Abstract: An object of the present invention is to provide a method for producing a metal hydroxide fine particle, which can produce metal hydroxide fine particles with favorable crystallinity and small particle sizes. The present invention provides a method for producing a metal hydroxide fine particle by reacting a metal ion with a hydroxide ion in a solvent, which includes a mixing and reacting step of supplying the metal ion, the hydroxide ion, and a silane coupling agent to a reaction field to mix and react the ions.

Abstract: Magnesium oxide powders having a large diameter of crystallite, and having a favorable crystallinity are provided. Magnesium oxide powders: having peak widths at half-height of the peaks on a (111) plane, a (200) plane and a (220) plane of each no greater than 0.20 degrees as determined with a powder X-ray diffraction method carried out using a Cu—K? ray; and having a crystallite diameter of no less than 700 ?.

Abstract: The present invention relates to a fluorine-containing magnesium oxide powder using a vapor phase reaction and a method of preparing the same and more particularly to a fluorine-containing magnesium oxide powder brings about a cathode-luminescence emission having a peak within a wavelength range of 220 to 320 nm upon being excited by electron beams. The present invention provides a fluorine-containing magnesium oxide powder using a vapor phase reaction that sprays fluorine-containing gas and oxygen-containing gas to magnesium vapor, and the purity of magnesium oxide containing fluorine (i.e. the purity of fluorine-containing magnesium oxide) of 0.001 to 2 wt % is at least 98 wt % and a BET specific surface area thereof is 0.1 to 50 m2/g.

Abstract: The present invention relates to a fluorine-containing magnesium oxide powder using a vapor phase reaction and a method of preparing the same and more particularly to a fluorine-containing magnesium oxide powder brings about a cathode-luminescence emission having a peak within a wavelength range of 220 to 320 nm upon being excited by electron beams. The present invention provides a fluorine-containing magnesium oxide powder using a vapor phase reaction that sprays fluorine-containing gas and oxygen-containing gas to magnesium vapor, and the purity of magnesium oxide containing fluorine (i.e. the purity of fluorine-containing magnesium oxide) of 0.001 to 2 wt % is at least 98 wt % and a BET specific surface area thereof is 0.1 to 50 m2/g.

Abstract: A process of producing a ceramic powder including providing a plurality of precursor materials in solution, wherein each of the plurality of precursor materials in solution further comprises at least one constituent ionic species of a ceramic powder, combining the plurality of precursor materials in solution with an onium dicarboxylate precipitant solution to cause co-precipitation of the ceramic powder precursor in a combined solution; and separating the ceramic powder precursor from the combined solution. The process may further include calcining the ceramic powder precursor.

Abstract: The present invention discloses a continuous calcination vessel which can be used to prepare calcined chemically-treated solid oxides from solid oxides and chemically-treated solid oxides. A process for the continuous preparation of calcined chemically-treated solid oxides is also provided. Calcined chemically-treated solid oxides disclosed herein can be used in catalyst compositions for the polymerization of olefins.

Abstract: Magnesium oxychloride cement is formed by mixing a magnesium chloride (MgCl2) brine solution with a magnesium oxide (MgO) composition in a selected stoichiometric ratio of MgCl2, MgO, and H2O that forms the 5 phase magnesium oxychloride cement composition. Although Sorel cements formed from the mixture of MgCl2, MgO can form a variety of compounds, the inventive systems and methods provide for controlling the cement kinetics to form the five phase magnesium oxychloride cement composition and results in an improved and stable cement composition. Various fillers can be optionally added to form preferred cement materials for uses as diverse such as road stripping, fire-proofing, fire barriers, cement repair, and mortar.

Abstract: A method for the production of Mg(OH)2 nanoparticles, by means of polyol-mediated synthesis, from an Mg precursor as well as a base. The particles produced with this method have a diameter between 10 nm to 300 nm, have a mono-disperse particle distribution, and are present in non-agglomerated form. They can be converted to MgO particles by means of calcination.

Abstract: Multi-step metal compound oxidation process to produce compounds and enhanced metal oxides from various source materials, e.g. metal sulfides, carbides, nitrides and other metal containing materials with metal oxides from secondary reaction steps being utilized as an oxidation agent in the first reactions.

Abstract: A method for the production of Mg(OH)2 nanoparticles, by means of polyol-mediated synthesis, from an Mg precursor as well as a base. The particles produced with this method have a diameter between 10 nm to 300 nm, have a mono-disperse particle distribution, and are present in non-agglomerated form. They can be converted to MgO particles by means of calcination.

Abstract: A process of reacting a metal chloride, especially chromium (III) chloride, with an alkali metal oleate at a temperature of from about 30° to about 300° C., and especially at about 70±1° C., in a solvent to form a metal oleate complex, especially a chromium-oleate complex, and reacting the complex with oleic acid at a reaction temperature of about 300° C. or above in a solvent having a boiling point of higher than the reaction temperature, and precipitating and isolating metal oxide nanocrystals, especially chromium (III) oxide nanocrystals, which are useful as a catalyst in hydrofluorination reactions. Other metal oxide nanocrystals produced by this process include nanocrystals of vanadium oxide, molybedenum oxide, rhodium oxide, palladium oxide, ruthenium oxide, zirconium oxide, barium oxide, magnesium oxide, and calcium oxide are also synthesized by similar process scheme using their respective chloride precursors.

Abstract: Disclosed is a process for preparing fine metal oxide particles, comprising the following steps of reacting a reactant mixture comprising i) water, ii) at least one water-soluble metal nitrate and iii) ammonia or ammonium salt at 250–700° C. under 180–550 bar for 0.01 sec to 10 min in a reaction zone to synthesize the metal oxide particles, the metal nitrate being contained at an amount of 0.01–20 wt % in the reactant mixture; and separating and recovering the metal oxide particles from the resulting reaction products. According to the present invention, nano-sized metal oxide particles are synthesized, while the harmful by-products generated concurrently therewith are effectively decomposed in the same reactor.

Abstract: There is disclosed a method of recovering chlorine gas from calcium chloride comprising the steps of introducing calcium chloride into a heat-resistant vessel which is provided with a gas inlet pipe and a gas outlet pipe, heating the calcium chloride up to at least the melting point thereof while introducing an inert gas from the gas inlet pipe into the vessel to produce fused salt of calcium chloride, and heating the interior of the vessel up to at least 1073K and switching a gas to be introduced from the gas inlet pipe from the inert gas to oxygen to allow the fused salt of calcium chloride to react with the oxygen to obtain chlorine gas and calcium oxide, the chlorine gas being subsequently rapidly and continuously discharged from the vessel through the gas outlet pipe.

Abstract: The present invention provides an improved process for the manufacture of zirconium boride by reacting boric acid, a Zirconium compound and magnesium and leaching the resulting product mixture to obtain zirconium boride with high purity.

Abstract: A method of producing fine particles of an oxide of a metal, comprising the steps of: preparing an acidic solution which contains ions of the metal; precipitating fine particles of a hydroxide of the metal by adding an alkaline solution to the acidic solution; collecting the fine particles of the hydroxide of the metal precipitated in a mixed solution of the acidic solution and the alkaline solution; mixing fine particles of a carbon with the collected fine particles of the hydroxide of the metal; and heat-treating a mixture of the fine particles of the hydroxide of the metal and the fine particles of the carbon at a predetermined temperature in a non-reducing atmosphere, whereby the fine particles of the oxide of the metal are produced.

Abstract: A process is disclosed for regenerating an aqueous acid halide leachant from a spent aqueous metal halide leach liquor. The process comprises introducing into a fluidized bed or spray roaster a hydrocarbon fuel, an oxygen-enriched oxidizing gas and the aqueous metal halide leach liquor; pyrohydrolyzing the aqueous metal halide leach liquor by combustion of the hydrocarbon fuel with the oxygen-enriched oxidizing gas to produce an acid halide-containing gas fraction and a metal oxide-containing solid fraction; separating the gas fraction from the solid fraction, recovering heat energy from the acid halide-containing gas fraction and absorbing the gas fraction in water to produce the aqueous acid halide leachant. The oxygen-enriched oxidizing gas has an oxygen concentration of greater than about 21 percent by volume, preferably greater than about 50 percent by volume, more preferably greater than about 80 percent by volume, and even more preferably greater than about 90 percent by volume.

Abstract: Alkaline earth metal alkylene diamides of Ba, Sr, Ca and a method for their production.

Abstract: A process for the preparation of nanostructured materials in high phase purities using cavitation is disclosed. The method comprises mixing a metal containing solution with a precipitating agent and passing the mixture into a cavitation chamber. The chamber consists of a first element to produce cavitation bubbles, and a second element that creates a pressure zone sufficient to collapse the bubbles. The process is useful for the preparation of mixed metal oxide catalysts and materials for piezoelectrics and superconductors.

Abstract: This invention relates to a generic process for producing a refractory oxide which comprises reacting an aqueous hydrogen fluoride solution or its derivatives with: at least one metal fluoride reactant; or at least one metal fluoride reactant and at least one metal oxide reactant; or at least one metal oxide reactant, to produce either a colloidal mixture or a solution; drying either the colloidal mixture or solution; heating the dried product to produce a solid state metal hydroxyfluoride; heating the hydroxyfluoride to a temperature at which it chemically decomposes into a cationically-homogeneous and nanostructured solid state metal oxyfluoride; and performing one of the following heating steps: (i) to a solid state decomposition-temperature where the oxyfluoride chemically decomposes into a refractory oxide; or, (ii) to a molten state decomposition-temperature where the oxyfluoride chemically decomposes into a refractory oxide; or, (iii) to a vapor state decomposition-temperature where the oxyfluoride che

Abstract: A method for preparing an oxide (P), which includes the steps of (i) forming a solid phase compound (O) based on an oxide containing molecular entities (1) chosen from optionally substituted ammonium, diammonium, diazan-ium or diazandium, the entities being distributed within the solid matrix, and (ii) eliminating the entities (1) from the solid phase compound (O) by reacting the solid phase compound (O) with a gaseous stream containing a break-down reactant for the entities (1), and isolating the resulting solid material (P).

Abstract: The present invention provides a process for preparing a flame retardant quality magnesium hydroxide which includes providing a magnesium salt solution; and a source of ammonia; adding a stochiometric excess of ammonia to the solution to form a magnesium hydroxide precipatate; and subjecting the magnesium hydroxide to a hydrothermal recrystallization.

Abstract: A process for producing ultra-fine barium titanate particles. In the first step of this process, a ceramic precursor material containing a metal cation, a nitrogen-containing material, a solvent, and an anion capable of participating in an anionic oxidation-reduction reaction with the nitrogen-containing material, is provided; the nitrogen-containing material contains at least three nitrogen atoms, at least one oxygen atom, and at least one carbon atom. In the second step of the process, droplets of such ceramic precursor material are formed. In the third step of the process, the droplets are dried until particles which contain less than about 15 weight percent of solvent are produced. In the fourth step of this process, such particles are ignited in an atmosphere which contains substantially less than about 60 weight percent of the solvent's saturation value in such atmosphere.

Abstract: Magnesium hydroxide of the formula Mg(OH).sub.2 having a crystallite size in the direction <004> greater than 150 .ANG. and smaller than 500 .ANG., an aspect ratio in the range from 2 to 5, a strain in the direction <004> not greater than 4.2.times.10.sup.-3 and a strain in the direction <110> not greater than 3.0.times.10.sup.-3. 50% of secondary particles with diameters smaller than 1.4 .mu.m and 100% of secondary particles with diameters not greater than 4.0 .mu.m, and a specific surface, determined by the BET method, smaller than 25 m.sup.2 /g. It is prepared by a two-step procedure; in the first step, magnesium nitrate is treated by an alkaline substance, preferably by ammonia, in an aqueous medium, with 1.5 to 6.0-multiple excess of ammonia, at a temperature of not more than 85.degree. C., at the atmospheric pressure, causing that basic magnesium nitrate is formed which, in the second step, decomposes at a temperature of 110.degree. to 150.degree. C.

Abstract: A fibrous composite metal hydroxide containing a small amount of hexagonal-plate-like magnesium hydroxide and being therefore advantageously useful as a reinforcing material for resins and rubbers. The crystal water elimination temperature thereof can be set at any point between the crystal water elimination temperature of magnesium hydroxide and that of aluminum hydroxide. This fibrous composite metal hydroxide is excellent in flame retardancy and acid resistance. The fibrous composite metal hydroxide has an aspect ratio of about 10 or more, an average diameter of approximately 0.1 to 10 .mu.m and an average length of approximately 2 to 1,000 .mu.m, and having the formula (1),M.sup.2+.sub.x Mg.sub.1-x (OH).sub.2 (1)wherein M is at least one member selected from Mn, Fe, Co, Ni, Cu and Zn and x is defined by 0.005<x<0.5.

Abstract: Novel magnesium hydroxide having a fine, plate-like crystalline structure, a median particle size of up to about 1 micron and a particle size distribution in which about 90% of said magnesium hydroxide particles are less than about 3.5 microns is prepared by a flash precipitation process in which less than or greater than an equivalent amount of alkaline material is reacted with a magnesium salt in a concentrated aqueous mixture thereof. Ultrasonic mixing means is used to combine heated aqueous streams of an alkaline material and a magnesium containing solution followed by a post heat treatment. The magnesium hydroxide is especially useful in providing flame retardancy in admixture with thermoplastic resins.

Abstract: This invention is directed to the formation of homogeneous, aqueous precursor mixtures of at least one substantially soluble metal salt and a substantially soluble, combustible co-reactant compound, typically an amino acid. This produces, upon evaporation, a substantially homogeneous intermediate material having a total solids level which would support combustion. The homogeneous intermediate material essentially comprises highly dispersed or solvated metal constituents and the co-reactant compound. The intermediate material is quite flammable. A metal oxide powder results on ignition of the intermediate product which combusts same to produce the product powder.

Abstract: A process for the production of a magnesium oxide having high hydrolysis resistance and high fluidity, which comprises:(A) a step of reacting a water-soluble magnesium salt with an alkaline substance in such an amount that is not more than 0.95 equivalent weight based on 1 equivalent weight of the water-soluble magnesium salt, at a temperature of not more than 40.degree. C.,(B) a step of heating the resultant reaction product and its reaction mother liquor at about 50.degree. to 120.degree. C. to form a magnesium hydroxide,(C) a step of forming particles having an average secondary particle diameter of about 5 to 500 .mu.m by using a spray drier,(D) a step of firing the particles at about 1,100.degree. to 1,600.degree. C., and(E) a step of pulverizing the resultant fired product under conditions which do not substantially destroy the average secondary particle diameter obtained in the above step (C).

Abstract: A process for preparing compound metal oxides, superconductive compound oxides, is disclosed. The process comprises preparing an aqueous solution containing a predetermined content ratio of chloride, nitrate or acetate of a rare earth metal, an alkaline earth metal and copper, said content ration corresponding to the composition of the object compound metal oxide, adjusting the pH of the solution to 1.5-2.0, adding oxalic acid in an amount such that the concentration of the residual oxalic acid becomes 0.05 M/l-0.1 M/l, collecting the thus formed precipitate and firing it.

Abstract: A process for the preparation of pure magnesium oxide, especially suitable for the preparation of refractory products, from magnesium silicate and magnesium hydrosilicate materials such as olivine, serpentine, garnierite, or the like, the starting material being decomposed (digested) with hydrochloric acid, the residues being separated from the decomposition slurry and the sesquioxides to be regarded as contaminants and other contaminants being precipitated from the crude brine thus obtained by the addition of crude serpentine as a pH increasing substance, the precipitates being separated and the magnesium chloride solution thus obtained being subjected to thermal decomposition, particularly by spray calcination, whereby magnesium oxide is obtained and hydrogen chloride is recovered.

Abstract: A lightweight magnesia clinker containing magnesium oxide in an amount of more than 85 wt. % and having an apparent porosity of more than 40 vol. % and a bulk specific gravity of less than 2.0 g/cm.sup.3 is disclosed. In the lightweight magnesia clinker, the amount of magnesia clinker particles having a particle diameter of smaller than 3 mm is more than 90 wt. % of the amount of all magnesia clinker particles, and the amount of pores formed in the magnesia clicker particles having a pore size of smaller than 50 .mu.m is more than 90 vol. % of the amount of all pores. A process for the preparation of said lightweight magnesia clinker is also disclosed.

Abstract: A process is disclosed for producing a homogeneous mixture of co-precipitated carbonate salts capable of reacting together in an oxygen atmosphere at an elevated temperature to form a superconducting ceramic which comprises forming a first solution by dissolving in a first solvent maintained at a temperature of from about 15.degree. to 35.degree. C. a rare earth compound, an alkaline earth metal compound, and a copper compound capable of reacting with a carbonate ion to form an insoluble precipitate of carbonate salts in the solvent used to form the solution; forming a second solution containing a carbonate-forming compound dissolved in a second solvent miscible with the first solvent; blending the first and second solutions together at a temperature of from about 0.degree. to 15.degree. C.

Abstract: A process for preparing compound metal oxides, a superconductive compound oxides for instance, is disclosed. The process comprises preparing an aqueous solution containing a predetermined content ratio of chloride, nitrate or acetate of a rare earth metal, an alkaline earth metal and copper, slightly basifying the solution to form hydroxides of the rare earth metal and copper and then introducing carbon dioxide to form carbonate of the alkaline earth metal, collecting the thus formed mixed precipitate of hydroxides and carbonate and firing it.

Abstract: A method for producing a magnesia powder for use as an electrical insulating material. A magnesia clinker powder is washed with an aqueous solution of an acid. The acid radical content of the powder is subsequently reduced to 0.015% by weight or less by washing the powder with water or by subjecting the powder to a heat treatment.

Abstract: A process for the preparation of copper oxide superconductors which comprises (1) mixing and grinding yttrium nitrate hydrate, copper nitride, and an oxidizing agent such as barium peroxide in a suitable solvent; (2) forming a paste thereof; (3) applying the paste to a substrate; (4) heating the substrate with the paste thereon; and (5) therafter cooling. The process yields copper oxide superconducting compounds in a purity of at least 80 percent.

Abstract: A process for the preparation of copper oxide superconductors which comprises (1) mixing copper nitride, an oxidizing agent such as barium peroxide, and yttrium oxide; (2) forming pellets of the aforementioned mixture; (3) heating the pellets; and (4) thereafter cooling the pellets. The process yields copper oxide superconducting compounds in a purity of from about 60 to over 95 percent.

Abstract: A process for producing magnesium oxide and/or hydrates thereof from predominantly magnesium or magnesium-calcium raw materials, and optionally producing calcium carbonate, whereby the raw material is roasted if necessary to form a mixture of magnesium oxide and calcium oxide. The calcium oxide is then dissolved from the mixture using an aqueous solution containing an organic amine and a salt of an organic amine with an acid capable of forming a soluble calcium salt with said organic amine. Separating the solution from the undissolved magnesium oxide and treating the solution with carbon dioxide will cause the dissolved calcium to be precipitated and calcium carbide.

Abstract: Superior homogeneity in ceramic materials is achieved by forming an aqueous solution of trichloroacetates of certain metals, heating the solution to decompose the trichloroacetates to form carbonate precipitates, and recovering the carbonate precipitates. The latter can be calcined to form superconductors. For example, oxides, or carbonates of Y, Ba, and Cu are dissolved in aqueous trichloroacetic acid and the solution is heated to decompose trichloroacetate ions and to form mixed carbonates, which precipitate. The precipitate is recovered and calcined to form a superconducting material.

Abstract: A continuous process for the manufacture of a metal salt solution is described which provides more economical products with higher quality than current processes. The process is safer, both to operating personnel and to the environment, than currently used processes. The process comprises feeding an aqueous metal compound slurry, e.g., a metal oxide/hydroxide slurry and a mineral acid, e.g., nitric acid, and water to a reactor which includes a zone of extreme mixing and agitation, most preferably a cross-pipe reactor provided with an optional static in-line mixer. A cross-pipe reactor provides complete and efficient reaction by providing greater surface area, high agitation and a long reaction time.

Abstract: Magnesium hydroxide of a substantially spherical particle form having an average particle size of from 5 to 500 .mu.m and a specific surface area of from 25 to 1 m.sup.2 /g.

Abstract: Magnesium hydroxide of a fine plate-like particle form having an average particle size (d) of from 0.2 to 0.8 .mu.m as measured by a light transmission type liquid phase sedimentation method, wherein the proportion of particles having a particle size of d+0.5 .mu.m or larger is not higher than 50% by weight based on the weight of the total particles, and the particle thickness distribution is such that the proportion of particles having a thickness of 0.05 .mu.m or less is not higher than 5% by number and the proportion of particles having a thickness of 0.2 .mu.m or more is not higher than 20% by number.

Abstract: A process for producing highly pure magnesium hydroxide, which comprises reacting magnesium hydroxide starting material containing impurities, with an aqueous solution containing a water-soluble calcium salt and carbon dioxide to form an aqueous solution containing a magnesium salt and calcium carbonate precipitates whereby said impurities are transferred to the precipitates, filtering off the precipitates, then reacting the aqueous solution containing the magnesium salt, with ammonia to form a slurry comprising magnesium hydroxide solid and an aqueous solution containing an ammonium salt, and filtering the slurry to obtain highly pure magnesium hydroxide solid and an aqueous solution containing the ammonium salt.

Abstract: A magnesium oxide having a cubic system needle-like crystal structure and a length-to-diameter ratio, determined by an electron microscope at a magnification of 10,000, of at least about 5; and a process for producing a magnesium oxide having a cubic system needle-like crystal structure, which comprises calcining a basic magnesium compound having a needle-like crystal structure expressed by the following formulaMg(OH).sub.2-nx A.sub.x.sup.n-.mH.sub.2 Owherein A.sup.n- represents a monovalent (n=1) to tetravalent (n=4) anion, x is 0.2.ltoreq.x.ltoreq.0.5, and m is 0<m.ltoreq.2,or a magnesium hydroxide having a needle-like crystal structure, at a temperature of not less than about 400.degree. C. to convert it to the magnesium oxide.

Abstract: Magnesium is removed from brine by contacting the brine with calcium hydroxide at temperatures above about 80.degree. C. but below the boiling point of the brine. The contacting results in the formation of magnesium hydroxide precipitate which is substantially insoluble in the mother liquor at those temperatures and strontium hydroxide which is dissolved in the mother liquor. When the contacting is carried out at a temperature above about 90.degree. C., magnesium hydroxide precipitate is fast settling and filterable; accordingly, it is removed from the mother liquor by a conventional process, such as filtering. The mother liquor is then cooled to cause the precipitation of at least a substantial part of strontium hydroxide present in the mother liquor. The precipitate of strontium hydroxide is recovered by a conventional process such as filtering. If precipitation upon cooling is insufficient, carbon dioxide gas is introduced into the mother liquor to effect the precipitation of strontium hydroxide.

Abstract: Slaked lime (calcium hydroxide) is obtained by contacting quicklime (calcium oxide) with an aqueous solution containing at least one anion selected from the group consisting of Cl, Br and NO.sub.3 ions in a concentration of about 0.1 to about 5 mole/liter at a temperature of about 10.degree. C. to about 65.degree. C. Magnesium hydroxide can be produced by reacting the aforesaid slaked lime with magnesium chloride or magnesium nitrate in an aqueous medium, the amount of slaked lime being about 0.5 to about 0.95 equivalent per equivalent of the magnesium compound, and thereafter heat-trating the reaction product in an aqueous medium at a temperature of about 150.degree. C. to about 250.degree. C.

Abstract: Magnesium oxide and a gaseous mixture containing hydrogen chloride and carbon dioxide are prepared by selectively dehydrating magnesium chloride hexahydrate to form the dihydrate and subjecting the dihydrate to a hydropyrolytic treatment with oxygen and coke to form the magnesium oxide and gaseous mixture.

Abstract: A method for leaching magnesium from a magnesium hydroxide-containing composition, especially a mineral, which comprises contacting said composition with an aqueous solution of an ammonium salt whose corresponding magnesium salt is soluble in said aqueous solution to thereby produce said soluble magnesium salt; separating said aqueous solution from said composition; and transforming the magnesium of said soluble magnesium salt into an insoluble magnesium compound. The method is particularly useful for leaching magnesium from brucite-containing chrysotile asbestos fibers, to yield both a magnesium compound and brucite-free, dispersed chrysotile fibers.

Abstract: The present invention relates to a process for the recovery of magnesium oxide of high purity in which the magnesium oxide is obtained by thermal decomposition of a magnesium chloride brine previously purified. The magnesium chloride brine itself is obtained by decomposition of impure starting material with hydrochloric acid and purified before the thermal decomposition. In doing so the brine obtained by the decomposition is first concentrated and the separation of the impurities is effected only then. Calcium is separated in form of calcium sulfate. Optionally calcium sulfate and other impurities may be separated together.

Abstract: Fibrous magnesium hydroxide having a hexagonal needle-like crystal structure. The fibrous magnesium hydroxide can be produced by drying a basic magnesium compound having a needle like crystal structure expressed by the following formulaMg(OH).sub.2-nx.A.sub.x.sup.n-.mH.sub.2 Owherein n is 1 or 2, A.sup.n- represents a monovalent or divalent anion, x is 0.2.ltoreq.x.ltoreq.0.5, and m is O<m.ltoreq.2,under conditions which do not cause a loss of its needle-like crystal form so that a part of the water of crystallization is liberated from the magnesium compound; and contacting the dried magnesium compound with an alkali in a liquid medium which is inert to the magnesium compound and does not dissolve the magnesium compound.

Abstract: A magnesium hydroxide of low lime and boron content is produced from a brine containing magnesium chloride and over 1 ppm boron (on a B.sub.2 O.sub.3 basis) by treating it to reduce its CO.sub.2 content to less than 15 ppm and reacting it with an excess of active lime in a first reaction stage, decanting the spent brine from the precipitated high lime magnesium hydroxide, and then reacting the high lime magnesium hydroxide with additional brine in a second reaction stage to produce a magnesium hydroxide containing less than 1% CaO and less than 0.1% B.sub.2 O.sub.3 on the ignited basis. A portion of the high lime magnesium hydroxide from the first reaction stage is recycled to that stage as seed. Before being discarded, the spent brine from the first reaction stage may be reacted with treated brine to precipitate magnesium hydroxide of relatively high CaO and B.sub.2 O.sub.3 content.

Abstract: Bivalent or multivalent metal chloride in aqueous solution is decomposed in the presence of oxygen to produce HCl and the corresponding metal oxide. Hydrochloric acid recovered by adiabatic absorption from the decomoposition gas is concentrated by extractive distillation in contact with concentrated metal chloride solution. The resulting solution is concentrated by heat exchange with the hot decomposition gas. At least part of the solution of high concentration is supplied to the thermal decomposition stage at a metal chloride rate corresponding to the metal chloride content of the incoming aqueous liquor.