Nitriding is a process of heating steel in an atmosphere of

In the electrolytic refining of metals,the electrolysis of an aqueous solution of its complex salt is performed using an impure metal as the anode and a strip of pure metal as the cathode. This method cannot be used for the refining of which of the following metals?

The zone refining of metal is based on the principle of

How many of the following can be purified by using zone refining method?
$Ni, B, Ti, In, Ge, Mn, Ag, Si, Ga$

Explain the electrolytic refining of metals.

Copper sulphate is prepared by blowing a current of air through copper scrap and dilute $H_2SO_4$. Dilute $HNO_3$ is also added: