881 
Al, Al” 436, 
Hence the resistance that remains when aluminium is made from 
anode to cathode, is chiefly the resistance of the coating of Al, O,. 
In the earlier paper cited here a great resistance was simply 
assigned to the solid solution of oxygen in aluminium, and too little 
stress was laid on the fact that the strong disturbance of the 
aluminium may iead to the formation of an aluminium surface that 
is very poor in ions and electrons. 
Since 1914 researches on the electromotive behaviour of aluminium 
have been made in my laboratory, first by Miss Riw1in, and after- 
wards continued by Mr. pr Gruyrer, both as regards commercial 
aluminium and amalgamated aluminium. 
Working with very pure commercial aluminium, the polarisation 
and the curves of activation in different aluminium-salt solutions, 
have been determined, in which again, just as with iron, the strongly 
positively catalytic influence of halogen-ions came to light. 
A closer examination of the valve action is in progress, and also 
the thermic and electromotive investigation of the system mercury- 
aluminium. In connection with this investigation there are other 
thermic and electromotive investigations being made on systems 
mercury-metal, as mercury-magnesium, mereury-tin ete. As a pecu- 
liarity it may be mentioned here that, as was already found by 
De Leeuw®) in tin, mercury exerts an accelerating influence on 
enantiotropic conversions, so that, where a point of transition in the 
pure metal is not, or hardly, to be observed, this is generally very 
clearly seen on addition of a little mercury. | 
A good example of this is furnished by aluminium, for which a 
point of transition at + 580° was found with great clearness from 
the investigations of amalgams rich in aluminium. 
Also with a view to this the investigation mercury-metal with 
other important metals will be continued. 
General Anorg. Chemical Laboratory 
of the University. 
Amsterdam, Jan. 30, 1920. 
» 
1) These Proc. 
55” 
