Actinium in an Electric Field. 



549 



the amount of emanation used, for values of V up to 600 volts 

 or thereabouts. Above V = 600, A v was independent of the 

 amount of emanation used, when the amount was not exces- 

 sively large. The curves in fig. 2 represent the results of 

 these experiments and give an idea of the ratio of amounts 

 used in these experiments. Very excessive amounts have not 

 been tried, but there are strong indications that the above 

 independence would no longer hold good. 



The points on the curves represent the percentage of the 

 total activity which is deposited on the cathode, for a given 

 amount of emanation. As has already been mentioned, the 

 activities on the case (anode) and the central electrode 

 (cathode) were measured separately and from these measure- 

 ments the above values of the cathode percentage calculated. 

 A condensed table, in which the values have been interpolated 

 from the curves to correspond to given amounts of emanation 

 at points sufficiently near the experimental values, is given 

 below, for purposes of reference : 



Table I. 



Am ounts 



Percentage Cathode Activity. 



in 

 divs /sec. 







10 



20 



40 



120 



200 



600 



980 



1700 



volts 



volts 



volts 



volts 



volts 



volts 



volts 



volts 



volts 



•50 



17 



32'8 







85-1 





937 



94'7 





1-5 



14-0 



20-3 



41-0 



59'0 



83-9 





93-0 







2-0 



132 



18 9 



37*5 



54-5 



82-4 



88'0 









2-5 



13-2 



18*0 



34-5 



52*8 



81-2 



87'5 



93-6 



94-8 





3'5 



15*5 



17-0 



30-1 



49*2 



78-8 



86*3 



93*4 





94'9 



5-0 



13'2 



16*5 



266 



452 



76 5 



85-5 



93 4 



95-0 





8-0 



13*2 



15*0 



24-0 



40-0 



73-0 



83-5 



93-0 



95-0 



94-9 



It is to be noticed that the curves for 600 volts, 980 volts 

 and 1700 volts are horizontal ; the last two being coincident. 



Owing to the presence of neutral deposit particles, even at 

 the highest potentials employed, it is necessary to correct, for 

 diffusion, all the experimental values of the distribution of 

 activity. This was done by obtaining experimental values for 

 the distribution in the absence of an external electric field (0 

 volts), so that diffusion alone was operative. It was found that 

 the deposits on the central rod and the case were in the ratio 

 of 1 to 6'6 approximately. This ratio is quite different from 

 the ratio of the areas of the central rod and case, which was 1 

 to 37. It is evident that if we corrected for diffusion on the 

 supposition that the diffusion distribution was proportional to 

 the exposed areas, we would get higher values for the cathode 

 percentage. 



