Oxygen

Oxygen combines readily with many elements to form hundreds of thousand useful organic compounds.   Oxygen enrichment of fuel in furnaces that produce iron and steel is the largest commercial use of oxygen.   It is also used to make synthesis gas for ammonia, methanol, and ethylene oxide, and in oxy-acetelene welding.   It is used extensively in hospitals to provide additional respiration to patients. ^{Lide 4-20}

Oxygen is essential to life.   About 2/3 of of the human body is composed of oxygen compounds.   Animal and plant compounds contain oxygen.   Oxygen is the oxidizer in all animal respiration and plants give off oxygen during photosynthesis.   Ozone, O₃, a highly active compound, is formed by the action of an electrical discharge or ultraviolet light on oxygen.   Its presence in the atmosphere prevents harmful ultraviolet rays of the sun from reaching the earth's surface.

Oxygen was discovered independently by Carl Scheel, a Swedish chemist, and Joseph Priestley, a British chemist.   Oxygen gas comprises 21% of the atmosphere by volume from which it can be obtained by liquification and fractional distillation.   It also is the most common element on earth, comprising 49.2% of the earth's crust and about two-thirds of the human body and nine-tenths of water. ^{Lide 4-20}