Section: 6 | Permittivity (Dielectric Constant) of Gases |
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One or more tables in this document differ to those in the book. This is due to space restrictions in the book.
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The table 'TABLE 2. Permittivity of Saturated Water Vapor as a Function of Temperature' has one or more different columns to those in the book version.
How to Cite this Reference
 The recommended form of citation is: John R. Rumble, ed., CRC Handbook of Chemistry and Physics, 103rd Edition (Internet Version 2022), CRC Press/Taylor & Francis, Boca Raton, FL. If a specific table is cited, use the format: "Physical Constants of Organic Compounds," in CRC Handbook of Chemistry and Physics, 103rd Edition (Internet Version 2022), John R. Rumble, ed., CRC Press/Taylor & Francis, Boca Raton, FL.

PERMITTIVITY (DIELECTRIC CONSTANT) OF GASES

Table 1 gives the relative permittivity ε (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 µ are also included. The density dependence of the permittivity is given by the equation

$\frac{\epsilon -1}{\epsilon +2}={\rho }_{\text{m}}\left(\frac{4\pi N\alpha }{3}+\frac{4\pi N{\mu }^{2}}{9kT}\right)$

where ρm is the molar density, N is Avogadro’s number, k is the Boltzmann constant, T is the temperature, and α is the molecular polarizability. Therefore, in regions where the gas can be considered ideal, ε – 1 is approximately proportional to the pressure at constant temperature. For nonpolar gases (µ = 0), ε –1 is inversely proportional to temperature at constant pressure.

The number of significant figures indicates the accuracy of the values given. The values of ε for air, Ar, H2, He, N2, O2, and CO2 are recommended as reference values; these are accurate to 1 ppm or better. Column definitions for Table 1 are as follows.

 Column heading Definition Name Name of gas; listed alphabetically by name Mol. form. Molecular formula for gas ε Relative permittivity (dielectric constant) at 20 °C and 1 atmosphere pressure (101.325 kPa) µ Permanent dipole moment, in Debye units (1 D = 3.33564 × 10–30 C m)

Table 2 gives the permittivity of water vapor in equilibrium with liquid water as a function of temperature (derived from Ref. 4).

References

1. Maryott, A. A., and  Buckley, F., Table of Dielectric Constants and Electric Dipole Moments of Substances in the Gaseous State, National Bureau of Standards Circular 537, 1953.
2. Harvey, A. H., and Lemmon, E. W., Int. J. Thermophys. 26, 31, 2005 [for nonpolar gases and light hydrocarbons] [https://doi.org/10.1007/s10765-005-2351-5]
3. Landolt-Börnstein, Numerical Data and Functional Relationships in Science and Technology, New Series, Group IV, Vol. 4, Springer-Verlag, Heidelberg, 1980 [for data at high pressures].
4. Fernández, D. P., Goodwin, A. R. H., Lemmon, E. W., Levelt Sengers, J. M. H., and Williams, R. C., J. Phys. Chem. Ref. Data 26, 1125, 1997 [for water vapor] [https://doi.org/10.1063/1.555997]

TABLE 1. Permittivity of Selected Gases at 20 °C and 1 Atmosphere Pressure

 Name Mol. form. ε μ/D Continued on next page... Acetylene HC≡CH 1.00124 0 Aira 1.0005360 0 Ammonia NH3 1.00622 1.4718 Argon Ar 1.0005169 0 Boron trifluoride BF3 1.0011 0 Bromomethane CH3Br 1.01028 1.8203 Butane C4H10 1.00266 0.05 Carbon dioxide CO2 1.0009217 0 Carbon monoxide CO 1.00065 0.10980 Chloroethane C2H5Cl 1.01325 2.05 Chloroethene CH2=CHCl 1.0075 1.45 Chloromethane CH3Cl 1.01080 1.8963 Cyclopropane C3H6 1.00178 0 Dimethyl ether CH3OCH3 1.0062 1.30 Ethane C2H6 1.001403 0 Ethylene CH2=CH2 1.00135 0 Fluoromethane CH3F 1.00973 1.858 Helium He 1.0000645 0 Hydrogen H2 1.0002532 0
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