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Nature volume 114, pages 3032 (05 July 1924) | Download Citation

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LONDON. Royal Society, June 19.—J. C. McLennan and G. M. Shrum: On the luminescence of nitrogen, argon and other condensed gases at very low temperatures. Experiments are described on the luminescence of nitrogen and argon at the temperature of liquid hydrogen under electronic irradiation. The spectra of the light emitted by both elements contains wavelengths close to but not coincident with that corresponding to the auroral green line. Both solid nitrogen and solid argon phosphoresced brilliantly under electronic excitation. From these experiments there is no confirmation of Vegard's theory that the auroral green line originates in vaporous solidified nitrogen.— H. Grayson Smith: On the fine structure of the band spectra of sodium, potassium and sodium-potassium vapours. Four bands of the blue-green group of the band absorption spectrum of sodium and three bands of the red group of the band spectrum of potassium have been examined. Two values of the moment of inertia of the normal sodium molecule have been found from different bands, 2-515 and 2-286? 10-39 gm.cm.2. Assuming that the molecule is diatomic, the corresponding values for the distance between the nuclei are 1:151 and 1-098-8 cm. The moment of inertia of the potassium molecule is 18-39 × 101-39 gm.cm.2, so that the distance between the nuclei of a diatomic molecule is 3-069? 10-8 cm., which is in fair agreement with X-ray measurements. Two bands of a new group found by Barratt in the absorption spectrum of a mixture of sodium and potassium vapours give a moment of inertia of 6-615 × 10-39 gm.cm A This agrees with the supposition that these bands are due to NaK molecules, the distance between the nuclei being 2.137? 10-8 cm.—Lord Rayleigh: (1) The non-luminous oxidation of phosphorus in an oxygen atmosphere. The views on phosphorescent combustion of phosphorus developed in former papers require that phosphorus vapour, when apparently inactive in an atmosphere of oxygen, should in reality be combining with it at isolated centres, though the action fails to spread. Either this action or the ordinary phosphorescent com-bustion can be caused to occur at one given pressure and external temperature. The rate of oxygen absorption is widely different in the two cases. With a given area of phosphorus surface, the rate of action is enormously increased by allowing a large oxygen space around it. The action occurs in the volume of the gas space, and therefore between oxygen and phosphorus vapour. (2) The light of the night sky: its intensity variations when analysed by colour filters. The comparison light is a uranium salt rendered self-luminous by radioactivity. Three alternative colour filters are provided; one of these approximately isolates the green aurora line. A red and a blue filter isolate the regions of the spectrum on either side of this line, excluding the line itself. The light of the sky as seen through these is equalised with the standard by means of neutral tinted glasses. Owing to faintness of the light, colour differences are not perceptible. Systematic observations of the auroral light for fifteen months, and of the other components for seven months, show variations which are far too large to be explained by changes in atmospheric transparency. The highest values of the auroral light were found during October 1923, which was the middle of a period of three months showing considerable sunspot activity. For the rest of the time there were few spots. The auroral light varies very little over the whole range of latitude from England to the Cape of Good Hope. The polar aurora is contrasted with this non-polar aurora. The latter may be a phenomenon of phosphorescence, the luminosity being excited by the sun during daytime and carried round by the earth's rotation as in the phosphoroscope. The light of the night sky is much richer in red, measured relative to blue, than is daylight. In this respect it approximates to the light of a J-watt incandescent lamp.—W. G. Palmer and F. H. Constable: The catalytic action of copper. Pt. IV. By measuring the velocity of dehydrogenation of alcohol passing over copper film catalysts when the temperature of the catalyst is rising and again when it is falling, a measure of the tempera-ture coefficient of the change is obtained. Above a temperature of 2800 C. the adsorbed alcohol film becomes unimolecular, and the aldehyde bombarding the bare copper surface polymerises and causes decay of the activity by covering the surface. No evidence of decay due to sintering was obtained during the experiments, which lasted up to five hours. The catalytic activity varied with the temperature of reduction of the copper oxide in a periodic manner; in general the greater the activity of the catalyst the less the temperature coefficient. Reduction at 4200 C. seems to change both the grain structure and the nature of the surface. The “heat of activation “of an alcohol molecule is held to vary with the arrangement of the atoms in the surface on which it is ad-sorbed.—Rev. A. L. Cortie: The 27-day period (interval) in terrestrial magnetic disturbance. At a period approaching minimum solar activity (May 1921-July 1923), the persistence of notable magnetic disturbances in series at a 27-day interval, when the sun was entirely free from spots, and even sometimes of bright faculae and flocculi, led to two long sequences of such disturbances, May 12, 1921-April 13, 1923, containing 26 synodic recurrences, and October 27, 1921-July 10, 1923, embracing 23 recurrences. In each sequence, from the magnetic data alone, a mean solar latitude has been computed, and a mean solar longitude, which fit accurately two regions of intermittent solar activity, one in the sun's northern hemisphere, and the other in the hemisphere. Moreover, these two regions, separated by about 1800, practically contained all the sunspots that had appeared in the period discussed. But there is no parity between the intensity of sunspot or floccular activity, and of magnetic disturbance. In the period discussed, magnetic disturbances occurred without, but not independently of, solar activity in a restricted area.—E. K. Rideal and C. G. L. Wolf: The destruction of rennin by agitation: a case of catalysis at an air-liquid interface. Rennin solutions undergo a chemical destruction when agitated, due to a chemical reaction occurring at the air liquid interface. The second reactant is a capillary active substance which is present in ordinary rennin solutions, but can be removed by dialysis. The dialysable reactive constituent is probably a fatty acid.—W. G. Palmer: The use of the coherer to investigate adsorption films. Loose contacts or “coherers” formed of tungsten-tungsten, carbon-tungsten, and platinum-platinum surfaces have been studied with particular regard to the action of the gas surrounding them. The voltage required across the contact to effect full metallic conduction is, for a given gas, a constant practically independent of the pressure of the gas and varying between wide limits for different gases. The cohering action may be due to the evaporation of an adsorbed film of gas under electrical stress. From the critical voltage the latent heat of evaporation of the film is calculated.—R. J. Lang: On the ultraviolet spark spectra of some of the elements. The wavelengths are given for the following elements: carbon, calcium, titanium, vanadium, chromium, manganese, cobalt, arsenic, molybdenum, cadmium, tin, antimony, tellurium, cerium, platinum, gold, thallium, lead, bismuth, uranium, in the ultraviolet region. They range from? =2000 A to? =224?—W. J. Astbury and Kathleen Yardley: Tabulated data for the examination of the 230 space-groups by homogeneous X-rays. Diagrams are given, one for each of the 230 space-groups, showing the distribution of symmetry elements and the relative positions and orientations of the molecules in the unit cell; and accompanying these diagrams are tables giving the fundamental Bravais lattice, the number of asymmetric molecules per cell, the abnormal spacings to be expected, and the possible

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