Capacitance Measurements on Selenium Rectifiers: Evidence of Anomalous Dispersion

The paper presents evidence showing that, contrary to the generally accepted view, the capacity of a selenium rectifier at audio frequencies may vary with the frequency of measurement The magnitude of the variation depends on the metal used as counter-electrode Thus in the frequency range 300-2,000 c/s little variation occurs with antimony or bismuth, but with cadmium there is a considerable decrease in capacitance. The effect is considered due to polarization arising from the relative motion in the selenium lattice of the negatively charged impurity centres and positive ions which diffuse into the selenium from the counter-electrode