(Chemical symbol: N). A gaseous element that occurs freely in nature and constitutes about 78% of the atmosphere. It is a colorless, odorless and relatively inert gas, although it combines directly with magnesium, lithium and calcium when heated with them. Nitrogen occurs in all living things as an essential element. When mixed with oxygen and subjected to electric sparks, it forms nitrogen peroxide. Atomic weight, 14.008; melting point, -210.5″C (-347°F); boiling point, -195°C (-3 19°F); specific gravity, 0.967 (air).
Nitrogen is produced either by liquefaction and fractional distillation of air, or by heating a water solution of ammonium nitrate (a mixture of ammonium chloride and sodium nitrite). For a description of the liquefaction process, see OXYGEN PRODUCTION.