Abstract: In the production of a synthetic fluorspar of low silicon dioxide content wherein hexafluosilicic acid is added in an amount ranging from slightly below up to about stoichiometric amount to an aqueous calcium carbonate suspension at a temperature from about 0.degree. to 40.degree. C., and the calcium fluoride formed is separated off from the dilute silica sol and optionally washed out, the improvement which comprises reacting the calcium carbonate with the hexafluosilicic acid in such a way that the pH-value of the fully reacted solution amounts to between about 3.6 and 4.6, and adding a fast-reacting proton acceptor to the reaction mixture immediately before separation of the calcium fluoride in amount sufficient to raise the pH to about 5.0 to 6.4, preferably about 5.8 to 6.2. Suitable proton acceptors include the alkali metal and ammonium hydroxides carbonates and hydrogen carbonates or alkaline earth metal hydroxide.

Abstract: Hydrogen is produced from water by first reacting I.sub.2, SO.sub.2 and H.sub.2 O to make hydrogen iodide and sulfuric acid. A substantial molar excess of SO.sub.2 and I.sub.2 in the reaction zone creates a lighter sulfuric acid-bearing phase and a heavier polyiodic-acid-bearing phase. The heavier phase is separated, degassed and then contacted with phosphoric acid to permit distillation of HI of low water content and recovery of I.sub.2 as a separate fraction. Hydrogen is recovered from HI vapor, as by thermal decomposition.

Abstract: Concentrated magnesium chloride solutions are prepared from industrial liquors or brines by debrominating the liquor with chlorine, neutralizing the debrominated liquor up to a ph value of 3-6, adding a stoichiometric excess of calcium chloride to the neutralized liquor at temperatures in the range of 30.degree.-50.degree. C to form a calcium sulfate dehydrate crystallizate, separating the crystallizate from the mother liquor, adding a sufficient amount of carnallite to the mother liquor to increase the MgCl.sub.2 content thereof to 270-330 g/l after cold decomposition of the added carnallite and concentrating the resulting solution in two or more steps in the direct current in an evaporator with crystallization characteristics up to a final concentration of 440 to 470 g/l MgCl.sub.2 whereafter the concentrated magnesium chloride solution is separated from crude crystallized carnallite and sodium chloride formed during the concentration.

Abstract: In the production of aluminum chloride suitable for subsequent electrolytic reduction to metallic aluminum control of both the purity and the particle size is achieved by control of the entrance velocity of the aluminum chloride vapors in a fluidized bed, control of the fluidized bed temperature, and selective removal of the condensed particles from the bottom of the fluidized bed.

Abstract: Disclosed is a process for the production of sulphur hexafluoride comprising the steps of reacting fluorine and molten sulphur, removing lower-boiling by-products, separating a portion of the sulphur hexafluoride from higher-boiling by-products and treating the residue containing the higher-boiling by-products at a temperature between about 450.degree. and 800.degree. C. for a period of time between about 0.1 and 25 seconds. The treatment step may be carried out in the presence of elementary fluorine, and provision may be made for recycling the treated or untreated residue to the reaction stage. An apparatus for carrying out the process is also disclosed.

Abstract: A process for the preparation of bromine and hydrogen bromide, which comprises reacting ammonium bromide with an oxygen containing gas at temperatures of from 200.degree. to 800.degree. C in the presence of oxidation catalysts is disclosed. Catalysts based on platinum group metals favor formation of HBr. Most other metal catalysts cause chiefly formation of bromine.

Abstract: A process for the preparation of bromine and hydrogen bromide, which comprises reacting ammonium bromide with an oxygen containing gas at temperatures of from 200.degree. to 800.degree. C. in the presence of oxidation catalysts is disclosed. Catalysts based on platinum group metals favor formation of HBr. Most other metal catalysts cause chiefly formation of bromine.

Abstract: A process for the production of aluminum chloride comprises providing a mixture of high purity activated carbon and alumina and bubbling chlorine gas therethrough, the mixture being kept at a temperature in the range of 500.degree. to 775.degree. C. Aluminum chloride is removed from the mixture as a vapor and condensed.

Abstract: A process for the production of high purity silicon characterized by the employment of an electric arc heater in which a silicon halide is reacted with hydrogen to produce liquid silicon and gaseous co-products.

Abstract: A process for the production of hydrogen/deuterium-containing gas in which the enriched condensate obtained from the production of a hydrogen/deuterium-containing gas mixture is collected and subjected to a direct exchange of isotopes with the feedsteam admitted to the process. Such condensate can be brought into direct exchange of isotopes with the gas water vapor mixture within the process, viz. ahead of the CO conversion section. The exchange of isotopes may be performed according to the counter-current principle. If it is intended to maintain in the hydrogen/deuterium-containing gas a certain definite content of water vapor whose phase condition is superior to the condition achieved when using normal cooling water, this gas, at least 0.6 kg/m.sup.3 of gas, is subjected to an exchange of isotopes with the water fed additionally into the process.

Abstract: A solid, particulate reactant is continuously added to a first zone and a liquid reactant is continuously added to a second zone. A conduit between the zones allows the solid and liquid reactants to pass counter-currently between the zones, the reaction being accomplished on contact between the reactants. During steady state operation, a clear layer is established in each zone above a slurry layer of the particles in solution. The clear layer is withdrawn from the top of each zone and introduced at the bottom thereof causing agitation in the slurry layer which promotes the reaction. The solid reactant is withdrawn from the second zone while the spent liquid reactant is withdrawn from the first zone.

Abstract: Technical-grade silicon is purified to produce silicon having less than 1 ppm of electrically effective impurities therein, particularly boron and phosphorus, by treating molten technical silicon with a hydrogen containing gas in the presence of water so as to remove such impurities from the molten silicon.

Abstract: Synthetic rutile is made from ilmenite by pre-oxidizing it, reducing it in a fluid bed, thereafter aeration leaching it, optionally acid leaching, and drying.

Abstract: The content of sodium sulfate (and less soluble sulfates) in rock salt (halite) can economically be reduced from levels as high as 5 weight percent to levels as low as about 0.1 weight percent by the process of the invention. The halite is crushed to a certain particle size range and particles less than 0.5 mm in effective diameter are removed while (or after) the crushed material is subjected to attrition washing with a low sulfate, high NaCl brine. The washed, coarse particles are rinsed with a low sulfate brine, drained and dried to an extent appropriate to their contemplated use.

Abstract: Method of production of synthetic fluorite with a selected specified grain size to be obtained, by submitting the calcium carbonate to a reaction with fluoride ions present in an aqueous solution, consists therein that calcium carbonate is used having a grain size substantially the same as the selected grain size for the synthetic fluorite to be obtained. The fluoride ions for the reaction with the calcium carbonate are supplied in the form of a solution of ammonium fluoride and/or potassium fluoride and/or sodium fluoride. The process is conducted at a temperature chosen within the range of 50.degree. C to 150.degree. C, under a pressure reduced, atmospheric or elevated, within the range of 0.5 to 10 atm, and preferably at the boiling temperature or at a temperature not too far from the boiling point, especially in a reaction system containing ammonium fluoride.

Abstract: A balanced closed cycle silicon refinery has been developed for producing electronic silicon from industrial grade silicon. Impurities comprising approximately 1% of the industrial grade silicon are removed during the refinery process to produce the purified silicon, while only a relatively small percentage of make-up chemicals are added to the system. In the refinery, hydrogen chloride is reacted with the impure silicon in a halide reactor to provide trichlorosilane and silicon tetrachloride and hydrogen. The trichlorosilane and/or silicon tetrachloride are purified to remove the impurities, and then reacted with the hydrogen from the halide reactor in a fluidized bed reactor to produce the purified silicon and an effluent comprised of unreacted trichlorosilane, silicon tetrachloride, hydrogen, and the by-product hydrogen chloride.

Abstract: Process for the recovery of pigment-grade iron oxide and technical hydrochloric acid of predetermined molarity, from iron chloride solutions such as pickling solutions containing hydrochloric acid. The iron chloride solution is concentrated until the molarity of the chloride ion therein is the same as the molarity of the hydrochloric acid which it is desired to produce. Concentrated sulfuric acid in slight stoichiometric excess relative to the iron, is then added to the iron chloride solution, which solution is thereafter evaporated to dryness. The distillation from this evaporation is hydrochloric acid of the predetermined molarity, and the dry residue is iron sulfate. The iron sulfate is calcined to drive off sulfur dioxide and sulfur trioxide and to leave iron oxide which may contain sulfates; and to remove these latter, the iron oxide is leached with dilute hydrochloric acid and is thereafter washed with water. The washed iron oxide is dried and micropulverized to produce a red iron oxide pigment.

Abstract: A process for purification of mercuric iodide (HgI.sub.2) to be used as a source material for the growth of detector quality crystals. The high purity HgI.sub.2 raw material is produced by a combination of three stages: synthesis of HgI.sub.2 from Hg and I.sub.2, repeated sublimation, and zone refining.

Abstract: A hot-pressed optical body which is free from absorption bands due to carbon dioxide, water, hydroxyl ion and acid fluorides in the ultraviolet, visible and near-infrared wavelength regions. Typically, the optical body is formed from a powder of an alkaline earth metal fluoride, alkali metal fluoride, or rare earth metal fluoride. One or more absorption bands due to a single impurity may be reduced or eliminated, or bands due to plural impurities may be reduced or eliminated sequentially, or simultaneously. The optical body is made by flowing a reactive, reducing gas, optionally, in combination with hydrogen fluoride gas, directly into the die cavity containing a pressable ionic fluoride powder, and either hot-pressing or extruding the powder.

Abstract: Hydrogen is produced from water by reacting I.sub.2 SO.sub.2 and H.sub.2 O to make hydrogen iodide and sulfuric acid. SO.sub.2 is present in a substantial molar excess with respect to the available H.sub.2 O and I.sub.2 is also present in excess to cause the formation of a lighter sulfuric acid-bearing phase and a heavier hydrogen iodide-bearing phase. The heavier phase is separated from the lighter phase, degassed to remove SO.sub.2 and then treated with additional HI and I.sub.2 to cause the formation of a light immiscible fraction containing sulfuric acid and water which is removed to substantially reduce the sulfur content of the degassed phase. Finally, the hydrogen iodide product is separated and decomposed to produce hydrogen.