﻿10 



S 4 



250 Dr. 0. Hahn on the Ionization Ranges 



The curves b and c, fig. 4, show the curves obtained 4 and 21 

 days respectively after preparation. The curve a represents 

 the normal curve of radioactinium itself immediately after 



Ficr. 4. 



















- 



OQ <p 



















() 

























o<i> 



















( 



1 





^ 

















V 



*"-© 



a 



\^ 



^ir^ 





^ 



\ 



<T^ 















* 





12 3 4 5 6 7 



Ionization. 



separation on the same scale. It is seen from curves h and c 

 that the ionization commences to increase at a distance of 

 about 6* 6 cms. This is due to the a rays from actinium X, 

 which we have seen have a range of 6'55 cms. 



The activity of a preparation of radioactinium reaches a 

 maximum about 20 days after preparation. The curve c, 

 obtained about that time, is more regular than b, and no 

 sudden changes of slope of the curve can be noticed. 



The marked disturbance produced by the emanation was 

 clearly shown by variation of the experimental conditions. 

 The set of brass tubes 1*1 cm. high was removed and a similar 

 set of tubes 0'4 cm. high substituted. In this case, the 

 air-current removes a greater portion of the emanation. The 

 lower part of the curve obtained in this way showed a dis- 

 tinct bend downwards. In another experiment the air-current 

 was interrupted. The emanation consequently diffused 

 upwards, and the curve obtained near the source bent upwards 

 instead of downwards. Possibly better results would have 

 been obtained if holes had been bored through the active 

 porcelain crucible in order to allow a more direct action of 

 the air- current. 



