Manchester Memoirs, Vol. liv. fipio), No. 8. 



VIII. Note on Radio-active Recoil. 



By Sidney Russ, D.Sc. 



Read December 14th, igog. Received for prin'.iiig December i8th, igog. 



It has been shown that when Radium Emanation is 

 condensed at the bottom of a tube, and the space above 

 it evacuated, particles of the Active Deposit are radiated 

 up the tube.* 



This phenomenon has been attributed to the recoil of 

 the atom when an alpha particle is emitted from it. 



If the emanation be allowed to remain condensed for 

 a time sufficient for it to attain radio-active equilibrium 

 with its products, it might be expected that Radium A 

 and Radium B would be projected up the tube in equal 

 numbers as the result of the expulsion of a particles 

 by the emanation and Radium A. The change from 

 Radium B to Radium C is only accompanied by the 

 emission of j3 particles, the recoil due to which is much 

 less energetic than in the above cases. Under certain 

 conditions, however, the recoil of Radium C has been 

 shown to take place, but in the phenomena under exami- 

 nation it will be seen that its effect is hardly appreciable. 

 A disc suspended above the condensed emanation will be 

 the recipient of active deposit particles, which adhere to 

 it. After an exposure for a suitable time the disc may be 

 removed, and the decay curve of its activity tested with 

 the aid of an electrometer by means of the alpha rays 

 emitted from it. The object of the present investigation 



* Russ and Makower, Proc. Roy. Sac, A., vol. 82, 1909. 

 Februa?y ist, igio. 



