An investigation of the spectrum of ionium

Abstract

The preparation of ionium described by Prof. Rutherford in the footnote consisted of a mixture of the oxides of ionium and thorium. The percentage of ionium oxide in the preparation is not known. It can be calculated, however, provided we know both the period of ionium and the number of α -particles emitted by 1 grm. of the substance per second. The latter has been determined by Dr. H. Geiger, who found that 1 grm. expelled 10 8 α -particles per second. The period, however, is not known with certainty. Soddy has found that, on certain assumptions, it is at least 100,000 years, and this is the only experimental result that we have at present.