A static method for determination of vapour—liquid equilibria and saturated liquid molar volumes at high pressures and temperatures using a new variable-volume cell

Abstract

A new static apparatus is described which uses a variable-volume cell, as in the work of Meskel-Lesavre et al. (1981), for the simultaneous determination of vapour—liquid equilibria and saturated liquid molar volumes; the ranges of pressure and temperature are extended up to 60 MPa and 573 K. Variation of volume in the equilibrium cell is obtained by deformation of a bellows strained by a pressurizing liquid. The pressure P is recorded at a given temperature as a function of the volume of a mixture, the composition of which is known accurately by weighing each component. Not too close to the critical point, the P versus V diagram displays a well-defined break point indicating the bubble point, the coordinates of which are the bubble pressure and the saturated molar volume of the liquid phase multiplied by the total number of moles. Several tests have been performed to check the reproducibility and reliability of the experimental determinations. The experimental results at 323.1, 348.1 and 423.1 K for methane— n-nonane are in good agreement with those of Shipman and Kohn (1966). The isotherm at 423.1 K is extended to higher pressures.