ABSTRACT
The present point of view of regarding radium as a substance which is undergoing slow transformation was first put forward definitely by Rutherford and Soddy in the paper entitled 'Radioactive Change', in the following terms: In the case of radium, however, the same amount, must be changing per gram per year. The first consisted in an examination to see whether in course of time radium appeared in a solution of uranium initially freed from radium. The second depended upon an examination of the relative amount of radium and uranium in radioactive minerals. A part of the contaminated actinium solution, previously mentioned, was chemically treated to free it from radium. For this purpose, ammonium sulphide was added; this precipitated the actinium and left the radium in solution. The observed constant growth of radium in the solution shows that the parent of radium has a slow rate of change.
