312 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



the strong acids and bases, however, the experimental data indicate that 

 the speed of one of the ions, at least, undergoes a marked change at 

 concentrations below 10~ 2 N. The nature of the process to which this 

 change is due remains uncertain. 



8. Reactions in Electrolytic Solutions. Electrolytic solutions, in 

 water at least, are characterized by the speed with which they take place, 

 as well as by their reversibility. This property of electrolytic solutions 

 has been cited in support of the ionic theory; and, indeed, the reactions 

 among electrolytes clearly indicate some common condition as a result 

 of which they take place with great facility and, as a rule, with the 

 accompaniment of a comparatively small energy change. It is only in 

 a few other systems that reactions similarly take place with great speed, 

 and many of these are irreversible. Reactions in fused salts and in the 

 metals, however, resemble those in electrolytic solutions in many re- 

 spects. There is little question but that reactions in fused salts are ionic 

 in character. While available data are extremely meager in the case 

 of the metals, there is evidence which indicates that here, too, reactions 

 may be ionic. 



In a few instances, in water as well as in some other solvents, solu- 

 tions of electrolytes do not reach equilibrium at once when an elec- 

 trolyte is dissolved. In those cases which have been studied in detail, 

 it has been shown that intermediate reactions occur which greatly influ- 

 ence the properties of the solution; so, for example, certain of the metal- 

 ammonia salts, when first dissolved in water, yield solutions which are 

 very poor conductors of the current, but which, on standing, show a 

 marked increase in conductance. Here, unquestionably, the gradual 

 increase of the conductance is due to a reaction as a result of which the 

 metal-ammonia complex is affected. The original complex is not capable 

 of ionization, while the resulting product is ionized. These particular 

 reactions are accounted for by Werner's theory. Aside from a few cases 

 of this type, solutions of electrolytes reach a condition of equilibrium 

 as soon as the process of solution is completed. 



It will be unnecessary, here, to discuss reactions in aqueous solutions 

 since these are familiar to everyone who has studied the elements of 

 chemistry. Since solutions in non-aqueous solvents are ionized, we may 

 expect that similar reactions take place in solutions in these solvents. 

 The nature of the reactions will, of course, depend upon the nature of 

 the solvent as well as upon that of the dissolved electrolytes. 



The multiplicity of electrolytic reactions in aqueous solvents is in 

 part due to the electrolytic properties of water itself. As we have seen, 

 water is ionized to a slight extent into hydrogen and the hydroxyl ions. 



