1492 
able phenomenon, viz. this that though e.g. for a base metal the 
solubility of the metal ions is very great and those of the electrons 
very small, the solubility product of a base metal possesses a com- 
paratively large value. 
The case we meet with here, is quite independent of all others, 
because in the solubility product of a metal, metal ions and electrons 
occur, which influence each other and carry each other along, so 
that they neutralize each other electrically except for a very small 
fraction. 
It is now clear that where the solubility of the metal ions is 
very great, and that of the electrons very small, the metal ions will 
not go into solution so much as when the electrons did not check 
the action, and that reversely the electrons will go more into solution 
than when they were not attracted by the metal ions. Thus the 
eaceedingly remarkable case presents itself that the liquid coexisting 
with a base metal, is unsaturate as far as metal ions are concerned, 
but supersaturate with respect to the metal as far as electrons are 
concerned. This is accordingly the reason why the metal is negative 
with respect to the liquid. For a noble metal exactly the reverse is 
found. Thus we see that according to these considerations a much 
clearer idea of the electromotive equilibrium can be obtained than 
was the case with the old view. 
The equation (28), which was as onesided as equation (26), which 
was used up to now, can be of great service to us in many cases. 
We have already seen that a noble metal, so a metal with a 
very smal! solubility product, immerged in a solution of a mixture 
of a ferro- and ferri salt, is not attacked. With regard to the said 
solution the metal is an unassailable electrode, and electrons of the 
equilibrium 
VAA HCO Ne Jey Eee ONO! nee en an (6) 
pass from the solution to the metal, while the ionisation equilibrium 
of the metal shifts. 
Here where the two homogeneous equilibria in the solution have 
only one component, viz. the electrons, in common, the application 
of our electron equation (28) immediately gives the potential difference, 
when we consider that from equation (9) follows: 
je CE A ODE (29) 
(Be) 
hence : 
(Or) = K Ce) 
