Section III., 1908. [ 1^^ ] Tkans. R. S. C. 



X. — Some Further Results on the Absorption of Thorium Emanationf- 



by Charcoal. 



By E. W. Boyle, M.Sc. 



(Communicated by Dr. H. T. Barnes, and read May 26, 1908.) 



In a previous paper tn the Society ^ the writer showed that the 

 absorption of thorium emanation by cocoanut charcoal 



(1) follows the same law as for ordinary gases, viz., that the 

 absorption is increased by a lowering, and decreased by a 

 raising of the temperature of the charcoal, 

 and (2) depends greatly on the speed of tlie gas current which con- 

 ducts the emanation through the charcoal, so that the greater 

 the speed the less is the absorption, and vice versa. 



In the mathematical discussion in that paper, it was assumed, 

 other conditions being the same, that the volume of the charcoal, or, what 

 amounted to the same thing, the mass of it, was the miportant factor 

 in determining the amount of absorption. But it was pointed out that 

 the same considerations would hold if, as it was natural to thinlv, the 

 surface which the charcoal exposed to the emanation was the important 

 factor instead of the mass. 



Further, an experiment described in the paper showed that as the 

 temperature of cocoanut charcoal was raised its absorbing power was 

 decreased until at the temperature of 310° C. the charcoal had become 

 non-abs.orptive. 



The present paper consists of a few notes giving the results of 

 experiments on these last two points, and of others which show the 

 different absorbing powers of cocoanut, animal, and ordinary wood char- 

 coal, and the effect of temperature on them. 



Apparatus. 

 A flow method of experiment was used. 



' " The Effect of Temperature and of Velocity of Gas Current on the 

 Absorption of Radioactive Emanations by Charcoal." — P W. Boyle. — 

 Trans. Roy. Soc. of Canada, May, 1907. 



