6o 



ELECTROCHEMICAL INVESTIGATION OF LIQUID AMALGAMS 



The outcome may be stated as follows : The temperature coefficient of 

 the electromotive force of a cell made from liquid amalgams is as a matter 

 of fact approximately equal to the ideal potential of the cell (calculated 

 from the relative concentrations of the amalgams) divided by the absolute 

 temperature. The result is independent of the temperature: the increase 

 of potential is a linear function. This has already been shown experi- 

 mentally. 50 



One may well inquire concerning the ultimate significance of this 

 phenomenon ; and the following suggestion is offered as a tentative 

 explanation. 



In these cells, the change of heat capacity during the reaction is very 

 small. Hence according to the theorem recently advanced by one of the 

 present authors, 61 the free energy output of the chemical part of the change 

 may be expected to be equal to the total energy output, and both would 

 be expected to remain invariable with the temperature. Thus the part of 

 the electromotive force due to the chemical change would have no tem- 

 perature coefficient, and all the change of potential with temperature must 

 be ascribed to the change in the osmotic work. This would be expected 

 to be linear, and directly dependent upon the concentrations as it is actually 

 found to be, at least approximately. The rule would be expected to hold 

 only when no change of heat capacity occurs in the reaction. Thus these 

 troublesome and time-consuming measurements have shed new light upon 

 the mechanism of the galvanic cell, and have justified the labor expended 

 upon them. 



TABLE 18. Calculation of E. M. F., by Cody's Equation. 



* These are reduced to o from the observations at 23". 



This conclusion may be drawn from the table on p. 22. 



81 Richards, Proc. Am. Acad., 36, 300 (1902); Zeitschr. phys. Chem., 42, 138 

 (1902). This theorem has been elaborated by Nernst in a very interesting way. 

 (See Nernst's Silliman Lectures.) "Thermodynamics and Chemistry," page 56, 

 New York, 1907. 



