AN ELECTROCHEMICAL INVESTIGATION OF THE THERMODYNAMIC PROPERTIES OF CERIUM STANNIDE (CESN3) AND LIQUID TIN-CERIUM ALLOYS

The thermodynamic properties of the intermetallic compound CeSn3 and t he tin-rich liquid tin-cerium alloys in equilibrium with CeSn3 were st udied by a high-temperature galvanic cell technique using the reversib le concentration cell Ta, Ce parallel to CeCl3, LiCl-KCl (eutectic)par allel to Ce-Sn (two-phase alloy), Ta in the temperature range 723-873 K. The standard Gibbs energy of formation of CeSn3 from pure solid cer ium and pure liquid tin varies with temperature according to the equat ion Delta G(f(CeSn3))(0) = -260.08 + 0.0476T (+/-2) kJ mol(-1) The act ivity coefficients, excess partial molar free energies, enthalpies and entropies of cerium in the saturated liquid alloys have been computed from the e.m.f. data obtained in this study and the data for the solu bility of cerium in liquid tin. The activity coefficients of cerium in liquid tin with reference to solid cerium can be expressed as ($) ove r bar G(Ce)(XS) = RT ln tau(Ce) = -249 + 0.059T (+/-2) kJ mol(-1).