﻿y-Ray Activity of Radium Emanation. 301 



detectable y« radiation was excited in the walls by the impact 

 of the a. particles emitted by the emanation. The amount of 

 this excited radiation was, however, very small when the 

 walls of the tube were composed of atoms of low atomic 

 weight, and for a lining of pure paper the 7-ray activity of 

 the emanation and its products was found to rise practically 

 from zero. Under such conditions the 7 radiations from 

 the tube are due only to the products radium B and 

 radium C. 



Taking the number of emanation atoms disintegrating per 

 second at initial time as unity, the number of radium-B atoms 

 disintegrating per second at any subsequent time t is 



X 2 \ s 2 



-Kit 



\ = 1,2,3 



where \ 1? X 2 , A, 3 are the transformation constants of the 

 emanation and the products A, B, and C respectively. This 

 quantity is tabulated for various times up to 220 minutes at 

 the end of this paper (Table II.). 



Similarly, the number of radium-C atoms disintegrating 

 per second at time t is 



\= 1, 2.3,4 



Tables for this quantity for various times up to 258 

 minutes have been given by Moselev and Makower * and by 

 Rutherford t- 



The rise in 7-ray activity of a tube filled initially with 

 pure emanation can therefore be represented by 



KXoAs^T 



e-M 



(A 2 -X 1 )(X 3 -X 1 ) 

 \ =1,2,3 



+ (1-K)A 2 \ 3 \ 4 g e ~ Xl * 



1,2, 3, 4 



where K is the fraction of the ionization, measured under 

 given absorption conditions, due to radium B when in radio- 

 active equilibrium with radium C. 



Thus it is necessary to determine "K." Since the 7 rays 



•• Moselev and Makower, Phil. Mag. vol. xxiii. p. 302'(1912). 

 t Rutherford, 'Radioactive Substances/ p. 490. 



