II. Energy of Röntgen and becquerel rays, and the energy required to produce an ion in gases

Abstract

The primary object of the investigations described in this paper was the determination of the amount of energy required to produce a gaseous ion when Röntgen rays pass through a gas, and to deduce from it the energy of the radiation emitted per second by uranium, thorium, and other radio-active substances. In order to determine the “ionic energy” (as it will be termed for brevity), it has been necessary to make a special investigation to measure accurately the heating effect of X rays when the rays are absorbed in metals, and also the absorption of the rays in gases. The method employed to determine the ionic energy was briefly as follows :—The total energy of the rays emitted per second was determined by measuring the heating effect of a known proportion of the rays when absorbed in a metal. The total number of ions produced by complete absorption of the rays in the gas was deduced from measurements on the current produced by the ionization of a known volume of the gas and of the absorption of the rays in the gas, assuming the value of the ionic charge recently determined by J. J. Thomson.