Section III., 1909. [ S3 ] Trans. R. S. C. 



IV. — On the Active Deposit from Actinium in Uniform Electric Field'^. 

 By W. T. Kennedy, B.A. 



Communicated by Professor J. C. McLennan, and read before the Royal 

 Society of Canada on May 2G, 1909. 



Introduction. 



In a number of experiments which have been carried on with the 

 emanations and the emanation products from the radioactive sub- 

 stances, it has been shown by Rutherford ^ that with thorium 

 emanation, the amount of activity imparted to a rod charged 

 negatively was independent of the pressure imtil a pressure of 

 10 mm. was reached, and that below this pressure it decreased 

 as the pressure in the containing vessel was lowered. At 1/10 

 mm. pressure it was only a small fraction of its maximum amount. 

 Makower ^ has shown similar effects with the excited activity from ra- 

 dium emanation. Further, Eutherford ^ experimenting with radium 

 emanation, found that at atmospheric pressure the greater part of the 

 lactive deposit went to the cathode, while only about 5 per cent went to 

 the anode. From these results he has drawn the conclusion that while 

 most of the active deposit particles of radium are positively charged, some 

 at least must carry a negative charge in as much as they are drawn to 

 the anode in electric fields. 



'More recentty Euss * shewed tliat when positively and negatively 

 charged electrodes were placed in a vessel containing either air, sulphur 

 dioxide, or hydrogen charged with the emanation from radium, that the 

 irelative amounts of the active deposits obtained on the two electrodes 

 varied with the pressure at which the exposures were made. "With all 

 three gases, the active deposit on the negative electrode gradually de- 

 creased as the pressure was lowered, while that obtained on the positive 

 electrode showed a corresponding increase, until ultimately at the lowest 

 pressure investigated, the amounts of the active deposit obtained on the 

 two electrodes were approximately equal. 



In a second paper, Euss ^ gives an account of a similar set of ob- 



1 Rutherford, Phil. Mag-., Feb., 1900. 



2 Makower, Phil. Mag., Nov., 1905. 



3 Rutherford, Phil. Mag., Jan., 1903. 

 4 Russ, Phil. Mag., May, 1908. 



■^! Russ, Phil. Mag., June, 1908. 



