Sodium metatungstate is the inorganic compound with the formula Na₆ ₂W₁₂O₄₀ sometimes written 3Na₂WO₄·9WO₃·H₂O. It also called 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 ₂W₁₂O₄₀/nowiki>^6-, which features six-coordinated tungsten(VI) centers interconnected with doubly- and triply bridging oxo ligands. Due to its very high

solubility In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solub ...

in water (max. density 3.1 g/cm³), SPT is widely used as to produce "heavy liquid" for

gravity separation Gravity separation is an industrial method of separating two components, either a suspension, or dry granular mixture where separating the components with gravity is sufficiently practical: i.e. the components of the mixture have different specific ...

(sink /float analysis) and density gradient centrifugation. It has significant advantages when compared to

zinc chloride Zinc chloride is the name of inorganic chemical compounds with the formula ZnCl2 and its hydrates. Zinc chlorides, of which nine crystalline forms are known, are colorless or white, and are highly soluble in water. This salt is hygroscopic and e ...

solution or the toxic halogenated carbons for sink-swim analysis. Aqueous SPT is non-toxic (unlike the denser

Clerici solution Clerici solution is an aqueous solution of equal parts of thallium formate (Tl(HCO2)) and thallium malonate (Tl(C3H3O4)). It is free-flowing and odorless. Its color fades from yellowish to colorless when diluted. At 4.25 g/cm3 at , saturat ...

), non-flammable, odorless, reusable and additionally it has a low viscosity.

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Further reading