Radioactive Properties of Uranium. 



57 



of higher to lower concentration, the following experiment 

 was made. 



Fifty grams of uranium nitrate were treated with ether 

 and from the remaining ether solution 15 grains were 

 obtained consisting of uranium nitrate but almost completely 

 freed from UrX. When the ether had been evaporated, some 

 drops of nitric acid were added to the uranium nitrate and 

 this was dissolved in hot water. The solution was evaporated 

 till it lost all the excess of water, and then was kept at the 

 temperature of the room for some minutes while it crystallized 

 forming a dry plate of crystal. The ft activity of this plate 

 measured 65. 



. In the other vessel 25 gr. of uranium nitrate were heated 

 on the water-bath till it melted in its water of crystallization. 

 This solution was then taken off the water-bath, and when 

 the crystallization started 9 gr. of the hot solution were 

 poured on the surface of the first plate of crystal. The 

 solution crystallized then in a few minutes, forming the upper 

 laj'er of the former plate. 



In this manner a plate was made artificially wdiich did not 

 contain in the lower layers any UrX at all, but on the surface 

 it did contain an excess of UrX. 



The plate was cut off from the dish and the activity from 

 both surfaces was measured. The results are shown in the 

 table, where T gives the time in hours after the crystallization. 



Table V. 



T (in hours). 



. 

 2-5 . 



18 . 

 20-7 . 

 27-5 . 

 43-3 . 



Activity of the plate 



when turned with 



the upper surface 



to electroscope. 



. 1035 



. . 865 



. 665 



. 637 



. 619 



. 585 



T(in hours; 



O'l . 

 0-8 . 

 2-5 . 



18 . 

 20-7 . 

 27-5. 

 43-7. 



Activity of the plate 



when turned with 



the lower surface 



to electroscope. 



196 



221 



239 



367 



417 



430 



488 



It is seen that the activity measured from the upper surface 

 decreases, and that from the bottom surface increases, both 

 approximating to a common value. 



This experiment shows that when we have a plate of 

 crystal of uranium nitrate in which the substance UrX is 

 unequally distributed, UrX diffuses from the places where it 

 is in higher concentration to places where its concentration 

 is lower. 



This diffusion of UrX therefore explains the first rapid 



