The Dielectric Constants of Air and Hydrogen at High Pressures

The dielectric constants of air and hydrogen at pressures from 71.8 to 334.7 atmospheres at 20°C have been measured. The values were obtained by measuring, with a capacity meter of the heterodyne type, the variation with pressure of the capacity of a fixed condenser fitted into the pressure vessel. The frequency was 2500 kilocycles. The dielectric constants obtained are slightly lower than those of Tangl and Broxon for pressures about 80 atmospheres. The Clausius-Mosotti function $\frac{(\epsilon -1)}{d(\epsilon +2)}$ was calculated for each pressure. The change with pressure for air is small and irregular, average 1.43. For hydrogen the value decreased uniformly from 1.16 at 71.8 atmospheres to 0.99 at 334.7 atmospheres.