Quasi-Chemical Method in the Statistical Theory of Regular Mixtures

The quasi-chemical equations in the statistics of "regular" mixtures are deduced by assuming non-interference among local configurations. This method is capable of yielding higher and higher approximations by choosing a larger group of lattice sites as the local configuration under consideration. The comparative accuracy of different approximations can be judged by a simple criterion. Further applications to ferromagnetism and to the order-disorder transition in alloys, and their results are discussed. Equations for ternary mixtures or mixtures of even more components are given. The asymmetry of solubility of one solute in two immiscible solvents and the order effect of ${\mathrm{Ag}}_2$Hg${\mathrm{I}}_4$ serve as the interesting examples of the ternary case.