formula:

or

appearance:

White crystals or light yellow-green transparent solution

properties:

Very easily soluble in water, pH-neutral solution, maximum possible density of solution: 3,1 g/cm3 at 25° C

features:

non-toxic
non-flammable
odourless
reusable
density may be adjusted by dilution from ρ = 1,1 - 3,1 g/cm3
low viscosity
easy-to-use
sinks and floats may be easily cleaned with water after use
environmentally friendly

application:

The heavy liquid solution is prepared by dissolving sodium polytungstate in de-ionized water. Te resulting compound is a salt which is easily soluble in water. The maximum attainable density of the solution in water at room temperature is 3.1 g/cm3. Further chemical properties of the solution may be ascertained by studying the diagrams. These show density as a function of the sodium polytungstate content (Fig. 1) and viscosity as a function of density (Fig. 2). As may be seen from Fig. 2, viscosity increases only slightly with densities up to 2.5 g/cm3. This process also allows the fine granules to be separated. The use of a laboratory centrifuge will speed up the separation process.

structure:

This is a 12-fold aggregated isopolytungstate with a molar mass of 2986.12 g/Mol. The structure of polytungstate is modelled using octahedrons in which the oxygen ions are located in the corners and the tungsten ions in the middle of the octahedrons. When represented as a spherical model, the oxygen ions form a dense spherical shell while the tungstate ions fill the open spaces in the octahedra.
Because of this structure this substance may be considered a “true” metatungstate, represented structurally as . It is known that in “true” metatungstates both of the oxygen ions are located in the central empty space of the polyanion and that they are unable to penetrate the external shell of the spherical casing.
Solid crystalline sodium polytungstate is not hygroscopic and may be stored for an unlimited period at room temperature.

notes:

The following points should be observed when using aqueous polytungstate solutions:

1. Only distilled or de-ionized water should be used.
2. All containers must be sealed properly after use.
3. Only containers made from glass, synthetic materials or stainless steel should be used.
4. Do not bring the solution into contact with reduced substances.
   The resultant blue colouring will not, however, affect the achievement of the required
   density in any way. Colour may be removed from the solution and a blue colouration
   prevented by the addition of a few drops of hydrogen peroxide.
5. The Sinks and floats used should not contain any water soluble ions.
   Pb2+-, Ag+-, Sn2+- and Ba2+ - ions in particular form deposits which are difficult to dissolve.
   If these ions should be present in the samples these must be washed with hot water prior
   to the – sink/swim analysis.

analysis:

Solid sodium polytungstate contains at least 86 % ± 1 % WO₃.

The quantity of bound water in sodium polytungstate may vary slightly.

Typical analysis values (not guaranteed values) are:
Al ≤ 0.0015 %; As ≤ 0.012 %; Cu ≤ 0.001 %; Fe ≤ 0.005 %; Mo ≤ 0.005 %; Si ≤ 0.005 %; Ti ≤ 0.001 %.

form of supply:

A standard delivery of sodium polytungstate will be of a ready-to-use aqueous solution with a density of 2.82 ± 0.02 g/cm3 or with densities of ≥ 3.0 g/cm3 in 1 kg, 5 kg, 10 kg and 25 kg.

Sodium polytungstate may also, however, be supplied in crystalline form or as granules batches in batches of 1 kg, 5 kg, 10 kg and 25 kg.