Abstract: A form of calcium carbonate having a blocky rhombohedral crystal structure and properties including a surface area of from about 3 to about 15 m.sup.2 g, an average discrete particle size of from about 0.2 to about 0.9 micron, wherein the discrete particles have an aspect ratio less than about, 2:1 and a particle size distribution such that at least about 60 weight percent of the particles have a size within 50 percent of the equivalent discrete particle spherical diameter, suitable for use as a filler material in papermaking to improve the optical properties of the resulting paper, is disclosed. An accelerated heat-aging process, including embodiments thereof which utilize hydrothermal techniques, for rapidly producing this form of calcium carbonate, and a related form of calcium carbonate having a hexagonal prismatic crystal structure and the same properties, in large quantities to meet the demand of the papermaking industry, as well as a method for using these materials in papermaking, are also disclosed.

Abstract: A method is proposed for the preparation of porous calcium carbonate particles of which each of the particles is not an aggregate but has ink bottle-shaped pores each not communicating with the others. The method comprises: (a) blending particles of heavy calcium carbonate having a specific particle size distribution with from 0.1 to 0.3% by weight of a porosity-forming agent, e.g., sodium chloride; (b) calcining the powder blend at a temperature in the range from 800.degree. C. to 1000.degree. C. to decarbonate the calcium carbonate particles into particles of calcium oxide having pores developed therein; (c) slaking the particles of calcium oxide with steam to convert the calcium oxide particles into particles of calcium hydroxide; (d) drying the particles of calcium hydroxide at a temperature in the range from 100.degree. C. to 350.degree. C.; and (e) carbonating the dried particles of calcium hydroxide with carbon dioxide gas at a temperature in the range from 600.degree. C. to 750.degree.C.

Abstract: The present invention relates to a process for the preparation of substantially spherical monocrystalline vaterite, in particular, of vaterite having a determined size.

Abstract: A monodisperse spherical, ellipsoidal or plate-like vaterite calcium carbonate almost free from secondary aggregation is disclosed. The vaterite type calcium carbonate is prepared by the steps of adding 5-20 times mol equivalent of water with respect to unslaked lime to a methanol suspension of 0.5-12 weight % of unslaked lime and/or slaked lime (in case of slaked, conversion is to be made into unslaked lime of the same mol) to prepare of a mixture of methanol, unslaked lime and/or slaked lime and water, letting carbon dioxide gas through said mixture, adjusting the temperature in the carbonation reaction systemto not less than 30.degree. C. before arrival of conductivity within carbonation reaction system at the maximal point on conductivity variation curve in the carbonation reaction system and adjusting the time from start of carbonation reaction to the point where the conductivity is 100.mu. S/cm to be less than 1,000 minutes.

Abstract: A form of calcium carbonate having a blocky[-six-sided] rhombohedral crystal [habit ] structure and [a morphology, with] properties including a surface area of from about 3 to about 15 m.sup.2 /g, an average discrete particle size of from about 0.2 to about 0.9 micron, wherein the discrete particles have an aspect ratio less than 2, and a particle size distribution such that at least about 60 weight percent of the particles have a size within 50 percent of the equivalent discrete particle spherical diameter, suitable for use as a filler material in papermaking to improve the optical properties of the resulting paper, is disclosed.

Abstract: An improved method for the production of synthetic hydrotalcites having high purity (99+%) and small particle size (<2 microns) is disclosed. This method used inexpensive and available reactants and is suitable for commercial scale production. A source of magnesium, such as magnesium hydroxide; a source of aluminum from a mixture of alumina trihydrate and an alkali metal aluminate; and a source of carbonate, such as sodium bicarbonate, are reacted under hydrothermal conditions at a temperature of between 160.degree.-200.degree. C. to produce synthetic hydrotalcite.

Abstract: The calcium carbonate is prepared by:(a) slaking quicklime in an aqueous medium;(b) carbonating and neutralizing the suspension of slaked lime formed in step (a) using a gas comprising carbon dioxide; and(c) separating the precipitated calcium carbonate formed in step (b) from the aqueous medium in which it is suspended. There is added 0.01% to 15% by weight, based on the weight of dry calcium oxide, of a reagent having one or more active hydrogen atoms (or a salt thereof), to the aqueous medium in which the quicklime is slaked in step (a).The reagent is selected from the group consisting of triethanolamine, mannitol, diethanolamine, bicine, morpholine, tri-isopropanolamine, N-ethyl diethanolamine, N,N-diethylethanolamine and sodium boroheptonate.

Abstract: The processing of leaching residues from barium sulfide leaching is described. Sodium sulfide as well as a solid which is useful as an additive for fired clay products, particularly bricks, are obtained as valuable reaction products.

Abstract: Disclosed is a process for producing aragonite crystal form calcium carbonate with an acicular shape characterized by premixing aragonite crystal calcium carbonate and Ca(OH).sub.2 to prepare an aqueous slurry, adding a water-soluble phosphoric acid compound into the aqueous slurry, and introducing CO.sub.2 gas into the aqueous slurry to cause the carbonation reaction to take place. According to the present invention, aragonite crystal form calcium carbonate in an acicular shape with a large particle size is produced.

Abstract: A colored precipitated calcium carbonate having a strong color fastness in water is produced by preparing an aqueous slurry containing calcium hydroxide and a water-soluble dye, for example, a direct dye, introducing a carbon dioxide-containing gas into the aqueous slurry, and collecting the resultant colored precipitated calcium carbonate from the aqueous slurry at a pH of 8.2 or more thereof.

Abstract: For a treatment of the residues which become available as dry dust in the purification of exhaust gas and contain, inter alia, 5 to 12% by weight CaO and have a conductance in excess of 6000 .mu.S/cm, a process is proposed in which the residues are fluidized with purified exhaust gas in a circulating fluidized bed system consisting of a fluidized bed reactor, separator and recycling line and the CaO contained in the residues is reacted with the CO.sub.2 contained in the exhaust gases to form CaCO.sub.3.

Abstract: The invention provides a method for the preparation of a calcium carbonate powder of which the particles have a platelet-like particulate configuration and which is useful as a pigment or filler in various products with superiority to kaolin clays and mica powders. The method is a two-step carbonation method of a milk of lime of which the first step is performed by blowing carbon dioxide into the milk of lime until 10 to 70% of the calcium hydroxide is carbonated and the second step is performed by admixing the thus partially carbonated milk of lime with an aqueous carbonating solution containing an alkali metal carbonate or ammonium carbonate and an alkali metal hydroxide or ammonium hydroxide in specified concentrations to complete the carbonation of the calcium hydroxide.

Abstract: The present invention is directed to an improved method for carrying out a exothermic chemical reaction with carbon dioxide in an aqueous environment. In the method, a fluid solution containing at least one chemical reactant which is exothermically reactive with carbon dioxide is provided. Liquid carbon dioxide is then injected into the solution of the chemical reactant at a pressure above the triple point of at least about 60 psig. The injection of the liquid carbon dioxide takes place under turbulent conditions wherein the liquid carbon dioxide expands to provide carbon dioxide vapor. The carbon dioxide vapor superheats to approach the exothermic reaction temperature which occurs between the carbon dioxide vapor and the chemical reactant. The chemical reactant and the carbon dioxide react in the dispersion exothermically to produce a chemical reaction product.

Abstract: An improved method for causticizing the green liquor formed in a kraft paper plant by contacting the green liquor with lime to thereby form white liquor followed by clarifying the white liquor by removing the lime mud therefrom in a clarifier is disclosed wherein the improvement lies in removing the lime mud from the clarifier at a predetermined rate.

Abstract: Disclosed is a calcium carbonate which is 25 to 55 m.sup.2 /g in BET specific surface area, 5 to 110 in the ratio of BET specific surface area (m.sup.2 /g)/mean particle size (.mu.m), at least 120 ml/100 g in oil absorption as determined by the Ogura method and at least 1.8 g/g in water absorption, and process for preparing the same. The calcium carbonate is formulated into a coating composition for forming a heat-sensitive recording layer or intermediate layer of a heat-sensitive recording paper or for forming an ink-jet recording paper.

Abstract: This invention concerns a process for the preparation of large surface area, finely divided precipitated calcium carbonate which comprises introducing carbon dioxide into an aqueous slurry of greater than about five weight percent calcium hydroxide containing an anionic organopolyphosphonate polyelectrolyte, starting the introduction at a temperature above about 7.degree. C. and below about 18.degree. C., continuing the introduction until calcite precipitation is substantially complete and adding a quantity of polybasic acid to the slurry in an amount greater than about 0.3% by weight of the precipitated calcium carbonate. This invention also concerns said large surface area, finely divided precipitated calcium carbonate which has been coated with a fatty acid derivative and polymeric compositions which contain such coated calcium carbonate.

Abstract: A precipitated alkaline earth metal carbonate is produced by calcining raw alkaline earth metal carbonate, for example a calcium carbonate, under conditions such that substantially all the chemically combined carbon dioxide is driven off to form an oxide, slaking the oxide in water to form a suspension of the corresponding alkaline earth metal hydroxide, allowing the suspension to cool to 45.degree. C. or below, and then carbonating the hydroxide in suspension in water with substantially pure carbon dioxide in the presence of a dithionite bleaching reagent to form a precipitate of an alkaline earth metal carbonate of increased brightness and purity. The precipitate may then be separated from the aqueous medium by, for example, filtration.

Abstract: Process for causticizing a water solution containing alkali carbonate with calcium oxide and hydroxide by bringing the water solution containing alkali carbonate into contact with the calcium oxide or hydroxide and by separating the alkali hydroxide solution arisen in the causticizing from the calcium carbonate precipitate. The water solution containing alkali carbonate is conducted through a bed which has been formed by mixing calcium oxide and calcium carbonate in the causticized alkali solution and by removing the excess alkali solution.

Abstract: A process for producing calcium carbonate from calcium hydroxide derived from, for example, limestone, comprises injecting a gas containing carbon dioxide into a recirculating stream flowing in a recycle piping system in communication with a reaction vessel. The carbon dioxide containing gas is injected at a turbulent area located in the recycle piping system. By controlling reaction parameters including pH and temperature, novel calcium carbonate products are formed by the process.

Abstract: Disclosed is a novel process of producing needle-shaped calcium carbonate particles. In the process of the present invention, aqueous calcium hydroxide solution is added to an aqueous medium bath with a temperature of not less than 60.degree. C. into which carbon dioxide gas or a carbon dioxide-containing gas is being blown to generate needle-shaped calcium carbonate particles. The temperature of the aqueous medium bath is kept not less than 60.degree. C. during the addition of the aqueous calcium hydroxide solution. Then the generated needle-shaped calcium carbonate particles are recovered.

Abstract: An electrode provided with an alkali or alkaline earth hydroxide constituent which upon heat treatment in the presence of carbon dioxide is converted to a carbonate constituent.

Abstract: The invention concerns a causticizing procedure by which from soda liquor derived from a sulphate cellulose digesting process and from unslaked lime is produced white liquor for reuse in the digesting process, over lime slaking and a subsequent causticizing reaction proper. It is essential in the invention that the lime slaking is carried out using white liquor, whereafter the causticizing reaction proper is allowed to take place between the slaked lime and soda liquor combined therewith. The requisite white liquor is obtained by recirculating part of the white liquor produced by the causticizing process, to the slaking step, where it either completely or partially replaces the soda liquor employed in prior art. By using white liquor, one avoids the foaming, interfering with the process, which is encountered in the slaking step.

Abstract: Dry, stable carbonating agents comprised of a carbohydrate/metal bicarbonate complex are disclosed. The complex is prepared by reacting a carbohydrate with a metal hydroxide or oxide at a temperature not exceeding 25.degree. C. to form a carbohydrate/metal hydroxide adduct to which carbon dioxide is then introduced to form the complex. The complex is then immediately dried, preferably by freeze drying. The carbonating agents are particularly useful as components of dehydrated beverage powders. Upon rehydration, the complex releases carbon dioxide and carbonates the beverage. Additionally, upon rehydration the complex promotes the solubilization of the carbohydrate components in the beverage.

Abstract: A precipitated calcite of substantially spherical morphology having an average spherical diameter of from 2 to 10 microns and a specific surface area of from 1 to 15 square meters per gram is prepared by introducing carbon dioxide gas into an aqueous slurry of calcium hydroxide containing dissolved polyphosphate in the amount of from 0.1 to 1.0 percent, calculated as grams of phosphorus per 100 grams of the calcite equivalent of the calcium hydroxide, the starting temperature of the carbonation being 15.degree. to 50.degree. C. The spherical calcite is particularly suitable for use in dull finish coated paper.

Abstract: A process of recausticizing kraft green liquor in which the green liquor containing sodium carbonate is passed in a stream in admixture with particles comprising slaked lime, in which stream the liquid phase becomes progressively weaker in sodium carbonate and stronger in sodium hydroxide. Lime is added in order to provide a continuous supply of slaked lime for reaction with the sodium carbonate, and the stream is passed to a solids/liquid separator which recovers liquid phase from said stream, strong in NaOH, continuously and separately from the solid phase of the stream, as white liquor. The rate of the recausticizing reaction is limited by the rate of diffusion of carbonate ion into the solid particles, and of hydroxyl ion out of the solid particles. Typically, these rates limit the amount of causticizing achieved to less than the equilibrium value.

Abstract: The present invention seeks to provide a method in which the soda lye obtained as a result of cellulose cooking process and unslaked lime are used for producing white liquor which can be re-used in the cooking process. In this method, the heat released by the slaking of lime with soda lye is recovered by a high pressure slaking process wherein the heat is transferred, either to the steam separating from the lye, which steam is then led to the desired application, or to some other medium to be heated. The present invention is characterized in that the soda lye to be causticized is divided into two parts, one of which is used for the slaking of lime by adding to it all the unslaked lime needed for the causticizing process, and that, following slaking, the two volumes are brought together for the actual causticizing reaction involving the total amount of lye needed. The present invention provides the advantage that the amount of lye needed is smaller, and so the temperature can be increased.

Abstract: There is provided a process for preparing caustic soda solutions from naturally occurring alkaline minerals comprising double salts of sodium carbonate and calcium carbonate. The process comprises heating said naturally occurring alkaline minerals to temperatures sufficient to dehydrate and partially decarbonate said alkaline minerals and provide an intermediate product of a mixture of sodium carbonate and calcium oxide. This intermediate then is contacted with water to effect causticization of the sodium carbonate and provide a recoverable phase comprising an aqueous solution of caustic soda.

Abstract: The invention provides particulate calcium carbonate having incorporated therein from 0.1 to 10% by weight, based on the weight of calcium carbonate, of polymaleic acid or a water-soluble salt thereof.

Abstract: An internal combustion engine having a plurality of cylinders each comprising a first intake valve, a first intake passage connected to the corresponding cylinder via the first intake valve, a second intake valve, and a second intake passage connected to the corresponding cylinder via the second intake valve. A second throttle valve is provided for each second intake passage and opens when the load of the engine is increased beyond a predetermined level. A blind common connecting passage is provided, which has a plurality of branch passages each being open to the corresponding second intake passage located downstream of the corresponding second throttle valve.

Abstract: A causticization method including the steps of calcining limestone in the presence of additive means for producing lime of increased lime efficiency relative to the lime that would result from calcining such limestone without the presence of the additive means, lime efficiency being determined on a sodium carbonate solution for which conditions, other than the character of the lime, are fixed, and subsequently feeding the lime of increased lime efficiency into the sodium carbonate solution for producing sodium hydroxide and calcium carbonate from the sodium carbonate.

Abstract: A method for recovering a magnesium carbonate of high purity from an aqueous magnesium hydroxide slurry is disclosed. The slurry contains at least 1 percent of magnesium hydroxide and consists of water, magnesium hydroxide and impurities normally associated with magnesium hydroxide slurries. The method involves carbonating the slurry with sufficient carbon dioxide to dissolve a substantial proportion of the magnesium hydroxide therein as magnesium bicarbonate, continuing carbonation until a solution saturated with magnesium bicarbonate is formed, a portion of the magnesium bicarbonate is converted to a crystalline magnesium carbonate and substantially all dissolved calcium is precipitated, so that the slurry contains dissolved magnesium bicarbonate, a crystalline magnesium carbonate precipitate and a calcium carbonate precipitate.

Abstract: A process for the preparation of finely divided precipitated calcite in which carbon dioxide is introduced into an aqueous calcium hydroxide slurry containing anionic organopolyphosphonate polyelectrolyte with the carbonation started at a temperature above about 7.degree. and below about 18.degree. C.

Abstract: Fibrous hydrotalcites having a hexagonal needle-like crystal structure. The fibrous hydrotalcites are produced by contacting a basic magnesium compound having a needle-like crystal structure and expressed by the following formula (2)Mg(OH).sub.2-n'x.sbsb.2 A.sub.x.sbsb.2.sup.n'.spsp.-.m.sub.2 H.sub.2 O (2)wherein A.sup.n'.spsp.- represents a monovalent or divalent anion, n' is 1 or 2, and x.sub.2 and m.sub.2 are numbers satisfying the following conditions,0.2.ltoreq.x.sub.2 .ltoreq.0.5,O.ltoreq.m.sub.2 .ltoreq.2,with a compound capable of providing a trivalent metal cation and being soluble in a liquid reaction medium which is chemically inert and is a non-solvent for the basic magnesium compound, the contacting being carried out in said liquid reaction medium under conditions which do not cause a loss of the needle-like crystal form of the basic magnesium compound, while maintaining the ratio of M.sup.3+ to the sum of Mg and M.sup.3+ at O<M.sup.3+ /(Mg+M.sup.3+).ltoreq.0.

Abstract: Mineral filler such as calcium carbonate, having at most 15% by weight of particles which are smaller than 0.2 .mu.m with a corresponding spherical diameter, method of preparation, and use thereof are provided.

Abstract: The invention provides calcium carbonate particles comprising a core and projections formed thereon, and process for preparing same. The calcium carbonates of this invention are useful as fillers and pigments for rubbers, plastics, papers, etc. because of their peculiar configuration and unique properties.

Abstract: This invention relates to stable, fluid magnesium-containing dispersions and the preparations thereof by the high temperature dehydration of Mg(OH).sub.2 to MgO in a dispersant-containing fluid.

Abstract: Bone china is produced by including a boron-containing substance in the composition in water-insoluble form. Use of the boron-containing compound results in a lowering of the firing temperature and widening of the firing temperature range.

Abstract: A process for treating "brine mud" as produced in brine purification processes and for the coproduction of a calcium sulphate and magnesium carbonate which comprises(i) carbonating a slurry of "brine mud" in sodium chloride brine with carbon dioxide to produce a slurry of solids comprising calcium carbonate and a liquor comprising magnesium bicarbonate and sodium chloride.(ii) separating the slurry produced by the carbonation stage (i) into moist solid calcium carbonate and a liquor comprising magnesium bicarbonate and sodium chloride.(iii) heating the liquor from (ii) to produce a slurry of solids comprising magnesium carbonate, a liquor comprising sodium chloride, and gaseous carbon dioxide.(iv) separating the slurry from (iii) into moist hydrated magnesium carbonate and a liquor comprising sodium chloride and(v) drying the moist hydrated magnesium carbonate.

Abstract: An improvement in the method of preparing high alkali value overbased magnesium sulfonate lubricant additives from commmercially available grades of magnesium oxide is disclosed.

Abstract: Chain structured corpuscular calcium carbonate is produced by a carbonation of calcium hydroxide suspended in water in the presence of a chelating agent and a water soluble metal salt.

Abstract: The invention disclosed provides a new improved chemical method for combustible fuel production by converting carbon dioxide in the atmosphere to a carbonate following which the recovered carbonate is combined with hydrogen gas to produce combustible fuels e.g. methane and methanol. The present method provides means for fuel generation and may advantageously use heat and radiation energy derived from nuclear reactors.This application implies certain environmental advantages, in that burning of fuels containing carbon derived only from atmospheric CO.sub.2 would not add to the CO.sub.2 content of the atmosphere. Recycling of lime as CaO or Ca(OH).sub.2 would eliminate the problem of disposing of those materials as encountered by others teaching use of carbonates but not using such a closed cycle.

Abstract: Precipitated calcium carbonate of uniform particle size is produced by contacting a suspension of calcium hydroxide with a carbon dioxide-containing gas in three steps. The particle size of precipitated calcium carbonate can be optionally selected by suitably adjusting reaction conditions.

Abstract: Cubic calcium carbonate crystals of uniform size are prepared by contacting with CO.sub.2 a starting aqueous suspension containing Ca(OH).sub.2 and cubic CaCO.sub.3 crystals less than 0.1.mu.m in size, adding Ca(OH).sub.2 to the suspension resulting from the first step and contacting the resultant mixture with CO.sub.2.

Abstract: Calcium carbonate is manufactured by the carbonation of an aqueous suspension of calcium hydroxide in the presence of a complex-forming agent for calcium ions which is added subsequently to the primary nucleation stage, and preferably during a first carbonation stage. Optionally there is also added a long-chain fatty acid or long-chain fatty acid salt, preferably after a final carbonation stage.

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.