5 ms·

Another way to dissolve oil in water is to increase the pressure and temperature. Supercritical water is a non-polar solvent!

littlestymaar 3y ago
Do we know how and why that works?
- cperciva 3y ago
  How and why are difficult words. I mean, in some senses we don't even know why water is wet. My very limited understanding of the subject is that in supercritical water there are larger clumps of H2O molecules surrounding the isolated H+ and OH- ions and this affects the solvent behavior. Note that the chemistry of supercritical water is something which is very hard to study -- needing to keep a sample under extreme conditions means that you can't probe it in many of the normal ways. My father did groundbreaking work in this area using Muon Spin Spectroscopy, because he could shoot a beam of muons into a sample which was otherwise inaccessible. (Shameless plug: My father recently retired and wrote a book on the topic with two of his colleagues. If you search for "Muon Spin Spectroscopy Percival" you should find it in all the usual places.)
  - dylan604 3y ago
    > I mean, in some senses we don't even know why water is wet. That's something that made me go "wait, what?" But then after waiting, and thinking about it, it is just a question that I've never even considered. It's one of those things where I really wished I had better understanding of chemistry.
    - iraqmtpizza 3y ago
      Wish some of this pathological humility could find its way into climate science.
      - fuzzfactor 3y ago
        >we don't even know why water is wet. As a chemist it makes me want to take a dip in the ocean. To try and figure it out ;)
        082349872349872 3y ago
        Water is wet when you take that dip because it has a small contact angle with skin; is that still chemistry or are we now in physics?
        selimthegrim 2y ago
        I think they mean quantum mechanically, or London dispersion forces or dipoles
      - selimthegrim 3y ago
        You don't think there's millions of man-hours of work behind the models, including quite a bit of atmospheric chemistry?
        iraqmtpizza 3y ago
        There has been half a century of work put into string theory and there is no shred of humility there, pathological or otherwise. Amount of work put in is irrelevant.
        selimthegrim 3y ago
        Fairly well understood partial differential equations which are physically validated or isotopic atmospheric chemistry are a little bit different than string theory
        iraqmtpizza 3y ago
        You're not sounding very humble right now

littlestymaar 3y ago

Do we know how and why that works?

cperciva 3y ago
How and why are difficult words. I mean, in some senses we don't even know why water is wet. My very limited understanding of the subject is that in supercritical water there are larger clumps of H2O molecules surrounding the isolated H+ and OH- ions and this affects the solvent behavior. Note that the chemistry of supercritical water is something which is very hard to study -- needing to keep a sample under extreme conditions means that you can't probe it in many of the normal ways. My father did groundbreaking work in this area using Muon Spin Spectroscopy, because he could shoot a beam of muons into a sample which was otherwise inaccessible. (Shameless plug: My father recently retired and wrote a book on the topic with two of his colleagues. If you search for "Muon Spin Spectroscopy Percival" you should find it in all the usual places.)
- dylan604 3y ago
  > I mean, in some senses we don't even know why water is wet. That's something that made me go "wait, what?" But then after waiting, and thinking about it, it is just a question that I've never even considered. It's one of those things where I really wished I had better understanding of chemistry.
  - iraqmtpizza 3y ago
    Wish some of this pathological humility could find its way into climate science.
    - fuzzfactor 3y ago
      >we don't even know why water is wet. As a chemist it makes me want to take a dip in the ocean. To try and figure it out ;)
      - 082349872349872 3y ago
        Water is wet when you take that dip because it has a small contact angle with skin; is that still chemistry or are we now in physics?
        selimthegrim 2y ago
        I think they mean quantum mechanically, or London dispersion forces or dipoles
    - selimthegrim 3y ago
      You don't think there's millions of man-hours of work behind the models, including quite a bit of atmospheric chemistry?
      - iraqmtpizza 3y ago
        There has been half a century of work put into string theory and there is no shred of humility there, pathological or otherwise. Amount of work put in is irrelevant.
        selimthegrim 3y ago
        Fairly well understood partial differential equations which are physically validated or isotopic atmospheric chemistry are a little bit different than string theory
        iraqmtpizza 3y ago
        You're not sounding very humble right now