Equilibrium potentials of Pb-Bi liquid alloys in molten eutectic mixture of potassium chloride and lithium chloride at temperatures 723-873 К have been measured. The alloys composition was changed from 20 to 80 mol % of bismuth. The activity and activity coefficients of lead as well as its partial thermodynamic functions have been calculated on the basis of experimental data. Negative deviations from ideality have been found. The knowledge of electrode potentials is necessary in order to solve technological problems of metals extraction from alloys. The lead-bismuth phase diagram is a simple one with eutectic point at 55 mol% of bismuth [1]. The bismuth ions equilibrium concentrations in melts containing 48 mol % of PbCb in NaCl-KCl equimolar mixture have been calculated from literature data [2-4].