Rutherford and Boltwood — Radium and TJra 



mum. 



solution was removed, introduced into a bulb of about 100 cc 

 capacity and diluted to about 50 cc with distilled water. The 

 contents of the bulb were boiled vigorously for about ten 

 minutes and the tubular orifice of the bulb was then sealed by 

 fusion. 



After a period of exactly four days had passed the emana- 

 tion which had accumulated in the bulb was removed by con- 

 tinued boiling of the solution, and was transferred to an 

 air-tight electroscope and its activity measured. The leak due 

 to the emanation was equal to 4*27 divisions per minute, and 

 the calculated leak corresponding to the maximum equilibrium 

 quantity of emanation was 8*44 divisions per minute. On the 

 basis of 0'27 mg of pure radium bromide originally taken, the 

 amount of radium contained in the solution in the bulb was 

 1*57 XlO" 5 milligram. 



The leak corresponding to the equilibrium quantity of 

 radium emanation formed by the radium associated with one 

 gram of uranium in a natural mineral was next determined. 

 The mineral chosen was a pure North Carolina uraninite con- 

 taining 68*2 per cent of uranium. The leak in the same elec- 

 troscope corresponded to 206 divisions per minute per gram 

 of uranium. From the above numbers it can readily be calcu- 

 lated that the quantity of radium associated with one gram 

 of uranium in a radio-active mineral is equal to approxi- 

 mately 3-8xl0~ 7 gram. 



The value of the new number is about one-half that of the 

 old. On the present basis the ores of uranium per ton of 

 2,000 pounds will carry about 0*0034 gram of radium for 

 every per cent of uranium present. A ton of 60 per cent 

 uranium ore will therefore carry about 0*20 gram of radium 

 equivalent to 0*35 gram of radium bromide. These numbers 

 are more nearly in accord with the quantities of radium 

 extracted from the ores in actual practice than were those 

 derived on the basis of the former standard. 



April, 1906. 



