Boltwood — Ionium, a New Radio-active Element. 381 



carried out by a method similar to that which he has described 

 would appear to indicate that the activity which can be attrib- 

 uted to thorium, from monazite, when free from all thorium 

 disintegration products can not be greater than about seven 

 per cent of the activity of the same thorium when equilibrium 

 amounts of its disintegration products are present. This is 

 so nearly of the same order of magnitude as the relative activ- 

 ity of the ionium undoubtedly associated with the thorium, 

 that there would appear to be some question as to the correct- 

 ness of Hahn's conclusions. 



The results which I have obtained on the rate of growth of 

 radium in solutions of ionium, indicating that the half-value 

 period of radium is about 2000 years, will be given in a later 

 paper. 



Summary. 



It has been found that uranium minerals contain a new 

 radio-active element, to which the name "ionium" has been 

 given. The chemical behavior of ionium is similar to that of 

 thorium, from which it can not be separated by the usual 

 reactions characteristic for thorium. 



Ionium emits an a radiation having a range of about 2'8 cm 

 in air, and probably also a /3 radiation. Results obtained on 

 the growth of radium in solutions of ionium indicate that it 

 is the immediate substance from which radium is formed. 

 It is therefore undoubtedly a disintegration product of uranium 

 intermediate between uranium X and radium. The relative- 

 activity of radium and ionium in minerals is in agreement 

 with this assumption. 



New Haven, Conn., 

 February 28, 1908. 



Am. Jour. Sci.— Fourth Series, Vol. XXV, No. 149.— May, 1908. 

 26 



