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Selenium is found in metal sulfide ores, where it substitutes for sulfur. Commercially, selenium is produced as a byproduct in the refining of these ores. Minerals that are pure selenide or selenate compounds are rare. The chief commercial uses for selenium today are glassmaking and pigments. Selenium is a semiconductor and is used in photocells.
Selenium is a nutrient that is naturally present in many foods, added to others and is also available as a dietary supplement in pill, powder and liquid form, explains Perri Halperin, a ...
Selenium is produced by roasting the coinage metal selenides X 2 Se (X = Cu, Ag, Au) with soda ash to give the selenite: X 2 Se + O 2 + Na 2 CO 3 → Na 2 SeO 3 + 2 X + CO 2; the selenide is neutralized by sulfuric acid H 2 SO 4 to give selenous acid H 2 SeO 3; this is reduced by bubbling with SO 2 to yield elemental selenium. Polonium and ...
Selenium is toxic in high concentrations. As sodium selenite, the chronic toxic dose for human beings was described as about 2.4 to 3 milligrams of selenium per day. [7] In 2000, the US Institute of Medicine set the adult Tolerable upper intake levels (UL) for selenium from all sources - food, drinking water and dietary supplements - at 400 μg/day. [8]
Selenides (R−Se−R), also called selenoethers, are the selenium equivalents of ethers and sulfides. One example is dimethylselenide ((CH 3) 2 Se). These are the most prevalent organoselenium compounds. Symmetrical selenides are usually prepared by alkylation of alkali metal selenide salts, e.g. sodium selenide. Unsymmetrical selenides are ...
Silver selenide (Ag 2 Se) is the reaction product formed when selenium toning analog silver gelatine photo papers in photographic print toning.The selenium toner contains sodium selenite (Na 2 SeO 3) as one of its active ingredients, which is the source of the selenide (Se 2−) anion combining with the silver in the toning process.
α-SnSe is classified as a layered metal chalcogenide. [6] It includes a group 16 anion (Se 2−) and an electropositive element (Sn 2+), and is arranged in a layered structure. Tin(II) selenide (SnSe) crystallizes in the orthorhombic structure that is related to the rock-salt structure. It is isomorphous to germanium selenide (GeSe). [7]
A new Clean Label Project report suggests some protein powders contain heavy metals lead and cadmium. See which ones are safe here, plus what an expert advises.