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486 Prof. F. Soddy on the Relation 



error in the determination of the quantities of radium, due to 

 the changes in the electroscope and reading microscopes, and 

 in the methods employed. 



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'2 



Production of Radium from Impurities separated frem Uranium. 



Fig. 2 shows the graphs for the uranium preparations 

 III. and IV. The quantities of radium are plotted against 

 the time as full lines, and the growth of radium is plotted 

 against the square of the time as dotted lines. The actual 

 lines drawn are those theoretically calculated from the 

 formula, used in the last paper, 



Ra/U = i\ 2 X 3 T 2 x3-4xl0- 7 , 



where Ra is the growth of radium in grains from U grams of 

 uranium in T years, 3*4 x 10 " 7 is the factor taken to represent 

 the ratio between radium and uranium in equilibrium, and 

 the product of the periods of average life of ionium and 

 radium, 1/\ 2 X 3 , is put at 237,500,000 years. 



