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Dr. G. von Heresy on the 



The radioactive substances whose properties are discussed 

 in this paper are included in the three active deposits of 

 radium, thorium, and actinium. The radiations emitted, 

 and the half-value periods of transformation of the con- 

 stituent products, are shown in the table below. The 

 nomenclature is that given bv Rutherford and Geiger, 

 Phil. Mag. Oct. 1911, p.' 621. 



Substance. 



Radiation. Period. 



I 





a 3'0 minutes. 



P, y 26 8 minutes. 



a, Bi y 19'5 minutes. 



B 



C 





Thorium A 



B 



a '14 second. 

 |8 10-6 hours. 

 a 55 minutes. 



C 





a '002 second. 

 j8 36 minutes. 

 a 2] 5 minutes. 



B 



C 



It will be seen that there is a remarkable similarity between 

 the nature of the radiations from the corresponding products. 

 It will also be shown that there is a corresponding similarity 

 in their electrochemical properties. It is consequently very 

 convenient to speak of the B or C products, meaning in the 

 former case radium B, thorium B, and actinium B, and in 

 the latter case radium 0, thorium C, and actinium 0. 



An active deposit was obtained in the usual way on a 

 platinum electrode, and then dissolved in HC1, HN0 3 , or 

 H 2 S04, according to requirement, and evaporated to dryness. 

 It was then treated- with distilled water, and as soon as a 

 B product was in equilibrium with a C product an 

 electrolyte was added to it. If, for instance, the action 

 of zinc on the radium active deposit was being investi- 

 gated, the active deposit was dissolved in H 2 S0 4 , and the 

 (KaB) Jl (S04)y 1 + (BaC) J . 2 (S0 4 ) 2/2 solution evaporated to dry- 

 ness, redissolved, and added to a solution of zinc sulphate. 



In some experiments the active deposit was collected on 

 the surface of metallic sodium, which was then dissolved in 

 water, the active deposit dissolving also. This second method 



