Thermodynamics of Bismuth in the Molten Ag−Bi−Sn System

Abstract

An experimental thermodynamic study has been performed on some liquid alloys of the ternary system Ag-Bi-Sn by making use of the torsion-effusion method. Through the measurement of the vapor pressure of Bi in thermodynamic equilibrium with the liquid phase, the Bi activity as a function of Bi atomic fraction, X Bi , was obtained. Three ternary alloys having a fixed ratio p = X Sn /X Ag (p: 0.095; 0.200; 0.333) were examined starting from the original alloy composition and changing X Bi by selected short isothermal vaporizations of Bi. In this way, it was found that all the alloy tested had positive deviations from ideality. Some thermodynamic quantities were evaluated at T = 1000 K. They are Bi mixing partial molar quantities such as Δ mix G T (Bi), Δ mix H T (Bi), and Δ mix S T (Bi) and mixing integral molar quantities, i.e., Δ mix G T (XS) and Δ mix G T (re), which are excess and real, respectively.