82 MR. S. W. J. SMITH ON THE NATURE OF ELECTROCAPILLARY PHENOMENA. 



first described. Fig. 9 shows a curve for n KI, and another for the same solution, 

 with the exception that the \n KI, in which the capillary was first immersed, was 

 replaced by n KNO,, the degree of dissociation of which is 16 per cent, less than that 

 of in KI. The calculated potential difference between n KNO, and \n KI is rather 

 less than '001 volt an amount which would be barely perceptible on the scale to 

 which the curves are drawn-i-so that the appreciable separation between the parallel 

 portions of the curves is most probably due in part to the effect of the different 

 concentrations of the potassium ions upon the surface tension. 



Fig. 9. 



tpoo 



ZjOOO 



,000 



4000 



5,000 



6,000 



Since it is beyond the purpose of the present paper to deal with the quantitative 

 nature of the possible ion effects upon the surface tension, it will be unnecessary to 

 give further instances which show that the observed surface tension is, in general, 

 partly determined by the chemical nature of the solution. It may, however, be 

 remarked that there is nothing unusual in the supposition that as the potential 

 difference reckoned from the solution to the electrode increases, the kation effect 

 becomes pronounced, while conversely, when it diminishes, the anion effect becomes 

 increasingly evident. For if the potential difference be altered in the above sense, 

 through a sufficient range, we get an obvious combination of the mercury with the 

 anion (and not simply a molecular layer of the compound) on the one hand, and Avith 

 the kation (amalgam) on the other. Whether the formation of these compounds 

 proceeds suddenly when the potential differences between the solution and the 

 electrode reach certain amounts, or whether they are gradually led up to through 

 intermediate stages in which the surface films contain only molecular quantities of the 

 compounds, of gradually-increasing concentration, is a question concerning the answer 

 to which we have imperfect knowledge. 



