THERMODYNAMIC ACTIVITIES OF COPPER IN COPPERMAKING SYSTEMS (KNUDSEN EFFUSION, PLATINUM, VAPOR PRESSURE)

The vapor pressure of pure copper and the partial vapor pressures of Cu over Cu-Fe, Cu-Pt and Cu-Fe-Pt alloys in the temperature range 1240 to 1360(DEGREES)C were measured by the Knudsen effusion method in conjunction with a vacuum electrobalance. An attempt was made to determine the possible errors in the method by studying the effect of the area of the orifice in the effusion cell on the measured vapor pressure and by considering the influence of surface depletion. The Cu-Fe binary system shows stong positive deviations from Raoult\u27s law for both components over the entire range of composition. The thermodynamic properties of Cu-Pt alloys were calculated from the vapor pressure data. The activities of copper and platinum exhibit strong negative deviations over the entire range of composition. The activity of iron in the solid phase region was calculated by Gibbs-Duhem integration of the experimentally-determined activities of copper. The calculated values are in good agreement with these obtained by a heterogeneous equilibrium technique