22 Dr. Hofmann on the true Composition of Chlorindatmit. 



Erdmann did not look for nitrogen in chlorindatmit as he 

 had found none in chlorindoptene. Did chlorindoptene consist 

 of equal equivalents of chlorindoptenic acid and chlorindatmit, 

 such a compound (assuming chlorindatmit to be an azotized 

 body) would contain 3'61 percent, nitrogen, a quantity which 

 could not have been overlooked. It is, however, not com- 

 posed of a like quantity of each element, but the chlorindop- 

 tenic acid predominates very much, so that the amount of 

 nitrogen is much reduced, and may be easily overlooked. On 

 the other hand, the proportion of carbon and hydrogen cannot 

 essentially alter, as chlorindoptenic acid and chlorindatmit 

 contain nearly equal quantities. 



To determine this question by experiment, I treated with 

 chlorine, according to Erdmann's method, a quarter of a 

 pound of reduced and again oxidized indigo suspended in 

 water. Although the operation was conducted in sunshine, 

 yet it was only after three or four days that the indigo was 

 converted into the brownish-yellow body. The whole mass, 

 together with the fluid, was poured into a retort and distilled 

 over an open fire. In the receiver a yellow crystalline sub- 

 stance condensed and swam on the surface of the water, which 

 had also passed over and contained hydrochloric acid. The 

 distilled product was saturated with potash ley, which com- 

 municates a dark colour to the fluid from the solution of a 

 portion of the crystals, and the whole was again submitted to 

 distillation. By gently warming the retort, a vapour was 

 evolved which condensed in the neck in the form of fine white 

 crystals like hairs, about an inch long, which, on bringing 

 the fluid to the boiling-point, passed over with the watery 

 vapours as an oil and again crystallized in the receiver. The 

 crystals were separated by filtration and dried. The investi- 

 gation was confined to the single question, whether chlorin- 

 datmit so prepared contained nitrogen or not? 



On passing the vapour of chlorindatmit over fused potas- 

 sium a large quantity of cyanide of potassium was formed, 

 which evolved freely hydrocyanic acid on the addition of an 

 acid. A mixture of a proto- and persalt of iron produced a 

 gray-brown precipitate, which assumed the pure colour of 

 Berlin blue by the addition of a little hydrochloric acid. 

 Further, on heating with the soda-lime mixture a quantity of 

 ammonia was given off". Chlorindatmit therefore contains 

 nitrogen. 



From the preceding facts several conclusions may be 

 drawn. 



1st. The body produced by the action of chlorine on ani- 



