E170 or Calcium carbonate, inorganic compound, is one of the most common minerals found in rock agglomerates throughout the world and consists mainly of: calcium, carbon, oxygen. It is the primary component of eggshells, snails, pearls and marine organisms. Calcium carbonate is the active ingredient in agricultural lime and is created when calcium ions in hard water react with carbonate ions to create limescale.

The name "calcium carbonate" is derived from its chemical composition: one calcium ion combined with one carbonate ion.

Calcium carbonate is not typically synthesized in a laboratory or industrial setting because it is readily available in nature. However, it can be synthesized by mixing solutions of calcium ions and carbonate ions. The resulting precipitate is calcium carbonate.

Here is a simple example of how this can be done:

• Preparation of solutions. A solution of calcium chloride (CaCl₂) and another solution of sodium carbonate (Na₂CO₃). These are the sources of the calcium ions and carbonate ions, respectively.
• Mixing of solutions. A sodium carbonate solution is added to the calcium chloride solution while the compounds are mixed.
• Formation of precipitate. As the solutions mix, a precipitate of calcium carbonate forms. The reaction is: CaCl₂ + Na₂CO₃ -> CaCO₃ + ₂NaCl.
• Isolation of product. The calcium carbonate precipitate can be collected by filtration, then washed and dried to obtain the pure compound.

It appears in the form of a white powder  insoluble in water colorless, odorless and tasteless.

What it is used for and where

Food

Ingredient included in the list of European food additives as  dye E170.

Constructions (cement, plasters, asphalt).

The use of calcium carbonate precipitate protect concrete surface against the ingress of harmful external agents (1).

Medical

The synthesised biobased Calcium carbonate nanocrystals had demonstrated to be an effective carrier for delivery of anticancer drug doxorubicin (DOX). Findings suggest that Calcium carbonate nanocrystals hold tremendous promise in the areas of controlled drug delivery and targeted cancer therapy (2).

Dentin hypersensitivity reduction in adults with a clinical diagnosis of dentin hypersensitivity (3).and indicated as a treatment in cases of calcium deficiency in elderly subjects and in combination with therapies for osteoporosis (4). Calcium carbonate is able to increase calcium levels and neutralise plaque acids (5).

Cosmetics

Colorant. Ingredient CI 77220 whose primary function is to colour the solution in which it is inserted in a temporary, semi-permanent or permanent manner, either alone or in the presence of complementary components added for colouration.

Safety. It is an ingredient that has no particular health warnings and can therefore be used in all cosmetic products.

and is widely used by industries:

• Adhesives, sealants
• Rugs
• Environment (process of desulfurization of combustion gases)
• Fertilizers
• Food and pharmaceutical
• Glass and ceramics
• Products for the home
• Paints and surface coatings
• Paper
• Plastics and composites
• Rubber and elastomers

For more information:   

Calcium carbonate studies

Typical commercial product characteristics Calcium carbonate

Appearance	White powder
pH	9.0-10.5
Boiling Point	333.6ºC at 760mmHg
Melting Point	825°C
Flash Point	197ºC
Density	2.93 g/mL at 25 °C(lit.)
Refraction Index	1.6583
PSA	63.19000
HCL insoluble content	≤0.20%
Volatile content below 105℃	≤1.00
Free Alkali	≤0.10%
Whiteness degree	≥90%
Oil Absorption	50-60ml/g
Sedimentation volume	≥2.2-2.8 ml/g
Fe	≤0.12%
Mn	≤0.01%
Average Particle	0.5-15um
Mesh	400/800/1000/1250/1500
Safety

• Molecular Formula   CCaO₃  CaCO₃
• Molecular Weight  100.086 g/mol
• Exact Mass    101.962982
• CAS    471-34-1
• UNII    H0G9379FGK
• EC Number   207-439-9
• DSSTox Substance ID  DTXSID3036238    DTXSID9050486    DTXSID90109374    DTXSID80163829
• IUPAC  calcium;carbonate
• InChI=1S/CH2O3.Ca/c2-1(3)4;/h(H2,2,3,4);/q;+2/p-2 
• InChl Key      VTYYLEPIZMXCLO-UHFFFAOYSA-L
• SMILES   C(=O)([O-])[O-].[Ca+2]
• MDL number  MFCD00010906
• PubChem Substance ID    329749202
• ChEBI  3311
• ICSC    1193
• RXCUI    1897  
• RTECS   EV9580000    FF9335000
• Beilstein      8008338
• NCI  C332

Synonyms :

• CI 77220
• Calcite (Ca(Co3))
• Aragonite
• Cupric carbonate
• C50 (carbonate)
• Carbonic acid, calcium salt (1:1)

References____________________________________________________________________

(1) Van Tittelboom K, De Belie N, De Muynck W, Verstraete W. 2010. Use of bacteria to repair cracks in concrete. Cem. Concr. Res. 40:157–166. 10.1016/j.cemconres.2009.08.025

(2) Shafiu Kamba A, Ismail M, Tengku Ibrahim TA, Zakaria ZA. A pH-sensitive, biobased calcium carbonate aragonite nanocrystal as a novel anticancer delivery system. Biomed Res Int. 2013;2013:587451. doi: 10.1155/2013/587451.

(3) Collins JR, Richardson D, Sotero K, Mateo LR, Mauriz I. Beneficial effects of an arginine-calcium carbonate desensitizing paste for treatment of dentin hypersensitivity. Am J Dent. 2013 Apr;26(2):63-7.

(4) Wang J, Tao S, Jin X, Song Y, Zhou W, Lou H, Zhao R, Wang C, Hu F, Yuan H. Calcium Supplement by Tetracycline guided amorphous Calcium Carbonate potentiates Osteoblast promotion for Synergetic Osteoporosis Therapy. Theranostics. 2020 Jul 9;10(19):8591-8605. doi: 10.7150/thno.45142.

(5) Lynch RJ, ten Cate JM. The anti-caries efficacy of calcium carbonate-based fluoride toothpastes. Int Dent J. 2005;55(3 Suppl 1):175-8. doi: 10.1111/j.1875-595x.2005.tb00055.x.