When only weak precursor-support interaction exists, the support acts merely as a physical surface. In this case, the catalyst dispersion is typically lower than in the case of strong interaction. Metal particles develop though crystallization of precursor in the pore-filling solution during solvent evaporation. Crystallite sizes are dictated by mass transfer during precipitation-crystallization of the dissolved component, which in turn is controlled by the conditions during solvent evaporation . Weak precursor-support interaction can be encountered in the following cases: (a)the support is inert,(b) the precursor ion has the same charge as the support surface,(c) the support is in a range of pH where it is not charged,(d) the adsorption sites of the support are occupied.