Thermodynamic similarity of phase-separating binary liquid mixtures having an upper critical temperature

Abstract

The pressure dependence of the phase-separation temperature (up to 200 MPa) has been determined by experiment along near-critical isopleths for twelve mixtures with an upper critical solution temperature: (an alkane + a perfluoroalkane or acetone or methanol). The experimental results are presented as F“ p p o , T T o , ( x x c) ≈ 1, c’ = 0 , where c = ( T o p o )( dp dT ) T o is the parameter of thermodynamic similarity. The Simon equation: ( p p o ) + 1 = ( T T o ) c , is used as the main approximation. The realizability of prolongation of isopleths into the region of extended liquid states ( p < 0) is discussed. A correlation c ∞ (B−1) V ̃ m, c E between the parameter c, the binodal amplitude B, and the reduced excess molar volume V ̃ m, c E has been discovered.