1864.] 



Colouring -matters derived from Coal-tar, 



345 



crystals. The chloride, when washed with tvater, loses every trace of 

 hydrochloric acid. 



The analysis of the base has led to the formula 



The composition of the chloride, which crystallizes from alcohol in 

 concentrically grouped needles, assuming a bluish tint by contact with the 

 air, is 



C,,H,,N, HCl. 



I do not believe that I am deceived in considering this compound as 

 diphenylamine, 



CeH 



H 



It deserves, however, to be stated that the strict experimental demon- 

 stration of this mode of viewing the compound is still wanting, the ethyla- 

 tion of the substance presenting difficulties that I have not yet been able to 

 overcome. I regret this gap, since the experience acquired in the study of 

 xenylamine, isomeric with diphenylamine, 



H J H 



and which for several weeks I regarded as the secondary phenyl-base, 

 points out the necessity of consistently carrying out the process of ethyla- 

 tion in the examination of bases of this kind. 



Diphenylamine exhibits a peculiar reaction, which, while it appears to 

 reveal its relation to the colour-generating aniline, enables us to recognize 

 the presence of the new base. In contact with concentrated nitric acid, 

 diphenylamine, as well as its salts, assumes at once a magnificent blue 

 coloration. The reaction succeeds best by pouring concentrated hydro- 

 chloric acid upon a crystal of the base, and then adding the nitric acid drop 

 by drop. Immediately the whole liquid becomes intensely indigo-blue. 

 Minute quantities of diphenylamine may in this manner be readily traced. 

 I have thus been enabled to ascertain the presence of this body, or, at all 

 events, of a substance exhibiting this particular reaction, in the products 

 of distillation of rosaniline, leucaniline, and even of melaniline. The last 

 experiment deserves particularly to be noticed, since it affords the general 

 method for the production of the secondary aromatic monamines, which 

 was hitherto wanting. 



The substance possessing the blue colour is formed also by the action of 

 other oxidizing agents. On adding chloride of platinum to a solution of 

 •the chloride, the liquid at once assumes a deep-blue colour. Only, from 



