﻿the Active Deposit of Radium in ait Electric Field. 715 



the distribution of activity, nevertheless a decided interaction 

 has been found to take place between the restatoms and the 

 ions produced by the radiations which accompany the forma- 

 tion of these particles. 



The results of previous experimenters with regard to the 

 distribution of the active deposit under various conditions 

 have shown a lack of agreement which in our present ex- 

 periments has been traced to the fact that the potentials 

 employed were often far from sufficient to saturate even 

 approximately the radioactive ions. 



2. Experimental Procedure. 



The radium emanation used in our experiments was obtained 

 from two sources, for the use of both of which we are in- 

 debted to the kindness of Prof. Boltwood. One source con- 

 sisted of a solution of radium salt contained in a glass vessel 

 so constructed as to permit vigorous bubbling when a current 

 of gas was passed through it ; the o:her source was a quantity 

 of carnotite contained in a glass jar, which was adjusted to 

 permit of rapid connexion to the testing vessel. 



The emanation was in most cases passed through glass- 

 wool and phosphorus pentoxide before entering the test 

 vessel ; no effect on the distribution was observed, however, 

 by omitting these precautions. 



Different forms of test vessels were employed ; the vessel 

 which was used practically throughout and to which all our 

 experiments apply, unless mention is made to the contrary, 

 consisted of a brass cylinder with an aluminium bottom and 

 a brass central electrode sprung into a stout brass holder so 

 as to permit of rapid detachment. The vessel was provided 

 with a guard tube which Mas connected to earth ; this guard 

 tube was slightly tapered so as to make a good fit with the 

 ebonite plug which supported the central electrode. Stop- 

 cock grease was employed to ensure complete tightness. 



The dimensions of this vessel were as follows : — 



Height of containing portion 140 mm. 



Inner diameter 58 „ 



Exposed length of central electrode .101 „ 



Diameter of central electrode 1*83 „ 



The measurements of the activity of the central electrode 

 were made in a vessel identical to the above except that as 

 mentioned below no ebonite and in consequence no guard 

 tube was employed. 



The diagram of connexions and the disposition of apparatus 



