Full Title

Silicon; Compounds thereof ( C01B21/00, C01B23/00 take precedence; persilicates C01B15/14; carbides C01B32/956) > Silicon oxides; Hydrates thereof > Silica; Hydrates thereof, e.g. lepidoic silicic acid > Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof (preparation of aerogels by dehydrating gels C01B33/158; treatment to enhance the pigmenting or filling properties C09C)