Abstract
LONDON.
Physical Society, May 10.-Prof. A. Schuster, F.R.S., president, in,the chair.-Dr. J. A. Barker and Dr. G. W. C. Kaye: The generation of electricity by carbon at high temperatures. The experiments described owe their origin to some contamination phenomena which were encountered when tubes of refractory rare earths were baked in carbon-tube resistance furnaces at temperatures from 1500° C. upwards. It was found that the tubes often had their outer surfaces carbonised to an appreciable depth, while the inner surfaces, though freely exposed, were much less attacked. The blackening was presumably caused by particles shot from the carbon walls of the furnace with velocity high enough to penetrate the refractory material after crossing a few millimetres of air at atmospheric pressure. The preliminary experiments on the nature of these particles were carried out by the use of two insulated exploring electrodes of carbon inserted into an alternating-current furnace. They were connected externally to a battery of cells, and the potential-current curves were determined for the electrode gap in the furnace at a number of temperatures. No appreciable current could be detected at temperatures below about 1400° C., but as the temperature rose it was found that quite small E.M.F.'s gave rise to steady currents of relatively enormous magnitude. For example, with 8 volts, currents up to 10 amperes have been obtained at a temperature of about 2500° C. The relation between current and temperature was found to be of an exponential character.-S. Bntterworth: A method of measuring small inductances. The author shows how Anderson's method may be modified so that, while still retaining the usual standards of capacity, very small inductances may be measured. As in Anderson's method, balance is attained by a simple resistance adjustment. The conditions of maximum sensibility are indicated, and experimental results are quoted in which an inductance of 20 microhenries is compared with a capacity of o-i mfd. The method may also be employed to compare a very low capacity with the usual mica standards of capacity.-H. A. Colwell and Dr. S. Russ: The conversion of starch into dextrin by X-rays. When solutions of starch are irradiated for several hours by X-rays of moderate penetrating power, the opacity and viscosity of the solutions are markedly diminished. These physical changes are attended by chemical changes; there is a partial conversion of the starch into soluble starch and dextrin. A quantitative estimation of the amount of dextrin formed after the starch solution had been irradiated for eight and a half hours showed that it corresponded to about 5 per cent, of the amount of starch initially present. When solutions of dextrin were subjected to a similar exposure of X-rays, no conversion of this substance into glucose was obtained.
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Societies and Academies . Nature 89, 337–339 (1912). https://doi.org/10.1038/089337a0
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DOI: https://doi.org/10.1038/089337a0