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| Sodium selenite | |
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| Identifiers | |
| CAS number | [10102-18-8] |
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| Properties | |
| Molecular formula | Na2SeO3 |
| Molar mass | 172.938 |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references |
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Sodium selenite is a chemical compound with the formula Na2SeO3. This salt is the most common water soluble forms of selenium. The industrial production of selenium often involves the extraction of selenium dioxide from residues obtained during the purification of copper metal. Acidification of solutions of selenium dioxide followed by reduction with sulfur dioxide gives elemental selenium.
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Synthesis and fundamental reactions
The sodium selenite salt is usually prepared by the reaction of selenium dioxide with sodium hydroxide:
- SeO2 + 2 NaOH → Na2SeO3 + H2O
Acidification of selenium dioxide gives selenous acid, which, unlike sulfurous acid, is isolable.[1]
Akin to the related salt sodium sulfite, Na2SeO3 features a pyramidal dianion SeO32- with C3v symmetry. Oxidation of this anion give sodium selenate, Na2SeO4.
Applications
Together with the related barium and zinc salts, sodium selenite is mainly used in the manufacture of colorless glass. Its pink coloration cancels out the green color imparted by iron impurities.[2]
Safety
Selenium is an essential element (animals require selenium for selenium-dependent enzymes such as glutathione peroxidase.[3]). Sodium selenite is currently used in some food supplements in microgram quantities, but it is toxic at higher levels, the acute toxicity differs from the chronic toxicity which for selenite the chronic toxic dose for human beings is about 2400 to 3000 micrograms of selenium per day for a long time.[4]. See MSDS.
References
- ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
- ^ Bernd E. Langner "Selenium and Selenium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2002. doi:10.1002/14356007.a23_525 Article Online Posting Date: June 15, 2000
- ^ Linus Pauling Institute at Oregon State University lpi.oregonstate.edu
- ^ Wilber CG, Toxicology of selenium 1980 Clinical Toxicology volume 17, pages 171-230,(page211).
External links
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