Sodium selenite

Sodium selenite

Identifiers
CAS Number	10102-18-8 Y 26970-82-1 (pentahydrate) Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:48843 Y
ChEMBL	ChEMBL112302 Y
ChemSpider	23308 Y
ECHA InfoCard	100.030.230
EC Number	233-267-9
KEGG	D10530 Y
PubChem CID	24934
RTECS number	VS7350000
UNII	HIW548RQ3W Y 0WV4L961ZV (pentahydrate) Y
UN number	2630
CompTox Dashboard (EPA)	DTXSID0032077
InChI InChI=1S/2Na.H2O3Se/c;;1-4(2)3/h;;(H2,1,2,3)/q2*+1;/p-2 Y Key: BVTBRVFYZUCAKH-UHFFFAOYSA-L Y InChI=1/2Na.H2O3Se/c;;1-4(2)3/h;;(H2,1,2,3)/q2*+1;/p-2 Key: BVTBRVFYZUCAKH-NUQVWONBAC
SMILES [Na+].[Na+].[O-][Se]([O-])=O
Properties
Chemical formula	Na2O3Se
Molar mass	172.948 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 ethanol
Structure
Crystal structure	tetragonal
Pharmacology
ATC code	A12CE02 (WHO) (Oral), B05XA20 (WHO) (Parenteral)
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H300, H317, H331, H411
Precautionary statements	P261, P264, P270, P271, P272, P273, P280, P301+P310, P302+P352, P304+P340, P311, P321, P330, P333+P313, P363, P391, P403+P233, P405, P501
NFPA 704 (fire diamond)	3 0 0
Safety data sheet (SDS)	ICSC 0698
Related compounds
Related compounds	Sodium sulfite Sodium selenate Sodium selenide sodium biselenite
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

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

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.

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.^[2] 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.^[4]

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.” ^[5]

Sodium selenite has been proposed as an effective suicide agent.^[6]

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.^[7] 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.^[8] The European Food Safety Authority reviewed the same safety question and set its UL at 300 μg/day.^[9]

See also

• Selenite (ion)

References

External links

• Linus Pauling Institute page on selenium