Liquid ozone is bluish black and solid ozone is violet-black. Compounds Oxygen, which is very reactive, is a component of hundreds of thousands of organic compounds and combines with most elements. Uses Plants and animals rely on oxygen for respiration. Hospitals frequently prescribe oxygen for patients with respiratory ailments. Isotopes Oxygen has nine isotopes.
Natural oxygen is a mixture of three isotopes.
Commercial oxygen consumption in the U.S. is estimated at 20 million short tons per year and the demand is expected to increase substantially. Oxygen enrichment of steel blast furnaces accounts for the greatest use of the gas. Large quantities are also used in making synthesis gas for ammonia and methanol, ethylene oxide, and for oxy-acetylene welding.