GIFT OF PROF. W.B. RISING INTRODUCTION TO CHEMICAL-TECHNICAL ANALYSIS BY PROF. F. ULZER AND DR. A. FRAENKEL DIRECTORS OF THE TESTING LABORATORY OF THE ROYAL TECHNOLOGICAL MUSEUM, IN VIENNA (AUTHORIZED TRANSLATION) WITH APPENDIX BY THE TRANSLATOR HERMANN FLECK, NAT. Sc. D. INSTRUCTOR IN CHEMISTRY, UNIVERSITY OF PENNSYLVANIA PHILADELPHIA P. BLAKISTON'S SON & CO. 1012 WALNUT STREET 1898 II lo 2. COPYRIGHT, 1898, BY P. BLAKISTON'S SON & CO. PRESS OF an & Co., Preface. IT is generally conceded that it is advisable to give students of chemistry as broad an experience as possible in the use of analytical methods, in order to have them acquire skill in manipulation and to acquaint them with the important bearing of chemical analysis. This experience can, in a great measure, be obtained by supple- menting the usual preparatory courses in gravimetric and volu- metric analysis with instruction in the execution of methods which are being constantly applied in the analysis of industrial products. The authors of this book have had much experience in teaching chemical-technical analysis, and in the following pages have pre- sented many methods of this description in a series of examples, selected from a variety of products. They have been very fortunate in their choice, and have undoubtedly done much to assist the earnest student. The conviction that a course of this character would be wel- comed by English-speaking students, and helpful not only to them but also to many who are already engaged in industrial pursuits, has led the translator to publish the little volume in its present form. He has not edited the text, but has taken the liberty to add an appendix, in which are incorporated additional examples which actual labor- atory testing has shown to be highly instructive, as well as exceed- ingly valuable, in the direction of imparting skill in manipulation. In this connection, too, the translator would take occasion to acknowledge his great indebtedness to Mr. Walter T. Taggart, B. S., for valuable assistance rendered in the reading of the proof and the preparation of the index. H. F. (iii ) 237357 Table of Contents. PAGE I. Products of Technical Chemistry, i 1. Iron Pyrites, I 2. Pyrite Residuum, . 3 3. Sulphuric Acid, .... ...... 4 4. Fuming Sulphuric Acid and Anhydride, 5 5. Nitroso Acid (Nitrated Acid), . 7 6. Brine, 1 1 7. Crude Hydrochloric Acid, . . . . . . . .12 8. Soda, ; . . . . . . . . 13 9. Sodium Aluminate, . . . . . .''. . .17 10. Weldon Mud, 18 11. Boiler- Water, 20 12. Fuel, 27 13. Furnace Gases, .......... 32 II. Cement and Clay, ... ,35 1. Lime, . . . 35 2. Marl, 37 3- Clay, 39 A. Empirical-Technical Analysis, ...... 40 B. Rational Analysis, ........ 42 C. Analysis by Mechanical Means (Suspension), . . -43 D. Pyrometric Tests, . . . . . . . -45 III. Metallurgical Industry, 51 1. Iron, . . . . . . . . . . . 5 1 2. Zinc Blende, 57 3. Zinc Dust, ........... 59 4. Crude and Refined Copper, 60 IV. Alloys, 68 1. Phosphor- Bronze, ......... 68 2. White Metal, 69 3. Iron Alloys, .......... 70 V. Fertilizers, 72 1. Phosphate Fertilizers, 75 2. Potassium Fertilizers, ......... 77 3. Nitrogenous Fertilizers, ........ 78 4. Mixed Fertilizers, . . . . . . . . .78 (v) VI TABLE OF CONTENTS. PAGE VI. Sugar Industry, 79 1. Beets, 82 2. Beet Juice, Thin Juice, . 84 3. Crude Sugar, Filling Material, Green Syrup, Molasses, . . 84 4. Press Cake, 91 5. Lime Saccharate, ......... 91 6. Bone Black, .91 VII. Fermentation Industries, 95 1. Raw Products Containing Starch, 95 2. Starch, 99 3. Malt, 100 4. Yeast, . 103 5. Spirits, 105 6. Methyl Alcohol (Wood Spirit), 107 VIII. Fats, Waxes, Mineral Oils, . 109 A. F'ats, 109 1. General Methods, 109 2. Classification of Fats, 114 3. Investigation of a Few Common Fats, . . . .117 B. Waxes, . . . .121 1. Vegetable and Animal Waxes, . . . . .121 2. Mineral Waxes, . .125 C. Mineral Oils, 125 1. Mineral Lubricants, . . . . . . .126 2. Petroleum (Illuminating Oil), 129 3. Gas Oil, . . . 131 D. Products of the Fat Industry, 131 1. Materials Used in Oiling Wool, . . . . . 131 2. Soaps, 133 3. Turkey-Red Oil, .138 4. Glycerin, 140 IX. Mordants and Tanning Materials, ....... 143 A. Mordants, 143 1. Alumina Mordants, 143 2. Chromium Mordants, 145 3. Iron Mordants, ........ 146 4. Tin Mordants, 146 5. Antimony Mordants, 147 6. Copper Mordants, . . . . . . . . 147 B. Tanning Materials, . 147 1. Tanning Extracts, . . . . . . . .148 2. Raw Products, 149 X. Textile and Dyeing Industries, 151 1. Textile Fibers, 151 2. Bleaching Materials, 153 TABLE OF CONTENTS. Vli PAGE 3. Sizing Materials, 154 4. Finishing Materials, . . . . . . . . .156 5. Dye-Stuffs, .158 XI. Products of the Coal-Tar Industry, ...... 165 1. Crude Benzene, .......... 165 2. Crude Xylol, 165 3. Crude Anthracene, . . . . . . . . .166 4. Crude Carbolic Acid 167 5. Dimethyl Aniline, ......... 168 Appendix, A. White Paint (White Lead), 169 13. Manganese Dioxide, Bleaching Lime, Etc., .... 169 1. Manganese Dioxide, ........ 169 2. Bleaching Lime, ......... 172 3. Hydrogen Peroxide and Permanganate, . . . .172 C. Asphalt and Asphaltic Substances, . . . .... 172 D. Food Stuffs, 174 1. Milk, 174 2. Butter, .'77 3- Tea, 178 4. Coffee, . . . 179 5. Cocoa and Chocolate, . . . . . . . .180 6. Flour and Other Cereals, 182 7. Pepper, 183 Abbreviations. Be. =r Beaume. c.c. = Cubic Centimeter. C. Celsius. Cone. Concentrated. F. = Fahrenheit. Gr. = Gram, m.m. Millimeter. Temperature (Celsius is understood unless otherwise indicated.) I. Products of Technical Chemistry. IN this chapter a selection is made from the most important in- dustrial chemical products as well as from the raw materials used therein, and a description of the quantitative examination of the same is given. The methods described are followed by those em- ployed in the analysis of water, coal and furnace gas. 1. Iron Pyrites. The most important determination is that of sulphur. The error must not exceed . i per cent. In addition a water determination is usually conducted, and less frequently estimations of copper and arsenic. (#) Sulphur. Following the method of Lunge, which is adopted in the German Le Blanc soda factories, . 5 gram of finely-divided and bolted pyrite is covered with 10 c.c. of a mixture of 3 vols. nitric acid (sp. gr. 1.4) and i vol. fuming hydrochloric acid in an Erlen- meyer flask. A funnel is inserted and the contents are warmed until reaction begins. The flask is then removed from the water- bath, and the reaction proceeds of its own accord until nearly complete. The contents are warmed anew until the reaction is finished. Solution takes place in about ten minutes. Only small quantities of colorless substances, silica, barium sulphate, lead sul- phate, etc., but neither dark particles nor sulphur, may remain un- dissolved. The solution is evaporated to dryness in a porcelain dish with an excess of hydrochloric acid ; the residue is moistened with a few drops of hydrochloric acid, taken up with hot water, and filtered. In the filtrate, at a temperature of 60-70 the iron is precipitated with a slight excess of ammonia. The precipitate is thrown on a sufficiently porous filter and washed with hot water until i c.c. filtrate remains perfectly clear for several minutes on addition of barium chloride solution. The filtrate is acidified with hydrochloric acid, brought to boiling, and the sulphuric acid is 1 2 CHEMICAL-TECHNICAL ANALYSIS. precipitated with about 20 c.c. of a hot solution of barium chloride (10 per cent.). The remainder of the analysis is conducted in the usual manner. The sulphur in pyrite varies between 46 and 52 per cent. Spanish and Norwegian pyrites are characterized by their high percentage of sulphur. (^) Moisture. About 10 grs. sample are dried to constant weight in an air-bath at 105. Usually four hours are required for this operation. (V) Copper. According to the procedure of Duisberger-Hiitte,* five grams of the finely-ground and previously dried (100) min- eral are gradually brought into an inclined Erlenmeyer flask con- taining 60 c.c. nitric acid (sp. gr. 1.2). As soon as the ensuing violent reaction ceases the flask is heated and the contents are evap- orated until sulphuric acid vapors are evolved. The dry residue is then dissolved in 50 c.c. HC1 (sp.gr., 1.19), 2 grams sodium hypophosphite dissolved in 5 c.c. water are added, and the liquid is boiled to remove the arsenic and reduce the iron. An excess of concentrated HC1 is now added, followed by 300 c.c. hot water, and hydrogen-sulphide gas to saturation. The precipitate is filtered off and thoroughly washed. The filter is broken with a glass rod, and the contents are washed back into the precipitates in flask. The adhering particles on the filter, together with the main portion of the precipitate, are dissolved in nitric acid and the solution is evaporated to dryness on a water-bath. The residue is treated again with nitric acid and water, neutralized with ammonia, and a slight excess of dilute sulphuric acid is added. After cooling, the solu- tion is filtered, the flask and filter are washed with w r ater containing sulphuric acid, and the copper is determined electrolytically in the filtrate after adding 3 to 8 c.c. nitric acid, or gravimetrically with- out the addition of nitric acid as cuprous sulphide. From the per- centage found, .01 is deducted for bismuth and antimony. Any appreciable amount of copper in pyrite is easily recognized during the sulphur determination by the blue ammoniacal filtrate. (d} Arsenic. (Method of Reich, modified by McCay.) 0.5 gram of pyrite is dissolved in a porcelain crucible with nitric acid. The free acid is volatilized, 4 grams soda are added, and the mass is * Taschenbuch fur die Soda-, Pottasche- und Ammoniakfabrikation von Dr. G. Lunge. 2 Aufl. PYRITE RESIDUUM. 3 thoroughly dried on a sand-bath, when 4 grams saltpetre are added and the contents are heated to quiet fusion for ten minutes. The fusion is lixiviated with a small quantity of hot water, and to the filtered solution sufficient nitric acid is added to slightly acidify, after which the liberated carbonic acid is expelled by boiling. Silver nitrate is now added, and the solution is carefully neutralized with weak ammonia. All arsenic is obtained in the form of silver arsenate, which is dissolved in dilute nitric acid. The solution is either evaporated in a platinum capsule, dried and weighed as sil- ver arsenate ( Ag 3 As O 4 ), or titrated with ammonium sulpho -cyanide according to the method of Volhard. 2. Pyrite Residuum. The determination of sulphur in pyrite residuum, an operation not infrequently required, can be carried out under the directions given in Example i, except that, in order to avoid evolution of hydrogen sulphide, solution is advantageously effected by nitric acid and only a few drops of hydrochloric acid. Lunge* recommends for this purpose the following method : Exactly 2 grams of sodium-bicarbonate, whose strength has been previously estimated by titration, are thoroughly mixed with 3.2 grams finely -divided residuum in a nickel crucible of about 30 c.c. capacity. The mixture is heated first for 10 minutes with a small flame just touching the bottom, and afterwards for 15 minutes with a strong flame, without allowing the mass to melt. The crucible should be covered during this operation. The contents are poured out into a porcelain dish, the crucible is rinsed with water, and treated for ten minutes with a concentrated neutral brine in order to avoid subsequent escape of iron oxide through the filter. The undissolved portion is filtered off and washed until the filtrate ceases to give an alkaline reaction. After cooling, the liquid is titrated back with normal acid, using methyl-orange as an indica- tor. The difference between the number of c.c. hydrochloric acid (# ) necessary to neutralize 2 grs. bicarbonate and the number of c.c. () used in back titration, multiplied by the sulphur equiva- lent (i c.c. in acid = 0.016 gr. S) gives the amount of sulphur * Taschenbuch fur die Sodafabrikation, etc. 4 CHEMICAL-TECHNICAL ANALYSIS. present. Using the above amount of substance, the percentage of sulphur is : 3. Sulphuric Acid. A quantitative determination of the impurities is seldom made except, for example, for storage -battery purposes. The qualitative tests here given for detection of sulphurous acid, hydrochloric acid, and the oxides of nitrogen, lead, iron and arsenic, are accord- ing to the methods of Krauch. (# ) Sulphurous acid. To a weak yellow solution of iodine, previ- ously treated with starch paste, the diluted sulphuric acid is added. In presence of sulphurous acid decolorization takes place. Or the sulphurous acid is reduced with zinc or aluminium to hydrogen sul- phide, and the latter detected by means of lead-paper or an alkaline solution of sodium nitroprusside (very delicate). (<) Hydrochloric acid. Two grams sulphuric acid are diluted to 30 c.c. and a few drops of a silver nitrate solution are added. Presence of hydrochloric acid is indicated by turbidity. (), the stopcock (/) and the cup (//) is very similar to that of the original nitrometer. It differs therefrom, however, in that the tube (/?), used for decomposing the acid, is not graduated, and the FIG. 2. Lunge's Gasvolumeter. 10 CHEMICAL-TECHNICAL ANALYSIS. stopcock possesses, instead of an axial perforation, a second side- perforation, which establishes communication between the small tube (V) and the tube (Z>). In this part of the apparatus the decomposition of the acid is carried out exactly as before. The second part of the apparatus consists of three tubes (4), (-#), and (C), which are connected with each other by means of a three- way tube. (A~) is a glass measuring tube of 50 c.c. capacity, graduated in ^ c.c. and provided with the double-bored stopcock Qf), which establishes communication of (A} with the straight tube (/), as well as with the rectangular tube (*). () serves as a reduction tube. Under the wide portion, which has a capacity of 100 c.c., the tube, to the extent 100 c.c. to 125 c.c., is divided in ^ c.c., and is filled exactly with so much air that the volume of the latter at o and 760 mm. when dry amounts to 100 c.c. The volume V, which represents the space which 100 c.c. air at o and 760 mm. pressure would occupy at the observed temperature t and the pressure b, is found by the following equa- tion: V= v 73~r ; ; ^ One drop of cone, sulphuric acid is now introduced into (} ; mercury is poured in the tube ( C ) until the mark in (J?), representing the volume F, is reached, when it is closed by either carefully sealing the latter, care being taken not to warm (j9), or by closing a previously attached tight-fitting stopcock. The decomposition of the nitroso acid is then carried out in the reaction tube as previously described, and after (A) has been filled completely with mercury to the end of the small tube (/), by raising (C), the tubes (^) and (A) are placed side by side and ( C ) is connected by means of a rubber tube with () through (V) and (/) to the stopcock (#), the latter is closed, together with (/), and (JD} and (A) are disconnected. (C) is now raised until the mercury in (J?) rests at precisely 100. By * In very exact determinations, I mm. is subtracted for values of / up to 12 ; 2 mm. for values from 13-19, and 3 mm. for values from 20-25, to a U w for ex- pansion of the mercury. BRINE. 11 means of a double clamp-holder (C) and (^5) are moved up or down in concert until the mercury in (^4) and (jff) reaches the same level, but simultaneously, however, remains at 100 in (^9). Since the gas in (.#) is so far compressed as to occupy the same volume as at o and 760 mm. pressure, the readings in (A) repre- sent the gas reduced to the same normal condition. The tempera- ture in (A") and (^) is supposed to be the same, a condition quickly produced by the mercury. Ten minutes are required before the final adjustment of the apparatus, when large quantities of nitric oxide are used. By the use of these particular reaction tubes, the inconveniences of foam and slime and the compensation for an acid column are avoided. The eudiometer remains clean, in conse- quence of which a large number of determinations can be under- taken without constant cleaning. 6. Brine. The following determinations are usually carried out : Specific gravity, total chlorine, sulphuric acid, ferric oxide, alumina, lime, magnesia, and carbonic acid. In addition, qual- itative tests for potassium, bromine and iodine are made, and some- times these constituents are determined quantitatively. (a) Specific gravity. This is determined by means of the pyknometer in the usual manner. () Total chlorine. 10 c.c. brine are diluted to 1000 c.c. A gravimetric or volumetric determination of chlorine in 25 c.c. is made. (c) Sulphuric acid. To 50 c.c. brine a few drops of hydrochloric acid are added. (Sodium chloride is precipitated in this instance from the very concentrated brine solution.) One to two volumes of water are added, and the hot solution is precipitated with barium chloride. (//) Ferric oxide and alumina. 250 c.c. brine, previously heated with a small quantity of nitric acid, are precipitated after addition of ammonium chloride with ammonia. The precipitate, of which there is usually a small quantity, is filtered, and both constituents are weighed together. The presence of iron can be ascertained previously in a separate portion of the brine, oxidized with nitric acid, by the addition of ammonium sulpho-cyanide. 12 CHEMICAL-TECHNICAL ANALYSIS. (?) Lime is precipitated with ammonium oxalate in the filtrate from d. The precipitate is treated in the usual manner. (/) Magnesia. To the filtrate from the lime sodium hydrogen phosphate is added. The precipitate which forms is weighed as magnesium pyrophosphate. () Carbonic acid. 1-2 drops methyl-orange are added to ^ liter brine. The solution is then titrated with ^ normal hydro- chloric acid to red coloration. (2HC1 = iCO 2 .) (Ji) Potassium, bromine and iodine. The qualitative tests for these three bodies can be carried out in the following manner : A large quantity of the brine is evaporated to y$ its original vol- ume. Any salt which separates is filtered off or thoroughly drained. The filtrate is again evaporated, and any salt which separates is removed as before. The mother-liquor is then divided into two portions. In the one, by means of platinic chloride, a test is made for potassium, which is precipitated in form of yellow crystalline potassium -platinic chloride. To the other solution, which must be frequently agitated, chloroform and chlorine-water, drop by drop, are added. Iodine will first be precipitated a fact readily noticed by the violet color of the chloroform. Later, bromine is recog- nized by the lemon or yellow color imparted to the chloroform layer. The quantitative estimation of these three bodies will not be described here. The results found are arranged according to the same principles which will be considered later under the determination of the more exact composition of boiler-water. 7. Crude Hydrochloric Acid. This substance may contain as impurities : sulphuric acid, sul- phurous acid, chlorine, arsenic and iron compounds, alumina, lime, alkali metals, hydrobromic acid and hydriodic acid. The chlorine is usually to be attributed to the presence of nitrous acid in the sulphuric acid. Arsenic and iron compounds arise from the crude sulphuric acid. Qualitative tests for these various impu- rities are made by the usual method. (See also Sulphuric Acid.) For the qualitative estimation of arsenic Krauch recommends the following procedure: To i.o gr. hydrochloric acid, diluted with 10 SODA. 13 c.c. water, 5 c.c. freshly -prepared hydrogen sulphide water are care- fully added, so as to form a supernatant layer. In the absence of arsenic no coloration and no yellow ring should form between the two liquids when warm or cold. Of the quantitative determinations particular attention is called to those of arsenic, iron and sulphurous acid. (a) Arsenic. In order to reduce any arsenic acid present, sul- phurous acid is conducted into the solution for a protracted period. The latter, after expulsion of the sulphurous acid, is saturated with hydrogen sulphide, when arsenic is precipitated as trisulphide. The precipitate is filtered, thoroughly washed, dissolved from the filter with ammonia, and evaporated in a weighed glass or porcelain dish, after which the trisulphide remaining is dried at 100 and weighed. () Iron. A measured quantity of the acid is treated with zinc, free from iron, in a current of carbonic acid, in order to reduce all the iron present. To the copiously diluted acid a 20 per cent, solution of manganous chloride or sulphate is then added, and the liquid is titrated with an accurately standardized, about ^ normal, potassium permanganate solution. (c) Sulphurous acid. This is oxidized with permanganate, iodine or hydrogen peroxide to sulphuric acid, and precipitated with barium chloride. Sulphuric acid originally present must likewise be estimated and subtracted from the above. 8. Soda. At present soda is derived principally from two well-known pro- cesses the Le Blanc and the ammonia soda process. That from the former may contain, as chief impurities : sodium sulphate, sodium chloride, sodium silicate, sodium aluminate, sodium hydrate, sodium sulphide, sodium sulphite, ferric oxide, calcium carbonate, silica and carbon. Ammonia soda is mostly very pure, and contains as a rule only sodium chloride (^ to about 2^ percent.), at times sodium bicarbonate, and at the most only traces of sodium hydrate. At the same time it must be admitted that at present the Le Blanc soda comes into commerce in a very pure state on account of the general demand for soda containing not more than 0.4 per cent, matter insoluble in water, o.i per cent, matter insoluble in hydro- chloric acid, and about 0.02 percent, ferric oxide. 14 CHEMICAL-TECHNICAL ANALYSIS. Following are the methods of investigation for technical soda selected with regard to its possible impurities. It is hardly neces- sary to state that the simultaneous presence of many of the impuri- ties cited, such as hydrate and bicarbonate of soda, for instance, is excluded. It is an advantage to find out qualitatively the presence of individual constituents such as sodium hydrate, sodium sulphide, and sodium sulphite. The qualitative examination for sodium hydrate is similar to the quantitative. The soda solution is precipitated with an excess of barium chloride, and the filtrate is tested for alkali by means of litmus or phenol-phthalein. The presence of sulphide of soda is determined by means of an alkaline solution of sodium nitroprus- side or lead-paper. To test for sodium sulphite a sample is acidified with acetic acid, starch paste is added, and notice is taken whether a slowly-added dilute iodine solution is decolorized. Quantitative Examination. 53 grs. soda (corresponding to one-half the molecular weight) are first dissolved in warm water in a large beaker glass, allowed to stand for ^ hour, and then filtered through a dried and weighed filter into a liter flask. After washing the filter the flask is filled to the mark. The residue is dried at 100 to constant weight, which represents the matter " insoluble in water." Should a more thor- ough examination of this be necessary, the filter is again moistened with water and lixiviated with hot dilute hydrochloric acid. Ferric oxide, alumina, calcium carbonate and magnesium carbonate are dissolved. If the filter now be washed, dried and weighed, it will contain the silica and carbon. By ignition of the filter the carbon is burned off, and the ash which is weighed consists only of silica. In the acid filtrate iron only is usually quantitatively estimated. To accomplish this ammonia is added, and the resulting ferric hydrate is dissolved in i : 4 sulphuric acid, reduced with zinc and titrated with permanganate. The remainder of the insoluble matter, after deducting ferric oxide, silica and carbon, may be considered as cal- cium carbonate. Examination of the Aqueous Solution. (a) Total active soda (with acid). 50 c.c. solution, representing 2.65 grs. soda, are titrated with hydrochloric acid (preferably ^ SODA. 15 normal), with addition of methyl -orange, and the result is calculated as sodium carbonate. This includes as sodium carbonate sodium hydrate, sodium sulphide, sodium sulphite, sodium silicate, sodium aluminate, and finally sodium bicarbonate. (<) Sodium sulphate. 50-100 c.c. solution are acidified slightly with hydrochloric acid, and the hot solution is precipitated with barium chloride. ( ) parts by weight lime, as in the case a, an equiva- lent amount of soda.* 12. Fuel. The methods described are applicable to all kinds of fuel an- thracite, bituminous, lignite, etc. As a rule, the determinations made in a coal analysis are water, ash, sulphur, and an elementary analysis. In addition to these, nitrogen and phosphorus, as well as the yield of coke, are frequently estimated. (#) Water. The estimation of water in fuel. The sample must be coarsely ground, about pea size, since during the process of pulverization considerable moisture is given off. Coal, especially anthracite coal, possesses the property of absorbing oxygen upon protracted drying, thereby causing an increase in * The derivation of these methods of calculation of Kalmann may be found in the Mittheilung des K. K. technolg. Gewerbe Museum, 1890. 28 CHEMICAL-TECHNICAL ANALYSIS. weight. It is best to heat about 2050 grs. material in a weighing tube provided with a well -ground stopper, which is removed during the time of heating, and to weigh the same from hour to hour until no further loss occurs. Should perhaps the last weight show an in- crease, the previous result is accepted. (^) Ash. The ignition is best carried out in a muffle, when, as a rule, one hour will be sufficient. Should a muffle not be accessible, about i gr. finely -divided coal is placed in a small platinum capsule and covered with the lid of a larger crucible. Heat is applied at first with a small flame to avoid sintering. Later the lid is re- moved, the capsule is tilted on the triangle, the lid is likewise brought into an inclined position on the capsule, and the latter is heated protractedly to a red heat with an ordinary-sized flame. When the ash appears uniform, which is usually the case after 2-3 hours, the capsule is weighed. The ash is now moistened with a few drops of alcohol, when any particles of carbon will rise to the surface, where they may be easily recognized. The alcohol is ignited and driven off, and the capsule is reweighed. This process is finally repeated a second time. Lunge advises the use of a plati- num crucible, which is placed in the round opening of an inclined asbestos plate. Only the part of the crucible protruding beneath is heated. The air used for oxidation does not admix with the gases produced by the flame, and therefore acts more energetically. (V) Sulphur. Sulphur is present in fuels in the form of sulphides (mostly pyrite), sulphates (calcium sulphate), and in combination with organic substances. The estimations usually made are : Total sulphur and sulphur present in form of metallic sulphides + sulphates. Sometimes a separate determination of sulphur due to sulphates is also made. Total sulphur according to Eschka. About i gr. finely-divided coal is thoroughly mixed in a platinum crucible by means of a thick platinum rod, with 1.5-2 grs. of an intimate mixture of 2 parts pure ignited magnesia and i part anhydrous sodium carbonate. The crucible is inclined on the triangle, or in the perforated asbestos plate, without a lid, and the lower half only is brought to a red heat. Heat is applied for about i hour, with frequent stirring by means of the platinum rod. In that time the mass, at first gray, will have assumed a bright red or brown color. . The contents are cov- FUEL. 29 ered with hot water and rinsed into a beaker, the crucible is boiled out again, and bromine water is added until the liquid assumes a bright yellow color. This is done in order to oxidize any remain- ing sulphides. The solution is heated, filtered, and the filtrate is acidified with hydrochloric acid. It. is then boiled in a draught- chamber until the deep brown colored liquid becomes colorless, and is then precipitated with barium chloride. The magnesia-soda mixture had better be prepared in quantity. When sulphur is present in small quantity in this mixture, a con- siderable portion is used for a sulphur determination, and the corre- sponding quantity of the latter is subtracted from the total sulphur. Sulphur present as sulphides and sulphates. According to Drown, a saturated solution of bromine in caustic soda, sp. gr. 1.25, to which sufficient caustic soda to absorb any free bromine has been added, is used to advantage for oxidation. About i gr. of the finely pulverized substance is moistened with 10 c.c. of this solution. It is then heated and acidified with hydrochloric acid. In the space of 10 minutes two quantities, 20 c.c. each, of the solu- tion, are again added, and each time the solution is acidified with hydrochloric acid. After the last addition of acid, the mass is evap- orated to dryness, dried at iio-ii5 in an air-bath to convert silica into insoluble form, taken up with hydrochloric acid, filtered, and the filtrate is precipitated with barium chloride. The method is especially useful for anthracite coal. Sulphate sulphur. A considerable quantity of the sample is first incinerated, and a weighed quantity of the ash, 2-3 grs., is lixivi- ated with hot water. In order to oxidize any calcium sulphide formed, the solution is boiled with hydrogen peroxide or a few drops of bromine. It is then acidified with hydrochloric acid and pre- cipitated with barium chloride. (d) Elementary analysis. The execution of this is too well known to describe. It is, however, necessary to add special pre- cautions pointed out by Bockmann, and also the authors. While the estimation of hydrogen, as a rule, can be carried out with ease and accuracy, a difference in parallel determination of y 2 to 24 P er cent - i s noticeable in determining the carbon, even when great care is exercised. The reason for this lies in the already mentioned tendency of carbon to sinter. In order to avoid this as 30 CHEMICAL-TECHNICAL ANALYSIS. much as possible, it is advisable to conduct the first part of the combustion slowly. This can be accomplished by at first using a current of air (not immediately of oxygen) and by moderately heat- ing the portion of the tube in proximity to the substance. It is also advisable not to have the substance too finely divided, thereby avoiding an immediate violent action. The finish of the preliminary step, which may be termed coking, is easily observed. The remain- ing operation is then carried out at a high heat in a current of oxy- gen, the flow of which through the wash -bottle is regulated to about 20 bubbles in every 10 seconds. Charging the combustion tube is done in the usual manner. For many well-founded reasons it has been found decidedly advantageous to substitute for granular copper oxide a series of oxidized copper spirals. The addition of a silver or bright copper spiral is wholly unnecessary on account of the minute quantities of chlorine and nitrogen. On the other hand, an absorbent of the combustion- products of the sulphur is absolutely necessary. In the absence of such, sulphurous and sulphuric acid readily enter the absorption- bulbs, are absorbed, and increase the weight. It is only necessary, according to Fisher, to keep the oxide of copper in the front of the tube at a low red heat, whereby the oxide itself acts as a retainer of the combustion-products of sulphur. Nevertheless, it appears more advisable to fill the front part of the tube, which is allowed to protrude about 28 cm., with dry, coarsely-divided lead peroxide. The latter is placed in a tin case provided with a thermometer, and is heated to 180 during the combustion. Further, be it noted that the dehydrated substance had best be used, and that a hydrogen determination be simultaneously con- ducted. The water thus found is deducted from the total water. (e) Nitrogen. The method is found under the accurately de- scribed procedure of Kjeldahl in the chapter " Fertilizers." 0.8 i gr. finely-divided coal is used in the determination. (/) Phosphorus. This is always determined in the ash, and not the original substance. 12 grs. ash, obtained best by ignition in a muffle, are digested for a considerable length of time with hydro- chloric acid in a porcelain dish, whereby, according to Muck, the phosphorus is quantitatively dissolved. The solution is evaporated to dryness, moistened with hydrochloric acid, and 100-150 c.c. FUEL. 31 water are added. It is warmed on a water-bath, filtered into a second porcelain dish, and evaporated repeatedly almost to dryness with addition of nitric acid. The liquid is diluted with water acidified with nitric acid and precipitated in a beaker with molyb- date solution.* The remaining treatment is carried out in the well-known manner more fully described in the chapter on "Fertilizers." (g) Coke, i gr. finely-divided coal is weighed in a smooth- walled platinum crucible, which it fills to the height of 30-35 mm., and the crucible is placed on a thin platinum triangle so as to bring its base 3 cm. from the mouth of a Bunsen burner. Strong heat is applied to the tightly-closed crucible from the beginning. The burner, which is provided with a protecting cone, should have a flame 18 cm. in height. Heat is applied until no luminous flame issues from between crucible and lid, an operation lasting 1^-2 minutes. The sooty film on the crucible-lid is also weighed. By following these directions accurately results may be obtained which agree within .2-. 4 per cent. Arrangement of results. The results are as frequently based on air-dried as on dehydrated material. Oxygen is indirectly deter- mined by deducting the sum of the water, carbon, hydrogen, sul- phur,f nitrogen and ash found from 100. So called " disponible hydrogen ' ' is that which remains upon deducting the quantity of hydrogen used to form "chemically -bound water" with the oxygen, e.g. , y% of the oxygen, together with that present as hygroscopic water, from the total hydrogen. Absolute heating value. To calculate this, the formula lately recommended by Schwackhofer is employed, SoooC + 2o,oooH + 2qooS-6ooW E - calories, 100 in which the symbols C, H, S, W represent the percentages of carbon, "disponible" hydrogen, sulphur and water (hygroscopic and chemically bound). If the absolute heating value (E) be divided by 637, there results * Preparation, see under V, "Fertilizers." f Excluding sulphur existing as sulphate. 32 CHEMICAL-TECHNICAL ANALYSIS. the evaporative efficiency, that is, that weight of water at o which is changed to steam at 100 by one kilogram of coal. 13. Furnace Gases. The investigation of gases of a furnace serves to regulate the feed- ing of the latter. Carbonic acid, oxygen, carbon monoxide and nitrogen, the latter by difference, are determined in furnace gases. For this purpose the apparatus of Orsat, whose arrangement is seen in the following illustration, Fig. 3, is best used : FiG. 3. Orsat's Apparatus. The gas burette A is bound to the leveling flask B, which is filled with water. By raising B, A is filled with water to the uppermost mark ; by lowering B gas is drawn through the tube C, or from the absorption vessels D, E, F; by repeatedly raising B, simultaneously opening the stopcocks of D, E or F, the gas may be led into any of the latter. To establish the necessary communications the cocks D, , F, and the three-way cock A are provided. In order to in- crease absorption the vessels >, E and F are provided with a large FURNACE GASES. 33 number of narrow glass tubes. D is used to absorb carbonic acid, and is filled with no c.c. caustic potash solution (sp. gr. 1.20-1.8). E serves to absorb oxygen, and contains pyrogallic acid or thin phosphorus sticks immersed in water. In the latter case black paper surrounds the vessel to protect the contents from the action of light. Finally, for the absorption of carbon monoxide, the vessel Fis filled with cuprous chloride solution prepared by shaking 200 grs. commercial cuprous chloride with a solution of 250 grs. am- monium chloride in 750 c.c. water in a stoppered flask, into which there is placed, later, a copper spiral which reaches to the bottom. Before using, i vol. ammonia (sp. gr. 0.905) is added to 3 vols. of this solution. Complete absorption takes place only upon pro- longed contact ; and, furthermore, the reagent must be frequently re- newed. The absorption reagents are kept in the rear tubes, and are brought into those in front only when the apparatus is in use. This is accomplished by establishing communication with the out- side air by means of stopcock #, closing d, e and /, filling A with water by raising B, arranging a to close off A, lowering B and opening the stopcock d. The liquid is thereby drawn from the rear into D. In a similar manner E and F are filled. The tube c, previously provided with a U tube, enclosing raw cotton to exclude dust, is now connected with the chamber from which the gas is to be taken, and by closing d, e and f and lowering B, a volume of gas sufficient to fill to the zero point is drawn.* The cock d is opened, B is raised, and the gas in the burette is forced into Z>. As soon as the water reaches the end division the flask is lowered, and the process is quickly repeated in order to bring the gas into thorough contact with the reagents. Finally the water-levels in flask and burette are brought to the same height, the stopcock d is closed, and the volume is read. The decrease in volume gives per cent, by volume of carbonic acid, since the bu- rette is divided into 100 c.c. In the same manner the oxygen is subsequently determined by absorption in , the carbon monoxide in F, and the nitrogen as remainder of 100. * To completely remove air contained in the tubes, the gas forced in by lower- ing B is passed out through exit in a, fresh gas is drawn in, and the process is repeated. 3 34 CHEMICAL-TECHNICAL ANALYSIS. For gases rich in hydrogen, such as water-gas, the apparatus of Orsat-Lunge is used. The latter is quite similar to the Orsat appa- ratus. The gas, freed from carbonic acid, oxygen and carbon monoxide, is mixed with a measured quantity of air, and is con- ducted through a capillary containing platinum asbestos or palla- dium asbestos. By heating the latter the hydrogen is burned. The residue is again measured in the burette, and ^ the decrease in volume is reckoned as hydrogen. (2 vols. hydrogen unite with i vol. oxygen,) II. Cement and Clay. THE raw materials for the products of this group are limestone, marl and clay. 1. Lime. (a) Moisture. 3-5 grs. sample are heated to constant weight in a drying oven at no 120. (<) Silica and clay, ferric oxide, alumina, lime and magnesia. About i gr. powdered sample is uniformly moistened with water in a porcelain dish, covered with a watch-glass, and decomposed by addition of moderately dilute hydrochloric acid. After the evo- lution of carbonic acid has ceased the mass is evaporated to dry- ness on a water-bath with constant stirring, completely dried by heating on an asbestos plate, and covered with sufficient concen- trated hydrochloric acid to completely dissolve all soluble matter. After a half-hour hot water is added, the solution is filtered, the precipitate is washed and weighed as silica and clay. To the hot filtrate, which has been oxidized with bromine water, ammonia is added to slight excess, the solution is boiled for a few moments, and the precipitate formed is filtered off. To free it from any adhering lime, the solution in hydrochloric acid and precipitation with am- monia may be repeated. Ferric oxide and alumina are determined together. A separate iron determination, when necessary, is con- ducted in another portion. The filtrate, now about 200 c.c. in volume, is brought to incipient boiling, the flame is removed, and ammonium oxalate is added to the point of complete precipitation and rapid deposition. A sufficient excess of ammonium oxalate is yet added to convert all magnesia into soluble magnesium oxalate. Finally the solution is diluted to 400500 c.c. and allowed to stand several hours in a warm place. Frequently magnesia is thrown down together with the lime, but by gradual addition of the ammo- nium oxalate the magnesia can be reduced to about .02 per cent. If exact results be required, the precipitation may be repeated a second time. 36 CHEMICAL-TECHNICAL ANALYSIS. For this purpose the clear liquid is decanted through a filter, the residue remaining in the beaker is stirred twice with hot water, and the clear liquid is decanted each time through the same filter. The precipitate in the beaker is redissolved in hydrochloric acid, and to the solution ammonia and ammonium oxalate are added in suffi- cient quantity. The reprecipitated calcium oxalate is allowed to stand one hour. The solution is then filtered through the same filter, the latter is washed thoroughly with hot water, dried, ignited for a time at a low heat, and is then ignited over a blast-lamp until constant weight is obtained. It is weighed as calcium oxide.* The filtrate from the lime is made slightly acid with hydrochloric acid and is concentrated on a water-bath to about one-third its volume. One-third the remaining volume of dilute ammonia is added, and when cool the magnesia is precipitated with sodium hydrogen phosphate. After three hours the solution may be filtered. The precipitate is washed with water containing about 3 per cent, ammonia, then dried and ignited in a. platinum crucible. The weight represents Mg 2 P 2 O r (V) Oxide of iron and sulphuric acid. Both constituents may when necessary be determined in the same operation. For this purpose about 10 grs. powdered sample are placed in a 250 c.c. flask, dissolved in hydrochloric acid, and diluted to the mark. Two hundred c.c. solution are filtered through a dry filter and precipitated with ammonia. The precipi- tate formed is dissolved in sulphuric acid (i 14), diluted with water, reduced with zinc and titrated with permanganate of potash. The filtrate from the sesquioxide of iron is acidified with hydrochloric acid, and the sulphuric acid is determined with barium chloride. (d*) Carbonic acid. Carbonic acid, as a rule, can be calculated by considering it bound to the calcium oxide and magnesia which remain after deducting that portion of the former attached to the sulphuric acid found. When large quantities of silica are present in which case lime can exist as calcium silicate a direct determi- nation of carbonic acid is made in the usual manner by absorption in tubes containing soda lime. * To check the result, it is advisable to titrate the calcium oxide with hydro- chloric acid. MARL. 37 ( (^) then equals . A clay is still considered refractory when -/TL this value lies between 3 and 4. The more refractory, the more these values are exceeded ; the less refractory, the lower the values sink below these limits. Example : The Zettlitzer kaolin, considered very refractory, and which possesses the following composition, gives the adjoining oxygen values : 4 50 CHEMICAL-TECHNICAL ANALYSIS. Constituents. Oxides. Per Cent. Oxygen. Per Cent. Silica 45.68 24.36 (b) Alumina 78.154 18.03 (a) .08 .02 1 Ferric oxide GO 18 , , . Magnesium oxide .... 38 ; I5 h^(c) Potassium oxide 66 .11 1 Loss on ignition I 7 OO The comparison of the fluxes with alumina taken as unity yields ' -:rr39.i3 (A}. Alumina compared with silica taken as unity .46 15.03 Accordingly, the formula of the clay would be 39.19 (A1 2 O s .i.35 SiO 2 ) -j- RO, and the quotient of refractoriness F= - z= 28,98. III. Metallurgical Industry. 1. Iron. THE following determinations are made, as a rule, for the various kinds of iron (pig iron, wrought-iron, etc.) : silicon, carbon, man- ganese, phosphorus, sulphur. Concerning sampling, let it be stated that wrought-iron and gray pig-iron can be obtained in desired form by boring, planing or turning, whereas white pig-iron and hardened steel can be broken up with a hammer and subsequently divided in a steel mortar. (#) Silicon. Following the method of Brown, 12 grs. iron of white pig-iron and steel a larger quantity are heated with nitric acid (sp. gr. 1.2) until everything has dissolved. 3540 c.c. sul- phuric acid (1:4) are then added, and the whole is heated on a sand- or water-bath until the nitric acid has volatilized. To the chilled liquid 40-50 c.c. water are then carefully added, after which it is heated to complete solution of iron salts and is filtered hot. The residue is washed first with hot water until iron is no longer detectible, and then with hot hydrochloric acid (sp.gr. 1.12) about four times, and finally with hot water to completely remove the hydrochloric acid. The moist filter is consumed in a platinum crucible at a low temperature and then ignited until the silica has become white, a point which with graphitic pig-iron is often not reached for 2-3 hours. Should the silica contain iron, it is fused with sodium-potassium carbonate. () Carbon. Total carbon and graphite are usually determined, and bound carbon is calculated by difference. (a) Total carbon. The iron is dissolved in neutral cupro-ammo- nium chloride solution, which is prepared by dissolving 300 grs. neutral cupro-ammonium chloride in one liter water or 340 grs. crystallized copper chloride and 214 grs. ammonium chloride in 1850 c.c. water. In the residue the carbon is determined as car- bonic acid by combustion. 52 CHEMICAL-TECHNICAL ANALYSIS. Procedure. i gr. pig-iron, 3-5 grs. steel or 510 grs. wrought- iron in pulverized condition are placed in an Erlenmeyer flask, and 50 c.c. of the above solution are added for every gram of iron. The solution is briskly agitated at first at ordinary temperature, later at a temperature of 40 to 50. The iron dissolves rapidly with separation of copper, which later dissolves likewise, leaving a residue consisting solely of carbon, silicide-, phosphide- and sulphide of iron. Should a precipitate of basic salts of iron form, several drops of hydrochloric acid are added to the solution. It is then filtered on an asbestos filter and subsequently on a filter pump. The first portions of the filtrate are tested for carbon, which may have passed through, by dilution with hydrochloric acid and water until transparent. It is then washed first with cupro-ammonium chloride, and later with hot water until chlorine is no longer de- tectible, then with alcohol, finally with ether ; whereupon the pre- cipitate is dried at a low temperature. The carbon on the asbestos filter is oxidized to carbonic acid by treatment with chromic acid and sulphuric acid. To determine the carbonic acid, apparatus for absorption of the latter is used, special care being taken to dry the evolving ga-es with pumice-stone, sulphuric acid and calcium chloride. In the generator of the apparatus is placed the carbon deposit, together with the asbestos-tube, which has been carefully cut with a file. 40 c.c. concentrated sulphuric acid are added, fol- lowed, when cool, by 8 grs. crystallized chromic acid. The flask is then attached to the apparatus and gently warmed. The gases evolved first pass through an upright condenser, then through the drying apparatus, and finally into the absorption vessels, which consist of two tubes containing soda-lime. The second vessel, however, is also filled about y$ its capacity with calcium chloride. In addition, a protecting tube filled with calcium chloride is at- tached. Heating is continued until evolution has ceased and sulphuric anhydride fumes appear in the condenser. An aspirator is then attached, and air, freed from carbonic acid, is drawn through the system for some time. The soda-lime tubes are then detached and weighed. Recently methods have been proposed to determine the carbon volumetrically. That of Lunge and Marchlewski is particularly suited to this purpose. According to the latter, .5-5 grs. of the IRON. 53 iron under investigation are repeatedly agitated in a flask with a saturated copper sulphate solution for 1-6 hours. The flask is then connected with a condenser and a suitable gasometer and warmed with the quantity of chromic-sulphuric acid mixture necessary to insure oxidation. The authors have constructed for this purpose special forms of generators and gas burettes. An exact description of these would lead too far. They may be found in the Zeitschrift fiir angewandte Chemie, Jahrgang 1891, S. 412. The apparatus is obtainable from J. G. Cramer, in Zurich, C. Desaga, in Heidel- berg, and others. (/?) Graphite. 4-5 grs. iron are dissolved by warming with dilute hydrochloric acid. The residue is filtered on an asbestos bed. The latter is washed with hot water until the filtrate, on addition of silver nitrate, no longer opalesces. It is then washed 4-5 times with dilute caustic potash, followed by alcohol, to remove potash, and finally with ether. After drying, the graphite is oxidized like the total carbon with chromic acid and sulphuric acid. (<:) Manganese. Of the many methods proposed for this deter- mination, that of Volhard only will be described here. Principle. If to a neutral or slightly acid solution of a manga- nese salt, permanganate of potash be added at 80 C., a complete precipitation of the manganese ensues. The equation Mn 2 O 7 -f 3MnO = 5MnO 2 , originally proposed for this method, is incorrect under the conditions given, according to Volhard, inasmuch as a precipitate containing manganous oxide, 5 MnO a . MnO is formed. If, however, a solution of a zinc, lime or magnesium salt be added, a peroxide containing zinc oxide, lime or magnesia will be precipitated. Observing these facts, manganese in iron may be determined by adding zinc oxide to the solution containing all the iron in the ic and all manganese in the ous condition. Ferric oxide is precipi- tated, while an equivalent amount of zinc is dissolved. The solu- tion is then titrated with permanganate of potash. Standardization. The permanganate is standardized on iron in the usual manner, and is then calculated into manganese units (of manganous oxide) by use of the equation ioFe(= 2KMnO 4 )= 3Mn. Experiment. About 4 grs. sample (less, if it contain much manganese) are dissolved in nitric acid (sp. gr. 1.2) ; the solution 54 CHEMICAL-TECHNICAL ANALYSIS. is evaporated to dryness, and the residue is heated for about i hour on a sand- or air-bath. Thereupon it is dissolved in warm hydro- chloric acid; 20 c.c. sulphuric acid (i : i) are added, and the whole is heated until sulphuric acid volatilizes. It is then taken up with water and washed into a 500 c.c. graduated flask. The excess of acid is nearly neutralized with sodium carbonate, and, while being agitated, freshly calcined zinc oxide, suspended in water, is added until the solution, which gradually turns dark brown, suddenly congeals from separation of the entire ferric oxide. Water is then filled in to the mark, and 100 and 250 c.c. respectively of the clear filtrate are withdrawn for titration with permanganate, which should be approximately TO normal. The solution to be titrated is heated to about 80 C. It is vig- orously shaken while the permanganate is introduced until the liquid above the flocculent precipitate, which settles rapidly, is of a pink color. It is then boiled, and when the color has disappeared, more permanganate is added until a permanent color remains. Modification by Ulzer and Brull* In order to overcome the not inappreciable difficulty of detecting the end reaction of the titration with permanganate, 20 c.c. of a .5 per cent, solution of hydrogen peroxide may be added to the above solution, which has been freed from ferric oxide by means of zinc oxide and filtered. This is followed by the addition of caustic soda as long as a pre- cipitate forms, after which it is boiled. Manganese is precipitated as 5MnO r MnO. Upon cooling, oxalic acid of known strength is added, together with pure dilute nitric acid. It is then digested at a low heat until the precipitate redissolves, after which it is heated almost to boiling, and the excess of oxalic acid is titrated with permanganate. () of about 5 liters capacity. Suffi- cient hot water is added to bring the total volume to 34 liters. About 50 c.c. cone, hydrochloric acid are added, and a brisk con- tinuous current of hydrogen sulphide is conducted in, until com- plete precipitation is indicated by the rapid settling of the precipi- tate and a perfectly colorless supernatant liquid. The precipitate (~) contains all the copper, bismuth, arsenic, antimony and tin. Iron, nickel, cobalt and zinc remain in solution. Flask, solution and precipitate are weighed ; the weight of the flask is deducted and the weight of liquid and precipitate thereby ascertained. The weight of precipitate is found by calculating the copper contained therein into copper sulphide. If this be deducted also, the weight of liquid alone is obtained. As soon as the precipitate has well settled, as much of the clear liquid as possible is drawn off with a siphon. If the remaining liquid, precipitate and flask be now weighed together, the difference between it and the former weight gives the weight of liquid siphoned off. By simple proportion the corresponding quantity of original substance contained therein can be calculated. This solution, filtered if necessary, serves for the determination of iron, nickel, cobalt and zinc. For this purpose it is evaporated as far as possible in a porcelain dish on a water-bath and the excess of sulphuric acid is volatilized over a naked flame. The residue is heated with water and nitric acid, filtered, treated with an excess of ammonia, and the precipitate formed is dissolved in hydrochloric acid and reprecipitated with ammonia. The opera- tion is repeated if necessary, and the precipitate is finally weighed as ferric oxide. To the collected filtrates more ammonia is added, followed by acetic acid to slight acid reaction. Hydrogen sulphide is conducted into the heated solution, whereby cobalt, nickel and zinc are precipitated. These are filtered off, dried, removed as far as possible from the filter, and dissolved in nitric acid and a little CRUDE AND 11EFINED COPPER. 63 hydrochloric acid. The filter ash is added, the liquid is evaporated on a water-bath, taken up with water and a little hydrochloric acid, and then exactly neutralized with sodium carbonate, using methyl- orange as indicator. A slow current of hydrogen sulphide is now led in for a brief period. A few drops of dilute, preferably very weak, alkaline sodium acetate solution are added, whereby an ap- preciable darkening of the precipitate should not ensue. A very slow current of hydrogen sulphide is again led in for a few minutes, and the zinc sulphide formed is allowed to settle for a few hours. It is filtered in a double filter, washed with water containing hydro- gen sulphide, and the zinc is determined as sulphide in the usual manner. The filtrate from the zinc is best completely evaporated to expel hydrogen sulphide. The residue is taken up with hydrochloric acid and water, filtered if necessary, and the cobalt and nickel are then precipitated with an excess of caustic potash. They are first of all determined together. Should a separation be desired, which as a rule will not be required on account of the preponderance of nickel, one of the usual methods is employed. To the residual liquid and precipitate (^) in flask (Z>~) potassium or sodium hydrate is added to slight alkaline reaction. A sufficient quantity of light yellow potassium or sodium sulphide solution is then added, together with TOO c.c. (= one -half) of the liquid in flask (j9). The flask is then placed in a warm place, and frequently agitated to bring all sulphides of antimony, tin and arsenic into solution. It is then diluted to 34 liters with water and weighed, and as much as possible of the clear liquid is withdrawn. The remainder, together with flask and sediment, is weighed, and the amount of copper corresponding to the liquid withdrawn is calcu- lated as before. The flask and precipitate are preserved. In order to estimate antimony, tin and arsenic, the liquid is filtered, if necessary, and acidified with hydrochloric acid. The sulphides of these metals and much sulphur are precipitated. These are allowed to settle for a time, and are then filtered and dried. Thereupon precipitate and filter are placed in a flask and extracted with carbon disulphide to free from the greater part of the sulphur. The solution is filtered and the residue is warmed with dilute ammonium sulphide, whereby the sulphides dissolve. After this 64 CHEMICAL-TECHNICAL ANALYSIS. has been filtered and the filter has been thoroughly washed it is warmed, and pure hydrogen peroxide is added until the color has disappeared and the sulphur has been thoroughly oxidized. It is now evaporated to dryness in a spacious porcelain dish and oxidized with fuming nitric acid. The latter is expelled as far as possible, and potassium hydrate is added to distinct alkaline reaction, after which the whole is washed into a large silver crucible. A few pieces of stick caustic soda are placed in the crucible, which is heated carefully in a sand-bath until the water has been completely expelled. The residue is then gradually heated to continued fusion, and finally over a naked flame. The crucible contents, now perfectly clear, are lixiviated with water until the insoluble particles have separated as a powder, when about ^ the volume of alcohol is added. The crucible is covered, and the contents are occasionally stirred during the 24 hours in which it is allowed to stand. The undissolved sodium antimonate is filtered and washed with dilute alcohol (i : i), to which a few drops of sodium hydrate solution have been added. Stannate and arsenate of sodium remain in the filtrate (-^). The precipitate of sodium antimonate on the filter is repeatedly covered with a warm solution of tartaric acid in dilute hydrochloric acid until all has dissolved. The solution is diluted, heated and precipi- tated with hydrogen sulphide. Orange sulphide of antimony forms. Should the precipitate be rendered dark from silver sulphide arising from the crucible, it is redissolved by warming with ammonium sulphide, filtered from the sediment and reprecipitated with hydro- chloric acid. The hydrogen sulphide is expelled by conducting into the flask a current of carbonic acid. It is then filtered on a previously dried and weighed filter, after which it is dried and weighed. To expel the last traces of water and sulphur when large quantities of antimony sulphide are concerned, an aliquot portion of the dried precipitate is placed in a porcelain boat, which is introduced into a glass tube and moderately heated. Pure dark -gray trisulphide of antimony is thus obtained. With small quantities it suffices to wash the dried precipitate on the filter repeatedly with carbon disulphide, dry and weigh. Hydrochloric acid is added to filtrate (J?) to acid reaction. Thereby a white precipitate of arsenate of tin now and then appears. Without taking notice of this, the tin and arsenic are CRUDE AND REFINED COPPER. 65 precipitated with a current of hydrogen sulphide. These are fil- tered on a dried and weighed filter, washed with hydrogen sulphide water, dried and weighed. A separation of tin from arsenic in the precipitate, which usually contains a considerable amount of sulphur, is conducted in the following way : An aliquot portion of the same is placed in a bulb tube bent at a right angle on one side. The straight side is attached to a hydrogen sulphide generator by means of a calcium chloride drying tube. The bent part is connected by a rubber stopper to a Peligot tube filled with ammonia (about i : 2). This tube, finally, may be attached to a second absorption vessel. The bulb is then heated in a current of hydrogen sulphide. Sulphide of arsenic and sulphur which are evolved collect in the ammonia, while sulphide of tin remains in the bulb. The bulb- tube is detached and heated strongly in a current of air, which is conducted through. The sulphide of tin is thereby changed to oxide, and this is weighed on cooling. The tin is calculated from it. The solution of sulphide of arsenic is washed into a beaker, acidified with hydrochloric acid, chlorate of potash is added, and the liquid is warmed moderately. Sulphide of arsenic dissolves. Any sulphur remaining is filtered off. The arsenic in the filtrate is determined as magnesium pyroarsenate in the usual manner, and from it the arsenic is calculated. Bismuth is determined by re- peatedly adding a large quantity of water containing sodium sul- phide to the remaining liquid and precipitate in flask (-D), shaking, and drawing off as much liquid as possible. The residue is covered with hydrochloric acid, nitric acid is gradually added, and the whole is allowed to stand in a warm place. A gradual solution of the precipitate takes place, with separation of pure sulphur. Too energetic action causes retention of copper sulphide. The sulphur is filtered off, washed, and the solution is evaporated repeatedly with hydrochloric acid. When the latter is almost completely ex- pelled, water is added, and the small amount of residue remaining is filtered off. The latter consists principally of basic bismuth chlo- ride. To purify the same, it is dissolved in dilute hydrochloric acid, treated with caustic potash to alkaline reaction, potassium cyanide is added, and the bismuth is precipitated with sodium sul- phide, while sulphide Of copper remains dissolved in the cyanide 5 66 CHEMICAL-TECHNICAL ANALYSIS. of potash. The precipitate is thrown on a previously dried and weighed filter, repeatedly washed with carbon disulphide, and weighed as sulphide of bismuth. Sulphur is determined by adding ammonia to 400 c.c. of the liquid remaining in (A), until the greater part of the free nitric acid has been neutralized, and after the addition of a few drops of barium nitrate solution is allowed to remain in a warm place. In the presence of appreciable traces of sulphur, probably contained in the form of sulphurous acid in the copper, a small precipitate of barium sulphate is formed which is filtered and weighed. In another 400 c.c. solution still in flask (A), the phosphorus is determined. To accomplish this the liquid is repeatedly evaporated with hydrochloric acid to expel nitric acid. The residue is dissolved in hot water, placed in a weighed flask of 2 liters capacity, and diluted with hot water to about 1200 c.c. This solution is completely, pre- cipitated at about 70 C. with hydrogen sulphide. The sulphides are allowed to settle and as much clear supernatant liquid as possible is drawn off. Flask, remaining liquid and precipitate are weighed, and, as before, the corresponding amount of copper in the sepa- rated liquid is calculated. The solution is filtered, evaporated to small bulk with repeated additions of nitric acid, and the phos- phorus is determined in the usual manner. (See also Chapter V. , Fertilizers.) The method of Hampe is used to determine, in the bullion, the oxygen which is combined partly with metals and partly with sulphur. The thoroughly cleaned copper is first filed. The filings are sieved through a hair sieve and the iron particles are with- drawn by means of a magnet. The powder is next boiled with dilute caustic potash to rid it of traces of fat, etc. The liquid is poured off, and the powder is washed and hurriedly dried. The estimation of oxygen is calculated by loss of weight upon ignition in a current of hydrogen. A hard glass bulb tube, drawn out at both ends, is suitable for this purpose. It is first heated in a current of dry air and then allowed to cool. It is weighed ; 10-20 grs. dry copper powder are thereupon placed in the tube, which is reweighed. Dry carbonic acid from a Kipp generator is then con- ducted through the tube. The generator is set in action two hours before use, and to purify and dry the carbonic acid it is led through CRUDE AND REFINED COPPER. 67 the following system : A solution of bicarbonate of soda, a tube filled with lumps of bicarbonate, a wash-bottle containing silver nitrate solution, a tube containing pumice-stone saturated with the latter solution, a wash-bottle containing cone, sulphuric acid, and finally a calcium chloride tube. The carbonic acid is allowed to pass through the tube containing the copper for five minutes, after which it is very moderately heated to free from all traces of water. A sublimate of arsenic acid will form when the heat applied is too strong. Pyrogenous products should not form. Upon cooling in carbonic acid, the latter is replaced by air and the tube is weighed. The loss of weight should equal only a few milligrams. A very slow current of pure hydrogen is then conducted over the copper. Thereupon the latter is at first moderately heated, and later to glow- ing, for about fifteen minutes. During the application of heat, water forms, whereas, with impure copper, a sublimate of arsenic, antimony and lead, forms in the bulb and adjacent to it. This sub- limate should in no case issue from the tube. Therefore the tube should be drawn out sufficiently long, and the hydrogen current should be correspondingly slow. When the copper contains sul- phurous acid, some hydrogen sulphide is evolved with the steam. In order to estimate its quantity, the gases are led through an alka- line lead solution or a bromine-hydrochloric acid mixture, and the sulphur is estimated from the sulphuric acid formed. After the copper has thoroughly cooled in hydrogen, dry air is again con- ducted through and the tube is weighed. The loss in weight, less the sulphur evolved as hydrogen sulphide, gives the amount of oxygen present. IV. Alloys. 1. Phosphor-Bronze. THIS usually contains copper, tin and phosphorus, and frequently also lead and zinc. The presence of other constituents, however, like arsenic and iron, is not excluded,* on account of which a qualitative analysis should always be conducted first. 3 grams of the broken-up alloy, taken for quantitative analysis, are covered with water, and nitric acid is carefully added. Heat is generated, and decomposition takes place. It is brought to a finish by heating with a small flame. It is evaporated to dryness in a porcelain dish, dissolved in nitric acid, and water is added, after which it is filtered and washed out with hot water ( residue A and filtrate B). Residue A contains all the tin, together with all phosphorus (as phosphate of tin), some copper and some of the lead. It is ignited and weighed. Thereupon it is fused in a porcelain crucible with carbonate of soda and sulphur. The fusion is lixiviated with hot water. The small residue is filtered off, and estimated either directly as subsulphide of copper by ignition with sulphur in an atmosphere of hydrogen, or else, if necessary, a separation of copper from lead is carried out by means of sulphuric acid in nitric acid solution. The filtrate containing the phosphoric acid and tin is acidified with hydrochloric acid. The sulphide of tin is filtered off, the filtrate evaporated to dryness on a water-bath, and taken up with nitric acid. The phosphoric acid is precipitated with molybdate solution, and the determination is continued in the usual manner. The copper, calculated into cupric oxide, plus the phosphoric anhydride formed from the phosphorus, is deducted from the total residue, and the remainder is calculated as oxide of tin. The filtrate B, after addition of sulphuric acid, is evaporated to dryness, to precipitate lead, and the sulphuric acid completely # No account of the presence of these is taken in the following method of quan- titative analysis. WHITE METAL. 69 expelled. The residue is then taken up with water, washed with water containing sulphuric acid, then with alcohol, and is finally ignited and weighed. Filtrate from the lead sulphate is placed in a 250 c.c. graduated flask, and diluted to the mark. In one portion of 50 c.c. the copper is estimated as sulphide by means of hydrogen sulphide, while in the remaining 200 c.c. the metals present in less quantity may be determined. For this purpose copper is precipi- tated with hydrogen sulphide, and filtered off. The nitrate is evaporated to dryness, taken up with a few drops of hydrochloric acid, neutralized exactly with sodium carbonate, and hydrogen sulphide is run in. Sulphide of zinc is precipitated. Upon addi- tion of a few drops of a dilute solution of sodium acetate and renewed addition of hydrogen sulphide, the precipitation is com- pleted. The precipitate is allowed to stand for a time, filtered, and determined as zinc sulphide by ignition with sulphur in a current of hydrogen. To the copper contained in the filtrate B, that which was contained in residue A must be added. The same holds good for any lead found in the residue. 2. White Metal. This contains tin, as a rule, as chief constituent, together with antimony and also zinc. Copper and lead are frequently present in minute quantities, although sometimes in large quantities. Arsenic, mercury, nickel and iron may be present. The quantitative analysis covering the presence of tin, antimony, copper, lead and zinc will be described. 1-2 grs. alloy are dissolved in nitric acid, as previously described, evaporated nearly to drynesss, taken up with dilute nitric acid, filtered, and washed with water containing ammonium nitrate. (Filtrate A. Residue B. ) Filtrate A contains copper, lead and zinc, whose separation is conducted as given under Phosphor-Bronze. Residue B contains all tin and antimony, besides small quantities of copper, lead and zinc. It is dried, ignited and weighed. A weighed portion of the same is fused with soda and sulphur, and the fusion is lixiviated with water. Should the residue be small, it may be directly ignited with sulphur in a current of hydrogen, and considered as the sulphide of one of the three metals, copper, lead 70 CHEMICAL-TECHNICAL ANALYSIS. and zinc, depending on the predominance of one or another as shown by the qualitative tests or the quantitative analysis of filtrate A. Should there be considerable residue, it is dissolved in hot dilute nitric acid, and the individual constituents are separated and determined. The amount of these (in form of oxides) is deducted from the substance used for fusion, whereby tin oxide and antimony oxide (SnO 2 and Sb 2 O 4 ) remain. These are recalculated from the aliquot portion used on the total residue. In order to separate tin and antimony, another portion of the residue B is fused with caustic soda in a silver crucible, and the fusion is lixiviated until the insol- uble portion is powdered. One-half volume of alcohol is added, and allowed to stand 24 hours with repeated stirring. It is then filtered off and washed with dilute alcohol (i : 2). The sodium antimonate remaining in the filter contains a small quantity of cop- per, whereas traces of lead or zinc will remain in solution with the tin, and can be precipitated by careful addition of sodium sulphide. After filtration from this minute precipitate, hydrochloric acid is added to precipitate tin sulphide, which is quantitatively estimated as tin oxide by careful oxidation and ignition with ammonium car- bonate. If this be calculated on the total residue, and subtracted from the sum of the oxides of tin and antimony previously found, there remains the antimony tetroxide, from which antimony is calculated. 3. Iron Alloys. Iron is alloyed with other substances besides those mentioned under the investigation of iron, in order to impart to it certain properties, principally hardness and toughness. Some of these substances are chromium, tungsten, titanium, aluminium and nickel. For instance, there is contained in tungsten steel 9 per cent. W. ; in chromium steel, 2-4 per cent. Cr. ; in ferro-chrom, 29-49 per cent. Cr. ; in ferro-aluminium, 6.8-10 per cent. Al., and in nickel steel, 8-10 per cent. Ni. With reference to chro- mium and nickel estimations, ferro-chrom and nickel steel serve as illustrations of such alloys. Ferro-chrom. 1-4 grs. of sample, powdered as fine as possible, are boiled ^ hour in a large beaker with 500 c.c. water and 50 c.c. sulphuric acid (i : i). Usually all dissolves. Should a residue remain, however, after continued heating, it is filtered off, washed, IRON ALLOYS. 71 incinerated in a platinum capsule, and fused with a mixture of two parts fused borax and three parts soda for three hours at a high heat, preferably in a muffle. The fusion is dissolved in water, acidified with sulphuric acid, and added to the first filtrate. The united filtrates are brought to boiling, and a concentrated perman- ganate solution is added to the same until red coloration sets in. The excess of permanganate is reduced with manganous sulphate, after which it is washed into a liter flask filled to the mark after cooling, well shaken, and filtered through a ribbed filter. An ali- quot part of this solution, which is colored yellow in presence of the smallest quantities of chromium, is treated with 50 or 100 c.c. ferrous ammonium sulphate solution (containing 20 grams of the salt and 10 c.c. sulphuric acid (i : i) to the liter), after which the excess of ferrous salt is titrated back with -& normal permanganate. At the same time the same quantity of ferrous ammonium sulphate solution is titrated with permanganate, and from the quan- tity of the latter now used the first is deducted. The differ- ence represents the ferrous oxide oxidized by the chromic acid from which chromium can easily be calculated. 2CrO 3 = 6 Fe O. Nickel steel. 2-4 grs. sample are dissolved in nitric acid (sp. gr. 1.2). After dissolving, 1020 c. c. sulphuric acid (i : i) are added, and the whole is evaporated until sulphuric acid begins to volatilize. The residue is dissolved in water, and the solution is gradually poured into a 500 c.c. flask in which 50 c.c. sulphate of ammonium solution (containing 500 grs. of the salt in a liter of water) and 130 c.c. cone, ammonia have previously been placed. It is then diluted to the mark, well mixed, and filtered through a ribbed filter. Two hundred and fifty c.c. of the filtrate are taken, and in this the nickel is determined either electrolytically or by precipitation with ammonium sulphide, or hydrogen sulphide,* in a solution slightly acidified with acetic acid. In case copper was present in the nickel steel, it will be found in the ammoniacal solution. The copper, in the solution strongly acidified with hydrochloric acid, may be removed with hydrogen sulphide. Estimation of nickel is then conducted with the filtrate. * In the latter case the precipitate of nickel sulphide is dissolved in hydro- chloric acid, with addition of nitric acid or potassium chlorate, and then precipi- tated with caustic potash. It is finally transformed into metallic nickel by reduc- tion in a current of hydrogen. V. Fertilizers. THESE may be divided into three groups, according to their active constituents: i. Phosphate fertilizers; 2. Potash fertilizers; 3. Nitrogenous fertilizers. In addition to these, mixed fertilizers are used which may contain all three constituents. Combined methods exist for the estimation of phosphoric acid, potash and nitrogen. These will be described first of all. (a) Phosphoric Acid. Phosphoric acid may be determined gravimetrically or volumet- rically. The gravimetric methods are the molybdate and citrate methods. In both the phosphoric acid is determined finally as magnesium pyrophosphate. It is determined volumetrically by titration with uranium acetate. (a) Molybdate method. Separation from all other bases is accomplished by use of ammonium molybdate, whereby all phos- phoric acid is precipitated in the form of a compound of varying composition. Phosphoric acid is determined from this. To do this, 200 c.c. molybdate solution are added to a solution containing phosphoric acid (not exceeding .2 gr. P 2 O 5 ), which is then kept for 15-20 minutes at a temperature of 7080 C. After standing three hours the supernatant liquid is filtered off, and the precipitate, as much as possible of which is allowed to remain in the beaker, is washed with a 1 5 per cent, solution of ammonium nitrate, containing 10 c.c. nitric acid to the liter. The washings are thrown on the same filter. The beaker, holding the main por- tion of precipitate, is placed under the funnel. A warm 2^ per cent, ammonia solution is poured on the filter in just sufficient amount to dissolve the precipitate upon it. It is then washed with cold ammonia of the same strength until a red coloration (molyb- date reaction) no longer appears on adding ferrocyanide of potassium to a drop of the filtrate placed on a porcelain plate. The quantity FERTILIZERS. 73 of ammonia used (150 c.c.) should just about suffice to dissolve the precipitate in the beaker on shaking. If not, more ammonia is added, and a clear solution is obtained. To this, for every . i gr. P 2 O 5 , TO c. c. magnesium mixture are added, drop by drop. It is stirred for some time without touching the sides of the beaker, and is filtered after at least three hours' standing. The precipitate is washed with 2 ^ per cent, ammonia until a portion of the filtrate, acidified with nitric acid, opalesces but slightly. Further manipu- lation is conducted in the usual manner. Reagents used are prepared as follows : Molybdate solution : 150 grams crystallized ammonium molybdate and 400 grams ammonium nitrate are dissolved in a liter of water, and the solution is poured into an equal volume of nitric acid (sp. gr. 1.19). The solution should be kept in the dark. Magnesium mixture: 100 grams magnesium chloride and 140 grams ammonium chloride are dissolved in 1300 c.c. water, and diluted to two liters with 24 per cent, ammonia. It is filtered after standing in a stoppered flask for several days. (j3) Citrate method. By use of this method the precipitation of phosphates of lime, iron, etc. , by ammonia is prevented by citric acid. A quantity of solution containing phosphoric acid (not exceeding .2 gr. P 2 O.) is treated with 100 c.c. citrate solution (prepared by dissolving 150 grs. citric acid in water, adding 500 c.c. 24 per cent, ammonia, and diluting to 1500 c.c.). If necessary, more ammonia is added, whereby turbidity must not ensue. The excess is neutral- ized with a few drops of nitric acid, and 25 c.c. magnesium mixture are added. The precipitate is treated as under (a). The method is easily carried out and is much used. Since on the one hand some magnesium ammonium phosphate is dissolved by the excess of citric acid, and, on the other hand, small quantities of phosphate of lime, etc., are precipitated, the errors are balanced. ( r ) Uranium method. This method, which is considered as universally known, can only be used to determine water-soluble phosphoric acid. It is now rarely used, at any rate. (b) Potassium Oxide. This is determined as the double salt 2KCl.PtCl 4 by using pla- tinic chloride. It is only necessary that nothing but chlorides be 74 CHEMICAL-TECHNICAL ANALYSIS. present, of which those of sodium, calcium and magnesium form platinum salts, soluble in alcohol, whereas that of potassium chlo- ride is insoluble. Should there be sulphates present, as is usually the case, they are converted into chlorides by adding a boiling chloride of barium solution (avoiding excess as much as possible) to the liquid, to which i c.c. hydrochloric acid has been added, without regarding a possible residue. The filtrate,' or an aliquot portion of the same, is evaporated down to about 15 c.c. bulk, and sufficient platinic chloride is added to convert all salts present into double salts ( i gr. platinum to .5 gr. substance). It is stirred with a glass rod, evaporated to about 10 c.c., and 90 per cent, alcohol is added. After stirring for a while, and permitting to stand, it is filtered on a filter, moistened with alcohol, and washed with alcohol until the washings have become colorless. The precipitate may be dried at 130 and weighed. But since it can contain small quantities of chlorides insoluble in alcohol, it is better to incinerate, filter and place contents in a porcelain crucible, and to ignite the residue separately with small quantities of pure oxalic acid at a high temperature. (c) Nitrogen. Nitrogen can be present as ammonia (ammonium salts), as nitrates, or as organic nitrogenous compounds. It may finally be present as a combination of two or three of these forms. (a) Nitrogen as ammonia. The estimation is carried out by heating with caustic soda and absorbing the ammonia evolved in standardized acid. The operation is well known. When nitrogenous organic matter is simultaneously present, which is partially decom- posed by boiling caustic soda with formation of ammonia, soda- lime or freshly calcined magnesia is used. (/?) Nitrogen as nitrates is estimated in an eudiometer graduated into tenths, as nitric oxide, which is caught up after liberation from the nitric acid, which is reduced with ferrous chloride (method of Schulze-Tiemann or Schlosing- Wagner). (>) Organic nitrogen. Various methods proposed for this esti- mation have been replaced by the method of Kjeldahl, the modi- fied form of which, by Wilfarth, will be described here. 1-2 grs. substance are covered with 20 c.c. cone, sulphuric acid in a long- FERTILIZERS. 75 necked, round-bottom flask of about 150 c.c. capacity. .7 gr. freshly prepared yellow mercuric oxide (or .5 gr. mercury) is added, and the whole is heated on a wire gauze, at first moderately, and finally to a brisk boiling. It is better to fasten the flask in a clamp in an in- clined position in order to avoid loss by sputtering, and also to avoid the direct heating of the frequently uneven bottom of the flask. The liquid is heated until colorless. It is allowed to cool and is poured into an Erlenmeyer flask of about 3^ liter capacity, con- taining some water, and is then thoroughly rinsed out. After cool- ing, an excess* of about 30 per cent, caustic soda is added, together with 25 c.c. of a 10 per cent, potassium sulphide solution. The latter precipitates all the mercury in the form of mercuric sulphide and simultaneously decomposes the mercury amides, from which the ammonia is expelled very slowly by alkalies. A few pieces of gran- ulated zinc are added, to prevent bumping on distillation. By distilling, all the ammonia is volatilized and is collected in a receiver containing 20 c.c. of half-normal sulphuric acid and 50 c.c. of water. The excess of acid is titrated and the nitrogen is calculated (iH. 2 SO 4 is equivalent to 2N). In order to prevent alkali from being carried over, different forms of apparatus have been proposed. As a rule, a bulb tube is placed in the flask and connected with a condenser. Distillation is finished at the end of from 20-30 minutes. The contents of the flask usually heat up considerably, but a loss of ammonia is not to be feared, even when not cooled. The most important fertilizers belonging to each of the three groups will now be described. 1. Phosphate Fertilizers. They may be divided into : A. Phosphates containing water-insoluble phosphoric acid. (a). Crude phosphates. | (). Artificially-pre- Mineral phosphates. Bone phosphates. Guano phosphates. pared phosphates. Phosphate slags. B. Phosphates containing water-sohible phosphoric acid. Superphosphates . * The amount necessary is easily calculated approximately from the sulphuric acid used. 76 CHEMICAL-TECHNICAL ANALYSIS. A. Phosphates Containing "Water-Insoluble Phosphoric Acid. Contain phosphoric acid principally in form of tricalcium phos- phate, which, together with iron and aluminium present, is very slowly soluble. In order to determine phosphoric acid in crude phosphates of sub-group (0) phosphorite, apatite, bone meal, animal charcoal and Baker guano, 5 grs. substance, finely powdered, are boiled with 20 c.c. cone, nitric acid and 50 c.c. cone, sulphuric acid for ^ hour, and the solution, plus residue, is poured into a ^ -liter graduated flask, diluted to the mark and thoroughly agitated, after which it is filtered through a dry ribbed filter. In 50 c.c. of the filtrate the phosphoric acid is determined by the molybdate method. Should the citrate method be preferred, however, the substance is dissolved in 30 c.c. concentrated sulphuric acid, instead of the above mixture. The remaining operation is conducted as in p (P. 73)- A nitrogen determination, according to Kjeldahl, as well as the detection of less valuable phosphates, is usually undertaken in bone- dust. The latter is detected by a high percentage of matter insolu- ble in hydrochloric acid (sand) and presence of ferric oxide and alumina. Thomas slag is the most important product of the phosphate slags in sub-group (<). To determine the phosphoric acid in this, 10 grs. powdered material are moistened with water, and stirred with 5 c.c. of a mixture of equal parts sulphuric acid and water. As soon as the mass begins to harden, 50 c.c. concentrated sulphuric acid are added, and the whole is heated for ^ -hour on a sand-bath until white vapors arise. Meanwhile the mass is continually stirred. After cooling, it is carefully diluted with water, washed into a YZ -liter flask, diluted to the mark, well mixed, and allowed to stand several hours, in order to allow gypsum to separate. It is then filtered through a dry ribbed filter, and the phosphoric acid is deter- mined in 50 c.c. filtrate by the citrate method. B. Phosphates Containing Water-Soluble Phosphoric Acid. To these belong principally the superphosphates obtained by dis- solving crude phosphates in sulphuric acid, and which contain the monocalcium phosphate CaH 4 (PO 4 ) 2 , which is soluble in water. FERTILIZERS. 77 Since the decomposition, however, is never perfect, there are present, beside these, di- and tri calcium phosphate, the quantity of which increases on standing for a long time, due to the action of aluminium and iron compounds present. The latter process is termed phosphoric acid reversion. The phosphoric acid in commercial phosphates is, therefore, present in three forms : (a) Monocalcium phosphate, CaH 4 (PO 4 \. This is soluble in water, and, together with free phosphoric acid, is estimated as water-soluble phosphoric acid. (3) Dicalcium phosphate, CaHPO 4 . This is insoluble in water, but is, on the contrary, soluble in ammonium citrate. At times it is determined, together with the phosphoric acid present in form of iron or aluminium phosphate, as ''citrate-soluble" or "reverted" phosphoric acid. (c) Tricalcium phosphate, Ca s (PO 4 ) a , is insoluble in water and ammonium citrate. The phosphoric acid corresponding to this is designated as insoluble phosphoric acid. () Estimation of water-soluble phosphoric acid. Twenty grams of superphosphate are placed in a liter flask,* and thoroughly agitated for y z hour with 800 c.c. water. The liquid is then diluted to the mark, well mixed, filtered through a dry ribbed filter, and the phosphate is determined by the citrate method in 50 c.c. filtrate. (/?) Estimation of total phosphoric acid. Five grams of superphosphate are suspended in 20 c.c. water, and then boiled with 100 c.c. concentrated nitric acid for ^ hour. The mixture is washed into a ^ -liter flask, diluted to the mark, filtered through a dry ribbed filter, and the phosphoric acid is de- termined in 50 c.c. filtrate by the molybdate method. The estima- tion of citrate-soluble phosphoric acid, concerning the value of which views differ, will not be further described. 2. Potassium Fertilizers. The main source of these is the discarded Stassfurter salts, which consist chiefly of potassium and magnesium salts. The most im- portant are Sylvite, 5KC1 + NaCl ; Carnallite, KC1 + MgCl 2 -f * Agitators worked by hand or water-power are very convenient. 78 CHEMICAL-TECHNICAL ANALYSIS. 6H,O ; Kainite, KC1 -f MgSO 4 -f 3H 2 O ; and Schonite, K 2 SO 4 + MgSO 4 + 6H 2 O. In these the per cent, of potassium oxide is usually determined by one of the methods mentioned (p. 73). 3. Nitrogenous Fertilizers. According to the division previously given, there belong in this group ammonium sulphate, potassium and sodium nitrates or a mixture of both (with an average percentage of nitrogen equalling 14.5-16 per cent.), dried-blood powder (12-15 per cent. N, about i per cent. P 2 O 5 ), horn meal (7-14 per cent. N, 5-6 per cent. P 2 O 5 ), pow- dered hide (6-10 percent. N). 4. Mixed Fertilizers. These are artificial mixtures of phosphorus, potassium and nitro- genous fertilizers, such as potassium -superphosphate, ammonium- superphosphate, saltpeter -superphosphate or natural products. To the latter belong Peru guano, dried-meat powder, fish-guano and dung. Peru guano, formed from bird excrement and carcasses of marine animals, but less weathered than guano phosphate, contains, on the average, 8-n per cent, nitrogen and 10-20 per cent, phosphoric acid. Dried meat powder, made out of meat and bones of dead ani- mals, contains 6-7 per cent, nitrogen and 10-15 per cent, phos- phoric acid. Fish guano, made out of fish refuse, contains 5-12 per cent. N, 13-16 per cent. P 2 O 5 . Dung, the mixture of solid and fluid excrement of cattle, horses, sheep, swine, together with litter, contains all three plant-nour- ishers in varying amounts. They may be confined within the fol- lowing limits: Potassia, .40-. 6 7 per cent.; phosphoric acid, .16-. 28 per cent., and nitrogen, .34-. 83 percent. VI. Sugar Industry. THE investigation of sugar and saccharine products, such as beets, thin juice, molasses, etc., extends as a rule to the estimation of cane sugar, invert sugar, water, alkalinity, ash, and sometimes color. Concerning the methods employed for this purpose the follow- ing may be said : (a) Cane sugar. This may be determined from the specific gravity or by polarization. (a) Specific gravity. Only in pure sugar solutions can sugar be estimated by means of specific gravity. Should other substances be in solution, they effect the specific gravity in different ways. In such solutions only an apparent value (for dry substance) ex- pressed in per cent, of sugar, can be obtained. The determination of specific gravity is conducted either with one of the usual forms of applicable apparatus, such as densimeter, pyknometer, hydrostatic balance, in which cases the percentage of sugar corresponding to the specific gravity must be referred to in a corresponding table, or by means of an areometer specially con- structed for the purpose, the saccharometer of Balling or Brix. On account of its graduation direct sugar percentage readings can be made. In this case it is advantageous to use such saccharometers on which the scale is extended over a set of several consecutive spindles, and on which tenths per cent, can be easily read. When the saccharometers are used to read volume percentage, an error, provided for on the instrument, due to change in volume by temperature, is taken into account. Pyknometers and hydrostatic balance are then used when only small quantities of substance are obtainable. (/?) Polarization. It is taken for granted that the principle on which these instruments rest, as well as the arrangement of the same, is known. Recently the apparatus of Soleil-Ventzke-Scheib- 80 CHEMICAL-TECHNICAL ANALYSIS. ler and the half-shadow apparatus of Schmidt and Haensch, have come into use. The former is adjusted for a transition color, a pale bluish violet, the latter for an even, faint shadow on both halves. The normal weight for both forms equals 26.048 grams; that is, a solution of 26.048 grs. pure cane sugar in 100 c.c. in a tube 200 mm. in length causes a rotation of 100, or i corres- ponds with .26048 gr. sugar in 100 c.c. With the use of this normal weight and normal tube (200 mm.) the per cent, of sugar can consequently be read off directly. When a 100 mm. or 400 mm. tube is used, the degrees are to be doubled or halved. Polarization is always preceded by clarification and decoloriza- tion with a solution of lead acetate (basic lead acetate). Cane sugar is dextro -rotary ( + ); invert sugar laevo-rotary ( ). () Invert sugar possesses the property of reducing Fehling's solution (see Reagents, p. 90) with separation of suboxide of copper. On the basis of this precipitated suboxide, which is reduced to metallic copper, the amount is determined by a method described later. The results obtained by polarization are influenced by the laevo-rotary power of invert sugar. Therefore, in the presence of the latter a different procedure, that of Clerget,* is followed in the estimation of cane sugar. The description of this is given further on. Syrup, molasses, etc. , frequently contain invert sugar. (*:) Water. The use of small, flat-bottomed porcelain or enam- eled sheet-iron capsules is advisible for fluid or semi-fluid products. Drying is done on a water-bath or in an air bath at 80-90 to be- gin with. Further drying should take place at 105 under the in- fluence of a current of dry air, in order to expel the last traces of water. Stammer recommends the use of a special apparatus for this purpose. In the absence of the latter an ordinary air-bath is made to answer. It is also recommended to mix the substance with a glass rod (4-5 grs. molasses, 8-10 grs. syrup and dense juices) with 20 grs. ignited quartz sand, free from dust, in a small porcelain capsule. This is then weighed and placed in an air-bath at 100 for % hour. It is then thoroughly stirred with a rod until a homogeneous mass is obtained and dried in an air-bath to constant weight. * The same method is also made use of in the presence of raffinose. SUGAR INDUSTRY. 81 (V) Alkalinity. This is influenced by the presence of free alkali, lime and free ammonia in the saccharine substance. It is estimated by titration with normal or one-tenth normal acid, usually nitric acid, and is calculated into per cent. lime. The indicator used is usually neutral, bluish-violet litmus tinc- ture, which is added to the liquid. But in using deeply-colored substances, such as molasses, the indicator is not added, but instead, after each addition of acid the liquid is tested with a strip of bluish- violet, sensitive litmus paper. (e) Ash. The residue left on ignition of a sugar, including the mechanically admixed impurities in the same, is called the "ash." The residue of a sugar free or freed from these impurities is called the "salts." The latter consists mainly of alkali sulphates or chlorides and carbonates arising from alkali salts of organic acids. Potassium predominates in these alkalies. Sometimes calcium car- bonate, arising from soluble organic calcium salts, is found. These salts hinder crystallization of a part of the sugar and conse- quently cause a loss in the yield ; and furthermore, even though this no longer holds good under the present conditions, one part salts is calculated to yield a decrease of five parts sugar. The complete ignition of a sugar is hard to accomplish by combustion, since the easily fusible alkali salts withhold small particles of carbon from combustion. Too strong a heat should likewise be avoided on account of possible volatilization of alkali chlorides. The inciner- ation is therefore conducted as follows : The weighed sugar is charred in a spacious platinum dish until gas is no longer evolved. The coke is then moistened with water and crushed to a paste with a pestle. After the addition of a little hot water, heating and filtering, the residue on a small filter is repeatedly washed with hot water, and the filter and residue together are incinerated in the platinum dish. The filtrate added to this is evaporated to dryness on a water-bath, moistened with ammonium carbonate, dried at 100 and moder- ately ignited. The clean white residue is weighed. In this manner the "ash" (carbonate ash) is ascertained. If the estimation of " salts " also be desired, a weighed quantity of sugar is dissolved in water (about 25 grs. sugar in 250 c.c). The turbid solution is filtered, a portion of the filtrate is evaporated in a platinum dish, charred and heated as before. 6 82 CHEMICAL-TECHNICAL ANALYSIS. Much simpler and quicker is the method of Scheibler. 3-5 grs. sugar are moistened with sulphuric acid in a platinum dish. After a few minutes the sugar blackens and decomposes. It is then heated over a very large flame, whereby thorough charring takes place with much swelling, hissing and gas evolution. To com- pletely burn off the remaining coke the dish is placed in a muffle. The action of the sulphuric acid converts the salts into sulphates, the weight of which is naturally higher than that of the salts orig- inally present. The increase of weight equals almost exactly 10 per cent. , by which the amount found must be decreased. The re- mainder is designated as sulphate ash. (/) Color. The Stammer Colorimeter is used for this purpose ; however, the determination is rarely carried out. The crude and refined products of the sugar industry which are subject to investi- gation are beets, beet juice, weak juice, dense juice, filling material, green syrup, molasses, osmosis fluid and cane sugar. 1. Beets. The former assumption, that the sugar content in the juice of the beet bears a fairly constant relation to that of the beets (about i : .95), has been recently proven erroneous for different reasons, and therefore methods have been found for the direct determina- tion of sugar in the beet. The " extraction " and " digestion" methods are recommended for this purpose. (, whose lower end is provided with an exit tube which extends to the floor of the two-neck flask E. Pinchcock p is placed on a piece of rubber tubing between D and E. By forc- ing air into flask E, preferably with an elastic ball, the water pres- ent in E can be forced into C and D. On the other hand, by opening the pinchcock/ it may be let out of Cand D into E. Operation, The normal weight (1.7 grs.) required by the appa- ratus of the finely -powdered bone black is weighed out and placed in the thoroughly dried flask A. The gutta-percha vessel S is then filled with hydrochloric acid of 1.12 density (2 vols. cone, hydro- chloric acid, i vol. water) and carefully placed, with forceps, in A, so that it rests on the glass side in a slanting position. BONE BLACK. 93 After raising the water in C to the zero mark by forcing air into the flask E and simultaneously opening the clip /, A is closed with the well-greased stopper. FIG. 9. Scheibler's Apparatus. Any air pressure and consequent change in the level of the liquid in C and D are removed by opening the clip q once. The vessel A is taken between thumb and middle finger of the right hand, 94 CHEMICAL-TECHNICAL ANALYSIS. while the forefinger presses the stopper. The flask is then inclined sufficiently to allow the acid to escape from the gutta-percha holder. Decomposition, which ensues, is sustained and augmented by care- ful continued shaking of the flask A. Simultaneously the clip/ is opened with the left hand, and as much water is allowed to flow into E as is necessary to bring both levels in tubes C and D to about the same height ; that in D somewhat higher than in C. When water in C ceases to descend on prolonged agitation of A, the decomposition is complete. 5-10 minutes are allowed to elapse in order to allow pressure and temperature to equalize, after which the levels in C and D are brought to the same height by carefully opening the clip q. The level in C is read off, as well as the temperature of a ther- mometer placed in the apparatus. The direct percentage of car- bonate of lime is found, by means of these two numbers, on the ac- companying tables calculated by Scheibler. () If the free acids, as found in (a), as well as the fatty acids found present as soap, as in (/?), be subtracted from the total fatty acids, there remains that which is present as neutral fat and which can be reckoned into neutral fat with sufficient accuracy by multi- 100 plying by ---. 2. Soaps. Soaps are mainly alkali salts of fatty acids, in fact, sodium and potassium salts. 134 CHEMICAL-TECHNICAL ANALYSIS. Soda soaps are hard and come into the market under the name of compact soaps, cut or filled soaps. Potash soaps are soft and are known as soft soaps. Lately, however, hard potash soaps (Schicht's patent) have appeared. For many industrial purposes, substances such as rosin (rosin soaps), borax, water-glass, sodium alumin- ate, soda (to increase alkalinity), are added to soaps. Further- more, adulterants, such as chalk, heavy spar, starch, clay, etc., etc., are frequently encountered. Analysis of Pure Soaps. These may contain, beside the alkali salts of fatty acids, free alkali, alkaline carbonates, free fatty acids and neutral fats.* In ad- dition, a considerable quantity of water is always present. (a) Water. About 5 grs. of soap, removed from the center, in form of shavings, are dried at 50 for 1-2 hours. The temper- ature is then gradually raised to 100-110 and the soap is dried to constant weight. Soft soaps are placed in a 100 c.c. beaker containing a small gl^ss rod, and the bottom of which is covered 1.3 cm. deep with ignited quartz sand. Beaker + sand + rod are weighed, f About 5 grs. soap are added and the whole is reweighed. 25 c.c. alcohol are added, and the mass is heated on a water-bath and stirred. The beaker is then placed in a drying oven and dried to constant weight at 110. () Total fat and total alkali. 10-20 grs. fine cut soap are dissolved in about 100 c.c. hot water in a beaker. An excess of standardized sulphuric acid is added (50 80 c.c. normal acid) and the whole is heated in a water-bath con- taining boiling water until a clear layer of fatty acids is formed. It is now allowed to cool. In case the fatty acids refuse to solidify a weighed quantity of wax, paraffin or stearic acid, approximately equal in weight to the soap taken, is added, and the mass is re- heated and again allowed to cool. The fatty acid cake, now solid, is removed from the beaker with a glass rod, and is washed off with water. The washings are caught in the beaker. It is externally * Manifestly, a simultaneous presence of free alkali and free fatty acid is im- possible. f All weighings should be made as nearly as possible at the same time, because the quantity of water in soaps readily changes. SOAPS. 135 dried with filter paper and kept in a cool place. The solution re- maining in the beaker is filtered, the filter is washed well, and the filtrate is titrated back, using methyl orange as an indicator. The total alkali, representing that combined with fatty acids, free alkali and alkaline carbonates, is calculated from the acid required for decomposition. The total fat is determined by dissolving the particles adhering to the beaker in ether, filtering the latter through the previously em- ployed filter into a weighed glass vessel containing a glass rod. After the ether has been volatilized, the fatty acid cake is also placed in the vessel and is heated with a small flame, with constant stirring, until the crackling sound, caused by escaping steam, has ceased, and the vapors of fatty acids have begun to make their appearance. Upon cooling, the glass dish is weighed and the added paraffin, etc. , is deducted. The total fat is thus obtained. Any neutral fats, as well as fatty acids, will be present. (c) Alkaline carbonates and free alkali. Qualitative test. A portion of soap is warmed and dissolved in alcohol, filtered, and any residue is w r ashed with alcohol. Free alkali is detected by the red color which will form on addition of phenol-phthalein to the filtrate. On the other hand, the residue on the filter is dissolved in water and tested for alkaline carbon- ates by warming with phenol-phthalein. Quantitative determination. About 10 grs. soap are treated as above, care being taken, however, in washing with the alcohol, which is best done by using a hot water funnel during filtration. The alcoholic filtrate, as well as the aqueous solution of the well- washed residue, is titrated with ^ normal acid, using phenol-phthal- ein as indicator in the first instance and methyl orange in the second. After the free alkali and alkali carbonate have been deducted from the total alkali found, as in (^) (everything calculated as alkali ox- ide), there remains the alkali which is bound to the fatty acids. This can also be directly determined by dissolving a weighed quan- tity of soap in water, decomposing it with an excess of hydro- chloric acid, thus using the separated fat in a moistened filter, washing, dissolving the fatty acid in alcohol by placing filter and contents in a beaker with alcohol, and finally titrating with alkali, using phenol-phthalein as indicator. 136 CHEMICAL-TECHNICAL ANALYSIS. As a rule the alkali in hard soaps is calculated as sodium oxide and that of soft soaps as potassium oxide. On the assumption that both potash and soda are present in a soap, 5 grs. of the latter are burned in a platinum dish until only a charred mass remains. This is covered with water, filtered and washed. In the aqueous filtrate a check determination of total alkali may be conducted by titration with hydrochloric acid, after which a determination of potassium is made in the usual way with platinic chloride. (See Fertilizers, P- 73-) (*/) Free fatty acids. When the alcoholic soap solution does not change color on addition of phenol-phthalein (a proof of the absence of free alkali), free acid, which may be present, can be de- termined by titration with caustic soda. (>) Neutral fat. A considerable quantity of fine shaved soap is weighed off, dried and extracted in a Soxhlet extractor with ether. In order to remove traces of soap which may perchance have gone into solution, the ethereal extract is shaken out 23 times with water in a separatory funnel. Then, if necessary, it is filtered, the ether is volatilized, and the residue is weighed after the usual treat- ment in a current of air. It also contains any free fatty acids which may have been present. The latter may be deducted after determination (//) has been made, or they may be directly titrated. Summary of analysis. The percentage of fatty acids must not be placed as such in the analysis, but must first be reckoned into anhydrides. No great error is experienced in simply deducting 3.25 per cent, from every 100 parts fatty acid.* In order to ascertain the nature of the fat from which a soap has been made the separated fatty acids are tested for melting point, freezing point, specific gravity, iodine number, saponification num- ber, etc. Determination of Foreign Admixtures in Soaps. (a} Examination of residue insoluble in alcohol. To determine the total amount of the same, a weighed quan- tity of soap is dried and warmed on a water-bath with 8-10 times the quantity of alcohol. It is then filtered through a weighed * Instead of this a quantity of water, equivalent to the alkali which is bound to fatty acids, may be deducted. SOAPS. 137 filter, washed with alcohol, dried and weighed. The residue is ex- tracted with cold water and the solution is tested for chlorides, sul- phates, carbonates, silicates and borates of the alkalies. If neces- sary, quantitative determinations of these constituents may be made in the usual manner. The residue from the aqueous extraction is ignited to destroy or- ganic matter, is weighed, and the ash is qualitatively and quantita- tively examined. It is advisedly examined for chalk, clay, in- fusorial earth, etc. Any organic matter, such as dextrine, contained perhaps in the residue from the alcohol extraction, is dissolved in cold water and can be reprecipitated from its aqueous solution by alcohol. Starch can be detected under the microscope as well as by the blue colora- tion with iodine. () Glycerin, quantitative estimation, i-io grs. soap are dis- solved in water or in methyl alcohol when organic substances, in- soluble in methyl alcohol, are present. The solution is filtered, the alcohol is volatilized, the fatty acids are separated with dilute hydrochloric acid, and the glycerin in the acid filtrate is estimated according to the method of Benedikt and Zsigmondy. (See Gly- cerin, p. 141.) (V) Rosin. In the qualitative test for rosin in soaps, or in the fatty acids separated from the latter, the reaction of Storch and Morowski (p. 129) is used. The method used in the quantitative estimation of rosin in the mixture of the latter with fatty acids, which is separated by mineral acids, has, until recently, been that of Gladding. It depends on the fact that the silver salts of fatty acids are insoluble in ether, whereas silver resinate is soluble in the latter. Lately preference has been given the method of Twitchell. It depends on the property of fatty acids forming esters when hydrochloric acid gas is conducted into their solution, whereas rosin does not react under the same conditions. 2-3 grams rosin-fatty acid mixture are dissolved in 10 times the volume of absolute alcohol in a flask. A brisk current of hydro- chloric acid gas is led in. Meanwhile, the temperature is kept under 20 by good cooling. At first the gas is rapidly absorbed. After a period of about % of an hour the esters formed separate on the surface and further absorption ceases. The flask is withdrawn from 138 CHEMICAL-TECHNICAL ANALYSIS. the cooling mixture, is allowed to stand ^ hour, is diluted with 5 times the volume of water, and boiled until the acid solution clari- fies. The resinic acids can be determined either gravimetrically or volumetrically. (a) Gravimetric method. The contents of the flask are placed in a separatory funnel and shaken up with petroleum ether. The acid layer is drawn off, the petroleum ether layer is washed and shaken up with a solution of 5 grs. caustic potash, dissolved in 5 c.c. alcohol and 50 c.c. water. The resin is saponified and the soap formed remains dissolved in the aqueous layer which separates com- pletely from the petroleum ether layer. The soap solution is drawn off and the petroleum ether is washed first with dilute potassium hydrate solution and then with water. The collected aqueous extractions are decomposed with dilute hydrochloric acid. The precipitated resinic acids are dissolved in ether, the ether is distilled off, and the residue is dried at 100 and weighed. (/5) Volumetric method. The contents of the flask are shaken up with about 75 c.c. ether in a separatory funnel, the acid layer is drawn off, and the etherial layer is washed with water until acid re- action with litmus paper has ceased. 50 c.c. alcohol are added and the solution is titrated with ^ normal alkali, using phenol - phthalein as indicator. The resinic acids are saponified, whereas the fatty esters remain unattacked. The resinic acid equivalent is taken as 346 in the calculation. 3. Turkey-Bed Oil. Turkey-red oil is a product of reaction between concentrated sulphuric acid and chilled castor oil,* to which ammonia has been added in quantity sufficient to impart the property of forming a complete emulsion when a sample is shaken with water. Turkey- red oil contains a water-soluble constituent consisting of " ricinol- sulphuric acid," and which can be salted out of its aqueous solu- tion with salt, very dilute sulphuric acid and hydrochloric acid. The " ricinoleic sulphonic " acid is not decomposed by boiling water or alkali solutions, whereas, when boiled with dilute acids, it * Sometimes other oils. TURKEY-RED OIL. 139 is converted into ricinoleic acid and sulphuric acid. That portion of turkey-red oil which is insoluble in water consists mainly of ricinoleic acid, and contains, in addition, some neutral fat, and per- haps polyricinoleic acids, together with anhydrides of ricinoleic acid and the above mentioned acids. Good castor oil should yield a fairly permanent emulsion with water, should dissolve to a clear solution in ammonia, and should not become turbid thereafter on addition of much water. Chemical Examination. According to Benedikt, this applies principally to the determin- ation of total fat. In more exact analyses, the neutral fat, sulphonic acid, ammonia, soda and sulphuric acid are determined by the methods employed by the above author. (a) Total fat. By this is understood the sum of the water-insol- uble constituents of the acidified oil (fatty acids, oxy fatty acids and neutral fat) and the oxy fatty acids obtained by the decomposi- tion of the soluble fatty sulphonic acids. About 4 grs. sample are stirred with 20 c.c. water, which are gradually added, in a thin hemispherical glass dish of about 125 c.c. capacity, which has pre- viously been weighed, together with a small glass rod. When the liquid is turbid, a drop of phenol -phthalein is added, followed by ammonia to faint alkaline reaction. It is now mixed with 15 c.c. of sulphuric acid, is diluted with an equal volume of water and 68 grs. stearic acid are added, whereupon it is heated to faint ebullition. When the fatty acids have separated in a clear layer, it is allowed to cool. The solid cake is raised with a glass rod, rinsed with water, and placed on filter paper. The fat particles attached to the walls are collected by heating the liquid in the dish until the particles have united to i or 2 drops. The dish is re- moved from the water-bath and inclined, so that the drops reach the glass walls, where they immediately solidify and cling. The liquid is now poured off, the fat cake is placed in the rinsed dish and heated with a small flame in a manner similar to that employed in the total fat estimation in soap (p. 134). The cooled-off cake residue is weighed and the weight of stearic acid added is deducted. (^) Neutral fat. About 30 grs. sample are dissolved in 50 c.c. water, 20 c.c. ammonia and 30 c.c. glycerin are added, and the mass is shaken out twice with quantities of 100 c.c. ether. Small 140 CHEMICAL-TECHNICAL ANALYSIS. traces of soap, which are taken up by the ether, are removed by shaking with water. The ether is then distilled off and the residue is dried first in a water-bath, then in an air-bath, and is finally weighed. (t~) Soluble fatty acids. (Fatty sulphonic acids.) 5-10 grs. sample are dissolved in 25 c.c. water in a pressure flask. 25 c.c. fuming hydrochloric acid are added, and the flask is heated in an oil-bath at 130150 for an hour. Its contents are then diluted with water, poured into a beaker and filtered from the fat layer. To insure easy manipulation an indefinite quantity of stearic acid may be added, the solution heated, and again allowed to cool. A sulphuric acid determination is made in the filtrate by means of barium chloride. The sulphuric acid found in () Cotton. The dried sample, freed from fat, is placed in a boiling-hot 10 per cent, solution of caustic potash; the boiling is continued for 15 minutes, when the whole is poured into a beaker filled with distilled water. The remaining cotton is re- moved, wrung out, well washed, and finally dried at 100 to con- stant weight. (, hour in a current of carbonic acid or in a flask provided with a Bunsen valve, and the excess of ferrous salt is titrated back with permanganate. From the ferrous ammonium sulphate oxidized, the active oxygen can be calculated, and from this, by the above equation, the persulphate is found. Ammonium persulphate is the common form. 3. Sizing Materials. These serve on the one hand for the preparation of dressings, on the other hand for the laying on of coloring matter in calico print- ing. The different kinds of starch and flour, dextrin, gums, traga- canth, albumin, casein, and many others, are used. The investiga- tion of these products is often difficult and uncertain. Starch, dextrin and a few reactions for gums only will be described. (a) Starch. The chemical examination of starch has already been described in Chapter VI. Microscopic means are employed to distinguish between the different varieties. (b) Dextrin. Dextrin is obtained by the action of dilute acids on starch at high temperature, also by heating per se ; and it contains, in addi- tion, water, ash, maltose, starch, and other organic substances. The determinations of these constituents, as well as the acidity, are conducted according to Hanofsky as follows : * Contribution from the K. K. tech. Gewerbe- Museum, Jhrg. 1895, p. 310. f See Appendix. SIZING MATERIALS. 155 25 grs. dextrin are placed in a flask of 500 c.c. capacity and are well shaken with cold water, filled to the mark, allowed to settle, and are filtered through a ribbed filter. In the filtrate, maltose, dextrin and acidity are determined. () Maltose. This is determined by the cuprous oxide, which it has the power to precipitate from Fehling's solution. Since the power of reduction changes with the concentration, the latter must be made the same always. A test is made, therefore (similar to that of invert sugar, p. 85,), to determine how much of the solution is required to reduce 10 c.c. Fehling's solution. In the actual determination 12 c.c. less are taken, and are diluted with sufficient water to bring the total volume to 5758 c.c. The liquid is run into a porcelain dish in which 10 c.c. Fehling's solu- tion have previously been placed. It is heated to boiling, and is kept in that state exactly 4 minutes. The precipitated cuprous oxide is thrown on the asbestos filter, and is treated further in the usual manner. Using the concentration referred to, 113 copper 100 anhydrous maltose, the percentage of maltose so found = M. (/?) Dextrin. 50 c.c. solution are diluted to 200 c.c., and are heated to incipient boiling on a reflux with 15 c.c. hydrochloric acid (sp. gr. 1.125) for two hours. Dextrin and maltose are thereby changed to dextrose, the solution is filtered into a 500 c.c. flask, is nearly neutralized with caustic soda, and diluted to the mark. The dextrose in 25 c.c. is determined with Fehling's solu- tion. If the dextrose in per cent. = D, the dextrin will be .9 (D-i.05 M), since 20 parts dextrose correspond to 19 parts maltose. (7) Acidity. 50 c.c. solution are titrated with one-tenth nor- mal alkali, using phenol-phthalein as indicator. The quantity of one-tenth normal alkali calculated in 100 grs. substance is desig- nated the acidity. (fl) Starch. 2.5-3 g rs - dextrin are mixed with 200 c.c. water and are treated with 15 c.c. hydrochloric acid (sp. gr. 1.125), as in (/3). The solution is nearly neutralized, diluted to 500 c.c., and likewise treated for the dextrose in 25 c.c. Maltose, dextrin and starch are converted into dextrose. If the percentage of dex- trose = D, then the percentage of starch will be 9 (D-D)- 156 'CHEMICAL-TECHNICAL ANALYSIS. (77) Water and ash are determined in the usual manner. If the water = W per cent, and the ash A per cent., the " other organic constituents ' ' present will be TOO (Mdtose+Dextrin+Starch-fW + A). (c) Gums. Of the many kinds of gums, gum arabic, gum Senegal and gum tragacanth are chiefly used. These three varieties can be distinguished in pure condition by their appearance. Gum arabic is more easily, gum Senegal less readily soluble in water, whereas gum tragacanth is scarcely soluble at all, but swells up to a slimy mass, which distributes itself through- out a sufficient quantity of water. Gums are frequently adulterated with dextrin. Lieberman has proposed the following tests for the detection of gum Senegal and dextrin in gum arabic. The gum is dissolved in hot water, treated with an excess of caustic potash and some copper sulphate, slightly warmed and filtered. The milky filtrate is boiled. A perceptible precipitate of cuprous oxide indicates the presence of dextrin. The precipitate formed by the action of caustic potash in the copper sulphate, and which contains the gum acids, is washed with water, dissolved in dilute hydrochloric acid, and precipitated with alcohol. It is allowed to settle for %-i day, when the supernatant liquid is poured off. The precipitated gum in the vessel is washed with alcohol, dissolved in hot water, and to it are added an excess of caustic potash and some copper sulphate. A balled-together precipitate, quickly ascending to the surface, indicates gum arabic, whereas a more divided, fine flocculent precipitate discloses gum Senegal or an admixture of the same. In the first instance, in ad- dition, an aqueous solution, boiled with caustic potash, should turn amber yellow. If the amber color arise in the second case under the same conditions a mixture of Senegal gum and gum arabic is present, whereas a faint yellow or no color indicates Senegal gum alone. 4. Finishing Materials. The number of substances used for dressings is very large and is on the increase. In consequence only the most important will be FINISHING MATERIALS. 157 selected, and the part which they play in finishing will be men- tioned. () Sizing material. These were treated of in the previous chapter. (/3) Substances which make the goods soft, pliable and hygro- scopic : Glycerin, grape sugar, fats, tallow, stearin, paraffin, cocoa- nut oil, wax, ozokerite, calcium chloride, zinc chloride, sodium and ammonium salts. (y) Loading materials. Gypsum, chalk, barium sulphate (per- manent white), sulphate of magnesium, sodium and zinc, talc, china clay, magnesium chloride, barium chloride, barium carbon- ate, lead sulphate. (?) Antiseptics. Phenol, creosote, salicylic acid, tannin, cam- phor, oxalic acid, zinc salts, boracic acid, borax, alums, aluminium sulphate, formic acid, etc. (e) Water-proof materials. Fats, varnishes, resins, paraffin, tannin, basic aluminium acetate and aluminium soaps. Besides these there may be contained materials which render the fabric fire- proof, such as boric acid, phosphates, silicates, etc., and such as impart metallic lustre to the goods : metallic sulphides, metal- dust, etc. With this array of substances no general method of investigation of finishing materials can be given. In the following, the analysis of two simple, frequently occurring products are described : (0) Finishing material containing starch paste and chloride of magnesium. (a) Starch. 1020 grs. material are heated for three hours to incipient boiling in a 500 c.c. flask with 200 c.c. water and 20 c.c. hydrochloric acid (sp. gr. 1.125). To avoid evaporation of the water a reflux is used. Upon cooling, the contents are poured into a 500 c.c. measuring-flask, and an excess of caustic soda is added to precipitate all the magnesia capable of precipitation by alkali. The solution is filled to the mark and is rapidly filtered through a dry filter. In 25 c.c. filtrate the dextrose formed by inversion is 158 CHEMICAL-TECHNICAL ANALYSIS. estimated by means of Fehling's solution, as is described under starch (p. 99). (/?) Magnesia and chlorine. The determination of these constit- uents in the ash is not possible on account of the easy decomposi- tion of magnesium chloride. The presence of starch likewise in- terferes with the precipitation. The latter is therefore inverted with dilute nitric acid as in (a) and in one portion the chlorine, and in another portion the magnesa are determined by the usual methods. O) Water and ash. An exact determination of these constitu- ents cannot be accomplished on account of the easy decomposition of magnesium chloride and the tenacity with which water adheres. Nevertheless, approximate results can be obtained by drying a weighed portion at about 100 to almost constant weight and in- cinerating the residue. The water of crystallization of magnesium chloride is for the greater part still present after drying. () Finishing material, containing starch paste, fat and sulphate of zinc. () Starch, zinc oxide and sulphuric acid. 1020 grs. material are inverted as before with hydrochloric acid, separated from the fat by nitration through a moistened filter, and diluted to 500 c.c., after approximate neutralization with caustic soda. The starch is determined as before in 25 c.c. of this solution. Other measured portions are used for the determinations of zinc oxide and sulphuric acid by the usual methods. () Fat. Since the fat separated in (a) does not usually answer for further examination, a larger portion of the finishing material is preferably taken. It is inverted with hydrochloric acid, and the separated fat is extracted repeatedly by shaking with ether. The collected ethereal extractions are freed from ether by distillation and the last portions of the solvent are removed by a current of air, after which the residue is weighed. It contains the total fat. In the latter, the usual constants, such as saponification number, iodine number, etc. , can be determined in addition to unsaponifiable por- tions of the fat. The nature of the latter is thus ascertained. 5. I>ye-Stuffs. These are divided into natural and artificial dye stuffs, according to their origin. According to their use, they may be divided into basic, acid, mordant and direct cotton dye-stuffs. DYE-STUFFS. 159 To these are added a number of dye-stuffs formed directly on the fiber, such as "vat" dyes, diazotized dyes and aniline black. Each of these groups represents a special dyeing process, which will be briefly discussed here. Basic dyes, applied to cotton. The material to be dyed must first be mordanted. Mordanting is usually conducted in the following manner : The cotton is first placed in a bath of tannin at 60 for about 12 hours, after which it is thoroughly wrung out and placed in a bath of tartar emetic, 10-20 grs. per liter, or the correspond- ing amount of antimony salt [SbFl 3 . (NH 4 ). 2 SO 4 ]. Thereupon it is washed well and dyed in the bath containing the dye at a tempera- ture of 5060 until the bath is exhausted. Applied to wool. Takes place in a bath which is either neutral or slightly acidified with acetic acid. The bath is gradually heated to boiling. Applied to silk. Takes place in neutral, slightly acid (acetic) or separate soap bath, with gradually heating to about 70. Among the basic dyes belong fuchsin, auramin, malachite green, victoria blue, methyl violet, etc. Acid dyes find use chiefly in dyeing wool. Dyeing is conducted in a bath containing 24 per cent, sulphuric acid, or 2-5 per cent, sulphuric acid and 10-15 P er cent. Glauber salt, or 5-10 per cent, sodium bisulphate. A gradual rise in temperature and eventually continuous boiling are required. The group of basic dyes is very extended. There may be men- tioned, for instance : Ponceau, naphthol black, alkali blue, patent blue, acid fuchsin, acid violet. Mordant dye-stuffs. The dyeing of cotton as well as of wool re- quires previous mordanting. Aluminium, chromium and iron mor- dants are chiefly used. Mordanting wool is accomplished by boil- ing 1-2 hours in the solution of the mordant (3-4 per cent, potas- sium bichromate, 6 10 per cent, aluminium sulphate, 4-6 per cent, ferrous sulphate) with the addition of sulphuric acid (i per cent.), acid potassium tartrate (3-8 per cent.), or oxalic acid (1-2 per cent).* Cotton mordanting must be accomplished by an artificial fixation * Recently lactic acid has also found use. 160 CHEMICAL-TECHNICAL ANALYSIS. with chemical precipitants. The cotton is first placed in a fairly strong solution of the mordant (aluminium sulphate, aluminium acetate, chrome alum, chromium fluoride, ferric nitrate). It is then pressed out and passed through a bath containing soda, chalk, am- monium carbonate, etc. Finally it is well washed. Iron and tin baths are used mostly for silk. As a rule, a simulta- neous ''weighting" occurs, and sometimes also the silk becomes colored, as, for instance, with acetate of iron and tannin. In such cases the operation must be repeated several times. Dyeing mordanted goods is conducted in neutral baths. On ac- count of the insolubility of many mordant dyes, the bath must be kept in motion during the process of dyeing. Also, in order to insure uniform dyeing, the temperature must increase very slowly. To the mordant dyes belong the large group of alizarin dyes and most of the natural dye-stuffs, blue wood, yellow wood, red wood, cochineal, etc. Direct cotton dye-stuffs. (Benzidine colors also dye vegetable fibers directly.) Dyeing is usually conducted in weak alkaline baths (soda, soap, 2-5 percent.; borax, sodium aluminate, 5-10 per cent. , and sometimes in neutral, salt, Glauber salt, or weakly acid baths). The operation usually takes place at a boiling tempera- ture. This group is also very large. To it belong, among others, benzopurpurin, chrysamin, benzoazurin, diamine blue, diamine black. "Vat" dyeing is almost exclusively conducted with indigo.* The insoluble indigo blue or indigotin contained therein must first be transformed in the vat into soluble indigo white. Reducing agents mostly used are ferrous sulphate (iron vat), zinc dust (zinc vat), hyposulphurous acid (hydrosulphite vat). The fabric im- pregnated with indigo white is rapidly colored blue by oxidation in the air. Diazotized dyes. Benzidine dye-stuffs can be diazotized in the fiber and developed in a bath containing dissolved phenols, naph- thols or amines. A new color is formed which is similar to the original, but more perfect, and which is distinguished for its fast- ness. The developers mostly used are phenol, resorcin, /S-naphthol, * Recently the artificially prepared indophenol has come into use. DYE-STUFFS. 161 m. phenylenediamine, naphthylamine ethers, amido diphenylamine, and others. The colors produced are also called ingrain or devel- oped colors. As an example, the diazotizing of primuline, first attempted, may be mentioned. The goods are dyed as usual at first. They are then washed and placed in a diazotizing bath con- taining in 200 parts water i part sodium nitrite and the requisite quantity of sulphuric or hydrochloric acid (sulphuric acid, about twice as much, and hydrochloric acid, about three times as much as the quantity of sodium nitrite). The diazotizing bath is kept cool by addition of ice. After short immersion, the goods are rinsed in cold water and are placed in the developing bath. This may con- sist of an alkaline solution of phenol, resorcin, /3-naphthol, a solution of m. phenylaminediamine hydrochloride, etc. The developing bath is usually kept cold. The goods are subsequently rinsed. Somewhat different from this is the production of insoluble azo dye-stuffs on fiber which has not been previously dyed. The colors so produced are termed " ice colors." They are pre- pared for dyeing, especially for the printing, of cotton goods. The goods to be dyed are first impregnated with an alkaline solution of a-naphthol, and are then drawn through a diazo solu- tion. In this manner there is produced in the filter an azo dye- stuff which is quite fast toward water and very fast toward acid and alkali. As an example, the production of the very beautiful paranitraniline red may be mentioned. 144 grs. ,9-naphthol are dis- solved in 10 liters water, and 145 grs. caustic soda (sp. gr. 1.333), with addition of 500 grs. turkey-red oil. The goods are impreg- nated with this solution and dried. They are afterwards placed in the diazotizing bath. The latter is obtained by dissolving in a boiling solution of 69 grs. paranitraniline in 200 c.c. hydrochloric acid and 200 c.c. water. To the cooled solution i liter cold water, and, after thorough cooling, 500 grs. ice are added. It is then diazotized with 250 c.c. twice normal nitrite solution, is di- luted to 10 liters and treated with 300 grs. sodium acetate before using. The goods, which are removed from the diazotizing bath, are well rinsed, slightly soaped at 40, and dried. Aniline black is a dye-stuff which is formed on the fiber by the oxidation of aniline. Potassium bichromate or chlorate are usually used as oxidizers. It can be produced on cotton, wool or silk. 11 162 CHEMICAL-TECHNICAL ANALYSIS. Method of Testing. The best means of determining the value and strength of a dye- stuff is by comparative dye tests. To this end a " type " or stand- ard sample may be employed for comparison ; or, when a choice is to be made between several kinds of the same dye, the process may be undertaken with all the samples. In the first case dyeing is con- ducted under the same condition until the same shade is obtained, and a comparison is made between the amounts of dye used. They are merely proportional to the value of the dye-stuff. In the second case dyeing is conducted with dyes in quantity of equal price and the colors produced are compared. A process of dyeing is selected which is as simple as possible, and which gives reliable value for the strength of the dye and the clearness of the shade. In order, for instance, to avoid mordanting the cotton, wool may be used with basic dyes. The quantity of mordant is rather taken somewhat higher than required in actual practice when mordant dyes are used. Wool is mordanted in the manner previously mentioned. Strips of cotton calico* printed with iron and aluminium mordants are prefer- ably used instead of cotton. The quality of dye chosen should not be too large, because lighter shades are more easily compared. In case the bath is not exhausted, a second, and, if necessary, a third sample is placed in the same, until exhaustion is complete. The samples to be dyed should possess equal weight, and for carded wool, cotton yarns or calico, should equal about 10 grs. If necessary, they are first mordanted and dyed in porcelain or glass vessels. In order to preserve uniform heat, the vessel is placed in an oil- or glycerin -bath. The quantity of water used is about 50 times the weight of the goods when these are wool, and 30 times the weight when cotton is used. The evaporated water is replaced from time to time. To prepare the dye-stuff solution, i gr. per liter of coal-tar colors is used, and 10-20 grs. dye-wood extracts per liter. 10-20 grs. insoluble dye-pastes are weighed off, mixed with one liter water, and thoroughly shaken before using. The dye-stuff solu- tion is added from a burette or pipette and manipulated as pre- viously stated. After dyeing, the goods are washed, and, if neces- sary, soaped. If, for example, in one case 70 c.c., in another * These may be readily purchased. DYE-STUFFS. 163 56 c.c. of two solutions containing blue wood extract (in both cases TO grs. extract per liter) were used, their value will be the reverse : 56 : 70 or 80 : 100. Tests for impurities. Inorganic admixtures are easily recognized by the increased ash. The nature of these is determined in the examination of the latter. Organic impurities, such as starch and dextrin, remain behind on extraction with alcohol in many cases, and can thus be determined quantitatively. FIG. 13. Indigo Extraction Apparatus. Special Methods of Investigation. Special methods of investigation are also applied, in addition to the dye tests, to certain natural dye-stuffs. Of these the examina- tion of indigo for indigotin, according to Schneider, will be men- tioned. This depends on the solubility of indigotin in naphthalene. 30-50 grs. pure naphthalene, which has been previously melted to expel water, are placed in the Erlenmeyer flask, K, of the accom- panying apparatus (Fig. 13). The Erlenmeyer flask may be re- placed by a wide-necked test-tube. 164 CHEMICAL-TECHNICAL ANALYSIS. Thereupon about .3 gr. of air-dried indigo is placed in the ex- traction capsule H (these are for sale by Schleicher and Schull), mixed with ignited bar-sand by means of a spatula, or by shaking, and covered with a small paper plate. It is then hung in the flask by two wires which are inserted into the sides of the capsule. The wires are pressed against the inner walls by the cork *$*. Through a hole in the latter there is placed a condenser-tube R, provided with a slanting end extending into the capsule, and which may have an opening at a in order to facilitate the issue of the naph- thalene vapors. This is not indispensable, however. The naph- thalene is now gradually brought to boiling, when the vapors, which are condensed in the tube, drop into the capsule and extract the indigotin.* Any solidified naphthalene in the tube may be re- moved by heating. Heat is applied until the naphthalene which flows from the capsule remains nearly colorless for a time. It is then allowed to cool, the contents of the flask are covered with ether, and after all soluble matter has gone into solution the residue is thrown on a dried and weighed filter, is well washed with ether, dried at 100 and weighed as indigotin. In a separate portion of the sample the water is determined by drying at 100, and the ash is determined by first subliming off the indigotin with a small flame and afterwards igniting briskly to constant weight. Becognition of Dye-stuffs. The behavior of the dye-stuff with acids, alkalies and reducing agents serves as a means of identification. The reactions bearing on this, most of which depend on changes of color and decolor- ization, and which can also be used to identify a dye on the fiber, are specially treated of in the excellent work of G. Schultze and P. Julius, i.e., " Tabellarische Uebersicht der kiinstlichen organ - ischen Farbstoffe. ' ' A detailed description at this point would be too extensive. * Indigo red is also extracted by naphthalene, but on subsequent treatment with ether it dissolves, while indigo-blue remains undissolved. XI, Products of the Coal-Tar Industry. I. Crude Benzene. (0) DETERMINATION of petroleum hydrocarbons. 100 grs. crude benzene are nitrated with a mixture of 150 grs. nitric acid (42, Be.) and 220 grs. concentrated sulphuric acid. The product obtained is carefully washed with water and very di- lute alkali, after which it is dried and subjected to fractional dis- tillation. The petroleum hydrocarbons, which distil up to 150, are measured. (<) Fractional distillation. 100 c.c. crude benzene are placed in a distilling bulb in which a thermometer is placed in such a manner that the upper end of the mercury reservoir is parallel with the lower point of contact of the exit tube. Connected with the distilling bulb is a condenser, at the end of which a measuring cylinder is placed. Heat is now gently applied, and the tempera- ture at which the first drop goes over is recorded as the beginning of boiling. Distillation is continued rapidly and yet in such a manner that the drops may be counted as they run into a cylinder. The volume of the distilled fluid is read off every 5. At 100 the flame is removed, the tube is allowed to drain, and the volume of the distillate is recorded. Thereupon distillation is continued until complete. The following table shows the course of distillation of 90, 50 and 30 per cent, benzene : Amount Distilled in c.c. up to yj Cf. p . q ./- p 85 900 95 100 105 "5 120 90 per cent. 50 " 82 88 20 72 5 84 30 9 5o ? 5 64 t 94 .882 .880 30 " ... 2 12 30 42 92 90 .875 2. Crude Xylol. Determination of the three xylols according to Lewinstein. The method, which is little used, practically depends on the difference 166 CHEMICAL-TECHNICAL ANALYSIS. in behavior of these substances with dilute nitric acid, and, further- more, with cone, and fuming sulphuric acid. 100 c.c. crude xylol are boiled, while constantly agitated, with 40 c.c. nitric acid (sp. gr. 1.4) and 60 c.c. water for ^ i hour. As soon as the evolution of red fumes has ceased, the acid is sepa- rated from the hydrocarbons in a separatory funnel. The latter are washed with dilute alkali and distilled in a current of steam. The solution of the hydrocarbons (# ) in the distillate, consisting of metaxylol and hydrocarbons of the fatty series, is measured and thereupon shaken for a half-hour with i ^ times the volume cone, sulphuric acid. Metaxylol is thereby dissolved as sulphonic acid, whereas the aliphatic hydrocarbons remain. If their volume (b} be deducted from the previous volume (#), the difference (a-b) will equal the metaxylol present. To determine the paraxylol, 100 c.c. crude xylol are shaken for half an hour with 120 c.c. cone, sulphuric acid. Ortho- and meta- xylol dissolve as sulphonic acids. When, upon further addition of sulphuric acid, the latter remains colorless, the volume of the un- dissolved oil, which consists of paraxylol and aliphatic hydrocar- bons, is read off. Let this == c. The oil is now drawn off from the acid and shaken with an equal volume of fuming sulphuric acid, containing 20 per cent, anhydride. Paraxylol dissolves and the fatty hydrocarbons remain unattacked. If their volume = d, then the difference, c-d, will yield the amount of paraxylol present. If the sums of the volume percentages of meta- and paraxylol and the aliphatic hydrocarbons be added, and their sum subtracted from 100, the difference will represent orthoxylol. 3. Crude Anthracene. The determination of anthracene by the method of Luck (modi- fied by Meister, Lucius and Briining) depends on the property of anthracene to yield anthraquinone on oxidation with chromic acid in acetic acid solution. The latter compound is not attacked by further action of chromic acid and of sulphuric at 100. On the contrary, the other constituents of anthracene (acenaphthene, fluo- rene, phenanthrene, carbozol, fluoranthene, etc.), are either com- pletely destroyed or converted into sulphonic acids, which are solu- ble in water or alkalies, i gr. crude anthracene is covered with CRUDE CARBOLIC ACID. 167 45 c.c. glacial acetic acid in a 500 c.c. flask. The flask is pro- vided with a double-bored stopper, through one opening of which a separatory funnel is inserted, while through the other there issues an adapter, which is connected with a condenser. To the boiling solution of anthracene, 15 grs. chromic acid in 10 c.c. glacial acetic acid and 10 c.c. water are gradually added. The chromic acid is added at intervals of 2 hours. The solution is boiled 2 hours, stood aside for 12 hours, diluted with 400 c.c. water, and after 3 hours is filtered from the separated anthraquinone. This is washed first with pure water, then with boiling alkali, and finally again with water. It is then rinsed from the filter into a small flat porcelain dish. The water is evaporated, and the residue, after being dried at 100, is heated on a water-bath with 10 times the volume of fuming sulphuric acid (68 Be.). The solution so obtained is allowed to stand for 12 hours in a moist place, is diluted with 200 c.c. cold water, and the pure anthra- quinone formed is filtered off. The latter is washed as before, rinsed into weighed capsules, dried at 100 and weighed. There- upon the anthracene is volatilized by heating, and any remaining ash is deducted from the weight first obtained. The anthraquinone so found is then calculated into anthracene. 207.5 anthraquinone = 177.58 anthracene. 4. Crude Carbolic acid. Determination of phenol. 120 grs. crude acid are distilled from a small bulb, which is attached to a condenser, until about 8 grs. remain.* The distillate is dissolved in ether and shaken out with 10 per cent, caustic soda in a separatory funnel. The ethereal layer is washed several times with dilute alkali, and the aqueous layer is washed several times with ether. The united alkaline extractions are decomposed with hydrochloric acid (i : i), which is added to acid reaction, and extracted with ether. After the ethereal solutions have been washed with water and the acid liquid with ether in a separatory funnel, the ethereal solutions are placed in a weighed flask. The ether is distilled off as far as possible, and * This procedure is suitable because the subsequent extraction with ether is more easily accomplished, and a sharper separation of the two layers is obtained. 168 CHEMICAL-TECHNICAL ANALYSIS. the last traces are removed by attaching the flask to a dephlegmator or Linnemann column and heating the same over a wire gauze until an inserted thermometer indicates above 100. The contents are then allowed to cool and are weighed, together with the flask. 5. Dimethyl Aniline. The approximate determination of monomethyl aniline can be accomplished by the rise in temperature on mixing with an equal volume of acetic anhydride. Every degree rise in temperature corresponds to approxi- mately ^ per cent, monomethyl aniline. On mixing pure di- methyl aniline with acetic anhydride, a depression of )^ is ob- served. Each test requires 4 c.c. The monomethyl aniline may be more exactly determined by the method of Nolting and Boasson by allowing nitrous acid to act on the product. Monomethyl aniline is thereby converted into ether- soluble methyl-phenyl-nitroso amine C 6 H 5 N (NO) (CH 8 ), whereas dimethyl aniline hydrochloride is converted into the hydrochloride of nitroso dimethyl aniline C 6 H 4 (NO).N (CH 3 ). HC1, which can- not be extracted by ether from its aqueous solution. According to Nietzki, 30 grs. dimethyl aniline are dissolved in 80 grs. cone, hydrochloric acid and about y 2 liter water. The solution is well cooled and 38 grs. sodium nitrite are run in. After a while the solution is repeatedly extracted with ether, the ethereal solutions are united, the ether is evaporated off, and the residual oil is dried over sulphuric acid and weighed. The nitroso amine found, when multiplied by .786, gives the monomethyl aniline originally present. Appendix. A. White Paint (White Lead). A WHITE paint consists of a white pigment ground in a suitable oil, usually linseed oil. A very common form, and for general uses the best, is that termed " white lead," which is essentially the pigment white lead 2PbCO 3 .Pb(OH) 2 ground with linseed oil. Other pigments, not necessarily adulterants, which may be ad- mixed or per se are barium sulphate, lead sulphate, zinc oxide, zinc carbonate, zinc sulphide, strontium sulphate, calcium sulphate, calcium carbonate, magnesite, kaolin and silica. These and others are brought into the market in one form or another under various names. Mineral oils, rosin oil, etc., may be present with the dry- ing oil of the paint. These may be detected, after separation from the pigment, by other methods given in the chapter on Oils. Analysis. In a small Erlenmeyer flask about 5 grs. paint are weighed out. This is repeatedly washed by decantation with pure ether until a few drops of the latter leave no non-volatile residue on evapora- tion. The residue is thrown on a filter or else freed from adher- ing traces of ether by a current of air. The collected ethereal ex- tractions are evaporated, and, after expelling the last traces of ether in the usual way, the residual oil is weighed, and if necessary ex- amined. The weight of the residue is gotten by difference. It is then subjected to analysis by the following scheme (see table on page 170). The residue may contain PbSO 4 , 2PbCO 3 .Pb(OH) 2 , BaSO 4 , CaSO 4 , CaCO 3 , BaCO 3 , ZnCO 3 ,'ZnO, SiO 2 , clay, etc. It is covered with hot acetic acid, diluted, heated and filtered. B. Manganese Dioxide, Bleaching Lime, Etc. The simplicity of the Lunge nitrometer (Fig. i) and its prin- ciple furnish a more extended use of the same in quantitative an- 170 CHEMICAL-TECHNICAL ANALYSIS. I* li II O B 5 " 3- 2 11 2"2-c =* "S s l^ g:-ig 55** tl li "&*. S- -g . . : S?a oS - d-S E2|g iliii M ^3 ; g d- 13 ^^^ gs^.l IS ill fe^-^ iliii 51111 BSff.rf lal Is*P.S h^l Illii 2 8 1-5 v -a iJ 2 3 1 -S 5 ^H3 1^ c . . O T3 2 S %% B a 'i 1 Sugar. M I Per cent. Per cent. Per cent. Per cent. Per cent. Per cent. Per cent. Unroasted coffee Roasted coffee 11.23 1.15 13.27 1448 18.17 19.89 3-92 4 75 12.07 13.98 I.2I 1.24 ( Telus .66 < gums and (^ dextrin. Water, ash and caffein are estimated as in tea. (a) Fat. 2-3 grs. finely powdered sample are placed in an * A more reliable method is that of Councler and Schroeder, Zeit. fur anal. Chem., 25, 121. 180 CHEMICAL-TECHNICAL ANALYSIS. extractor with petroleum ether and extracted for several hours. The petroleum ether is distilled off, and the residue, which is quite pure, is dried and weighed. Fiber* 2 grs. substance are washed several times by decantation with ether and boiled for ^ hour on a reflux with 200 c.c. 1.25 per cent, sulphuric acid in an Erlenmeyer flask. The solution is filtered through linen, and the filtrate is refiltered through a Gooch crucible. The two residues are washed, reunited and boiled in the same flask with 200 c.c. 1.25 per cent, caustic soda. Filtration and washing are conducted as before. The contents of the linen are washed with alcohol into the crucible and then washed with ether, dried at 110 and weighed. It is then incinerated and the ash is deducted. Adulterants may be inorganic coloring matter, etc., in which case, the percentage and nature of the ash would give some indication. Organic adulterants consist of artificial beans, which are usually made of flour, chicory and sugar caramel, which forms on the roasted bean when the unroasted bean is treated with sugur solu- tions. Roughly, the presence of the first named may be detected by covering the sample with water. Natural beans float, whereas artificial beans sink. The test is not always conclusive. The coffee bean contains no starch, and therefore flour in any form can be recognized by the starch reaction. Chicory maybe suspected when the ash contains much over .03 per cent, chlorine. Careful incin- eration is advised in this case. Burnt sugar or caramel is detected by the rapid darkening of water on which a little coffee is sprinkled. Comparative microscopic examinations afford the safest clues. 5. Cocoa and Chocolate. Cocoa, the ground product of the decorticated cocoa bean, forms the basis of all cocoa preparations. The average composi- tion, according to J. A. Wanklyn, is : Per cent. Fat (cocoa butter), 50.00 Theobromin, . . . . . . . . 1.50 Starch, . . . . . , . . . 10.00 Albumin, etc., . . . . . . 18.00 Gum, . . . .. . . . . . . 8.00 Coloring matter, . . .' . . . ; . 2.60 Water, . 6.00 Ash, . . . 3.60 * U. S. Dept. Agriculture Bulletin, No. 13. COCOA AND CHOCOLATE. 181 When incorporated with refined sugar it forms chocolate. Fre- quently the expressed and "defatted" substance is used for the above. Both varieties, mixed with various kinds of starch, sugar and flavoring extracts, constitute cocoa preparations. In soluble cocoa preparations the former is previously defatted, treated with ammonia to destroy the cellular structure, and then with necessary reagents to transform the albuminoids to a soluble form. The use of the above substances in moderation is for many reasons allowable, but their abuse is considered adulteration. Min- eral matter, weighting material, etc., may be present as adulterants. The analysis embraces the determination of water, fat, starch, theobromin, sugar, nitrogenous matter and ash. (a) Water. 2-5 grs. rasped or powdered sample are dried to constant weight at 105. (&) Fat. 2 grs. rasped or powdered sample are, if necessary, mixed with sand and extracted with ether. The ether is distilled off and the fat is dried at 100 and weighed. If previous "de- fatting" and addition of foreign fat be suspected, the usual constants are determined. The iodine number of genuine cocoa butter is about 34, Kottstorfer's about 200. (V) Sugar. The residue from (^) is extracted with cold water and an aliquot portion is inverted. The remaining operation is as on p. 86. (d) Starch. The residue from (V) is boiled with water and in- verted. In an aliquot portion of the solution the starch is deter- mined as in p. 99. To determine the nature of the starch a mi- croscopic examination is necessary. (e) Theobromin is determined asunder theine, caffein (p. 179), except that the sample is first defatted with petroleum ether and the final extraction is done with boiling 80 per cent, alcohol. The residue left on expelling the latter is, if necessary, purified with petroleum ether, dried and weighed. (/) Nitrogenous matter is determined by the Kjeldahl process, p. 74- ( g) Ash. 5 grs. sample are incinerated in a platinum dish and weighed. The fact that the dry cocoa bean contains about 1.5 per cent, of phosphoric acid is of importance. 182 CHEMICAL-TECHNICAL ANALYSIS. 6. Flour and Other Cereals. The analyses comprise the determination of water, ash, starch, fat, nitrogenous matter, water extract and wood fiber. Adulterants would mainly be present in form of inorganic weighting material. (#) Water. 2-5 grs. sample are dried at 105 to constant weight. () Ash. 2-5 grs. sample are incinerated in a platinum dish, cooled and weighed. Frequently the ash is difficult to free from carbon particles. In this case careful addition now and then of crystals of pure ammonium nitrate aids the incineration. (