LONDON. Royal Society, January 31.—A. Mallock: Summary of the results obtained from experiments made during the years 1918-1923 of the effects of temperature on the properties of metals. The results relate to the properties of iron and steel in the neighbourhood of the critical temperature. The principal change which occurs at that temperature is an abrupt alteration in specific heat, which, as the metal passes to the high-temperature state, is reduced to about one-third of its previous value. The coefficients of rigidity and thermal expansion undergo no discontinuous change. The rigidity decreases slowly as the temperature rises to a low red heat, but at higher temperatures the change is rapid. At a bright red heat the metal still retains elastic properties, but with greatly increased viscosity, and thus oscillations which depend on rigidity are quickly damped out. The presence of small quantities of silicon, sulphur, phosphorus, and manganese in the samples used prevents any absolute conclusion being formed as to the effect produced by carbon alone, but it is clear that carbon lowers the critical temperature, and prolongs the time occupied in changing, from the high to the low temperature state while the metal is cooling.—A. K. Goard and E. K. Rideal: Catalytic and induced reactions. Pt. I.: An electrode of special type has been devised whereby it is possible to effect the comparison of the potentials of certain substances which behave irreversibly towards the platinum electrode. The action of cerous salts in effecting the induced oxidation of Eotassium arsenite, and the catalytic oxidation of ve reducing sugars, have been investigated from the point of view of oxidation potential. In the former case the potentials observe the order: Cerous salt (inductor)-arsenite (acceptor)-equilibrium mixture-perceric salt; in the latter, the order: Reducing sugar-cerous salt-perceric salt. Pt. II.: Schon-bein's reaction (the separation of iodine from potassium iodide solution in the presence of hydrogen peroxide and ferrous salts) conforms to the schemes for coupled and catalytic reactions described in Part I. of this paper. Direct evidence has been obtained of the formation of a peroxide of iron by the action of hydrogen peroxide upon ferrous sulphate in neutral solution; it decomposes according to a mono-molecular law. This peroxide has been shown, by the method of electrometric titration under special conditions, to possess the essential formula Fe2O5.—H. B. Dixon and G. Greenwood: On the velocity of sound in gases and vapours, and the ratio of the specific heats. The velocity of sound in certain vapours and condensable gases was determined by timing the passage of a sound-wave between the two ends of a coiled lead pipe filled with the vapour or gas between,20° C. and 100° C., and comparing the rates with the velocity of sound through air in the same pipe. From the velocities found in the pipe the velocities in the “free “gas are calculated, and from these results the specific heats of the gases and vapours are computed.—J. R. Partington and A. B. Howe: The ratio of the specific heats of nitrogen and of oxygen. The adiabatic expansion method of determining accurately the ratio of the specific heats of a gas has been applied to nitrogen and oxygen. The gas was contained under pressure in a spherical copper globe of about 60 litres capacity, immersed in a water-bath maintained at constant temperature by means of an electrical thermostat, and is put into communication with free air so that equalisation of pressures takes place adiabatically. Pressure was measured on an oil manometer. The bolometer was used in conjunction with an Einthoven string galvanometer and a post-office box. The galvanometer was used as a null instrument, the lowest temperature attained during expansion being reproduced by adding ice to the bath. The temperatures were determined by a standardised mercury thermometer. The following values were obtained:
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Apr 1, 1925
Edward M Crowther + 1
Open Access