448 Active Deposit of Radium in an Electric Field. 



radioactive ions have lost their charge in spite of the strong 

 electric field (of the order of 500 ^--) established between A 

 and B. 



This anomalous behaviour o£ the recoil atoms, which has 

 been noted by many observers % is not a little surprising. 

 It is usually suggested that they are of larger mass or size 

 than ordinary ions; but this view is incompatible with the 

 well-established fact that the mobility of radioactive ions 

 is the same as that of ordinary gaseous ionsf. A more 

 detailed investigation of the properties of recoil atoms is now 

 in progress. 



Summary. 



1. A method permitting the accumulation of uncharged 

 radioactive reooil atoms in a vessel not containing emanation 

 is described, and the distribution of these atoms in an electric 

 field is investigated (sec. 2 and 3). 



2. The role of the electric wind in the process of distri- 

 bution of the active deposit of radium in an electric field is 

 established by means of various experiments, and the origin 

 of the anode activity is explained (sec. 5, 6, 7, and 8). 



3. The properties of large radioactive particles suspended 

 in gases are studied (sec. 4 and 10). 



4. A method of concentrating active deposit of radium on 

 plates in the absence of an electric field is described 

 (sec. 9). 



5. The rate of recombination of radioactive ions is shown 

 to be greater than that of ordinary gaseous ions (sec. 11). 



This work was mainly carried out at the Physical Labo- 

 ratory, Manchester University. I wish to express my best 

 thanks to Professor Sir Ernest Rutherford for his interest in 

 this work and his kindness in supplying me with large 

 quantities of radium emanation. 



I wish also to thank Madame Curie, in whose laboratory 

 the preliminary experiments were carried out, and Prof. A. 

 Debierne, for the encouragement and kindness shown me 

 during my stay at the laboratory. 



The Physical Laboratory, 



The University, Manchester. 



June, 1917. 



* WertensteiD, These, Paris, 1913 ; Lucian, Phil. Mag. Dec. 1914 ; 

 Wellisch (loc. cit.) ; &c. 



t Kutherford, Phil. Mag. v. p. 95 (1903) ; Franck, Ver. d. D. Phys. 

 Ges. xi. p. 397 (1909) ; Franck und Meitner, Ver. d. D.Phys. Ges. 1909; 

 Ratner, C. P. civ. p. 453 (1912). 



