An Analysis of Coexistence Curve Data for Several Binary Liquid Mixtures Near Their Critical Points

Abstract

Experimental data on the coexistence curves for nine binary liquid systems, which meet strict criteria of precision, purity of components, and experimental method, are analyzed in the neighb~rhood of the critical point. The data are examined in terms of a general equation of state which is nonanalytic at the critical point. The results of the computer analysis using weighted non-linear least squares procedures present evidence that some symmetry features of classical equations of state remain; and within the experimental errors in the data all systems are consistent with the critical exponent ,B = 0.34.The asymptotic behavior of the diameter is examined and evidence is provided for a curved diameter in some cases; however, it is concluded that the available data are not extensive enough to make a firm conclusion concerning the shape of the diameter. Experimental methods are briefly criticized and mention is made of the experimental direction that future work should take. Special attention is given to estimating the reliability of the conclusions that may be drawn from a given set of data.

A small angle neutron scattering investigation of the concentration fluctuations in the solutions of potassium in molten potassium bromide

“…Preliminary data [28] at a 2 % accuracy show the existence of a strong negative volume excess in the vicinity of the miscibility gap. These data significantly straighten up the tilt of the rectilinear diameter and give the best agreement between the f3 value obtained from equations (17) and 18and what is expected from the scaling laws [27], considering what hasBbeen obtained already for y and v, i.e. f3 = 0.30 ± 0.05.…”

Effects of finite size on the critical behavior of fluid films

“…(T-Tc)/Tc], and find A = 1.9110.03. Stein and Allen (1973) have fit the bulk lutidine +water coexistence• curve data of ' Loven and Rice (1963) and found A* = 1.95 i 0.70. Thus our value t for A* and hence A3 appears to be reasonable.…”

“…proportional to 80. We take 80 as the order parameter of the system (Stein and Allen, 1973) and so its behavior is governed by the coexistence curve scaling form…”

Thermodynamics of liquid‐liquid equilibria including the critical region

“…It has often been suggested that volume fractions, rather than mole fractions should be used because coexistence curves for binary mixtures are then more nearly symmetric. Unfortunately, this choice of variables does not necessarily guarantee that the true (1 -a) = 0.88 will be observed; for the system 3-methyl pentane/nitroethane, for example, Stein and Allen (1973) obtained (1 -a) = 0.62 from the precise measurements of Wims et al (1969), using volume fractions. In this regard, complete agreement between theory and experiment has not been achieved.…”