The process of zone refining is used in the purification of

Zone refining or Fractional crystallisation:- Elements such as Si, Ge, Ga, etc.,
which are used as semiconductors are refined by this method. Highly pure metals
are obtained. The method is based on the difference in solubility of impurities in
molten and solid state of the metal. A movable heater is fitted around a rod of the
impure metal. The heater is slowly moved across the rod. The metal melts at the
point of heating and as the heater moves on from one end of the rod to the other
end, the pure metal crystallises while the impurities pass on the adjacent melted
zone.