The zone refining process of metals is based on the principle of :
Zone refining is particularly used when metals are required in high degree of purity. It is based on the principle that when an impure metal in a molten state is allowed to cool, only the metal crystallizes while the impurities remain present in the molten state (mass) or meltSo the zone refining process of metals is based on the principle ofGreater solubility of the impurities in the molten state than in the solid.
Hence option D is correct.