T H E 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHrCAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



♦ 



[SIXTH SERIES.] 



JUNE 1910. 



LXXXVI. Radium D and its Products of Transformation. 

 By G. N. Antonoff*. 



WHEN the activity of a body which has been exposed 

 to the radium emanation for some time is measured, 

 it is found that after the initial products, radium A, radium B, 

 and radium 0, have disappeared, there still remains a residual 

 activity. This was first noticed by Mme. Curie and examined 

 in detail by Rutherford f, who found that the active matter 

 was complex and consisted of at least three successive pro- 

 ducts which he called radium D, radium E, and radium F. 

 Radium D was found to be a ray less product of long period 

 of transformation (the " period" being- the time taken for a 

 product to be half transformed), radium E a /3-rav product 

 with a period of about six days, and radium F an a- ray 

 product with a period of about 140 days. It is now de- 

 finitely known that the polonium of Mme. Curie is identical 

 with radium F, and that the primary source of activity in 

 radio-lead separated from radioactive minerals is radium D. 

 Rutherford's results were extended and completed by Meyer 

 and v. SchweidlerJ, who examined in particular the products 

 of radio-lead, and showed that they were identical with 

 radium D, radium E, and radium F. By comparison of the 

 /3-rav activity of radium E and radium C, Rutherford § 



* Communicated by Professor E. Rutherford, F.H.S. 

 t Phil. Ma- yiii. p, 636 (1904); x. p. 291 (1905). 

 t Wien. Ber. cxv. Abt. ii a, May 1906. 

 § ' Radioactivity,' -2nd edition, p. 405 (1900). 



Phil Mag. S. 0. Vol.* 19. Xo. 114. June 1910. 3 H 



