Introducing heavy liquids

Introducing SPT

Commentaries & Opinions

Fields of use


• The inorganic salt sodium polytungstate results in an aqueous, neutral solution.

• SPT is a Non-Toxic high density agent.

• Has a low viscosity at high concentration.

• Easily adjustable densities from 1.0 g/ml to 4.2 g/ml

• Is ecology safe and simple to handle. Can be discarded easily.

• Has No obnoxious smell, no corrosive properties, not flammable.

• Stable in the pH-range of 2-14.

• Laboratory centrifuges can be used.

• Excellent recovery, substantially no losses and thus SPT is less expensive than TBE.

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• SPT makes a light yellow solution.

• Sodium Polytungstate (SPT) is available in powder, granulate and liquid form.


• Mineral Separation, Conodont Research & Earthquake Research.

• Density Gradient Centrifugation.

• As an inactive, non radioactive simulant in nuklear reaktor technology.

• Separation of not soluble materials having different densities, like separation of minerals from gangue.


• for request

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• For Europe and other countries e-mail:

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Introducing heavy liquids

General Information

A description of heavy liquids and some of their uses

Heavy liquids are dense fluids or solutions used to separate materials of different density through their buoyancy. Materials with a density greater than the heavy liquid will sink, while materials with a density less than the heavy liquid will float on the liquid surface.

In the mineral industry, heavy liquids are commonly used in the laboratory to separate the "light" minerals such as quartz and clay from the "heavy" minerals. The density used for this type of separation is about 2.85 g/ml, nearly three times the density of water. Heavy liquid separations are carried out for varied reasons, depending on the industry. The mineral sands industry uses heavy liquid separations to check the grade of samples in their process, and to determine the efficiency of their industrial hydrocyclone separations. The diamond exploration industry uses heavy liquids to separate the dense "indicator" minerals from sand and clay.

Another use of heavy liquids is in paleontology. Typically, these heavy liquid separations are conducted at a lower density (e.g. 2.2 g/ml) since the separation is not between minerals of different types, but between fossil bones and minerals.

Organic heavy liquids

The organic heavy liquids form the "older" generation of heavy liquids. Two of the organic heavy liquids most commonly in use are bromoform and tetrabromoethane (TBE). Of these, bromoform has the lower viscosity (1.8 cP) but is considered more hazardous to work with because it has the higher vapour pressure (5.9 mm Hg at 25C). TBE has a higher viscosity (9 cP) and a lower vapour pressure (0.02 mm Hg at 25C).

Another organic heavy liquid, used when higher densities are required, is diiodomethane. Diiodomethane has a density of 3.31 g/ml, a vapour pressure of 1.2 mm Hg at 25 C, and a low viscosity of 2.6 cP.

The three commonly used organic heavy liquids all have problems with toxicity, and must be handled in a fume hood. Diiodomethane is moderately toxic by subcutaneous and other routes. Bromoform has been shown to cause severe liver damage and is poisonous by ingestion. There is evidence that it is a human mutagen and a neoplastigen on experimental animals, so it is potentially carcinogenic. TBE is poisonous by inhalation or ingestion and is a moderate irritant to the skin. It is a neoplastigen and mutagen with animals.

These liquids have the problem of being volatile and potentially causing health problems. For this reason, they are being phased out in the USA.

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Introducing SPT

sodium polytungstate, sodium metatungstate


The highly soluble inorganic salt sodium polytungstate when dissolved in water, can be used to replace the toxic and possible carcinogenic organic liquids traditionally used for gravity separation work. (See Toxicology/Ecology, Introducing heavy liquids)

Sodium Polytungstate is mainly used for mineral separation and for the density gradient centrifugation. (see Field of use)

The inorganic salt sodium polytungstate is available in powder form and results in an aqueous, colorless, transparent neutral solution. It has No obnoxious smell, no corrosive properties, not is flammable. SPT Is ecology safe and simple to handle. It has excellent recovery (up to 95%) and therefore substantially no losses and thus SPT is less expensive than TBE. It can be discarded easily. The densities can be adjusted from 1.0 g/cm3 to 3.1 g/cm3 as required in a simple way. (see How to use)

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Commentaries & Opinions

by users of sodium polytungstate:

John Callahan, Professor of Geology, Appalachian State University

....I would again like to thank you for providing all of us with a safe heavy liquid, and I want to wish you every success in your marketing efforts... Other advantages are that the heavy mineral separates can be cleaned with distilled water, and the specific gravity of the sodium polytungstate solution can be changed by adding either distilled water or powdered sodium polytungstate... the use of sodium polytungstate is recommended as a safe way to carry out effectively heavy mineral separations

D. H. Jungner, Radiocarbon Dating Laboratory, University of Helsinki

... We are using this liquid continuously for mineral separation in our laboratory and are very satisfied.

Susan Bailey, USAE Waterways Experiment Station, Vicksburg, MS - USA

... I am very impressed with the safty and versatility of sodium polytungstate and hope that I will be able to find a use for the product in my research.

Der Topographic & Geologic Survey, Harrisburg, PA.

... Justification for the use of Sodium Polytungstate and Tungsten Carbide - Presently we use Clerici`s Solution which has a maximum specific gravity of 4.25 for heavy liquid separations, or gravity separations according to density, which is extremely toxic. Both compounds listed above are non-toxic and less hazardous to use.

Dr. Stanley T. Krukowski, New Mexico Institute of Mining, Socorro

... The solution has been used successfully for the recovery of conodonts from insoluble residues, the separation of various feldspar species and inorganic mineral fractions (ash) from coal... a consequential advantage of the compound is the liberation of conodonts entrained in endolithic filaments ... advantage 1) safety: The use maintenance and storage of the compound pose no known health problems nor call for any special protective measures against fire hazard or corrosion. 2) Effectiveness: Recovery rates of near 100% of the conodont elements were realized, and only the interfacial method (Merrill 1985) can boast similar efficiency but the solvent and substrate of this method are not safe. 3) Familiarity: Laboratory technicians familiar with heavy liquid separations methods need not undergo major reeducation of technique ... no new investment in laboratory space and equipment is required ...

Dr. Dan Chaney, Vertebrate Preparations Laboratory, US Museum of Natural History

... Separation of micro-vertebrate remains from a concentrate by floating the fine fraction of the matrix off in a heavy liquid solution, is the quickest and most efficient way to recover elements of a fauna that might otherwise be overlooked. We are no longer using the carcinogenic bromides because of the severe health risks. The processing of matrix for the recovery of micro-vertebrate elements is important and, with the use of sodium polytungstate, can be accomplished safely and efficiently. The advantage that this material has over the Interfacial Method (Merill, 1985, S:V:P: News Bulletin, June No. 134, Page 56) are safety and ease of use. The material, at first glance, will appear expensive. However, in the light of safety, the ease of handling, and most importantly (where cost is considered) only minimal loss of parent material due to incomplete or continually process small batches of concentrates.

Dr. Steven Forman, Institute of Arctic and Alpine Research, University of Colorado

... We have recently used your non toxic heavy liquid and marveled in its easy use and recoverability. This new heavy liquid is of great use to thermoluminescence researchers as well as geologists and soil scientists.

Dr. Ann Wintle, Sub Department of Quaternary Research, University of Cambridge

... I hope that everyone will be using your liquid and will not have killed themselves with bromoform or tetrabromoethane.

Dr. Galina Hütt, Institute of Geology, University Tallinn, Soviet Union

... and we have poisoned ourselves for so many years, but now we are no longer concerned about our health. It is possible to perform other work in the same room during mineral separations. Since the regeneration is quite good and simple, I feel the price is more than adequate.

Morteza Fattahi, The school of geography, Oxford University, England

... Thank you very much for the fax and information about your company. At the same time I thank your branch in Germany for sending me the good news about characteristic of sodium polytungstate. Now I am more happy and confident in using this liquid gold.

Glen K. Merrill, Professor of Geology, University of Houston-Downtown

... For the very difficult samples I commonly process a combination (IM, magnetic separation, sodium polytungstate) must be employed dependent upon the nature of the residue. Sodium polytungstate forms a valuable tool in this succession of techniques ... I wish your product every success because it is badly needed and deserves to succeed. That being said, however, I´m distressed to say that virtually every conodont lab I visit is still using tetrabromoethane. Some things are very hard to change.

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Fields of use

of sodium polytungstate

The highly soluble inorganic salt sodium polytungstate when dissolved in water, can be used to replace the toxic and possible carcinogenic organic liquids traditionally used for gravity separation work. The non toxic high density agent, sodium polytungstate (SPT), was originally invented for the mineral separation and it is used since the last eighteen years for separation of insoluble materials of different densities. Besides the mineral separations SPT has been used in these other industries & research: Coal, precious metals, diamond, archeological, construction, paleontology (conodont research), thermoluminescence research.

One of the latest new research fields where SPT is being used is in earthquake science to study tectonic changes in the earth´s crust! Sometu’s sodium polytungstate is also used to optimize the plumbing system of nuclear reactors on a test rig. Here SPT is used as an inactive, non radioactive simulant for Uranyl Nitrate solutions.

SPT is currently used by mineralogists, geologists, geophysicists, archaeologists and paleontologists around the world. A density Gradient Centrifugation can be used.

For more information and questions regarding SPT contact Sometu.

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