Abstract: A process for producing rhombic or barrel shaped precipitated calcium carbonate. Quicklime is slaked in an aqueous solution containing about 0.1% to about 2% by weight of a sugar, based upon the weight of the CaCO.sub.3 to be produced. Carbon dioxide is added to the slaked lime slurry at a preferred temperature of about 50.degree. F.-70.degree. F. until the pH drops from about 11-12 to about 7-8.

Abstract: A finely powdery magnesium hydroxide especially suitable as a flame-retardant filler for plastic compounds, in which the particles are provided optionally with a thin coating of a surfactant. The grain size of the magnesium hydroxide, measured by laser diffraction, is below 10 .mu.m. The median value of the grain size is greater than 0.8 .mu.m, and the maximum of the median value of the grain size is 3 .mu.m. The contents of water-soluble ionic impurities, viz. Ca.sup.++, Na.sup.+, K.sup.+, SO.sub.4 --, Cl.sup.-, of the magnesium hydroxide are below the following limits (in parts by weight): Ca.sup.++ <1000 ppm, Na.sup.+ <20 ppm, K.sup.+ <20 ppm, SO.sub.4 --<1500 ppm, Cl.sup.- <1000 ppm. The contents of Mn, Cu and Ni are below the following limits (in parts by weight): MnO<100 ppm, NiO<100 ppm, CuO<10 ppm.

Abstract: A process for removing sulfur dioxide from flue gases where calcium sulfate and magnesium hydroxide are produced, with the magnesium hydroxide separated in an impure state and purified by addition of water thereto to dissolve contaminant calcium sulfate. The calcium sulfate preferentially dissolves to form an aqueous solution and purified magnesium hydroxide is separated therefrom. At least a portion of the resultant aqueous solution of calcium sulfate is returned to the wet scrubbing system as make-up water to replenish water lost from the aqueous medium during scrubbing of the flue gases.

Abstract: A method for synthesizing alkaline earth metal-containing ceramic materials by sol-gel processing is described, wherein a sol containing alkoxides or other soluble precursors for a selected ceramic composition, and additionally containing one or more dissolved alkaline earth metal/crown either complexes, is gelled, dried and fired to convert the precursors and complexes to a polycrystalline ceramic product. The crown ether complexes improve alkaline earth metal solubility and the homogeneous incorporation of these metals into the precursor gels and final crystalline products.

Abstract: A process for economically producing tabular acicular gypsum crystals in a continuously stirred reactor is disclosed. The process involves establishing a steady state atmospheric pressure reaction zone of about 20% to about 25% by weight solids of gypsum crystals in water at a temperature of about 50.degree. C. to about 60.degree. C. with continuous mild agitation. Calcium sulfate hemihydrate is fed to the reaction zone at a rate to maintain a low level of supersaturation, and a suspension of gypsum crystals in water containing crystals of a mean particle length at least greater than 45 microns is withdrawn.

Abstract: A process for the production of pure magnesium chloride liquor from siliceous magnesium minerals comprises the steps of continuously leaching the siliceous magnesium mineral with a hydrochloric acid solution at a temperature higher than 50.degree. C. but below the boiling point and in such a manner as to maintain the pH of the slurry below 1.5 to prevent the formation of silica gel, continuously reacting such slurry with a reactive magnesia in order to raise the pH to 4.0-7.0 to precipitate substantially all the impurities from solution while preventing silica gel formation, and performing a solid/liquid separation of the slurry on suitable filtration equipment to obtain pure magnesium chloride liquor.

Abstract: The invention relates to a method of treating power station residues in the form of bulk material, particularly the filter ash from power stations, by hydrating the lime content by adding moisture and by further wetting of the bulk material, with an opportunity for constantly feeding in material to be processed and discharging processed material, and also to an apparatus for carrying out the method. In order to provide a method and an apparatus by which large quantities of power stations residues (ash) can be quickly and safely treated at economic and comparatively low cost, it is according to the invention proposed that the bulk material supplied should pass through a succession of different spatially substantially separate treatment zones be moved mechanically at adjustable intensity throughout the entire process, be differently treated in each treatment zone, be caused to react and transported along a reaction line under control.

Abstract: A process for removing sulfur dioxide from a flue gas in a wet scrubber with an aqueous slurry formed from calcium hydroxide and magnesium hydroxide with magnesium hydroxide or magnesium oxide recovered therefrom. A thickened sludge from a thickener containing calcium sulfite solids is separated and an aqueous sulfite solution removed, with a first portion of the solution returned to the thickener while a second portion thereof is oxidized to form a sulfate solution. Lime is added to the sulfate solution to precipitate calcium sulfate and form an aqueous magnesium hydroxide suspension, with the precipitated calcium sulfate separated from the magnesium hydroxide suspension which may be dewatered to form a magnesium hydroxide product or calcined to produce magnesium oxide.

Abstract: A process for obtaining available elements from seawater is described, which process includes two separation steps. The first separation step involved adjusting the pH of seawater to a low pH by adding a strong acid having sulphate ion, adding a strongly alkaline agent thereto in amount sufficient to provide a high pH and separating the precipitate formed thereby from the filtrate. The second separation step involves concentrating the filtrate, cooling the concentrated filtrate and separating a precipitate thereby formed. Each precipitate and each filtrate obtained in these steps has characteristic components and can be utilized for many purposes, for example, for food additives, as a solvent for paint, as combustion aids, or as alkaline agents for neutralization etc.

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: Magnesia pellets are formed from finely-divided, highly reactive, lightburned magnesia (MgO) particles by granulating such powders in conventional equipment using either an organic liquid or an organic liquid-binder mixture. The organic liquid may be an alcohol or a ketone the alkyl groups of which, independently, can have from 1 to 4 carbon atoms. Magnesium chloride and water are among disclosed binders which may be used in combination with said organic liquid. The organic liquid should be more than about 80% of any admixtures with water.

Abstract: A porous hydroxyl apatite material is disclosed which is made from calcium-rich basic skeletons of lime-encrusting algae converted into hydroxyl apatite and which serves for use as artificial bone, artificial tooth root, augmentation material, stabilization material, artificial hollow bodies or defect filling material.

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 process is provided for producing dry calcium hydroxide by slaking finely divided or ground, softly burnt lime by carrying out the blending of slaking liquid consisting of 30 to 50 parts by volume water and 70 to 50 parts by volume organic solvent with the lime at a temperature below 45.degree. C. in a mixing vessel, subsequently transferring the reaction mixture into a main reaction vessel where the mixture is heated by means of a heating device to a temperature of from 50.degree. to 70.degree. C., and carrying out the final reaction in another reaction vessel. In the mixing vessel, the ratio of lime to slaking liquid is selected in a way such that a final reaction temperature of 85.degree. to 110.degree. C. is reached in the final reaction vessel.

Abstract: The invention relates to the treatment of purge solutions formed in the process of the extraction of zinc by electrolysis.According to the invention, the purge solution, which consists of a part of the purified solution rich in zinc sulfate, is subjected to electrodialysis in the presence of an anion exchange membrane so that a catholyte is formed which is depleted in zinc and in sulfate and which contains magnesium. The catholyte can then be precipitated by neutralization, after recovery of the remaining zinc.Application to the extraction of zinc from its ores.

Abstract: The invention is an improved lime slaker in which the lime is combined with the slaking liquor in a vertical conduit which extends below the level of the liquor in the slaker vessel. The slaking liquor is introduced into the conduit at a high velocity tangential to the interior surface of the conduit to flush the lime into the vessel. The slaker includes a vertical vent pipe that extends through the bottom of the vessel. In a preferred embodiment, the inlet of the vent pipe is surrounded by an entrainment separator. Removable covers permit convenient access for inspection and cleaning of the conduit and the vent pipe.

Abstract: A process for making magnesium hydroxide which comprises treating brine with an adsorptive magnesium hydroxide whereby at least part of the boron ions contained in the brine are adsorbed on to the adsorptive magnesium hydroxide, the brine being mixed counter-currently with the adsorptive magnesium hydroxide in a series of stages such that at each stage the brine is successively contacted with adsorptive magnesium hydroxide from a succeeding stage and there is recovered from the final stage a brine of reduced boron ion content, reacting the brine of reduced boron ion content with alkali to precipitate a low boron magnesium hydroxide and recovering the low boron magnesium hydroxide.

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: A process for the recovery of calcium chloride produced in the conversion of metal chloride by-products of chlorination to hydrous metal oxides. The hydrous metal oxides and other by-products of chlorination are insoluble in an aqueous solution of at least about 75 weight percent calcium chloride having a generally neutral pH and temperature between about 174 degrees centigrade and about 200 degrees centigrade. Calcium chloride also is readily recovered from the above solution.

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: A process for the electrolytic production of a chloride-free mixture consisting essentially of sodium and potassium nitrates is disclosed. In this process, an anolyte brine comprised of a mixture of sodium and potassium chlorides dissolved therein is electrolyzed in a membrane type electrolysis type cell to produce a mixed alkali metal hydroxide catholyte solution. The catholyte is reacted with nitric acid to form a mixed potassium-sodium nitrate solution. By properly adjusting the ratio of potassium chloride to sodium chloride concentration in the anolyte brine, a final nitrate product containing about from about 40% to about 80% NaNO.sub.3 and from about 60% to about 20% KNO.sub.3 by weight can be produced. The resulting product, after drying is suitable for use in many solar panel heat transfer applications.

Abstract: A process for making an industrially usable gypsum from fluoroanhydrite in which fluoroanhydrite is contacted with a fluid reaction medium slurry containing soluble sulfate ions and a substantial proportion of small gypsum seed crystals to rapidly hydrate a large proportion of the fluoroanhydrite to a coarser, substantially pure gypsum. The slurry is clarified to separate coarse purified gypsum reaction product, and the reaction medium is reconstituted and recycled containing gypsum crystals less than the desired reaction product size and constituting about 50-90% of the total solids of the reconstituted fluid reaction medium.

Abstract: A process and apparatus for producing a low sulfur content hot reducing gas by desulfurizing hot reducing gas by contacting the sulfur-bearing hot reducing gas or carbonaceous material with a particulate calcium oxide desulfurizing agent to thereby produce a product gas stream and a byproduct calcium sulfide composition, and then recovering sulfur from the calcium sulfide composition by contacting the calcium sulfide composition with hot liquid water at a temperature and corresponding pressure sufficient to maintain steam in the system and wherein a major portion of the calcium sulfide composition has a particle size of less than about 6 mesh to thereby convert the sulfide to calcium hydroxide and hydrogen sulfide. A preferred process uses this low sulfur content gas to reduce iron ore, and especially wherein ore, calcium oxide and carbonaceous material are reacted in a shaft furnace.

Abstract: A process for the purification of salt brine having magnesium and calcium hardness includes the steps of treating a saturated salt brine containing magnesium and calcium ions with an alkali metal carbonate and an alkali metal hydroxide in a preselected sequence and in amounts in excess of stoichiometric proportions to form firm, readily settleable, filterable floc precipitate particles of insoluble compounds of magnesium and calcium, suspended in the treated brine and passing the resultant suspension to a filtering unit to separate and remove the floc precipitate and to provide a purified salt brine.

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: A process and apparatus for producing a low sulfur content, hot reducing gas by desulfurizing hot reducing gas by contacting the sulfur-bearing hot reducing gas with a bed of a particulate calcium oxide desulfurizing agent to thereby produce a product gas stream and a byproduct calcium sulfide composition, and then recovering sulfur from the calcium sulfide composition by contacting the calcium sulfide composition with hot liquid water at a temperature and corresponding pressure sufficient to maintain steam in the system and to thereby convert the sulfide to calcium hydroxide and hydrogen sulfide and to produce a liquid water stream containing sulfur, and then combining the sulfur-containing water stream with a fresh water stream and recycling this water stream for contacting the calcium sulfide composition. Preferably water vapor produced in the contacting step is condensed and returned to the system in the final stage of contacting the calcium sulfide composition with hot liquid water.

Abstract: Disclosed is a process for producing and then rapidly recovering magnesium hydroxide from an aqueous liquid containing magnesium ion. The magnesium hydroxide is produced by treating the aqueous liquid with lime. The particles of magnesium hydroxide are then recovered from the liquid by causing rapid agglomeration and separation of the magnesium hydroxide particles.

Abstract: Disclosed is a process for refining a magnesium and nickel containing ore, comprising the steps of grinding the ore; preparing a slurry of the ground ore in sulfuric acid containing less than ten percent of water; adding water to the acid-ore slurry in an amount which is effective to initiate a sulfation reaction; allowing the sulfation reaction to continue, utilizing the heat of the sulfation reaction to heat the acid-ore slurry, whereby water-soluble metal sulfates and insoluble residue are formed; leaching the sulfation product with water to extract the water-soluble metal sulfates in solution; separating the metal sulfates solution from the insoluble residue; precipitating from the solution metals other than Mg as hydroxides; separating the solution from the metal hydroxide precipitate; concentrating the solution sufficiently to precipitate CaSO.sub.4 ; separating the concentrated solution from the precipitate; recovering dehydrated MgSO.sub.

Abstract: Highly pure lithium chloride suitable for use in production of lithium metal by electrolysis is obtained directly from impure natural or other lithium chloride brines by an integrated process in which the brine is first concentrated by solar energy to a lithium chloride concentration of about 3%, after which the brine is treated with lime and calcium chloride to convert such impurities as boron, magnesium and sulfate to a calcium borate hydrate, magnesium hydroxide and calcium sulfate dihydrate, respectively, and separating the precipitated calcium sulfate dihydrate from the brine. The brine is then further concentrated to 40% or more lithium chloride by means of solar or other energy, during which concentration step the calcium borate hydrate, magnesium hydroxide and calcium sulfate dihydrate precipitate from the brine. The highly concentrated brine is subjected to evaporation at a temperature above 101.degree. C. to produce anhydrous lithium chloride which is further heated to a temperature of 200.degree.

Abstract: Boron, as well as magnesium and sulfate impurities, are removed from or at least substantially reduced in a lithium containing brine to minimize lithium losses on further concentration of the brine by adding to the brine an aqueous slurry of slaked lime and a solution of calcium chloride to form a calcium borate hydrate, magnesium hydroxide and calcium sulfate dihydrate, the last named compound being precipitated and separated from the brine. On further concentration of the brine, calcium boron hydrate and magnesium hydroxide precipitate and they are also removed from the brine. In an alternate procedure, the pH of the brine is adjusted to 8.0-8.4 by addition of hydrochloric acid to form a calcium borate hydrate, which on further evaporation, is also separated from the brine. The brine is then concentrated further to recover lithium values.

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: 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: A process is disclosed for recovering recoverable chlorine from chemical plant waste streams.An aqueous stream containing recoverable chlorine is reacted with an alkali metal hydroxide, such as sodium hydroxide, to form a slurry of solid particles of alkaline earth metal hydroxide, such as calcium hydroxide, suspended in a liquid. The calcium hydroxide is filtered or otherwise separated from the liquid. The liquid is admixed with an organic alcohol to form an organic-aqueous solution. A halogenating agent, such as chlorine, is reacted with the organic-aqueous solution to form a solution of organic hypochlorite in an organic phase and an aqueous phase.The solution of organic hypochlorite is phase separated to form aqueous and organic phases. The aqueous phase containing sodium chloride may be recycled for use as a reactant in a chlor-alkali electrolytic cell.

Abstract: In the alkaline pulping of cellulose and particularly in the step wherein green liquor is converted to white liquor by causticizing or the addition of calcium hydroxide, it has been found that the addition of any of three specially selected organic phosphonate reagents, namely, nitrilotris(methylenephosphonic acid) (Dequest 2000); 2-phosphonobutane-1,2,4-tricarboxylic acid (Bayer PBS-AM); and hexamethylenediaminetetrakis(methylenephosphonic acid) (Nalco 7691/Dequest 2051), accelerates the speed of the reaction to the right. These acid compounds and their soluble alkali metal and ammonium salts have proved effective in increasing the acceleration rate to the right of the causticizing reaction and the production of the titratable sodium hydroxideCaO+H.sub.2 O.fwdarw.Ca(OH).sub.2ca(OH).sub.2 +Na.sub.2 CO.sub.3 .fwdarw.2NaOH+CaCO.sub.3 .dwnarw.these additives give up to a 2-4% increase in causticizing conversion to NaOH when applied at 0.

Abstract: An aqueous sodium chloride solution for use in production of caustic soda in an electrolytic cell having a cation exchange membrane is purified by adding to said solution a chemical reagent for precipitation separation of impurities remove silica through co-precipitation with a slurry of the precipitates of impurities which are circulated through said solution.

Abstract: In a process for purifying raw brine containing dissolved strontium, calcium and magnesium impurities wherein the raw brine is treated by contacting the brine with sodium carbonate for precipitation of strontium and calcium carbonate, contacting the brine containing the strontium and calcium carbonate solids with sodium hydroxide for precipitation of magnesium hydroxide, and removing strontium carbonate, calcium carbonate and magnesium hydroxide solids from the sodium chloride brine, the improvement which comprises passing at least a portion of said removed solids to the zone wherein the raw brine is contacted with sodium carbonate.

Abstract: In the preparation of homogeneous lime water solution for use in the purification of waste water, a lime water suspension is used as starting material. The lime water suspension is supplied at the bottom of a compartment in which it is caused to rise in order to leave at the upper part, while passing lamellas during its upward movement. The lamellas are arranged in such a way that they will create a sludge zone at their lower part in the compartment, in which zone the rising lime suspension is filtered, whereas they create at their upper part in the compartment a clarification zone in which fine particles are separated.

Abstract: In an industrial process of preparing high-purity magnesia from an impure magnesium-containing starting material, wherein the starting material is dissolved in HCl and the resultant acidic solution is subjected to a multistep treatment for precipitating the impurities out of the solution, the precipitate is separated from the residual purified magnesium chloride solution, and the magnesium chloride is thermally decomposed to obtain magnesia, the purified magnesium chloride solution is first concentrated and sulfate ions are then added thereto to precipitate calcium ions from the concentrated solution as calcium sulfate.

Abstract: Barium hydroxide is continuously produced from barite by:1. reducing barite with carbon at elevated temperatures and hot-leaching the reaction mixture to extract raw barium sulfide;2. partially oxidizing the barium sulfide from step (1) by treatment with oxygen-containing gases and precipitating the resulting barium hydroxide in crystalline form and removing same;3. oxidizing the barium polysulfide contained in the mother liquor from step (2) to difficultly soluble barium thiosulfate by treatment with oxygen-containing gases and removing same; and4. recycling the barium thiosulfate from step (3) to reduction step (1).

Abstract: Aqueous process streams or waste waters destined for merging with public waters sometimes contain deleterious amounts of heavy metals, e.g., lead (Pb) compounds. The heavy metal compounds may be substantially removed or reduced to harmless levels by treating the acidic aqueous streams with chromate or dichromate ions, then heating the solution to oxidize organics and/or heavy metal-organics, then raising the pH to an alkaline pH to precipitate the heavy metal chromate, and separating the heavy metal chromate from the aqueous stream.

Abstract: Brine from a conventional treatment process is pre-filtered prior to the electrolysis of same by a method which includes the steps of: (a) heating the brine, (b) adding sodium carbonate thereto, (c) stirring the solution, (d) allowing the solution to settle, and (e) passing the solution through an absolute membrane filter. The filter "polishes" the brine feed by removing the high hardness ions.

Abstract: A process for removing boron contaminant from magnesium halide-containing brine wherein the brine is contacted with active magnesia to precipitate boron-containing magnesium hydrate and to remove at least 50%, and up to at least 95%, by weight of the total boron content of the untreated brine, without reduction of the magnesium halide content of said brine. The active magnesia is employed in an amount of from about 0.1% to about 10% by weight, preferably from about 2% to about 6% by weight, of the untreated brine, which may be heated e.g., from about 140.degree. F to the boiling point thereof, prior to contact with said active magnesia. Subsequently, the treated brine can be used, by reacting it with dolime, to form magnesium hydroxide which, in turn, can be calcined to produce MgO, each of which is a high-purity-low-boron product, i.e., less than 150 ppm boron on an oxide basis, and preferably less than 75 ppm. In addition, the MgO will contain less than 1.

Abstract: Chemical and aqueous components of sludge derived from lime treatments of raw water supplies are recovered by procedures involving carbonation of the sludges to effect a phase separation between magnesium and calcium components. When the magnesium content of the raw water is intolerable in the treated water, a magnesium carbonate is recovered from the liquid phase by its decarbonation, and the aqueous component of the liquid phase is recycled to recover the water values of the treated sludge. When the magnesium content of the raw water can be tolerated in the treated water, the liquid phase magnesium bicarbonate solution is recycled to the water treatment plant.

Abstract: Sulfate solutions containing at least one valuable metal from the group: Fe, Ni and Co, particularly solutions resulting from the leaching of lateritic ores or concentrates, are treated to recover the valuable metal. The latter is precipitated by treating the solution with magnesium hydroxide. The resulting magnesium-containing solution is treated with lime under controlled conditions to precipitate relatively fine particles of magnesium hydroxide and relatively coarse particles of gypsum. The difference in particle size is relied on to separate the magnesium hydroxide (for recycling) from the gypsum (which is calcined to regenerate lime).

Abstract: Magnesia of very high purity is produced industrially from a magnesite waste material wherein impurities are present in such amounts that the weight ratio of the precipitable hydroxide ions, calculated as the sum of Fe.sub.2 O.sub.3 + Al.sub.2 O.sub.3 + Cr.sub.2 O.sub.3 + Mn.sub.3 O.sub.4 to the sum of SiO.sub.2 + TiO.sub.2 + B.sub.2 O.sub.3, is at least 1 : 3. The starting material is dissolved in hydrochloric acid of 15-32% concentration, the impurities are precipitated by adjusting the pH of the acidic solution to 4 - 9, and the purified magnesium chloride solution is thermally decomposed into magnesia and hydrochloric acid gas, the latter being recycled to form the hydrochloric acid of the stated concentration for dissolving the starting material.

Abstract: A vapor phase process for preparing allylic alcohols which comprises reacting an allylic ester of a lower alkyl carboxylic acid with a lower alkanol in the presence of a transesterification catalyst comprising magnesia.

Abstract: A process for recovering the calcium values and sulfide values from a calcium sulfide-containing material is disclosed. The calcium sulfide-containing material dispersed in an aqueous medium is digested in the presence of hydrogen sulfide under conditions to provide a mole ratio of S.sup.-.sup.-/Ca.sup.+.sup.+ of between 1.5 and 2.0. After filtration to remove undissolved solids, the mother liquor is stripped with an inert gaseous medium, e.g. nitrogen, steam, etc., whereby hydrogen sulfide is stripped therefrom with the concomitant formation of calcium hydroxide which is subsequently separated by filtration. The gaseous overhead from the stripping operations may be fractionated to form a recycleable hydrogen sulfide-containing stream.