Question

How does recrystallization work? I see it as an impure compound is dissolved in a hot solvent. At room temperature and high temperatures, the impurities are dissolved. However, the pure compound is only soluble at high temperatures and went cooled back to room temperature, it crystallizes whereas the impurities stay dissolved in solution. Is that how it works?

Answer 1

The principle behind recrystallization is that the amount of solute that can be dissolved in a solvent increases with increase in temperature. Hence, a solution is created by dissolving a solution in a hot solvent. Since the temperature is high, more amount of solute can be dissolved in the solvent before it reaches saturation. Once this is done, the temperature is reduced to room temperature. At this temperature, the saturation point would be lesser. Hence, all the extra solute recrystallizes out.