Permittivity Dielectric Constant of Gases

This table gives the relative permittivity e (often called the dielectric constant) of some common gases at a temperature of 20 °C and pressure of one atmosphere (101.325 kPa). Values of the permanent dipole moment p in Debye Units (1 D = 3.33564 x 10 C m) are also included. 

All the parameters in equation (9-44) except the polarizability a can be measured directly, oc is the excess polarizability, that is, the difference between the polarizability of the solute and that of the displaced solvent in dilute solutions. The polarizability of gases is related to the dielectric constant 8 via e — 1 = 4na(N/V), where N is the number of molecules in the volume V. Correspondingly, the difference in relative permittivity (dielectric constant) for solution and solvent must be considered in dilute solutions. 

Most gases exhibit a relative electrical permittivity (i.e., dielectric constant) close to that of vacuum, that is, close to unity. Values of relative permittivity of gases may also be obtained from the data on refractive indices measured for radio frequencies by using the relation ... 

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