Sodiumpolytungstate

Chemical Description

Properties of aqueous

Polytungstate Anions

Trace elements

pH range of sodium polytungstate

Density of SPT

Viscosity of SPT

Density Relationship - SPT and Tungsten Carbide

Chemical Description

of sodium polytungstate

Sodium Polytungsteate (SPT) is the generic name for the compound here involved: The specific compound involved is sodium metatungstate Na6(H2W12O40), which is a spherical molecule having 40 oxygen atoms on its outer shell, 12 tungsten atoms in tetrahedal configurations in an inner shell and 2 hydrogen atoms in the center, all surrounded by 6 sodium cations.

Computer enhanced 10 million enlargement of 16 polytungstate anions (H2W12O40). Actual size is 1 nm or 10 A diameter of the individual spherical molecule.

The analytical data is:

WO3 (tungsten trioxide) = 86.66%; Na (sodium) = 4.50 % H2O (water) = 8.84%

Sodium Polytungstate contain only a very low concentration of Carbon and has a low viscosity at high concentration. The solution of the white crystalline powder has a adjustable density from 1.0 to 3.1 g/ml. Ph-scale is approximate 3 at 4000 g/l water by 20°C. Note that SPT solution is stable in the pH-range 2-4. Please see Material Safety Data Sheet for further information.

to top of page

Properties of aqueous

sodium polytungstate solutions

The sodium polytungstate molecule is an aggregate of twelve monomeric units, with a molar mass of 1986 g/mol. This substance is freely soluble in water, the resulting solutions exhibiting neutrality although the molecule is also stable over a wide pH range. At room temperature (25 °C), the sodium polytungstate mass fraction of an aqueous saturated solution is 0.8.

The compound also has a tendency to supersaturation, a property which is of importance when density measurments are carried out with highly concentrated polytungstate solutions (important for the separation of minerals of differing densities).

The agent can have a density of up to 3.1 g/ml and has a low viscosity at high concentrations. The viscosity increases only insignificantly up to a density of about 2.5 g/ml. Accordingly also separations in the fine grain range are possible within shorter periods.

In the case of separation of water-insoluble solid mixtures of different densities, the densities of the solutions of the polytungstate can be increased up to 4.6 g/ml by adding to the solutions high density materials such as tungsten carbide of suitable grain size so as to form a suspension.

to top of page

Trace elements in sodium polytungstate

Trace elements:

As < 5ppm*; Bi < 2ppm; C < 40ppm; Co < 1ppm; Cu < 1ppm; Fe < 1ppm; Mn < 1ppm;

Mo < 2ppm; Nb < 6ppm; Ni < 1ppm; P = 8ppm; Pb < 1ppm; Sb = 2ppm;

Si = 17ppm; Sn = 7ppm; Sr < 1ppm; Ta < 1ppm; U < 10ppm;

*ppm = parts per million

NOTE: The trace elements can be removed quantitatively from the separated goods by a few washings with water.

pH range of sodium polytungstate

Depending on concentration of sodium polytungstate the pH range is between 2 and 3.

Sodium Polytungstate is stable between the pH-range 2 and 4.

to top of page

Density of Sodium Polytungstate

The density of aqueous sodium polytungstate solution as a function of the mass portion at 77°F 25°C.

to top of page

Viscosity of sodium polytungstate

The viscosity of aqueous sodium polytungstate solution as a function of density portion at 77°F (25°C).

to top of page

Density Relationship - SPT and Tungsten Carbide

Density of a heterogenous mixture of aqueous sodium polytungstate solution and tungsten carbide as a function of the solid material volume portion starting from a saturated aqueous sodium polytungstate solution

to top of page

home