82 CARBONATE OP AMMONIA. 



in water ; like potash and soda, it has a very strong 

 affinity for acids, and is, therefore, hardly ever met 

 with in its free state, but always in combination with 

 carbonic, or some other acid. It is far less abundant 

 or common than the other alkalies, potash and soda; 

 for its principal source is the decay of animal and 

 vegetable substances, which contain nitrogen. 



154. The most important of the salts of ammonia 

 are the carbonate, the muriate, the sulphate, and the 

 phosphate: the carbonate, which is the salt produced 

 during the decay of organic matters, was formerly 

 called salt of hartshorn, because it was mostly pro- 

 cured by burning horn; it is now, however, obtained 

 from the tar-water and refuse ammoniacal liquors of 

 the gas-works. A considerable quantity of ammonia 

 is formed during the distillation of coal, which always 

 contains a little nitrogen, and, therefore, gives off a 

 small quantity of ammonia ; this combines with a por- 

 tion of the carbonic acid formed by the burning of 

 the carbon of the coal, and collects in the hydraulic 

 main, or first condenser, of the gas-works; hence, also,' 

 carbonate of ammonia is always an ingredient of 

 soot. 



155. Carbonate of ammonia is not obtained direct 

 from the gas liquor, as it would then be impure from 

 the tar, and other substances which exist in the gas- 

 water. The ammoniacal water is generally first con- 

 verted into a sulphate or muriate, and this is decom- 

 posed by heating it with chalk ; carbonate of ammonia, 

 which is volatile, rises in vapor, whilst sulphate or 



