Ml!. S. W. .1. SMITH ON TIIK NATURE OP ELECTUOCAPII.I. \n I'HKNnMENA. 83 



IlKLATION BETWEEN THE ELECTROCAPILLARY CURVES FOR KC1 AND KI AND 

 DROPPING ELECTRODE MEASUREMENTS FOR SOLUTIONS OP THESE SALTS. 



There is a point in connection with the explanation <4' dropping electrode 

 phenomena which, as it is closely connected with the question of the potential 

 difference between KC1 and KI, may perhaps be mentioned here. If it be granted 

 that the potential difference between KC1 and $n KI can be considered negligible, 

 it follows from the experiments described below that the potential difference between 

 dropping mercury and KC1 (under the conditions described by PASCHEN) is very 

 different from that between dropping mercury and KI. And, at the same time, it 

 follows that if the potential difference between a KC1 solution and mercury is zero 

 when the surface tension is a maximum, then, when the latter is a maximum in KI 

 solution, the potential difference from the solution to the electrode has a considerable 

 magnitude. 



The result obtained by PASCHEN* (following up the experiments of OsrwALDf) for 

 chlorides and iodides, among other salts, that the E.M.F. required to produce the 

 maximum surface tension for a given solution is practically identical with the E.M.F. 

 of a cell containing the same solution and having as electrodes a similar large mercury 

 electrode to that used in the electrometer, and a dropping electrode of which the jet 

 becomes discontinuous in the surface of the solution seems, at first sight, a striking 

 confirmation of the Helmholtz theory of the electrometer. But, in fact, it is suffi- 

 cient for this result that the potential difference between mercury and the solution 

 when the surface tension is a maximum is the same as the potential difference 

 between the dropping electrode (of the Paschen type) and the solution. 



A dropping electrode and a capillary electrode were connected up as in the 

 diagram. 



U 



* PASCHEN, ' Wied. Ana.,' 41, 1890. 

 t Of. OSTWALD, ' Lehrbuch,' 2, 938. 



M _' 



