How Nitrogen Is Obtained
Nitrogen is produced commercially almost exclusively from air, most commonly by the fractional distillation of liquid air. In this process, air is first cooled to a temperature below that of the boiling points of its major components, a temperature somewhat less than - 328°F (-200°C). The liquid air is then allowed to warm up, allowing the lower-boiling-point nitrogen to evaporate from the mixture first. Nitrogen gas escaping from the liquid air is then captured, cooled, and then liquefied once more.
This process produces a high-quality product that generally contains less than 20 parts per million of oxygen. Both an "oxygen-free" form of nitrogen (containing less than two parts per million of oxygen) and an "ultra-pure" nitrogen (containing less than 10 parts per million of argon) are also available commercially.
A number of methods are available for preparing nitrogen from its compounds in the laboratory on a small scale. For example, a hot aqueous solution of ammonium nitrite decomposes spontaneously to give elemental nitrogen and water. The heating of barium or sodium azide (NaN3 or Ba[N3]2) also yields free nitrogen. In another approach, passing ammonia gas over a hot metallic oxide will result in the formation of free nitrogen, the free metal, and water. Yet another route is the reaction between ammonia and bromine, resulting in the formation of nitrogen and ammonium bromide.
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