Open AccessThe emission of electricity from various substances at high temperatures
Publication year - 1914
Publication title -
proceedings of the royal society of london. series a, containing papers of a mathematical and physical character
Language(s) - English
Resource type - Journals
eISSN - 2053-9150
pISSN - 0950-1207
DOI - 10.1098/rspa.1914.0068
Subject(s) - barium , emissivity , crucible (geodemography) , impurity , electricity , carbon fibers , cathode , materials science , metallurgy , chemistry , mineralogy , physics , composite material , optics , organic chemistry , computational chemistry , quantum mechanics , composite number
In previous papers an account was given of experiments in which ionisation currents of great magnitude were obtained from carbon at high temperatures. It was remarked that the largest currents appeared to be associated with the expulsion (at about 2000°C.) of impurities, such as silica, alumina and iron, which are always present in commercial carbon. Such a result is perhaps not surprising in view of Wehnelt's work on the alkaline earths and their large electronic emissivity when raised to a white heat, as for example in a Wehnelt cathode. Furthermore, Sir J. J. Thomson showed some years ago that oxides, when raised to a red heat in a crucible, gave out an excess of negative electricity, the most copious streams coming from the oxides of calcium and barium. The currents generated were such as were readily indicated by an electroscope.