PRECIPITATED CALCIUM CARBONATE

Precipitated Calcium Carbonate occurs in nature as limestone in various forms, such as marble, chalk, and coral. 
Precipitated Calcium Carbonate is probably the most widely-used raw material in the chemical industry. 
Precipitated 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

Precipitated Calcium Carbonate also is used to produce quicklime, hydrated lime and a number of calcium compounds. 
Precipitated 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.
Precipitated Calcium Carbonate: A white solid,CaCO3, which is only sparingly solublein water. 
Precipitated Calcium Carbonate decomposes on heating to give calciumoxide (quicklime) and carbondioxide. 
Precipitated Calcium Carbonate occurs naturally as theminerals calcite (rhombohedral; r.d.2.71) and aragonite (rhombic; r.d.2.93). 

Rocks containing Precipitated Calcium CarbonatePrecipitated Calcium Carbonate dissolve slowly in acidifiedrainwater (containing dissolved CO2)to cause temporary hardness. 
In thelaboratory, Precipitated Calcium Carbonate is precipitatedfrom limewater by carbondioxide. 
Precipitated Calcium Carbonate is used inmaking lime (calcium oxide) and isthe main raw material for theSolvay process.
Precipitated Calcium Carbonate is a naturally found material in chalk, limestone, and marble. 
Precipitated Calcium Carbonate is composed of three elements which include carbon, oxygen, and calcium. 
Precipitated Calcium Carbonate is formed by reacting carbon dioxide with slaked or burnt lime. 
Precipitated Calcium Carbonate can be used for a variety of applications ranging from industrial, food to agriculture.
Precipitated Calcium Carbonate is a chemical compound with the chemical formula CaCO3. 

Precipitated 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 Precipitated Calcium Carbonate or resembling it are described as calcareous. 
Precipitated Calcium Carbonate is the active ingredient in agricultural lime and is produced when calcium ions in hard water react with carbonate ions to form limescale. 
Precipitated 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.
Precipitated Calcium Carbonate is a chemical compound that can be found in natural limestone, marble and seashells. 
Precipitated Calcium Carbonate is used as an industrial mineral for the production of lime and cement, as well as a chemical agent in wastewater treatment. 
Precipitated Calcium Carbonate has been shown to have synergistic effects with sodium carbonate when used to treat sewage effluent. 
Precipitated Calcium Carbonate also has a high solubility in water, which makes it suitable for use in the production of concrete. 
The reaction mechanism is dependent on the particle size and temperature. 
The thermal expansion coefficient of Precipitated Calcium Carbonate is 2.6x10^-5/°C, meaning that it expands by 0.26% per degree Celsius increase in temperature.

Precipitated 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
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.
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: Precipitated Calcium Carbonate (471-34-1)

Precipitated 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.
Precipitated Calcium Carbonate occurs as an odorless and tasteless white powder or crystals.

Physical properties    
Precipitated Calcium Carbonate is a naturally occurring compound found in organisms and throughout the earth’s crust. 
After quartz, Precipitated Calcium Carbonate, primarily in the form of calcite, is the most common mineral found in the crust. 
Geologically, Precipitated Calcium Carbonate exists in several mineral forms: calcite, aragonite, and vaterite. 
Calcite is the most common Precipitated 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 Precipitated Calcium Carbonate depends on the conditions at its formation such as temperature and pressure.

Precipitated Calcium Carbonate has the molecular formula of CaCO3 and the molecular weight of 100.0924 g/mol. 
Precipitated 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. 
Precipitated Calcium Carbonate is the main ingredient in eggshells of birds and pearls obtained from oysters.
Precipitated 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. 
Precipitated Calcium Carbonate occurs in nature as limestone in various forms, such as marble, chalk, and coral.
Precipitated Calcium Carbonate or precipitated chalk has excellent absorption properties. 
Precipitated 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.

Uses    
Humans primarily use Precipitated 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, Precipitated Calcium Carbonate is also used in numerous industrial processes. 
Two forms commonly used are ground Precipitated Calcium Carbonate (gcc) and precipitated calcium carbonate (pcc).
Precipitated Calcium Carbonate is used widely in papermaking as filler and coating pigment to whiten paper. 
Precipitated 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.
Precipitated Calcium Carbonate is used as a very mild abrasive for hand polishing nickel, gold, silver, or plated ware, buttons, and similar materials.

The second most common industrial use of Precipitated Calcium Carbonate (after papermaking) representing the largest use of gcc is in the production of plastics. 
Precipitated Calcium Carbonate is used in the production of polyvinyl chloride (PVC), thermoset polyesters, and polyolefins. 
Precipitated Calcium Carbonate can be used to replace resins that are more expensive. 
Similar to its use in the paper industry, Precipitated Calcium Carbonate is used as an optical brightener and whitening agent. 
Precipitated Calcium Carbonate also is used to increase strength and absorb heat during exothermic processes.
Precipitated Calcium Carbonate is also used in the production of polyethylene and polypropylene. 

Precipitated Calcium Carbonate is an additive to paints and coatings for several purposes including particle size distribution, opacity control, weather resistance, pH control, and anticorrosion. 
Precipitated Calcium Carbonate is used to buff er acidic soils.
Precipitated Calcium Carbonate has also been used to mitigate the effects of acid precipitation on water bodies. 
Another environmental application of Precipitated Calcium Carbonate is for gas desulfurization in scrubbers used to reduce sulfur emissions from air pollution sources.
Precipitated Calcium Carbonate is probably the most widely used raw material in the chemical industry. 
Precipitated Calcium Carbonate has numerous applications, primarily to produce cement, mortars, plasters, refractories, and glass as building materials. 

Precipitated Calcium Carbonate is also used to produce quicklime, hydrated lime and a number of calcium compounds.
Precipitated Calcium Carbonate is the calcium salt of carbonic acid which is used as an anticaking agent and dough strengthener. 
Precipitated Calcium Carbonate is available in varying particle sizes ranging from coarse to fine powder. 
Precipitated 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. 
Precipitated Calcium Carbonate has a ph of 9–9.5. 
Precipitated Calcium Carbonate is the primary source of lime (calcium oxide) which is made by heating limestone in a furnace. 

Precipitated 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. 
Precipitated 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. 
Precipitated 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.

Production Methods    
Precipitated 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.
Precipitated Calcium Carbonate also may be precipitated by mixing solutions of calcium chloride and sodium carbonate.

Pharmaceutical Applications    
Precipitated Calcium Carbonate 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. 
Precipitated Calcium Carbonate is the most common and least expensive calcium supplement. 
Precipitated 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.
Precipitated 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. 
Precipitated 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    
Precipitated Calcium Carbonate is a naturally occurring white solid that is sparingly soluble in water. 
Precipitated Calcium Carbonate is most commonly used to neutralize soil acidity to the required level in a process called liming.
The major sources of Precipitated Calcium Carbonate are calcitic limestone, dolomitic limestone, marl, chalk and marble. 
Precipitated Calcium Carbonate is made by passing carbon dioxide (CO2) into limewater. 
Pure Precipitated Calcium Carbonateis assumed to have a 100% neutralizing value. 
The values of other liming materials are measured against the neutralizing value of pure Precipitated Calcium Carbonate. 
Precipitated Calcium Carbonate, on heating, decomposes to give calcium oxide (quick lime) and carbon dioxide.
Limestone, which consists mainly of Precipitated 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
The vast majority of Precipitated 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).
Alternatively, Precipitated Calcium Carbonate is prepared from calcium oxide. 
Water is added to give calcium hydroxide then carbon dioxide is passed through this solution to precipitate the desired Precipitated 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
In a laboratory, Precipitated Calcium Carbonate can easily 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.