53 



murh more quickly here than for pure Al, but not yet so rapidly 



as for Ag. 



Amalgamated Aluminium. 



That the amalgamated aluminium goes into solution much more 

 rapidly than the non-amalgamated aluminium also appears from 

 what follows. If a new aluminium electrode is put in the just men- 

 tioned mercury layer, which covers the bottom of the vessel with 

 the Al3(S04)3-solution, this electrode assumes the mercury potential. 

 The tension difference with the auxiliary electrode is then namely 

 -f- 0,6 Volt, which tension difference is also found when a plati- 

 num electrode is used instead of an aluminium electrode. If the same 

 experiment is, however, made with an amalgamated Al-electrode, 

 (he tension difference with the auxiliary electrode is — 0,78 Volt. 

 It follows from this that if the ordinary aluminium partially immer- 

 sed in mercury, failed entirely to maintain its potential difference 

 with respect to the electrolyte in consequence of too slow solution, 

 the amalgamated aluminium does not quite succeed in this either, 

 but it almost succeeds, for instead of — 1,27 Volts its tension with 

 respect to the auxiliary electrode has namely become — 0,78 Volt. 



It is perhaps not superfluous to elucidate this phenomenon in a 

 few words. With immersion of the aluminium electrode in the mer- 

 cury a short circuited element aluminium-electrolyte-mercury is obtai- 

 ned, in which the aluminium is the negative pole, and therefore 

 sends ions into solution. If now the setting in of the internal equili- 

 brium took place with great rapidity, the aluminium would be able 

 to maintain its unary potential difference, and in this case the ten- 

 sion of this electrode with respect to the auxiliary electrode would 

 have remained — 1.27 Volts. Now we find — 0,78 Volt, proving 

 that the state of internal equilibrium was disturbed to a certain 

 extent after all, and the metal has become a little less base by 

 dissolving. If, as was described, the same experiment is made with 



