Abstract: A method is described according to which articles of quartz glass, particrly quartz crucibles for use in crucible pulling according to Czochralski of high-purity synthetic quartz glass can be produced. High-purity silicon tetrachloride is hydrolized with water. The hydrolysis product is separated, dried, shaped, sintered and superficially fused.

Abstract: The invention relates to a process for treating elemental silicon and ferrosilicon with slag having the following analytical composition:______________________________________ K.sub.2 O from 2 to 13% by weight Na.sub.2 O from 0 to 2% by weight .SIGMA. K.sub.2 O + Na.sub.2 O from 2 to 13% by weight SiO.sub.2 from 45 to 72% by weight Al.sub.2 O.sub.3 from 0 to 30% by weight .SIGMA. SiO.sub.2 + Al.sub.2 O.sub.3 from 60 to 78% by weight CaO from 0 to 30% by weight MgO from 0 to 30% by weight .SIGMA. CaO + MgO from 15 to 30% by weight CaF.sub.2 from 0 to 10% by weight MgF.sub.2 from 0 to 10% by weight .SIGMA. CaF.sub.2 + MgF.sub.2 from 0 to 10% by weight .SIGMA. CaO + MgO + CaF.sub.2 + MgF.sub.2 from 15 to 30 % by weight ______________________________________and impurities resulting from the raw materials.

Abstract: Waste gases resulting from the production of silicon in connection with the ormation or decomposition of chlorosilanes, which gases always contain hydrogen chloride, can be worked up without removal of the hydrogen chloride. For this purpose, the waste gases which, after separation from the chlorosilanes, only contain hydrogen and hydrogen chloride, are subjected to combustion with addition of air and, after addition of silicon tetrachloride, the result being highly dispersed SiO.sub.2. The hydrogen chloride then remaining in the gaseous phase is returned to the process stream for production of trichlorosilane.

Abstract: Process for producing large-size, self-supporting plates of silicon deposd from the gaseous phase on a substrate body, which comprises heating a graphite substrate to deposition temperature of silicon, which is deposited on the substrate from a gaseous compound to which a dopant has been added until a layer of about 200 to 650 .mu.m has formed, subsequently melting 40-100% of this layer from the free surface downward, resolidifying the molten silicon by adjustment of a temperature gradient from the substrate body upward, and finally separating the silicon therefrom. The plates so formed are used primarily for making solar cells.

Abstract: Trichlorosilane or silicon tetrachloride is prepared by reacting metallic uminum-containing silicon in a reaction zone with hydrogen chloride or chlorine at a temperature between about 260.degree. and about 1200.degree. C, the reaction gas is then cooled to 40.degree. to 130.degree. in a cooling zone through which the velocity of flow is maintained at between 3 and 30 meters per second, and finally filtered.

Abstract: A process for producing large-size, substrate-based semiconductor material of silicon deposited on a substrate body from the gaseous phase, which comprises the steps of heating a substrate body by direct current passage to deposition temperature, contacting said body with a gaseous silicon-containing mixture to which a dopant has been added, until a deposit having a thickness from about 10 to 200 .mu.m has been formed, subsequently melting 80 to 100% of the deposited silicon layer from the free surface downward, and resolidifying the molten silicon by adjustment of a temperature gradient from the substrate body upward. Large-sized plates obtained by cutting up the semiconductor material are used as solar cells.

Abstract: Halogenosilanes and halogenogermanes which are contaminated by a boron-coining impurity are purified by treatment with an effective amount of a hydrated metal oxide or a hydrated silicate containing from about 3 to about 8% by weight of water, and then distilling the treated halogenosilane or halogenogermane at a temperature about 3.degree. to about 15.degree. C above its boiling temperature, and at atmosphere pressure.

Abstract: Process for the determination of the boron content of pure halogensilanes pecially silicon tetrachloride and trichlorosilane, which contain up to 0.1% of atoms of acceptors and donors, which comprises the steps of converting the halogen silanes into the gaseous state in a testing apparatus by contacting said halogensilanes with an evaporator surface heated to a temperature ranging from 80.degree. C to 350.degree. C, passing the generated gases to a support heated to the decomposition temperature of the gases whereby the released silicon is deposited on the support, removing the support and the deposit thereon from the testing apparatus and determining the boron content by calculation from the measured value of the specific resistance of the support plus the deposited silicon. It should be understood that all parts of the testing apparatus which come into contact with the generated gas, with the exception of the support heated to the required deposition temperature, should be at the temperature above 80.