The electrical properties of sea-water for alternating currents

Abstract 1. Introductory with Summary of Previous Work. In a recent communication the author gave the results of an experimental investigation of the electrical properties of some samples of soil under alternating current conditions at frequencies from 100 to 10,000 kilocycles per second. It was considered desirable to carry out similar measurements on sea-water since this forms a large portion of the earth’s surface over which electric waves are transmitted in the practice of radio communication. Taking sea-water as a typical electrolyte, a knowledge of its electrical properties is also of importance in connection with research in physical-chemistry. The study of the properties of sea-water at radio-frequencies dates back to about 1906 when interest in this subject was aroused by the theoretical work of Sommerfeld and Zenneck on the propagation of electric waves over the earth’s surface. The results of measurements at audio-frequencies on ninety samples of sea-water collected from the Mediterranean Ocean were published by Hill in 1907. Similar conductivity measurements on water form the North Sea were described by Schmidt in 1911, the mean value obtained at a temperature of 20° C. being 3·6 × 1010 e. s. u. (corresponding to a resistivity at 25 ohm-cm.). Uller pointed out that for the same salt-content and temperature, Hill’s results for the Mediterranean gave a conductivity value about 65% higher that Schmidt’s for the North Sea.