1872.] On Colouring -matters derived from Aromatic Azodiamines. 431 



IV. " Colouring-matters derived from Aromatic* Azodiamines." By 

 A. W. Hofmann, Ph.D., F.R.S., and A. Geygsb, Ph.D. Re- 

 ceived June 12, 1872. 



I. Azodiphenyl Blue. 



About three years ago one of us* laid before the German Chemical 

 Society the results of some experiments on the naphthaline dye commerci- 

 ally called Magdala Red. These experiments showed that the dye in ques- 

 tion represents three molecules of naphthylamine which have lost three mo- 

 lecules of hydrogen, and that it is formed by the action of naphthylamine 

 on azodinaphthyldiamine with separation of one molecule of ammonia. 



C 20 H 1S N 3 + C, H 9 N = C M H 21 N, + H 3 N. 



Azodinaphthyldiamine. Naphtbylamine. Naphthaline red. 



The idea occurred to us of studying this reaction in other series and in 

 other combinations. Preliminary experiments showed at once that aniline, 

 as well as toluidine salts, readily act on azodinaphthyldiamine, forming per- 

 fectly similar red colouring-matters ; and the question finally presented 

 itself, whether to this group of dyes might not belong also the blue body 

 which MM. Martius and Griessf produced by treating azodiphenyldia- 

 mine with salts of aniline, as mentioned in their interesting paper on Amido- 

 diphenylimide, but which has not as yet been more minutely investigated. 



The solution of this question by experiment appeared all the more de- 

 sirable, since the composition of a compound likely thus to be formed 

 would in all probability coincide with that of violaniline which MM. 

 Girard, De Laire, and Chapoteaut^: obtained by the oxidation of pure ani- 

 line. We have perfoimed these experiments. 



For the preparation of the blue colouring-matter derived from azodi- 

 phenyldiamine, which, for the sake of shortness, we will call azodiphenyl 

 blue, equal weights of the pure azo base and aniline chlorhydrate with 

 twice the weight of alcohol were heated in hermetically sealed tubes to 

 1G0° C. for four or five hours. After the lapse of this time a dark blue 

 pasty mass had been formed ; no gaseous compounds were produced in the 

 reaction. For the purpose of purification, the crude product, which was 

 at once recognized to be a chlorhydrate, was treated with boiling water 

 in order to remove unaltered aniline salt and sal-ammoniac formed in 

 the process ; it was then dissolved in alcohol with addition of chlor- 

 hydric acid, and precipitated by soda. The base thus separated was 

 carefully washed with water to free it from soda, and then dissolved in 

 boiling alcohol ; the liquid was then mixed with chlorhydric acid and sub- 

 mitted to distillation. As soon as half the alcohol had passed over, a dark 



* Hofmarm, 'Berichte,' 1869, pp. 374, 412. 



t Monatsbcrichte dor rcrliner Akadcinie, 18G5, p. G10. 



\ Comp. Rend. torn, lxiii. p. 964. 



