Relative Activity of Radium and Uranium. 59 



73*0 per cent, of uranium, the radium in equilibrium with 

 1 oram of uranium in the mineral was equivalent to a leak 

 of 1170 divisions per minute. The quantity of radium in 

 lOc.c. of solution B, therefore, was the same as that in 

 equilibrium with 0*06^8 g. of uranium, and in 10 c.c. of solu- 

 tion G with 0*0007 g. of uranium. 



The «-ray activity of the radium itself was determined in 

 the following manner: — 



Portions of solutions B and C 10 c.c. in volume were taken, 

 and the barium and radium present were precipitated as 

 sulphate under standard analytical conditions. The precipi- 

 tates were removed and ignited as promptly as possible and 

 the time at which the ignition was carried out was noted. 

 The weight of the precipitate was determined and the material 

 was quickly ground to a fine powder with ethyl alcohol. 



/3 OO 

























































/200 





















I 

 s 













\ 























//oo 































^ 



.-'"^ 

























/ooo 













Y£ I - 

 re2Z- 





1-/OJ 



• 



































































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 continued over a period of six to seven 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 



