Abstract
LONDON. Royal Society, February 12.—Sir J. J. Thomson, president, in the chair.—J. W. McBain and C. S. Salmon: Colloidal electrolytes. Soap solutions and their constitution. For the first time a comprehensive theory of soap solutions has been set up. This has led to a definition of colloidal electrolytes, a class the members of which will probably prove more numerous than acids and bases put together. They are salts in which one of the ions has been replaced by an ionic micelle. The ionic micelle in the case of soap exhibits an equivalent conductivity equal to that of potassium ion, and double that of the palmitate ion which it has replaced. Its formula may correspond to (P′)n m(H2O), but more probably it is (NaP)x(P′)n m(H2O), where P′ is the anion of the fatty acid in question. In concentrated solutions soaps exist chiefly in colloidal form, together with sodium or potassium ion, equivalent to the ionic micelle present, whereas in dilute solution both un-dissociated and dissociated soaps are crystalloids of simple molecular weight. In mixtures of soaps the tendency is to form more micellæ. Addition of electrolytes, however, exerts opposing influences, dehydrating and driving back dissociation. The conception of the ionic micelle serves to explain the behaviour of solutions of dyestuffs, indicators, and proteins. A modification of the dew-point method is described, which has enabled measurements of osmotic activity and “molecular weight” to be carried out, free from the uncertainties of interpretation of the results obtained for colloids bv the osmometer method, and superseding the well-known but erroneous data of Krafft.— C. C. Farr and D. B. Macleod: The viscosity of sulphur. The results are discussed of a number of experiments, under a great variety of conditions, on the viscosity of sulphur with temperatures rising and falling between 123° C. and 278° C. The method employed was that of rotating cylinders, usually with a bifilar suspension. A unifilar suspension was, however, employed in the neighbourhood of the point of minimum viscosity. Great care was taken to secure that the sulphur had actually attained the temperature indicated bv the thermometer used. The effects were observed of prolonged heating, also the effects of the absorption, of gases, especially NH3 and SO2. The relation of the viscosity to the amount of “insoluble sulphur” present is considered.—C. V. Raman and B. Banerji: Kaufmann's theory of the impact of the pianoforte hammer.—Comdr. T. Y. Baker and Prof. L. N. G. Filon: A theory of the second order longitudinal spherical aberration for a symmetrical optical system. The authors obtain a formula for the longitudinal spherical aberration in a symmetrical optical system of the type
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Societies and Academies . Nature 104, 712–715 (1920). https://doi.org/10.1038/104712b0
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DOI: https://doi.org/10.1038/104712b0