Alumina, $A l_{2} O_{3}$ is a bad conductor of electricity and has very high melting point, so before subjecting to electrolysis, it is mixed with fluorspar $\left(C a F_{2}\right)$ and cryolite $\left(N a_{3} A l F_{6}\right),$ which lower its melting point and make it more conducting. Mainly $C a F_{2}$ and $N a_{3} A l F_{6}$ mixed with $A l_{2} O_{3}$ for converting in molten state.