301 
Fifty grams of uranium nitrate were treated with ether and 
from the remaining ether solution 15 grams were obtained consi- 
sting of uranium nitrate but almost completely free from UrX. 
When ether had been evaporated some drops of nitrie acid were 
added to uranium nitrate and this was dissolved in hot water. The 
solution was evaporated till it lost all the excess of water, and 
then was kept at the temperature of the room for some minutes 
where it erystallized forming a dry plate of erystal. The activity 
of this plate measured 65. 
In the other vessel 25 gr of uranium nitrate were heated on 
the waterbath till it melted in its water of crystallization. This 
solution was then taken off the waterbath and when the erysialli- 
zation started, 9 gr of the hot solution were poured on the surface 
of the first plate of erystal. The solution erystallized then in a few 
minutes forming the upper layer of the former plate. 
In this manner a plate was made artificially which did not 
contain in the lower layers any UrX at all, but on the surface it 
did contain an excess of UrX. 
The plate was eut off from the dish and the activity from both 
surfaces was measured. The results are shown in the table where 
T gives the time in hours after the erystallization. 
Table V. 
Activity of the plate Activity of the plate 
when turned with the when turned with the 
T (in hours) upper surface to T (in hours) lower surface to 
eleetroscope. electroscope. 
0 1035 0:1 196 
2:5 865 0:8 221 
18 665 2:5 239 
20 637 18 367 
27:5 619 20:7 417 
43:3 585 21:5 430 
437 488 
It is seen that the activity measured from the upper surface 
decreases, and that from the bottom surface increases both appro- 
ximating to a common value. 
This experiment shows that when we have a plate of erystal 
