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electrodes with different quantities of mercury may be made before- 
hand, and then they may be immersed in a non-aqueous solution 
of an aluminium salt, to determine the electric potential. 
Without entering here further into the method of experimenting, 
we will state already now that the coexisting electrolyte is always 
relatively richer in aluminium than the mixed crystal, so that it 
could be deduced with certainty from this that the E,X-figure of 
the system Al-Hg belongs to the second type. . 
But what is remarkable is that though in virtue of the concen- 
tration of the coexisting phases it would be expected that the potential 
of the Aluminium in an Al-salt solution becomes less negative on 
addition of a little of a mercury salt, just the reverse takes place, 
and even to a very considerable degree. 
This exceedingly remarkable phenomenon shows that, as was 
already pre-supposed before, the mercury dissolved in aluminium is 
a catalyst for the internal conversions in the aluminium. The metal 
magnesium, which is being examined by Mr. Beck, behaves in an 
analogous way, but the effects are less. 
In a following communication we shall enter more deeply into 
the interesting phenomenon mentioned here. 
Laboratory for General and Inorganic 
Chemistry of the University. 
Amsterdam, June 1920. 
