o6 



Dr. T. Godlewsk 



>ki on some 



5. Diffusion of UrX. 



The results obtained in the preceding section can now be 

 used to explain the first rapid decay of /3 activity of uranium 

 nitrate after crystallization from the water solution. 



We saw that in the case when uranium nitrate was 

 obtained by evaporation from the solution, and not bv 

 crystallization, this first decay was not exhibited. Moreover, 

 it was pointed out that when the hot solution was stirred 

 during crystallization, no increase of activity at the end of 

 the crystallization was observed. It must now be noted that 

 in this case we did not get any decay after crystallization. 



We see then that the first rapid decay is the decay of the 

 excess of activity produced artificially by crystallization, 

 when the latter caused the uneven distribution of UrX 

 throughout the plate. 



This suggests the probability that the decay of ft activity 

 in the first days after crystallization is produced by the 

 diffusion of UrX from the upper layers of the plate, where 

 it was in greater concentration, to the lower, where its 

 concentration is smaller. Thus, if we observe the decay of 

 activity when the upper surface is turned to the electro- 

 scope, we should expect to see the analogous increase when 

 the bottom of the plate faces the electroscope. Experiment 

 showed this to be the case. Some of the experimental 

 results are shown in Table IV., where T gives the time 

 reckoned in hours from the moment of crystallization. 



Table IV. 



T. 





 16 

 42 



68 



13 activity of the plate 

 when turned with the 

 upper* surface to the 



electroscope. 

 . . 1840 

 . . 1310 

 . . 1030 

 . . 1010 



0-1 

 16 

 42 

 68 



The same experiment made with 





 1 

 2 



3-7 

 4-5 

 23 



. 760 



0-1 



. 740 



1 



. 730 



2 



. 720 



3-6 



. 700 



4-5 



. 690 



23 



j3 activity of the plate 

 when turned with the 

 lower surface to the 

 electroscope. 

 ... 528 

 . . . 747 

 ... 731 

 ... 950 



very thin plate. 



... 570 



... 600 



... 620 



... 630 



. . . 650 



... 680 



In order to completely establish that we here 

 with the diffusion of UrX through the plate f 



om 



have to do 

 the layers 



