ELECTROMOTIVE FORCES IN PYRIDINE 51 



ELECTROMOTIVE FORCES AND ELECTRODE POTEN- 

 TIALS IN PYRIDINE AND ITS BINARY MIXTURES 

 WITH WATER, METHYL ALCOHOL AND 

 ETHYL ALCOHOL. 



F. S. MORTIMER AND J. N. PEARCE. 

 HISTORICAL. 

 The systematic study of the electromotive forces in non-aqueous 

 solvents was begun by Jones, 1 By using cells of the type: 



Ag-AgNO, aq -AgN0 3 non-aq- A g 



with the same concentration of the salt in each solvent, he hoped 

 to be able to calculate the degree of dissociation in the non- 

 aqueous solutions. It soon became apparent, however, that the 

 solution pressure of a metal varies from solvent to solvent. Sub- 

 stituting the values found by Vollmer 2 for the degree of dissocia- 

 tion of silver nitrate in ethyl alcohol, he calculated the ratio of 

 the solution pressure of silver in alcohol and in water to be be- 

 tween 0.021 and 0.024. In all of these measurements the alcoholic 

 solutions are positive with respect to the water solutions. 



Kahlenberg 3 measured the electrode potential of ten different 

 metals in 0.10 N solutions of their salts in about thirty solvents. 

 The electrodes dipped into the solutions which were contained 

 in open vessels, connection between the cells being made by strips 

 of filter paper. The diffusion potential was neglected and ap- 

 parently no definite temperature was maintained. From his re- 

 sults, which he stated were only qualitative in nature, he con- 

 cluded that the solution pressure varies not only with the different 

 solvents and their mixtures, but also with the nature of the dis- 

 solved substances. He also tested and found that Faraday's 

 laws hold for non-aqueous solutions. 



Wilson 4 measured the electromotive forces of concentration 

 cells in alcoholic solutions of silver nitrate at both 0° and 25°. 

 While the values of the electromotive forces calculated from con- 

 ductivity data deviated somewhat from those experimentally 

 determined, he concluded that the Nernst equation will be found 

 to hold as well as in non-aqueous solutions. 



J Zeit. physik. Chem., 14. 346, 1894. 

 dissertation, Halle, 1892. 

 3 Jour. Physical Chem., 3, 379, 1899. 

 'Am. Chem. Jour., 35, 78, 1906. 



