Sodium selenite

Sodium selenite usually is prepared by the reaction of selenium dioxide with sodium hydroxide:F. Féher, "Sodium Selenite" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 432.

:SeO₂ + 2 NaOH → Na₂SeO₃ + H₂O

The hydrate converts to the anhydrous salt upon heating to 40 °C.

According to X-ray crystallography, both anhydrous Na₂SeO₃ and its pentahydrate feature pyramidal SeO₃²⁻. The Se-O distances range from 1.67 to 1.72 Å.{{cite journal|last1=Wickleder|first1=Mathias S.|title=Sodium Selenite, Na₂SeO₃|journal=Acta Crystallographica Section E|volume=58|issue=11|year=2002|pages=i103–i104|issn=1600-5368|doi=10.1107/S1600536802019384|bibcode=2002AcCrE..58I.103W }} Oxidation of this anion gives sodium selenate, Na₂SeO₄.{{cite journal |doi=10.1107/S1600536813028602|title=Sodium Selenite Pentahydrate, Na₂SeO₃·5H₂O|year=2013|last1=Mereiter|first1=Kurt|journal=Acta Crystallographica Section E|volume=69|issue=11|pages=i77–i78|pmid=24454013|pmc=3884237}}

Together with the related barium and zinc selenites, sodium selenite is mainly used in the manufacture of colorless glass. The pink color imparted by these selenites cancels out the green color imparted by iron impurities.Bernd E. Langner "Selenium and Selenium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry (published on-line in 2000) Wiley-VCH, Weinheim, 2002 {{doi|10.1002/14356007.a23_525}}

Because selenium is an essential element, sodium selenite is an ingredient in dietary supplements such as multi-vitamin/mineral products, but supplements that provide only selenium use L-selenomethionine or a selenium-enriched yeast.

The US Food and Drug Administration approved a selenium supplement to animal diets; the most common form is sodium selenite for pet foods. According to one article, "not much was known about which selenium compounds to approve for use in animal feeds when the decisions were made back in the 1970s .. At the time the regulatory action was taken, only the inorganic selenium salts (sodium selenite and sodium selenate) were available at a cost permitting their use in animal feed.”

{{cite journal|last1=Schrauzer|first1=GN|title=Nutritional selenium supplements: product types, quality, and safety|journal=Journal of the American College of Nutrition|volume=20|issue=1|pages=1–4|year=2001|pmid=11293463|doi=10.1080/07315724.2001.10719007|s2cid=12668227}}

Sodium selenite has been proposed as an effective suicide agent.{{cite book|last=Nitschke, Philip|url=https://www.worldcat.org/oclc/1003529499|title=The peaceful pill ehandbook|publisher=|others=Stewart, Fiona, 1966-|date=28 February 2016|isbn=978-0-9758339-1-9|edition=January 2021|location=Bellingham, WA|pages=192|oclc=1003529499}}

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.{{cite journal|last = Wilber|first = C. G.|title = Toxicology of selenium|year = 1980|journal = Clinical Toxicology|volume = 17|pages = 171–230|doi = 10.3109/15563658008985076|pmid = 6998645|issue = 2}} 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.{{cite book | vauthors = ((Institute of Medicine)) | title = Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids | chapter = Selenium | publisher = The National Academies Press | year = 2000 | location = Washington, DC | pages = 284–324 | doi = 10.17226/9810 | pmid = 25077263 | isbn = 978-0-309-06935-9 | chapter-url = https://www.nap.edu/read/9810/chapter/9 | author1-link = Institute of Medicine }} The European Food Safety Authority reviewed the same safety question and set its UL at 300 μg/day.{{citation| title = Tolerable Upper Intake Levels For Vitamins And Minerals| publisher = European Food Safety Authority| year = 2006| url = http://www.efsa.europa.eu/sites/default/files/efsa_rep/blobserver_assets/ndatolerableuil.pdf}}

• Selenite (ion)
• Selenous acid

{{reflist}}

• [http://lpi.oregonstate.edu/infocenter/minerals/selenium/ Linus Pauling Institute page on selenium]

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Category:Selenites

Category:Sodium compounds

Category:Dietary minerals

Category:Dietary supplements