Cold liquid

[Airmid]

Hi folks!

Reading through this forum I was amazed to find so many nice and knowledgeable people in one spot. So what better place than this to ask my question?

 

Here goes: I'm looking for a substance that's liquid between 120K-170K, that's capable of dissolving water(ice) and other simple (organic) molecules, and that's not too rare.

I already looked into the well documented mixture of ammonia and water, but it doesn't really seem to work for my temperature range. H2S mixed with water looked promising, until I hit a reference that it doesn't really mix with water but forms a clathrate instead (is that correct?).

Next I tried to find information about substance like CS2, OCS, H2CS and the like, but couldn't really find any relevant information about how they behave as liquids and solvents at low temperatures.

Do you think these are promising, or could you point me to information about them? Do you have other ideas?

 

Thanks!

Airmid.

[jdurg]

What you're essentially looking for is a polar solvent that will be liquid at temperatures between that of dry ice and liquid nitrogen. Hate to dissapoint you but I'm pretty sure you won't find one. The reason for this is that polar substances have pretty strong intermolecular attractions to each other which means that it's difficult to separate them. Therefore, they have higher melting and higher boiling points than similarly shaped, non-polar substances. In order to dissolve ice crystals, your solvent would need to be somewhat polar since water is a very polar substance. In addition, whatever it is must not react with the water. That's even more of a problem.

 

In addition, if the substance needs to be able to dissolve simple organic molecules (which are typically not very polar at all) then it will have a harder time dissolving the ice crystals as well. There MAY be a substance that exists which is what you are looking for as I don't know the properties of every chemical on earth, but I can assure you that there is no common material which will suit your needs.

[DV8 2XL]

There might be a mixture of halogenated alcohols that would do what you want but I don't think any are off-the-shelf products. But I would start my search in that quarter.

[Airmid]

Thanks for your replies, folks!

 

jdurg: ah yes, thanks for reminding me about polarity *crosses out some of entries on the idea list*.

 

DV8: thanks! *adds another entry to the idea list*

 

I'm currently looking into the possibilities of mixing liquid H2S and liquid SO2. At high temperatures they react, but it's quite a nice reaction, creating water and elemental sulfur. I haven't found anything yet about their behaviour at very low temperatures, though. Do you think there's any chance they might form an eutectic mix?

 

Airmid.

[jdurg]

Just remember that H2S is an incredibly deadly gas which ranks up there with cyanide in terms of "ability to make you dead". SO2 is an incredibly corrosive gas that reacts somewhat exothermically with water (though not as intensely as SO3) to form sulfurous acid. You don't want to have either of those two boiling away on you as it would cause some pretty severe damage.

[Airmid]

Nope, I wouldn't. But don't worry, I have no intention to actually carry out experiments like that in my kitchen. *grins*

 

Airmid.

[Caver451]

You know, you can mix dry ice with ethanol (which IS a polar solvent) and the resulting slurry will get you to around 195K. That extra 20K or so too much? Ethanol's melting point is about 160K.

 

-Caver

[woelen]

Thanks for your replies' date=' folks!

 

jdurg: ah yes, thanks for reminding me about polarity *crosses out some of entries on the idea list*.

 

DV8: thanks! *adds another entry to the idea list*

 

I'm currently looking into the possibilities of mixing liquid H2S and liquid SO2. At high temperatures they react, but it's quite a nice reaction, creating water and elemental sulfur. I haven't found anything yet about their behaviour at very low temperatures, though. Do you think there's any chance they might form an eutectic mix?

 

Airmid.[/quote']

H2S and SO2 only react, when also some water is present. Perfectly dry SO2 and perfectly dry H2S do not react. When a small amount of water is present, then quickly all material reacts, because in the reaction, also water is formed. The reaction product, however is terribly complex. You indeed get elemental sulfur, but also tons of other reaction products (thiosulfate, polythionic acids, sulphuric acid, polysulfanes). Have a look at Wackenroder's solution at Google. This covers this reaction in detail, in the presence of water. The reaction is increadibly complex and still only partially understood.

[Airmid]

Caver: That's a very good suggestion, especially if those 2 behave like a eutectic mixture. I will look into it, thanks!

 

woelen: I've read a lot of stuff dealing with the Claus reactions. Very interesting, and yes, very complex.

You say liquid H2S and liquid SO2 won't react. That's good news. The overall reaction (2 H2S + SO2 <-> 3/n Sn + 2 H2O) is highly exothermic, but of course that's no guarantee that it actually takes place. Besides, like you said, there's a whole lot of partial reactions involved, and I suppose that water is required in a crucial step. So far so good.

Now suppose I mix liquid H2S and liquid SO2, stir well, and drop an ice cube in it. Would that activate the reactions, but at a very slow rate because of the low temperature, or would the whole mix explode, because of a chain reaction effect? I owe you already, but if you can give me your best guess, I'll owe you ever more *smiles*

 

Airmid.

[woelen]

It is hard to say whether an explosion will occur in that case. I don't expect so, but there are a few factors, which could cause "explosion-like" reaction.

1) Temperature rise, due to exothermic reaction

2) Liquids becoming a gas again due to heating up

3) Formation of additional water, causing even faster reaction.

In practice I think that you will see a violent, but not explosive reaction, unless you confine the reaction mixture to a small space.

 

Mixing liquid SO2 and H2S seems a dangerous experiment to me anyway. Even traces of water can initiate a reaction. You must be absolutely sure that the material is REALLY dry.