of Radium and Uranium. 



11 



as that in equilibrium with 0-0698 g. of uranium, and in 

 10 cc. of solution C with 0-0607 g. of uranium. 



The a-ray activity of the radium itself was determined 

 in the following manner : 



Portions of solutions B and C 10 cc. in volume were 

 taken, and the barium and radium present were precipi- 

 tated as sulphate under standard analytical conditions. 

 The precipitates were removed and ignited as promptly 

 as possible and the time at which the ignition was car- 

 ried out was noted. The weight of the precipitate was 

 determined and the material was quickly ground to a 















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fine powder with ethyl alcohol. Films of this material 

 were then prepared in the manner already described and 

 the activity of these films was measured in the a-ray 

 electroscope. Measurements of the activity were con- 

 tinued over a period of 6 to 7 hours and the increase 

 with the time (due to the growth of the emanation and 

 other active products) was noted at definite intervals. 



Preparatory to the precipitation of the sulphates the 

 radium-barium solutions were kept at a temperature 

 slightly below the boiling point for a period of four 

 hours in order to remove any emanation as formed and 

 to permit the other products (radium A, radium C) to 



