Determination of selenium in selenium enriched yeast.
Kennedy, Kenneth Michael
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Selenium, although a rare mineral, is widely distributed in minute amounts in virtually all materials of the earth’s crust, its average abundance is approximately ~0.09ppm. Selenium is rarely found in its native state i.e. in elemental form, instead it is usually found as an oxide as selenite and selenate or in sulphur or porphyry copper deposits. The greatest abundance of selenium is found in igneous rocks, in hydrothermal deposits, and in the massive sulphide and porphyry copper deposits that are mentioned above. Known deposits of selenium are insufficient to permit their mining for the element alone and consequently it would be far too expensive to mine for its own commercial benefit. Virtually all production of selenium is via its extraction from copper refinery slimes along with the recovery of precious metals. (National Research Council, 1976b) Selenium is obtained commercially by treatment of anode slimes produced during the electrolytic refining of copper. The principal sources of selenium are the sulphidic copper ores in Canada, the United States and in Russia as a result the majority of literature dealing with selenium is from these non-European countries. This is not to say that there is no selenium outside these countries, some of the soils of Ireland contain reasonable amounts of selenium.
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