Liquid ozone is bluish black and solid ozone is violet-black. Ozone is toxic and exposure should not exceed 0.2 mg/m# (8-hour time-weighted average - 40-hour work week). Pollutants in the atmosphere may have a detrimental effect on this ozone layer. Ozone's presence in the atmosphere (amounting to the equivalent of a layer 3 mm thick under ordinary pressures and temperatures) helps prevent harmful ultraviolet rays of the sun from reaching the earth's surface. Ozone (O 3), a highly active compound, is formed by the action of an electrical discharge or ultraviolet light on oxygen. The liquid and solid forms are a pale blue color and are strongly paramagnetic. The gas is colorless, odorless, and tasteless. In the laboratory it can be prepared by the electrolysis of water or by heating potassium chlorate with manganese dioxide as a catalyst. About two thirds of the human body and nine tenths of water is oxygen. The element and its compounds make up 49.2%, by weight, of the earth's crust. The atmosphere of Mars contains about 0.15% oxygen. Oxygen under excited conditions is responsible for the bright red and yellow-green colors of the Aurora Borealis.Ī gaseous element, oxygen forms 21% of the atmosphere by volume and is obtained by liquefaction and fractional distillation. Oxygen is the third most abundant element found in the sun, and it plays a part in the carbon-nitrogen cycle, the process once thought to give the sun and stars their energy. Its atomic weight was used as a standard of comparison for each of the other elements until 1961 when the International Union of Pure and Applied Chemistry adopted carbon 12 as the new basis. Joseph Priestley is generally credited with its discovery, although Scheele also discovered it independently. The behavior of oxygen and nitrogen as components of air led to the advancement of the phlogiston theory of combustion, which captured the minds of chemists for a century. Oxygen's key role in combustion make it necessary for smelting steel and in oxy acetylene welding.įrom the Greek word oxys, acid, and genes, forming.
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