digests nitrobenzole with a solution of arsenious acid in a strong lye of caustic soda; places the arsenical solution in a tubulated retort, heats it to the boiling point, and then allows the nitrobenzole to fall in, drop by drop. Under these circumstances, nitrobenzole is transformed into aniline, which distils over; and it is only necessary to saturate with an alcoholic solution of oxalic acid to obtain perfectly pure oxalate of aniline. 4. Reduction by protosalts of iron.-Sulphate, oxalate, and protochloride of iron have no sensible action upon these nitro compounds; but an iron salt, with a weak acid, the protoacetate, for example, is quickly acted upon. No gas is evolved. Sesquioxide of iron is precipitated, partly in the state of basic acetate, and the organic base is formed. Béchamp was the discoverer of this method of forming the artificial organic bases from the nitrocompounds. To prepare aniline by this method, nitrobenzole is poured into a solution of protoacetate of iron; the latter is almost immediately reduced, an evident sign of the oxidation of the protoxide of iron. If the vessel containing the mixture be placed in a bath heated to 212° F., a yellow ochreous deposit is soon formed, and no gas is evolved. If the solution of acetate of iron contains twelve equivalents of that metal to every equivalent of nitrobenzole, the aromatic odour of the nitrated compound disappears, and gives place to the peculiar odour of acetate of aniline. The following is the reaction which takes place: C.H.NO, +6 (Fe}0) + HO=C.H,N+3 (Fe 0,) HS As this process is not so advantageous as the following, we shall not describe it further. Béchamp ascertained that by distilling a mixture of nitrobenzole, iron filings, and acetic acid, aniline is formed, in accordance with the following equation : C. H, NO,+0+ 4 Fe = H Fel O, + C, H, N FeS He places in a large retort 1 part of nitrobenzole, 1-2 parts of bright iron filings, and 1 part of concentrated commercial acetic acid, free from mineral acid. The quantity of acetic acid should be sufficient to cover the iron filings completely. The reaction soon commences, without the aid of heat; it becomes exceedingly brisk, the temperature rises, the liquid begins to boil, and all will be lost if the receiver be not well cooled. The results of the reaction are, aniline, acetate of aniline, and a little nitrobenzole, which escapes the reaction. When the retort is cooled, the contents of the receiver are poured into it. Heat is then applied to the apparatus, and the whole is distilled to dryness. An excess of a solution of caustic potash is added to the distillate, when the hydrated aniline separates and rises to the surface, and may be removed and dehydrated in the usual manner. The residue of the mixture of iron filings, acetic acid, and nitrobenzole, which remains in the retort after the distillation, still contains a considerable amount of aniline. To obtain this, the retort must be washed out with water acidulated with sulphuric or hydrochloric acid, the solution filtered, and then evaporated to dryness. The dry residue is then mixed with quicklime, and placed in a retort of iron or refractory ware, and distilled; the aniline thus obtained must be rectified.* APPENDIX K. 990. Separation of the three ethyl-ammonias.-Although the differences between the boiling points of the three ammonias is considerable,— Ethylamine Diethylamine Boiling point. 18° C 57.5° Triethylamine 91° they cannot be separated by fractional distillation. Hofmann found that even after ten fractional distillations the bases were far from being pure. Hofmann has lately discovered a simple and elegant process by which the three ethyl bases may be easily and perfectly separated. This process consists in submitting Kopp "On the Preparation of Artificial Colouring Matters."- Chemical News, vol. ii. And Béchamp "On the Action of Protosalts of Iron on Nitronaphthaline and Nitrobenzole."—Chemical Gazette, vol. xiii., 1855. the anhydrous mixture of the three bases to the action of anhydrous oxalate of ethyl. By this treatment, ethylamine is converted into diethyl-oxamide, a beautifully crystalline body, very difficultly soluble in water; diethylamine into diethyl-oxamate of ethyl, a liquid boiling at a very high temperature; whilst triethylamine is not affected by oxalic ether. By the action of oxalic ether upon ethylamine, two substances may be formed, viz., ethyloxamate of ethyl, and diethyloxamide. In practice it appears that the second of these compounds only is produced. In the action of oxalate of ethyl upon diethylamine, two similar phases may be distinguished, capable of producing, respectively, (1) Diethyloxamate of ethyl,[(C2 O2)" (C2 H;)}0], and (2) Tetrethyloxamide (C2 O2)* In practice the first of these two compounds only is generated. The action of oxalate of ethyl upon triethylamine might have involved the formation of the secondary oxalate of tetrethylammonium. under the circumstances under which I have worked, the two substances do not combine. The product of the reaction of oxalate of ethyl upon the mixture of the ethyl bases, when distilled in the water-bath, yields triethylamine free from ethylamine and diethylamine. The residue in the retort solidifies, on cooling, into a fibrous mass of crystals of diethyloxamide, which are soaked with an oily liquid. They are drained from the oil and recrystallized from boiling water. Distilled with potassa, these crystals furnish ethylamine free from diethylamine and triethylamine. The oily liquid is cooled to 0°C., when a few more of the crystals are deposited; it is then submitted to distillation. The boiling point rapidly rises to 260°. What distils at that temperature is pure diethyloxamate of ethyl, from which, by distillation with potassa, diethylamine, free from ethylamine and triethylamine, may be obtained.* · Since the time that Dr. Hofmann communicated the above report to the Royal Society, on the separation of the three bases, he has added the following as a note to another paper: The separation of the ethyl-bases has been since repeatedly carried out. The process, as described in the Proceedings,' admits of a slight improvement. I proposed to separate the mixture of diethyloxamide and diethyloxamate of ethyl by filtration, and to purify the former by recrystallization from boiling water, the latter by exposure to a temperature of 0°. The separation is simpler and more perfect by submitting the mixture at once to the action of boiling water, when diethyloxamide dissolves, the diethyloxamate of ethyl remaining as an insoluble layer floating upon the hot solution, from which it may be separated by a tap-funnel."+ This method can also be adopted for the separation of the methyl-ammonias. (See "Compt-Rendus," tom. lv., 1862, page 749). AMIDES. 991. "By this term chemists have designated a very large class of substances derived from ammonia by substituting, for the hydrogen, acid radicals whose presence destroys the fundamental character of ammonia, viz., its power of combining with acids. The amides have * Dr. Hofmann "On the Separation of the Ethyl-Bases.”—Proceedings of the Royal Society, vol. xi., No. 42. "Action of Chloracetic Ether on Triethylamine and Triethylphosphine," by Dr. Hofmann.-Proceedings of the Royal Society, vol. xi., No. 48. been often defined as neutral derivatives of ammonia, similar in constitution to the amines; but the division of the ammonia-derivatives into amines and amides, is essentially artificial; there is, in fact, a gradual transition from one group to the other, and frequently we meet with substances, the position of which in the system is uncertain. The saline compounds of many amines are so extremely weak that they are decomposed by mere contact with water. On the other hand, recent researches have proved that in several substances long considered as well-established amides, the basic character of the mothercompound is far from being extinct, and that, under special circumstances, combinations with acids may be formed, in many respects analogous to the ammoniumsalts, but of comparatively little stability. A much more characteristic mark of distinction between the amines and amides is furnished in the deportment of the two classes under the influence of decomposing agents. As yet very few processes are known in which the amines yield up, in any form, the radicals whose introduction into ammonia has produced them. The amides, on the other hand, are readily decomposed into ammonia and the hydrated oxides of their radicals. The simplest manner of distinguishing an amine from an amide, consists in boiling the compound under examination with potash, when the amine remains unaltered, the amide evolving ammonia with formation of a potassium salt. 992. "With very few exceptions, the amides are artificial compounds. Some of the processes which give rise to their formation are of very general applicability, so as to admit of the production of an almost unlimited number and variety of these substances." MONAMIDES. 993. The amides derived from one molecule of ammonia are designated by this term; they are subdivided, like the monamines, into three classes, according to the number of the hydrogen equivalents of ammonia which are replaced, thus: Primary monamides. Secondary monamides. Tertiary monamides. HN BN BN |