a particles from Thorium and Actinium Products. 653 



experiments to effect a separation have, however, so far been 

 unsuccessful. 



The following table gives the values of all the ranges of 

 the a particles which have been given by us in this and 

 previous papers. The values for radium emanation, radium A, 

 and radium are those given by Bragg and Kleeman. 

 The ranges are given for the temperatures 0° G. and 15° C , 

 and for convenience the initial velocities of expulsion of the 

 a. particles are added. The velocities v are calculated from 

 the equation i? 3 = aR, where R denotes the range of the 

 a particles and a is a constant*. The initial velocity of 



the « particles from radium C is taken as 2'06 x 10° — f . 



r sec. ' 



Ranges of a particles. 



Substance. 



Ran 

 0°C. 



ges at 

 1 15° O. 



Initial velocity. 



Uranium 1 



2-37 cm. 



2-75 



2-85 



3-13 



3-94 



4-50 



6-57 



3-58 



2-58 

 3-67 

 4-08 

 4-74 

 5-40 

 4-55 

 8-16 



4-36 

 4-17 

 5-40 

 6-16 

 5-12 



2-50 cm. 



2-90 



3-00 



3-30 



4-16 



4'75 



5-94 



3-77 



272 



3-87 

 4-30 

 5-00 

 5-70 

 4-80 

 8-60 



4-60 

 4-40 

 570 

 6-50 

 5-40 



1-47 10^' 



1-54 sec - 



1-56 



1-61 



1-74 



T82 



2-06 



1-68 



1-51 

 1-70 

 1*75 



1-85 

 1-93 

 1-82 

 2-21 



1-80 

 1-77 



1-93 



202 

 1-89 



Uranium 2 



Ionium 



Radium 



Ra Emanation 



Radium A 



Radium C 



Radium F 



Thorium 



Radiothorium 



Thorium X 



Th. Emanation 



Thorium A 



Thorium C r 



Thorium C 2 



Radioactinium 





Act. Emanation 



Actinium A 



Actinium C 





In fig. 4 (p. 654) the logarithms of the transformation 

 constants of the products are plotted against the logarithms of 

 the ranges of the « particles. The relations for the uranium- 

 radium and the actinium series have been given before, and 

 are repeated with very slight changes. The points repre- 

 senting the products of the thorium series also lie approxi- 

 mately on a straight line which falls between and is parallel 



* H. Geiger, Proc. Eoy. Soc. A. lxxxiii, p. 506 (1910). 

 f E. Rutherford, Phil Mag-, xii. p. 348 (1906). 



