Deflexion by Electrostatic Field of Radium B. 875 

 Conclusion. 



It has been shown above that from a pencil of ft rays 

 which is absorbed by aluminium according to an exponential 

 law, rays of widely different penetrating powers can be 

 separated out. It follows, therefore, that absorption of 

 ft rays according to an exponential law is no criterion of 

 homogeneity. The experiments confirm the results obtained 

 by Gray by the photographic method. 



We wish to express our best thanks to Prof. Rutherford 

 for the kind interest he has taken in this research. 



Physical Laboratories, 



The University, Manchester. 



Aug. 19th, 1910. 



XC VI. The Deflexion by an Electrostatic Field of Radium B 

 on Recoil from Radium A. By Sidney Russ, D.Sc, and 

 Walter Makower, M.A., D.Sc* 



Introduction. 



IN a previous paper f an account was given of some 

 attempts made to determine whether radium C is 

 electrically charged when it recoils from radium B ; but the 

 experiments made for this purpose failed to reveal any such 

 charge. The formation of radium C from radium B is accom- 

 panied only by the emission of /3-particles, and it was thought 

 that a transformation involving the expulsion of an a-particle 

 might afford a more satisfactory case for investigation. 

 Experiments were therefore undertaken on the recoil of 

 radium B from radium A. In this transformation the atom 

 of radium B should be negatively charged after recoil, if the 

 process is accompanied simply by the expulsion of an 

 a-particle, as is usually supposed. If, however, there is a 

 simultaneous evolution of /3-particles, the recoiling atom 

 might be electrically neutral or even positively charged. 

 It will be remembered that radium A on formation from the 

 emanation in air at atmospheric pressure does in fact acquire 

 a positive charge, so that it is concentrated on the negative 

 electrode when the emanation is subjected to an electric 

 field |. The following experiments were made with the 

 object of determining whether the radium B is charged when 



* Communicated by the Authors, 

 t Makower and Russ, Phil. Mag 1 . Jan. 1910. 

 X Rutherford, Phil. Mag-. Feb. 1900. 

 3M2 



