On the variation with temperature of the viscosities of the gases of the argon group

In continuation of the determinations of viscosity already recorded, measurements of the temperature variation for the five gases of the argon group have now been obtained. The apparatus used was of the same type as that described in the above papers, with certain modifications to render it suitable for working at different temperatures. Unfortunately, the method is only practicable for a somewhat limited range of temperature. On the one hand, the temperature must be lower than that at which the vapour pressure of mercury becomes appreciable, on account of the very high viscosity of the latter; on the other hand, it must not approach the solidifying point of mercury. At 100° C. the vapour-pressure of mercury is about 1/5 mm. This was judged to be as much as could be safely neglected, and observations were therefore taken at two temperatures only, viz., atmospheric temperature and the temperature of steam. However, although these limitations render observations over a large range impossible, they still allow interesting comparisons to be made of the temperature variations of the different gases. Incidentally, redeterminations of the ratios of the viscosities of the gases to that of air have also been obtained with an entirely new apparatus.