2ND VIRIAL-COEFFICIENTS OF CHLOROMETHANE AND CHLOROETHANE FROM MEASUREMENTS OF THE EXCESS ENTHALPY OF (0.5N(2)- THE EXCESS ENTHALPY OF (0.5CH(3)CL+0.5C(2)H(5)CL)(G)(0.5CH(3)CL)(G), AND (0.5N(2)+C2H5CL)(G) )

A gas-mixing flow calorimeter has been used to measure the excess mola r enthalpy HmE of (nitrogen + chloromethane)(g), (nitrogen + chloroeth ane)(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 omega as a disposable parameter. From the va lue of w that fitted the HE measurements, values of the second virial coefficient B and the isothermal Joule-Thomson coefficient phi = B - T (dB/dT) were calculated. The values of B for chloromethane are in good agreement with other work, but at low temperatures those for chloroet hane are less negative than previous measurements. The excess enthalpy of (chloromethane + chloroethane) is fitted using the mean value of w for the pure components. (C) 1998 Academic Press.