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JUL 13 1920 



THE MSoaai j|u« 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Art. I. — The Relative Activity of Radium and the 

 Uranium with which it is in Radioactive Equilibrium;* 

 by J. H. L. Johnstone and B. B. Boltwood. 



Although the matter has been nnder consideration and 

 discussion for a number of years, the genetic relation- 

 ship between the earlier members of the uranium family 

 of radio-elements. is still a matter of considerable uncer- 

 tainty. It is generally conceded that both ionium and 

 actinium are products of the radioactive disintegration 

 of uranium, but the exact point of origin of actinium 

 and its immediate parentage have remained somewhat 

 obscure and uncertain. 



The work of Boltwood 1 on the relative a-ray activity 

 of uranium minerals and the uranium which they con- 

 tained demonstrated a constancy of relationship between 

 the radioactive constituents of the older minerals and 

 clearly indicated a close genetic relation between ura- 

 nium and actinium. His determination of the activities 

 of the more stable a-ray products relative to the activity 

 of the associated uranium showed a simple and direct 

 relation to exist between the products ionium, radium 

 and polonium, but showed an abnormally low value for 



* The experimental results given in this paper and the general theoretical 

 conclusions are taken from a dissertation on the "Belative Activity of 

 Uranium and Kadium" presented on April 27, 1916, by J. H. L. John- 

 stone in fulfillment of the requirements for the degree of Doctor of Phi- 

 losophy in Yale University. The chief reason for the delay in publication 

 was the entry of Dr. Johnstone into active military service with the 

 Canadian forces in May, 1916. The work was carried out in the Sloane 

 Physical Laboratory of Yale University. 



1 This Journal, 25, 269, 1908. 



Am. Jour. Sci. — Fourth Series, Vol. L, No. 295. — July, 1920. 

 1 



