Sodium selenite

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Sodium selenite
Sodium selenite.jpg
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.030.230 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 233-267-9
KEGG
PubChem CID
RTECS number
  • VS7350000
UNII
UN number 2630
  • InChI=1S/2Na.H2O3Se/c;;1-4(2)3/h;;(H2,1,2,3)/q2*+1;/p-2 Yes check.svgY
    Key: BVTBRVFYZUCAKH-UHFFFAOYSA-L Yes check.svgY
  • InChI=1/2Na.H2O3Se/c;;1-4(2)3/h;;(H2,1,2,3)/q2*+1;/p-2
    Key: BVTBRVFYZUCAKH-NUQVWONBAC
  • [Na+].[Na+].[O-][Se]([O-])=O
Properties
Na2O3Se
Molar mass 172.948 g·mol−1
Appearancecolourless solid
Density 3.1 g/cm3
Melting point 350 °C (662 °F; 623 K) [1] (decomposes over 300 °C (572 °F; 573 K))
89.8 g/100mL (20 °C (68 °F; 293 K)) [2]
Vapor pressure < 0.00133 hPa (1.93×10−5 psi) (20 °C (68 °F; 293 K)) [2]
Structure [3]
Pbcm (pentahydrate)
a = 6.5865 Å, b = 17.2263 Å, c = 14.7778 Å
(pentahydrate)
1676.70 Å3 (pentahydrate)
8 (pentahydrate)
Pharmacology
A12CE02 ( WHO )(Oral), B05XA20 ( WHO ) (Parenteral)
Hazards
GHS labelling: [2]
GHS-pictogram-skull.svg GHS-pictogram-exclam.svg GHS-pictogram-pollu.svg
Danger
H300+H330, H315, H317, H319, H411
P260, P264, P270, P271, P272, P273, P280, P284, P301+P310+P330, P302+P352, P304+P340+P310, P305+P351+P338, P333+P313, P337+P313, P362, P391, P403+P233, P405, P501
NFPA 704 (fire diamond)
[1]
NFPA 704.svgHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
4
0
0
>400 °C (752 °F; 673 K) [2]
0.2 mg/m3 (as selenium) [4] (TWA)
Lethal dose or concentration (LD, LC):
7 mg/kg (oral, rat) [1]
3.3 mg/kg (oral, sheep) [4]
NIOSH (US health exposure limits): [4]
PEL (Permissible)
0.2 mg/m3 (TWA, as selenium)
REL (Recommended)
0.2 mg/m3 (TWA, as selenium)
IDLH (Immediate danger)
1 mg/m3
Related compounds
Other anions
Other cations
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Sodium selenite is the inorganic compound with the formula Na2SeO3. This salt is a colourless solid. The pink coloured pentahydrate Na2SeO3·5H2O is the most common water-soluble selenium compound.

Contents

Synthesis and fundamental reactions

Sodium selenite usually is prepared by the reaction of selenium dioxide with sodium hydroxide: [5]

SeO2 + 2 NaOH → Na2SeO3 + H2O

The hydrate converts to the anhydrous salt upon heating to 40 °C (104 °F).

According to X-ray crystallography, both anhydrous Na2SeO3 and its pentahydrate feature pyramidal SeO2−3. The Se−O distances range from 1.67 to 1.72 Å. [6] Oxidation of this anion gives sodium selenate, Na2SeO4. [3]

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. [7]

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." [8]

Sodium selenite has been proposed as an effective suicide agent. [9]

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 mg of selenium per day. [10] 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/d. [11] The European Food Safety Authority reviewed the same safety question and set its UL at 300 μg/d. [12]

See also

References

  1. 1 2 3 "SDS - Sodium selenite". fishersci.com. ThermoFisher Scientific. 21 December 2025. p. 3. Retrieved 28 January 2026.
  2. 1 2 3 4 Sigma-Aldrich Co., Sodium selenite.
  3. 1 2 Mereiter K (2013). "Sodium Selenite Pentahydrate, Na2SeO3·5H2O". Acta Crystallographica Section E. 69 (11): i77–i78. doi: 10.1107/S1600536813028602 . PMC   3884237 . PMID   24454013.
  4. 1 2 3 "Selenium compounds". Immediately Dangerous to Life or Health Concentrations. National Institute for Occupational Safety and Health.
  5. ↑ Féher F (1963). "7. Sulfur, Selenium, Tellurium - Sodium Selenite". In Brauer G (ed.). Handbook of Preparative Inorganic Chemistry. Vol. 1 (2nd ed.). New York, NY: Academic Press. p. 431-432.
  6. ↑ Wickleder MS (2002). "Sodium Selenite, Na2SeO3". Acta Crystallographica Section E. 58 (11): i103–i104. Bibcode:2002AcCrE..58I.103W. doi:10.1107/S1600536802019384. ISSN   1600-5368.
  7. ↑ Langner BE (2002). "Selenium and Selenium Compounds". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a23_525. ISBN   978-3-527-30673-2.
  8. ↑ 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. S2CID   12668227.
  9. ↑ Nitschke P, Stewart F (January 2021). The peaceful pill ehandbook. Bellingham, WA: Exit International. p. 192. ISBN   9798739653055.
  10. ↑ Wilber CG (1980). "Toxicology of selenium". Clinical Toxicology. 17 (2): 171–230. doi:10.3109/15563658008985076. PMID   6998645.
  11. ↑ 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.
  12. ↑ Tolerable Upper Intake Levels For Vitamins And Minerals (PDF), European Food Safety Authority, 2006
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