Patent ID: 7803341

Claim:
Fine dry silica particles obtained by an inter-flame reaction of a siloxane compound without containing halogen in the molecules thereof, and having a BET specific surface area of 20 to 55 m 2 /g, wherein the water suspension containing said fine silica particles at a concentration of 1.5% by weight has an optical absorbance τ for light of a wavelength of 700 nm satisfying the following formula (1): τ≦240S −1.4 −0.07 (1) wherein S is the BET specific surface area (m 2 /g) of the fine dry silica particles, wherein said find dry silica particles have an iron content of less than 20 ppm, an aluminum content of less than 5 ppm, a nickel content of less than 5 ppm, a chromium content of less than 5ppm, a sodium content of less than 3 ppm and a chlorine content of less than 3 ppm.