Some measurements on thermomolecular pressure ratios in hydrogen and in neon

Summary The authors measured the thermomolecular pressure ratios for hydrogen and neon at the ends of a capillary, wide 0.0728 cm, the temperature at one end being 77°K, at the other end 14 to 20°K, in the pressure range from 0 to 20 μb. The results deviate somewhat from Weber and Schmidt's 1) formula VII a ′, which was principally based on measurements on helium. The authors calculate new constants valid for hydrogen and neon. They further derive values for the coefficient l occurring in the differential equation which determines, for the nearly molecular condition of an open gas, the thermomolecular pressure ratio in a tube in which a temperature gradient exists.