Write the principles of the following methods.
(i) Froth floatation method           

(ii) Electrolytic refining

(ii) In electrolytic refining process a slab of impure copper is used as anode and a thin sheet of pure copper as cathode. The copper sulphateis used as electrolytic solution. By passing electricity through the cell copper is dissolved from the anode and deposited on cathode. The impurities either remain in solution or collect as an insoluble gangue.