Vapour pressure of diethyl phthalate

Abstract

Measurements of vapour pressure in the liquid phase and of enthalpy of vaporisation and results of calculation of ideal-gas properties for diethyl phthalate are reported. The method of comparative ebulliometry, the static method, and the Knudsen mass-loss effusion method were employed to determine the vapour pressure. A Calvet-type differential microcalorimeter was used to measure the enthalpy of vaporisation. Simultaneous correlation of vapour pressure, of enthalpy of vaporisation and of difference in heat capacities of ideal gas and liquid/solid phases was used to generate parameters of the Cox equation that cover both the (vapour + solid) equilibrium (approximate temperature range from 220 K to 270 K) and (vapour + liquid) equilibrium (from 270 K to 520 K). Vapour pressure and enthalpy of vaporisation derived from the fit are reported at the triple-point temperature T = 269.92 K ( p = 0.0029 Pa, Δ vap H m = 85.10 kJ · mol −1 ), at T = 298.15 K ( p = 0.099 Pa, Δ vap H m = 82.09 kJ · mol −1), and at the normal boiling temperature T = 570.50 K (Δ vap H m = 56.49 kJ · mol −1). Measured vapour pressures and measured and calculated enthalpies of vaporisation are compared with literature data.