Manchester Memoirs, Vol. liv. (1909), No. 6- 



VI. " Production of Helium by Radium ," 

 By Professor E. RUTHERFORD, F.R.S., 



AND 



Dr. B. B. BoLTWOOD. 



Received and read November jolh, igog. 



Since the demonstration by Ramsay and Soddy of 

 the production of heh'um by radium, it has been of great 

 importance to determine accurately the amount of hehum 

 produced by a known quantit}' of radium. It has been 

 shown by Rutherford, Geiger, and Royds that the 

 o particle emitted by radium and its products is an atom 

 of helium. In addition Rutherford and Geiger have 

 calculated by counting the a particles and determining 

 their charge that one gram of radium in equilibrium 

 should produce 158 cubic mms. of helium per year. The 

 first systematic measurements of the production of helium 

 by radium were made last year by Sir James Dewar.* 

 His experiments indicate that radium in equilibrium pro- 

 duces helium at a constant rate equivalent to 135 cubic 

 mms. per gram per year — a result in fair agreement with 

 the calculated quantity. 



Another determination has recently been made by 

 the writers using a barium-radium salt containing about 

 2(X) milligrams of radium, loaned by the Vienna 

 Academy of Sciences. The salt, chemically treated 

 to remove polonium and radium D, was placed in 

 a platinum capsule which was in turn sealed in an 

 exhausted tube of hard glass. At the end of 83 days, the 



♦ Pioc. Koy. Sor., A. 8 1, 280 (iqo8). 

 December 24/h, igog. 



