Conversion of impure bauxite to sodium aluminate:
Al2O3.2H2O + 2NaOH {\overset{ 150^o C - 200^oC}{\longrightarrow}} 2NaAlO2 + 3H2O
Conversion of sodium aluminate to aluminium hydroxide:
NaAlO2 + 2H2O {\overset{ 50^o C - 60^oC}{\longrightarrow}} NaOH + Al(OH)3
Conversion of Al(OH)3 – to pure alumina – heat on Al(OH)3:
2Al(OH)3 {\overset{ 1100^oC}{\longrightarrow}} Al2O3 + 3H2O
Precipitated Al(OH)3 is ignited to give pure alumina [Al2O3]