Abstract
LONDON.
Physical Society, November 26.-Dr. A. Russell, vice-president, in the chair.-J. Guild: Obtaining and maintaining a bright hydrogen spectrum, with special reference to the 4341 line. The paper treats of the conditions of pressure, discharge, etc., most suitable for the production of a bright hydrogen spectrum, such as is required for refractometry and similar purposes. The rapid deterioration of the tubes with use is shown to be caused by a rise of pressure due to the evolution of hydrogen by the electrodes. The trouble may be obviated by sealing an auxiliary bulb of ij or 2 litres capacity to the discharge tube. This reduces the rate of pressure variation and prolongs the useful life of the tube nearly a hundredfold. The use of capacity and inductance is. shown to be very helpful with partially deteriorated tubes.-A. Griffiths, J.. M. Dickson, and C. H. Griffiths: The determination of the coefficient of diffusion of potassium chloride by an analytical method. This paper represents an attempt to develop an analytical method of determining the coefficient of diffusion of a salt in water capable of giving consistent and accurate results. The lower ends of a number of vertical and. parallel diffusion tubes terminate in a reservoir of large capacity containing a solution of potassium chloride. The greater part of the reservoir is above the lower ends of the tubes, and by gravity the solution at the lower ends is kept at an approximately constant concentration. The upper ends of the tubes are covered with a cap provided with an outlet and an inlet tube. Water enters the cap by the inlet tube, and a weak solution containing the diffused salt leaves the cap by the outlet tube. Time, which may be as long as a fortnight, is allowed for the attainment of the steady state, and an individual experiment may last six weeks. The quantity diffused is obtained by chemical analysis. In the case of a solution containing 0-2237 gram of potassium chloride to the cubic centimetre (a $N solution) the " mean diffusivity" with respect to water is 1703 x io˜5 (C.G.S. units) at a temperature of 18-5° C.
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Societies and Academies . Nature 96, 444–446 (1915). https://doi.org/10.1038/096444b0
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DOI: https://doi.org/10.1038/096444b0