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, f luoromethane and ethanenitrile. Some isochoric data on fluoromethane a re added. Literature data on fluoromethane are also used. It is shown that the virial coefficients of these polar molecules depend on the fo urth power of the reduced dipole moment, a much more dramatic dependen ce than that of the cohesive energy of the liquid. The second virial c oefficient 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 impor tant for highly polar molecules.