ammonia

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A colorless, pungent gas, NH₃, extensively used to manufacture fertilizers and a wide variety of nitrogen-containing organic and inorganic chemicals.

from The Century Dictionary.

• noun The great value of ammonia as a fertilizer, chiefly in the form of ammonium sulphate, renders the question of its supply on a large scale one of much importance. Until recent years it was obtained mainly from the watery ammoniacal liquor which is a by-product of the manufacture of coal-gas for illuminating purposes. This source of supply has been seriously threatened by the extension, especially in the United States, of the use of carbureted water-gas, in making which little or no ammonia is obtained. Notable improvements, however, have been made in methods for the recovery of ammonia from the waste gases of coke-ovens, shale-works, and blast-furnaces, and very considerable amounts are now obtained from these previously neglected sources. One of the most interesting results secured with the aid of the high temperature of the modern electric furnace is the synthetical production of ammonia from the nitrogen of atmospheric air and the hydrogen of water. Carbon in the form of coke is mixed with lime and the mixture intensely heated in the presence of atmospheric nitrogen, giving rise to carbon-monoxid gas and calcium cyanamide (CaCN₂). The latter, heated with water under pressure, yields calcium carbonate and ammonia (CaCN₂ + 3H₂O = CaCO₃ + 2N H₃). It appears that cyanamide itself may serve, when used directly as a fertilizer, to furnish assimilable nitrogen to growing plants.
• noun The modern name of the volatile alkali, NH₃, formerly so called to distinguish it from the more fixed alkalis.
• noun [capitalized] In zoöl.: An old quasi-generic name of Spirula. Breyn, 1732. A genus of arachnidans.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Chem.) A gaseous compound of hydrogen and nitrogen, NH3, with a pungent smell and taste: -- often called volatile alkali, and spirits of hartshorn.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun inorganic chemistry A gaseous compound of hydrogen and nitrogen, NH3, with a pungent smell and taste.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a water solution of ammonia
• noun a pungent gas compounded of nitrogen and hydrogen (NH3)