Chemistry and Physics. 321 



6. Slow Transformation Products of Radium. — An article 

 by Prof. E. Rutherford, in the September number of the Philo- 

 sophical Magazine, closes with the following summary of the 

 products recognized in the slow transformation of radium. 



" The results of the comparison of the products of radium 

 with those contained in polonium, radio-tellurium, and radio-lead 

 are summarized below. 



Products 

 i old 

 adio- 

 lead. 



Radium D = product in neio radio-lead, no rays. 



Half transformed in 40 years. 

 Radium E = gives out /3 rays, separated with bis- 

 in old J muth, and iridium. Half transformed in 6 



Radio- 

 Radium F = product in polonium and radio tellurium. 

 Gives out only a rays. Half transformed in 143 

 days. 



The family of substances produced by the disintegration of 

 radium, together with the time for each to be half transformed, 

 is shown diagrammatically in the figure. 



RADIUM EMAN. RAD-A RAO-B RAD.C RAOD RAD-E RAO.F 



/.SOOJjrs. -tdyS \3*)iqs. ZJrrjirjO. ZSnjirjs, i i 'tOyrs. 6</ys. WSc/l/S. 



Radio-Lead FtADio-Tzot-uPluM. Polonium 



Active Deposit rapiochange Active depositSlowChance 



It is now fully established by the researches of Boltwood, 

 Strutt, and McCoy that the amount of radium present in radio- 

 active minerals always bears a constant 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 uranium. This pro- 

 portionality is a strong indication that radium is produced from 

 uranium ; and a conclusive proof of this point of view is given 

 by the experiments 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 radio- 

 active 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 supposing that one or more products 

 of slow period of transformation intervene between UrX and 

 radium. The uranium-radium family and their connection with 

 one another is summarized below. 



