Sodium selenate is the inorganic compound with the formula , not to be confused with sodium selenite. It exists as the anhydrous salt, the heptahydrate, and the decahydrate. These are white, water-soluble solids. The decahydrate is a common ingredient in multivitamins and livestock feed as a source of selenium. The anhydrous salt is used in the production of some glass. Although the selenates are much more toxic, many physical properties of sodium selenate and sodium sulfate are similar. Production Sodium selenate is produced by oxidation of selenium, first with nitric acid, producing selenous acid. The selenous acid is neutralized to form sodium selenite. The sodium selenite is oxidized in a basic medium hydrogen peroxide to form a selenate, which is then spray-dried. Se + 2HNO → HSeO + NO + NO HSeO + NaCO → NaSeO + HO + CO NaSeO + HO → NaSeO + HO. It was prepared shortly after the discovery of selenium by Jöns Jacob Berzelius in 1817. Industrial uses Glass manufacturing One of the earliest applications of sodium selenate was in the glass industry. Selenium produces a red hue in glass. The molten glass is treated with sodium selenate and then arsenic trioxide to reduce the compound and provide elemental selenium. Sodium selenate is also used as a decolorizing agent in glass production. The red hue it gives glass is complementary to the green hue given by ferrous oxides in the manufacturing process. When used together, the two compound produce a colourless glass. Pesticide Sodium selenate is a common ingredient in some insecticides used against mites, aphids, and mealybugs. For most insects, a dose of 10mg/kg is enough to be fatal. It is also used in some fungicides. Bio-fortification of crops Sodium selenate is effectively used for bio-fortification of crops hence fortifying food/feed to mitigate selenium deficiency in humans and livestock. It can be applied as foliar spray or via rooting medium e.g. added in fertilizers. Dietary supplement Chosen for its selenium content and high solubility, sodium selenate is a common ingredient in over-the-counter vitamin supplements. Selenium is a trace essential element. Sodium selenate and selenite are also common in premix animal feed. Neither compound has demonstrated a difference in the amount of selenium absorbed. The US FDA regulates that animal feed contain no more than 5ppm selenium content. Controversy arose in 2009 when a group of 21 polo horses died from selenium poisoning from