Abstract
LONDON. Royal Society, November 13.—Sir Arthur Schuster: On the total reflection of light. The light Which enters the optically rarer medium at or beyond the critical angle is an effect of diffraction originating near the boundary of the refracting surface. It derives its energy from the incident beam and must diminish the intensity of the reflected light. Thus there can be no total reflection in the strict sense of the word. The ratio of the energy dissipated by diffraction to the total energy of the incident light is inversely proportional to the length of the refracting surface, and therefore tends towards zero as the size of the refracting surface increases. At the critical angle the light dissipated by diffraction amounts to about one per cent, of the incident light, when the length of the refracting surface is 5 cm. The numerical value is subject to correction depending on the approximate nature of the investigation.—W. J. Adam and J. W. W. Dyer: The molecular structure of thin films. Pt. VI. Five long-chain alcohols have been examined. The area of cross-section of the chain in the alcohols is the same as in the acids, within 2? per cent., and the CH2OH group occupies 22-6 sq. U. of area. The acetates of these alcohols pack with the heads occupying 23 sq. A.U., and form expanded films of the same kind as other esters. The methyl ethers of the alcohols do not form stable films. Highly unsaturated acids, with three and five double bonds in the chains, behave much like oleic acid, which only has one double bond. Arachidic acid and its derivatives behave normally. Substituted acetamides show a solid film with chains close-packed at low temperatures, and this melts at a definite temperature, raised by compression, to a liquid film of area 24-2 sq. A.U. This melting seems to be due to the molecules acquiring sufficient kinetic energy other than translational to break up the solid structure. Hydrocarbon chains more than 27 carbons long tend to mask the typical phenomena in condensed films. Pentserythritol tetrapalmitate, which has four chains attached to a common centre through polar groups, and should normally have these four chains directed to the corners of a tetrahedron, orients all the chains vertically in the surface. These are not quite close-packed until a compression of about 20 dynes per centimetre is applied.—T. Alty: The cataphoresis of gas bubbles in water. The velocity of a gas bubble in water is independent of the gas used. It is proportional to the applied field throughout the whole range of diameters, the maximum velocity being 4-1? 10-4 cm./sec./volt/cm. at a diameter of about 0-1 mm. The highest velocity is only attained in water of specific conductivity 8-5? 10″6 ohms″1. In water of specific conductivity 1-8? 10-6 ohms-1, the charge on the bubble is very small, and is occasionally reversed during the course of an experiment. Two bubbles appear to repel each other.—D. R. Hartree: Some relations between the optical spectra of different atoms of the same electron structure. I.—Lithium-like and sodium-like atoms. Relations between values of corresponding terms of the spectra of different atoms of the same electron structure are worked out for the Bohr atom model with a central field. The relations are different according as the series electron does or does not penetrate into the core. The theoretical relations agree fairly closely with such experimental data as are available.—P. A. M. Dirac: The conditions for statistical equilibrium between atoms, electrons and radiation. The principle that every process which occurs in an assembly in thermodynamic equilibrium is exactly balanced by the reverse process occurring to the same extent is applied to the general case of w-body encounters, both radiative and non-radiative processes being considered. Van't Hoff's isochore is of universal validity, even for radiative processes and with relativity mechanics. From Planck's law of radiation it is deduced that every process by which radiation is emitted is stimulated by external radiation of the same frequency, the ratio of stimulated to spontaneous emission being independent of the nature of the process, and inversely proportional to the cube of the frequency.—Ida Doubleday: Boundary lubrication-further consideration of the influence of the composition of the solid face.—Christina C. Miller: The Stokes-Einstein law for diffusion in solution. Dilute solutions of iodine in a large number of solvents of different viscosity were used. According to the Einstein-Stokes expression, which is based on the assumption of large particles moving amongst relatively small molecules, the product [diffusion-coefiicient? velocity should be constant for all solvents. The product in the case of organic solvents actually varied between 850 and 1544; for aqueous solutions of alkali halide of different concentrations the variation was between 826 and 1216. According to Sutherland, on the opposite assumption that small dissolved molecules move amongst relatively large molecules, the value of the product in the extreme case should be 1-5 times as great as the value given by the Einstein-Stokes expression. If acetylene tetrabromide be excepted, the ratio for any two products actually falls between 1 and 1-5.—Helen S. French and W. J. Lowry: Studies of co-ordination, Pt. I. Absorption spectra and co-ordination of some cupric compounds. The absorption-spectra of the cupric compounds, both organic and inorganic, are dominated by (i.) a red or infra-red band, which is characteristic of the cupric atom, and (ii.) an ultraviolet band or general absorption, which depends mainly on the anion or organic radical. The colour of the cupric compounds depends on the character of the narrow region of transmission between these two absorptions.—L. F. Bates: On the range of y-particles in rare gases. A scintillation method was used, and the value found for helium, after repeated purification of the gas used, is very different from that found by previous observers, due probably to the big effect of small quantities of impurities in reducing the range. Henderson's theory of the loss of energy of an x-ray in passing through matter, whilst accounting for approximately the same fractional loss of energy in all the rare gases, does not account for the whole loss. There is a rough linear relation between the logarithms of the observed stopping powers and the logarithms of the atomic weights of the rare gases, but it does not take the simple form given by Bragg and Kleeman.—D. H. Black: The 3-ray spectrum of mesothorium 2. Thirty-one lines were detected and their energies calculated. The majority of these lines are considered to be due to the conversion of 7-rays in the absorption levels of the atom itself. In all, eight 7-rays have been classified, and it has been possible to account for seven of these quite satisfactorily by the system of transitions between levels in the nucleus.—J. Keith Roberts: The thermal expansion of crystals of metallic bismuth. The thermal expansion of crystals of metallic bismuth parallel and perpendicular to the vertical axis, by comparison with that of crystalline quartz, are practically constant from ordinary temperatures up to 2400 C. Bismuth melts at about 2700 C. The constant expansion coefficients over this range are:-Perpendicular to the axis, 12-0×10-6; parallel to the axis, 16-2.
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Societies and Academies. Nature 114, 772–775 (1924). https://doi.org/10.1038/114772b0
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DOI: https://doi.org/10.1038/114772b0