Radium Emanation hi) Coconut Charcoal. 783 



solutions, the amount absorbed from the one one-fifth solution 

 in 3 hours shonld be '9 for tube B and a little less for tube A. 

 This is in good agreement with tig. 1. 



Fur. 1. 



8 11 16 20 



EXPOSURE (Houts). 



The results of these experiments show that in the early 

 stages not much of the emanation is allowed to pass through 

 the charcoal unabsorbed. In the later stages, however, much 

 of the emanation is allowed to pass. 



From fig. 1 it follows that if we suppose complete absorp- 

 tion to occur for exposures of 3 hours or less, then B for a 

 21-hours exposure absorbs about 62 per cent, of the emanation 

 sent through it. The state of affairs is probably very similar 

 to that discovered by McBain * for the absorption of hydrogen 

 by charcoal, viz. that the absorption is twofold : a quick 

 effect — a surface condensation — being followed by a slower 

 effect — a diffusion into the interior. 



III. 



Effect of the Humidity of the Air. 



As no drying agent was used in the experiments described 

 in II., the results may be due to the fact that as time went on 

 the charcoal tube attached to the radium solution would 



* Phil. Mas. Dec. 1909. 



