Dr. Hofmann on the Metamorphoses of Indigo. 503 



I endeavoured to prepare dichlorisatine by dissolving isa- 

 tine or chlorisatine in potash and passing a stream of chlorine 

 gas through the solution of isatinate or chlorisatinate of potash. 

 The result was however unfavourable. No dichlorisatine was 

 formed, but in its stead a tarry matter, which floated on the 

 surface of the fluid; it was insoluble in water but soluble in 

 alcohol. I was equally unsuccessful in dissolving chlorisatine in 

 nitric acid and addingto the solution afew drops of hydrochloric 

 acid. A violent reaction ensued, and the decomposition had 

 evidently proceeded too far. There remained, therefore, only 

 to fall back upon the method employed by Erdmann to pre- 

 pare this substance, and of which Laurent had also made use 

 in his investigation. It consists in treating indigo directly 

 with chlorine. In this process, under every circumstance, 

 there is formed a mixture of chlorisatine and dichlorisatine, 

 the quantity of the latter, according to Erdmann, greatly pre- 

 ponderating. Chlorisatine and dichlorisatine can only be 

 separated from each other by crystallization with extreme dif- 

 ficulty. The amount I had obtained was too small to think 

 of trying to separate them in this way ; I therefore at once 

 submitted the mixture with hydrate of potash to distillation. 



The distilled product contained, besides chloraniline, another 

 basic substance, collecting on the surface of the fluid, which 

 crystallized in long prisms. This substance was manifestly 



nothing but dichlorisatine, Cjg^ pi^ ^N. The crystals which 



could be picked out of the fluid unfortunately were not suf- 

 ficient in amount for a combustion. As I have, however, 

 more completely studied the corresponding bromine com- 

 pound, which is much more easily prepared, I considered it 

 useless to occupy myself longer with this substance. 



C. Trichloraniline [Amachlophenose). Cjg < r^^ > N. 



Isatine, in which 3 equivalents of hydrogen are replaced by 

 three of chlorine, is as yet not known. The preparation of 

 trichloraniline could not hence be made by persevering in the 

 method hitherto used. It is however procured, as above men- 

 tioned, by the direct action of chlorine on aniline or the chlo- 

 rinated base. 



By submitting to distillation with hydrate of potash the 

 crude product of the action of chlorine on these two bodies, 

 which contains a mixture of chlorophenissic acid and trichlor- 

 aniline, the first remains in the retort in combination with 

 potash, while the latter passes over into the receiver with the 

 watery vapour, and collects on the surface of the liquid in 



