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| Names | |
|---|---|
| IUPAC name Sodium tungstate | |
| Identifiers | |
3D model (JSmol) | |
| ChemSpider | |
| ECHA InfoCard | 100.033.389 |
| EC Number |
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| RTECS number |
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| UNII | |
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| Properties | |
| Na2WO4 | |
| Molar mass | 293.82 g/mol (anhydrous) 329.85 g/mol (dihydrate) |
| Appearance | Whiterhombohedral crystals |
| Density | 4.179 g/cm3 (anhydrous) 3.25 g/cm3 (dihydrate) |
| Melting point | 698 °C (1,288 °F; 971 K) |
| 57.5 g/100 mL (0 °C) 74.2 g/100 mL (25 °C) 96.9 g/100 mL (100 °C) | |
| Solubility | slightly soluble inammonia insoluble inalcohol,acid |
| Structure | |
| Rhombic (anhydrous) orthorhombic (dihydrate) | |
| Hazards | |
| GHS labelling:[1] | |
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| Warning | |
| H302 | |
| P264,P270,P301+P317,P330,P501 | |
| Safety data sheet (SDS) | External MSDS |
| Related compounds | |
Othercations | Lithium tungstate Caesium tungstate |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Sodium tungstate is theinorganic compound with the formula Na2WO4. This white, water-soluble solid is thesodium salt oftungstic acid. It is useful as a source oftungsten for chemical synthesis. It is an intermediate in the conversion of tungstenores to the metal.[1]
Sodium tungstate is obtained by digestion of tungsten ores, the economically important representatives of which are tungstates, in base. Illustrative is the extraction of sodium tungstate fromwolframite:[1]
Scheelite is treated similarly usingsodium carbonate.
Sodium tungstate can also be produced by treatingtungsten carbide with a mixture ofsodium nitrate andsodium hydroxide in a fusion process which overcomes the high exothermicity of the reaction involved.
Severalpolymorphs of sodium tungstate are known, three at only one atmosphere pressure. They feature tetrahedral orthotungstate dianions but differ in the packing motif. TheWO2−
4 anion adopts a structure like sulfate (SO2−
4).[2]
Treatment of sodium tungstate withhydrochloric acid gives thetungsten trioxide or its acidic hydrates:
This reaction can be reversed using aqueous sodium hydroxide.
The dominant use of sodium tungstate is as an intermediate in the extraction of tungsten from its ores, almost all of which aretungstates.[1] Otherwise sodium tungstate has only niche applications.
In organic chemistry, sodium tungstate is used as catalyst forepoxidation ofalkenes and oxidation ofalcohols intoaldehydes orketones. It exhibits anti-diabetic effects.[3]
Solutions of sodium and lithium metatungstates are used in density separation. Such solutions are less toxic thanbromoform andmethylene iodide, but still have densities that fall between a number of naturally coupled minerals.[4]
Sodium tungstate is acompetitive inhibitor ofmolybdenum; because tungsten is directly below molybdenum on the periodic table, it has similar electrochemical properties. Dietary tungsten reduces the concentration of molybdenum in tissues.[5] Some bacteria usemolybdenum cofactor as part of their respiratory chain; in these microbes, tungstate can replace molybdenum and inhibit the generation of energy by aerobic respiration. As such, one niche use of sodium tungstate is in experimental biology—where it has been found that adding sodium tungstate to the drinking water of mice inhibits the growth ofEnterobacteriaceae (a family of endogenous opportunistic pathogens) in the gut.[6]
Sodium tungstate has been researched as a potential treatment for infertility under the code OXO-001.[7][8][9]
