653 
Chemistry. — “Some Particular Cases of Current potential Lines.” 1. 
By Dr. A. H. W. Arrr. (Communicated by: Prof. F; A, 
HOLT.EMAN). 
(Communicated in the Meeting of June 24, 1916.) 
1. Zntroductton. When a metal is immersed in a solution that 
contains the ions of this metal, there arises between the metal and 
the solution a potential difference, which when equilibrium has set 
in, is given by the formula: 
0.058 
E = Vet — Vso, == €& + a Tog OPT vere ce (1) 
for a temperature of 18°, in which formula cis the concentration, 7 
the valency of the ion, and « the value that the potential difference 
has when the ion concentration is 1. 
If the metal is made cathode, the potential difference changes, 
and the change is the greater as the current density is greater. The 
line indicating the potential difference at the cathode (or anode) as 
function of the current density is the current potential line or more 
strictly speaking the currentdensitypotential line. The course of 
this line has been theoretically examined for some cases. For a 
theoretical treatment it is required in the first place that also for 
the electrolysis permanent equilibrium between the metal and the 
solution is assumed to exist, so that the above given equation is 
always valid. 
The change of / when the current circulates is then the con- 
sequence of a change of c, or «, or of both. As e is a constant for 
a given metal and solvent and at constant temperature and pressure, 
s can only change when the metal that deposits electrolytically, has 
other properties than the metal of the cathode, This is e.g. the case 
when the metal separates in another modification which is not in 
equilibrium with the first form of the metal, or when the inner 
composition of the metal is another. *) 
In the following considerations we shall leave out of account this 
possibility, henee we shall assume that # is constant, and examine 
in what way c depends on the current density, which then at the 
same time enables us to know the dependence of / on the current 
density. 
The simplest case is here that the dissolved electrolyte is entirely 
1) Smits and Arrr, These Proc. XVI, p. 699; XVII, p. 37 and 680; XVIII, 
p. 1485. 
