180 Dr. 0. Hahn on Radioactinium. 



temperatures may possibly effect a separation of radio- 

 actinium from actinium, but this point has not yet been 

 examined. 



For convenience, the disintegration series of actinium is 

 given, together with the period of the products and the 

 radiations they emit : — 



Time to be half 

 Product. transformed. Radiation. 



Actinium ? Rayless. 



Radioactinium about 19*5 days. a rays. 



a 



?■> 



Actinium X 10*2 davs. 



i 



Emanation 3*9 sees. a ,, 



.1. 



Actinium A") ,. 36 mins. Ravless. 



f active J 



Actinium B ) ^ 2 mins. a, ($, & y rays. 



Summary of Results. 



The results brought out in this paper are chiefly sum- 

 marized below : — 



(1) A new product called " radioactinium " exists in 



the disintegration series of actinium. This new 

 product is produced directly from actinium and is 

 the direct parent of actinium X. 



(2) The transformation of actinium into radioactinium 

 is rayless. 



(3) Radioactinium emits only a rays and is half trans- 



formed in about 19'5 days. 



(4) The methods of separation employed for the isolation 



of radioactinium throw no definite light on its 

 properties. 



The present research was done at the McGill Physics 

 Building at Montreal (Canada). Now that my visit to 

 Montreal has come to an end, I record with much pleasure 

 my gratitude to Prof. Rutherford for his kindness, interest, 

 and ready help during the whole of my stay at the McGill 

 University. 



Berlin : Chemical Institute of the University. 



