REESE LIBRARY OF THK UNIVERSITY OF CALIFORNIA. . . &> /J.^ No. Accession No . /$ fa fa fa) - p U U L? ELECTROLYSIS AND ELECTROSYNTHESIS OF ORGANIC COMPOUNDS. BY DR. WALTHER LOB, Privatdocent in the University of Bonn. AUTHORIZED TRANSLATION FROM THE AUTHOR'S ENLARGED AND REVISED EDITION BY H. W. F. LORENZ, A.M., Ph.D., Graduate of the University of Berlin. FIRST EDITION. NEW YORK : JOHN WILEY & SONS. LONDON : CHAPMAN & HALL, LIMITED. 1898. Copyright, 1898, BY H. W. F. LORENZ. ROBERT DRUMMOND, rRINTER. NEW YORK. AUTHOR'S PREFACE TO THE AMERICAN EDITION. IN the two and a half years that have passed since the appearance of the first edition of the present work, the application of the electric current in organic chemistry has undergone such a marked development that the book in its original form could no longer claim to give an adequate idea of our present knowl- edge of organic electrolysis and electrosynthesis. During these last two years in particular a series of important researches which systematically invade this new field of chemistry have been brought out in rapid succession. Since I am now engaged in the preparation of a new German edition, the desire of Dr. H. W. F. Lorenz to translate the book affords an excellent opportunity for presenting the revised and completed edition directly to his fellow countrymen. I hope that his excellent translation may also tend to draw the attention of his American colleagues to this broad IV AUTHOR'S PREFACE TO AMERICAN EDITION. and interesting field, and that electricity, possessing such a diversity of applications, may soon obtain a recognized position in organic chemistry. In the realization of this hope the author and translator see a rich reward for their efforts. Dr. WALTHER LOB. BONN, June, 1898. TRANSLATOR'S PREFACE. IN presenting this excellent little work, with the permission of the author, to the English-reading public, scarcely anything remains to be added to what Dr. Lob has already said in his prefaces to the German and American editions. He has read the manu- script and made the necessary changes and additions so as to have it correspond to the second German edition which is about to appear. The translator has adhered as closely as possible to the original text. He has made some additions and added a table of contents and a complete index, which he thinks will enhance the value of the book. To Dr. B. B. Boltwood of the Sheffield Scientific School of Yale University, who has had the kind- ness to revise the manuscript, grateful acknowledg- ments are due for his painstaking and valuable services. SPRINGFIELD, OHIO, November, 1898. AUTHOR'S PREFACE TO THE FIRST GERMAN EDITION. THE object of electrochemistry is, among others, that of performing, with the aid of the electric current, reactions which have up to the present been carried out by the employment of other forms of energy. Its very nature suggests the possibility of solving synthetical and analytical problems which have as yet remained unanswered. In this respect its province is both that of inorganic and organic chemistry. Experi- ments have recently been made for utilizing electricity in the latter. Few only of the many tasks presenting themselves have been undertaken. This book aims to give, as briefly as possible, a review of what has already been accomplished, and at the same time to create an interest in the performance of experiments on the electrolysis and electrosynthesis of organic compounds. AACHEN, Electrotechnical Laboratory of the Polytechnic Institute. November. 1895. vi CONTENTS. INTRODUCTION xi I. ELECTROLYSIS AND ELECTROSYNTHESIS OF ALIPHATIC COMPOUNDS. i. (a) Hydroxyl Compounds. Methyl alcohol Ethyl alcohol Propyl alcohol Butyl alcohol (lodoform, Chloroform, Brornoform). [Aristol, Nosophene.] 1-6 Glycol Glycerine Glyceric aldehyde Chloral hydrate Hexatomic alcohols Mannite Grape sugar Cane sugar Dextrine Gum arable Collodion Starch 6-10 (b) Ketones. Acetone Chlor-acetones Brom-acetones Isonitroso-ace- tone Acetyl-acetone 10-1 1 (c} Acids. Formic acid Formyl chloride Formamide Acetic acid Kolbe's experiments, Kekule's theory, etc. Rohland's experiments: capronic, caprylic and heptylk acids, unde- cylenic and oleic acids Acetic acid, continued Chlor- acetic acids Cyan-acetic acid Thio-acetic acid 1 1-20 Propionic acid Butyric acid; isobutyric acid, Hamonet's conclusions Valeric acid Capronic acid CEnanthylic acid 20-24 Oxalic acid Malonic acid Succinic acid Glutaric acid Pyrotartaric acid Itaconic acid Citraconic acid Mesa- conic acid Malic acid Tartaric acid Bourgoin's deduc- tions KSkule; maleic, brom-malelc and fumaric acids.. 25-31 VUl CONTENTS. EXPERIMENTS OF MILLER AND HOFER. (1) Glycolic acid Ordinary lactic acid Sarco-lactic acid a-Oxy-butyric acid a-Oxy-isobutyric acid Tartaric acid Hydracrylic acid /S-Oxy-butyric acid PhenyU/3-lactic acid Methyl-glycolic acid Mandelic acid Glyceric acid Phenyl-glyceric acid Malic acid Racemic acid Ethyl-tartaric acid 31-33 (2) Electrosy ntheses : Butyric ethyl ester Succinic ethyl ester Capronic and isobutyl-acetic ethyl esters Ethyl alco- hol Ethyl esters of propionic, butyric, and valeric acids Ethyl-succinic ester. [ CH a O 3 - C a H a O 4 -> CO - CO 2 . Whether any intermediate products have escaped observation, and the nature of these, can naturally be determined only by new and careful experiments. Since organic substances, apart from acids, bases, and salts, are poor conductors of electricity, the addi- tion of a mineral acid to an organic electrolyte pro- duces a complication of conditions, since oxidation reactions occur in combination with substitutions. After it is once made possible to establish and regu- late the oxidizing and reducing effects of the current, the field of substitution reactions is the one which offers the most promising results. (b) Ketones. Acetone. Acetone has been electro lyzed by Mul- der, 1 Riche,* and Friedel. 1 The electrolysis of an acetone solution acidified with sulphuric acid gave carbon dioxide, acetic acid, and formic acid. In hydrocloric acid solution mono-chlor-acetone and di- chlor-acetone could be isolated; in hydrobromic acid 1 Jahresber. f. Chemie, 1859, p. 339. 1 Comp. rend., 49, 176. * Ann. Chem. Phar., 112, 376. OF ALIPHATIC COMPOUNDS. II solution mono-brom-acetone. Wilde ' investigated the action of the electric spark on acetone vapor in Torricelli's vacuum. Acetylene was formed in the gas mixture and carbon was deposited on the sides of the vessel. According to Maquenne * acetone vapor is decomposed by the electric discharge into hy- drogen, ethane, and carbon monoxide, a small quantity of acetylene and carbon dioxide being formed. On the other hand, Hemptinne* syntheticized both ace- tone and aldehyde by passing a silent electric dis- charge through a mixture of carbon monoxide and ethane, the gases being kept cool by the use of a freezing mixture. Isonitroso-acetone. Ahrens and Meissner 4 tried to reduce this compound electrolytically to amido- acetone. They, however, obtained dimethyl-pyra- zine, ketine, C,H 8 N,, in small quantity. Acetyl-acetone. 6 Acetyl-acetone in an alcoholic solution on electrolysis gave tetracetyl-^. THH ^ Acids. I UNIVERSITY The investigation of acids has beefr^much-^nlore extensive than that of those classes of bodies which have been thus far discussed. The conditions here 1 Bull. soc. chim., [2] 5, 267. * Bull. soc. chim., 39, 306; ibid. t 40, 60. 1 Bull. Acad. roy. Beige, [3] 34, 269. 4 Chem. Ber., 30, 532. 6 Ahrens, Handb. d. Cheoiie, p. 482 (1896). 12 ELECTROLYSIS AND ELE CTROS YN THESIS are much simpler, since the acids are mostly good conductors of electricity, both in solution and in the free condition, as well as in the form of salts. Kolbe's ' classical investigations on the electrolysis of organic compounds, in which he demonstrated the formation of the hydrocarbons from the acids, are the foundation of later investigations. A continuation along the same line are the researches of Kekule, a Brown and Walker, 3 Mulliken, 4 and Weems. 5 They employed the electric current as a valuable means for effecting the synthesis of a complete series of com- pounds. For the sake of clearness the researches here given will be arranged chiefly in accordance with their chemical characteristics. Formic Acid. Although up to this point, in the in- vestigations mentioned, it has been necessary to con- sider chiefly oxidizing reactions, we now enter upon a field comprising those reactions which involve the process of reduction, and in which compounds of a relatively high stage of oxidation are the starting- points. The electrolytic formation of formic acid from oxalic acid, as observed by Royer, 6 is a reduc- tion reaction of this nature. 1 Lieb. Ann., 69, 257. 8 Lieb. Ann., 131, 79. 8 Lieb. Ann., 261, 107. 4 Amer. Chem. Journ., 15, 523. 6 Amer. Chem. Journ., 16, 569. 6 Comp. rend., 70, 731; Bull. soc. chim., [2] 14, 226. OF A L IP HA TIC COMPO UND S. 1 3 Wilde 1 found that the action of the electric spark on gaseous mixtures of oxygen and alcohol, hydrogen and carbon dioxide, methane and carbon dioxide pro- duced formic acid. Losanitsch and Jovitschitsch 8 obtained formic acid by treating carbon monoxide or dioxide and water in Berthelot's ozone apparatus. The behavior of the acid itself as well as its salts has been made the subject of thorough investigation car- ried out chiefly by Brester, 3 Renard* and Bourgoin, 6 Bartoli and Papasogli. 8 The progress of the decomposition is accompanied by the evolution of carbon dioxide and oxygen at the positive pole and hydrogen at the negative pole. The quantitative relations of the decomposition products vary with the concentration of the solution and the density of the current. The reactions occur accord- ing to the following equations: HCOOH = HCOO + H, HCOO + HCOO = H a + 2CO a , 2HCOO + H 3 O = 2HCOOH + O. It is therefore theoretically impossible to effect the complete decomposition of the formic acid present. In the electrolysis of sodium formate, carbon dioxide Bull. soc. chim., [2] 5, 267. Chem. Ber., 30, 135. Zeitsohr. f. Chemie, 1866, p. 60. Ann. chim. phys., [5] 17, 289. Ann. chim. phys., [4] 14, 157. Gazz. chim., 13, 22 and 88. 14 ELECTROLYSIS AND ELECTROS YN THESIS and formic acid are in fact always formed at the posi- tive pole and hydrogen and sodium hydroxide at the negative pole. The discussion of the other salts is unnecessary since their behavior is quite analogous. For my I Chloride (?) has been obtained by Losanitsch and Jovitschitsch from a mixture of carbon monoxide and hydrochloric acid by the action of the electric discharge, and by a like method formamide has been prepared from carbon monoxide and ammonia. Acetic Acid. Acetic acid is formed in the electroly- sis of methyl and ethyl alcohol when the electric spark is passed through a mixture of alcohol vapor and oxygen, or methane and carbon dioxide. On the other hand acetic acid can be converted into alcohol by electrolytic reduction, if the acid is substituted in place of nitric acid in the porous cup of a Bunsen element. 1 Glacial acetic acid is a poor conductor of electricity. According to Lapschin and Tichanowitsch a its decom- position when effected with the use of 900 Bunsen elements yields at the anode, carbon monoxide and carbon dioxide; at the cathode, carbon and a small quantity of a gas the nature of which could not be established. Bourgoin, 3 on electrolyzing the dilute 1 Tommasi, TraitS d'Electrochimie, 724; Comp. rend., 69, 1374; ibid., 70, 731; Chem. Ber., 29, 1390. * Neue Peters. Acad. Bull., 4, 81. 3 Ann. chim. phys., [4], 14, 157. OF ALIPHATIC COMPOUNDS. 15 acid, observed hydrogen at the negative pole and oxygen, carbon dioxide, and traces of carbon mon- oxide at the positive pole. The reactions involved in the decomposition of the alkali salts are more interesting. Kolbe, 1 on decom- posing a concentrated solution of potassium acetate, obtained a hydrocarbon in addition to other decom- position products. According to the idea then pre- vailing acetic acid underwent oxidation in the sense that it was thereby changed into carbon dioxide and methyl, both of which appeared at the positive pole, while at the negative pole only hydrogen was evolved, and a part of the methyl was oxidized to methyl oxide. The hydrocarbon evolved was in fact ethane, which always accompanies the decomposition of potas- sium acetate solutions, while the other decomposition products formed vary with the density of the electric current and the temperature of the solutions. Thus Kolbe identified methyl ether and methyl acetate in the solution, while Bourgoin observed no decomposi- tion products other than carbon monoxide and dioxide. Jahn, a who employed currents of very low electrode density, obtained by the electrolysis of an almost saturated solution of sodium acetate only car- bon dioxide, ethane, and hydrogen. The formation 1 Lieb. Ann., 69, 279. * Grundriss d. Elektrochemie, 1895, p. 292. 1 6 ELECTROLYSIS AND ELECTROSYNTHESIS of ethane can be explained by assuming either the direct oxidation of the acetic acid, or the decomposition of the anion, CH 3 COO\ _ c H 4- 2 CO CH 8 COO/- ^""t U '' Kkule l advanced a theory based on the phenom- ena of decomposition, and from this deduced certain formulae which make i* possible to predict the nature of the products resulting from the electrolysis of monobasic and dibasic acids of the fatty acid series. Since, however, the reaction is influenced by the slightest variation of conditions, his formulae hold good only in the case of the decomposition of per- fectly pure substances, a condition seldom met in practice. Lob a is in favor of accepting the theory advanced by Kekule, who in the case of phthalic and acetic acids sought by experiment to prove the intermediate formation of the anhydride, while Schall 8 assumes the formation of an acid superoxide: R.COO -- h R.COO = R.COO\ R.COO/ R.COO\ ^ TJ , -m R.COO/ = a ' 1 Lieb. Ann., 131, 79. 8 Ztschr. f. Elektrochemie, 3, 42. 3 Ztschr. f. Elektrochemie, 3, 83. . OF A LIP HA TIC COMPO UNDS. 1 7 This conclusion is drawn from the observed fact that the dithionic acids upon the electrolysis of their alkali salts give acid supersulphides which correspond with the superoxides: R.CSS -L- R.CSS = R.CSS\ ( UNIVERSIT R ' CSS/ 'V^u In contrast to the acid superoxides, the acid super- sulphides are stable compounds. The reactions and the corresponding electrolytic products which occur in the electrolysis of the alkali salts of the fatty acids were thoroughly investigated by Rohland, 1 who electrolyzed the alkali salts of capronic, caprylic, and heptylic acids. Potassium Capronate gave normal decane, C, H M ; Potassium Caprylate analogously gave normal tetra- decane, C J4 H 30 ; while Potassium Heptylate gave besides dodecane, C 12 H 26 , a small quantity of an unsaturated hydrocarbon, probably octylene, C 8 H 18 . The fatty acids with ethylene bond behave differ- ently. In their case no smooth reaction occurs. The electrolysis of undecylenic acid, for example, yielded a mixture of several unsaturated hydrocarbons, a result similar to that obtained in the investigation of potas- sium oleate, the only outcome of which was a mixture of various compounds which could not be separated. 1 Ztschr. f. Elektrochemie, 4, 120. 1 8 ELECTROLYSIS AND ELECTROS YN THESIS Kolbe and Kemp * obtained by the electrolysis of a concentrated potassium acetate solution, at the anode, hydrogen, methyl-acetic ester, methyl-formic ester, ethane, ethylene, and carbon dioxide; at the cathode, hydrogen and potassium hydroxide. In an alkaline solution of the same salt Bourgoin' obtained a mix- ture of sodium formate, but so far as hydrocarbons were concerned could only prove the presence of ethane and ethylene. Besides the alkali salts, the copper, lead, man- ganese, and uranium salts were subjected to electroly- sis by Dupre, 3 Wiedemann, 4 Despretz, 6 and Smith. 6 The metals were precipitated at the anode, a portion of the manganese and lead in the form of superoxides. According to Bauer, 7 in the electrolysis of the acetic acid salts of metals possessing a constant valence (K, Na, NH 4 , Mg, Ca, Zn, and Al), when cold, moderately dilute solutions and relatively high current densities are employed, gases consisting chiefly of ethane and carbon dioxide are given off at the anode. No inconsiderable quantities of ethylene are formed in the case of calcium, magnesium, and potas- 1 Journ. prakt. Chemie, [2] 4, 46. 8 Ann. chim. phys., [4] 14, 157. 8 Archiv. ph. nat., 35, 998. 4 Pogg. Ann., 104, 162. 5 Comp. rend., 45, 449. 6 Chem. Ber., 13, 151. 1 Dissert. Giessen, 1897; Wied. Beibl., 21, 601. OF ALIPHATIC COMPOUNDS. 1 9 sium acetate solutions. Very small amounts on the contrary result from the electrolysis of the sodium, ammonium, and zinc salts. At the boiling tempera- ture the gases consist mostly of oxygen and contain in addition a little carbon dioxide and a very small quantity of ethane. Metals with several valences change to the higher valence. Monochlor-acetic Acid, according to Kolbe, 1 breaks up on electrolysis into hydrochloric and acetic acids, as a result of the action of the electrolytic hydrogen : CH S C1.COOH + 2H = CH 8 COOH + HC1. Trichlor-acetic Acid gives the same products and in addition also, according to Elbs, tri-chlor-methyl ester, CC1,.CO 3 .CC1 3 . Cyan-acetic Acid. Moore 3 obtained at the positive pole carbon dioxide besides traces of nitrogen, and ethylene cyanide ; at the negative pole hydrogen and potassium hydroxide, bodies analogous to the decom- position products of sodium acetate. Thio-acetic Acid." This compound gives acetyl disulphide. 5 The acid is formed at the positive pole if a solution of pure acetic acid which has been sat- urated with hydrogen sulphide is subjected to elec- 1 Tommasi, Trait6 d'Electrochimie, 1889, p. 750. 2 Journ. prakt. Chemie, [2] 47, 1104; ibid., [2] 55, 502. 8 Chem. Ber., 4, 519. 4 Zeitschr. f. Elektroch., 3, 42. 6 Chem, Ber., 3, 297. 2O ELECTROLYSIS AND ELECTROS YNTKESIS trolysis and a slow current of the gas is conducted through the solution during the operation. Propionic Acid. The electrolysis of a concentrated solution of sodium propionate was carried out by Jahn 1 and yielded, when the density of the currents employed was not too great, hydrogen, ethylene, and carbon dioxide, but no butane. Butyric Acid. The two butyric acids were elec- trolyzed by Bunge. 2 With isobutyric acid it was not possible to obtain hexane, but the normal acid yielded some butane besides larger quantities of propylene. The great influence of concentration, current den- sity, and especially of temperature is again empha- sized in the researches of Bunge. The various conditions which were followed by the individual in- vestigators explain sufficiently the frequent differences occurring in the results. The repetition of an elec- trolytic experiment is only possible when an exact statement of all the factors is given. This require- ment is, however, entirely omitted in the published experiments above mentioned. Careful and reliable investigations on the electroly- sis of the potassium salts of butyric and isobutyric acids have been published by M. F. Hamonet. 3 His 1 Grund. d. Elektroch., 1895, 293. 8 Journ. d. russ. phys. Gesellsch., I, 525. 3 Comp. rend., 123, 252. OF ALIPHATIC COMPOUNDS. 21 apparatus consisted of a copper beaker 23 cm. high and 8 cm. in diameter, which served as the cathode. A porous earthenware cell, which contained the anode and was closed with a three-hole stopper, stood in the beaker. Through the perforations of the stopper passed a thermometer, a gas-conducting tube, and the electric conductor leading to the anode. The anode used in some experiments was a platinum wire i mm. in diameter and 2 m. in length, in others a platinum cylinder 14 cm. high and 2.5 cm. in diameter. This variation of current density was, however, of second- ary importance. Solutions of the potassium salts having a specific gravity of 1.08-1.12 were used as the electrolyte. Current strengths of 4-5 amperes were reached with a difference of potential at the poles of 6-8 volts. The electrolysis was continued 2-3 hours, the solution being kept cool. The following results were obtained : Potassium Butyrate, CH 8 .CH,.CH 2 .COOK. 225 g. propylene bromide (CH 3 .CHBr.CH 2 Br), corre- sponding to 47 g. propylene (CH 2 CH = CH 2 ); 1 8 g. isopropyl alcohol (CH,.CHOH.CH 3 ); 4.5 g. butyric isopropyl ester (CH 3 .CH 3 .CH 3 .COOCH(CH 8 ) a ); 4.5 g. complicated products, which became resinous when the ester was saponified by boiling with alkali hydroxide. 22 ELECTROLYSIS AND ELECTROS 'YN THESIS Hexane (CH 3 .CH 2 .CH 2 .CH a .CH 2 .CH 3 ) and propyl alcohol (CH 3 .CH a .CH a OH) could not be detected. They could, therefore, only have been formed in extremely small quantities. The very remarkable formation of isopropyl alcohol can only be explained by assuming the hydration of propylene or the molec- ular rearrangement of the group CH 8 .CH,.CH a . Potassium Isobutyrate, (CH 9 ) a :CH.COOK. This salt gave 300 g. propylene bromide (CH,. CHBr.CH a Br), equivalent to 62 g. propylene (CH 3 . CH:CH a );20 g. isopropyl alcohol ((CH 3 ) a :CHOH); over 12 g. isobutyric isopropyl ester, ((CH,),: CH.COOCH(CH 8 ) a ); 6 g. of an oil having a pepper-like odor and boiling at 130-160. In this case also the paraffine isohexane (CH 3 ),:CH. CH :(CH 8 ) a was not formed. Hamonet draws the following conclusions from these results: I. The equation 2C.H M+l .COO-= C.H 4K+2 + 2CO., representing the reaction in the electrolysis of the alkali salts of the fatty acids, which since the experi- OF ALIPHATIC COMPOUNDS. 2$ ments of Kolbe has been almost universally accepted, can no longer claim to represent the true fact in the case, since no or almost no paraffines result from this operation. 2. The olefine C M H 2W sometimes predominates among the products formed by the electrolysis of the alkali salts of the fatty acids, The general nature of the reactions is represented by the following equation : 2C,H 1 , + I .COO = C.H - + 1 .COOH + C.H M + CO.. 3. An alcohol with n carbon atoms is always formed if the acid contains (n + i) carbon atoms. The struc- ture of the alcohol is not always that which is expected. Frequently more than a third of the energy of the current is expended in the formation of the alcohol. Whether the alcohol is generated by the saponification of the ester present, according to the equation 2CH 2B + ,COO- = C.H M + I .COOC.H,. +1 + CO,, or whether it is formed by the hydration of the defines, C,H 1(I + H 2 O = C w H aM+1 OH, is still uncer- tain. To decide this question a more thorough investiga- tion of the substances resulting from the electrolysis 24 ELECTROLYSIS AND ELECTROS YNTHESIS of compounds possessing higher molecular weights is required. Valeric Acid. Kolbe 1 electrolyzed the potassium salt and obtained as the chief product octane (di- isobutane), [J'\CH.CH,.CH..CH/[:{*. Besides this there appeared as decomposition prod- ucts water, carbonic acid gas, butylene, and the butyl ester of valeric acid. Brester," who performed his experiments under different conditions, obtained at the anode a gaseous mixture of carbon dioxide, butylene, and oxygen. Capronic Acid. A concentrated solution of the potassium salt gave decane and traces of the amyl ester of capronic acid, both of which are normal decomposition products. The electrolyses were made by Brazier and Gossleth, 3 by Wurz, 4 and by Rohland. (Enanthylic Acid. The normal acid was electro- lyzed by Brazier and Gossleth 6 , under conditions similar to those for capronic acid, and gave two hydrocarbons, C ia H 26 and* C n H 24 , in addition to hydrogen, potassium carbonate and acid potassium carbonate. 1 Lieb. Ann., 69, 257. * Jahresber. f. Chem., 1859, P- 86; ibid., 1866, p. 87. Tommasi, Traite d'Electroch., 1889, p. 757. 4 Ibid. 6 Ibid. OF ALIPHATIC COMPOUNDS. 2$ Oxalic Acid. The deportment of the saturated solu- tion of the free acid on electrolysis was determined by Brester, 1 Bourgoin, 2 Balbiano and Alessi, 3 Bunge, 4 and Renard. 6 The general result was that oxygen and carbon dioxide were obtained at the anode and hydrogen at the cathode. It is possible to completely oxidize oxalic acid to carbon dioxide. On this prop- erty depends the great importance of oxalic acid in quantitative electrolytic analysis, into which it has been introduced by Classen. 8 The ability of ammonium oxalate to form soluble double salts with many difficultly soluble or insoluble metallic salts is in accord with the favorable conduct of the acid on electrolysis, by which operation it may be entirely removed from the solution in the form of gas. The reducing effects of the current on oxalic acid were also observed. Thus on electrolyzing both the free acid and its sodium salt Balbiano and Alessi were able to prove the presence of glycolic acid. The oxidation is not complete if the electrolysis is conducted in the cold solution, carbon monoxide as well as carbon dioxide being then formed at the positive pole. 1 Jahresber. f. Chemie, 1866, p. 87. 8 Comp. rend., 67, 97. 3 Gazz. chim., 1882, p. 190; Chem. Ber., 15, 2236. 4 Chem. Ber., 9, 78. 5 Ann. chim. phys., [5] 17, 289. 8 Classen, Quan. Analysis by Electrolysis (Wiley & Sons, N. Y.). 26 ELECTROLYSIS AND ELECTROS YNTHESIS The decomposition reactions of oxalic acid salts are entirely analogous to those of the free acid. In alka- line solution the oxidation proceeds more rapidly than in neutral solution because of the better conductivity of the alkalies. Malonic Acid. This acid was investigated by Bour- goin. 1 In a concentrated solution of sirupy consis- tency it, like oxalic acid, is only slowly oxidized to carbon dioxide, with the evolution of hydrogen. A strongly concentrated solution of the unaltered acid is found surrounding the positive electrode, even after an electrolysis of long duration. On the electrolysis of the sodium salt carbon monoxide is also present in the escaping gas mixture. The ratio of the different gases, carbon dioxide, carbon monoxide, and oxygen, remains fairly constant during the period of electroly- sis (85.8$, 9.7*, 4.5*). In alkaline solution the decomposition products are the same as in neutral solution, the ratio only of the separate gases being different, and varying with the duration of the electrolysis. Succinic Acid. Bourgoin 2 and Kekule 3 found that the free acid underwent oxidation with difficulty, only a small quantity of carbon monoxide in addition to some oxygen and carbon dioxide being formed. 1 Ann. chim. phys., [i] 14, 157; Comp. rend., 90, 608. 8 Bull. soc. chim., [2] 9, 301; ibid., 21, 1695. 3 Lieb. Ann., 131, 84. OF ALIPHATIC COMPOUNDS. 2J The neutral sodium salt gave the same products, as did also the alkaline solution of this salt, except that in the latter experiment the formation of carbon monoxide predominated. If, however, four molecular equivalents of sodium succinate were treated with one equivalent of sodium hydroxide, ethylene and a little acetylene could also be detected. Kolbe 1 states that methyl oxide is also formed ; Bourgoin, however, was unable to confirm this statement. Glutaric Acid. The results which Reboul and Bourgoin 2 obtained with this acid are the following: The greater part of the acid remains unchanged, while a small part only is decomposed according to the equation C.H.O. + 70 = 2CO, + 3 CO + 4 H.O. A hydrocarbon of the composition was not formed. Similar observations were made in the electrolysis of potassium glutarate, likewise in alkaline solution. Pyrotartaric Acid. The investigators just men- tioned, on electrolyzing a solution of the neutral potassium salt, observed the immediate precipitation 1 Lieb. Ann., 113, 244. 1 Comp. rend., 84, 1231. 28 ELECTROLYSIS AND ELECTROS 'YN THESIS of the acid salt. (Different behavior from glutaric acid, in the case of which the formation of the acid salt does not take place.) After a time the crystals disapppear, the free acid being regenerated. In alkaline solution also, the formation of the acid salt occurs, after a longer period of electrolysis. Never- theless the continuous, though limited, evolution of carbon dioxide and carbon monoxide is a proof of partial oxidation. Itaconic Acid. The concentrated solution of the alkali salt electrolyzed by Aarland 1 gave a hydrocar- bon isomeric with allylene, C 3 H 4 , which is said to have the formula CH 2 = C = CH 2 . Along with this compound, some propylene was formed, while a por- tion of the acid was always regenerated. Citraconic Acid. 3 The concentrated solution of the sodium salt, likewise electrolyzed by Aarland, yielded, besides a hydrocarbon, C 3 H 4 , small traces of acrylic and mesaconic acid. Mesaconic Acid, under the same conditions, gives the same hydrocarbon and traces of acrylic and itaconic acid. Malic Acid. The electrolysis of malic acid was per- formed by Bourgoin* and Brester. 4 The free acid, 1 Journ. prakt. Chem., [2] 6, 256. 2 Journ. prakt. Chem., J, 142. 8 Bull. soc. chim., [2] 9, 427. 4 Jahresb. f. Chem., 1866, p. 87. OF ALIPHATIC COMPOUNDS. 2$ which is only slowly decomposed, and the neutral alkali salt both gave the same products, carbon dioxide and a little carbon monoxide and oxygen. After the completion of the experiment the solution contained some aldehyde and acetic acid. Tartaric Acid (Dextrorotary). For our knowledge of the deportment of this acid on electrolysis we are also indebted to Bourgoin. 1 The free acid is partially oxidized to carbon dioxide and carbon monoxide, while the solution contains acetic acid. Neutral potassium tartrate gives principally carbon dioxide besides a little carbon monoxide and oxygen, acid potassium tartrate being at the same time deposited. In alkaline solutions the gases carry with them traces of ethane, the formation of which is due to potassium acetate which is found present in the solution at the end of the operation. Before proceeding to a discussion of the acids still to be considered, the deductions which Bourgoin 3 draws from his numerous experiments will be men- tioned briefly. He regards the intermediate formation of the anhydride as the most important process in the electrolysis of organic acids, since by the splitting off of oxygen this produces secondary oxidation products. He considers, moreover, the transformation of the acid anhydride into the hydrate, by the addition of 1 Comp. rend., 65, 1144. 1 Annal. chim. phys., [4], 14, 157. 3O ELECTROLYSIS AND ELECTROSYNTHESIS water, and the oxidation of the acids by oxygen formed from the acid itself as belonging to the secondary processes. This explanation coincides with the fact that water is not an electrolyte, or at least only a poor one, and acts chiefly as a dissociation medium. The typical reactions in the electrolysis of acetic acid are, for instance, the following: Electrolytic decomposition, 2CH S .COOK = > - o + Q + K,. Characteristic oxidation, A too strict adherence to the chemical arrangement is not conducive to clearness. After mentioning the investigations of Kekule, 1 the later experiments of Miller and Hofer, Brown and Walker, etc., will be discussed in this connection. Kekul ' investigated the electrolysis of maleic acid and brom-maleic acid. The former gave acetylene, besides a small quantity of succinic and fumaric acid; the latter, on the contrary, gave only hydrobromic acid and carbon monoxide. Like malic acid, fumaric acidj at the beginning of the experiment, gave only pure acetylene, but after the operation had continued 1 Lieb. Ann., 131, 79. OF ALIPHATIC COMPOUNDS. 31 for some time the acetylene was found to be mixed with oxygen. EXPERIMENTS OF MILLER AND HoFER. 1 I. The investigations carried out by Miller and Hofer are improvements over those previously made, since they give a much clearer insight into the process of the decomposition. In the method which was employed, namely, that of allowing the solutions to slowly flow over the electrodes, the compounds first formed were removed from the region of electrolytic action. In this way it was possible to isolate certain sub- stances which would otherwise have undergone secondary decomposition. In the researches cited below, however, accurate data concerning current relations are lacking. Classen 3 has accurately ex- plained what data are necessary for repeating an elec- trolytic experiment. Glycolic Acid. The concentrated solution of the sodium salt yielded at the positive pole formaldehyde in large quantities and some formic acid, the latter breaking up from the action of the current into carbon monoxide and dioxide. 1 Chem. Ber., 27, 461. * Classen, " Quan. Analysis by Electrolysis," page 23. 32 ELECTROLYSIS AND ELECTROS YN THESIS Ordinary Lactic Acid. As Kolbe ' had already dis- covered, the concentrated solution of the potassium salt gave carbon dioxide and acetic aldehyde. The investigators above mentioned also remarked the presence of some formic acid. When the solution about the positive pole was kept slightly alkaline, aldol and crotonic aldehyde were formed instead of acetic aldehyde. Sarco-lactic Acid. When the solution surrounding the positive pole was kept neutral a concentrated solution of the sodium salt yielded acetic aldehyde and carbon dioxide. ^-Oxy-butyric Acid. This substance was converted into carbon dioxide, propionic aldehyde, and formic acid. <*-Oxy-isobutyric Acid. This compound gave car- bon dioxide, carbon monoxide, and acetone. Tartaric Acid. From the electrolysis of a concen- trated solution of potassium tartrate, carbon dioxide, carbon monoxide, oxygen, a little formic aldehyde, and some formic acid were obtained, but no acetic acid and ethylene, as stated by Bourgoin. Hydracrylic Acid. Resin and a little formic acid were found present in the electrolyte about the posi- tive pole. /?-Oxy-butyric Acid. From this acid were obtained carbon monoxide, carbon dioxide, crotonic aldehyde, 1 Lieb. Ann., 113, 214. OF ALIPHATIC COMPOUNDS. 33 a little formic acid, a resin, and a number of unsatu- rated hydrocarbons which were not further investi- gated. Phenyl-/?-lactic Acid. The solution after electroly- sis contained benzaldehyde, besides resinous bodies. Methyl-glycolic Acid. The solution of this acid after electrolysis contained formic aldehyde, formic acid, and possibly methyl alcohol. Oxygen, carbon monoxide, and carbon dioxide were evolved. Mandelic Acid. The electrolysis of this acid re- sulted in the formation of benzaldehyde and the gases mentioned above. Glyceric Acid. Like mandelic acid, glyceric acid was decomposed into carbon monoxide, carbon diox- ide, and oxygen, formic aldehyde and formic acid being found in the solution. Phenyl-glyceric Acid. The products resulting from the electrolysis of this acid were the same as those obtained from mandelic acid. Malic Acid. This compound yielded carbon diox- ide, oxygen, carbon monoxide, acetic aldehyde, and crotonic aldehyde. Racemic Acid. On the electrolysis of this acid the gases given above were obtained and also an aldehyde which was not further investigated. Ethyl-tartaric Acid. This gave the same gases, but any other gases which may have been formed were not identified. 34 ELECTROLYSIS AND ELECTROS YNTHESIS 2. Electrosyntheses. The same investigators re- cently 1 added to our knowledge on this subject by submitting to electrolysis solutions containing the potassium salts of mono-basic acids and the ethyl esters of the mono-potassium salts of dibasic acids dis- solved in equi-molecular proportion. This was in accordance with the experiments made by Brown and Walker. In this way they prepared butyric ethyl ester from potassium acetate and potassium- ethyl succinate. The synthesis of the ethyl ester of valeric, capronic, and isobutyl-acetic acid was also effected. The reactions all take place according to the follow- ing equation: XCOOK + COOKY.COOC 2 H 5 = K 2 + 2CO, + XY.COOC a H 5 . In accordance with a similar principle they obtained ethyl alcohol from potassium acetate and potassium glycolate. If potassium-ethyl malonate was taken as one of the salts and a solution of this with potassium acetate, propionate, or butyrate was electrolyzed there was formed the ethyl ester of propionic, butyric, or valeric acid, respectively. v. Miller" applied this method to a number of other mixtures. Thus upon the electrolysis of a mix- ture of acetic ester with tricar bally lie ester, one third 1 Chem. Ber., 28, 2427; Zeitschr. f. Elektroch., 4, 55. 3 Ztschr. f. Elektroch., 4, 55. OF ALIPHATIC COMPOUNDS. 35 of which was saponified, there was formed principally ethyl-succinic ester. If aromatic ester acids were electrolyzed with potassium acetate a similar synthesis occurred. By this method a-niethyl-hydrocinnamic ester, C 6 H 6 - CH 2 - CH - COOC 3 H 6 , CH was prepared from potassium-ethyl benzyl-malonate and potassium acetate. Dibenzyl-succinic ester is formed at the same time, according to the reaction of C. Brown : C 6 H B - CH 2 - CH - COOC 2 H 6 C 6 H 5 - CH, - CH - COOC 2 H 6 . This reaction does not take place if potassium acetate is not present. If the deportment of the alkali salts of the mono- basic oxyacids upon electrolysis is analogous to that of sodium acetate the chief products to be expected are symmetrical glycols: 2C n H ro (OH)COO - = C M H W (OH), + 2CO,. According to Walker's 1 experiments this is not generally the case. From the potassium salt of mandelic acid the expected product, i.e., a mixture of hydrobenzoin and isohydrobenzo'in, is formed only in small quantities; benzaldehyde, however, is formed in larger quantities. 1 Journ. Chem. Soc., 45, 1278, 36 ELECTROLYSIS AND ELECTROS YN THESIS The alkali salts of oxyacids give, in addition to the above, many other substances, principally aldehydes, and the results are the same even if the attempt is made to weaken the action of the electrolytic oxygen by converting the alcohols into esters. Thus from the sodium salt of glycolic acid (CH,OH. COOH), ethyl-glycolic acid (CH.OC.H..COOH), and a-lacttc acM (CH 9 .CH(OH)COOH) the chief product obtained is acetic aldehyde, and it is quite possible that the production of hydrobenzom and isohydrobenzom from mandelic acid is due to the electrolytic reduction of the benzaldehyde originally formed. This view is supported by the investigations of Kauffmann, 1 who actually obtained hydrobenzom and isohydrobenzoin by the direct electrolytic reduction of benzaldehyde. Elbs 3 emphasizes the fact that it is not necessary to suppose that aldehydes are a result of secondary oxidation produced by the oxygen available in the region of the anode, but that their formation can also be regarded as analogous to that of ethylene from propionic acid: 2CH 3 .CH a .COO - = CH 3 .CH 2 .COOH 2CH 3 .CH(OH)COO - = CH 3 .CH(OH).COOH CH 3 .CHO. 1 Ztschr. f. Elektroch., 2, 367. 8 Jahrbuch. d. Elektroch., 3, 295. OF ALIPHATIC COMPOUNDS. 37 A still further advance in this field is the successful substitution of iodine and of nitro-groups by elec- trolysis. On electrolyzing propionic acid and potas- ium iodide in aqueous solution fi-iodo-propionic acid was formed, due to the int i rim ill ill fgPjmtliii 1 1 of succmic acid : OF THE r UNIVERSITY COOH.CH 3 .CH a .COOK + KI = ICH 2 .CH 2 .COOH + 2K + C0 2 . Nitro-ethane was probably obtained in small quan- tities from sodium propionate and sodium nitrite. ELECTROSYNTHESES OF BROWN AND WALKER.' A systematic synthesis with the aid of the electric current was first attained in the researches of Brown and Walker. Their investigations are based partly on the fact observed by Kolbe that monobasic fatty acids yield hydrocarbons, and partly on the results of the experiments of Guthries, 2 who found that the ester group is electrolytically inactive. These facts justified the hypothesis that the mono-esters of dibasic acids would behave, under the action of the current, like monobasic acids, i.e., carbon dioxide 1 Lieb. Ann., 261, 107; ibid., 274, 41. ? Lieb. Ann., 99, 65. 38 ELECTROLYSIS AND ELECTROSYNTHESIS would be split off and esters of higher dibasic acids would be formed according to the equations 2C,H 6 .OOC - CH a - COOK =C 2 H 6 .OOC-CH a -CH a -COOC 2 H B +2K a +C0 2 , 2C 2 H 6 - OOC.CH 3 .CH 2 .COOK =C a H 6 .OOC.CH 2 .CH a .CH 2 .CH a .COOC a H 6 Their experiments, conducted in fairly concentrated solutions with currents of high density, completely confirmed this supposition. Under these conditions the following syntheses were made: I . Succinic acid from ethyl-potassium malonate. 2. Adipic acid from ethyl-potassium succinate. 3. Suberic acid from ethyl-potassium glutarate. 4. Sebacic acid from the ethyl-potassium salt of adipic acid. 5. n-Dodecane-dicarboxylic acid from the ethyl- potassium salt of suberic acid. 6. n-Deca-hexane-dicarboxylic acid from the ethyl- potassium salt of sebacic acid. If the ethyl-potassium salts of substituted acids are taken as a starting-point it is possible to obtain disubstituted acids according to the above reaction. 1. Ethyl-potassium methyl-malonate gave the two symmetrical dimethyl-succinic acids, having the melt- ing-points 193 and 121. 2. Ethyl-pctassium ethyl-malonate gave the corre- OF ALIPHATIC COMPOUNDS. 39 spending symmetrical diethyl-succinic acids, with the melting-points 192 and 130. 3. Ethyl-potassium dimethyl-malonate gave tetra- methyl-succinic acid. 4. From ethyl-potassium diethyl-malonate a sub- stance of the composition C 14 H 2e O 4 , which differs from the expected tetraethyl-succinic acid by C 2 H 4 , was obtained. The nature of this body has not yet been determined. Hydrobromic acid splits off alcohol the compound C ia H ao O,, which has perhaps the furfurane formula (C 2 H & ),:C-C:(C a H 6 ),, i i O : C C : O being formed. All these reactions did not take place smoothly, but were accompanied by secondary reactions, principally oxidations, which were limited as much as possible by working with strong concentrated solutions and low temperatures. Moreover, the formation of esters also is always possible according to the equation 2CH..COO - = CH,COOCH, + CO 3 ; and, finally, the formation of unsaturated esters may take place as illustrated in the simplest case: 40 ELECTROLYSIS AND ELECTROS YN THESIS 2C,H 6 COO - = C a H 4 + CO, + C 2 H B COOH, 2C 2 H 6 OOC.CH 2 CH,.COO - = 2C 2 H 5 OOC.CH 2 -CH 2 .CH : CH 3 +C 2 H 6 OOC.CH 2 .CH 9 .COOH+CO a . In this way it was possible to isolate methyl-acrylic acid by the electrolysis of ethyl-potassium dimethyl- malonate, and ethyl-crotonic acid by electrolyzing a solution of the ethyl-potassium salt of diethyl-malonic acid. On the electrolysis of sebacic acid the ethyl ester of an unsaturated acid, CH 9 : CH(CH 2 ) 6 .COOH, was formed. Brown and Walker 1 also electrolyzed the sodium- ethyl salt of camphoric acid and obtained two esters which they were able to separate by means of frac- tional distillation. One of these (boiling-point 212- 213) on being saponified yielded an unsaturated monobasic acid, C 9 H 14 O 2 , campholytic acid ; the other, having a higher boiling-point (240-242), was the neutral ester of a dibasic acid, C 18 H 30 O 4 , to which Walker gave the name of camphothetic acid. The experiments are of great importance, because they prove the dibasic nature of camphoric acid, a fact which is doubted by Friedel. Walker and Henderson 5 found, moreover, that upon the electrolysis of concentrated aqueous solu- tions of the potassium salt of allocamphoric ester there 1 Lieb. Ann., 274, 71. 1 Journ. Chem. Soc., 67, 337. OF ALIPHATIC COMPOUNDS. 4! are formed as chief products the ethyl esters of a dibasic acid, C 18 H a8 (COOH) a , and of a monobasic acid, C 8 H 13 COOH: /COOC a H 6 __ , /COOC a H 6 . /COOC a H 6 /COOC a H 6 2. 2U C 8 H 13 COOC a H 5 . It has been found on further investigation l that besides the strongly dextrorotary unsaturated acid designated as allocampholytic acid, C 8 H 13 COOH, an isomeric acid is formed which, although slightly dextrorotary as obtained, is perhaps even laevorotary in an entirely pure condition. The latter on being heated to 200 splits off carbon dioxide and yields a hydrocarbon, C 8 H 14 , which boils at 120-122 and appears to be identical with laurolene, made from camphoric acid. A ketonic acid, C 8 H 3 O.COOH, melting-point 228, is also found as an additional product of the electroly- sis of potassium allocamphoric ethyl ester. The authors conclude from their observations that cam- phoric acid contains the group H H-C- 1 r/H |\COOH - C-COOH. 1 Journ. Chem. Soc., 69, 748. 42 ELECTROLYSIS AND ELECTROS YNTHESIS It is expected that these results will give the struc- tural formula for camphoric acid. Following the experiments of Brown and Walker, Schields ' investigated the deportment of ethyl-potas- sium maleate and fumarate on electrolysis. His results confirm the experiments of Kekule. During the electrolysis carbon dioxide, oxygen, and unsat- urated hydrocarbons were evolved, and the unchanged maleic or fumaric acid and the corresponding ethyl esters, respectively, remained in the solution. From these experiments it would appear that un- saturated acids form no synthetic products on elec- trolysis, and the aromatic acids phthalic acid and benzyl-malonic acid conduct themselves in a similar manner. Finally may be mentioned the electrolysis of ethyl-potassium oxalate, which yielded ethylene in addition to carbon dioxide. ELECTROSYNTHESES OF MULLIKEN' AND WEEMS. S Mulliken electrolyzed the sodium compounds of the diethyl esters of dibasic acids in alcoholic solution and obtained the same compounds which were formed when sodium was removed by iodine. He thus made: 1 Lieb. Ann., 274, 64; Journ. Chem. Soc., 69, 737. 2 Amer. Chem. Journ., 15, 323. Ibid., 1 6, 569. OF ALIPHATIC COMPOUNDS. 43 1 . Ethane-tetracarboxylic ester from sodium-diethyl- ma Ionic ester. 2. Ethane-hexacarboxylic ester from sodium-met hane- tricarboxylic ester. 3. Tetracetyl-ethane from acetyl-acetone. 4. A thick oil which contained a small quantity of diacetyl-succinic ester from aceto-acetic ester. The conclusion reached by Mulliken, that in the electrolysis of certain weak organic acids a portion of the anions unite in pairs without undergoing decom- position, was closely examined by Weems as to its general applicability and as to the exact nature of the chemical changes which take place. All direct attempts to oxidize malonic ester with hydrogen per- oxide, potassium permanganate, and chromic acid, and to produce an effect similar to that caused by the current, were without success. Weems, on electrolyzing the sodium salt of methyl- malonic ester in alcoholic solution, obtained dimethyl- ethane-tetracarboxylic ester; ethyl-malonic ester yielded diethyl-ethane-tetracarboxylic ester; and aceto-acetic ester was changed to diacetyl-succinic ester. In the electrolysis of cyan-acetic ester the formation of dicyan-succinic ester could not be observed; like- wise a union of the anions of benzyl-malonic ester, acetyl-malonic ester, and acetyl-dicarboxylic ester did not take place. Electrolysis of acid amides in the 44 ELECTROLYSIS AND ELECTROS 'YN THESIS form of their sodium or mercury compounds yielded unchanged amides. The review which has been given of the investiga- tions on the electrolysis of the aliphatic carboxylic acids is believed to include all present information on this subject. Of the investigations mentioned, an advance is shown only in those of Kolbe-Bourgoin, Brown-Walker, and Mulliken-Weems. The action of the electric current has been used, in these cases at least, for effecting a limited number of organic syn- theses. A number of papers on the action of the electric current on compounds containing cyanogen and sulphur will next be mentioned. 2. Cyanogen Compounds. Cyanogen. Berthelot J observed that cyanogen was decomposed into its elements by the action of the electric spark. The slightest trace of water in the gas caused the formation of hydrocyanic acid and acety- lene. By submitting moist cyanogen gas to the action of the voltaic arc Buff and Hofmann 8 noted the formation of carbon dioxide, carbon monoxide, and ammonia. Cyanogen can be obtained by the electrolysis of a solution of potassium ferrocyanide. 3 1 Comp. rend., 82, 1360. * Lieb. Ann., 113, 135. 8 See potassium ferrocyanide. p. 45. OF ALIPHATIC COMPOUNDS. 45 Hydrocyanic Acid. Electrosynthesis : Berthelot l obtained hydrocyanic acid by passing the electric spark through a mixture of acetylene and nitrogen. The reaction is, however, reversible. On allowing the electric spark to act on hydrocyanic-acid gas it was decomposed into acetylene and nitrogen. Hydro- cyanic acid is also obtained by passing the electric spark through mixtures of ethylene or aniline vapor with nitrogen, acetylene with nitric oxide (Hunting- ton a ), nitrogen with benzol (Perkin 3 ), etc. Electrolysis: In sulphuric-acid solution hydro- cyanic acid breaks up smoothly, according to Gay- Lussac, 4 into hydrogen and cyanogen. Concentrated hydrocyanic acid to which a drop of sulphuric acid has been added gives carbon monoxide and ammonia (SchlagdenhaufTen 5 ). Potassium Cyanide. In the investigation of this salt, conducted by the author last mentioned, it was found that no oxygen escaped at the anode, but the potassium cyanide was oxidized to potassium cyanate. Potassium Ferrocyanide. This compound gives at the anode hydrocyanic acid and Prussian blue and at the cathode hydrogen and potassium hydroxide Bull. soc. chim., 13, 107. English patent, 14855; German patent, 93852. Jahresb. f. Chem., 1870, p. 399. Gilbert's Ann., 1811-1815; Ann. chim. phys., 78, 245. Jahresb. f. Chem., 1863, p. 305. 46 ELECTROLYSIS AND ELECTROS 'YN THESIS (Perrot 1 ); also cyanogen, according to Schlagden- hauffen. 8 Potassium Ferricyanide likewise gives on electro- lysis Prussian blue at the anode. Sodio-nitro-prusside. On electrolyzing a dilute solu- tion of this salt for a prolonged period Weith 3 noted the formation of ammonia and the precipitation of metallic iron; at the positive electrode Prussian blue appeared, and nitrogen, oxygen, and, if the operation was long continued, nitric oxide also were given off. In a concentrated solution much ammonia was formed at the cathode and nitric oxide appeared at the anode. Prussian blue can also be obtained according to Luckow's method 4 for the general preparation of in- soluble compounds. Nitriles. Ahrens, 6 by means of the electrolytic addition of hydrogen, succeeded in converting nitriles into primary amines, while simultaneously with the reduction a partial saponification of the nitriles occurred, as represented by the following equation: R.CN + 2H 2 O = R.COOH + NH,. Aceto-nitrile. This substance yields only a small quantity of ethylamine, although a considerable 1 Tommasi, Traite d'Electrochimie, 720. * Jahresb. f. Chem., 1863, p. 305; J. prakt. Chem., 30, 145. 1 Jahresb. f. Chem., 1863, p. 306; ibid., 1868, p. 311; Bull. soc. chim., [2] 10, I2i. 4 German patent, 91707. 6 Ztschr. f. Elektroch., 3, 99. Of ALIPHATIC COMPOUNDS. 47 quantity of /z-propylamine is formed from n-propio- nitrite. The reduction of aromatic nitrites takes place with- out the occurrence of secondary reactions. This is illustrated in the formation of benzylamine from benzo-nitrile and of phenyl-ethylamine from benzyl- cyanide. 3. Compounds Containing Sulphur. Mercaptans. Bunge ' electrolyzed the alkali salts of mercaptans and observed the formation of disulphides at the positive pole. In the case of the sulpho-com- pounds, however, the free acids were regenerated. Sodium-isethionate. The same author also investi- gated sodium isethionate, but could note the formation of only the free acid at the positive pole. Methyl-sulphuric Acid. This acid, investigated by Renard, 3 yielded hydrogen at the negative pole, while formic acid, carbon dioxide, carbon monoxide, and trioxy-methylene, besides free sulphuric acid, were found present at the positive pole. Potassium - trichlor - methyl Sulphate. This com- pound, electrolyzed by Bunge, 8 gave hydrogen and alkali at the negative pole, at the positive pole 1 Chem. Ber., 3, 911. 8 Ann. chim. phys., [5] 17, 289; Comp. rend., 90, 175, 531; ibid., 92, 965. * Chem. Ber., 3, 911. 48 ELECTROLYSIS AND ELECTROS YN THESIS oxygen, carbonic-acid gas, chlorine, sulphuric acid, and perchloric acid. Potassium-trichlor-methyl Sulphonate This salt was electrolyzed by Kolbe l in neutral concentrated aque- ous solution and gave the following results: The solution became strongly acid and contained free hydrochloric and sulphuric acid. Hydrogen was gradually evolved at the negative pole. After the decomposition was complete the solution contained potassium perchlorate, which was also observed in the case of potassium-trichlor-methyl sulphate. Ethyl-sulphuric Acid. Ethyl-sulphuric acid gave, according to Renard, 2 on being subjected to electroly- sis, at the negative pole hydrogen, and at the positive pole acetic acid, some formic acid, aldehyde, and sul- phuric acid. In concentrated solution a greater pro- portion of acetic acid was formed. The potassium salt on electrolysis breaks up, according to Hittorf, 3 into K and OSO 2 .OC a H 6 . Potassium-isoamyl Sulphate, according to Guthries, is decomposed into oxygen, valeric acid, and sul- phuric acid. Potassium Xanthate. C. Schall 4 obtained, by the electrolysis of potassium xanthate in aqueous solution, xanthogen supersulphide, as might be expected: 1 Journ. prakt. Chem., 62, 311. * Ann. chim. phys., [5] 17, 289. 1 Pogg. Ann., 106, 530. 4 Ztschr. f. Elektroch., 2, 475. OF ALIPHATIC COMPOUNDS. 49 O.C 2 H ft /O.C.H. /O.C,H 6 \ 2CS = CS CS \S- \S S/ Dimethyl-dithiocarbamic Acid. According to Schall ' the electrolysis of the potassium salt of dimethyl- dithiocarbamic acid resulted in the formation of tetra- ethyl-thiuram disulphide, [CS.N(C,H.),],S,. Thiophene. This compound under the influence of the electric discharge absorbs as much as 8.6$ of its own weight of nitrogen, (C 4 H 4 S) 2 N being formed (Berthelot 3 ). 1 Ztschr. f. Elektroch., 3, 83. * Ann. chim. phys., n, 35. ELECTROLYSIS AND ELECTROSYNTHESIS OF AROMATIC COMPOUNDS. THE data on the results of investigation in this branch of the subject are considerably more limited than in the case of the aliphatic series. One of the reasons for this is the difficulty with which the ben- zene nucleus undergoes oxidation, a condition which permits of comparatively few reactions. Nearly all the reactions involve substituted groups only. In almost all cases the benzene nucleus remains un- altered. In accordance with the method of presentation pre- viously adopted, the investigations on the electrolysis of the hydroxyl compounds will be first discussed in the following synopsis. i. Phenols. Phenol. Bunge, 1 Bartoli and Papasogli 9 submitted phenol to the action of the electric current, Bunge I Chem. Ber., 3, 296. II Gazz. Chim., 14, 19. 51 52 ELECTROLYSIS AND ELECTROS YNTHESIS observed that the decomposition of potassium pheno- late was analogous to that of an acid or a salt; the potassium phenolate was split up into K (cathion) and C 6 H 5 O (anion), the latter combining with water to form phenol, with the liberation of oxygen. Bartoli and Papasogli, on electrolyzing solu- tions of phenol in potassium and sodium hydroxide, and using electrodes of coke, graphite, and platinum, obtained an acid having the composition C 7 H 6 O 4 , which melted at 93, reduced ammoniacal silver solu- tion and Fehling's solution on being heated, and when in aqueous solution was not precipitated by acids. When, however, coke was used as the positive elec- trode, an extensive decomposition of the phenol occurred and a resin was formed. On subjecting a neutral potassium phenolate solu- tion to the action of the electric current they were able to isolate a compound, C 66 H 48 O a2 , soluble in alkali and precipitated from such solutions by mineral acids. This latter compound on being oxidized with nitric acid formed picric acid. When allowed to remain in solution in the presence of dilute acids for a prolonged period, it underwent decomposition according to the following equation: C, t H <8 0,, + H.O = C 4 ,H0 lt + C..H..O.. The electrolysis of neutral sodium phenolate solu- OF AROMATIC COMPOUNDS. 53 tion gave an acid with the formula C M H, O 8 which likewise is decomposed on boiling with dilute acids: C 29 H 30 8 = C 17 H 10 6 + C la H 10 0,. The compound C 1Q H 10 O 8 is soluble in alcohol, melts at 75, and is isomeric with the hydroquinone ether, obtained by Etard from chlorchromic acid and phenol. It has the composition Christomanos 1 observed that while sodium acts only very slowly on dissolved monobrom-benzene, diphenyl can speedily be obtained by placing sodium in the solution and connecting this metal with the positive pole of a battery of two Bunsen elements, whose electrodes are immersed in the solution; di- phenyl is likewise obtained by using zinc instead of sodium. Phenyl-mercaptan. Bunge a investigated phenyl- mercaptan in the same manner as the corresponding alkyl compound. Phenyl-disulphide, (C.H B ) a S a , was formed at the positive pole. 1 Gazz. Chim., 1875, p. 402. 1 Chem. Ber., 3, 911. 54 ELECTROLYSIS AND ELECTROSYNTHESIS 2. Aldehydes and Ketones. Benzaldehyde. Kauffmann, 1 by the electrolysis of benzaldehyde in a 12-15$ solution of potassium bi- sulphide, obtained at the cathode a mixture of hy- dro-benzoin and iso-hydrobenzoin. According to his statements, 2 an alcoholic solution of sodium hydroxide is more suitable for the reaction than the aqueous solution of bisulphide. Other aldehydes and ketones show a behavior similar to benzaldehyde. Tetramethyl-diamido-benzophenone. Michler's ke- tone, /C 6 H 4 N : (CH 3 ) 9 J \C 6 H 4 N : (CH,y gives the corresponding benzhydrol, /C 6 H 4 .N : (CH.). (HO)CH \C.H 4 .N :(CH,) a Aceto - phenone, C 6 H 6 .CO.CH S . Aceto - phenone yields aceto-phenone pinacone, C.H ^-C \C(OH).C(OH). Ztschr. f. Elektroch., 2, 365. 4, 461. OF AROMATIC COMPOUNDS. 55 Benzile. The aromatic di-ketone benzile, C,H 6 CO. CO.C 6 H 5 , gives peculiar results. On reduction in an alkaline alcoholic solution a whole series of bodies is formed, i.e., benzoic acid, benzilic acid, tetraphenyl- erythrite, C a8 H, 6 O 4 = C.H^HOH C e H 5 .COH C 6 H,COH C.H..CHOH, and a substance, C, 8 H a6 O s , containing one less atom of oxygen, which has probably the constitution C.H .(j;OH C,H 6 .CH C 8 H 5 .CHOH. Tetraphenyl-erythrite is also formed by the direct reduction of benzoin. Anthraquinone, H / /CO \C H 4 ^ 6 *' According to Weizmann, 1 this compound when in sulphuric acid solution is converted by electrolytic oxidation into monoxy-, dioxy-, and trioxy-anthra- 1 French Pat. 265292. 56 ELECTROLYSIS AND ELECTROS YN THE SIS quinone. The cathode fluids employed were solutions of alkalies, alkali carbonates, chromates, permanga- nates, acidulated water, and dilute acids. Both direct and alternating currents were used. On the elec- trolysis of anthraquinone and potassium hydroxide alizarine is formed. Nitro-aldehydes and nitro-ketones will be discussed in the chapter on nitro-compounds. 3. Acids. Benzoic Acid. Benzoic acid and its salts were ex- amined by several investigators, first by Matteuci, 1 then by Brester, 8 and most thoroughly by Bourgoin. 8 The result of all these investigations is to show that here no secondary reactions take place, as was observed in the case of the fatty acids, but that the only effect of the current is to produce a separation into hydrogen (or metal) and the acid radical, the latter regenerating the acid at the positive pole. In an alkaline solution it is possible to so increase the oxidation that the benzoic acid is destroyed. The decomposition products which then appear at the anode are carbon dioxide, carbon monoxide, and sometimes acetylene. The odor of bitter almonds is also frequently observed. A thorough investigation 1 Bull. soc. chim., 10, 209. Jahresb. f. Chem., 1866, p. 87. 8 Bull. soc. chim., 10, 431. OF AROMATIC COMPOUNDS. 57 on the electrolytic decomposition of sodium benzoate was made by Lob. 1 He employed a current having a potential of 6-7 volts and a current density of 15-20 amp., and obtained a small quantity of a substance containing sodium, the empirical formula for which was C,H.O.Na, but the chemical nature of which has not yet been determined. There is formed besides this compound a small amount of benzaldehyde, as well as acetylene and carbon monoxide. Under no circumstances do diphenyl or other hydrocarbons occur, nor do fatty acids appear, which is otherwise generally the case in an oxidation of this character. Thio-benzoic Acid. On electrolyzing this acid Bunge' obtained the bisulphide of benzoyl. Sulpho-benzoic Acid. This acid is not changed by the current according to the statements of the same investigator. Phthalic Acid. Bourgoin * states that the electrolysis of this acid and of its neutral or alkaline salts resulted in the formation of the unchanged acid at the positive pole. The appearance of small quantities of carbon dioxide and carbon monoxide, however, was an evi- 1 Zeitschr. f. Elektroch., 2, 663, ibid., 3, 3. J Chem. Ber., 3, 296. 8 Jahresb. f. Chem,, 1871, p. 631. 58 ELECTROLYSIS AND ELECTROS YN THESIS dence that a small portion of the acid had undergone oxidation. The potassium salt of the mono-ethyl ester of phthalic acid, when electrolyzed by Brown and Walker, 1 became dark-colored and a resinous sub- stance was formed, but the isolation of any new electrolytic product was not possible. Phenyl-acetic Acid. This acid electrolyzed in the form of its potassium salt by Slawik 8 yielded free phenyl-acetic acid. Cinnamic Acid. Cinnamic acid, investigated by Brester, 8 showed a similar behavior in the electrolysis of both the free acid and the neutral solutions of its salts. Benzyl-malonic Acid. When this acid in the form of its ethyl-potassium salt was submitted to elec- trolysis by Brown and Walker 4 it showed a behavior materially different from that of malonic acid. The solution became dark-colored and contained no new compound. If oxidation occurred it was a complete oxidation into carbon dioxide and carbon monoxide, such as has been observed in the case of the unsatu- rated acids. 1 Lieb. Ann., 274, 67. 9 Chem. Ber., 7, 1051. Jahresb. f. Chem., 1866, p. 87. 4 Lieb. Ann., 274, 67. OF AHOMAT1C COMPOUNDS. 4. Amido-Compounds. Aniline. Destrem * investigated the action of the electric spark from an induction apparatus on aniline vapor and observed a decomposition into acetylene, hydrogen, hydrocyanic acid, and nitrogen. E. Ro- tundi a electrolyzed aniline. Since pure aniline is an extremely poor conductor he made the solution suit- able for electrolysis by the addition of ammonia. After a period of three days, during which hydrogen was continually evolved at the negative pole and a tarry substance was deposited at the positive pole, Rotundi interrupted the electrolysis and was able, with more or less certainty, to establish the following processes : 1. The formation of diazo-compounds: C e H 6 NH a (HNO.) + HNO a = C 6 H 6 N 3 NO, + 2H S O. 2. The formation of diazo-amido-compounds: 2C fl H B NH a + HNO, = C 6 H 6 N 3 NHC 6 H 6 + 2H 3 O. C 9 H 5 N 2 NO 3 + C 6 H 6 NH a = C e H 6 N a NH.C 8 H 6 + HNO,. 3. The formation of azo-compounds by direct oxi- dation of aniline: 2C 6 H 6 NH, + 2O = 2H 3 O + C 6 H 6 N a C 6 H 6 . 1 Jahresb. f. Chem., 1884, p. 272. 2 Atti. d. R. Acad. d. Scienze d. Torino, 39, 4 ; Jahresb. f. Chem., 1884, p. 270. 6O ELECTROLYSIS AND ELECTROSYNTHESIS 4. The formation of amido-azo-compounds by molecular rearrangement of diazo-amido-compounds. The nitrous and nitric acids were oxidation products of the ammonia which was added. INVESTIGATIONS OF GOPPELSROEDER.' These relate to aniline and its derivatives, and aim at preparing the most important dyes of the aniline series. Although the reactions which take place in the cell have not as yet been explained, the researches form valuable material for consideration. Goppels- roeder has gathered the technical results in a small pamphlet: " Farbelektrochemische Mitteilungen " (Muhlhausen, 1889). If a galvanic current is conducted through acid or neutral aqueous solutions of aniline there is formed at the positive pole, besides other coloring matters, ani- line black, C 24 H ai N 4 Cl. Under similar conditions dyes are obtained at the positive pole from the salts of toluidene, methyl- aniline, diphenylamine, ditolylamine and phenyl-tolylamine. Naphthylamine salts give naphthylamine violet. On electrolysis of anthraquinone and potassium hydroxide, Goppelsroeder succeeded in obtaining alizarine. 8 1 Dingier, Polytech. Journal, 221, 75; ibid., 223, 317 and 634; ibid.) 224, 92 and 209. * See also p. 56. OF AROMATIC COMPOUNDS. 6 1 All these reactions are to be attributed to the action of electrolytic oxygen. In the brief survey which will here be given it is not possible to go into the details of the researches. The following literary data will serve as a guide: Research I. 1 Preparation of aniline black. Research 2. 2 Electrolysis of aniline with excess of aniline. Electrolysis of toluidene. Electrolysis of mixtures of aniline with toluic acids. Research 3.' Electrolysis of aniline and toluidene salts in the presence of nitrate, nitrite, or chlorate of potassium in aqueous solution. Research 4." Electrolysis of the salts of methyl- aniline. Electrolysis of the salts of diphenylamine. Electrolysis of the salts of methyl-diphenylamine. Electrolysis of phenol. Electrolysis of the salts of naphthylamine. Research 5. 5 Conversion of anthraquinone into ali- zarine by the electrolysis of a mixture of anthra- quinone and potassium hydroxide. Liebmann's fl attempts to make quinone by the electrolytic oxidation of aniline or electrolytically prepared aniline black were unsuccessful. 1 Dingier, Polytechn. Journ., 221, 75. * Ibid., 223, 317. 3 Ibid., 223, 634. 4 Ibid., 224, 92. 6 Ibid., 224, 209. ' Ztschr. f. Elektroch., 2, 497. 62 ELECTROLYSIS AND ELECTROS 'YN THESIS Hydroquinone in an aqueous solution acidified with sulphuric acid could be quantitatively converted into quinone at the anode: 2C.H 4 (OH) a + O = H,0 + C 6 H 4 (OH) a .C,H 4 0, The same compound was also formed when alter- nating currents were used. Voigt, 1 by the electrolytic oxidation of suitable mixtures of bases, prepared rosaniline, chrysaniline, safranine, and p-leucaniline. His object in these researches was the same as that of Goppelsroeder; namely, the preparation of the important dyes of the aniline series. If electrolytic oxygen is permitted to act upon aniline, dissolved in concentrated acetic acid solution, acetanilide is formed; by using a dilute solution, however, amido-hydroquinone is obtained. So far as can be learned from the literature these investigations have not been concluded, which is also the case with those of Poising, 8 who by the oxidation of p-phenylene-diamine obtained a beautiful blue dye similar to indigo. Poising obtained p-phenylene-diamine by the elec- trolytic reduction of amido-azo-benzene. From the electrolysis of benzene -p-phenylene-diamine 1 Ztschr. f. angew. Chem., 1894, p. 107. 1 Ztschr. f. Elektrochemie, 2, 30. OF AROMATIC COMPOUNDS. 63 there likewise resulted at the anode a blue dye, which showed a behavior analogous to that of the dye obtained from p-phenylene-diamine. 5. Electrolytic Reduction of Nitro-Compounds. In general, azo-, hydrazo-, and amido-compounds result from the electrolytic reduction of nitro-com- pounds. In this way Kendall 1 obtained aniline from nitre-benzene, and Elbs a and Haussermann * prepared the normal reduction products of nitfo-phenol. The formation of azoxy-, azo-, amido-, or hydrazo-com- pounds was dependent upon whether acid or alkaline solutions were employed. If nitro-benzene is reduced in a concentrated acetic or formic acid solution, to which a few drops of concentrated sulphuric acid (to increase the conductivity) have been added, the corresponding salts of benzidene result; a fact further confirmed by Lob. 4 According to the investigations of the same author, in the electrolysis of an ammoniacal solution azo- benzene is formed as the chief product and hydrazo- benzene as a secondary product. Gattermann and Koppert * obtained p-amido-phenol- 1 German Pat., 21131. 2 Journ. prakt. Chem., 49, 39. 1 Chem. Zeitung, 17, 129, 209. 4 Ztschr. f. Elektrochem., 3, 471. 5 Chem. Zeitung, 17, 210. 64 ELECTROLYSIS AND ELECTROS 'YN THESIS sulphate by the reduction of nitro-benzene-sulphonic acid. Noyes and Clement, 1 on the reduction of nitro- benzene in a concentrated sulphuric acid solution, obtained p-amido-phenol-sulphonic acid. Gatter- mann, a starting with a similar solution, by varying the conditions of the experiment obtained directly p-amido-phenol. He explains the reaction by assum- ing the intermediate formation of phenyl-hydroxyl- amine, which on further reduction changes by molec- ular rearrangement into the final product. By similar treatment were formed: an amido-cresol-monosulphonic acid 3 from o-nitro- toluene; the o-p-diamido-phenol from m-dinitro-benzene; diamido-cresol from o-p-dinitro-toluene; o-p-diamido-phenol from m-nitr aniline; a diamido-cresol from o-nitro-p-toluidene; the same diamido-cresol from p-nitro-o-toluidene; an amido-salicylic acid from m-nitro-benzoic acid; an amido-cresotinic acid from m-nitr o-p-toluic acid; a corresponding amido-oxy acid from nitro-terephthalic acid; a corresponding amido-oxy-acid from nitro-isophthalic acid; 1 Chem. Ber., 26, 990. 8 Ibid., 26, 1840. 8 Ibid., 27, 1929. OF AROMATIC COMPOUNDS. 65 an amido-naphthalene-sulphonic acid from a^oe^-nitro- naphthalene-sulphonic acid. The following is true in all these cases where the reduction is carried out in a concentrated sulphuric acid solution: The nitro-groups are completely reduced to amido- groups and a hydroxyl-group is taken up, always in a para-position to one of the amido-groups. As in the case of o-nitro-toluene sometimes also a sulpho-group is taken up. p-nitro- toluene on electrolysis behaves differently. Here the final product has the composi- tion C 14 H u N,O a , and its formation is as follows: p-Amido-benzyl alcohol is formed from p-tolyl- hydroxylamine (an intermediate product in the reduc- tion of p-nitro-toluene) by molecular rearrangement, _ /CH 3 OH The amido-benzyl alcohol thus formed condenses with one molecule of nitro-toluene (under the influ- ence of the sulphuric acid), water being split off ' : u /CH,OH , r TT /CH, _ ' H Cehl *\N0 3 nitro-amino-o-benzyl-toluene, C.H 4 - -CH -C 6 H 8 /3 + Ha0 1 Chem. Ber., 26, 2810, 66 ELECTROLYSIS AND ELECTROS YN THE SIS In a third paper 1 Gattermann applies this reduction to a large number of compounds which for lack of space cannot here be enumerated. The nature of the reaction is the same in all cases. The esters of the carboxylic acids show the same behavior as the acids themselves. These reduction products have all become the sub- jects of patents. 2 Lob and Gattermann have produced direct and in- direct evidence that the amido-phenols are actually formed by the molecular rearrangement of phenyl- hydroxylamine, which occurs as an intermediate product. Lob 3 has found that p- and o-chlor-aniline are ob- tained by the electrolytic reduction of nitro-benzene suspended in fuming hydrochloric acid, nitro-benzene dissolved in alcoholic hydrochloric acid, and nitro- benzene dissolved in mixtures of hydrochloric and acetic acid. With hydrobromic acid the correspond- ing brom-anilines are formed. The reaction takes place as shown in the following equations: 2. C 6 H 6 NHOH+ HCl = C 6 H 6 NHCl+H a O 1 Chem. Ber., 2J, 1927. * German Patent, 75260 and additions to the same, 3 Ztschr. f. Elektrochem., 3, 46. OF AROMATIC COMPOUNDS. 67 3. C,H 6 NHC1 = NH, ^CC1 and HC I II I UNIVERSIT NH. H Cl The phenyl-chloramine formed by the action of hydrochloric acid on phenyl-hydroxylamine changes, by molecular rearrangement, into o- and p-chlor- aniline. Gattermann 1 has obtained direct proof of the inter- mediate formation of phenyl-hydroxylamine by adding benzaldehyde to the solution at the beginning of the electrolysis. He was thus able to isolate a condensa- tion product of phenyl-hydroxylamine with benzalde- hyde. In this way he obtained benzylidene-phenyl- hydroxylamine, O C.H 6 N- -CH,C 6 H 6 , from nitre-benzene ', benzy lidene-o-tolyl-hydroxylamine, C 6 H 6 .CH - N.C 6 H 6 .CH 8 , from o-nitro-toluene, and the corresponding benzyl- idene compounds from m-nitro-toluene, p-nitro-toluene, nitro-p-xylene, and m-nitro-benzoic acid. The presence of formaldehyde in the electrolytic 1 Chem. Ber., 29, 3040. 68 ELECTROLYSIS AND ELECTROS YN THESIS reduction of nitro-compounds produces an effect entirely different from that caused by the addition of benzaldehyde. The phenomena occurring in this case have been thoroughly investigated by Lob. 1 The fundamental object of his researches differs from that of Gattermann, in that Lob undertakes to establish the separate phases of the reduction of the nitro-group. This he accomplishes by the addition of formal- dehyde to the electrolyte under varying conditions, and as a result the intermediate products, at the moment of their formation, combine with formal- dehyde, producing condensation compounds which do not undergo further decomposition. By regulating the potential and density of the current the reaction can at will be checked at a perfectly definite phase of the reduction. In the electrolysis of nitro-benzene by this method there were formed : 1. p-Anhydro-hydroxylamine-benzyl alcohol, , H /NH.OH ' n *\CH 3 OH n ' which may also be directly prepared by the action of formaldehyde on phenyl-hydroxylamine. 2. Methylene-di-p-anhydro-amido-benzyl alcohol, F /NH.C.H.CH^ L CH '\NH.C 6 H 4 CH 2 / Ztschr. f. Elektroch., 4, 428. OF AROMATIC COMPOUNDS. 69 a condensation product of formaldehyde and aniline. The behavior of p-nitro-toluene is different, since in this case, the p-position being occupied by the nitro- group, an analogous reaction with formaldehyde is impossible. While p-nitro-toluene is converted in an alkaline solution smoothly into azo-toluene and in an acid solution into p-toluidene, nearly equal quantities of two different products are obtained in the presence of formaldehyde, viz. : 1. p-Dimethyl-toluidene. 2. Dimethylene-ditoluidene. The nature of the reaction is such that the reduc- tion proceeds until p-toluidene is formed, and not till then does a condensation with formaldehyde occur: 2C 6 H 4 .CH 8 .NH a + 2CH 2 = 2H,O. The dimethylene-ditoluidene thus formed on further reduction breaks up into dimethyl-toluidene and toluidene, the latter becoming again subject to the action of the formaldehyde : f 4H=* CH 8 ,C 6 H 4 .N(CH 8 ) a + H s N.C.H i CH i . A state of equilibrium exists between the dimethyl- 7O ELECTROLYSIS AND ELECTROSYNTHESlS toluidene and the dimethylene-ditoluidene at the end of the operation. A further application 1 of Gattermann's reaction has been found in the case of aromatic nitr amines* which if reduced in a concentrated solution of sul- phuric acid give amido-phenol derivatives. The process can also be applied to the esters of nitro- carboxylic acids 8 and results in the formation of amido-phenol-carboxylic esters. Nitro-sulphonic acids * show a similar behavior, while the p-nitro- or p-nitroso-alkyl-anilines* and toluidenes, as the case may be, are reduced to p-amido-derivatives of alkylated m-oxy-anilines or their homologues. The nitro-derivatives of the quinoline* series show a deportment similar to that of the derivatives of benzene. Nitre-aldehydes ^ which Gattermann 7 has also chosen for the subject of thorough investigation, conduct themselves differently from the nitro-compounds thus far described. If the nitro-aldehydes are reduced there are formed either the free aldehyde-phenyl-hydroxylamines, or German Pat., 77806. Ibid.. 78829. Ibid.. 79865. Ibid., 81621. Ibid... 81625. Ibid., 80978. Chem. Ber., 29, 3037; German Pat. 85198. OF AROMATIC COMPOUNDS. 7 1 condensation products of the same with the nitro- aldehyde present. The nitro-benzylidene-aldehydo- phenyl-hydroxylamines are thus formed : + 4H = H ' + C H '\NHOH. 2. /CHO U H \ /O\ \N - CH.C 6 H 4 .NO 9 . p-Nitro-benzylidene-p-aldehydo-phenyl-hydroxylamine y C.CHO C.NO, # \ / ^ HC CH HC CH I II II I ' HC CH HC CH V/ /o\ \ c // _N -- CH- may thus be prepared from p-nitro-benzaldehyde. From m-nitro-benzaldehyde an analogous compound is formed. Gattermann, 1 on reducing several aromatic nitro- ketones, obtained the corresponding derivatives of amido-phenols. By a similar treatment amido-oxy-acetophenone, 1 Chem. Ber. , 29, 3034. 72 ELECTROLYSIS AND ELECTROS YNTHESIS is formed from m-nitro-acetophenone ; amido-oxy-ben zophenone, from m-nitro-benzophenone ; and amido-oxy-phenyl-p- tolylketone, from m-nitro-phenyl-p-tolylketone. The process which Straub ' employs to prepare hydrazo-compounds from nitro-hydrocarbons is yet to be mentioned. The chief feature of his experiments is that the original material and all intermediate products are retained in solution during the electroly- sis by the selection of a suitable solvent, and the hydrazo-compounds are withdrawn from the action of the current by precipitation. Straub attains this end by subjecting the nitro- hydrocarbons to electrolytic reduction in a solvent made a conductor by the addition of potassium hy- droxide. The quantity of the liquid used must be sufficient to keep in solution the azo- and azoxy-com- pounds corresponding to the nitro-hydrocarbon. Noyes and Dorrance 3 have applied Gattermann's reaction to p-nitraniline and some other substances. In this way they obtained p-diamido-benzene sulphate 1 German Patent, 79731. 8 Chem. Ber., 28, 2349. OF AROMATIC COMPOUNDS. 73 from p-nitr aniline, p-ami^o-phenol-sulphonic acid from p-nitro-phenol, and p-amido-phenol-sulphonic acid from p-chlor-nitro-benzene. They explain the reactions in the following manner: C H ' C H ( -' H 'CH, " C ' H '\CH,OH, . /NO, C 6 H S CH 3 \NH a /NO, The phenomena of the reduction of nitro-com- pounds in alkaline solution have been investigated by Lob. 1 In his first experiments he used nitro-benzoic acids and nitro-phenols. It was found that m-nitro- and p-nitro-benzoic acid were smoothly reduced to the corresponding azo-acids, while the o-acid under simi- lar conditions yielded o-azoxy-benzoic acid and o-hy- drazo-benzoic acid. The nitro-phenols in alkaline solutions gave amido-phenols. The fact that the reduction in an alkaline solution may be carried as far as the azo-phase has been made 1 Zeitschr. f. Elektroch., 2, 529: ibid., 3, 45. 74 ELECTROLYSIS AND ELECTROS YN THESIS use of by Lob * in performing a direct electrosynthesis of the mixed azo-bodies and azo-dyes. The com- ponents of the compounds desired, in exactly equi- molecular proportions, are reduced under conditions which render the union of the two residues possible. In this way azo-compounds are obtained in which the substituents are in the meta-position compounds which could not be prepared by the Griess method. Kaufmann and Hof a subjected m-nitro-benzal- dehyde to reduction in alkaline solution and thus obtained m-azo-benzoic acid as the principal product and m-azo-benzyl alcohol as a secondary product. By the electrolysis of m-nitro-benzaldehyde Lob 3 ob- tained m-azo-benzoic acid and m-azo-benzyl alcohol as secondary products. The chief product consisted of a mixed azo-body, azo-m-benzyl-alcohol-m-benzoic acid, m - CH 3 OH.C 6 H 4 .N : N.C,H 4 .COOH - m. The Gesellschaft f. Chem. Industrie of Basel* prepare orange dyes by using as cathode fluid an alkaline solution of the yellow condensation products of p-nitro-toluene-sulphonic acid, CH '- C H '\S0 3 H 1 Ztschr. f. Elektroch., 4, 530. 8 Chemiker Zeitung, 1896. * Ztschr. f. Elektroch., 4. 4 English Pat., 22482. OF AROMATIC COMPOUNDS. ?5 (namely, a mixture of azoxy-stilbene-disulphonic acid, azo-stilbene-disulphonic acid, and dinitro-stilbene- disulphonic acid). The reduction, however, must not be continued until amido-compounds result. Other reduction processes are used by the Badische Aniline u. Sodafabrik ' for making naphthazarine from a^a- dinitro-naphthalene or a^a^-dinitro-naphthalene. In these cases intermediate products are first formed in the electrolytic reduction, and these are transformed into naphthazarine by heating. The Basel company 2 mentioned above obtains triphenyl-methane dyes by the electrolytic reduction of nitro-leuco-bodies of the type NO a C e H 4 .CHR a , (4) (i) which result in the formation ofthecarbinoles NH-C,H 4 .COH.R, (4) Ahrens 4 accomplished the electrolyut reduction of py.ridine and the derivatives of pyridine, and obtained piperidine from pyridine, and pipecoline from pico- line. In these electrolyses lead cathodes and 10$ solutions of sulphuric acid were employed. If strong sulphuric acid and a platinum cathode 1 German Pat., 79406. * German Pat., 84607. 3 In these formulae A" denotes aromatic radicals with primary, secondary, or tertiary amido-groups, or with hydroxyl-groups. 4 Ztschr. f. Elektroch., 2, 577, 580. ? ELECTROLYSIS AND ELECTROSYNTHESIS were used there was formed a substance containing nitrogen and sulphur, the chemical nature of which has not yet been determined. Nitro-piperidines on electrolytical reduction give piperylhydrazines, ammonia is split off, and piper- idine is in part regenerated. Nitroso-a-pipecoline gives, in addition to ammonia, <*-pipecoline and a-methyl-piperylhydrazine. In a like manner from nitroso-aldehyde-copellidine (CH 3 .C 2 H B .C 6 H 8 : N.NO) there is formed ammonia, a large proportion of copellidine (CH 3 .C a H B .C 5 H 8 : NH), and also the corresponding methyl-ethyl-piperylhy- drazine: CH 3 .C a H 5 .C 6 H 8 :N.NH a . Quinoline in 10$ sulphuric-acid solution gave a polymeric dihydro-quinoline and tetrahydro-quinoline (Ahrens '). Quinaldine, likewise in sulphuric-acid solution, gave dihydroquinaldine and tetrahydro-quinaldine. 6. Electrolytic Oxidation of Nitro-compounds. The influence which the nitroso- and nitro-groups exert on the other substituents is especially shown in oxidation reactions, which here occur much more readily than in the case of compounds which have not 1 Chem. Ber., 29, 1123. OF AROMATIC COMPOUNDS. TJ been nitrated. By the electrolytic oxidation of nitroso- piperidine Ahrens ' obtained dipiperidyl (C 10 H ao N Q ). Elbs 3 secured a satisfactory yield of p-nitro-benzyl alcohol from p-nitro -toluene. The introduction of hydroxyl-groups into azo-ben- zene, which Heilpern 3 succeeded in accomplishing, can also be regarded as an oxidation process. If azo- benzene be dissolved in as small a quantity of cone, sulphuric acid as possible and this solution be sub- jected to electrolytic action at the anode, chiefly tetra- oxy-azo-benzene is formed : C 13 H 10 O 4 N a = (OH) 2 C 6 H,N : NC 6 H 8 (OH) a . According to a patent 4 benzoyl-sulphone-imides can be prepared by the electrolytic oxidation of toluene- sulphone -amides ; for example, o-benzoyl-sulphone- imide, or saccharine, from o-toluene-sulphone-amide : """XCH, '+ 3 C61 The corresponding p-compound, and p-nitro-o- toluene-sulphone-amide, . NO 9 .CH 3 .C 9 H,.SO,NH, show a similar behavior. Yellow mordant dyes are obtained by the Badische Aniline u. Sodafabrik * by the oxidation of aromatic 1 Ztschr. f. Elektroch., 2, 579. * Ibid. t 2, 522. Ibid., 4, 89. 4 F. v. Heyden's Nachfolger, German Pat.. 85491. 6 German Pat., 85390. 78 ELECTROLYSIS AND ELECTROS YN THESIS oxycarboxylic acids in sulphuric acid solution, by the use of ammonium persulphate or by electrolysis. A whole series of acids have been investigated: m-dioxy- benzoic acid, gallic acid, tannin, the ethyl ester of gallic acid, gallamide ((OH) s C 8 H a CO.NH 2 ), o-, m-, and p-oxy-benzoic acids, cresotinic acid, etc. 7. Electrolysis of Alkaloids. 1 Caffeine, Theine, C 8 H ]0 N 4 O 2 . On permitting the electric current to act for several days on a solution of caffeine acidified with sulphuric acid Pommerehne * obtained amalic acid, formic acid, ammonia, and methylamine. Atropine, C 1T H 23 NO 3 . From the neutral sulphate of atropine crystallized atropine is gradually precipitated at the cathode, while at the anode carbon dioxide, carbon monoxide, oxygen, and nitrogen are evolved. The acid sulphate behaves in a similar manner, but the evolution of nitrogen was not observed. Opium. If opium is subjected to the action of the electric current the acid goes to the cathode and the base to the anode. Thus meconic acid (oxy-pyrone- dicarboxylic acid) was found at the positive pole and morphine (C 17 H 17 NO(OH) 2 ) at the negative pole. 1 Donate Tommasi: Trait6 d'Electrochimie, Th6orique et Prac- tique, Part 4, 788. 2 Arch. f. Pharm., 235, 364. OF AROMATIC COMPOUNDS. 79 Bourgoin, however, showed that the reaction does not take place smoothly, but is always accompanied by secondary reactions. Morphine. Pommerehne, 1 by the electrolysis of a solution of morphine acidified with sulphuric acid, obtained, after a few days, crystals of oxy-dimorphine sulphate. The solution became dark-colored. Codeine (methyl-morphine), C 17 H 17 NO(OH)O.CH,. On the electrolysis of the neutral sulphate hydrogen is evolved, codeine is precipitated, and the solution turns brown. The acid sulphate undergoes more complete decomposition, and carbon dioxide, carbon monoxide, oxygen, and nitrogen are split off. Cotarnine, 2 C ia H 1B NO 4 . This compound is converted by the electrolytic hydrogen quantitatively into pure hydro-cotarnine, (C,,H, t NO,),.H,0. Quinine, C ao H a4 N a O 2 . Although the neutral sul- phate is a very poor conductor, the acid sulphate is readily decomposed into carbon dioxide, carbon mon- oxide, and nitrogen. The color of the solution changes to a dark brown. Cinchonine, 3 C 19 H 2Q N 2 O. On the electrolysis of the nitrate of this compound an oil-like body appears at the anode. 1 Arch. f. Pharm., 235, 3*4. * German Pat., 94949. 3 Journ. prakt. Chem., 72, 73. 80 ELECTROLYSIS AND ELECTROS YNTHESIS Strychnine, 1 C 31 H aa N a O a . The neutral sulphate suffers but little change. The solution becomes slightly colored, hydrogen and oxygen are given off, and crystals of strychnine collect on the cathode. The acid sulphate behaves in a like manner, except that in its case the formation of carbon dioxide and carbon monoxide as well as oxygen and nitrogen shows that a part of the substance undergoes complete decomposition. In strongly acid solutions the split- ting off of nitrogen does not occur. Brucine, 1 C 83 H 26 N a O 4 . A solution of the neutral sulphate turns red and the sulphate is decomposed. Hydrogen is evolved at the negative pole, but the brucine completely absorbs the oxygen at the positive pole. The acid salt is very energetically decomposed, becoming first red and then brown. At the anode carbonic-acid gas, carbon monoxide, oxygen, and ni- trogen escape. Besides the gases mentioned, the above alkaloids break up into other products, principally complicated compounds containing nitrogen. 8. Camphor and Glucosides. Terpentine hydrochloride. This compound on elec- trolysis in the melted condition or in an alcoholic acetic-acid solution gave camphor, C 10 H 16 O (Richard- son a ). 1 Bull. soc. chim., 12, 400. J English patent, 3555. OF AROMATIC COMPOUNDS. 8 1 Salicine, C 1S H 18 O V Salicine on electrolysis yielded salicylic aldehyde and salicylic acid (Tichanowitsch 1 ). 9. Electrolysis of Blood. The defibrinated blood of a dog was submitted to electrolysis by Becquerel. He made use of platinum electrodes and a current furnished by a battery of three Daniel cells. At the negative pole he observed the following phenomena: The blood became brown and alkaline, and con- tained neither white nor red corpuscles; it possessed the property of gradually dissolving blood-corpuscles and had the odor of putrid meat. At the positive pole undecomposed and partially decomposed blood-corpuscles were present in large quantities. The fluid gave a precipitate of albumen with nitric acid, mercuric chloride, and lead acetate. 10. Electrolysis of Albumen. When an albumen solution was electrolyzed by Dumas and Prevost, under conditions similar to those used by Becquerel for blood, the alkali metal went to the negative pole, hydrogen was evolved, and acetic and phosphoric acids appeared at the positive pole. The result of this is that the albumen is coagulated 1 Chem. Centralblatt, 1861, p. 613. 82 ELECTROLYSIS AND ELECTROS YNTHES1S at the negative pole (by the alkali present), while at the positive pole the solution remains clear. As Lassaigne has shown, pure albumen in aqueous solution is a non-conductor of electricity; the addition of salts or acids is therefore necessary in its elec- trolysis. ii. Electrolysis and Electrosynthesis with Alternating Currents. If the polarity of the current does not change altogether too rapidly, since oxidation and reduction occur successively at each pole, it is possible to accomplish electrolyses and electrosyntheses with alternating currents. Experiments with this end in view have been made by Drechsel. 1 Dehydration is a case of simultaneous reduction and oxidation. The supposition that in living organisms carbamide is pro- duced from ammonium carbamate by the splitting off of water prompted Drechsel to make experiments in this direction. 3 If an aqueous solution of ammonium carbamate was electrolyzed with a current from a battery of 4-6 Grove elements and platinum electrodes were used, carbamide was obtained independently of the elec- Journ. prakt. Chem., 22, 476. Ibid. OF AROMATIC COMPOUNDS. 83 trode material when alternating currents were em- ployed. The reactions are supposed to be either H 2 O, II. NH 2 .CO.ONH,+ 2H =r NH 3 .CO.NH, + H a O, or I. NH 2 .COONH 4 + 2H = NH a .CONH 4 + H 2 O, II. NH a .CO.NH 4 + O = NH a .CO.NH a + H.O. The fact that the platinum electrodes were strongly attacked, with the formation of platinum salts, caused Gerdes ' to investigate the platinum bases. As the principal product he found a compound to which he gave the following formula: /ONHJ p /NH 3 NH,0\ J \ONH 3 } 1 t XNH 3 NH 3 0/ L and the chloride of which is said to have the composi- tion CINHXp/NH, NH 3 C1 Q NH,CI >J: L1 *^ Ha * Gerdes also examined the nitrate and sulphate of this base. In the course of further researches 2 Drechsel found that when alkaline solutions were used platinum was present in the electrolyzed fluid. Copper when used as electrode showed a similar behavior; lead was less 1 Journ. prakt. Chem., 26, 257. * Ibid., 29, 229. 84 ELECTROLYSIS AND ELECTRO SYNTHESIS attacked, gold but very slightly, and palladium not at all. The formation of the phenol ester of sulphuric acid in living organisms is supposed, like carbamide, to be the result of dehydration. Taking this into consid- eration, Drechsel carried out the following experiment: A saturated solution of acid magnesium carbonate was mixed with an equal volume of a solution of magnesium "sulphate and the mixture was saturated with commercial carbolic acid. 1 When this solution was electrolyzed for thirty hours with alternating currents and platinum elec- trodes were used, the following products were ob- tained: 1. ^-Diphenol. 7. Succinic acid. 2. Pyrocatechin. 8. Malonic acid (?). 3. Hydroquinone. 9. n-Valeric acid (?). 4. Phenol ester of sul- 10. n-Butyric acid (?). phuric acid. n. Some cyclohexanone," 5. Oxalic acid. C 6 H 10 O. 6. Formic acid. According to Drechsel the formation of the phenol ester of sulphuric acid is probably represented by the following equations: I. C 6 H 6 OH+HO.SO 8 H+O=C 6 H 5 .OOSO 3 H+H,O, II. C 6 H 6 .OOSO 3 H + 2H = C 6 H 5 .SO 3 H + H a O. 1 Journ. prakt. Chem., [2] 29, 229. 2 Jbib. t [2] 38, 67. OF AROMATIC COMPOUNDS. 8$ Later Drechsel ' electrolyzed normal capronic acid with alternating currents. The electrolytic solution contained, in a volume of 3 liters, 200 g. of capronic acid as magnesium salt and was nearly saturated with acid magnesium carbonate. Platinum electrodes were used. At the end of the experiment the following compounds could be identified in the solution: 1. Valeric acid. 5. Adipic acid. 2. Butyric acid. 6. Oxy-capronic acid. 3. Oxalic acid. 7. Glutaric acid. 4. Succinic acid. In a still later research on the electrolysis of pheno with alternating currents Drechsel 2 detected phenyl- sulphuric acid, dioxy-benzenes, a number of acids of the fatty acid series, arid in addition to these an oil which he identified as hydro-pheno-ketone, CH, /\ H,C C : O I , H,C CH, \/ CH, and whose phenylhydrazine compound he was able to isolate. Drechsel regards the hydro-pheno-ketone as the origin of the fatty compounds formed. By the 1 Journ. prakt. Chem., 34, 135. .. 3$, 6$. 86 ELECTROLYSIS AND ELECTROSYNTHESIS. direct addition of water to this compound capronic acid results, and this then breaks up into the acids and other decomposition products mentioned above. A critical review of the subject-matter which has here been presented will bring out, concerning the electrolysis and electrosynthesis of organic com- pounds, several important points which promise to be of great assistance, at no very distant date, in con- nection with future research in the field of organic chemistry. These points may be summarized as fol- lows: the oxidation reactions which occur in the electrolysis of acids of the aliphatic series, the reduc- tion reactions in the case of the aromatic series, and, lastly, the reactions involving substitutions, concern- ing which but few researches have been published. Of these the first is apparently the most promising. Since in all the experiments which have thus far been made the dependence of all reactions upon current density, temperature, and concentration is clearly evident, the attention of experimenters is again called to the importance of exact data con- cerning the conditions of experiment. AUTHORS. PAGE Aarland 28 Ahrens n, 46, 75, 76, 77 Alessi. 25 Almeida 2, 4 Balbiano * 25 Bartoli 7, 13, 51, 52 Bauer 18 Becquerel 3, 81 Berthelot 44, 45, 49 Bourgoin 13, 14, 18, 25, 26, 27, 28, 29, 32, 44, 56, 57, 79 Brazier 24 Brester 8, 13, 24, 25, 28, 56, 58 Brown 12, 30, 34, 35, 37, 40, 42, 44, 58 Buff 44 Bunge 20, 25, 47, 51, 52, 53, 57 Christomanos 53 Classen 6, 25, 31 Clement 64 Connel 4 Deheran 2, 4 Despretz 18 Destrem 59 Dorrance 72 Drechsel 82, 83, 84, 85 Dumas 81 Dupre 18 87 88 A UTHORS. PAGE Elbs 5,6, 19, 36, 63, 77 tard 53 Pulsing 62 Friedel 10, 40 Gattermann 63, 64, 66, 67, 68, 70, 71, 72 Gay-Lussac 45 Gerdes 83 Goppelsroeder 60, 62 Gossleth 24 Guthries 37,48 Habermann 2, 3, 4 Hamonet 20 Haussermann 63 Heilpern 77 Hemptinne u Henderson 40 Herz 5, 6 Hittorf 48 Hof 74 Hofer 9, 30, 31 Hof man n 44 Huntington 45 Jahn 3, 15, 20 Jaillard 2 Jovitschitsch 13, 14 Kauffmann 36, 54, 74 Kekule 12, 16, 26, 30, 42 Kemp : 18 Kendall .' 63 Kolbe 12, 15, 18, 19, 23, 24, 27, 32, 37, 44, 48 Koppert 63 Lapschin 14 Lassaigne 82 Liebmann 61 Lob 6, 16, 57, 63, 66, 68, 73, 74 Losanitsch 13, 14 Luckow 46 A UTHORS. 89 Ludersdorf 4 Maquenne 2, n Mattenci 56 McCoy 7 Meissner n Messinger 6 Miller 9, 3. 3*. 34 Moore 19 Mulder 10 Mulliken 12, 42, 43, 44 Noyes 64, 72 Papasogli .' 7. 13, 5i, 52 Perkin . , 45 Perrot ' 2, 46 Pommerehne 78, 79 Pre vost 81 Quet, M 2 Reboul 27 Renard 2, 4, 6, 8, 13, 25, 47, 48 Richardson 80 Riche 4, 10 Rohland 17 Rotundi, E 59 Royer 12 Schall, C 16, 48, 49 Schields 42 Schlagdenhauffen 45, 46 Schonbein 3 Slawik 58 Smith 1 8 Stone 7 Straub 72 Tichanowitsch 14, 81 Tommasi 7 Voigt 62 Vostmann Walker 12, 30, 34, 35, 37. 4O, 42, 44, 58 QO A UTHORS. PAGE Weems 12, 42, 43, 44 Weith 4; Weizmann 55 Wiedemann 18 Wilde 11,13 Wttrz 24 INDEX. PAGB Acetanilide 62 Acetic acid... 3, 4, 7, 10, 14, 18, 19, 29, 32, 34, 35, 48, 62, 81 Acetic aldehyde 4, 8, n, 29, 32, 33, 36, 48 Acetic ester 3, 4, 15, 34 Aceto-acetic ester 43 Acetone t 10, 32 Aceto-nitrile 46 Aceto-phenone 54 Aceto-phenone pinacone 54 Acetyl-acetone 1 1, 43 Acety 1-dicarboxylic ester 43 Acetyl disulphide 19 Acetylene 2, n, 27, 30, 45, 56, 57, 59 Acetyl-malonic ester 43 Acids, aromatic 56 Acids, fatty n, 85 Acid superoxides 16, 1 7 Acid supersulphides 17 Acrylic acid 28 Adipic acid 38, 85 Albumen bi Alcohol aldehydes g Alcohols. . . I, 23, 75 Aldehyde, see acetic aldehyde. Aldehyde-phenyl-hydroxylamines /I Aldehyde resin 4 Aldeh\dcs 9, 36, 54 Q2 INDEX. PAGE Aldol 32 Alizarine 61 Alkaloids 78 Alkyl-oxy-anilines 70 Allocamphoric acid 40, 41 Allylene 28 Amalic acid 78 Amides 43 Amido-acetone n Amido-azo-benzene 62 Amido-azo-compounds 60 Amido-benzyl alcohol 65 Amido-compounds 59, 63, 75 Amido-cresol-monosulphuric acid 64 Amido-cresotinic acid 64 Amido-hydroquinone 62 Amido-naphthalene-sulphonic acid 65 Amido-oxy-acetophenone 71 Amido-oxy-benzophenone 72 Amido-oxy-phenyl-p-tolylketone 72 Amido-phenol-carboxylic esters 70 Amido-phenols , 6^, 66, 70, 71, 73 Amido-phenol sulphate 63 Amido-phenol-sulphonic acid , 64, 73 Amido-salicylic acid 64 Amines 46 Ammonium carbamate 82 Anhydride, formation of 16, 29 Anhydro-hydroxylamine-benzyl alcohol 68 Aniline 45, 59, 60, 61, 62, 63, 69 Aniline black 60, 61 Aniline dyes 60, 62 Anthraquinone 55, 60, 61 Aristol 6 Atropine 78 Azo-acids 73 Azo-benzene 63, 77 INDEX. 93 PAGE Azo-benzoic acid 74 Azo-benzyl alcohol 74 Azo- m-benzyl-alcohol-m-benzoic acid 74 . Azo-compounds 59, 63, 72, 74 Azo-dyes 74 Azo-stilbene-disulphonic acid 75 Azo-toluene 69 Azoxy-benzoic acid 73 Azoxy-com pounds 63, 72 Azoxy-stilbene-disulphonic acid 75 Benzaldehyde 33, 35, 36, 54, 57, 67, 68 Benzene 45 Benzene-phenylene-diamine 62 Benzhydrol 54 Benzidene 63 Benzile 55 Benzilic acid 55 Benzoic acid 55, 56 Benzo-nitrile 47 Benzoyl-sulphone-imides 77 Benzylamine 47 Benzyl-cyanide 47 Benzylidene compounds 67 Benzylidene-phenyl-hydroxylamine , 67 Benzylidene-tolyl-hydroxylamine 67 Benzyl-malonic acid 35, 42, 43, 58 Blood 81 Brom-anilines 66 Brom-maleic acid. 30 Bromoform 6 Brucine .... ... 80 Butane 20 Butyl alcohol 4 Butylene 24 Butyric acid 20, 34, 84, 85 Butyric ethyl ester 34 Butyric isopropyl ester... ,,,, , 21 94 . INDEX. PAGE Caffeine 78 Campholytic acid 40 Camphor 80 Camphoric acid 40, 42 Camphothetic acid 40 Cane sugar 8 Capronic acid. 17, 24, 85, 86 Capronic amyl ester 24 Capronic ethyl ester 34 Caprylic acid 17 Carbamide 84 Carbinoles 75 Chlor-acetic acids 4 Chloral hydrate 7 Chlor-anilines , 66, 67 Chlor-nitro-benzene.. .> 73 Chloroform 6 Chrysaniline 62 Cinchonine 79 Cinnamic acid 58 Cinnamic aldehyde 4 Citraconic acid 28 Codeine 79 Collodion 9 Copellidine 76 Cotarnine 79 Cresotinic acid 78 Crotonic acid 40 Crotonic aldehyde 32, 33 Cyan-acetic acid 19 Cyan-acetic ester 43 Cyanogen 44, 46 Cyanogen compounds 44 Cy clohexanone 84 Decahexane-dicarboxylic acid 38 Decane 17, 24 Dehydration 82 INDEX. 95 Dextrine 9 Diacetyl-succinic ester 43 Diamido-benzene sulphate 72 Diamido-cresol. 64 Diamido-phenol 64 Diazo-amido-compounds 59 Diazo-compounds 59 Dibenzyl-succinic ester 35 Dichlor-acetone 10 Dicyan-succinic ester 43 Diethyl- ethane-tetracarboxylic ester 43 Diethyl-malonic acid 39, 40 Diethyl-succinic acids 39 Dihydro-quinaldine 76 Dihydro-quinoline 76 Di-isobutane 24 Dimethyl-dithiocarbamic acid 49 Dimethylene-ditolidene 69 Dimethyl-ethane-tetracarboxylic ester 43 Dime thy 1-malonic acid 39, 40 Difnethyl-pyrazine, ketine n Dimethyl-succinic acids 38 Dimethyl-toluidenes 69 Dinitro-benzene 64 Dinitro-naphthalenes 75 Dinitro-stilbene-disulphonic acid 75 D in itro- toluene 64 Dioxy-anthraquinone 55 Dioxy-benzenes 85 Dioxy-benzoic acid 78 Diphenol 84 Diphenyl 53 Diphenylamine 60, 61 Dipiperidyl 77 Disulphides 47 Dithionic acids 17 Di-thymol-di-iodide , , , . 6 96 INDEX. PAGE Ditolylamine 60 Dodecane 17 Dodecane-dicarboxylic acid 38 Dyes, aniline 60, 62 Dyes, orange 74 Dyes, triphenyl-methane 75 Dyes, yellow mordant 77 Esters 36, 38, 39 Ethane * 2, 4, u, 15, 16, 18, 19, 29 Ethane-hexacarboxylic ester 43 Ethane-tetracarboxylic ester 43 Ethyl alcohol i, 2, 3, 5, 13, 14, 34, 39 Ethylamine 46 Ethyl-crotonic acid 40 Ethylene.. 2, 1 8, 20, 27, 32, 36, 42, 45 Ethylene cyanide * 19 Ethylene glycol 9 Ethyl-glycolic acid 36 Ethylidene oxy-ethyl ester 4 Ethyl-malonic acid 38 Ethyl-malonic ester ... 43 Ethyl-succinic ester 35 Ethyl-sulphuric acid 4, 48 Ethyl-tartaric acid 33 Formaldehyde 3, 31, 32, 33, 67, 68, 69 Formamide 14 Formic acid 6, 7, 8, 10, 12, 14, 18, 31, 32, 33, 47, 48, 78, 84 Formic ester 4 Formyl chloride 14 Fumaric acid 30, 42 Furfurane 39 Gallamide 78 Gallicacid 78 Gallic ethyl ester 78 Glucose 6, 7, 8 Glucosides 80 Glutaric acid , . , 27, 28, 38, 85 INDEX. Glyceric acid ^FNIVCTKWV 7> 33 Glyceric-aldehyde Vp 7 * * * 7 Glycerine ^^AUKO^^:, 6, 7, 8 Glycolic acid 6, 7, 25, 31, 34, 36 Glycols 6, 7, 35 Grape sugar 8 Gum arabic 9 Heptylic acid 17 Hexane 20, 22 Hydracrylic acid 32 Hydrazo benzene 63 Hydrazo-benzoic acid 73 Hydrazo-compounds 63, 72 Hydrobenzoln 35, 36, 54 Hydrocarbons 12, 37, etc. Hydro-cotarnine 79 Hydrocyanic acid 44, 45, 59 Hydro-phenoketone 85 Hydroquinone 62, 84 Hydroquinone ether , 53 Hydroxylamine derivatives 64-68, 71 lodoform ...... 5 lodo-propionic acid 37 Isobuty 1-acetic acid 34 Isobutyl-acetic ethyl ester 34 Isobutyric acid 20, 22 Isobutyric-isopropyl ester 22 Isohexane 22 Isohydrobenzoin 35, 36, 54 Isonitroso-acetone 1 1 Isopropyl alcohol 21, 22 Itaconic acid 28 Ketones 10, 54 Lactic acids 32, 36 Laurolene 41 Leukaniline 62 Maleic acid , , .30, 42 98 INDEX, PACK Malic acid 28, 33 Malonic acid 26, 34, 38, 42, 58, 84 Malonic ester 43 Mandelic acid 33, 35 1 36 Mannite 8, g Mannonic acid 8 Meconic acid , 78 Mercaptans c . .47, 53 Mesaconic acid , 28 Methane 3, 13 f 14 Methyl-acetic ester 18 Methyl-acrylic acid 40 Methylal 3 Methyl alcohol i, 2, 14, 33 Methylamine , , 78 Methyl-aniline 60, 61 Methyl-diphenylainine 61 Methylene-di-p-anhydro-benzyl alcohol 68 Methyl ether 15 Methyl-ethyl-piperyl-hydrazine 76 Methyl-formic ester 18 Methyl-glycolic acid. 33 Methyl-hydrocinnamic ester , 35 Methyl-malonic acid 38, 43 Methyl morphine 7g Methyl-piperyl-hydrazine 76 Methyl-sulphuric acid , -3, 47 Michler's ketone 54 Monobrom-acetone n Monobrom-benzene 53 Monochlor-acetic acid 19 Monochlor-acetone 10 Monoxy-anthraquinone 55 Morphine 78, 79 Naphthazarine 75 Naphthylamine. 60, 61 Naphthylamine violet ,..,,.,,, 60 INDEX. 99 Nitramines = 70, 72 Nitraniline 64, 73 Nitriles 46 Nitro-acetophenone 72 Nitro -aldehydes 56, 70, 71 Nitro-alkyl-anilines 70 Nitro- alkyl-toluidenes .. , 70 Nitro-arni no-benzyl -toluene. 65 Nitro -benzaldehydes 71, 74 Nitro-benzene 63, 64, 66, 67, 68 Nitro-benzene-sulphonic acid 64 Nitro- benzoic acids 64, 67, 73 Nitro-benzophenone 72 Nitro-benzyl alcohol 77 Nitro-benzylidene-aldehydo-phenyl-hydroxylamine 71 Nitro-carboxylic acids, esters of 7 Nitro compounds, oxidation of 76 Nit ro-compounds, reduction of 63 Nitro-ethane , . * 37 Nitro-groups 37, 65, 76 Nitro-hydrocarbons 72 Nitro-isophthalic acid 64 Nitro-ketones , 56, 71 Nitro-leuco-bodies 75 Nitro-naphthaiene-sulphonic acid 65 Nitro-phenol. 63, 73 Nitro-phenyl-tolylketone 72 Nitro-piperidines 76 Nitroso-aldehyde-copellidine ". 76 Nitroso-alkyl-anilines 70 Nitroso-alkyl-toluidenes, 70 Nitroso-groups k 76 Nitroso-pipecoline 76 Nitroso-piperidine * 76 Nitro-sulphon ic acids 70 Nitro-terephthalic acid 64 Nitro-toluenes 64, 65, 67, 69, 70, 77 1OO INDEX. PAGE Nitro-toluene-sulphone-amide 77 Nitro-toluene-sulphonic acid 74 Nitro-toluic acid 64 Nitroxylene 67 Nosophene 6 Octane 24 Octylene 17 CEnanthylic acid 24 Olefines 23 Oleic acid 17 Opium 78 Oxalic acid 8, 10, 12, 25, 42, 84, 85 Oxy-acids 35, 36 Oxy-anilines 70 Oxy-benzoic acids. 78 Oxy-butyric acids 32 Oxy-capronic acid 85 Oxy-carboxylic acids 78 Oxy-dimorphine sulphate 79 Oxy-isobuty ric acids . . . , 32 Oxy-pyrone-dicarboxylic acid 78 Phenol 51, 61, 84, 85 Phenol-sulphuric acid 84 Phenyl-acetic acid 58 Phenyl-chloramine , 67 Phenyl-disulphide 53 Phenylene-diamine 62, 63 Phenyl-ethylamine 47 Phenyl-glyceric acid 33 Phenyl-hydroxylamine 64, 66, 67, 68 Phenyl-lactic acid 33 Phenyl-mercaptan 53 Phenyl-sulphuric acid 85 Phenyltolylamine , 60 Phthalic acid 16, 42, 57 Picoline 75 Picric acid 52 INDEX. 10 1 PAGE Pipecoline 75. ?6 Piperidine 75, 76 Piperylhydrazines 76 Potassium cyanate 45 Potassium cyanide 45 Potassium ferricyanide 46 Potassium ferrocyanide 44 > 45 Potassium-isoamyl sulphate. 48 Potassium-trichlor-methyl sulphate 47 Potassium-trichlor- methyl sulphonate 48 Potassium xanthate 48 Propionic acid 20, 34, 36, 37 Propionic aldehyde 32 Propionic ethyl ester 34 Propio- nitrile 47 Propyl alcohol 4, 22 Propylamine 47 Propylene 20, 21, 22, 28 Propylene bromide 21, 22 Prussian blue 45, 46 Pyrazine II Pyridine 75 Pyrocatechin 84 Pyrotartaric acid. 27 Quinaldine 76 Quinine 79 Quinoline ...70, 76 Quinone 61, 62 Racemic acid 33 Resinous bodies , 7, 21, 32, 33, 52, 58 Rosaniline 62 Saccharic acid 8 Saccharic aldehyde 8 Saccharine 77 Safranine 62 Salicine 81 Salicvlic acid 81 102 INDEX. fAGR Salicylic aldehyde 81 Sebacfc acid 7, 38, 40 Sodium-diethyl-malonic ester 43 Sodium-isethionate 47 Sodium-methane-tricarboxylic ester 43 Sodium-nitro-prusside 46 Starch 9 Strychnine 80 Suberic acid 38 Succinic acid 26, 30, 34, 37, 38, 84, 85 Sugars 8 Sulpho-benzoic acid 57 Sulpho-compounds 47 Tannin 78 Tartaric acid 29, 32 Terpentine hydrochloride .... 80 Tetracetyl-ethane 1 1 , 43 Tetradecane , 17 Tetraethyl-succinic acid 39 Tetraethyl-thiuramdisulphide 49 Tetrahydro-quinaldine 76 Tetrahydro-quinoline 76 Tetra-iodo-phenol-phthalein 6 Tetramethyl-di-amido-benzophenone 54 Tetramethyl-succinic acid 38, 39 Tetraoxy-azo-benzene. . . 77 Tetraphenyl-erythrite 55 Theine 78 Thio-acetic acid 19 Thio-benzoic acid 57 Thiophene 49 Thymol , 6 Toluene-sulphone-amides 77 Toluic acids , 61 Toluidenes 60, 61, 69 Tolyl-hydroxylamines = 65 Tricarballylic ester. 34 INDEX. 103 PAGE Trichlor-acetic acid 19 Trichlor-methyl ester 19 Trioxy-anthraquinone 55 Trioxy-methy lene 6, 7, 8, 47 Triphenyl-methane dyes 75 Undecylenic acid 17 Unsaturated acids 17, 42 Unsaturated esters 39 Unsaturated hydrocarbons 17, 33, 42 Valeric acids 24, 48, 84, 85 Valeric butyl ester. ...; , 24 Valeric ethyl ester 34, Xanthogen supersulphide 48 SHORT-TITLE CATALOGUE OF THE PUBLICATIONS OF JOHN WILEY & SONS, NEW YORK, LONDON: CHAPMAN & HALL, LIMITED. 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Baldwin's Steam Heating for Buildings 12mo, 2 50 Benjamin's Wrinkles and Recipes 12mo, 2 00 Carpenter's Testing Machines and Methods of Testing Materials 8vo. Chordal's Letters to Mechanics 12mo, 2 00 Church's Mechanics of Engineering 8vo, 6 00 " Notes and Examples in Mechanics 8vo, 2 00 Crehore's Mechanics of the Girder 8vo, 5 00 Cromwell's Belts and Pulleys 12mo, 1 50 " Toothed Gearing 12mo, 1 50 Compton's First Lessons in Metal Working 12mo, 1 50 Dana's Elementary Mechanics 12mo, 1 50 Dingey's Machinery Pattern Making 12mo, 2 00 Dredge's Trans. Exhibits Building, World Exposition, 4to, half morocco, 10 00 Du Bois's Mechanics. Vol. I., Kinematics 8vo, 3 50 Vol. II.. Statics 8vo, 400 Vol. III., Kinetics 8vo, 350 Fitzgerald's Boston Machinist 18rno, 1 00 Flather's Dynamometers 12nio, 2 00 Rope Driving 12mo, 200 Hall's Car Lubrication 12mo, 1 00 Holly's Saw Filing 18mo, 75 Johnson's Theoretical Mechanics. An Elementary Treatise. (In the press.} Jones Machine Design. Part I. , Kinematics 8vo, 1 50 Part II., Strength and Proportion of Machine Parts. Lanza's Applied Mechanics 8vo, 7 50 MacCord's Kinematics 8vo, 5 00 Merriman's Mechanics of Materials 8vo, 4 00 Metcalfe's Cost of Manufactures 8vo, 5 00 Michie's Analytical Mechanics 8vo, 4 00 Mosely's Mechanical Engineering. (Mahan.) 8vo, 5 00 12 Ilichards's Compressed Air I2mo, $1 50 Robinson's Principles of Mechanism 8vo, 3 00 Smith's Press- working of Metals 8vo, 8 00 The Lathe and Its Uses 8vo, 6 00 Thurstou's Friction and Lost Work 8vo, 3 00 ' ' The Animal as a Machine 12mo, 1 00 Warren's Machine Construction 2 vols., 8vo, 7 50 Weisbach's Hydraulics and Hydraulic Motors. (Du Bois.)..8vo, 5 00 " Mechanics of Engineering. Vol. III., Part I., Sec. I. (Klein.) 8vo, 500 Weisbach's Mechanics of Engineering Vol. III., Part I., Sec. II (Klein.) 8vo, 500 Weisbach's Steam Engines. (Du Bois.) < 8vo, 500 Wood's Analytical Mechanics 8vo, 3 00 " Elementary Mechanics 12mo, 125 " " " Supplement and Key 125 METALLURGY. . IRON GOLD SILVER ALLOYS, ETC. Allen's Tables for Iron Analysis 8vo, 3 00 Egleston's Gold and Mercury 8vo, 7 50 " Metallurgy of Silver 8vo, 750 * Kerl's Metallurgy Copper and Iron 8vo, 15 00 * " Steel Fuel, etc 8vo, 1500 Kunhardt's Ore Dressing in Europe 8vo, 1 50 Metcalf's Steel A Manual for Steel Users 12mo, 2 00 O'Driscoll's Treatment of Gold Ores 8vo, 2 00 Tiiurston's Iron and Steel 8vo, 3 50 Alloys 8vo, 250 Wilson's Cyanide Processes 12mo, 1 50 MINERALOGY AND MINING. MINE ACCIDENTS VENTILATION ORE DRESSING, ETC. 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