Cathode : carbon electrodes
Anode : Fe tank lined with carbon bricks
Electrolyte : Na3AlF6 + BaF2
Bottom layer : Impure aluminium consists of Cu, Si etc in molten state.
Middle layer : molten mixtureof Fluorides of Na, Ba,Al andAl2O3
Top layer : pure molten aluminium.
On passing the current, Al is deposited at cathode from the middle layer and an equivalent amount of Al from the bottom layer moves into the middle layer leaving behind the impurities.
Chemical refining methods:
(2) Parting Process:
(6) Vapour phase refining:
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