Question

Which methods are usually employed for purifying the following metals (i) Nickel (ii) Germanium?
Mention the principle behind each one of them.

Answer 1

1. For purifying nickel generally Mond's process is used.

In Mond's process.This process involves the fact that carbon monoxide combines with nickel readily and reversibly to give nickel carbonyl which is a volatile complex and readily degrades back into nickel and carbonmonoxide at higher temparatures.

2. Generally germanium is purified by zone refining method. The principle of this process is that impurities are more soluble in molten state of the metal than in solid state.In the process of zone refining,a circular mobile heater is fixed at one end of the rod of a impure metal. As the heater moves, molten zone also moves along with it. As a result, pure metal of the melt crystallizes out and impurities pass on to the adjacent molten zone. This process is repeated several times which leads to segregation of impurities at one end of the rod.