[BOYLE] ABSORPTION OF THORIUM EMANATION BY CHARCOAL 149 



charcoal weighed 2.17 gms., animal charcoal 2.25 gms., and wood char- 

 coal 0.77 gms. The curves show that the amount of absorption must 

 always depend on the nature of the absorbent, oocoanut charcoal being 

 the best and wood charcoal the worst absorber of the three. In fact, 

 two samples of the same kind of charcoal can show appreciably 

 different absorptive powers. I have had samples of cocoanut charcoal, 



160 



140 



Or 



z 



2 so 



y~ 

 <i. 



N 



~eo 

 o 



-fO 



20 



4 6 8 10 



Flow in cc per sec 



r/G s 



taken from different lots, showing considerable difference in this respect, 

 the better absorbers being softer, less gritty, and less dense than the 

 others. 



Temperature affects wood and animal charcoals as regards their 

 absorptive powers in the same way as it affects cocoanut charcoal. 



The results are here given, Fig. 5, Table III, of an experiment 

 which shows this fact in the case of wood charcoal. For animal char- 

 coal the results are of the same nature and are not given. 



