The present invention is directed to pulverulent mixtures comprising hydrogen peroxide and hydrophobized, pyrogenically prepared silicon dioxide powder, preferably with a methanol wettability of at least 40. The pulverulent mixtures exhibit good storage stability and can be used for the controlled release of hydrogen peroxide and/or oxygen. The invention also includes methods of making these pulverulent mixtures and methods of using the mixtures in detergents, cleaning compositions, topical medications, antimicrobials and other products.