Question

The principle of fractional crystallisation is involved in which one of the following processes?

• A. Van Arkel's method
• B. Distillation
• C. Cupellation
• D. Zone refining

Answer 1

Answer: (D)

Zone refining

Fractional crystallization is a method of refining substances based on differences in solubility. Zone refining is a group of similar methods of purifying crystals, in which a narrow region of a crystal is molten, and this molten zone is moved along the crystal (in practice, the crystal is pulled through the heater). The molten region melts impure solid at its forward edge and leaves a wake of purer material solidified behind it as it moves through the ingot. The impurities concentrate in the melt, and are moved to one end of the ingot.

Hence, the principle of fractional crystallisation is involved in zone refining.