Patent ID: 6994834

Claim:
A surface-modified fine silica powder having an adsorbing ability for an anion source compound, wherein said powder is obtained by a surface-modified treatment process comprising more than 10 mmol of a treating agent containing an amino group is added under dry-process in nitrogen atmosphere to 100 g of the fine silica powder which is a fumed-silica obtained by a flame hydrolysis method, having the specific surface area of 50 to 400 m 2 /g by the BET method; and after holding the treating agent and the fine silica powder under heating to at least 200° C. and vigorous stirring, the obtained powder has been surface-modified, and wherein the nitrogen content of said surface-modified fine silica powder is 0.3 to 1.0%, and wherein the ratio of the absorbed anion source compound of the surface-modified fine silica powder to the unmodified fine silica powder is more than 150%.