Electrochemical studies of calcium chloride-based molten salt systems

Conductance and EMF studies of CaCl₂-based melts were performed in the temperature range 790°C - 990°C. Conductivity data collected using magnesia tubes and capillaries showed deviations from the data recommended by the National Bureau of Standards. These deviations are attributed to the slow dissolution of magnesia by the CaCl₂-CaO melt. Conductivity data for molten CaCl₂ using a pyrolytic boron nitride capillary were in reasonable agreement with the recommended data; however, undissolved CaO in CaCl₂ may have caused blockage of the pyrolytic boron nitride capillary, resulting in fluctuations in the measured resistance. The utility of the AgCl/Ag reference electrode in CaC₂-AgCl and CaCl₂-CaO-AgCl melts, using asbestos diaphragms and Vycor glass as reference half-cell membranes, was also investigated. Nernstian behavior was observed using both types of reference half-cell membranes in CaCl₂-AgCl melts. The AgCl/Ag reference electrode also exhibited Nernstian behavior in CaCl₂-CaO-AgCl melts using a Vycor reference half-cell membrane and a magnesia crucible.