The surface of @-Al2O3 is inert because it is dehydroxylated and hence cannot develop surface charge. Hence ,catalysts based on @-Al2O3 have typically low dispersion. Interaction between support and catalyst precursor can be affected by the combination of precursor and support used. When the support surface is negatively charged in solution, as is the case with silica,the metal will not be adsorbed if is contained in the anion, as in H2PtCl6, but will be adsorbed if it is present in the cation, as in [Pt(NH3 )4]Cl2. No adsorption occurs even when [Pt(NH3 )4]Cl2 is used as the precursor if the pH is below 6. Silica has a zeta-potential value of almost zero for pH 0-6, indicating that in this pH range the charge of the surface is practically zero, and hence it behaves as an inert support. The above picture of the support-precursor interaction is simplistic, but it provides a framework within which the behavior of a large number of support-precursor systems can be understood.