16 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



Hydrochloric acid, for example, in the pure state has a conductance even 

 lower than that of water. When dissolved in water, however, the con- 

 ductance of hydrochloric acid is much greater than that of ordinary salts 

 dissolved in the same solvent. This class also includes solutions of 

 various organic oxygen and nitrogen compounds in the liquid halogen 

 acids. This behavior, moreover, is not restricted to acids, since solu- 

 tions of many bases, such as ammonia, result from a mixture of two 

 components neither of which possesses considerable conductance in the 

 pure state. Where an electrolytic solution results from a mixture of two 

 components which are themselves non-conductors, it is probable that 

 reaction takes place when the two components are brought together, as 

 a result of which an electrolyte is formed. 



Apparently, electrolytic solutions result in all cases when typical 

 salts are dissolved in liquids up to sufficiently high concentrations. The 

 property of forming electrolytic solutions with dissolved salts is thus 

 not peculiar to water or solvents of the water type, but is a property 

 common to all fluid media. It is true that the phenomena are materially 

 altered as the nature of the solvent medium changes, but otherwise, if 

 the solutions are sufficiently concentrated, the order of the conductance 

 values will not differ greatly in different solvents. 



Among the various properties of the solvent medium which appear 

 to have a marked influence upon the properties of the resulting electro- 

 lytic solution, the dielectric constant stands out as the most important 

 factor. As the dielectric constant of the solvent medium decreases, the 

 conductance of the resulting solutions is altered, but the power to con- 

 duct the current is never lost, no matter how low the dielectric constant 

 of the solvent medium may be. Thus, solutions of salts of organic bases 

 in chloroform conduct fairly well. 



From the standpoint of the development of chemistry, solutions of 

 electrolytes are of first-rate importance. Electrolytic solutions exhibit a 

 variety of phenomena and admit of a variety of reactions which are not 

 to be found in the case of any other system of substances. A great 

 variety of reactions take place at the electrodes when solutions of elec- 

 trolytes are electrolyzed, and, when solutions of electrolytes are mixed, 

 reactions take place between the constituent electrolytes. Reactions be- 

 tween electrolytes are characterized by the extreme facility with which 

 they occur. It is only in exceptional cases that the rate of such reac- 

 tions is sufficiently low to admit of measurement. In solutions of elec- 

 trolytes, therefore, we are dealing essentially with systems in equilibrium. 

 This is of importance in their theoretical treatment, since thermodynamic 

 principles may be readily applied to systems in equilibrium. 



