THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Art. XXVIII. — On the Ultimate Disintegration Products of 

 the Radio-active Elements ; by Bertram B. Boltwood. 



In a paper by Rutherford and Soddy,* the authors have 

 called attention to the probability that an intimate knowledge 

 of the composition of radio-active minerals will lead to the 

 recognition and identification of the ultimate, stable products 

 formed by the disintegration of the relatively unstable radio- 

 active elements, f 



It is an extremely impressive fact that it was from the some- 

 what meager information available on the occurrence of helium 

 in radio-active minerals, and from the consideration of the data 

 derived from the experiments of one of them on the nature of 

 the expelled alpha particle, that in 1902 the same authors were 

 enabled to make that brilliant prediction of the production of 

 helium J which was afterwards confirmed by the experiments 

 of Ramsay and Soddy. 



The natural minerals represent chemical systems which are 

 in most instances of extreme antiquity, their original formation 

 having frequently taken place during the earliest geological 

 periods of our planet. With the assistance of the data supplied 

 by geology and mineralogy, it is often possible to assign the 

 origin of a given mineral to some definite geological period and 

 to arrange a series of different individuals roughly in the order 



*Phil. Mag. (6), v, 576 (1903). 



f " In the naturally occurring minerals containing the radio-elements these 

 changes must have been proceeding steadily over very long periods, and, un- 

 less they succeed in escaping, the ultimate products should have accumulated 

 in sufficient quantity to be detected, and should therefore appear in nature 

 as the invariable companions of the radio-elements." — Rutherford and Soddy, 

 loc. cit ^ 



fPhil. Mag. (6), iv, 582. 



Am. Jour. Scl— Fourth Series, Vol. XX, No. 118. — October, 1905. 



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