72 IOWA ACADEMY OF SCIENCE 



The electrode potentials have been determined for the same 

 solvents at both temperatures. They are much higher in water, 

 methyl alcohol and ethyl alcohol than in pyridine. In all sol- 

 vents they are highest in the most concentrated solution, de- 

 creasing rapidly with the first dilutions and then almost linearly 

 with further dilution. The electrode potentials in the binary 

 mixture of pyridine with each of the other solvents decrease 

 very rapidly with the first addition of pyridine. With further 

 increase in the per cent of pyridine the values decrease gradu- 

 ally to that in pure pyridine. For the water pyridine series, be- 

 ginning with twenty-five per cent pyridine, the decrease in the 

 value of the electrode potential is linear with the per cent of 

 pyridine. 



The average temperature coefficients of electrode potentials 

 have been calculated for each of the pure solvents and their 

 binary mixtures. All are found to be positive except those in 

 the dilute solutions in pure water. In water-pyridine mixtures 

 the temperature coefficients increase continuously to the value 

 in pyridine. In both alcoholic mixtures with pyridine they go 

 through maximum values. 



The heats of ionization of silver in the pure solvents and their 

 binary mixtures are found to be much higher in water, methyl 

 alcohol and ethyl alcohol than in pyridine. As the per cent of 

 pyridine is increased in its mixtures with each of the other sol- 

 vents, the heat of ionization decreases at first very rapidly and 

 then more slowly to its value in pure pyridine. 



The solution pressure of silver nitrate has been calculated 

 for each of the pure solvents. It is much higher in pyridine 

 than in either of the two alcohols or water. 



Physical Chemistry Laboratory, 

 The State University op Iowa. 



