ELECTROCHEMICAL THERMODYNAMICS 735 



ramifications which would develop upon considerations of the 

 variations of these quantities with temperature and pressure. 

 Suffice it to say that everything comes back to the experimental 

 evaluation of the chemical potentials of electrolytes, which 

 would have been impossible without the fundamental contribu- 

 tion of Gibbs. 



Retrospect and Prospect 



We have emphasized the completeness and exactness of 

 Gibbs' treatment of the perfect electrochemical apparatus. If 

 we work in the spirit of the original method, then we must 

 eliminate uncertainties inherent in the use of cells such as those 

 containing liquid junction potentials. The invention and use 

 of the concentration cell without liquid junction is an excellent 

 illustration of an exact method of study. However, the power 

 of this experimental method only becomes apparent when we 

 introduce the chemical potentials and develop the general 

 thermodynamics of Gibbs in its relation to such cells. But 

 even this has not been enough. Extra-thermodynamical con- 

 siderations which must be experimentally verified and finally 

 proved by fundamental electrostatic theory have been required, 

 and will continue to be necessary before the intricate subject of 

 the nature of the ionic state in solutions will be unravelled and 

 explained. But there will be nothing in these modifications to 

 detract from the value of the contribution of the first master of 

 this subject. 



