of Radium and Uranium. 9 



scribed by McCoy and Leman. 16 It was found to be 

 9-1 per cent. In applying the correction, the value for 

 the ratio of the activity of the radium products (radium 

 emanation, radium A and radium C) to the activity of 

 the radium with which they are in equilibrium, as found 

 by McCoy and Leman, namely 4-11, was made use of, 

 as was also the ratio of the activity of radium to the 

 activity of the uranium with which it is in equilibrium 

 (049) which was derived in the course of the present 

 investigation (see p. 12). 



The correction has the following form, 



3570 +(785 X 4-11 X 0-49 X 0091) = 3715, 



which gives an activity of 3715 divisions per minute per 

 gram of uranium as the activity of the mineral due to 

 uranium and its products in a complete state of equi- 

 librium. 



From this final result we are able to calculate the 

 value sought, namely, the ratio of the activity of the ura- 

 nium with its equilibrium amounts of disintegration 

 products to the activity of the uranium (uranium I -f 

 uranium II) alone. 



This is 3715/785 = 4-73, which is in good agreement 

 with the value 4-69 found earlier by Boltwood. 



Ratio of the Activity of Radium to the Activity of the Uranium 

 with which it is Associated. 



If the transformation of the atoms of uranium I into 

 atoms of uranium II takes place directly without the pro- 

 duction of any side products, and the transformations 

 uranium II — ionium — radium proceed in the same direct 

 manner, then the relative activities of the three mem- 

 bers — uranium I, uranium II, radium — should be pro- 

 portional to the two-thirds power of the ranges of the 

 a-particles emitted by the respective elements, namely, 

 the activities should be proportional to 



(2-37)§, (2/75)1, (3'13)§ 



where the numbers in parentheses are the ranges at 0°C. 

 of the a-particles from uranium I, uranium II and 

 radium, respectively. Any departure from this pro- 

 portionality will indicate an irregularity in the mode of 



16 Phys. Eev., 6, 185, 1915. 



