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The stability of colloidal alumina in the presense of selected inorganic anions (NO3-, Cl-, I-, SO42-, and [Fe(CN)6]3-) has been studied by a potentiometric titration technique. The dependencies of the critical concentrations of coagulation on the solution pH were determined for all studied anions, as well as the regions of coagulation and stability of the system. It has been shown that the critical concentrations of coagulation decrease along with an increase in the pH, which is interpreted by coagulation theory and the electrical layer model. Differences between the critical concentrations of coagulation at the same pH value for monovalent anions are explained based on their hydration degree differences, while the discrepancies between the experimental data and the theoretical values given by the Schultze–Hardy law are interpreted in light of specific sorption of sulfate anions and the general specificity of the investigated system. Based on a parallel stability study of colloidal alumina prepared in the laboratory and of a commercial product, the same stability behavior in the presence of KCl has been found.