Studies on the Flow of Gaseous Mixtures through Capillaries. I The Viscosity of Binary Gaseous Mixtures

Abstract

(1) Viscosities of six following simple gases and seven binary gaseous mixtures have been measured by the transpiration method over the temperature range between 20° and 100 °C.&H_2,CH_4,C_2H_2,C_3H_6,C_3H_8,H_2∼CH_4,H_2∼C_2H_2,&H_2∼C_2H_6,H_2∼C_3H_6,CH_4∼C_2H_2,C_2H_2∼C_3H_6,C_3H_6∼C_3H_8.(2) The viscosities of the first four mixtures attain maximum values at definite compositions, which are about 20% of H2 for the mixture H2∼CH4 and about 70–80% of H2 for the other three.(3) Of several formulae proposed to express the viscosity of gaseous mixtures, that in which Kuenen’s consideration of the persistence of molecular velocity is introduced seems to be the most appropriate. The results of observation can be expressed satisfactorily by that formula, if we take a proper value for one of Sutherland’s constants which is due to the attraction between the different molecules and can not be determined directly.(4) The theoretical consideration of this Sutherland’s constant by Schmick and London have been examined by thirty-two examples.(5) The conditions for the occurrence of a maximum and a minimum points have been obtained from the discussion of the viscosity formula and these have been examined numerically for fifty-five mixtures, and found to be always correct except for only five cases.The viscosity-composition curve deviates in general from a straight line. The deviation depends on the ratios of molecular weights, molecular diameters, and Sutherland’s constants of two component gases. Especially the maximum point is very liable to occur if the ratio of two molecular weights is great.(6) It has been shown that, if the persistence of molecular velocity be neglected, the condition for the occurrence of a maximum point cannot be fulfilled and the consideration of the persistence is absolutely necessary to explain this point.(7) The composition of the maximum point displaces with the change of temperature. This is found to be due to the difference of Sutherland’s constants of two component gases.(8) The mean free path of each component gas has been calculated. Generally the smaller mean free paths increases in the presence of molecules with the greater mean free paths and vice versa, excepting a few cases.