Abstract
Viscosities and second virial coefficients of five molecular gases considered cannot be reproduced by a single pair potential function for central forces. Contributions of quadrupole interactions to the second virial coefficient, but not the viscosity, account adequately for the differences over wide ranges of temperature for the following values of molecular quadrupole moments (in units of 10—26 esu): H2, 0.52; N2, 1.90; CO, 2.81; CO2, 4.59; C2H4, 3.92. These are compared with other estimates, and the legitimacy of the assumptions is discussed.