THE VIRIAL-COEFFICIENTS AND THE EQUATION OF STATE BEHAVIOR OF THE POLAR COMPONENTS CHLORODIFLUOROMETHANE, FLUOROMETHANE AND ETHANENITRILE

Burnett p,rho,T measurements are reported for chlorodifluoromethane, fluoromethane and ethanenitrile. Some isochoric data on fluoromethane are added. Literature data on fluoromethane are also used. It is shown that the virial coefficients of these polar molecules depend on the fourth power of the reduced dipole moment, a much more dramatic dependence than that of the cohesive energy of the liquid. The second virial coefficient becomes much more negative and the third much more positive compared with those of non-polar molecules. The fourth, which can be neglected for non-polar molecules, becomes negative again and is important for highly polar molecules.