Abstract: Acicular ferromagnetic chromium dioxide is stabilized by treatment with an alkali metal hydroxide in an aqueous alkaline suspension at elevated temperatures.

Abstract: Finely divided homogeneous powders of yttrium-stabilized, essentially quadratic zirconia have a narrow particle size distribution, and are prepared by (a) adjusting the pH of a mixed aqueous solution of zirconyl and yttrium acetates to a value of at least 5, (b) eliminating the solvent from such mixed aqueous solution, and (c) pyrolyzing the solid residue resulting from the step (b).

Abstract: Sinterable, morphologically and chemically homogeneous stabilized zirconia fine powders, e.g., yttrium-stabilized zirconia powders, are prepared by heat treating aerosol droplets which comprise a mixed precursor solution of at least one inorganic zirconium salt and at least one inorganic salt of a zirconia-stabilizing element, said heat treating including (a) heating the aerosol droplets to a temperature of from 400.degree. to 500.degree. C. for a period of time of from 4 seconds to 2 hours, and thereafter (b) calcining such droplets at a temperature of from 650.degree. to 1,250.degree. C.

Abstract: The present invention includes metal oxide foam particles and a method of making the same. A decomposable metal salt feed solution is injected into a hot atomizing gas. The mixture of hot atomizing gas and feed solution is maintained in the reactor until the feed solution converts to metal oxide foam particles. The metal oxide foam particles have a high specific surface area.

Abstract: A ZrO.sub.2 powder of very fine particle size adapted especially for the making of high density ceramics is produced by chlorinating a zirconium source material, such as zircon sand, to produce crude ZrCl.sub.4 solids; the solids are dissolved to form a ZrOCl.sub.2 solution from which ZrOCl.sub.2 crystals are precipitated; the crystals are dried and milled to a desired particle size; and the crystal particles are subjected to direct oxidation under controlled conditions to produce a very fine ZrO.sub.2 powder especially adapted to the making of high density ceramics.

Abstract: Zirconium based granules are produced by the steps of forming an aqueous solution of a zirconium compound such as zirconium acetate, combining the aqueous solution with a phase stabilizer, and then heating the solution to evaporation at a temperature below about 180.degree. C. preferably below thereby forming amorphous zirconium based granules.In an alternate embodiment, an alcohol solution of a zirconium compound such as zirconium propoxide in propanol is acidified and hydrolyzed with water. The partially or fully hydrolyzed zirconium complex is mixed with a phase stabilizer to form a homogeneous solution. The solution is then subjected to evaporation at a temperature below about 180.degree. C. or below to form amorphous zirconium based granules.Zirconia fibers are produced by making aqueous solution of the amorphous zirconium based granules containing the phase stabilizer to the desired viscosity, fiberizing the solution, and finally converting the fibers under appropriate conditions.

Abstract: The invention relates to a process for the production of granular sodium perborate monohydrate having good mechanical strength. The process is characterized in that sodium silicate having an SiO.sub.2 /Na.sub.2 O molar ratio comprised within the range of from 0.4 to 2.0 is added to granular sodium perborate tetrahydrate while this is being kept in movement and the so processed perborate tetrahydrate is dried until perborate monohydrate is obtained.

Abstract: Magnesia partially stabilized zirconia materials, having a cubic phase zirconia content in the range 70 to 25 percent (by volume) and a metal oxide additive which forms an insoluble zirconate, and a microstructure in the form of grains of stabilized cubic phase zirconia containing precipitates of tetragonal phase zirconia, are produced for use at low (less than 400.degree. C.) intermediate (between 400.degree. C. and 700.degree. C.), high (700.degree. C. to 1000.degree. C.) or very high (greater than 1000.degree. C.) temperatures. The higher the temperature of use of the ceramic material, the more the tetragonal precipitates need to be transformed into monoclinic phase zirconia. The extent to which the tetragonal precipitates are transformed is controlled by the way in which a fired, pressed mixture of the ceramic components is cooled from about 1400.degree. C. to about 1000.degree. C. An "ageing" of the ceramic material may be effected by an isothermal hold, preferably at 1350.degree. C. and then at 1100.

Abstract: The present invention involves a method for producing a variety of barium titanate based powder products consisting of submicron, dispersible primary particles having narrow size distributions. The method, in its broadest aspects, involves heating an aqueous slurry of PbO, or Pb(OH).sub.2, and Ca(OH).sub.2 with a stoichiometric excess of the hydrous oxides of Ti(IV), Sn(IV), Zr(IV) and Hf(IV) to a temperature not exceeding 200.degree. C. Thereafter, the resulting slurry temperature is adjusted to between 50.degree. and 200.degree. C. and a solution of Ba(OH).sub.2 and Sr(OH).sub.2, having a temperature of 70.degree. to 100.degree. C. is added within a period of five minutes or less to the slurry. About 10 minutes after the addition of the Ba(OH).sub.2 and Sr(OH).sub.2 solution is completed, the slurry is heated to a temperature not exceeding 225.degree. C. to ensure formation of a stoichiometric perovskite product. Thereafter, the slurry is cooled and the solid product is recovered.

Abstract: Seeding of beta type alumina compositions in which the alumina in the raw batch is microcrystalline boehmite results in significant increase in hardness, density and strength, as compared to unseeded beta alumina, when fired under similar conditions.

Abstract: A fine powder of stabilized zirconia a process for its preparation and application of the powder in ceramic compositions to obtain good mechanical, thermomechanical and electrical properties.A zirconia hydrate sol having a pH between 0.5 and 5 and containing elementary acicular crystals having dimensions of from about 10 to 500 .ANG. which are agglomerated into submicron aggregates of from abuot 100 to 5000 .ANG. in diameter is mixed with a solution of a stabilizing agent, preferably yttrium; the suspension is dried; the dried suspension is calcined at a temperature of from about 700.degree. C. to 1,300.degree. C. for preferably from about 30 minutes to 24 hours; and if needed, the powder obtained is milled.

Abstract: An article of manufacture is provided comprising a polycrystalline cubic aluminum oxynitride having a density of at least 98% of theoretical density, and being transparent to electromagnetic radiation in the wavelength range from 0.3 to 5 micrometers with an in-line transmission of at least 20% in this range.A method of preparing the optically transparent aluminum oxynitride is also provided comprising the steps of forming a green body of substantially homogeneous aluminum oxynitride powder and pressureless sintering said green body in a nitrogen atmosphere and in the presence of predetermined additives which enhance the sintering process. Preferred additives are boron and yttrium in elemental or compound form.

Abstract: Substantially spherical mono-sized particles of zirconia can be prepared by the forced hydrolysis of an aqueous solution of zirconyl chloride. A zirconyl chloride solution having a molarity up to about 0.4 is heated for at least 72 hours at a temperature of at least 95.degree. C. to generate suspended particles of hydrated zirconium oxide, which are recovered and calcined to provide the mono-sized zirconia powders. In preferred embodiments, mono-sized powders of a mixture of zirconia with one or more of its stabilizing metal oxides is prepared by precipitating the metal in the form of its hydroxide onto pre-formed zirconium-containing particles.

Abstract: Inorganic metal oxides having high surface area and pore volume are prepared by spray drying. The admixture which is spray dried to yield the metal oxides is produced from reactants comprising at least one hydrolyzable metal compound, a sufficient amount of water to at least partially hydrolyze the metal compound and an organic solvent. The admixture is supplied as a plurality of droplets to a reaction zone operated under conditions of temperature and pressure below the critical temperature and pressure of the reactants but sufficient to produce a product comprising metal oxide powders and a gas comprising organic solvent vapors. The powders are separated from the gas in a known fashion and collected. Spray drying of non-aqueous systems unexpectedly produces metal oxides having properties generally intermediate conventionally produced oxides and aerogels.

Abstract: The invention relates to gas-tight sintered translucent aluminum oxide having a density of at least 99.5%, which contains at most 1000 ppm by weight of MgO. According to the invention, the aluminum oxide also has a content of Er.sub.2 O.sub.3 lying between 20 ppm by weight and 200 ppm by weight. The material thus obtained has a great mechanical strength, a high resistance to attack by sodium and a satisfactory translucence. Thus, the material is very suitable for use as wall material for the discharge vessels of high-pressure discharge lamps.

Abstract: A process for forming a homogeneous mixture of yttrium oxide and zirconium oxide involves dissolving yttrium oxide and hydrochloric acid in water, precipitating yttrium hydroxide by adding ammonium hydroxide to the solution and dissolving yttrium hydroxide in acetic acid, adding zirconium oxide to the resulting solution which is thereafter spray dried to yield an agglomerate having uniformly distributed yttrium acetate throughout and thereafter converting the yttrium acetate to yttrium oxide to yield an agglomerate having uniform distribution of yttrium oxide and zirconium oxide. The yttrium oxide/zirconium oxide agglomerates have a particle size of from about 20 to about 200 microns. The intermediate agglomerate contains a uniform distribution of yttrium acetate and provides a composition which can be converted to a yttrium oxide/zirconium oxide agglomerate having a homogeneous mixture of the two components.

Abstract: A method of preparing substantially homogeneous aluminum oxynitride powder is provided comprising the steps of reacting gamma aluminum oxide with carbon in the presence of nitrogen, and breaking down the resulting powder into particles in a predetermined size range. A method of preparing a durable optically transparent body from this powder is also provided comprising the steps of forming a green body of substantially homogeneous cubic aluminum oxynitride powder and sintering said green body in a nitrogen atmosphere and in the presence of predetermined additives which enhance the sintering process. Preferred additives are boron, in elemental or compound form, and at least one additional element selected from the group of yttrium and lanthanum or compounds thereof. The sintered polycrystalline cubic aluminum oxynitride has a density greater than 99% of theoretical density, an in-line transmission of at least 50% in the 0.3-5 micron range, and a resolving angle of 1 mrad or less.

Abstract: NaBrO.sub.2.3H.sub.2 O crystals with excellent storage stability which contain at least 30 wt. % of NaBrO.sub.2.3H.sub.2 O and 0.5-5.0 wt. % of NaOH. The crystals are produced by precipitation from NaBrO.sub.2 solutions containing NaOH and impurities and are very useful as oxidizing and brominating agents.

Abstract: A process for making a fully or a partially stabilized zirconia is disclosed. The process comprises making an aqueous solution of zirconium sulfate in admixture with an inorganic or organic water soluble salt of one or more metals selected from the group consisting of Be, Mg, Ca, Sr, Ba, Ra, Sc, Y, La, Ac, Ce, Hf, Th and Al. The aqueous solution is atomized into a solvent at least partially miscible with water with the solvent being agitated during the addition of the solution. The coprecipitated metal salt formed is separated from the solvent, washed with inert solvent or solvents, dried, and calcined.

Abstract: Sinterable metal-oxygen composition powders are prepared by mixing aqueous solutions of the metal salt and of poly(acrylic acid), or its ammonium salt, to form a precipitate which is dried, ignited to remove the organic composition and calcined to form the metal oxide or metal-oxygen compound powder.

Abstract: The invention is characterized by two main methods of producing stabilized or partially stabilized zirconia powders with controlled particle size by use of complexing agents and hydrothermal treatment. A further embodiment of the invention is characterized by a combination of the first two methods to produce powders containing more than one major particle size. The invention also allows use of low cost readily available starting material, controlled doping level and incorporation of dual constituents such as MgO, CaO; Y.sub.2 O.sub.3, MgO; or Y.sub.2 O.sub.3, CaO in the structure for production of stabilized zirconia. Triply stabilized zirconia containing Y.sub.2 O.sub.3, MgO and CaO may also be produced. A final embodiment of the invention allows the production of dually and triply stabilized zirconia by hydrothermal treatment without the use of complexing agents.

Abstract: Sub-micron sized powders of the ceramic metal oxides such as zirconia, alumina, titania, etc. are produced by precipitation upon mixing aqueous or aqueous/organic solutions of salts of the corresponding metal(s) with substantially 95% solutions of ammonia donors such as hexamethylenetetramine which are capable of reacting with water to give ammonia. The precipitates are treated with an alkali metal hydroxide to remove adsorbed organic matter, neutralized after completion of this treatment with acid, then washed with ammoniated water to remove any residual soluble salt and/or organic matter, dried, and calcined. The powders thus produced are readily sintered to high density ceramic bodies after conventional pressing or casting into a desired shape.The process is especially suited to the production of zirconia powders, either pure or doped with conventional stabilizing oxides such as yttria, magnesia, or lime.

Abstract: An improved process for the production of potassium sulfate crystals by the reaction of saturated solution of potassium chloride with langbeinite in the solid phase at a temperature of from 45.degree.-55.degree. C., thereby forming potassium sulfate crystals and magnesium chloride solution comprising the step of conducting the reaction in the presence of a growth enhancer comprising monosulfonated or monosulfated surfactant and a neutralized disulfonated surfactant in a weight ratio of from about 0.14 to 0.69.

Abstract: A process for preparing acicular .alpha.-FeOOH by partially neutralizing and then oxidizing a ferrous salt solution in the presence of phosphoric acid or a salt thereof to form seed crystals of .alpha.-FeOOH and optionally further oxidizing said solution while neutralizing said solution with an alkali to grow said seed crystals, wherein pyrophosphoric acid or a salt thereof is used as said phosphoric acid and the seed crystals of .alpha.-FeOOH are formed at a temperature of 50.degree. to 100.degree. C. The .alpha.-FeOOH obtained according to the process of this invention is composed of fine particles and appreciably improved in acicularity and particle size distribution. Also, a magnetic recording medium made from the magnetic iron oxides derived therefrom in a usual way have a low noise characteristic and, are excellent in coercivity and other magnetic properties.

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: The undesirable abrupt expansion and contraction of ammonium nitrate in the temperature range of use of a rocket motor and explosives (-55.degree. C. to 80.degree. C.) is eliminated by the addition of 0.5 to 2% by weight of a crystal growth inhibitor, specifically potassium fluoride (KF).

Abstract: Lanthanum sulfide is maintained in the stable cubic phase form over a temperature range of from 500.degree. C. to 1500.degree. C. by adding to it small amounts of calcium, barium, or strontium. This novel compound is an excellent thermoelectric material.

Abstract: The present invention provides a process for improving the rheological properties of a suspension of precipitated silica by the addition of an aluminum compound, thereby producing a sprayable suspension or slurry with a pH of greater than 3.5, a solids content of at least about 15% by weight, which may be spray dried to form silica in either powder or microbead form. In a preferred embodiment, the aluminum compound added to the suspension is in the form of sodium aluminate.

Abstract: This invention provides a process for producing a fine grain metastable tetragonal zirconia which has an average particle size less than about 1000 angstroms in diameter.The process involves multistage thermolysis of precursor solids comprising a homogeneous mixture of .beta.-ketonate compounds of zirconium and a stabilizer metal such as yttrium.

Abstract: An article of manufacture is provided comprising a polycrystalline cubic aluminum oxynitride having a density of at least 98% of theoretical density, and being transparent to electromagnetic radiation in the wavelength range from 0.3 to 5 micrometers with an in-line transmission of at least 20% in this range.A method of preparing the optically transparent aluminum oxynitride is also provided comprising the steps of forming a green body of substantially homogeneous aluminum oxynitride powder and pressureless sintering said green body in a nitrogen atmosphere and in the presence of predetermined additives which enhance the sintering process. Preferred additives are boron and yttrium in elemental or compound form.

Abstract: Sub-micron sized powders of the ceramic metal oxides such as zirconia, alumina, titania, etc. are produced by precipitation from substantially anhydrous solutions of salts of the corresponding metal(s) with substantially anhydrous solutions of alkali metal hydroxides. The precipitates are subsequently washed with water to remove any residual soluble salt and/or solvent, then are dried and usually calcined. The powders thus produced are readily sintered to high density ceramic bodies after conventional pressing into the desired shape.The process is especially suited to the production of zirconia powders, either pure or doped with conventional stabilizing oxides such as yttria. In a typical example, a zirconia powder doped with 5.4% by weight of yttria is prepared by adding a solution of zirconium tetrachloride and yttrium chloride in anhydrous ethanol to a solution of sodium hydroxide in anhydrous ethanol. After washing, drying at 105.degree. C., and calcining at 500.degree. C.

Abstract: A process for producing acicular magnetite or maghemite of high axial ratio, which comprisespreparing an iron (II) hydroxide suspension at a pH of at least 11 with a magnesium sulfate or magnesium chloride in an amount of 0.5 to 7.0 atomic % based on the amount of the iron (II) hydroxide in the suspension and calculated as the ratio of Mg to Fe (II),oxidizing the resultant suspension with the oxygen-containing gas to form an acicular iron (III) oxide hydroxide in the form of particles having a long axis length of 0.3 to 2.0 .mu.m and an axial ratio of more than 20:1,reducing said acicular iron (III) oxide hydroxide into the acicular magnetite, and oxidizing the resultant acicular magnetite to form the acicular maghemite, if necessary.

Abstract: The use of calcium chloride hexahydrate as a heat accumulating agent for latent heat accumulators is improved when as a nucleating agent (so as to avoid supercooling) special caesium salts, bismuth salts and/or lead salts are used.

Abstract: Particulate red amorphous phosphorus is stabilized against oxidation and phosphine formation by the use of a combination of titanium dioxide or titanium phosphate and an organic resin, usually an epoxy resin, a melamine-formaldehyde resin or a urea-formaldehyde resin.

Abstract: A high frequency dielectric ceramic composition is described, said composition being represented by the formula: Ba(Zr.sub.x Zn.sub.y Ta.sub.z)O.sub.7/2-x/2-3y/2, wherein 0.02.ltoreq.x.ltoreq.0.13, 0.28.ltoreq.y.ltoreq.0.33 and 0.59.ltoreq.z.ltoreq.0.65 (where x+y+z=1). The ceramic composition has a complex perovskite structure, provides a high dielectricity and high Q value at high frequency and selectively provides a temperature coefficient of resonant frequency with a center value of 0 ppm/.degree.C., without using high sintering temperatures and/or long sintering times.

Abstract: A method of preparing substantially homogeneous aluminum oxynitride powder is provided comprising the steps of reacting gamma aluminum oxide with carbon in the presence of nitrogen, and breaking down the resulting powder into particles in a predetermined size range.A method of preparing a durable optically transparent body from this powder is also provided comprising the steps of forming a green body of substantially homogeneous cubic aluminum oxynitride powder and sintering said green body in a nitrogen atmosphere and in the presence of predetermined additives which enhance the sintering process. Preferred additives are boron, in elemental or compound form, and at least one additional element selected from the group of yttrium and lanthanum or compounds thereof. The sintered polycrystalline cubic aluminum oxynitride has a density greater than 99% of theoretical density, an in-line transmission of at least 50% in the 0.3-5 micron range, and a resolving angle of 1 mrad or less.

Abstract: A method for continuously controlling the formation of crystal fines in a continuous crystallizing process in which product crystals are produced in a crystallizing zone from crystallizable material in a mother liquor, and in which product crystals are thereafter recovered. The invention is practiced by adding a flocculant, specific to the crystallizable material, to the mother liquor at a rate effective to cause flocculation of particles of crystallizable material in the mother liquor. One embodiment of the invention is practiced in a process for producing sodium bicarbonate crystals by adding anionic polyacrylate and/or polyacrylamide polymers to a sodium carbonate-containing feed brine received in a carbonator.

Abstract: A liquid melt becomes converted to crystalline form at a particular temperature either spontaneously or when artificially nucleated. The liquid releases heat at crystallization. If the liquid is in a supercooled state when it begins to crystallize, its temperature will rise from the particular temperature at which it is nucleated.Another liquid material is mixed with the liquid to be crystallized. The liquid additive has properties of forming a metastable solid together with the crystallizing material. When the liquid additive exsolves, the crystalline aggregate is weakened and is easily decomposed into fragments of small size. The liquid additive materials may include monohydric alcohols, diols and triols. The liquid additive material may be included in the liquid to be crystallized, in small amounts, amounts to two percent (2%) to five percent (5%) being typical.

Abstract: Process for preparing magnesium nitrate hexahydrate without the need for filtering aids. A process for preparing magnesium nitrate hexahydrate essentially comprises: (a) forming a magnesium oxide or magnesium carbonate suspension in melted magnesium nitrate hexahydrate at a suspension temperature in excess of 90.degree. C.; (b) adding a nitric acid solution to the suspension while stirring thereby forming a reaction mixture containing additional magnesium nitrate hexahydrate; (c) filtering the liquid reaction mixture to obtain a clear magnesium nitrate hexahydrate filtrate; (d) discharging as product a part, corresponding to the amount of magnesium oxide or magnesium carbonate introduced, of the liquid magnesium nitrate hexahydrate obtained as clear filtrate; (e) utilizing the remaining part as liquid medium for the conversion of magnesium oxide or magnesium carbonate with nitric acid.

Abstract: Poly N,N-dimethylaminomethyl acrylamide, when added to clarified trona solutions, improves the crystals subsequently formed from these solutions. Preferably, the poly N,N,-dimethylamino methyl acrylamide crystal modifier is used in conjunction with a water-soluble cationically charged coagulant.

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: This invention relates to a method of producing articles which generate heat at a substantially constant temperature for an extended period of time and which are able to remain in a stable state until such time as the generation of heat is desired. The method also relates to supercooled fluids produced by such methods. The method involves the processing of supercooled fluids such as hypo to produce this stable state. As a first step, a suitable material such as ethylene glycol may be added to the supercooled fluid to stabilize the supercooled fluid and to decrease the generation of heat in the supercooled fluid to obtain a desired temperature. The mixture is then heated to a relatively high temperature considerably above the melting temperature of the supercooled fluid. With the mixture at the high temperature, water is added to provide a particular specific gravity and an alkali is added to provide a particular pH.

Abstract: Zirconia ceramics consisting mainly of ZrO.sub.2 and Y.sub.2 O.sub.3 in a molar ratio of Y.sub.2 O.sub.3 /ZrO.sub.2 of 2/98.about.7/93 and consisting of crystal grains having a mixed phase consisting essentially of tetragonal phase and cubic phase or having a phase consisting essentially of tetragonal phase, the average size of the crystal grains being not larger than 2 .mu.m, has a high strength and shows little deterioration of strength due to the lapse of time, and is suitable as a solid electrolyte for oxygen concentration cells, machine parts for internal combustion engines, thermistors, cutting tools and other industrial materials.

Abstract: A method of selective formation of anhydrite crystals, to the predominant exclusion of formation of gypsum and bassanite, by addition of a small but effective amount of a selective crystallization inhibitor, which inhibits the formation of gypsum and bassanite crystals, but not anhydrite crystals.

Abstract: A liquid melt becomes converted to crystalline form at a particular temperature either spontaneously or when artificially nucleated. The liquid releases heat at crystallization. If the liquid is in a supercooled state when it begins to crystallize, its temperature will rise from the particular temperature at which it is nucleated.Another liquid material is mixed with the liquid to be crystallized. The liquid additive has properties of forming a metastable solid together with the crystallizing material. When the liquid additive exsolves, the crystalline aggregate is weakened and is easily decomposed into fragments of small size. The liquid additive materials may include monohydric alcohols, diols and triols. The liquid additive material may be included in the liquid to be crystallized, in small amounts, amounts to two percent (2%) to five percent (5%) being typical.

Abstract: A magnesia partially stabilized zirconia ceramic material possessing from about 2.8 to about 4.0 wt percent magnesia, and made from a zirconia powder containing no more than about 0.03 percent silica is described. The ceramic material has a microstructure, produced as a consequence of the method by which the material is made, which provides both high strength and good thermal shock resistance properties. This microstructure comprises grains of cubic stabilized zirconia within which are formed, during cooling from the firing temperature, precipitates of tetragonal zirconia. These precipitates are elliptical in shape, with a long axis of about 1500 Angstrom units. Additionally, some of the tetragonal zironcia precipitates are made to transform into a non-twinned microcrystalline monoclinic form of zirconia by reducing the temperature of the material to below 800.degree. C., then subsequently holding the material at a temperature in the range from 1000.degree. C. to about 1400.degree. C.

Abstract: The average size of Glauber's salt crystals formed by crystallization of Na.sub.2 SO.sub.4 from aqueous solution in systems comprising Na.sub.2 SO.sub.4, H.sub.2 O and Glauber's salt is decreased by including a fluorine-containing surfactant in the system.

Abstract: An improved process for the manufacture of ammonium nitrate prills and granules in which a water soluble aluminium salt is added to the process stream prior to the concentrate, which is then used in the prilling or granulating process, being formed.

Abstract: Dicalcium phosphate dihydrate containing a sufficient amount of trimagnesium phosphate and/or tetrasodium pyrophosphate to inhibit spontaneous hydrolysis and/or decomposition of the dicalcium phosphate dihydrate is widely used as a dental polishing agent with and without added fluoride. Now it has been found that dicalcium phosphate dihydrate containing a sufficient amount of pyrophosphate to provide hydrolytic stability to the dicalcium phosphate can have improved fluoride stability when about 0.1 weight percent to about 5 weight percent of trimagnesium phosphate, and about 0.1 weight percent to about 3 weight percent of at least one pharmaceutically acceptable condensed phosphate salt is added to the formulation. In the preferred embodiment less than 2 percent sodium tripolyphosphate provides satisfactory results.

Abstract: Dicalcium phosphate dihydrate containing a sufficient amount of trimagnesium phosphate and/or tetrasodium pyrophosphate to inhibit spontaneous hydrolysis and/or decomposition of the dicalcium phosphate dihydrate is widely used as a dental polishing agent with and without added fluoride. Now it has been found that dicalcium phosphate dihydrate containing a sufficient amount of pyrophosphate to provide hydrolytic stability to the dicalcium phosphate can have improved soluble fluoride stability when at least 0.1 weight percent of trimagnesium phosphate and a pharmaceutically acceptable polyphosphate salt are each added to the formulation. In the preferred embodiment, less than 2 percent pentasodium tripolyphosphate provides satisfactory results.