# Any example of colloidal solution where liquid Helium is solvent?

I would like to see any information, if it exists, about colloidal solutions where Helium is "solvent".

Background of that question is, I'm wondering giving surface energy effects, how potentially small can be water ice particles at low temperatures.

• Problem is that helium has very low density, so particles would tend to plummet to the bottom IMO. – Mithoron Jul 14 '16 at 19:26
• @Mithoron Yes, considered it as issue, although background have another few layers of backgrounds, one of them is sedimentation coefficient and brownian motion. I come-up with that question after thinking about ultra centrifugal separation. So this way it's not an issue but more what I would like to have. Methods of getting fine particles also not clear in this case, so it's more about how theoretically fine they could to be in such circumstances. Not sure at all if Helium may have some effect of preventing them to agglutinate. – MolbOrg Jul 14 '16 at 19:44

## 2 Answers

A solution implies that there are solvent-solute interactions. Helium is about the most chemically inert atom there is. In the case of water ice, the hydrogen bonding will be orders of magnitude stronger than the van der Waals forces, so colloids will not be stable at 'normal' pressures. I guess if I were looking for a colloid in He(liq), I'd look at N2 or perhaps H2. We've made a lot of progress since I had colloidal (surface) chemistry class, but I doubt that we could predict size of particles in any such system. But I don't know.

• as helium is diamagnetic, yes probably ice particles will to agglutinate.But which size ice particles will stop to merge. this way it's less interaction with He, but more properties of fine particles. Although H in He, specially isotopes hm interesting. Also I will try to search later information about less extreme "solvent". Actually I did, but not so deep at the moment. – MolbOrg Jul 14 '16 at 21:09

This is a question to physics department. Chemists only see liquid helium when refilling NMR instruments. Boiling point and comfort working with changes in this order: He < H2 < N2< NH3 < H2O. I didn't find any papers regarding colloidal systems in N2. So, chances are nobody looked into He yet. Try a deep search on N2 colloids first.

Currently colloidal systems are interesting as drug delivery methods (water, water soluble polymers as a solvent) or nanotechnology (organic solvents at room temperature). There isn't enough motivation to study colloids at low temperatures at the moment.

• that's physical chemistry, but more physics, yes. On se.physics looks like colloids discussed less then here. I also quick searched(gdoogdled), and also have not found, but have not expected it to be found so easy, too narrow. This way I decided to ask collective wisdom - maybe some one have saw something interesting. Can be used to refine(sort) asteroid materials as example(maybe). Selective drug transport, yes good, interesting field, useful. – MolbOrg Jul 14 '16 at 23:09
• @MolbOrg Which physicists? Majority of them are searching for energy sources. They see matter (including colloidal systems) as a substrate to transfer beloved energy. – sixtytrees Jul 15 '16 at 1:07
• Biophysicists, they are totally mad, for good). Maybe other xxx-physicists too. There are some amount of them of different kind. – MolbOrg Jul 15 '16 at 1:49