Emulsions EI containing aq. Na2SiO3 and cyclohexane and EII containing aq. HCl and cyclohexane, each containing a nonionic unsaturated oxyethylenated fatty alcohol (RO(CH2CH2O)(n)H, R = C-16-C-22, n = 7), prepared at 19,000 rpm, were dosed, EI into EII, at 10,000 rpm at room temp. Silica released as a third emulsion was destabilized at 80degreesC and, after the org. phase had been distilled off, filtered, dried 48 h/105degreesC, and surface-modified 1h with 3-mercaptopropyltrimethoxysilane (I) prehydrolyzed (to avoid aging) in (4:1) MeOH-H2O, and the solvent was distilled off. As I was increased, 0, 3, 5, and 10 wt. parts, bulk d. rose, 168 to 285 g/L, absorption of H2O, paraffin oil, or dibutyl phthalate fell, sp. surface and pore volume rose and then fell, pore size was almost unaffected, and inbuilt C and S rose. The modified SiO2 showed enhaced hydrophobicity and dispersion.