Calculation of thermodynamic properties from the miscibility gap in the phase diagram of Zn-Pb system by means of NRTL equation

In this paper, the NRTL equation approach has been used for a calculation of the activity coefficients of the components in a binary alloy system showing liquid phase immiscibility. The parameters needed for the calculation are the energy parameters, (g12–g22), (g21-g11) and the non-random parameter, α, which are determined by solving the NRTL equation with the aid of genetic algorithm. The calculation was carried out numerically for an immiscible phase in the binary alloy system, Zn-Pb. The agreement between the calculated and experimentally determined values of activity coefficient is excellent, indicating the validity of the NRTL equation model for the description of immiscible solutions.