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CARBONATE OP AMMONIA.

always in combination with carbonic, or some otheracid. It is far loss abundant or common than the otheralkalies, potash and soda ; for its principal source is thedecay of animal and vegetable substances which con-tain nitrogen.

150. The most important of the salts of ammonia are,the carbonate and the muriate and the sulphate: thecarbonate, which is the salt produced during the decayof organic matters, was formerly called salt of hartshorn,because it was mostly procured by burning horn; it isnow, however, principally obtained from the combustionof coal, which contains a small quantity of nitrogen,and therefore during burning gives off a small quantityof ammonia, which combines with a portion of the car-bonic acid formed by the burning of the carbon of tbecoal; hence carbonate of ammonia is always an ingre-dient of soot.

151. Carbonate of ammonia is largely obtained fromthe refuse matters of gas-works, where immense quan-tities of coal being decomposed, the salts of ammoniacollect in large quantity. Carbonate of ammoniapossesess the peculiar pungent smell of pure ammonia,though far less powerfully ; because being but partiallyneutralised by carbonic acid and united to it by but afeeble affinity, it is constantly escaping from its com-pound, evaporating into the air.

152. The muriate of ammonia, commonly called sal-ammoniac, which used also formerly to be obtained byburning animal substances, is now procured from the