Abstract: Some thermodynamic parnmeters of Pd-In alloys with 2 to 70 at. H indium have been determined in the temperuture range 800 to 1000℃ from e.m.f measurements ongalvanic cells with an onsen-cotzducting solid electrolyte. Heats of tnising calculated hem the activities are in excellent agreement with calorimetric data. The relative partial excess hee enengy of indiurn assumes unnsually larpe negative values ap to-174kJ/mol for Pd-rich alloys. Two efficts are discussed to account for the non-idealproperties: The rise Of Fermi enerpy as the valence electron8 of indium enter the 4dand 5sP bands of the alloy and the lattice distortion brought about by the differentmolar volumes of the cofnponents. The rise of the Fermi enerpy, as determlned fromthe activity data, indicates a strict adherence of the alloys to the rigid band model.

Key words: galvanic cell, activity data, Fermi energy, lattice distortion, rigid band model