Spectra of the Elements Tantalum-Uranium. 



49 



A comparison with the values of Moseley for tantalum- 

 gold shows that his a-, /3-, and 7-lines correspond to our « 1? 

 fix, and /3 2 . His values, however, are practically all about 

 1 per cent, greater than ours. 



In their excellent research on the soft 7-rays from radium B 

 Rutherford and Andrade * have determined the spectrum of 

 these rays after a similar method to the writers'. They have 

 also shown that lead, the characteristic radiation of which 

 was excited by the /3-rays from an emanation- tube, gave the 

 same characteristic lines as radium B. In this way the 

 isotopy of radium B and lead was directly experimentally 

 proved. As Rutherford and Andrade, in the case of 

 radium B, have found a great many lines, a comparison 

 with the lines found by the writers for lead may be of 

 interest. This is given in Table X VI. The agreement is, 

 as seen, very good, especially for the strongest lines. 



Table XVI. 



Radium B. 



Lead. 



Soft y-ray spectrum 



X-ray spectrum 



(Rutherford and Andrade). 



(Siegbahn and Friman). 



Angle of reflexion . 



Intensity. 



Angle of reflexion. ! Intensity. 



/ 

 12 16 



Dl 



12 9-8 



3 



12 3 



8 



12 3 



10 



11 42 



m 







11 17 



f 



11 10-5 







11 



f 







10 48 



f 







10 32 



m 



10 28-5 



2 



10 18 



m 



10 19-1 



2 



10 3 



s 



10 3-6 



9 







9 54-1 



2 



9 45 



m 



9 44-5 



2 



9 23 



f 







8 43 



m 







8 34 



m 



8 36-3 



3 







8 22-8 



1 



8 16 



m 



8 20-3 



1 



8 6 



m 



8 5-3 



1 



For an evaluation of the numerical results, further investi- 

 gations of a greater range are necessary. Such researches 

 are at present going on in this laboratory. 

 Physical Laboratory, 

 University of Lund. 

 Feb. 10, 1916. 



* Phil. Mag. xxvii. p. 854 (1914). 

 Phil. Mag. S. 6. Vol. 32. No. 187. July 1916. E 



