Sodium metaborate

Sodium metaborate
	Sodium metaborate monomer
	Sodium metaborate trimer
Names
	IUPAC name Sodium metaborate
Identifiers
CAS Number	7775-19-1 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:75227;
ECHA InfoCard	100.028.992
EC Number	231-891-6;
PubChem CID	145326;
RTECS number	ED4640000;
UNII	Z6Q395A23R ;
CompTox Dashboard (EPA)	DTXSID2034386 ;
	InChI InChI=1S/BO2.Na/c2-1-3;/q-1;+1 Key: NVIFVTYDZMXWGX-UHFFFAOYSA-N;
	SMILES B(=O)[O-].[Na+];
Properties
Chemical formula	NaBO2
Molar mass	65.80 g·mol−1
Appearance	Colorless crystals
Odor	Odorless
Density	2.464 g/cm3 (anhydrous)
Melting point	966 °C (1,771 °F; 1,239 K)
Boiling point	1,434 °C (2,613 °F; 1,707 K)
Solubility in water	16.4 g/(100 mL) (0 °C) ; 28.2 g/(100 mL) (25 °C) ; 125.2 g/(100 mL) (100 °C)
Solubility	insoluble in ether, ethanol
Structure
Crystal structure	trigonal
Thermochemistry
Heat capacity (C)	65.94 J/(mol·K)
Std molar; entropy (S⦵298)	73.39 J/(mol·K)
Std enthalpy of; formation (ΔfH⦵298)	−1059 kJ/mol
Hazards
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	2330 mg/kg (rat, oral)
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Sodium metaborate is a chemical compound of sodium, boron, and oxygen with formula NaBO₂.^[3] However, the metaborate ion is trimeric in the anhydrous solid, therefore a more correct formula is Na₃B₃O₆ or (Na⁺)₃[B₃O₆]³⁻. The formula can be written also as Na₂O·B₂O₃ to highlight the relation to the main oxides of sodium and boron.^[2] The name is also applied to several hydrates whose formulas can be written NaBO₂·nH₂O for various values of n.

The anhydrous and hydrates are colorless crystalline solids. The anhydrous form is hygroscopic.^[4]

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