87 
phenomenon it seems desirable first to indicate the significance of 
this course of the potential. 
2. At first the aluminium electrode was immersed in the aqueous 
solution of Al,(SO,),, and then a solution of HgCl, was added. 
Directly after this addition aluminium goes into solution, and mercury 
is deposited, which will have been preceded by the discharge of 
Bsr toviie,. 
As bas been said the equilibrium-/,X-diagram of the system 
Al-Hg-electrolyte must belong to the type in which the potential of 
the three-phase equilibrium Al-phase-electrolyte-Hg-phase lies between 
the potentials of the two metals (in internal equilibrium), i.e. on 
addition of a mercury salt the solubility product of the aluminium 
decreases more greatly in the formula: 
0.058 Lal 
f= = log ar) ® 
if 
in consequence of mercury dissolving in the aluminium, than the 
relative concentration of the aluminiam-ions in solution, which 
remains even practically constant. 
Now it is clear that a certain time is required for the solution 
of mercury in the aluminium, and that in the very first moments 
there will be pure aluminium, on which mercury has precipitated. 
Hence at first La, will not have been changed by dissolved mercury, 
and as also (Aly) has practically remained the same, it might be 
expected that in the beginning / does not change. In this reasoning 
an important factor has, however, been overlooked, viz. the fact 
that the aluminium is attacked! Electrons and ions are withdrawn - 
from this metal with great rapidity when mercury is precipitated, 
and non-activated aluminium being a very inert metal, disturbance 
in noble direction can then oeeur. But this disturbance can only be 
observed for a short time, for the precipitated mercury will soon 
dissolve somewhat in the aluminium, and give rise to activation, 
which according to the more recent view means a conversion in 
the direction of the internal equilibrium. 
Hence a change of the potential in noble direction is followed by 
a minimum and a great change in base-direction. When once the 
aluminium has been activated, and has more or less reached the 
state of internal equilibrium, the equilibrium between the stable 
mixed crystal phase, the liquid mereury phase, and the electrolyte 
in the boundary layer will soon have been established, and the 
potential will remain constant for some time. 
As, however, the electrolyte in the boundary layer practically 
