摘要：

This paper describes a new statistical approach to the theory of multicomponent systems. A 'conformal solution' is defined as one satisfying the following conditions: (i) The mutual potential energy of a molecule of species L$\_{r}$ and one of species L$\_{s}$ at a distance $ho $ is given by the expression u$\_{rs}$($ho $) = f$\_{rs}$u$\_{00}$(g$\_{rs}ho $), where u$\_{00}$ is the mutual potential energy of two molecules of some reference species L$\_{0}$ at a distance $ho $, and f$\_{rs}$ and g$\_{rs}$ are constants depending only on the chemical nature of L$\_{r}$ and L$\_{s}$. (ii) If L$\_{0}$ is taken to be one of the components of the solution, then f$\_{rs}$ and g$\_{rs}$ are close to unity for every pair of components. (iii) The constant g$\_{rs}$ equals ${extstyle\frac{1}{2}}$(g$\_{rr}$ + g$\_{ss}$). From these assumptions it is possible to calculate rigorously the thermodynamic properties of a conformal solution in terms of those of the components and their interaction constants. The non-ideal free energy of mixing is given by the equation $\Delta ^{\ast}$G = E$\_{0}\underset r<so{\Sigma \Sigma}$ x$\_{r}$x$\_{s}$ d$\_{rs}$, where E$\_{0}$ equals RT minus the latent heat of vaporization of L$\_{0}$, x$\_{r}$ is the mole fraction of L$\_{r}$ and d$\_{rs}$ denotes 2f$\_{rs}$-f$\_{rr}$-f$\_{ss}$. This equation resembles that defining a regular solution, with the important difference that E$_{0}$ is a measurable function of T and p, which makes it possible to relate the free energy, entropy, heat and volume of mixing to the thermodynamic properties of the reference species; and the predicted relationships between these quantities agree well with available data on non-polar solutions. The theory makes no appeal to a lattice model or any other model of the liquid state, and can therefore be applied both to liquids and to imperfect gases, and to two-phase two-component systems near the critical point.

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