The Distribution of the Active Deposit of Radium 

 IN AN Electric Field. — By G. H. Henderson, M. A., 

 Instructor in Physics, Dalhousie University,* Halifax. 



(Read 10 May 19 10) 



I. Introductory. 

 The experiments described in this paper were suggested 

 by the results of a previous investigation, by the writer^, of 

 the analogous problem for thorium. In the former paper 

 it was shown that all the active deposit particles (or rest- 

 atoms) of thorium could be collected on the negative electrode 

 in a strong electric field. Hence all the rest-atoms, at least 

 at the end of their recoil, are positively charged. 



In the case of radium, however, early investigators found 

 that only from 90 to 95% of the total active deposit was 

 positively charged. But their results were little more than 

 qualitative in nature. More recently Eckmann^ came to 

 the 'conclusion that 98% of the rest-atoms were positively 

 charged and the remaining 2% negatively charged. The 

 experiments of Walmsley^ seemed to show that, even in the 

 strongest fields, the fraction of the rest-atoms which was 

 positively charged reached a maximum, leaving a small 

 fraction uncharged. The methods of both experimenters, 

 however, are open to very serious objections; the most 

 important is the fact that they both used a cylindrical testing 

 vessel with a central electrode, and then assumed that 

 the total active deposit was the sum of the deposits 

 obtained on it when first cathode and then anode. They 

 thus neglected the considerable amount of deposit which 

 collected on the case of the vessel itself. 



♦Contriljutions from the Science Laboratories of Dalhousie University (Physics]. 



. Henderson, Trans. N. S. Inst. Sci., XIV. pt. 1, p. 1. 

 *. Eckman, Jahr. der. Radioakt., May, 1912. 

 3. Walmsley, Phil. Mag., Oct., 1914. 



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