Abstract: Silica base material for dentifrice having excellent transparency, prolonged stability, and desired abrasiveness; has a specific surface area of 270-500 m.sup.2 /g as measured by BET method and 5-60 m.sup.2 /g by CTAB method, gives virtually amorphous X-ray diffraction pattern after firing at 1100.degree. C., and has a refractive index of 1.455-1.470. This base material can be prepared by reacting an alkali metal silicate solution with hydrochloric acid or sulfuric acid in the presence of an electrolyte, controlling the ratio of the rate of addition of chloride ion or sulfate ion to be at least 3:2 between the acidification stage in which the pH at the completion of the reaction is brought to 3.5 or less, and the silica crystallization stage in which the pH of the reaction system if brought to 10.0, and carrying out the acidification stage within 30 minutes.

Abstract: The present invention provides a synthetic amorphous zirconium-bonded silicate obtained by reacting, as main starting materials, a water-soluble alkali-metal silicate with an inorganic zirconyl salt and a mineral acid, in which zirconium is bonded to silica at the ratio of ZrO.sub.2 to SiO.sub.2 being 0.1 to 10 weight percent, which silicate is useful as a dentifrice base material and also as a filler for rubber.

Abstract: Silica base material for dentifrice having excellent transparency, prolonged stability and desired abrasiveness, has specific surface areas measured by BET method and CTAB method of 5-60 m.sup.2 /g respectively with a difference therebetween of less than 40 m.sup.2 /g, and having a refractive index of 142-1.45. This base material can be prepared by reacting an alkali metal silicate solution with hydrochloric acid or sulfuric acid in the presence of an electrolyte in two stages, a silica crystallization stage in which the pH of the reaction system is brought to 10.0, and a neutralization stage in which the pH of the reaction system is brought to 8.0-6.5, completing the neutralization stage within 30 minutes and aging the neutralized mixture for at least 10 minutes. The ratio of the rate of addition of chloride or sulfate ions between the neutralization and crystallization stages is at least 5:3.