Boltwood — Production of Radium from Uranium. 239 



Art. XXYII. — The Production of Radium from Uranium / 

 by Bertram B. Boltwood. 



i 



The hypothesis that radium is a disintegration product of 

 uranium has been greatly strengthened through the demonstra- 

 tion of the fact that in radio-active minerals the quantity of 

 radium is directly proportional to the quantity of uranium 

 present.* On the basis of the disintegration theory a propor- 

 tionality of this sort is to be expected between the parent 

 element and its radio-active successor. 



Additional data on this highly important question are how- 

 ever desirable, and a single experiment likely to further eluci- 

 date the problem has been independently undertaken by a 

 number of different investigators. This experiment consists in 

 observations conducted on a carefully purified uranium salt 

 with a view to determining whether, with the lapse of time, 

 measurable quantities of radium will be produced within it. 

 If radium is a direct product of uranium through the inter- 

 mediate stage of uranium-X and if the average life of radium 

 is approximately 1,000 years, then it can readily be deduced 

 that, with the delicate methods of measurement at command, 

 the quantity of radium formed in a few hundred grams of 

 uranium salt will be readily detectable and measureable after 

 the lapse of a period no longer than a month. If, however, 

 one or more transition products of a relatively slow rate of 

 change intervene between the substance uranium-X and radium, 

 the production of radium will be so protracted that no quantity 

 of it sufficiently great to permit its detection will be formed 

 within a greatly extended period. 



The difficulties involved in the experimental demonstration 

 of the growth of radium do not appear to be great. Uranium 

 forms no radio-active, gaseous disintegration product, while the 

 radium emanation affords a most convenient means of quanti- 

 tatively estimating any radium which may be present. A 

 solution of a carefully purified uranium salt can therefore be 

 prepared and can be tested at intervals for radium emanation. 

 If radium is formed from the uranium its existence will be 

 indicated by the presence of radium emanation in the uranium 

 solution. 



Three papers in which an experiment of this character is 

 described have been published by Mr. Soddy.f In the first 



* Boltwood, Phil. Mag. (6), ix, 599; Strutt, Proc. Roy. Soc. Lond., lxxvi, 

 88; McCoy, Berichte d. deutsch. chem. Ges., xxxvii, 2641. 



f"The Life-history of Radium," Nature, lxx, 30; " The Origin of 

 Radium," Nature, lxxi, 294; "The Production of Radium from Uranium," 

 Phil. Mag. (6), ix, 768. Mr. Whetham has also published two contributions 

 on the same general topic (Nature, lxx, 5; ibid., lxxi, 319) in which he states 



