A re-examination of the light scattered by gases in respect of polarisation. I.—Experiments on the common gases

Source abstract

Abstract In an earlier paper I showed that the light scattered by gases free of dust was not perfectly polarised, but that a residual defect of polarisation remained, which was characteristic for each gas. This was an entirely new field of investigation, and the experimental methods for detecting and measuring a very minute effect had to be worked out. As is the universal experience, many improvements suggested themselves in the course of the work, and after an interval it was decided to repeat a part of it again, with many modifications in detail, designed to give the most accurate numerical results that seem at present obtainable. This has now been done, with results which, speaking generally, confirm the earlier investigation, except in one important particular. It was decided to limit the present investigation to the permanent gases, thus excluding the vapours of organic substances. The latter are inevitably absorbed by the blacking which it is necessary to use on the inside of the vessel, and when the substance under investigation is changed they may come off and give rise to contamination. Moreover, there is the tendency of some of these substances to form fogs under the influence of light. It would have been premature to include them in a first attempt to establish accurate methods. Pioneer determinations were given in the former paper, and are believed to be substantially correct.