Calcium carbonate – CaCO3 – Cao – Ca(OH)2

Calcium carbonate is a chemical compound with the chemical formula CaCO3. It is commonly used in medicine as a calcium supplement or an antacid. Calcium carbonate is an active ingredient in lime. It is found in the form of rocks all over the world, as a major component of the shells of clams, snails and slugs. It is the main cause of hard water.

Calcium carbonate is found naturally in the following minerals and rocks:
Aragonite
Calcite
Chalk
Limestone
Marble or marble
Travertine
Eggshells are up to 95% calcium carbonate.
To test whether a mineral or rock contains calcium carbonate, strong acids, such as hydrochloric acid, can be used. If the sample contains calcium carbonate, it will fizz and produce carbon dioxide gas (CO2) and water (H2O). Weak acids, such as acetic acid, will also react, but less vigorously. All of the rocks listed above react with acids.
Preparation
Most calcium carbonate used industrially is mined from quarries or rock. Pure calcium carbonate (e.g., pharmaceutical grade) is prepared from quarries (usually marble) or it can be produced by passing carbon dioxide gas through a calcium hydroxide solution according to the following reaction:
Ca (OH) 2 + CO2 → CaCO3 + H2O
Chemical properties
See also: Carbonate
Calcium carbonate shares the typical properties of carbonates. In particular:
Reacts with strong acids, releasing carbon dioxide:
CaCO3 + 2HCl → CaCl2 + CO2 + H2O
When heated, carbon dioxide is released (above 825 °C in the case of CaCO3), to form calcium oxide, commonly known as quicklime:
CaCO3 → CaO + CO2
Calcium carbonate will react with water containing dissolved carbon dioxide to form water-soluble calcium bicarbonate.
CaCO3 + CO2 + H2O → Ca(HCO3)2
This reaction is important in the erosion of limestone and the formation of caves, causing hard water.
The installation process of
This substance is used mainly in the construction industry as building stone, marble or as a constituent of cement or from it to produce lime. Limestone often contains magnesium carbonate.
Calcium carbonate is widely used as an extender in paints, particularly in matte emulsion paints where typically about 30% of the paint mass is chalk or marble.
Calcium carbonate is also widely used as a filler in plastics. Typical examples include approximately 15–20% chalk in unplasticized PVC (uPVC) water pipes, and 5–15% stearate-coated chalk or marble in uPVC window frames. Finely ground calcium carbonate is a key component in microporous films used in baby diapers and some building films due to the nucleation of pores around the calcium carbonate particles during film manufacture by biaxial stretching.
Calcium carbonate is also widely used in a variety of work and homemade adhesives, sealants, and decorative fillers. Ceramic tile adhesives typically contain about 70-80% limestone. Decorative anti-cracking fillers contain similar amounts of marble or dolomite. It is also mixed with putty for stained glass windows, and as a resist to prevent glass from sticking to kiln shelves when firing enameled or painted objects at high temperatures.
Calcium carbonate is also widely used in medicine as a low-cost dietary calcium supplement, antacid, and/or phosphate binder. It is also used in the pharmaceutical industry as a base for tablets made from other pharmaceuticals.
Calcium carbonate is known as “whitener” in ceramic glazing where it is used as a common ingredient in many glazes in the form of a white powder. When a glaze containing it is fired in a kiln, the white lime acts as a fluxing agent in the glaze.
It is also commonly known as chalk because it is the main ingredient of blackboard chalk. Modern chalk can be made from either calcium carbonate or gypsum, hydrated calcium sulfate CaSO4·2H2O.
In North America, calcium carbonate has begun to replace kaolin in the production of glossy paper. Europe has been producing alkaline or acid-free paper for many decades. Carbonate is available in the form of ground calcium carbonate or precipitated calcium carbonate. This precipitate is very fine and has a controlled particle size, in the range of about 2 microns in diameter, making it useful for coating paper.
As a food additive, it is used in some soy milk products as a source of supplemental dietary calcium.