Emanation in the Lower Regions of the Atmosphere. 3 



emanation-charged air contained in the first aspirator was 

 passed into the vessel. The leak was again taken. 



Now when radium emanation is passed into a testing vessel 

 the leak in the vessel does not remain constant. The active 

 deposits Tladium A, B, C, &c, are deposited on the walls of 

 the vessel, and the total activity of the contents of the vessel 

 increases for about three hours, after which it gradually 

 decreases, very slowly at first, and then at the rate of the 

 decay of the emanation (half value in 3'86 days). Fig. 1 

 shows the curve of activity obtained in one particular case 

 (Nov. 6, 1908) from the emanation driven off from the 













Fig. 1 





























-*- 



5- 



























s 





/" 

















13 





















o 



\ 



















o 



\ 



1 





















i 



■) 3 



( 



y 



30 < 



2 



30 i 



3 



30 



TIME. 



Curve showing how the leak in the testing vessel after it has been 

 tilled with air containing radium emanation varies with the time. 



charcoal after an exposure to the air. It takes about 

 3 minutes to pass a bottle full of gas into the vessel. This 

 is indicated by the shaded area. Some observers make a 

 point o£ taking the leak at the time of maximum activity 

 which occurs after the emanation has been in the vessel 

 3 hours. There is, however, as Soddy and Mackenzie * first 

 pointed out, a temporary maximum which occurs after the 

 emanation has been in the vessel about 10 minutes- The 

 leak is practically steady for about 15 minutes after this, and 

 much time is saved if the reading of the leak is taken during 

 this interval. This is especially true if it is required to 



* Phil. Mag. Aug. 1907. 

 B 2 



