Nitrogen

Nitrogen, chemical element, symbol N; for physical constants see Periodic Table. Nitrogen was discovered by Daniel Rutherford in 1772. It is present in air to the extent of 78% and is commercially obtained by the liquefaction and fractional distillation of air. Nitrogen is a colorless, odorless, and chemically inert gas. When heated, however, it combines directly with magnesium, lithium, or calcium. The largest use of elemental nitrogen is in the Haber process, where nitrogen is heated under pressure to form ammonia. In the Ostwald process it is oxidized to nitric acid. Millions of tons of elemental nitrogen are produced in the United States each year. Nitrogen is used as an inert atmosphere for the production of electronic components and in the annealing of steel. In liquid form it is used as a refrigerant. Nitrogen compounds are used in the manufacture of fertilizers, explosives, and pharmaceuticals.