509 Summary I t is pointed out th at the charge distribution in a diatomic molecule will be a function of the zero-point energy of the nuclear vibration, and hence th at the forces of attraction and repulsion between two such molecules will depend upon the nuclear masses. In the case of the Coulomb repulsion the magnitude of this effect is estimated by the quantitative treatm ent of a simple model. Calculated numerical data are given which indicate that this effect of the nuclear mass should

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... d to a measurable difference between the second virial coefficients of hydrogen and deuterium, though there are several other factors which would also contribute to the observed difference.