THE IXTEKMOLECULAK KXCKAXGE OF ATOMS OF THE SAME KIM) 1 (jT 



5. Lead Chloride (Active) and Tetraphenyl Lead in Pyridine 



Tetraphenyl lead, Pb(CgH5)4, can be prepared in accordance with the 

 <lcscription by P. Pfeiffer and P. Truskier^. The compound can be 

 recrystallized from hot pyridine or amyl alcohol. 



Tetraphenyl lead (1.70 gm) and then 0.92 gm of lead chloride were dissol- 

 \ (hI in 95 ml of pyridine at the temperature of the boiling water bath 

 and, after heating for l^ hr, the solution was cooled to about 35° C. 

 A mixture of the two substances crystallized from which the lead chlor- 

 ide was extracted by boiling with water. The lead chloride showed the 

 same activity as before the experiment. 



Measurement with 0.180 gm of each substance : Lead chloride before 

 the experiment, 7.39 scale divisions per min ; lead chloride after the 

 experiment, 7.32 scale divisions per min. 



6. Plumbous Acetate (Active) and Tetraphenyl Lead in Amyl Alcohol 



Some acetate (0.70 gm) and 1.00 gm of the tetraphenyl compound were 

 dissolved in 70 ml of hot amyl alcohol and the solution w^as kept near 

 its boiling point for 15 min. Crystallization of tetraphenyl lead took 

 place gradually on cooling and became complete overnight. The filtered 

 product was thoroughly washed with amyl alcohol, ethyl alcohol and 

 hot water, in succession, and dried in a vacuum desiccator. This sample 

 proved to be completely inactive whereas a sample of the lead acetate 

 prepared as a standard was very radioactive. 



Measurement with 0.800 gm of each substance: Tetraphenyl lead after 

 the experiment, less than 0.02 scale divisions per min ; lead acetate 

 (standard substance), 180.0 scale divisions per min. 



7. Lead Nitrate (Active) and Diphenyl Lead Nitrate in Dilute Ethyl Alcohol 



Diphenyl lead nitrate crystallizing with two molecules of water, viz. 

 (r6H5)2Pb(N03)2 + 2 HgO, was prepared by the method of A. Polis^ 

 by adding tetraphenyl lead to nitric acid. 



1 P. Pfeiffer and P. Truskier, Ber. dtsch. chem. Ges. 37, 1125 (1904) ; cf. 

 K. A. Hoffmann and V. Wolfl, Ibid. 40, 2428 (1907). 



'^ A. PoLis, B. 20, 717 (1887). This information was confirmed by P. Pfeiffer 

 and P. Truskier, Ber. dtsch. chem. Ges. 37, 1125 (1904). — The observation already 

 made by Polis that the formation of diphenyl lead nitrate is disturbed by the 

 appearance of dark coloured substances when the hot concentrated nitric acid 

 is cooled a Httle below its boiling point is an interesting one. Only the boiling 

 acid can therefore effect the smooth course of all intermediate steps since, other- 

 wise, the reaction takes a diffcient coiirsc. 



