Boltwood — Production of Radium by Actinium. 537 



Art. XLIX. — Note on the Production, of Radium by Acti- 

 nium j by Bertram B. Boltwood. 



[Contributions from the Sloane Physical Laboratory of Yale University.] 



The attempts on the part of several different investigators 

 to experimentally demonstrate the growth of radium in ura- 

 nium solutions, while they have given somewhat widely differ- 

 ing results, have nevertheless served to demonstrate conclu- 

 sively that the quantity of radium formed in a given time from 

 a known weight of uranium is very much smaller than would 

 be expected from the disintegration theory if radium is a direct 

 product of uranium. Thus Soddy* has stated that the amount 

 of radium formed in a commercial salt of uranium during a 

 period of eighteen months was only one five-hundredth of the 

 amount to be expected from the theory, while the writerf has 

 shown that in a purified salt of uranium the amount of radium 

 formed in 390 days can not be over one sixteen-hundredth of 

 the amount which the theory would require. 



The constancy of the ratio between thequantities of uranium 

 and radium which are found in the natural minerals is, how- 

 ever, a convincing proof of the close relationship of these ele- 

 ments to one another. On the basis of the assumption that 

 radium is a disintegration product of uranium, it is necessary 

 to show that some intermediate product of a relatively slow 

 rate of change exists between them. In the search for such an 

 intermediate product the supposition that actinium was this 

 product has been gradually strengthened. A considerable 

 mass of experimental data which has been collected all points 

 to the conclusion that the quantity of actinium in a mineral is 

 directly proportional to the amount of uranium present and 

 that, accordingly, actinium is a product of uranium. The 

 following experiment was, therefore, undertaken to demon- 

 strate the position of actinium with respect to radium. 



A kilogram of carnotite ore containing about twenty per 

 cent of uranium was treated with an excess of dilute hydro- 

 chloric acid aud the insoluble portion was separated from the 

 solution. The sulphides precipitated by hydrogen sulphide 

 were then removed. To the solution thus obtained was added 

 about one-half gram of thorium nitrate followed by a solution 

 of several grams of oxalic acid. The slight precipitate which 

 formed after the mixture had stood for several days was com- 

 pletely removed, the oxalates were converted into nitrates, and 

 the nitrates in dilute solution w 7 ere again submitted to the pre- 



* Nature, lxxi, 294, 1904 ; Phil. Mag. (6), ix, 768, 1905. 

 f This Journal, xx, 239, 1905. 



