CHEM 143A Chapter Notes - Chapter 6: Boiling Point, Crystal Growth, Miscibility
6 Jul 2020
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If the compound dissolves immediately, your compound is probably too soluble in the solvent for recrystallization to be effective. If no solubility is observed, heat the solvent to its boiling point. If complete solubility is observed, cool the solution to induce crystallization: the formation of crystals in 10 20 min suggests that you have a good recrystallization solvent. If no cloudiness appears, the compound is too soluble in this solvent pair. 10% excess solvent: slowly add more cold solvent to the heated mixture until the solid just dissolves when the solution is boiling; then add about 10% excess solvent. If you do not have any seed crystals, scratch the bottom of the flask vigorously with a glass stirring rod. If crystallization still does not occur, there is probably too much solvent. 2: boil off some of the solvent in the hood and cool the solution again.
