Nitrogen

Nitrogen exists in the atmosphere as a free diatomic gas, and there is a great deal of it: about 78.1% of air by volume.

It is a component element of animal and plant proteins. It is also found in soil air, in organic matter such as humus, and in nitrates, nitrites and ammonium compounds.

Physical properties

• It has neither colour nor smell.
• It does not support combustion, and is a little lighter than air.
• It dissolves in water only slightly.

Chemical properties

• It is a gas of very low reactivity. At very high temperatures, though, it reacts with non-metals such as oxygen, hydrogen, carbon and silicon, and with metals such as magnesium and aluminium.
• In the presence of a strong electric arc, nitrogen combines with the oxygen of the air to form unstable nitric oxide. That reacts further with oxygen to form nitrogen dioxide, an acidic gas. This process happens naturally during lightning.
• Under special conditions nitrogen reacts with hydrogen to form ammonia. Industrially, ammonia is produced by this method, and it is then a raw material for making nitrogenous fertilisers and explosives.
• Metals such as magnesium react with nitrogen when heated, forming the nitride of the metal.

Uses

• Producing ammonia industrially, and chemical fertilisers.
• Filling electric bulbs and thermometers, since it is an inactive gas.
• Providing a nitrogen atmosphere in making electronic devices, so fine metal parts do not meet oxygen.
• As a blanketing gas when storing reactive chemicals — it is nitrogen that is sealed inside packets of milk powder.
• Liquid nitrogen as a very low temperature cooling agent.
• Filling vehicle tyres.