Second virial coefficients of chloromethane and chloroethane from measurements of the excess enthalpy of (0.5N2+ 0.5CH3Cl)(g), and (0.5N2+ C2H5Cl)(g). The excess enthalpy of (0.5CH3Cl + 0.5C2H5Cl)(g)

A gas-mixing flow calorimeter has been used to measure the excess molar enthalpyHmEof (nitrogen+chloromethane)(g), (nitrogen+chloroethane)(g), and (chloromethane+chloroethane)(g) at standard atmospheric pressure over the temperature range 250 K to 390 K. The measurements are analysed using the corresponding states correlation of Tsonopoulos with the acentric factor ω as a disposable parameter. From the value of ω that fitted theHmEmeasurements, values of the second virial coefficientBand the isothermal Joule–Thomson coefficient φ=B−T(dB/dT) were calculated. The values ofBfor chloromethane are in good agreement with other work, but at low temperatures those for chloroethane are less negative than previous measurements. The excess enthalpy of (chloromethane+chloroethane) is fitted using the mean value of ω for the pure components.