Abstract: The present invention provides a method for reducing the amount of hydrogen chloride contained in a gas stream by reacting the hydrogen chloride with ammonia in the gas phase so as to produce ammonium chloride. The combined gas stream is passed into a condensation and collection vessel and a cyclonic flow is created in the combined gas stream as it passes through the vessel. The temperature of the gas stream is reduced in the vessel to below the condensation temperature of ammonium chloride in order to crystallize the ammonium chloride on the walls of the vessel. The cyclonic flow creates a turbulence which breaks off the larger particles of ammonium chloride which are, in turn, driven to the bottom of the vessel where the solid ammonium chloride can be removed from the vessel. The gas stream exiting from the condensation and collection vessel is further cleaned and additional ammonium chloride is removed by passing through additional filters.

Abstract: An inorganic acid typified by H.sub.2 SO.sub.4 is added to an aqueous slurry of (NH.sub.4).sub.3 AlF.sub.6 and either Al(OH).sub.3 or Al.sub.2 O.sub.3, and the resulting mixture is kept for a while under the atmospheric pressure at or somewhat above room temperature. The acid is added preferably in such an amount that the pH of the slurry after completion of the reaction is 4 to 7.

Abstract: A process is disclosed for the preparation of arsenic trifluoride which comprises reacting arsenic trichloride with one or more molten fluoride salts.

Abstract: A method of preparing carboxylic acids is provided by heating an acylhydroximyl halide in an aqueous medium at elevated temperatures.

Abstract: In the production of an ammonium fluoride solution by precipitating hexafluosilicic acid from its solution with ammonia and from the resulting suspension separating off the silicon dioxide precipitated, the improvement which comprises thoroughly mixing the hexafluosilicic acid solution and ammonia at a temperature of about 40.degree. to 90.degree. C, in such proportions that the suspension obtained contains at least 1% of free ammonia and at most 22% of ammonium fluoride, the average residence time of the reactants in the precipitation zone being at least 4 minutes. Advantageously, the silicon dioxide is separated off from the suspension obtained without previous cooling, the resulting ammonium fluoride filtrate is left standing for at least 30 minutes to permit flocculation of silicon dioxide contained therein and the flocculated silicon dioxide is separated off.

Abstract: A method for the thermochemical production of hydrogen from water is disclosed in which barium iodide, carbon dioxide, ammonia and water are allowed to react with one another and give rise to barium carbonate and ammonium iodide, the ammonium iodide thus produced is thermally decomposed to produce hydrogen, iodine and ammonia, and the hydrogen thus produced is recovered as the product. The by-produced barium carbonate is allowed to react with the iodine remaining after the separation of hydrogen thereby to produce barium iodide, carbon dioxide and oxygen, and the barium iodide and carbon dioxide are recycled to the reaction system. The ammonia which remains after the separation of hydrogen is also recycled to the reaction system. By causing the by-products occurring in the various reactions to be recycled to the relevant reaction systems, hydrogen is efficiently produced from water at a reaction temperature of not more than 800.degree. C.

Abstract: The invention relates to a process of the treatment of sodium silico fluoride. In the invention, sodium silico fluoride is decomposed with a relatively high concentration of an aqueous ammonium solution or an ammonia gas to produce a mixed aqueous slurry solution of ammonium fluoride containing sodium fluoride and silica gels as solid materials, the obtained mixed aqueous slurry solution is separated to the ammonium fluoride solutions containing sodium fluoride and silica gels, respectively, by means of a physical method and then sodium fluoride, silica gels and the aqueous ammonium fluoride solution are manufactured in high purity and good yield, respectively. In the other way, the mixture of sodium fluoride and silica gels are separated from said mixed aqueous slurry solution by means of the filter, washed with water and dried. The dried mixture is separated to sodium fluoride and silica gels by means of a physical method.

Abstract: A method of processing of waste gases containing hydrogen fluoride and silicon tetrafluoride or hydrogen fluoride, silicon tetrafluoride and sulfur dioxide by absorption of hydrogen fluoride and silicon tetrafluoride or hydrogen fluoride, silicon tetrafluoride and sulfur dioxide from waste gases by water solutions containing ammonium compounds such as ammonium carbonate, ammonium bicarbonate and ammonium fluoride. In addition to these ammonium compounds the absorption solutions contain sodium fluoride and ammonia. The absorption process produces a water solution containing ammonium fluoride and the precipitate of sodium fluosilicate. This solution is treated with sodium carbonate after which the precipitate of sodium fluoride is separated from the solution and the latter is delivered for absorption.

Abstract: Gases containing hydrogen cyanide, ammonia and hydrogen sulfide are purified by first washing the gas with a suspension of solid sulfur to fix the hydrogen cyanide as ammonium thiocyanate and ammonium thiosulfate. The resulting suspension is then subjected to a wet-oxidation wherein the thiosulfate and a part of the thiocyanate is converted into sulfuric acid and ammonium sulfate afterwhich the resulting liquid containing unreacted thiocyanate is decomposed into an ammonium salt and is recovered from the oxidation and decomposition steps.