Sodium metaborate
Sodium metaborate is a chemical compound of sodium, boron, and oxygen with formula NaBO2. 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. The name is also applied to several hydrates whose formulas can be written NaBO2·nH2O for various values of n.
Sodium metaborate monomer | |
Sodium metaborate trimer | |
| Names | |
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| IUPAC name
Sodium metaborate | |
| Identifiers | |
3D model (JSmol) |
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| ChEBI | |
| ECHA InfoCard | 100.028.992 |
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PubChem CID |
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| UNII | |
CompTox Dashboard (EPA) |
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| Properties | |
| 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) |
| 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 | |
| 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 | |
The anhydrous and hydrates are colorless crystalline solids. The anhydrous form is hygroscopic.
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