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Electrical Properties of Water and Aqueous Solutions at Millimeter Waves
Recently Saxton and Lane¹ calculated the electrical properties of aqueous solutions in the range of millimeter waves and showed that, owing to large dipole losses in this frequency region, the effective electrical conductivity of distilled water is comparable with the electrical conductivity of a concentrated solution of common salt, while the dielectric permittivity is considerably reduced in comparison with the static value.
The measurements made later² also showed good agreement with this theory. This same sharp increase in conductivity due to dielectric losses and the dependence of the latter on the presence of impurities leads to a curious result—the electrical conductivity of tap water becomes lower than that of distilled water. Some measurement results are given in the table.
| Substance | Temperature in °C | Dielectric permittivity | Electrical conductivity (mho/meter) |
|---|---|---|---|
| Distilled water | 23.5 | 23 | 55 |
| Tap water | 24 | 24 | 56 |
| Saturated aqueous solution of salt (6.2-normal) | 25 | 21 | 53 |
The indicated experiments serve as good confirmation of the theory of dispersion in polar liquids.
N. M.
Cited Literature
- A. Saxton and J. Lane, Wireless Eng. 29, 269 (1952).
- P. Hertel, A. Straiton, C. Tolbert, J. app. Phys. 24, 956 (1953).