430 Mr. S. Ratner on the Distribution of the Active 



Distribution of uncharged Radioactive Atoms in an 

 Electric Field. 



2. The progress of the present work has been greatly 

 facilitated by preliminary experiments carried out by means 

 of a method which permits the investigation of the distri- 

 bution of radioactive recoil atoms in a vessel not containing 

 emanation. 



This may generally be realized by an arrangement shown 

 in principle in fig. 1. Four insulated brass plates A, B, C, 

 and D form two condensers AB and CD. The plates B 



Fig. 1. 



- D 



and C are provided in the centre with circular apertures, 

 and are connected by a tube t. The central part of the 

 plate D may be taken out and replaced by a similar plate. 

 A small disk R, coated with radium A is placed in the centre 

 of the plate A and the plate B is negatively charged, the 

 experiments being carried out at atmospheric pressure. 

 Under these conditions a stream of positively charged recoil 

 atoms of radium B passes from the disk R towards the 

 plate B with the velocity of ordinary gaseous ions. A 

 certain part of them lose their charge by recombination with 

 negative ions before they reach the plate B, and then they 

 are carried by the electric wind which arises in the con- 

 denser AB owing to the intense ionization produced by 

 radium A and to the electric force between the plates. It 

 has been shown in a previous note* that under these con- 

 ditions the electric wind is directed towards the plate B, 

 passing by inertia the tube t, so that the neutral atoms of 

 radium B are carried towards the plate D. Experiments 

 show that practically the whole of the activity is deposited 

 on the plate D, the activity remaining on the inner surface 

 of the tube t being very small, even when it is so long as 

 150 cm. 



Various experiments have been undertaken in order to 

 * C. R, clviii. p. 565 (1914). 



