Question

With respect to the Hall Heroult process, justify the following:

Cryolite and fluorspar must be added to the electrolytic mixture.

Answer 1

Cryolite and fluorspar are added to the electrolytic mixture because their addition:

1. lowers the fusion point of the mixture i.e., mixture fuses around 950°C instead of 2050°C.
2. enhances the mobility of the fused mixture by acting as a solvent for the electrolytic mixture.
3. enhances the conductivity of the mixture since, pure alumina is almost a non-conductor of electricity.