+ oe Nye oben vibee ‘ eesti “ As ee tele peta ae ik epee dees § Be Ne rdhhien eee im Pod yr) re eae ae rE Mee eats ie “ Sela sie ere” rere se Soha rec nat * | ag ea ; SN iSoy Calva ce a +5 *, pee f haee " mere) : : : ; : | , th aes Sie tical o2 9) shee ee : : . : : ; the ee ne ey’ 48h eT 43 @aates ee ey be erate eres AH See ¢ 610 wom tee ass SRO Sok re e*. mio eee . - OF) eeatestor cate ORS yy aay Me A Porn Oe ee ed ey nots es ee « i ai 3 i Ye 4 4A +34 ore eat eaels seed ¢ Sy Es Se Ce se wee Sr var re. a oe eels ety ae ee tele gee Males eer he tieaete Ko « * vy haw ee ¥i ata 4 * ee auth ba ae od on ee Gat tn ee hae 2 ee? A he FRANKLIN INSTITUTE LIBRARY PHILADELPHIA Class.G../.(.. Hoskin ees Accession. /7.97-QS | Led ) Mi a fy i : re. x e > ’ t ‘ 4 f. \ Nal * : aie = rt —_ TEXTILE CHEMISTRY TEXTILE CHEMISTRY AN INTRODUCTION TO THE CHEMISTRY OF THE COTTON INDUSTRY BY F. J. COOPER OF THE TECHNICAL COLLEGE, BLACKBURN J 0 ¢ ) 2 ) - oO 4 = ; - ; - : = = by : ? - 26 e i : , , ) >» o < ) @ 93003 @ 0 ) oa oD 3 3 ? WITH 240 DIAGRAMS ry = NEW YORK E. P. DUTTON AND COMPANY PUBLISHERS PREFACE DVANCED manuals on various branches of the textile indus- As are fairly numerous, but often the proper appreciation of them is considerably impaired by a lack of elementary chemical knowledge on the part of students and workers who are most interested in their contents. This book is intended to supply this deficiency. For several years the matter incorporated in this volume has been the basis of instruction introductory to the systematic study of the technical processes of Sizing, Bleaching, Dyeing and Finishing, and the Chemistry of Mill Stores and Materials. It has been put into permanent form only after considerable experiment and experience. The Syllabus of the Union of Lancashire and Cheshire Institutes in Textile Chemistry is admittedly framed on it and the ground covered includes the subjects of the Syllabus of the City and Guilds of London Institute in “‘ Chemistry as Applied to the Cotton Industry,” Subject -28E in the programme of the Department of Technology ; it is hoped, therefore, that the book will be particularly suitable for classes in Technical Schools conducted under the regulations of these bodies. But it should appeal also to the young studious cotton operative who desires to increase his technical knowledge, and to those in posi- tions of authority in mills who wish to know something of the nature, preparation, and properties of the materials used in the various pro- cesses through which cotton must pass in its journey from fibre to marketable cloth. The attempt has been made—it is hoped successfully—to produce a manual which shall serve not only as a textbook for a school course which includes lectures and practical work, but also as a complete laboratory manual for those who cannot obtain special practical instruction, and finally as a trustworthy guide for the private student. The user hardly needs to be reminded that it should be worked through in an experimental manner; every exercise should be per- formed by, or demonstrated to, the student, and no attempt should be made to “cram up” the information it contains. Several friends have been good enough to read and criticize the manuscript when ready for the press, of whom I wish to thank CT a vi TEXTILE CHEMISTRY publicly Mr. Harold Hunter, of the Battersea Polytechnic ; Mr. H. G. Leigh, of this College; and Mr. R. B. Duerden, of Nelson. Many pieces of apparatus described in this book are new and original and not included in the usual trade catalogues of makers of Scientific Apparatus, but arrangements have been made with Messrs. Batrp & Tatnock, LTD., 34, Gr. Ducitrn STREET, MANCHESTER, to supply the same, and all communications relating thereto should be addressed to them and not to the publishers or author. Small cotton hanks and dyes for experimental purposes may be obtained from Messrs. ‘‘ COMMERCIAL LABORATORIES,” Hart CHAMBERS, VICTORIA STREET, BLACKBURN. Finally, I desire to express my gratitude.to Dr. R. H. Pickard, F.R.8., for the opportunities he gave me, when he was Principal here, of developing this scheme of work in the day classes, and for the interest he took in it to make it successful. F. J. COOPER BLACKBURN, LANCGs, SECTION I II III IV VI Vil VIII CONTENTS PAGE CHEMICAL DIAGRAMS. CHEMICAL TooLs and how to use them. Balances; Bunsen Burner; Thermometers ; Hydrometers 1 Guass MANIPULATION ; Cork-boring; Fitting up Simple Pieces of Apparatus : , ‘ ‘ : 15 StmpLE Processes. Solution, Evaporation, Distillation, Crystallization, Filtration, Boiling, Melting. Deter- mination of Melting-points and Specific Gravities. Effects of Heat ; Ignition. Determination of Moisture and Ash : ; : CLASSIFICATION OF Matter. Identification of Common Substances. Physical and Chemical Changes WatTER. Chemical and Physical Properties; Tests for Purity ; Hard and Soft Waters ; Suitability for Trade and Domestic Purposes. Simple Water Analysis GaAsEs. General Characteristics ; Laws of Boyle, Charles. Diffusion. Identification of Gases. ArrR—Physical and Chemical Properties ; Chief Constituents ; aes ; Impurities ; Principles of Ventilation OxyYGEN; Oxidation and Reduction ; Oxides ; Lavoisier’s Theory of Combustion Acrps, ALKALIS, Basss, Satts. Indicators. Preparation and Properties of SunPpHURIC, Nitric, and HyprRo- CHLORIC Acids, and AMMONIA. ; : : 4 Vii 20 34 40 47 61 66 Vili TEXTILE CHEMISTRY SECTION IX Tue ELemMents or Coemicat THEeory. Atomic Theory ; Atomic and Molecular Weights; Laws of Chemical Combination; Equivalents and their Determination ; Valency. Symbols, Formule, Equations; Simple Chemical Arithmetic : : ; j : X Carson. Destructive Distillation of Wood and Coal; Carbon Dioxide ; Carbon Monoxide ; Water Gas ; Marsh Gas; Benzol; Hydrocarbons; Alcohols; Aldehyde ; Acetic Acid; Carbohydrates—Sugar, Starch, Cellulose XI CHLORINE, Preparation and Properties; Hypochlorites. Sulphur Dioxide ; Hydrogen Peroxide; Ozone . XII Aluminium, Zinc, Magnesium, and their chief Salts. Sul- phur and some of its Compounds. Analysis of a Simple Salt APPLICATION OF CHEMISTRY TO TEXTILES XIII Tue Natura Fisres. Use of the Microscope for Exam- ination of Fibres; Effect of Heat, Acids, and Alkalis on Cotton, Wool, and Silk Fibres ; Chemical Tests for Identification of Fibres; Determination of Moisture, Ash, Cellulose, etc., in Samples of Raw Me and Moisture and Ash in Wool and Silk XIV THE MaAcHIneERY. Examination of Coal for Moisture, Ash, and Calorific Value. Lewis Thompson and Roland Wild Calorimeters. The Testing of Flue Gases for Oxy- gen, Carbon Dioxide, and Carbon Monoxide. The Testing of Boiler-feed Water. Boiler Compositions. Classi- fication and Properties of Oils; Mineral Oils, Fatty Oils, Lubricating Oils. Determination of Viscosity, Flash-point, Bye weniger and bint 3s Matter XV Sizinc. EHlementary Study of the Chief Substances used in Sizing Cotton Yarn, e.g. Starches, Softeners, Soaps, Weighting Materials, Metallic Chlorides. Determina- tion of Ash, Moisture, Gluten, Fatty Acid, etc., in various Sizing Ingredients, and the Detection of Com- mon Impurities. Fermentation, Mildew, and Function of Antiseptics. Testing of Size ‘‘ Residues ” PAGE 80 101 125 139 158 168 183 CONTENTS SECTION XVI BriEacumne. Nature of Colour, Function of Detergents; Chief Bleaching Agents. Principles of, and Processes for Bleaching Cotton ‘ ; ‘ i XVII Dyertne. The Chief Methods adopted for Dyeing Yarn on an Experimental Scale with Substantive, Basic, Sulphur and Mineral Colours. Testing dyed Samples for Fast- ness to Light, Washing, etc. . ‘ , ¢ ; XVIII Mercerizina. Process of, and Detection of Mercerized Cotton : INDEX ix PAGE 205 214 227 229 tah TEXTILE CHEMISTRY SECTION I I. HOW TO DRAW DIAGRAMS q oe correct representation of chemical apparatus is a very important preliminary to the study of chemistry. Very few lessons are complete unless accompanied by sketches or diagrams of the articles used in the various preparations. In order to reduce to a minimum the time spent in drawing dia- THE UNIT Fig 1 grams, and to ensure that they shall be fairly uniform, some system should be adopted. The following method will be found to be as satisfactory as any, and more so than most. 2 1 2 TEXTILE CHEMISTRY All lines should be drawn first in pencil (where necessary with the aid of a ruler), and then the completed diagram inked in freehand throughout. Every diagram in this book has been produced in this manner. ; Circles should be drawn by tracing round a halfpenny (Fig. 1), and the diameter of this circle should be considered as a unit of length upon which is based the dimensions of the figures. The flask is drawn, as shown in Fig. 2, by making the circle, drawing a vertical diameter, and continuing it one unit. Parallel lines are drawn on each side of this, the width between being equal to } of the © unit length. Shoulders are put on where they meet the circle, the — CHEMICAL DIAGRAMS 3 bottom is formed by cutting a segment at the base, and the flange is formed by drawing short straight lines at right-angles. The method for drawing a retort is shown in Fig. 3. The triangular flask is evolved from an equilateral triangle of sides 14 units long (Fig. 4). Corks should be drawn with lines which are continuations of the neck of the flask, etc. (Fig. 5). Figs. 6 and 7 show (much enlarged) how holes should be represented in diagrams of corks. 4 TEXTILE CHEMISTRY Glass tubing and glass bends should be drawn as two parallel lines, the corners being rounded off, the outside one last, as shown in Figs. 8, 9, 10. Fig. 11 gives the construction lines necessary for drawing the tubes in a laboratory wash bottle. The beaker (Fig. 12), gas jar (Fig. 13), test tube (Fig. 14), and tripod (Fig. 15) are all very easily drawn. Rectangles form the skeletons for the aspirator (Fig. 16), bell jar (Fig. 17), and Woulf bottle (Fig. 18). CHEMICAL DIAGRAMS 5 Displace- - ment Collection Fig 19 Durette Parallel lines form the basis upon which are constructed the following: gas jar collecting a gas by displacement, pipette, burette, Liebig condenser, and retort stand (Figs. 19 to 23). Fig. 24 illustrates the correct way to represent the bunsen burner. The arrangement when heating a crucible supported by a pipeclay 6 TEXTILE CHEMISTRY triangle resting on a tripod is given in Fig. 25. The combination shown in Fig. 26 represents an evaporating dish placed on a sand bath being heated by a bunsen burner provided with a rose. Liebig Condenser Fig.26 Frade If a gas is being collected by displacement of water in a pneumatic trough, the diagram is drawn as shown in Fig. 27. A gas CHEMICAL DIAGRAMS 4 jar is standing on a beehive shelf. Liquid is always represented as a continuous straight line for the surface, with dotted lines under it. Other diagrams frequently required are:—Wuriz or distillation Distillation Flask flask (Fig. 28), acid or thisile funnel (Fig. 29), drying tower (Fig. 30), U tube (Fig. 31), retort stand and clamp supporting boiling-tubes, etc. (Fig. 32). The method of construction of a potash bulb is shown in three stages in Fig. 33 (1, 2, 3). 8 TEXTILE CHEMISTRY 7 a Se — wes - = a f a r ! a ‘ba oP in’ a es “a a ; DEN mond 7 ZANE We | ae ~ | ay Xx at “if AG y ft \ ep ponaitaes \\ bt pes pao — ra a5 a et II. CHEMICAL TOOLS Every trade has its tools. In chemistry we call them apparatus. Those described in the following pages are of very general use and necessary for the work which follows. 1. The Balance. This is the most important piece of apparatus a chemist possesses ; without it he can do nothing: in fact chemistry (3) ftash Bulb Fiadd was not a science till its workers used a balance. Good and accurate balances are now easily obtainable. form of. student’s balance is shown in Fig. 34. Adjust. Screw CHEMICAL TOOLS 9 A box of weights containing grams and fractions of a gram must always be provided for use with a balance. Figs. 35 and 38 show in section the usual shape of brass gram weights, which are arranged in a box as shown in plan in Fig. 36. Note that the 20’s and 2’s are duplicated. A groove is cut in front for the tweezers (Fig. 37) with which weights are always moved. Fractions of a gram are often kept in a separate box or a separate compartment. They are usually numbered in milligrams and range from 500 to 10. F1¢.37 SSS SSS SSS Fig. 36 They are made of platinum, German silver, or aluminium in the form of foil (Fig. 39) or wire bent into various shapes. Fig. 40 is a new and very good form in which the wire is so bent that the weight in milligrams is seen at a glance. If it is required to weigh more accurately than to 10 mg. a rider is used on the beam. This article (Fig. 41) is a stirrup of aluminium wire which weighs exactly 10 mg., and if placed in the pan of the balance acts as a weight of 10 mg. But if it be placed on the beam it only weighs that amount if placed at the end. If the beam be divided into 10 equal spaces between the knife- 10 TEXTILE CHEMISTRY edge and the pan, as in Fig. 42, and the rider is placed on one of these divisions, it will weigh less thanl0 mg. If on division 1, it will weigh I mg.; on division 2, 2 mg.; on division 3, 3 mg., etc. THE PRocESS OF WEIGHING WITH A BALANCE 1. Test the balance to see if it is accurate—that is so when the pointer swings an equal distance on each side of the zero mark. 2. Substances must always be placed on a watch glass or other receptacle—never on the bare pan. 3. Weights should be placed on the right-hand pan. Commence with the largest ; remove it if it is too heavy, allow it to remain if too light ; and add in descending order, missing none. ig 41 4. Do not put anything on or remove anything from the pans whilst the balance is swinging—always bring it to rest first. 5. When a correct balance is obtained count up, first the number of whole grams, then the number of milligrams, and write down with a decimal point between, e.g. 25 grams 830 mg. = 25-830 grams. If the mg. had amounted to 83 only, a cipher would have been entered in the hundred column, e.g. 25-083. EXERCISES 1. Find the weight of a crucible and lid. 2. Weigh a beaker or an evaporating dish. 3. Perform a “ difference weighing,” i.e. :— Weigh a tube containing some sand, empty some out, and reweigh the tube. Calculate how much sand was removed. CHEMICAL TOOLS Il 4. Check the accuracy of exercise 3 by first weighing a watch glass alone, adding the expelled sand, and weighing again. Borda devised a method for correctly weighing a substance on an incorrect balance. ‘The substance is put on one pan of the balance, and a counterpoise on the other. This counterpoise is made of a pill- box and shot and sand. - Shot is added to the empty pill-box one at a time until just too heavy ; the last shot is then taken out, and grains of sand added a few at a time, until the pointer of the balance is at zero on the scale. The substance is now removed from the pan and weights are put in its place until the counterpoise is properly balanced. ‘Then this weight is the same as that of the original substance. 2. The Joly Balance. This instrument con- sists of a delicate spring suspended from a sup- port. At the end of the spring hangs a pointer and a pan; and when required, a glass bob (Fig. 43). The pointer moves in front of a scale attached to which is a mirror so that its position can be correctly read. From Hooke’s law we know that the elongation of the spring is (within limits) proportional to the stretching force. Therefore if a substance is put on the pan, and the reading taken, the sub- stance removed from the pan, and weights added until the same reading is obtained, the weight of the substance is thereby obtained. When taking a reading, the pointer should exactly hide its own F; 4 image in the mirror. te ‘4 JORODOO OO VED EXERCISES 1. Find the elongation of the spring for a load of 1 gram. 2. Find the elongation produced by adding the glass float, and hence calculate its weight. 3. Weigh a watch glass with it and compare result with that obtained with an ordinary balance. 4. Find the apparent loss in weight when the glass float is weighed in water and—if possible—other liquids, e.g. alcohol, sulphuric acid, glycerine, ammonia solution, zinc chloride solution. 3. The Bunsen Burner. The heating apparatus for general use in the laboratory is the bunsen burner (Fig. 44), which is capable of giving two distinct flames, known as the luminous and non-luminous 12 TEXTILE CHEMISTRY according to whether the air-hole at the base is closed or open. For ordinary purposes the non-luminous flame is used. The figure shows the correct method of heating ; the hot blue zone of the flame should just reach the bottom of the substance to be heated. 4. Thermometers are used for registering temperature. A good thermometer is a necessity ; ordinary boxwood and paper-backed patterns are of no use for scientific work. They must be treated very carefully. The instruments are gradu- ated in degrees Fahrenheit or Centigrade, the latter being generally used by scientists. As a rule the degrees are numbered at each 10 Figd4 (Fig. 45), one figure being on each side of the graduation mark. The 5 line is longer than the others. The relationship between the degree Fah. and the degree Cent. is shown in Fig. 46, from which it can be seen that a degree Fah. is $ of a degree C. 5. Hydrometers are old-fashioned, inaccurate, and non-scientific pieces of apparatus; there are several modifications and empirical scales. They are however still frequently used in trade, although it is time they gave place to better apparatus. Their construction is based on the principle of buoyancy or flota- tion. Ifa solid, heavier at one end than the other, and lighter on the whole than a liquid, be placed in that liquid, it will tend to float in the liquid so that the heavier end is underneath (Fig. 47). CHEMICAL TOOLS 13 The heavier this end is made, the deeper the solid sinks in the liquid ; and the denser the liquid, the higher a given solid floats in it. A body of this kind, when made in a long thin form, is called a hydrometer (Fig. 48). In the top part is a paper scale of degrees, which are quite empirical. Scientific data for relative densities are always given as Specific Gravity—not in degrees. Rule to convert degrees 7'waddell to sp. gr. Multiply by 5, add 1,000, divide the number thus obtained by 1,000. E.g. convert 38° Tw. to sp. gr. Sp. gr. 1-19. To convert sp. grs., reverse the process, ie. multiply by 1,000, subtract 1,000, then divide by 5. E.g. convert a sp. gr. of 1-76 to ° Tw. 14 TEXTILE CHEMISTRY Beaume’s Hydrometer Scales. (a) Lighter than water. 144 Say ee Sp. gr. = Bo 134 and ° B. = anaes 134. .(b) Heavier than water. 144 ie 144 ° = B. = —_ —, Peoes 144— B. ane Ate Sp. gr. Note.—‘‘ Twaddell”’ hydrometers cannot be used for liquids lighter than water. Of the many distinct Beaume scales, the above are the two best known. SECTION II I. GLASS MANIPULATION (a) O cut glass tubing. Place the tube flat on the bench, make one cut with a triangular file ; take in both hands (Fig. 49), the nick in front, and give a “ pull bend.” (6) To bend glass tubing. Heat in the yellow portion of a bat’s- wing or fish-tail flame (Fig. 50), holding the tube with both hands, gently rotating it all the time. The elbows should rest on the bench and the hand be held as shown in Fig. 51, which is a side view. When the glass is quite soft it should be removed from the flame and bent into the required shape, and held fast until it sets. Fig. 52 shows the appearance of good glass bends. Fig. 53 shows faulty ones, due to overheating, careless bending, using wrong flame, etc. 15 16 TEXTILE CHEMISTRY As an exercise make bends of the shape and dimensions given in Fig. 54 A to F. (c) To smooth glass ends. Use the non-luminous flame ; hold as shown in Fig. 55, rotating all the time, till the glass just melts. (d) To make a jet. Heat tube in a bunsen flame, remove, draw out in both directions. Cut off as shown by the dotted lines (Fig. 56), and smooth both ends. (e) To make a closed tube or bulb tube. (. First make a jet, then close the end by \ holding it in the bunsen flame (Fig. 55). Vs Gently blow down the open end, holding the tube vertical (Fig. 57). If the tube is to be closed only, and no bulb blown on it, \ ( the thickness should be uniform, neither sharp \ or ‘‘ blobbed ” (Fig. 58). ee Fig 561 Fig 57 Note.——Always allow hot glass to cool on an asbestos mat, and smooth all cut ends. II. CORK-BORING Select a cork slightly too large for tube, flask, etc., and roll it with gentle pressure under the foot to make it soft. Select a cork-borer — slightly smaller than the tubing being used. Hold the cork in the left hand, cork-borer in the right (Fig. 59), and bore with a screw motion, without excessive pushing. Get nearly through and then place the cork against a hard surface to finish, in GLASS MANIPULATION 17 order to obtain a clean cut. Withdraw the borer by screwing in the reverse direction. Fig. 60 shows plan and section of corks bored with one and two holes respectively. The test for a well-bored cork is the appearance of the boring—removed by pushing out with a smaller borer. This should be a perfect cylinder. ~~ =a = Tig 58 Fig 59 Practice on waste corks until proficiency is attained. To insert glass tubing in a cork, first wet the tube and then screw it in with both hands close together. If pushed or forced in, the glass will break and a serious cut may result. 18 TEXTILE CHEMISTRY II. FITTING UP APPARATUS The following diagrams represent apparatus commonly used in laboratory practice, and the student is advised to set up each one in order to acquire manipulative dexterity. Fig 64 Minsik L GLASS MANIPULATION 19 Fig. 61 is of the laboratory wash bottle which contains distilled water. Fig. 62 is a simple melting-point apparatus that will be used later. Fig. 63 represents a test tube provided with a gas leading tube, clamped on a retort stand. The evolved gas is often collected over water. Fig. 64 shows how this is done in a pneumatic trough with a beehive shelf and gas jars. Fig. 65 is a diagram of a simple condensing arrangement for preparation of a small quantity of distilled water. SECTION III SIMPLE PROCESSES I. SOLUTION ATER is a solvent, i.e. a liquid which is capable of dis- solving substances. When a substance dissolves in a \ \ liquid, it disappears to sight as a separate substance— it may however impart a colour. The substance itself is said to be soluble in the solvent and the liquid thereby produced is called a solution. Water is not a universal solvent, but it will dissolve more sub- stances than any other known liquid. A few substances which are insoluble, i.e. not soluble in water, are silver chloride, barium sulphate, most fats and oils. Sulphonated oils, such as Turkey red oil, are soluble in water. Liquids which are soluble in other liquids are said to be miscible. Alcohol and glycerine are miscible with water; oils are not miscible with water as a general rule. Gases vary considerably with respect to their solubilities in water. The most soluble gases are ammonia, hydrochloric acid, sul- phur dioxide, sulphuretted hydrogen. The least soluble are hydrogen, oxygen, nitrogen, air, and carbon monoxide. The extreme solubility of ammonia in water can be illustrated by means of the apparatus shown in Figs. 66 and 67. As a rule the solubility of a solid substance is increased by heat- ing the liquid (an exception is lime). Gases are expelled from solution by boiling the liquid—some completely, some only partially, as with hydrochloric acid. Next to water the most important solvents are :— (2) Alcohol and Methylated Spirit, which dissolves shellac, iodine, fats, resins, camphor, etc. Solutions in alcohol are called tinctures. (6) Carbon disulphide, which dissolves sulphur, phosphorus, fats, and oils. (c) Ether—dissolves fats, iodine, india-rubber. (d) Chloroform—dissolves fats, gums, resins, iodine. 20 SIMPLE PROCESSES 21 (e) Benzene—dissolves fats, rubber, and many organic substances. The dissolved solid can be recovered from solution by evaporating off the solvent, and the solvent can also be obtained if the product of evaporation be condensed—the process being known as distillation. The liquid which distils overis known as the distillate. Distillation may be used to prepare a com- pound—as nitric acid (q¢.v., page 72 et seq.), or to separate two mixed liquids, such as alcohol and water. The piece of apparatus in which the vapour is cooled is called a condenser. Fig. 22, page 6 , shows a Liebig condenser, and . Fig. 68 the worm form. An arrangement i Dink for preparing large quantities of distilled +3 water is shown in Fig. 69. . 2 Solution sometimes raises the température ( & .. Water produced Hydrogen used = -033 — -029 = -004 gm. Ratio = 1: 7-25. Chief uses for water— 1. Domestic purposes—washing, cleansing, food, drink. 2. To generate steam for motive and other purposes. 3. For motive purposes—water mills, turbines, etc. 4. Irrigation, navigation, solution, etc. 5. Water vapour forms an “earth blanket.” SECTION VI I. GASES GAS has neither definite shape nor size; it possesses the property of expansibility. Some gases are light, some heavy, some coloured, some invisible, some elements, some com-_ pounds, some mixtures, some soluble in water, some nearly insoluble, but certain properties they have in common. Relative Soly. in Name of Gas. Density. Talay, Smell, Colour, etc. Element ; No smell Mixture Smell due to im- purities Compound No smell Pungent Nitrogen . Carbon monoxide No smell Air ‘ Nitric oxide : Oxygen . ; Hydrogen sulphide , Hydrochloric acid Carbon dioxide . Nitrous oxide . Sulphur dioxide . Chlorine , Bromine . Brown fumes in air No smell Fotid smell White fumes in air Faint acid smell Laughing gas Suffocating Green colour Brown colour HE OO OOOROROBA To find the weight of a given volume of gas, exhaust a globe and counterpoise it (Fig. 91). Fill with gas and reweigh. Jind its volume by measurement of diameter and calculation. Volume of ie y Bata ae aot 3 7 To find the solubility of a gas, fit up the apparatus as shown in Fig. 92 (or Figs. 66, 67, pages 18,19). The graduated tube is filled with the gas over mercury and the solvent is put in the cup. When the tap is cautiously opened, a few drops will fall into the tube and float on the mercury. The tap is closed, and the liquid 47 48 TEXTILE CHEMISTRY allowed to exert its solvent action on the gas. As it does so the mercury rises in the tube. Some general methods for prepara- tion of gases— 1. Boil liquids. Water, ether, alcohol, carbon disulphide. 2. Heat solids. Wood, coal, iodine, chlorate of potash. 3. Treat solids with acids. Copper and nitric acid—brownish red gas. Copper and sulphuric acid—sul- phur dioxide. Zinc and hydrochloric acid — hydrogen. Marble and hydrochloric acid— carbon dioxide. Salt and sulphuric acid—hydro- chloric acid. Manganese dioxide and hydro- chloric acid—chlorine. Fig 9 Pr ee eee a a GASES 49 4. Treating a liquid with a solid. Water and sodium or potassium give hydrogen (Fig. 98). 5. From a mixture of two gases remove one. Burn phosphorus in air —nitrogen is left (Fig. 107, page 54). 6. Electrolysis of liquids. Water to hydrogen and oxygen (Fig. 88, page 45). Some general methods for collecting and storing gases. 1. In gas jars or tubes over a liquid, usually water, in a pneumatic trough (Fig. 94). 2. By displacement of air (Fig. 95). For gases heavier than air, see Fig. 95 (a). 29 ” lighter 29 oe) 9 95 (0). 3. Passing into an aspirator (Fig. 96). By this arrangement the volume collected or used can be measured exactly. A) Fie 95 bb) Fig 96 GENERAL PROPERTIES OF GASES All gases expand when heated and contract when cooled, and the rates at which they do so are the same in all cases—approximately 1/273 of the volume at O0°C. for each degree Centigrade. This general property is summarized and expressed mathematically in the form called Charles’ Law. A simple piece of apparatus for its experimental verification is shown in Fig. 97. The flask A is full of gas (say air). It is kept immersed in the beaker B by a lump of lead C. The mouth of the flask is closed by a cork, through which passes a delivery tube D. When the water is heated the gas expands, the excess being driven out through the tube. The temperature is taken before heating the gas, and the heating continued until the water boils. The expansion is measured by allowing the flask to cool with the end of the tube under water, when the water rushes back to fill the place of the expelled gas. The volume of A is measured, and then the 4 50 TEXTILE CHEMISTRY increase calculated for 1 c.c. for 1 degree Centigrade rise in temperature. Accurate determinations of the coefficient of increase of volume of a gas at constant pressure can be made by using the form of apparatus illustrated in Fig. 98, which was designed by the author and used in his physics laboratory at the Mundella School, Nottingham, some twenty-five years ago. cgi ipa, ei op Selle a atiens Rane Pe SR 5 ee ee a te ye et ee eT em a The “ Constant-pressure Air Thermometer’ shown in this diagram was first published a the author (and awarded first prize) in con- nexion with a competition organized by Messrs. Newnes in their publication Technics in 1904. It is republished with their permission. Method of Using. The gas is enclosed in one limb of a U tube by means of mercury, which can be kept at constant level by withdrawing from the tube joined to the bottom of it, or by filling in at the top of the longer limb. The portion of the tube containing the gas is graduated so that volumes may be read, and these graduations are continued on the other limb to enable a constant level to be obtained accurately. GASES 51 The bath is filled with cold water, the pressure adjusted, and the volume and temperature read. Steam is then passed in and the tem perature gradually raised. At intervals of (say) 10°C. the pressure is again equalized and the volumes determined. The expansion per unit volume for unit rise in temperature may then be calculated. Boyle’s Law. The volume occupied by a gas is also dependent upon the pressure on the gas ; this is illustrated in a pop-gun or air-gun. Boyle investigated the problem of “the spring of air” long ago and found that for a given mass of gas at a constant temperature the volume was inversely proportional to the pressure, i.e. a Pressure of Gas Fia.101 Fig.102 If the pressure was doubled the volume was halved. oe) ”? ”? trebled 9 5 made one-third. 2 i », quadrupled __,, +>, One-fourth, etc. His apparatus is illustrated in Fig. 99. Pressure gauges may be constructed on this principle. Ifthe tube is open at the end, it is called a manometer (Fig. 100), and it can be used to measure the pressure of a gas, say the domestic gas supply, in inches of water. Diffusion. The particles of which gases are composed are always in motion. They are thus able to :— 1. Mix with each other irrespective of relative densities, e.g. if a jar of hydrogen be inverted over a jar of oxygen, at the end of a few minutes each jar will be found to contain an explosive mixture of oxygen and hydrogen (Fig. 101). 52 TEXTILE CHEMISTRY 2. Pass through a solid partition which contains pores, such as unglazed porcelain (Fig. 102). This phenomenon is known as dif- fusion. Graham, who investigated the problem, found that the rate of diffusion was inversely proportional to the square root of the densities of the gases, e.g. density of hydrogen = 1, density of oxygen = 16. Square roots of these numbers = 1 and 4. Then rates of diffusion are 1:4. IDENTIFICATION OF GASES Many gases, if they are pure, can be recognized easily by certain simple tests, thus :— (a) Action on a glowing splint. CO). ates 5, 2 lighted taper. (c) “1 ,, wet litmus paper—red and blue. CMe ,, lead acetate paper. (e) 4, 4, potassium chromate paper. (f) A ,, Starch paper. Gye ve, ,, Starch iodide paper. (ie) nee. ,, a drop of ammonia on a glass rod. Gases recognized— 1. From their appearance—chlorine (green), hydrochloric acid (white fumes), nitrogen peroxide and bromine (brown), iodine (violet). 2. By their odour—chlorine (irritating), ammonia (pungent), sul- phuretted hydrogen (fcetid), sulphur dioxide (suffocating). 3. By glowing splint test—oxygen and nitrous oxide (re-ignite). 4. By combustibility—hydrogen, sulphuretted hydrogen, carbon monoxide. PRACTICAL EXERCISES Try to identify the gas evolved in each of the following experi- | ments :— . Heat a mixture of potassium chlorate and manganese dioxide. . Warm some ammonium chloride with caustic soda. . Act on sodium sulphite with dilute hydrochloric acid. . Heat lead peroxide with strong hydrochloric acid. . Warm some aluminium with caustic soda solution. . Heat oxalic acid crystals with strong sulphuric acid. II. THE ATMOSPHERE. Oo rF WH Air is the most important of man’s necessities. We can live several — days without food, several hours without water, but not more than ~ two or three minutes without air. Its physical and chemical proper- ties have been subjects of investigations for generations, and the following conclusions have been established :— ne See Raed , bes = aia ly a ee ee eg ee Sp RT ee ae, Sen ee ee AIR 53 (a) It is necessary to life and combustion. All other gases are useless, poisonous, or asphyxiating so far as animals are concerned. To get a fire up, we must allow air to have access to the coal. To put it out, we cover it up to prevent air getting to it. (6) Fresh air is also necessary, or (c) Its power of supporting combustion is limited. To illustrate this, burn a candle under a bell jar (Fig. 103). Other facts illustrating the same truth are the Black Hole of Calcutta episode, the necessity for ventilation of inhabited buildings, open-air treatment of consumption. F1G.105 FIG. LO4 (d) Boyle noticed that when metals were exposed to, or heated in contact with, air, they were altered in appearance and gained in weight, forming what he called a calx. Examine the calces of lead, copper, iron, zinc, mercury. (ec) In these processes a portion of the air is used up. This can be demonstrated by putting a muslin bag of iron filings in a jar of air and inverting over water for several days (Fig. 104), or using phosphorus in a longer tube (Fig. 105). Lavoisier’s original apparatus is shown in Fig. 106. He treated mercury for several days in his retort, and found that the air gradually decreased in volume until there was no further contraction, and that specks of red appeared on his mercury. When these specks were strongly heated, they yielded a gas which gave the same volume as that lost by the air, but this gas was much more active 54 TEXTILE CHEMISTRY than original air, and was identical with a gas, named oxygen by him, obtained by other methods. (f) The portion left does not act like original air, and was called dephlogisticated air, or azote, now named nitrogen. Therefore (g) The atmosphere is considered to consist of two gases at least. To determine the proportion in which these two gases exist. (The original method of Lavoisier is unsuitable for general use.) The sim- plest way is to burn some phosphorus in a bell jar of air standing in some water. The phosphorus can be ignited by warming the end of Fig. 107 a metal rod and quickly inserting the stopper which carries it. The volumes of original and residual air should be marked with strips of gummed paper (Fig. 107). | Accurate method. Use the apparatus shown in Fig. 108, which consists of a bottle containing a known volume of air, fitted with a rubber stopper through which pass the delivery end of a stoppered burette and a manometer tube. Put into the burette a little strong solution of ‘‘ Pyro ” in water, and fill up with caustic soda solution. Read level of liquid in the burette. Allow a little pyro-soda to pass into the bottle and shake carefully. Some of the oxygen is absorbed, and, the pressure of air in AIR 55 the bottle being thereby decreased, one arm of the mercury falls, and the other rises in the manometer. Allow more solution to flow into the bottle until the surfaces of the mercury columns become perma- nently level. Read the burette, and so find the volume of liquid passed into the bottle—this is equal to the volume of oxygen in the original volume of air. Calculate the percentage. The volume of nitrogen is found by difference. In round numbers the result should be 21 per cent. of oxygen, 79 per cent. nitrogen by volume. Other constituents. Careful and exact experiments have shown that, besides oxygen and nitrogen, there are present in air (a) water vapour; (b) carbon dioxide; (c) argon; (d) traces of nitric acid, ammonia, ozone, etc.; (e) solid matter; (f) living organisms known as bacteria or germs. The presence of water vapour is proved by rain, clouds, etc., and by the exposure of hygroscopic substances to air, e.g. strong sulphuric acid increases in weight and gets weaker. Solid caustic soda or potash becomes wet. Dried cobalt chloride (on filter paper) becomes pink in a damp atmosphere. At 0° C. 1 cu. metre of air can hold about 5 grams of water vapour. ood Ua ag Ae - ae eh i Shi Paes ~ ni mapo US) ,, ts Bey si, peels (14) 4 a mee Cabs; ie wer 2 rm Wiisoere wa he ” 30°C. 1 ” ” 29 9 9 30-0 ce) 9 ” Therefore its point of saturation depends upon the temperature. Air near its point of saturation is said to be humid, and it has a very enervating effect on the human system, particularly at the higher temperatures. A certain degree of humidity is necessary in a weaving shed. For certain classes of goods the ordinary atmospheric condition of Lanca- shire is sufficient to ensure it, but for others it is necessary to supply an artificial humidity. ‘To guard against this being carried to excess, the manufacturer who steams is compelled to determine and record three times per day data from which the percentage humidity of his shed can be calculated. To determine relative humidity. The only accurate way for finding humidity, is to pass a known volume of air through a desiccating agent which can be weighed before and after the experiment. This necessi- tates accurate apparatus, and requires considerable time, during which the proportion of moisture present can have changed considerably. Therefore it is not usual to use this method, but one due to Mason known as the wet and dry bulb hygrometer, in conjunction with Glaisher’s Tables, which have been compiled from results obtained by an accurate method. 56 TEXTILE CHEMISTRY Two thermometers are needed, the bulb of one being covered with muslin, which is kept wet by immersion in a small vessel of water. If the air be not saturated with moisture, evaporation takes place from ‘this muslin, with the result that the temperature of this thermometer is lowered. The drier the atmosphere, the more the evaporation and consequently the lower the reading will be (Fig. D et 109). | To find percentage humidity. Take the reading of each thermometer simul- OR taneously. WR Say dry bulb reading is 22°C. uslin 4. Wet 29 ” 9 18°C. Find the difference 22 —18 = 4° C. Water Use the table as follows :— Fic. L109 Go to the line for the dry bulb reading, i.e. 22, 7 and in this line find two factors :— (a) That given in the 0 column = 19-7. CO) Sitse - , difference 4 column = 12-9. 12:9 x 100 Then percentage humidity = a x 100 or 19-7 HUMIDITY TABLE Reading of Factors ” when Difference between wet and dry Bulb is Dry Bulb in deg. C. 0 1 2 —_———— | | LN DIDHAN Or OL 9 9 Db Ot 69 G9 ND BO Rt bo bo WDD NNNDDN HH BB Be Bee eee FAO WO BDAWN SD OIAAPE WWM MOOS OOK NOANONOPRRP PK ONO WD O1O LO RD bo DOD DDD BS ee ee eS Re eS eee een eee Se DMNOOORAWODMATNWWDOKWRAWONAOS DD DD DD DOD Ee Nase Noa Di ge PR atch am ictal ont fle cl onda whi ghar ea OWWAWOTNRPWNK KE NWOANON DOD BS 0D DD DD ee ee ee eS Fi 0S SOS ae EN eS BOS Te See OK AWWOMAHAANUITNIAWOKWHAOCWoONs* BSD ee BS Fo 00 30 We G9 BS BS Re e908 ote Se OU CES NOK WARPNOCHOCOKWANTORNTNAHS BD i ; DS DAT D OB 69 WD SO HD ATH DN Tri HO AEH oOOPWWWROATNOHE PDH DOTS ell moni sorlll cool woe aeeelll eel eal oad Tah ener tha Ri ide i ed : CON OWATWUDGSOWNWDNAOKP OKO te eel cael cell aoe asl ee lc wich oC ab air eliaidicts : ate AWO HHS HDPE RON TOW WWOWO MN = 65-5 per cent. a ie oe yp ie ee at Pai ae AIR 57 Home Office Regulations provide that no artificial humidification will be allowed in any weaving shed where steaming is carried on when the wet bulb reading of the hygrometer exceeds 75 deg. Fah. (i.e. 24°C.). Previously steam was allowed to be infused until the wet bulb thermometer registered as high as 91° F. or 33°C. The readings have to be entered three times a day jointly by representatives of the firm and the operatives. The presence of carbon dioxide is proved by aspirating a good volume of air through baryta water or lime water (Fig. 110), which is turned milky by the gas. It is derived from the combustion of carbon and carbon compounds, and respiration of animals. The assimilation of it by plants keeps the gas from accumulating in excess of -04 per cent. by volume. It may however be locally in excess, e.g. in crowded rooms, smoky towns, mines, etc. Carbon dioxide in air can be estimated approximately by the Angus Smith test, and accurately by the Pettenkofer method. The other constituents require more accurate and refined methods for their identification. Estimation of carbon dioxide in air by Angus Smith method: Take bottles of various capacities ranging from 100 c.c. to 580 c.c. and fill them with samples of the air to be tested. To each add 14 c.c. of a clear saturated solution of lime water and shake. Note the smallest bottle in which a milkiness is produced. Refer to the graph (Fig. 111) and find the percentage of carbon dioxide which is given for its capa- city, e.g. if 185 c.c. then percentage = -1; 300 c.c. = -06 per cent. ; 445 c.c. = -04 per cent. At its best, Smith’s test is but a rough-and-ready method. The Pettenkofer Method in one or other of its numerous modi- fications is always used if we require a quantitative result. Its manipulation is delicate and requires much practice before accuracy is attained, particularly in normal air determinations. As an exercise for the beginner, good and interesting results can be obtained with it for expired air working ag follows :— TEXTILE CHEMISTRY 58 In the small flask put made by shaking baryta with 5) -saturated baryta water Arrange apparatus as shown in Fig. 112. 20 c.c. of semi +39 U1 at 0g, peters 00% eh Ea pooe ; “29007 "22 QOL “UZYOUS PUD PIPpo 21D adPOM uly] P2FAINJDOS IDI]D JO IZ] VY ‘APMsay 2143 so u2y02 $> prorrposd St SOUP YW 1 YNYA In THY JO MNOg as2ppouss Mp, 30 Anroodwo 24 7 Sy ae er es Tee | AIR 59 distilled water, and when saturated decanting, and diluting with an equal volume of water. Blow air from the lungs slowly through this solution and measure the water expelled from the aspirator, which will be approximately equal to the volume of expired breath. A suitable amount to pass through is 1,000 c.c. When finished, disconnect the flask. In a similar flask put another 20 c.c. of the original baryta water, and to each add 2 or 3 drops of an indicator called phenolphthalein. A pink colour is produced. Now from a burette run in a standard solution of oxalic acid containing 5-65 grams of the pure acid dissolved in one litre of water. Find the volume required just to destroy the pink colour in each case. It will be found that less is required by the baryta through which expired air has passed. The difference can be utilized to measure the amount of carbon dioxide which has passed through. Suppose the difference = 37 c.c. Now | c.c. of oxalic acid of above strength = 1 ¢.c. carbon dioxide. Then 37 c.c. Pe 29 ” 9 = 37 ¢.c. 9 9 which is present in (say) 1,000 c.c. of expired air, i.e. = 3-7 per cent. The amount of carbon dioxide in air can be taken as an index to the efficiency of the ventilation of a building. A high percentage of the gas means a vitiated and unhealthy atmosphere. A Parliamentary Committee Report issued in 1909 said, “ The greatest evil in a mill is the lack of efficient ventilation,” and this remark could well be extended to English buildings generally, including dwelling-houses, and particularly bedrooms. Principles of ventilation are well understood by scientific experts, but the application of them seems to make very little headway, due to general ignorance or carelessness and stupidity on the part of the British public. ~ One of the purest atmospheres in a public building in the United Kingdom is that of the British House of Commons. This is due partly to the fact that (as a rule) the number of people in it is small, but chiefly because it is ventilated on a system. The “ draught ” is supplied by a shaft running up one of the famous towers, and the air drawn in is washed, warmed, filtered, and then allowed to enter under the benches. It rises towards the ceiling and is extracted at such a rate that no strong current is produced. Air which contains dust is distinctly dangerous to health. Pro- fessor Tyndall once made the famous remark, “‘ Shut your mouth, and save your life,” meaning thereby that you should breathe through the | nose, the hairs in which arrest many of the solid particles. Every solid particle is a small world on which may rest hundreds 60 TEXTILE CHEMISTRY of spores, microbes, or germs capable of producing pulmonary and gastric troubles and, it may be, disease and death. A simple piece of apparatus which can be used to trap and estimate the bacteria in air is shown in Fig. 113. A is a small tube containing sterile water through which air may be drawn by attaching to B, which in its turn is connected to C by means of a flexible rubber tube. Tic 113 By suction at the tube D the water can be started running from B to C, which thus causes a similar volume of air to bubble through A. By interchanging the flasks when C is empty, and repeating the process, more air is bubbled through the water in A, and if the volume of water used is known the exact volume of air passed through can be calculated. | An aliquot part of the water in A is plated on sterilized gelatine or agar and cultivated, when each bacteria will produce a “ colony ” if incubated at a suitable temperature. SECTION VII I. OXYGEN XYGEN is the most abundant element in the world—half the () crust of the earth, eight-ninths of water, and one-fifth of air is composed of it. It was originally obtained from calx of mercury, first as an “unidentified spirit ’’ by Eck de Sulzbach in 1489, and later by Priest- ley in 1774. Scheele had prepared the gas in 1773, but had not pub- lished the fact. The gas can be prepared in a great many ways, the most important of which are :— 1. By heating oxides which evolve the gas, e.g. mercuric oxide, manganese dioxide, silver oxide, barium peroxide, red lead, lead peroxide, etc. 2. By heating potassium chlorate, particularly if mixed with man- ganese dioxide (Fig. 114). This is the usual laboratory method of obtaining the gas. 61 62 TEXTILE CHEMISTRY 3. By heating certain substances with sulphuric acid, such as potassium dichromate, potassium permanganate, manganese dioxide. 4. From bleaching powder by warming it with water to which has been added a little cobalt nitrate (to produce cobalt oxide, which acts as the decomposing agent). 5. By evaporation of liquid air. Nitrogen boils at a higher tem- perature than oxygen, so, if liquid air be distilled under certain condi- tions, oxygen is first evolved. ‘This is how oxygen is now prepared commercially: 6. By the interaction of solutions of potassium permanganate and hydrogen peroxide in the presence of sulphuric acid (Fig. 115). Inside the small bottle is a smaller one. Hydrogen peroxide is put in one, acidified potassium permanganate in the other, and the bottle is then connected with the Hempel burette. On tilting the apparatus, the liquids mix, oxygen is evolved and collects in the limb of the burette. a | Fig.116 Fig. 117 Oxygen is a very active gas; glowing splints, carbon, phosphorus, sulphur, and even iron wire burn in it with great energy, in most cases to form oxides. The operation is conducted with a deflagrating spoon as shown in Fig. 116. T'o determine the volume of oxygen evolved by heating a substance which yields it, use the apparatus shown in Fig. 117. Weigh the empty tube, put the substance in and reweigh. Attach it to the aspirator as shown and collect the water expelled from the delivery tube. Measure it and calculate the volume obtained from 1 gram of the substance. As an exercise, use potassium chlorate. T'o find the weight of oxygen expelled when a substance is heated, or to find the weight which combines with a substance when heated in air, use a crucible, etc. (Fig. 44, page 12). ee ee me a ae ee OXYGEN 63 EXERCISES 1. Find the weight of oxygen expelled from 100 grams of potassium chlorate when strongly heated. 2. Take a piece of magnesium ribbon about 2 feet long, clean it with sand-paper, weigh it and divide into two equal parts. Burn one piece in air by heating on a crucible lid over a bunsen flame. Carefully collect all the calx and weigh. Compare with the weight of magnesium used. Dissolve the other piece in two or three drops of dilute nitric acid on a crucible lid. Heat to dryness and until all brown fumes are driven off. Again collect the white powder, weigh and compare with the weight of calx from the previous experiment. ‘Taste to see if it is magnesia (Magnesium oxide). II. OXIDATION AND OXIDES The act of chemical union with oxygen is known as oxidation. If the substance which is oxidized is an element, the compound produced is called an oxide. An older name is calx. Nearly every element combines with oxygen under one condition or another, directly or indirectly, to form an oxide, and some produce 2, 3,4, oreven 5. More than 100 different oxides have been prepared. Iron oxidizes in moist air to form iron oxide ; it is termed rusting. Lead and copper both tarnish in air, especially if heated, due to oxidation. | N.B.—Tarnishing does not always denote oxidation, e.g. the tarnish on silver is due to the formation of a sulphide, not an oxide. Phosphorus, sodium, potassium need only to be exposed to air for a few seconds to bring about oxidation. Aluminium, zinc, magnesium, tin, mercury do not easily oxidize to a notable degree in ordinary air at ordinary temperatures. Other oxides may be produced by calcination or roasting, i.e. heating in air or oxygen. Mercuric oxide, magnesium oxide, tin oxide, zinc oxide, the oxides of carbon and sulphur may all be prepared in this way. Another method which may be employed is to use substances which will readily yield oxygen, such as nitric acid, bleaching powder, potas- sium chlorate, hydrogen peroxide, etc., and which are therefore called oxidizing agents, e.g. :— 1. Add strong nitric acid to tin, white tin oxide is formed. 2. Take some cobalt nitrate solution in a test tube. Add two or three drops of sodium hypochlorite (note the formation of black oxide of cobalt). Add it to an emulsion of bleaching powder and water and gently warm. ‘Test the gas evolved. What is it ? 3. Heat, with constant stirring, a small piece of lead in a crucible 64 TEXTILE CHEMISTRY lid. Note the changes that occur. ‘Try to get some litharge. Did you? If so, state what it was like. 4. Oxidize some red lead by warming it with dilute nitric acid. Describe the product. How many oxides of lead have you seen? — Compare and contrast them. 5. Take a few drops of mercuric chloride. (Be careful: this is a — deadly poison.) Add caustic soda solution. What happens ? Filter off the precipitate. Carefully dry it and then heat it strongly in a small ignition tube. Can you identify the gas evolved ? Ifso, state what it is. III. COMBUSTION is often an act of oxidation. Lavoisier was the first chemist to explain it — assuch. The old theory was that when a substance burned it lost some- — thing, known as phlogiston, and it was then — unable to burn again until it had been treated — with a substance rich jin phlogiston, such as — carbon, which supplied it with some. | Lavoisier’s theory of combustion was, that — when a substance burned it gained something, — that something being oxygen, obtained either — from the air or a substance capable of yielding — it. , This explains why substances burn in ordi- nary air or oxygen, and why they refuse to burn in the inactive four-fifths of air which contains no oxygen. fic. 118 Apparently when a candle burns it loses weight, but if an apparatus be arranged for it to burn in, so that all the products of combustion are trapped and also weighed, it is found that there is a gain and not a loss (Fig. 118). Sulphur and carbon burn in gunpowder at the expense of oxygen in nitre, which is one of the constituents of gunpowder. As a rule, chemical combination with oxygen results in the produc- — tion of a large amount of heat, sometimes sufficient to make the body : red, or even white hot, and sometimes flame is produced. | This is very liable to occur in heaps of oily cotton waste. The oil is oxidized by the oxygen of the air and gradually the temperature is — raised until it is sufficient to produce and ignite a vapour from the oil ; and so we get the starting of a fire, which still is far too common in ' Lancashire mills. Pg Re te eae ea La ene te oe a ae eee eee he Sinema ie IV. BREATHING is also an act closely connected with oxidation, being a process for supplying oxygen to the blood and removing carbon dioxide from it. OXYGEN 65 The warmth and sustenance for the human body is produced by the slow oxidation in the tissues of the carbon and hydrogen taken as food. This results in the formation of a large amount of carbon dioxide and water—the former being carried by the blood to the lungs, where it is liberated into the air chambers and then expelled through the mouth in the act of breathing. For this purpose the average volume of air needed by an adult is 1,500 gallons per day. V. OXIDES of the different elements differ in various ways, e.g. state, effect pro- duced by heat, solubility in liquids. Solids. Lime (calcium oxide), baryta (barium oxide), zinc oxide, oxides of iron, magnesium, copper, tin, mercury, lead. Liquids. Water (oxide of hydrogen), nitrogen peroxide. Gases. Carbon monoxide, carbon dioxide, sulphur dioxide, nitrous oxide, nitric oxide, ozone (oxide of oxygen). When heated, some evolve oxygen, e.g. mercuric oxide, red lead, silver oxide, chromium trioxide, and all peroxides. Some do not yield oxygen, e.g. lime, baryta, alumina, sand, zinc oxide, water (except at very high temperatures). They vary very much in respect to solubility in water and other common solvents :— Very soluble in water. Phosphorus pentoxide, hydrogen peroxide, sulphur trioxide, sodium oxide, potassium oxide. _ Moderately soluble in water. Carbon dioxide, sulphur dioxide, baryta. Slightly soluble in water. Lime, iron oxide. Nearly insoluble in water. Lead oxide, sand. Soluble in dilute nitric acid. Bismuth, copper, zinc oxides, barium peroxide, litharge. Insoluble in dilute nitric acid. ‘Tin oxide, antimony trioxide, lead peroxide, sand. Oxides are usually classified as :-— 1. Acidic Oxides. Those which combine with the elements of water to form acids—e.g. oxides of sulphur, carbon dioxide, oxides of nitrogen (usually non-metals). 2. Basic Oxides. Those which combine with the elements of water to form bases (metallic oxides)—e.g. sodium and potassium oxides, lime, baryta. _ 3. Peroxides—which yield oxygen on Petre and which do not react with water to form acids or bases, e.g. manganese dioxide, lead peroxide, barium peroxide, hydrogen peroxide. 5 SECTION VIII I. ACIDS, ALKALIS, BASES, SALTS HESE are important classes of compounds which are very closely related one to the other. Some hundreds of acids are known, nearly a score of — alkalis, about 100 bases, and thousands of salts. Each class exhibits cer- tain distinctive characteristics by means of which it may be identified. — Acids possess a sour taste; change the colour of certain natural colours; react with alkalis and bases to produce salts; always contain the element hydrogen and conduct electricity in solution. It was stated by Lavoisier that oxygen was the real acidifying ~ principle, but this has been disproved. ’ Alkalis have a caustic taste and a soapy feel; they also change certain colours, react with acids to form salts, and as a rule are very soluble in water. Bases are compounds which neutralize acids to form salts and contain a metallic element. : Salts are compounds in which the hydrogen of the acid has been replaced, partly or entirely, by a metal. They are usually (a) of a solid and crystalline nature, (b) neutral to litmus, (c) when in solution decomposed by the passage of an electric current. Salts may be normal, in which all the replaceable hydrogen has been replaced by a metal; acid or hydrogen, in which some has not been replaced ; basic, which contain a greater quantity of the metallic radicle than is sufficient to replace completely the hydrogen; and double, which contain more than one metal. 1 Copper sulphate, zinc chloride, magnesium chlorides common salt, Glauber salt, Epsom salt, sodium carbonate, are examples of normal salts; sodium bicarbonate, nitre cake are acid salts; copper car- bonate, white lead are basic; and alum is a double salt. q Examine samples of the following :— : (a) Acids. Acetic, boric, citric, hydrochloric, nitric, oleic, oxalic, palmitic, salicylic, stearic, sulphuric, tannic, tartaric. | (b) Alkalis. Caustic soda, caustic potash, quicklime, ammonia, washing soda, baryta. ; 66 ACIDS, ALKALIS, BASES, SALTS 67 (c) Bases. Metallic oxides such as black copper oxide, litharge, zinc oxide, mercuric oxide. 'To study the action of acids and alkalis on coloured bodies, use solutions of the following indicators :— (a) Litmus in water. (6) Methyl orange in water. (c) Phenolphthalein in 50 per cent. alcohol. (dq) Lacmoid in 50 per cent. alcohol. (e) Congo red on paper. (f) Cochineal in 25 per cent. alcohol. Note that acids may turn blue litmus to red ; lacmoid to red; methyl orange to pink ; cochineal yellowish red ; Congo red to blue. Further, certain of these indicators are not affected by certain acids, e.g. the fatty acids—oleic, stearic, and palmitic—do not change methyl orange. Note that alkalis turn litmus and lacmoid to blue; methyl orange to yellow ; phenolphthalein to pink ; cochineal to violet. Note that bases (other than alkalis), as a rule, have no action on indicators. Preparation of Salts. When acids and alkalis or bases react, a chemical change results, a salt being formed. This is termed neu- tralization, e.g.:— — 1. Take some dilute hydrochloric acid in a dish and add a drop or two of litmus. Now add caustic soda, drop by drop, till the litmus is just turned purple. Evaporate down to dryness. The residue is common salt. 2. In a similar way neutralize caustic potash with nitric acid and obtain solid nitre. Salts may be obtained also by the following methods :— 3. Dissolve copper oxide in hot dilute sulphuric acid, evaporate to a small bulk, and cool to crystallize out the copper sulphate. 4, Dissolve zinc in dilute hydrochloric acid, and concentrate to obtain zinc chloride. Note that so long as there is any free acid in this solution, Congo red is turned blue, but when entirely neutralized no effect is produced on the indicator. Salts of hydrochloric acid are called chlorides. » nitric a » nitrates. ,, sulphuric sie ,, sulphates. » acetic “A » acetates. » citric # » citrates. » carbonic oe ,, carbonates. », tartaric “f ,, tartrates. » oxalic a ,, , oxalates. 68 - TEXTILE CHEMISTRY Salts of palmitic acid are called palmitates. » Oleic a 5 oleates. », Phosphoric __,, - phosphates. Many salts are without action upon indicators, but some do affect — them, e.g. :— 4 Copper sulphate turns blue litmus red, so does zine chloride, while — sodium carbonate turns red litmus blue. : Fats may be looked upon as salts (esters they are called) of certain — organic acids, of which an enormous number are known. Here the © base is glycerine, not a metallic oxide, although metallic oxides will — combine with the fatty acids. Palm oil is largely a glyceride of palmitic acid. Mutton fat contains a large quantity of glycerine stearate. Lard contains a considerable amount of glycerine oleate; while — Beef fat is a mixture of the glycerides of stearic, oleic, and palmitic — acids (chiefly the former). Lead plaster is made by boiling olive oil with litharge, and is really i lead oleate. Compounds of metallic oxides and fatty acids are sometimes termed metallic soaps, and their production is often a cause of serious ~ trouble during sizing operations if incompatible ingredients have been — used in the mixing. 3 Esters are all hydrolyzed on boiling with caustic alkalis, ie. the — glycerine is regenerated and the alkali salt of the fatty acid formed. This new salt is called a soap, the process often being termed on that account saponification. Soft soaps are usually potash soaps, and hard soaps are generally — soda soaps, but not always so, as the nature of the fat or oil used has a — considerable influence on the physical properties of the soap formed. II. SULPHURIC ACID It is almost impossible to overrate the great commercial and indus- trial importance of this well-known acid. South-west Lancashire and North-east Wales are full of factories for its manufacture, and the normal annual production of the acid in Great Britain alone is two million tons out of four million tons consumed yearly. ; It was prepared originally from ferrous sulphate (green vitriol) by 4 the action of heat, which expelled sulphur trioxide and water vapour, that united in the receiver to form the acid and which, being of an oily nature, was named oil of vitriol. d In the seventeenth century it was prepared by heating sulphur and nitre, which can be illustrated by using the apparatus shown in Fig. — 119. The mixture of sulphur and nitre is gently heated until the ACIDS, ALKALIS, BASES, SALTS 69 sulphur burns in the nitre. Sulphur trioxide distils over and is col- lected in the water contained in the bend, thus forming a dilute solution of sulphuric acid. The first sulphuric acid works was established in Richmond in 1740. After that time the industry rapidly extended and the method of manufacture was greatly improved. Gay Lussac devised a means of trapping the most valuable by-product and Glover invented a method for using it over again. The cost of manufacture was thus greatly reduced, and the use of the acid became much more general. Further reduction in the cost of production was effected (but at the expense of purity) by using pyrites instead of sulphur to yield the sulphur dioxide. The principle of the English method of manufacture is illustrated in Fig. 120. Sulphur is heated in a hard glass tube through which air is passing. This forms sulphur dioxide, which is carried forward with excess of air through a flask containing nitric acid, which when warmed liberates nitric oxide. The mixture of sulphur dioxide, air and nitric oxide now passes to the large boiling-tube, where it meets with steam, with the result that sulphuric acid is produced and falls to the bottom of the tube. The nitric oxide acts as the agent which brings about the change, and is not itself used up. If the gases from the tube are passed through 70 TEXTILE CHEMISTRY a flask containing strong sulphuric acid, the nitric oxide will be absorbed and not lost to the process. It can be used over again by putting the liquid into the flask which contains the nitric acid. These flasks correspond to the Glover and Gay Lussac towers in the manufacturing plant, details of which can be obtained from the larger chemistry textbooks. The current through the apparatus is maintained by running water from the aspirator. The Contact Process for the manufacture of sulphuric acid: The purest and strongest acid is now made by a catalytic contact process, on the perfecting of which enormous sums of money and much labour and research have been expended. The laboratory method of working is simple to carry out and easy to understand (Fig. 121), but on the manufacturing scale it is much more difficult to accomplish successfully. A catalyst is a substance which acts as an accelerator of a chemical change. The precise action is not definitely known. Ostwald com- pares it to a “chemical oil.” Manganese dioxide and cobalt oxide both act as catalysts in the preparation of oxygen from potassium chlorate and bleaching powder respectively. Bigaics The contact process has been worked principally on the Continent for the production of an acid which was necessary to the dye industry, — and which could not be produced by the English chamber process. — There is no doubt but that it will ultimately displace the older method, — particularly as during the last few years other catalytic agents besides — platinum have been used successfully. 4 For the experimental illustration oxygen gas from an aspirator a O and sulphur dioxide from a siphon §S are forced through strong sul- phuric acid in a bottle D, to dry them. They are then passed over — gently heated platinized asbestos in a hard glass tube P. Here they © combine to form sulphur trioxide, which is led into water W, thereby — forming sulphuric acid. ; 4 ACIDS, ALKALIS, BASES, SALTS 71 Sulphuric acid comes into the market in various strengths, usually packed in carboys (Fig. 79, page 30). Chamber acid has a strength of 62 per cent. to 70 per cent. and is used for making salt cake and fertilizers. Its sp. gr. is about 1-6. An acid of 78 per cent. to 80 per cent. is used for many technical purposes, including the manufacture of superphosphate. Its sp. gr. is about 1-72. This is collected at the foot of the Glover tower. Double oil of vitriol (D.O.V.) has asp. gr. up to 1-84 and a strength between 93°5 per cent. and 98-3 per cent. The impure acid is often termed brown oil of vitriol (B.O.V.), due to its colour (sp. gr. 1-72). “Commercial ” acid will always contain impurities such as iron, arsenic, lead, and copper. It should never be used in the preparation of food-stuffs or drugs. By the contact process a pure acid is produced of 100 per cent. strength, and besides this, sulphur trioxide is dissolved in it to give fuming sulphuric acid containing sometimes as much as 45 per cent. excess of the trioxide. This is used chiefly for the production of intermediate products for the manufacture of dye-stuffs. Strong sulphuric acid, when mixed with water, produces an enor- mous amount of heat; on this account the acid should always be added to water, and not water to acid. Its great affinity for water can be shown in various ways, e.g. Expose a weighed dish of it to air and weigh again after several hours; it will have increased considerably, and have become weaker. Add some to a little starch or sugar; it is dehydrated, leaving a black mass of carbon. The test for the identification of sulphuric acid is to add a few drops of nitric acid and then a solution of barium nitrate. If a white pre- cipitate is produced, the acid or one of its salts is present. The use of barium chloride is not suitable in the presence of lead, which sulphuric acid is always liable to contain. Uses.——Among the enormous number of uses to which sulphuric acid is put, some of the most important are: Manufacture of chemi- cals such as sodium carbonate, hydrochloric acid, nitric acid, alum, phosphorus ; of explosives of all kinds ; of fertilizers, such as sulphate of ammonia; of superphosphate ; of artificial silk; in the dyeing, bleaching, and electroplating industries. Ill. NITRIC ACID or aqua fortis (which means strong water) was known to the alchemists and was largely used for dissolving metals, nearly all of them being soluble in it. It is a compound containing 1-6 per cent. hydrogen, 22-2 per cent. nitrogen, and 76-2 per cent. oxygen. Like sulphuric acid it has an enormous industrial application. 72 TEXTILE CHEMISTRY PREPARATION | 1. From nitre or saltpetre and sulphuric acid. Nitre is potassium nitrate. When it is heated with strong sulphuric acid it is decomposed, nitric acid being liberated as a gas. If this gas is cooled it condenses to liquid nitric acid. On a small or laboratory scale the operation is usually performed as shown in Fig. 122, which should require no further explanation. 2. From Chile saltpetre and sulphuric acid. Nitre is too expensive and too rare to use on the commercial scale. Therefore the cheaper x (fe cake sodium nitrate is used in its place, and instead of glass vessels, iron retorts and porcelain bottles are employed. Fig. 123 shows in section the usual English plant. A more modern — retort, which is in use in America, is shown in Fig. 124. At the end — of the condensing bottles a tower filled with coke is sometimes placed, down which trickles water. This absorbs the last trace of nitric acid, which would otherwise escape into the air. ; The chemicals used are Chile nitre which has been purified until it — ACIDS, ALKALIS, BASES, SALTS 73 contains 98 per cent. to 99 per cent. of sodium nitrate and is free from sodium chloride, and sulphuric acid of sp. gr. 1-7. These will give a nitric acid up to a sp. gr. of 1-38. For stronger acid, a stronger sample of sulphuric acid must be used. The reaction between moderately hot sulphuric acid and sodium nitrate results in the production of nitric acid and sodium hydrogen sulphate. If the temperature be increased further, more nitric acid would be liberated with the production of sodium sulphate (salt cake or Glauber salt), but the manufacturer finds that the high temperature at which the operation must be conducted results in the decomposition of a large quantity of the nitric acid thereby produced. Consequently it is usual to stop at the first reaction, and the chemical which is drawn from the retort is sodium hydrogen sulphate —technically known as nitre cake. Nitre cake can be used instead of sulphuric acid in certain industrial applications, e.g. bleaching, the manufacture of baking powder, etc. (See Partington, “ Industrial Chem.,”’ pages 161, 162 ; or “J.8.C.L.,” 35, 857, 1916; or “Chem. Tr. Journ.,’”’ 1916, 28, 109, 393, for full lists.) 3. From the air. The beds of natural nitrates in India, Chile, Egypt, etc., are being exhausted rapidly, and nearly twenty-five years ago Sir William Crookes suggested the inexhaustible air as a source of supply. When a mixture of oxygen and nitrogen is “ sparked ”’ electrically under certain conditions it produces oxides of nitrogen which, dissolved in water, form nitric acid (Cavendish’s discovery). Crookes showed that air can be burned to nitric and nitrous acids in a powerful electric are. There are now several successful schemes for applying these facts to the commercial production of nitric acid and calcium nitrate. It is carried out in Norway (Norwegian saltpetre) by the Birkeland and EKyde method, in which a large flame, produced by a current of high voltage, is spread over copper-surface electrodes by the action of an electromagnet, the current alternating fifty times per second. The nitric oxide produced is rapidly cooled and then combined with oxygen to form nitrogen peroxide, which is afterwards absorbed by water to form nitric acid, or by lime to form nitrate of lime. During the Great War, Germany rapidly developed this and other methods until she was no longer dependent upon the natural nitre beds for the production of nitric acid, but obtained it all from the air. Commercial nitric acid can be purified by redistillation with sul- phuric acid in glass vessels, and the brown colour, which is due to nitric _ oxide dissolved in the liquid, removed by warming the acid to 70° C. and passing a current of carbon dioxide through it (Fig. 125). 74 TEXTILE CHEMISTRY Chemically pure acid is made by either :— 1. Using perfectly pure materials, or 2. Treating commercial acid with barium nitrate (to precipitate sulphuric acid) and silver nitrate (to precipitate chlorine and hydro- chloric acid), and then redistilling with pure sulphuric acid at a low temperature. PROPERTIES A colourless liquid of sp. gr. varying from 1-29 (46 per cent.) to 1-41 (67-5 per cent., ordinary conc.) and 1-53 (100 per cent.). The sp. gr. is best determined with an hydrometer (see page 29), or by using a Joly balance (see pages 29, 30). Boiling-point, 86° C. oe Warm x Sikes a. Fig.126 F1G.125 Es Very active oxidizing agent—many interesting experiments can be — performed to illustrate this property :— j 1. Put some warm dry sawdust on a porcelain tray in a fume ~ chamber, add some strong nitric acid and stir. Dense fumes of nitric oxide are evolved and the mass will in all probability burst into flame. 2. Place a small crucible on sand in the bottom of a wide beaker, — and in the crucible put a few c.c. of a mixture of equal parts of strong — nitric and strong sulphuric acids. By means of a long tube drawn out to a jet, allow drops of turpen- tine to fall into the crucible. The turpentine is immediately oxidized and bursts into flame. 3. Put 2 grams of sugar in a large test tube, add 5 c.c. of strong nitric acid and warm. The sugar is oxidized to oxalic acid, which can — be obtained by crystallization. | Conduct this eet in a fume chamber or out of doors on | ACIDS, ALKALIS, BASES, SALTS 75 account of the dense fumes of the deadly oxides of nitrogen that are evolved. 4. Drop a few c.c. of the strong acid on a lump of metallic tin. Itis converted into white tin oxide. 5. Take a small wide-mouth flask, put in it some nitre and conc. sulphuric acid, and gently heat it on a sand bath (Fig. 126). As soon as the flask is full of nitric acid vapour, drop in 1 c.c. of carbon disul- phide, and immediately apply a light to the mouth of the flask. The carbon disulphide burns with a bright blue flame. It is an intensely strong acid, e.g. add a drop of acid on the end of a glass rod to a litre of water, the solution will turn blue litmus red ; Congo red, blue; and methyl orange, pink. It has a very pronounced and often corrosive action on organic matter, e.g. :— 1. A feather is made yellow and destroyed if dipped in it. 2. It turns flour yellow. This can be used as a test to distinguish between pure starch and wheat or other flour. The experiment should be made in a white basin or dish. 3. It stains the fingers yellow and produces a similar effect on other bodies, e.g. indigo, proteids, silk. In the case of silk, we can produce a permanent orange colour on it if it be soaked first in dilute nitric acid and then in ammonia solution. This is sometimes called the Xanthoproteic Reaction. The test for the identification of nitric acid is its action on a cold strong solution of ferrous sulphate, which is turned black by it. The black substance is decomposed on heating. A nitrate will give the same reaction if it is first treated with strong sulphuric acid. USES OF NITRIC ACID 1. In the preparation of gun-cotton. Make a mixture of equal volumes of strong nitric and strong sulphuric acids. Immerse in it for fifteen minutes small tufts of cotton wool. Remove with a glass rod and wash free from acid. Dry in air. It is very inflammable ; burn a small piece on a filter paper, and if it has been properly prepared it will burn away without igniting the paper. 2. In the manufacture of nitro-glycerine and dynamite, blasting gelatine, cordite, smokeless powders, etc. 3. For the production of T.N.T. (which is made by nitrating toluene), and of nitro-benzene, sometimes called oil of mirbane, used as a deodorizer in certain textile preparations and as artificial almond flavouring. 4. For the preparation of picric acid, which is made from phenol (carbolic acid) and nitric acid. 76 TEXTILE CHEMISTRY 5. In the manufacture of Chardonnet artificial silk, celluloid, etc. 6. For the preparation, of nitrates, such as silver nitrate (used in photography, pharmacy, for mirrors, marking ink, etc.) ; ammonium nitrate (used in the newer explosives) ; strontium nitrate (red fire) ; barium nitrate (green fire). 7. As a pickling or cleansing liquor for copper. 8. In the manufacture of dextrine from starch, and of dyes from coal-tar products. TIG. 127 IV. HYDROCHLORIC ACID, also known as muriatic acid and spirits of salt, is made foe common ~ salt by heating with moderately strong sulphuric acid. Fit up the apparatus shown in Fig. 127. In the flask put some rock salt and a little water. Add strong sulphuric acid through the ~ thistle funnel. Hydrochloric acid gas will be evolved, at first without — heat, and may be collected in the gas jar. Fill several jars ; then attach a filter funnel to the end of the tube, and collect some of the gas in water placed in an evaporating dish. It — ACIDS, ALKALIS, BASES, SALTS 17 will be necessary to heat the mixture in the flask towards the end of the experiment. With the gas perform the following experiments :— 1. Test its combustibility, and also if it will support combustion. 2. Note that it fumes in air, and much more so when in contact with a drop of strong ammonia solution held on the end of a glass rod. 3. Test its action on litmus paper and Congo red paper. 4. Test its solubility in water by inverting a jar in a pneumatic trough half full of water. Also test with litmus paper, and with a solution of silver nitrate, the water through which the gas has been passed. A white precipitate will be produced with silver nitrate if hydrochloric acid is present. Hydrochloric acid comes into commerce as a solution in water usually of about 32 per cent. strength (sp. gr. about 1-16), which can be diluted as required. SS Cee On the industrial scale the flask is replaced by an iron pot and the heating is done in two stages in a double furnace. Fig. 128 is a sketch of the plant used. Salt and sulphuric acid are heated first in the pot A, and the gas evolved passes by means of the pipe B to the towers C, which are filled with coke, and down which a stream of water trickles. The solution of hydrochloric acid is drawn off at the bottom. In the second stage the damper D is opened, the contents of A raked into the furnace E, which is heated from a coke fire at F. The gas again passes into the pipe B by means of G, and so to the collecting towers. The residue in E is called salt cake, and is chiefly sodium sulphate. Hydrochloric acid is used in the manufacture of chlorine, and for making chlorides, and in calico-printing, bleaching, dyeing, etc. EXERCISES Prepare (a) zinc chloride by dissolving zinc in hydrochloric acid ; 78 TEXTILE CHEMISTRY (6) magnesium chloride by dissolving magnesia in the acid ; (c) calcium chloride by dissolving chalk in it. Test the solubility of the following metals and oxides in dilute and in strong acid: Copper and copper oxide, iron and iron rust, lead and ~ litharge, mercury and mercuric oxide. V. AMMONIA Sal-ammoniac (meaning a salt of ammonia) was first prepared by the Arabs centuries ago, by heating camel refuse in or near the temple of Jupiter Ammon, in the Libyan Desert, and so received its name from that building. The gas itself is called ammonia or volatile alkali, and can be obtained easily from sal-ammoniac by heating it with lime or caustic __ soda (Fig. 129). It was formerly obtained by heating horn, and so received the name “spirits of hartshorn.” ~ Gauze Collar At the present day an important source of our ammonia supply is — gas liquor. When coal is distilled at gasworks, a large quantity of — ammonia is evolved, which is collected by solution in water. This solu- — tion is known as ammoniacal, or simply gas, liquor. The liquid is mixed — with quicklime and gently heated, the ammonia which is evolved being — led by means of pipes into acid—either sulphuric to make sulphate of — ammonia, or hydrochloric, to make sal-ammoniac or ammonium chloride. — An enormous amount of ammonia is now prepared synthetically — from hydrogen and nitrogen. From this source it is entirely free from — coal-tar products. a Ammonia is usually supplied in commerce as a strong solution in — water. From this the dry gas may be obtained by using the apparatus shown in | Figs. 130 and 131. Z PROPERTIES . e- Very pungent odour, colourless, caustic taste, turns red litmus blue, fumes in contact with hydrochloric acid gas, due to formation of solid — ammonium chloride. q ACIDS, ALKALIS, BASES, SALTS 79 Of all gases it is the most soluble in water—the solution is called ammonium hydrate. At ordinary temperatures 1 volume of water will dissolve between 700 and 800 volumes of ammonia. The solution is attended by considerable increase in volume, and decrease in density, so that strong ammonia has a sp. gr. of 0-88. Fig. 66, page 18, shows the apparatus usually used to illustrate the great solubility of am- monia in water. It is a very light gas, being only slightly more than half as heavy as air. It is fairly easily condensed to a liquid which has a considerable industrial application as a refrigerating agent for the production of blocks of ice. Ammonia does not burn in air, but if it is first mixed with oxygen it will do so, producing a greenish yellow flame. Fig. 132 illustrates a form of apparatus which can be used. Ammonia is used for neutralizing acids in dye-stufis; by dyers when milder alkali than soda is needed or when volatility is desired ; in the manufacture of Turkey red oil; as a fixing agent for certain metallic mordants. Ammonium chloride is used for aniline blacks, and ammonium carbonate (sal volatile), which may be prepared by heating ammonium sulphate with chalk and collecting the sublimate, is used as a substitute for dunging in dyeing Turkey reds. Ammonium acetate, made by mixing equivalent quantities of ammonia and acetic acid, is used with alizarines, and as a stripping agent for dyed wool and silk. Ammonium oxalate is sometimes used in wool-dyeing. SECTION IX THE ELEMENTS OF CHEMICAL THEORY I. THE ATOMIC THEORY HAT the ultimate constitution of matter is, will probably — : N | never be thoroughly known; but that does not prevent — speculation upon the point. Ideas of this kind are called — theories, and the one accepted at the present day is that proposed by Dalton, who adapted it in 1808 from an ancient Greek idea. . The main principle of it is that matter is not infinitely divisible— _ that ultimately a point is reached beyond which it is impossible to — divide up the substance by any physical or chemical operations. We then reach a small particle called the atom. | There is very little direct proof of the truth of this theory, and it might at any time have to be abandoned, should newly discovered © facts oppose it, but at the present time it is accepted for many reasons that will appear as the study of chemistry is continued. | By this theory atoms are assumed to be :— 1. Elementary in their nature. Therefore there can be only the same number of sorts as there are elements. 2. Endowed with a mutual attractive force called chemical affinity or attraction, by virtue of which, when brought into intimate contact, — they combine with one another. This chemical affinity varies with the — kind of atom. a 3. Absolutely indestructible. 4. (If of the same kind) Of equal mass and alike in all respects. Note.—Nothing is said about the shape of an atom, nor the size. Dalton originally used certain symbols to denote them, such as © for oxygen, © for nitrogen, © for hydrogen, @ for carbon, @ for sulphur, — @ for phosphorus, etc., and hence the idea arose that they were thought — to be spherical. . ; From assumption 2 (above), it is apparent that we shall often have — aggregations or groups of atoms. These are known as Molecules. Molecules may be made up of atoms all of the same kind, in which case — 80 THE ELEMENTS OF CHEMICAL THEORY 81 we have elements, or different kinds of atoms may unite, forming compounds. A molecule may be defined as the smallest mass of any element or compound which can be supposed to exist alone and have all the properties of that element or compound. As a rule, molecules of elements consist of two or more atoms ; the exceptions are zinc, potassium, sodium, cadmium, mercury (one atom each) ; arsenic, phosphorus (four atoms); ozone (three atoms). Molecules of compounds do not contain a very large number of atoms—seldom more than ten. The exceptions are the compounds of carbon, which sometimes contain hundreds, e.g. starch is thought to have 4,200 atoms per molecule. The atomic theory’s best bulwark is the support given it by the laws of chemical combination, which are completely explained by it ; in fact, it was from a careful study of two of them that Dalton was led to formulate it. II. ATOMIC AND MOLECULAR WEIGHTS We shall here consider what is meant by atomic and molecular weights. The methods by which they may be determined are too difficult for beginners to follow. As an atom is so small, it is of course utterly impossible to weigh one directly ; therefore the mass is given relatively, and originally the number which denoted the atomic weight of an element expressed the number of times it was as heavy as one atom of hydrogen. It was found that one atom of oxygen was nearly sixteen times as heavy as one atom of hydrogen. Now in practice it is much easier to experimentally determine atomic weights with reference to oxygen rather than hydrogen. And if ;; of the atomic weight of oxygen be considered as unity, the atomic weight of hydrogen becomes 1-008 instead of 1. This system of calculation is the one adopted in the International Table of Atomic Weights. For all elementary purposes the variation is negligible. List of Approximate Atomic Weights of the Commoner Elements Metals Beuwumm = fo 5... OT Magnesium . . . . 244 Settee er. ek. «137 Manganese . . . . 59 On ae ea: 4 dletoury Go 2 BS Se ee) Beracuucgic, C.D Potassiim: .. ». =7 > 2a Beever, =. 1 t& «. . 64 Silvéetes) oa). eS Peeks | | «56 Soditim: ©. =.) (ae eee i ee ee 1 Titi 2 Soka 2 pene ee RO Ge ew 2 ORG 6 82 TEXTILE CHEMISTRY Non-metals Boron aera aie forges 2) Hydrogen 4... 220eeame 1 Bromine) 24 Nas oe Iodine . 3 Carbon Feats MEE ek ae Nitrogen © <7) 2) (eee 14 Chiorine 40) p03y) 4 ee OO eee wee oo A ACORN 2a 2 ve ae ee Fe 4 POUT HAr 2 eee nee Ba By the molecular weight is meant the number of times the molecule of an element or compound is as heavy as one atom of hydrogen or yg of one atom of oxygen. For elements that contain two atoms, this will be twice the atomic — weight. For compounds it is the sum of the weights of all the atoms in the molecule. II. THE LAWS OF CHEMICAL COMBINATION Scientific laws are not made—they are discovered. ‘Their applica- tion is the opposite to “‘ man-made laws.” If the individual breaks the law of the land, he is penalized—in other words, the individual has to conform to the law. In science the law — has to conform to individual experiment. Should experimental work — fail to agree with the law, the law is assumed to be stated wrongly. The following laws have, so far, never been contradicted by accurate _ experiment, but have been confirmed in thousands of instances. 1. Proust’s Law of Constant (or fixed, or definite) Proportion. The same compound always contains the same elements united together in exactly the same proportion by weight. E.g. calcium carbonate, whether it occurs as chalk, or Iceland spar, — or calcite, or marble, or aragonite, or egg shell, or oyster shell, always — contains in 100 grams of it 40 of calcium, 12 of carbon, and 48 of — oxygen. A Magnesium oxide, whether made by heating magnesium in air or — by ignition of the nitrate or carbonate, or in any other way, always — consists of 24 parts of magnesium to 16 of oxygen. 2. Dalton’s Law of Multiple Proportions. When the same two elements combine together to form more than one compound, the — proportions by weight in the other compounds are always some simple — multiple of the proportion found in the simplest compound, § E.g. Hydrogen and oxygen unite to form two compounds, (a) water, in which the ratio of hydrogen to oxygen is 1 to 8, and (0) hydrogen peroxide, in which the ratio is 1 to 16 (8x 2). q Copper and sulphur unite to form two sulphides in which the pro- 7 portion of copper and sulphur are respectively 64: 32 and 128:32. Nitrogen and oxygen form a series of compounds—the oxides of - THE ELEMENTS OF CHEMICAL THEORY 83 nitrogen—in which the following proportions of nitrogen and oxygen are found :— Nitrous oxide : . 28:16, ie. 28:16 Nitric as See Sastre ae LO ke Nitrogen trioxide . owas 3. 2a lO oo Nitrogen peroxide . , 25704 , 28:16 4 Nitrogen pentoxide Sie eb tell Baur le eis itp as This phenomenon i is quite explicable if we imagine the respective elenients “ moving about ”’ in certain definite entities, such as atoms. 3. Richter’s Law of Reciprocal (or equivalent) Proportions. When two different elements unite with the same quantity of a third element, the proportions in which they do so will be the same as, or some simple multiple of, the proportions in which they unite with each other. This is best illustrated by a diagram. Let A, B, C represent respectively three elements. Suppose B combines with A in the : Hy drogen VA ot os "Sulphide Bi4 16C aS BoC 14 16 C Carbon sisi Duadenad 64 Fig.133 Figis+ proportion 14:1; and suppose C also combines with A in the propor- tion 16:1. (Note same quantity of A.) Then B will combine with C in the proportion 14:16, or some simple multiple of this proportion (Fig. 133), e.g. in marsh gas 12 parts of carbon are combined with 4 of hydrogen. In sulphuretted hydrogen 64 parts of sulphur are combined with 4 of hydrogen ; and we find in carbon disulphide that 12 parts of carbon are combined with 64 of sulphur—which supports the truth of the Law of Reciprocal A tions (Fig. 134). _ EXPERIMENTS ILLUSTRATING THE Laws or CHEMICAL COMBINATION 1. To determine the Composition of Magnesiwm Oxide made in Three Ways. Weigh very accurately three pieces of bright magnesium ribbon. Each piece should weigh at least 0-1 gram, but not more than 0-2 gram. ‘Treat as follows : 84 TEXTILE CHEMISTRY Piece No.1. Put it in a weighed porcelain crucible and heat it over a hot flame until it burns and is completely converted into white magnesium oxide. Prevent the escape of any of the light powder by holding the lid at an angle just above the top of the crucible, using the __ tongs. Let the vessel cool and then weigh. ‘The increase in weight represents oxygen which has combined with metal to form the oxide. Piece No. 2. Put this in a small weighed evaporating basin, and, after covering with a watch-glass to prevent loss during solution, add two or three drops of dilute nitric acid. Repeat until the metal is dissolved. Put the dish on a water bath, and when all the water has — evaporated, heat over a hot flame until the magnesium nitrate is com- __ pletely converted into the oxide. N.B.—Magnesium nitrate fuses when heated, and decomposes with liberation of nitric oxide to pro- duce infusible white magnesium oxide. Weigh dish and contents, and calculate the proportion of oxygen to magnesium in this sample. Piece No.3. Put this in a small beaker and again dissolve in nitric 2 : acid ; dilute this solution with a few c.c. of water and then add sodium carbonate solution to produce magnesium carbonate. Filter to collect — the precipitate on filter paper and dry over a small flame. “4 When dry, transfer it to a weighed crucible, and heat very strongly — until the carbonate is again converted into the oxide. N.B.—The ~ carbonate loses weight on heating, the oxide does not. ’ Carefully tabulate the results you obtain, showing clearly the © | proportion of oxygen to magnesium in each sample, expressing the — quantity as per cent. oxygen and per cent. magnesium in each case. 2. To determine the Relationship between the Proportions in which — Oxygen unites with Lead to form Lead Peroxide and LIntharge. q Weigh a crucible and put in it a few grams of lead peroxide, care- — fully determining its weight. Heat this gently over a small flame, © stirring at intervals with a small piece of iron wire until it is converted © into litharge. a Take care that it does not fuse. N.B.—Litharge is buff in colour. — Find the loss in weight—which represents the first portion of oxygen liberated. After weighing add a few pieces of solid potassium cyanide, put the lid on and fuse up the mixture. Ultimately a button of molten lead will be formed in the bottom of the crucible. Cool, wash out all the soluble salts, dry, and weigh. Find the second loss due to oxygen, and compare the two results. N.B.—Potassium cyanide is a deadly poison (a salt of prussic acid); therefore take the greatest pre- cautions in handling it. 7 3. Compare the Proportions of Sulphur and Copper in Compe Sulphide. Make one sample by dissolving a weighed amount of copper in THE ELEMENTS OF CHEMICAL THEORY 85 nitric acid, and precipitating the sulphide with excess of ammonium sulphide, filtering, drying, and weighing. Make the other sample from pure precipitated copper by heating gently in a crucible with flowers of sulphur. The cake formed should be broken up several times, and a little more sulphur added each time. Finally, the excess sulphur should be very carefully burnt off with the lid of the crucible removed. IV. THE LAW OF GASEOUS VOLUMES (Gay Lussac) (which must not be confused with the physical law relating to expan- sion of gases, known as the Law of Charles or Gay Lussac). When chemical action takes place between gases, either elementary or compound, the volume of the gaseous product bears a simple relation to the volumes of the reacting gases, e.g. :— 1 volume of hydrogen unites with 1 volume of chlorine to form 2 volumes of hydrogen chloride. 1 volume of nitrogen unites with 3 volumes of hydrogen to form 2 volumes of ammonia. 1 volume of oxygen unites with 2 volumes of carbon monoxide to form 2 volumes of carbon dioxide. 2 volumes of hydrogen unite with 1 volume of oxygen to form 2 volumes of steam, etc. These are often called two-volume formula gases. A “two-volume formula” is generally written [7]. Thus (J of hydrogen, (J of chlorine = [7] of hydrogen chloride. [1] of nitrogen, (] C1] of hydrogen = [7] of ammonia. By examining these expressions we can arrive at the relationship between the original and resulting volumes of the reacting gases. N.B.—This notation must not be used for solids, e.g. this is wrong : (1) of carbon, [7] of oxygen = [7] of carbon dioxide. In common language we may sum up the law as follows: ‘“‘ Gases always combine in equal bulks or 1 part by bulk of one with 2 or 3 parts of the other.” EXPERIMENTAL METHODS FOR DEMONSTRATING THIS RELATIONSHIP FOR SOME OF THE COMMONER GASES 1. To show that 2 Volumes of Hydrogen unite with 1 Volume of Oxygen to form 2 Volumes of Steam. Fit up the graduated eudiometer tube surrounded with a jacket as shown in Fig. 135. Pass in hydrogen until it fills two graduations, when the pressure is equal in each limb of the eudiometer. Now add oxygen till the third graduation is reached. Circulate steam (or, better, amyl alcohol vapour) until the gases are heated to at least 86 TEXTILE CHEMISTRY 100° C. and again adjust the pressure. The volume of gas has in- creased ; mark this position on the outside of the jacket. Put a screw clip on the rubber tube connecting the eudiometer with the levelling tube, and then “ spark ” the gas, taking care to first cover the appara- tus with a thick duster in case the tube bursts. Unscrew the clip and adjust the pressure. It will be found that the volume now occupied by the steam will be two-thirds of the Sol® Water at? Mercury £1g.436 volume occupied by the mixed gases just before the spark was passed. — 2. To show that 1 Volume of Hydrogen combines with 1 Volume of — Chlorine to form 2 Volumes of Hydrogen Chloride. a For this experiment, two glass bulbs with side tubes are required — filled with the mixed gases obtained by the electrolysis of strong hydro- — chloric acid. It is desirable, although not essential, that each side — tube be provided with a glass tap (Fig. 136). 3 One of them (say A) is wrapped in red paper and put away in @ © THE ELEMENTS OF CHEMICAL THEORY 87 dark cupboard and the other is exposed to diffused daylight, but not sunlight, for several days until all green colour has disappeared. The bulbs are placed over separate vessels containing mercury, into which the end of one of the side tubes is made to dip, and the tap on this tube is opened. It will be found that the result in each case is the same, namely, no gas comes out of the bulb and no mercury passes into it ; the volumes of original gas and resulting gas are thus identical. On the top of the mercury in the vessel under A is put a solution of potassium iodide, and the end of the tube is raised until it reaches this liquid. The solution commences to rise because it dissolves the free chlorine. When it exactly half fills the bulb, it stops. If the bulb be now transferred to a deeper vessel, depressed in it, and the top tap opened, the gas expelled will be found to be all hydrogen. In the vessel under B should be put water, and on bringing the end of its tube in contact with this liquid, it will be found that all the gas is soluble in it, i.e. it is all hydrochloric acid gas. If the capacity of a bulb be called 2 volumes, half the capacity will count as 1 volume, from which we obtain the relationship 1 volume of hydrogen combines with 1 volume of chlorine to form 2 volumes of hydrogen chloride. 3. Z'o show that 1 Volume of Nitrogen combines with 3 Volumes of Hydrogen to form 2 Volumes of Ammonia. For this demonstration we assume the truth of the value obtained in the previous experiment, namely, that hydrogen and chlorine combine in equal volumes. A tube about a yard in length is required, provided with a well- fitting rubber stopper through which passes a dropping funnel with a well-ground glass tap (Fig. 137). The stopper is removed and the tube completely filled with chlorine. This is best done over strong brine. The stopper is reinserted and strong ammonia solution put into the funnel. The tap is very carefully turned and a few drops of the liquid allowed to enter the tube. The ammonia is immediately decomposed by the chlorine to form hydrochloric acid with liberation of nitrogen, the energy of combina- tion being sufficient with the first two or three drops to produce flashes of light. A little more ammonia is run in and the tube inverted several times until all the chlorine is used. Dilute sulphuric acid is now put into the funnel and run into the tube. This neutralizes the excess of ammonia, and dissolves the ammonium chloride crystals that have also been formed. Water is then allowed to enter until the tube is full of liquid and gas, which will be so when a bubble of gas attempts to pass up through the funnel. The gas left in the tube is measured and compared with the volume of chlorine used. The result will be as 1 isto 3. The residual gas can now be proved to be nitrogen, and as 3 volumes of hydrogen were 88 TEXTILE CHEMISTRY required to satisfy 3 volumes of chlorine, the ratio of nitrogen to hydrogen in ammonia must be | to 3. 4. To show that Carbon Dioxide and Sulphur Dioxide each contains its own Volume of Oxygen. A small flask is fitted with a tight-fitting rubber stopper through which pass two copper rods and a glass tube. To the ends of the former, which are to be put inside the flask, is attached a spiral of thin platinum wire. The glass tube is bent into the form of a double right- angled bend, for use with a manometric tube (Fig. 138). F1G.137 FIG.139 A small piece of charcoal or sulphur is put in the spiral, the flask _ filled with oxygen (by means of a tube not shown in the figure), and — the level of mercury in the manometer tube is marked. The ends of © the copper rods are connected to the terminals of a suitable battery — and a current of electricity is passed through, with the result that — the platinum becomes red-hot, which heats the carbon or sulphur — sufficiently to make it burn to carbon dioxide or sulphur dioxide. _ Due to the heating effect, the volume of gas is increased, but when — it is allowed to cool down to the original temperature, it is found that the final volume is the same as the original. In other words carbon ~ dioxide or sulphur dioxide contains its own volume of oxygen. e THE ELEMENTS OF CHEMICAL THEORY 89 5. T'o show that Nitrous Oxide contains an equal Volume of Oxygen, Nitric Oxide half its Volume of Oxygen, and Sulphuretted Hydrogen its own Volume of Hydrogen. For all these determinations the same piece of apparatus can be used—known as a “thumb tube” (Fig. 139). It is filled with one of these gases and put over a vessel containing mercury, the level of which is marked on the tube. A small pellet of metal (potassium for the oxides of nitrogen, and tin for sulphuretted hydrogen) is pushed under the surface of the mercury in the dish and allowed to rise to the surface of the mercury in the tube. The finger is then put under the end of the tube and the pellet jerked into the horizontal portion. This is then carefully heated. The potassium combines with the oxygen in the oxides of nitrogen, liberating nitrogen ; and the tin decomposes the sulphuretted hydro- gen, forming tin sulphide and liberating hydrogen. The gas is allowed to cool and the level of mercury compared with the original, from which the ratios will be found to be as that stated above. V. AVOGADRO’S LAW states that “‘ equal volumes of all gases under the same conditions of temperature and pressure contain the same number of molecules.”’ This law is now admitted to be as true as the other four, but its proof is beyond the requirements of a student of elementary chemistry, as it requires more than an elementary knowledge of mathematics and physics. At this stage it must be accepted. EQUIVALENTS When chemical reaction occurs between certain substances, notably acids and metals, it is found that one element has usually replaced another element in one of the compounds present. Further, a certain mass of one element is found to displace con- sistently the same quantity of the other element. ‘These two quan- tities are said to be equivalent. It is convenient in practice to adopt some one element to which all the others refer, and thus the equivalent of an element is defined as the number of parts (or grams) of an element which are replaceable by, or combine with, or are chemically equal to, one part (or gram) of hydrogen. EXERCISES IN DETERMINATION OF EQUIVALENTS As in a great many of these determinations a volume of hydrogen will be collected, which must be converted into a mass, the first exer- 90 TEXTILE CHEMISTRY cise is to determine the relationship which exists between these two quantities. 1. To determine the Mass of 1 Intre of Hydrogen. Use the special apparatus, diagrams of which are shown in Figs. 140 and 141. Carefully weigh the light apparatus (Fig. 140) when fitted up with a small piece of magnesium rod in the T.T., covered with water, and strong sulphuric acid partly filling the drying bulb. Attach it to the collecting apparatus A to A’; arrange the level of water in aspirator and gauge tube to be the same by drawing off water at B. To Flask Gently warm the T.T. Air is expelled through acid. Cool. Acid is drawn into outer tube, and hydrogen is liberated, passes through the drying bulb and into the aspirator, causing the water in gauge tube gradually to rise. Draw off water at B into a 250 c.c. flask at such a rate as will keep the surfaces of the water level. When all action is over (1) Read thermometer in aspirator (say #¢° C.). (2) Read atmospheric pressure on barometer (say P mm.). (3) Detach the light apparatus and carefully weigh to find the loss in mass, which gives the mass of hydrogen evolved (say=m grams). THE ELEMENTS OF CHEMICAL THEORY 91 (4) Carefully find the volume of water collected by filling up the 250 c.c. flask from a burette—which gives the volume of hydrogen evolved (say = a@c.¢.). Volume corrected to N. ee P. (i.e. 0° C. and 760 mm. pressure) a yee (00367 x a * This has a mass of m grams. m *, 1 litre weighs ep | T+ (00367 xt ~ 760 Correct value = -0899 gram. 2. To determine the Equivalent of a Metal by dissolving in Acid and collecting the evolved Hydrogen. map LbY Boyle’s and Charles’s law]. Ditute Acid SL (in glass vessAl ) Pane Magnesium Fi¢442 Several variations of apparatus are given according to the metal to be used. (a) Magnesium. Weigh out very accurately about -1 gram of freshly cleaned magnesium ribbon. Put it into the bottom of a narrow T.T., and fill with water by dropping into a small glass or enamelled-iron pneumatic trough. Fill the larger tube—half with dilute sulphuric acid and half with water—close with thumb, place in trough, slip in the T.T. (Fig. 142) and raise to vertical position. When the magnesium is all dissolved, take the temperature of the water and transfer the tube carefully to a tall cylinder of water to bring to atmospheric pressure, which is equal to the barometric pressure (Fig. 143). Mark the level with a strip of paper, and find the volume of the gas by pouring in water from a measuring vessel. Correct this volume to 0° C. and 760 mm. pressure, and convert into a mass (in grams) by means of the value found in Exercise 1. By “ Rule of Three,” find How many grams of magnesium would be required in order to liberate 1 gram of hydrogen (i.e. the equivalent of magnesium). 92 TEXTILE CHEMISTRY The apparatus shown in Figs. 144 and 145 can also be used. (b) Zinc, Iron, Aluminium. Use the apparatus shown in Fig. 144. Carefully weigh a small piece of metal and place in T.T. Fill it with water, and close the tap. Place dilute acid in the funnel, fill the collecting tube, invert i into the funnel, and open the tap. The acid flows down and ultimately acts upon the metal—the gas evolved being collected in the closed tube. The temperature of the gas must be determined in each case, and the volume corrected to atmospheric pressure as shown in Fig. 143. Correct the volume and find its mass as in (a) above. : For zinc and iron, use either dil. sulphuric or dil. hydrochloric acid. La < es os * o] aed THE ELEMENTS OF CHEMICAL THEORY 93 For aluminium use either caustic soda solution or hydrochloric acid (1 volume water, 1 volume strong acid). It is desirable, and in some cases necessary, to warm gently. Apparatus shown in Fig. 145 is to be used with aluminium and caustic soda. Be careful that the stoppers fit very tightly and are of rubber. Calculate how many grams of the given metal are required to liberate 1 gram of hydrogen. 3. To determine the Equivalent of a Metal by Precipitation with another whose Equivalent has been already determined. (a2) Prepare a solution in water of a soluble salt of the metal whose equivalent is to be determined, e.g. For copper, use copper sulphate. » sdlver, ,, silver nitrate. 5 . -t8n, ,, stannous chloride in hydrochloric acid. » lead, ,, lead acetate. (0) Carefully weigh a quantity of the precipitating metal, which must be as pure as possible. Zine (foil) will precipitate copper, silver, tin, lead. Copper (foil) will precipitate silver (in hot solution). Magnesium will precipitate silver, iron, cobalt, zinc, nickel, gold, platinum, bismuth, tin, mercury, copper, lead, cadmium. Iron will precipitate copper. Add the precipitating metal to the solution contained in a small beaker, stir from time to time with a glass rod, until all the precipi- tating metal is dissolved. Collect every particle of the precipitated metal, either on a filter paper (of known mass) or in a small crucible ; wash well first with hot distilled water, then with alcohol; and dry in a steam oven. When completely dry, weigh. Finally, calculate the equivalent of one metal in terms of the other ; and then, to obtain the equivalent in reference to hydrogen, multiply this result by the equivalent of the known metal. 4. To determine the Equivalent of an Element by preparing a Com- ' pound of the Element with another whose Equivalent has been previously determined. (a) Oxygen. (i) Prepare tin oxide. Use a known mass .of granulated tin. Place it ina crucible and add strong nitric acid from a pipette drop by drop (Fig. 146). When all the tin is oxidized, ignite and weigh. (1) Calculate what mass of oxygen has combined with the equi- valent weight of tin. (2) Prepare magnesium oxide by the action of dilute nitric acid on a known mass of the metal, and perform similar calculations. 94. TEXTILE CHEMISTRY (0) Silver. Prepare pure silver oxide by allowing baryta water to filter into a small flask of silver nitrate solution. Cork at once and shake ; allow the oxide to settle ; decant liquid; wash several times with hot water, and dry in steam oven. Put two or three grams into a hard glass tube of known mass. Attach to an aspirator, heat, and collect the evolved oxygen. Find its mass—check by weighing the residue in the tube. Calculate the amount of silver which combines with eight grams of oxygen. Table of Approximate Equivalents Hydrogen = 1 Sodium = 23 Carbon =) 00 Tron =i 20 Nitrogen = 4-7 Copper. o=982 Oxygen om 8 Zinc = O27 Aluminium = 9 Chlorine = 35:5 Magnesium = 12-2 an = 59 Sulphur = 16 Silver = 108 Equivalence is an experimental fact and shows no variation— except that certain elements (that form two series of salts) give one or other of two values, depending upon which class of‘ compound is being experimented with, e.g. Mercury 100 or 200. Copper 32 ior :~(64. Tin 59 or 118. Iron 18-67 or 28. These values are related to each other as 1: 2, 2: 3, etc. THE THEORY OF VALENCY is an attempt to explain, chiefly from logical considerations, the phenomenon of equivalency. It is found that if the atomic or com- bining weight of an element be divided by its equivalent, in every instance the quotient is a whole number (1, 2, 3,4,5). These numbers are assumed to measure the ratio of chemical combining powers of the respective elements. Table of Valencies or Atomicities Monads, . Diads. Triads. Tetrads. Pentads, Chlorine Calcium Aluminium Carbon Nitrogen Hydrogen Copper Nitrogen Tin Phosphorus Potassium Iron Phosphorus Silver Zinc Sodium Lead Magnesium Oxygen Sulphur Tin ea, Oo oe a ae eee Ene re eS a ae MB -aty » Sia art A SARL ORB EE a4 ~~ Lou THE ELEMENTS OF CHEMICAL THEORY 95 Those giving a quotient of 1 are termed monads or monovalent elements. Those giving a quotient of 2 are termed diads or divalent elements. Those giving a quotient of 3 are termed triads or trivalent elements. The relationship existing among atomic weight, equivalence, and valency may be summarized as :— At. Wt. V and as in most cases At. Wt. = Molecular Wt. ~ 2 and Molecular Wt. = Vapour Density x 2, Therefore Atomic weight — Valency = Equivalent or EK = v.d. V a Thus if the vapour density of an element = 16 and its equivalent is 8, its valency is ae 2 (i.e. it is divalent). GRAPHIC REPRESENTATION OF VALENCY Ammonia Gas H—N—H Mercuric Oxide Hg=O | Carbon Dioxide O=C=O H Caustic Soda Na—O—H. Hydrogen Chloride H—Cl Cl Water H—O—H H—O O Seiphisin: Avid \sJ H—o” No Copper Oxide Cu=O Potassium Chlorate panes K—0—OK Aluminium Chloride AlCl Cl LA Magnesium Chloride MeN ve Chloroform H—C<—Cl Na Calcium Hydroxide \ Nitric Acid YN—O—H oF H—O—Ca—OH SYMBOLS, FORMULZ AND EQUATIONS Symbols were devised by Dalton to represent one atom of the respective elements. He used circles, e.g. O, ©, O, ®, for certain of the non-metallic elements, and circles containing letters for the metals. . Berzelius brought symbolic representation to its present form by omitting the circles and using initial letters throughout, e.g. :— 96 Aluminium . Chlorine Iron (Ferrum) Mercury (Hvdrareyrdin) Hg Silver (Argentum) Phosphorus . Barium . Copper (Cuprum) Lead (Plumbum) Sodium (Natrium). Calcium . The symbol denotes :— 1. One atom of the element. 2. The number of parts by weight given as its atomic or combining weight. It is not to be used as an abbreviation for the name nor as chemical shorthand. Combinations of symbols are termed Formule. They (usually) represent the proportions by weight and the number of atoms in which TEXTILE CHEMISTRY Hydrogen Magnesium . Oxygen . Potassium (Kalium) Carbon Iodine Nitrogen Sulphur Zinc ar etc. the elements exist in one molecule of the compound. If a multiple of the atomic weight is denoted, this multiple is written as an index figure to the symbol at the botiom, e.g. H., O3, Pa, Cl,. A bracket has the same significance as in arithmetic, e.g. (COOH). means twice all the symbolic value in the bracket. A figure in front of an expression has the same value as before a bracket, and carries its influence to the end of the expression. 7H,O means seven times the sum of H, and O. The formula of a substance represents one molecule of that q substance. Formulz of some Common Compounds Hydrochloric Acid . Sodium Chloride Calcium Chloride Potassium Chloride. Ammonium Chloride Ferric Chloride . Silver Chloride . Lead Chloride Magnesium Chloride Zine Chloride Nitric Acid . Silver Nitrate Sodium Nitrate Potassium Nitrate . Copper Nitrate . Sulphuric Acid . . . HCl . NaCl . CaCl, ee <0) . NH,Cl . Fe,Cl, Copper Sulphate Ferrous Sulphate Magnesium Sulphate Zinc Sulphate Barium Sulphate Calcium Sulphate Ammonium Sulphate . Sodium Sulphate Potassium Sulphate Carbon Dioxide Calcium Carbonate Sodium Carbonate . Sodium Bicarbonate Calcium Bicarb. Ammonium Carbanated Potassium Chlorate. . FeSO,.7H,0 . MgSO,.7H,0 — . ZnSO,.7H,0 — : BaSO, . CaSO, . KCIO; eg! eS) ee Pama SZ Honor git a pe CuSO,.5H,0 — (NH,).SO,4 CaH 2(CO 3) 2 (NH,),CO; THE ELEMENTS OF CHEMICAL THEORY 97 Potassium ee Mercuric Oxide. . . HgO BIG. ys K.Mn,Og WARS (SIG ce Sd iat AUD Puormiamy . . . CHC, Ozone . ot Gala Water . . 7 sO Sodium Hydrate . . NaOH Carbon Monoxide Jet yy & 8) Calcium Hydrate . . Ca(OH), Sulphur Dioxide. SO, Barium Hydrate . . Ba(OH), Silicon Dioxide (sand) . SiO, Copper Hydrate . . Cu(OH), Manganese Dioxide. . MnO, Potassium Hydrate. . KOH Magnesium Oxide . . MgO Hydrogen Sulphide. . H,S Sulphur Trioxide . . SO; Carbon Disulphide. . CS, Copper Oxide . . . CuO Ferrous Sulphide . . FeS Nitrous Oxide . . . N,O Ammonia . i NH, Nitric Oxide. . . . NO Ammonium Hydrate . NH,OH Barium Peroxide . . BaO, Mercuric Iodide. fee: Litharge ee 2 2 EDO AUT Al,(SO,)s- K,80,.24H,O hed ueed . .... «.Pb,0, Bleaching Powder . . Ca(OCl)Cl Lead Peroxide . . . PbO, Oxalic Acid. . . . (COOH), Ferric Oxide . . . Fe,O;3 (Ethyl) Alcohol a este. OH Calcium Oxide . . . CaO AN EQUATION represents quantitatively a chemical change or reaction. + on the left means ‘“ chemically reacting with.” + on the right means “ and.” = or > means “ produces, forms, yields,” etc. An equation always contains at least two formule. The only points of equality are: (1) That the sum of the combining weights on one side must equal the sum of the combining weights on the other. (2) The number of atoms of each element must be the same on each side. To solve an arithmetical example an equation should be used in the following manner : : Step 1. Select the correct equation. Enter the respective combining weights. 3. Total them up for each formula. 4. Underline the terms required. 5. Get the statement for “rule of three.” 99 EXAMPLE ““How much copper would be required to produce 8 grams of copper nitrate by the action of nitric acid on the metal ? ” Step 1. 3Cu + 8HNO, = 3Cu(NO;), +4H,0 + 2NO Pe See G4 1 14 14 14 tie) cok ute 48 Parad aryl 1G 30 x 2 63 x 8 64 18 x 4 188 x 3 eo. 102 504 564. 72 60 A ~ 98 TEXTILE CHEMISTRY Step 5. 564 grams of copper nitr. are obtd. from 192 grams of copper, A 192 therefore 1 gram or 5 ate T= oe ” Faq ei 3 192 x 8 99 grams 399 99 are 99 eer. 7,F Ge: 9 9 == 2-72 grams. Equations representing some well-known Chemical Reactions Hg +1 = Hgl. Mercury and iodine combining to form mercuric iodide. Fe +S = FeS. Iron and sulphur combining to form ferrous sulphide. FeS + H,SO, = FeSO, + HS. Ferrous sulphide and dil. sulphuric acid reacting to produce ferrous sulphate and sulphuretted hydrogen gas. 2Na + 2H,O = 2NaOH + H,. Sodium acting on water to produce sodium hydrate (caustic soda) with the liberation of hydrogen gas. 3Fe + 4H.0 = Fe,0, + 4H. -Iron heated in a current of steam—black oxide of iron formed and hydrogen liberated. Zn + H,SO, = ZnSO, + Hg. Zine and dil. sulphuric acid react to produce zinc sulphate and hydrogen. 2KCI1O; = 2KCl + 30,. Potassium chlorate is decomposed by heat into oxygen and potassium chloride. SO, + O = SO,. Sulphur dioxide and oxygen passed over heated platinized asbestos unite to form sulphur trioxide. CuO + H, = Cu + H,0. Copper oxide heated in a current of hydrogen is reduced to metallic copper, with formation of water. CaO + CO, = CaCOQOs. Calcium oxide (lime) exposed to carbon dioxide combines to form chalk. The following equations represent chemical changes that have taken place while performing some simple experiments in the labora- tory. Write in words the meaning of each in a similar manner to that shown above. 1. Mg + O = MgO 5. Zn + 2HCl = ZnCl, + Hy . Fe + H,SO, = FeSO, + H, . CuSO, + Fe = FeSQ, + Cu . 2HgO = 2Hg + O, . HCl+ NH, = NH,Cl bo = =} = + aN an © oS = MnCl, + 2H,O+ Cl, 3. CuO + H,SO, = CuSO, + H,O 4. Cc + O, = CO, ole ot | THE ELEMENTS OF CHEMICAL THEORY 99 10. CaCOs + 2HCl 19. Zn + CuSO, = ZnSO, + Cu 11. HCl + NaOH = NaCl + H,O 21) BP, + 60, = 2P.0, 12. Na,CO, + 2HCl 22, 2Ke, -+ 30, = 2Fe,0, = 2NaCi + H,O + CO, 23. He + O = HgO 18. SO, +0 + H,0 = H,SO, 24, KOH + HNO, = KNO, + H,O 14. 2H,0 = 2H, + O 25. CaCl, + 2AgNO, 15. 3Fe + 4H,O = Fo,0, + 4H, = 2AgCl + Ca(NO,), 16. Mg + H,SO, = MgSO, + H, 26. NH,Cl + NaOH 17. CO+0 =CO, = NH, + NaCl+ H,O 18. Na,S + 2HCl = H,S + 2NaCl EXERCISES IN CHEMICAL ARITHMETIC 1. How much oxygen can be obtained by igniting 20 grams of potassium chlorate ? 2. For how long must steam be passed over red-hot iron at the rate of 2 grams per minute, in order to produce 8 grams of hydrogen ? 3. How much ammonium chloride is required in order to prepare 10 grams of ammonia from a mixture of ammonium chloride and lime ? 4. How much chlorine could be obtained by acting on 5-6 grams of manganese dioxide with excess of hydrochloric acid and warming the mixture ? 5. How much rock salt would it be necessary to use in order to prepare a 20 per cent. solution of hydrochloric acid in water, using 100 grams of water ? 6. How much water can you obtain by reducing 25 grams of copper oxide with hydrogen ? 7. How much carbon is required to reduce 165 grams of carbon dioxide to carbon monoxide ? 8. How much sulphur is there in 268-3 grams of crystallized zine sulphate ? 9. How much zinc is required to precipitate 100 grams of lead from a solution of its nitrate ? 10. How many lb. of nitrogen are contained in 1 ton of ammonium sulphate and sodium nitrate respectively ? 11. How much carbon is there in 1 kilogram of cane sugar ? RELATIONSHIP BETWEEN THE VOLUME AND MASS OF ‘GASEOUS ELEMENTS AND COMPOUNDS If equal volumes of different gases (under the same conditions of temperature and pressure) be accurately and carefully weighed, it is found that their weights vary (Section VI, page 47). The lightest is hydrogen, 1 litre of which at N.T.P. weighs 0-0899 gram—some- times called 1 crith. Oxygen weighs 16 times as much, ammonia 8-5 times, hydrogen chloride 18-25 times, etc. This relative density of a gas in relation to hydrogen is called its Vapour Density. (See Table, page 47.) Now, Avogadro’s Law states that these litres all contain the same 100 TEXTILE CHEMISTRY number of molecules. ‘Therefore the same ratio (i.e. v.d.) gives the relative weights of the respective molecules of gas. Then, as we have thus obtained the weight of each molecule of gas in terms of the weight of one molecule of hydrogen, the question comes, ‘* What is the weight of 1 molecule of hydrogen in terms of our unit, i.e. the weight of 1 atom of hydrogen ?’’ Careful chemical research has answered this as “two.’”? Therefore the molecular weights of gases are obtained by multiplying the v.d. by 2. Now, if 1 litre of hydrogen at N.T.P. weighs -0899 gram, then 22-4 litres of hydrogen will weigh 2:02 grams, i.e. twice the atomic weight (1-01) of hydrogen. Thus 22-4 litres of any elementary or compound gas at N.T.P. will weigh its molecular weight in grams. EXERCISES 1. Find the volume of hydrogen (at N.T.P.) which would be evolved by treating 10 grams of zinc with hydrochloric acid. 2. What volume of oxygen at N.T.P. would be produced by strongly heating 5 grams of potassium chlorate ? 3. What weight of common salt would be required to furnish sufficient hydrogen chloride to neutralize 100 grams of a 30 per cent. solution of caustic soda ? What would be the volume of the gas at NTP. t narra ee ae es ee coh ark SECTION X CARBON AND SOME OF ITS COMPOUNDS tary condition it occurs as diamond and graphite. Combined with other elements like hydrogen, oxygen, and nitrogen, it forms thousands of compounds which are essential to life and vital processes generally. From many of these compounds carbon can be prepared in an amorphous condition, e.g. charcoal, lampblack, gas carbon, etc. The phenomenon of an element occurring in different physical conditions is termed allotropy, and the varieties are known as allotropic modifica- tions. Diamonds are octahedral crystals of high sp. gr. (3-5), are ex- tremely hard, and highly refractive to light. These two properties are mainly responsible for the two chief uses, i.e. for rock boring and cutting, and use as a gem. Lavoisier showed by burning a diamond in oxygen—when carbon dioxide was produced—that it contained carbon, and later Davy showed that it was pure carbon. Graphite, also known as black-lead or plumbago, is a greyish black solid with a distinct lustre, and occurs very widely distributed throughout the world, i.e. Iceland, Siberia, Ceylon, Canada, etc. It is now produced in large quantities artificially at Niagara by the Acheson process. It is used as (1) a lubricant, (2) a polishing medium for shot, ironwork, gunpowder, etc., (3) an ingredient in the “lead” of pencils, (4) a film for electrotyping, (5) an ingredient in plumbago crucibles. It is soft and soapy in texture, and is attacked when warmed with a mixture of potassium chlorate and nitric acid. Amorphous carbon occurs in many forms, e.g. charcoal, gas, carbon, lampblack, and may be prepared from almost any organic tissue or substance—wood, starch, cheese, sugar, coal, turpentine, etc. The older style of charcoal production was to make heaps of wood, cover with sods, and set the mass on fire. This was extremely waste- ful, and when wood is carbonized to-day it is destructively distilled in ovens in a similar way to that adopted for coal, the result being that 101 Ors: is the most wonderful of all elements. Inthe elemen- 102 TEXTILE CHEMISTRY many valuable by-products are obtained of which pyroligneous acid (used as a source of acetic acid), methyl alcohol, and acetone are the most important. The destructive distillation of wood can be illustrated on a small scale by using the apparatus shown in Fig. 147. The test tube con- tains sawdust. In bottle A some of the most easily condensed pro- ducts are obtained. Bottle B, containing water, serves to wash the gas free from others, and an inflammable gas passes along, which may be ignited at C. Lampblack is prepared by burning oil in a small supply of air. A very smoky flame is produced, due to the presence of finely divided carbon. This soot is collected on blankets hung in chambers through which the smoke is made to pass, a process similar to the collection in chimneys. Lampblack is used for printer’s ink and black paints. It will not bleach. F1G.148 Charcoal of a much purer quality than that obtained by the destructive distillation of wood is prepared by adding strong sulphuric acid to a concentrated solution of sugar in water. The black mass produced is washed free from acid and dried. Coke and gas carbon are obtained in the destructive distillation of coal. The former contains about 90 per cent. of carbon, Aes latter nearly 100 per cent. Animal charcoal is prepared by roasting bones. Its average composition is 10 per cent. carbon, 88 per cent. calcium phosphate, and 2 per cent. other substances. It has a very considerable application in industry as a deodorizer and decolorizer, but it requires frequent re-ignition if its efficiency is to remain unimpaired. Coal, to the large deposits of which in this country England largely owes her commercial supremacy, is a very impure form of COMPOUNDS OF CARBON 103 carbon, and includes compounds of carbon with hydrogen, nitrogen, etc. It is a mixture evidently formed from a geological deposit of ancient luxurious tropical vegetation. It is the chief British fuel, and the source of one of the chief means of artificial illumination. For the latter purpose it is destructively distilled to produce “coal gas.”’ Fig. 148 shows the principle of the method. R represents the retort containing the coal, H the hydraulic main, T the tar-pit, C the coolers, S the scrubber for removing by solution the ammonia produced, P the purifier (containing iron oxide or lime), and G the gasometer. Coal tar, which consists of a mixture of a very large number of compounds of carbon, is also destructively distilled, and the products, as they are evolved at different temperatures, are collected in several fractions. ‘The residuum is known as pitch. From these fractions chemicals are obtained which severally serve as the starting-points in the manufacture of a series of ‘‘ intermediate products,” these in their turn being used for the preparation of :— (a) Coal-tar dyes; (6) flavouring, sweetening, and colouring materials; (c) drugs and disinfectants; (d) perfumes; (e) explo- sives ; (f) organic solvents. The chief compounds of carbon include those with :— 1. Oxygen. The Ox1pEs.—Carbon monoxide, carbon dioxide. 2. Hydrogen. The HypRocaRBons.—Marsh gas, acetylene, ethyl- ene, benzene, toluene, naphthalene, anthracene. 3. Oxygen and hydrogen. The CaRBoHYDRATES (starches, sugars), ALCOHOLS, ALDEHYDES, ErHeErs, AcIDs. 4, A metal and oxygen. The CarBonaTEs, such as chalk, marble, aragonite, witherite, ironstone, soda ash, magnesite, etc. A few of these compounds will now be considered in detail. Carbon dioxide. A heavy, colourless gas is found to be produced as a result of combustion, respiration, and fermentation, which has been known at various times under various names, e.g. gas sylvestre, choke-damp or after-damp, fixed air, chalk gas, carbonic acid gas, carbonic anhydride, but which is usually termed carbon dioxide. It is present in fresh air, mixed fairly uniformly, to the extent of 0-03 per cent. to 0:04 per cent. by volume, and is found in certain natural mineral waters, e.g. Apollinaris, Johannis, Perrier, Apenta. It also exudes from vents and fissures in volcanic regions. Its presence in air is due almost entirely to respiration and com- bustion. From it it is assimilated by plants and vegetation generally, being converted in the “leaf laboratories’ into starch and sugar. The earth crust contains many carbonates, which are metallic oxides in combination with the gas, 104 TEXTILE CHEMISTRY T'o prepare the Gas :— 1. Act on a carbonate with acid, e.g. marble and dilute hydro- chloric, magnesite and dilute nitric, sodium carbonate and sulphuric (Figs. 149, 150). 2. Heat charcoal in a good supply of air or oxygen (Fig. 151). 3. Ignite certain carbonates, e.g. chalk, magnesite. 4. Ferment sugar with yeast (Fig. 152), keeping the temperature about 30° C. Enormous quantities of carbon dioxide are obtained F1G L5L in this way from breweries and distilleries, condensed into bottles, and used in the manufacture of mineral waters. PROPERTIES It is a heavy colourless gas (14 times as heavy as air). Many experiments may be performed to illustrate this property, e.g. a beaker full of it may be weighed and compared with the weight of the same beaker when full of air ; it may be poured from one gas jar to another like a liquid ; a soap bubble that would fall in air may be floated in a bell jar of the gas (Fig. 153). ad eee g Oe Te CARBON DIOXIDE | 105 The soap bubble is best blown by using a piece of glass tubing about 4 inch diameter, which contains a plug of cork in which “ gutters ” have been cut. It will not support ordinary combustion, e.g. a taper, a candle flame, and even that from burning turpentine will be extinguished by it ; but it will support the combustion of burning magnesium, with the liberation of carbon and the formation of magnesium oxide (black and white residue). | It is very soluble in caustic soda, forming sodium carbonate. It is soluble in water, especially under pressure. Soda-water, beer, lemonade, champagne contain it, and thereby “ sparkle ” when opened. FiG.153 It is easily liquefied. ‘“Sparklets ” contain liquid carbon dioxide. It has a feeble taste, slightly acid reaction when dissolved in water, and a pleasant smell. Uses. 1. For making mineral waters. 2. For extinguishing fires—hand grenades. 3. As a refrigerating agent—liquid carbon dioxide plants are very efficient. 4. For aeration of bread and pastry—baking powder liberates it. 5. As an asphyxiating agent—the lethal chamber at the famous Lost Dogs’ Home in Battersea is worked with it. 6. For medicine—Seidlitz powders, health salts, fruit salts, when mixed with water, liberate it. 7. As an indicator of impurities in an atmosphere—e.g. in mills and schools. 8. As food for plants. 106 TEXTILE CHEMISTRY PRACTICAL EXERCISES 1. Test for Carbonates. Use specimens of each of the following carbonates : Calcium carbonate, sodium carbonate, barium carbonate, ammonium carbonate. Test the action of dilute acid on each. Note if carbon dioxide is evolved. Use the apparatus shown in Fig. 154. Then determine which of the following substances are carbonates or contain carbonates: Iceland spar, egg shell, washing soda, mag- nesite, oyster shell, oxalic acid, cryolite, baking powder, old mortar. 2. To distinguish Chalk from Quicklime :— (a) Add water, and note result—solubility, temperature. (b) Try effect of heat on each, and note if any alteration occurs in weight. (c) Try effect of dilute hydrochloric acid on each. 3. Experiment with the by-product from the manufacture of carbon dioxide from marble and hydrochloric acid, which is calcium chloride. Evaporate the liquid to dryness, abstract the solid calcium chloride, and describe its colour, texture, action on exposure to air. Ae 4. T’o determine the Mass of Carbon Dioxide evolved by the action of an AcID on a given mass of a carbonate :— This is done, as a rule, by “ difference,” i.e. the carbon dioxide is expelled into the air, and the residue is weighed ; which is very simple in principle, e.g. perform the following experiments :— (a) Half fill a small flask (2 oz. capacity) with dilute /hydrochieas acid, and accurately weigh it (= a@ grams). (b) Accurately weigh a small lump of marble (= 6 grams). (c) Drop the marble into the flask and allow the acid to dissolve it completely. Carbon dioxide is expelled. (d) When action has ceased, weigh again (= c grams). Then 6 grams = mass of carbonate taken, and a + b —c = mass of carbon dioxide evolved. 100(a + b — c) Percentage of carbon dioxide in marble = 5 = de, 4 x, CARBON DIOXIDE 107 Compare the result obtained with the correct percentage (44 per cent.). The error is due to the following causes :— (a) Some of the carbon dioxide is left dissolved in the liquid. This tends to decrease the percentage. (6) Water is evolved with the gas. This tends to increase the result. (c) Carbon dioxide fills the flask in place of air. This decreases the percentage. The first error can be corrected by just boiling the liquid over a small naked flame after all action in the cold has ceased ; the third by sucking out the carbon dioxide; the second necessitates a special device for drying the gas as it passes out. Fig. 155 shows a simple method, using cotton wool; the gas is sucked out with a glass tube, not shown in the figure. In Fig. 156 a drying-tube filled with pieces of fused calcium chloride, or pumice moistened with strong sulphuric acid, is used. The carbonate is weighed into the flask; the small test tube contains strong hydro chloric acid. F1G.158 F1G.160 Fig. 157 is merely a modification of Fig. 156. Dzlute acid is put into the tube ; the carbonate is weighed into the small test tube, which contains a small hole in the bottom. Fig. 158 is similar in principle. The strong hydrochloric acid is con- tained in the pipette, and the entran-e of it is regulated by a small clip. Figs. 159 and 160 show other forms of drying apparatus in which a few drops of strong sulphuric acid are used in place of the moistened pumice. Fig. 161 is Schrotter’s, one of the standard pieces of apparatus for this determination. The carbonate is put in by removing the stopper. The pipette contains the acid to decompose it, and the drying arrangement contains strong sulphuric acid. 108 TEXTILE CHEMISTRY Fig. 162 is a very efficient apparatus designed by the author some years ago and made by Messrs. F. E. Becker & Co., of Hatton Wall, London. To use the apparatus, remove the rubber stopper carrying the pipette and drying bulbG. Weigh the test tube, both before and after putting in the carbonate (difference in mass= weight of carbonate used). Into the small test tube C put a few drops of strong sulphuric acid. Remove stopper, and by suction, fill the pipette A with acid, say hydrochloric, pinch the rubber tube B, and replace. Put into E a little water, replace the stopper and hang the whole to the specific- gravity hook of a balance and weigh. Ue A Slightly squeeze the rubber tube B between the finger and thumb, as in diagram, and allow a few drops of acid to drop from A. The liberated gas escapes through the drying apparatus G. When the action is over, remove the stopper, and attach B to a suitable ap- paratus, and aspirate until the carbon dioxide in E is eliminated. Replace stopper and weigh the whole apparatus—the loss of weight represents the evolved carbon dioxide. If still greater accuracy is desired, it is well to arrange this ap- paratus in combination with tubes and aspirator as shown in Fig. 163. A is the decomposition apparatus used as described above. CARBON DIOXIDE 109 It is connected at 1 with B, which will absorb the carbon dioxide evolved from A. The gain in weight of B should equal the loss in A. C is an aspirator by means of which a current of air can be drawn through A in order to expel every trace of carbon dioxide from it. To do this, after the decomposition of the carbonate is complete, the top of the acid pipette is connected at 2 with the tube D, through which the air has to pass before it reaches A. D contains caustic soda and sulphuric acid to ensure that when it enters A it contains no moisture and carbon dioxide. 5. T'o determine the Mass of Carbon Dioxide evolved by the action of heat on a carbonate :— Not all carbonates are decomposed by the action of heat. Use for this exercise precipitated chalk or magnesite. NN Thoroughly dry a porcelain crucible by heating it for five minutes over the bunsen flame, cool, and weigh it very accurately. Put in sufficient of the carbonate to form a layer about one-eighth of an inch thick on the bottom of the crucible, and reweigh to find the amount used. Heat strongly over the bunsen flame or put in a muffle furnace for one hour, with the lid of the crucible removed. Cool in a desiccator and weigh again. Find and record the loss that has occurred. Reheat in a similar manner for ten or fifteen © minutes, cool and reweigh. Find and record the second loss. If it exceeds 0-001 grams, repeat the heating until no greater loss is obtained, when it may be assumed that the carbonate is completely decomposed. 110 TEXTILE CHEMISTRY Find the total loss and calculate to a percentage. The weighings should be recorded as follows :— Mass of crucible ++ Carbonate 9 9 only wee ” Then amount of carbonate used = gm Crucible + Carbonate before heating a 3 29 ah re) after ” — 2” First loss = ‘gm Crucible + Carbonate after first heating a wy ee) as 2? re) second » =. 29 Second loss a gm and so on. 6. Black’s Researches on Chalk, or to compare quantitatively the composition (with respect to the proportions of the two oxides they contain) of marble, Iceland spar, egg shell, precipitated chalk, oyster shell, etc. (a) Determine the percentage of calcium oxide present in each of the following substances—express as CaO = x per cent. (6) Determine the percentage of carbon dioxide present in the same substances—express as CO, = y per cent. | 1. By action of heat alone. 2. By action of acid. Substances to ~ be used: Precipitated chalk, marble, Iceland spar, egg shell (cleaned and dried), oyster shell, calcite, calc spar. Methods to be followed are those just described. Take care to powder the substance thoroughly if it is not in that condition, and use small quantities for the experiments. Collect and tabulate the results :— Composition. Substance used. Pereentage Percentage Percentage CaQ. COz. Total. Chalk. Marble CARBON DIOXIDE 111 From an inspection of the series of results, what deductions do you make ? 7. To determine the Volume of Carbon Dioxide evolved by the action of an acid on a carbonate. Fit up the apparatus as shown in Fig. 164. Test to see if it is perfectly air-tight ; until it is so, it is useless to proceed. Weigh out into the flask (preferably by use of a weighing-bottle) a few grams of the carbonate. Cover it with about 10 c.c. of water. Fill the pipette with strong hydrochloric acid, and refit the flask. Liberate the acid a few drops at a time until the carbonate has com- pletely dissolved ; then warm the liquid to expel the dissolved gas. Allow the gas to cool down to the temperature of the laboratory, FIG. 164 taking care to keep the end of the delivery tube from the aspirator under the surface of water in, or from, the collecting vessel. Measure the volume of water collected, deduct the volume of acid run into the flask, and if an accurate result be required, correct this volume to N.T.P. Calculate the volume of gas obtainable from 1 gram of the carbonate. Why is the “ Winchester ” used ? Would it be necessary (say) in the case of hydrogen being the evolved gas ? Why should the tube leading from the flask go to the bottom of the Winchester, and that which leads out of it come from the top ? What relationship must there be between the volume of the Winchester and the volume of gas evolved ? ' 112 TEXTILE CHEMISTRY Perform the experiment at least twice and take the average of the results if they are nearly identical. Carbon monoxide or carbonic oxide is the lower oxide of carbon. It is of considerable industrial importance, being used in metallurgical operations, reverberatory furnaces for reducing purposes, as an adulterant for coal gas, etc. Methods of Preparation :— 1. Pass carbon dioxide over heated carbon (Fig. 165). An iron tube should be used, and the stream of carbon dioxide should be a slow one. The same preparation goes on in a clear fire (Fig. 166). The carbon dioxide first formed is reduced in the centre by the hot coke to carbon monoxide, which then burns to produce the dioxide again. 2. Pass air over strongly heated coke or anthracite. A mixture of carbon monoxide and nitrogen is obtained, known commercially as “ generator ’”’ or “ producer ”’ gas. 3. Pass steam over red-hot anthracite or coke. A mixture is produced known as “ water gas.” This gas, which has an average composition of 50 per cent. hydrogen, 40 per cent. carbon mon- oxide, 5 per cent. carbon dioxide, and 5 per cent. nitrogen, is used largely as gaseous fuel and as a reducing agent. It can be made very luminous by mixing it with a very small proportion of unsaturated hydrocarbons, and in this form it is used in America in lieu of coal gas. 4, From formic acid, by heating it with strong sulphuric acid. The former can be looked upon as a compound made up of water (H,O) and carbon monoxide (CO). Hot sulphuric acid abstracts the water and liberates the gas. CARBON MONOXIDE 113 5. The usual lecture preparation is from oxalic acid and strong sulphuric acid (Fig. 167). Oxalic acid may be looked upon as being composed of water (H,0), carbon dioxidé (CO,), and carbon monoxide (CO). When heated with strong sulphuric acid, the water is abstracted and both oxides of carbon are liberated. The dioxide is scrubbed out by passing the mixture through two wash bottles containing baryta water, and then through two containing strong caustic soda solution. The gas is present in coal gas in small quantity, in the vapour evolved from lime kilns, and in blast furnace gas. It is produced at-all times when carbon is burnt in an insufficient supply of air—hence *‘ slow combustion ”’ stoves, such as are often met with on the Con- tinent, are liable to emit it, and many fatal accidents have occurred due to defective ventilation in connexion with their use. Zola’s death was due to this cause. Ba(OH), NaOH PROPERTIES It is a colourless gas, tasteless. and practically odourless; very slightly soluble in water, and a little lighter than air. It is extremely poisonous—l1 per cent. in air is fatal to human beings. It burns with a blue lambent flame, the temperature of which is 1,400°C., to form carbon dioxide; it does not support combustion, and has no action on lime water or litmus paper. It explodes when mixed with an equal volume of air or half its own volume of oxygen, and is extremely difficult to liquefy. It acts as a powerful reducing agent at high temperatures. It is absorbed by a solution of cuprous chloride in hydrochloric acid (Fig. 168). The gas is delivered up the Crum tube and a solution of cuprous chloride passed from the cup a few drops at a time. As the gas is absorbed, the mercury rises. It unites directly with certain elements, for example nickel, potas- 8 ; 114 TEXTILE CHEMISTRY sium, and iron, to form carbonyls. The carbonyl of chlorine, COCI,, is known as phosgene gas, which on exposure to moist air forms hydro- chloric acid gas and carbon dioxide. It was used in the Great War as a “‘ poison” gas. Marsh gas or methane is a gas which is produced by the decay of vegetable matter, particularly in swampy districts. A sample may be collected often from a stagnant pool by piercing the bottom mud with a stick. The bubbles of gas as they reach the surface may be ignited. A large percentage of coal gas is methane. It is prepared usually for experimental purposes by heating a mixture of fused sodium acetate and soda lime in a test tube provided with a collar of wire gauze, to prevent cracking the glass (Fig. 169). F1G.168 The gas produced will be found to be lighter than air, and to burn with a fairly luminous flame to form water vapour and carbon dioxide. It is also explosive when mixed with air or oxygen. Analysis of the gas shows that it is composed of hydrogen and carbon only ; it is therefore termed a hydrocarbon. The proportion by weight in which the constituents exist is 12 of carbon to 4 of hydrogen ; the “ picture ’’ of the molecule is thus given as :— H H—C—H or CH,. | H HYDROCARBONS 115 By other chemical reactions it is possible to prepare or isolate from natural substances, like crude rock oil, other hydrocarbons, e.g. ethane, propane, butane, pentane, hexane, etc., and analyses of these com- pounds show that their molecular compositions are represented by the formule C,H,, C;H;, C,H,., Cs;Hi., C.Hi4, etc., the increases in molecular weights being identical (CH.). Such a series of com- pounds is known as an homologous series, and the graphic formule used to represent them are derivable from marsh gas by substitution of the CH, or methyl group in place of the hydrogen atom at the end of the chain. 7 H H in fds Bagel H H HH HCOOH H-C-C-0-H H-C-¢-C-C-H, ete ee hk HH HH Theoretically, there will be an infinite number of possible hydrocar- bons of this series ; as a matter of fact a very large number has been isolated from American rock oil, which is, to all intents and purposes, a mixture of them. When the crude petroleum is fractionally distilled—that is, heated to a gradually increasing temperature, the distillates being carefully collected separately as they are evolved at the various temperatures —first gases,.then liquids of low boiling-points, and then liquids of higher boiling-points are obtained which are used on an enor- mous scale in everyday life, as petrol, paraffin, lubricating oils, salves, etc. These fractions, known as mineral oils, are all mixtures of hydrocarbons of the paraffin series (as it is termed), the first con- taining the lower members of the series, and the latter the higher ones. They are very stable and inert substances, resisting the action of most chemical reagents, particularly acids and alkalis; consequently a mineral oil stain is very difficult to remove from a fabric. In Scotland (and, it is now claimed, in some parts of England) certain shale deposits when distilled in a similar manner yield similar oils, the residual portion of which is known as paraffin wax. The great Russian deposits contain benzoline or benzine, a mixture of higher members of the same series. Coal tar yields benzene (C,H), a hydrocarbon which cannot be correctly represented as an open chain. Kekulé suggested that carbon and hydrogen were arranged as a ce ring 9 me \ 116 TEXTILE CHEMISTRY Benzene, C,H,. Benzene and other hydrocarbons of the same series are obtained from the destructive distillation of coal tar, e.g. naphthalene and anthracene :— Naphthalene, C,,H;3. jee seh 3! 6 b 6 AG H-C GC CG C—H ele ae H—O. | C:2 Cages AZ Dae C C C Been | He) RE Anthracene, C,¢H4o. COMPOUNDS OF CARBON 117 Naphthalene is used as the starting-point in the synthetic prepara- tion of indigo in one important process, and anthracene is the raw product from which is manufactured alizarine (the active colouring principle in madder), used in Turkey red dyeing. Other hydrocarbons are known, e.g. acetylene and ethylene, which are considered to be “ unsaturated ’? compounds. H H foe -H ee Acetylene, C,H. H H Ethylene, C,H,. Substitution Compounds “‘ When methane is mixed with chlorine and exposed to sunlight, a violent reaction occurs, but when the chlorine is diluted with carbon dioxide, and allowed to act gradually, chlorine substitution products are obtained.” — An analysis of these compounds shows that their molecular com- position is represented by the formule :— CH,Cl Mono-chloro-methane. CH.Cl, Di-chloro-methane. CHCl, Tri-chloro-methane (chloroform). CCl, Tetra-chloro-methane (carbon tetrachloride). It is evident that these compounds are methane in which the hydrogen has been replaced by chlorine ; in other words, a substitution has taken place :— H oe ie ie alee Se Cl nce Cl Gr apaes cl AC Chloroform is not yet prepared by this process commercially, the usual way being to act on bleaching powder with ethyl alcohol and distil the mixture on a water bath (Fig. 170). Suitable quantities to use are 180 grams of bleaching powder, 400 c.c. of water, and 11 c.c. of alcohol in a one-litre flask. The heating must be gradual, and there is considerable frothing. The distillate contains alcohol and water as well as chloroform, which settles to the bottom of the mixture. The sp. gr. of chloroform is 1-5, and its boiling-point is 61:5° C. 118 TEXTILE CHEMISTRY Alcohols. This class of compounds can be looked upon as hydroxyl (O—H radicle) substitution products of the hydrocarbons, &.g.i— H H H ae ioe Pa a, are Ha? Nee ee Methyl alcohol, CH;,0H. Ethyl alcohol, C,H,OH. Again we find an homologous series. More than forty alcohols were prepared by Dr. R. H. Pickard, F.R.S., and his research assistants in the chemical laboratories of the Blackburn Technical College a few years ago. Methyl alcohol, also known as wood spirit, and wood naphtha, is obtained in the destructive distilla- tion of wood and beetroot sugar refuse. Its chief uses are as a sol- vent for gums and resins in the varnish industry ; in the preparation of coal-tar dyes; and as an adulterant of ethyl alcohol, in the preparation sold as methylated spirit. Ethyl alcohol, or ordinary alcohol, is prepared by the fermentation of sugar, the weak solution thereby produced being fractionally distilled. Boiling-points Methyl = 66°C. Ethyl = 78-3° C. Specific gravity (at ordinary tem- peratures) Methyl = 0-793 Ethyl = 0-8 Amyl alcohol or fusel oil is a mixture of two or more alcohols higher in the series than ethyl alcohol. : Glycerol (glycerine) is also an alcohol, and contains three hydroxyl groups—C,H ,(OH);. Cetyl alcohol, C,,H3;;0H, is present in spermaceti wax. Chinese wax and beeswax contain alcohols higher still in the fatty series. Phenol (commonly known as carbolic acid) is a compound of the benzene series which resembles an alcohol in some respects :— COMPOUNDS OF CARBON 119 | | or C,H,OH. Ethers. This class of organic compounds is analogous to oxides, the basic radicle being replaced by one or more hydrocarbon radicles, e.g. — H H | | a or (CH;),.0, methyl ether. | H H (C.H;).0, or ethyl ether, i.e. ordi- nary or sulphuric ether. CH,.0.C.H;, or methyl ethyl ether. The two latter may be prepared by what is known as the continuous etheri- fication process. Ethyl alcohol or methylated spirit is carefully run into half its own volume of strong sulphuric acid, without allowing the temperature to rise unduly. It is then distilled at a temperature of 140° C. (in the liquid), a slow stream of alcohol or methylated spirit being passed in as the ether distils off (Fig. 171). Ether gives off dangerously inflam- mable vapour, and great care should be taken to keep flames away from it. Bottles of ether should be kept on the floor and never on a laboratory bench. Very disastrous consequences have occurred due to inattention to this simple precau- tion. Ethyl ether, sp. gr. at 15°C. = 0-7; b.p. = 35°C. Ethyl ether dissolves in 120 TEXTILE CHEMISTRY ten times its own volume of water, and is miscible with alcohol and other organic liquids in all proportions. Chief Uses. As a solvent for fats, oils, resins, etc., and as an anesthetic in surgery. Aldehydes. When a slow stream of air is passed through methyl alcohol some of it vaporizes; and if the gaseous mixture be passed over heated copper gauze, and then the product so formed into water, it will be found that a solution is obtained which has very characteristic properties (Fig. 172). It has a pungent smell, will reduce an ammoni- acal solution of silver nitrate (oxide) to metallic silver, and will restore the colour of Schiff’s reagent, which is made by decolorizing a dilute solution of magenta in water, with a stream of sulphur dioxide. This solution is known as formalin, and it is possible to make it of 40 per cent. strength, in which condition it is usually sold. It is used in large quantities in the manufacture of artificial dyes, and as an antiseptic. The gas is termed formaldehyde, and it has been found to have the composition 2 parts by weight of hydrogen, 12 of carbon, and 16 of oxygen; in other words, there are 2 atoms of hydrogen, 1 atom of carbon, and 1 of oxygen in the molecule, (or graphically) H—C=0 | H Other compounds exhibiting similar properties and containing the radicle CHO have been prepared ; and as they apparently are alcohols which have been deprived of two atoms of hydrogen, they are named aldehydes (Alcohol dehydrogenatum). The name Form indicates that on further oxidation the acid so obtained is formic. The next member of the series is Acetaldehyde. Benzaldehyde, or artificial oil of almonds, or (in the crude form) oil of mirbane, is the simplest benzene aldehyde, C,H,CHO. ACIDS OF CARBON 121 Acids. Hundreds of carbon acids have been prepared and their compositions investigated, and as a result it is firmly established that they all contain the monovalent group COOH, termed the carboxyl radicle. The lowest member of the paraffin series is formic acid, H.COOH, the next is acetic acid, CH,COOH. When these acids react with alkalis to produce salts, it is the hydrogen in the COOH group which is replaced by the metallic base, e.g. :— Sodium formate : : . H.COONa. Potassium acetate f ‘ obs CUOKS: » Calcium acetate ; ; . (CH;.COO) Ca. Oxalic acid is termed a di-basic acid because it contains two carboxyl groups. Its formula is written (COOH).. Sodium oxalate is therefore (COO) ,Na.. Calcium oxalate, (COO) Ca. Other important acids are :— Butyric acid C,H,.COOH (in butter fat). Palmitic acid C,;H;,.COOH (from palm oil). Oleic acid C,,H;;.COOH (from olive oil). Stearic acid C,,H;;.;COOH (from tallow). Note.—Fats are salts of the “fatty acids,” in which the hydrogen of the carboxyl group has been replaced by the tri-hydric alcohol glycerol, instead of a metal. Thus :— From oleic acid (3 molecules) From glycerol (C,,H33.COO); == == O,H;,. For the preparation of these fatty acids, the fat is first saponified by boiling it with caustic soda or potash. Double decomposition occurs, the alkali salt of the acid being formed (which is known as a soap), together with glycerol. The soap can then be hydrolyzed by the addition of a mineral acid, another double decomposition resulting with the formation of the fatty acid (often insoluble in water) and the production of the alkali salt of the mineral acid. As fats always contain more than one glyceride, although one is usually in excess, further manipulations are necessary if a pure fatty acid is required. Acetic acid is prepared by three processes :— (a) Fermentation of dilute alcoholic solutions containing small amounts of nitrogenous and phosphatic food-stuffs, such as beer or light wines, by the microscopically small plant named Mycoderma aceti or mother of vinegar. 122 TEXTILE CHEMISTRY (b) By the quick vinegar process. A large vat (Fig. 173) is made into three compartments by means of two grids, the space between being filled with beech shavings. Holes are bored at intervals in the sides of the barrel to allow air to enter. In the top compartment A vinegar is put, which slowly drops into B by travelling down the pieces of string that hang through the holes in the top grid. The shavings thus become covered with Mycoderma acett present in the vinegar. Dilute alcohol is now put into A, and it ultimately finds its way into C, from which it siphons off at intervals. After two or three passages the alcohol is completely oxidized to acetic acid. (c) From pyroligneous acid, obtained by the destructive distillation of wood. Soda ash is added to the crude distillate to produce sodium acetate, which is crystallized out, purified aN by recrystallization, and then fused. The fused sodium acetate is then f =k \ treated with strong sulphuric acid and OSS ae distilled, when acetic acid is evolved. ( ey A | This is further purified by freezing out \ a Nee “t the acetic acid. Anhydrous acetic acid has a m.p. of 16-5° C. and a b.p. of 118° C. Oxalic acid may be prepared by oxidizing cane sugar (1 part) with strong nitric acid (6 parts) ; and a modification of this process is used industrially for nearly the whole production of oxalic acid. Sawdust is made into a paste with a strong solution of a mixture of equal parts of caustic soda and caustic potash, heated in iron pans to 210° C.; the mixed oxalates of sodium and potassium are extracted with water, and boiled with lime. The resulting calcium oxalate is decomposed with dilute sulphuric acid, separated from the calcium sulphate, concentrated, and crystallized. Formic acid is prepared by heating a mixture of oxalic acid and glycerine and condensing the distillate ; a temperature of 110° C. should be maintained whilst the process is in operation. Formic acid is being used very considerably in the textile industry to-day, and with great success. | Carbohydrates (so called because the ratio of hydrogen to oxygen found in them is the same as that in water) form a class of compounds of complicated chemical structure, the nature of which is not yet thoroughly known. There are two groups :— CARBOHYDRATES 123 1. Sugars: (a) The glucoses (C,H,.0.),.- (b) The sucroses or cane sugar (C,,H,,0,)). 2. Starches and cellulose (C,.H,,0;). Glucose, grape sugar, or dextrose, C,H,,0,, occurs naturally in fruits and honey, and is also prepared industrially in large quantities from starch. One method in use is to raise to boiling-point water containing 1-5 per cent. sulphuric acid. Into this is then run gradually a mixture of starch and water, and boiling is continued for half an hour. The mixture is neutralized with chalk, and concentrated, the calcium sulphate being precipitated. The clear syrup is further concentrated in vacuum pans until it is a thick viscous liquid or a solid. It contains about 70 per cent. glucose, about 30 per cent. maltose, dextrine, and calcium salts of organic acids. If the presence of a small quantity of salt be not objected to, hydrochloric acid may be used instead of sulphuric, and the neutrali- zation effected with sodium carbonate ; the boiling should be continued for at least an hour. A much purer substance can be obtained by boiling cane sugar with dilute acid (see invert sugar). | Glucose is less sweet than cane sugar. Its solubility is: 10 in 12 of cold water ; 1 in 50 of cold alcohol; 1 in 5 of boiling alcohol. It is not blackened easily when treated with strong sulphuric acid, and it is immediately fermented by yeast. It is used for making alcohol, in confectionery and jam, and by dyers and calico-printers as a thickening ingredient. Cane sugar, C,,H..0,,, is the most important of the naturally occurring sugars, and forms an essential article of human diet. Many vegetables and plants contain it, some in sufficient quantities to pay to extract it, e.g. sugar cane, maple tree, beetroot. It is very soluble in water, dissolving to the extent of 67 in 23 at 20° C., and to almost any degree in hot. It is insoluble in alcohol, fuses at 160°C., and does not crystallize on cooling. It is readily blackened by strong sulphuric acid, and is very sweet. It is not fer- mentable by yeast until changed to glucose, and does not reduce Fehling solution. Levulose is found in many ripe fresh fruits and in honey ; it is some- times known as fruit sugar. It is much sweeter than glucose and nearly as sweet as cane sugar. Honey is a mixture of one-half levulose, one-third to one-half dextrose, and some cane sugar. The former is soluble in cold alcohol, and dextrose in boiling alcohol. Lactose or milk sugar, C,,H,,0,,.H,O, is present in milk, and can be obtained by concentrating and crystallizing the whey. Cow’s milk 124 TEXTILE CHEMISTRY contains 4:7 per cent. When heated to 130° C. the water of crystalli- zation is evolved. It is sweeter than cane sugar, but less soluble, e.g. 1 in 6 of cold water, 1 in 2:5 of hot water, and insoluble in alcohol. Maltose, C,,H,.0,,;.H.O, is formed from starch by the action of a ferment, diastase, produced when barley germinates. Grain containing this ferment is known as malt. The best temperature for the conver- sion of starch into sugar by malt is 65° C. Its chief use is as a ferment- able sugar in the preparation of alcohol, as it very readily ferments with yeast. It is less soluble in alcohol than dextrose. Suitable formula for its preparation : Into 350 c.c. of boiling water run 100 grams of starch completely mixed with 100 c.c. of cold water, and stir well. When the temperature has fallen to 65° C., add 7 grams of crushed malt, and keep the mixture at 65° (on a water bath) for one hour. At the end of that time test for sugar and starch. When maltose is boiled with dilute acids it is converted into glucose. Invert sugar contains equal quantities of dextrose and levulose. It can be prepared by dissolving cane sugar in water, adding a little sulphuric or hydrochloric acid, and keeping on a water bath for half an hour at 100°C. The acid is neutralized by addition of barium carbonate or caustic soda, and evaporated to a syrup. 99 20° C. 93 39 > 9% 3? 1 >) 99 40° C. 39 19 9) 99 39 Boiling expels all the gas. It is easily liquefied by pressure (and so comes into commerce in glass siphons and iron bottles), and by cooling (Fig. 187). Pass the previously dried gas into a small bottle surrounded with a freezing mixture of salt, ice, and calcium chloride. Inquid sulphur dioxide is a fairly mobile liquid: poured into water it freezes it, due to rapid evaporation. At 0° C. a pressure of 14 atmo- spheres condenses the gas to a liquid. At ordinary pressures a tem- perature of — 10° C. condenses it. It dissolves phosphorus, iodine, resins, etc. Uses. Sulphur dioxide is largely used as a bleaching agent for goods which must not be bleached by chlorine, e.g. straw, silk, sponge, flannel, blankets, and wool articles generally. Its action in bleaching is due to the gas decomposing the water, which must be present, to form sulphur trioxide, thereby liberating hydrogen, which reduces the colouring to a more or less colourless compound. Alkalis often restore the colour, e.g. flannel which has been well washed with soap returns to its original yellow colour. The gas is used for fumigating purposes, and in the liquid state it finds application as a refrigerating agent. The best test for the identification of sulphur dioxide is its action on potassium chromate paper or solution, which it turns green. Hydrogen peroxide, H,O,. Only two compounds of hydrogen and oxygen are known—water and hydrogen peroxide, which may be looked upon as oxide of water. It is prepared by the action of several acids on barium peroxide, e.g. carbonic, hydrochloric, sulphuric, phosphoric, and hydrofluoric. In all cases the temperature must be kept low enough to prevent the decomposition of the hydrogen peroxide formed. If made with sulphuric acid, the acid must be diluted considerably. On the commercial scale it is often prepared with the aid of phos- phoric acid, but for laboratory purposes the best results are obtained by using hydrofluoric acid. 134 | TEXTILE CHEMISTRY A well-made cigar box should be soaked in hot paraffin wax, and then coated with a layer of that substance ; a suitable wooden stirrer should be treated in the same way. The box should be partly filled with ordinary hydrofluoric acid diluted with four or five times its own volume of water. Barium peroxide is fed in with constant stirring until the liquid is no longer acid. The precipitate of barium fluoride is allowed to settle, when a strong solution of hydrogen peroxide will be found in the supernatant liquid. Sodium peroxide may also be used, the reaction with hydrochloric acid being— Na,O, + 2HCl = 2NaCl + H,0,. The aqueous solution obtained as above is concentrated in vacuo, over strong sulphuric acid. It comes into commerce labelled 10 volumes, 20 volumes, etc., which means that when treated with acidified potassium permanganate, 1 volume of solution yields 10 or 20 volumes of oxygen. (N.B.—Half of this, however, comes from the perman- ganate) :— K,Mn,0, + 5H,0, + 3H,SO, =~ K.SO, + 2MnSO, ate 8H,O = 5O,. PROPERTIES In the pure condition it is a colourless, odourless, syrupy liquid, of very bitter taste, sp. gr. 1-45, and very unstable. Diluted with water, in which condition it is usually met with, it is a very active oxidizing substance, and a powerful bleaching agent, e.g. :— PbS + H,O, = PbSO, + 4H,O (the reaction which occurs when it is used to “restore”’ oil paintings). H,O, + H, = 2H,0 (hydrogen oxidized to water). LABORATORY EXERCISES IN THE PREPARATION AND ESTIMATION OF HYDROGEN PEROXIDE 1. Preparation. Weigh out about 30 grams of barium peroxide. To 40 c.c. of “ bench ” dilute sulphuric acid add 160c.c. of water. Stir into this the barium peroxide, a gram or so at a time, keeping the temperature from rising. When all has been added, allow it to settle and pour off the clear supernatant liquid, which should be a dilute solution of hydrogen peroxide. BaO, + H,SO, = H,O, + BaSQ,. 2. Tests. Add some of it to a solution of potassium iodide—iodine is liberated, and turns the solution yellow. Collect it by shaking up with two or three drops of chloroform—a violet solution in the latter liquid is obtained. HYDROGEN PEROXIDE 135 Add some to a dilute solution of potassium permanganate—the latter is decolorized. Dip a piece of filter paper into a solution of lead acetate, expose it to sulphuretted hydrogen gas until it is converted into black lead sulphide, dry it and then place in a solution of hydrogen peroxide. The sulphide will be oxidized to white lead sulphate. 3. Hstimation of Amount in Solution by titrating against Potassium Permanganate. Take 10 c.c. of a solution of hydrogen peroxide in a flask, add excess of dilute sulphuric acid, and run in from a glass-stoppered burette a standard solution of permanganate, till a pink colour is just permanent. A suitable strength of permanganate is one known as N/10, i.e. a solution containing 3-163 grams per litre. From an examination of the equation representing the reaction as given on the previous page, it will be seen that 316-3 grams react with 170-1 grams of hydrogen peroxide to form 160 grams of oxygen. Now N/10 permanganate contains -003163 grams of K,Mn,O, per c.c., and suppose the volume required = v c.c., Then amount of H,O, in 1 c.c. of original solution = 170-1 -003163 x v 3163 10 Perform the experiment three times and find the average. A 10-volume solution should contain about -03 grams per c.c. 4, Hstimation by collecting the Oxygen evolved when mixed with acidified Permanganate. Use the apparatus shown in Fig. 188. Fisa 4 oz. flask into which is put a measured volume of hydrogen peroxide solution, say 10 c.c., and an equal quantity of dilute sulphuric acid. G is a burette which contains a fairly strong solution of potassium permanganate, and which can be run into F as desired, by means of a glass tap. E is a tube leading from F to a gas-collecting apparatus B made out of an inverted 100 c.c. burette. D is a swivel made from the neck of a broken Wurtz flask, in which works the gauge tube C. To experiment :—- 4 Put peroxide solution and acid into F, and permanganate into G, taking care that the teat of the burette is filled. Fill B with water and fit up as shown in diagram. Open tap T to adjust pressure, and read the level of water at A. Run in permanganate from G until the solution in F is permanently pink. Readjust gauge tube C so that the top is level with the water surface in B. | Determine, by reading the new level, the volume of water expelled from B, subtract volume of liquid run in from G. = 0001701 X v grams. 136 3 TEXTILE CHEMISTRY This gives volume of oxygen obtainable by using 10 c.c. of hydrogen peroxide ; calculate for 1 c.c. . O Ozone. QO, or 0,0 or | »o is a gas found in small quantities in O the atmosphere in certain districts. Its formation is said to be due to electrical action. Ozone is easily produced from oxygen or air, the process being termed ozonization, e.g. :— 1. An electrical machine working in air yields an amount that is easily recognized by the sense of smell. 2. If air be passed slowly over freshly scraped and moist yellow phosphorus, and the gas tested as it issues, it will be found to be ozonized (Fig. 189). 3. Oxygen is passed through a glass vessel the outside and inside of which are respectively connected to the terminals of an induction coil. Fig. 190 shows Ostwald’s form, in which connexion is made to the coil by platinum wires dipping into dilute sulphuric acid. Copper wires will also serve the purpose if cleaned after previous use. Fig. 191 shows a Siemen’s ozone tube, and Fig. 192 a simple modification of the same. Ozone is also produced :— 1. When dilute sulphuric acid is electrolysed, especially if the ~ current be strong and the electrodes made of thin platinum wire. 2. When a red-hot platinum spiral is suspended in ether vapour. 3. When manganese dioxide, or potassium permanganate, or OZONE 137 barium peroxide is acted upon by sulphuric acid to produce oxygen, ozone is always liberated. PROPERTIES The chemical properties of ozone are very characteristic, although in some cases they are very analogous to those of hydrogen peroxide. It has a penetrating and rather unpleasant odour somewhat resembling chlorine ; when heated it is decomposed into oxygen; it is slightly soluble in water (0-45 per cent. by volume), condenses to a liquid at — 181° C., and in that condition it is highly explosive. It has powerful oxidizing and bleaching properties due to the ease with which it decomposes to liberate oxygen in an atomic condition. ~ Tago - infotL ) FIG.190 LABORATORY EXERCISES WITH OZONE 1. Investigate its action on a solution of potassium iodide. 2. What happens when “starch iodide” paper is brought into | contact with it ? 3. Perform the Houzeau test. Take a piece of litmus paper which has been made faintly acid with very dilute nitric acid, and dip it into a solution of potassium iodide. Expose it to ozone. It is immediately turned blue. Reaction: 2KI + O, + H,O = 2KOH + I, + O,. The caustic potash (KOH) is alkaline, and this turns the red litmus blue. 4. Pass ozonized oxygen through a piece of rubber tubing. The gas which emerges has lost its ozone. Why ? 5. Pass some through a heated glass tube. What happens ? a TEXTILE CHEMISTRY 6. Shake some up with a globule of mercury and note that “ tails ” are produced. Can you explain this ? Estimation of the Percentage of Ozone in a Sample of ozonized Oxygen. Brodie’s method: The apparatus used is a special form of pipette shown in Fig. 193. Its capacity between m and m’ is known. It is first filled with strong sulphuric acid by opening tap a, and closing tap 0, and the pipette put in a vessel containing water at a definite temperature. The end near @ is connected to the supply of ozonized gas and sufficient drawn in to fill the pipette to the mark m. Tap a is closed, a vessel containing a solution of potassium iodide is placed under the Fig.193 other end of the pipette, and tap b opened. The gas from m’ to m is now forced through the iodide solution, and finally the iodine liberated by this volume estimated. A simpler and equally efficient apparatus is shown in Fig. 194, which is made by bending the stem of a pipette. Ozonized oxygen may be made in it (A), or passed into it. To estimate the ozone, it should be inverted in a wide test tube containing strong sulphuric acid, and whilst it is slowly depressed in this liquid, the other end should be immersed in a solution of potassium iodide. When the strong sulphuric acid reaches the graduation mark the volume of gas denoted by the capacity of the pipette has been bubbled through the iodide solution. The free iodine is then estimated by means of a standard solution of sodium thiosulphate. SECTION XII ALUMINIUM T has been estimated that this element forms one-eighth of the | earth’s crust, but although so plentiful only one or two of its compounds can, up to the present, be successfully worked for the metal—and these are by no means the most plentiful. The metal is now prepared entirely by electrolysis. The electrolyte is a fused mass of cryolite, fluorspar, and alumina. Fig. 195 represents in principle the construction of the cell, the temperature of which is nearly 900°C. The oxygen which is liberated combines with the carbon of the electrodes to form carbon monoxide, the metal sinking to the bottom of the chamber, from which it is periodically tapped. The alumina, Al,O3;, is the portion of the electrolytic liquid which is decomposed, the fluorspar and cryolite acting as the flux and solvent. The annual production of aluminium has increased enormously during the last twenty or twenty-five years, and the price has rapidly fallen. Whereas in 1855 the commercial quality cost £3 10s. per oz. and was a chemical curiosity, it is now (normally) 6d. a lb. 139 140 TEXTILE CHEMISTRY PROPERTIES It is a “tin white’ metal of great tensile strength, very ductile and malleable, extremely sonorous, and has a low sp. gr. (2-6); _ its melting-point is 625° C. It does not tarnish in ordinary air at ordinary temperatures, but burns when strongly heated to form a white oxide called alumina (Al,0,;). Nitric acid has not much action on it, but it is dissolved by hydrochloric to form the trichloride. Aluminium is much more readily attacked by alkalis, particularly caustic soda, potash, and washing soda. A solution of common salt will act upon it, and so will organic acids in the presence of this com- pound—consequently alkaline liquids must not be boiled in aluminium vessels. It is a powerful reducing agent, and is used in the “ Thermit ” process in the powdered condition for reducing oxides of iron, man- ganese, chromium, etc., to the metallic condition in small welding operations. Several important alloys are made from it, of which the best known are aluminium bronze (90 per cent. copper, 10 per cent. aluminium) and magnalium (90 per cent. aluminium, 10 per cent. magnesium, etc.). | Uses. For metallic parts of airships, aeroplanes, balances, cooking utensils, surgical instruments, paint, reducing agent, ornamental and decorative purposes. In some ways its use is restricted by the difficulty experienced in soldering it—no really satisfactory method of doing this has been invented yet. Chief Compounds of Aluminium. 1. The Alums. These are double sulphates; the potassium salt was one of the earliest compounds of the metal prepared. Al,(SO,);. K,S0O,.24H,0. 2. Clay. Kaolin, or China clay, contains a large percentage of © the metal. Its composition is Al,O3;.2Si0,.24H.0. Clay of all kinds consists essentially of silica and alumina in varying proportions, associated with smaller quantities of lime, magnesia, oxides of iron, and alkali metals. 3. Cryolite. 3NaF.AIF;. Largely used as a flux in certain metal- lurgical operations. 4. Aluminium oxide, Al,O,—alumina. In a natural condition it occurs associated with small quantities of other metallic oxides as bauxite, corundum, emery, ruby, amethyst, sapphire, topaz, turquoise. 5. Aluminium trichloride, Al,Cl,, used for carbonizing cotton in mixtures of cotton and wool, is prepared in the anhydrous condition ALUMINIUM, ZINC, MAGNESIUM 141 by passing chlorine gas over heated aluminium foil, and for ordinary purposes by the action of strong hydrochloric acid on the metal and concentrating the solution. 6. Other salts used for textile purposes are the acetate, made by dissolving the hydroxide in acetic acid, or by the addition of lead or ‘ calcium acetate solution to a solution of aluminium sulphate. The impure commercial acetates of aluminium are used by dyers and calico-printers as mordants for alizarine reds, and on that account are known in trade as “ red liquor.” Aluminium acetate is a very efficient “ shower-proofing ”’ chemical for cotton or wool cloth. The material to be treated is put for some hours in a warm solution of the salt (strength 8°-10° Twaddell), then passed through a soap solution containing 50-75 grams of soap per litre at a temperature of about 45°C., dried in a hot chamber and calendered. Japan wax, gums, oils, paraffin, wax, etc., are sometimes added to the soap bath. Preparation of Alum. 1. In the laboratory, by adding aluminium sulphate to potassium sulphate in proper proportions and crystallizing from the hot solution. 2. From alum stone—Al,(SO,)3;.K,S0,.2Al,0;.8H,O. The material is calcined and then the liquid lixiviated with hot water when the Al,O; remains undissolved. The alum may be crystallized out after sedimentation. Or, the calcined mass is treated with sulphuric acid to dissolve the oxide and then before crystallization the requisite amount of potassium sulphate is added. The former method produces what is called Roman alum. The iron present as an impurity may be separated by filtration and recrystallization. 3. From alum shale, which is a rocky mass consisting of aluminium silicate and iron pyrites. It is first roasted and exposed to air and moisture. The pyrites is oxidized and sulphuric acid is formed, which acts upon the shale, making aluminium sulphate. The mass is lixiviated, concentrated, and potassium chloride added. The iron sulphate which has also been formed is decomposed to chloride, and potassium sulphate produced. When concentrated it is well stirred to ensure the precipitation of the alum in small crystals—the product being known as “ meal.” 4. From bauxite (Al,0;). This mineral is roasted, treated with sulphuric acid, and lixiviated with water. The solution is concentrated, potassium chloride added and then crystallized. 5. From clay. Purified and calcined China clay is boiled with oil of vitriol for several hours, then with several times its weight of water till it makes a syrup. It is filtered and cooled, the correct amount of potassium sulphate added and then crystallized. 142 TEXTILE CHEMISTRY Alum is very soluble in hot water, but only slightly in cold :— 100 grams of water at 0°C. dissolve 3-9 of alum. 93 399 be) 50° C. Bs 44-1] \ 99 ” 99 re) 100° C. 9 357-5 » It is insoluble in alcohol; when heated it melts and dissolves in its own water of crystallization, which is gradually expelled, until at a dull red heat a non-crystalline and anhydrous substance is obtained called burnt alum, which is much less soluble in water than the crystalline form. The chief use for alum is as a mordant in dyeing. When sodium carbonate or sodium hydrate is added to alum solution, till the pre- cipitate first formed is redissolved, a basic alum (called neutral alum) is formed. This compound very readily gives up alumina to fibres impregnated with it. If the fibres coated with this mordant be now passed through solutions of certain colouring matters, the two unite to form a coloured “lake ’’ which is not removed by boiling water. - Aluminium sulphate, also known as cake alum, patent alum, concentrated alum, and in the impure condition containing considerable quantities of iron, as alumino-ferric, is prepared by dissolving alu- minium hydroxide, bauxite, or clay in sulphuric acid. It has an acid reaction and is used instead of alum for many purposes. Aluminium hydroxide is formed as a white gelatinous precipi- tate when caustic alkalis are added to solutions of aluminium salts. It has considerable application as a precipitating and clarifying agent. ZINC Zinc, its alloys and compounds, are of great practical importance. The metal itself is used in large quantities for coating sheet iron (so-called galvanized iron), and in the powdered condition as a reducing agent for indigo. Brass, bronze, and German silver—in all of which zinc is present— have a very wide application. Zinc oxide is used as a pigment, and zinc chloride is the most generally used antiseptic in the cotton industry. Other important compounds are white vitriol, or zinc sulphate, zinc carbonate, and zinc sulphide. The ores used for the extraction of the metal are :— 1. Calamine or zinc carbonate. 2. Blende, black jack or zine sulphide. (‘The colour of this ore is due to the presence of sulphide of iron as an impurity.) 3. Red zinc ore—an impure oxide. _ Extraction. The ore is first calcined to convert it into the oxide, and then it is mixed with carbon and strongly heated in retorts, when the oxide is reduced first to the metallic condition and then vaporized. The gaseous metal is condensed in receivers. | ALUMINIUM, ZINC, MAGNESIUM 143 In the Belgian process the retorts are small, being about 3-4 ft. long and 9 in. in diameter, as many as 80 being put in one furnace, each holding a charge of about 40 lb. The Silesian furnace contains about 30 retorts, @ shaped in section, and are much larger than those used in Belgium, each holding a charge of 5 cwt. The condensing-chambers are attached to the mouths of the retorts as shown in Fig. 196. The metal so obtained is called “ spelter’’ and is very impure— lead, iron, tin, antimony, arsenic, copper, cadmium, magnesium, and aluminium may all be present. It may be purified by redistillation, but a better product is obtained if it is dissolved in acid, the carbonate produced by precipitation, and this compound reduced with charcoal made from sugar. Zinc is very malleable at a temperature of 121° C., but when heated to 204° C. it again becomes brittle and can be powdered up in a mortar. When exposed to air it is slowly attacked to form zinc oxide, which gradually changes to the carbonate; and this layer when completely formed over the surface protects it from further oxidation. The metal is very soluble in dilute acids, alkalis, and slightly in boiling water or steam. The salts of zinc so formed are very poisonous, and therefore zine vessels are not suitable for cooking utensils. Galvanized cisterns for storing water are on that account objectionable unless they be coated finally with a layer of tin. Zinc chloride is a very important textile chemical, and is made by dissolving all sorts of waste zinc, ashes and skimmings, in hydro- chloric acid. It can also be made by dissolving calamine in the same acid. Commercial zinc chloride is liable to contain several impurities, the methods for detecting which are given in Section XV, pages 188-189. The manufacturer endeavours to produce a product free from acid and iron. For use in this country it is usually sold as a strong solution in water—about 100°-104° Twaddell, but for export purposes it is further concentrated till it sets as a solid on cooling and contains up to 95 per cent. of anhydrous zinc chloride. The substance known in the cotton trade as “zinc,” or “ anti- septic’ is zinc chloride. Occasionally the term “anti” is used to denote magnesium chloride. | Idd TEXTILE CHEMISTRY By boiling a solution of zine chloride of sp. gr. 1:7 with excess of zinc oxide, a basic or oxychloride is obtained which dissolves silk and is used to estimate that material when mixed with wool and vegetable fibres. Zinc chloride is very hygroscopic, and a very efficient “‘ fungicide ” for cotton. It is very soluble in water, slightly in alcohol; has a melting-point of 250°C., and a boiling-point of 730°C., but while being heated to that temperature, particularly if water be present, considerable decomposition results, hydrochloric acid being evolved with reduction to oxychloride. Zinc sulphate, known in the crystalline condition as “ white vitriol,” ZnSO,.7H,O, can be made by dissolving the metal in dilute sulphuric acid, or roasting the ores and then treating them with the acid and recrystallizing. It has some application in dyeing and caliadroanennen ; it is used in the tanning industry as a preserving and clarifying agent, as an astringent in eye “ lotions,” and as a dryer for boiled oil when used in paint. Zinc oxide and zinc sulphide are both used as pigments. The former can be prepared by burning the metal in air, and the latter by precipitating from solutions of the chloride or sulphate with sul- phuretted hydrogen in alkaline solution, or heating an intimate mixture of zinc dust with half its weight of powdered sulphur. Compounds of zinc heated on charcoal in an oxidizing flame give a white infusible residue. If this be allowed to cool and a few drops of cobalt nitrate solution dropped on it and the mass again heated, a very distinctive green residue is formed. MAGNESIUM AND ITS CHIEF COMPOUNDS The element itself does not occur free in nature, but it is present in several minerals, the most important being :— 1. Magnesite or magnesium carbonate, MgCOQ3. 2. Dolomite or magnesium limestone—mixed carbonates of magnesium and calcium. 3. Kieserite—magnesium sulphate, MgSO,.H,0. 4, Carnallite—magnesium and potassium chlorides :— MgCl.KC16H,.O. 5. Epsom salts—magnesium sulphate, MgSO,.7H,O. 6. Various silicates, e.g., talc, horneblende, asbestos, olivine, meerschaum, serpentine. . The metal is prepared by the electrolysis of the fused chloride. A temperature of 700°C. is obtained by surrounding an iron crucible with burning “ gaseous fuel.” ‘The crucible is the cathode. The ALUMINIUM, ZINC, MAGNESIUM 145 anode is a stout carbon rod, surrounding which is a porous cylinder to convey away the liberated chlorine. PROPERTIES OF THE METAL Sp. gr. 1:75; melting-point, 632°C.; boiling-point, 1,100° C. It is a silver-white metal, ductile at high temperatures and fairly malleable. It oxidizes slowly in moist air, but not in dry air or oxygen. Heated in air, it burns, giving a dazzling white flame rich in chemical rays. On this account it is used as an artificial illuminant in photography, but, owing to the production of a white smoke of magnesium oxide, it cannot be used long at a time. Burning mag- nesium is often employed to examine and compare dyed fabrics for shade. Heated in steam, it decomposes it, forming the oxide and liberating hydrogen. Lighted, and plunged into carbon dioxide, it continues to burn, decomposing the gas with liberation of carbon and formation of magnesium oxide. Heated in nitrogen, it combines with it to form a nitride, Mg,N,. This was one of the earlier methods adopted for the isolation of argon from the atmosphere. It is very soluble in dilute acids and solutions of ammonium salts, with liberation of hydrogen, this occurring even with nitric acid if it be sufficiently dilute and a few inches of magnesium ribbon used. It is insoluble in caustic potash or ee It is a powerful reducing agent at high temperatures. ‘The chief compounds of magnesium are the chloride, oxide, sulphate, and carbonates. Magnesium chloride (MgCl.) can be prepared :— 1. From the natural carnallite by fractional crystallization. Mag- nesium chloride is much more soluble than potassium chloride, and thus remains in the mother liquor after most of the latter has been deposited. The crystals when formed by further concentration have the composition MgCl,.6H,O, and are very deliquescent. 2. By burning the metal in chlorine :— Mg + Cl, = Mg(l,. 3. By dissolving the metal in hydrochloric acid :— Mg + 2HCl = MgCl, + H,. 4. By dissolving the oxide in hydrochloric acid :— MgO + 2HCl = MgCl, + H,.O. 5. By dissolving the carbonate in hydrochloric acid :— MgCO, + 2HCl = MgCl, + H,O + COQ,. To obtain the anhydrous salt, concentration of the solution to dryness will not suffice, as it undergoes a series of chemical changes which are represented finally by the equation :— MgCl,.6H,0 = MgO + 2HCl + 5H,0. 10 146 TEXTILE CHEMISTRY Although the anhydrous chloride is never required for textile purposes, this reaction is very important because it explains what happens in “singeing’’ when a cloth contains magnesium chloride. In this case it is the liberated hydrochloric acid which, acting on the cotton, converts it into hydrocellulose and so produces tendering of the fabric. If ammonium chloride be added to a solution of magnesium chloride, a double salt is formed, MgCl,.NH,Cl.6H,O. When this is heated it is first dehydrated, and then the ammonium chloride vola- tilizes, leaving the anhydrous magnesium chloride as a fused mass, which congeals to a white crystalline solid. Magnesium chloride is a very deliquescent substance, and on this account it is largely used as a sizing ingredient, particularly in the “heavy trade.” Its use is attended with considerable danger unless zine chloride or some equally efficient antiseptic be used with it, as it has no antiseptic properties whatsoever. The substance is often known under the name of “ anti’—a most unfortunate term, as it tends to convey the impression that it has preservative properties. | Magnesium oxide or magnesia (MgO) is obtained by :— 1. Burning magnesium in air or oxygen. 2. Calcining magnesium nitrate (MgNO;), = MgO + 2NO, + O. 3. Calcining the carbonate or basic carbonate :— MgCO; = MgO + CO,. 4. Converting the chloride into carbonate, and then gently igniting the dried powder. If excess of sodium carbonate is added and the mixture well boiled, the composition of the carbonate produced is 2MgCO;.Mg(OH)..2H,O. On ignition this becomes 3MgO + 2CO, +3H,0. The hydroxide is obtained by dissolving the oxide in water. Solubility of the oxide is about 1 in 55,000 of cold water, and Jess in hot. Magnesium sulphate (MgSO,) occurs naturally in the Stassfurt deposits as kieserite, MgSO,.H,O. Upon treating this with water and recrystallizing, the pure salt is obtained as MgSO,.7H,0. It is present in many mineral springs, and from its occurrence in one of them has been named Epsom salts. When the carbonate is treated with dilute sulphuric acid, the following reaction occurs :— Mg0O, + H.SO, = MgSO, + H,O + CO,. If magnesium limestone is used, sulphates of lime and magnesia are both formed. The former, being insoluble, may be removed by sedimentation, but obtained in this way the magnesium sulphate is not so pure as that made from kieserite. SULPHUR 147 The salt has a bitter taste ; it is completely dehydrated at 200° C. ; its solubility at ordinary temperature is 126 in 100 of water. It has a considerable application in medicinal saline mixtures, and in textiles it is used as a finishing material in certain kinds of finishes for cotton cloth. For this purpose it is advisable that it should be free from traces of magnesium chloride, as the presence of the latter may lead to partial solution of the sulphate when the cloth is in a humid atmosphere. When the cloth becomes drier, the sulphate recrystallizes in the fibre, which results in tendering of the fabric, particularly if it be repeated once or twice. Magnesium carbonate, MgCO;, occurs naturally as magnesite, and as magnesium limestone mixed with calcium carbonate. It is decomposed by heat much more easily than calcium carbonate to form the oxide with liberation of carbon dioxide. SULPHUR This is an element which occurs in large quantities in nature, both in the free state and in combination. 1. As native sulphur (i.e. sulphur uncombined, but mixed with earthy matter) in all volcanic districts, e.g. Italy, Sicily, Iceland, United States. 2. Forming sulphides with certain metals, it occurs in most ores, e.g. pyrites or iron sulphide, copper pyrites, galena or lead sulphide, zine blende, cinnabar or mercury sulphide, etc. 3. Sulphates which contain sulphur combined with a metal and oxygen, e.g. gypsum, alabaster or calcium sulphate, heavy spar or barium sulphate, kieserite or magnesium sulphate, etc. Sulphur is prepared chiefly from native sulphur, but considerable quantities are also obtained from alkali waste and coal-gas waste. 1. From native sulphur. It is liquated where found, i.e. it is stacked on the side of a slope, covered with a turf roof and fired, the entrance of air being reduced to a minimum. Some is burnt, which supplies the heat to melt the rest, which then flows along the sloping floor until it gets outside the stack (Fig. 197). This simple process separates it from a considerable quantity of the earthy matter with which it was mixed. In this condition it is generally shipped. It is afterwards purified by redistillation (Fig. 198). 2. From alkali waste (Mond’s process). Alkali waste is a mixture of calcium sulphide and. calcium oxide. It is suspended in water and oxidized by blowing a current of air through it. This produces such compounds as calcium thiosulphate, calcium polysulphides, calcium hyposulphide, etc., and liberates a large quantity of sulphur. It is alternately oxidized and lixiviated, and finally hydrochloric acid is 148 TEXTILE CHEMISTRY added to precipitate the remainder of the sulphur, which is purified as before by distillation. 3. From coal-gas waste, which is hydrated ferric oxide which has absorbed the sulphuretted hydrogen from coal gas. It is exposed to air and moisture, by which means sulphur is liberated. The mass is afterwards distilled. 4. By mixing sulphur dioxide and sulphuretted hydrogen gases in the presence of water vapour sulphur is precipitated. Sulphur can be prepared in at least four distinct varieties or allotropic modifications. 1. Rhombic sulphur, made by dissolving sulphur in carbon di- sulphide, filtering and allowing the clear liquid to evaporate slowly at ordinary temperature. : 2. Prismatic sulphur, prepared by care- fully melting sulphur in a beaker, allowing it to stand until it has partly solidified, and then pouring away the still liquid portion. Prismatic crystals line the sides and bottom of the beaker. 3. Plastic sulphur is formed when melted sulphur is poured in a thin stream into cold Fig. 199 water (Fig. 199). 4. White amorphous sulphur is produced when carbon disulphide is exposed to sunlight, or when hydrochloric acid is added to ammonium sulphide. It is insoluble in carbon disulphide. PROPERTIES OF THE RHOMBIC AND STABLE VARIETY Insoluble in water; soluble in carbon disulphide; burns with a pale blue flame to form sulphur dioxide; non-conductor of SULPHUR 149 electricity ; bad conductor of heat; yellow in colour; melts at 114°C. to a pale yellow liquid, which is very mobile. Heated still further, the liquid gradually darkens in colour and becomes more and more viscous, until at 230° C. it is almost black and can scarcely be poured from the vessel; heated to a higher temperature, it becomes somewhat less viscid but still remains black, and ultimately a f1g.200 To Use.—Put in the acid and iron sul- phide. Open the tap—the acid acts on the sulphide and liberates the gas, which passes through the solution. When enough has passed, close the tap; the gas then collects and forces the acid back into its own tube, thus stopping the action. The acid and sulphide tubes are connected by india-rubber tubing. boils at 448°C. In cooling it goes through similar changes in the reverse order. Sulphur is used largely in the manufacture of sulphuric acid, ebonite, vulcanite, matches, gunpowder, dye-stuffs, sulphides, etc., and also as a fungicide and insecticide. Hydrogen sulphide, or, as it is commonly termed, sulphuretted hydrogen, is by far the more important of the two compounds which sulphur forms with hydrogen. It is found dissolved in certain natural mineral waters, e.g. at Harrogate, and it is evolved from active volcanoes. 150 TEXTILE CHEMISTRY Preparation :— / 1. If the pure gas be required, antimony trisulphide is treated with strong hydrochloric acid. | | 2. For ordinary purposes ferrous sulphide (made by melting powdered sulphur with iron filings until combination results) is acted upon with dilute sulphuric acid or moderately strong hydrochloric acid in one or other of the forms of apparatus shown in Figs. 200-203. The correct method of using each form is given under its own illustration. ; In Fig. 201 the iron sulphide is placed in the vessel A, and water in the wash bottle D. Hydrochloric Acid (1 : 1) is poured through the fic.202 Acid is put in the top bulb, from which it passes to the bottom and then to the centre. When in use the aspirator containing the acid should As soon as it reaches the sul- be placed on a block of wood. phide the tap should be closed. After using the gas the tap should be closed, then the As the gas accumulates the acid aspirator containing the acid put on the bench and the is forced back. one containing the sulphide put in its place. funnel E and into the reservoir F until the bottle G is filled, and the acid begins to fall on the sulphide in A. The evolved gas passes up through the water in D, and is drawn off at the tap H, which is placed outside the cabinet, away from the working parts of the apparatus. When the tap is closed the acid is driven into the bottle G, and thence to the reservoir F. Communication between G and A can be stopped by the clip I. Used acid is withdrawn from A into the basin B by removing the glass rod C. ; 3. It may also be prepared from its elements by direct union, by passing a stream of hydrogen and sulphur vapour through a strongly heated tube. HYDROGEN SULPHIDE 151 4. The gas is also produced when organic matter containing sulphur decays, e.g. eggs. When coal is distilled, sulphuretted hydrogen is evolved, and on that account the coal gas is “scrubbed ” before it reaches the gasometer. PROPERTIES Colourless gas; extremely foetid smell and very poisonous if breathed into the lungs. It is on this account that the gas is generated in special forms of apparatus, which should be kept (and used) in a fume chamber if possible. It is soluble in water to the extent of about 3 in 1 at ordinary temperatures. Its solution is acid to litmus, and decomposes after a time on exposure to air—sulphur being precipitated. The gas burns with a bright blue flame, producing sulphur dioxide and water. It forms an explosive mixture with oxygen when mixed in the proportion of 2 to 3. When passed into strong sulphuric acid it is decomposed—sulphur dioxide, water, and sulphur being formed. It is absorbed by lime, but calcium chloride has no action on it. In contact with metals, or when passed into metallic solutions, it produces sulphides, e.g. tin, lead, silver, etc. The “lead reaction ”’ is used as a test for the gas. The chief use for hydrogen sulphide is as a laboratory reagent. Its reactions in this respect form the basis of the ordinary methods of analytical chemistry. It is also used—generally in the form of ammonium sulphide—for “ oxidizing ”’ (sic) copper and silver in art metal work. Preparation of Hydrogen Sulphide—experiments illustrating its Proper- ties. Its action on metallic Solutions in the Formation of Sulphides. Arrange the apparatus shown in Fig. 200. Place ferrous sulphide in left-hand vessel and hydrochloric acid —half strong, half water—in the other. Open the clip; the acid flows amongst the iron sulphide and evolves sulphuretted hydrogen. Tests. 1. Is it soluble in water ? 2. Describe its smell. 3. Does it burn? Does it support combustion ? 4. Action on lead acetate paper. Note its action on “ metallic solutions.” © Pass a stream of sulphuretted hydrogen through each in turn. Note. 1. Whether a precipitate of a sulphide is produced, i.e. Is it soluble or insoluble in water ? 2. The colour of the precipitate (if there be one). 152 TEXTILE CHEMISTRY Test :— Filter off,\ 3. Its solubility in hydrochloric acid. wash, and divide 4. a », ammonia. the precipitate 5. ts », nitric acid. into five parts in 6 7 ,, ammonia disulphide. separate T.T.’s. a yf », ammonium chloride. Carefully record all your results. Note what a large number of metallic solutions yield sulphides when treated with hydrogen sulphide, and the great similarities when treated with certain reagents. There are also many points of difference when individually considered, especially in regard to colour. It is on this account that the reactions of the sulphides of the metals are most often used as the basis of analytical chemistry. SoME OF THE PRINCIPLES OF ANALYSIS I. Sulphides which are insoluble in hydrochloric acid—that is, if a solution of any of these metals be first acidulated with hydrochloric acid and then the gas passed through: these sulphides will be pre- cipitated :— Mercury (ous, ic) silver, lead (partly), copper, cadmium, bismuth, tin (ous and ic), antimony, and arsenic (often called the copper group). All the rest of the sulphides are soluble either in hydrochloric acid or water. II. Sulphides which are soluble in hydrochloric but insoluble in ammonium hydrate :— Iron (ous and ic), chromium, aluminium, nickel, cobalt, zinc, manganese, magnesium. (Iron and zinc group.) III. Sulphides which are soluble in acid, alkali, and water :-— Barium, strontium, calcium, potassium, sodium, ammonium. IV. Silver, mercury (ous), and lead (partly) are precipitated as chlorides when the hydrochloric acid is added to the solution. (Silver group.) It is also possible to subdivide the groups. Thus— In the copper group : arsenic, antimony, and tin sulphides are all soluble in ammonium disulphide. (Arsenic sub-group.) In the iron and zinc group : The hydrates of iron, chromium, and aluminium are insoluble in water. Therefore when ammonium hydrate is added to solutions of salts of these metals, a precipitate is produced before sulphuretted hydrogen is passed. Again, magnesium sulphide is not precipitated in the presence of ammonium chloride. Its phosphate is insoluble in water. In Group III a division may be made by precipitating barium, strontium, and calcium as carbonates—which are all insoluble in water. (Barium group.) | These operations are generally referred to as Grouping. QUALITATIVE ANALYSIS 153 The order of working will therefore be as follows :— 1. Prepare a solution of the salt in water. 2. Add enough hydrochloric acid to make the solution acid to litmus paper. A preciptiation indicates presence of silver group. (Silver, mercury (ous), lead.) No precipitation indicates the absence of silver group. 3. Filter off the precipitate (if there be one). 4. Pass through the solution (or filtrate) sulphuretted hydrogen gas. A precipitation indicates presence of copper group. Filter off and test its solubility in ammonium disulphide. If insoluble—absence of arsenic sub-group. If soluble—it is arsenic, tin, or antimony. Insoluble in ammonium disulphide, and is :— (a) Black—mercury (ic), lead, or copper. (6) Brown—bismuth. (c) Yellow—cadmium. No precipitation with sulphuretted hydrogen—shows absence of copper group. | 5. Boil the solution (or filtrate) for a few minutes, add a few drops of nitric acid, and boil again. (This is to get rid of the hydrogen sulphide and oxidize the iron.) 6. Add ammonium chloride and then ammonium hydrate. A wprecipitation—presence of iron sub-group (iron, chromium, aluminium). No precipitation—absence of iron sub-group. 7. Filter off the precipitate (if there be one). 8. Pass through the solution (or filtrate) sulphuretted hydrogen. A precipitation indicates presence of zinc sub-group. (a) Zinc—white precipitate. (b) Manganese—flesh-coloured precipitate. (c) Nickel and cobalt—black precipitate. No precipitation—absence of zinc sub-group. 9. Filter off precipitate (if there be one). 10. Add to solution (or filtrate) ammonium carbonate. A precipitation—barium, strontium, or calcium carbonates. No precipitation—absence of barium group. 11. To filtrate or solution add sodium phosphate, when mag- nesium phosphate will be precipitated if a magnesium salt were present. 12. Potassium, sodium, and ammonium are identified separately and by other means. In order that the student shall be able to apply simple tests to identify textile chemicals and mill stores it is very advisable that he 154 TEXTILE CHEMISTRY should have some knowledge of analytical processes, and a suitable exercise at this stage is the analysis of a simple salt. SCHEME FOR THE ANALYSIS OF A SIMPLE SALT Preliminary Tests. 1. Heat the substance alone in a small dry test tube. Odour of sulphur dioxide—hydrosulphuric or sulphurous acid. Evolution of carbon dioxide—carbonic acid. Metallic sublimation—mercury. Yellow hot, white cold—zinc. 2. Treat with dilute hydrochloric acid, and determine the nature of the gas or vapour evolved (see page 52). 3. Treat with strong sulphuric acid. 4, Treat with strong sulphuric acid and lead peroxide. 5. Put a grain or two in a watch-glass, add strong hydrochloric acid ; dip into it a platinum wire, and find Colour the “flamereaction.” (For method of hold- ing the wire in the colourless bunsen flame, see Fig. 204.) “ Green—barium, copper, boric acid. Glass Yellow—sodium. handle Violet—potassium (red through indigo prism or cobalt glass). Red—calcium (lime). Crimson—strontium. 6. Make a borax bead by fusing some borax on the end of a platinum wire. Fuse in a minute portion of the substance and note the colour of the bead. Blue—cobalt, copper. Violet—manganese. 7. Fuse a little on charcoal in the reducing flame of a blowpipe. Beads or scales of metal—silver, copper, iron, cobalt, nickel, tin, lead, bismuth, and antimony. 8. Fuse some more on charcoal in oxidizing flame. Cool, and then moisten the residue with a solution of cobalt nitrate. Reheat in the same flame— Blue residue—aluminium. Green residue—zinc. Pink residue—magnesium. 9. Prepare a solution (a) in water, or if insoluble (b) nitric acid or (c) hydrochloric acid. (d) If not soluble in water or dilute acid, fuse with fusion mixture, and then boil the “melt” with water. Filter. In the filtrate examine for acids, and test the residue, after dissolving in hydrochloric acid, for bases. Tig, 20¢ QUALITATIVE ANALYSIS 155 To detect the Basic Radicle :— 1. To one portion of the solution add a solution of caustic soda. (a) White precipitate soluble in excess—lead, zinc, antimony, aluminium, tin. (6) White precipitate insoluble in excess—bismuth, cadmium, magnesium, calcium, barium, strontium, manganese (darkens). (c) Yellow precipitate—mercury (ic). - (d) Black precipitate—mercury (ous). (ec) Blue precipitate—copper, cobalt. (f) Dark brown precipitate—silver. (g) Dirty green precipitate—iron (ous). (h) Reddish brown precipitate—iron (ic). (7) Green soluble in excess—chromium. (7) Green insoluble in excess—nickel. (k) Evolution of ammonia gas—ammonium. (1) No precipitate—arsenic, potassium, sodium, ammonium. 2. To another portion add hydrochloric acid. White precipitate—lead, mercury (ous), silver. Wash this precipitate with warm ammonia. No change—lead. Dissolves—silver. Blackens—mercury. 3. If no precipitate has been produced with the acid, to the same _ solution add sulphuretted hydrogen gas. Black precipitate—mercury (ic), lead, copper. Dark brown precipitate—bismuth, tin (ous). Yellow precipitate—cadmium, arsenic, tin (ic). Brick red precipitate—antimony. 4. If no precipitate in Nos. 1 and 2, to a fresh portion of solution add ammonium chloride and ammonia. Dirty green precipitate—iron (ous). Reddish brown precipitate—iron (ic). Green precipitate—chromium. White precipitate—aluminium. 5. If no precipitate in No. 4, to the same solution add ammonium sulphide. Black precipitate—nickel, cobalt. White precipitate—zinc. Buff precipitate—manganese. 6. If no precipitate in No. 5, to the same solution add ammonium carbonate solution. White precipitate—barium, strontium, calcium (distinguish by flame reactions). 156 TEXTILE CHEMISTRY 7. If no precipitate in No. 6, boil down the same solution, add more ammonia and then sodium phosphate. White crystalline precipitate—magnesium. To detect the Acidic Radicle :— Test solution with litmus. If acid, neutralize with ammonia (any precipitate may be filtered off and neglected) ; if alkaline, neutralize with nitric acid. 1. To some of the neutral solution add silver nitrate. If a precipi- tate is produced, divide it into two parts. (a) Try the effect of heat on one part. (b) Determine if soluble or insoluble in nitric acid with the other part. If the precipitate be soluble in nitric acid and is :— (a) White, rapidly darkening—it may be thiosulphuric. (b) White, darkened by heat—it may be sulphurous, boric, carbonic. (c) White, dissolved on heating—it may be acetic. (d) White, unaltered by heat—it may be oxalic, tartaric, citric. (ec) Yellow—it may be phosphoric, arsenious. (f) Brown—it may be arsenic. (9) Red—it may be chromic. If the precipitate be insoluble in nitric acid and is :— (a) White, turns purple—it may be hydrochloric. (6) White—it may be hydrocyanic. (c) Yellowish white—it may be hydrobromic. (d) Yellow—it may be hydriodic. (ec) Black—it may be hydrosulphuric. Confirmatory tests with the original solution should be applied to distinguish :— Thiosulphuric—with hydrochloric acid gives a yellow precipitate and evolves sulphur dioxide. Sulphurous—with hydrochloric acid gives off sulphur dioxide. Carbonic—with hydrochloric acid evolves carbon dioxide. Boric—acidify with hydrochloric, dip in turmeric paper, dry it, the paper turns green. Acetic—warmed. with strong sulphuric acid—odour of vinegar. (a) Add calcium chloride solution. (1) White precipitate in the cold—oxalic, tartaric. (2) White precipitate on boiling—citric. (b) Heat another portion with strong sulphuric acid. (1) Blackens—tartaric. (2) No blackening—ozalic. Phosphoric—add a little of the original solution to ammonium molybdate solution warm—yellow precipitate. QUALITATIVE ANALYSIS 157 Arsenic or Arsenious—put some of the original substance in an ignition tube with a small piece of charcoal and heat in bunsen flame—mirror of metallic arsenic sublimes. Chromic—Lead acetate gives a bright yellow precipitate. Hydrochloric Heated with chlorine evolved a peroxide | Hydrobromic and bromine evolved strong Bere) Hydriodic acid iodine evolved Hydrocyanic (Prussian blue test)—add solutions of ferrous sul- phate and ferric chloride, then excess of caustic soda. Boil, cool, and acidify with hydrochloric acid. Hydrosulphuric—add hydrochloric acid—sulphuretted hydrogen evolved. 2. If silver nitrate does not give a precipitate in the neutral solution all the above-named acids are absent. Acidify a fresh portion of the solution with nitric acid, and add a solution of barium nitrate. . White precipitate = sulphuric acid. 3. If still no precipitate, test the original substance as follows :— Dissolve in water (all nitrates are soluble in water). To this solution add a few c.c. of strong sulphuric acid, carefully cool the mixture, and when cold, pour on the top of it a strong cold solution of ferrous sulphate. A “ brown ring” at the junction indicates nitric acid. APPLICATION OF CHEMISTRY TO TEXTILES ALTHOUGH in its narrowest sense the term “textile” refers to the process of weaving only, by convention it has now a much wider significance, and is taken to include other branches of the manufacture of cotton, wool, and silk. In a similar sense we desire to use the term “ textile chemistry,” applying it with reference to instruction in the principles of all branches of the industry and particularly to the properties of the materials that are necessary to produce finished cloth from raw fibre. Textile chemistry in its more advanced form consists of a specialized study of each of the separate processes, and therefore the subject should be continued under the various branches, such as dyeing, sizing, bleaching, etc. SECTION XIII THE NATURAL FIBRES HE chief natural fibres in use in this country for textile pur- poses are cotton, wool, linen, and silk, of which the first two are by far the more important. Besides these a considerable amount of artificial silk is used. The characteristic appearance of fibres can be seen best under the microscope. The principle of the construction of this instrument is illustrated in Fig. 205. The object under examination is placed just beyond the focus (F) of a lens (called the objective) of short focal length. Rays of light passing through this lens produce on the other side an enlarged inverted image (first image). If a screen be placed in this position, the image will appear as a picture on it. If no screen be interposed, but another lens (eyepiece), of longer focal length, be placed between the 158 THE NATURAL FIBRES 159 observer’s eye and this image, at a distance from the first image of a little less than its focal length, the rays from the image in passing through this latter lens are refracted in such a manner that an image of this image (second image) is produced, resulting in further magnification. Fig. 206 is a sketch of a Leitz microscope, and one that is very suitable for textile purposes. Before using a microscope the essential parts should be known, and a student using one for the first time should seek the aid of some person who has previously used one, as the instrument can be damaged very easily. The particular microscope illustrated consists of a brass stand with a substantial base—to the stand being attached, by means of a rack and pinion, a brass tube. Screwed to the bottom of this tube is a set of lenses called the objective; and fitting in the top is another set termed the eyepiece. The tube also can be made longer by the manipulation of the draw-tube. Under the objective is a brass platform with a hole in the centre known as the stage. On this is placed the glass slide containing the object to be examined under the microscope. Beneath the stage is a mirror capable of turning in all directions, to reflect the light through the object. The magnifying power of the microscope is obtained by the com- bination of objective and eyepiece, and (if necessary) increasing the distance between them by using the draw-tube. Using a 2 inch objective and a No. 1 eyepiece, the magnification is about 60 lineal multiplications, i.e. 3,600 times the real area; but magnifications are always expressed as lineal—called diameters. Using a 4 inch objective and a No. 3 eyepiece, it is possible to magnify to 450 diameters. This is quite high enough for all ordinary purposes in textile chemistry. 160 TEXTILE CHEMISTRY To Use the Microscope First screw in the objective, insert the eyepiece, and place the instrument on a very firm table or bench. Arrange the source of light at a suitable distance from the base, and look down the tube with one eye. Turn the mirror until the brightest effect is produced. Next prepare the slide—instructions for which will be given in the proper place—and place it on the stage so that the ends are held by the clips, and the portion under the cover glass is over the hole in the stage. Look down the tube and carefully turn the rack and pinion until the object is nearly focused, then turn the micrometer screw which gives the fine adjustment, until the object is exactly focused. It requires only practice to learn to correctly manipulate a micro- scope, and anyone after a few patient trials should be able to use it. Cover glasses should be used always—even over cotton fibres—and it is often an advantage to mount the specimen in liquid. The microscopic appearance of fibres as represented in textbook diagrams is frequently much more ideal than that usually met with, and the beginner often fails to recognize the specimen unless it has been specially prepared. The illustrations here given (Figs. 207-212) are drawings from actual photographs of samples as usually met with, and have not been specially selected. THE NATURAL FIBRES 161 Slides should be made by teasing out fibres with a needle and placing a few in the middle of the glass. by means of silk sieves. It is usually a nearly pure starch, but the ash is higher than with farina, and is sometimes of a gritty nature. It presents a very typical appearance under the microscope (Fig. 927, page 185). The ends of the granules are distinctly truncated. If too much sago is used in size mixings, the warps are made too stiff, which, if not apparent to the touch, makes its presence evident by cutting the healds. | On this account it is usual in the Nelson district to steep the sago overnight in cold water and boil up in the morning. The boiling should be more prolonged than with farina. Low-grade sago flour is liable to be contaminated with sea water. It is therefore necessary to test samples for the presence of chlorides. MAIZE OR CORN STARCH This starch is produced in enormous quantities in America, where methods for its extraction have been brought to a high state of per- fection. Many years ago there was considerable prejudice against this starch as a sizing ingredient, but to-day it is much more popular, particularly the better brands. The paste produced from it is very thick, opaque, and somewhat liable to mildew rapidly. When dried it has a harsher feel than that of most other starches, but it is very adhesive and may be boiled for a long time with “open” steam without fear of deterioration. This boiling tends to reduce its natural harshness. Maize starch is often used in conjunction with flour for heavy sizing. During the period of the war, when farina was almost unobtainable, it became necessary to use it in “ pure ” and “light” sizing, and in many cases it is still being retained—so satisfactory has it proved. Corn starch should be carefully scrutinized under the microscope, 188 TEXTILE CHEMISTRY and a sample showing small and regular granules will be found as a rule to give the better results. The ash should be practically nothing. Many proprietary brands of starchy materials contain maize starch as one of the ingredients. CASSAVA This is a “root” starch produced largely in South America. It is prepared as a food starch under the name of tapioca. It is seldom that the cotton manufacturer buys it in the pure form, although he certainly gets it in certain sizing starches that are sold under special trade names. Cassava under the microscope appears in somewhat hemispherical granules (Fig. 229, page 185). They gelatinize readily to produce a thin and not particularly adhesive paste. RICE Rice starch is chiefly used as a laundry starch. The qualities which make it desirable for this application are those which militate against its use as a sizing starch. The granules are small, harsh, and when dried produce a very rough yarn and a cloth of “ boardy feel.” Many sizing flours contain small proportions of rice flour or rice starch, these admixtures enabling the user to obtain various cloth effects, particularly in regard to feel. | ) LABORATORY EXERCISES IN THE EXAMINATION OF STARCHES 1. Test solubility in cold water by shaking, filtering, and testing the filtrate with tincture of iodine. 2. Put a few drops of a cold emulsion in boiling water. Allow it to cool—note if a jelly is produced. Take some of this in another tube, shake up with more cold water, add iodine, and note production of the blue colour. Boil some of this and note that the colour disappears and probably returns on cooling. 3. To some starch paste add a few drops of caustic soda solution. Test a portion of this with iodine—no blue colour is produced. Neutralize another portion with acetic acid and then add iodine— the blue colour appears. Therefore, to test for starch always proceed as follows :— Shake up the substance in cold water, boil the mixture, test with litmus paper to determine if it is alkaline. If so, neutralize with acetic acid, cool the liquid, and then add a drop or two of tincture of iodine. If it turns blue, starch is present. 4. Determine the percentage of ash and water in starches. (See Section III, pages 31-33.) SIZING 189 Examine permanent slides of various starches under the microscope and try to identify them. Carefully sketch in your notebook the shape of the granules of each variety. Prepare samples of starch for examination under the microscope :— Add about enough starch to cover a sixpence to a test tube half full of cold water; shake well and take out one drop on the end of a glass rod. Put this on the middle of a clean microscope slide and carefully drop on it a glass cover slip so that no air bubbles are held under it. Place on top a piece of filter paper and gently press. Prepare in this way samples of farina, flour, maize, and sago ; and - also farina which has been boiled. Flour should be tested for mineral impurities, other starches, and mildew. An increased ash content indicates mineral adulteration, which may also be detected by shaking up the flour in a test tube with chloroform, when the clay, gypsum, etc., settles to the bottom, while flour floats. Maize, rice, tapioca may be readily detected under the microscope. Another valuable test to apply to flour is to add to 20 grams of flour a mixture of 70 c.c. of absolute alcohol, 25 c.c. of water, and 5 c.c. of strong hydrochloric acid. Put it in a large tube and digest in a beaker of hot water for some time. Allow it to stand to cool for an hour. Examine the appearance at the end of that time. If the liquor is— (a) Perfectly colourless, it is pure wheat flour ; (b) Blood red, it contains ergot ; (c) Purpie red, it contains mildew ; (d) Yellow, it contains barley or oat flour ; (e) Orange yellow, it contains pea flour. To determine the amount of gluten in flour :— Weigh out 20 grams of flour, put it in a 4-5 inch evaporating basin, and add water a few drops at a time, stirring with a glass rod until it is made into a lump of dough, not a paste. With a little practice, and if too much water is not added, it is possible to gather every particle of the flour into one ball on the end of the glass rod. Take a piece of washed cotton cambric of moderately low texture (say 40 picks to the inch) about 6 inches square, and after thoroughly wetting it, put the dough in the middle, tie up tightly with string— allowing plenty of room for the flour to swell—and knead in a basin of water or under the tap until all the starch is washed out. This point is reached when the water runs perfectly clear from the bag. The kneading must be thorough, but care must be taken that nothing is forced through the bag, which should now contain the gluten. Open the bag, carefully collect the gluten into one lump, and roll 190 TEXTILE CHEMISTRY it between the palms of the hands until it begins to stick. At this point it should be weighed on a small piece of aluminium, and the weight recorded as “ wet gluten.” It may now be dried in a steam oven (a process which may take several days), when it will be found that in the wet condition it weighs 2-64 times its dry weight. Consequently, if an early result is required it is usual to weigh wet and divide this weight by 2-64. The quality of the gluten may be determined by stretching the mass as it is being dried between the palms of the hands. Students are advised to make mixtures of genuine flour with other starches, particularly maize, and note the difference in appearance and adhesiveness of gluten obtained therefrom. Softeners. Ingredients of this class are added to counteract the harshness which would be produced in the fibre by coating it with pure starch. Many fats and oily substances are used, of which the following are important :— TALLOW Tallow is a well-known natural fat extracted from the sheep or ox. In the animal the fat is contained in little bags called sacs, and the tallow-chandler has to get it free from this membrane, which is not composed of fat. This is termed rendering. The old process was to melt over a fire and press the fat, which will never produce a white tallow—and the method is now practically extinct. The modern process is to extract with steam at a pressure of about 50 lb. to the square inch. The principle of the method is shown in Fig. 231. The fat is placed in an iron cylindrical chamber, provided with a wooden floor and two doors—one at the top and one near the bottom. Through the chamber runs a pipe that conveys the steam, which escapes from it at intervals. This melts the fat which rises to the top and can be drawn off at the delivery taps. The bottom door is for the removal of the membranous residue. A safety valve is put on the top of the vessel. By this method, if good and fresh materials have been used, a good and nearly pure tallow, free from dirt and foreign matter, will be obtained. It is evident, therefore, that very little skill and only simple apparatus are required to produce good tallow ; but many things affect the quality before it reaches the user, e.g. :— Hardness depends upon the breed, age, food, and sex of the animal. Oil-cake feeding gives a softer fat than grazing the animal. Acidity is the result of age ; mutton tallow goes “rancid ” sooner than beef tallow of the same quality. Two explanations to account for this acidity have been advanced :— SIZING 191 1. When exposed to air it undergoes change due to the action of ferments, whereby acids are produced. 2. In the presence of light and oxygen (in air) certain constituents of the tallow are oxidized to acids. At the present time, the second cause is considered to be the more potent. Water present is largely determined by the honesty or dishonesty of the renderer. The addition of a small amount of caustic potash during rendering—which produces a potash soap—greatly assists the “Steam Fig. 234 * tallow to absorb water as it sets. Such tallow will give an alkaline reaction with the usual indicators. Some characteristic Properties of good Tallow. All pure fats should be odourless, tasteless, colourless, and should not darken when exposed to air. The nearer tallow approaches to these qualities, the purer it is as a rule. All taste, colour, and smell are due to the presence of small quantities of substances other than fat. Fat should be neutral when in solution, e.g. if some tallow be dissolved in’ ether, divided into two portions, and a piece of red lacmoid paper be placed in one and blue in the other, there should be no alteration in either. Tallow is completely soluble in carbon disulphide, chloroform, ether, and alcohol. It is insoluble in water, but is capable of absorbing water. If the fat be melted in a long tube which is kept hot by surrounding it with a hot-water jacket (Fig. 232) the two liquids will separate—tallow 192 TEXTILE CHEMISTRY collecting at the top, water at the bottom. If the tube is graduated it is very easy to calculate the proportion present. This is due to the fact that, bulk for bulk, tallow is lighter than water. The sp. gr. of tallow is not a constant quantity for all samples. Beef tallows at 15° C. range from 0-925 to 0-953. Mutton ,, ., . », 0:937 ,, 0-960. A good average is 0:94. If determined in the liquid condition at 100° C. and compared with water at 15° C. the range is from 0-885 to 0-863. The melting-point should be 111°-113° Fah. or 44—45° C. Beef tallow may range from 42-6° to 50°C. As it gets older it falls, but never below 40° C. Mutton tallow has a melting-point of about 47°C. As it gets older it tends to rise. The Testing of Tallow. A great deal of useful information respecting a tallow can be obtained by performing the following experiments with it :— 1. Find its melting-point. (See Section III, page 28.) 2. Test its solubility in chloroform or carbon disulphide. Any insoluble matter is an impurity. 3. Test the solution as obtained above with (a) lacmoid, (6b) methyl orange. The latter will detect mineral acids, and the former free fatty acids or alkalis. 4, Dry and weigh a small evaporating basin half full of small pieces of pumice. Add a few grams of tallow, and heat in a steam oven for several hours until the loss is constant. The loss is due to expulsion of water. 5. Boil some tallow with dilute nitric acid, cool to solidify the fat, filter and warm some of the filtrate with ammonium molybdate solution. A distinct yellow coloration or precipitate indicates a phosphate—which is due to the presence of bone fat. 6. Burn a weighed quantity in a crucible and find the percentage of ash present. From pure tallow it is almost nil. 7. Boil two or three drops of tallow with alcoholic potash solution for several minutes and then add an equal quantity of warm water. A white turbidity or precipitate indicates the presence of paraffin oil or paraffin wax, or similar adulteration. SOAP. Soap is a substance which has been known from very early historical times. We find it mentioned in literature which is quite 2,000 years old, and during recent years a soap factory has been discovered in the remains of Pompeii. . ° SIZING | 193 Except that the manufacturer has discovered how to add things which are not soap, the process of making is almost identical with that of the ancients. There are two sorts of soap: (1) Hard or soda soaps; (2) soft or potash soaps. In all cases it is made by the action of an alkali on a fat or fatty acid or oil. A fat is acompound which can be split up into a fatty acid and glycerine. The alkali neutralizes the acid in the fat and liberates glycerine. The neutral product is called a soap, which is essentially the sodium (or potassium) salt of the fatty acid. On a small scale soap may be prepared in the following ways :— 1, Shake up ammonia with olive oil—a white solid results which is largely soap. 2. Make a strong solution of caustic soda; add this to palm oil, stir well, and allow it to stand. In a short time the temperature rises and solid palm oil soapis formed. This is known as the “ cold process ” of soap-making. 3. Make a solution of tallow in alcohol, add some caustic soda previously dissolved in water, and simmer on a water bath for half an hour. Add salt to the liquid, and soap is precipitated from solution. Soaps as now manufactured contain (if unadulterated) from 40 per cent. to 50 per cent. of moisture, from 40 per cent. to 45 per cent. of fatty acid, from 7 per cent. to 10 per cent. of combined alkali, and very little free alkali. Yellow soaps contain resin, mottled soaps iron, and an almost endless list of adulterants and additions has been compiled. Starch, clay, talc, chalk, oils, sugar, sulphur, sand, etc., etc., are some of these additions which may be added to produce a soap suitable for some special purpose. Pure hard soap contains 31 per cent. of water—it is impossible to make it with less. If it does not yield this quantity it has been dried since manufacture. Soap-flakes often contain less than 10 per cent. In cocoa-nut oil soap the water may reach 75 per cent. to 80 per cent., and it may still appear a fairly solid soap. The analysis of a good sample of soap yielded the following results : 55 per cent. fatty acid, 9 per cent. fixed alkali, 36 per cent. glycerine and water. The value of a soap is largely determined by the quality and quantity of fatty acid present ; any hard soap with more than 64 per cent. has been dried, any with less has been intentionally reduced. Free alkali, which may be detected by adding a drop of phenol- phthalein to a freshly cut surface, when a pink colour is produced, is not—except that it indicates a badly made soap—very objectionable 18 194 TEXTILE CHEMISTRY from a sizing point of view. In fact, a slight alkalinity in soap will neutralize undesirable acidity in a rancid tallow. The chief reason for using soap in a size mixing is that its presence assists in the more perfect emulsification of the fat and thus a more uniform liquid is produced. Some sizers use no soap as such, but they add a small sana of caustic soda. During boiling this alkali reacts with some fat to form soap, and therefore they are using it although not adding it as a separate ingredient. Soap is also present in many trade softeners and sizing compositions. Soap must not be used in the presence of metallic chlorides or some of the value of each is destroyed. For sizing purposes a good soft soap or a hard soap made by the cold process is to be preferred to an ordinary hard soap, as soft soaps and cold-process ones often contain all the glycerine present in the original fat. The testing of soap should include these determinations :— 1. Water. Take a sample from the middle of the bar if hard, or below the surface if soft. Weigh quickly on a tared watch glass and then shred it if hard soap, and dry in an air oven at a temperature of 105° C. till no further loss in weight occurs. Calculate to a percentage. 2. Find the amount of ash. (See Section III, pages 32 and 33.) 3. Fatty acid. Weigh out 25 grams of the sample and dissolve in a beaker of water on a water bath. When it is near boiling-point add a few drops of methyl orange, and then strong hydrochloric acid till the indicator has been turned a distinct pink colour. This liberates the fatty acid. Boil gently till the acid forms as an oily layer on the top of the liquid. Add 5 grams of stearic acid or paraffin wax, warm up until the two are thoroughly mixed, and then allow the vessel and contents to cool. Carefully remove the cake, dry on filter paper, and weigh. Deduct the weight of wax (which was added to ensure that it set solid) and calculate to a percentage on the amount of soap used. GLYCERINE This substance has a certain application in sizing—less, probably, than it deserves—as besides acting as a softener it is nyeronens and has mild antiseptic properties. Glycerine may be obtained from fats by subjecting ‘heat to the action of superheated steam at a temperature of 300° C., but as a rule most commercial glycerine is obtained as a by-product in the two industries of soap-making and candle-making. This glycerine is often contaminated with many undesirable substances, and is very dark in colour—sometimes almost black— SIZING 195 and although then cheap, it is useless to the sizer on account of the darkening effect it would produce in the size. If, however, it is only slightly brown it may be used, provided certain impurities are absent. As good glycerine is expensive, many “ glycerine substitutes ” are on the market; these are often only solutions of glucose sugar, and are almost useless for sizing purposes. Glycerine mixes in all proportions with water and alcohol, but is insoluble in carbon disulphide and chloroform. Taste is a very good test to apply to glycerine—if impure, it is distinctly unpleasant. A good sample of commercial glycerine yielded the following results on analysis :—Sp. gr. 1-3, 80 per cent. to 82 per cent. real glycerine, 10 per cent. ash, and gave no precipitate on being added to strong hydrochloric acid. The Testing of Glycerine. Sufficient information as to its suitability for use as a sizing ingredient will be obtained by performing the following experiments :— 1. Find its sp. gr. (See Section III, pages 29 and 30.) 2. Add some to an equal volume of strong hydrochloric acid in a test tube. Invert the tube two or three times to thoroughly mix the two liquids, and then allow the mixture to stand for half an hour. If at the end of that time no white precipitate has been deposited, it may be assumed that salt is not present in sufficient quantity to condemn it. 3. Test for presence of glucose by diluting with an equal volume of water and then boiling it with some Fehling solution. If sugar is present the blue colour is destroyed, and a red precipitate is produced. 4. Test for lime by adding some crystals of ammonium oxalate to some which has been diluted with twice its own volume of water. Shake well at intervals—a white precipitate indicates the presence of _ salts of lime. WAXES Chemically, waxes are quite distinct from fats, but the classification is not based on their physical state, e.g. Japan wax is really a fat, and sperm oil is a wax. Of the substances commonly known as waxes, the ones used in sizing are :—Japan wax, paraffin wax, spermaceti, and wool grease. Japan wax and spermaceti are both expensive substances and are used in very small quantities in mixings ; their use seems to be “ faddy ” rather than essential in many cases, but spermaceti wax and paraffin wax crystallize from tallow and in some pure mixings are used by reason of this property, as thereby a peculiar feel and appearance are obtained. : 196 TEXTILE CHEMISTRY Japan wax has a high melting-point and is sometimes used for cloth sent to hot and very humid countries, e.g. Java. Paraffin wax and wool grease are much more widely used, and in some cases they are very desirable or even necessary ingredients, but the former is a very dangerous ingredient to put into size if the cloth is to be afterwards bleached or dyed. Because of the extraordinarily high price of tallow now prevailing, many manufacturers have been induced to use other forms of grease. One of the most successful has been wool grease, the best qualities of which are not usually sold under that name. This substance is excreted through the skin by sheep and collects in the wool by absorption. In wool washing it is extracted in a very impure condition. When highly purified a very valuable neutral wax is obtainable which is sold under the name of Lanoline, and has been largely used in the preparation of ointments, due to the very char- acteristic property it possesses of being readily absorbed by the skin. The crude “ recovered”’ or ‘‘ Yorkshire”’ grease is a mixture of free and combined fatty acids and alcohols. It is a dark yellow or brown viscous substance of melting-point 39°C. to 42°C., sp. gr. 0:973 at 15° C., and has a distinct smell of sheep. CHINA CLAY Of all weight-giving substances used in sizing none is so successful as good China clay. Magnesium sulphate, gypsum, barytes, and other compounds have been used, but it has been demonstrated to the sizer that it rarely pays to use them except for the more common kinds of cloth. In nearly all parts of this country clay is found in the soil, but in only a few districts is it of the kind necessary for the sizer’s use, i.e. kaolin or China clay. This kind is found in geological deposits in Cornwall and Devon, where older rocks have been weathered and destroyed, and the small particles of aluminium silicate have been collected by the action of water. The deposits have become dry, and thus form the natural beds of clay. These beds contain particles of sand, mica, and iron salts which were present in the original rock. The method of treatment is to mix up the mineral with water : the clay, being lighter than sand, remains in the top layer of liquid, which is run off and then allowed to settle. If this is repeated several times a clay free or nearly free from impurities is obtained. It is then dried in kilns. Physically, clay is a very fine white powder, which has a great capacity for absorbing water, and, owing to this absorption and its SIZING 197 fineness, becomes plastic. It is soft and soapy to the touch, and when breathed upon it emits a characteristic earthy odour. For sizing purposes it should be free from iron, grit,and lime. It should possess also an unctuous feel—plasticity is not the quality desired. It should not be coloured artificially. The amount of moisture present in commercial China clays often varies very considerably. This is due generally to imperfect drying ; but even if the clay be thoroughly dried at steam heat, a certain amount of water remains, varying from 10 per cent. to 12 per cent., which is only expelled at red heat. For heavy sizing especially, it is very desirable that the sizer should know the excess of moisture above this 12 per cent., which might be called the “‘ strength ” of the clay. This may be determined by drying in a steam oven, or better, at 105° C. to 110° C. for several hours, until the loss is constant. An aluminium tray is a suitable receptacle to use for the purpose. The sizer whose speciality is heavy sizing would do well to determine the percentage of “ free ” (i.e. expelled at 105° C. to 110° C.) and ““ com- bined ” (expelled at red heat) moisture in his various samples of clay. An example of this is given on page 33. Mellor states that the best temperature at which to determine “ hygroscopic ” (i.e. free) moisture is 109° C. to 110° C. For the loss on ignition (i.e. combined moisture) for Cornish China clays, previously dried at 110° C., he gives the following figures :— reas ae per cent. | mhese calculations are Mean of six ; j 12-5 # is made on the dr ied, Ideal Bn ee not natural, clay. LABORATORY EXERCISES WITH CHINA CLAY 1. Test for chalk by adding hydrochloric acid. If present, effer- vescence will result. Filter, and to the filtrate add ammonium oxalate—a white precipitate is obtained if chalk, or plaster of paris, or gypsum is present. 2. Grit should be detected by shaking a few grams with water, allowing the mixture to stand for two or three minutes, pouring off the top layer, and examining the sediment. This may be done by rubbing it between two glass microscope slides or by examination under the microscope. 3. The presence of artificial colouring may often be detected by adding a few drops of strong ammonia and stirring with a glass rod. 4. Boil some with hydrochloric acid, filter and divide it into two parts. To one add potassium ferrocyanide—a blue colour is produced 198 TEXTILE CHEMISTRY if iron is present, the depth of tint depending upon the quantity in solution. A clay suitable for sizing purposes will show only a faint colour. To the other portion add ammonia and boil. A reddish brown precipitate indicates the presence of an undesirable amount of iron in solution. METALLIC CHLORIDES These substances are used to give either weight or antiseptic properties, or both, to the twist. Those most frequently used are (1) zinc chloride; (2) magnesium chloride ; (3) calcium chloride. Beside these, another sometimes gets into the size—due to adultera- tion of ingredients—i.e. (4) sodium chloride. Of these, the only antiseptic is zinc chloride. Zinc chloride, mag- nesium chloride, and calcium chloride are all deliquescent bodies (i.e. they abstract moisture from damp air). Calcium chloride and sodium chloride are not desirable ingredients to have in size except in very small proportions. Zinc chloride is made on the commercial scale from scrap zine or zinc ashes and skimmings or compounds of the metal that have been produced as by-products in certain manufacturing processes, by mixing the raw material with hydrochloric acid. The resulting liquor is treated to free it from iron and other undesirable impurities and concentrated to a syrup-like mass containing about 45 per cent. of anhydrous chloride of zinc, having a sp. gr. of 1-51—-1-52 (102-104° Tw). For export it is usually evaporated till nearly all the water is ex- pelled and it sets as a white solid containing zinc equivalent to 98 per cent. or more of zinc chloride. Commercial zinc chloride is seldom pure, as the cost of removal of all impurities would make it a very expensive chemical; nor is it necessary for sizing purposes that this highest degree of purity be attained. It is sufficient as a rule that free mineral acid and iron be absent, and that less than 1 per cent. of sodium chloride be present. The tests for these impurities may be conducted in the following manner :— 1. Salt or Sodium Chloride. Pour some into a test tube half full of strong hydrochloric acid, and after mixing allow it to stand for half an hour. [f salt be present to a greater extent than 1 per cent. it will be precipitated in small white crystals. 2. Iron Salts. Boil a few drops with pure nitric acid and then add one drop of it (on the end of a glass rod) to some potassium thiocyanate solution in another test tube. The production of a blood- red colour shows the presence of iron. The depth of the colour depends SIZING 199 upon the amount of iron in solution—if it be but faint the sample may be passed as fit for use. 9 Free Acid. The indicator used must be either Congo red paper (which is turned blue), or methyl orange solution (which is turned pink) by free mineral acid. As a rule the manufacturer tries to produce a solution which is slightly basic in character, that is, it contains a little oxychloride of zinc in solution. LABORATORY EXERCISES I. Examine samples of zinc chloride, (a) solid, (6) in solution ; and perform the following experiments with them :— Solid 1. Expose to air on a watch glass for half an hour ; note what happens. 2. Test solubility in a small quantity of water. 3. Note effect of adding more water to this, then addition of dilute hydrochloric acid. 4. Take a small piece in a porcelain crucible ; heat strongly and note all changes. Solution 1. Test for zinc by adding am- monia and ammonium sulphide. 2. Test for salt by adding some to an equal quantity of strong hydrochloric acid. 3. Test reaction to litmus, meth- yl orange, and Congo red. 4. Test for presence of iron by potassium thiocyanate. 5. Test for calcium by adding ammonium chloride, ammonia, and ammonium oxalate. II. Heat some zinc oxide on charcoal with the mouth blow-pipe, using the oxidizing flame. Note colour—hot and cold. When cold, moisten residue with a few drops of cobalt nitrate solution. Reheat, and again note the colour. Repeat the experiment, using in turn, on a fresh spot on the charcoal: alumina, magnesia, clay, “ anti- septic,” “zinc,” “* septic.” III. Prepare a solution of zinc chloride by dissolving zinc powder or granulated zinc in commercial hydrochloric acid, using excess of the metal. When action has ceased filter through glasswool (It will dissolve filter paper) and concentrate to a syrup. Find its specific gravity, and test it for the presence of free acid and iron. Magnesium Chloride. This substance is a white crystalline, very deliquescent salt, the chief source of which is the enormous Stassfurt deposit in Germany—not far from Jena. From these mines it comes into commerce in an exceedingly pure condition. In our own country there are large deposits of dolomite and mag- nesium limestone—which are compounds of lime and magnesium carbonates. Upon treating with hydrochloric acid the carbonates are converted into chlorides. The magnesium chloride is less soluble than 200 TEXTILE CHEMISTRY the calcium (lime) chloride, and is crystallized out first. By this method of preparation the chloride of magnesium always contains chloride of calcium as an impurity. It can be detected by adding to a solution of magnesium chloride the following solutions in the given order :—Ammonium chloride, ammonia, ammonium oxalate. Gently warm. A white precipitate is formed if calcium chloride is present. Magnesium chloride is cheap, very deliquescent, and thus gives weight to the yarn or cloth, but it must not be used in the presence of soap, or without the addition of an antiseptic, as magnesium chloride itself is not one. Calcium chloride must not be confused with bleaching powder _—which is not, strictly, chloride of lime at all, although often so ‘called. This is not a suitable compound to use in size mixings— lime salts never are. It is very cheap, being formed as a by-product in many chemical industries, and thus it is often used to adulterate other chlorides. It is very deliquescent, but has no antiseptic value, and it must not be present in mixings that contain soap. FERMENTATION, MILDEW, ANTISEPTICS For perhaps thousands of years it has been known that if a sugar solution be exposed to air and warmth it is gradually converted into a liquid having very different properties, and that if this liquid be further exposed it becomes sour. Later it was noticed that bubbles were formed during the process, and hence arose the term fermentation. Attempts to explain why wine was converted into vinegar were made as early as 1670; and Dr. Willis (who died in 1675) considered that all vital actions were due to different kinds of fermentation. Liebig investigated many cases of fermentation and came to the conclusion that the process was due to the action of ferments. It remained for Pasteur to experiment exhaustively in the subject, and as a result of his researches he advanced the view that fermentation was the result of vital action. Later investigators have shown that both causes operate. When starch is taken into the mouth and mixed with the saliva excreted from the glands of that organ, it is thereby brought into contact with a ferment known as ptyalin, which at the temperature of the body converts the starch into sugar. A similar ferment is present in the growing barley grain, and if barley is kept warm and moist, sugar is formed. It is the same with other grains—the nature of the changes and substances produced being determined by the character of the particular ferment. SIZING 201 When milk goes sour it is due to the fact that fermentation has taken place and has produced some acid. Pasteur showed that if milk is kept out of contact with air it could be preserved for months without turning sour. Tyndall proved that it was only necessary to “ filter ” the air that surrounded the milk and it could still be kept sweet. It was demonstrated that the necessary agent to set up milk fermentation was a “germ” from the air. The same cause explains the fermentation of sugar, but here we have a simple cell (yeast). And in the case of vinegar we have a similar organism—the Mycoderma acett. Spores (or seeds) from certain other plants—still low in the scale of - life, but higher than those already mentioned—are always present in air and are ever seeking a “ soil” suitable for their development and growth. The materials that are required by fungi for luxurious growth are ammonia and phosphates. The common name for these is mildew—the botanical, fungi ; and the microbiologist has identified thousands of different species. Then there are other bodies known as bacteria, which feed and multi- ply in numberless media ; and many virulent diseases are attributed to their action, e.g. cholera, plague, lockjaw (tetanus), yellow fever, typhoid fever, etc. In fact this world teems with life of all sorts, the “low ” type being much more plentiful and prolific than the “ higher ” forms. Given certain conditions, the chief of which are warmth, moisture, and suitable food, they will flourish and multiply at an enormous rate. But if they do not multiply, the most virulent of them appear to be harmless and even unappreciated by the ordinary senses. Now to apply these facts to explain fermentation and mildew as met with in the cotton industry. When flour is mixed with water and exposed to the air it rapidly comes into contact with certain germs, or it may contain ferments derived from the natural grain. These commence to convert the gluten which is present in the flour into small quantities of other chemicals, probably carbon acids, ethers, alcohols, etc. Pure starch will not ferment because there is no plant food in it suitable for the growth of germs. : Sizers know that flour which has been fermented for a reasonable time is less liable to mildew than a paste which has not been fermented. The explanation is that some of the substances which are the products of fermentation are slightly antiseptic in their nature. An antiseptic is a substance which by its presence prevents the growth of low forms of animal and vegetable life. Many substances are known to act in this manner, amongst which are zine chloride, mercuric chloride, copper sulphate, carbolic acid (phenol), iodoform, formalin, glycerine, etc. 202 TEXTILE CHEMISTRY Mercuric chloride, or corrosive sublimate, is the most efficient, but so deadly poisonous in its effects on the human system that it must not be used for trade purposes on any account. It receives its application for sterilizing in typhoid fever and cholera, the virulent germs of which it is able to destroy thoroughly. Iodoform is much too expensive for general use; it is used in. surgery. Glycerine is fairly efficient if the cloth is not subjected to very damp conditions, but it is not suitable for heavy sizing. Formalin or formaldehyde is effective under certain conditions as a preventive of mildew, but it is much more effective against putrefactive bacteria. It must be remembered that this chemical is very volatile, and is lost by boiling. It is very effective for fumigating a room in which a scarlet-fever patient has been living, but to claim that it is equally active in the destruction of mildew spores (as was suggested in the celebrated “ weavers’ cough ”’ epidemic at Burnley a few years ago) is claiming too much for it. ' Carbolic acid is prepared from coal tar and is purified by recrys- tallization. It is possible thus to obtain a very pure product. This quality is rather expensive for sizing purposes, but stains may result on the cloth with less pure grades. Carbolic is a most efficient anti- septic for prevention of bacterial growth, but to prevent mildew it must be actually in contact with the material in the solid or liquid condition ; its vapour is not equally effective with respect to the prevention of fungoid growth. Another objection to phenol is its characteristic odour, which is not liked in cloth. Copper sulphate, or blue vitriol, is a cheap and well-known chemical which has great power as a fungicide, in fact perhaps the best that is available at the present time; but for textile purposes the quality used in agricultural spraying mixtures is unsuitable. It is essential to use a grade that contains but a trace of iron salts, and it must also be free from uncombined sulphuric acid. There are other objections to its use, such as liability to produce copper stains, and its action as a catalyst (page 70) in the presence of certain other textile materials. Zinc chloride, first suggested by Sir W. Burnett, and consequently sometimes known as Burnett’s disinfecting fluid, is, generally speak- ing, the most satisfactory antiseptic for cotton goods. The substance is sometimes called ‘‘ antiseptic,’ which is not desirable, for, as we have already noted, this is a name used for the whole class of substances. Zinc chloride is deliquescent as well, and probably this property has had something to do with its popularity, but for heavy sizing it stands unrivalled at the present time. For certain goods and in special circumstances it is inadmissible. SIZING 203 In these circumstances it is often difficult to recommend a suitable substitute, but salicylic acid is sometimes permissible. This is another very efficient fungicide, but it will change the colour of certain direct dyes such as Congo red, and in that event it would be better to use sodium salicylate, which however is, weight for weight, only about half as efficient. From this short account of antiseptics it will be seen that the question “ Which is it advisable to use ? ” is often by no means an easy one to answer. The action of antiseptics has not been thoroughly explained ; all that can be definitely stated is that they appear to be substances which are capable of either killing low forms of life or bringing about suspended animation. In their presence, even if all the conditions conducive to a successful growth are fulfilled, multiplication does not take place or is very considerably retarded. Some chemicals are more potent in this direction than others, and thus we find that ultimately fermented flour will mildew in spite of the presence of the antiseptic bodies which have been produced. In the case of dry starch, it is found that no fermentation takes place, but a starch paste will mildew. All natural starches contain some nitrogen compounds, and the plant probably first feeds on these ; later the constituents of the starch, in conjunction with the nitrogen of the air, form a sufficient soil. . The action of caustic soda as a “ preservative” (it can hardly be called an antiseptic) when boiled with the starch to form the paste is probably due to its destructive action upon nitrogenous matter, so reducing the available food. Tyndall showed conclusively that moisture was absolutely neces- sary to fungoid growth. A substance which is perfectly dry will never mildew, but add water to it even in small quantities (i.e. in the form of moisture), and it is liable to mildew at any time. Now size and sized goods always contain water. Cotton itself is hygroscopic, and will abstract moisture from the air, and deliquescent bodies like calcium and magnesium chlorides add greatly to the lia- bility. Therefore the greater the amount of water or deliquescent present in the size or on the yarn and cloth, the larger is the amount of antiseptic required in order to prevent the formation of mildew. LABORATORY EXERCISES IN THE TESTING OF “‘ RESIDUES ” You are provided with samples of typical ashes of various sizing in- gredients, etc., labelled Ato H. Examine them asinstructed below :— A (hard soap). Add a few drops of dilute hydrochloric acid. Test gas evolved for carbon dioxide. Dip a platinum wire in the liquid 204 TEXTILE CHEMISTRY and test for sodium in the flame (yellow). What was the probable composition of the ash, and was it completely soluble in acid ? B (soft soap). Repeat as for A, and in addition dissolve some in dilute nitric acid. Concentrate and crystallize. Note shape of crys- tals. Are they sodium nitrate or potassium nitrate, or both ? C (glycerine). Extract the portion soluble in water, and test it for salt by adding a few drops to strong hydrochloric acid. Add dilute hydrochloric acid to some more and test in the flame for calcium (red). Also test the solution with ammonia and ammonium oxalate. What was the ash ? D (size). Extract portion soluble in water and test it for sodium carbonate asin A above. Extract the residue with dilute hydrochloric acid and test the extract for magnesium with ammonium chloride, ammonia and sodium phosphate (white precipitate). Test the residue from second extraction for clay by heating on charcoal with blowpipe, moistening with cobalt nitrate, and reheating (blue mass). KE (sago). Test solubility in dilute acids, including aqua regia. Fuse some with fusion mixture, lixiviate, and test solution for silica with hydrochloric acid (gelatinous precipitate). Also test grittiness between two pieces of glass. F (cloth). Dissolve in dilute hydrochloric acid and add am- monium chloride and ammonia (precipitate = aluminium). Filter, and to filtrate add ammonium sulphide (precipitate = zinc). Filter, and to filtrate add ammonium carbonate (no precipitate = absence of cal- cium). Then add sodium phosphate (precipitate = magnesium). G (clay). Test this for :— (a) Carbonate, with dilute hydrochloric acid. (6) Calcium, by flame reaction. (c) Bleaching powder, by mixing some with starch paste. Then add a little acetic acid, followed by two or three drops of potassium iodide. (Blue colour of iodine is liberated by chlorine evolved from bleaching powder.) H (dressing material). Extract with water and test separate portions for :— (a) Copper. Addition of ammonia produces blue colour. (6) Sulphate. Barium nitrate gives a white precipitate insoluble in nitric acid. (c) Magnesium. White precipitate with ammonium chloride, ammonia, and sodium phosphate. Test the well-washed residue from the water extraction for barium in the flame, after moistening with hydrochloric acid. SECTION XVI THE PROCESS OF BLEACHING HE Nature of Colour. Colour is a physiological sensation produced by the phenomenon known as light. Light is a form of energy, the most important source for the production of which, so far as this universe is concerned, is the sun. Other sources are often called artificial. From the sun, ninety-two million miles distant, the energy is radiated by vibration of a medium that appears to be unappreciated Violet by our senses, the rate of travelling being about 186,000 miles per second ; that is, the time of passage is about eight minutes. It is now more than 250 years since Sir I. Newton showed, by placing a glass prism in the path of the sun’s rays, that a band of colours could be obtained therefrom (Fig. 233). This demonstration is usually referred to as “the Newtonian Experiment to show the composite nature of white light.” The explanation of this phenomenon is that as the rays of light pass through glass they are not all bent or refracted to the same extent, and. thus on emergence they are more or less sorted out. The red rays are refracted least, and violet rays most ; and between these two extremes occur yellow, green, and blue. This power of being able to resolve a composite light is not limited to glass nor to the phenomena of refrac- tion through glass. All substances do three things to rays of light: (1) Absorb them, (2) transmit them, (3) reflect them. If a substance absorbs all, or nearly all, the rays that fall upon it, it is said to be black ; those bodies which absorb very few and reflect nearly all are termed. white. 205 206 TEXTILE CHEMISTRY Other substances absorb some and reflect others, and as our optic nerve (by means of which we see) only conveys to our brain the sensation produced by those rays which actually irritate it, that is, the rays which are reflected from the substance, our perception of colour will depend very largely upon the nature of the reflected rays. Bodies vary much in the power of selective absorption (and conse- quent reflection), as can be demonstrated by many interesting experi- ments, e.g. if a bunch of flowers be illuminated with white light the individual flowers will absorb certain rays and reflect others, and the kind reflected will in all probability differ in each case, and thus we say the flowers are of different colours. But if the light falling upon them be of one wave-length only, that is, of one colour, a different effect is produced. Suppose the illuminating source is produced by holding crystals of common salt in a bunsen flame. This radiates chiefly what is termed yellow light, and thus only the yellow flowers appear in their usual colour, and the rest will appear to be black, the depth of shade depend- ing upon the thoroughness of absorption. But if the bunch be illuminated with the light from burning mag- nesium—a very white light, and.one particularly rich in blue and violet rays—the individual flowers appear in their usual colours, and probably brighter, and showing differences in tint much better than in ordinary daylight. This explains why materials appear to give different shades and colours in daylight, electric light, gas light, etc. White substances reflect back the light they receive practically unchanged. Now in bleaching the intention is to so alter the surface of the material that it shall reflect back as much white light as possible. To some extent this is done by exposure to sunlight itself, and also by polishing the surface, but to produce a dead white the particles at the surface which show a selective absorption or reflecting capacity must be removed altogether, or altered until they will reflect the incident light practically unchanged. That is the rationale of bleaching. Bleaching is a chemical process entirely, and in many cases one of oxidation (Section VII, page 63). Many chemicals are capable of changing the constitution of natural and other substances by oxida- tion, but the same chemical is not always so efficient with different substances, and in other cases certain destructive chemical action may result. Therefore many substances are in use. They are known as bleach- ing agents. BLEACHING 207 Chlorine (the preparation and properties of which have been con- sidered in Section XI, pages 125-130) is the chief bleaching agent in use for cotton. Owing to technical difficulties the gas is not applied directly, put as some compound which is capable of yielding it, such as bleaching powder or sodium hypochlorite. Water must be present also. The explanation of the reaction is that chlorine decomposes water, liberating oxygen in the nascent or atomic condition. The oxygen then oxidizes the natural colouring matter. Nearly all natural substances when oxidized become white, Le. the new compound produced reflects back more light than its prede- cessor. This may be illustrated by passing a stream of chlorine through a dilute solution of a dye. With bleaching powder an acid must be added to liberate chlorine. This is one reason for souring the goods. Any acid will do, even carbonic, produced from the carbon dioxide in air to which it is ex- posed. On a small scale acetic is the safest to use, but the bleacher uses sulphuric or hydrochloric. Sodium hypochlorite acts in a similar way, even without acid, but the addition of the latter promotes the action. Sulphur dioxide (for preparation and properties of which see Section XI, pages 132-133) is not used for cotton, but is chiefly used for bleaching straw, wool, etc. It is considered that the nature of the chemical reaction is here different from that with chlorine. In some cases the sulphur dioxide itself combines with the coloured body, and in others it decomposes the water which is present, liberating hydrogen, which in its turn reduces the coloured body. , Articles (particularly wool) bleached with sulphur dioxide are not - permanently decolorized. When washed with soap or exposed to air, the colour returns, owing to re-oxidation. In order that the bleaching operation may be a success it is neces- sary that the chemical shall come into intimate contact with the material, hence the necessity for removal of all grease and dirt, which is done by use of chemicals known as detergents. Those generally used are sodium carbonate or soda ash, caustic soda, lime, soap, resin, etc., for cotton, and ammonium salts for wool. Textile materials may be and are bleached at all stages of manufac- ture, but the most important application is to cotton cloth. In this process there are five distinct operations :— 1. Singeing and washing if necessary. 2. Removal of sizing materials and impurities in the cotton by (a) Boiling with lime under pressure. 208 TEXTILE CHEMISTRY (6) Acidifying to decompose lime soaps. (c) Boiling with resin soap if a “ madder” bleach is required. (zd) Boiling with soda ash under pressure. (e) Washing. 3. Treatment with bleaching powder, termed “ Chemicking.” 4. Souring or treatment with weak acid, to remove the lime and liberate the rest of the chlorine from the bleaching powder. 5. Final washing and drying. Singeing is done to remove all loose fibre from the face of the cloth, and is performed by rapidly passing the fabric over a hot plate or through a flame from a,series of bunsen burners. Sometimes the pro- SINGEING sesure APPARATUS RS S eas Cl ot h Fig 258 cess is repeated, and sometimes, if a very smooth finish is required, it is carried out a third time (Fig. 238). Washing is done in special machines in which the cloth is subjected to the action of wooden beaters, and as a rule the wet material is allowed to stand piled up for some hours after washing, in order that the starch may start fermenting, which assists in its subsequent removal... Boiling with lime or alkali is done in large iron vessels called kiers, the process being termed bowking. Kiers vary considerably in size and design, but Fig. 234 may be considered to represent the type in most general use. The bottom A is filled with smooth stones to provide drainage. On the top is packed the cloth B. Steam is allowed to enter the U-shaped BLEACHING 209 pipe at C. Near the bottom it passes an injector pipe D, which is fed from the bottom of the kier. Therefore as the steam rushes up branch E it carries with it the liquid from the kier, and as it empties itself in the form of a spray, establishes a circulation in the kier. Pipe G is for running off the liquor at the end of the boil. A safety valve, pipes for filling the vessel with water or alkali, and a man-hole are also fixed in the top of the kier. They are made to hold any amount of cloth up to two tons, and in exceptional cases more than that. They are often ten to Water —> twelve feet in height and four site alve to six feet in width. Manhole el ‘ <— A lime boil needs from six CANI\WS =C to twenty-four hours, according to the quantity of cloth being treated. = The resin soap and lye boils = are extended over three or B four hours. Washing, chem- icking, and souring of the bowked cloth is carried out in a machine such as is shown in Fig. 235. O The cloth is passed in rope WAC A form between squeezing rollers, and, guided by means of wooden pegs, it passes round a roller in G Fig23+ the bottom of the box which contains the acid or bleaching solution. If it is being washed the water is sprayed on to it just before it enters the box. The strength of acid used is such that it stands at 3° to 4° Tw., i.e. a sp. gr. of 1-015 to 1-02. Bleaching-powder solution has to be very carefully prepared to ensure the absence of lumps, which would produce oxy-cellulose, and so tender the cloth. The strength generally used is about 3° Tw. During the last few years considerable headway has been made with the process known as electric bleach, in which sodium hypo- chlorite is prepared electrolytically from common salt, and the solution so obtained is used instead of bleaching powder. Several forms of apparatus are on the market for making the bleach liquor, the essential point in their construction being that the liquid shall be thoroughly agitated during the decomposition, and its temperature kept from rising above 30°C. Under these conditions solutions of sodium chloride of various degrees of concentration can be electrolyzed by 14 D 210 TEXTILE CHEMISTRY currents of suitable strength, and the liberated ions caused to combine in the solution instead of escaping from it. In the Oetell electrolyzer, illustrated in Fig. 236, this is effected by using plates of gas carbon placed close together, the liquid being circu- lated by the liberated bubbles of hydrogen, which cause it to rise and flow over the glass partitions, from which it again finds its way to the bottom of the cell. The production of this “ electric bleach liquor ” can be well illus- trated with the apparatus shown in Fig. 237. The large boiling-tube B (about 2 inches in diameter) is closed with a rubber bung through which pass two carbon pencils C which are connected to the poles of a secondary battery giving a voltage of between 6 and 8 volts. Besides these the stopper holds a dropping funnel A, the end of which reaches to the bottom of the vessel B, a piece of glass tubing D, which also goes to the bottom, and a delivery tube E which passes to the bottom of a reservoir EF, and which can be closed by means of a tap G. To use the apparatus to prepare sodium hypochlorite, put a solu- tion of common salt in A, open both taps, and allow it to flow into B. When the vessel is about half full close both taps, and pass the electric current. Gas is liberated from both rods, in one case to a much greater extent than the other, and as it collects above the surface of the liquid BLEACHING 211 in B and is unable to escape, the liquid is gradually forced up tube D into vessel A again. The action of the current causes a partial destruction of the carbon rods and therefore it is advisable to introduce a filtering arrangement at the top if a clear liquid is desired. At intervals the liquid may be passed back again into B and the gas collected in a test tube from E and proved to be hydrogen by the usual tests for that gas. OUTLINE DIAGRAM OETELL ELECTROLYSER ‘To Dynamo Fig.230 carbons eae DD sont circulation Sol? fate Inney { 1 Vessel. Hole | _| glass “ie tt, hy PSs HS CEE | P 5 Hole Salt Solution ; * Cuter Vebsel) It is claimed for this bleaching liquid that it is not more costly than bleaching powder, that it is more efficient, and less liable to tender the goods, and also that it produces much less troublesome waste, and in particular no lime by-products. Whether the above claims be fully substantiated or not, there is no doubt but that it enables bleaching to be carried on much more efficiently on the small commercial scale, particularly in laundries and small mills where the manufacturer does his own bleaching and dyeing. 212 TEXTILE CHEMISTRY Mather & Platt, who also make an electrolyzer in which the circu- lation is effected by using a small pump, state that the electric pressure : 1 | csi Hydrogen Fig 237 generally convenient is 100 to 110 volts, and their standard electro- lyzer is made for this electromotive force, ‘Two cells can be placed in series if the pressure available is 200-220 volts. BLEACHING 213 The current required for a full output of the standard-size cell is 80-100 amperes. It may be somewhat interesting to know that the preparation sold under the name of “ Milton” is sodium hypochlorite made in this manner. The chemistry of the process may be represented as (a) Decomposition of salt into sodium and chlorine. (b) Decomposition of water by the sodium with production of caustic soda and hydrogen. , (c) Reaction of chlorine with caustic soda to produce sodium hypochlorite and hydrogen. At the same time small quantities of other compounds are pro- duced. SECTION XVII DYEING aE HE chief methods adopted for dyeing cotton yarn on an experimental scale with :— (a) direct, (b) basic, (c) sulphur dye-stuffs, (d) mineral colours. Dyeing is the art of producing a colour (or change of colour) on fibres, cloths, fabrics, and other articles. SUBSTANCES THAT HAVE BEEN AND ARE USED FOR DYEING Until about sixty years ago (1856) the substances used were natural dye-stuffis obtained either from plants and animals such as woad, indigo, cochineal, madder, cutch, logwood, turmeric, annatto; or certain chemicals (minerals) such as iron, lead, and manganese salts. Some of these are still used, but since 1856 the number and variety of dye-stuffs have been enormously extended by the preparation of the aniline and other dyes from coal tar, thousands of which are now on the market. | Alizarine (the dye-stuff in madder) is now prepared entirely from the same source, and indigo is largely so manufactured. Of the old natural dye-stuffs practically only two remain—logwood and cutch. Can all fibres be dyed with all these thousands of dye-stuffs ? They cannot; there is considerable variation in this respect. . As a rule animal fibres (like wool and silk) have a much greater affinity for dyes than vegetable fibres (like cotton), and therefore we find that similar treatment or identical dye-stuffs will not produce identical results in cloths made from mixed fibres. Again, it is found that to produce permanent and good colours many processes, and the application of several chemicals, are some- times needed, e.g. Turkey red used to take months to produce, and even now it requires days. Hence dye-stuffs have been divided into classes, largely governed by the method of dyeing that is possible with them ; and of these, the class in which there is the largest number at the present time is that known as ‘‘ The Directs,”’ \ 214 DYEING 215 This name was given because the colour could be applied direct to the cotton fibre without first treating it with a fixing chemical. The first Operation in Dyeing. The first step is always preparation of fibre or fabric. Dye liquor must penetrate the fibre in order to produce a permanent or level result. ‘Therefore all fat and filling, and injurious substances, must be removed, and if the colour desired is a light shade, the natural colour of the yarn must be removed by bleaching. To get rid of the fat and the grease cotton is boiled in a solution of very dilute caustic soda, or a 1 per cent. solution of soda ash for some time, and afterwards well rinsed in clean hot water. This is called ** boiling out.” Application of Dye-stuff to Cotton Fibre. It is applied in solution. Many dye-stuffs are soluble in water, others in water containing a few drops of acetic acid or a few grains of sodium carbonate. Some require the presence of a caustic alkali, and others a chemical called sodium sulphide. Ordinary direct cotton colours are usually dissolved in water, with the addition of a little sodium carbonate or sodium phosphate to make the solution more perfect. To determine the Quantity of Dye-stuff to use :— First select on a pattern card (which is the result of experimental dyeing by the dye-maker) the shade desired. This will give (1) Percentage of dye-stuff required ; (2) percentage of assistants, as the chemicals are called which are used in the dye bath. This percentage refers to the weight of the material to be dyed ; therefore the next step is to weigh the cotton in the dry condition, and then to calculate the weight of dye-stuff and chemicals to be dissolved in the bath. Suppose the pattern card said 2-5 per cent. dye, 20 per cent. - Glauber salt, 1-5 per cent. soda ash, and the material to be dyed was a 10-gram hank, the required quantities would be dye 0-25 gram, Glauber 2 grams, soda ash 0°15 gram. For experimental dyeing, as the quantities required are so small, it is usual to make up standard solutions, i.e. solutions of definite volume containing a known weight of dye; e.g. 1 gram of dye in 100 c.c. of water: then 10c.c. will contain 0-1 gram, and if 25 c.c. of this solution be used we should get 0-25 gram without directly weighing this small quantity. The Volume of the Dye Bath. As the quantity of liquor will affect the strength of the solution, and the strength of the solution will materially affect the shade and other features of the dyed goods, the ~ volume of the dye bath is a very important factor. For hand-dyed yarn it is usual to keep the ratio between 1:12 216 TEXTILE CHEMISTRY and 1: 20—different makers vary slightly. Assume our instructions are 1:15. This means that if the goods weigh 1 gram the volume of the bath should be 15 c.c., or, for 10 grams, a volume of 150 c.c. So after adding the dye and assistants to the dye pot, the total volume is made up to 150 c.c. and stirred. The Temperature at which it is desirable to carry on the Dyeing Operation. The most successful dyeing is obtained by entering the goods when the bath is warm (say at 60° C.), then gradually raising to the boil, and keeping at the boil for about thirty minutes. If the bath is too hot when the yarn is entered, the colour “rushes on” and produces uneven dyeing. How the Goods should be entered, and other Precautions and Manipula- tions that are necessary during the Process. The hanks should be put into the bath in a uniformly wetted condition, but not running with cold water (‘‘ wetted out ’’). They should be wrung well, shaken out to ensure even wetting, and immersed as quickly and completely as possible. They should be turned all the time they are dyeing, to ensure evenness and to keep the bath at a uniform temperature. The water used must not be hard (particularly with magnesium salts) or uneven dyeing will result. Reasons for adding the various Assistants to the Bath. Sodium carbonate is added to ensure complete solution and to make an alkaline bath, which is necessary when dyeing cotton with direct colours. Glauber salt (sodium sulphate) is to render the dye-stuff less soluble, in other words, to throw the dye out of solution, so that more is taken up by the fibre. As it is, these baths are never exhausted, seldom more than one-third of the dye being abstracted. Common salt is used for a similar reason ; it is cheaper than Glauber, but not quite so good for light shades. Sodium phosphate is better than either, but it is much more expensive. The Manipulations necessary after Removal of Yarn from the Dye Bath. Directly the yarn is removed from the bath it should be well washed in running cold water until all loose dye liquor is removed, well wrung, and dried in the air. Sometimes it is soaped after washing, i.e. it is worked for ten minutes in a dilute solution of pure soap and water at a temperature of 40°-60°C., and then dried without rewashing. This brightens the colour and increases its fastness somewhat. ‘¢ Basic Dyes.”’ As a rule, for brilliancy of shade, the direct dyes are much inferior to another class called the basics—so named because they react with certain acids in a very similar manner to basic radicles, to form colour salts. | ; The earliest discovered of these were mauvine and fuchsine. Others are methyl violet and methylene blue. Because of the great — DYEING 217 intensity of the colouring principle, very little dye-stuff is required for a large quantity of goods. They have not nearly so large an application as directs, chiefly for two reasons :— | 1. They are much more fugitive to light and washing. 2. For vegetable fibres they cannot be dyed in one operation. (For animal fibres they can.) The fibre must be mordanted with certain chemicals in order that the colour shall not wash out. Mordanting. A mordant is a substance which is capable of being absorbed by a fibre, and which, when brought into contact with a dye-stuff, forms a compound with it in the interstices of the fibre, and thus prevents its easy removal by washing. This compound is usually called a “Jake.” Substances which are capable of acting as mordants to cotton are :— (a) A solution of albumen or white of an egg in cold water, fixed by passage of the impregnated yarn through hot water. (b) Tannic acid. (c) Turkey red oil. (dq) The direct cotton colours. The cotton yarn is well worked in these, but if tannic acid is used another process is necessary to fix it on the fibre before putting it into a dye bath. Several substances can be used for this purpose: the two in general use are (a) tartar emetic; (6) ferrous sulphate. — The iron salt is used only for dark shades. Mordanting and Fixing. The process is carried out in this way: The boiled out yarn is put in a bath of cold tannic acid, boiled up, and then allowed to cool down or “ feed ” in it for some hours—say all night. After removal the yarn is squeezed uniformly and put into the cold fixing bath for an hour or more. Of course the yarn is turned at intervals during the immersion. After removal from the fixing-bath it is squeezed and rinsed, when it is ready for the dye bath. Quantities of Mordant and Fixer to be used. Tannic acid, from 0-5 per cent. for light up to 8 per cent. for dark shades ; tartar emetic, from 0-25 per cent. for light up to 4 per cent. for dark shades. Preparation of Dye Bath. The method is similar to that described for directs, the calculation for quantities required being identical. The bath is generally made not quite so “ short ”—20 of liquor to 1 of goods being usual—and no soda ash or Glauber salt is added, but as a rule a little dilute acetic acid is advisable. The temperature when the yarn is entered should not exceed 40° C., and it may be colder with advantage. If higher, the colour tends to rush on and uneven dyeing is the result, 218 TEXTILE CHEMISTRY The bath is then raised very gradually nearly to the boil, and kept so until the total time of immersion has amounted to half an hour. Washing and soaping follow as with directs. Precautions in Dyeing Basics. To obtain really good results in dyeing basic colours, several precautions are necessary. One of the most important is the necessity for pure water. Hardening salts produce uneven dyeing much more readily than with directs, due to precipitation of the colour. Peaty matter and the slightest trace of iron salts also spoil the shade. LABORATORY EXERCISES IN THE DYEING oF CoTTON YARN WITH DIRECT AND Basic COLOURS The method which I have found to be most satisfactory for initiating elementary students of textile chemistry into the art of practical Fig. 230 dyeing is to provide them with standard solutions of dye-stuffs and chemicals and the following set of instructions. “Ten-gram ”’ hanks, bleached and unbleached, are also available. At Nelson, where they were purchased ready for use, two-fold 20’s and two-fold 40’s soft spun yarn was dyed. At this College we are supplied from our own spinning department, and as a rule single-twist is used. A little more care is necessary in the dye bath on this account. The dyeing is done in porcelain beakers of at least 300 c.c. capacity, which are suspended from removable copper lids in sets of four. They are surrounded with water in a copper vat, which is heated by and a 4 DYEING 219 stands upon a ring or Argand gas burner standing on a sheet of asbestos placed on an iron grid to protect the bench (Fig. 239). Dyeing-sticks made of }-inch glass rod are used. Some of these are bent at 45° to permit the complete immersion of the yarn while in the liquor. Each student is expected to dye light and dark shades of at least two direct and two basic colours, to take them down to the weaving- shed after they have been dried and inspected, to wind them on pirns and weave them up as weft for a good weft face cloth. Part of the woven sample is retained by the student and part by the College. COPY OF INSTRUCTIONS GIVEN Instructions for Dyeing Direct Cotton Colours You are provided with the following :— Four 10-gram bleached hanks for light shades. Four 10-gram unbleached hanks for dark shades. Standard solutions of these dyes :— Direct yellow C Direct green B of a strength that 10 c.c. contains Trisulphon violet B 0-05 gram. Chloramine sky-blue FF Also : Soda ash solution for boiling out yarn (1 per cent. strength). Soda ash standard solution, 10 c.c. containing 0-075 gram. Common salt ,, i‘ 10 c.c. * 2-5 a Glauber salt _,, - 10 c.c. - 1:0 eo I. Boil out the unbleached yarn in the 1 per cent. solution of soda for half an hour. Rinse well in hot and then cold water until all chemical is removed. Squeeze well and shake out. Soak the bleached yarn in hot water,then in cold, squeeze and shake. II. Prepare the following dye baths, and work them four at a time, two workers to the set, so that each student has two hanks to turn and dye. (a) For light shade (1 per cent.) Chloramine sky-blue FF. 20 c.c. of dye solution (i.e. ‘1 gram). 10 c.c. of Glauber solution (i.e. 1 gram or 10 per cent.). 10 c.c. of soda ash solution (i.e. 075 gram or -75 per cent.) 150 c.c. of water. (b) For dark shade (4 per cent.) same colour. 80 c.c. of dye solution (i.e. -4 gram). 10 c.c. of salt solution (i.e. 2:5 grams or 25 per cent.). 10 c.c. of soda ash solution. 90 c.c. of water. 220 TEXTILE CHEMISTRY (c) For light shade (-5 per cent.) Direct green B. 10 c.c. of dye solution (i.e. -05 gram). 10 c.c. of Glauber solution (i.e. 10 per cent.). 10 c.c. of soda ash solution (i.e. *75 per cent.). 160 c.c. of water. (d) For dark shade (3 per cent.) same colour. 60 c.c. of dye solution (i.e. -3 gram). 10 c.c. of salt solution. 10 c.c. of soda ash solution. 110 c.c. of water. (e) For light shade (-5 per cent.) Direct yellow C. 10 c.c. of dye solution (i.e. -05 gram). 10 c.c. of Glauber solution. 10 c.c. of soda ash solution. 160 c.c. of water. (f) For dark shade (2 per cent.) same colour. 40 c.c. of dye solution (i.e. -2 gram). 10 c.c. of salt solution. 10 c.c. of soda ash solution. 130 c.c. of water. (g) For light shade T'risulphon violet B (-25 per cent.). 5 c.c. of dye solution (i.e. -025 gram). 10 c.c. of Glauber solution. 10 c.c. of soda ash solution. 165 c.c. of water. (h) For dark shade (2 per cent.) same colour. , 40c.c. of dye solution (i.e. -2 gram). 10 c.c. of Glauber solution. 10 c.c. of soda ash solution. 130 c.c. of water. III. Raise the dye bath to 50° C., stirring at intervals. Take the bent glass rod in the left hand and a straight one in the right. Hang the hank on the bent rod, hold it vertically over the dye pot, and then drop it down so that the bottom of the hank enters first, and the bent rod last of all. Use the straight rod to help to immerse it com- pletely. Atintervals lift up the bent rod so that about a quarter of the hank is held out of the dye liquor, and then, by passing the straight rod under it, turn the hank ; i.e. lift up a portion in the air and move it to the other side of the bent rod. Repeat with the fresh portion which has come up out of the pot—the passage of the hank being similar to that of an endless rope over a pulley. Continue dyeing at the boil for half an hour. IV. Remove, wash under the tap or in a vessel containing plenty of cold water, and put into a soap bath at 60°C. for ten minutes. DYEING 221 Squeeze, but do not wash again. Shake out well and hang over a glass rod to dry in the air. Label each hank with your name and particulars of colour and percentage of dye used. Instructions for Dyeing Basic Colours on Cotton The porcelain trough labelled “ A” contains thirty 10-gram hanks of cotton yarn that have been “feeding” for about 12 hours in a solution of tannic acid containing 6 grams in 2,000 c.c. of water at 40°C. These are to be used for light shades. The trough labelled ‘“‘ B ” contains the same number which have been steeping in a solution of double the strength, i.e. 12 grams of tannic acid in 2,000 c.c. of water. These hanks are to be used for dark shades. Proceed to FIx your own hanks in the correct solution of tartar emetic which is provided. Solution “‘C” contains 1-5 gram of tartar emetic per 1,000 c.c. This is for fixing hanks from “A ”’ for light shades. Solution “‘D” contains 3 grams per 1,000 c.c. and is for hanks from ‘“B” for dark shades. Take out three hanks for each shade, gently squeeze them, shake out, and put each set into 200 c.c. of the correct fixing solution in a porcelain pot and work in the cold for 15 minutes. Remove, squeeze, and rinse with water slightly. | Work in a slightly warm soap bath for two or three minutes, wring out, and rinse well. They are now ready for the dye bath. [This step may be omitted if time is limited. ] While the hanks have been fixing the dye bath should be prepared, 1. In a porcelain pot put 100 c.c. of cold water. 2. Add 2 c.c. of a 10 per cent. solution of acetic acid. 3. Enter the yarn and turn it two or three times. 4. Remove the yarn for a few seconds. 5. Add the dye solution (for quantities required see below), stir well, and add sufficient water to make the total volume of the bath 200 c.c. 6. Re-enter the yarn and work in the cold bath for 10 minutes, . then slowly raise the temperature to 60°C. Work the yarn all the time, and when it has been in for about 45 minutes in all, remove it. 7. Wash in cold water, soap in just warm soap bath, squeeze, shake out, and dry as before. Quantities of dye solution required for dyeing one 10-gram hank :— Bismark brown, light shade 0-75 per cent.,i.e. 15 c.c. of solution Do. Bete yj) o Fe = 60 Re ‘A Brilliant green, light __,, 0-5 4 5 os WLU eae 4 Do. dark 29 2 9 oe) 40 29 99 222 TEXTILE CHEMISTRY Methyl violet, light shade 0-25 per cent., i.e. 5 c.c. of solution Do. dark 99 1 29 29 20 ” 99 Methylene blue, light sya eae yr Bee an Do. dark 2 99 > 40 be) 99 All the above standard solutions were made up by dissolving 5 grams of dye-stuff in 1 litre of water to which a few drops of acetic acid had been added previously. The Sulphur or Sulphide Colours The sulphur or sulphide colours form a class of direct cotton dyes which are | (1) Insoluble in water, but soluble in sodium sulphide. (2) Oxidizable in air. (3) Very fast to light, washing, milling, alkalis, acids, cross-dyeing, and stoving (sulphur dioxide). (4) Not very resistant to chlorine. In trade they are known under other names, e.g. thion, katigen, thionol, cross dye, immedial, kyrogene, thiogene, etc. They are rapidly displacing aniline blacks, indigo, catechu browns, khaki, logwood blacks, etc. They form excellent bottoms for basics and indigo. For experimental dyeing it is not advisable to prepare standard solutions. A larger amount of dye-stuff is required to produce the corresponding depth of shade than is the case with directs or basics. From 1 per cent. to 4 per cent. for light shades, and 8 per cent. to 12 per cent., or even 15 per cent., for dark shades, is required. The dye solution is prepared by mixing the indicated quantities of dye-stuff, sodium sulphide, and soda ash with boiling water till all is dissolved. The amount of sodium sulphide required varies with the make and brand of dye, and whether the sulphide used is calculated as concentrated or crystallized. 1 gram of conc. sod. sulphide = 2 grams of the cryst. variety. Single brands of colour usually require half their weight of sodium sulphide (conc.), and extra brands an equal amount. The addition of Glauber salt to the dye bath (if required) is made after the colour has been dissolved. Then add the rest of the water (at boiling temperature) to make a volume of 20 to 1 of the cotton. Soda ash used is from 4 per cent. to 10 per cent., Glauber from 20 per cent. to 30 per cent. (or salt 15 per cent. to 25 per cent.). Some- times 2 per cent. of Turkey red oil is added to the bath. Dyeing Cotton with Sulphur Colours. For most colours, the yarn should be entered at the boil and the source of heat immediately with- drawn. Light blues are best dyed at 30° to 40° C., dark blues at 50° to 70° C., mercerized yarn at 70° to 80° C., and some can be dyed in the cold, but in this case the bath should be more concentrated. DYEING 223 The dyeing should last # hour to 1 hour, and the hanks should be turned every few minutes. While so doing they should not be exposed to the air, but kept under the surface of the liquid. If the cotton is mercerized, more sodium sulphide is needed, and no common salt should be used. When dyeing is finished the yarn should be removed quickly, thoroughly squeezed, quickly rinsed (to prevent unequal development), well shaken in the air, and soaped. As exercises dye 10-gram hanks of cotton as follows :— (1) 5 per cent. sulphur blue. (2) 10 per cent. do. (3) 1 per cent. sulphur black. (4) 10 per cent. do. : 3 per cent. sod. sulphide (conc.). Using for (1) 9 P 7 are te ( ) and (3) 10 2 Glauber salt. 10 - sod. sulphide (conc.). Using for (2) et and (4) 60 < Glauber salt. The Mineral Colours. In spite of the fact that the “coal tar dyes ” have obtained such prominence in the industry, the use of cer- tain mineral colours is by no means extinct, and it is doubtful if they will ever be completely driven off the market for certain classes of trade. The chemistry of the process should be first studied by perform- ing the following experiments :— 1. Prepare the following solutions :— (a) Lead acetate, by dissolving a few crystals of “sugar of lead ” in water. (b) Potassium dichromate in water. (c) Manganous chloride, by acting on manganese dioxide with strong hydrochloric acid, filtering and boiling till excess of chlorine is expelled. (d) Ferrous sulphate and ferric chloride. (ec) Potassium ferrocyanide—use yellow prussiate of potash. 2. To lead acetate solution add some potassium chromate solution. Note the formation of a yellow precipitate of lead chromate (chrome yellow). Divide this precipitate into three portions, to :— (a) Add nitric acid and note that it dissolves. (6) Add a little boiling lime water. Note change of colour to chrome orange. - (c) Add excess of caustic soda and that note it dissolves. 3. To a little of the manganous chloride solution add two or three drops of caustic soda. Note the formation of a white precipitate, which rapidly darkens on addition of more soda or on boiling. 224 TEXTILE CHEMISTRY Divide the precipitate into three parts, and to (a) Add a little bleaching-powder solution—note increased darkening (manganese bronze) ; (6) Add some potassium dichromate solution and note a similar result ; (c) Add sodium hypochlorite solution and note what happens. 4. To separate portions of ferrous sulphate solution add :— (a) Caustic soda; (b) sodium carbonate solution. To each add some bleaching-powder solution. Note formation of iron buff. Repeat the experiments with ferric chloride solution. 5. Mix ferrous sulphate and ferric chloride solutions, and then add potassium ferrocyanide. Note production of Prussian blue. Dygrina MINERAL COLOURS 1. Chrome Yellow. Prepare a solution of basic lead acetate by mixing 12 grams of commercial sugar of lead, 6 grams of litharge, 35 c.c. of water. Stir up at intervals for five or six hours. Dilute with water till its sp. gr. is 1:05 (10° Tw.). Allow it to settle or filter. Work the previously boiled-out yarn in this for half an hour. Wring well, shake, and put it into a bath of potassium dichromate solution containing 8 grams per litre. Remove, wash thoroughly, treat with a weak solution of Turkey red oil in water and dry. 2. Chrome Orange. Treat hanks that have been dyed chrome yellow (but which have not been oiled) rapidly in a bath of clear boiling lime water. Turn very rapidly two or three times, remove as soon as the colour is fully developed, and rinse twice. Enter in a warm bath containing soap, a little soda ash, and cotton- seed oil. Squeeze and dry without further rinsing. 3. Iron Buff. Evenly impregnate the yarn with a solution of ferrous sulphate, squeeze, and pass it through a weak solution of caustic.soda or soda ash or lime water. Then pass it through a weak solution of bleaching powder. Rinse and dry. To produce a much brighter and better shade of iron buff :— Use a solution of “nitrate of iron” of from 2° to 6° Tw. Nitrate of iron is prepared from ferrous sulphate as follows :— Take 340 grams of ferrous sulphate, dissolve it in water, add 20 c.c. s conc. sulphuric acid and 20 c.c. of conc. nitric acid. Boil for some _ DYEING 225 time, keeping the volume constant. Filter: a dark red liquid is produced. Dilute it till correct sp. gr. is obtained. 4. Prussian Blue. _ Dye the cotton iron buff and then pass it through a solution of potassium ferrocyanide acidified with sulphuric acid. 5. Manganese Bronze. Impregnate the yarn with a solution of manganous chloride. Fix it in a hot solution of caustic soda containing 30 grams per litre. Rinse it in a weak solution of bleaching powder (strength 1° Tw.). ° Wash and dry. TESTING DyED SAMPLES It is very essential that every dyed sample should be submitted to certain tests, and that a systematic record of the same should be pre- served. The plan illustrated on the next page will be found a suitable one for beginners. To carry out the tests proceed as follows :— 1. Fastness to Light. Take a piece of glass about 4 inches by 6, and cut a piece of white cardboard the same size. Bind them together along one edge by means of a strip of photographic adhesive “ leather- ette.”’ On the top of the cardboard put a piece of black paper, on the top of this a piece of white filter paper, and on the top of this a few strands of the dyed yarn which is to be tested. Cover half of it with two thicknesses of black paper and let the glass fall into position. The remaining three edges can now be bound, or two rubber bands can be passed round. The whole arrangement can now be exposed to bright direct sun- light for days, or weeks (if necessary). The degree of fastness is judged by comparing the portion exposed with the portion that was kept under the black paper. Generally speaking, sulphur and mineral dyes are fast to light ; basics very fugitive (particularly the lighter shades), and directs vary considerably. 2. Fastness to dilute Acids and Perspiration. Steep in cold 25 per cent. solution of acetic acid for five minutes. Wring, wash, and dry. 3. Fastness to Washing. This test can be made in two ways :— (a) Steep for five minutes in a 1 per cent. solution of sodium carbonate. (6) Plait with a few threads of undyed yarn and boil for ten minutes in a 1 per cent. soap solution. If the colour “‘ bleeds,” the undyed yarn will be tinted, and it should also be filed in the record. 15 226 TEXTILE CHEMISTRY SPECIMEN PAGE oF RECORD Name of Colour used \.......00:00s00050cc00s504¢s00use9 skeen ean Class of Dye: Substantive or Direct Cotton Colour................... Shade Light Medium Dark Exhaust Percentage Dye used . . —- —_—— ioe Be kad Percentage Glauber or Salt — — eaeeeoner eee Percentage Soda Ash . . — —— ieee ened Samples of above, showing fastness to :— LLAGIA 2 Fee lite ney O O . Dil. Acids O O . Washing . Boe O O 1 Sirippiig sae. oe sa O O io. O O . Bleaching ao -~» WwW bd Beamer ks ...ccsccoccccccsscucecsanecsceaccesdeees suncecouyeceneanaelne: tn =aa= === 4. Fastness to ‘‘ Stripping.” Plait with white yarn and boil in pure water for fifteen minutes. Look for (a) tinting of white yarn ; (5) coloration of water ; (c) loss of colour on the dyed yarn. 5. Fastness to Bleaching. There is considerable misconception with respect to what is known as “ fastness to bleaching ” and “ bleach- ing colours.” Almost any colour can be wholly or partly bleached if the bleaching process be intense enough. Modern laundries as a rule use bleaching chemicals in a manner which acts much more drastically than is the case in ordinary calico-bleaching, and it is unreasonable to ask for fastness to bleaching in an unlimited sense. The test here given is a reasonable one, and is similar to that applied by one of the largest manufacturers of “ cloths to stand bleaching * in Lancashire. Make a solution of fresh bleaching powder, strength 5 grams per 100 c.c., and filter. Steen the dyed yarn in the (cold) filtrate for ten ativan’ Remove, and without squeezing or washing put it in dilute acetic acid or dilute sulphuric acid (1° Tw.) for ten minutes. Remove, wash well under running water, and dry in the air. SECTION XVIII MERCERIZING MERCERIZATION OR MERCERIZING OF COTTON This word was coined from the name of the discoverer of the phenomenon. John Mercer, whilst experimenting in 1860 with caustic soda solu- tion and cotton yarn, found that if the concentration reached about 20 per cent.,and the fibre was steeped in it for 5 to 10 minutes, and afterwards removed and thoroughly washed, certain very noticeable changes had been produced :— 1. There was a shrinkage in length, varying between } and } of the original. 2. If the cotton was dried the weight was greater than that of the original by approximately 5 per cent. 3. The strength of the yarn was also increased by anything up to 60 per cent. 4. The fibre was made “ fuller.” 5. It showed an increased affinity for dyes. This effect was not confined to cotton in the form of yarn—similar results could be produced in cloth. Mercer patented his process with the idea of putting on the market a stronger and fuller yarn and cloth. Unfortunately mercerized cotton was not a commercial success in Mercer’s lifetime, and in fact made very little progress until another property regarding it was discovered some thirty years later. Since then it has increased enormously in popularity. This important characteristic is produced by stretching the cotton during or after immersion in the alkali, and keeping it so during the washing process. | The fibre is thus prevented from contracting, with the result that an external lustre is produced. It is true that the increase in strength is reduced—being less than 40 per cent. instead of 60 per cent., but the “silky ” effect obtained more than counterbalances this deficiency. The chemistry of the process as worked out by Gladstone is :— While the cotton is immersed in the soda solution a compound of cellulose and sodium oxide is formed. 15* 228 TEXTILE CHEMISTRY During the washing this is decomposed by the removal of the sodium and the substitution of hydrogen (from the water) in its place. This results in the production of a hydrate of cellulose. Assuming the empirical formula of cellulose to be (Cg5H1.0;5). we can represent the changes as follows :— (C,.H1,05)2 + 2Na0H — (C,H,.0;).Na.O + H,O. (C,H,,0;),Na,0 + 2H,0 = (C,H,,0;)..H,0 + 2NaOH. Mercerized cotton. The examination of mercerized cotton under the microscope shows that the fibre has been somewhat untwisted, the walls being con- siderably increased in thickness, the hollow flattened ribbon being changed to a thickened cylinder with practically no hollows (Fig. 240). Poor-quality or short-staple cotton is not suitable for mercer- izing, and the best results are obtained by using 2-fold - Egyption or Sea Island which has been previously | bleached. | The strength of caustic soda used should be between 50°-70° Tw. and the operation should be conducted at a temperature of 60° Fah. After washing with water the lustre may be increased by washing with dilute acetic acid and the silky effect may be still further in- (@) creased by a special calendering process. The best chemical test to apply to yarn or cloth to _ detect mercerization is to treat the cotton with a cold : saturated solution of zine chloride, potassium iodide, Fi Ug. 240 and iodine. | The reagent is prepared by dissolving 30 grams zinc chloride (pure solid) hog’, potassium iodide lin 24 c.c. of water. 1 gram _ iodine It should be kept in a small glass stoppered bottle. . If the sample is white it may be used without previous preparation. If it is coloured it must be first bleached and dried before the test is applied. A very small piece (if cloth) or a few strands (if yarn) are im- mersed in the dry condition for 2 or 3 minutes in the liquid, and then transferred by means of a glass rod to an evaporating dish nearly full of water. By means of the rod the cotton is kept under the surface of the water and moved about to wash it. If the cotton has not been mercerized the dark blue colour will gradually become fainter and ultimately disappear. In the case of mercerized cotton the colour remains a distinct blue. | INDEX Acrtic acid, preparation and pro- perties of, 121, 122 Acetylene, 117 Acids, definitions and preparation of, 66 — reactions for detection of, 156, 157 Action of chemicals on fibres, 162 — heat on fibres, 162, 163 Adhesives used in sizing, 174 Adulterations in flour, 189 Alcohol as a solvent, 20 Alcohols, 118 Aldehydes, 120 Alkalis, definition and preparation of, 66 Alkali waste, 147 Allotropic forms of sulphur, 148 Alloys, 34 Alum, properties of, 36, 139-142 — solubility of, 142 — — uses of, 140 Alumina, 140 Aluminium, preparation and _pro- perties of, 36 — bronze, 140 — chief compounds of, 140-142 — determination of equivalent of, 93 — sulphate, 142 Ammonium chloride, 36 — — crystals, '24 — hydrate, preparation and properties of, 78 — — use in dyeing, 79 Amy] alcohol, 118 Analysis of a simple salt, 154-157 — air, 54, 55 — — accurate method, 54 — water, 43 Animal charcoal, 102 Anthracene, 116 Antiseptics, definition of, 201, 174 — examples of, 201 Apparatus for preparation of pure water, 42 Artificial silk, 161 Ash in cotton, 165 — — oils, 178 — — silk, 167 — — wool, 166 » British thermal unit, 169 , Bzrodlie’s apparatus estimation Ozdne;”’ ; °;’ ° 229 , > 9 9 @ Pea? 2 g9 2B > > , > @3 90993 > 23 999 9999 Aspirator, 4 Atmosphere, The, 52-60 Atomic theory, 80 — weights, 81 Atoms, 80 Avogadro’s law, 89 ~ BacteriA, collection of, 60 Balance for weighing, 8 Bases, 66, 67 Basic alum, 142 — reactions, 153-155 Beaker, 3 Beaume’s scale, 14 Belgian process for zinc, 143 Bell jar, 4 Bending glass tubing, 15 Benzene, 21, 115, 116 Black’s researches on chalk, 110 Bleaching agents, 207 — powder, preparation, properties, etc., and use of, 37, 127, 128, 131, 209 — with chlorine, 126, 127, 207, 205, 213 — — sulphur dioxide, 207 Boiler feed water, 174 — — — compositions for, 174, 175 Boiling and evaporating compared, 27 — point, apparatus for determination of, 27, 28 — process of, 27 Borax beads, 154 Borda’s method of weighing, 11 BO.Va 71 Bowking, 209 Boyle’s experiments with air, 53 — law, 51 Bradford conditioning house standard, 166 Breathing, 64 — volume of air required for, 65 ¥9°? > "9 4 a o > ? pf 9 > @ SCevecee © 2 . 3@ 29429009 ) a) Bunsen burner, 6 — — method of using, 11, 12 Burette,.5> 35° a 20) 9992 "a" @ 2 ; ) 2 9a > » Sa a , > 99d , ,a~o > ec « ‘China:clay; 146 $5 fet 8 ts ee 230 Burnett’s disinfecting fluid, 202 Burnt alum, 142 Butyric acid, 121 CAKE alum, 142 Calcium chloride in sizing, 200 Calx, 53 Cane sugar, 123 Carbolic acid, 202 Carbohydrates, 122-124 Carbon-amorphous, 101 — and its compounds, 101-124 — properties of, 35 Carbonates, analysis of by acid, 106— 109 — — heat, 109 — tests for, 106 Carbon dioxide, Angus Smith test for, 57 — — — — table, 58 — — estimation of, 106-109 — — inair, 57 — — Pettenkofer test, 57-59 — — preparation and properties of, 103-105 — — uses for, 105 Carbon disulphide as a solvent, 20 Carbonization of cotton, 140 Carbon monoxide, preparation and properties of, 112, 114 Carboy, 30 Carded cotton, 164 Carnallite, 144 Cassava starch, 188 — — microscopic-appearance of, 185 Castner’s process, 129, 130 Catalyst, 70 Caustic soda, properties of, 37 Cellulose, 123 — in cotton fibre, 164 Centigrade degrees, 12 Cetyl alcohol, 118 Charcoal, 102 — reactions, 154 Charles’ law, 49, 50 — — determination of, 50 Chemical arithmetic, examples in, 99 — change, definition and examples of, 37-39 — — identification of, 38 — tests for identification of fibres, 163 — tools, 8-14 — theory, 80-100 Chemicking, 208 — machine for, 210 ‘ Ce eee BS — £ < “ < j ‘ i oo % 6% ying Keres eo” « ® cn @ ~— ‘ignition of, 33 — — in sizing, 196, 197 oe (— .- moissure im, LOT oe ose €éte“e © GEE « a & eeu ee ‘ €é 6 ¢ TEXTILE CHEMISTRY Chloroform as a solvent, 20 — preparation and properties of, 117 Chloros, 131 Chlorine, plant for preparation of, 128, 129 — preparation and _ properties of, 125, 131 — uses for, 127 Chrome, orange, 224 — yellow, 224 Clarke’s process for water softening, 41 Classification of matter, 34, 35 Coal, 102, 103 — analysis of, 168-172 — ash in, 168, 169 — calorific value of, 169-172 — determination of moisture in, 168 — gas, 103 — — waste, 148 — tar, 103 — — asa source of ammonia, 78 Cocoa-nut oil soap, 193 Coke, 102 Colour, nature of, 205 Condensed water, 174 Cold saturated solution, preparation of, 23, 24 Combustion, Lavoisier’s theory of, 64 — process of, 64 Composite nature of white light, 205, 206 Composition of cotton fibres, 163, 164 — — raw wool, 166 — — water, 45 Compounds, definition of, 34 — examples of, 35 Conditioning of cotton, 164 — — wool, 166 Constitution of air, 55 Cooper’s viscometer, 181, 182 Copper, determination of equivalent of, 93 — properties of, 35 — oxide, properties of, 35 — sulphate, 202, 36 Cork boring, 16 Correction of volume of gas to N.T.P., Cotton fibres, diagrams of, 161 Crucible, 6 Cryolite, 140 Crystallization, 22, 24 Crystals, 22 - Deacon process for chlorine, 129 : Degree of solubility, determination of, 4 Detection of acidic radicles, 156, 157 — — chlorides in cotton, 164, 165 — — metallic radicles, 152-155 INDEX Detergents, 207 Determination of ash in cotton, 165 — — — — substances, 32, 33 — — moisture in cotton, 165 Dextrine, properties of, 37 Dextrose, 126 Diagrams, 1-7 Diffusion of gases, 51 Direct dyes, 215, 216 Distillation, apparatus for, 21 — process of, 21 — flask, 7 — water, apparatus for, 21 Distilled water, apparatus for, 21 — — preparation of, 21 Dolomite, 144 D.O.V., 71 Drawing of diagrams, 1-7 Drawn silver, 164 Drying tower, 7 Dust in air, 59, 60 Dyeing cotton with basics, 216, 217 — — — directs, 215, 216 — — — minerals, 223, 224 — — — sulphurs, 222, 223 Dyeing, processes of, 214-226 Eau de Javelle, 130 — — Labaraque, 130 Effect of solution on weight, 23 Effects of heat, examples of, 31 — — — on substances, 31 Electric bleach, 209, 210 Electrolytic decomposition water, 45 — — — apparatus for, 45 Elements, definition of, 34 — examples of, 34 Epsom salts, 144 Equations, list of, 98, 99 — meaning of, 97 — use of, 97 Equivalents, definition of, 89 — determination of, 89-94 — — — by precipitation, 93 — table of values for, 94 Estimation of iron in water, 174 Ether as a solvent, 20 Ethers, preparation and properties of, 119 Ethyl alcohol, 118 — ether, 119 Ethylene, 117 Evaporation, process of, 23 Exercises in solution, 22 — — use of balance, 10 Exercises with Joly balance, 11 Experimental dyeing “‘ Directs,’ 219, 220 Experiments with starch, 188, 189 Eyepiece, 159 231 FAHRENHEIT degrees, 12 Farina, microscopic appearance, 185 — preparation and properties, 186, 187 Fastness to acids, 225 — — bleaching, 226 — — light, 225 — — perspiration, 225 — — stripping, 226 — — washing, 225 Fatty acids, 121 Fatty oils used for textile purposes, 176 Feeding, 221 Fermentation, 200, 201 Ferments, 200 Ferrous suphate, properties of, 36 Fibres, microscopic appearance, 161 Filtration, process of, 25, 27 Filtering media, 27 Fitting up apparatus, 18, 19 Fixing, 217 Flame reactions, 154 Flash point apparatus, 178 Flask, 1 Flour, 37 — ash in, 184 — moisture in, 184 — preparation and properties of, 184— 186 — starch in, 184 Flue gases, examination of, 172-174 Formaldehyde, preparation and pro- perties of, 120 Formalin, preparation and properties of, 12 — asan antiseptic, 202 Formic acid, 121, 122 Formuls, list of, 96, 97 — meaning of, 96 Free acid in oils, determination of, 178 — alkalis in oils, 178 — fatty acid in oils, determination of, 182 Fresh air, 53 GALVANIZED iron, 142 Gas carbon, 102 Gases, 34 — apparatus for solubility of, 20 — classification of, 47 — collection of, 49 — determination of density of, 47 — general properties of, 47-52 — relative densities of, 47 . — solubility of, 20, 47 — table of properties of, 47 Gas jar, 3 — liquor, 78 Generator gas, 112 Germs in air, 60 . 232 Glass bends, 2, 3, 15, 16 — bulbs, making of, 16 — jets, making of, 16 — manipulation, 15-17 — tubing, 3 Glucose, properties of, 36, 123 Gluten, estimation of, 186, 189 — in flour, test for, 186 Glycerides, 68 Glycerine as an antiseptic, 202 — preparation and properties of, 194, 195 — tests for, 195 Graham’s law, 52 Grape sugar, 123 Graphite, 101 Gun cotton, 75 HARDNESS of water, 41 — definition of, 43 — permanent, 43 — temporary, 43 Hard water, 41 Heating glass tubing, 15 Homologous series, 115 Honey, 123 Hooke’s law, 11 Houzeau’s test, 137 Humidity, 55-57 — Home Office regulations, 57 — in mills, 57 — table, 56 Hydrocarbons, preparation and pro- perties of, 114-117 Hydrochloric acid, electrolysis of, 126 — — plant for manufacture, 77 — — preparation and properties of, — — uses, 77 Hydrogen peroxide, estimation of, 135 — — preparation and properties of, 133-135 — sulphide, preparation and _ pro- perties of, 149-152 Hydrometers, 12, 13 — use of, 29 Hypochlorites, preparation and pro- perties of, 130 Hypochlorous acid, 130 IDENTIFICATION of common substances, 35-37 — — gases, tests for, 52 Impurities in cotton fibre, 164 Indicators, 67 Instruction for dyeing basic colours, 221 Invert sugar, 124 Iodoform, 202 Iron buff, 224 TEXTILE CHEMISTRY Iron, equivalent of, 92 — properties of, 36 JouLy balance, 11 Kaotrn, 140 Kiers, 208, 209 Kieserite, 208, 209 LABORATORY experiments with clay, 197, 198 — still, 21 Lactose, 123, 124 Lakes, formation of, 142 Lampblack, 102 Lanoline, 196 Lavoisier’s apparatus, 54 — experiments with air, 53 Law of constant proportion, 82 — — gaseous volumes, 85 — — multiple proportion, 82 — — reciprocal proportion, 83 Laws of Chemical combination, 82-89 — — — — experiments to illustrate, 83-85 Lavozone, 131 Lead peroxide, properties of, 36 — properties of, 36 — plaster, 68 Levulose, 123 Lewis Thompson calorimeter, 171, 172 Liebig condenser, 6, 21 Linen, microscopic appearance, 161 Liquids, 34 Liquid sulphur dioxide, 133 Maenatium, 140 Magnesite. 144 Magnesium, determination of equiva- lent of, 91 — preparation and properties of, 36, 144, 145 — carbonate, preparation and pro- perties of, 147 — — decomposition of, 146 — chloride in sizing, 199-200 — — preparation and properties of, 145, 199 — oxide, 146 ¢ — sulphate, preparation and pro- perties of, 146, 147 Magnifying power, 159 Maize starch, microscopic appearance, 185 — — preparation and properties of, 187, 188 | Maltose, 124 Manganese bronze, 225 — dioxide, properties of, 35 Manometer, 51 ° INDEX Manipulation during dyeing, 216 Marble, properties of, 36 Marsh gas, preparation and properties, 114 Mass of 1 litre of hydrogen, determina- tion of, 90 Mather and Platt electrolyzer, 212 Melting point apparatus, 17 — — determination of, 27, 28 Mercerized cotton under microscope, 228 Mercerizing, process of, 227 Mercerization, test for, 228 Mercuric chloride as an antiseptic, 202 — oxide, properties of, 36 Metals, examples of, 34 — properties of, 34 Metallic chlorides in sizing, 198 Methane, preparation and properties of, 114 Methyl alcohol, 118 — ether, 119 — group, 115 Microscope, construction and use of, 158-160 Microscopic appearance of starches, 185 Mildew, 201 Milk sugar, 123, 124 Milligram weights, 10 Milton, 131, 213 Mineral oils, 176, 177 Mixtures and pure substances com- pared, 35 — definition of, 35 — examples of, 35 Moisture in air, 55 — — cotton fibre, 164 — — wool fibre, 166 Molecular weights, 81 Molecules, 80, 81 Mordanting, 217 Mordants, aluminium, 142 — for basic dyes, 217 Mule spun yarn, 164 Mycoderma aceti, 201 NAPHTHALENE, 116 Native sulphur, 147 Natural fibres, 158-167 Neutralization, 67 Newtonian experiment on white light, 205 Nitrate of iron, 224 Nitre cake, 73 — crystals, 24 Nitric acid, experiments to illustrate properties of, 74, 75 — — from nitre, 72 — — percentage composition of, 71 — — plant, 72 233 Nitric Acid, preparation and properties of, 71-75 — — uses for, 75 Nitrobenzene, 75 Norwegian nitre, 73 OBJECTIVE, 159 Oetell electrolyzer, 210, 211 Oil of vitriol, 68 Oils, classification of, 175 — ether, extraction of, 176 — examination of, 177-182 — expressing, 175 — preparation and properties of, 175- 182 — rendering, 175 Oleates, 68 Oleic acid, preparation and properties of, 121 Oxalic acid, preparation and _pro- perties of, 121 Oxidation, 63 Oxides, 63, 65 — acidic, 65 — basic, 65 — classification of, 65 — examples of, 65 — insoluble, 65 — soluble in nitric acid, 65 — — water, 65 Sane or agents, 63 Oxygen, estimation of volume of, 62, 63 — from bleaching powder, 62 — — liquid air, 62 — — mercuric oxide, 61 — — potassium chlorate, 61 — — potassium permanganate, 62 — preparation, apparatus used for, 61, 62 — — and properties, 61-65 Ozone, estimation of, 138 — experiments with, 137, 138 — Houzeau’s test, 137 — Ostwald’s apparatus, 136 — preparation and properties, 136-138 — tube, 136 PAETCHNER’S solution, 131 Palmitates, 68 Palmitic acid, properties of, 121 Papin digester, 28 Paraffin wax, 115 Parozone, 131 Pasteur’s experiments, 200, 201 Patent alum, 142 Percentage of water, determination of, 31, 32 Peroxides, 65 Petroleum, 115 — oil, fractions from, 177 234 Phenol, 118, 119 Phosgene gas, 114 Phosphates, 68 — in tallow, test for, 192 Physical change, definition and exam- ples of, 37-39 Picric acid, 75, 119 Pipette, 5 Pneumatic trough, 6 Potash bulb, 8 Potassium chlorate, properties of, 36 — nitrate, properties of, 36 Precipitates and their nature, 27 Preliminary tests in analysis, 154 Preparation of gases, general methods for, 48, 49 — — sodium hypochlorite by elec- trolysis, 210-212 Preservatives in size, 203 Pressure gauge, 51 Principle of the hydrometer, 13 Principles of analysis, 152-154 Process of weighing, 10 Producer gas, 112 Production of colour, 206 Properties of cotton fibre, 163-165 — — wool fibre, 165, 166 Prussian blue, 225 Pure hard soap, 193 — water, preparation of, 41 — — properties of, 41, 42 Ratz of filtration, factors governing, 27 Raw cotton, 163 Recovered grease, 196 Red lead, 36 — liquor, 141 Redwood viscometer, 179 Refraction of light, 205 Relation °F. to ° C., 13 — sp. gr. to ° Tw., 13 Relative humidity, determination of, 55, 56 Rendering of tallow, 190 Residues and ashes, examination of, 203, 204 Retort, 1 — stand, 6 Rhombic sulphur, 148, 149 Rice starch, 188 — — microscopic appearance of, 185 Rider, 10 Rock oil, 177 Roland Wild calorimeter, 170 Roving, 164 Saao, microscopic appearance of, 185 — preparation and properties of, 187 Sal-ammoniac, 78 — — crystals, 24 TEXTILE CHEMISTRY Salicylic acid as an antiseptic, 203 Salt, properties of, 36 Salts, examples of, 67 — preparation and properties of, 66, 67 Saponification, 68 Saturated solution, 21, 22 Schiff’s reagent, 120 Scotch shale oils, 177 Scutched cotton, 164 Sea water, constitution of, 41 Separation, Soluble and insoluble sub- stances, 25, 26 Shower proofing, 141 Siemens ozone tube, 136 Silesian process (zinc), 143 Silk, composition of, 167 — microscopic appearance, 161 — properties of, 166, 167 Simple viscometer, 180 Singeing machine, 208 — process, 208 Sizing ingredients, classification of, 184 — of cotton yarn, 183-204 Smoothing glass tubing, 16 Soap, preparation and properties, 192- 194 Sodium carbonate, properties of, 37 Sodium hypochlorite, 131 Softeners used in sizing, 174 Softening of water, 41 Solids, 34 Solution, process of, 20, 22 Solubility of ammonia in water, 79 — — apparatus, 18, 19 — gases, determination of, 47 — solids in water, 22 — tallow, 191 Solvents, 20 Souring, 208, 210 Specific gravity bottle, 29 — — definition of, 29 — — determination of, 29 — — liquids, 29 — — oils, 177 — — solids, 30 — — waxes, 30 Spelter, 143 Spirits of hartshorn, 78 Standard hard water, preparation of, 44 — soap solution, preparation of, 44 — solutions, preparation of, 25 Starch, properties of, 37 Starches, 123, 124 Stearic acid, properties of, 121 Substances dissolved in natural waters, 4] Substitution compounds, 117 Sucroses, 123 Sugar (cane), 36 INDEX Sugars, 123 Sulphates, 147 Sulphides, 147 Sulphur dioxide, preparation and pro- perties, 132, 133 — — uses, 133 Sulphites, 132 Sulphuretted hydrogen, preparation and properties of, 149, 151 — — reactions with, 150, 151 Sulphuric acid, action of metals on, 71 — — contact process, 70 — — English process, 69, 70 — — identification of, 71 — — preparation and properties of, 68-71 — — Specific gravity of, 71 — — strengths of, 71 — — uses of, 71 Sulphuric ether, 119 Sulphur or sulphide colours, 222 — — — properties of, 222 — — — trade names for, 222 — preparation and properties, 36, 147-149 Symbols, meaning of, 95, 96 Symbols, table of, 96 Synthesis of Water, 45, 46 Systems of crystallography, 22 TABLE of hardness, 44 — — viscosities, 182 Tallow, preparation and properties of, 190-192 Temperature of dye bath, 216 Testing soap for ash, 194 — — — free alkali, 194 — — — water, 194 — tallow, 192 — zine chloride, 199 Tests for pure water, 42 Textile chemistry, definition of, 158 Thermometers, 12 Thistle funnel, 7 Tinctures, 20 T.N.1., 75 Total solids in water, 43 Tripod and gauze, 4 Twaddell graduations, 13 Tweezers, 9 Two volume formula gases, 85-89 Tyndall’s experiments, 201, 203 Union cloth, microscopic appearance of, 161 7 Unwashed wool, 166 Use of soap in sizing, 194 Uses for water, 46 235 VALENCY, graphic representation of, 95 — table of, 94 — theory of, 94, 95 Ventilation of buildings, 59 — principles of, 59 Viscosity of oils, determination of, 179-182 Volume and mass of gases, relation between, 99 — of carbon dioxide, from carbonates, 111 — — dye bath, 215 Volumetric composition of ammonia, 87, 88 — — — carbon dioxide, 88 — — — gases, 85-89 — — — hydrogen chloride, 86, 87 — — — — sulphide, 89 —- —— —=+ pitric oxide, 89 — — — nitrous oxide, 89 — — — steam, 85, 86 — — — sulphur dioxide, 88 Wasu bottle, 17 Washed wool, 166 Washing machine, 210 Water, dissolved solid in, 41 — gas, 112 — in tallow, 191 — rain, 40 — — gases in, 40 — softening plant, principle of, 44, 45 — sources of, 40 — suspended solids in, 40, 41 axes used in sizing, 195, 196 Weighing bottles, 32 Weighting materials in sizing, 174 Weights for use with balance, 9 Weldon mud, 129 — recovery process, 128 Wet and dry bulb thermometer, 56 Wheat starch, microscopic appearance of, 185 Wool grease, 196 Wool, microscopic appearance of, 61 Woulfe bottle, 4 YORKSHIRE grease, 196 Zino, chief compounds of, 143, 144 — chloride, 143, 144, 198 — equivalent, determination of, 92 — oxide, 144 — preparation and properties of, 36, 142, 143 sulphate, 144 sulphide, 144 chloride as an antiseptic, 202 — impurities in, 198, 199 (aed Printed in Great Britain by Butler & Tanner, - - ) Y , i — r,s ‘ Date Due "3 3125 00060 4716 r Pe fats hagas Fak. ae o hg ee ee rf = Paris ee ee role - Pee iets n.8 6, 4 = vere achly brea ace At ahs Be wc nee wv “<9 OR er: & Re ee Or ENS etre pita ae eae te a Pears ttt : eisai ith eatctee hae : path nae wing tig times ore nt ot iat pear elt MD : toe esis Cole se ees Eee py Pointe ao . 4 Gc a's +" * RP RN Ray oe IESE sas: REA, Lipsie FET fete ice Ct itor te ry