FIELD: industrial inorganic synthesis. SUBSTANCE: silicate interacts with acidifying substance to form suspension that is then separated and solid product dried. According to invention, initial bath containing silicate and electrolyte is first formed and, prior to separation, reaction mixture is supplemented with aluminum compound. Separation of suspension is carried out by way of filtration and stratification, the latter operation being performed in presence of another aluminum compound. Precipitated silicon dioxide has specific surface 140 to 200 sq.m/g, oil absorption capacity less than 300 ml/100 g, average diameter of particles (after ultrasonic disagglomeration) below 3 mcm, coefficient of ultrasonic disagglomeration above 10 ml, aluminum content at least 0.35 wt %. Silicon dioxide obtained is designed for application as reinforcing agent in elastomers. EFFECT: improved rheological and mechanical properties of elastomers. 32 cl, 4 tbl, 8 ex
