a colloidal dispersion having carrier particles of silica having a particle size from 3 nm to 100 nm to which silver ions have been adsorbed , preferably in an amount of 0 . 0005 - 5 silver ions per nm2 of silica particle surface . the surface of the carrier particles of silica suitably contains aluminumsilicate sites . it also relates to a process for making a colloidal dispersion comprising providing a silica sol , adding a solution of silver nitrate to the silica sol under agitation yielding a colloidal dispersion with silver ions adsorbed on the surface of the silica particles . the dispersion is usable as a biocide in e . g . coatings , adhesives and sealants , in surface treatment and impregnation of organic materials , in surface treatment and impregnation of inorganic materials , in textiles , garments and shoes , in medical disposables , in plastics and rubbers , in water and air purification , and in crop protection .