THE DIELECTRIC CONSTANTS OF ARGON, CARBON DIOXIDE, NITROGEN, AND OXYGEN DETERMINED AT AN AUDIO FREQUENCY

Abstract

Values of the relative permittivities, or dielectric constants, of four gases have been measured at an audio frequency of 1592 c.p.s. with an accuracy comparable to that obtained in the microwave or optical regions. The method is based on the characteristics of the computable cross-capacitance configuration which permit the accurate calculation of changes of capacitance due to variation of dimensions with gas pressure, aided by the improved capacitance measurements now available. The results obtained are as follows: These results verify the extrapolation of the optical refractivity data to zero frequency for argon, nitrogen, and oxygen in which the atomic polarization constant is zero. On the other hand carbon dioxide, which has a strong infrared vibration–rotation spectrum, may not be extrapolated from optical data, but must be measured at the lower frequencies.The measured values of these reference gases may be used to calibrate other permittivity apparatus and so extend the data on other substances.