A Determination of the Dielectric Constants of Five Gases by a High Frequency Method

Dielectric constants of hydrogen, oxygen, nitrogen, air, and C${\mathrm{O}}_2$.—Special cylindrical gas condensers were constructed so as to have a minimum of solid dielectric in the field, and the small capacities were measured by the method of heterodyne beats, originally used by Hyslop and Carman. A photographic record of the beats on a moving film was secured, one side of the wedge slit being fastened to a tuning fork and the other to the diaphragm of a telephone actuated by the beats. The results reduced to 1 atm. at 0°C, accurate to about one per cent of the difference from vacuum, are: hydrogen 1.000263, oxygen 1.000507, nitrogen 1.000555, air 1.000540, and C${\mathrm{O}}_2$ 1.000948. The values for ${\mathrm{N}}_2$ were found to be independent of the frequency between 1230 and 600 meters, and to be proportional to the pressure from 44 to 69 cm. The values for air, ${\mathrm{N}}_2$ and ${\mathrm{O}}_2$ differ by 8 per cent from those of Boltzmann and of Rohmann.