544 



Mr Satterly, B,adium- content of Charcoal. 



Radium-content of some varieties of charcoal. 



In my experiments* on the absorption of radium emanation 

 from the air I have had occasion to measure the rate at which 

 radium emanation is generated by the charcoal after the charcoal 

 has been heated to a bright red heat and all its previous store 

 cleared out. From these results, with the knowledge of the 

 amount of emanation produced by a known mass of radium in 

 a known time, it is possible to calculate the radium-content of 

 the charcoal. 



The results are given in Table IV. 



Table IV. 



For purposes of comparison with the figures in the last column 

 it may be mentioned that the average radium-content of rock and 

 soil is 1'4 X 10~i2 gm. per gm., and that wood charcoal contains 

 1_5 7^ of ash. 



I wish to express my best thanks to Prof. Sir J. J. Thomson 

 for his kindly interest in these experiments. 



* Phil. Mag. Oct. 1908, July 1910. 

 X ibid. July 1910, p. 7. 



t ibid. Oct. 1908, p. 597. 



