NITROGEN, N., at. wt. 14.01, color less, odorless, tasteless gas, forming, ap proximately, four-fifths of the atmos phere. Slightly lighter than the air. Discovered in 1772 by Rutherford, in the University of Edinburgh. It can be pre pared by passing air over some reagent which will readily react with and ab sorb oxygen, such as reduced iron, alka line, pyrogallol, or phosphorus; or by liquefying air and distilling, when the more volatile nitrogen is vaporized. Ni trogen is found in all vegetable and ani mal life, usually in organic combination, and in varying quantities in the earth's crust in both organic and inorganic com bination. It is a necessary constituent of plant and animal food. Certain leg umes have the power of fixing the nitro gen of the air by means of root nodules, and obtain their supply in this way, while electric discharges in the atmos phere cause the union of nitrogen and oxygen, the resulting oxides of nitrogen being washed into the soil by rain. These sources are not sufficient, how ever, to enrich the soil to the extent needed for intensive cultivation, and by far the greater part of nitrogen is added, either in the form of decompos ing organic matter (barnyard manure, guano, etc.) or inorganic salts (nitrates,
ammonium sulphate, etc.). The most commonly used inorganic nitrogenous fertilizer is sodium nitrate or Chili salt petre, NaNO,, but it is believed that the supply of this material will become ex hausted in less than forty years. More over, nitrogen in the form of nitric acid, nitrates, or ammonia is an important raw material in the manufacture of ex plosives, dyes, sodium bicarbonate, and other products, while ammonia is widely used for refrigeration. The supply of nitrogen in the atmosphere is practically inexhaustible, the air over every acre of ground being estimated to contain 31,000 tons of nitrogen, and many attempts have been made to manufacture nitro genous compounds from this source. Three methods have given successful re sults on a manufacturing scale: (1) the formation of ammonia by combining the nitrogen with hydrogen; (2) the forma tion of oxides of nitrogen by passing an electric arc through air, and (3) the for mation of cyanamide by absorbing nitro gen in calcium carbide, heated to white heat in an electric furnace.