ACTION OF NITRIC ACID ON INDIGO. 353 



The most abundant had the appearance of a resin. The 

 other was of an orange-colour, and disseminated in this in 

 the form of clots. These were both separated from the li- 

 quid, washed with cold water, and then boiled. The resin- 

 ous matter congealed on cooling; and the orange-coloured 

 substance, after having dissolved, fell to the bottom in small 

 grains, which did not adhere to each other. 



11. The water, that had been employed to separate these The liquid 

 two substances, was added to the liquor (10) left in the'^'^''^^'^'^- 

 retort, and then distilled. INitric acid, prussic acid, amer. Products. 

 and a little ammonia, passed into the receiver. The con- Yielded crystals 

 centrated liquor on cooling let fall crystals formed of the »( ^mer and aa 

 amer of Welther, and of the benzoic acid of Messrs. 

 Fourcroy and Vauquelin. Having dissolved these in hot 



water, I obtained by cooling the crystallized acid^ retaining 

 a little amer; and by evaporating the liquid fine yellow scales 

 of amer. 



12. The liquid, which had furnished the crystals (11) of ^^^ oil from 

 amer and acid, after boiling down let fall a red liquid *m6- water. 

 stance resembling a fat oil. 



13. The supernatant liquor (12) was evaporated to dry- More of this, 

 ness, and hot water poured on the residuum. Oxalate o/,^"'' oxalate of 

 lime was left undissolved ; and the water, on cooling, let 



fall some oily matter, and afterward a yellow sediment, 

 toMchoC as pretty soft, and differed from the oily matter only 

 in the proportion of its principles. 



14. I shall now proceed to examine, 1st the amer; 2d,Theproducte 

 the acid substance, which has been compared to benzoic ^*™"^ 



-acid; 3d, the resin. The other products being only com- 

 pounds of these three, I shall not speak of them under se- 

 parate heads; but I intend in a future paper to return to 

 the substance of an oily appearance, 



§ III. Art 1. Of the Amer. 



15. The scales of amer, which I mentioned (11), re- The amer im- 

 tained a little resin, whence they derived a deep yellow ^"^^' 

 colour; and a small quantity of the acid, which has been 



called the benzoic, but which I shall designate under the 

 name of volatile acid, 

 SuppLEMENT.—VoL. XXX. A a AVhen 



