Ans: Removal of impurities from an impure metal is called refining.
The electrolytic refining of copper is done in an apparatus shown below
The block of impure copper is made as anode. The cathode is made of a thin plate of pure copper. The electrolyte is a solution of copper sulphate, containing a small amount of dilute sulphuric acid. On passing electric current, copper dissolves from the anode into the electrolyte. An equivalent amount of copper from the electrolyte is then deposited on the cathode. Crude copper contains very small amounts of iron, silver and gold. The more reactive metals, such as iron, dissolve in the solution and remain there. The less reactive metals, such as silver and gold, fall below the anode in the electrolytic cell as anode mud. These metals are recovered in the native state.