432 



Messrs. A. W, Hofmann and A. Geyger on [June 20, 



blue and slightly crystalline salt was found to be deposited on cooling. 

 This salt is insoluble in water, but readily dissolves in alcohol, especially 

 when heated. The solution is of a deep violet-blue colour, which is fixed 

 by wool and silk, but cannot possibly be compared to the tints of the 

 substituted rosanilines for brilliancy or beauty. The blue chlorhydrate is 

 perfectly insoluble in ether. When soda is added to the concentrated 

 alcoholic solution of the salt, the base is separated as a dark-brown powder 

 which is insoluble in water, but dissolves in alcohol and ether with a red- 

 brown colour. On addition of chlorhydric acid, the alcoholic solution as- 

 sumes a pure blue tint ; the ethereal solution, on the other hand, becomes 

 perfectly colourless, the blue salt being precipitated. Treated with gra- 

 nulated zinc in presence of alcohol and chlorhydric acid, the solution of 

 the salt is decolorized, but becomes blue again on exposure to the air. An 

 attempt to prepare a leuko base in this manner failed ; nor was an experi- 

 ment made with ammonium sulphide more successful. 



Analysis of the chlorhydrate just described, as well as of some other 

 salts derived from it, showed that the reaction between azodiphenyldiamine 

 and aniline indeed takes place, exactly as our knowledge of the analogous 

 experiment in the naphthaline series had led us to expect. In forming the 

 blue body one molecule of azodiphenyldiamine and one molecule of 

 aniliue unite with separation of one molecule of ammonia, 



C 12 H n N 3 + C 6 H 7 N = C 1? H 15 N, + H 3 N. 



Azodiplienyldiarnine. Azodipkenyl blue. 



Chlorhydrate. — This salt, the preparation of which we have described, 

 has been repeatedly examined. Analyses of the compound dried at 100° C. 

 led to the formula 



C 13 H 15 N S ,HC1. 



The salts of azodiphenyl blue show but little stability. The chlorhy- 

 drate just mentioned loses a portion of its acid even by recrystallization 

 from alcohol. The salt with 11*28 per cent, chlorine, after a single re- 

 crystallization from alcohol, contained only 9*85 per cent. In fact the 

 normal salt cannot be obtained except in presence of an excess of chlorhy- 

 dric acid. When we tried to purify the crude product of the reaction by 

 washing out the soluble salts and reerystallizing it without addition of acid, 

 the percentage of chlorine fell in one case to 5*9, and in another even as 

 low as 2*1 per cent. By merely drying at a higher temperature, the salt 

 loses a portion of its acid. The normal salt, which for a considerable time 

 had been dried at a temperature of 150° C, had lost nearly all its acid. 



lodhydrate. — This salt is obtained like the chlorhydrate, viz. by treat- 

 ing the free base with iodhydric acid. In its properties ; t scarcely differs 

 from the chlorhydric salt. To establish the formula, we navt limited our- 

 selves to an estimation of the iodine in the salt dried at 100° C. The for- 

 mula of the compound is 



C 18 H 15 N 35 HI. 



