Ammonia

Ammonia, colourless, pungent gas, NH₃, highly soluble in water. A saturated aqueous (water) solution of ammonia contains 45 per cent ammonia by weight at 0° C (32° F) and 30 per cent at ordinary room temperatures. On solution in water, ammonia becomes ammonium hydroxide, NH₄OH, which is strongly basic and similar in chemical behaviour to the hydroxides of the alkali metals.

Ammonia was known to the ancients, who derived both the name and the substance from sal ammoniac, which was produced at the Temple of Jupiter Ammon in Libya by the distillation of camel dung. During the Middle Ages in Europe ammonia was obtained by heating the horns and hoofs of oxen and was called spirits of hartshorn. Free ammonia was obtained by the German alchemist Basil Valentine; its composition was determined by the French chemist Comte Claude Berthollet in about 1777.

In the 19th century the principal source of ammonia was the destructive distillation of coal; it was an important by-product of the manufacture of fuel gases. Today most ammonia is produced synthetically from hydrogen and nitrogen by the Haber process. Ammonia is an important refrigerant and is widely used in the chemical industries, especially in the manufacture of fertilizer, nitric acid, and explosives.

Ammonia melts at -77.7° C (-107.9° F), boils at -33.35° C (-28.03° F), and has a density of 0.68 at its boiling point and 1 atm (760 torrs) of pressure.