chemical products for commercial and scientific purposes, siliceous powder and granulate, especially 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 catalysis; pressed products of quartz glass powder or quartz glass granulate, especially for use as a basic material for the manufacture of quartz glass products and as a carrier and packing material in catalysis; quartz glass products for use in the chemical industry, in the electrical industry, in the semi-conductor industry and for laboratory purposes, especially cuvettes, inspection glasses, flasks, crucibles, dishes, beakers, frits, ground slides, trays, diffusion tubes, bells, epitaxy tubes, boats, catalyzer carriers; quartz glass products for optical equipment, such as lenses, prisms, plates, filters, mirrors, mirror carriers, optical guides; optical fibers; quartz glass, vitreous fused silica, as well as semi-finished products manufactured thereof, especially tubes, rods, plates, blocks; semi-finished quartz glass products for the manufacture of optical fibers; quartz glass powder and quartz glass granulate as an intermediate product for the manufacture of quartz products