Very slow partial neutralization of 5 × 10−4 to 6 × 10−2 M solutions of AlCl3 and Al(ClO4)3, using either finely ground dolomite or NH3 as the base, resulted in the formation of polynuclear hydroxyaluminum cations without the appearance of any solid phases. Certain properties of the polynuclear cations did not change and no solids formed during an aging period of two years. The properties of the polynuclear cations examined were their rate of reaction with 8-hydroxy-quinoline and hydrolysis constants using formulas suggested in the literature. In contrast, the concentration of the polynuclears decreased, although very slowly, during aging. This decrease was accompanied by the appearance of a second type of polynuclear hydroxyaluminum cation, which apparently has the same OH/Al mole ratio but is much less reactive than the first type.