Thermodynamic properties of solid palladium-silver alloys

Abstract

The vapor pressure of silver over solid silver and over nine palladium-silver alloys has been measured by the torsion-effusion method in the temperature range 1100–1300°K. The chemical activities, as well as the free energies, entropies, and enthalpies of formation of the alloys at 1200°K have been computed from the vapor pressure data. The activities of silver exhibit large negative deviations from ideal behavior over the entire compositional range. The activities of palladium, computed by graphical integration of the Gibbs-Duhem relation, deviate positively in the palladium-rich alloys and negatively in the silver-rich alloys. The thermodynamic properties are considered in terms of existing thermodynamic data. The excess entropies and enthalpies, both of which are negative, are discussed in relation to the changes that occur in the characteristic properties of palladium and silver upon alloying.