Mi; S. W. J. SMITH ON TIIK NA'ITIIK <'F I.I.Ki I 'l;< CAl'II.l.AKY I'HKNo.MKNA. Ill 

 In a cell of the type 



M,X, MX. 



II-: 



let ir ni and ir nt be the respective potential differences between mercury and the 

 solutions (calculated on the Helmholtz theory of the capillary electrometer), and let 

 7T r . l>e the potential difference between the liquids and TT, the observed E.M.F. of the 

 cell, then we should have 



"ft = ""it, fl"*, ~\~ f|2' 



ROTHMUND has made observations upon cells of this type and has found values for 

 ir t , TT,,, and TT^ for a number of different solutions. The following table gives the 

 results of some of his experiments : 



He estimates the possible error in the determination of ir Hl and ir ni from the curves to 

 be not greater than O'Ol volt.* 



Referring to such experiments, NERKST says : " While, therefore, the Ilelmholtz 

 hypothesis concerning electrocapillarity is found to be in good agreement with the 

 osmotic theory ... as far as the qualitative side of the phenomena goes, we come 

 upon ferious contradictions so soon as we proceed to a quantitative OomparMOO. As 

 results of the electrocapillary meth<xl of measuring contact potentials, we obtain the 

 following table : 



Ha 



KCl 

 KC1 

 KCl 

 KCl 



11,80, 

 HQ 

 KCNS 

 KI 



025 

 022 

 IGl 

 247 

 419 



010 

 028 

 000 

 000 

 000 



Column 1 gives the symbols of the solutions examined ; column 2 contains the 

 values of the potential differences between them deduced from the Helmholtz theory 

 of the electrometer ; and column 3 gives the values of the same potential differences 

 calculated according to the osmotic theory. The differences are great, and not 

 explicable as errors of observation."! 



* RoTHMrsn, 'ZeiU. f. Physik. Chemie,' 15. 

 t NKRNST, ' Wicd. Ann.,' 58, Bcilage, 1896. 



