Societies and Academies

Abstract

LONDON. Royal Society, February 26.—Sir William Crookes, O.M., president, in the chair.—Lord Rayleigh: The diffraction of light by spheres of small relative index.—Prof. H. E. Armstrong and Prof. F. P. Worley: Studies of the processes operative in solutions. XXXI.—Sulphonic acids and sulphuric acid as hydrolytic agents: a discussion of the constitution of sulphuric and other polybasic acids and of the nature of acids. XXXII.—The influence of sulphonates on the hydrolytic activity of sulphonic acids: a contribution to the discussion on the influence of neutral salts.—Prof. H. E. Armstrong, R. T. Colgate, and E. H. Rodd: Morphological studies of benzene derivatives. V.—The correlation of crystalline form with molecular structure: a verification of the Barlow-Pope conception of “valency-volume.”—Prof. E. Wilsen: The magnetic properties of iron when shielded from the earth's magnetism. When iron is subjected to a considerable magnetising force, a species of polarisation is produced which has the effect of reducing the permeability and increasing the dissipation of energy due. to magnetic hysteresis for given values of the magnetic induction. The residual effects can be removed by careful demagnetisation or annealing. It was thought by analogy that the earth's magnetic force would also have a polarising influence upon exposed iron, and this is the subject of the present paper. An effort has been made to remove the residual effects of the earth's magnetism by placing the specimen, which is of ring form, in a magnetic shield, and carefully demagnetising it. The magnetic properties of the material were then examined in the usual manner with a ballistic galvanometer, and a comparison made with those obtained from the exposed or unshielded specimen. It has been found that the permeability of freshly demagnetised and shielded iron, corresponding to a given value of the magnetic induction, is considerably larger than in the case of the unshielded specimen.—Dr. J. N. Pring: The occurrence of ozone in the upper atmosphere. In the Alps, at an altitude of 2100 metres, the mean concentration of ozone is about 2.5 parts by volume in one million of air, and at an altitude of 3600 metres, about five parts in one million of air. In this country the mean quantity found between ground-level and an altitude of 20 kilometres was about two parts by volume in one million. No trace of either hydrogen peroxide or nitrogen peroxide could be detected in these cases. Measurements made in the laboratory on the action of ultraviolet light on air showed that a definite equilibrium amount of ozone is obtained, and that this value increases with fall in temperature, but decreases rapidly with fall in pressure. The formation of hydrogen peroxide or nitrogen peroxide by ultra-violet light radiation could not be detected.—W. A. D. Rudge: A meteoric iron from Winburg, Orange Free State. In this paper some account is given of the structure, and mechanical and magnetic properties, of the Winburg meteorite, which is stated to have fallen in 1881. It appears to be composed of large crystals of ferrite with veins and crystals of an iron nickel alloy. The total amount of nickel is not more than 3 per cent.—W. A. D. Rndge: The electrification produced during the raising of a cloud of dust. During the raising of a cloud of dust a considerable amount of electrification occurs. Insulated conductors held in a stream of dust become charged to a potential of some hundreds of volts. The dust particles seem to be charged by friction amongst themselves, some with positive, others with negative, electricity.—Prof. W. M. Thornton: The electrical ignition of gaseous mixtures. This is an experimental examination of the mechanism of ignition of gaseous mixtures by electric sparks. It is found that there are two distinct types of curve connecting percentage of gas in air and the least current which, when broken, causes ignition by the break-spark. In one, characteristic of continuous currents, the current required is proportional to the percentage of gas present; in the other, of the alternating-current type, it is a quadratic function of the percentage, having a minimum, at the mixture giving combustion, midway between CO and CO2. Ignition by continuous-current break-sparks is largely ionic or electronic, but by alternating currents is more nearly a simple thermal process. The gases examined were hydrogen, carbon disulphide, benzene, alcohol, and the paraffin series up to pentane.