The acid-base properties of GaAl12 and GeAl12 molecules have been investigated and compared to those of the Al-13 molecule using alkalimetric titration at two concentrations of the Keggin complex. As in the case of Al-13, the positive charge of both GaAl13 and GeAl12 is entirely lost within half a pH unit if the concentration of the Keggin molecules is low (1.25 muM). We find that GeAl12 is significantly more acidic than either the GaAl12 or the Al-13 molecules. As positive charge is removed from the Keggin complexes by deprotonation, they tend to aggregate, resulting in titration curves that flatten out at higher Z values. Molecule-molecule interactions appear to be more distinct at elevated concentrations of the Keggin complexes (12.5 muM).