68 



ADVENTURES IN RADIOISOTOPE RESEARCH 



Walke (10) while reproducing Fermi's results and also ours as to the 

 preparation of ^^K from scandium, was unable to reproduce our ex- 

 periments in which ^"-^K was prepared from calcium. This negative result 

 induced us to repeate our experiments, this time by bombarding with 

 fast neutrons as much as 1 kgm of calcium carbonate. These were dissolved 

 in a minimum amount of HCl, precipitated by a minimum amount of 

 ammonium oxalate, which sufficed to precipitate all calcium after 

 dissolving 100 mgm of sodium chloride as carrier. Before we finished 

 these experiments, a second paper of Walke (12), (13), was publis- 

 hed in which he describes succesful experiments in producing ^'-K 

 from calcium, thus corroborating our statement. 



ACTIVITY OF SCANDIUM 



After the removal of the radio-potassium produced, the scandium 

 was still showing a weak activity which could not be removed by 

 chemical operations and which is possibly due to a radioactive isotope 

 of scandium. The decay of the weak activity of scandium observed for 

 240 days is seen from Table 4, which shows the presence of a very 

 weak activity decaying with a period longer than a year. We could 

 not follow up this very weak activity further but concentrated our inte- 

 rest on another period obtained after activating for 24 days in a 

 paraffin block which contained emanation-beryllium sources of an 

 average strength of 50 millicuries. The result obtained is seen from 

 Fig. 3a ; the half- life works out to be 90 i 5 days. 



Table 4. — Activity of a Scandium .Samplk aktkr Removal of 



Potassium 



In the nexl sv\ of experiments we activated simultaneously three 

 scandium preparations for 50 days with radium -])eryllium sources of 

 a strength of about 200 millicuries : one in tli(> usual way inside the 



