Mineral solids in heavy liquids

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Insoluble plastic or mineral particles can be separated based on their sedimentation behaviour with the help of an adjustable density solution.

Sodium polytungstate (SPT) is an inorganic salt that dissolves well in water (650 g of solids can dissolve in 100 mL of water). This makes it possible to produce low-viscosity aqueous solutions with densities of 1.1 g/cm³ to 3.1 g/cm³, which are suitable for float-and-sink analyses, for example to separate aluminium and copper (photo). Unlike the organic – and usually toxic – alternatives frequently used earlier, such as bromoform, tetrabromomethane (TBE) or diiodomethane, SPT does not pose any danger to humans, animals or the environment when used properly.

Areas of application for float-and-sink analyses range from geology and mineralogy to polymer chemistry to virology and biochemistry. In geology and mineralogy, the aim is to separate rock samples; in mining float-and-sink analyses facilitate quality control of ores and coal. In polymer chemistry plastics are separated; in virology DNA and cells are separated and the particles are examined to determine their sedimentation behaviour. Biochemistry uses SPT as a material for binary and ternary density gradient centrifugation, while it is used in industry for quality assurance for glass and for recycling processes. SPT is reusable in many applications.

Although the density of a homogeneous, Newtonian SPT solution is a maximum of 3.1 g/cm³, it is possible to increase the density and thus the field of application as well: Adding fine tungsten carbide particles (particle size 1 μm) to an SPT solution with a density of 3.0 g/cm³ results in a suspension with a density of 4.6 g/cm³ (SPT-4). The sedimentation in this

suspension is so slow that it can be worked with for over two to three hours without significantly impacting the separation process.

Mineralogists and gemmologists can use the suspension made of tungsten carbide particles in SPT solutions to separate and distinguish between gemstones such as

diamonds with a density of 3.5 g/cm³ from zirconia with a density of 5.8 g/cm³.

Please notice that we are offer SPT as solid (prepare your heavy liquid on your own SPT-1 and SPT-2), as ready-to-use solution (with different reiquired densities, SPT-3), special solutions for individual applications (very pure SPT-0, stabilized for base metals SPT-5, lower viscosity LVP). Also available SPT-3R, recycled SPT solution, which is cheaper and often suitable for standard applications.

For more information visit:

Homepage: www.heavy-liquid.com

Contact: service@heavy-liquid.com

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