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Calcium carbonate has the molecular formula of CaCO₃ and 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.

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 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 is used as a very mild abrasive for hand polishing nickel, gold, silver, or plated ware, buttons, and similar materials.

calcium 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.

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.

Cal-Sup (3M Pharmaceuticals); Children’s Mylanta Upset Stomach Relief (Johnson & Johnson-Merck Consumer); Chooz (Schering- Plough HealthCare); Mylanta Soothing Lozenges (Johnson & Johnson-Merck Consumer).

Notclassified

Calcium 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.

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. 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.

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

Phosphate binding agent

Calcium supplement

Calcium 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

PrimaryIrritant (monocarbonate). Calcium carbonate is used as asource of lime, as a neutralizing agent, in manufacturing ofrubber, plastics, paint and coatings, sealants, paper, dentifrices, ceramics, putty, polishes and cleaners, insecticides,inks and cosmetics, whitewash, Portland cement, antacids,in analytical chemistry, and others.

Potentially hazardous interactions with other drugs
Can impair absorption of some drugs, e.g. iron, ciprofloxacin.

If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts theskin, remove contaminated clothing and wash immediatelywith soap and water. Seek medical attention immediately. Ifthis chemical has been inhaled, remove from exposure,begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR ifheart action has stopped. Transfer promptly to a medicalfacility. When this chemical has been swallowed, get medical attention. Give large quantities of water and inducevomiting. Do not make an unconscious person vomit.

Under the influence of gastric acid, any residual carbonate will be converted to carbon dioxide and water. Any unbound calcium not involved in the binding of phosphate will be variable and may be absorbed. Calcium is absorbed mainly from the small intestine by active transport and passive diffusion. About one-third of ingested calcium is absorbed although this can vary depending upon dietary factors and the state of the small intestine. 1,25-Dihydroxycholecalciferol (calcitriol), a metabolite of vitamin D, enhances the active phase of absorption. Excess calcium is mainly excreted renally. Unabsorbed calcium is eliminated in the faeces, together with that secreted in the bile and pancreatic juice. Minor amounts are lost in the sweat, skin, hair, and nails.

Calcium carbonate is stable and should be stored in a well-closed container in a cool, dry place.

Scoop up and place in suitable container.Discard with regular trash.

The space lattice of CaCO3 belongs to the triagonal system, and the sodium nitric acid structure has a space group of D⁶_3d. It isarhombohedron crystal, with a basis comprising two molecules, and it has a lattice constant of a=0.636 nm, a=46°6'. Ca₁ positions (1/4, 1/4, 1/4), Ca₂ (3/4, 3/4, 3/4), C₃ (0, 0, 0) and C₄ (1/2, 1/2, 1/2), andCtakes the middle of Ca–Ca. The O atom positions the corner of the triangle, the plane of which is perpendicular to the optical axis, Ca–C–Ca–. This includes C and O3, as C4 shift position by 60° with the O3 of C3. The behavior of CO 2K 3 is different for light oscillating perpendicularly to the optical axis (O-ray) and light oscillating parallel to the axis (E-ray), which is the origin of the uniaxial negative crystal.

Incompatible with acids and ammonium salts.

GRAS 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.