Recrystallization (or Crystallization) is a technique used to purify solids. This procedure relies on the
fact that solubility increases as temperature increases (you can dissolve more sugar in hot water than in cold
water). As a hot, saturated solution cools, it becomes supersaturated and the solute precipitates (crystallizes)
out. In a recrystallization procedure, an impure (crude) solid is dissolved in a hot solvent. As this solution
is cooled, the pure product crystallizes out and the impurities stay dissolved.