Precipitated silicas

A process for the production of the precipitated silica with the following physicochemical parameters:

• ______________________________________ BET surface area 35 to 350 m.sup.2 /g BET/CTAB surface area ratio 0.8 to 1.1 Pore volume 1.6 to 3.4 ml/g Silanol group density (V.sub.2 = 6 to 20 ml NaOH consumption) Average aggregate size 250 to 1500 nm CTAB surface area 30 to 350 m.sup.2 /g DBP value 150 to 300 ml/100 g V.sub.2 /V.sub.1 by Hg porosimetry 0.19 to 0.46 DBP/CTAB 1.2 to 2.4 ______________________________________
• said process comprising mixing water and commercial water glass to form a dilute solution having a pH of 8-9, simultaneously adding concentrated sulfuric acid and a solution of commercial water glass to the dilute solution at a precipitation temperature in the range 60.degree. to 95.degree. C. while continuously stirring and maintaining pH at a value of 8 to 9 to cause a reaction between the alkali silicate and mineral acid which forms a precipitation suspension, continuing the reaction to a solids concentration in the precipitation suspension of 90 to 120 g/l, adjusting the pH value to less than or equal to 5, filtering out the precipitated silica, washing and drying.