14 Johnstone and Bolttuood — Relative Activity 



with radium in uranium minerals, and by the impossi- 

 bility of tracing the origin of actinium to any point in 

 the series subsequent to radium. 



"We will now proceed to a consideration of the two 

 alternatives, (a) and (b) mentioned in the preceding 

 paragraph. As a preliminary to this the relative activi- 

 ties of the other members of the main-line series can be 

 calculated from the ratio experimentally determined for 

 the uranium and radium. Geiger's equation is employed 



I = Kk m 



and the results obtained are given in table V. The cal- 

 culations are made on the assumption that the simplest 

 (1:1) relation exists between all the products following 

 -and including ionium. 



Table V. 



Eange of a-particle Eelative Activity 



Element in cm. (at 0°C.) Calc. Found 



Uranium 1 2-37 



Uranium II 2-75 1-00 1-00 



Ionium 2-95 046 



Vadium 313 0-49 0-49 



Emanation 3-94 057 



Badium A 4-50 062 



Eadium C 6-57 0-80 



Eadium F 3-64 053 



Sum = 4-47 

 Relative activity of actininm and 

 actinium products as determined 

 experimentally by Boltwood. 19 = 0-28 



Total = 4-75 

 Total activity as determined (p. 9) 4-73 



The very close agreement between the total activities as 

 calculated and as found is purely accidental and merely 

 indicates that the value given for the activity of the 

 actinium products by difference (4-73-447 = 0-26) is 

 practically the same as that suggested by Boltwood as a 

 result of his experiments. 



The ranges of the a-particles from uranium, radium 

 and each of the actinium products and also the value of 

 the two-thirds power of the range are given in table VI. 



VJ This Journal, 25, 297, 1908. 



