how can you calculate ionic mobilities of calcium and oxide ions in molten cacl2,when TiO2 is on electrochemical reduction with molten cacl2 at 955 0C

Dear student,

The basic underlying principle of the FFC Cambridge process is that metallic calcium is quite soluble in its own molten chloride salt: molten calcium chloride dissolves up to a few mole percent calcium metal (3.9 mol% Ca at 900 °C). This molten salt dissolved, molten calcium metal is free to wander about in the melt, including diffusing into and reducing crystalline titanium and other metal oxides. The calcium mobility in the melt is both a blessing and a curse: it's a blessing for providing this  reduction of titanium dioxide, but a curse when it comes to current efficiency, because the cathode-reduced metallic calcium can also wander back to the anode, and get reoxidised with the evolved gases there. For this reason, the electrolytic production of pure calcium metal from its molten chloride involves an iron rod cathode that must be gradually raised, and a layer of calcium metal deposits as a continuation of the iron rod. Should the calcium rod be left to soak in the molten salt, it would simply wash away as it forms, and recycle to the anode. 

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