SILICA POLYMORPH AND PROCESS FOR PREPARAING SAME

摘要

10638 SILICA POLYMORPH AND PROCESS FOR PREPARING SAME Large crystals of a silica polymorph having a characteristic x-ray diffraction pattern, a specific gravity of 1.70 ? 0.05 g/cc.and a mean refractive index of 1.39 ? 0.01 after calcination in air at 600.degree.C., are prepared by a hydrothermal process in which fluoride anions are included in the reaction mixture. The crystals, which can be as large as 200 microns, exhibit a substantial absence of infrared adsorption in the hydroxyl-stretching region and also exhibit an exceptional degree of hydrophobicity. S P E C I F I C A T I O N _ _ _ _ _ _ _ _ _ _ _ _ _