Dispersion comprising particles of a surface-modified, hydrophilic silica, where A) the particles of the surface-modified, hydrophilic silica comprise an aluminium atom and a hydrocarbon radical, a) the aluminium atom is bonded via an oxygen atom to a silicon atom of the particle surface, b) the hydrocarbon radical comprises a silicon atom which is bonded to a carbon atom of the hydrocarbon radical, c) possess an average particle diameter d50 in the dispersion of 40-200 nm, preferably 60-150 nm, and B) the pH of the dispersion is 8 or more.