THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[SIXTH SERIES 



OCTOBER 1914 



L. Experiments on the' Active Deposit of Radiu ms rtty 

 E. M. Wellisch, Assistant Professor of Physics, Yale 



University *. 



Introductory. 



1. TN a previous paper f the experimental result was 

 X described that when radium emanation is mixed with 

 any gas, there is a definite limit to the fraction of the active 

 deposit which settles on the cathode in an electric field. 

 This limiting value is independent of the pressure of the gas, 

 provided the latter is high enough to prevent appreciable 

 recoil on to the walls of the containing vessel ; it is, however, 

 in general, dependent on the nature of the gas with which 

 the emanation is mixed. The values assigned in the previous 

 paper were 89*2 per cent, for air and hydrogen, 80*7 per cent, 

 for carbon dioxide, and 10 per cent, for ethyl ether. 



The physical meaning of this limiting value is that it 

 represents the fraction of the total number of deposit 

 particles which possess a positive charge at the end of the 

 recoil path, before either columnar or volume recombination 

 has had a chance to become operative. The small value of 

 the limit in the case of ethyl ether was surprising and was 

 ascribed to the large density of ionization produced by the 

 deposit particle during its motion of recoil. It had pre- 

 viously been shown that with air or hydrogen the deposit 



* Communicated by the Author. 



f Wellisch, Phil. Mag. [6] vol. xxvi. p. 623 (1913). 



Phil Mag. S. 6. Vol. 28. No. 166. Oct. 1914. 2 E 



