60 PROCEEDINGS OF THE AMERICAN ACADEMY. 



from the cells so far measured seem of such value that I give them in this 

 preliminary jjaper, hoping to extend the investigation to other salts and 

 metals in the near future. 



For dilute water solutions the variation of the potential hetween a 

 metal and a solution of a salt, whose kation is the metal of the electrode, 

 is given by the well known Nernst formula,* 



^^ - ^^ = V ^°s« ^' 



where E^, E^, are the respective potentials for the concentrations C^, C, ; 

 R, the gas constant ; T, the absolute temperature; and m, the valency of 

 the metal. In the derivation of this formula the gas law, jo v= 11 T, is 

 applied to the dissolved salt, and complete dissociation is assumed. In 

 case the dissociation is not complete, Ci, Co, denote the concentration of 

 the dissociated part. 



For fused salts, in case the solutions are sufficiently dilute, we might 

 expect the same or an analogous formula to hold. Any experimental 

 evidence, however, for the applicability of the gas law to fused salt solu- 

 tions, or as to the amount of dissociation, has been lacking. 



Accordingly, the first question to be determined was whether or not, 

 for any measureable range of concentrations, the potential difference 

 would vary according to the Nernst formula. 



So far all my observations have been upon silver electrodes immersed 

 in fused mixtures containing varying amounts of silver salts. Most of 

 the cells measured were simple silver nitrate concentration cells of the 



type, 



Ag 



TiAgNOs 

 in 



a:oAgN03 

 y,KN03 + y^NaNOs 



Aff. 



The mixture of potassium and sodium nitrates, rather than either alone, 

 was used as solvent in order to obtain a lower melting point. 



Experimental. 



General. — In a few preliminary measurements I tried keeping the 

 temperature constant with an air bath, but was unable to attain much 

 constancy, and therefore substituted a vapor bath. The practical ar- 

 rangement of the cell in its constant temperature vapor bath is shown in 

 the opposite figure. 



* See Nernst, Zeit. fiir phjs. Cliemie, IV. 129, 1889. 



