Patent ID: 8048817

Claim:
An amorphous silica powder containing Al in an amount of from 0.03 to 20 mass % as calculated as Al 2 O 3 measured by the following atomic absorption spectrophotometry, wherein the average particle size is at most 50 μm, and when the amorphous silica powder is divided according to the average particle size into two powders, a powder having a particle size smaller than the average particle size has a higher content as calculated as Al 2 O 3 than a powder having a particle size larger than the average particle size: atomic absorption spectrophotometry: 1 g of a sample is weighed on a platinum dish, 20 ml of special grade reagent hydrofluoric acid and 1 ml of special grade reagent perchloric acid are added, the platinum dish is left at rest in a sand bath heated at 300° C. for 15 minutes and then cooled to room temperature, pure water is added to prepare 25 ml of a solution, and the Al amount of the solution is quantitatively determined by using an atomic absorption photometer from an analytical curve.