Thermodynamic properties of dilute Cu–Fe–Pb solutions

The effect of iron on the activity of lead in the Cu–Fe–Pb solution containing 0·02–0·10 molfraction of iron and 0·02–0·06 molfraction of lead at 1473 and 1673 K was investigated. The activity of lead in the solution was measured by holding the Cu–Fe–Pb solution under investigation and a Cu–Pb standard solution with known thermodynamic properties, in a sealed crucible at a known argon pressure until equilibrium was established between the gas phases common to both solutions, and the solutions. In the equilibrium state the activity of lead in both solutions will be the same, according to Raoult's law. The effect of copper and iron vapours on the equilibrium was neglected because the rates of vaporization of these constituents in the experimental conditions are very low. The interaction parameter of iron and lead €Pb ^Fe in the Cu–Fe–Pb solution was determinedfrom the experimental results. It was found that over the concentration range examined, the Wagner linear equation describes accurately the experimental values of the activity coefficient of lead.