Measurement of the Thermodynamic Quantities for the Ag-S System by the E.M.F. Method

Abstract

The E.M.F. method using solid oxide electrolyte was applied to determine the sulfur activities for the Ag-S system. The oxygen partial pressures for the system equilibrated with the atmospheric pressure of SO₂ were measured by the following galvanic cell:
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The equilibrium sulfur pressures were calculated from the measured oxygen partial pressures using published data on the molar Gibbs energy of coexisting gas species.
The activities of sulfur in the one-phase-melts or some two-condensed-phase equilibria were evaluated for the compositions up to 32 mol per cent S over the temperature range 867 to 1538 K.
It was found that the sulfur activities for the equilibrium Ag (s)-Ag₂S (s) were in good agreement with those reported by other investigators using the E.M.F. method with different electrolytes. The eutectic and the monotectic temperature estimated by the present activity measurements were found in good agreement with results of earlier works. The boundary of the miscibility gap in the liquid state, however, was found to extend a little wider in the low sulfur content region than that reported in the literature.
The thermodynamic functions of liquid Ag-S solution were determined from the present results. These functions show that this solution behaves like a solution associated with the complex Ag₂S.