CHEM 143A Chapter Notes - Chapter 6: Hydrogen Bond, Seed Crystal, Boiling Point
6 Jul 2020
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Introduction to recrystallization (pg 221: recrystallization - when a crystalline material (solute) dissolves in a hot solvent. B. and then returns to a solid in a cooled solvent by crystallizing. Impurities in the original crystalline material are usually present at a lower concentration than in the substance being purified: thus, as the mixture cools, the impurities tend to remain in solution while the highly concentrated product crystallizes. If the solubility is too large, it is difficult to recover the compound. If the solubility is too small, a very large volume of solvent will be needed to dissolve the compound or it simply may not dissolve sufficiently for recrystallization to be effective, Seed crystals: always set aside a small amount of the crude crystalline product to use as seeds for catalyzing the formation of crystals in the event that recrystallization does not occur. If no crystals appear in the cooled solution, it could mean that the solution is not saturated.
