LST Heavy Liquid

Physical Characteristics

Safety

Back to the Heavy Liquid menu

For more information, send e-mail to: vpatrick@cyllene.uwa.edu.au

Physical Characteristics

LST solids contain heteropolytungstates in the form of extremely soluble, colourless hydrated crystals. Concentrated aqueous solutions of LST form colourless or pale yellow heavy liquids. LST heavy liquid is normally used with an aqueous base. However, the LST crystals are also highly soluble in acetone and alcohols, and can form dense liquids in these organic solvents. This provides a range of methods for the use and recycling of LST heavy liquids.

Back to LST menu

Safety

The driving force behind the introduction of the LST heavy liquid has been the need for a dense liquid to replace the undesirable dense organohalides such as tetrabromoethane (TBE) and bromoform. During the development of a suitable heavy liquid, safety was the prime consideration. Performance, i.e. high stability and low viscosity, was then optimised.

Detailed toxicity studies have been conducted on the components of LST heavy liquid in order to register the new substance for use in Australia. Worksafe approval for use in Australia was obtained in January 1996.

Tests indicate that LST heavy liquids are unlikely to be a significant skin irritant. However, water proof gloves should be worn during the use of LST. LST solids are an eye hazard because of their irritancy when allowed to remain in contact with the eyes, and eye protection is required when using the LST heavy liquid. LST heavy liquids are of low toxicity. LST heavy liquids do not present any hazards from volatile vapours and do not require expensive fume extraction systems.

Back to LST menu

Thermal Stability

LST heavy liquid maintained at a temperature of 80 C for over two weeks showed no observable change. The high thermal stability of LST heavy liquid allows it to be boiled to evaporate water and regain its original high density. The stability of LST heavy liquid means that recycling is rapid, simple and effective.

Back to LST menu

Operating Density

At 25 C LST heavy liquids can be used at any density up to 2.95 g/ml by diluting with water or by concentrating to remove water. The recommended operating density as a replacement for bromoform is 2.80 to 2.85 g/ml. At this density the viscosity is low, and the likelihood of crystallisation is reduced. Densities up to 3.5 g/ml can be achieved at higher temperatures. The maximum density of LST heavy liquids is given for a range of temperatures in Figure 1.

density graph

Back to LST menu

Viscosity

Low viscosity is a feature of LST heavy liquids. Grain separations in LST heavy liquid occur at about the same speed as when using TBE, but without the occupational hygiene risk of organohalides. The exact viscosity of the LST heavy liquid will vary with its temperature and density (Figure 2), and is typically about 11 cP.

viscosity graph

Back to LST menu

Storage and Use

LST heavy liquids can be stored indefinitely in closed plastic or glass containers. LST heavy liquids may cause corrosion of metals, so contact of LST with metals should be avoided during storage and heavy liquid separations. If subject to very cold conditions, crystals may appear in LST heavy liquids. These will redissolve upon warming the heavy liquid.

Back to LST menu

Suppliers of LST heavy liquid

Currently the only manufacturer of LST heavy liquid is Central Chemical Consulting.

There is also a US web site at heavyliquids.com

Back to LST menu