ELECTROLYTIC DISSOCIATION 35 



"osmotic" theory of voltaic electricity has been based and 

 substantiated by experiment. (Nernst.) 



6. Conversely, any difference of electrical potential in the 

 solution must produce a motion of the ions. Here we have 

 the Clausius hypothesis of electrolysis. The introduction of 

 electrodes disturbs the equilibrium of the solution, the posi- 

 tive ion moves to the cathode, where it gives up its charge, 

 while the negative ion does the same at the cathode. It is 

 only when the ions are relieved of their charges that they are 

 capable of attacking the metal of the electrodes, or of de- 

 composing water, causing the well-known secondary effects; 

 charged, and in the paralyzing presence of an opposite charge, 

 they are supposed to be incapable of doing this. In this 

 connection may be cited an experiment which appears in- 

 comprehensible unless free ions are assumed to exist in the 

 solution. Dilute sulphuric acid, contained in a flask whose 

 exterior was coated with tin foil, was connected by a wick 

 with aLippmann electrometer; upon giving a positive charge 

 to the exterior of the flask the electrometer indicated the 

 presence of positive electricity, and some bubbles of hydro- 

 gen were evolved near it. Consequently, the flask, being a 

 modified Leyden jar, negative ions (SO 4 ) had collected on the 

 interior, while the corresponding hydrogen had been driven 

 over toward the electrometer. 



7. Properties like density, refractive power, capillarity 

 and viscosity of saline solutions, whose numerical values ap- 

 pear to depend upon the sum of two factors characteristic of 

 the acid and of the metal, should show this additive nature 

 best where the salts are most dissociated; this appears to be 

 the case. 



8. We have now to consider the chemical side of the 

 hypothesis, and we are met by the startling assertion that 

 those acids show the greatest degree of dissociation which we 



