CALCIUM CARBONATE

Calcium carbonate occurs in nature as limestone in various forms, such as marble, chalk, and coral. 
Calcium carbonate is probably the most widely-used raw material in the chemical industry. 
Calcium carbonate has numerous applications, primarily to produce cement, mortars, plasters, refractories, and glass as building materials. 

CAS:    471-34-1
MF:    CCaO3
MW:    100.0869
EINECS:    207-439-9

Synonyms
PRECIPITATED CHALK;PARIS WHITE;aeromatt;akadama;albacar;albacar5970;albafil;albaglos

Calcium carbonate also is used to produce quicklime, hydrated lime and a number of calcium compounds. 
Calcium carbonate 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 occurs in nature as limestone in various forms, such as marble, chalk, and coral. 
Calcium carbonate is probably the most widely-used raw material in the chemical industry. 
Calcium carbonate has numerous applications, primarily to produce cement, mortars, plasters, refractories, and glass as building materials. 
Calcium carbonate also is used to produce quicklime, hydrated lime and a number of calcium compounds. 
Calcium carbonate 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.
A white solid,CaCO3, which is only sparingly solublein water. 

Calcium carbonate decomposes on heating to give calciumoxide (quicklime) and carbondioxide. 
Calcium carbonate occurs naturally as theminerals calcite (rhombohedral; r.d.2.71) and aragonite (rhombic; r.d.2.93). 
Rocks containing calcium carbonate dissolve 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.
Calcium Carbonate (CaCO3) is a naturally found material in chalk, limestone, and marble. 
Calcium carbonate is composed of three elements which include carbon, oxygen, and calcium. 
Calcium carbonate is formed by reacting carbon dioxide with slaked or burnt lime. 
Calcium carbonate can be used for a variety of applications ranging from industrial, food to agriculture.

Calcium carbonate is a chemical compound with the chemical formula CaCO3. 
Calcium carbonate is a common substance found in rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skeletons and pearls. 
Materials containing much calcium carbonate or resembling it are described as calcareous. Calcium carbonate is the active ingredient in agricultural lime. 
Limescale is calcium carbonate produced when calcium ions in hard water react with carbonate ions. 
Calcium carbonate has medical use as a calcium supplement or as an antacid, but excessive consumption can be hazardous and cause hypercalcemia and digestive issues.

Calcium carbonate Chemical Properties
Melting point: 825 °C
Boiling point: 800 °C
bulk density: 300-1400kg/m3
density: 2.93 g/mL at 25 °C (lit.)
refractive index: 1.6583
storage temp.: Store at +5°C to +30°C.
solubility: 5 M HCl: 0.1 M at 20 °C, clear, colorless
form: random crystals
color: White-beige to slightly beige-gray
Specific Gravity: 2.93
PH: 9.91(1 mM solution);9.91(10 mM solution);9.91(100 mM solution);
Flame Color: Red-orange
Odor: Odorless
PH Range: 8
Water Solubility: Insoluble
Thermal Conductivity: 0.92 W/(m·K); 2.259 W/(m·K)
λmax λ: 260 nm Amax: ≤0.09
λ: 280 nm Amax: ≤0.06
Merck: 14,1657
BRN: 8008338
Solubility Product Constant (Ksp): pKsp: 8.54
Exposure limits    NIOSH: TWA 10 mg/m3; TWA 5 mg/m3
Dielectric constant: 6.1（Ambient）
Stability: Stable. Incompatible with acids, fluorine, ammonium salts, alum.
Cosmetics Ingredients Functions    BULKING BUFFERING ABRASIVE ORAL CARE COLORANT OPACIFYING
Cosmetic Ingredient Review (CIR): Calcium carbonate (471-34-1)
InChI: 1S/CH2O3.Ca/c2-1(3)4;/h(H2,2,3,4);/q;+2/p-2
InChIKey: VTYYLEPIZMXCLO-UHFFFAOYSA-L
Hardness, Mohs: 2.0 - 5.0
Hardness, Shore H: 10 - 60
Modulus of Elasticity: 10.0 - 80.0 GPa
Drilling Hardness: 50
Hardness, Knoop: 75 - 120
Hardness, Vickers: 105 - 136
CAS DataBase Reference: 471-34-1(CAS DataBase Reference)
EPA Substance Registry System: Calcium carbonate (471-34-1)

Calcium 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.

Physical properties    
Calcium 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.
Calcium carbonate has the molecular formula of CaCO3 and the molecular weight of 100.0924 g/mol. 
Calcium carbonate 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. 

Calcium carbonate 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.
Calcium carbonate or precipitated chalk has excellent absorption properties. 
Calcium carbonate provides a matte finish and moderate coverage. 
High levels of this material will cause an undesirable, dry, powdery feel and should be avoided.

Chemistry
Calcium carbonate shares the typical properties of other carbonates. 
Notably, Calcium carbonate:
reacts with acids, releasing carbonic acid which quickly disintegrates into carbon dioxide and water:
CaCO3(s) + 2 H+(aq) → Ca2+(aq) + CO2(g) + H2O(l)
releases carbon dioxide upon heating, called a thermal decomposition reaction, or calcination (to above 840 °C in the case of CaCO3), to form calcium oxide, CaO, commonly called quicklime, with reaction enthalpy 178 kJ/mol:

CaCO3(s) → CaO(s) + CO2(g)
reacts with gaseous hydrogen to form methane and water vapor plus solid calcium oxide or calcium hydroxide depending on temperature and product gas composition. 
Various metals including palladium and nickel are catalysts for the reaction.
Calcium carbonate reacts with water that is saturated with carbon dioxide to form the soluble calcium bicarbonate.

CaCO3(s) + CO2(g) + H2O(l) → Ca(HCO3)2(aq)
This reaction is important in the erosion of carbonate rock, forming caverns, and leads to hard water in many regions.
An unusual form of calcium carbonate is the hexahydrate ikaite, CaCO3·6H2O. 
Ikaite is stable only below 8 °C.

Uses    
Humans 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. 
Calcium carbonate 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. 

Calcium carbonate also is used to increase strength and absorb heat during exothermic processes.
Calcium carbonate is also used in the production of polyethylene and polypropylene. 
Calcium carbonate 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.

Calcium carbonate is probably the most widely used raw material in the chemical industry. 
Calcium carbonate has numerous applications, primarily to produce cement, mortars, plasters, refractories, and glass as building materials. 
Calcium carbonate is also used to produce quicklime, hydrated lime and a number of calcium compounds.
Calcium Carbonate is the calcium salt of carbonic acid which is used as an anticaking agent and dough strengthener. 
Calcium carbonate is available in varying particle sizes ranging from coarse to fine powder. 
Calcium carbonate 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. 
Calcium carbonate has a ph of 9–9.5. 
Calcium carbonate 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. 
Calcium carbonate is also termed limestone.
Made 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.
Calcium carbonate is used as a very mild abrasive for hand polishing nickel, gold, silver, or plated ware, buttons, and similar materials.

Pharmaceutical Applications    
Calcium 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. 
Calcium carbonate 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.

Agricultural Uses    
Calcium carbonate (CaCO3) is a naturally occurring white solid that is sparingly soluble in water. 
Calcium carbonate 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.

Preparation    
Calcium 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 Methods    
Calcium 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.

Preparation
The vast majority of calcium carbonate used in industry is extracted by mining or quarrying. Pure calcium carbonate (such as for food or pharmaceutical use), can be produced from a pure quarried source (usually marble), or prepared from calcium oxide. 
Water is added to give calcium hydroxide then carbon dioxide is passed through this solution to precipitate the desired calcium carbonate, referred to in the industry as precipitated calcium carbonate (PCC). 
This process is called carbonatation.

CaO + H2O → Ca(OH)2
Ca(OH)2 + CO2 → CaCO3 + H2O
Calcium carbonate can be crystallized from calcium chloride (CaCl2), by placing an aqueous solution of CaCl2 in a desiccator alongside ammonium carbonate [NH4]2CO3.
In the desiccator, ammonium carbonate is exposed to air and decomposes into ammonia, carbon dioxide, and water. 
The carbon dioxide then diffuses into the aqueous solution of calcium chloride, reacts with the calcium ions and the water, and forms calcium carbonate.

Reactions    
Calcium 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 ¯
Calcium carbonate is reduced to calcium carbide when heated with coke or anthracite in an electric furnace:
2CaCO3+ 5C→(high temperature)→2CaC2+ 3CO2

Biochem/physiol Actions    
Calcium carbonate is a naturally occurring compound that reduces T4 absorption and enhancess serum thyrotropin levels. 
Calcium carbonate also precludes osteoporosis induced by thyrotropin-suppressive doses of levothyroxine in postmenopausal women. 
Additionally, Calcium carbonate reduces diarrhea in individuals with protease inhibitor-induced HIV-infection.