products made of quartz glass for use in the chemical industry, in the electronic industry, in the semiconductor industry and for laboratory use; especially crucibles, trays, bowls, belljars, flanges, boats/wafer carriers, tube reactors for diffusions and epitaxial growth, catalyst carriers; products made of quartz glass for optical devices like lenses, prisms, plates, optical filters, mirrors, mirror plates, waveguides; optical fibers; quartz glass, translucent fused quartz, and semifinished products made from these materials, especially tubes, rods, plates, blocks; semifinished products made of quartz glass for manufacturing of optical fibers