562 



Professor Svante ArrJienius 



[June 3, 



Ostwald sbows in a most convincing manner the correctness of the 

 views of the theory of electrolytic dissociation. 



It has been objected to this theory, that according to it it might 

 be possible by diffusion to separate both ions, e.g. chlorine and 

 sodium, from another in a solution of sodium chloride. In reality 

 chlorine diffuses about 1 • 4 times more rapidly than sodium. But 

 the ions carry their electric charges with them. Therefore if we 

 place a solution of sodium chloride in a vessel and we pour a layer 

 of pure water over it, it is true that in the first moments a little 

 excess of chlorine enters the water. By this the water is charged 

 negatively, and the solution under it positively, so that the sodium 



Per m ana aruxtts 

 Fig. y. 



ions are driven out from the solution with a greater force than I the 

 chlorine ions. As soon as that force is 1*4 times greater than this, 

 the chlorine ions travel just as slowly as the sodium ions. It is not 

 difficult to calculate that this case happens as soon as the chlorine 

 ion is contained in the water in an excess of about the billionth part 

 of a milligramme over the equivalent quantity of sodium. This ex- 

 tremely minute quantity we should in vain try to detect by chemical 

 means. By electrical means it succeeds pretty well, as Nernst has 

 demonstrated experimentally for his concentration elements. There- 

 fore, the said objection is valid against the hypothesis of a common 

 dissociation of the salts, but not against a dissociation into ions, that 



