Die durch die Anwesenheit von Eisen(III)-ionen bedingten Phasengleichgewichte kristalliner Aluminiumhydroxide des Nordstrandits,Hydrargillits und Bayerits

The investigation of ageing processes of coprecipitated aluminium and iron hydroxides—Al_0,5Fe_0,5(OH)₃, initially amorphous, reveals the major influence of Fe³⁺-ions on the transformation steps among the aluminium hydroxides.By combined X-ray and IR examination it has been found that the ageing of amorphous aluminium hydroxide in the presence of iron ions leads to the surprising coexistence of all known, well defined crystalline trihydroxide species of aluminium, namely nordstrandite, gibbsite and bayerite. Iron ions for their part transform from amorphous stage of hydroxide at the beginning into hydrohematite.The change in temperature orpH conditions of the milieu, or the change of both the parameters results in only one or two modifications from those aluminium hydroxides mentioned above.