Abstract:EMFs of fortytwo Na/Na_xPb_1-x (x=0.043 !33～0.987 8) cells were measured by using a Na｜Na⁺ βAl₂O₃｜Na_xPb_1-x solid electrolyte cell. The EMF and its temperature coefficient of the Na/Na_xPb_1-x (liquid)， activity coefficient of the sodium in Na_xPb_1-x， sodium partial molar entropy - S (Na) and partial molar enthalpy -H (Na) were also calculated as a function of x (Na). For the liquid Na/Na_xPb_1-x cell， the linear relationship between dE/dT，- S (Na)， -H (Na) and x(Na)， respectively， were deflected at x(Na)= 0.083， 0.20， 0.39， 0.48， 0.52 which correspond to the rich lead phase， NaPb₄ entectic point， NaPbNaPb₃entictic point and NaPb compound analogous to transformation of phase region inthe NaPb system. The results indicate that chemical complex exist in the molten Na_xPb_1-x near the temperature of liquids line in NaPb phase diagram. The moing temperatures of NaPb alloys and entectic temperatures of NaPb₄， NaPbNaPb₃and NaPbNa₄Pb₉ have been determined from the dependence of the cell EMFon component and temperature.

Key words: sodium betaalumina; solid electrolyte; sodiumlead alloy; thermodynamic function