297 
first of all shown by variation af @ activity. Since these results 
can neither be explained by the existence of a new product nor 
by a change in absorbing power there remained the possibility 
that the process of erystallization alone influences the 8 activity of 
‚uranium nitrate. In order to show whether this was really the case, 
the following experiments were undertaken. 
The hot solution of uranium nitrate eontaining only the water 
of erystallization was put under the eleetroscope. After about two 
minutes the disturbance of the gold leaf produced by heating 
effect ceased, and it was then possible to investigate the effect due 
to the process of erystallization by measurements of the activity. 
The experiments showed that at the moment when the crystalliza- 
tion started, the £ activity commenced to increase very rapidly 
reaching the maximum when the erystallization was finished. 
The following is an example of the experimental results obtai- 
ned. 25 grams of uranium nitrate were dissolved in some water 
and evaporated in a flat glass dish on a water bath until it lost 
all the excess of water. The dish eontaining this hot solution of 
uranium nitrate in water of erystallization was then put under the 
eleetroscope. After three minutes the activity could be measured 
with aceuraey. The results are shown in Table III where T is 
the time in minutes from the moment when the solution was taken 
off the waterbath. 
Table III. 
T (in minutes) Activity 
3 900 
4 890 
5 910 
6 900 
At this period the erystallization started. 
8 1000 
10 1150 
12 1250 
14 1390 
it 1530 
22 1710 
27 1780 
