The most widely used method for refining impure metals is electrolytic refining.

Electrolytic  refining  means  refining  by  electrolysis.  Metals  such  as  copper,  zinc,  tin,  lead,  chromium, nickel, silver and gold are refined electrolytically.

• For refining an impure metal by electrolysis:

A thick block of impure metal is made the anode. A thin strip of pure metal is taken as the cathode. A water soluble salt is taken as the electrolyte. On  passing  current  through  the  electrolyte,  the  impure  metal  from  the  anode  dissolves into  the electrolyte. An equivalent amount of pure metal from the electrolyte is deposited on the cathode. The  soluble  impurities  go  into  the  solution,  whereas  the  insoluble  impurities  settle  down  at  the bottom of the anode and are known as the ‘anode mud’.