Direct determination of the imperfect gas contribution to the refractive index of ethylene and a discussion of the quadrupole moment

The experimental value of the second refractivity virial coefficient of ethylene obtained directly is higher than the classically calculated theoretical value. The quadrupole moment of ethylene determined by combining the results of the second dielectric virial coefficient and the second refractivity virial coefficient compares very favorably with the one derived from the microwave absorption as well as the value obtained directly by the method of induced birefringence.