CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF 

 HARVARD COLLEGE. 



SOME ELECTROCHEMICAL AND THERMOCHEMICAL 

 RELATIONS OF ZINC AND CADMIUM AMALGAMS. 



By Theodore William Richards and Gilbert Newton Lewis. 



Presented October 12, 1898. Received October 17, 1898. 



Introduction. 



The nature of amalgams, although a matter of much interest, especially 

 in the light of the modern theory of solutions, is still obscure. The 

 subject has been studied from the standpoint of electrochemistry by 

 several investigators, notably by Meyer, * who observed the electromo- 

 tive forces of cells of the following type: — Dilute zinc amalgam of 

 concentration x ; Solution of zinc salt ; Dilute zinc amalgam of con- 

 centration y. Since the total change in a cell of this kind consists in 

 the transfer of metal between amalgams of different concentrations, the 

 electrical energy obtained is equal to the maximum osmotic work obtain- 

 able by the process. On the assumption that the zinc in the dilute 

 amalgam obeys the laws of dilute solution, Meyer derived the following 

 expression : — 



^=L908|.riog-|; (1) 



in which E represents electromotive force ; ^, the electrochemical equiv- 

 alent, in grams, of the metal carried in one second from one amalgam 

 to the other ; J/, the molecular weight of the metal in the amalgam ; 



T^ the absolute temperature ; log — , the common logarithm of the ratio 



of concentration of the amalgams. By comparing with this formula the 

 experimental results, Meyer showed with sufHcient exactness that in 

 dilute amalgams the molecules of the metals studied by him are mon- 

 atomic. If, on the other hand, the atomic weight is substituted for M 

 in the formula, the agreement between the calculated and his observed 

 electromotive forces is not close enough to show whether the dilute 



* Zeitschr. phys. Chera., VIL 477 (1891), 



