558 Dr. A. S. Eve on the Number of Ions produced by 



leaf with the active deposit was hung by a thread at 50 cm. 

 from the centre of the electroscope. When measuring the 

 7 ray ionization, the ft rays were partly absorbed by a zinc 

 cylinder round the leaf, partly deflected by a powerful 

 magnetic field. The electromagnet and cylinder were 

 removed when the /3-ray ionization was measured. 



At *a time when the radium B present was 57 per cent, of 

 the radium C, the ft rays gave 11*7 divisions/minute, and the 

 y rays 03. Hence, taking a = *0033, and /x — 'OW for the 

 two cases 



*/l-17 + -57*/2-56 = ll-7. 



.*. #=10"9, the number of divisions a minute due to 

 radium C alone, whence 



K/K' = 10-9/0-3 = 36. 



Again, when radium B was 29 per cent, of radium in 

 quantity, the ft rays caused 7*5, and the y rays '24 division/ 

 minute, so that 



i/l-17 + *29ff/2-56 = 7'5 and # = 7'8. 



Hence K/K' = 7'8/-24 = 33. 



The mean value obtained in this way was K/K' = 34, and 

 since K' = 3'74x 10 9 from (1), it follows that 



K = l-27xlO n (3) 



Hence the total number of ions produced by the ft rays 

 from one curie of radium C in air at atmospheric pressure is 



4wKlfi= 4ttx 1-27 x 10 1 7'004 = 4-0 x 10 u . . (4) 



The corresponding value for radium B is about 13/75 of 

 this, or about 



0-7xlO u (5) 



And, due to the ft rays from both, 4*7 x 10 14 . 



(4) Instead of assuming the values for /ll as above, its 

 value was actually determined for distances from 40 to 100 

 cm., and was found to be between *012 and *013. Tbis 

 magnitude suggests the joint effect of radium C and radium B, 

 The value of jm did not, however, appear to decrease with the 

 time as the proportion of radium C to radium B increased. 

 There seems to be, therefore, proceeding from radium C a 

 large number of low velocity ft rays, somewhat similar to 

 those from radium B. If the value for K/K' is determined 

 with a value for fju intermediate between *004 and '012, 



