Thermodynamic properties of fluorine compounds. Part X. Critical properties and vapour pressures of pentafluorobenzene, chloropentafluorobenzene, 2,3,4,5,6-pentafluorotoluene, and pentafluorophenol

Abstract

Critical temperatures and pressures of pentafluorobenzene, chloropentafluorobenzene, 2,3,4,5,6-pentafluorotoluene, and pentafluorophenol have been measured. Vapour pressures of the first three compounds only have been measured in the range from 100 kN m^–2 up to the critical pressure, and the values obtained, together with others at lower pressures reported in an earlier paper, have been fitted well by fifth-order Chebyshev polynomials over the entire range of measurement. New equations for representation of the values obtained at lower pressures have been computed on the basis of the International Practical Temperature Scale of 1968. Estimates of the critical pressure of each of the substances are compared with the observed values, and the general behaviour of the vapour-pressure curves of these substances is discussed.