254 On the Nature of Electro-capillary Phenomena. 



a. The form of the electro-capillary curve is remarkably dependent 

 upon the nature and concentration of the electrolyte, and depolarisa- 

 tion is quite insufficient to account for the dependence. 



'!). The conclusion that the potential difference between the solution 

 and the capillary electrode is zero when the surface tension has its 

 maximum value, leads to the necessity for assuming large potential 

 differences between certain solutions. 



4. The hypothesis that the potential difference between equally con- 

 centrated solutions of potassium chloride and iodide is negligible 

 possesses a high degree of probability. It has been shown by previous 

 observers that if this hypothesis be true the points of maximum surface 

 tension on the electro-capillary curves for the above solutions cannot 

 have the significance which Helmholtz's theory gives them. 



It is shown in the paper that the first hypothesis of the Lippmann- 

 Helmholtz theory is in striking accord with this hypothesis concerning 

 the potential difference between KC1 and KI when the very definite 

 "descending" branches of the electro-capillary curves are considered. 



5. If both the hypotheses just mentioned be true, we get the result 

 that the surface tension of mercury (for a certain range of potential 

 differences) in two solutions is the same for a given potential difference 

 between the mercury and the respective solutions, if the solutions are 

 equally concentrated and possess the same kation. 



6. An extension of this result shows that it is indifferent whether the 

 kation be K, Na, or H. 



7. The relation found for the KC1 and KI curves can be extended 

 to the other known cases in which the electrometer curves and liquid 

 potential difference calculations seem to be contradictory, in such a 

 way as to account for the apparent contradiction. Several of the cases 

 are examined. 



8. The results in 4, 5 r and 6 would give a direct and accurate method 

 of finding the potential differences between equally concentrated solu- 

 tions, and could be extended to the case of solutions of different con- 

 centrations. 



9. The probability that the electro-capillary curves are never com- 

 pletely free from influences other than electrostatic is shown by an 

 examination of the relations between the curves for unequally concen- 

 trated solutions of the same salt. 



10. In confirmation of results obtained by G. Meyer, in a slightly 

 different way, it is shown that if the potential difference between KC1 

 and KI is very small, the potential fall from a half normal solution of 

 KI to a dropping electrode of the Paschen type is about a quarter of a 

 volt greater than that from a half normal solution of KC1 to the same 

 electrode. 



In the same way the potential fall from KI to mercury when the 

 surface tension is a maximum is about a quarter of a volt greater than 



