Several series of fumed silicas and mixed fumed oxides produced and treated under different conditions were studied in gaseous and liquid media using nitrogen and water adsorption-desorption, mass spectrometry, FTIR, NMR, thermally stimulated depolarization current (TSDC), photon correlation spectroscopy (PCS), zeta potential, potentiometric titration, and Auger electron spectroscopy methods. Aggregation of primary particles and adsorption capacity (V-p) decrease and hysteresis loops of nitrogen adsorption-desorption isotherms becomes shorter with decreasing specific surface area (S-BET). However, the shape of nitrogen adsorption-desorption isotherms can be assigned to the same type independent of S-BET value. The main maximum of pore size distribution (gaps between primary nonporous particles in aggregates and agglomerates) shifts toward larger pore size and its intensity decreases with decreasing S-BET value. The water adsorption increases with increasing S-BET value; however, the opposite effect is observed for the content of surface hydroxyls (in mmol/m(2)). Associative desorption of water (2(&3bond; Si-OH) -> &3bond; Si-O-Si&3bond; + H2O) depends on both the morphology and synthesis conditions of fumed silica. The silica dissolution rate increases with increasing S-BET and pH values. However, surface charge density and the modulus of zeta-potential increase with decreasing S-BET value. The PCS, H-1 NMR, and TSDC spectra demonstrate rearrangement of the fumed silica dispersion depending on the S-BET value and the silica concentration (C-SiO2) in the aqueous suspensions. A specific state of the dispersion is observed at the C-SiO2 values corresponding to the bulk density of the initial silica powder. (c) 2005 Elsevier Inc. All rights reserved.