a b s t r a c tThermodynamic properties of Ga-In eutectic alloys saturated with praseodymium were determine d for the first time employing the electromotive force method. The equilibrium potentials of the Pr-In alloys saturate d with praseodym ium (8.7-12.1 mol.% Pr) and Pr-Ga-In alloys (containing 0.0012-6.71 mol. % Pr) were measured between 573-1073 K. Pr-In alloy containing solid PrIn 3 with known thermodynamic properties was used as the reference electrode when measuring the pot entials of ternary Pr-In-Ga alloys. Activity, partial and excessive thermodynamic functions of praseodym ium in alloys with indium and GaIn eutectic were calculated. Activity (a), acti vity coefficients (c) and solubility (X) of praseodymium in the studied temperat ure range can be expressed by the following equations: lga aÀPr(In) = 4.425 À 11965/T ± 0.026. lga aÀPr(Ga-In) = 5.866 À 14766/T ± 0.190. lgc aÀPr(Ga-In) = 2.351 À 9996/T ± 0.39. lgX Pr(Ga-In) = 3.515 À 4770/T ± 0.20.