Abstract
LONDON. Royal Society, June 18.—Lord Rayleigh: Luminous vapour from the mercury arc and the progressive changes in its spectrum. This investigation deals with the luminous stream of vapour observed when mercury distils away from the arc in vacua. The lines of the arc forming known -spectrum series are for the most part strongly developed in the vapour stream. An exception is line 1850 iP-iS, which is strong in arc, but inconspicuous in vapour. Higher members of various series appear in greater relative intensity in vapour than in the arc. The continuous spectrum of mercury, not noticeable when the vapour first emerges, becomes more conspicuous as the vapour matures. In the limit the spectrum tends to consist simply of line '2537 and continuous spectrum. If the vapour is passed through a metal tube maintained at negative potential, the luminosity of the line spectrum in general tapers down to a sharp point, beyond which it disappears. Line 2537 behaves differently. Much of its light tapers down to a point which, however, is beyond the place where the other lines are extinguished, but a residuum is of a different origin and does not admit of extinction. The light of the band spectrum also passes on.-J. C. McLennan and G. M. Shrum: On the origin of the auroral green line 5577 A and other spectra associated with the aurora borealis. In studying the effect of large admixtures of helium on the spectrum of oxygen, a hitherto unknown line has been photographed. The wave-length of this line has been found to be 5577-35 +0-15 A. It is very sharp and is subject to great fluctuations in intensity. Evidence has been produced to prove that this line is identical with the auroral green line X =5577-350 +0-005 A. This line must be attributed to some hitherto unknown spectrum of oxygen, and it is not a limiting member of the ordinary band spectrum of oxygen. Helium has been used to bring out the bands of nitrogen, with an intensity distribution similar to that found in the aurora. The possibility of metastable helium acting as the exciting agent in the auroral spectrum has been discussed.-J. C. McLennan and A. B. McLay: On the series spectrum of gold. Absorption spectra of the vapours of gold, silver and copper in the Schumann region have been investigated. The second members of principal series of doublets in the gold arc spectrum are X =1646-71 (I vac.) and X =1665-75 (I vac.). Similarity exists between the term systems gold I, copper I, and zinc II, in respect of their inverted $ terms, and the term systems of gold I and copper I in respect to certain special TT terms. The term systems silver I and cadmium II have not been shown to include either inverted 5 terms or the special type of IT terms mentioned.-W. A. Bone, D. M. Newitt and D. T. A. Townend: Gaseous combustion at high pressures, Pt. V. The authors describe further experiments upon the explosion of hydrogen-air and carbon monoxide-air mixtures at initial pressures up to 175 atmos. It is shown, inter alia: That, in general, and except where N2-activation intervenes, as in carbon-monoxide-air explosions, time for the attainment of maximum pressure diminishes as initial pressure increases. The "corrected "PmjPi ratios for explosion of any and all mixtures investigated increased in notable degree with initial firing pressure, due probably to increasing opacity of the gaseous medium to the radiation emitted during explosions. There were no signs of "after-burning "in any of the explosions when Pi exceeded about 10 atmos., although it could usually be detected when Pi =3 atmos.-W. T. David: The effect of infra-red radiation upon the rate of combustion of inflammable gaseous mixtures. Two types of apparatus were employed: In one, radiation from an electrically-heated wire coil was passed into the explosion vessel through a window of fluorite or quartz. Pressure-time curves were taken during the explosion of identical mixtures, first when radiation was passed into the explosion vessel, and then when no radiation was passed in. In the other, gaseous mixtures were exploded in a vessel the interior surface of which was silver-plated, and could, therefore, be made either reflecting (by polishing) or absorbent (by coating with, dull black paint); by this means it was possible to vary the radiation density of those types of radiation emitted by the burning gases during the explosion period. Pressure-time curves were taken during explosion of identical mixtures taken first when the walls of the vessel were polished, and then when blackened. For hydrogen and air, carbon-monoxide and air, and methane and air mixtures, an increased rate of combustion was found in all cases when the superimposed (first type) or increased (second type) radiation could be absorbed by the reacting gases. Absorption of radiation by reacting gases promotes combustion; intra-molecular energy (rotational and vibrational) of reacting molecules is the factor (or one factor) concerned in combustion.-R, K. Schofield and E. K. Rideal: The kinetic theory of surface films. Surface tension-concentration curves for aqueous solution of a number of capillary active organic substances give evidence in the case of dilute solutions in support of the unimolecular character of the adsorbed films. The analogy between the lowering, F, of the surface tension, and a three-dimensional gas or osmotic pressure, postulated by Traube, has been critically examined. For weak solutions when F exceeds some 10 dynes per centimetre, the surface phase is relatively highly condensed, and the equation F (A - B) =#RT, analogous to that of Amagat connecting the pressure and volume of highly compressed gases, is obeyed. In this equation, A is area occupied by a gm. mol. of active substance at interface, B is limiting area of a gm. mol. under high compression, and' i/x is a measure of lateral molecular cohesion. The values of x for fatty acids show that at a water-air interface, lateral molecular cohesion increases with length of hydro-carbon chain. There is little or no cohesion between such molecules at a water-benzene interface. Sucrose molecules do not cohere at water-mercury interface.-H. M. Macdonald: The condition that the ratio of the intensities of the transmitted and reflected electric waves at the interface between two media is independent of their plane of polarisation. For a state of steady electrical oscillation between a closed surface separating two different dielectric media and a conductor inside this surface, the condition is that the ratio of the specific inductive capacities of the two media is equal to the ratio of their magnetic permeabilities. For a medium in which the ratio of the specific inductive capacity to the magnetic permeability is constant, the intensity is constant along a ray which cuts the surfaces of constant specific inductive capacity orthogonally; when the surfaces of specific inductive capacity are concave towards an inner surface, and the specific inductive capacity diminishes outwards, the path of any other ray is concave towards the inner surface. -C. V. Raman and L. A. Ramdas: The scattering of light by liquid boundaries and its relation to surface-tension. Parts I. and II.-H. Weiss: The application of X-rays to the study of alloys.-F. R. Weston: The flame spectra of carbon monoxide and water gas. The results of a spectrographic study of the flame of carbon monoxide, burning in air and various other supporting atmospheres, are described. In the flame of pure (undried) carbon monoxide, two sets of independent interactions occur simultaneously:-(a) direct interactions between CO and O (without any intervention of steam], exciting radiations which give rise to the continuous and banded parts of the spectrum and to the characteristic blue colour of the flame, and (6) interactions between CO and OH2 molecules, which originate the "steam-lines "in the spectrum. When hydrogen is gradually added to the burning gas, the relative proportions of the first-named interactions diminish rather rapidly.
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Societies and Academies. Nature 115, 998–1000 (1925). https://doi.org/10.1038/115998b0
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DOI: https://doi.org/10.1038/115998b0