ANILINE 179 



decomposition of aniline, which have boon so ably investigated by Fritzscho, Zinin, 

 Hofmann, Gerhardt, and other chemists. 



Since this was written, the aniline dyes have received such an important develop- 

 ment, that it is necessary to give a more detailed description of these beautiful colours. 



It appears desirable that a Dictionary of the Arts should comprehend a succinct 

 history of the discovery of a body -which has performed so important a part in the 

 advancement of a special industry as Aniline has done. 



In 1826 Unverdorben, a German chemist, when exposing indigo to destructive 

 distillation, discovered an oily substance which formed crystalline compounds with 

 acids, to which he gave the name of Crystalline. Eunge, also a German, subsequently 

 observed in coal-tar oil a substance capable of forming saline compounds, and of 

 striking a violet-blue colour with chloride of lime. To this he gave the name of 

 Kyanol, blue oil. At a later period, Fritzsche, when investigating the action of 

 potash on indigo, obtained a quantity of a basic oil, which he analysed, and to which 

 he gave the name of Aniline. Zinin, about the same time, found that Nitrobenzol, 

 when submitted to the action of sulphuretted hydrogen, was converted into a peculiar 

 and, as he thought, a new substance, to which he gave the name of Benzidam (an 

 ammonia derived from Benzol). Hofmann was the first who submitted crystalline, 

 kyanol, aniline, and benzidam to careful experimental comparison, and proved them 

 to be identically the same substance, which now took its place in chemistry under 

 the name of aniline. 



In 1825 Michael Faraday, during an examination of the oily products separated 

 in the compressed oil-gas holders then largely used discovered Benzol, which he 

 then described as a bicarburetted hydrogen. On this important discovery, Dr. 

 Hofmann remarks : ' In this investigation, as indeed throughout the whole series of 

 his immortal researches, Faraday's object was the elaboration of truth for its own 

 intrinsic value and beauty ; and in the same spirit has the work been continued by 

 those, who, after Faraday, engaged in the further scientific examination of this subject. 

 Nobody in those early days of benzol, when the substance simply existed as a 

 laboratory curiosity, dreamed of the brilliant career looming in the distance for this 

 body, nor of the marvellous transformation it was destined to undergo. But the 

 experience of the last few years in this matter has only corroborated the old axiom, 

 which cannot be too often repeated, that the search after the true, for its own sake, 

 leads on to the discovery of its natural corollaries, the useful and the beautiful. For 

 those, indeed, lie folded up in truth, to be in due time evolved therefrom, even as the 

 great tree unfolds itself from out the little seed.' 



Mitscherlich, some years later, found that benzoic acid, distilled with caustic 

 potash, gave a colourless volatile liquid, identical with the hydrocarbon discovered by 

 Faraday ; and hence the name this substance now retains Benzol. Dr. Hofmann, 

 in 1845, proved the presence of benzol in coal-tar oil, and in 1848 Mansfield showed 

 that an inexhaustible quantity of it could be procured from that source. See 

 BENZOL. 



Now, the crude tar of the gas-works is subjected to regulated distillation. Thus is 

 obtained separately naphtha or light oil (oily liquid lighter than water), and then dead, 

 oil or heavy oil (oily liquid heavier than water), and finally remaining in the retort 



S'tch. From the light oil, benzol is separated by further fractional distillation, 

 itscherlich showed, if this benzol is dissolved in fuming nitric acid, and the clear 

 liquid mixed with water, a compound (nitrobenzol) is precipitated as a dense yellow 

 liquid. This is the well-known artificial oil of bitter almonds, which is now prepared 

 easily and economically on a large scale. It was Zinin, already named, who dis- 

 covered that sulphuretted hydrogen converted this nitrobenzol into aniline, and who, 

 believing the substance thus produced to be a new one, described it under the name of 

 benzidam, or an ammonia derived from benzol. (See NITBOBENZOL.) 

 The successive changes of benzol are thus expressed in chemical symbols. 



First change. 

 Transformation of benzol into nitrobenzol. 



C"H + HNO> = C'H'NO" + H 2 



Benzol. Nitric Nitrobenzol. Water* 

 Acid. 



Second change^ 

 Transformation of nitrobenzol into aniline. 



C 6 H S NO* + 3H a S ~ C'H'N + 2H 4 + 3S 



Nitro- Sulphuretted Aniline. Water. Sulphur 

 benzol. Hydrogen. 



Xi 



