and therefore: 
RT C : 
A ian ea stadse Fe Rients 
which is the well known formula of Nernst. This formula repre- 
sents A as dependent on the concentration ¢ of the Hig sate in the 
solution. C is a constant. 
If we express A in Volts, and introduce Briggian logarithms, we 
get as a factor 0,0002, and the equation becomes: 
1 
C 
A =0,0001 Tlog—. . . . 1. « (28) 
For mercury at 18° the quantity C is 10-237, when we namely 
++ 
put ¢=1 for normal concentration of the Hgs-ions. For normal 
solutions we get therefore as the value of the difference of potential 
CP ize 291" 2): 
A = 0,0291 x — 33,7 = — 0,980 Volts, 
as also NEUMANN and others have found [with the exceedingly 
ont 
small concentration of Hg, Cl, in an normal KCl-solutions, A=—90,616 
Volts (OsTWALD)]. 
From formula (2e) it is clear, that A will reverse its sign, when 
e= C, 1.e. 10- “normal. 
III. Let us now calculate the surface-tension as a function 
of A or a. 
de 
Fig. 3. 
To that purpose we increase the surface s virtually with an element 
ds. In that element a new state of the surface must be established. 
We have called @ the total increase of the thermodynamic energy 
per unit of surface, accompanying this change; therefore an increase 
of the surface with ds will involve an increase in energy with 
Qe vereen tr ere) 
