Sodium metatungstate is the

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

with the formula Na₆ ₂W₁₂O₄₀ 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 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 chemical substance, substance, the solute, to form a solution (chemistry), solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form su ...

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 Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be use ...

. It has significant advantages when compared to

zinc chloride Zinc chloride is an Inorganic chemistry, inorganic chemical compound with the chemical formula, formula ZnCl2·''n''H2O, with ''n'' ranging from 0 to 4.5, forming water of hydration, hydrates. Zinc chloride, anhydrous and its hydrates, are colo ...

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.

References

Further reading