70 



ADVENTURES IX RADIOISOTOPE RESEARCH 



and by Walke( 12), under bombardment with fast neutrons the following 

 two reactions occur as well : 



MSc+5n = MSc + 3^n 

 ifSc + in = llSc + 2 In 



the scandium isotopes obtained emit positrons and have half- lives of 

 4 and 43 hours respectively ; it was presumably the last mentioned 

 reaction which we observed. 



Scandium 44 was also produced (13) by the action of a-particles on potas- 

 sium 41 and (11) by the action of deuterons on calcium 43, w hile scandium 43 

 was produced (1 1) by the action of a-particles on calcium 40, and (2) by the 

 action of deuterons on calcium 42. 



Walke was furthermore successful in producing scandium 42 under 

 the action of a-particles on potassium 39, and of scandium 41 under the 

 action of deuterons on calcium. The list of the known radioactive iso- 

 topes of scandium is seen from Table 5. 



Table 5. — • Active Isotopes of Scandium 

 (According to Walke [11]) 



We measured the reduction of counts when covering an active scandium 

 preparation decaying with a period of 90 days with aluminium foils 

 of varying thickness. The result obtained can be seen from Table 6. 



Table f>. — Absorption in Aluminium of the /S-rays 

 Emitted by Scandium 



(half- \aluc thic-kncss : 13 ± 1 mgm/cm'') 



