Chemicals for commercial and scientific purposes, namely, siliceous powder and granulate, for use as a filler, additive, as an auxiliary flow agent, as a pigment, as a basic material for the manufacture of quartz glass products, and as a carrier and packing material in a catalysis; pressed chemical preparations of quartz glass powder or quartz glass granulate for use as a basic material for the manufacture of quartz glass products and as a carrier and packing material for catalysis