872 ] Colouring-matters derived from Aromatic Azodiamines. 433 



We have finally analyzed the 



Picrate. — It is easily formed when the alcoholic mother-liquor of the 

 chlorhydric salt of azodiphenyl blue is precipitated by an alcoholic solution 

 of picric acid. The picrate is a blue powder perfectly insoluble in water 

 and ether, and only very slightly soluble in boiling alcohol. For analysis, 

 the precipitated salt was carefully washed with water and dried at 100° C. 

 Its composition is represented by the formula 



C„ H 18 N 7 = C 18 H M N 3> C H 3 (NO,), O. 



As has been already stated in the beginning of this note, the colouring- 

 matter which we call Azodiphenyl blue possesses exactly the same com- 

 position as violaniline, which MM. Girard, De Laire, and Chapoteaut have 

 prepared by oxidizing pure aniline, 



3C G H 7 N-3HH=C 18 H 13 N 3 . 



Are these two bodies identical ? We had hoped to be able to decide this 

 question by experiment ; our researches have, however, for the present 

 taken a different direction, so that the question remains an open one. 



If instead of an aniline salt the chlorhydrates of toluidine and naphthyl- 

 amine are allowed to act on azodiphenyldiamine, as might have been 

 expected, blue dyes with properties perfectly similar to those of azodiphenyl 

 blue are produced. It is extremely probable that these compounds are 

 respectively 



C„H„N, «ndC„H„N,. 

 These formulas must, however, still be established by analysis. 



The attempts here briefly sketched at producing new colouring-matters 

 were capable of expansion in another direction. Indeed, instead of sub- 

 mitting azodiphenyldiamine to the action of toluidine and naphthylamine, 

 the idea suggested itself of starting from azoditolyldiamine, which would 

 then be treated with aniline and naphthylamine salts. 



An azoditolyldiamine exactly corresponding to azodiphenyldiamine 

 remains as yet unknown. In all his experiments Dr. Martius, who, as he 

 informs us, has repeatedly attempted the preparation of this compound, 

 has invariably obtained only the isomeric body diazoamidotoluol, which 

 is decomposed on boiling. We have not been more fortunate in our efforts 

 to produce the true analogue of azodiphenyldiamine. On passing a 

 rapid current of nitrous acid through toluidine heated to fusion on a 

 saturated solution of common salt, the liquid base after some time solidifies 

 to a crystalline mass, which may be easily purified by washing with water 

 and recrystallizing from alcohol. In this way well-formed dark lemon- 

 coloured needles are obtained. The analysis of this body, dried in vacuo, 

 shows that it certainly possesses the composition 



C u H u N r 



However, on boiling this substance with chlorhydric acid, it is readily 

 decomposed to cressol and toluidine, giving off quantities of nitrogen, 

 O u H 15 N 3 + H 2 = C 7 1I 8 + C 7 H 3 N + 2N. 



