Fig. 5. 



"ansformation Products of Radium. 



305 



X 33 





0> Tj 



• * 



/- 



•A 



one another is summarized 



The family of substances 

 produced by the disintegration 

 of radium, together with the 

 time for each to be half trans- 

 formed, is shown diagramma- 

 tically in fig. 5. 



It is now fully established by the 

 researches of Boltwood, Strutt, 

 and McCoy that the amount of 

 radium present in radioactive 

 minerals always bears a con- 

 stant ratio to the amount of 

 uranium. The investigations of 

 Boltwood, in particular, have 

 shown a surprisingly good 

 agreement between the content 

 of radium and uranium for 

 minerals obtained from various 

 localities, which differ very 

 widely in their content of ura- 

 nium. This proportionality is 

 a strong indication that radium 

 is produced from uranium ; and 

 a conclusive proof of this point 

 of view is given by the experi- 

 ments of Soddy and Whetham, 

 who find that there is a slow 

 growth of radium in uranium 

 which was initially freed from 

 radium. In addition, the actual 

 amount of radium in radioactive 

 minerals is of the right order 

 of magnitude to be expected 

 from theoretical considerations, 

 if uranium is the parent of 

 radium. 



Soddy finds that the present 

 growth of radium from uranium 

 is only a very small fraction of 

 the theoretical amount. This is 

 most simply explained by sup- 

 posing that one or more products 

 of slow period of transformation 

 intervene between UrX and 

 radium. The uranium-radium 

 family and their connexion with 

 below. 



