726 



Prof. A. F. Kovarik on 

 Table II. 



Distance 12*3 mm. 



Potential Difference llo volts 



P.D. in volts. 



Actinium D 

 b} r recoil. 



Distance 

 in mm. 



Actinium D 

 by recoil. 







trace 







10 



4-9 



0-2 



100-0 



135 



13-8 



6 3 



91-2 



20 



34-1 



11-5 



86-2 



30 



55-6 



123 



80-5 



50-5 



74-5 



160 



74-2 



70 



85-5 



22-5 



43-5 



110 



87-0 



32-0 



1V1 



207 



100-0 









was observed, while with a distance of only 0'2 mm. the 

 amount was readily measured, and was about 3 per cent, 

 of that obtained with a strong field. With a distance of 

 0*2 mm. two volts produced approximate saturation. 



Kfect of the Surface of the Plate used for the 

 Active Deposit. 



It was noticed during the progress of these experiments 

 that the same amount of actinium D by recoil was not 

 obtained when the active deposit was collected on different 

 plates. This was found to be due to the surface of the plate. 

 "Wertenstein* has recorded a similar observation. The figures 

 in Table III. will show the importance of the " polish " of 

 the surface. 



Table III. 



j 



Plate. 



Actinium C by 



recoil. 



1 



100 

 92 



78 

 62 





2 





3 





4 









The plate No. 1 was smooth tinfoil on glass. It gave the 

 best results. Plate 4 was a copper plate roughened by means 

 of emery-paper. Plate 3 was a smooth copper plate, and 

 plate 2 was No. 3 polished to some extent by means of 



L. Wertenstein, Le Radium, vii. p. 288 (1910). 



