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



applied between the electrometer terminals was about a tenth of a volt. The probuMc 

 error of each of the box resistances was less than a tenth per cent., and the constancy 

 of the potentiometer current was tested by means of a standard Clark cell, of which 

 the E.M.F. at 15 was known to be within one-tenth per cent, of 1'434 volts. 

 The accuracy of the potential measurement was therefore considerably greater than 

 that which could be conveniently given to the surface tension observations. 



(d.) The Ekctrocapillary Curves for KC1 and KI. 



1. Preliminary Experiment. Before proceeding to the experiments of the ordinary 

 capillary electrometer type, mention may be made of a simple means by which very 

 suggestive results as to the relation between capillary curves may be obtained. 



A vessel for containing the solution is constructed of the shape shown in the figure. 



Fhe mercury forming the large electrode is placed at the bottom of the main tube. 

 The point of the capillary is brought within the smaller tube. The vessel is first 

 filled with a solution of one of the salts (say JnKI), and the capillary curve is 

 determined. Withdrawing air from the apparatus by means of the side tube at the 

 top of the main tube, the liquid rises in the latter and falls in the narrow tube. After 

 the small tube has been nearly emptied, it is filled to the level of the liquid in the 

 main tube with a solution of the other salt (say JnKCl), and the capillary curve is 

 again taken. 



Fig. 5 shows the forms of the resulting curves for the solutions in question. The 

 numbers from which the curves were constructed are as follow : 



