304 Prof. E. Rutherford on Slow 



due to radium E, which is half transformed in six days, and 

 the a ray activity to radium F. 



This conclusiou is further confirmed by experiments on the 

 effect of heat on the activity of these substances. By heating 

 to a full red-heat, the a ray activity was lost in a few seconds. 

 This is in agreement with my experiments on radium F, which 

 is volatilized at about 1000° C. 



Salts of gold, silver, and mercury added to the radio-lead 

 were found to show only a ray activity on removal. This is 

 explained by supposing that radium F alone is removed with 

 these substances. Bismuth salts, on the other hand, showed 

 initially both a, and j3 ray activity, but the latter rapidly died 

 away. This is in agreement with the experiments of Mine. 

 Curie, who found that radioactive bismuth at the moment of 

 separation possessed both a and j3 ray activity, but that the 

 latter soon disappeared, 



The a. and ft ray activity of the radio-lead is much 

 reduced by the precipitation of bismuth added to the solution, 

 but recovers itself again with time. This result is exactly 

 what is to be expected if radio-lead contains radium D, E, 

 and F. Radium E and F are removed with the bismuth, but 

 the parent substance radium D is left behind, and in conse- 

 quence a fresh supply of radium E and F is produced. 



While further experiment is required to settle conclusively 

 whether the products separated from radio-lead are identical! 

 with radium E and F, there can be little doubt that such is 

 the case. 



The evidence at present is not sufficient to decide whether 

 the lead, immediately after its separation from pitchblende, 

 contains only radium D, or whether radium E also appears 

 with it. It seems likely, however, that the bismuth which is 

 present in the solution with the lead will retain both radium 

 E and F, and that the presence of these products in old radio- 

 lead is due to their production after separation by the parent 

 substance radium D. 



The results of the comparison of the products of radium 

 with those contained in polonium, radio-tellurium, and radio- 

 lead are summarized below. 



Radium D = product in new radio-lead, no rays. 

 Half transformed in 40 years. 

 Products Radium E = gives out ft rays, separated with 

 in old bismuth, and iridium. Half transformed 



Radio- ^ in (3 days, 



lead. Radium F = product in polonium and radio- 



tellurium. Gives out only a, rays. Half 

 transformed in 143 days. 



