558 ACTION or NITRIC ACID ON INDIGO. 



we find, that combustion docs not take place, till the char- 

 coal is predominant. 



This confirms This fact appears to confirm the existence of nitric acid 



the opiaion of . , ., .i_ . ji • -e -i 



forming ache- *" amer ; because it seems, that the oxigen, if it were com- 



mical union bined directly with the carbon, hidrogen, and nitrogen, 

 *^ * ■ would attack the hidrogen, as soon as the combination be- 



tween the principles of the amer was loosened by heat, 

 rather than remain attached to the carbon, waiting till the 

 temperature of the latter was sufficiently raised, to admit 

 its combining M'ith it*. On the hypothesis, that amer is a 

 compound of nitric acid with a combustible formed of hi- 

 drogen and carbon f, we can better understand what passes, 

 on heating it gently. In this case, part of the hidrogen, a 

 little carburetted, is evolved at a temperature too low to 

 separate ihe, principles of the nitric acid, so that the nitric 

 acid, when it has reached the temperature at which tliis 

 separation is effected, acts on a combustible, that has al- 

 ready lost a part of its hidrogen, and consequently finds it- 

 self more carburetted than it was before. 

 The detonating The detonation of amer ought to be loud, because it 

 powerof amer contains oxigen enough to saturate the greater part of its 

 combustible elements, and form gaseous compounds with 

 them : but, as it is volatile, it follows, that one portion 

 escapes combustion ; and that this takes place successively, 

 increased hy a because the heat is not uniform. Thus we can account for 

 fixed alltah, (]^g effect produced by an alkaline base, when it is com- 

 bined with amer, and when this compound is made to de- 

 tonate. In this case, the amer, being rendered more fixed, 

 becomes much more detonating ; because, as the heat is 

 allowed to accumulate, its elements separate simultaneously, 

 and still more and thus produce a more forcible detonation. This is the 

 by a rtietallic ^g^y jj^ which Messrs. Fourcroy and Vauquelin view the 

 action of the base ; and in proof of its truth it is to be 

 observed, that the detonation is in general so much the 

 stronger, in proportion as the base, with which the amer is 



* It is well known, that, in almost all cases, where hidrogen 

 united with other combustible substances is present with oxigen, 

 the oxigen attacks the hidrogen preferably to the others. 



t Containing perhaps a little oxigen and nitrogen. 



combined^ 



