Liquid air nitrogen

Industrially, elemental nitrogen is extracted from the air by the fractional distillation of liquid air from which carbon dioxide and water have been removed. The major fractions are nitrogen, b.p. 77 K and oxygen, b.p. 90 K, together with smaller quantities of the noble gases. 

On other occasions tank trucks have been filled with the wrong material. In particular, liquid oxygen or liquid air has been supplied instead of liquid nitrogen. One incident, the result of confusion over labeling, was described in Section 4.1 (f). 

In general, auxiliary refrigeration is used for temperature requirements from 80-85°F to as near absolute zero as the process demands. The usual petrochemical and chemical range does not go much below — 200°F. This section does not include low-temperature air separation for oxygen, nitrogen, argon, etc., or the separation of process gases at liquid air temperatures. 

Manufacture By distillation of liquid air, the same as nitrogen. Most oxygen is used captively, less than 20% of production being sold on the merchant market. 

Ammonia is synthesised from its elements nitrogen and hydrogen. The nitrogen is obtained by the fractional distillation of liquid air. The hydrogen is obtained by the reaction of methane (from natural gas) with steam. 

The water passing through the condenser C was then cut off, and a stream of nitrogen substituted for the chlorine. This swept the phosphorus trichloride into D, where it was trapped. The next stage of the operation was to sweep the phosphorus trichloride from D into the graduated vessel E, the latter being cooled in liquid air while D was gently warmed. When the transference was complete, the temperature of E was allowed to rise to room temperature and the volume of phosphorus trichloride produced measured on the scale. Yield, ca. 90 per cent. 

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