Dentifrice compositions

A dentifrice composition comprising the steps of:

• a. a precipitated silica, wherein said silica is prepared by the following steps:
• i) providing an aqueous solution of sodium silicate having a concentration of about 8.0 to 35 weight percent, and an Na.sub.2 O:SiO.sub.2 ratio of about 1 to 3.5:1;
• ii) providing a sulfuric acid aqueous solution having a concentration of about 6 to 35 percent;
• iii) charging to a reactor about 1 to 5 percent of the stoichiometric amount of said sodium silicate solution with agitation;
• iv) heating said solution of said sodium silicate to a temperature in the range of about 80.degree. to 90.degree. C.;
• v) slowly adding to said reactor, sulfuric acid and the remainder of said sodium silicate solution, said addition being conducted over a period of time wherein the sodium silicate is metered into the reaction mixture at the rate of about 7 to 12 liters per minute and the sulfuric acid is metered into the reactor at the rate of about 1 to 4 liters per minute;
• vi) continuing the addition of sodium silicate and sulfuric acid to said reactor over an addition time of about 40 to 60 minutes;
• vii) stopping the sodium silicate solution addition but continuing the sulfuric acid solution addition with agitation until a final pH of 5.0 to 5.8 is obtained in the reactor to provide a precipitated silica in the reaction liquor;
• viii) raising the temperature of said reaction mixture to a temperature of about 90.degree. to 98.degree. C. for a time of about 10 minutes to 1 hour while continuing agitation;
• and
• ix) curing the reaction mixture by boiling said mixture for a period of at least about 30 minutes to two hours to cause formation of substantially uniform particle size precipitated silica;
• x) cooling the reaction mixture and recovering the precipitated silica;
• and
• b. from about 0.1% to about 99% of an orally-acceptable dentifrice carrier.