THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



«©• 



[FIFTH SERIES.] 



MAY 1900. 



XL. Note on the Theory of Solution Pressure. 

 By S. R. Milner, D.Sc* 



THE theory of electrolytic solution pressures put forward 

 by Nernst accounts for the existence of a contact 

 difference of potential <P between a metal and an electrolyte 

 containing the metal ions at an osmotic pressure p^ of 

 amount 



RT 



.Pi 



*=^rkg£, (1) 



ne 



P 



ne being the charge passing through an electrode when a 

 gram ion of the metal is deposited electrolytically, and P a 

 constant depending on the nature of the metal. P is 

 generally taken as representing the actual pressure with 

 which metallic ions tend to go into solution ; though the un- 

 satisfactoriness of this view has been pointed out in a recent 

 paper in this Magazine by Dr. Lehfeldt f — the values of P 

 are in many cases so great that they cannot represent actual 

 physical pressures. 



Several thermodynamical proofs of Nernst's formula have 

 been given!. It seems to me that in general in these proofs 

 the mode of application of the second law is not perfectly 

 stringent, in that the electrical work done in passing a unit 

 charge through the surface is equated to the corresponding 



* Communicated bv the Author, 

 t Phil. Mag-., November 1899. 



1 Nernst, Theoretische Chemie, 2nd edit. pp. 665 ; Jahn, Gnoulriss 

 der Electrochemie, p. 194 ; Leblanc, Elevtrochemie, p. 153 (Eng. trans.). 

 Phil. Mag. S. 5. Vol. 49. No. 300. May 1900. 2 G 



