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One can salt CO2 out of solution by adding salt to carbonated water. Can one do the reverse? If one adds more and more CO2 to the water under pressure, can you drive out the salt?

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NaCl is vastly more soluble than carbon dioxide, so this method won't work. You can get some NaCl to precipitate (assuming you have a concentrated solution) by bubbling HCl in, thanks to the common-ion effect, so you could for example get pure NaCl from rock salt this way. But somehow I don't think that's the situation you have in mind :-)

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  • $\begingroup$ The OP mentioned pressure, so technically speaking you can put as much CO2 into the solution as much you want. I think his question is primarily about if this equilibrium can be pushed into the reverse direction with enough pressure. The answer is yes, and you are completely right that it is not much practical. $\endgroup$ – Greg Jul 31 '14 at 4:05
  • $\begingroup$ Good point, but "as much as you want" is not correct. BTW, pressure alone will drive out the salt, since at 10,000 atm or so water will freeze at room temperature (www1.lsbu.ac.uk/water/phase.html) I'm not sure how much CO2 you can dissolve before that; best I could find is that at 100 MPa (1000 atm) the mole fraction of CO2 in H2O is about 0.03, and the curve is quite flat already; see pubs.acs.org/doi/pdf/10.1021/ie980768g ‎-- Anyway, you have a good point and I'll modify my answer after waiting to see if there are more comments. $\endgroup$ – Silvio Levy Jul 31 '14 at 4:22
  • $\begingroup$ Very good points! Thank you for cleaning it up. $\endgroup$ – Greg Jul 31 '14 at 5:08

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