I have read online that suppose I am trying to purify compound_A, which contains an impurity, lets call that compound_B, that the solvent that I choose for recrystallization must either: 1) dissolve compound_A but not compound_B, so that compound_B can be filtered out after dissolving compound_A in the solvent or 2) Both compound_A and compound_B must both be completely soluble in the solvent (at least when it`s hot) so that when crystallization starts to occur, compound_B remains in the solvent. I have a question. I do my own experiments and I am trying to recrystallize a compound, let`s call it compound*. I know that compound* is impure. The solvent Im using is water. Now, the hot water dissolves both compound* and its impurity. So according to what I read online I would expect the impurity remain in the solvent while crystallization occurs (i.e. while the solution is cooling to room temperature). However, after leaving the solution for several hours, there is no more solvent. That is, everything has been crystallized. Does this mean that the resulting crystals are just as impure as my original compound? Does it contain the original impurity that I was trying to get rid of? All help would be appreciated.