What procedure did you follow? To get recrystallization you must saturate (or nearly saturate) a solution at a high temperature, then let is cool down to a lower temperature. You get the most recrystallization if the solubility at high temperature is much higher than at low temperature. You need graphs of solubility v. temperature for you four salts. The ones for NaCl and KCl can be found in many textbooks and at:
http://Galileo.phys.Virginia.EDU/education/outreach/8thgradesol/TempSolubility.htm
I have not found graphs or tables for CaCl2 and MgCl2.
Recrystallization is about is about solubility at different temperatures, not about ionic charge.
I did a project for lab chemistry where my aim was to see which substance, from a selection of 4 chlorides, recrystallises from a solution to form the most crystals. The 4 chlorides were KCl, NaCl, MgCl2 and CaCl2.
KCl and NaCl didn't form any crystals, they formed a saturated solution whereas MgCl2 and CaCl2 formed crystals. It seems as if the charges on the positve ion of the chloride are important here; but why? How do I explain my results? Conclusion??
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