286 Wellisch — Experiments on Active Deposit of Radium. 



Inasmuch as the concentration is zero at r — a and r = b, it is 

 obvious that there must be a position r 1 where the concentra- 

 tion is a maximum. 



By differentiating (3) with respect to v we find 



r' = 



2 log - 

 a 



In the steady state the deposit particles may be regarded as 

 streaming towards the central rod or the case according as they 

 are situated within or without the cylinder r = r r (Fig. 1.) 



Fig. 1. 



The relative distribution on central rod and case will then 

 be proportional to the volumes cut off by the cylinder r = /•,. 



i. e. 



activity on central rod _ ir (r^ — a a ) 



total activity 



7T {b'-a 2 ) 



2log- 

 a 



(*) 



The first term, which in most cases is the more important, is 

 the same as the electrical capacity per unit length of the con- 

 denser. 



By integrating equation (3) the total number of deposit par- 



