Question

Explain: (i) Zone refining (ii) Column chromatography.

Answer 1

(i) Zone refining
It is used for refining $Si,B,Ga,In$ etc. Impurities are more soluble in the molten state of metal than in solid state. There is a circular mobile heater at one end of a rod of impure metal. Heater and the molten zone moves from one end to another end. Pure metal crystallizes out of the melt and the impurities pass onto the adjacent molten zone. Repetition of this process several times segregates impurities at one end of a rod. The end with impurities can then be cut off.
(ii) Column chromatography.
It is used for the separation and purification. It is based on the difference in the tendency for adsorption of a metal and its impurities on a suitable adsorbent. Different components of a mixture are differently adsorbed on an adsorbent.