THE GRAND PARTITION-FUNCTION OF DILUTE BIREGULAR SOLUTIONS

It has been demonstrated that the grand partition function (GPF) of bi regular solutions contains in one single equation such thermodynamic p rinciples as Henry's law, Raoult's law, the Gibbs-Duhem relation, Raou ltian activity coefficients and their finite power series, Wagner's re ciprocity, Schenck-Frohberg-Steinmetz's interchange, Lupis-Elliott's a dditivity, Mori-Morooka's disparity, and Darken's quadratic formalism. The logarithm of the Raoultian activity coefficient of species i, 1n gamma(i), should not be expressed by the Taylor series expansion, lest its truncation infringe the Gibbs-Duhem equation. The GPF methodology establishes that In yi is not a vector but a scalar point function, f ree from any path dependence. While Darken's quadratic formalism emplo ys three parameters to describe a ternary solution, the present biregu larity approximation offers an alternative using seven empirical param eters, in case better accuracy is needed.