52 Dr. T. Godlewski on some 



4. The Effect of Crystallization on the ft Activity 

 of Uranium Nitrate. 



We shall return now to the initial rapid decay of the /3 

 activity of uranium nitrate immediately after it was 

 crystallized in the form of plates from the aqueous solution. 



A decay quite analogous to that shown in the first part of 

 the curves II and III was also obtained, when uranium 

 nitrate had been crystallized from the pure aqueous solution, 

 when no ether separation was applied. 



The following is one example : — 



25 grams of uranium nitrate was dissolved in a small 

 amount of water ; the solution was evaporated on a water- 

 bath till it lost all its excess of water. This solution of 

 uranium nitrate in its water of crystallization was kept for 

 some minutes at the temperature of the room, where it 

 crystallized, forming a compact dry plate. The variation of 

 activity with the time was then measured, and one of the 

 examples is given in Table II., where T is time reckoned 

 in hours from the moment of crystallization. 



Table II. 



T (in hours). f3 Activity. 



1310 



2-25 1130 



4-5 1030 



23 895 



44-5 880 



52 . 885 



71 875 



95 880 



120 . 890 



We see that immediately after crystallization the /3 activity 

 decays, reaching a minimum after about two days. 



The measurements of Meyer and Schweidler were then 

 once more confirmed. The fact that the minimum was 

 reached in a shorter time after crystallization in the experi- 

 ments of the writer than in those of Meyer and Schweidler, 

 is fully explained by the difference in experimental con- 

 ditions which greatly influence this period. 



This decay of activity after crystallization at first suggests 

 the existence of some other product besides UrX. But the 

 absence of the complementary recovery curve contradicts 

 this supposition. And further, the rate of decay of radio- 

 active products is generally independent of conditions. In 

 these experiments, however, the time when the minimum was 



