Key points are not available for this paper at this time.
Viscosities of nine gases, determined by the oil-drop method. ---Millikan determined the value of e, the elementary charge, from measurements of the rate of fall of charged droplets in air, assuming the coefficient of viscosity to be 1, 823 10^-7. Now that e is known, the method may also be used to determine coefficients of viscosity. Using carefully purified gases, tested spectroscopically and by density measurements, the results of long series of measurements in argon, helium, hydrogen, methane, ethane, isobutane, nitrous oxide, and carbon dioxide, when reduced to 23^, come out, respectively, 2, 210, 1, 981, 880, 1, 079, 927, 755, 1, 449, and 1, 471, each times 10^-7. These agree with such other reliable determinations as are available for comparison, and are probably accurate to within 0. 3 per cent. Isobutane is the first gas whose viscosity has been measured near its condensation point. Coefficients of slip and of diffuse reflection for clock oil drops in the above nine gases. ---As pointed out by Millikan, from hydrodynamic and kinetic theory, the constant A in the correction term for Stokes' Law, (1+Ala), is equal to the coefficient of slip divided by the mean free path l, and also to 0. 7004 (2-f) f, where f is Maxwell's coefficient of diffuse reflection, hence from measurements of A both may be computed. The values of A for the nine gases were found to vary with the gas from 0. 811 for hydrogen to 0. 901 for helium, and they give corresponding values of f varying from 0. 926 to 0. 874. The results for air and CO₂ agree closely with those of Van Dyke. Determination of the elementary charge by the droplet method. ---The measurements in air give, incidentally, (4. 770. 014) 10^-10 e. s. u. , in good agreement with Millikan's more accurate value, 4. 774. 005.
Yoshio Ishida (Tue,) studied this question.