THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Art. XL. — On Ionium, a JVew Radio-active Element; by 

 Bertram B. Boltwood. 



[Contributions from the Sloan e Physical Laboratory of Yale University.] 



In a preliminary paper published about five mouths ago* it 

 was stated that a highly radio-active substance, which differed 

 in general properties from any of the known radio-elements, 

 could be separated by certain chemical operations from ura- 

 nium minerals. In the present paper it will be shown that 

 the earlier conclusions were correct, and that there occurs in 

 uranium minerals a previously unidentified radio-element hav- 

 ing distinctive physical and chemical properties. 



Introduction. 



The discovery of a new radio-element, " actinium," was an- 

 nounced by Debierne in two papers which appeared in the 

 Comptes rendus de V Academie des sciences for October, 1899, 

 and April, 1900 f. In these papers, which were characterized 

 by the lack of precise experimental details and the absence of 

 explicit statements, the chemical properties of actinium were 

 described as very similar to those of thorium, from which it 

 had not been found possible to separate it completely. The 

 following reactions;}; were given as characteristic for the new 

 substance : 



(1) Precipitation in hot solutions, slightly acidified with 

 hydrochloric acid, by an excess of sodium thiosulphate. The 

 active matter is contained almost entirely in the precipitate. 



* Boltwood, this Journal, xxiv, 370, 1907; Nature, lxxvi, 544, 589, 1907. 

 f Vol. cxxix, p. 593 ; vol. cxxx, p. 906. 



\ It will be noted that the first three reactions given are characteristic for 

 thorium. 



Am. Jour. Sci. — Fourth Series, Vol. XXV, No. 149. — May, 1908. 

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