Amorphous precipitated silica products and method for their production

A method for producing amorphous, precipitated silicas having improved chemical and physical properties including high abrasiveness and low wet cake moisture content prior to the drying thereof, said method comprising the steps of:

• acidulating an aqueous solution of an alkali metal silicate having an SiO.sub.2 /X.sub.2 O mol ratio in the range of from about 2.0 to 2.7 wherein X is selected from the group consisting of sodium, potassium, and lithium with an acid selected from the group consisting of sulfuric acid, nitric acid, and hydrochloric acid;
• said aqueous alkali metal silicate solution having a concentration on the order of about 1.0 to 2.5 pounds silicate per gallon, said acid being added as a dilute solution thereof and having a concentration of from about 10 to 25% by weight acid based on the weight of the solution thereof;
• continuing the addition of said acid until that point at which precipitation of said silica just begins;
• interrupting and discontinuing the addition of said acid to said silicate at said point;
• aging the resulting aqueous reaction mass for a period of time sufficient to obtain an equilibrium condition of the reactants comprising said reaction mass;
• continuing the addition of said acid to said aqueous mass following said aging period while simultaneously adding an alkali metal silicate therewith and until the precipitation of said silica is complete, adjusting the pH of the mass to acid, separating the precipitated silica from said aqueous reaction mass and recovering the precipitated silica material.