Dr. Hofmann on the Metamorphoses of Indigo. 389 



desired compound would likewise be crystalline, by which the 

 investigation would be rendered essentially easier. 1 resolved 

 therefore to make my experiments in this direction. 



Action of Chlorine on Aniline. 



I began by carefully repeating ray earlier experiments, but 

 obtained exactly the same results. 



As the action of chlorine on aniline immediately forms 

 hydrochloric acid, I chose a solution of the base in this acid, 

 and passed through it slowly a stream of the chlorine. After 

 a few moments the fluid became violet, thickened and depo- 

 sited a brown resinous matter, which fell to the bottom of the 

 vessel. On submitting the whole fluid to distillation, a cry- 

 stalline substance was deposited in the neck of the retort in 

 the form of white needles, consisting of a mixture of two dif- 

 ferent bodies, which are easily separated by a second distil- 

 lation with potash; an indifferent crystalline substance passes 

 over, of which I shall immediately speak, and chlorophenissate 

 of potash remains in the retort. The resinous matter sub- 

 mitted alone to distillation gave likewise a large quantity of 

 chlorophenissic acid. 



In no case could I obtain any other results than the above, 

 however much I modified my experiments by employing a 

 more or less diluted solution, and substituting a watery solu- 

 tion of chlorine instead of the gas. I soon found that the de- 

 sired end could not be attained in this direct way, and had 

 consequently to have recourse to an indirect method. 



Aniline, originally discovered by Unverdorben* among the 

 products of distillation of indigo, was afterwards produced by 

 Fritzschef on submitting anthranilic acid to the same pro- 

 cess, and by ZininJ through the action of sulphuretted hy- 

 drogen on nitrobenzid. The idea occurred to me to try the 

 action of chlorine on anthranilic acid, and should it so happen 

 that in this way out of the anthranilic acid 0,4 H^ NO4 by the 



substitution of chlorine, a compound, C14 ■< n/"** ^^04^, 



could be obtained possessing the properties of anthranilic 

 acid, it was highly probable that by its distillation the desired 

 base would be obtained. It was also probable that by the ac- 

 tion of chlorine on nitrobenzide, C12 H5 NO4, it would like- 



* Poggend. Jnn., Bd. viii. S. 397. 



f Bui. Scient. de St. Petersb., t. vii. No. 12, and t. viii., and Liebig's Jnn., 

 Bd. xxxvi. p. 87. 



X Bui. Scient. de St. Petersb., t. x. No. 18, and Liebig's Ann., Bd. xliv. 

 p. 283. 



§ n = 1 or 2. 



