124 ACTION OF AQUEOUS AMMONIA ON 



equilibrium in which electrons migrate freely from one kind of 

 lead ion to the other. 



+ + + + ++-> ++ + + + + 



Pb^ + PB^ <r- Pba + PbB^ 



If this is a typical example of a general principle, we should 

 expect an analogous freedom of movement of electrons between 

 metallic mercury and mercuric compounds. Therefore in the 

 equilibrium Hg^CU^Hg + HgCU, no separation of isotopic forms 

 would be expected. 



In conclusion I wish to acknowledge my indebtedness to 

 P. D. AIcLarren, M. D., C. M., for the loan of the centrifuge 

 used in this investigation. 



References 



(1) E. Mitcherlich, Pogg. Ann., 29, 193 (1833); H. St. C. 

 Deville and L. Troost, Compt. Rend., 45, 821 (1857); L. Troost, 

 Compt. Rend., 95, 135 (1882); R. Rieth, Ben, 3, 666 (1870). 



(2) \V. Odling, J. Chem. Soc, 17, 211 (1864); H. De- 

 bray, Compt. Rend., 83, 330 (1868); E, Erlenmeyer, Liebig's 

 Ann., 131, 124 (1864); W. Harris and V. Meyer, Ben, 27, 

 1842 (1894); V. Meyer, Ben, 27, 3143 (1894); 28, 264 (1895). 



(3) A. Smith and A. W. C. Menzies, J, Am. Chem. Soc, 

 32, 1541 (1910); Zeit. phys. Chem., 76, 713"(1911). 



(4) H. B. Baker, J. Chem. Soc, 77, 646 (1900). 



(5) E. Beckmann, Zeit. anorg. Chem., 55, 175 (1907). 



(6) C. R. Bury, J. Am. Chem. Soc, 43, 1602 (1921). 



(7) T. Andrews, Phil. Mag., (3) 32, 321, 426 (1848). 



(8) F. W. Aston, Phil. Mag., (6) 39, 611 (1920). 



(9) R. J. Kane, Phil. Mag., (3) 11, 504 (1837). 



(10) C. Barfoed, J. Prakt. Chem. (2) 39, 214 (1889). 



(11) H. Saha and K. N. Choudhuri, Zeit. anorg. Chem., 

 67, 357 (1910). 



(12) J. G. F. Drnce, Chem. News, 123, 153 (1921); 126, 

 225 (1923). 



