On the Colouring Matters produced from Aniline. 547 



" Letter to the Council from Sir George Everest, C.B., on the 

 Expediency of re-examining the Southern Portion of the Great Indian 

 Arc of the Meridian ; and Report of a Committee thereupon." 



March 6. — Major- General Sabine, President, in the Chair. 



" On the Colouring Matters produced from Aniline." By A. W. 

 Hofmann, Ph.D, LL.D, F.R.S. &c. 



In a note on the Action of Tetrachloride of Carbon on Aniline 

 submitted to the Royal Society on the 1 7th of June, 1858, I have 

 described a crystalline basic derivative of aniline formed by the 

 coalescence of three molecules of ammonia, viz. carbotriphenyltri- 



amine, 



rjiv 



C 19 H 17 N 3 =(C 6 H 5 ) 3 

 EL 



r ^3» 



the formation of which is accompanied by that of a coloufing matter 

 of a magnificent crimson colour. 



It may be useful to quote here the passage * of the paper referred 

 to, in which the formation of the colouring matter is mentioned. 

 "On submitting a mixture of 3-^- parts by weight of aniline and 

 1 part of bichloride of carbon, both in the anhydrous state, for 

 about thirty hours to a temperature of 170° C, the liquid will be 

 found to be converted into a black mass, either soft and viscid, or 

 hard and brittle, according to time and temperature. 



" This black mass, which adheres firmly to the tubes in which the 

 reaction has been accomplished, is a mixture of several bodies. On 

 exhausting with water, a portion dissolves, while a more or less solid 

 resin remains behind. 



" The aqueous solution yields, on addition of potassa, an oily preci- 

 pitate containing a considerable portion of unchanged aniline ; on 

 boiling this precipitate with dilute potassa in a retort, the aniline 

 distils over, whilst a viscid oil remains behind, which gradually 

 solidifies with a crystalline structure. Washing with cold alcohol 

 and two or three crystallizations from boiling alcohol render this 

 body perfectly white and pure, a very soluble substance of a magni- 

 ficent crimson colour remaining in solution. 



" The portion of the black mass which is insoluble in water dis- 

 solves almost entirely in dilute hydrochloric acid, from which it is 

 reprecipitated by the alkalies in the form of an amorphous pink or 

 dingy precipitate soluble in alcohol with a rich crimson colour. The 

 greater portion of this body consists of the same colouring principle 

 which accompanies the white crystalline substance." 



The action of tetrachloride of carbon on aniline yields only a com- 

 paratively small quantity of the crimson pigment ; the temperature 

 of the exposure, and the relative proportions in which the two sub- 

 stances act upon one another, have the greatest influence upon the 

 results of the reaction. The white crystalline base, and the base 

 dissolving with a crimson colour, are by no means the only products ; 



* Proceedings of the Royal Society, vol. ix. p. 284. 



20 2 



