TREATISE ON GENERAL AND INDUSTRIAL ORGANIC CHEMISTRY TREATISE ON GENERAL AND INDUSTRIAL ORGANIC CHEMISTRY BY DR. ETTORE MOLINARI PROFESSOR OF INDUSTRIAL CHEMISTRY AT THE ROYAL MILAN POLYTECHNIC AND AT THE LUIGI BOCCONI COMMERCIAL UNIVERSITY TRANSLATED FROM THE THIRD ENLARGED AND REVISED ITALIAN EDITION BY THOMAS H. POPE, B.Sc., A.C.G.I., F.I.C. PART I WITH 254 ILLUSTRATIONS PHILADELPHIA P. BLAKISTON'S SON & CO. 10 1 2 WALNUT STREET 1921 Printed in Great Britain. TRANSLATOR'S PREFACE IN this translation it has been deemed undesirable in most cases to convert the metric weights and measures into those of the English system, but, in general, prices are given in British currency, twenty-five lire being taken as the equivalent of one pound sterling. Where quantities are given in tons, the latter are to be read as metric tons of 1000 kilograms or 2204' 6 Ib. avoirdupois. The abbreviations employed for the different units of weights and measures are those in common use, and temperatures are expressed in degrees Centigrade in all cases. THOMAS H. POPE. 457665 PREFACE TO THE THIRD ITALIAN EDITION THE second edition of this treatise, which appeared in 1913, has been exhausted for over two years, while the Spanish and English versions have also been completely sold. The publication of this new edition has been delayed owing to the vicissitudes of the war, which, although apparently at an end, has left industrial, commercial and social upheaval behind it. The most serious and urgent problem now preoccupying all so-called civilised countries is that of production, which should lead to the rapid recovery of the wealth and reserves destroyed by the monstrous conflict which sacrificed, on the altar of international imperialism, upwards of fifteen millions of human lives. A clamant need is the speedy transformation of the improvised and super- fluous industries of war into peace industries. Never before have the interests of humanity imposed such serious tasks on the technologist, particularly on the chemist. The aid of science is necessary in order to arrive, as rapidly and economically as possible, at the most intense production of the materials furnished by nature and consumed by society. This is necessary in the interests of all, since, even when the legitimate restlessness of nations sacrificed by the dominating castes shall have resulted in a new social order, less barbarous, less chaotic and less unjust than that now in force, increased output will be more than ever of importance for the welfare of the new humanity. In this edition, from which new English, French and Spanish editions are being prepared, account is taken of the industrial progress in the various branches of chemistry and of statistical data up to the end of the year 1913. For the period of the war, only data referring to Italy can be guaranteed. The statistics and prices for the years of war are of transitory importance and are recorded as curiosities reflecting the abnormalities of this historic period. Fiscal tariffs cannot be given, since in all countries these have under- gone change and will not be. systematised for some time yet. THE AUTHOR. MILAN. VI A NEW treatise on Organic Chemistry might, in view of the existence of the excellent works of Bernthsen and Holleman, be considered superfluous. Both of these books, which differ little in the manner in which the subject is developed, are, however, confined to a theoretical and systematic exposition of the many organic compounds, the industrial side of the question and the applications of these compounds being almost entirely neglected. It is hence difficult for the student to ascertain which of the thousands of substances described are really of practical importance. Modern teaching of chemistry adheres in a too one-sided manner to the old but fruitful idea of Liebig, that " to obtain a sound practical man it is necessary to train a good theorist." This conception was taken too literally, although it gave good results when chemical industry was in its infancy, since in those days any theorist could easily introduce new and important methods. But to-day, when the industry has attained the adult stage has advanced to such an extent and become so varied and complex, being stimulated incessantly by keen national and international competition, which demands rapid changes and improvements the valuable time of the young technician cannot be wasted in a protracted and sometimes sterile apprenticeship. Present-day conditions require, therefore, some such expansion of Liebig's maxim as the following : In order to produce, rapidly and with increased certainty, a sound, practical man, it is necessary to train a good theorist and to initiate him into both the theoretical and the practical study of the more salient industrial problems. It does not suffice that the young chemist, about to begin his industrial or teaching career, should have a thorough knowledge, for instance, of the various syntheses and constitutional formulae of the sugars. He should also be acquainted with at least the general outlines of the industrial processes and of the technique of the manufacture of sugar, beginning with the slicing of the beets and proceeding to the exhaustion of the pulp, defecation, saturation, filtration with filter-presses, boiling, and vacuum concentration in multiple- effect apparatus, refilling and centrifugation of sugar crystals, utilisation of residues, and so on. He should, indeed, understand the plant and chemical processes of the more important industries, as these often find application in the manufacture of products of a secondary or entirely new character. What would avail a study of the wonderful artificial colouring-matters derived from coal-tar, with the inexhaustible syntheses composing their theo- retical basis, if it were limited to a simple mnemonic exercise for the student and no notice were taken of the interesting practical applications to the dyeing of the various textile fibres ? Nor should the young student ignore statistics of production; he should be able to appreciate the importance of variations in the exportation and importation of the principal chemical products, and to judge of the economic and social conditions with which such variations correspond. After a brief novitiate, he should be in a position to point out the more viii PREFACE TO THE FIRST ITALIAN EDITION striking technical defects and the more marked difficulties met with in par- ticular industrial processes and to suggest rational and not fanciful remedies. It is this space, the vacant region representing a suitable fusion of theo- retical with applied chemistry, which requires filling. This I have attempted in the present work, which of itself is certainly insufficient to cover the whole of the ground. The difficulties encountered in preparing the volume on Inorganic Chemistry are multiplied in dealing with Organic Chemistry, and this is the case as regards the collection and confirmation, not only of the statistical data but of the chemical processes giving the best results in practice. For in any particular industry it has often been found that the results of investi- gations are in such disaccord with the practical data as to render it a matter of great uncertainty what conclusions should be presented to the reader. Inquiries addressed to manufacturers resulted in aggravation of this uncertainty, what was confirmed on the one hand being denied on the other, and plant guaranteed by one firm to be the best being decried by a competing firm. It hence became necessary to apply directly to the operatives- working a given process and to draw conclusions from the whole of the data and information thus obtained. It is thus that readers may explain the contradictions between different authorities on one and the same subject, and also the fact that the conclusions reached by the author with reference to certain industrial processes are not always in accord with those given in other treatises. The intention has certainly not been to prepare a complete treatise on technological chemistry and still less on chemical technology. The work having to be restricted within limits of space approximating to those of vol. i, the author has descended to details only with some of the principal industries and especially with those best adapted to give a general idea of the different applications of chemical processes and of chemical technics. To this end the author has dwelt preferably on the industries of illumin- ating gas, sugar, alcohol, beer, acetic acid, dyeing, textile fibres, fats and soaps, explosives, etc. From these examples the student may gather much instruction applicable to many other industries not dealt with in detail. Repetition has been avoided and time and space saved by frequent refer- ences to arguments already developed in vol. i, Inorganic Chemistry. Advice and collaboration are desired from readers and colleagues in order that gaps in the present work may be filled and inaccuracies and defects remedied. E. MOLINARI. MILAN. CONTENTS PAGE TRANSLATOR'S PREFACE . v PREFACE TO THE THIRD ITALIAN EDITION. vi PREFACE TO THE FIRST ITALIAN EDITION vii PART I. GENERAL PURIFICATION OF ORGANIC COMPOUNDS 2 Crystallisation, 2 ; sublimation, boiling-point, fractional distillation, 2 ; rectification, 3; melting-point, 5; specific gravity, 7. ANALYSIS OF ORGANIC COMPOUNDS 7 Qualitative composition, 7 ; quantitative estimation : of carbon and hydrogen, 8; of nitrogen, 10; of halogens, 12; of- sulphur and phosphorus, 13. CALCULATION OF EMPIRICAL FORMULA 13 DETERMINATION OF MOLECULAR WEIGHT BY CHEMICAL MEANS . 14 POLYMERISM . 14 VALENCY OF CARBON, CONSTITUTIONAL FORMULA, ISOMERISM . 15 Theory of radicals and types, 15; structural formulae, 17; rational formulae, 18. METAMERISM, PSEUDOISOMERISM, TAUTOMERISM, DESMOTROPY . 18 STEREOISOMERISM OR SPACE ISOMERISM ...... 19 Stereoisomerism in derivatives with doubly linked carbon (alloisomerism) 21 ; stereoisomerism of nitrogen, 22 ; separation and" transformation of stereoisomerides, 23. HOMOLOGY AND ISOLOGY . 24 PHYSICAL PROPERTIES OF ORGANIC COMPOUNDS IN RELATION TO THE CHEMICAL COMPOSITION AND CONSTITUTION ... 24 Crystalline form, 24; solubility, 25; specific gravity, 25; molecular volume, 25 ; melting-point, 25 ; boiling-point, 25 ; heat of combustion and of formation, 25 ; heat of neutralisation, 26. Optical Properties : colour 26 ; refraction, 27 ; influence on polarised ligh^, 27; magnetic rotatory power, 28. Electrical conductivity, 29. CLASSIFICATION OF ORGANIC COMPOUNDS 29 OFFICIAL NOMENCLATURE 29 PART II. DERIVATIVES OF METHANE AA. HYDROCARBONS (a) SATURATED HYDROCARBONS . 31 Natural formation and general methods of preparation, 31 ; table of saturated hydrocarbons, 32; Methane, 33; properties, preparation, fire-damp, deton- ating mixtures, industrial preparation, 34-36; Ethane, 36; Propane, 36; Butanes, 37; Pentanes, 37; Hexanes, 37; Higher Hydrocarbons, 37. ix x CONTENTS PAGE Illuminating Gas : history, 38; components, 40; retorts, 41; furnaces, 45; purification, 45; hydraulic main, 45; naphthalene separators, 46; separation of ammonia, 47 ; scrubbers, 48 ; separation of sulphur compounds and cyanogen compounds, 49; exhausters, 53; pressure regulators, 53; gasometers, 54; pressure regulators for consumers, 55; transport to a distance, 56; gas-meters, 56; yield, value and price, 58; statistics, 59; physical and chemical testing of gas, 60; illuminating power, 62; comparison between various sources of light, 64; oil-gas, 64. Petroleum Industry : history, localities of production, 65 ; orig'n of petroleum, 67 ; fishing industry, 69 ; composition and properties of crude petroleum, 70 ; extraction and industrial treatment, 73 ; distillation, 75 ; chemical purification, 78; tanks, transport, 80; uses and statistics, 81; tests for lighting petroleum, 83 ; Treatment of crude benzine, 84. Treatment of Petroleum Residues : (A) Lubricating oils, 86; "cracking," manufacture of benzine from naphtha, 87 ; requirements in and analysis of lubricating oils, 90; statistics, 93. (B) Vaseline, 93. (C) Paraffin wax, 94; from petroleum residues, 94 ; from lignite tar and pyropissite, 95 ; oils for gas, 98; asphalte, pitch and bitumen, 99; bituminous shale, 100. Ichthyol, 103; ozokerite, 104; statistics of paraffin wax, 105; cerasin, 105. (6) UNSATURATED HYDROCARBONS 106 I. Ethylene Series (alkylenes or olefines), C re H 2re , 106 ; official nomenclature, 106 ; methods of preparation, 107 ; constitution, 108. Ethylene, propylene, butylenes, amylenes, cerotene, and melene, 108-109. II. Hydrocarbons of the Series, C ra H 2n _2 : A. With two double Unkings (diol- efines or allenes) : allene, erythrene, isoprene, piperylene, dlallyl, conylene, 109 110. B. With a triple linking (acetylene series) : metallic acetylides, acetylene, 110-114. III. Hydrocarbons of the Series C n H 2n _ 4 and C w H 2n _ 6 , 114. BB. HALOGEN DERIVATIVES OF HYDROCARBONS Table of the halogen derivatives . . . . . . . . .115 I. Halogen Derivatives of Saturated Hydrocarbons : properties, 114; pre- paration, 115. Methyl chloride, 116. Methyl iodide, 117. Ethyl chloride, 117. Isopropyl iodide and butyl iodides, 117. Methylene, ethylene, and ethylidene halogen derivatives, 118. Chloroform, 118-121. lodoform, 121. Polychloro- derivatives, 122. II. Halogen Derivatives of Unsaturated Hydrocarbons, 123; allyl chloride, 123. Tetrabromoethane, 123. CC. ALCOHOLS I. SATURATED MONOHYDRIC ALCOHOLS 124 Nomenclature, 125. Methods of formation of monohydric alcohols, 125. Table of monohydric saturated alcohols, 126. Methyl Alcohol, 127-130. Ethyl Alcohol, 130. Solid alcohol, 131. Bacteriology, 132. Enzymes, 134. Oxy- dases, peroxydases, 135. Biogen hypothesis, toxins, liquid crystals, origin of life, 137. Industrial preparation of alcohol : prime materials, 140. Alcoholic fermentation, 145. Yeast industry, 149. Factors facilitating 6r retarding fermentation, 151. Practice of fermentation, 152. Losses and yields, 153. Table for the calculation of the attenuation of fermented saccharine worts, 154. Amylo process, 155. Distillation of fermented liquids, 158. Rectification of alcohol, 164. Other raw materials for alcohol manufacture, 166. A'.cohol from fruit, 167. Alcohol from woody matter, 167. Alcohol from the sulphite liquors of paper works, 169. Alcohol from wine, lees, withered grapes, 169. Alcohol from green maize, 171. Synthetic alcohol, 171. Refining and purifi- CONTENTS xi PAGE cation of spirit, 172. Tests for the purity of alcohol, 172. Fusel oil, 172. Alcohol meters, 173. Quantitative estimation of alcohol, 174. Windisch's table, 175. Uses and denaturation of alcohol, 176. Statistics and fiscal regulations, 179. Utilisation of distillery residues, 182. Alcoholic Beverages : Wine, 184. Alcoholism, 184. Marsala, 190. Ver- mouth, 190. Cider, 190. Liqueurs, 190. Fermented milk (kephir, koumis, galazin), 191. Beer, 191 : barley, hops, water, germination, kilning of malt, mashing, Balling's table, 192-201 ; infusion and decoction mashing, 201 ; boiling of the wort with hops, 203 ; fermentation, 204 ; attenuation, 207. The Nathan-Bolze rapid process, 08 ; lacking, pitching of casks, 209 ; pasteurisation, 210 ; alcohol- free beer, 211 ; composition of beer, 211 ; analysis of beer, 212; statistics, 212. Sodium ethoxide and calcium ethoxide, 214. Higher Alcohols, 214; propyl, butyl, amyl, etc., 214-216. II. UNSATURATED MONOHYDRIC ALCOHOLS : vinyl, allyl, propargyl, etc., 216. III. POLYHYDRIC ALCOHOLS. (A) Dihydric alcohols or glycols, 216. (B) Tri- hydric alcohols : glycerol, 217. (C) Tetra- and poly-hydric alcohols : acetyl number, 224. Erythritol, arabitol, mannitol, dulcitol, sorbitol, 225-226. DD. DERIVATIVES OF ALCOHOLS (A) DERIVATIVES OF MONOHYDRIC ALCOHOLS . . . . .226 I. Ethers, 226 ; methyl ether, 228 ; ethyl ether : properties, industrial preparation, 229-232. II. Thio-alcohols and Thio-ethers, 233. Sulphonal, 233. III. Alkyl Derivatives of Inorganic Acids, 234: (1) of sulphuric acid, 235; (2) of sulphurous acid, 235; (3) of nitric acid, 235; (4) of nitrous acid, 235; (5) nitro-derivatives of hydrocarbons, 235; (6) various acids, 237; (7) Deriva- tives of hydrocyanic acid : (A) Nitriles ; (B) Isonitriles, 237-239. IV. Nitrogenated Basic Alkyl Compounds (amines), 239 ; methylamine, 240 ; dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, 241 ; alkylhydrazines, azoimides, a- and /3-alkylhydroxylamines, diazo-compounds, 241-242. V. Phosphines, Arsines, and Alkyl-metallic Compounds. Grignard re- action, 242-243. . VI. ALDEHYDES AND KETONES . . . . . . . 243 (a) Aldehydes : Functions, constitution, chemical properties, 244. Acetal derivatives, 245. Aldoximes, hydrazones, semicarbazones, hydr- oxamic acids, 246. Formaldehyde : preparation, properties and analysis, 247. Acetaldehyde, acetal, 250. Higher aldehydes, 251. Chloral and its hydrate, 251 . Aldehydes with unsaturated radicals : acrolem, croton- aldehyde, citral, etc., 251-252. (6) Ketones : Properties, preparation, 252. Ketoximes, isonitroso- ketones, 253. Acetone, 253; mesityl oxide, phorone, butanone, 255-256. Ketenes, 256. (B) DERIVATIVES OF POLYHYDRIC ALCOHOLS 256 JEthyl ether of glycol, glycolsulphuric acid, Ethylenecyanohydrin, Ethylene oxide, 256; Taurine, Glycide alcohol, Glycerophosphoric acid, etc., 257. Nitric ethers of glycerol, 258. Explosives : Theory of explosives, 259. Chemical reactions of explosives : heat of explosion, 259; mechanical work of explosives, 260; temperature of ignition, 261 ; pressure of the gases, 261 ; charging density, 262 ; crushers, 262 ; specific pressure, 262. Velocity of explosion, 263; shattering and progressive xii CONTENTS PAGE explosives, 263; velocity of combustion, 263; initial shock and course of ex- plosion, 264 ; determination of explosion, 264 ; explosive wave, 265 ; explosion by influence, 265 Classification of explosives, 266. Black powder, 266; manufacture, 267. Prismatic powder for cannons, 272. Nitroglycerine and dynamites, 273. Trinitroglycerine, 275; manufacture, 277; uses, 282. Dyna- mites, 282 ; with inactive absorbents, 283 ; with active bases, 285. Nitros' arch, 285. Nitrocellulose, 285. Guncotton : preparation, manipulation, compres- sion, uses, 288-294. Collodion-cotton for gelatine dynamite, dynamite and smokeless powders, 294. Smokeless powders, 295. Powder B, 296. Gelatine .' dynamites, 298. Military smokeless powders, 300. Smokeless and flameless explosives, 303. Shattering explosives, 303. Picric acid, 303. Trinitrotoluene, 304. Sprengel explosives, 304. Chlorate and perchlorate powders, 304. Safety explosives, 305. Detonators and caps, 308. Fulminate of mercury, 308. Fuses, 310. Various powders, 311. Destruction of explosives, 312. Storage and carriage of explosives, 312. Analysis and testing of explosives, 313. Uses, 318. Statistics, 319. EE. ACIDS I. SATURATED MONOBASIC FATTY ACIDS, C n H 2n O 2 319 Table, 320. General methods of preparation, 320. Affinity constants, 321. Separation, 324 ; constitution, 324. Formic Acid, 324. Acetic Acid, 328 : Oudeman's table of specific gravity, 329; manufacture, 329; distillation of wood, 330; utilisation of wood-waste, 333; pyroligneous acid, 335; calcium acetate, 337. Uses, statistics, and price of acetic acid, 339. Manufacture of vinegar, 340. Analysis of vinegar, 344. Salts of Acetic Acid : potassium, sodium, ammonium, calcium, ferrous and ferric acetates, neutral and basic aluminium acetates, silver acetate, neutral and basic lead acetates, chromic, stannous, and copper acetates, 345-348. Propionic Acid, 348. Butyric Acids : (1) Normal butyric acid, 348; (2) isobutyric acid, 349. Valeric Acids : (1) Normal valeric acid,; (2) isovaleric acid; (3) ethylmethyla-cetic acid; (4) trimethylacetic acid, 349. Higher Acids : Caproic, heptoic, caprylic, nonoic, undecoic, lauric, myristic, 349-350. Palmitic Acid, 350. Margaric acid, 350. Stearic acid, 350. Cerotic acid, 351. II. MONOBASIC UNSATURATED FATTY ACIDS . . " . .. .351 A. OLEIC OR ACRYLIC SERIES : Table, 351. General methods of forma- tion, 351 ; general properties, 353. Acrylic Acid, C 3 H 4 2 , 354. Crotonic Acids, C 4 H 6 2 : (a) vinylacetic acid, 355 ; (ba) solid crotonic acid, 355 ; (6/3) liquid crotonic acid, 355; (c) methylmethyleneacetic acid, 356. Pentenoic Acids, C 5 H 8 2 : (a) angelic acid, 356 ; (6) tiglic acid, 357. Pyroterebic Acid, C 6 H 10 2 , 357. y-AHylbutyric Acid, C 7 H 12 O 2 , 357. Teracrylic Acid, C 8 H 14 O 2 , 357. Citronellic Acid, C 10 H 18 O 2 ; rhodinic acid, 358. Undecenoic Acid, C U H 20 2 , 358. Hypogaeic Acid, C 16 H 30 O 2 , 358. Oleic Acid, C 18 H 34 O 2 , 358. Elaidic Acid, 359 ; Iso-oleic Acid, 359 ; A^-oleic acid, 359. Erucic Acid, C 22 H 42 2 , 360; Brassidic Acid, 360; Isoerucic Acid, 360. B. UNSATURATED ACIDS OF THE SERIES C ra H 2ra _ 4 2 . . .360 (a) Acids with a Triple Linking (propiolic series) : Table, 360. Preparation, 360; properties, 261. Propiolic Acid, C 3 H 2 2 . Tetrolic Acid, C 4 H 4 2 . De- hydroundecenoic Acid, C n H 18 O 2 . Undecolic Acid, 361. Stearolic Acid, C 18 H 32 O 2 . Tariric Acid. Behenolic Acid, C 22 H 40 O 2 , 362. (6) Acids with two Double Linkings (diolefine series), 362. /3-Vinylacry- lic Acid, C 5 H 6 2 . Sorbinic Acid, C 6 H 8 2 . Diallylacetic Acid, C 8 H 12 O 2 . Geranic Acid, C 18 H 32 O 2 . Linolic Acid; Drying oils, 363. a-Elseostearic Acid, 364. C. ACIDS WITH THREE DOUBLE LINKINGS, C^H^^O^ Citrylidene- acetic Acid, C 12 H 18 O 2 . Linolenic and Isolinolenic Acids, C 18 H 30 2 . Jecorinic Acid, C 18 H 30 2 , 364. CONTENTS xiii PAGE III. POLYBASIC FATTY ACIDS ......... 364 A. SATURATED DIBASIC ACIDS, ^H^CO.^, 364; Table, 365; pre- paration, properties, 365. Oxalic acid, C 2 H 2 O 4 , 366. Salti of oxalic acid, 368. Malonic Acid, C 3 H 4 O 4 , 368. Ethyl malonate, its use in syntheses, 368. Table of malonic add derivatives, 369. Succinic Acid, C 4 H 6 4 , 370. Amber, 370. Homologous derivative?, 871. Isosuccinic Acid, 371. Pyrotartaric acids, C 4 H 9 4 : glutaric acid, pyrotartaric add, 372. Higher Homologues, 372. ft- Methyladipic, Suberic, Azelaic and Sebacic acils, 372. B. UNSATURATED DIBASIC ACIDS, C tt H 2ra _ 4 O 2 . . . .373 OLEFINEDICARBOXYLIC ACIDS : Table, S73, Fumaric Acid, 374. Maleic Acid, C 4 H 4 O 4 . Itaconic Acid, C 5 H 6 4 . Mesaconic Acid, C 5 H 6 4 , 374. Citra- conic Acid, C 5 H 6 4 . Glutaconic Acid, C 5 H 6 O 4 . Pyrocinchonic Acid and Anhydride, C 6 H 8 4 . Korner and Menozzi reaction of amino-acids, 375. Hydro- muconic Acids, C 6 H d O 4 . Diolefinedicarboxylic Acids. Acetylenedicarboxylic Acids, 376. C. TRIBASIC ACIDS, etc ...... . . . .376 Tricarballylic Acid, C 3 H 6 (COOH) 3 . Camphoronic Acid, C 9 H 14 6 . Aconitic Acid, CgHgOe, 376. D. TETRABASIC ACIDS 376 FF. DERIVATIVES OF ACIDS .1. HALOGEN DERIVATIVES . 377 (a) Halogenated Acids, 377. Table, 378. Cyano-acids, 377. Monochlor- acetic Acid, 379. (6) Acid Halides : chloran hydrides ; aoetyl chloride; acetyl icdide, etc., 379-380. II. ANHYDRIDES 380 Properties, preparation, Table, 380-381. Acetic Anhydride, 381. III. HYDROXY-ACIDS 383 A. SATURATED DIVALENT MONOBASIC ACIDS .... 383 Preparation, properties, constitution, 383; lactides, lactones, 384. Glycollic Acid, OH ' CHg * COOH, and its derivatives (anhydride, glycollide. etc.), 384. Glycocoll, 385. Lactic Acids, 2 H 4 (OH)(COOH) : (1) i-Ethylidenelactic acid (of fermentation), 386; Alanine, 389. (2) d-Ethylidenelactic (or sarcolactio) acid. (3) 1-EthyI- idenelactic acid. (4) Ethylenelactic acid, 389. Hydroxybutyric Acids, C 3 H 6 (OH)(COOH) : a-Hydroxybutyric acid. a-Hydr- ox isobutyric acid. /3-Hydroxybutyric acid, 389. Higher Hydroxy-Acids. Hydroxyvaleric, hydroxycaproic, hydroxymyristic, hydroxypalmitic, hydroxystearic, 389. B. UNSATURATED MONOBASIC HYDROXY-ACIDS . . .389 a-, ft-, y-, and S-Hydroxyolefinecarboxylic acids: Ricinoleic acid; ricinoleinsul- phonic acid and Turkey-red oil (sulphoricinate), 390-391. C. POLYVALENT MONOBASIC HYDROXY-ACIDS .... 391 Glyceric Acid, C 2 H 3 (OH) 2 (COOH). Dihydroxystearic acid, C 1? H 33 (OH) 2 COOH, Erythric Acid, C 3 H 4 (OH) 3 COOH. Pentonic acids. Arabonic Acid. Hexonic Acids, 392. Heptonic Acids, 393. xiv CONTENTS PAGE D. MONOBASIC ALDEHYDIC ACIDS (Aldehydic Alcohols and Dialdehydes) 393 Glyoxylic Acid, CO 2 H CHO. Glycuronic, Formylacetic, and f-Hydroxy- acrylic Acids, Gly collie Aldehyde, Glyceraldehyde. Aldol. Glyoxal, 393. * E. MONOBASIC KETONIC ACIDS (Keto -alcohols, Diketones, and Keto-aldehydes) . 394 General properties. Methods of preparation, a-, (J-, and y-Ketonic acids. Syntheses with ethyl acetate, 394-395. Pyruvic Acid, 396. Acetoacetic Acid. Ethyl Acetoacetate, 396 Levulinic Acid, 397. KETONIC ALCOHOLS : Acetonealcohol. Dihydroxyacetone. Butanol- one, 397-398 DIKETONES : Diacetyl. Dimethylglyoxime. Acetylacetone, 398-399. KETO-ALDEHYDES : Pyruvic Aldehyde and Acetoacetaldehyde. Hydroxymethyleneacetone. Levulinaldehyde, 399 F. POLYVALENT DIBASIC HYDROXY-ACIDS AND THEIR DERIVATIVES . 399 Tartronic Acid, 399. Malic Acid and higher homologues, 399-40,). TARTARIC ACIDS : (1) d-Tartaric Acid, 400. (2) 1-Tartaric Acid. (3) Racemic Acid. (4) Mesotartaric Acid, 401. TARTAR INDUSTRY : Manufacture of Tartar, 402. Analysis of tartar, 403. Statistics, 403. Manufacture of tartaric acid, 407 ; uses and statistics, 409. A tificial tartaric acid, 410. Trihydroxyglutaric, Saccharic and Mucic Acids, 410. DIBASIC KETONIC ACIDS, 410. Mesoxalic Acid. Oxalacetic Acid. Acetonedicarboxylic Acid. Dihydroxytartaric Acid, 410-411. G. POLYVALENT TRIE ASIC HYDROXY-ACIDS 411 Ethane- and Piopane-tricarboxylic Acids, 411. Tricarballylic Acid. Aconitic acid, 411. Citric Acid. 412. Tests for citric acid, 413. Citrus industry, 413. Statistics, 417. Salts of citric acid, 418. Higher p olybasic hydroxy-acids, 419. IV. THIO-ACIDS AND THIO-ANHYDRIDES 419 Thioacetic Acid. Ethanthiolic Acid. Acetyl Sulphide. Ethyl Thioacetate. V. AMIDO-ACIDS, AMINO-ACIDS, IMIDES, AMIDINES, THIOAMIDES, IMINO-ETHERS AND ANALOGOUS COMPOUNDS . . . .419 A. Amido-Acids and their Derivatives : Primary, secondary, and tertiary amides; alkylated amides. Preparation and properties of amides, 419-421. Formamide ; Acetamide, diacetamido ; OxamicAcid; Oxamide; Succin- amic Acid ; Succinamide ; Glycollamide, diglyoollirnide ; Malamic Acid, Malamide, 421. B. IMIDES AND IMINO-ETHERS : diacatam'de, iminohydrin of glycollic acid; Oximide, Succinimide, pyrrole, pyrrolidine, succinanil; Glutarimide, 421-422. C. AMINO-ACIDS AND THEIR DERIVATIVES : Glycocoll, sarcosine, betaine, aceturic acid ; Serine ; Leucine ; Aspartic Acid, glutamic acid ; Ethyl Diazoacetate; Lysine, ornithine, putrescine, taurine, cysteine, cystine; Aspara- gine, Aspartamide, homoaspartic acid and homoasparagine, 422-425. D. AMIDO- AND IMIDO-CHLORIDES : acetamido-chloride, acetimino- chlorid?, 425. E. THIOAMIDES : thioacetamide, 425. F. IMINOTHIOETHERS : acetiminothiomethyl hydriodide, 425. CONTENTS xv PAGE G. AMIDINES : acetamidine, 426. H. HYDRAZIDES AND AZIDES : diacethydrazide, 426. I. HYDROXYLAMINE DERIVATIVES OF ACIDS : hydroxamic acids, amidoximes, isuret, 427. VI. CYANOGEN COMPOUNDS .427 Cyancgen : paracyanogen ; rubeanhydric acid and flaveanhydric acid. Cyanogen Chloride. Cyanic Acid : potassium and ammonium cyanates. Ethyl Isocyanate. Cyanuric Acid : Ethyl cyanurate and isocyanurate. Fulminic Acid, Fulminuric Acid, 427-429. THIOCYANIC ACID AND ITS DERIVATIVES. Potassium, Ammonium, Mercuric, Silver, and Ferric Thiocyanates. Ethyl Thiocyanate. Allyl Thiocyanate, 429^30. MUSTARD OILS : methyl, ethyl, propyl, Allyl, 430. CYANAMIDE AND ITS DERIVATIVES. Calcium cyanamide. Diethyl- cyanamide. Dicyanodiamide. Melams : Melamine, Ammeline, Ammelide, 430-431. VII. DERIVATIVES OF CARBONIC ACID . . . . . .431 Esters of carbonic acid. Ethyl carbonate, ethylcarbonic acid. Chlorides of Carbonic Acid. Chlorocarbonic acid, ethyl chlorocarbonate and chloroformate. Amides of Carbonic Acid. Carbaminic acid, urethane, urea, semicarbazide, acetylurea, allophanic acid, ureides, biuret, hydantoic acid, hydantoin, 431-433. DERIVATIVES OF THIOCARBONIC ACID : thiophosgene, trithiocarbonic acid, potassium xanthate, xanthonic acid, dithiocarbamic acid, diethylthiourea. Thiourea, 433-434. GUANIDINE AND ITS DERIVATIVES : nitroguanidine, aminoguanidine, diazoguanidine, hydrazo- and azo-dicarbonamide, glycocyamine, sarcosine, creatine, creatinine, 434-435. URIC ACID AND ITS DERIVATIVES : ureides, uro-acids, diureides; para- banic acid, barbituric acid, dialuric acid, alloxan, oxaluric acid, alloxanic acid, cholestrophane, methyluracil, alloxanthine, murexide, allantoin, purine, di- methylpseudouric acid, theophylline, caffeine, hypoxanthine, xanthine, adenine, guanine, uric acid, 435-437. Theobromine, cocoa and chocolate, caffeine or theine, coffee and its substitutes, guanine, xanthine, adenine, 437-441. PART I. GENERAL IN Vol. I. of this treatise l is given a brief summary of the history of chemistry and of those portions of physico-chemical theory which are necessary for the interpretation of chemical phenomena. Hence, this course of organic chemistry assumes in the reader a knowledge of the fundamental chemical laws and ideas, methods of determining molecular weights, and so on. The separate treatment of the carbon compounds, which is termed organic chemistry, is a purely didactic convenience and somewhat of a habit, there being no sound foundation to justify a distinction between organic and inorganic chemistry. This division of the subject dates back to the time of Lemery, who, in 1 675, regarded the substances of the animal and vegetable kingdoms as distinct from those of the mineral kingdom, and to 1820, when Berzelius justified the separation by stating that the preparation of organic compounds required the intervention of vital force, whilst inorganic compounds could be prepared artificially in the laboratory. This view was, however, abandoned when, in 1828, Wohler succeeded in preparing urea (found in urine) from inorganic material in the laboratory, and when, later, acetic acid was prepared arti- ficially. Subsequently, the number of so-called organic compounds obtained synthetically has increased almost without limit. There exists to-day no reason for a distinction between organic and inorganic compounds; the first comprise a group of carbon compounds embracing an immense number (over 150,000) of substances, which exhibit certain common characters and are conveniently studied by themselves. It had already been recognised by Lavoisier that all so-called organic compounds, originating in organised bodies, contain carbon, hydrogen, and oxygen, and that many of them, especially those of the animal kingdom, contain also nitrogen and sometimes sulphur, phosphorus, halogens, and metals. The study of organic compounds is as old as the human race, which, from the most remote times, has prepared alcohol and acetic acid from vegetable juices (the must of the grape and other fruit, etc.). After the discoveries of Lavoisier and the investigations of Berzelius, organic chemistry began to acquire special importance, and Liebig, by intro- ducing simple and exact methods for the analysis of organic compounds, rendered most valuable help to the wonderful theoretical and practical develop- ment which has been shown by this branch of chemistry during the past fifty years, and which has been largely responsible for the impulse given to progress and civilisation in the nineteenth century. In order to study the innumerable derivatives of carbon, to be able to obtain separate individuals and to characterise them by means of their chemical and physical properties, then to group and classify them and to deduce in a more or less general way the laws they obey, it was necessary to isolate and prepare in the pure state these separate chemical individuals. 1 E. Molinari, " Inorganic Chemistry "; translated by T. H. Pope, 1920. VOL. II. 1 2 OR G A N I C C H E M I S T R Y PUP j HC AT I ON C-F ORGANIC SUBSTANCES The purification of organic substances is not so easy to effect as might at first appear. Pure substances are characterised by certain physical constants (boiling-point, melting- point, crystalline form, etc.), which serve to show if a substance is in a suitable condition for chemical analysis. The chemical processes of purification may be deduced from the chemical properties of the substances themselves, as described in Parts II and III of this treatise; general physical methods effect purification by means of suitable solvents (water, alcohol, ether, light petroleum, acetic acid, benzene, acetone, chloroform, carbon disulphide, etc.), which separate certain substances from others more or less soluble ; or, in many cases, purifica- tion is brought about by crystallisation, a solution of the impure substance in a suitable hot solvent depositing on gradual cooling or partial evaporation of the solvent the pure substance in characteristic and well-defined crystalline forms, which may be controlled by measuring the angles and determining the axial ratios of the crystals. Impurities separate sometimes before and sometimes after the crystallisation of the substance under examination, so that recourse is had to fractional crystallisation, which, when repeated, may give excellent results. In certain cases, substances are purified by sublimation. 1 When pure, a liquid has a constant boiling-point for a definite pressure (Vol. I., p. 85), and this is determined by dis- tilling the liquid in a flask with a lateral tube, a thermometer being arranged in the neck of the flask without its bulb dipping into the boiling liquid. The temperature of the vapour gives the boiling-point of the liquid ; the vapour escapes from the side-tube and is condensed by means of a Liebig's condenser, formed of an inclined glass tube surrounded by a wider tube through which water circulates from the lower to the upper end (Fig. 2). The boiling-point of a very small quantity of substance may be accurately determined by means of the arrangement shown in Fig. 3 : a few drops of the liquid are introduced into a small tube, d, closed at the bottom and drawn out into a narrowed part. Into the liquid dips a capillary tube, sealed at the point a by fusing the glass. The tube is FIG. 1. attached to the thermometer, c, and the whole immersed, to the depth of a few centimetres, in a liquid having a boiling-point higher than that of the liquid under examination. Heat is now gradually applied, superheating being prevented by the air-bubbles issuing from the lower end of the capillary tube. When the boiling-point is reached, bubbles form very rapidly at the bottom of the liquid, and the boiling-point is read off on the thermometer. Certain substances which readily decompose on boiling at the ordinary pressure can be distilled unchanged at a constant, but somewhat lower, temperature by lowering the pressure, i. e., by distilling in a vacuum (see later). For this purpose use is made of a mercury or water pump (Sprengel). When two liquids are mixed, they may be separated almost completely by fractional distillation, if there is a wide interval of temperature between their boiling-points. In consequence of the partial pressure of the components, at different temperatures mix- tures distil over which contain varying proportions of these components ; the liquid with the lower boiling-point first preponderates in the distillate, while at higher temperatures that with the higher boiling-point predominates. On repeated redistillation of the two extreme fractions separately, the two liquids may be obtained in the pure state. In certain cases, however, a mixture of two liquids does not exhibit a regular progression in the vapour pressure corresponding with the preponderance of one or other of the two components. There are, indeed, liquids which, when mixed in certain proportions, show a minimum vapour pressure lower even than that of the less volatile^ component whilst, 1 Sublimation takes place with many solid substances and consists in the passage from solid to vapour on gentle heating, and from the state of vapour to the solid crystalline condition when the vapours come into contact with a cold body, these changes taking place directly and not by way of the liquid state. Usually the substance is placed on a clock-glass, covered by a per- forated filter-paper and by a funnel; when the clock-glass is heated on a sand-bath, the pure sublimed crystals collect on the walls of the funnel (Fig. 1). In some cases, the sublimation is carried out in a vacuum. RECTIFICATION 3 on the other hand, a mixture of two liquids sometimes has a vapour pressure greater than that of its more volatile constituent ; the two liquids cannot then be separated by fractional distillation, especially when their boiling-points are not far apart. 1 In these cases good FIG. 2. FIG. 3. results are obtained practically by employing so-called rectification, this consisting in distilling the liquid mixture through a Le Bel and Henninger (1874) rectifying tube (Fig. 4), which is fitted at regular intervals with discs of platinum gauze, and above these takes the form of a series of two or more bulbs, a lateral tube being so placed as to lead the liquid condensing in any bulb baek to the bulb below it. When the liquid boils, the mixed vapours pass up the tube and meet the first gauze disc, where the vapour of the less volatile liquid is condensed in greater proportion than the other, so that the vapour reaching the second gauze is richer in that of the more volatile liquid; a similar process occurs at the successive gauzes and in the bulbs above them, so that the vapour passing through the uppermost bulb is that of the more volatile liquid, and this passes down the side- tube (at the mouth of which the thermometer is placed) to the condenser. During this rectification the cooling produced by the outer air and the consequent condensation of the vapours result, in the rectifying tube, in a stream of liquid flowing down the walls of the tube; this liquid film meets the ascending vapours and gives up to them its more volatile constituent and takes up from them their less volatile com- ponent, so that only the vapour of the more volatile liquid reaches the top of the tube, while the less volatile liquid is returned. Similar results are obtained by HempeVs rectifying column (1881), which is filled with glass beads (Fig. 5). With this also the phenomenon of rectification which goes on often 1 Theory of Fractional Distillation. We shall see later the relations existing between the boiling-point and the composition and chemical constitution of organic substances (homologous series, isomerides, etc.). Of interest at the present juncture is the behaviour on distillation of a mixture of two liquids which dissolve one in the other in all proportions. According to Wanklyn and Berthelot, when a mixture of equal weights of two liquids is distilled, the proportions of the two in the distillate depend not only on their proportions in FIG. 4. FIG. 5. 4 permits of the separation of liquids with boiling-points quite close together. This phenomenon has important applications in the alcohol industry (see later), in the manu- facture of oxygen and nitrogen from liquid air, in the preparation of liquid sulphur dioxide (Vol. T., pp. 280 and 340), and in many other industries. FIG. 6. - In many cases substances (liquid or solid) are purified by distillation in a current of steam, certain of them being volatile under these conditions even when their boiling- points are above that of water; in the distillate the substance often separates owing to its insolubility in water. An arrangement used in the laboratory is shown in Fig. 6, steam being generated in A and passing through the substance to be distilled in the flask, B, which may be heated directly with a flame. In some instances the distillation is effected by means of superheated steam (150 to 350), which is obtained by passing steam through a coil of iron or copper tubing heated with a bunsen burner (Fig. 7). FIG. 7. A number of substances decompose when heated at the ordinary pressure, whilst they distil unchanged in a more or less perfect vacuum, owing to a marked lowering of the the original liquid and on their vapour pressures at the boiling-point of the mixture itself, but also on the reciprocal adhesion of the constituent liquids and on their vapour densities. When a mixture of two miscible liquids, in equal weights, is distilled, the quantity of each component which distils may (disregarding certain exceptions) be calculated by multiplying the vapour pressure (at the boiling-point of the mixture) by the vapour density. Hence it can be under- stood how, in some cases, the less volatile substance distils in greater quantity. Even if the vapours that distil over contain equal volumes of the two vapours (that is, equal numbers of molecules), the condensed liquid will contain a greater proportion by weight of the constituent with the higher molecular weight. This explains why water, with a low vapour density, causes MELTING-POINT 5 boiling-point. Of the many different forms of apparatus employed in the laboratory for this purpose, that of Bredt is illustrated in. Fig. 8. An ordinary thick-walled distilling flask, A, is used, its side-tube being connected with the condenser a and with the collecting apparatus, which consists of a flask, d, and three tubes, e, of thick glass, and is joined to the condenser by means of a perforated stopper ; the pump by which the air is withdrawn from the whole apparatus is connected with the tube c, which communicates also with a manometer to show the extent of the vacuum attained. Superheating and consequent bumping of the liquid are avoided by the insertion of the tube b, the lower end of which is drawn out to a capillary and dips below the surface of the liquid, while the upper end is closed with a piece of rubber tubing fitted with a screw-clip; by means of this tube, into which also the thermometer may be introduced, a slow current of air or other inert gas, controlled by means of the screw-clip, is allowed to bubble through the liquid during the distillation. The flask is heated in a bath of oil or fusible alloy, and, if the distillate is very dense, no water need be passed through the condenser. The first portion distilling over at a definite temperature is collected in d, and when the temperature rises suddenly, the collecting apparatus is rotated so that the distillate is collected in one of the tubes, e ; when the thermometer no longer indicates a constant temperature another of the tubes, e, is employed, and so on. MELTING-POINT. Whilst with liquids the boiling-point is generally used as a criterion of purity, for solids the melting-point is mostly employed for this purpose, and in certain cases also the boiling-point. So long as the substance is impure, the melting- point is usually too low. The melting-point is determined by introducing a few centigrams of the substance into a very narrow, almost capillary glass tube, closed at the bottom substances with higher boiling-points (ethereal oils, naphthalene, etc.) to distil, since, although the latter have low vapour pressures, their molecular weights are high. Of frequent occurrence are mixtures of two miscible (one in maximum or minimum ratio to the other) liquids, which, on distillation, do not separate, but distil together in unaltered proportions at constant temperature. Thus, 16 parts of alcohol and 84 of CC1 4 boil at 64-9, and 32 parts of alcohol and 68 of benzene at 67-8; if 59-8 parts of CC1 4 (b.-pt. 76-4) are added to a mixture of 12 parts of alcohol with 32-2 of benzene, which begins to boil at 67-8, the boiling- point of the ternary mixture falls to 65-8. Further, alcohol, water, and benzene in certain proportions yield a ternary mixture which boils at a lower temperature than any of its separate components and cannot be separated into the latter; if, however, excess of benzene is added, repeated distillation yields the benzene and water together with part of the alcohol, so that pure alcohol finally remains (Young, 1894 and 1902; Kablukov, Solomonov, and Galine, 1903; Golodetz, 1912). A mixture of 31 per cent, of acetic acid (b.-pt. 118) with 69 per cent, of toluene (b.-pt. 110-4) boils completely without separation at 104. With 2 per cent, of acetic acid, benzene (b.-pt. 80-4) forms an inseparable mixture boiling at 80, which is the minimal boiling- point for benzene -acetic acid mixtures. If to 100 grams of the above toluene-acetic acid mixture are added 1800. grams of benzene (rather more than is required to give a benzene -acetic acid mixture with 2 per cent, of the acid), the liquid commences to boil at 79-6, and up to 81-8 1900 grams distil, containing always about 1-85 % of acetic acid, the residue consisting of 31 grams of pure toluene. Toluene containing 19-6 per cent, of water boils unchanged at 84-1, and if 67 grams of water are added to 400 grams of the above toluene -acetic acid mixture, distillation yields in succession, (1) between 84 and 85, 355 grams containing all the toluene and about 4 per cent, of acetic acid, which is separable by a further distillation, (2) about 28 grams of 65 per cent, acetic acid, and (3) about 82 grams of 95 to 98 per cent, acetic acid, about one-half of this being of 100 per cent, strength. A mixture of 60-5 grams of benzene, 242 grams of toluene, and 39-5 grams of methyl alcohol (the last gives with 60-5 per cent, of benzene a mixture boiling unchanged at 58-35) yields at 58-2 to 59-8, 94 grams containing methyl alcohol and benzene in the above ratio, and at 110, 228 grams of pure toluene. From a mixture of benzene and methyl alcohol, pure benzene may be separated by distillation in presence of carbon disulphide. On distilling a mixture of two liquids not soluble one in the other, the corresponding vapours do not influence one another, and the total pressure of the vapours is given by the sum of the pressures of the two liquids at the temperature of distillation. The boiling-point of the mixture is the temperature at which the sum of the vapour pressures of the components equals the atmospheric pressure ; it should be mentioned that the boiling-point of such a mixture is neces- sarily lower than that of the more volatile liquid, since here also Dalian's law of partial pressures (Vol. I., pp. 73, 619) holds. Naumann (1877) showed that, in the vapour distilling from such a mixture, the ratio between the volumes of the components corresponds with the ratio between the vapour pressures of the two liquids at the boiling-point of the mixture ; hence the weights of the two components are obtained by multiplying these ratios by the corresponding densities (or molecular weights). By means of this rule, Naumann succeeded in determining the mole- cular weights of various substances simply by distilling mixtures of them. A mixture of water and isoamyl alcohol (b.-pt. 135) has a constant boiling-point of 96, and distils continuously in the ratio of two volumes of water and three volumes of the alcohol. 6 ORGANIC CHEMISTRY (Fig. 9), the tube being attached to the bulb of a thermometer dipping into a beaker of concentrated sulphuric acid, oil, or paraffin wax, which serves to transmit heat to the substance. A small glass stirrer serves to prevent superheating of the liquid, and, when the substance is pure, it melts entirely within a degree and generally becomes transparent. When the temperature of the bath approaches the melting-point, the flame is lowered and the bath heated gently so that the temperature rises half a degree every four or five seconds ; only in exceptional cases should rapid heating be continued. 1 To determine the melting-point of a fat, a tube drawn out to a capillary and sealed at the lower end (Fig. 10a) is held in an inclined position, and one or two drops of the fused and filtered fat introduced into the enlarged part (Fig. 10a, A). When the fat is solidified, the tube is kept in a cool place for twenty-four hours, after which it is attached vertically to the bulb of a thermometer ; it is then heated in a suitable bath, note being taken of the temperature at which (1) fusion begins, (2) the fat flows down and obstructs the capillary (Fig. 106), and (3) the completion of fusion is indicated by the entire liquefaction and transparency of the fat. FIG. 9. FIG. 10. FIG. 11. The melting-point of a fat may also be determined by drawing it in the fused condition into a capillary tube blown out at the middle into a bulb, which is half filled with the fat (Fig. 11) ; the upper end of the tube is kept*closed with the finger until the fat becomes solid, the empty part of the tube being then bent round as shown and attached, upside down, to a thermometer, the whole being afterwards gradually heated in a beaker of water. When the fat begins to melt it flows into the lower part of the bulb (Fig. 11 A b, right-hand view), and when it is completely fused it becomes transparent. For fats and paraffin waxes, or waxes in general, and for soft fats (for example, lubricants) especially, an important determination is that of the dropping-point, which is carried out, according to Ubbelohde's method (1905), by filling with the fat a glass capsule, e (Fig. 12, natural size), 10 mm. long and 7 mm. wide, with an orifice 3 mm. in diameter in the base; a very small thermometer bulb is immersed in the fat and the capsule then affixed to the thermometer with a metal sheath having an aperture at c, and three points, d, which 1 Exact determinations require correction of the thermometric reading to allow for the cubical expansion of the mercury and glass of that part of the thermometer not immersed in the heated liquid. The observed melting-point, t, is to be increased by na (t t^), where n = 0-000160 (the mean cubical expansion of mercury in an ordinary glass tube), a is the number of degrees between the surface of the -heated liquid and the top of the mercury column and t t the air temperature about half-way up the mercury column. EXAMPLE: If the indicated melting-point is 80 (t), while the thermometer dips into the liquid as far as the 15 mark, so that a = 65 (i. e., 80 15), and the temperature half-way up the mercury column is 30 (^), the correction becomes 0-000160 X 65 X (80 30) = 0-52, and the corrected melting-point 80-52. QUALITATIVE ANALYSIS 7 determine the position of the capsule ; the thermometer is then fixed in a test-tube 4 cm. in diameter, dipping into a beaker of water, which is heated so that the temperature rises one degree per minute. At the orifice of the capsule a drop begins to form at a certain time, and when this falls the temperature is read, and is usually corrected by subtracting 0-5 to obtain the real instead of the apparent dropping- point. This method has been adopted for the examination of lubricating oils supplied to the Italian navy and railways. The specific gravity of liquids also serves to determine their purity, and the various forms of apparatus used for measuring it are described in Vol. I., p. 75. ANALYSIS OF ORGANIC SUBSTANCES As will be seen later, many so-called organic substances are composed of carbon and hydrogen combined in various proportions ; a large number of them contain also oxygen, while nitrogen is often present and sometimes sulphur, halogens, metalloids, and metals. Analysis of these compounds may be merely qualitative, when only a know- ledge of the constituent elements is required, or it may be quantitative, when the percentage amount of each of the elements present is determined. QUALITATIVE COMPOSITION. When organic substances are heated on platinum foil they either burn with a flame or leave a carbonaceous residue. The presence of carbon and hydrogen may be demonstrated by heating a little of the substance, mixed with cupric oxide, in a test-tube fitted with a delivery tube, the gas evolved being passed into a clear solution of barium hydroxide : if the latter becomes turbid, owing to the formation of barium carbonate, the presence of carbon is proved, and if drops of water condense in the cold upper part of the tube the substance must contain hydrogen. The presence of nitrogen may, in many cases, be shown by the smell of burning wool or nails developed when a little of the substance is heated on platinum foil. A more general and certain test is that devised by Lassaigne (1843) : 2 to 3 centigrams of the substance are fused with a piece of metallic potassium or sodium (0-2 to 0-3 gram) in a test-tube, which is broken by plunging it while still hot into a beaker containing FIG. 12. 10 to 12 c.c. of water. The alkaline solution of potassium cyanide formed is filtered, mixed with a few drops of ferrous sulphate and ferric chloride solutions and boiled for two minutes, by which means potassium ferrous cyanide is formed (when nitrogen is present in the substance) ; the liquid is acidified with hydro- chloric acid, which dissolves the ferrous and ferric oxides, the resulting ferric chloride reacting with the potassium ferrocyanide to form the characteristic Prussian blue, or at least a green solution which deposits Prussian blue on standing. In absence of nitrogen, only a yellow colour is obtained. To certain nitrogenous substances this test is not applicable (e.g., to diazo-compounds, which evolve nitrogen too readily), and in such cases either the potassium is replaced by a mixture of potassium carbonate and powdered magnesium (Castellana, 1904), or the substance is fused with sodium peroxide and the mass tested for nitrate by means of diphenylamine (Vol. I., p. 234). As early as 1825 Faraday detected nitrogen by heating the substance in a tube with caustic soda and soda-lime, the evolution of ammonia being shown by means of litmus paper; spurting of small portions of the soda on to the litmus paper should be prevented by passing the vapour emitted first through a tube containing glass wool (see later, Quantitative Determination) . The presence of halogens (Cl, Br, I) is determined by heating the substance with pure lime, dissolving in water and nitric acid and precipitating the halogen with silver nitrate. Also, in many cases, the substance may be heated with fuming nitric acid and silver nitrate in a sealed tube (see later, Quantitative Analysis), by which means the silver halogen salt is formed directly (Carius). 8 ORGANIC CHEMISTRY Sulphur also may be detected by the Carius method, the substance being heated in a sealed tube with fuming nitric acid, and the sulphuric acid formed from the sulphur of the organic compound, precipitated with barium chloride; or by heating the substance with pure sodium peroxide, a sulphate is formed. By heating the substance in a test-tube with metallic sodium and dissolving the mass in a little water a solution of sodium sulphide is obtained which blackens a piece of silver foil or a silver coin. Phosphorus and other elements are detected by the Carius method, the substance being oxidised with fuming nitric acid and the liquid tested for the corresponding acid (phosphoric, etc.). QUANTITATIVE COMPOSITION (ELEMENTARY ANALYSIS). Lavoisier was the first to devise an apparatus for analysing organic substances by burning them with oxygen under a bell-jar ; while Gay-Lussac, Thenard, and Berzelius successively improved this process by burning the substance in presence of potassium chlorate. Gay-Lussac, however, showed that certain nitrogenous substances cannot be burned with the chlorate, and suggested as a general and more certain oxidising agent cupric oxide, which when hot gives up its oxygen, transforming the carbon and hydrogen of any organic compound into carbon dioxide and water respectively, while the nitrous compounds are reduced to free nitrogen by passing the products of combustion over red-hot copper turnings. It is, however, to Liebig that the credit is due of rendering this method of organic analysis simple and exact and of devising simple and ingenious forms of apparatus for absorbing the products of combustion. Even to-daydisregarding improvements in combustion furnaces and modifications of the absorption apparatus the determination of carbon and hydrogen (the oxygen is estimated by difference) is carried out by what is virtually the method employed by Liebig. 1 1 The method most commonly used is as follows : 0-15 to 0-30 gram of the substance is weighed in a small porcelain boat, which is then filled with powdered cupric oxide, previously heated to redness and perfectly dry ; the boat is then introduced into the position c of the hard glass combustion tube (Fig. 13), this being 70 to 90 cm. long, or 10 to 12 cm. longer than the combustion furnace, which is heated by 25 to 30 gas flames (Fig. 14). FIG. 13. a = 5 cm. free; 6 = 12 cm. spiral of oxidised copper gauze; c 8 to 10 cm. for the boat; d = 3 cm. copper spiral; e = 40 to 45 cm. granulated cupric oxide; / = 3 cm. oxidised copper spiral or 12 cm. of reduced copper spiral for nitrogenous substances; g = 5 cm. free. The other parts of the tube are reserved for the previously heated copper spirals and granu- lated cupric oxide (Fig. 13). When a fresh combustion is to be made, all that it is necessary to do is to remove the spiral b and the boat and to introduce the new substance into the tube, which is already charged in d, e, and / and is not allowed to cool below 40 to 60. 14. The combustion is earned out in the furnace shown in Fig. 14, the tube being clo-'ed at a with a good cork and a glass tap which can be connected at will with a gasometer containing ir or one containing oxygen, which should, however, before reaching the combustion tube ough tubes containing potassium hydroxide to remove the carbon dioxide, and then COMBUSTION 9 For determining carbon and hydrogen in nitrogenous substances the above method is modified only by inserting in the combustion tube, in place of the spiral/ (Fig. 13), one of reduced copper gauze l about 15 cm. long, this serving to fix the oxygen from the oxides of nitrogen resulting from the combustion and to liberate the nitrogen, which passes unchanged through the absorption apparatus. If the substance to be analysed contains sulphur or a halogen, the combustion is made with lead chromate in place of the granular copper oxide, and the heating is more gentle to avoid fusion of the chromate. By this means the sulphur remains fixed in the tube as lead sulphate and the halogens as halogen salts of lead. Halogens may also be fixed on a spiral of silver foil about 10 cm. long placed at / (Fig. 13), the substance being combusted as usual with cupric oxide; if both nitrogen and a halogen are present the copper and silver spirals are used together. A new apparatus, which admits of the combustion of organic substances being very rapidly carried out, has been devised by Carrasco and Plancher (1 904-1 906) . 2 through drying tubes containing calcium chloride. At the other end the combustion tube communicates at b, first with a tared tube, c, containing granulated calcium chloride to absorb the water formed during combustion ; then follows the tared apparatus, d, containing potassium hydroxide solution (30 to 35 per cent.), which absorbs the carbon dioxide from the burnt substance and is furnished with a calcium chloride tube to retain the moisture given off by the potassium hydroxide solution. Finally follows a calcium chloride tube, e, which is not weighed, and prevents moisture entering the apparatus from the air. Before the combustion is started the apparatus is tested to ascertain if it is perfectly air- tight. This is done by closing the tap a, and sucking into e eight or ten bubbles of gas ; the slight rarefaction produced in the interior of the combustion tube causes the potash solution to rise in the first large bulb to a level which should remain constant for some minutes. The burners at the end 6 are then gradually lighted until the portion /and almost all of the portion e are heated to redness. The spiral b is then gradually heated from the a end, the heating being gradually extended under the boat so that the substance is completely burnt. During the combustion bubbles of air are passed into the tube from the gas-holder so as to' transport the gases produced into the absorption apparatus ; during the last ten to fifteen minutes a gentle current of oxygen is passed through, and then the flames are extinguished and air again passed for ten to fifteen minutes. In this way all the gases from the combustion are removed from the combustion apparatus and the copper oxide is completely reoxidised, so that the tube is ready for the next combustion. The increases in the weights of the potash and calcium chloride apparatus give the amounts of carbon dioxide and water respectively formed during the combustion, and, since 44 parts of carbon dioxide correspond with 12 parts of carbon and 18 parts of water with 2 of hydrogen, the quantities or percentages of carbon and hydrogen in the substance. can be calculated. The sum of these two percentages, when subtracted from 100, gives that of the oxygen, excepting where the substance contains nitrogen, which is determined directly by methods given later. In this way the percentage composition is determined. 1 The reduction is effected in a separate glass tube, through which a current of hydrogen is passed while the spirals are heated ; when the copper has assumed its characteristic red colour, the flames are extinguished and the spirals allowed to cool in the current of hydrogen, being afterwards kept in desiccators ready for use; or, better, when reduction is complete and the spirals are still hot, the tube is exhausted and is kept so until cold, so as to avoid the danger of hydrogen remaining occluded by the copper. 2 It consists of a small external combustion tube, c (Fig. 15), of hard glass, and about 20 cm. long and 2 cm. wide, and slightly expanded at the lower closed end. The tube is closed at the top by a rubber stopper, /, through which passes a porcelain tube, e, wound round with an electric re-istance formed of platinum -iridium wire, d; along the interior of the porcelain tube passes a thick silver wire, which starts from d, the negative pole, and ends in a small platinum wire loop and serves to convey the current (3 amps, at 20 volts). The oxygen for the combustion traverses OS and the upright tube of the stand, and passes through the porcelain tube to the bottom of the combustion tube. In the stopper, /, is fastened a piece of nickel tube, b, which is united to the + pole and to the platinum spiral, d, and serves at the same time for the escape of the gases formed by the combustion to the tube r. The gases are absorbed by the^usual tared apparatus (u = calcium chloride, p = concentrated potassium hydroxide solution), but with nitrogenous or halogenated substances the gases are first passed through a U-tube containing lead dioxide heated to 180 by means of a small furnace, ra. The connections a and b are insu- lated from one another by porcelain and rubber. When the current passes through the resistance the glass tube is heated to redness, and the substance (0-12 to 0-20 gram), mixed with cupric oxide or, better, with platini.ed porous porcelain powder, and placed at the bottom of the glass tube, is burned by heating the outside of the tube directly with a bunsen flame. The combustion is very soon completed, the platinum -iridium spiral apparently accelerating the oxidation cata- lytically ; apart from the time occupied by the weighings, this method requires fifteen to twenty minutes, and usually gives good results. For the analysis of fairly volatile liquids or of sub- stances which readily sublime, the lower part of the combustion tube is drawn out almost 10 ORGANIC CHEMISTRY An electrical method for determining carbon, hydrogen, and sulphur in organic substances was also proposed by Morse and Gray in America in 1906. QUANTITATIVE DETERMINATION OF NITROGEN. (1) Dumas' Method. The nitrogenous organic substance (0-2 to 0-3 gram) is heated in a hard glass tube similar to that shown in Fig. 13, but closed at the end, a. The portions a and b contain sodium hydrogen carbonate or magnesium carbonate; between b and c is placed a small plug of copper gauze, in c granulated copper oxide, and in d powdered copper oxide. Then follows a space 10 cm. in length in which is placed the substance to be analysed, this being weighed and mixed with powdered cupric oxide ; next comes granulated cupric oxide, and in / a spiral of reduced copper, 10 to 12 cm. long. 1 The extremity, g, of the tube is connected by means of a gas delivery tube with a graduated tube (25 or 50 c.c.) placed upside down in a basin of mercury and filled half with mercury and half with concentrated potassium hydroxide solution. This graduated tube may have the form devised by Dumas and shown in Fig. 16; the gas from the com- bustion tube passes into the tube a, furnished with a clip, m, thence through a little mercury in the bottom of the tube b, which is filled with potassium hydroxide solution and is in communication with a reservoir, c, of this solution. 2 horizontally, and the substance is mixed with platinised porcelain powder (2 to 3 per cent, of platinum); liquids may also be heated in a separate tube and the vapour then injected into the combustion tube. FIG. 15. 1 In this case the copper spiral may be rapidly reduced by heating it over a large non-luminous gas flame and dropping it into a thick-walled test-tube containing -J- c.c. of ethyl or, better, methyl alcohol; the tube is immediately closed by a rubber stopper through which passes a glass tube. The latter is connected with a pump until the spiral is cold. 2 The operation is begun by heating the combustion tube at the point whore the mag- nesium carbonate lies ; the carbon dioxide thus evolved expels the air from the apparatus into b, whence it is driven by raising the reservoir, c, and opening the cock at the top of b. The KJELDAHL'S METHOD 11 When several determinations of nitrogen are to be carried out the procedure is some- times simplified by using a combustion tube open at both ends, like that of Fig. 13, the magnesium carbonate or sodium bicarbonate being omitted and the combustion tube being connected at a with a small Kipp's apparatus for the evolution of carbon dioxide (marble and hydrochloric acid), care being taken to free the apparatus from all air by a prolonged current of carbon dioxide. (2) KjeldahVs Method (Dyer's modification). 0-5 to 1 gram of the substance is placed in a hard glass flask (200 to 300 c.c.) with a long neck, into which penetrates the stem of a funnel used to cover the flask (Fig. 17). ! 20 c.c. of concentrated sulphuric acid (66 Be.) and a drop of mercury (which acts as a catalytic oxidising agent) are added, and the contents of the flask are heated, at first gently and finally more strongly, until vigorous boiling sets in. 10 grams of potassium sulphate are then added, a little at a time, the heating being continued until the liquid is decolorised, by which time the whole of the nitrogen is transformed into ammonium sulphate. After the flask has been allowed to cool, its FIG. 16. FIG. 17. contents are washed out with water into a flask already containing 200 to 300 c.c. of water. 3 to 4 grams of zinc dust (which decomposes ammoniacal compounds of mercury and prevents bumping by the evolution of hydrogen) are then added, and the flask closed with carbon dioxide is absorbed by the potash solution, and when no more air collects in b the mag- nesium carbonate is no longer heated. The copper spiral and the copper oxide are now gradually heated in the same way as for the estimation of carbon and hydrogen, the heating being slowly extended until it reaches the substance itself. Oxides of nitrogen are decomposed by the copper spiral, so that all the nitrogen is evolved in the free state and collects in b. Finally the nitrogen remaining in the combustion tube is driven into b by means of carbon dioxide formed by again heating the magnesium carbonate. At the end of the operation, in order to measure the nitrogen, a graduated tube filled with water is inverted over d, and the cock at the top of b having been opened, the reservoir, c, is raised until all the gas passes into the graduated tube. The latter may then be removed to a large cylinder full of water and when, after a few minutes, the gas has assumed the temperature of the water (shown by an accurate thermometer) the tube, grasped by a clip (the hand would warm it), is arranged so that the level of the liquid inside it coincides with that outside, and the volume (v) of the gas read off. At the same time the atmospheric pressure (b) is read, and the exact temperature (/) of the water. The percentage of nitrogen (p) in the substance is then calculated by means of the following formula : P M&- 10). 0-12511 V. 760(1 + 0-003677<)' where s indicates the weight of substance taken, w the pressure of water vapour expressed in mm. of mercury (see Vol. I., p. 35), and 0-0012511 gram the weight of 1 c.c. of moist nitrogen at O c and 760 mm. (Rayleigh and Ramsay). ORGANIC CHEMISTRY a rubber stopper through which pass a tapped funnel containing 120 to 160 c.c. of con- centrated sodium hydroxide solution (30 to 35 per cent.) and a glass bulb (Figs. 18 and 19) communicating with a simple condensing tube dipping into a flask containing a measured volume of standard sulphuric acid and a drop of methyl orange. In order to prevent spurting of the caustic soda and its introduction into the condenser tube, the glass bulb is fitted with a delivery tube curved towards the wall of the bulb ; it is, however, as well to push into this tube, almost as far as the bulb, a small plug of glass-wool or asbestos. Solutions of soda more concentrated than 35 per cent, often lead to spurting. About one- half of the liquid is distilled and the excess of sulphuric acid remaining in the collecting flask determined by titration with alkali. Hence the amount of ammonia fixed by the acid may be calculated and so the percentage of nitrogen in the substance analysed. In Figs. 17 and 19 are shown forms of apparatus with which it is possible to carry out several determinations simultaneously. Kjeldahl's method cannot be used as it stands for the analysis of organic substances which contain nitrogen either united to oxygen (nitro-compounds) or forming part of a pyridine or similar nucleus (quinoline, etc.). In such cases the method is modified as described under Aromatic nitro-derivatives (Part III). FIG. 18. FIG. 19. (3) Will and Varrentrapp's Method. This method is based on the principle that almost all nitrogenous organic substances (which do not contain nitrogen linked to oxygen, such as the nitro-compounds), when they are heated with an alkali hydroxide or, better, with soda-lime (see Vol. I., p. 618), yield hydrogen, which transforms the nitrogen into ammonia. Little use is made of this method to-day. QUANTITATIVE DETERMINATION OF THE HALOGENS. The method most commonly used is that of Carius. The substance (0-15 to 0-2 gram) is weighed out in a small tube, which is then introduced into a large, hard glass tube 30 to 40 cm. long and 2 to 3 cm. wide, closed at one end and containing about 2 c.c. of fuming nitric acid and about 0-5 gram of solid silver nitrate ; this introduction is effected in such a way that the acid does not enter the small tube. The large tube is then softened near the open end by heating in the blow-pipe flame and gradually drawn out to a point (Fig. 20, A), the walls of the tube being allowed to thicken during the fusion (Fig. 20, B, shows the upper part of the tube on a larger scale) . After being allowed to cool in a vertical position, the tube is introduced into a thick- walled iron sheath, which is closed with a screw-cap. It is then safe to incline the tube and introduce it into a bomb-furnace (Fig. 21), which holds four or more tubes and is raised slightly at one end ; this is heated for 4 to 6 hours, the tem- perature being raised gradually to about 250. Sometimes the tubes burst owing to the great internal pressure, but without danger from flying fragments of glass owing to the protection of the iron sheaths and of the folding shutters at the ends of the furnace, these being lowered during the heating. At the end of the operation, when the tube is cool, it is taken from the iron sheath, held in a vertical position, and its point (Fig. 20, A a) softened in a bunsen flame. When the pressure in the tube has been thus relieved, a scratch is made with a file at the point marked b, and the file-mark touched with a red-hot glass rod, with the result that the upper part of the tube breaks off. The tube is then carefully emptied and washed out into a CALCULATION OF FORMULAE 13 beaker with water, the small tube, held in pincers or a piece of platinum wire, being well washed inside and outside before removal. The liquid is heated and the precipitated silver halogen compound is then collected on a filter, washed, dried in an oven, detached from the filter and heated in a weighed porcelain crucible until it just begins to melt. After being allowed to cool in a desiccator, the crucible is weighed and the amount of halogen contained in the organic substance calculated from the weight of silver haloid. QUANTITATIVE DETERMINATION OF SULPHUR AND PHOSPHORUS. This is carried out by the Carius method in the same way as for halogens, except that no silver nitrate is introduced into the tube. At the end of the heating, the sulphur is obtained as sulphuric acid or the phosphorus as phosphoric acid, estimation of the amounts of these acids being effected by the ordinary methods. The halogens, sulphur and phos- phorus, may also be determined after fusion of the substance with pure sodium peroxide. CALCULATION OF THE EMPIRICAL FORMULA. From the results of the elementary analysis of an organic substance may be calculated the percentage composition, i. e., the quantity of each component in 100 parts of b A 1 A FIG. 20. FIG. 21. substance. To deduce the chemical formula, that is, the proportions in which the different atoms enter into the molecule, the percentage weight of each component is divided by the corresponding atomic weight, the numbers thus obtained giving the proportions between the numbers of atoms of the different elements. These numbers sometimes give directly the numbers of atoms contained in the molecule, but in other cases they represent multiples or submultiples of the real numbers of atoms. If, for example, lactic acid is analysed, the percentage composition is found to be : C, 40 per cent. ; H, 6'6 per cent. ; 0, 53 "4 per cent. ; by dividing these numbers by the corresponding atomic weights, the following numbers are obtained: C, 3'3 (i.e., ?); H, 6'6 ( G -j?) ; and 0, 3'3( 5 -2 ? 4 ). These proportions have a common factor, 33, and division by this gives 1C, 2H, and 10, i. e., CH 2 O, which is an empirical or minimum formula, the simplest formula express- ing the proportions between the numbers of atoms of the different elements. This minimum formula does not, however, represent the molecular magni- tude, and, in fact, analyses of formaldehyde, acetic acid, grape sugar, etc., give the same percentage composition and the same minimum formula, CH 2 O, which must hence be a submultiple of the formulae of these substances. 14 ORGANIC CHEMISTRY A knowledge of the percentage composition is not sufficient to determine the true molecular formula; the molecular magnitude, i.e., the molecular weight, must also be known in order to permit of a choice between the various multiples. By making use of one of the methods described in Vol. I., " In- organic Chemistry " (pp. 34 et seq.), the molecular weight of lactic acid is found to be 90, so that, of the various possible formulse, CH 2 O (mol. wt. 30), C 2 H 4 2 (mol. wt. 60), C 3 H 6 3 (mol. wt. 90), C 4 H 8 O 4 (mol. wt. 120) .... C 6 H 12 6 (mol. wt. 180), etc., only C 3 H 6 3 corresponds with lactic acid. Even this formula and the empirical formula, however, tell nothing concerning the grouping of the atoms in the molecule which, as is explained in the following pages, is given by the constitutional formula. DETERMINATION OF THE MOLECULAR WEIGHT BY CHEMICAL MEANS In lactic acid one-sixth of the hydrogen may be substituted by a metal, so that there must be at least six (or a multiple of six) atoms of hydrogen in the acid, the empirical formula being necessarily at least trebled, giving C 3 H 6 3 . To ascertain if this is the true formula, a derivative of the acid is prepared, such as the silver salt, which may easily be obtained pure. Analysis of this salt shows it to contain 54-8 per cent, of silver, and the atomic weight of silver being 107-7, calculation indicates that the residue of the lactic acid combined with 107-7 parts of silver weighs 89. Assuming that only 1 atom of silver has entered the lactic acid in place of 1 of hydrogen (as may, indeed, be deduced from the fact that the quantity of hydrogen in the salt is five-sixths of that originally present in the acid), the weight of the lactic acid would be 89 -f 1, or 90. The true formula of the acid would hence be that corresponding with a molecular weight of 90, . e., C 3 H 6 3 . For acid substances in general this cJiemical method may be employed for determining the molecular weight, making use of the silver salt and determining if the acid is mono-, di-, or tri-basic (that is, ascertaining if the silver replaces 1, 2, or 3 atoms of hydrogen), the calculation being then based on the presence of 1, 2, or 3 atoms of silver in the salt. For basic substances, the molecular magnitude may be determined chemically by analysing the platinichlorides, the formulae for which are always of the type of that of ammonium platinichloride : PtCl 4 (NH 3 -HCl) 2 , the ammonia being replaced by the organic base, which is mono- or di-acid, according as it replaces one or two molecules of ammonia in the platinichloride. For other (indifferent) organic substances derivatives are prepared by substituting chlorine atoms for one or more hydrogen atoms, the proportion of chlorine being then estimated ; the calculation is then similar to that described above. The chemical method for determining the molecular magnitude does not always give certain results : experimental difficulties sometimes occur and often entail great labour. Consequently the determination of molecular weights is usually effected by physical methods : vapour density method, cryoscopic method, ebullioscopic method, etc., these being all described and illustrated in Vol. I. (Part I). POLYMERISM It sometimes happens that the analysis of different substances shows them to have the same percentage composition, although their chemical and physical properties are different ; thus, for example, acetic acid, lactic acid, glucose, etc., contain the same elements, C, H, and O, in the same proportions, there being 2n hydrogen atoms and n oxygen atoms for n carbon atoms. Accurate study of these compounds and determination of the molecular magnitude (molecular weight) show that the differences depend on the true formulae being multiples of the minimum or empirical formula. Thus, whilst the molecule of acetic acid is represented by C 2 H 4 O 2 , that of lactic acid RADICLES AND TYPES 15 corresponds with C 3 H 6 O 3 , and that of glucose with C 6 H 12 6 . These molecules are hence all multiples of a hypothetical complex CH 2 O, the ratios (but not the absolute quantities) between carbon, hydrogen, and oxygen being the same (1:2:1) in all cases. These compounds are termed polymerides and the phenomenon is known as polymerism. In some instances, however, it happens that the molecular magnitude is not sufficient to differentiate certain compounds, which, besides containing the same elements in the same proportions (equal percentage compositions), have also the same molecular magnitudes, although differing in their physical and chemical properties. To explain the existence of these isomeric compounds, the chemical nature of carbon must be studied more in detail. VALENCY OF CARBON, ISOMERISM, AND CONSTITUTIONAL FORMULA On the foundation of multivalent radicles, 1 discovered by Odling, and of the investigations of Frankland (1852), which showed that nitrogen, 1 Theory of Radicles and Types. In the first twenty years of last century, various compounds were discovered which stood in apparent contradiction to the electro-chemical theory of dualistic formulae, put forward by Berzelius (Vol. I., p. 46); in fact, in certain compounds the hydrogen (electro-positive) was replaced by chlorine (electro-negative) without appreciably changing the chemical characters of the original compounds. It was then that chemical compounds came to be represented by unitary formula, no account being taken of the grouping of the atoms in the molecule. Gradually, however, as the number of new organic substances increased, certain analogies became evident in their chemical behaviour. In studying cyanogen Gay-Lussac (1815) had indeed met, in various reactions and in various substances, the residue or radicle CN, which behaved as a monovalent element (like the halogens), combining with one atom of different monovalent metals, etc. In 1832 Liebig and Wohler discovered and studied a monovalent atomic group or radicle, benzoyl, C 7 H 6 0, which was found in oil of bitter almonds combined with an atom of hydrogen (C 7 H 6 0); on oxidation by the air, this essence became transformed into benzoic acid, C 7 H 6 2 , which with PC1 5 gave benzoyl chloride, C 7 H 5 OC1, and this, in its turn, gave the aldehyde C 7 H 6 0, when treated with nascent hydrogen, or benzoic acid under the action of water. All these compounds contain the monovalent benzoyl nucleus, C 7 H 5 0, which passes unchanged from one to the other by combining with monovalent atoms or groups. In 1833, in a classic work, Bunsen studied another radicle, cacodyl, which is a monovalent organic arsenic /-ITT residue, As etc ' From the fourth type, Hofmann and Wurtz deduced theoretically and prepared in the labora- tory a large number of compounds, part or all of the hydrogen atoms of ammonia being replaced ; C 2 H 5 ) C 2 H 5 | CH 3 | for example, ethylamine, H rN ; diethylamine, G 2 H 5 N ; trimethylamine, CH 3 > N ; acetamide, Hj H) CH H IN, etc. To explain the existence of polybasic acids and various other substances, Odling, Williamson, and Kekule had recourse to the idea of multiple types, sulphuric acid being regarded as derived H Q H) Q from the double water type, TT{ , thus S0 2 j-^, and similarly succinic acid, C 4 H 4 O 2 -Q, etc.; H } H J - for glycerol a triple type was assumed, and so on. H l H I In 1856 Kekul6 introduced another very important type, that of marsh gas, jj VC, with H J tetra valent carbon, to which he referred numerous organic compounds ; also certain compounds PTT i NH 2 "| 3 H may be referred both to marsh gas and to ammonia, for example, methylamine, H -N, or r > C, H ' nj and from these different methods of considering the constitution and the reference to different types, were deduced various processes for preparing one and the same compound from different starting materials. ISOMERISM 17 carbon atoms among themselves and which can be saturated by different elements (usually H, O, N), giving rise to an enormous number of organic compounds. 1 The physical and chemical differences of these compounds, termed isomerides, are explained by the different grouping or linking of the atoms in the molecule. In their chemical transformations, isomerides give up or exchange quite different atomic groups or atoms, owing to the different functions and positions occupied by these atoms or groups in the molecule. The first cases of isomerism were discovered by Berzelius in 1833 during an investigation of racemic acid. It is hence not sufficient to represent organic compounds by an empirical molecular formula, the structural or constitutional formula, deducible from the graphic representation of the chains illustrated above, being necessary in many cases to distinguish between isomerides. To decide which of two isomeric formulae should be assigned to a given substance, various chemical reactions are carried out with the substance, study of the resultant new products indicating the constitutional formula. 2 1 The following are some of these hypothetical carbon atom chains : C^ C/ &- C/ C^ C< C- |\ || \ HI II x (1) I); (2) ||>; (3) ||j ; (4) C= ; (5) C_; (6) C ; (7) C ; Cf C/ C |/ |/ \, \\ / C(- C/ C/ C/ Hexavalent Tetravalent Divalent \ \ \ . \ A \ C= C C C (8) ; (9) C-C-,etc. (10) (11) || | ; C- -C<=V- ; \/ < i A >C C< C C C C C (13) I I ; (14) I || ; (15) | || | >C C< C C C C C \o/ \N/ \0/\0/ A I I Among these chains are two (Nos. 8 and 9) containing four carbon atoms and having equal numbers of free valencies. By saturating these ten free valencies with ten H atoms two com- pounds are obtained (these have actually been prepared) which contain equal numbers of C and H atoms, and have therefore the same percentage composition and the same molecular weight. 2 An example will render these ideas clear : It is found that ethyl alcohol (ordinary liquid alcohol) and gaseous methyl ether have different physical and chemical properties, although they possess the same percentage composition and the same molecular magnitude, represented by the formula C 2 H 6 0. The constitutions or internal molecular structures of the two compounds are determined by a study of the following chemical reactions : treatment of the alcohol with hydro- chloric acid gives first a compound C 2 H 6 C1 (ethyl chloride), one atom of monovalent chlorine having replaced one atom of oxygen and one of hydrogen or a hydroxyl residue, OH. By means of nascent hydrogen, the chlorine atom of ethyl chloride may be replaced by a hydrogen atom, giving the compound C 2 H 6 (ethane). These reactions are hence expressed by the following equations : (1)'C 2 H 5 OH + HC1 = H 2 + C 2 H 5 C1; (2) C 2 H 5 C1 + H 2 = HC1 + C,H 6 ; ethane, H \ /' H however, can have only the constitution, H^C C\-H, i. e., CH 3 CH 3 , so that the alcohol will H/ X H H\ /OH have the constitution H-/C C< H W \H On the other hand, it is found, by various reactions, that the six hydrogen atoms of methyl ether present no difference one from another, and, no matter under what conditions hydriodic acid acts on the ether, it eliminates the oxygen as water, and another product is obtained which contains only one carbon atom in the molecule : The reaction hence takes place according to the equation : It is evident, then, that in methyl ether the six hydrogen atoms are united homogeneously VOL. II. 2 18 ORGANIC CHEMISTRY Use is not always made of constitutional formulae, since they are not simple and are often inconvenient to write; hence attempts are made to simplify them by indicating the more important groups or residues, contained in the molecule and giving at the same time an idea of the constitutions and of the functions of these groups ; this is done by means of the so-called rational formula. The rational formula of ethyl alcohol will be C 2 H 5 OH, in which the monovalent OH residue, characteristic of all the alcohols, is separated; that of acetic acid will be CH 3 COOH, the group COOH being characteristic of, and common to, all organic acids, etc. METAMERISM. Constitutional and rational formulse explain clearly isomerism in general and also the special case bearing the name metamerism. When, to an atom of a polyvalent element are united one or more groups in their different isomeric forms, we have special cases of isomerism for definite groups of substances. 1 PSEUDOISOMERISM, TAUTOMERISM, DESMOTROPY. A substance sometimes contains atomic groups that occupy a very precarious (labile) position, since they exert certain influences one on the other and under given conditions may react in different ways, giving now one new substance and now another ; this explains how it is that some compounds having a well-defined chemical character may, under some conditions, behave like substances with other chemical characters, without it being necessary to assume a true change of constitution. Thus, for example, some of the derivatives of cyanic acid, CN ' OH, behave like derivatives, sometimes of the formula N = C OH and sometimes of the formula NH = C = 0, when the hydrogen atom is replaced by a given radicle. The same is the case for derivatives of cyanamide, N C NH 2 , and of carbodiimide, NH = C = NH, and of the two non- I I nitrogenous types, -C(OH) = C CO and CO CH - CO , where a hydrogen atom oscillates between the two carbon atoms. These compounds exist usually in only one form, the more stable one, but in the derivatives this stable form, simply on heating, is transformed into tbe labile one. For this phenomenon Baeyer proposed the name pseudoisomerism, and others that of desmotropy ; it may be assumed that the Other isomeride is present in minimal quantity, not detectable by ordinary reagents. These forms may be distinguished sometimes by chemical reactions, but more generally by the molecular refraction, dielectric constant, magnetic rotation, electrical conductivity, etc. (Under the heading Ethyl acetoacetate, Knorr and Meyer's method for separating the two forms is described.) In various substances, where several hydroxyls are present in more or less to the two atoms of carbon and that the carbon atoms are joined, not directly, but indirectly, by means of an oxygen atom, which is readily eliminated. The constitutional formula of methyl ether will hence -be : H \ / H H^C C^H or CH 3 CH 3 . H/ \H >C 3 H 7 r For example, in the compound, N\~ H , the monovalent group C 3 H 7 may be present in /CH 3 its isomeric forms, i. e., either as CH, GEL CH, or as C^H . Although there is con- \CH 3 siderable resemblance between these two compounds, their different constitutions are manifested in certain chemical and physical properties. The following compounds are also metameric /CH 3 X CH 3 isomerides : Nx-C 2 H 5 and N^ CH 3 ; in fact, although the percentage compositions and molecular ^CH 3 magnitudes are the same in both cases, the substituent groups of the ammonia molecule are different and the compounds belong to different categories disubstituted and trisubstituted ammonias. STEREOISOMERISM 19 adjacent positions, there is often a tendency for intramolecular transformation to take place with condensation of two of these groups and separation of a molecule of water, giving rise to isomeric anhydrides, ethers, ketones, or alcohols, etc. In their turn, these derivatives or isomerides, which may be transformed one into the other, give rise to distinct classes of compounds ; this isomerism is called tautomerism, and may be regarded as dynamic rather than static isomerism. STEREOISOMERISM OR ISOMERISM IN SPACE. We have already seen that, by the tetra valency of carbon and its property of uniting with itself to form various chains, it is possible, in certain cases, to explain the existence of isomerides, which have the same percentage composition and molecular magnitude, but different groupings within the molecules. Many cases of isomerism, foreseen from theoretical considerations, have since been actually met with and different isomerides have been prepared artificially- after their existence had been foretold. For a long time, however, certain compounds were known for which ordinary isomerism did not provide any explanation; among these the most important, from an historical point of view also, are the four dihydroxysuccinic acids (tartaric acids), of which two (ordinary tartaric acid and racemic acid) were studied by Berzelius as long ago as 1830. To these must be added Isevo-rotatory tartaric acid and mesotartaric acid, discovered by Pasteur. All these compounds have the same internal grouping of the atoms, although they are isomerides ; it is not possible to distinguish between them by chemical reactions, but they may be clearly differentiated by their physical behaviour : they form Jiemihedral, i. e., symmetrical, but non-superposable crystals (related as an object to its image in a FIG. 22. mirror) : they have, too, different actions on polarised light, the plane of which is turned to the right by some and to the left by others. These acids are hence known as physical or optical isomerides. Pasteur attempted to explain this isomerism by supposing the atomic groups to be arranged unsymmetrically in the molecule, in some cases in a dextro-rotatory spiral and in others in a Isevo-rotatory spiral, or arranged at the vertices of an irregular tetrahedron. When other similar isomerides the lactic acids had been discovered, J. Wislicenus, in 1873, suggested that isomerism of this kind could be explained only by regarding the groups or atoms of these compounds as arranged in space so as to form distinct configurations. This isomerism in space (stereoisomerism) was explained by van 't Hoff and Le Bel (1874), independently, by means of the hypothesis of the asymmetric carbon atom. The starting-point of this hypothesis was Kekule's idea (1867) of regarding, for the sake of convenience, the carbon atom .as situated at the centre of a regular tetrahedron, and its four affinities as directed towards the four vertices, i. e., arranged homogeneously in space (Figs. 22, 23). If these affinities are satisfied at the vertices by monovalent atoms or atomic groups, the following cases present themselves : no isomerism is possible in the compounds Ca 3 b, Ca 2 6 2 , Ca 2 be, and Ca b 2 c, where a, b, and c indicate either atoms other than carbon or groups of atoms (I, H, OH, etc. ) ; the compound CH 2 I 2 exists in only one form, and if we put the four atoms (H 2 and I 2 ) at the apices of the carbon tetrahedron, no matter how their positions may be changed, it is not possible to find two different, i. e., non-superposable, arrangements. If, however, the four groups or atoms combined with the carbon atom are all different, e. g., Cabcd, two isomerides are possible, and in this case the carbon atom is termed asymmetric ; in fact, if these atoms or groups are arranged, in one case, so that the circle a, b, c has a sense opposite to that in which the hands of a clock move (Fig. 24, I) (called, therefore, dextro-rotatory isomerides, and indicated by d- or by the sign -J- ) and, in the other, in the opposite sense (Fig. 25, II) (termed Icevo-rotatory 20 ORGANIC CHEMISTRY isomerides, like levulose, and indicated by I- or ), two non-congruent configurations are obtained; these cannot be superposed, one on the other, in such a way that the same groups occupy the same positions in the two cases. These two figures represent two different isomerides and are related in the same way as an object to its mirror-image or as the left hand to the .right. Such isomerism is called enantiomorphism. These two different arrangements of the atoms round the asymmetric carbon atom also explain how it is that, when polarised light traverses these molecules, its plane of polarisation is rotated, in one case to the right and in the other to the left. Van 't Hoff and Le Bel pushed their deductions still further, and showed that the dextro-optical deviation should be numerically equal to the leevo-optical deviation of the corresponding isomeride. This has been confirmed practically, and it also follows that when a pair of FIG. 27. FIG. 28. such isomerides are mixed in equal proportions, there should result an optically neutral mixture, thus giving rise to a special inactive or racemic isomeride. A substance with only one asymmetric carbon atom always gives three stereoisomerides (for example, three lactic acids). It has also been deduced theoretically and proved practically that all optically active compounds contain at least one asymmetric carbon atom,* although not all compounds con- taining asymmetric carbon atoms are optically active, since the molecules may contain groups which neutralise each other's activity. Many examples illustrating these principles will be discussed later in the special part of this book ; meanwhile mention may be made of the most important of these compounds : leucine, asparagine, coniine, the lactic acids (hydro xypropionic acids), etc., which contain one asymmetric carbon atom and give, in each case, three stereoisomerides. FIG. 30. These cases of stereoisomerism, and those which follow, will be understood more easily if studied by means of cardboard tetrahedra with differently coloured vertices. When the substance contains two asymmetric carbon atoms, the number of stereo- isomerides increases as follows : If we take two tetrahedra like that shown in Fig. 26, 1, or Fig. 28, II, representing two similar molecules which contain only one asymmetric carbon atom and in which the groups a, b, and c, satisfying three of the valencies, are arranged in a dextro-rotatory sense, and 1 Or else an asymmetric atom of nitrogen (see later) or sulphur, tin, etc. The exceptions to this rule are very rare and uncertain, one of the cases most discussed during recent times (1909- 1910) being l-methylcydohexylidene-l-acetic acid, which does not appear to contain an asymmetric carbon atom, but is optically active. A L L O I S O M E R I S M 21 superpose one tetrahedron on the other, so that the free valencies satisfy one another, there results a new isomeride, i. e., a molecule with two dextro-rotatory asymmetric carbon atoms, as shown in Figs. 27 and 29. * If we joiri two Isevo-rotatory carbon atoms (Fig. 28, II), that is, the mirror image of Fig. 26, I, a Isevo-rotatory isomeride (Fig. 30, II) is obtained. Finally, if one dextro-rotatory (Fig. 26, I) and one laevo-rotatory asymmetric carbon atom (Fig. 28, II) are united, a third stereoisomeride is obtained, which is permanently optically inactive (Fig. 31, III), the effect produced on polarised light by one asymmetric carbon atom being destroyed by the effect of the other. In order to understand these stereochemical speculations better, we may apply them to the isomerism of tartaric acid, which has the formula C 4 H 6 O 6 , and contains two asym- metric carbon atoms (marked with _ asterisks) to which are joined the groups OH, CO 2 H, and H : CO 2 H F CCLH FIG. 33. If, for the letters a, b, and c of the tetrahedra considered above, we substitute the groups OH, CO 2 H, and H, and if the tetrahedron of Fig. 26, 1 (which we shall call + A ) be represented as if projected on to a plane, thus : a C c or OH O H (dextro- \ I VI b CO,H rotatory), and that of Fig. 28, II ( A), thus: cC a or H C OH (tevo-rotatory), I/ \ S b C0 2 H we arrive at the following stereoisomerides of tartaric acid : I. By joining two + A atoms, we get d-tartaric acid (Fig. 29 or 32, I). II. By joining two A atoms, we get Z-tartaric acid (Fig. 30 or 32, II). III. By joining one + -4 atom with one A atom, we have the permanently inactive mesotartaric acid (t-tartaric acid), as may be seen in Fig. 31, III, or 32, III. IV. By mixing, mechanically, equal parts of acids I ( + ) and II ( ), there results racemic acid, apparently inactive, but from which, by mechanical means (by hand with the aid of a lens), the two forms of crystals may be separated. It is often assumed that the two asymmetric carbon atoms can rotate independently on the common axis joining them, so that if the groups of one asymmetric carbon atom exert an attraction or influence on those of the other, a most favourable position could be attained, a chemical reaction being sometimes possible between one group and another with separation of, say, water and loss of the freedom of rotation ; to the new isomerism thus created we shall refer shortly. STEREOISOMERISM IN DERIVATIVES WITH DOUBLY LINKED CARBON (ALLOISOMERISM). By means of the tetrahedra, we can show a double linking between two carbon atoms by arranging one side of one tetrahedron (carbon atom) in contact with a side of the other (Fig. 33). With such an arrangement, even without asymmetric carbon atoms, isomerism is possible. In fact, a compound i^>C = G<^, forms the following isomerides : (1) that shown in Fig. 34, where the two similar atoms or groups of atoms, e. g., a and a, although 1 Looking at the order in which the letters a, b, and c come in the two asymmetric carbon atoms, it would seem that these are not dextro-rotatory, but this is because the upper carbon atom has been turned through 180 from its position in Fig. 26; if its base is brought down, its identity with the other dextro-rotatory atom becomes evident. 22 ORGANIC CHEMISTRY aCb united to two different carbon atoms, occupy adjacent positions : || , or cts-positions a C b (cis-isomerism); such a molecule exhibits plane-symmetry, the two pairs of similar groups lying to the left and right, respectively, of the perpendicular plane containing the common side (double linking); (2) that shown in Fig. 35, a K~ ' 3 " where two similar groups occupy non-adjacent or diagonally opposite or irons- positions || , this form exhibiting centro-symmetry. y JG 34 Yia 35 Similarly, a compound of the type a >C = C so that the explosive limit (5-5 per cent, of CH 4 ) may be reached without discovery in this way. When mines are being excavated, safety explosives (which see) are used to avoid fires and explosions. Sometimes. the coal ignites in'certain parts of the mine; in such cases, work is not suspended, but these parts are isolated by i walls, and if the fire becomes threatening, recourse is had (usually with success) to the sealing of the mine and subsequent inundation with water or filling of the galleries with carbon dioxide. When an explosion occurs in a mine, a large amount of carbon monoxide is formed, which poisons the workers, who can, however, sometimes be saved if they can be made to breathe, sufficiently promptly, under a bell containing compressed air (Mosso's Method; Vol. I., p. 190). 36 ORGANIC CHEMISTRY the present day is carried out rationally and on a vast industrial scale, the gas (issuing from suitably constructed wells) passing to large gasometers which distribute it directly to factories and houses, where it is employed for power, heating, and lighting (with the Auer mantle), the price being about 3J cents per cubic metre. The gas utilised in the United States of America represents the following values in pounds sterling: in 1882, 40,000; in 1890, 1,400,000; in 1894, 2,800,000; in 1899, 4,000,000; in 1906, 9,600,000; in 1908, 11 '4 milliards of cu. metres were, used and in 1911, 15 milliards (14,000,000). These gases have the sp. gr. 0-624 to 0-645, and a calorific value of about 9000 cals. per cu. metre. The composition varies between the following limits : CH 4 , 80 to 95 per cent. ; H, 0-5 to 1-5 per cent, (sometimes 15 per cent.) ; C 2 H 4 , 0-3 to 4 per cent. ; CO, to 0-6 per cent. ; CO 2 , 0-3 to 2-5 per cent. ; O, 0-35 to 0-80 per cent. ; N, 0-5 to 3-5, together with traces of H 2 S. In Canada, 400 wells are being used, giving, in 1907, gas of the value of 1 20,000. In England, wells have been sunk since 1900 which yield 400,000 cu. metres of gas per day. The spring at Wels, in Austria, which gave 57,000 cu. metres of gas per day in 1894, yielded only 500 cu. metres per day in 1901. At Kissarmas, near Sarmas (Hungary), a well yielded in 1909 1,700,000 cu. metres of almost pure methane per twenty-four hours at a pressure of 30 atmospheres. The first source of natural gas in Germany was discovered in 1910 at Neuengamme at a depth of 248 metres, the gas issuing at 25 atmospheres' pressure and maintaining for a long time the per- centage composition : CH 4 , 91-6 ; H, 2-3 ; C0 2 , 0-2 ; O, 0-7 ; N, 4-4 ; heavy hydrocarbons, 0-8. The gases obtained from the deposits of potash salts at Stassfurt (see Vol. I., p. 530) have a varying composition : CH 4 , 5 to 40 per cent. ; H, 1 1 - to 80 per cent. ; N, up to 40 per cent. ; helium and neon, 1 per cent. The value of these methane springs may be estimated from the fact that one ton of coal yields only 300 cu. metres of gas. The gas which is used at Salsomaggiore (Piacenza) for public lighting purposes and which issues from the earth together with petroleum and saline waters containing iodine, has the sp. gr. 0-692, and the following percentage composition (Nasini and Anderlini, 1900) : CH 4 , 68; C 2 H 6 , 21 ; heavy hydrocarbons, 1 ; N, 8. In Italy, 1,520,000 cu. metres of these gases, of the value 2280, were used altogether in 1902, 6,737,500 cu. metres in 1908, and 8,270,000 cu. metres, of the value 8760, in 1909. Important sources of these gases have been recently discovered in Hungary (in 1911 at Klausenburg, where the well gave 800,000 cu. metres per day of gas containing 99 per cent, of methane in 1913), England (at Heathfield a well gave as much as 500,000 cu. metres per day), and in Denmark (since 1872). ETHANE, C 2 H 6 This gas is found dissolved in crude petroleum, and is one of the principal constituents of the North American gas-wells of Delamater, near Pittsburg. It is a gas which can be liquefied at by means of a pressure of 24 atmospheres and then has the sp. gr. 0-446 ; at the ordinary pressure it becomes liquid and boils at 84 and is solid and melts at 172. It is almost insoluble in water ; 1 vol. of absolute alcohol dissolves 1 \ vols. of it. It burns with a faintly luminous flame, and is more readily soluble than methane. In the laboratory it is prepared by the general methods already given (p. 33). PROPANE, C 3 H 8 (METHYLETHYL, CH 3 'C 2 H 5 or DIMETHYLMETHANE, CH 2 (CH 3 ) 2 ) This is a gas like ethane and becomes liquid at 44, or under 5 atmospheres' pressure at 0, the liquid at having the sp. gr. 0-535 ; it solidifies and melts at 45. It is slightly soluble in water, and absolute alcohol dissolves 6 vols. of it. With water under pressure and at temperatures below it forms a solid hydrate, which decomposes at + 8-5. The illuminating power of propane is about \\ times that of ethane. It is best prepared, in the laboratory, by reducing isopropyl iodide by means of the copper-zinc couple, or by reducing acetone or glycerol with hydriodic acid : C 3 H 5 (OH) 3 + 6H= 3H 2 O+ C 3 H 8 or CH 3 CO CH 3 + 4H = H 2 O + C 3 H S . glyceroi acetone HIGHER PARAFFINS 37 BUTANES, C 4 H 10 (Two Isomerides) (a) Normal Butane, CH 3 CH 2 CH 2 CH 3 (diethyl), is a gas which liquefies at -f- 1, and at has the sp. gr. 0-600. It is found in Pennsylvanian petroleum, and is prepared in the laboratory by the ordinary methods (p. 33). CTT (b) Isobutane, CH 3 CH< nH . 3 (trimethylmethane or methylpropane), is a gas which (jtl 3 becomes liquid at 115; it is contained in petroleum and is prepared by the usual methods in the laboratory. PENTANES, C 5 H 12 x These hydrocarbons are found especially in the petroleum products boiling a little above 0, and are placed on the market under the names of rhigolene and cymogen for anaesthetic purposes and for the manufacture of artificial ice. The three isomerides predicted by theory are known : (a) Normal pentane, CH 3 [CH 2 ] 3 CH 3 , is a colourless, mobile liquid boiling at -f 37-3, having the sp. gr. 0454 at 0, and solidifying only at about 200 ; it is hence used for making low-temperature thermometers, and as a lubricant in the Claude liquid air machine (Vol. I., p. 345). It occurs abundantly in Pennsylvanian petroleum. (b) Isopenfane, CH 3 CH CH 2 CH 3 (methyl-2-butane or ethylisopropyl), is a light CH 3 colourless liquid boiling at 30-4, and having the sp. gr. 0-622 at 20. It is found in large quantities in petroleum, and may be prepared artificially from isoamyl iodide by the ordinary methods (p. 33). riTT /-ITT (c) TetramethylmetJwme, r , T r 3 !>C<; riT _ r 3 (dimethyl-2-propane), is found in the gases from UrL 3 OrL 3 petroleum, and is liquid at -f 9 and solid at 20. It may be obtained in the laboratory either by chlorinating acetone, CH 3 CO CH 3 , by means of phosphorus pentachloride and treating the dichloropropane thus formed with zinc methyl : ^ 3 CH 3 C1 + < CH 3 ~ 2 CH 3 CH 3 or from tertiary butyl iodide by the action of zinc methyl :__ j _ ^ 3 T CH 3 I , which, when released (by a lever, h), opens automatically a small window in the cover; at the same instant a small oil-flame passes through the window and is immediately withdrawn, the window then closing. The petroleum receiver is surrounded by an air-chamber, A, which is heated to 55 in the reservoir, W, regulated by the thermometer t z . For every 0-5 increase of temperature of the petroleum, the spring is released, this being continued until the flame ignites and explodes the mixed petro- leum vapour and air. The slight explosion sometimes extinguishes the flame. The temperature shown at this moment by the thermometer ^ is that of inflammability (flash-point), which is, however, influenced by the atmospheric pressure and should be corrected by -f- 0-035 for every mm. of pressure above 760 mm. In Italy, Germany, and Austria the sale of petroleum for lighting purposes is prohibited if it shows a flash-point below 21 in the Abel apparatus; otherwise explosive vapours could be formed in ordinary lamps, even at 30 or 32, which would be dangerous. A petroleum inflammable at above 60 (Abel) cannot be used for lamps. A rough-and-ready test to detect if a petroleum is dangerous consists in pouring a little into a glass and throwing into it a lighted match ; if the latter is extinguished, the petroleum is safe. The illuminating power is determined with the Lummer and Brodhun photometer (see Fig. 77, p. 63). To determine the moisture or water, which does not separate well in the distilla- tion of certain Calif ornian petroleums, Robert and Fraser (1910) proposed adding calcium carbide and measuring the quantity of acetylene formed, this depending on the amount of water present. BENZINE 85 The crude benzine is redistilled in small horizontal or vertical boilers, usually heated by superheated steam either in a jacket or in closed coils inside the boiler, the condensed water being collected outside the boiler. When there are many volatile products, an apparatus similar to that used in the rectifica- tion of spirit is employed (see chapter on Alcohol ) ; the heating is effected by means of iron (not copper) coils, through which steam passes, and the dephlegmation is carried out first with water and then with air. Such a system of rectifying columns is to-day in general use, and the condensation of the vapours and the cooling of the condensed benzine are effected by the crude benzine, which is thus fractionated and fuel at the same time economised. A special apparatus for condensation and rectification, devised by Veith, consists of five iron double-walled cylinders (with water-circulation), connected in series and ter- minating in a sixth cylinder containing a coil with many turns for the condensation of the vapour from the preceding cylinder. The coil is cooled by ice and cold water, which then passes successively into the jackets of the other five cylinders and gradually becomes heated. These five cylinders are three-fourths full of pure iron turnings free from oil. The vapours from the boiler in which the benzine is distilled pass through cylinders 1 to 5, in each of which that part condenses which is liquefied at the temperature of the water circulating in the jacket. The least volatile products condense in the first cylinder and the most volatile ones in the final coil. At the bottom of each cylinder is a pipe with a tap communicating with a tank. The apparatus for distilling and rectifying benzine are so constructed that the vapour above the boiling liquid which is mixed with air is separated' from the liquid, e. g., by metal gauze, so that in case of fire or explosion the liquid does not ignite. Baku petroleums give only 0-2 per cent, of benzine, and those of Grosny (Russia) about 4-5, per cent. In 1902, 341,000 tons of naphtha were distilled at Grosny, 14,000 tons of benzine (about 4 per cent.) being obtained. Pennsylvanian petroleums give up to 12 per cent, of benzine, and those from Campina (Roumania) 3 to 5 per cent. ; a petroleum from Anapa (Caucasus) gave 28 per cent. Italian petroleums from Emilia yield 30 to 35 per cent, of benzine. After the fractional distillation of the benzine the separate portions are often refined by treatment with concentrated sulphuric acid mixed with 0-2 per cent, of potassium dichromate and 0-01 per cent, of lead oxide. Fuming sulphuric acid also gives good results, but animal charcoal and magnesium hydrosilicates are not very satisfactory. The treatment is carried out in closed vessels with mechanical stirrers (the use of compressed air being inapplicable here), similar to, but smaller than, those used for refining petroleum (see Fig. 88, p. 78). After removal of the acid, the benzine (not stirred) is treated with a spray of water, which is then withdrawn from below. The benzine is next mixed for some minutes with 1 to 2 per cent, caustic soda solution which is decanted off, two washings with water then following. In some works a single refining of the crude benzine, prior to rectification, is preferred, counter- current apparatus in series effecting continuous refining. The benzines obtained by destructive distillation according to the cracking process (see pp. 33 and 87) cannot be refined by means of sulphuric acid, since they are rich in unsaturated hydrocarbons, which give considerable heating with the acid. Such benzines are of less commercial value than ordinary benzines, to which they are added in small proportions. Benzine is produced mainly at Baku and in Pennsylvania, but some is refined in Germany and large quantities are sent to Europe from the East Indies from Java, Sumatra, and Borneo ; Galicia and Roumania also yield large quantities. Commercial benzines are of various qualities, and as they consist of mixtures of different hydrocarbons, they have no well-defined characters, their densities and boiling-points varying between certain limits established by commercial usage and depending on the origin of the product. Thus, American automobile benzines (petrols) have the sp. gr. 0-695 to 0-705, and the b.-pt. 60 to 100, whilst for Indian benzines the sp. gr. is 0-705 to 0-715 and the b.-pt. 65 to 120. It would be more rational to lay down the rule that the first drop should not distil below 60 and the last drop not above 100 (or 120 for Indian benzine), and that at 95 (105 for Indian) at least 95 per cent, should distil, and that at 100 (or 120) not more than 1 per cent, of residue should remain. Rational rectification of crude petroleum benzines yields the following products. 86 ORGANIC CHEMISTRY Rhigolene (see p. 37), used sometimes as a solvent and as an anaesthetic, has the sp. gr. 0-600 to 0-630 and the b.-pt. about 35 (more volatile products form cymogen), and consists mostly of pentane and isopentane. Gasolene has the sp. gr. 0-630 to 0-666, boils at 40 to 50, and contains hexane and some of its isomerides ; it serves to carburet the feed-air for special lamps and in some cases as a solvent. Petroleum ether contains pentane, hexane, and higher hydrocarbons, boils at about 50 to 60, has the sp. gr. 0-660 to 0-670 (in Russia and America it is divided into various qualities boiling between 50 and 80), and is soluble in twice its volume of alcohol-ether and also in chloroform and carbon disulphide; it dissolves fats, resins and rubber and is also used to carburet air ; the good qualities do not colour an equal volume of stilphuric acid when shaken with it; if adulterated with tar benzene, it emits an odour of bitter almonds when shaken with a mixture of equal volumes of concentrated nitric and sulphuric acids. 1 Benzine for removing spots boils at 70 to 90 and has the sp. gr. 0-700 to 0-720; if too volatile, it leaves a ring on the fabric in place of the spot. Benzine for cleaning has the sp. gr. 0-725 to 0-730 and distils completely below 100 (otherwise it imparts an unpleasant odour to the fabric). Solvent benzine is used to extract fats from industrial products (wool, bones, etc. ) and also alkaloids ; the different qualities boil between 80 and 150 (sp. gr. 0-710 to 0-735). American heavy engine benzine has the sp. gr. 0-735 to 0-755, and the Indian variety, 0-750 to 0-770; the more expensive automobile benzine is sometimes adulterated with this cheaper product, especially for motor lorries. Benzine to replace oil of turpentine is used for paint and has a sp. gr. sometimes as high as 0-800. The consumption of benzine in the various countries of Europe amounted in 1908 to : 115,000 tons in Germany, 130,'000 tons in France, 100,000 tons in England, 10,000 tons in the Netherlands, 110,000 tons in Russia, 20,000 tons in Roumania, 10,000 tons in Austria and Galicia, and 25,000 tons in other countries. The United States produced 800,000 tons of benzine in 1908 and the Dutch Indies 260,000. In succeeding years the consumption increased enormously owing to the rapid development of -motoring. 2 The price of light and heavy benzines doubled between 1909 and 1914 (in Germany the light products cost 12 16s., and the heavy ones 8 per ton in 1909). The average consumption per kilometre may be taken as 180 grams for motor-cars and 600 grams for heavy commercial vehicles (these use also the cheaper heavy benzines). TREATMENT OF PETROLEUM RESIDUES A. Lubricating Oils. 7J. Vaseline. C. Paraffin Wax. (A) LUBRICATING OILS. The crude petroleum residue remaining in the boilers even at 300 (astatki or masut) 3 forms a brownish black mass with a greenish reflection, 1 A more certain test is the very sensitive indophenine reaction, due to thiophene (q. v. ), which is always present in benzene from tar. 2 France imported the following amounts of petroleum benzine (especially from the United States) : 170,000 tons in 1913, 172,000 in 1914, 214,000 in 1915, and 325,000 in 1916. The output of benzine in the United States was 12,000,000 barrels (of 159 litres) in 1909, while in 1913 that for motoring alone amounted to about 17,000,000 barrels. The quantities of crude benzine imported by Germany (one -half from the Dutch Indies and the rest from Austria, Roumania, and Russia) were : 133.813 tons in 1909 and 188,000 in 1911, the pure benzine imported being 5864 tons in 1909 and 7387 in 1910. The output in Germany was 133,765 tons in 1910, and 165,058 tons (1,440,000) in 1911. The Italian production and importation of benzine were as follows (tons) : 1905 1910 1912 1913 1914 1915 191C 1917 Production . 2,000 4,000 3,000 2,000 2,000 2,000 Importation . 3,000 11,000 23,000 30,000 41,000 54,000 109,000 109,000 Roumania produced 231,000 tons of benzine in 1910, and the Argentine imported benzine to the value of 344,000 in 1909. 3 Masut contains, on the average, 87-5 per cent. C, 11 per cent. H, and 1-5 per cent. 0; it has a mean sp. gr. of 0-91, an ignition temperature of 110, and a calorific value of 10,700 cals. When used as a fuel it is gasified, the vapours, mixed with compressed air, burning completely; it is often burnt directly after pulverisation with compressed air or steam. In view of the great calorific value of petroleum residues and their increasing production, new outlets have been sought for them ; they should have a great future as a substitute for coal in the heating of boilers, steam-engines, ships, etc. As has been already stated, however, this use of it is diminishing in Russia, although con- tinually extending in the United States. In Italy attempts have been made (1911) to burn CRACKING 87 dense and sometimes semi-solid at ordinary temperature, and often with a burnt, faintly creosotic smell; it has the sp. gr. 0-900 to 0-950 and the coefficient of expansion 0-00091 ; that of Baku contains no paraffin wax and hence does not freeze, and gives inflam- mable vapour even at 120 to 160. When these residues are discharged from the boiler, in order to cool them and so prevent them taking fire they are passed through the tubes which serves to heat the crude petroleum before introducing it into the boiler. At Baku the residues, which form almost two-thirds of the crude naphtha, are largely used as a fuel for the distillation vessels and also for locomotives and marine engines, the calorific power being 9700 to" 10,800 cals. and 1 kilo being able to evaporate as much as 14 to 15 kilos of water. Utilisation of a great part of these residues was commenced after the first American and Scotch samples (from shale oils) were exhibited at the International Exhibition at Paris in 1867. In Russia enormous quantities of residues, of almost no commercial value, accumulated every year. Their utilisation was initiated in 1873 at Balachna (near Nijni Novgorod) and later at Baku by the Ragosin process for preparing the best lubricating oils (those of Baku are highly valued) by distilling the residues by means of superheated steam, so as to avoid the formation of empyreumatic odours. 1 The distillation of these oils, and also that of the oils transuding during the refining of paraffin wax (see later), is now carried out in long horizontal boilers, since in vertical ones which were used at one time the vapours, in contact with the heated walls, give products of profound decomposition and of bad odour. Direct-fire heating may be partly it, after pulverisation, directly under boilers, and it might be used advantageously if it did not cost at the factory more than about 2 8s. per ton, coal giving 8000 cals. costing 1 Ss. ; the cost of transport is, however, excessive, increasing the price from 8s. to 12s. at the refinery to 2 8s. in Italy. The Customs duty (Italy) is only Is. Td. per ton. The heavy oils extracted from petroleum residues are largely used for special engines of the Diesel type. 1 " Cracking " Process. In some cases it is convenient to convert the heavy mineral oils (and also the masut) into petroleum for lighting, use being made of the process of cracking. This is based on the fact, established in 1872 by Thorpe and Young, that, when the vapours of heavy petroleums are superheated, they yield gaseous hydrocarbons (6 to 8 per cent.) usually poorer in hydrogen (ethylene series) and lighter liquids which may be used as second-quality petroleum. The operation is carried out in a vertical boiler (Fig. 95), placed in a furnace so that its walls are strongly heated by the hot fumes circulating round them. The boiler is not completely filled with masut, so that the vapours evolved, coming into contact with the red-hot walls above the liquid, are decomposed ; after separation in a dephlegmator of the heavy oil carried over, the vapours are progressively liquefied in ordinary con- densers or refrigerators, yielding lamp oil, benzine, etc., whilst the remaining gas is used for heating or for gas-engines. A mineral oil from Ohio treated by this process gave the following products : 25 per cent, of benzine (sp. gr. "0-650 to 0-745), 33 percent, of lighting petroleum (sp. gr. 0-800 to 0-840), 10 per cent, of light paraffin oils for burning (sp. gr. 0-854 to 0-859), 31 per cent, of solid paraffin wax and paraffin oil (sp. gr. 0-870 to 0-925), and 3 per cent, of coke and loss. Manufacture of Benzene from Naphtha. Attempts in this direction had already been made as early as 1875, and later Ragosin and Nikiforow, Krey, Laing, Dewar, and Redwood attacked the problem, but without practical success. Recently Nikiforow appears to have succeeded, and he has devised a plant for treating 2400 tons of crude naphtha and producing 262 tons of benzene. He subjects the naphtha to two distillations under different pressures, in a retort first at 500 and then at 1000. In this way 38 per cent, of tar containing 50 per cent, of aromatic compounds is obtained, together with an abundant supply of gas which serves for heating, lighting, and power purposes. After redistillation and rectification of the first of these products, a final yield of 12 per cent, of benzene and toluene is obtained, 3 per cent, of naph- thalene, 1 per cent, of anthracene, and various secondary products. Benzene thus prepared will apparently cost 10 per ton and the aniline oil (used in dyeing) obtainable from it would cost about one-half as much as that on the market in Russia. J. Hausmann (Ger. Pat. 227,178, 1909) also obtains benzene and its derivatives by passing the vapours of mineral oil into red-hot tubes, and into contact with catalytic agents (oxides of iron, lead, and cerium, sulphate of iron, etc.). FIG. 95. 88 ORGANIC CHEMISTRY used in conjunction with internal heating by superheated steam at 220, and the distillation is facilitated by carrying it out in a vacuum (see p. 77). Fig. 96 shows the plant used by Nobel Brothers at Baku. The condensation is effected in long, parallel, slightly slanting pipes, d, d v d z (40 to 50 cm. in diameter), communicating FIG. 96. alternately at the ends. The first of these is cooled by air alone, the second by water, and the third by very cold water that circulates in a coil; H is an exhaust-pump. At the bottom of each of these pipes is a discharge pipe for the mineral oil coiidensates, which pass to water-separators ; thus three qualities of oil are obtained in three separate tanks : 20 to 25 per cent, of lamp oil, sp. gr. below 0-890; 6 to 10 per cent, of spindle oil, sp. gr. 0-890 to 0-900; 25 to 30 per cent, of engine oil, sp. gr. 0-900 to 0-920; 3 to 4 per cent, of cylinder oil, sp. gr. 0-925 ; 3 per cent, of tar ; and 5 per cent, of loss. The quantity of steam consumed varies from 100 to 150 per cent, of the amount of oil distilled and the Section J.fC. FIG. 97. quantity of masut treated every twenty-four hours corresponds with about double the volume of the boilers. A somewhat different apparatus, which has also given good results for the distillation of tar and of its heavy oils, is that made by the firm of Hirzel in Leipzig. The large boiler, BV, with a convex base (Figs. 97 and 98) is divided longitudinally by a metal partition, 1, which allows the two halves of the boiler to communicate at the end, 7 ; the distillation products enter at the tube 4, connected with the horizontal pipe 5, from which the liquid descends to the bottom of the first half of the boiler along the tubes 6 ; the superheated LUBRICATING OILS 89 steam enters by the tube 3, which is forked half-way down the boiler and connects with a battery of horizontal perforated pipes, 2, running along the bottom of the boiler. The liquid moves slowly in a comparatively thin layer from the first to the second half of the boiler, passing through the space 7, and issuing at the tube 8; the vapours are collected in the dome, W, containing perforated discs to condense the drops carried over with the vapours, the latter proceeding through the tube a to the rectification or fractional distilla- tion apparatus. In 1911 the Hirzel apparatus was also used by a large Italian firm of metallurgical coke manufacturers and tar distillers. All these crude mineral lubricating oils, after being freed from moisture by heating, are refined by prolonged shaking in apparatus similar to that shown in Fig. 110 with 5 to 10 per cent, of concentrated sulphuric acid (containing not more than 0-01 per cent, of nitrous acid) and, after decantation of the black acid, with 0-4 to 0-8 per cent, of a con- centrated caustic soda solution (23 Be.), just as with lamp oil, but at 60 to 65, this being followed by washing with hot water. The largest proportions of the reagents are used with the denser, darker oils, the stirring being then effected with mechanical stirrers instead of with air. In these refining operations 3 to 5 per cent, of the mineral oil is lost during the acid treatment and 4 to 6 per cent, during the alkaline treatment. The residues in the boilers, if they are not solid coke, but pasty, are dissolved in benzene as a black varnish for iron, or are used as an adhesive in the manufacture of briquettes from coal-dust, or as a fuel. According to Ger. Pats. 161,924 and 161,925, it is proposed to treat crude mineral oils with a saturated solution of sodium chloride and carbonate, to blow air in for some time, and finally to distil in presence of an oxide of manganese. To render mineral oils inodorous, or nearly so, they are treated in the hot with formalde- hyde, and, after addition of alkali or acid to the mass, a current of steam is passed through (Ger. Pat. 147,163). According to Ger. Pat. 153,585, the 20 per cent, of crude mineral 011 is distilled with superheated steam at 180 in presence of 1 per cent, of aqueous lead acetate solution. The distillate is free from sulphur and forms a lighting or gas-engine oil; the residue, after filtration, forms a denser and almost odourless lubricating oil. In some cases petroleum is deodorised by agitating with chloride of lime and a sma,ll quantity of hydrochloric acid, decanting it, shaking with lime to fix the chlorine, and sometimes adding a little amyl acetate or essence of fennel ; treatment with soda lye is also resorted to, and, better still, both for mineral oils and petroleums, with sodium peroxide. Latterly, mineral oils soluble in water have acquired importance for lubricating machinery, for greasing textile fibres to be combed, and for watering the streets to prevent dust. They are prepared by the Boleg process (Ger. Pats. 122,451, 129,480, 148,168, 155,288) : the mineral oil is heated in a closed vessel, fitted with a condenser, at a temperature of 60 to 70 or above by means of indirect steam; at the same time finely divided compressed air, after addition of a little caustic soda solution, is injected ; a small quantity of resin soap or a sulphoricinate is subsequently introduced, the air- current being continued meanwhile, and finally the whole mass is heated under pressure in an autoclave. Emulsions of mineral oils with water are obtained by addition of pyridine or quinoline bases or amino-acids. To obtain from dark mineral oils less coloured oils, and in some cases oils as colourless as water (e. g., vaseline oils), the oil is passed slowly at 30 to 50 through a series of tall, communicating cylinders, sometimes kept hot by means of steam jackets (batteries of tubes arranged in a system similar to the diffusors used for extracting sugar from beets : see chapter on Sugar) , and charged with layers of decolorising clay separated by perforated discs or gauze to prevent the mass from becoming too compact and thus hindering the permeation of the oil. These clays are found more especially in North America, but occur also in Great Britain and, in inferior quality, in other countries ; they are similar to fuller's earth, but the best is Florida earth, consisting of aluminium and magnesium hydrosilicates (see Vol. I., p. 738), previously subjected to slight roasting. The mineral oil remaining in the filters is recovered by displacing it by heavy tar oil (very cheap) and displacing the latter with water. The exhausted fuller's earth may be regenerated by extracting the oil it contains by means of benzine ; the latter is recovered by distillation, and that remaining in the earth by a current of steam. After this treatment the fuller's earth is heated in a revolving, 90 ORGANIC CHEMISTRY cylindrical metal cylinder (like that used for cement; see Vol. I., p. 760), cooling being effected in a lower, revolving cylinder sprayed with water. With each repetition of this treatment, the earth loses in decolorising power. Decolorisation is also effected by bone-black or, best of all, by residues from the manufacture of potassium ferrocyanide, which exhibit very great decolorising power (50 per cent, more than American clay) ; owing, however, to the new methods of manu- facturing ferrocyanide, these residues are becoming scarcer and more expensive (they contain 30 to 40 per cent, of animal charcoal, considerable quantities of silica and silicates, and a little ferric oxide). The darker mineral oils are partly decolorised with sulphuric acid, sometimes together with dichromate. 1 In the case of certain dark mineral oils, repeated filtration through fuller's earth is replaced by purification with sulphuric acid and soda, but this occasions greater losses. Carts are often greased with the so-called consistent fats obtained by mixing 15 to 23 per cent, of calcium soaps and mineral oils with 1 to 4 per cent, of water (if there is no water the mass remains liquid, and if there is not a little free fatty acid emulsification ceases after a time and the calcium soap separates). REQUIREMENTS IN AND ANALYSIS OF LUBRICATING OILS. Lubricating oils serve to diminish the friction between metal surfaces in motion ; by adhering strongly, although in very thin layers, to these surfaces they prevent contact between them and hence friction and heating, without sensible increase of the resistance owing to the internal friction of the oil. Lubrication is due partly to chemical phenomena (formation of metallic soaps) but more especially to physical phenomena not well understood. Liquids which moisten surfaces (unlike mercury) exhibit great adhesive or capillary force and penetrate into the finest cracks. This capillary force (external friction) for thin layers of oil increases with diminution of the radius of curvature, and is sufficiently great to prevent direct contact of two surfaces between which the liquid is interposed, no matter how great the pressure. Thus, the resistance between the bearing and the revolving shaft it supports depends almost exclusively on the internal friction of the lubricating oil, i. e., on the viscosity of the oil. 2 Of two oils with equal viscosities, the preference is naturally 1 For the thorough decolorisation of vaseline oil the following operations are carried out : (1) Drying or dehydration; (2) treatment with 10 to 15 per cent, of fuming sulphuric acid and FIG. 99. FIG. 100. separation of the tarry matters formed; (3) neutralisation with caustic soda solution (10 to 12 Be.); (4) separation of the alkali and washing with water; (5) clarification with 4 to 5 per cent, of pure 50 per cent, alcohol and removal of the milky layer deposited; (6) bleaching with dry fuller's earth and subsequent filtration. 2 For lubricating oils it is important to determine the viscosity (due especially to polynaph- thenes), and this is usually effected by means of the Engler viscometer (Figs. 99 and 100), formed FLASH POINT 91 given to the one containing the smaller proportion of substances liable to undergo change (asphalte, resin, soaps, etc.). Even the best lubricating oils, when in use, are subject to more or less marked alteration (oxidation, pulverisation, emulsification, etc.), which is evident especially in ring lubrication or in the lubrication of turbines, where the oil is changed at infrequent intervals ; in such cases, oils of the highest quality should be used, as replacement is expensive (some oil-boxes contain 100 to 200 kilos of oil). More rapid is the alteration of lubricants used for engines or steam- cylinders, where the temperature is 150 to 200 or even 250, part of the oil undergoing decomposition with separation of small particles of coke and asphalte. In these cases it is important to determine the flash-point of the oil l (so that danger of ignition of the oil may be avoided); use may also be made of the formolite reaction and of the reaction with fuming acid (see p. 71). In general, where there is much pressure the viscous oils are suitable, and in other places liquid oils, although in practice mixtures of these two kinds are advantageously employed. Oil for lubricating steam cylinders at high temperatures should be resistant to great heat and to the mechanical and chemical action of steam, and should not give inflammable products at a lower temperature than 220, or 300 where superheated steam is employed ; it should possess great adhesive power and viscosity and should not contain of a brass vessel, A (sometimes gilt inside), provided with a cover, A lt through which passes the thermometer, 2483 In 1910 Germany produced 5292 tons of vaseline of the value 36,000. France imported 173 tons in 1913, 73 in 1914, 935 in 1915, and 828 in 1916, and exported 107 tons in 1913 and 156 in 1916. (C) PARAFFIN WAX. This was first found in petroleum by Fuchs in 1809, and Reichenbach obtained it from wood-tar in 1830, and showed its great importance as an illuminant. Hard paraffin wax melts at 54 to 60, has sp. gr. 0'898 to 0'915, and forms a white, translucent mass used for the manufacture of paraffin candles ; it is soluble in ether (1'95 per cent.), petroleum benzine (11 '7 per cent.), carbon disulphide (13 per cent.), turpentine (6 per cent.), toluene (3'9 per cent.), chloroform (2*4 per cent.) or benzene (2 per cent.), and to slight extents in alcohol (0'22 per cent.), acetic acid (0*06 per cent.), acetone (0'26 per cent.), or acetic anhydride (0*025 per cent.). By fractional distillation of paraffin wax in a vacuum Mabery (1912) isolated tricosane (see Table, p. 32), tetracosane, pentacosane, hexacosane, octocosane, and nonocosane (m.-pt. 62 to 63). Soft paraffin wax with m.-pt. 42 to 48 and sp. gr. 0'88 to 0'89 is used as an adjunct in wax and stearine candles, to impregnate wooden matches, in dressing textiles, and as a preventive of frothing during the concentration of saccharine juices (see Sugar) ; it serves also as an insulator of electrical conductors and as a cold bath in the manufacture of hardened glass. Most of the paraffin wax and paraffin wax oil is obtained from ozokerite (see later), the tar distilled from the bituminous lignites of Saxony and Thuringia (pyropissite) and from the bituminous shales of Scotland and Australia, and also from boghead coal and from the residues of American and Austrian petroleum. 1 I. PARAFFIN WAX FROM PETROLEUM RESIDUES. For this purpose an apparatus consisting of three vertical concentric cylinders is used ; in the inner and outer ones circulates a non-solidifying brine, which has a temperature of 20 and serves to separate the paraffin wax from the mineral oil in the middle cylinder (see also p. 78). According to Tanne and Oberlander,Ger.Pats. 226,136 and 227,334, paraffin wax is obtained from petroleum and tar residues by dissolving them in hot benzine and glacial acetic acid ; on cooling, the solutions deposit paraffin wax, cerasin, or ozokerite; see also Process of Miss Az). To free the flakes of paraffin wax from the adhering oil the cold mass is pressed in filter-presses (up to 15 atmos. ) and the cakes thus formed are finally squeezed in hydraulic presses, as is done in the case of stearine (see this); the blocks of wax are then spread out in a warm chamber, where the last traces of coloured oils flow away. In the Weiser process the hydraulic presses are replaced advantageously by filtering tubes wound round with- 1 There is also at Messel, near Darmstadt, a special layer of very soft and moist bituminous coal, consisting of clay and lignite, its bitumen, like that of the shales, being insoluble in the ordinary solvents. This coal contains 45 per cent, of water and 30 per cent, of ash, and on distillation yields 6 to 7 per cent, of tar and 6 per cent, of gas (see p. 103 ). PARAFFIN WAX 95 linen; the paraffin wax from the filter-press is broken up and forced into these tubes, being afterwards removed by steam and sent to the sweating chamber. The sweated oils are refined to prepare lubricating mineral oils (see p. 76). The sweated paraffin wax is refined by means of sulphuric acid and decolorising agents, in the same way as cerasin is refined. If the petroleum oils are distilled in a vacuum, mineral oils are obtained which give a greater yield of paraffin wax. According to Tanne and Oberlander (Ger. Pat. 238,489, 1911), treatment of mineral oil residues or lignite tars with 10 to 20 per cent, of carbon tetrachloride readily gives paraffin wax or cerasin in good yields. II. PARAFFIN WAX FROM LIGNITE TAR AND FROM PYROPISSITE. This special lignite, pyropissite, now almost exhausted, is obtained from deposits of oily and resinous woods which, according to Potonie and Heinhold, underwent fossilisation during the tertiary epoch. It is extracted moist (up to 55 per cent, of water) from the mines in Saxony and Thuringia, especially in the neighbourhopd of Halle a/S., where the deposits are 35 to 40 metres below the surface and have a thickness of 2 to 5 metres over an area of about a square kilometre. It forms a blackish-brown, more or less plastic mass, greasy to the touch, and when dry is yellowish- brown, friable and easy to burn; its sp. gr. is 0-9 to 1-1. In the dry state it gives up to alcohol 20 per cent, of its weight of a substance, m.-pt. 75 to 86, giving paraffin oil on distillation. 1 The rational industrial distillation of these more or less fatty lignites or of the corresponding bitumens was commenced in Saxony and Thuringia after 1858 by C. A. Eiebeck (after unsuccessful attempts to carry out the distillation in the usual way, no matter what the type of the lignite) and improved later by Wernecke. The distillation of the broken lignite is carried out in large vertical refractory (chamotte) retorts, 8 metres high and 2 metres wide, placed in a suitable furnace so that the external walls are heated by rational circulation of the hot gases. Inside the retort are arranged conical, cast-iron rings superposed one on the other with a certain distance between, their diameter being 12 to 20 cm. less than that of the retort (see Figure of a similar apparatus used for the distillation of sawdust : chapter on Acetic Acid). The lignite, 2 with not 1 E. Erdmann gives the following results of analysis and distillation, referred to 100 parts of dry matter (the moisture is 33 to 35 per cent. ) : OH OS (volatile) Ash Tar Coke Gas Pyropissite . . 7M2 11-63 9-43 O'lO 7-72 65 20 15 Bituminous lignite . 64-83 7'62 19-18 0'48 7'89 38 42 20 The sulphur content of bituminous lignites never exceeds 2 per cent. The distillation products of these lignites consist, to the extent of 40 to 50 per cent., of slightly alkaline water (2 to 3 Be. with 0-03 to 0-07 per cent. NH 3 ) from which it does not pay to recover the ammonia, and which are used only for the direct irrigation of the soil adjacent to the works ; they sometimes form a troublesome waste product, which must be treated and filtered before running into rivers, or they may be poured on to the ash-heap. One ton of bituminous lignite yields 130 to 140 cu. metres of gas containing : 10 to 20 per cent, of C0 2 , 0-13 per cent, of 0, 1 to 2 per cent, of heavy hydrocarbons, 5 to 15 per cent, of CO, 10 to 25 per cent, of CH 4 , 10 to 30 per cent, of H, 10 to 30 per cent, of N, and 1 to 3 per cent, of H 2 S. The gas has a calorific value of more than 3000 cals. per cubic metre and, after removal of the H 2 S, serves for use in gas-engines, 1 to 1'5 cu. metres being consumed per H.P.- hour (one retort deals with about 3 tons of the lignite in twenty-four hours, producing about 400 cu. metres of gas). The gas is freed from ammonia by washing with water. After quenching, the coke remaining from the distillation contains about 20 per cent, of water and volatile products, 20 per cent, of ash, and 60 per cent, of carbon. When dry, its calorific value is about 6000 cals. and, with many works, the profits are made by the sale of the coke. 2 Now that the deposits of pyropissite are almost exhausted and the paraffin wax industry of Saxony and Thuringia has been subjected to the competition, first, of ozokerite (after 1870), and then (after 1880) to the more serious one of the American paraffin wax extracted from Ohio petroleums which has invaded all the markets of the world- it has been recently discovered that when pyropissite is distilled a great part of the paraffin wax is destroyed, much better yields being obtained by extracting direct with suitable solvents (benzine, toluene, alcohol, carbon disulphide, carbon tetrachloride, acetone, etc.), which, after evaporation, leave a waxy mass ; when this is purified with fuming sulphuric acid, it yields an almost white product of great value montan wax (Bergwachs), similar to cerasin (mineral wax). The remedy for the paraffin wax crisis of Saxony and Thuringia has arrived too late, since the valuable wax has been squandered by distillation. Other layers of lignite from the region of Halle a/S. are being worked to-day, and these are extracted in the hot with benzine; the solution of bitumen extracted is first purified by thorough cooling, the paraffins being thus separated while the resins 96 ORGANIC CHEMISTRY less than 30 per cent, and not more than 60 per cent, of water, is charged in lumps at the top and descends gradually in the free annular space between the walls of the retort and the edges of the rings. When it reaches the bottom it consists of nothing but coke, which is discharged occasionally, fresh lignite being introduced at the top; the gaseous pro- ducts are evolved at 140 to 150 by a large tube at the top, and the liquid products (tar) flow down the walls of the rings and are collected by a lower tube. The retorts are maintained at a dull red heat. From a cone at the bottom the coke is discharged every hour at a temperature of 400 and is quenched with water. The vapours emitted are drawn off and gradually condensed in apparatus consisting of superposed iron tubes with a cooling surface of 80 to 100 square metres enclosed in a casing. The gases which do not condense are led under the hearth to heat the furnace, fuel being thus saved ; formerly 5 to 6 tons of inferior coal were used per 10 tons of lignite distilled, but later only 1 to 1-2 tons were necessary, less labour being required (one workman per twenty furnaces) and the yield per furnace being increased (by more than 25 per cent. ). The gases passing from the hearth round the furnace and retorts have a temperature of 500 to 700. x Batteries of 10 to 12 retorts for each condensation unit are employed. In each furnace 3-5 to 4 tons of lignite in pieces the size of walnuts are distilled in twenty-four hours. The lignites now distilled give only 4 to 8 per cent, of tar. Lignite tar is brownish yellow to black in colour, has a peculiar odour, and liquefies between 25 and 30, giving a greenish fluorescence. Its specific gravity is 0-850 to 0-910 at 44. It has an alkaline reaction (from ammonia, ethylamine, etc. ) and contains about 20 to 25 per cent, of paraffin wax 2 ; it distils between 80 and 400, the bulk between 250 and 350, and has an unpleasant odour, sometimes of hydrogen sulphide. The best lignites give the less dense tars. According to the nature of the tar (which is previously washed with acid and water 3 ) the paraffin wax is obtained from it in the following ways (see also Part III, Distillation of Tar) : (these are recovered by evaporation of the solvent; they melt at 50 to 60 and form 15 to 25 per cent, of the crude bitumen) remain in solution. The bitumen separated in the cold is redis- solved in benzine and treated with concentrated sulphuric acid, the mass being kept mixed and slowly heated to boiling. Animal charcoal is added and the liquid filtered, passed over fuller's earth (see p. 89), and neutralised by passing in a little gaseous ammonia. After distil- lation of the solvent there remains a yellowish or almost white paraffin wax melting at 82 to 85 (Ger. Pat. 216,281, 1907). 1 For every quality of lignite and every type of furnace preliminary trials should be made to ascertain the most suitable temperature for obtaining the proper decomposition of the bitumen so as to form a tar poor in benzene and its homologues, naphthalene, etc. (produced by an exces- sively high temperature, although absence of these substances indicates too low a distillation temperature, the high condensed products of the methane series then containing unaltered bitumen and the gases some proportion of ethylene and acetylene; when the temperature is too high, the gases contain hydrogen and light hydrocarbons ). Distillation in steam affords no advantage, since much unchanged bitumen then occurs with the tar and no ammoniacal liquor is then obtained; such liquor is, however, formed in abundance when Scotch shales are steam -distilled . 2 In these lignite tars and bitumens Kramer and Spiller (1902) found an ester and the corre- sponding monobasic acid, but no glycerides or poly basic acids. Hiibner (1908) found two ketones, C 16 H 32 and C^E^O, and a humic acid containing 8-39 per cent, of sulphur, although other investigators found only 5 per cent, and 1-7 per cent, of sulphur. 3 The purification of lignite tars and their distillation products is effected by means of acid and alkali. In the first treatment with acid, use is made of 0-25 to 0-5 per cent, of sulphuric acid of 50 Be., which removes traces of water and part of the basic products (pyridine). The second treatment with 3 to 5 per cent, of sulphuric acid of 66 Be. (in two portions) serves for the removal of all the residual basic products and part of the unsaturated hydrocarbons, which otherwise would undergo oxidation and resinification, and would impart a dark colour to the oils ; the sulphuric acid also causes slight oxidation (rendered evident by the marked odour of S0 2 ) as well as polymerisation and substitution. The action of the acid takes place in the cold, except with the tar itself and with the crude paraffin wax, which require heat. The pitch and resin formed on treatment with sulphuric acid are insoluble and are deposited on the walls of the vessel. After a rest of three hours, the acid is separated by decantation and the residue washed twice with water (perhaps with a little added calcium hydroxide) to eliminate the last traces of acid, and then treated with 4 to 6 per cent, of pure caustic soda solution (38 to 40 Be. ). Treatment with alkali is applied, not to the tar itself, but only to its distillation products, a small amount of the alkali (or recovered alkali solution) being first used and then the bulk of the alkali ; the so-called creosotes (which consist of phenol and its homologues and impart a bad colour and smell to the oil) are thus removed- -after a stand of three hours. The alkali treat- ment should not precede that with acid, since there are products soluble in both alkali and acid and it is more economical to eliminate the bulk of these by means of sulphuric acid and those WAX FROM LIGNITE TAR 97 ( 1) To the lignite bitumen or tar to be distilled, 0-2 to 0-5 per cent, of slaked lime or of solid caustic soda is added to fix the hydrogen sulphide and part of the creosote. The distillation is continued until only a solid residue of coke remains. With 2-5 tons of tar the distillation occupies about ten hours, about 0-6 ton of small coal and 0-05 ton of lignite being consumed. One workman suffices to control the distillation in ten stills and another to supervise the condensation plant. It is possible also to distil in a vacuum, the degree of evacuation being low at the beginning. Sometimes distillation at ordinary pressure in a slow current of steam (maybe superheated) is preferred. Use is nowadays made of Wernecke's continuous apparatus (see Part III : chapter on Tar). When the price of paraffin oils is too low, light illuminating oils, etc. (see note, pp. 75, 76 : Benzine from Naphtha) may be obtained by distilling them under pressure. With very dense tars, in order to separate the creosote and certain resinous substances more efficiently, vacuum distillation in large direct-fired boilers is resorted to. This yields 25 to 50 per cent, of fatty oils, 50 to 65 per cent, of crude paraffin wax, and 7 to 9 per cent, of coke, which is burnt, together with the gases from the distillation, to heat the boilers. The mass of crude paraffin wax is purified with acid and alkali, or with acid and subsequent distillation. The more solid part is then separated from the oily part by cooling the mass in vessels holding 100 to 200 kilos, around which circulates a very cold solution (the non-solidifying liquids used for ice-machines, see Vol. I., pp. 261, 621 ). When the oily or buttery part (which is distilled for the extraction of solar oil and second-grade paraffin) is separated by filtration from the crystallised paraffin wax, the cakes of the latter are pressed in hydraulic presses at 150 atmos. to remove the 20 per cent, of oil still contained in them. The solid cakes which remain are yellowish in colour, and are purified by melting them several times with 10 to 15 per cent, of benzine and pressing them at 200 atmos. in a hydraulic press. To get rid of the smell of benzine the paraffin wax is heated in iron cylinders with high-pressure steam, the hot wax being then passed through the decolorising material [animal charcoal, ferro cyanide residues, or magnesium hydrosilicate clay (see p. 89)]. The small quantity of this material retained by the paraffin wax is finally removed by filtration through paper, the wax being then allowed to solidify in large shallow moulds. Miss Az has recently suggested the purification of crude paraffin wax by treating it either fused or as powder, between 60 and 70, with a solvent (methyl or ethyl alcohol, acetone, or acetic acid or anhydride). The paraffin wax is insoluble and the impurities soluble in these solvents. Paraffin wax thus purified appears to be of better quality than that purified in the ordinary way (see above : Weiser's process). The tar is sometimes distilled above a certain temperature with superheated steam; remaining, which are less soluble and more easily removable, by means of soda; with this procedure less secondary decomposition occurs. The acid treatment is carried out in cylindrical wrought-iron tanks with conical bases lined with pure lead 4 mm. thick, the mass being stirred for about half -an-hour by a stream of air. Tars free from bitumen are best treated with 0-25 per cent, of sulphuric acid of 50 Be., then with 3 to 4 per cent, of acid of 66 Be., and finally with hot water containing a little milk of lime, formation of emulsions being avoided by thorough agitation. Distillation of the tar then gives paler products, a higher yield of paraffin wax and less loss of gas, etc. If the tar contains bitumen, or if vacuum distillation is employed, such preliminary treatment with sulphuric acid is inadvisable. The blue fluorescence shown by some of these distillation oils is removed by shaking them with 0-25 to 0-5 per cent, of nitronaphthalene, which separates on standing and is then decanted off. The waste Hack acids may be used for making fertilisers (superphosphates, etc), while the acid resins and pitches may bo redistilled to the extent of two-thirds, the remaining one-third serving as tar (goudron ) or, if denser, as asphalte. Sometimes, however, these resins and pitches are mixed with alkali creosotes, the water (which contains sodium sulphate) being removed and the resin distilled, while in some cases they are pulverised by means of steam and burnt under the boilers (calorific power, 8000 cals. ). The alkali creosote may also be used for impregnating pit-props, or crude creosote may be liberated by treatment with dilute sulphuric acid or carbon dioxide (flue gases). Acid pitch may be obtained by diluting the black acid mass with water, since it is not soluble in dilute acid. The pitchy and resinov-s masses which separate may be distilled again, various products (see later) being obtained. Fairly pure concentrated sulphuric acid may be recovered (according to U.S. Pat. 956,276, 1910) from the black acid by allowing it to fall in a thin stream into a retort containing pure sulphuric acid heated to boiling, the acid distilling off being condensed in the usual way (see Vol. I., p. 308). This acid may also be decomposed in the hot to obtain SO 2 (U.S. Pat. 956,184, 1910). VOL. II. 7 98 ORGANIC CHEMISTRY in other cases only the benzines (photogens) and the light oils are distilled, the residue being cooled to a low temperature and the solid paraffin wax which separates centrifugated to eliminate the tar and heavy oils. When the tars are very dense (above 0-900) Krey finds it convenient to distil them under a pressure of about 10 atmos., thus raising the tempera- ture to 400 to 450. This yields 60 per cent, of distilled oil of sp. gr. 0-830, which is largely used for the preparation of oil-gas (see p. 64), 10 per cent, of gas, and 30 per cent, of residual oily tar. (2) With light and very pure tars a greater yield of paraffin wax is obtained more cheaply by treating the tar directly with concentrated sulphuric acid, washing with water, and subjecting to fractional distillation over calcium hydroxide. Crystallisation, pressing, and bleaching are carried out as described above. The following scheme shows the different operations, and the final yields in a tar distillation (the brackets unite products which are worked up together, generally by distillation; the ultimate products are shown in italics) : Tar (sp. gr. 0- 830-0- 890) 33 % Crude oil 63 % Crude paraffin wax Crude solar oil Bed oil Pasty mass I Expressed oil 10 % paraffin wax I (m.-pt. 5l-60) lass II Crude s( )lar oil Re< I oil Pasty n 1 1 12%(sp.g r. 0-860-0-880) 2 % photogens (sp. gr. 0-800-0 810) 10 % solar oil (sp. gr. 0-825-0-830) 10 % yellow oil (sp. gr. 0-850-860) solar oil residues 3 % fatty oil (sp. gr. 0-880-0-890) 1 % pasty distillate (m.-pt. 30-38) 20 % dark' paraffin oil (sp. gr. 0-890-0-920) 4 % soft paraffin wax (m.-pt. 42-48) Photogen is a species of benzine similar to that of petroleum, but obtained by the distillation of wood, lignite, and coal ; it is used in the purification of paraffin wax, in the carburetting of lighting gas, and for removing spots from fabrics. Yellow oil is used for the extraction of fats and for cleaning; red oil (sp. gr. 0-860 to 0-880) has various uses, and serves well for the manufacture of oil-gas (see p. 64); the fatty oils and dark paraffin oils (0'880 to 0-925) are used as oil for gas l and for making cart-grease ; the yellow and red oils (0-880 to 0-900) are used as thinner lubricants. 1 Oils for Gas. From the time when gasworks began to mix gas obtained by the carbonisa- tion of bituminous coal with carburetted water-gas and with oil-gas (in 1905 Germany produced 30 000,000 cu. metres, England 500,000,000 cu. metres, and the United States 1,550,000,000 cu'. metres of carburetted water-gas), the use of mineral oils for carburetting the water-gas and for producing oil-gas has increased considerably. These oils for gasifying are obtained partly by the distillation of lignite and shale tars (see above and p. 102), but more especially by the distillation of petroleum residues (solar oil, intermediate to true petroleum and lubricating oils). The value of these oils increases with the narrowness of the temperature limits within which they boil ; these limits are usually 100 apart, and it is of no consequence whether they be 200 and 300, 'or 250 and 350 ; they should contain less than 25 per cent, of unsaturated hydrocarbons (soluble in concentrated sulphuric acid of sp. gr. 1-83), otherwise they give too much tar and coke on gasification ; they should contain not more than 30 per cent, of creosote, but a high propor- tion of paraffin wax is advantageous. In the United States 600,000 tons were consumed in 1908; ASPHALT E, PITCH AND BITUMEN 99 The washing of tar and of its distillates with alkalies and acids yields resinous masses with varying proportions of creosote oil and distillation of these at different temperatures yields goudron or asphalte tar, or artificial bitumen, 1 which is used in the manufacture of impermeable about 220,000 tons were imported into England in 1906, 320,000 in 1909, and 260,000 in 1910; about 4153 tons of mineral oil (sp. gr. 0-83 to 0-88) were imported into Germany in 1906, 29,600 in 1908, and 46,500 in 1910 for the carburetting of water-gas; Germany itself produces a further quantity of about 300,000 tons of oil for gasifying, 13,000 tons being used for producing oil-gas on the railways, and 9000 tons for mineral-oil engines. For the carburetting of gas these oils should cost less than 4 16s. per ton. The amount of cart-grease imported into Italy is about 300 tons per annum, and that exported about 120 tons (800). 1 Asphalte, Pitch, and Bitumen. When tar from the distillation of wood (or lignite) is heated until all the volatile products are eliminated, there remains a black mass which, when cold, assumes a glassy consistency and forms pitch, used particularly for caulking ships, for preparing shoemakers' thread, and for making cements impermeable to water, etc. When coal-tar is completely distilled it leaves a more or less hard black residue coal-pitch which is used for ordinary asphalting and for making varnishes, lacs, and coal briquettes (see Vol. I., p. 459). Pitch is also prepared expressly by prolonged heating of tar in a current of air or with sulphuric acid. Bitumen (mineral pitch) bears sometimes the unsuitable name, natural asphalte, and forms a brittle, blackish brown mass, which, on heating, softens between 100 and 135 ; it has the sp. gr. 1-10 to 1-20 and the hardness 2. It burns readily, with a very smoky flame, is insoluble in water, alkali or acid, slightly soluble in alcohol or ether, and readily soluble in benzene, carbon disulphide, and turpentine (in which it ceases to be soluble after exposure to light, and is hence used in photo-lithography). The best bitumen is found at the surface of the Dead Sea in Palestine, and in greater quantities at the Pitch Lake in the island of Trinidad, this having an area of 50 to 60 hectares (120 to 150 acres) and a depth of '50 metres, and forming a fairly hard mass ; it abounds also in Syria, Utah, Venezuela, and Cuba, and at Dax (France). That of Trinidad contains 40 to 50 per cent, of pure bitumen and 30 per cent, of mineral substances, the remainder con- sisting of organic substances and water (about 25 per cent.). It is broken up on the spot by means of hatchets into brownish-black lumps permeated with bubbles and is heaped up, the interstices then gradually filling. The rights of working belong to the New Trinidad Lake Company, which pays 5s. per ton to the British Government. By means of a telferage line 1 kilometre in length, it is carried to the port, where it is roughly refined by melting at 160 to 170 in open vessels heated with steam coils to separate part of the mineral substances, water and volatile matter, the product thus obtained containing 56 to 58 per cent, of pure bitumen, having the sp. gr. 1-40 to 1-43 and softening at 85 to 95; the portion soluble in petroleum ether bears the name petrolene, and consists of liquid hydrocarbons of the CH 2n _ 4 series, whilst the insoluble part is known as aspJialte and is composed of solid substances, which are partly oxygenated and undergo oxidation in the air. Up to the present time this lake, which is partly covered with vegetation, has yielded over a million tons of asphalte and its level has been lowered about 1-25 metres; nowadays about 250,000 tons of bitumen are extracted from it per annum. The amount of change, or efflorescence, which bitumen will undergo under the action of air and light may be estimated by determining the proportions of carbenes present, i. e., the products insoluble in carbon tetrachloride, but soluble in carbon disulphide. Pure bitumen is used for making black sealing-wax, black lacs, and varnishes, and also lamp- black; the lower qualities serve for coating wooden structures (boats, telegraph poles), for cardboard, for roofs, and damp walls, etc. (see later). In order to distinguish natural from artificial bitumen, about 1 gram of the substance is heated to 200, cooled, powdered, and treated with 5 c.c. of 80 per cent, alcohol; if the latter turns yellow and exhibits fluorescence, artificial bitumen is indicated, whilst if the alcohol remains almost colourless, the bitumen is natural. By the term asphalte (natural) is meant minerals, porous rocks, and earth containing bitumen. Bituminous rocks are slightly porous and the bitumen they contain ( 10 to 15 per cent.) easily flows away when they are heated in suitable furnaces. Asphaltic rocks, however, are porous limestone impregnated with bitumen (6 to 12 per cent., or even over 20 per cent.), which does not flow away on heating : they are used for the preparation of asphalte mastic by powdering and fusing them homogeneously with a certain quantity of bitumen. This mastic is cooled in moulds and is used directly for paving streets and terraces, either alone or mixed with fine sand or gravel. Powdered asphalte may also be used for paving, by spreading it out hot and compressing it with heavy cast-iron double rollers heated inside. In California, large quantities of artificial asphalte are prepared by prolonged injection of air into dark mineral oils (sp. gr. 0-9333 to 0-9859) heated at 650. Fusion of colophony at 250 and addition of sulphur yields an asphalte which is similar to that of Syria and is used in photography. Natural asphalte occurs abundantly near Neuchatel, in the Department of Ain (France), in the neighbourhood of Hanover, and in Italy at Lettomonapello (the product of this locality is worked at S. Valentino, near Chieti ), and especially at Ragusa and Castelluccio, near Modica (in the Sicilian province of Syracuse). These Sicilian asphalte rocks consist of pure, more or less hard chalk, impregnated with 7 to 14 per cent, of bitumen, and until 1858 were used solely, and to-day are used partly, for the manufacture of building stone. Almost the whole of this rock is exported, the exportation amounting to 1782 tons in 1878, 2186 in 1882, 26,587 (26,587) in 1894, 12,140 in 1897, 47,440 in 1899, 55,307 in 1903, 72,746 in 1905, 89,808 (88,012) in 1908, 100 ORGANIC CHEMISTRY pasteboard for roofing, in rendering woodwork and masonry (especially in damp houses) damp-proof, and also in the manufacture of ultramarine. III. Another important source of paraffin wax is furnished by the Bituminous Schists, which are especially abundant in the Lothians in Scotland (at Broxburn, Bathgate, etc. ), where at depths of 600 to 1200 metres layers 2 to 4 metres in thickness are found over an area 95 kilometres long and 8 to 13 kilometres wide. In 1848 Young and Meldrum began to work and purify a special oil issuing from the surface of the soil in Derbyshire (see note, p. 66), and, having exhausted this deposit and not finding others, they succeeded in preparing mineral oils, which had been already intro- duced for illuminating purposes, by distilling cannel coal, which gave much lower but remunerative yields. In about 1860 they discovered that the interesting Scotch deposits of boghead coal gave a yield of oil much greater than cannel coal, and in 1864 and 1866 were erected the two works at Bathgate and Addiwell, which became world famous. The deposits of boghead coal were exhausted in four or five years, and were then replaced by the more abundant, although less fertile, deposits of bituminous schists (shales) in which Scotland is so rich. These shales have been formed by the slow deposition of fish at the bottom of and 85,947 (47,759 to Hamburg, 10,125 to London, 4040 to Buenos Aires, 3800 to Antwerp, 3000 to New York, 2800 to Rouen, 2720 to New Orleans, 2605 to Rotterdam, 2537 to Greece, 2014 to Alexandria, 1707 to Hungary, 1050 to Calcutta, etc.) in 1909. The mean price of the rock at the port is 1 per ton. These Sicilian deposits were studied by Delia Fonte and Moschini in 1884, Ragusa in 1901, Manzella in 1906, Maderna in 1906 and 1909, and Coppadoro and Schiavo- Leni in 1908-1910. For street paving these powdered rocks should contain less than 2 per cent, of residue insoluble in hydrochloric acid (clay and silica) and should be free from pyrites (in the air this is converted into soluble ferrous sulphate, which results in disintegration of the pave- ment); the proportion of bitumen (extracted by chloroform from the well-powdered material, dried at 100, in a Soxhlet apparatus) should be more than 8 per cent, and less than 13 per cent. Various firms export asphalte ready powdered from Sicily and manufacture asphalte mastic (see above) by mixing, in the hot, powdered asphaltic rock with either Trinidad bitumen or bitumen obtained by distilling the richer rocks (12 to 25 per cent, of bitumen). By the name asphaltite are known certain bitumens found naturally in veins and among these Marcusson (1914) includes Syrian asphalte or bitumen, Gilsonite, Grahamite, and Albertite. These are more expensive than other bitumens, and, being harder and more shiny and more easily powdered, are used more especially in the lac industry. They are distinguished chemic- ally from asphaltes and bitumens by their content of organic acids, organic sulphur and matter soluble in CS 2 and CC1 4 . As they contain less than 7 per cent, of oils resistant to sulphuric acid, they are to be regarded as products of more advanced decomposition than bitumen. STATISTICS AND PRICES. The Italian output of asphaltes and bitumens is as follows (tons) : 1910 1912 1933 1914 1915 1916 1917 Natural asphalte rock . 162,212 181,397 171,097 119,853 47,650 16,829 Powdered asphalte rock 26,137 34,648 40,573 17,200 11,279 5,607 Asphalte in cakes (bituminous mastic) .... 13,953 16,612 13,961 13,772 11,460 8,477 Artificial asphalte 8,580 6,200 6,000 4,700 Compressed asphalte bricks . 943 1,164 1,790 2,249 2,187 1,618 Crude bitumen 457 549 393 326 355 786 . Refined bitumen 672 283 426 531 775 960 Solid bitumen, importation. . 3,365 3,548 4,300 2,924 4,139 1,090 1,381 ,, ,, exportation . 26,125 13,158 6,596 6,367 6,720 121 111 The production of pitch in Italy was 7220 tons in 1909, 11,964 (25,920) in 1912, 17,746 in 1915, and 30,182 (122,668) in 1916. Great Britain imported 68,389 tons of asphalte and bitumen in 1909 and 69,398 tons (168,000), together with 12,000 tons of pitch (excluding that from coal tar), valued at 66,000 (the exports being of the value 720,000 ), in 1910. The output of oily shales was 2,967,700 tons in 1909, 3,130,000 (430,000) in 1910, 3,280,143 in 1913, and 3,268,666 (837,240) in 1914. In Germany there were fifteen works treating asphalte rocks (costing about 8s. 6d. per ton ) in 1910, the quantity treated being 76,964 tons (giving 4400 tons of asphalte) in 1909, and 81,335 tons (giving 4640 tons of asphalte) in 1910. The imports were 130,062 tons in 1908 and 98,370 (exports 14,200 tons) in 1909; 103,000 tons were produced in 1905, 89,000 (40,000) in 1908, and 77,500 in 1909. The prices are : for the tar (goudron), 3 5s. per ton; Archangel pitch, I, 11 4s.; Swedish pitch, 9 -4s.; coal pitch, 2 to 2 8s.; lignite pitch, 2 8s. to 3 4s.; stcarine pitch, 7 4s. to 14 8s.; Syrian asphalte, I, 34; asphalte in fine powder, 70. SHALE : CU -I:'- '<:< 101 the sea, with interposition of deposits of clay, which even now bears the imprints of the fish. They are greyish-black or brownish, with a lamellar structure, and have the sp. gr. 1-71 to 1-87. 1 The invasion of American petroleum in about 1880 created a serious crisis in this industry, which was partially saved by new and improved technical methods introduced by engineers and chemists, especially by Beilby, Henderson, Crichton, and Bryson ; the by-products were more completely utilised, the furnaces improved, fractional distillation apparatus brought into use, the ammoniacal liquors utilised, the tar, coke, gas, and final residues employed as fuel, and the labour reduced to a minimum ; the mineral oil came to occupy a secondary position, attention being paid to the production of paraffin wax and high-class lubricating oils for engines. The furnaces and retorts used in Scot- land for the distillation of bituminous shale have undergone continuous improvement. Horizontal retorts gave way to vertical ones, and of these the most perfect types are the Henderson retorts, brought into use in about 1895 at Broxburn, and the Bryson retorts, applied later at Pumpherston, both being modifications of the old vertical retorts of Young and Beilby (called also Pentland retorts). The furnace with Bryson retorts is shown in Fig. 103. The retorts are 9 metres high, have a circular section with a mean diameter of 90 cm., and hold 4-5 cu. metres of shale in lumps of walnut size (the old Henderson retorts contained 3 and the old Pentland retorts 1 cu. metre). The lower . l In France these bituminous schists, which abound in the basin of the Autun and at Buxiere- les-Mines, form two strata which are 1 to 2 metres thick and extend over an area of 18,000 hectares (44,460 acres ), the best deposits being at a depth of 80 metres. They were first worked in 1837 by Selligne in consequence of the studies of Reichenbach (1830), and the industry became a nourishing one about 1860 ; in 1864, 128,550 tons of shale were distilled, producing 4750 tons of crude oil, destined principally to prepare oil-gas in the large towns. The invasion of American petroleums also overthrew this industry, which now survives on account partly of the Customs duty and partly of the adoption of Scotch distil- lation furnaces (Fig. 103), which give improved yields. In Australia, especially in the neighbourhood of Sydney, extensive deposits (from a few centimetres to 2 metres thick) of bituminous shale occur which, according to Potonie, origin- ated in oily algae, and are hence to be regarded as coals rather than as shale. On distillation they give 68 per cent, of oils, 14 per cent, of gas, 11 per cent, of crude paraffin wax, and 7 per cent, of ash. A bituminous schist from Midlothian (Scotland) gave on analysis : 20 per cent, carbon, 0-7 per cent, nitrogen, 1-5 per cent, sulphur, the rest being mineral matter; it gave up nothing soluble to ether. Another sample showed 2-7 per cent, water, 24-3 per cent, tar, and 73 per cent, residue (ash). Certain French shales give only 5 to 6 per cent, of tar, whilst those from Australia give as much as 60 per cent., but are poor in paraffin wax. Unlike that of bituminous lignites, the tar of shale cannot be extracted by solvents. FIG. 103. 102 R G A -K1" C CHEMISTRY two-thirds, 6, of the retorts is of refractory bricks (chamotte) and the upper part, a, of cast-iron fixed with mastic into the chamotte part. The shape is slightly conical, and at the upper end is a large sheet-iron hopper, c, containing sufficient broken shale to feed the retort for twenty-four hours. The mouth at the bottom of the retort is restricted somewhat and is closed with a hinged grid or disc, which is divided into two parts and may be opened by the lever arms, k, so as to discharge, every five to six hours or more frequently, part of the exhausted shale into the sheet-iron hopper, d, where it cools to some extent ; at the same time fresh material enters the retort at the top. The retorts with their hoppers below are united in pairs, a single discharge orifice, s, serving the two. In each retort 5 tons of shale are distilled per twenty -four hours. The furnaces are heated by the non- condensable gases from the distillation, these being intro- duced through the pipes A and B. The distilled products are evolved at the top through the tubes e and are aspirated through the tubes / to the condensing plant. This consists of batteries of vertical wrought- or cast-iron tubes, wh'ich are 60 cm. in diameter at the beginning and 45 cm. at the end of the battery and rest on adjacent but separate tanks, in which the various products collect as they are gradually condensed by the cold external air- (cooling with water with the object of diminishing the number of tubes has not given good results; in some cases, batteries of small air-cooled tubes are used). Batteries of forty to sixty furnaces are controlled by four workmen by day and two by night (the hoppers, c, are charged during the daytime). The gases heating the retorts have a tempera- ture of about 700 at the bottom and 400 at the top, flow of the bitumen before distilla- tion and the production of obstructions being thus avoided. In some instances the retorts are also heated internally by means of superheated steam. With regular working 100 kilos of shale give 8 to 10 kilos of tar. The yield is about 6 per cent, of gas, 8 per cent, of ammoniacal liquor (ammonium carbonate), 12 per cent, of crude oil (tar), and 7 per cent, of residue (4 to 5 per cent, of which consists of combustible matter). The crude oil con- tains less than 0-03 per cent, of sulphur ; the gas evolved contains 21 to 23 per cent. C0 2 , 1 to 4 per cent. CO, 12 to 24 per cent. H, 1-6 per cent, of heavy hydrocarbons, 8 to 20 per cent. CH 4 , 1-2 to 4 per cent. O and 35 to 43 per cent. N. 1 The crude oil is dark green, has the sp. gr. 0-865 to 0-895 at 44, and is semi-solid at ordinary temperatures owing to the paraffin wax present. This oil is treated by virtually the same methods as are used for lignite tar, that is, by continuous distillation in a current of steam, so as to obtain purer products. The first distillation gives : green naphtha, (0-753) and green oil (0-858), which are purified by acid and alkali and then redistilled : the first gives commercial mineral oil (also solar oil) and the second light oils and paraffin wax, which is separated by cooling from the blue oil, which serves as a good lubricant when refined. The paraffin wax is purified by the process given above (paraffin wax of lignite tar). The gas evolved during the distillation of crude shale oil showed, in one instance, the following percentage composition : heavy hydro- carbons, 14-5 ; methane, 59 ; ethane, 26-5 ; hydrogen, traces ; CO, C0 2 , and O, nil. When this gas is cooled, a light benzine for automobiles is obtained. 1 One hundred kilos of Scotch shale gives on distillation in modern furnaces as much as 30 cu. metres of gas (only 14 with the older furnaces) containing, for instance, 22-08 per cent. CO 2 , 1-18 per cent. 0, 1-38 per cent, heavy hydrocarbons, 9-77 per cent. CO, 3-70 per cent. CH 4 , 55-56 per cent. H, and 6-33 per cent. N; the very high content of hydrogen is due to the action of the water-vapour on the red-hot residues of the shale. The distillation residues, consisting almost entirely of mineral matters, have no value, and are used for filling holes in the ground ; in some few cases, the residues (coke ) contain as much as 12 per cent, of combustible substances and are then mixed with better fuel and burnt in the furnaces. In 1876, when horizontal retorts were used, the cost of 100 litres of tar, including the value of the raw shale, was estimated at 8s. ; in 1879, with Henderson vertical retorts, at 4s. Gd., and in 1897, with the new retorts, at 3s. 6d. The gases used for heating the furnaces consist of 80 per cent, of water-gas and 20 per cent, of distillation -gas and tar vapours (2 per cent. ). In some modern works the quantity of gas is increased by passing steam in at the bottom of the furnace, this, with the carbon remaining in the hot, exhausted shale, giving water-gas rich in hydrogen and carbon monoxide. The waters distilled from shale form three-fourths by weight of the distillate have the sp. gr. 4 Be., and contain ammonia and pyridine. The ammonia is recovered as crystallised sulphate by the method used in gasworks. Each ton of shale gives 5 to 6 kilos of ammonium sulphate, which in many factories is the sole source of profit. Benzene is also obtained from the gas by washing the latter with paraffin oil in a coke tower or scrubber. ICHTHYOL 103 A ton of bituminous schist (of the value of 12s. Qd.) yields about 8 kilos of naphtha, 115 kilos of crude oil (green oil), and 13 kilos of ammonium sulphate. From 100 kilos of green oil are then obtained 31 kilos of burning oil, 13 kilos of lighting oil, 11 kilos of middle oil, 15 kilos of paraffin wax, and 15 to 20 per cent, of gas, water, and loss, the remainder being coke (about 3 per cent. ), which is used as a black pigment. In 1873, 524 tons of oily shales were treated in Scotland, in 1893 about 2,000,000 tons, and in 1909 3,000,000 tons, giving 280,000 tons of crude oil. The Scotch shale- oil refineries produced in 1908 90,000 tons of burning oil, 16,000 tons of engine oil, 40,000 tons of gas-oil, 40,000 tons of lubricating oil, 25,000 tons of paraffin wax, and 60,000 tons of ammonium sulphate. In 1908 134,163 tons of bituminous shale, of the value 72,400, were produced in Italy. In France 219,000 cubic metres were distilled in 1890. In Germany 80,000 tons of lignite tar (corresponding with 600,000 tons of lignite) are distilled annually, and the products obtained (9000 tons of paraffin wax two-thirds hard and one-third soft 5000 tons of solar oil, and 3500 tons of heavy oil) have a value of about 880,000.! Tar can be purchased from the lignite distilleries at little more than lOd!. per quintal (2 cwt. ) and, treated as above, yields 14s. 5d. to 16s., taking as the average selling prices per quintal : paraffin wax, 3 12s. ; solar oil, 10s. 5d. ; yellow oil of paraffin, 12s. lOrf. ; dark oil of paraffin, 10s. 5d. The competition of the Galician product lowered the price of paraffin wax in 1910 and 1912 to 20 per ton. In various countries there are special bituminous shales which have originated from the decomposition of immense heaps of fish accumulating at the bottom of former seas, the decomposition products being interlayered with clay and then carried by geological convulsions to the surface of the earth and to the summits of mountains. These shales abound in the residues of numerous different fish and also in vegetable d6bris, and the bitumen or oil obtained from them by distillation contains large proportions of organic sulphur (2 to 10 per cent. ) and nitrogen (24 per cent. ), which impart to the crude oil an unpleasant odour and a deep brownish-yellow colour with greenish reflection. The most important deposit of these ichthyolic shales, which are worked industrially for the preparation of ichthyol 2 (used extensively in medicine, especially for the treatment 1 The bituminous coal of Messel (see note, p. 94) is utilised in a special way, the vapour derived from the drying of the coal being employed in the upper part of the vertical retort to produce water-gas. The vapour is injected by means of a blower into the bottom of the retort, where it meets red-hot coke, all the nitrogen of the latter being transformed into ammonia, which issues with the water-gas and the vapours from the distillation at a point about one-third up the retort, (Ger. Pat. 200,602, 1906). This process for utilising the nitrogen of the coke is derived from that patented by A. Grouven in 1878 (hence prior to the Mond process) for the utilisation of the nitrogen of peat.. To fix the ammonia of the gases and vapours, these are passed into a species of Glover tower, in which they are washed by a spray of dilute sulphuric acid, the ammonium sulphate solution obtained being concentrated to crystallisation by means of the heat of the furnace and of the distillation products, which are thus appreciably cooled. The tar from the Messel coal has the sp. gr. 0-855 to 0-860 at 44. 2 Ichthyol is an oil of sp. gr. 0-865 which is obtained between 100 and 255 during the dry distillation of ichthyolic bituminous shale. On distillation it yields, besides a highly luminous gas, 5 to 7 per cent, of crude ichthyol. On distillation, these shales lose 30 to 40 per cent, of their weight. The Besano oil is richer in pyridine bases than that of Seefeld, which contains 1 per cent, of them (Baumann and Schotten, Contardi and Malerba). Treatment of this oil (when redistilled it is almost colourless and contains 2-5 per cent, or more of sulphur) with concentrated sulphuric acid yields ichthyolsulphonic acid containing 10 to 15 per cent. S (like sulphoricinates ) and forming salts (ichthyolsulphonates) with soda, or better with ammonia, which are used in the cure of skin diseases. Ammonium ichthyolsulphonate (C 22 H, 6 6 S 3 (NH 4 )2 ?), which commonly bears the name of ichthyol, forms a dense, reddish brown liquid, soluble in water, and its solution gives a black resinous deposit with HC1 and yields NH 3 when treated with KOH ; it dissolves also in a mixture of alcohol and ether. When heated in the air it burns without leaving a residue, while at 100 it does not lose more than 50 per cent, of its weight (water). If a current of steam is passed on to the surface of boiling ichthyol, the latter is rendered almost odourless (Knoll & Co., Ger. Pat. 118,542, 1899), but deodorisation with hydrogen peroxide destroys the medicinal properties ; the deodorised product is termed desichthyol. The best qualities of ichthyol contain between 3 to 5 per cent, and 8 per cent, of sulphur as sulphonic group and between 4-5 per cent, and 14 per cent, of sulphur as SH, the total sulphur amounting to 12 to 18 per cent, and the combined ammonia to 2-5 to 4-3 per cent. Aniline is an ammonium ichthyolsulphonate purified by means of alcohol; its aqueous solution dissolves 104 ORGANIC CHEMISTRY of painful sores and inflammations) occur at Seefeld and at Beith, near Innsbruck in the Tyrol ; similar deposits are found in various parts of Italy. IV. Another source^ one of the most important, of paraffin wax is Ozokerite (or mineral wax}. It is found in England, Russia, and America, but the deposits of greatest industrial and historical importance are those of Galicia (that of Boryslaw gives 3000 tons and that of Dzwiniacz about 1000 tons per annum, while those of Pomiarki and Starunia are of inferior quality), where it occurs in seams as much as a metre in thickness. It was discovered by Doms when searching for petroleum, and from 1860-1870 was worked by the Landesberg process for the extraction of a kind of paraffin wax, which competed keenly with that of Saxony and Thuringia (from lignite, see p. 95) ; in 1870, Pilz and Ujhelyi found that simple treatment of ozokerite twice with concentrated sulphuric acid, followed by decolorisation - with prussiate black (see Vol. I., p. 840), yields cerasin, a product of greater value than, and similar to, beeswax. 1 In the State of Utah, the industrial treatment of ozokerite was begun in 1888, and in 1890 already yielded as much as 600 tons of crude cerasin. In recent years the decolorisation of ozokerite has been simplified, but whereas with paraffin wax fuller's earth (see Vol. I., p. 738; also this Vol., chapter on Vegetable Oils) may be used as a decolorising agent in place of prussiate black (which is increasing in price owing to diminished production), this does not serve in the case of cerasin. A special decolorising material, termed francolite or tonsile, gives, however, complete decolorisation at one-half the cost, after a single treatment of the ozokerite with sulphuric acid ; extrac- tion of the decolorised residues with benzine is then somewhat difficult, but the difficulty is overcome by using trichloroethylene (see p. 122), which is denser, and by extracting in lead-lined apparatus. Ozokerite forms an amorphous mass of a yellow, brown, greenish, or black colour and of varying consistency ; the harder varieties show a fibrous fracture ; the specific gravity is 0*85 to 0'95, and the m.-pts. of the various commercial varieties are 84 to 86, 65 to 76, and 55 to 65 ; these contain less than 5 per cent, of moisture and volatile products. Pure ozokerite contains 85 to 86 per many substances insoluble in water (camphor, volatile oils, phenol, etc.). The ichthyolsul- phonates of the heavy metals are only slightly soluble in water. Of the many other derivatives (and substitutes, e. g., thyd, obtained by treating tar-oils with sulphur), mention may be made of ichthyoform (blackish brown, inodorous), prepared by treating ichthyolsulphonic acid with formaldehyde and used as an antiseptic for the intestines and instead of iodoform for curing wounds ; it costs 4 per kilo and ammonium ichthyolsulphonate 1 per kilo. 1 The material from the mines (shafts 80 metres or more in depth), which contains admixed earth and stones, is placed in open vessels holding 300 litres and heated by direct fire heat ; the mineral matter settles to the bottom and is separated by decantation. This matter still con- tains 10 per cent, of wax, which is extracted with benzine (extraction wax); both this and the decanted part (fusion wax) form the prime materials treated in the refineries found in all countries. The refining is carried out in large iron boilers holding up to 3000 kilos of the crude wax, half a metre being left free to take the scum which forms. The fused mass is kept at 115 to 120 for four to five hours and is stirred to liberate all the water; 15 to 25 per cent, (according to the quality of the wax) of fuming sulpmiric acid containing 65 per cent, of free S0 3 is then added, in a thin stream, to the mass, which is thoroughly stirred meanwhile; the temperature rises slowly to 165 and then to 175, with vigorous evolution of S0 2 and formation of froth, which may overflow and take fire if the hearth is not well isolated. The oxidisable impurities separate as a black mass (asphalte) and the excess of sulphuric acid evaporates. The vessel is covered and provided with a draught-pipe to carry off the acid vapours. When emission of S0 2 ceases, the mass is heated to 180 to 200 and then allowed to cool slowly, being neutralised and decolor- ised with 5 to 6 per cent, of cyanide Uack [which is the residue from the old method of making yellow prussiate (see Vol. I., p. 840) and contains animal black, alkaline earth carbonates and phosphates, and iron oxide and sulphide] or with blood carbon, and is sent hot to the filter- presses. The mass obtained is still slightly yellow and is whitened by further treatment with sulphuric acid. When beeswax is to be imitated, turmeric, quinoline yellow or other coal-tar dye is added, together with a little Peru balsam to impart the required odour. The filter-press residues are mixed with sawdust or, better, with rice husks, and extracted with benzine to recover all the cerasin ; after recovery of the benzine, the insoluble residue is used as fuel. PARAFFIN WAX STATISTICS 105 cent, of carbon and 14 to 15 per cent, of hydrogen, and hence consists principally of paraffins, together with a small proportion of defines ; it is soluble in benzine, turpentine, petroleum, ether, and carbon disulphide, but only slightly so in alcohol. It forms an excellent electrical insulator, and may be used in place of gutta-percha. According to Hofer, ozokerite has been formed by the slow evaporation, during many centuries, of petroleum rich in paraffin wax. On distillation it yields : 2 to 8 per cent, of benzine, 15 to 20 per cent, of naphtha, 36 to 50 per cent, of paraffin wax, 15 to 20 per cent, of heavy oils, and 10 to 20 per cent, of residual solids. STATISTICS AND PRICE OF PARAFFIN WAX. The importation of paraffin wax, cerasin and vaseline into Italy was as follows (tons) : 1905 1908 1910 1912 1913 1914 1915 1916 1917 Paraffin wax . 8878 11932 19153 25584 24557 21042 32436 33638 26278 Cerasin . . 41-7 111 88 110 76 89-3 40 18-5 3-2 Vaseline . 110-5 109-4 124 109-4 84 116 288 471 In 1908 fourteen factories in Germany treated 70,000 tons of lignite tar, worth about 160,000, and produced 45,000 tons of oil, 11,000 tons of crude paraffin wax (equal to 7600 tons of the pure wax, worth 220,000), and 8000 tons of creosote, tar, and pitch, of the total value of 450,000; about 1,000,000 tons of lignite were distilled and 350,000 tons of coke left. For several years, however, the industry has been stationary. In 1910 Germany imported 17,000 tons of paraffin wax and wax candles, besides 46,500 tons of gas- oil. In order to offer more effective resistance to the crushing competition of Austria (Galicia), the five largest German works combined in 1913, with a capital of more than 3,200,000, three small factories remaining outside of the combine. France imported 624 tons of ozokerite in 1913, 483 in 1914, and 335 in 1915. Galicia produced 2116 tons of ozokerite and 62,000 of paraffin wax in 1910. The United States exported 75,000 tons of paraffin wax in 1905, 90,000 in 1910, and 96,000 (1,440,000) in 1911 ; 95 per cent, of the American output is in the hands of the Standard Oil Company. The petroleum of Tscheleken (Russia) contains up to 8 per cent, of paraffin wax and is treated in a Baku works, which produced 34 tons of wax in 1908, 160 in 1909, 600 in 1910, and 700 in 1911. In 1907 Great Britain produced 3500 tons of paraffin wax, and in 1909 imported 50,000 tons (1,400,000) and exported 17,000 tons (408,000); in 1910, 14,000 tons were exported. The Scotch shales yielded 23,000 tons of paraffin wax in 1910. Spain imported paraffin wax to the value of 90,400 in 1909-and 112,000 in 1910. The market price of paraffin wax varies somewhat with its melting-point : first quality white, m.-pt. 38 to 40, costs 39 per ton; that with m.-pt. 42 'to 44, 41 ; m.-pt. 48 to 50, 43; m.-pt. 56 to 58, 46; m.-pt. 60 to 62, 50. That used in pharmacy, m.-pt. 74 to 76, costs as much as 96, and the crude wax about 29. For some years before the war the price was lowered considerably, owing to the large output in Galicia, whence it was exported even at 16 per ton. Pure white cerasin resembles wax, melts at 62 to 80, has the sp. gr. 0-918 to 0-922, and is dextro-rotatory. It is used in making candles, in perfumery, as dressing for textiles, in making boot- and floor-polish, waxed paper, pomades and cosmetics, crayons, etc. It is subject to' much adulteration 1 owing to its high price. Before the war, first quality yellow cerasin, m.-pt. 62 to 63, cost 54 per ton; second quality, 46^ that with m.-pt. 68 to 70, 60, and the white variety, m.-pt. 52 to 63, 66. 2 1 The analysis of paraffin wax, vaseline, cerasin, mineral oils, etc., is described in treatises dealing with the analysis of industrial products, e. g., Villavecchia's " Applied Analytical Chemistry," Vol. I. 2 A mixture of cerasin and paraffin wax may be detected by the following tests : a glass rod 3 mm. in diameter is immersed to a depth of 1 cm. in the fused substance, extracted, allowed to cool, and hung in a test-tube heated externally with water. If the wax drops above 66, it is pure cerasin, whereas if it drops below 66 it is regarded as mixed with paraffin wax or as the latter alone. The dropping -point may be determined also with the Ubbelohde apparatus (p. 6). Addition of colophony is recognised by the acid number or saponification number, colophony being saponifiable and cerasin not. 106 Cerasin has been made in continually diminishing quantity since 1913, owing to its cost, and even in making candles has been replaced more or less completely by paraffin wax. The high price of cerasin depends on that of ozokerite, which is now partially exhausted and occurs to some extent at great depths (300 metres at Boryslaw and 100 metres at Dzwiniacz). The ozokerite worked in Austria-Hungary in 1877 amounted to 8961 tons; in 1885, 13,000 tons; and in 1894, 6742 tons. The exportation of cerasin was 3594 tons in 1891, and 2382 tons in 1895. In the United States the production of refined ozokerite, which was 160 tons in 1888, rose in 1892 to 75,000 tons, of the value of 4,000,000. (b) UNSATURATED HYDROCARBONS I. ETHYLENE SERIES : C n H 2fl (Alkylenes or defines) Two groups belong to this series : the olefine group, the first member of which is ethylene, C 2 H 4 , the succeeding ones being open-chain hydrocarbons with a double linking between two carbon atoms, since hydrogen, halogens, ozone, etc., can be readily added to them, transforming them into saturated compounds of the paraffin series. The other group yields additive products only with difficulty, and its members are formed of closed carbon-chains (cyclic compounds}. The first term is trimethylene or cyclopropane, hexamethylene and higher compounds being known : H CH 2 /\ H 2 C CH Trimethylene H 2 C< >CH 2 H Hexamethylene The carbon atoms in these last compounds are all in the same conditions and cannot be differentiated. The cyclic compounds will be studied as a separate section of the aromatic series (Part III). The following Table gives the more important members of the olefine series (the numbers in parentheses representing boiling-points under reduced pressure) : Melting- point Boiling- point Melting- point Boiling- point Ethylene, C 2 H 4 . - 169 - 103 Decylene, C 10 H 20 172 Propylene, C 3 H 6 -48 Endecylene, C n H 22 195 Butylene (3 isoms. ), | ^ C H 1 " -5 ; + 1 ' Dodecylene, C^H^j . Tridecylene, C 13 H 26 - 31 (96) 233 * 8 (y 6 Tetradecylene, C 14 H 28 . - 12 (127) Amylene (5 isoms. ), Pentadecylene, C 15 H 30 247 c 5 H i<>; Hexadecylene (Cetene) \ 40 ( 274 Normal amylene + 35 C 16 H 32 / : \ (155) Hexylene, C 6 H 12 68 Octadecylene, C 18 H 36 . + 18 (179) Heptylene, C 7 H 14 98 Eicosylene, C 20 H 40 Octylene, C 8 H 16 124 1 Cerolene, C 27 H 54 + 58 Nonylene, C 9 H 18 153 Melene, C 30 H 6(1 . + 62 The official nomenclature of the defines is the same as that of the paraffins, excepting that the final ane is changed into ene (thus ethylene, which is isologous with ethane, is called ethene, and so on; see also p. 29). These unsaturated hydrocarbons differ little in their physical properties from the corresponding saturated homologues. ETHYLENE HYDROCARBONS 107 The first terms up to C 4 H 8 are gases, and after C 5 H 10 come liquids with increasing boiling-points, these gradually approaching one another as with the paraffins; the higher members are solid and, like the paraffins, have the sp. gr. 0'63 to 0'79, are insoluble in water, but soluble in alcohol or ether. The chemical properties differ somewhat from those of the saturated com- pounds. Thus, they readily take up HC1, HBr, HI, Cl, Br, I, fuming H 2 S0 4 , hypochlorous acid (giving chloro-alcohols or chlorhydrins, e. g., CH 2 : CH 2 -f HC10 = CH 2 C1 ' CH 2 OH), hyponitrous acid, ozone, etc., forming compounds of the saturated series. Cl is added more easily than I (see Iodine number : chapter on Fats), Br occupying an intermediate position, whilst HI is added more easily than HBr, and this more easily than HCl. With these acids, the halogen is added to the carbon atom with which the least hydrogen is combined. Ethylene unites with fuming sulphuric acid at the ordinary temperature and with the ordinary acid at 165, forming ethylsulphuric acid, C 2 H 5 S0 3 H ; with higher compounds, the acid radicle passes to the less hydrogenated carbon atom. They often polymerise under the action of sulphuric acid or zinc chloride ; for example, amylene, C 5 H 10 , forms C 10 H 20 , and C 15 H 30 gives C 20 H 40 . They are readily oxidisable, for example, with potassium permanganate or chromic acid (not with nitric acid in the cold), the chain being then broken at the double linking, with formation of oxygenated compounds (acids) con- taining fewer carbon atoms in the molecule. Careful use of permanganate results initially in the addition of two hydroxyl groups without breaking .the chain and forming dihydric alcohols (glycols), for example, OH CH CH OH. 1 Almost all compounds with a double linking between atoms of carbon give Baeyer's reaction, that is, they rapidly discharge the violet colour of a dilute solution of potassium permanganate and sodium carbonate, with formation of a reddish-brown flocculent precipitate of hydrated manganese peroxide. This reaction is not given by reducing substances like aldehydes or by certain aromatic compounds (phenanthrene, etc.). With tetranitromethane they give a yellow or brown coloration (the nitro- derivatives and organic acids being exceptions), tautomeric enolic compounds also reacting in this way (see p. 18 : I. Ostromislenski). All compounds with doubly linked carbon atoms give the ozone reaction (Harries, 1905, and Molinari, 1907), that is, when dissolved in a suitable solvent they fix, quantitatively and in the cold, the ozone contained in a current of ozonised air passed through the solution; in this property they differ from compounds with either a triple linking or a benzene double linking (E. Molinari, Ann. Soc. Chim. Milan, 1907, 116). Of interest also are the formolite and nitric acid reactions (see pp. 71, 91). METHODS OF PREPARATION. (1) They are formed, together with petroleum, in the dry distillation of wood, lignite, coal, paraffin wax ("cracking," see pp. 87, etc.). 1 From what has been said up to the present, it is obvious that a double linking does not signify a firmer union between carbon atoms ; it is simply a conventional sign. The breaking of the chain, by oxidising agents, at the double linking is to be attributed to the ease of formation of intermediate products (e. g., dihydric alcohols) rather than to a less attraction existing between carbon and carbon at that point. Such readiness to react may, according to Baeyer, be explained by regarding the affinities of the carbon atom as orientated or grouped at four poles arranged like the vertices of a regular tetrahedron (see pp. 19 et seq.). If two carbon atoms unite by a double linking, the poles at the surface of the carbon atoms become displaced and approach one another, so that there results a certain tension which explains the readiness with which the double linking reacts or opens. After the initial oxidation leading to these intermediate products, further action of the oxidising agent, as a general rule, oxidises or breaks the chain at a point where oxygen already exists, that is, where the oxidation is already begun (see Part III, The Hypothesis of the Partial Valencies of the Benzene Nucleus). 108 ORGANIC CHEMISTRY (2) By eliminating water from the alcohols, C n H 2n . jOH, by heating them with dehydrating agents (H 2 S0 4 , P 2 5 , ZnCl 2 , etc.); a stable intermediate product is sometimes formed, e. g., ethylsulphuric acid, C 2 H 5 HS0 4 , which at a higher temperature gives ethylene and sulphuric acid. Higher alcohols and ethers are resolved, merely on heating, into olefines and water. (3) From saturated halogen derivatives, C n H n+1 X (X = halogen), especially from secondary and tertiary bromo- and iodo-derivatives, by heating them with alcoholic potash, or by passing their vapours over heated lime or lead oxide, etc. C 5 H n I + C 2 H 5 OK = KI + C 2 H 5 OH + C 5 H 10 . The mixed ether, C 5 H U O ' C 2 H 5 , may also be formed to some extent. (4) From dihalogenated compounds by heating with zinc : C 2 H 4 Br 2 + Zn = ZnBr 2 + C 2 H 4 . (5) By electrolysis of dibasic acids of the succinic acid series : C 2 H 4 (COOH) 2 = C 2 H 4 + 2C0 2 + H 2 . (6) Unsaturated compounds are obtained by heating the condensation products of the ketenes (q.v.). CONSTITUTION OF THE OLEFINES. In this group it is assumed that between two carbon atoms there exists a double linking : H 2 C = CH 2 , H 2 C = CH CH 3 , etc., the presence.of two free valencies, thus, H 2 C CH 2 or HC CH 3 , being excluded for the following reasons | | A In unsaturated compounds the addition of halogen does not take place at a single carbon atom, so .that ethylene chloride, C 2 H 4 C1 2 , has not the formula CH 3 CHC1 2 , which is that of ethylidene chloride obtained from acetaldehyde, CH 3 CHO, by replacement of the O by C1 2 (by the action of PC1 5 ). Since ethylene chloride is chemically and physically different from ethylidene chloride, the former must have the constitutional formula, CH 2 C1 CH 2 C1, and the third formula for ethylene, CH 3 CH<^ is thus excluded. The second formula is not probable because, if the existence of free valencies is assumed, they could occur also in non-adjacent carbon atoms, and thus give rise, in the higher hydrocarbons, to numerous isomerides which have, however, never been prepared (if propylene had two free valencies, four isomerides should exist, instead of only one); further, the addition of halogen always takes place at two contiguous carbon atoms (see Note on preceding page). Finally, the assumption of free valencies in organic compounds is inadmissible in view of the unsuccessful attempts to prepare methylene (or methene), CH 2 , for instance, by elimin- ating HC1 from methyl chloride, 2CH 3 C1 = 2HC1 -f 2CH 2 < ; the two methylene residues always condense, forming ethylene, as the two valencies cannot remain free. ETHYLENE, C 2 H 4 (Ethene), H 2 C = CH 2 . This is a gas, becoming liquid at 103 and solid at 169, or liquid at under 44 atmos. pressure. It is very slightly soluble in water or alcohol. It has a somewhat pleasant smell and burns with a luminous flame ; indeed, illuminating gas, which contains 2 to 3 per cent, of ethylene, owes part of its luminosity to this gas. When mixed with 2 vols. of chlorine it burns with a dark-red flame, carbon being deposited and HC1 formed. At a red heat it yields C, CH 4 , C 2 H 6 , C 2 H 2 , etc. ; with hydrogen in presence of spongy platinum or, better, powdered nickel at 300, it is converted into ethane. It is prepared in the laboratory by heating alcohol with excess of sulphuric acid; as an intermediate product, ethylsulphuric acid is formed, this giving ethyle-ne when heated : C 2 H 5 OH + H 2 SO 4 = H 2 O + C 2 H 5 HS0 4 ; C 2 H 5 HS0 4 = H 2 SO 4 + C 2 H 4 . Pure ethylene is obtained (1) by passing a mixture of carbon monoxide and hydrogen over finely divided nickel or platinum at 100 : 2CO -J- 4H 2 = C 2 H 4 -j- 2H 2 ; (2 ) by dropping alcohol on to phosphoric acid at 200 to 220 ; or -(3) from ethylene bromide and a copper zinc couple. DIOLEFINES 109 PROPYLENE, C 3 H 6 (Propene), CH 2 = CH CH 3 . This may be prepared by heating glycerol with zinc dust or from isopropyl iodide and potassium hydroxide. It is a gas which liquefies at 48 and is isomeric with trimethylene. BUTYLENES, C 4 H 8 (Butenes). Three isomerides, the a, ft, and y, are known, and are obtained by treating normal, secondary, and tertiary butylene iodides respectively with potassium hydroxide : CH 2 - CH CH 2 CH 3 CH 3 CH - CH CH 3 . C C Butene-1 (a-butylene) Butene-2 (/3-butylene) 2-Methylpropene (isobutylene) Tetramethylene or cylobutane is isomeric with the butylenes. AMYLENES, C 5 H 10 (Pentenes). Of the various isomerides theoretically possible several have been prepared. By heating/^seZ oil (of distilleries) with zinc chloride, pentanes and various isomeric amylenes are formed which may be separated by means of the different velocities with which HI is added" to them, or by the property possessed by some of them of dissolving in the cold in a mixture of concentrated sulphuric acid and water in equal parts, forming amylsulphuric acid, whilst, the others either do not react or give condensation products (di- and triamylenes). NORMAL OCTYLENE or CAPRYLENE, C 8 H 16 , is formed as a secondary product in the preparation of octyl iodide (from octyl alcohol and phosphorus iodide). It is a colourless liquid, b.-pt. 124, and with concentrated nitric acid forms nitro- and dinitro- octylene. CEROTENE, C 27 H 54 , and MELENE, C 30 H 60 , are similar to paraffin wax, and are obtained by distilling Chinese wax or beeswax. II. HYDROCARBONS OF THE SERIES, C w H 2n _ 2 A. With Two Double Linkings (Diolefines or Allenes) Of the few known terms of this series, the first and best investigated is ALLENE, H 2 C : C : CH 2 (propandiene) : this is a colourless gas which differs from its isomeride allylene in not forming metallic derivatives; it is obtained by eliminating one atom of bromine from tribromopropane by means of potassium hydroxide and the remaining two by zinc dust, its constitution being thus rendered evident : CH 2 Br CHBr CH 2 Br->CH 2 : CBr CH 2 BrCH 2 : C : CH 2 . ERYTHRENE, C 4 H 6 (Pyrrolilene or Butan-1 : 3-diene), CH 2 : CH CH : CH 2 , is a gas found in illuminating gas, and when heated with formic acid gives erythritol. ISOPRENE, C 5 H 8 , boils at 37 and is obtained by distilling rubber. On the other hand, with concentrated HC1, it condenses, regenerating rubber or forming terpenes, C 10 H 16 , CTT CjgH^, etc. Since dimethylallene, pTT 3 ]>C C : CH 2 , gives, with 2HBr, a dibromide, CH r 3^>CBr CH 2 CH 2 Br, which is identical with that obtained from isoprene + 2HBr, v the constitution of isoprene must be - \C CH : CH 2 . CH/ Isoprene was prepared for the manufacture of synthetic rubber by decomposing turpentine in various ways, first by Tilden in 1882, and later by Woltereck (1909), Wallace (1909), Harries (1910), and Silberrad (1910 : see Eng. Pats. 19,701 and 27,908 of 1909, and 4001 of 1910). The Badische Anilin-und Soda-Fabrik (French Pat. 425,885 and Addition No. 14,542, 1911) passes vapours of turpentine or, better, of limonene, dipentene, carvone, etc., over metallic filaments rendered red-hot by the passage of an electric current, the product being diluted either with indifferent gases or by evacuation. Harries (1910) obtains isoprene by heating halogenated derivatives of isopentane at 600 in presence of basic oxides, carbonates, or organic salts. According to U.S. Pat. 1,206,419 (1912) isoprene (or diolefines in general) is obtained on passing the vapours of dihalogenated paraffins [e. g., trimethylethylene bromide (CH 3 ) 2 : Br CHBr CH 3 ] at 300 into a vacuum over heated barium chloride (catalyst) and washing the resulting vapours in water to fix the HBr. 110 ORGANIC CHEMISTRY The normal isomeride, PIPERYLE'NE, CH 2 : CH CH 2 - CH : CH 2 (Pentan-1 : 4-diene) boils at 42 and is obtained from piperidine. DIALLYL, C 6 H 10 (Hexine), is prepared by the general reaction the action of sodium on allyl iodide which indicates its constitution : 2CH 2 : CH CH 2 I + 2Na = CH 2 : CH CH 2 CH 2 CH : CH 2 + 2NaI. CONYLENE, C 8 H U (1 : 4-octadiene), CH 2 : CH CH 2 CH : CH CH 2 CH 2 CH 3 , 'boils at 126, and is obtained from coniine. B. Hydrocarbons with Triple Linkings (Acetylene Series) The most important members of this series are : Acetylene, C 2 H 2 (ethine), HC = CH, gas. Allylene, C 3 H 4 (propine), CH 3 'C = CH, gas. Crotonylene, C 4 H 6 (2-butine or dimethylacetylene), CH 3 C ' C CH 3 , boils at 27. Ethylacetylme, C 4 H 6 (3-butine), CH 3 CH 2 C : CH, boils at 18. Methylethylacetylene, C 5 H 8 (3-pentine), CH 3 CH 2 C \ C CH 3 , boils at 55. n-Propylacetylene, C 5 H 8 (4-pentine), CH 3 CHg CH 2 C \ CH, boils at 48. CH Isopropylacetylene, C 5 H 8 (3-methyl-l-butine), CH 3 >CH'C j CH, boils at 28. 3 Several of these compounds (the first three) are formed during the dry distillation of coal and other complex substances, and are hence found in lighting gas. In the laboratory they are obtained by the following methods : (a) By electrolysing acids of the fumaric acid series (see later) : COOH CH ; CH COOH = H 2 + 2CO 2 + HC : CH. (6) By heating with alcoholic potash the halogenated compounds (best the bromo-derivatives), C n H 2n X 2 and C B H 2n _. 2 X 2 , gradual elimination of halogen hydracid (of HBr or, in presence of KOH, of KBr and H 2 O) occurs : C 2 H 4 Br 2 = HBr + C 2 H 3 Br > HBr + C 2 H 2 . In general, starting from the saturated hydrocarbons, C n H 2n + 2 , the action of halogen and elimination of halogen hydracid gives an unsaturated hydrocarbon, C B H 2n ; addition of halogen to this and subsequent removal of halogen hydracid gives a still less saturated hydrocarbon, C B H 2n _ 2 , and so on. Elimination of 2HC1 from the compounds C B H 2n Cl 2 , obtained from alde- hydes or from certain ketones (methylketones, C B H 2n+ 1 - CO CH 3 ) by the action of PC1 5 , yields always a trebly linked compound, in which, however, one of the carbon atoms is always united to a single, characteristic hydrogen atom : C == CH ; for example, acetaldehyde gives ethylidene chloride, CH 3 CHC1 2 , which then yields 2HC1 + CH I CH ; while acetone, CH 3 CO CH 3 , gives chloro- acetone, CH 3 CC1 2 CH 3 , and this 2HC1 -f CH 3 C = CH, the elimination of halo- gen hydracid never occurring in such a way as to give compounds with two double linkings, such as CH 2 : C : CH 2 . Acetylene derivatives are obtained also by heating the acids of the propiolic series (see later). Compounds with this characteristic hydrogen atom C = CH have a feebly acid character and form solid metallic derivatives (acetylides) when treated with an ammoniacal solution of copper chloride or silver nitrate : copper acety- lide, Cu ' C : C ' Cu, H 2 0, having a reddish-brown colour and apparently the con- stitution Cu 2 CH CHO, since with hydrogen peroxide it gives acetaldehyde, CH 3 ' CHO (Makowka, 1908) ; and silver acetylide, AgC CAg, which is white and insoluble in water or ammonia and, in the dry state, is extremely explosive, simple rubbing being sufficient to explode it. With hydrochloric acid it regenerates acetylene in a pure state. ACETYLENE 111 The proof that it is the characteristic hydrogen atom which is replaced by metals lies in the fact that acetylene derivatives from other ketones (not from methylketones) do not give metallic acetylides : CH 3 CH 2 CO CH 2 CH 3 -> CH 3 CH 2 CC1 2 CH^ CH 3 > 2HC1 4- CH 3 C i C CH 2 CH 3 . Four atoms of a halogen or of hydrogen may be added to the hydrocarbons of the acetylene series, saturated compounds being formed ; as a rule, however, only two atoms are readily added, although under the action of light four halogen atoms may be added almost always. The compounds of the define series may, however, be distinguished from those of the acetylene series by means of the ozone reaction, since compounds with a triple linking do not fix ozone from ozonised air at all (Molinari; see p. 107). The hydrocarbons of the acetylene series take up a molecule of water in presence of mercury salts, giving rise to complex mercuric compounds, which, with HC1, give as final product an aldehyde or ket(5ne of the saturated series : CH 3 C i CH (allylene) + H 2 = CH 3 CO CH 3 (acetone) or CH ! CH + H 2 O = CHg'CHO (acetaldehyde). The last reaction serves to illustrate the transformation of inorganic into organic substances (see later, chapter on Alcohol). In the acetylene series, also, condensation or polymerisation is possible, three molecules of acetylene, when heated, yielding benzene, C 6 H 6 ; three molecules of dimethylacetylene, C 4 H 6 , giving, with concentrated sulphuric acid, hexa- methylbenzene, C 6 (CH 3 ) 6 , and allylene, C 3 H 4 , similarly yielding trimethylbenzene (mesitylene), C 6 H 3 (CH 3 ) 3 . In the higher compounds, the position of the triple bond is deduced from the oxidation products, since, as with substances with a double linking, the breaking of the chain occurs at the multiple linking. When certain acetylene derivatives, e. g., XC = C * CH 3 , are heated with sodium, the triple bond changes its position, the products being sodium deriva- tives of isomeric hydrocarbons, X CH 2 C : CH (these give metallic acetylides, but the original compounds do not); when these are heated with alcoholic potash, the reverse change occurs. ACETYLENE, C 2 H 2 (Ethine), HC : CH. Without having isolated or char- acterised this compound, Davy obtained it in 1839 in a very impure condition, by treating with water the product obtained by heating together potassium carbonate and carbon, which should yield potassium. Berthelot first obtained it pure (and named it) in 1859, by passing ethylene or alcohol or ether vapour through a red-hot tube ; he prepared it also by means of a voltaic arc passing between two carbons in an atmosphere of hydrogen. In 1862, Wohler prepared it by treating calcium carbide (obtained by heating carbon with an alloy of zinc and calcium) with water. It is formed in the incomplete combustion of various hydrocarbons and of illuminating gas (e. g., in the flame of a bunsen burner alight at the bottom). The industrial preparation of acetylene has assumed great and unforeseen practical importance since 1870, when it became possible to prepare calcium carbide on an enormous industrial scale by means of the electric furnace (see " Calcium Carbide Industry," Vol. I., p. 638) : C \ HI >Ca 4- 2H 2 = Ca(OH) 2 + HC ! CH. V Acetylene is a colourless gas, sp. gr. 0'92 (1 litre weighs 1/165 grams), with a pleasant odour when pure and a disagreeable one when impure (as usually 112 ORGANIC CHEMISTRY obtained). At -f- 1 under a pressure of 48 atmos. it forms a highly refractive, mobile, colourless liquid, sp. gr. 0'451, and, on evaporating rapidly, partially solidifies in the form of snow, m.-pt. 81. One volume of acetylene gas dissolves in I'l vols. of water, -or in vol. of alcohol or in 20 vols. of saturated salt solution; 1 litre of acetone dissolves 24 litres of acetylene, or 300 litres at 12 atmos., or about 2000 litres at 80, its volume being then increased fourfold. Permanganate oxidises it, giving oxalic acid, and chromic acid acetic acid. It is an endothermic compound, requiring for its formation from its elements, 61,000 cals. ; it is hence very unstable and is readily decomposed by the detona- tion of a mercury fulminate cap or by an electric discharge, developing as much heat as an equal volume of hydrogen on conversion into water. The explosion takes place much more readily and is much more dangerous with the compressed gas and still more so with the liquid. Acetylene decomposes at 780 and, when mixed with air, fgnites at 480. One cubic metre (1'165 kilos) of acetylene, in burning, develops 14,350 Cals. (12,300 Cals. per kilo), whilst ordinary coal-gas gives about 5000 Cals. When mixed with air or, better, with oxygen it forms a detonating mixture which explodes with great energy in contact with an ignited body. The explosion is violent even with 1 vol. of acetylene and 40 vols. of air ; it reaches its maximum violence with 1 vol. of the gas and 12 vols. of air (2 '5 vols. of oxygen), whilst scarcely any explosion but mere burning takes place with 1 vol. of acetylene and 1'3 vols. of air (as has been already stated on p. 34, ordinary illuminating gas only explodes when at least 1 vol. is present to about 20 vols. of air). Explosive mixtures of acetylene are more dangerous than those of coal-gas owing to the greater speed of propagation of the explosion (e. g., with 1 vol. of acetylene and 40 of air), the explosive force being thus increased (see section on Explosives) ; further, acetylene contains less hydrogen and hence forms less water, the condensation of the gases resulting from the explosion being consequently smaller. The wide limits of the explosive mixtures (from 2 '4 to 130 vols. of acetylene per 100 vols. of air) are explained by the fact that this gas, being an endothermic compound, reacts or decomposes with great facility. In contact with copper, bronze, silver, etc., acetylene readily forms explosive acetylides (see p. 110), x but when perfectly dry does not attack metals. It was at first thought that acetylene, like carbon monoxide, was poisonous, but experiments made during the last few years have shown that animals do not die in an atmosphere containing 9 per cent, or, in some cases, even 20 per cent, of the gas. When, however, the acetylene is highly contaminated with sulphides and phosphides, it may be poisonous. With an ordinary gas-jet, acetylene burns with a reddish, smoky flame, but by passing the gas at a pressure of 60 mm. through two jets nearly meeting at an angle, a white, highly luminous, fan-shaped flame is obtained without the dark middle portion of the ordinary bat's- wing coal-gas flame. One kilo of chemically pure calcium carbide should yield theoretically 349 litres of acetylene, and good commercial carbide yields practically 300 litres. The luminosity of 1 The ready formation of metallic acetylides, especially that of copper, led Erdmann (1907) to devise a rapid and exact analytical method for the direct quantitative precipitation of copper from any solution and in presence of any metals (except Ag, Hg, An, Pd, and Os, which must be previously eliminated ) : the feebly alkaline solution of the copper salt is reduced until decolorised with hydroxylamine hydrochloride, C 2 H 2 being then passed through and the precipitated copper acetylide collected on a filter, washed with water and pumped off ; together with the filter-paper it is introduced into a porcelain crucible, treated with 10 to 15 c.c. of dilute nitric acid (sp. gr. 1-15) and eight to ten drops of concentrated nitric acid (sp. gr. 1-52), dried on a water-bath, heated rapidly to redness and weighed as CuO. The acetylene used for this precipitation should be washed with lead acetate solution. USES OF ACETYLENE 113 acetylene in comparison with that of other substances has already been referred to on p. 64. A proportion of 2 vols. of air to 3 of acetylene gives the maximum luminosity, and at the present time special incandescent mantles are made for use with acetylene. The impurities present in ordinary acetylene (98 to 99 per cent, purity) are : N, NH 3 , CO, H 2 S, and PH 3 , the last three of which are poisonous. The gas is purified by passing it through an acid solution of a metallic salt. Lunge and Cederkreutz recommend chloride of lime (hypochlorite) for purifying acety- lene, care being taken that the mass does not heat, as this would be dangerous. Latterly it has been suggested to fix the PH 3 by passing the gas through concentrated sulphuric acid (64 Be.) saturated with As 2 O 3 . A good purifying material is made by preparing a paste of calcium hypochlorite, quicklime, sodium silicate, and powdered calcium carbide, this remaining porous when allowed to dry in the air. USES. When the great calcium carbide industry was started, it appeared as though acetylene would be used solely as a competitor of illuminating gas, electricity, petroleum, etc., but most of the acetylene is now employed in cutting metals, while calcium carbide is largely used for the manufacture of calcium cyanamide (see Vol. I., p. 371). The use of liquid acetylene would be very convenient, but is highly dangerous, since a sharp blow or other accident might easily produce a terrible explosion. It is still too expensive to employ in place of benzene for carburetting coal-gas. Dis- solved in acetone (Claude and Hess, 1896), which dissolves a large quantity of it (vide infra), it is used to great advantage for the oxy '-acetylene blowpipe in place of oxy-hydrogen. With the latter, for every cubic metre of oxygen 4 cu. metres of hydrogen are used practically (theoretically 2 cu. metres), whilst the same amount of oxygen burns 'with 600 litres of acetylene (theoretically 400 litres), which costs much less than 4 cu. metres of hydrogen. The oxy-acetylene flame exhibits at the centre a shining point, which has a temperature of 2800 to 3000, and to weld iron sheets 1 mm. thick requires 50 to 75 litres of acetylene per hour, 5 metres being welded in this time. With a slight excess of oxygen large tubes are easily cut and steel blocks perforated. Acetylene dissolved in acetone, especially if the solution is ab orbed by porous material, is not at all dangerous and may be transported in iron cylinders. In moderate quantities acetylene dissolved in acetone is sold compressed in iron bottles capable of yielding 650 litres of the gas; these bottles are convenient for lighting mines, railway carriages, automobiles, etc. In the United States 300,000 of such bottles were used in 1913, while in Germany 6000 were used for automobiles alone. Acetylene is utilised in the preparation of numerous chloro-derivatives which have various practical applications, e. g., in the manufacture of indigo, acetaldehyde, acetic acid, and alcohol (see below). It is used also in the synthesis of thiophene (Steinkopf's method : see chapter on Thiophene), and also in that of rubber (according to Heinemann) ; when heated, a mixture of acetylene and ethylene condenses to butandiene, CH 2 : CH CH : CH 2 , this being converted by methylation into isoprene, CH 2 : C(CH 3 ) CH : CH 2 , which is polymerised by concentrated hydrochloric acid with formation of synthetic rubber. By repeated passage of a mixture in equal volumes of acetylene and hydrogen through tubes heated electrically to 650 to 800, considerable polymerisation of the acetylene is effected with formation of about 60 per cent, of tar containing 20 per cent, of benzene, a certain amount of naphthalene, and a little toluene, anthracene, diphenyl, fluorene, etc. (R. Meyer, 1912). Large quantities of acetylene are decomposed by the electric discharge to make very pure hydrogen and lamp-black (see Vol. I., pp. 142, 458 ; also B. P. Pictet's Ger. Pat. 255,733, 1909). The hope of manufacturing synthetic alcohol economically from acetylene had died out, but during the European War the enormous rise in the price of alcohol turned attention to this synthesis, although the industrial experiments which followed could not be sustained in normal times (see later : Alcohol). Even for engines it is still too dear to use. Acetylene can, however, be used conveniently with a rational plant and relatively small gasometers connected with iron tubes which carry the gas direct to the burners (when prepared from pure carbide), but it is necessary to avoid the use of copper or bronze in any part of the gasometers, pipes, and taps, in VOL. II. 8 114 ORGANIC CHEMISTRY order to avoid explosions, which are almost always due to the formation of copper acetylide. 1 In testing the purity of acetylene the only quantitative determination usually made is that of the hydrogen phosphide, which should not occur in greater proportion than 1 gram per cubic metre, since, besides being poisonous and having an unpleasant smell, it facilitates the formation of explosive metallic acetylides. (The estimation-of the impurities in carbide is described in Vol. L, p. 639.) III. HYDROCARBONS OF THE SERIES, C n H 2n _ 4 and C n H 2n _ 6 DI ACETYLENE, C 4 H 2 (Butandiine), CH i C C : CH, is a gas and forms the usual metallic acetylides. DIPROPARGYL, C 6 H 6 (Hexan-1 : 5-diine), CH i C'CH 2 'CH 2 -C \ CH, is isomeric with benzene, boils at 85, and can take up 8 atoms of bromine. It is obtained from diallyl, C 6 H 10 , and readily forms metallic acetylides. HEXAN-2 : 4-DIINE, CH 3 C ': C C ': C' CH 3> is also isomeric with benzene. BB. HALOGEN DERIVATIVES OF THE HYDRO- CARBONS The Table on page 115 summarises the physical properties of the more important halogen derivatives of the hydrocarbons, the first column giving the hydrocarbon residue (alkyl) united with the halogen. I. HALOGEN DERIVATIVES OF SATURATED HYDROCARBONS PROPERTIES. Very few are gases, several are liquids, and those which contain many atoms in the molecule are solids. The iodo-compounds boil at higher temperatures than the corresponding bromo- and chloro-compounds. They are very slightly, if at all, soluble in water, but are readily soluble in alcohol, ether, and glacial acetic acid. Most of them burn easily, and ethyl and methyl chlorides colour the edges of the flame green. Some of them, containing few carbon atoms, produce ancesfliesia, e. g., CHC1 3 , CH 2 C1 2 , C 2 H 3 C1 3 , C 2 H 5 Br, C 2 H 5 C1. Generally they do not react with silver nitrate, since these compounds are not dissociated in solution, and do not give free halogen ions (see Vol. I., pp. 96, 98 et seq.). In alcoholic solution, ethyl iodide gives a little precipitate in the cold, and ethyl bromide in the hot, whilst the chloride gives no precipitate at all, with silver nitrate. The bromo- and iodo-compounds exhibit great reactivity and effect the most varied and interesting reactions and syntheses; methyl iodide reacts the most readily of all, the reactivity diminishing with increase of molecular weight. The halogens of these compounds may easily be replaced by H (by sodium - amalgam, or zinc dust and hydrochloric or acetic acid). 1 The numerous types of apparatus for generating acetylene may be divided into three groups : (1) Those where the carbide and water are in separate vessels communicating by a tube furnished with a tap which automatically opens more or less and so diminishes or increases the supply of the gas. To prevent the carbide, or rather the lime formed, from holding water and generating gas even after the tap is closed, the carbide is impregnated with an indifferent sub- stance, e. g., paraffin wax, stearine, oil, sugar (to dissolve the lime as calcium saccharate), etc. One inconvenience of this procedure is that at'some places the carbide, in presence of little water, becomes excessively heated and may produce an explosion, which is dangerous if the gas is under pressure. (2) Those where the carbide is suspended at a certain part of the vessel containing the water; acetylene is then generated when the level of the water rises to the carbide and ceases automatic- ally when it falls. (3) Those where the carbide and water are separated, a small quantity of carbide being dropped into excess of water. This would be the most rational method, but is perhaps not the most convenient owing to the difficulty of powdering the carbide (often very hard) without allowing it to absorb moisture. HALOGENATED PARAFFINS 115 These derivatives may, to some extent, be transformed one into the other, e. g., the chlorides into iodides by treatment with KI or CaI 2 , and the iodides into the fluorides (more volatile than the chlorides) by means of silver fluoride. Alkyl Names of the Alkyls and Isomerides Chlorides Bromides Iodides B.-pt. Sp.gr. B.-pt. Sp. gr. B.-pt. Sp. gr. a SATUEATED DERIVATIVES (1) Afonosubslituted CH 3 Methyl - 23-7 0-952 (0) + 4-5 1-732 (0) + 45 2-293 (18) C 2 H5 Ethyl + 12-2 0-918 (0) 38-4 1-468 (13) + 72-3 1-944 (14) C 3 H 7 n-Propyl + 46-5 0-912 (0) 71 1-383 (0) 102-5 1-786 (0) Isopropyl 36-5 0-882 (0) 60 1-340 (0) 89 1-744 (0) C 4 H 9 n-Butyl (primary) 78 0-907 (0) 101 1-305 (0) 130 1-643 (0) Isobutyl 68-5 0-895 (0) 92 1-204 (16) 119 1-640 (0) sec.-Butyl . 119-120 1-626 (0) tert.-Butyl 55 0-866 (0) 72 1-215 (20) 100 1-571 (0) CjHji n-Amyl (primary) 107 0-901 (0) 129 1-246 (0) 156 1-543 (0) Isoamyl, (OH 3 ) 2 : CH- 101 0-893 (0) 121 1-236 (0) 148 1-468 (0) OH 2 -OH 2 -X tertiary-Butylmethyl 0-879 (0) 1-225 (0) 1-050 ?(0) (CH 3 ) 3 (C-OH 2 -X active- Amyl 97-99 0-886 (15) 118-120 1-221 (20) 148 1-524 (20) 6 H 13 (OH 2 )(0 2 H 6 )OH-CH 2 -X n-Hexyl (primary) 134 0-892 (16) 156 1-193 (0) 182 1-461 (0) C 8 H 17 n-Hexyl (secondary) n-Heptyl (primary) n-Octyl (primary) 159 180 0-881 (16) 0-880 (16) 144 179 199 1-113 (16) 1-116 (16) 168 201 221 1-453 (0) 1-386 (16) 1-345 (16) (2) Disubstituted >CH 2 Methylene, CH 2 X2 42 97 180 -CH 2 -CH 2 - Ethylene 84 . 131 . CH 3 -CH 2 < Ethylidene (or ethydene) 57 108 (3) Trisubslituted CHX 3 (chloroform, 61 151 solid bromoform, iodoform) m.-pt. 119 CH 3 'CC1 3 methylchloro- 74 . 188 form (a-trichloroethane) CHjjCl-CHCljj (/3-tri- 114 220 - chloroethane) CH 2 X-OHX-OH 2 X (tri- 158 chlorohydrin, tri- bromohydrin) (4) Polysubstituted OX 4 (carbon tetra- 77 solid chloride, iodide) C 2 01g perchloroethane solid m.-pt. 187 (6) UNSATURATED DERIVATIVES (1) Ethylenic series OS, : CH-X Vinyl chloride, etc. -18 23 56 Allvl 46 70 101 C 2 H 2 _:X 2 **- i t-j * ,, Dichloroethylene 55 C 2 H X 3 Trichloroethylene 88 n ~v O 2 ; A. 4 Tetrachloroethylene 121 (2)' Acetylene series no ; ox Monochloro- and mono- gas gas bromo-acetylene i METHODS OF PREPARATION, (a) By the action of halogens on satur- ated hydrocarbons : chlorine and bromine react directly at the ordinary temperature on the gaseous hydrocarbons, and on heating with the liquid ones. The first halogen atom is fixed more readily than the succeeding ones, and the addition of iodine facilitates the reaction with bromine and chlorine, since the iodine forms, for example, IC1 3 , which readily gives nascent chlorine, IC1 3 = IC1 -f C1 2 (i. e., it acts like Sb01 5 , which yields SbCl 3 -f C1 2 ). By saturating with chlorine and heating under pressure energetic chlorinations may be affected. Methane, ethane, propane, etc., exchange their hydrogen atoms one by one for chlorine atoms, the completely substituted compounds (C 2 C1 6 , C 3 C1 8 , etc., and especially the higher ones), on further energetic chlorination, being resolved 116 ORGANIC CHEMISTRY into other completely chlorinated compounds containing less numbers of carbon atoms: C 2 C1 6 + C1 2 = 2CC1 4 ; C 3 C1 8 + C1 2 = C 2 C1 6 + CC1 4 , a little hexa- chlorobenzene, etc., being always formed as well. Iodine scarcely ever acts directly on the hydrocarbons, since the HI formed acts in the opposite sense on the iodo -products. The reaction proceeds only in presence of iodic acid or mercuric oxide, which fixes the hydriodic acid as it is formed. The iodo-compounds are easily obtained from zinc-alkyls and iodine. When the halogens act directly, the more energetic (F or Cl) replaces the weaker (Br or I). The iodo-compounds may, however, be easily obtained by first preparing the magnesium compounds of the alkyl chlorides or bromides and treating these with iodine : Alkyl-Mg-Cl + I 2 = Alkyl-I + MglCl. (b) Unsaturated hydrocarbons, with the halogen hydracids, give saturated monosubstituted derivatives : C 2 H 4 + HBr C 2 H 5 Br, ethyl bromide, etc. ; if the halogens act directly, disubstituted saturated products are obtained : C 2 H 4 -f- C1 2 = C 2 H 4 C1 2 , ethylene dichloride. Propylene, CH 3 CH : CH 2 , reacts with HI, giving isopropyl iodide, CH 3 CHI CH 3 , which is decomposed by alcoholic potash, yielding propylene ; normal propyl iodide, CH 3 CH 2 CH 2 I, which also yields propylene when HI is removed from it, may thus be converted into isopropyl iodide. Similar behaviour is exhibited by the butyl iodides. The halogen always goes to the carbon atom united with the lesser number of hydrogen atoms : CH 3 CH : CH 2 + HI- = CH 3 CHI CH 3 . (c) The alcohols, C n H 2n+1 OH, with the halogen hydracids give : C n H 2n+1 OH + HBr = H 2 O -f- C n H 2n+1 Br, but the reverse action also proceeds, and to limit this, excess of the halogen hydracid is used and the water formed is fixed, e. g., by addition of zinc chloride. Further, the chlorine of the phosphorus chlorides also replaces hydroxyl : PC1 3 -f 3C 2 H 5 OH = P(OH) 3 + 3C 2 H 5 C1, or, better, PC1 5 + C 2 H 5 OH = POC1 3 + HC1 -f- C 2 H 5 C1. This reaction is of importance for the preparation of the bromo- and iodo-compounds : 3CH 3 OH -f P + 31 = 3CH 3 I + H 3 P0 3 ; the bromine or iodine first acts on the phosphorus to form PBr 3 or PI 3 , this then reacting with the alcohol. The polyhydric alcohols act in the same way; for example, glycerol, C 3 H 5 (OH) 3 , reacts with PC1 5 , giving trichlorohydrin, CH 2 C1 CHC1 CH 2 C1. The resulting halogenated products are easily separated by distillation, as the phosphorous acid does not distil. In these, as in most other chemical reactions, secondary products are always formed ; these are often very complex, and form viscous resins of unknown composition. (d) The aldehydes and ketones yield disubstituted products : for example, ethylidene chloride, CH 3 CHC1 2 , is obtained from acetaldehyde, CH 3 CHO, and dichloropropane, CH 3 CC1 2 CH 3 , from acetone, CH 3 CO CH 3 , by the action of PC1 S . METHYL CHLORIDE (Chloromethane), CH 3 C1. This is prepared by passing hydrogen chloride into boiling methyl alcohol containing half its weight of zinc chloride in solution, or by heating 1 part of methyl alcohol with 3 parts of concentrated sulphuric acid and 2 parts of concentrated hydrochloric acid. Industrially it may be obtained by heating methyl alcohol and crude, concen- trated hydrochloric acid together in an autoclave, the mass issuing from the hot autoclave as gas being washed with water and concentrated hydrochloric acid and the residual dry chloromethane liquefied by cooling at the pressure of the autoclave itself. Douane (U.S. Pat. 777,406) suggested an apparatus for continuous manufacture. ALKYLHALIDES 117 It is also obtained to-day in appreciable quantity, by the old Vincent process, from the final residues of the beet-sugar industry, which are evaporated and then dry-distilled. In this way an abundant quantity of trimethylamine is formed ; this is neutralised with HC1, and the hydrochloride distilled at 300. A regular evolution of methyl chloride and trimethylamine is thus obtained : 3N(CH 3 ) 3 HC1 = 2CH 3 C1 + 2N(CH 3 ) 3 + CH 3 NH 2 , HC1. Trimetbylamine hydro- Trimethyl- Methylamine hydro- , chloride amine chloride (residue) The chloromethane, distilled as a gas, is purified with HC1, dried with CaCl 2 , and liquefied in steel cylinders under pressure, just as is done with carbon dioxide (Vol. L, p. 480). It is a colourless gas of ethereal odour, and at 24 '09 becomes liquid, then having the sp. gr. 0*952 (at 0). Water dissolves one-fourth of its volume, and alcohol rather more. It burns with a green-edged flame. - In the liquefied condition it is used as a local anaesthetic ; it is used also to extract perfumes from flowers^ and in considerable quantities for the manu- facture of dyestuffs (methyl green), especially for methylation, but the greatest amount is employed in cooling machines. In France there are about 100 ice- machines which use methyl chloride instead of liquefied NH 3 , C0 2 , or. S0 2 . In brass cylinders containing from 1 to 30 kilos it is sold at 11s. to 14s. Qd. per kilo, in addition to the cost of the cylinder, which is 20s. for the 1-kilo, 25s. 6d. for the 3-kilo, and 3 16s. for the 30-kilo size. METHYL IODIDE, CH 3 I, is prepared from methyl alcohol, phosphorus, and iodine as described later for ethyl iodide. It is a liquid of sp. gr. 2-293, boiling at 45 ; with excess of water at 100 it is decomposed into hydrogen iodide and methyl alcohol. ETHYL CHLORIDE (Chloroethane), C 2 H 5 C1, was termed by Basil Valentine " Spiritus salis et vini," or spirit of sweet wine. It is obtained from ethane and chlorine, or by passing hydrogen chloride into a solution of zinc chloride and ethyl alcohol. It is formed also as a secondary product in the manufacture of chloral. It boils at + 12-2 and burns with a flame having green edges. It is a local anaesthetic and is soluble in alcohol, but only slightly so in water. It costs from Is. Id. to 4s. per kilo in metal cylinders containing 1 to 30 kilos. ETHYL IODIDE, C 2 H 5 I, is prepared by digesting 10 grams of red phosphorus with 80 grams of absolute alcohol for twelve hours and gradually adding 100 grams of iodine ; the mixture is then heated for two hours under a reflux condenser and the ethyl iodide distilled on the water-bath, washed with dilute alkali and with water, and dried by means of calcium chloride. When yellow instead of red phosphorus is used, much less of it is required and the reaction is more rapid, boiling being unnecessary; yellow phosphorus is, however, inconvenient to work with. From 3 to 4 kilos of ethyl iodide are obtained from 3 kilos of iodine. According to Ger. Pat. 175,209, ethyl iodide is obtained quantitatively if diethyl sulphate is slowly added to the calculated amount of hot potassium iodide solution. It boils at 72-3 and has the sp. gr. 1-944 (at 14) ; it is highly refractive and dissolves in alcohol or ether. It decomposes when heated with water at 100. Chlorine converts it into ethyl chloride and bromine into ethyl bromide. In the light it slowly decomposes with separation of iodine, which colours the liquid brown, but it remains colourless in presence of a drop of mercury. It is used as an inhalation for the treatment of asthma. It costs about 28s. to 32s. per kilo. ETHYL FLUORIDE, C 2 H 5 F, is liquid, at 48, burns with a blue flame, and does not attack glass. From PROPANE two series of isomeric compounds are derived : CH 3 CH 2 CH 2 X, prepared from normal propyl alcohol, and CH 3 CHX CH 3 , derived from isopropyl alcohol, and hence from acetone. ISOPROPYL IODIDE (Iodo-2-propane) CH 3 CHI CH 3 , is obtained from glycerol, phosphorus and iodine, small amounts of allyl iodide and propylene being also formed. The butyl compounds occur in four isomeric modifications : NORMAL BUTYL IODIDE (Iodo-i-butane), CH 3 CH 2 CH 2 CH 2 I. SECONDARY BUTYL IODIDE (Iodo-2-butane), CH 3 CH 2 CHI CH 3 . 118 PTT ISOBUTYL IODIDE (Methyl-2-iodo-s-propane), , 3 >CH CHJ. ^1 3 PTT TERTIARY BUTYL IODIDE (Methyl-2-iodo-2-propane), ^ 3 >CI CH y l^llg The constitutions of the four isomerides are deduced from those of the corresponding butyl alcohols, from which they are obtained by the action of hydriodic acid. Of the AMYL derivatives eight isomerides are known. METHYLENE CHLORIDE (Dichloromethane), CH 2 C1 2 , bromide and iodide (see Table, p. 115). ETHYLENE COMPOUNDS, CH 2 X CH 2 X, are formed from ethylene by the addition of halogens or from glycol, C 2 H 4 (OH) 2 and halogen hydracids. ETHYLIDENE (or Ethydene) COMPOUNDS, CH 2 CHX 2 , are obtained by sub- stituting the oxygen of the aldehydes by halogens. ETHYLENE CHLORIDE (Dichloro-i : 2-ethane), CH 2 C1 CH 2 C1 (Dutch liquid, 1795) boils at 84. The IODIDE, BROMIDE, and CHLORIDE with alcoholic potash give acetylene and glycol. ETHYLIDENE CHLORIDE (Ethydene chloride or Dichloro-i : i-ethane), CH 3 CHC1 2 , is obtained from aldehyde and phosgene : CH 3 CHO + COC1 2 = CO 2 + CH 3 CHC1 2 , chloral (which see) being also formed ; it boils at 57. CHLOROFORM (Trichloromethane), CHC1 3 . Chloroform was discovered by Liebig and Souberain and its constitution shown by Dumas in 1835. It is a colourless liquid with a sweet ethereal smell and taste ; it dissolves only to a slight extent in water (0*7 per cent.), but is soluble in alcohol or ether. It boils at 61'2, and its vapour pressure at 20 is 160 mm. of mercury; its specific gravity is 1*5263 at and 1*500 at 15, referred to water at 4. It is non-inflammable, and it dissolves resins, rubber, fats, and iodine, with the last of which it gives violet solutions. Chromic acid transforms chloroform into phosgene (COC1 2 ), while potassium amalgam gives acetylene. With potassium hydroxide it gives potassium formate and chloride : CHC1 3 + 4KOH = 3KC1 + H C0 2 K + 2H 2 O. With ammonia at a red heat it gives hydrocyanic and hydrochloric acids : CHC1 3 + NH 3 = HCN + 3HC1. Exposed to light and air, it decomposes partially into Cl, HC1, and COC1 2 , but it can be kept in yellow bottles, while that for pharmaceutical use keeps better if 1 per cent, of absolute alcohol is added. The presence in it of more than 1 per cent, of alcohol is shown by shaking the chloroform in a test-tube with a granule of pure permanganate, a yellowish-brown spot forming round the latter and also on the glass where it rests. It is the most efficacious anaesthetic (Simpson, 1848), but in some cases may cause death if not used with great care, since it acts on the heart ; to diminish this effect, it is mixed with atropine or morphine. 1 The harmful 1 From coal-tar products various anaesthetics or hypnotics are produced synthetically, and these have been of great service to medicine, especially to surgery, rendering possible the execution of the most complicated operations without any pain to the patient. At first substances were used which produced general anaesthesia of the organism, but they were accompanied by many inconveniences, sometimes by fatal results. Indeed, the anaesthetic is transported by the blood into contact with the higher nervous centres by which pain is felt, producing poisoning and paralysis of them, often lasting for some time; at the same time an influence is felt by the centres controlling the action of the heart and of respira- tion, this being the cause of the danger and disturbance produced by general anaesthesia. The nerve-currents start from the periphery, from the points where the surgical operation is to begin, and are transmitted to the brain, which transforms them into painful sensations, and it is by influencing the cerebral centres by anaesthetics that pain is avoided ; anaesthesia ceases, however, to be dangerous if the peripheral nervous centres at the beginning of the nerve-currents are paralysed without the latter reaching the brain. Thus local anaesthesia is much more rational CHLOROFORM 119 effects of chloroform are due sometimes to its decomposition products, especially to phosgene, COC1 2 . The use of chloroform has been suggested to render pigs insensible, so as to kill them painlessly and to skin them more easily. Also, in fattening them, they are subjected to periodic inhalations of chloroform, which renders them more restful. Chloroform is sometimes used for dissolving rubber and gutta-percha, for extracting alkaloids and ethereal oils, and, together with acetone and alkali, for preparing acetone-chloroform or chloretone, which has a slight camphor-like odour, melts at 80 to 81, and serves as a hypnotic, as a local anaesthetic and as an antiseptic. PREPARATION. It is prepared from (1) ethyl alcohol or (2) acetone, by heating with chloride of lime and water. In the former case there is always an appreciable evolution of CO 2 , which originates in the oxidation of the alcohol, and liberates HC1O and so forms aldehyde and hence chloral, CC1 3 CHO, this, in presence of lime, yielding chloroform and calcium formate : 2CC1 3 CHO + Ca(OH) 2 = 2CHC1 3 + Ca(HC0 2 ) 2 . If the decomposition of the hypochlorite is rapid, evolution of oxygen may occur. The reaction taking place in the industrial process is perhaps best interpreted by the equation : 4C 2 H 5 OH + 16CaOCl 2 = 3Ca(HC0 2 ) 2 + 13CaCl 2 + 8H 2 + 2CHC1 3 . With acetone the reaction would be as follows, trichloroacetone being formed as an intermediate product : 2CH 3 CO CH 3 + 6CaOCl 2 = Ca(C 2 H 3 O 2 ) 2 (calcium acetate) + 2CHCL + 3CaCl 2 + 2Ca(OH) 2 . In a very pure form for pharmaceutical use it is obtained by treating chloral with aqueous caustic soda solution, sodium formate being also formed : / H CC1 3 C^ + NaOH = CHC1 3 + H CO 2 Na. ^O To obtain very pure chloroform from the impure product, Anschiitz treats the latter with salicylic anhydride, C 6 H 4 CO 2 , which forms a crystalline mass only with chloroform, (C 6 H 4 CO 2 ) 4 , 2CHC1 3 ; this, after separation from the mother-liquor, is heated on the water- bath, when pure chloroform distils off. Pictet Chloroform is pure chloroform obtained from the commercial product by freezing it at 80 to 120; the impurities remain in the liquid, the crystals giving pure chloroform. INDUSTRIAL PREPARATION. A considerable amount of chloroform is prepared even to-day from chloride, of lime and alcohol, but the latter should not contain fusel oil. In America, F. W. Frericks suggests the arrangement shown in Fig. 104 for the manu- facture of chloroform. In the boiler B 550 litres of 94 per cent, alcohol and 2550 litres of water (giving 20 per cent.of alcohol in the mixture) are heated by a steam coil to 60 to 70, a fluid paste (free from lumps) prepared in the tank A (furnished with a stirrer) from 500 kilos of chloride of lime (35 per cent, of available chlorine) and about 1000 litres of water being then run in continuously through the funnel a and tube b to the bottom of B. The reaction is instantaneous, and when all the hypochlorite has been added, the temperature is maintained at 60 (B being jacketed) until the whole of the chloroform is distilled off and condensed in the coil C ; the distillation is followed either by means of a hydrometer under the bell-jar e, through which the condensate passes, or by diluting* sample with water : and less dangerous, since the insensibility extends only to one organ or one region of the subject of the operation. So that, to chloroform, ether, etc., was added, in 1885, cocaine, which paralyses only the sensitive peripheral nerves without influencing the motor nerves. By studying anaesthetic and hypnotic substances chemists were able to determine what specific atomic groups produced anaesthetic properties in a molecule. Thus, with many of these substances, it was found to be the hydroxyl group which induced sleep, especially when it is united to carbon joined at the same time to several alkyl groups ; replacement of the hydroxyl by other groups resulted in the disappearance of the anaesthetic properties. Also various amino-acid groups, under certain definite conditions, give rise to anaesthetics. To enumerate all the members of the vast group of anaesthetics which chemistry has placed at the disposal of surgery would be out of place here, but the following few examples may be mentioned : a-eucaine, &-eucaine, ortho/orm, alipine, holocaine, and, on the other hand, sulphonal (see later), trional, dormiol, hedonal, veronal (see later), etc. Other properties of anaesthetics are described in Part III, in the section on Alkaloids. 120 ORGANIC CHEMISTRY no chloroform should separate. The chloroform is then drawn off through the tap d and the distillation continued at a temperature above 60, the alcohol passing over being col- lected in D and then passed into E ; this distillation is stopped when the distillate contains less than 2 per cent, of alcohol. The concentration and quantity of this dilute alcohol (about 1800 litres) are determined, the liquid being then forced through the tube g into B, which has been previously emptied through h. Further alcohol is then added to give the amount first used, and a second operation with 500 kilos of calcium hypochlorite carried out. By this process 100 kilos of pure chloroform are obtained on the average from 1022 kilos of calcium hypochlorite (with 35 per cent, of available chlorine) and 77 kilos of 94 per cent, alcohol, whereas with the proportions of reagents formerly in use as much as 100 kilos of alcohol and 1300 kilos of hypochlorite were consumed. In recent years successful use has been made of the method of making chloroform from acetone, which is now obtainable cheap and very pure (quite neutral and with less than 0-05 per cent, of aldehyde), the chloroform thus prepared being highly pure. Except for the reaction vessel, the plant is similar to that of the alcohol process. This vessel is fur- nished, besides with a jacket, with an efficient stirrer and, in its upper part, with a perforated or gauze disc to break the froth, since the reaction is at first rapid and, if not regulated, may become violent and dangerous. To the mixture (free from lumps) of calcium hypo- chlorite (250 kilos) and water (800 litres), heated to 50 in the boiler, is slowly (in about an hour) added 28 litres of acetone, the mass being cooled to prevent the tem- perature from exceeding 55 at first, and 60 at the end of the addition. The condensed chloroform of- sp. gr. 1-5 is collected, while that finally distilling over with sp. gr. 1-45 (by heating to 85) is set apart for the succeeding operation, as it contains a little acetone. The crude chloroform obtained is washed with a little water and sodium carbonate, then stirred with one-third of its FIG. 104. volume of water and decanted from the latter, and afterwards washed two or three times, in a lead-lined vessel fitted with a stirrer, with a little 66 Be. sulphuric acid until the acid is no longer turned brown. After the acid has been thoroughly removed from the chloroform, this is washed with water, dried over CaCl 2 , and distilled from a copper still. The washing with water and the drying may be omitted, the chloroform being then distilled with a little soda to neutralise traces of acid and the first and last portions of the distillate kept separate. The bulk of the chloroform distilled is highly pure and the yield is 205 kilos of a crude product from 100 kilos of acetone and 1110 kilos of hypochlorite (about 34 per cent, of active Cl) ; 175 kilos of pure chloroform 1 are obtained. 1 TESTS FOR CHLOROFORM. Minute quantities of chloroform may be detected by heating a little of the liquid gently with a few drops of aniline and of alcoholic potash solution, the characteristic repulsive odour of phenylcarbylamine (phenyl isocyanide) being formed. Pure chloroform for medicinal use should not be acid or give a precipitate with silver nitrate solution or redden potassium iodide solution ; on evaporation it should not leave a residue of water or odorous substances, and it should not darken with concentrated sulphuric acid. To test for the presence in it of carbon tetrachloride, 20 c.c. are treated with a solution of 3 drops of aniline in 5 c.c. of benzene ; turbidity or separation of crystals of phenylurea indicates with certainty the presence of the tetrachloride. To ascertain if it contains alcohol it is treated with a very dilute potassium permanganate solution, which is decolorised in presence of this impurity. Its estimation is effected by treating a given weight with Fehling's solution (see under Sugar Analysis ) and heating the mixture in a closed bottle on a water-bath for some hours (until the odour of chloroform disappears ), the cuprous oxide, formed according to the equation, CHC1 3 + 2CuO + 5KOH = K 2 C0 3 + 3H 2 + 3KC1 + Cu 2 0, being weighed. One molecule of chloro- form corresponds with 2 atoms of copper. It may be determined also by heating with alcoholic potash in a reflux apparatus on the water- bath ; it is then diluted with water, the alcohol distilled off, and the potassium chloride formed (together with potassium formate, see preceding page) titrated with a standard silver nitrate solution, This method serves for the estimation of all alkyl-hcdogen compounds. IODOFORM 121 During recent years the industrial preparation of chloroform has again been attempted by electrolysing an aqueous solution of KC1 (20 per cent.) into which alcohol or acetone is slowly introduced ; if the temperature is kept at about 60, the chloroform distils off as it is formed. In this process 1 h.p.-hour is consumed to produce 40 grams of chloroform (L. Zambelleti, 1899). According to the Besson process (Ger. Pat. 129,237), continuous production and a good yield are obtained by heating, in a vessel divided into cells communicating below, alcohol previously chlorinated to the sp. gr. 35 Be. with chloride of lime and alkali in the hot. Attempts have been made to prepare chloroform industrially by reducing carbon tetrachloride in the hot with nascent hydrogen : CC1 4 + H 2 = HC1 + CHC1 3 , but the product is contaminated with CC1 4 and CS 2 (used in making the CC1 4 ) which are eliminated with difficulty. Erlworthy and Lange (Fr. Pat. 354,291, 1905) propose to produce chloroform from methane and chlorine diluted with indifferent gases (N, CO 2 ) by subjecting the mixture to the action of light in suitable retorts : CH 4 + 6C1 = 3HC1 + CHC1 3 , but the process has apparently not been applied in practice, although in 1913 improved results were obtained with ultra-violet rays. The pre-war price of industrial chloroform was about 8 per 100 kilos ; redistilled cost 2s. lOd. per kilo; the pharmacopoeial preparation 2s. 2d.; puriss. from chloral, 6s. 5d. to 9s. Id. ; Pictet's, 12s. per kilo, and that of Anschiitz IQd. per 50 grams. Part of the chloroform consumed in Italy is imported from abroad, the Italian output prior to the war being about 10 tons per annum. In 1909 Germany exported 150 tons of chloroform, while Great Britain imported 16 cwt. and exported 14 cwt. in 1910. The United States imported 8 cwt. in 1910. IODOFORM (Tri-iodomethane), CHI 3 , was discovered by Serullas in 1822, and its constitution was established by Dumas who, unlike his predecessors, did not overlook the very small proportion of hydrogen (0'25 per cent.) present. It is formed by heating ethyl alcohol or acetone with iodine and sufficient alkali hydroxide or carbonate to decolorise the iodine (Lieben's reaction) : C 2 H 5 OH + 81 + 6KOH = CHI 3 + H COOK -f 5KI + 5H 2 O. This reaction (separation of yellow crystals and formation of a character- istic odour) is so sensitive that it serves for the detection of 'minute traces (1 : 2000) of ethyl alcohol or acetone in other liquids (waiting twelve hours for the separation of crystals if the amount of alcohol is small); the same reaction is, however, given by isopropyl alcohol, acetaldehyde (and by almost all compounds containing the group CH 3 CO ), but not by methyl alcohol, ether, or acetic acid. For the practical preparation of iodoform 32 parts of K 2 C0 3 are dissolved in 80 parts of water and 16 parts of alcohol, the mixture being heated to 70 and 32 parts of iodine gradually added. The separated iodoform is filtered off and the iodine of the potassium iodide in the filtrate utilised as follows : 20 parts of HC1 are added and 2 to 3 parts of potassium dichromate, the liquid being then neutralised with K 2 CO 3 , mixed with a further 32 parts of K 2 CO 3 , 16 parts of alcohol and 6 parts of iodine. On heating, a second quantity of iodoform separates, and after this or another similar operation the mother-liquor is treated to recover the iodine from the potassium iodide. It has been proposed to prepare iodoform by treating the metallic acetylides (see p. 110) wifch iodine and caustic soda. It seems that practical use is now made of the electrolytic process, using a bath of 6 parts KI, 2 parts soda, 8 vols. alcohol, and 40 of water at 60 to 65. The iodine to be used in the reaction is set free at the anode, and to avoid the formation of a little iodate with the KOH formed at the cathode the latter is enclosed in parchment paper. When pure, iodoform crystallises in hexagonal, yellow plates (sp. gr. 2), insoluble in water but soluble in alcohol or ether. It has a penetrating and persistent odour, recalling partly that of saffron and partly that of phenol. It melts at 119, readily sublimes, and is volatile in steam. When heated with either alcohol or reducing" agents, it gives methylene iodide, 122 ORGANIC CHEMISTRY It is used in surgery as an important antiseptic, which, however, acts indirectly on bacteria by means of the decomposition products formed from it under the action of the pus of wounds or of the heat of the body. TESTS FOR IODOFORM. It should leave no residue on sublimation and should dissolve completely in alcohol or ether. It is estimated by heating about 1 gram with about 2 grams of silver nitrate and 25 c.c. of concentrated nitric acid (free from chlorine) in a reflux apparatus so that the liquid does not boil; when the nitrous vapours have disappeared the liquid is diluted with water to 150 c.c. and heated, the silver iodide being collected on a tared filter, dried and weighed : 1-789 grams Agl corresponds with 1 gram iodoform. Owing to its disagreeable odour, it has been to some extent replaced latterly by Xeroform, which is a tribromophenoxide of bismuth, C 6 H 2 Br 3 O OH, Bi 2 O 2 , obtained by the action of bismuth chloride on sodium tribromophenoxide, and forming a tasteless, odourless, yellow powder insoluble in water or alcohol; it is used also as a disinfectant for the intestines, and costs 44s. to 48s. per kilo, whilst iodoform costs only 24s. to 28s. a kilo. CARBON TETRACHLORIDE (Tetrachloromethane), CC1 4 (see Vol. I., p. 470). POLYCHLORO-DERIVATIVES OF ETHYLENE AND ETHANE. 1 Asymm. 1 Since 1908 (Ger. Pats. 196,324, 204,516, 204,883, etc.), the Chemische Fabrik Griesheim- Elektron of Frankfort, and the Usines electriques de la Lonza of Geneva have placed on the market, as non-inflammable solvents for industrial purposes, six chlorinated compounds obtained as colourless liquids by the action of chlorine on acetylene. They are all good solvents for fats, resins, rubber, bitumen, sulphur, etc., and can replace advantageously benzine, carbon disulphide, and alcohol, since they are not inflammable and their vapours do not form explosive mixtures with air; over carbon tetrachloride they have the advantage of not attacking the metal parts of the extraction apparatus, and the loss on extraction varies from 0-3 to 0-8 per cent.; they are, however, dearer than the ordinary solvents and seem to be injurious to health. Acetylene tetrachloride (tetrachloroethane) was prepared in 1903 by the Consortium fur elektrochemische Industrie of Nuremberg (Ger. Pat. 154,657) by the interaction of acetylene and chlorine in presence of antimony chloride as catalyst. Dichloroethylene, used in the manufacture of thio- indigo, is formed quantitatively from tetrachloroethane by the action of ordinary metals in the hot in presence of a little water (Ger. Pat. 217,554). Trichloroethylene is obtained from tetra- chloroethane by heating it with lime (Ger. Pat. 170,900 ) ; by treatment of the products gradually forming with lime and chlorine alternately, C 2 HC1 5 , C 2 C1 4 and C 2 C1 6 (solid) may be prepared. With trichloroethylene various organic syntheses may be effected. Thus, with sodium ethoxide it yields dichlorovinyl ether, C 2 HC1 2 OC 2 H 5 ; this, in its turn, exhibits marked reactivity, and on addition of Cl or HC1 gives saturated products which, on distillation, liberate ethyl chloride and form mono- and di-chloroacetyl chlorides, C 2 H 2 C1 2 and C 2 HC1 3 0. With water in presence of a trace of HC1 (as catalyst) at the ordinary temperature, dichlorovinyl ether gives quantitatively ethyl chloroacetate, CH 2 C1 COOC 2 H 5 (Ger. Pats. 210,502 and 216,716), which was first obtained from acetic acid and is now more economically derived from acetylene ; it is used in numerous important syntheses, including that of indigo. The properties of these compounds are given in the following Table : DICHLORO- ETHYLENE TRICHLORO- ETHYLENE TETRA- CHLORO- ETHYLENE TETRA- CHLORO- ETHANE PENTA- CHLORO- ETHANE HEXA- CHLORO- ETHANE C 2 H2Cl2 C 2 HC1 3 C 2 C1 4 C 2 H 2 CI 4 C 2 HC1 5 C 2 C1 6 Common name . Dieline Trieline Etiline Tetraline Pentaline Specific gravity . 1-278 (1-25) 1-471 1-628 1-600 1-685 (1-70) 2 Boiling-point 52 (55) 85 (88) 119 (121) 144 (147) 159 (185) Vapour pressure at 20 205 mm. 56 17 11 7 3 Specific heat at 20 0-270 0-223 0-216 0-268 0-266 Heat of evaporation 41 cals. 57-8 50 52-8 45 . Freezing-point . - 73 - 19 36 - 22 Uses and properties . Keadily dis- Dissolves fats, Serves well Dissolves re- Keadily dis- Has an solves rub- paraffin wax for remov- sins and var- solves cellu- odour like ber and vaseline ing spots nishes, like lose acetate camphor, better than turpentine for artificial and serves benzine and alcohol silk and as an insec- Ger. Pats. 201,705 204,516 216,070 Ger. Pats. 171,900 206,854 and dissolves cellulose ace- tate for films and artificial cinemato- graph films ticide 254,068 silk Trichloroethylene, C 2 HC1 3 , is used also as a non-inflammable solvent in chemical cleaning works, in the manufacture of oils and fats, in making lacs, and in one of the syntheses of indigo : with sodium ethoxide it gives dichlorovinyl ether, which with water yields ethyl chloroacetate, ALCOHOLS 123 HEPTACHLOROPROPANE was prepared in 1910 by Boeseken and Prins from tetra- chloroethylene and chloroform in presence of aluminium chloride as catalyst. II. HALOGENATED DERIVATIVES OF UNSATURATED HYDROCARBONS These are obtained from saturated halogen derivatives by partial elimination of the halogen hydracid : C 2 H 4 Br 2 = HBr + C 2 H 3 Br. They are formed also by incomplete saturation, with halogens or halogen hydracids, of the less saturated hydrocarbons : C 2 H 2 + HBr = C 2 H 3 Br (see Table in footnote). Bromoacetylene, CH j CBr, is a gas liquefying at 2 and ignites spontaneously in the air. It gives brilliant luminescent effects, even if mixed with air. It ozonises atmospheric oxygen, but the latter is not ionised, as is the case with phosphorus. The allyl compounds, C 3 H 5 X, are formed from allyl alcohol by the action either of halogen hydracid or of phosphorus and halogen. ALLYL CHLORIDE (Chloro-3-propene-i), CH 2 : CH CH 2 C1; the bromide and iodide have analogous constitutions. These are related to the natural allyl compounds (garlic oil and mustard oil). Two stereoisomerides are known : H C Cl H C Cl a-chloropropylene. and iso-a-chloropropylene, \\ H C CH.j CHg C H TETRABROMOETHANE, CHBr 2 CHBr 2 (improperly termed acetylene bromide) is prepared industrially in the impure state bypassing bromine in at the top of a cooled earthen- ware coil and acetylene in at the bottom, the liquid product collecting at the bottom : C 2 H 2 + 2Br 2 = C 2 H 2 Br 4 + 64 cals. It boils at 215 with partial decomposition and does not solidify at 20. It contains 92-5 per cent, of bromine and has a high specific gravity (2-943), and on this account is used for the mechanical separation of mineral components; thus large quantities are employed to separate diamonds (sp. gr. 3-35) from the sands of Western Africa (sp. gr. 2-4). It is despatched in vessels similar to those used for bromine. It is obtained pure by treatment with alcohol and zinc dust, which converts it into dibromoacetylene ; the latter is then purified by distillation and transformed into the tetrabromo-cqmpound by means of bromine. CC. ALCOHOLS These form an important group of organic compounds containing one or more characteristic hydroxyls, the hydrogen of which has pronounced reactive properties, so that numerous series of other compounds are derived from the alcohols. They have a neutral reaction, although their chemical behaviour is analogous to that of the inorganic bases which always contain the anion OH'. The majority of these alcohols are colourless liquids, but those of high molecular weights are oily, solid, and sometimes yellowish. The first members of the series are soluble in water, but with increase of molecular weight the solubility decreases and the smell, generally slight, also tends to disappear. They are often found in nature either free or combined with organic acids, in the fats, waxes, fruits, essential oils, etc. According to the number of hydroxyl groups they contain, they are divided into mono-, di-, . , . polyhydric alcohols, and may belong either to the saturated or to the unsaturated series already , studied in connection with the hydro- carbons of which they retain the fundamental characters; added to the latter are those characteristic of the alcoholic group, which we shall study generally with the monohydric alcohols. and this, with aniline in presence of calcium carbonate, forms the ethyl ester of phenylglycine ; with potassium carbonate the latter gives the corresponding potassium salt, which gives rise to indigo on condensation with calcium silicide (see Vol. I., p. 500). The existence of cis- and trans-stereoisomerides of symmetrical diMoroethylene, CHC1 : CHC1, appears proved. 124 ORGANIC CHEMISTRY I. SATURATED MONOHYDRIC ALCOHOLS The specific gravity of these is always lower than that of water, and up to the C 16 member they distil unchanged at the ordinary pressure ; beyond that reduced pressure must be employed. That alcohols always contain a hydroxyl group, OH, may be shown by the following chemical reactions : The alcohols may be obtained by the action of silver hydroxide, Ag OH (which certainly contains the group OH), or even of the alkalis or hot water, on halogenated hydrocarbons : C B H 2n + X I + AgOH = Agl -f C n H 2 + nl OH. With the halogen hydracids the hydroxyl separates from the alcohols in the form of water: C n H 2n+1 OH + HBr H 2 O + C B H 2n + 1 Br ; the same happens with oxyacids, the so-called esters being formed: C n H 2n+1 OH + HN0 3 = H 2 O + C B H 2B+1 N0 3 . Just as sodium and potassium react with water, liberating hydrogen, so do they act on the alcohols, from which only the typical hydrogen (hydro xylic), not united directly to carbon, is eliminated: C B H 2B+1 OH + Na = C B H 2n+ ^Na (sodium alkozide) + H. Magnesium alkoxides are also easily obtained. With phosphorus trichloride, however, the hydroxyl group is eliminated : PC1 3 = 3CyB^ + 1 Cl + P(OH) 3 . On p. 17 the difference in constitution between ethyl alcohol and methyl ether has been demonstrated. If the x hydroxyl group occurs in place of a hydrogen atom in the methyl group ( CH 3 ) at the extremity of the hydrocarbon chain, the primary alcohols are obtained, all con- taining the characteristic group CH 2 OH i. e., Of ), e. g., propyl alcohol, \OH ' CH 3 CH 2 CH 2 OH, and by oxidation of these alcohols are formed first aldehydes with / X the characteristic group I X. Cf^ j, and then acids with the characteristic carboxyl group COOH ( i. e., C'f ]. Substitution of a hydroxyl for a hydrogen atom in an \OH intermediate methylene group ( CH 2 ) in the saturated hydrocarbon chain yields secondary (TT \ i. e.^C-^p-Ti ) and on oxidation give ketones containing the special group ]>CO. Finally the substitution of the hydrogen of a branched hydrocarbon may take place in the methinic group (=CH), giving tertiary alcohols with the characteristic grouping =C OH, the other three valencies of the carbon being united to three carbon atoms. When the secondary alcohols are oxidised they cannot give either acids or ketones with an equal number of carbon atoms, but, if the oxidation is energetic, the chain breaks, and then acids and ketones may be formed, but with less numbers of carbon atoms. According to B. Neave (1909), primary, secondary, and tertiary alcohols may be distinguished by the Sabatier and Senderens reaction (see p. 35), by passing the vapour of the alcohol over finely divided copper heated at 300 : the primary alcohols form hydrogen and aldehydes (recognisable by Schiff's reaction; see section on Aldehydes), the secondary ones give hydrogen and ketones (detectable by semicarbazide hydrochloride solution) and the tertiary alcohols give water and unsaturated hydrocarbons (which decolorise bromine water). The primary alcohols and the corresponding ethers have the highest boiling- points, the tertiary ones and, in general, those with branched chains showing the lowest boiling-points. In the group of alcohols the isomerism and the number of isomerides are FORMATION OF ALCOHOLS 125 similar to those of the halogenated derivatives of the hydrocarbons, since the halogen atom is here replaced by a hydroxyl group. The names of the primary alcohols are made from those of the corresponding hydro- carbons (see p. 30), with the termination ol, and those of the secondary and tertiary alcohols are derived from the names of the hydrocarbons with the longest non- branched chains; or the secondarjfcfjid tertiary alcohols may be regarded as derivatives of methyl alcohol or carbinol, CH 3 JH, formed by substitution of the hydrogen atoms of the methyl group. We have, hence, two different, but still equally clear, systems of nomenclature. For example : (1) Normal butyl alcohol : CH 3 CH 2 CH 2 CH 2 OH = butan-1-ol or n-propylcarbinol. 2 l (2) Secondary butyl alcolwl : CH 3 CH 2 CH(OH) CH 3 = butan-2-ol or methylethyl- carbinol. 123 (3) Isobulyl alcohol : CH 3 CH CH 2 OH = 2-methylpropan-3-ol or isopropylcarbinol. 3 1 23 CH 3 (4) Tertiary butyl alcohol : CH 3 ^-C CH 3 = 2-methylpropan-2-ol or trimethylcarbinol. /\ CH 3 OH PROCESSES OF FORMATION OF MONOHYDRIC ALCOHOLS. As well as from the halogen derivatives, the alcohols may usually be obtained by decomposing esters with acids, alkalis, or superheated water. This reaction is termed saponification or hydrolysis : C 2 H 5 O NO 2 + KOH = KNO 3 + C 2 H 5 OH. In a general way, the primary alcohols are formed by reducing the acids (C n H 2n O 2 ) or aldehydes (C n H 2n O) with nascent hydrogen : CH 3 C exp. .1 . ... .. -. . .. --. - -'- ' ' gary J imp. ~~* "^ *"""' ~~ Russia . prod. 4,500 5,580 exp. imp. - United States prod. 2,900 2,700 3,650 exp. imp. France . prod. 2,700 2,428 2,392 2,182 2,987 2,596 exp. imp. Great Britain prod. 1,284 1,500 . exp. imp. 15,300 Holland . prod. 351 exp. - imp. Belgium . prod. 389 exp. imp. Sweden . prod. 200 220 402 451 exp. imp. 12 Norway . prod. 43-7 11-3 imp. 7-3 30-5 Italy . . prod. 293 800 2 419 297 260 349 372 398 exp. 25 59 71 95 220 imp. Denmark . prod. 154 155 exp. Switzerland . prod. 54 57 53 imp. 130 112 129 Turkey . prod. exp. imp. 175 Bulgaria . prod. 27 45 Whole world . prod. 21,000 1 When, after the European War, the State monopoly of alcohol was mooted in Italy and France, the producers advised the respective Governments to lower the price of power alcohol to f 1 per hectolitre so as to render advantageous its use on a large scale for motive power, lighting and heating, any loss being counterbalanced by an increase in the price of potable alcohol. 2 This exceptional production corresponds with the famous cognac year (see Note, p. 181). The output was 80,000 hectolitres in 1878, 165,000 in 1888, and 187,000 in 1898-1899. 180 ORGANIC CHEMISTRY For every 100 litres of alcohol consumed as beverages the following amounts are used for industrial purposes : 54 litres in Germany, 19 in Austria, 18 in France, and 14 in Great Britain. These figures indicate the countries most addicted to alcoholism (see p. 184). The importation and exportation of alcohol for Italy are as follows (hectolitres) : 1905 1908 1910 1911 1913 1915 1917 fimp. Spirit in cask -{ ^exp. 2,508 19,688 822 31,756 641 38,604 647 2,067 624 4,476 133 137,715 9,853 485 Cognac, casks /imp. about and bottles \exp. _ 1,330 940 1,460 300 1,500 4,250 1,200 1,420 1,175 715 265 5,600 690 170 Sweetened and 1 . spiced spirits, > casks & bottles J exp> 3,145 18,540 2,940 38,540 3,974 46,815 2,480 33,600 2,420 25,600 980 22,300 555 6,690 The alcohol produced in Italy is obtained from the following raw materials (the numbers represent hectolitres) : l Cereals Molasses Beet Wine Vinasse Fruit, etc. Campaign of 1904-5 . 90,000 72,600 59,000 83,000 1,725 1908-9 . 128,883 1910-11 . 64,934 154,195 8,857 16,436 46,698 5,520 1911-12 . 59,865 125,538 9,653 1,251 57,848 6,330 1912-13 . 112,143 141,609 22,942 2,941 62,341 7,155 1913-14 . 561,390 175,784 31,075 10,281 88,062 10,246 1914-15 . 129,994 177,496 13,214 10,849 72,622 10,785 1 In 1913 there were in Italy 26 large distilleries using starchy substances, molasses, beet and dried grapes and 2673 using fruit, wine, vinasse, honey, etc. In 1904-1905 the spirit dis- tilleries consumed 23,400 tons of maize, 600 of durra, and 1700 of barley, rye, millet and rice; also 28,000 tons of molasses and 5300 of other materials. To these must be added 575,000 hectolitres of wine, 260,000 tons of vinasse, and 1370 tons of fruit. In 1908-1909, 368,000 tons of vinasse containing 3 to 4 per cent, of cream of tartar and about 4 per cent, of alcohol were treated ; the mean production of vinasse is 800,000 tons. In Italy there are three sugar works which also make alcohol (in 1911-1912 about 75,000 hectolitres of molasses) and one factory at Cavarzere (Venetia) which obtains alcohol directly from the beet (4000 hectolitres in 1911-1912). In 1911-1912 the distilleries of the Italian Distilling Company (at Milan, Savona, Padua, etc.) produced 25,000 hectolitres from cereals; the Corradini Distillery of Leghorn produced 10,000 hectolitres from cereals and the firm of Schiapparelli of Turin, 8000 hectolitres. In the United States spirit distilleries consumed 1,270,000 tons of maize and about 100,000 tons of molasses (besides about 5000 tons of molasses for rum ) in 1912. In 1912-1913 there were in the United States 398 (in 1911-1912, 417) grain distilleries, 22 (18) molasses distilleries, and 450 (386) fruit distilleries, the materials used being 11,000,000 (12,000,000) hectolitres of grain giving almost 6,000,000 hectolitres of whisky, and 2,300,000 hectolitres of molasses giving 1,000,000 hectolitres of whisky. Further 130,000 hectolitres of molasses were used to make 103,000 hectolitres of rum, while 300,000 hectolitres of fruit spirit are also produced. In Germany 80 per cent, of the alcohol comes from potatoes (the cultivation of which occupies 3,300,000 hectares out of a total cultivated area of 26,000,000 hectares). In 1 911-1912 the output was 3,451,000 hectolitres of spirit, the materials used being : 1,856,626 tons of potatoes (2,520,000 tons in the previous year), 508,737 tons of grain, 49,100 tons of other starchy substances, 82,360 tons of molasses, 193,701 tons of beer residues, 336,000 tons of fruit, 324,000 tons of wine and vinasse, and 35,600 tons of yeast and fermentation residues. In 1912, 150,000 hectolitres of alcohol were used in Germany to manufacture vinegar, 3300 for lead acetate, 36,500 for celluloid, 5500 for pegamoid, 32,500 for esters, 2100 for photographic gelatine, 8350 for dyestuffs, 225 for chloroform, 208 for iocloform, 4200 for coloured lacquers and 32,000 for other lacquers, 2650 for solid soaps, etc., and 5641 for scientific purposes. In Hungary 1,000,000 hectolitres of alcohol were consumed in 1910, the distilleries employing 4500 workpeople. In Austria 60 per cent, of the alcohol made is obtained from potatoes, about one-half of the Austrian output being furnished by Galicia, where there were 900 distilleries in 1911. In 1912 about 29,000 hectolitres of alcohol were converted into vinegar. In France alcohol was protected by a Customs' duty of 2 16s. per hectolitre before the TAXATION OF ALCOHOL 181 In Italy the tax for manufacturing alcohol was 21s. per hectolitre at 100 per cent, in 1871, 4 in 1883, 6 in 1885, and 7 4s. in 1887; to this the sale-tax of 2 Ss. was added in 1888 (so that the consumer paid about 23 pence per litre in taxation alone ! ) ; the sale-tax was abolished in 1904. A rebate of 90 per cent, of the tax is made on exported alcohol (added to marsala, vermouth, etc. ). In 1903 alcohol obtained by distilling wine and vinasse and destined for industrial use was exempted of all taxation, and to alleviate the crisis in the wine industry it was proposed, but in vain, to grant a substantial bounty to the distillers of wine and vinasse. In 1911 the tax was raised to 10 16s. per anhydrous hectolitre at 15-56, in 1914 to 13 4s., and in 1919 to 20. In other countries also, modifications have been made during the past few years in the fiscal regulations regarding alcohol, for the purpose principally of increasing the revenue. 1 European War. In 1910 the output of 2,182,074 hectolitres of industrial alcohol was obtained : 21-6 per cent, from cereals, 23-5 per cent, from molasses, and 54-9 per cent, directly from beet; 420,000 hectolitres of potable spirit were made from wine. In preceding years the quantities of alcohol (hectolitres) obtained from different materials were as follows : From starchy matters From molasses From beetroot From wine From cider Total 1885. 567,768 728,523 465,451 23,240 20,908 1,864,514 1897 . 484,637 734,819 798,484 83,719 26,579 2,208,140 1901 . 269,074 1,006,933 578,628 330,966 115,220 2,437,964 1904 . 380,710 626,722 992,149 88,509 2,181,362 C t\ V i 4* 1908 . 362,500 448,000 1,260,000 468,000 \ 2,600,000 In 1911 1,073,628 hectolitres of alcohol were obtained from beet and in 1912, owing to the smaller beet crop, 1,014,690; 510,400 hectolitres were made from molasses in 1911 and 465,123 in 1912. In Russia 50 per cent, of the alcohol is derived from potatoes, which grow well under the soil and climatic conditions prevailing there; the mean starch content of Russian potatoes is 18 per cent., the limiting proportions being 11 per cent, and 22 per cent. 1 France Germany . Great Britain Austria-Hungary Belgium . Italy Spain Netherlands Sweden . . Norway United* States Switzerland Russia Tax per hectolitre s. 8 16 6 3 28 8 3 15 16 10 16 2 4 15 5 16 13 6 9 16 Monopoly Monopoly Year 1913 1912 1913 1911 1912 1911 1913 1911 1913 1913 1911 1912 1911 In Italy the revenue from the alcohol tax has amounted to : Bevenue 15,978,312 10,145,612 18,595,435 4,477,373 2,179,677 1,658,080 739,757 3,299,664 1,288,992 288,000 32,182,061 289,965 (63,501,812 (net) \83,534,099 (gross) 1906 1,556,004 1907 1,206,053 1908 575,902 1909 954,320 1910 1,546,768 1912 1,917,512 1914 1,315,457 In Germany the manufacturing tax of ordinary non -denatured alcohol varied prior to 1909 from 64s. to 72s. per hectolitre, this being entirely repaid on exported alcohol, which in certain cases also enjoyed a bounty of 9s. Before 1909 the tax was based on the volume of the wort, so that all distillers tried to work with concentrated worts (up to 25 Brix). Nowadays the payment is made on the volume of anhydrous alcohol produced, and the tax varies according to the production, which is established every ten years for each factory (contingent production}. On this contingent quantity the tax is 105 marks (shillings) per anhydrous hectolitre, excess pro- duction paying 125 marks. There are then supplementary taxes of 4 to 14 marks to protect the small factories, so that a hectolitre of alcohol, costing of itself 28s. to 32s., costs, with taxes, 7 4s. to 8 8s. The German Government received about 8,000,000 in alcohol taxes in 1908-1909 and expect in the future to raise this to 14,000,000. The increase in the tax for military expenditure was opposed by the socialists and clerical party with abstinence propaganda, and the consumption of alcohol fell in 1909-1910 by over 600,000 hectolitres. After 1909 the tax amounted to about 37s. for ordinary, and 19s. for denatured, spirit, and was increased still further later; as a result 182 ORGANIC CHEMISTRY UTILISATION OF DISTILLERY RESIDUES. All the components of the prime materials used in the production of alcohol are found (excepting the carbohydrates : starch and sugar) in the residues (grains, spent wash) left after the distillation of the alcohol. These residues formerly formed inconvenient refuse (1 ton of grain gives 60 hectolitres of residues), since they readily undergo putrefaction and, if discharged into rivers or canals, contaminate the water. In exceptional cases, when the distilleries are in large agricultural centres, the residues are used in the wet state for cattle-food, but more commonly they are evaporated and dried, these dried grains being highly valued as a concentrated fodder, rich in proteins 1 and having a restricted ( 1 : 3 to 1 : 5 ) nutritive ratio (ratio between nitrogenous and non-nitrogenous substances). 2 In the fresh residues two-thirds of the part which is not water is dissolved and the remaining third suspended in the water. Potatoes give about 10 per cent, of dried residue, malt about 40 per cent., and maize 45 to 50 per cent. It will hence be understood how distilleries have greatly increased the raising of cattle and consequently production of stable manure, thus contributing to the fertilisation of lands formerly unfertile. The economics of the drying of these residues has always constituted a difficult problem owing to the presence of more than 90 per cent, of water in which part of the nutritive products is dissolved and to the fact that the dried residues sell at 4 to 5 10s. per ton. In many cases the liquid portion is abandoned and the solid part separated by filter-presses or centrifuges, but if the liquid part cannot be got rid of, even after addition of lime, ferrous sulphate, etc., it is best to evaporate it by means of the hot fumes from the flues, the opera- tion being hastened with disc-stirrers of large surface and with fans. The evaporation is sometimes carried out in a vacuum apparatus (see Sugar) furnished with stirrers, by which means a marked economy in fuel is effected (see also Vol. I., pp. 563 and 568). Of the various drying systems (Hatschek, Meeus, Porion and Mehay, Venuleth and Ellenberg, Theisen, Biittner and Meyer, etc. ), we shall deal only with that of Donard and Boulet, which has been applied with advantage in France and recently also in Italy. The solid residue from the filters or centrifuges (perhaps mixed with the evaporated residue of the liquid portion), still containing more than 50 per cent, of water, is carried by mechanical transporters into the vacuum drying apparatus (Fig. 151), consisting of a horizontal cast-iron cylinder rotatable about a hollow axis through which the steam enters or issues ; its length and diameter are 2-5 metres. Inside are a number of tubes (heating area about 60 sq. metres) into which steam is passed from D, the condensed water being discharged without coming into contact with the mass to be dried. At the the consumption of industrial spirit, which had ri?en from 0-32 litre to 2-3 litres per head, dimin- ished in 1912 to 1-3 litres per head per annum, while that of spirits fell from 6-2 litres to 3 litres in 1912. Potato spirit is made in 6400 large factories, that from cereals in 730 large and 6600 small factories, that from molasses in 27 special distilleries, and that from wine, fruit, and yeast in about 60,000 small distilleries. In Germany, besides the concession of untaxed denatured alcohol to all industries, non-denatured alcohol is also allowed free of tax to scientific laboratories and for medicinal uses and military explosives. The alcohol of spirituous beverages imported into Germany pays a Customs' tax of about 14 16s. per quintal. In Great Britain the spirit duty amounted to about 30,000,000 in 1907. In France alcohol for drinking pays a tax of 10 per hectolitre, whilst industrial spirit is untaxed (as in Germany), and is sold at about 4-5 pence per litre. 1 AVERAGE PERCENTAGE COMPOSITIONS OF THE PRINCIPAL RESIDUES Beetroot Potato Rye Maize Durra Barley Liquid Dried Liquid Dried Liquid Dried Liquid Dried Liquid Dried Liquid, Dried Water . 91-0 10-12 94-0 8-10 91-0 10-12 90'6 10-12 I 90.3 10-12 75-0 14-0 Proteins . 0-9 6-7 1-3 18-24 1-9 22-28 2'0 24-26 2-0 ,24-26 4-0 20-0 Non - nitrogenous \ matter / 7-2 60-65 2-6 45-55 5-2 48-52 4'9 35-40 5-1 30-34 10-0 46-0 Fatty matter . 1-3-1-6 0-2 3-4 0-3 5-6 1-0 12-16 0-7 12-14 1-7 7-0 Cellulose I 0-9 I 13 ' 15 0-9 9-11 1-0 5-7 ro 10-12 1-1 14-16 5-0 16-0 Ash / t 10-12 0-5 1-2 0-6 4-6 0'5 5-6 0'8 i 7-8 1-3 5-0 2 For fodder, the nutritive values of the proteins, fats, and digestible non -nitrogenous substances are in the proportions 3 : 2 : 1, so that the commercial value of a fodder, expressed in nutritive units, is given by : nitrogenous substances X 3 + fatty substances X 2 -f non -nitrogenous substances, given by the percentage composition of the digestible components, DISTILLERY RESIDUES 183 other end, by means of the perforated axis, G f , the interior of the cylinder communicates with a double-action exhaust pump to carry away the vapour from the grains which are heated in a vacuum of 700 mm., while the cylinder slowly rotates (three turns per minute). The charge consists of 2 to 3 tons of solid grains, which are dried (to 15 per cent, moisture, it then keeping well) in less than four hours, the coal consumption being about 150 kilos. By thus drying at a relatively low temperature (in a vacuum ) and out of contact with air, the oil of the grains does not become rancid. Since maize-grains contain as much as 15 to 18 per cent, of fat, it is sometimes con- venient to extract them in one of the forms of apparatus described in the section on Fats. Special interest attaches to the residues from Molasses and Beet, since these contain special nitrogenous compounds (amino-acids) and a large proportion of potassium salts utilisable for fertilisers or for chemical products. The evaporation of the liquid part of these residues may be carried to a certain stage (11 Be. in the hot or 14 in the cold) in the ordinary vacuum plant, the mass being subsequently completely evaporated and the residue calcined in suitable furnaces (Porion model in France and Belgium) which are similar to the reverberatory furnaces or muffles used in the preparation of sodium sulphate (see Vol. I., p. 174). Care must be taken riot to fuse the mass, which, when discharged, should still be FIG. 151. carbonaceous and, indeed, sufficiently so to cause it to burn when placed in heaps outside the furnaces ; the greyish or blackish mass thus obtained is known in France as salin (see Vol. I., p. 545; process for recovering pure potassium carbonate). 1 By this treatment, however, all the nitrogen compounds are lost, but in some cases these are used for the extraction of methyl chloride (see p. 116). During recent years the utilisation of these nitrogenous substances has assumed great importance : according to the Effront patents (1907), the amino-acids are utilised by enzymic processes 2 for the preparation of organic acids and ammonium sulphate (with 1 A sample from an Italian distillery showed the following percentage composition : water, 11 ; insoluble matter (carbon, sand, etc.), 10; KjS0 4 , 9-5; KC1, 18; KzC0 3 , 43-7; Na 2 C0 3 , 6-5; potassium phosphate, 0-5. 2 Ehrlich was the first to show that the fermentation of amino-acids is produced by amidases. Effront (1908) found that amidases occur especially in top beer-yeasts and in aerobic yeasts which, in seventy -two hours at 40 are able to transform, e. g., all the nitrogen of an alkaline asparagine (see this) solution, and almost all the nitrogen of the yeast itself into ammoniacal nitrogen, organic acids being formed at the same time. Use is made more especially of butyric bacteria (or tho?e often occurring in the soil), which act in an alkaline medium. From 1911 to 1914 the Effront process was employed in the Nesle (Somme) works with satisfactory results. The hot wash from the spirit rectifying column is cooled in large vessels (900 hectolitres) to 40 to 45, neutralised with lime or crude potash and given an alkalinity of 15 to 20 c.c. of normal caustic soda per litre; a little colophony (see note, p. 167) is added together with nutrient material for the bacteria, e. g., 50 to 200 grams of aluminium sulphate and 10 to 50 grams of manganese and magnesium phosphates and chlorides per hectolitre. A pure 5 to 7 per cent. 184 ORGANIC CHEMISTRY each hectolitre of alcohol produced correspond 25 kilos of ammonium sulphate and 35 grams of organic acids, principally acetic, propionic, and butyric). Since 1902, the Dessau Sugar Refinery, and since 1904 the Ammonia Company of Hildesheim, have utilised the nitrogen compounds as potassium cyanide and ammonium sulphate. In 1907 the Ammonia Com- pany utilised 60 per cent, of the nitrogen of the residues, producing potassium cyanide to the value of 80,000 and ammonium sulphate to the value of 20,000. ALCOHOLIC BEVERAGES 1 WINE. Only the liquid obtained by the spontaneous alcoholic fermentation of the must of fresh grapes, without any addition, should be called wine. The fermentation is spontaneous owing to the presence on the grapes of Saccharomyces cerevisice. culture of butyric acid bacteria, already acclimatised to the concentrated wash is then introduced and a current of air passed through the liquid for six to ten hours. Vigorous action then ensues with evolution of carbon dioxide and hydrogen, the whole of the organic nitrogen being trans- formed in three days into ammonia and various proportions of trimethylamine, acetic and pro- pionic acids, considerable amounts of butyric acid, glycerol and tartaric, citric and succinic acids, etc., as potassium salts. The Nesle works obtains per hectolitre of 100 per cent, alcohol, 30 kilos of ammonium and trimethylamine sulphates, 30 kilos of fatty acids,' 4 kilos of succinic acid, 2-5 kilos of malic, citric and tartario acids, 2 to 4 kilos of glycerine, and 30 kilos of potassium sulphate. When this mixture is rendered distinctly alkaline and distilled, the trimethylamine and ammonia are evolved, these being passed over a mixture of ammonium and trimethylamine sulphates. In this way the gaseous ammonia displaces the trimethylamine from its sulphate, forming ammonium sulphate, the trimethylamine liberated being either fixed by passing it into water, or sent through a tube heated to 1000 and thus transformed into hydrocyanic acid (from which cyanides are made) and methane. The alkaline residue left in the distilling vessel is acidified with sulphuric acid and the volatile monobasic acids (acetic, butyric, etc. ; the dibasio acids and the glycerol do not distil) together with water distilled off; to the distillate is added anhydrous aluminium sulphate to absorb the water (which cannot be separated by distillation), the insoluble acids thus separated being rectified. In the Nesle works 600 kilos of acetic acid and 1000 kilos of butyric acid were produced per day in 1914. The glycerine, dibasic acids and potassium sulphate were recovered by evaporating the residue to dryness. These works were closed in 1914 owing to the nauseous odours emitted. 1 The average annual consumption per head in litres of absolute alcohol in the form of different beverages is as follows : Beer Wine Spirits Total Germany . .4-8 0-66 4-1 9-5 Austria -Hungary France Great Britain Belgium . Denmark Sweden . Russia United State* Italy 1-7 2-1 5-1 8-9 1-3 17-5 3-5 22-3 8-3 0-2 2-3 10-8 8-7 0-6 3-7 13-0 2-6 7-0 9-6 2-3 0-06 3-9 fi-26 0-2 2-5 2-7 3-4 0-28 2-7 6-38 0-1 12-0 2-0 14-1 In Sweden 27 litres of alcohol in the form of spirits were consumed per inhabitant in 1830. In Italy the consumption was 6-5 litres per head in 1874 and 10-23 litres in 1898. In Norway the consumption of spirits, which was 40,000 hectolitres in 1864, fell to 15,000 in 1910, but increased in 1911. The abuse of alcoholic beverages is leading to the ruin and decadence of certain nations, since it is largely the cause of depopulation and produces actual decay of the human organism. Alco- holism produces a diminution in stature, as is shown by the increased numbers of those unfit for military service ; it quickly leads to crime and folly, and renders the organism easily attackable by all kinds of disease, its effect being felt to the third generation. Alcohol acts as a poison which first excites and exalts, then intoxicates and depresses the psychic faculty more or less permanently. The abuse of wine and spirits is the real cause of much intestinal catarrh and of certain visceral lesions, and sometimes leads to chronic nephritis, heart- injury, enlargement and inflammation of the liver, hepatic cirrhosis, cerebral apoplexy, progressive paralysis, and often to madness. Among the industrial classes it is thought that alcohol warms, prevents cold, and gives greater strength during work, but this is a great error based on appearances. Almost as soon as it is swallowed, the alcohol of wine and spirits is absorbed by the blood by means of the capillaries and brought into contact with all parts of the organism ; the nervous centres are then more or less paralysed, and the numerous capillaries under the skin dilate, since an increased amount of blood rushes to the skin itself. The drinker has, indeed, a red face, but the sensation of great heat is only superficial; if the surroundings are cold, the heat of the body is more easily dispersed. ALCOHOLISM 185 In many districts the fermentation is carried out on rational lines, selected yeasts being employed to impart the taste and aroma of wines of definite types. This explains why drunken men, sleeping on the roads in the winter, quickly die of cold. Nansen, the famous Polar explorer, withstood temperatures 52 below zero without using alcoholic liquors. The International Congress on Industrial Diseases, held at Milan in 1906, declared that the use of alcohol " is unnecessary for the nourishment of the workman, and becomes harmful where the work is heavy or long. As regards useful effects in the food rations of the worker, alcohol may be advantageously replaced by sugar, coffee, and tea." Alcohol may diminish the using-up of fat in the organism and hence the consumption of proteins, but as a food it is very costly and of little effect. Those accustomed to wine and beer may use it in moderation, although these bever- ages are of no advantage to the organism ; the use 01 spirits should be abolished and it should be made a crime to give spirits or even wine to children. During the last few years alcohol-free wines have been prepared by crushing grapes from the best vineyards and subjecting the must to nitration and pasteurisation (heating to 60) so as to render it clear and to prevent fermentation ; the wine is then stored in hermetically sealed , sterilised bottles. These wines retain the taste and fragrance of the grape and have considerable nutritive value, since the sugar of the grape remains unchanged (15 to 20 per cent.). Alcohol also has a harmful effect on the reproduction of man, this explaining the slou-ness or the absence of increase in population of nations consuming much alcohol ; as in France, where 6,000,000 was spent in 1898 on so-called aperitives (absinthe, bitters, etc.) alone. In Great Britain 60,000,000 is spent annually on spirits, and even in Switzerland 6,000,000. In 1913 England alone spent 140,000,000 on alcoholic beverages, Scotland 16,000,000 and Ireland 14,000,000, the average being 3 12s. per inhabitant; the number of public-houses was 141,000 (1 for 330 persons). In the same year there were 364,400 police-court cases of drunkenness, 2802 men and 2074 women dying of alcoholism, which also caused 3605 suicides and 2488 attempted suicides. Drink causes the direct or indirect death of about 45,000 people annually in France, 40,000 in Germany, 50,000 in England, 20,000 in Belgium, and 100,000 in Russia. In Italy, L. Ferriani stated that 627 cases of death in 1904 were evidently due to acute alcoholism. Dr. Ma ram bat affirms that in France 72 per cent, of the criminals and 70 per cent, of the individuals (121,688) appearing annually before the courts make excessive use of alcoholic liquors. In Ger- many, A. Baerfpund that 41-7 percent. (13,706) of the prisoners (32,837) were addicted to drink; in Switzerland, it is 41 per cent., and in England, 33 per cent, of those sentenced at the Assizes. In Holland, four-fifths of the crime is attributed to alcohol, and in Sweden three-fourths. Similar figures to the above have been given for Italy. In various countries it has been found that 25 per cent, of the lunatics are excessive alcohol drinkers. In the Salpetriere Hospital of Paris, 60 out of 83 babies afflicted with epilepsy had alcoholic parents. In Germany, 30,000 persons are attacked every year by alcoholic delirium and other cerebral disturbances due to abuse of alcohol. Alcoholism in Germany was a national calamity as early as the fifteenth and sixteenth centuries, when to the enormous consumption of beer was added that of brandy and, later, of cereal and potato spirit. After the eighteenth century, when the production of cereal and potato spirit became a great industry, their consumption as beverages increased enormously. In 1905 the annual expenditure for alcoholic drinks amounted to 47.v. per head, or 8 for every person over fifteen years old, making a total of 120,000,000 for the whole of Germany, or about 80,000,000 for the working classes, corresponding with 12 per cent, of their wages. Every year there are 200,000 cases of inebriety, and 75 per cent, of the crimes against the person are the result of drunkenness. The question of alcoholism is closely connected with the social problem, as it is especially among the working classes and the ignorant and ill-nourished that the victims are found. Abstainers are less liable to illness and usually live longer, as is shown by the following statistics. The Tables of the Sceptre Life Association for eleven years (1884-1894) show that the mortality in the temperance section (abstainers) was 57 per cent., and that in the general section (non- abstainers ) 81 per cent. In times of epidemics nine out of ten non -abstainers die and only two out of ten abstainers. The introduction of the alcoholic tendency into Africa, as a result of colonisation, wrought such havoc among the natives that the International Congresses against Alcoholism held in Brussels in 1899 and 1906 adopted various prohibitive and fiscal measures to save the black race of Africa from the terrible plague. Many remedies for alcoholism have been proposed, but singly they are almost all inefficacious, though more useful if combined. Increase of the price of drink and diminution of the number of shops have proved almost useless in France, Belgium, and England. In England, however, the latest increase in taxation has diminished by one-third the consumption of spirit; the amount of beer drunk has fallen from 31-4 to 25-8 litres per head per annum, whilst the consumption of tea and wine has increased. In the United States the enormous taxes on alcohol have not diminished the consumption of liquors. Sweden has obtained good results by making a State monopoly of alcoholic drinks, by granting licence to sell only to trustworthy persons, by giving them special facilities for, and large profits on, the sale of other beverages and of food, by abolishing profit on alcoholic drinks, and by making the licensees responsible for cases of drunkenness on their premises. This example has been partially followed in America and England, and many temperance associations have helped by opening establishments where good food and drink are obtainable at low prices, alcohol being banned. In the United States from 1920 onwards the manufacture of any alcoholic drink, including wine and beer, will be prohibited, so that the grapes (250,000 tons per annum) of the prolific Californian vineyards will be used to make alcohol-free wine, syrups, jams, etc. Another 186 ORGAN 1C CHEMISTRY Grape must has the sp. gr. 1-08 to 1-10 and contains 70 to 86 per cent, of water, 16 to 36 per cent, of sugar (glucose and levulose, which reduce Fehling's solution) ; 1 to 3 per cent, of cream of tartar, tartaric, malic, and tannic acids ; 0-4 to 1 per cent, of colouring, aromatic, extractive, gummy, and protein substances, and mineral salts. If the musts have to be transported over long distances, either they are concentrated in a vacuum or by freezing, or the fermentation is interrupted for a time by filtering them. One ton of grapes gives 600 to 700 litres of must and 300 to 350 kilos of unpressed or 160 to 200 of pressed residue (marc). By fermentation in open vats the sugar is transformed, more or less completely, in seven or eight days into alcohol, large quantities of carbon dioxide being developed and a little glycerol, succinic acid, etc., always being formed. With more than 25 per cent, of sugar, sweet wines are obtained, and with less, dry wines. Fermentation cannot yield more than 15 to 16 per cent, of alcohol, as with more than this proportion the yeast dies. After the principal fermentation, when the wine, without the marc, is placed in casks of chestnut or oak, a slow fermentation goes on, this ceasing in the winter ; with increase in the alcohol-content and lowering of the temperature, the yeast and part of the tartar (slightly soluble in alcoholic liquids ) are deposited. In the spring, the clear wine is decanted into clean (sulphured ? ) casks, which are kept full. It may now be placed on the market, or it may be further matured by clarifying it in the cask (by shaking with albumin and a little tannin and allowing to stand) and by decanting and filtering it several times during the course of a year or more before placing in well-cleaned bottles ; the latter are corked by machinery with paraffin-waxed corks. As time goes on, the wine acquires a pleasing aroma owing to esterification of small quantities of the alcohol, this process being hastened some- times by pasteurisation, which consists in passing the wine rapidly through coils heated to about 60; this treatment also arrests certain incipient diseases, which would otherwise end by spoiling the wine (acidity, etc. ). Sparkling wines are obtained by saturating the cold wine with carbon dioxide during bottling or by bottling sweet wines, the ^rmentation of which continues slowly in the corked bottle ; in the latter case, however, a deposit forms at the bottom of the bottle. In order to obtain wines of constant type on a large scale, co-operative wineries have been recently instituted in France, these collecting the grapes or must from a whole district, mixing it and preventing it from fermenting by saturating it in the cold with sulphur dioxide (70 grams liquid S0 2 per hectolitre); in this way, not only the yeasts, but also the moulds, bacteria, and unpleasant odours are destroyed and the must can then be kept for months in closed vessels. When part of the must is to be converted into wine, it is heated at 50 to 60 in a vacuum by allowing it to pass down a kind of rectifying column (Barbet, Ger. Pat. 195,235, 1906), the sulphur dioxide thus removed being recovered; selected yeast or other wine rich in yeast is then added, the resulting wmes being of uniform and improved character, although somewhat rich in sulphates. These desulphurated musts might well be used as non-alcoholic wines. There are also special yeasts capable of destroy- ing SO 2 in the musts and of starting fermentation. In Italy much was said in favour of co-operation in 1909 and 1910, but no trial has been made on a large scale. The proportions of the most important components of wine vary between wide limits, owing to variation of the vines, soil, climate, system of wine-making, and season (certain wines contain manganese, sometimes as much as 27 mgrms. per litre). It is hence difficult to ascertain if there has been an artificial addition of constituents similar to those naturally present in the wine, so that considerable dilution with water and addition of alcohol, glycerol, tartar, sugar, etc., are not easy to detect if they do not exceed such limits. Natural wines may contain 8 to 16 per cent, of alcohol, 1-6 to 4 per cent, (for dry wines, and as much as 20 per cent, or more for sweet wines) of dry extract (obtained by evaporating a definite volume to dryness on a water-bath and drying in an oven at 100), 0-5 to 1-5 per cent, of various acids and tartar (expressed as tartaric acid) and 0-15 to 0-45 per cent, of mineral substances (ash, obtained by calcining the dry extract); the glycerol effective factor against alcoholism is education and explanation of the evil effects of the habit : in schools, churches, barracks, the streets, workshops, books, reviews, newspapers, advertisements indeed everywhere should an intelligent campaign be waged against alcoholic liquor which, as Gladstone said in the House of Commons, commits more slaughter in our days than the three historic plagues : famine, pestilence, and war, since it decimates more than famine and pestilence and kills more than war, and is in all cases a disgrace often lowering man below the level of the brute. WINE STANDARDS 187 varies from one-seventh to one-fourteenth part of the alcohol. Naturally these variations are much smaller for wines of a certain quality and year and obtained from one and the same district, for which the results of numerous analyses have been collected. In Italy the following minimum legal limits have been established as those which must be reached for a wine to be called natural (except in cases where genuine wines of the same origin and year are shown to give lower limits) : alcohol, 8 per cent, by volume in white wines, 9 per cent, in red; dry extract without sugar, 1-6 (white), 2-1 (red); total acidity expressed as tartaric acid, 0-5 (white), 0-6 (red); ash, 0-15 (white), 0-2 (red); alkalinity of the ash (for nonplastered wines) in cubic centimetres of normal alkali per litre, 11 (white), 16 (red); the glycerol should be from one-seventh to one-fourteenth by weight of the alcohol, and the relation between ash and extract (for dry wines or for sweet wines after deducting the sugar) should be about 1 : 10; plastering, 1 expressed as sulphuric acid, should not exceed 0-2 per cent. In France and now also in Italy, in deciding if a wine is watered, use is made of Gautier's rule (corrected), according to which the sum of the percentage of alcohol by volume and the total acidity (as sulphuric acid) per litre should reach the value 12-5 for red wines and 11-5 for white wines. Use is sometimes made of Halphen's rule (1906-1913), the results, of which are credited by some and discredited by others (Issoglio and Possetto, 1914; Astruc and Mahoux, 1908- 1911; Prandi, 1914; Pratolongo, 1917; Scurti and .Rolando, 1917; Galeazzi, 1916, etc.). According to this rule, the ratio (x) between the fixed acidity (expressed as sulphuric acid and increased by 0-7) and the percentage of alcohol by volume (y) should differ by not more than 0-120 from the theoretical value calculated from the expression x = 1-160 0-07 y; thus, for a wine with 10-2 per cent, of alcohol and fixed acidity 3-88, x = (3'88 + 0-7)/10-2 = 0-449, while the theoretical value would be 1-160 (10-2 x 0-07) = 0-446. Wines weak in alcohol or tartar do not keep well in the warm weather. A weak wine may be improved by either mixing with stronger wines or concentrating by freezing, water then separating in the form of ice (this method, in use even in the Middle Ages, has recently been patented in Italy ! ). New wine has sometimes the smell and taste of rotten eggs, i. e., of hydrogen sulphide; this may be remedied by decanting it into casks in which sulphur has been burnt : 2H 2 S + S0 2 = 2H 2 + 3S. 2 1 In order to prevent certain diseases to which southern wines low in acidity are liable, recourse is had to the addition of sulphites, or potassium metabisulphite (see Vol. I., p. 544), which increase the quantities of sulphuric acid and sulphates. Thus some wines remain clear in the bottle, but become turbid and dark on exposure to the air ; this disease, termed casse, is prevented by addition of potassium metabisulphite, which also arrests secondary fermentation. To make certain weak wines keep better in summer in tapped casks, calcium sulphite is added, this giving a slow evolu- tion of sulphur dioxide. The keeping qualities of certain wines are improved by 'plastering, which consists in adding to the fermenting must a certain quantity of gypsum (calcium sulphate), but the total sulphates are restricted by law to 2 grams per litre (calculated as normal potassium sulphate), excessive pro- portions of sulphates being considered injurious to health. It was formerly thought that the gypsum with the cream of tartar would give rise to insoluble calcium bitartrate and acid potassium tartrate, but instead of the latter normal potassium sulphate is the more probably formed : 2C 4 H 5 OeK + CaS0 4 = C 4 H 4 6 Ca + C 4 H 6 6 + K 2 S0 4 (Magnanini and Ventura, 1902; Bussy and Buignet, 1865; Pollacci, 1878; Roos and Thomas, 1896; Manzato, 1896 and, especially, Borntrager, 1917 and 1918). Incipient sourness of wine may be corrected by adding normal potassium tartrate or, better, potassium carbonate in amount calculated on the quantity of volatile acids (acetic, etc.) present, and subsequently clarifying. 2 To desulphur musts and wines use is sometimes made of a small quantity of urotropine (hexameihylenetetramine), which decomposes into ammonia and formaldehyde, the latter fixing the sulphur dioxide; such addition may be detected, according to Fonzes-Diacon and Bonis (1910), by distilling 25 c.c. of the \vine with 3 drops of sulphuric acid, acidifying the first 5 c.c. of distillate with 1 c.c. of sulphuric acid, and observing if it colours a solution of ruchsine decolorised with sulphur dioxide. The residue from the distillation is rendered alkaline with magnesium hydroxide and distilled, the vapours distilling over being condensed in a known volume of N/10 sulphuric acid, which is titrated back to ascertain how much ammonia distils over from the urotropine. Even in a dilution of 1 : 50,000, urotropine may be detected by addition of mercuric chloride, which forms a precipitate in the shape of many-rayed stars. With white wine the reaction is obtained directly after addition of a little hydrochloric acid; red wine is shaken first with solid lead acetate and then with sodium phosphate, and filtered, the filtrate being tested with HgCl 2 . Milk is acidified with HC1, shaken with solid ammonium sulphate, filtered and, if turbid, shaken with petroleum ether, the reaction being then applied (Rosenthaler, 1913). 188 ORGANIC CHEMISTRY From the vinasse remaining after the wine is drawn off a little rather rougher wine may still be obtained by subjecting it to considerable pressure, and from the pressed vinasse alcohol (see above) and tartar (see later) may be extracted. The testing or analysis of wine is usually limited to determining the alcohol (by the method described on p. 174), dry extract, ash (see above), glycerol, plastering, and total acidity, and to testing for the addition of colouring-matter and other adulterations. The complete analysis of wine is described in Villa vecchia's "Applied Analytical Chemistry," Vol. II., pp. 175 et seq. Statistics. The countries which produce the most wine are France, Italy, and Spain. For Italy the statistics are very contradictory, and even the official ones are erroneous ; for instance, the production for 1909, which was given officially as 40,000,000 hectolitres, was officially corrected in 1910 to 60,000,000 hectolitres. In various countries the output has been greatly diminished owing to invasion by phylloxera. 1 The average annual output of grapes in Italy in 1909-1916 was 6,400,000 tons ; in 1912, 67,000,000 and in 1913 8,000,000 tons were produced. Italy imports on an average 900,000 bottles of fine wines, of the value 100,000, per annum. 2 In Milan in 1909 duty was paid on 1,000,000 hectolitres, the Corporation receiving 420,000, and the consumption per head being 200 litres. In 1905 Italy exported to Germany 124,000 quintals of dessert grapes, whilst France exported only 78,000 quintals. In 1892 Italy exported about 260,000 hectolitres of wine to Germany, but less amounts in subsequent years. 3 1 Phylloxera (P. vastatrix and P. viti folia) is an insect allied to the aphides and about 1 mm. long. It lives on the roots, leaves and tendrils of the vine, and quickly kills the latter, the roots blackening and decomposing. It was introduced into Europe on vines imported from America. The French vineyards were devastated by it in the period 1876-1889 (see above : " Statistics "). the ordinary remedies (flooding, carbon disulphide, potassium trithiocarbonate, etc.; see Vol. I., pp. 495, 547) being without avail, owing to the violence of the attack. Almost all the French vines had to be destroyed and replaced by American phylloxera-resisting vines on which were grafted the French vines, these giving grapes of the original qualities. Hungary was also hit hard by phylloxera, the output of wine falling from 7,000,000 hectolitres in 1880 to 2,000,000 in 1902. In Italv phylloxera has spread alarmingly, the vineyard areas attacked being : 2458 hectares in 1879; 75,612 in 1889; 351,033 in 1899; 410,260 in 1909, and 605,305 in 1911. 2 The output of wine in other countries is as follows (thousands of hectolitres) : 1902 1907 1908 1909 1910 1911 1912 1913 1914 1915 Germany . 2,000 2,4^2 3,135 2,020 846 2,922 2,019 1,005 921 2,698 Austria 5,200 4,250 8,142 6,252 2,546 3,836 3,970 4,352 3,615 Hungary . 2,000 3,792 8,023 4,364 2,764 4,939 . Bulgaria . 2,300 866 1,643 1,318 770 551 715 Spain 16,000 118,384 18,557 14,716 11,283 14,747 16,465 17,105 16,168 8,789 Greece 1,000 3,230 3,182 3,042 Portugal . 5,000 6,869 4,074 . 4,910 Roumania . 2,700 967 2,283 1,270 1,713 993 1,589 1,158 660 1,670 Russia 2,300 . 2,310 2,600 Serbia 500 536 856 394 153 Switzerland . 681 925 408 408 854 903 264 507 870 Corsica 254 194-4 193-4 159 147 . .125 42 Algeria 7,853 7,803 8,228 8,414 8,833 . ' Tunisia - 357 345 350 250 440 290 300 200 125 Turkey & Cyprus* 2,000 1,800 Argentine . 1,500 2,843 3,350 3,900 3,817 4,085 5,000 5,144 4,823 4,515 Chile 2,500 1,893 2,260 2,227 1,331 1,904 2,262 2,943 3,080 1,614 Uruguay 185 162 170 147 105 194 165 165 114 Australia . 327 202 250 209 266 226 277 214 United States . 1,100 . 1,166 (tons of grapes) Whole World . 126,000 142,000 161,560 157,500 89,850 127,500 144,000 138,000 146,000 105,500 3 The import duties levied by different countries on Italian wines before the war were as follows: Germany, 29s. per quintal; Belgium 18s. Qd.; Holland 34s.; Great Britain 23s. for wines with less than 14-84 per cent, of alcohol, and 54s. Qd. for stronger ones; Russia, 45s.; United States, 54. 6df. ; and British India, 33s. Qd. PRODUCTION OF WINE The following figures represent hectrolitres (1 hectolitre = 22 gallons) : 189 France Italy Production Production Exportation * 1875 83,000,000 28,000,000 363,000 1879 25,000,000 34,000,000 1,075,000 (phylloxera) 1887 24,333,000 34,000,000 3,603,000 (2,800,000 to France) 1889 23,000,000 22,000,000 1,440,000 (commercial treaty with France broken in 1887) 1893 59,000,000 32,000,000 2,362,000 (750,000 to Austria-Hungary ; 300,000 to Switzerland, 2 and 426,000 to America) 1897 32,000,000 28,000,000 2,400,000 1901 58,000,000 44,000,000 1,334,000 1902 35,000,000 2,164,000 (976,300 to Austria-Hungary) 1904 42,000,000 1,200,000 (Austro-Hungarian market lost by new commercial treaty) 1905 57,000,000 28,000,000 980,000 (worth 1,400,000) 1908 66,500,000 52,000,000 1,200,000 1909 66,000,000 60,000,000 1,450,000 (France has a vine area of 1,625,630 and Italy of 3,500,000 hectares) 1910 28,723,000 29,293,000 1,812,000 (2,400,000) 1911 53,879,156 42,655,000 960,722 (plus bottled wine to the value of (of which 8,900,000 in Al- 400,000) : geria and 160,000 in Corsica) 1912 63,831,000 44,123,000 863,970 (1,440,000) 1913 52,000,000 52,240,000 1,466,600 (2,440,000, plus bottled wine worth (wjth Algeria) 520,000) 1914 70,134,160 43,000,000 1,785,500 (with Algeria) 1915 25,000,800 19,000,000 742,000 (European war) 1916 44,800,000 39,000,000 398,000 (1,280,000) (of which 8,800,000 in Al- geria) 1917 42,000,000 48,000,000 1,024,000 (3,840,000) (with Algeria) 1918 36,408,000 2,560,000 (9,600,000, plus bottled wine worth 560,000) 1919 30,000,000 The wine (hectolitres) exported from Italy to different countries is as follows : 1909 1910 1911 France .... 43,725 73,560 45,446 Germany . . . 193,960 93,868 85.130 Switzerland . . . 922,950 637,300 332,415 Egypt .... 32,000 23,420 9,620 Argentine . . . 211,620 241,900 165,977 Brazil .... 129,589 156,226 136,980 United States . . . 138,180 126,522 70,200 Other countries . . 124,613 140,887 111,760 2 The following is a statistical resume of the wine imported into From 1906 1908 1910 1912 Italy . . 137,843 531,776 828,559 - 200,000 France . 273,731 363,769 216,909 Spain . . 123,587 415,052 422,775 Austria . 53,411 69,634 110,608 Greece . 9,370 12,209 64,874 1912 23,679 19,022 200,565 7,000 153,720 176,695 73,320 84,200 Switzerland 1913 570,000 1913 235,578 46,640 569,465 8,300 148,954 186,485 99,224 117,985 (hectolitres) 1914 693,000 190 Among the many taxes imposed by Italy to settle the enormous war debts was one (dated September 30, 1919) of 9*. 6d. per hectolitre on wine produced and on that remaining from 1918. MARSALA. This is a liqueur wine made for the first time at Trapani in 1773 by J. Woadhouse of Liverpool to compete with the world-famous Madeira. In 1812 another large establishment was started by the Englishman, Benjamin Ingham, and in 1840 Vincenzo Florio's factory, which has since become the most celebrated. The prime material for the manufacture of Marsala is white Trapani wine with 13 per cent, of alcohol, to which is added (in quantity varying for different types of Marsala) the must (cotto) of very mature white grapes, concentrated in open boilers until two-thirds has evaporated ; then is added, in varying amount, sifone, obtained by filling a cask to the extent of three-fourths with clear must from a very ripe white grape, and one-fourth with pure alcohol (free from tax if for export), mixing and allowing to age so as to develop the Marsala aroma. Mixtures of these three components in different proportions give the various brands of Marsala : the Italian brand is the least alcoholic (16 to 17 per cent.), the original English brand the strongest (up to 24 per cent, of alcohol), while the Margherita and Garibaldi brands are of intermediate strengths and are sweeter. In 1905 Italy exported in cask 29,765 hectolitres of Marsala, worth 83,280, and 51,000 bottles, value 2040; in 1908, 24,900 hectolitres; in 1910, 32,500; in 1912, 30,381 and in 1913, 28,695 hectolitres (103,302) in cask and 3000 (19,200) in bottle. VERMOUTH. This was prepared formerly in Tuscany, but nowadays almost exclu- sively in Piedmont, where the industry was started in 1835 by Giuseppe Cora and A. Marendazzo. The prime material for manufacturing vermouth is the muscat wine of Asti and of the Monferrato heights, which contains 6 to 1 1 per cent, of alcohol and 2 to 4 per cent, of sugar; with this is mixed 2 to 5 per cent, of a vinous infusion of aromatic drugs, in which worm wood predominates, and which contains also sweet flag, juniper, gentian, etc. ; finally alcohol is added to bring the strength up to 15 to 18 per cent, and sugar to the density of 5 to 9 Be. (if for exportation, 90 per cent, of the alcohol and sugar taxes are refunded). Sparkling vermouth is made by saturating it with CO 2 in the cold under pressure. It cannot be said that in the manufacture of Marsala and vermouth all the rational methods prescribed by modern cenotechnics are followed. 1 The production of vermouth in Piedmont is now about 300,000 hectolitres, the exports (especially to America) being 8960 hectolitres in cask and 64,980 in bottle in 1906; 7874 in cask and 83,300 in bottle in 1908; 10,176 (27,680) in cask and 100,000 (464,920) in bottle in 1909; 20,400 (53,040) in cask and 173,760 (760,000) in bottle in 1910; 25,000 in cask and 94,000 in bottle in 1911 ; 32,000 in cask and 131,500 in bottle in 1912, and 34,300 (119,360) in cask and 133,600 (720,000) in bottle in 1913. CIDER. This is an alcoholic drink obtained by the partial fermentation of the juice of apples and pears (perry). It is largely used in the north of France, in Germany, and in Switzerland. It is consumed almost immediately it is made. In France the production varies from 8,000,000 to 30,000,000 hectolitres, part of which is distilled to produce alcohol (30,000 to 70,000 hectolitres of alcohol). LIQUEURS. These contain 40 to 70 per cent, of alcohol. The finest are those obtained by collecting the first, more highly alcoholic distillate from other fermented liquors. Such are brandy (prepared by distilling vinasse or wine and containing 45 to 55 per cent, of alcohol), cognac, kirschwasser (obtained especially from the cherries of the Black Forest), rum (prepared principally in Jamaica by distilling fermented cane-sugar molasses), mara- schino (prepared from small Zara cherries), -gin (from juniper berries), atole or chica of South America, arrack of the Arabs and Indians (prepared from rice, cane-sugar, and coconuts), schnapps of the Germans (potato spirit), etc. The other class of liqueurs comprises those obtained from aromatic substances, sugar, and more or less concentrated pure alcohol. In this way are obtained rosoli, anisette, absinthe (alcoholic decoction and distillation with wormwood) much used in France and the principal cause of the terrible effects of alcoholism (p. 184) creme de menthe, creme de cafe, etc. ; ratafia from fruit must, spirit, and sugar ; Chartreuse (the most celebrated 1 In Italy and also in other countries vermouth may not be coloured with aniline dyes, but the Municipal Hygiene Authority of Milan limits such prohibition to vermouth wine, colouring being allowed if the product is declared simply as vermouth (as with liqueurs). KEFIR 191 was that prepared by the Carthusian monks, before their expulsion from France in 1904, from balm-mint, cinnamon, saffron, hyssop, angelica, sugar, alcohol, and other ingredients), coca (from Bologna), curacao (first prepared from two kinds of orange in the island of Curasao in the Antilles), kummel (in Russia the best kinds are obtained by distilling brandy or alcoholic liquids with Dutch cumin seeds and dissolving pure sugar in the highly alcoholic distillate). It is unnecessary to mention that all liqueurs, even the most celebrated, are more or less poorly imitated in all countries with mixtures in no way resembling the original types, but the latter always command very high prices. Cognac is a brandy prepared especially in Charente by very carefully distilling weak wines of special vintages and refining and maturing the product in casks of Angouleme or Limousin oak, which gradually imparts to the spirit a pale yellow colour and a character- istic aroma. The finer and older brands sell at as much as 40 per hectolitre (see note, p. 180). FERMENTED MILK. This bears the following names according to the locality and method of its preparation and the nature of the milk from which it is made : kephir, koumis, galazin, leben (Egypt), and mazun. The first three of these are the best known. KEPHIR, or Kefir, is of very ancient origin among the Caucasian highlanders, who nowadays make enormous use of it and jealously keep the secret of its preparation. There is a legend to the effect that Allah was the first to make it, and that he recommended it as a remedy for various diseases. Kephir is simply cows' milk (fresh or skim) fermented by the addition of a special ferment in the form of granules, which the Russians call "fungi " and the Tartars "grain or millet of the Prophet," as they regard it as discovered by Mahomet. It was only in 1882 that Dr. Dmitrieff called the attention of the rest of Russia and of Europe to kephir and its great recuperative properties in cases of lung diseases. Kern and, later, Freudenreich showed that the alcoholic fermentation of milk with millet of the Prophet is due to the simultaneous action (symbiosis) of the new Saccharomyces kephiri (similar to ordinary Saccharomyces ellipsoideus), a streptococcus, and a bacillus. The alcoholic fermentation of milk-sugar with evolution of CO 2 takes place rapidly and is always accompanied and followed by acid fermentation (lactic acid), which partially dissolves the casein (propeptones ) and forms a very fine coagulation, almost a frothy emulsion. In practice the kephir granules (or about 2 grams of kephir-extract per litre of milk) are softened with tepid water (30 to 35) for a couple of hours, the milk being then added and the mixture shaken every hour for eight hours ; it is then sealed in clean bottles fitted with mechanical stoppers and is shaken now and then, the temperature being maintained at 15 to 20 ; in twenty-four hours' time the kephir is ready ; it forms a slightly alcoholic and acidulated dense, frothing liquid. If the kephir is left in closed bottles for two days, the pressure increases and the mass becomes more acid and more liquid ; by the third day it becomes extremely acid and contains up to about 2 per cent, of alcohol, and after this it is inadvisable to drink it. In Italy kephir or kephir-extract is placed on the market by the Borgosatollo Dairy (Brescia) and kephir dried in vacua is also prepared (Rosemberger, Ger. Pat. 198,869, 1907). KOUMIS is similar to kephir, and of equally ancient origin, but is prepared from mares' milk. In Russia there are various sanatoria which make efficacious use of large quantities of koumis. The composition of the latter has been found to be : Water, 94 per cent. ; CO 2 , 0-9; ethyl alcohol, 1-7; lactic acid, 0-7 ; lactose, 1-3 (before fermentation 5-5); fats, 1-3; proteins, 2-3 (largely peptonised); salts, 0-3. GALAZIN is obtained by placing skim (cow's) milk, with 2 per cent, of sugar and 0-3 per cent, of beer-yeast in strong, tightly stoppered bottles, and allowing fermentation to proceed for twenty-four hours at 16 ; from the second to the sixth day the proportion of alcohol rises from 0-3 to 1-5 per cent. Galazin is less nutritious than kephir or koumis. BEER This is another alcoholic liquor saturated with CO 2 and is obtained by fermenting aqueous decoctions of barley-malt and hops. The ancient Egyptians were acquainted with the manufacture of beer and held it in great regard. Later it became known to the Ethiopians and the Hebrews, but the Greeks 192 ORGANIC CHEMISTRY never acquired a taste for beer. The industry was taken by the Armenians from Egypt into the interior of Asia, and still later beer was manufactured in Spain and France, but it was never consumed by the Romans. In Germany beer has been made from time immemorial. A marked improvement in the manufacture of beer dates from the time of Charles the Great, when hops were first used. Lager beer (see later) was prepared as early as the thirteenth century, and its use has since greatly extended in various countries. In England the manufacture has flourished since the fifteenth century, the famous porter being first made at the beginning of the eighteenth century. The improvement made in brewing operations by the introduction of scientific methods has led to a very considerable development of the industry in Germany and elsewhere. In all stages of the manufacture the greatest cleanliness is now practised, the walls and floors as well as the vessels being frequently disinfected by means of dilute calcium bisulphite solution (1 per cent.), or hydrofluoric acid solution, or ozone (see Vol. I., p. 202). 1. A. BARLEY x should satisfy the following requirements : 1 Barley (botanical species Hordeum) used for making beer is of two types : two-rowed (Fig. 152), in which the corns are arranged in the ear in two rows, one on each side, and six-rowed FIG. 152. FIG. 153. (Fig. 153), in which there are three rows of corns on each side of the ear. Barleys of different kinds may, to some extent, be recognised by the form of the small bo-tal bristle found at the base of the corn inside the longitudinal furrow. The value of barley for brewing purposes is largely influenced by the nature of the soil, climate, methods of cultivation, and manuring. Barley is cultivated in all countries and in all climates in Holland and also in Sicily. It is difficult to keep varieties pure, since they become modified during growth owing to crossing. Only by the rational system of selection initiated by Dr. Nilsson at the Svalof Institute is it possible to fix different varieties with constant, well-marked characters suited to the various districts in which at one time they originated. From a commercial point of view, the weight of a barley is of importance and good qualities give a weight of 40 grams per 1000 corns, or 62 to 67 kilos per hectolitre for thin barleys and as much as 70 kilos per hectolitre for the larger ones. The grains should have a floury and not a HOPS 193 (a) When moistened and kept at 25 to 30, 80 per cent, of the corns should germinate in forty-eight hours and 90 to 95 per cent, in seventy-two hours. (b) Those are preferred which are heaviest (60 to 70 kilos per hectolitre) and contain about 62 per cent, of starch, about 10 per cent, of protein, and 12 to 14 per cent, of moisture. The richer the barley in proteins, the less is the amount of dry extract yielded by the malt; thus a barley with 11 per cent, of albuminoids gives a malt yielding at most 76 per cent, of dry extract, whilst one with 7 per cent, of albuminoids gives a malt yielding 81 to 82 per cent. Often, however, the barleys richer in starch are poorer in nitrogen. (c) The skin should be thin and the colour pale yellow, the ends of the corns not being brown. Barley starch swells at 50, and with water forms a paste at 80. With diastase it begins, unlike potato starch, to sac- charify as soon as it is com- pletely transformed into paste. B. Wheat is sometimes used, together with barley, for pale beers. C. Maize is used in America after being skinned and de- germed, the germ being rich in oil. Prepared maize and rice are used in Great Britain. D. Rice is used in America and Scandinavia with the barley. 2. HOPS. The female flowers, dry and mature, of FIG. 154. Humulus lupulus (Fig. 154) are used, these containing 10 to 17 per cent, of a powder, lupulin which can be separated by shaking and sieving), possessing the aromatic and bitter principles which bestow on the beer its aroma and keeping qualities. 1 vitreous appearance when cut through, and there should be few broken corns, as these do not germinate and become mouldy on the malting floor. Germination tests, made on 500 or 1000 corns, should show at least 95 per cent, of germinated corns in five to six days. With barley harvested under wet conditions, the ends of the corns are darkened. The world's -production of barley in 1906 was 31,500,000 tons, in 1910 31,000,000 tons, and in 1913 36,600,000 tons. In 1910 (and also in 1913) France produced 1,080,000 tons (17,000,000 hectolitres from an area of 737,300 hectares). In 1913 Germany produced 3,673,200 tons, Austria 1,750,000, Hungary 1,730,000, Bulgaria 300,000, Denmark 600,000, Spain 1,500,000, Great Britain 1,500,000, Roumania 600,000, Russia 12,100,000, United States 3,900,000, Canada 1,050,000, Japan 2.370,000 and Algeria 1,090,000. Italy produces on the average 220,000 tons of barley per annum and imported the following quantities of malt (mainly from Austria and Germany) : 1908 1910 1912 1913 1914 1916 Tons . . 12,400 17,800 19,108 15,843 18,200 8,890 . . 89,240 128,080 244,582 202,790 276,800 157,000 1 In regions where hops are cultivated on an industrial scale, the agriculturists whose lands border on the hop gardens are compelled by law to destroy any male hop plants accidentally growing in their fields. The non -fertilised female flowers do not bear fruit. The best hops are cultivated in Bohemia (at Saaz), Bavaria, Posen, Wiirtemberg, Baden, and Alsace-Lorraine, where they are picked towards the end of August. If they are too ripe the bracts of the hop-cones open and lupulin is lost. The most extensive cultivation of hops takes place in the United States. The hop should have a bright yellowish green, and not a brown, colour, and the bracts should not be open ; a too green colour indicates that the hops have been picked in an unripe condition. VOL. II. 13 194 ORGANIC CHEMISTRY 3. WATER. Formerly water for brewing purposes was invested with a mysterious importance, but nowadays the water is tested in a much more rational and rigorous manner. Preference used to be given to moderately soft water, but now waters of medium hardness are regarded as best, as it is found that a certain quantity of calcium sulphate aids fermentation, but if the water is too hard, less extract is obtained from the The seeds have no value for brewing purposes, the largest hops being of least value. They should not have an unpleasant odour. Since the fresh hops contain 75 to 85 per cent, of moisture, so that they will not keep, it is necessary to dry them in the air or in ovens at 25 to 30 in a strong current of dry air, until they contain only 12 to 15 per cent, of moisture ; they will then keep well, even for a year or more. Their keeping qualities may be improved by sulphuring them (with S0 2 ) either when dry or during the drying. Sulphuring is, however, often applied to inferior hops to mask their defects. The better qualities are seldom sulphured and, when they are well dried, are kept tightly compressed in large sacks or in evacuated metal cylinders. They may also be kept in a very cool place (cold store). The bitter flavour and keeping properties imparted by the lupulin of hops depend mainly on their content of humuUne, which is a sesquiterpene, C 15 H 21 , and on that of the a- and fi-bitter aciclf, which varies from 6 to 18 per cent. The o-acid is humulene, C 20 H 32 5 , and the -acid, lupitlinic acid, C 25 H 36 O 4 ; both are insoluble in water and very bitter, and may be determined by Lintner's method as follows : 10 grams of an average sample of the hops are heated in a flask graduated at 505 c.c., with 350 c.c. of light petroleum (b.-pt. 30 to 50) for six hours on a water- bath at 40 to 45, an efficient reflux condenser being fitted to the flask. When the latter is cold, it is filled to the mark with light petroleum and shaken, the contents then being filtered. 100 c.c. of the filtrate, mixed with 80 c.c. of alcohol, is titrated with decinorma"! potassium hydroxide solution in presence of 10 to 15 drops of phenolphthalein solution. If much fat is present an aliquot part of the light petroleum solution is evaporated and the residue extracted with methyl alcohol, which does not dissolve the fat and, on evaporation, gives the bitter acids ; these may then be weighed. The quality and commercial value of hops are influenced largely by the nature of the soil and the quality of the manure used, as well as by the variety of the hop itself. Chemical composition does not always give satisfactory indications for judging of the value of hops, and this is almost always done by men experienced in valuing hops. Hops eive up to alcohol 22 to 30 per cent, of extract, about two-thirds of which is composed of a resin" giving the bitter flavour and acting as an antiseptic towards certain bacteria injuriously affecting the keeping of the beer, although it has no influence on the yeast. The flavour of the beer is also considerably affected by the tannin contained in the hop to the extent of 2 to 4 per cent. The determination of the ethereal extract is also employed in judging of the quality of hops ; with good qualities, after evaporation of the ether, 27 to 28 per cent, of residue is left (see above, Lintner Test). Germany imported 2800 tons of hops in 1908 and 2636 tons in 1909, the exports being 12,400 and 8800 tons respectively in 1908 and 1909. The United States imported 2800 tons in 1911 and exported 7000 tons. The International Agricultural Institute of Rome gives the following statistics of hop production : TT ftons . Hungary { hectarfcs Belgium France . Great Britain Russia United States / tons . \hectares ( tons . \hectares / tons . \hectares tons . / tons . \ hectares 1908 1910 1911 1912 1913 1914 1915 26,340 35,865 20,411 27,460 10,628 26,658 20,563 26,966 10,618 27,048 23,237 27,685 14,563 23,737 18,748 25,364 16,512 21,281 8,613 19,919 20,146 20,304 ' 8,564 20,260 16,444 18,480 867 1,142 834 926 1,153 1,357 1,796 2,176 , ~ 3,863 2,060 3,102 2,047 3,075 2,101 4,612 2,283 3,355 2,405 2,485 5,157 3,030 3,232 2,741 2,630 2,843 3,973 2,832 3,568 2,951 3,191 2,731 2,227 2,214 23,916 15,751 15,377 13,308 16,664 13,377 18,971 14,095 12,987 14,437 25,770 14,836 12,935 14,060 4,428 2,949 3,293 4,423 7,699 6,388 19,913 22,514 23,438 24,208 28,530 19,693 26,907 Whole / tons . world \hectares 103,894 85,784 70,015 99,635 77,022 96,725 82,599 84,000 68,515 67,000 69,489 69,068 71,586 66,875 The output of hops per hectare (2-47 acres) varies from 14 to 30 cwt. Australia produces 800 to 900 tons of hops, the area under their cultivation being 500 to 600 hectares. STEEPING 195 malt and hops. Iron is also harmful, and especially so are waters contaminated with bacteria. 1 The principal operations in the manufacture of beer are as follow : (1) CLEANING OF THE BARLEY, to remove dust, soil, stones,' damaged and light corns, etc., by means of sieves, fans, etc. (2) STEEPING OF THE BARLEY for two or three days in water at 11 to 12 in order that it may absorb the water necessary for germination (about 45 per cent.). For this purpose use is generally made of the Neubecker tank (Fig. 155), made of iron plates, open at the top and cone-shaped at the bottom. In the middle is a wide perforated pipe, E, which is surrounded by the barley (500 to 3000 kilos). The water is supplied by the pipe W , and is discharged through the perforations of E, thus covering the barley ; it is then discharged from the top of the tank through the pipe U, the lighter FIG. 155. 1 Water for brewing should contain only small proportions of carbonates, since these partially neutralise the primary phosphates of the wort, whereas for the enzymic functions inherent to the mashing of the malt the acidity of the malt (primary phosphates) should be preserved. The mashing process is characterised by the degradation of the starch by diastase and by the decomposition of the protein substances by means of peptases. The secondary phosphates are alkaline to methyl orange (the primary phosphates being neutral) and hinder these enzymic processes. Carbonates tend to diminish the acidity, thus : 4KH 2 P0 4 + 3CaC0 3 = 3C0 2 + 3H 2 + Ca 3 (P0 4 ) 2 + 2K 2 HP0 4 . Sulphates, however, tend to restore the acidity and transform the secondary into primary phosphates : 4K 2 HP0 4 + 3CaS0 4 = Ca 2 (P0 4 ) 2 + JSKjSOj + 2KH 2 P0 4 ; the beneficial effect of gypsum is thus explained. The carbonates (calcium bicarbonate) may be eliminated by boiling the water or by passing air for half ah hour through the water at 85, all the calcium carbonate and most of the magnesium carbonate being thus deposited ; if the temperature is lowered to 60 magnesium carbonate redissolves, so that the water should be filtered hot. The cautious decomposition of the carbonates with mineral acids or, better, with lactic acid has been suggested. The proportion of gypsum present in the water is often increased artificially. For pale beers (Pilsener) the water is preferably less hard, even though it contains only little gypsum. Excess of the latter affects the flavour of the beer, as it is left finally as potassium sulphate (see above), which has a decided taste ; this is readily observed on adding 20 to 25 grams of potassium sulphate per hectolitre to beer made with a moderately soft water. In the case of dark beers the influence of the salts of the water is less apparent, since the torrefied malt is more acid and the caramel and sugar impart to the beer a marked taste, which masks other flavours. Even for dark beers, however, a water of only moderate hardness is to be preferred. The water of the Munich breweries contains a medium proportion of carbonates (the residue, 28 grams per hectolitre, contains 25 grams of carbonates) and very little gypsum ; artificial increase of the latter is, however, never suggested, although common in Britain. Also for steeping barley a moderately hard water is best. The compositions of various waters are as follows (parts per 1,000,000) : Good Medium Bad Dry residue ...... 250-450 450-550 550-700 Ferric oxide and alumina (Fe 2 3 ,Al 2 O 3 ) 0-1-5 1-5-2-5 3 Lime (CaO) 120-150 150-200 200-300 Magnesia (MgO) ..... 20-50 50-80 80-120 Sulphuric acid (S0 3 ) 20-60 60-80 100-200 Ammonia . . trace-1-5 Nitrites and Nitrates ..... 0-0-5 0-5-1-5 Organic matter (as oxygen absorbed) 0-4-1-5 1-5-2-0 2-3 Hardness (French degrees) .... 15-25 25-35 35-50 Number of bacteria per 1 c.c. 50--500 500-4000 4000-10,000 These numbers are only indicative and must not be taken too strictly. 196 ORGANIC CHEMISTRY floating corns being carried away. After seven or eight hours the water is run off through the tap C, and the moist barley left exposed to the air for five or six hours. Fresh water is then introduced and left for ten to twelve hours, after which it is run off and the grain exposed for five or six hours, and so on. This procedure is continued for thirty to fifty hours in summer or seventy to one hundred hours in winter, the corns having in that time absorbed about 40 per cent, of water. Steeping of the barley in lime-water has been suggested as a means of preventing abnormal fermentations (Windisch, 1901) and of obtaining beer of improved aroma and flavour. In some cases steeping is preceded by washing of the barley in running water in rotating cylinders, or else compressed air is forced into the steeping vessels at frequent intervals, so as to stir the barley. The steep- water becomes yellowish brown and acid, and after some time undergoes lactic and butyric fermentations. At the end of the operation, the barley is discharged through the lower aperture, A, by undoing the screw, B, and raising the tube E, by means of the lever, D. (3) GERMINATION OF THE BARLEY. The steeped barley is carried to the spacious malting floor, which is fitted with numerous windows to allow of the renewal of the air when desired, and is arranged so that the temperature may be maintained constant at 12 to 16 ; this end is often attained by the use of semi-underground cellars, which should, however, be well ventilated. On the impermeable floor (of cement or asphalte), the barley is spread out in a layer 50 to 60 cm. deep, and on the second day the mass is moved with wooden shovels so as to reduce the depth to 30 to 35 cm., this being further reduced to 15 cm. on the third day. Every eight or ten hours the grain is turned, the floor being kept well ventilated. The temperature gradually rises, but should not be allowed to exceed 20 ; if necessary it may be moderated by turning more often and thinning out the barley. After the second day the radicles begin to sprout and later the plumule. In eight to ten days the rootlets become twice or three times as long as the corn and the transformation of nitrogenous material into diastase is at its maximum (Fig. 156 shows the various stages in the ger- mination of barley). The germination should then be interrupted so as not . to lose any part of the diastase formed, the green malt then containing about 40 per cent, of moisture. A floor of 20 sq. metres is sufficient for only 1000 litres of steeped grain. If the piece dries too much, it is moistened by sprinkling with water. In order to prevent mould-growth when the floor is free, it, and also the walls, are washed with 1 per cent, calcium bisulphite solution, the floors being then well dried by ventilation. 1 The germination is now sometimes carried out on the pneumatic system, use being made of the Galland apparatus (Figs. 157 and 158), which consists of a double sheet-iron drum, T, rotated by means of the wheels, b (two rotations, each occupying forty minutes, every six to eight hours). The inner drum is perforated and is filled to the extent of four- fifths with barley from the steeping tank, W ; along the axis of the cylinder passes a pipe which is also perforated. Air sucked in by a fan, Z, is moistened in A by means of pulverised water, and from L passes into the jacket of the drum, then through the perforations and the 1 In Germany beer must be made from malted barley alone; in 1912 the German breweries used 1,300,000 tons of barley (almost exclusively two-rowed), of which a small part only was imported from Austria. Barley contains 60 to 70 per cent, of starch, 0-5 to 2 per cent, of saccharose, 2 to 3 per cent, of fat, and 8 to 14 per cent, of proteins. At least 95 per cent, of the barley corns should germinate (germinative capacity), the germinative power, i.e., the rapidity of germination, also being of importance; with a good barley, not less than 95 per cent, of the corns should germinate within three days. A barley with a germinative capacity of 85 to 90 per cent., and a similar germinative power is preferable to one having a germinative capacity of 100 per cent, and a germinative power of only 70 per cent. In general barley rich in proteins is poor in starch and hence yields a malt of low extract, whereas protein-poor barley is rich in starch and gives a malt yielding a high extract. During mashing the starch passes almost completely into solution, whilst only about one-third of the protein substances is dissolved, the remaining two-thirds being found in the grains. Barley contains a diastase capable of saccharifying dissolved starch, but incapable of dissolving starch ; the latter end is attained by means of the diastase formed during the germination of the barley. FIG. 156. GROWING OF MALT 197 grain to the central pipe, TO. Thence it proceeds to 8, and so through the fan Z to the shaft ; a thermometer here shows the temperature of the air, and if this becomes too high the speed of the fan is increased. If 100 kilos of barley is taken and the air enters at 12 and issues at 20, 4500 cu. metres of air is required per hour; if the air is to leave at 16, 10,000 cu. metres per hour is necessary. The germination lasts eight to nine days. FIG. 157. FIG. 158. To stop the germination, a current of dry air, heated to 22 to 25 or mixed with gas rich in CO 2 (to diminish the supply of oxygen), is supplied; in a short time the moisture content of the grain is reduced from 40 per cent, to 20 to 25 per cent. For a malting to give continuously 2000 to 5000 kilos per day, three to four steeping-tanks are used, these feeding six to eight Galland drums arranged in batteries (Fig. 159) ; 6 to 10 horse-power is required for turning the drums, driving the fans, etc. FIG. 159. The water necessary for steeping amounts to about 10 to 12 times the weight of the barley, rather less being required to moisten the air for pneumatic malting. The steep- water may hence be used again for the latter purpose if at any time the water-supply is scarce. Another system of malting, used especially in France, is that of Saladin (shown in perspective in Fig. 160, while Fig. 161 shows a longitudinal section of one of the vessels, 198 ORGANIC CHEMISTRY and Fig. 162 a transverse section of the vessels). There is one vessel, made of concrete and fitted with a perforated false bottom of sheet-iron, for each day that the germination lasts (eight to nine days). These vessels, B, communicate under the false bottom with a channel containing a fan which draws moistened air through the mass of barley in the vessel (50 cm. deep). Above each vessel is a slow mechanical turner, A, with a number of screws which rotate in the barley as the turner passes along the vessel. The turner may be trans^ ported from one vessel to another and is put into operation twice a day at first (the tempera- ture of the barley being 12 to 14), then four times a day (at 15 to 18), and finally twice a day (at 18 to 15). In some maltings a saving is_effected by operating the fan only at FIG. 160. intervals when the temperature rises. Dry air, drawn along the channels, 8, is finally passed through the malt. The advantages of the various mechanical processes over the old system of malting are that they may be worked continuously and at any season of the year, while they occupy less space, allow of efficient regulation of temperature, economise labour and general expenses and diminish the percentage of waste. (4) KILNING OF MALT. The germinated barley is too moist to keep sound, and as breweries require large stocks of malt this must be dry and capable of being kept. If the moisture is reduced to 6 per cent, by air alone the germination process is stopped, and on subsequently raising the temperature to 60 a slight diastatic saccharification occurs, 1 I p p~ [7r^)A (Sri *-,0^ \ "1 i 1 1 : QDnTJOOGTinDDCtinn 3DCDDDDOOD ' L r 1 ' 1 i | c L i 1 s- FIG. 161. FIG. 162. this being greater in amount if the moisture is kept at 12 to 15 per cent. ; beyond 70 the diastase is destroyed and certain substances formed which give good flavour, aroma and fullness of_taste to the beer and at the same time furnish food for the yeast. When the temperature exceeds 100 part"of the maltose is caramelised for the making of dark beers and a considerable amount of nitrogenous substances, which would cause the beer to keep badly, rendered insoluble. In order not to destroy too much of the diastase and to make malt suitable for pale beers the drying must first be conducted with only slightly warm air. When the proportion of moisture has reached 5 to 6 per cent, the diastase is able to withstand a temperature of 60 to 70 without losing much of its activity, whilst if the malt is heated when it contains too much moisture (15 to 20 per cent.) the diastase is rapidly destroyed. The drying is carried out in a current of warm air (or of air mixed with the hot gases from a coke or KILNING OF MALT 199 anthracite fire), which passes through the green malt placed in layers 15 to 20 cm. deep on wire or tile floors, often arranged one above the other. Above the upper floor is a chimney, which increases and facilitates the draught started by suitable fans. The air is heated by passing directly over a fire or through batteries of tubes heated in the usual way. During the drying the malt is turned by a suitable mechanical device, at first every two hours and later on continuously. The temperature of the air gradually rises, during the course of eighty-four to ninety hours, by 30 to 35 (during the first few hours germination still pro- ceeds feebly, causing increase in the diastase), and ends at 100 to 110 (for dark beers). Drying is usually effected in less than forty-eight hours, and it is only beyond 80 that the diastase partially loses its saccharifying properties (at 90 it loses 50 per cent, and at 100 85 per cent. ) ; this loss is, however, an advantage, since a too highly diastatic malt leads to excessive saccharification and hence to increased attenuation in the subsequent fermentation, so that the beer tastes less full. The peptases also are destroyed beyond 90, so that the nitrogenous substances are dissolved to a less extent and the beer hence keeps better. Fig. 163 shows diagrammatically a section of a two- floor malt-kiln in which the air is heated in the tubing, t, surrounding the ducts carrying the hot fumes from the coal burning on the grate, F. The hot air then traverses the malt on the floors, B and C, and issues from the chimney, D, the turning apparatus, a, being kept in motion mean- while. To obtain 100 kilos of dry malt in twenty-four hours (maximum temperature 90 to 100) 20 kilos of coal are required. For making dark beers of the Munich type part of the kilned malt is further roasted at about 200 in suitable rotating iron cylinders heated by direct fire ; this treatment leads to the formation of caramel, which colours the beer, the malt being then called coloured malt. The temperatures on the malting-floors and kiln are registered by automatic devices which construct diagrams showing the temperature at any particular moment. Nowadays malt for pale beers is sometimes heated only to 25 to 30. The kilned malt leaves the kiln with 2 to 5 per cent, of moisture, and is then cooled and stored in silos or large bins. A malt kept for only one or two months is to be preferred to an older one. 1 1 The commercial value of a malt is determined largely by its yield of extract, which is measuied as follows : 45 grams of ground malt are placed in a tared flask with 200 c.c. of water, the temperature being kept at exactly 45 for half an hour and then raised 1 per minute up to 70, this temperature being maintained until the liquid no longer gives a blue colour with iodine; the time required at 70 to reach this point is noted (saccharification test}. The mass is then cooled and water added to bring its total weight up to 450 grams; after mixing and filtering through a dry filter, the density of the liquid is determined at 15 and by Windisch's or Schulze's tables the corresponding quantity of extract deduced. The latter may also be obtained from Balling's tables (see below), note being taken that they yield low values, the deficit being 0-08 gram per cent, for specific gravities up to 1-01 ; 0-345 for specific gravities up to 1-05; 0-48 for specific gravities up to 1-06; and 0-4 for specific gravities up to 1-08. If the maltose is to be determined directly, 10 grams of the filtered saccharine liquid (corresponding with 1 gram malt) are diluted to 100 c.c., various quantities of this liquid being then titrated with Fehling's solution, 1 c.c. of which corresponds with 0-0075 gram of maltose. C. Lintner (1886-1908) has modified the Kjeldahl method for determining the diavtatic power of malt as follows : 25 grams of the ground malt are extracted for 6 hours with 500 c.c. of water at the ordinary temperature, the mixture then being filtered; 2 c.c. (for pale malts) or 8 c.c. (for dark malts) of the filtrate is added to 100 c.c. of 2 per cent, soluble starch solution and the N mixture left for exactly half an hour, at the end of which time 10 c.c. of .^ caustic soda solution is added. Into a number of test-tubes, each containing 5 c.c. of Fehling's solution, are intro- duced varying quantities of the saccharified starch solution (e. g., from 1 to 6 c.c.); the tubes are next immersed for ten minutes in a boiling water-bath and then taken out, and the pre- cipitated cuprous oxide allowed to settle ; it can then be seen in which of the tubes the Fehling's solution is just completely reduced and in which it is just not reduced. A more exact result FJG. 163. 200 ORGANIC CHEMISTRY Malt kilned with fumes direct from a coal fire communicates to the beer a certain flavour from the smoke. Also, when coal is employed which contains arsenic, the latter becomes deposited on the malt and hence finds its way into the beer. Arsenic may also be present in the glucose often used in brewing ; in this case it is introduced by the employment of arsenical sulphuric acid in the manufacture of the glucose from starch. (5) CLEANING AND GRINDING. Before the malt is mashed it is freed from dust and rootlets by means of rotating drums of metal gauze (a kind of sieve) furnished with fans. It is then ground, but not too finely, the husks being kept whole as far as possible, since they serve in the subsequent operations as filtering material ; if the malt is ground too fine it cannot be exhausted, as the liquid will not drain off. A suitable form of mill is the Excelsior Mill, made by Messrs. Krupp (Figs. 164 and 165). The shaft, g, fitted with fast and loose pulleys, s and t, may be shifted from right to left or vice versa through the stuffing-boxes, m, by means of the lever, d. One toothed disc, a, is fixed, whilst the other, b, rotates with the axis, g, and is so adjusted that the teeth pass through the tooth spaces of the other disc. The malt from the hopper, /, falls between the two discs, where it is may be obtained by using quantities of the saccharified starch solution intermediate to those corresponding with these two tubes. When 0-1 c.c. of the cold water malt extract, acting for one hour on 10 c.c. of 2 per cent, soluble starch solution, forms just sufficient maltose to reduce 6 c.c. of Fehling's solution, the malt is said to have the diastatic power 100 ; if 0-2 c.c. of the malt extract is required, the diastatic power is taken as 50, and so on. BALLING'S TABLE Sp. gr. at 17-5 Degrees Balling or grams of saccharose Sp. gr. at 17'5 Degrees Balling or grams of saccharose Sp. gr. at 17-5 Degrees Balling or grams of saccharose Sp. gr. at 17-5 Degrees Balling or grams of saccharose per 100 grams liquid per 100 grams liquid per 100 grams liquid per 100 grains liquid 1-0010 0-250 1-0210 5-250 1-0410 10-142 1-0610 14-904 1-0020 0-500 1-0220 5-500 1-0420 10-381 1-0620 15-139 1-0030 0-750 1-0230 5-575 1-0430 10-619 1-0630 15-371 1-0040 1-000 1-0240 6-000 1-0440 10-857 1-0640 15-604 1-0050 1-250 1-0250 6-244 1-0450 11-095 1-0650 15-837 1-0060 1-500 1-0260 6-488 1-0460 11-333 1-0660 16-070 1-0070 1-750 1-0270 6-731 1-0470 11-571 1-0670 16-302 1-0080 2-000 1-0280 6-975 1-0480 11-809 1-0680 16-534* 1-0090 2-250 1-0290 7-219 1-0490 12-047 1-0690 16-767 1-0100 2-500 1-0300 7-463 1-0500 12-285 1-0700 17-000 1-0110 2-750 1-0310 7-706 1-0510 12-523 1-0710 17-227 1-0120 3-000 1-0320 7-950 1-0520 12-761 1-0720 17-454 1-0130 3-250 1-0330 8-195 1-0530 13-000 1-0730 17-681 1-0140 3-500 1-0340 8-438 1-0540 13-238 1-0740 17-909 1-0150 3-750 1-0350 8-681 1-0550 13-476 1-0750 18-136 1-0160 4-000 1-0360 8-925 1-0560 13-714 1-0760 18-363 1-0170 4-250 1-0370 9-170 1-0570 13-952 1-0770 18-590 1-0180 4-500 1-0380 9-413 1-0580 14-190 1-0780 18-818 1-0190 4-750 1-0390 9-657 1-0590 14-428 1-0790 19-045 1-0200 5-000 1-0400 9-901 1-0600 14-666 1-0800 19-272 Correction of Degrees Balling for Various Temperatures Determin- ation made at tsmpera- ture of Correction of degrees Balling Determina- tion made at tempera- ture of Correction of degrees Balling XSSe" SssS attempera- &. Determina- tion made at tempera- ture of Correction of degrees Balling f Deg. Deg. Deg. Deg. 4 -0-43 11 -0-22 17-5 24 + 0-27 5 -0-40 12 -0-19 18 + 0-02 25 + 0-32 6 -0-37 13 -0-16 19 +0-05 26 4 0-37 7 -0-34 14 -0-13 20 + 0-09 27 + 0-42 8 -0-31 15 -0-10 21 +0-13 28 + 0-48 9 -0-28 16 -0-06 22 +0-17 29 + 0-54 10 -0-25 17 -0-02 23 + 0-22 30 + 0-60 MASHING 201 ground, the ground malt (grist) being discharged at n. For the sake of economy the discs are toothed on both faces, so that when one face is worn the other may be used. The total loss in weight suffered by the barley during steeping, germination, kilning, cleaning, and grinding amounts to about 20 per cent. (6) MASHING. This consists in subjecting the ground malt to the action of warm water so that the diastase may act on the starch and convert it into soluble products. The temperature at which the maximum extract is obtained is about 65, whilst at 55 the starch is only very slightly attacked by diastase, and above 70 diastase loses its saccharifying pro- perties very largely and the wort niters through the grains (husks; see later) with difficulty this effect is aggravated by coagulation of part of the proteins. The quantity and quality of the water have an influence on the mashing, the presence of calcium sulphate facilitating the for- mation of maltose and maltodextrins and increasing the amount of nitro- genous substances dissolved. From 1 ton of malt 20 to 30 hectolitres of beer are made. There are two systems of mashing : the infusion method (at 65 to F IG . 164. 72), used only in top-fermentation breweries, and the decoction system, used for bottom-fermentation and sometimes for top-fermentation beers, and with highly diastatic malt or when unmalted barley is used with the malt. (I) The infusion process, used largely in England and Scotland, less in France and still less in Germany, is usually carried out in one of two ways : (i) Rising infusion, where the malt is first mixed to a paste with 10 per cent, of cold water and then with hot water "in the ratio of two parts of water to one part of malt, so that a temperature of 40 is FIG. 165. attained. To raise the temperature of 1 kilo of malt (which has a specific heat of about 0-5) from 20 to 40 requires 10 Calories, which can be supplied by 2 litres of water at 45, the latter falling to 40 on losing 10 Calories; owing, however, to unavoidable loss of heat, water at 48 to 50 should be used. This mixing is done in a circular mash-tun of metal or wood, furnished with a perforated false bottom several centimetres above the true bottom, in which are fitted the pipes supplying the hot water (Fig. 166). The mashing and subsequent mixing are effected by efficient mechanical stirrers or rakes. 202 ORGANIC CHEMISTRY As soon as the mash has reached the temperature of 40 water at 80 is gradually introduced, the temperature being raised to 63 to 65 in half an hour. It is next mixed for sixty to seventy minutes, the liquid being then discharged by opening the taps under the false bottom so that the liquid passes through the grains and is conducted to the copper. The residue in the tun is mixed for fifteen minutes with water at 75, the liquid being run off and the grains finally washed with water at 85, all these extracts passing to the copper. In this way almost complete saccharification is attained and the subsequent fermentation produces considerable attenuation. If a less attenuation is desired, either a higher temperature (72 to 73) is used in place of 65, or high-dried malt is used. (ii) Descending infusion, which is rarely used, consists in bringing the mass directly to a temperature of 65 to 70 with very hot water and then allowing it to fall slowly to 35 to 40. Neither of these methods admits of the use of rice or maize, the starch of which is attacked by diastase only after the starch has been heated with water to 80 to 85. Hence with such material the decoction process is used. FIG. 167. (II) Decoction Process. This is largely used in North Germany, Austria, and Belgium, and allows of the use of unmalted barley, rice, maize, wheat, etc. The malt grist is first mixed to a paste with cold water so as to dissolve the diastase, this being carried out in a metal vessel without a false bottom ; by the addition of small quantities of boiling water the temperature of the mass is raised gradually to 35. From one-third to one-half of the turbid wort (Dickmaische) is transferred to a double-bottomed copper heated with steam. In many cases coppers with direct-fire heat are used, these being furnished with chains which scrape on the bottom and so prevent caramelisation of the mass which settles (Fig. 167 shows a complete decoction or infusion plant). The wort transferred to the copper is boiled for twenty to forty minutes and is then returned to the original tun, where it raises the temperature to about 55. Another one-third or one- half is similarly removed, boiled, and returned, the temperature being thus raised to 65 ; the saccharification has then reached a maximum and the mash become thinner. The complete disappearance of starch is controlled by the reaction with iodine. About one-half of the wort is again removed, boiled, and returned, the temperature being thus raised to 75. During all these operations continual stirring is maintained. The greater the number of decoctions made the greater will be the density of the wort and the darker the beer. The turbid wort is either allowed to deposit in tuns with false bottoms, as shown in Fig. BOILINGOFTHEWORT 203 166, or passed through filter-presses (see Sugar Industry) to clarify it, the grains remaining in the form of cakes being well washed. 1 When considerable quantities of other cereals are to be used with the malt use is made of a Henze pressure apparatus, as described under Distilling (Fig. 106, p. 142). The wort thus obtained is boiled with a certain quantity of hops until a certain degree of concentration has been effected. This boiling finally destroys the diastase, intensifies the colour of the wort and aerates it, and oxidises various substances producing acid bodies ; it completely sterilises the liquid, which is also clarified owing to the precipitation of nitro- genous substances, partly by the tannin of the hops. The decoction of the hops is carried out in a separate vessel, the boiling liquid being continually circulated until the hops are exhausted. The decoction is then added to the boiling wort, principally towards the end of the operation ; if added earlier the hop extract loses some of its aroma. Direct addition of the hops to the copper is still practised, although the method is not a very rational one ; it is better to pass the boiling wort from time to time into a separate vessel containing the hops and then back to the copper, this procedure being repeated until the hops are exhausted. In general, 400 to 500 grams of hops are used per hectolitre of beer, or 1-2 to 2'5 kilos for every cwt. of malt mashed. More hops are usually employed for beers to. be kept for some time (lager beer, stock ale) than for draught beer, and more for beers of the Pilsen type than for those of the Munich type. The lupulin powder contained in the hop gives up resins and essential oils, while the leaves give tannin and the stalks somewhat bitter substances ; the whole gives the bitter taste and aroma of the beer, and causes the latter to keep better. A temperature of 75 (Pasteur) is sufficient to sterilise a hopped beer, since the resins have a marked antiseptic action. The boiling of the wort is carried out in copper vessels (see Fig. 167, a) heated by direct fire or by indirect steam (passed through coils or through the double bottom of the copper), the boiling being continued for four to six hours with dilute worts (infusion), and only one and a half to two hours with the more concentrated decoction worts ; as a rule boiling is continued until the density reaches a certain value for the particular kind of beer to be made (see later). The temperature during boiling should be gradually raised and registered. In many modern breweries there are automatic registering thermometers which show the whole course of these operations. When the boiling is finished the wort is allowed to stand for a time, and the Inland Revenue officials then generally make their first measurements (they calculate that 1 kilo of dry malt should give 25 litres of wort with a density of 1 Balling, 5 litres at 5, etc., an allowance being made of 10 per cent.). The copper is then dis- charged, the hops being strained off, and the. wort pumped to the cooler, which is usually at the top of the building. These coolers are large shallow vessels of iron (or copper or wood ) in which the coagulated proteins are deposited ; the temperature here is not allowed to fall below 55 to 60, otherwise contamination with harmful organisms (butyric, lactic, etc.) might occur. In Italy the tax on the manufacture of beer is calculated from the volume, temperature, and specific gravity of the wort in the cooler (see'later). In the cooler, part of the water evaporates, this being as much as 4 per cent, in the summer. The wort is next cooled rapidly by suitable refrigerators to 2 to 3 (for bottom fermentation) or 12 to 15 (for top fermentation). One form of refrigerator which is much used consists of a number of superposed, communicating horizontal tubes (Fig. 168). In the tubes of the upper half water circulates, and in those of the second half brine at a temperature of 6 or 8 from a refrigerating machine (see Vol. I., p. 260). The wort flows down in a thin skin over the outside of the tubes, meanwhile dissolving an appreciable quantity of air. The cooled and aerated wort flows down to the fermenting vessels placed in cool rooms; for bottom fermentation these are cooled to about by pipes conveying cold 1 The grains are composed of the whole of the husks of the malt, coagulated proteins, pentosans, fat, maltose, and dextrin. They serve as excellent cattle-food, biit if not consumed in the course of 24 hours, they undergo change ; they may, however, be placed in silos or dried in a suitable apparatus (see Fig. 151, p. 183). Wet grains contain 70 to 80 per cent, of water, 4 to 6 per cent, of protein, 1 to 3 per cent, of fat, 8 to 14 per cent, of extractive substances, 1 to 3 per cent, of ash, and 3 to 9 per cent, of cellulose. Dried grains contain 6 to 18 per cent, of water, 17 to 26 per cent, of protein, 4 to 9 per cent, of fat, 35 to 55 per cent, of extractive substances, 3 to 12 per cent, of ash, and 9 to 20 per cent, of cellulose ; they have a brown colour, a pleasing odour of new bread, and a sweet taste ; they make a good fodder to follow wheat or oat bran. 204 ORGANIC CHEMISTRY brine. The wort from the coolers is turbid and should be filtered through conical cloth bags or filter-presses. In some modern breweries the coolers are omitted in order to avoid any possible contamination (which is, however, difficult with hopped wort at 60) and the wort is passed direct from the copper to the closed refrigerator and the filter-press, aeration being afterwards effected with air filtered through cotton-wool. The refrigerators consume considerable quantities of water, and where this is scarce the warm water from the refrigerators is cooled by means of pulverisers or by causing it to flow down over twigs, the evaporation thus caused often lowering the temperature below that of the air (see section on Sugar). The boiling of the wort has hence effected a concentration, the preparation of a sterile (aseptic) liquid, and the extraction of the useful principle of the hop, the tannin of which has partially precipitated the proteins. If pale beer is to be brewed the wort may, if necessary, be clarified during the boiling by the addition of a little tannin. During the cooling on the coolers the wort takes up the oxygen necessary for the oxidation of the resins, for clarifying it and, more especially, for aiding the development and multiplica- tion of the yeast during the initial stages of the fermentation. Contact of the wort with tin, e. g., tinned vessels, is to be avoided, as turbidity of the beer may be caused thereby, especially if the wort is acid or rich in carbon dioxide. FERMENTATION. From the density (degrees Balling) or the dry extract of the wort, the extract yielded by the materials may be deduced, and, under favourable conditions, the dry extract amounts to about 70 per cent, of the weight of the malt, whilst with bad working it may be as low as 45 per cent. When ready for fermentation the wort contains mainly maltose, malto- dextrinSj dextrins, a little saccharose, glucose, and levulose, besides nitrogenous substances partially peptonised and transformed into amino-acids; also lactic acid and potassium phosphates. Fermentation with yeast converts the carbohydrates more or less completely into alcohol and carbon dioxide. 1 1 In addition to what has been said on pp. 133 and 146 on ferments and yeasts in general, the following is of interest, especially to the brewing industry : All yeasts which attack only saccharose, maltose, glucose, and levulose, giving alcohol and carbon dioxide, are feebly attenuating yeasts of the so-called Saaz type (e. g., the beer-yeasts of Liege, which yield fairly full-tasting sweet beers containing little alcohol). Other yeasts are also capable of fermenting the combined maltose of maltodextrins by means of a special enzyme studied by Delbriick, maltodextrinase ; these yeasts give the maximum attentuation and form the so-called Frohberg type, producing alcoholic, highly attentuated beers even from weak worts. Between these types Saaz and Frohberg there exist intermediate ones giving in 4 days at 25 to 27, well-defined attentuations in a normal wort. Certain other yeasts are capable of fermenting dextrin combined as maltodextrins, since they contain an enzyme which Delbriick has termed dextrina^e. Such is the Schizosaccharomyces Pombe, separated from the millet beer of the Egyptians. These yeasts constitute the so-called Logos type. Wild yeasts are all strongly attenuating and may produce turbidity in finished, slightly fermented beers, which they referment. The yeasts intermediate to the Saaz and Frohberg types, and also Frohberg yeasts themselves, are especially active in the secondary fermentation; they increase the apparent fullness of the beer, even when this is light, and maintain a continuous and desirable evolution of carbon dioxide by slowly fermenting the malto- dextrins and even dextrins. In order to grow and multiply, yeasts require, in addition to carbohydrates and free oxygen, nitrogenous substances, but they cannot make use of nitrates, or ammonium salts, or even the true proteins; they can, however, utilise the decomposition products of the latter, namely, the ammo-acid, 1 ! (such as asparagine) produced by the proteolytic enzymes secreted by healthy yeasts. They require also mineral substances, e. g., calcium and potassium phosphates. The oxygen of the air is, as has been said, indispensable to the development and multiplication FIG. 168. FERMENTATION 205 The concentration of the wort most favourable to the multiplication of yeast is 15 Balling (corresponding with a specific gravity of 1'OG). 1 A too dilute wort or one prepared with an excessive proportion of non-germinated grain has not sufficient assimilable nitrogenous food (amino-acids), and this is remedied by the addition of zymogen, which is a commercial product. During the period when the yeast develops (first stage of the fermentation) little alcohol and much carbon dioxide are produced. Two distinct methods of fermentation are in use : top fermentation, used generally in Great Britain, Belgium, and Holland, and largely in France, and also, at one time, exclusively in Italy ; and bottom fermentation, usually employed in Germany, Austria, and Denmark, and in general use in countries where beers of the Munich and Pilsen types are made. In hot countries it is easier to regulate bottom fermentation (by refrigeration) than top fermentation, since in summer the temperature of the air is often high enough to have an injurious effect on top fermentation. Hence, as a refrigerating plant is necessary, the bottom fermentation system is preferable. The difference between bottom and top yeasts is that the latter are covered with viscous, mucilaginous substances and readily stick together and carry bubbles of carbon dioxide developed in the wort to the surface and so produce a rapid fermentation; the former, however, fall to the bottom of the fer- menting vessel, and even under the microscope are not found in large masses. Top yeasts develop well only at temperatures above 12 best at about 24 and effect complete fermentation in four to six days, whilst the bottom yeasts develop below 10 and, after the vigorous primary fermentation at 6 to 8 (eight to ten days for Munich beer, ten to fourteen for Vienna beer, and twelve to sixteen for Pilsen beer), continue the maturation of the beer for two or three months by a secondary fermentation at a low temperature (0 to 2) ; this procedure gives beers of less attenuation which can be produced or con- sumed even in summer (lager beer). Top-fermentation beers are almost always more highly attenuated, are consumed at once (draught beer), and are made more especially in the cold weather ; they can, however, be kept, and in some cases stock beers are made on this system. The advantages and disadvantages of the two processes are as follow : Top fermentation does not require costly refrigerating plant, and hence lends itself to the construction of small breweries; further, the beer can be sold immediately, and the capital, although small, thus frequently renewed each year. The control and successful working of top fermentation are, however, more difficult, owing to ready contamination with numerous harmful bacteria which find at 15 to 20 the most favourable conditions for their development, especially in the summer; in bottom-fermentation beers only yeasts can develop at to 2. With top fermentation, in which at first yeasts of the Saaz type and those intermediate to the Saaz and Frohberg types predominate, there develop later bacteria and also Frohberg yeasts (especially during the secondary fermentation), and both of these render difficult the preparation of a clear beer which does not become turbid after fermentation ; on the other hand, a bright beer is easily and naturally obtained by bottom fermentation. In summer then, unless an abundant supply of cold water and also cool cellars are available, and rigorous precautions and disinfection are resorted to, it is very difficult to prepare top fermentation beer, whilst the low temperature required for bottom fermentation can be attained at any season of the year by refrigerating plant. Bottom fermentation gives of yeast, and well-aerated worts facilitate the multiplication during the first few days, when only C0 2 and H 2 are produced; when, however, the supply of free oxygen diminishes or ceases, the yeast produces more especially alcohol and carbon dioxide. There are also saccharomyces which are solely aerobic and form membranes on the surface of the wort, producing only carbon dioxide and water and destroying the alcohol produced by other yeasts. 1 The strengths of the worts for beers of different types are : 9 to 10 Balling for light beers ; 12 to 13 for draught beers (Schenkbier); 15 to 20 for double beers (Bock or Salvator beer); and up to 25 for table beers. 206 ORGANIC CHEMISTRY beers of a more constant type, since the mother-yeast from successive fermentations does not become contaminated so easily as, and hence requires renewal less frequently than, with top fermentation. 1 When a large amount of yeast is added to a wort the fermentation is initiated and completed more rapidly; with small quantities the same result is obtained, but after a longer time, so that there is more danger of contamination. Usually 250 to 300 grams of pressed yeast is used per hectolitre of wort rather more for strong worts. Especially with top, but also with bottom fermentation, it is most important that all instruments, vessels, and rooms should be kept clean and disinfected. For this purpose, boiling water is used and also dilute solutions of hydrofluoric acid, ammonium fluoride, ammonium fluosilicate, calcium bisulphite, or calcium hypochlorite. In all cases, however, great care must be taken to remove the disinfectant completely with abundant supplies of hot water, in order that the yeast may not be injured. Chloride of lime is eliminated by rinsing first with bisulphite solution and then with hot water. Even traces of bisulphite (sometimes added during mashing to prevent the action of lactic ferments) must be com- pletely eliminated, otherwise, during the alcoholic fermentation, which is a process of reduction, they may yield hydrogen sulphide and so give a bad taste and odour to the beer. (Bacteria capable of producing hydrogen sulphide sometimes develop in beer.) The yield and quality of the beer may be improved by adding a pure culture of lactic acid bacteria (prefer- ably Bacillus Delbriicki, see p. 152) at the time of pitching (i. e., addition of the yeast). Whatever system of fermentation is used, it is always divided into two phases : the primary or vigorous, and the secondary. The primary fermen- tation begins twelve or twenty-four hours after pitching, when the yeast has grown to some extent at the expense of the dissolved oxygen, and continues for three or four days in the case of top fermentation or for ten to twelve days with bottom fermenta- tion ; considerable quantities of carbon FIG. 169. dioxide are developed, these forming a dense, white, frothy head on which may be seen brownish spots of hop resin or agglutinated bacteria. In top fermentation, this first head is removed, the next darker one being collected for pitching purposes. In the bottom fermentation system, and in large modern breweries in general, in order that the yeast may be kept as pure as possible, the pitching is carried out in the manner described on p. 152 for distilleries. 1 With top fermentation, the type and taste of the beer are determined by the united activity of a number of different yeasts and bacteria which are present in given equilibrated proportions, these becoming modified as contamination increases. When the yeast is renewed, the pure yeast naturally gives a different taste to the beer, and this inconvenience cannot be avoided by preparing a mixture of yeasts and bacteria similar to that normally present in the partially contaminated top fermentation. New pure yeasts are less resistant to contaminating sur- roundings than old ones are. Attempts are made to-day to keep the fermentation pure as long as possible by the use of good hops, the resins of which exert an agglutinating and paralysing action on the bacteria, so that these can be removed from the tun with the first scum forming on the surface of the fermenting wort ; the purer yeast of succeeding heads is then collected for pitching subsequent worts. When the collection of the yeasts is delayed, that of the Frohberg type increases. With the object of maintaining the cultures naturally pure and constant, Effront has proposed the addition of abidic acid a component of lupulin and of colophony to agglutinate and render innocuous the bacteria in fermenting worts (see also p. 167). Thus, after elimination of the ATTENUATION OF BEER 207 During the primary fermentation, a considerable quantity of heat is evolved, and to prevent the temperature exceeding 22 to 25 in top or 7 to 8 in bottom fermentation, attemperating coils, through which cold water (top) of brine (bottom) passes, are used to cool the fermenting wort (F, Fig. 169). Each fermenting vat is provided with a slate, etc., on which are noted, each day, the temperature and the specific gravity of the wort; the attenuation should reach 58 to 62 per cent, in the primary fermentation and 70 to 75 per cent, in the secondary fermentation, in order that the beers may keep in the warmer rooms of the consumers. 1 When the vigorous fermentation is ended, the head falls and almost disappears, carrying to the bottom of the wort the suspended yeast ; in this way the secondary fermentation is started, this being allowed to proceed for fifteen to twenty days in the trade casks placed in cellars at 10 to 12 (for top fermentation); the beer is then cleared, filtered, and sold. In bottom fermentation, on the other hand, the secondary fermentation is completed in large tuns pitched inside (see later) ; these are not quite filled bacteria with the first scums, purer yeast can be collected and washed with pure water or, better/ with water containing a little hydrofluoric acid or ammonium fluoride (5 to 10 grams per hecto- litre), which attacks the bacteria, but not the yeast. It cannot, however, be denied that, in general, washing produces considerable weakening of yeast, which may be reinvigorated by preliminary growth in sterilised, unhopped wort. 1 Determination of the Attenuation and of the Apparent and Real Extracts of Beer. The apparent extract is deduced from the density of the well-shaken (to remove C0 2 ) beer and the corresponding number of degrees Balling. The real extract is deduced from the specific gravity (and Balling's tables) of the beer freed from alcohol by evaporating it to one-third of its volume and making the residue up to the original volume. The original extract of the wort may be calcu- lated with moderate accuracy by adding to the real extract the amount of alcohol (determined as in wine, p. 174) multiplied by 1-92. The degree of real attenuation (A) is referred to 1 hectolitre of wort and indicates how many parts per 100 of the extract of the wort are transformed into alcohol and carbon dioxide ; it is obtained by means of the following formula : A = ^JL* x 100, where D represents the percentage of extract in the wort and d the percentage of real extract of the beer. In practice, the percentage of extract is sometimes replaced by the degrees Balling, but the results thus obtained are not very exact. If we make D = 15 Balling and d 5, the real attenuation becomes : ig 5 A = 15 X 100 = 66-66 per cent. It cannot, however, be denied that Balling degrees refer to kilos of sugar or of extract in 100 kilos of solution, so that a wort showing 15 Balling (sp. gr. 1-0615) contains 15 kilos of extract per 100 kilos of wort, or 15-922 kilos (i. e., 15 X 1-0615) in a hectolitre of wort; the beer, free from alcohol, showing 5 Balling, has a sp. gr. 1-020, and 1 hectolitre contains 5-100 kilos of extract, so that 10-822 kilos of extract has been fermented and the true attenuation is 10-822 15^922 x 10 = 6 7-6 per cent. Practical brewers find it more convenient, in considering the degree of attenuation of a wort, to calculate the degree of apparent attenuation (A') from the apparent extract of the beer d by means of the formula, A' j^ X 100; for example, a wort of 16 Balling has the sp. gr. 1-0658 and 1 hectolitre contains 17-05 kilos of extract, while the beer, with 7 Balling of apparent extract, has the sp. gr. 1-0281, corresponding with 7-20 kilos of extract per hectolitre The 17-05 7-20 apparent attenuation is hence 17.05 X 100 = 57-9 per cent. The attenuation may be deduced in a rather less exact manner if instead of degrees Balling is used degrees of the legal densimeter (i. e., the figures in the second decimal place of the specific gravity, a value of 1-063 for the latter thus corresponding with 6-3 on the legal densimeter). In the above example, 16 Balling corresponds with sp. gr. 1-0658, hence with 6-58 on the densi- meter; similarly, 7 Balling corresponds with 2-81 densimeter degrees. Hence the apparent attenuation is given by : g.gg 2-81 A' = g^g X 100 = 57-3 per cent., which differs little from the value calculated above from the degrees Balling, and is sufficiently exact for practical purposes. Hence, both for real and apparent attenuation, Balling's tables may be dispensed with, it being sufficient to determine the specific gravity. It should be noted that the legal density expresses the weight of wort contained in the volume occupied by 1 kilo of water measured at 17-5. 208 ORGANIC CHEMISTRY and are kept for one to three months in cellars maintained continually at to 2, where the beer acquires the desired attentuation and its characteristic flavour. The yeast which is deposited in the fermenting vessels may be collected, pressed (p. 149) and sold to bakers or small brewers. In some breweries the carbon dioxide is now drawn off from the fermenting vats, which are fitted with covers, by pumps and, after being passed through potassium permanganate solution to purify it, the gas is then liquefied (see Vol. I., p. 480) ; it may be either utilised in the brewery itself or sold. The fermenting vessels and the storage casks are constructed of oak or pitch-pine. The use of glass vats has been proposed, as these retain the pure flavour of the beer ; such a vat to hold 42 hectolitres cost about 40 before the war. The inner walls of the vats are sometimes coated with shellac, paraffin wax or pitch. The cellars have walls and floor of concrete (1 metre higher than the first aqueous border of the subsoil) so that they may be washed when necessary ; the roof is of brickwork. These cellars are furnished with draughts to remove the carbon dioxide, with double doors (always on the north side) to prevent the entry of warm air from outside and with electric lighting so that windows, which dissipate the cold, may be avoided. The vats and casks are raised 50 to 60 cm. from the ground and are inclined slightly forward so that they may be emptied completely and easily cleaned from outside. Along the ceiling run pipes for the circulation of cold brine (bottom fermen- tation), which maintain a temperature below 6 in the fermentation cellars and one of to 2 in the lager cellars. Ten or fifteen days before the beer is run off from the lager vessels which have been several times filled up to avoid contact of the beer with the air and consequent danger from acetic ferments the bung-hole is tightly closed so as to supersaturate the beer under slight pressure with carbon dioxide, which is still developed more or less feebly according to the state of maturity of the beer. If a beer contains, say, 0-15 to 0-25 per cent, of CO 2 before the bung-hole is closed, it will subsequently contain 3 to 8 per cent., which considerably enhances the keeping properties. Nathan-Bolze Rapid Process (Ger. Pat. 135,539, 1900). This process was tested on an industrial scale in 1904 in the Fermentation Institute at Berlin, and gave satisfactory results. The application of the process has not, however, progressed as rapidly as was hoped for a process which allows of mature beer being prepared in eight to ten days, and works under conditions of sterilisation formerly attainable only in the laboratory or in the manufacture of spirit by the Amylo process (p. 155). The hot, sterile wort from the copper passes into a large, hermetically sealed, sterile vessel of enamelled iron (a special resistant enamel being employed) surrounded by an iron jacket through which water can be passed. These vessels have a capacity of 125 hectolitres or more and are called Hansena vessels. They are provided with powerful stirrers (Fig. 170), which keep the wort in con- tinual motion during the fermentation and thus accelerate the transformation of the maltose into alcohol and carbon dioxide. After the temperature of the wort has been lowered to 50 by passing water through the jacket and the diminution of pressure (owing to the condensation of steam) compen- sated by the admission of sterilised air, the latter (which has served also to aerate the wort) is replaced by carbon dioxide, the cooling being continued to 10. The pure yeast is then introduced through suitable pipes, the mass being slightly stirred .atr intervals of an hour. The gas developed is removed in order to hasten the fermentation, and is washed with permanganate, part of it then being compressed (see above). The carbon dioxide which is not compressed is utilised to remove the new beer flavour from beer already fermented in the Hansena vessels; the gas is passed in at the bottom (after removal of the yeast sediment) at the ordinary temperature, the mass being continually stirred mean- while, it being the carbon dioxide which effects the elimination from the beer of the volatile products to which the disagreeable taste and odour of new beer are due. The gas issues from the top of the vessel, passes to the purifiers and is again conducted through the beer, this process being continued for ten hours on end. The primary fermentation is finished is less than three days, and, after the passage of gas through the beer is completed, the temperature is lowered to and the beer saturated for twenty-four hours with slightly compressed carbon dioxide. The beer is finally filtered and delivered to the trade casks, where it keeps well even in the hot weather. Such a process, simple, rapid, and economical (the cost of the beer being diminished 209 by about 2s. 6d. per hectolitre), although it does not give a very delicate flavoured beer, should be suitable to hot countries and to small breweries. Several European breweries already work on these lines, and in 1907 one was constructed at Milan to employ a modification of the Nathan patent, consisting of a system intermediate to the old process with open fermenting vessels and that devised by Nathan; in this case enamelled iron vessels are used both for the primary fermentation and for the maturation (three to four weeks). These vessels cost about 1 for each hectolitre of capacity. If to the Nathan process is added the Meura system of mashing (1891) which has rendered the preparation of the wort as simple as possible by mashing the finely ground malt in a horizontal cylinder fitted with stirrers so that the mash may be rapidly cooled or heated and wort ready for passing to the filter-press and thence to the copper obtained in an hour it will be under- stood how the manufacture of ordinary beer has been shorn of those practical and theoretical difficulties long regarded as insurmountable. RACKING OF BEER. Beer is delivered to the con- sumer in bottles and in casks, and should be perfectly bright, cold, and supersaturated with carbon dioxide. To render it bright, the old method of clarification with gelatine or of nitration through bags has now been largely replaced by the use of the filter-press, which acts more rapidly and yields brilliant beer. The filtration is carried out in suitable frames through filter-cloths or, better, through finely divided cellulose (such as is used in paper- making) under a pressure of about half an atmosphere. These filter-presses are the same in principle as, and little different in form from, those which are used for the filtration of saccharine liquids and are described in the section on Sugar. (In England, beer in cask is clarified by mixing with the beer a small quantity of finings, which consist of isinglass " cut " or dissolved in an acid, such as tartaric, sulphurous, etc. ; these finings are gradually deposited on the bottom of the cask and carry down with them any suspended protein substances, hop-resins, etc.) Bottling is to-day carried out with all the care employed in the preparation of sparkling wines. A few lines may be devoted to the preparation of beer-casks, since the methods employed are peculiar to the brewing industry. In order that beer for retail consumption may retain its flavour, it must be kept cool and saturated with carbon dioxide up to the moment when it is drawn off into the customers' glasses, and for this purpose the use of liquid carbon dioxide with the arrangement shown in Vol. I., p. 483, is well adapted. RESIDING OR PITCHING OF CASKS. The keeping of beer sound depends largely on the cleanliness of its surroundings and of the vessels in which it is stored. Hence VOL. II. 14 210 ORGANIC CHEMISTRY the casks, returned empty from the customers, are first well scrubbed and washed both inside and outside with water under pressure by means of automatic plant (Fig. 171), and are then disinfected by means of formalin vapour or other antiseptics, or, better still, by pitching the internal surface with natural or artificial resins, which should be transparent and have a melting-point of about 50 ; in this process, which was first used in Bavaria, and is nowadays largely employed all over the Continent, aromatic resins are no longer used, mixtures of colophony with other residues from the distillation of turpentine being prepared by fusion and then rendered more elastic by the addition of resin oil (10 per cent. ). Use is sometimes made of a fused mixture containing 50 parts of Burgundy pitch, 20 of stearine, 10 of Japan wax, 10 of paraffin wax, 5 of Venetian turpentine, and 5 of gum dammar. To free the casks from the old resin and coat them again every time they are returned to the brewery, they are heated inside by means of air supplied from a Boots blower, B (Fig. 172) and heated by passing through red-hot coke, the hot air being forced into the casks through the tubes, D, for five minutes. The old pitch is discharged and the new pitch (about 200 to 250 grams per hectolitre), fused and heated to 250, introduced into the sterile cask. The bung-hole is then closed, the cask rotated automatically for a few minutes, the excess of pitch poured out, and the rolling of the cask continued until it is cold. The lager- vessels used for the maturation of the beer are treated in a similar way. PASTEURISATION. Beer, more than wine, is subject to numerous changes and diseases (turbidity due to inferior materials, incomplete saccharification or excess of proteins; acidity caused by acetic or lactic acid; stinking fermentation produced by various bacteria, etc. ), and it is difficult to remedy these inconveniences except by improve- ment in the methods of working. In order that beer may remain unchanged -when kept for a long time in bottle or when sent to hot places, it is advisable to pasteurise it. The FIG. 171. FIG. 172. bottles are tightly stoppered and placed in vessels containing cold water, which is then gradually heated to a maximum of 60 to 65, this temperature being maintained for ten minutes; the vessels should be covered so as to avoid danger from breakages. The water-bath is subsequently allowed to cool slowly to the ordinary temperature. Top- fermentation beers are rarely pasteurised, as they sometimes acquire an unpleasant flavour under this treatment ; bottom-fermentation beers, however, undergo no change and keep good even for ten years. In large breweries, very efficient pasteurising apparatus is employed, the bottles being moved automatically in suitable vessels through which the water moves in the opposite direction. Of the many improved forms in use at the present time, the Gasquet circular type is COMPOSITION OF BEER 211 shown in Fig. 173. Here the chambers are filled successively .with baskets of bottles, which are raised by suitable cranes. The water, at a gradually rising temperature, is drawn from each chamber by means of a tube communicating with a pump, heated by a central thermo-syphon, and then passed on to the succeeding chamber. A bell rings every five minutes as a signal for the bottles of a cool chamber to be removed and replaced by fresh ones. The bottles are made of a special glass, which diminishes the proportion of breakages to less than 1 per cent. ALCOHOL-FREE BEER. A proposal has recently been made to manufacture beer containing no alcohol by treating wort directly at with yeast which has previously been subjected to special treatment effecting the destruction of almost all the zymase but not that of the peptase and other proteolytic enzymes ; the carbohydrates hence give no alcohol, the proteins alone being decomposed. These yeasts remove the flavour of fresh wort, the beer being used before alcoholic fermentation begins (Ger. Pat. 180,128). COMPOSITION AND ANALYSIS OF BEER. The most varied types of beer are found in different countries, and of each type there are usually the two qualities pale and dark. 1 The density varies from TO 10 to TO 30, and the amount of alcohol usually from 3'5 to 4'5 per cent, by volume, although export beers often contain 5 to 5'5 per cent, of alcohol, and certain special 1 The compositions of some of the best-known beers are as follow : Alcohol Extract Ash Beat attenuation Per cent. Per c'jnt. Per cent. Per cent. by vol. by vol. by vol. by vol. Pale Berlin beer ..... 3-91 4-85 0-14 60-50 Berlin lager beer ..... 4-00 6-15 0-20 54-70 Export Bavarian beer .... 4-78 10-67 0-29 45-44 Munich Spaten beer ( at Munich) 3-23 6-61 0-28 48-40 ,, ,, (at Milan) . 5-23 Sal va tor beer , ... 4-64 9-08 0-28 49-00 Spaten table beer .... 7-0 10-35 57-40 Bock 4-20 7-10 54-20 white beer ..... 3-51 4-73 59-58 Vienna lager beer ..... 3-62 6-01 54-50 Pilsen beer ...... 3-47 4-97 59-00 North of France beer .... 3-20 4-04 61-20 Amsterdam beer ..... 4-30 7-0 . 36-40 Brussels Iambic ..... 6-94 3-30 . 78-00 Belgian faro ...... 4-33 6-1 62-80 Bass's pale ale . . . 6-15 6-87 64-00 Scotch pale ale ..... 8-50 10-90 . 59-9 Dublin stout ...... 7-23 6-15 . 70-64 London porter ...... 5-40 6-00 63-3 American beer ...... 5-89 6-45 63-15 Milan beer : Pilsen type .... 3-92 5-43 0-21 57-91 ,, Munich type . . . . 3-50 |6-58 0-20 64-63 Porretti beer (Varese) .... 3-98 [5-66 0-22 57-45 Italia beer (made at Milan by the modified Nathan-Boize process) .... 4-78 6-00 0-22 59-43 The real attenuation (or degree of fermentation, see p. 207) is calculated by multiplying the percentage of alcohol by 1-92 (= d'), and adding to this product the extract of the beer, d; this gives the extract, D, contained in the wort prior to fermentation and then the attenuation or 2) _ ^ percentage of extract fermented = =r- X 100. Some English breweries make stout from a mixture of 65 per cent, of pale malt, 10 per cent. of black malt (for colour) , 10 per cent, of caramelised malt and sometimes 10 per cent, of cane- sugar and 5 per cent, of maize. This very dark beer is attenuated to a relatively small extent, and retains a full, sweet taste, this being partly due to the almost entire absence of gypsum in, and the small total hardness of, London water; for these beers few hops are used. Export stout is made from worts having gravities as high as 25 Balling, whilst porter is lighter in char- acter. The pale beers of Berlin are made with a good proportion (75 per cent.) of malted wheat. 212 ORGANIC CHEMISTRY beers still more. . The amount of extract also varies considerably, being as much as 12 per cent, for certain types of beer ; for ordinary beers it lies between 5 and 6 per cent. (1 per cent, being maltose). The proportion of ash is generally less than 0'3 per cent. The amount of carbon dioxide dissolved varies from 0'15 to 0-40 per cent. The analysis of beer is carried out in a similar manner to that of wine, but the carbon dioxide is eliminated by heating the beer to 40 and shaking for several minutes before the specific gravity and acidity are determined; the latter does not exceed 0-3 per cent, and is expressed as lactic acid (1 c.c. N/10-alkali = 0-009 gram lactic acid) or as cubic centimetres of normal alkali used per 100 c.c. of beer. To avoid frothing during the distillation of the alcohol, 1 a little tannin is added. The nitrogenous substances are deter- mined on the extract of 40 c.c. of the beer by Kjeldahl's method (p. 11 ), the proportion of FIG. 173. nitrogen being multiplied by 6-25 to give the corresponding amount of proteins. The reducing sugar is determined by means of Fehling's solution and is calculated as maltose (see Note, p. 199). Beers are often tested for added salicylic acid, fluorides, sulphurous acid, etc. (see Villavecchia's " Applied Analytical Chemistry," Vol. II., p. 164). STATISTICS. In Italy the brewing industry has never been in a flourishing condition, owing to the abundance and cheapness of wine possibly more commonly drunk than water. The beer manufactured from remote epochs in Italy. was made by the top-fermen- tation process and was of poor quality ; it did not keep well in summer, was stored care- lessly by the retailers, and was consumed for only about a couple of months in the year close to where it was produced. Technical improvements have been introduced tardily, but nowadays the industry is largely concentrated into a few large breweries using the most modern methods and controlled by technical experts from other countries. In 1911 eighty-six breweries were working in Italy. About one-half of the beer imported into Italy is supplied by Austria -Hungary, about one-third by Germany, and one-tenth by Switzerland : 1 The proportion of alcohol may be calculated indirectly by means of the formula, A = (s/S) ~ S, where A indicates the percentage of alcohol, s the specific gravity of the beer, S the specific gravity of the beer freed from alcohol and made up to the original volume; the alcohol Table (p. 175) gives the percentage by weight corresponding with the value of 8/8 and division of this percentage by 8 gives the true percentage of alcohol. BEER STATISTICS 213 PRODUCTION, IMPORTATION, AND CONSUMPTION OF BEER IN ITALY Consumption 1880 1890 1894-5 . 1900 1903 1904 1905-6 . 1906-7 . 1907-8 . 1908-9 . 1909-10 . 1910-11 . 1911-12 . 1912-13 . 1913-14 . 1914-15 . Production hectols. 116,000 160,900 95,500 154,000 185,000 220,000 304,000 360,000 400,000 473,000 563,000 598,000 721,000 673,000 652,300 526,000 Imports hectols. in cask. 46,900 99,500 60,000 54,750 70,000 80,000 90,000 94,494 95,213 88,100 89,737 83,365 97,700 90,000 66,000 12,000 Total Per head hectols. litres. 163,000 0-57 260,000 0-86 156,000 0-50 209,000 0-66 255,000 0-79 300,000 0-92 394,000 1-20 455,000 1-50 495,000 1-60 561,000 1-80 651,000 2-00 680,000 2-10 815,000 2-40 763,000 2-30 718,000 2-20 538,000 1-70 The consumption of beer in Italy takes place mostly in the towns of the north and centre, and the average consumption per head in Milan, Turin, or Rome is at least ten times that for the whole country. The production and consumption of beer in different countries are as follows (thousands of hectolitres) : 1881 1900 1905 1908 1910 1913 Mean con- sumption per head (litres) Germany . 35,000 67,000 66,000 69,500 64,000 68,000 /118 (1909) UOl (1910) Austria- Hungary 12,000 20,000 20,400 19,000 25,000 80 Great Britain . 45,000 59,000 59,000 58,000 60,667 153 Belgium . 9,000 14,000 14,000 16,000 16,000 211 France 8,000 9,000 13,700 14,000 16,000 32 United States . 19,000 48,000 64,000 70,000 73,000 63 Russia 7,000 6,500 6,200 11,500 5 Spain 1,000 400 Switzerland 1,000 1,500 3,000 Holland 1,800 38 Norway 500 31 Sweden 2,850 56 Denmark . 350 104 Japan 294 280 354 New Zealand 2,456 Argentine, Chili, Brazil 2,241 1,100 Whole world 271,000 275,000 In Northern Germany the mean annual consumption per head was only 98 litres, whereas in the Grand Duchy of Baden it amounted to 158 litres ; for Lille the quantity was 360 litres. Delbriick calculated that in 1911 almost 160,000,000 was invested in breweries through- out the world, barley to the value of 14,400,000 and hops to the value of 1,600,000 being used in the brewing of beer. In 1900 the breweries in Germany numbered 10,000. In 1909 Bavaria produced 18,000,000 hectolitres of beer, Wurtemberg 5,500,000, Baden 3,000,000, and North Germany 38,000,000. 214 ORGANIC CHEMISTRY In 1911 the Schultheiss Brewery of Berlin made 1,500,000 hectolitres of beer and the Dreher Brewery of Schwechat (Vienna) 1,100,000 hectolitres. A large brewery near New York produces annually 900,000 barrels of beer, its ice machines having a daily capacity of 1600 tons. The brewery of Guinness & Co., Dublin, makes about 3,500,000 hectolitres of stout per year. In Italy the brewing tax was 5d. up to 1891, when it was raised to ll|d. (causing a temporary diminution in the consumption at that time) per saccharometer degree per hectolitre, measured with the decimal saccharometer at 17-5 on the wort from the cooler, an allowance of 12 per cent, being made for loss during the subsequent operations; the tax varied from a minimum of 9s. 6d. to a maximum of 15s. 4d. per hectolitre, according to the strength of the beer. Imported beer pays 2s. 5d. more, or the importers can demand the tax to be levied on the extract degrees, these being increased by twice the number of alcohol degrees. On exported beer the duty is refunded to the extent of 9s. 6d. per hectolitre. The exchequer collected 180,000 in 1905-1906, 211,800 in 1906-1907, and 320,000 in 1910-1911 as tax of manufacture. During the war the duty was raised to Is. 5d. per hectolitre-degree, and it is proposed to increase it to 2s. 5d. in 1920. In Germany beer costs about 12s. per hectolitre, or rather more with the extra taxation of 1910. In Italy the cost is about 32s. (that imported from well-known breweries about 40s. per hectolitre). VARIOUS DERIVATIVES OF ETHYL ALCOHOL SODIUM ETHOXIDE, C 2 H 5 -ONa, may be obtained by dissolving metallic sodium in absolute alcohol : C 2 H 5 -OH + Na = C 2 H 5 -ONa + H; when the dense mass is cooled, the crystallised ethoxide separates with 3C 2 H 5 -OH, which it loses only when heated to 200 in a current of hydrogen, a soft white powder remaining. The latter separates directly when the calculated quantity of sodium is dissolved in absolute alcohol previously dissolved in ether or toluene and heated in a reflux apparatus. The ethoxide is also obtained when sodium hydroxide is dissolved in concentrated alcohol. With excess of water sodium ethoxide decomposes into alcohol and caustic soda. The ethoxide is largely used in organic syntheses and to remove water and alcohol; before the war it cost 28s. to 32s. per kilo. CALCIUM ETHOXIDE (C 2 H 5 O) 2 Ca, is formed on dissolving metallic calcium in alcohol or by heating calcium carbide with absolute alcohol. ALCOHOLS HIGHER THAN ETHYL ALCOHOL PROPYL ALCOHOLS, C 3 H 8 O. The two isomerides theoretically possible are known : (1) Normal, CH 3 CH 2 CH 2 OH (propanol-1 or ethylcarbinol). This may be obtained from fusel oil (p. 165) by fractional distillation, or from its bro mo-derivative, or by the action of magnesium ethyl chloride on trioxymethylene. It has an agreeable odour, b.-pt. 97, sp. gr. 0-804, and is readily soluble in water, but insoluble in cold saturated calcium chloride solution (unlike ethyl alcohol). On oxidation it gives propionic acid, which proves its constitution. (2) Sec. Iso-Propyl Alcohol, CH 3 CH(OH) CH 3 (propanol-2 or dimethykarbinol), is a colourless liquid, b.-pt. 81, sp. gr. 0-789. It is obtained from isopropyl iodide and hence indirectly from glycerol, or by reducing acetone with sodium amalgam, the constitution attributed to it being thereby confirmed. BUTYL ALCOHOLS, C 4 H 10 O. The four isomerides, predicted by theory, are known : (1) Normal Butyl Alcohol, CH 3 CH 2 CH 2 CH 2 OH (butanol-l or propylcarbinol), is a liquid, b.-pt. 117, sp. gr. 0-810, and has an irritating odour ; 12 vols. of water at 22 dis- solve only 1 vol. of it, this being separated from the solution by the addition of a soluble salt. It is found in fusel oil and may be obtained by fermenting glycerol or mannitol (yield 8 to 10 per cent.) with Bacillus butylicus (contained in the excreta of cows). It may also be prepared synthetically by the various general processes (p. 125). Its constitution is indicated by its syntheses and by the possibility of transforming it into normal butyric acid by oxidation. (2) Secondary Butyl Alcohol, CH 3 CH 2 CH(OH) CH 3 (butanol-2 or ethylmethyl- carbinol), is a liquid with an intense, peculiar odour, b.-pt. 100, sp. gr. 0-808. It may be HIGHER ALCOHOLS 215 obtained by treating the tetrahydric alcohol, erythritol, C 4 H 6 (OH) 4 , with hydriodic acid or by the interaction of normal butylene and hydriodic acid and hydrolysis of the resulting iodide. CH (3) Isobutyl Alcohol, ~ 3 ;>CH CH 2 OH (methylpropanol), is termed also butyl alcohol of fermentation, since it abounds in the fusel oil of potatoes, from which it may be extracted by forming the corresponding iodo-compound. It is a colourless liquid, b.-pt. 107, sp. gr. 0-806, and has a characteristic alcoholic smell. Its constitution is deter- mined by the fact that, on oxidation, it yields isobutyric acid, the constitution of which is known. PTT (4) Tertiary Butyl Alcohol, ,3>C(OH)-CH 3 (trimethylcarbinol or methyl-2-propanol), 3 occurs in small proportion in fusel oil, and may be prepared by the action of hot 75 per cent, sulphuric acid on isobutylene, which thus takes up 1 mol. of water. When pure, it forms rhombic prisms or plates, m.-pt. 25-5, sp. gr. 0-786 (solid), b.-pt. 83. On oxidation it gives acetic acid, acetone, and carbon dioxide. AMYL ALCOHOLS, C 5 H n . OH. The eight isomerides theoretically possible are known, the most important being : (1) Normal Amyl Alcohol, CH 3 CH 2 CH 2 CH 2 CH 2 OH (pentanol-1), b.-pt. 138, sp. gr. 0-817, is of little importance, and is obtained by reducing normal valeraldehyde or by the other general methods. CH (2) Amyl Alcohol of Fermentation, ^ H 3 >CH CH 2 CH 2 OH (methyl-3-butanol-l or isobutylcarbinol), is a liquid, b.-pt. 131, sp. gr. 0-810, and is solid at 134. It dissolves in 50 vols. of water at 13-5, but in presence of a little ethyl alcohol its solubility is greatly increased. It has a higher bactericidal action than other alcohols, and, owing to its toxicity, great precautions are taken in its manufacture to protect the health of the workpeople ; if it could be obtained at a low price, it might be used for making isoprene and hence synthetic rubber. It imparts its characteristic smell and burning taste to fusel oil, in which it abounds. It is to this alcohol that the poisoning effect of spirits is principally due. It occurs naturally in Roman chamomile oil and is obtained industrially from fusel oil (see note, p. 165). It is used in large quantities to prepare amyl acetate, which serves as an excellent solvent for cellulose acetate. Prior to the war it cost 80 to 120 per ton. In 1911 the United States produced 250 tons. Germany exported 82 tons in 1910, 56 in 1911, and 124 in 1912, and imported 2-7 tons in 1910, 36 in 1911, and 197 in 1912. c TT (3) Active Amyl Alcohol, ;2 5 >CH CH 2 OH (methyl-2-butanol-l or 2-methylbutan- LJ1 3 l-ol), boils at 128, has the sp. gr. 0-816, and is found with the amyl alcohol of fermentation. It contains an asymmetric carbon atom (see p. 19) and is Isevo -rotatory, whilst the halogen compounds and the valeric acid derived from it are dextro-rotatory; also the dextro- isomeride of this acid yields a Isevo -rotatory iodide. pTT (4) Tertiary Amyl Alcohol, r , w 3 ^>C(OH) CH 2 CH 3 (methyl-2-butanol-2 or amylene Utl 3 hydrate or dimethylethylcarbinol) is an oily liquid with a faint odour of mint. It boils at 102 and is prepared from amylene ^>y the indirect addition of water under the influence of sulphuric acid. It exerts a soporific effect. HIGHER ALCOHOLS. Of these may be mentioned : Primary normal hexyl alcohol or hexanol, CH 3 [CH 2 ] 4 CH 2 OH (14 of the 18 hexyl alcohols predicted by theory are known), which may be obtained from caproic acid, C 6 H ]2 O 2 , and is found as butyric and acetic esters in the ethereal oil of the seeds of Heracleum giganteum and in the fruit of Hera- cleum spondylium : it boils at 158 (under 740 mm. pressure), and has the specific gravity 0-820. Caproyl or isohexyl alcohol, (CH 3 ) 2 : CH CH 2 CH 2 CH 2 OH, b.-pt. 150, is found in vinasse and in fusel oil. Heptyl (or wnanthyl) alcohol, C 7 H 16 0; of the 38 possible isomerides, 13 are known. Normal octyl alcoJwl, C 8 H 18 O, is contained in Heracleum spon- dylium and Heracleum giganteum ; secondary octyl alcohol (or capryl alcohol or methylhexyl- carbinol) is formed on distilling castor-oil. Other higher alcohols are obtained by reducing the corresponding aldehydes with zinc dust and acetic acid ; they are solid, like paraffin wax. Cetyl or normal hexadecyl alcohol, Cj^H^O, combined with palmitic acid, forms the principal component of sperm oil. Ceryl alcohol (cerotin), C 26 H 5 .j OH, occurs as cerotic 216 ORGANIC CHEMISTRY ester in Chinese wax and in wool-fat ; it melts at 76 to 79. Melissyl or myricyl alcohol, C 30 H 61 OH ( ? ), is found as the palmitic ester in beeswax and carnauba wax, and is obtained free by saponification with alcoholic potash. II. UNSATURATED MONOHYDRIC ALCOHOLS These are similar to the saturated alcohols, but, as they contain one or two double linkings, they behave like the olefines and diolefines in taking up two or four atoms of hydrogen, halogens, etc., to give saturated compounds. If they contain a triple linking, C = CH, they form explosive metallic compounds, as does acetylene (p. 110). VINYL ALCOHOL, CH 2 : CH . OH (Ethenol), appears to be present in commercial ether, but it has never been isolated, attempts to synthesise it leading, as is the case with other similar compounds, to an isomeride acetaldehyde, CH 3 CHO ; the formation of the latter is explained by the addition of a molecule of water to the alcohol, and immediate loss of a molecule of water from the compound thus formed. ALLYL ALCOHOL, CH 2 : CH CH 2 OH (Propenol), is a liquid of pungent odour, density 0-8573 at 15, b.-pt. 98, and readily soluble in water. It is formed in small quantity in the distillation of wood (crude methyl alcohol contains 0-2 per cent., and the final products of the rectification, distilling at 80 to 100, 50 per cent, of it). Industrially it is obtained by heating glycerol (4 parts) with crystallised oxalic acid (1 part) or formic acid and 0-3 per cent, of ammonium chloride; below 130 CO 2 is evolved with formation of glycerol formic ester, CH 2 (OH) CH(OH) CH 2 COOH, which begins to decompose at 205 to 210 and is completely decomposed at 260, with evolution of CO 2 and H 2 O. The crude allyl alcohol is distilled off (at 195 to 200) and is redistilled until oil no longer separates, when a small portion of the distillate is treated with potash. From the distillate the allyl alcohol is obtained as an oil by addition of potash, the oil being decanted off, dried by prolonged contact with lump caustic potash, again distilled and dried over potassium carbonate which has been recently heated and then over baryta. The yield is 22 to 25 per cent, of the weight of oxalic acid taken. Cl, Br, CN, and HC10 can be added on to it directly, but not H. When cautiously oxidised, it takes up and H 2 O, giving glycerol or even acrolem (allyl aldehyde) and acrylic acid, which shows it to be a primary alcohol. It is used to prepare allyl bromide and iodide (see below), esters of salicylic and cinnamic acids, etc. The price of the alcohol is 28s. to 32s. per kilo, the chemically pure product costing twice as much. Derivatives of allyl alcohol occur in the vegetable kingdom. Thus oil of garlic contains diallyl disulphide and triallyl trisulphide, and mustard oil, allyl thiocyanate (or allylthio- carbimide), C 3 H 5 N : C : S. Mustard oil is obtained from pressed mustard oil seeds (which contain it as the glucoside of potassium myronate, this being easily decomposed by the enzyme myrosin), and is also prepared artificially by distilling allyl iodide with potassium thiocyanate. The natural product (containing 94 per cent, of allyl isothio- cyanate) cost before the war 2 per kilo and the artificial oil 12s. per kilo. It is used for preparing mustard compounds and serves as a vesicatory, etc. CITRONELLOL, C 10 H 20 O, is found in attar of rc^es. PROPARGYL ALCOHOL, CH | C CH 2 OH (Propinol), is a liquid with a pleasant odour, lighter than water, b.-pt. 114. GERANIOL, C 10 H 18 O or (CH 3 ) 2 : C : CH CH 2 CH 2 C(CH 3 ) : CH CH 2 OH, is a pleasant-smelling oil, b.-pt. 121 under 17 mm. pressure. It is obtained from geranium oil, and on oxidation gives citral (the corresponding aldehyde) which occurs in mandarin oil and in essences of orange and lemon and to a very considerable extent (60 per cent. ) in verbena oil. III. POLYHYDRIC ALCOHOLS (a) DIHYDRIC ALCOHOLS OR GLYCOLS, C n H 2n (OH) 2 Substitution of two hydrogen atoms, joined to different carbon atoms, by two hydroxyl groups gives dihydric alcohols, containing two alcoholic groups. It is not, however, possible to have two hydroxyl groups united to the same carbon atom although similar compounds are known for the ether POLYHYDRIC ALCOHOLS 217 derivatives known as Acetals (see later) since even if they could be formed they would immediately lose a molecule of water, forming aldehydes or ketones. The dihydric alcohols, owing to their sweet taste, were called Glycols by Wurtz, who prepared them by transforming a dihalogenated hydrocarbon into the corresponding diacetyl-ester by means of silver acetate and then saponi- fying the diacetyl compound either by baryta or sodium hydroxide or by boiling with water and lead oxide or sodium carbonate solution : CH 2 Br CH 2 -0'COCH 3 + 2CH 3 COOAg = 2AgBr + | CH 2 Br CH 2 COCH 3 Ethylene bromide Diacetylglycol CH 2 COCH 3 CH 2 OH + 2KOH = 2CH 3 COOK + | (glycol) CH 2 COCH 3 CH 2 OH A special group of glycols, the pinacones, containing two adjacent tertiary alcohol groups (=C ' OH), are formed by reducing the ketones with sodium and water, or, better, together with isopropyl alcohol, by electrolysing a dilute solution of sulphuric acid and acetone, the latter being reduced at the negative pole : CH 3 C(OH) CH 3 3CH 3 CO CH 3 + H 4 = CH 3 CH(OH) CH 3 + ; CH 3 C(OH) CH 3 this pinacone (2 : 3-dimethyl-2 : 3-butandiol), melts at 38, boils at 172 and crystallises with 6H 2 O. When distilled with dilute sulphuric acid, it is trans- formed into pinacoline, (CH 3 ) 3 C * CO ' CH 3 , with separation of H 2 O and transposition of an alkyl group. The glycols have an almost oily appearance ; their solubility and sweetness increase with the molecular weight, while the specific gravity and boiling-point are much higher than those of the monohydric alcohols with equal numbers of carbon atoms. The hydroxyl groups of the glycols behave like those of mono- hydric alcohols, so that the glycols can give rise to ethers and esters, alkoxides (sodium, etc.), halogen compounds (e. g., the chlorohydrins), aldehydes and acids, besides which they may give up 1 mol. of H 2 O forming anhydrides. ETHYLENE GLYCOL (Ethan- 1 : 2-diol), C 2 H 4 (OH) 2 , is a dense liquid, b.-pt. 198, and, on oxidation, yields glycollic acid, CO 2 H CH 2 OH and oxalic acid, CO 2 H CO 2 H. PROPYLENE GLYCOLS. Two isomerides are known: a-Propylene Glycol, OH CH 2 CH(OH) CH 3 (propan-1 : 2-diol), boils at 188 and is formed on distillation of glycerol with sodium hydroxide. It contains an asymmetric carbon atom and, by ths action of certain ferments, the Isevo -rotatory isomeride may be isolated. /3-Propylene Glycol boils at 216 and is formed by the bacterial decomposition of glycerol, as well as by the usual synthetical methods. In the higher glycols, when the two hydroxyl groups have four carbon atoms between them (y-glycols), water is readily separated and furan derivatives, analogous with pyrrole and thiophene compounds, formed. (b) TRIHYDRIC ALCOHOLS, C H H 2M _ 1 (OH) 3 These are colourless, dense liquids with a sweetish taste and readily soluble in water ; they contain at least three carbon atoms and three hydroxyl groups, and are hence capable of forming three series of esters by combination with a monobasic acid. GLYCEROL (or Glycerine), C 3 H 5 (OH) 3 , or OH 'CH 2 -CH(OH) 'CH 2 OH (Propantriol), was discovered by Scheele in 1779. Chevreul and Braconnot 218 ORGANIC CHEMISTRY (1817) found it as a component of all oils and fats. Its formula and con- stitution were established later (Pelouze, Wurtz, and Berthelot). It occurs abundantly in nature, not in the free state, but combined with higher fatty acids in the form of esters (glycerides), which form the fats and oils; these contain 9 to 11 per cent, of combined glycerol. It exists free in rancid fats and is formed in small proportions in the fer- mentation of sugar (all wines contain 0*98 to T67 per cent.). During the European War glycerol was prepared in Germany to some extent by biological processes and was sold in the pure state under the name of protol. 1 Industrially glycerol is obtained principally from factories where fats are decomposed (stearine- and soap-works). Synthetically it may be obtained by transforming propylene (from isopropyl iodide), by means of chlorine in the hot, into dichloropropane, C 3 H 6 C1 2 , which, with iodine chloride, gives the trichloro-derivative, C 3 H 5 C1 3 ; the latter, when heated with water at 170, gives glycerol : CH 2 C1 CHC1 CH 2 C1 + 3H 2 O = 3HC1 + OH CH 2 CH(OH) CH 2 OH. This formation of glycerol and also that by the oxidation of allyl alcohol, CH 2 ' CH CH 2 * OH, demonstrate the constitution of glycerol. On the other hand, it is possible to prepare glycerol synthetically from the elements by way of acetylene, acetaldehyde (p. 110), acetic acid, acetone (by distillation of calcium acetate), isopropyl alcohol (by reduction), propylene, and thence, as above, to glycerol (Friedel and Silva). PROPERTIES. Glycerol (also termed glycerine) is an oily, colourless, dense liquid of sp. gr. T2641 at 15, and 1-26413 + (15 t) 0'000632 at any other temperature, t. It is highly hygroscopic when concentrated, but this property is no longer shown when the glycerol contains 20 per cent, of water. It dis- solves in water and in alcohol in all proportions, heat being generated when 58 parts of glycerol are mixed with 42 parts of water. Glycerol has a sweet taste. It is insoluble in ether or chloroform; it dissolves to the extent of 5 per cent, in drji acetone and to a greater degree in aqueous acetone. It boils at 290 with partial decomposition, but it may be distilled unchanged in a vacuum (at 10 mm. pressure it boils at 162). It crystallises at 40 or at a higher temperature if it contains water ; the separated crystals melt only at 22. When heated for a long time at 130 to 160 in presence of sulphuric acid, glycerol loses one or more molecules of water, giving anhydrides or ethers of glycerol or polyglycerines (A. Nobel, 1890); W. Will (1904) arrived at the same result by heating glycerol for seven to nine hours at 290 to 295 and distilling off the water formed. This treatment yields about 60 per cent, of diglycerine, C 3 H 5 (OH) 2 O * C 3 H 5 (OH) 2 , and a little tri- and polyglycerines ; all these products may be esterified like glycerol and yield, e. g., tetranitrodiglycerine, which does not congeal even at 20 and has an explosive power like trinitro- 1 The process used appears to be that of Connstein and Liidecke, based on the observation that the amount of alcohol formed during fermentation diminishes and that of glycerol formed increases as sodium sulphite is added to the saccharine liquid in increasing proportions. The results obtained with a 10 per cent, sugar solution containing also small amounts of ammonium sulphate, sodium phosphate, and potassium salts, are illustrated by the following figures : Sulphite employed . Glycerol formed Alcohol ,, Aldehyde ,, Carbon dioxide formed 25 50 100 113 196 271 400 287 233 24 58 86 396 358 294 When the fermentation is finished, the yeast (recoverable) is removed by filtration and the aldehyde and alcohol by distillation. From the residual liquid salts and acids are separated by means of calcium chloride and excess of the latter by sodium carbonate, the liquid being filtered and concentrated ; glycerol slightly contaminated with glycol is thus obtained. GLYCERINE 219 glycerine (see also C. Claessen, Ger. Pats. 181,754 and 198,768, 1907). Accord- ing to U.S. Pats. 978,443 (1910) and 13,234 (1911), glycerol readily polymerises when heated at 275 in presence of 0'5 to 1*0 per cent, of sodium acetate, 70 per cent, being polymerised in an hour. When heated rapidly and strongly it decomposes, yielding partly acrolem with the characteristic pungent odour. Also when heated with P 2 5 or KHS0 4 , it loses 2H 2 0, giving acrolem, CH 2 : CH CHO. One hundred parts of glycerol dissolve the following quantities of mineral salts : 98 of sodium carbonate, 60 of borax, 50 of zinc chloride, 40 of potassium iodide, 10 of boric acid, 50 of tannin ; bromine, ammonia, ferric chloride, etc., are also dissolved. Glycerol has the refractive index 1*476 at 13 and in aqueous solution the index varies proportionally with the dilution. By means of Lenz's table, the concentration of glycerol solutions may be r determined from either the specific gravity or the index of refraction : Percentage of glycerol Degrees Baum6, Beck, Gerlach Sp.gr. at 12 to 14 Index of refraction at 12-5 to 12-8 Percentage of glycerol Degrees Baume. Beck, Gerlach Sp. gr. at 12 to 14 Index of refraction at 12-5 to 12-8 100 30-7 1-2691 1-4758 54 18-0 1-1430 1-4065 99 30-4 1-2664 1-4744 52 17-4 1-1375 1-4036 98 30-1 1-2637 1-4729 50 16-9 1-1320 1-4007 97 29-8 1-2610 1-4715 48 16-2 1-1265 1-3979 96 29-6 1-2584 1-4700 46 15-5 1-1210 1-3950 95 29-4 1-2557 1-4686 44 15-0 1-1155 1-3921 94 29-1 ! 1-2531 1-4671 42 14-3 1-1100 1-3890 93 28-9 | 1-2504 1-4657 40 13-6 1-1045 1-3860 92 28-7 ! 1-2478 1-4642 38 13-0 1-0989 1-3829 91 28-5 1-2451 1-4628 36 12-3 1-0934 1-3798 90 28-2 1-2425 1-4613 34 11-5 1-0880 1-3772 88 27-7 1-2372 1-4584 32 11-0 1-0825 1-3745 86 27-1 1-2318 1-4555 30 10-3 1-0771 1-3719 84 26-6 1-2265 1-4525 28 9-6 1-0716 1-3692 82 26-1 1-2212 1-4496 26 9-0 1-0663 1-3666 80 25-6 1-2159 1-4467 24 8-3 1-0608 1-3639 78 25-1 1-2106 1-4438 22 7-6 1-0553 1-3612 76 24-5 1-2042 1-4409 20 6-9 1-0498 1-3585 74 24-0 1-1999 1-4380 18 6-1 1-0446 1-3559 72 23-5 1-1945 1-4352 16 5-6 1-0398 1-3533 70 23-0 1-1889 1-4321 14 4-9 1-0349 1-3507 68 22-3 1-1826 1-4286 12 3-8 1-0297 1-3480 66 21-6 1-1764 1-4249 10 3-4 1-0245 1-3454 64 21-0 1-1702 1-4213 8 2-8 1-0196 1-3430 62 20-3 ! 1-1640 1-4176 6 2-1 1-0147 1-3405 60 19-8 1-1582 1-4140 4 1-3 1-0098 1-3380 58 19-2 1-1530 1-4114 2 0-7 1-0049 1-3355 56 18-6 1-1480 1-4091 The specific gravity may be corrected for the temperature by adding or subtracting 0'7 per cent, for each degree* above or below 15. The specific viscosity (p. 90) varies greatly with the water-content. Glycerol has the interesting property of preventing the precipitation of various metallic hydroxides (*. e., it keeps them dissolved); for instance, in presence of glycerol, potassium hydroxide does not precipitate salts of chromium, copper, etc. With alkalis it forms slightly stable soluble alkoxides. It does not reduce silver or cupric salts, and hence cannot contain aldehyde groups; 220 ORGANIC CHEMISTRY it is not coloured by concentrated sulphuric acid or by sodium hydroxide on boiling. The halogens act on glycerol, not as substituting, but as oxidising agents. It inverts cane-sugar and renders starch soluble ; 100 parts of glycerol and six of starch at 190 give starch soluble in water, and the starch may be separated from the glycerol, when cold, by precipitation with alcohol. Like the other polyhydric alcohols (glycols, erythritol and its isomerides, also glucose and its isomerides galactose, etc. but not cane-sugar, quercitol or dextrin) glycerol, when added in sufficient quantity, transforms the alkaline reaction of borax solutions into an acid reaction, thus allowing of the deter- mination of boric acid and borax by titration. Under the action of certain schizomycetes, glycerol yields normal butyl alcohol, butyric acid and, partly, ethyl alcohol. Being a trihydric alcohol, glycerol is able to form esters of three types (mono-, di- and tri-), according a*S one, two, or three hydroxyl groups are replaced by inorganic or organic acid residues. In this way the glycerides may be regenerated ; for example, when excess of stearic acid is heated with glycerol at 200 under reduced pressure until no more water separates, tristearin is formed. When cautiously oxidised, glycerol forms first glyceric acid, OH ' CH 2 CH'(OH) COOH, which undergoes further oxidation to tartronic acid, COOH CH(OH) COOH, so that it is proved that glycerol contains two primary alcohol groups (' CH 2 OH) ; also, as tartronic acid still exhibits alcoholic characters, it must contain a secondary alcohol group. The con- stitution of glycerol is hence completely proved. USES OF GLYCEROL. The bulk of the glycerol manufactured is used for the preparation of nitroglycerine and hence of dynamite (see later) ; to some extent it serves for the manufacture of glycerinacetin, which is employed in making explosives and in printing textiles. It is also used to give body to light wines (termed Scheelisation, after Scheele, the discoverer of glycerol). It is employed in the manufacture of liqueurs, syrups, preserves, and sweet- meats, since it is sweet and dense, and, to some extent, anti -fermentative. It is added to chocolate, tobacco, cosmetics, textiles to be dressed, and leather goods, since it does not dry and keeps them soft or pliable. It is also used in extracting from flowers and herbs delicate perfumes which would undergo change if extracted by distillation. It is employed as a non-congealing and lubricating liquid (a solution of sp. gr. 1'13) in gas-meters and in hydraulic pumps; for greasing iron objects to prevent them from rusting ; for making copying-ink, soap, and shoe-polish ; for preserving anatomical preparations, etc. INDUSTRIAL PREPARATION. Glycerol is obtained almost exclusively as a secondary product in the treatment of fats. Until the year 1885 only the aqueous residues of stearine works were worked up (the fats are decomposed with lime, sulphuric acid, steam, or ferments), but nowadays almost all the alkaline lyes of soap factories (where the fats are treated directly with caustic soda and then with salt) x are utilised. Of the 9 to 11 per cent, of glycerol contained in fats, 8 to 10 per cent, may be recovered (only 4 per cent, when the decomposition is effected by sulphuric acid, the maximum yield being obtained when water or enzymes are used). The treatment of the dilute solutions of crude glycerol varies with their origin : soap- lyes (which are sometimes concentrated in fhe soap-works and sold to the glycerol refiners ) are treated with 0-1 to 0-2 per cent, of lime or ferrous sulphate and mixed by means of an air-jet; the liquid is decanted, slightly acidified with hydrochloric acid and skimmed; a small quantity of aluminium sulphate is then added, the liquid being decanted, rendered 1 These lyes have an alkaline reaction and, on analysis, one of them (somewhat dense) gave the following results : water, 61 per cent. ; glycerol, 16-5 per cent. ; salts, 22 per cent, (eight- tenths of which were NaCl, one-tenth Na 2 SOj, and one-tenth Na 2 C0 3 ). The specific gravity varies from 3 to 7 Be., and the proportion of glycerol usually from 6 to 12 per cent. 221 slightly alkaline, passed through a filter-press and concentrated in open boilers furnished with stirrers until sodium chloride begins to separate ; subsequent concentration to the sp. gr. 28 Be. is carried out in a vacuum, the salt deposited being gradually removed. This crude glycerol contains 85 to 90 per cent, of glycerol and 1 per cent, of salts, and has a dark yellow or brownish colour. Sometimes the alkali is removed from the soap lyes by adding a little resin and boiling, so that the resin soap formed is carried to the surface and may be decanted (to be utilised by adding to ordinary soap). The free lime may also be precipitated with an oxalate or with carbon dioxide and the sulphates with barium chloride. The concentration is not carried out in open vessels, as, when the aqueous solutions are vigorously boiled, the steam given off carries away appre- ciable quantities of glycerol. The concentration is hence carried to a certain point in an apparatus (Fig. 174 shows the Droux apparatus and Fig. 175 that of Morane), fitted with rotating coils or hollow lenticular discs, in which steam under pressure circulates. The apparatus is covered __^^_~- in and the steam from the solution ^bst^PHfflP 1 *" - -'..'-' issues rapidly through a tube com- municating with an aspirator. When the density reaches 18 to 20 Be. the solution is decanted or filtered and then further concentrated in a FIG. 174. vacuum to 27 to 28 Be. In some cases the glycerol thus obtained (or after dilution with water ), while still boiling, is decolorised by adding animal charcoal and filtering through a filter-press. This glycerol always contains a small quantity of dissolved salts. To purify it, its temperature is raised to 110 to 120 by means of superheated steam, the acids or more volatile products being thus eliminated. It is then distilled with superheated steam at 170 to 180, at which temperature all the pure glycerol passes over. This is rectified in one apparatus at 22 Be. and in a second, under diminished pressure and with superheated steam, to 28 Be., at which concentration almost all the salt separates. In general the coloration produced on distillation is less with a slightly alkaline, than with an acid, glycerol. The vacuum distilla- tion is sometimes effected by a triple-effect apparatus (Pick type, see Vol. I., p. 567; also section on Sugar), with which it is easy to remove the salt, as it separates without interrupting the distillation. These forms of apparatus for purifica- tion and distillation are named after their inventors (Hagemann, Scott, Jobbins, van Ruymbeke, Lehmann, Heckmann, etc.). The Heckmann process consists in dis- tilling the aqueous glycerine, already con- centrated to beyond 20 Be., in a boiler, A (Fig. 176), into which steam superheated to 200 to 220 and under half an atmo- sphere pressure is passed by means of a perforated coil ; the temperature of the liquid should not exceed 170, since otherwise a small part of the glycerol decomposes. In order to prevent the scum being carried over with the steam and glycerol, a perforated disc, o, fitted with a vent-pipe is fixed two-thirds of the way up the boiler. The vapours issue by the pipe B, and are condensed in the reservoir, C, which is heated to 80 to 90 with indirect steam circulating in the jacketed bottom, D. Above the reservoir is a rectifying column, with a dephlegmator, K, similar to, but much lower than, that used for the rectification of alcohol (see p. 158). During the distillation, a slight vacuum is maintained in the whole apparatus by means of a suction pump, V, so that principally water- vapour and only a little glycerol are evolved from the reservoir, C. The glycerol vapour separates in the column and returns to the FIG. 175. 222 ORGANIC CHEMISTRY reservoir, whilst .the condenser, M, condenses only the water-vapour, which is controlled by its density, colour, and taste in the test-glass, N, and is then collected in the tank, O. In C the glycerol finally reaches a concentration of 95 to 99 per cent. The rectifying column is sometimes replaced by a series of communicating, vertical copper tubes (Fig. 177) which fractionally condense the glycerol- and water- vapours from the boiler, B (heated partly by direct fire), into which passes steam from v, superheated in the furnace, T. By means of the pump, Z, a vacuum is maintained in the whole apparatus, so that, as the distillation proceeds, fresh glycerine from the reservoir, A, may be drawn into the boiler. In the first cylinder or condensing tube, which soon reaches a FIG. 176. temperature of 100, almost pure glycerol separates, whilst in the succeeding tubes, cooled only by the surrounding air, more and more dilute glycerine and finally water separate. Below each tube is a horizontal cylinder, these serving to collect the glycerols of different concentrations, some of which are subjected to redistillation. In this way is obtained the best dynamite glycerine, which must have a specific gravity of 1-263 (98 to 99 per cent.), and should not contain lime, sulphuric acid, chlorine, or arsenic. To eliminate traces of colour and empyreumatic products, the liquid is digested with boneblack (washed with acid and dried) ; the final portions of water are expelled by heating in a vacuum. FIG. 177. Besides by means of boneblack or special vegetable charcoal, complete decoloration may also be effected by sodium hydrosulphite or, better, by the zinc-formaldehyde sulph- oxylate compound (see Vol. I., p. 588). Very pure glycerol has been obtained by main- taining it at for some time and then inducing crystallisation by a few pure crystals obtained separately by cooling to 40 (Kraut's process). The degree of purity is increased by a second crystallisation. Purification by an osmotic process has also been attempted but with unsatisfactory results. During the last few years the glycerine liquids from the biological or catalytic decom- position of fats (see section on Fats) have also been worked up : they are first neutralised TESTING OF GLYCERINE 223 or, better, rendered slightly alkaline with milk of lime and, after being left for some time, the liquid is decanted or filtered off, concentrated to 15 Be. in vacuo, again allowed to stand to deposit a further quantity of lime, decolorised by passing through a carbon filter and again concentrated to 28 B6. Various attempts have also been made to recover the glycerine from the waste liquors from the manufacture of alcohol, but as yet without much success (Ger. Pats. 114,492, 125,788, 129,578, 141,703, and 147,558). STATISTICS AND PRICES. The production and trade in glycerine (from stearine and soap-works) in different countries is shown by the following figures (tons) : x 1890 1900 1905 1908 1910 1912 1913 1918 f__-j /stearine France 4 P ro ' \soap . 6,000 3,500 | 12,000 14,000 [exp. 3,856 7,450 7,000 6,811 {, /stearine 3,000 2,000 . 3,000 * " exp. 2,000 8,000 2,730 1,580 9,000 - __ imp. . 5,373 {, /stearine P ' \soap 1,200 5,500 1 | 16,000 exp. 10,000 12,000 imp. 3,360 {prod. 180 190 215 294 220 505 exp. 833 1,763 2,282 1,259 imp. 198 270 789 761 6,828 (, /stearine ' \soap . 10,000 13,000 } - 20,000 7""* exp. . 10,000 imp. 16,000 18,000 Whole ~\ , f stearine world )P rod - (soap . 26,000 14,000 40,000 40,000 | 72,000 80,000 The following qualities of glycerine are distinguished : 2 (A) Crude glycerine from the 1 In 1910 Spain produced 2500 tons of glycerine, 893 tons being exported. The annual output in Italy prior to the war amounted to about 350 tons of glycerine for pharmaceutical purposes, 100 tons of dark glycerine residues for use on the railways, and about 150 tons of pure glycerine for dynamite, for which also glycerine was imported. During the war the Italian imports were : 1914, 335 tons (1094 exported) ; 1915, 791 (40 exported) ; 1916, 1590 ; 1917, 4189, and 1918, 6828 (almost all from the United States), valued at 2,600,000. Three-fourths of the French output is due to Marseilles, where, before the war, a single refinery produced 2500 tons yearly ; the exports were mainly to the United States. German imports and exports were as follows (tons) : 1910 . 1911 . 1912 . 1913 . Crude Glycerine f ^\ Imports Exports 4685 1688 5143 2463 6875 2316 5374 2237 Pure Glycerine Imports Exports 914 2596 1241 2394 1186 3736 1107 3937 2 Tests for Glycerine : the crude, pale at 28 Be\, contains 0-5 per cent, of ash and is not rendered turbid by HC1, and only faintly so by lead acetate ; that separated from sulphuric acid saponifications, besides having a bad smell and taste, gives 3 to 5 per cent, of ash and 84 to 86 per cent, of glycerine, a turbidity (fatty acids) or precipitate being produced by HC1 or lead acetate. The glycerine to be used for nitroglycerine and dynamite is subjected to the following tests : the water is calculated from the loss in weight of 20 grams heated for ten hours at 100 and for a few hours at a slightly higher temperature. Five grams, after being heated in a platinum dish at 180 until no further evolution of vapour takes place, is weighed, and should then undergo no further diminution in weight when again heated for a short time ; it is then ashed in the usual way and the ash tested for metals and salts. Glycerine for nitroglycerine should have been distilled at least once, should not contain sugar or fatty acids, should have a neutral reaction and should contain no lead, calcium, or other metals or foreign metalloids ; only traces of Cl, As, and Fe are allowed : the specific gravity should exceed 1-26 at 15. The purest glycerine (puriss). does not contain more than 0-03 per cent, of ash and not more than 0-2 per cent, of extraneous organic substances which do not evaporate at 175, and for dynamite these two should not exceed 0-25 per cent. Oxalic acid is detected by neutralising with ammonia, acidifying with acetic acid and precipitating with CaCl 2 . The glycerine content is determined from the density 224 ORGANIC CHEMISTRY candle- or soap-works ; the saponification glycerine from candle- making is the better (since fats of higher quality are used for candles) and, although it is darker, it is more easily decolorised than that from soap lye. (B) Refined glycerine, which is subdivided into : pale, white, for dynamite, and chemically pure. The price of glycerine has undergone considerable fluctuation owing to various causes, often to collusion between speculators. Thus between 1867 and 1880, it varied between 12 and 42 per ton, while financial manoeuvres raised the price to 88 in 1881, since when the glycerine of soap lyes has been largely utilised. In 1884 the price of dynamite glycerine fell to 24 per ton. In 1908-1909 the price of No. II dark brown crude glycerine at 24 Be. was 15 per ton and at 28 Be. 18; for the light brown variety, 23, and for the pale at 28 Be. 40. Yellow refined at 28 Be. cost 46 ; white refined No. I, 48 at 28 Be. and 45 at 30 Be. ; free from lime for soap, 50 at 28 Be. and 54 at 30 Be. Finally the purest double- distilled for nitroglycerine at 31 Be. cost 60 per ton. At the beginning of 1910 these prices were increased by 25 per cent., and towards the end of 1910 by 50 per cent, or even 70 per cent. At the beginning of 1911 they were still higher, mainly owing to the large amount required in North America for making dynamite for the Panama Canal and other public works. During the European War glycerine for dynamite cost as much as 320 to 360 per ton. C. TETRA- AND POLY-HYDRIC ALCOHOLS These are usually sweet, crystalline substances which decompose near their boiling-points. They are distinguished one from another by the crystalline forms of their phenylhydrazine derivatives. They do not reduce Fehling's solution, and hence differ from the carbo- hydrates, but are derived from these by reduction. The valency of an alcohol is given by the number of alcoholic hydroxyls it contains, and hence by the number of monobasic acid residues it can fix to form a neutral ester. Acetic anhydride serves well for this purpose, the hydrogen atoms of the hydroxyl groups being replaced each by an acetyl group, CH 3 CO : l C 6 H 8 (OH) 6 + 6(CH 3 C0) 2 = 6CH 3 COOH + C 6 H 8 (0 CO CH 3 ) 6 . Mannitol Hexacetylmannitol (the air-bubbles being removed by heating), use being made of the Table on p. 219 ; in Germany a special Berthelot scale is used indicating one degree higher than the Baume scale, 26 Berthelot corresponding with a specific gravity of 1-210, 28 with 1-230, 29 with 1-240, and 30 with 1-250. The index of refraction is determined at the temperature indicated in the Table. In many cases the glycerine is estimated directly by means of the acetyl number (see succeeding Note), but the method in which the glycerine is oxidised by hot permanganate and potassium hydroxide to oxalic acid and the latter precipitated as calcium oxalate should be rejected. The fairly rapid Hehner-Richardson- Jaffe method, improved by Tortelli, is used more successfully : the glycerine is destroyed with dichromate and sulphuric acid, and the amount of dichromate used up (or, according to Gautter and Schulze, the amount of C0 2 evolved) measured by titration with sodium thiosulphate, or, better, ferrous ammonium sulphate. This method assumes that the glycerine contains no chloride, nitrate, or extraneous organic matter; these impurities may, in any case, be eliminated by means of silver oxide (chlorides), and lead acetate and calcium carbonate (organic matter), decoloration being then effected by heating with animal charcoal. 1 In this way is determined the so-called acetyl number which is so widely used in the analysis of. fats and oils. With these, the test is made on the insoluble fatty acids obtained by saponifying 40 to 50 grams of the fat with 40 c.c. of KOH solution (sp. gr. 1-4) and 40 c.c. of alcohol, this mixture being heated for half an hour on the water-bath, after which it is diluted with a litre of water and boiled for three-quarters of an hour in an open beaker to eliminate the alcohol. The liquid is acidified with sulphuric acid and boiled until the fatty acids separate in a trans- parent condition, when they are removed by means of a separating funnel, washed twice with hot water and dried in an oven at 100 to 105. To determine the acetyl number, a few grams of the substance containing the hydroxyl groups (or about 20 grams of hydroxylic fatty acids) is treated with two or three times its volume of acetic anhydride and a few drops of concen- trated sulphuric acid (formerly in place of the sulphuric acid fused sodium acetate, in quantity equal to the acetate anhydride, was used, the mixture being heated for two hours on the water- bath in a reflux apparatus). The mass heats spontaneously, and in a few minutes acetylation takes place ; it is then allowed to cool, calcium carbonate being added to precipitate the sulphuric acid, and the liquid filtered. The filtrate is distilled or evaporated to separate the acetate in a liquid or crystalline condition. In the case of the fatty acids, the filtrate is, however, diluted with 600 to 700 c.c. of water MANNITOL 225 Esters may also be prepared with bromobenzoic acid, the bromine in the resultant product being determined and the number of hydroxyl groups deduced therefrom. Well-defined compounds are also formed with benzal- dehyde and are employed in separating the constituents of different mixtures. ERYTHRITOL (Butantetrol), OH CH 2 CH(OH) CH(OH) CH 2 OH, is found in nature in the free state in Protococcus vulgaris, and as orsellinic ester (erythrin) in lichens and other algae. It forms crystals, m.-pt. 112, b.-pt. 330, and is slightly soluble in alcohol and insoluble in ether. It is obtained by decomposing d-glucose or synthetically from croto- nylene, and its constitution is deduced from the fact that it yields secondary normal butyl iodide on reduction with hydriodic acid. A similar reaction takes place with the higher polyvalent alcohols with normal chains. The four possible stereoisomerides are known, the most common being the one now described, which is optically inactive. PENTA-ERYTHRITOL has the formula C(CH 2 OH)) 4 , and melts at 253. ARABITOL, C 5 H 7 (OH) 5 (Pentahydroxypentane), crystallises in acicular prisms, m.-pt. 102, has a sweet taste and is formed by reducing the corresponding sugar, arabinose, with nascent hydrogen ; reduction of xylose similarly yields xylitol. MANNITOL, C 6 H 8 (OH) 6 (Hexanhexol), occurs abundantly in the vegetable kingdom (the larch, celery, sugar-cane, Agaricus integer containing 20 per cent, of mannitol, etc.), but especially in the manna ash (Fraxinus ornus), the dried juice of which forms ordinary manna ; x from this alcohol extracts pure mannitol, which may be decolorised by repeated and boiled for thirty to forty minutes in an open beaker to remove the acetic acid, a slow current of C0 2 being passed into the bottom of the liquid to prevent bumping. The supernatant liquid is then siphoned from the acetyl compound, which is boiled with another 500 c.c. of water and so on, this operation being repeated until the washing water no longer has an acid reaction. The acetylated derivative is then collected on a filter, washed and dried in an oven. Of this compound, 0-5 to Igram is dissolved in pure, neutral alcohol, and the solution heated for forty-five minutes on the water-bath in a 150 c.c. flask, fitted with a reflux condenser, with a definite volume (30 to 50 c.c.) of seminormal alcoholic potash. When cold, the liquid is titrated with seminormal hydrochloric acid in presence of phenolphthalein to determine the excess of alkali which has not taken part in the splitting of the acetic ester. One hydroxyl group for every gram-mol of substance corresponds with 56 grams of KOH fixed. With the fatty acids, which contain also the carboxyl group, the procedure is as follows : 3 to 4 grams of the acetyl derivative is dissolved in pure, neutral alcohol and the acidity of the carboxyl group (acetyl acid value) determined by titration with N/2-alkali ; the neutralised liquid is boiled with a known volume in excess of N/2-alcoholic potash for a short time on the water- bath, retitration with N/2 -hydrochloric acid giving the excess of alkali not combined with acetyl groups. The alkali combined (after the first neutralisation), expressed in mgrms. of KOH per 1 gram of acetyl compound gives the acetyl number. With the fatty acids the sum of the acetylated acid number and the acetyl number is termed the acetyl saponification value. From the acetyl number (N), the molecular magnitude (M ), of the alcoholic substance may be deduced , * i Tut 56 ' 100 ,o by the formula : M = ^ - 42. 1 Manna is extracted more particularly from Fraxinus ornus and Fraxinus rotundifdia, which are widespread in Sicily and Calabria and from which it readily flows through long vertical incisions made in summer and autumn. It seems to occur in the rising sap before this reaches the leaves, and is thought by some to be produced by enzyme actions. Crude, commercial manna contains 12 to 13 per cent, of water, 10 to 15 per cent, of sugar, 32 to 42 per cent, of mannitol, 40 to 41 per cent, of mucilaginous substances, organic acids and nitrogenous matter, 1 to 2 per cent, of insoluble substances and 1 to 2 per cent, of ash. Australian manna (from Myoporum platycorpum) contains as much as 90 per cent, of mannitol. ' In the neighbourhood of Palermo, Fraxinus roslrata, which gives an inferior manna, is cultivated. The manna tree grows in fertile, dry and even rocky soil and is incised in its tenth year and in the following ten or fifteen years. It is then cut back and the new branches incised in the seventh year and the succeeding ten or fifteen years. It is then again cut back, this procedure being continued for eighty or a hundred years. One hectare with 4500 trees gives as much as 100 kilos of manna per annum. It is harvested in August and September. Manna is used as a mild purgative for children. It has a sweetish taste, is soluble in water or alcohol, and, besides mannitol, contains various sugars such as stachyose and mannalriose. To extract the mannitol, the crude manna is dissolved in half its weight of water containing white of egg. The solution is boiled for a few minutes and strained, and the filtered mass, solidified by cooling, pressed in bags, or, better, centrifuged and washed at the same time with a large quantity of cold water. It is redissolved in water and the solution boiled with animal charcoal, filtered under pressure, crystallised and centrifuged. The mother-liquors are used to dissolve fresh quantities of the crude manna. The fineness of the crystals depends on the con- centration and on the temperature of the air; in some cases the crystallisation is disturbed by continually stirring the mass. VOL. II. 15 226 ORGANIC CHEMISTRY treatment with charcoal. In manna it was discovered by Proust in 1806. It is obtained synthetically by reducing fructose or glucose : C 6 H 12 O 6 + H 2 = C 6 H 14 O 6 . The optically inactive, Isevo- and dextro-rotatory forms are known, the last being the most common ; the optical activity is slight, but is rendered more apparent by the addition of borax. When heated it loses water giving anhydrides (mannitan, C 6 H 12 O 5 , and mannide, C 6 H 10 O 4 ); in a vacuum it distils unchanged. One hundred parts of water dissolve 16 parts by weight of mannitol at 16. From alcohol it crystallises in triclinic acicular prisms and from water in large rhombic prisms having a sweet taste and melting at 160. Stereoisomeric with mannitol is DULCITOL, C 6 H 8 (OH) 6 , which occurs in a number of plants and in Madagascar manna. It forms sweet, monoclinic prisms, m.-pt. 188, and is almost insoluble in water, even in the hot. Synthetically it may be prepared by reducing lactose and galactose. It is optically inactive even in presence of borax. Another stereoisomeride of mannitol is sorbitol, which melts at 104 to 109, or at 75 when crystallised with 1H 2 0. It may be obtained synthetically by reducing d-glucose or d-fructose. In presence of borax it shows a slight dextro-rotation. Other stereoisomerides are TALITOL and IDITOL; these isomerides are usually separated by means of the acetals they form with benzaldehyde. DD. DERIVATIVES OF THE ALCOHOLS A. DERIVATIVES OF MONOHYDRIC ALCOHOLS I. ETHERS These are generally formed by eliminating 1 mol. of water (for example, by concentrated sulphuric acid or by hot hydrochloric acid) from 2 mols. of alcohol, which condense to form 1 mol. of ether in the same way as 2 mols. of an acid give an anhydride : C 2 H 5 OH _ TT n , C 2 H 5 v.~ CH 3 -OH i" CH 3 ' Ethers are not formed by secondary or tertiary alcohols. The first term of the series, methyl ether, is gaseous, and the succeeding terms become liquid and then solid as the molecular weight increases, the ethereal odour of the first members being gradually lost. The empirical formulae of the ethers show them to be isomeric with the alcohols, but their constitution results from Williamson's synthesis, according Sometimes the manna solutions are first subjected to lactic fermentation, by which means considerable quantities of calcium lactate are obtained ; the mannitol is then extracted from the residual liquors. Mannitol is not fermented by beer-yeast, but with chalk and. sour cheese it gives a consider- able amount of alcohol, volatile acids, carbon dioxide, and hydrogen. When cautiously oxidised with nitric acid, it forms d-mannose and rf-fructose, whilst with the Sorbose bacterium it gives only the latter sugar. Mannitol has a slight Isevo-rotation ( 15) which is increased by alkali and changed in sign by borax. It dissolves in 6-5 parts of water at 18, in 80 parts of 60 per cent, alcohol at 15, or in 1400 parts of absolute alcohol ; it is insoluble in ether. Manna in casks costs 3s. to 5s. per kilo; assorted, Is. Id. ; in lumps, \d. The average price of manna (from Cefalu) on the Genoa Exchange gradually rose from about 2s. Id. in 1901 to about 4s. Id. in 1910, when pure crystallised mannitol cost 7s. to 10s. per kilo. The best qualities of manna are those from Cefalu, Gerace, and Smauro ; of inferior quality is the Capaci variety, which is produced also at Cinisi, Belmonte, Castellamare del Golfo, etc. The Sicilian production, which represents almost the entire production of the world, was about 360 tons in 1900, 700 in 1902, 510 in 1905, 690 in 1906, 455 in 1908, and less than 300 (owing to the bad season) in 1910. The output of mannitol in 1910 was 50 tons, but usually about 300 tons of manna are treated per annum for the production of mannitol about 100 tons one-third or one-fourth of which is consumed in Italy. The exports of manna from Italy are as follows (tons) : 1908 1910 1912 1913 1914 1915 1916 1917 , 1918 Tons . . 178 312 377 350 267 231 278 245 206 Value, . 26,285 105,560 48,510 83,400 70,000 ETHERS 227 to which they are obtained by the action of a sodium alkoxide on the halogen derivative of an alcohol : C m H 2m+1 ONa + IC n H 2n+1 = Nal + C w H 2m+1 O C n H 2n+1 If in the sodium alkoxide the sodium were not united to the oxygen, b.ut directly with carbon, this reaction would give an alcohol and not an ether; indeed, if sodium ethoxide were NaCH 2 CH 2 OH, it would, with methyl iodide, give propyl alcohol : CH 3 I + NaCH 2 CH 2 OH = Nal + CH 3 CH 2 CKj ' OH. In reality, however, methyl ethyl ether, and not propyl alcohol, is obtained, this proving the constitution of the metallic alkoxides and of the ethers, in which all the hydrogen atoms are equivalent. The interaction of silver oxide with alkyl halides (see p. 17) also leads to the formation of ethers : 2C 2 H 5 I + Ag 2 = 2AgI + C 2 H 5 O C 2 H 5 , If the alkyl radicles of an ether are similar, it is a simple ether, e. g., ethyl ether, C 2 H 5 ' C 2 H 5 , whereas if the radicles are different, the result is a mixed ether, e. g., methyl ethyl ether, C 2 H 5 ' CH 3 . Sabatier, Senderens, and Mailhe (1909-1910) obtained ethers of different types, some mixed and of the aromatic series, by passing the superheated vapours of alcohols (250 to 350) over metallic oxides (titanium, thorium, tungsten, or, best of all, aluminium). The yield is quantitative, no ethylene hydrocarbons being formed, as is the case when sulphuric acid is used. The process is continuous and pseudo- catalytic, unstable aluminium alkoxide being formed as an intermediate product : (C 2 H 5 O) 6 A1 2 A1 2 3 + 3(C 2 H 5 ) 2 O. In some cases this general method may be advantageously employed industrially. When the ethers are prepared from the alkoxides in alcoholic solution there should not be an excess of water (more than 50 per cent. ) present, otherwise the alkoxide decomposes into alcohol and alkali hydroxide and no ether is formed. Also when sulphuric acid (or HC1) is used in the preparation, an equilibrium sets in between the reacting products intermediate and final this equilibrium being regulated by the mass law, so that a certain yield cannot be exceeded except by eliminating some of the new products formed (e. g., by gradually distilling the ether; see later) : (a) C 2 H 5 OH + H 2 S0 4 = C 2 H 5 S0 4 H + Ethylsulphuric acid (6) C 2 H 5 S0 4 H + C 2 H 5 OH - H 2 S0 4 + C 2 H 5 O C 2 H 5 . The sulphuric acid is regenerated and can transform fresh alcohol into ether ; theoreti- cally, then, the initial quantity of sulphuric acid should be sufficient to transform an infinite quantity of alcohol into ether, but in practice it is necessary to add a small quantity of the acid each time, as some of it is-oised up in the formation of sulphur dioxide, ethylene, and sulphonated products. Thus, in practice the process is not continuous in the strict sense of the term, since in the phase (a) water is formed, and this cannot all be eliminated by distillation, but after a time accumulates in such quantity as to establish an equilibrium between the formation of ether and the decomposition of ethylsulphuric acid, alcohol and sulphuric acid thus being regenerated. The ethers are very stable and scarcely react in the cold with alkalis, dilute acids, sodium or phosphorus pentachloride. When superheated with water and a little mineral acid, ether is converted back into alcohol : C 2 H 5 C 2 H 5 + H 2 S0 4 = C 2 H 5 OH + C 2 H 5 S0 4 H, and the same change occurs on saturating ether at with gaseous hydrogen iodide : (C 2 H 5 ) 2 + HI = C 2 H 5 OH + C 2 H 5 I, the hydrogen iodide subsequently converting the alcohol also into ethyl iodide ; when mixed ethers are taken, the iodine unites preferably with the radicle 228 ORGANIC CHEMISTRY containing the lesser amount of carbon. PC1 5 also decomposes the ethers on heating : (C 2 H 5 ) 2 + PC1 5 _ POC1 3 + 2C 2 H 5 C1. The halogens give substitution products just as they do with the hydro- carbons, but nitric acid gives oxidation products. In the ethers are reproduced all the cases of isomerism presented by the alkyl groups from which they are derived, there being consequently numerous cases of metamerism (see p. 18), e. g., methyl amyl ether, CH 3 ' C 5 H n , is metameric with ethyl butyl ether, C 2 H 5 * C 4 H 9 , and also with dipropyl ether, C 3 H 7 O * C 3 H 7 , all these having the empirical formula C 6 H 14 0. METHYL ETHER, CH 3 O CH 3 (Methoxymethane), is a gas, but liquefies at 23, and then has the sp. gr. 1-617; it resembles ethyl ether. One volume of water dissolves 37 vols. of the gas, and 1 vol. of sulphuric acid 600 vols. of it. ETHYL ETHER, C 4 H 10 O (Ethoxyethane), C 2 H 5 C 2 H 5 . This was pre- pared for the first time in the sixteenth century by Valerius Cordus from spirit of wine. It was formerly thought to contain sulphur, and was therefore given the name sulphuric ether, still in use. Its true composition was established by Saussure and by Gay-Lussac (1807 and 1815), and the constitution was enun- ciated by Laurent and Gerhardt and confirmed experimentally by Williamson. It was thought for a long time that the sulphuric acid employed in the manu- facture of ether possessed the sole function of fixing and subtracting water from the alcohol. Since, however, it was found that water formed in the reaction always distilled with the ether, this hypothesis became invalid, and Berzelius and Mitscherlich attributed the reaction of etherification to the catalytic action of the sulphuric acid. Later on Liebig maintained that the ether is formed by the direct decom- position of the intermediate product (ethylsulphuric acid) with separation, in the hot, of S0 3 . Graham, however, succeeded in showing that ethylsulphuric acid, when heated alone at 140, does not give ether, but that the latter is formed in presence of alcohol. In 1851 Williamson gave the true explanation of the process by dividing the reaction into two phases (a and b, see preceding page) ; the secondary products, explaining the loss of sulphuric acid (see above), were discovered later. Etherification takes place also if the sulphuric acid is replaced by phos- phoric, arsenic, boric, or hydrochloric acid. Sulphur dioxide, which is formed and lost in this process, is not produced if the sulphuric acid is replaced by an aromatic sulphonic acid, for instance, C 6 H 5 ' S0 3 H, or. the corresponding chloride, C 6 H 5 S0 2 C1 (Kraft and Ross, Ger. Pat. 69,115), the temperature of the reaction being then slightly above 100: (a) C 2 H 5 OH + C 6 H 5 S0 3 H - H 2 + C 6 H 5 S0 2 OC 2 H 5 . (b) C 2 H 5 OH + C 6 H 5 S0 2 OC 2 H 5 = (C 2 H 5 ) 2 + C 6 H 5 S0 3 H. J. W. Harris's process (U.S. Pat. 711,656) may have an industrial future; in this, acetylene and hydrogen give ethylene which, with H 2 S0 4 , forms ethylsulphuric acid, the latter then forming ether under the action of water. Good results are also given by the use of methionic acid, ~CH 2 (S0 3 H) 2 , proposed by Schroeter and Sondag in 1908 ; with this acid all the higher ethers may be prepared and 10 per cent, of the acid (on the weight of alcohol) is sufficient to give a continuous distillation of ether. Senderens transforms alcohol vapour quantitatively into ether by passing it over calcined, precipitated alumina heated exactly to 260 (see p. 227). PROPERTIES. Ether is a colourless, very mobile liquid of pleasant ETHYL ETHER 229 odour, boiling at 34-9, solidifying at 129 if dry, and at 40 if aqueous, and melting at 113 ; it has the sp. gr. 0'712 at 25, 0*7196 at 15, 0*7289 at 6*9, or 0*736 at 0. Contamination of ether by water and alcohol may be detected at once by the specific gravity, which reaches the value 0*735 at 15 when the maximum proportion of water, namely, 7*5 per cent., is present. Commercially the density of ether is given in degrees Baume (scale for liquids lighter than water). The vapour density of ether at various temperatures in millimetres of mercury is as follows : Temperature 20 10 + 10 20 30 40 50 70 90 110 120 Pressure . G7'5 113-4 183'4 286'4 433 636 910 1271 2308 3898 6208 7702 On evaporation, it produces intense cold. It inflames very readily, but is not inflammable when mixed with 35 to 50 per cent, of carbon tetrachloride. With air it forms explosive mixtures (p. 34). It is obtained anhydrous by distilling over a little sodium. J. Meunier (1907) has found that mixtures of ether vapour and air are inflammable and explosive when they contain between 75 and 200 mgrms. of ether per litre of air. As ether vapour is much heavier than air (mol. wt. 74), it tends to collect in a dense, invisible layer on the floor or bench and may cause fire or explosion. It is soluble in concentrated hydrochloric acid. In the pure, dry state it is stable in the air, but it assumes an acid reaction if water or alcohol is present. Water dissolves 6*5 per cent, of ether at 19, and ether dissolves about 2'25 per cent, of water at 20. When 20 c.c. of water is shaken in a cylinder with 20 c.c. of pure ether and then left at rest, the volume of the aqueous layer increases by 2 c.c. (solubility of ether in water ; a small portion of the water passes into the ether) ; if the ether contain alcohol, the increase in volume of the water will be greater than 2 c.c., whilst if much alcohol be present, a single solution will be formed. Addition of water to a solution of one part of ether in three parts of alcohol results in dissolution of the water and in separation of a little of the ether, whilst in a solution of one part of ether in four parts of alcohol water dissolves without causing separation of ether. Aqueous ether may be recognised by the turbidity produced on shaking it with a small quantity of carbon disulphide. Ether dissolves in large amount in sulphuric acid (monohydrate), forming ethylsulphuric and ethionic acids and ethyl sulphate ; 92*5 per cent, sulphuric acid readily dissolves ether almost or quite unchanged, but when heated, this solution forms ethyl sulphate and ethionic acid, which at a high temperature yields ethylene (1 vol. of sulphuric acid dissolves 1*67 vols. of ether). If, however, the sulphuric acid is diluted to 55 Be. (after fixation of the ether), the ether may be recovered more completely (see note, p. 232). It is an excellent solvent for many organic substances, especially for fats. It combines with certain inorganic substances (chlorides of tin, aluminium, phosphorus, antimony, etc.) as ether of crystallisation. With chlorine in the cold it gives successively : monochloroethyl ether, CH 3 CHC1 * ' C 2 H 5 (b.-pt. 98); ethyl dichloroethyl ether, CH 2 C1 CHC1 C 2 H 5 (b.-pt. 145); ethyl trichloroethyl ether, CHC1 2 CHC1 C 2 H 5 (b.-pt. 170 to 175), and penta- chloroethyl ether, (C 2 C1 5 ) 2 0, which boils at 68, decomposing into C 2 C1 6 and trichloroacetyl chloride, CC1 3 CO Cl. Ether dissolves Br, I, FeCl 3 , HgCl 2 , AuCl 3 , and chromic acid. The action of light on ether produces small quantities of hydrogen peroxide, acetaldehyde, acetic acid, and vinyl alcohol. In contact with platinum black it ignites. When poured into a cylinder of chlorine it explodes and forms hydrogen chloride, whilst in the dark the slow reaction yields perchloroether. 230 ORGANIC CHEMISTRY Ether is an anaesthetic and was used as such before chloroform; it is again coming into use at the present time, as it is less dangerous, although it produces certain disturbing effects, for example, in the lungs. For this purpose it must be used in a highly purified condition; use of a cork in the bottle is sufficient to alter it. When mixed with liquid carbon dioxide, it lowers the temperature to 79'5 below zero. It decomposes at above 500, giving acetaldehyde. INDUSTRIAL PREPARATION OF ETHER. Use was formerly made in many works of Sussenguth vessels, which are double-walled and made of iron and lead-lined. Later large iron pots, homogeneously leaded, were adopted, these being heated by high- pressure steam circulating either through a jacket or false bottom, or, more efficiently, through leaded copper coils arranged inside the vessel (e. g., Barbet type, Fig. 178). At 135 to 140, however, these wear out within a few months, even when made of heavy lead castings. Hempel endea- voured to lessen this trouble by making the lower half of the vessel of a single casting of hard lead, with the heating coils in the FIG. 178. FIG. 179. thickness of the walls; such vessels, although very expensive, are highly durable and require less frequent repair. Until a few years ago crude ether, contaminated with water, alcohol and sulphur dioxide was made and then subjected to purification and rectification in another part of the works. Nowadays, however, general use is made of continuous process plants, which give directly pure ether, these being constructed by Messrs. Barbet (France), Eckelt (Berlin), and F. H. Meyer (Hanover). Fig. 179 shows the arrangement of an ether plant designed by H. Meyer : The pot a contains the mixture of alcohol (5 parts of 90 per cent., free from fusel oil) and sulphuric acid of 66 Be. (9 parts, free from nitric and nitrosyl- sulphuric acids when copper vessels are used), this being heated by means of indirect steam to the temperature at which ether forms. From the tank a', situated just under the roof, a continuous, regular stream of alcohol flows into a, and is there converted into crude ether, the vapour of which, after traversing the safety vessel b, where spray is retained, is washed with soda solution in the column c and then rectified in the column/. Here mainly the water and alcohol are condensed, the aqueous alcohol descending to the rectifying column MANUFACTURE OF ETHER 231- .w'j, where the water is discharged at the bottom, while the alcohol vapour passes to the dephlegmator i 3 and then to the condenser &; the pure concentrated alcohol is collected in the tank m. The rectified ether vapour from the column j^ proceeds to the dephleg- mator / 2 / 3 , and the liquid ether through the three purifying and drying cylinders g, g v and <7 2 to the carboys ss. The ether vapour escaping from g, g v and g z is condensed in the coil h by means of brine from a refrigerating plant and the condensate collected in h v Some manufacturers use a mixture of 5 parts of 95 per cent, alcohol and 12 parts of sulphuric acid of 66 Be. Theoretically 124-3 parts of pure alcohol are required per 100 parts of ether. The practical yield of ether is about 95 per cent, of the theoretical, about 0-5 kilo of sulphuric acid being consumed per 100 kilos of ether. Heckmann's apparatus for working on a small scale is shown in Fig. 180 : A is the alcohol reservoir which feeds the alcohol regularly through the tap, a, and the glass vessel, 6, to the still, B, containing the sulphuric acid ; indirect steam under pressure is supplied to the coil, e. The ether continually distilling over is condensed in the coil, C, immersed in cold water. The premises where the distilling apparatus is situated are usually separated by thick walls from the condenser, in order to avoid the danger of fire and explosion. Some premises are fitted with channels and draught-apparatus for rapidly dispersing any vapour which may find its way into the air. The distilled vapour is condensed in closed apparatus, the only outlet to which is a tube opening on the roof. The maximum detonation occurs when 1000 litres of air contains 125 grams of ether vapour, but slight detonations also take place with 38 grams or 200 grams of the vapour; in the last case the gaseous mass is inflamed by a lighted substance or an electric spark. If the temperature of etherification exceeds 140, the yield diminishes, as a considerable quantity of ethylene is then formed : C 2 H 5 OH = H 2 + C 2 H 4 . On the other hand, if the temperature falls below 130, a large amount of alcohol distils without reacting. The alcohol for making ether is denatured so as to be exempt from taxation, and in Germany animal oil (Dippel's) is added, this being then fixed and decomposed by the sulphuric acid. In Italy the alcohol is denatured with sulphuric acid. D. Annaratone (Ger. Pat. 231,395, 1909) obtains increased yields of ether by passing alcohol vapour, superheated to 130, into a column filled with pebbles, among which the sulphuric acid is circulated or sprayed; for 100 kilos of ether only 180 kilos of steam is required for heating instead of 700 kilos used in the old process. From the top of this column issue the ether vapour and the excess of alcohol vapour, the latter being condensed in a superposed rectifying column kept at a convenient temperature; the ether vapour is rectified in a subsequent column, where a little alcohol is condensed, and then passes to the refrigerating coils, in which it is completely condensed. The condensed alcohol is brought continuously to the desired concentration by means of a suitable rectifying column. P. Fritzsche (1912) suggests the manufacture of ether by fixing the ethylene of oil-gas (see p. 61) by means of sulphuric acid, the resulting ethylsulphuric acid being diluted and heated to give ether and sulphuric acid. USES AND PRODUCTION. Ether is used in small quantity as an anaesthetic, and in large quantities in the manufacture of collodion and artificial silk (1000 kilos of silk require about 5000 kilos of ether), as well as for smokeless powders (Powder B). 1 It serves also 1 Recovery of ether from the air. In the manufacture of smokeless powders and especially of powder B (see later : Explosives), enormous quantities of ether, mixed with alcohol, are used. In the Ferrania (Savona) works of the Societa Italiana Prodotti Esplodenti, where powder B FIG. 180. 232 ORGANIC CHEMISTRY as a solvent for numerous organic compounds in dye and perfume factories. In Ireland it is drunk as a liqueur a refined form of alcoholism. The amount of ether manufactured in Germany in 1902 was about 2000 tons, without counting that now made in large quantities for the production of artificial silk by the Chardonnet-Lehner process. In Italy large amounts of ether were manufactured prior to 1910 when the artificial silk works used the Chardonnet process. During the European War it was made for preparing smokeless powder (Powder B) ; it is protected by a Customs duty of 72 per ton. In 1907, Gulinelli's distillery (Ferrara) alone produced 359 tons of ether. Owing to the crisis in the Italian artificial silk industry, the production had fallen considerably in 1910. Ether exempt from duty was sold in Germany before the war at 40 per ton if its sp. gr. was 0-722, whilst the price of the pharmacopceial product, sp. gr. 0-720, was 90. Taxed ether, distilled over sodium and chemically pure, cost 4s. per kilo. In 1909, ether for artificial silk manufacture cost 2 11s. per hectolitre in Belgium and 2 14.s. in Austria. In general ether costs one and a half times as much as alcohol. TESTS FOR ETHER. Ether containing water or alcohol has a specific gravity between 0-720 and 0-733. When 20 c.c. of ether is shaken with 5 c.c. of water, the latter should not assume an acid reaction. Ozone or hydrogen peroxide may be detected by means of potassium iodide solution, which is turned brown in the dark in the course of an hour. White ignited copper sulphate is rendered green or blue by aqueous ether. Eder (1876) and Dan Tyrer showed that cadmium iodide is insoluble in absolutely dry ether, 0-64 per cent, of the iodide being dissolved for each 0-1 per cent, of water present. In a mixture of alcohol and ether, Fleischer and Frank (1907) determine the proportions of the two components by shaking 10 c.c. of the mixture in a graduated tube with 5 c.c. of benzene and 6 c.c. of water : the increase in volume of the water shows the amount of alcohol and that of the benzene the amount of ether. Various ^chlorinated derivatives of ether are known. Ethyl Peroxide, C 2 H 5 O C 2 H 5 , is prepared by introducing ethyl groups into hydrogen peroxide by means of ethyl sulphate; it is a liquid, b.-pt. 65, difficultly soluble in water and very readily inflammable, but is moderately stable towards chemical reagents. In 1901 Baeyer prepared also the Hydrate of Ethyl Peroxide, C 5 H 2 O OH, as a colour- less liquid, which possesses strong oxidising properties, dissolves in water, boils at 95, and forms barium and other salts. is made, a plant capable of producing 20,000 kilos of ether per day is at work. In some of the large French works making powder B, the daily consumption of ether exceeds 100 tons, although 50 per cent, of it is recovered. The recovery of the ether is hence a problem of great import- ance. The air drawn from the galleries or chambers where the powder B (which contains about 35 per cent, of ether and 18 per cent, of alcohol) is dried contains as much as 400 grams of ether and alcohol per cubic metre. Part of this air is passed through a refrigerating chamber at 15 and issues with only 20 to 30 grams of ether per cubic metre ; it is then mixed with the portion which has not been cooled and again traverses the drying galleries or chambers at 40, and thus becomes saturated again with alcohol and ether. This air is circulated by means of fans having a capacity of 10,000 to 15,000 cu. metres per hour; the part which is cooled con- stitutes only one-sixth or one-tenth of the whole volume. The solvent condensed by the cooling contains 60 per cent, of ether and 40 per cent, of alcohol. After this treatment the powder B still contains more than 20 per cent, of solvent and is dried completely in a gentle current of air, which takes up less than 35 grams of ether-alcohol per cubic metre and is usually not passed through the recovery apparatus. By this system about 56 per cent, of the ether and 36 per cent, of the alcohol used are recovered. According to another system the ether is fixed by passing the air through concentrated sulphuric acid, which is afterwards diluted and heated, the bulk of the ether being thus liberated (see p. 229) ; about 60 per cent, of the total solvent is thus recovered. The use of castor-oil in place of sulphuric acid has also been' suggested, this fixing both ether and alcohol and subsequently giving them up in good yield. J. H. Bregeat fixes the alcohol and ether of the air by means of cresol (see later : Benzene derivatives), b.-pt. 195 to 205, which absorbs even 5 grams of these compounds per cubic metre of air; all the alcohol and ether is recovered from the solution by heating the latter in iron vessels at 125 to 130, the cresol being afterwards cooled and used again. In this way 92 to 95 per cen"t. of the alcohol and ether is recoverable, the cost being one-half of that incurred when sulphuric acid is used and one-third of that of the freezing method. MERCAPTANS 233 II. THIO-ALCOHOLS AND THIO-ETHERS These have the same constitution as the alcohols and ethers, excepting that the oxygen is replaced by sulphur. They are very volatile and inflam- mable liquids, almost insoluble in water and having repulsive garlic-like odours ; in the higher members, however, the odour diminishes and the solubility in water vanishes, although they continue to be soluble in alcohol or ether. (a) THIO-ALCOHOLS (or Mercaptans or Thiols or Alkyl Hydrosulphides), C n H 2)i + 1 SH, have lower boiling-points than the corresponding alcohols. They are feebly acid in character and form salts called Mercaptides, e. g., with mer- curic oxide. They are soluble in concentrated alkali solutions. They may be regarded as hydrogen sulphide in which one atom of hydrogen is replaced by an alkyl radicle, e. g., ethanthiol or ordinary Mercaptan, C 2 H 5 SH. As acids they are monobasic, and salts are formed with metallic sodium or potassium ; the lead salts are yellow and are obtained by the action of lead acetate in alcoholic solution. Nitric acid transforms the mercaptans into alkylsulphonic acids : C 2 H 5 SH + 3O = C 2 H 5 S0 3 H. With iodine, the salts of sodium, etc., give disulphides : 2C 2 H 5 SNa + I 2 = 2NaI + (C 2 H 5 ) 2 S 2 , which, with hydrogen, give mercaptans, and with nitric acid disulpJioxides, (C 2 H 5 ) 2 S 2 2 ; concentrated sulphuric acid gives disulphides and is itself reduced to sulphur dioxide. (b) THIO-ETHERS (or Alkyl Sulphides), (C n H 2rt + 1 ) 2 S, are neutral, readily volatile liquids, and afford a good illustration of the variability of the valency of sulphur (di- to hexa-valent). They may be regarded as derived from hydrogen sulphide by replacement of the two hydrogen atoms by alkyl groups. With salts they form double compounds, e. g., ethyl sulphide with mercuric chloride gives (C 2 H 5 ) 2 S, HgCl 2 . They combine with halogens, giving, for instance, (C 2 H 5 ) 2 SBr 2 , whilst when treated with dilute nitric acid they fix an atom- of oxygen, yielding, e. g., (C 2 H 5 ) 2 SO, ethyl sulphoxide : with more energetic oxidising agents, a further oxygen atom is taken up with formation of sulphones, e. g., Diethylsulphone, (C 2 H 5 ) 2 SO 2 . With hydrogen, the sulphoxides give sulphides, but the sul- phides are not reduced. They combine with alkyl haloids, forming sulphonium compounds, e. g., ethyl iodide and ethyl sulphide give Triethylsulphonium Iodide, (C 2 H 5 ) 3 SI, which reacts like metallic iodides with silver hydroxide, yielding Triethylsulphonium Hydroxide, (C 2 H 5 ) 3 S * OH. METHODS OF FORMATION. They are obtained: (1) by heating alkyl haloids or salts of alkylsulphuric acids with an alcoholic or aqueous solution of potassium sul- phide or hydrosulphide : C 2 H 5 Br + KSH = KBr + C 2 H 5 SH; 2C 2 H 5 Br + K 2 S = 2KBr + (C 2 H 5 ) 2 S ; 2C 2 H 5 SO 4 K + K 2 S = 2K 2 S0 4 + (C 2 H 5 ) 2 S. (2) By the action of phosphorus pentasulphide, P 2 S 5> on ethers. Mixed sulphides also may be obtained by these and various other methods. METHYL HYDROSULPHIDE (Methanthiol), CH 3 SH, is found among the gases from the anaerobic decomposition of proteins (for instance, in the intestines of animals). It is a nauseous liquid, lighter than water and boiling at 6. METHYL SULPHIDE, (CH 3 ) 2 S, is a liquid, b.-pt. 37, having a disagreeable ethereal odour. ETHYL HYDROSULPHIDE (Ethanthiol, Ethylmercaptan, or Mercaptan), C 2 H 5 SH, is a liquid, b.-pt. 36, having a repulsive odour and is used for the preparation of sulphonal. 1 With sodium ethoxide in alcoholic solution it gives Sodium Mercaptide, C 2 H 5 SNa, in white crystals; Mercuric Mercaptide, (C 2 H 5 S) 2 Hg, has also been obtained. 1 SULPHONAL is an important anaesthetic (see p. 118) and is obtained by saturating an acetone solution of ethylmercaptan with gaseous hydrogen chloride or by treatment with zinc chloride, the mercaptol, C(CH 3 ) 2 (SC 2 H 5 ) 2 , thus formed being oxidised by potassium perman- ganate to form sulphonal, C(CH 3 ) 2 (S0 2 C 2 H 6 ) 2 , which crystallises in colourless, odourless, insipid 234 ORGANIC CHEMISTRY ETHYL SULPHIDE, (C 2 H 5 ) 2 S, is a liquid, b.-pt. 92, insoluble in water, and forms a crystalline bromide, (C 2 H 5 ) 2 SBr 2 . ETHYL DISULPHIDE (Ethanodithioethane), (C 2 H 5 ) 2 S 2 , boils at 151, and is obtained by the action of iodine on mercaptan. ETHYL SULPHOXIDE (Ethanosulphoxy ethane), (C 2 H 5 ) 2 SO, is a dense liquid, soluble in water, and readily reducible. ETHYLSULPHONE (Ethanosulphonethane, Diethylsulphone), (C 2 H 5 ) 2 S0 2 , boils unchanged and does not undergo reduction. TRIMETHYLSULPHONIUM IODIDE, (CH 3 ) 3 SI, obtained from sulphur and methyl iodide, forms white crystals soluble in water and with silver hydroxide gives the Hydroxide, (CH 3 ) 3 SOH, which is an energetic base and displaces ammonia from its salts. III. ETHERS OF ALCOHOLS WITH INORGANIC ACIDS Ethers formed from an alcohol residue and an acid residue are termed Compound Ethers or Esters. We shall here describe those derived from mineral acids and shall consider organic acid esters more in detail when the acids themselves have been studied. The esters may be regarded as derived either from acid by the replacement of the acid hydrogen by an alkyl residue, as with the salts, or from alcon ols by replacement of the hydroxylic hydrogen by an acid radicle : HN0 3 . . . KN0 3 . . .'C 2 H 5 -N0 3 or C 2 H 5 -OH . . . C 2 H 5 -0(N0 2 ) . . . C 2 H 5 O(S0 3 H) . Monobasic acids form only one class of esters, viz., normal esters. Dibasic acids form two series of esters, normal and acid : e. g., C 2 H 5 HS0 4 , acid ester, and (C 2 H 5 ) 2 SO 4 , normal ester. Tribasic acids give three kinds of esters with constitutions analogous to those of the salts. The Normal Esters are neutral liquids of agreeable odour, moderately volatile and insoluble in water. The Acid Esters have acid reactions, are less stable, odourless, soluble in water, and volatile without decomposition. In general, these esters are decomposed by alkali or water at a high tempera- ture (150 to 180), the components being regenerated; this change is known as Saponification : C 2 H 5 N0 3 + KOH = C 2 H 5 'OH -f KN0 3 . FORMATION. (1) They are usually formed by the interaction of the components (absolute alcohol -f- acid), the water which gradually forms being fixed and the resulting ester distilled. With some acids, the corresponding salts in presence of concentrated sulphuric acid at 100 to 130 are taken, so that the acid is obtained in the nascent state and the ester driven off as it is formed. They are more readily obtainable by saturating the mixture of alcohol and salt with gaseous hydrogen chloride. (2) From the silver salt of the acid and an alkyl iodide : Ag 2 S0 4 + 2C 2 H 5 1 = 2AgI + S0 4 (C 2 H 5 ) 2 . (3) From the alcohol or alkoxide with the chloride of the acid : SOC1 2 + 2C 2 H 5 OH = 2HC1 + SO(OC 2 H 5 ) 2 ; and POC1 3 + 3C 2 H 5 ONa = 3NaCl + PO(OC 2 H 5 ) 3 (ethyl phosphate). (4) By passing the vapours of the acid and alcohol together over a catalyst as much as 50 per cent, of the ester is obtained. prisms, m.-pt. 125 to 126, boiling unchanged at 300. It dissolves slightly in water, alcohol or ether in the cold, but is readily soluble in boiling water or alcohol. When heated in a tube with powdered wood charcoal, it emits the repulsive odour of mercaptan, one-four hundred millionth of a milligram of which is detectable. If is sold at 24s. per kilo. VARIOUS ESTERS 235 1. ESTERS OF SULPHURIC ACID AND ALKYLSULPHURIC ACIDS. These are generally prepared from fuming sulphuric acid and alcohol, or from silver sulphate and alkyl iodide or from alcohol and sulphuryl chloride, S0 2 C1 2 + 2C 2 H 5 OH = 2HC1 + S0 2 (C 2 H 5 O) 2 ; acid esters (alkylsulphuric acids) also exist. Tertiary alcohols do not form these esters. Ethyl Sulphate, (C 2 H 5 ) 2 SO 4 , is an oily liquid with an odour of mint and a pronounced acid character ; it boils at 208 and is easily saponified, even by boiling with water alone. It is formed by heating ethylsulphuric acid : 2C 2 H 5 S0 4 H = S0 4 H 2 + S0 4 (C 2 H 5 ) 2 . Ethylsulphuric Acid, C 2 H 5 SO 4 H (C 2 H 5 S0 3 H), is formed as an initial product in the manufacture of ether (p. 228). It is soluble in water and is distinguished from sulphuric acid by the solubility of its calcium, strontium, barium, and lead salts. It gives well crystallised salts, the potassium salt being largely used for preparing ethyl derivatives, e. g., when it is dry-distilled with potassium bromide : KBr + C 2 H 6 SO 4 K = S0 4 K 2 + C 2 H 5 Br. 2. DERIVATIVES OF SULPHUROUS ACID : (a) Sulphurous Esters ; (b) Sul- phonic Acids. (a) Ethyl Sulphite, S0 3 (C 2 H 5 ) 2 , and ethylsulphurous acid, C 2 H 5 S0 3 H. The latter is known also in the form of salts and both are readily saponified, since the sulphur is not directly united with carbon : CH 3 CH 2 S0 2 H. (6) Ethylsulphonic Acid, C 2 H 5 SO 3 H, is obtained by the reaction C 2 H 5 I + SO 3 Na 2 = Nal + C 2 H 5 S0 3 Na; or by oxidising the thioalcohols : C 2 H 5 SH + O 3 = C 2 H 5 S0 3 H ; or thus : 2C 2 H 5 I + Ag 2 S0 3 = 2AgI + (C 2 H 5 ) 2 S0 3 (ethyl ethylsulphonate). Sulphonic acid compounds are not saponifiable; diethylsulphonic acid is saponifiable to the extent of one-half, since in the sulphonic acids the sulphur is united with carbon : CH 3 CH 2 S0 2 OH ; the presence of hydro xyl is shown by the fact that with PC1 5 it forms C 2 H 5 SO 2 CI, which with hydrogen gives ethylsulphinic acid, C 2 H 5 SH0 2 , the salts of the latter reacting with alkyl haloids to form sulphones. Sulphonic acids are strong acids and give salts soluble in water. 3. ESTERS OF NITRIC ACID. These are explosive if heated rapidly and undergo saponification when boiled with an alkali. Tin and hydrochloric acid reduce them, giving Hydroxylamine, NH 2 OH, the nitrogen being separated from the radicle as in saponification. METHYL NITRATE, CH 3 O-NO 2 , obtained by treating a mixture of methyl alcohol and potassium nitrate with concentrated sulphuric acid, is a colourless oil of unpleasant odour and sweet taste. It boils at 66, has the sp. gr. 1-182 at 22, is soluble in alcohol or ether, but insoluble in water, and is explosive and dangerous to handle. Ethyl Nitrate : C 2 H 5 O NO 2 , a liquid boiling at 86, is obtained from absolute alcohol and concentrated nitric acid, the formation of the dangerous nitrous products being prevented by addition of a little urea. 4. ESTERS OF NITROUS ACID. These are easily obtained by passing nitrogen trioxide (N 2 3 ) into the alcohols, or by treating the latter with alkali nitrites and sulphuric acid. They are reduced by nascent hydrogen, giving alcohol and ammonia. Ethyl Nitrite, C 2 H 5 O NO, was at one time called nitric ether. Dissolved in alcohol, it bears the name Spiritus cetheris nitrosi, and is used to modify the taste of various substances. It is also used for preparing diazo-compounds. 5. NITRO-DERIVATIVES OF THE HYDROCARBONS. These are isameric with nitrous esters, but they boil at higher temperatures than the latter and are distin- guished from them by being non-saponifiable and by giving organic amino-compounds on reduction, as long as the nitrogen is not severed from the organic radical : CH 3 N0 2 (nitromethane) + 3H 2 = 2H 2 O + CH 3 NH 2 . They are formed by treating alkyl iodides with silver nitrite : CH 3 I + AgN0 2 = Agl + CH 3 N0 2 ; 236 ORGANIC CHEMISTRY with the higher members of the series, the nitrous esters are formed at the same time and may be separated by distillation. Of the various methods of formation, mention may be made of that based on the action of dilute nitric acid, in the hot and under pressure, on the paraffins : C 6 H 14 + HN0 3 = C 6 H 13 - N0 2 + H 2 O. Hexane Nitrohexane Concentrated nitric acid does not give nitro-compounds with the paraffins, but with aromatic hydrocarbons it reacts readily. The difference in constitution between nitro-derivatives, e. g., H 3 C N0 2 , and nitrous esters, e. g., H 3 C 0'- N : O, explains their different relations as regards saponification. This also confirms the hypothetical constitution of nitrous acid, : N OH. The hydrogen of the carbon atom united to nitrogen may be partially substituted by metals or bromine, since it has acquired acid characters for instance, NaCH 2 N0 2 but the acidify- ing influence of the nitro-group is not extended to the hydrogens of the other carbon atoms. These nitroparaffins react with nitrous acid differently according as they are primary, secondary, or tertiary : ,H 2 N OH (a) Nitroethane, CH 3 - Cf + N0 2 H = H 2 + CH 3 - Cf i. e., ethyl- X N0 2 X N0 2 nitric acid, salts of which are red. CH S . ,H CH 3 N=0 (6) Secondary Nitropropane, X C( + N0 2 H - H 2 + CH/ X N0 2 C propylpseudonitrole, which forms blue salts. (c) Tertiary derivatives give no reaction. These reactions serve well to distinguish primary, secondary, and tertiary alcohols. Nitroethane may be used in the manufacture of explosives to lower the freezing-point of nitroglycerine. CHLOROPICRIN, CC1 3 . NO 2 , sp. gr. 1-692, boils at 112, and is formed by the simultaneous action of nitric acid and chlorine on various organic compounds. It is also obtained when a mixture of 60 grams of picric acid, 7 kilos of water and 1-5 kilo of calcium hypochlorite is heated by direct steam, the oily chloropicrin which distils over being washed with very dilute soda solution, decanted, dried, and distilled. It is soluble in alcohol, ether, or benzene and slightly so in water. It is a powerful and irritating lachrymatory and was largely used during the European War. 1 When superheated it 1 CHEMISTRY AND THE WAR. Among the poisonous gases and liquids used during the war are the following : phosgene, chlorine, bromine, cyanogen bromide, bromoacetone, aromatic arsines, nitrous vapours, acrolei'n, allyl isothiocyanate, phosphorus, tin and arsenic chlorides, benzyl bromide, etc. The terrible mustard gas or yprite consists of &&'-dichloroethyl sulphide, S(CH 2 CH 2 C1) 2 , which is a yellowish, neutral, odourless oil of sp. gr. 1-27, m.-pt. 7, b.-pt. 217 to 219 (decomposing slightly). It is almost insoluble in water, has a high vapour pressure, and produces extraordinarily lachrymatory and poisonous effects, even when brought into contact with the skin ; it easily penetrates clothing. It was first used by the Germans against the British at Ypres on July 20, 1917, and afterwards at Nieuport and Armentieres; on these two cities as many as 50,000 mustard gas shells per day were dropped for several days. In Germany 50 to 60 tons were made per day, in France 20 tons, and in America 40 tons. It is slowly saponified by hot alkali, and dissolves in alcohol, ether, benzine, etc. ; with halogens it yields substitution products. By oxidising agents (hydrogen peroxide, permanganate, ozone, calcium hypochlorite, etc.) it is easily transformed into harmless compounds, SO(CH 2 CH 2 C1) 2 and S0 2 (CH 2 -CH 2 C1) 2 . In Germany mustard gas was made by heating glycol chlorohydrin on a water-bath with concentrated aqueous potassium sulphide and then evaporating and taking up the residue in absolute alcohol to get rid of sodium chloride. The syrupy residue left after expulsion of the alcohol was treated with phosphorus pentachloride, the mass being afterwards poured on to ice and the oil separated. In England (and America) mustard gas was made by the interaction of ethylene and sulphur chloride : 2C 2 H 4 + SCI. = S(CH 2 CH 2 C1) 2 . The ethylene was obtained in 85 per cent, purity by passing alcohol vapour over lumps of kaolin heated at 500 to 600 in retorts, titanium oxide being used as catalyst; in England increased yields were obtained by using coke impregnated with phosphoric acid in place of kaolin and titanium. The reaction between C 2 H 4 and SC1 2 (or S 2 C1 2 ) takes place at 30 to 35 and is regulated by cooling. To render the mustard gas more injurious and more volatile, it was mixed with carbon tetrachloride or chlorobenzene. Partial protection was afforded by rubber clothing and by bathing with permanganate. ' Two mustard gas works were under construction in Italy when the Armistice was proclaimed. NITRILES . 237 explodes. When its solution or aqueous emulsion is reduced with iron turnings and a little acetic acid (other acids are unsuitable), it is transformed into methylamine. With stannous chloride it gives cyanogen chloride, while when heated at 100 with aqueous ammonia it yields guanidine. NITROMETHANE, CH 3 N0 2 , is obtained from methyl iodide and silver nitrate or, better (but still in poor yield) by distilling an aqueous solution of potassium chloroacetate (1 part) and potassium nitrite (3 parts), the distillate being separated from the water, dried with lime and rectified. It forms an oil of ethereal odour and is denser than water, in which it is slightly soluble ; it bpils at 101 and burns with a pale flame. When reduced with iron and acetic acid it gives methylamine, while with HC1 at 150 it yields hydroxylamine and formic acid, and with hot, fuming sulphuric acid, carbon monoxide and hydroxylamine sulphate. One of its hydrogen atoms is readily replaceable by metals; with alcoholic potash solution it forms crystals of CH 2 K NO 2 + C 2 H 5 OH, the alcohol being expelled in a sulphuric acid desiccator. The mercury salt is explosive. It is a good solvent for smokeless powders and in the proportion of 10 per cent, lowers the freezing-point of nitroglycerine to 10. DINITROMETHANE, CH 2 (N0 2 ) 2 , forms yellow crystals exploding at 200. Its potassium salt, CHK(N0 2 ) 2 , is obtained when hydrogen sulphide is passed into an ammoniacal solution of potassium bromodinitromethane. TRINITROMETHANE (Nitroform), CH(N0 2 ) 3 , is obtained as ammonium salt when trinitroacetonitrile is heated with water : C(NO 2 ) 3 CN + 2H 2 = C0 2 + C(N0 2 ) 3 NH 4 . It forms white crystals, m.-pt. 15, and at 100 decomposes with explosion. It dissolves in water to a yellow solution and acts as a strong acid; on reduction with tin and hydrochloric acid it gives hydrocyanic acid. TETRANITROMETHANE, C(N0 2 ) 4 , obtained by heating nitroform with concen- trated sulphuric and fuming nitric acids, forms 'white crystals, m.-pt. 13, and boils unchanged at 126 ; it is insoluble in water, but dissolves in alcohol or ether. It is non- inflammable, has no acid reaction, and, mixed with petroleum, is used as an explosive of the Sprengel type (see Explosives). R. Schenck (Ger. Pat. 211,198, 1908) prepared tetranitromethane in various ways. NITROETHANE, C 2 H 5 -N0 2 , has m.-pt. 113, and nitropropane, m.-pt. 130. Dini- troethane has b.-pt. 185 to 186; trinitroethane, CH 3 -C(N0 2 ) 3 , m.-pt. 56, is obtained from methyl iodide and the silver salt of trinitromethane. Tetranitroethane is obtained as dipotassium derivative by treating bromopicrin with potassium cyanide; it is readily decomposed, even by cold dilute sulphuric acid. Hexanitroethane, C(N0 2 ) 3 ' C(N0 2 ) 3 , was prepared in 1914 by W. Will as an explosive by treating the pure potassium salt of tetranitroethane at a temperature of 3 to 5 with concentrated sulphuric acid and then with nitric-sulphuric acid, the mass being finally heated for ten minutes at 60 to 70, and then cooled and poured into water; when freed from acid it is obtained from ether in white crystals which have a slight camphor smell, melt at 142, and give a yellow solution in benzene or toluene; with afcoholic soda it gives tetrani- troethane, while under prolonged heating at 75 it forms yellow vapours. It is moderately resistant to shock and friction, and when mixed with hydrogenated organic compounds yields explosives of practical use although of limited stability. Various esters of hyponitrous, phosphoric, boric, silicic acids, etc., are known. DERIVATIVES OF HYDROCYANIC ACID A. NITRILES. B. ISONITRILES These compounds are formed by the substitution of the hydrogen of hydrocyanic acid by an alkyl radical, but they are not true esters, as they do not give the acid and alcohol again on hydrolysis. A. NITRILES (or Alkyl Cyanides), are either liquid or solid, and have a pleasant, faintly garlic-like, ethereal odour. They are lighter than water, in which the first terms are soluble without undergoing change. They boil at about the same temperatures as the corresponding alcohols. 238 ORGANIC CHEMISTRY PREPARATION. 1. They are obtained by distilling a potassium alkyl- sulphate with potassium cyanide or with anhydrous potassium ferrocyam'de, or by heating the cyanide at 180 with methyl iodide : CH 3 I + KCN = KI -f CH 3 CN (methyl cyanide or acetonitrile) . 2. Distillation of ammonium salts of monobasic acids yields amido- compounds which, with a dehydrating agent (P 2 5 , P 2 S 5 or PC1 5 ), give nitriles : (a) CH 3 ; COOH + NH 3 = H 2 + CH 3 CO NH 2 ; Acetic acid Acetamide (6) CH 3 CO NH 2 - H 2 = CH 3 CN. Acetonitri'.e or Methyl cyanide. 3. The higher nitriles are formed from the acid-amides containing one more carbon atom or from the primary amine containing the same number of carbon atoms, by treatment with sodium hydroxide and bromine ; or from the aldehydes which, with hydrocyanic acid, give the nitriles of higher acids, the so-called cyanohydrins or hydroxynitriles, liquid compounds easily saponified with regeneration of the aldehyde : ,0 /OH CH 3 Cf + HCN = CH 3 CH< X H X CN' Acetaldehyde Ethylidenecyanohydrin PROPERTIES. When boiled with alkali or acid, or treated with super- heated steam, nitriles give ammonia and an acid, from which products they may also be formed : (a) CH 3 CN -f H 2 O = CH 3 CO NH 2 (aeetamide) ; (6) CH 3 CO NH 2 + H 2 = CH 3 CO OH + NH 3 . This reaction is of importance for the synthesis of organic acids since, starting from a given alcohol and transforming it into iodide and then into nitrile, an acid of the saturated series containing an extra carbon atom is obtained. If the cyanide is treated with hydrogen sulphide instead of water, thiocetamide, CH 3 CS NH 2 , is obtained. With hydrochloric acid, the nitriles form chloramides or chlorimides, whilst with ammoniacal bases they give amidines (see later). Nascent hydrogen converts them into amines : CH 3 *CN + 2H 2 = CH 3 CH 2 NH 2 (ethylamine). By potassium or by gaseous hydrogen chloride the nitriles are polymerised. ACETONITRILE (or Methyl Cyanide), CH 3 . CN, is found among the products of the distillation of beetroot molasses and of tar. It is soluble in water and boils at 82. B. ISONITRILES (Isocyanides or Carbylamines) are colourless liquids which have a faint alkaline reaction and boil at rather lower temperatures than the corresponding nitriles. They are insoluble in water, but dissolve in alcohol or ether. They have repellent odours and are poisonous. They are obtained by the interaction of alkyl iodides with silver cyanide (whilst with potassium cyanide the nitriles are obtained) : C 2 H 5 I + AgCN = Agl + C 2 H 5 NO ; ' they are also formed by treating the primary amines with chloroform and alcoholic potash (see p. 120); also later under Amines). Although they are stable towards alkalis, the isonitriles are readily decom- posed by water, giving formic acid and the corresponding amino-base containing one carbon atom less than the isonitrile : CH 3 NC + 2H 2 = H-COOH + CH 3 NH 2 . AMINES 239 From the nitrites they are distinguished also by the different additive compounds which they form with halogens, hydrogen chloride, hydrogen sulphide, etc. At high temperatures certain isonitriles change into nitriles. CONSTITUTION OF THE NITRILES AND ISONITRILES. The nitriles have the carbon atom of the cyanogen group attached to the alkyl radicle and when they are hydro- lysed only the nitrogen is removed as ammonia. Acetonitrile would hence have the constitution, CH 3 C = N. The isonitriles, on the other hand, readily form amino-bases with loss of an atom of carbon that of the cyanogen group the nitrogen remaining with the radicle. Methyl isocyanide or methylcarbylamine would hence have the formula CH 3 N = C. IV. NITROGENATED BASIC ALKYL COMPOUNDS (AMINES) If one or more of the hydrogen atoms of the ammonia molecule is replaced by one or more alky] radicles, substances called Amines are formed; these have a basic character, which is in some cases more marked than that of ammonia itself (in the dissociation of compounds of the ammonia type, free anions, OH', are formed). They were discovered by Wurtz in 1848, and were studied systematically by A. W. Hofmann in 1850-1851. To ammonia they present other chemical analogies. They have disagreeable ammoniacal odours ; with mineral acids they form white, crystalline, deliquescent salts which are extremely soluble in water and have a basic nature, the nitrogen then becom- ing pentavalent ; for the first members of the series the electrical conductivity is very high, higher indeed than that of ammonia, since N/100 solutions are almost completely dissociated. . Like ammonia, they give, with platinum chloride, crystalline platini- chlorides, e. g., methylamine platinichloride, (NH 2 CH 3 , HCl) 2 PtCl 4 ; they also form double salts with gold chloride, NH 2 C 2 H 5 , HC1, AuCl 3 . They precipitate heavy metals from solutions of their salts, and, in excess, sometimes redis- solve them. The first terms are gases, after which come unpleasant smelling liquids soluble in water. The higher members are odourless and insoluble in, and lighter than, water ; they are soluble in alcohol and in ether. The ammonia derivatives are deliquescent solids, and in their behaviour greatly resemble potassium hydroxide, etc. According as they contain one or more alkyl radicals, these bases are called primary or aminic, secondary or iminic, tertiary or nitrilic, quaternary or ammoniacal. PROCESSES OF FORMATION, (a) By heating an alkyl halogen com- pound with ammonia : (1) NH 3 + C n H 2n+1 I = HI + aH 2B+1 NH 2 ; the halogen hydracid formed unites with the ammonia and with the amine, converting these partly into the corresponding salts ; distillation with potassium hydroxide then gives : KI -f H 2 + the free base, C n H 2n + 1 NH 2 . The latter, which is partly free before treatment with potash, may in its turn react with a second molecule of the alkyl halogen compound, giving a secondary amine ; (2) C n H 2n+1 -NH 2 + C B H 2B+1 I = (C n H 2B+1 ) 2 NH, HI; the free base, which may be liberated by distilling with KOH, reacts with a third molecule of the alkyl halogen compound, yielding a tertiary amine ; (3) (C n H 2n+1 ) 2 NH + C n H 2n + 1 I=(C B H 2n+1 ) 3 N, HI. Finally, the tertiary base, which remains free or may be liberated, reacts with a fourth molecule of the halogen derivative, giving the salt of the quaternary base ; (4) (C n H 2n + 1 ) 3 N + C B H 2B + 1 I = (C B H 2n+1 ) 4 NI, which is no longer a crystal- line ammonia base and is not decomposed by potassium hydroxide, being more energetic than the latter; the hydrogen iodide formed unites with the amines if such are still present. When heated, the iodide of the quaternary base is converted back into the tertiary base and alkyl iodide, whilst with 240 ORGANIC CHEMISTRY silver hydroxide it gives the corresponding solid alkylammonium hydroxide. In this general reaction, the four bases are always formed together, although more of one or another is obtained according to the nature of the alkyl group, the temperature, the duration of the reaction, and the quantity of ammonia present. The separation of the bases in this mixture is not easy, and when these are present as salts, distillation with potassium hydroxide yields the primary, secondary, and tertiary amines, whilst the quaternary ammonium compound remains unchanged. The three bases or the corresponding salts are separated partly by crystallisation or by fractional distillation, or, better, by means of ethyl oxalate, C 2 2 (C 2 H 5 0) 2 , which gives solid or liquid oxamides [e. g., solid dimethyloxamide, C 2 2 (NH' CH 3 ) 2 and the ethyl ester of dimethyloxaminic acid, C 2 H 2 (OC 2 H 5 ) N(CH 3 ) 2 , which boils at 243 and is soluble in water, alcohol or ether]. Amines may also be prepared by the following reactions : (6) By the action of potassium hydroxide on alkyl isocyanates, e. g., ethyl isocyanate, C 2 H 5 NCO + 2KOH = K 2 C0 3 + C 2 H 5 NH 2 ; (c) By reducing nitro-compounds, nitrites, oximes, or hydrazones with nascent hydrogen. (d) Primary amines may be obtained by heating the ethylnaphthylamines with caustic soda, and secondary amines in the same way from nitrosodialkyl- anilines. PROPERTIES. The amines do not undergo hydrolysis and are resistant to the action of acids, alkalis, and, to some extent, oxidising agents. The hydrogen combined with the nitrogen of amines may be replaced not only by alkyl groups (see above], but also by acid radicals (e. g., by acetyl, CH 3 - CO') and mixed amines with alkyl and acidic groups may also be obtained. A characteristic and sensitive reaction of the primary .amines is that with chloroform in presence of alkali, which gives rise to the unpleasant-smelling isonitriles : CHC1 3 + CH 3 NH 2 + 3KOH = CH 3 NC + 3KC1 + 3H 2 0. In alcoholic solution the primary and secondary bases form, with carbon disulphide, derivatives of thiocarbaminic acid, and only when these are derived from the primary bases can isothiocyanates be obtained. It is easier to distinguish (and separate) primary, secondary, and tertiary amines by their reactions with nitrous acid. When a hydrochloric acid solution of the mixture is treated with a concentrated solution of sodium nitrite, the primary amine yields the corresponding alcohol (soluble in water), with evolution of nitrogen : C n H 2n+1 NH 2 + NOOH = H 2 + N 2 + C n H 2n+1 OH. The Secondary amines give oily nitrosamines, almost insoluble in water : (C B H 2n+1 ) 2 NH + NOOH = H 2 + (C n H 2n+1 ) 2 N NO ; with feeble reducing agents, the nitrosamine is transformed into a hydrazine, whilst with more energetic reducing agents or with concentrated hydrochloric acid the secondary amine is regenerated, showing that the nitrous residue NO is joined to the iminic nitrogen and not to the carbon. The tertiary amine does not react with nitrous acid and is hence left unchanged in the solution, from which it may be obtained by distillation in presence of caustic soda. Finally, the three classes of amines may be distinguished by the quantities of methyl iodide with which they react to produce the final quaternary base (see preceding page), with generation of greater or less quantities of ionisable compounds (titratable HI). METHYLAMINE, CH 3 . NH 2 , is found ready formed in certain plants, e. g., in the dog- mercury weed (Mercurialis perennis). It is formed in the distillation of wood and occurs in beetroot and bone residues and in herring brine. It is prepared from methyl chloride and ammonia, the resulting hydrochloride being separated from the ammonium chloride AMINES 241 by dissolving the former in a little water (the ammonium chloride is less soluble), filtering by suction and crystallising the filtrate with the help of ammonia ; the secondary amine formed at the same time is separated as nitroso-deiivative, which with concentrated hydrochloric acid regenerates the base. Plochl prepares methylamine by heating a mixture of -formaldehyde with one-half of its weight of ammonium chloride. It is a gas like ammonia (but, unlike this, burns in the air) and precipitates various metallic salts, but, when added in excess, does not dissolve nickel and cobalt hydroxides ; it is more highly basic and more soluble in water (1 vol. dissolves 1150 vols. at 12-5 and 959 vols. at 25) than ammonia, and has a strong odour of ammonia and rotten fish. It becomes liquid at 7 and at 11 has the sp. gr. -0699. It is formed by the action of NaOH and Br on acetamide, and also by the reduction of chloropicrin (see p. 236). Its hydrochloride, CH 3 -NH 2 ,HC1, m.-pt. 225, is a crystalline, deliquescent substance extremely soluble in alcohol. With aluminium sulphate its sulphate forms an alum containing 24H 2 0. DIMETHYLAMINE, (CH 3 ) 2 NH, is a liquid boiling at + 7, and is formed, together with acetic acid, in the distillation of wood. TRIMETHYLAMINE, (CH 3 ) 3 N, is a gas which liquefies at+ 3, and has an intense odour of rotten fish. It is found in various plants (Arnica montana, shoots of the pear- tree, etc. ), and in herring brine. It is formed by the decomposition of betaine during the distillation of beetroot molasses (p. 117). ETHYLAMINE, C 2 H 5 NH 2 , may be prepared as follows : 30 parts of ethyl alcohol are saturated in the cold with ammonia and the liquid heated in an autoclave at about 55 with 8 parts of liquid ammonia and 10 parts of ethyl chloride. When the vigorous phase of the reaction is at an end, the water-bath surrounding the autoclave is brought to boiling; which is maintained for four to five hours. After cooling, the excess of ammonia is allowed to escape and is used to saturate the alcohol for a succeeding operation. The residue in the autoclave is neutralised with hydrochloric or sulphuric acid and the salts separating on concentration filtered off by suction, dried and extracted with alcohol (which does not dissolve the mineral salts). After evaporation of the alcohol, the mixed bases are liberated by means of alkali and are fractionated in a column 4 metres in height. The bulk of the product is diethylamine, the ethylamine remaining in solution at a concentration of 15 to 20 per cent. DIETHYLAMINE (and, similarly, dimethylamine) is now often prepared by decom- posing paranitrosodiethylanil'ne (as hydrochloride) with boiling 5 per cent, caustic soda solution (in the proportion of 1 : 20), the base distilling over being dissolved in hydrochloric acid. The yield is almost theoretical, and the paranitrosophenol remaining in the yellow solution may be used for making para-aminophenol. ETHYLAMINE is a liquid, b.-pt. + 19, and smells strongly of ammonia, which it surpasses in basicity. It dissolves very readily in water with generation of heat. It dissolves aluminium hydroxide (like methylamine, but unlike ammonia) and to a small extent cupric hydroxide, but not ferric or cadmium hydroxide. DIETHYLAMINE, (C 2 H 5 ) 2 NH, is a liquid, b.-pt. 56, and does not dissolve zinc hydroxide. TRIETHYLAMINE, (C 2 H 5 ) 3 N, is an oily liquid which precipitates metals from their salts, but does not redissolve the precipitates. It has a strongly alkaline reaction and boils at 89. It is extremely soluble in cold water, but above 20 it becomes completely insoluble, separating from the water in an oily layer. A group of nitrogen compounds which may be considered as formed by the condensa- tion of ammonia (hydrazine, azoimide, Tiydroxylamine, etc.) has been already mentioned in Vol. I., p. 376. The alkyl derivatives of hydroxylamine, NH 2 OH, are divided into two groups : a-alkylhydroxylamines, in which the alkyl replaces the hydroxylic hydrogen, NH.yOR, and which hence have an ether character and do not reduce Fehling's solution; and (3-alkylhydroxylamines, in which the alkyl radical replaces an amino-hydrogen and is therefore joined to the nitrogen, R NH OH ; these reduce Fehling's solution even in the cold and on energetic reduction yield primary amines. Also the Alkylhydrazines, RNH NH 2 , R 2 N NH 2 , etc., unlike amines, reduce Fehling's solution in the cold and give characteristic reactions with aldehydes and ketones. The Diazo-compounds of the methane series are of slight importance, whilst those of the aromatic series are a very important class of compounds; the former differ from the la'.ter VOL. II. 16 242 ORGANIC CHEMISTRY in that the characteristic divalent nitrogen group, N = N , has its valencies saturated by only one carbon atom. They may be obtained by diazotising, by means of nitrous acid, aliphatic amines with the amino-group united to a carbon atom, the other valencies of which are saturated by a carbonyl (CO) or cyanogen group and by at least one hydrogen atom. Diazomethane, CH 2 N 2 , which is a yellow, odourless, poisonous gas, is prepared from hydroxylamine and dichloromethylamine, or by the action of an alkali on nitrosomethyl- urethane, CH 3 - N(NO) CO OC 2 H 5 . Oxidation of aromatic hydrazones (see p. 246; also Monoses) yields diphenyldiazomethane and similar compounds. V. PHOSPHINES, ARSINES, AND ALKYL METALLIC COMPOUNDS Like ammonia, the hydrogen derivatives of phosphorus, arsenic, antimony, etc., give rise to alkyl compounds which have very feebly basic characters and very unpleasant odours. 1. PHOSPHINES. These are gases or colourless liquids with repulsive odours. Their basic properties and their stability towards water become more marked as the number of alkyl groups increases. They are readily oxidisable with nitric acid, the remaining hydrogen atoms of the PH 3 being transformed into hydroxyl groups. The quaternary phosphonium bases are very strongly basic, and, unlike the corresponding ammonium bases, they lose an alkyl group in the form of a saturated hydrocarbon when heated, the residue being a trialkylphosphonium oxide. C n H 2rt+1 PH 2 (C n H 2B+1 ) 2 PH (C B H 2n+1 ) 3 P (C n H 2n+1 ) 4 P-OH Primary phosphine Secondary phosphine Tertiary phosphine Tetralkylphosphonium hydroxide C n H 2n+1 PO(OH) 2 (C n H 2rt+1 ) 2 PO-OH (C n H 2n + 1 ) 3 PO Alkylphosphonic acid Dialkylphosphonic acid Trialkylphosphine oxide The primary and secondary phosphines are formed by heating phosphonium iodide with alkyl iodides and zinc oxide, whilst the tertiary phosphines and phosphonium derivatives are obtained from hydrogen phosphide, PH 3 , and alkyl halogen compounds. 2. ARSINES. Well-known primary and secondary compounds are : methylarsenic dichloride, CH 3 AsCl 2 (liquid, b.-pt. 135); dimethylarsenic chloride, (CH 3 ) 2 AsCl (b.-pt. 100); dimethylarsine, (CH 3 ) 2 AsH (b.-pt. 36); dimethylarsenic acid or cacodylic acid, (CH 3 ) 2 AsO OH, etc. The tertiary arsines are obtained by the action of sodium arsenide, AsNa 3 , on alkyl iddides : 3C 2 H 5 I + AsNa 3 = 3NaI + As(C 2 H 5 ) 3 ; they are liquids slightly soluble in water, with which they do not form bases. The quaternary arsonium compounds, e. g., (CH 3 ) 4 AsI (tetramethylarsonium iodide ), obtained from the tertiary arsines and alkyl iodides, are, however, very energetic and are able to give, with moist silver oxide, tetramethylarsonium hydroxide. The derivatives of cacodyl [(CH^s - As(CH 3 ) 2 ] were studied by Bunsen (1837-1843), who obtained cacodyl oxide, (CH 3 ) 2 As-0-As(CH 3 ) 2 , by distilling arsenic trioxide with potassium acetate (this reaction serves as a delicate test for acetates in mixtures) : As 2 3 + 4CH 3 COOK = 2C0 2 + 2K 2 C0 3 + [As(CH 3 ) 2 ] 2 0. With hydrochloric acid, cacodyl oxide gives cacodyl chloride, (CHg^sCl. Many of these cacodyl compounds are liquids which ignite in the air and have nauseating odours ; the cacodyl behaves like a true electro-positive element. 3. Various alkyl derivatives are known of antimony (stibines), boron, silicon, bismuth, tin, etc., but these are of little pract'cal importance. 4. ALKYLMETALLIC (Organometallic) DERIVATIVES. These are ob- tained from various metallic chlorides or from the metals themselves (Zn, Hg, Mg, Al, etc.) by the action of halogen derivatives of the hydrocarbons. GRIGNARD'S REACTION 243 They are generally colourless liquids with low boiling-points, and some of them are violently decomposed by water and ignite in the air. Of importance for many organic syntheses are the zinc-alkyls (see pp. 33, 125). ZINC METHYL : Zn(CH 3 ) 2 , is a colourless, highly refractive liquid, sp. gr. 1'39, b.-pt. 46, and has an intense, repulsive odour; it ignites in the air, forming zinc oxide, and with water gives methane and zinc hydroxide. It is formed in two phases, as follows, and is separated by distillation : (a) CH 3 I -f- Zn = Zn(CH 3 )I (zinc methyl iodide, solid); (b) 2Zn(CH 3 )I = Znl -f Zn(CH 3 ) 2 . GRI GN ARD ' S REACTION. Mention has already been made of the use of this reaction in synthesising the saturated hydrocarbons (p. 33). One molecule of a monohalogenated (Br or I) compound, in presence of absolute ether, combines with an atom of magnesium : Mg -f- C 2 H 5 Br = C 2 H 5 MgBr (ethyl magnesium bromide), and with compounds containing several carbon atoms there is always formed, as a secondary product, a saturated hydro- carbon. The ether probably takes part in the reaction, forming an intermediate product, C 2 H 5 -Mg.Br[(C 2 H 5 ) 2 0]. The latter, and also the alkyl magnesium halogen^ compounds, when dissolved in ether, are highly reactive and form additive compounds with aldehydes, ketones, and even esters of mono- and poly-basic carboxylic acids; with water these additive compounds then give the corresponding secondary and tertiary alcohols, the reaction occurring in the following two phases (R = alkyl) : /O Mgl R CHO + R'Mgl = R C^-R' -> -f H 2 = I Mg OH + R CH(OH) R Aldehyde Alkyl mag- \H Secondary nesium iodide alcohol /OMg Br H.COOC 2 H 5 +C 2 H 5 MgBr=C 2 H 5 -C^H -> +C 2 H 6 -MgBr = Ethyl formate OCoHc /OMgBr Br Mg OC 2 H 5 + C 2 H 5 C^-H -* + H 2 = BrMgOH + C,H 6 CH(OH) C 2 H 5 ^C 2 H 5 Diethylcarbinol If esters of other monobasic acids are used instead of a formic ester, tertiary alcohols are obtained, whilst esters of dibasic acids give dihydric alcohols. Hence, by means of the Grignard reaction, the carboxylic oxygen of any acid (starting from the corresponding ester) is ultimately replaced by two alkyl residues. Similar behaviour is shown by acid chlorides and anhydrides, which also contain carbonylic oxygen ( CO ). With nitriles, ketonimides and ketones are obtained : , R-CN+R'M g I=R-C( -> +H 2 = \R' IMgOH + R C( : NH) R' -> + H 2 = NH 3 + R-CO R' (ketone). Further, with dry C0 2 , alkyl magnesium compounds give organic acids : R'Mgl + C0 2 = R' COOMg I -> + HX = IMgX + R' COOH (acid). Other most varied organic syntheses have been rendered possible of late years by the Grignard reaction. VI. ALDEHYDES AND KETONES : C n H 2n O The elimination of two atoms of hydrogen by means of an oxidising agent (e. g., potassium dichromate and dilute sulphuric acid, or sometimes even the oxygen of the air) from a primary or secondary alcohol yields an aldehyde or a ketone : R CH 2 OH + O = H 2 + R CHO (aldehyde), or R CH(OH)R / + = H 2 + R CO R' (ketone). 244 ORGANIC CHEMISTRY The aldehydes have a strong reducing action, as they fix oxygen and become converted into acids with fhe same numbers of carbon atoms, whilst the ketones resist oxidising agents, and, if these are very energetic, are oxidised to acids containing fewer carbon atoms than the original ketones. (a) ALDEHYDES The first members of this series are neutral liquids with pronounced and often disagreeable odours (formaldehyde is a gas) and are soluble in water, whilst the higher ones gradually become solid and insoluble. Their boiling- points are much lower than those of the corresponding alcohols. The aldehydes are formed when a calcium or barium salt (or even two salts) of a monobasic organic acid is dry distilled with calcium or barium formate (reducing agent) : (R COO) 2 Ca + (H'COO) 2 Ca = 2CaC0 3 + 2R CHO. , They are also obtained on heating with water compounds containing two halogen atoms united to the same carbon atom : CH 3 CHC1 2 (ethylidene chloride-) + H 2 = 2HC1 + CH 3 CHO. The constitution of the aldehydes may be deduced from their methods of 7 formation (e. g., the latter) and the characteristic aldehyde group is C\ X H PROPERTIES. They are substances of considerable and varied reac- tivity. With oxidising agents they are transformed into acids, and this reducing property is readily manifested in their reduction of ammoniacal silver nitrate solution (22 per cent, ammonia solution and 10 per cent, of dilute silver nitrate diluted with its own volume of 10 per cent, sodium hydroxide solution ; or 1 gram of silver nitrate dissolved in 30 c.c. of water and dilute ammonia added as long as no precipitate forms) or of Fehling's solution (the latter, however, is not reduced by aldehydes containing as many as 8 or 9 carbon atoms). In their turn, the aldehydes are reconverted into the primary alcohols when reduced with nascent hydrogen; with PC1 5 , they give ethylidene chlorides again. Hydrocyanic acid, ammonia, sodium hydrogen sulphite, and sometimes alcohol and acetic anhydride (also the alkyl magnesium halogen compounds : see above, Grignard's Reaction) form characteristic additive products with the aldehydes : CH 3 CHO + 2C 2 H 5 OH (+ a little HC1) = H 2 + CH 3 CH(OC 2 H 5 ) 2 (acetal) which is an ether of the hypothetical glycol (dihydric alcohol), CH 3 CH(OH) 2 ; the latter, however, does not exist in the free state, since two hydroxyl groups cannot remain joined to one and the same carbon atom, excepting in the case of chloral hydrate (see later} and a very few other substances. 1 They combine with sodium and ammonium bisulphites (very concentrated solutions) forming crystalline bisulphite compounds soluble in water and slightly so in alcohol : ,0 .OH C X C 2 H 5 CC + S0 3 HNa = C 2 H 5 C^O S0 2 Na, H and these compounds, when heated with dilute acid or with alkali (even Na 2 C0 3 ), liberate the aldehyde again. This reaction hence renders possible the separation of aldehydes from other substances. 1 See Table on opposite page. ALDOL CONDENSATION 245 The aldehydes combine with ammonia, forming crystalline aldehyde- ammonias soluble in water and slightly so in alcohol but insoluble in ether, for example, CH 3 CH(OH)(NH2), which gives the aldehyde again when heated with a dilute acid. But formaldehyde, with ammonia, readily forms poly- merised derivatives, e. g., hexamethylenetetramine, (CH 2 ) 6 N 4 (see later). With hydrocyanic acid they form cyanohydrins (p. 238). An interesting change is the aldol condensation, that is, the condensation of 2 mols. of an aldehyde brought about by prolonged heating with dilute mineral acids, dilute alkalis, or even aqueous solutions of sodium acetate Possibly a molecule of water is first added to one of the aldehydes : CH 3 C H H 2 = GH 3 CH OH OH this hypothetical hydrate then condensing with another molecule of aldehyde, with separation of water and formation of a hydro xyaldehyde (aldol) : /"\TT /~V /~\ CH 3 -CH/ +CH 3 -C/ =H 2 + CH 3 -CH(OH)-CH 2 -C^ \rm- \ H \ H (ft -Tiydroxybutyr aldehyde). These aldols in their turn readily lose a molecule of water, forming an unsaturated aldehyde, which may also be obtained directly (aldehyde condensation) by heating the original aldehyde with a dehydrating agent such as zinc chloride : CH 3 C\^ H X H // CH 3 -CH:CH-Cf H The aldehydes, especially form-, acet-, and prop-aldehydes, etc., exhibit a tendency to polymerise, in the mere presence of a little hydrochloric or sulphuric acid, sulphur dioxide, zinc chloride, etc. Acetaldehyde, for example, gives DERIVATIVES OF ACETALS Name Formula Boiling-point Specific gravity ALKYL DERIVATIVES Methylal . CH 2 (OCH 3 ) 2 41-3-41-7( 749-8 mm.) 0-862 (18) Diethylmethylal . CH 2 (OC 2 H 5 ) 2 87 0-834 (20) Dipropylmethylal CH 2 (OC 3 H 7 ) 2 136 0-834 (20) Diisopropylmethylal Diisobutylmethylal CH 2 (OC 3 H 7 ) 2 CH 2 (OC 4 H 9 ), 118 164 0-831(20) 0-824 (20) Diisoamylmethylal CH 2 (OC 5 H U )" 2 + H 2 206 0-835 (20) Dihexylmethylal CH 2 (OC 6 H 13 ) 2 174- 175 0-822 (15) Dioctylacetal CH 3 -CH(OC 8 H 17 ) 2 289 0-848 ( 15) Dimethylacetal CH 3 -CH(OCH 3 ), 63 0-865(22) Diethylacetal CH 3 -CH(OC 2 H 5 )" 2 102-9 0-831(20) Dipropylacetal CH 3 -CH(OC 3 H.) 2 147 0-825 (22) Diisobutylacetal CH 3 -CH(OC 4 Ho)., 170 0-816 (22) Diisoamy la cetal CH 3 -CH(OC 5 H n )" 2 211 0-835 ( 15) ACID DERIVATIVES Methylenediacetate CH 2 (0- CO- CH 3 ) 2 170 . Ethylenodiacetate CH 3 - CH(0- CO- CH 3 ) 2 169 1-073 ( 15) Ethylenedipropionate CH 3 -CH(0-CO-0 2 H 5 ) 2 192 1-020(15) Ethylenedi tm ty ra te CH 3 -CH(0-CO- C,H 7 ), 215 0-985 (15) Ethylenediisovalerate * CH 3 - CH(0-CO- C,,H 9 )" 2 225 0-947 (15) 246 ORGANIC CHEMISTRY two isomerides : paraldehyde, m.-pt. 10, b.-pt. 124, and metaldehyde, which sublimes at 100 : /)-CH(CH 3 ) x 3C 2 H 4 O = CH 3 CH< 0. These no longer react with ammonia, sodium bisulphite, silver nitrate, and hydroxylamine, but they yield the aldehyde again when distilled in presence of a small quantity of dilute sulphuric acid. With alkalis, even dilute alkalis, many aldehydes, especially the more simple ones of the fatty series, resinify, whilst some give rise to an alcohol and an acid : S 2HC\ (formaldehyde) + H 2 O = CH 3 OH + H C0 2 H (formic acid). X H With halogens the aldehydes give substitution products, and with hydrogen sulphide various complex products (ihioaldehydes, etc.) with characteristic odours. With hydroxylamine, aldehydes form aldoximes, which are resolved into their components when boiled with acids, and yield nitriles when treated with dehydrating agents : CH 3 CHO + NH 2 OH = H 2 + CH 3 CH : N OH. A similar action is exhibited by the hydrazines (as hydrochloride or acetate in acetic acid solution containing sodium acetate ; the most suitable is phenyl- hydrazine), which give characteristic, stable, and often crystalline compounds, termed hydrazones : CH 3 CHO + C 2 H 5 NH NH 2 (ethylhydrazine) = H 2 -f- CH 3 CH : N'NH C 2 H 5 (acetaldehyde ethylhydrazone) ; by nascent hydrogen (4H) this is converted into 2 mols. of primary amine : 2CH 3 CH 2 NH 2 . With oxidising agents the phenylhydrazone gives diphenyldiazomethane, (C 6 H 5 ) 2 C:N 2 . Characteristic of the aldehydes is also the formation of crystalline semicar- bazones by the action of the hydrochloride of semicarbazide, NH 2 CO NH NH 2 (obtained by the interaction of potassium cyanate and hydrazine hydrate) : B ' CHO + NH 2 CO NH NH 2 = H 2 + B CH : N NH CO NH 2 . Both the hydrazones and semicarbazones serve for the separation of the aldehydes from other substances and for their quantitative determination. From aqueous liquids aldehydes are separated by means of metanitrobenz- hydrazide, with which they form insoluble condensation products. A gaseous mixture containing as little as 0*5 mgrm. of formaldehyde per 100 c.c. precipitates grey, metallic mercury in the cold when passed through Federer's mercuric solution. Finally a characteristic qualitative reaction which is given generally by the aldehydes and is very sensitive is that of Schiff. It consists in shaking the liquid to be tested with a solution (0'02 per cent.) of fuchsine previously decolorised by a current of sulphur dioxide. Traces of an aldehyde produce a reddish-violet coloration (it is uncertain if pure ketones also give this reaction). Another reaction characteristic of the aldehydes and not given by ketones is that with benzosulphinehydroxamic acid or with nitrohydroxylaminic acid, OH NO : N ' OH, which forms hydroxamic acids, R Csf , the latter X producing a cherry-red coloration with ferric chloride. FORMALDEHYDE 247 FORMALDEHYDE (or Methanal), H'CHO, was discovered by A. W. Hofmann in 1868 by passing air saturated with methyl alcohol vapour over a red-hot platinum spiral. Kekule obtained it pure in 1892. If it occurs out of contact with air, the oxidation of methyl alcohol in presence of the catalyst is endothermic : CH 3 OH = CH 2 O + H 2 28 Cals. ; as a secondary reaction part of the aldehyde may decompose with formation of CO and H 2 and development of 3'6 Cals. On the large scale it is hence neces- sary to prolong the heating so as to maintain the most suitable temperature for the copper catalyst (500 to 600), which rapidly loses its activity under such conditions. In presence of oxygen (theoretically 200 litres of air measured at 15 per 100 grams of methyl alcohol), however, the reaction is exothermic, but the reaction, CHg OH + O = CH 2 + H 2 O + 30'2 Cals., which should be the primary reaction, is not verified. It seems rather that the copper catalyst gives an oxide, which with the carbon monoxide and hydrogen formed (according to the first equation) would regenerate the copper with formation of H 2 O and CO 2 and generation of sufficient heat to cause the reaction, once started, to proceed without further heating. Formaldehyde is a gas which irritates the eyes and liquefies at 21 to a mobile, colourless liquid having the sp. gr. 0'8153~(or 0'9172 at 80) and solidifying at 92. It is very soluble in alcohol or water (52'5 per cent.), and is placed on the market in the form of 40 per cent, (by vol. or 36 per cent, by weight) aqueous solution 1 under the name of formalin or farmol; this aqueous solution gradually undergoes change (it lasts at most six months), so that the commercial product often contains 12 to 15 per cent, of methyl alcohol, this being added to prevent separation of polymerised compounds (see later). The heat of formation of the gaseous aldehyde is 25 Cals., the heat of solution in water being 15 Cals. 1 The concentrations of commercial aqueous solutions of formaldehyde may be deduced from the specific gravities by means of the following table (Auerbach, 1905) : 18 p.gr.at'J 1-0064 1-0090 1-0126 1-0172 1-0218 1-0311 1-0410 1-0568 1-0719 1-0853 1-1057 1-1158 Grams of CH 2 9 in 100 c.c. of solution 2-24 3-50 4- 60 6-51 8-37 11-08 14-15 19-89 25-44 30-17 37-72 41-87 Grams of OH 2 O in 100 grams of solution 2-23 * 3-45 4-60 6-30 8-0 10-74 13-59 18-82 23-73 27-80 34-11 37-53 If the aldehyde is pure and leaves no residue, the percentage by volume, if greater than 23, should be increased by about 5. The analysis of commercial formalin is based on the following reaction of Blank and Finken- beiner : 2CH 2 + 2NaOH + H 2 2 = H 2 + 2H 2 + 2H C0 2 Na. Three grams of the formal- dehyde solution is poured into a long-necked flask containing 25 c.c. of 2N-caustic soda solution (free from carbonates), the liauid being mixed and 50 c.c. of hydrogen peroxide solution (neutral- ised or of known acidity ) carefully added, 3 minutes being taken to make this addition. After seven to eight minutes, the excess of alkali remaining is titrated with 2N-sulphuric acid. With every cubic centimetre of the 2N-alkali that has reacted corresponds 0-06 gram of formaldehyde. Litmus purified several times with alcohol should be used as indicator. The estimation of the aldehyde may also be carried out with ammonia (see succeeding Note ). Brautigam (1910) suggested the determination of formaldehyde by adding to it excess of clear calcium hypochlorite solution. After a time the solution deposits calcium carbonate, which is filtered, washed, and weighed ; 1 mol. of CaC0 3 corresponds with 1 mol. of formaldehyde. To determine the methyl alcohol which may be present, 5 c.c. of the solution, diluted with 100 c.c. of water, is distilled with an excess of ammonia (about 10 c.c. of concentrated ammonia), 50 c.c. of the distillate being collected in a 100 c.c. flask and made up to volume with water. The methyl alcohol in 5 c.c. of this solution, which contains only negligible traces of formaldehyde, is determined by the iodine method (see p. 129). 248 A question which has been under discussion for many years is the possible formation of formaldehyde as the first product in the natural synthesis of carbohydrates (see Sugar) in the leaves of plants, from carbon dioxide under the influence of chlorophyll. Numerous sensitive reagents have been employed to detect microscopically the tran- sitory formation of formaldehyde in living leaves, but almost all these reagents are poisonous to plants and no decisive results have been obtained, even those of Pollacci (1907), who distilled the leaves with water and tested for formaldehyde in the distillate, being doubtful. Schryver (1910) has succeeded in establishing the formation of aldehyde in green plants in sunlight, by making use of a very sensitive reagent (detecting 1 part of aldehyde per million) consisting of a solution of phenylhydrazine, potassium ferricyanide, and hydrochloric acid; this reagent gives a red coloration with formaldehyde or with the methylene derivative which chlorophyll would form with the aldehyde. Angelico and Catalano (1913) have demonstrated the presence of formaldehyde in the juices of green plants by means of a very sensitive reagent, atractylin, which is the active component of the glucoside of Atractylis gummifera. Treatment of a trace of atractylin with two or three drops of concentrated sulphuric acid yields a yellow coloration, which changes to violet and then to blue on addition of a drop of a very dilute solution of formaldehyde; this reaction appears to be specific for formaldehyde. PROPERTIES. Formaldehyde polymerises to a white buttery mass of paraformalde- Tiyde, 6CH 2 + H 2 O, which is also formed in soft flocks when the aqueous aldehyde is evaporated. Paraformaldehyde dissolves in hot water and then shows all the properties of a solution of formaldehyde. Treatment of formaldehyde solution with concentrated sulphuric acid results in the separation of a white crystalline mass of polyoxymethylene (improperly termed trioxymethylene), of which four modifications (a, ft y and 8 oxymethylenes) are known; these are insoluble in alcohol or ether, have m.-pts. 165 to 172, and behave like formaldehyde when heated or in aqueous solution. True a-trioxy- methylene, produced under definite conditions (e. g., with a trace of sulphuric acid) from formaldehyde vapour in the hot, forms white, pliable, acicular, highly refractive crystals, m.-pt. 63, which sublime readily and are soluble in water, alcohol, or ether; its true constitution is CH 2 CH 2 . O CH 2 O These different solid polymerides of formaldehyde yield vapour of the latter when heated, and hence serve as convenient and portable disinfectants (as pastilles), being sold under various trade names (triformol, paraformol, etc.). With ammonia formaldehyde gives, not an aldehyde-ammonia, but hexamethylene- tetramine (urotropine), 1 C 6 H 12 N 4 , which is crystalline and of feebly monobasic character; this compound is used as an antifermentative to preserve milk and to fix the excess of sulphurous acid in wine (see note, p. 1 87 ), and medicinally as a solvent for uric acid in the treatment of uric arthritis. With hot, dilute caustic sodsu solution the aldehyde does not resinify, but gives methyl alcohol and formic acid (see above); with the concentrated alkali it yields only formic acid and nascent hydrogen, and in these conditions exerts a strong reducing action and separates Ag, Au and Hg from their salts. Formaldehyde is one of the most active substances chemically and lends itself to many varied organic syntheses. Under the action of minimal proportions of certain alkalies, e. g., lime water, it undergoes condensation to glycollic aldehyde, OH CH 2 CHO, and then to formose, C 6 H 12 6 , the principal component of which is a-acrose or inactive fructose. 1 This reaction was proposed by L. Legler in 1883 as a means of estimating formaldehyde in commercial solutions: 6CH 2 + 4NH 3 = (CH 2 ) 6 N 4 + 6H 2 ; the reaction is, however, slow and the method not very accurate. F. Hermann (191 1 ) has rendered it more rapid and exact in the following manner. Four cubic centimetres of the formalin is weighed into a 150 c.c. flask with a ground stopper, and about 3 grams of pure powdered ammonium chloride and exactly 25 c.c. of 2N-caustic soda (equivalent to 50 c.c. of normal soda) added. The flask is stoppered, and shaken, and, when the mass is cool, 50 c.c. of water and 4 drops of 1 per cent, methyl orange are added and the excess of alkali titrated with normal sulphuric acid. Deduction of the volume of acid required from 50 c.c. gives the volume of soda used in liberating, from the ammonium chloride, a corresponding amount of nascent ammonia, which instantly transforms the aldehyde into hexamethylenetetramine. The latter is, however, monobasic and reacts with part of the sulphuric acid, and, in order to obtain the number of grams of formaldehyde in the quantity of formalin taken, the number of cubic centimetres of soda arrived at above must be multiplied by the factor 0-06. If the formalin be acid initially, the acidity must be determined separately by titration with soda in presence of phenolphthalein and the 50 c.c. of soda increased accordingly. MANUFACTURE OF FORMALDEHYDE 249 With bisulphite solution and zinc dust it yields hydrosulphite compounds (see Vol. I., p. 586). A characteristic and very sensitive reaction of formaldehyde is that proposed by Rimini, according to whom a mixture of phenylhydrazine hydrochloride, sodium nitro- prusside, and caustic soda is coloured blue even by minimal traces of the aldehyde. Formaldehyde gives Schiffs reaction (see above) even in presence of a certain amount of sulphuric acid, whilst acetaldehyde does not. MANUFACTURE. In 1886 O. Loew replaced the platinum used as catalyst by copper, the yield of aldehyde thus obtained being 31 per cent, of the theoretical yield. In 1908 Orloff devised a large-scale plant in which rectifying columns were used, igniters composed of heaps of platinised asbestos taking the place of the initial heating. Platinum being excluded on account of its high price and iron owing to its low yield, either silver gauze or asbestos impregnated with silver was used as catalyst, the yield being almost theoretical (Ger. Pat. 228,697; U.S. Pats. 1,067,668 and 1,100,076). The most suitable temperature for the formation of the aldehyde is about 450, decomposition into CO and H 2 occurring if this is surpassed. The catalytic layer should not exceed a certain thickness. The methyl alcohol is used at a concentration of 90 per cent., but 98 per cent. is better, provided that not more than 1 per cent, of acetone is present. In order to obtain the proper proportion between alcohol and air (1 part of alcohol and 0-36 part of oxygen), the latter is passed through alcohol heated to about 52 ; about 35 per cent, of the alcohol FIG. 181. should distil unchanged, whilst 65 to 70 per cent, is transformed into aldehydes. An apparatus designed by Orloff and modified by F. H. Meyer is shown in Fig. 181. The vessel 2 contains a supply of air furnished by the compressor 1, this passing gradually into the saturator 4, where it meets a spray of alcohol from the tank 3. By means of steam coils the saturator is kept at 52, the air, saturated with alcohol vapour, at this temperature proceeding to the catalysing chamber 5, in which the alcohol is partially oxidised to aldehyde. The mixture of aldehyde, alcohol, nitrogen and water vapour from 5 enters at the bottom of the rectifying column 6, in which the temperature is regulated so that a 40 per cent, aqueous formaldehyde solution condenses ; this is discharged into the separator 8, and thence into the vessel B. The excess of alcohol vapour passes from the top of the column to the condenser 7, the condensed alcohol being collected in the tank 12 and thence pumped to the tank 3, into which a further amount of alcohol is forced by the pump 14- The nitrogen and other gases escaping from 11 are washed with a little water in the tower 9 before being dispersed into the air ; the small amount of dilute methyl alcohol thus recovered is rectified in the column 10, from which the condensed water is discharged at A, while the alcohol vapour from the top of the column is condensed in 11, the liquid flowing into the tank 12. The catalyser is formed of a bundle of six copper tubes 60 cm. long and 5 cm. in diameter, fixed to tubulated plates so as to form, in the cylinder containing these tubes, a distribut- ing chamber at the entrance, and a collecting chamber for the oxidised gases at the exit, of the tubes. At the front end of each tube is a compact roll of fine copper gauze, forming a sort of plug 11 cm. long, this being preceded by a small tuft of platinised asbestos which 250 ORGANIC CHEMISTRY automatically ignites the alcohol vapour. The formaldehyde condensing in the column 6 (if the height and temperature of this are properly regulated) contains 14 per cent, of methyl alcohol, 52 per cent, of water and 40 per cent, of formaldehyde. Various modifications in the saturator have been suggested (see Ger. Pat. 106,495, 1898). Ignition of the alcohol vapour by means of electrical resistances in the catalysing apparatus has also been attempted (W. Lob, 1912). Various endeavours which have been made to prepare formaldehyde from methane (e. g., by mixing it with an equal volume of air and using granulated copper at 600 as catalyst) have not yet given satisfactory results (Ger. Pats. 109,014, 214,155, 286,731, etc.), the yields being very low. Further, practical success has not attended the preparation of formaldehyde, either by reducing formic acid vapour mixed with hydrogen in presence of various metals at high temperatures (Ger. Pat. 185,932, 1905), or by heating tin formate at 180 so as to decompose it into C0 2 and formaldehyde (Ger. Pat. 183,856). USES. Formaldehyde has considerable antiseptic power, even in aqueous solution ; its use in foodstuffs is prohibited. It is largely used at the present time in 1 to 3 per cent, solutions as a disinfectant in houses and for the preserva- tion of readily putrescible substances (1 part in 2000 kills bacteria and 1 in 1000 also spores). Its vapour has an acute and penetrating odour and irritates the eyes. On account of the property possessed by formaldehyde of combining with proteins to form insoluble and stable products, it is used in the manufac- ture from casein of articles of a horny consistency (galalitTi) and in making imitation pegamoid; also in preparing photographic films with gelatine, for rendering insoluble or hardening coloured gelatine for textile printing, and for hastening the tanning of skins. It causes the polymerisation and resinifica- tion of phenols (see Formolite reaction of petroleum, pp. 71 and 91) and is consequently used in large quantities in making baekelite (see Part III : chapter on Phenol) and neradol, which replaces tannin in the tanning of hides. The hydrosulphite derivatives (see above) are largely employed in the dyeing and printing of textiles. Owing to its great reactivity, it is largely used in organic syntheses, e. g,, in the manufacture of aniline dyes. Solid and liquid disinfectants containing free aldehyde are prepared in large number. Thus, lysoform consists of a soap solution of formaldehyde, and mixtures or compounds of the aldehyde with sugar, oil, quinones, amines, creosote, ichthyol (see p. 103), ricinoleic acid (ozoform), etc., are also sold. STATISTICS AND PRICES. The price of commercial 40 per cent, formaldehyde is about 40 per ton, while pure, powdered paraldehyde costs 4s. to 5s. per kilo. Germany consumed about 500 tons of formaldehyde per annum before the war. Italy produces it in varying amounts, as much as 60 tons per annum being sometimes made prior to the war, when the importation was about 250 tons per year. For France the movements of the aldehyde are as follows (tons) : 1910 1914 1915 1916 Importation . . 469 391 1047 613 Exportation 25 16 83 33 ACET ALDEHYDE (Ethanal), CH 3 CHO, is a colourless, mobile liquid, sp. gr. 0-801 (at 0), b.-pt. 21, and solidifies at 121. It has an agreeable but suffocating odour, and it polymerises with moderate ease, giving the paraldehyde and metaldehyde (see above). It dissolves in water, alcohol, or ether, and is readily converted into acetic acid by oxidising agents. It is prepared by pouring a mixture of 3 parts of 90 per cent, alcohol and 4 parts of concentrated sulphuric acid slowly into a solution of 3 parts of potassium dichromate in 12 of water, the liquid being kept cool meanwhile. The solution is then heated in a reflux apparatus on a water-bath and subsequently distilled. The mixture of alcohol, aldehyde, and acetal thus obtained is heated to 50 and the aldehyde vapour passed into cold ether. On passing ammonia into this solution, crystallised aldehyde-ammonia, CH 3 CH(OH) NH 2 , CHLORAL 251 separates; this,*wlien pressed and distilled with dilute sulphuric acid, gives pure acetalde- hyde. The commercial aldehyde is obtained from the foreshots of alcohol distillation, from which it is separated by simple fractional distillation. It is of importance in many organic syntheses and in the production of silver mirrors. The price of 50 per cent, solutions before the war was 2s. per kilo, that of the 95 to 99 per cent, product 3*. Qd., and that of the purest aldehyde 15-s. 1 METHYLAL, H CH(OCH 3 ) 2 , ACETAL, CH 3 CH(OC 2 H 5 ) 2 (see p. 245). PROP ALDEHYDE, C 2 H 5 . CHO, is found among the tarry products from the distillation of wood. Valeraldehyde, C 4 H 9 CHO, boils at 92 and begins to show a diminution in solubility in water. Normal heptaldehyde (cenantaldehyde), C 6 H 13 CHO, is found among the products of decomposition of castor-oil when this is subjected to distillation in a vacuum. Nonyl aldehyde, C 8 H 17 CHO, occurs in the oxidation products of oleic acid or, better, in the decomposition products of the ozonide of oleic acid (Harries, Molinari, etc.); it boils at about 192. CHLORAL (Trichloroethanal), CC1 3 'CHO, is the most important halo- genated derivative of the aldehydes. It is a dense liquid with a peculiar, penetrating odour and boils at 94 '4. It is prepared by passing chlorine into pure alcohol (96 per cent.) for some days, the hydrochloric acid formed being collected. At first the mass is cooled, but is afterwards heated to 60 and then to 100, the stream of chlorine being suspended when a little of the liquid dissolves completely in water. The reaction may be accelerated by addition of a trace of iodine or ferric chloride. The final product is heated to boiling under a reflux condenser with an equal amount of concentrated sulphuric acid in a lead-lined apparatus. After evolution of hydrogeji chloride has ceased, the liquid is distilled until the temperature of the vapour reaches 100, the distillate being subsequently rectified and the fraction boiling at 94 to 97 collected separately. If this chloral is mixed with an equimolecular proportion of water it forms a crystalline mass of chloral hydrate (see below), which may be pressed and crystallised from chloroform, CS 2 or benzene. Chloral is also prepared electrolytically : the bath contains potassium chloride solution at 100 and is fitted with a diaphragm; alcohol is passed into the anode chamber, where chlorine is formed, and the hydrogen chloride produced at the anode (carbon) is neutralised by the potassium hydroxide formed (1 h.p.-hour yields 50 grams of chloral) ; the cathode is of copper. Chloral gives the reactions of the aldehydes and is used in medicine as an anaesthetic and soporific, being first treated with water to form the crystalline OTT CHLORAL HYDRATE, CC1 3 'CH<^, which is readily soluble in water (m.-pt. 57) ; this is one of the few compounds having two hydroxyl groups united to the same carbon atom. The crystalline alcoholates or Acetals, CC1 3 ' CH(OH) OC 2 H 5 and CC1 3 CH(OC 2 H 5 ) 2 , corresponding with this hydrate, are known. Chloral costs about 6s. per kilo. ALDEHYDES WITH UNSATURATED RADICALS ACRALDEHYDE (Propenal, Acrolei'n, or Allyl Aldehyde), CH 2 : CH CHO, is formed when fats are burned, owing to loss of water by the glycerol present ; a similar change takes place when glycerol is heated with potassium hydrogen sulphate or boric acid. By distillation of 200 c.c. of concentrated glycerine with 10 grams of potassium bisulphate 1 The estimation of acetaldehydc is based on the following reaction (Seyewetz and Bardin) : 2Na 2 S0 3 + 2CH 3 CHO + H 2 S0 4 = Na 2 S0 4 + (CH 2 CHO, NaHS0 3 ) 2 . The aldehyde is diluted to 7 to 8 per cent, and about 10 c.c. of this solution is poured into 40 c.c. of 10 per cent, pure sodium sulphite solution. After the addition of a few drops of neutralised alcoholic phenolphthalein solution the liquid is cooled to 4 to 5 and titrated with normal sul- phuric acid until it is decolorised. This occurs when no further combination of aldehyde and sulphurous acid takes place. This determination is not affected by the presence of alcohol, acetal, or paraldehyde. 252 ORGANIC CHEMISTRY X at 105 to 110 and rectification of the first distillate (140 to 150 c.c.), 3# c.c. of acrolein are obtained. Acrolein, which may also be obtained by the oxidation of allyl alcohol, is a liquid, b.-pt. 524, and has a characteristic pungent odour. When oxidised, it yields acrylic acid and, when reduced, allyl alcohol. It has all the chemical properties of the aldehydes and polymerises in the course of a few hours. With ammonia, it gives a solid, basic condensation product, soluble in water : 2C 3 H 4 O + NH 3 = H 2 + C 6 H 9 ON (acrolein- ammonia, which gives picoline on distillation). Owing to its double linking, acrolein unites with 2 mols. of sodium bisulphite, and the resulting product, when boiled with acid, gives up only one bisulphite molecule, namely, that combined with the aldehyde group. CROTONALDEHYDE, CH 3 CH : CH CHO, is obtained by distilling the corre- sponding aldol, CH 3 CH(OH) CH 2 CHO, at 140 or by the dehydrating action of zinc chloride or sodium acetate on the saturated aldehyde. It is a liquid boiling at 104 and possessing a penetrating odour, and its constitution is shown by the fact that it yields crotonic acid when oxidised with silver oxide. CITRAL (or Geranial), (CH 3 ) 2 C : CH CH 2 CH 2 C(CH 3 ) : CH CHO, is a liquid of pleasant odour, b.-pt. 229, and occurs in many essences (of mandarin, citron, lemon, orange, and most abundantly 60 per cent. in that of Verbena indiana or lemon-grass, from which it is separated by means of its bisulphite compound). It may also be obtained by the gentle oxidation of the corresponding alcohol, geraniol, which boils at 230. It exists in two stereoisomeric forms, the cis- and trans-modifications. When oxidised with potas- sium bisulphate at 170, citral is transformed into cymene (with a closed ring) with separation of water. CITRONELLAL, (CH 3 ) 2 C : CH CH 2 CH 2 CH(CH 3 ) . CH 2 CHO, is found with citral in citron oil and boils at 208. PROPARGYL ALDEHYDE, CH | C CHO, is a solid, m.-pt. 60, and is obtained from dibromoacrolein by way of the acetal. As it contains the group CH : C, it forms metallic derivatives (see pp. 110 and 112). (b) KETONES (R CO R') -These have the carbonyl group attached to two alcohol radicals and, if the latter are similar, are known as simple ketones and, if different, mixed ketones. The first member must contain at least three carbon atoms. They present the same cases of isomerism as the secondary alcohols, and are metameric with the aldehydes. Up to the C n -compound they are liquid and beyond that solid, but all are less dense than water. They resist feeble oxidation, but energetic oxidising agents (dichromate and dilute sulphuric acid) break the chain of the ketone at the carbonyl group, thus forming an acid with a lower number of carbon atoms : CH 3 CO CH 3 + 40 = H 2 + CO 2 -f CH 3 C0 2 H. In mixed ketones, however, the carboxyl is united mainly to the smaller alkyl radical (R or R'), but the acid with the higher alkyl is always formed to some extent. With ammonia, the action is different from that in the case of aldehydes : water is eliminated from 2 or 3 mols. of ketone and di- and tri-ketonamines (or acetona- mines), e. g., C 6 H 13 ON, formed. Further, the ketones do not polymerise, but they form condensation products. They do not react with ammoniacal silver solutions or with Fehling's solution, and are hence not reducing in character (difference from aldehydes). With phosphorus pentachloride they give the corresponding dichloro- derivatives; for instance, acetone gives 2-dichloropropane, CH 3 * CC1 2 ' CH 3 . On reduction, they yield secondary alcohols, and with very energetic oxidis- ing reagents (H 2 2 , etc.) they form characteristic polymerised ketonic per- oxides, e. g., [(CH 3 ) 2 C0 2 ] 2 , [(CH 3 ) 2 CO 2 ] 3 . With ethyl orthoformate they give acetals, (CH 3 ) 2 C(OC 2 H 5 ) 2 , and similarly with mercaptans they form Mercaptols, e. g., (CH 3 ) 2 C(SC 2 H 5 ) 2 , which, when oxidised with permanganate, gives Sulphonal, (CH 3 ) 2 C(SO 2 C 2 H 5 ) 2 (see pp. 119 and 233). K E_T O N E S 253 Ketones, which generally contain the group CH 3 'OO, form, with sodium bisulphite, compounds which are crystalline and hence readily separable from other substances :, OTT (CH 3 ) 2 CO + S0 3 HNa = (CH 3 ) 2 CC Z H 4 , melts at 104 and boils at 146. Teiramethylenediamine is called also Putrescin TAURINE (Aminoethylsulphonic Acid), NHj CHj CH2 SO 3 H, is found in com- bination with cholic acid (as Taurocholic Acid) in the bile of various animals and also in the- lungs and kidneys. It forms monoclinic prisms soluble in hot water but insoluble in alcohol, and has a neutral reaction, the basic and acid groups neutralising one another. It is not hydrolysable. Of the derivatives of Glycerol, the Chlorhydrins or esters of hydrochloric acid are of interest ; they are liquids soluble in alcohol or ether, and, to a less extent, in water. With hydrochloric acid, glycerol forms the MonocUorhydrin, C 3 H 5 (OH) 1 C1, of which two isomerides (a- and /?-) are known, and the Ztichiorhydri*, C 3 H 5 (OH)C1 2 , also existing in two isomeric forms. Either of these, when treated with PQj, gives the tricUoro- derivative, CgHjClg. 1 At the present time interest attaches also to the forming and acetins, which are used in the manufacture of non-congealing explosives. 2 1 According to Ger. Pat. 180,668, the monochlorhydrin is made by heating for fifteen hours in an autoclave at 120 3 a mixture of 100 parts of glycerol with 150 parts of hydrochloric acid (sp. gr. 1-185). The water is distilled off and the residue subjected to fractional distillation in a vacuum (15 mm. pressure) ; alter the acid and water have been eliminated, the monochlorhydrin distils over at 130 to 150, and the unaltered glycerine at 165 to 180. If it is to be nitrated and used for explosives, it is sufficient to get rid of the water and acid. According to Fr. Pat, 370,224, the monochlorhydrin may also be obtained by shaking glycerine with the calculated quantity of sulphur chloride at a temperature of 40 to 50 ; the water formed is distilled off in a vacuum at 60 to 70. The a-MonocUorhydrin, CH,C1 CH(OH) CH, OH, is obtained (according to Fr. Pat. 352,750) by passing hydrogen chloride into glycerine heated to 70 to 100. Like glycerine itself, the chJorhydrins are easily nitrated, yielding non-congealing explosives (see later). * Monoacetin, CjHj(OH \(O COCH,), is obtained by heating forten to fifteen hours at 100 a mixture of 10 parts of glycerol with 15 parts of 40 to 100 per cent, acetic acid, the weak acetic acid (25 to 30 per cent.) that distils over being condensed separately. Ten parts of 70 per cent. ^OL. H. 17 258 ORGANIC CHEMISTRY GLYCIDE ALCOHOL, CH 2 CH CH 2 OH, is a liquid, b.-pt. 162, soluble in alcohol \0/ or ether, and also in water, with which it gives glycerol again; with hydrochloric acid it gives the chlorhydrin. It may be regarded as derived from glycerol by the removal of a molecule of water, and is prepared by the separation of HC1 from the a-monochlorhydrin by means of bartya. It is isomeric with propionic acid and reduces ammoniacal silver solution. Separation of hydrogen chloride from the dichlorhydrin yields Epichlorhydrin, CH 2 CH CH 2 C1, which may be regarded as the hydrochloric ester of glycide alcohol. \o/ It boils at 117, has an odour like that of chloroform and is insoluble in water. It is isomeric with propionyl chloride and monochloroacetone, and serves as a good solvent for nitrocellulose, celluloid, hard resins, organic dyestuffs, etc. GLYCEROPHOSPHORIC ACID, OH CH 2 CH(OH) CH 2 O PO(OH) 2 , is optically active, as also are its calcium and barium salts (Isevo-rotatory). It is interesting from the fact that when the hydroxyl-groups are esterified with palmitic, stearic, or oleic acid, and the phosphoric residue united to choline, it gives rise to the important group of lecithins, which are optically active : OR CH 2 CH(OR') CH 2 PO(OH) CH 2 CH 2 N(CH 3 ) 3 OH, where R and R' are fatty acid residues. Lecithins are found in the brain, yolks of eggs, and many seeds and are soluble in alcohol, and, to a less degree, in ether ; they give salts with acids and with bases and yield solid compounds with chloroplatinic acid or cadmium chloride. They are saponified by baryta, with formation of choline, fatty acids, and glycerophosphoric acid. Of the nitric esters of glycerine, the most important is trinitroglycerine or glyceryl trinitrate., C 3 H 5 (ONO 2 ) 3 , which is one of the most powerful explosives. We shall hence study it from the industrial standpoint, first dis- cussing certain general notions concerning explosives. The manufacture of the latter constitutes one of the most interesting industries of organic chemistry, partly because of the varied mechanical appliances which it requires. EXPLOSIVE SUBSTANCES The name explosive substances, or explosives, is given, in general, to those solid and liquid bodies which, under the influence of heat, percussion, electrical discharge, etc., are transformed instantaneously and completely or nearly so i n to a gaseous mass with an enormously increased temperature. If the reaction takes place in a closed space, the gases thus produced and heated exert a very considerable pressure which can be immediately trans- formed into mechanical work, the enclosing substance and all the surround- ing objects being shattered with great violence and noise. Such a phenomenon (or effect) constitutes a so-called explosion, and if it attains very great rapidity and power it is termed a detonation. For a constant quantity of gas produced in an explosion, the effect will be the greater the higher the temperature developed in the reaction. acetic acid is then added and the weak acid up to 40 per cent., which distils at 120- collected apart. After this the temperature is raised in three hours to 250, the weak acid still being kept separate. The crude monoacetin remaining contains about 44 per cent, of combined acetic acid and about 0-8 per cent, of the free acid. This acetin is soluble in water and serves well for the manufacture of explosive and non-congealing nitroacetins (see Explosives) and for gelatinising the nitrocellulose of smokeless powders (Vender, Ger. Pat. 226,422, 19C6). The diacetin is obtained by heating gtycerine with glacial acetic acid at 200 to 275; it boils at 280. The triacetin, C 3 H 5 (0 CO CH 3 ) 3 , is found in the seeds of Eronymus eiiropceus and is prepared artificially from the tribromhydrin and silver acetate or industrially from the diacetin and glacial acetic acid at 250. It boils at 268, has the sp. gr. 1-174 at 8, and is used as a tanning material. THEORY OF EXPLOSIVES 259 THEORY OF EXPLOSIVES. The chemical reactions and physical phenomena of explosives are produced under conditions differing greatly from those in which physical and chemical properties of substances are usually studied. The pressures, temperatures, and velocities with which we have to deal in ordinary phenomena are of a very different order from that of the enormous pressures of the gases in the interior of the earth's crust, which are measured in hundreds of thousands or millions of atmospheres. So also the temperatures in various stars, e. g., in the sun, reach thousands of degrees, and the veloci- ties of the planets hundreds of kilometres per second. The phenomena now to be con- sidered, although they do not attain these enormous magnitudes, still do approach them. Indeed, explosions give pressures of tens of thousands of atmospheres, temperatures of thousands of degrees, and velocities (of projectiles) of thousands of metres per second. Almost all explosive substances contain oxygen (furnished by chlorates, nitrates, nitro groups, etc.), only very few, such as nitrogen chloride and iodide, and aniline ful- minate, being without it. Mixtures of oxidising agents with readily combustible substances (sulphur, carbon, sugar, etc. ) are explosive, but they are less powerful than those composed of single compounds which explode by themselves. This is because the elements necessary for complete combustion are in much greater proximity, being present in the molecule of the explosive itself; examples of such explosives are nitroglycerine, guncotton, mercury fulminate, picric acid, etc. The determination of the theoretical power of an explosive requires a knowledge of : (a) the chemical reaction accompanying the explosion, so that the heat of the reaction, the temperature, and the volume and relative pressure of the gases formed may be deduced ; (b) the velocity of the reaction. In order to understand the theory of explosives, it is indis- pensable to call to mind the fundamental principles of thermochemistry and of thermo- dynamics, for which the reader is referred to the brief account given in Vol. I., pp. 51 and 54. (a) The chemical reaction is deduced from the difference in composition between the explosive and the products resulting from the explosion. When there is sufficient oxygen in the explosive to produce complete combustion, the nature and quantities of the gases may be calculated a priori, and from their heats of formation their temperature may be deduced. The total combustion of nitroglycerine, when exploded in a closed space, gives the following products (a) : 2C 3 H 5 (N0 3 ) 3 = 6C0 2 + 5H 2 + 3N 2 + 0. When there is deficiency of oxygen, as in guncotton and other substances, it is not easy to foretell the products of the reaction, as these vary with the conditions in which the explosion occurs, and usually several reactions take place simultaneously. Further the gases found after the explosion of such products are probably not always those formed at the instant of the explosion, as at such high temperatures certain substances (H 2 0, CO 2 , etc.) may undergo dissociation with absorption of heat. 1 (b) The heat developed in the explosion is deduced by calculation from the thermo- chemical data of the equation, but the practical result is not in accord with the theoretical calculation, since part of the heat (25 to 30 per cent. ) that should theoretically be developed is transformed into mechanical work, which is what is utilised in practice. In calculating theoretically the heat of explosion, the heat of formation of the explosive (from the elements : see p. 25) is subtracted from the heat that should theoretically be developed in the reaction. The heat of explosion varies, however, according as it is determined at constant volume or at constant pressure ; in the latter case the explosion of nitroglycerine, for example, is effected in the open air, since then the volume varies, but the pressure is only that of the atmosphere. The heat of formation of nitroglycerine from its elements (see p. 25) is given by th following equation (b) : C 3 + H 5 + N 3 + O 9 = C 3 H 5 (N0 3 ) 3 + 98 Ca!s. The heat of reaction of nitroglycerine may be calculated from equation (a) given 1 The following Table gives the percentage compositions of the gases resulting from the normal explosion of various explosives in the calorimetric bomb : CO C0 2 O 2 CH 4 H 2 N 2 Nitrocellulose powder 46-87 16-8 0-08 1-26 20-44 14-9 Gelatine dynamites Carbonite . Picric acid Trinitrotoluene . 34-0 32-68 0-75 10-0 21-0 36-0 19-2 2-8 27-6 14-4 61-05 3-46 0-34 1-02 13-18 21-1 57-01 1-93 0-11 20-45 18-12 260 ORGANIC CHEMISTRY above, from which it is seen that 2 mols. or 454 grams of nitroglycerine yield 6CO 2 + 5H 2 O + 3N 2 + O. The heat of formation of 6C0 2 is 6 X 97 = 582 Gals., and that of 5H 2 O, 5 X 68-5 = 342-5 Gals. For the nitrogen and oxygen there is no development of heat, since they are not combined, so that the total heat of reaction calculated on the gases formed in the explosion of 2 gram-mols. of nitroglycerine will be 924-5 (i. e., 582 -f- 342-5) Gals. From this must be subtracted the heat of formation from the elements of 2 mols. of nitroglycerine, since on decomposing under these con- ditions of temperature the explosive first of all liberates its atoms, absorbing as much heat as is evolved in its formation from its elements (reaction b), i. e., 196 (98 X 2) Gals, per 2 mols. The atoms thus liberated combine immediately to give the gases which result from the explosion, the heat of formation of which has already been calculated. The true theoretical heat of explosion at constant pressure for 454 grams of nitro- glycerine will hence be 728-5 (i. e., 924-5 196) Gals., or for a kilo, 1603 Gals. The heat of reaction at constant volume the explosion occurring in a closed vessel is rather higher, the heat corresponding with the expansion of the gas (see Vol. I., pp. 27 and 52) not being absorbed, as no expansion takes place ; theoretically the heat at constant volume is calcu- lated to be 1621 Gals, per kilo. 1 Sarrau and Vieille, by direct practical measurements, found the heat of explosion of nitroglycerine at constant volume to be 1600 Gals., which confirms the accuracy of the calculation. With substances which themselves contain insufficient oxygen for complete com- bustion during explosion, it is not easy to calculate theoretically the heat of explosion, since the products of the reaction are not exactly known; in such cases, various direct practical determinations must be made. On the other hand, the presence of C0 2 alone and the absence of CO in the gaseous products of an explosion are insufficient to indicate an adequate amount of oxygen in the explosive, since in certain cases (e.g., with trinitrotoluene, etc.) carbon separates during explosion. If the gases contained CO the effect of the explosion might be greater than if CO 2 were formed with simultaneous separation of inert carbon. The mechanical work, in kilogram-metres, yielded by an explosive is calculated by multiplying the number of calories developed in the explosion of 1 kilo of the substance by the mechanical equivalent of heat (= 425, see Vol. I., pp. 51 and 52). For various explosives this mechanical work (or potential energy) is given in the following Table : Nitroglycerine . (1 kilo) = 1600 Gals. X 425 = 680,000 kilogram-metres Explosive gelatine . . =1530 =650,000 Dynamite ... = 1178 = 500,000 Guncotton ... = 1074 = 456,000 Fine sporting powder . = 849 = 360,000 Potassium picrate . . =780 330,000 Fulminate of mercuiy . =403 =170,000 Nitrogen chloride . . =339 = 144,000 Owing to various causes, the total theoretical energy of explosives cannot be utilised practically; e. g., the expansion of the gases at the moment the projectile leaves the cannon or gun, the friction, the heating of the barrel, etc., all constitute losses of the useful effect of the explosive. It is not easy to calculate theoretically the temperature of the gases at the moment of explosion, since the specific heat of the gases at such high temperatures cannot be deter- mined, but is certainly rather higher than the ordinary value. Further, at such tem- peratures dissociation phenomena occur which cannot be defined; these, however, lower the temperature, although not greatly, since with the great pressures developed the disso- ciation is minimal. On the other hand, with the means we possess, it is not possible to measure these temperatures directly, and only approximately can they be determined for black powder. In general, however, they are very high and in some cases exceed 4000 1 For every gram-molecule of a substance passing from the solid or liquid to the gaseous state, owing to the new volume occupied, 590 small calories (Vol. I., pp. 27 and 52) are absorbed. In the explosion of 2 mols. of nitroglycerine, 14-5 mols. of gas (6C0 2 + 5H 2 + 3N 2 -f 0) are formed, and these, on expanding, will absorb 14-5 X 590 = 8550 small calories, or 8-5 Cals. per 454 grams of nitroglycerine, i. e., 18 Cals. per kilo. This, added to 1603, the heat of reaction at constant pressure, gives 1621 Cals. as the heat of reaction at constant volume. THEORY OF EXPLOSIVES 261 (for instance, by burning ballistite in the air, platinum with m.-pt. 1800 is easily melted), but even these temperatures, deduced indirectly, are much lower than those calculated theoretically. 1 The temperature of ignition does not usually coincide with the temperature of explosion, since explosion is caused not so much by the temperature as by the pressure and other factors to be considered later; so that for explosion to occur, special conditions (detonators) are necessary. For some substances, however, e. g., black powder, non-compressed gun- cotton, etc., the temperature of ignition, given in the following Table, is identical, or almost so, with that of explosion : Fulminate of mercury . . . 200 Non-compressed guncotton . . 220 to 250 Nitroglycerine .... 218 (explodes at 240 to 250) Black powder .... 288 There are thus explosives which explode when merely ignited with a match and others which are exploded indirectly by means of detonators. The volume of the gases formed in the explosion may be calculated with reference to and 760 mm., taking account of the fact that at the moment of explosion the water is in the state of vapour. In practice, however, it is of more importance to calculate the volume at the temperature of explosion, when a knowledge of the gases formed is possible, as is the case with nitroglycerine, And, in general, with explosives containing sufficient oxygen for their complete combustion. It is, however, not easy to calculate the volume of gas formed by products containing an insufficiency of oxygen, like guncotton, etc., with which the gases vary quantitatively and qualitatively according to the type of explosion; in such cases the volume must be determined directly. The volume of gases is calculated (see Vol. I., pp. 26 et seq.) by means of the general formula, V (l + 0-003670 "* - ~^p where Vt is the required volume at the temperature of explosion t, V is the volume at and 760 mm. pressure (which can be found from the weight of the gases formed), and 0'00367 is the coefficient of expansion for all gases. For such high temperatures and pressures, however, the coefficient of expansion is rather higher than that resulting from Gay-Lussac's and Boyle's laws, but this difference is compensated for by the somewhat higher specific heat of the gas at high temperatures, in consequence of which more than the theoretical quantity of heat is absorbed. In any case, both for volume and for pressure, use may be made of van der Waals' equation (see Vol. I., p. 42), which was modified for the gases from explosives by Sarrau. 2 The pressure of the gas is deduced from the general formula given above, Vt being 1 Indeed, water- vapour, formed from H 2 + 0, should have theoretically the temperature 7927 (see Calculation, Vol. I., p. 465), but in the most favourable practical conditions the oxy- hydrogen flame does not exceed 2500. For carbon dioxide the heat of formation is 97,000 cals., and the specific heat 0-217, so that for 44 grams of C0 2 gas (gram-mol.) the temperature attain- able would be ~rr r^ys = 10,160, and allowing for the fact that along with the 6 mols. of 44 /x U'^il / C0 2 and 5 of H 2 0, the 3 mols. of N 2 and half a mol. of oxygen formed in the explosion of nitro- glycerine are also to be heated the theoretical temperature of the gases from the explosion would be about 7000. This theoretical temperature is determined in general by the formula t = , , , . Tr^t, where p, p', p" . . . are the weights of the gases formed in the ex- plosion, s, s', s" . . . their specific heats, and C the total heat in calories. 2 Clausius replaced the van der Waals equation by the following more exact expression : RT f(T) p = - , ~ir ~\z where f(T) denotes a decreasing function of the temperature T and 7 is a constant. Sarrau rendered the value of f(T) definite by making it equal to K~S.~ T , where 2 and K are two new constants. For explosion gases at a very high temperature and relatively small volume, the second term of the equation is, according to Sarrau, negligible, so that there remains RT 262 ORGANIC CHEMISTRY diminished by the volume v of the mineral, non-gasifiable residue (in the case of dynamite or other mixtures), so that : V (\ + 0-00367 t) Vt-v with nitroglycerine, guncotton, etc., v = 0. P is the maximum theoretical force of an explosive, starting from its volume (solid) at the ordinary temperature, but the effect of a given explosive will be the greater as its density increases, that is, the greater the weight for the same volume; for guncotton, for example, the effect will be the greater for the same volume, the more it is compressed. Thus the relative specific gravities of different explosives are of importance, and in fact fulminate of mercury, which has a high specific gravity (five times that of ordinary powder and three times that of nitroglycerine), has a maximum rapidity of reaction and is the most powerful detonator, being capable of exerting a force of about 27,000 kilos per square centimetre (atmospheres), this being about treble that given by any other known explosive. In practice, pressures higher than any imaginable may be attained when the volume occupied by a given weight of explosive in a closed vessel is less than the critical volume of the gas developed, since this critical volume (Vol. I., p. 28) cannot be diminished by any pressure, however great. If we term charging density the ratio between the weight of the explosive in grams and the volume in cubic centimetres occupied by it in absolutely filling its envelope (as though it were liquid or fused), this charging density corresponds with the specific gravity of the explosive; if this density equals or exceeds the reciprocal of the limiting 'volume [-) into which the gases developed (critical volume) can be compressed, the pressure attained will be infinitely great and will rupture any enclosing vessel, no matter how resistant it may be. The reciprocal of the critical volume of the gases pro- duced in the explosion is termed the critical specific volume (or limiting density), and comparison of this with the density of charge leads to consequences of practical importance. Limiting density Specific gravity of of the gases the explosive Black powder .... 2-05 1-75 Nitroglycerine. . . . 1-40 1-60 Powdered guncotton . .1-16 1-20 Picric acid . . . .1-14 1-80 Fulminate of mercury . . 3-18 4-42 Thus, black powder has a charging density (or specific gravity) of 1-75 to 1-82, which does not reach the limiting density, so that even if it is exploded in its own volume it does not break the envelope if the latter is strong enough to withstand the pressure developed, namely, about 29,000 kilos per square centimetre. For granular powder, the density of which is 1, the pressure is only 6000 kilos. FIG. 182. The real density (specific gravity) of compressed gun- cotton is 1-2, that of nitroglycerine 1-6, and that of picric acid 1-8, all of these being superior to the limiting densities of the corresponding gases ; so that when they explode in their own volume, all of these explosives burst the most resistant envelope, and, in such cases, the velocity of the explosive wave becomes infinitely great. Fulminate of mercury, although it has the high limiting density 3-18 (owing to the low critical volume, v), has the specific gravity 4-42 (to which the density of charge approximates) and behaves like nitroglycerine, etc. As it is difficult to calculate a priori the pressures exerted by explosives, it is preferable to determine them relatively by measuring certain effects of the gases at the instant of explosion; this is done, for instance, by observing the crushing or deformation of small cylinders of copper or lead, which are termed crushers (Fig. 182). The total pressure depends on the character of the explosive and on the nature of the explosion (see later), but more especially on the density of charge. The specific pressure of an explosive is a constant (a), given by the ratio of the pressure (p) to the corresponding density of charge (d) of the explosive itself : a ^. This specific VELOCITY OF EXPLOSION 263 pressure a is characteristic of any explosive and expresses the pressure developed by unit weight (1 gram) of an explosive in unit volume (1 c.c. ). The specific pressure is not always the maximum pressure that can be exerted, this depending, as we have seen, on the charging density in its relation to the critical volume. Velocity of reaction or explosion. The duration of the explosion is of great importance, since on it depends the greater or less utility of the explosive for different purposes. The more rapid the explosion the better is the heat developed utilised, so that this may be used almost entirely in heating and expanding the gases and so increasing the pressure considerably. If, however, the reaction is slow, a large portion of the heat is dissipated by radiation and conduction. Explosives with an extremely rap.'d reaction produce special effects, as they shatter the envelope or rock in immediate contact with the explosive into minute fragments an effect often not desired. These are termed shattering, percussive or high explosives and their properties are utilised in certain cases, as, for example, where a small cavity is to be made in a rock so that a large quantity of a progressive or propulsive explosive may be subsequently introduced. If the reaction, although rapid, is not instantaneous, the explosion produces other effects, for instance, the cleaving of large stones or rocks and the projection of fragments lying near the explosive ; this progressive or rending action is the effect usually desired by miners. So also progressive explosives are used for charging guns which throw projectiles. According as the gasification takes place more or less instantaneously (the one or the other effect may be obtained with the same substance by adding inert materials to, say, dynamite, or mixing paraffin wax with guncotton), explosives are more or less shattering. Thus, panclastite (N 2 4 + CS 2 ) and fulminate of mercury are more shattering than gun- cotton, the latter more than dynamite and nitroglycerine, and this more than smokeless powder, which is a progressive explosive. Many substances explode only with detonators (of fulminate of mercury) and the cause of the explosion in such cases is not only the high temperature produced by the explosion of the detonator, but more especially the great immediate pressure resulting from the instantaneous production of gas, this pressure and the sudden shock provoking the decomposition of the molecules of the explosive (Berthelot, Abel, Vieille). The duration of explosion or of gasification of the detonator is 500 times less than that of the explosive material, and the greater relative amount of heat developed in a certain time by detonators explains their greater shattering power compared with that of progressive explosives. The duration of reaction for detonators is only about T ^V^ of a second, the extraordinary effect of these explosives being due to the enormous amount of energy developed (1600 Gals, for nitroglycerine) in this short time and in the small space containing them. 1 As has been already stated, the shattering effect of a substance is rendered evident by exploding a few grams of it on a cylinder of metal (crusher) and the actions of different explosives are compared by means of these deformed and disfigured crushers. Fig. 183 B shows a leaden cylinder before the explosion, whilst A shows the same cylinder after 10 grams of dynamite (a progressive explosive) has been exploded on it and C the result of the explosion of 10 grams of panclastite (from nitrotoluene). One and the same explosive substance may be made to give either a shattering or a 1 The velocity of combustion (or of deflagration] is sharply distinguished from the velocity of the explosive reaction and is made use of in certain cases, e. g., in the throwing of projectiles (expansive and progressive action). The velocity of combustion of explosives depends on, and increases with increase of, the pressure at which they decompose. Another factor influencing the mode of combustion of explosives is the maximum velocity with which the pressure develops. The exponent of the power of the pressure, which admits of passing from one value to the other in the increase of the pressure, is called the modulus of progressivity, and serves to characterise the various explosives. Thus, this modulus varies from 1-25 to 1-50 for black powders and from 1-86 to 1-87 for smokeless powders, whilst that of picric acid is 2-82 and that of Favier's explosive (12 per cent, of dinitronaphthalene + 88 per cent, of ammonium nitrate) 3-25. As will hence be seen, these last two explosives have the dangerous property of furnishing accidental super- pressures, owing to undulatory phenomena which always accompany the combustion of sub- stances inflammable with difficulty. In smokeless powders, the moderate progressivity com- pared with the great power constitutes a valuable safeguard in their use in firearms ; in this they are surpassed only by black powders, which are, however, much less powerful. 264 ORGANIC CHEMISTRY progressive effect by varying the velocity of the reaction, this usually depending on the power of the initial shock which causes the explosion and on the physical condition of the explosive. The greater the density of the latter the less shattering it is ; thus gelatinised guncotton is less shattering than the compressed cotton and this less so than the powdered cotton (see preceding page). The more powerful the initial shock the greater is the amount of kinetic energy trans- formed into heat and hence the higher the temperature developed; therefore, also, the greater is the pressure of the resultant gases and the more rapid and powerful the effect of the explosive. The effects vary considerably with the manner in which the explosion is induced; thus, if a flame is brought near to non- compressed guncotton, the latter burns rapidly but does not explode, whilst if it is compressed and subjected to the action of a cap (detonator) of fulminate of mercury, a real and very powerful explosion occurs; similar phenomena are observed with nitroglycerine and dynamite. 1 DETERMINATION OF THE EXPLOSION. In order to- induce the explosive reaction of a substance, it is sufficient to bring it at a single point to a certain initial decomposition temperature (by percussion, detonation, etc.), the sharp decomposition at this point then producing a new shock which heats the neighbouring points to the decomposition tempera- ture, and so on, the explosion being thus communicated to the whole mass by a true explosive wave, which is enormously more rapid than simple burning. From this will be understood the great importance of detonators, which do not serve merely for ignition ; the difference will also be apparent between an ordinary explosion by ignition and per- cussion and that induced by fulminate of mercury deton- ators. When the phenomenon of explosion is studied more closely, it becomes evident that the gases produced at the point of ignition tend to expand and hence to diminish the pressure at that point and also the rapidity of explosion, but if this initial expansion is impeded the pressure and hence the velocity of decomposition increase rapidly. In practice miners obtain this effect by filling the cavity containing the explosive with a tamping of earth or stone. The same end may also be attained by increasing considerably the mass of the explosive and the surface of ignition, and this explains why certain sub- stances burn, without exploding, in small quantities (guncotton, nitroglycerine, etc.), or when the ignition is confined to a limited area, whilst a powerful explosion may occur when a large quantity of explosive is used or when it is surrounded by a source of considerable heat. 1 The percussive force (kinetic energy) of an explosive serves best to establish the shattering power and is calculated by C. E. Bichel by means of the formula ~ 2 , where m denotes the mass of the gases formed in the explosion, or the weight of the explosive divided by 9-81, and v is the velocity of detonation (i. e., the time elapsing from the beginning of the explosion to its com- pletion throughout the whole mass). For 1 kilo of an explosive gelatine (92 per cent, of nitro- glycerine and 8 per cent, of collodion cotton) with the charging density, 1-63, Bichel gives a velocity of detonation of 7700 metres per second, so that the percussive force in absolute units 1 X 7700 2 wil1 be : Q.gl x 2 ~ 3 ' 021 ' 916 kilogram -metre-seconds ; for black powder (with a charging density 1-04) exploded under the same conditions in a closed vessel with a detonating cap, the velocity of detonation is 300 metres per second, so that ^ * = 4587 kilogram -metre- seconds ; for kieselguhr dynamite (75 per cent, nitroglycerine) the velocity of detonation is 6818, and hence the percussive force, 2,369,272 kilogram -metres per second ; for a gelatine- dynamite (63-5 per cent, nitroglycerine, 1-5 per cent, collodion cotton, 27 per cent, sodium nitrate, 8 per cent, wood meal), with a charging density of 1-67, the velocity of detonation is 7000 and the percussive force 2,497,452; for trinitrotoluene, with a charging density of 1-55, the velocity was 7618, and the percussive force 2,957,896 ; guncotton, with a charging density of 1-25, had a velocity of 6383, the percussive force being 2,076,589; and picric acid, with a charging density of 1-55, gave the velocity of detonation 8183, and the percussive force 3,412,920 kilogram -metre-seconds. FIG. 183. EXPLOSION BY INFLUENCE 265 For shattering explosives (e. g., fulminate of mercury) no tamping is used, since the reaction is so rapid that the atmospheric pressure, that is, the air itself with its inertia, is sufficient to maintain the pressure of the gases. Even fulminate of mercury, if ignition is effected by an electric contact (which heats a platinum wire to redness) and under an evacuated bell-jar, burns without exploding, thus confirming the tamping action of the air in the case of detonators and even of ordinary explosives ; in fact, if a roll of dynamite is exploded on a bridge, the latter is cut in two owing to the tamping action of the air. The explosive wave produced in the explosion of gaseous mixtures and of liquids and solids is only slightly related to waves of ound. The latter is transmitted from crest to crest with but little kinetic energy, with a small excess of pressure and with a velocity depending only on the nature of the medium in which it is propagated and of equal magni- tude for vibrations of all kinds, the intensity diminishing in proportion to the square of the distance from the origin. The intensity of the explosive wave, on the contrary, remains constant, as it propagates the chemical transformation through the mass of the explosive substance, communicating from point to point of the decomposing system an enormous amount of potential energy and a great excess of pressure. The sound-wave is propagated in a mixture of hydrogen and oxygen with a velocity of 514 metres per second at 0, but the velocity of the explosive wave or chemical wave in the same mixture (exploded at a point) is 2841 metres. The velocity of propagation of the explosive wave depends on the chemical nature of the explosive, on the volume it occupies (hence on the density), and on the reaction of decomposition; the last determines the intensity of the wave and depends on the initial shock. Consequently different effects may be obtained from one and the same explosive by varying the cap (or detonator : see later), and if the latter is weak or insufficient the explosion is only partial or amounts to a simple deflagration, thus causing loss. With guncotton, the velocity of this wave varies from 3800 to 5400 metres per second according to the compression or density; with nitroglycerine it is 1300, with dynamite 2700 to 3600, with explosive gelatines as much as 7700, with picric acid 6500 to 8000, with nitromannitol 7700, and with trinitrotoluene 7200 metres per second. This velocity depends only on the nature of the explosive and not on the pressure, but i,t varies to some extent with the nature of the envelope. For instance, in a rubber tube having a thickness of 3-5 mm. and an internal diameter of 5 mm. and covered with cloth, ethyl nitrate gives a velocity of 1616 metres, whilst in glass tubes of various diameters and thicknesses the value is 1890 to 2480 metres. The propagation of the explosive wave bears no relation to that of ordinary combustion (which is much slower). The former occurs when the inflamed gaseous molecules acquire the maximum velocity or energy of translation, i. e., act with the whole of the heat developed in the chemical reaction. Explosion by Influence. If dynamite cartridges are arranged in a long row on a flat solid at distances of 30 cm. or on a metal disc at a distance of 70 cm., explosion of the first with a fulminate cap results in the rapid and successive explosion of the remaining ones simply by influence and without the need of detonators or fuses. Air does not conduct the wave of explosive influence as well as solids, and if the cartridges are suspended in the air by wires such explosion by influence does not occur. Water conducts the explosive wave to a certain distance, but the influence gradually diminishes with increasing distance from the centre of explosion. There have been cases in which the shock of a large charge of guncotton has exploded neighbouring torpedoes; to avoid these inconveniences, so-called safety explosives are now used (see later), or the explosives are rendered less sensitive by gelatinising them or by mixing them with various substances, such as camphor, paraffin wax, etc. These explosive waves are first propagated through the explosive itself, not by a single shock which would gradually weaken as it advanced but by a very rapid series of such shocks produced by the propagation of the explosion from point to point of the whole mass of the explosive, the kinetic energy being thus regenerated along the whole course of the wave in the exploding substance. An explosive wave is thus distinguished from an ordinary sound-wave by the fact that the latter becomes enfeebled as it advances, whilst the former is characterised by the uniformity of the energy transmitted from point to point by a series of numerous and successive explosions throughout the exploding mass. Only the last of these explosions is transmitted with its energy to the surrounding air and to the matter on which the 266 ORGANIC CHEMISTRY explosive rests, and, since it is no longer reinforced (by other shocks), it weakens as it becomes more remote. Hence explosion by influence is not due to the fact that the distant explosive transmits or propagates the explosive wave through its own mass, but is owing to the arrest and transformation, at the point of impact, of the mechanical energy it being capable of similar (but not of all) waves into heat energy, able to cause decomposition and explosion of the substance itself. For a long time it was thought that nitrogen iodide could be exploded by the simple note la struck by a musical instrument ; this idea is now contested, but it is certain that some substances, on exploding, cause only the note la of the scale to vibrate. The effects of large charges of dynamite (25 to 1000 kilos) when freely exploded are dangerous to buildings and to life for a distance of 500 metres and are felt as far away as 3 kilometres (L. Thomas, 1904). Certain explosives decompose gradually under the action of ultra-violet rays. CLASSIFICATION 'OF EXPLOSIVES. Explosives are to-day so numerous and are prepared from such different mixtures and serve such a variety of purposes that a rigorous or rational classification is difficult or impossible. Also with a large number of classes there would be many substances which might belong to more than one of them. It will hence be preferable to limit ourselves to a description of the various explosives without any prearranged classification. They will be taken in the following order : ( 1 ) Black powder; (2) Nitroglycerines and dynamites; (3) Nitrocellulose; (4) Smokeless or progressive powders; (5) Shattering explosives (aromatic nitro-derivatives and picrates) ; (6) Explosives of the Sprengel type; (7) Chlorate and perchlorate powders; (8) Safety explosives; (9) Detonating explosives and caps ; (10) Various explosives. BLACK POWDER (GUNPOWDER) This explosive, which was the first to be employed in firearms, and was the only one available for military and industrial purposes until after the middle of the nineteenth century, 1 has latterly become relatively unimportant owing to the discovery of dynamite and smokeless powders. Ordinary black powder is a mixture of potassium nitrate, sulphur, and carbon in vary- ing proportions according to the purpose for which it is required. 2 For black military powders, used in guns and cannon in Italy, France, England, Russia, 1 It is stated, but without any real confirmation, that the Chinese knew of gunpowder as early as the first century of the Christian era, and that they used it for throwing projectiles ; more certain is it that they employed mixtures of sulphur, nitre, and carbon to make rockets. Also the ancient Indians used powders for the preparation of a kind of artificial fire. Greek fire, used in Greece in the seventh century, was obtained with explosive powder and probably originated in China. The Arabs were acquainted with inflammable mixtures from very remote times, whilst true gunpowder, containing sulphur, carbon, and nitre, was prepared by them only in the thirteenth century, probably after they had learnt the manufacture from the Chinese. They, however, studied its propulsive properties and constructed the first primitive guns. In Germany it is stated that it was the monk Berthold Schwarz (a native of Freiburg, where a monument is now erected to him) who recognised the power of gunpowder in about 1310 and used it for the first time in Europe in firearms ; so that the discovery, not of the powder, but of guns for throwing projectiles, is due to Schwarz. After the middle of the fourteenth century, gunpowder came into use in Germany, then in Sweden, Russia, and elsewhere for guns and cannons. Macchiavelli records that by 1386 the Genoese and Venetians had learnt from the Germans the use of powder with guns. According to Libri, cannons were made at Florence as early as 1326. The projectiles were made first of stone, then of stone covered with iron ; leaden shot began to be used in 1347, and in 1388 Ulrich Beham cast the first iron shot, which became general in the fifteenth century. The mixing of the ingredients to make the powder was first carried out by hand, and it was only in 1525, in France, that powders were graded and granu- lated, the mixing being effected in vertical mills like those used for expressing oil from olives. 2 After a series of experiments in Brussels in 1560, the best proportions for the ingredients were found to be : nitre, 75 per cent. ; carbon, 15-62 per cent. ; and sulphur, 9-38 per cent. A thirteenth-century manuscript states that the Arabs used 74 per cent, nitre, 15 per cent, carbon, and 11 per cent, sulphur. A black powder dating from 1627 and discovered in 1905 during excavation, contained 40 per cent, nitre, 24 per cent, sulphur, and 37 per cent, carbon. In 1800 Berthollet recommended as the most effective proportions : 80 per cent, of nitre, 15 per cent, of carbon, and 5 per cent, of sulphur. Berthelot has recently calculated the theoretically best proportions to give a maximum development of heat, his results being : 84 per cent, nitre + 8 per cent, sulphur + 8 per cent, carbon ; this calculation assumes that the reagents are chemically pure, which in practice is not the case, and that the fineness and mixing of the ingredients are perfect. GUNPOWDER 267 China, and the United States, the maximum power is obtained without an excessive rapidity of explosion (so as not to injure the gun too much) with 75 per cent, of potassium nitrate, 15 per cent, of carbon, and 10 per cent, of sulphur, the density being increased by compress- ing and polishing the grains; in Germany the proportions used are 74, 16, and 10 respectively. In China until a few years ago erroneous proportions were still employed, namely, 61-5, 23, and 15-5. The chemical reactions occurring during the explosion of black powder vary according as the explosion takes place under pressure or at the ordinary pressure (deflagration). In the first case, Abel and Nobel obtained, from 1 gram, of ordinary powder, 0-585 gram of solid products, and 0415 gram of gas (258 c.c. ), according to the following equation : 16KN0 3 + 21C + 7S = 13CO 2 -f- SCO + 5K 2 C0 3 + K 2 S0 4 + 2K 2 S 3 + 16N; in addition there are formed traces of potassium thiocyanate and thiosulphate, and ammonium carbonate, whilst traces of sulphur and nitre remain unchanged, as the proportions taking part in the above reaction are 77-7 nitre, 10-54 sulphur, and 11-86 carbon. With 1 gram of powder exploded at the ordinary pressure, they obtained 0-769 gram of the same solid products, and 0-321 gram of gaseous products (about 193 c.c.), thus : 16KN0 3 + 13C +6S = 11C0 2 + 21^003 + 5K 2 S0 4 + K 2 S + 16N; traces of other products are also formed, since this equation represents 82-4 per cent, nitre, 9-5 sulphur, and 8 carbon. Sporting powder should burn more rapidly, and hence contains more nitre and a brown wood-charcoal of superior quality. In different countries the nitre varies from 75 to 78 per cent., the carbon from 12 to 15 per cent., and the sulphur from 9 to 12 per cent. Nowa- days, however, most sporting powders are of the smokeless type with a nitrocellulose basis. 1 With mining powders the production of a large quantity of gas is required, so that the amounts of sulphur (13 to 18 per cent.) and of carbon (14 to 21 per cent.) are increased, the nitre being consequently diminished (60 to 72 per cent. ) ; if, however, the proportion of nitre is made too small, the explosion becomes very slow, more CO is produced, and the gases are partly able to escape through the fissures produced before the end of the explosion, the useful effect being thus diminished. Hard rocks require increased rapidity of explosion, but with tufa or granite (to obtain large blocks) greater slowness of explosion is necessary. In many countries, especially in the United States, large quantities of black mine powder with a basis of sodium nitrate are made for prompt consumption. Such powders were first patented in 1857 by the Frenchman Du Pont de Nemours (now proprietor in America of the largest explosives works in the world ; during the European War 400 tons of nitrocellulose per day, besides enormous quantities of other military explosives, such as trinitrotoluene, picric acid, powder B, cordite, etc., were made at this factory); in 1910 this firm produced 45,000 tons of black sodium nitrate powder (74 per cent, nitrate, 10 per cent, sulphur, 16 per cent, wood charcoal), which is marketed in zinc cases to protect it from moisture. It is a more progressive powder than the ordinary one containing potassium nitrate. MANUFACTURE OF POWDER. The prime materials should be prepared with great care. The sulphur should contain no trace of sulphuric acid, so that stick sulphur and not flowers of sulphur is used ; if necessary, it is purified by distillation, and should yield less than 0-25 per cent, of residue on combustion. At the present time, use is also made of the sulphur recovered from soda residues (see Vol. I., pp. 206 and 596). The potassium nitrate is sometimes replaced by sodium nitrate, but the latter is more hygroscopic and impure. The nitre should contain less than 1 part of chlorides per 3000, and should 1 Smokeless sporting powders are of two kinds : light, with granules gelatinised superficially, / and condensed, which have completely gelatinised granules and are prepared like ordinary smoke- less powders (see later, pp. 295, 296), being often scrap from these cut to various sizes. The former or light powder is made by mixing the different components and coarsely granulating the moistened (with water or solvent or liquid ingredient) mass through sieves; these granules are rounded by subjecting them to a rotary and oscillatory movement on circular cloths moved horizontally by eccentrics, then partially'drying at 50 to 60 and afterwards treating in revolving drums. The grains are finally gelatinised superficially by spraying with a solvent (e. g., acetone, which gelatinises nitrocellulose, this being one of the usual components) and at the same time keeping it in motion in a vessel with a double bottom, through the jacket of which water at 50 to 60 circulates. The powder is then dried completely in a current of warm air (at 40 to 50). 268 ORGANIC CHEMISTRY be free from perchlorates. 1 Both English nitre from India and German conversion nitre are used, after suitable purification. The wood charcoal should be highly porous and should burn easily without leaving an appreciable quantity of ash ; 2 in different countries, different kinds of wood are used : in Spain, flax and vine stalks ; in Germany, dogwood, the alder, and the willow ; in France, the poplar, lime, etc. ; and in Italy, hemp stalks, etc. In some cases, charcoal from sugar, dextrin, maize, cork, etc., is used. Charcoal obtained at temperatures exceeding 430 is of no use for gunpowder. PULVERISATION AND MIXING OF THE INGREDIENTS. In early times the ingredients were ground and mixed by hand in mortars, but machine mills were used as 1 For many years the superiority of English powders could not be explained, and it was attributed to the use of Indian nitre, refined in England, whilst all over Europe, conversion nitre, prepared in Germany, was employed. On the other hand, the Germans showed that their nitre was very pure, as it contained only 0-5 per cent, of chlorides, and they regarded the preference for English powder as the result of prejudice. In 1894, however, the elder Hellich showed that the conversion nitre contained also perchlorate and chlorate which were not shown in the estima- tion of the chlorides. Spontaneous explosions of powder in Servia in 1896 were ascribed by Panaotovic to the use of nitre containing perchlorates. In 1897, Kelbotz showed that the perchlorate is not distributed homogeneously through the crystals of nitre, but that some of the latter contain more (and are more explosive) and others less ; hence the superiority and uniformity of powders free from perchlorate were explained. The perchlorate in nitre is estimated by Selckmann's method (1898) by fusing 5 grams of the nitre with 20 grams of pure lead in scales; the fusion is first gentle for 15 minutes until the mass becomes pasty, after which the temperature is raised for a short time. The mixture of potassium nitrite, lead oxide, and chlorides is poured into water and the chlorides estimated, the excess over the amount originally present being due to the chlorides. 2 Under similar conditions, the readiness with which powder burns is increased by increased combustibility of the charcoal. Hence it is necessary not only to use a suitable method of pre- paring the charcoal, but also to make careful choice of the wood to be carbonised. Light, soft wood is preferred, and of the different parts of the plant the best are branches at least three years old (5 to 8 cm. in diameter); the bark is rejected. For powders to be used in guns, hazel or dogwood (Rhamnus frangula) or hemp stalks are used, whilst for cannon and mining powders, preference is given to white willow (Salix alba), alder, poplar, etc. Hemp-stalk charcoal burns the best, and about 40 parts of it are obtained from 100 of the stalks ; hazel-wood gives only 33 per cent, of charcoal. The wood, freed from bark and well dried in the air for two or three years, still contains about 20 per cent, of moisture. When heated out of contact with the air, it evolves combustible gases, but the greater part of the wood blackens without burning and forms charcoal. It is of importance to determine the best conditions for carbonisation. When the temperature is not very high (280 to 340), a light, reddish, readily combustible charcoal is obtained, whilst at higher temperatures a black, denser charcoal is obtained which burns slowly and badly, although it is a better conductor of heat and electricity. Rapid carbonisation gives a diminished yield, but the charcoal is lighter and more friable. The charcoal is ground just before using, as in the powdered state it is much more hygroscopic and may also inflame spontaneously. Charcoal prepared at 270 is partially soluble in caustic soda solution, whilst it is insoluble if prepared at above 330. Carbonisation of wood in heaps or pits is no longer employed, since the resulting charcoal is impure and non-uniform, owing to the impossibility of regulating the temperature. So that at the present time powder factories always resort to charring by distillation, or charring in fixed or movable cylinders, as proposed by the English bishop, Landlofi, at the end of the eighteenth century. The distillation may be carried out in fixed horizontal cylinders (two to each furnace), 1-5 metre long and 0-65 metre in diameter, but with this arrangement discharging is difficult and sometimes the heated charcoal ignites. It is better to use fixed vertical cylinders with openings at the bottom for emptying, or movable vertical cylinders, which can be rotated from time to time during the heating. In every cylinder, a space is left for the introduction of a pyro- meter to indicate the temperature of the wood. The furnace is first heated gently, and after three hours yellowish fumes, composed of water, acetic acid, methyl alcohol, etc., begin to distil. After this, the distillation continues without further heating of the cylinder. The gases are led by pipes under the hearth, where they burn at first with a bright red flame and towards the end of the distillation with a bluish red flame. When the distillation is finished, the cover of the cylinder is raised and the charcoal discharged into suitable movable drums, which are immediately closed to exclude the air. Into the cylinder, while still hot, another charge of wood is at once introduced. Each charring lasts at least ten hours. In three or four days the charcoal is cold and is then removed lump by lump from the cooling drums, any that is in- sufficiently burnt being rejected. The colour of the charcoal is coffee-black, the fracture being velvety and of the same colour. An improved process of distilling wood by means of superheated steam, proposed by Violette in 1847 and improved by Gossart in 1855, was abandoned on account of its excessive cost. In 1899, H. Guttler in Germany suggested the replacement of the superheated steam by hot carbon dioxide in order to obtain a rapid charring ; after the operation, the mass may be quickly cooled by a current of cold carbon dioxide. MANUFACTURE OF GUNPOWDER 269 early as 1350. In the seventeenth century, the use of wooden stamps became widespread, but these were the cause of many" explosions, so that the vertical mills again came into use, the powder being kept moistened with water during grinding. After 1754 ordinary roll mills were used. At the present time the ingredients are powdered separately, then partial mixtures of sulphur and charcoal, and charcoal and nitre, are made, these being finally united and intimately mixed. The finer the materials are powdered the better will be the resulting powder. The charcoal and the sulphur may be powdered in the Excelsior mill (see p. 201, Figs. 164, 165), the product then being sieved and the coarse particles reground. The nitre is received from the refiner in the form of flour and only requires sieving. The binary mixtures are prepared by placing the powdered substances in special iron drums (Fig. 184), 1-1 to 1-2 metres in diameter, and 0'6 to 1-2 metres long. On the inner periphery of the drum are 12 to 16 transverse ribs, 3 to 4 cm. thick. Hard phosphor- bronze balls, 15 to 20 mm. in diameter, are introduced with the two substances through the aperture a, which corresponds with the hinged cover 6, fixed on the cylindrical wooden casing surrounding the drum. This wooden casing is connected with a leather or cloth FIG. 184. FIG. 185. bag, c, by which the mixture is finally discharged into the barrels, d, these being closed hermetically so as to prevent contact with the air, which might cause ignition (see Vol. I., Pyrophoric Substances). The drum is rotated about 15 to 20 times per minute for eight to ten hours, 100 to 150 kilos of the bronze balls being used per 200 kilos of the mixed substances ; the balls are given a bumping motion by the peripheral ribs and so increase the fineness of the powder. When the aperture, a, furnished with a coarse net, is opened at the end, the powder is discharged and the balls retained for a subsequent operation (see also the figures of ball mills, Vol. I, pp. 651, 652). The ternary mixture is prepared by mixing either binary mixture with the third con- stituent or the two binary mixtures (carbon + sulphur, and carbon + nitre) in the required proportions Ln a rotating cylinder provided with stirrers, or, better, in a drum similar to that just described. After this the mass is moistened with water and mixed, and then introduced into a stamp mill (like that shown in Vol. I., p. 653), where it is kept moistened (with about 10 per cent, of moisture) without caking. The stamps make 30 to 60 blows per minute, and their action is continued for at least twelve hours for cannon powder, eight hours for mining powder, and twenty-four hours for sporting powder. The cakes thus obtained then pass to the granulating machine. In many factories, however, the use of stamps has been abandoned, these being replaced by vertical iron runners (Fig. 185) about 1-6 metres in diameter and 40 cm. thick, and weigh- 270 ORGANIC CHEMISTRY FIG. 186. ing about 5000 kilos each. They rotate on a very hard iron plate 2 metres in diameter. The two runners are placed at different distances from the central shaft, which is actuated by bevel wheels above (as in the figure) or below; suitable scrapers detach the powder sticking to the runners, and others bring the powder from the edge to the centre and so under the runners. The incorporation is continued for three hours in the case of military powder and for five hours with sporting powder, the velocity of the runners being 10 to 12 revolutions per minute at first and only 1 revolution in 20 minutes towards the end of the operation, so that highly compressed cakes may be obtained. About every hour the mass is moistened with 1 to 1-5 litres of water for a charge of 20 kilos, the amount of water used depending on the hygrometric state and temperature of the air. The water dissolves the nitre, which is thus distributed uniformly and in a finely divided state throughout the whole mass. In some factories, compression of the moistened ternary mixture is effected by means of hydraulic presses (Fig. 186) between a number of separate layers of copper or ebonite, a pressure of 100 atmos. being applied for three-quarters of an hour. This procedure yields very compact cakes, having the density 1-7 to 1-8. It was formerly the custom in France, and is still in Germany, to use roller-presses (laminoirs) (Fig. 187) formed of three superposed rolls ; the lowest one, C, of cast-iron, is driven directly and transmits the movement to the middle one, B, which is coated with paper; this then drives the uppermost one, A, of chilled cast-iron. The endless band, D, collects the mixture falling from the hopper, E, and carries it between B and A, between which a pressure of 15 to 25 tons can easily be obtained by means of the lever, L, and weights, P. A knife is arranged so as to scrape the com- pressed powder from the band. As a rule, moist compression gives a more uniform and also a denser mass. After compression the cakes still contain 5 to 8 per cent, of moisture, and they are allowed to stand for seven to eight days in well- ventilated magazines. After this, those from the hydraulic presses or roller-presses are first partly dried (see later) and then granulated, whilst those from the stamps or incorporating mills, being less moist, are granulated directly. GRANULATION. This operation serves the purpose of preventing the separation of the constituents, and of rendering the powder less hygroscopic and less com- pact (but not less dense), since the combustion of the granules is more rapid than that of the fine compact powder; also, the finer the granula- tion the more rapid is the combustion and the greater the mechanical effect. The finest grains are used for sporting powders, then come those for military rifles, the coarsest grains being for cannon. If sporting powder were used for military rifles, the barrel would wear out rapidly and might even FIG. 187. split. It was only after 1445 that powder for artillery was granulated, it being found that the effect was greater than that of the non-granulated and non-compressed powder. Com- pression with stamps or rolls came into general use in France after 1525, the compressed mass being then broken up with wooden hammers and granulated ; for this purpose, the mass was spread out on a large sieve and covered with a heavy disc of wood, the sieve being then rotated and oscillated until all the powder passed through it in grains. Later the Leftvre graining machine was devised, and this is still in use in France and GRANULATION OF POWDER 271 Germany ; this machine grades the grains into different sizes and also eliminates all dust, powders showing more regular and rapid combustion being thus obtained. This machine (Figs. 188 and 189) is analogous to the plane-sifter used for flour. It consists of an octagonal board with sides, a, having a diameter of 2-5 metres and suspended from the ceiling by 8 ropes, b. This receives a circular motion by means of an eccentric formed of a vertical shaft, c, with an elbow-joint. This shaft is rotated at the rate of 75 revolutions per minute by the cog-wheels, B. On the board are fixed 8 or 10 triple sieves, S, to which the powder to be granulated is supplied by leather or cloth tubes, e. The powder falls on to the first wooden sieve, A, with a mesh of 3 to 4 mm., 'the coarse lumps being gradually broken by a disc of wood, c, weighing 700 grams. The grains then pass on to a second sieve, B, of metal, 3 to 4 cm. below, and then, to the lowest FIG. 188. FIG. 189. one, C, which is of hair and retains the grains of the required size, whilst the dust falls into D and thence through the leather pipe, g, into the barrel, p ; the uniformly grained powder is discharged into q through /. More common at the present time is the granulating machine with fluted rolls, first suggested in 1819 by the Englishman, Colonel Congreve, and subsequently improved in various ways. This machine (Fig. 190) consists of several pairs of bronze rolls, A, B, C, fluted longitudinally and transversely. The lumps of powder from the breaker, D, are raised to E by an endless band, and fall on to the first rolls, A, furnished with small pyra- midal teeth projecting 10 mm., then on to the second rolls, B, with finer teeth (3 mm.), and finally on to the smooth rolls, C, which give the powder the ap- pearance of shining scales. This distance between the rolls is adjustable, and the teeth are kept clean by means of a brush. The granulated powder falls on to a series of superposed sieves, S, which are oscillated at the rate of 150 vibrations per minute, and so grade the powder, the final dust FIG. 190. being discharged at ra. Blasting powder, which has the size of peas, is not passed through the smooth rolls. By varying the mesh of the sieves, grains of any desired magnitude are obtainable. Congreve's granulating machine gives a yield four or five times as great as that of Lefevre (for the same consumption of power) and also forms less dust. DRYING. The granulated powder is sometimes dried by spreading it out in layers 5 cm. deep on cement floors exposed to the air and sun and mixing it occasionally with rakes ; this drying is continued until the moisture is reduced to 3 per cent. The dust and residues from all the operations are mixed with the ternary mixture before compression. Artificial drying, which is independent of climatic conditions, is however, more 272 ORGANIC CHEMISTRY commonly used. In early times the powder was placed in copper pans heated directly over the fire, but this led to many explosions ; later it was spread out on cloths in a chamber heated by a stove in the centre, but this also was dangerous even when the stove was out- side the chamber. Nowadays drying is generally effected by air (used for the first time in England in 1780) which is heated by a network of steam-pipes and is injected into a drying-room containing the powder spread on cloth in layers 5 to 15 cm. deep, mixing with wooden rakes being resorted to about every two hours. The air passes through the powder and is carried off by flues ; the drying takes 8 to 10 hours. The fire of the steam- boiler is at least 100 metres from the drying-room. Dry powder can be powdered between the fingers, giving a pale, grey powder, but if not dry it is dark and sticks to the hands. In some factories the air used is previously dried (and is employed cold if the nitre present tends to effloresce, but hot in other cases) by being forced with a fan, A (Fig. 191), through fused, spongy calcium chloride or con- centrated sulphuric acid contained in a leaden vessel, D. Thence it passes into the chest, E, filled with -lumps of quicklime, which holds back any acid carried over. It is then heated in the brickwork chamber, B, by a number of pipes, c, supplied with steam at d; the warm, dry air then proceeds through the tube, V, to the drying-rooms. The proposal has also been made to dry powder by heating it in a vacuum, but such a process is too costly and its efficiency low. Drying need not be complete, since the powder has still to be glazed. GLAZING. The dried grains are rough, angular, and highly porous. In order to give a brighter appearance to the powder and to render it more uniform and dense and less si V FIG. 191. FIG. 192. hygroscopic, it is treated in wooden glazing drums (Champy drums, similar to those used for the binary mixtures ; see above) after having been passed through a fine sieve to free it from adherent dust. The inner walls of the drum are first moistened and the drum slowly rotated while the powder is being introduced until about 300 kilos are present, the Velocity being then raised to 12 to 14 revolutions per minute ; the finer the granulation the more rapid must be the rotation. In this way the powder becomes heated to about 50 and assumes a gloss ; care must, however, be taken that it does not become too hot, and towards the end of the glazing the rotation must be slackened. A little graphite is sometimes added (0-25 per cent.) to render the powder less hygroscopic and more glossy and to facili- tate the rounding process. Glazing takes four to five hours for blasting powders and fifteen to twenty hours for sporting powder. Glazing is due to the rubbing of the grains one against the other. The powder is subsequently dried completely in the usual drying-rooms, or the panels of the drum may be opened so as to allow of the escape of the warm, moist air. Polishing and sorting are carried out, after the glazing and drying, to remove the last traces of dust and separate the different sizes of grains. For these purposes a battery of sieves similar to those of the Lefevre and Congreve graining machines is used, the sieving being repeated several times. The dust contains about 75 per cent, of carbon. PRISMATIC POWDER FOR CANNON. It was shown by San Roberto as early as 1852 that cannon give better results if charged with compressed cartridges of regular form, and the American, General Rodman, proposed in 1860 to make large grains of regular shape. The use of such powder was extended in Russia by General Doremus, and also in other countries, but was found to give better results for blasting than for military powder. In England, Armstrong's grains, in the form of hazel-nuts, met with great success and are still used. In 1879, by means of special hydraulic presses (cam-presses), Wischnegradsky prepared the first prismatic powders, six or seven holes being left in each prism (Fig. 192) NITROGLYCERINES 273 to diminish the initial pressure on the cannon and give a more regular combustion. Every prism is 25 mm. high and 40 mm. in diameter, and weighs 40 grams ; it has the density 1-66 and bears the mark C.66. It is used for 15 to 26 mm. guns, whilst that for larger cannon has the same volume but the sp. gr. 1-75 (marked C.75). The brown prismatic powder of Rottweil of Hamburg has the sp. gr. 1-86 (C.86), and is used for large cannon, since it burns slowly, gives little smoke, keeps well and imparts to the projectile a high initial velocity, which increases until the mouth of the cannon is reached ; it is prepared with rye-straw charcoal and contains 78 per cent, of nitre, 3 per cent, of sulphur, and 19 per cent, of brown charcoal. The Italian chocolate powder contains 79 per cent, of potassium nitrate, 18 per cent, of carbon, and 3 per cent, of sulphur. PACKING. Powder is packed in bags containing from 50 kilos, these being placed in barrels or cases coated inside with paper and outside with cloth. Each case bears a label of a colour indicating the nature of the powder (rifle, cannon, etc.). Sporting powder is placed in tin boxes holding 100, 200, 500, 1000, or 2000 grams, these being then arranged in cases containing 25 kilos. Powder for firing volleys or ball is converted directly into cartridges, which are then stored in cases in sawdust, cotton waste, or similar packing. CHARACTERS AND PROPERTIES OF BLACK POWDER. It has a slate-grey colour, and, if too black, either it is damp or it contains too much charcoal. Certain military powders have a brown colour, as they are prepared with reddish-brown charcoal. If rubbed on a sheet of paper it should not leave a dirty mark, as, if it does, it contains dust or moisture. When a small heap of powder is ignited on a sheet of white paper it should burn rapidly without leaving a residue or burning the paper; if very black spots remain, there is excess of charcoal, or if yellow ones, excess of sulphur. On exposure to the air, good powder absorbs only 1'5 to 2 per cent, of moisture, whilst as much as 14 per cent, may be absorbed by inferior powder. If the moisture-content of powder is only 5 per cent, it may be removed without damage to the powder, but nioister powders cannot be restored to their original strength by drying, since the grains become covered with a crust of nitre. The finer the powder and the richer in charcoal, the more hygroscopic it is. The temperatures of ignition and explosion are the same, and ignition or explosion can be produced by red-hot iron or any ignited substance, or with less ease by percussion, shock, or discharge. It is more difficult to ignite by a blow of iron on copper, or copper on copper, than by one of iron on iron or brass, or of brass on brass, etc. Powder ignites more readily by a spark or red-hot body than by a gas-flame. Guncotton burns on powder without igniting it. Different powders ignite between 270 and 320 according to the form of the granulation. NITROGLYCERINES AND DYNAMITES The name nitroglycerine is given improperly to nitric esters of glycerine, since they do not contain true nitro-groups (N0 2 ) united directly with carbon,' as is often the case in benzene derivatives. On the contrary, the union is effected through an intermediate oxygen atom, so that these compounds should rather be called glyceryl nitrates. Being a trihydric alcohol, glycerine can form three such compounds, the only one known until quite recently being trinitroglycerine, containing 18-5 per cent, of nitrogen and having very considerable industrial importance. In 1903, Mikolajczak prepared also pure DINITROGLYCERINE, C 3 H 5 - OH(ON0 2 ) 2 , containing 15-4 per cent, of nitrogen, and he proposed to use it as an explosive, as it possesses almost all the ballistic advantages of trinitroglycerine and is not easily frozen ; it is, however, very hygroscopic and readily soluble in water and in acids. In 1904 he proposed to add it to trinitroglycerine to render the latter more highly resistant to frost, and since then it has been manufactured on an industrial scale at Costrop (Gel-many). As early as 1890 Wohl (Ger. Pat. 58,957) had already described various properties of monc- and di-nitroglycerines, including the power of lowering the freezing-point of trinitroglycerine. VOL. n. 18 274 ORGANIC CHEMISTRY In 1906 Will showed that sometimes the dinitro-compound raises, instead of lowering, the solidifying point of trinitroglycerine. Dinitroglycerine is prepared by nitrating 100 parts of glycerine with 400 parts of nitric- sulphuric mixture containing 8 to 12 per cent. H 2 O, 60 to 70 per cent. H 2 SO 4 , and 15 to 32 per cent. HN0 3 ; at the end of the reaction, the mass is poured into an equal volume of water, and the acid neutralised with calcium carbonate, when the dinitroglycerine separates as a dense, floating oil. During the reaction, the temperature is maintained at 18 to 20 by cooling with ice. Dinitroglycerine is also formed on dissolving trinitro- glycerine in sulphuric acid and then diluting the solution with a little water. In whatever way it is prepared (e.g., by treating 1 part of glycerine with 2 parts of sulphuric acid, separating by means of lime the glycerinedisulphuric acid formed and treating this with nitric acid, as proposed by Escales and Novak, 1906), a mixture of the two possible iso- merides is always obtained: dinitroglycerine K (i.e., ay-), N0 3 -CH 2 -CH(OH)-CH 2 -NO 3 , and dinitroglycerine F (i. e., a /?-), NO 3 -CH 2 'CH(N0 3 )-CH 2 -OH, which was studied by W. Will (1908). The mixture forms an almost colourless or faintly yellow oil, sp. gr. 1-47 at 15, which freezes at below 30 to a glassy mass, this distilling almost undecom- posed at 146 under reduced pressure (15 mm.) ; at 15 it is soluble to the extent of 8 per cent, in water and at 50 to the extent of 10 per cent. In dilute sulphuric or nitric acid it dissolves in all proportions and by sulphuric acid (up to 70 per cent. ) it is transformed into mononitroglycerine and then into glycerine. It is very hygroscopic and, when dry, dissolves or gelatinises nitrocellulose (guncotton or collodion-cotton) very well. The two isomerides may be separated by taking advantage of the fact that, in the air, the F com- pound absorbs 3 per cent, of water and is transformed into a crystalline hydrate, 3(C 3 H 6 O 7 N 2 ) + H 2 0, whilst the other remains liquid. The .F-form gives a nitrobenzoyl- derivative melting at 81, the corresponding compound of the ./f-isomeride melting at 94. In the dry state, the dinitroglycerines are as useful for explosives as the trinitro-compound, but when moist they are much inferior. A mixture of 50 per cent, dinitro- and 50 per cent, trinitro -glycerine freezes below 20. Of MONONITROGLYCERINE, C 3 H 5 (OH) 2 N0 3 , the pure a- and /3-isomerides are known (W. Will, 1908). These are not true explosives and dissolve to the extent of 70 per cent, in water. The a-compound melts at 58 and boils at 155 to 160 under 15 mm. pressure. Nitrochlorhydrin, C 3 H 5 C1(N0 3 ) 2 , and Tetranitrodiglycerine (see p. 218) have also been proposed as non-congealing explosives, but better still for this purpose are the nitroacetins (V. Vender) (see later). 1 1 Dinitromonochlorhydrin is obtained, according to F. Roewer (1906), by nitrating the monochlorhydrin in the same manner as glycerine is nitrated (see later), and is then quickly separated from the top of the nitric-sulphuric acid mixture as an oil which is easily rendered stable by washing with water and soda. It forms a faintly yellow, mobile oil of aromatic odour, sp. gr. 1-541 at 15, soluble in alcohol, ether, acetone, or chloroform, but insoluble in water and in acids. At 180 it gives yellow vapours, and at 190 boils without detonation or deflagration, and with only slight decomposition; under a pressure of 15 mm. it distils unchanged at 121 to 123 as an almost colourless oil. It is much more stable towards pressure than nitroglycerine, although possessing almost the same explosive properties. It does not freeze even at 30 and is not hygroscopic. It dissolves nitrocellulose, forming explosive gelatine, and mixes readily with nitroglycerine, giving non-congealing dynamites (with 5 to 20 per cent, of nitrochlorhydrin, Ger. Pat. 183,400), these being prepared by nitrating directly a mixture of glycerine and chlorhydrin. In order to avoid the inconvenient effects on miners of the hydrochloric acid formed in the explosion of nitrochlorhydrin, potassium nitrate is added ; during the explosion this is transformed into potassium carbonate, which neutralises the acid. Dinitroacetylglycerine, C 3 H 6 (ONO 2 ) 2 (OCOCH 3 ), is obtained by nitrating the monoacetinin the same apparatus as is used for nitroglycerine, but using an acid mixture containing a pre- ponderance of nitric acid, e. g., 65 per cent. HN0 3 and 35 per cent. H 2 S0 4 . The dinitroacetyl- glycerine, being somewhat soluble in water, is lost to some extent during the washing. It is a yellowish oil, sp. gr. 1-45 at 15, and is soluble in alcohol, acetone, ether, nitroglycerine, or nitric acid, and almost or quite insoluble in water, benzene, or carbon disulphide. It contains 12-5 per cent, of nitrogen and with double its weight of nitroglycerine gives a mixture with 16-5 per cent, of nitrogen, which has a lower freezing-point (below 20) than any other mixture of these substances. It serves well for preparing non-congealing dynamites, and as it dissolves nitrocellulose easily it may be used for gelatinising smokeless powders. Dinitroformylglycerine, C 3 H 8 (ONO 2 ) 2 (O CHO ), is prepared in a similar manner to the pre- ceding compound, or, together with nitroglycerine, by nitrating the product obtained by heating two parts of glycerine with one part of oxalic acid for twenty hours at 140. Nitroformin and ' nitroacetin have explosive powers rather inferior to that of nitroglycerine. TRINITROGLYCERINE 275 CH 2 N0 2 TRINITROGLYCERINE, CHO N0 2 or C 3 H 6 (0 N0 2 ) 3 . CH 2 0-N0 2 This was discovered in February 1847 by Ascanio Sobrero, 1 who called it Pyroglycerine and established its explosive properties but regarded its industrial manufacture as too dangerous. Its chemical composition was determined by Williamson in 1854. At first it was used only in small doses as a medicine, owing to its marked power of inducing dilata- tion of the blood vessels, and afterwards its 1 per cent, alcoholic solution was administered in 1 gram doses under the name glonoin, especially by American doctors, in cases of cardiac neuralgia, nervous disorders, hemicrania, hiccough and sea-sickness. Later, after various unavailing attempts, Alfred Nobel succeeded in applying it industrially, and in 1863 established two nitroglycerine factories, one at Stockholm and the other at Lauenburg, near Hamburg; the former blew up in 1864, while the ship "European," carrying nitro- glycerine, blew up in Colon harbour, and other explosions occurred in England, at Sydney, at San Francisco, etc. In spite of the large consumption of nitroglycerine in many countries, these accidents were followed by the almost universal prohibition of its manufacture. Fortunately just at this time Nobel discovered a very happy solution of the problem which completely eliminated this danger, by mixing the nitroglycerine with inert substances (kieselguhr or infusorial earth) and thus obtaining dynamite, this being to-day at the head of the great explosives industry. PROPERTIES. When pure it is a dense, almost colourless or faintly yellow liquid of sp. gr. 1'6 at 15, T604 at 11, 1-588 at 25, and when it freezes its density increases by almost one-tenth. It is odourless and has a sweetish, burning taste. It is almost insoluble in water (0'16 to 0'20 per cent, being dissolved at 15), is not hygroscopic, and dissolves easily in concentrated alcohol, ether, benzene, chloroform, glacial acetic acid, toluene, nitrobenzene, phenol, acetone, olive oil, and concentrated sulphuric acid (sp. gr. T845), and to a less extent in nitric acid and still less in hydrochloric acid; it is, however, insoluble in carbon disulphide, glycerine, petroleum, vaseline, tur- pentine, benzine, carbon tetrachloride, and the nitric-sulphuric acid mixture used in its manufacture. In solution it will not explode. It evaporates spontaneously and in very small quantities even at 50, and if gradually heated to 109 it begins to decompose with evolution of brown nitrous vapours. _ Its specific heat is 0'356, and its heat of solidification 23 to 24 Cals. At a red heat it evaporates without decomposing, but if it begins to boil vigorously during the heating, there is danger of explosion. According to Champion, pure nitroglycerine in small quantities boils, giving yellow vapours, at 185, evaporates slowly at 194 and rapidly at 200, burns quickly at 218 and detonates with difficulty at 241, violently at 257, feebly at 267, and feebly with flame at 287 (being in the spheroidal state). When heated in small quantities in thd bunsen flame, it burns without exploding, and if spread in a thin layer on paper it ignites with difficulty and burns only partially. Explosion of nitroglycerine can be induced either by violent percussion at a temperature of 250, or by energetic detonation (e. g., by explosion of fulminate of mercury). Nitroglycerine may be easily supercooled below its solidifying point. Kast (1905) showed that nitroglycerine represents a case of monotropic allotropy 1 Ascanio Sobrero was born at Casalmonferrato on October 12, 1812. He studied first medicine and then chemistry. In 1840 he went to complete his chemical studies in the laboratory of the celebrated Pelouze at Paris, where he stayed two years, and in 1843 he worked in Liebig's laboratory at Giessen. In 1845 he became Professor of Applied Chemistry at Turin, where he taught until 1883. He died on May 26, 1888, after a modest life, during which he filled various honorary social positions. It was always his aim that science should not be made a pretext or means of dishonourable undertakings or of business speculations. 276 ORGANIC CHEMISTRY (see also Vol. I., p. 208), i. e., it has two freezing-points, + 2'1 and -}- 13'5 , corresponding with different crystalline forms. 1 The heat of transformation of 1 gram of liquid nitroglycerine into the solid labile form is 5*2 cals., and that of the latter into the solid stable isomeride 28 cals., this being obtained by seeding with a crystal of the stable form and stirring at (Hibbert and Fuller, 1913). When frozen, nitroglycerine explodes with more difficulty than in the liquid form. Pure nitroglycerine will not redden blue litmus paper or turn starch paste and potassium iodide blue, unless it contains free acids or nitrous compounds due to partial decomposition. Impure nitroglycerine readily decomposes and may explode spontaneously, whilst in the pure state it keeps indefinitely. A sample of nitroglycerine (200 grams) prepared by Sobrero in 1847 is still kept under water in the Nobel factory at Avigliana. When decomposing, nitroglycerine turns green, owing to the formation of N 2 O and N 2 O 3 ; CO 2 , CO, H 2 O, N, and O (see also p. 259) are also successively formed. In exploding, 1 litre of nitroglycerine produces 1298 litres of gas, which, at the temperature of explosion, occupies a space of 10,400 litres. In large doses nitroglycerine is poisonous and its vapour causes headache (especially at the back of the head), giddiness, and vomiting. These effects are produced even by working with or simply touching nitroglycerine, and are cured by means of cold compresses on the head, by breathing fresh, pure air, and by drinking coffee and taking suitable doses of morphine acetate. Workmen who handle the nitroglycerine paste during the manufacture of the various dynamites become habituated to it in two or three days and afterwards feel no ill effects. Nitroglycerine is moderately easily decomposed by alcoholic potassium hydroxide (with separation of glycerine), and, when necessary, this reaction is employed to destroy and render harmless small quantities of nitroglycerine; similarly benches or floors on which nitroglycerine is spilt are washed with caustic alkali solutions : C 3 H 5 (ON0 2 ) 3 + 5KOH = KN0 3 + 2KN0 2 + CH 3 COOK + H COOK + 3H 2 ; a little ammonia is also formed. With reducing agents it gives ammonia and glycerine, whilst with concentrated sulphuric acid it yields nitric acid and glycerinesulphuric acid. 2 1 Both nitroglycerine and also dynamites and smokeless powders prepared from it are liable to sob'dify, and although they are then more stable (or as stable as the liquid, as was shown by Hess, Dupre, Cronquist, Will, etc.) the thawing is accompanied by danger, and when not carried out with great precautions has often led to fatal explosions, these being sometimes caused by the mere rubbing of the crystals. Indications will be given later of the precautions taken in magazines to prevent freezing, and mention may be made here of the attempts which have been made to render nitroglycerine non-congealable. As early as 1895 it was proposed to add nitrobenzene* to nitroglycerine to lower the freezing-point, and later the use of orthonitrotoluene was suggested, but the practical results were not very satisfactory in either case, the depression of the freezing- point being very small. Substances were required which were almost as explosive as trinitro- glycerine, and were insoluble in water and stable on heating, and, in addition, were good solvents for nitrocelluloses (for making smokeless powders). These conditions were well satisfied by the nitroformins and nitroacetins tested by Nobel as early as 1875. but rendered practically useful in 1906 by V. Vender. The best results are given by dinitromonoacetin, which is obtained from the monoacetin of glycerine prepared by the, ordinary method used for esterifying alcohols with acids (see later: Esters). Forty parts of the monoacetin are introduced slowly into a mixture of 100 parts of nitric acid (sp. gr. 1-530) and 25 parts of oleum or Nordhausen sulphuric acid (containing 25 per cent, of free S0 3 ), the mass being cooled so that the temperature does not exceed 25. The whole is then poured into water and washed with cold and afterwards with hot (70) dilute soda. By this means an oil is obtained having sp. gr. 1-45 and containing 12-5 per cent, of nitrogen ; it is insoluble in water, carbon disulphide or benzine, but dissolves un- changed in nitric acid, nitroglycerine, methyl or ethyl alcohol, acetone, acetins, etc. Even in the cold, it has considerable solvent and gelatinising power for collodion-cotton and guncotton (with 13-4 per cent, of nitrogen ) and the resulting explosive gelatines do not freeze even at 20. Naukhoff (1908) has proposed the addition of nitromethane or nitroethane to dynamite to lower its freezing-point; mono- and di-nitroglycerines also give good results (see pp. 273, 274). In 1866, Rudberg patented in Sweden the addition of nitrobenzene to obtain non-congealing dynamites, fii the Arendonck factory (Belgium) Leroux in 1903 successfully used liquid dinitrotoluene to render dynamite incongealable ; Mikolajczak in 1904 utilised dlnitroglycerine for the same purpose. The number of accidents has been reduced to one-half in this way. 2 In certain practical cases the following reactions may be of interest : Nitroglycerine is not altered by prolonged contact with nitrates of Ca, Co, Na, Ba and K, with chlorides of Ca, Ba MANUFACTURE OF NITROGLYCERINE 277 Characteristic Reactions. According to Weber, small quantities of nitroglycerine are detected by treatment with aniline and concentrated sulphuric acid ; a reddish- purple coloration is obtained which turns green on addition of water. To establish the purity and keeping qualities of nitroglycerine, the nitrogen is determined and Abel's heat test carried out (see later, Testing of Explosives); if it is satisfactory, 2 c.c. of it withstands 15 to 25 minutes' heating at 82 without giving sufficient nitrous vapours to be detectable by means of starch and potassium iodide paper. This reaction is, however, given by nitroglycerine kept for a few days at a temperature exceeding 45, or for a long time below this temperature. PREPARATION. It is obtained by the action of a mixture of nitric and sulphuric acids on glycerine : C 3 H 5 (OH) 3 + 3HN0 3 = 3H 2 + C 3 H 5 (N0 3 ) 3 . The mono- and dinitro-compounds are probably formed as intermediate products of this reaction. The presence of sulphuric acid, which plays no apparent part in the change, is usually regarded as being necessary to maintain the nitric acid at a high concentration, i. e., to decompose the hydrates formed by nitric acid with the water from the reaction (HNO 3 , H 2 HN0 3 , 3H 2 O) and so regenerate mono- hydrated nitric acid, which acts on the glycerine (Kullgren, 1908). If the function of the sulphuric acid were merely to fix the water, phosphoric acid could be used in its place, but if this is done no nitroglycerine is obtained (see succeeding Note). The excess of the nitric-sulphuric mixture which is always used helps to produce a moderately complete separation of the nitroglycerine, which has a slightly lower density, so that it is possible to recover the acids employed. Although nitroglycerine is soluble in sulphuric or nitric acid alone, it does not dissolve in the mixed acids, but if one of the two acids is in large excess, a con- siderable amount of nitroglycerine remains in solution and is lost. In the nitration, the whole of the glycerine cannot be added at one time, since sufficient heat would in that way be developed to produce decomposition and explosion of the nitroglycerine instantaneously formed. It is also not convenient to reverse the operation, that is, to add the mixed acids gradually to the glycerine, the greater density of the latter rendering rapid and homogeneous mixing difficult : it is hence preferable to run the glycerine slowly into the acid mixture and to keep the latter continually and thoroughly stirred and cooled. MANUFACTURE. The theoretical proportions of the reacting substances * would be 100 parts by weight of glycerine and 205-43 of pure nitric acid, the theoretical yield of trinitroglycerine being then 246-74 parts. On a large scale, however, the whole of the nitric acid does not come into immediate contact with the whole of the glycerine, and it is hence better to use a slight excess of nitric acid (240 parts or even more); the amount and Fe, with sulphates of K, Na and Ca, or with calcium carbonate. With silver nitrate it gives a black precipitate of silver oxide, while with stannous chloride it precipitates tin peroxide and forms a mirror at the surface. It reduces potassium dichromate partly to chromate, and gives a slight precipitate of copper oxide with copper sulphate and a voluminous precipitate and nitrous vapours with ferrous sulphate. Sulphides, including hydrogen sulphide, decompose nitroglycerine slowly with separation of sulphur and glycerine. 1 The prime materials used in the manufacture of trinitroglycerine should be subjected to rigorous control ; the glycerine should be pure and distilled and should satisfy the requirements indicated on p. 222. The nitric acid should have a specific gravity of 1-500 (48 Be. or about 95 per cent. HN0 3 ) and should not contain more than 1 per cent, of nitrous acid (the final mixture less than 0-3 per cent.), i. e., it should not be yellow, as otherwise an increased amount of heat is evolved during nitration and the yield is lowered. The sulphuric acid should be pure, with a sp. gr. of 1-8405 (i. e., at least 96 per cent. H 2 S0 4 ) and acid "containing more than 0-1 per cent, of arsenic should be avoided ; lead and iron should also be absent as they might lead to reduction. When nitrations are carried out with nitric-sulphuric acids almost free from water ( 1 to 2 per cent. ) the sulphuric acid is replaced by oleum or Nordhausen acid (see Vol. I., p. 317), i. e., acid containing ' 20 per cent, or more of dissolved sulphur trioxide. According to Markovnikov (1899) the sulphuric acid first forms the intermediate product, OH SO, ONO,, with the nitric acid. 278 ORGANIC CHEMISTRY of sulphuric acid employed always exceeds that of the nitric acid (about 1 times). In modern factories the following proportions are often used : 100 kilos of glycerine, 240 to 270 kilos of nitric acid (96 per cent.), and 330 to 360 kilos of sulphuric acid (96 per cent., partly oleum). In the best factories the practical yield was formerly 200 to 210 kilos of nitroglycerine per 100 of glycerine. In 1900, however, the French works began to make use of highly concentrated acid mixtures (the 5 to 6 per cent, of water being diminished to 2 to 3 per cent, by mixing oleum in place of sulphuric acid of 66 Be. with the concentrated nitric acid). Later Nathan and Bintoul employed mixtures containing only 1 to 1-5 per cent, of water, the yields rising to 225 to 228 per cent. Yields of 232 per cent, were then obtained by means of water-free mixtures, from which the nitroglycerine separates better owing to its less solubility and to the greater difference in density. The yield may be improved still further and the duration of the nitration reduced to one-half by cooling the acid mixture during the reaction by means of brine from a refrigerating machine, the temperature being thus maintained at about 10. The highest yields appear to be obtained with a mixture containing 46 per cent, of HN0 3 and 54 per cent, of H 2 S0 4 (Hofcoimmer, . -l$12). The low value of the practical compared with the theoretical yield (246-7) is due to the fact that towards the end of the reaction there is very little free nitric acid and the last portions of glycerine added are nitrated only with difficulty, and hence remain dissolved in the sulphuric acid. The mixture of nitric and sulphuric acids, which is prepared separately, is made by pouring the sulphuric acid slowly into the nitric acid (not vice versa) in an iron vessel, the mixture being kept well cooled and stirred. With this procedure there is no danger of the acid spurting, and no production of nitrous fumes, since the development of heat is gradual. This mixture is forced by means of elevators (Montejus) or pulsometers working with co-mpressed air (Vol. I., p. 302) into tanks which feed the leaden apparatus in which the glycerine is nitrated. During recent years, many vitriol and explosives works have made considerable use of Kuhlmann emulsors (or Mammoth pumps) for raising concen- trated acids, which are rendered lighter by emulsifica- tion with air (see illustration, Vol. I., p. 304). The leaden nitration apparatus is shown in Fig. 193. It is surrounded by a wooden jacket inside which water circulates. Inside the vessel are peripheral leaden coils through which large quantities of cold water are continually passed by means of the two tubes D. The tubes G lead dry compressed air to the bottom of the liquid, which is thus kept thoroughly mixed. The tube F serves as exit for the air, and for any nitrous vapours which may be evolved and may be observed through the window, / ; these vapours are recovered in small condensation towers sprinkled with a little water. The cold acid mixture is first intro- duced through the pipe G. The glycerine, at a temperature of 20 to 25 (if colder it would be too viscous), is measured in the reservoir, M, and is passed, by means of compressed air supplied through O, slowly into the tube H, and thence into a perforated circular pipe at the bottom of the apparatus. Two thermometers, E, show the temperature of the reacting mass at any moment. The bottom of the apparatus is slightly inclined and at the lowest part is inserted a large stoneware tap, K, with an ebonite screw containing an aperture of at least 5 cm. It is convenient to have two of these taps so that, in case of danger, the whole of the mass may be rapidly discharged into a vessel of water underneath (drowning of the nitroglycerine). In such an apparatus, the same quantity of nitroglycerine is produced each time and the NITRATION OF GLYCERINE 279 -p IG treatment of 100 kilos of glycerine requires less than half an hour. 1 In America as much as 2000 kilos of glycerine are worked at one time in open vessels provided with stirrers, but the risk, in case of explosion, is greatly increased. At the conclusion of the operation the nitroglycerine (sp. gr. 1-6) floats on the acids (sp. gr. 1-7) and is separated by means of a suitable decanting apparatus (Fig, 194) to the bottom of which the whole mass is passed through the tube K. The apparatus consists of a leaden tank with its base sloping towards the centre and supported by a wooden structure ; the cover, C, is raised on wooden joists, B. The tube Z>, with the glass window, E, serves to carry off any gas which may be evolved; a thermometer is inserted into the vessel at t. The tube shown at the bottom and in the centre of the apparatus communicates with two or three taps, H, and is also fitted with a window, F. After half an hour, the nitro- glycerine in this vessel separates into a distinct layer, as may be seen through /. The surface of separation of the two layers coincides very nearly with the tap J, so that the nitroglycerine may be discharged almost completely through the tube J into the lead-lined wooden tank, L. 2 The acid that remains is discharged through one of the taps, H, it being noted 1 Before the reaction is started the acid mixture in the apparatus is cooled to 15 to 18, a stream of air (as dry as possible) being passed through it and cold water being circulated through the coils. If brine from an ice machine is used, the temperature may be lowered to 8 to 10. The temperature during the reaction should not exceed 25 to 30 ( 18 to 20 if brine is used), and it may be regulated by passing the cooling water more or less rapidly through the coils, and, if necessary, through the wooden jacket; increase of the air-current also helps to lower the temperature. Rise of temperature and consequent explosion were at one time due principally to the use of impure glycerine, but nowadays are generally due to slight escape of water from the coils. In order to avoid such danger, the apparatus and coils are tested at least once a day, usually in the evening, when the plant is free ; water under pressure is forced into the coils and jacket and left until the morning, when any leak can be detected. Although the apparatus is constructed of very thick plates, the lead corrodes in time ; tests made with aluminium apparatus (proposed by Guttler) have not been very successful. Some works now employ more solid vessels of wrought- or cast-iron, which are more easily cooled. Boutmy and Faucher (1872) avoid the dangers of violent reactions by first dissolving, e. g., 100 parts of glycerine in 320 of sulphuric acid and then pouring the solution into a mixture of 280 parts of nitric and 280 of sulphuric acid. After twelve hours the reaction is complete, the yield being 190 per cent., calculated on the weight of the glycerine taken. This method did not give good results in England, but has been applied in France. The procedure is, however, irrational, since the operation occupies twelve hours, the duration of the contact of the acid with the nitroglycerine and hence the danger period being prolonged. A factory using this method did, indeed, blow up and the process was then abandoned. Kurtz (Ger. Pats. 6208 and 8493) increases the yield and accelerates the reaction by emulsify- ing the glycerine with air and passing it under the acid mixture, a more intimate mixture being thus obtained. R. Evers (Ger. Pat. 183,183, 1902), instead of mixing with a current of air, which always carries off a little acid, passes the acid mixture and glycerine at the same time through a pulveriser into the apparatus. 2 Not infrequently, owing to the formation of a colloidal froth of silicic acid, the nitroglycerine separates very slowly from the acids, two or three hours being sometimes required for a good separation and the danger of decomposition thus increased. Various investigations have been made with a view to discover a means of preventing such slow separation, which is often due to the use of glycerine of poor quality or of impure acids. Good results have been obtained by the addition, before the mass is discharged into the separator, of a small quantity of sodium fluosi- licate, the bubbles of hydrofluosilicic acid thus developed causing rapid separation of the nitro- glycerine. Reese (Brit. Pat. 20,310, 1905) adds at the beginning of the reaction, about 0-002 per cent, of sodium fluoride, calculated on the weight of the glycerine. According to Ger. Pat. 249,579 of 1911, 0-02 to 0-05 per cent, of finely powdered talc or kaolin (on the weight of the glycerine) may be added to the acid before the reaction is started. 280 ORGANIC CHEMISTRY through F when a turbid layer appears, as this separates the acid from the nitroglycerine and contains various nitro-products and certain impurities. 1 The tap, H, is then closed and this liquid is passed through other taps into suitable washing and decanting vessels (see later). The nitroglycerine in L is .washed with water and is then agitated by passing compressed air through the perforated pipe, N, for about fifteen minutes ; the nitroglycerine is allowed to settle and the water decanted off by means of -the upper tap, M . The washing with water is repeated two or three times, all the washing water being collected in a single tank. 2 Finally the nitroglycerine is passed into a similar 1 The acid separated from the nitroglycerine and containing about 70 to 73 per cent. H 2 S0 4 , 9 to 10 per cent. HNO 3 , 15 to 16 per cent. H 2 O, and 3 per cent, of dissolved nitroglycerine, is collected in leaden tanks in which it remains for one or two days, during which time a small quantity (about 0-5 per cent.) of nitroglycerine separates at the surface. The dangers of this slow separation are sometimes avoided by neglecting the nitroglycerine which separates after four to five hours ; to avoid danger in succeeding nitrating operations, a large proportion of the nitroglycerine remain- ing dissolved is decomposed by adding cautiously 4 to 5 per cent, of water, so as to raise the temperature to 35 to 40 and then again mixing the mass by means of air (part of the trinitroglycerine is thus transformed into soluble dinitro- gly cerine ). These recovered acids, which are utilised again, are first denitrated in the apparatus shown in Fig. 195. This consists of a tower A, 4 to 5 metres high, composed of six or seven rings of volvic stone in one piece, fitted by means of grooves and luted with powdered asbestos and a little sodium silicate. The inner and outer diameters are respectively 30 to 40 cm. and 50 to 65 cm. These rings are surrounded by tightly fitting cast- iron hoops. The internal space is filled with fragments of silica (quartz), glass or stoneware, resting on a grid of volvic stone or earthenware. The acid to be denitrated passes from the tank D down *** the tower as a spray, while a current of FIG. 195. steam, superheated to about 350 and mixed with a little hot air (at 400) is passed in at the bottom through the cock a. The acid feed is regulated so that sulphuric acid at about 150 collects at the base of the tower, while the nitric acid vapour issuing through the tube C has the temperature 110 to 120. By introducing this hot mixture into the tower, steam is economised and the nitric acid condensing in the stoneware pipes G is rendered more con- centrated (usually 60 to 65 per cent., although with care 85 per cent, may be reached) and, if sufficient air is used, contains little nitrous acid (3 to 5 per cent.). The gases not condensed in the pipes G are completely condensed in the ordinary stoneware .towers fed with a little water or dilute nitric acid (see Vol. L, p. 388), being passed from one tower to the other until acid of 32 to 36 Be is obtained. The sulphuric acid at last reaches the bottom of the tower, A, where it collects in the basin, E, and thence passes through the leaden cooling coil, F. The acid thus obtained is darkened by the impurities present and has a density of about 56 to 58 Be ; it is usually concentrated in the Kessler apparatus or in Gaillard towers (see Vol. I., p. 308). During recent years, instead of the sulphuric and nitric acids being recovered and concen- trated separately, it has been found preferable to send the acid mixture after decomposition of the dissolved nitroglycerine (see above) directly but carefully into the vessels (already con- taining the sodium nitrate) in which nitric acid is made. Some prefer to revivify the acid mixture, i.e., to bring it up to its original strength by adding the necessary quantities of fuming nitric and sulphuric acids, so that it may be used again for the production of fresh quantities of nitro- glycerine ; for this purpose, sulphuric anhydride or oleum is added slowly to the required amount of concentrated nitric acid and the mixture then poured into the weak acid. For this process of recovering the weak acids (by which the 2-5 per cent, or so of nitroglycerine dissolved in the acid is recovered) to be employed, a cheap supply of sulphuric anhydride or oleum must be available (oleum at less than 40s. per ton ). 2 The wash-waters from all the preceding operations are collected in an inclined lead-lined tank called the labyrinth, which is divided into a number of chambers by vertical leaden walls perforated alternately at the top and bottom. The wash-waters enter slowly at one end of the tank and traverse a long up-and-down course, gradually depositing the emulsified or suspended drops of nitroglycerine before the opposite end of the tank is reached. The nitroglycerine collected at the bottom is discharged through suitable taps and added to that in the washing apparatus. NATHAN-THOMSON PROCESS 281 FIG. 196. vat where it is stabilised, i. e., washed alternately with very dilute soda solution and water until the wash- water no longer has an acid reaction towards litmus and the nitroglycerine has a feeble alkaline reaction (0-01 of alkalinity, which disappears later). In the British Government factory at Waltham Abbey, Nathan, Thomson, and Rin- toul (Brit. Pats. 15,983, 1901 ; and 3020, 1903) prepare nitro- glycerine in large leaden vessels (a, Fig. 196) with inclined bottoms ; 300 to 500 kilos of glycerine are allowed to run into an anhydrous acid mixture in the proportion of 267 kilos of H 2 S0 4 and 243 kilos of HN0 3 per 100 kilos of glycerine, and at the end of the operation, after 50 to 60 minutes' rest, the acid recovered from a preceding operation is passed from the tank, c, to the bottom of a. In this way the nitroglycerine is displaced and caused to discharge through s into the washing vessel, e, exit for the vapours being supplied by the tube o. When all the nitroglycerine has been forced out, a little of the acid mixture is drawn off by the pipe i, 2 to 3 per cent, of water being then slowly added to the re- mainder, which is mixed meanwhile with a current of air. By this means the dissolved nitroglycerine is decomposed and the dangers of slow separation in any of the vessels avoided (see preceding Note). The acid is immediately de- nitrated, after sufficient has been passed into the tank, c, to displace the nitro- glycerine of the succeeding operation. 6 is the tank in which fresh acid is mixed, / the vessel for drowning, g that for stabilising, and h the filter for the nitro- glycerine, these two being at a considerable distance from e, so that the nitro- glycerine may be conducted to them as soon as it has undergone its initial rough washing. The nitrating apparatus is shown in section in Fig. 197. Yields of as much as 230 per cent, are obtained with this Nathan-Thomson process, which is now used in all countries. 282 ORGANIC CHEMISTRY FILTRATION. The washed nitroglycerine is carried in hardened rubber or ebonite buckets to the filters, which are merely wooden frames covered with woollen cloth or felt to retain the impurities, scum, gummy matters, etc. By covering these cloths with a layer of dried salt, the emulsified water also can be held back. The cloths rapidly become blocked and are frequently renewed. -The filtration is often, especially in England, effected by means of the apparatus shown in Fig. 198. This consists of a lead-lined tank, A, with inclined base. In the lid is inserted a leaden cylinder, G, with a metal gauze bottom on which rests a filtering cloth, N, and on this a layer of sodium chloride, 0, covered by another filtering cloth kept stretched by a leaden ring, Q ; the free part of this cloth is folded, stretched, and fixed by a conical leaden weight, S. In place of salt, a sponge may be em- ployed to retain the water. In some cases complete separation of the water from nitro- glycerine is obtained by leaving the latter at rest for a couple of days in a tepid place (30) and then decanting it, but there is then some risk, owing to the prolonged accumulation of large quantities of nitroglycerine. In the working of nitroglycerine, each operation is usually carried out in a separate building, that in which the explosive is produced being at a very high elevation, the nitro- glycerine then flowing to lower points for the succeeding operations. All these buildings are of wood so as to diminish the damage in case of explosion. The floors of the sheds in which the nitroglycerine is produced and of those where it is treated in the liquid state are covered with sheet-lead with raised edges so that the material may be caught in case of breakage. Where the nitroglycerine is worked in a pasty state (for dynamites) the flooring is of wood free from crevices. If nitroglycerine is accidentally spilled, it should be immediately wiped up with sponges. The channels through which nitro- glycerine passes from one shed to another are in the form of gutters furnished with removable covers and are fitted with a longitudinal pipe through which warm water may be circulated in winter and the danger FIG. 198. of freezing avoided. A disadvantage attend- ing the use of these channels is that an explosion in one shed is propagated along the channels to all the other sheds. Hence the precaution is taken of disconnecting one section of a channel when not in actual use. In many factories the nitroglycerine is transported in rubber pails (see above). The windows of the sheds are smeared with whitening, as the presence of curved parts in the naked glass might possibly result in the focussing of light on the explosive material and in the explosion of the latter. USES OF NITROGLYCERINE. Small quantities are sometimes used in medicine to induce dilation of the blood-vessels, but practically the whole of the production is used as an explosive. In America it has been long in use in the pure state for large mining operations ; Mowbray freezes it and trans- ports it in large quantities on trains from the factory to the place of consump- tion, as he regards it as less sensitive in the frozen state, but this view is generally contested. It has also been transported without danger in solution in methyl or ethyl alcohol, from which it is re precipitated with water at its destination. Almost all the nitroglycerine made is used in the manufacture of various kind of dynamites, dynamite gelatines, explosive gelatines, smokeless powder, etc. DYNAMITES. This generic name is given to explosives obtained by gelatinising or absorbing nitroglycerine by various other substances. We have already mentioned that Alfred Nobel, the father of dynamite, had from 1860-1864 various explosions of nitroglycerine, sometimes of that recovered from the alcohol in which it had been transported (see above). In his attempts DYNAMITES 283 to diminish the dangers of nitroglycerine by diluting it with inert substances, Nobel discovered in 1866 that it is absorbed by kieselguhr (infusorial earth) x in considerable proportions (up to 81 per cent.), and that in this state its power is diminished but little, while it can be safely handled and transported. He found further that this dynamite is exploded only by means of a fulminate of mercury cap. If the absorbing substances are inert, like infusorial silica (kieselguhr), sawdust, cellu- lose, etc., they form dynamites with inactive absorbents, which contain about 72 to 75 per cent, of nitroglycerine, 24-5 per cent, of kieselguhr, and 0-5 per cent, of soda for the No. 1 quality, and less nitroglycerine (up to 50 per cent. ) in the Nos. 2 and 3 qualities. In the new types of dynamite, however, the solid matter consists of active substances, e. g., nitrocellulose, which take part in the explosion. These are dynamites with active absorbents, the absorbents or bases being again divided into nitrates or inorganic oxidising bases and organic nitro-absorbents (collodion-cotton, etc. ). I. MANUFACTURE OF DYNAMITE WITH INACTIVE ABSORBENTS. The kieselguhr used must be suitably prepared. It is first spread out in furnace chambers and gently heated to eliminate moisture and organic matter, and is then more strongly calcined in reverberatory or muffle-furnaces, excessive heating, being avoided, as it may destroy the absorbing properties. It is then ground to fine powder and sieved. The flour thus obtained should not contain more than 1 per cent, of moisture and should be immediately filled into sacks and consumed the same day, as otherwise it might absorb moisture. It consists of silica with traces of oxides of iron and aluminium. The nitroglycerine is weighed in buckets of hard guttapercha or lacquered wood and 1 Kieselguhr is found in a very pure state in the Liineburg moors, near Unterliiss in Hanover, at Oberhohe near Ebsdorf (Prussia), at Tiitelwiese near Berlin, at Bilin (Bohemia), and in an inferior quality in Scotland, Norway, and Italy. It consists almost exclusively of the siliceous FIG. 199. remains of diatoms, and contains also traces of iron and organic matter. It is unsuitable if it contains aluminium sulphate. Its particles are formed of empty tubes perforated in all directions, and it is this structure which renders kieselguhr so highly absorbent. Under the microscope, it presents the appearance shown in Fig. 199. At the present time kieselguhr dynamite has been almost entirely replaced by new types (gums or gelatines) described later. The kieselguhr of Algeria (Orano) forms one of the richest deposits known, its composition being moderately constant, as is shown by the following percentage compositions of two samples (1911): H 2 O SiO a NaCl CaCO 3 MgSO 4 Impurities Orano type ... 5-7 72-6 0-3 14-8 2-2 4-2 Cherchell type ... 6-1 80-4 0-2 4-4 1-6 8-1 In 1914 a deposit of a million tons was found in Chili. 284 ORGANIC CHEMISTRY is carefully taken to the mixing -Jwuse, where it is poured into wooden troughs lined with sheet-lead, and containing the absorbent. Skilled workmen then mix the mass rapidly by hand ; sometimes rubber gloves are worn, but usually the men prefer to do without gloves, as the hands become accustomed to the action of the nitroglycerine in two or three days. It is important to obtain a homogeneous mixture, so that not the least portion of the kieselguhr remains free from nitroglycerine. After this hand-mixing the mass is rubbed through brass-wire sieves (2 to 3 meshes per centimetre) arranged above lead-lined wooden troughs. The dynamite is placed on the sieve with a wooden spatula and pressed through with the palm of the hand; here, too, the use of rubber gloves is not popular with the operatives. In the troughs the dynamite is in the form of fine grains, which should not be too dry or too greasy. If too dry, it is passed again through the sieve or mixed with more nitroglycerine, whilst if too greasy it is mixed with a further amount of kieselguhr. It is then placed in small portions in rubber bags or in wooden boxes lined with sheet-zinc and is removed to the building where the cartridges, used especially in mines, are prepared. Here the dynamite is transformed by simple presses into rolls, 19, 23, or 26 mm. in diameter. A very simple press devised by 0. Guttmann is shown in Fig. 200. The dynamite is intro- duced into the cloth bag, m, and falls into the tube, I, being pressed into this by the lignum vitae or ivory piston, p, at the end of the bar, d, which is actuated by the lever, i; the cylinder of dynamite issuing from the bottom of the tube, I, is broken by hand into definite lengths, which are wrapped in parchment paper or waxed paper. The ordinary length is 10 cm. (discharge cartridges) or 2-5 to 5 cm. (primers). These cartridge machines are sometimes worked by pulleys and motors. In some cases the boudineuses illustrated later are used. After the dynamite is wrapped up, packets of 2-5 kilos are placed in cardboard boxes, which are wrapped and tied round and filled in tens into wooden cases. For military purposes the cartridges are put directly into metal boxes with a socket in the lid for inserting the detonator. For use under water these metal boxes are sometimes used, and sometimes sausage- skins or rubber bags. These cartridge buildings are usually small, with light walls and roof ; only two or three operatives work in "each, high earthen banks separating one building from the next, so that the effects of an explosion may be mitigated. Dynamite containing 70 to 75 per cent, of nitro- glycerine is known commercially as dynamite No. 1 and those with 50 per cent, and 30 per cent, as No. 2 and No. 3 respectively. In place of kieselguhr various other absorbents are used at the present time, e. g., wood meal (cellulose) mixed with inert mineral salts (calcium carbonate, sodium bicarbonate, etc. ). First in America and then in Austria fulgurite was prepared with 60 per cent, of nitro- glycerine, the remaining 40 per -cent, consisting of wheaten flour and magnesium carbonate. At Cologne, Miiller prepared a Wetter-dynamite (safety dynamite, for use in mines containing firedamp; see later) by mixing 10 parts of ordinary dynamite with 7 parts of crystalline sodium carbonate; the water-vapour formed on explosion surrounds the flame and the explosive gases and thus prevents explosion of the firedamp. Many varieties of these dynamites are used to a greater or less extent in practice, e. g., carbodynamite, containing 90 per cent, of nitroglycerine and 10 per cent, of carbonised cork, sebastine, lithodastite, carbonite, etc. (see later, pp. 307, 311). Properties of Dynamite with Inert Bases. This forms a pasty mass of reddish yellow, red, or grey colour according to the quality of the infusorial earth employed; to ensure a uniform colour about 0-25 per cent, of burnt ochre is often added. It is odourless and has the sp. gr. 14 and the pasty consistency of wet modelling clay ; the inside of the wrapper should show no traces of nitroglycerine (sweating). It is much less sensitive to pressure and percussion than nitroglycerine and, in small portions, may be lighted and burned without exploding. FIG. 200. NITROCELLULOSE 285 It can, however, be exploded by powerful percussion or detonation, or by red-hot metal, or by heating suddenly to a high temperature or for a long time at 70 to 80. Dynamite freezes at temperatures below -f- 8 and then becomes less sensitive ; before being used it must be carefully thawed in warming-pans, surrounded by water at a tem- perature not exceeding 60 ; it must never be thawed on a heated metal plate. Thawed dynamite should be used carefully, as a little nitroglycerine exudes during thawing. Most of the dynamite made is used as an explosive in mines and for firearms ; for cannon it has little use, owing to the danger caused by sweating during the thawing, so that for military purposes explosives are used which are safer to transport and not so sensitive to shock or to discharge (explosion by influence). For non-congealing dynamites, see note on p. 276. II. DYNAMITES WITH ACTIVE BASES, (a) Pulverulent Dynamites with Inorganic Nitrates. Immediately after the discovery of dynamite with a silica base came the idea of replacing the inactive substance, which diminished the force of the nitrogly- cerine, by active substances, so that the explosive power of the dynamite might be increased. In America such dynamites are often made with 40 per cent, of nitroglycerine, 45 per cent, of sodium nitrate, 14 per cent, of wood-pulp, and 1 per cent, of magnesium carbonate ; these dynamites are well suited for mines where no great power but considerable safety is required. In Europe mixtures of nitroglycerine, ammonium nitrate, fine sawdust, sodium nitrate, carbon, etc., are made; e.g., 20 per cent, nitroglycerine, 36 per cent, sodium nitrate, 25 per cent, ammonium nitrate, 18-5 per cent, roasted rye flour, and 0-05 per cent. soda. In Austria Trauzl in 1867 prepared a pasty mixture of nitroglycerine with guncotton, which was not affected by water and was exploded only by fulminate of mercury detonators. This product was not successful, but similar and improved preparations were subsequently made. About this time Abel in England prepared glyoxiline by soaking defibred guncotton and potassium nitrate in nitroglycerine ; this also was unsuccessful. (b) Blasting Gelatine and Gelatine Dynamite. Since these contain nitrocellulose, they will be mentioned later (see Smokeless Powders, p. 294), after the manufacture of nitrocellulose has been described. Statistics of dynamite : see later, at the end of the chapter on Explosives. Various attempts have been made, but without practical success, to use nitro-deriva- tives of carbohydrates as explosives. Mention may be made of : nitromannitol, discovered almost simultaneously early in 1847 by Flores Domont and Menard and by Ascanio Sobrero, who named it fulminating mannitol and obtained it in a similar manner to nitroglycerine. It is composed mainly of hexanitromannitol, C 6 H 8 (ONO 2 ) 6 , which consists of white crystals melting at 112 to 113, while the crude product, containing tetra- and penta-nitromanni- tols, melts at 80; it dissolves to some extent in alcohol (1-35) and better in ether (1-24), and has the density 1-6 or, when compressed, 1-8. It is a shattering explosive, highly sensitive to shock. NITROSTARCH could not formerly be obtained sufficiently nitrated, but octonitroslarch, C 12 H 12 10 (N0 2 ) 8 , containing nearly 16-5 per cent, of nitrogen, may be prepared by the process of Hough of New York (Ger. Pat. 172,549, 1903, improved later); this consists in treating the starch with a mixture of 3 parts of 95 per cent nitric acid, 2 parts of 98 per cent, sulphuric acid and sufficient S0 3 to yield an anhydrous mixture containing 2 per cent, of free SO 3 , a further quantity of oleum with 2 per cent, of free SO 3 being added during the nitration. It appears that nitrostarch was tried as a military explosive in the United States prior to the European War. NITROCELLULOSE (Guncotton or Pyroxyline and Collodion-Cotton) This substance should, to be in order, be described later, after cellulose (which is a carbohydrate with many alcoholic groups and with a molecular formula polymeric with C 6 H 10 O 5 ) has been studied, but as its properties and 286 ORGANIC CHEMISTRY uses are closely connected with those of explosives, it is considered opportune to include it in the present section. 1 CONSTITUTION OF NITROCELLULOSE. The relation C n H 2m O m of the com- ponents of cellulose being expressed by the more simple formula (C 6 H 10 O 5 ) n it is found that the maximum degree of nitration consists in the introduction of three nitric acid residues per molecule of C 6 H 10 O 6 , so that guncotton was given the name trinitrocellulose, and was repre- sented by the formula C 6 H 7 5 (N0 2 ) 3 . Since the use of more dilute acids results in the combination of a less proportion of nitric acid residues, it is supposed that a mononitro- and a dinitro-cellulose are also formed. It was found later by Eder that there exist nitrocelluloses with compositions intermediate to those of tri- and di-nitrocelluloses, and others between the mono- and di-nitro-compounds, so that it must be supposed that cellulose has a formula at least double that of the simple one given above, but the mononitrocellulose corresponding with this doubled formula C 12 H 20 O 10 , L e., (C 6 H 10 H 5 ) 2 , has not yet been prepared. Still later Vieille, by accurate study of the nitrocelluloses prepared with acids of various concentrations, succeeded in preparing eight different types of nitrocellulose, this result indicating that Eder's formula, which predicted only six, could no longer serve. Vieille then proposed for cellulose a formula double that of Eder, i. e., C^H^Ogo or (C 6 H 10 5 ) 4 , according to which twelve nitrocelluloses are theoretically possible; eight of these, from endeca- to tetra-nitrocellulose have been actually prepared. Mendeleev, having found nitrocelluloses intermediate to or identical with these twelve, but different from those studied by Vieille in being soluble in a mixture of alcohol and ether, proposed the doubling of Vieille's formula, so that cellulose becomes C^H^O^ or (CyS^O^g. To-day, however, it is thought that these differences are due to mechanical mixtures of the various nitro- celluloses rather than to separate chemical compounds, and further, that the nitration is gradual and leads from the more simple to the more complex forms. 1 In 1833 Braconnot observed that when starch or wood is treated with concentrated nitric acid, a mucilaginous solution is obtained which, on addition of water, yields a white powder soluble in a mixture of alcohol and ether; this powder, which burns vigorously, he called xyloidin. In 1837, by immersing cellulose (flax, cotton, paper, etc.), for a few seconds in concentrated nitric acid and washing it immediately with a large quantity of water, so that it retains its original fibrous form, Pelouze obtained a product which is highly inflammable and explodes on percussion ; he regarded it as xyloidin (in reality it was guncotton), and recommended it for making fireworks. In 1846, Schonbein at Basle, and some months later, and independently, Bottger at Frankfort discovered that the nitration of cellulose takes place much more easily and completely if the cotton is treated with a mixture of concentrated nitric and sulphuric acids (industrially this method was used in 1846 by Hofmann and by Muspratt). In order to utilise industrially the guncotton thus obtained, the two discoverers combined and kept their process secret. After the initial difficulty in getting this new explosive taken up in practice, the extraordinary power of guncotton and its great advantages over black powder aroused considerable enthusiasm. Scarcely, however, had it come into general use in various countries than a number of spontaneous and fatal explosions in guncotton factories and magazines, by which whole buildings were razed to the ground, created such a panic that its manufacture was everywhere abandoned. The process of nitration was then already known to Knop and Karmarsch, and to others, who manu- factured guncotton by this simple process. In 1846, Sobrero made use of the nitric-sulphuric mixture for the preparation of nitroglycerine. In 1853, the Austrian, Captain von Lenk, ascertained how to render guncotton safe. The Austrian Government acquired from Schonbein and Bottger the process of manufacture (at a price stated to be 30,000 florins, or 2500) and maintained the secret of avoiding the spontaneous decomposition of guncotton until 1862. Then von Lenk communicated the secret to the French and English Governments, and in 1864 patented the process in America. Whilst in America the manufacture was undertaken on an enormous scale, in Austria and England it was again suspended on account of further terrible explosions in the factories themselves; these were explained by the English workers as due to the insufficient purification of the nitrocellulose by von Lenk. In 1865, Abel discovered the method of bestowing absolute safety and keeping qualities on the nitrocellulose. He used first of all the process of washing proposed in 1862 by the Englishman J. Tonkin, which consisted simply in complete washing with abundant supplies of water; the nitrated cotton was then defibred or pulped in " hollander " machines similar to those employed in paper factories and the wet pulp subjected to considerable pressure. From that time the manufacture extended to all countries, in spite of an English factory being blown up in 1871 (apparently a criminal act), and in recent times it has acquired new and increased importance owing to the discovery of smokeless powder. The process universally used at the present time in the manufacture of guncotton is that indicated by Abel. Before the discovery of smokeless powder, guncotton had limited applications and was not used in mines, since, in the form in which it was prepared, it had an excessive shattering action, whilst in mines progressive explosives are usually required. GUNCOTTON 287 Nitrocelluloses with more than 12-83 per cent, of nitrogen were at one time regarded as being insoluble in alcohol-ether, but Abel showed that there are nitrocelluloses with 13-2 per cent, of nitrogen and still soluble in this mixture, whilst others with only 12-8 per cent, are insoluble, and that this depends on the method of preparation the duration of action of the mixed acids, the ratios and concentrations of the latter, and the temperature at which they act and on the nature, purity, and dryness of the cotton. Only by following exactly the directions is it possible to obtain a constant percentage of nitrogen and complete solubility or insolubility in the mixture of alcohol and ether. It was also once thought that guncotton was a nitro-compound in the true sense of the word, i. e., that the N0 2 groups were united directly to carbon, but first Bechamp and then others showed that it is a true nitric ester which can be saponified, with regenera- tion of the cellulose, by alkalis, alkaline salts, ammonium sulphide, or ferrous chloride. It has been further shown that with the maximum of nitrogen an oxynitrocellulose is obtained [oxycellulose is (C 6 H 10 6 ) 3 + (C 6 H 10 6 ) n , so that the nitrocellulose will be C 6 H 7 (N0 2 ) 3 O 5 + C 6 H 7 (N0 2 ) 3 6 , and this with ferrous chloride gives oxycellulose; nitro- mannitol, treated similarly, gives mannitol and not oxymannitol]. PROPERTIES OF GUNCOTTON. Under the microscope nitrocellulose has the same appearance as ordinary cotton, but in polarised light it appears iridescent. When moistened with a solution of iodine in potassium iodide and then with sulphuric acid, nitrocellulose becomes yellow and cellulose blue. It is somewhat less white than ordinary cotton, is rather rough to the touch and crackles when pressed with the fingers ; it becomes electrified when rubbed and then appears phosphorescent in the dark. It is soluble in ethyl acetate (as shown by Hartig in 1847), nitrobenzene, benzene, acetone, etc., but insoluble in water, alcohol, ether, acetic acid or nitroglycerine, although a mixture of nitroglycerine and nitrocellulose is soluble in acetone, forming a jelly, cordite (see later). It resists the action of dilute acids, but is decomposed slowly by concen- trated sulphuric acid or hot alkali, and is completely dissolved by hot sodium sulphide. Decomposition is also effected by iron and acetic acid or by ammonium sulphide or ferrous chloride (Bechamp). Flocculent, loose guncotton has the sp. gr. 0*1, whilst the powder (pulp) has the sp. gr. 0*3 and is exploded by shock or percussion only at the point where it is struck, the explosion not being propagated to the whole mass. When ignited, it burns so rapidly that even when it is placed on black powder, the latter does not burn. In the form of cord, it burns more slowly and may be used as a rapid fuse. When wet or compressed it has a specific gravity varying from 1 to 1'3 (the absolute sp. gr. is 1*5) and it then burns slowly and cannot be exploded by percussion or by ordinary detonators ; explosion can, however, be induced by detonating a little dry guncotton with a fulminate of mercury cap. The shattering power diminishes with increase of the density, which reaches a maximum on gelatinisation (see later : Progressive Smokeless Powders). The decomposition proceeds according to the equation : 2C 6 H 7 2 (ONO 2 ) 3 = 5CO + 7C0 2 + 8H + 3H 2 + 6N. Less compressed guncotton gives more CO and H in comparison with the C0 2 and H 2 0, and hence has a less effect, the development of heat being smaller. No ash or smoke is formed, and 1 kilo of guncotton yields 741 litres of gas (the water being liquid, or 982 litres if the water is in the state of vapour), which is inflammable and, owing to the presence of carbon monoxide, poisonous. The temperature of combustion has been given as 6000 (i. e., 1071 Cals. is developed by 1 kilo), and in practice exceeds 4000 and may produce a pressure of 15,000 atmos. Unless guncotton is carefully prepared, it undergoes gradual change and may explode spontaneously, especially in the light, and to this are probably 288 ORGANIC CHEMISTRY due the great explosions which occurred formerly (1848-1862). Even dry, granulated guncotton becomes harmless and safe to handle if it is immersed for a moment in ethyl acetate, as it becomes coated with a gelatinous layer which dries and preserves it, if moist, from further evaporation. Guncotton is transported in large quantities in the wet state in wooden boxes placed in others of zinc which are sealed hermetically to retain the moisture. It is stored in dry magazines which are situate at least 150 (better 500) metres from any habitation and are not surrounded by earthworks so that the more serious effects due to projection of debris may not be added to those of an explosion MANUFACTURE OF GUNCOTTON. Hanks of purified cotton, free from impurities, are employed. This cotton should fulfil certain requirements. 1 In place of cotton it is economical in some cases to use filter- paper, unsized paper, parch- ment paper or paper cellulose, but such substances are less convenient than cotton as they easily undergo pulping to an almost pulverulent mass, which leads to losses and requires different conditions for nitration. The pure cotton is placed loose on trays which are arranged in a drying-stove heated by means of gilled pipes through which steam circulates; the heating is continued until the proportion of moisture is less than 0-5 per cent., after which the cotton is allowed to cool for twelve to fifteen hours in hermetically sealed boxes. If not pure the cotton is best defatted by boiling it for two to three minutes with 2 per cent, sodium hydroxide solution ; it is then washed with water and subsequently treated with very dilute nitric acid in the hot. In some cases it is also bleached with a weak solution of hypo- chlorite, well rinsed with water and dried in a hot-air oven at 100 to 115 as above. When almost dry it is carded, dried completely, and, while still hot, placed in hermetically sealed boxes so that no more moisture may be absorbed. Nitration is then effected with a mixture of concentrated nitric and sulphuric acid, as follows : FIG. 201. 3 parts of pure sulphuric acid of sp. gr. 1-840 (95-6 per cent. ) are poured into 1 part of pure nitric acid of sp. gr. 1-500 (95 per cent.), mixing taking place immediately and completely without the aid of stirrers. In this way a mixture containing about 72 per cent, of H 2 SO 4 , 23-5 per cent. HN0 3 , and 4-5 per cent. H 2 is obtained. If the acid mixture contains much nitrous acid, it may yield cellulose nitrite, which contains only 2-5 per cent, of nitrogen, is insoluble in acetone and is less stable than ordinary nitrocellulose (Nicolardot and Chertier, 1910). The mixture is then delivered with the help of an acid elevator (Monlejus) into the nitration apparatus, consisting of a cast-iron vessel, A (dipping pot) (Fig. 201), standing in a larger vessel, G, through which cold water circulates from H to J. The cotton is im- mersed in small portions (300 to 800 grams) in the acid-bath and is stirred with an iron fork. In England 1 kilo of cotton is used per 160 kilos of the acid mixture, while in Germany 1 kilo of cotton is taken for every 40 kilos of acid ; after a short time (fifteen to thirty minutes ) the nitrated cotton is removed with iron forks and is placed to drain on a cast-iron grid 1 Cotton for nitrocellulose should be pure white and should not contain dust or fibres of jute, hemp, or flax, or woody matter or pods; these impurities, when separated by hand from- 200 grams of the cotton, should not exceed 0-5 gram. The filaments should not be too short, other- wise they form a paste during nitration. A small piece thrown into water should sink in two minutes. It should not contain more than 0-9 per cent, of substances soluble in ether (fats, etc. ) ; in many factories 0-5 per cent, is not allowed. In England the amount of fat allowed is 1-1 per cent, extracted with ether in four hours in a Soxhlet apparatus (see Analysis of Fats). The moisture, determined by heating the cotton in an oven at 100 until its weight remains constant, should not exceed 6 per cent, and the cotton merchant is debited with any excess and also with the cost of drying. When moistened with a few drops of water, the cotton should maintain a neutral reaction. The ash, estimated by heating a few grams of the cotton to redness in a platinum capsule until it becomes quite white and of constant weight, should not amount to more than 0-3 per cent. NITRATION OF COTTON 289 (grate), B and C, arranged on one side above the vessel ; before it is taken away, it is pressed with a cast-iron plate, F, connected with a lever, D E. The acid mixture is renewed when it has treated 30 to 50 per cent, of its weight of cotton ; also after each portion of cotton is removed from the bath, fresh acid mixture, equal to ten times the weight of the cotton taken out, is added in order to make up for what has been absorbed and combined. On the German system (where less acid is used) renewal takes place more frequently. Above each of the nitrating vessels is a hood with a strong draught to carry off the nitrous vapours which are always evolved. Excessive rise of temperature or use of weak acid mixtures (with more than 9 per cent, of water) gives guncotton which contains less nitrogen and is not completely soluble in alcohol-ether, as is required in practice. In some factories the nitration is carried out in a number of small, deep and narrow, hemispherical vessels of cast-iron mounted on trolleys. These are charged in order with certain weights of acid mixture (30 to 50 kilos) and dry cotton (2 to 4 kilos), and, after thorough mixing, the trolleys are pushed into an oblong lead-lined chamber provided with as many doors as there are trolleys. A powerful aspirator draws the nitrous vapours into a wooden flue. A battery of soaking-pots is used in such a way that when the last is intro- duced into the chamber the first has already finished reacting (thirty to forty minutes), and as the pots are of metal and relatively small and are in a strong draught, the heat developed is readily dispersed. The pots are removed from the chamber and taken to the FIG. 202. FIG. 203. neighbouring centrifugal machines, into which the contents of the pots, which are mounted on pivots, are tipped. The centrifuges are similar to those employed in sugar factories (see Sugar) and have a steel or leaded steel rotating basket ; aluminium ones have also been tried, but not with great success. A few minutes' centrifugation at 900 to 1000 revolutions per minute removes the greater part of the acid from the guncotton ; the latter is immediately taken to the washing machines, while the acid recovered is revivified in the manner described on p. 280. If drops of water or lubricating oil fall on to the cotton during centrifugation, the mass sometimes undergoes sudden decomposition with formation of a dense cloud of brown vapour ; this does not constitute a serious danger, since usually it is not accompanied by explosion. In some factories the nitration is nowadays carried out directly in the centrifuges, which may be of naked or leaded steel or even of earthenware, although these are heavier and more fragile (see Figs. 202, 203). The latter consist of a double- walled earthenware basket, the inner wall, d and a, but not the outer one, being perforated ; the two walls being a slight distance apart, an annular space, c, is left, which has an outlet above in a number of holes, s, in the edge of the bush. The whole is bound with steel hoops, t, to prevent danger from projection in case of fracture. The dry cotton (7 to 8 kilos or more) is arranged peripher- ally inside the perforated basket, the acid being supplied by the tube, ra; the basket, sur- rounded by the jacket, b, and the cover, z, both of earthenware, is set in motion by the shaft, p, driven by the belt, r. The acid is driven uniformly through the cotton by centri- fugal force, rises through the ring space, c, and issues from the holes, s, into the channel, e, whence a pipe, /, carries it to an elevator to be circulated again. The operation is of short VOL. n. 19 290 ORGANIC CHEMISTRY duration, and the red vapours are emitted from the tube, g. During nitration, the velocity of the drum is relatively low, but at the end the velocity is increased ; the nitrated cotton can then be taken away at once to be washed. Use is, however, preferably made of steel centrifuges with circulation of the acid, as proposed by Selwig and Lange; the basket, d, is perforated (Fig. 204) and the cover is of aluminium and hinged, and is furnished with a large tube, o, communicating with the pipe of an aspirator, n. The basket is moved slowly and filled with the nitric-sulphuric mixture (e. g., 70 per cent. H 2 SO 4 , 23 per cent. HNO 3 and 7 per cent, water) up to the top edge; the cotton is then introduced in packets (1 kilo per 40 to 50 kilos of acid) and the basket given a velocity of 20 to 30 turns per minute. This movement causes the acid to circulate continuously through the cotton, and in half an hour the nitration of 6 to 8 kilos of cotton is complete; the acid is then discharged and the velocity increased to remove as much acid as possible from the cotton, which is taken out and washed in the ordinary way. Use is now made of centrifuges 1 to 1-1 metres in diameter, and 14 to 18 kilos of cotton are nitrated at a time. Sometimes, especially in summer, the nitrocellulose decomposes in the centrifuge itself, FIG. 204. producing vast columns of reddish-brown vapour; as a rule, not explosion, but merely deflagration occurs. Such decomposition takes place the more readily at the end of the centrif ugation, especially if this is unduly prolonged or excessively rapid ; often the cause is the spurting of water or lubricant into the centrifuge, but it may be the presence of impurities in the cotton or a workman spitting into the centrifuge. Since August 1905 in the Royal Gunpowder Factory at Waltham Abbey (where 2000 tons are produced per annum), guncotton has been made by the displacement process of J. M. and W. Thomson, improved by Nathan, which is briefly as follows (Ger. Pat. 172,499, 1904). Into the earthenware basins, which have perforated double bottoms and aluminium covers (Fig. 205) and are connected in groups of four by means of leaden pipes and also communicate with an exhauster, G, 600 litres of the nitric-sulphuric mixture is placed; about 10 to 12 kilos of cotton is then introduced in small portions into each vessel and pressed with perforated stoneware discs divided into septa so that the acid exactly covers the cotton and scarcely fills the orifices of the discs ; a layer of water about 1 cm. deep is then cautiously introduced on to the perforated disc, which separates the cotton and acid from the superposed water and thus prevents the two liquids from mixing, the fumes being largely absorbed by the water. The nitration lasts about two and a half hours, and at the end water is introduced above the perforated plate, this displacing at the bottom a corresponding quantity of the acid ; the acid thus recovered (90 per cent.) is reinforced with oleum and strong nitric acid. The displacement lasts three hours, after which the mass is centrifuged and the cotton washed, rendered stable, pulped, etc. WASHING OF NITROCELLULOSE 291 Since guncotton should have a very definite nitrogen content, different from that of collodion-cotton used to gelatinise nitroglycerine (see later), the process of nitration is care- fully followed by numerous rapid analyses until suitable conditions are found for obtaining a constant product ; after this has been done, the final control is sufficient. It has been proposed to follow the extent of nitration of cellulose by observing its behaviour towards polarised light. In recent years it has been shown that guncotton of more constant type and more readily rendered stable is obtained if the acid mixture is renewed for each nitration ; the last processes described are hence to be preferred. There has been much discussion concerning the relative suitability . of centrifuges and Nathan- Thomson vessels for nitra- tion. It now seems estab- lished that, even in the latter, either guncotton or collodion-cotton may be prepared, provided that the conditions of the re- action, the temperature, the time, and the concentration and composition of the acids are suitably and thoroughly studied. The plant of a works using centrifuges is the more expensive, requires the greater upkeep expenses and contaminates the air with acid fumes. The nitrocotton obtained by the Thomson process is the- more stable, since the dis- placement of the acid by water is accompanied by slight heating, which allows of the decom- position of the unstable secondary products and the elimination of the sulphonitric cellulose. For the economical working of the Thomson process, the earthenware vessels must be of good quality, so as to avoid breakages ; such vessels are now easily procurable. With the FIG. 205. Fia. 206. centrifuge system concentrated acid is recovered, but part of it is lost ; with the Thomson vessels the whole of the acid is recovered, but about 25 per cent, of it is diluted with 20 to 25 per cent, of water and has to be denitrated. The degree of nitration and the stability of nitrocotton may be estimated by measuring the viscosity of its solutions, nitro-oxycelluloses giving more fluid solutions than nitro- cellulose. Nitro-oxy cellulose has little stability and is formed from cotton which has been highly bleached with chlorine prior to nitration (Picst, 1913). The theoretical yield of dry guncotton is 185 kilos per 100 kilos of dry cotton ; in practice 170 to 175 kilos is obtained. WASHING. The nitrocellulose from the centrifuge is passed directly into the oval- washing vessel (see Fig. 206), which has a longitudinal partition down the middle (like the hollander machines used in paper-making), and in which a shaft furnished with beaters 292 mixes the whole mass with water ; the latter is constantly renewed and the washing con- tinued until the acid reaction towards litmus paper disappears (two to three hours). The washed guncotton is either centrifuged again or put to drain in wooden baskets. Although it no longer exhibits an acid reaction, yet, as was shown by J. Tonkin in 1862 and by Abel in 1865 (in England), it still contains acid, or rather unstable sulphuric esters, in the small channels of its fibres. To separate these remaining traces of acid, the nitrocellulose is rendered stable by the Robertson system, which consists in boiling it for two consecutive periods of twelve hours each with water in wooden vats fitted with perforated false bottoms (one vat holds even more than 1000 kilos of the cotton), beneath which steam is passed. Then follow four more boilings of four hours each with water (formerly one or two boilings with calcium carbonate were also carried out), and finally two or three boilings each of two hours with fresh water. This system of washing, which lasts altogether thirty-six to forty-eight hours, is preferable to that in which the boilings are short at the beginning and long at the end, and especially to that where boiling with soda is interposed, as the soda hydrolyses the nitrocellulose and transform it partially into collodion-cotton poor in nitrogen and soluble in alcohol-ether. In France boilings of sixty to eighty or even one hundred hours are employed. Some of the boiling may be dispensed with if the nitrocellulose is steamed in closed vats. In 1911, Baschieri simplified the Robertson system by boiling the nitrocellulose (roughly washed and centrifuged) for two hours in 0-05 per cent, sulphuric acid solution, then washing twice in cold water, boiling for two hours with 0-1 per cent, sodium carbonate solution, and finally washing twice with cold water. By this method the nitrocotton is rendered ready for pulping with a minimum loss of nitrogen, the maximum stability being thirty- five minutes at 70 or, with the Abel test, 135. The acid bath serves especially for the elimina- tion of the unstable and soluble sulphonitric celluloses. PULPING. In spite of all the washing and boiling to which it is subjected, the gun- cotton persistently retains a trace of acid, and to remove this, the cotton is thoroughly defibred (pulped) as was proposed by Tonkin and by Abel in 1865. This operation .s carried out in hollanders similar to those used for the preceding washing and identical with those used in the manufacture of cellulose for paper (see later, section on Paper, for figures and cross-sections). Pulping lasts from five to eight hours, according to the fineness required, but if it is incomplete, inconveniences are met with in the subsequent compression, the desired density not being attainable; also if pulping is carried too far, the compression is disturbed in another way. Guttmann proposed the use of hot water in pulping, and this possesses several advantages in addition to saving time. In the large hollanders, as much as 600 to 800 kilos of guncotton can be treated at one time. In some cases a little calcium carbonate is added to guncotton to preserve it and to neutralise any residual acid ; it is added in powder just before the completion of pulping, but its use is not to be recommended, as it tends gradually to produce slight decomposition of the nitrocellulose. STABILISING. Guncotton (and also collodion-cotton) thus prepared does not usually answer the rigorous tests to which it is subjected (see later, Tests of Stability), and is ren- dered stable by again boiling it for some hours with water in large wooden tanks (sometimes lined with lead), jets of steam, and also of air to keep the mass moving, being passed in for eight to twelve hours. By mixing in this way the nitrocottons from different nitrations, a mass is obtained which is perfectly homogeneous, even as regards nitrogen content, this being difficult to achieve otherwise. In order to separate the water, the mass is placed in suitable centrifuges fitted with drums of fine metal gauze entirely surrounded by linen ; in other cases, the water is separ- ated as in paper-mills, by placing the mass in chambers having perforated brass floors covered with cloth, the pulp drained in this way being finally centrifuged. The water separated from the pulp is allowed to stand in suitable vessels to deposit the finer fibres it has carried away. After centrifugation, the pulp contains about 25 to 30 per cent, of water and in this state it can be kept safely in zinc boxes, in which it can be transported if it is slightly compressed and the cover of the box soldered; in moist wooden boxes or in paper wrapping nitrocotton readily becomes coated with mould. If properly prepared, guncotton should not contain more than 3-5 to 4 per cent, of collodion-cotton (soluble in alcohol-ether), but in England 7 to 8 per cent, is allowed. Excessively prolonged boiling COMPRESSION OF GUNCOTTON 293 increases the proportion soluble and lowers somewhat the nitrogen content; immoderate action of alkali produces a little hydronitro cellulose. COMPRESSION OF GUNCOTTON. For military purposes, that is, for cartridges and for the blocks used for charging torpedoes, the still moist guncotton is strongly com- pressed, to render it safer and more powerful owing to the increased charging density (see above), which reaches the value 1-2 with pressures of 500 to 1000 atmos. or 1-35 with still greater pressure. Fig. 207 shows in section a Taylor and Challen hydraulic press used for this purpose; this is set up in an isolated room and can be controlled from a distance so as to avoid any great amount of damage in case of explosion during the compression, this mostly happening if any hard foreign body chances to be present in the guncotton. To obtain the greatest density, the pulp is first washed with hot water and slightly compressed in the mould, d, by means of the lever, h, the water being drawn away under the perforated base, c (covered with steel gauze), by a pump connected with the tube, b. The partitions, I, are raised and the mould passed through an aperture in the wall, M (which serves as a protection for the workmen), and thus above the plate, n, of the hydraulic press ; this plate is kept horizontal by four columns, $'. The mould is raised by the piston, t, FIG. 207. of the press so that it is pressed against a die, r, fixed to the cover, q. This cover is held fast by the four columns so that the die penetrates the mould and compresses the cotton under a pressure of 800 to 1000 atmos. The degree of humidity after the compression is about 12 to 14 per cent., and at each operation a block of 1 kilo is made, the shape being adapted to that of the projectile. Thus compressed, guncotton is so hard and compact that it can be worked quite safely with the plane, saw, or boring tool, a fine jet of water being directed at the point where the cutting is taking place. To prevent compressed guncotton from losing moisture and from becoming mouldy, it is dipped in molten paraffin wax, or, better, it is immersed for a moment in ethyl acetate (or acetone), which dissolves a little nitrocellulose at the surface and forms a kind of impermeable varnish. Since 1898, in some large works charges have been prepared in a single piece, either for grenades or for torpedoes, etc., by means of the powerful press devised by Rollings (Brit. Pat. 23,449, 1899). USES OF GUNCOTTON. Until 1890, moist compressed guncotton had replaced all other explosives for the charging of torpedoes. It is used also for filling grenades, which are then covered with molten paraffin wax to unite the grenade and the explosive ; explo- sion is effected by a detonator of dry guncotton. It is made also into compressed cartridges for use in mines, a cavity being left for the detonating cap and the fuse. Since 1890, guncotton as a high explosive for military purposes has been replaced gradu- ally and advantageously by picric acid and trinitrotoluene (T.N.T. ), which are melted and 294 ORGANIC CHEMISTRY poured directly into the projectiles, bombs, mines, etc. During the European War all the old stocks of guncotton were consumed, use being afterwards made solely of these aromatic nitro-derivatives and of various mixtures of them (see later). Mixtures of granulated guncotton and nitrates are placed on the market under the names of tonite, potentite, etc. Abel obtained beautiful pyrotechnic effects by saturating guncotton with solutions of various mineral salts capable of imparting different colours to the flame. Guncotton is sometimes used for filtering acids, alkalis, and solutions of permanganate, being resistant to these reagents in the cold. Also it is employed in some cases as an electrical insulator and for bandaging purulent sores and wounds, being first saturated with potassium permanganate. COLLODION-COTTON FOR GELATINE DYNAMITE, DYNAMITE, AND SMOKELESS POWDERS. During the last fifty years, a different, less nitrated nitro- cellulose, collodion-cotton, has assumed very great importance in the manufacture of smoke- less explosives. On the other hand, guncotton itself has, of late years, been largely replaced by compressed, crystalline, or fused trinitrotoluene, or by picric acid (see Part III), especially for military and naval purposes. Collodion-cotton was at one time thought to be dinitro- cellulose, soluble in a mixture of alcohol and ether, but it has now been shown to be a mixture of various soluble nitro-compounds, which are formed under conditions different from those yielding guncotton. Collodion-cotton should have a constant nitrogen-content, and it should be readily soluble (to the extent of at least 95 per cent.) in a mixture of alcohol (1 part) and ether (2 parts), giving a dense viscous solution; this solubility may, however, be increased by prolonged heating under pressure with water acidified with sulphuric acid, which permits of the preparation, from this collodion-cotton, of artificial silk better than the Chardonnet variety (Chandelon, Ger. Pat. 255,067, 1911-1912). Collodion-cotton is soluble also in dichlorohydrin (p. 257). If it answers these requirements, it gelatinises nitroglycerine well and dissolves completely in it ; attention is, however, also paid to the time necessary for gelatinisation. For photographic plates, extensive use was formerly made of ethereal- alcoholic solutions of soluble nitrocellulose (collodion), and in this case importance was attached not so much to the viscosity as to the proportion of nitrocellulose which would yield an elastic film of marked resistant properties. For this purpose, the nitration is carried out at a temperature of at least 40 to 50, so that the resulting collodion is less viscous ; also the nitrocellulose is not pulped. The cotton is immersed for sixty minutes or longer in a mixture of 1 part of 95-5 per cent, sulphuric acid (sp. gr. 1-840) and 1 part of 75 per cent, nitric acid (sp. gr. 1-442) (this mixture contains 48 per cent, of H 2 SO 4 , 37-5 per cent, of HNO 3 , and 14-5 per cent, of H 2 0), at a temperature of about 40. The more concentrated the acid and the more prolonged its action, the higher will be the nitrogen- content, but the viscosity will not be decreased ; a high temperature, however, results in diminution of the proportion of nitrogen and also of the viscosity. More commonly nitration is carried out in the cold in the manner described for making guncotton, only the composition of the acid mixture being modified : with a content of 22, to 25 per cent, of nitric acid, guncotton is obtained if the acid mixture contains less than 10 per cent, of water and collodion- cotton if more than 10 per cent, of water (up to 15 to 18 per cent. ), according to the desired nitrogen percentage and solubility in alcohol-ether. To the International Congress of Applied Chemistry, London, 1910, Saposhnikov com- municated a series of interesting investigations (1906-1909) on the practical conditions required to establish beforehand the type of the resulting nitrocellulose (percentage of nitrogen and solubility), the results being expressed as curves referred to triangular co-ordinates. After nitration collodion-cotton intended for the manufacture of gelatine dynamite goes through all the operations of washing, pulping, and boiling employed with guncotton. Collodion-cotton for gelatine dynamite or smokeless powder must be subjected to a drying process, while for smokeless powders the water is expelled in another way. Since the centrifuged pulp still contains 30 per cent, of water, whilst nitrocellulose begins to decompose at 70 (or even at 50 if badly prepared) and in the dry state is very sensitive to shock or percussion, the drying of collodion-cotton constitutes a very dangerous opera- tion. At one time it was dried by means of indirect steam on iron plates heated to 40 to 50, but, using the ordinary precautions, it may be dried on cloths in a current of warm air. SMOKELESS POWDERS 295 When dry, it sometimes becomes electrified on rubbing, or even by an air current, and this phenomenon explains the frequent spontaneous fires formerly occurring in the drying ovens. Guttmann prefers to dry the collodion-cotton on copper plates connected with the earth by wires (to discharge the electricity). These plates are perforated with conical holes 0-25 mm. wide at the top and 1 mm. at the bottom ; strips of leather are used to prevent rubbing of the metal parts. In these ovens, the pulp is spread out and is subjected to the action of a current of air heated to 40 (in some cases, also dried : see p. 272 ), and in two days the mass is dry, not more than 0-1 per cent, of moisture being then present. The dried material is then carefully placed in rubber bags and stored in air-tight boxes. The drying ovens are provided with alarm-thermometers, which also regulate the temperature automatically. The workmen should wear rubber boots with copper nails and in the Waltham Abbey Factory the leather transmission belts are soaked in glycerine to prevent their electrification. Drying in a vacuum is also employed (especially with fulminate of mercury and smoke- less powders), and is then more rapid and takes place at a lower temperature, while FIG. 208. the danger of an explosion is diminished owing to the absence of the tamping effect of the atmospheric pressure (see p. 264). One of the commonest dryers working under reduced pressure is shown in Fig. 208; it is fitted with cloths and has double walls to allow of the circulation of steam, hot air, or hot water (see also p. 297 ). Collodion- cotton for making ballistite (see later) should contain 11-75 to 11-95 per cent, of nitrogen, whilst that for ordinary gelatine dynamites contains as much as 12 per cent., almost completely soluble in alcohol-ether. The distinction between collodion-cotton and guncotton on the basis of the percentage of nitrogen present is not a rigorous one, since it was shown by Roscoe (during the lawsuit in 1893 between the British Government and Nobel concerning the ballistite patent) that, by suitable modification of the quantity of water and of the ratio between the nitric and sulphuric acids in the nitrating mixture, a nitrocellulose which contains 12-83 per cent, of nitrogen and is soluble in alcohol-ether, or one which contains 12-73 per cent, of nitrogen and is insoluble, may be obtained. SMOKELESS POWDERS. Even 50 years ago attempts were made to diminish the smoke produced by ordinary gunpowder by diminishing the amount of sulphur present, but its relations to the nitre and carbon cannot be greatly altered. Potassium nitrate was 296 ORGANIC CHEMISTRY then replaced by ammonium nitrate, but this was found to be too hygroscopic ; yet later, ammonium picrate was employed with better, but still not satisfactory, results. In 1864 Schulze prepared a smokeless powder from nitrocellulose obtained from pure wood-cellulose. It gave good results with sporting guns, but was too shattering for use in warfare, and the same was the case with a smokeless powder prepared in 1882 by Walter Reid by granulating nitrocellulose and gelatinising it superficially with alcohol and ether. The true solution of this important problem is due to Vieille, who in 1884 found that the shattering action of guncotton could be transformed into a progressive (or propellant) action by destroying the fibrous structure with suitable solutions. To attenuate the rapidity of explosion of guncotton it must be made" as dense as possible (theoretically the fibre free from interstices has the density 1-5), and this cannot be done practically with fibrous cotton (even when pulped ) as a pressure of 4000 atmospheres would be necessary. Vieille, however, dissolved or gelatinised the nitrocellulose and then recovered it by evaporating the solvent ; thus was prepared powder B, the first military smokeless powder. With the smokeless powder prepared by Vieille in 1885 the velocity of projectiles from cannon was increased by 100 metres per second over that obtained with ordinary powder, the pressure in the cannon being the same in the two cases ; hence guns of smaller calibre could advantageously be employed. This amounted to a revolution in the region of ballistics . The gelatinisation is effected by solvents of nitrocellulose, i. e., by ether, acetone, ethyl acetate, nitroacetylglycerine, tetra- and penta-chloroethane, etc. (see p. 122). SMOKELESS PROGRESSIVE POWDERS SMOKELESS POWDERS OF PURE NITROCELLULOSE : POWDER B. Powder B was applied in France as a military explosive in 1886, and was used solely as a propellant powder up to the outbreak of the European War. During the war ballistite (see later) also was made in France and powder B in Italy, Great Britain and America, the French process being employed ; briefly this is as follows : By means of a suitable k'neading machine an intimate mixture is made of 66 to 70 parts of guncotton (known in France as CP 1 ), and 30 to 34 parts of moist collodion- cotton (termed CP 2) (with about 25 to 30 per cent, of moisture). The moisture is not removed by drying in an oven, which would be dangerous, but is displaced by means of 95 per cent, alcohol (Messier process, 1892) in suitable hydraulic presses ; each chamber is charged with about 27 kilos (calculated dry) of mixed nitrocellu- lose, which is supported on a perforated metallic disc on the bottom of the chamber. After the moist cotton has been pressed slightly with the piston, about 18 kilos of alcohol is intro- duced and forced through the cotton, gradually displacing the water, which is discharged through the apertures at the base and is followed by dilute and then by concentrated alcohol ; when the latter issues with its original density, the whole of the water has been displaced. About two-thirds of the alcohol recovered has a concentration of about 50 per cent, and, after direct distillation to separate it from suspended cotton and from part of the water, is rectified to bring it to 95 per cent, strength to be used in succeeding operations (about 5 per cent, of the alcohol is lost in each operation). The nitrocotton remaining in the press is extracted by means of a counter-piston, which forces it upwards in cakes impregnated with 10 to 11 kilos of alcohol (per 27 kilos of dry nitrocotton). The operation in each chamber occupies five minutes. These multiple dehydration presses with continuous automatic action produce up to 12 to 15 tons of dehydrated nitrocotton per day, the best form being made by Messrs. Champigneul (Paris). In some powder B factories, instead of Champigneul presses (which before the war cost about 1600 and during the war as much as 6000), use is made of hydro-extractors, the nitrocotton (40 to 45 kilos) in the moving centrifuge being treated with a spray of 95 per cent, alcohol. Each centrifuge with a perforated drum 1 metre in diameter and a final velocity of 1100 revolutions per minute gives an output of 1600 kilos of dehydrated nitro- cotton per twenty-four hours. Almost twice as much alcohol, however, is consumed in the centrifuges as in the presses and the percentage loss is greater ; one-half of the alcohol is recovered at about 68 per cent, strength and the rest at 40 to 50 per cent. ; the latter is distilled and rectified and the former used for the first treatment in a subsequent operation, being then recovered at 40 to 50 per cent, strength ; a second treatment of the nitrocotton with 95 per cent, alcohol yields 68 per cent, alcohol. POWDER B 297 Gelatinisation of the nitrocotton is effected most completely and rapidly with a mixture of 66 per cent, of ether and 34 per cent, of alcohol, i. e., 2 vols. of ether and 1 vol. of alcohol (135 kilos of the mixture for 100 kilos of nitrocotton calculated dry), account being taken of the alcohol already present in the nitrocotton. The materials are thoroughly kneaded in a kneading machine, the mass being afterwards discharged into zinc tubs and there left, hermetically sealed, for twenty-four hours for the completion of the gelatinisation. By means of hydraulic presses similar to those used for food pastes, the pasty mass is converted into strips or ribbons varying from 3 to 6 cm. in width according to the type of powder and about 1mm. in thickness. The ribbons are cut into lengths of about 2 metres, hung on rods and dried in a current of air at 40, the alcohol and ether being recovered with the help of freezing machines (see note on p. 231). The strips, still containing 25 per cent, of solvent, are then cut to the desired width and length (usually 15 to 20 cm.) and after- wards dried on brass gauze for five to six hours at 55 to 60 in a stream of air, from which a little solvent may be recovered. FIG. 209. In some works this drying is effected under reduced pressure (see Fig. 208), special apparatus being used for the recovery of the solvent, as shown in Fig. 209 ; P represents the pump which evacuates the condensation chamber of the solvent C, this communicating with the oven E. The vapours from the wide tube at the top of the oven are condensed in C by means of a bundle of tubes through which water is circulated by the pump A, The warm water from the top of the condenser is heated in the coil tank R and then circulates in the oven. The condensed solvent is collected in S and rectified. The ribbons, which still contain about 10 per cent, of solvent, are next placed vertically in compact bundles in cases which are immersed for eight or nine hours in vessels of water at 50. The water discharged from the bath after each operation contains 3 to 4 per cent, of alcohol and is discarded. After draining, the strips are kept in a second drier for some days, until the percentage of solvent (water, alcohol and traces of ether), is reduced to 1-3 to 1-8, and are finally exposed to the air for some days under sheds, thus acquiring a stable composition, which, together with the ballistic effect, remains unchanged even after prolonged storage. To obtain uniformity in powder B, strips from different operations are well mixed, the 298 ORGANIC CHEMISTRY mass being translucent and of a pale brownish-yellow colour. Before being despatched it is tested by the ordinary stability tests. Waste powder B is utilised by softening it with 150 per cent, of alcohol-ether and adding it, little by little, to the mass in the kneading machine. During the European War, the Angouleme works in France produced about 120,000 kilos of the powder per day, the alcohol and ether consumed amounting to some dozens of tons ; the Ferrania factory of the Societa Italiana Prodotti Esplodenti had an output of 15,000 kilos per day. Gelatine Dynamites, etc. As we have already seen in dealing with the theory of explo- sives, the explosion of nitroglycerine is accompanied by the liberation of unused oxygen ; on the other hand, it is known that guncotton does not contain sufficient oxygen for the complete combustion of the carbon and hydrogen present in the nitrocellulose molecule. In 1875, A. Nobel conceived the happy idea of associating the two substances by dis- solving in nitroglycerine a certain quantity of soluble nitrocellulose, that is, that used in the manufacture of collodion. This procedure gives gelatines of varying consistency accord- ing to the quantity of nitrocellulose (collodion-cotton) dissolved. Blasting gelatine is made from 90 to 93 per cent, of nitroglycerine and 7 to 10 per cent, of dry collodion-cotton ; gum dynamites, on the other hand, contain about 97 per cent, of nitroglycerine and 3 per cent. of collodion-cotton, and when they are mixed with about one-third of their weight of absor- bent substances (wood-meal, rye-flour, sodium or ammonium nitrate) they form the ordinary modern dynamites, called gelatine dynamites, which are still plastic, although less so than the gum dynamites, and are also less violent, and hence serve well for mining purposes. A common type of gelatine contains, for instance, 62-5 per cent, of nitroglycerine, 2-5 per cent, of collodion-cotton, 25-5 per cent, of sodium nitrate, 8-75 per cent, of wood-meal, and 0-75 per cent, of sodium carbonate (which would be best excluded); it has the sp. gr. 1-5, is exploded with a No. 3 fulminate of mercury cap, and is sold in Austria for No. I dynamite, whilst gelignite is sold for No. II dynamite and contains 45 to 50 per cent, of gum dynamite and about 50 per cent, of absorbents as above. At Christiania a non-congealing gum dynamite is made from blasting gelatine and a little nitrobenzene and ammonium nitrate; it has a specific gravity of 1-49 and is less effective than the gelatine dynamites. For military purposes (torpedoes, cannon, etc.), as much as 4 per cent, of camphor is added in Italy, Austria, and Switzerland ; these gelatines are thus rendered insensitive and very safe, and they require special detonators (e. g., a mixture of 60 per cent, of nitroglycerine and 40 per cent, of collodion- cotton or compressed guncotton). In certain commercial products the collodion-cotton is replaced by nitrated wood or straw, while nitrobenzenes, nitrotoluenes (especially liquid dinitrotoluene ), etc., are used instead of nitroglycerine. 1 1 It is impossible at the present time to compare the various commercial brands of dynamite of different countries or even of one country, so varied are the types and the ratios of the com- ponents, sometimes when the commercial name is the same. Thus No. 1 ammonia dynamite (French) contains 40 per cent, of nitroglycerine, 45 per cent, of ammonium nitrate (this, when pure, is not hygroscopic), .5 per cent, of sodium nitrate, and 10 per cent, of wood-meal or wheat- flour; the No. 2 quality of the same brand contains 20 per cent, of nitroglycerine, 75 per cent. of ammonium nitrate, and 5 per cent, of wood-meal. In Germany, the name Gelatine Dynamites is given to all mixtures prepared from explosive gum (96 per cent, nitroglycerine gelatinised with 4 per cent, collodion-cotton) and nitre as absorbent. In England, however, No. 2 gelatine dyna- mites are called gelignites, and are often formed of 65 per cent, of the gum and 35 per cent, of absorbents (75 per cent, nitre, 24 per cent, wood-meal wood-pulp used for paper, in a dried state and 1 per cent, of soda). In Austria, dynamite I is made from 65-5 per cent, of nitro- glycerine, 2-1 per cent, of collodion -cotton, 7-41 per cent, of wood-meal, 24-85 per cent, of nitre, and 0-26 per cent, of soda ; dynamite II contains 46 per cent, of nitroglycerine, etc., and dynamite II A, 38 per cent, of nitroglycerine, etc. In France, gelatine dynamites are called gums, and are prepared in very varied forms, e. g., gum M B with 74 per cent, of nitroglycerine, gum D with 69-5 per cent., and gum E with 49 per cent. ; then there are dynamite gelatine 1, 2o, 26, and 2c (the last with 43 per cent, of nitroglycerine, etc. ), etc. In Belgium, gelatine dynamites are called forcites; forcite extra contains 74 per cent, of nitroglycerine, superforcite 64 per cent.,forcite No. 2 36 per cent., etc. In England the types most commonly used are : dynamite No. I, with 75 per cent, of nitro- GELATINE DYNAMITES 299 Gelatine and gum dynamites have the appearance of plastic masses, the latter, which has the sp. gr. 1-6, being especially horny and translucent. Gum dynamite sometimes exudes a little nitroglycerine and so loses in shattering force ; when heated for a long time at 70, it swells up, becomes spongy and decomposes with formation of red, nitrous vapours ; it sometimes ignites in metal boxes when exposed to the sun. It is less sensitive even than dynamite (about six times less) to percussion and special caps of gelatine dynamite are required to explode it. It serves well for use in war, since it is insensitive to discharges, and to render it still less prone to detonation by influence it is mixed with a little camphor. When 20 per cent, of collodion-cotton is dissolved in nitroglycerine, a gum dynamite is obtained which is not exploded by the most powerful caps, and ballistite, which contains 30 to 50 per cent, of collodion-cotton, requires special detonators. After freezing and thawing, it becomes more sensitive and dangerous, as is the case with dynamite. It has a greater shattering power than dynamite and acts better than this under water, which does not wash away the nitroglycerine so easily. Exudation of nitroglycerine occurs more readily than with dynamite and causes some degree of danger. It is used as a basis for the manu- facture of smokeless powder. Gelatine dynamite is safer to handle and store than ordinary dynamite, which it is largely replacing. The manufacture of these gelatinised dynamites requires collodion-cotton, which is very carefully prepared and is completely soluble in a mixture of alcohol and ether, in addition to which it must possess as great a proportion of nitrogen as possible. When it is not well prepared, although it dissolves in alcohol and ether, it is not readily and entirely soluble in nitroglycerine, or it does not retain the latter completely for a long time. The quality of the collodion-cotton depends, then, on the choice of a good cotton and on exact conditions of nitration duration, purity of acids, temperature. This should then be finely subdivided (pulped) and dry, so that it can be passed through a fine sieve before being mixed with the nitroglycerine, in which it does not dissolve well if moist. This operation of gelatinisation and kneading is termed in French petrinage. The necessary quantity of nitroglycerine is placed in wide, shallow vessels of copper or lead heated externally by hot water (50 to 60). After thirty to sixty minutes, when the temperature has reached 45 to 50, the required amount of dry, powdered collodion- cotton (and the other absorbent substances used for ordinary dynamites, such as cellulose, flour, starch, nitrate, etc. ), is added in small quantities and mixed now and then with a wooden spade. It is then left for a couple of hours and afterwards thoroughly mixed by hand, just as dough is mixed, so as to form a homogeneous, soft paste ; this, on cooling, forms a more or less hard, elastic, translucent gelatine which constitutes the gelatine or explosive gum. If, instead of collodion-cotton alone, absorbents are also used, gelatine dynamites are obtained ; these are converted into rolls and cartridges with the machines already described (p. 284). When the gelatine is not intended for the manufacture of glycerine ; gelignite with 65 per cent, of gelatinised nitroglycerine (97 per cent, of nitroglycerine), 25 per cent, potassium nitrate, and 10 per cent, wood -meal; blasting gelatine with 93 per cent, of nitroglycerine and 7 per cent, of collodion-cotton; gelatine dynamite with 80 per cent, of gela- tinised nitroglycerine (with 3 per cent, of collodion-cotton), 15 per cent, of potassium nitrate, and 5 per cent, of wood-meal. In Italy there is dinamite-gomma A (or simply gomma A, corresponding with the French gomme extra-forte ) formed from 92 per cent, of nitroglycerine and 8 per cent, of collodion -cotton ; gomma B (corresponding with the French gomme a la soude) with 83 per cent, of nitroglycerine, 5 per cent, of collodion-cotton, 8 per cent, of sodium nitrate, 3-7 per cent, of wood-meal, and 0-3 per cent, of sodium or calcium carbonate or ochre. Commercially, however, the strength is given in terms not of nitroglycerine, but of gelatine, that is, the starting material is taken as a gelatine formed by gelatinising 94 per cent, of nitroglycerine with 6 per cent, of collodion-cotton, to which are then added the various absorbents ; thus gomma B contains 88 per cent, of gelatine (equivalent to 83 per cent, of nitroglycerine ). In Italy the old kieselguhr dynamite is no longer used and is replaced by the so-called gdatine-dinamiti, which are marked with various letters and numbers ; thus No. 0, containing 74 per cent, nitroglycerine, 5 per cent, collodion-cotton, 15-5 per cent, sodium nitrate, 5 per cent, wood-meal, and 0-5 per cent, carbonates ; G. D. No. 1, with 70 to 72 per cent, nitroglycerine, etc. ; G. D. No. 2, with about 48 per cent, nitroglycerine ; and dinamite No. 3, with 25 per cent, nitroglycerine, 54 per cent, sodium nitrate, 19 per cent, wood-meal and cellulose, and 2 per cent, soda and yellow ochre. During recent years there have also been pre- pared in Italy gelatine-dinamiti suggested by Dr. Leroux with 8 to 10 per cent, of the nitro- glycerine (of No. 1 ) replaced by as much liquid dinitrotoluene, which gelatinises cotton well and gives non -congealing dynamites, more economical and almost as powerful as, sometimes more powerful than, the corresponding gelatine'dynamites ; these act well in open mines, but give large quantities of unpleasant fumes, and hence are unsuitable for use in galleries, etc. 300 ORGANIC CHEMISTRY ballistite (see later), the conversion into cartridges is effected by means of an Archimedean screw machine (boudineuse), similar to sausage-making machines (Fig. 210). The mixing for causing gelatinisation, especially if other substances besides collodion- cotton are added, may be carried out in mechanical kneading machines (Fig. 211) mounted on a wooden platform, b, which can be raised by screws and cog-wheels, g, e, and h, resting on supports, a a ; on this platform is a double-walled, copper pan, i j, which can be sur- rounded with hot water and can be moved on rollers. Above are the bevel-wheels and pulleys for working the stirrers, q and r. The nitroglycerine is first heated to 50 by raising the temperature of the water in the jacket of the copper pan, the latter being then raised so as to submerge the stirrers j the ' ingredients necessary to give the required type of gelatine dynamite are then added. Mixing is complete in an hour. Other forms of kneading machine are also used, e. g., the FIG. 210. Werner-Pfleiderer machine, which is i employed for smokeless powders and for bread-making. After cooling, the plastic dynamite, which has a yellowish, translucent appearance, is removed from the kneading machine to a separate building to be converted into cartridges. This is done in special machines (boudineuses) (Fig. 212 and 213), furnished with endless screws, which force the dynamite or gum from a hole, B, in continuous rolls, these being collected in definite lengths in a casing of parchment paper or paraffin waxed paper, (7. B. Military Smokeless Powders. These approach the gum dynamites in character, but contain more collodion-cotton, so that they are safer towards shock and useful as propellants (only slightly shattering). The most important type is that pre- pared by Nobel in 1888 under the name of ballistite (after he had been preparing since 1878 gum dynamite by gelatinising nitroglycerine with 6 to 10 per cent, of collodion- cotton). Ballistite contains about 50 jper cent, of nitroglycerine and 50 per cent., or even more, of collodion- cotton (with 11-2 to 11-7 per cent. N). The nitroglycerine for ballistite should be highly stable (for at least twenty minutes at 80 by the Abel test), while the collodion-cotton should have a stability of twenty-five minutes at 71 by the Abel test; for the finished ballistite the stability should reach thirty minutes at 80. To incorporate these two substances thoroughly and so that there is no danger in the subsequent operations, use is made of Lundholm and Sayer's process, by which the constituents are united in presence of a liquid able to dissolve neither of them. This liquid is merely water, 0-5 to 1 per cent, of aniline or phenylamine, or, as suggested by Spica, phenanthrene, being added to fix the nitrous acids liberated and thus increase the stability of the ballistite. The pulped collodion-cotton, containing 30 per cent, of water, as it comes from the centri- fuges (after stabilisation with 15 parts of hot water per 1 part of nitrocotton) is introduced into a cylinder of sheet-lead or aluminium containing water at 60. The mass is well stirred by compressed air and the finely divided nitroglycerine passed in by means of a compressed - FIG. 211. 301 air injector. The agitation is continued until all the nitroglycerine is incorporated with the cotton, none remaining suspended in the water. The whole mass in then discharged into a vessel underneath with walls and bottom of fine brass gauze or silk. When it has drained well, the material is removed and left in heaps for some weeks in order that the gelatinisation may be completed. The further treatment consists of coarse sieving, centrifuging to remove non-incorporated water, and a first rolling between two rolls almost touching and heated to about 50 to 60 by means of internal steam (Fig. 214 ). It is thus obtained in thick non- homogeneous leaves; to the material used to form these leaves are added cuttings and waste of finished ballis- tite, which is first softened by immer- sion for some hours in tepid water. The leaves are then rolled a second time between rolls which are more exactly calibrated and adjustable (see Fig. 214 a), and are heated, thinner sheets of definite thickness being thus obtained. All extraneous bodies (scraps of wood, paper, cotton, etc.) are removed by forceps and the sheets are examined against the light to detect any other heterogeneous particles. The ballistite is then cut into strips and these into squares, which are seasoned or stabilised by spreading them on cloth under sheds and leaving them for two or three weeks, after which the material undergoes no further change, and is ready to be tested and stored. FIG. 213. FIG. 212. FIG. 214. FIG. 2 14 a. Ballistite is almost brown in colour, has the sp. gr. 1-63 to 1-65, and is practically unaffected by moisture; it inflames at 180 without exploding. The gases formed in its explosion contain no nitrous vapours and do not corrode the firearms to any extent. Such 302 ORGANIC CHEMISTRY corrosion is caused especially by the very high temperature produced by the explosion of the ballistite and by the friction of the hot gases. With lapse of time a very small part of the nitroglycerine appears to evaporate, the strength and properties of the ballistite being thereby modified. For this reason ballistite is replaced to some extent by solenite and cordite, which contain less nitroglycerine. 1 With some smokeless powders, attempts have been made to replace the nitrocellulose by nitrated starch and the liquid solvents by the corresponding vapours, but no advantage has yet been procured in this way. Explosive gelatines may also be obtained by adding metallic nitrates (of barium or potassium ) to the collodion-cotton ; these have diminished power but possess the advantage of being readily inflammable. Mixtures of collodion- cotton and nitropentaerythritol have recently been prepared for the use of large-bore artillery. PROPERTIES OF SMOKELESS POWDERS. Those formed of nitro- cellulose alone are hard ; ballistite is not so hard, and even in thick strips can be bent and then broken like a very hard paste. They are very resistant to the action of water and so have a great advantage over ordinary black powders, which are destroyed by water. They also possess the advantages of a high density, 1*6 or more (see p. 262). The velocity imparted to the projectile increases with the percentage of nitrogen in the smokeless powder ; for one and the same velocity, the explosive which develops the lowest pressure causes the least wear of the barrel and is also the most safe. Whilst Vieille's smokeless powder (gelatine of pure guncotton) withstands all ordinary conditions of temperature and moisture, ballistite, on the other hand, gradually loses nitroglycerine and so undergoes change of its properties if the humidity of the atmosphere oscillates much. These conditions are, however, rarely met with in practice, and ballistite is used not only by the Italian army and navy, but also by other Governments, and is in some ways superior to the cordite used in the British and also, to a certain extent, in the Italian armies. In 1906, the proportions of the components of cordite were varied slightly and the form altered to that of ribbons, being then known as axite. Smokeless powders withstand the blow of a projectile and require special detonators, fulminate of mercury not giving good results. They are exploded by compressed guncotton caps, which in their turn are exploded by fulminate of mercury. If accidentally ignited, smokeless powders are not very dangerous, since they do not explode, but regard must be paid to the very high temperatures (above 3000) produced, as these will melt iron, stone, etc. 1 Cordite, prepared by Abel in 1889, is a smokeless powder in filaments like hollow twine. Modern cordites contain 65 per cent, of .guncotton (not collodion-cotton), 30 per cent, of nitro- glycerine, and sometimes 5 per cent, of vaseline. Guncotton, which is insoluble (to the extent of 90 per cent. ) in alcohol, ether, or even nitroglycerine, may also be gelatinised by the action of a common solvent, e. g., acetone, which gives a colloidal solution persisting even after evapora- tion of the solvent. The dry guncotton is first mixed by hand with nitroglycerine, the mass being then introduced into an ordinary kneading machine, which is of bronze and is jacketed to allow of water-cooling ; the acetone (20 kilos per 100 kilos of the paste ) is then added and kneading continued for at least 3 hours, after which the vaseline is mixed in for some time. The mass tends to heat'and must be cooled. At the end of the operation, lumps of the paste, roughly cylindrical in form, are introduced into the cylinder of the cordite press, which is similar to that used for making macaroni. The threads of varying thickness, length, and shape of cross-section thus obtained are then dried at 40 for five to eight days, and afterwards left for three or four weeks in the air to undergo stabilisation. Solenite, prepared in a similar manner in thin threads, is used in Italy as a rifle powder, and consists of 36 per cent of nitroglycerine, 61 per cent, of nitrocellulose (one-half guncotton and one-half collodion-cotton), and about 3 per cent, of mineral oil. Powder C2, made in England by Messrs. Chilworth and also, since 1910, by the Nobel Dyna- mite Company of Avigliana, resembles cordite, and consists of 70'5 per cent, of nitrocellulose (two-thirds collodion, one-third guncotton), 23'5 per cent, of nitroglycerine, 5 per cent, of va&eline, and 1 per cent, of sodium bicarbonate; gelatinisation is facilitated by the use of acetone. PICRIC ACID 303 SMOKELESS AND FLAMELESS EXPLOSIVES. From a military point of view, a great advance was made by the replacement of black powder by smokeless powders, since the latter do not obscure the artilleryman's view and also render difficult the exact location of the battery by the enemy. It still remained possible, however, especially at night-time and with large guns, to determine the position of these, since, as the projectile leaves the muzzle, the hot gases resulting from the explosion extend into the air, producing flames 50 cm. or even a metre in length. A few years prior to the European War successful attempts were made in various countries (Germany, Roumania, etc.) to eliminate these flames almost completely by addition to the explosive of certain substances, especially small proportions of diphenylamine, diphenyldimethylurea, neutral ammonium oxalate, etc. Herein probably lies the reason why the big German guns were able to fire on Dunkirk and Paris from a distance of a hundred kilometres without discovery. Analogous results are obtained with the so-called safety mine explosives (see p. 305). In 1906 Duttenhofer patented the addition of potassium bicarbonate to smokeless powders to diminish the flame, but the results thus yielded are not highly satisfactory. Stabilisers for smokeless powders and dynamites. To render these explosives physically more stable, that is, less sensitive to shock, it is sufficient to mix intimately with them paraffin wax, vaseline, camphor (see celluloid), mineral oil, castor oil, etc., in more or less large proportions (1 to 10 per cent. ). To stabilise explosives chemically by retarding or preventing their spontaneous decom- position, various additions are made. Thus, after the first cases of such decomposition with powder B, Vieille suggested the addition of a little amyl alcohol (2-4 per cent. ), which doubled the stability; in 1896 it was found that a far higher stability still was effected by 2 per cent, of diphenylamine. Aniline, which acts similarly but less efficaciously, has long been added to ballistite. The last stabilisers have the property of fixing any traces of nitrous acid formed during the slow decomposition of the powder, thus preventing rise of te'mperature and slackening the decomposition. These substances are, of course, sometimes used to mask incipient decomposition at the time the explosives are to be examined. Of the numerous other stabilisers suggested, the following, which have given good results, may be mentioned : ammonium and sodium ammonium oxalates, urea, nitro- guanidine and mercuric chloride (this only masks the reactions by which the stability is controlled). SHATTERING EXPLOSIVES AROMATIC NITRO-DERIVATIVES : PICRATES PICRIC ACID (melinite, shimose, lyddite, pertite). As early as the fifteenth century an alchemist obtained an explosive substance by treating a kind of tar with aqua regia, but this acquired no importance in comparison with ordinary gunpowder. The explosive properties of picric acid, C G H 2 (NO 2 ) 3 OH, and its salts were studied in the second half of the nineteenth century and assumed considerable importance when, in 1886, Turpin prepared melinite from 70 per cent, of picric acid and 30 per cent, of collodion-cotton previously rendered soluble with alcohol and ether; this was regularly used for some years by the French army in place of dynamite. At the present time fused picric acid (m.-pt. 122; sp. gr. 1-64-1-66) is poured into cartridges containing a fulminate of mercury cap and powdered picric acid. The manufacture of picrc acid from carbolic acid, and also its properties, are described in Part III (chapter in Aromatic Nitro- derivatives). Weight for weight, picric acid is less effective than dynamite, but, measured by volume, its power is greater than that of dynamite, the specific gravity of which is 1-5. It has also the advantage over dynamite in that it does not freeze, being already in the solid state. In England, melinite was followed in 1888 by lyddite, containing about 87 per cent, of picric acid, 10 per cent, of nitrobenzene, and 3 per cent, of vaseline. This is poured in a molten state into the cartridges and is exploded with ammonium picrate detonators ; it is highly resistant to shock. It undergoes decomposition fairly readily, giving poisonous gases, containing about 61 per cent, of carbon monoxide and 13 per cent, of carbon dioxide. For this reason picric acid and all similar compounds cannot be used in the galleries of mines. The ease with which picrates form in contact with iron, lime etc., has led to many disasters, since picrates are readily exploded by shock. The insides of bombs and projectiles to be charged with picric acid are varnished, as also are the capsules fcr the caps. Fusion of 304 ORGANIC CHEMISTRY picric acid is carried out in aluminium vessels; at a temperature somewhat above the melting-point, picric acid is highly sensitive and dangerous. During the European War, in order to increase the quantity of explosive with a basis of picric acid, use was made on an enormous scale of a fused mixture of 60 per cent, of picric acid and 40 per cent, of dinitrophenol (m.-pt. 111-5; for preparation, see Part III). This has explosive powers almost equal to those of picric acid, and is more stable and less dangerous to handle, while it has the great advantage that its melting-point is below 90, that of picric acid being 122. Further, for this mixture use may be made of moist picric acid, since the water separates completely and floats on the mass during the fusion ; the danger involved in drying the picric acid is thus avoided. TRINITROTOLUENE. Some years before the European War picric acid had been replaced in Germany, Italy and, partly, in England by trinitrotoluene, which melts at 80-5 and has the same power, but is more stable and less dangerous to make and to handle ; further, it does not combine with metals. Part III contains a description of the properties and manufacture of this product, which was used during the war on a vast scale by all the belligerents. Another explosive which was largely used in the war and is cheap, easily prepared, safe to handle, and moderately powerful, consists of an intimate mixture of 12 per cent, of dinitronaphthalene (a mixture of various isomerides, see Part III) and 88 per cent, of ammonium nitrate; the mixture was compressed, but not excessively, in the projectile. This product (and others similar) was patented in 1885 by Favier and in France, during the war, bore the name schneiderite, being made at the Creusot works of Messrs. Schneider ; in Italy it was made by the Societa Italiana Prodotti Esplodenti (S.I.P.E.) of Cengio and was termed siperite. Various other mixtures with bases of atomatic nitro-derivatives (nitrocresols, etc. ) were used during the war. SPRENGEL EXPLOSIVES. In 1871 H. Sprengel, starting from the fact that explosion is nothing but instantaneous combustion, conceived the idea of preparing explosives by mixing a readily combustible substance with one possessing considerable oxidising pro- perties; the substances separately are not explosive, but become so when mixed, mixing taking place only at the spot where the explosive is to be used. In January 1871, a few months before Sprengel's discovery, Silas R. Devine had prepared and used a mixture of potassium chlorate and nitrobenzene, but he kept the process secret ; in 1880 he prepared rackarock powder, formed by mixing the potassium chlorate and nitrobenzene just before use (see below). This idea was taken up later by Hellhoff, who mixed nitric acid with nitrated hydro- carbons, and more effectually by Turpin and by R. Pictet, who mixed nitrogen peroxide (N 2 4 ) with various nitrated organic compounds and also with CS 2 (pandastite, fulgurite, etc.), but these explosives never came into practical use. Another form of explosive of the Sprengel type is that with ammonium nitrate as base ; this has been largely used during recent years and is five or six times as powerful as gunpowder. The most important of these explosives is Favier powder (1885), which, in its different forms, usually consists of a mixture of ammonium nitrate and nitronaphthalenes, and sometimes contains also sodium nitrate, aluminium, etc. (see later : Prometheus Powder). CHLORATE AND PERCHLORATE POWDERS (Partly of the Sprengel type) CUorate powders, first proposed by Berthollet in 1785 to obtain greater power, and containing potassium chlorate instead of nitre, have not been very successful, and even when a part of the nitre is restored, accidental explosions often occur, owing to the great sensitiveness to shock. In America, Devine (1881) retains the potassium chlorate, but keeps the ingredients of the powder separate until required (as is done with the Sprengel explosives (see. above); thus rackarock for blasting contains 79 per cent, of potassium chlorate and 21 per cent, of nitrobenzene (liquid), mixed sometimes with picric acid, sulphur, etc. These powders are rendered less sensitive to shock by mixing with a little wax (e. g. Brank's powder). In 1896, at St. Petersburg, Jevler prepared promelheus from a solid portion (90 per cent, potassium chlorate + 10 per cent, of manganese dioxide + a little SAFETY EXPLOSIVES 305 ferric oxide), and a liquid portion (55 per cent, of mononitro benzene + 18 per cent, of turpentine oil + 27 per cent, of naphtha ) ; a factory for this explosive was erected in Italy in 1905, but it was destroyed by a terrific explosion in 1909, ten persons being wounded and five killed. In 1901 donnar was placed on the market; it contains 56 per cent, of chlorate and 24 per cent, of potassium permanganate for the solid part, and 16 per cent, of nitrobenzene and 4 per cent, of turpentine for the liquid part. Also nitronaphthalene and castor oil (5 to 8 per cent.) are used to render the mixture more stable, e. g., with cheddite and with pierrite : 80 per cent, of chlorate + 12 per cent, nitronaphthalene + 6 per cent, castor oil + 2 per cent, picric acid (or, better, 2 per cent, dinitrotoluene ), the whole being well mixed ; this powder has double the power of ordinary blasting powder. To replace dynamite, miedziankite, consisting of 90 per cent, of chlorate and 10 per cent, of petroleum, has been suggested (1912). More advantageous still are thought to be the potassium perchlorate powders (Nisser powder, 1865, contains: perchlorate, 10-5; nitrate, 44-5; bichromate, 2; ferrocyanide, 1-5; sulphur, 15-5; charcoal, 19-5; and vegetable substances, 6-5 per cent. ). Better still are those containing ammonium perchlorate, recently invented by U. Alvisi (manlianite : 72 per cent, perchlorate, 14 - 75 charcoal, 13-25 sulphur; Cannel powder : 80 per cent, of perchlorate, and 20 per cent, of cannel coal ; cremonite, with 48-85 per cent, of ammonium perchlorate, and 51-15 per cent, of ammonium picrate ; and the kratites obtained by mixing perchlorates with nitroglycerine and with nitrocellulose). Perchlorate powders should be used cautiously, and to render them less sensitive without imparing their great shattering power, they are mixed with urea, guanidine, dicyanodiamidine, etc. ; if nitrate is added, the chlorine is partly fixed, and the explosions then obtained are especially suited to mines with thin and extended seams. Hydrogen chloride also is formed to some extent in the explosion ; 2NH 4 C10 4 = 2HC1 + 2N + 3H 2 + 5O, the theoretical temperature of the explosion being 1084 and the volume of gas liberated 1615 litres of gas per kilo of the explosive. In 1905 a patent was taken out for a powder containing 47 per cent, of ammonium nitrate, 1 per cent, of charcoal, 30 per cent, of orthonitrotoluene, and 20 per cent, of very finely powdered aluminium, the whole being compressed under a pressure of 5000 kilos per square centimetre, and then moistened with nitrotoluene in a water-bath at 67. SAFETY EXPLOSIVES (for Mines Rich in Firedamp). 1 Firedamp (see p. 34) is a mixture of methane and air and is formed particularly in coal-mines. It burns at 450 and inflames at 650 ; in presence of spongy platinum it burns even at 200. For ignition to occur, a certain time at least some seconds is necessary. For instance, at 650 about 10 seconds elapses before the explosive mixture ignites, whilst at 1000 ignition occurs in 1 second. This explains why, for example, the gases produced at a temperature of 2000 by shattering explosives do not always fire the explosive mixture, the explosion occurring with enormous rapidity (scarcely measurable). The danger of ignition is diminished by decrease of the quantity of gas formed, i. e., of explosive used for each charge; the very hot gases produced expand rapidly and become cooled, so that they are unable to cause ignition of the firedamp. Further, if the heat of the gases is efficiently utilised to give the 1 The frequent explosions occurring in mines have led scientific men to make' attempts to mitigate their effects and to render them less common. In the tremendous explosion of March 10, 1906, in the Courriere mines (France) there were 1000 victims, 600 being killed ; thirteen workmen were rescued alive after twenty days. Commissions have been appointed in France (1880), Russia (1887), Austria (1891), and other countries. In England the question has been studied by Macnab (1876) and Abel (1886); in France by Mallard and Lo Chatelier (1883), Watteyne, etc.; in Germany by Winckhaus (1895), very systematically by C. E. Bichel and Mettegang (1904-1907), who devised various ingenious forms of indicating apparatus, Beyling (1903-1907) and Heise (1898); and in Austria by Siersch (1896), Bohm (1886), Mayer (1889), and Hess (1900). The studies of Bichel more especially have shown that the safety of an explosive for use in mines (especially coal-mines) depends simultaneously on several factors, each of which must lie within definite limits, excess of one of these not being able to compensate for deficiency of another. Thus, for example, ordinary black powder, which has almost all the requisites of a safety explosive, cannot be employed, for the sole reason that the duration of its flame is too long and so renders it dangerous. The principal factors establishing the safety of an explosive are : velocity of explo- sion, temperature of the gases formed, length of the flame, duration of the flame, and quantity of explosive used in each explosion. The results of experiments made in England and America up to 1913 show that the safety of mine explosives is influenced also by the diameter of the cartridge, the density of the charge, the granulation, the tamping, and the degree of moistness of the air. VOL. ii. 20 306 ORGANIC CHEMISTRY maximum amount of mechanical work (splitting of the rock), the risk of firing is diminished ; hence follows the necessity of a good tamping for each charge in order that the escape of the gases without performing work may be prevented. Explosion in the open is more likely to ignite firedamp. In mines the use of a powerful detonator is advantageous, in order that the explosion may be sharp and rapid. Mine explosives should contain sufficient oxygen to produce only C0 2 and not the poisonous CO. Instead of calculating the temperature and duration of explosion, it is preferable in practice to make direct experiments with small cannons placed against a rock at the bottom of a long, wide iron tube or test-chamber (20 cu. metres), containing an explosive gas. Dis- charge of the cannons should not ignite the gas if the explosive is safe. In France it is prescribed by law that in mines explosives 'must be used which give gases of maximum degree of oxidation but no inflammable gas (CO, H 2 ) or solid carbide : further, the tempera- ture of detonation, calculated according to a formula of Mallard and Le Chatelier, must not exceed 1500 (or for certain piercing operations, 1900). Gunpowder, dynamite, and blasting gelatine readily cause explosion of firedamp in mines, their temperatures of explosion exceeding 2200 (as shown by Mallard and Le Chatelier). 1 In order to meet the requirements of a safety explosive, various ingenious processes are employed to lower the temperature of the gases from the explosion sufficiently to prevent them giving a flame. The charges are wrapped up and the tamping made with water or with gelatine containing 98 per cent, of water (or with special sponges saturated with water, etc.). Salts containing much water of crystallisation have also been used for tamping, but without good results, the tamping being simply projected to a distance without evaporation of the water. A safer plan consists in mixing the explosive directly with such salts, the water of crystallisation then evaporating with considerable absorption of heat, at the instant of explosion. Finally, use is made of explosives with ammonium nitrate as base, the temperature of explosion of the nitrate being only 1130 and the reaction occurring thus : NH 4 N0 3 = N 2 + 2H 2 + 0. Since, however, the explosive effect of ammonium nitrate is small, it is combined with other substances, e. g., with dynamite or with Favier's explosive. In some cases, in addition to the nitrate, ammonium chloride is used, this undergoing dissociation with absorption of heat from the gases. To lower the temperature of the flame, and especially to obtain smokeless and flameless 1 Dynamite and especially gunpowder, if exploded without tamping, will certainly ignite firedamp or even the coal-dust suspended in the air of coal-mines. The dangeris diminished, but not excluded, by tamping, so that even in 1853 the Englishman Elliot suggested replacing the explosives by quicklime, a large compressed charge of which is placed in a cavity in the rock; the pipe from a pressure water-pump is then introduced and a good tarnping effected. The water, coming into contact with the lime, increases the volume of the latter two to five times, and, with the steam formed at the same time, pressures of 500 atmos. can be obtained. In 1880 the use of lime cartridges was fairly general in mines, but they were abandoned later owing to the unsatis- factory results given. No better fortune befell cartridges of quicklime, water, and sulphuric acid, or powdered aluminium and sulphuric acid (which develop hydrogen), or chlorine and ammonia compressed separately and then united, or compressed explosive mixtures of oxygen and hydrogen. In 1876, Macnab suggested tamping gunpowder charges with water, but this did not always prevent explosion of the firedamp ; the same system applied to dynamite by Abel in 1886 gave better results. In some cases, the water is replaced by moist substances (sand, moss, etc. ), which yield good results. In mines which give much coal-dust there is the greatest danger of disaster when large charges (of more than 100 to 150 grams) are used, and when the coal contains 22 to 35 per cent, of Volatile products. Although firedamp ignites at 650, explosives can be used which have a temperature of explosion only slightly below 2200 (roburite, 1616; westphalite, 1806; carbonites for coal- mines, 1820 to 1870, etc. ), since the gases cool on expanding. Even these explosives are, how- ever, dangerous if the charges are large (above 300 grams for roburite and westphalite, and above 1000 grams for the carbonites), since then a momentary pressure on the air is developed (especially if the velocity of explosion is high) and a decided rise of temperature. Explosives which, in charges of 600 to 800 grams, do not ignite the explosive mixture in the test-chamber, may be safely used in fiery mines. The length and duration of the flame of the explosion are, however, of the greatest importance, and ordinary black powder is, as stated above, very dangerous in such mines owing solely to the marked duration and length of the flame. More dangerous still are those explosives which cause considerable dilatation of the leaden blocks (see later, Fig. 230, p. 317), and those which give, among their products of explosion, carbon monoxide and hydrogen, but not oxygen, since these gases on burning (rapidly) withdraw oxygen from the flame of the explosive and almost stifle it. A good safety explosive ceases to be such if it is not always prepared with the same care and of equal uniformity from the same materials. FLAMELESS EXPLOSIVES 307 powders, addition of nitrodicyanodiamidine or dicyanodiamide (see Vol. I., p. 371) has been tried with success. Use has also been made of vaseline, oil of paraffin, camphor or 2 to 5 per cent, of sodium oxalate, tartrate, or citrate (Ger. Pat. 243,846). Various kinds of such explosives give good results, e. g., grisounite, containing 44 per cent, nitroglycerine, 12 per cent, nitrocellulose, and 44 per cent, crystallised magnesium sulphate (MgSO 4 -f 7H 2 O); also roburite, with 82 per cent, of ammonium nitrate and 18 per cent, of dinitrobenzene ; Nobel's wetter-dynamite, with 53 per cent, nitroglycerine, 14-3 per cent, kieselguhr, and 32-7 per cent, magnesium sulphate; securite, with 37 per cent, ammonium nitrate, 34 per cent, potassium nitrate, and 29 per cent, nitrobenzene ; westphalite, FIG. 215. 100 grams of Gelatine Dynamite FIG. 216. 100 grams of Dynamite (Kieselguhr) FIG. 217. 100 grams Roburite FIG. 218. 100 grams Carbonite FIG. 219. 100 grams Grisounite containing 94 per cent, ammonium nitrate, and 6 per cent, resin ; carbonite, with 25 per cent, nitroglycerine, 40 per cent, wood-meal, 30-5 per cent, potassium nitrate, 4 per cent, barium nitrate, and 0-5 per cent, sodium carbonate ; ammoncarbonile contains 82 per cent, of ammonium nitrate, 10 per cent, of potassium nitrate, 4 per cent, of nitroglycerine, and 4 per cent, of wheat flour; vigorite, containing 30 per cent, nitroglycerine, 49 per cent, potassium chlorate, 7 per cent, potassium nitrate, 9 per cent, wood-pulp, and 5 per cent, magnesium carbonate. Even these substances are not, however, safe in the absolute sense of the word; with such additions of inert products, the explosives lose in force but gain in safety. In 1896 Schoneweg, and then Siersch, starting from the hypothesis that the smaller the 308 ORGANIC CHEMISTRY flame produced in an explosion, the safer will be the explosive, photographed, on dark nights, the flames produced by the free explosion of 100-gram cartridges. As will be seen from Figs. 215 to 220, these flames are of value, although they are not absolutely decisive, since the non-luminous (ultra-violet) rays also act on the photographic plate. In Fig. 215 is seen a small luminous spot detached from the principal flame, this being due either to the surrounding gas being rendered incandescent by the shock of the explosion, or to subsequent inflaming of the gases of the explosion. DETONATORS AND CAPS FULMINATE OF MERCURY, (C* N O) 2 Hg, the composi- tion and constitution of which are given later (see Fulminic Acid), FIG. 220. wag discovered by Howard in 1799, and studied as regards its 100 grams Gelatine Dy- constitution by Gay-Lussac, Liebig, Gerhardt, Kekule, etc. The namite, with tamping . _ . J . *? i_ -r\ -n of wet paper rs ^ mercurv fulminate cap was made in 1815 by Durs Egg. Its manufacture requires great care and exact proportions of the reagents. So long as fulminate of mercury is moist it presents no danger, but it must be handled with extreme care when dry. It is best prepared by Chandelon's process : into a glass vessel of about 4 litres capacity is placed 100 grams of mercury, to which is added 1000 grams of nitric acid of 40 Be. (sp. gr. 1-383), the liquid 'being stirred until all the mercury is dissolved. The greenish liquid is allowed to cool to about 20 and is then poured into a flask of at least 5 litres capacity containing 635 grams of 90 per cent, alcohol ; bumping or fuming of the liquid is of no consequence. Very soon the liquid begins to boil spontaneously, to become decolorised and to evolve gas and white poisonous vapours (CO, ethyl nitrate and acetate), and then yellow vapours of nitrogen peroxide. The mass darkens slightly, and when the maximum fuming occurs, 80 grams of 90 per cent, alcohol are added a little at a time, and then a further quantity of 55 grams of alcohol, the boiling being thus somewhat attenuated. After it has been left until the white vapours have disappeared, there appears on the bottom a voluminous whitish powder, which is the fulminate of mercury. The operation lasts altogether fifteen to twenty minutes, and should be carried out under a hood with a strong draught, or else the flask should be fitted with a stopper and wide delivery tube to carry the vapours to a flue. The product is poured on to a filter, washed ten to fifteen times with water until the wash- water no longer shows an acid reaction * and the filter with the fulminate spread out on other absorbent paper in the air (not in the sun) until it is almost dry (about 20 per cent, of moisture being left, since then it may be kept safely in cardboard boxes). To dry it completely and safely, vacuum drying-ovens at a temperature below 40 are now used. The reaction between alcohol and mercuric nitrate begins only in presence (that is, after the formation) of nitric oxide, the alcohol being then converted into aldehyde ; indeed, if the alcohol is replaced by acetaldehyde the reaction proceeds better and more completely (Munroe, 1912). Theoretically 100 grams of mercmy should yield 142 grams of the fulminate, but practi- cally about 125 to 128 grams are obtained. The preparation of 1 kilo of fulminate requires 8 kilos of alcohol, which is only partially recovered by passing all the vapour emitted during the reaction into a vessel of water. In the dry state, it is sold at 9s. 6d. to 12s. per kilo ; when not used at once, it is stored under water. If necessary, it may be purified by dis- solving in hot water (solubility 1 : 130), from which it crystallises on cooling. It is whitish or sometimes faintly yellow (if a small quantity of HC1 or NaCl is added to the nitric acid used in its manufacture, white crystals are obtained), poisonous and soluble in alcohol. 2 1 The filtrate and the wash-water are utilised by first neutralising with milk of lime or calcium sulphide (or by decomposing with hydrochloric acid ) ; from the precipitate the mercury is recovered, whilst witheriteis added to the liquid to form barium nitrate ; the alcohol is recovered by distillation. 2 Analysis of Fulminate of Mercury (Brownsdon's method) : the fulminate is first purified by dissolving it in potassium cyanide and reprecipitating it with dilute nitric acid ; it is filtered, carefully dried, and a weighed quantity of 0-04 to 0-05 gram dissolved in 30 c.c. of water. One gram of thiosulphate is then added and the liquid shaken and made up to 100 c.c. with water. The free alkali in 25 c.c. of this solution is then estimated by titration with N/10-sulphuric acid in presence of methyl orange as indicator. DETONATORS 309 It has an extraordinary shattering power owing to its very great rapidity of explosion. It is exploded by a blow or by brisk rubbing, and gives a pressure of 27,400 atmos. When heated slowly it explodes at 152. All objects used in its manipulation must be of wood, not of iron. Since it is scarcely ever used alone for preparing caps, but is mixed with 15 to 20 per cent, of potassium chlorate and about 25 per cent, of antimony sulphide, it is some- times, in order to avoid explosion, made into a paste with a thick solution of gum, the required quantity being poured into each copper cap (which contains about 15 or 20 mgs. of fulminate for sporting caps, or 1 to 1-5 grams for caps to be used with dynamite cartridges) , these being then very carefully dried in vacuum drying ovens. When, however, these mixtures are prepared in the dry state, in order to prevent explosion the mixing is carried out in the apparatus shown in Figs. 221 and 222. In a leather box, e, a leather bag,/ (the so-called " jelly- bag "), is suspended by the loops, h, attached to the gutta-percha ring, g. To the bottom of the bag and to the ring, g, are joined several cords on which are FIG. 221. FIG. 222. threaded rubber rings, alternately large and small. Another cord, n, attached to the lever, p q s, admits of the bottom of the bag being raised and lowered so as to mix the ingredients. When mixing is complete, the bottom of the bag is drawn completely up, so that the contents fall into the space between the bag and the box and thence into the collecting vessel, v. The workman is protected from the effects of a possible explosion during the operation by a semi-cylindrical wrought-iron screen, t. The caps are then very carefully charged by compressing the mixture with a suitable machine or press, which gives a pressure rising gradually to 260 atmos 1 . (pure fulminate will stand 7000 atmos. without exploding, but in presence of other substances, e. g., sand or coke powder, or other hard body, it will explode with a very small pressure). During the charging the operative is always sheltered by iron screens. DETONATORS (Caps, Fuses). Detonators serve to produce explosion of explosive substances. For black powders it is sufficient to produce a spark in the mass by means of a heated fuse, but with nitroglycerine or guncotton explosives, neither the fuse nor the black powder causes explosion, ignition being the most they produce. In these cases 310 ORGANIC CHEMISTRY use is made of fulminate of mercury caps, which explode by simple percussion or heat, and produce a true explosive wave capable of inducing the instantaneous decomposition, i. e., the explosion even of large masses of explosive, provided that the cap is of suitable size ; if, however, too little fulminate is used, part of the charge does not explode. Moist or paraffined compressed guncotton requires more powerful caps of dry guncotton, these being then exploded by fulminate of mercury detonators. Ignition caps, unlike detonating caps, contain also a little potassium chlorate. Smokeless powders require ignition caps with a very hot flame, which is obtained by adding to the fulminate a combustible substance or, as proposed by Brownsdon and the King's Norton Metal Company, a little powdered aluminium. In 1900 Bielefeld found that it suffices to place a small quantity of mercury fulminate on trinitrotoluene or other aromatic nitro-derivative to obtain an excellent detonator, and in Germany a large proportion of the caps have a basis of trinitrotoluene. Tetranitro- methylaniline (tetryl) is also manufactured as a detonator. According to Wohler and Matter (1907), the fulminate may be replaced by a small amount of silver azide, and in 1908 Hyronimus suggested lead azide, Pb(N 3 ) 2 (see Vol. L, p. 376) as a substitute, but thi? is not always advantageous. Whereas formerly, for kieselguhr dynamite, use was commonly made of fulminate caps No. 3, and only in exceptional cases of No. 5 (double strength), nowadays, especially FIG. 223. FIG. 224. FIG. 225. for safety explosives, No. 6 caps are mostly employed, and sometimes No. 8 (2 grams of mercury fulminate) to obtain complete explosion. The explosion of detonators or caps, and hence of the cartridges or charges of explosive, both in blasting and military operations, is effected electrically or with fuses. Fuses should burn with a definite velocity, so as to allow the miners to reach a place of safety before the explosion. This requirement is satisfied by the Bickford fuses (devised in 1831 by the Englishman, Bickford). These consist of a compact cord prepared in a special manner from jute or cotton threads, which are spun round one another in opposite directions and are rendered impermeable by tar or gutta-percha. These fuses or cords, 5 mm. thick, have an empty central core, which is then filled with finely granulated, com- pressed powder. They then burn with a velocity of 1 metre in ninety seconds. To explode black powder, it is sufficient to fix the fuse into the mass of the charge, which explodes as soon as the flame reaches it. These Bickford fuses became of practical importance only in 1867, when the use of dynamite in mines commenced. For dynamite, gelatine dynamite, and explosive gums or gelatines, use is made of a fulminate of mercury detonator which explodes a dynamite cartridge, this then causing explosion of all the other cartridges (without caps) surrounding it. The fuse is cut clean and introduced into the bottom of the copper cap containing the fulminate, and is fixed to the cap by squeezing it with suitable pincers (Fig. 223). The parchment paper at one extremity of the cartridge is then opened and the cap thrust into the cavity left for it (Fig. 224), the paper being then tied tightly round the fuse with string so that the cap and fuse cannot become detached from the cartridge (Fig. 225). VARIOUS POWDERS 311 Ordinary fuses, which are very irregular, are obtained by soaking soft cotton cord with lead or potassium nitrate; such fuses must be well dried before use, as they are hygro- scopic. The cord may also be impregnated with a paste of gum and fine black powder and then dried. Almost instantaneous fuses may be made from guncotton. The importance of tamping after the introduction of the cap into the charge has already been mentioned ; if the explosion is carried out in the open, the charge is covered with earth or stones. Electric fuses are used, especially for dynamite and fulminate caps, and serve well for producing the simultaneous explosion of several charges, this giving a greater effect than separate explosions ; they are also useful in galleries which contain firedamp, as the latter would be exploded by a burning fuse. A spiral of thin platinum wire is fixed in contact with a little dry guncotton above the fulminate of the cap. The two ends of the wire are connected separately with two insulated wires joined to a small battery, accumulator, or hand dynamo, which heats the wire and so causes explosion. tJse is often conveniently (since the fragile platinum spiral is eliminated) made of an electric spark formed between two platinum points very near to one another in a mixture of potassium chlorate and antimony sulphide contained in the cap ; in this case the sparking is effected by a device similar to a Leyden jar (Bornliardt exploder) which gives a high-tension current, or by one utilising induced currents (Breguet exploder) ; these may be placed at a distance from the charge by lengthening the conducting wires. At one time ignition was effected by means of a high tension current from a frictional machine, Breguet alone using low tension current, but the tendency nowadays is to employ the latter, together with magnetic ignition, the danger of igniting the inflammable gases of mines being thus diminished. Formerly, very long conducting wires could not be used owing to the weakening of the current at the igniting extremities, but nowadays relays are inserted at various points and maintain the current constant. Lauer and Tirmann make friction igniters, which are operated at a distance by means of wires. Girard obtains detonating fuses by filling leaden tubes with nitrohydrocellulose and then drawing them out to the diameter of ordinary safety fuses. Similar fuses were made subsequently to 1906 with fillings of melinite or, better, trinitrotoluene. The best of these fuses are those with instantaneous ignition proposed by General Hess and used in the Austro-Hungarian Army : these were first formed of four threads covered with fulminate of mercury, but in 1903 Hess rendered their action slower by adding 20 per cent, of hard paraffin wax to the fulminate. When knotted, these instantaneous fuses behave as detonating caps and electric ignition may be dispensed with ; they may be cut and beaten without danger. With detonating fuses (1910) containing compressed powdered explosive with a detona- ting velocity of 5000 metres per second (picric acid or trinitrotoluene), the wick is bent and the bend fixed into the cap, whilst the two ends are brought near to the outside and ignite simultaneously. Where the explosive waves meet the shock is such that the waves reinforce one another, producing a velocity of detonation of 10,000 metres per second ; in this way the charge is more completely exploded. VARIOUS POWDERS. During recent years there has been very keen rivalry between different makers to prepare new powders for special purposes (even for shooting pigeons ! ), and also blasting powders more economical than black powder. For powders to be used immediately or stored in very dry magazines, the potassium nitrate is replaced by sodium nitrate (although this is more hygroscopic), which is cheaper and gives a larger proportion of oxygen; the charcoal has also been partially replaced by other organic substances (tar, sawdust, flour, and even horsedung). These powders, often short-lived, are given most extravagant names (violette, gunn, fulopite, pyrolite, pudrolite, etc.). Normanite is an English powder for use in mine galleries, and is composed of 33 per cent, nitroglycerine, 45 per cent. KNO 3 , 1-5 per cent, of collodion- cotton, 8 per cent, of wood- meal, 11 per cent, of ammonium oxalate, and 1-5 per cent, of wood charcoal. Faversham contains 80 to 90 per cent, of ammonium nitrate, 9 to 11 per cent, of T.N.T., and various other products. Rexite contains 7-5 per cent, of nitroglycerine, 66 per cent, of ammonium nitrate, 14 per cent, of sodium nitrate, 7-5 per cent, of T.N.T., 4 per cent, of wood-meal, and .less than 1 per cent, of moisture. Ammonal, which was used as a shattering explosive during the 312 ORGANIC CHEMISTRY European War, was employed first in mines, and contains 3 per cent, of coarsely powdered aluminium, 4 per cent, of T.N.T., and 93 per cent, of ammonium nitrate. It was proposed by Escales and Dekmanin 1899-1900, and burns slowly, exploding only with powerful caps. Other special types of dynamite are mentioned on p. 284. DESTRUCTION OF EXPLOSIVES. In various cases it is necessary to destroy explosives, when these have altered or undergone partial decomposition, or when residues are left from samples submitted for analysis. With black powder it is sufficient to im- merse it in water and so dissolve out all the nitre, and then to burn the barely dry insoluble residue. Water does not, however, destroy nitroglycerine or the various dynamites ; with these the caps are carefully removed and also the wrapper (including the parchment paper), the cartridges being placed in contact one with the other on a long strip of paper in a field free from stones and away from any building; they are then sprinkled with petroleum, and a long fuse, attached to the first cartridge, lighted. In this way the car- tridges burn without exploding. With frozen dynamite cartridges which have undergone change, it is dangerous to handle them, and they must be very carefully exploded one by one in the open with a fulminate cap and fuse. Nitroglycerine may be made into a paste with sawdust and burnt as described above. Small quantities of explosives may be burnt in pieces the size of a pea, and small dynamite residues may be decomposed by heating on a water-bath and frequently stirring with concentrated alcoholic caustic soda solution. STORAGE AND CARRIAGE OF EXPLOSIVES. Explosives factories are placed at a distance of about 1000 metres from any dwelling-house or frequented street. The ideas underlying the construction of magazines are very varied. In some countries (Austria, Italy, France, and, in part, Germany) the prepared explosives are distributed in a number of small magazines far from the factory, and constructed of wood so as to minimise the danger from projection in case of explosion; they are separated by large mounds of earth as high as the magazine, so that the explosive wave or projected material may not reach neighbouring magazines. Also in some magazines a kind of wide bridge covered with earth is constructed over the magazine to annul or attenuate the effect of projectiles falling from above. In England, however, it is assumed that, owing to the perfection of the systems of manufacture and of chemical and physical control of explosives, explosion is not to be regarded as possible, so that large, very solid magazines are built, either wholly of cement or partly of iron, the walls being half a metre thick. The distance between the separate magazines varies from 100 to 200 metres,- according as the amount of explosives stored is more than 2000 or 10,000 kilos. The flooring is of wood, and the magazines are heated in winter by means of steam-pipes in order to prevent freezing of the explosives. In general there are no windows, but only double doors and small apertures ; artificial illumination, which is rarely used, consists of lamps placed outside the apertures or electric lamps hermeti- cally sealed with gutta-perojaa and fitted with several glass coverings ; in some cases the electric lamps are immersed in water. Any person entering a magazine must wear felt slippers or leather boots without nails. The most serious danger is not that of accidental explosion, but that of lightning. When storms threaten all work is suspended, while the magazines are protected from lightning by all the most modern appliances. 1 Even the methods of packing explosives and loading 1 In general the protection afforded by lightning conductors is due to the fact that lightning is rendered harmless if it meets good and sufficiently extensive conductors of electricity. There is, however, always great danger if inside or outside the buildings protected there are large masses of good conducting materials, such as the iron and lead pipes of dynamite factories, as these may cause deflection of the lightning even from its path in the lightning conductors. At the Nobel dynamite factory at Krummel, on the Elbe, there was a great explosion in 1900, lightning striking the iron compressed-air pipe and being thus led to the vessels full of nitro- glycerine, which consequently exploded. Franklin's principle, according to which a metal rod furnished with points should serve to discharge to earth the large electric charges of the clouds, is not applicable to the protection of explosive factories, since such rods on factories do not discharge the clouds to a sensible extent, but can only serve to conduct the lightning to earth after the shock. Much more rational is Faraday's method of attempting to discharge the electricity of the clouds or to conduct the lightning by so many metallic wires as to prevent it from subdividing, no secondary circuits which might produce sparks being, however, formed. According to Faraday, the most certain protection against lightning consists of a metal cage surrounding or covering the building to be protected, and many military explosives stores are effectually protected in this manner. In 1900, Professor Weber proposed the protection of the Krummel explosives factory by fixing to ANALYSIS OF EXPLOSIVES 313 them on wagons for transport are subject to detailed regulations : by legislation dating from 1875 in England and from 1905 and 1909 in Germany, and in Italy by a series of laws and regulations of various dates. In every case, a despatch must be preceded by a permit and by a warning to all the stations on the route. Explosives are despatched only on certain days and in certain trains. In Germany, chlorate and perchlorate travel with- out restrictions. Owing to the great stability of modern explosives, only 6 out of 265 accidents due to explosives occurred during transport. ANALYSIS OF EXPLOSIVES. The quantitative determination of the components of black powder is comparatively simple : 10 to 20 grams of the sample is dried in an oven until constant weight (moisture) and is then extracted with hot water, which dissolves the nitre, this being weighed or analysed separately. From the dried residue the sulphur is extracted by carbon disulphide in a Soxhlet extraction apparatus. The residue then contains the charcoal, graphite, and any impurities (sawdust, mineral carbon, etc.) which may be identified under the microscope. The density of the powder is determined by means of a densimeter, and the size of the grains and the quantity of dust by suitable sieves. The analysis of dynamites and of smokeless powders is more complicated and must be carried out with great care. In dynamites with inert bases the proportions of nitroglycerine, moisture, and inert substance are determined : 8 to 10 grams of the dynamite, cut into pieces the size of peas, with a wooden or bone spatula, are weighed on a clock-glass and left in a desiccator over calcium chloride (not sulphuric acid) for some days until of constant weight : the loss in weight gives the moisture. The dried mass is extracted with pure dry ether free from alcohol, in a Soxhlet apparatus (as in the extraction of fat, which see) , the heating being effected with water at 50 to 60 and the ether subsequently distilled with water at 40 to 50 away from the neighbourhood of a flame. The nitroglycerine becomes turbid when almost all the ether is evaporated, but clear again when the evaporation is complete ; the nitroglycerine is dried until constant in weight in a vacuum desiccator over calcium chloride. The residue left in the extractor (kieselguhr or other inert matter) is dried at 60 to 70 and weighed. It is spmetimes sufficient to determine the nitroglycerine by difference from the weight of this residue ; the result is exact enough and the operation more rapid and less dangerous. Dynamites with active bases sometimes have complex compositions and the analysis is not always so easy; 1 in general, the nitroglycerine and collodion-cotton are separated iron columns galvanised wire-netting (88 meshes per sq. metre) furnished with metal points so as to form a kind of roof a metre or more above the factory. The columns also are provided at the top with metal points and serve to conduct the electric discharge to the earth. In the wires forming the network sharp curves are avoided in order to facilitate conduction and hinder any divergence of the lightning. Above the buildings of the Krummel factory there are 24,000 metres of metal wire with five million points, which may contribute in some measure to discharge the clouds, and would certainly conduct the lightning to earth after a discharge. The ideal method would consist in using copper wire 1 cm. in diameter, but the expense of this would be enormous. The earth-contact is made in wet places with iron plates or rails one or two metres under the soil. Also the metal piping (if not replaceable by rubber tubing) and apparatus of the various parts of the factory are connected with the earth- conductors of the lightning conductors, so as to avoid the formation of sparks in the discharge of the lightning. It has also been suggested that, where possible, the large vessels in the separate buildings should be electrically insulated, both from the lightning conductors and from the earth. 1 For dynamites with active bases (containing nitroglycerine, collodion-cotton or guncotton, nitrates, sawdust, etc.), Stillman and Austin (1906) propose a method of analysis which is briefly as follows : The moisture is determined on 10 grams as above ; the dry mass is then extracted several times in the cold with a mixture of 1 part of alcohol and 2 parts of ether. The residue (.4) is dried and weighed (for its analysis see later), the solution being left to evaporate in the cold to 100 c.c., to which is added 100 c.c. of chloroform to precipitate the collodion-cotton. The liquid is decanted on to a tared, dry, cloth filter on to which all the collodion-cotton is brought by means of chloroform ; the filter is dried in an oven at 40 and then in a desiccator and weighed (as a check, it is redissolved in alcohol and ether, reprecipitated with chloipfonn, collected on a filter and dried at 40, the collodion being then detached from the filter, completely dried on a watch-glass in a desiccator and weighed). After the collodion-cotton is separated, the decanted and filtered liquids are evaporated in a tared vessel, dried in a vacuum and the remaining nitroglycerine weighed. If the nitroglycerine contains traces of nitrates, these are extracted by repeated treatment with small quantities of water, the solution being then evaporated and the nitrates weighed. If along with the nitroglycerine there are also resin, paraffin wax, and traces of sulphur, it is titrated with excess of normal alcoholic caustic soda in the hot, the excess of alkali being then 314 from the residue by alcohol and ether, from which the collodion-cotton is precipitated with chloroform. The resistance to heat of nitroglycerine and of djTiamite is determined as with nitro- cellulose (see below), the nitroglycerine being extracted from dynamite by displacement with water, and the gelatine explosives being mixed with double their weight of chalk prior to extraction with solvents; it should withstand a temperature of 70 for at least fifteen minutes without colouring starch and potassium iodide paper. In contact with sensitive blue litmus paper it should not give the slightest reddening, as this would indicate incipient decomposition. Exudation of nitroglycerine from dynamite, in either the cold or the hot, shows faulty manufacture. With nitrocellulose, besides testing its solubility in a mixture of 1 part of alcohol and 2 parts of ether which dissolves collodion- cotton but not guncotton, the nitrogen is often estimated in the Lunge nitrometer (Vol. I., p. 578) by shaking with concentrated sulphuric acid; or Schlosing's method, as used in France, may be employed to ascertain the type of the nitrocellulose : in a 150 c.c. flask are placed 25 grams of pure, powdered, ferrous sulphate, 0-7 to 0-8 gram of nitrocellulose, and 70 to 80 c.c. of hydrochloric acid; the flask is shaken and then fitted with a stopper through which pass a delivery-tube and another tube conveying a current of carbon dioxide ; when all the air is expelled the delivery-tube, dipping into a vessel of mercury, is covered with a graduated tube filled half with mercury and half with caustic soda solution. The flask is then heated to boiling, when the liquid blackens and in ten minutes all the nitric oxide is evolved, the last traces of this gas being driven out by a stream of carbon dioxide. The volume of gas gives the amount of nitrogen. The amount of non-nitrated cotton is determined by boiling 5 grams of the substance with a saturated solution of sodium sulphide, the liquid being decanted after a stand oi twenty-four hours and the treatment with sodium sulphide repeated ; the residue is finally collected on a tared cloth filter, washed with boiling water, then with dilute hydrochloric acid, and lastly with boiling water again ; it is then dried and weighed. The resistance to heat (Abel's heat test) of nitrocellulose is of importance, as it serves as a control during manufacture and is used also as a test for nitroglycerine : a wide-mouthed glass flask, A (Fig. 226), 20 cm. in diameter, and with no neck, is almost filled with water and is covered with a leather disc pierced by four holes provided with wire clips for holding test-tubes ; the flask is heated below by a small lamp, F, placed under a metal gauze and determined with normal acid in presence of phenolphthalein : 1 c.c. of normal alkali used in the saponification corresponds with 0-0757 gram of nitroglycerine (in case no resin is present). After the titration, the liquid is evaporated almost to dryness to eliminate the alcohol, and is then diluted with water and shaken with ether in a separating funnel. The ethereal solution is separated and evaporated, and the residual paraffin wax weighed. The aqueous liquid after separation of the ethereal solution, is heated with a little bromine to oxidise the sulphur; it is then acidified with HC1, boiled, and the resin collected on a tared filter, whilst in the filtrate the sulphuric acid formed by oxidation of the sulphur is precipitated with BaCU. The nitroglycerine may be estimated by difference, by subtracting from the original weight the insoluble residue, A, the paraffin wax, the resin, the small amount of sulphur, and the nitrates. The residue, A, insoluble in alcohol and ether (see above), is extracted with hot water; the undissolved part is dried at 70 and weighed (B = sawdust + sulphur + any insoluble mineral substances); the sulphur is extracted with carbon disulphide, and weighed, this weight sub- tracted from B giving the sawdnst, from which also the weight of ash left after calcining is subtracted if inorganic substances are present. , The aqueous solution obtained from A is evaporated, dried at 110 and weighed (C nitrates + carbonates + any woody extract); it is then treated with a little nitric acid, evaporated, dried and weighed (D) ; from the difference between C and D the C0 2 evolved and hence the carbonates can be calculated. The mass, D, is melted, heated to redness, cooled, treated with a little dilute nitric acid, evaporated, dried at 110 and weighed (E); this weight gives the sodium and potassium nitrates. Subtraction of the weights of nitrates (E) and carbonates from C gives that of the extractive matters and of ammonium nitrate, if this is present ; the latter may be determined in the aqueous liquid, A, by estimating the ammonia evolved in the ordinary way. PRESSURE AND HEAT OF EXPLOSION 3X5 surrounded by a screen, D. The central aperture carries a thermometer, and one of the others a thermo-regulator (if necessary) , whilst in the remaining ones are placed test-tubes which contain the nitrocellulose (1 to 3 grams) or nitroglycerine (2 c.c.) and dip into the water. Each of the stoppers of the test-tubes is fitted with a hook of glass tubing on which is hung a piece of starch-potassium-iodide paper moistened at the upper part with a drop of dilute glycerine. The temperature of the bath is maintained at 82 ; in France Powder B is tested at 110 and in other countries smokeless powders are tested up to 130, a current of air being passed over the heated explosive. The test is finished when a faint brown coloration appears at the edge of the glycerine. A good guncotton will withstand heating at 82 for half an hour without browning the paper. If nitrocellulose is stabilised by the incorporation with it of a little sodium bicarbonate or calcium carbonate, it becomes less stable to the Abel test. 1 Measurement of the Pressure and Heat of the Gases Developed by Explosives. The power of an explosive is deduced principally from the quantity of heat produced on explosion (see p. 259), this being measured in the Berthelot-Mahler calorimetric bomb (see Vol. I., p. 461 ). Deflagration is induced by means of an electric spark, and if considerable pressure is maintained in the bomb by means of air (or nitrogen in the case of guncotton, as this is deficient in oxygen, which should not be supplied if the conditions of an ordinary explosion are to be repro- duced), the products of deflagration are almost identical with those of explosion. The bomb is specially con- structed with various accessories to allow of the analysis and measurement of the gases produced in the decom- position, at either low or high pressure, of the explosive. The pressure of the gases produced by the explosion in a resistant chamber, C (Fig. 227), of soft sheet steel wrapped round with steel wire, is measured indirectly by determining the crushing of a small copper cylinder, Z (crusher), 13 mm. high and 8 mm. in diameter, placed between a fixed base, d, and a hardened steel piston, a, of known surface which transmits the pressure of the gases. The chamber, C, is fixed by two massive wrought- iron plates, D and D', held together by six thick rods, B. Deflagration is caused by rendering incandescent a platinum wire between the two terminals, b. In order to obtain exact results it is indispensable that there be no escape of the gas, which would also cause gas being at a temperature of 2000 to 3000 and atmospheres. The deformation of the crushers is shown in almost the natural dimensions in Fig. 182 on p. 262. The sensitiveness of explosives to a blow is determined empirically by allowing a given 1 According to Will (1902) and Egerton (1913), this test is very sensitive, being able to detect 0-0000016 gram of nitrous acid in 100 grams of explosive. However, some years ago certain English manufacturers added various substances (e.g., mercuric chloride, formaldehyde, etc.) to mask the instability of their powders. It must also be borne in mind that the sensitiveness of the reaction may be influenced by the method of preparation of the starch-iodide powder. The test is carried out in a pure atmosphere removed from the smallest traces of nitrous acid vapour. Since decomposition in powders is gradual, the duration of the test (e. g., thirty minutes ) should be noted. Angeli test : When explosives with a basis of nitric esters contain solvent (ether, alcohol, acetone, etc. ) or stabilising substance, the Abel test is insufficient, since the reaction of the nitrous vapours is prevented or retarded. In 1917 Angeli proposed to replace the Abel test by a qualita- tive test of the acidity carried out as follows : A portion of the powder cut into thin flakes is shaken in a test-tube with water containing a few drops of a 0-2 per cent, alcoholic solution of dimetliyla- mincazobenzene, q.v>, Part III); if the> flakes remain yellowish, they are not acid and have kept well, but if they turn red, they are acid and have undergone alteration. Silvered vessel test: This is used in England and Italy, and consists in determining the number of hours required for the temperature of the explosive kept in a silvered flask (100 c.c. or up to 3000 c.c.) in a thermostat at 80 to rise by 2. FIG. 227. danger from projection, the a pressure of several thousand 316 weight of iron (ram, see Fig. 228) to fall from various heights on to a certain amount of explosive placed on an iron block, the height of the fall being increased until explosion occurs. The sensitiveness to heat is measured roughly by throwing small pieces of the explosive on to mercury heated to successively increasing temperatures until deflagration takes place. When the power of an explosive cannot be determined directly or by comparison of the practical effects, indirect tests must be employed, although these do not always correspond with the actual effects. To avoid uncertainty, the expression power of an explosive, f, is applied to the product of the volume, v , of gas (reduced to and formed from unit weight of the explosive), the pressure, p , in mm., and the absolute temperature, T (calculated from the products of the reaction), this product being divided by 273, so that : FIG. 228. . 273 ' The power of progressive explosives may be determined indirectly by Guttmann's power gauge (Fig. 229) : on a hollow block of steel, a, (diameter of cavity 35 mm.), are screwed two steel blocks, b, and a small firing-plug, g. A trigger, m, which can be released from a distance by means of a cord, serves to explode the plug. The apparatus is charged by unscrewing one of the blocks, b, and introducing first a cylinder of drawn lead, 40 mm. long and 35 mm. in diameter, which closes hermetically the wide mouth of the right-hand cone : then a steel disc and one of cardboard of such thickness that it makes 20 grams of powder rest just in the middle. This powder, which is intro- duced next, is situate just under the cap, n. Then follow a disc of cardboard, one of steel, and a block of lead similar to the first, this closing the cavity to the left, when the block, 6, is again screwed on. The gases produced by the explosion have no outlet, and so force the leaden blocks into the conical holes to the right and left. The height of the leaden cones projecting is compared with that obtained with a standard explosive and thus gives the power of the explosive. For shattering explosives, on the other hand, good results are obtained with Trauzl's lead block, which is in the form of a cylinder 200 mm. in height and diameter. In the middle FIG. 229. is a cavity, 110 mm. deep and 20 mm. wide, into which 15 to 20 grams of the explosive is placed. A fulminate cap, connected with wires for firing, is inserted and the bore tamped with well-compressed sand and chalk. After the explosion, the capacity of the cavity is measured with water. Fig. 230 shows several of these blocks after testing with various explosives. A charge of 15 grams of No. 1 dynamite gives a volume of 705 c.c., and deducting from this 30 c.c. for the original volume, and 30 c.c. produced by the 1-5 grams VELOCITYOF PROJECTILES 317 of fulminate in the cap, there remains 645 c.c. due to the explosive, i. e., 43 c.c. per gram. To obtain comparable results with explosives of the same class, charges of equal weights must be taken, otherwise different values are obtained for the same explosive; there are, besides, other causes of error, which give only a relative value to this method of determining the power. I \ FIG. 230. Measurement of the Initial Velocity of Projectiles. For this purpose use is made of Le Boulenge's chronograph (Figs. 231 and 232), which gives the velocity, V, by measuring the time, T, taken by the projectile to traverse the known distance, D (20 to 50 metres), between two wire frames, G, G' (Fig. 231), which are cut through by the projectile im- mediately after it leaves the gun and are connected electrically with two quite distinct points of the chronograph, the apparatus being so arranged that T lies between 0-05 and 0-15 second; V = w. The chronograph is formed of two electro-magnets, a and e (Fig. 232, or C and C', Fig. 231), joined to the batteries B and B', and to the corresponding FIG. 231. FIG. 232. wire frames, G and G'. The magnet, a, attracts a tubular bar (c, d, Fig. 232, or C, Fig. 231 ) of the chronometer, which terminates at the top in a soft iron point and is enlarged at the bottom ; the magnet, e (or A' in Fig. 231 ), attracts a rod,/ (or C", Fig. 231 ), of the registrar. The chronometer bar is surrounded by a thin zinc or copper tube. The registrar is of soft iron, has the same weight as the chronometer, and is pointed at the top and enlarged at the bottom. When the projectile traverses the first frame, G, it interrupts the current of the electro -magnet, A, and the chronometer bar, C, becomes detached from A (Fig. 231) and begins to fall freely. When it traverses the second frame, G', it interrupts the current 318 ORGAN 1C CHEMISTRY of the electro-magnet, A', and the registrar, C', falls and releases a hook which liberates a horizontal spring pointer, this immediately striking the falling chronometer bar. The mark on this bar will be the higher the lower the initial velocity of the projectile. Suitable tables deduced from simple formulae 1 give the required velocity. The velocity of detonation is difficult to determine, since it depends largely on the resist- ance of the enclosure containing the explosive and on other circumstances. It is determined roughly but with sufficient exactitude, under similar conditions, by placing a number of cartridges in a continuous row and joining the two wires of the Le Boulenge chronograph to points in the row at a certain distance apart. USES OF EXPLOSIVES. The largest consumption of explosives is that of armies and navies, whilst in various civil operations these substances are also employed : in the tunnelling of mountain ranges ; in lessening manual labour in the ploughing -of the soil ; for disintegrating rocks to provide material for the construction of houses to displace the all too numerous deserts; and further, for preparing blocks of material to be wrought by the genius of man into monuments attesting to posterity the varied and incessant progress of human thought and labour. In practice a sharp distinction is made between progressive explosives, used more especially in mines for detaching large masses of rock and for excavating (for coal, minerals, gold, and diamonds), and shattering explosives (dynamite, etc.), employed for such purposes as demolishing walls, bridges, and large trees, or breaking the ice at the surface of rivers and lakes when navigation is pre- vented. To demolish a large tree it is sufficient to surround it with a string of dynamite cartridges, explosion of one of which will cause explosion of the others ; to break iron, e. g., a railway rail, or cut a bridge, one or more cartridges are placed on it, covered with a light tamping of earth and exploded. In sub- aqueous works modern smokeless explosives are of great service, since to their great power is added their stability towards water, which acts as an excellent tamping. 2 The use of explosives in agriculture, particularly with the view of utilising the enormous stocks remaining in all countries after the European War, has become an accomplished fact. As early as 1870 De Hamm of Vienna anticipated the employment of dynamite in agriculture, and in 1878, Sobrero, in a communication to the Turin Academy of Sciences, 1 A test is first made in which the chronometer bar and the registrar fall simultaneously. The height, h, at which the former is struck corresponds with a time, t, which must always be allowed for in the subsequent measurements, as it represents the time required by the registrar to release the spring. According to the law of bodies falling freely, h = lgt z , so that t \J ~_ ; in practice, when a time, T, elapses during the passage of the projectile from G to G', the mark /2// on the chronometer bar at the height, H, corresponds with a time, T + t = \J . The difference v ff between these two measurements gives the time required, the velocity being then deduced from D the formula : V = 2 The Mont Cenis tunnel, which connects Italy and France, and is 12,233 metres in length, was commenced in August 1857 and, as it was assumed that the blasting would be carried out with black powder, it was calculated that twenty-four years would be required to complete the work. After 1865, however, dynamite became available, and the work was finished eleven years earlier than was anticipated, 1000 tons of explosive being used and 2,800,00'0 expended. The St. Gothard tunnel (14,920 metres), joining Italy and Switzerland, was completed in six years and a half (1873-1880), and cost 10,400,000. During the piercing of the Simplon, 1640 tons of gelatine explosives were used, mostly with a content of about 92 per cent, of nitroglycerine. In constructing the harbour of Genoa, the Nobel Company exploded simultaneously a number of mines with a total charge of 6000 kilos of dynamite. For the removal in 1905 of a rock that partially obstructed the Danube at Greisen- stein, a mine was laid with 11,700 kilos of dynamite; 280,000 cu. metres of rock were detached at a cost of about three-halfpence per cubic metre. In the American Independence Day fetes, a million pounds worth of fireworks are consumed every year. FATTY ACIDS 319 made definite proposals in this direction. Various practical applications were afterwards made in America, Germany and elsewhere, and in 1918-1919 rigorous and systematic tests, carried out by specialists in America, France and Italy (with trinitrotoluene and picric acid) showed that highly compact and semi-rocky soils may be broken down satisfactorily in this way ; cartridges of 100 or 200 grams were placed less than 1 metres apart at a depth of about 60 cm., good tamping being provided. Explosives are used economically only when the usual means present great difficulties. In the United States a single factory produced in 1911 explosives to the value of 120,000 for agricultural purposes. STATISTICS OF EXPLOSIVES. The consumption of explosives in time of war is enormous. Every shot of a large gun, which does not always hit the mark, costs hundreds of pounds. The world' 's production of explosives prior to the European War reached a total of 350,000 to 400,000 tons, almost the half of this amount being made in the United States. According to O. Guttmann, the production of explosives with nitroglycerine as base amounted in 1909 to more than 62,000 tons, distributed as follows : United States, 20,000 tons (in 1912, over 22,000 tons); Ger man y, 10,300; England, 8100; the Transvaal, 8000 ; Canada, 5000; Spain and Portugal, 3500 ; Austria-Hungary, 2300; France, 1500; Switzerland, Australia, and Norway and Sweden, 600 each; Russia, Italy, and Holland and Belgium, about 500 each; and Greece, 175 tons. 1 EE. ACIDS I. SATURATED MONOBASIC FATTY ACIDS, C n H 2n 2 These are termed fatty acids because some of them are contained in fats, from which they are prepared. All contain the characteristic group, C0 2 H, the 1 The output of military explosives in different countries in 1913 and during the first two years of the European War is shown approximately by the following figures (tons) : Great United Whole Britain Germany France Italy States Eussia Japan Austria world 1913 . 18,000 60,000 15,000 3,500 8,000 6,000 4,000 5,000 150,000 1915 . 120,000 360,000 160,000 15,000 130,000 60,000 50,000 90,000 1,065,000 1916 . 200,000 540,000 300,000 45,000 190,000 100,000 90,000 150,000 1,805,000 In addition to its enormous home consumption, Germany exported, in 1906, 2136 tons of black powder, of the value 320,000 ; 4791 tons of other explosives, worth 372,000 ; and 7300 tons of cartridge charges for guns and artillery, of the value 1,000,000. In 1913 the total German exports of explosives were valued at 4,000,000 and the imports at 72,000. The out- put of dynamite in Germany was 2000 tons in 1880, 4000 in 1890, 8000 in 1909, and 11,000, besides 15,000 of safety explosives with a basis of ammonium nitrate, in 1912. Before the war, some of the German explosives factories paid dividends of 25 per cent, or more. In the United States the industry is a rapidly growing one. While the total production was 3,400,000 (including 40,000 tons of dynamite) in 1900, it rose in 1905 to 5,920,000, of which 1,760,000 represented black powder; 320,000 nitroglycerine ; 2,600,000 dynamite ; 800,000 smokeless powder; and 35,200 guncotton. In 1909 the capital invested in explosives works in the United States amounted to 10,000,000, the output comprising 85,000 tons of dynamite, 4500 tons of safety mine explosives, 14,000 tons of nitroglycerine, 6000 tons of black powder, 45,000 tons of shattering explosives, etc., the total value being 8,000,000 (in 1904, 6,000,000), and the power used 28,600 horse-power. During the period of their neutrality, the United States manufactured enormous quantities of explosives for home consumption and for the Allies, especially France, Great Britain, and Russia. About 205,000 tons were made for home consumption in 1915, and more than 225,000 tons in 1916; the value of the exports was 2,000,000 in 1914 and 153,400,000 in 1916. When the European Allies became able to supply their own needs, the American factories continued to produce on an even vaster scale for the needs of their own country in the war. In 1910 Great Britain exported 630 tons (172,000) of smokeless powders and 7200 tons (720,000) of dynamite, 450 tons (37,600) of the latter being imported. In 1907, Great Britain consumed 7000 tons of black powder and exported 3597 tons (3500 in 1910 ). Before the European War single factories in England made as much as 10,000 tons of dynamite per annum. Japan, which before the war possessed two Government factories for military explosives, im- ported from Great Britain and Germany various explosives, to the value of 100,000, in 1910. In Belgium the consumption of mining explosives in 1910 was about 1473 tons, 229 tons being black powder. In the same year Austrian mines used about 2395 tons of different explosives, 1600 tons being dynamites of various types, while in the Transvaal mines explosives to the value of 1,440,000 were consumed. 320 ORGANIC CHEMISTRY hydrogen of which is replaceable by metals. With every hydrocarbon or every primary alcohol of the methane series corresponds a monobasic fatty acid. The first members are liquids having a pungent odour, and are soluble in water, alcohol, or ether, and boil without decomposing ; then' follow members of an oily consistency, less soluble in water, and with unpleasant smells like that of rancid butter or perspiration ; beyond C 10 they are solid, insoluble in water, and soluble in alcohol or ether, and distil unchanged only in a vacuum. The first members (up to C 9 or C 10 ) are volatile in steam. It will be seen from the Table that the boiling-points of these acids rise regularly with increase in the number of carbon atoms, but the melting- points are higher in an acid with an even number of carbon atoms than in those immediately below and above with uneven numbers. TABLE OF THE SATUKATED MONOBASIC FATTY ACIDS Formula Name Melting-point Boiling-point Specific gravity CH 2 2 Formic + 8-3 101 1-2187 (20) C 2 H 4 2 Acetic + 16-5 118 1-0502 (20) C 3 H 6 O 2 Propionic - 22 141 1-013 (0 CTT (~\ (Normal butyric - 7-9 162 0-978 (0 4 n 8 U 2 \Isobutyric - 79 154 0-965 (0 Normal valeric - 58-5 185 0-956 (0 C H O Iso valeric -51 174 0-947 (0 Trimethylacetic + 34-35 163 0-905 (50) * Methylethylacetic 173-174 0-938 (20) C 6 H 122 Normal caproic (hexoic) 1-5 205 0-945 (0 1 C 7 H 14 2 Normal heptoic - 10 223 0-921 (15) C 8 H 162 Caprylic (octoic) + 16-5 237-5 0-910 (20) C 9 H 182 Pelargonic (nonoic) + 12-5 186 \ 0-911 (12) C 10 H 202 Capric (decoic) + 31-4 200 aj 0-930 (37) C 11 H 222 Undecoic 28 212 H p C 12 H 242 Laurie 44 225 1 0-875 \ "s C 13 H 26 O 2 Tridecoic 40-5 236 O< '3 C 14 H 282 Myristic 54 248 0-862 tUD C 15 H 302 Pentadecoic 51 257 a S Palmitic 62-6 268 8 0-853 "5 C 17 H 342 Margaric 60 277 49 S C 18 H 36 O 2 Stearic 69-3 287 0-845 J ' where k is a constant depending solely on the nature of the equilibrium that is, on the nature of the reacting bodies and on the temperature ; k is hence a measure of the tendency of an acid to dissociate and is called the affinity constant. The following Table gives the numbers referring to acetic acid and two of its chloro-derivatives : Acetic Acid Monochloroacetic acid Dichloroacetic acid A 100 a 10" * A 100 a 10A A 100 a 10A 16 6-5 1-67 1-79 56-6 14-6 155 _ _' _ 32 9-2 2-38 1-82 77-2 19-9 155 269-8 70-2 5170 64 12-9 3-33 1-79 103-2 26-7 152 309-9 80-5 5200 128 18-1 4-68 1-79 136-1 35-2 150 338-4 88-0 5040 256 25-4 6-56 1-80 174-8 45-2 146 359-2 93-4 5160 512 34-3 9-14 1-80 219-4 56-8 146 375-4 97-6 1024 49-0 12-66 1-77 265-7 68-7 147 383-8 99-7 In this Table A denotes the molecular conductivity corresponding with the dilution v, 100 a the extent of dissociation in per cent., and 10 5 Jc the affinity constant multiplied by 100,000. This affinity constant has a markedly constitutive character ; it increases, for instance, if a substituent of negative nature, such as OH. Cl, N, N0 2 , etc., enters a molecule and decreases if positive groups such as NH 2 enter. The following examples may be given : Formic acid . . . , k = 127-0 . 10 - B Acetic acid . . . ' . . . . . . . 1-8 . 10 - 5 Propionic acid . . . 1-3 . 10 ~ 5 Substitution with halogens and similar groups. Monochloroacetic acid . . . . . . . . &= 155.10" 5 Dichloroacetic = 5100. 10 ~ 5 Trichloroacetic about 120,000 . 10 - 5 Eromoacetic 138. 10 ~ 5 Cyanoacetic 370. 10 ~ 5 Thiocyanoacetic 260. 10 ~ 5 /3-Iodopropionic ........ 9-0.10" 5 Substitution by hydroxyl. Glycollic acid, OH CH 2 COOH k= 15-0. 10 ~ 5 Lactic acid, CH 3 CH( OH) COOH 14-0. 10 - 5 -Hydroxypropionic acid, OH CH 2 CH 2 COOH . . . 3-1. 10 ~ 5 Substitution by NH Z . a-Aminopropionic acid (alanine), CH 3 CH(NH 2 ) COOH . . k = 9-0. 10 ~ 5 For further examples and greater details, see R. Abegg's " The Electrolytic Dissociation Theory." New York, 1907. 324 ORGANIC CHEMISTRY Separation of the fatty acids from mixtures of them is not always easy, and is sometimes effected by taking advantage of their greater or less volatility either in steam or in a vacuum, or by precipitating with magnesium acetate or barium chloride, since in alcoholic solution the higher acids are precipitated first. Use is also made of the fractional solution of the calcium, barium, or lead salts in various solvents (alcohol, ether, etc.), or of fractional neutralisa- tion followed by distillation of the acids not neutralised. From an aqueous mixture of formic, acetic, butyric, and valeric acids, the last two may be separ- ated by extraction with benzene, from which they may be isolated by shaking with baryta water. Further separation may then be effected as above. Constitution of the Fatty Acids. That these acids actually contain carboxyl groups, COOH, is indicated by the different ways in which they are formed and decomposed, but the most characteristic method of preparation consists of the hydrolysis of the nitriles, which are obtained from the alkyl iodides by the action of potassium cyanide (see p. 238). Two molecules of water react with one of nitrile, giving ammonia and a higher acid : CH 3 C i N + 2H 2 = NH 3 + CH 3 COOH. The nitrogen of the nitrile being detached, the group COOH must neces- sarily be formed, since, from reasons already mentioned, the formation of a group C(OH) 3 is excluded, as three free hydroxyl groups cannot remain united to one carbon atom (although the corresponding ortho-ethers are known and also acetals, see pp. 217, 251 and 252). FORMIC ACID, H C/ \OH Methanoic Acid It was shown as early as the seventeenth century that ants contained a special acid, which was characterised later as formic acid, and was separated (by distilling with water) from the wood ant, the migratory ant, bees (and hence from crude honey), the hairs of the nettle, pine leaves, perspiration, urine, etc. Gerhardt was the first, in 1850, to show that C0 2 and formic acid are obtained when oxalic acid is heated in presence of sand. In 1855 Berthelot, and later Lorin obtained good yields of the acid in 60 per cent, or even 75 per cent, concentration by heating crystal- lised oxalic acid with anhydrous glycerol in a reflux apparatus ; this reaction yields first CO 2 , H 2 and formic acid in the form of glyceride, HC0 2 [C 3 H 5 (OH) 2 ], this being hydrolysed by the water of crystallisation of a further quantity of the oxalic acid, with regeneration of the glycerol and liberation of formic acid. For 100 kilos of formic acid, 300 kilos of oxalic acid are consumed. For some years formic acid has been more economically obtained by decomposing formates prepared synthetically. In 1856, Berthelot found that a minimal amount of formic acid is obtained when CO acts on concentrated sodium hydroxide solution at 200. Better yields were procured in 1880 by Merz and Tibirica by the use of powdered caustic soda (as soda-lime with 6 per cent, of moisture) at 200. 2>m ^ u ^^ ride exported J The calcium acetate is imported principally from the United States and partly also from Austria. In Germany itself more than 16,000 tons of the acetate are made annually. In 1910 Germany imported 4800 tons of dilute pyroligneous acid (less than 30 per cent, strength) for purification. The output of calcium acetate in the United States x was 400,000 tons in 1900 and about 800,000 tons in 1914, one-half being exported (360,000 tons in 1911). The acetic acid consumed in the United States amounted to 14,000 tons in 1900 and 13,500 tons in 1905, 14 per cent, being used in making dyes, 3 per cent, for lead acetate, 25 per cent, in paper- making, 45 per cent, in the textile industries (dyeing), 14 per cent, for making white lead, and 9 per cent, for other purposes. In 1910 the wood from 200,000 hectares (490,000 acres) of forest was distilled in France, various products of the value 600,000 being obtained. The amounts of calcium acetate imported and exported were as follows (ions) : 1913 1914 1915 1916 Importation . . 180 969 498 790 Exportation . . 315 41 729 60 Great Britain imported 3500 tons of calcium acetate in 1909 and 4300 tons (86,400) in 1910. In 1909 Brazil imported acetic acid to the value of 120,000. TLc price of the acid varies with the purity and concentration; ordinary commercial 30 per cent. (sp. gr. 1-041) was sold before the war at about 12s. ; the 40 per cent, acid (sp. gr. 1-052) at 15s. to 16s. ; and the 50 per cent, acid (sp. gr. 1-061) at 20s. per cwt. The pure acid costs 25 per cent, more than the commercial at the same concentration, and the pure glacial (99 to 100 per cent.) 44s. to 46s. per cwt. 2 MANUFACTURE OF VINEGAR Vinegar is formed by the acetic fermentation (by means of Mycoderma aceti, Bacillus aceticus, or Bacterium aceti, see p. 145, Fig. 116, a) of saccharine liquids which have under- gone alcoholic fermentation, such as wine, beer, cider, etc. Since this transformation of alcohol into acetic acid takes place merely on exposure of these liquids to the air, it is 1 In the United States the distillation of wood has been organised, both technically and commercially, as a large modern industry, all the works being combined to a syndicate, which regulates the trade in calcium acetate with the whole world. In 1900 1,767,380 cu. metres of wood were distilled and in 1907 about 4,391,000 cu. metres (only 10 per cent, of resinous wood) in 100 distilleries, the mean yield being 0-5 cu. metre of charcoal, 8 to 10 litres of 82 per cent, methyl alcohol, 22 to 25 kilos of 80 to 82 per cent, calcium acetate, and 15 to 20 litres of tar per cu. metre of wood, and with a consumption of 0-6 cu. metre of wood for heating the retorts, stills and other plant. One-half of the output of the United States is supplied by Michigan and one- fourth by Pennsylvania. In Canada there are wood-distilling works at Quebec, Ontario and Montreal, where also products from other factories are treated. Altogether 2300 workpeople are employed, the annual output being 80,000 tons of wood charcoal, of the value 120,000, 14,000 tons of calcium acetate, of the value 100,000, 400 tons of acetone, worth 240,000, and 1400 casks of formaldehyde, worth 100,000. 2 Testing of Acetic Acid. Better than by the specific gravity the strength is determined by titrating a weighed quantity of the acid with normal caustic soda solution (1 c.c. = 0-06004 gram of acetic acid) in presence of phenolphthalein. When the acid contains more than 2 per cent, of water it no longer dissolves cedarwood oil or oil of turpentine. Metallic impurities are detected by diluting 10 c.c. to 100 c.c., neutralising with ammonia and adding ammonium sul- phide and then ammonium oxalate : the pure acid should show no alteration or precipitate. If sulphuric acid is absent, the acid, diluted with 10 volumes of water and treated in the hot with barium chloride, gives no precipitate even on standing for some hours. In absence of hydro- chloric acid, dilution and addition of nitric acid and silver nitrate produces no turbidity. Absence of empyreumatic products is shown by mixing 5 c.c. of the acid with 15 c.c. of water and 5 c.c. of centinormal permanganate solution : the liquid should not become decolorised in fifteen mimites. For the detection of other organic acids in acetic acid and other tests, see notes on pp. 338 and 344. VINEGAR 341 probable that vinegar and hence acetic acid was the first acid known to man. The same result is obtained by treating alcohol with various oxidising agents (chromic acid, ozone, manganese dioxide and sulphuric acid, etc.), hut acetaldehyde is also largely formed in these cases, which hence do not compete in practice with the biological process. The composition of vinegar 'was studied by Berzelius (1814), and Kiitzing in 1837 showed the importance of the living organism of the mother-of- vinegar to the formation of acetic acid, while Turpin in 1840 examined and characterised these micro-organisms more exactly. According to Liebig, the transformation of alcohol into acetic acid is brought about by the catalytic action of certain nitrogenous substances capable of fixing oxygen from the air and of yielding it to the alcohol. In 1868, however, Pasteur showed that this pheno- menon is caused by a vegetable organism, Mycoderma aceti, formed of small, oblong cells (about 3 micro-mm. long), slightly constricted in the middle (where segmentation then takes place) and often arranged in chains. When these multiply at the surface of the alcoholic liquid, they form first a thin membrane which gradually thickens, and when this membrane is formed in the body of the liquid it becomes mucilaginous and spreads through the whole liquid, giving a compact mass the so-called mother-qf-vinegar reaching to the surface. It develops very well in slightly alcoholic liquids (3 to 6 per cent., but better with 13 per cent, of alcohol, and still more readily in presence of about 1 per cent, of acetic acid and 0-1 per cent, of phosphate); the most favourable temperature is about 30, aceti - fication ceasing at 45 or below 5; the action is retarded by light. When the acetic membrane becomes submerged, the fermentation ceases and only recommences with the formation of a fresh superficial membrane, which can absorb oxygen from the air and transfer it to the alcohol : 1 CH 3 CH 2 OH + 2 = H 2 + CH 3 COOH. According to this equation, the theoretical yield is 60 grams of acetic acid per 46 grams of alcohol, but the practical yield is 15 to 20 per cent, less than this; under the most favourable conditions, a liquid containing 10 per cent, of alcohol by volume yields a vinegar with 10 per cent, of the acid by weight. When almost all of the alcohol is converted into acetic acid, part of the latter begins to decompose into H 2 -4- C0 2 ; this change may be avoided by continuing to add alcohol to the acetic liquid or by causing the mother-of- vinegar to sink, and decanting the liquid. The old or slow wine vinegar process, known as the Orleans process, 2 has been replaced almost everywhere by the more rapid German 1 This explains the harmful effect of vinegar worms (small worms belonging to the Nematodes ), which form a transparent, white, slimy mass moving -along the walls of the vessel, and breaking the skin of Mycoderma aceti at the surface of the liquid and hence causing it to sink. i_ Another enemy of vinegar is the vinegar mite (an insect J mm. in length ), which multiplies at an enormous rate and accumulates in large masses in the vinegar, succeeding in interrupting the acetic fermentation and starting putrefactive changes. In order to prevent the entry of these insects into the vats and casks, the latter are smeared out- side with a ring of birdlime, to which the mites become fixed. Direct sunlight also hinders the development of the worms. Also Mycoderma vini hinders the develop- ment of Mycoderma aceti, and equally harm- ful to acetic fermentation are antiseptic substances in general, sulphur dioxide and empyreumatic substances (including those of pyroligneous acid). Blue and violet light (hence white light, but not red or yellow light) likewise retard the growth of Mycoderma aceti. 2 This process is one of the oldest, and was formerly, and is still, carried out more especially in the town of Orleans, by filling a number of superposed casks (Fig. 245) to the extent of one- eighth of their volume with good wine vinegar and then adding each week about 10 litres of wine (or wine-dregs, containing 8 to 10 per cent, of alcohol, filtered through beech shavings in the vat, E; white wines are preferable). When the casks are about half -full, the vinegar is made, and two-thirds of it is drawn off and either filtered through beech chips or allowed to deposit in the vat, R', underneath ; the addition of 10 litres of wine per week is then continued. By means of the stove, X, the temperature is maintained at 25 to 30. This method gives a fine, aromatic vinegar, but it is very slow and cannot be interrupted when desired. Pasteur prepared vinegar of an inferior quality more rapidly by adding a little vinegar to wine in wide, shallow vats and then sowing on the surface a little pure Mycoderma aceti from another vat. FIG. 245. 342 ORGANIC CHEMISTRY FIG. 246. after one or two complete circula- process, proposed by Schiitzenbach in 1823 and subsequently greatly improved. As early as 1730, however, Boer have prepared vinegar and in some places his method is used even to-day by means of two vats standing on feet and communicating at the bottom by means of a tube. One vat is filled with the wine, but the other is only about half filled, the vinasse not being submerged. Every twelve hours the full vat is half emptied into the other. If the temperature is kept at 25 to 30, acetification is complete in 12 to 15 days. In the German or quick vinegar process, wooden vats, 2-5 to 3 metres high and 1-5 to 2 metres in diameter, are used (Fig. 246). These are filled almost completely with beech shavings, which are supported on a perforated false bottom, L, and covered with a wooden disc with perforations traversed by cords held by knots so as to form a uniform spray of the alcoholic liquid (8 to 10 per cent.), mixed with one-fifth of its volume of wine vinegar, over the wood chips. Six or seven glass tubes passing through the upper disc allow of a continuous circulation of air, which enters at the periphery of the lower part of the vat through the holes, Z, and through the pipe, R, passes through the shavings which become gradually warmed as acetification proceeds and issues through the apertures, Z f , at the top. The temperature is shown by a thermometer, T, inserted in a glass tube, reaching to the middle of the vat. When the temperature exceeds 40, it is lowered by a more rapid passage of the alcoholic liquid, which collects at E and is discharged by the siphon, H, to be conveyed to the top of the vat and again circulated through the shavings, this process being continued until acetification is complete. In some cases three such vats are superposed, the liquid passing down through them all ; tions the operation is complete, although the amount of acid formed is not equal to that of the alcohol in the original liquid. The liquids thus obtained contain up to 12 to 13 per cent, of acetic acid (14 per cent, cannot be exceeded, as the Mycoderma would then be killed) and, if the operations are conducted with care, less than 10 per cent, of the alcohol used is lost ; other- wise, especially if the temperature becomes too high, so that part of the alcohol evaporates, the loss may amount to 30 to 50 per cent. Vinegar of an inferior quality is largely prepared nowadays from various alcoholic liquids made from cereals, starch, beetroot, or molasses, just as in- dustrial alcohol is prepared, but such vinegar lacks the pleasant aroma of wine vinegar. During recent years, however, especially in Germany, alcohol vinegar has been greatly improved by using pure cultures of selected bacteria. In 1912, about 30,000 hectolitres of alcohol were converted into vinegar in Austria and 150,000 in Germany. It has been proposed to accelerate acetification by means of compressed air, but greater success has attended the Michadis or Luxemburg method, in which acetification is carried out in rotating casks (5 to 6 hectolitres) filled with beech shavings (washed first with hot water and then with hot vinegar) and traversed by two osier tubes, one along the horizontal axis and the other along the vertical axis, to allow of the circulation of air. The shavings are washed with wine vinegar, and the cask about half filled with wine (Fig. 247). During the first three days the casks are rotated three times a day and subsequently six times a day. Acetification is complete in about eight days. An ingenious, rapid, and continuous method for the manufacture of vinegar is that of Villon (Fig. 248), which makes use of two drums (2 metres by 2 metres), B B, arranged FIG. 247. MANUFACTURE OF VINEGAR 343 inside in the form of a spiral. The iron spirals are covered or varnished with gutta-percha, and are 30 metres in length, the coils being 10 cm. apart and the spaces between filled with beech shavings (washed with HCI ) or charcoal. The drums rotate in opposite directions, the left-hand one rotating once in five minutes and dipping up each time 8 litres of the alcoholic liquid from the vessel, C, this liquid being then passed through the axial tube to FIG. 248. the second drum, which discharges it into the other dish, C. The liquid then passes to a similar pair of drums and thence to a third pair, on leaving which the vinegar is ready ; by this means 1000 litres are produced in twenty hours. By means of the pump, R, a current of air is drawn through each drum to the centre, whence it passes~through the tube, V, to a cooling coil, S, to condense the small amount of acetic acid vapour it carries over. Another continuous and very rapid method, which avoids loss of acetic acid or aldehyde and diminishes the labour necessary by establishing more intimate contact between the alcoholic liquid and the subdividing material, is that in which the stave acetifier (Figs. 249 and 250) is used. This consists of a wooden box, P, about 1 metre wide and 2 metres high, terminating at the top in a channel, R. The box is filled with nine or ten layers of thin beech sticks, placed vertically and very close one to the other. The position of the sticks in one layer is crossed with respect to that of the sticks in the next layer. These sticks are held apart by small strips of wood so as to allow of the passage of a thin film of liquid downwards and of the air upwards. The total surface of the sticks in an apparatus of the dimensions stated above amounts to more than 1000 sq. metres, so that the oxidation is extraordinarily rapid, while the working, which may continue uninterruptedly for years, is extremely regular and simple. The air enters at a lateral slit, Z, at the bottom, this being covered with gauze to prevent access of harmful insects, and the draught is regulated by a slider in the exit-channel, JB; the vinegar is discharged at E. The thermometer, T, shows the temperature of the air as it leaves. The figure shows also the contrivance for feeding the apparatus regularly and continuously with the alcoholic liquid. The latter is contained in the tank, B, in which is a wooden float, F , moving along three vertical rods, L, and carrying the glass siphon, W, terminating in a rubber tube with a regulating clip, n. The liquid from the siphon falls into a tube, G, and thence through the tube, A C, to the vessel, H (3 litres capacity), and, when this is full, it discharges through the siphon, r, on to the perforated plate, V, which distributes the liquid as a fine spray over FIG. 249. FIG. 250. 344 ORGANIC CHEMISTRY the bundles of sticks, and is traversed by several glass tubes to allow of the escape of the ascending air. In this way the flow of liquid from B is independent of the amount of liquid present in it at any instant (that is, of the pressure it exerts ). The clip, n, is regulated so that the vessel, H, is refilled and discharges its 3 litres of liquid every one or two hours (or in any other prearranged time). Attempts have been made to replace the ordinary biological acetification by chemical oxidation of the alcohol by means of platinum black or even of ozone, but neither method has attained to practical importance. Vinegar is kept in full casks in stores like those used for wine, but it is not injured by a high air-temperature. An excess of air in the vessels and the continued presence of the mother-of- vinegar lower its strength, and, when this becomes too low, putrefaction may develop. Its keeping properties and aroma may be enhanced by pasteurisation (see pp. 186, 210) at 50 to 60. A weak vinegar may be strengthened and kept if a little pure acetic acid is added to it. WINE VINEGAR (white or red) is distinguished from other vinegars by its aroma, due partly to ethyl acetate and to small proportions of aldehydes. It usually contains 6 to 9 per cent, of acetic acid and less than 1 per cent, of alcohol, and has the density 1-015 to 1-020. The extract and the ash have the same compositions as those of wines, the former being rich in cream of tartar. BEER VINEGAR contains 4-5 to 6 per cent, of extract rich in maltose, dextrin, albuminoids, and phosphates, and exempt from cream of tartar. This vinegar also contains less acetic acid and, since it does not keep so well as that from wine, is used to break down excessively strong vinegars. ARTIFICIAL VINEGARS, prepared from purely alcoholic liquids or from acetic acid and a colouring material such as caramel, have very little extract and no cream of tartar, whilst the percentage of acetic acid sometimes reaches 12 or 13. In the ANALYSIS OF VINEGAR, the density of the extract and the ash are deter- mined as with wine (p. 186). The content of acetic acid cannot be estimated exactly with standard alkali solution, since other acids (tartaric, succinic, etc. ) present influence the titration; nor do the graduated tubes (acetometers) give accurate results. A more exact determination is effected by distilling the acetic acid in a current of steam, as in the analysis of calcium acetate (p. 337). Adulteration of vinegar, which is somewhat frequent, is detected by the following tests: Real wine vinegar exhibits certain relations between the acetic acid and extract. In wine the ratio is 4 parts of alcohol for about 1 of extract, after deduction of the sugar present in sweet wines; assuming a loss of 15 per cent, of the alcohol during the conversion into vinegar, a pure wine vinegar with 5-31 per cent, of acetic acid should contain 1-08 per cent, of extract; one with 7-15 per cent, of acid, 1-44 per cent, of extract; one with 8-9 per cent, of acid, 1-8 per cent, of extract, and one with 10-7 per cent, of acid, 2-16 per cent, of extract, the ratio of acid to extract always being about 4-9 : 1. Addition of malt or beer vinegar is recognised by its reduction of Fehling's solution, or by concentrating 80 c.c. of the vinegar to about 2 c.c. and then adding alcohol : the formation of a white precipitate -(dextrin) soluble in much water indicates such adulteration with certainty. If mineral acids have been added, 4 or 5 drops of a dilute alcoholic solution of methyl violet (1 : 10,000) will give a greenish colour with 25 c.c. of the vinegar; also, with zinc sulphide, hydrogen sulphide is evolved ; finally, after the vinegar has been heated with a trace of starch, it will not give a blue colour with iodine. The presence of sulphuric acid in vinegar is detected by the white precipitate formed with barium chloride, hydro- chloric acid by that given by silver nitrate, and oxalic acid by the formation of a white precipitate with calcium chloride. Artificial colouring-matters are detected in the same way as in wine and beer, and pyroligneous acid by the furfural reaction (see this). The price of good wine vinegar is little less than that of wine, but artificial vinegars are cheaper. France produces annually 600,000 to 700,000 hectolitres of vinegar, but in Italy the pro- duction is much less, owing to the competition of artificial vinegar and to the excessive duty of 17s. 6d. per hectolitre; in 1904-1905 the thirty-eight Italian vinegar factories con- sumed 6160 hectolitres of alcohol, the output of artificial vinegar being 60,000 hectolitres. In 1912 55,000 hectolitres of artificial vinegar were made. In Germany 70 per cent, of the ACETATES 345 vinegar is made from alcohol, the consumption of the latter being 41,110 hectolitres in 1911-1912 and 23,000 hectolitres in 1912-1913. DERIVATIVES OF ACETIC ACID SALTS OF ACETIC ACID. These are termed acetates, and are all soluble in water (the least soluble are silver and mercurous acetates). They are readily formed by neutralising acetic acid with metallic oxides or carbonates, previously dissolved in water. Pure anhydrous acetic acid or its alcoholic solution does not decompose alkaline carbonates, so that C0 2 precipitates potassium carbonate from an alcoholic solution of potassium acetate, acetic acid being liberated. Even in aqueous solution, acetic acid undergoes only slight dissociation, but the acetates are considerably dissociated and diminish the dissociation and hence the acid characters of acetic acid (see Vol. I., p. 100). POTASSIUM ACETATE (Normal), CH 3 COOK, melts at 229 and is soluble in water or alcohol. It is obtained by neutralising potassium hydrogen carbonate (KHCO 3 ) solution with acetic acid and evaporating to dryness. The acid acetate, CH 3 COOK, C 2 H 4 2 , is obtained by dissolving the normal acetate in acetic acid and separates from the latter in crystals which melt at 148 and decompose at 200, liberating anhydrous acetic acid. A Diacid Potassium Acetate, CH 3 COOK, 2C 2 H 4 O 2 , melting at 112, is also known. The commercial refined normal acetate costs about 3 per cwt. SODIUM ACETATE, CH 3 COONa, crystallises from water with 3H 2 O, melts at 100, loses water and solidifies at a higher temperature and then melts only at 319. In the cold it dissolves to some extent (1 : 23) in alcohol or in its own weight of water, giving a feebly alkaline solution and considerable lowering of temperature. It is prepared by neutralising pyroligneous acid almost completely with sodium carbonate and concentrating the solution (after removal of the tar from the surface) to 27 Be. ; the crystals which separate on cooling are centrifuged, but are always reddish brown. The mother-liquors (which readily become mouldy) are taken to dryness and lightly roasted to burn the tarry products. Crude sodium acetate is preferably prepared by treating calcium acetate solution with sodium sulphate and then with a little soda to precipitate all the lime ; the filtered or decanted solution is evaporated to dryness, heated to 250, redissolved in water, concentrated, and allowed to crystallise. According to C. Bauer, pure sodium acetate, free from the reddish-brown colour, may be prepared directly from pyroligneous acid by neutralising with sodium carbonate, and adding to the solution concentrated to 27 Be., 2 per cent, of caustic soda, the liquid being then allowed to crystallise in wide and shallow wooden vessels. The crystals are separated by centrifugation and redissolved, the small amount of free caustic soda being then neutral- ised with commercially pure acetic acid; the solution is boiled to expel the excess of acetic acid, concentrated to 27 B6., and left to crystallise. Acid sodium acetates are also known. Sodium acetate serves for the preparation of pure acetic acid, and is used in dyeing, etc. Before the war, crude red sodium acetate was sold, according to its degree of purity, at 145. to 18s. per cwt. ; the white purified crystals (pharmaceutical) at 24s. to 28s. ; and the doubly refined and fused anhydrous product at 52s. AMMONIUM ACETATE, CH 3 COONH 4 , is obtained by neutralising hot glacial acetic acid with a current of dry ammonia or with ammonium carbonate. The pure crystals which separate melt at 113 to 114 and, although not highly hygroscopic, dis- solve readily in water, giving an alkaline solution; the solution in acetic acid deposits the acid acetate melting at 66. The salt acts as a sudorific and dissolves lead oxalate and sulphate. It is used to some extent in dyeing. The commercial brown solution at 10 Be. costs 1 per cwt. and the pure solution of the same density 25s. ; chemically pure crystals cost 5 per cwt. CALCIUM ACETATE, (CH 3 COO) 2 Ca + 2H 2 O. The preparation of the commercial product has already been described on p. 336. The pure salt is obtained by repeated crystallisation from water, and costs up to 48s. per cwt. Its solubility in water diminishes with rise of temperature up to a certain point and subsequently increases. For Statistics, see p. 339. 346 ORGANIC CHEMISTRY FERROUS ACETATE (Pyrolignite of Iron), (CH 3 COO) 2 Fe. The crude product, used as a mordant in the dyeing and printing of textiles, is obtained from pyroligneous acid and iron filings, or from calcium pyrolignite and a concentrated solution of ferrous acetate ; the tarry substances present preserve it from oxidation. A solution of 20 Be. costs 6s. per cwt. and one of 30 Be. 8s. 6d. The pure product is prepared by dissolving freshly prepared ferrous hydroxide in 30 per cent, acetic acid. FERRIC ACETATE, (C 2 H 3 O 2 ) 3 Fe, used as a mordant in dyeing, is obtained from the ferrous salt and sodium acetate. It gives a reddish-brown solution in the cold, but in the hot and in presence of a large amount of water, a reddish- brown mass of basic ferric acetate, Fe(C 2 H 3 2 ) 2 OH, separates; it is this which fixes the colouring- matters. ALUMINIUM ACETATE (Normal), Al(C 2 H 3 O 2 ) 3 ,is obtained from aluminium sulphate and the corresponding quantity of lead acetate. It is known only in solution, in which it gradually undergoes spontaneous decomposition into acetic acid and the basic acetate : A1(C 2 H 3 2 ) 3 + HaO = A1(C 2 H 3 O 2 ) 2 OH + C 2 H 4 O 2 . When the solution of the basic acetate is boiled, aluminium hydroxide and acetic acid separate : A1(C 2 H 3 O 2 ) 2 OH + 2H 2 = A1(OH) 3 + 2C 2 H 4 2 . It is used in dyeing, in the printing of textiles and in the preparation of waterproof fabrics. For the last purpose, the material is first soaked in aluminium acetate solution and then heated or steamed, A1(OH) 3 thus being deposited in the pores of the fabric, which is rendered impervious to water. BASIC ALUMINIUM ACETATE, A1(C 2 H 3 O 2 ) 2 OH + 1JH 2 O, is obtained crystalline by evaporating a solution of the normal acetate cautiously at a temperature not exceeding 38; it is soluble in water. Dilute solutions (4 to 5 per cent.) of the normal acetate gradually deposit, on the walls of the containing vessel, a porcelain-like crust of a basic acetate with 2H 2 or 2H 2 O : this is insoluble in water. It is used, like the normal salt, in dyeing, textile-printing, etc. SILVER ACETATE, C 2 H 3 O 2 Ag, is obtained crystalline by adding silver nitrate to a concentrated solution of an acetate (e. g., that of ammonium). It is a characteristic salt, crystallising from water in shining needles (solubility 1 : 100 at 20, 2-5 : 100 at 80). When calcined in a porcelain crucible, it leaves, like all organic silver salts, pure metallic silver. NORMAL LEAD ACETATE (Sugar of Lead), (CH 3 COO) 2 Pb + 3H 2 0, forms monoclinic plates or crystals, has a disagreeable, sweetish taste, is poisonous, and exhibits a faintly acid reaction. It is slightly soluble in alcohol and more so in water (1 part dissolves in 1*5 parts of water at 15, in 1 part at 40, or in 0'5 part at 100). It loses the water of crystallisation over sulphuric acid or at 100,and then melts above 200. It is used as a mordant in the dyeing and printing of textiles and also in the preparation of various lead salts and paints and certain pharmaceutical products; further, for conferring hot-drying properties on linseed oil to be used for varnishes. Italy produced 45 tons in 1904, 80 in 1906, 140 in 1908, 200 (5280) in 1911, 39 in 1914, and 200 (12200) in 1915. Germany exported 1765 tons in 1905, 2078 (52,000) in 1906, 1677 in 1909, 1288 in 1910, 2080 in 1911, 1664 in 1912, and 1626 in 1913. The refined crystalline product was sold before the war at 24s. to 28s. per cwt., and the chemically pure at 36s. It is best prepared commercially by the Bauschlicher-Bauer method (1892-1905) from commercial pure 60 per cent, acetic acid (see Tests on pp. 338 -and 340) and pure litharge containing 99 per cent, of PbO. 1 A pitch-pine vat is fitted with a tight cover with three apertures : the central one for the shaft of a wooden stirrer, another for a copper cooling coil to condense the acetic acid vapours, and the third for the neck of a large wooden hopper, by means of which the litharge is dropped on to a wooden distribut- ing roller provided with teeth and placed under the lid. The required quantity of acetic acid is heated to 60 by a copper steam coil in the bottom of the vat, and the litharge 1 It should contain neither iron, which would colour the crystals, nor aluminium, which would render filtration difficult. ACETATES 347 gradually added in the proportion of 103 kilos per 100 kilos of 60 per cent, acetic acid ; each 100 kilos added requires about an hour to dissolve if the stirrer is kept in motion and the temperature does not exceed 65. The solution has a density of 70 to 72 Be. and, if it does not show an acid reaction, it is slightly acidified with acetic acid, 1 and the mother- liquor (35 to 37 Be. ) from a preceding operation added in such amount that the density becomes 50 to 52 Be. The solution at 65 is then allowed to clarify in a couple of tightly closed wooden vats, each fitted with a horizontal rail carrying strips of lead dipping into the liquid so as to remove the small amount of copper present. After five to six hours the solution is passed through a cloth filter-press with wooden channels, and is then left to crystallise in wooden vessels for eight to ten days until the density of the mother-liquor falls to 35 Be. in winter or 37 in summer. If the solution is kept at 60, as crystals separate the vessel may be fed with fresh, more concentrated solution until a thick layer of crystals is obtained ; it is then allowed to cool for some days. After the liquid has been decanted, the mass of. small crystals (more concentrated and hotter solutions give larger crystals) is treated in a copper centrifuge and dried in wooden boxes placed in a vacuum apparatus at a temperature not exceeding 30. 2 MONOBASIC LEAD ACETATE (Subacetate of Lead), (C 2 H 3 O 2 ) 2 Pb + PbO + H 2 O, and Dibasic Lead Acetate, (C 2 H 3 O 2 ) 2 Pb + 2PbO, are obtained by melting the normal acetate with a greater or less proportion of litharge (3 : 1 for the monobasic salt) on the. water-bath; the former is readily soluble and the latter only slightly so (1 : 18 at 20 and 1 : 5-5 at 100) in water. The lead acetate of the pharmacopoeia is a 2 per cent, solution of the monobasic salt, and is used as a medicine ; this salt is used also for weighting silk, for decolorising vegetable juices, and for preparing white lead and aluminium acetate. The anhydrous salt former'y cost 52s. per cwt. NORMAL CHROMIC ACETATE, Cr(C 2 H 3 O 2 ) 3 + H 2 O, is obtained from calcium or lead acetate and chrome alum or chromic sulphate. It gives a violet solution, which becomes green, without decomposing, when heated. Basic Chromium Sulphate is obtained in a similar way from basic chromium sulphate or by adding ammonia or sodium hydroxide or carbonate to a solution of the normal acetate. The basicity increases with the amount of alkali, the compound, Cr 2 (C 2 H 3 2 ) 5 OH, being gradually converted into Cr 2 (C 2 H 3 O 2 ) 2 (OH) 4 or even more basic salts still. The more basic the acetate the more will it decompose on boiling and the more readily it will serve as a mordant in dyeing or, better, in printing, since the reducing action of the textile fibres or of the colouring-matters or of other organic substances added, results in the separation of the true mordant, Cr(OH) 3 , which forms stable lakes with the dyes (alizarin, hsematein from log- wood, etc. ). Commercial chromium acetate solutions at 20 Be. were sold before the war at 16s. per cwt., those of 40 Be. at 28s., and the solid at 60s. ; the chemically pure acetate cost 8s. per kilo. STANNOUS ACETATE, Sn(C 2 H 3 O 2 ) 2 , is obtained by treating stannous chloride with lead acetate or by dissolving freshly precipitated stannous hydroxide in dilute acetic acid. Its solution is used as a mordant or corrosive in printing cotton with substantive dyes (see this, Part III). The 20 to 22 Be. solution formerly cost 24s. per cwt. NORMAL CUPRIC ACETATE (Crystallised Verdigris), Cu(C 2 H 3 O 2 ) 2 + H 2 O, is obtained by dissolving the basic acetate (true verdigris) in acetic acid or, better, by decom- posing copper sulphate solution with lead acetate. It forms clinorhombic, dark green prisms and is readily soluble in hot water (1 : 5) or in alcohol. It is used in medicine and has been suggested as a means of combating the Peronospora which attacks the vine. Before the war it cost 2s. 6d. per kilo. 1 The subsequent crystallisation is rendered difficult if the solution contains basic acetate, the presence of this being inferred from the turbidity produced on mixing a little of the liquid with an equal volume of 1 per cent, corrosive sublimate solution. 2 Analysis of lead acetate is effected by dissolving 5 grams of it in water, precipitating the lead with a known quantity, in slight excess, of normal sulphuric acid, making up to 250 c.c., and then adding a volume of water about equal to that of the precipitate. In 50 c.c. of the nitrate, the sulphuric acid is precipitated with barium chloride, the weight of the resulting barium sulphate giving the quantity of sulphuric acid which has remained in combination with the lead. Another 50 c.c. of the filtrate is titrated with normal caustic potash, the total acidity thus found being due to acetic acid and excess of sulphuric acid ; deduction of the latter then gives the amount of acetic acid existing in combination in the lead acetate' 348 ORGANIC CHEMISTRY BASIC COPPER ACETATE (Verdigris), [2Cu(C 2 H 3 O 2 )OH] + 5H 2 O, is obtained by arranging sheets of copper with flannel saturated with hot vinegar, acetic acid, or acid vinasse, in between. The crust of acetate is detached from the plates and sold in cakes either dry or with 30 to 40 per cent, of moisture. It forms blue needles or scales, which effloresce in the air and become green, owing to loss of water. It dissolves only slightly in water and, when heated in the dry state, gives off acetic acid and water. When pure, it is completely soluble in excess of ammonium carbonate solution. Jt was formerly used as a colouring-matter, but is now used for the preparation of SchweinfurtK 1 s green (copper aceto-arsenite), Cu(C 2 H 3 2 ) 2 , 3CuAs 2 4 , by mixing with the requisite proportion of arsenious anhydride solution ; this gives a beautiful green colouring- matter, which is still used to some extent, although it is very poisonous owing to the evolution of hydrogen arsenide in the air. In cakes or balls, the basic acetate formerly cost 3 per cwt., whilst the refined powder cost 4 to 5. PROPIONIC ACID, C 3 H 6 2 or CH 3 CH 2 COOH This acid is obtained by hydrolysing ethyl cyanide (see p. 238), or by oxidising propyl alcohol with chromic acid, or by the action of certain micro-organisms on calcium lactate. It is, however, usually prepared by fermenting wheat-bran, or is extracted from crude pyroligneous acid, being formed in small quantity (2 to 4 per cent. ) in the dry distillation of wood. For some years it has been manufactured by the Effront process (see p. 183) from the residues of beetroot molasses : 1000 kilos of molasses yield 75 kilos of ammonium sulphate and 95 to 120 of fatty acids consisting largely of propionic acid (see also section on Sugar). It occurs in perspiration, in the fruit of GingJco biloba, and in colophony tar. It is a liquid of sp. gr. 0-996 at 19 and resembles acetic acid in odour and in physical and chemical properties. It is, indeed, not possible to separate these two acids by dis- tillation and rectification, but this may be done by means of the lead salts, basic lead pro- pionate, 3Pb(C 3 H 5 2 ) 2 , 4PbO, being very slightly soluble in hot water, although soluble in cold. It boils at 141 and solidifies at -22. It forms crystalline salts soluble in water, and its esters have a fruity aroma. Chemically pure propionic acid formerly cost 32s. per kilo, and the commercial acid 14s. 6d., but nowadays the Effront process yields a much cheaper commercial acid, which in practice may be used to replace formic and acetic acids, these being more difficult to purify. BUTYRIC ACIDS, C 4 H 8 O 2 Two isomerides are known of different structures, their constitutional formulae being deduced from their methods of synthesis. (1) NORMAL BUTYRIC ACID (Butanoic or Propylcarboxylic Acid or Buty- ric Acid of Fermentation), CH 3 CH 2 CH 2 COOH, is the more important of the two isomerides and exists in butter in the form of glyceric ester to the extent of 4 to 5 per cent. It is formed also in sweat and occurs in solid excreta and in decomposing cheese, as well as among the products of fermentation of glycerine. It is obtained practically, not by synthesis (see p. 320), but by the butyric fermentation of starch-paste in presence of a little tartaric acid, putrefied meat or cheese being added after a few days (pure cultures of special bacteria are also used at the present time) ; it is obtained also from acid skim milk by treatment with powdered marble and converting the calcium lactate into calcium butyrate, then into the sodium salt, and finally, by means of H 2 SO 4 , into the free acid. It is also obtained from molasses residues by Eff rent's process (see above). It forms an oily liquid, sp. gr. 0'958 at 14, boib'ng at 162 and solidifying in scales at 19. It dissolves in water, alcohol, or ether, burns with a bluish flame, and gives crystalline, slightly soluble salts. Calcium Butyrate, (C 4 H 7 2 ) 2 Ca -f H 2 O, is less soluble in hot than in cold water. HIGHERACIDS 349 The esters have pleasant, fruity odours, and are used to produce artificial rum. Commercial concentrated butyric acid cost before the war 4s. per kilo ; the 50 per cent, acid, 2s. Qd. ; and the chemically pure (100 per cent.), 5s. IQd. The concentrated esters were sold at 2s. Qd. to 5s. per kilo. CH (2) ISOBUTYRIC ACID (2-Methylpropanoic or Dimethylacetic Acid), COOH, resembles the preceding acid, but is less soluble in water. It boils at 154 and solidifies at 79, and occurs free in arnica and carob roots and as ester in chamo- mile oil. . It may be obtained by the ordinary synthetic processes and is less resistant than the normal acid to oxidising agents. The pure acid formerly cost 40s. per kilo and the commercial acid about one-half as much. The Calcium Salt, Ca(C 4 H 7 O 2 ) 2 , is more soluble in hot water than in cold. VALERIC ACIDS, C 5 H 10 O 2 The four isomerides predicted by theory are known. (1) NORMAL VALERIC ACID (Pentanoic or Propylacetic Acid), CH 3 . [CH 2 ] 3 . COOH, is a dense liquid (sp. gr. 0-956 at 0), boiling at 185 and solidifying at 58-5. It is obtained synthetically from propylmalonic acid or butyl cyanide, and is met with in pyroligneous acid ; it is slightly soluble in water. The pure product cost before the war 5d. per gram. (2) ISOVALERIC ACID, n 3 > CH ' CH 2 ' COOH > is found fre e or in the form of 3 esters in animals (fat of the dolphin, sweat of the feet, etc.) and vegetables (roots of Valeriana officinalis), and from the latter may be extracted by boiling with solutions of soda or by distilling with water containing phosphoric acid. It is a liquid (sp. gr. 0-947 at 0), boiling at 174 and solidifying at -51; it has a disagreeable odour of stale cheese. It is often obtained by oxidising fusel oil with dichromate and sulphuric acid. The pure acid costs 96s. per kilo. Its esters are used as artificial fruit essences, and cost from 10s. to 16s. per kilo. (3) ETHYLMETHYLACETIC ACID (Methyl-2-butanoic or Active Valeric Acid), CH _, 3 >CH COOH, is optically active, as it contains an asymmetric carbon atom (see S H 5 p. 19) ; it occurs naturally with iso valeric acid. The inactive mixture of the two oppositely active acids may be resolved into its active components by means of the brucine salts. It boils at 174. (4) TRIMETHYLACETIC ACID (Dimethyl - 2 - propanoic or Pivalic Acid), (CH 3 ) 3 : C COOH, is a solid, m.-pt. 35, b.-pt. 163. It has an odour resembling that of acetic acid, and it may be obtained from tertiary butyl cyanide. HIGHER ACIDS Of the numerous isomerides theoretically possible and of the many actually known, mention will be made only of some of the more important which occur naturally and are usually of the normal structure and with even numbers of carbon atoms. NORMAL CAPROIC ACID, C 6 H 12 2 or CH 3 [CH 2 ] 4 COOH, is a liquid boiling at 205 and solidifying at -1-5. It is volatile in steam, has an unpleasant odour like rancid butter, and is found free in Limburger cheese and coco-nut oil, and as glyceride in goats' butter. It is formed on oxidising proteins or higher fatty acids (unsaturated). HEPTOIC ACID (CEnantic Acid), C 7 H 14 O 2 or CH 3 [CH 2 ] 5 COOH, is formed on oxidation of castor oil or cenanthaldehyde. It is a liquid boiling at 220 and solidifying at 20. It differs from its lower homologues by exhibiting a slight odour of fat. CAPRYLIC ACID (Octoic Acid), C 8 H ]6 O 2 or CH 3 [CH^ COOH, solidifies at 16-5 and boils at 237-5 ; it is found in coco-nut oil and as glyceride in ordinary butter and that of goats. NONOIC ACID (Pelargonic Acid), C 9 H 18 O 2 or CH 3 [CH 2 ] 7 COOH, is a liquid boiling at 254. It is formed by oxidising oleic acid or by decomposing the ozonide of oleic acid (Molinari and Soncini, 1905) with dilute alkali. In nature it occurs in Pelargonium roseum. 350 ORGANIC CHEMISTRY DECOIC ACID (Capric Acid), C^H^C^ or CH 3 [CH^ COOH, is a solid, melting at 31-4 and boiling at 200 under 100 mm. pressure. It also is found in coco-nut oil and goats' butter. UNDECOIC ACID, C n H 22 O 2 or CH 3 [CH 2 ] 9 . COOH. Distillation of castor oil under reduced pressure yields the unsaturated undecenoic acid, C U H 20 2 , which gives undecoic acid on reduction with hydrogen. It melts at 28 and boils at 212 (100 mm.). LAURIC ACID, C 12 H24O 2 or CH 3 [CH^,, COOH, is a solid, melting at 44 and boiling at 225 (100 mm.); it occurs in the form of glyceride in laurel berries. MYRISTIC ACID, ^H^Gg or CH 3 -,[CH 2 ] 12 . COOH, melts at 54 and boils at 248 (100 mm.). It is found as glyceride (myristin) in the nutmeg (Myristica moschata) and in ox-gall, and abounds in the seeds of Virola Venezuelensis. PALMITIC ACID (Hexadecoic Acid), C 16 H 32 O 2 or CH 3 [CH 2 ] 14 COOH, forms a moderately transparent white mass, which readily softens and melts at 62*6. It is insoluble in water and crystallises from alcohol in scales or needles. It boils unchanged at 268 under 100 mm. pressure, or, with partial decomposition, at 339 to 356 under the ordinary pressure. It is one of the normal components of animal and vegetable fats, in which it occurs as a glyceride (palmitin), and is easily obtained, together with oleic acid, from palm oil by hydrolysing and then decomposing the soap formed; the palmitic acid is then isolated by fractional crystallisation. Japanese vegetable wax or Carnaiiba wax consists almost exclusively of palmitin. The industrial treatment of fats and oils for the extraction of the corresponding fatty acids (palmitic, stearic, and oleic) will be described in the section dealing with the manufacture of soap and candles. Commercial palmitic acid is also known by the inaccurate name of 'palmitin and is likewise manufactured by melting oleic acid with potassium hydroxide (Varrentrapp's reaction) : C 18 H 34 O 2 + 2KOH = H 2 + CH 3 C0 2 K -f- C^H^OaK (potassium palmitate, which gives palmitic acid under the action of mineral acid). Its alkali salts (soaps) are soluble in alcohol or water, but considerable dilution of the aqueous solutions results in the separation of an acid salt and liberation of alkali. Whilst in alcoholic solution these soaps show virtually normal molecular weights, the aqueous solutions show no rise in the boiling- point, the soaps thus behaving as colloids in these solutions (see Vol. I., p. 105). The Bother salts (palmitates) are insoluble in water and, in some cases, soluble in alcohol ; mineral acids liberate palmitic acid from them. Before the war, the commercial acid cost 2 per cwt., the refined product 4, and the doubly refined 25s. Qd. per kilo. MARGARIC ACID, C 17 H 34 O 2 or CH 3 [CH 2 ] 15 COOH, was for a long time thought to exist in fats, but it has been shown that a mixture of palmitic (C 16 ) and stearic (C 18 ) acids was being dealt with. Synthetically it is obtained by hydrolysing cetyl cyanide, C 16 H 33 CN, and by other methods. It melts at 60 and distils unchanged at 277 under 100 mm. pressure. STEARIC ACID, C 18 H 36 O 2 or CH 3 . [CH 2 ] 16 . COOH, which is improperly known commercially as stearine (and is then mixed with palmitic acid), and its separation from oleic acid, will be described when dealing with candles. As glyceride, it occurs with that of oleic acid as one of the principal con- stituents of fats and oils, and is usually prepared industrially from beef suet. Synthetically it may be obtained by the reducing action of hydrogen on oleic acid (see this), and the constitution of the latter being known, that of stearic acid follows directly. Industrial application is now made of this process (see Oleic acid). It forms a somewhat soft white mass, melting at 69'3, and crystallises from alcohol in shining scales. It boils unchanged at 287 under 100 mm. UNSATURATED ACIDS 351 pressure or with partial decomposition at 359 to 383 under the ordinary pressure. It is insoluble in water, soluble slightly in light petroleum, and more readily in alcohol, ether, benzene, or carbon disulphide. Its salts behave like those of palmitic acid. The lead salts of these high fatty acids are obtained by boiling the fats or oils with lead oxide and water. This lead soap is used for the preparation of lead plaster, which is used in medicine and in the manufacture of varnish. Stearic acid made into a paste with gypsum forms a kind of artificial ivory. Italy imported, especially from France, England, and Belgium, the following amounts of stearic acid : 1908 Tons . 1,250 Value, 1910 1,445 63,560 1912 621 1913 920 32,020 1914 698 1915 423 1916 119 1917 1918 58 152 19,773 CEROTIC or CEROTINIC ACID, C 27 H 54 O 2 , is found free in beeswax (together with Melissic Acid, C 30 H 60 O 2 ), as ester in Chinese wax and as glyceride in the fat of raw wool. It melts at 78'5 and is converted by oxidising agents into various acids with lower molecular weights. II. UNSATURATED MONOBASIC FATTY ACIDS A. OLEIC or ACRYLIC SERIES, C n H 2n _ 2 O 2 (Olefine-carboxylic Acids) Empirical formula Name of acid Constitutional formula Melting- point Boiling- point 3 H 42 Acrylic acid ... . . OH, : CH CO 2 H 13 140 (Vinylacetic acid . CH,, : CH OK C0 2 H 39 163 4 H 6 2 Solid crotonic acid Liquid crotonic acid CH, CH : CH CO 2 H (cis) CH, OH : CH C0 2 H (tram) 72 15-5 181 169 Metacrylic acid . CK : C(CH 3 ) CO.H 16 161 ( Angelic acid . CH' C CO,H 6 H 8 2 (8 structural isomerides and one J stereoisomeride) j l.Tiglic acid II OH 3 C H CH,C CO,H 45 185 II 65 198-5 H C CH 3 p 6 TT 10 r> 2 C,H^0 2 (Not all stereoisomerides known) Pyroterebic acid . Do. y-Allylbutyric acid Do. Teracrylic acid (CHgV : : OH CH 2 CO 2 H (CnV).: : COOS 4 ,,) CH 2 COoH 15 207 226 218 C, H 18 O 2 Do. Citronellic acid . CH^ : 0(CH 3 ) [CHJs OH(CH 3 ) CHj CO 2 H 152 (18 mm.) OHO Do. Undecenoic acid . CH : OH ' [CHojo CO 2 H 24-5 213-5 11 20 2 "2 (100 mm.) Ol6 H 3<>02 Do. Hypogaeic acid fOleicacid . CH, [OH,] 7 CH : CH [CHJ 5 CO 2 H OH, [CH^ OH : CH [CHjj CO 2 H (ri*) 14 223 Ol8 H 340 2 Do. l.Elaidicacid CH 3 [OH2] 7 CH : CH \GB 1 ' C0 2 H (trans') 51 (10 mm.) 225 (10 mm.) Ol8 H 340 2 T, / Iso-oleic acid 1 Aaj3-oleic acid . CH, [CHJa OH : CH [CHJg CO 2 H ( ?) OH 3 [CHJ 14 - CH : CH CO 2 H 44 58 / Erucic acid CH 3 [CH^lj * CH : CH [CH^jjj C0 2 H 34 254-5 (10 mm.) OHO Do. -vBrassidic acid CH, [OHJ, CH : CH [CHJ,, C0 2 H 65 256 22 42 2 I * (10 mm.) I Isoerucic acid CH 3 [CHJg- CH : OH [CHjlj,,' CO 2 H ( ?) 55 ~ The importance of these acids is due to the fact that certain of them occur as glycerides in many fats and oils. GENERAL PROCESSES OF FORMATION. The following are the most important of these : (1) The unsaturated halogen derivatives of unsaturated alcohols may be transformed into cyanogen derivatives, which give the corresponding acids on hydrolysis (see p. 238) : CH 9 : CH CH 9 OH -> CH, : CH CH 9 Br-> CH 2 : CH CH 2 CN CH 2 : CH CH 2 COOH. 352 ORGANIC CHEMISTRY (2) Oxidation of unsaturated alcohols and aldehydes with mild oxidising agents (silver oxide or the oxygen of the air) which do not attack the double linking ; allyl alcohol and acrolei'n give acrylic acid. (3) Of general use is Perkin's reaction, applicable especially to the aromatic series, but of service also for the fatty series : when an aldehyde is heated with the sodium salt of a saturated fatty acid in presence of an anhydride (e. g., acetic anhydride) and then treated with water, the resulting products are the saturated acid corresponding with the aldehyde used and an unsaturated acid, which always has the double linking between the a- and ^-carbon atoms, the a-carbon atom being that adjacent to the carbonyl group, CO. If the chain united to the aldehyde group is denoted by R, the intermediate phases of this reaction are probably as follow : (a) R CHO + CH 3 CO CO CH 3 give, by aldol condensation, R CH(OH) CH 2 CO O CO CH 3 ; this unstable compound immediately separates water, giving R CH : CH CO CO CH 3 , treatment of this product with water yielding the unsaturated acid : (6) R- CH : CH CO CO-CH 3 +H 2 = CH 3 'COOH + R-CH:CH-COOH. It is evident that, if only one hydrogen atom is united to the carbon atom adjacent to the carbonyl group of the original anhydride, the first phase of the reaction, but not the second, will be possible, so that only a saturated hydroxy-acid will be obtained : R CHO + CH CO O CH + H 2 O = R CH(OH) C COOH + (CH 3 ) 2 : CH COOH. The presence of the sodium salt of the fatty acid is indispensable to all these reactions, but its function has not yet been explained. (4) Similar to Perkin's synthesis is the reaction between an aldehyde (or an a-ketonic acid, R CO COOH, which possibly loses C0 2 and thus gives an aldehyde) and malonic acid in presence of glacial acetic acid, a mixture of unsaturated monobasic acids with the double linking in the a /?- or /? y- position being obtained and C0 2 split off : (a) R CH 2 - CHO + CH 2 < = R CH 2 CH(OH) Malonic acid (b) 2R CH 2 CH(OH) CH<^^ = 2C0 2 + 2H 2 + R CH 2 CH : CH COOH + R CH : CH CH 2 COOH. a j3-acid y-acid It should be noted that this reaction always gives also a condensation product of 1 mol. of the aldehyde and 2 mols. of malonic acid, this product then losing C0 2 and yielding a saturated dibasic acid : R CH < CH ( COOH )2 - 9CO 4- R CH< CH 2 ' COOH L ^CH(COOH) 2 - 2LU2 1 ^CH 2 COOH (5) When monohalogenated saturated fatty acids (especially those with the halogen in the /3-position) are heated with alcoholic potash, or sometimes even with water alone, a molecule of halogen hydracid is eliminated and the unsaturated acid formed (similar to the reaction giving unsaturated hydro- carbons, p. 108) : CH 2 I CH 2 COOH = HI + CH 2 : CH COOH. /S-Iodopropionic acid Acrylic acid OLEFINE-CARBOXYLIC ACIDS 353 (6) By separating a molecule of water from monohydroxy-acids by means of distillation or a dehydrating agent (H 2 S0 4 , PC1 5 , P 2 5 ) or sometimes by merely heating with caustic soda solution, the unsaturated monobasic fatty acids are formed : CH 3 CH(OH) CH 2 COOH = H 2 + CH 3 CH : CH COOH. /3-Hydroxybutyric acid Crotonic acid GENERAL PROPERTIES. The number of double bonds is ascertained by the same methods as are applied to unsaturated hydrocarbons (see p. 107) by addition of either halogen or ozone. These unsaturated acids are more energetic than the corresponding saturated acids with the same numbers of carbon atoms, as may be seen from their ionisation constants (Vol. I., pp. 102 et seq.). They are more easily oxidisable than the corresponding saturated acids, powerful oxidising agents rupturing the carbon atom chain at the double linking, the position of which may hence be established by a study of the compositions of the two acids formed. When boiled with 10 per cent, caustic soda solution, unsaturated acids with a double linking (A ) in the /ty-position undergo displacement of this linking with the partial formation of unsaturated acids with a double bond in the apposition (Fittig, 1891-1894); this is formed from an intermediate hydroxy-acid, an equilibrium being established as indicated below : R CH : CH CH 2 COOH + H 2 O ^t R CH 2 CH(OH) CH 2 COOH < (3 -y-acid /3-Hydroxy-acid H 2 -f R CH 2 CH : CH COOH. a (3-acid In general this reaction preponderates towards the formation of the a/?-acid and not vice versa, the carboxyl group apparently exerting an attraction on the double linking. When an unsaturated acid is fused with caustic soda or potash, the double linking is displaced, giving an a/?-acid, the new molecule immediately splitting at the double bond, the resultant products being acetic acid and another saturated acid. This displacement of the double linking was unknown until a few years ago, so that oleic acid, for example, which gives palmitic and acetic acids quantitatively when fused with potash, was regarded as an ap -unsaturated acid. It has, however, been shown (see later) that the double bond of oleic acid is in the middle of the molecule, the action of the potash causing displacement of this bond before the molecule is resolved : CH 3 [CH 2 ] 7 CH : CH [CH 2 ] 7 COOH -* CH 3 [CH 2 ] 14 CH : CH COOH Oleic acid a /3-Oleic acid CH 3 [CH 2 ] 14 CH : CH COOH + 2KOH -f = CH 3 [CH 2 ] 14 COOK + H 2 + CH 3 COOK. Potassium palmitate The acids of the oleic or acrylic series, and unsaturated compounds in general, exhibit a tendency to polymerise ; the mere action of sodium alkoxide on the crotonic esters produces, in addition to other reactions, the following change : CH 3 C0 2 -CH 3 CH 3 C0 2 -CH 3 II II CH CH CH CH 2 II II II I CH CH C CH II II C0 2 'CH 3 CH 3 C0 2 -CH 3 CH 3 Methyl crotonate Methyl dicrotonate VOL. ii. 23 354 ORGANIC CHEMISTRY Instances of stereoisomerism among unsaturated compounds have already been described on pp. 21 and 22, and it is only necessary to state here that, of the two stereoisomerides corresponding with one and the same formula, one is less stable than the other, into which it is easily and directly transformed (the inverse change only takes place indirectly) by mere heating or by the action of concentrated sulphuric acid, caustic soda, a little nitrous acid, or a trace of bromine in the presence of light. ACRYLIC ACID (Propenoic Acid) C 3 H 4 O 2 or CH 2 : CH COOH This acid was prepared for the first time (Redtenbacher, 1843) by oxidising acrolein, CH 2 : CH CHO, with silver oxide. It is now more readily obtained indirectly, by the action of gaseous hydrogen chloride, which gives /3-chloropropaldehyde, CH 2 C1 CH 2 CHO, this being converted by nitric acid into the corresponding /3-chloropropionic acid, CH 2 C1 CH 2 COOH ; when the last compound is boiled with a solution of alkali, it loses HC1, yielding acrylic acid. Another convenient synthesis is the following : allyl alcohol (a, see below) with bromine gives dibromopropyl alcohol (b), which, on oxidation, yields a/3-dibromopropionic acid (c), and this, by the action of either zinc in presence of dilute sulphuric acid (or water) or reduced copper (containing iron) loses bromine and gives acrylic acid (d) : CH 2 CH 2 Br CH 2 Br CH 2 II I I II ' CH - CHBr -> CHBr -> CH I I I I CH 2 -OH CH 2 -OH COOH COOH abed Acrylic acid is a liquid soluble in water and having a pungent odour almost like that of acetic acid : it has the sp. gr. 1-0621 at 16, boils and polymerises at about 140, and when cooled forms tabular crystals melting at 13. With nascent hydrogen, it is trans- formed into propionic acid, whilst, when fused with potash, it gives acetic and formic acids. CROTONIC ACIDS, C 4 H 6 2 Isomeric unsaturated acids of this formula are possible theoretically two stereo- isomerides and the others structural isomerides. The following acids have actually been prepared : (a) CH 2 : CH CH 2 COOH, vinylacetic add ; H C C0 2 H (ba) || , cis /3-methylacrylic acid (solid crotonic acid); H C CH 3 H C CO 2 H (b(3) , trans /2-methylacrylic acid (liquid crotonic acid); CH 3 C H OH (c) CH 2 : C CHBr > CHBr > CH I I I I CH 9 CH 9 CH,, CH I I I CN CN CO 2 H C0 2 H Vinylacetic acid is a very hygroscopic liquid, which solidifies when cooled to a low temperature; it melts at 39 and boils at 163. Its calcium salt, (C 4 H 5 O 2 ) 2 Ca, H 2 O, crystallises from water in shining needles. When boiled with 5 per cent, sulphuric acid solution, it is transformed into the solid crotonic acid, CH 2 : CH CH 2 COOH -> CH 3 CH : CH COOH. This transposition of the double linking is effected also by boiling with caustic soda solution, but in fhis case a preponderance of /3-hydroxybutyric acid is formed at the same time. H C C0 2 H (60) ORDINARY or SOLID CROTONIC ACID, || (cis fi-methylacrylic H C CH 3 acid or cis ethylideneacetic acid ; also wrongly known as u-crotonic acid). Its constitution follows from its synthesis from a-bromobutyric acid (or rather its ester) by the elimination of HBr under the action of alcoholic potash : CH 3 CH 2 CHBr C0 2 H = HBr + CH 3 CH : CH C0 2 H. From water (solubility 1 in 12) the acid crystallises in shining needles melting at 71 to 72; it boils at 181 to 182, has an odour resembling that of butyric acid, and is found free in crude pyroligneous acid. Its calcium and barium salts contain no water of crystal- lisation and are very soluble in water. When gently oxidised in alkaline solution with permanganate, it gives aft-dihydroxy- butyric acid, CH 3 CH(OH) CH(OH) C0 2 H, which cannot form a lactone, so that neither of its hydroxyl groups is in the y-position ; the double linking of the crotonic acid must hence be between the a- and /3-carbon atoms. When halogen hydracids are added to it, the halogen goes to the /2-positiou. With nascent hydrogen it gives butyric acid. H C CO 2 H (6/3) LIQUID CROTONIC ACID, || (trans (3-methylacrylic acid or iso- CH 3 C H crotonic or allocrotonic acid ; known improperly as /3-crotonic acid). This acid is prepared from ethyl acetoacetate, which, with PC1 5 , gives probably a chloracetic ester, the latter losing a molecule of HC1 and yielding the two stereoisomeric chloroisocrotonic acids (or 1 This /8 y-dibromobulyric acid, when boiled with water, gives a fi-bromdbutyrolaclone : CH 2 Br CH 2 CHBr = HBr + CHBr CH 2 COOH CH 2 CO Lactones are not usually formed by acids brominated in the a- or fl-position, but only with those where the bromine atom is in the y-position. It may hence be concluded that the double linking in vinylacetic acid is also in the # y-position, since its brominated derivative gives a lactone, which is formed only when there is halogen in the y-position. 356 ORGANIC CHEMISTRY the corresponding ethyl esters); these two isomerides may be separated, the one formed in greater proportion being readily, and the other difficultly, distilled in steam. The latter gives solid, and the other liquid, crotonic acid on reduction with sodium amalgam : (a) CH 3 CO CH 2 CO OC 2 H 5 + PC1 5 = CH 3 CC1 2 CH 2 CO OC 2 H 5 + POC1 3 . Ethyl acetoacetate Intermediate product (6) CH 3 CC1 2 CH 2 CO OC 2 H 6 = CH 3 CC1 : CH CO OC 2 H 5 + HC1. , Two stereoisomerides (c) CH 3 CC1 : CH CO OC 2 H 5 + H 2 = CH 3 CH : CH CO OC 2 H 5 + HC1. Ethyl ester of crotonic acid The isocrotonic acid thus obtained is liquid, but is not pure, as it always contains ordinary crotonic acid and a little tetrolic acid, CH 3 C C C0 2 H. Only within recent years (1895 and 1904) has it been separated from these admixtures, either by means of its sodium salt, which is more soluble in alcohol, or by means of its quinine salt, which is less soluble in water, than that of crotonic acid. After such purification it is found that pure liquid crotonic acid forms crystals melting at 15-5 and boiling at 169 under the ordinary pressure or at 74 under a pressure of 15 mm. The calcium salt, (C 4 H 5 2 ) 2 Ca, 3H 2 0, forms large prisms, and the barium salt, (C 4 H 5 O 2 ) 2 Ba, H 2 0, large plates. When heated above 100, it is converted partially into normal crotonic acid, and in order to avoid this change during distillation the operation is carried out in a vacuum ; the transformation is instantaneous and quantitative in presence of a trace of bromine in aqueous solution or of carbon disulphide under the influence of direct sunlight. That the structure of isocrotonic acid is the same as that of crotonic acid and not of vinylacetic acid is supported by the fact that isocrotonic acid gives no lactonic derivative (see above) and also by the fact that the peroxyozonides of these two acids, obtained by Harries and Langheld (1905) by the action of ozonised oxygen and having the structure CH 3 CH CH C , give with water the same decomposition products, namely, | N>:0 0-0-0 hydrogen peroxide, acetaldehyde, and glyoxylic acid, CHO C0 2 H. (c) METHYLMETHYLENEACETIC ACID (a-Methylacrylic, Metacrylic or Me- CH thylpropenoic Acid), CH 2 : C mav ^e obtained by separation of water from a-hydroxyisobutyric acid and also by elimination of a molecule of HBr from a- bromoisobutyric acid : PTT CH 3 CBr C0 2 H = HBr + CH 2 : C<^ 3 H CH 3 This synthesis indicates the constitution of metacrylic acid, which is confirmed by the observation that reduction of this acid by means of sodium amalgam gives isobutyric acid, this having a known constitution. Metacrylic acid crystallises readily from water in shining prisms which melt at + 16 and boil at 161, or at 60 to 63 under 12 mm. pressure. It has a strong but not unpleasant odour of bad mushrooms and occurs in Roman chamomile ; it dissolves very readily in alcohol or ether. It exhibits a marked tendency to polymerise, more especially at 130, but also in the cold when in contact with concentrated hydrochloric acid. The calcium salt forms crystals very soluble in water. PENTENOIC ACIDS, C 5 H 8 2 Several isomeric pentenoic acids are known, those which have been most closely studied being : (a) ANGELIC ACID (a-Ethylidenepropionic, a/3-Dimethylacrylic or 2-Methyl-2- CH 3 C CO 2 H butenoic-i Acid), . The double linking in this acid must be in the CH 3 C H a /3-position, and not in the y-position, since lactonic derivatives are unknown. On protracted heating it is transformed into the stereoisomeric tiglic acid. PENTENOIC ACIDS 357 Angelic acid was first found in, and is still obtained from, the roots of Angelica arcangelica, and occurs as ester in Roman chamomile oil. The pure crystals melt at 45, boil at 185, and are only slightly soluble in water or volatile in steam. CH 3 C CO 2 H (b) TIGLIC ACID, || , often occurs with angelic acid and is formed in the H C-CH 3 decomposition of various more complex organic compounds. It can be prepared synthetically from acetaldehyde and ethyl a-bromopropionate in presence of zinc, a hydroxy-acid being formed as an intermediate compound. It forms transparent crystals, m.-pt. 65, b.-pt. 198-5, and is slightly soluble in cold and readily in hot water; it has a pleasant smell and is volatile in steam. PYROTEREBIC ACID (2-Methyl-2-pentenoic-5 Acid), SJ? 3 >C: CH- CH 2 - COOH, Lrl 3 is formed by the distillation of an oxidation product (terebic acid) of oil of turpentine (together with the lactone of isocaproic acid, see below). (CH 3 ) 2 : C CH(C0 2 H) CH 2 '| | " = C0 2 + (CH 3 ) 2 : C : CH CH 2 COOH. O CO Pyroterebic acid Terebic (yy-dimethylparaconic) acid That pyroterebic acid really has this constitution is shown by the fact that, on reduction with hydriodic acid, it gives isocaproic acid of the known constitution (CH 3 ) 2 : CH CH 2 CH 2 COOH. The position of the double linking is confirmed by the great ease with which it is converted into isocaproic lactone on prolonged boiling or by the action of a small quantity of hydrobromic acid : (CH 3 ) 2 : C : CH CH 2 COOH -> (CH 3 ) 2 : C CH 2 CH 2 O CO Pyroterebic acid is a colourless liquid solidifying at 15 and boiling at 207; it is lighter than water, which dissolves it with difficulty." y-ALLYLBUTYRIC ACID (i-Heptenoic-y Acid), CH 2 : CH [CH 2 ] 4 C0 2 H, is obtained from cycloheptanone (or suberone) by Wallaces reaction, passing through the oxime, amine, etc. : CH 2 CH 2 CH 2 v CH 2 CH 2 CH 2 COOH I ' / C0 -* I CH,j CHC : CH [CH 2 ] 2 CH(CH 3 ) CH 2 CO 2 H (2 : 6-Dimethyl-2-octenoic-8 acid). 358 ORGANIC CHEMISTRY It is a liquid boiling at 152 under 18 mm. pressure, has a faint odour of capric acid and is obtained by the oxidation of citronellal (an aldehyde, C 10 H 18 O, abundant in ethereal oils). One of the two formulae must be attributed to Rhodinic Acid (laevo -rotatory), obtained by oxidising rhodinol, C 10 H 20 O. An inactive i-Rhodinic Acid is also known, this being obtained by the reduction (sodium in amyl alcohol) of geranic acid, (CH 3 ) 2 : C : CH CH 2 CH 2 C(CH 3 ) : CH C0 2 H, the hydrogen being added only at the a/3-double linking. UNDECENOIC ACID, CH 2 : CH [CH 2 ] 8 CO 2 H. The position of the double linking in this acid is confirmed by the fact that, on oxidation, the acid yields considerable quantities of Sebacic Acid, CO 2 H [CH 2 ] 8 C0 2 H. It is obtained (about 10 per cent. ) on distilling castor oil under reduced pressure. It forms crystals melting at 24-5 and boils unchanged at 213-5 (100 mm.). When reduced with hydrogen iodide, it gives normal undecoic acid, the non-branched character of the carbon atom chain being thus proved. HYPOG^IC ACID, CH 3 [CH 2 ] 7 CH : CH [CH 2 ] 5 - CO 2 H, was formerly thought to exist in Arachis hypogcea, but the acid there present has been shown to be another acid (arachic acid). It may be prepared by fusing stearolic acid with potash, an intermediate product with two double bonds being probably formed : CH 3 [CH 2 ] 7 C I C [CHjg CH 2 CH 2 CO 2 H -> Stearolic acid CH 3 [CH 2 ] 7 CH : CH [CH^ CH : CH C0 2 H -> Hypothetical intermediate acid CH 3 CO 2 H + CH 3 [CH 2 ] 7 CH : CH [CH 2 ] 5 C0 2 H. Acetic acid Hypogseic acid OLEIC ACID, C 18 H 34 O 2 (CH 3 [CH 2 ] 7 CH : CH [CH 2 ] 7 CO 2 H) This acid is very abundant in nature in the form of glyceride (triolein), especially in vegetable and animal oils and fats. After hydrolysis of the fat, the fatty acids are liberated and from these the oleic acid separates, as it is liquid, whilst the others are solid. Although Chevreul discovered oleic acid at the beginning of the nineteenth century, it was only in 1846 that its composition was definitely established by Gottlieb. In the subsequent section dealing with soap and candles, the method of preparing commercial oleic acid or " oleine " on a large scale will be described in detail; at the present juncture, only the constitution and the methods of obtaining pure oleic acid will be considered. Oils rich in olein (olive oil, almond oil, lard, etc.) are hydrolysed with caustic potash in the hot, the fatty acids being separated from the transparent soap thus obtained by means of hydro- chloric acid ; these acids are then heated for several hours with lead oxide at 100, and the resulting lead salts dried and extracted with ether. This solvent dissolves only the lead oleate, the oleic acid being freed from the lead by means of hydrochloric acid. The oleic acid thus obtained is purified by transforming it into the barium salt and crystallising this from dilute alcohol, or by repeatedly freezing (at 6, 7) and squeezing the solid oleic acid, which, when pure, melts at 14 and has the specific gravity 0'900 in the liquid state ; it has neither smell nor taste and, in alcoholic solution, shows no reaction towards litmus. In the air and when kept for a long time, the acid turns brown, assumes an acid reaction and taste, and undergoes partial oxidation. Under a pressure of 10 mm., it boils unchanged at 223; it may also be distilled without alteration by means of steam superheated at 250. The salts of oleic acid (and of other high fatty acids) form the soaps ; the alkali salts are soluble in water and separable from this by salt (NaCl), in OLEIC ACIDS 359 saturated solutions of which they are completely insoluble. The calcium, barium, lead, etc., salts or soaps are insoluble in water. The action of concentrated sulphuric acid is mentioned later (see Iso-oleic Acid). An important and characteristic reaction of oleic acid is its almost quantita- tive transformation, by a little nitrous acid (also by heating at 200 with sulphurous acid or sodium bisulphite), into the stereoisomeric Elaidic Acid, which separates from alcoholic solution in white scales melting at 51 to 52 and boiling unchanged at 225 under a pressure of 10 mm. 1 That these two isomeric acids have direct (normal) carbon-atom chains is shown with certainty by the- fact that, on reduction (e. g., with hydriodic acid and phosphorus or directly with hydrogen, as in the industrial hardening of oils : see later, section on Hydrolysis of Fats), each of them takes up two hydrogen atoms giving stearic acid, which is known to have an unbranched carbon-atom chain ; also with bromine, they give dibromo-derivatives of stearic acid, and, with permanganate, dihydroxyslearic acid, C 18 H 34 O 2 (OH) 2 . 2 ISO-OLEIC ACID, CjgH^Og. With concentrated sulphuric acid, elaidic and oleic acids give Stearinsulphuric Acid, C^H^O SO 3 H) CO 2 H, which, with hot water, loses sulphuric acid and gives hydroxy 'stearic acid, C^Hg^OH) CO 2 H (with the OH at the position 10). When distilled under reduced pressure (100 mm.) or with superheated steam, this acid loses water and gives a considerable quantity of a white, solid acid iso-oleic acid which is readily soluble in alcohol and slightly so in ether, from which it crystallises in plates, melting at 44 to 45. The addition of the molecule of water to oleic or elaidic acid should take place at the central double linking (provided the sulphuric acid does not previously displace this linking) and the subsequent separation of water should occur at two carbon atoms adjacent to the double linking, so that the probable constitution, of iso-oleic acid is, CH 3 [CH 2 ] 8 CH : CH [CH 2 ] 6 C0 2 H. Various facts are, however, known which throw doubt on the accuracy of this formula. ACID (2-Octadecenoic-i Acid), CH 3 [CH 2 ] 14 CH : CH CO 2 H, is 1 From an industrial point of view the transformation of a liquid fatty acid into a solid one is of interest, but this change is not utilisable in practice as it proceeds well only with fairly pure and fresh oleic acid, and not with the commercial acid, which may be old and possibly polymerised (see also later, section on Hydrolysis of Fats). 2 The position of the double linking in the molecule was under discussion for a number of years, and until quite recently this linking was held to be at the end of the chain next the carboxyl group, i. e., in the o /3-position, CH 3 [CH 2 ] 14 CH : CH COOH, since fusion of these two acids with caustic potash resulted in the formation of palmitic acid (Varrentrapp's reaction, p. 350). This proof no longer seemed sufficient, however, when it was shown that fusion with potash generally displaced the double bond. On the other hand, Baruch (1894) succeeded in eliminating hydrogen bromide from the dibromidc of oleic acid, thus obtaining stearolic acid, which has a triple bond in the middle of the molecule. Also the products of oxidation (by permanganate) of oleic acid consist partly of pelargonic and azelaic acids, which contain nine carbon atoms, this reaction hence indicating that the oleic acid molecule breaks in the middle of the chain, at the position of the double linking. The most certain proof of the constitution of oleic acid has been advanced only recently as a result of the study of the ozonide of oleic acid and of its decomposition products (E. Molinari and Soncini, 1905 and 1906; C. Harries, 1906). The ozone is added quantitatively at the position of the double bond (see p. 107), and, according as ozonised air (E. Molinari) or ozonised oxygen (Harries ) is employed, so the simple ozonide : CH 3 [CH 2 ] 7 CH - CH [CH 2 ] 7 COOH or a peroxide of the ozonide : CH 3 [CH 2 ] 7 CH CH [CH 2 ] 7 C OH I! O II O - is obtained. Decomposition of these ozonides (of oleic and elaidic acids) with dilute alkali or water in the hot results in the formation of acids (nonoic, azelaic, and others) or aldehydes (nonyl and semiazelaic) with nine carbon atoms, showing that the molecule is ruptured at the position of the central double linking. 360 ORGANIC CHEMISTRY prepared by the removal of 1 mol. of halogen hydracid from the a-halogen derivative of stearic acid. It forms white crystals melting at 58 to 59, does not take up ozone in cold chloroform solution, and gives palmitic acid when treated with permanganate. ERUCIC ACID (9-Docosenoic-22 Acid), CH 3 [CH 2 ] 7 CH : CH [CH 2 ] n CO 2 H, is found as glyceride in the oils of black and white mustard, and in those of grape-seed and ravison, from which it is readily extracted. It is obtained crystalline from alcohol in shining needles melting at 34, and boils at 254-5 under a pressure of 10 mm. It forms a lead salt soluble in hot ether, as does oleic acid, and, like the latter, it is readily transformed into its stereoisomeride, Brassidic Acid, by the action of a little nitrous acid or of sulphurous or hydrobromic acid in glacial acetic acid solution. This isomeride crystallises from alcohol in leaflets melting at 65, and boils at 256 under a pressure of 10 mm. ; its lead salt is slightly soluble in hot ether. These two isomerides are not reduced by sodium amalgam, but with hydriodic acid they yield the saturated behenic acid, C 22 H 44 O 2 . When fused with potash, they give arachic (C 20 H 40 O 2 ) and acetic acids. They yield various oxidation, bromination, and esterification products. They have normal carbon-atom chains and the position of the double linking is indicated by the fact that nonoic acid, CH 3 [CH 2 ] 7 COOH, and brassylic acid, C0 2 H [CH 2 ] U CO 2 H (and also a little arachic acid ), are among the products of oxidation by nitric acid, while elimination of HBr from the dibrominated product gives the corresponding behenolic acid, which has a triple bond and is of known constitution. ISOERUCIC ACID, CH 3 [CH 2 ] 8 CH : CH [CH 2 ] 10 CO 2 H ( ? ), is obtained by adding hydrogen iodide to, and then removing it from, erucic acid (just as with iso-oleic acid), and it appears that the double linking is not displaced during these changes, since decom- position of the dibromide of this acid (i. e., elimination of HBr) gives the same behenolic acid as is given by erucic acid, while oxidation with nitric acid also gives nonoic and brassylic acids. Isoerucic acid should hence have the same constitution as erucic and brassidic acids, so that, contrary to theoretical indications, three isomerides would seem to exist; this requires confirmation. This" acid melts at 54 to 56. B. UNSATURATED MONOBASIC ACIDS OF THE SERIES, C n H 2n _ 4 2 The members of this series may be divided into two groups, as is the case with the hydrocarbons of the diolefine and acetylene series (see p. 109) : acids having a triple linking (propiolic series) and those having two double linkings (diolefine series). (a) ACIDS WITH TRIPLE LINKING (Propiolic or Acetylenecarboxylic Series) Name Constitutional formula Melting- point Boiling-point C3H 2 C>2 Acetylenecarboxylic (propiolic') acid ....... HO C C0 2 H 9 83 (50 mm.) 0411402 Methylacetylenecarboxylic (tetrolic) acid .... CH 3 i C C0 2 H 76-5 v203 C5HgO2 Ethyl-acetylenecarboxylic acid C..HB -c c CO.H 50 CH 8 O 2 Propyl- C 3 H 7 -0 C0 2 H 27 125 (20 mm.) C6H 8 2 Isopropyl- C 3 H 7 C COjH 38 115 C 7 H 1D 2 n-Butyl- CiH 9 -0 C CO 2 H . - 135 C 7 H 10 O 2 tert.-Butyl- C 4 H 9 -0 CO 2 H 47 116 CgH 12 O 2 n-Amyl- C 6 H U -0 CO 2 H 5 149 CjH^Ojj n-Hexyl- C 6 H 13 C C CO 2 H 10 c . CwHwOjj n-Heptyl- 7 H 15 C C C0 2 H 6-10 166 (20 mm.) Ci2H 2 o0 2 n-Nonyl- C 9 H 19 -0 ' CO 2 H 30 CjjHxgOjj Dehydroundecenoic acid OH : C ' [CH-jg] UO 2 H 42-8 175 (15 mm.) CuHigO 2 Undecolic acid CH 8 C i C[CH 2 ], C0 2 H 59-5 Ci8H 82 O 2 Stearolic acid OH S [CH 2 ], C ; C ' rOH 2 ] 7 CO 2 H 48 CisH 3 2O 2 Tariric acid CH 3 ' [CH 2 ] 10 ' C C [CH 2 ] 4 ' CO 2 H 50-5 C^tUoOj Behenolic acid CH 3 [CHjj] 7 C = C [UHJii ' CO 2 H 57-5 PREPARATION. These acids may be obtained by the following reactions : From a sodium alkyl acetylidfe (suspended in ether), by the action of CO 2 (a) or of ethyl chloroformate (b) : PROPIOLIC ACIDS 361 (a) CH 3 C C Na -f CO 2 = CH 3 C : C CO 2 Na. Sodium met.hylpropiolate (6) C 3 H 7 C i C Na + Cl CO OC 2 H 5 = NaCl + C 3 H 7 C C CO OC 2 H 5 . Ethyl propylacetylenecarboxylate Various other acids of this series having the triple linking at a distance from the carboxyl group (and hence much more stable than the preceding, which, when heated, lose CO 2 and give acetylene hydrocarbons) are obtained by the elimination of 2HBr (by the action of alkali) from acids of the oleic series, this reaction being similar to that taking place with unsaturated hydrocarbons (see p. 110) : CH 3 [CH 2 ] 7 CHBr CHBr [CH 2 ] 7 C0 2 H = Dibromide of oleic acid 2HBr + CH 3 [CH 2 ] 7 C : C [CH 2 ] 7 C0 2 H. Stearolic acid PROPERTIES. Acids of the type R C ! C ' C0 2 H, when treated with sodium in absolute alcoholic solution, take up 4 atoms of hydrogen, giving acids of the saturated series ; they also combine easily with 2 atoms of bromine, but the second pair of bromine atoms, required to produce saturation, are added only with difficulty (the action of light facilitates the reaction) ; when boiled with alcoholic potash, they take up a molecule of water, forming saturated /?-ketonic acids : R C ! C C0 2 H + H 2 = R CO CH 2 C0 2 H; with aqueous potash, however, they yield methyl ketones, R CO CH 3 , separation of C0 2 also taking place; tert.-butyltetrolic acid does not react. The amines and hydrazine also give characteristic reactions with these acids. The esters of the acids have pleasant odours and are used in perfumes. Acids with a triple bond do not unite with the ozone of a current of ozonised air (E. Molinari, 1907 and 1908), but yield peroxyozonides with ozonised oxygen (Harries, 1907; seep. 359). PROPIOLIC ACID (Propinoic, Propargylic, or Acetylenecarboxylic Acid), CH : C . C0 2 H, is obtained by heating the aqueous solution of potassium acetylene- dicarboxylate : C - C0 2 H C - H III = C0 2 + III C-C0 2 K' C-C0 2 K Propiolic acid is a liquid with a more intense odour than acetic acid; "it has the sp. gr. 1-139, is soluble in water, alcohol, or ether, solidifies at 4, melts at 9, and distils unchanged at a pressure of 50 mm. The alkali and alkaline-earth salts are extremely soluble in water. From its esters, metallic acetylides (p. 112) are readily prepared. Under the action of light and in a vacuum, it undergoes partial polymerisation, yielding benzenetricarboxylic acid. TETROLIC ACID (2-Butinoic or Methylpropiolic Acid), CH 3 C : C CO 2 H, is obtained by eliminating HC1 from the /3-chloro-derivative of crotonic or isocrotonic acid. It crystallises from water in rhombic plates, melting at 76-5 and boils unchanged at 203, but it distils only with difficulty in a current of steam. Under the action of sodium in alcoholic solution (but not with sodium amalgam in aqueous solution), it takes up hydrogen with formation of butyric acid. When oxidised with permanganate in alkaline solution, it yields acetic and oxalic acids. DEHYDROUNDECENOIC ACID (i-Undecinoic-n Acid), HC i C [CH 2 ] 8 CO 2 H, obtained by heating dibromoundecenoic acid with alcoholic potash, melts at 42-8. On oxidation, it forms sebacic acid, C0 2 H [CH 2 ] 8 C0 2 H. It readily forms acetylides. Treatment with alcoholic potash at 180 converts it into the isomeric Undecolic Acid (2-undecinoic-ll acid), CH 3 C j C [CH 2 ] 7 C0 2 H, melting at 59-5; the latter 362 ORGANIC CHEMISTRY is hence formed with the dehydroundecenoic acid, if the reaction referred to above takes place at a high temperature. Oxidation of undecolic acid yields azelaic acid, CO 2 H [CH 2 ] 7 C0 2 H ; it does not give acetylides, owing to the absence of the charac- teristic acetylenic hydrogen atom (see p. 110). STEAROLIC ACID (9-Octadecinoic-i Acid), CH 3 [CH 2 ] 7 C ! C [CH 2 ] 7 C0 2 H, is readily obtained by boiling dibromostearic acid (prepared by brpminating oleic or elaidic acid) with alcoholic potash. It melts at 48, and under the influence of sulphuric acid takes up water, giving a ketostearic acid. When oxidised with permanganate, it takes up 2 atoms of oxygen, giving diketostearic acid, whilst with nitric acid it is resolved into nonoic and azelaic acids (it is, however, stable in the air, and thus differs from oleic and linolic acids) : C - [CH 2 ] 7 CH 3 CO [CH 2 ] 7 CH 3 III -> 1 7* CH 3 [CH 2 ] 7 C0 2 H + C0 2 H [CH 2 ] 7 -C0 2 H. C [CH 2 ] 7 C0 2 H . CO [CH 2 ] 7 CO 2 H Nonoic acid Azelaic acid Stearolic acid Diketostearic acid Stearolic acid unites with 2HI, and the resulting diiodostearic acid, when heated with alcoholic potash, gives stearolic acid again, but in two isomeric forms, having the triple linking in the 8 to 9 and 10 to 11 positions respectively. The constitution of stearolic acid was confirmed by Harries (1907) by decomposing the peroxyozonide of the acid, obtained by the action of ozonised oxygen (ozonised air does not yield an ozonide, see pp. 107, 359) : .0-C-[CH 2 ] 7 .CH 3 Of | | /OH + 2H 2 - N> - C [CH 2 ] 7 . C/ x o = o Peroxyozonide of stearolic acid H 2 2 + CH 3 [CH 2 ] 7 C0 2 H + C0 2 H [CH 2 ] 7 C0 2 H. Nonoic acid Azelaic acid TARIRIC ACID (6-Octadecinoic-i Acid), CH 3 [CH 2 ] 10 C C [CH 2 ] 4 CO 2 H, is isomeric with stearolic acid and melts at 50-5 ; as glyceride, it forms the principal com- ponent of the fat of the fruit of Picramnia camboita. It is the first compound with a triple bond resulting from the vital process of an organism. It is stable in the air and yields stearic acid on reduction with hydriodic acid, so that its molecule contains a normal carbon atom chain. Energetic oxidation with permanganate or nitric acid yields lauric acid, CH 3 [CH 2 ] 10 C0 2 H, and adipic acid, CO 2 H f CH ] 4 C0 2 H. BEHENOLIC ACID (9-Docosinoic-22 Acid), CH 3 [CH 2 ] 7 C [CH 2 ] U CO 2 H, melting at 57-5, is obtained from the dibromide of erucic or brassidic acid, in the same way as stearolic acid is formed from oleic acid. Its constitution follows from its behaviour towards reducing and oxidising agents and from the transformation of its oxime (Beckmann). (b) ACIDS WITH TWO DOUBLE BONDS, C K H 2rt _ 4 O 2 (Diolefinic or Sorbinic Series) These acids are prepared synthetically by methods analogous to those used for obtaining a/?-unsaturated acids, for example, by treating a/3-unsaturated aldehydes with malonic acid in presence of pyridine : CH 2 : CH CHO + CO 2 H CH 2 C0 2 H = Acroleln C0 2 + H 2 + CH 2 : CH : CH : CH C0 2 H. /3-Vinylacrylic acid The acids of the sorbinic series, in which the two double linkings are con- jugated that is, one in the aft- and the other in the ^5-position and there- fore separated by a simple linking may be reduced by sodium amalgam in DIOLEFINIC ACIDS 363 aqueous solution (in presence of a stream of CO 2 to fix the alkali ) ; only two hydrogen atoms are then added, one for each double linking, and a new double linking remains in the place of the simple linking previously separating the two original double bonds : X CH : CH CH : CH C0 2 H + H 2 = X CH 2 CH : CH CH 2 C0 2 H. When these sorbinic acids are oxidised with permanganate, two hydroxyl groups enter at the a/S-double linking, while the chain is broken at the yd- double linking with formation of an aldehyde (which then undergoes oxidation) and racemic acid : X CH : CH CH : CH C0 2 H -> X CHO + C0 2 H CH(OH) CH(OH) -C0 2 H. Racemic acid When they are heated with aqueous ammonia, 2 mols. of the latter are added at the double linking and two diamino-acids formed. On heating, acids of the sorbinic series readily polymerise ; hence, when they are heated with lime or baryta, not only is C0 2 removed and diolefine hydrocarbons obtained, but di- and tri-molecular condensation occurs, giving more complex hydrocarbons which are probably of cyclic structure. yg-VINYLACRYLIC ACID (i : 3-Pentadienoic Acid), CH 2 : CH CH : CH CO 2 H, is synthesised by the method given above. It forms prisms showing a grey reflex, and dissolves slightly in cold water, but readily in hot. At 80 it melts to a mobile liquid, which, at 100 to 115, becomes dense and syrupy and then suddenly decomposes with evolution of gas. In carbon disulphide solution it unites with four atoms of bromine. SORBINIC or SORBIC ACID (2 : 4-Hexadienoic Acid), CH 3 CH : CH CH : CH C0 2 H, occurs in considerable quantities in mountain-ash berries. It melts at 134-5, boils at 228 with partial decomposition, is odourless and dissolves readily in alcohol or ether. DIALLYLACETIC ACID (i : 6-Heptadiene-4-methyloic Acid), CH 2 : CH CH 2 CH(CO 2 H) CH 2 CH : CH 2 , is obtained synthetically from acetoacetic acid by two separate introductions of the allyl residue. It is a liquid, sp. gr. 0-950, b.-pt. 219 to 222, and has an unpleasant smell. Oxidation with nitric acid leads to the rupture of the carbon atom chain at the two double linkings and formation of tricarballylic acid : GERANIC ACID (2 : 6-Dimethyl-2 : 6-octadienoic-8 Acid), (CH 3 ) 2 : C : CH CH 2 CH 2 C(CH 3 ) : CH C0 2 H, is obtained either by oxidation of the corresponding aldehyde (citral) with silver oxide, or by elimination of water from citraloxime by the action of acetic anhydride and hydrolysis of the resulting nitrile with alcoholic potash. It has also been obtained, by a series of reactions, from methylheptenone, (CH 3 ) 2 : C : CH CH 2 CH 2 CO-CH 3 . It is a colourless liquid of not very pleasing odour and boils at 153 under a pressure of 13 mm. When shaken with 70 per cent, sulphuric acid it yields, among other products, the isomeric a-cyclogeranic acid, melting at 106 : \> 3 \/ 3 HC CH C0 2 H > H 2 C CH CO 2 H Hr< r* r*TT IT r< r* /~0 CH 2 CO X Succinic anhydride CH 2 CO CH O CH 2 CO Glutaric anhydride The ready formation of these anhydrides by the reaction of the two terminal carboxyl groups (, a/) is readily explained by arranging the carbon atoms 366 in space (see pp. 19 et seq.), with their valencies in the directions of the angles of regular tetrahedra. Thus, with succinic acid, which contains four carbon atoms, the two hydroxyls of the carboxyl groups are found to be moderately close together (Fig. 251), whilst in glutaric acid the two hydroxyls are almost superposed, so that water readily separates, forming a closed ring (Fig. 252). Similarly the amides (which see) or the ammonium salts of these acids readily form imides (see later), which may be hydrolysed like the amides : CH 2 COONH 4 CH 2 C(\ = 2H 2 0+ | >NH CH 2 COOH CH 2 COT Monoammonium succinate Succinimide COOH - OXALIC ACID (Ethandioic Acid), | , has been known from the COOH earliest times, since it occurs frequently in nature in plants, especially in FIG. 251. FIG. 252. sorrel, in the form of acid potassium oxalate, and also as incrustations of calcium oxalate in plant-cells and in the roots of rhubarb. It is often formed in the oxidation of organic substances (sugar, wood, starch, etc.) by nitric acid or permanganate, orl)y fused caustic potash. It is obtained synthetically by heating sodium or potassium formate rapidly (best in a vacuum at 280) : 2H COONa = Na 2 C 2 4 -j- H 2 (the reverse change, from oxalic to formic acid, has already been referred to on p. 324), or by passing carbon dioxide over metallic sodium heated to about 350 : 2Na + 2C0 2 = Na 2 C 2 4 . Its industrial manufacture was, until recently, carried out exclusively by the method devised by Gay-Lussac in 1829 and applied by Dale in 1856 : sawdust (1 part) moistened with caustic potash solution (2 parts, sp. gr. 1'4) or a mixture of 4 parts of KOH and 6 parts of NaOH is heated at about 240 and frequently stirred on iron plates until a greenish-yellow mass is formed. While still hot, this is dissolved in water and the solution filtered and con- centrated to 38 Be. When cold, the solution deposits crude sodium oxalate, which is dissolved in a small quantity of boiling water and precipitated as insoluble calcium oxalate by means of lime. The precipitate is made into a paste with water and the oxalic acid liberated by addition of sulphuric acid. The liquid is decanted and concentrated until the whole of the calcium sulphate OXALIC ACID 367 separates, the oxalic acid being then allowed to crystallise out and subsequently purified by repeated recrystallisation. When sugar (saccharose) is obtainable at a very low price, it may be oxidised with nitric acid (sp. gr. T4) in the cold in presence of O'l per cent, of vanadic oxide, V 2 O 5 , but for the process to pay, the nitrous vapours evolved must be recovered for the regeneration of the nitric acid. From 100 kilos of sugar 140 kilos of oxalic acid may be obtained, while Molinari and Fedeli (1914) obtained more than 160 kilos of the acid (see also Naumann, Moeser, and Lindenbaum's Ger. Pat. 183,022, 1907, and Ger. Pat. 208,999). At the present time, the acid and also the various alkaline oxalates are prepared by Goldschmidt's process (see p. 324), which consists in heating a mixture of potassium or sodium formate with a little potassium carbonate in presence of a small proportion of potassium oxalate and a slight excess of alkali (3 to 4 per cent. ). According to Ger. Pat. 229,853 of 1908 about 30 parts of sodium formate and 0'3 part of borax or boric acid are heated together at 400 in an iron vessel and well stirred for thirty to forty minutes. Another method of manufacture (Fr. Pat. 413,947, 1910) consists in allowing the formate to fall into an empty pot maintained at 550 to 600 by means of a metal-bath ; if the temperature of the mass introduced is kept for half an hour above 400 the formate is converted almost quantitatively into pulverulent oxalate (150 kilos per sq. metre of heated surface); see also Kirchner's Ger. Pat. 269,833, 1914. From the oxalate thus obtained the oxalic acid is liberated by means of sulphuric acid (see above) ; the final, somewhat impure mother-liquors may be utilised to make iron oxalate, which, on calcination, yields an excellent English red. PROPERTIES. Oxalic acid crystallises in odourless, colourless, trans- parent prisms, H 2 C 2 O 4 -f- 2H 2 0, which have a marked acid taste, effloresce in the air, and have the sp. gr. 1*64. The solubility at various temperatures, expressed as grams of the acid dissolving in 100 grams of water, is as follows : Temperature . 10 20 30 40 50 60 70 80 90 Solubility . 5-2 8 13-9 23 35 51-2 75 117-7 204-7 345 The crystals lose their water of. crystallisation partly at 30 and completely at 110 to 120, but melt at 99 in the residual water; the anhydrous acid melts and decomposes at 187 and sublimes at a higher temperature. When heated moderately strongly or treated with concentrated sulphuric acid, oxalic acid decomposes into CO, C0 2 , and H 2 0. It is somewhat poisonous. USES. It is used in the dyeing and printing of woollen textiles and yarns ; it serves for bleaching straw, removing rust stains from fabrics, purifying glycerine, stearine, tartaric acid, and cream of tartar from the last traces of lime, cleaning brass, etc. To some extent it is used for the manufacture, by electrolytic reduction, of glycollic acid (see later), which is used in dyeing and printing textiles. Large quantities of the acid are used for the extraction of rare earths from monazite (see Vol. I., p. 504). STATISTICS AND PRICES. Commercial crystallised oxalic acid 1 was sold before the war at 28s. to 30s. per cwt., while the purified acid cost 40s., and the chemically pure 64s. During the war the price rose to 20. The Italian imports of oxalic acid are as follows : 1 Testing of Oxalic Acid. The acid is estimated by means either of normal caustic soda solution in presence of phenolphthalein, or of decinormal potassium permanganate solution in presence of sulphuric acid in the hot : 2KMn0 4 + 5H 2 C 2 O 4 + 3H.J304 = K 2 S0 4 + 10C0 2 + 8H 2 + 2MnS0 4 . Ammoniacal impurities are detected with Nessler's reagent (Vol. I., p. 690), and, when pure, the acid should leave no ash, and 0-5 gram of it should dissolve completely when shaken with 100 c.c. of ether. 368 ORGANIC CHEMISTRY 1908 1910 1912 1913 1914 1915 1916 1917 1918 Cwts. . 1,920 3,780 5,470 5,784 4,104 2,452 1,184 2,958 1,788 Value 6,424 8,097 8,582 50,286 The United States imported 1650 tons of oxalic acid in 1911 and 1800 tons in 1913. In Russia, four factories produced about 850 tons of oxalic acid in 1909, by heating sawdust with alkali. In 1908 Germany exported 5100 tons of oxalic acid and potassium oxalate, 4470 tons (128,000) in 1909, 5015 tons in 1911, and 5693 tons in 1913. SALTS OF OXALIC ACID. Owing to the presence of two carboxyl groups in the molecule, oxalic acid gives both acid and neutral salts. The alkaline oxalates are soluble in water and are often used instead of the acid, especially in dyeing. NORMAL POTASSIUM OXALATE, K 2 C 2 O 4 , used to be obtained by neutralising the acid with potassium carbonate, concentrating and allowing to crystallise. Nowadays it is prepared by Goldschmidt's method (see above). It dissolves in three parts of water, crystallises with 1H 2 0, and readily effloresces in the air. It costs 42s. to 44s, per cwt., or, when chemically pure, 3. ACID POTASSIUM OXALATE (or Potassium Hydrogen Oxalate), KHC 2 O 4 , is obtained by dissolving the neutral oxalate (1 mol. ) and oxalic acid (1 mol.) in water, concentrating and allowing to crystallise, when it separates with 1H 2 O. It has a bitter, acid taste, is poisonous, and dissolves in 14 parts of hot water. POTASSIUM TETROXALATE (Commercial Salt of Sorrel), KHC 2 O 4 -f H 2 C 2 O 4 -f 2H 2 0, does not effloresce or lose its water of crystallisation in the air. It is obtained by mixing a hot, saturated solution of potassium oxalate with the calculated amount of saturated oxalic acid solution. It costs 42s. to 44s. per cwt., or, if chemically pure, 64s. CALCIUM OXALATE, CaC 2 O 4 , crystallises with 2H 2 and is obtained from a solution of a soluble oxalate, containing either ammonia or acetic acid, by addition of a soluble calcium salt. It is insoluble in water or acetic acid. FERROUS OXALATE, FeC 2 O 4 , or, better, Ferrous Potassium Oxalate, K 2 Fe(C 2 O 4 ) 2 + H 2 O, gives a yellow aqueous solution owing to the colour of its cation, FeC 2 O 4 ". It possesses strong reducing properties and is largely used on this account, while it serves also as a good photographic developer. POTASSIUM FERRIC OXALATE, K 2 Fe 3 (C 2 O 4 ) 3 , gives a green aqueous solution owing to the colour of its cation, Fe(C 2 O 4 ) 3 '". In the light it yields C0 2 and potassium ferrous oxalate, and it is used in the platinotype method of photography. CO H MALONIC ACID (Propandioic Acid), H 4 C 3 4 or CH 2 <^2^ > forms crys tals melting at 132 and is readily soluble in water (1 : 14 at 15), alcohol, or ether. It occurs in the beetroot and is obtained synthetically by hydrolysing cyanoacetic acid prepared from a hot aqueous solution of potassium chloroacetate and potassium cyanide : Ohloroacetic acid Cyanoacetic acid Malonic acid Like all compounds containing two carboxyl groups united to the same carbon atom, it evolves CO 2 when heated above its melting-point, acetic acid being formed. Higher monobasic acids are similarly obtained from alkylated malonic acids . CH 3 . CH 2 CH 2 CH<^H = co ^ + CHg . CHg . ^ . ^ . CQ ^ Normal propylmalonic acid Normal valeric acid ro r H Malonic acid forms an ester, ETHYL MALON ATE, CH 2 <::r 2 ' :&**, which is of great cu 2 L 2 5 importance, since it allows of the synthetical preparation of the most varied higher dibasic acids, and from these, by loss of carbon dioxide, of the corresponding monobasic acids. This ester is obtained by passing gaseous hydrogen chloride into cyanoacetic acid dissolved in absolute alcohol ; it is then separated by distillation, as it boils at 198. At 15 it has the sp. gr. 1-061. The hydrogen atoms of the methylene group of this ester may be replaced by one or two atoms of sodium (or halogens ) giving highly reactive sodiomalonic esters. The sodium in these may be substituted by one or two alkyl groups simply by treatment with an alkyl iodide, sodium iodide being separated at the same time. The resulting products are ETHYL MALONATE SYNTHESES 369 higher homologues of the malonic ester, and hence yield the corresponding homologues of malonic acid on hydrolysis. The hydrolysis of the esters of dibasic acids by alkali takes place in two stages, the second ester group being hydrolysed more slowly than the first. HOMOLOGUES OF MALONIC ACID Name of acid Formula Melting- point of acid Boiling-point of the diethyl ester Methylmalonic CH 3 -CH(C0 2 H) 2 about 130 190-193 Dimethylmalonic . (CH 3 ) 2 :C(C0 2 H) 2 192-] 93 196 Ethylmalonic C 2 H 5 -CH(C0 2 H), 112 210 Diethylmalonic (C 2 H 5 ) 2 :C(C0 2 H) 2 124 230 6 Propylmalonic C 2 H 5 -CH 2 -CH(C0 2 H) 2 93-5 219-222 Dipropylmalonic (C a H 5 .CH 2 ) 2 :C(C0 2 H) 2 156 248-250 Isopropylmalonic (CH 3 ) 2 :CH-CH(C0 2 H) 2 86 213-214 Methylethylmalonic (CH 3 )(C 2 H 5 )C(C0 2 H) 2 118 207-208 Butylmalonic C 2 H 5 -CH 2 -CH 2 -CH(C0 2 H) 2 98-5 sec. Butylmalonic . C 2 H 5 .CH(CH 3 )-CH(C0 2 H) 2 76 224-225 Isobutylmalonic (CH 3 ) 2 :CH-CH 2 .CH(C0 2 H) 2 107 225-226 Diisobutylmalonic . [(CH 3 ) 2 :CH-CH 2 ] 2 C(C0 2 H) 2 145-150 245-255 Methylpropylmalonic (CH 3 )(C 2 H 5 -CH 2 )C(C0 2 H) 2 106-107 220-223 Methylisopropylmalonic . [(CH 3 ) 2 CH](CH 3 ):C(C0 2 H) 2 124 221 Pentylmalonic C 2 H 5 CH 2 CH 2 CH 2 CH(C0 2 H) a 82 Tsoamylmalonic . . (CH 3 ),CH CH 2 CH 2 CH(CO 2 H) 2 98 240-242 Diisoamylmalonic . [(CH 3 ) 2 CH CH 2 CH 2 ] 2 C(C0 2 H) 2 147-148 278-280 2-Methylbutylmalonic (CH 3 )(C 2 H 5 )CH CH 2 CH(C0 2 H) 2 90-91 244-246 tert. Amylmalonic . (CH 3 ) 2 (C.H 5 )C CH(C0 2 H) 2 238 sec. Amylmalonic . (C 2 H 5 ) 2 CH-CH(C0 2 H) 2 52-53 242-245 Methyliso butylmalonic (CH 3 ) 2 CH -H 2 C(CH 3 )(C0 2 H) 2 122 230-235 Ethylisopropylmalonic (CH 3 ) 2 CH-C(C 2 H 5 )(C0 2 H) 2 131-131-5 232-233 Cetylmalonic . CH 3 .[CH 2 ] 15 -CH(C0 2 H) 2 121-5-122 Dicetylmalonic [CH 3 -(CH 2 ) 15 ] 2 :C(C0 2 H) 2 86-87 Dioctylmalonic [CH 3 -(CH 2 ) 7 ] 2 :C(C0 2 H). 75 338-340 Treatment of ethyl malonate (1 mol.) with sodium (1 or 2 atoms) results in the evolu- tion of hydrogen and the formation of the solid mono- or di-sodiomalonic ester : The sodium of the monosodio-compound may be replaced by an alkyl group and the remaining methylene hydrogen then replaced by sodium, which may subsequently be substituted by an alkyl group different from the first. An example of this synthesis is as follows (see also later : Glutaric Acid) : Na ' CH 3 I = Nal CH C 2 H 5 CH C 2 H 5 I Nal CH Hydrolysis of the final ester yields Methylethylmalonic Acid. Homologues of succinic acids may be obtained as follows : *2 ' C 2 H 5 Ethyl sodiomethylmalonate NaBr + CH- Ethyl a-bromopropionate C0 2 -C 2 H 5 C 2 H 5 CO C VOL. II. 24 370 ORGANIC CHEMISTRY When this complex ester is saponified and the acid thus formed heated to expel CO., from one of the carboxyl groups united to the same carbon atom, symmetrical dimethyl- succinic acid is obtained : C0 2 H CO 2 H CO 2 H Also 2 mols. of ethyl sodiomethylmalonate (or ethyl sodiomalonate or its homologues) may be condensed in ethereal solution by means of bromine or iodine : C0 2 -C 2 H 6 C0 2 -C 2 H 5 r*n -P TT 2CH 3 CNa<^2 '^ + I 2 = 2NaI + CH 3 C - - C CH 3 C0 2 .C 2 H 5 C0 2 .C 2 H 5 Ethyl dimethylethanetetracarboxylate Hydrolysis of this ester gives the corresponding acid and the latter loses 2C0 2 on heat- ing, yielding dimethylsuccinic acid. Similarly succinic acid may be obtained from ethyl sodiomalonate, and homologous, symmetrical alkylsuccinic acids by condensing 2 mols. of ethyl sodioalkylmalonate containing alkyl groups higher than methyl : CO,H C0 9 H CO..H CO,H r r i ' r CH 3 C - C CH 3 = 2C0 2 -j- CH 3 CH - CH CH 3 Dimethylsuccinic acid C0 2 H C0 2 H SUCCINIC ACIDS, C 4 H 6 O 4 (Two Isomerides) (a) ORDINARY SUCCINIC ACID (Butandioic or Ethylenesuccinic Acid), C0 2 H CH 2 CH 2 - CO 2 H, occurs in nature in various plants, in the unripe grape, in certain lignites, and, more especially, in amber, from which it is obtained by distillation or fermentation. 1 Alcoholic fermentation also yields a small amount of succinic acid, which thus forms a normal constituent of wine. Ehrlich (1909) has shown that, in the alcoholic fermenta- tion of sugar, the succinic acid is formed from the glutamic acid resulting from the decomposition of the cells of the ferment. Numerous syntheses also lead to the formation of succinic acid; e. g., the reduction by hydrogen of fumaric or maleic acid, these being unsaturated dibasic acids, C 4 H 4 O 4 ; hydrolysis of ethylene cyanide, CN CH 2 CH 2 CN, obtained from ethylene bromide, C 2 H 4 Br 2 (see above); reduction of the hydro xy-acids, 1 Amber is found on the shores of Denmark and along the coast of the Baltic, in the neigh- bourhood of Konigsberg, Holstein, and Mecklenburg, in Finland, Siberia, and the Urals ( Jekater- inenberg ), and rarely in Sicily and Spain. It consists of fossil resins (succinite, allingite, beckerite, glessite, geclanite, etc.). That thrown up on to the seashore is transparent, shiny, yellowish, pale (gedanite and succinite) or yellowish -brown (beckerite and stantienite ), while that mined is covered with an opaque, hard crust. It is odourless and tasteless, and when rubbed with a cloth becomes electrified. It is insoluble or almost so in ether, cold alcohol and other ordinary solvents, but it gradually dissolves, to the extent of 30 per cent., in boiling alcohol ; in chlor- hydrin it dissolves somewhat and turns brown. By boiling alkalies it is partially saponified. It softens and swells at 150 to 180, melts at 250 to 300, and dry-distils at above 400, giving succinic acid and yellow amber oil (of repulsive smell; sp. gr. 0-95; soluble in alcohol, ether or petroleum ether; used for varnishes) and leaving a residue termed amber colophony, used for making varnishes. Amber has the sp. gr. 1-050 to 1-090, the acid value 15 to 34, the saponification number 86 to 150, and the iodine number 57 to 58. It consists of 70 per cent, of the succinic ester of succinoresinol and 28 per cent, of abietinsuccinic acid; some- times it contains a little sulphur (succinite). It is sometimes adulterated with copal resin (which is, however, soluble in various solvents). An excellent substitute for it is baekelite (see Phenol). Amber is used for ornaments, especially for the mouthpieces of pipes and cigar-holders. Scrap amber is either distilled, or used for making varnish, or softened in the hot with carbon disulphide and pressed, or pressed directly at 200 under 400 atmospheres' pressure to make block amber. The output in Prussia before the war was 400 to 450. tons per annum. Italy imported, before the war, 300 to 400 kilos per year at a price varying from 2 to 12 per kilo. SUCCINIC ACIDS 371 malic and tartaric acids, by means of hydriodic acid ; heating of ethyl ethanetricarboxylate above its melting-point : CO^H Various alkylsuccinic acids are obtained by syntheses with ethyl malonate. HOMOLOGUES OF SUCCINIC ACID Kama of Acid Composition of acid V-'-' -- -.'- - of acid Melting point of 1 the anhydride ^ Methylsuccinic ..... C 5 HA 112 37 Ethylsuccinie ...... CgH 10 O 4 99 Liquid symm. Dimethylsuccinic (fumaroid) . C 6 H 10 O 4 209 43 (maleinoid) . C 6 H 10 4 129 91 asymm. .... CjHjA 140-141 31 Propylsuccinic ..... C 7 H 12 O 4 91 Liquid Isopropylsuccinic ..... CjH u 4 114 symm. Methylethylsuccinic (fumaroid) C^A 180 (maleinoid) C^BjA 101-102 Liquid asymm. ... C^HjA 104 Trimethylsuccinic ..... C 7 H 12 4 152 38 Butylsuccinic ...... CgH 14 O 4 81 Isobutylsuccinic ..... CgHjA 109 Liquid symm. Methylpropylsuccinic (fumaroid) CgH 14 O 4 158-160 (maleinoid) . CgHjA 92-93 Methylisopropylsuccinic (fumaroid) CgHjA 174-175 ; 46 (maleinoid) CgH 14 O 4 125-126 Liquid Diethylsuccinic (fumaroid) CgH 14 O 4 189-190 (maleinoid) . CgH 14 O 4 129 asymm. .... CgH 14 O 4 86 oa-Dimethyl-a-ethylsuccinic CgHjA 139-140 Tetramethylsuccinic ; CgH 14 O 4 Mf 147 Isoamylsuccinic ..... CgHjA 75-76 n-Hexylsuccinic ..... C 10 H 18 O 4 87 57 symm. Dipropylsuccinic (fumaroid) . C 10 H 18 4 182-183 Liquid (maleinoid) . C 10 H 18 4 119-12r H n-Heptylsuccinic ..... CU^^A 90-91 symrn. Difsobutylsuccinic (fumaroid) C 12 H 22 O 4 195 Liquid (maleinoid) CjaHgA 97-98 Tetraethylsuccinic ..... C 12 H 22 O 4 149 86 Tetrapropylsuccinic . . . . C 'l6 H 304 137 Pure succinic acid crystallises in monoclinic plates, m.-pt. 182, b.-pt. 235, having a disagreeable acid taste. When subjected to distillation, it loses water and yields succinic anhydride. Its solubility in water is 1 : 20 at the ordinary temperature, and it is highly resistant to the action of oxidising agents. Calcium succinate is soluble in water ; ferric succinale is used in the estimation of iron. (6) ISOSUCCINIC ACID (Ethylidenesuccinic or Methylpropandioic Acid^, CO H CH 3 CH<^p_. 2 TT, forms needles or prisms which melt at 130 : with evolution of CO 2 and formation of propionic acid. It is more soluble in water than its isomeride, but yields no anhydride. It is obtained by synthesis from ethyl malonate, or by treatment of a-bromopropionic acid with KCX and subsequent hydrolysis. 2Na CH<2 + CH 2 I 2 = 2NaI + CH 2 CH 2 = 2C0 2 372 ORGANIC CHEMISTRY PYROTARTARIC ACIDS, C 5 H 8 O 4 (Four Isomerides) (a) GLUTARIC ACID (Normal Pyrotartaric or Pentadioic Acid), C0 2 H CH 2 CH 2 CH 2 CO 2 H, forms crystals melting at 97'5 and is readily soluble in water. It is obtained from 1 mol. of methylene iodide and 2 mols. of ethyl sodiomalonate, the intermediate product being hydrolysed and 2 mols. of C0 2 then eliminated by heating : /-m ^ _ . C0 2 * C 2 H 5 j ' C 2 H 5 c*c\ r* TI <^2 ^2 n 5 CH 2 C0 2 H CH 2 P*TT C*f\ TI v^-tL 2 Uwtjil Glutaric acid p (b) PYROTARTARIC ACID (Methylbutandioic Acid), C0 2 H CH 2 CH CO 2 H CH 3 is formed, together with pyruvic acid, when ordinary tartaric acid is subjected to dry distillation; synthetically it is prepared from ethyl acetoacetate. It forms small tri clinic crystals melting at 117 and its anhydride is known. Since it contains an asymmetric carbon atom, it exists in two optically active stereoisomerides . HIGHER HOMOLOGUES The dialkylsuccinic acids (see above) contain two asymmetric carbon atoms and give rise to important cases of stereoisomerism. Together with the horno- logues of glutaric and adipic acids, they are found among the products of decom- position of the terpenes and hence serve to establish the composition of these. /3-METHYLADIPIC ACID, C0 2 H CH 2 CH(CH 3 ) CH 2 CH 2 C0 2 H, melts at 85 and occurs along with menthol, etc., in the oxidation products of numerous ethereal oils. SUBERIC ACID (Octandioic Acid), C0 2 H [CH 2 ] 6 C0 2 H, is obtained by boiling cork waste or fatty oils with nitric acid ; it melts at 141 and its anhydride at 62, while its ethyl ester boils at 281. Distillation of the calcium salt yields suberone (ketoheptamethy- lene). AZELAIC ACID, C0 2 H [CH 2 ] 7 CO 2 H,is now obtained easily and cheaply by decom- posing the ozonides of oils and of the corresponding unsaturated fatty acids, especially of oleic acid (E. Molinari, Soncini, and Fenaroli, 1906-1908). The acid oiiginally cost 24 per kilo, but can now be sold for a few shillings. -It is obtained well crystallised from benzene or from water, in which it dissolves easily in the hot but only slightly in. the cold (1-648 per cent, at 55, "0-817 per cent, at 44-5, 0-214 per cent, at 22, and 0-212 per cent, at 15); it is soluble also in alcohol or ether, melts at 106, and gives a calcium salt which dissolves in cold but not in hot water. SEBACIC ACID (Decandioic Acid), CO 2 H [CH 2 ] 8 CO 2 H, melts at 133 and is formed when oleic acid is dry-distilled or when stearic or ricinoleic acid is oxidised with nitric acid. Its anhydride melts at 78 and its diethyl ester boils at 196. Sebacic acid is now used industrially for the separation of thorium from the rare earths (see Vol. I., p. 505). OLEFINEDICARBOXYLIC ACIDS 373 HIGHER HOMOLOGUES OF OLEFINEDICARBOXYLIC ACIDS Name of Acid Structure Melting-point of acid Melting-point of the anhydride Boiling-point of the anhydride Dimethylfumaric (a-methyl- mesaconic) CH, CX : CX OH, 239-240 Ethylfumaric (y-methylmesa conic) CH, OH, OX : CHX 194-196 Ethylmaleic (y-methylcitra conic) CH, CH, OX : CHX 100 Liquid 229 a-Methylitaconic . CH, : OX OHX CH, 150-151 8 62-63 . . y-Methylitaconic . OH, OH : CX CH,X 166-167 Propylfumaric CH, CH 2 CH, CX : CHX 174-175 . . Propylmaleic OH, CH, CH, CX : CHX 93-95 243-245 y-Ethylitaconic CH, OH, OH : CX OH 2 X 162-167 Allylsuccinic Isopropylfumaric . CH, : CH CH, CHX CH,X (CH 8 ),OH CX : OHX 92-93 185-186 Liquid About 20 Isopropylmaleic . (CH 8 ) 2 CH CX : CHX 91-93 + 5 138 (61 mm ) yy-Dimethylitaconic (te aconi ) /pTT \ r~i . p"V" . pTT "Y" 160 161 44 197 (22 mm.) y-Methylene-y-methylpj ro- tartaric CH, : C(CH 3 ) OHX CH,X 146-147 Liquid - . Methylethylmaleic CH, CH, OX : CX CH, ,, 230 a-Ethylitaconic OH, : CX CHX CH 2 CH, 150 52 ay-Dimethylitaconic OH, CH : CX CHX CH, 202 Liquid 131 (16 mm.) aa-Dimethylitaconic OH, : OX OX(CH,), 142-5 210-215 Butylfumaric 0,H 6 CH, CH, CX : CHX 170 Butylmaleic . 2 H S CH, CH. CX : OHX 80 . y-Propylitaconic . CjHs CH 2 CH : CX CH 2 X 159-160 . . Isobutylfumaric . (CH,) 2 CH OH, CX : CHX 183 Isobutylmaleic (CH 3 ) 2 CH CH 2 OX : OHX 78-81 y-Isopropylitaconic (OH 8 \CH OH : OX CH,X 189-192 . . Methylpropylmaleic Methylisopropylmaleic CH, OH, OH, OX : OX CH. (CH,),CH CX : OX CH, Liquid 241-242 240-242 Diethylmaleic y-Methyl-a-ethylitaconic 0,H, OX : CX 2 H 6 CH, CH : CX OHX 2 H 6 136 " 239-240 143 (12 mm.) CHO Fumaric acid 444 B. UNSATURATED DIBASIC ACIDS I. OLEFINEDICARBOXYLIC ACIDS, C n H 2n _ 4 O 4 C0 2 H-CH CH CO..H C 6 H 8 4 C C H C O Maleic acid Mesaconic acid Citraconic acid Itaconic acid Glutaconic acid . Pyrocinchonic acid HC C0 2 H HC C0 2 H C0 2 H C CH 3 CH CO 2 H CH, C CO,H x . CH-C0 2 H CH 2 : C C0 2 H CH 2 CO 2 H C0 2 H CH : CH CH 2 CO 2 H CH 3 C C0 2 H melts at 200 (sublimes) 130 boils at 160 202 91 161 132 CH 3 C C0 2 H Pyrocinchonic an- hydride CH, C CO o CH, C CO' C 6 H 8 O 4 a/3-Hydromucic acid CO 2 H CH 2 CH 2 CH : CH C0 2 H 96 boils at 223 169 (stable) C0 2 H CH 2 CH : CH CH 2 CO 2 H 195 (labile) As far as the carboxyl groups are concerned, these acids have chemical properties similar to those of the saturated dibasic acids (see p. 364), whilst, as they are unsaturated compounds, they are able to combine with 2 atoms of hydrogen or halogen or with 1 mol. of a halogen hydracid. 374 ORGANIC CHEMISTRY They are usually prepared from the mono- and di-halogen substitution products of succinic acid and its homologues by removing either 1 mol. of halogen hydracid (by heating with KOH) or 2 atoms of halogen : CH 2 CO 2 H HBr + CO 2 H CH I - II CHBr C0 2 H CH C0 2 H Monobromosuccinic acid Fumaric acid Distillation of the saturated dibasic hydroxy-acids results in the removal of 1 mol. of H 2 O and the formation of unsaturated acids. The most interesting cases of stereoisomerism were considered on p. 21. When fumaric acid is either heated or treated with PC1 5 , POC1 3 , or P 2 O 5 , it is converted into maleic anhydride. Maleic acid is transformed into fumaric acid by heating at 200 in a sealed tube or by the action of bromine or of various acids in presence of sunlight. FUMARIC ACID (trans-Butendioic Acid), C 4 H 4 4 or C0 2 H CH, II HC CO 2 H forms small white prisms which have a marked acid taste and are almost insoluble in water; it does not melt, but sublimes at about 200, subsequently losing water and becoming converted largely into maleic anhydride. It is moderately widespread in certain vegetable organisms, e. g., in fungi, truffles, Iceland moss, and especially in Fumaria officinalis. It may be pre- pared by the ordinary synthetical methods and also by the action of phosphorus and bromine on succinic acid, the product obtained being decomposed by heating with water. It is stereoisomeric with maleic acid (see p. 22) and its reduction to normal succinic acid by means of nascent hydrogen confirms its constitution, which is also deduced from the decomposition of the corresponding ozonide (Harries). The Silver Salt, C 4 H 2 O 4 Ag 2 , is slightly soluble in water, and the same is the case with the barium salt, C 4 H 2 4 Ba + 3H 2 O, which in boiling water becomes insoluble and separates in the anhydrous form, C 4 H 2 O 4 Ba. MALEIC ACID (cis-Butendioic Acid), C 4 H 4 O 4 or CH CO 2 H, forms large CH C0 2 H prisms melting at 130 and having an unpleasant taste ; it boils at 160, losing water and becoming converted partially into maleic anhydride. It is readily soluble in water. . Its ready transformation into maleic anhydride is explained by the stereo- chemical relations considered on pp. 21 et seq., and in many general methods of preparing the acid, the anhydride is first obtained. The Barium Salt, C 4 H 2 4 Ba + H 2 O, is soluble in hot water, from which it crystallises well. Electrolysis of the alkali salts of fumaric and maleic acids yields acetylene. When heated with sodium hydroxide at 100, these two acids are converted into inactive malic acid. ITACONIC ACID (Methylenesuccinic Acid), C 5 H 6 O 4 or CH 2 : C C0 2 H, is a white CH 2 C0 2 H substance melting at 161 and non-volatile in steam. It is obtained by the action of water on its anhydride, the latter being formed by the interaction of citraconic anhydride and water at 150. Hydrogen converts it into pyrotartaric acid and permanganate into hydroxyparaconic acid. On electrolysis it yields allene, CH 2 : C : CH 2 . MESACONIC ACID (Methylfumaric Acid), C 5 H 6 O 4 or CO 2 H C CH 3 , is formed by II HC CO,H GLUTACONICACID 375 heating citraconic or itaconic acid with water at 200 or by treatment of citraconic acid with dilute HNO 3 or concentrated NaOH, or with traces of bromine in sunlight. It is difficultly soluble in water, melts at 202, and does not distil in steam. When electrolysed it forms allylene, CH 3 C | CH, while with hydrogen it gives pyrotartaric acid and with permanganate, pyrotartaric and oxalic acids. It forms a barium salt, C 5 H 4 O 4 Ba + 4H O. CITRACONIC ACID (Methylmaleic Acid), C 5 H 6 4 or CH 3 C CO 2 H, is formed from II HC CO 2 H the corresponding anhydride and water. It melts at 91, differs from the two preceding acids by being very soluble in water, distils in steam and readily gives the anhydride again. On electrolysis it yields allylene, while with hydrogen it forms pyrotartaric acid. GLUTACONIC ACID, C 5 H 6 O 4 or C0 2 H CH : CH CH 2 CO 2 H, is isomeric with the three preceding acids, and is obtained by hydrolysing the corresponding ester with HC1 ; it melts at 132 and the hydrogen of its CH 2 - group is replaceable by sodium (see p. 368). Of the higher homologues of these acids mention may be made of the alkylitaconic acids, with which, on heating with NaOH solution, the position of the double linking changes, gives alkylmesaconic and alkylaticonic acids (Fittig), e. g., isobutylaticonic acid, (CH 3 ) 2 CH CH : CH CH(C0 2 H) CH 2 C0 2 H, which melts at 93 ; with alkalis these acids undergo the reverse change to some extent. The calcium and barium salts of the alkylmesaconic acids are readily soluble in water, and those of the alkylitaconic acids slightly soluble. Of these homologous acids, the following deserve mention : PYROCINCHONIC ACID (Dimethylmaleic or Dimethylfumaric Acid), C 6 H 8 O 4 or CO 2 H C = C CO 2 H. Of the two stereoisomerides, only dimethylmaleic acid was until CH 3 CH 3 recently known, and then only as the anhydride, namely, pyrocinchonic anhydride (m.-pt. 96, bi-pt. 223). Dimethylmaleic acid cannot exist in the free state, as it immediately gives up water, forming the anhydride ; its esters are, however, known. CH 3 C COv The anhydride, M), may be prepared in various ways, e. g., by distilling in CH 3 C CO/ steam the product of the interaction of pyrotartaric acid and sodium succinate, but a better yield is obtained by first preparing the nitrile of methylacetoacetic acid and distilling this in a vacuum. According to A. Bischoff, the stereoisomeride, Dimethylfumaric Acid, CH 3 C C0 2 H. C0 2 H C CH 3 could not, owing to stereochemical considerations, be formed in the free state, but Fittig and Kettner (1899) and also E. Molinari (1900) have succeeded in isolating it in various ways. 1 It forms white crystals, m.-pt. 152 ; its amido-derivatives have also been prepared. Bauer (1904) made the interesting observation that dimethylfumaric acid and, in general, compounds containing carboxyl or alkyl or phenyl groups or bromine atoms united to two carbon atoms connected by a double linking, do not unite with bromine. 1 Fittig and Kettner, making use of the property of various acids, homologous with citraconic acid, of. yielding the corresponding fumaroid isomeride when simply heated with alkali, obtained from yrocinchonic anhydride the two acids : one melting at 151, to which is ascribed the constitution H a : G C0 2 H (&-methylitaconic acid), and another melting at 240 and regarded as CH 3 C C0 2 H p C CH; CH C0 2 H C0 2 H C CH 3 (dimethylfumaric acid). It is highly probable, for the following reasons, that the latter constitu- tion should be attributed to the acid melting at 151 : By a long series of investigations (1881 to 1896), Korner and Menozzi showed that, in general, the treatment of a-amino*acids with methyl iodide in presence of caustic potash yields the corresponding betaines (condensed alkyl-substituted amines), but the fi-amino-acids, if similarly treated, always yield the corresponding unsaturated, non-nitrogenous acids of the fumaroid type (betaines being probably formed as intermediate products). As the same &-amino-acid can be obtained from the two stereoisomeric unsaturated acids, this general reaction renders it possible to pass from a maleinoid unsaturated acid to the corresponding fumaroid stereoisomeride. By applying this reaction to pyrocinchonic anhydride, E. Molinari arrived at the expected stereoisomeride (dimethylfumaric acid), melting at 152. 376 ORGANIC CHEMISTRY HYDROMUCONIC ACIDS, C 6 H g O 4 . Of these are known ( 1 ) the a^-unsaturated acid, C0 2 H CH 2 CH 2 CH : CH CO 2 H, which is stable and melts at 169 ; with permanganate S y ft a it yields succinic acid. (2) The unstable y-acid, C0 2 H CH 2 CH : CH CH 2 C0 2 H, which melts at 195 and is obtained by reducing muconic acid; when heated with alkali, it is converted into the stable isomeride, whilst with permanganate it gives malonic acid, C0 2 H CH 2 C0 2 H. Of the DIOLEFINEDICARBOXYLIC ACIDS, only Muconic Acid, CO 2 H CH . CH CH : CH CO 2 H, melting above 260, need be referred to. Of the ACETYLENEDICARBOXYLIC ACIDS, mention will be made only of Acetylenedicarboxylic (Butindioic) Acid, C0 2 H C C C0 2 H, which melts and decomposes at 175; it crystallises with 2H 2 O. It is obtained on removing HBr from dibromo- or isodibromo-succinic acid by means of potash. Diacetylenedicarboxylic Acid, CO 2 H C : C C : C CO 2 H + H 2 O, turns dark red in the light and explodes at 177. When reduced with sodium amalgam, it yields hydro- muconic acid. Tetracetylenedicarboxylic Acid, CO 2 H -C:C-C:C-CiC-C:C- C0 2 H, forms white crystals which blacken rapidly in the light and explode violently on heating. C. TRIBASIC ACIDS These have usually been obtained synthetically, and are not very stable, since they readily yield carbon dioxide and dibasic acids when heated ; their esters, however, exhibit increased stability. Their properties and methods of preparation vary according as the carboxyl groups are united to one or to various carbon atoms. Of the many such acids known, the following may be mentioned : TRICARBALLYLIC ACID (symm. wato'-Propanetricarboxylic or Pentanedioic-3- methyloic Acid) CH 2 . CO 2 H, occurs in the deposits left on concentrating beet-sugar juices CH CO 2 H CH 2 C0 2 H in vacuo. Synthetically it is obtained by converting glycerol into the tribromohydrin or allyl tribromide, which is treated with potassium cyanide to give the corresponding tricyano-compound, the latter being then hydrolysed to tricarballylic acid; the con- stitution of the acid is thus proved. This acid forms white, prismatic crystals melting at 166. It may also be prepared by reducing unsaturated tricar boxylic acids (e. g., aconitic acid ). C0 2 H C0 2 H C0 2 H CAMPHORONIC ACID (aa^-Trimethylcarballylic Acid), CH 3 C C CH 2 CH 3 CH 3 is formed on oxidising camphor, of which it serves to indicate the constitution ; it melts at 135. ACONITIC ACID is an unsaturated tribasic acid of the constitution CO 2 H CH 2 C(C0 2 H) : CH C0 2 H, and is found in beetroot, sugar-cane, Aconitum napellus, etc. It is obtained synthetically by eliminating C0 2 from citric acid by the action of heat or of various reagents. It melts at 191, losing CO 2 , and forming itaconic anhydride. It dissolves readily in water and with nascent hydrogen generates tricarballylic acid, its structure being indicated by this reaction. D. TETRABASIC ACIDS These are formed from ethyl sodiomalonate (see p. 368) by means of an unsaturated ester, e. g., of fumaric acid. When heated, they lose C0 2 , forming tribasic and, better, dibasic acids. Olefinetetracarboxylic Acids are also known. HALOGENATED ACIDS 377 FF. DERIVATIVES OF THE ACIDS I. HALOGEN DERIVATIVES One or more of the hydrogen atoms of an alkyl group united with carboxyl may be replaced by halogens, the carboxyl group being left intact. The halogen derivatives of the acids, thus obtained, are more markedly acid in character than the original substances. They are obtained by the action of chlorine or bromine in sunlight or, better, by heating the acid with the halogen in presence of a little water or sulphur. On the other hand, the hydroxyl of the carboxyl group may be replaced, forming acid halides : CO X (by treating the acid with phosphorus chloride or bromide). That the halogen has replaced the hydroxyl group is shown by the fact that these acid halides yield the original acids when treated with cold water, whilst halogens are not displaced from alkyl residues in this way. These acid chlorides and bromides readily give the monochloro- and mono- bromo- acids when treated further with chlorine or bromine. (a) HALOGENATED ACIDS When the carbon atom (a), to which the carboxyl group is attached, is not united directly with hydrogen [e. g., in trimethylacetic acid, (CH 3 ) 3 C C0 2 H], bromine is not taken up (see p. 375). The constitution of a halogenated acid, or rather the position of the halogen atom, is deduced from that of the corre- sponding hydrpxy-acid (containing a hydroxyl group in place of the halogen) obtained by heating the halogenated acid with sodium carbonate solution or with water and lead oxide. On the other hand, the passage from hydroxy-acid to the corresponding halogenated acid may be effected by treatment with phosphorus chloride or bromide. The acid character becomes more marked on passing from the iodo- to the bromo- and then to the chloro-compounds, and also increases with the number of'halogen atoms in the molecule. While the a-halogenated acids readily yield the corresponding hydroxy- acids, the /S-acids yield the corresponding unsaturated acids (see p. 352) and may even lose C0 2 , giving unsaturated hydrocarbons, but the y-halogenated acids, when heated with sodium carbonate solution or with water alone, give up a molecule of halogen hydracid and yield, not the unsaturated acids, but lactones (see p. 355). When halogenated acids are prepared by the interaction of an unsaturated acid with a halogen hydracid (e. g., HI), the halogen becomes attached to the least hydrogenated carbon atom (see p. 116). Thus, with a zl^-acid, where the double linking is between the a- and /3-carbon atoms, the halogen unites with the latter. The halogenated and poly-halogenated acids exhibit isomerism, since the halogen atom may be joined to the a, /3, y, etc., carbon atom, or several halogen atoms may be united with one and the same carbon atom or with different ones. When heated with potassium cyanide, the mono-haloid acids yield cyano- acids : CH 2 C1 COOK -f KCN = KCL+ CN CH 2 COOK. Potassium chloroacetate Potassium cyanoacetate With sodium sulphite they give dibasic sulpho-acids, the sulphonic group of which is readily replaced by hydroxyl by boiling with alkali : Na 2 S0 3 + Cl CH 2 COONa = NaCl + S0 3 Na CH 2 COONa Sodium sulphoacetate With reference to the affinities of the halogenated acids, see Note on p. 323. 378 ORGANIC CHEMISTRY i^-Siij o -g PJ, | _C5 CO o ft i I W cs o rS ^ w i r& o O +3 ^ _> ^H T'i| 'S' ^ . 'C *-i. o S o 8 a M ^. 6 1 M i> cS W 'eg ^2 F o '-f " o J 3 _ a r + fl r^ 1 "3 -$ 3 o g "^ "^ McS . IN o e ^ " o ^1 1 | : _o ^ " N - i c 1C Q, 1 d*jl HH >. 05 jd '3 c O 03 gs ^ .In Q 1 Q TJ 1 M >> 'I 1 I be a C! _O 1 i O J3 rt 5 ^ '* Q H H bc3 Cl is g-a ^' rt Gives malonii 3 W 2 + 3 fi |t From propion 1 O /3-Bromoacryl _0 o ^> 1 a 1 49 Q ft o o o o I 1 lO i CO 00 o I 1 00 S Oi O5 1 00 ^^ 00 I 1 10 .y i^ p i P- 1 O o 1 o- R o o V [ [ |H Wo o . rrj ' hH IN O HH ' o ^ ' ^ M jj ' 'eo ^ 5 8 o W o S W o W o W o WWW O O ACIDHALIDES 379 MONOCHLORACETIC ACID (Chlorethanoic Acid), CH 2 C1 COOH, is prepared by the general method, that is, by passing dry chlorine into hot acetic acid in presence of acetic anhydride, phosphorus, or sulphur (with 1 per cent, of sulphur, an 80 per cent, yield is obtained). It forms rhombic crystals which corrode the flesh and melt at 62; on solidification an unstable modification is obtained which, for some time, melts at 52; it boils at 186. When heated with water or alkali it gives Hydroxyacetic Acid (glycollic acid), OH CH 2 CO 2 H; with ammonia it yields Aminoacetic Acid (glycine or glycocoll), NH 2 CH 2 C0 H. & & t The properties of the other halogenated acids are given in the Table on the preceding page. (b) ACID HALIDES Of these compounds the most important are the chlorides of the acid radicals, which are termed acichlorides or chloranhydrides. Although acetyl chloride, CH 3 CO ' Cl, is readily obtainable, it has not been found possible to prepare formyl chloride, H CO Cl, a mixture of CO + HC1 being always obtained. These compounds are usually colourless liquids, which have pungent odours and fume strongly in the air, the moisture in the latter liberating hydrogen chloride. Their boiling-points are below those of the corresponding acids, and they distil without decomposing; the higher members are, however, solid and do not distil unchanged even in a vacuum. The principal methods for preparing these substances are as follows : (a) The organic acid is heated for a short time on the water-bath with PC1 5 (with higher acids), PC1 3 (with acids below C 10 ) or, in some cases, sulphuryl chloride, S0 2 C1 2 : C n H 23 CO OH + PC1 5 = C U H 23 CO Cl + HC1 + POC1 3 , Laurie acid the phosphorus oxychloride and hydrochloric acid being eliminated by dis- tillation in vacuo ; or, 3CH 3 CO OH + 2PC1 3 = 3CH 3 CO Cl -f 3HC1 + P 2 3 , the acetyl chloride thus formed being separated by distillation, .while the P 2 3 is left in the residue. (b) With thionyl chloride the acids yield the chloranhydrides, the other products formed at the same time being volatile and hence easily removable : X CO OH + SOC1 2 = X CO Cl + HC1 + SO 2 . (c) In some cases the acid is treated simply with HC1 in presence of a dehydrating agent, (P 2 5 ) : CH 3 CO OH + HC1 = H 2 + CH 3 CO Cl. CHEMICAL PROPERTIES. The great reactivity of the chlorine atom of these substances renders them of considerable importance in chemical syntheses. Water, ammonia (amines), and alcohols decompose them in the cold with great violence : CH 3 CO Cl + H 2 O = HC1 + CH 3 CO OH CH 3 CO Cl + NH 3 = HC1 + CH 3 CO NH 2 (acetamide) CH 3 CO Cl + C 2 H 5 OH = HC1 + CH 3 CO OC 2 H 5 (ethyl acetate). With organic salts they yield anhydrides : CH 3 CO Cl + CH 3 CO ONa = NaCl -f CH 3 CO O CO CH 3 . Sodium amalgam reduces them to aldehydes and then to alcohols. ACETYL CHLORIDE (Ethanoyl Chloride), CH 3 CO Cl, is a liquid boiling at 51 and having the sp. gr. 1-105 at 20. It is prepared by mixing 5 parts of glacial acetic acid and 4 parts of phosphorus trichloride in the cold, heating for a short time at 40 and, 380 ORGANIC CHEMISTRY after evolution of HC1 ceases, distilling the acetyl chloride and purifying it by rectification. Water decomposes it with development of heat. It is employed in organic synthesis, since it readily yields acetyl derivatives of alcohols and of primary and secondary amines. The commercial product costs 3s. to 4s. per kilo, and the chemically pure 14s. The boiling-points of the higher homologues of acetyl chloride rise with the molecular weight and, with isomerides, that with the normal constitution has the highest boiling- point; the specific gravity diminishes as the molecular weight increases. Acetyl iodide boils at 108, propionyl chloride at 108 (the bromide at 104 and the iodide at 127); normal butyryl chloride boils at 101 (the bromide at 128 and the iodide at 146) and isobutyryl chloride at 92 (the bromide at 116); isovaleryl chloride boils at 114 (the bromide at 143 and the iodide at 168) and trimethylacetyl chloride, (CH 3 ) 3 C-CO-Cl i at 105. II. ANHYDRIDES The anhydrides of organic acids were discovered by C. Gerhardt in 1851 and correspond with those of the inorganic acids, that is, they may be regarded as products of the condensation of 2 mols. of acid with expulsion of 1 mol. of water. Here also, the organic anhydrides, when they are at all soluble, take up water and regenerate the acids. With organic acids, however, more varied and interesting cases are presented, since 2 mols. of different acids may condense (mixed anhydrides), while internal anhydrides may be formed by condensation between the two carboxyl groups of a dibasic acid. The anhydrides may be regarded also as oxides of acid radicals, e. g., acetic /-ITT . rir\ anhydride, prr 3 . pry>O, or acetyl oxide, (CH 3 C0) 2 0. 3 PROPERTIES. The first members of the series are liquid, the higher ones solid ; they generally dissolve but slightly in water, their transformation into acids being very slow. They have a neutral reaction and are soluble in ether and often in alcohol. With ammonia and the primary and secondary amines, they form amides and ammoniacal salts : (CH 3 CO) 2 O + 2NH 3 = CH 3 CO NH 2 (acetamide) + CH 3 CO ONH 4 (ammonium acetate). When heated with an alcohol, they give the corresponding ester and acid : (CH 3 CO) 2 + C 2 H 5 OH = CH 3 COOC 2 H 5 -f CH 3 COOH. With halogen hydracids in the hot they yield the halides of the acids and the free acids : (CH 3 CO) 2 + HC1 = CH 3 CO Cl + CH 3 COOH. With the halogens they give acid halides and halogenated acids : (CH 3 CO) 2 O + C1 2 = CH 3 CO Cl + CH 2 C1 C0 2 H. Aldehydes combine with anhydrides, forming esters, while sodium amalgam reduces anhydrides to aldehydes and alcohols. GENERAL METHODS OF PREPARATION, (a) By the action of acid chlorides on the dry alkali salts of the corresponding acids : CH 3 CO Cl + CH 3 COONa = NaCl + j* '. ^Q>O. (b) The same result is obtained by the action of phosphorus oxychloride (or phosgene, COC1 2 ) on a mixture of the alkali and alkaline-earth salts of the corresponding acid, the acid chloride being formed as an intermediate product. (c) The higher anhydrides are obtained from the corresponding acids by the action of acetyl chloride : CH 3 COC1 -f 2X COOH = HC1 + CH 3 COOH + (X C0) 2 0. ACETIC ANHYDRIDE 381 (d) The formation of anhydrides from the acids by the subtraction of water (by means of P 2 5 ) gives low yields, the best being obtained with palmitic and stearic acids (using acetic anhydride in the hot as dehydrating agent). The properties of the best-known anhydrides are given in the following Table : Formula Name Melting- point Boiling-point Specific gravity (CH 3 -C0) 2 Acetic anhydride . . 136-5 1-078 (at 21) (C 2 H 5 -CO) 2 Propionic anhydride 168-6 1-034 (atO) (C 3 H 7 -CO) 2 norm. Butyric anhydride 192 0-978 (at 12-5) Isobutyric anhydride 182 0-958 (at 16-5) (C 4 H 9 -CO) 2 Isovaleric anhydride 215 Trimethylacetic anhydride 190 (C 5 H n -CO) 2 norm. Caproic anhydride 242 0-928 (at 17) C 6 H 13 -C0) 2 CEnanthic anhydride + 17 257 0-912 (at 17) (C 7 H 15 -CO) 2 Caprylic anhydride - 1 186 (15mm.) (C 8 H 17 -CO) 2 Pelargonic anhydride + 16 207 (CuH 2 3-CO) a O Laurie anhydride . .1+41 166 (vacuum) (C 13 H 27 -CO) 2 Myristic anhydride . . +51 198 (C 15 H 31 -CO) 2 Palmitic anhydride 55-66 (C 17 H 35 -CO) 2 Stearic anhydride . . 72 ACETIC ANHYDRIDE (Ethanoic Anhydride), (CH 3 CO) 2 O, is of importance industrially owing to its use in many organic syntheses, as it readily gives acetyl derivatives with alcohols or with primary or secondary amines. It is a suitable reagent for determining how many hydro xyl groups an organic substance contains (see Acetyl Number, p. 224). The largest industrial consumption of acetic anhydride is for making acetylcellulose used for non-inflammable cinematograph films and for aeroplane dope ; its use for artificial silk is also anticipated (see : Textile fibres). Large quantities of the anhydride are likewise employed in making organic dyes, perfumes and drugs. It is a colourless, very mobile liquid, b.-pt. 139-5, sp. gr. 1-078 at 21 and 1-0876 at 15, index of refraction 1-39069 at 15; it has a pungent odour. It dissolves without alteration in 10 parts of cold water and is converted into acetic acid only when heated, the last portions only on prolonged boiling. 1 It is prepared by dropping 5 parts of acetyl chloride on to 7 parts of dry powdered sodium acetate, which is kept cool meanwhile. The mixture is subsequently gently heated for a short time and the anhydride then distilled off on a sand-bath. The commonest method of preparing it industrially appears to be that utilising the 1 Since commercial acetic anhydride often contains considerable proportions of acetic acid (10 to 25 per cent.), determination of its strength by titration requires the following precautions : A weighed quantity (about 0-5 gram) of the anhydride is introduced into a flask containing N 100 c.c. of clear baryta water of known titre (corresponding, for example, with 94 c.c. of lf . HC1), the liquid being then boiled for about half an hour under a reflux condenser fitted with a soda- lime tube to prevent access of C0 2 . It is then allowed to cool somewhat, the excess of baryta being rapidly titrated with decinormal hydrochloric acid in presence of a drop of phenolphthalein. Another method of hydrolysing the acetic anhydride consists in boiling it as above for forty-five minutes with at least 100 times its weight of freshly-boiled water (free from CO..) ; the cold liquid is then titrated with decinormal caustic soda in presence of phenolphthalein. The acidity is calculated as though it were all due to acetic acid, the excess of the resulting percentage over 100 being multiplied by 5-67 to give the percentage of acetic anhydride in the sample analysed ; subtraction of this number from 100 gives the percentage of acetic acid present. Thus, if the titration indicates 115-86 per cent, of acetic acid, the percentage of acetic anhydride will be 15-86 X 5-67 = 89-92 and that of acetic acid, 100 89-92 = 10-08. sulpl Sulphurous anhydride present (rarely) as impurity is determined by means of iodine solution, phuric acid by barium chloride, and hydrochloric acid by decinormal silver nitrate solution with potassium chromate as indicator. 382 ORGANIC CHEMISTRY reaction between sodium acetate and sulphuryl chloride l (see Vol. I., p. 330), which, occurs in two phases : 2CH 3 C0 2 Na + S0 2 C1 2 = Na 2 S0 4 + 2CH 3 CO Cl CH 3 CO 01 + CH 3 C0 2 Na = NaCl + (C 2 H 3 0) 2 O. In practice rather more than the theoretical quantity of sodium acetate is used, and all the operations are carried out in closed vessels to prevent access of moisture and loss of sulphuryl chloride with its unpleasant odour. The sodium acetate should previously- be dried at 140 to reduce the moisture content to 0-1 per cent., and the sulphuryl chloride used should distil to the extent of 92 per cent, between 68 and 69-5 and should have the sp. gr. 1-675. Fig. 253 represents a scheme for an acetic anhydride works : The sodium acetate is subjected to preliminary heating in 1 and is then dried completely in three vacuum vessels below (2d, 26, 2c), the suction pump being at 10. The perfectly dry salt is distributed in several apparatus fitted with stirrers on the ground-floor (3a-3gr), the sulphuryl chloride being introduced from the tank 4 and measured in 4a-4gr. In order FIG. 253. t . that the temperature may not rise much, the sulphuryl chloride is fed gradually into each vessel, which is fitted with a small reflux condensing column. When the reaction is finished the different apparatus act as stills and are put into communication with the vacuum pump 10 through the collecting vessels Qa-Qg and the condensers for the crude acetic anhydride, 5a-5g ; 7 is the general collecting tank for the crude product, which contains about 90 per cent, of the anhydride, the remainder being acetic acid, acetyl chloride, sulphur dioxide and other secondary products. The anhydride is purified by distillation in a vacuum over anhydrous sodium acetate, followed by vacuum rectification (by means of pump 11) in a continuous column apparatus, 9-9rf; 0-3-1 per cent, of fuming nitric acid (U.S. Pat. 1,069,168, 1913) or ozonised air may be used in the purification. 1 Of the numerous patents for the industrial preparation of acetic anhydride, the following may be mentioned : treatment of sodium or calcium acetate with either sulphuryl chloride or phosphorus oxychloricle and C0 2 , or a mixture of C! and SOo (Ger. Pats. 161,882, 163,103, and 167,304, 1905) ; treatment of sodium acetate at 200 with silicon tetrafluoride (Ger. Pats. 171,787 and 171,146, 1906); Ger. Pats. 222,236 and 241,898 (Goldschmidt); Ger. Pats. 244,602 and 273,101 (Afga); Fr. Pat. 17,674, 1913, and Addition 448,342 (Dreyfus); action of S0 3 + CC1 4 on sodium or calcium acetate (U.S. Pat. 1,113,927, 1914). HYDROXY-ACIDS 383 During the European War synthetic acetic acid factories were erected in Great Britain, France and Italy (see p. 339), these making acetic anhydride. Before the war the price of the anhydride in Germany was for large parcels 4-5 per cwt., and for small amounts, up to 9; the chemically pure product cost 12. The anhydrides of di- and poly-basic acids are not of great importance and are con- sidered to some extent in dealing with the corresponding acids (succinic, pyrocinchonic, etc.); with water they yield the acids with moderate readiness (see pp. 365 and 375). III. HYDROXY-ACIDS A. SATURATED DIVALENT MONOBASIC ACIDS These may be regarded as derived from monobasic acids by the replacement of an atom of hydrogen (not that of the carboxyl group) by a hydroxyl group. These acids possess, at the same time, acidic and alcoholic characters and are hence termed divalent monobasic acids or divalent alcohol acids. The hydroxyl and the carboxyl groups may be substituted at the same time, the compounds then exhibiting the general properties of the acids and alcohols, in addition to new and special characters varying with the position occupied by the carboxyl relatively to the hydroxyl (see pp. 355 and 357). They are usually syrups, which may undergo crystallisation ; in comparison with the corresponding fatty acids, the hydroxy-acids are more soluble in water and in alcohol, but less soluble in ether. They do not distil unchanged and often lose water, forming anhydrides. GENERAL METHODS OF PREPARATION, (a) By oxidising dihydric alcohols so as to transform the primary alcoholic group into carboxyl. (6) By boiling unsaturated acids with sodium hydroxide, so that a molecule of water is added at the double bond. (c) By substituting the halogen of a monohalogenated monobasic acid by hydroxyl ; this is effected by treatment with KOH or with silver acetate, the diacetate formed in the latter case being hydrolysed by heating with sodium carbonate : CH 2 C1 COOH + H 2 O = OH CH 2 C0 2 H + HC1. Monochloracetic acid Glycollic acid (d) a-Hydroxy-acids are obtained by hydrolysing the nitriles formed on treating the aldehydes or ketones (having one atom of carbon less) with hydrocyanic acid : 2H 2 O = NH 3 + CH 3 CH(OH) COOH. Ethylidenecyanohydrin Glycolcyanohydrin, OH CH 2 CH 2 ON, yields ethylenelactic acid, OH CH 2 CH 2 COOH. (e) By the action of nitrous acid on amino-acids : COOH CH 2 NH 2 + NO OH = H 2 + N 2 + COOH CH 2 OH. Qlycocoll (/) By reducing aldehydic or ketonic acids : CH 3 CO COOH + H 2 = CH 3 CH(OH) COOH. Pyruvic acid Lactic acid (g) By oxidation of acids containing a tertiary carbon atom, > CH COOH, with permanganate. PROPERTIES AND CONSTITUTION. The constitutions of these acids can always be deduced from the syntheses indicated above. That they con- tain an alcoholic group is shown by the fact that the hydroxylic hydrogen may be replaced by an alkyl group, giving true non-hydrolysable ethers. Simi- larly the presence of a carboxyl group is shown by the formation of hydrolysable 384 ORGANIC CHEMISTRY esters. The isomerism exhibited is the same as with the haloid derivatives of the acids. The number of alcoholic hydroxyl groups is determined by the acetyl number (see p. 224). The reactivity, which corresponds with the dissociation constant, increases with the proximity of the hydroxyl to the carboxyl group. a-, /3-, 8-, and cZ-hydroxy-acids are distinguished also by the products resulting from the elimination of one or more molecules of water. Thus, a-hydroxy-acids, when heated, lose 2 mols. of H 2 O per 2 mols. of acid, the hydroxyl group of the one reacting with the carboxyl group of the other ; the compound formed is called a lactide and is a double ester, which yields the acid again on hydrolysis with hot water or dilute acid : CO - CH CH 3 COOH CH(OH) CH 3 | = 2H 2 O + 00 CH 3 CH(OH) COOH CH 3 -CH-CO 2 mols. Lactic acid Lactide Further, a-hydroxy-acids, if heated with sulphuric acid, yield the aldehydes or ketones from which they can originate (see above), formic acid being also formed. The /3-acids, however, lose only 1 mol. of water, giving unsaturated acids (see p. 352), while, when boiled with 10 per cent, potassium hydroxide solution, they give at the same time a/3- and ay-unsaturated acids a reversible reaction leading to a position of chemical equilibrium; when heated with sulphuric acid they form acids of the acrylic series. The y- and 8 -acids lose 1 mol. of water, yielding lactones (internal anhydrides): OH CH a CH 2 CH 2 COOH = H 2 + CH CH CH CO y-Hydroxybutyric acid o Butyrolactone which are almost always formed when attempts are made to liberate these hydroxy-acids from their salts. The lactones are neutral liquids soluble in water, alcohol, and ether; they distil unchanged and with alkali form the salts of the corresponding hydroxy-acids. When the hydroxy-acids are heated with hydrogen sulphide, they furnish the corresponding fatty acids. GLYCOLLIC ACID (Hydroxy acetic or Ethanoloic Acid), OH CH 2 COOH, crystal- lises in needles or plates melting at 80, and is soluble in water, alcohol, or ether. In nature it is found in immature eggs and in the leaves of the wild vine. It may be obtained by the general methods given above and also by oxidising alcohol or glycol with dilute nitric acid or by reducing oxalic a'cid with nascent hydrogen. 1 It is usually prepared by hydrolysing monochloracetic acid with KOH [general method (c)]. 1 Of some interest is the formation of the various anhydrides of glycollic acid, these being formed by the removal of 1 mol. of H 2 O from 2 mols. of the acid as follows : (1) From the two alcohol groups, giving a true ether with two free acid groups, OTT POOTT COOH' di $y collic acid > ni.-pt. 148 ; (2) from the two carboxyl groups ; this should give OTT OTT OO the anhydride of glycollic acid, QTT . X^- 2 . prp^' w ^ c h * s not 3^ ^ nown 5 (*) from one alcohol OTTT f (*TT OO and one acid group, giving a true ester, glycolglycottic acid, PQQJI 2 . njj ^*0. Also loss of 2H 2 from the two alcoholic and acidic groups gives either (1) Diglycollic anhydride (anhydride and ether at the same time), 0<^ 2 ] QQ>O (melting at 97 and boiling at 240), or, when each molecule of water separates from 1 alcoholic and 1 acidic group, (2) the isomeric glycollide, ' melfcin g at 86 - GLYCOCOLL 385 According to Ger. Pats. 194,038 and 204,787, glycollic acid is now prepared industrially by reducing oxalic acid electrolytically in the following manner : The cathodic liquid consists of a solution of 7 parts of crystallised oxalic acid in 33 parts of water and 1 1 parts of concentrated sulphuric acid, while the anodic liquid, separated by means of a diaphragm, is 30 per cent, sulphuric acid ; the electrodes are of lead and the current density 26-250 amperes per sq. metre of cathode surface. According to Ger. Pat. 257,878 (1912) the acid may be prepared also by heating, for eight to nine hours at 175 to 200 in an autoclave fitted with a stirrer, about 30 parts of trichloroethylene, 50 parts of quicklime, and 250 parts of water, with traces of copper salts as catalyst ; with caustic soda the reaction is more rapid : C 2 HC1 3 + 4NaOH = H 2 + 3NaCl + OH CH 2 CO 2 Na. Glycollic acid is now used with advantage to replace tartaric acid in textile printing, as it has a greater solvent action on tannates of dyestuffs, which hence penetrate the fabric better and give more stable colours without injuring the fibre. The ammonium salt of glycoilic acid serves to fix dyes on wool, while the aluminium and tin salts are used in alizarin and alizarin orange printing (1914). Glycollic acid forms a calcium salt, (OH CH 2 COO) 2 Ca -j- 3H 2 0, insoluble in water. The most important derivative of glycollic acid is GLYCOCOLL (Glycine or Aminoacetic or Aminoethanoic Acid), COOH CH 2 NH 2 , which is the first member of the amino-acid series so important to vegetable physiology. It is obtained, together with secondary products, by the action of concentrated ammonia solution on monochloracetic acid : CH 2 C1 COOH + 2NH 3 = NH 4 C1 + NH 2 CH 2 COOH. It is always formed in the decomposition of hippuric acid (benzoylglycocoll) with HC1, or by the action of acid or alkali on gelatine. It may also be obtained by the reduction of ethyl cyanocarboxylate by means of nascent hydrogen or from cyanogen and boiling hydriodic acid. Its homologues are prepared synthetically in various ways, e. g., by treating aldehyde- ammonias with hydrocyanic acid and hydrolysing the amino-cyanides thus obtained with HC1. Glycocoll crystallises in rhombic columns soluble in 4 parts of water but insoluble in alcohol or ether ; it has a sweetish taste and melts and decomposes at 230. The fact that the amino -group cannot be expelled by hydrolysis establishes the structure of glycocoll. It behaves as both acid and base, forming salts with acids and also with bases. Its copper salt separates in large, dark blue needles on dissolving cupric oxide in hot glycocoll solution : (C 2 H 4 2 N) 2 Cu -f H 2 O. With ferric chloride it gives an intense red coloration. When heated with baryta, it loses C0 2 , forming methylamine; with nitrous acid it gives glycoJlic acid. Various alkyl and other derivatives have been obtained synthetically from glycocoll : CH 2 NH COCH 3 CH 2 NH CH 3 CH 2 N(CH 3 ) 3 I ; I ; I I COOH COOH CO Aceturic acid Sarcosine Betaine (derived from caffeine and from creatine) (from the beet) With nitrous acid, the esters of glycocoll yield ETHYL DIAZOACETATE, N \ NH 2 CH 2 COO C 2 H 5 + HN0 2 = 2H 2 + || >CH COOC 2 H,, which is a W yellow oil boiling at 141 and readily decomposes and reacts with evolution of nitrogen ; it serves for the synthesis of pyrazole. LACTIC ACIDS, OH . C 2 H 4 . CO 2 H The two structural isomerides foreseen by theory are known: a- and /3-hydroxypropionic acids. Also the a-acid exists in two stereoisomeric VOL. IT. 25 386 ORGANIC CHEMISTRY forms (I laevo- and d = dextro-rotatory) owing to the presence of an asymmetric carbon atom (p. 19) and in an inactive form (i = inactive), con- sisting of a mixture in equal proportions of the two stereoisomerides. These lactic acids form anhydrides similar to those of glycollic acid (see above). The lactic acids give Uffelman's reaction, that is, they cause the amethyst- coloured solution obtained on adding a drop of ferric chloride to a dilute salicylic acid solution to turn yellow ; this reaction is given also by citric, oxalic, and the tartaric acids. (1) i-ETHYLIDENELACTIC ACID (I + d) (2-Propanoloic or a-Hydroxy- propionic Acid or Ordinary Lactic Acid of Fermentation), CH 3 CH(OH) COOH, is found in milk rendered acid by the action of the lactic acid bacillus (see Fig. 116, p. 145), in milk-sugar (also cane- and grape-sugars, gum, starch, etc.) which undergoes acid fermentation (lactic fermentation) even in absence of air, although oxygen facilitates the change. Cabbage fermented with vinegar and salt (Sauerkraut), gastric juice, putrefied cheese, fresh fodder siloed, and fermented muscular juices and the brain 1 also contain free lactic acid. When pure it melts at 18 and boils at 120 under 12 mm. pressure, but usually it forms a dense syrup soluble in water, alcohol, or ether. It is opti- cally inactive, as it consists of a racemic mixture of dextro- and laevo-acids (see p. 21). The two modifications may be separated by crystallisation of the strychnine salts or by cultivating in the solution Penicillium glaucum, which first destroys the laevo-acid (see p. 23). When heated, the active acid is transformed, to the extent of one-half, into the optical enantiomorph, so that the inactive racemic acid is obtained. If kept in a desiccator, it is partly converted into anhydride owing to loss of water. When distilled under reduced pressure, it yields water, carbon dioxide, and lactide (see above). If heated with dilute sulphuric acid it decomposes, like many other a-hydroxy-acids, into acetaldehyde and formic acid. PREPARATION. Of the various processes for the preparation of lactic acid, 2 only 1 It appears now to be proved that the lactic acid in the human organism is formed in proportion to the muscular and cerebral work, and, together with carbon dioxide, which is also a waste product of the cells of the organism during wakefulness, produce* sleep. While we sleep, the blood carries off these waste products more easily, the cells then recovering their function and their sensibility. The connection between sleep and fatigue is well known, and is shown not only by the fact that after great muscular or cerebral fatigue sleep is more profound, but by the results of the following experiment : if the blood of a very tired dog is injected into the veins of another dog in a normal state, this dog soon exhibits signs of great fatigue and goes to sleep ; these results are not observed if the blood injected is that of a non-fatigued dog. During heavy muscular labour, the air expired contains more C0 2 than in a state of repose and more still than during sleep. The carbon dioxide diminishes the oxygen so much needed by the muscles and brain, so that the activity of these remains depressed. As is well known, lactic acid has a depressing action on the nervous cells, injection of the acid into the veins of any person inducing symptoms of fatigue and sleepiness and finally sleep. The continuance of sleep is due to the fact that the blood flows more slowly to the brain, to which it hence carries less oxygen. It appears, indeed, to be proved that in general five or six hours' sleep very deep for two hours is sufficient for the blood to wash away these waste products of active cellular work and to restore activity to all the cerebral centres. 2 Kiliani treats 500 grams of inverted sugar with 250 grams of water and 15 grams of sulphuric acid at 50 to 60 for two hours, and then adds gradually 400 c.c. of concentrated caustic soda solution (1:1), the liquid being kept boiling meanwhile. The soda is subsequently neutralised with 50 per cent, sulphuric acid and the solution left for twenty -four hours to deposit crystalline sodium sulphate. The lactic acid is extracted with alcohol which does not dissolve the sulphate the alcohol being recovered by distillation. The crude lactic acid remaining is diluted, saturated with zinc carbonate and evaporated ; the zinc lactate is then allowed to separate, and is filtered off, redissolved in hot water and decomposed with H 2 S. After filtration, the liquid is concentrated in vacua, pure lactic acid being thus obtained. Various other methods have been tried. For instance, 3 kilos of cane-sugar and 15 grams of tartaric acid are dissolved in 13 litres of boiling water. In a few days' time, after the cane- sugar has been converted into glucose and levulose, 4 litres of acid milk and 100 grams of putre- fied cheese (also 1-5 kilos of zinc carbonate to fix the lactic acid, which otherwise would arrest the lactic fermentation) are added and the mixture left for-a week at a temperature of 40 to LACTIC ACID 387 that used industrially on a large scale will be described, since for some years the manu- facture from whey has been abandoned owing to the low yields, the difficulty of eliminating the salts and various organic compounds, and the facility with which contamination by butyric organisms occurs. Use is now always made of starchy materials, especially of potato starch, which is intimately mixed with two parts of cold water, the mixture being well stirred and treated with six parts of boiling water until a slightly opalescent liquid free from even the smallest lumps is obtained. The mass is cooled in a vat to 60 and treated with the diastase solution (green malt equal in amount to 15 per cent, of the weight of the starch is macerated and occasionally shaken during three hours with four times its weight of water at the ordinary temperature, the filtered liquid then containing the diastase); the saccharification of the starch is carried out at 55 to 60 and finally at 65, until the iodine reaction for starch fails. The wort thus obtained (see also : Manufacture of Alcohol, pp. 143, 201 ) is treated with 50 per cent, of powdered calcium carbonate, 5 per cent, (on the weight of the starch) of sterilised skim milk and with wort (1 litre per 100 litres) from a vat in which a pure lactic acid organism (a little Bacillus Delbriicki may be added) is actively developing. The temperature is kept at 40 to 50, and the mass is vigorously mixed two or three times per day so that the lactic acid may be fixed by the calcium carbonate ; after a week crusts of calcium lactate begin to separate. The fermentation is continued for three to four days longer, until indeed a sample of the liquid, freed from chalk and carbonic acid, ceases to reduce Fehling's solution (see later: Sugars). This fermentation consists solely of a decomposition, C 6 H 12 6 = 2C 3 H 6 O 3 , and is accompanied by neither generation of C0 2 nor absorption of water. In the fermenting rooms the greatest cleanliness is necessary, in order to prevent infection with extraneous bacteria. If such infection (recognisable by the bad smell and by lack of the crystalline crusts of calcium lactate, so that fine granules of calcium carbonate alone are* visible when the liquid is stirred) does occur in any vat, the contents of the latter should be boiled to sterilise it and the lactic fermentation again started at 55 to 60. 45, by which means the maximum production of lactic acid is obtained. The acid separates as zinc lactate in crystalline crusts which, after purification (by recrystallisation ), are suspended in water and decomposed with H 2 S in order to remove the zinc as insoluble sulphide. The filtered liquid is concentrated to a syrupy consistency and then extracted with ether, which does not dissolve the impurities (zinc salts, mannitol, etc.); on evaporation of the ether, pure syrupy lactic acid is obtained. Besides the decomposition of the sugar, various secondary reactions always accompany lactic fermentation, and the yield of the acid is scarcely 20 per cent, of the weight of the sugar taken. A better yield is, however, obtained by Larrieu's process (Fr. Pat. 206,506), which consists in treating starch paste with malt and hot water (as in the ordinary industrial process). Jacquemin prepares the acid from worts similar to those employed in breweries (barley mashed at 50 with malt, then boiled to destroy the diastase and cooled to 45) by the addition of pure lactic ferment and calcium carbonate. After five to six days, the mash is filtered and concentrated, the calcium lactate being then decomposed in the usual way with sulphuric acid. Dreher works in a similar manner, but with glucose solutions containing 1 per cent, of nutrient substances for the ferment (e.g., sodium phosphate, nitre, salt, etc.). Industrially, however, lactic acid was formerly always obtained from milk residues (whey or molasses of milk-sugar, which remain after the removal of the butter from the milk in the separator; also cheese by coagulation with rennet in the hot). The whey is concentrated in open vessels or, better, in vacuum pans, to 16 Be., and is then introduced into wooden vessels in which, at a temperature of 40, the lactic ferment is added in the form either of part of the liquid from a previous fermentation or of putrefied cheese. Powdered chalk is added to neutralise the acid formed, the liquid being stirred from time to time and the fermentation allowed to continue for ten to twelve days. After decantation, the calcium lactate is decomposed with dilute sulphuric acid, the liquid mass being well mixed, and the iron separated if necessary by means of potassium ferrocyanide. In some cases, before the calcium lactate is decomposed, it is separated by concentrating the solution, and is recrystallised from a little hot water, which should dissolve 20 per cent, of it, and then treated as usual with dilute sulphuric acid. The calcium sulphate formed is removed by passing the mass through a filter-press (see figure in the section on Sugar) and the clear lactic acid solution concentrated in a double- or triple-effect apparatus until it attains a concentration of 50 per cent. The further small quantity of gypsum which is then deposited is separated by filtration, the resulting yellowish-brown liquid repre- senting commercial, crude, 50 per cent, (by weight) lactic acid. This should not contain more than 1-5 per cent, of ash, and should not contain sulphate or reduce Fehling's solution. The lactic acid prepared from the molasses of milk-sugar factories is more impure than the above. Lactic acid is also obtained (1905) from a mixture of bran and barley. 388 ORGANIC CHEMISTRY At the end of the fermentation the liquid is rendered alkaline by addition of milk of lime, boiled with decolorising charcoal, and filtered hot through filter-presses, the calcium lactate crystallising out on cooling (in some factories the calcium lactate solution is decom- posed directly by means of sulphuric acid, the liquid being boiled with charcoal and potas- sium ferrocyanide to expel iron filtered and boiled to syrupy lactic acid). The calcium lactate crystals are collected in a vacuum-filter, the mother-liquors being reconcentrated and the crystals, dissolved in boiling water, treated with- pure sulphuric acid until the liquid colours Congo red paper deep violet (showing excess of mineral acid) and filtered to remove the calcium sulphate. The colourless liquid is concentrated in a vacuum apparatus (lead-lined or enamelled) to a strength of 50 per cent. The wash- waters from the calcium sulphate serve for making the milk of lime. From 100 kilos of starch 135 kilos of com- mercial 50 per cent, lactic acid is obtainable, but this contains also other organic acids and at 200 leaves a residue of 5 to 6 per cent. ; with further purification the yield diminishes. If the heating is too prolonged during the concentration, lactide is formed to some extent. Very pure lactic acid is obtained by extracting the crude product with ether or amyl alcohol which does not dissolve the impurities (sugar, gum, mineral substances) and steam-distilling in vacuo. An English patent (No. 26,415, 1907) describes the preparation of pure, concentrated lactic acid by the distillation of the commercial 50 per cent, acid in a rapid current of air or of an indifferent gas. In some cases purification is effected by crystallisation of the zinc salt. USES. Until a few years ago the uses of lactic acid were limited to the preparation of soluble lactates for medicinal purposes, but its manufacture has recently been con- siderably extended owing to its employment in the dyeing of wool, silk, etc., in place of tartaric acid, tartar and oxalic acid for the reduction of the chromium compounds with which wool to be treated with fast dyes (alizarin dyes, etc. ) is mordanted. For the same reasons it is advantageously employed in the chrome tanning of skins, its value in this case being sometimes regarded as due to its ability to keep calcium salts in solution and thus prevent the formation of certain white harmful deposits. The crude 50 per cent, acid is most commonly sold, and it is necessary to ascertain whether by 50 per cent, is meant 50 kilos per 100 litres or per 100 kilos of solution; in the former case the strength of the acid is only 43 per cent, by weight (L e., 100 kilos contain 43 kilos of acid). Commercial, brown, 50 per cent, lactic acid cost about 32s. per cwt. before the war; the paler, yellow product of the same strength, 52s. ; the pure (sp. gr. 1-21 ), 3s. Id. per kilo, and the chemically pure, 12s. per kilo. Before the war importation of lactic acid into Italy was subject to a duty of 6s. per cwt. The amounts of the Italian imports and exports are as follows (tons) : w 1908 1910 1912 1913 1914 1915 1916 1917 1918 Importation . 65 49 40 51 40 10-7 0-9 0-8 0-2 Exportation . 4-8 4-6 0-5 8 0-1 French importation - 155 156 72 89 Before the war Germany exported the following quantities of lactic acid and lactates : 1909 1910 1911 1912 1913 Tons . . . 1044 1278 1807 1771 2049 Salts of Lactic Acid are generally soluble to some extent in water. Calcium lactate, (C 3 H 5 3 ) 2 Ca -f 5H 2 0, forms mammillary aggregates of white needles soluble in 9-5 parts of cold water, and in all proportions in boiling water ; it is insoluble in cold alcohol. The water of crystallisation is evolved in a vacuum desiccator or on heating to 100. At 250 it loses H 2 O, giving calcium dilactate, which is less soluble in alcohol than the original salt. Calcium lactophosphate, obtained by neutralising lactic acid with gelatinous calcium phosphate, dissolves to some extent in water and is used for treating rickets and diseases of the bones. Ferrous lactate, (C 3 H 5 3 ) 2 Fe + 3H 2 O, is obtained by treating boiling aqueous calcium lactate solution with ferrous chloride solution, greenish- yellow crystals separating on cooling ; it is used in medicine. Zinc lactate crystallises with 3H 2 0. HYDROXY-ACIDS 389 ' ALANINE, CH 3 CH(NH 2 ) COOH, is obtained from the corresponding aldehyde- ammonia by the action of hydrocyanic acid. From the inactive, synthetic compound, the active stereoisomerides are separated by means of the strychnine or brucine salts. The action of PC1 5 expels both the hydroxyl- and the amino-groups, giving lactyl chloride, CH 3 CHC1 COC1, which gives a-chlorpropionic acid, CH 3 CHC1 COOH, when treated with water. (2) d-ETHYLIDENELACTIC ACID (Paralactic or Sarcolactic Acid) differs from ordinary lactic acid only in the greater solubility of its zinc salt (+ 2H 2 O), and the less solubility of its calcium salt (+ 4H 2 0). It is found in Liebig's extract of meat, and it is contained in the muscular juices, and is also formed in certain lactic fermentations. (3) J-ETHYLIDENELACTIC ACID is formed during the fermentation of aqueous cane-sugar solutions by Bacillus acidi Icevolactici. (4) ETHYLENELACTIC ACID (Hydracrylic, /3-Hydroxypropionic or 3-Propanoloic Acid), OH CH 2 CH 2 COOH, differs from its isomerides in that, when heated, it loses a molecule of water, giving, not the anhydride, but acrylic acid, CH 2 : CH C0 2 H. Further, with oxidising agents it gives, not acetic acid, but oxalic acid and carbon dioxide. It con- tains no asymmetric carbon atom and is hence optically inactive. It may be prepared synthetically from (1) /3-iodopropionic acid, or (2) ethylene, CH 2 : CH 2 , by addition of hypochlorous acid, giving OH CH 2 CH 2 C1, which is then converted into the nitrile OH CH 2 CH 2 CN, hydrolysis of the latter giving ethylenelactic acid. The acid is a colourless, syrupy liquid and forms a calcium salt (+ 2H 2 O) and a readily soluble zinc salt (+ 4H 2 O). HYDROXYBUTYRIC ACIDS, OH C 3 H 6 CO 2 H Five isomerides are theoretically possible, four being known : two a-acids, one fi-acid, and one y-acid (prepared only as salts ). a-HYDROXYBUTYRIC ACID, CH 3 CH 2 CH(OH) C0 2 H, melts at 43 and is syn- thesised as the inactive, racemic form, which may be resolved into its active components by means of brucine (see p. 23). a-HYDROXYISOBUTYRIC ACID (Acetonic or 2-Methyl-2-propanoloic Acid), OH C(CH 3 ) 2 . CO 2 H, melts at 79, boils at 212, and is obtainable by various synthetical methods from dimethylacetic acid, acetocyanohydrin, a-aminobutyric acid, etc. ^-HYDROXYBUTYRIC ACID, CH 3 CH(OH) CH 2 CO 2 H, is obtained by oxidising aldol or reducing acetoacetic acid, these methods of formation indicating its constitution. It forms a syrup and its Isevo-isomeride is found in the blood and in diabetic urine. HIGHER HYDROXY-ACIDS a-HYDROXYVALERIC ACID, CH 3 CH 2 CH 2 CH(OH) CO 2 H, melts at 29. a-HYDROXYISOVALERIC ACID, (CH 3 ) 2 CH CH(OH) CO 2 H, melts at 86. PT-T OH METHYLETHYLGLYCOLLIC ACID, r ii l >C CO 2 -f C 2 H S OH + CH 3 2 - CO 5 - CH 2 CHR C0 2 C 2 H 5 . y f Properties of Ketonic Acids. While the a- and y-ketonic acids are stable, the /3-acids readily lose CO 2 , giving the corresponding ketones. Reduction of y-ketonic acids yields, not hydroxy-acids, but y-lactones. As we saw was the case with malonic acid (see p. 369), the esters of ft- ketonic acids contain a hydrogen atom readily replaceable by metals, e. g., ethyl sodioacetoacetate, CH 3 CO CHNa CO 2 C 2 H 5 . Further, ketonic acids readily form condensation products; with aniline they give quinolines; with phenylhydrazine, pyrazoles, etc. PYRUVIC ACID, CH 3 CO C0 2 H, is obtained by the dry distillation of tartaric or racemic acid, an intermediate product in the reaction being possibly glyceric acid (formed by loss of C0 2 ), which then loses water and yields pyruvic acid. It is formed also by oxidising lactic acid with permanganate or by hydrolysing acetyl cyanide. Pyruvic acid is a liquid with an odour of acetic acid and of meat-extract, and is soluble in water, alcohol, or ether. It boils at 165 and solidifies at 9. It is a more energetic acid than propionic owing to the presence of a carbonyl group in close proximity to the carboxyl. Its constitution is indicated by the fact that with nascent hydrogen it gives ethylidenelactic acid. It readily forms condensation products (e. g., benzenes ; and with ammonia, pyridine compounds). When heated at 150 with dilute sulphuric acid, it loses C0 2 , forming acetaldehyde. Electrolysis of a con- centrated solution of potassium pyruvate results in the union of the anion of the acid, CH 3 * CO COO' with the ion OH', cyanogen and acetic acid being formed ; at the same time two anions combine with loss of 2C0 2 and formation of diacetyl, CH 3 CO ' CO CH 3 . This represents the general behaviour of potassium salts of ketonic acids on hydrolysis. Of interest is its conversion into ethyl alcohol and also into acetaldehyde and C0 2 by enzyme action (see Note, p. 136). Of the derivatives, cysteine (a-amino-/?-thiolactic acid), SH CH 2 CH(NH 2 )' C0 2 H, and cystine, the corresponding disulphide, may be mentioned. a-Ketobutyric acid, CH 3 CH 2 CO C0 2 H, has no special importance. ACETOACETIC ACID (^-Ketobutyric acid), CH 3 CO CH 2 CO 2 H, is obtained in the free state by cautious hydrolysis of its ester, and forms an extremely acid liquid soluble in water, in which it gives a red coloration with ferric chloride ; when heated, it readily loses C0 2 with production of acetone. ETHYL ACETOACETATE, CH 3 CO CH 2 C0 2 C 2 H 5 , is of far greater importance than the free acid, owing to the very varied syntheses in which it finds application. This ester is obtained in the form of its crystalline sodium derivative by the action of sodium and alcohol (sodium ethoxide) on ethyl acetate (see above). Ethyl acetoacetate (freed from sodium by means of acetic acid) is a liquid having a pleasant, fruity odour, and dissolves readily in alcohol or ether and slightly in water, in which it gives a red coloration with ferric chloride. It ETHYL ACETOACETATE 397 has a neutral reaction and the sp. gr. T030 ; it boils at 181 and is found in diabetic urine. When boiled with dilute alkali or dilute sulphuric acid, it undergoes ketonic decomposition, forming C0 2 , acetone and alcohol : CH 3 CO CH 2 CO 2 C 2 H 5 + H 2 = CO 2 + C 2 H 5 OH + CH 3 CO CH 3 . With concentrated alcoholic potassium hydroxide, it undergoes acid decomposition, producing 2 mols. of acetic acid : CH 3 CO CH 2 C0 2 C 2 H 5 + 2H 2 = C 2 H 5 OH -f 2CH 3 CO 2 H. Its great reactivity is due to the readiness with which one of the hydrogen atoms is replaceable by metals (Ba, Al, Zn, Ag, Cu, etc., in ammoniacal solu- tion), especially by sodium. Ethyl sodioacetoacetate, CH 3 CO CHNa C0 2 C 2 H 5 , is a white solid soluble in water, while ethyl acetoacetate is soluble in alkali, from which it is reprecipitated by acids. The sodium is readily replaced by different alkyl groups by the action of the corresponding alkyl iodides (see the analogous syntheses with Ethyl Malonate, p. 369). Since the compounds thus obtained can be subjected to either acid or ketonic decomposition, it will readily be seen how very varied acids and ketones may be obtained by means of ethyl acetoacetate. For instance, the action of normal octyl iodide on ethyl sodioacetoacetate yields methyl nonyl Tcetone, a constituent of oil of rue : CH 3 CO CHNa C0 2 C 2 H 5 + CH 2 I [CH 2 ] 6 CH 3 = Nal + CH 3 CO OTu 2 u 2 i 5 this compound, by ketonic decomposition, giving methyl nonyl ketone, which must hence have the normal structure, CH 3 * CO CH 2 * [CH 2 ] 7 CH 3 . Further, by eliminating the sodium from thyl sodioacetoacetate by means of iodine, the two residues combine, forming ethyl diacetylsuccinate : 2CH 3 CO CHNa C0 2 C 2 H 5 + I a = 2NaI + CH 3 CO CH C0 2 C 2 H 5 CH 3 CO CH C0 2 C 2 H 5 and this ester, on ketonic decomposition (boiling with 20 per cent, potassium carbonate solution), reacts with 2H 2 O and gives 2CO 2 , 2C 2 H 5 OH and acetonyl- acetone, CH 3 CO * CH 2 CH 2 CO CH 3 , which has a normal carbon-atom chain 4321 and is a 1 : 4 diketone. Ethyl acetoacetate also combines with formaldehyde (in presence of diethylamine), with acetone and with ammonia; with aniline it gives di- phenylcarbamide. With one or two mols. of sulphuryl chloride it gives ethyl chloracetoacetate (b.-pt. 194, sp. gr. 1*19 at 14) or ethyl dichlor acetoacetate, CH 3 CO CC1 2 C0 2 C 2 H 5 , which boils at 206 and has the sp. gr. 1*293 at 16. LEVULINIC ACID, CH 3 CO CH 2 CH 2 CO 2 H, is obtained synthetically by the acid decomposition of the product of reaction of ethyl acetoacetate and ethyl chloracetate. It may be prepared by boiling hexoses, cane-sugar, cellulose, gum, starch, etc., with concentrated hydrochloric acid. It melts at 33 and boils at 239 with slight decomposition, or at 144 under 12 mm. pressure. It is sometimes used in the printing of textiles. KETO-ALCOHOLS ACETONEALCOHOL or ACETYLCARBINOL (Propanolone), CH 3 - CO CH 2 OH, is formed by heating either grape-sugar with fused potassium hydroxide or a mono-halo- genated acetone with barium carbonate. It is a liquid which boils almost unchanged at 147 and reduces Fehling's solution even in the cold. 398 ORGANIC CHEMISTRY DIHYDROXY ACETONE or GLYCEROSE, OH CH 2 CO . CH 2 OH, is formed together with glyceraldehyde by oxidising glycerol with nitric acid. It has a sweet taste and may indeed be regarded as a triose sugar. It crystallises in colourless plates and reduces Fehling's solution in the cold. BUTAN-2-OL-3-ONE (Dimethylacetol), CH 3 CO CH(OH) CH 3 , also reduces Fehling's solution and is obtained by reducing diacetyl. It is a liquid soluble in water and boils at 142. The higher homologue, acetoisopropyl alcohol, CH 3 CO CH 2 CH (OH ) CH 3 , b.-pt. 177, is also known and is formed by the condensation (by means of alkali) of aldehyde with acetone. Removal of water from this compound yields Ethylideneacetone, CH 3 CO CH : CH CH 3 , boiling at 122. DIKETONES All diketones give mono- and di-oximes, and mono- and di-hydrazones, the latter (as with the aldehydes) bearing the name of osazones and being usually yellow. They often exhibit tautomerism and give rise to various cyclic condensation products. DIACETYL or a-DIKETOBUTANE (Butandione), CH 3 CO CO CH 3 ,is prepared by the general method for diketones, namely, by treating methyl ethyl ketone, CH 3 CO C 2 H 5 , with amyl nitrite and a little HC1, the CH 2 group being transformed into C : NOH, giving an isonitrosoketone, thus : CH 3 CO CH 2 CH 3 + N0 2 C 5 H n -- * CH 3 CO C CH 3 N-OH; when boiled with dilute sulphuric acid, this compound loses the hydroxyiminic group (as hydro xylamine), the diketone remaining. It is a yellow liquid which has a penetrating odour, dissolves in water and boils at 88, giving yellowish-green vapour (sp. gr. 0-973 at 20). With hydrogen peroxide, diacetyl is converted quantitatively into 2 mols. of acetic acid : CH 3 CO CO CH 3 + H 2 2 - 2CH 3 C0 2 H. CH 3 C : N OH DIMETHYLGLYOXIME (Diacetyldioxime), | , forms shining, white CH 3 C : N OH crystals, m.-pt. 234-5, insoluble in water, but soluble in alcohol or ether. It is obtained by shaking 50 grams of methyl acetoacetate in the cold with a solution of 30 grams of NaOH in 750 grams of water, allowing to stand for twelve hours, and adding 25 grams of sodium nitrite and a little methyl orange; to the mass, cooled with ice, 30 per cent. sulphuric acid is gradually added until the yellow coloration changes to reddish. Three hours later an aqueous solution of 25 grams of hydroxylamine hydrochloride is added, and sufficient soda crystals to render the reaction alkaline. The dimethylglyoxime crystals separating are collected on a suction-filter, washed with water and dried (yield 55 per cent. of the ester used). Dimethylglyoxime is the most sensitive reagent for ferrous salts, but is now used more especially for the quantitative separation of nickel from cobalt, since in neutral or ammoniacal solution a 1 per cent, alcoholic solution of the oxime precipitates nickel, but not cobalt or other metals. Prior to the war it cost 5 4s. per kilo. ACETYLACETONE, CH 3 CO CH 2 CO CH 3 . The best general method for pre- paring 1 : 3-diketones consists in treating an ester with sodium ethoxide : /ONa R CO 2 C 2 H 5 + C a H 5 ONa = R C^ OC 2 H 5 ; \OC 2 H 5 this compound, when treated with a ketone, R' CO CH 3 , loses 2 mols. of alcohol and yields R C , from which the sodium is expelled by a dilute acid. This enolic form, X CH COR' MALIC ACID 399 ,OH C^ , readily passes into the ketonic form, CO CH 2 , thus giving the X CH- compound R CO CH 2 CO R'. Another general method for obtaining 1 : 3-diketones consists in treating the sodium derivatives of acetylene homologues with an acid chloride and then acting on the acetylenic product with sulphuric acid, so that it combines with water : CH 3 [CH 2 ] 4 C i CNa + CH 3 CO Cl = NaCl + CH 3 [CH 2 ] 4 C i C CO CH 3 ; Amylacetylene Acetyl chloride the latter + H 2 O > CH 3 [CH 2 ] 4 CO CH 2 CO CH 3 . As in ethyl acetoacetate and ethyl malonate, the two hydrogen atoms of the methylene group between the two carbonyl groups are here also replaceable by metals, giving volatile compounds which are soluble in chloroform, benzene, etc., and differ from true salts, their solutions exhibiting very slight electrical conductivity. Acetylacetone has a pleasant odour and boils at 137. When boiled with water it yields acetone and acetic acid. ACETONYLACETONE (y-Diketohexane or Hexa-2 : 5-dione), CH 3 CO CH 2 -CH 2 CO CH 3 , is obtained by ketonic decomposition of the product of interaction of ethyl acetoacetate and ethyl chloracetate (see also Levulinic Acid); it boils at 194 and has an agreeable smell. KETO-ALDEHYDES AND HYDROXYMETHYLENEKETONES PYRUVIC ALDEHYDE (Methylglyoxal or Propanolone), CH 3 CO CHO, is a volatile oil obtained by decomposing its oxime (isonitrosoacetone ) with dilute acid (see Diacetyl ). ACETOACETALDEHYDE, CH 3 CO CH 2 CHO, was formerly thought to have been obtained in the free state, but more exact study has now shown the compound in questioa to be the unsaturated isomeride, HYDROXYMETHYLENEACETONE, CH 3 CO CH : CH OH, which has an acid character and is obtained by the interaction of acetone and ethyl formate in presence of sodium ethoxide (see Ethyl Acetoacetate). It boils at 100 and readily condenses into 1:3: 5-triacetyl benzene, C 6 H 3 (CO ' CH 3 ) 3 . LEVULINALDEHYDE (Pentanal-4-one), CH 3 CO CH 2 CH 2 CHO, boils at 187. It is obtained as a decomposition product of the ozonide of rubber (q. v.). F. POLYVALENT DIBASIC HYDROXY-ACIDS AND THEIR DERIVATIVES TARTRONIC ACID (Hydroxymalonic or Propanoldioic Acid), C0 2 H CH(OH) * CO 2 H, is formed by the spontaneous decomposition of nitrotartaric acid and is obtained synthetically by oxidising glycerol with potassium per- manganate, by eliminating bromine from bromomalonic acid by the action of moist silver oxide, or by reducing Mesoxalic Acid, CO(CO 2 H) 2 . It crystallises with |H 2 and melts at 184, losing C0 2 and forming polyglycollides. It is soluble in water, alcohol, or ether. MALIC ACID (Hydroxysuccinic or Butanoldioic Acid), C0 2 H CH(OH) CH 2 CO 2 H, occurs in abundance in unripe fruits (apples, grapes, quinces, and sorb-apples, from which it is extracted). Its crystals melt at 100 and it dissolves in wtiter or alcohol and, to a slight extent, in ether. When subjected to dry distillation, it gives fumaric acid and maleic anhydride. Synthetically it is obtained from maleic or fumaric acid or asparagine, and also by the action of moist silver oxide on bromosuccinic acid, and by the reduction of tartaric acid by means of hydriodic acid. As it contains an asymmetric carbon atom, malic acid forms three optically different stereoisomerides, all of which are known. Natural malic acid is laevo- rotatory, that derived from cZ-tartaric acid dextro-rotatory, and that obtained 400 ORGANIC CHEMISTRY by other syntheses inactive but resolvable into active components by fractional crystallisation of the cinchonine salt. It gives an acid calcium salt readily soluble, and a normal salt slightly soluble in water. The presence of the alcoholic group is proved by the formation of acetylmalic acid (see p. 224). For the amido-derivatives, asparagine, etc., see later. Of the higher homologues of malic acid, the following are known : Four isomeric acids, C 3 H 5 (OH)(C0 2 H) 2 (a- and fi-hydroxyglutaric acids, itamalic and citramalic acids); diaterebinic acid, C 5 H 9 (OHJ(C0 2 H) 2 , which readily forms a lactone, and terebinic acid, C 7 H 10 O 4 . TARTARIC ACIDS, C0 2 H CH(OH) CH(OH) C0 2 H These are dibasic and tetravalent, as they contain two secondary alcoholic groups. The presence of two asymmetric carbon atoms leads to the existence of four stereoisomerides, which have already been considered on pp. 20-21 : (1) ordinary or d-tartaric acid; (2) Z-tartaric acid; (3) racemic or para- or di-tartaric acid; (4) i- or meso- or anti-tartaric acid. They are obtained synthetically from dibromosuccinic acid, C0 2 H CHBr CHBr * C0 2 H, and moist silver oxide, from glyoxal cyanohydrin, from glyoxylic acid by reduction, from mannitol by oxidation with nitric acid, and from f umaric or maleic acid by oxidation. (1) d-TARTARIC ACID. This is the ordinary tartaric acid, which occurs abundantly as such, and as monopotassiuin tartrate (tartar) in many fruits especially in the grape, and hence in wine, from which it is extracted in a manner to be described. Dextro-rotatory tartaric acid forms hemimorphic, monoclinic prisms with a decided and pleasant acid taste. It is readily soluble in water or alcohol and almost insoluble in ether. One hundred parts of water dissolve 114 parts of the acid at 0, l25'7 at 10, 139'4 at 20, 156-2 at 30, 176 at 40, 195 at 50, 217-5 at 60, 243'6 at 70, 273'3 at 80, 306'5 at 90, and 343'3 at 100. The acid melts at 170, giving rise to various anhydrides and to pyruvic and pyrotartaric acids; ultimately it carbonises with an odour of burnt bread or, if the temperature is raised considerably, of burnt sugar. Energetic oxidising agents convert it into tartronic acid or dihydroxy- tartaric acid and finally into formic acid, carbon dioxide, etc. In the hot, it reduces ammoniacal silver solutions (see*p. 413 for a sensitive reaction for tartaric acid). Certain bacteria transform it into succinic acid. When burned, tartaric acid and tartrates emit an odour of burnt bread, thus differing from citric acid and citrates, which give a pungent odour. Even in the hot, it resists the action of sulphuric acid of 62 Be. Owing to the presence of alcoholic groups, tartaric acid, like glycerol, hinders the precipitation by alkali of many metallic oxides, e. g., of cupric oxide in Fehling's solution (containing caustic soda, copper sulphate, and sodium potassium tartrate; see Sugar Analysis), the intensely blue, soluble C0 2 Na CH Ov compound, /Cu, being formed; this compound is not pre- C0 2 K CH V cipitable by alkalis, since the copper no longer functions as cation, but is - O CO CH 0, contained in the anion, /Cu, which migrates to the positive O CO CH V pole or anode when the salt is electrolysed. Tartaric acid is used in dyeing, in the wine industry, in the preparation of aerated beverages (lemonade), in medicine, etc. TARTRATES 401 The following salts of tartaric acid may be mentioned, acid potassium tartrate being considered more in detail later. ACID POTASSIUM TARTRATE (Cream of Tartar), CO 2 H CH(OH)- CH(OH) CO 2 K, is slightly soluble in water or in dilute alcohol, and has a pleasant acid taste. For its commercial preparation, see Tartar Industry. NORMAL POTASSIUM TARTRATE, C 4 H 4 O 6 H 2 + |H 2 O, is readily soluble in water and separates from highly concentrated solutions in monoclinic prisms. One hundred grams dissolves in 75 grams of water at 2, in 66 grams at 14, in 63 grams at 23, or in 47 grams at 64. SODIUM POTASSIUM TARTRATE (Rochelle Salt), C 4 H 4 O 6 NaK + 4H 2 O, is pre- pared by neutralis.'ng cream of tartar solution with sodium carbonate. Copper and iron, present as impurities, are removed by means of hydrogen sulphide, the solution being then heated with good animal charcoal, filtered, concentrated and allowed to crystallise; the Rochelle salt separates in thick columns readily soluble in water and slightly so in alcohol. One hundred grams of the crystallised salt dissolves in 170 grams of water at 6. It is used to reduce silver salts in the silvering of mirrors and also for medicinal purposes and to prepare Fehling's solution. It costs about 72s. per cwt. CALCIUM TARTRATE, C 4 H 4 O 6 Ca + 4H 2 O, occurs ready formed in the grape and in senna leaves. The crystallised salt (1 part) dissolves in 352 parts of boiling water or in 6265 parts at 15. It is readily soluble in cold sodium hydroxide solution, from which it separates in the hot as a white jelly, to be redissolved on cooling. It dissolves in acetic acid, thus differing from calcium oxalate. It is soluble also in alkali tartrates and in ammonium salts. The crystalline tartrate loses part of its water of crystallisation at 60, 15 p cent, at 110, and the whole at 130. TARTAR EMETIC (or Potassium Antimonyl Tartrate), C 4 H 4 6 (SbO)K + |H 2 O, is prepared by precipitating SbOCl from a solution of SbCl 3 by means of water, boiling the precipitate with soda solution and dissolving the Sb 2 O 3 thus formed in a solution of four or five times its weight of potassium hydrogen tartrate in 50 parts of water. After filtra- tion and concentration the solution deposits, on cooling, efflorescent, trimetric pyramids, which are soluble in water (1 : 13 at 20, 1 : 6 at 50) but insoluble in alcohol. At 100 it loses its water of crystallisation and at 220 the double molecule loses water of constitution and gives 2KSbC 4 H 2 6 . It is poisonous and is used in medicine as an emetic and in dyeing cotton as a mordant for basic dyes (price about 4 16s. per cwt.). Germany imported 202 tons in 1908 and 391 in 1909, the respective exports being 1030 and 1090 tons in the two years. (2) Z-TARTARIC ACID differs from the d-acid only in the opposite sign of its rotation and in the opposed hemihedry of its crystals. Mixing of the concentrated aqueous solu- tions of the two acids results in development of heat and the formation of inactive tartaric acid. (3) RACEMIC ACID (Paratartaric Acid), (C 4 H 6 6 ) 2 + 2H 2 O, represents a mixture of dextro- and laevo-tartaric acids in equal proportions, and is hence optically inactive (see p. 21 ). When heated alone or, better, in presence of concentrated caustic soda solution, either the d-acid or the meso-acid (see later) is transformed into racemic acid. The latter is obtained from the mother-liquors of ordinary d-tartaric acid. The molecular weight, determined cryoscopically or from the vapour densities of the esters, corresponds with the simple molecule, C 4 H 6 O 6 . It forms triclinic crystals which effloresce in the air, and is less soluble than the active acids. From sodium ammonium racemate crystals, (C 4 H 4 6 ) 2 Na 2 (NH 4 ) 2 + 2H 2 O; Pasteur separated those showing dextro- from those showing laevo-hemihedry, thus resolving racemic acid into its optically active constituents. Only in the crystalline state is the molecule of racemic acid regarded as double that of tartaric acid, whilst in dilute aqueous solution it is assumed to be decomposed completely into the two optical antipodes. (4) MESOTARTARIC ACID, C 4 H 6 O 6 + H 2 O r is optically inactive (p. 21) and is not merely a mixture of the active compounds. It is obtained by prolonged boiling of d-tartaric acid with excess of caustic soda. Its potassium salt is more soluble in water than those of the other tartaric acids. VOL. ii. 26 402 ORGANIC CHEMISTRY THE TARTAR INDUSTRY MANUFACTURE OF POTASSIUM BITARTRATE (Cream of Tartar or Potassium Hydrogen Tartrate). Although the crude prime material of this industry is very abundant in Italy in wine residues, it is only within the last few years that the working has been placed on a rational basis, the tartar being refined and tartaric acid prepared. Although these prime materials are subject to an export duty (10|(Z. per cwt. ), the exportation from Italy amounted to about 17,800 tons, worth 480,000, in 1905, and 17,850 tons, worth 416,000, in 1910. The treatment of these products requires, besides special technical ability, also considerable quantities of fuel, and to this are partly due the difficulties of the Italian manufacturers. Cream of tartar occurs abundantly in the green extremities of vine-shoots and in the grape, and part of it remains in the pressed vinasse. The vinasse of southern grapes con- tains as much as 4 per cent, of cream of tartar, and that of other grapes from 2 to 2-5 per cent. Vinasse that has not been in contact with the fermenting must, and that of second wines have practically no commercial value. 1 Another portion of the cream of tartar which remains dissolved in the must gradually separates (lees) as fermentation proceeds cream of tartar being less soluble in alcoholic liquids (wine) and finally part of it is deposited as a crystalline crust on the walls of the casks during the winter, the solubility being less in the cold. The following table shows, for various temperatures : I, the number of grams of cream of tartar dissolved by 100 grams of water ; II, the number of grams dissolved by 100 grams of 10 per cent, aqueous alcohol solution ; and III, the number of grams contained in 100 c.c. of the saturated solution. 5 10 15 20 25 30 40 50 60 70 80 90 "lOO I. 0-320 0-360 0-400" 0-470 0-570 0-680 0-900 1-31 1-81 2-40 3-20 4-50 5-70 C-90 II. 0-141 0-175 0-212 0-253 0-305 0-372 0-460 0-570 0-710 III. 0-370 0-376 0-411 0-843 1-020 1-450 1-931 2-475 3-160 4-050 5-850 Alcoholic potassium acetate solution transforms cream of tartar partly into the normal tartrate, whilst the presence of free acetic acid hinders such transformation. Tartaric acid causes a slight diminution in the solubility of tartar in wine, whereas mineral acids increase this solubility. These crude products are of different colours according as they are obtained from white wines (white tartar) or red wines (red tartar), and according to the degree of purity. Fresh wine lees (forming about 5 per cent, of the wine) are slimy, of a dirty red colour, and contain yeasts, colouring-matters, cream of tartar (10 to 25 per cent.), and calcium tartrate (6 to 20 per cent. ). Italian wine lees are the richest in potassium bitartrate and the poorest in calcium tartrate. When removed from the vats, the lees are placed to drain in strong bags suspended by cords, the bags being afterwards tied up and pressed slightly in a press. They are then removed from the bags and dried in the air, being turned from time to time. When pressed and almost dry, they contain more than double as much tartar as when in the fresh state (about 10 per cent, of moisture, 6 to 10 per cent. of lime, 3 to 5 per cent, of sarid, 25 to 40 per cent, of tartaric acid). In some large wineries 1 One quintal of grapes yields 30 to 35 kilos of vinasse and 65 to 70 of must, so that the annual Italian production of 40,000,000 quintals would correspond with 15 to 20 million quintals of vinasse, containing, on the average, more than 3 per cent, of tartar, i. e., a total of about 700,000 quintals (70,000 tons) of tartar. The vinasse distilled in Italy in 1909 amounted to 368,000 tons, which should have yielded 11,000 tons of cream of tartar, but this was largely lost. The tartar is estimated by the method of Carles : a kilo of the vinasse is chopped and mixed, and 100 grams weighed and boiled for ten minutes with 700 c.c. of water in a litre flask, the liquid being subsequently made up to the mark with distilled water. Five hundred cubic centimetres of the filtered solution is concentrated to about ICO c.c., 70 c.c. of saturated calcium acetate solution being then added to the boiling liquid; after mixing, the liquid is allowed to cool for twelve hours, the precipitated calcium tartrate being then collected on a tared filter, washed with water, dried at 60, and weighed. Multiplication of the result by 2 and deduction of 5 per cent, (to allow for the volume occupied by the vinasse in the litre flask) gives the calcium tartrate per 100 grams of vinasse; further multiplication by 0-723 gives the corresponding amount of potassium hydrogen tartrate. Ciapetti has rendered this method more exact by transforming the calcium tartrate (by potassium bioxalate in the hot) into potassium hydrogen tartrate, filtering and washing the residue, concentrating the filtrate and adding alcohol to precipitate the potassium bitartrate; the latter is washed, redissolved in hot water and titrated with decinormal caustic soda solution (see below, Analysis of Tartar). TARTAR INDUSTRY 403 the lees are passed directly to the filter-presses, cakes which are readily dried being thus obtained. The crude tartar contains 45 to 70 per cent, of potassium bitartrate and calcium tartrate, and, if washed and crystallised once from hot water, this content may increase to 75 to 87 per cent., 1 the product being then placed on the market under the name of crystals. As a rule 60 to 70 per cent, of the total tartar is extracted from the vinasse after the alcohol has been distilled off with steam in the manner indicated on p. 170. The forms of apparatus there shown give almost saturated, boiling solutions of tartar (the remaining vinasse being centrifuged or pressed to remove all the tartaric liquors), which are allowed to cool in shallow, wooden vessels. In these vessels are hung, after some time, strings 1 Analysis of Tartar. Tartar being a rather expensive substance (3 to 4 per cwt.), it is frequently adulterated with sand, gypsum, etc. It is always bought and sold on its strength, the potassium bitartrate or the total tartaric acid (thus including both the calcium tartrate and the free tartaric acid) being determined. A homogeneous sample is finely ground and sieved, the residue being again ground. A test which is not very exact, but is rapid and largely used, is the direct titration test. The coarse impurities, sand, clay, sulphur, woody matter, yeasts, etc., are estimated by boiling a known weight of the crude tartrate with water acidified with HC1, and collecting, washing, drying, and weighing the residue on a tared filter; the residue is sometimes ashed. The calcium carbonate is determined by treating with an acid in the calcimeter and measuring the carbon dioxide evolved, and the total lime, including that of the tartrate, by calcining a given weight of the tartar, dissolving out the potassium carbonate, treating the residual calcium car- bonate with excess of standard nitrous acid solution, and measuring the excess of the acid by titration with soda solution. The total lime is, however, best estimated by dissolving 2 grams in HC1, neutralising with ammonia, precipitating with ammonium oxalate, and heating on a water-bath, the precipitate being subsequently collected on a filter, ignited in a platinum crucible and weighed as CaO. The titration test of the quantity of acid potassium tartrate is carried out by dissolving a weighed amount (2 to 3 grams) of the tartar in water and titrating the boiling solution with N/4-sodium hydroxide solution, using very sensitive litmus paper as indicator; 1 c.c. of N/4-caustic "soda solution corresponds with 0-047 gram of potassium bitartrate. Multiplication of the amount of bitartrate by 0-798 yields the corresponding amount of tartaric acid. For international trade, the potassium bitartrate is nowadays estimated by the filtration process, which largely excludes errors due to the presence of tannin substances and other impurities which also react with litmus : 2-35 grams of the substance (crude tartar, sludge or lees ) are heated to boiling for five minutes with 400 c.c. of water in a 500 c.c. flask; water is again added and the whole cooled, made up to 500 c.c., mixed and filtered through a folded filter. Of the filtrate 250 c.c. are heated to boiling and titrated with N/4-potassium hydroxide solution (standardised with pure bitartrate), sensitive litmus paper being used as indicator. For more exact determinations, Rammer's recrystallisat!on method is employed : 4-7025 grams of substance (molecular weight of tartar divided by 40) are heated to boiling with 30 to 40 c.c. of water in a 100 c.c. flask, the solution being then neutralised with N/4-caustic soda, of which 1 to 2 c.c. in excess are added. The volume is made up to 100 c.c. and of the filtered solution, 20 c.c. are rendered decidedly acid with acetic acid and treated with 100 c.c. of a mixture of alcohol and ether, which separates the potassium bitartrate completely in crystals. These are collected on a filter, washed with alcohol and ether, rcdissolved in boiling water, and titrated with N/20-soda solution. Determination of the total tartaric acid. This gives the total content of potassium bitartrate, calcium tartrate, and free tartaric acid. The Goldenberg-Geromont hydrochloric acid process, which was formulated as follows at the Congress of Applied Chemistry at Turin in 1902, is generally used : Six grams of the substance are treated for eight to ten minutes in a small beaker with 9 c.c. (for products poor in tartar) or 18 c.c. (for richer products) of cold HC1 (sp. gr. 1-10), the whole being then washed into a 100 c.c. flask, made up to volume, mixed, and passed through a dry pleated filter. Fifty cubic centimetres of the filtrate are boiled for ten to fifteen minutes in a tall 250 to 300 c.c. beaker with 5 (or 10) c.c. of concentrated potassium carbonate solution (66 grams in 100 c.c. of water), the liquid being then washed into a 100 c.c flask, cooled, made up to volume, and filtered through a pleated filter. Fifty cubic centimetres of this filtrate are taken to dryness in a half -litre dish, redissolved in 5 c.c. of boiling water, and vigorously stirred with 4 to 5 c.c. of glacial acetic acid ; when the liquid is cold, 100 to 110 c.c. of 96 per cent, alcohol are mixed in. and the potassium bitartrate allowed to deposit. This is filtered under pressure, the dish, rod, and filter being repeatedly washed with alcohol. The filter and the bitartrate are then washed into the same dish with boiling water, with which the volume is made up to about 300 c.c. The liquid is then boiled and titrated with N/4-alkali, the end -point being determined with sensitive litmus paper. To eliminate the error due to the volume occupied by the impurities in the original flask, 0-7 per cent, is deducted from the total content in the case of low-grade tartars (containing less than 20 per cent, of bitartrate) and 0-7 (n X 0-02) in the case of those containing 20 to 50 per cent., n being the excess percentage over 20 ; beyond 50 per cent, the correction becomes almost zero. 404 ORGANIC CHEMISTRY studded with tartar crystals, on which less impure crystals gradually form. The deposit forming on the walls of the vessels is of a leS3 degree of purity, and that on the bottom contains many coloured impurities. In five to six days the crystallisation is complete, more rapid and complete separation being attained in very cold places or by the use of artificial cooling. The mother-liquors decanted from the tartar may be utilised again for extraction of vinasse, but when they become too rich in impurities or mucilaginous sub- stances, they are either used as fertilisers, since they contain potassium salts, or, better, are treated (Carles, 1910) at boiling temperature with 60 grams of potassium ferrocyanide per hectolitre, the iron, alumina, copper, etc., present being thus removed ; the clarified liquid is treated with lime to separate calcium tartrate, the potassium salts being recoverable from the filtered solution by the Alberti process (see later). 1 The dregs deposited during the extraction of the oream of tartar from the vinasse contain, in the dry state, 30 to 60 per cent, of potassium bitartrate and 10 to 20 per cent, of calcium tartrate. The refining of crude tartar from vinasse, lees, etc., is very difficult with the poorer products, and in practice rich and poor materials are often mixed so as to give a content of 60 to 65 per cent, when a highly refined tartar is not required. The crude tartar or other mixture should first be ground and then sieved to remove pieces of wood and other impurities. In order to destroy certain impurities and protein substances and hence hasten the filtration of the subsequent aqueous solutions, the lees or low-quality tartar is treated with concentrated sulphuric acid (60 Be.) or heated in revolving iron cylinders until the temperature reaches 160 to 180, the loss in weight being 8 to 12 per cent, (water together with 2 to 3 per cent, of cream of tartar). It is then intro- duced into a perforated copper cylinder placed almost on the bottom of a large wooden vessel furnished with copper or aluminium steam coils. Care is taken not to use an excess of water, which would involve waste of fuel, and generally 6 to 8 parts of water are taken per 1 part of tartar. A hood is usually fitted over the vessel to carry off the steam from the boiling solution. In order -to transform the calcium tartrate present into potassium bitartrate, 3 kilos of hydrochloric acid (20 Be. ), and 3 kilos of potassium sulphate (previously dissolved in 20 litres of water) are added to the water per kilo of lime (CaO) contained in the calcium tartrate (see method of determination given above). The liquid is stirred occasionally, boiled for an hour and allowed to settle for about a further hour, after which either the bitartrate solution is decanted by means of a tap a short distance from the bottom, or the whole mass is passed through a filter-press. The liquid is left to cool in a cold place in ordinary crystallising vessels, or, better, in copper or aluminium basins, a somewhat impure and reddish-brown tartar crystallising out. Rather purer tartar may be obtained by collecting the crystals separating while the solution is cooling to 35 or 40, small crystals being ensured by occasional stirring ; the tepid mother-liquors are then decanted and crystallised in a cold place. 1 In many places the vinasse is placed in vats fitted with false bottoms, steam being passed in below while a spray of mother-liquor (red liquors) falls from above; as many hectolitres of these liquors are employed as there are quintals of vinasse. In this manner, the first solution of the tartar is obtained almost boiling and almost saturated ; it is purified by percolating slowly through the vinasse (the steam expels the air and condenses ). A second extraction gives a less completely saturated solution, which is utilised for further extractions. Finally, the vinasse is not pressed but is washed with water and a little hydrochloric acid to extract the calcium tartrate, exhaustion being then obtained by means of cold water (Tarulli's method). The mother-liquors from the crystallisation, when they become too impure or, in some cases, even after the first crystallisation, are treated with milk of lime to precipitate all the dissolved tartar, while the liquors from the second and third extractions are used for fresh quantities of vinasse. To obtain purer solutions from the vinasse, to avoid losses occasioned by the presence of lime in the water, and to extract calcium tartrate at the same time, Ciapetti exhausts the vinasse with dilute solutions of sulphurous and hyclrosulphurous acid which do not dissolve the colour- ing-matters or the pectic or albuminoid substances -and allows refined, white cream of tartar (!) to crystallise out; tho mother-liquors are utilised further. This method was tried in various works, but did not give the results expected of it. Extraction on the Ciapetti system may also be carried out in the series of stills used for the distillation of the vinasse (see later, Tartaric Acid, Gladysz Process). The fresh vinasse or the deposits, if not to be worked up at once, may be kept for some months if tartaric fermentation which would destroy part of the cream of tartar is prevented, either by addition of 0-05 per cent, of sodium thiosulphate or by maintaining the vinasse strongly compressed, under chalk and sand, in wooden vats (tartaric fermentation is caused principally by Bacillus saprogenes vini). The yields of tartar and alcohol are determined on a small quantity (5 kilos) of the_ vinasse in a small Savalle distilling and macerating apparatus. 405 The brown mother-liquors are used repeatedly to. dissolve fresh quantities of the crude tartar substances in the hot. The brown crystals are detached from the crystallising vessels by means of suitable spatulas and redissolved, in a wooden vessel similar to that previously used (with a perforated bottom for the crystals), in ten to twelve times their weight of water, which is boiled by indirect steam supplied through copper or aluminium coils. Decolorisation is effected by adding, after half an hour's boiling, about 1 per cent, of animal charcoal (well washed with hydrochloric acid and thoroughly rinsed ; for very impure tartar from lees as much as 6 to 8 per cent, of animal charcoal is used). After mixing and an hour's boiling, about 1 per cent, of kaolin free from chalk (washed with HC1) is well mixed in in the hot and the liquid either filter-pressed or left for two to three hours so that the kaolin may carry down all the suspended charcoal. In some cases the solutions are clarified by adding tannin and gelatine (50 grams of the latter and 250 of tannin dissolved separately) after the kaolin and before filtration. The pale yellow, clear solution is decanted (the first and last portions, which are rather turbid, being kept separate) and crystallised in wooden crystallising vessels or in copper or aluminium basins ; in three or four days the crystallisation is complete. The mother-liquors are used to dissolve fresh brown crystals, since they contain a little free tartaric acid which dissolves many of the impurities better than water does, and so results in the separation of purer crystals. After the removal of the mother -liquor, the crystals are washed repeatedly with very pure water (condensed), a trace of hydrochloric acid being added to the first washing water if the crystals show any superficial turbidity. They are finally dried on cloths in a desiccator at 60 with the help of a current of air. In France and also in certain Italian factories, Carles has applied a method of extracting the tartar which consists in treating 100 parts of the crude, powdered tartar with 400 parts of water at 70, containing sufficient sodium carbonate to transform all tfce potassium bitartrate into the highly soluble sodium potassium tartrate (1:1-2). This solution is decanted or filtered and treated with more than the amount of hydrochloric or sulphuric acid necessary to neutralise the soda added; this leads again to the formation of the slightly soluble potassium bitartrate, which crystallises out (96 per cent, purity) on cooling. Vinasse is also extracted more readily by this alkaline method. The recent process of Cantoni, Chautems and Degrange (1910) refines the tartar almost in the cold and effects a marked economy of chemical products. This method serves well also for poor products (20 per cent, lees), which are heated as described above and washed first with cold sodium carbonate solution in a series of vessels, next slightly with water, and finally, slowly and systematically with dilute hydrochloric acid. In the first case, sufficient soda is added to convert the tartar almost completely into sodium potassium tartrate, which is highly soluble and may be extracted with the minimum quantity of water. The treatment with hydrochloric acid dissolves the remainder of the tartar and also the calcium tartrate. The amount of the acid used is chosen so that, when the alkaline and acid solutions are united, it neutralises the soda first used. The hydro- chloric acid solution is mixed previously with the amount of oxalic acid required to preci- pitate the whole of the lime present in the crude tartar as calcium tartrate, while sufficient potassium chloride is added to the alkali solution to transform all the tartaric acid, existing as calcium tartrate, into potassium bitartrate. Mixing of the two solutions in the cold results in the precipitation of almost? all the-cream of tartar in a white, highly pure state, and of the calcium oxalate. After filtering, the dark mother-liquors areTsept for subsequent operations, while the solid residue is treated with the calculated (on the/solubility of the tartar) quantity of water at 90, a little oxalic acid being added to render the calcium oxalate less soluble. The mass is then filtered or centrifuged (if necessary, decolorised with a small amount of animal charcoal), the clear liquid, on cooling, depositing refined tartar of a purity of 99 to 99-5 per cent. The mother-liquor is used to initiate the solution of further quantities of crude tartar, etc. Oxalic acid may -be recovered from the calcium oxalate. A process which allows of the conversion of calcium tartrate into potassium bitartrate consists in boiling, say, 100 kilos of the calcium tartrate (85 per cent.) with 1500 litres of water and 53-5 kilos of potassium bisulphate (or a mixture of 35 kilos of the neutral sulphate and 24-6 kilos of sulphuric acid at 60 Be.) for half an hour, decanting and filtering the liquid, from which pure potassium bitartrate (up to 98 per ce'nt. ) crystallises on cooling. This process is a modification of that of Martignier (Fr. Pat. Nov. 23, 1889), who 406 ORGANIC CHEMISTRY transforms calcium tartrate into normal potassium tartrate by decomposition with normal potassium sulphate; after filtration and concentration and addition of the calculated amount of sulphuric acid, the solution deposits potassium tartrate. If the cream of tartar crystals are not pure but contain small proportions of calcium tartrate, they do not give perfectly clear solutions in water. When the pale mother-liquors from the final refining are somewhat impure, they are used in place of the brown liquor to dissolve the crude material, the highly impure brown liquors being used in the manufacture of tartaric acid or added in small amounts to the prime tartaric materials. STATISTICS AND USES. Italy exported and imported the following quantities of tartar materials : Crude tartar and cask deposits Wine lees Pure cream of tartar Year Imported Exported Imported Exported Imported Exported Tons Value (*) Tons Value () Tons Value ()' Tons Value () Tons Value () Tons Value () 1906 492 17,701 16,828 605,824 Includ edin cru de tarta r, etc. 35 2,082 19 1,241 1908 106 3,587 10,405 353,773 231 2,581 8,311 93,081 66 3,564 16 948 1910 275 9,004 10,278 337,120 161 1,673 7,574 78,760 63 3,392 32 1,944 1912 172 - 8,594 . 156 6,169 88,834 119 8,839 . 1913 273 11,361 8,505 353,791 456 6,571 4,054 58,376 34 2,491 . 1914 360 18,694 9,964 518,107 443 6,766 6,298 80,533 332 31,901 600 57,600 1915 1,412 107,312 7,897 600,164 564 11,737 2,391 49,722 105 17,347 1,456 241,613 1916 541 41,108 4,670 354,928 2,076 43,177 40 836 18 2,921 976 161,933 1917 228 25,047 6,693 776,400 326 13,048 111 17,632 1 286 729 189,592 1918 15 1,617 6,809 789,867 384 15,344 1,041 41,656 605 157,214 The exports from Italy are sent mostly to France, Great Britain, and the United States. The total Italian production of tartar, etc., in 1905 has been estimated at 1,600,000, the world' s production being valued at about 2,800,000 (probably too low). Crude tartar and lees pay an export duty from Italy of Is. Qd. per quintal, no import duty being levied ; refined tartar pays an import duty of 3s. 2d. Italy contains about 200 crude cream of tartar works, but only very few manufacturing refined tartar. Great Britain imported (usually one-half from France and one-fourth from Germany) 3200 tons of cream of tartar in 1918, 4000 in 1910, 3890 in 1912, and 3980 in 1913. For Germany the importation (of crude tartar and calcium tartrate) and exportation (of pure cream of tartar) are (tons) : Importation Exportation 1908 2691 1225 1909 2026 1154 1910 3067 1783 1912 4258 2199 1913 6310 3353 In 1910 France produced 12,000 tons of crude tartar and more than 6000 tons of refined cream of tartar. The imports and exports are as follows (tons ) : Wine residues ( imports \exports Crude tartar (imports \exports Tartar crystals, etc. f imports \exports Refined cream of tartar f imports \exports 1913 10,876 1,992 1,417 9,415 163 16 4,408 1914 8,561 1,867 1,140 5,500 26 25 3,499 1915 8,038 932 1,279 4,973 247 48 3,208 1916 5,575 666 887 4,216 26 49 2,268 At least one-half of the refined cream of tartar is exported to Great Britain. The United States imported 14,000 tons of cream of tartar in 1910, 13,800 in 1911, 13,000 in 1912, and 14,000 (560,000) in 1913. ' Before 1913 the United States levied an ad valorem import duty of 5 per cent, for low- grade and 25 per cent, for high-grade cream of tartar. After 1913 a new tariff was to come into force, but now that the war is over the question remains unsettled as in other countries also. MANUFACTURE OF TARTAR 1C ACID 407 The price of crude and refined tartar products varies widely, even in one and the same year, according to the requirements of the markets and also to speculation in raw materials and refined products. Before the war crude cream of tartar was sold at \\\d. to 14df. or even less per unit or kilo of the pure tartar in 100 kilos of crude product, and the refined at Is. Qd. to Is. lid. During and since the war the price of the crude material has become quadrupled and that of the refined product quintupled. Cream of tartar is largely used in dyeing, in the bichromate mordanting of fast wool dyes, etc., and in the printing of textiles. Considerable quantities are used in the United States, Australia, Japan, China and India for preparing powder which is added to dough to render the bread light and elastic ; this powder contains 69 per cent, of tartar and 31 per cent, of sodium bicarbonate. 1 MANUFACTURE OF TARTARIC ACID. This acid is prepared by decomposing its salts (cream of tartar, lees, calcium tartrate, etc.), the dark mother-liquors and the deposits and sludges of cream of tartar factories being most commonly employed. Attempts were at one time made to liberate the acid from its soluble salts by treating these, in hot solutions, with hydrofluosilicic acid, which separates as insoluble potassium fluosilicate, the solution of tartaric acid remaining being filtered, concentrated and crystal- lised. The potassium fluosilicate is treated with calcium carbonate to convert it into soluble potassium carbonate and insoluble calcium fluosilicate, which yields hydrofluosilicic acid under the action of an energetic acid. Tartaric acid has also been prepared by treating solutions of its salts with potassium carbonate and then with barium chloride, the latter precipitating the neutral potassium tartrate partly formed by the former reagent. At the present time, however, the method most commonly used consists in treating boiling cream of tartar solutions with milk of lime or powdered calcium carbonate. In this way one-half of the tartar is converted into insoluble calcium tartrate and the other half into the soluble normal potassium tartrate, the latter being then separated as the insoluble calcium salt by addition of calcium sulphate or chloride : 2C 4 H 5 6 K + CaC0 3 = H 2 + CO 2 + C 4 H 4 O 6 Ca + C 4 H 4 O 6 K 2 ; C 4 H 4 6 K 2 + CaS0 4 = K 2 SO 4 + C 4 H 4 O 6 Ca. The acid is liberated from calcium tartrate by means of sulphuric acid : C 4 H 4 6 Ca + H 2 S0 4 = CaSO 4 + C 4 H 6 O 6 . According to the nature of the materials employed, various procedures are adopted. Crude tartar is freed from coarser impurities by passing through a wide-meshed sieve, heated if necessary (see, above ), ground to a fine granular condition and placed in a wooden vessel, where it is treated with eight to ten times its weight of boiling water. The mass is well mixed with a stirrer and heated to boiling by a steam jet, most of the tartar then dissolving. A paste of calcium hydroxide (sieved ) is then added until a small portion of the liquid gives only slight effervescence with calcium carbonate (as a rule, 160 grams of quick- lime, made into a 10 per cent, paste, are required for each kilo of potassium tartrate), the mixture being then boiled for fifteen minutes. In this way calcium tartrate is precipitated, while normal potassium tartrate remains in solution. The latter is then precipitated as calcium salt by boiling with a slight excess of gypsum or of calcium chloride solution (300 grams of the chloride per kilo of tartrate used ) for about two hours ; a little precipitated calcium carbonate is finally added to precipitate the neutral tartrate as completely as possible. In some cases, however, the liquid is left slightly acid to prevent separation of iron and aluminium salts. It is, indeed, necessary to ensure the absence from the various reagents (lime, chalk, gypsum, etc.) of iron, aluminium, and especially magnesium, the latter forming magnesium tartrate, which is ultimately found as magnesium sulphate in the tartaric acid after the calcium tartrate 1 Cream of Tartar in Bread-making. When bread is made with yeast, an appreciable amount of sugar, derived from the flour, is lost owing to its conversion into alcohol and carbon dioxide. The yeast may be replaced by 500 grams of cream of tartar and 225 grams of sodium bicarbonate per 50 kilos of flour, the doughed mixture being left to stand until evolution of carbon dioxide commences ; it is then divided into loaves and baked, good light bread being thus obtained. Production of C0 2 by means of bicarbonate and hydrochloric acid has also been proposed, addition of salt being then unnecessary. Some years ago Candia suggested the use of compressed C0 2 for this purpose, the composition of the dough thus remaining quite unchanged. 408 ORGANIC CHEMISTRY has been treated with sulphuric acid. The boiling liquid is kept mixed and is afterwards either allowed to cool to 40 and decanted or passed immediately to the filter-press ; after repeated washings with hot and cold water, the crude, dry tartrate is placed on the market and the nitrate either rejected or evaporated to obtain the potassium chloride present. Where, however, the calcium tartrate is converted into tartaric acid, it is not necessary to filter and dry it, the tartrate, after the first decantation, being mixed with various separate amounts of water, which are drawn off when the precipitate settles. The calcium tartrate remaining may then be treated in the same vessel with sulphuric acid as described above. The procedure is rather more complicated in the case of wine lees (sediments, sludge, etc. ), as the tartrate cannot be extracted merely by treatment with water and filtration, owing to the presence of considerable amounts of mucilaginous protein substances (fer- ments), which impede filtration, so that they are either treated with concentrated sulphuric acid (60 Be.) or heated (see above). The moist lees (drained in bags and pressed) contain as much as 8 per cent, of cream of tartar, or, if dried in the sun, still more. These lees are nowadays worked by the Dietrich and Schnitzer process (1865) : they are first powdered and mixed by means of stirrers and then heated for five to six hours in iron autoclaves (4 metres high and 1-4 wide for 15 quintals of lees ) at 4 to 5 atmos. pressure, direct steam being admitted by copper coils and the air first allowed to escape. The albu- minoids are thus coagulated, together with large quantities of colouring-matters, and the mass may then be easily filtered, but before this, it is discharged into a lead-lined wooden vessel (holding 10 to 12 cu. metres) containing 3 cu. metres of water and the amount of hydrochloric acid (20 to 22 Be. ) corresponding with the quantity of tartar previously determined (100 kilos of potassium bitartrate require 60 kilos of hydrochloric acid at 20 Be., or 54-5 kilos at 22 Be. ). The mass is well mixed and passed through the filter- press, in which it is washed with water. The tartaric acid is then separated from the solution as calcium tartrate, as described above. Lees may be treated economically and well by the process of Cantoni, Chautems, and Degrange described above. To utilise the potash salts of the filtrate from the calcium tartrate, A. Alberti (U.S. Pat. 957,295, 1910) decomposes the organic substances in the hot with calcium chloride, filters and concentrates in a vacuum. The second phase of the manufacture of tartaric acid consists in the decomposition of the calcium tartrate by means of sulphuric acid (see above) and in the subsequent crystallisation of the tartaric acid. The calcium salt in the decantation or washing vessels, or as cakes from the filter-presses, is broken up and suspended in five to six times its weight of water in lead-lined wooden vessels furnished with stirrers covered with lead and with coils for indirect steam-heating. After the liquid paste has been well stirred, the sulphuric acid, previously diluted, is added in such amount that, after an hour's stirring at 60 to 70, there is still a slight excess of sulphuric acid, detectable by the faint green coloration imparted to a solution of methyl violet. Top great an excess of sulphuric acid produces blackening of the tartaric acid solution during concentration, whilst deficiency of sulphuric acid results in the formation of turbid, impure tartaric acid crystals ; when a little free sulphuric acid is present, fine shining crystals are obtained. Usually 1 kilo of sulphuric acid at 66 Be. is employed per 3 kilos of dry calcium tartrate. The solution is boiled for a couple of hours, left to cool, and the calcium sulphate which forms separated by means of a filter-press, washed with a little tepid water (this being added to the filtrate), and then with much cold water (this being used for treating subsequent quantities of calcium tartrate). The tartaric acid solutions were at one time concentrated in shallow, lead-lined, wooden vessels containing leaden steam-coils, but nowadays concentration is carried out in vacuum pans which are similar to those described later in dealing with the sugar industry and are of hard lead and of considerable thickness. The liquid is evaporated until it becomes almost syrupy, and is then discharged into wooden vessels containing stirrers, which cool the concentrated solution rapidly and thus cause the tartaric acid to separate in small crystals. The cold mass is quickly separated from the mother-liquor in a centrifuge, the crystals being washed with a fine spray of cold water. The mother-liquors are then concentrated until they give crystals, this process being carried out three times ; they are finally treated with milk of lime to separate the residual tartaric acid as calcium tartrate, which is filtered and worked up with the other TARTARIC ACID STATISTICS 409 calcium tartrate. The tartaric acid crystals are dissolved in one-half their weight of boiling water (if necessary, the solution is decolorised with animal charcoal and filtered) and the liquid left to crystallise, the crystals thus obtained being centrifuged and dried on sheets of lead in a current of air at 30; the mother-liquors are used to dissolve fresh quantities of the small crystals. The final yield is about 90 to 95 per cent, of the total tartaric acid in the prime materials when these are poor (e. g., lees with 20 to 25 per cent, of tartar) or 97 to 99 per cent, when richer prime materials (70 to 80 per cent, of tartar) are used. A process still little used, but worked successfully for many years in the Montredon factory near Marseilles, is that of Gladysz (Ger. Pat. 37,352, October 15, 1885), which is based on the following observations : (1) When calcium tartrate is suspended in water and saturated with sulphur dioxide, soluble calcium bisulphite is formed and the tartaric acid liberated ; (2 ) when this solution is heated to 66, the sulphurous acid is expelled and all the tartaric acid precipitated as pure crystallised calcium tartrate; (3) if in (1) potassium bitartrate is used instead of calcium tartrate, potassium bisulphite and tartaric acid are formed, and on heating the liquid to 80, sulphur dioxide is evolved and pure potassium bitartrate separated in a crystalline state ; (4) potassium tartrate, when treated with calcium bisulphite, gives potassium bisulphite and calcium bitartrate ; the latter separates at 100, when the potassium bisulphite gives, with lime, calcium bisulphite and caustic potash, which can also be utilised. In practice Gladysz proposed to suspend the tartar in lumps in lead-lined wooden vessels, and into these hermetically sealed and arranged in a series of five or six to pass sulphur dioxide. The solutions (10 to 12 Be. ) thus obtained are sent to the concentration apparatus, which communicates with towers to condense the sulphur dioxide (see Vol. I., p. 280). When the latter is completely evolved, the liquid is kept at 125 for a short time to separate crystalline calcium tartrate, which is collected by means of a centrifuge, while the solution is concentrated further and allowed to cool in shallow lead-lined wooden vessels to deposit the potassium tartrate. As a rule, however, the hot potassium tartrate solution is treated directly with calcium chloride and a little lime, so that it yields insoluble calcium tartrate, which is more easily separated. From this calcium tartrate, pure tartaric acid is then obtained in the ordinary way. Although theoretically no sulphur dioxide should be lost in this process, in practice about 15 per cent, is lost in winter and 20 per cent, in summer. The Gladysz process, somewhat modified by Ciapetti, is used in Italy in the manufacture of tartar from vinasse, lees, etc. (see p. 404). USES AND STATISTICS OF TARTARIC ACID. This acid is used in considerable quantities to replace the more expensive citric acid in the preparation of beverages, liquors, and aerated waters, and in wine-making. Large quantities are consumed in the mordanting of wool and silk, to reduce chromium salts, etc., in the printing of textiles, manufacture of dyes, photography, medicine, etc. Refined tartaric acid pays an import duty in Italy of 8s. per quintal and in the United States and Spain of 25 per cent, ad valorem. Italy possesses the following large tartaric acid factories : at Carpi, Agnano (Pisa), Barletta, Milan, and Casalmonferrato (the last of these was transferred to Milan in 1920). The last three are the more important, and are able to produce together as much as 5000 tons per annum. The world's production in 1905 was about 11,000 tons, of which Italy produced 670 tons; England and the United States, each more than 2500; Germany, about 1500; France, about 800 (1300 in 1910); and Austria-Hungary about 1000 tons. Germany exported 1700 tons of the refined acid in 1908, 2100 in 1910, 1850 in 1911, 2673 in 1912, and 2956 in 1913; the imports were 458 tons in 1910, 379 in 1911, 428 in 1912, and 325 in 1913. For Italy the imports and exports are as follows : 1908 1910 1912 1913 1914 1915 1916 1917 1918 T T ftons . 138 298 146 40 20 87 26 0-7 2-5 s \value, 27,380 4,594 2,314 20,952 6,264 280 1,000 TT / tons ] > 928 2 > 177 2 > 516 2 ' 846 2 > 963 3 > 634 3 ' 292 2 > 413 J' 971 5 \ value, 196,000 324,467 355,536 872,256 790,132 965,080 788,400 Great Britain imported 1700 tons of tartaric acid in 1908, 2050 in 1910, 2000 in 1912, and 2300 in 1913, and exported 335 tons in 1911 and 835 in 1913. 410 ORGANIC CHEMISTRY For France the importation and exportation are as follows (tons ) : 1913 1914 1915 1916 Importation ... 501 374 273 305 Exportation ... . 1350 1073 1027 914 In 1907, four Russian factories, worked by a syndicate, produced 600 tons of tartaric acid and sold it at 200 per ton. The Argentine imported 95 tons of tartaric acid in 1904, 465 in 1909, 729 in 1910, and 868 (almost three-fourths from Italy) in 1911. In 1911 a factory capable of making 330 tons per annum was erected at Buenos Aires. The price of tartaric acid is variable for the reasons mentioned on p> 407. Some years before the war the price was about 140 per ton, in 1911 it approached 100, and during the war it rose in Italy to 360 or even 560 per ton, while after the war ended in 1919 it varied from 440 to 520 per ton. ARTIFICIAL TARTARIC ACID. In 1889 a process was patented by Basset, and in 1891 a similar but improved one by Naquet for obtaining tartaric acid from starch (1 to 5 of water) by saccharifying with an equal weight of hot sulphuric acid (51 Be.), then adding double this quantity of sulphuric acid and almost as much sodium nitrate and heating at 100. When the reaction becomes very vigorous, the temperature is moderated and the heating continued at 80 to 90 for two to three days, the evaporated water being first replaced and the liquid concentrated to a syrup when evolution of gas ceases. In this manner all the saccharic acid is decomposed; the sulphuric and oxalic acids are then neutralised with calcium carbonate and the tartaric acid subsequently worked up in the usual manner by way of its calcium salt. One hundred kilos of starch should give theoretically 140 of calcium tartrate, corre- sponding with 56 kilos of tartaric acid, but in practice the yield of the acid does not exceed 55 to 60 per cent, of this theoretical amount. TRIHYDROXYGLUTARIC ACID, CO 2 H [CH(OH)] 3 CO 2 H. should exist in four stereoisomeric forms, of which the dextro-, laevo- and racemic (m.-pt. 127) compounds are known. They are obtained by the oxidation of xylose or arabinose, and, on reduction, give glutaric acid, their constitution being thus confirmed. SACCHARIC ACID, CO 2 H [CH(OH)] 4 - CO 2 H, forms ten stereoisomerides, which are all known and are closely related to the sugars. Saccharic acid is formed as a rule in the oxidation of sucrose, glucose, mannitol, and starch (e. g., with nitric acid ). It is deliquescent and soluble in water, and when heated or fused is converted into saccharone, which is a dextro-rotatory lactone melting at about 150. MUCIC ACID, CO 2 H [CH(OH)] 4 CO 2 H, is the stereoisomeride of saccharic acid which is constantly inactive. It is obtained on oxidising lactose, dulcitol, gum, etc., and forms a white powder very slightly soluble in water. KETONIC DIBASIC ACIDS Esters of these acids, like those of /?-ketonic acids (ethyl acetoacetate, etc. ; see p. 396), show both ketonic and acid decompositions, and also a new one in which carbon monoxide separates. MESOXALIC ACID (Dihydroxymalonic Acid), CO 2 H CO CO 2 H + H 2 or CO^H C(OH) 2 CO 2 H, shows ketonic behaviour in agreement with the first formula, but the molecule of water cannot be separated from the deliquescent prisms even at 100, and, further, derivatives (esters, etc.), are known which correspond better with the second formula, whilst the latter also explains well why mesoxalic acid, when heated with water, loses C0 2 and gives glyoxylic acid, C0 2 H CH(OH) 2 . The structure of the acid likewise follows from its formation by the action of barium hydroxide on ethyl dibromomalonate : CBr 2 (C0 2 C 2 H 5 ) 2 + Ba(OH) 2 = BaBr 2 + C(OH) 2 (C0 2 C 2 H 5 ) 2 . Its ketonic constitution is confirmed also by the fact that it gives tartronic acid, C0 2 H CH(OH) C0 2 H, on reduction. OXALACETIC ACID (Butanonedioic Acid), CO 2 H CH 2 C0 2 CO 2 H, is not known in the free state, but is formed as ester by condensation of ethyl oxalate and ethyl acetate in presence of sodium ethoxide (see Ethyl Acetoacetate). It also splits up in two ways TRICARBALLYLIC ACID 411 according as it is treated with dilute sulphuric acid (giving pyruvic acid, CO 2 , and alcohol) or with alkali (giving oxalic and acetic acids ). Being a ketone, it forms an oxime. The alcoholic solution is coloured dark red by ferric chloride and hence corresponds with the enolic form, C 2 H 5 O CO CH : C(OH) C0 2 C 2 H 5 . This ester, like ethyl aceto- acetate, is used in many syntheses, the hydrogen of the methylene group being replaceable by sodium, etc. ACETONEDICARBOXYLIC ACID (Pentanonedioic Acid), CO 2 H CH 2 CO CH 2 CO 2 H, forms crystals which melt at 135, losing 2CO 2 and giving acetone. It is formed by the action of concentrated sulphuric acid, in the hot, on citric acid : CH 2 C0 2 H CH 2 C0 2 H CH 2 C0 2 H CH 2 C0 2 H Citric acid The constitution of citric acid is shown by its formation from acetonedicarboxylic acid by the action of hydrogen cyanide and subsequent hydrolysis. The hydrogens of the two methylene groups are replaceable by sodium, so that this acid may be used in syntheses similar to those effected by ethyl acetoacetate. DIHYDROXYTARTARIC ACID, C0 2 H CO CO CO 2 H -f 2H 2 0, or, better, CO 2 H C(OH) 2 C(OH) 2 CO 2 H, melts and decomposes at 98 and forms a sodium salt, which is sparingly soluble and decomposes readily into CO 2 and sodium tartronate, C0 2 H CH(OH) C0 2 Na. It is obtained by the action of nitrous acid on an ethereal solution of pyrocatechol, guaiacol, etc., and also by the spontaneous decomposition of nitrotartaric acid. Sodium bisulphite converts it into glyoxal, while with hydro xylamine it forms the dioxime corre- sponding with the diketonic form. With phenylhydrazinesulphonic acid, it forms tartrazine, a beautiful yellow colouring-matter largely used in dyeing wool and silk. Of the higher ketonic acids the following may be mentioned : hydro- chelidonic acid (acetonediacetic acid), CO(CH 2 CH 2 C0 2 H) 2 ; diaceiosuccinic CH 3 CO CH C0 2 H CH(CO CH ) CO H acid, ; a,nd diacetylglutaric acid, CH 2 <~TT/nrk rrtr\ nrfu CH 3 -CO-CH-C0 2 H (H s)' AH the esters of which give rise to tetrahydrobenzene derivatives or, in presence of ammonia, to pyridine derivatives. G. POLYVALENT TRIBASIC HYDROXY-ACIDS ETHANETRICARBOXYLIC ACID, C0 2 H CH 2 CH(CO 2 H) 2 , and ASYM. PROPANETRICARBOXYLIC ACID, CO 2 H CH 2 CH 2 CH(C0 2 H) 2 . These two acids are stable in the form of esters, but in the free state they readily decompose, liberating C0 2 and forming dibasic acids. TRICARBALLYLIC ACID (Symm. Propanetricarboxylic or Pentadioic- 3-methyloic Acid), CO 2 H CH 2 CH(C0 2 H) CH 2 C0 2 H, melts at 163 and is very soluble in water. It is found in unripe beets and occurs abundantly in the deposits of the vacuum pans of sugar factories. Synthetically it is obtained from aconitic acid l by the addition of hydrogen and from citric acid, which loses its hydroxyl group when treated with hydriodic acid. CH C0 2 H II 1 Aconitic Acid is the corresponding unsaturated acid, C C0 2 H . It melts at 191, and is CH., COjH readily soluble in water ; it is an energetic acid and is converted into tricarballylic acid by nascent hydrogen. It is prepared by heating dry citric aoid, which loses a molecule of water. It occurs naturally in the sugar-cane, beet, Aconitum napellus, etc. 412 ORGANIC CHEMISTRY Its constitution is shown by its synthesis from glycerol by way of the tribromhydrin and tricyanohydrin, C^H 5 (CN) 3 , the latter being hydrolysed CH 2 . CO 2 H OH CITRIC ACID, C ^OH I I I ' 2H I ' 2H ' 2H CH 2 C1 -CH 2 C1 CH 2 C1 CH 2 -CN CH 2 -C0 2 H Citric acid was prepared some years ago (Fabrique de produits chimiques de Thann et de Mulhouse) by Wehmer's biological process (Ger. Pat. 72,957 of 1893), according to which glucose is fermented by certain moulds (Citromyces Pfefferianus and Glaber, and Mucor pyriformis), the yield being about 55 per cent, of the sugar. 2 1 The following table gives the percentage by weight in aqueous solutions of different densities : Degrees Baume . .246 10-5 12 14 18 22 26 28 30 32 34 Per cent, of citric acid . 4 8 12 20 22 26 34 42 50 54 58 62 6fi * The formation of citric acid by the action of micro-organisms on sugar was studied in detail also by Maze and Perrier in 1904, by Herzog and Polotzky in 1909, and by Buchner arid Wiistenfeld in 1909 with Citromyces citricus. Allthese authors found that such organisms are able to live in highly acid media and that, under certain conditions, especially when there is a scarcity of nutrient nitrogenous substances, they can transform as much as 50 per cent, of the sugar into citric acid. A current of air passed through the fermenting liquid does not aid the development of the organisms, but at the same time does not oxidise the citric acid formed ; lack of air, however, retards the fermentation. The presence of inorganic ammonium salts and of calcium carbonate results in a good yield and in good separation of calcium citrate. Various tests were made with 20 per cent, solutions of sugar (sucrose, which is rapidly inverted ) containing 0-5-1 per cent, of inorganic salts (ammonium phosphate or nitrate, etc.); in ten to twelve days or, in some cases, in thirty -five days, 40 to 50 per cent, of the sugar undergoes conversion into calcium citrate (Wehmer, 1912). The formation of the citric acid by direct oxidation (as occurs in acetic or oxalic fermentation) is excluded, and Maze advances the hypothesis that the acid is derived rather from the decomposition of Jthe protein substances forming the ferments themselves, whilst Buchner assumes the intermediate formation of parasaccharinic acid. , Wehmer (1913) confirms the observation of earlier experimenters that calcium citrate is CITRUS INDUSTRY 413 When heated for a long time with water, citric acid forms a little aconitic acid, into which it is transformed completely by concentrated hydrochloric acid. It is readily oxidised to acetone, oxalic acid, and carbon dioxide. Like tartaric acid, citric acid hinders the precipitation of the metallic hydroxides from their salts by ammonia. 1 Citric acid is used in large quantities for lemonade and in pharmacy and for effervescent drinks (citrate of magnesia); it is employed also in dyeing and in textile printing. It is used also in aqueous solution (or as fresh lemon juice) as a substitute for vinegar. It is often employed, in preference to tartaric acid, to increase the acidity of wine so as to improve its colour and keeping qualities (100 grams per hectolitre is sufficient, whereas about 400 grams of tartaric would be necessary to produce the same effect, since two-thirds of it undergoes precipitation as potassium bitartrate). A certain amount of citric acid is used in the analysis of superphosphates. CITRUS INDUSTRY Citric acid is manufactured from the juice of lemons yielded especially by the following three plant species : Citrus limonium, Citrus bergamia (bergamot), and Citrus limetta (or wild lemon cultivated by the British in Guiana and the West Indies). Lemons are cultivated most extensively in Sicily and Calabria, and to a considerable extent also in Spain. The cultivation is of little importance in Greece, the Sandwich Islands, and the West Indies, but is rapidly increasing in Australia. During recent years the production of oranges and lemons has made rapid strides in California and in Florida, 2 where it is obtainable in good yield also from glycerol, and finds also that citric acid is produced only as calcium citrate (i. c., in presence of calcium carbonate) and never aa free acid, possibly because the latter undergoes instantaneous decomposition or transformation into other substances (not into organic acids); in any case the biological formation from glycerine denotes the possibility of a synthetic process, which is somewhat rare (see p. 137). From lactose and ethyl alcohol citric acid has not been prepared. According to Zahorski (U.S. Pat. 1,069,168, 1913) citric acid may be obtained from sugar (glucose, levulose, etc.) by adding 15 per cent, of citric acid to a culture of Sterigmatocystis nigra and using this culture for the gradual seeding of the saccharine solution. 1 Tests and Reactions for Citric Acid. Deniges reaction is characteristic and serves to detect small quantities of the acid ; the solution is heated to boiling -with one-twentieth of its volume of Deniges' reagent (5 grams of mercuric oxide, 80 c.c. of water, and 20 c.c. of concentrated sulphuric acid ), 3 to 10 drops of approximately decinormal potassium permanganate solution being added ; a white, crystalline precipitate is formed immediately even with traces of citric acid. The reaction is not masked by the presence of tartaric, oxalic, malic, sulphuric, or phosphoric acid, although the amount of permanganate used must then be slightly increased. Haussler (1914) gives the following reaction for detecting small amounts of citric acid even in presence of other organic acids (proteins and sugars are first eliminated by successive treat- ment with lead acetate, H 2 S and calcium carbonate) : 2 c.c. of the dilute citric acid solution (even 0-1 per cent.) is evaporated to dryness in a dish with 2 c.c. of alcohol containing a little vanillin, 3 to 4 drops of 25 per cent, sulphuric acid being added to the residue and the dish heated for fifteen minutes on a water-bath : the mass then becomes an intense violet and dissolves in water to a green solution, which, even in high dilution, is coloured an intense red by addition of ammonia. The presence of tartaric acid- -which is a common adulterant in citric acid may be detected by the addition of potassium acetate, the acid potassium citrate thus formed being readily soluble, whilst acid potassium tartrate is only slightly soluble. Minimal quantities of tartaric aoid may be also detected as follows : 1 gram of the powdered substance is heated for a few minutes on the water-bath with 1 c.c. of 20 per cent, ammonium molybdate solution and a few drops of 0-25 per cent, hydrogen peroxide solution; in presence of even 0-001 gram of tartaric acid, a bluish coloration is obtained. The presence of oxalic acid is easily discovered, since in the cold and in arnrnoniacal solution calcium oxalate is insoluble, whilst calcium citrate is soluble. 2 The lemon orchards in Sicily are found especially on the coast from Palermo to Cefalu (about one-fifth of the total production of lemons and oranges) and on the coast near Messina (more than double that of Palermo-Cefalu), usually on irrigated lands, but sometimes in cool non-irrigated districts. The stocks are obtained from the seed of the wild orange (called by the Sicilians arancio agro, or sour orange ). The plants from these seeds are planted out in the orchards in their third year and are placed from 3 to 5 metres apart, according to the nature of the soil, to the wind, and to custom. After a year the stock is grafted from an adult plant. Fructifi- cation occurs after a further three years and reaches its maximum in ten years. The flowering 414 ORGANIC CHEMISTRY already about double that of Sicily. It is pleasing to note that plantations of oranges alone are being more and more largely replaced by those of lemons. In German East and West Africa, plantations of lemons were advantageously replacing those of rubber before the war. Only the refuse lemons (one-fourth of the total production) are used for the manufacture of citric acid, as they cost only one-half as much as the picked fruit. The first operation to which the lemons are subjected is peeling, a workman removing the peel with three cuts of a knife, cutting the lemon in two and throwing it into a tub ; the peel is collected separately for the preparation of essence. A skilled operative can peel more than 4000 lemons a day. From 8000 lemons, pressed in a suitable press, 700 litres of juice, containing 4-5 to 6 per cent, of citric acid, are obtained; only 9 to 10 per cent, of the total acid exists as calcium citrate. 1 The juice does not keep well (better if of the lemons on the same plant is progressive and lasts the whole of May ; from the latter half of June to the beginning of October the plants are watered every fortnight. The maturation of the fruit is gradual from November to the end of April and the harvest is gathered in three periods, the best fruit being those of the middle one December to February; the last fruit, plucked in April and the beginning of May, are poorer in juice and thicker in the peel. In the coast district of Messina, the harvest finishes at the beginning of March. Lemons have also been forced in Sicily during the past few years, the highly valued summer fruit being thus obtained; these are called verddli (high quality) and bianchetti (lower quality). In this case the plants are not watered during June and July, the leaves withering and all the young fruit .falling. In August, water in abundance is given at intervals, and Sodium nitrate applied as fertiliser. The plant then suddenly becomes very vigorous, and in a few days is covered with new flowers, the fruit ripening rapidly from the end of May to the close of the summer, and that gathered in June or July being of the highest quality. Such plants give an increased crop, especially if manured, and the fruit commands more than double the ordinary prices. This procedure is followed in orchards where the soil is not moist and can be left to dry completely and where the lemons are not alternated with oranges or other crops requiring watering. Under favourable conditions, a good lemon plant should yield on an average 1000 lemons a year (some very large plants give several thousands). The price varies considerably, 8.9. to IQs. per 1000 being paid for the fruit on the tree and as much as 24s. for the gathered fruit; forced lemons cost at least 20s. per 1000, the price in 1907 exceeding 40s. The cost of gathering, packing, and freight to the port varies from Is. Id. to 3s. 2d. per 1000. The refuse lemons, which form about one-fourth of the crop (or more if the demand for lemons is small), cost about half as much as the other fruit (5s. to 6s. per 1000 on the average), although on rare occasions the price reaches 8s., and in 1908, at the height of the crisis, it fell to 2s. per 1000. 1 Fresh lemon juice, contains also 7 to 9 per cent, of glucose, 0-2 to 0-8 per cent, of saccharose (according as the lemons are sour or ripe), certain extractive, gummy, and pectic substances (about 0-2 per cent, for ripe and 0-8 per cent, for unripe fruit), and about 0-5 to 0-7 per cent, of inorganic salts. The presence of these substances renders it impossible to crystallise the citric acid merely by concentrating the juice, even when all the glucose is transformed into alcohol (5 to 6 per cent.), so that, even at the present time, the citric acid is separated by Scheele's classical and rather costly process, according to which it is first converted into calcium citrate. The high price of fuel has prevented the establishment of the citric acid industry in Sicily, and the preparation of the acid has been monopolised for a long time by England and, at the present time, largely by Germany. Both these countries receive the raw material from Sicily, to a small extent as lemons packed in barrels containing sea -water, partly as concentrated juice (agro cotto), but mostly as calcium citrate. In consequence of the development of lemon -growing in Spain, and especially in California and Australia, and also owing to an agreement entered into by the manufacturers of citric acid, the condition of the Sicilian growers became so critical that in 1903 the Italian Minister of Agriculture offered a prize of 6000 for improvements in the industry or new processes of value to the cultivators. This sum was largely wasted by Commissions who achieved nothing or by rewarding certain favoured individuals. However, at the end of 1904, Professor Restuccia, of Messina, announced to the Government the discovery of a process for the direct extraction of citric acid by simple concentration of the juice, to which was previously added a trace of a substance the nature of which he did not reveal (picric acid !) and a little animal charcoal, but this process only led to further waste of money. In 1910, Peratoner and Scarlata suggested the following new process for extracting the essence and citric acid from the lemons directly, without conversion of the acid into the calcium salt. The juice obtained by squeezing the minced lemons in hydraulic presses is partly distilled in a vacuum on a water-bath at 60 to recover the essence and then concentrated in vacua at 70 until it acquires a syrupy consistency (one-tenth of the original weight). When the syrup is cold, all the citric acid is extracted by treatment with a mixture of alcohol and ether, in which many of the impurities are insoluble. The alcohol and ether are recovered by distillation, and the residue diluted with a little water, filtered, and concentrated in vacua ; after standing for twelve to twenty-four hours it sets to a yellowish red crystalline mass which, after defecation and decolorisation in the ordinary way (animal charcoal, etc.), gives pure colourless crystals, OILOFLEMON 415 pasteurised at 63 to 65), and is usually concentrated at once in open pans with direct- fire heating until the specific gravity reaches 60 on the citro meter (1-2394, or 28 Be.), and the product represents a blackish decoction containing 300 to 4.00 grams of citric acid per litre (that from the bergamot of Calabria and Messina contains 300 grams, while that produced in the Sandwich Islands and in the Republic of Dominica from lemons of the limetta species has a density of 1-32 and contains about 575 grams of citric acid per litre). The boiling decoction is passed through a cloth and is collected in casks for transport. The commercial value of the juice (agro cotto) depends on the content of citric acid, and is determined either by diluting the juice and titrating with normal caustic soda or by precipitating in the hot as calcium citrate and weighing the latter. This estimation is preceded by a qualitative examination to ascertain if salt has been added to increase the specific gravity (test with silver nitrate in presence of a little nitric acid) or if sulphuric or hydrochloric acid has been added to raise the degree of acidity (test with silver nitrate or barium chloride in presence of a little nitric acid). In the large modern factories, the juice is treated in almost the same manner as in the manufacture of tartaric acid (see p. 407) : into 100-hectolitre masonry vessels provided with stirrers and cold-water coils are placed 20 hectolitres of concentrated juice and 80 hectolitres of water, the liquid being then well mixed for thirty minutes and allowed to ferment, the glucose being thus converted into alcohol and the juice clarified. By passing very cold water through the coil the temperature of the liquid is lowered to 5, and a large part of the dissolved and suspended extractive and mucilaginous matters separated ; in presence of a little tannin, these matters coagulate *nd do not redissolve (50 litres of sumach extract at 10 Be. are sufficient, the liquid being stirred for fifteen to twenty minutes immediately after the addition). The solution is then passed to the filter-presses and thence into 20-hectolitre wooden vats or into brickwork vessels similar to the preceding ones, but provided with perforated coils for direct-steam heating. The boiling liquid is now neutralised exactly with dense milk of lime or with powdered calcium carbonate. The latter causes frothing and sometimes overflow of the liquid, but precipitates a purer calcium citrate, whilst the hydroxide throws down many pectic and colouring matters. In some cases two-thirds of the acidity is neutralised with calcium hydroxide and the remainder by the carbonate. For every 100 kilos of citric acid present (titrated) 45 kilos of quicklime (57 of slaked lime or 80 of the carbonate) are added. After stirring while hot, the insoluble tricalcic citrate which forms immediately is passed at once through the filter-presses and washed for ten minutes with very hot water, for ten minutes with tepid water, and for five minutes with cold water, which should remain almost colourless. In some parts of Sicily, calcium citrate is prepared in a primitive method (with slaked lime often containing magnesia, which yields soluble magnesium citrate, this being lost) and is sold dry with a content of 64 per cent, of citric acid. 300 kilos of calcium citrate of this strength require, on the average, 100,000 lemons, the peel of which yields 37 kilos of essence, selling at 6*. 4d per kilo. 1 The total cost of manufacturing calcium citrate and essence the yield being 60 to 70 per cent. The remaining acid may be separated from the mother-liquor as citrate. In spite of the favourable opinion expressed by Professors Garelli and Paterno, this process does not seem to have been applied practically. Meanwhile the crisis in the citrus industry, which had apparently lessened as a result of the good crops and prices of 1906 and 1907, became aggravated in 190.8 owing to the diminished demand for lemons, to the American crisis, to the agreement between the producers of citric acid to limit the amount of raw material required thus lowering prices and exhausting the usual stocks of treated products and, finally, to the abundant production, since refuse lemons did not sell for 2s. Gd. per 1000 at the beginning of 1908 and did not pay for gathering. Various measures have been taken by the Italian Government to protect the citric acid industry in Sicily, but it should be possible, in the present advanced condition of technical chemistry, to develop this industry without such aid. The sulphuric acid required is now made in Sicily itself, and by the use of multiple-effect evaporating plant, the consumption of coal may be reduced to a minimum. In 1911 a large citric acid factory was erected in the vicinity of Palermo by the firm of Golden berg, from Winckel, near Wiesbaden (see later). 1 Oil of lemon is extracted from the skin and peel by pressing the latter by hand against a sponge and then separating the liquid from the sponges ; this liquid deposits the residues on standing and is afterwards decanted off and filtered. In place of this hand -pressing, which yields 0-15 per cent, of oil, special machines are used in some factories. From the waters (on standing) and from the residues remaining after decantation (by pressing), an inferior oil is recovered. Distillation of such waters yields distilled oil, which is not ot very high quality. 416 ORGANIC CHEMISTRY from 100,000 lemons was, before the war, about 10. The cakes of calcium citrate from the filter-presses are mixed in 20-hectplitre lead-lined vessels with 15 hectolitres of cold water, the lime of the citrate being then neutralised exactly with dilute sulphuric acid (1 : 5) (with 100 kilos of citric acid in the juice correspond 400 kilos of this dilute acid); a slight excess of sulphuric acid is always added, since the presence of unaltered calcium citrate would hinder the crystallisation of the citric acid. The acid is added in portions at the rate of 5 litres per minute, the liquid being kept well mixed and direct steam applied through a perforated leaden coil. The mass is boiled for ten to fifteen minutes, the steam being then suspended and the whole mixed for thirty minutes. The calcium sulphate is then removed by means of a filter-press and is washed with 200 litres of boiling water, which is added to the first filtrate, and then with cold water, which is afterwards used for treating fresh calcium citrate. The citric acid solutions from the filter-presses contain only minimal quantities of sulphuric acid and certain blackish extractive matters. Concentration of the solution was formerly carried out in lead-lined wooden vessels, 4 metre's long, 2 metres wide, and 25 cm. deep, containing closed steam coils. Evaporation should be rapid and the temperature should never exceed 65 to 70. When the liquid reaches 46 (sp. gr. 1-3), almost all the calcium sulphate previously remaining in solution separates; the clear liquid is then siphoned into a similar vessel underneath, the concentration being continued until a crystalline skin forms at the surface of the liquid, which is next transferred to wooden crystallising vessels, 2 metres X 70 cm. x 20 cm. (deep) ; the inner surface is polished with plumbago. After two days, the dark brown mother-liquors are removed and the yellowish-brown crystals centrifuged. In order to separate traces of dissolved iron from the mother-liquor, this is treated with a little potassium f errocyanide and filtered ; two or three further crops of dark- coloured crystals are obtained, the very dark mother-liquor finally obtained being added to fresh lemon- juice. In modern factories the citric acid solution, freed from calcium sulphate by filter- pressing, is concentrated in vacuum apparatus, just as in the sugar and tartaric acid industries, the density 45 to 50 Be. in the hot being attained. In this way, the temperature does not exceed 60 to 65, and with a triple-effect apparatus not only rapidity, but also economy of fuel is attained (see Vol. I., pp. 563, 568, and also section on Sugar). In order to remove the calcium sulphate remaining in solution, the concentration is effected in two phases : in the first to 26 to 28 Be., the liquid being then cooled in suitable vessels in which the gypsum deposits; the residual liquid is then concentrated further to 48 to 50 Be. This liquid is discharged into the crystallising vessels, which are of lead-lined wood and of large surface; the mother- liquors are reconcentrated and recrystallised two or three times, and are finally worked up to crude calcium citrate. The blocks of crystals left in the crystallising vessels are broken up with wooden mallets and centrifuged. In 1912, Messrs. Schimmel and Company obtained a yield of 0-3 per cent, of the oil from the peel by chopping the latter fine, making a liquid paste with water and distilling at a pressure of 50 to 60 mm.; oil thus prepared does not keep so long as the pressed oil (at most a year). Immature lemons gathered in December-February yield the finest essence (about 450 grams per 1000 lemons). The oil is stored in tinned copper vessels and is sold by the old English pound of 12 ounces or 318 grams. Its density is 0-854 to 0-861, and its rotatory power + 60 to + 64 in a 10 cm. tube at 20, and it distils mostly between 173 and 178. It is yellow and undergoes change in the air and light. It dissolves easily in absolute alcohol, ether, benzene, or 5 vols. of 90 per cent, of alcohol. It contains about 90 per cent, of limonene and 5 to 8 per cent, of citral, and it is often adulterated with oil of turpentine, lemon terpenes or oil of orange. By a law passed in 1897, such adulteration is forbidden. Deterpened essence, obtained by distilling from the oil in a vacuum 80 to 90 per cent, of the terpenes and distilling the residue in a current of steam, is a yellow oil of sp. gr. 0-89, with an intense smell of lemons, and is highly soluble in alcohol; it consists mostly of citral. Its exportation, for making perfumes, pastry and beverages is as follows (kilos) : 1908 1910 1912 1913 1914 Oil of orange . 173,265 (152,473) 143,285 53,803 48,103 42,838 bergamot . 74,842 (95,798) 64,788 71,343 63,093 61,757 lemon . 476,842 (228,884) 425,076 517,596 456,303 603,000 1915 1916 1917 1918 Oil of orange . ' 70,672 96,057 72,347 312,820 (557,948) bergamot . 105,553 157,165 133,800 821,809 (2,136,703) ,. lemon . 744,000 655,522 522,486 1,629,740 (717,086) CITRUS INDUSTRY STATISTICS 417 The brown crystals first obtained are refined and decolorised by dissolving them in rather more than double their weight of water (to a solution of 20 Be.) and boiling the solution with animal charcoal previously treated with hydrochloric acid, as already mentioned in considering the refining of tartaric acid (p. 404). The hot liquid is filter-pressed under low pressure and is re-filtered until it becomes clear and free from particles of charcoal. The filtrate is concentrated in a vacuum at about 60 to 65 until crystals of citric acid form, and is then heated to 90 and discharged into lead-lined wooden crystallising vessels, in which it is stirred at intervals so as to obtain small crystals ; after forty-eight hours these are* centrifuged and washed in the centrifuge with pure citric acid solution, just as is done with sugar (see later). If chemically pure citric acid free from metals is required, the concentration is carried out in thickly-tinned vessels and the crystallisation in wooden vessels ; the traces of iron present are eliminated by addition'of a little potassium ferrocyanide and sodium sulphide. In all the washing and refining operations, pure water with little hardness is always employed. STATISTICS AND PRICES. The importance of the Italian citrus industry is shown by the following figures : 1909 Output of citrus fruits (tons) . 8,400 Area under cultivation (hectares) - Exportation of oranges (tons) . 110,899 value.fi . . . 443,600 of lemons (tons) . 256,063 value J 1911 1913 1914 1915 1916 1917 1918 7,865 8,765 8,016 7,591 7,000 . 113,000 108,400 108,400 128,343 130,600 133,080 129,161 104,290 34,662 42,558 924,080 1,044,802 1,330,805 1,291,614 1,251,480 830,856 406,880 258,689 304,541 308,389 204,992 209,804 150,291 91,169 921,826 1,448,660 1,949,062 2,220,400 1,639,938 1,678,440 2,104,072 2,176,368 Spain exported 92,900 tons of oranges in 1889, 300,000 tons in 1899, 470,400 tons in 1908, and 500,000 tons (about 2,200,000) in 1912. Before the war France produced about 2000 tons of oranges per annum. In 1912 California exported 400,000 tons of oranges. In Florida the orange crop amounted to about 170,000 tons (5,000,000 boxes) in 1894- 1895j but the exceptional frost of the following winter destroyed almost all the trees and the crop was reduced to 2500 tons. The trees were afterwards replaced and the crop reached about 165,000 tons (880,000) in 1909 and almost 270,000 tons in 1912-1913. The citric acid imported into and exported from Italy (Calabria and Sicily) was as follows : 1908 1910 1912 1913 1914 1915 Imports (tons) 164 109 127 105 32 18 Value, . 24,332 - 18,870 7,040 5,370 Exports (tons) 2-3 0-8 2-3 220 599 755 1916 26 7,890 1,045 1917 1918 832 754 Value, 32,634 131,736 226,650 313,380 349,440 316,596 The output of citric acid in Italy in 1912 was still below 200 tons, and in 1914 it reached 800 tons, the capacity of the factories being 1600 tons. The Sicilian exports and imports of calcium citrate (in casks called pipes, holding 305 kilos) 2 were as follows (especially to the United States, France, and Great Britain) : 1905 1908 1910 1912 1913 1914 1915 1916 1917 1918 Tons . . 4126 7710' 6476 7680 3813 5688 6704 7279 5838 3736 Value X 1000 181 401 414 488 242 428 509 553 724 463 1 While in other years the picked lemons for use as fruit sold for 12s. or even 16s. per 1000 (i. e., 1J cantaros = about 125 kilos), and the forced fruit for as much as 32s., the quotations in July 1908 were as follow : ripe lemons (gathered in winter and spring), 5s. 4rf. to 8s. per 1000 ; verdelli, 17s. Qd. to 20s. ; bianchetti, 8s. to 10s. ; for pressing, 2s. to 2s. 4d. Subsequently prices have always been higher. 2 M. Spica (1910) has suggested a simple, rapid, and exact method for the analysis of calcium citrate, the content of citric acid being obtained from the volume of carbon monoxide generated when the citrate is heated with concentrated sulphuric acid. Two grams of the citrate, mois- tened in a flask on the water-bath, are treated with 25 c.c. of concentrated sulphuric acid. By means of a current of carbon dioxide, all the carbon monoxide is driven into a nitrometer similar to that illustrated in Fig. 16 (p. 11), the carbon dioxide being absorbed in caustic soda. Each cubic centimetre of CO at and 760 mm. corresponds with 0-009407 gram of citric acid, C 6 H 8 7 + H 2 O; the method cannot be used with citrate adulterated with oxalate or tartrate. VOL. ii. 27 418 ORGANIC CHEMISTRY The output of calcium citrate in Sicily in 1913 was 6000 tons, besides 800 pipes of con- centrated juice ; in 1914 the output was 6687 tons, and in 1918, 9087 tons (see note, p. 414). The mean price fixed was 52 per ton in 1905, 80 in 1907, 50 in 1909, and 53 12s. in 1910. In 1909, owing to the economic crisis, exportation diminished considerably and in certain months the price fell to 40 per ton. During the war the sale price for the citrate (64 per cent.) was fixed at 280 per ton for the years 1917-1919. The agro cotto exported in 1905 amounted to 1200 tons (35,520), and in 1908 to 750 tons (22,000); subsequently practically only calcium citrate was exported. In 1913, the freight for calcium citrate from Sicily to Marseilles was about 10s. per ton, and to London 16s. In 1903, 281 works in Calabria and Sicily for the preparation of agro cotto employed a total of 4000 workmen and 240 h.p. The annual production of refined citric acid in Europe was about 4000 tons in 1913, and the price varied from 108 to 140 per ton. In general the price rises and falls with that of tartaric acid, the difference between the prices of the two acids being due to the different degrees of acidity (3 carboxyls in one case and 2 in the other) and molecular weights [152 for tartaric acid and 210 for citric acid (+ H 2 0)]. If all the juice transformed into calcium citrate for exportation were treated in Sicily, the annual output would amount to 3000 to 4000 tons of citric acid, which would suffice to supply the whole of Europe. The French imports and exports are as follows (tons ) : Citric acid T . ( imported Juice (exported exported 1913 134 31 29 452 1914 58 12 58 249 1915 1916 19 146 11 131 37 95 272 207 In the West Indies the crude citrus materials produced corresponded with 1000 tons of calcium citrate in 1913 and with 1200 tons in 1914. The Argentine imported 111 tons of citric acid in 1910 and 208 tons in 1911. For Germany the imports and exports are as follows (tons): Imports Exports 1902 306 163 1905 379 1909 193 358 1910 206 381 1911 178 553 1912 162 550 1913 310 528 In addition, 360 tons of lemon juice were imported into Germany in 1908 and 170 tons in 1909. The import duty in Italy was formerly 4 per ton, but was raised in 1909 to 20 to protect a large factory, with 40,000 capital, erected in 1910-1911 near Palermo by the firm of Goldenberg ; during the war this factory became solely Italian, with the title Fabbrica Chimica Arenella, and it now supplies Italian needs and is able to export a considerable quantity of citric acid (see above). In Austria there are two citric acid factories, which, in 1906, imported 54 tons of calcium citrate from Sicily, 145 from Turkey, and 435 from Greece. France has two factories, these importing 1811 tons of Sicilian calcium citrate in 1906. In Germany there are nine citric acid works and four of pure citrates, 1318 tons of Sicilian calcium citrate being imported in 1908. In England there are ten works, almost all in London. The United States have three very large factories which produce more than 1000 tons of citric acid and import also a certain quantity from Europe, although the protective duty is 31 10s. per ton ; calcium citrate, which is all imported (in 1911 about 2800 tons, of the value 160,000), is free from duty. SALTS OF CITRIC ACID. Being tribasic, this acid forms three series of salts, as well as two different monosubstituted acids and two disubstituted acids. The alkali salts are all soluble in water, almost all of the others being insoluble, although dissolving in alkali citrates owing to the formation of double salts; in such solutions, the metals are no longer precipitable by ammonia, phosphates, or alkali carbonates. When heated, many citrates give salts of aconitic acid. CALCIUM CITRATE, (C 6 H 6 O 7 ) 2 Ca 3 + 4H 2 O. If calcium hydroxide is added to a dilute solution of citric acid, no precipitate forms in the cold but one separates in the hot. AMIDES 419 In presence of ammonia, calcium chloride gives no precipitate in the cold, while that formed in the hot partly dissolves on cooling but does not dissolve in caustic soda, and so differs from calcium tartrate (see p. 401). In moderately concentrated solutions, calcium chloride precipitates calcium citrate, although incompletely, even in the cold; in the hot, precipitation is complete. The water of crystallisation is wholly expelled at about 200. Calcium citrate is soluble in ammonium citrate with formation of a double salt precipitable by alcohol. The manufacture and statistics of calcium citrate are considered above. BARIUM CITRATE is less soluble in cold water than the calcium salt. MAGNESIUM CITRATE, (C 6 H 5 O 7 ) 2 Mg 3 , is formed by dissolving magnesium car- bonate in citric acid solution. It is used as a purgative and is then prepared by heating a mixture of 105 parts of powdered citric acid with 30 parts of magnesium oxide cautiously at 100 to 105, pouring the fused mass on to porcelain tiles and powdering when cold. Large quantities of effervescent magnesia are prepared nowadays as a purgative and refreshing drink by mixing magnesium citrate with sodium bicarbonate and small pro- ' portions of citric acid and sugar, and granulating the mass with addition of a little glucose. Citric acid and, to some extent, magnesium citrate are often adulterated with tartaric acid, which is cheaper. CITRATE OF IRON is obtained as a dark red colloidal solution by dissolving ferric hydroxide in cold citric acid solution. Such solutions of different concentrations give, on heating, various citrates of iron which are soluble in ammonium citrate and more or less soluble in water, and have been studied in recent years in relation to their colloidal character. Of the HIGHER POLYBASIC HYDROXY-ACIDS the following may be mentioned : Desoxalic acid, C0 2 H CH(OH) C(OH)(C0 2 H) 2 , which forms deliquescent crystals and, when boiled with water, loses C0 2 and gives uvic acid ; hydroxycilric acid (dihydroxytri- carballylic acid), C 3 H 3 (OH) 2 (C0 2 H) 3 , found in the beet; acetonetricarboxylic acid and various acids which contain four, five, or even more carboxyl groups and are of synthetic and not of natural origin. IV. THIO-ACIDS AND THIO-ANHYDRIDES These may be regarded as acids or anhydrides in which an oxygen atom is replaced by sulphur, as in THIOACETIC ACID (Ethanthiolic Acid), CH 3 CO SH, which is obtained by the action of phosphorus pentasulphide on acetic acid and is a colourless liquid boiling below 100, giving an odour of acetic acid and hydrogen sulphide ; these two compounds are also formed by the action of water on the acid. ETHANTHIOLTHIOLIC ACID, CH 3 CS SH, is a dithio-acid, and ACETYL SULPHIDE, (CH 3 CO) 2 S, a thio-anhydride. The esters corresponding with these acids, e. g., ETHYL THIOACETATE, CH 3 CO SC 2 H 5 , a liquid boiling unchanged and yielding the acid and mercaptan on hydrolysis, are also known. V. AMIDO-ACIDS, AMINO-ACIDS, IMIDES, AMIDINES, THIOAMIDES, IMINO-ETHERS, AND ANALOGOUS COMPOUNDS A. AMIDO-ACIDS (AMIDES) AND DERIVATIVES Like the amines (see p. 239), the amides may be regarded as derivatives of ammonia, the hydrogen atoms of which are replaced, not by alkyl, but by acid radicals. There are thus primary, secondary, and tertiary amides, which are obtained by the replacement of one, two, or three atoms of hydrogen, and are sharply distinguished from the amines, as they are readily hydrolysed by alkali, acid, or superheated water, giving ammonia and the corresponding acids. They are generally crystalline substances soluble in alcohol or ether, and the lower members, especially of the primary amides, dissolve also in water. Their boiling-points are much higher than those of the corresponding amines. Amides are also known in which one or two atoms of the ammoniacal 420 ORGANIC CHEMISTRY hydrogen are replaced by alkyl radicals, i. e., alkylated amides, e. g., ethyl- acetamide or acetylethylamine, CH 3 CO NH C 2 H 5 , and dimethylacetamide, CH 3 CO N(CH 3 ) 2 , from which, on hydrolysis, only the acid is separated, the alkyl residue or residues remaining joined to the amino-group, forming non-hydrolysable amines. PREPARATION. (1) By dissolving an alkyl cyanide (nitrile) in con- centrated sulphuric acid, either with or without concentrated acetic acid, concentrated hydrochloric acid or hydrogen peroxide, a molecule of water is added : CH 3 CN + H 2 O = CH 3 CO NH 2 . By heating acids or anhydrides with nitriles, secondary or tertiary amides are formed. (2) The action of ammonia solution or solid ammonium carbonate on acid chlorides yields primary amides, whilst, if the ammonia is replaced by an amine, an alkylated amide is obtained : CH 3 CO Cl + 2NH 3 = NH 4 C1 + CH 3 CO NH 2 CH 3 CO Cl + 2NH 2 C 2 H 5 = C 2 H 5 NH 2 , HC1 + CH 3 CO NH C 2 H 5 . Ethylamine hydrochloride Ethylacetamide On the other hand, the anhydrides give, with ammonia, the primary anhydride and an ammonium salt. (3) By heating ammonium salts of the fatty acids in closed vessels at about 250, primary amides are formed : CH 3 CO 2 NH 4 = H 2 + CH 3 CO NH 2 . PROPERTIES. Unlike the amines, the amides have only a very feeble basic character, owing to the presence of the negative acid radical, and only the primary ones give additive products with acids, e. g., CH 3 * CO NH 2 , HC1, acetamide hydrochloride, which is decomposed even by water. Also certain sodium and mercuric derivatives are known, e. g., (CH 3 CO - NH) 2 Hg, which exhibit the amides as feebly acid compounds, one of the hydrogen atoms of the amido-group being replaceable by metals. With nitrous acid, amides react similarly to primary amines, giving the acid and liberating nitrogen : CH 3 CO NH 2 + N0 2 H = H 2 + N 2 -f CH 3 C0 2 H. Removal of water from primary amides by means of phosphorus penta- chloride or pentoxide results in the formation of alkyl cyanides (nitriles). By the gradual action of bromine in presence of alkali, the corresponding amine with one less carbon atom is finally obtained, while urea derivatives, such as methylacetylurea, CO<-KTTT . prr 3 , are formed as intermediate pro- 3 ducts, these being decomposable by excess of alkali ; an intermediate bromo- compound, e. g., acetobromamide, CH 3 CO NHBr, is also formed, this giving the amine with liberation of C0 2 : CH 3 -CO NHBr + KOH = KBr + C0 2 + CH 3 NH 2 . When, however, the acid residue contains more than five carbon atoms, the nitrile is obtained instead of the amine, which is acted on by the bromine : C B H 2n+1 CH^ NBr 2 = 2HBr + C B H 2n+1 CN. Since the nitriles may be con- verted into the acids containing one less carbon atom than the amides from which they originate, it is hence possible to pass gradually from higher acids to more and more simple ones. The ready hydrolysability and the methods of formation of amides confirm their constitutional formula, X CO ' NH 2 . With the alkali salts, however, the existence of the isomeric modification, X C(OH) : NH (see Tautomerism, pp. 18 and 394) is assumed, but if the hydrogen of the hydroxyl or amino- group is replaced by an alkyl residue, no tautomeric forms occur, only true I HIDES 421 structural isomerides, X CO NHR and X C(OR) : NH. The latter are termed imino-ethers and are derived from the hypothetical imino-hydroxides of the acids, e. g., CH 3 * C(OH) : NH. They are prepared by the action of a nitrile on an alcohol in presence of gaseous hydrogen chloride; thus, with HCN, the hydrochloride of formiminic ether, CH(OC 2 H 5 ) : NH, is obtained as a white powder. It is worthy of mention that Effront decomposes ami no-acids on an industrial scale by means of special ferments so as to obtain fatty acids and ammonia from them (see pp. 183 and 348). FORMAMIDE (Methanamide), H CO NH 2 , prepared as described above, is a liquid which is soluble in water and alcohol, boils at 200 with partial decomposition, and gives ammonia and carbon monoxide when rapidly heated ; with P 2 O 5 it yields HCN, and with chloral, an additive product, chloralamide, which is used as an antiseptic and hypnotic. ACETAMIDE (Ethanamide), CH 3 CO NH 2 , forms needles melting at 82 and boils at 222. Diacetyl-derivatives l are obtained less easily. Diacetamide, (CH 3 COjgNH, melts at 78, boils at 223, and is obtained by heating acetamide with acetic anhydride. OXAMIC ACID, CO 2 H CO NH 2 , is the monamide of oxalic acid and is obtained as a white, crystalline powder, slightly soluble in cold water, when ammonium oxalate is heated. OXAMIDE, NH 2 CO CO NH 2 , is the diamide or normal amide of oxalic acid, and is obtained by the partial hydrolysis of cyanogen or by distillation of ammonium oxalate. In appearance it closely resembles oxamic acid and it is insoluble in water or alcohol and is readily hydrolysed ; elimination of water (by P 2 O 5 ) from it leads to cyanogen (see p. 240). SUCCINAMIC ACID, CO 2 H CH 2 CH 2 CO NH 2 , is analogous to oxamic acid, and succinamide, NH 2 CO CH 2 CH 2 CO-NH 2 , is prepared similarly to oxamide, to which it is analogous ; succinamide crystallises from water in shining needles, and decomposes at 200 into ammonia and succinimide. Of the amides of hydroxy -acids, only the following need be mentioned : GLYCOLLAMIDE, OH CH 2 CO NH 2 , which is obtained by treating the ester of glycollic acid with ammonia or, better, by heating ammonium tartronate at 150, melts at 120 and has a sweet taste. The diglycollamides, NH 2 CO CH 2 CH 2 C0 2 H and (CH 2 CO NH 2 ) 2 0, are also known, the latter, on heating, giving ammonia and diglycol- pTT r*A limide, 0<; 2 ' ;C;> NH which melts at 142. V^HJJ i_/u MALIC ACID, CO 2 H CH 2 CH(OH) CO 2 H, forms two amides by means of its two carboxyl groups, an amine by means of its alcoholic group (aspartic acid), and also an amino-amide (asparagine ). MALAMIC ACID, NH 2 - CO CH 2 - CH(OH) CO 2 H, is known best as its crystalline ethyl ester, which is formed by the action of ammonia on an alcoholic solution of ethyl malonate. MALAMIDE, NH 2 CO CH 2 CH(OH) CO NH 2 , is formed by the action of ammonia on ethyl malonate in the dry state. B. IMIDES AND IMINO-ETHERS Attention must be drawn, not so much to the secondary amides [in which two hydrogen atoms of ammonia are replaced by two acid residues, as in diacetamide, (CH 3 CO) 2 NH, which contains the iminic group, NH] or to the ^ tautomeric form of the primary amides (with X Cf corresponds the X NH 2 1 In general, diacelylamines or diacylamines of the fatty or aromatic series are obtained by one of the following methods : (1) By heating isocyanic esters with acetic anhydride; (2) by the action of a current of HC1 in the hot on the primary amides : 2CH 3 CO NH 2 -f- HC1 = (CH 3 CO ) 2 NH + NH 4 C1 ; part, however, undergoes decomposition : (CH 3 CO ) 2 NH =; CH 3 CN + CH 3 CO.H ; (3) from amines and acid chlorides, either with or without pyridine ; (4) by heating nitriles with acids ; (5) by heating amines with acetic anhydride in a sealed tube at 200 ; from urea and acetic anhydride in the hot, etc., etc. The melting-points of some acylamines are as follows : butyramide, 115 ; dibutyramide, 101 ; isobidyramide, 129; di-iscbutyramide, 174; propionamide, 79; dipropionamide, 153. 422 ORGANIC CHEMISTRY /OH /OR isomeride X C^ , which is well known in the form of imino-ethers, X C^ , /OH or, in the case of the imidohydrin of glycollic acid, OH CH 2 C^ > in the X NH free state) as to the imides of certain dibasic acids. CCK OXIMIDE, | /NH (perhaps with the double formula), is formed on ccr elimination of water from oxamic acid (by PC1 5 ). CH 2 -C(X SUCCINIMIDE, | "/NH, is obtained by heating succinic anhydride CH 2 ' CCT in a current of ammonia or by heating the diamide or rapidly distilling mono- ammonium succinate, as has been mentioned on p. 365, where the reason was given for the ready formation of the closed-ring internal anhydrides. Succinimide melts at 126 and boils at 288, crystallises with 1H 2 O and exhibits the characters of an acid, the iminic hydrogen, influenced by the two carboxyl groups, being replaceable by acids. On the other hand, when they are treated with alkali, these imides give the amides from which they originate, CH 2 COv CH 2 C0 2 H a molecule of water being added : | /NH -f- H 2 = | CH 2 CW CH 2 CO NH 2 It is interesting that, when succinimide is distilled over zinc dust, it yields CH : CHv pyrrole, \ /NH, while, if it is heated in alcoholic solution with sodium CH : CH' CH 2 CH 2 v (reduction), it gives Pyrrolidine, | /NH. CH 2 CH 2 ' CH 2 CO, Also Phenylsuccinimide (Succinanil), | /N ' C 6 H 5 , is known and its CH 2 CO' various transformations confirm the symmetry of its own structure and consequently also that of succinimide. CH CO GLUTARIMIDE, CH 2 < 2 . ^Q>NH, is obtained by distilling ammonium 8 glutarate ; it melts at 152 and gives a little pyridine when heated with zinc dust. C. AMINO-ACIDS AND THEIR DERIVATIVES In the amino-acids, it is the hydrogen in direct union with carbon that is replaced by the NH 2 -group, the carboxyl group remaining intact, so that these compounds have both acidic and basic functions, and may hence be readily separated from other substances, since after the carboxyl is esterified, salts such as the hydrochlorides of the ammo-group are formed. These substances and their derivatives are of considerable importance in animal and vegetable physiology, since they are found among the products of the gradual synthesis and decomposition of the proteins in the living organism; they are also of interest theoretically, as they form intermediate products in various chemical syntheses. The a-amino-acids are readily obtained by the action of ammonia on the cyanohydrins of ketones and aldehydes and hydrolysis of the remaining nitrile group : GLYCOCOLL 423 OH /NH 2 CN \CN Nifcrile of lactic acid Nitrilc of alanine /NH 2 /NH 2 CH 3 C^H + 2H 2 = NH 3 + CH 3 C H X CN \C0 2 H Alanine (a-Aminopropionic acid) They are also formed generally by reducing the oximes of ketonic acids or, better, by the action of ammonia on halogenated acids : C0 2 H CH 2 C1 + NH 3 = HC1 + C0 2 H CH 2 NH 2 . We may also mention the interesting Korner-Meno/zi reaction (see note, p. 375), which allowed these authors, by inverting the reaction, to pass from the esters of unsaturated acids (fumaroid or maleinoid form) to a single form of the corresponding saturated ami no-acids by simple treatment with ammonia (or even an alkylamine in alcoholic solution). PROPERTIES. With nitrous acid, the amino-acids give hydroxy-acids with elimination of nitrogen, and they give many reactions analogous to those of the hydroxy-acids and varying with the position of the amino-group. Two molecules of an a-amino-acid readily lose 2 mols. of water, giving a kind of anhydride with an imido-ketonic character : C0 2 H CH 2 NH a CO CH 2 NH = 2H 2 + | | NH 2 CH 2 C0 2 H NH CH 2 CO The y-amino-acids, however, give internal anhydrides analogous to the lactones and termed Lactams : C0 2 H CH 2 CH 2 CH 2 NH 2 = H 2 O + CO CH 2 CH 2 CH 2 - NH The 5-amino-acids, when heated, evolve ammonia and give unsaturated acids. The amino-acids resist the action of boiling alkali solutions, but when fused with caustic soda they yield the sodium salts of the monobasic acids, ammonia being liberated. On dry distillation (best in presence of baryta) they yield amines and C0 2 , e. g, CH 3 CH(NH 2 ) C0 2 H = CH 3 CH 2 NH 2 + C0 2 . The stereoisomerides may be separated by means of the strychnine or brucine salts, etc. GLYCOCOLL (Glycine, Aminoacetic or Aminoethanoic Acid, or Amine of Glycollic Acid), CO 2 H CH 2 - NH 2 , is formed on boiling gelatine with alkali [BafOHJJ or acid (dilute H 2 S0 4 ) or on heating hippuric acid (benzoylglycocoll ) with dilute acid: C0 2 H * CH 2 NH CO C 6 H 5 + H 2 O = C0 2 H CH 2 NH 2 + C 6 H 5 C0 2 H (benzoic acid). Synthetically it is obtained from monochloracetic acid and concentrated ammonia (see p. 385); if the ammonia is replaced by methylamine, sarcosine, C0 2 H CH 2 NH CH 3 , m.-pt. 115, is obtained, or if by trimethylamine, betaine (see p. 385) is formed : C0 2 H CH 2 C1 + N(CH 3 ) 3 = HC1 + CO CH 2 N(CH 3 ) 3 . O- Betaine, C 5 H n O 2 N, crystallises with 1H 2 0, which it loses at 100 or in a desiccator over sulphuric acid. It dissolves in water or alcohol, from which it is precipitated by ether, or as betaine hydrochloride by hydrochloric acid. This solid hydrochloride is soluble in water, which hydrolyses it to a considerable extent, the solution then behaving like 424 ORGANIC CHEMISTRY hydrochloric acid. Owing to this property it is sold, under the name of acidol, in pastilles containing exact and suitable doses for stomach complaints, and replaces solutions of hydrochloric acid for this purpose ; the same effect as that of the acid is thus obtained by use of a solid product. Betaine is a feeble base, and is not decomposed even by boiling aqua regia ; at high temperatures it decomposes, giving trimethylamine. It occurs abun- dantly in beet-sugar molasses (10 to 12 per cent., besides 1 to 2 per cent, of leucine and isoleucine and 5 to 7 per cent, of glutamic acid), from which it is extracted by means of alcohol; after evaporation of this solvent, it is separated as hydrochloride. The action of tertiary amines, other than trimethylamine, with monochloracetic acid gives various compounds to which is given the name of BETAINES. Substitution in the amino -group of the amino -acids also yields other interesting compounds, e. g., Aceturic Acid (acetylglycocoll), CO 2 H-CH 2 -NH-CO-CH 3 , melting at 206. The properties of glycocoll and its salts are given on p. 385. In the amino-acid group is also found SERINE or a-amino-/3-hydroxypropionic acid, CO 2 H CH(NH 2 ) CH 2 OH, which is obtained on boiling silk gelatine with dilute sulphuric acid or synthetically from glycollic aldehyde, ammonia, and hydrocyanic acid. LEUCINE (a-aminoisocaproic acid), C0 2 H CH(NH 2 ) CH 2 - CH(CH 3 ) 2 , is obtained synthetically by hydrolysing the nitrile of isovaleraldehyde-ammonia, and is usually found with glycine among the products of decomposition of the proteins by acid or alkali, and is then optically active (the carbon atom adjacent to the carboxyl being asymmetric). ASPARTIC ACID (Aminosuccinic Acid), C0 2 H CH 2 CH(NH 2 ) C0 2 H, is one of the most important products obtained by the decomposition of proteins by acid or alkali. It occurs in abundance (Isevo-rotatory) in beet-sugar molasses, and has been prepared by various synthetic methods, e. g., by the action of ammonia on bromosuccinic acid. Three stereoisomerides are known, two of them being optically active owing to the presence of an asymmetric carbon atom. They are obtained in small, tabular, dimetric crystals, soluble to some extent in hot water. Their cold solutions and also acid solutions of the dextro-rotatory acid have a sweet taste, but hot solutions or alkaline solutions of the Isevo-rotatory acid are without taste. They give the general reaction of amines and amides with nitrous acid, being converted into malic acid. 1 The higher homologue of aspartic acid is Glutamic Acid (a-aminoglutaric acid), C0 2 H CH(NH 2 ) CH 2 CH 2 CO 2 H. Among the DI AMINO- ACIDS we have 'Lysine, CO 2 H CH(NH 2 ) [CH 2 ] 4 NH 2 , which is obtained by the action of acids on proteins or by synthetical methods ; on putrefaction it gives pentamethylenediamine. Ornithine, CO 2 H CH(NH 2 ) [CH 2 ] 3 NH 2 , is the lower homologue of lysine and gives tetramethylenediamine (putrescine) on putrefaction. Taurine (Ethyleneaminosulphonic Acid), S0 3 H CH 2 CH 2 NH 2 , is found in ox-bile combined with cholic acids as taurocholic acid (for properties of taurine, see p. 257 ). Cysteine (Thioserine), CO 2 H CH(NH 2 )- CH 2 - SH, is formed by the reduction of cystine, CO 2 H CH(NH 2 )- CH 2 - S S CH 2 - CH(NH 2 ) C0 2 H, which occurs in urinary sediments (calculi). ASPARAGINE, NH 2 CO CH 2 CH(NH 2 ) C0 2 H, is the amide of aspartic acid. It was first found in asparagus, but is moderately widespread in almost all vegetables (beet, potatoes, beans, vetches, peas, etc.), especially during the germination period, and the dry seeds of certain lupins contain as much as 30 per cent. The constitution of asparagine is confirmed by the various syntheses leading to its. production. 1 By the action of nitrous acid on the ethyl ester of glycocoll, Curtius obtained Ethyl Diazo- N \ acetate, || >CH C0 2 C 2 H 5 , as a yellow oil with a peculiar odour; when heated it explodes, while N/ with water it loses nitrogen and forms ethyl glycollate. ASPARAGINE 425 It crystallises with 1H 2 in laevo-hemihedral, trimetric prisms, soluble in hot water but insoluble in alcohol or ether. With aqueous cupric acetate solution, it forms a blue, well-crystallised copper salt, (C 4 H 7 3 N 2 ) 2 Cu, insoluble in water. It is isomeric with malamide, from which it differs in the possession of both acid and basic characters. It is Isevo-rotatory and has an unpleasant, insipid taste, but vetch seedlings contain a dextro-rotatory asparagine which has a sweet taste (Piutti, 1886), but does not unite with the laevo-rotatory form also present in the seedlings to give the inactive modification. Pasteur stated that the substance composing the nerves of the palate behaves as an optically active combination which acts differently towards the dextro- and Isevo- asparagines. Asparagine is converted into aspartic acid by hydrolysis and into malic acid by the action of nitrous acid. ASPARTAMIDE, NH 2 CO CH 2 CH(NH 2 ) CO NH 2 , is the diamide or normal amide of aspartic acid. Numerous higher homologues of aspartic acid (Homo-Aspartic Acids) and of asparagine (Homo-Asparagines) are known. D. AMIDO- AND IMIDO-CHLORIDES With both the primary amides and also the alkylated amides, the oxygen is readily replaced by chlorine by the action of PC1 5 . Thus, acetamide gives acetamido-chloride, CH 3 CC1 2 NH 2 , and ethylacetamide, ethylacetamido-chloride, CH 3 CC1 2 NH C 2 H 5 . Both of these compounds readily lose HC1, forming imino-chlorides, e. g., acetimino.-chloride, CH 3 CC1 : NH, and ethylacetimino-chloride, CH 3 CC1 : N-C 2 H 5 . These imino-chlorides, like amido-chlorides, are readily decomposed by water into hydrogen chloride and amide.- These chlorinated compounds react easily with aromatic substances and with hydrogen sulphide, ammonia, and amines, the chlorine being thus replaced by sulphur or by amino- residues, forming ihioamides, e. g., CH 3 CS NHX, and amidines, e. g., CH 3 C(NH 2 ) : NX 2 . E. THIOAMIDES These are well-crystallised compounds, more acid in character than the amides, and hence capable of forming metallic derivatives and of dissolving in alkali. Besides by the reaction just mentioned they are obtained by the addition of H 2 S to nitriles : CH 3 CN + H 2 S = CH 3 CS NH 2 (thioacetamide or ethanelhioamide) ; on heating, the opposite change occurs. Phosphorus pentasulphide replaces the oxygen of amides by sulphur, thus forming thioamides. With H 2 S, isonitriles give the alkylated thioamides of formic acid, CN X + H 2 S - H CS NHX. Thioamides are readily hydrolysed (by alkali, hot water, etc.), with formation of H 2 S, NH 3 (or amine), and the corresponding acids : X CS NHX' + 2H 2 O = X C0 2 H + NH 2 X' + H 2 S. F. IMINOTHIOETHERS The thioamides (and especially their, derivatives ) can ex'st in the isomeric or tauto- meric form, X C(SH) : NH, in which the hydrogens of both the sulphydryl and theimino- group are replaceable by alkyl groups, Iminothioethers, e. g., X C(SX') : NH, being then formed. These are prepared by the action of alkyl iodides on the thioamides (also from thioalcohols, nitriles, and gaseous hydrogen chloride), e.g., CH 3 CS NH 2 + CH 3 I = /S CH 3 CH 3 - C/ , HI (acetiminothiomethyl hydriodide). >NH The iminothioethers are easily hydrolysed (by HC1), forming ammonia and esters of thio-acids ; /S CH 3 CH 3 C^ + H 2 = NH 3 + CH 3 - CO SCH 3 . 426 ORGANIC CHEMISTRY G. AMIDINES When the amides or alkylamides are heated with amines in presence of a dehydrating agent (like PC1 3 ), the oxygen of the amide is substituted by an imino -residue : NH / <; ^NR NHX' X CO NHX' + R NH 2 = H 2 O + X These compounds are obtained also from thioamides, isothioamides, iminochlorides, or iminoethers by the action of ammonia or of primary or secondary amines : NH CH 3 CS NH 2 + NH 3 = H 2 S + CH 3 Cf (acetamidine or ethanamidine). \NH 2 NH NH X Cf + R NH 2 = X Cf + HSX'. \SX' \NHR When nitriles are heated with the hydrochlorides of primary (of the aromatic series also) or secondary amines (not with NH 4 C1), alkylamidines are obtained : CH 3 CN + R NH 2 = CH 3 C( : NH)- NHR. Properties. The amidines (or amimides) are bases and usually of the aromatic series; they are easily hydrolysed (by boiling with alkali or acid), giving (when theiminic hydrogen is not replaced by an alkyl group) ammonia (or an amine) andanitrile; the same change occurs on dry distillation. With H 2 S they give first an additive product : /NHX'; X C( :NH) -NHX' + H 2 S = X C^SH NH 2 this product then decomposes in two senses, giving (a) X CS NHX' + NH 3 and (6) X-CS NH 2 + X' NH 2 . With CS 2 , amidines give thioamides and, at the same time, thiocyanic acid or an alkyl thiocyanate. H. HYDRAZIDES AND AZIDES Introduction of an acid residue into hydrazine, H 2 N NH 2 (see Vol. I., p. 376), gives the primary hydrazides or monoacylhydrazides, e. g., CH 3 CO NH NH 2 (acetylhydrazide) and H-CO-NH-NH 2 (formhydrazide, m.-pt. 54); two acid radicals give secondary hydrazides or dihydrazides, e. g., CH 3 CO NH NH CO CH 3 (diacethydrazide, which melts at 138 and is prepared from hydrazine hydrate and acetic anhydride). They are readily hydrolysable, and reduce ammoniacal silver nitrate solution in the cold and Fehling's solution on heating. The primary hydrazides are more highly basic than the amides, and so give more stable salts. Nitrous acid acts on primary hydrazides, forming azides, which are derivatives of hydrazoic acid (see Vol. I., p. 376) : CH, CO NH - NH, + HNO, = 2H 9 + CH- CO H/'ll These resemble the acichlorides in many properties, but are explosive (silver and lead azides, see p. 310) and, when heated with alcohol, give urethanes and liberate nitrogen: / N CH 3 CO N< || + C 2 H 5 OH = N 2 + CH 3 NH C0 2 C 2 H 5 , meihylureihane, \N which may be hydrolysed with formation of C0 2 , alcohol, and methylamine. It is hence possible to pass from an acid to an amine with one carbon atom less, by way of the hydrazide and azide. CYANOGEN COMPOUNDS 427 I. HYDROXYLAMINE-DERIVATIVES OF ACIDS Hydroxylamine or its residues may be united to acid residues, forming Hydroximic (or hydroxamic) Acids, e. g., CH 3 C( : N OH)OH (ethylhydroxamic acid, m.-pt. 59), and Amidoximes, X C( : N OH) NH 2 . The hydroxamic acids have an acid character and are formed, with evolution of ammonia, by the action of hydroxylamine on amides. Also Formyloxime Chloride, CH( : N OH)C1, is known, this being obtained by treating mercury fulminate in the cold with HC1 ; it forms needles, which are readily decomposable, volatile, and soluble in ether. The Amidoximes are formed by the addition of nitriles to hydroxylamine, CH 3 CN + NH 2 OH = CH 3 C( : NOH)NH 2 . If hydrogen cyanide is employed, ISURET (Methanamidoxime or Methenylamidoxime), CH(:NOH)NH 2 , isomeric with urea, would be obtained. VI. CYANOGEN COMPOUNDS Some cyanogen compounds, especially Hydrocyanic Acid, HCN, potassium cyanide, and ferro- and ferri -cyanides, have already been dealt with in Vol. I., pp. 497, 547, and 840. We have to consider here the numerous and varied organic derivatives of cyanogen, which are of some interest as they often exist in polymerised forms and almost always in two isomeric modifications, sharply differentiated by their chemical properties : derivatives of nitriles, X'C : N, and of isonitriles, C j N' X (see also p. 237). CYANOGEN, (CN) 2 , is a highly poisonous gas with a pungent odour recalling that of bitter almonds ; it is liquid at 21 and solid at 34. It is found in the gas from blast-furnaces and occurs largely in the tail of Halley's comet, which approached the earth in May 1910. It is obtained by the elimination of water from ammonium oxalate or oxamide (NH 2 CO CO NH 2 ) by the action of P 2 5 in the hot, or by heating a solution of copper sulphate with potassium cyanide, and is commonly prepared by heating cyanide of silver or of mercury, Hg(CN) 2 = Hg -f- (CN) 2 ; as a secondary product, PARACYANOGEN, (C 3 N 3 ) 2 , or (CN) W is formed as a brown powder. It burns with a purple flame, dissolves readily in alcohol or water (4 : 1), and its solutions gradually become brown, with formation of oxalic acid, formic acid, hydrocyanic acid, ammonia, and urea, and deposition of Azulmic Acid (brown powder). With H 2 S it forms the thioamides : RUBEANHYDRIC ACID, NH 2 CS CS ' NH 2 , and FLAVEANHYDRIC ACID, NC CS NH 2 . CYANOGEN CHLORIDE, NC Cl, is of importance in the synthesis of many cyanogen compounds, and is formed by the action of chlorine on hydrocyanic acid or metallic cyanides : NC H -f- C1 2 = HC1 + NC Cl. It is a colourless gas which is easily liquefied, boils at 15-5, has a pungent odour, and dissolves in water. In presence of HC1 it polymerises, forming CyanogenTrichloride (melts at 145, boils at 190 ). With KOH it forms potassium cyanate, NCOK. CYANIC ACID, NC OH, is a liquid of penetrating odour and only slight stability, even at the ordinary temperature. It is obtained by the dry distillation of cyanuric acid (q. v. ) and condensation of the vapours in a freezing mixture. It undergoes change, even at the ordinary temperature and with slight explosions, into a compact, white isomeride, which is polymerised iso- cyanic acid or cyamelide, (0 : C : NH ) x ; this, on dry distillation, gives cyanic acid again. Its salts are more stable, but when attempts are made to liberate the acid from these by the action of mineral acids, immediate hydrolysis occurs : NC OH + H 2 = CO 2 + NH 3 . If it is liberated by dilute acetic acid, the isomeric cyanuric acid is obtained. The alkyl derivatives of cyanic acid exhibit two isomeric forms : Cyanates, N : C OX, and Isocyanates, O : C : NX. Potassium Cyanate, NCOK, forms white scales soluble in alcohol or water, and is 428 ORGANIC CHEMISTRY obtained by oxidising solutions of potassium cyanide by means of potassium perman- ganate or dichromate, or by fusing potassium cyanide or ferrocyanide with PbO, or Mn0 2 NCK + = NCOK. Ammonium 'Cyanate, NC-ONH 4 , is isomeric with, urea, into which it can be converted. It is obtained by neutralising cyanic acid with ammonia and forms a moderately stable, white, crystalline mass. ETHYL ISOCYANATE, CO : NC 2 H 5 , is prepared by distillirig potassium cyanate with either potassium ethyl sulphate or ethyl iodide. It is a liquid of penetrating odour and boils at 60. It does, not behave as a true ester (true esters of cyanic acid do not exist), since the action of acid or alkali yields, not alcohol, but ethylamine; CO : NC 2 H 5 + H 2 O = CO 2 + C 2 H 5 NH 2 . Hence the nitrogen is united directly to the alkyl group, so that the structure is not N C OC 2 H 5 , but O : C : NC 2 H 5 . Ethyl isocyanate is instantly decomposed by water, forming derivatives of urea ; the latter are also formed by the action of ammonia or amino-bases. CYANURIC ACID, (NC) 3 (OH) 3 , is a polymeride of cyanic acid and on heating urea which contains the constituents of ammonia and cyanic acid either alone or in a current of chlorine so as to eliminate the elements of ammonia, there remain those of cyanic acid, which polymerise to cyanuric acid. It crystallises with 2H 2 in prisms, effloresces in the air, and is readily soluble in hot water. When heated with HC1, it hydrolyses slowly to NH 3 and C0 2 ; with PC1 5 it gives the chloride of cyanuric acid. It is a tri basic acid and forms a violet, crystalline copper salt ; its sodium salt is insoluble in concentrated alkalis. Like cyanic acid, it gives rise to two series of derivatives, e. g., Ethyl Cyanurate, (NC) 3 (OC 2 H 5 ) 3 , which is a colourless liquid giving alcohol on hydrolysis. It is only slightly stable, and is readily transformed into the isomeride of the other series, Ethyl Isocyanurate, (CO) 3 (NC 2 H 5 ) 3 , which is formed by polymerisation of ethyl isocyanate, or by distilling the cyanurate with potassium ethyl sulphate. On hydrolysis it gives ethylamine, this confirming its constitution, which is shown by the following closed-ring formulae to be clearly different from that of ethyl cyanurate. OC 2 H 5 /\ /\ C 2 H 5 -N N-C 2 H 5 N N O:C C:O C 2 H 5 C C-OC 2 H 5 \N/ I Ethyl cyanurate C 2 H 5 Ethyl isocyanurate FULMINIC ACID, C : NOH, is readily volatile but unstable, and is decomposed by concentrated hydrochloric acid into hydroxylamine and formic acid, chloroformyloxime, CHC1 : N OH, being formed as intermediate product. Kekule regarded fulminic acid as a nitroacetonitrile, N0 2 CH 2 CN, but Nef subsequently attributed to it the consti- tution C : N-OH, the carbon being divalent. With bromine, mercury fulminate (see p. 308) gives the compound Br C : N I I Br C : N O Silver fulminate is even more explosive than the mercury salt. Palazzo (1907-1910) has prepared various additive products of fulminic acid with different acids (HBr, HI, HSCN, HNO 2 , N 3 H ). With hydrazoic acid at 12, he obtained two isomerides with different constitutions, probably with intermediate formation of Triazoformoxime : CH N OH N 3 H + C:NOH=tJ>C:N-OH - > || 3 N N : N Triazoformoxime N-hydroxytetrazok (m.-pt. 145) The other isomeride also is possibly a tetrazole derivative. THIOCYANIC ACID By the action of hydrogen sulphide on mercury fulminate suspended in water, Cambi (1910) obtained and isolated the Formothiohydroxamic Acid predicted by Nef : H C : NO H H-S FULMINURIC ACID, C 3 H 3 3 N 3 , is isomeric with cyanuric acid (see above), and two true isomerides are described: (1) a-Isofulminuric acid, obtained in 1884 by Ehrenberg by treating mercury fulminate suspended in ether first with gaseous hydrogen chloride and afterwards with concentrated ammonia solution, "is infusible, and insoluble in water or alcohol, and gives a deep red coloration with ferric chloride; (2) (3-isofulminuric acid, obtained in 1884 by Scholvien, melts at 196. Ulpiani (1912) maintains the existence of only one fulminuric acid, to which he attributes the formula : NH 2 -CO-C THIOCYANIC ACID AND ITS DERIVATIVES THIOCYANIC ACID (Rhodanic Acid), NC SH, is a yellow liquid of penetrating odour, stable only when anhydrous in a freezing mixture or when in very dilute aqueous solution. At ordinary temperatures it polymerises to a yellow mass. It is obtained from its mercury salt (see later) by the action of hydrochloric acid. In concentrated aqueous solution, it undergoes conversion- into a yellow crystalline mass of Perthiocyanic Acid, (CN) 2 S 3 H 2 . Cyanogen Sulphide, (NC) 2 S, may be regarded as a kind of anhydride of thiocyanic acid, and is obtained from silver thiocyanate and cyanogen iodide. It forms colourless plates which have a pungent odour and are readily soluble in water. Thiocyanuric Acid, (NC) 3 (SH) 3 , is polymeric with thiocyanic acid, and is obtained by the action of sodium sulphide on cyanogen chloride. It is a yellow powder and gives salts corresponding with a tribasic^acid. Its trimethyl salt is formed by polymerisation of ethyl thiocyanate by heating at 180. POTASSIUM THIOCYANATE (or Rhodanate), NC SK, see Vol. I., p. 841. AMMONIUM THIOCYANATE (or Rhodanate), NC SNH 4 , forms colourless, tabular crystals soluble in alcohol, and readily so in water. It is obtained by heating together CS 2 and NH 3 (see also Vol. I., p. 841). When heated it is transformed into the isomeric thiourea. It serves for the preparation of other thiocyanates, and is extracted in large quantities from the exhausted Laming mixture of gasworks (see p. 49), which contains 1 to 4 per cent, of it. MERCURIC THIOCYANATE, (NC S) 2 Hg, is prepared from a mercuric salt and ammonium thiocyanate, and forms a white, insoluble powder which swells up to a very considerable extent when heated (Pharaotis serpents). SILVER THIOCYANATE is precipitated as a white mass on mixing silver nitrate and ammonium thiocyanate. The latter gives, with ferric salts, a dark red coloration of FERRIC THIOCYANATE (sensitive indicator in the titration of silver with thio- cyanate) and this, with potassium thiocyanate, gives a violet double salt, (NC S) 6 FeK 3 . Hydrogen sulphide decomposes the thiocyanates, NC SH + H 2 S = NH 3 + CS 2 , while with concentrated sulphuric acid, addition of water and decomposition into ammonia and carbon oxysulphide occur NC SH + H 2 = COS + NH 3 . For thiocyanic acid there are two series of isomeric derivatives, corresponding with the two general formulae : N : C SX (alkyl thiocyanate) and S : C : N X (mustard oils). ETHYL THIOCYANATE, NC SC 2 H 5 , is a colourless liquid with a marked odour of garlic ; it boils at 142 and is very slightly soluble in water. It is formed by the action of cyanogen chloride on mercaptides, or by distillation of potassium thiocyanate with potassium ethyl sulphate. As it has the constitution of a true ester, it is hydrolysed by alcoholic potash with formation of alcohol and potassium thiocyanate, but in certain 430 ORGANIC CHEMISTRY reactions it behaves like the isomeric mustard oils. Nascent hydrogen converts it into mercaptan, since the alkyl is united to sulphur, and the action of nitric acid in the hot yields ethylsulphonic acid. ALLYL THIOCYANATE, NC SC 3 H 5 , boils at 161, and has a garlic-like odour; it undergoes change into the isomeric mustard oil, slowly at the ordinary temperature and more rapidly on distillation. The Mustard Oils (Isothiocyanates) are obtained from the corresponding thiocyanates simply by heating. They are also formed by the action of carbon disulphide on the corresponding primary amines, CS 2 -f- X * NH 2 = H 2 S + S : C : NX, this change taking place by way of the intermediate alkylamine salt of alkyldithiocarbamic acid (see later], which is distilled with mercuric chloride. Mustard oils are formed also when an alkylated thiourea is distilled with phosphoric or concentrated hydrochloric acid. Their structure is indicated by their formation of primary amine on hydro- lysis : S : C : NX + 2H 2 = C0 2 + H 2 S + X NH 2 . The isothiocyanic acid, S : C : NH, from which these mustard oils are regarded as derived, is not known in the free state. METHYL MUSTARD OIL (Methyl Isothiocyanate), SC : NCH 3 , melting at 34 and boiling at 119; Ethyl Mustard Oil, SC : NC 2 H 5 , boiling at 134; and Propyl Mustard Oil, SC : NC 3 H 7 , boiling at 153, are of little importance. More interesting is ALLYL MUSTARD OIL (or Ordinary Mustard Oil ; Allyl Isothiocyanate), S : C : NC 3 H 5 , which is prepared by distilling Sinapis nigra (black mustard ) with water ; it is obtained synthetically by the reactions given above. It is a liquid with a pungent odour recalling that of mustard and raises blisters on the skin ; it is sparingly soluble in water and boils at 150-7. CYANAMIDE AND ITS DERIVATIVES CYANAMIDE, NC NH 2 , is a white crystalline substance, melting at 40 and dissolving very slightly in water, alcohol, or ether. It is obtained by passing a current of cyanogen chloride into an ethereal solution of ammonia : 2NH 3 + NC Cl = NH 4 C1 + NC NH 2 , and is also formed by desulphurising thiourea, NH 2 CS * NH 2 , by means of HgO, which removes H 2 S. It is obtained abundantly and in a pure state by extracting calcium cyanamide (see later) systematically with water, neutralising the saturated solution with sulphuric acid, filtering from the calcium sulphate, concen- trating in a vacuum, again filtering from the gypsum, concentrating anew, and extracting the crystalline mass formed on cooling with ether, which does not dissolve gypsum, dicyanamide, and other impurities. Evaporation of the ether yields pure cyanamide in almost theoretical yield (Baum, 1910). With lapse of time, or rapidly at 150, cyanamide changes into the poly- meric dicyanodiamide '(see later). It behaves both as a weak base forming unstable crystalline salts and as a weak acid giving metallic salts, e.g., NC NHNa, NC NAg 2 , etc. The most important of these is calcium cyan- amide, NC NCa, which was considered in detail in Vol. I, pp. 369 et seq., in the discussion of the utilisation of atmospheric nitrogen; it is formed by the action of nitrogen on heated calcium carbide and forms an excellent nitrogenous fertiliser. In presence of dilute acid, cyanamide fixes a molecule of water, giving urea : NC NH 2 + H 2 = NH 2 CO NH 2 ;' with hydrogen sulphide it yields thiourea. Cyanamide also gives two series of isomeric alkyl derivatives of the general formulae, N | C * NX 2 and XN : C : NX. Compounds of the latter formula are derived from the hypothetical carbodi-imide, NH : C : NH ; for example, carbodiphenylimide, C 6 H 5 N : C : NC 6 H 5 , boiling at 330, is well characterised. CARBONIC ACID DERIVATIVES 431 DIETHYLCYANAMIDE, NC N(C 2 H 5 ) 2 , is formed by the action of ethyl iodide on the silver salt of cyanamide, its structure being indicated by the products CO 2 + NH 3 + NH(C 2 H 5 ) 2 obtained on hydrolysis with dilute acid. Methyl- and elhyl-cyanamide are also known. DICYANODIAMIDE, (NC NH 2 ) 2 , is formed, as has already been mentioned, from .NH cyanamide ; certain of its reactions indicate the structure NC NH Cf (Bamberger ). \NH 2 It forms acicular crystals or small flat prisms. When heated strongly and rapidly, it is converted into a white insoluble powder, MELAM, C 6 H 9 N U or [(NC^NH^jgNH, this being an imide of melamine, into which it is transformed by sulphuric acid or ammonia. MELAMINE (Cyanurtriamide), (NC) 3 (NH 2 ) 3 , is a crystalline basic substance, insoluble in alcohol or ether. When it is boiled with acid, the amino-groups are gradually replaced by hydroxyl groups, giving AMMELINE, (NC) 3 (NH 2 ) 2 OH, then AMMELIDE, (NC) 3 NH 2 (OH) 2 , and finally Cyanuric Acid, (NC) 3 (OH) 3 . As usual, the alkyl derivatives form two isomeric series, derivatives being known of a hypothetical Isomelamine, (CNH) 3 (NH) 3 , among these being the polymerised alkyl- cyanamides. VII. DERIVATIVES OF CARBONIC ACID True carbonic acid, O : C(OH) 2 , is not known in the free state, since two hydroxyl groups cannot exist in combination with the same carbon atom (see p. 216), but it is supposed to exist in aqueous solution, and salts corre- sponding with this formula are stable and well known (carbonates and bicar- bonates). Also important organic derivatives, similar to those already studied for other dibasic acids (amides, chlorides, esters, etc.), are known. The acid derivatives are less stable than the normal ones. ESTERS OF CARBONIC ACID ETHYL CARBONATE, CO(OC 2 H 5 ) 2 , is a liquid which is insoluble in water, boils at 126, and has a pleasant odour. It is formed by the interaction of ethyl chlorocarbonate and alcohol : C 2 H 5 OH + Cl CO OC 2 H 5 = HC1 + CO(OC 2 H 5 ) 2 , and also from silver carbonate and ethyl iodide. Mixed esters, containing different alkyls, also exist. ETHYLCARBONIC ACID, CO(OH) OC 2 H 5 , is known only as salts, e.g., Potassium Ethylcarbonate, CO (OK) OC 2 H 5 , which is obtained by the action of C0 2 on an alcoholic solution of potassium ethoxide and forms shining scales, giving alcohol and potassium carbonate when treated with water. CHLORIDES OF CARBONIC ACID Carbon Oxychloride (phosgene), COC1 2 , has already been described (Vol. I., p. 492). CHLOROCARBONIC ACID, COC1 OH, is the acid chloride of carbonic acid, but is not stable, and, when liberated, decomposes into C0 2 and HC1. Its esters are, however, well known, the action of phosgene on absolute alcohol giving, for example, ethyl chloro- carbonate (Ethyl Chloroformate), Cl CO OC 2 H 5 , thus : C 2 H 6 OH + COC1 2 = HC1 + Cl CO OC 2 H 5 . This ester is a liquid, having a pungent odour, boiling at 93 and readily decomposing under the action of water ; it is used largely in organic syntheses to introduce carboxyl into the molecule. AMIDES OF CARBONIC ACID The acid amide, NH 2 CO OH, is Carbamic Acid, and the normal amide, NH 2 CO NH,, urea. CARBAMIC or CARBAMINIC ACID, NH 2 CO OH, is obtained as ammonium salt ammonium carbamate, NH 2 CO ONH 4 by the direct union of dry CO 2 and NH 3 ; a white mass is thus obtained which, even at 60, dissociates into C0 2 + NH 3 . In aqueous solution this salt does not precipitate solutions of calcium salts at the ordinary tem- perature, since calcium carbamate is soluble, but in the hot the salt decomposes into C0 2 and NH 3 and gives a precipitate of calcium carbonate. 432 ORGANIC CHEMISTRY Ethyl carbamate or URETHANE, NH 2 CO OC 2 H 5 , is also well known and is obtained by the action of ammonia on ethyl carbonate, CO (OC 2 H 5 ) 2 + NH 3 = C 2 H 5 OH + NH 2 CO OC 2 H 5 , or, more easily, by treating ethyl chlorocarbonate with ammonia : COC1(OC 2 H 5 ) + 2NH 3 - NH 4 C1 + NH 2 CO It melts at 48 to 50, is soluble in water, and is used as a soporific. The following are also known : iodourethane, NHI CO OC 2 H 5 ; ethylur ethane, NHC 2 H 5 CO OC 2 H 5 (boils at 175); nitrourethane, NO 2 NH CO OC 2 H 5 ; carbamidyl chloride, NH 2 CO Cl (melts at 50 and boils at 61); and diethyl iminodicarbonate, NH(CO OC 2 H 5 ) 2 , which is the imide of urethane. Urethane derivatives are readily hydrolysable with alkalis and yield ammonia and urea when heated. UREA (Carbamide), CO(NH 2 ) 2 , is the final oxidation product of nitrogenous com- pounds in the living organism, and the adult human being produces about 30 grams of it a day ; it is found in general in the urine of carni vora (where it was first discovered ) and in other animal fluids. It crystallises in shining needles soluble in water and in alcohol, but insoluble in ether ; it melts at 132 and sublimes in a vacuum. It is formed from ammonium cyanate by simple rearrangement under the action of heat (Wohler): NC ONH 4 = CO(NH 2 ) 2 . Escales (1911) found that when urea is distilled or sublimed in a vacuum, the reverse reaction, i. e., formation of ammonium cyanate, occurs, Urea is obtained also by the action of ammonia on ethyl carbonate or carbamic acid : CO(OC 2 H 5 ) 2 + 2NH 3 = 2C 2 H 5 OH + CO(NH 2 ) 2 . Many other reactions give urea, e. g., oxidation of thiourea, action of water on cyanamide, best in the cold and in presence of hydrated manganese peroxide as catalyst (Ger. Pat. 254,474, 1910 ; U.S. Pat. 796,713) ; it may also be prepared from COCl 2 and NH 3 , etc. In the laboratory it is prepared by treating with barium carbonate the urea nitrate obtained by evaporating urine in presence of nitric acid, or by heating ammonium sulphate solution with potassium ferro cyanide or cyanate : (NH 4 ) 2 S0 4 + 2NCOK = K 2 S0 4 + 2CO(NH 2 ) 2 . In the future urea will probably be prepared on an enormous industrial scale according to the scheme of the Badische Anilin-und Soda-Fabrik of Ludwigshafen and Oppau. Synthetic ammonia is obtainable by the Haber process (see Vol. I., p. 373), and an abun- dant supply of CO 2 is obtained in the preparation from water-gas of the hydrogen necessary for the synthesis of ammonia. Thus ammonium sulphate may be made economically according to the reaction, NH 3 + C0 2 + H 2 O + CaS0 4 == CaC0 3 + (NH 4 ) 2 S0 4 , and urea from C0 2 and NH 3 in an autoclave : CO 2 + 2NH 3 = H 2 + CO(NH 2 ) 2 . Since urea contains more than 46 per cent, of nitrogen, its use as a high-grade nitrogenous fertiliser is anticipated when it can be manufactured to compete with other fertilisers. When heated it is decomposed into ammonia, biuret (see later), cyanuric acid, and ammelide. It is readily hydrolysed by acids, alkalis, or even hot water : CO(NH 2 ) 2 + H 2 = C0 2 + 2NH 3 , and is decomposed by nitrous acid or sodium hypochlorite : 2HN0 2 + CO(NH 2 ) 2 = 3H 2 + C0 2 + 2N 2 . Owing to this property urea is used as a stabiliser (so-called !) for explosives, decom- position being retarded and the nitrous vapours fixed (see p. 303 ). It exhibits the properties of a base and of a weak acid, giving salts with acids (e. g., Urea Nitrate, CO(NH 2 ) 2 , HN0 3 , which is soluble in water and slightly so in nitric acid, and with concentrated sulphuric acid gives the highly acid Nitrourea, NH 2 CO NH NO 2 , and with bases, e. g., CO(NH 2 ) 2 , 2HgO. It also crystallises with other salts, e. g., CO(NH 2 ), + NaCl + H 2 O, CO(NH 2 ) 2 + AgNO 3 , etc. Mercuric nitrate precipitates urea quantitatively from its neutral aqueous solutions as 2CO(NH 2 ) 2 + Hg(NO 3 ) 2 + 3HgO. Urea forms various alkyl derivatives; thus ethyl cyanate and ethylamine give symm. or a-diethylurea, which is isomeric with unsymm. or /3-diethylurea, NH 2 CO N(C 2 H 5 ) 2 ; CO NC 2 H 5 + C 2 H 5 NH 2 = CO(NHC 2 H 5 ) 2 . The constitutions of these alkyl derivatives are determined by study of the products of their hydrolysis. NH Readily hydrolysable alkylisoureas, NH : C<^~v V 2 , are also known. THIOCARBONIC ACID DERIVATIVES 433 SEMICARBAZIDE, NH 2 CO NH NH 2 , which is obtained from potassium cyanate and hydrazine hydrate, may also be regarded as a derivative of urea. It has already been seen that this base (which melts at 96) gives crystalline compounds (semicarbazones) with ketones and aldehydes (see p. 246 ). CARBAZIDE (Carbohydrazide), CO(NH NH 2 ) 2 , melts at 152, and is obtained from esters of carbonic acid by the action of hydrazine hydrate. Acetylurea, NH 2 CO NH CO CH 3 , and Allophanic Acid, NH 2 CO NH CO^ (not known free, but as salts ), are obtained from acid chlorides and urea. The formation of ureides (compounds of urea and mono- and dibasic acids) takes place with monobasic divalent acids or with an alcohol and acid. Such a reaction gives Hydantoic Acid (glycoluric acid), NH 2 CO NH CH 2 C0 2 H, which, when evaporated in ,NH CO presence of HC1, loses water and forms Hydantoin, CO^ | , the latter giving first \NH CH S hydantoic acid and then C0 2 , NH 3 , and glycine on hydrolysis. When urea is heated at 160, 2 mols. condense with separation of ammonia and /CO NH, / formation of Biuret, NH<^ , which crystallises with 1H 2 O and is soluble in water \nr> . -\TTT \^\J ' -LNXTo or alcohol ; in alkaline solution it gives a characteristic violet coloration with a little copper sulphate. DERIVATIVES OF THIOCARBONIC ACID More or less complete substitution of the oxygen of carbonic acid by sulphur gives a series of unstable compounds, which form stable alkyl deriva- tives and exhibit various cases of isomerism indicated by varying products of hydrotysis. These numerous sulphur compounds are reducible to three types, according as they contain (1) the nucleus SCCH 2 ; tartronic acid, dialuric acid, and mesoxalic acid, alloxan, COCO. If, however, only one molecule of water is eliminated, one amino- and one carboxyl-group remaining unchanged, uro-acids are obtained, e.g., oxaluric acid, NH 2 CO ' NH CO ' C0 2 H, and alloxanic acid (from mesoxalic acid). These ureides are usually well crystallised, and are aminic and also markedly acid in character. On hydrolysis, they give first the corresponding uro-acid and then urea and free acid. They are sometimes formed on oxida- tion of di ureides (see below) ; thus parabanic acid is obtained by oxidising uric acid with nitric acid. The alcohol-acids and the aldehydo-acids also give such condensations (see above), yielding, for example, hydantoin, kydantoic acid, and allanturic acid (from glyoxylic acid). When 2 mols. of urea take part in the condensation, diureides are obtained, these forming the group containing uric acid, a) HN -- CO (6) I 0) (2) CO (5) C NH\ 1 II >CO (8) (3) NH -- C NH X (4) (9) and its derivatives : xanthine, caffeine, theobromine, guanine, hypoxanthin e, alloxanthine, purpuric acid, allantoin, etc. The positions of the substituent groups are indicated by the bracketed numbers shown in the above formula for uric acid. During recent years successful attempts have been made, by means of -ethyl cyanoacetate, to synthesise all these xanthine bases and to convert them, one into the other (see Berichte der deutsch. chem. Gesells., 1899, 32, p. 435). As a general rule, the ureides and diureides have a more or less marked acid character and, as they contain no carboxyl group, this acidity is explained 436 ORGANIC CHEMISTRY as due to the existence of these compounds in tautomeric forms, just as is the case with succinimide, CH 2 >NH. In the latter it is assumed that CH 2 CO' the iminic hydrogen atom is very mobile and undergoes displacement and union with the oxygen of the neighbouring carbonyl group, a double linking between carbon and nitrogen being formed and an acid hydroxyl group capable of forming salts with metals. The tautomeric formula of Succinimide CH 2 C(OHk xN : C OH would hence be CH, CO N, and that of Parabanic Acid, N : C OH similar formulae hold for uric acid and barbituric acid, the latter functioning as a dibasic acid (in this case, however, the acid character is perhaps to be attributed to the hydrogen of the methylene group, CH 2 ). Several diureides are found in nature, e.g., in guano, in the urine and muscles of carnivora, in the excreta of serpents, in articular concretions, and in certain plants (theobromine in cocoa, caffeine, etc.), The constitutional formulae of the more important diureides are as follow : CO ,N(CH 8 ) CO \ I X N(CH 3 ) CO C0( ,NH-C(CH 3 ) X CH O -CO' Dimethylparabanic acid (Cholestrophane) Metbyluracil < / | CO-NH I CO-NH < CO-HN > Alloxanthine NH - > NH CH CO CO CH. CH, Murexide N-C-N II II >CH CH C NH/ I i N=CH Purino N CO I i CO CH NH CO NH 2 N CO Dimethylpseudouric acid 2 CO NH' Allantoin N C N \ CC1 CC1 C NH Trichloropurine CO C NH^ CH 3 -N CO Theophylline JCH ^1 3 S ( v II / CH )O C N(CH 3 )/ i II CH V_y II C- >H -NH/ CO 1 c- > -NH/ CH 8 -1 I CO I yH -CO NH CO Caffeine Hypox: mthine Xanthine CH N C N I! II CH C NH ! I N = C NH 2 Adenine \CH NH C N I II NH:C C NH' ! I NH CO Guanine \ CH COCOA AND CHOCOLATE 437 URIC ACID, C 5 H 4 O 3 N 4 . Syntheses of uric acid are many and various ; from cyano- acetic acid, or.glycocoll or isodialuric acid, by heating with urea; from aminobarbituric acid and potassium cyanate ; from ethyl acetoacetate and urea, passing through methyl - uracil, nitrouracil, hydroxyuracil, and isodialuric acid. The following scheme represents the various steps of the synthesis frpm malonic acid : 1 NH 9 CO -OH NH CO NH CO I i I 1 li CO CH 2 > CO CH 2 > CO C:N-OH > I I II' II NIT CO -OH NH CO NH CO Urea Malonic acid Barbituric acid Violurie acid NH OC NH CO NH CO I ! II II CO CH-NH 2 > CO CH NH X > CO C NIL II I I >co i || >co NH CO NH CO NH/ NH C NH/ Uramil Pseudouric acid Uric acid Uric acid is a feeble dibasic acid (see above), and forms a white, amorphous substance insoluble in alcohol or ether and almost insoluble in water. It dissolves, however, in concentrated sulphuric acid, from which it separates unchanged on dilution with water. It is extracted from guano, the excrements of serpents, and the urine of carnivora. Evaporation of uric acid with dilute nitric acid and treatment of the residue with ammonia yields murexide, which forms yellowish green crystals which" give a purple aqueous solution, turning blue on addition of alkali (characteristic reaction for uric acid ). THEOBROMINE (3 : 7-Dimethyl-2 : 6-dioxypurine), C ? H 8 O 2 N 4 or CH 3 N C N. II >CH CO C N(CH 3 )/ NH CO is extracted by means of boiling alcohol from cocoa, 2 de-fatted and made into a paste with 1 The constitution of uric acid was demonstrated first by Medicus, and later, by various syntheses, by E. Fischer (Liebig's Annalen, 1882, 215, p. 253). The presence of a chain, C C C , and of a carbonic acid residue is shown by the formation of urea and alloxan when uric acid is treated in the cold with nitric acid. The presence of four imino-groups is deduced from the fact that, by introduction of four methyl groups and subsequent hydrolysis, the four atoms of nitrogen are eliminated as methylamine. A large part of the uric acid molecule is rendered evident jby the formation of allantoin (of known constitution) on oxidation with alkaline perman- ganate, and by the formation of methylurea and methylalloxan on oxidation of dimethyluric acid. 2 Cocoa and Chocolate. Cocoa is placed on the market in the form of large violet seeds of Theobroma cacao, which grows well in the Antilles, Mfexico, Guatemala, Java, Borneo, Esmeralda (equator), etc. The red or brown mature fruits resemble cucumbers, each containing fifty to sixty seeds like beans. The seeds are separated from the pulp, heaped in casks for four to five days to initiate the fermentation which increases the aroma, and then dried in the sun. The chemical composition of the decorticated seeds differs considerably with the variety : fatty substance (cocoa-butter), 40 to 55 per cent.; proteins, 10 to 18 per cent.; cellulose, 3 to 6 per cent. ; sugars and starch, 8 to 15 per cent. ; theobromine, 0-8 to 2-5 per cent. ; ash, 3 to 4 per cent. Cocoa-butter (or cacao-butter) is extracted by pressing the seeds hot, and forms a faintly yellow mass of pleasing odour; it melts at 29 to 31, and contains the glycerides of arachic, palmitic, oleic, stearic, and lauric acids. In the manufacture of chocolate, the seeds are washed in suitable sieves- and then gently and cautiously heated for thirty to forty minutes to facilitate skinning. They are next crushed in mortars or rotating cylinders, the flour obtained being made into a paste with sugar and worked for a long time on heated stone rollers, different ingredients and flavouring matters being added to give the different kinds of chocolate ; the homogeneous paste then passes to the moulds. 438 ORGANIC CHEMISTRY lime. Synthetically it is obtained by treating the lead salt of xanthine with methyl iodide, or from methyluric acid and phosphorus oxychloride. It forms white, anhydrous crystals which have a bitter taste and dissolve only slightly in water, alcohol or ether. It is soluble in acids or alkalies, and at 290 volatilises without melting. It behaves as a weak acid and as a weak base. With methyl iodide the silver salt yields caffeine. With concentrated nitric acid, chlorine and ammonia, it gives the same reactions as caffeine (see below). In the form of different salts, theo bromine is used as a stimulant and diuretic. Before the war it cost about 72s. per kilo. CAFFEINE or THEINE, C 5 H(CH 3 ) 3 O 2 N 4 + H 2 O, is trimethylxanthine or methyl- theobromine (for constitution, see p. 436). It is an alkaloid formed in varying proportions (0-5 to 2 per cent. ) in coffee seeds. 1 The leaves of the coffee plant C9ntain up to 1-3 per cent., Good chocolate contains from 40 to 60 per cent, of cocoa, the rest being sugar ; ordinary qualities contain 10 to 15 per cent, of starch. The amounts of cocoa imported by various countries are as follows (tons ) : United States Germany Great Britain France Holland (one half re-3xported) Belgium (one half re-exported) Spain Switzer- land Italy 5J190T . 39,239 34,515 25,900 23,180 22,870 / 5,963 5,652 7,124 1,456 1910 . 52,546 43,941 32,046 25,076 34,229 9,881 5,517 9,089 1,886 1912 . 69,447 55,085 34,145 ; 26,890 41,858 13,023 5,241 10,342 2,432 1913 . 70,660 52,878 35,543 27,610 46,810 11,620 6,166 10,248 2,457 1914 . 80,479 42,416 26,085 52,375 6,911 10,078 2,275 1916 . 110,050 90,237 37,172 21,112 7,504 14,705 6,746 1918 . , 5,863 The cocoa crop in the British colony of the Gold Coast increased from 5770 tons in 1904 to 40,640 tons in 1911; in the German colonies, especially the Cameroons, the crop rose from 1454 tons in 1905 to 5500 tons in 1912. Italy imported and exported the following quantities of chocolate : Importation Exportation fTons 1908 . 1,090 . 230 1910 1,500 180,000 230 30,704 1913 2,078 216,160 1914 1,627 1916 876 273 308 362 38,266 69,544 1918 211 59,120 336 107,584 Before the war the price of cocoa was about 4 per cwt. 1 Coffee consists of the seeds of one of the Rubiacese (Coffea arabica) which grows naturally in Southern Ethiopia and Arabia,~and is cultivated on an enormous scale in India, the Antilles, Madagascar, and South America. It is an evergreen plant, 6 to 9 metres high and of pyramidal habit, with greyish branches and lanceolated leaves, the flowers (at the base of the leaf) being white and pleasant-smelling, like jessamine. The fruit forms drupes like cherries, the epicarp passing from yellow to green to red to brownish, and the mesocarp being yellow, pulpy and of agreeable taste. The endocarp is divided into two compartments surrounded by coriaceous membrane and each containing a seed, which has one convex and one flat, furrowed face, and is covered by a friable pellicle ; the endosperm (albumen ) is yellowish or greenish and horny. Coffee berries are composed of cellulose (18 per cent. ), fatty matters (12 per cent. ), gummy and saccharine substances (10 per cent.), nitrogenous compounds (12 per cent.), mine^jQ salts (4 to 5 per cent.), a tannin (caffetannic acid, 8 per cent.), caffeine (0-8 to 1-3 per cent.), caffearine, and water (11 per cent.). When roasted, coffee develops aroma and loses 15 to 20 per cent, in weight, but increases in volume by one-third, while the sugar caramelises and the cellulose carbonises partially, forming a brown oil which is denser than water, dissolves in ether, and constitutes the aromatic substance (caffeone). Roasted coffee contains, on the average, 1-5 per cent, of water, 13 per cent, of nitrogenous substances, 0-8 per cent, of sugars, 13-5 per cent, of fats, 4-8 per cent, of ash, 0-9 per cent, of caffeine, and 46 per cent, of non -nitrogenous substances ; to hot water this coffee gives up about 25 per cent, of its weight. The form of the seed varies with the kind of the coffee (Coffea mauritiana, laurina, liberica, etc. ). Mocha coffee berries are small and the Australian ones large, whilst those from the Antilles are intermediate in size. The quality of coffee is influenced by the methods of cultivation and preparation : by the ordinary or dry method the fruit is dried in the sun, so that it may be freed from the parchment- like membrane and partly from the silvery pellicle by beating in a husking machine. In the West Indies and Brazil, however, more use is now made of the wet process, in which the fresh fruit is carried by a stream of water into a de-pulping machine fitted with revolving channelled or toothed discs or cylinders, the seeds after this treatment being covered only with the parchment integu- ment and with a little pulp, which is eliminated by fermentation and subsequent washing ; finally COFFEE SUBSTITUTES 439 larger proportions occurring in the leaves of the tea plant (1-2 to 4 per cent.), 1 in cola nuts (2 to 3 per cent. ), in mate leaves (or Paraguay tea ; about 1 per cent. ) and in guarana paste (made from the seeds of Paullinia sorbilis, grown in Brazil : 3 to 5 per cent. ). the seeds are dried in the sun or in an oven, and may then be freed from the parchment by de- corticating machines. One hundred kilos of fresh fruit gives about 20 kilos of berries for sale, these being rendered shiny by shaking them dry in sacks or in levigating apparatus, in which finely powdered colouring matters (indigo, ultramarine, chromium salts, curenin, graphite, etc. ) are often introduced. The cultivation of coffee has received a considerable impulse in Brazil, where as much as 800,000 tons (more than three-fourths of the total production of the world) is now produced. Of the Antilles coffees, the most highly valued is that from Porto Rico. The principal commercial varieties of coffee are named after the countries where they are grown. The output in different countries is as follows (tons ) : Brazil Other American countries Asia and" Oceania (except Arabia) Africa and Arabia Whole world 1900-1901 1904-1905 1909-1910 . 1913-1914 675,700 632,000 1,150,000 680,000 170,000 181,400 36,000 85,000 46,100 39,500 26,000 36,000 11,300 8,200 1,500 (?) 1,000 (?) 910,000 861,000 1,300,000 850,000 (?) In 1902 the mean consumption per head in kilos amounted to : Holland, 6-6 ; Norway, 5-3 ; Sweden, 5-2; United States, 5-1; Belgium, 4-7; Denmark, 3-4; Germany, 3; France, 2-2; Austria, 0-9; Italy 0-5; Spain, 0-5; Great Britain,. 0-43. The total importation is as follows (tons ) : Belgium Holland Germany France (one-third (two-thirds g?', e Italy Spain re-exported) re-exported) 1 1907 189,600 53,596 101,570 113,350 117,857 426,487 21,476 11,292 1910 171,000 47,600 112,000 50,000 120,000 364,876 25,287 i 12,838 1912 171,000 34,200 111,240 50,000 116,250 427,516 27,627 13,378 1913 168,000 43,000 115,280 53,480 144,950 387,000 28,659 15,129 1914 52,680 116,420 124,950 458,620 28,197 13,733 1916 82,880 153,000 89,000 529,297 48,961 16,383 1918 ; 51,638 , In 1900 Italy imported 14,100 tons of coffee, in 1908 22,760, and in 1910 25,300 tons (1,062,080) (about four- fifths from Brazil) ; the Customs' duty was 60 per ton until 1909, after which it was lowered somewhat. Pre-war prices per cwt. at Genoa, exclusive of duty, were : .Mocha, 4; Porto Rico, 72s. ; Peru, 50s. ; Salvador, 56s. ; San Domingo, 44s. (washed 60s. ) ; Santos, 42s. ; Rio, 38s. ; Bahia, 36s. In 1909, coffee became a State monopoly in Italy, the retail price being raised in January, 1920, to 14s. to 17s. (18 to 22 lire ) per kilo, according to the quality; before the war, the price was 3s. 6d. to 4s. Qd. (including Is. 2d. duty ). Coffee Substitutes. These are now numerous, and as a rule contain no caffeine, being obtained by roasting roots, saccharine fruits, cereals, leguminous seeds, etc. On roasting, the saccharine substances form caramel and other bitter substances giving colour, taste and smell to the aqueous decoction. Chicory coffee contains, on the average : water, 8 per cent. ; nitro- genous substances, 7 ; fats, 2-5; sugar, 16; non-nitrogenous extractives, 52 (9 per cent, induline and 12 per cent, caramel); cellulose, 10, and ash, 5 per cent.; about 65 per cent, is soluble in water. Beet coffee, carrot coffee, etc., are also sold, and in Germany and Austria large quantities of fig coffee are used, this being often mixed with coffee made from dates, carobs, lupins, wheat, rye, barley, maize, malt, acorns, chestnuts, arachis nuts, etc. These substitutes may be distinguished from coffee by microscopic examination, by their small proportion of fat (1 to 3 per cent., whereas coffee contains up to 14 per cent.), and by the high content of saccharine substances (3 to 50 per cent., while coffee contains 2 per cent, at most). 1 Tea is an evergreen shrub (Thea viridis, Thea bohea, and Thea assamica), cultivated in China, Japan, British India, Java, Ceylon, and Brazil. The leaves are similar to those of the white willow, and contain various enzymes, of importance being an oxydase which, under suitable conditions of temperature and moisture, transforms the green matter into a black substance (the tannins being oxidised ). The oxydase is more sensitive to heat than other enzymes producing the aroma, so that if the leaves are heated- for more than an hour at 70 for green tea or at 80 for black tea, the maximum aroma is developed, while the tannin (oxidised) and theine (volatilised) are diminished in amount and the soluble substances increased (Sawamura, 1912). For black tea 440 ORGANIC CHEMISTRY Industrially caffeine may be extracted from coffee, tea, or mate leaves, in which it is partly combined with tannic acid, by decomposing the compound with water and then treating with chloroform, which readily dissolves it (from coffee it may be extracted directly with benzene, which takes out the oil also ; after evaporation of the benzene, the caffeine is separated by means of water, the oil remaining insoluble ). Tea residues may be extracted directly with solvents such as alcohol, previous pulping with lime (as used in the case of guarana paste) not being always necessary. During the war a certain amount of caffeine was obtained in Italy by extraction of the soot deposited in the flues of the apparatus used for roasting' coffee. Synthetically caffeine may be prepared by methylating 3-methylxanthine, 1 : 7-dimethyl- xanthine (paraxanthine ) or 3 : 7-dimethylxanthine (theo bromine) by means of methyl iodide and caustic soda. Pure caffeine forms white, silky, odourless needles of bitter taste ; at 100 it loses the molecule of water of crystallisation, and it sublimes readily and melts at 228 to 230. It dissolves readily in chloroform, to some extent in boiling water, slightly in alcohol or cold water, and very slightly in ether. It dissolves in acids forming unstable crystallisable salts. When heated gently to dryness with a little chlorine water and concentrated nitric acid, it leaves a reddish- yellow residue which gives a purple- violet coloration with a little ammonia. Before the war it cost 2 per kilo, but during the war it was sold in Italy at 12 (300 lire) per kilo. GUANINE, C 5 H 5 ON- (constitution given above), is a di-acid base, but forms salts also with bases. It is a white powder insoluble in water but soluble in ammonia. On oxidation with potassium chlorate and hydrochloric acid, it gives carbon dioxide, para- banic acid, and guanidine. the leaves ar allowed to wither and soften in the sun, and are then rolled up and covered with moist cloths to accelerate the fermentation, which transforms the green into black substances. Rolling of the leaves results in rupture of the cells and expression of the juice which facilitates the fermentation ; when the latter ceases (in a few hours) the material is spread either on iron plates heated over direct fire or on gratings heated with hot air (not over 80 ). To prepare green tea, the withered leaves are subjected to rapid treatment with boiling water or steam to destroy the oxydase (the enzymes producing the aroma are more resistant), so that the green colour may be preserved. The prepared tea is kept in sealed boxes of metal foil, in order that extraneous odours may not be absorbed. From 4 kilos of leaves 1 kilo of dry tea is obtained. Commercially the numerous varieties are grouped into three types : green, black, and scented, the last two being slightly fermented. The active alkaloid is Theine (see above). The best infusion of tea is obtained by macerating for thirty minutes in cold water and then adding boiling water, the liquid being poured off before it becomes very brown and excessively rich in tannin (20 grams of tea per litre of slightly hard water). The world's output of tea is about 600,000 tons, and is furnished almost entirely by Asia [55 per cent, from China and the rest from India (120,000 tons), Ceylon (85,000 tons), Japan (28,000 tons), Formosa, and Java]. The consumption of tea in different countries is shown by the following amounts imported (tons ) : Great Britain Belgium (one-sixth Eussia Trance Holland (two-thirds Spain Italy re-exported) fc re-exported) 1907 143,846 92,856 44,959 1,155 4,174 766 143 74 1910 150,522 70,172 44,501 1,261 4,970 749 156 74 1912 163,771 68,509 44,772 1,309 5,508 1,051 187 87 1913 165,580 78,513 40,378 1,207 5,467 586 214 95 1914 168,705 78,271 44,466 1,980 6,461 122 75 1916 171,306 78,400 47,522 2,645 8,185 202 106 Other imports were in 1913 (tons): Canada, 16,300; Austria, 2,000; Denmark, 467; Roumania, 350; Switzerland, 528; Argentine, 1880; Chili, 1746; Persia, 4770, and Australia, 16,940. Before the war, tea was sold in Italy at 3s. to 6s. per kilo (including the import duty of 2s. ), according to the quality. XAN THINE, ADENINE 441 XANTHINE, C 5 H 4 O 2 N 4 (constitution given above), is a white powder and acts as both acid and base. It is obtained from guanine by the action of nitrous acid, and its lead salt reacts with methyl iodide, giving theo bromine. ADENINE, C 5 H 5 N 5 (constitution given above), forms shining needles and is a base occurring in tea and in ox-pancreas. It is formed by decomposition of the nuclein of the cell-nuclei and is hence of physiological importance. INDEX ABRIN, 138 Abrus prrecatorius, 138 Acetaldehyde, 250 Estimation, 251 Acetals, 245 Acetamide, 238, 421 Acetamidine, 426 Acetamido-chloride, 425 Acetates, 345-348 Acetic anhydride, 380 Acetifiers, 342 Acetimino-chloride, 425 Acetiminothiomethyl hydriodide, 425 Acetins, 257, 274 Acetoacetaldehyde, 399 Acetobromamide, 420 Acetometers, 344 Acetonamines, 252 Acetone, 129, 254 Acetonealcohol, 397 Acetone-chloroform, 119 Acetonitrile, 238 Acetonylacetone, 399 Acetoxime, 252 Acetyl chloride, 379 iodide, 380 number, 224 sulphide, 419 Acetylacetone, 398 Acetylcarbinol, 397 Acetylcellulose, 381 Acetylene, 111 hydrocarbons, 110 Acetylethylamine, 420 Acetylglycocoll, 424 Acetylhydrazides, 426 Acetylides, 110, 361 Acetylurea, 433 Achroodextrin, 141 Acichlorides, 379 Acid, Abietic, 206 Acetaldehydedisulphonic, 257 Acetic, 328 Acetoacetic, 396 Acetonediacetic, 411 Acetonedicarboxylic, 411 Acetonetricarboxylic, 419 Acetonic, 389 Aceturic, 385, 424 Acetylenecarboxylic, 361 Acetylenedicarboxylic, 376 Aconitic, 376, 411 Acrylic, 354 Adipic, 357, 362 Alkylphosphonic, 242 Allanturic, 435 Allocroto'nic, 355 Allophanic, 433 Alloxanic, 435 y-Allylbutyric, 357 442 Acid, Allylsuccinic, 373 Aminoacetic, 379, 385, 423 Aminoethylsulphonic, 257 a-Aminoglutaric, 424 a-Amino-j8-hydroxypropionic, 424 a-Aminoisocaproic, 424 o-Aminopropionic, 423 Aminosuccinic, 424 a-Amino-j8-thiolactic, 396 Amylacetylenecarboxylic, 360 Amylmalonic, 369 Angelic, 356 Arabonic, 392 Arachidic, 320 Aspartic, 424 Azelaic, 365, 372 Azulmic, 427 Barbituric, 435, 437 Behenic, 320 Behenolic, 360, 362 Brassidic, 360 Brassylic, 360, 365 Bromosuccinic, 374 Butylacetylenecarboxylic, 360 Butylfumaric, 373 Butylmaleic, 373 Butylmalonic, 369 Butylsuccinic, 371 Butyric, 348 Cacodylic, 242 Caffetannic, 438 Camphoronic, 376 Capric, 350 Caproic, 349 Caprylic, 349 Carbamic, 431 Carbaminic, 431 Cerotic, 351 Cetylmalonic, 369 Chloroacetic, 379 a-(B-, 7-) Chlorobutyric, 378 Chlorocarbonic, 431 o-(0-) Chloropropionic, 378 Citraconic, 22, 375 Citramalic, 400 Citric, 412 Citronellic, 357 Citrylideneacetic, 364 Crotonic, 22, 354 Cyanic, 427 Cyanoacetic, 377 Cyanuric, 428, 431 Cyclogeranic, 363 Decamethylenedicarboxylic, 365 Decoic, 350 Dehydroundecenoic, 361 Desoxalic, 419 Diacetosuccinic, 411 Diacetylenedicarboxylic, 376 Diacetylglutaric, 411 INDEX 443 Acid, Dialkylphosphonic, 242 Diallylacetic, 363 Dialuric, 435 oS-Diaminovaleric, 392 Diaterebinic, 400 j87-Dibromobutyric, 355 j8-Dibromopropionic, 378 Dicetylmalonic, 369 Dichloracetic, 378 aa-(aB-) Dichloropropionic, 378 Diethylmaleic, 373 Diethylmalonic, 369 Diglycollic, 384 o8-Dihydroxybutyric, 355 Dihydroxymalonic, 410 ajS-Dihydroxypropionic, 392 Dihydroxystearic, 359, 390, 392 Dihydroxytartaric, 411 Diisoamylmalonic, 369 Diisobutylmalonic, 369 Dimethylacetic, 349 o0-Dimethylacrylic, 356 Dimethylarsenic, 242 Dimethylfumaric, 375 aa-(cr/-, 77-) Dimethylitaconic, 373 Dimethylmaleic, 375 Dimethylmalonic, 369 Dimethyloxaminic, 240 Dimethylparabanic, 436 Dimethylpseudouric, 436 Dimethylsuccinic, 371 Dioctylmalonic, 369 Dipropylmalonic, 369 Dithiocarbamic, 434 Dithiocarbonic, 433 Dithiocarbonylic, 433 Dodecamethylenedicarboxylic, 365 Elaeostearic, 364 Elaidic, 359 Erucic, 360 Erythric, 392 Ethanetricarboxylic, 411 Ethanthiolic, 419 Ethan thioltbiolic, 419 Ethylacetylenecarboxylic, 360 Ethylcarbonic, 431 Ethyleneaminosulphonic, 424 Ethyleaelactic, 389 Ethylenesuccinic, 370 Ethylfumaric, 373 Ethylhydroxamic, 427 Efchylideneacetic, 355 Ethylidenelactic, 386 Ethylidenepropionic, 356 Ethylidenesuccinic, 371 Ethylisopropylmalonic, 369 a-(7-) Ethylitaconic, 373 Ethylmaleic, 373 Ethylmalonic, 369 Ethylmethylacetic, 349 Ethylnitric, 236 Ethylsulphonic, 235 Ethylsulphuric, 108, 235 Ethylsulphurous, 235 Flaveanhydric, 427 Formic, 324 Formothiohydroxamic, 429 Formylacetic, 393 Fulminic, 428 Fulminuric, 429 Fumaric, 22, 374 Galactonic, 392 Geranic, 358, 363 Glucoheptonic, 393 Acid, Gluconic, 392 Glutaconic, 375 Glutamic, 424 Glutaric, 366, 372 Glyceric, 220, 392 Glycerophosphoric, 258 Glycolglycollic, 384 Glycollic, 379, 384 Glycolsulphuric, 256 Glycoluric, 433 Glycuronic, 393 Glyoxylic, 393 Gulonic, 392 Heptoic, 349 Heptylacetylenecarboxylic, 360 Heptylsuccinic, 371 Hexahydrostearic, 364 Hexantetroloic, 392 Hexylacetylenecarboxylic, 360 Hexylsuccinic, 371 Hippuric, 423 Hydantoic, 433, 435 Hydracrylic, 389 Hydrazoic, 426, 434 Hydrochelidonic, 411 Hydrocyanic, 427 Hydromucic, 373 Hydromuconic, 375 Hydroxyacetic, 379, 384 3-Hydroxyacrylic, 390, 393 o-(fl-)Hydroxybutyric, 389 a-Hydroxycaproic, 389 Hydroxycitric, 419 Hydroxyethylsulphonic, 257 o-(^)-Hydroxyglutaric, 400 a-Hydroxyisobutyric, 389 a-Hydroxyisovaleric, 389 Hydroxymalonic, 399 Hydroxymethylsulphonic, 257 o-Hydroxymyristic, 389 Hydroxyoleic, 390 a-Hydroxypalmitic, 389 j8-Hydroxypelargonic, 390 a-Hydroxypropionic, 386 i3-Hydroxypropionic, 389 o-Hydroxystearic, 389 Hydroxysuccinic, 399 a-Hydroxyvaleric, 389 Hypogaeic, 358 Ichthyolsulphonic, 103 Idonic, 392 Iminodithiocarbamic, 433 Iminodithiocarbonic, 433 Iminothiocarbamic, 433 ^-lodopropionic, 378 Isethionic, 257 Isoamylmalonic, 369 Isobutylaticonic, 375 Isobutylfumaric, 373 Isobutylmaleic, 373 Isobutylmalonic, 369 Isobutyric, 349 Isocrotonic, 22, 355 Isocyanic, 427 Isoerucic, 360 a-(/8) Isofulminuric, 429 Isolinolenic, 364 Iso-oleic, 359 Isopropylacetylenecarboxylic, 360 Isopropylfumaric, 373 7-Isopropylitaconic, 373 Isopropylmaleic, 373 Isopropylmalonic, 369 Isosaccharinic, 392 INDEX Acid, Isosuccinic, 371 Isovaleric, 349 Itaconic, 374 Itamalic, 400 Jecorinic, 364 0-Ketobutyric, 396 Lactic, 383, 386 Laurie, 320, 350, 362 Leucinic, 389 Levulinic, 390, 397 Lignoceric, 320 Linolenic, 364 Linolic, 363 Lyxonic, 392 Malamic, 421 Maleic, 22, 374 Malic, 399, 421 . Malonic, 368, 437 d-Mannonic, 392 Margaric, 350 Melissic, 351 Mesaconic, 22, 374 Mesotartaric, 401 Mesoxalic, 399, 410 Metacrylic, 356 Metasaccharinic, 392 Methionic, 228, 257 Methylacetylenecarboxylic, 360 a-Methylacrylic, 356 3-Methylacrylic, 355 -Methy]adipic, 372 Methylbutylmalonic, 369 l-Methylcyclohexylidene-4-acetic, 20 Methylenedisulphonic, 257 7-Methylene-7-methylpyrotartaric, 373 Methylenesuccinic, 374 Methylethylglycollic, 389 Methylethylitaconic, 373 Methylethylmaleic, 373 Methylethylmalonic, 369 Methylfumaric, 374 Methylisobutylmalonic, 369 Methylisopropylmaleic, 373 Methylisopropylmalonic, 369 a-(y-) Methylitaconic, 373 Methylmaleic, 374 Methylmalonic, 369 Methylmethyleneacetic, 356 Methylpropiolic, 361 Methylpropylmaleic, 373 Methylpropylmalonic, 369 Monochloroacetic, 379, 383 Monothiocarbamic, 433 Monothiocarbonic, 433 Monothiocarbonylamic, 433 Monothiocarbonylic, 433 Mucic, 410 Muconic, 376 Myristic, 350 Nitrohydroxylaminic, 246 Nonoic, 349, 360 Nonylacetylenecarboxylic, 360 (Enanthic, 934 Oleic, 358 Aa/3-Oleic, 359 Oxalacetic, 410 Oxalic, 366 Oxaluric, 435 Oxaniic, 421 Palmitic, 350 Parabanic, 435, 436 Paralactic, 389 Paratartaric, 401 Pelargonic, 349 Acid, Pentadecoic, 320 Pentylmalonic, 369 Perthiocyanic, 429 Picric, 303 Pimelic, 365 Pivalic, 349 as. Propanetricarboxylic, 411 s. Propanetricarboxylic, 376, 411 Propargylic, 361 Propinoic, 361 Propiolic, 361 Propionic, 348 Propylacetylenecarboxylic, 360 Propylfumaric, 373 Propylitaconic, 373 Propylmaleic, 373 Propylmalonic, 369 Propylsuccinic, 371 Pseudouric, 437 Purpuric, 435 Pyrocinchonic, 375 Pyroligneous, 335 Pyrotartaric, 372 Pyroterebic, 357 Pyruvic, 383, 396 Racemic, 21, 400 Rhamnohexonic, 393 Rhodanic, 429 Rhodinic, 358 Ribonic, 392 Ricinelaidinic, 390 Ricinoleic, 390 Ricinoleinsulphonic, 390 Roccellic, 365 Rubeanhydric, 427 Saccharic, 410 Saccharinic, 392 Salicylic, 212 Sarcolactic, 389 Sativic, 364 Sebacic, 358, 365, 372 Sorbic, 363 Stearic, 350 Stearolic, 358, 362 Suberic, 365, 372 Succinatmc, 421 Succinic, 370 Talonic, 392 Tariric, 362 Tartaric, 21, 400 Artificial, 410 Manufacture of, 407 Tartronic, 220, 399 Taurocholic, 257, 424 Telfairic, 364 Teraconic, 373 Teracrylic, 357 Terebic, 357 Terebinic, 400 Terpenylic, 357 Tetrabromostearic, 364 Tetracetylenedicarboxylic, 376 Tetrahydroxystearic, 364 Tetrolic, 356, 361 Thioacetic, 419 Thiocyanic, 429 Thiocyanuric, 429 Tiglic, 357 Tricarballylic, 363, 376, 411 Trichloroacetic, 378 Trihydroxyglutaric, 410 Trimesic, 393 Trimethylacetic, 349 aa-Trimethyltricarballylic, 376 INDEX 445 Acid, Trithiocarbonic, 433 Undecenoic, 358 Undecoic, 350 Undecolic, 361 Uric, 435 Valeric, 349 Vinylacetic, 354 0-Vinylacrylic, 363 Violuric, 437 Xanthic, 434 Xanthonic, 434 Xylonic, 392 Acidol, 424 Acids, Affinity constants, 321 Heats of neutralisation of organic, 26 Alkylsulphonic, 233 Alkylsulphuric, 235 Amino, 422 Dibasic, 234 Dihydroxystearic, 389 Diolefinedicarboxylic, 376 Halogenated, 377 Heptonic, 393 Hexabromostearic, 364 Hexahydroxystearic, 364 Hexonic, 392 Homoaspartic, 425 Hydroxamic, 246, 427 Hydroximic, 427 Hydroxy, 383 Hydroxyolefinecarboxylic, 389 a-Ketonic, 395 -Ketonic, 395 7-Ketonic, 396 Ketonic dibasic, 410 Lactic, 20, 385 Monobasic, 234 Monobasic aldehydic, 393 Monobasic ketonic, 394 Olefinecarboxylic, 351 Olefinedicarboxylic, 373 Polybasic fatty, 364 Pyrotartaric, 372 Saturated dibasic, 364 Saturated monobasic fatty, 319 Succinic, 370 Tartaric, 21, 400 Tetrabasic, 376 Tribasic, 234, 376 Unsaturated dibasic, 373 Unsaturated monobasic fatty, 351 Unsaturated monobasic, of the series C n H 2n _ 4 O a 360 with two double bonds, 362 with three double bonds, 364 " with triple linking, 360 Aconitum napellus, 376, 411 Acraldehyde, 251 Acrolein, 251 Acrolelnammonia, 252 Acrose, 393' Adenine, 436, 441 Affinity constants, 32 1 Agglutinins, 139 Agro cotto, 414, 415 Alanine, 389, 423 Albumin, Living, 137 Alcohol, Absolute, 130, 172 Acetoisopropyl, 398 Acetone, 397 Allyl, 216, 327 Amyl, 126, 165, 215 Butyl, 125, 126, 214 Caproyl, 215 Alcohol, Capryl, 215 Ceryl, 126, 215 Cetyl, 215 Decyl, 126 Denatured, 176 Dodecyl, 126 Ethyl, 130 Glycide, 258 Heptyl, 126, 215 Hexadecyl, 126, 215 Hexyl, 215 Isobutyl, 126, 215 Isohexyl, 215 Isopropyl, 126, 214 Melissyl, 216 Methyl, 127-130, 173 Myricyl, 126, 216 Nonyl, 126 Octodecyl, 126 Octyl, 126, 215 (Enanthyl, 215 of crystallisation, 126 Pentadecyl, 126 Propargyl, 216 Propyl, 126, 214 Tetradecyl, 126 Tridecyl, 126 Undecyl, 126 Vinyl, 216 Alcohol, Amylo process, 155 Denaturation, 176 Effront process, 167 Fiscal regulations, 179 from beet, 168 from calcium carbide, 171 from fruit, 167 from lees, 169 from molasses, 166 from sulphite liquors, 169 from vinasse, 169 from wine, 169 from wood, 167 Industrial preparation of, 140 meters, 173 motors, 178 Rectification of, 164 Solid, 131 Statistics, 179 Synthetic, 171 Tests, 172, 174 Windisch's Table, 175 Yield, 153 Alcohols, 123 Aldehydic, 393 Constitution of, 124 Derivatives of monohydric, 226 of polyhydric, 256 Dihydric, 216 Higher monohydric, 214 Ketonic, 394, 397 Nomenclature, 125 Polyhydric, 217, 224 Primary, 124, 125 . Saturated monohydric, 124, 126 Secondary, 124, 125 Tertiary, 124. 125 Tetrahydric, 224 Trihydric, 217 Unsaturated, 216 Alcoholene, 178 Alcoholism, 130, 184 Alcoholometer, Gay-Lussac, 174 Tralles, 174 Alcoholometry, 174 446 INDEX Aldehyde-ammonias, 245 Aldehydes, 116, 124, 243, 244 Determination by Strache's method, 255 Schiff's reagent- for, 246 with unsaturated radicals, 251 Aldehydo-catalase, 134 Aldoketenes, 256 Aldol, 393 Aldols, 245 Aldoximes, 246 Alembics, 158 Algae, 68 Aliphatic compounds, 29 Alipine, 119 Alkoxides, 124 Alkyl halides, 114 Estimation of, 120 Alkylenes, 106 Alkylhydrazines, 241 Alkylhydroxylamines, 24 1 Alkylisoureas, 432 Alkyls, 30 Allantoin, 436 Allene, 109, 374 Alloisomerism, 21, 22 Alloxan, 435 Alloxanthine, 436 AHyl bromide, 123 chloride, 123 iodide, 123 isothiocyanate, 430 mustard oil, 430 thiocyanate, 430 Allylene, 110, 375 Amber, 370 Amidases, 183 Amides, 253, 419 of carbonic acid, 431 of hydro xy-acids, 421 Amidines, 238, 425, 426 Amido-chlorides, 425 Amidoximes, 427 Amimides, 42 Amines, 239 Amino-acids, 419 Derivatives of, 422 Aminoguanidine, 434 Ammelide, 431 Ammeline, 431 Ammonal, 311 Ammoncarbonite, 307 Ammonium carbamate, 431 cyanate, 428 ichthyolsulphonate, 103 thiocyanate, 429 Amygdalin, 136 Amylacetylene, 399 Amylase, 133, 134 Amylene, 109 hydrate, 215 Amylo process, 155 Amylodextrin, 141 Amylomyces Rouxii, 155, 156 Anaesthesia, 114, 118 Anaesthetics, 118 Analysis, Elementary, 8 Qualitative, 7 Quantitative, 8 Anhydrides, 380 Internal, 380 Mixed, 380 Antialdoximes, 253 Anti-bodies, 138 Antiketoximes, 253 Antilactase, 138 Antimorphine, 138 Antipepsin, 138 Antirennet, 138 Antiricin, 138 Antiseptics, 151 Antitoxins, 138 Arabitol, 225 Arginine, 392 Aromatic compounds, 29 Arrack, 190 Arsines, 242 j^rtificial parthenogenesis, 138 Ascomycetes, 133 Asparagine, 20, 424 Aspartamide, 425 Aspergillus oryzae, 155 Asphalte, 99 Artificial, 99 mastic, 99 Asphaltite, 100 Astatki, 77, 86 Asymmetric syntheses, 137 , Asymmetry, Absolute, 22 Relative, 22 Atole, 190 Atractylin, 248 Attenuation of fermented liquids. 153, 154, 207 Axite, 302 Azides, 426 Azodicarbonamide, 434 Bacillus aceticus, 145, 340 acidi laevolactici, 389 acidificans longissimus, 152 butylicus, 214 Delbrucki, 149 ethaceticus, 392 saprogenes vini, 404 Bacteria, Acetic, 145, 340 Butyric, 145 Chromogenic, 133 Lactic, 145 Pathogenic, 133 Reproduction of, 132 Saprophytic, 133 Zymogenic, 133 Bacteriology, 132 Baekelite, 370 Balling's Table, 200 Ballistite, 300 Barley, 192 Malting of, 195 Bases, Aminic, 239 Ammonium, 239 Arsonium, 242 Iminic, 239 Nitrilic, 239 Primary, 239 Quaternary, 239 Secondary, 239 Tertiary, 239 Beckmann rearrangement, 253 Beer, 191 Alcohol-free, 211 Analysis, 211 Attenuation, 207 Cask pitching, 209 Composition, 211 Detection of antiseptics in, 212 Fermentation, 204 Mashing, 201 Pasteurisation, 210 INDEX 447 Beer, Racking, 209 Statistics, 212 Benzene from naphtha, 87 Benzine, Crude, 84 Benzoyl, 15 Bergamot, 413 Betaine, 385, 423 hydro-chloride, 423 Bilineurine, 257 Biogen theory, 137 Bismuth tribromophenoxide, 122 Bisulphite aldehyde compounds, 244 Bitumen, 99 Biuret, 133 Blastomycetes, 133 Blood, 137 Boghead coal, 100 Boiling point, 2, 25 Boudineuse, 284, 300 Brandy, 190 Bromoacetylene, 123 Butandiene, 113 Butandiine, 114 Butandione, 398 Butanes, 37 Butanolone, 398 Butanols, 214 Butanone, 256 Butantetrol, 225 Butenes, 109 Butyl iodides, 117, 118 Butylenes, 109 Butyramide, 421 Butyrolactone, 384 Butyryl chlorides, 380 Cacao butter, 437 Cacodyl, 15, 242 chloride, 242 oxide, 242 Cadaverine, 257 Caffeine, 438 Calcium acetate, 337 butyrate, 348 carbide, 11 citrate, 415, 417 cyanamide, 430 dilactate, 388 ethoxide. 214 formate, 328 lactate, 388 oxalate, 368 tartrate, 40 1 Calorimeter, Junker's gas, 61 Cannel coal, 100 powder, 305 Capillarimeter, 176 Caprylene, 109 Caps, 309 Carbamide, 432 Carbamidyl chloride, 432 Carbazide, 433 Carbenes, 99 Carbinol, 125, 127 Carbocyclic compounds, 29 Carbod'iimide, 18, 430 Carbodiphenylimide, 430 Carbodynamitc, 284 Carbohydrazide, 433 Carbon, Asymmetric, 19 chains, 16 Estimation of, 8 oxychloride, see Phosgene. Carbon sulphochloride, 433 tetrachloride, 122 Valency of, 15 Carbonic acid esters, 431 Carbonite, 284, 307 Carbonites, 306 Carboxyl, 124 Carbyl sulphate, 257 Carbylamines, 238 Cart-grease, 98 Castor oil, 390 Catalases, 135 Catalysts, Inorganic, 136 Organic, 136 Cellase, 134 Cerasin, 69, 105 Cereals, Starch-content of, 141 Cerotene, 109 Cerotin, 215 Ceryl cerotate, 216 Chamberland flasks, 147 Champy drums, 272 Charcoal, Wood, 268 Chartreuse, 190 Cheddite, 305 Chica, 190 Chlamydomucor oryzse, 155 Chloral, 251 hydrate, 251 Chloralamid<% 421 Chloramides, 238 Chloranhydrides, 379 Chloretone, 119 Chlorhydrins, 107, 217, 257 Chlorimides, 238 Chlorocruorin, 137 Chloroe thane, 117 Chloroform, 118 Pictet, 119 Tests for, 120 Chloromethane, 116* Chlorophyll, 133 Chloropicrin, 236 o-Chloropropylene, 123 Chocolate, 437 Cholestrophane, 436 Choline, 257 Chronograph, Le Boulenge's, 317 Cider, 190 Citral, 216, 252, 416 Citrates, 418 C'itromyces citricus, 412 Pfefferianus and Glaber, 412 Citronellal, 252, 358 Citronellol, 216 Citrus bergamia, 413 industry, 413 limetta, 413 limonium, 413 Classification of organic substances, 29 Coagulation, Enzymic, 134 Coal, Cannel, 100 -dust in mines, 34 for gas, 39 gas, 38 tar, 99 Cocaine, 119 Cocci, 133 Cocoa, 437 Coffee, 438 substitutes, 439 Cognac, 190, 191 Collodion cotton, 285, 294 Combustion furnace, 8 448 INDEX Condensation, Aldehyde, 245 Aldol, 245 Condenser, Liebig's, 2 Conductivity, Electrical, 29 Conidia, 133 Coniine, 20, 110 Conylene, 110 Coolers, Wort, 204 Cordite, 287, 302 Cracking of oils, 87 Cream of tartar, 401, 402 Creatine, 435 Creatinine, 435 Cremonite, 305 Creosote oil, 99 Crotonaldehyde, 252 Crotonylene, 110 Crushers, 262, 315 Crystalline form, 24 Crystallisation, 2 Crystals, Hemihedral, 19 Liquid, 139 Mixed, 23 Curacao, 191 Cyamelide, 427 Cyanamide, 18, 430 Cyanates, 427 Cyanide black, 104 Cyanides, Alkyl, 237 Cyano-acids, 377 Cyanogen, 427 chloride, 427 compounds, 427 of coal-gas, 50 sulphide, 429 trichloride, 427 Cyanohydrins, 238 Cyanurtriamide, 431 Cyclic compounds, 106 Cycloheptanone, 357 Cyclohexane, 71 Cyclo-olefines, 29 Cycloparaffins, 29 Cyclopentane, 71 Cyclopropane, 106 Cymene, 252 Cymogen, 37 Cynarase, 139 Cysteine, 396, 424 Cystine, 396, 424 Cytase, 134 Decane, 32 Degree of dissociation, 322 fermentation, 153 viscosity, 90 Degrees Brix, 153 Dehusker, 145 Denaturants, 177 Denatured alcohol, 176 Densimeter, Legal, 207 Dephlegmators, 77, 158, 162 Derricks, 66, 74 Desichthyol, 103 Desmobacteria, 133 Desmotropy, 18 Detonation, 258 Detonators, 309 Dextrase, 147 Dextrinase, 134, 204 Diacetamide, 421 Diacethydrazide, 426 Diacetyl, 398 Diacetylene, 114 Diacetylglycol, 217 Dialdehydes, 393 Diallyl, 110 Diamalt, 140 Diamino-acids, 424 Diastase, 133, 134, 141 Diastofor, 140 Diazo-compounds, 241 Diazoguanidine, 434 Diazomethane, 242 Dibutyramide, 421 Dicetyl, 32 Dichlorethane, 118 Dichlorhydrin, 257 Dichlormethane, 118 Dicyanodiamide, 431 Dieline, 122 Diethylamine, 241 Diethylcarbinol, 126, 243 Diethylcyanamide, 431 Diethylenediamine, 257 Diethylsulphone, 233 Diethylthiourea, 434 Diglycerol, 218 Diglycollamides, 421 Diglycollimide, 421 Dihydrazides, 426 Dihydroxyacetonase, 147 Dihydroxyacetone, 147, 398 Dihydroxydiethylamine, 257 Di-isobutyramide, 421 Diketobutane, 398 Diketohexane, 399 Diketonamines, 252 Diketones, 398 Dimethylacetamide, 420 Dimethylacetol, 398 Dimethylamine, 241 Dimethylarsenic acid, 242 chloride, 242 Dimethylarsine, 242 Dimethylcarbinol, 214 Dimethylethylcarbinol, 126, 215 Dimethylglyoximej 398 Dimethylmethane, 36 Dimethyloxamide, 240 Dimorphism, 24 Dinitroacetylglycerine, 274 Dinitroethane, 237 Dinitroformylglycerine, 274 Dinitroglycerine, 273 Dinitromethane, 237 Dinitromonochlorhydrin, 274 Diolefines, 109 Diplococci, 133 Dipropargyl, 114 Dipropionamide, 421 Distillation, Fractional, 2, 75 of fermented liquids, 158 Theory, 3 Vacuum, 4 Wood, 330 Distillery residues, Utilisation, 182 Disulphides, 233 Disulphoxides, 233 Dithioglycol chloride, 257 Dithiourethane, 434 Diureides, 435 Docosane, 32 Dodecane, 32 Donnar, 305 Dormiol, 119 Dotriacontane, 32 449 Dropping-point of fats, Drying ovens for explosives, 271, 294 Dulcitol, 226 Durra, 141, 182 Dynamites, 273, 282 Analysis, 313 Gelatine, 298 Gelatinised, 2J>9 Gum, 298 Manufacture, 283 Properties, 284 Safety, 284 with active bases, 285 with inert bases, 283 Ebullioscope, 176 Echinochrom, 137 Effusiometer, Bunsen's, 62 Ehrlich's side chain theory, 138 Eicosane, 32 Electrical conductivity, 29 Emulsin, 134 Emulsor, Kuhlmann, 278 Enantiomorphism, 20 Enantiotropy, 130 Enzymes, 23, 133, 134 Equilibrated action, 136 Synthetic action, 136 Epichlorhydrin, 258 Erythrene, 109 Erythritol, 109, 225 Erythrodextrin, 141 Esters, 124, 234 Ethanal, 250 Ethanamide, 421 Ethanamidine, 426 Ethandial, 393 Ethandiol, 217 Ethane, 24, 36 Polychloro-derivatives of, 122 Ethanol, 130 Ethene, 108 Ethenol, 216 Ether, 228 Industrial preparation, 230 Petroleum, 37, 76 Properties, 228 Recovery from air, 231 Tests, 232 Uses, 231 Ethers, 226 Ethine,30, 111 Ethyl, 30 acetate, 395 acetoacetate, 395, 396 bromide, 115 bromopropionate, 369 carbonate, 431 chloride, 115, 117 chloracetoacetate, 397 chlorocarbonate, 431 chloroformate, 431 cyanurate, 427 diacetylsuccinate, 397 diazoacetate, 385, 424 dichloroacetoacetate, 397 fluoride, 115, 117 formate, 328, 395 hydrosulphide, 233 hydroxycrotonate, 394 iodide, 115, 117 isocyanate, 428 isocyanurate, 428 malonate, 368 VOL. II. Ethyl methyl ketone, 256 mustard oil, 430 nitrate, 235 nitrite, 235 oxalate, 240 peroxide, 232 hydrate, 232 phosphate, 234 sodioacetoacetate, 396, 397 sodiomalonate, 369 sodiomethylmalonate, 369 sulphate, 235 sulphide, 234 sulphite, 235 sulphoxide, 234 thioacetate, 419 thiocyanate, 429 Ethylacetamide, 420 Ethylacetamido-chloride, 425 Ethylacetimino-chloride, 425 Ethylacetylene, 110 Ethylamine, 241 ethyldithiocarbamate, 434 hydrochloride, 420 Ethylcarbinol, 214 Ethylcyanamide, 431 Ethylene, 106, 108 bromide, 118, 217 chloride, 118 cyanide, 256 iodide, 118 monothiohydrate, 257 oxide, 256 Polychloro-derivatives, 122 Ethylenecyanohydrin, 256 Ethylenediamine, 257 Ethylhydrazine, 246 Ethylidene chloride, 118 Ethylidene compounds, 118 Ethylideneacetone, 398 Ethylidenecyanohydrin, 238, 256 Ethylmagnesium bromide, 243 Ethylmercaptan, 233 Ethylsulphone, 234 Ethylurethane, 432 Etiline, 122 Eucaine, 119 Excelsior mill, 200, 269 Exhausters, 53 Explosion, 258 by influence, 265 Determination of, 264 Heat of, 259 Pressure of gases, 261 Velocity of combustion, 263 projectiles, 317 reaction, 263 Volume of gases, 261 wave, 262 Explosive, Favier's, 263, 304 Explosives, 258 Abel's test for, 314 Analysis of, 313 Charging density of, 262 Classification of, 266 Destruction of waste, 312 Non-congealing, 274, 276 Progressive, 263 Safety, 35, 305 Sensitiveness of, 315 Shattering, 263, 303 Sprengel's, 304 Stabilisation of, 292 Statistics of, 319 29 450 INDEX Explosives, Storage of, 312 Theory of, 259 Uses of, 318 Fats, Consistent, 90 Dropping-point of, 6 Fehling's solution, 255, 400 Fermentation, Alcoholic, 132, 145, 152, 204 Lactic, 151, 387 Fibrinogen, 137 Firedamp, 34, 305 Fishery statistics, 69 Fodder, Molassic, 166 Nutritive value of, 182 Forcite, 298 Formaldehyde, 247 Formalin (Formol), Analysis of, 247 Formamide, 421 Formates, 327 Formhydrazide, 426 Formins, 257 Formolite reaction, 71, 91 Formula, Constitutional, 15, 17 Empirical, 13 Structural, 15, 17 Formulae, Rational, 18 Unitary, 15 Formyl chloride, 379 Formyloxime chloride, 427 Francolite, 104 Fruit essences, Artificial, 349 Fulgurite, 284, 304 Fuller's earth, 80, 89 Fulminate of mercury, 308 Analysis of, 308 Fumaria officinalis, 374 Furfuraldehyde (Furfural), 173 Furnace, Combustion, 8 Gas, 45 Fusel oil, 109, 146, 165, 172 Fuses, 309 Bickford, 310 Electric, 311 Galalith, 250 Gafezin, 191 Gas, Air, 60 Blue, 58 Illuminating, 38 et seq* Marsh, 33 meters, 56 Oil, 65, 98 producer, 45, 60 Riche, 60 Water, 58, 98 Gases, Permanent, 34 Gasolene, 37, 76 Gasometers, 54 Gaultheria procumbens, 127 Gelatine, Blasting, 285 dynamites, 285, 298 Gelignite, 298 Geranial, 252 Geraniol, 216, 252 Gin, 190 Glass, Hardened, 94 Glonoin, 275 Glutarimide, 422 Glyceraldehyde, 393 Glycerides, 218 Glycerol (Glycerine), 36, 146, 217 Industrial preparation, 220 Qualities of, 223 Refractive index, 219 Glycerol, Statistics, 223 Tests for, 223 Uses, 220 Glycerose, 398 Glyceryl trinitrate, 258 Glycine (Glycocoll), 379, 385, 423 Glycocyamidine, 435 Glycocyamine, 434 Glycogen, 137 Glycol, 217 Glycol acetates, 256 chlorohydrin, 256 dinitrate, 256 Ethyl ethers of, 256 mercaptan, 257 Glycollamide, 421 Glycollic aldehyde, 393 Glycollide, 384 Glycols, 216 Propylene, 217 Glycolsulphuric acid, 256 Glycosine, 393 Glyoxal, 393 Glyoxaline, 393 Glyoxiline, 284 Goudron, 99 " Grains," 203 Grape must, 186 Greek fire, 266 Green naphtha, 102 oil, 103 Schweinfurth's, 348 Grisounite, 307 Guanamines, 434 Guanidine, 434 Amino derivative of, 434 Diazo, 434 nitrate, 434 Nitro-derivative of, 434 Guanine, 436, 440 Guncotton, 285 Compression of, 293 Manufacture of, 288 Properties of, 287 Pulping of, 292 Stabilisation of, 292 Thomson and Nathan's process for, 290 Uses of, 293 Gunpowder, 266 Manufacture, 267 Haemocyanin, 137 Hsemoerythrin, 137 Haemoglobin, 135 Halides, Acid, 377, 379 Halogens, Detection of, 7 Estimation of, 12 Hansena fermentation vessels, 208 Hardened glass, 94 Heat of combustion, 25 explosion, 259 formation, 25 of explosives, 259 neutralisation, 26 Hedonal, 119 Helianite, 328 Heneicosane, 32 Hentriacontane, 32, 37 Henze autoclaves, 143 Heptachloropropane, 123 Heptacosane, 32, 37 Heptadecarte, 32 Heptaldehyde, 251 Heptane, 32, 37 INDEX 451 Heracleum giganteum, 127, 130, 215 spondylium, 215 Heterocyclic compounds, 29 Hexacetylmannitol, 224 Hcxacontane, 32, 37 Hexacosane, 32 Hexadecane, 32 Hexadione, 399 Hexamethylbenzene, 111 Hexaraethylene, 106 Hexamethylenetetramine, 187, 248 Hexandiine, 114 Hexanes, 32, 37 Hexanhexol, 225 Hexanitroethane, 237 Hexanol, 215 Hexine, 110 Holocaine, 119 Homoasparagines, 425 Homology, 24 Hops, 193 Decoction of, 203 Humulus lupulus, 193 Hydantoin, 433, 435 Hydramine, 257 Hydraulic gas main, 45 press, 270 Hydrazides, 426 Hydrazodicarbonarnide, 434 Hydrazones, 246 Hydrocarbons, 29, 31 of petroleum, 71 of the CnH2n-2 series, 109 of the C n H 2n -4 and C n H 2n -6 series, 114 Saturated, 29, 31 Unsaturated, 29, 106, 116 with triple linkings, 1 10 Hydrogen, Estimation of, 8 Nascent, 33 Tyoical alcoholic, 124 Hydrolysis, 125, 442 Enzymic, 134 Hydroxy-acids, Higher, 389 poly basic, 419 Polyvalent dibasic, 399 monobasic, 391 tri basic, 411 Saturated monobasic, 383 Unsaturated monobasic, 389 /3-Hydroxybutyraldehyde, 245 Hydroxyethylamine, 257 Hydroxyethyltrimethylammonium hydrox- ide, 257 Hydroxylamine, 235 derivatives of acids, 427 Hydroxymethyleneacetone, 396, 399 Hydroxymethyleneketones, 399 Hydroxynitriles, 238 Hyphomycetes, 133, 155 Hypnotics, 118 Hypoxanthine, 436 Ichthyoform, 104 Ichthyol, 103 Ichthyolsulphonates, 103 Iditol, 226 Illuminating gas, 38 Analysis of, 60 Calorific value of, 39, 61 Composition of, 40 History of, 38 Lighting power of, 62 meters, 56 Physical and chemical testing of, 60 Illuminating gas. Price of, 58 Properties of, 40 Purification of, 45 et seq. Separation of naphthalene from, 46 Statistics of, 59 Yield of, 58 Imides, 421 Iminocarbamide, 434 Iminocarbamideazide, 434 Iminochlorides, 425 Iminoethers, 420, 422 Iminothioethers, 425 Iminourea, 434 Index of refraction, 27 Injectors, Korting, 53 Invertase (Invertin), 134 lodoform, 121 reaction, Lieben's, 131 Tests for, 122 lodopropane, 117 lodourethane, 432 Ironac, 328 Isobutane, 37 Isobutyl iodide, 118 Isobutylcarbinol, 126, 215 Isobutyramide, 421 Isocyanates, 427 Isocyanides, 238 Isocyclic compounds, 29 Isoleucine, 424 Isology, 24 Isomaltose, 136 Isomelamine, 431 Isomerides, 17 Boiling-points of, 25 Melting-points of, 25 Metameric, 18 Optical, 20 Racemic, 21 Isomerism, 15, 17 Cis- and trans-, 22 Space, 19 Isonitriles, 237, 238, 240, 427 Isonitrosoketones, 253, 398 Isopentane, 37 Isoprene, 109, 113 Isopropyl iodide, 116, 117 Isopropylacetylene, 1 10 Isovaleryl chloride, 380 Isuret, 427 Ivory, Artificial, 351 Kephir, 139, 191 Kerosene, 72 Ketenes, 256 Keto-aldehydes, 394, 399 Ketoketenes, 256 Ketones, 116, 124, 243, 252 Strache's estimation of, 255 Ketonimides, 243 Ketoximes, 253 Beckmann's transposition of, 253 Kieselguhr, 275, 283 Kirschwasser, 190 Koji, 155 Koumis, 191 Kratites, 305 Kummel, 191 Laccase, 134 Lactams, 423 Lactases, 134 Lactates, 388 ' Lactic acid bacillus. 145, 387 452 Lactides, 384 Lactone, Bromobutyric, 355 Isocaproic, 357 Lactones, 355, 377, 384 Lactyl chloride, 389 Lager beer, 203, 205 Lamp, Carcel, 62 Hefner- Alteneck, 62 Law of Dalton, 5 Hess-Berthelot, 25 of refraction, 27 Lead plaster, 351 Sugar of, 347 Leben, 191 Lecithins, 258 Lees, Wine, 170, 402, 408 Lemons, Cultivation of, 413 Treatment of, 414 Leucine, 20, 424 Leucocytes, 139 Levulinaldehyde, 399 Life, Origin of, 137 Light, Polarised, 27, 395 Sources of, 64 Standards of, 62 Ligroin, 37, 76 Limonene, 416 Lipase, 134 Liqueurs, 190 Liquids, Specific gravity of, 7 Lithoclastite, 284 Lupulin, 193, 203 Lyddite, 303 Lysine, 392, 424 Lysins, 139 Lysoform, 250 Magnesia, Effervescent, 413 Magnetic rotation, 28 Maize, 142, 193 Malamide, 421 Malt, 141, 196 Cleaning of, 200 Diastatic power of, 199 Evaluation of, 199 Green, 196 Grinding of, 200 Kilning of, 198 Mashing of, 201 Maltase, 134, 141 Malting, 196 Maltodextrinase, 134, 204 Maltose, 134, 199 Mammoth pump, 278 Manlianite, 305 Manna, 225 Mannatriose, 225 Mannide, 226 Mannitan, 226 Mannitol, 225 Hexacetyl, 224 Hexanitro, 285 Maraschino, 190 Marmite, 149 Marsala, 190 Mashing apparatus, 20 1 Masut, 77, 86 Medziankite, 305 Melam, 431 Melamine, 431 Melene, 109 Melibiase, 134 Melinite, 303 Melting-point, 5, 25 INDEX Mercaptans, 233 Mercaptide, Mercuric, 233 Sodium, 233 Mercaptols, 252 Mercury fulminate, 308 Mesityl oxide, 253 Mesitylene, 111 Metaldehyde, 250 Metalepsy, 15 Metamerism, 18, 228 Meters, Alcohol, 173 Automatic gas, 58 Dry gas, 56 Gas, 56 Methanal, 247 Methanamide, 421 Methanamidoxime, 427 Methane, 24, 33 Derivatives of, 31 Industrial uses of, 35 Preparation of, 35 Properties of, 34 Methanol, 127 Methanthiol, 233 Methene, 108 Methenylamidoxime, 427 Methoxymethane, 228 Methyl, 30 chloride, ll(i cyanide, 238 ether, 228 iodide, 117 isothiocyanate, 430 mustard oil, 430 nonyl ketone, 397 sulphide, 233 Methylacetylurea, 420 Methylal, 251 Methylamine, 240 hydrochloride, 117, 241 Methylbutanol, 215 Methylcyanamide, 431 Methylene, 108 bromide, 115, 118 chloride, 115, 118 iodide, 115, 118 Methylethylacetylene, 1 10 Methylethylcarbinol, 214 Methylglyoxal, 399 Methylheptenone, 363 Methylisopropylcarbinol, 12G Methylpropane, 37 Methylpropanol, 215 Methyluracil, 436 Methylurethane, 426 Microbes, 132 Micrococci, 133 Micron, 133 Milk, 134 Fermented, 191 Molasses, Beet, 166 Molecular volume, 25 Monoacetin, 257 Monoacylhydrazides, 426 Monochlorhydrin, 257 Mononitroglycerine, 274 Morphine, 138 Morphotropy, 24 Moulds, 132 Mucors, 133, 155, 156, 412 Murexide, 436, 437 Muscarine, 257 Mustard, Black, 430 oils, 430 INDEX 453 Muta-rotation, 28 Mycoderma aceti, 340, 341 vini, 341 Myristin, 350 Naphtha, 65 Naphthalene, Estimation in coal-gas 61 from coal-gas, 46 Naphthenes, 71 Neradol, 250 Neurine, 257 Nisser powder, 305 Nitriles, 237, 427 Nitroacetins, 274 Nitrocellulose, 285 Constitution of, 286 Nitrochlorhydrin, 274 Nitro-derivatives, 235 Nitroethane, 236, 237 Nitroform, 237 Nitroformins, 274 Nitrogen, Detection of, 7 Estimation by Dumas' method, 10 Kjeldabl's method, 11 Will and Varrentrapp's method, 12 Stereoisoinerism of, 22 Nitroglycerine, 275 Filtration of, 282 Manufacture of, 277 Stabilisation of, 281 Uses of, 282 Nitroguanidine, 434 Nitrohexane, 236 Nitromethane, 237 Nitropropane, 237 Nitrosamines, 240 Nitrostarch, 285 Nitrourea, 432 Nitrourethane, 432 Nomenclature, Official, 29 Nonane, 32 Nonodecane, 32 Nonyl aldehyde, 251 Number, Acetyl, 224, 225 Acetyl acid, 225 Acetyl saponification, 225 Acid, 105 Octadiene, 110 Octane, 32 Octocosane', 32 Octodecane, 32 Octylene, 109 (Enanthaldehyde, 251 (Enoxydase, 134 Oil, Acetone, 255 Allyl mustard, 430 Castor, 390 Ethyl mustard, 430 for gas, 98 Gelatinised vaseline, 93 Lemon, 415 Methyl mustard, 430 Paraffin, 76 Paraffin wax, 94 Propyl mustard, 430 Resin, 92 Shale, 102 Solar, 72, 98 Turkey-red, 390 Oil-gas, 64 Oils, Engine, 92 Flash-point of, 83, 91 for gas, 98 Oils, Heavy, 76 Mineral lubricating, 86 Mustard, 430 Spindle, 92 Vaseline, 89 Viscosity of, 83, 90 Olefines, 106 Constitution of, 108 Nomenclature of, 106 Preparation of, 107 Table, 106 Oleine, 358 Opsonins, 139 Optical activity, 19, 69 antipodes, 23 properties, 26 Organo-metallic compounds, 242 Ornithine, 392, 424 Ortho-ethers, 324 Orthoform, 119 Oxalates, 368 Oxamide, 421 Oxidation, Enzymic, 135 Oximide, 422 Oxy-acetylene blowpipe, 113 Oxydases, 134 Oxygenases, 135 Ozoform, 250 Ozokerite, 31, 69, 94, 104 Ozonides, 359 Palmitates, 350 Palmitin, 350 Panclastite, 304 Paracyanogen, 427 Paraffin wax, 94 Analysis, 105 Statistics, 106 Paraffins, 29, 31 Paraformaldehyde, 248 Paraglobulin, 137 Paraldehyde, 246 Parthenogenesis, Artificial, 138 Partial pressures, 5 Pasteur flasks, 147 Pasteurisation, 186, 210 Pastinaca sativa, 130 Penicillium glaucum, 23 Pentacosane, 32 Pentadecane, 32 Pentaerythritol, 225 Pentahydroxypentane, 225 Pentaline, 122 Pentamethylenediamine, 257 Pentanediene, 110 Pentanes, 37 Pentanol, 205 Pentatricontane, 32 Pentenes, 110 Peptase, 134 Peroxydases, 135 Peroxyozonides, 356 Petrinage, 299 Petrolene, 99 Petroleum, 65 coke, 78 Composition of, 70 Crude, 70 Desulphurising of, 80 Distillation of, 75, 76 ether, 76, 86 Extraction of, 73 Flash-point of, 84 fountains, 73 454 INDEX Petroleum, History of, 65 Illuminating power of, 84 Optical activity of, 69 Origin of, 67 Pipe-lines for, 75 Properties of, 70 Purification of, 78 Refining of, 78 residues, 86 Specific gravity of, 70, 72 Statistics of, 81 tanks, 80 Tests for lighting, 83 Transport of, 75 Uses of, 81 Viscosity of, 83 Petroline, 76 Pharaoh's serpents, 429 Phenylsuccinimide, 422 Phlegm, 158 Phorone, 256 Phosgene, 118, 431 Phosphines, 242 Phosphorus, Detection of, 8 Estimation of, 13 Photogen, 98 Photometer, Bunsen's, 63 Lummer and Brodhun's, 63 Phylloxera, 188 Picoline, 252 Pierrite, 305 Pinacoline, 217 Pinacones, 217 Pinnoglobin, 137 Piperazine, 257 Piperidine, 1 10 Piperylene, 110 Pitch, 99 Coal, 99 Mineral, 99 Plastering of wines, 187 Platinichlorides, 14 Polarimeters, 28 Polarisation of light, 27 Polyglycerines, 218 Polymerism, 14 Polymethylenes, 29 Polymorphism, 24 Potatoes, Starch-content of, 13, 141 Powder B, 296 Black, 266 Powders, Brown prismatic, 273 Chlorate, 304 Chocolate, 273 Mining, 267 Perchlorate, 304 Prismatic, 272 Prometheus, 304 Smokeless, 295, 298, 300, 302, 303 Smokeless sporting, 267 Sporting, 267 Various, 311 Precipitins, 139 Pressed yeast, 149 Propaldehyde, 251 Propane, 32 Propanol, 214 Propanone, 254 Propantriol, 217 Propargyl aldehyde, 252 Propene, 109 Propenol, 216 Propine, 110 Propionamide, 421 Propionyl chloride, 380 Propyl iodide, 115 mustard oil, 430 Propylcarbinol, 214 Propylene, 109 Propylpseudonitrile, 236 Proteolytic action, 134 Protococcus vulgaris, 225 Protol, 218 Protoplasm, 137 Pseudoisomerism, 18, 394 Ptomaines, 257 Ptyalin, 134 Purification by physical methods, '2 Purine, 436 Putrescine, 257 Pyropissite, 95 Pyroxyline, 285 Pyrrole, 422 Pyrrolidine, 422 Pyrrolilene, 109 Pyruvic aldehyde, 399 Racemisation, 23 Rackarock, 304 Radicles and types, Theory of, 1 5 Reaction, Baeyer's, 107 Blank and Finkenbeiner's, 247 Deniges', 413 Formolite, 71 Grignard's, 33, 243 Kamarowsky's, 172 Korner and Menozzi's, 375, 423 Lieben's, 121, 129, 131 Melsen's, 339 Perkin's, 352 Rimini's, 131, 172 Sabatier and Sendcrens', 35, 67, 124 Schiff's, 246 Scudder and Riggs', 129 Uffelman's, 386 Yarrentrapp's, 350 Wallach's, 357 Reactions, Reversible, 136 Reversible enzymic, 136 Reagent, Deniges', 413 Schardinger's, 134 Schiff's, 172 Rectification, 3, 158 of alcohol, 158 Rectifier, Hempel, 3 Perrier, 166 Savalle, 159 Reductases, 134 Refraction constant, 27 Refractometer, 83 Refrigerator for wort, 204 Kentschel's, 144 Rennet, 134, 138 Rhigolene, 37 Rhizoporus oligosporus, 155 Rhodinol, 358 Rice, 193 lUcho-Jialphen test, 83 Ricin, 138 Robin, 138 Robinia pseudacacia, 138 Roburite, 306, 307 Rochelle salt, 401 Rubber, Synthetic, 109, 113 Rum, 190 Saccharimeters, 28 Saccharometer, Balling, 153 INDEX 455 Saccharomyces cerevisirp, 134, 137, 145, 184 Saccharomycetes, 133 Saccharone, 410 Salin, 183 Salt of sorrel, 368 Rochelle, 401 Sanguemelassa, 166 Saponification, 234 Saponin, 138 Sarcosine, 385, 423, 435 Sawdust, Utilisation of, 333 Scheelisation, 220 Schists, Bituminous, 100 Schizomycetes, 132 Schizosaccharomyces Pombe, 204 Schnapps, 190 Schneiderite, 304J Scrubbers, 48 Securite, 307 Semicarbazide, 246, 433 Semicarbazones, 246, 433 Separators, Naphthalene, 46 Tar, 46 Series, Aliphatic, 29 Ethylene, 106 Fatty, 29 Homologous, 24 Isologous, 24 Paraffin, 31 Serine, 424 Sero-therapy, 138 Serum, Physiological, 139 Serum-albumin, 137 Shale, 100 Shalonka, 75 Shimose, 303 Siperite, 304 Smokeless powders, 295, 298, 302, 303 Military, 300 Soap, 350, 358 Antiseptic, 79 Sodium acetonebisulphite, 253 ethoxide, 131, 214 Solanine, 138 Solenite, 302 Solubility of organic compounds, 25 Solvents, Non-inflammable, 122 Sorbitol, 226 Sorbose bacterium, 226 Sorrel, Salt of, 368 Specific gravity, 25 refraction, 27 rotation, 28 Spent wash, 157, 182 Sphserobacteria, 133 Spirilla, 133 Spirit, Crude wood, 128 Denatured, 173, 176 of sweet wine, 117 of wine, 130 Purification of, 172 Wood, 128 Spiritus tetheris nitrosi, 117 Spirobacteria, 133 Spores, 132 Stachyose, 225 Standard scrubber, 48 Staphyloooccus, 133, 151 Starch, 133 Estimation of, 141 Saccharification of, 143 Steam, Superheated, 4, 77 Stearine, 350 Stereoisomerides, Separation of, 23 Stereoisomerism, 19 of nitregen, 22, 253 Stibines, 242 Streptococci, 133 Sublimation, 2 Succinamide, 421 Succinanil, 422 Succinates, 366, 371 Succinimide, 366, 421, 422, 436 Sucrase, 134 Sugar of lead, 346 Sulphonal, 119, 233, 252 Sulphones, 233 Sulphonium compounds, 233 Sulphoricinate, 390 Analysis of, 391 Sulphur, Detection of, 8 Estimation of, 13 Superheated steam, 4, 77 Syntheses, Asymmetric, 137 Talitol, 226 Tamping, 264 Tanks, Macdonald, 69 Weiss, 69 Tantiron, 328 Tar, Coal, 99 Distillation of, 88, 97 Lignite, 96 Mineral, 67 Statistics, 100 Statistics of lignite, 105 Wood, 99 Tartar, 402 Analysis of, 403 Cantoni's process, 405 Cream of, 401, 407 emetic, 401 Goldenberg's process, 403 industry, 402 Statistics of, 406 Tarulli's method, 404 Tartrates, 401 Tartrazine, 411 Taurine, 257, 424 Tautomerism, 18, 394 Tea, 439 Tension theory of valency, 107 Tetanolysin, 139 Tetrabromoe thane, 122 Tetrachloroethane, 122 Tetrachloromethane, 122 Tetracosane, 32 Tetradecane, 32 Tetraline, 122 Tetralkylphosphonium hydroxide, 242 Tetramethylarsonium compounds, 242 Tetramethylenediamine, 257 Tetramethylmethane, 37 Tetranitrodiglycerine, 218, 274 Tetranitroethane, 237 Tetranitromethane, 237 Theine, 438 Theobromine, 437 Theophylline, 436 Theory of explosives, 259 fractional distillation, 3 radicles, 15 substitution, 15 types, 15 valency, Baeyer's tension, 107, 366 Thioacetamide, 238, 425 Thioacids, 419 Thioalcohols, 233 456 INDEX Thioaldehydes, 246 Thioamides, 425 Thioanhydrides, 419 Thiocarbamide, 434 Thiocyanates, 429 Thioethers, 233 Thioketones, 253 Thiols, 233 Thiophosgene, 433 Thioserine, 424 Thiourea, 434 Thiourethane, 434 Thyol, 104 Tonsile, 104 Toxins, 137 Velocity of reaction of, 139 Trauzl's lead block, 316 Trialkylphosphine oxide, 242 Trialkylphosphonium hydroxide, 242 Triazoformoxime, 428 Trichloromethane, 118 Trichloropurine, 436 Tricosane, 32 Tridecane, 32 Trieline, 122 Triethylamine, 241 Triethylenediamine, 257 Triethylsulphonium hydroxide, 233 iodide, 233 Triformol, 248 Trihydroxytriethylamine, 257 Tri-iodomethane, 121 Triketonamines, 252 Trimethylacetyl chloride, 380 Trimethylamine, 117, 241 hydrochloride, 117 Trimethylbenzene, 111 Trimethylcarbinol, 215 Trimethylene, 106 Trimethylmethane, 37 Trimethylsulphonium iodide, 234 Trinitrocellulose, 286 Trinitroglycerine, 258, 275 Trinitromethane, 237 Trinitrophenol, 303 Trinitrotoluene, 304 Triolein, 358 Trional, 119 Trioxymethylene, 248 Tristearin, 220 Trithioketones, 253 Tryptase, 134 Tumelina, 166 Turkey-red, 391 oil, 390 Tyndall phenomenon, 69 Types, Multiple, 16 Theory of, 16 Tyrosinase, 138 Undecane, 32 Uramil, 437 Urea, 1, 431, 432 Alkyl derivatives of, 432 nitrate, 432 Nitro-derivative of, 432 Urease, 139 Ureides, 433, 435 Urethane, 432 Uro-acids, 435 Urotropine, 187, 248 Valency, 16 Tension theory of, 107 Valeraldehyde, 251 Vaporiraeter, Geissler, 174 Vaseline, 93 Artificial, 93 oil, 89 Gelatinised, 93 Velocity of esterification, 23 Verdigris, 347, 348 Vermouth, 190 Veronal, 119 Vigorite, 307 Vinasse, 158, 188, 404 Vinegar, 340 Adulteration of, 344 Analysis of, 344 Artificial, 344 German process, 341 Luxemburg process, 342 Malt, 344 Michaelis process, 342 mite, 341 Wine, 344 worms, 341 Viscometer, Engler's, 90 Vital force, 1 Waggon-still, 76 Waterproof fabrics, 346 Wax, Algse, 68 Carnauba, 350 Chinese, 216, 351 Japanese vegetable, 350 Mineral, 94 Montan, 95 Paraffin, 94 Westphalite, 306, 307 Wetterdinamit, 284, 307 Wheat, 193 Wine, 184 Alcohol-free, 185, 186 Analysis of, 188 Statistics of, 188 Wood charcoal, 268 Distillation of, 330 spirit, 127, 128 Poisoning with, 128 Xanthine, 436, 441 Xanthogenamide, 434 Xeroform, 122 Xylitol, 225 Xyloidin, 286 Yeast, 134, 137, 140, 145, 149, 204 Acclimatised, 151 Frohberg, 204 industry, 149 Logos, 204 Pressed, 149 Pure, 147 Saaz, 204 Wild, 204 Zinc alkyls, 33, 243 lactate, 388 Zymase, 134, 139, 147 Zymogen, 205 RETURN CIRCULATION DEPARTMENT TO* 202 Main Library LOAN PERIOD 1 HOME USE 2 3 4 5 6 ALL BOOKS MAY BE RECALLED AFTER 7 DAYS Renewals and Recharges may be made 4 days prior to the due date. Books may be Renewed by calling 642-3405. DUE AS STAMPED BELOW LIBi ^ARY USE ONLY" J JL 1 8 1988 CIR4 'ULAT/ON DEP7 J DECEIVED r \iu\- 1T. FORM NO. DD6, UNIVERSITY OF CALIFORNIA, BERKELEY BERKELEY, CA 94720 U.C. BERKELEY LIBRARIES UNIVERSITY OF CALIFORNIA LIBRARY