Phase equilibria, and critical temperatures and pressures, of fluid (benzene+hexafluorobenzene)

Abstract

Curves of dew pressure and bubble pressure against temperature have been established for four values of the mole fraction x at temperatures between about 450 K and the critical temperature for {(1 - x)C 6H 6 + xC 6F 6}. The critical temperatures and critical pressures have also been measured. Although both a positive and a negative azeotrope are known to exist at temperatures between 303 and 343 K, no azeotrope has been found at any temperature above 450 K. Interpolation, by means of Chebyshev polynomials fitted to dew pressures (or bubble pressures) for our high-temperature values and Gaw and Swinton's low-temperature values, suggests that, as the temperature is raised above 343 K, the positive and negative azeotropes disappear together at a horizontal point of inflexion that occurs at about 443 K. Such an azeotropic bound does not appear to have been discussed before.