22 POPULAR SCIENCE MONTHLY. 



the same law as the emanation lost its activity. Eamsay and Collie 

 found that the emanation had a new and definite spectrum similar in 

 some respects to that of the argon group of gases. 



There can thus be no doubt that the emanation is a transition sub- 

 stance with remarkable properties. Chemically it behaves like an 

 inert gas and has a definite spectrum and is condensed by cold. But, 

 on the other hand, the gas is not permanent, but disappears, and is 

 changed into other types of matter. It emits during its changes about 

 one million times as much energy as is emitted during any known 

 chemical change. 



From the similarity of the behavior of the emanation of thorium 

 and actinium to that of radium, we may safely conclude that these 

 also are new gases which have only a limited life and change into 

 other substances. 



6-6-6-0- 



Tlior-tuni<. 71hor.X. £rma notion Thcrr A 7~hor & Thar C 



6-6-0 



Ura niary? C/t-o n i u m X Final Pr-od ' uc t 



&-6-0-&- 



O 



Actinium Achn.X £*r\anohoY\ flchnA Acti'n.S Actin.C 



Fig. 1. 



The non-volatile products of the radioactive bodies can be dis- 

 solved in strong acids and show definite chemical behavior in solution. 

 They can be partially separated by electrolysis and by suitable chemical 

 methods. They can be volatilized by the action of high temperature 

 and their differences in this respect can be utilized to effect in many 

 cases a partial separation of successive products. There can be little 

 doubt that each of these radioactive products is a transition sub- 

 stance possessing, while it lasts, some definite chemical and physical 

 properties which serve to distinguish it from other products and from 

 the parent element. 



• 



