A method of separating oxygen, nitrogen, argon and other gases present in air. The liquid air process liquefies air by repeated cycles of cooling, compression, and expansion.

The process makes use of the differences in the boiling points of the major elements in liquid air to separate these components. The boiling point for oxygen is 183°C (-297°F) and for nitrogen, -196°C (-320.4″F). These low temperatures are reached partly by refrigeration and partly by the Joule-Thomson effect, whereby rapidly expanding gas is cooled by expansion. See CRYOGENICS and OXYGEN PRODUCTION.