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Calcium carbonate

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Calcium carbonate Basic information
Calcium carbonate Chemical Properties
  • Melting point:825 °C
  • Density 2.93 g/mL at 25 °C(lit.)
  • refractive index 1.6583
  • storage temp. Store at RT.
  • solubility 5 M HCl: 0.1 M at 20 °C, clear, colorless
  • form random crystals
  • color White-beige to slightly beige-gray
  • Specific Gravity2.93
  • PH9.5-10.5 (100g/l, H2O, 20℃)(slurry)
  • Water Solubility Insoluble
  • λmaxλ: 260 nm Amax: ≤0.09
    λ: 280 nm Amax: ≤0.06
  • Merck 14,1657
  • BRN 8008338
  • Solubility Product Constant (Ksp)pKsp: 8.54
  • Stability:Stable. Incompatible with acids, fluorine, ammonium salts, alum.
  • CAS DataBase Reference471-34-1(CAS DataBase Reference)
  • EPA Substance Registry SystemCarbonic acid calcium salt (1:1)(471-34-1)
Safety Information
Calcium carbonate Usage And Synthesis
  • UsesCalcium carbonate (CaCO3) can be in the form of an odorless crystal or powder and is one of calcium’s most stable compounds, better known in its natural state as limestone, marble, chalk, calcite, oyster shells, and the minerals marl and travertine. Calcium carbonate is the source of lime and is used as a “filler” for many products, including paints, plastics, and foods (bread), and as an antacid.
  • DescriptionCalcium carbonate occurs in nature as limestone in various forms, such as marble, chalk, and coral. It is probably the most widely-used raw material in the chemical industry. It has numerous applications, primarily to produce cement, mortars, plasters, refractories, and glass as building materials. It also is used to produce quicklime, hydrated lime and a number of calcium compounds. It is produced either as powdered or precipitated calcium carbonate. The latter consists of finer particles of greater purity and more uniform size. They also have many important commercial applications. Various grades of precipitated calcium carbonate are used in several products, such as textiles, papers, paints, plastics, adhesives, sealants, and cosmetics.
    calcium carbonate block
    calcium carbonate block
  • Chemical PropertiesCalcium carbonate occurs in two forms—hexagonal crystal known as calcite, and orthorhombic form, aragonite. Calcite decomposes on heating at 825°C, aragonite melts at 1,339°C (at 102.5 atm). Density 2.71 g/cm3 (calcite), 2.83 g/cm3 (aragonite); insoluble in water (15mg/L at 25°C); Ksp 4.8x10–9 ; soluble in dilute mineral acids.
  • Chemical PropertiesCalcium carbonate occurs as an odorless and tasteless white powder or crystals.
  • Physical propertiesCalcium carbonate is a naturally occurring compound found in organisms and throughout the earth’s crust. After quartz, calcium carbonate, primarily in the form of calcite, is the most common mineral found in the crust. Geologically, calcium carbonate exists in several mineral forms: calcite, aragonite, and vaterite. Calcite is the most common calcium carbonate mineral, whereas vaterite is a very rare form. The different mineral forms of calcium carbonate are based on their crystalline structure. The form of calcium carbonate depends on the conditions at its formation such as temperature and pressure.
  • Physical propertiesCalcium carbonate has the molecular formula of CaCO3and the molecular weight of 100.0924 g/mol. It is a common substance found in rock in all parts of the world, and is the main component of the shells of many marine organisms such as snails and conches. It is the main ingredient in eggshells of birds and pearls obtained from oysters.
    Calcium carbonate is the active ingredient in “limestone” used as “agricultural lime” and is the principal cause of “hard water” since most subterranean streams used for fresh water come from wells where underground water flows through limestone beds which are eroded due to its passage. Calcium carbonate occurs in nature as limestone in various forms, such as marble, chalk, and coral.
  • UsesHumans primarily use calcium carbonate as a primary source of calcium to combat osteoporosis. Most limestone is used today as construction material. In addition to its use as a construction material, calcium carbonate is also used in numerous industrial processes. Two forms commonly used are ground calcium carbonate (gcc) and precipitated calcium carbonate (pcc).
    Calcium carbonate is used widely in papermaking as filler and coating pigment to whiten paper. Calcium carbonate is used in place of more expensive optical brightening agents in paper and as a fill to replace more expensive wood pulp fiber; it also helps control the pH in an alkaline range.
    The second most common industrial use of calcium carbonate (after papermaking) representing the largest use of gcc is in the production of plastics. It is used in the production of polyvinyl chloride (PVC), thermoset polyesters, and polyolefins. Calcium carbonate can be used to replace resins that are more expensive. Similar to its use in the paper industry, it is used as an optical brightener and whitening agent. It also is used to increase strength and absorb heat during exothermic processes.
    Calcium carbonate is also used in the production of polyethylene and polypropylene. It is an additive to paints and coatings for several purposes including particle size distribution, opacity control, weather resistance, pH control, and anticorrosion. Calcium carbonate is used to buff er acidic soils.
    Calcium carbonate has also been used to mitigate the effects of acid precipitation on water bodies. Another environmental application of calcium carbonate is for gas desulfurization in scrubbers used to reduce sulfur emissions from air pollution sources.
  • UsesCalcium Carbonate is the calcium salt of carbonic acid which is used as an anticaking agent and dough strengthener. it is available in varying particle sizes ranging from coarse to fine powder. it is practically insoluble in water and alcohol, but the presence of any ammonium salt or carbon dioxide increases its solubility while the presence of any alkali hydroxide reduces its solubility. it has a ph of 9–9.5. it is the primary source of lime (calcium oxide) which is made by heating limestone in a furnace. calcium carbonate is used as a filler in baking powder, for calcium enrichment, as a mild buffering agent in doughs, as a source of calcium ions in dry mix desserts, and as a neutralizer in antacids. it is also termed limestone.
  • UsesMade by adding soluble carbonate to a calcium salt solution. The white powder or crystals are soluble in acid but not in water. Calcium carbonate was used to neutralize gold toning baths and as a fine abrasive added to water and alcohol for cleaning glass plates before they were coated with photographic binders.
  • UsesCalcium carbonate is probably the most widely used raw material in the chemical industry. It has numerous applications, primarily to produce cement, mortars, plasters, refractories, and glass as building materials. It is also used to produce quicklime, hydrated lime and a number of calcium compounds.
  • Production MethodsCalcium carbonate is obtained from natural limestone deposits. The purified compound, known as precipitated calcium carbonate, is synthesized from limestone. Limestone is calcined to calcium oxide and carbon dioxide in a kiln. The products are recombined after purification. Calcium oxide is hydrated  with water to give a slurry called milk of lime, which is then carbonated by bubbling CO2 through it. The reactions involved in the process are as follows:
    CaCO3 CaO + CO2
    CaO + H2O Ca(OH)2
    Ca(OH)2+ CO2→CaCO3+ H2O
    The crystal sizes required for various commercial applications may be controlled by temperature, pH, concentrations, and mixing rate.
    Calcium carbonate also may be precipitated by mixing solutions of calcium chloride and sodium carbonate.
  • PreparationCalcium carbonate may also be produced by mixing solutions of calcium chloride and sodium carbonate. In some cases, the presence of sodium is objectionable so that the ammonium carbonate salt is preferable.
  • Production MethodsCalcium carbonate is prepared by double decomposition of calcium chloride and sodium bicarbonate in aqueous solution. Density and fineness are governed by the concentrations of the solutions. Calcium carbonate is also obtained from the naturally occurring minerals aragonite, calcite, and vaterite.
  • Definitioncalcium carbonate: A white solid,CaCO3, which is only sparingly solublein water. Calcium carbonatedecomposes on heating to give calciumoxide (quicklime) and carbondioxide. It occurs naturally as theminerals calcite (rhombohedral; r.d.2.71) and aragonite (rhombic; r.d.2.93). Rocks containing calcium carbonatedissolve slowly in acidifiedrainwater (containing dissolved CO2)to cause temporary hardness. In thelaboratory, calcium carbonate is precipitatedfrom limewater by carbondioxide. Calcium carbonate is used inmaking lime (calcium oxide) and isthe main raw material for theSolvay process.
  • ReactionsCalcium carbonate decomposes to calcium oxide and CO2 on heating. Treatment with dilute mineral acids produces corresponding calcium salts with liberation of CO2:
    CaCO3+ 2HCl →CaCl2+ H2O + CO2
    In the presence of CO2 it dissolves in water with the formation of bicarbonate:
    CaCO3+ H2O + CO2→Ca2++ 2HCO3 ¯
    It is reduced to calcium carbide when heated with coke or anthracite in an electric furnace:
    2CaCO3+ 5C→(high temperature)→2CaC2+ 3CO2
  • brand nameCal-Sup (3M Pharmaceuticals); Children’s Mylanta Upset Stomach Relief (Johnson & Johnson-Merck Consumer); Chooz (Schering- Plough HealthCare); Mylanta Soothing Lozenges (Johnson & Johnson-Merck Consumer).
  • Agricultural UsesCalcium carbonate (CaCO3) is a naturally occurring white solid that is sparingly soluble in water. It is most commonly used to neutralize soil acidity to the required level in a process called liming.
    The major sources of calcium carbonate are calcitic limestone, dolomitic limestone, marl, chalk and marble. Calcium carbonate is made by passing carbon dioxide (CO2) into limewater. Pure calcium carbonate is assumed to have a 100% neutralizing value. The values of other liming materials are measured against the neutralizing value of pure calcium carbonate. Calcium carbonate, on heating, decomposes to give calcium oxide (quick lime) and carbon dioxide.
    Limestone, which consists mainly of calcium carbonate, is called calcitic limestone or high calcium limestone. Limestone containing more than 10% magnesium carbonate is called dolomitic limestone or dolomite. These forms contain about 12% magnesium. Agricultural dolomitic limestone is a fine, grey to white powder of a double carbonate of calcium and magnesium with 12.8% magnesium and 17% calcium. The double carbonate is much less soluble in water than the individual carbonates.
  • Pharmaceutical ApplicationsCalcium carbonate, employed as a pharmaceutical excipient, is mainly used in solid-dosage forms as a diluent. It is also used as a base for medicated dental preparations, as a buffering agent, and as a dissolution aid in dispersible tablets. Calcium carbonate is used as a bulking agent in tablet sugar-coating processes and as an opacifier in tablet film-coating.
    Calcium carbonate is also used as a food additive and therapeutically as an antacid and calcium supplement.
  • Pharmaceutical ApplicationsCalcium carbonate (CaCO3) can be found in clinical applications such as antacids, but not that an excessive intake can be hazardous.
    A variety of calcium salts are used for clinical application, including calcium carbonate, calcium chloride, calcium phosphate, calcium lactate, calcium aspartate and calcium gluconate. Calcium carbonate is the most common and least expensive calcium supplement. It can be difficult to digest and may cause gas in some people because of the reaction of stomach HCl with the carbonate and the subsequent production of CO2.
    Calcium carbonate is recommended to be taken with food, and the absorption rate in the intestine depends on the pH levels. Taking magnesium salts with it can help prevent constipation. Calcium carbonate consists of 40% Ca2+, which means that 1000 mg of the salt contains around 400 mg of Ca2+. Often, labels will only indicate the amount of Ca2+ present in each tablet and not the amount of calcium carbonate.
  • SafetyCalcium carbonate is mainly used in oral pharmaceutical formulations and is generally regarded as a nontoxic material. However, calcium carbonate administered orally may cause constipation and flatulence. Consumption of large quantities (4–60 g daily) may also result in hypercalcemia or renal impairment. Therapeutically, oral doses of up to about 1.5 g are employed as an antacid. In the treatment of hyperphosphatemia in patients with chronic renal failure, oral daily doses of 2.5–17 g have been used. Calcium carbonate may interfere with the absorption of other drugs from the gastrointestinal tract if administered concomitantly.
    LD50 (rat, oral): 6.45 g/kg
  • storageCalcium carbonate is stable and should be stored in a well-closed container in a cool, dry place.
  • IncompatibilitiesIncompatible with acids and ammonium salts.
  • Regulatory StatusGRAS listed. Accepted for use as a food additive in Europe. Included in the FDA Inactive Ingredients Database (buccal chewing gum, oral capsules and tablets; otic solutions; respiratory inhalation solutions). Included in nonparenteral medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.
Calcium carbonate Preparation Products And Raw materials
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