ACTION OF NITRIC ACID ON INDIGO S61 



without emitting much light. An alkaline coal remained, 

 retaining carbonic acid and prussic acid. There was also a 

 little undcomposed volatile acid. 



The gaseous product consisted in great part of carbonic Caseous pro- 

 acid and nitrogen. ^^""^^ 



30. Lime, barytes, or strontian water, gives the solu- The acid com- 

 tion of volatile acid a fine yellow colour. On boiling down ^"t^V"'^^ ''"^ 

 the compound of the acid and barytes, small orange- 

 coloured crystals are formed by cooling, which, when ex- 

 posed to heat, do not detonate, but grow red hot, and 

 afterward leave a coal, that throws out a number of little 



red sparks as it burns. 



All these compounds are decomposed by sulphuric, nitric, 

 or muriatic acid. 



The volatile acid did not appear to me to decompose the 

 muriate or nitrate of potash like amer. 



31. The volatile acid boiled with oxide of silver dissolves oxide of sUver, 

 it; but, if the solution be boiled too long, it grows black, 



and the oxide of silver appears to be reduced. 



Assisted by heat it decomposes carbonate of lead, dis- oxide of lead, 

 solves part of the oxide, and deposits, on cooling, small 

 orange-coloured crystals, which melt without detonating. 



It dissolves red oxide of iron, and acquires a hyacinthineand oxide •£ 

 red colour. '"''"'• 



All these compounds appeared to me to be acid. 



§ III. Art. III. Of the resinous Matter. 



32. The resinous matter, which had been separated from Purification og 

 the orange-coloured matter by boiling water (10), was sub- the '■esmou* 

 jected anew to the action of this agent, till the water came 



off very slightly coloured. This required a considerable 

 time. The insoluble residuum was treated repeatedly with 

 boiling water, the resin was dissolved; and a mixture of 

 oxalate of lime, sand, &c. remained. 



S3. The resin was separated from the alcohol hy adding its propertiea. 

 •water, and the liquid evaporated. The resin thus obtained 

 was brown, very slightly bitter, and gave a faint yellow 

 tinge to the water in which it was boiled. This water did 

 not precipitate gelatine, and did not give a red colour ta 

 sulphate of iron, but threw down with it a slight precipitate. 



It 



