54 IOWA ACADEMY OF SCIENCE 



They also determined the solution pressure of silver in each of 

 the three solvents, as well as the heats of ionization for the pure 

 solvents and their fifty per cent binary mixtures. 



In the hope that still further light may be thrown upon the 

 influence of solvent upon the electrochemistry of solutions, a 

 fourth solvent, pyridine, has been added to the series. To those 

 who are familiar with pyridine and its properties, little need be 

 said. Unlike the three liydroxy-compounds of the previous work, 

 its molecule has the ring structure with one nitrogen atom in 

 the ring. For many salts it is an excellent solvent and the 

 solution of these salts in pyridine is accompanied by a very con- 

 siderable evolution of heat. Silver nitrate, like many of these 

 salts, separates from its solution in pyridine with pyridine of 

 crystallization ; its power to form solvates of high complexity is, 

 therefore, obvious. Of the four solvents named, pyridine has 

 the smallest dielectric constant, yet with many salts it gives solu- 

 tions possessing fairly good electrical conductivity. 



In the present work the electromotive forces of concentration 

 cells and the electrode potentials of silver against solutions of its 

 ions have been redetermined for solutions of the metal in water 

 and the two alcohols at 0° and 25°. Further, similar data have 

 been obtained for solutions of silver nitrate in pure pyridine 

 and for its binary mixtures with water, methyl alcohol and ethyl 

 alcohol, respectively. 



MATERIALS AND SOLUTIONS. 



Water — The water used was prepared according to the method 

 of Jones and Mackay 11 . Repeated measurements showed it to 

 have a specific conductivity of approximately 2.0xl0- 6 mhos. 



Ethyl Alcohol — Ordinary 95 per cent alcohol was allowed to 

 stand over fresh quicklime for two or three weeks. It was then 

 decanted and distilled. The distillate was allowed to stand over 

 anhydrous copper sulphate for one week and then redistilled. 

 This distillate was refluxed with metallic calcium for ten hours 

 and again distilled. Finally, it was refluxed for two hours with 

 silver nitrate to remove aldehydes and other reducing agents. 

 The distillate from this treatment was collected and preserved 

 in dry glass-stoppered bottles, being protected from the air dur- 

 ing distillation by phosphorus pentoxide tubes. In each distilla- 



"Ara. Chem. Jour., 19, S3, 1897. 



