Solution:

• The refining of a metal by electrolysis is known as electrolytic refining.
• In the electrolytic method of obtaining aluminium from purified bauxite, cryolite is added to the charge in order to dissolve bauxite and render it a conductor of electricity.
• In this process, the bottom of the electrolytic cell is coated with carbon and made up of iron.
• It have tree fused layers :-
  Lower layer :- contain alloy of copper and impure aluminium
  Middle layer :- Contains cryolite and barium fluoride.
  Upper layer :- Contains pure aluminum that acts as cathode.