The impact of the dissolved quantity of aluminum on the calculation of surface charge from titration experiments of hydrated gamma-alumina was investigated. Two methods were developed to correct this effect: direct determination of aluminum in solution in batch titration experiments and application of a dissolution rate model in continuous titration experiments. There is a large effect of dissolution on surface charge determination for pH > 10 and pH < 4.5. Application of these correction methods to these pH ranges lead to apparent saturation surface charges of 1.3 and 2.3 at nm(-2), respectively. The last value seems to be the real proton-active site density, while the hydroxyl-active site density cannot be reached for easily achievable basic pH values. (C) 2003 Elsevier Inc. All rights reserved.