For the crystallization purpose the combination of solvent process is known to be an effective process. But the solvent pair one have to choose crucially. The solvent which is completely in soluble into the other solvent can not work as a good solvent pair for the crystallization. The crystallization of any compound by the solvent pair process is depend upon the slow diffusion of a less polar solvent to the polar solvent or vice-versa.
If a compound is soluble in a polar solvent the slow diffusion of relatively low polar solvent will make crystal of the compound. But anyhow the solvents which are completely not immiscible to each other will not work for the purpose. Thus diethyl ether and water solvent pair can not be used for the crystallization process.
