Calcium chloride is deliquescent, it is hygroscopic, so much so that it dissolves in the water it has attracted by hygroscopy.

Sulfuric acid is hygroscopic, even if not anhydrous. So a solution containing water can be hygroscopic.

Is a concentrated solution of calcium chloride that was created by the solid salt attracting water still hygroscopic, attracting more water?

If yes - down to which concentration is that the case?

  • 2
    $\begingroup$ It will attract more water until the vapor pressure over the solution matches the ambient vapor pressure. $\endgroup$ Dec 5, 2019 at 22:37
  • 2
    $\begingroup$ Interesting. My daughter in 5th grade tried to make crystals from magnesium chloride for a science fair project along with other salts. The water never evaporated to yield crystals. By adding MgCl2 to the liquid we were able to get crystals appear for a short time but then it absorbed more water. That leaves a possibility that we could cool the solution to produce crystals by reducing the solubility which would also lower the vapor pressure of the solution so is is possible that there is a temperature at which the MgCl2 would not be dissolved in its water as well as some humidities. $\endgroup$ Dec 6, 2019 at 0:19
  • 2
    $\begingroup$ Even the saturated solution of table salt is hygroscopic at relative humidity >75%. $\endgroup$
    – Poutnik
    Dec 6, 2019 at 5:17


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Browse other questions tagged or ask your own question.