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Calcium carbonate
Other names Limestone; calcite; aragonite; chalk; marble
Identifiers
CAS number [471-34-1]
Properties
Molecular formula CaCO3
Molar mass 100. Limestone is a Sedimentary rock composed largely of the Mineral Calcite ( Calcium carbonate: CaCO3 Calcite is a carbonate mineral and the most stable polymorph of Calcium carbonate ( Ca[[carbon C]] O 3 Aragonite is a Carbonate mineral, one of the two common naturally occurring polymorphs of Calcium carbonate, Ca[[carbon C]] O 3 Chalk (ʧɔːk is a soft white porous Sedimentary rock, a form of Limestone composed of the Mineral Calcite. Marble is a nonfoliated Metamorphic rock resulting from the Metamorphism of Limestone, composed mostly of Calcite (a crystalline form of CAS registry numbers are unique numerical identifiers for Chemical compounds Polymers biological sequences mixtures and Alloys They are also referred to A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Molar mass, symbol M, is the Mass of one mole of a substance ( Chemical element or Chemical compound) 087 g/mol
Appearance White powder.
Density 2. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different 71 g/cm³ (calcite); 2. Calcite is a carbonate mineral and the most stable polymorph of Calcium carbonate ( Ca[[carbon C]] O 3 83 g/cm³ (aragonite)
Melting point

825 °C Decomposes
Boiling point

Decomposes
Solubility in water Insoluble
Structure
Molecular shape Linear
Hazards
Main hazards Not hazardous. Aragonite is a Carbonate mineral, one of the two common naturally occurring polymorphs of Calcium carbonate, Ca[[carbon C]] O 3 The melting point of a solid is the temperature range at which it changes state from solid to Liquid. The boiling point of a liquid is the temperature at which the Vapor pressure of the liquid equals the environmental pressure surrounding the liquid Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. Water is a common Chemical substance that is essential for the survival of all known forms of Life. Molecular geometry or molecular structure is the three- Dimensional arrangement of the Atoms that constitute a Molecule. Occupational safety and health is a cross-disciplinary area concerned with protecting the Safety, Health and welfare of people engaged in
NFPA 704
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0
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R-phrases R36, R37, R38
S-phrases S26, S36
Flash point Non-flammable. Symbolism The four divisions are typically color-coded with blue indicating level of Health Hazard, red indicating R-phrases (short for Risk Phrases) are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous R-phrases (short for Risk Phrases) are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous R-phrases (short for Risk Phrases) are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous R-phrases (short for Risk Phrases) are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous S-phrases are defined in Annex IV of European Union Directive 67/548/EEC: Safety advice concerning dangerous substances and preparations. S-phrases are defined in Annex IV of European Union Directive 67/548/EEC: Safety advice concerning dangerous substances and preparations. S-phrases are defined in Annex IV of European Union Directive 67/548/EEC: Safety advice concerning dangerous substances and preparations. The flash point of a flammable liquid is the lowest Temperature at which it can form an ignitable mixture in air
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references

Calcium carbonate is a chemical compound with the chemical formula CaCO3. In Chemistry, the standard state of a material is its state at 1 bar (100 Kilopascals exactly A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by Mass. A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20 Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the It is a common substance found as rock in all parts of the world, and is the main component of shells of marine organisms, snails, and eggshells. In Geology, rock is a naturally occurring aggregate of Minerals and/or Mineraloids The Earth's outer solid layer the ‘ Lithosphere A seashell, also known as a sea shell, is the Common name for a hard protective outer layer a shell or in some cases a " test " that was created The word snail is a Common name that can be used for almost all members of the Molluscan class Gastropoda which have coiled shells in the The term eggshell is a term for the outer covering of a hard-shelled egg, and some forms of eggs with soft outer coats Calcium carbonate is the active ingredient in agricultural lime, and is usually the principal cause of hard water. Agricultural lime, also called garden lime, is a Soil additive made from pulverized Limestone or Chalk. Hard water is the type of Water that has high Mineral content (in contrast with Soft water) It is commonly used medicinally as a calcium supplement or as an antacid, but high consumption can be hazardous. Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20 An antacid is any substance generally a base or Basic salt, which counteracts stomach acidity.

Contents

Occurrence

Calcium carbonate is found naturally as the following minerals and rocks:

Chemical properties

See also: Carbonate

Calcium carbonate shares the typical properties of other carbonates. A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific Aragonite is a Carbonate mineral, one of the two common naturally occurring polymorphs of Calcium carbonate, Ca[[carbon C]] O 3 Calcite is a carbonate mineral and the most stable polymorph of Calcium carbonate ( Ca[[carbon C]] O 3 Vaterite ( Ca[[carbon C]] O 3 is a mineral a polymorph of Calcium carbonate. Chalk (ʧɔːk is a soft white porous Sedimentary rock, a form of Limestone composed of the Mineral Calcite. Limestone is a Sedimentary rock composed largely of the Mineral Calcite ( Calcium carbonate: CaCO3 Marble is a nonfoliated Metamorphic rock resulting from the Metamorphism of Limestone, composed mostly of Calcite (a crystalline form of Travertine is a Sedimentary rock. It is a natural chemical precipitate of Carbonate minerals; typically Aragonite, but often recrystallized to In Chemistry, a carbonate is a salt or Ester of Carbonic acid. Notably:

  1. it reacts with strong acids, releasing carbon dioxide:
    CaCO3(s) + 2HCl(aq) → CaCl2(aq) + CO2(g) + H2O(l)
  2. it releases carbon dioxide on heating (to above 840 °C in the case of CaCO3), to form calcium oxide, commonly called quicklime, with reaction enthalpy 178 kJ / mole:
    CaCO3 → CaO + CO2

Calcium carbonate will react with water that is saturated with carbon dioxide to form the soluble calcium bicarbonate. Calcium oxide ( CaO) commonly known as burnt lime, lime or quicklime, is a widely used Chemical compound. Calcium oxide ( CaO) commonly known as burnt lime, lime or quicklime, is a widely used Chemical compound. In Thermodynamics and molecular chemistry, the enthalpy (denoted as H, h, or rarely as χ) is a quotient or description of Calcium bicarbonate (Ca(HCO32 also called calcium hydrogen carbonate, does not refer to a known solid compound it “exists” only in a solution

CaCO3 + CO2 + H2O → Ca(HCO3)2

This reaction is important in the erosion of carbonate rocks, forming caverns, and leads to hard water in many regions. Erosion is the carrying away or displacement of solids ( Sediment, Soil, rock and other particles usually by the agents of currents such as wind Carbonate rocks are a class of Sedimentary rocks composed primarily of Carbonate Minerals The two major types are Limestone and Dolomite A cave is a natural underground void large enough for a human to enter Hard water is the type of Water that has high Mineral content (in contrast with Soft water)

Preparation

The vast majority of calcium carbonate used in industry is extracted by mining or quarrying. Pure calcium carbonate (e. g. for food or pharmaceutical use), can be produced from a pure quarried source (usually marble).

Alternatively, calcium oxide is prepared by calcining crude calcium carbonate. Calcium oxide ( CaO) commonly known as burnt lime, lime or quicklime, is a widely used Chemical compound. Calcination (also referred to as calcining) is a thermal treatment process applied to ores and other solid materials in order to bring about a Thermal decomposition Water is added to give calcium hydroxide, and carbon dioxide is passed through this solution to precipitate the desired calcium carbonate, referred to in the industry as precipitated calcium carbonate (PCC):[1]

CaCO3 → CaO + CO2
CaO + H2O → Ca(OH)2
Ca(OH)2 + CO2 → CaCO3 + H2O

Uses

Industrial applications

The main use of calcium carbonate is in the construction industry, either as a building material in its own right (e. Calcium hydroxide, traditionally called slaked lime, hydrated lime, or pickling lime, is a Chemical compound with the chemical formula Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single g. marble) or limestone aggregate for roadbuilding or as an ingredient of cement or as the starting material for the preparation of builder's lime by burning in a kiln. Marble is a nonfoliated Metamorphic rock resulting from the Metamorphism of Limestone, composed mostly of Calcite (a crystalline form of In the most general sense of the word a cement is a binder a substance which sets and hardens independently and can bind other materials together

Calcium carbonate is also used in the purification of iron from iron ore in a blast furnace. Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 Iron ores are rocks and Minerals from which Metallic Iron can be economically extracted A blast furnace is a type of metallurgical Furnace used for Smelting to produce metals generally Iron. Calcium carbonate is calcined in situ to give calcium oxide, which forms a slag with various impurities present, and separates from the purified iron. [2]

Calcium carbonate is also used in the oil industry in drilling fluids as a weighting material to increase the density to control downhole pressures. The petroleum industry includes the global processes of exploration, extraction, refining, transporting (often by Oil tankers and pipelines Drilling a very deep hole is a very costly business The hole size is kept very small as the drilled depth increases because it is to cased and cemented after wards

Calcium carbonate is widely used as an extender in paints,[3] in particular matte emulsion paint where typically 30% by weight of the paint is either chalk or marble.

Calcium carbonate is also widely used as a filler in plastics. [3] Some typical examples include around 15 to 20% loading of chalk in uPVC drain pipe, 5 to 15% loading of stearate coated chalk or marble in uPVC window profile. Fine ground calcium carbonate is an essential ingredient in the microporous film used in babies' diapers and some building films as the pores are nucleated around the calcium carbonate particles during the manufacture of the film by biaxial stretching. "Nappy" redirects here For other uses see Nappy (disambiguation and Diaper (disambiguation. It has also been mixed with ABS, and other ingredients, to form some types of compression molded "clay" Poker chips. Acrylonitrile butadiene styrene or ABS, ( Chemical formula (C8H8· C4H6·C3H3Nn is

Calcium carbonate is also used in a wide range of trade and DIY adhesives, sealants, and decorating fillers. [3] Ceramic tile adhesives typically contain 70 to 80% limestone. Decorating crack fillers contain similar levels of marble or dolomite. It is also mixed with putty in setting stained glass windows, and as a resist to prevent glass from sticking to kiln shelves when firing glazes and paints at high temperature. For the Blackford Oakes novel see Stained Glass (novel The term stained glass refers either to the material of coloured Glass or to the art

Calcium carbonate is known as whiting in ceramics/glazing applications,[3] where it is used as a common ingredient for many glazes in its white powdered form. Ceramics and ceramic art in the art world means artwork made out of clay bodies and fired to form a ceramic. When a glaze containing this material is fired in a kiln, the whiting acts as a flux material in the glaze. In the various subfields of Physics, there exist two common usages of the term flux, both with rigorous mathematical frameworks

In North America, calcium carbonate has begun to replace kaolin in the production of glossy paper. Kaolinite is a Clay mineral with the chemical composition Al 2 Si 2 O 5( OH)4 Europe has been practicing this as alkaline papermaking or acid-free papermaking for some decades. Carbonates are available in forms: ground calcium carbonate (GCC) or precipitated calcium carbonate (PCC). The latter has a very fine and controlled particle size, on the order of 2 micrometres in diameter, useful in coatings for paper.

Used in swimming pools as a pH corrector for maintaining alkalinity "buffer" to offset the acidic properties of the disinfectant agent. Alkalinity or AT is a measure of the ability of a solution to neutralize acids to the Equivalence point of carbonate or bicarbonate

It is commonly called chalk as it has been a major component of blackboard chalk. Chalk (ʧɔːk is a soft white porous Sedimentary rock, a form of Limestone composed of the Mineral Calcite. Chalk may consist of either calcium carbonate or gypsum, hydrated calcium sulfate CaSO4·2H2O. Gypsum is a very soft Mineral composed of Calcium sulfate dihydrate with the Chemical formula Ca[[sulfur S]] O 4·2 Calcium sulfate is a common laboratory and industrial chemical

Health and dietary applications

500 milligram calcium supplements made from calcium carbonate
500 milligram calcium supplements made from calcium carbonate

Calcium carbonate is widely used medicinally as an inexpensive dietary calcium supplement or antacid. An antacid is any substance generally a base or Basic salt, which counteracts stomach acidity. [4] It may be used as a phosphate binder for the treatment of hyperphosphatemia (primarily in patients with chronic renal failure). Phosphate binders are a group of medications used to reduce the absorption of Phosphate and taken with meals and snacks Hyperphosphatemia is an Electrolyte disturbance in which there is an abnormally elevated level of Phosphate in the Blood. Chronic kidney disease (CKD also known as chronic renal disease, is a progressive loss of renal function over a period of months or years It is also used in the pharmaceutical industry as an inert filler for tablets and other pharmaceuticals. A tablet is a mixture of active substances and Excipients usually in powder form pressed or compacted into a solid [5] Calcium carbonate is also used in Homeopathy. It is one of the constitutional remedies.

Excess calcium from supplements, fortified food and high-calcium diets, can cause the "milk alkali syndrome," which has serious toxicity and can be fatal. In 1915, Bertram Sippy introduced the "Sippy regimen" of hourly ingestion of milk and cream, and the gradual addition of eggs and cooked cereal, for 10 days, combined with alkaline powders, which provided symptomatic relief for peptic ulcer disease. Over the next several decades, the Sippy regimen resulted in renal failure, alkalosis, and hypercalemia, mostly in men with peptic ulcer disease. These adverse effects were reversed when the regimen stopped, but it was fatal in some patients with protracted vomiting. Milk alkali syndrome declined in men after effective treatments for peptic ulcer disease. But during the past 15 years, it has been reported in women taking calcium supplements above the recommended range of 1200 to 1500 mg daily, for prevention and treatment of osteoporosis, and is exacerbated by dehydration. Calcium has been added to over-the-counter products, which contributes to inadvertent excessive intake. Excessive calcium intake can lead to hypercalcemia, complications of which include vomiting, abdominal pain and altered mental status. Hypercalcaemia (in American English '''Hypercalcemia''' is an elevated calcium level in the Blood. [6]

A form of food additive is designated as E170. Food additives are substances added to food to preserve flavour or improve its taste and appearance [7] It is used in some soy milk products as a source of dietary calcium; one study suggests that calcium carbonate might be bioavailable as the calcium in cow's milk. Soy milk (also called soya milk, soybean milk, or soy juice) and sometimes referred to as soy drink/beverage is a beverage made from In Pharmacology, bioavailability is used to describe the fraction of an administered Dose of unchanged drug that reaches the Systemic circulation, one of [8]

Ecological applications

In 1989, a researcher, Ken Simmons, introduced CaCO3 into the Whetstone Brook in Massachusetts. [9] His hope was that the calcium carbonate would counter the acid in the stream from acid rain and save the trout that had ceased to spawn. Although his experiment was a success, it did increase the amounts of aluminium ions in the area of the brook that was not treated with the limestone. This shows that CaCO3 can be added to neutralize the effects of acid rain in river ecosystems. "Riverine" redirects here For the use of that term in Maritime geography, see there Currently calcium carbonate is used to neutralize acidic conditions in both soil and water. [10][11]

Calcination equilibrium

Equilibrium Pressure of CO2 over CaCO3[12]
550 °C 0. 055 kPa
587 °C 0. 13 kPa
605 °C 0. 31 kPa
680 °C 1. 80 kPa
727 °C 5. 9 kPa
748 °C 9. 3 kPa
777 °C 14 kPa
800 °C 24 kPa
830 °C 34 kPa
852 °C 51 kPa
871 °C 72 kPa
881 °C 80 kPa
891 °C 91 kPa
898 °C 101 kPa
937 °C 179 kPa
1082 °C 901 kPa
1241 °C 3961 kPa

Calcination of limestone using charcoal fires to produce quicklime has been practiced since antiquity by cultures all over the world. Calcination (also referred to as calcining) is a thermal treatment process applied to ores and other solid materials in order to bring about a Thermal decomposition Calcium oxide ( CaO) commonly known as burnt lime, lime or quicklime, is a widely used Chemical compound. The temperature at which limestone yields calcium oxide is usually given as 825 °C, but stating an absolute threshold is misleading. Calcium carbonate exists in equilibrium with calcium oxide and carbon dioxide at any temperature. At each temperature there is a partial pressure of carbon dioxide that is in equilibrium with calcium carbonate. In a mixture of Ideal gases each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume At room temperature the equilibrium overwhelmingly favors calcium carbonate, because the equilibrium CO2 pressure is only a tiny fraction of the partial CO2 pressure in air, which is about 0. 035 kPa.

At temperatures above 550 °C the equilibrium CO2 pressure begins to exceed the CO2 pressure in air. So above 550 °C, calcium carbonate begins to outgas CO2 into air. But in a charcoal fired kiln, the concentration of CO2 will be much higher than it is in air. Indeed if all the oxygen in the kiln is consumed in the fire, then the partial pressure of CO2 in the kiln can be as high as 20 kPa.

The table shows that this equilibrium pressure is not achieved until the temperature is nearly 800 °C. For the outgassing of CO2 from calcium carbonate to happen at an economically useful rate, the equilibrium pressure must significantly exceed the ambient pressure of CO2. And for it to happen rapidly, the equilibrium pressure must exceed total atmospheric pressure of 101 kPa, which happens at 898 °C.

Solubility

With varying CO2 pressure

Calcium ion solubility
as a function of CO2 partial pressure at 25 °C
\scriptstyle P_{\mathrm{CO}_2} (atm) pH [Ca2+] (mol/L)
10−12 12. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single In a mixture of Ideal gases each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume pH is the measure of the acidity or alkalinity of a Solution. 0 5. 19 × 10−3
10−10 11. 3 1. 12 × 10−3
10−8 10. 7 2. 55 × 10−4
10−6 9. 83 1. 20 × 10−4
10−4 8. 62 3. 16 × 10−4
3. 5 × 10−4 8. 27 4. 70 × 10−4
10−3 7. 96 6. 62 × 10−4
10−2 7. 30 1. 42 × 10−3
10−1 6. 63 3. 05 × 10−3
1 5. 96 6. 58 × 10−3
10 5. 30 1. 42 × 10−2

Calcium carbonate is poorly soluble in pure water. The equilibrium of its solution is given by the equation (with dissolved calcium carbonate on the right):

CaCO3 ⇋ Ca2+ + CO32– Ksp = 3. 7×10–9 to 8. 7×10–9 at 25 °C

where the solubility product for [Ca2+][CO32–] is given as anywhere from Ksp = 3. Solubility equilibrium is any type Chemical equilibrium between solid and dissolved states of a compound at saturation. 7×10–9 to Ksp = 8. 7×10–9 at 25 °C, depending upon the data source. [13][12] What the equation means is that the product of molar concentration of calcium ions (moles of dissolved Ca2+ per liter of solution) with the molar concentration of dissolved CO32– cannot exceed the value of Ksp. The mole (symbol mol) is a unit of Amount of substance: it is an SI base unit, and almost the only unit to be used to measure this This seemingly simple solubility equation, however, must be taken along with the more complicated equilibrium of carbon dioxide with water (see carbonic acid). Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Water is a common Chemical substance that is essential for the survival of all known forms of Life. Carbonic acid (ancient name acid of air or aerial acid) has the formula H2CO3 Some of the CO32– combines with H+ in the solution according to:

HCO3– ⇋ H+ + CO32–    Ka2 = 5. 61×10–11 at 25 °C

HCO3– is known as the bicarbonate ion. In Inorganic chemistry, bicarbonate ( IUPAC -recommended nomenclature hydrogencarbonate) is an intermediate form in the Deprotonation Calcium bicarbonate is many times more soluble in water than calcium carbonate -- indeed it exists only in solution. Calcium bicarbonate (Ca(HCO32 also called calcium hydrogen carbonate, does not refer to a known solid compound it “exists” only in a solution

Some of the HCO3– combines with H+ in solution according to:

H2CO3 ⇋ H+ + HCO3–    Ka1 = 2. 5×10–4 at 25 °C

Some of the H2CO3 breaks up into water and dissolved carbon dioxide according to:

H2O + CO2(dissolved) ⇋ H2CO3    Kh = 1. 70×10–3 at 25 °C

And dissolved carbon dioxide is in equilibrium with atmospheric carbon dioxide according to:

\frac{P_{\mathrm{CO}_2}}{[\mathrm{CO}_2]}\ =\ k_\mathrm{H} where kH = 29. 76 atm/(mol/L) at 25 °C (Henry constant), \scriptstyle P_{\mathrm{CO}_2} being the CO2 partial pressure. Henry's Law may sometimes refer to Lenz's Law In Chemistry, Henry's law is one of the Gas laws, formulated by William Henry.

For ambient air, \scriptstyle P_{\mathrm{CO}_2} is around 3. 5×10–4 atmospheres (or equivalently 35 Pa). The last equation above fixes the concentration of dissolved CO2 as a function of \scriptstyle P_{\mathrm{CO}_2}, independent of the concentration of dissolved CaCO3. At atmospheric partial pressure of CO2, dissolved CO2 concentration is 1. 2×10–5 moles/liter. The equation before that fixes the concentration of H2CO3 as a function of [CO2]. For [CO2]=1. 2×10–5, it results in [H2CO3]=2. 0×10–8 moles per liter. When [H2CO3] is known, the remaining three equations together with

H2O ⇋ H+ + OH– K = 10–14 at 25 °C

(which is true for all aqueous solutions), and the fact that the solution must be electrically neutral,

2[Ca2+] + [H+] = [HCO3–] + 2[CO32–] + [OH–]

make it possible to solve simultaneously for the remaining five unknown concentrations (note that the above form of the neutrality equation is valid only if calcium carbonate has been put in contact with pure water or with a neutral pH solution; in the case where the origin water solvent pH is not neutral, the equation is modified).

The table on the right shows the result for [Ca2+] and [H+] (in the form of pH) as a function of ambient partial pressure of CO2 (Ksp = 4. 47×10−9 has been taken for the calculation). At atmospheric levels of ambient CO2 the table indicates the solution will be slightly alkaline. The trends the table shows are

1) As ambient CO2 partial pressure is reduced below atmospheric levels, the solution becomes more and more alkaline. At extremely low \scriptstyle P_{\mathrm{CO}_2}, dissolved CO2, bicarbonate ion, and carbonate ion largely evaporate from the solution, leaving a highly alkaline solution of calcium hydroxide, which is more soluble than CaCO3. Calcium hydroxide, traditionally called slaked lime, hydrated lime, or pickling lime, is a Chemical compound with the chemical formula
2) As ambient CO2 partial pressure increases to levels above atmospheric, pH drops, and much of the carbonate ion is converted to bicarbonate ion, which results in higher solubility of Ca2+.

The effect of the latter is especially evident in day to day life of people who have hard water. Hard water is the type of Water that has high Mineral content (in contrast with Soft water) Water in aquifers underground can be exposed to levels of CO2 much higher than atmospheric. As such water percolates through calcium carbonate rock, the CaCO3 dissolves according to the second trend. When that same water then emerges from the tap, in time it comes into equilibrium with CO2 levels in the air by outgassing its excess CO2. The calcium carbonate becomes less soluble as a result and the excess precipitates as lime scale. This same process is responsible for the formation of stalactites and stalagmites in limestone caves. A stalactite ( Greek stalaktites, (Σταλακτίτης from the word for "drip" and meaning "that which drips" is a type of Speleothem A stalagmite (from the Greek stalagma ("Σταλαγμίτης" "drop" or "drip" is a

Two hydrated phases of calcium carbonate, monohydrocalcite, CaCO3·H2O and ikaite, CaCO3·6H2O]], may precipitate from water at ambient conditions and persist as metastable phases. Monohydrocalcite is a mineral that is a hydrous form of Calcium carbonate, CaCO3·H2O Ikaite is the mineral name for the hexahydrate of Calcium carbonate, CaCO3·6H2O Precipitation is the formation of a Solid in a Solution during a Chemical reaction.

With varying pH

We now consider the problem of the maximum solubility of calcium carbonate in normal atmospheric conditions (\scriptstyle P_{\mathrm{CO}_2} = 3. 5 × 10−4 atm) when the pH of the solution is adjusted. This is for example the case in a swimming pool where the pH is maintained between 7 and 8 (by addition of NaHSO4 to decrease the pH or of NaHCO3 to increase it). From the above equations for the solubility product, the hydratation reaction and the two acid reactions, the following expression for the maximum [Ca2+] can be easily deduced:

[\mathrm{Ca}^{2+}]_\mathrm{max} = \frac{K_\mathrm{sp}k_\mathrm{H}} {K_\mathrm{h}K_\mathrm{a1}K_\mathrm{a2}} \frac{[\mathrm{H}^+]^2}{P_{\mathrm{CO}_2}}

showing a quadratic dependence in [H+]. The numerical application with the above values of the constants gives

pH 7. 0 7. 2 7. 4 7. 6 7. 8 8. 0 8. 2 8. 27 8. 4
[Ca2+]max (10-4mol/L or °F) 1590 635 253 101 40. 0 15. 9 6. 35 4. 70 2. 53
[Ca2+]max (mg/L) 6390 2540 1010 403 160 63. 9 25. 4 18. 9 10. 1

Comments:

Solubility in a strong or weak acid solution

Solutions of strong (HCl) or weak (acetic, phosphoric) acids are commercially available. A Strong acid is an Acid that Ionizes completely in an Aqueous solution (not in the case of Sulfuric acid as it is diprotic Hydrochloric acid is the Solution of Hydrogen chloride ( H[[Chlorine Cl]] in water A weak acid is an Acid that does not completely donate all of its hydrogens when dissolved in water Acetic acid, also known as ethanoic acid, is an organic chemical compound, giving Vinegar its sour taste Phosphoric acid, also known as orthophosphoric acid or phosphoric(V acid, is a mineral (inorganic acid having the Chemical formula They are commonly used to remove limescale deposits. Limescale is the hard off-white chalky deposit found in kettles hot-water boilers and the inside of inadequately maintained hot-water central heating systems The maximum amount of CaCO3 that can be "dissolved" by one liter of an acid solution can be calculated using the above equilibrium equations.

[A] (mol/L) 1 10−1 10−2 10−3 10−4 10−5 10−6 10−7 10−10
Initial pH 0. 00 1. 00 2. 00 3. 00 4. 00 5. 00 6. 00 6. 79 7. 00
Final pH 6. 75 7. 25 7. 75 8. 14 8. 25 8. 26 8. 26 8. 26 8. 27
Dissolved CaCO3 (g per liter of acid) 50. 0 5. 00 0. 514 0. 0849 0. 0504 0. 0474 0. 0471 0. 0470 0. 0470

where the initial state is the acid solution with no Ca2+ (not taking into account possible CO2 dissolution) and the final state is the solution with saturated Ca2+. For strong acid concentrations, all species have a negligible concentration in the final state with respect to Ca2+ and A− so that the neutrality equation reduces approximately to 2[Ca2+] = [A−] yielding \scriptstyle[\mathrm{Ca}^{2+}] \simeq \frac{[\mathrm{A}^-]}{2}. When the concentration decreases, [HCO3−] becomes non negligible so that the preceding expression is no longer valid. For vanishing acid concentrations, we recover the final pH and the solubility of CaCO3 in pure water.

[A] (mol/L) 1 10−1 10−2 10−3 10−4 10−5 10−6 10−7 10−10
Initial pH 2. 38 2. 88 3. 39 3. 91 4. 47 5. 15 6. 02 6. 79 7. 00
Final pH 6. 75 7. 25 7. 75 8. 14 8. 25 8. 26 8. 26 8. 26 8. 27
Dissolved CaCO3 (g per liter of acid) 49. 5 4. 99 0. 513 0. 0848 0. 0504 0. 0474 0. 0471 0. 0470 0. 0470

We see that for the same total acid concentration, the initial pH of the weak acid is less acid than the one of the strong acid; however, the maximum amount of CaCO3 which can be dissolved is approximately the same. This is because in the final state, the pH is larger that the pKA, so that the weak acid is almost completely dissociated, yielding in the end as many H+ ions as the strong acid to "dissolve" the calcium carbonate.

[A] (mol/L) 1 10−1 10−2 10−3 10−4 10−5 10−6 10−7 10−10
Initial pH 1. 08 1. 62 2. 25 3. 05 4. 01 5. 00 5. 97 6. 74 7. 00
Final pH 6. 71 7. 17 7. 63 8. 06 8. 24 8. 26 8. 26 8. 26 8. 27
Dissolved CaCO3 (g per liter of acid) 62. 0 7. 39 0. 874 0. 123 0. 0536 0. 0477 0. 0471 0. 0471 0. 0470

where [A] = [H3PO4] + [H2PO4−] + [HPO42−] + [PO43−]. We see that phosphoric acid is more efficient than a monoacid since at the final almost neutral pH, the second dissociated state concentration [HPO42−] is not negligible (see phosphoric acid ). Phosphoric acid, also known as orthophosphoric acid or phosphoric(V acid, is a mineral (inorganic acid having the Chemical formula

See also

Travertine calcium carbonate deposits from a hot spring
Travertine calcium carbonate deposits from a hot spring

References

  1. ^ Solvay Precipitated Calcium Carbonate: Production. A hot spring is a spring that is produced by the emergence of geothermally heated Groundwater from the earth's crust. " Gesso " is the Italian word for " Board chalk " (akin to the Greek word " Gypsum " and is a powdered form of the Cuttlefish are marine animals of the order Sepiida belonging to the Cephalopoda class (which also includes Squid, Octopuses Cuttlebone, also known as cuttlefish bone, is a hard brittle internal structure found in all members of the family Sepiidae, commonly known as Cuttlefish Marble is a nonfoliated Metamorphic rock resulting from the Metamorphism of Limestone, composed mostly of Calcite (a crystalline form of Solvay S. A. (2007-03-09). Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 590 - Bahram Chobin is crowned as king Barham VI of Persia. Retrieved on 2007-12-30. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1460 - Wars of the Roses: Battle of Wakefield. 1816 - The Treaty of St
  2. ^ Blast Furnace. Science Aid. Retrieved on 2007-12-30. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1460 - Wars of the Roses: Battle of Wakefield. 1816 - The Treaty of St
  3. ^ a b c d Calcium Carbonate Powder. Reade Advanced Materials (2006-02-04). Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 211 - Roman Emperor Septimius Severus dies leaving the Roman Empire in the hands of his two quarrelsome sons Retrieved on 2007-12-30. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1460 - Wars of the Roses: Battle of Wakefield. 1816 - The Treaty of St
  4. ^ Calcium Carbonate. Medline Plus. National Institutes of Health (2005-10-01). "NIH" redirects here For other meanings of NIH see NIH (disambiguation. Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. Events 331 BC - Alexander the Great defeats Darius III of Persia in the Battle of Gaugamela. Retrieved on 2007-12-30. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1460 - Wars of the Roses: Battle of Wakefield. 1816 - The Treaty of St
  5. ^ Herbert A. Lieberman, Leon Lachman, Joseph B. Schwartz (1990). Pharmaceutical Dosage Forms: Tablets, 153. ISBN 0824780442.  
  6. ^ Gabriely I, Leu JP, Barzel US (May 2008). "Clinical problem-solving. Back to basics". N. Engl. J. Med. 358 (18): 1952–6. doi:10.1056/NEJMcps0706188. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 18450607.  
  7. ^ Food-Info.net : E-numbers : E170 Calcium carbonate. 080419 food-info. net
  8. ^ Y. Zhao, B. R. Martin and C. M. Weaver (2005). "Calcium Bioavailability of Calcium Carbonate Fortified Soymilk Is Equivalent to Cow's Milk in Young Women". J. Nutr. 135 (10): 2379-2382.  
  9. ^ Associated Press. The Associated Press ( AP) is an American News agency. The AP is a Cooperative owned by its contributing Newspapers radio "Limestone Dispenser Fights Acid Rain in Stream", New York Times, 1989-06-13. Year 1989 ( MCMLXXXIX) was a Common year starting on Sunday (link displays 1989 Gregorian calendar) Events 1525 - Martin Luther marries Katharina von Bora, against the Celibacy rule decreed by the Roman Catholic Church for  
  10. ^ R. K. Schreiber (1988). "Cooperative federal-state liming research on surface waters impacted by acidic deposition". Water, Air, & Soil Pollution 41 (1): 53-73. doi:10.1007/BF00160344. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
  11. ^ Dan Kircheis; Richard Dill (2006). Effects of low pH and high aluminum on Atlantic salmon smolts in Eastern Maine and liming project feasibility analysis (reprinted at Downeast Salmon Federation). National Marine Fisheries Service and Maine Atlantic Salmon Commission.
  12. ^ a b CRC Handbook of Chemistry and Physics 44th ed.
  13. ^ Selected Solubility Products and Formation Constants at 25 °C. California State University, Dominguez Hills. "To educate is to give vision to the blind speech to the voiceless empowerment to the disenfranchised

External links

PubChem is a Database of chemical Molecules The system is maintained by the National Center for Biotechnology Information (NCBI a component The Anatomical Therapeutic Chemical Classification System is used for the classification of drugs It is controlled by the WHO Collaborating Centre for Drug ATC code A02 is a division of the Anatomical Therapeutic Chemical Classification System and part of the A Alimentary tract and metabolism. ATC code A12 is a division of the Anatomical Therapeutic Chemical Classification System and part of the A Alimentary tract and metabolism section

Dictionary

calcium carbonate

-noun

  1. (inorganic chemistry) A colourless or white inorganic compound, CaCO3, occuring as chalk, limestone, marble etc; reacts with acids to liberate carbon dioxide.
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