EQUILIBRIUM ELECTRODE-POTENTIALS OF TUNGSTEN IN MELTS OF THE NA2WO4-WO3 SYSTEM

The emf of cells W \ (1 - x) Na2WO4 + x WO3 \ 0.80 Na2WO4 + 0.20 WO3 \ O2, Pt were measured at temperatures of 1100-137-3 K for mole fractio ns, xunderbar, of 0.01 to 0.50. It was shown that the equilibrium elec trode potentials of tungsten are determined by the activity of ditungs tate ions in the melt; they are satisfactorily described by the Nernst equation. A new mechanism was suggested for the electrochemical step. The temperature dependence of the standard electrode potential of tun gsten, correlation equations linking the activity coefficients of the ditungstate ions to their concentration, and certain thermodynamic cha racteristics of the formation of molten sodium ditungstate and its dil ute solutions were obtained.