• The method to obtain aluminium from alumina by the electrochemical method was invented by Charles Hall and Paul Héroult.
• Electric current cannot pass through the solid form of alumina, and the melting point of alumina is also very high. Hence, cryolite is added to alumina in a small amount to carry out electrolysis easily.
• This mixture acts as a good conductor of electricity. Addition of feldspar also lowers the melting point of alumina. Thus, a mixture of alumina, cryolite and feldspar is subjected to electrolysis to obtain pure aluminium.
• For electrolysis, an iron vessel with an inner layer coated with carbon-layered graphite is used. This acts as a cathode.
• The carbon rods are joined with a copper clamp and immersed in an electrolyte. These rods act as the anode.
• On passing electric current, molten aluminium is deposited at the cathode and oxygen gas is released at the anode.

At the cathode : 2Al³⁺(l) + 6e^– → 2A(l)