mers 
leed | 
If, therefore, a current density prevails given by equation (9), the 
liquid just at the anode is saturate with Ag, (CN),, but not in more 
distant parts of the diffusion layer, as here the concentration of CN 
is greater, and the silver cyanide dissolves under formation of Ag (CN,). 
Hence the layer of silver cyanide will not become thicker for constant 
current density. 
If the current density is increased, not enough CN-ions will diffuse 
to the anode to form again complex ions with the Ag,(CN), formed 
by the nme Ag(CN),. Part of the cyanogen ions will now yield 
Ag,(CN), with the silver of the anode. This part will be the greater 
as the current density is greater. For a given value of the latter 
practically all the Ag(ON), and CN will be consumed to yield 
Ag,(CN), at the anode. For a still greater value of d the silver will 
then go into solution as Ag. 
So long as the Ag,(CN), is deposited only on the anode and not in 
the liquid, the following equation holds with close approximation : 
1 117 | 
ds) -{[D, (Ci—eta) + D, (C3—e3a) | sb te dots! 1 eee) 
or in connection with a and 1 
1 17 / VKL | 
de So ier D, (¢ rae “) | ve sa 
C2a 
This equation combined with: 
EBE=e + 0.058 "log c2a 
yields the current potential he 
When at last the current density becomes so great that the quan- 
tity of Ag(CN, and CN diffusing to the anode, is not great enough 
to maintain this current density, silver ions will also go into solution, 
which precipitate at some distance from the anode as Ag,(CN),. 
‘This corresponds then with the precipitation of AgCl in the liquid, 
as has been treated in § 4. These two cases are, however, not 
properly comparable, as at the precipitation of AgCl the liquid is 
everywhere saturate with AgCl, whereas in the case of Ag,(CN), 
the liquid in the diffusion layer is saturate with silver cyanide up 
to a certain distance from the anode, but not the whole liquid. 
Consequently an equation of the current potential line will hold here 
which agrees with that for AgCl in its main points, but not entirely. 
Fig. 2 gives the current tension line of a solution which is 0.1» 
with respect to Ag(CN), and 0.1n with respect to CN. The portion 
BA holds for cathodic polarisation, AZ for anodic - polarisation. 
