Pyrogenic silicon dioxide powder and dispersion thereof

Of the present invention to provide a heat method for manufacturing silica powder, carbon content of its surface area is 5 to 600m2/g and less than 500ppm, its characteristic is that dibutyl phthalate absorption rate that is less than or equal to 1.2G di-n-butyl phthalate/100g SiO2 per square meter of surface area and thickening rate was below 15mPa · s per square metre of surface area. Its is through following steps system have, will gaseous TMOS and/or TEOS together with air or rich oxygen air, and separate to will hydrogen into burning Manager in the, make the gas mixture in and the burning Manager connected of reaction room in the of flame in the for reaction, then with known method will solid reaction product from gas flow in the separation, the burning Manager in the of λ value for 0.95 to 1.5, also to the reaction room provides sufficient of II times air, make the reaction room in the of λ value for 0.8 to 1.6. This invention provides aqueous dispersion containing silicon dioxide powder, as well as the powder and use in the dispersion.