Sodium selenite

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Not to be confused with Selenite (mineral). ‹See Tfd›
Sodium selenite
Natriumseleniet t.png
Identifiers
CAS number (hydrate: 26970-82-1) 10102-18-8 (hydrate: 26970-82-1) YesY
PubChem 24934
ChemSpider 23308 YesY
UNII HIW548RQ3W YesY
EC number 233-267-9
UN number 2630
ChEBI CHEBI:48843 YesY
ChEMBL CHEMBL112302 YesY
RTECS number VS7350000
ATC code A12CE02
Jmol-3D images Image 1
Properties
Molecular formula Na2O3Se
Molar mass 172.94 g mol−1
Appearance colourless solid
Density 3.1 g/cm3
Melting point decomposes at 710 °C
Solubility in water 85 g/100 mL (20 °C)
Solubility insoluble in alcohol, ethanol
Structure
Crystal structure tetragonal
Hazards
MSDS ICSC 0698
EU Index 034-003-00-3
EU classification Very toxic (T+)
Dangerous for the environment (N)
R-phrases R23, R28, R31, R43, R51/53
S-phrases (S1/2), S28, S36/37, S45, S61
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Related compounds
Related compounds Sodium sulfite
Sodium selenate
Sodium selenide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references

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.

Synthesis and fundamental reactions[edit]

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[edit]

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 some food supplements.

The US Food and Drug Administration approved a selenium supplement to animal diets, however 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[edit]

Selenium is toxic in high concentrations. The chronic toxic dose for human beings is about 2.4 to 3 milligrams of selenium per day.[5]

See also[edit]

References[edit]

  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 Structure Reports Online 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)) 17 (2): 171–230. doi:10.3109/15563658008985076. PMID 6998645. 

External links[edit]