﻿the Active Deposit of Radium in an Electric Field. 



19 



made showed that in the process of removing one rod and sub- 

 stituting another less than 2 per cent. o£ the emanation escaped. 



A result of one set o£ measurements is given below : — 



With + 4 volts on case and 10 minutes exposure, activity 

 o£ cathode 10 minutes after removal is represented by an 

 electrometer rate of l'l mm. per sec. 



With same applied potential and strong Rontgen rays 

 passing through the vessel during the whole time of exposure 

 the corresponding rate was *88. 



As a rough idea of the relative currents involved the 

 following figures are given ; in these instances the rates were 

 determined with the extra capacity added to the system. 



Ionization current immediately after introduction of 

 emanation and with + 160 volts on case : 3'3 mm. per sec. ; 

 with 4 volts rate was 105 ; 

 with 4 volts and Rontgen rays rate was 5*21. 



In the last two instances there was, of course, a deposit of 

 activity on the walls of the vessel. 



Other experiments were made with the same object, in 

 some instances large amounts of activity being previously 

 concentrated on the walls of the vessel so as to increase still 

 further the ionization. The results were of the same nature, 

 viz. to show a small decrease in the amount of activity 

 deposited on the cathode when additional ionization was 

 produced ; the decrease could be accounted for if we adopt 

 the view that the restatoms behave as positive ions, and are 

 subject to increased recombination with the negative ions 

 produced by the application of the extraneous radiation. 



4. Experiments with Larger Potentials. Air at 1 atmosphere. 



Experiments were next made to ascertain the percentage 

 of the total activity that was deposited on the cathode when 

 larger positive potentials were applied to the case. The 

 result of this set of measurements is given below (Table [.), 



Table I. — Emanation in Air at 1 atmosphere. 



Potential in 



Percentage cathode 





volts. 



activity. 





18 



42-7 





160 



791 





300 



85-9 





975 



866 





2250 



86-9 





2800 



88-5 





3250 



89-0 





4C00 



91*3 





