vi PpOCEEDINGS. {^October 2Qth, igoy. 



is necessary to suppose that radium is produced fiom another 

 substance of long period of transformation. There is an 

 undoubted genetic connection between uranium and radium, 

 for investigation has shown that the amount of radium in 

 minerals is in all cases proportional to their content of uranium. 

 If this be the case, radium should gradually appear in a pre- 

 paration of uranium, initially freed from radium. No such 

 growth of radium has been observed over a period of several 

 years although a very minute growth of radium can be easily 

 detected. This is not necessarily inconsistent with the 

 disintegration theory for if one or more products of slow trans- 

 formation exist between uranium and radium, no appreciable 

 growth of the latter is to be expected in a short interval. A 

 search for this intermediate product has recently proved success- 

 ful. Boltwood found that a preparation of actinium, initially 

 freed from radium, grew radium at a constant and rapid rate. 

 Boltwood at first considered that actinium was this intermediate 

 product and that actinium changed directly into radium. The 

 growth of radium in actinium solutions was confirmed by the 

 writer, who had commenced experiments in that direction three 

 years before. The experiments showed, however, that actinium 

 did not, as Boltwood supposed, change directly into radium. 

 By a special method, a preparation of actinium was obtained 

 by the writer which showed no appreciable growth of radium 

 over a period of 240 days. The growth of radium, if it occurred 

 at all, was certainly less than i/5ooth of that ordinarily observed. 



In another case, a solution of actinium was obtained which 

 produced radium faster than the normal. 



These results are completely explained by supposing that a 

 new substance of slow transformation is present with actinium, 

 and this substance is transformed directly into radium. This 

 parent of radium has distinct chemical properties, which allow it 

 to be separated from both actinium and radium. The absence 

 of growth of radium observed in the actinium solution mentioned 

 above is due to the fact that, by the special method, the parent 

 of radium had been completely separated from the actinium. 



