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Usage hints:

Jan 19, 2011:
Use glass or plastic containers and implements when handling LST Heavy Liquid.


Common questions answered


We hope that most of your questions about LST Heavy Liquid will be answered on this page, but if you do have a query we haven't covered here, please go here to send us your query.

QUESTIONS


We currently use heavy liquids in a centrifuge and then freeze the vials in liquid nitrogen - does freezing affect LST heavy liquid?

How sensitive is LST heavy liquid to slight changes in room temperature?

Can we get LST heavy liquid in solid form?

Has LST heavy liquid been known to react with any minerals being tested?

What is the chemical nature of LST heavy liquid?

How long will it take for my LST heavy liquid to be delivered?

What does greater thermal stability mean concerning LST heavy liquid and sodium polytungstate?

Is LST heavy liquid less sticky to use than sodium polytungstate?

How does the price of LST heavy liquid compare with SPT?

How many litres of SG 2 could you make from one litre of SG 2.85 LST heavy liquid?

Will LST heavy liquid be adversely affected if left on the hotplate and totally dried out?

Is there an MSDS (Material Safety Data Sheet) available for LST heavy liquid?

My LST heavy liquid has turned dark blue/grey/black. What causes this, is the LST heavy liquid damaged, and how can I get the LST heavy liquid back to the original state?

Is the vapour pressure of LST heavy liquid at room temperature the same as that for the solvent? (water)

Is there any form of reactivity by LST heavy liquid with plastic materials?

At your web address "corrosion of metals" is mentioned. Can you offer any insights on the room-temperature reactivity of LST heavy liquid with silver, gold, copper, iron, zinc, and aluminum?

Do you have a European distributor?

Has LST heavy liquid been evaluated for toxicity etc. in the US? (OSHA)



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ANSWERS


Q 1. We currently use heavy liquids in a centrifuge and then freeze the vials in liquid nitrogen - does freezing effect LST heavy liquid?

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 50oC in order to re-form the liquid more quickly.

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Q 2. How sensitive is LST heavy liquid to slight changes in room temperature?

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 10oC 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.

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Q 3. Can we get LST heavy liquid in solid form?

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.

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Q 4. Has LST heavy liquid been known to react with any minerals being tested?

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.

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Q 5. What is the chemical nature of LST heavy liquid?

LST heavy liquid is comprised of lithium heteropolytungstates (80-85 wt%) in water.

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Q 6. How long will it take for LST to be delivered?

Delivery by air courier takes one week to most locations. The courier requires a street address for delivery, and a contact telephone number at the receiving organisation.

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Q 7. What does greater thermal stability mean concerning LST heavy liquid and sodium polytungstate?

Customers have reported that SPT solutions produce a white insoluble material when heated at 100-120oC 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).

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Q 8. Is LST heavy liquid less sticky to use than sodium polytungstate?

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.

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Q 9. How does the price of LST heavy liquid compare with SPT?

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.

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Q 10. How many litres of SG 2 could you make from one litre of SG 2.85 LST heavy liquid?

One litre of LST heavy liquid (2.85 g/ml) makes exactly 1.85 litres of heavy liquid at a density of 2.00.

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Q 11. Will LST heavy liquid be adversely affected if left on the hotplate and totally dried out?

Not normally, but it is possible to decompose LST heavy liquid if it is heated strongly enough. Decomposition requires temperatures above 150-200oC. 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 200oC 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 150oC 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 110oC, 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 110-120oC. 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.

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Q 12. Is there an MSDS (Material Safety Data Sheet) available for LST heavy liquid?

Yes, You can get the MSDS here. We also supply an MSDS with every order.

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Q 13. My LST heavy liquid has turned dark blue/grey/black. What causes this, is the LST heavy liquid damaged, and how can I get the LST heavy liquid back to the original state?

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 80oC 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. See the Recycling section of this web page.

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Q 14. Is the vapour pressure of LST heavy liquid at room temperature the same as that for the solvent? (water)

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.

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Q 15. Is there any form of reactivity by LST heavy liquid with plastic materials?

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.

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Q 16. At your web address "corrosion of metals" is mentioned. Can you offer any insights on the room temperature reactivity of silver, gold, copper, iron, zinc, and aluminum with LST heavy liquid?

Practical experience has indicated that good quality chemical-resistant stainless steel ("316" S/S) is fine with LST heavy liquid, even at elevated temperatures (80-90oC). We doubt whether LST heavy liquid reacts with gold or silver, but haven't tried it. Copper, iron, zinc and aluminium all react with LST heavy liquid and are not compatible.

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Q 17. Do you have a European distributor?

Yes. Their contact details are given here.

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Q 18. Has this material been evaluated for toxicity etc. in the US? (OSHA)

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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I want to know more about LST Heavy Liquid



While we have tried to answer the most common questions you may have, we understand that you may need to know more. If you have any other questions, use this link and we will get back to you soon with an answer: info@heavyliquids.com




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