LST Heavy Liquid For the World
Common LST questions answered
We hope that your questions about LST Heavy Liquid are answered on this page, but if you do have a query we haven't covered here, please go here to send us your query.
Some of the reasons for using LST Heavy Liquid include:
- its low viscosity,
- it is non-toxic which means that you do not need to use fume hoods or other special equipment,
- it is the most thermally stable heavy liquid,
- it is most readily recycled,
- it gives the fastest separations,
- it is capable of going to higher densities.
LST Heavy Liquid is comprised of lithium heteropolytungstates (80-85 wt%) in water.
Customers have reported that SPT solutions produce a white insoluble material when heated at 100-120°C during evaporation of washings. The heteropolytungstate anions in LST Heavy Liquid are chemically different, and are more stable to heat than the metatungstate anions in sodium polytungstate (SPT) and lithium metatungstate (LMT).
Yes, quite significantly. As a 'rule of thumb', SPT is twice as viscous as LST Heavy Liquid at the same density. At the lower densities such as SG 2.0 there is not a large difference, since both viscosities are low, at around 3 cP. At high densities such as 2.9 g/mL, SPT is more than twice as viscous as LST Heavy Liquid.
Because of LST's lower viscosity, density separations are faster and more complete, and grains are more easily washed clean. If you accidentally dry out an LST solution, you will be pleased to know that LST solids also dissolve faster in water than SPT solids.
LST heavy liquid does not react with most plastic materials. Polyethylene, polypropylene, PVC, TPX, etc. used on a daily basis with LST heavy liquid show no ill effects. Some nylon materials can be affected by the slight acidity (pH 4) of LST heavy liquid, and its mild oxidising effect.
LST is manufactured as a liquid for several reasons. The liquid contains very little water (about 15% by weight), is generally easier for customers to use, allows us to check the quality more rigorously, and allows us to produce a more uniform product. The solids can vary quite widely in water content, and therefore there would almost inevitably be some variation in water content if we sold LST as solids. However for specialist uses, we can supply LST as a solid, but would have to charge extra since it would be a custom order and not part of our usual process.
LST Heavy Liquid has a pH around 4, so it is mildly acidic. We haven't had any feedback of LST Heavy Liquid reacting with minerals, although reactive alkaline minerals such as limestone may be able to react very slowly. We have only detected such reactions after many hours or days of contact with a sample. The other type of minerals which may react are reducing minerals such as sulfides.
It requires approximately 2.34 kg of Sodium Polytungstate and 510 mL of water to make one litre of SPT solution with SG 2.85. You can compare the price of 2.34 kg SPT from your supplier with the price of one litre of LST Heavy Liquid.
Delivery by air courier takes one week to most locations. The courier requires a street address for delivery, and a contact name and telephone number at the receiving organisation.
After use, LST Heavy Liquid is easily recovered. Simply wash the separated minerals with deionised water, filter and then concentrate the water washings by boiling. This process recycles LST Heavy Liquid with greater than 99% efficiency. An overall scheme for use in an industrial laboratory can be found here.
One litre of LST Heavy Liquid (2.85 g/mL) makes exactly 1.85 litres of LST Heavy Liquid at a density of 2.00.
Practical experience has indicated that good quality chemical-resistant stainless steel ("316" S/S) is fine with LST Heavy Liquid, even at elevated temperatures (80-90°C). Copper, iron, zinc and aluminium all react with LST Heavy Liquid and are not compatible.
LST Heavy Liquid can be used at densities greater than 3 by evaporating or boiling off some of the water. This document gives the procedures to prepare, store and use LST Heavy Liquid at higher densities.
Yes, you can get the SDS here. We also supply an SDS with every order.
Yes. Their contact details are given here.
The blue colouration is a well known chemical reaction which polytungstates and heteropolytungstates can undergo when chemically reduced. In common chemistry parlance you have formed the 'heteropoly blues'. This can occur when a reducing agent comes in contact with the heavy liquid. At high temperatures, such as might occur if the heavy liquid crystallised on a hotplate, even dust/dirt can sometimes act as a reducing agent. You can also get this colour if the LST Heavy Liquid is contaminated by contact with iron. There are two ways to get rid of the dark colour. The easiest way when dealing with small quantities is to add a few drops of 30% hydrogen peroxide solution (H2O2) to re-oxidise the LST Heavy Liquid. You don't need to overdo the addition of hydrogen peroxide. Typically you need add no more than 1 mL of 30% (H2O2) for every 200 mL of affected LST Heavy Liquid, but it will depend on how much reduction there is. You can then heat the discoloured LST Heavy Liquid and hydrogen peroxide at about 80°C to make the reaction go faster (it will fizz a little!), or if you prefer just wait overnight for the blue to disappear. To remove the colour from large quantities of LST Heavy Liquid, it might be better to pump the full strength LST Heavy Liquid through a clean "activated carbon" water cartridge.
Not normally, but it is possible to decompose LST Heavy Liquid if it is heated strongly enough. Decomposition requires temperatures above 150-200°C. During trials we have caused partial decomposition of LST Heavy Liquid by leaving it on a hotplate for long periods of time at high temperatures.
Hotplates often reach temperatures above 200°C when turned up more than half-way, and any crystallised LST can reach this excessive temperature if the solid is at the bottom of the beaker. If the LST Heavy Liquid forms a not-very-soluble white solid after heating at high temperatures, then the LST Heavy Liquid might have been partly decomposed by excessive heat. If that is the case, discard the less soluble material and check that the remaining LST can reach its full strength. Because of this, it is good policy to use a thermostatted hotplate and set the maximum temperature to 150°C if you think that there is a chance it could dry out.
While LST Heavy Liquid is present as a liquid or solution, evaporation of water keeps the temperature below 110°C, so you can have the hotplate set somewhat higher. It is preferable to evaporate washings by placing the LST Heavy Liquid in shallow pyrex or polypropylene containers in a fan-forced oven set at 110-120°C. Then, even if the LST dries out totally, there is no damage; you just add a little water to the solid to reconstitute the LST Heavy Liquid.
LST Heavy Liquid expands and contracts like any other liquid, such as water, and its density varies accordingly. The expansion of LST Heavy Liquid expansion is only fractionally more than that of water, and the specific gravity of LST Heavy Liquid is not unusually sensitive to slight changes in room temperature. The density of LST Heavy Liquid changes by approximately 0.01 g/mL for a 10°C temperature change.
Other changes such as evaporation or crystallisation can affect the density. For example, if LST Heavy Liquid is left with a large surface area open in a draught (such as in a fume cupboard), then evaporation can cause the density to change.
The vapour pressure of water above LST Heavy Liquid (SG 2.85) is slightly lower than the vapour pressure of water above pure water. This is typical of many inorganic salts in water.
Extreme cold will cause the LST Heavy Liquid to freeze and become solid, but will not affect the chemical components. On thawing the LST Heavy Liquid, it would help to stir and heat the LST Heavy Liquid at say 50°C in order to re-form the liquid more quickly.
LST Heavy Liquid has had a full evaluation for toxicity in Australia. It has an acute toxicity close to sodium chloride: its LD(50) is >2,000 mg/kg for rats, and it is not usual to test at higher rates than this. The toxicity testing was conducted at specialist laboratories in Australia and the USA, using accepted protocols.
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