posted by Cheech on .
How are INSOLUBLE impurities removed during recrystallization? How are SOLUBLE impurities removed?
If I understand the question, for insoluble materials add enough solvent to dissolve the major material you want to keep but doesn't dissolve the insoluble material, filter, then recrystallize the material from solvent.
Soluble materials are removed by choosing solvents in which the solubility of the impurity is different than the solubility of the material you want to keep. Through several recrystallizations the soluble materials can be removed at the expense of leaving some of the material you want to keep behind in the solvent.