Relation between Range of ol Rays and Charges emitted. 741 



The actinium series, too, must then be complex as the same 

 reversal exists here. Indeed, Mile. Blanquies * found some 

 evidence that the a rays emitted from actinium are 

 complex. 



That uranium, too, is complex was observed by An ton off f f 

 The branch product Ur Y emits soft ff rays, and some evidence 

 was found that it emitted a. rays. As Rutherford X remarks, 

 " The possibility of a branch product of uranium is of great 

 interest, as affording a possible explanation of the origin of 

 actinium/'' If now we suppose Ur Y— as emitting a. + ff rays — 

 to consist of two products, one emitting a rays, the other 

 emitting ff rays (and the same must be supposed for Ra, 

 Th X, Ac X, Ra Ac — which all emit both a. and ff rays), 

 then the product of Ur Y 2 falls together with Act. and might 

 be identical with it. 



rAQ 



5 10 15 



Number of cha roes £xp£l l ed . 



EO 



If we accept for UrII the value given by G-eiger and 

 Nuttall, then the uranium series cannot unite in the radium 

 series, as the values for U II and Io are nearly identical. If, 

 however, the range 2'90 cm. is attributed to Ur Y and in part 

 that of 2*50 to Ur II also, while the range +1*6 cm. found by 

 Friedmann § is attributed to Ur also as emitting two a rays of 



* C. R. cli. p. 57 (1910) ; Le Radium, vi. p, 230 (1909), vii, p. 159 



t Phil. Mag. xxii. p. 419 (1911). 



X Loc. cit. p. 45. 



§ Wien. Ber. cxx. p. 1361 (1911). 



Phil Mag. S. 6. Vol. 25. No. 149. May 1913. 3 E 



