V. Bakerian Lecture.— The succession of changes radioactive bodies

Abstract

In previous papers by Rutherford and Soddy it has been shown that the radioactivity of the radio-elements is always accompanied by the production of a series of new substances with some distinctive physical and chemical properties. For example, thorium produces from itself an intensely radioactive substance, ThX, which can be separated from the thorium in consequence of its solubility in ammonia. In addition, thorium gives rise to a gaseous product, the thorium emanation, and also to another substance which is deposited on the surface of bodies in the neighbourhood of the thorium, where it gives rise to the phenomenon known as ‘excited activity.’ A close examination of the origin of these products shows that they are not produced simultaneously, but arise in consequence of a succession of changes originating in the radio-element. Thorium first of all gives rise to the product ThX. The ThX produces from itself the thorium emanation, and this in turn is transformed into a non-volatile substance. A similar series of changes is observed in radium, with the exception that there is no product in radium corresponding to the ThX in the case of thorium. Radium first of all produces an emanation, which, like thorium, is transformed into a non-volatile substance. In uranium only one product, UrX, has been observed, for uranium does not give off an emanation and does not in consequence produce excited activity on bodies.