Which methods are usually employed for purifying the following metals :
(i) Nickel
(ii) Germanium

Explanation

Purification of Nickel : Nickel is refined by mond process . It is based upon the principle that nickel is heated in presence of carbon monoxide to form nickel tetracabonyl which is volatile then it is heated upto 450-470 k to obtain pure metal .
`Ni + 4CO overset(330-350k)(to) Ni(CO)_(4) , Ni(CO)_(4) to Ni4CO`
(ii) Purification of Germanium : It is purified by zone refining method . It is based upon the fact that the impurities are more soluble in the melt than in the solid state of metal .