- ACTION OP NITRIC ACID ON INDIGO. $57 



the nitric or muriatic acid a compound more soluble in 

 water than amer; the latter therefore is separated by the 

 force of crystallization. In the second experiment, the 

 amer and potash, being more fixed than the nitric or muriatic 

 acid, combine ; while the acid flies off by the expansive 

 power of heat. 



Amer combines very well with ammonia, and the result Union of amer 

 is small yellow scales, which scarcely detonate on being ^^^^ ^'""^^"^'^s 

 heated. 



21. Amer unites with lime, barytes, and strontian, and the earths, 

 forms compounds soluble in water. It requires but a very 



small quantity of lime, or even of carbonate of lime, to 

 turn the crystals of pure amer yellow. The mere contact 

 of common paper is sufficient, to produce this effect. 



22. Amer dissolves oxide of silver, and forms with it oxide of silver, 

 needles of a rich gold colour; but they grow black by ex- 

 posure to air. A similar compound may be obtained by 



pouring amer into a solution of silver, and leaving it to 

 evaporate spontaneously. 



It dissolves carbonate of lead, and forms with it acicular carbonate of 

 crystals, which are not very soluble, unless they contain ^*^*^'*» 

 an excess of amer. 



It equally dissolves red oxide of mercury. an<l «xide of 



All these compounds detonate when heated. 



23. The theory of the detonation of amer is easily com- Theory of its 

 prehended. When its temperature is raised, part of the*^^*°"^"^"* 

 nitric acid is converted into nitrous gas. The other and 



greater part is wholly decomposed ; the oxigen of the acid 

 attacks the combustible principles of the vegetable matter, 

 and forms water with the hidrogen, and carbonic acid with 

 the carbon ; the whole, or part, of the nitrogen of the 

 nitric acid forms prussic acid, and perhaps ammonia, with 

 some of the hidrogen and carbon ; another portion of hi- 

 drogen, uniting with carbon, forms oily inflammable gas. 

 The residualcoal is so much the more bulky, in proportion 

 as the amer has been less strongly heated, because then the 

 most dilatable principles are first evolved. 



One thing to be observed in the action of a gentle heat Fixity of tha 

 on amer is the fixedness, that the constituent principles o^ "jJ^"J *^*^ '" 

 uitric acid appear to have acquired in this compound : for 



