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We did a very simple lab like one you would do in highschool showing that you can seperate the phases of water and ethanol using salt. As simple as it sounds, we could not get it to work no matter what we tried—until finally a student assistant used tap water instead of DI water and we saw the phase transition.

Why did the tap water work and not the DI water??

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  • $\begingroup$ It should have worked. Was you DI water contaminated or you didn't add enough salt in DI to cause separation. Tap water has divalent cations like calcium, magnesium which can affect the salting out effect. $\endgroup$
    – M. Farooq
    Oct 26 at 13:56
  • $\begingroup$ My hypothesis is tap water salts form fine precipitate when mixed with ethanol, forming centers for creation of water phase. $\endgroup$
    – Poutnik
    Oct 26 at 14:13
  • $\begingroup$ You really need tons of salt and saltparticulates therein should be sufficient to cause phase separation. I call such experiments, one time flukes. DI water works, you just need enough salt. $\endgroup$
    – M. Farooq
    Oct 26 at 15:48
  • $\begingroup$ @M.Farooq It would still be interesting to compare it side by side. I would not exclude possible oversaturation. $\endgroup$
    – Poutnik
    Oct 26 at 15:55

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