Oxygen is the most abundant chemical element by mass in the Earth’s biosphere, air, sea and land. Oxygen is the third most abundant chemical element in the universe, after hydrogen and helium (Emsley, 2001).
The greatest commercial use of oxygen gas is in the steel industry: ‘Apparatus for introducing oxygen into molten steel’ (1949).
Large quantities of oxygen are also used in the manufacture of a wide range of chemicals including nitric acid: ‘Oxygen-enrichment columnar absorption process for making nitric acid’ (1980), and hydrogen peroxide: ‘Production process of hydrogen peroxide by oxidation of secondary alcohols with molecular oxygen in liquid phase’ (1999).
Oxygen is also used to make epoxyethane (ethylene oxide): ‘Method for preparing epoxyethane from oxygen and ethylene’ (2017), used as antifreeze and to make polyester, and chloroethene, the precursor to PVC.
Oxygen gas is used for oxy-acetylene welding and cutting of metals: ‘Acetylene-Oxygen Welding Torch’ (1912).
A growing use is in the treatment of sewage and of effluent from industry: ‘Waste water treatment with oxygen’ (1978).