Disintegration Products of Uranium. 425 



Curve 1 is the decay curve of: the uncovered preparation, 

 and curve 3 the decay curve through 0*01 cm. of aluminium. 



Ksr. 3. 



If the activities in curve 3 are multiplied by 2*15, curve 2 

 representing the total activities of UrX is obtained. Curve 4, 

 which is the decay curve of the product, was obtained by 

 taking the difference between curves 1 and 2. It should be 

 noted that curve 2 coincides with curve 1 about ten days 

 after separation of the uranium X, indicating that no other 

 product except UrX then remains. 



The period of the new product deduced from the curve is 

 1*5 days. A number of other curves obtained in a similar 

 manner gave about the same period of decay. It is proposed 

 to call the new product uranium Y (UrY). 



It is now necessary to consider the types of radiation 

 emitted by this new product. Special experiments were 

 made to test whether any a rays were present. It is 



