360 



ACTION OF NITRIC ACID ON INDIGO. 



Properties of 

 this substance. 



Decomposed 

 by heat. 



Gaseous pro- 

 ducts. 



The acid more 

 soluble in hot 

 water than in 

 cold. 



Nitric acid con- 

 verted it into 

 amer. 



It is soluble in 

 solution of 

 potash. 



The compound 

 decomposed by 



heat. 



deposited, which were tinged yellow by a little resin ; and 

 afterward a substance of an oily appearance^ which was 

 composed of volatile acid, amer and resin. 



26. The crystals of volatile alkali have a taste slightly 

 acid, bitter, and astringent. 



Thrown on redhot iron, one part is volatilized, another 

 is decomposed, and leaves a coal that fuses. 



They may be sublimed in white needles, by heating them 

 gently in a phial. 



Heated in the glass ball already described (16), they 

 melt; part is volatilized into the jar; and what remains in 

 the ball grows black, and leaves a bulky coal, which is 

 slightly fusible. Much less gas is formed than in the deto- 

 nation of amer. 



The gasses produced in this experiment have an em- 

 pyreumatjc vegetable smell. Distilled water absorbs more 

 than three fourths, and then appears to contain nothing 

 but carbonic acid, except the undecomposed portion of the 

 volatile acid. I could not obtain any prussic acid from it 

 by distillation. The gaseous residuum insoluble in water 

 and potash consists of nitrogen. I had not enough to de- 

 termine, whether it contained any hidrogen. 



27. The volatile acid is far more soluble in hot water than 

 in cold. The solution has a very slight yellow colour. It 

 reddens litmus paper. It does not precipitate gelatine like 

 amer ; atrd differs from it in giving a fine red to all the salts 

 of iron at a maximum, but it does not change the colour of 

 the salts at a minimum. 



28. Nitric acid at 40° [sp. gr. 1 386] boiled on the vo- 

 latile acid converted it into Welther's amer. Muriatic acid 

 appeared to have no action on it. 



29. The volatile acid dissolves very well in solution of 

 potash; or in its carbonate, if assisted by heat, and car- 

 bonic acid is evolved. On boiling down this solution, which 

 is of an orange colour, small red acicular crystals are form- 

 ed. These are^much more soluble in water than the com- 

 pound of amer and potassium, are much less bitter, and do 

 not detonate, but swell when placed on a redhot iron. On 

 exposing them to the action of heat in the glass ball, first a 

 yellow vapour was disengaged, after which they melted, 



-without 



