﻿THE 



LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OP SCIK 



[SIXTH SERIES.*] 



MARCH 1915. 



XXXVIII. The Condensation of Thorium and Radium 

 Emanations. By Alexander Fleck, B.Sc* 



A LARGE number of experiments have been made on 

 the temperature of condensation and other properties 

 of these emanations. As a result of their first experiments, 

 Rutherford and Soddy t found that they were condensed at 

 the same temperature, but more precise measurements made 

 them conclude that while radium emanation condensed at 

 — 155° Cj thorium emanation, on the other hand, was con- 

 densed over a range of temperature varying from —120° C. 

 to —155° C. The well-known experimental facts concerning 

 the chemical non-separability of certain groups of radio- 

 elements from one another and from certain common 

 elements have received a theoretical explanation by the 

 generalization of Russell, Fajans and Soddy, governing the 

 evolution of the radio-elements through the Periodic Table. 

 The elements which appear to be chemically identical occupy 

 the same place in the Periodic Table and are termed 

 "isotopic" elements. The three radioactive emanations are 

 isotopic but, as they belong to the family of chemically inert 

 gases, they are, of course, chemically indistinguishable. 

 Professor Soddy suggested that it would be of interest to 

 examine whether the thorium and radium emanations could 

 be separated from one another by condensation, or whether, 

 as suggested by the work of Sir J. J. Thomson and Ashton 



* Communicated by Professor F. Soddv, F.R.S. 



t Rutherford and Soddy, Phil. Ma«r. [6] v. p, 561 (1903). 



Phil. Mag. S. 6. Vol. 29. No. 171. March 1915, Z 



