Boltioood — Ionium , a New Radio-active Element. 367 



was, however, given later by Halm,* who showed that they 

 were due to the existence of a product which Hahn named 

 "radio-actinium." It is interesting to note, in passing, that 

 Marckwald states that the thorium precipitated from a solution 

 of rare earths containing "emanium" was at first highly active 

 but had lost its activity some months later. 



The question of the similarity of actinium and emanium is 

 discussed by Debierne in the Physikalische Zeitschrift of Jan- 

 uary 1, 1906. This paper adds little to the information con- 

 tained in earlier publications, but the following quotationf 

 is of interest : 



" Ich muss hinzufugen, dass ich mich bei alien meinen Ver- 

 suchen darauf beschrankt habe, nur Praparate zu verwenden, 

 die nach einer gewissen Zeit eine konstante Aktivitat behielten. 

 Von diesen Praparate enthielten einige erhebliche Betrage an 

 Thorium. . . . Der Name Aktinium muss fur die neue Sub- 

 stanz vorbehalten bleiben, die die Anfangsursache cler Padio- 

 activitatserscheinungen ist. Was die Gieselsche Substanz 

 anbelangt, so habe ich schon gezeigt, dass sie mit Aktinium 

 identisch ist, und diese Identitat wird jetzt allgemein zugegeben. 



" Ich will nochmals daran erinnern, das in meiner ersten 

 Mitteilung liber Aktinium (C. r., April, 1900) die fallung mit 

 seldenen Erden als eine der Eigenschaften der neuen Substanz 

 angegeben ist : . . . [doch] habe ich hinzufiigt, ' dass man 

 jedoch nicht versichern konne, ob die aktive Substanz das Tho- 

 rium bei alien seinen Peaktionen begleiten wiirde'." 



The identity of the emanations evolved by preparations of 

 actinium and emanium has been demonstrated by a number of 

 experimenters. Our knowledge of the physical and chemical 

 properties of the actinium products is due chiefly to the 

 researches of Hating and Levine.§ 



In the papers published by Hofmann and Zerbanf much 

 stress was laid on the differences in activity shown by thorium 

 preparations which had been obtained from certain minerals 

 containing various proportions of uranium.' Not only were 

 marked differences noted in many instances, but the subse- 

 quent behavior of certain of these preparations was quite irreg- 

 ular, some of the preparations losing and others gaining in 

 activity. In some cases what was believed to be an entirely 

 inactive thorium salt was obtained,!^ and the authors reached 

 the conclusion that the specific activity of thorium was depend- 

 ent solely on the amount of uranium with which it was associ- 



* Ber. d. chem. Ges., xxxix, 1605, 1906 ; Phil. Mag., xiii, 165, 1907. 

 f Phys. Zeitschr., vii, p. 16. 

 j Loc. cit. 



§ Phys. Zeitschr., vii, 513, 812, 1906 ; ibid., viii, 129, 1907. 

 || Ber. d. chem. Ges., xxxv, 531, 1902 ; ibid., xxxvi, 3092, 1903. 

 ^[Also Hofmann and Strauss, Ber. d. chem. Ges., xxxiii, 3126, 1900. 



