48 ADVENTURES IN RADIOISOTOPE RESEARCH 



fractions, those of scandium oxide, sodium chloride, and calcium 

 oxalate, were then determined. The two first mentioned preparations 

 were found to be active, the activity of the scandium oxide decaying 

 very slowly and that of the sodium chloride fraction having a half-life 

 of 10 to 16 hours. The activities are due to the formation of |fiSc and 

 t|K respectively ; the reactions leading to these products are 



liSc + Jn = IfSc 

 and 



45 

 21' 



Sc + on = ilK + la 



The mass numbers occuring in these equations follow from the fact 

 that scandium has only one stable isotope, ^^Sc. The calcium oxalate 

 investigated was inactive ; we are thus unable to find any evidence 

 for the reaction IfSc + Jn = loCa -{-\B. which possibly takes place also. 

 The activity which cannot be separated from scandium is presumably 

 due to iiSc ; most of this activity decays with a period of about two 



months 



While \IK emits hard ^-rays having a half value thickness of 0.19 

 gm/cm2 Al, 2iSc emits soft /^rays with a half value thickness of 0.01 gm/ 

 cm2 Al. 



Yttrium 



We investigated (2) samples of yttrium oxide kindly given us by the 

 late Baron Auer v. Welsbach, by Prof. Prandtl, and by Prof. Rolla. 

 The two first named preparations were used some time ago by Honig- 

 SCHMiD to determine the atomic weight of yttrium and investigated 

 by one of us on that occasion by X-ray spectroscopy. While the investi- 

 gation of Baron Auer's preparation revealed the presence of some 

 dysprosium, that of Prandtl was found to be of the highest purity. 

 The great purity of this preparation and of that of Rolla was also 

 shown by their behaviour under neutron bombardment : No initial 

 decay with the period of dysprosium (2.5 h.) could be observed, the sole 

 period being one of 70 h., which we found to be the period of decay of 

 yttrium. Auer's preparation decayed initially with a half-life of 2.5 h.. 

 which was obviously that of dysprosium ; but afterwards it showed a 

 70 h. period like the other preparations. The molecular volumes of 

 corresponding compounds of yttrium and dysprosium are only very 

 slightly different*, so these elements are unusually closely related chemi- 



* The volumes of the octahydrosulfates differ by less than 0.8% (G. v. Hevesy, 

 Z. anorg. Ch. 147, 217 ; 150, 68 (1925) and the ionic radii by about the same amount 

 (V. M. GoLDSCHMiDT, Ullrich and Barth, Oslo. Acad. Proc. Nr. 5 (1925). 



