Measurements on the viscosity of helium gas between 293 and 1.6°K

Abstract

Summary Measurements on the viscosity of helium gas from room temperatures to 1.63°K were made by the oscillating disc method. The agreement with the measurements of Kamerlingh Onnes and Weber (capillary flow method) and of Vogel (oscillating disc), both to temperature of liquid hydrogen, is rather good. The results we obtained for the temperature dependence of the viscosity agree fairly well with that calculated by Uehling, who considered the influence of quantum mechanics on the mean free path of the molecules. At 20.38 and 4.23°K the dependence on pressure, from 1 atm to about 10−4 mm, was examined. At ordinary pressures no variation (Enskog dependence) of the viscosity, to an amount surpassing 1% (limit of experimental accuracy) was found. In the low pressure range (mean free path of the molecules larger than or comparable with the plate distances), however, the viscosity η tends to zero with decreasing pressure p. The curve η versus p is composed of two parts: a nearly straight part and a curved one. The experimental curves for the temperatures mentioned above can be represented by the formula η = η∞ P/(η∞ α + P), α being a constant parameter. For 20.38 and 4.23°K α is found 72 and 36 respectively, ratio 2.0. This value is in rather good harmony with what the assumption of Maxwell velocity distribution gives, viz. 2.17, the ratio of the square roots of the absolute temperatures.