Societies and Academies

Abstract

LONDON Royal Society, March 14. M. L. E. OLIPHANT, A. E. KEMPTON and LORD. RUTHERFORD: The accurate determination of the energy released in certain nuclear transformations. If changes of mass are taken into account, the law of conservation of energy holds closely for the transformations of the isotopes of lithium when bombarded by ions of ordinary and of heavy hydrogen. The masses of Li6 and Li7 are found to be 6-0143 ± 0-0002 and 7-0148 ± 0-0002 respectively, in good agreement with the mass spectroscopic values 6-0145 ± 0-0003 and 7-0146 ± 0-0006 found by Bainbridge. By application of the laws of conservation of momentum and energy, the mass of the hydrogen isotope of mass 3 is found to be 3-0152 ± 0-0002. Attention is directed to the factors involved in determining the mean ranges of expelled particles and to the difficulties of interpretation when more than two particles are emitted in a single transformation. While there is good agreement in the case of lithium, which involves the masses of particles measured in terms of helium, a number of nuclear reactions in beryllium and other elements show large discrepancies on the accepted mass scale. These reactions, as well as those in lithium, can be brought into line by assuming a small error in the helium oxygen ratio. H. J. TAYLOR: The tracks of a-particles and protons in photographic emulsions, a-particles and protons give tracks in photographic emulsions, which are visible, after development, as rows of grains in straight lines. These tracks have been studied, using special emulsions more suitable for such work than those commercially obtainable. Exposure of a plate to a neutron source gives rise to well-defined tracks, which are due to the protons ejected by the neutrons in their passage through the gelatine of the emulsion. The method is, however, unsuitable for quantitative study of neutron energies.