Abstract
LONDON. Royal Society, April 14.—Prof. C. S. Sherrington, president, in the chair.—Prof. K. Onnes, Sir R. Hadfleld, and Dr. H. R. Woltjer: The influence of low temperatures on the magnetic properties of alloys of iron with nickel and manganese. A series of iron-manganese and iron-nickel alloys with a range of percentages of manganese and nickel respectively has been tested in order to investigate the influence of cooling to very low temperatures (liquid hydrogen and liquid helium) on their magnetic properties, especially to ascertain whether the iron-manganese alloys which are non-magnetic at atmospheric temperature become magnetic by so doing. Samples are tested quickly one after another at a temperature of 20° K. The iron-manganese alloys containing the higher percentages of manganese cannot be made magnetic at atmospheric temperature by cooling to the boiling point of liquid hydrogen or liquid helium. The existence of one magnetic and one non-magnetic, or at most slightly magnetic, manganese-iron compound is probable, and the non-magnetic properties of the higher manganese-iron alloys may be explained by their means.—C. N. Hlnshelwood and E. J. Bowen: The influence of physical conditions on the velocity of decomposition of certain crystalline solids. The velocity of decomposition by heat of potassium permanganate and ammonium bichromate. For solids the temperature coefficient of the reaction velocity does not allow calculation of a “heat of activation” or “critical increment” of the reacting molecule, according to the method of Trautz, Lewis, and others, for various physical reasons connected with the propagation of the reaction from the surface into the interior. The lowering of the velocity of decomposition of potassium permanganate in solid solution in potassium perchlorate indicates that the heat of activation of the permanganate is increased by the physical process of solid mixture. By equating this assumed increase in the heat of activation to the observed heat of solid mixture obtained from the calorimetric measurements of Sommerfeld, approximate quantitative agreement is found between the. observed rates of decomposition of potassium permanganate, in various solid solutions and those calculated.—Prof. H. Briggs: The adsorption of gas by. charcoal, silica, and other substances. The method of determining the adsorptive capacity of a substance at liquid-air temperature is described, and results are. given of the capacity and manner of preparation or occurrence of thirty-six substances. Charcoal and silica are compared, especially as relates to nitrogen and hydrogen, to illustrate preferential adsorption; the influence of chemical composition on gas adsorption is discussed. The effect of the compressibility of the initial layer when the density of an adsorbent is determined by the immersion method is considered. An evaluation is made of (a) the volume of solid matter, (b) that of the interstitial space between the granules, and (c) that of the internal gaseous space for silica and coconut charcoal. The density of the nitrogen adsorbed at—190° C. by silica and charcoal is calculated from experimental data. From these results it is possible to estimate the error affecting the density of charcoal ascertained from water-immersion. The conditions affecting adsorption at low and high saturation are given. The presence of capillaries is not sufficient to account for adsorption. A high-capacity silica may be deactivated, but remain porous. Graphite, which has no pores, adsorbs eas at —190° C. The evidence leads to the conclusion that deactivated silica is vitreous. A vitreous solid, like a crystal, is probably a polymer. Activation is considered to be the ettect of disrupting the solid polymers.—N. K. Adam: The properties and molecular structure of thin films of palmitic acid on water. Part i. Langmuir's views have been confirmed and extended. Films on water exhibit a resistance to lateral compression commencing at 22x10-sq. cm. per molecule, and increases linearly with reduction of area until the force is sufficient to buckle the film. Collapse then sets in, and no further increase of force is regularly found necessary to diminish the area to zero. A metastable condition of increased resistance to collapse may occur. The compression curves point to the resistance being due to repulsion between the insoluble molecules, arranged in a single layer on the surface, each molecule being attracted to the water by its carboxyl group. When collapse of the uni-molecular film occurs, the molecules ejected are seen to aggregate into fine lines many molecules in thickness. The observed areas agree with the dimensions calculated from molecular volume studies, and the compressibility of the films is of the same order as for liquids in bulk. The effect of acidity of the water on the films may be due to the greater attraction of alkaline solutions than acid for carboxyl groups. The observations indicate that the molecules are immersed further in alkaline than in acid solutions, even when alkalinity is insufficient to cause complete solution. In still more alkaline solutions immersion becomes complete, and the molecules probably pass from the film into aggregates, having the hydrocarbon chains in the centre and the carboxyl groups on the surface. This structure is suggested for the "ionic micelle "of soap solutions.—E. P. Metcalle and B. Ven-katesachar: The absorption of light by electrically luminescent mercury vapour. Mercury vapour at low pressures, rendered luminous by the passage of small electric currents, exerts powerful selective absorption. A list of wave-lengths found to be absorbed is given. Photometric observations' are recorded on the absorption and emission of 5461 A. by columns of mercury vapour of different lengths and carrying different currents. The relation between the ratio (emission/ absorption) and the current density is linear. The lines 5461 A. and 4359 A. have been reversed so as to appear dark lines on the white-light spectrum of a carbon arc and of the sun. The reversal of 5461 A. has been studied in detail.
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Societies and Academies. Nature 107, 285–287 (1921). https://doi.org/10.1038/107285b0
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DOI: https://doi.org/10.1038/107285b0