Sodium metatungstate

Sodium metatungstate
Identifiers
CAS Number	314075-43-9;
3D model (JSmol)	Interactive image;
EC Number	412-770-9;
PubChem CID	71311259;
	InChI InChI=1S/6Na.H2O.39O.12W/h;;;;;;1H2;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;/q6+1;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;6-1;;;;;;;;;;;; Key: YVQUUPJGDSQKML-UHFFFAOYSA-N;
	SMILES O.[O-][W](=O)(=O)[O-].[O-][W](=O)(=O)[O-].[O-][W](=O)(=O)[O-].O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.[Na+].[Na+].[Na+].[Na+].[Na+].[Na+];
Properties
Chemical formula	H2Na6O40W12
Molar mass	2985.99 g·mol−1
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

The [W₁₂O₄₀]^8- cage. Metatungstates feature the doubly protonated derivative of this cage, i.e. [H₂W₁₂O₄₀]^6-.^[1]

Sodium metatungstate is the inorganic compound with the formula Na₆[H₂W₁₂O₄₀], sometimes written 3Na₂WO₄·9WO₃·H₂O. It is also referred to as sodium polytungstate (SPT). This salt has been used in the manufacture of dense aqueous solutions. Sodium metatungstate exists as white solid. The anion is the polyoxotungstate [H₂W₁₂O₄₀]^6-, which features six-coordinated tungsten(VI) centers interconnected with doubly- and triply bridging oxo ligands.

Due to its very high solubility in water (max. density 3.1 g/cm³), SPT is widely used as to produce "heavy liquid" for gravity separation (sink /float analysis) and density gradient centrifugation. It has significant advantages when compared to zinc chloride solution or the toxic halogenated carbons for sink-swim analysis. Aqueous SPT is non-toxic (unlike the denser Clerici solution), non-flammable, odorless, reusable and additionally it has a low viscosity.^[2]

References

↑ Asami, M.; Ichida, H.; Sasaki, Y. (1984). "The structure of hexakis(tetramethylammonium) dihydrogendodecatungstate enneahydrate, [(CH3)4N]6[H2W12O40].9H2O". Acta Crystallographica Section C. 40: 35–37. doi:10.1107/S0108270184002924.
↑ Munsterman, Dirk; Kerstholt, Susan (1996). "Sodium polytungstate, a new non-toxic alternative to bromoform in heavy liquid separation". Review of Palaeobotany and Palynology. 91 (1–4): 417–422. Bibcode:1996RPaPa..91..417M. doi:10.1016/0034-6667(95)00093-3.

Gregory, Murray R.; Johnston, Keith A. (1987). "A nontoxic substitute for hazardous heavy liquids—aqueous sodium polytungstate (3Na2WO4.9WO3.H2O) solution (Note)". New Zealand Journal of Geology and Geophysics. 30 (3): 317. doi:10.1080/00288306.1987.10552626.
Bolch, C. J. S. (1997). "The use of sodium polytungstate for the separation and concentration of living dinoflagellate cysts from marine sediments". Phycologia. 36 (6): 472–478. doi:10.2216/i0031-8884-36-6-472.1.
Six, J (1999). "Recycling of sodium polytungstate used in soil organic matter studies". Soil Biology and Biochemistry. 31 (8): 1193–1196. doi:10.1016/S0038-0717(99)00023-1.
Savage, N. M. (1988). "The use of sodium polytungstate for conodont separations" (PDF). Journal of Micropalaeontology. 7 (1): 39–40. Bibcode:1988JMicP...7...39S. doi:10.1144/jm.7.1.39. S2CID 129701930.

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[1] Asami, M.; Ichida, H.; Sasaki, Y. (1984). "The structure of hexakis(tetramethylammonium) dihydrogendodecatungstate enneahydrate, [(CH3)4N]6[H2W12O40].9H2O". Acta Crystallographica Section C. 40: 35–37. doi:10.1107/S0108270184002924.

[2] Munsterman, Dirk; Kerstholt, Susan (1996). "Sodium polytungstate, a new non-toxic alternative to bromoform in heavy liquid separation". Review of Palaeobotany and Palynology. 91 (1–4): 417–422. Bibcode:1996RPaPa..91..417M. doi:10.1016/0034-6667(95)00093-3.

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References

Further reading