Thermodynamic behavior in binary metallic solutions

The applicability of Krupkowski’s formalism $$begin{gathered} ln gamma _1 = omega left( T right)left( {1 - X_1 } right)^m hfill ln gamma _2 = omega left( T right)left[ {left( {1 - X_1 } right)^m - frac{m}{{m - 1}}left( {1 - X_1 } right)^{m - 1} + frac{1}{{m - 1}}} right] hfill end{gathered} $$ in interpreting experimental data is shown for several binary systems. Both dilute and concentrated solutions are considered. In dilute solutions (Henry’s law region) these equations exclude constant values of the activity coefficients. These formulae withm>1 satisfy Raoults law and Henry’s law as limiting cases. However, experimental data indicate that only in two systems, namely Zn-Sn and Zn-Bi,γ _Zn ⁰ =γ _Zn over a finite composition range. Whenm is close to unity, as is the case for the Zn-Sn and Zn-Bi systems Raoult’s law is not satisfied untilX _Zn is infinitesimally close to unity. Data for concentrated zinc solutions for both systems support this conclusion. A comparison of Krupkowski’s method with Darken’s quadratic formalism was also carried out, and it was shown that both methods give similar results whenm=2.