I have a book at home called Chemical Thermodynamics for Process Simulation (I have the first edition) and at the very beginning of chapter 2 of the book one may read the following:

CO2-water system at high pressure

No reference is given. I have never found anything about it so far and I am curious to know whether this statement is true.

  • 4
    $\begingroup$ Yes, supercritical liquid may have higher density then liquid. $\endgroup$
    – Mithoron
    Oct 11, 2019 at 17:39
  • $\begingroup$ The crucial point is that CO2 at high pressure, and moderately above room temperature, becomes a super critical fluid and not a gas. $\endgroup$
    – MaxW
    Oct 11, 2019 at 17:42
  • 2
    $\begingroup$ The difference between a liquid and a gas is not as clearcut as the question implies. $\endgroup$ Oct 11, 2019 at 17:55
  • 1
    $\begingroup$ There is no fundamental reason why a not yet supercritical gas cannot also have a higer density than some liquid at the same conditions, is there? $\endgroup$
    – Karl
    Oct 11, 2019 at 19:14
  • $\begingroup$ @Karl There isn't, but even in different conditions that would be rather extreme example. $\endgroup$
    – Mithoron
    Oct 11, 2019 at 19:40

1 Answer 1


Yes! Here's a video of Cody floating NaK (liquid) or ethanol/water (liquid) on compressed xenon (gas): https://youtu.be/AsP4yMY-a6U


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