134 



ADVEXTTIRES IN RADIOISOTOPE RESEARCH 



page 130. This quantity is determined as follows : The retarding power 

 of lead and of chlorine for a-radiation is known, whence the range of u- 

 radiation in PbClg can be obtained. The ranges of a-radiation and recoil 

 particles in air are known. On the assumption that the ratio of the 

 ranges in air is equal to the ratio in lead chloride, the range of recoil 

 particles in lead chloride calculated from the above data is 7.5 X 10-^ cm. 



-5 

 'S 



-7 



-S 



-9 



-10 



-11 

 logD 



~^^ 125° 150° IPS'* 200° 225° 250° 275° 300° t 



Fig. 2. Self-diffusion of Pb in PbClg and Pbl.^. a Strahlon = a-iadiation 

 RuckstoBstrahlen = recoil radiation 



in the discussion of the experiments with Pbig a method will be described 

 which permits experimental testing of the correctness of the above 

 value. In order to make sure that vaporization effects have not influ- 

 enced the results experiments have also been performed at reduced 

 pressure and these have yielded the same results as those at the ordinary 

 pressure. 



Attempts to condense TliB oxide or sulphide instead of the chloride 

 were made, in order to obtain information on the effect of a possible 

 incomplete formation of ThB chloride on the experimental results. It is 

 evident from Fig. 1 that the results were not essentially different, owing 

 to the fact that the lead ion surrounded by many chlorine ions soon loses 

 its oxygen partner. The treatment of the PbOlg pellet with chlorine or 

 HCl. after condensing the active material, is also without effect on the 

 result. 



