90 
aluminium mixed-erystal phase, which at the ordinary temperature 
is only a tew atom percentages, and in virtue of the fact that the 
electrolyte c practically contains no mercury, it may be expected 
that the line s, /, ¢ is situated only exceedingly little lower than 
the point a. But when as here in these investigations the electrolyte 
is a solution on which the activated aluminium acts, and the metal 
is, therefore, attacked with separation of mercury, the potential 
will yet be found too little negative either through disturbance or 
through change of the concentration of the metal phases, unless the 
state of formation of the hydrogen could annul this effect. 
As, however, the coexisting electrolyte of the three-phase equili- 
brium lies certainly very strongly one-sided on the aluminium side 
in the system Al-H-electrolyte, the state of formation of the hydrogen 
can here exert no appreciable influence on the potential. Our con- 
clusion is, therefore, that the observed maximum negative potential 
will be less strongly negative than that of the pure aluminium in 
the state of internal equilibrium. If the electrode has already been 
entirely mercurized locally, the potential will of course be found 
much too little negative. The most negative potential was found by 
immersion of an Al-electrode activated with mercury in a pure 
Al,(SO,),-solution. This was —1,58 with respect to the 1N calomel 
electrode or Hy = —1,29. Pure aluminium is always disturbed in 
noble direction, and to this we owe the usefulness of this metal 
for all kinds of technical and domestic purposes. Pure aluminium 
in the state of internal equilibrium would, indeed, be as unsuitable 
for these purposes as magnesium and calcium. 
Fig. 3. 
The further course of the potential after the maximum negative 
