ELECTROCHEMICAL-BEHAVIOR OF THE TITANIUM CHLORIDES IN VARIOUS ALKALI CHLORIDE BATHS

In order to determine the best conditions for the electrolytic production of titanium we have studied the electrochemical behaviour of TiCl4 in various molten chloride baths. We have shown that the potentials of the reduction steps of TiCl4 depend strongly on the nature of the cations. When the melt contains no Ti(IV) complexing agent, as in BaCl2-CaCl2-NaCl, the IV → III step proceeds via the reduction of gaseous TiCl4. When the bath contains a complexing cation, such as K+, Rb+ or Cs+, TiCl4 gives the complex anion TiCl2-6. In BaCl2-KCl-LiCl at 450 °C, the IV → III step occurs in two waves; the first is related to the reduction of the TiCl2-6 anion, the second to the reduction of gaseous TiCl4. The subsequent steps III → II and II → 0 arise at the same potentials as in BaCl2-CaCl2-NaCl. As we progressively substitute for KC1 with CsCl, the reduction of TiCl2-6 becomes more pronounced and the other reaction decreases. In CsCl-LiCl, Ti(III) is strongly complexed and the reduction to the metallic state proceeds in a single step Ti(III) → Ti(0). © 1979.