Final answer:
For recrystallization, use as little hot solvent as is necessary to dissolve the compound when the solvent is hot, allowing maximum recrystallization on cooling.
Step-by-step explanation:
In the process of recrystallization, the amount of hot solvent employed should be as little as possible that can still completely dissolve the compound when the solvent is hot. As the solution cools, the compound's solubility decreases and it precipitates out, leaving the impurities in the solution. Thus, using too much solvent would result in less efficient recrystallization, as more of the compound would remain dissolved in the solvent at lower temperatures, reducing the yield of purified compound.