Physical Chemistry Third Edition

30 1 The Behavior of Gases and Liquids

(a)(b)(c)(d)

Figure 1.6 Liquid–Gas Equilibrium near the Critical Point.(a) At a temperature slightly

above the critical temperature. The density of the fluid depends slightly on height, due to

gravity. (b) At the critical temperature, and showing the scattering of light known as critical

opalescence. (c) and (d) At subcritical temperatures, showing a definite meniscus. From

J. V. Sengers and A. L. Sengers,Chem. Eng. News, June 10, 1968, p. 104. Used by permis-

sion of the copyright holder.

Tie lines

Tcisotherm

P T

0

Vm

Figure 1.7 Surface Giving Pressure as a Function of Molar Volume and Temperature

for a Typical Pure Substance in the Liquid–Vapor Region (Schematic).