ELECTROLYSIS AND ELECTRO-CUEMISTRY. 



241 



Thus, taking a combination arranged according to the scheme 



Ag I 0-1 AgNOa I 0-01 AgNOa | Ag 



in which silver electrodes are placed, one in decinormal and one in centi- 

 normal solutions of silver nitrate, we get from the sum of the electromotive 

 forces of its various junctions 



v+u 



P\ 



where jd, and p^ denote the osmotic pressures of the silver ions in 

 decinormal and centinormal solutions of silver nitrate respectively. 

 In the scheme 



Ho 



H&Cl, 



01 HCl I 0-01 HCl 



Hg,Cl, 



Hs 



we have the first and the last contact identical, so that we may consider 

 the 'depolariser,' mercurous chloride, as the electrode, and thus get a cell 

 whose action depends on the negative chlorine ions. Its electromotive 

 force will be 



By this method the following table was constructed byNernst,i giving 

 a comparison between the observed and calculated values of the electro- 

 motive force of concentration cells. C, and C, denote the concentration 

 of the two solutions in gram -equivalents per litre. 



The equations indicate that, in cells with both electrodes of the same 

 metal, the electromotive force will be greater if the concentration of the 

 ions of the metal in the solution round one electrode is made very small. 

 This can easily be Hone by placing the electrode in a solution which pre- 



1897. 



Zeitt. phynkal. Chevi. vol. iv. p. 161 (1889). 



