Theory of Electrolytic Dissociation. 281 



It is well known that a finite electromotive force is needed 

 to effect electrolytic decomposition ; but, when the process is 

 examined more closely, it is found that the reverse electro- 

 motive force of polarization exists only at the electrodes. If 

 this reverse force is eliminated, by the use of alternating 

 currents or otherwise, the conduction proceeds in conformity 

 with Ohm's law, that is, the current is proportional to the 

 electromotive force, so that any force, however small, causes 

 a corresponding current. Thus within the liquid there are 

 no reverse forces of polarization, and consequently no work 

 is done by the current in causing reversible electrolytic 

 separations. The freedom of passage indicated by the facts 

 of electrolysis must therefore exist, whether a current flows 

 or not ; the function of the electric forces is merely directive, 

 and the only work expended is done against that frictional 

 resistance to the motion of the ions which is called the ionic 

 viscosity. 



So far our results show that under all conditions the ions 

 possess the freedom necessary for their passage through the 

 liquid. That freedom may, however, on the facts enumerated, 

 be secured by a possibility of interchange between the 

 oppositely electrified parts of two dissolved molecules at the 

 instant of collision, or to the successive formation and decom- 

 position of molecular aggregates. Let us trace the con- 

 sequences of such suppositions. 



In accordance with the elementary principles which hold 

 o-ood for the chance encounters of a large number of moving 

 particles,, the frequency of collision, or the number of mole- 

 cular aggregates formed per second, will be proportional 

 to the square of the number of dissolved molecules. Now, 

 on the view suggested, the motion of the ions, and therefore 

 the average ionic mobility, will depend on such chance 

 collisions, and be proportional to the frequency with which 

 they occur. The velocity of the ions under a given potential 

 gradient will thus be proportional, approximately at any rate, 

 to the square of the concentration of the solution. The 

 quantity of electricity conveyed per second under a given 

 electromotive force, that is, the conductivity of the solution. 

 must depend on the product of the relative velocity of the 

 ions and the number of ions per unit volume. It follows 

 that, on any hypothesis of molecular interchanges, the con- 

 ductivity of a solution will be approximately proportional 

 to the cube of the concentration. This result i> quite contrary 

 to observed facts. In dilute solutions, the conductivity is 

 nearly proportional to the first power of the concentration, 

 and. as the concentration increases, the conductivity usuallv 



