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Selenium dioxide imparts a red colour to glass. It is used in small quantities to counteract the colour due to iron impurities and so to create (apparently) colourless glass. In larger quantities, it gives a deep ruby red colour. Selenium dioxide is the active ingredient in some cold-bluing solutions.
Industrial production of selenium usually involves the extraction of selenium dioxide from residues obtained during the purification of copper. Common production from the residue then begins by oxidation with sodium carbonate to produce selenium dioxide, which is mixed with water and acidified to form selenous acid (oxidation step).
Sodium selenite usually is prepared by the reaction of selenium dioxide with sodium hydroxide: [1] SeO 2 + 2 NaOH → Na 2 SeO 3 + H 2 O. The hydrate converts to the anhydrous salt upon heating to 40 °C. According to X-ray crystallography, both anhydrous Na 2 SeO 3 and its pentahydrate feature pyramidal SeO 3 2−.
Selenium forms two oxides: selenium dioxide (SeO 2) and selenium trioxide (SeO 3). Selenium dioxide is formed by the reaction of elemental selenium with oxygen: [5] + It is a polymeric solid that forms monomeric SeO 2 molecules in the gas phase. It dissolves in water to form selenous acid, H 2 SeO 3.
Sodium chloride (table salt, rock salt) – NaCl; Sodium chlorite – NaClO 2; Sodium hypochlorite – NaOCl; ... Selenium dioxide – SeO 2; Selenium disulfide ...
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 ...
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Selenous acid is easily formed upon the addition of selenium dioxide to water. As a crystalline solid, the compound can be seen as pyramidal molecules that are interconnected with hydrogen bonds. In solution it is a diprotic acid: [3] H 2 SeO 3 ⇌ H + + HSeO − 3 (pK a = 2.62) HSeO − 3 ⇌ H + + SeO 2− 3 (pK a = 8.32)