Sodium selenite

Sodium selenite is the inorganic compound with the formula Na2SeO3. This salt is a colourless solid. The pentahydrate Na2SeO3(H2O)5 is the most common water-soluble selenium compound.

Not to be confused with Selenite (mineral).
Sodium selenite
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.030.230
EC Number
  • 233-267-9
KEGG
RTECS number
  • VS7350000
UNII
UN number 2630
Properties
Na2O3Se
Molar mass 172.948 g·mol−1
Appearance colourless solid
Density 3.1 g/cm3
Melting point decomposes at 710 °C
85 g/100 mL (20 °C)
Solubility insoluble in ethanol
Structure
tetragonal
Pharmacology
A12CE02 (WHO)
Hazards
Safety data sheet ICSC 0698
Very toxic (T+)
Dangerous for the environment (N)
R-phrases (outdated) R23, R28, R31, R43, R51/53
S-phrases (outdated) (S1/2), S28, S36/37, S45, S61
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
0
3
0
Related compounds
Related compounds
 Sodium sulfite
Sodium selenate
Sodium selenide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

Synthesis and fundamental reactions

Sodium selenite usually is prepared by the reaction of selenium dioxide with sodium hydroxide:[1]

SeO2 + 2 NaOH → Na2SeO3 + H2O

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

Akin to the related salt sodium sulfite, Na2SeO3 features a pyramidal dianion SeO32−.[2] Oxidation of this anion gives sodium selenate, Na2SeO4.

Applications

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.[3]

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.” [4]

Safety

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.[5] In 2000, the U.S. 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.[6] The European Food Safety Authority reviewed the same safety question and set its UL at 300 μg/day.[7]

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See also

References
  1. F. Féher, "Sodium Selenite" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 432.
  2. Wickleder, Mathias S. (2002). "Sodium selenite, Na2SeO3". Acta Crystallographica Section E. 58 (11): i103–i104. doi:10.1107/S1600536802019384. ISSN 1600-5368.
  3. 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
  4. Schrauzer, GN (2001). "Nutritional selenium supplements: product types, quality, and safety". Journal of the American College of Nutrition. 20 (1): 1–4. doi:10.1080/07315724.2001.10719007. PMID 11293463.
  5. Wilber, C. G. (1980). "Toxicology of selenium". Clinical Toxicology (Free full text (see p. 211))|format= requires |url= (help). 17 (2): 171–230. doi:10.3109/15563658008985076. PMID 6998645.
  6. Institute of Medicine (2000). "Selenium". Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC: The National Academies Press. pp. 284–324. doi:10.17226/9810. ISBN 978-0-309-06935-9. PMID 25077263.
  7. Tolerable Upper Intake Levels For Vitamins And Minerals (PDF), European Food Safety Authority, 2006
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