174 PHYSICS OF THE ELECTRON 



They can be partially separated by electrolysis and by suitable chem- 

 ical methods. They can be volatilized by the action of high tempera- 

 ture, 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 

 substance, possessing, while it lasts, some definite chemical and phys- 

 ical properties which serve to distinguish it from other products and 

 from the parent element. 



The radioactive products derived from each radio-element, together 

 with the type of radiation emitted during their disintegration, are 

 shown graphically in Fig. 1. 



riu-rn . TTior. X ma noTior, 77>or- /} Ttior. B 7%or C 



O 



Ui~a n i </ rn X Final fr-oolitcf 



Actirt X. ~rna n a h'on /Icfin.A Acffn-B Ac.fm C 



2 



The radiations from actinium have not so far been examined suf- 

 ficiently closely to determine the character of the radiation emitted 

 by each product. There is some evidence that a product, actinium 

 X, exists in actinium corresponding to Th X in thorium. It has not, 

 however, been very closely examined. 



The question of nomenclature for the successive products is impor- 

 tant. The names Ur X, Th X have been retained, and also the term 

 emanation. The emanation from the three radio-elements in each case 

 gives rise to a non-volatile type of matter which is deposited on the 

 surface of the bodies. The matter initially deposited from the radium 

 emanation is called radium A, radium A changes into B, and B into 

 C, and so on. A similar nomenclature is applied to the further pro- 

 ducts of the emanation of thorium and actinium. This notation is 



