Calcium carbonate (CaCO3)
Calcium carbonate (CaCO3) is an inorganic salt of calcium and carbonate, found naturally as limestone, chalk and marble. It is a white, odourless solid that is practically insoluble in water and reacts with acids to release carbon dioxide. It is supplied in pharmaceutical, food, reagent and industrial grades for uses including antacids, calcium supplements, excipients and fillers.
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Calcium carbonate
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What is calcium carbonate?
Calcium carbonate (CAS 471-34-1; molar mass approx. 100.09 g/mol) is an ionic compound of Ca²⁺ and CO₃²⁻. It occurs naturally in three main crystalline polymorphs: calcite, aragonite and the less stable vaterite. It is practically insoluble in water but dissolves in dilute acids with effervescence, releasing carbon dioxide. On strong heating it decomposes to calcium oxide (quicklime) and carbon dioxide, which is the basis of lime production.
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Which grades are available, and how do they differ?
Commercially, calcium carbonate is described as either ground calcium carbonate (GCC), milled from natural minerals, or precipitated calcium carbonate (PCC), manufactured synthetically with more controlled particle size and purity. Grades commonly include:
- Pharmacopoeial grades meeting USP, EP (Ph. Eur.) or BP monographs, used as an active ingredient (antacid, calcium supplement) and as an excipient.
- Food grade, authorised in the EU as food additive E170 and often specified to FCC.
- ACS / analytical reagent grades for laboratory use, including as a primary standard in some titrimetric methods.
- Industrial grades used as fillers in paper, plastics, paints and construction materials.
Procurement teams should check the CoA for assay, loss on drying, acid-insoluble matter and heavy metal limits against the relevant specification.
What regulatory and safety points apply?
Calcium carbonate is registered under REACH (EC 207-439-9) and listed on the TSCA inventory. It is generally not classified as hazardous under GHS, although fine powders may cause mechanical irritation and nuisance dust; always consult the supplier's SDS. Store it dry and away from acids.
Related concepts
Calcium oxide, calcium hydroxide, calcium chloride, calcite, aragonite, precipitated calcium carbonate (PCC), ground calcium carbonate (GCC), pharmaceutical excipients, food additives (E numbers) and pharmacopoeial monographs.
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