T (in hours) 6 Activity 
45 1030 
23 895 
44:5 880 
52 885 
hl 875 
jr 
0 co 
© © 
a mn 
© © 
© © 
We see that imınediatelly after erystallization, the 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 erystallization in the experiments of the writer 
than in those of Meyer and Schweidler is fully explained by the 
difference in experimental conditions which greatly influence this 
period. 
This decay of activity after erystallization 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 radioactive products is generally 
independent of eonditions. In these experiments, however, the time 
when the minimum was reached, as well as the form of the curve, 
was dependent upon many factors. In different experiments, the 
relative values of the activity at the minimum point and the rates 
of decay, were dependent upon the thickness of the plate of ery- 
stals, and upon the concentration of the solution from which the 
crystals were obtained. In consequence, it would be difficult to 
suppose the existence of some other product. 
The supposition of Meyer and Schweidler!) that the phenomena 
are produced by some changes in absorbing power of the plates 
of erystals eannot explain the observed fact. when we take into 
consideration that the activity measured by «@ rays does not exhi- 
bit the same behaviour. The experiments of Meyer and Schweidler 
showed that the @ activity remained practieally constant. The writer 
made also experiments which completely confirmed this fact. And 
every change in absorbing power of the plates would be, of course, 
!) Meyer and Sehweidler Loc. cit. p. 1075 (19). 
