Ammo'nia, a gas (NH3), which is dissolved by water with great avidity, making an alkaline liquid called ammonia-water or, by chemists, ammonium hydroxide, which is the common form in which it is used. The name is probably derived from the temple of Ammon in the Libyan desert, where ammonia was produced. The name hartshorn is also used, because the shavings of horns have been used to prepare it. It is composed of nitrogen and hydrogen, and is obtained chiefly from the waste liquors of the manufactories of illuminating gas. Ammonia gas may be changed to a liquid or solid by cold and pressure. An important use of liquid ammonia is in the manufacture of ice. (See Ice.) Ammonia unites with acids to form ammonium salts. The carbonate is much used for smelling salts, the chloride is used in soldering and in medicine, and the sulphate and other salts are valuable fertilizers.
