THE ACTION <)1" XKITROXS OX THE RAHE EAKTH ELEMEXTS 



53 



This element shows an activity having a long- life as first stated by 

 RoNA (6) who finds 1hat the /?-rays emitted are half absorbed by 0.015 

 cm Al. E. Neuningek and 1^]. Roxa* found recently a period of 4 



300 



100 



50 



30 



lOOr 



50 



Lu 



\ 



30 



20 



10 



V- 



Lu 



\' 



10 



20 dav5 



10 20 30 «) 50 



100 davs 



Fif,'. 2. I.utecium Decay Curve. 



a) showing the sliort period and the beginning of the 7 days' period. 



b) showing the measured points for the 7 days' period and the curve 



obtained after subtracting the residual activity. 



(± ^2) months. After bombarding 100 mgm TmOg, kindly lent us by 

 Prof. Jantsch, w ith about 100 mc for 23 days we obtained 60 counts per 

 minute, while 100 mgm of dysprosium activated to saturation with the 

 same source gave about 4000 counts per minute. The activity of this 

 preparation decayed with a period of about 3.5 months ; a thulium 

 preparation activated to saturation would therefore exhibit an activity 

 about i/j„ of that of dysprosium. 



Ytterbium 



The activity of ytterbium (2), (3) decays with a period of 3.5 h. 

 As ytterbium has the isotopes 171, 172, 173, 174, and 176, it cannot be 

 decided whether the activity is due to the formation and decay of ^7oYl> 



*E. Neuninger and E. Ro>a, Wien. Anz. 73, J",;) (1936). 



