Thorium Lead—An Unstable Product

Abstract

THE work of Boltwood and Holmes some years ago on the occurrence of lead and uranium in minerals rendered it very improbable that the end product of thorium could be lead. From recent generalisations, however, in respect to radio-elements and the periodic law, it is to be expected that the end products of the radio-active elements should all be isotopic with lead. One method of attacking the problem is the determination of the atomic weight of lead extracted from uranium and thorium minerals. On the assumption that radium G and thorium E are stable, a knowledge of the composition of the mineral from which the lead has been extracted enables one to calculate the expected value for the atomic weight of the lead. Comparison of this value with that found experimentally gives a means of testing whether radium G and thorium E are stable or not.