I have a salt in water and I want to evaporate the water. I'm wondering, what will be differences (if any) in the character of the crystals in a few scenarios:

  1. Slow evaporation - let the solution sit in open air and allow natural evaporation
  2. Use vacuum to evaporate the water quickly
  3. Vacuum + heat to evaporate/boil the water quickly

Thanks in advance.

  • 1
    $\begingroup$ This is an excellent situation for some careful experimentation to determine which method of evaporation comes closest to giving the crystals that you want. Evaporation rate depends on the vapor pressure of the solvent, a function of temperature, its mole fraction in the solution and surface area. Condensation location depends on physical constraints of the vapor and partial pressure of the vapor. $\endgroup$
    – jimchmst
    Oct 7, 2022 at 14:44

1 Answer 1

    1. may be vulnerable to collect dust by prolonged contact to air, if not protected. It may be preferable as slow evaporation leads to big, more pure and well built crystals and vice versa.
    1. may be a good trade off between evaporation speed and agressiveness of the method. Rotating evaporation vacuum devices are frequent way to go.
    1. may violate salt stability, promoting decomposition or formation of lower hydrates. There may be mechanical salt loses and contamination of equipment by the salt or the liquid. Generally is boiling a bad idea, unless the time is priority.

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