108 ADVENTURES IN RADIOISOTOPE RESEARCH 



A weight of 1 .00 gm of lead nitrate and 1 .59 gni of the diphenyl compound 

 wore dissolved in 30 ml of 48 % hot alcohol in the presence of two drops 

 of dilute nitric acid. Since there was no deposit within ^ hr, the solution 

 was evaporated almost to dryness on a w-ater bath and the crystalline 

 mixture taken up in 30 ml of 95 % hot alcohol, lead nitrate then being 

 deposited on controlled cooling. This was treated six times with boiling 

 absolute alcohol and dried in a vacuum. A sample of the original lead 

 nitrate served as the standard sample. 



Measurement with 0.355 gm of each substance : Lead nitrate before 

 the experhnent, 5.55 scale divisions per min ; lead nitrate after the 

 experiment, 5.80 scale divisions per min. 



S uiuniary 



(1) It has been found that organically bound lead atoms do not undergo 

 intemiolecular place exchange in a homogeneous phase. 



(2) Such place exchange occurs to an extent corresponding to that calculated 

 from probability when the lead atoms are dissociable. 



(3) Radioacttive indicator methods were employed to obtain these results. 



