Sodium tungstate

Sodium tungstate
Names
	IUPAC name Sodium tungstate
Identifiers
CAS Number	13472-45-2 ;
3D model (JSmol)	Interactive image;
ECHA InfoCard	100.033.389
PubChem CID	26052;
RTECS number	YO7875000;
UNII	64LRH4405G ;
CompTox Dashboard (EPA)	DTXSID4021420 ;
	InChI InChI=1S/2Na.4O.W/q2+1;;;2-1;;
	SMILES [O-][W](=O)(=O)[O-].[Na+].[Na+];
Properties
Chemical formula	Na2WO4
Molar mass	293.82 g/mol
Appearance	White rhombohedral crystals
Density	4.179 g/cm3 (anhydrous) ; 3.25 g/cm3 (dihydrate)
Melting point	698 °C (1,288 °F; 971 K)
Solubility in water	57.5 g/100 mL (0 °C) ; 74.2 g/100 mL (25 °C) ; 96.9 g/100 mL (100 °C)
Solubility	slightly soluble in ammonia ; insoluble in alcohol, acid
Structure
Crystal structure	Rhombic (anhydrous) ; orthorhombic (dihydrate)
Hazards
Safety data sheet	External MSDS
Related compounds
Other cations	Lithium tungstate; Caesium tungstate
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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	Infobox references

Sodium tungstate is the inorganic compound with the formula Na₂WO₄. This white, water-soluble solid is the sodium salt of tungstic acid. It is useful as a source of tungsten for chemical synthesis. It is an intermediate in the conversion of tungsten ores to the metal.[1]

Preparation and structure

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 from wolframite:[1]

Fe/MnWO₄ + 2 NaOH + 2 H₂O → Na₂WO₄•2H₂O + Fe/Mn(OH)₂

Scheelite is treated similarly using sodium carbonate.

Sodium tungstate can also be produced by treating tungsten carbide with a mixture of sodium nitrate and sodium hydroxide in a fusion process which overcomes the high exothermicity of the reaction involved.

Several polymorphs of sodium tungstate are known, three at only one atmosphere pressure. They feature tetrahedral orthotungstate dianions but differ in the packing motif. The WO₄²⁻ anion adopts a structure like sulfate (SO₄²⁻).[2]

Reactions

Treatment of sodium tungstate with hydrochloric acid gives the tungsten trioxide or its acidic hydrates:

Na₂WO₄ + 2 HCl → WO₃ + 2 NaCl + H₂O

Na₂WO₄ + 2 HCl → WO₃.H₂O + 2 NaCl

This reaction can be reversed using aqueous sodium hydroxide

Uses

The dominant use of sodium tungstate is as an intermediate in the extraction of tungsten from its ores, almost all of which are tungstates.[1] Otherwise sodium tungstate has only niche applications.

In organic chemistry, sodium tungstate is used as catalyst for epoxidation of alkenes and oxidation of alcohols into aldehydes or ketones. It exhibits anti-diabetic effects.[3]

Solutions of sodium and lithium metatungstates are used in density separation. Such solutions are less toxic than bromoform and methylene iodide, but still have densities that fall between a number of naturally coupled minerals.[4]

Sodium tungstate is a competitive inhibitor of molybdenum. Dietary tungsten reduces the concentration of molybdenum in tissues.[5]

gollark: Complaining about scalpers is just going after the obvious issues and ignoring the fact that *there are not enough GPUs*.

gollark: It might lead to more expensive GPUs in the long run due to increased segmentation killing the second hand market.

gollark: Scalpers only exist because demand outstrips supply. Due to mining and shortages.

gollark: What? That's ridiculous.

gollark: I'm kind of conflicted on the Nvidia thing, because on the one hand I really don't like hardware being artificially limited and on the other I also don't like mining and want cheap GPUs.

References

Lassner, Erik; Schubert, Wolf-Dieter; Lüderitz, Eberhard; Wolf,, Hans Uwe (2005). "Tungsten, Tungsten Alloys, and Tungsten Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a27_229.CS1 maint: extra punctuation (link)
Carl W. F. T. Pistorius "Phase Diagrams of Sodium Tungstate and Sodium Molybdate to 45 kbar" J. Chem. Phys. 1966, volume 44, 4532.doi:10.1063/1.1726669
The Antidiabetic Agent Sodium Tungstate Activates Glycogen Synthesis through an Insulin Receptor-independent Pathway. The Journal of Biological Chemistry, Vol. 278, No. 44, Issue of October 31, pp. 42785–42794, 2003.
Improved density gradient separation techniques using Sodium Polytungstate and a comparison to the use of other heavy liquids. Report, U.S. Geological Survey, 1993.
Considine, Glenn D., ed. (2005). "Molybdenum". Van Nostrand's Encyclopedia of Chemistry. New York: Wiley-Interscience. pp. 1038–1040. ISBN 978-0-471-61525-5.

External links

The Anti-Diabetic Effects Of Sodium Tungstate Revealed, ScienceDaily, Aug. 28, 2009

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[Ullmann-1] Lassner, Erik; Schubert, Wolf-Dieter; Lüderitz, Eberhard; Wolf,, Hans Uwe (2005). "Tungsten, Tungsten Alloys, and Tungsten Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a27_229.CS1 maint: extra punctuation (link)

[2] Carl W. F. T. Pistorius "Phase Diagrams of Sodium Tungstate and Sodium Molybdate to 45 kbar" J. Chem. Phys. 1966, volume 44, 4532.doi:10.1063/1.1726669

[3] The Antidiabetic Agent Sodium Tungstate Activates Glycogen Synthesis through an Insulin Receptor-independent Pathway. The Journal of Biological Chemistry, Vol. 278, No. 44, Issue of October 31, pp. 42785–42794, 2003.

[4] Improved density gradient separation techniques using Sodium Polytungstate and a comparison to the use of other heavy liquids. Report, U.S. Geological Survey, 1993.

[Nostrand-5] Considine, Glenn D., ed. (2005). "Molybdenum". Van Nostrand's Encyclopedia of Chemistry. New York: Wiley-Interscience. pp. 1038–1040. ISBN 978-0-471-61525-5.