Ammonia
A colorless irrespirable gas, of an extremely pungent and caustic taste, lighter than air (sp. gr. 0.59). It exists in very minute quantities in the atmosphere, rain-water, fog, and dew. Ammonia is the only known compound of nitrogen and hydrogen; it is a constant product of the decomposition of organic substances which contain nitrogen. It is produced from the destructive distillation of horns and hoofs, but the liquor of the gas-works furnishes the chief source of commercial ammonia. Being a gas it is called volatile alkali to distinguish it from those which are fixed, or solid. Owing to the fact that it was derived from the horns of harts, it is commonly called spirits of hartshorn. See ALKALI.