At greater current densities Al^Oj can separate from this solution 

 of oxygen in aluminium, but then the electrode is no longer reflect- 

 ing, and it cannot be made reflecting again by cathodic polarisation. 

 This layer of Al^Og can also possess a great resistance, but the 

 primary feature of tlie phenomenon is in all cases the formation of a 

 solution of oxygen in aluminium, which possesses a great resistance. 



If we now proceed to the description of the experiments with 

 amalgamated aluminium, we will begin with stating that when in 

 the just described experiment the aluminium electrode was raised 

 out of the mercury, after amalgamation had set in, and the lower 

 opening of the auxiliary electrode was placed against the extremity 

 of the aluminium wire, this part of the aluminium had undergone 

 a great change, and had become negatively electrical with respect 

 to the auxiliary electrode. The tension difference amounted to — 0.9 

 Volt, and still increased slowly. At the place where the aluminium 

 had been in contact with the mercury, it had therefore become 

 much baser, and had visil)ly become somewhat amalgamated. 



That amalgamated aluminium is baser than the non-amalgamaled 

 metal, was known, but the exact value of this dilference in tension 

 was not met with in the literature. To determine this difference in 

 tension, an aluminium electrode was amalgamated by immersion in 

 a solution of HgCl,, after which this electrode was compared with 

 the auxiliary electrode. We found that the amalgamated Al obtained 

 in this way was still baser than the just mentioned Al, for the 

 tension of this electrode with respect to the auxiliary electrode 

 amounted now to — 1.27 Volts. 



That the amalgamation for aluminium has a very particular effect 

 follows moreover from this that amalgamated aluminium possesses 

 a much greater chemical reactive power than the ordinary alumi- 

 nium. Amalgamated aluminium immersed in water gives a very 

 considerable generation of hydrogen, and it oxidizes so rapidly when 

 exposed to the air that the metal is immediately covered with a 

 layer of oxide, the liberated heat raising the temperature of the metal 

 very noticeably. 



In consideration of all this it seems more than probable to us 

 that the action of mercury is here positively catalytic, and that mer- 

 cury therefore, when dissolving in aluminium, brings the metal in 

 internal equilibrium, which condition corresponds to a greater con- 

 centration of the simpler, so more reactive kinds of molecules. 



The anodic polarisation of the amalgamated state is almost as 

 slight as for silver, as a proof that the internal equilibrium sets in 



