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I. 



Electrochemical Investigation of Liquid Amalgams of 

 Thallium, Indium, and Tin. 



BY THEODORE W. RICHARDS AND J. HUNT WILSON. 



INTRODUCTION. 



The change in free energy during a chemical reaction may be regarded 

 as composed of at least two separate quantities, one which may be said to 

 be due to the affinities involved in the reaction, the other depending upon 

 the relative concentration of initial substances and products. The calcula- 

 tion of the magnitudes of these quantities is a matter of prime importance, 

 for free energy is the driving agency of all earthly things. Unfortunately 

 the actual determination of changes of free energy is only possible in the 

 case of easily reversible reactions, and these form a comparatively small 

 part of many examples of chemical change. 



Of great theoretical importance in this connection are the reversible 

 galvanic cells, which involve in their action simply the dilution of liquid 

 amalgams, and consequently suffer no appreciable change of heat capacity. 

 The study of such cells can furnish much light upon the second of the two 

 independent quantities which together constitute the total free energy of 

 a reaction, namely, concentration effect. Von Turin pointed out the 

 analogy between such cells and the concentration elements first investi- 

 gated by Helmholtz and offered the first consistent theory of amalgam 

 cells. G. Meyer measured cells of this type, but much more accurate data 

 have been obtained at Harvard University. The object of this recent work, 

 which concerned itself with cells containing zinc and cadmium amalgams 

 over a considerable range of concentration, was to test the application of 

 the gas law to solutions of this type, as well as to apply the equations of 

 Helmholtz and of Cady to the data. Great accuracy was sought. Since 

 the two metals presented widely different phenomena, and since both of 

 these metals are bivalent, it seemed desirable to extend the work by meas- 

 uring similar cells, employing a wide variety of other metals with other 

 valencies. In this way a more complete survey of the possibilities would 

 certainly be obtained. 



