ARTIFICIAL ACTIVITY Oi' JIAIWII'M AM) SOMK OTllKK ELEMENTS 



69 



paraffin block, 1 Ik^ second one in a paraffin l)iock but Avil h 1 he preparation 

 surrounded by a shield of cadmium, which al)Sorbed nearly 100% of 

 the C-neutrons, and th(> 1hird one with fast neutrons. The result of the 

 activation of the first named sample is seen from Fi^. 3b. The investig- 

 ation of the second sample led to the result thai in the presence of 



~i I 1 1 r 



20 40 60 80 100 



200 days 



Fii^. 3. Dot-ny Curve of .Scandium InadiatL-d in a Paraffin Block for 



a) 24 Dav.s h) .'>() Davs. . 



cadmium the artificial radioactivity of scandium is reduced to 2% of 

 the value obtained in the absence of cadmium. From Fig. 3 there 

 follows for the half-life period of scandium the value 90 zb 5 days. 

 Quite recently Walke (11), by making use of Lawrence's powerful cyclo- 

 tron, bombarded scandium with deuterons and obtained a period of 

 85 i 2 days. 



We want furlhermorci to mention an early experim(>nt in which we 

 bombarded scandium with fast neutrons emitted by a mixture ol 

 600 millicuries emanation and beryllium powder ; we observed a period 

 of decay of about 50 hours. As shown by Pool, Cork, and Thornton (8). 



