Radium and its Disintegration Products

Abstract

IN NATURE of December 6, 1906, Mr. H. S. Allen has suggested that the difficulty encountered in introducing actinium with its four α-ray products between uranium and radium can be removed by assuming that the α particle is one-half of the helium atom, and he has applied this suggestion in a table showing six α-ray changes between uranium and radium. There would appear to be two serious and insurmountable objections to this view, however, viz., (1) the continuation of the same line of reasoning would lead to the assumption of no less than seven α-ray changes between radium and its final disintegration product, lead, while but four are known; and (2) the activity of the actinium in equilibrium with radium in minerals is entirely too low to permit any such conclusion.