Sodium selenite

Sodium selenite
Identifiers
CAS Number	10102-18-8 ; 26970-82-1 (pentahydrate) ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:48843 ;
ChEMBL	ChEMBL112302 ;
ChemSpider	23308 ;
ECHA InfoCard	100.030.230
EC Number	233-267-9;
KEGG	D10530 ;
PubChem CID	24934;
RTECS number	VS7350000;
UNII	HIW548RQ3W ; 0WV4L961ZV (pentahydrate) ;
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 Key: BVTBRVFYZUCAKH-UHFFFAOYSA-L ; 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	350 °C (662 °F; 623 K) (decomposes over 300 °C (572 °F; 573 K))
Solubility in water	89.8 g/100mL (20 °C (68 °F; 293 K))
Vapor pressure	< 0.00133 hPa (1.93×10−5 psi) (20 °C (68 °F; 293 K))
Structure
Crystal structure	monoclinic (anhydrous); orthorhombic (pentahydrate);
Space group	Pbcm (pentahydrate)
Lattice constant	a = 6.5865 Å, b = 17.2263 Å, c = 14.7778 Å (pentahydrate)
Lattice volume (V)	1676.70 Å3 (pentahydrate)
Formula units (Z)	8 (pentahydrate)
Pharmacology
ATC code	A12CE02 (WHO) (Oral), B05XA20 (WHO) (Parenteral)
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H300+H330, H315, H317, H319, H411
Precautionary statements	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)	4 0 0
Autoignition; temperature	> 400 °C (752 °F; 673 K)
Threshold limit value (TLV)	0.2 mg/m3 (as selenium) (TWA)
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	7 mg/kg (oral, rat)
LDLo (lowest published)	3.3 mg/kg (oral, sheep)
	NIOSH (US health exposure limits):
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	Sodium sulfite; Sodium selenate; Sodium selenide; Sodium biselenite;
Other cations	Copper(II) selenite; Iron(III) selenite;
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

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.