BAEYER’S METHOD
	Baeyer’s method is suitable for the purification of bauxite if it contains excess of iron oxide Fe2O3.
	DETAIL OF THE PROCESS
	When finely divided bauxite is treated with strong caustic soda, then bauxite is converted into     sodium aluminate.                                   Al2O3.nH2O + 2NaOH ® 2NaAlO2 + 2(n)H2O     NaOH = 45%     The solution is filtered to remove Fe2O3.     The fused mass is extracted with water leaving behind both impurities. Sodium aluminate is then     heated up to 50oC to 60oC in the presence of CO2. The precipitates of aluminum hydroxide are     formed.                                 2NaAlO2 + 3H2O + CO2 ® 2Al(OH)3 + Na2CO3     The precipitates of Al(OH)3 are washed to remove Na2CO3, dried and ignited at about 1500oC to get     pure alumina.                                                 2Al(OH)3 ® Al2O3 + 3H2O
	SERPEK’S METHOD
	Serpek’s method is used for the purification of bauxite if it contains excess amount of silica (SiO2).     DETAILS OF THE PROCESS:     The powdered bauxite is mixed with carbon and heated up to 1800oC and a current of nitrogen is     passed, aluminum nitride is obtained.                                     Al2O3.nH2O + 3C + N2 ® 2AlN + 3CO + (n)H2O     Silica is converted in to silicon (Si).                                                         SiO2 + 2C ® Si + 2CO     Aluminum nitride on hydrolysis with hot water produces precipitates of Al(OH)3.                                                    AlN + 3H2O ® Al(OH)3 + NH3     The precipitates of Al(OH)3 are washed to remove Na2CO3, dried and ignited at about 1500oC to get     pure alumina.                                                       2Al(OH)3 ® Al2O3 + 3H2O
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