Molecular Multipole Moments Determined from Viscosity and Second Virial Coefficients

The quadrupole moment of CO2 molecule and the octopole moment of CH4 molecule have been estimated from the temperature dependence of second virial coefficients. The central potential employed was the Kihara model for which the force constants were derived from the temperature dependence of dilute gas viscosity on the assumption that the multipole moments had no measurable effect on the viscosity. The values of the moments obtained are very reasonable. The shape parameter of the CO2 molecule has been calculated and discussed.