Abstract
LONDON. Royal Society, May 14.—“The Combination of Hydrogen and Chlorine under the Influence of Light.” By P. V. Bevan. Communicated by Prof. J. J. Thomson, F.R.S. The first point studied in this investigation was the initial expansion, or Draper effect, when light is allowed to fall on a mixture of hydrogen and chlorine. This expansion was shown to be due to heat developed by the combination of the hydrogen and chlorine to form hydrochloric acid. The heat effect was measured by the change in resistance observed in a fine platinum wire sealed through the bulb in which the gas mixture was exposed to light. The investigation then considers the period of induction of Bunsen and Roscoe, and the effects of various intensities of light on the rate of combination. Experiments were also made on the effect of illuminating chlorine before mixing with hydrogen, and the original observation of Draper—that the combination takes place more readily after this preillumination—was confirmed. If, however, the gases be bubbled through water after preillumination of chlorine, this effect is destroyed, and the gases behave like the ordinary mixture. To obtain evidence of an intermediate compound, the gases were submitted to sudden expansion producing supersaturation. When the gases were dust free a nucleus-forming substance occurred after illumination, sen that on the expansion a cloud was formed when the super-saturation reached a certain amount. In the non-illuminated gas mixture no cloud-producing substance could be observed with yellow light. This cloud is produced in chlorine alone. In the mixture of hydrogen and chlorine the cloud appears before any hydrochloric acid is formed. The theoretical part of the paper considers the action as taking place in three stages, combination to form complex molecules containing hydrogen chlorine and water molecules occurring, and then a break down of this complex system giving hydrochloric acid and water. The view thus taken explains the chief features of the induction period, and can be extended to apply to other similar actions where a catalyser is necessary for the progress of the action.
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Societies and Academies . Nature 68, 116–120 (1903). https://doi.org/10.1038/068116a0
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DOI: https://doi.org/10.1038/068116a0