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



the activity concentrated on the electrode P when the 

 additional source of ionization Q is introduced into the vessel 

 and placed in a position opposite to it ; column IV. the same 





Table I. 





I. 



II. 



III. 



IY. 



1 



35 



120 



5-5 



1 



42 



95 



4-5 



1 



26 



135 



6 



with the disk Q fixed in the centre o£ the electrode P. The 

 activity reaching the plate by diffusion (column I.) is taken 

 as unity in each of these series of experiments. 



The course of the experiments was as follows : The disk R 

 is exposed for about 20 minutes to a large quantity of ema- 

 nation in a slightly modified form of the exposing vessel of 

 Wertenstein *, which allows a rapid removal of the active 

 disk without any appreciable loss of emanation. One minute 

 after the exposure, the disk R is placed in the centre of the 

 plate A, and the plate P exposed for 10 minutes under the 

 various conditions to the neutral recoil atoms entering 

 the cube K. The activity was found to be uniformly distri- 

 buted on the plate P, and since the disk Q is small, compared 

 with P, the experiments of eolumn IV. are not appreciably 

 affected by putting Q in the centre of P. In some experi- 

 ments the centre of P, when not occupied by the disk Q, was 

 covered with a piece of aluminium foil of the same size, which 

 could be removed after the exposure of P. 



The activities were measured by a rays, using a Wilson 

 tilted electroscope whose sensibility could be varied within 

 large limits. Measurements were made when the activity 

 of radium B had reached its maximum value, at which time 

 the activity remains practically constant for about 30 minutes. 

 Experiments with needle electrodes and "screened" elec- 

 trodes, which will be described later on (see sec. 7 and 8), 

 in connexion with the results given above, show that the 

 distribution of uncharged radioactive atoms in an electric 

 field is not merely a process of diffusion, as it is generally 

 believed. Owing to the electric wind which is always 

 present under these conditions, the neutral carriers of active 

 matter acquire a definite motion towards the electrodes. The 

 * L. Wertenstein, Thtee, Paris 1913, p. 40. 



