Chapman and Cowling have related the coefficients of viscosity, diffusion, thermal diffusion, and heat conductivity to a set of integrals, Ωn(l)(T) involving the law of force between pairs of molecules. We have evaluated these integrals for l=1, n=1, 2, 3; l=2, n=2, 3, 4, 5, 6; l=4, n=4, assuming that the energy of attraction is inversely proportional to the sixth power of the separation and the energy of repulsion is inversely proportional to the twelfth power. This assumption is excellent for spherical non‐polar molecules and a big improvement on the Sutherland assumption. The mathematical analysis was very difficult but the results are simple. The transport integrals are evaluated for all temperatures in terms of the maximum energy of interaction and the collision diameters. This gives a ``corresponding states'' relationship which should apply to extremely hot and extremely cold temperatures where good experimental data are not available. The molecular constants can be obtained very accurately from experimental viscosity data, and they agree with values previously obtained from equation of state data.

1.
S. Chapman and T. G. Cowling, Mathematical Theory of Non‐Uniform Gases (Cambridge University Press, Teddington, 1939).
2.
The S(l)(K) are simply related to the Chapman and Cowling functions, φ(l), by the equation
S(l)(K) = 4φ(l)/gr02[2−{1+(−1)l}/(l+1)]
. Here g is the initial velocity along the line of centers.
3.
C. F. Curtiss and J. O. Hirschfelder, The Kinetic Theory of Multicomponent Systems of Gases (University of Wisconsin, Madison, July 1947), CF‐727. Here an attempt is made to derive this factor but its validity is somewhat questionable.
4.
John G.
Kirkwood
,
J. Chem. Phys.
15
,
72
(
1947
).
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© 1948 American Institute of Physics.
1948
American Institute of Physics
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