292 
and Schweidier was that my uranium nitrate was deprived even 
of its water of crystallization by evaporation, while in the experi- 
ments of the above named authors the uranium nitrate was cery- 
stallized from the solution. This proves that the rapid decay of 
activity oceurs only when uranium nitrate is erystallized, but it 
does not oecur when it was obtained from the solution by evapo- 
ration which had been carried so far that the water of erystalli- 
zation was driven off. 
This fact being established the subsequent experiments were made 
in the same manner as the experiments of Meyer and Schweidler. 
After separation of the ether solution, the aqueous solution contai- 
ning an excess of UrX was concentrated on the water bath, and 
was then left for a short time at the temperature of the room. 
The great part of the uranium nitrate erystallized at the bottom 
of the dish forming a compact plate, on the surface of which 
the rest of the solution remained. This mother liquor was poured 
off into another dish and was kept on the waterbath until the 
solution lost all except the water of erystallization. The solution, 
after it was taken off the waterbath, erystallized at the tempera- 
ture of the room forming a compact dry plate. 
The whole process of preparation and measurement was repea- 
ted many times. Table I gives one of the series of experiments. 
T denotes the time in days from separation to measurement. The 
B activity is expressed as the ratio of the activity of the investi- 
gated product to the B activity of a standard amount of uranium 
oxide taken as 1000. The £ activity is expressed in the same units 
throughout this paper. 
Table I. 
Ether portion Water portion 
Plate of erystal 
First erystal plate ä 
J® P from mother liquor 
m Activity T Activity sh Activity 
0:25 - 19 0:10 366 0:12 2190 
1 57 0:32 281 0:33 1370 
2 84 0:75 210 0:75 1270 
3 131 1:12 zuls: 1:12 1125 
5:3 190 1:64 236 1:68 1090 
63 220 2:9 285 2:9 1090 
