General information: Solid, crystalline sodium polytungstate is not hygroscopic and has an unlimited shelf life at room temperature.
The sink-float substance should not contain ions which are soluble in water. In some instances, Pb2+-, Ag+-, Sn2+– und Ba2+ ions in particular may form largely insoluble precipitates spontaneously or after a period of time. If these soluble ions are present in samples, we recommend that you wash them beforehand with hot water.
If SPT-4 is used, stir the solution thoroughly before use.
What are the key product details for sodium polytungstate?
What are the safety-related and physical specifications of sodium polytungstate?
What are the benefits of SPT (sodium polytungstate, sodium metatungstate)?
How do I adjust a density by dissolving a solid?
In order to produce a heavy liquid solution, the SPT (SPT-0, -1, -2) must be dissolved in de-ionised water (ultrasound bath optional). The higher the concentration, the higher the density (checked e.g. with a hydrometer). The maximum achievable density of an aqueous solution is 3.1 g/cm³ at room temperature. The density can be lowered by adding water, or increased by evaporating the solution in a beaker (preferably with a large surface) at 70°C in a drying chamber. The liquid must not be boiled! You can also add solid SPT to increase the density again.
Producing the solution in this way allows fine granules, particles or solids to be separated by density (sink-float process). A laboratory centrifuge accelerates the separation process.
How do I adjust the density by adding water?
You can reduce the density of an SPT solution as required by adding de-ionised water.
If you have reduced the density of the solution too much, you can increase it again by evaporating the solution in a beaker at 70°C in a drying chamber. The liquid must not be boiled!
How is the viscosity linked to the density?
Viscosity is shown in the following table and diagram as a function of density at 25°C. As seen in the figure, the viscosity only increases very slightly to a density of 2.5 g/cm³. This also allows separation within the fine grain range. The use of laboratory centrifuges can also accelerate the separation process here. If you need a very low viscosity please ask for LVP-3.
What is the ideal pH value for sodium polytungstate?
The pH value of the solution depends on the density. A solution with a density of 3.0 g/cm³ typically has a pH value of around 3. The solution has long-term stability at this pH value (several years). Each SPT solution must therefore be stored at a pH value of 3.
The pH value can quickly be changed e.g. to a pH of 7 by adding e.g. NaOH. After completion of the test at the increased pH value, the solution should generally be reduced again to a pH of 3 using e.g. a few drops of HCl.
What is the structural composition of sodium polytungstate?
It is a 12-fold aggregated isopolytungstate with a molar mass of 2986.12 g/Mol.
According to the models, polytungstate has a octahedral structure, in which oxygen ions are found in the corners and tungsten ions in the centre of the octahedra. As the spherical model shows, the oxygen ions form a very dense spherical shell, in which the tungsten ions are found in the open spaces of the octahedra.
In a true metatungstate, the two hydrogen atoms are present in the central cavity of the polyanion, and cannot penetrate the spherical shell.
What are the analysis results for sodium polytungstate?
Solid sodium polytungstate contains at least 86% ± 1 % WO₃.
Bound water in the sodium polytungstate may vary very slightly.
What international registrations are in place for sodium polytungstate?
TC-Tungsten Compounds is a developer, patent holder and producer of sodium polytungstate (also sodium metatungstate) and supplies international customers from both the research and industrial sectors with its environmentally friendly, non-toxic SPT 0 to 5 product line. In collaboration with H.C. Starck, the family-run company based in Grub am Forst also distributes selected tungsten chemicals in small quantities.