A GENERAL ISOMORPHISM APPROACH TO THERMODYNAMIC AND TRANSPORT-PROPERTIES OF BINARY-FLUID MIXTURES NEAR-CRITICAL POINTS

A general isomorphism approach to critical phenomena in binary fluid m ixtures that may exhibit complex critical-line behavior is developed b y relating the two relevant scaling fields to linear combinations of t hree physical field variables. These physical field variables are rela ted to the temperature and chemical potentials of the two components. The proposed approach includes crossover from vapor-liquid critical be havior to liquid-liquid critical behavior and incorporates also the cr itical behavior near other special points on critical loci. It is show n that the key factor which determines the apparent behavior of the th ermodynamic and transport properties of near-critical mixtures is the shape of the critical locus. The number of system-dependent coefficien ts that determine the asymptotic critical behavior is elucidated. The choice of zero-points of entropy and energy in binary mixtures is also discussed. The approach provides a powerful tool for predicting therm odynamic and transport properties of fluid mixtures in the critical re gion.