﻿7 Radiation from Radium B. 303 



ratio of the ionizations produced in the measuring-vessel by 

 the disintegration of an atom of radium B and radium is 

 taken as 14'5 : 100. The curves have been drawn to an 

 arbitrary scale, so that the maximum activity is 100, and the 

 times are reckoned from the end of the recoil. The points 

 marked with circles in fig. 1 represent the results obtained 

 when the surface rendered active with radium B was placed 

 near an ordinary -y-ray electroscope such as is in general use 

 in this. laboratory. These electroscopes, which are made by 

 Mr. C. W. Cook at the University Works, Manchester, 

 consist of an aluminium case 2 mm. thick lined with lead 

 3 mm. thick. The deposit of radium B was obtained inside 

 a glass tube 1 mm thick. 



From the agreement between curve B and the experi- 

 mental points it appears that the assumptions made in drawing 

 the curve suit the experimental conditions. Stated somewhat 

 differently, when radium B and radium are in equilibrium, 



radium B contributes 



14-5 



1-145 



r - =12'1 per cent, of the tot; 



ionization. 



Tne points marked with crosses in fig. 1 represent the 



Fie. 1. 



i00 



80 



60 





4 8 12 16 20 c4 28 32 36 



MlNU TfS 



Rise of activity from RaB. Recoil 30 seconds. 



results obtained with an additional 1*175 cm. of lead inter- 

 posed in the path of the rays. The points lie on curve A 

 and show that in this case all the radiation is duo to radium C. 



