P.J. McElroy

(Vapour + liquid) equilibria of (n-hexane + n-hexadecane), (n-hexane + n-octane), and (n-octane + n-hexadecane)

Abstract Vapour pressures using a static method have been measured for ( n -hexane + n -hexadecane), ( n -hexane + n -octane), and ( n -octane + n -hexadecane) at 298.15 K. The results have been fitted using a polynomial and agreement within experimental error was obtained. Excess molar Gibbs free energies calculated from the results and plotted against carbon number have been shown to agree well with the principle of congruence.

Surface tension and its effect on vapor pressure

Abstract Derivations of the Kelvin equation for the effect of surface tension on vapor pressure often incorrectly imply that the cause of changed vapor pressure is the work involved in generating surface phase. The falacy of this is demonstrated in a rigorous derivation of the equation and an explanation for the continual perpetration of the misunderstanding is presented.

Compression-Factor Measurements on Methane, Carbon Dioxide, and (Methane + Carbon Dioxide) using a Weighing Method

Abstract Compression factors Z have been measured using the direct method of measuring mass, volume, temperature, and pressure. It is demonstrated that using a high-sensitivity mass comparator results can be obtained with accuracies comparable to more demanding traditional indirect methods. Z values for {(1 − y )CH 4 + y CO 2 } with y = 0, 0.25, 0.5, 0.75, and 1 are reported at temperatures of 303.15, 313.15, 323.15, and 333.15 K. The results are found to be in agreement with the “GERG” equation of state for natural-gas components. Second and third coefficients derived from the results have been compared with literature values and with predictions of the Tsonopoulos equation using k 12 values estimated from critical-point measurements.

Compression-factor measurements on ethane and (ethane + carbon dioxide) using a direct method

Abstract Compression factors Z for ((1 − y )C 2 H 6 + y CO 2 ) with y = 0.25, 0.5, 0.75, and 1 are reported at temperatures (303.15, 313.15, 323.15, and 333.15) K. The method used required direct measurement of mass, volume, temperature, and pressure. Second and third unlike-interaction virial coefficients have been determined from the Z results. The De Santis and Grande correlation (3rd) and the Tsonopoulos correlation (2nd) are shown to predict the results well. Agreement with the “GERG”-equation values is found to be good also except for the case of pure ethane.

Accurate second virial coefficients of n-alkanes

Abstract Second virial coefficients are reported for n -pentane, n -hexane, and n -heptane in the temperature range 298.15 K to 373.15 K. The measurements are compared with those of other workers and the differences are examined. It is believed that the method used in this work leads to results which are a more accurate representation of second virial coefficients than has hitherto been obtained.

(Vapour + liquid) equilibria of (n-hexane + n-octane + n-hexadecane)

Abstract Vapour pressures and derived excess molar Gibbs energies are presented for (n-hexane + n-octane + n-hexadecane). The results are compared with those for independently measured binary mixtures as a test of the extension of the principle of congruence to the excess molar Gibbs energies of ternary mixtures. The results are also examined for internal consistency with the principle of congruence using the expectation of unity activity coefficient of one component in mixtures in which the average chain length of the ternary mixture is the same as that of the component whose activity coefficient is being considered.

Interaction second virial coefficients for (benzene + cyclohexane)

Abstract An apparatus and procedure are described for measurement of the pressure change on mixing of two gases initially at equal pressure. Interaction virial coefficients obtained from measured pressures of mixing for (benzene + cyclohexane) at temperatures 300, 315, 323, 348, and 373 K are reported and compared with theoretical predictions. Adsorption problems in the stainless-steel apparatus were encountered and the effect on the results is discussed.

Enthalpies of mixing of binary vapours

Abstract A calorimeter has been designed and built for the measurement of enthalpies of mixing of condensable vapours. The apparatus has been tested by measuring the heat capacity of benzene and has been used to measure the enthalpy of mixing of (benzene + cyclohexane). These measurements are in good agreement with results obtained with earlier models of the apparatus in this laboratory and with results obtained by other workers. The consistency of the results derived from measurements of the volumes of mixing at constant pressure and pressure changes on mixing at constant volume is demonstrated. Enthalpies of mixing are shown to be a useful complement to volumetric measurements in the determination of the interaction second virial coefficient for binary mixtures.

Solubilities of Carbon Dioxide and Methane in Polyetheretherketone and Polyethersulfone

Abstract The solubilities of carbon dioxide and methane in polyethersulfone and polyetheretherketone have been measured at 298.2 K and pressures ranging from 2.7 to 5.1 MPa by using a weighing method. The solubility of carbon dioxide, in cm−3 (STP)cm−3 is almost twice that of methane for both polymeric materials.