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Excerpt from Various Photo-Electrical Investigations It is well known that the photo-electrical sensitivity of selenium is brought about by heat treatment at the proper temperature. It was, therefore, of interest to make similar tests upon various samples of molybdenite, especially since it is not known what temperature changes the natural mineral may have undergone. The first tests consisted in heating a sample of molybdenite to a low red for a moment by passing an electrical current through it. Starting with a sample of mos2 which was photosensitive, it was found that heating it to 700° C. For a Short time destroyed the sensitivity. A similar heat treatment of nonsensitive Samples of mos, did not render them sensitive. In another test, a sample of photosensitive mos2 was heated to a low red on a metal plate till it had become covered with white oxide. After standing for 24 hours and after peeling ofi the oxide, the intrinsic photo-electrical sensitivity (ratio of light current dark current) was practically the same (30 per cent) as that of the unheated sample. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.