298 Wellisch — Experiments on Active Deposit of Radium. 



The cylinder used in the present experiment had a height of 

 14: cm and a radius of 2'9 cm . So that we have I = 7*0 and 

 1 = 2-9. 



Using Gray and Mathews' Tables, the following are the first 

 five values of X n : 



\ = -829 ; A 2 = 1-93 ; A 3 = 2'98 ; A 4 = 4'07 ; A 5 = 5'15 

 g/lj — e— A n z # .,,... 



e 2,j, e-Ki 1S P ractlca % indistinguishable from unity and 



3 



^ _L = 2-592. 



1 /v n 



From (8) we obtain for the number of active particles in the 

 gas in the steady state : G = 103*1 ir S. (9) 



Without the correction for vertical diffusion we obtain 



123*8 ^ i. e. 20 per cent in excess. Let Q be the number of 



particles produced per minute in the gas contained in the 

 cylinder 



.-. Q = 1207rb 2 lq 



. G 103-1 



1 



•0146 



" Q 120 



¥lD " 



D 



so that D =-0146 % 



(or 







(10) 

 It is apparent from the above that to obtain D we must 



determine the ratio ^ ; in order to accomplish this, it is nec- 

 Gr 



essary to measure the ionization currents resulting from Q and 

 G under similar conditions. Put briefly, the method employed 

 was to deposit certain ascertainable fractions of Q and of G on 

 a central rod introduced into the cylinder in the manner 

 described in Section 5. These deposits could then be com- 

 pared by measuring the ionization currents to which they gave 

 rise in a second cylinder ; it was easy to verify from the decay 

 curves thus obtained that these fractions were deposited on 

 the rod chiefly in the form of RaA. 



The experimental procedure was as follows : the emanation, 

 mixed with air carefully dried and freed from dust, was passed 

 into the cylinder and allowed to remain for several days. A 



