Papers from the Geophysical Laboratory, Carnegie Institution of Washington Volume 406-522

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1921 Excerpt: ...substantial confirmation of the first results, Deville and Troost maintaining from experiments of their own that Becquerel's platinum bulb was permeable to hot gases, and that his results must of necessity be too low. To this contention Becquerel replied convincingly by using a porcelain bulb himself (still retaining air as the expanding gas), with both the constantvolume and constant-pressure methods of measurement, and announced a result (891) even lower than his previous determinat1on. Notwithstanding this, Deville and Troost were unwilling to regard the result as conclusive, and looked upon the discrepancy between Becquerel's earlier and later results (932 and 891) with unconcealed suspicion. They reiterated their belief that the platinum bulb was permeable and that Becquerel's results with porcelain bulbs were still too low through failure to expose the bulb directly to the zinc vapour. Becquerel's bulb had been shielded from the direct action of the zinc by a protecting tube. Deville and Troost then repeated their own measurements and again obtained their earlier result. Becquerel, following, insisted that his measurements with the platinum bulb were not seriously affected by permeability to hot gases, a property with which ho appeared to be familiar, and explicitly criticised the use of iodine by Deville and Troost. The discussion ended here for the moment without a decisive issue, but subsequent experience has substantially confirmed Becquerel in his contention and his numerical results. The high value obtained by Deville and Troost was undoubtedly due chiefly to the dissociation of the iodine at high temperatures. The real catastrophe in the development of the gas-thermometer, however, does not lie in the uncertainty of the results obtained with it...