﻿of the a. Hays of Radiothorium. 



89 



dissolved and the solution poured into a flat platinum cover, 

 where it was carefully evaporated. Then the platinum cover 

 was strongly heated for some time by means of a blowpipe. 

 Thorium A was practically all driven off, and also a large 

 proportion of thorium B and C. 



A few hours after heating, the thorium X should be nearly 

 freed from the active deposit, but, of course, still gives off 



10 



| 4 



Fijr. 3. 



G 



I 













J 



f 



U 















< 

 ( 



(4 





j^i-^ 









b 





^^L 



■~~~t=^-^ 















a 















3 4 



Ionization. 



the emanation in a large amount. Curve A, in fig-. 3, shows the 

 ionization of thorium X under the above described conditions. 

 It is seen that at a distance of about 5'7 centims. the 

 ionization increases rapidly, showing that the a. particles from 

 a strong radioactive product enter the ionization-chamber at 

 that distance. Above 5*7 centims., and continuing to 

 S'6 centims., there is a weak ionization due to a small quantity 

 of thorium C, which still remained with the thorium X. The 

 a. particles of range 5*7 centims. undoubtedly belong to the 

 thorium X, but it is difficult to fix with certainty the actual 

 range closer than one or two millims., on account of the dis- 

 turbances, even with a strong air-current, due to the large 

 amount of emanation which is continuously released. 



In order to see how far the emanation disturbed the 

 accuracy of the determinations, the measurements were 



