The Kinetic Theory of Gases leads to a number of relations between the diffusion, conductivity and viscosity coefficients of gases, and the large measure of confirmation of these has been the greatest triumph of that theory. Most of these relations have been shown by S. Chapman and Enskog to be independent of any particular model of the molecule. In the case of the dependence of viscosity upon temperature, however, the theory gives different results for different molecular models, and the determination of the temperature coefficient of viscosity can therefore be of service in the elucidation of molecular forces.