Societies and Academies

Abstract

LONDON. Royal Society April 6.—Sir Archibald Geikie, K.C.B., president, in the chair.—Hon. R. J. Strutt: The Bakerian lecture. A chemically active modification of nitrogen produced by the electric discharge. The leading facts established are:—(1) That pure nitrogen, from whatever source, subjected at a low pressure to the iar discharge, undergoes some modification which causes it to glow for a short time after it has been sucked away from the discharge. (2) The glow which is emitted while the gas returns to its normal condition is not destroyed by the removal of ions. It is weakened by heating, intensified by cooling. This seems to favour the view that it is due to the recombination of dissociated atoms. (3) The modified nitrogen acts on ordinary phosphorus, combining with it, and at the same time forming much red phosphorus. (4) It combines with sodium and also with mercury at a gentle heat (say 150° C.), forming in the latter case an explosive compound, and in each case developing the line spectrum of the metal concerned. It also develops the line spectra of other metals, probably combining with them. (5) It develops the band spectra of compounds, when these are vaporised in it, giving in many cases spectra of substances too unstable to be examined at the temperature of the Bunsen flame. (6) It attacks acetylene, and substances like ethyl iodide or chloroform, setting the halogen free when there is one, and combining with the carbon to form cyanogen. This is proved by the brilliant cyanogen spectrum produced, and by direct chemical tests, such as formation of Prussian blue. (7) It attacks nitric oxide, with formation, strangely enough, of nitrogen peroxide, a more oxidised substance.—A. Holmes: The association of lead with uranium in rock-minerals, and its application to the measurement of geological time.—Prof. E. T. Whittaker: The dynamical value of the molecular systems which emit spectra of the banded type. It is now widely believed that when the spectrum emitted by a luminous body is of the banded type, the small vibrators which give rise to the radiation are the molecules of the substance, as distinguished from atoms or ions. This result is applied in the main body of the paper in order to suggest a dynamical system, which is formed of two members in the same way as a diatomic molecule may be supposed to be formed of two atoms, and which has free periods of vibration related to each other by the same formula as holds in the case of banded spectra. This formula presents a certain peculiarity, in that the frequency of vibration occurs in it linearly, whereas in the equation for determining the free periods of dynamical systems in general the frequency enters by its square. It is shown that from this peculiarity in the radiation of a molecule certain inferences may be drawn regarding the dynamical character of the connection between the atoms within the molecule. It is shown that a somewhat modified mechanism would emit radiations connected by the same law as that which Balmer found for the hydrogen lines.