Which method is used for separation of crystals of alum (phitkari) from impure samples?

Crystallization

The correct answer is option 3. Crystallization.

Crystallization is the method used for the separation of crystals of alum (phitkari) from impure samples. In this process, a solution containing the impure alum is allowed to cool, leading to the formation of crystals. The crystals can then be separated from the remaining liquid, which may contain impurities. This method relies on the differences in solubility at different temperatures, allowing the purification of the substance through the formation of well-defined crystals.