of Radium from Uranium. 



775 



a radioactivity of the two elements and the number of changes 

 in which a rays are expelled in the two cases. The quantity 

 of radium actually produced even after 500 days is far too 



Fiff. 1. 



75 



50 



25 









• 





& 



/ / 







50 



D/irs. 



100 



150: 



small to be represented on the diagram, and as a matter of 

 fact amounts to about one atom of radium for every 3 x 10 11 

 atoms of uranium. 



This result was arrived at in the following manner : — A 

 quantity of Giesel's purest radium bromide weighing 1*1 

 milligrams was dissolved in water in a small closed test-tube, 

 into which inlet and outlet tubes provided with taps were 

 sealed. The emanation accumulating for a known time was 

 swept out by a current of air into a gas-burette, and the 

 volume measured. After thorough mixing of the contents of 

 the gas-burette a small known volume was delivered into a 

 second gas-burette, again diluted to a knowm volume, mixed, 

 and a small known fraction delivered into a third burette, 

 The dilution was performed so that about one-millionth of 

 the original emanation was finallv obtained and delivered 



