Viscosity of the isotopes of hydrogen and their intermolecular force potentials

Improved, absolute measurements of the viscosity of the three isotopes of hydrogen at 22, 25 and 28°C as well as of the three resulting viscosity ratios are described. The ratios have been determined by a direct calculation and with an uncertainty of ±0.09 %.The results are consistent with the hypothesis that the three species interact with slightly different intermolecular force potentials. The order of magnitude of these differences is estimated following Diller and Mason.