Sodium selenite
| Sodium selenite | |
|---|---|
 | |
| Identifiers | |
| CAS number | 10102-18-8  |
| PubChem | 24934 |
| ChemSpider | 23308 |
| UNII | HIW548RQ3W |
| EC number | 233-267-9 |
| UN number | 2630 |
| ChEBI | CHEBI:48843 |
| ChEMBL | CHEMBL112302 |
| RTECS number | VS7350000 |
| ATC code | A12 |
| Jmol-3D images | {{#if:[Na+].[Na+].[O-][Se]([O-])=O|Image 1 |
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| 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 |
 0
3
0
|
| Related compounds | |
| Related compounds | Sodium sulfite Sodium selenate Sodium selenide |
(verify) (what is: / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa) | |
| Infobox references | |
Sodium selenite is a salt, a colourless solid, and the most common water-soluble selenium compound. It has the formulas Na2SeO3 and Na2SeO3(H2O)5 (CAS#26970-82-1). Respectively, these are the anhydrous salt and its pentahydrate. This hydrated salt is the more common one. The hydrated and anhydrous salts behave identically for most purposes, although their molar masses differ.
Synthesis and fundamental reactions
Sodium selenite usually is prepared by the reaction of selenium dioxide with sodium hydroxide:
- SeO2 + 2 NaOH → Na2SeO3 + H2O
Akin to the related salt sodium sulfite, Na2SeO3 features a pyramidal dianion SeO32–.[1] 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.[2]
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.” [3]
Safety
Selenium is toxic in high concentrations. The chronic toxic dose for human beings is about 2.4 to 3 milligrams of selenium per day.[4]
See also
References
- ↑ 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.
- ↑ 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
- ↑ Schrauzer, GN (2001). "Nutritional selenium supplements: product types, quality, and safety". Journal of the American College of Nutrition 20 (1): 1–4. PMID 11293463.
- ↑ 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.
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