AMMONIA. Volatile alkali, first ob tained by Priestly in a gaseous form, from sal-ammoniac, whence its name. It is a volatile gas, composed of one equivalent of nitrogen and three equivalents of hy drogen. It is found in the vegetable and animal kingdom. Urine decomposing always contains it : hence the use of that substance in making alum, scouring. wool, &e. Ammonia is tbund united with na tive oxide of iron, in charcoal, and all soils which are turned up and exposed to the air. Rain water contains traces of ammonia derived from the air, in which it is present in minute quantities. Ammonia cannot be made by the direct union of its elements : one of these sub stances must be in the nascent state. The usual mode of manufacturing is to mix sal-ammoniac, or hydro-ehlorate of ammonia reduced to powder, with an equal weight of fresh slaked slime ; these are to be put into a retort, with just so much water as makes the mass become lumpy ; on applying a gentle heat to the retort, the ammonia comes off in large quantities as a gas, and if desired pure, may be collected in vessels over the pneu matic trough. By this process the lime re moves the hydrochloric acid, forms with it chloride of calcium and water, and the ammonia is set free ; if received into ves sels of water, it dissolves very speedily, water at 50° taking up 670 times its vo lume of gas, and the density of the solu tion diminishes as the strength increases.
A saturated solution of ammonia contains 326 per cent. of gas, and has a sp. gr. of -8750.. This is called liquid ammonia, and is the liquor ammonia; of the pharmaco peia; it is colorless, transparent, very pungent, and has well marked alkaline properties. It weakens by exposure to air or heat, the ammonia flying off rapidly. It blues red litmus, and changes vegeta ble blues to green: it turns turmeric and vegetable yellows brown, and unites with acids to form a numerous class of salts.
Organic bodies which contain nitrogen, in fermenting yield ammonia, and gene rally at the same time carbonic acid. When hoofs, bones, tendons, horns, &c., are heated in iron cylinders, they are de composed, and carbonate of,inninonia is set free along with an empyreumatic oil: when freed from the latter it is termed spirit of hartshmn. The gluten of corn, wheat, and other cerealia, yield ammonia when heated ; it is also found in soot, and in great abundance when bituminous coal is heated to redness, as in the manufac ture of gas.