78 MR. S. W. J. SMITH ON THE NATURE OF ELECTROCAP1LLARY I'HKNO.MKNA. 



Fig. 8 shows the electro-capillary curves for half-normal, one-tenth normal, and 

 one-twentieth normal solutions of potassium and sodium chlorides. In every case the 

 mercury of the large electrode was covered with a layer of calomel before the intro- 

 duction of the solution into the electrometer cell. The appreciable departure of the 

 curves from one another at the lower surface tensions may be partly due to the 

 appreciable effects of depolarization, since the conductivity of a KC1 solution is about 

 20 per cent, greater than that of the corresponding NaCl solution. Apart from this 

 departure at lower surface tensions, it is seen that the curves for corresponding 

 solutions coincide within the limits of experimental error. 



If we are to assume that the kations K and Na affect the surface tension in the 

 same way, the E.M.F. of the cell of the type 



Hg 



NaCl j KC1 

 HgCl HgCl 



Hg 



should be merely the potential difference between the solutions. 



The following are the calculated potential differences between the solutions and the 

 observed RM.F.s of the cells : 





