microscope shows the presence of small particles of an earthy appearance it is an indication of too little wood having been used in boiling, these particles consisting of neutral calcium sulphite. They can be most readily re- moved by an addition of hydrochloric acid to the wash- water, but cellulose thus treated requires a larger quantity of chlorine in bleaching. A change in color of the at first pure-white cellulose during washing is due to small quanti- ties of iron which reach the mass chiefly through the wash- water and iron utensils. This iron may also be removed by acidulating the wash-water with hydrochloric acid. The finished cellulose may either be immediately used for the manufacture of paper, or it may be freed from the larger portion of water by pressure. If, however, it is to be kept without undergoing a change, it has to be com- pletely dried, as otherwise it becomes readily mildewed, especially when exposed to heat. Other methods for the manufacture of cellulose by the sulphite process differ in details only from Mitscherlich's process above described, all being based upon the proposi- tion that by boiling wood under an increased pressure with solution of calcium bisulphite the encrusting substance is dissolved and the mass need only be thoroughly washed to yield a material available for the manufacture of paper. PREPARATION OF CELLULOSE WITH THE ASSISTANCE OF THE ELECTRIC CURRENT. KELLNER's PROCESS. This process diff'ers essentially from the methods pre- viously described, and is based upon a very ingenious ap- plication of the electric current, the latter being used for decomposing common salt solution. When an electric cur- rent of suitable strength is allowed to act upon a solution of sodium chloride (common salt), caustic soda, free chlorine 74 CELLULOSE, AND CELLULOSE PRODUCTS. and hypochlorous acid are formed. By allowing these bodies to act alternately at a suitable temperature upon wood, the lignin will in a certain time be completely de- stroyed and pure cellulose remain behind. For carrying out his process, Kellner uses the apparatus, shown in Fig. 31, consisting of three boiling vessels B, A and L, which are connected one with the other by the pipes H, J, M, TV and K, the positive pole of a source of electricity (a dynamo) entering at R and the negative pole at S. When the apparatus is to be used, the boilers A and B are charged through the manholes E with wood prepared in the usual manner, and common salt solution is then allowed to run in until it becomes visible in the fluid-indicator L which is located in the interrji^iiary boiler. Coils of pipe through which high-pressure steam is conducted lie in the boilers A and B. Heating is continued until the temperature of CELLULOSE FROM WOOD, OR CHEMICAL WOOD-PULP. 75 the common salt solution has been brought to 262.4° F., when the electric current is closed, whereby the common salt solution is decomposed, caustic soda, free chlorine and hypochlorous acid being formed. The fluids containing these bodies ascend from M and N through J J, act upon the wood contained in A and B, and reunite in the vessel L. The gases accumulating in L are conducted through the valve V and the pipe T into the condenser P. As will be seen from the above description, the wood in one of the boilers is treated with caustic soda lye and that in the other with chlorine and hypochlorous acid, both of these bodies having a destructive effect upon the encrusting substance. To make the process entirely uniform, the direction of the electric current is from time to time re- versed, so that the wood which has been treated with caustic soda is exposed to the action of the chlorine and vice versa. By reason of the powerful chemical action of the caustic soda and chlorine alternately exerted at short intervals upon the wood, the operation proceeds with greater rapidity and smoothness than by any other method, and cellulose in a perfectly bleached state is directly obtained from the apparatus. These advantages should certainly be sufficient to insure to Kellner's process extended application in prac- tice. PREPARATION OP CELLULOSE PROM STRAW. While all efforts to prepare from the straw of our varieties of grain a cellulose suitable for the manufacture of finer qualities of paper were for a long time in vain, recent en- deavors in this direction have been crowned with success, and this material is now worked on a large scale by several factories. In working straw for cellulose, the preparatory operations form a very important part of the process. The straw has not only to be freed from adhering earth, weeds, etc., but also as far as possible from the knots of the indi- 76 CELLULOSE, AND CELLULOSE PRODUCTS. vidual stalks, these knots offering far greater resistance to the action of the chemicals than the tubular portions. The operation is commenced by opening the bundles of straw and shaking out the weeds as much as possible. The straw is then cut very fine in a straw-cutter and cleaned by means of a fan. The current of air in the latter should be of such a force that the particles of stalks are positively carried away, while the heavier bodies, including the knot- pieces, fall to the bottom. If the operation is properly carried on, the greater portion of the knot-pieces, as well as the grain still contained in the straw, will be found in the mass collected in front of the fan, while the cut straw which has been blown away consists chiefly only of tubular particles of stalks. For the further working of the winnowed straw the soda process is generally used, the encrusting substance of the straw being much more readily dissolved in the alkaline fluid than that of wood. Hence, boiling may be effected under considerably less pressure, three to, at the utmost five, atmospheres being in most cases sufficient. The great volume occupied by the finely-cut straw is an objectionable feature which might necessitate the employ- ment of boilers of very large dimensions. This may, how- ever, be overcome by pressing down the straw in the boiler, while the lye is allowed to enter from below. By the action of the lye the bulk of the straw is very rapidly decreased and 1,100 pounds of straw can in this manner be readily worked at one time. Horizontal cylindrical boilers of the revolving type have been found most suitable for working straw. The boiler having in the above-mentioned manner been filled with straw and lye, a portion of the latter is discharged, so that the boiler is only one-third full of lye. Steam is then in- troduced through the hollow trunnions of the boiler and the latter is made to revolve slowly — once in one or two minutes — around its axis. By boiling, the straw is con- CELLULOSE FROM V'OUxy, OR CHEMICAL WOOD-PULP. 77" verted into a pasty mass, and boiling has to be continued until samples taken from the boiler show the complete dis- integration of the knotty particles. The boiler is then placed so that the man-hole is turned downward, and the pasty contents are allowed to run out. Since the individual particles adhere together in the form of fibres, the entire mass is passed through a stuff-mill consisting of a stationary bed-stone and a revolving runner. Since the characteristic yellow coloring-matter of the straw is not decomposed by boiling with the alkali, the re- sulting cellulose would also be of a yellow color, and hence the mass has to be bleached. Before this is done, it must, however, be completely freed from alkali by washing, special apparatus being employed for this purpose. Bleaching by means of chloride of lime is effected in the hollander, 11 to 22 pounds of chloride of lime being re- quired for every 220 pounds of dry straw. During the process of bleaching, the mass must be kept in constant motion, and the operation should be effected at the ordinary temperature, since at an increased heat, the cellulose itself would be attacked by the chlorine and carbonic acid be evolved from the mass. The treatment with chloride of lime must be succeeded by thorough washing and, in case the finished product is not to be immediately used for the manufacture of paper, it has to be freed from water by hydraulic presses. According to different statements, the yield of finished cellulose varies very much, but it appears to be chiefly de- pendent on the state of maturity of the straw used. From all that can be learned on the subject, a yield of 72.6 to 88 pounds of dry cellulose from every 220 pounds of straw used may be calculated on. Besides the straw of the different varieties of grain, other parts of plants are utilized for the preparation of cellulose for the manufacture of paper, esparto (from Stipa tenacissima) especially being largely employed in England for that 78 CELLULOSE, AND CELLULOSE PRODUCTS. purpose. The leaves of the esparto plant present the ad- vantage of being very readily disintegrated, an increase in the pressure during boiling not even appearing necessary. The cellulose obtained from esparto is said to be distin- guished by great firmness and pliability, so that it is suit- able for the manufacture of very firm, white writing-papers. The quantitative yield also is said to be very satisfactory, 92.4 to 110 pounds of cellulose being obtained from 220 pounds of raw material. Jute bagging, which has been used for shipping trans- atlantic products, is also utilized, when it can be had in sufficient quantities, for the preparation of cellulose, and this cellulose is especially suitable for the imitation of gen- uine Manila paper which is prepared from the fibres of Manila hemp, Musa textilis. The first step in working jute in the form of cuttings or " butts," spinner's waste and bagging, is to cut up the material in a rag-cutting machine. The comminuted mass is then brought into a rag-boiler and for some time boiled under slight pressure — 1| atmos- pheres — with a comparatively large quantity of lime — 25 to 35 per cent, of the weight of the jute. It is then washed in a half-stuff hollander and ground. As a rule, it is finally slightly bleached with chloride of lime. UTILIZATION OF EXHAUSTED LYES AND THEIR NEUTRALIZATION. The fluids which have served for the preparation of cellulose from wood contain, in addition to a consider- able quantity of organic substance, the total quantity of mineral substances employed in their preparation. Partly for economic, and partly for hygienic, reasons, these sub- stances have either to be reconverted into such products as can be again utilized in succeeding operations, or it must be endeavored to change them in such a manner that they (Hiay, without risk, be discharged into a natural water- course, river or creek. CELLULOSE FROM Wuui/, vji. CHENIICAL WOOD-PULP. 79 When working with the soda process, efforts are generally made to recover the soda as lar as possible. The exhausted lyes contain the soda largely in the form of organic com- binations which can be broken up by heat, carbonate of soda remaining finally behind, which may be again used for the preparation of lye. In order to recover the soda, the exhausted lyes are evaporated to dryness, and the re- sulting solid mass is calcined under the access of a strong current of air. The organic substance is thereby completely destroyed, the residue consisting of calcined (anhydrous) soda. Since the evaporation of such large quantities of fluid as -result in the manufacture of cellulose, requires a consider- able amount of fuel, the apparatus- used for the purpose should be so constructed as to allow of the heat produced being utilized to the fullest extent. Numerous propositions having more or less the object in view, namely, the saving of fuel, have from time to time been made. However, reverberatory furnaces are most frequently used for calcining the evaporated mass, the still very hot fire gases escaping from the furnace being utilized for heating shallow pans in which the lyes are constantly more and more concen- trated, and finally converted into a solid mass ready for calcination in the furnace. The quantity of soda recovered is of course considerably smaller than that originally used, a portion of it having been lost in the wash waters, but the latter do not contain enough of it to make their evaporation profitable. How- ever, if the operation is properly conducted, from 60 to 66 per cent, of the soda used may be recovered. When work- ing with the sulphite process, it is of the utmost importance to change the lyes so as to be able to discharge them, with- out risk, into running water. According to Mitscherlich, this is to be effected by greatly diluting the lyes, as well as the water used in washing the cellulose. However, it must be borne in mind that very large quantities of exhausted 80 CELLULOSE, AND CELLULOSE PRODUCTS. lye are daily produced in a cellulose plant. Every quart of exhausted sulphite lye contains, in round numbers, 3 ounces of organic substance in solution and, in addition, the total quantity of mineral substances contained in the original lye. However, since the lyes contain considerable quantities of sulphites which become decomposed in water, sulphur- etted hydrogen being evolved, it will be readily understood that the waters of even a quite considerable stream will, in the course of time, become polluted to such an extent as to kill the fish inhabiting them, sulphuretted hydrogen being an exceedingly violent poison for them. It would, therefore, seem absolutely necessary to neutral- ize the lyes as much as possible before discharging them into a water-course. According to a process proposed for this purpose by A. Frank, the exhausted lye from a boiling is mixed in a large cistern with a sufficient quantity of milk of lime to form neutral calcium sulphite which, being a salt that dissolves with difficulty, settles to the bottom, and after having been freed as far as possible from the fluid in a filter-press, can be re-used for the preparation of sulphite lye. The fluid having been separated from the neutral calcium sulphite is freed in another receptacle from the ex- cess of lime by the introduction of smoke gases containing much carbonic acid, while the oxidation of a considerable quantity of organic substance is effected by conducting compressed air through the fluid. The fluid thus far puri- fied is conducted upon an irrigation field and, after re- maining there for some time, is discharged into running water. The calcium sulphite thus regained covers a con- siderable portion of the expense incurred in carrying out the process. The sulphite lyes may also be utilized in tanning, but being of a very dark color, they impart this color to the leather, and besides make it brittle. However, this draw- back may be overcome, and, according to a process proposed CELLULOSE FROM WOOD, OR CHEMICAL WOOD-PULP. 81 by Honig, the lye, previous to being concentrated by evap- oration, is deprived of its color by treating it with zinc dust and sulphuric acid, a sufficient quantity of the latter to decompose all the sulphites contained in the fluid being required. In carrying out this process, the resulting large quanti- ties of sulphurous acid may, of course, be utilized for the preparation of fresh lye, a portion of the expense incurred being thereby covered. 6 VEGETABLE PARCHMENT. When unsized paper, which should, however, contain no wood-pulp, is for a short time subjected to the action of quite concentrated sulphuric acid, the cellulose undergoes a peculiar physical change. The paper loses considerably in thickness, assumes a transparent appearance, becomes harder and acquires a condition reminding one of horn, be- coming at the same time about five times as tenacious as the original material. AVhen paper thus treated is moist- ened, it loses its rigidity and acquires the condition of animal bladder. If stretched tight and allowed to dry, it regains its former horn-like condition. The chemical com- position of vegetable parchment is exactly the same as that of cellulose and, hence, the change effected by parchment- izing in the above-described manner is simply a physical one. Concentrated solution of zinc chloride produces the same parchmentizing effect as sulphuric acid, but in prac- tice this process is not used, because it is far more expensive, and the complete removal of the poisonous zinc salt is far more troublesome than that of sulphuric acid. The parchmentizing action of sulphuric acid is explained as follows : A solution of cellulose in concentrated sulphuric acid is first formed to a certain depth upon the surface of the paper, but so soon as the latter is taken from the sul- phuric acid and brought in contact with a large quantity of water, the solution is immediately decomposed to free sulphuric acid and amyloid, the latter cementing the indi- vidual cellulose fibres together to a uniform mass. By this (82) VEGETABLE PAE.CHMEXT. bo cementation the paper acquires its extraordinary strength and transparent appearance. NATURE OP THE PAPER TO BE PARCHMENTIZED. For the production of vegetable parchment of the proper quality, paper especially made for this purpose has to be used, it being of the utmost importance that it should not contain a filling stuff of any kind, and that it consists of nothing else but cellulose. It must, therefore, neither be sized nor contain an addition of a foreign body. In manufacturing paper intended for parchmentizing it has to be taken into consideration that its bulk is consider- ably decreased by the process, and hence it has to be made of sufficient thickness. To make the process of parchment- izing effectual, it is necessary for the paper to become com- pletely impregnated with the acid the moment it comes in contact Avith it, it being only under tliese conditions that the momentary solution of the cellulose in the sulphuric acid takes place, not only upon the sui face, but also thi'ough^ out the entire bulk, of the paper. Hence paper to answer these requirements must, on the one hand, bo of suitable thickness, and, on the other, should not be subjected to great pressure in passing through between the rolls. In this manner a loose, spongy paper is obtained, Avhicli is of comparativel}' little value for other purposes, but by reason of its porous, felt-like nature is especially well adapted for the preparation of vegetable parchment. As previously mentioned, by bringing paper in contact with sulphuric acid an actual solution of cellulose in the acid takes place, which must, however, be again rapidly decomposed. This fact renders it impossible to impregnate the paper throughout its entire bulk when the latter exceeds a certain limit, because before the acid could penetrate into the interior, a comparatively thick layer on the surface would be completely dissolved. However, if parchment of greater thickness is to be prepared, recourse may be had to 84 CELLULOSE, AND CELLULOSE PRODUCTS. a process which is based upon the fact that paper just parch- mentized is very stick}' when taken from the sulphuric acid bath. Two, three, or even four, breadths of paper are simultaneously subjected — each by itself — to the action of the sulphuric acid, and when taken from the latter are passed together — one on top of the other — between rolls, whereb}'^, on the one hand, a considerable portion of adher- ing acid is squeezed out, and, on the other, the breadths of paper are inseparably cemented together. SULPHURIC ACID USED FOR PARCHMENTIZING. In order to obtain parchment of always the same quality, sulphuric acid of the same concentration and temperature has to be employed, and allowed to act upon the paper for a certain time. While the first-mentioned factors can be readily ascertained, the time during which the acid has to act depends largely on practical experience, and has to be fixed for every kind of paper by a few experiments on a small scale. Sulphuric acid of a specific gravity between 1.659 (58° Be.) and 1.754 (63° B4.) has, after many experi- ments, proved most suitable for use. Larger quantities of a fluid of the desired concentration are at one time prepared by mixing concentrated sulphuric acid with water, the mixture being allowed to stand by itself until its temper- ature is reduced to at least 60° F., because acid of a higher temperature acts too energetically upon the paper, and the latter might in consequence be readily converted into a slimy mass. Many manufacturers prefer even to work with acid of quite a low temperature because all the operations can then be carried on more leisurely. The mixing of larger quantities of sulphuric acid with water being disagreeable work requiring great precaution, most of the manufacturers of parchment paper work with so- called chamber acid, which has a specific gravity in round numbers of 60° B^., and can be directly used, besides being considerably cheaper than highly concentrated sulphuric acid. VEGETABLE PARCHMENT. 85 When working with acid of G0° B^., at a temperature not exceeding 60° F., five seconds' contact with the acid suffice for parchmentizing thinner varieties of paper. Thicker papers require a correspondingly longer time, and very thick papers are passed through the acid reservoir so slowly as to remain submerged upwards of 20 seconds. It must, however, be borne in mind that by coming in contact with the paper, the acid in the parchmentizing ves- sel becomes slightly heated, and hence to prevent it from acting too energetically upon the paper, the velocity with which the latter is drawn through the acid has to be some- what increased after the operation has for a short time been in progress. When the paper has remained the required time in the acid it is as rapidly as possible withdrawn from the action of the latter, this being effected by bringing it in contact with large quantities of water, by which the acid is diluted to such an extent that the cellulose is no longer affected by it. The last remnants of sulphuric acid adhering to the parchment are removed by treatment with an alkaline fluid. PARCHMENTIZING APPARATUS. For the manufacture of parchment paper on a large scale, an apparatus is used, the essential features of which are as follows : The endless paper to be worked is wound on a roll from which it can be smoothly unrolled under a slight pull, and is next carried under glass rolls beneath the surface of the sulphuric acid, the latter being contained in a lead- lined trough. By arranging several rolls in the trough the paper is for a suitable time exposed to action of the acid, and is finally lifted from it in a perpendicular direction. As soon as it appears above the lev^l of the fluid it is car- ried through between two rolls with sufficient pressure for the greater portion of acid to fall back into the lead-lined trough. The paper is now carried over glass rolls into a long trough filled with clean water, in which the greater 8G CELLULOSE, AND CELLULOSE PEODUCTS. portion of still adhering acid is rinsed off. Since this first wash water becomes highly heated, it is advisable to charge the trough at the start with very cold water. From the first trough the paper reaches another one, in which it is further treated with water, it being best to have the water in this trough constantly running in a direction counter to that of the paper. This water absorbs but a very small quantity of sulphuric acid from the paper, and is allowed to run off from the wash-trough. It is advisable to sprinkle both sides of the paper, as it rises from the second trough, with fine jets of water from two horizontal pipes. The last traces of acid still adhering to the paper are removed by passing it through a trough filled with water, which is constantly kept alkaline by small quantities of caustic soda lye or ammonia. After again being treated with clean water the paper is subjected to strong pressure between rubber rolls or wooden rolls covered with felt. It then passes between adjusting rolls, and finally reaches hollow iron rolls heated by steam for the purpose of drying the finished parchment. While drying, the parchment has to be subjected to strong tension both lengthways and laterally, otherwise it would contract very much and acquire an uneven and wrinkled surface. Since the sulphuric acid used in the preparation of parchment is only highly diluted, without being otherwise changed, provision should be made for its recovery. This can best be effected by having the first w^ash-trough into which the paper passes directly from the sulphuric acid vat, of but a small size and furnishing it with a large discharge valve, as well as with quite a large water-supply pipe. Two horizontal sprinkling pipes are also fixed over this trough. "When the content of acid in the first wash water has increased to such an extent as to amount to 20 per cent, of the entire quantity of fluid, the discharge valve and the VEGETABLE PARCHMENT. 87, sprinkling pipes are opened. The contents of the trough run off in a few seconds, the acid being during this time washed from the paper by the sprinkling pipes. When the trough is empty, the discharge valve is immediately closed and the trough refilled with water by opening the cock of the large water pipe, the sprinkling pipes being finally closed. With a small-sized trough, a large valve, and a water pipe of considerable diameter, the discharge of the very acid water, as well as the refilling of the trough is so rapidly effected that the supply of water furnished during this time by the action of the sprinkling pipes is sufficient and the operation need not be stopped, and thus very large rolls of endless paper can, without interruption, be made into parchment. The wash water from the first trougli when it contains about 20 per cent, of sulphuric acid, can be readily worked to sulphuric acid of 60° Be., it being only necessary to evaporate it in a shallow lead pan heated by steam till the acid has acquired its ordinary concentration. When work- ing with the more concentrated commercial sulphuric acid, the wash water is utilized in place of pure water, for dilut- ing the acid. However, as in this case, an excess of sul- phuric acid would before long accumulate in the factory, it is advisable to use, instead of ordinary commercial acid, fuming sulphuric acid, the latter by reason of its content of sulphur trioxide requiring much more water for dilution to G0° Be. PROPERTIES OP PARCHMENT PAPER. By the conversion of ordinary paper into parchment its bulk is considerably decreased as well as its content of ash, but its specific gravity is much increased. The principal feature, however, is the increase in absolute strength, which makes parchment especially suitable for book bindings and all other purposes for which strength is a requisite. The changes paper undergoes by parch mentizing are shown for three different varieties of it, in the table below : 88 CELLULOSE, AND CELLULOSE PRODUCTS. Raw paper . Parchment paper. Eaw paper Parchment paper. Raw paper . . . Parchment paper. Thickness milli- meters. Specific gravity. 0.234 0.152 0.178 0.113 0.134 0.088 0.617 0.964 0.543 0.937 0.624 0.927 Absolute strength per square millimeter Kilogrammes. 1.415 6.436 1.483 5.111 1.503 5.777 Content of moisture per cent. 6.785 8.778 7 071 8.483 6.978 9.160 Content of ash. 633 0.496 0.645 0.458 0.678 0.559 As previously mentioned, the preparation of parchment of special thickness presents some obstacles, it being diffi- cult to saturate in a short time thick paper with sulphuric acid and to remove the latter rapidly. In this case two or more breadths of paper are treated, each by itself, with sulphuric acid and the first wash water, and then passed together, under quite heavy pressure, between rolls. T-je surfaces of the breadths of paper are at this time still suffi- ciently sticky to make it possible to combine the breadths so intimately to a single one, that the joint cannot be seen even by examining the cross section of the dried parchment with the microscope. By the use of an apparatus of suit- able construction, as many as four breadths may thus be combined in one and, though the thickness of the latter does not exceed that of ordinary drawing paper, its strength is actually surprising. Particular care must be taken in washing parchment of such special thickness, as it would in a short time be decomposed if a small quantity of sulphuric acid should happen to remain in its interior. RENDERING PARCHMENT PAPER FLEXIBLE. If parchment paper is to be deprived of its characteristic stiffness and hardness and to be rendered flexible, the object may be attained by suitable treatment with strongly hy- VEGETABLE PARCHMENT, 89 groscopic bodies, glycerin being especially adapted for the purpose, as it is perfectly harmless and there can be no objection to the use of a material treated with it, for wrap- ping up articles of food. Parchment not intended for the latter purpose may be rendered flexible by the use of a con- centrated solution of magnesium chloride, calcium chloride or of another highly hygroscopic salt. The operation is carried on as follows : The finished parchment, before it has been dried, is allowed to run over a roll dipping par- tially into a vessel containing concentrated glycerin, a thin layer of the latter, regulated by a scraper, adhering to the roll and being transferred to the parchment. Parchment thus treated does not contract very much in drying and remains flexible to a certain degree. By reason of its great density parchment paper is easily colored, the separation of the coloring matter in it being readily efi^ected by placing it in a suitable solution. Ani- line colors are generally employed, fuchsin being used for r* d. The alcoholic solution of fuchsin is poured into boil- ing water and when thoroughly distributed in it, the parch- ment is introduced. For blue, water-soluble blue or indigo carmine is used ; for violet, aniline-violet, or the parchment is first colored red and then blue. Yellow is obtained with picric acid ; orange, with fuchsin and picric acid ; and green, with picric acid and indigo-carmine. The behavior of vegetable parchment towards the ordi- nary adhesive agents, such as mucilage, paste, glue, etc., is very unfavorable, they either do not adhere at all or crack off very readily. A somewhat better adhesion is effected by first applying alcohol, and then the adhesive agent to the parts of the parchment to be joined together, or by laying a strip of very thin ordinary paper between them. The best material for the purpose of joining together parchment paper is chromium glue, prepared by allowing glue to swell up in water to w^hich a quantity of potassium dichromate equal to 2 per cent, of the weight of the dry glue has been 90 CELLULOSE, AND CELLULOSE PRODUCTS. added. When swelled up, the glue is dissolved by heating in water, the solution being kept in the dark until used. Chromium glue is used b}' coating the pieces to be joined with the solution, pressing them together and exposing them to the light, the chromium glue being thereby con- verted into an insoluble combination which onl}' swells up, without, however, dissolving if brought, even for a longer time, in contact with water. Vegetable parchment finds many applications. It is made into very strong pads for certain important writings, is employed for the manufacture of receptacles for articles of food, for instance, sausage casings, further for durable book bindings, etc., and large quantities of it are also used for osmotic purposes, it possessing the property of allowing the passage of fluids, such as solutions of salt, sugar, etc. VULCANIZED CELLULOSE (VULCANIZED FIBRE). Under this name a material is brought into the market by some English factories which, as regards its properties, is claimed to be very suitable as a non-conductor of heat and for insulating electric lines. According to Foster it consists essentially of a product which, as regards its mode of manufacture, closely resembles vegetable parchment, but it has the advantage that it can be made in pieces of any desired thickness, Avhich with vegetable parchment can only be done within very narrow limits. According to the description, vulcanized fibre is prepared by treating cellulose in a loose form, or in the form of paper, with a fluid consisting chiefly of sulphuric acid, to which, however, have been made such additions as will neutralize the progressive action of the acid when allowed to remain for a longer time in contact with the vegetable fibre. This is claimed to be attained by dissolving metallic zinc, and next dextrin, in the sulphuric acid. According to the patent specification, the process is as follows : For every 32 parts of ordinary sulphuric acid 1 part zinc is used, the mixture VEGETABLE PARCHMENT. 91 being allowed to stand quietly till all the zinc is dissolved and the fluid has again acquired the ordinary temperature. In the fluid thus obtained, which represents a solution of zinc sulphate in an excess of sulphuric acid, dextrin is dis- solved, the proportion used being 1 part of dextrin to 4 parts of solution. While, as previously mentioned, the adhesive power of paper treated with sulphuric acid alone, disappears in a short time so that haste has to be made in combining two or more breadths of paper, paper treated in the above-men- tioned solution retains its adhesive and cementing powers for a much longer time, so that any number of breadths can be leisurely combined to one plate, or loose cellulose may bo shaped. The finished articles are first treated with solu- tion of common salt in water, and finally completely freed from adhering salts by long-continued washing with water. In the common-salt bath a transformation is claimed to take place, so that sodium sulphate and zinc chloride are formed which can be readily removed by washing. Very thick plates or otiicr thick articles may, it is claimed, be prepared from the mass by coating the parts to bs cemented together with the above-described solution, by which they are rendered adhesive and can be made into a single piece by pressing or rolling. Vulcanized fibre is found in commerce in two forms, namely, as a hard mass closely resembling wood in its properties, and as a soft, flexible and elastic substance be- having similarly to leather. The hard mass can be worked with the knife and saw, can be planed and turned, and, in a fresh state, can by pressure be molded into any desired shape ; two pieces may be glued together like wood. On account of being insendble to moisture and air, and by reason of its exceedingly slight power of conducting elec- tricity, the mass is claimed to be especially suitable for the manufacture of insulators for electrical purposes. The elastic mass is recommended for all purposes for which, at 92 CELLULOSE, AND CELLULOSE PKODUCTS. the present time, leather or vulcanized rubber is generally used, for instance, for packing, valves, etc. In the description given above the statements made in the patent specifications have been accurately followed, and an attempt has been made to prepare vulcanized fibre in accordance with them, but entirely satisfactory results could not be obtained. While it cannot be denied that parch- mentizing in the fluid containing zinc and dextrin takes place more slowly than when working with sulphuric acid alone, it was impossible to obtain a mass approaching in solidity that of wood, or even of horn. The incompact masses could be quite completely freed from the acid and salts by repeated treatment with water, but this was very incompletely the case with the masses subjected to stronger pressure, so that in drying they fell to pieces by reason of sulphuric acid remaining behind. These observations jus- tify the conclusion that several things essential for the pre- paration of the vulcanized fibre mass have not been given in the patent specification, and that the product cannot be made by simply following the statements contained therein. V. PRODUCTION OF SUGAR AND ALCOHOL FROM WOOD-CELLULOSE. The fact that cellulose may be converted into ferment- able sugar by boiling it for some time with dilute mineral acid has been known for a long time. Although, theoreti- cally, the conversion of cellulose into sugar appears a very simple process, in practice on a large scale numerous diffi- culties are encountered. Although the first experiments in this direction were made as early as 1854, no process has been discovered up to the present time which could be used on a large scale with any prospect of success. Nevertheless, it would not seem that a mistake is made in saying that with the preparation of fermentable sugar from cellulose it will be exactly the same as with the production of pure cellulose from wood, several processes for that purpose being now known after many unsuccessful experiments had been made, and that a method for the production of fer- mentable sugar from wood-cellulose, which can be practi- cally applied, will also be finally found. In all the attempts to obtain fermentable sugar from cel- lulose, wood has heretofore been employed as the initial material, and that the results obtained with its use have comparatively given but little satisfaction, may possibly be chiefly due to the fact, that in the wood the individual vas- cular bundles, consisting of cellulose, are so firmly cemented together by the lignin as to make them in a high degree proof against the action of chemicals. Since a way for the destruction of the lignin and render- ing the cellulose accessible to the action of chemicals has (93) 94 CELLULOSE, AND CELLULOSE PEODUCTS. been found in the progress made in this direction in the manufacture of cellulose, it seems reasonable to suppose that the time is drawing nearer when the question as re- gards the production of larger quantities of fermentable sugar from cellulose, relatively wood substance, will also bo solved. OLDER METHODS. - The first attempts to produce on a larger scale ferment- able sugar from wood were made b}' Zetterlund. He used fir sawdust and boiled it with 8 per cent, of its weight of h\'drochloric acid under a pressure of IJ pounds per square inch. After boiling for 8 hours, a fluid containing 3.38 per cent, of dextrose was obtained, and after 11 hours, 4.38 per cent. Calculated to sawdust, 19.G7 per cent, of the latter had been transformed. The fluid, after being separated from the solid residue, was neutralized with soda and then contained a quantity of common salt equal to the quantity of hydrochloric acid used. The fluid was brought into fermentation with yeast prepared from 22 pounds of malt extract and the fermented mass was subjected to dis- tillation. The yield of alcohol from 990 pounds of saw- dust amounted to 26.5 quarts. As will be seen from the figures given above, there is a considerable increase in the quantity of sugar obtained when boiling is continued for more than 8 hours. As the correct basis for an explanation of this increase, it may well be assumed that at the beginning of the action of the hydrochloric acid upon the wood, the tendency of the entire chenncal process was to attack the lignin by the acid and hence, as a preparatory operation, a gradual laying bare of the vascular bundles took place. Only after this process had progressed to a certain extent, the acid commenced to act upon the cellulose itself, a much more abundant forma- tion of sugar taking place than in the former period. There can scarcely be any doubt that with the use of a higher pressure and longer boiling, far larger quantities of SUGAR AND ALCOHOL FROM WOOD-CELLULOSE. 95 sugar can be obtained from the wood than with Zetterlund's process. Since, for the purpose of obtaining celhilose, the disinte- gration of the wood may also be effected by acid, Bachet and Machard attempted to combine the production of sugar and cellulose in one process, so that the sugar solution might, in a certain measure, be obtained as a by-product in the manufacture of cellulose. (See p. 51). According to their process, the wood is boiled with dilute acid, the acid together with the sugar formed washed out with water and the remaining mass is comminuted in a hollander, bleached with chlorine gas and finally treated with soda lye. The product thus obtained cannot be called either mechanical pulp or cellulose, it being an intermedi- ary between both products but, as regards its properties, approaches more closely bleached mechanical pulp than ceHulose. On a large scale the operation is carried on as follows: The wood — fir or pine — is cut into thin discs. Four thousand four hundred pounds of these discs are brought into a vat together with 2,000 gallons of water and 1,700 pounds of crude hydrochloric acid, and boiled for 12 hours by direct steam, hence under ordinary pressure. The resulting fluid having been separated from the solid contents of the vat, is neutralized with upwards to 99 per cent, of calcium carbonate and fermented in the usual manner. I^y distilling the fermented fluid, a corresponding quantity of alcohol is produced, it being, however, not stated how large a quantity of it is obtained from the 4,400 pounds of wood used. : . It is remarkable that according to Bachet and Machard's statements, neutralization of the acid should be effected by lime, since the fluid must then contain a corresponding quantit}^ of calcium chloride, and it is very questionable whether the fermentation of the sugar can proceed regu- larly in the presence of such a large quantity of a calcium salt. •■,.-'. . , . ■ . ,' 96 CELLULOSE, AND CELLULOSE PRODUCTS. In addition to the processes above described, there are some other methods for the production of alcohol from wood, of which, however, but little is known, very likely for the reason that satisfactory results were noi obtained. One of these methods relates to the production of alcohol from beech. In this case, dilute sulphuric acid is made use of for the formation of sugar. Boiling is effected under a comparatively high pressure — 7 to 8 atmospheres — and continued for 10 to 12 hours. The final result was a com- paratively very small yield of raw alcohol of a disagreeable odor, while the solid mass which remained in the boiler showed a dark-brown color, had a disagreeable odor, and was not fit for anything but fuel. The failure of this experiment ma}'^ be explained from the process itself. At the high temperature which a fluid standing under a pressure of 7 to 8 atmospheres must acquire before it reaches the boiling point, the sugar already formed is again changed, and the production of a larger quantit}'^ of it entirely excluded. The poor quality of the raw alcohol obtained may be due to the properties of the wood used, beech containing a very large quantity of ex- tractive substances, which by the action of sulphuric acid very likely yield bodies of a disagreeable odor characteristic of the raw alcohol. That amongst these bodies are such as gradually acquire a dark color under the influence of the air, is shown by the fact that the raw alcohol in a very short time became dark brown. By repeated rectification, this disagreeable odor could only be diminished, its entire removal being impossible, and neither could the alcohol by rectification be brought to a state in which it remained colorless, becoming wine-yellow when for a short time ex- posed to the air. NATURE OF THE WOOD TO BE WORKED. The nature of the wood to be worked appears to exert great influence upon the yield of alcohol in general, as well SUGAR AND ALCOHOL FROM WOOD-CELLULOSE. 97 as upon the quality of the product itself. Experiments made in this direction with pure cellulose gave much more satisfactory results than with wood itself, and the alcohol obtained could be quite readily purified by rectification. These facts serve as hints of how to proceed in order to ob- tain comparatively large yields of alcohol of sufllcient purity, as well as that great care has to be exercised in the selection of the wood to be used. Compact, heavy wood, containing large quantities of ex- tractive substances may at the outset be designated as un- suitable for the purpose. Such wood contains considerable quantities of lignin, tannin, coloring matter and other ex- tractive substances which cannot be converted into sugar, and hence beech, oak, chestnut, etc., are not available. The conifers — pine, fir, spruce, etc., — contain large quan- tities of rosin and volatile oils, the presence of which has a disturbing effect. Hence there is but little choice as re- gards the selection of wood for the production of alcohol, and only varieties with a white, incompact and soft wood can be used to advantage. Of the European varieties of wood, aspen, poplar, willow and linden, are the most suit- able materials for the purpose. A few remarks may here be made in reference to the ap- paratus to be used and the mode" of procedure in general. Since in starting a plant as, for instance, one required for working wood, machinery pla3's an important part, the entire execution of the plan is generally left to an engineer who puts up apparatus, boilers for boiling under pressure, etc., according to his own judgment without consulting the chemist as to the conditions the apparatus is to meet. The order in which the plant is to be managed is also, as a rule, indicated by the engineer who, in most cases, does not pos- sess the chemical knowledge, which is absolutely required if favorable results are to be obtained. Thus it may happen, as it actually did in the above- mentioned example, that wood is boiled under pressure 7 98 CELLULOSE, AND CELLULOSE PRODUCTS. with a comparatively very large quantity of sulphuric acid, the temperature becoming thereby so high that the newly- formed sugar was largely reconverted into other combina- tions and the yield in consequence was so small, that the entire expensive plant had to be abandoned and the ma- chinery sold for old metal. MORE MODERN METHODS. If the working of wood for the production of alcohol is to be carried on in a rational manner, i. e., in accordance with the laws of chemical science, it is absolutely necessary to proceed according to the following principles : The soft, white wood cut into thin discs should for a con- siderable time be submerged in running water, the object of this soaking being to free the wood as much as possible from water-soluble extractive matter such as albumen, tannin and other substances, so that only the vascular bundles cemented together by the lignin remain behind. The wood when sufficiently soaked is to be cut into small pieces as if it were to be worked for cellulose by the soda or sulphite process. This reduction is necessary, on the one hand, to give the w^ood a very large surface, thus present- ing to the acid manj' points of attack, and on the other, because the residue which remains behind after treating the wood with acid, can thus be best utilized for the prepar- ation of cellulose. Hydrochloric acid is most suitable for converting the cellulose into sugar, it being preferable to sulphuric acid, if only for the reason that even at a high temperature it does not form brown, coal-like combinations froiii the cell- ulose. Since by boiling under increased pressure a much larger quantity of sugar can be obtained than by boiling under ordinary conditions, an increased pressure will have to be worked with, and the use of a closed boiler would, therefore, seem to be one of the conditions for attaining favorable re- sults. SUGAR AND ALCOHOL FROM WOOD-CELLULOSE. 99 For boiling, a vertical, iron vessel furnished with a re- movable lid, steam heating and safety-valve will have to be used. Since iron is vigorousl}' attacked by the vapors of hydrochloric acid, the boiler will have to be lead-lined, this metal being least attacked by the vapors. In order to save the lead-lining, a wooden vessel which almost fills the boiler, may be placed in the latter. This wooden vessel serves for the reception of the comminuted wood and the fluid, and when boiling is finished and its fluid contents have been discharged, it is lifted from the boiler by means of a hoist. When the boiler has been charged with the coraminnted wood and dilute hydrochloric acid, the apparatus is closed air-tight and the fluid is brought to boiling by means of steam of such a tension that the contents of the boiler are not heated to above 230° or 233.6° F., boiling being con- tinued for a suitable time, and very likely 10 to 12 hours will be required until a sufliciently large quantity of sugar will have formed. There being no data on hand regard- ing the time required for obtaining the largest possible quantity of sugar, and this time varying probably for every variety of wood and for difl'erent concentrations of the acid, it must be determined by experiments. Such ex- periments or tests are made by taking every hour samples from the boiler and determining the content of sugar. If, in the disintegration of wood, the conditions should be similar to those in the disintegration of starch for the pur- pose of producing grapotsugar, it will be observed by the samples that the quantity of sugar formed within a certain time increases quite regularly until a period is reached when the further formation of sugar becomes very sluggish, so that for reasons of expediency the operation may be con- sidered finished. Since the hydrochloric acid does not undergo a change in converting a portion of the cellulose into sugar, but acts by its mere presence, the fluid at the end of the operation will LtfCi 100 CELLULOSE, AND CELLULOSE PRODUCTS. contain as much free hydrochloric acid as was originally present, and this acid has to be removed as far as possible. This may be effected, when the formation of sugar is com- plete, by connecting the lid of the boiler with a lead cool- ing coil in a cooling vat, and distilling off a portion of the fluid, boiling being continued under the ordinary pressure. The greater portion of the hydrochloric acid present in the fluid will thereby escape together with the steam, and will be again condensed in the cooling coil. The dilute hydro- chloric acid thus obtained may be used for the next operation. Distillation may be continued until the fluid contains only 3 per cent, of free acid, when the operation is interrupted. When this point has been reached, the fluid is dis- charged from the boiler, the boiling vessel hoisted from the latter, and replaced by another which has in the meantime been charged with wood, so that with the exception of the short time required for emptying and recharging the boiler, the operation can be carried on without interruption. The unchanged wood remaining in the boiler is still saturated with the acid, sacchariferous fluid. This fluid is obtained by repeatedly washing the wood with water, but it cannot be recommended to combine it with the fluid first obtained, otherwise the sugar solution would be too much diluted. The fluid used for washing the wood is utilized in the next operation in place of pure water, the hydrochloric acid as well as the sugar contained in it being thus completely exhausted. The sugar solution discharged from the boiler is now neutralized with soda to such an extent that its content of free hydrochloric acid is reduced to 1 per cent., the compo- sition of the fluid being then such that yeast can live in it, provided it is furnished with the requisite quantity of nour- ishing salts. This object may be attained by adding to the fluid cooled to about 86° F., 5 per cent, of yeast prepared from crushed SUGAR AND ALCOHOL FROM WOOD-CELLULOSE. 101 malt. It is, however, also possible to make use of a cheaper method by adding directly to the fluid salts serving as nu- triment of the 3^east, equal parts of potassium phosphate and ^ ammonium phosphate being very suitable for the purpose. One part of the nourishing salt for 1000 parts by weight of the fluid is used. These salts dissolving with ease in water, a solution of them is prepared in a small quantity of the fluid and uniformly distributed throughout the sugar solu- tion by stirring. Fermentation can be induced either by freshly-compressed yeast or by freshly-prepared distillery yeast. With the fluid at a temperature of 86° F., propagation of the yeast takes place very rapidly, and in a short time the fluid is in a state of vigorous fermentation. Regarding the quantity of compressed yeast to be used it may be said that \ part by weight of it suffices for 100 parts by weight of the sugar contained in the fluid. The fluid is now left to itself until fermentation is fin- ished, which with the high temperature at which it was in- duced, will be the case in, at the utmost, 36 hours. It is then drawn off from the yeast at the bottom of the vat, and immediately subjected to distillation. The yeast need not be removed from the vat but can be utilized in the next operation. Distillation of the fermented fluid should be effected in an apparatus which allows of the alcohol being rectified as far as possible, i. e., to somewhat above 96 per cent. Wood alcohol always has a peculiar odor due to small quantities of combinations, the chemical nature of which is not de- finitely known. Ho^rever, by careful rectification these bodies can be so completely separated from the alcohol that it possesses only the odor of the pure product. When soft, white varieties of wood are in the above described manner treated with hydrochloric acid, the resi- due remaining behind retains its color unchanged, provided the acid used is free from iron. However, ordinary crude 102 CELLULOSE, AND CELLULOSE PRODUCTS. hydrochloric acid, which will have to be used when working on a large scale, alwaj'S contains a certain quantity of iron, and the wood shows generally a slightly brownish color, so that when further worked to cellulose it does not yield an entirely pure white product, which can, however, be so made by bleaching. Supposing that 20 per cent, of the weight of the wood can be converted into fermentable sugar, and assuming that this quantity of sugar after fermentation and deduction of unavoidable losses yields in round numbers 10 liters of alcohol : by taking the value of 1 liter of alcohol at only 10 Pfennige * it will be seen that the alcohol obtained from 100 kilogrammes (220 lbs.) has a value of 1 mark,t and that the remaining 80 kilogrammes (193.6 lbs.) of wood arc available for further working into cellulose. Hence the calculated results, even with such small yields and low price of the alcohol produced as have been assumed above, are by no means unfavorable, and it might certainly prove a profitable undertaking for a chemist to investigate closely the subject, working especially with a view towards increas- ing the yield of sugar from the wood. Classen's process. The chemist Classen has recently devoted much time to the solution of the problem of producing directly-ferment- able sugar from wood, having adopted entirely new methods, which, according to his statements, have actually resulted in comparatively large yields. According to a process patented by him the wood is first treated with sulphuric acid, having a concentration of the so-called chamber acid — 50° to G0° Be. — and then sub- mitted to powerful mechanical pressure, the effect of the latter, it is claimed, being to convert a large portion of the *1 Pfennig = 0.23G cent. 1 1 Mark = 23. G cents. SUGAR AND ALCOHOL FROM WOOD-CELLULOSE. 103 cellulose contained in the wood into dextrose. (?) The mass need then only be diluted with water and boiled for some time at the ordinary pressure to accomplish complete (?) conversion into dextrose. Air-dry sawdust, which in this state contains in round numbers 15 per cent, of water, is used as raw material. A portion of the sawdust is intimately mixed with three- fourths its quantity of sulphuric acid of 57° Be., a mass of a peculiar greenish color being thereby formed. By ex- tracting this mass with water a fluid is obtained in which no sugar can be found. By subjecting it, however, to strong pressure by means of a powerful hydraulic press a vigorous chemical reaction takes place, the mass becoming highly heated and its color being changed to nearly black, so that it presents the appearance of wood which has been carbonized by highly concentrated sul2:)huric acid. On ex- tracting the pressed mass with water the latter shows a very distinctive sugar-reaction. According to close investigations, it is claimed that in consequence of the pressure, the greater portion (?) of the wood-fibre is converted into cellulose, and in addition there are present other bodies which, as regards their properties, occupy intermediate positions between dextrin and dextrose. For the conversion of all (?) the dissolved bodies into dex- trin, it suffices to mix the pressed mass with water in the proportion of 1 part of the substance originally used to 4 parts of water, and to boil it for half an hour in an open vessel. By this process a fluid is said to be obtained which is free from the intermediate products interfering with fer- mentation otherwise found in dextrose solutions prepared from wood. If the process above described is actually available in practice, it may be supposed that the first eff'ect produced by the sulphuric acid upon the wood is to destroy the en- crusting substance — the lignin — so that the pure cellulose becomes accessible to the further action of the acid. It re- 104 CELLULOSE, AND CELLULOSE PRODUCTS. mains still to be established by experiments, whether the conversion of this cellulose into dextrose cannot be attained by simply heating the green mass to a certain temperature without the use of strong pressure. A decided disadvantage of this process is, however, the use of a quantity of sulphuric acid which is exceedingly large in comparison with the quantity of wood to be worked, amounting in round numbers to 75 per cent, of the latter; and to bring the dextrose solution finally obtained into fermentation, this quantity of sulphuric acid must be nearly neutralized by the addition of lime. Hence, it will be necessary to recover the considerable quantity of dex- trose solution adhering to tlie resulting gypsum by system- atic washing of the latter. The quantities of gypsum which would finally accumulate in carrying on the opera- tion on a more extensive scale, would be very large and difficult to utilize, so that the cost of producing ferment- able sugar according to this process would be comparatively quite high. It would appear that the inventor of the above-described process was himself not entirely satisfied with the results, and continued his investigations in regard to the produc- tion of dextrose from wood in another direction. A note- worthy process, also patented by Classen, is based upon the principle that by the action of watery sulphurous acid at a higher temperature, wood-substance is disintegrated to such an extent that the presence of a very small quantity of sulphuric acid suffices for the conversion of a very consid- erable quantity of cellulose into fermentable sugar. In the commencement of the operation a fluid consisting of a concentrated solution of sulphurous acid containing 0.2 per cent, of sulphuric acid is used, or sulphurous acid alone is employed, the latter, at a certain stage of the pro- cess, being partially converted into sulphuric acid so that at the moment of its nascency it acts upon the cellulose. The maximum yield of dextrose is obtained by conduct- SUGAR AND ALCOHOL FROM WOOD-CELLULOSE. 105 ing the operation so that the formation of sulphuric acid takes place at a period when the temperature in the boiler is between 248° and 293° F. In this case, it is claimed, that from every kilogramme (2.2 lbs.) of Avood (dry sub- stance) at least 300 grammes (10.58 ozs.) of dextrose are obtained, of which, on an average, 80 per cent, is ferment- able. Hence, in round numbers 120 grammes (4.23 ozs.) of absolute alcohol would be obtained from 1 kilogramme (2.2 lbs.) of anhydrous wood-substance. The temperature required for the formation of dextrose after the wood has been previously disintegrated by the action of sulphurous acid, depends on the nature of the wood to be worked, a temperature of 267° F. sufficing for birch, while for fir one of upwards to 293° F. is necessary. While a certain quantity of dextrose is without doubt formed below these temperatures, it is a comparatively very small one. The production of sulphuric acid at a certain stage of the process may be effected in various ways, the simplest method being to introduce into the vessel atmospheric air or a gas mixture rich in oxygen, or by adding manganese suboxide or peroxide, which yield a portion of their oxygen, a corresponding quantity of sulphurous acid being thereby converted into sulphuric acid. From what has been said above, the main point of the process consists m treating the wood in an autoclave with the sulphurous acid solution until the temperature reaches 248° to 293° F., then bringing about the formation of sul- phuric acid and continuing heating for 10 to 15 minutes longer. Although Classen appears to lay great stress upon the fact that the sulphuric acid acts at the moment of its forma- tion upon the cellulose, he remarks directly in connection with the description of his process given above, that in place of sulphuric acid, a mixture of sulphurous acid with some other inorganic acid, for instance, hydrochloric acid of a lOG CELLULOSE, AND CELLULOSE PRODUCTS. concentration of 0.2 per cent, or more, may also be used. If such is actually the case, the particular action which the sulphuric acid is claimed to exert at the moment of its forma- tion, is virtually eliminated, and the use of sulphurous acid for the disintegration of the wood remains as the only main feature of the entire process. It must be admitted that the figures given above regarding the yield of fermentable sugar are excellent, and for this reason alone the process deserves serious consideration. Experiments made by Classen to effect the disintegration of the wood by means of chlorine or hypochlorides yielded favorable results also. The wood, together with a half per cent, chlorine water, is heated to between 248° to 293° F., and sulphurous acid is then introduced into the vessel and rapidly converted into sulphuric acid by the action of the chlorine. Another process, also patented by Classen, consists in the action of sulphuric acid, just formed from sulphuric anhy- dride, upon the wood. Vapors of sulphuric anhydride mixed with vapors of sulphur dioxide are conducted upon the moist sawdust. I'he sulphur dioxide on coming in contact with the water contained in the sawdust is con- verted into sulphurous acid, and the wood is by the latter disintegrated in the manner already explained. The sul- phuric anhydride on coming in contact with the water is transformed to sulphuric acid, which at the moment of its formation is said to possess great inverting power. Classen claims to effect the treatment of the wood with sulphuric anhydride in revolving lead-lined drums, and accelerates the operation by previously heating the drums to from 86° to 104° F. The resulting mass is then pressed until it is hard and of a dark color, when it is treated with four times its quantity of water, and after neutralization of the acid is subjected to fermentation. Classen has found it suitable to heat the mass treated with sulj)huric anhydride for some time in a closed vessel to between 257° and 275° F., the formation of sugar being thereby still further increased. SUGAR AND ALCOHOL PROM WOOD-CELLULOSE. 107 Sulphurous acid possessing in an uncommon degree the property of checking fermentation, it would appear abso- lutely necessary to free the fluid containing dextrose com- pletely from it before submitting it to fermentation, and this can only be with certainty effected by boiling continued for a longer time. Only when a test of the fluid as to the presence of sulphurous acid yields a negative result, the free acid still present can be almost completel}' neutralized, and the fluid set for fermentation. The presence of a smaller quantity of acid does not impede fermentation, but is rather beneficial, since yeast thrives very well in an acid fluid, while certain other organisms, which bring about by- fermentations, cannot develop it. A further modification of Classen's process consists in the wood being simultaneously exposed to the action of two acids at the moment of their liberation. The wood is first heated, together with sulphurous acid, to between 266° and 293° F., then allowed to cool to 248° or 266° F., when chlorine water is introduced into the fluid. In this case, sulphuric acid, as well as hydrochloric acid, is formed, and the presence of both of these acids is said to have a favora- ble effect upon the conversion of cellulose into dextrin. The quantity of chlorine to be used must be sufficiently large, so that at least 0.2 per cent, of sulphuric acid is formed. If, as previously stated, 120 grammes (4.23 ozs.) of pure alcohol can be obtained from 1 kilogramme (2.2 lbs.) of perfectly dry wood-substance by one of Classen's processes, it would be well adapted for working on a large scale. Regarding the residue of substance not converted into dex- trose, it could very likely not be utilized for any other purpose than for burning under the boilers of the plant. VI. PREPARATION OF OXALIC ACID FROM WOOD CELLULOSE. When an organic substance is heated, together with caustic alkalies, to a certain quite high temperature, it is completely decomposed, and among the products of decom- position is alvvaj's found a certain quantity of oxalic acid. The organic substances behave thereby, however, in such a manner that from bodies of animal origin but small quan- tities of oxalic acid can be obtained, while substances derived from the vegetable kingdom yield such a large quantity of it that it may almost be designated as the chief product of the processes of decomposition. A series of exact experiments with various substances of vegetable origin have led to the result, that the yield of oxalic acid is the greater the more closely the vegetable substances used approach the pure carbohydrates in their composition. In accordance with this, starch, pure cellulose, etc., give comparatively the largest yields of oxalic acid. Since, in addition to cellulose and lignin, wood contains but small quantities of other bodies, it is especially suitable for the preparation of oxalic acid, and the more so as sawdust, which otherwise is of but little value, is the best material for the purpose. Though there is considerable difference in the various kinds of wood as regards the extractive sub- stances contained in them, oak being, for instance, very rich, and poplar very poor in them, this fact exerts but little influence upon the yield of oxalic acid, Avhich justifies the conclusion that the extractive substances — tannin, col- oring matter, etc. — as well as the wood-substance itself, may (108) OXALIC ACID FROM WOOD-CELLULOSE. 109 l^e converted into oxalic acid. Since all substances con- taining cellulose form an equally good material for the production of oxalic acid, all waste products of this kind may be used, and in addition to sawdust, waste from the manufacture of wood-cellulose and vegetable parchment, as well as scraps of tissue of vegetable origin may be utilized. The formation of oxalic acid from the above-mentioned substances talces place by heating them together with a certain quantity of caustic alkali — potassium or sodium hydroxide, or a mixture of both — to above 392° F. It may, however, be mentioned as a remarkable fact that sodium hydroxide, when used by itself, gives but a very small yield of oxalic acid, while caustic potash forms con- siderably larger quantities, and the best results are obtained when both the alkalies, mixed in a certain proportion, are allowed to act upon the saw-dust. There is no theoretical explanation of these facts, which have been established by experiments made with the greatest exactness. thorn's investigations. According to investigations made in this direction by Thorn, 50 parts of sawdust heated with 100 parts of caustic soda to a temperature of 392° F. yield a quantity of crys- tallized oxalic acid equal to 30 per cent. By doubling the quantity of caustic soda a greater yield is obtained. Thus 25 parts of sawdust heated with 100 parts of caustic soda yielded, when melted in a dish at a temperature of 464° F., a quantity of oxalic acid which, calculated to 100 parts of sawdust, amounted to 42.30 per cent. However, an ex- periment made with the same quantities of both substances spread out in a thin layer and heated to 464° F. resulted in a yield of 52.14 per cent. Further investigations by Thorn refer to the quantities of oxalic acid which can be obtained by the action of a mixture of caustic soda and caustic potash upon sawdust. Thorn extended these investigations still further by examin- 110 'CELLULOSE, AND CELLULOSE PRODUCTS. ing into the behavior of the various mixtures when they were melted together with sawdust in dishes, or when the masses were heated in thin layers. The figures indicating the yield of oxalic acid under these different conditions give at the same time a hint of how the manufacture has to be ciirried on in order to obtain the greatest possible yield. 1. Yields of oxalic acid by heating sawdust with a mix- ture of caustic soda and caustic potash in thin layers — 2 parts of alkali hydroxide to 1 part of sawdust were used. Proportion between caustic Temperature, Yield of oxalic acid from potash and caustic soda. °F. 100 parts of wood. 20 80 374 19.78 20 80 892 21.50 20 80 464 30.04 30 70 374 21.38 30 70 464 38.39 40 60 374 14.00 40 60 £92 30.35 40 60 464 to 473 43.70 50 50 392 25.76 50 50 464 to 473 89.04 60 50 392 cO.57 CO 40 464 to 473 42.67 80 20 392 to 428 45.59 80 20 464 61.32 90 10 464 64.24 100 — 464 to 473 65.57 By treating the sawdust with one of the mixtures of caustic alkalies given above, its color is changed as soon as the temperature exceeds 284° to 302° F., becoming at first brownish, which soon yields to a greenish-yellow tone. The mass then acquires a pasty condition, and at 356° F. evolves heavy nebulous vapors. That at tliis temperature reaction commences to be most energetic is evident from the fact that the action continues even if further heating is entirely interrupted. The temperature of the mass then gradually rises to above 680° F., the mass swells up, evolves a large quantity of combustible gases and finally OXALIC ACID FROM WOOD-CELLULOSE. Ill carbonizes completely when a mixture of 90 parts of caustic soda, 10 parts of caustic potash and 50 parts of wood has originally been used. This proves that with the use of a mixture containing such a small quantity of caustic potash the production of somewhat larger quantities of oxalic acid would be impossible as the temperature of the mass could not be regulated. In the same degree as the quantity of caustic potash in the mixture is increased and that of caustic soda is de- creased, the reaction takes place less violeiltly, and it is possible to maintain the temperature of the mass within the limit of 464° F. According to the series of figures given above the best proportion between caustic potash and caustic soda would be to use 80 parts of caustic potash to 20 parts of caustic soda, or 90 parts of the former to 10 of the latter. The temperature has to be raised to above 464° F. in order to obtain a yield of over 60 per cent, of oxalic acid. As will be seen from the above-mentioned figures, a con- siderably larger yield of oxalic acid is obtained, if the mix- ture be heated in a thin layer, the great advantage of this mode of procedure, when working on a large scale, consist- ing in the fact that the temperature of a mass can be more readily kept within the prescribed limits than when work- ing in deep vessels. For this purpose. Thorn has deter- mined the following proportions : Proportion between caustic potash and caustic soda. 100 10 90 20 80 30 70 40 CO 60 40 80 20 100 Temperature, Yield of oxalic acid from °F. 100 parts of wood. 392 to 408 33.14 446 58.36 464 to 494 74.76 464 to 494 76.77 464 to 494 80.57 464 to 494 80.08 473 81.24 464 to 494 81.23 Solutions of quite high concentration (40° B6.) of the 112 CELLULOSE, AND CELLULOSE PEODUCTS. caustic alkalies containing potash and soda in appropriate proportions are first prepared, and heated to the boiling point. The sawdust is then introduced, the proportions being so chosen that for 2 parts of alkali hydroxide one part of wood is used. In introducing the sawdust care should be taken to see that it is uniformly distributed throughout the .fluid and, if the latter had a concentration of 40° Be., it will be completely absorbed by the sawdust. The mixture is then evenly spread out upon iron pans in layers not exceeding 0.39 inch in thickness and heated as uniformly as possible, the premature melting of the mass being as far as possible prevented by frequent stirring. However, as the temperature soon rises above 392° F., par- tial fusion can no longer be prevented, and the mass becomes moist and crummy. Heating is continued for 1 to 1|^ hours, the temperature being only gradually allowed to rise to 494° F. As shown by the table given above, a mixture of 40 parts of caustic potash and 60 parts of caustic soda gives exactly the same jneld of oxalic acid as pure caustic potash by itself, but the price of the latter being much higher than that of caustic soda, it will be of advantage to use in prac- tice the two alkalies in the proportion given above. The turbulent reaction during fusion may, it is claimed, be prevented, so that the preparation of oxalic acid takes place quietly and smoothly', by adding to the mixture of sawdust and alkalies heavy hydrocarbons, for instance, machine oil or vaseline oil, and, according to Capitaines and Hertlings, who have patented a process for this pur- pose, the use of caustic soda by itself suffices for the forma- tion of abundant quantities of oxalic acid. They use a soda lye of 1.35 specific gravity in the proportions of 40 parts of sodium hydroxide to 20 parts of sawdust and 1.5 parts of hydrocarbon combinations. The temperature need not exceed 392° F., and the resulting yield of oxalic acid is •claimed to amount to 140 parts for every 100 parts of wood. OXALIC ACID FROM WOOD-CELLULOSE. 113 PREPARATION OF OXALIC ACID ON A LARGE SCALE. With the use of the process introduced by Thorn, the preparation of oxalic acid is divided into the following operations : Preparation of the mixed caustic lyes and their concen- tration by evaporation to a specific gravity of 1.35. Mixing the lye with the sawdust and heating the mix- ture to the maximum temperature to be used. Production of sodium oxalate from the melt, conversion of it into calcium oxalate, and separation of the oxalic acid from the latter ; recrystallization of the crude oxalic acid. In preparing the mixed lyes the content of pure potas- sium carbonate and sodium carbonate in the potash and soda to be used has first to be determined, and the two salts must be mixed in such a proportion that the lye contains exactly 40 parts of caustic potash and caustic soda. The solution of the salts is made caustic in the usual man- ner by means of quicklime, and evaporated in iron pans to 1.35 specific gravity. It is then immediately mixed with the sawdust in the proportion of 1 part of the latter to 2 parts of alkali. MELTING APPARATUS. The apparatus for heating the mass to the maximum temperature required for the formation of oxalic acid must be of such a nature that the temperature of the mass can be readily regulated, and that the workmen are completely protected from the vapors evolved from the mass during heating. These vapors have a troublesome effect upon the respirator}' organs and eyes, and provision for their imme- diate removal has therefore to be made. This may be effected by placing over the plates upon which heating takes place, a jacket extending down as far as possible with- out impeding the work. The jacket terminates above in a shaft in which a very strong current of air is produced by a steam ejector or a fan. In this manner the vapors arising 114 CELLULOSE, AND CELLULOSE PRODUCTS. from the plates are imraediately carried away and blown into a high chimney or, still better, under the grate of a fireplace. Since in heating the mass the temperature must not ex- ceed 494° F., it would seem advisable to effect heating the plates b}'^ means of a current of hot air or superheated steam, the use of an iron box 4 to 6 inches deep and 6J feet long and wide being most suitable for the purpose. On the front of the box, i. e., the side turned towards the workmen, is a pipe through which the heated air or superheated steam passes into the box, the pipe being furnished with a stop- cock, by means of which heating can be regulated as desired. To prevent the mass spread out upon the surface of the box from acquiring in some places too high a temperature, it has to be frequently turned, and it is advisable not to use for this purpose iron hand-rakes, but to employ a mechan- ical contrivance similar to that used in malt-houses for turning the malt in the kiln. Such a contrivance can be run by a small motor so that the entire attention of the workmen is directed towards the mass in hand. The mass having been spread out upon the iron plate in a somewhat thicker layer than is possible without the use of a mechanical turning contrivance, a full current of steam or hot air is immediately admitted for the purpose of rapidly heating it and evaporating the water still adhering to it. To prevent caking, the turning apparatus is at once set to work. The temperature maj' now in a short time be brought to 392° or 410° F., and then gradually raised to 464° or 473° F. At this temperature the mass is kept for from one to one and a half hours, the admission of steam or hot air being so regulated that the temperature cannot rise any higher. The mass is now considered finished and removed from the heating apparatus by means of iron rakes. OXALIC ACID FROM WOOD-CELLULOSE. 115 WORKING UP THE MELT, The mass contains all the sodium held by it fixed to oxalic acid ; in addition it contains potassium carbonate and humus substances which give it a quite dark colora- tion. The mass is immediately thrown into a vessel con- taining a certain quantity of water, which is in a short time brought to boiling, and in this state rapidly dissolves the sodium oxalate. It is advisable to place in the vessel a steam coil to be able to directly heat the fluid. Only enough water is used for the boiling fluid to show a density of 35° Be. The boiling fluid is allowed to run through a filter of close linen into a vessel in which, under constant stirring, it is rapidly cooled to the ordinary temperature. Sodium oxalate dissolves with ease only in boiling water, it being but slightly soluble in cold water and, hence, by rapid cooling, a pasty mass consisting of very small crystals of quite pure sodium oxalate is obtained. This pasty mass is treated in a centrifugal for the removal of the mother-lye adhering to the crystals. In addition to a very small quantity of sodium oxalate, the mother-lye contains the total quantity of the potash used in the form of potassium carbonate, and the humus substances which have been formed by heating the mass. The mother-lye is utilized by converting the potassium car- bonate into caustic potash by means of quick-lime, and using it for the next operation. However, in the course of several operations, the humus substances accumulate to such an extent in the mother-lye as to render it inadvisable to make it again caustic. It is then utilized for obtaining jiure potassium carbonate, this being eff^ected by mixing it with a sufficient quantity of sawdust to make a mass which can be taken up with shovels. This mass is burnt in a small reverberatory fur- nace, and the residue of ash calcined until white. It then consists of almost pure potash which may be used for further operations. 116 CELLULOSE, AND CELLULOSE PRODUCTS. For the purpose of obtaining pure oxalic acid from the crude sodium oxalate, the oxalic acid is first fixed to lime, and the resulting calcium oxalate, which dissolves with dif- ficulty, is decomposed by sulphuric acid, a solution of the oxalic acid being thereby obtained. This operation is carried on by dissolving the crude sodium oxalate in boiling water in a vat furnished with a stirrer which is kept in constant motion. Milk of lime is then added to the boiling solution, whereby calcium oxalate, which dissolves with difficulty, and free caustic soda are formed. During the precipitation of the calcium oxalate, the fluid has to be constantly kept near the boiling point, as only under this condition, the precipitate turns out granular and settles rapidly on the bottom. A sample is from time to time taken from the vat, fil- tered, acidified first with an excess of acetic acid, and then solution of calcium chloride is added. If the sample still gives a precipitate it is an indication that the total quantity of the sodium oxalate has not been decomposed and more milk of lime has to be carefully added. When the sample shows that decomposition is complete, the stirrer is stopped, the precipitate allowed to settle, and the supernatant caustic lye is drawn off. The precipitate is then several times washed with water, and the wash-waters are combined with caustic lye first drawn off". The total quantity of fluid thus obtained is evaporated in iron pans until the soda lye shows a specific gravity of 1.35, and can then be utilized for work- ing fresh quantities of sawdust. The calcium oxalate having been sufficiently washed is brought into a lead-lined vessel upon the bottom of which rests a steam coil, and mixed with a sufficient quantity of water to form a thin paste. While steam is being intro- duced through the narrow apertures with which the steam coil is furnished, dilute sulphuric acid (of 15° to 20° Be) is allowed to run in. The quantity of sulphuric acid required can be approximately calculated, but in order to separate OXALIC ACID FROM WOOD-CELLULOSE. 117 all the oxalic acid and, at the same time, have no excess of sulphuric acid in the fluid, a sample of the latter has from time to time be tested. This is effected by bringing a small quantity of the white precipitate separated, which is to con- sist of gypsum, upon a filter, washing quickly with water, and then treating the mass with a small quantity of sul- phuric acid. The filtrate now obtained is mixed with solu- tion of potassium permanganate. If undecomposed calcium oxalate is still present in the vat, the fluid, which imme- diately after the addition of the potassium permanganate appears red, becomes discolored by the decomposition of the latter. If the fluid remains red, decomposition of the cal- cium oxalate is complete. PRODUCTION OP PURE OXALIC ACID. The vat now contains a solution of oxalic acid in water standing over the precipitate consisting of calcium sulphate. The solution is drawn ofi^, the precipitate is several times washed with water to obtain the last traces of oxalic acid, and the oxalic acid solution is finally highly concentrated by evaporation, the latter being effected in pans very similar to those used for evaporating solutions in the manu- facture of tartaric acid. The pans consist of large, shallow, lead-lined wooden boxes, furnished with a lead heating coil. Two such evaporating pans are placed one above the other so that the contents of the one placed at a higher level can be discharged into the lower pan. The oxalic acid solution is first brought into the upper pan and evaporated to a density of 15° Be. It is then allowed to cool and run into the lower pan. The reason for this interruption of the evaporation is that the dilute solution of oxalic acid contains quite a large quantity of gypsum in solution, and the latter separates completely only when the fluid has acquired the above-mentioned con- centration. After removing the precipitated gypsum from the bottom of the pan, the latter is again charged with 118 CELLULOSE, AND CELLULOSE PRODUCTS. crude oxalic acid solution. The solution in the lower pan is evaporated to 30° B6., and then left to crystallize either in large stoneware dishes or in lead-lined vats. It is ad- visable repeatedly to stir the fluid during cooling, small crystals which include but little mother-lye being thereby obtained. When the fluid in the cr^'^stallizing vessels has become entirely cold, the crystals are freed as far as possible from raother-lye by treatment in a lead-lined centrifugal, the crystals of crude oxalic acid thus obtained being available for many technical purposes as their slightly brownish color is not objectionable. An almost chemically pure product is produced from the crude oxalic acid by dissolving the latter in the smallest possible quantity of boiling water, and stirring into the hot solution a small quantity of finely-powdered animal cliar- coal. The fluid is then allowed to stand until the animal charcoal powder has settled on the bottom of the vessel, and the at first brownish fluid has become as clear as water. The hot solution is then allowed to run in a thin stream into the crystallizing vessel and the resulting crys- tals are completely dried by whirling in a centrifugal. The oxalic acid thus purified contains neither free sulphuric acid nor calcium oxalate, and may be considered a highly refined article. The mother-lye obtained by the first treatment of the crystals of crude oxalic acid in the centrifugal contains considerable quantities of free sulphuric acid, and the latter is made use of by employing the mother-lye in the next operation of decomposing the calcium oxalate, a smaller quantity of sulphuric acid being of course then required. VII. VISCOSE AND VISCOID. The products to which these terms have been applied, were first prepared, in 1892, by Bevan, Beadle and Cross. With reference to their properties it may be expected that in the course of time, they will find extended application in the industries, because from them can be prepared cellulose in a perfectly pure state in the form of completely homo- geneous masses of any desired size, and it is possible to color them, or mix them with a solid body so that a plastic mass is obtained, the nature of which allows of the most diverse technical applications. The main point of the invention lies in the fact that a combination of cellulose and soda forms, on addition of carbon disulphide, a substance, the solution of which is called viscose on account of its uncommon viscosity. When such a soda-cellulose-carbon disulphide solution is exposed to the air, a gradual disintegration of the combination takes place, the carbon disulphide evaporating and, in many cases, sulphuretted hydrogen also escaping from the mass. The latter becomes constantly of greater consistence, and when all the carbon disulphide has finally evaporated, pure cellulose intermingled with soda, which, however, can be readily removed by washing, remains beliind. To the cellulose thus obtained the term viscoid is applied. By ex- posure to a higher temperature the viscose solution is in a very short time decomposed. The progress of the conversion of viscose into viscoid can be regulated at will by the use of a suitable temperature, and during this time coloring-matter or any desired pulver- (119) 120 CELLULOSE, AND CELLULOSE PRODUCTS. ulent bodies may be incorporated witii the mass, which becomes constantly more thickly fluid, so that at the end of the operation a body is obtained resembling, as regards its properties, wood, horn or stone. If no additions are made, there is finally obtained pure cellulose in the form of a white mass, which in thin layers is, however, perfectly colorless, and this also allows of an entire series of special applications. A few masses which can be prepared from viscoid will later on be more closely described. The process for the preparation of viscose has been modi- fied by several technologists, but the main point remains the same in all the methods, namely, that soda-cellulose is first prepared and then converted by the addition of car- bon disulphide into viscoid, which is dissolved in water. Cellulose of various derivatives is used as raw material for the preparation of the viscose solution. Purified cotton may be employed just as well as cellulose obtained from wood, and cleaned scraps of cotton and linen fabrics may also be utilized. In paper mills, viscose is especially em- ployed for sizing finer qualities of paper, and for its prep- aration so-called half-stufi^, prepared from cotton and linen rags, is frequently employed, as well as waste-paper which must, however, be entirely free from wood-pulp. PREPARATION OF VISCOSE. For experiments on a smaller scale in the preparation of viscose, it is best to use as basis-materials purified cotton or paper free from mechanical wood-pulp, because in working other materials, the assistance of disintegrating and mixing machinery is indispensable, while the above-mentioned materials can be readily converted into soda-cellulose, and the latter into viscose. For working on a small scale, the cotton or paper is brought into a large rubbing dish and concentrated soda lye poured over it, the latter being distributed as uniformly VISCOSE AND VISCOID. 121 as possible throughout the mass by means of a pestle. Enough soda 13^6 is gradually added so that for about two parts by weight of dry cellulose, one part by weight of caustic soda is used, and the mixture when finished con- tains in round figures, six parts of water. When the entire quantity of caustic soda has been added, the dish is covered and allowed to stand for some time so that any fibres which may not have been moistened, can come in contact with the caustic soda. The mass consisting of soda-cellulose is then quickly pressed out, brought into a flask and 40 per cent, of its weight of carbon disulphide poured over it. The mass soon becomes transparent and gelatinous without, however, becoming fluid, its viscosity being so great that it liquefies only when a sufficient quantity of water is added. By allowing the flask to stand quietly, the particles w^hich have remained undissolved, settle gradually on the bottom, and the supernatant fluid of a yellowish color becomes almost entirely clear. This fluid consists of a solution of viscose in water. If a layer of this solution be uniformly distributed upon a glass plate — in the manner photographers do with collo- dion — it becomes in a short time gelatinous and finally solid and odorless. If now the glass plate be placed in water, changing the latter several times, the soda is dis- solved and, after drying, a perfectl}'^ colorless film of struct- ureless cellulose can be drawn off" from the glass plate. By mixing certain quantities of viscose solution with coloring substances or pulverulent bodies, experiments on a small scale may also be made for the production of masses with fixed properties. PREPARATION OF VISCOSE ON A LARGE SCALE. For the preparation of viscose on a large scale, such cellu- lose as is made for paper-manufacturing purposes is gener- ally used, a short-fibered product with fibres 0.059, or at the utmost 0.079, inch in length being generally selected, 122 CELLULOSE, ANP CELLULOSE PRODUCTS. because experience has shown that long-fibered cellulose requires a much longer time for conversion into soda- cellulose. Since the process proceeds in a correct manner only when the soda lye shows a certain degree of concen- tration, the cellulose should contain only a limited amount of water, not exceeding 50 per cent. Hence the content of water in the cellulose has to be accurately established, the quantities of further additions being determined thereby. The operation commences with the comminution of the cellulose. Small disintegrators were formerly used for this purpose, but at the present time the cellulose is worked in the same manner as for blotting paper, the knife of the hollander being so set as to obtain a product of as short a fibre as possible. The mass coming from the hollander is as far as possible freed from water in a centrifugal, and is then spread out in layers and left until it is air-dr3\ The quantitative proportions between cellulose and caus- tic soda used in practice vary within very wide limits. The use of more caustic soda than is absolutely necessary for the formation of soda-cellulose being mere waste, the quantity required for every fresh batch of cellulose should be accurately determined by an experiment on a small scale, because in working man}^ hundred pounds of cellu- lose one-half per cent, more or less of caustic soda represents a considerable sum. The proportions generally used are as follows : Air-dry cellulose, 25 to 33 parts ; caustic soda, 12.5 to 16 ; water, 52 to 55. The caustic soda, which should always be used in the form of a concentrated solution, is mixed with the cellulose, water being gradually added, because the at first highly concentrated soda solution acts more rapidly than when the entire quantity of water is at once used. It may here be remarked that the quantity of water given above includes the water contained in the air-dry cellulose. The commencement of the formation of soda-cellulose is VISCOSE AND VISCOID. 123 recognized by the behavior of the mass, it swelling up very much, and a considerable increase in the temperature also takes place. When the mass has acquired the appearance of crumbled bread it is an indication that the process is finished. In practice the preparation of soda-cellulose is effected by two different methods, and ever}' manufacturer, after having once adopted one of them, prefers it to the other. However, both are perhaps of equal value, and experience and practice play no doubt an important part in obtaining a product of suitable properties. According to one of the methods the celhilose is from the start worked with soda lye of the proper degree of concentration, while according to the other, an excess of soda lye is used, Avhich later on is removed. In working according to the first process, the celhilose is treated in a mill, similar in construction to a rag-engine used in the manufacture of paper for breaking up half-stuff. The cellulose is first for a few minutes worked by itself for the purpose of loosening it, and the soda lye is then allowed to run in in small portions at a time, a fresh quantit}' being only added when the first portion has been absorbed. If too much soda lye were at one time added the mass would become very slippery, and the runner of the mill would slide, instead of rolling, over it. When the total quantity of soda lye has been added the mill is kept in motion until the termination of the process is indicated by the mass becoming crumm3^ Since the mass may contain harder lumps, which might cause the formation of a non-homogeneous product, it is passed, after being taken from the mill, through a sieve with meshes not over 0.19 to 0.23 inch wide. The sifted mass is immediately brought into the storage vessels, which must be closed air- tight, though it may also be at once used for the prepara- tion of viscose. . For the preparation of soda-cellulose according to the other method, in which soda lye in excess is used, the cellu- 124 CELLULOSE, AND CELLULOSE PKODUCTS. * lose is first mixed with about ten times the quantity of soda lye of 15 to 18 per cent. The lye is allowed to act until the operation is finished, the portion of it which has not been absorbed is discharged, and the mass is treated in a centrifugal, a certain quantity of lye being thereby regained. By simply mixing the cellulose with the soda lye, lumps are frequently formed in the mass in consequence of the increase in volume which takes place, and the soda-cellulose after coming from the centrifugal has to be especially com- minuted and passed through a sieve. SODA-CELLULOSE. In storing soda-cellulose prepared according to one of the processes described above, it will sometimes be observed that it becomes heated to quite a high degree. This phe- nomenon can only be explained by assuming that the for- mation of soda-cellulose is only incompletely effected in the apparatus used for the purpose, and that it is gradually effected in the storage vessels. However, by this process a certain quantity of heat is liberated, which by reason of the wood of the barrels used for storage being a bad con- ductor, is kept together. Since the quality of the soda-cellulose is impaired by this development of heat, and there may be even danger of a fire breaking out in consequence of it, certain precautions, given below, should be observed in storing soda-cellulose. " The main point in the manufacture of soda-cellulose is to have the entire process finished as rapidly as possible, soda- cellulose being a body which absorbs with avidity carbonic acid from the air, and to bring the product immediately into the storage vessels, closing the latter air-tight. STORING SODA-CELLULOSE. Soda-cellulose being a combination of but slight con- stanc3% only such a quantity should, as a rule, be prepared in one operation as can be worked into viscose in three or VISCOSE AND VISCOID. 125 four days, experience having shown that a ver}'^ thickly- fluid viscose cannot be obtained from soda-cellulose which has undergone changes by long storing, the product in this case possessing but little viscosity. The injurious changes soda-cellulose undergoes appear the more quickly the higher the temperature is to which it is exposed. Hence means should be provided in every factory by which the product can be kept in an unchanged state from the moment it leaves the mill and has been passed through the sieve. Instead of bringing the pro- duct into a wooden vessel, it is allowed to fall into a large sheet-iron vessel which is surrounded with ice. When this vessel has been filled with the sifted mass, a ther- mometer is pushed into the center of the latter, and the vessel closed with a well-fitting lid. Soda-cellulose being a bad conductor of heat, some time is required for the mass to cool throughout, and it must be allowed to stand until the thermometer indicates a temperature of 41° to 43° F. The mass is then quickly packed into the storage barrels and the latter are placed in a cool cellar, best in an ice- house. The expense of the ice required is slight in com- parison to the loss incurred by the spoiling of a quan- tity of the product. In storing the soda-cellulose at such a low temperature larger vessels may also be used. How- ever, in storing the product at a higher temperature, the use of smaller barrels of about 220 lbs. capacity would at all events appear not advisable, since, as is well known, the heat from the outside acts more rapidly in a smaller vessel than in a larger receptacle. Comparative experiments have shown that soda-cellulose stored in an ice-house remained unchanged after two months, but its stability decreased with every degree of heat. A maximum temperature of 50° to 53.6° F. would appear to be most suitable for the storage room, and if arti- ficial cooling is not to be applied, the cold season of the year is best adapted for the manufacture of soda-cellulose. 12G CELLULOSE, AND CELLULOSE TRODUCTS. However, in many countries the manufacturer is, even in the cold season, subject to the caprices of the weather, and it is therefore advisable to combine a cooling plant with a viscose factor3\ Soda-cellulose, which was kept at 68° F. — the ordinary temperature of a room — became, as a rule, so changed in 60 to 70 hours that it could no longer be used. As regards the products formed by the decomposition of soda-cellulose in consequence of the action of too high a temperature, the appearance of acetic acid (formic acid ?), lactic acid and acetyl-lactic acid has been established. These combinations, however, can only appear with the complete decomposition of the cellulose. Hence it appears probable that the alteration of the soda-cellulose commences with a transposition inside the molecule of the cellulose, the conse- quence being that a large part of the substance is no longer soda-cellulose, and hence cannot form the combination to which the term viscose has been applied. The unpleasant observations made in working soda-cellu- lose in which alteration has already commenced are of vary- ing nature, but the fluid lacks chiefly the great viscosity and adhesive power which are its characteristic properties. The cellulose recovered from such a thin solution possesses b.ut little strength, and is so brittle that it can scarcely be worked. PEEPAEATION OF VISCOSE. Viscose is formed by simpl}'^ bringing together at the ordinary temperature soda-cellulose with carbon disulphide, the process taking place the more rapidly the more intimate the contact between the two bodies. Chemically the com- bination formed is cellulose sulphocarbonate. It is readily soluble in water and on exposure to the air is decomposed at the ordinary temperature, cellulose in the form of a color- less and structureless mass being separated. At a higher temperature decomposition progresses with great rapidit}'. In preparing viscose it must be borne in mind that car- VISCOSE AND VISCOID. 127 bon disulphide is a very volatile substance — its boiling point being at 118.4° F. — and vessels which can be closed absolutely air-tight have to be used. Carbon disulphide frequently contains small quantities of sulphur in solution and as this would have an injurious effect upon metallic vessels, apparatus entirely constructed of wood should be employed. The most suitable, and at the same time the most simple, apparatus for the preparation of larger quantities of viscose is a revolving barrel with quite a large bung-hole, which can be securely closed with a screw-cover. In place of a revolving barrel, a stationary barrel may also be used. The contents are mixed by means of a stirrer consisting of a shaft with shovel-like paddles with which the barrel is fur- nished. The proportion between soda lye and carbon disulphide is, by the way, 10 to 1. For 100 parts of soda-cellulose 10 parts of carbon disulphide are used, though a small excess of the latter is of no importance. When both the sub- stances have been brought into the apparatus, the latter is securely closed and set in motion, being thus kept uninter- ruptedly until the formation of the combination is com plete. The time necessary for this purpose depends largely on the temperature ; three hours being, as a rule, required with a temperature of 60° F., while with one of 77° to 86° F., the formation of the combination may be complete in one hour. The cellulose sulphocarbonate forms a loose mass, differ- ing in appearance from soda-cellulose only by its pale yel- low color. When brought in contact with water it should gradually be completely dissolved. If any flakes remain undissolved, it may be due to two causes, one of them being that all the cellulose has not been converted into soda- cell alose, and the other, that an insufficient quantity of carbon disulphide has been used, or that it has acted for too short a time. In the first case, the mass cannot be im- 128 CELLULOSE, AND CELLULOSE PRODUCTS. proved, but, in the second, an experiment may be made by continuing the manipulation in the revolving barrel with the addition of a certain quantity of carbon disulphide. When the proportions have been correctly chosen, a small excess of carbon disulphide remains, as a rule, behind. This may be recovered by attaching to the hollow shaft of the barrel a pipe ending in a coil which terminates in a vessel filled with ice. A small suction pipe is placed on the lower end of this ice vessel. The other end of the hol- low shaft of the revolving barrel is furnished with a small cock. This cock is opened and the suction pump set in motion while the barrel is slowly revolving, a current of air being thus sucked through the contents of the barrel whereby the excess of carbon disulphide is evaporated. The vapors on coming in contact with the ice are con- densed, and ice water and carbon disulphide run off into a collecting vessel placed at the lower end of the ice-holder. PREPARATION OF VISCOSE SOLUTION. For this purpose the contents of the revolving barrel are brought into a closed vessel which is furnished with a vigorously-acting stirring contrivance, and, after setting the latter in motion, water in small quantities is allowed to run in. Immediately after the first portions of water have been admitted, the mass commences to swell up very much, and would in a short time acquire such a degree of vis- cosity as to impede the motion of the stirrer. Hence more water is allowed to run in until the quantity of it admitted amounts to 1| times the weight of the soda-cellulose brought into the apparatus. The stirrer is kept in motion until solution is complete, when the viscose is immediately brought into the vessels in which it is to be stored or shipped. Viscose should as far as possible be protected from the access of air, being rap- idly decomposed on coming in contact with it. Viscose solution which is immediately to be used in factories where VISCOSE AND VISCOID. 129 it has been prepared, may be kept in an open vessel of wood or zinc-sheet. A layer of water is carefully poured upon it so that no mixing of the two fluids takes place ; this layer of water protecting the viscose from becoming decomposed. When viscose solution is allowed to stand open, a thin film of cellulose forms in a short time on the surface, and this has to be removed when the viscose is to be used. STORING VISCOSE. Since viscose is rapidly decomposed by the access of air, as well as at a higher temperature, special precautionary measures have to be taken to prevent decomposition when larger quantities of it are to be stored. ' As is the case with soda-cellulose, these precautionary measures consist in shut- ting out the access of air, and keeping the storage-room at a low temperature. The most simple plan is to store the viscose in a sheet- zinc cylinder provided around its upper edge with a gutter, into which fits the 1| to 2 inches deep rim of a sheet-zinc lid. The vessel having been filled, the lid is placed in the gutter and the latter filled with water, thus forming a kind of hydraulic joint, which renders the access of air to the contents of the cylinder impossible. The stability of the viscose is the greater the lower the temperature of the room in which it is stored. In rooms having a temperature of 77° F. or more, decomposition takes place very rapidly ; at the ordinarj' temperature of a room viscose cannot be kept longer than 5 or 6 days without undergoing a change, and stability for two weeks can only be counted upon with a temperature below 50° F. If, however, viscose solutions are stored in a room the temperature of which is kept, by artificial cooling, not much above the freezing point of water, the viscose can be kept in a perfectly unchanged state for a number of weeks. In- dependent of the assurance of preserving the viscose in an unchanged state, storing it at a low temperature offers a 9 180 CELLULOSE, AND CELLULOSE PRODUCTS. great advantage in working the material. The temperature of the viscose when taken from the storage vessel is of course quite low, and as it becomes gradually higher in the normal warmth of the work-room, there is no difficulty whatever in working it at the degree of heat best adapted for the work in hand. The shipping of viscose, especially during the warm sea- son of the year, is connected with many difficulties, which can only be overcome by special precautionary measures. Viscose. is shipped in closed sheet-zinc vessels, and when the latter are in a hot summer day forwarded by railroad, there is great danger as regards the stability of the product, since the temperature of freight cars exposed to the sun frequently reaches 95° F. or more. Hence the viscose, cooled down to a low temperature, should be shipped by fast freight, and the vessels containing it be protected as much as possible from heating by wrapping them in wet cloths. PROPERTIES OF VISCOSE SOLUTIONS. The commencement of the decomposition of a viscose solution is first of all recognized by the mass, at first only viscid and of about the consistency of a gum solution, be- coming thicker and acquiring the consistency of a warm glue solution at the beginning of coagulation. As decom- position-progresses the mass assumes the consistency of jelly. By taking it in hand at the right time, the mass may be restored to a useful condition by adding a suitable quantity of water, thus making it again more thinly-fluid. It is probable that changes constantly take place even in a perfectly available viscose solution, as shown by the be- havior of viscose when exposed in a thin layer to the air. In many cases decomposition simply takes place by vapors of carbon disulphide escaping frora the mass, which con- stantly becomes more thickly-fluid, and finally nothing but cellulose remains behind. In other cases it will, however, be noticed that sulphur- VISCOSE AND VISCOID. 131 etted hydrogen is evolved, and that the mass contains con- siderable quantities of sodium carbonate as well as sul- phides and trithiocarbonate. The appearance of these combinations can only be explained by the decomposition, by the action of the alkali, of a portion of the carbon disul- phide present. The decomposition of the viscose is very much influenced by the temperature at which it takes place. Viscose solu- tion exposed upon a glass plate to a temperature of but a few degrees above the freezing point is changed very slowly ; the mass constantly acquires greater consistence and a solid, structureless film consisting of cellulose remains finally behind. The higher the temperature, the shorter the time in which decomposition takes place and at 104° F., it pro- ceeds with great rapidity. When the temperature rises above 122° F., a homogeneous, coherent mass is no longer obtained, but one which here and there shows white spots which are produced by numerous small bubbles. At this high temperature decomposition takes place with such rapidity that the vapors evolved can no longer escape from the mass on account of its viscosity, but are retained in it like air-bubbles in rapidly freezing ice. At a still higher temperature, for instance, pouring the solution upon a highly heated plate, decomposition of the viscose takes place almost instantly, a mass of a very porous, spongy nature being obtained. In many cases, for instance, in using viscose for sizing paper, it might be desirable for decomposition to take place more rapidly at the ordinary temperature than usually is the case, and this may be done by replacing the soda in the viscose by ammonia. The decomposition of viscose prepared in this manner takes place at a much lower tem- perature than that of soda-viscose, and carbon disulphide and ammonia escape in abundance from the decomposing mass. As previously mentioned, the behavior of viscose in decomposing depends on the temperature and its age, and 132 CELLULOSE, AND CELLULOSE PRODUCTS. only by long, practical experience is it possible to judge from the start of its action in this respect. Hence to avoid disagreeable occurrences it is recommended to test a small quantity of every fresh viscose to be worked as to its be- havior, and to arrange the course of the work accordingly. CONVERSION OF VISCOSE INTO VISCOID. When a 0.15- to 0.19-inch-deep layer of a viscose solution in a vessel is exposed to a temperature not exceeding 40° F., a thin film is first formed, and, by exercising care, can be lifted off. If this film be brought into water it redissolves, and therefore it consists evidently of a combination having some resemblance to viscose, though it appears in a solid form. If, however, this film be for some time exposed to the air it loses its solubility in water, but swells up in it to a jelly-like mass. If finally it be exposed for from half an hour to an hour to a temperature of 212° F., it has become entirely indiff'erent to water and behaves towards it like a film of nitro-cellulose. Except for the production of very thin films and threads, viscose is seldom used by itself For the preparation of thicker plates from viscoid — this term being applied to con- gealed viscose — a special method has to be adopted in order to obtain a perfect product. First of all it is necessary to know how thick the plates will be which can be obtained from a viscose layer of determined thickness by its conver- sion into viscoid, and this is ascertained by a preliminary experiment on a small scale. For the preparation of thick plates or blocks, sheet-zinc vessels of appropriate depth are used and filled with viscose. The vessels are then exposed in a room perfectly free from dust to a uniform temperature of 95° to 104° F. until the mass remaining in them has acquired the requisite quality. In order not to be incon- venienced by the vapors of carbon disulphide and other products of decomposition escaping from the mass, it is advisable to place the vessel in a box furnished with a pipe VISCOSE AND VISCOID. 133 entering a chimney, and to keep the temperature of the box uniformly at the above-mentioned degree, by a few heating pipes. When a solid mass has been formed it is removed from the vessel and for some time heated at 212° F. Viscoid being a bad conductor, this heating must be continued the longer the thicker the plates are ; at any rate it must be continued till the plates when dipped in water no longer swell up. The plates are then laid in clean water, by which the salts contained in them are slowly dissolved, the water being renewed so long as soluble substances from the vis- coid are absorbed by it. When the work has been care- fully done the viscoid plates present the appearance of transparent glass. If the plates show here and there dull specks or white opaque spots, it is an indication of too high a temperature having been used in drying up the viscose, and that the mass is interspersed with small bubbles. BEHAVIOR OF VISCOSE TOWARDS METALLIC SALTS. When a viscose solution is brought together with a me- tallic salt, reciprocal decomposition takes place, the metallic oxide combining with the cellulose and the sulphocar- bonate, while the soda fixes the acid of the metallic salt. The new combinations thus formed have not yet been sufficiently investigated as to their availability in practice, though a few of them have found practical application in the manufacture of paper. By mixing magnesium sulphate with viscose, magnesium- viscose and sodium sulphate are obtained, and as both these salts are readily soluble in water, no precipitation takes place after adding the magne- sium sulphate. Magnesium-viscose possesses the property of decomposing with still greater rapidity than soda-viscose, which makes it very valuable for certain purposes, especially for sizing paper ; the sodium sulphate adhering to the de- composed mass being a readily soluble salt can without trouble be removed from the paper mass. 134 CELLULOSE, AND CELLULOSE PRODUCTS. By adding to a viscose solution the solution of a salt of a heavy metal, insoluble viscose of the metal added . is formed. With the exception of the zinc combination, which is used for sizing in the manufacture of paper, none of these combinations has become of technical importance. The proportional quantities of the bodies which are added to sodium-viscose for the purpose of obtaining other varie- ties of viscose, vary according to the object which the preparations in question are to serve. Thus, for instance, in paper mills 9 parts ammonium sulphate, or 15 parts magnesium sulphate, or 18 parts crystallized zinc sulphate are used for every 100 parts of a 10 per cent, soda-viscose. PREPARATION OP VISCOSE ACCORDING TO CROSS. According to a process recently patented by F. Cross, the quantity of caustic soda required for the preparation of vis- cose can be reduced one-half by treating the cellulose to be worked previous to submitting it to the action of the alkali, with dilute acids, at a temperature of between 212° and 284° F. This is of great advantage, because on the one hand, with the use of large quantities of caustic soda the cost of producing the article is considerably greater, and, on the other, the large content of alkali and sulphur in viscose prepared according to the older method is an impediment to its use for many purposes. The preparation of cellulose according to this process may be effected in various ways. According to one method the fibrous cellulose is treated as follows : Paper pulp, half- stuff, rags, waste paper, etc., are for a few hours boiled with dilute (2 per cent.) hydrochloric or sulphuric acid ; or the fluid is brought to the boiling point by itself when the cel- lulose is introduced, boiling being constantly kept up, and allowed to remain in the fluid until it has been converted into the brittle modification. According to another method, the cellulose is completely saturated at the ordinary tem- perature with dilute (2 per cent.) hydrochloric acid. The VISCOSE AND VISCOID. 135 excess of hydrochloric acid is then removed by treating the mass in a centrifugal, and the cellulose is completely dried at a temperature of between 140° and 176° F., care being taken that drying is uniformly eflPected. The transition of the cellulose to the brittle modification then takes place during drying. According to a third method given by Cross, the cellu- lose is for a short time treated with dilute (1 per cent.) sul- phuric acid in a digester under high pressure at a tempera- ture of between 212° and 284° F. In place of dilute sulphuric acid, dilute hydrochloric acid containing but J per cent, of acid may also be used. The quantit}^ of acid used should amount to five times the weight of the cellulose to be worked. The mass coming from the digester is freed from the acid fluid by washing, and pressed to reduce its content of water to between 50 and 40 per cent. The most advantageous proportional quantities of caustic soda and water to be used for the cellulose thus prepared are within the following limits : Cellulose 40 to 50, caustic soda 10 to 12, water 50 to 38 per cent. The soda lye is used in accordance with the content of water in the cellulose to be worked, and the further manip- ulation of mixing to soda-cellulose is generally effected in a crushing mill or other grinding contrivance, the operation being continued until the mass is perfectly homogeneous. The conversion of the soda-cellulose into viscose, and of the latter into viscoid, does not differ from the method previously described. PREPARATION OP VISCOSE ACCORDING TO SEIDEL. H. Seidel's process for the preparation of viscose differs but little from the one just described. According to the inventor's statements, 100 parts of sulphite-cellulose are for a few hours placed in dilute (1 per cent.) hydrochloric acid, the mass is then squeezed out and rinsed in water. It is then brought into intimate contact with a solution of 136 CELLULOSE, AND CELLULOSE PRODUCTS. 40 parts of caustic soda in 100 parts of water, and left to itself in a closed vessel for three days. One hundred parts of carbon disulphide are then brought into the vessel and distributed by stirring, when the mass is again allowed to repose for 12 hours. A yellow-colored solution is formed from which the viscose may be precipitated by alcohol or common salt solution. Viscose prepared from sulphite-cellulose dissolves with somewhat greater difficulty, but has the advantage of being lighter in color than other varieties, and can even be ob- tained entirely colorless. It is less suitable for the prepar- ation of plastic masses, but is remarkably well adapted for sizing paper. According to Seidel, transparent plates of viscose are ob- tained from cotton by treating cotton fabrics, according to the process just given, up to the period at which the addi- tion of carbon disulphide is to be made. Instead of adding the latter, the fabrics are hung in a room the atmosphere of which is saturated with carbon disulphide vapors, allow- ing them to remain for twelve hours. The rinsed fabric is stretched smoothly upon a glass plate, exposed for two days to the air, then completely dried in a drying closet, and finally placed in dilute hydrochloric or acetic acid. According to this process, plates are obtained which have the appearance of parchment, and by heating to 212° F., become so plastic that they may be given any desired shape. They can be bleached with chloride of lime and then form a perfectly colorless mass, which, when colored, retains its transparency. It may here be remarked that the process above described would seem to be of but little practical importance since viscoid plates can be prepared in a much simpler, and at the same time cheaper, manner from ordinary viscose by spreading a somewhat thicker layer of the latter upon a glass plate provided with a rim of appro- priate height, detaching the smooth plate from the glass plate, and treating it further in the usual way. The use of VISCOSE AND VISCOID. 137 cellulose in the form of cotton offers no advantage, but con- siderably increases the cost of production. The process above described may, however, be utilized to advantage for giving a loosely-woven, thin tissue the ap- pearance of a close and firm fabric. For this purpose the washed and dried tissue is unwrapped from a roll into a vessel containing the soda lye, remaining in it for several days so that a considerable quantity of soda-cellulose may be formed. The tissue is then freed from the greater portion of adhering fluid b}'^ subjecting it to strong pressure between two rolls. It is next loosely hung up in a chamber, the door and windows of which can be closed air-tight. A shallow vessel filled with carbon disulphide is placed upon the floor of the chamber and the latter closed air-tight. The tissue is allowed to remain in the chamber until the quite dark yellow color it acquires by the action of the car- bon disulphide remains constant. The chamber is then opened, thoroughly aired and the tissue is removed when it has again become white and per- fectly dry. It is then taken through a bath of dilute (2 to 3 per cent.) hydrochloric acid, washed and dried in a stretched state, this being necessary as otherwise it would shrink very much. Tissues thus treated appear nearly twice as thick as orig- inally, feel firm to the touch, and possess remarkable strength. These phenomena may be explained by the change the separate fibres of which each thread consists have undergone. Every fibre on its surface and to within a certain depth has been converted into viscose which pen- etrates the entire mass like varnish. The tissue taken from the carbon-disulphide chamber acquires, when moistened with water, a quality reminding one of a thoroughly soaked animal skin. When the viscose is again decomposed the separated cellulose cements the finest fibres of the threads most intimately together, and this explains the compact ap- 138 CELLULOSE, AND CELLULOSE PKODUCTS. pearance, firm feel, and great strength of the tissues thus treated. PREPARATION OF CHEMICALLY-PURE CELLULOSE-SULPHO- CARBONATE (vISCOSE). Viscose prepared according to the ordinary method is not a pure product consisting solely of the combination cellu- lose-sulphocarbonate, but always contains certain quantities of sodium carbonate, thiocarbonic acid and carbon disul- phide. According to the process of the Viscose Syndicate Limited, it can be freed from these bodies by treating the raw product with weak acids — lactic, formic or acetic acid — in excess, whereby the viscose is not changed, but the above-mentioned foreign bodies are rendered harmless. The fluid is then mixed with a water-withdrawing body, such as alcohol or common salt solution, and entirely pure viscose which separates as a mass of leathery appearance, is thus obtained. The product is again washed with dilute alcohol or common salt solution, and dried. Pure viscose obtained in the above-described manner, is a neutral, colorless and odorless mass, which rapidly dis- solves in water without leaving a residue, and is especially well adapted for sizing paper and fabrics. USES OF VISCOSE. Viscose, or viscoid prepared from it, is already used to a considerable extent in various industries, and it may be supposed that both these substances will find various tech- nical applications. Viscoid, as previously explained, is simply pure cellulose, and it being in a certain measure available in a fluid state in viscose, it is possible to obtain the cellulose in a solid form and to give the article thus ob- tained any desired color. Quite bulky bodies can be prepared from viscose, and any desired pulverulent substances may be incorporated with the mass as it becomes solid, so that the articles pro- VISCOSE AND VISCOID. 139 duced in this manner resemble, as regards their appearance and partially their properties also, horn, ivory, wood or stone. In the same manner transparent plates or very thin leaves may be prepared from viscoid, or they may be ob- tained in the form of exceedingly fine threads well adapted for spinning. From what has been said, it seems more than probable that viscose, as well as viscoid, may in the future strongly compete with celluloid, the cost of producing it being, on the one hand, less, and on the other, it is not nearly as inflammable as celluloid, the great combustibility of the latter requiring constant precaution in handling it. It would be impossible to give a detailed description of all the uses to which viscose and viscoid might be applied. However, the suggestions made here will be sufficient to guide the practical man in the preparation of masses with determined properties. USE OF VISCOSE IN THE MANUFACTURE OF PAPER. Since by the decomposition of viscose there remains be- hind a substance consisting of a product, which has to be designated as paper in the actual sense of the word, no better sizing-agent for paper can be imagined. In view of the good qualities of paper sized with it, the use of viscose for this purpose lias been widely adopted in the manufac- ture of paper, and large quantities of it are used. Although soda-viscose may be directly used for sizing paper, it is at present employed only in exceptional cases, the removal of the considerable quantities of alkaline salts which pass into the paper mass being an unpleasant operation. In place of soda-viscose, ammonium viscose, and the pre- viously-mentioned compounds of viscose with magnesium or zinc, are at present used, these combinations possessing the advantage of decomposing still more rapidly than soda- viscose. In addition to cellulose, ammonium viscose and 140 CELLULOSE, AND CELLULOSE PRODUCTS. magnesium viscose in decomposing yield throughout com- binations soluble in water, which can be readily removed by washing from the paper mass. Furthermore, in the decomposition of these varieties of viscose, a far less abundant separation of carbon disulphide takes place than is the case with soda-viscose, as well as with zinc-viscose. A further advantage of the use of ammonium or magne- sium viscose, as well as of zinc-viscose, is that a much smaller quantity of alum is consumed than is otherwise the case. Papers prepared with viscose are distinguished by a firmer feel and besides, by the addition of this substance^ great strength and extensibility are imparted to them. Viscose may be applied to all kinds of paper, to the coarsest qualities of wrapping paper as well as the finest varieties of writing paper. As shown by exact experiments, excellent results have been obtained by the application of viscose as a size to wrapping paper of which considerable strength is demanded, the breaking length as well as the elongation being in- creased 30 to 50 per cent. Thorough experiments in this respect have been made by the Versuchsanstalt at Charlottenburg, and the figures given below show plainly how^ the qualities of the papers are affected by an addition of viscose : Breaking Elongation Variety of paper. length in .^ ^^^ ^^^^_ meters. Brown wrapping paper from steamed wood 3575 1.80 Same, sized with 4 per cent, of viscose 4750 3.00 Brown wrapping paper from steamed wood 3200 0.90 Same, sized with 4 per cent, of viscose 4650 2.40 Brown wrapping paper from steamed wood 2225 1.40 Same, sized with 4 per cent, of viscose 2925 1.97 If fine qualities of paper, the beautiful, pure-white color of which is of importance, are to be sized with viscose, care VISCOSE AND VISCOID. 141 must be taken to use a product of a very light color, other- wise the paper acquires a very noticeable yellowish tinge. VISCOSE IN THE MANUFACTURE OF WALL PAPER. In a similar manner as in cloth printing, viscose may be directly used in the manufacture of wall paper as a thick- ening agent for the printing colors employed for producing the designs upon the wall paper. As compared with the ordinary thickening agents, viscose has the advantage that the colors printed with it adhere far more firmly to the paper than is the case with other colors which frequently stick so badly as to be effaced by slight rubbing. The use of viscose is of special advantage in the manu- facture of the so-called flock paper, which is made by sifting upon sized spots of the wall paper finely comminuted colored wool and, after drying, removing the excess of wool dust. From most of the flock papers the larger portion of the wool can be readily removed by vigorous rubbing with a brush, but if the paper be printed with viscose and immediately covered with wool dust, the latter cannot be removed. Me- tallic bronze, aluminium powder, etc., triturated with vis- cose to a printing color and printed upon the paper, look like gilding and silvering and retain for years their metallic appearance. Even wall paper, made in the ordinary way, if coated, when finished, with viscose solution acquires thereby the beautiful lustre characteristic to pure cellulose, and besides, it may be cleansed with a sponge moistened with water, solution of soap or soda without damage to its beautiful appearance. Wall paper which in the course of time has suffered from smoke and dust may by this treatment be restored to its original beauty. Washing may be repeated as often as desired, because the thin layer of cellulose upon the paper is perfectly water-proof and indiff^erent towards water and soap. Imitations of leather and velvet hangings can in no 142 CELLULOSE, AND CELLULOSE PRODUCTS. other way be made so beautiful and durable as with the use of viscose. By printing with viscose upon leather- brown paper, gold or silver bronze, and then coating its entire surface with viscose, it can, while still moist, be pro- vided with raised or depressed designs so that in appearance the finished wall-paper cannot be distinguished from gen- uine leather hangings. By printing designs of a certain form upon different places of the paper and covering them with wool powder of an appropriate color, then printing other places with vis- cose covering them also with different-colored wool powder, and thus continuing the operation, wall paper may be pro- duced having the appearance of velvet hangings of a determined ground color with variously-colored flowers, leaves, ornaments, etc., woven in. It is advisable to pass wall paper made in this manner with the lower non-printed surface down, over a heated roll with such rapidity that the viscose layer is during a few seconds heated to 212° F. By this heating the viscose becomes perfectly insoluble and the wall paper can without risk be rolled up. The examples given above suffice to show the important role viscose is likely to play in the manufacture of wall paper. VISCOSE IN CLOTH-PRINTING. In cloth-printing viscose may be used in various ways, namely, as a so-called resist and as a thickening and fixing agent for certain coloring matters. If a tissue of sheep's wool or silk be printed with various-colored designs by means of a viscose solution of appropriate strength, and the tissue be then passed over hot rolls, the proper places will be covered and impregnated with cellulose. The tissue may then be dyed in a dye-bath which yields its coloring matter to wool and silk, but not to cellulose, the result being a tissue showing a white design upon a colored ground. VISCOSE AND VISCOID, 143 If the printing color be prepared by stirring the finely pulverized coloring matter into thick viscose solution and the tissue be printed With it, it is only necessary for fixing the color in the most durable manner, to pass the printed tissue over heated rolls, the color being then imbedded in a layer of cellulose and cannot be removed. Viscose solution can to great advantage be used for mark- ing fabrics in mills, as well as a substitute for ink for mark- ing household linen, etc. For this purpose a viscose solu- tion sufficiently thickly-fluid to yield sharp impressions with a rubber stamp is used, a durable coloring matter being in- corporated with it, finely-divided carbon in the form of lamp-black being most suitable as it is not dissolved by any known body. The tissues are marked with the assistance of the rubber stamp and after drying in the air, the color is fixed by passing a hot flat-iron over the mark. The car- bon is then enclosed by cellulose, and the color is not only upon the surface of the tissue but has penetrated it through- out and is, therefore, indestructible. Even an attempt to dissolve the layer of cellulose enclosing the carbon, by treat- ment with cuprammonium solution, would result only in making the marking somewhat paler and less distinct, but it would be impossible to destroy it entirely, the particles of carbon adhering so tenaciously to the individual fibres of the tissue that they cannot be removed. In place of carbon any desired pulverulent coloring mat- ter may be used, but care must be taken that it is of such a nature as not to be changed by free alkali or carbon disul- phide. VISCOSE AS A SIZE OR DRESSING. The size or dressing generally used in the textile industry consists, as a rule, of gum-like substances, a paste prepared from various kinds of starch being partially employed for the purpose. However, these agents are entirely removed by washing the fabrics once or at the utmost twice, and the 144 CELLULOSE, AND CELLULOSE PRODUCTS. latter lose their good appearance and firm feel ; as well as the lustre given to ihem by the size or dressing. In addition the weight of the fabric is considerably de- creased, because the pipe clay or heavy spar which had been added as a loading agent to the size, has also been washed out. Viscose offers a means of sizing tissues in such a manner that they retain, even after repeated washing, their smooth- ness and lustre, and lose nothing in bod}^ Sizing with vis- cose is effected in various ways according to the object w^hich is to be attained. The simplest mode of sizing consists in drawing the tissue from a drum upon which it has been wrapped and passing it through a vat filled with viscose solution of suitable con- centration. By passing the wet tissue between two rubber rolls set close together, fixed above the vat, the excess oi fluid is removed and falls back into the vat. After drying, the tissue appears sized with a layer of viscoid, the thick- ness of which depends on the concentration of the viscose solution used. By passing the tissue again through the viscose solution and repeating the operation, under special conditions, for the third time, sizing is finally eff'ected to such an extent that all the pores of the tissue are closed with cellulose, and it is just as water-proof as if it had been impregnated with rubber. Loading agents may also be added to the viscose, thus imparting great weight to the tissue, which it, however, re- tains when washed, because the particles of the loading a,gent are cemented one to the other, as well as to the fibres of the tissue, by the insoluble cellulose. To impart to the tissue treated wdth viscose great smooth- ness, and at the same time a beautiful lustre, it is advisable to arrange the finishing machine so that the tissue after having been pressed out by the rubber rolls, passes under high pressure through two polished, hollow rolls heated b}'' steam. By this heating, the viscose is instantly con- VISCOSE AND VISCOID. 145 verted into insoluble cellulose and the latter is forced into the separate depressions of the tissue, thus imparting to the latter a smooth and lustrous surface. PREPARATION OP LEATHER-LIKE BODIES BY MEANS OF VISCOSE. The results of all the attempts to produce a substance with such physical properties, especially as regards tenacity and strength, that it would answer as a substitute for leather, have to be accepted only conditionally, and all products commended under the names of artificial leather or substi- tutes for leather have to be viewed with a certain mistrust as regards their durability and power of resistance. The reason for the failure to produce a substance which might satisfactoril}^ replace leather, is found in the nature of the latter material itself Leather is the portion of the animal skin to which the term corium is applied. When a piece of corium is exam- ined under the microscope, it will be seen to consist of in- immerable fibres twisted together, forming an extremely tough substance. By the tanning process the fibres of the corium are coated with a tanning substance which prevents the individual fibres, in drying, from adhering firmly to- gether as is the case in raw hide, the latter drying to a hard horny substance, while leather remains flexible. Hence, if a substance is to be produced which shall to a certain extent possess the characteristic strength, tenacity and durability of leather, it has to be prepared in such a manner that in structure it approaches that of leather. The main point is, therefore, to use a tissue of great strength and tenacity, and to envelop its individual fibres with a substance possessing also great strength and tenacity. With reference to these properties, viscose, or viscoid formed from it, plays, as will be directly shown, an important part, there being no other known body so suitable for the purpose. B^ence, in order to produce a substance which as regards •10 146 CELLULOSE, AND CELLULOSE PRODUCTS. its properties, is to resemble leather as closely as possible, a tissue of suitable quality has to be throughout saturated with viscose. Since in this manner masses may be prepared which re- semble the finest qualities of glove leather, as well as others which come up to sole leather, great care will have to be bestowed in the commencement of the operation upon the fabric to be manipulated. For very thin masses, which, as regards their properties, are to resemble glove leather, closely-woven cotton fabrics are very suitable, and as the strength of ever}'- kind of tissue is considerably impaired by bleaching, it is advisable to use only unbleached tissues except in case the material to be prepared is to be of a pure white color. For the imitation of thicker varieties of leather, such as uppers for shoes, a coarser fabric of strong, unbleached linen may be employed, as well as a tissue of very tough Manila hemp. Finall}^, for the imitation of the heaviest varieties of leather, thick fabrics of very tough fibres are used. Such fabrics should be prepared by com- bining the finest fibres by doubling to coarser fibres which, when interwoven, yield a tissue of special strength and tenacity. In working up these various fabrics into leather-like masses, they are throughout saturated with viscose solution and made uniform by subsequent mechanical treatment, care being taken to keep the structure of the fabric entirely in the back ground, giving the material as far as possible the appearance of leather. The viscose solutions used for impregnating the tissues should not be too thinly-fluid, a solution containing about 20 per cent, of viscose being probably most suitable. The use of a more highly concentrated solution would not seem to be advisable, because it is then so thickly-fluid as to penetrate only with great difficulty into the interior of the fabric. Entirely satisfactory results are only obtained when the tissue has been saturated throughout its entire thick- VISCOSE AND VISCOID. 147 ness, so that on examining with a magnifying glass the cross section of the finished product, the centre presents the same appearance as the portions nearer the surface. The first step in the operation is the removal of all moisture from the fabric by drying it thoroughly, best by means of hot air. It is then placed in a box, closed air- tight, in which it remains until cooled to the ordinary temperature, and ready for impregnation. The object of this drying is to open the pores of the fabric so that it can be readily penetrated by the viscose solution. Imitations of leather being, as a rule, colored, dyeing is effected at the same time as impregnation, the appropriate coloring matter being added to the viscose solution, the quantity of coloring matter required for the various kinds of fabrics being determined by experiments. Thick fabrics require less coloring matter than thin ones, because by reason of the fibres in the body of the tissue being also colored, the coloration on the surface appears more vivid than is the case with thin fabrics. The vat containing the viscose solution should on one side be provided with an opening for the entrance of the fabric winding off" a roll. The fabric is carried below the level of the fluid by three rolls revolving with ease. Over the second of these rolls is fixed a pair of rolls so arranged that the distance between the two rolls can at pleasure be decreased or increased. This pair of rolls is set to corre- spond with the thickness of the fabric so that after the latter has been impr-egnated with viscose solution, it is only pressed out sufficiently to throw off* the excess of fluid adhering to it, which falls back into the vat. The fabric is passed through the viscose solution with sufficient rapidity to allow of its being saturated through- out its entire thickness. The rate of speed must be slight for thick fabrics, and has to be determined by direct ex- periments. The fabric coming from the impregnating vat is passed through rolls heated to between 122° and 140° F., 148 CELLULOSE, AND CELLULOSE PRODUCTS. being slightly squeezed thereby wilhout being actually pressed. Heating to the above-mentioned temperature is best effected by hollow rolls heated by steam constantly passing through them. During the passage of the fabric between these heated rolls, the conversion of viscose into viscoid takes place, one hot pair of rolls being, as a rule, sufficient for thin fabrics, while for thick fabrics a second or third pair of rolls will have to be used. In place of using heated rolls, the fabric may be simply passed over loosely-lying rolls while a current of hot air as- cends from beneath, the viscose being, in this case, also de- composed. As has been previously explained, b}^ the decomposition of the viscose, vapors of carbon disulphide and other gases are constantly disengaged. To protect the workmen from these injurious vapors, the rolls through and over which the fabrics pass, should be placed in a closed box, and the latter be connected with a ventilator, which constantly sucks air into the box and carries it off. It is advisable to connect the ventilator to a fire-box in which the carbon disulphide vapors are burned to sulphurous and carbonic acids. When working on a large scale, it will certainly pay to recover and condense the carbon disulphide vapors. For this purpose provision has to be made for a long coil placed in a vessel filled with cold water, in which the warm air and the vapors carried along with it are first cooled to the ordinary temperature. From this preparatory cooler, the vapors are driven into a vessel filled with ice, in which the carbon disulphide vapor is condensed and runs off with the ice water. The fabrics having been carried through the heated rolls or over a current of hot air, are next exposed to strong pressure by being passed between smooth rolls, in order to give them an entirely smooth surface. They are then re- peatedly washed in water to free them from alkali, and are finally dried in the air or in artifically-heated rooms. VISCOSE AND VISCOID. 149 In working thick fabrics, one impregnation with viscose sohition is frequent!}^ found insufficient to saturate them throughout tlieir entire thickness. Such fabrics having been passed through tlie heated rolls and cooled to the ordinary temperature, are subjected to another treatment with viscose solution, the operation being exactly the same as previously described. The fabrics impregnated according to the process given above are now in the following condition : All the fibres of the fabric are enveloped by cellulose and the empty spaces between the separate threads and fibres are also filled with it, so that the whole represents quite a uniform mass of cel- lulose. However, the portion of the mass belonging to the fabric is, in consequence of its structure, exceedingly tough and strong, it having acquired these properties in a still higher degree by being enveloped and cemented by the cellulose. It will be seen that such a fabric, as regards its structure, may be compared with leather, the fibres repre- senting the skin tissue, while the cellulose which envelops them serves for their consolidation and reinforcement. The impregnated fabrics, when washed and again made air-dry, possess quite a high degree of elasticity and a cer- tain softness, and can without difficulty be further worked by mechanical means. By passing them through brightly polished rolls capable of producing great pressure, they ac- quire a very smooth surface and high lustre. After going through these rolls they may be passed through others en- graved in various ways, for instance, for the imitation of morocco leather. When coloring has been properly done, such imitation can scarcely be distinguished from the gen- uine product. However, success in giving a .fine appearance to an article to be used, is of onl}' secondary importance, since by coloring and pressing paper it may be given a striking re- semblance to morocco leather. But imitations of leather made according to the process given above, have in addition 150 CELLULOSE, AND CELLULOSE PRODUCTS. to appearance another valuable property, namely, strength and tenacity of substance. A piece of leather may be torn with greater ease than a piece of fabric of the same thick- ness impregnated with cellulose. Thick fabrics impregnated with cellulose may be used for shoe soles, since they have the advantage over leather soles of not becoming soft when exposed for a long time to damp- ness and shriveling to a hard mass as is the case with leather which by the action of moisture is deprived of a large portion of its content of tannin . Impregnated fabrics being entirely indifferent towards water are only gradually destroyed by the mechanical wear and tear in using the shoes. Leather belts for machines are, as is well known, quite expensive, as they have to be made of the heaviest and most carefully tanned qualities of leather. They may, however, be advantageously replaced by belts made of very strong fabrics impregnated with cellulose. Such belts up to 0.39 to 0.59 inch thick are produced by impregnating thinner fabrics and cementing them together with viscose solution. In the above explanations, the principal elements have been given which must be adhered to in the preparation of imitations of leather in order to obtain satisfactory results, and by observing them it will not be difficult for a manu- facturer who takes up the subject, to prepare various pro- ducts which possess the character of the leather to be imitated, and are distinguished by considerable strength. However, not only tissues can be converted into leather- like masses, but also fabrics of a felt-like nature, such as felt itself, further felted cotton, and pasteboard. When ordinary pasteboard prepared from mechanical wood-pulp be throughout saturated with viscose solution and then, under constantly increasing pressure, passed be- tween smooth rolls, a mass is obtained which in hardness considerably surpasses the best quality of pressing-board, and, as regards tenacity and elasticity, can only be com- VISCOSE AND VISCOID. 151 pared with very hard wood. It can be worked with all kinds of wood-working tools. On the other hand, it can, while still wet, be pressed into any desired form by suitable dies, and thus plates may be produced which equal in ap- pearance carved wood, and may to advantage be utilized in the manufacture of furniture. By the use of engraved plates which may also be provided with high reliefs, book covers of elegant appearance may be produced from paste- board thus prepared, these book covers having, independent of their cheapness, the advantage of being almost inde- structible. Since paste-board plates only 0.19 inch thick, possess, when impregnated with cellulose, a strength and power of resistance equal to that of quite thick boards, they would seem to be an excellent material for the construction of portable houses, such as are required for scientific expedi- tions, for the erection of observatories upon high mountains, etc. Such plates can be rendered fire-proof by treating them, while still moist, with alum solution, and then with water- glass solution, so that a house constructed from this light material can scarcely burn down. Genuine felt consists of tangled animal hair combined by fulling and beating to a quite solid, and at the same time porous, mass. By reason of its porous nature it can be readily impregnated with fluids. Felt plates impregnated with viscose solution completely retain their flexibility and suppleness, and being waterproof, may be used for hats, clothing, tents, etc. If, previous to their being treated with viscose solution, they are soaked in a saturated solution of borax in water, and then thoroughly dried, they become absolutely indestructible, the rotting of the felt by repeated exposure to moisture being prevented by the highly anti- septic properties characteristic of boric acid. Hence felt- plates prepared in this manner can be laid directly in the ground as a support for heavy machinery, and thus the 152 CELLULOSE, AND CELLULOSE PRODUCTS. noise of the latter, when resting upon an unyielding founda- tion, can be almost entirely obviated- VISCOSE IN THE MANUFACTURE OF ARTIFICIAL FLOWERS. For the manufacture of imitations of flowers, leaves, etc., variously-colored stuffs, as well as paper, are used, the sub- stances being appropriately shaped, then painted, and, if required, varnished. Although, as regards artistic execu- tion, such artificial flowers are beautiful, they delineate only in a very incomplete manner the appearance of natural flowers and leaves. Great progress was made by the introduction of celluloid in the manufacture of artificial flowers as this material can be readily colored any shade, and moulded into any desired form. The high lustre peculiar to articles of celluloid had, in this case, the effect of still further increasing the beauti- ful appearance of such artificial flowers. But they are un- fortunately quite expensive, and possess the farther disad- vantage of being extremely inflammable. However, in viscose the manufacturer has at his disposal a material which deserves consideration, it being not only very cheap, no more inflammable than ordinary paper, and possesses other advantages which make it very suitable for the object in question. The mode of application in the manufacture of artificial flowers would probably be to satur- ate thin, porous tissue-paper with appropriately-colored vis- cose, and to cut out the flowers, leaves, etc., by means of heated dies. By contact with the heated die, the viscose is rapidly changed to viscoid, and the leaves, etc., retain ex- actly the shape given to them by the dies. The leaves are smooth and lustrous and, of course, have all the properties belonging to viscoid. They ma}^ be immersed in water without losing their shape or suffering au}^ other injury, and when they have become unsightly by dust, they may even be cleansed by means of an atomizer and water. For especially delicate artificial flowers, pure viscose may VISCOSE AND VISCOID. 153 be used by allowing a thick viscose solution to dry upon glass plates to thin plates and making the leaves, etc., from the latter. By adding sufficient quantities of coloring matter to the viscose solntion, colored, transparent leaves of viscoid are obtained which, when worked into flowers, pro- duce a peculiar effect resembling that seen in glass 'flowers. VISCOSE IN PHOTOGRAPHY. Some kinds of photographic apparatus are so arranged that the picture is taken upon a transparent film, instead of upon a glass })late. Such a film can be produced of any length and wound upon a roll, and the use of such a pho- tographic apparatus is very convenient, especially in expe- ditions, as it requires but little space, and a large number of pictures can be readily taken. At present the films are almost exclusively made of celluloid membranes, which, however, are not so well adapted for the purpose as viscose, the latter being less in- flammable, and less sensitive to moisture and heat than celluloid. The preparation of films from viscose is a ver}'- simple matter. The length of a film being generally such that twelve pictures can be taken with one roll of it, a piece of plate glass corresponding in length to that of the roll of film has to be procured, allowing in addition a few centi- meters for the portion of the film secured to the I'oll. The film being, as a rule, larger in width than in thickness, the plate glass should be wide enough to allow of a large film- plate being at one time made, which is then cut up. The plate-glass is surrounded by a metal frame project- ing a few millimeters above it, its object being to prevent the viscose solution from running off the plate-glass. The latter is placed upon a stand provided with a ball-joint capable of being turned by friction, so that the plate-glass can be readily set in a level position. The viscose solution used for the preparation of films 154 CELLULOSE, AND CELLULOSE PRODUCTS. should be of such concentration that, when poured m a layer of a fixed depth upon the plate-glass, it yields, after drying, a membrane of sufficient thickness ; this can be readily ascertained by a few experiments. The viscose solution is poured upon the plate-glass by commencing in one corner of the latter, care being taken that no bubbles are formed, and as the fluid spreads out over the plate-glass, pouring is continued until the entire surface of the plate- glass is uniformly covered. The plate-glass is then left standing without being touched until the viscose layer is entirely congealed. It is then taken ofi" and heated upon a plate of aluminium sheet to 212° F., until it has become insoluble. It is then washed with water and completely dried in the air. The large plate of viscoid, which should have the appearance of colorless glass, is then cut up into strips of film of suitable length, and the latter are treated with chemicals to form a layer sensitive to light upon their surfaces. VISCOID MASSES. If a viscose solution be allowed to stand quietly at the ordinary, or a somewhat higher, temperature, it decomposes slowly, and a plate remains behind, the thickness of which depends on the depth of the original viscose solution. In order to obtain homogeneous viscose masses free from bubbles, the decomposition of the mass should not be has- tened by heating, as otherwise the vapors and gases escap- ing from the mass after it has already become thickly-fluid, would cause the formation of bubbles in it, such as may be observed in ordinary glass. If, on the other hand, the mass is allowed to stand at the ordinary temperature until it has acquired the consistence of solid jelly, it maybe care- fully lifted from the vessel containing it and placed upon a glass plate, the latter being allowed to lie in a place free from dust until the mass is entirely solid. It is then slowly heated to 212° F., so that it becomes heated throughout, VISCOSE AND VISCOID. 165 and then placed in water for the purpose of dissolving the salts present. By exposing such a block to a strong pres- sure, allowing it to stand under it for some time, a body is obtained which, in appearance, does not much differ from a block of glass. This pure viscoid may be worked with all kinds of tools. It can be sawed, drilled and worked in the lathe, and forms an excellent material for the manufacture of various fancy articles. If a coloring matter insoluble in water has been added to the viscose solution, the viscoid also appears colored. Since by mixing viscose with various indifferent bodies, masses may be prepared which present a pleasing appear- ance, and are much cheaper than pure viscoid by itself, they may be advantageously used for the production of numerous small fancy articles. When properly made they present almost exactly the same appearance as celluloid articles, but are much cheaper and not so inflammable. Viscose possessing great viscosity, considerable quantities of foreign bodies can be incorporated with it and the result- ing viscoid masses be nevertheless very strong, and of beau- tiful appearance. There are a large number of substances which may be used for filling viscoid masses, and in fact every kind of pulverulent body which is chemically indif- ferent to viscose may thus be employed. For the preparation of white masses there are, for instance, available, pulverized chalk, plaster of Paris, magnesium carbonate, zinc white, powdered talc (soapstone powder) and pulverized heavy spar, or preferably artificially-prepared heavy spar, the so- called permanent white, which is an extremely delicate powder. According to the substance used, there will be considerable difference in the resulting masses as regards weight, and partially also as regards lustre. Masses of a pure milk-white color and of comparatively slight specific gravity can be produced with the use of magnesium car- bonate, the latter being a pure white powder of very slight 156 CELLULOSE, AND CELLULOSE PRODUCTS. specific gravit3^ Masses prepared witli pulverized chalk or plaster of Paris, though light, are heavier than magnesium masses. The lightest viscoid masses of a white color are prepared by mixing with the viscose as a filling-substance bleached cellulose made from wood by the sulphite or soda process. A product of not quite such a pure white color, but never- theless of nice appearance, is obtained with the use of mechanical wood-pulp prepared from a white wood, for instance, aspen ; such masses have a very slight yellowish tint. Since viscose solution may be colored as desired, the white basis-masses given above may be used for the pre- paration of colored viscoid masses, though the latter may also be obtained by mixing with the white pulverulent filling substances other colored powders. Viscose solutions, even if quite dilute, possess a consider- able degree of viscosity, and the preparation of homogeneous masses with the use of filling-substances presents certain difficulties, uniform mixing of the solution with the pow- ders being only accomplished b}' long-continued manipula- tion. Besides, the various powders act diflcrently in this respect towards viscose, and it is advisable first to make experiments on a small scale. For this purpose a fixed quantity of dilute (at the utmost 10 per cent.) viscose solu- tion and a fixed quantity of the powder to be used for filling are employed, for instance, 1 quart of viscose and 22 lbs. of powder. Pour the viscose into a large, round vessel, smooth inside, for instance, a porcelain dish, and while one workman constantly stirs the viscose, another one pours the powder in a fine jet into the fluid until a thick paste is formed, which cannot be further worked with the stirrer. This paste is rolled out on a smooth plate — a marble slab being very suitable for the purpose — and the plate thus obtained is folded over and again rolled out, the operation being repeated until a uniform mass is obtained which is VISCOSE AND VISCOID. 157 still sufficiently plastic that, when subjected to quite a strong pressure in a mould, all the elevations and depres- sions are reproduced. The moulded articles are allowed to stand quietly until perfectly dry. The quality of these test-pieces furnishes accurate information regarding the properties of the mass. A viscoid mass of the proper quality should possess beau- tiful lustre, and be so hard and solid that it can only be broken with difficulty by A'igorous blows with a hammer. When the mass breaks under the hammer into several pieces, and consequently is brittle, it is indicative of too large a quantity of filling-substance having been used. In this case the fractures are very uneven, dull and lustreless, while, on the other hand, the fracture of a mass containing not too large a quantity of filling-substance should be con- choidal, with sharp, smooth edges, and lustrous. When the quality of the test-mass is found to come up to the standard, the composition of the mass for the prepa- ration of larger quantities of it can be calculated from the amount of filling-substance and viscose solution used. For the preparation of larger quantities of viscoid masses special mechanical contrivances have to be employed which allow of the thorough kneading together of the fluid and the powder. Mixing or klieading machines, such, for in- stance, as imitate kneading bread-dough by hand, are best adapted for the purpose, since with such machines any desired power may be applied. Mixing and kneading ma- chines of this kind performing excellent work are, lor in- stance, constructed by Werner and Pfleiderer, the work of thorough mixing being effected by an implement of peculiar construction, the so-called mixing paddle. A large number of machines of this kind are at present in use in bread bakeries, paint factories — in fact in all kinds of establish- ments where masses have to be mixed and kneaded — and are most suitable for the preparation of viscoid masses. However, to adapt them entirely for this purpose, the mix- 158 CELLULOSE, AND CELLULOSE PRODUCTS. ing vessel must be so arranged that it can be tightly closed, SO that the viscose does not decompose during the operation, since decomposition should only be effected when the plastic mass is brought into the form the jfinished article is to have. Fig. 32 shows the peculiar shape of a kneading and mixing paddle of a kneading and mixing machine constructed by Werner and Pfleiderer. In the commencement of the operation, the entire quan- tity of viscose solution to be worked is brought into the Fig. 32. mixing vessel, and through a funnel placed in the lid of the mixing vessel the powder is allowed to run in in a thin jet, while the mixing paddle revolves with moderate ve- locity. When, in consequence of the increasing viscosity of the mass, its resistance to the mixing paddle becomes greater, the velocity of the latter is increased, and thus continued until a sample taken from the mixing vessel shows the mass to be entirely uniform. The machine is then stopped, the viscoid mass taken out and immediately moulded. VISCOSE AND VISCOID. 159 The moulds used may be made of iron or brass, or of wood, gutta-percha, or of plaster of Paris impregnated with stearin. Moulds which are most frequently used should, of course, be made of metal, this material possessing the great- est power of resistance and being less subject to wear and tear. It depends on the article to be prepared whether it is to be moulded solid or hollow. Billiard balls, door-handles, buttons, ornaments in relief, etc., are moulded solid. For the preparation of balls, hemispherical moulds are used. They are pressed full of viscoid mass and, after coating two such hemispheres with a small quantity of thick viscose solution, they are joined together by vigorous pressure. In this manner cane-heads, door-knobs, etc., are made. For moulding hollow articles, plates of the thickness the articles are to have are first prepared from the mass. Such a plate is pressed into the hollow mould, the core portion of the mould is then laid upon it, and the mould thus put together is subjected to pressure in a press, by which anj excess of mass is forced from the mould. When the press is opened the core portion of the mould is first lifted off, and the article can then be readily detached by turning the mould over and giving it a gentle knock. Doll-heads are thus made in two halves, which are then cemented together with viscose solution. The articles when taken from the moulds being still soft have to be carefully laid upon a smooth board and allowed to remain in a place free from dust until they are solid, hard and dry. They are then finished by heating to about 212° F. In case the articles should turn out lustreless, a beautiful lustre can be given to them by applying a coat of dilute (10 per cent.) viscose solution. When the articles are to be painted, for instance, doll-heads, the colors are applied to the finished article, a coating of viscose solution being finally put on. The colors then lie under a thin colorless layer of cellulose similar to a coat of a protecting IGO CELLULOSE, AND CELLULOSE PRODUCTS. glaze, and the articles may be cleansed with soap and water without injury to the colors. Viscoid masses, the filling-substances of which consist of cellulose or mechanical wood-pulp, acquire a hardness not surpassed by hard wood, and may be advantageously used for machine parts which otherwise have to be made by hand from wood. Screws and nuts may thus, for instance, be made from the mass while still soft, and the}'^ do not require finishing by hand, because coming from the same mould they have the same gauge. In the same manner shuttles, spools, small cog-wheels, etc., may be prepared by pressing, the cost of producing such articles being, as may readily be conceived, very slight as compared with those made by hand from wood. Viscoid masses filled either with cellulose, mechanical wood-pulp, or indiff"erent mineral powders possess in a high degree the power of resisting atmospheric influences, and sufl'er neither from rain or frost. In consequence of these valuable properties they are well adapted for building pur- poses, for the exterior as well as the interior of houses. Mouldings, c^^nices, lion heads and other constructive orna- ments may be advantageously made of this mass, which is cheap, and at the same time capable of great resistance, and it may also be used for busts, statuettes and ceramic articles. YIII. NITRO-CELLULOSE (GUN-COTTON, PYROXYLIN). When pure cellulose is brought in contact with more or less concentrated nitric acid, a large number of combina- tions is formed, the kind of combinations which are formed depending on the concentration of the acid, as well as on the time it remains in contact with the cellulose. How- ever, there are two distinctly marked groups of combina- tions, one of them being distinguished by its members exploding with great violence when brought in contact with a red-hot body, as well as by concussion and percus- sion, and further by being indifferent towards solvents. The second group, to be sure, also contains explosive bodies, they being, however, distinguished by the property of com- pletely dissolving in certain fluids. Hence we may speak of explosive nitro-celluloses and soluble ones, but it must be expressly understood that an absolutely sharp boundary between these two groups is not known. The combinations formed by the action of nitric acid upon cellulose were simultaneously discovered by Braconnet, Schcinbein, Otto and Pelouze, the explosive products for blasting and military purposes being first prepared by them. The properties of the less explosive, but readily soluble, combinations, as well as the numerous uses to which they could be applied, became accurately known only at a much later time. The}' are at present so num- erous that several large industries — manufacture of arti- ficial silk and of celluloid — are based upon them. According to former opinions regarding the formation and composition of the combinations belonging to these 11 (16J) 162 CELLULOSE, AND CELLULOSE PRODUCTS. groups, they were considered as nitro-compounds. In accordance with this assumption, by treating cellulose with nitric acid, the water is withdrawn from the cellulose and replaced by nitryl, the radical of nitric acid. However, when it was found that by treating cellulose for a longer or shorter time, as well as at different temperatures, with vary- ing quantities of nitric acid, combinations containing differ- ent quantities of nitrogen were formed, it was sought to explain this phenomenon by the existence of different kinds of nitro-cellulose, and thus hypothetical compounds which were to contain 1 to 11 molecules of nitryl were arrived at. It was further considered justifiable to assume that nitro-celiuloses with a certain content of nitrogen are insoluble, while others constitute the soluble form. How- ever, since nitro-celluloses can be prepared which possess nearly the same content of nitrogen, but one of which is in- soluble and the other readily soluble, these opinions can no longer be considered correct. According to modern views regarding the composition of gun-cotton, it cannot be designated a nitro-compound, but has to be termed a nitric acid ester or ether, the proof of the correctness of this view being found in the behavior of gun-cotton towards different reagents. In treating gun- cotton with concentrated sulphuric acid it is slowly decom- posed, even at the ordinary temperature, and nitric acid is liberated. If gun-cotton be treated with potash-lye it is, even if only slightly heated, completely decomposed, potas- sium nitrate being formed, and the cellulose with all its properties reappears. Even ferrous chloride acts upon nitro-cellulose in such a way, that the formation of ferric chloride is caused by the nitric acid which is liberated, and cellulose is again formed. In view of these reactions the assumption that the so- called nitro-cellulose is a combination formed by the re- placement of the hydrogen in the cellulose by the radical nitryl can no longer be maintained, and the view that a NITRO-CELLULOSE (GUN-COTTON, PYROXYLIN). 163 series of combinations of cellulose with nitric acid — cellulose nitric acid esters — is in question, would seem to be correct. From this also results the assumption of a mono- cellulose, di-cellulose, tri-cellulose, up to endeca-cellulose, and the quantity of nitrogen found in the products depends on the concentration of the nitric acid used, as well as on the duration of the action of the acid upon the cellulose. Nitro-cellulose, in explosive as well as soluble form, may be prepared by bringing pure cellulose in contact with highly concentrated nitric acid, but as the latter by the absorption of water becomes in a short time less concen- trated, mixtures of nitric and sulphuric acids are generally used as nitrating fluids. Sulphuric acid being a body which fixes water with great energy, its purpose in this case, is to absorb the water which is formed, so that the concentration of the nitric acid remains the same. This assumption, however, does not agree with the facts which have been established in reference to the behavior of cellulose towards mixtures of very varying quantities of nitric and sulphuric acids. From investigations of the pro- ducts thus formed it would appear that the kind of combi- nation formed is very materially influenced by the larger or smaller quantity of sulphuric acid present. For an explanation of these facts we are indebted to the thorough investigations made conjointly by G. Lunge and E. Weintraub, and the points of practical importance for the preparation of nitro-cellulose will here be briefly given. The larger the quantity of sulphuric acid in the nitrating fluid in comparison with that of nitric acid, the more slowly the entire process is completed. By using ^ part of sul- phuric acid to 1 part of nitric acid, reaction is complete in half an hour. (It may be here remarked that the course of the reaction may be measured by the quantity of nitrogen present in the newly-formed nitro-product.) With the use of a mixture of 3 parts of sulphuric acid and 1 part of nitric acid the content of nitrogen in the product is in the 164 CELLULOSE, AND CELLULOSE PRODUCTS. course of half an hour much lower than with the use of the previous mixture. If, finally, a fluid of 8 parts sulphuric acid and 1 part nitric acid be employed, reaction is not complete even in a month. With a slower course of reaction the content of nitrogen in the product is also changed, i. e., with an increasing content of sulphuric acid in the nitrating fluid, final pro- ducts are obtained which contain less nitrogen than with the use of a smaller quantity of sulphuric acid. The presence of a very large quantity of sulphuric acid (more than 8 to 1) in the nitrating fluid appears to be the reason why, even after remaining for so long a time in con- tact with the fluid, a certain quantity of the cellulose itself remains unchanged and is not converted into a nitro- compound. In our opinion, an explanation of this phe- nomenon may be found in the fact that, in the commence- ment of the operation, certain fibres of the cellulose are already changed by the sulphuric acid in a manner similar to that when cellulose is converted into vegetable parchment, and thus become inaccessible to the action of the nitric acid. That the presence of a larger quantity of sulphuric acid in the nitrating fluid exerts a material influence upon the physical structure of the product has been confirmed by the investigations above referred to. With the use of a nitrating fluid containing but a small quantity of sulphuric acid — about :^ to |^ of the weight of nitric acid — a product is obtained which possesses greater strength than the cellulose originally used, the fibres ap- pearing strongly contracted. If, on the other hand, fluids rich in sulphuric acid (7 to 1 upwards) are employed, the dry'product represents a flnely-fibered powder. The process of nitration is completed the more rapidly the higher the temperature of the fluids is, it being effected in the shortest time at between 140° and 176° F. In prac- tice it is, however, not feasible to work with such a high temperature, the yield of nitro-cellulose becoming con- NITRO-CELLULOSE (gUN-COTTON, PYROXYLIN). 165 stahtly smaller with an increasing temperature, and a con- siderable portion of the substance passing into solution. When working with a nitrating fluid heated to 140° F., nitration may be considered complete in half an hour. The loss in cellulose was found, in this case, to amount to 1.95 per cent. By leaving the finished product in the hot fluid, 5.67 per cent, of it was in the course of 4^ hours again destroyed. With the use of a fluid heated to 176° F., the destructive processes became still more conspicuous, and nitration, in this case, was generally complete in less than a quarter of an hour. The loss in cellulose amounted to 6.25 per cent., increasing in half an hour to 27.45 per cent., and in three hours to 52.76 per cent. B}?^ nitration at higher temperatures, a change in the structure of the nitro-cellulose takes place, it becoming short-fibered and brittle, and the product prepared under these conditions appears, after drying, as a finely-fibered powder. Towards polarized light, nitro-cellulose acts in a very peculiar manner, it having been asserted by some investi- gators that the different degrees of nitration may be recog- nized from the appearance ot the fibres when observed in polarized light. However, Lunge and Weintraub specify this as not being pertinent. In polarized light the highest degrees of nitration appear pale to dark blue. However, important information re- garding the presence of unchanged cellulose is gained by examining nitro-cellulose in polarized light, the unchanged cellulose appearing pale yellow to reddish, and lights up more than nitro-cellulose. It is, however, impossible to determine from the picture in the polarizing microscope the quantity of non-nitrated cellulose. If the latter amounts to only 5 per cent., a large portion of the field of vision appears already of a yellow color, and, if the content of cellulose increases to 10 or 15 per cent., it is no longer 166 CELLULOSE, AND CELLULOSE PRODUCTS. possible to observe the polarizing phenomena of the nitro- cellulose, they being completely hid by those of the cellulose. Although the disclosures afforded by observing the fibres under the polarizing microscope are quite uncertain, they may nevertheless be utilized for gaining information in re- gard to the state of nitration as, for instance, is done hj Chardonnet, in testing the nitro-cellulose which is to be used for the preparation of artificial silk (see later on). When the field of view shows exclusively blue-appearing fibres, and no yellow ones can be seen, it is, at all events, a proof that the total quantity of cellulose used has been nitrated, and that the product is very likely completely soluble. In practice two main objects are especially to be attained in the preparation of nitro-cellulose, namely, the product must either be explosive to the highest degree, i. e., gun- cotton in the actual sense of the word, or it must dissolve in solvents without leaving a residue, the term collodion cotton being, in the latter case, generally applied to the product. In conducting the nitration of cellulose it is scarcely probable that a product is obtained which is in accordance with a positively determined combination, i. e., a nitro-cel- lulose of positively determined composition, the result being, on the contrary, always mixtures of various degrees of ni- tration with more or less changed cellulose. For practical purposes two products of diff'erent proper- ties come chiefly into question, namely, on the one hand, the preparation of a nitro-cellulose which, in exploding, produces the greatest dynamic effect and is suitable for the manufacture of blasting gelatine, and on the other, the pro- duction of a nitro-cellulose which can be completely dis- solved. The latter product has attained great importance for photographic use, and the manufacture of artificial silk. Information regarding the composition of nitro-cellulose produced by a certain process is sought to be obtained by NITRO-CELLULOSE (GUN-COTTON, PYROXYLIN). 167 establishing the quantities of nitrogen contained in them. While the French chemists calculate the nitrogen in the form of nitric oxide which can be obtained from 1 gramme substance (reduced to 0° and 760 millimeters height of bar- ometer), the English and German chemists give the content of nitrogen directly in per cent. Conjointly with J. Bebie, G. Lunge has recently occupied himself with the composition and properties of the various nitro-celluloses, and in the commencement of a very full article published in the " Zeitschrift fiir angewandte Chemie," 1901, these investigators give the relation between the modes of determination adopted by the French and German chemists, as shown in the table below, which af- fords a ready comparison between the two methods of ex- amination. Ccm. nitric Per cent. Name. Formula. oxide (NO) in Ig. nitrogen (N) in 1 g. Dodeca- C^.H^sOglNOa)!^ 226.17 14.14 Endeca- C2,H,A(N03)ii 215.17 13.47 Deca- S C2,H3„Oio(N03),o 203.35 12.75 Ennea- ' = C24H3iO„(N03)9 190.75 11.96 Octo- [ 13 C2,H320i2(N03)8 177.19 11.11 Hepta- C,,H330,3(N03), 162.36 10.18 Hexa- C,,H3,Oh(N03)6 145.93 9.15 Penta- a C2,H350i5(N03)5 127.91 8.62 Tetra- J c,,K,,o,,(m,), 107.81 6.76 According to the investigations of the above-mentioned scientists, the degrees of nitration from tetra-nitro-cellulose to deca-nitro-cellulose can only be obtained by treating cot- ton with nitric acid, while for still higher degrees of nitra- tion, mixtures of nitric and sulphuric acids have to be employed. Since in the preparation of nitro-cellulose on a large scale, mixtures of nitric and sulphuric acids are always used, such mixtures were almost exclusively employed in the above investigations. 168 CELLULOSE, AND CELLULOSE PRODUCTS. The influence exerted by the content of water in the acid mixture upon the process of nitration is shown by the table below : bb c o Nitrating mixtures. I— ( ^ ja g ^ ns O a o -ij -b'^^^ % Solubili ether (3:1 >^ Sulphuric acid SO4H2, Nitric acid HNO3. Water 217.73 13.65 1.50 177.5 45.31 49.07 5.62 210.68 13.21 5.40 176.2 42.61 46.01 11.38 203.49 12.76 22.00 — 41.03 44.45 14.52 200.58 12.58 60.00 167.0 40.68 43.85 15.49 196.35 12.31 99.14 159.0 40.14 43.25 16.61 192.15 12.05 99.84 153.0 39.45 42.73 17.82 184.78 11.59 100.02 156.5 38.95 42.15 18.90 174.29 10.93 99.82 144.2 38.43 41.31 20.26 155.73 9.76 74.22 146.0 37.20 40.30 22.50 148.51 9.31 1.15 138.9 t 36.72 39.78 23.50 133.94 8.40 0.61 131.2 35.87 38.83 25.30 103.69 6.50 1.73 — 34.41 31.17 28.42 The considerable differences appearing in the degrees of nitration between the soluble and insoluble parts might be explained by the dilution of the nitrating mixtures which occurs in the course of reaction, this dilution being due to the withdrawal of nitric acid and to the water formed by the process itself. It having, however, been established by the investigations that a difference of a few per cent, of water suffices to produce degrees of nitration which differ consid- erably one from the other, it follows that a uniform product is never obtained, but always a mixture of different degrees of nitration. To prevent this as much as possible in prac- tice, the operation should be so conducted that the quantity of nitrating fluid is very large in proportion to cotton, the effect of dilution being then less pronounced. If the nitrating mixture contains 16.6 per cent, of water a completely soluble product belonging to the group of actual collodion cottons is obtained. From 18 per cent. NITRO-CELLULOSE (gUN-COTTON, PYROXYLIN). 169 up, the content of nitrogen decreases very rapidly with the increase in the content of water. The entire group of soluble nitro-celluloses between 170 and 196 cubic cm. is defined by a content of water which only amounts to 4 per cent. (16.5 to 20.5 per cent.). Between 7 and 8 lies the octo-nitro-cellulose with a content of 177.2 cubic cm. of nitrogen which may be designated as the typical soluble nitro-cellulose — the actual collodion cotton. This product is always obtained by working with a nitrating mixture which contains 19.4-2 per cent, of water. This statement is of great importance for the practice, it pointing out the way in which the material required for the production of collodion for photographic purposes, as well as for the manufacture of artificial silk, can be pre- pared. According to statements made in this direction re- garding the manufacture of artificial silk according to Chardonnet, a nitrating fluid composed of 85 parts of sul- phuric acid and 15 parts of fuming nitric acid, is for 4 to 6 hours allowed to act upon cotton. However, several chem- ists in working according to this direction obtained no adequate results, and even with the use of a higher temper- ature, the results were not more favorable, as shown in the following table : Temperature. Duration of nitration. Ccm. NO in 1 gramme. Solubility. Yield. 86° F. 104° F. 4 hours. 7 hours. 199.89 209.90 17.14 15.54 160.2 143.1 The solubility of the products which were last obtained is only slight, nitration, however, being complete, and in polarized light all the fibres appear of a slightly steel-blue color. However, it may in this case be remarked that with nitro-cellulose with a content of nitrogen below 190 cubic cm., blue lighting up could never be observed. The solubility of nitro-celluloses with a content below 170 CELLULOSE, AND CELLULOSE PRODUCTS. 160 cubic cm. decreases, the degrees of nitration from hexa- nitro-cellulose downward being insoluble in ether-alcohol. According to Eders' investigations, which chiefly referred to the preparation of collodion-cottons, di-nitro-cellulose and tri-nitro-cellulose are soluble combinations. (See soluble gun-cotton or collodion-cotton later on). With a still greater increase in the content of water, the nitrating effect decreases very much, and the entire process seems to be turned in another direction, products possess- ing the properties of oxy-cellulose being now formed. They are soluble in dilute alkalies and can be again separated from these solutions by acids or alcohol. When brought in contact with basic coloring matters, they acquire an in- tense coloration, reduce Fehling's solution, and yield com- binations of phenyl-hydrazine. The effect of higher temperatures such as are used in the preparation of collodion cottons is shown by the summary, given below, of a few experiments made in this respect with the use of a nitrating fluid which contained 18.9 per cent, of water. Duration of nitration. Temperature Degrees F. Ccm. NO in 1 g. Solubility in ether-alcohol. Yield. 4 hours. 24 hours. 4 hours. 4 hours, i hour. 62.6 62.6 104 140 140 183.54 184.78 183.40 172.48 182.80 95.60 99.81 99.58 99.82 99.71 155.1 156.2 148.1 52.0 146.7 As shown by these figures, nitration was complete in 4 hours at the ordinary temperature and the yield was greater than at 104° F., but the product dissolved with greater dif- ficulty and less completely in the mixture of ether and alcohol. By increasing the temperature to 140° F., partial denitration took place rapidly. After 4 hours the content of nitrogen had dropped to 172.48 cubic cm. By allowing NITRO-CELLULOSE (GUN-COTTON, PYROXYLIN). 171 the acid to act, at such a high temperature, only for a short time, for instance, ^ hour, nitration is complete, but if this time be exceeded, a decrease in the content of nitrogen im- mediately takes place. Simultaneously with denitration, the structure of the cot- ton is also completely destroyed ; it crumbles to a delicate paste, a pulverulent mass remaining behind after drying. The structure of the nitrated cotton is also affected by the content of water in the nitrating fluid. Up to a content of water of 15 per cent., scarcely any change in the structure is observed, but from 18 per cent, up, the fibres are some- what contracted and the peculiar twist characteristic of cotton disappears. With a still larger content of water the structure of the fibres is almost completely destroyed ; the cavity is torn open, and the fibres crumble to small frag- ments which felt together in knotty masses. The destructive effect is greatest when the content of water reaches 23 to 25 per cent. Although all the nitro-celluloses up to the deca-combina- tion can be produced with the use of nitric acid alone, a mixture of nitric and sulphuric acids is generally used for the preparation of collodion cotton, a saving of nitric acid being thereby effected and the time of reaction shortened. With the use of a mixture of 1 nitric acid to 3 sulphuric acid the following figures were obtained : 1 a Ccm.NO. in Per cent. N. Solubility in ether- alcohol. Yield. Proportion of cellulose to nitric acid. 1 210.69 13.21 3.20 174 2 198.10 12.42 98.70 160 1 :30 3 186.00 11.72 99.28 157 4 174.81 10.96 99.50 148 5 187.30 11.74 99.98 159 1 :12 6 173.83 10.90 99.20 149 172 CELLULOSE, AND CELLULOSE PRODUCTS. The nitrating fluids used in these experiments were com- posed as follows : Experiment. 1 2 3 4 5 59.77 20.94 19.29 6 H,S04 .... HNO, .... H^O 62.18 21.91 15.91 61.53 20.02 18.45 60;30 19.71 19.99 38.88 19.60 21.52 58.34 20.62 21.04 The product obtained by experiment No. 2 closely re- sembles, as regards its content of nitrogen, as well as its solubility, the preparation to which the term pyro-collodion has been applied by Mendelejeff. The final results of further experiments made with the use of nitric and sulphuric acids in the proportions of 1 : 4 and 1 : 5 are given in the table below : . fe Ccm.NO in Proportion Proportion a Per cent, N. Yield. of HNO3 to of cellulose Ig- H2SO4. to HNOs. 1 192.65 12.08 163 2 179.10 11.23 153 1 :3.8 1:30 3 187.58 11.76 156 4 175.23 10.99 151 1:12 5 198.32 12.42 167 6 185.89 11.66 158 1:30 7 168.00 10.53 140 1 :5 1:8 8 149.12 9.35 The composition of the nitrating fluids used in these experiments was as follows : Experiment. HNO3 H,0. 1 and 3 2 and 4 5 6 7 64.85 14.90 20.25 63.84 16.96 18.20 62.52 16.46 21.02 67.60 13.66 18.74 66.37 13.04 20.59 64.11 13.62 22.27 NITRO-CELLULOSE (gUN-COTTON, PYROXYLIN). 173 The temperature used in all the experiments was the ordinary one of a room, and the duration of nitration 24 hours. With the use of nitrating fluids, the acid proportions of which were 1 : 3, 1 : 3.8, and 1 : 5, a few experiments were made at a higher temperature, and at 95° F., after allowing the acid mixture to act for only two hours, the same pro- ducts as under the above-mentioned conditions were ob- tained. When carrying on nitration according to a determined rule, attention has to be chiefly directed to the content of water in the nitrating fluid, the quality of the products obtained being less affected by the larger or smaller quan- tity of sulphuric acid. A special series of experiments, in which the proportion between nitric acid and water was strictly maintained, while the quantity of sulphuric acid was changed, showed that the products obtained with dilute mixtures have to be considered as nitro-oxycelluloses, or as mixtures of nitro-celluloses with nitro-oxycelluloses. Further experiments showed : 0cm. NO in Per cent. N. Yield. Nitrating fluid. Ig- H2SO4. HNO3. H2O. 217.26 219.28 220.66 219.34 218.73 13.62 13.75 13.83 13.75 13.71 173 174 175 175 175 60.00 62.10 62.95 63.72 64.56 27.43 25.79 24.95 25.31 24.65 12.57 12.11 12.10 10.97 10.79 Thus, products were obtained which, as regards their content of nitrogen (up to 13.83 per cent.), more closely approach hexa-nitro-cellulose (14.14 per cent.) than all previous ones produced with nitric and sulphuric acids. The feature of this experiment of value in practice is the fact, that nitro-celluloses with a high content of nitrogen 174 CELLULOSE, AND CELLULOSE PRODUCTS. may be obtained with acid mixtures quite rich in water. By a series of special experiments it was shown that a con- tent within very wide limits of hyponitric acid in the nitric acid exerts no influence whatever upon the course of the process. The valuable investigations of G. Lunge and J. Bebie conclude with giving analyses of various nitro-celluloses. Samples of collodion cotton were first examined. One of them marked A, came from a Belgian factory, and is used for the preparation of blasting gelatine, while the other, marked B, from a factory at Breitenbach near Ziirich, is manufactured for the purpose of preparing artificial silk. Sample A showed in 1 g. 196.7 Cc.NO = 12.33 per cent. N, a solubility in ether-alcohol of 95.49 per cent., and an exploding point of 389.3° F., after heating during 4' 46". Sample B showed an exploding point of 386.6° F. after heating during 4' 46". The most highly nitrated actual gun-cotton from the Eidgenoessischen Munitionsfabrik at Thun proved, in regard to its explosibility, almost identical with the less highly nitrated collodion cotton. In other samples, collodion cotton also showed a somewhat higher exploding point than well-washed gun-cotton, while prepar- ations not thoroughly washed exploded at much lower de- grees of heat. PREPARATION OP GUN-COTTON. The first requisite for the production of gun-cotton which will in every respect come up to the demands made on it, is the presence of entirely pure cellulose, either purified cot- ton being used, or more rarely a fine quality of paper con- taining only cellulose. However, the cost of production being, in the latter case, much higher than with cotton, the latter is always used for manufacturing on a large scale. Raw cotton contains always certain quantities of fat, wax- like substances, and coloring matter. To free it from these bodies, it is first boiled with weak soda lye in large wooden NITRO-CELLULOSE (GUN-COTTON, PYROXYLIN). 175 vats with the use of steam, then freed from lye by means of a centrifugal, and finally washed with water until all alka- line reaction has disappeared. It is then bleached with chlorine, washed in acidulated water, then in pure water, and is finally freed from water in a centrifugal, and dried. The dry cotton is stored, carefully protected from dust, till it is to be treated with nitric acid. Loose, as well as spun, cotton may be subjected to nitration, but many manufactur- ers prefer to use loosely-spun cotton, the hanks being more readily handled than the loose, bulky material. ACID USED FOR NITRATION. The conversion of cellulose into gun-cotton may be ef- fected by treating it with concentrated nitric acid alone. However, this process is not expedient, since by the absorp- tion of water the nitric acid soon becomes diluted to such an extent that it has to be replaced by fresh acid. At present mixtures of concentrated nitric and sulphuric acids are gen- erally used, the latter acid acting as a water-attracting body, and the concentration of the nitric acid is thus for a longer time maintained at the required degree. Nitration was formerly also effected by introducing thoroughly-dried and finely-pulverized saltpetre into concentrated sulphuric acid, a highly concentrated nitric acid being thus obtained. How- ever, many obstacles being met in completely removing the potassium sulphate, which dissolves with some difficulty, from the gun-cotton by washing, this process has been en- tirely abandoned, and at present mixtures of the two acids are only used. For the manufacture of very explosive products, nitric acid as concentrated as possible (specific gravity 1.500) should be used, but for readily soluble products, nitric acid of specific gravity 1.400, and containing in round numbers 65 per cent, of nitric mono-hydrate, suffices. The nitric acid must be entirely free from foreign bodies, and contain but a small quantity of hyponitric acid, the product stand- ing next to it. 176 CELLULOSE, AND CELLULOSE PKODUCTS. The sulphuric acid to be used is the highly concentrated white acid of commerce. It should be free from iron, and contain but a very small quantity (not more than 0.1 per cent.) of arsenic. Because of their properties, the storage of the acids is <5onnected with some difficulties. The nitric acid should be kept in the carboys in which it is shipped from the fac- tory until it is to be mixed with the sulphuric acid. The store-room in which the carboys are kept should be fire- proof, so that in case one of them bursts, and the straw in the basket used for packing ignites, the flames cannot spread. The carboys should be placed so that a bursted carboy can be drawn by means of a hook into the centre of the store-room, and the floor of the latter so planned that the acid can run off into a pit. Only after the burning basket has been entirely consumed, and the room has been thoroughly aired, can the latter be again entered. Pure -aluminium being indifferent towards concentrated nitric ^cid, boiler-like, closed vessels of this material might be used for storing it. Sulphuric acid of fixed concentration (not below 1.600 specific gravity), as otherwise hydrogen-gas would be evolved, may be kept in iron vessels, old steam boilers being frequently used for this purpose. Iron being brought into a passive state by concentrated nitric acid, nitration may be eff'ected in cast-iron vessels furnished with a con- trivance by means of which a large portion of the absorbed fluid may be withdrawn when the cotton has been suffi- ciently treated. When working on a very large scale, stoneware vessels standing in a large trough filled with water to prevent strong heating, are preferably used. For introducing and lifting out the cotton a strong glass-rod bent into a hook on •one end is employed. The nitrating fluid is the mixture of nitric and sulphuric -acids, in which the cotton to be nitrated is immersed. It NITRO-CELLULOSE (gUN-COTTON, PYROXYLIN). 1 77 depends on the proportions in which the two acids are mixed, whether a very explosive, but only slightly soluble, mass — gun-cotton in the actual sense of the word — is ob- tained, or a product only slightly explosive, but readily soluble, to which the term collodion-cotton may be applied. The proportions for both these products, as determined by numerous experiments in practice, are as follows : For explosive gun-cotton : 1 part nitric acid and 3 parts sulphuric acid. For soluble gun-cotton : Equal parts of nitric acid with 75 per cent, of nitric anhydride and concentrated sulphuric acid with 96 per cent, sulphuric anhydride. CONDITION OF THE NITRATING FLUID. The constancy of the composition of the acid mixture is of great importance for the production of a uniform pro- duct, whether explosive or soluble. However, in reality, it is quite a difficult matter to maintain this state of the acid mixture, because during nitration water is always formed, causing a dilution of the acid. Theoretically, a ■certain quantity of acid could be used at one time, but as this is impossible in practice, an effort has to be made to maintain as long as possible the concentration of the acid within certain limits. It would, therefore, seem advisable to use nitrating vessels of comparatively large size, the ad- vantage gained thereby being that the concentration of the a,cids is not to any considerable extent reduced by successive nitrations. By successive immersions of fresh quantities of cotton in the nitrating vessel, the level of the fluid will fall, but if it be restored to its original height, by a workman allowing fresh acid mixture kept in readiness to run in, the dilution of the acid in the nitrating vessel is decreased by this addition of concentrated acids. In this manner the operation may for a long time be continued without the necessity of removing the acid mix- ture on account of its containing too much water. How- 12 178 CELLULOSE, AND CELLULOSE PRODUCTS. ever, as a rule, the acid has to be earlier removed for another reason. Many fine fibres of gun-cotton collect gradually in the fluid in the nitrating vessel, and when immersing fresh cotton, adhere so firmly to the latter as to greatly retard the penetration of the nitrating fluid. This may to some extent be remedied b}^ taking the acid from the nitrating vessel and filtering it through glass-wool in a stoneware filter, or by bringing it into a tall reservoir and allowing it to stand quietly until the delicate fibres have deposited on the bottom and the supernatant acid is clear. The nitrating fluids, which have been removed from the nitrating vessels, are always regenerated to be again util- ized. In doing this it is absolutely necessary to determine by accurate analysis the quantities of nitric and sulphuric acids, as well as of water, contained in the fluids. Based upon this analysis, it can then be calculated how much of the most highly concentrated acids has to be added to re- store the proportion between the acids as required for nitration. Since by constant regeneration an excessive quantity of exhausted acid would in time be obtained, fuming sulphuric acid is frequently used in place of ordinary sulphuric acid, and when sulphur trioxide can be obtained in commerce at suitable prices, its use for the regeneration of the acid mix- ture may be recommended. As regards the nitric acid to be employed, it need scarcely be mentioned that it should be as highly concentrated as possible. EXECUTION OF NITRATION. Nitration of the cotton may, as previously mentioned, be eflfected in stoneware vessels as well as in a cast-iron appa- ratus. In any case the vessels must be placed in a room provided with contrivances for carrying off' the gases evolved during nitration, they having a deleterious effect upon the respiratory organs of the workmen. Hence a ventilating hood connecting above with a pipe is placed over each NITRO-CELLULOSE (gUN-COTTON, PYEOXYLIN). 179 nitrating vessel. These pipes terminate in a joint pipe, into which air is constantly sucked by a ventilating con- trivance. In smaller plants this air is forced through a layer of red-hot coal, the products of decomposition of the nitric acid being thus rendered innocuous for the neighbor- hood. In larger factories it is more economical to conduct the air loaded with products of decomposition of the nitric acid into a condensing tower and utilize it again for nitric acid. Fig. 33 represents an iron nitrating apparatus so arranged Fig. 33. that the gun-cotton nitrated in it can at the same time be quite vigorously pressed out. The cast-iron trough K, ob- liquely cut off on the side turned towards the workmen, is surrounded by a vessel T, through which water runs con- stantly, passing in at and passing out at 0^. The object of this arrangement is to carry on the operation always at the same temperature, and therefore hot or cold water is, according to the season of the year, conducted through T. ■ 180 CELLULOSE, AND CELLULOSE PRODUCTS. The contrivance for pressing out the nitrated cotton con- sists of a grate-like iron plate R, upon which can be placed a solid iron plate P, which is provided with a vertical part Cj serving as the fulcrum of a lever. When the cotton just lifted out from the acid mixture is spread out upon the grate-like plate by placing the solid plate upon it, it can be vigorously pressed by means of the lever, the acid pressed out running back into the vessel K. The plate P is connected with the vertical part C. To the latter is secured a chain which runs over a pulley and carries on the upper part the weight G. By this weight the plate P is raised to the pivot z z, so that the cotton lifted out from the nitrating vessel can be placed upon the grate- like plate R, and pressed by placing in position the lever which revolves around C'^ the cotton being thus compressed and the fluid pressed out falls back into K. The com- pressed cotton is pushed through the opening and falls into the vessel N, where it remains until a sufficiently large quantity for further manipulation has accumulated. The pipe S serves for the introduction of fresh quantities of acid, the latter being allowed to run in whenever the level of the fluid falls below a mark on the wall of the vessel K. For the complete protection of the workmen from the vapors evolved by the nitrating fluid, the entire apparatus is enclosed in a case of glass and iron, the two sliding win- dows P and P being opened only' when cotton is to be in- troduced, or taken out. The gases escape through the pipe L, passing into a chimney in which a gas flame is constantly burning so that the escaping products of decomposition of the nitric acid are completely burnt and cannot inconveni- ence the neighborhood. To preserve the iron parts of the case from destruction by the vapors, they are repeatedly painted with hot coal tar, care being taken to allow one coat to become thoroughly dry before applying the next one. If the coats are carefully applied and by retouching places which in the course of time show rust spots, the iron is per- fectly protected. NITRO-CELLULOSE (gUN-COTTON, PYROXYLIN). 181 In carrying on the operation of nitration, the nitrating vessel is first filled with the appropriate quantity of acid mixture which should be of the same temperature as that usually prevailing in the factory. The cotton, which should be perfectly dry, is then immersed in the fluid and pressed down to accelerate the escape of air. The proportion between acid and cotton by weight may vary very much, but the nitrating vessel must contain a sufficient quantity of fluid to allow of the cotton being rap- idly submerged so that it can quickly absorb the fluid. But a very short time is actually required for nitration, a piece of fine tissue-paper, for instance, becoming completely nitrated by immersing it for a few seconds only, in a mix- ture of nitric and sulphuric acids, and then rapidly washing it. It being, however, impossible uniformly to moisten in a short time a larger quantity of cotton, and no disadvan- tage being connected with the finished gun-cotton remain- ing somewhat longer in the acid mixture, no general rule regarding the time the cotton is to stay in the fluid can be given, every factory fixing this point for itself. When the cotton has remained for the prescribed time in the nitrating vessel, it is taken out, pressed, or allowed to drain off", and is then thrown into a vessel for the so-called after-nitration, which is, however, a misnomer, there being no after-effect of the nitrating fluid. It can only be supposed that the acid still remaining in the pores of the gun-cotton acts upon the portions of cellulose which have escaped its effects while in the nitrating fluid, and converts them also into gun- cotton. In place of employing the kind of vessels above described, nitration may also be eff'ected in a centrifugal apparatus and the nitrated cotton dried by centrifugal force. The nitrating drum in this apparatus is usuall}'^ constructed of wrought iron or steel, but these materials being subject to quite rapid wear, drums of aluminium have recentl}^ been introduced in some factories, it being claimed that this 182 CELLULOSE, AND CELLULOSE PRODUCTS. metal is capable of offering great resistance to the nitrating fluid. The perforated drum of the centrifugal is enclosed in a cast-iron jacket, and is impelled from below. During the operation it is closed, the vapors evolved being carried off by a pipe in the lid. The centrifugal is filled four-fifths full with acid mixture and, while slowly revolving the cot- ton is rapidly introduced, and the acid is for about thirty minutes allowed to act upon it. The acid is then allowed to run off, and the centrifugal is made to revolve very rap- idly so that the fluid adhering to the gun-cotton is whirled out, this operation being finished in a short time. The drum is then quickly stopped by means of a brake, and the gun-cotton, which now feels almost dry, is lifted out. The drum can then be immediately used for another operation. With the use of a nitrating centrifugal, so-called after- nitration is entirely dispensed with, and care must be taken that by the employment of a larger quantity of nitrating fluid, conversion of the cellulose into nitro-cellulose is com- pleted in the centrifugal, this being attained by taking a comparatively very large quantity of the acid mixture for a fixed weight of cotton. In some factories a quantity of acid mixture amounting to two hundred times the weight of cotton is used. Although nitration is rapidly effected in the centrifugal apparatus, its use is not free from danger, it having been observed that the cotton frequently ignites, this taking place generally towards the end of whirling out. This phenomenon may be explained by the rise in temperature in the cotton when pressed with great force against the circumference of the drum by the rapid revolution of the centrifugal. When working with the ordinary apparatus, and then leaving the gun-cotton to after-nitration, the operation in the various factories takes from three to twenty-four hours. It is advisable to furnish the vessels used for after-nitration NITRO-CELLULOSE (gUN-COTTON, PYROXYLIN). 188 with perforated bottoms through which the acid draining off from the mass can run off. WASHING THE GUN-COTTON. In the further manipulation of the gun-cotton, the fluid contained in its interior has to be removed, and replaced by pure water. Although this operation has the appear- ance of being very simple, it nevertheless requires close attention, since on the complete removal of the fluid depends not only the stability of the product, but also security in handling and storing it. It happens sometimes that in washing gun-cotton it ignites when introduced into the washing tank, and to reduce this danger to a minimum, the rooms in which nitration and after-nitration are effected should be entirely separated from the wash-room. The vessels used for after-nitration are placed alongside the par- tition wall through which holes have been cut. In the wash-room, underneath these holes, is an inclined table covered with lead. While one workman lifts by means of a pair of tongs the moist hanks from the vessels and passes them through one of the holes in the wall, another workman draws them from the table and places them immediately in the wash-tank. The wash-tank consists best of a trough divided in the centre by a board, which, however, should not extend to the ends of the trough. The wash-water flows in from the bottom at one end and runs off through a notch cut in the upper edge of the trough. By this arrangement, the water, together with the hanks placed in it, constantly circulates in the trough, all parts of the gun-cotton being thus brought into intimate contact with it. For the purpose of catching small particles of gun-cotton carried along by the water running off, a basket is placed underneath the notch in the trough. The gun-cotton remains in the wash-tank until, when rubbed with litmus-paper, the latter no longer reddens. 184 CELLULOSE, AND CELLULOSE PRODUCTS. It is then completely freed from water by whirling in a centrifugal. If gun-cotton, no matter how carefully washed, be left for some time to itself, it undergoes changes by the acid still remaining in the interior of the cells exerting a decompos- ing effect. This acid has, therefore, to be removed, which is generally accomplished by boiling or steaming. Boiling is effected in a large vat with a false perforated bottom. The vat having been filled with gun-cotton and water, steam is introduced below the perforated bottom. In some factories boiling is finished in three hours, while in others it is continued for up to three days. In order to ensure the removal of the acid the water may be mixed with ammonium carbonate, about f to 1 oz. per quart of water. Steaming after boiling has been highly recommended for obtaining a product absolutely free from acid. For this purpose the water is discharged from the boiling vat, and steam introduced below the false bottom until it commences to escape in a non-condensed state from the top. It is claimed to have been observed that by long- continued boiling the content of nitrogen in the gun-cotton is decreased, which, of course, must be an injury to it, and that this is not the case in continued steaming. However, by all these operations the gun-cotton has not been freed from the last traces of acid, and this purpose can only be attained by thoroughly comminuting it in the pres- ence of a large quantity of water. For masses of the fibrous nature of cotton the best apparatus is that known as a beater or hollander used in paper mills for working pulp. It con- sists of an oblong tank closed on both ends by semi-circular pieces. It is divided by a short, vertical partition into two parts. The floor of one part is sloped and. a box of knives is fixed into it. Over this box of knives revolves a cylinder also furnished with knives, and its distance from the lower knives can be regulated at will. By the revolution of the cylinder the water, with which the apparatus is filled, is NITRO-CELLULOSE (GUN-COTTON, PYROXYLIn). 185 constantly kept in a circling motion and the hanks of gun- cotton thrown into the water are drawn between the knives of the revolving cylinder and those fixed in the box, and cut up. As comminution progresses, the cutting cylinder is lowered until the distance between the knives has finally been reduced to fractions of a millimeter. A certain portion of the gun-cotton is for 4 to 8 hours treated in the hollander, or till the pulp — as the commi- nuted mass is called — has acquired the requisite degree of fineness. It is then tested by taking a sample by means of a ladle from the trough of the hollander, and allowing it to stand quietly for some time. The water is then carefully poured off" as long as it is quite clear. Fresh water is then poured upon the sample and after slightly agitating the vessel, the water is again allowed to run off. After this wash- ing operation, nothing should finally remain in the vessel ; if there should be a residue of plainly-perceptible, coarser fibres, it is proof of the manipulation of the mass not hav- ing been for a sufficiently long time continued. When the mass in the hollander has acquired the proper degree of fineness, it is discharged either by opening a valve in the bottom of the trough, or by sucking off with a pump. The separation of the comminuted gun-cotton from the water is generally effected by means of a centrifugal, the basket of which consists of closely-woven wire lined inside with linen cloths. Some fine particles of gun-cotton being neverthe- less carried along with the water, the latter is first allowed to run into a larger vessel, in which the particles of gun- cotton gradually settle on the bottom. The supernatant water is then carefully drawn off. By treatment in the centrifugal the content of water in the gun-cotton is reduced to about 30 per cent. It is brought into lead-lined wooden boxes and covered with a linen cloth, which keeps out the dust, but does not prevent the mass from drying slowly. Up to the time the gun-cotton is brought into the store- 186 CELLULOSE, AND CELLULOSE PRODUCTS. boxes the operations are the same, no matter whether an explosive product — actual gun-cotton — or a readily soluble product — collodion-cotton — is to be prepared. For both purposes, cotton perfectly free from water must be used. DRYING THE GUN-COTTON. Although gun-cotton can be heated to between 140° and 158° F. without igniting, no factory would dare to run the risk of drying larger quantities of it at such a high tem- perature, since its explosion might have frightful conse- quences. Drying even at temperatures below 122° F. is dangerous, dry gun-cotton being a body which becomes highly electric by slight friction, and by a stronger current of air passing over it enough electricity might be generated for a spark to leap over and ignite the entire mass. It is, therefore, necessary to use special precautions in drying gun-cotton. Drying upon frames covered with linen upon which the gun-cotton is spread out in thin layers, has the appearance of being a very simple process, but, according to Guttmann, it is objectionable, because the gun-cotton is thereby com- pletely insulated, and there is danger of an electric discharge, especially if drying is effected at a higher temperature. To be entirely secure from an electric tension, Guttmann uses for drying, copper-plates provided with conical open- ings with a diameter of I millimeter on top and of 1 milli- meter on the bottom, thus rendering it impossible for them to be stopped-up by the gun-cotton. The copper plates are covered on the edges with leather to prevent friction, and are placed one above the other in the drying room. They are connected one with the other by metallic strips, these conductors being continued into the ground. This arrange- ment renders an accumulation of electricity in the gun- cotton impossible, any electricity developed being directly conducted into the ground. Heating the drying room is effected by air being con- NITRO-CELLULOSE (gUN-COTTON, PYROXYLIN). 187 stantly conducted by a ventilator over a system of rib- heating enclosed in a box. The air thus heated passes beneath the drying plates, which are enclosed in boxes, and leaves them heavily loaded with moisture. To prevent heating above a fixed temperature, the drying boxes are furnished with electric thermometers which indicate by ring- ing a bell when the maximum temperature — which should not be above 104° F. — is exceeded. Perfectly dry gun-cotton — and this applies also to col- lodion-cotton — is an exceedingly hygroscopic body, and very rapidly absorbs moisture from the air. It must, therefore, when taken from the drying boxes, be immedi- ately packed in air-tight vessels, bags of rubber or of fabrics impregnated with rubber being used for the purpose. Well- made wooden boxes, the lids of which are made air-tight by rubber strips on the edges, may also be employed. If collodion-cotton has been prepared, it is advisable to dis- solve it immediately when it comes from the drying boxes, this having the additional advantage of the solutions, by standing for some time, becoming perfectly clear. EXPLOSIVE GUN-COTTON. The effect of highly explosive nitro-cellulose — the actual gun-cotton — intended for blasting purposes, will be the more powerful the smaller the volume into which it is com- pressed. It is, therefore, made into cylindrical or prismatic bodies of known weight, and tlie dynamic effect of such a block can at the outset be established. Gun-cotton can only be pressed while in a moist state, and even when sub- jected to the most powerful pressure always contains a cer- tain amount of water. Its explosive power is, however, not affected by this content of moisture, explosion being brought about by making, while pressing the block, a cylindrical opening in it in which a fuse of dry gun-cotton is inserted. When gun-cotton is to be compressed, it is stirred with luke-warm water to a thin paste, and in doing this, the pro- 188 CELLULOSE, AND CELLULOSE PRODUCTS. portion of weight of gun-cotton to that of water has to be known. This paste is, as a rule, first freed from the larger portion of water by hand-presses, the shape the finished piece is to have being also given to it. The article thus preparatively pressed is subjected in hydraulic presses to as strong a pressure as can be pro- duced. The presses must be so arranged that the water pressed out from the mass can escape, otherwise pressure would be ineffective, since fluids oppose great resistance to compression. In the presses variously shaped bodies of gun-cotton are produced, the most common shapes being cylinders or slightly conical pieces, because they can be most readily removed from the moulds of bronze. For certain purposes, for instance, for loading torpedoes, the gun-cotton is compressed in the form of cylindrical segments, which, when put together, make up a slightly tapering cylinder. Smaller pieces similar to the first ones are laid one above the other, a body fitting accurately into the charging space of the torpedo being thus formed. Compressed gun-cotton being very hygroscopic, the compressed articles, when fin- ished, are immediately coated with a water-proof lacquer. INCREASING THE STABILITY OF THE NITRO-CELLULOSE. The nitro-celluloses, so far as at present known, belong to the constant combinations, i. e., they remain entirely un- changed in the air or under water, a change taking place only in consequence of an exterior influence. This im- mutability, however, belongs only to products absolutely free from the slightest trace of free acid, nitro-celluloses which contain free acid, be it never so little, being subject to change, though it may progress very slowly. The change manifests itself first by the originally pure-white mass turn- ing yellowish and acquiring in the course of time a quite dark-brown color, and after a long time, the nitro-cellulose is even converted into a dark-colored, smeary mass. The author of this work noticed, in the course of thirty years, NITRO-CELLULOSE (gUN-COTTON, PYROXYLIN). 189 these phenomena in a small quantity of explosive nitro- cellulose prepared by himself and which was kept in a vessel closed with a ground-glass stopper. Strange to say, on opening the vessel, the mass showed no odor of nitric oxide, and it remained perfectly odorless until it passed into the smeary state. The gun-cotton above-mentioned having only been thoroughly washed with cold water contained probably small quantities of free acid. According to the process of A. Luck and C. F. Gross, the stabilit}^ of nitro-cellulose may be increased by treatment with metallic salts, their solutions being allowed to act either directly upon the nitro-cellulose, or with the co- operation of acetone. In the first case, the nitro-cellulose is for 30 to 60 minutes treated in a one per cent, solution of lead acetate or zinc acetate at a temperature of from 176° to 212° F. The nitro-cellulose is then washed until the wash water shows no trace of the metallic salt. According to the other process, acetone, to which has been added 1 per cent, of its weight of the metallic salt, is poured over the nitro-cellulose, the treatment being, in this case, for half an hour at the ordinary temperature. The fluid is finally drawn off, and the nitro-cellulose thoroughly washed. By both these methods of treatment, a basic salt is claimed to be formed from the residue of acid in the nitro-cellulose with the metal, thus, for instance, of the lead salt up to 2 per cent, of lead oxide being found in the form of a basic combination. According to 0. R. Schulz's process the nitro-cellulose is rendered very stable by bringing it, when freed from acid in the ordinary manner by washing, into a pressure-boiler, together with several times its weight of water, and heating to 275° F. By increasing the pressure up to 5 or 6 atmos- pheres the operation is in a short time finished, and the nitro-cellulose breaks up to a fine powder, in which form it is especially suitable for the manufacture of cartridges. If heating be effected at as low a pressure as 3 atmospheres— 190 CELLULOSE, AND CELLULOSE PRODUCTS. corresponding to 275° F. — the nitro-cellulose is also ren- dered stable, but heating has to be continued for a longer time. The nitro-cellulose thus treated in the boiler is finally washed in cold water for the removal of the soluble bodies. With the use of this process only 2V to ^V of the quantity of water necessary for washing by the ordinary method is said to be required. SOLUBLE GUN-COTTON OR COLLODION-COTTON. In describing the preparation of nitrated cotton, atten- tion has been drawn to the fact that there is no fixed boundary between explosive and soluble gun-cotton, but that the latter can be obtained by a suitable change in the proportions of the acid mixture. Experience has shown that this can be best accomplished by using equal parts of sulphuric and nitric acids as nitrating fluid. The nitric acid should contain 75 per cent, of nitric anhydride, and the sulphuric acid 96 per cent, of sulphuric anhydride. The fluid is allowed to act upon the cotton for from 60 to 90 minutes at a temperature of 104° F., and the resulting product is immediately washed. Collodion-cotton having recently become of great import- ance for the preparation of textile threads, to which the term artificial silk has been applied, greater demands are now made on it than formerly, when it was chiefly used for photographic and medicinal purposes. For these appli- cations it sufficed for the collodion-cotton to dissolve clear, and, after the evaporation of the solvent, yield a film pos- sessing a certain strength and elasticity. With reference to the use of collodion-cotton for the manu- facture of textile threads of very slight diameter, great value is at present attached to the preparation of a product yield- ing a solution of great viscosity, the manufacture of very thin threads being only possible with such a solution. It has been found that the duration of the action of the NITRO-CELLULOSE (gUN-COTTON, P\'R0XYLIN). 191 acid mixture upon the cotton exerts great influence upon the viscosity of solutions of collodion-cotton. The content of nitrogen is also said to be of considerable importance, though this is disputed by many investigators. It may here be emphasized that collodion-cotton is never entirely uniform as regards its composition, and that a pro- duct of quite uniform general properties can only be obtained by always working with cotton of the same degree of fineness, using an acid mixture of the same composition, and con- ducting the operation in the same manner as regards tem- perature and duration of the action of the acid mixture. All these conditions have, therefore, to be taken into con- sideration in the manufacture of large quantities of collo- dion-cotton of uniform quality. The manufacturers who require collodion-cotton have determined the correct pro- portions suitable for their purposes by exhaustive experi- ments, and if they treat their processes of nitration as secrets, they cannot be charged with assuming an air of mysteriousness. For the production of collodion-cotton, the solutions of which are to possess a great degree of viscosity, a higher temperature should never be used for nitration, and to pre- vent a rise in the temperature, it is advisable to place the nitrating vessels in a tank filled with cold water. The pro- cess of nitration progres,sing more slowly at a lower tem- perature, the cotton is allowed to remain a somewhat longer time in the acid mixture. It is then pressed and imme- diately washed, the same care being exercised as in washing explosive cotton. The object of comminuting the cotton in the hollander is, in this case, not only to remove the acids, but also to obtain the product in a very finely divided state, it being thus more readily brought into solution. According to the investigations of G. Lunge and J. Bebie, previously referred to, the solubility of nitro-celluloses is intimately connected with the content of nitrogen in the products ; gun-cotton, which contains as much nitrogen as 192 CELLULOSE, AND CELLULOSE PRODUCTS. possible, behaving differently towards various solvents. It dissolves in acetic ether, acetone, benzol and nitrobenzol, but not in nitroglycerine. It is, however, dissolved by a mixture of nitroglycerine and acetone, such a solution serv- ing for the preparation of one of the most effective blasting agents which is known under the name of blasting-gelatine. Complete solubility in a mixture of two parts of ether and one part of alcohol may be considered characteristic of properly prepared collodion-cotton, though there is a pro- duct which also dissolves in a mixture of ether and alcohol in which the proportion of the latter is much larger. If nitro-cellulose be treated at a moderate heat with alcoholic solution of caustic soda or caustic potash, the nitro-combination is in a very short time disintegrated, cellulose remaining behind. This reaction is of great importance for the production of threads and tissues from collodion solutions, as by reason of their great inflamma- bility they would be of no use whatever. However, when treated for a short time with solution of an alkali, they rank, as regards inflammability, with ordinary cotton tissue. It has from many sides been asserted that a good quality of collodion-cotton can only be obtained by nitrating line tissue-paper which consists almost entirely of pure cellulose. Direct experiments in this direction have proved that an excellent quality of collodion-cotton can actually be pre- pared from such paper, it being only necessary for the purpose of nitration, slowly to draw strips of the paper over glass rods placed horizontally in the nitrating vessel and allow them to drain off. If, however, the expense of pre- paring collodion-cotton from paper is compared with the cost of producing it from cotton, the calculation results in favor of cotton. It may be confidently asserted that all that is necessary is to free cotton from all foreign bodies, i. e., to convert it into pure cellulose, to be enabled to pro- duce from it as good a quality of collodion-cotton as from paper. NITRO-CELLULOSE (gUN-COTTON, PYROXYLIN). 193 COLLODION. Nitro-cellulose, with a certain content of nitrogen, is capable of dissolving in a number of fluids, and it then forms a viscous mass possessing great adhesive power, to which the term collodion has been applied. When collodion is left to itself until the solvent evaporates, the nitro-cellulose remains behind in the form of a structureless film, which is perfectly colorless, and is distinguished by considerable solidity and high lustre. Collodion found originally only limited application in the healing art, it being used for the purpose of closing wounds air-tight to prevent the colonization of organisms which cause gangrenous and other complications detri- mental to the healing process. Solutions of nitro-cellulose gained in importance only from the time when the use of collodion in photography became general, and they retained this importance until the photographic process turned more and more towards the so-called dry plates, the sensitized layer of which con- sists of gelatine. However, collodion regained its great importance by reason of the invention of the preparation of artificial silk, large quantities of it being at present manu- factured for this purpose. In speaking later on of the manufacture of artificial silk, the preparation of collodion for this purpose will be referred to, and only the varieties which are of importance for photographic purposes will here be discussed. COLLODION FOR PHOTOGRAPHIC PURPOSES. It has been found by special investigations that a not highly nitrated nitro-cellulose is best adapted for the pre- paration of collodion for photographic purposes as it dis- solves with the greatest ease. Several authors recommend the finest quality of tissue-paper as raw material for its preparation, but the same result is without question ob- 13 194 - CELLULOSE, AND CELl ULOSE PEODUCTS. tained by using, in place of this expensive material, a fine quality of purified cotton. A series of nitro-celluloses is known, the formation of which depends on the action for a varying time of the nitrating fluid and, partially, also on its concentration. According to Eber the composition of these combinations is as follows C}:^ (tbe formula for the cellulose having been taken double): Content of nitrogen. 1. Cellulose-hexanitrate, Cj2H,40^(N03)6 . . • . 14.14 pei* cent. 2. Cellulcse-pentanitrate, CijH.jOslNOaJs . . . 12.75 *' 3. Cellulose-tetra nitrate, CijHieOeCNOa)^ .... 11.11 " 4. Cellulose-trinitrate, Ci2H,707(NOs)3 9.15 6. Cellulose-dinitrate, C,2H,808(N03)2 6.76 " The cellulose hexanitrate is the insoluble explosive com- pound which, however, contains alwaj's small quantities of soluble substance. Cellulose pentanitrate is soluble in a mixture of alcohol and ether. It is obtained by leaving cotton for several hours (up to five) at the ordinary tempera- ture in contact with a mixture of equal parts of concen- trated sulphuric and nitric acids of specific gravity 1.40. ^The resulting cellulose, as mentioned above, is soluble in a mixture of alcohol and ether, but if the mixture contains only a small quantity of ether, the cellulose pentanitrate alone is dissolved, the admixed tetranitrate and trinitrate remaining undissolved. Cellulose tetranitrate may be obtained by bringing 0.63 oz, (18 grammes) of tissue paper cut up into thin strips, into a mixture of equal parts of sulphuric acid of specific gravity 1.845 and nitric acid of specific gravity 1.40, and allowing it to remain \ hour in the acid mixture, maintain- ing the temperature during this time at 176° F. The pro- duct obtained in this manner is identical with celloidin, an article furnished b}'' Scheering's factory at Berlin. Besides tetranitrate, trinitrate is also formed, and the separation of the two compounds is not readily accomplished. The tetra- NITRO-CELLULGSE (gUN-COTTON, PYROXYLIn). 195 nitrate is insoluble in ether as well as in alcohol, but dis- solves in a mixture of them, as well as in acetic ether, methyl alcohol, in a mixture of acetic ether and alcohol, and in glacial acetic acid. Cellulose trinitrate dissolves slowly at the ordinary tem- perature in absolute alcohol ; it is readily soluble in acetic ether, methyl alcohol and boiling glacial acetic, acid. A concentrated alcoholic solution acquires a milky appear- ance by the addition of ether. Cellulose dinitrate may be obtained in various ways. According to one method, it is formed by allowing highly dilute mixtures of nitric and sulphuric acids to act at a higher temperature upon cellulose until an abundance of red vapors is evolved, and the mass commences to dissolve. Dinitro-cellulose may also be obtained by mixing collodion solution containing 2 to 4 per cent, of nitro-cellulose with a quantity of alcoholic potash lye about three times as large as would be required for the neutralization of the nitric acid present. After one or two hours, the fluid is diluted with water and neutralized with dilute sulphuric acid, a floccu- lent precipitate being formed, which is carefully washed and dried. It consists of dinitro-cellulose which ignites with difficulty and detonates when heated to 347° F. It is readily soluble in a mixture of ether and absolute alcohol, as well as in absolute alcohol alone, in glacial acetic acid, acetic ether, acetone, and methyl alcohol, but only with great difficulty in pure ether. The behavior in drying of a solution of dinitro-cellulose in ether-alcohol is of special importance for the preparation of collodion for photographic purposes. By allowing such a solution to evaporate upon a glass-plate, a milky-turbid, soft film is formed which is not transparent, but only trans- lucent. As only a slight admixture of this dinitro-cellulose suffices for collodion to exhibit this phenomenon, this com- pound has to be considered as entirely unsuitable for the preparation of a good quality of collodion. 196 CELLULOSE, AND CELLULOSE PRODUCTS, For the production of collodion serviceable for photo- graphic purposes as well as for other applications, the collodion-cotton has to be perfectly neutralized. When a sample of the cotton is moistened with water, and after squeezing out the water, litmus paper is reddened by it, the acid adhering to the cotton has to be neutralized. For this purpose the cotton is for half an hour soaked in ammonia diluted with four times its quantity of water, then thoroughly washed, and completely dried upon a plate placed upon a pot of boiling water. For the preparation of the solution, 50 parts of ether and 50 parts of 95 per cent, alcohol are used for 2 parts by weight of dry cotton. The alcohol is first poured over the cotton, and when the latter has swelled up, the ether is added, solution being accelerated by vigorous shaking. A 2 per cent, collodion is in this manner obtained. The physical condition of collodion-cotton has a notice- able influence upon its solubility. Pulverulent cotton, which crumbles to dust when rubbed between the fingers, has to be dissolved in a mixture of 40 parts of alcohol and 60 parts of ether, otherwise the resulting collodion layer will not turn out solid. Collodion solution is best kept in glass bottles of small diameter in a cool, dark place where it is protected from shocks. After standing for some time the undissolved par- ticles of cotton fall to the bottom, where they form a quite heavy deposit, the supernatant fluid being perfectly clear. By carefully tilting the bottles, the clear fluid may be almost entirely poured off". The preparation of collodion solution for the purpose of manufacturing artificial silk diff'ers in many respects from the process above described, and will be referred to in detail in speaking later on of the manufacture of artificial silk according to Chardonnet. NITRO-CELLULOSE (gUN-COTTON, PYROXYLIN). J 97 ELASTIC MASSES FROM NITRO-CELLULOSE (ARTIFICIAL RUBBER.) A solution of nitro-cellulose in volatile solvents yields, after the evaporation of the latter, a layer of structureless nitro-cellulose, which, however, becomes extremely brittle by drying. This mass may to a certain extent be rendered more flexible by adding to the solution a small quantity of castor oil. The latter is dissolved in strong alcohol, and a quantity of the solution, amounting to about 2 per cent, of the weight of the dry nitro-cellulose, is added to the collodion. The castor oil, after the evaporation of the solvent re- maining, uniformly distributed throughout the nitro-cellu- lose, imparts to the latter a certain degree of flexibility, and prevents thin layers of the mass from becoming brittle, without, however, conferring upon them a higher degree of elasticity. For the production from nitro-cellulose of masses possess- ing considerable elasticity other means have to be adopted. The nitro-cellulose has to be dissolved in fluids having a high boiling point, and which consequently do not evap- orate in the air, but impart to the mass a soft, elastic property similar to that of collodion still containing rem- nants of the solvent. The following fluids possess these properties and are at the same time capable of dissolving nitro-cellulose : Nitro- benzol, nitrotoluol, dinitrotoluol, nitrocumol, nitronaph- thalin, etc. However, their use in practice is almost out of the question because they are too expensive. A uniform mass may, to be sure, be produced by bringing dry soluble nitro-cellulose in contact with one of these sol- vents or a mixture of them ; but long-continued manipula- tion is required. The object may, however, be attained in a more simple manner by first dissolving the nitro-cellulose in one of the volatile solvents ordinarily used, then adding one of the above-mentioned less volatile solvents, and allow- ing the volatile solvent to evaporate. 198 CELLULOSE, AND CELLULOSE PRODUCTS. For this purpose it is not necessary to prepare an entirely clear solution of nitro-cellulose in a volatile solvent, only enough of the latter being used to cause the nitro-cellulose to swell up so that a mass resembling very thick glue solu- tion is formed. A kneading apparatus allowing of thorough mechanical manipulation is used for preparing the mass. Since dur- ing this manipulation, the volatile solvent would evaporate, the kneading apparatus should be placed in a box which can be closed air-tight, and provision must be made for a contrivance by means of which a current of warm air can be passed through the apparatus. The nitro-cellulose having been intrpduced, the apparatus is closed, and the necessary quantity of solvent admitted. The most suitable solvent is a mixture of equal parts of ether and alcohol, though acetone or methyl alcohol may also be used. The mixing contrivance is then set in motion and kept going until the contents of the apparatus have been converted into a uniform mass in which no lumps of swollen, undissolved nitro-cellulose are noticed. The heavy volatile solvent is then introduced, and the mixing apparatus kept constantly in motion until the mass has again become homogeneous. This is the period at which the greater part of the volatile solvent may be regained by distillation. For this purpose a current of warm air is passed through the apparatus, and, when loaded with the vapors of alcohol and ether, is conducted through a cooling pipe in which the vapors are condensed. However, the entire quantity of volatile solvent must not be distilled off, otherwise the mass in the apparatus would become so viscous as to clog the kneading contrivance. The further manipulation of the mass is effected by rolls, the rest of the volatile solvent still contained in it being thereby completely evaporated. Rolling has to be several times repeated to make the mass thoroughly homogeneous. NITRO-CELLULOSE (gUN-COTTON, PYROXYLIN). 199 The nature of the masses finally obtained depends on the proportional quantities of nitro-cellulose and solvent. The more of the latter is present the more elastic the masses will be, and by a suitable change in the proportions, masses almost equal, as regards softness and elasticity, to a fine quality of rubber may be obtained. The smaller the quan- tity of solvent, the more solid and harder the resulting masses will be. These masses, when heated, acquire a higher degree of stablity, and can then by pressure be brought into any shape desired, and as they can be readily mixed with in- different bodies, articles of very varying appearance may be made of them. For mixing purposes, powders of cheap, indifferent bodies, such as chalk, asbestus, talcum, etc., are especially suitable. If other than white masses are to be prepared, any desired coloring matter may be mixed with the white powders, colored masses of very neat appearance being thus obtained. On account of their great elasticity, the term artificial rubber has been applied to these peculiar nitro-cellulose masses, and for many purposes they may serve as substitutes for rubber. . The above-described masses, consisting as they do largely of nitro-cellulose, are quite inflammable, without, however, exhibiting any explosive properties. The inflammability, however, becomes less with the use of a larger quantity of indifferent substances, it being thereby actually reduced to a very slight degree, and it may be still further decreased by superficially denitrating the finished articles. This is accomplished by dipping them for a short time in hot soda lye, the outer layers of nitro-cellulose being thereby con- verted into cellulose. An article thus treated will not ignite, even when brought in contact with a red-hot body, the point of contact being simply blackened by the carbon- ization of the outer cellulose layers. The elastic nitro-cellulose masses prepared according to the process above described, are by many investigators con- 200 CELLULOSE, AND CELLULOSE PRODUCTS. sidered as deserving the greatest attention of all the bodies which have been proposed as substitutes for rubber, they approaching nearest, as regards their properties, the genu- ine article, without, however, being capable of entirely re- placing it. CELLULOSE ESTERS. In addition to the esters yielded by cellulose by the action of nitric acid, analogous combinations with other acids may be prepared. But a small number of combina- tions belonging to this series are at present known, but it may be supposed that many of them may in the future ac- quire a certain importance for the industries. It has, therefore, been considered advisable to give a few facts regarding the nature and preparation of these combinations. CELLULOSE ACETIC ESTER. Cellulose tetra-acetate or cellulose acetic ester is prepared, according to Henckel-Donnersmark's process, from a mole- cular mixture of cellulose and magnesium acetate, and, therefore, 630 grammes (21.87 ozs.) of magnesium acetate have to be used for every 720 grammes (25.39 ozs.) of cellulose, pure cellulose prepared from cellulose sulpho- carbonate being said to be especially suitable for preparing the combination. The above-mentioned mixture of cellu- lose and magnesium acetate is intimately mixed in a kneading machine, the mixing vessel of which can be heated, with 810 grammes (28.57 ozs.) of acetyl chloride and 450 grammes (15.87 ozs.) of anhydrous acetic acid. When the chemicals commence to act one upon the other 4.5 liter (4.65 quarts) of nitrobenzol are added in very small portions at a time, a fresh quantity being only added when the previous one has been completely taken up by the mass. The addition of the nitrobenzol is so managed that about one-half of it remains when the temperature of the mass has risen to 158° F. This quantity is then at one time brought into the mixing vessel, and the mixing machine NITRO-CELLULOSE (GUN-COTTON, PYROXYLIN). 201 kept going for three hours longer. A thinly-fluid solution of the tetra-acetate still containing traces of unchanged cellulose and of lower acetates is thus obtained. The warm solution is poured into 22.5 liter (23.76 quarts) of alcohol, the acetate precipitating thereby as a white, finely-flocculent mass, which is separated from the fluid by filtration. This flocculent mass is washed with warm alco- hol, the washing fluid is added to the mother-lye, and the flocculent mass subjected to strong pressure. It is then, without previous drying, comminuted, stirred together with water, and boiled in the latter until the last traces of the solvent have been evaporated. The mass is then again filtered, washed first with warm water acidulated with a small quantity of hydrochloric acid to remove the last traces of the magnesium salt, and then with pure warm water, until the fluid running ofl" shows a neutral reaction. It is then again subjected to pressure and finally dried at a temperature not exceeding 176° F. Of the homologues of nitrobenzol, Henckel-Donnersmark has used with equal success o-nitrotoluol, p-nitrotoluol, o-nitro-ethylbenzol and the nitroxylols and nitrocumols from isopropyl-benzol. The composition of cellulose tetra-acetate corresponds to the formula C6H605(C2H30)4. The combination is in- soluble in methyl alcohol, ethyl alcohol, ethyl acetate, amyl acetate, acetones and ether ; it dissolves in ethyl-benzoate, chloroform, glacial acetic acid and nitrobenzol. The solu- tion in nitrobenzol congeals on cooling to a solid, perfectly transparent jelly. When a solution of cellulose tetra-acetate is poured upon a glass-plate and allowed to evaporate, the combination is left behind in the form of laminae of extraordinary trans- parency which show considerable solidity even when just of such a thickness as still to exhibit the iridescence of very thin layers. Towards the action of chemicals, the combi- nation shows a degree of indiflFerence which considerably surpasses that of nitro-cellulose, it being not attacked by 202 CEX,LULOSE, AND CELLULOSE PRODUCTS. alkalies, which produce no effect whatever even at a higher temperature. The combination is only destroyed by boil- ing it for several hours in alcoholic soda lye, cellulose re- maining behind which, however, retains the form of laminae, as well as the transparency. One property of the combination which may perhaps be- come of great technical importance, is its insulating power, which is better than that of rubber or gutta-percha. The acetate softens only at about 302° F., and is not inflam- mable. The great chemical indifference of this substance and its extraordinary insulating power may secure for it consider- able application in the electrical industry. For many pur- poses it might also serve as a substitute for celluloid, especially in cases where the use of this material is excluded by reason of its great inflammability. Since, as previously mentioned, very thin, but nevertheless very solid, laminae can be obtained by the evaporation of dilute solutions of the ester, such solutions might prove very suitable for lacquering metals to protect them from atmospheric action. According to L. Lederer an acetyl derivative of cellulose is prepared by bringing hydro-cellulose in contact with sul- phuric acid and acetic anhydride at a temperature, which should not be much above 158° F., the process being as follows : The cellulose is allowed for a few minutes to re- main in contact with dilute (3 per cent.) sulphuric acid. It is then pressed out, dried and heated for three hours at 158° F. Four times the quantity of acetic anhydride is then poured over it. A vigorous disengagement of heat immediately takes place, and the heat in the interior of the closed vessel must be so moderated by cooling that it does not exceed 158° F. The hydro-cellulose is gradually dis- solved and when reaction is complete, the mass is mixed with water, thoroughly washed, and dried. The acetylated cellulose thus obtained forms a white powder of a gritty nature, soluble in chloroform or nitro- NITRO-CELLULOSE (GUN-COTTON, PYROXYLIN). 203 benzol. According to Lederer, the acetyl-cellulose prepared in the manner above described, is especially suitable as a substitute for collodion, and for the preparation of articles resembling celluloid in appearance, but distinguished from it by being perfectly free from odor aiid not being inflam- mable. Lederer has later on modified his process by submitting the mass, after adding the acetic acid, to uninterrupted mechanical manipulation, the temperature, by constant cooling, being prevented from rising above 86° F. The mechanical manipulation is continued until the mass pre- sents the appearance of transparent paste, when, by the addition of water, the acet34-cellulose is separated and fur- ther worked. CELLULOSE BUTYRIC ESTER. Cellulose tetra-butyrate or cellulose butyric ester is pre- pared in a manner analogous to the acetate, and, as regards its propQrties, closely resembles the latter, but is distin- guished from it by being more readily soluble in the solvents above-mentioned, and dissolving also in ethyl ace- tate and in acetone. Laminse obtained from the butyrate by allowing solutions of it to evaporate, are somewhat softer and more flexible than laminse from the acetate. In addition to the above-mentioned esters, Henckel- Donnersmark has prepared a series of similar combinations, for instance, the double ester — cellulose aceto-butyrate — further, cellulose palmitate, cellulose phenyl-acetate, etc. As regards their properties, these combinations show a cer- tain resemblance to those previously described. Thus far, no application of them in the industries has become known. " SOLID SPIRIT." A peculiar use is made of cellulose acetate, according to statements by the " Farbenfabriken," formerly Fr. Boyer & ^^^f Co., for the purpose of bringing alcohol into a solid form — 204 CELLULOSE, AND CELLULOSE PRODUCTS. solid spirit. For the preparation of this peculiar product, 100 grammes (3.52 ozs.) of cellulose tri-acetate are dissolved in 500 grammes (17.63 ozs.) of glacial acetic acid and the solution is quickly brought into 2 liters (2.113 quarts) of alcohol. Cylindrical structures of a gristly nature are formed from which the excess of glacial acetic acid and alcohol is removed by pressure. They are then dried in the air and kept in closed vessels for use. When heated the product does not melt, and when ignited, burns uni- formly without leaving a residue. IX. ARTIFICIAL SILK. The substance to which the general term silk has been applied is the product of the larvae or caterpillars of different Lepidoptera of the genus Bombyx, and of a few other varie- ties. When the larva has attained its period of full growth, it contains in large vessels, almost occupying its entire body, a glutinous fluid which is either colorless or yellow, or sometimes orange-red. These vessels are by means of very small apertures connected with a spinner on the pos- terior of the larva, and while the latter spins its cocoon the glutinous fluid passes in unbroken lines through the aper- tures of the spinner. The glutinous fluid immediately coagulates under con- tact with air to a very thin thread, which is either colorless, yellow or orange-red, and represents the raw silk. How- ever, the latter does not consist of a uniform mass, but of two distinct bodies. The outer layer is gelatinous and gummy, forming the so-called silk-glue, and has to be re- moved previous to the further manipulation of the raw silk. The core enclosed by this outer layer is the actual silk sub- stance, or sericin, or fibroin. In addition to these substances, several other bodies, such as albumen, coloring matter, wax and fat, occur in silk. The composition of raw silk is, therefore, quite complex, and consists, as a rule, of 20 per cent, of the gelatinous substance ; 53 per cent, of actual silk substance or sericin ; 24 per cent, of albuminous combina- tions, and 3 to 4 per cent, coloring matter, fat and wax. By a special operation, called scouring or boiling, the raw silk is deprived of all other substances except the seri- (205) 206 CELLULOSE, AND CELLULOSE PRODUCTS. cin or fibroin, when it can be further worked by mechani- cal means. This operation is generally effected by repeat- edly boiling the raw silk with soap solutions. Viewed under the microscope, a thread of silk freed from its envelope of gummy matter appears as a massive cylinder (without cavity), resembling in its appearance a glass rod, and showing here and there very slight cross-stripes. The diameter of the individual threads is very slight, vary- ing according to the degree of fineness of the silk between 2-V and ^V of a millimeter. Notwithstanding this slight thickness, silk threads possess an uncommonly high degree of strength and elasticity by far surpassing in this respect all other textile fibres. Silk being not available in unlimited quantities and the demand for it being constantly on the increase, chemists have for a long time endeavored to produce it by artificial means, but the results have always proved unsatisfactory. However, efforts to obtain masses for the production of threads which, as regards fineness and lustre, closely re- semble actual silk and can be spun and twisted, have been more successful, but none of these substitutes for silk can, as regards strength and elasticity, compare with the natural })roduct, even the best of them being in this respect far in- ferior to it. VARIETIES OP ARTIFICIAL SILK. Three varieties of silk-substitutes or artificial silk may at present be distinguished and according to their origin may be designated as cellulose-silk, collodion-silk, and glue- or gelatine-silk. As the matter stands at present, pre-eminence above all other substitutes has to be given to collodion-silk, while glue-silk decidedly occupies the lowest place. However, cellulose-silk might in the future take precedence over collodion-silk, it possessing decided advantages over the latter. 1- J^RTIEICIAL SILK. 207 With reference to the historical development of the artifi- cial silk' industry, the' French chemist M. de Chardonnet was the first to occupy himself successfully with this sub- ject. As early as 1884 he deposited with the French Academic des sciences a sealed document, which, was opened November 7, 1887, and, bore the title Sur une matih-e textile artificielle resemhlant d la soie (on an artificial textile sub- stance resembling silk). The process for the production of a textile substance resembling silk suggested, in 1889, by Du Vivier, and designated by him as soie de France, can only be considered a modification of Chardon net's method. Du Vivier, as well as Lehner, uses solutions of nitro-cellulose for the produc- tion of textile threads, this being also the pith of the first invention, collodion being Chardonnet's initial material. Lehner also starts off with nitro-cellulose, but employs for its solution substances difi"ering from those used by Chardonnet, and mixes this solution with silk-fibroin pre- pared from silk waste, or with solution of artificial rubber prepared from drying oils. The fluid pressed into the form of a thread is conducted into a bath of oil of turpentine, or of a mineral oil, in which it coagulates, and the thread thus obtained, which is still soft and viscous, is stretched pre- vious to being reeled up. A. Millar utilizes for the production of textile threads the property of glue solution mixed with potassium dichromate, becoming insoluble on exposure to light. For this purpose a clear solution of gelatine is mixed with solution of potas- sium dichromate, the solutions being prepared in the pro- portion of 100 parts of gelatine to 2 or 2| parts of potassium dichromate. The fluid should only contain sufficient water to emerge from the narrow spinning apertures in the form of a viscous thread, which on exposure to light becomes insoluble. Hummel, of Leeds, converts pure gelatine solution into threads, dries them and prepares from 16 to 18 such 208 CELLULOSE, AND CELLULOSE PRODUCTS. threads, skeins, which are exposed to the vapors of formalin, whereby the gelatine is deprived of its solubility in water. Comparative experiments have shown that threads pre- pared from glue (gelatine) possess a comparatively high degree of brittleness, and in addition have the very dis- agreeable property of swelling up very much in moist air. Cadoret uses in his method an intermediary between Chardonnet and Millar's processes. He dissolves dinitro- cellulose in a mixture of ether and acetic acid, and mixes this solution with glue solution or albuminous substances, so that a fluid is formed which can be drawn out to thin threads. The latter acquire solidity by being drawn through a tannin solution, by which the glue substance or the albu- men is transformed into an insoluble body. The thread obtained by this process consists, therefore, of a mixture of dinitro-cellulose and the combination of tannin and glue, or albumen. The methods according to which textile threads are pre- pared from pure cellulose instead of nitro-cellulose difi^er ^essentially from those mentit^ned above. Several processes in this direction have becorae%nown, each of which may, however, be considered as originM, though of greatest im- portance is perhaps the method according to which a solu- tion of cellulose in cuprammonium is Maker ani Engineer's Reference Book: Containing a variety of Useful Information for Employers of Labor. Foremen a'*d Working Boiler-Makers. IroQ, Copper, and Tinsnutltf 20 HENRY CAREY BAIRD & CO.'S CATALOGUE. Draughtsmen, Engineers, the General Steam-using Public, and for the Use of Science Schools and Classes. By Samuel Nicholls. IUuS" trated by sixteen plaies, 1 2mo. ^2.50 NICHOLSON.— A Manual of the Art of Bookbinding : Containing full instructions in the different Branches of Forwarding, Gilding, and Finishing. Also, the Art of Marbling Book-edges and Paper. By James B. Nicholson. Illustrated. i2mo., cloth ^2.25 NICOLLS.— The Railway Builder: A Hand-Book for Estiniiiting the Probable Cost of American Rail- way Construction and Equipment. By WiLLlAM J. NiCOLLS, Civil Engineer. Illustrated, full bound, pocket-book form . J?2.00 NORMANDY. — The Commercial Handbook of Chemical An« alysis : Or Practical Instructions for the Determination of the Intrinsic oi Commercial Value of Substances used in Manufactures, in Trades, and in the Arts. By A. Normandy. New Edition, Enlarged, and to a great extent rewritten. By Henry M. Noad, Ph.D., F.R.S., thick i2mo. . . . Scarce NORRIS. — A Handbook for Locomotive Engineers and Ma- chinists : Comprising the Proportions and Calculations for Constructing Loco- motives; Manner of Setting Valves; Tables of Squares, Cubes, Areas, etc., etc. By Septimus Norris, M. E. New edition. Illustrated, I2mo $i-S^ NYSTROM. — A New Treatise on Elements of Mechanics : Establishing Strict Precision in the Meaning of Dynamical Terms; accompanied with an Appendix on Duodenal Arithmetic and Me trology. By John W. Nystrom, C. E. Illustrated. 8vo. $3.0* NYSTROM. — On Technological Education and the Construc- tion of Ships and Screw Propellers : For Naval and Marine Engineers. By John W. Nystrom, lati Acting Chief Engineer, U. S. N. Second edition, revised, with addi tional matter. Illustrated by seven engravings. i2mo. . ^i-2_ O'NEILL. — A Dictionary of Dyeing and Calico Printing: Containing a brief account of all fhe Substances and Processes it use in the Art of Dyeing and Printing Textile Fabrics ; with Practical Receipts and Scientific Information. By Charles O'Neill, Analy- tical Chemist. To which is added an Essay on Coal Tar Colors and their application to Dyeing and Calico Printing. By A. A. Fesquet, Chemist and Engineer. With an appendix on Dyeing and Calico Printing, as shown at the Universal Exposition, Paris, 1867- 8vo., 491 pages . . ^3.00 CRTON. — Underground Treasures*. How and Where to Find Them. A Key for the Ready Determination ui all the Useful Minerals within the United States. By James OSTON, A.M., Late Professor of Natural History in Vassar College, N. Y ; author of the " Andes and the Amazon," etc. A New Edi- tion, witli An Appendix on Ore Deposits and Testing Minerals (1901). Illustrated . ' $l-SO HENRY CARIiY BAIRD Sc CO.'S CATALOGUE. 21 OSBORN.— The Prospector's Field Book and Guide. In the Searcli For and the Easy Determination of Ores and Other Useful Minerals. By Prof. H. S. Osborn, LL. D. Illustrated by 58 Engravings. i2mo. Fifth Edition. Revised and Enlarged (1901) |i.50 OSBORN — A Practical Manual of Minerals, Mines and Mm ing: Comprising the Physical Properties, Geologic Positions, Local Occur- rence and Associations of the Useful Minerals; their Methods of Chemical Analysis and Assay ; together with Various Systems of Ex- cavatmg and Timbering, Brick and Masonry Work, during Driving, Lining, Bracing and other Operations, etc. By Prof. H. S. OsBORN, LL. D., Author of " The Prospector's Field-Book and Guide." 171 engravings. Second Edition, revised. 8vo. . . . $^.$0 OVERMAN. — Th(i Manufacture of Steel : Containing the Practice and Principles of Working and Making Steel. A Handbook for Blacksmiths and Workers in Steel and Iron, Wagon Makers, Die Sinkers, Cutlers, and Manufacturers of Files and Hard- ware, of Steel and Iron, and for Men of Science and Art. By Frederick Overman, Mining Engineer, Author of the " Manu- facture of Iron," etc. A new, enlarged, and revised Edition. By A. A. FESQl/iLT, Chemist and Engineer. i2mo. . . ^1.50 OVERMAN. — The Moulder's and Founder's Pocket Guide : A Treatise or. Moulding and Founding in Green-sand, Dry-sand, Loam, and Cement; the Moulding of Machine Frames, Mill-gear, Hollow- ware, Ornaments, Trinkets, Bells, and Statues; Description of Moulds for Iron, Bronze, Brass, and other Metals; Plaster of Paris, Sulphur, Wax, etc. ; the Construction of Melting Furnaces, the Melting and Founding of Metals ; the Composition of Alloys and their Nature, etc., etc. By Frederick Overman, M. E. A new Edition, to which is added a Supplement on Statuary and Ornamental Moulding, Ordnance, Malleable Iron Castings, etc. By A. A. Fesquet, Chem- ist and Engineer. Illustrated by 44 engravings. l2mo. . ^2.00 PAINTER, GILDER, AND VARNISHER'S COMPANION, Comprising the Manufacture and Test of Pigments, the Arts of Paint- ing, Graining, Marbling, Staining, Sign- writing, Varnishing, Glass- staining, and Gilding on Glass ; together with Coach Painting and Varnishing, and the Principles of the Harmony and Contrast of Colors. Twenty-seventh Edition. Revised, Enlarged, and in great part Rewritten. By William T. Brannt, Editor of " Varnishes, Lacquers, Printing Inks and Sealing Waxes." Illustrated. 395 pp. I2mo. . . . , $l.SO PALLETT.— The Miller's, Millwright's, and Engineer's Guide. Bv Henry Pallett. Illustrated. i2mo. . . . iSa.oo 22 riENRY CAREY BAIRD & CO.'S CATALOGUE. PERCY.— The Manufacture of Russian Sheet-Iron. By John Percy, M. D., F. R. S. Paper. ... 25 cts. PERKINS.— Gas and Ventilation: Practical Treatise on Gas and Ventilation, Illustrated. l2mo. ^1.25 PERKINS AND STOWE.— A New Guide to the Sheet-iron and Boiler Plate Roller : Containing a Series of Tables showing the Weight of Slabs and Piles to Produce Boiler Plates, and of the Weight of Piles and the Sizes of Bars to produce Sheet-iron ; the Thickness of the Bar Gauge in decimals ; the Weight per foot, and the Thickness on the Bar or Wire Gauge of the fractional parts of an inch; the Weight per sheet, and the Thickness on tlie Whe Gauge of Sheet-iron of various dimensions to weigh 112 lbs. per bundle; and the conversion of Short Weight into Long Weight, and Long Weight into Short. POSSELT. — Recent Improvements in Textile Machinery Re- lating to Weaving : Giving the Most Modern Points on the Construction of all Kinds of Looms, Warpers, Beamers, Slashers, Winders, Spoolers, Reeds, Temples, Shuttles, Bobbins, Heddles, Heddle Frames, Pickers, Jacquards, Card Stampers, etc., etc. 600 illus. . . $3 00 POSSELT. — Technology of Textile Design: The Most Complete Treatise on the Construction and Application of Weaves for all Textile Fabrics and the Analysis of Clotii. By E. A. Posselt. 1,500 illustrations. 4to ^S-OO POSSELT. — Textile Calculations: A Guide to Calculations Relating to the Manufacture of all Kinds of Yarns and Fabrics, the Analysis of Cloth, Speed, Power and Belt Calculations. By E. A. PosSELT. Illustrated. 4to. . $2.00 REGNAULT.— Elements of Chemistry: By M. V. Regnault. Translated from the French by T. FoRREST Betton, M. D., a«d edited, with Notes, by James C. Booth, Melter and Refiner U. S. Mint, and William L. Faber, Metallurgist and Mining Engineer. Illustrated by nearly 700 wood-engravings. Com- prising nearly 1,500 pages. In two volumes, 8vo., cloth . S6.00 RICHARDS.— Aluminium : Its History, Occurrence, Properties, Metallurgy and Applications, including its Alloys. By Joseph W. Richards, A. C, Chemist and Practical Metallurgist, Member of the Deutsche Chemische Gesell- schaft. Illust. Third edition, enlarged and revised (1895) . ^6.00 'RIFFAULT, VERGNAUD, and TOUSSAINT.— A Practical Treatise on the Manufacture of Colors for Painting : Comprising the Origin, Definition, and Classification of Colors; the Treatment of the Raw Materials ; the best Formulae and the Newest Processes for the Preparation of every description of Pigment, and the Necessary Apparatus and Directions for its Use ; Dryers ; tha Testing. Application, and Qualities of Paints, etc., etc. By MM. RiFFAULT, Vergnaud, and ToussAiNT. Revised and Edited by M. HENRY CAREY BAIRD & CO. S CATALOGUE. 23 F. Malepsyre. Traniiated from the French, by A. A. FESfj-armiy Chemist and Engineer. Illustrated by Eighty engravings. In one vol., 8vo., 659 pages ....-•• $S-^^ ROPER. — Catechism for Steam Engineers and Electricians: Inchiding the Constiuciion and Mauageinent of isieam Engines, Steam Bi-ilersand Electric Plants. By STEPHfcN Roper. Tvveniy- first edition, rewritten anil greatly enlarged by E. R. Kellkr and C. VV. Pike. 365 page.s. Illustrations. i8u)o., tucks, gilt. |2.oo ROPER.— Engineer's Handy Book: Containing Facts, Formulae, I'ables and Questions on Power, its Generation, Transmission and Measurement; Heat, Fuel, and Steam; The Steam Boiler and Accessories ; Steam Engines and their Parts ; Steam Engine Indicator; Gas and Gasoline Engines; Materials; their Properties and Strength ; Together with a Discussion of the Fun- damental Experiments in Electricity, and an Explanation of Dynamos, Motors, Batteries, etc., and Rules for Calculating Sizes of Wires. By Stephen Roper. 15th edition. Revised and enlarged by E. R. Keller, M. E. and C. W. Pike, B. S. (1899), with numerous illus- trations. Pocket-book form. Leather f3-50 ROPER. — Hand-Book of Land and Marine Engines : Including the Modelling, Construction, Running, and Management of Lanr" and Marine Engines and Boilers. With il'ustrations. Bf Stephen Roper, Engineer. Sixth edition. i2mo.,ti'cks, gilt edge. ROPER.— Hand-Book of the Locomotive : Including the Construction of Engines and Boilers, and the Construc- tion, Management, and Running of Locomotives. By Stephen Roper. Eleventh edition. i8mo., tucks, gilt edge . $2.^(i ROPER. — Hand-Book of Modern Steam Fi.'-e-Engines. With illustrations. By Stephen Roper, Engineer. Fourth edition, i2mo., tucks, gilt edge ....... ^3-50 ROPER. — Questions and Answers for Engineers. This little book contains all the Questions that Engineers will be asked when undergoing an Examination for the purpose of procuring Licenses, and they are so plain that any Engineer or Fireman of or dinary intelligence may commit them to memory in a short time. By Stephen Roper, Engineer. Third edition . . . $2.00 ROPER.— Use and Abuse of the Steam Boiler. By Stephen Roper, Engineer. Eighth edition, with illustrations. l8mo,, tucks, gilt edge ;5!2.0C ROSE. — The Complete Practical Machinist : Embracing Lathe Work, Vise Work, Drills and Drilling, Taps and Dies, Hardening and Tempering, the Making and Use of Tools Tool Grinding, Marking out Work, Machine Tools, etc. By JoSHUA Rose. 39s Engravings. Nineteenth Edition, greatly Enlarged with New and Valuable Matter. l2mo., 504 pages. . , ^2.50 ROSE. — Mechanical Drawing Self-Taught : Comprising Instructions in the Selection and Preparation of Drawing Instruments, Elementary Instruction in Practical Mechanical Draw- 24 HENRY CAREY BAIRD & CO.'S CATALOGUE. i"g) together with Examples in Simple Geometry and Elementary Mechanism, including Screw Threads, Gear Wheels, Mechanical Motions, Engines and Boilers. By JoSHUA RosE, M. E. Illuslrated by 330 engravings. 8vo , 313 pages .... ^4.00 ROSE.— The Slide- Valve Practically Explained: Embracing simple and complete Practical Demonstrations of th« operation of each element in a Slide-valve Movement, and illustrat- ing the effects of Variations in their Proportions by examples care, fully selected from the most recent and successful practice. By . Joshua Rose, M. E. Illustrated by 35 engravings . ^r.oo I ROSS. — The Blowpipe in Chemistry, Mineralogy and Geology: Containing all Known Methods of Anhydrous Analysis, many Work- ing Examples, and Instructions for Making Apparatus. By Lieut.- CoLONEL W. A. Ross, R. A., F. G. S. With 120 Illustrations. i2mo ^2.00 SHAW. — Civil Architecture : Being a Complete Theoretical and Practical System of Building, con- taining the Fundamental Principles of the Art. By Edward Shaw, Architect. To which is added a Treatise on Gothic Architecture, etc. By Thomas W. Sili.oway and George M. Harding, Architects. The whole illustrated by 102 quarto plates finely engraved on copper. Eleventh edition. 4to. ....... ^6.00 SKUNK. — A Practical Treatise on Railway Curves and Loca- tion, for Young Engineers. By W. F. Shunk, C. E. l2mo. JuU bound pocket-book form ;^2.oo SLATER.— The Manual of Colors and Dye Wares. By J. W. Slater. i2mo. ...... i^3.oo SLOAN. — American Houses : A variety of Original Desis^ns for Rural Buildings. Illustrated by 26 colored engravings, with descriptive references. By Samuel Sloan, Architect. 8vo. .75 SLOAN. — Homestead Architecture : C'jntainir.g Forty Designs for Villas, Cottages, and Farm-houses, with Eisays on Style, Construction, Landscape Gardening, Furniture, etc., etc. Illustrated by upwards of 200 engravings. By Samuel Sloan, Architect. 8vo. ... ..... IS2.50 SLOANE. — Ho.re Experiments m Science. By T. O'CoNOR SLC4.NE, E. M., A.M., F:-.. O. Illustrated by 91 engravings. i2mo. ....... |>l.oo SMEATON.— Builder's PocktSCompanion : V Containing the Elements of Building, Surveying, and Architecture; with Practical Rules and Instructions cor.''ected with the subject. » By A. C. Smeaton, Civil Engineer, etc. l2mo. SMITH. — A Manual of Political Economy. By E. Peshine Smith. A New Edition, to which is added a full Index. i2mo. $1-25 HENRY CAREY LaIRD & CO.'S CATALOGUE. 25 SMITH.— Parks and Pleasure- Grounds : Or Practical Notes on Country Residences, Villas, Public Parks, and Gardens. By Charles H. J. Smith, Landscape Gardener and Garden Architect, etc., etc. i2mo. .... ^2.oc» SMITH.— The Dyer's Instructor: Comprising Practical Instructions in the Art of Dyeing Silk, Cotton^^ Wool, and Worsted, and Woolen Goods ; containing nearly 8oo( Receipts. To which is added a Treatise on the Art of Padding; an(^ the Printing of Silk Warps, Skeins, and Handkerchiefs, and the! various Mordants and Colors for the different styles of such work* , By David Smith, Pattern Dyer. lamo. . . . ^1.50/ SMYTH. — A Rudimentary Treatise on Coal and Coal-Mining. By Warrington W. Smyth, M. A., F. R. G., President R. G. S.i of Cornwall. Fifth edition, revised and corrected. With numer- ous illustrations. i2mo. ...... $'^•7^ SNIVELY. — Tables for Systematic Qualitative Chemical AnaU ysis. By John H. Snively, Phr. D. 8vo. .... ^i.oo SNIVELY. — The Elements of Systematic Qualitative w-hemical Analysis : A Hand-book for Beginners. By John H. Snively, Phr. D. i6mo. ^2.00 STOKES. — The Cabinet-Maker and Upholsterer's Companion : Comprising the Art of Drawing, as applicable to Cabinet Work; Veneering, Inlaying, and Buhl- Work; the Art of Dyeing and Stain ing Wood, Ivory, Bone, Tortoise-Shell, etc. Directions for Lacker- ing, Japanning, and Vi.rnishing; to make French Polish, Glues, Cements, and Compos'. j ns; with numerous Receipts, useful to work men generally. Bv Stokes. Illustrated. A New Edition, with an Appendix upor .ench Polishing, Staining, Imitating, Varnishing, etc., etc. i2nio #1.25 STRENGTH AND OTHER PROPERTIES OF METALS; Reports of Experiments on the Strength and other Properties of Metals for Cannon. With a Description of the Machines for Testing Metals, and of the Classification of Cannon in service. By Officers of the Ordnance Department, U. S. Army. By authority of the Secre- tary of War. Illustrated by 25 large steel plates. Quarto . ^5-00 SULLIVAN. — Protection to Native Industry. By Sir Edward Sullivan, Baronet, author of " Ten Chapters 011 Social Reforms." 8vo , ;^i,OQ SHERRATT.— The Elements of Hand-Railing : Simplified and Explained in Concise Problems that are Easily Under- stood,. The whole illustrated with Thirty-eight Accurate and Origi- nal Plates, Founded on Geometrical Principles, and Showing how to Make Rail Without Centre Joints, Making Better Rail of the Same Material, with Half the Labor, and Showing How to Lay Out Stairs of all Kinds. By R, J. Sherratt. Folio. . . . ;^2.5o 2fi HENRY CAREY BAIRu & CO.'S CATALOGUE. SYME. — Outlines of an Industrial Science. By Daviu Syme. i2mo, . . ... $2.00 TABLES SHOWING THE WEIGHT OF ROUND, SQUARE, AND FLAT BAR IRON, STEEL, ETC., By Measurement. Clolh ...... 63 THALLNER.— Tool-Steel : ~ A Concise Handbook on Tool-Steel in General. Its Treatment in the Operations of Forging, Annealing, Hardening, Tempering, etc., and the Appliances Therefor. By OxTO Thallner, Manager in Chief of the Tool-Steel Works, Bismarckhiitte, Germany. From the German by VVilliam T. Brannt. Illustrated by 69 engravings. 194 pages. 8vo. 1902. ...... |2.oo TEMPLETON. — The Practical Examinator on Steam and th^ Steam -Engine : With Instructive References relative thereto, arranged for the Use of Engineers, Students, and others. By William Templeton, En- gineer. i2mo. ........ Ii.oo THAUSING.— The Theory and Practice of the Preparation of Malt and the Fabrication of Beer: With especial reference to the Vienna Process of Brewing. Elab- orated from personal experience by JuLlUS E. Thausing, Professor at the School for Brewers, and at the Agricultural Institute, Modling, near Vienna. Translated from the German by WiLLiAM T, Brannt, Thoroughly and elaborately edited, with much American matter, and according to the latest and most Scientific Practice, by A. ScHWARZ and Dr. A. H. Bauer. Illustrated by 140 Engravings. 8vo., 811; pages ^10.00 THOMPSON.— Political Economy. With Especial Reference to the Industrial History of Nations : By Robert E, Thompson, M. A., Professor of Social Science in the University of Pennsylvania. i2mo. .... ^1.50 THOMSON.— Freight Charges Calculator: By Andrew Thomson, Freight Agent. 24mo. . . ^1.25 TURNER'S (THE) COMPANION: Containing Instructions in Concentric, Elliptic, and Eccentric Turn. ing; also various Plates of Chucks, Tools, and Instruments; and Directions for using the Eccentric Cutter, Drill, Vertical Cutter, and Circular Rest; with Patterns and Instructions for woiking them, l2mo. . $1.00 TURNING : Specimens of Fancy Turning Executed on the Hand or Foot- Lathe : With Geometric, Oval, and Eccentric Chucks, and Elliptical Cutting Frame. By an Amateur. Illustrated by 30 exquisite Photographs. 4to J2.50 HEKRY CAREY BAIRB & CO.'S CATALOGUE. 27 ^AILE. — Galvanized- Iron Cornice-Worker's Manual: Containing Instructions in Laying out the Different Mitres, and Making Patterns for all kinds of Plain and Circular Work. Also, Tables of Weights, Areas and Circumferences of Circles, and other Matter calculated to Benefit the Trade. By Charles A. Vaile. Illustrated by twenty-one plates. 4to ^5.00 VILLE. — On Artificial Manures : Their Chemical Selection and Scientific Application to Agriculture. A series of Lectures given at the Experimental Farm at Vincennes, during 1867 and 1874-75. By M. Georges Ville. Translated and Edited by William Crookes, F. R. S. Illustrated by thirty-one engravinus. 8vo., 450 pages ...... $6,00 VILLE.— The School of Chemical Manures : Or, Elementary Principles in the Use of Fertilizing Agents. From the French of M. Geo. Ville, by A. A. Fesquet, Chemist and En- gineer. With Illustrations. i2mo. . , . . ^1.25 VOGDES. — The Architect's and Builder's Pocket- Companioa and Price-Book : Consisting of a Shoit but Comprehensive Epitome of Decimals, Duo- decimals, Geometry and Mensuration ; with Tables of United States Measures, Sizes, Weights, Strengths, etc., of Iron, Wood, Stone, Brick, Cement and Concretes, Quantities of Materials in given Sizes and Dimensions of Wood, Brick and Stone; and full and complete Bills of Prices for Carpenter's Work and Painting; also. Rules for Computing and Valuing Brick and Brick Work, Stone Work, Paint- ing, Plastering, with a Vocabulary of Technical Terms, etc. By Frank W. Vogdes, Architect, Indianapolis, Ind. Enlarged, revised, and corrected. In one volume, 368 pages, full-bound, pocket-book form, gilt edges ........ ^2.00 Cloth . . 1.50 VAN CLEVE.— The English and American Mechanic : Comprising a Collection of Over Three Thousand Receipts, Rules, and Tables, designed for the Use of every Mechanic and Manufac- turer. By B. Frank Van Cleve. Illustrated. 500 pp. i2mo. ^2.00 VAN DER BURG.— School of Painting for the Imitation of Woods and Marbles : A Complete, Practical Treatise on the Art and Craft of Graining and Marbling with the Tools and Appliances. 36 plates. Folio, 12x20 inches #10.00 WAHNSCHAFFE.— A Guide to the Scientific Examinatioo of Soils : Comprising Select Methods of Mechanical and Chemical Analyst and Physical Investigation. Translated from the German of Dr. F. Wahnschaffe. With additions by William T. Brannt. Illus- irated by 25 engravings. l2mo. 177 pages . . . #1.50 WALTON. — Coal-Mining Described and Illustrated: By Thomas H. Walton, Mining Engineer. Illustrated by 24 lax^ and elaborate Plates, after Actual Workings and Apparatus. ^5.00 2S liENRY CAREY BAIRD & CO.'S CATALOGUE. WARE.— The Sugar Beet. Including a History of the Beet Sugar Industry in Europe, Varietie of the Sugar Beet, Examination, Soils, Tillage, Seeds and Sowing, Yield and Cost of Cultivation, Harvesting, Transportation, Conserva tion, Feeding Qualities of the Beet and of the Pulp, etc. By Lewu S. Ware, C. E., M. E. Illustrated by ninety engravings. 8vo. ^4.00 WARN. — The Sheet-Metal Worker's Instructor: For Zinc, Sheet-Iron, Copper, and Tin-Plate Workers, etc. Contain- ing a selection of Geometrical ProMems ; also. Practical and Simple Rules for Describing the various Patterns required in the different branches of the above Trades. By Reuben H. Warn, Practical Tin-Plate Worker. To which is added an Appendix, containing Instructions for Boiler- Making, Mensuration of Surfaces and Solids, Rules for Calculating the Weights of different Figures of Iron and Steel, Tables of the Weights of Iron, Steel, etc. Illustrated by thirty- two Plates and thirty-seven Wood Engravings. 8vo. . ^3.00 WARNER. — New Theorems, Tables, and Diagrams, for the Computation of Earth-work : Designed for the use of Engineers in Preliminary and Final Estimates of Students in Engineering, and of Contractors and other non-profes. sional Computers. In two parts, with an Appendix. Part I. A Prac- tical Treatise; Part II. A Theoretical Treatise, and the Appendix. Containing Notes to the Rules and Examples of Part I.; Explana- tions of the Construction of Scales, Tables, and Diagrams, and a Treatise upon Equivalent Square Bases and Equivalent Level Heighta By John Warner, A. M., Mining and Mechanical Engineer. Illus- trated by 14 Plates. 8vo. |53.oo WILSON. — Carpentry and Joinery. By John Wilson, Lecturer on Building Construction, Carpentry and Joinery, etc., in the Manchester Technical School. Third Edition, with 65 full page plates, in flexible cover, oblong . . .80 WATSON. — A Manual of the Hand-Lathe : Comprising Concise Directions for Working Metals of all kinds, Ivory, Bone and Precious Woods; Dyeing, Coloring, and French Polishing; Inlaying by Veneers, and various methods practised to produce Elaborate work with Dispatch, and at Small Expense. By Egbert P. Watson, Author of " The Modern Practice of American Machinists and Engineers." Illustrated by 78 engravings. ^1.50 WATSON. — The Modern Practice of American Machinists and Engineers Including the Construction, Application, and Use of Drills, Latlie Tools, Cutters for Boring Cylinders, and Hollow-work generally , with the most Economical Speed for the same; the Results verified bj Actual Practice at the Lathe, the Vise, and on the Floor. Togethen HENRY CAREY BAIRD & CO.'S CATALOGUE. 29 with Workshop Management, Economy of Manufacture, the Steam Engine, Boilers, Gears, Belting, etc., etc. By Egbert P. Watson. Illustra'ed by eighty-six engravings. l2mo. . . . $2.50 WATT.— The Art of Soap Making : A Practical Hand-Book of the Manufacture of Hard and Soft Soaps, Toilet Soaps, etc. Fifth Edition, Revised, to which is added an Appendix on Modern Candle Making. By Alexander Watt. 111. i2mo ^3.00 WEATHERLY.— Treatise on the Art of Boiling Sugar, Crys- tallizing, Lozenge-making, Comfits, Gum Goods, And other processes tor Confectionery, etc., in which are explained, in an easy and familiar manner, the various Methods of Manufactur- ing every Description of Raw and Refined Sugar Goods, as sold by Confectioners and others. l2mo. ..... ^1.50 WILL,.— Tables of Qualitative Chemical Analysis : With an Introductory Chapter on the Course of rinalysis. By Pro- fessor Heinrich Will, of Giessen, Germany. Third American, from the eleventh German edition. Edited by Charles F. Himes, Ph. D., Professor of Natural Science, Dickinson College, Carlisle, Pa. 8vo. ^1.50 WILLIAMS.— On Heat and Steam : Embracing New Views of Vaporization, Condensation and Explo- sion. By Charles Wye Williams, A. I. C. E. Illustrated. 8vo. ^2.50 WILSON. — First Principles of Political Economy: With Reference to Statesmanship and the Progress of Civilization. By Professor W. D. Wilson, of the Cornell University. A new and revised edition. i2mo. ....... ^1.50 WILSON.— The Practical Tool-Maker and Designer: A Treatise upon the Designing of Tools and Fixtures for Machine Tools and Metal Working Machinery, Comprising Modern Examples of Machines with Fundamental Designs for Tools for tlie Actual Pro- duction of the work; Together with Special Reference to a Set of Tools for Machining the Various Parts of a Bicycle. Illustrated by 189 engravings. 1898. ....... ^$2.50 CONTENTS : Introductory. Chapter I. Modern Tool Room and Equipment. II. Files, Their Use and Abuse. III. Steel and Tempering. IV. Making Jigs. V. Milling Machine Fixtures. VI. Tools and Fixtures for Screw Machines. VII. Broaching. VIII. Punches and Dies for Cutting and Drop Press. IX. Tools for Hollow-Ware. X. Embossing : Metal, Coin, and Stamped Sheet-Metal Orna- ments. XI. Drop Forging. XII. Solid Drawn Shells or Ferrules; Cupping or Cutting, and Drawing ; Breaking Down Shells. XIII. Annealing, Pickling and Cleaning. XIV. Tools for IVaw Bench. XV. Cutting and Assembling Pieces by Means of Ratchet Dial Plates at One Operation. XVI. The Header. XVII. Tools for Fox Lathe. XVIII. Suggestions for a Set of Tools for Machining the Various Parts of a Bicycle. XIX. The Plater's Dynamo. XX. Conclusion — With a Few Random Ideas. Appendix. Index. WOODS. — Compound Locomotives: By Arthur Tannatt Woods. Second edition, revised and enlarged by David Leonard Barnes, A. M., C. E. 8vo. 330 pp. $s $1.00 32 HENRY CAREY BAIRD & CO.'S CATALOGUE. RICH ARDSON.— Practical Blacksmithing : A Collection of Articles Contributed at Different Times by Skilled Workmen to the columns of "The Blacksmith and Wheelwright," and Covering nearly the Whole Range of Blacksmithing, from the Simplest Job of Work to some of the Most Complex Forgings. Compiled and Edited by M. T. Richardson. Vol.1. 2IO Illustraiions. 224 pages. l2mo. , . ;^i.oo Vol. II. 230 Illustrations. 262 pages. lamo. . . |i.oo Vol. III. 390 Illustrations. 307 pages. i2mo. . . ^i.oo Vol. IV. 226 Illustrations. 276 pages. l2mo. . . jjSl.oo RICH ARDSON.— The Practical Horseshoer: Being a Collection of Articles on Horseshoeing in all its Branches' which have appeared from time to time in the columns of " '! he Blacksmith and Wheelwright," etc. Compiled and edited by M. T. Richardson. 174 illustrations ^i.oo ROPER. — Instructions and Suggestions for Engineers and Firemen : Ky Stephen Roper, Engineer. i8mo. Morocco . ^2.00 ROPER. — The Steam Boiler: Its Care and Management: By Stephen Roper, Engineer. i2mo., tuck, gilt edges. ^2.00 ROPER.— The Young Engineer's Own Book: Containing an Explanation of the Principle and Theories on which the Steam Engine as a Prime Mover is Based. By Stephen Roper, Engineer. 160 illustrations, 363 pages. i8mo., tuck . $2.50 ROSE. — Modern Steam-Engines: An Elementary Treatise upon the Steam-Engine, written in Plain language ; for Use in the Workshop as well as in the Drawing Office. Giving Full Explanation i of the Construction of Modern Steanv Engines : Including Diagrams showing their Actual operation. To- gether with Complete bat Simple Explanations of the operations of Various Kinds of Valves, Valve Motions, and Link Motions, etc., thereby Enabling the Ordinary Engineer to clearly Understand the Principles Involved in their Construction and Use, and to Plot out their Movements upon the Drawing Board. By Joshua .R.DSE. M. E. Illustrated by 422 engravings. Revised. 358 pp. . . ^6.00 ROSE. — Steam Boilers: A Practical Treatise on Boiler Construction and Examrnation, for the Use of Practical Boiler Makers, Boiler Users, and lAspectors; and embracing in plain figures all the calculations necessary in Designing or Classifying Steam Boilers. By Joshua Rose, M. E. Illustrated by 73 engravings. 250 pages. 8vo. .... ^2.50 SCHRIBER. — The Complete Carriage and Wagon Painter: A Concise Compendium of the Art of Painting Carriages, Wagons, and Sleighs, embracing Full Directions in all the Various Branches, including Lettering, Scrolhng, lujmanienting. Striping, Varnishing, and Coloring, with numerous Recipes for Mixing Color*. 73 Illus- tratjons. 177 pp. i2mo. . . . . . $i.nc