thereof, fumed silica and dispersion

Pyrogenically produced silica powder having a BET surface area of 30 to 90 m It is prepared by mixing at least one vaporous silicon compound, a free-oxygen containing gas and a fuel gas in a burner of known construction, inflamed this gas mixture at the mouth of the burner and burns in the flame tube of the burner, the solid obtained is separated from the gas mixture and optionally purified, wherein the oxygen content of the gas containing free oxygen is adjusted such that the lambda value is greater than or equal to 1, the gamma-value is between 1.2 and 1.8, the throughput between 0.1 and 0.3 kg of SiO Dispersion containing powder of the invention. The powder can be used as a filler in rubber, silicone rubber and plastics. The dispersion can be used for the production of glass bodies.