The thermal decomposition of dilute solutions of K2CO3 in the ternary fluoride eutectic (Li, Na, K)F (FLINAK) at 750°C was studied both by chemical analysis of quenched melts and in situ by a potentiometric method. The carbonate simultaneously vaporizes as M2CO3 and decomposes: CO32−=CO2+O2− , until a steady state is reached where the major part of the carbonate is retained in the melt. Voltammetric study of the carbonate reduction shows that the reduction is not direct but goes via the prior reduction of alkali metal: (1) M++e=M , (2) 4M+M2CO3=C+3M2O .

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Solubility products of nickel and cobalt oxides in molten normalNaCl (1100 K) and Na2SO4 (1200 K) have been measured by coulometric titration of the respective chlorides ( NiCl2 , CoCl2 ) and sulfates ( NiSO4 , CoSO4 ) with electrochemically generated oxide ion, using a stabilized zirconia electrode as an oxide pump. The metal oxide equilibria were complicated by competitive paths leading to Na2O2 , NaNiO2 , and NaCoO2 formation. Activity coefficients of soluble nickel and cobalt salts were also determined from a comparison of experimental data and thermodynamic calculations.

The oxidation of Na2O in molten normalNaCl was studied in the presence of oxygen (<10 Torr) at 830°C by two electrochemical techniques: cyclic voltammetry and chronopotentiometry. The results indicate the following reaction pathway2 O2−+O2⇌2 O22− 2 O2−⇌O22−+2e− O22−⇌O2+2e−The partial conversion of O2− to O22− in the melt results in two oxidizable species. Experimental data indicate that superoxide is absent from the Na2O‐normalNaCl melts.