ABSTRACT
All crystallizations are based on the same principle: a solid compound is fully dissolved in a solvent (or solvents) at a particular temperature, the conditions of the solution are changed such that the solution becomes supersaturated in the compound to be crystallized, and the compound then crystallizes from the solution. Many compounds can crystallize in more than one polymorphic form. For example, snow and hail are different polymorphs of ice. The polymorph you get depends on the conditions under which the crystallization takes place. Polymorphs have different melting points and stabilities, so if you have difficulty in obtaining good crystals from one crystallization system it is worth trying other systems.
