On the Mechanism of the Production of Zirconium and Hafnium Metals by Fused Salt Electrolysis

The electrochemical and thermodynamic behaviour of the molten solutions of ZrCl 4 and HfCl 4 with alkali metal chlorides or fluorides, has been investigated. These solutions should be considered as potential electrolytes for the recovery of the reactive metals Zr and Hf by fused salt electrolysis. Solubilities of Zr in melts containing, the higher valence chloride ZrCl 4 , have also been investigated. The measurements included the determination of parts of the corresponding phase diagrams, equilibrium vapour pressures and of the solubility of Zr metal in various electrolytes. With respect to the recovery of metals by fused salt electrolysis it is shown that the thermodynamic behaviour of the solutions has a pronounced effect on the mechanism of the electrode reactions.