Reason for use of fused cryolite (Na3AlF6) along with fluorspar (CaF2) which is added to the electrolytic mixture containing pure alumina.

Reason for use of fused cryolite (Na₃AlF₆) along with fluorspar (CaF₂) which is added to the electrolytic mixture containing pure alumina.

1. Electrolysis requires the electrolyte to be in liquid state.

2. Alumina has a very high melting point (> 2000ºC).

3. So, electrolysis of alumina is carried out at a much lower temperature by dissolving it in molten cryolite (Na₃AlF₆)

4. Cryolite has a lower melting point than alumina. The melting point of solution of alumina in cryolite is lower than cryolite.

5. It is further lowered by adding some fluorspar (CaF₂).

6. Thus, the solution of alumina in cryolite with added fluorspar is electrolysed at about 1000ºC.