Mi;, s. \v. j. SMITH ON im. X.UTIJK OF J-.u.rri;'n. \I-II.I..\KY I-III;MIMI.NA. <;; 



presumably independent of the nature of the anion ; hut it is obvious tli.-it we obtain 

 im in formation from the curves as to whet 1 MM- their sulisequent course is free from any 

 non-electrostatic influence depending UJMHI the kation. For the kation is the same 

 and of the same concentration in the two solutions. It is, however, easy to extend 

 the ahove observations so as to show that (granting the Nernst calculation gives ;it 

 least approximately the potential difference between unequally concent rated solutions 

 of the same salt), although the form of the lower portion <>f the descending curve 

 varies very little with the strength of tin- solution, yet the surface tension for a given 

 potential difference depends upon the strength of the solution. From this it 

 would appeal- that the surface tension does not depend upon the electrostatic effect 

 alone even when the anion effect has presumably disappeared ; but that, in fact, there 

 is also a kation effect which becomes evident as the solution becomes increasingly 

 positive with regard to the electrode. 



2. Final experiments showing tfte agreement of the first hypothesis of the Lippmann- 

 Ililmholtz theory ivith the Nernst-Planck theory of the potential difference between 

 KC1 and KI. We may, however, first apply to the ordinary electro-capillary curves for 

 equally concentrated solutions of KI and KC1, the result suggested by the curves 

 already given, that ultimately the descending branch of either curve is practically 

 unaffected by the nature of the anion, and that if it is then influenced by the kation, 

 the nature of the. influence is such that, in equally concentrated solutions of salts 

 possessing the same kation, the potential difference for a given surface tension is the 

 same in both solutions. It is found that the descending branches eventually 

 approximate very closely to parallelism. Considering the parallel portions, let IT, be 

 the E.M.F. required to be applied between the terminals to produce a given surface 

 tension for the KC1 solution, and let IT/ be the E.M.F. required to produce the same 

 surface tension for the KI solution. Then ir,ir.' is very approximately constant. Let 

 ;r H l)e the natural potential difference between the KC1 solution and mercury (the 

 electrode being considered positive to the solution), and let ' be the corresponding 

 quantity for theKI solution. Then on the first hypothesis of the ordinary electrometer 

 theory (applicable to any electrolytic cell), the potential differences between the solution 

 and the capillary for the two points of equal surface tension (one on each curve) are 



IT, ir n and ir,' ' 



respectively. Now if we suppose the potential difference is the same in the two cases 

 because the surface tension is the same, we get 



ir, ir n = IT, IT, 

 or 



TT. IT,,' = IT, ir t ' = a t 



where a, an observable quantity, is represented by the horizontal distance between 

 the parallel portions of the curves. Let now a cell be constructed of the form 



