Almost all solids are more soluble in a hot than in a cold solvent, and solution crystallization takes advantage of this fact. Thus, if a solid is first dissolved in an amount of hot solvent insufficient to dissolve it when cold,crystals should from when the hot solution is allowed to cool. Even after a solid has been recrystallized,it may still not be pure. Thus,it is important to determine the purity of the sample,and one of the easiest methods to do this is by determining the melting point of the solid.