REVERSIBLE ELECTRODE-POTENTIALS FOR FORMATION OF SOLID AND LIQUID CHLOROZIRCONATE AND CHLOROHAFNATE COMPOUNDS

The standard electrode potentials for the formation of the pure solid and molten compounds Li2ZrCl6, Li2HfCl6, Na2ZrCl6, Na2HfCl6, K2ZrCl6, K2HfCl6, Cs2ZrCl6, and Cs2HfCl6 have been calculated from measured vap our pressures corresponding to their thermal decomposition at equilibr ium and from available thermochemical data. Reversible potentials for the formation of Na2ZrCl6 and of K2ZrCl6 in solution according to the reaction Zr(s) + 2ACl (in ACl-A2MCl6) + 2Cl2(g, 1 atm) = A2MCl6 (in AC l-A2MCl6) where A is Na or K, have been calculated from available equi librium vapour pressures as functions of the mole fractions of the alk ali hexachlorocompounds. Standard potentials for the above reaction an d ''formal'' potentials are also given. The latter are useful in predi cting the electrochemical behaviour of dilute solutions of the hexachl orozirconates in alkali metal chlorides.