Dr. 0. Halm on Radioactmim 



i'o 



the same period as the a ray activity, viz.. with the period of 

 19'5 days. This is in agreement with the theory. 



Fiff. 2. 













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r 











































20 30 



TlM£ l/V O/IVS . 



Connexion of Radioactinium with Actinium. 



It is now necessary to consider the connexion of the new 

 product radioactinimn with actinium itself. 



Until recently, it was generally believed that actinium was 

 the direct parent of actinium X. The intermediate product 

 radioactinium had been overlooked. It was believed that 

 actinium itself did not emit any rays, and that therefore by 

 separation of actinium X it could be nearly completely freed 

 from activity. This, however, is not correct. 



M. Levin*, working in the same laboratory as the writer, 

 determined with great accuracy the residual a ray and ft ray 

 activity of actinium after actinium X had been completely 

 separated. By the well-known method of precipitation with 

 ammonia, by continued precipitations he was able to reduce 

 the emanating power of an actinium solution to one thousandth 

 of its initial value. The separation of actinium X was very 

 complete, but his actinium was still quite active. It always 

 showed a strong a ray activity not less than about 22-25 

 per cent, of its initial value. Levin states that this activitv 

 is due to the presence of radioactinium which is not separated 

 from actinium by means of ammonia. This conclusion is in 

 full harmony with the observations of the writer. 



In order to obtain actinium inactive, the radioactinium as 

 well as actinium has to be separated. It is difficult to effect 

 a complete separation of the radioactinium, when employing 



* Lac. cit. 



