III.

Industrial Fixation

The principal industrial nitrogen-fixation process today is the production of ammonia by passing a mixture of atmospheric nitrogen and hydrogen over a metallic catalyst (see Catalysis) at 500°-600° C (932°-1112° F). Ammonia is then oxidized to form nitric acid, which is in turn combined with ammonia to yield ammonium nitrate, used primarily in explosives and fertilizers (see Fertilizer). In another method, cyanamide, which is used as a fertilizer or in the production of cyanides, is produced by passing atmospheric nitrogen over heated calcium carbide in the presence of a catalyst.