Abstract: In the continuous production of oleum having a concentration of 10 to 45% by weight SO.sub.3 and/or sulfuric acid having a concentration of 94 to 100% by weight H.sub.2 SO.sub.4 by burning sulfur with atomospheric oxygen on the principle of overstoichiometric or understoichiometric burning, cooling the resulting SO.sub.2 -containing gas to 390.degree.-480.degree. C., catalytically reacting the cooled gas to SO.sub.3 -containing gas on a vanadium-containing catalyst on the principle of single- or double-contact catalysis, absorbing the SO.sub.3 -containing gas after cooling and, optionally, separating liquid from the gas after absorption, followed by recovering energy, the improvement which comprises effecting the burning of the sulfur with atomospheric oxygen in the presence of a dry SO.sub.2 -containing gas which contains up to 5,000 ppm (NO).sub.x expressed as NO.

Abstract: Nitrogen oxide is removed from flue gases of combustion plants or reaction gases by a process wherein the nitrogen oxide contained in the stream of gas is converted into a stochiometric composition of N.sub.2 O.sub.3 and removed from the gas stream.

Abstract: The present invention relates to a process for the preparation of trioganosilyl-terminated polydiorganosiloxanes by basic polymerization of cyclic diorganopolysiloxanes and triorganosilyl-terminated siloxanes, wherein, before the polymerization, a part of the cyclic diorganosiloxane is distilled off in the presence of the polymerization catalyst at a temperature which is at least 10.degree. C. below the polymerization temperature.

Abstract: In the continuous production of low-sulfur chromium(III)oxide pigment comprising the steps of reducing a finely divided alkali metal chromate in a heated hydrogen-containing reaction zone at a temperature of about 900.degree. to 1600.degree. C, and precipitating the resulting chromium(III)oxide in the form of an aqueous dispersion, the improvement which comprises passing the reduction products from the reaction zone to a dwell zone and generating heat within said dwell zone to maintain the temperature therein in the range of about 900.degree. to 1600.degree. C. Preferably the dwell zone temperature is within 200.degree. C of that in the reaction zone and is maintained by introducing excess hydrogen into the reaction zone and consuming it in the dwell zone by introduction of oxygen. The resulting pigments exhibit a fuller green color.

Abstract: In the production of a gypsum-based porous body of high strength by foaming a gypsum-water mixture containing alkali, hydrogen peroxide and a decomposition catalyst therefor, the improvement which comprises including in said mixture an acid-reacting compound with active hydrogen atoms in a quantity insufficient for complete neutralization of the alkali. The alkali is preferably calcium and/or magnesium oxide and/or hydroxide and the preferred acid-reacting compounds are phosphates and/or sulfates, especially potassium hydrogen phosphates. The acid-reacting compound is employed in an amount sufficient to neutralize about 5 to 50% of the alkali, the final pH being about 12 to 12.5.

Abstract: In the production of a gypsum-based porous body of high strength by foaming a gypsum-water mixture, the improvement which comprises including in said mixture about 0.1 to 1 part of a water-soluble aluminum compound per 100 parts by weight of gypsum, calcium oxide or calcium hydroxide in such a quantity that the final mixture has a pH-value in the range of about 10 to 13, a decomposition catalyst, and about 0.5 to 5 parts of hydrogen peroxide, expressed as a 35% solution, per 100 parts by weight of mixture, the ratio of solids to liquid being about 1 : 0.4 - 1.The preferred aluminum compound is aluminum nitrate. The preferred decomposition catalysts are manganese compounds such as manganates or permanganates, e.g. potassium permanganate.

Abstract: A process for indirect heat-exchange between a solids-containing gas and the inner wall of a heat-exchanger through which the solids-containing gas to be cooled or heated flows, comprising introducing a flushing medium separately from the solids-containing gas into the heat exchanger, the flushing medium being directed angularly at the wall and sweeping about said wall whereby said wall is kept substantially free from solid deposits. Advantageously the heat exchanger is circular in cross-section, the gas/solids mixture is introduced tangentially, and the flushing medium is discharged toward said inner wall through openings in an arm which rotates within the heat exchanger, means being provided to remove gases and solids from the heat exchanger.