PRODUCTS

E170 CALCIUM CARBONATE

E170 Calcium carbonate is also used as a firming agent in many canned and bottled vegetable products.
E170 Calcium carbonate can be used as a coloring agent to provide a white color, an acidity regulator to balance pH levels, an anti-caking agent to increase the fluidity of powdered products, A nutritional supplement to enrich calcium content, and in some products as a thickening agent to maintain consistency.

CAS Number: 471-34-1
EC Number: 207-439-9
Chemical Formula: CaCO₃
Molar Mass: 100.09 g/mol

SYNONYMS:
Calcium carbonate, Precipitated calcium carbonate, Ground calcium carbonate, Chalk, Limestone, Calcite, E170, Precipitated chalk, PCC, Calcium carbonate precipitated, Calcium carbonate powder, Ground calcium carbonate, White calcium carbonate, Aragonite, Calcite, Chalk, Lime, Limestone, Marble, Oyster, Pearl, Calcium carbonate, Aragonite, Calcite, Chalk, Lime, Limestone, Marble, Oystershell, Pearl, Carbonic acid calcium salt

As a food additive, E170 Calcium carbonate is designated E170, and it has an INS number of 170.
E170 Calcium carbonate is one of the most widely used mineral fillers globally due to its versatility and low cost.
E170 Calcium carbonate can be processed into different particle sizes and surface-treated forms to suit specific applications.

E170 Calcium carbonate's reaction with acids producing carbon dioxide is exploited in baking (leavening reactions) and effervescent formulations.
Environmentally, E170 Calcium carbonate is non-toxic and naturally abundant, making it environmentally benign.

E170 Calcium carbonate is an inorganic salt widely occurring in nature as minerals such as calcite, aragonite, and limestone.
E170 Calcium carbonate is a chemical compound with the chemical formula CaCO3.
E170 Calcium carbonate is a common substance found in rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skeletons and pearls.

Materials containing much calcium carbonate or resembling it are described as calcareous.
E170 Calcium carbonate is the active ingredient in agricultural lime.
Limescale is calcium carbonate produced when calcium ions in hard water react with carbonate ions.

Food additive E170 Calcium carbonate is a general name for salts of carbonic acid in which calcium is bound to the carbonate group.
Additive E170 Calcium carbonate belongs to the group of colorants, but it can also be used as an acidity regulator, leavening agent, and anti-caking agent.

In everyday life, E170 Calcium carbonate is well known as ordinary white chalk.
In nature, E170 Calcium carbonates occur in the form of the minerals calcite, aragonite, and vaterite.
These forms are widely distributed in the Earth's crust and form the basis of many sedimentary rocks, including limestone, marble, and chalk.

Living organisms also actively use E170 Calcium carbonate: shells of mollusks, corals, and sponge skeletons consist mainly of calcium carbonate.
For the food industry, additive E170 Calcium carbonate is obtained by mining and purifying chalk deposits, as well as from marble, which provides the highest degree of purity.

As a result of technological processing, a fine white powder is produced.
Calcium carbonate is an inorganic salt of carbonic acid, practically insoluble in water and ethanol.
The physical properties of additive E170 Calcium carbonate include white color, absence of odor, and crystalline structure.

When heated above 800°C, E170 Calcium carbonate decomposes into calcium oxide and carbon dioxide.
According to the International Food Additives Classification and Numbering System Codex Alimentarius: CXG 36-1989, food additive

E170 Calcium carbonate is divided into two subtypes:
E170 Calcium carbonate (i) – calcium carbonate, with the chemical formula CaCO₃;
E170 Calcium carbonate (ii) – calcium bicarbonate, with the chemical formula Ca(HCO₃)₂.

However, the General Standard for Food Additives (STAN 192-1995) includes only the first subtype — E170 Calcium carbonate (i) — calcium carbonate.
In European legislation, according to Regulation (EC) No. 1333/2008, the designation additive E170 Calcium carbonate refers exclusively to calcium carbonate.

E170 Calcium carbonate is practically insoluble in water and in alcohol.
E170 Calcium carbonate is one of the most widespread compounds on earth.
E170 Calcium carbonate is a food additive with multiple functions.

E170 Calcium carbonate is an acidity regulator, anti-caking agent, emulsifier, stabilizer and colorant.
E170 Calcium carbonate is part of the natural additives of mineral origin (chalk) category, and it can be found as E170 Calcium carbonate (i)-Calcium carbonate or E170 Calcium carbonate (ii)-Calcium hydrogen carbonate.

USES and APPLICATIONS of E170 CALCIUM CARBONATE:
Used as an acidity regulator, anticaking agent, stabilizer or color, E170 Calcium carbonate is approved for usage in the EU, US and Australia and New Zealand.
E170 Calcium carbonate is "added by law to all UK milled bread flour except wholemeal".
It is used in some soy milk and almond milk products as a source of dietary calcium; at least one study suggests that E170 Calcium carbonate might be as bioavailable as the calcium in cow's milk.

E170 Calcium carbonate is also used as a firming agent in many canned and bottled vegetable products.
Several calcium supplement formulations have been documented to contain the chemical element lead, posing a public health concern.
Lead is commonly found in natural sources of calcium.

Applications: E170 Calcium carbonate (E170) is a versatile additive in the food and cosmetics industries.
E170 Calcium carbonate can be used as a coloring agent to provide a white color, an acidity regulator to balance pH levels, an anti-caking agent to increase the fluidity of powdered products, A nutritional supplement to enrich calcium content, and in some products as a thickening agent to maintain consistency.

E170 Calcium carbonate has a wide range of applications.
In the food industry, E170 Calcium carbonate is used as a white colorant (E170), anti-caking agent, acidity regulator, and calcium fortification agent.

E170 Calcium carbonate is commonly found in bakery products, dairy substitutes, confectionery, and beverages.
In pharmaceutical applications, E170 Calcium carbonate is widely used as an antacid to neutralize stomach acid and as a calcium supplement for preventing or treating calcium deficiency.

E170 Calcium carbonate is also used as an excipient in tablets.
In the industrial sector, E170 Calcium carbonate is used as a filler and extender in plastics, paints, coatings, rubber, paper, and adhesives due to its cost-effectiveness and physical properties.
In agriculture, E170 Calcium carbonate is used to neutralize acidic soils (liming agent) and improve soil quality.

E170 Calcium carbonate is one of the most commonly used food additives (E170), serving primarily as a colorant, acidity regulator, and calcium source.
Due to its abundance, low cost, and favorable safety profile, E170 Calcium carbonate is extensively utilized in food, pharmaceuticals, and industrial applications.

E170 Calcium carbonate has medical use as a calcium supplement or as an antacid, but excessive consumption can be hazardous and cause hypercalcemia and digestive issues.
E170 Calcium carbonate is widely used as an extender in paints, in particular matte emulsion paint where typically 30% by weight of the paint is either chalk or marble.

E170 Calcium carbonate is also a popular filler in plastics.
Some typical examples include around 15–20% loading of chalk in unplasticized polyvinyl chloride (uPVC) drainpipes, 5–15% loading of stearate-coated chalk or marble in uPVC window profile.

PVC cables can use E170 Calcium carbonate at loadings of up to 70 phr (parts per hundred parts of resin) to improve mechanical properties (tensile strength and elongation) and electrical properties (volume resistivity).
Polypropylene compounds are often filled with E170 Calcium carbonate to increase rigidity, a requirement that becomes important at high usage temperatures.

Here the percentage is often 20–40%.
E170 Calcium carbonate also routinely used as a filler in thermosetting resins (sheet and bulk molding compounds) and has also been mixed with ABS, and other ingredients, to form some types of compression molded "clay" poker chips.

Precipitated E170 Calcium carbonate, made by dropping calcium oxide into water, is used by itself or with additives as a white paint, known as whitewashing.
In ceramic glaze applications, E170 Calcium carbonate is known as whiting, and is a common ingredient for many glazes in its white powdered form.

When a glaze containing this material is fired in a kiln, the whiting acts as a flux material in the glaze.
Ground E170 Calcium carbonate is an abrasive (both as scouring powder and as an ingredient of household scouring creams), in particular in its calcite form, which has the relatively low hardness level of 3 on the Mohs scale, and will therefore not scratch glass and most other ceramics, enamel, bronze, iron, and steel, and have a moderate effect on softer metals like aluminium and copper.

A paste made from E170 Calcium carbonate and deionized water can be used to clean tarnish on silver.
Fine ground E170 Calcium carbonate (GCC) is an essential ingredient in the microporous film used in diapers and some building films, as the pores are nucleated around the E170 Calcium carbonate particles during the manufacture of the film by biaxial stretching.

GCC and PCC are used as fillers in paper because they are cheaper than wood fiber.
Printing and writing paper can contain 10–20% E170 Calcium carbonate.
In North America, E170 Calcium carbonate has begun to replace kaolin in the production of glossy paper.

Europe has been practicing this as alkaline papermaking or acid-free papermaking for some decades.
PCC used for paper filling and paper coatings is precipitated and prepared in a variety of shapes and sizes having characteristic narrow particle size distributions and equivalent spherical diameters of 0.4 to 3 micrometers.

E170 Calcium carbonate is added to a wide range of trade and do it yourself adhesives, sealants, and decorating fillers.
Ceramic tile adhesives typically contain 70% to 80% limestone.
Decorating crack fillers contain similar levels of marble or dolomite.

E170 Calcium carbonate 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.
E170 Calcium carbonate is versatile and can be used as an acidity regulator, anti-caking agent, stabiliser, filler, or colourant.

In the food industry, E170 Calcium carbonate is used as a food additive.
E170 Calcium carbonate serves as an acidity regulator, pigment for colour and is used to add calcium to food.
E170 Calcium carbonate is used in baked goods, beverages, sweets, as a pigment in toothpaste and as an anti-caking agent in spices.

E170 Calcium carbonate can also be used as a food preservative and colour preserver, e.g. for organic apples.
E170 Calcium carbonate is also used as a firming agent in preserves.
E170 Calcium carbonate is contained in table salt as a trickling aid.

E170 Calcium carbonate is one of the few additives that are also permitted in organic food (EU Regulation 2021/1165).
E170 Calcium carbonate is used in some medicines and food supplements to increase the calcium content and as an excipient for tablet production.

E170 Calcium carbonate is also used in the cosmetics industry.
For the food and pharmaceutical industry, E170 Calcium carbonate is usually obtained from marble.
E170 Calcium carbonate is widely used as a surface colorant, anti-drying agent, canned fruit stabilizer and in pharmacy as a filling agent.

E170 Calcium carbonate is a source of calcium, being incorporated in some dietary supplements.
E170 Calcium carbonate also has the role of neutralizing gastric hyperacidity.
Uses of E170 Calcium carbonate: Bread, biscuits, confectionery, ice cream, cakes, sweets, canned fruit and vegetables

Other Uses of E170 Calcium carbonate: Cosmetics, face powder, bleaches, vitamin tablets, cigarettes
E170 Calcium carbonate is widely used medicinally as an inexpensive dietary calcium supplement for gastric antacid (such as Tums and Eno).
E170 Calcium carbonate may be used as a phosphate binder for the treatment of hyperphosphatemia (primarily in patients with chronic kidney failure).

E170 Calcium carbonate is used in the pharmaceutical industry as an inert filler for tablets and other pharmaceuticals.
E170 Calcium carbonate is used in the production of calcium oxide as well as toothpaste and has seen a resurgence as a food preservative and color retainer, when used in or with products such as organic apples.

-Agriculture and aquaculture uses of E170 Calcium carbonate:
Agricultural lime, powdered chalk or limestone, E170 Calcium carbonate is used as a cheap method of neutralising acidic soil, making it suitable for planting, also used in aquaculture industry for pH regulation of pond soil before initiating culture.
There is interest in understanding whether or not it can affect pesticide adsorption and desorption in calcareous soil.

-Household cleaning uses of E170 Calcium carbonate:
E170 Calcium carbonate is a key ingredient in many household cleaning powders like Comet and is used as a scrubbing agent.
Pollution mitigation

In 1989, a researcher, Ken Simmons, introduced E170 Calcium carbonate into the Whetstone Brook in Massachusetts.
His hope was that the E170 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 amount of aluminium ions in the area of the brook that was not treated with the limestone.
This shows that E170 Calcium carbonate can be added to neutralize the effects of acid rain in river ecosystems.
Currently E170 Calcium carbonate is used to neutralize acidic conditions in both soil and water.

Since the 1970s, such liming has been practiced on a large scale in Sweden to mitigate acidification and several thousand lakes and streams are limed repeatedly.
E170 Calcium carbonate is also used in flue-gas desulfurization applications eliminating harmful SO2 and NO2 emissions from coal and other fossil fuels burnt in large fossil fuel power stations.

-Plastics uses of E170 Calcium carbonate:
E170 Calcium carbonate is commonly used in the plastic industry as a filler.
When E170 Calcium carbonate is incorporated in a plastic material, it can improve the hardness, stiffness, dimensional stability and processability of the material

-Construction uses of E170 Calcium carbonate:
The main use of E170 Calcium carbonate is in the construction industry, either as a building material, as limestone aggregate for road building, as an ingredient of cement, or as the starting material for the preparation of builders' lime by heating in a kiln.

However, because of weathering mainly caused by acid rain, E170 Calcium carbonate (in limestone form) is no longer used for building purposes on its own, but only as a raw primary substance for building materials.
E170 Calcium carbonate is also used in the purification of iron from iron ore in a blast furnace.

The carbonate is calcined in situ to give calcium oxide, which forms a slag with various impurities present, and separates from the purified iron.
In the oil industry, E170 Calcium carbonate is added to drilling fluids as a formation-bridging and filtercake-sealing agent; it is also a weighting material which increases the density of drilling fluids to control the downhole pressure.

E170 Calcium carbonate is added to swimming pools, as a pH corrector for maintaining alkalinity and offsetting the acidic properties of the disinfectant agent.
E170 Calcium carbonate is also used as a raw material in the refining of sugar from sugar beet; it is calcined in a kiln with anthracite to produce calcium oxide and carbon dioxide.

This burnt lime is then slaked in fresh water to produce a calcium hydroxide suspension for the precipitation of impurities in raw juice during carbonatation.
E170 Calcium carbonate in the form of chalk has traditionally been a major component of blackboard chalk.
However, modern manufactured chalk is mostly gypsum, hydrated calcium sulfate CaSO4•2H2O.

E170 Calcium carbonate is a main source for growing biorock.
Precipitated E170 Calcium carbonate (PCC), pre-dispersed in slurry form, is a common filler material for latex gloves with the aim of achieving maximum saving in material and production costs.

HEALTH AND DIET of E170 CALCIUM CARBONATE:
E170 Calcium carbonate is widely used medicinally as an inexpensive dietary calcium supplement or gastric antacid.
E170 Calcium carbonate may be used as a phosphate binder for the treatment of hyperphosphatemia (primarily in patients with chronic kidney failure).

E170 Calcium carbonate is used therapeutically as phosphate binder in patients on maintenance haemodialysis.
E170 Calcium carbonate is the most common form of phosphate binder prescribed, particularly in non-dialysis chronic kidney disease.

E170 Calcium carbonate is the most commonly used phosphate binder, but clinicians are increasingly prescribing the more expensive, non-calcium-based phosphate binders, particularly sevelamer.
Excess calcium from supplements, fortified food, and high-calcium diets can cause 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 kidney failure, alkalosis, and hypercalcaemia, 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 arose.

Since the 1990s it has been most frequently reported in women taking calcium supplements above the recommended range of 1.2 to 1.5 grams 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.

BENEFITS of E170 CALCIUM CARBONATE:
E170 Calcium carbonates play an important role in the human body, being the main source of calcium, a microelement necessary for the formation of bones and teeth.
They participate in blood clotting processes, maintain constant osmotic pressure, and regulate enzyme activity and intracellular processes.
In medicine and pharmacy, E170 Calcium carbonate is widely used as a component of medicinal products and dietary supplements designed to compensate for calcium deficiency.
E170 Calcium carbonate is also used as an antacid to reduce stomach acid.

IN WHAT PRODUCTS CAN E170 CALCIUM CARBONATE BE FOUND?
E170 Calcium carbonate is commonly used to fortify foods and beverages with calcium, an essential mineral for bone health and other body functions.
E170 Calcium carbonate is added to a wide range of products:

Bakery Products and Biscuits:
E170 Calcium carbonate helps regulate acidity and improve dough handling.

Calcium-fortified Beverages:
E170 Calcium carbonate adds calcium content.

Breakfast Cereals:
E170 Calcium carbonate acts as an anti-caking agent.

Canned Fruits:
E170 Calcium carbonate helps firm up texture.

Chewing Gum:
E170 Calcium carbonate acts as a filler ingredient.

Glazes, Pills, and Confectionery Products:
E170 Calcium carbonate can be used as a coloring agent.

In general, E170 Calcium carbonate is a versatile and safe food additive found in a variety of processed foods.

SAFETY AND USAGE of E170 CALCIUM CARBONATE:
E170 Calcium carbonate is generally recognized as safe (GRAS) and is widely approved as a food additive (E170).
In normal dietary amounts, it is safe and beneficial as a calcium source.
In industrial handling, E170 Calcium carbonate dust may cause mild irritation to the respiratory tract, eyes, or skin, so appropriate protective measures should be taken.

BENEFITS of E170 CALCIUM CARBONATE:
E170 Calcium carbonate offers several advantages:
*Provides an important dietary source of calcium
*Neutralizes acidity in food and pharmaceutical formulations
*Improves texture and stability in food products
*Enhances opacity and whiteness
*Cost-effective and widely available

PHYSICAL AND CHEMICAL PROPERTIES of E170 CALCIUM CARBONATE:
E170 Calcium carbonate is typically a white, odorless, tasteless powder or crystalline solid.
E170 Calcium carbonate exists in several polymorphic forms, primarily calcite (most stable), aragonite, and vaterite.

E170 Calcium carbonate is practically insoluble in pure water but becomes soluble in water containing dissolved carbon dioxide due to the formation of calcium bicarbonate.

E170 Calcium carbonate is readily soluble in dilute acids with effervescence, releasing carbon dioxide gas.
E170 Calcium carbonate decomposes upon heating above approximately 825–900°C to form calcium oxide (quicklime) and carbon dioxide.

E170 Calcium carbonate is chemically stable under normal conditions and exhibits alkaline properties, acting as a mild base.
E170 Calcium carbonate's density is approximately 2.7–2.9 g/cm³ depending on the crystalline form.
The pH of aqueous suspensions is typically alkaline (around pH 9–10).

CHARACTERISTICS of E170 CALCIUM CARBONATE:
E170 Calcium carbonate is characterized by:
*High whiteness and opacity
*Low solubility in water
*Alkaline buffering capacity
*Multiple crystalline polymorphs
*Good chemical stability under ambient conditions
*Reactivity with acids (CO₂ release)

CHEMISTRY of E170 CALCIUM CARBONATE:
E170 Calcium carbonate shares the typical properties of other carbonates.
Notably, E170 Calcium carbonate:
reacts with acids, releasing carbonic acid which quickly disintegrates into carbon dioxide and water:
CaCO3(s) + 2 H+(aq) → Ca2+(aq) + CO2(g) + H2O(l)

releases carbon dioxide upon heating, called a thermal decomposition reaction, or calcination (to above 840 °C in the case of CaCO3), to form calcium oxide, CaO, commonly called quicklime, with reaction enthalpy 178 kJ/mol:
CaCO3(s) → CaO(s) + CO2(g)

reacts with gaseous hydrogen to form methane and water vapor plus solid calcium oxide or calcium hydroxide depending on temperature and product gas composition.
Various metals including palladium and nickel are catalysts for the reaction.

E170 Calcium carbonate reacts with water that is saturated with carbon dioxide to form the soluble calcium bicarbonate.
CaCO3(s) + CO2(g) + H2O(l) → Ca(HCO3)2(aq)

This reaction is important in the erosion of carbonate rock, forming caverns, and leads to hard water in many regions.
An unusual form of calcium carbonate is the hexahydrate ikaite, CaCO3•6H2O.
Ikaite is stable only below 8 °C.

PREPARATION of E170 CALCIUM CARBONATE:
The vast majority of calcium carbonate used in industry is extracted by mining or quarrying.
Pure calcium carbonate (such as for food or pharmaceutical use), can be produced from a pure quarried source (usually marble), or prepared from calcium oxide.

Water is added to give calcium hydroxide then carbon dioxide is passed through this solution to precipitate the desired calcium carbonate, referred to in the industry as precipitated calcium carbonate (PCC).

This process is called carbonatation.
CaO + H2O → Ca(OH)2
Ca(OH)2 + CO2 → CaCO3 + H2O
E170 Calcium carbonate can be crystallized from calcium chloride (CaCl2), by placing an aqueous solution of CaCl2 in a desiccator alongside ammonium carbonate [NH4]2CO3.

In the desiccator, ammonium carbonate is exposed to air and decomposes into ammonia, carbon dioxide, and water.
The carbon dioxide then diffuses into the aqueous solution of calcium chloride, reacts with the calcium ions and the water, and forms calcium carbonate.

STRUCTURE of E170 CALCIUM CARBONATE:
The thermodynamically stable form of E170 Calcium carbonate under normal conditions is hexagonal β-CaCO3 (the mineral calcite).
Other forms can be prepared, the denser (2.83 g/cm3) orthorhombic λ-CaCO3 (the mineral aragonite) and hexagonal μ-CaCO3, occurring as the mineral vaterite.

The aragonite form can be prepared by precipitation at temperatures above 85 °C; the vaterite form can be prepared by precipitation at 60 °C.
Calcite contains calcium atoms coordinated by six oxygen atoms; in aragonite they are coordinated by nine oxygen atoms.

The vaterite structure is not fully understood.
Magnesium carbonate (MgCO3) has the calcite structure, whereas strontium carbonate (SrCO3) and barium carbonate (BaCO3) adopt the aragonite structure, reflecting their larger ionic radii.

E170 Calcium carbonate, is a widely used food additive with a broad range of applications.
From modifying the texture of foods to enhancing nutritional content, E170 Calcium carbonate plays a significant role in the food industry.

E170 Calcium carbonate, is a natural compound found in rocks such as limestone, marble, and chalk.
E170 Calcium carbonate acts as an acidity regulator, anti-caking agent, emulsifier, stabilizer, and coloring agent.

E170 Calcium carbonate belongs to the category of natural mineral additives and can be found in the form of E 170(i) – Calcium Carbonate or E 170(ii) – Acidic Calcium Carbonate.
E170 Calcium carbonate is a white, odorless, and tasteless powder that is insoluble in water but soluble in acids, releasing carbon dioxide.

POLYMORPHS of E170 CALCIUM CARBONATE:
E170 Calcium carbonate crystallizes in three anhydrous polymorphs, of which calcite is the thermodynamically most stable at room temperature, aragonite is only slightly less so, and vaterite is the least stable.

CRYSTAL STRUCTURE of E170 CALCIUM CARBONATE:
The calcite crystal structure is trigonal, with space group R3c (No. 167 in the International Tables for Crystallography), and Pearson symbol hR10.
Aragonite is orthorhombic, with space group Pmcn (No 62), and Pearson Symbol oP20.
Vaterite is composed of at least two different coexisting crystallographic structures.
The major structure exhibits hexagonal symmetry in space group P63/mmc, the minor structure is still unknown.

CRYSTALLIZATION of E170 CALCIUM CARBONATE:
All three polymorphs crystallize simultaneously from aqueous solutions under ambient conditions.
In additive-free aqueous solutions, calcite forms easily as the major product, while aragonite appears only as a minor product.
At high saturation, vaterite is typically the first phase precipitated, which is followed by a transformation of the vaterite to calcite.

This behavior seems to follow Ostwald's rule, in which the least stable polymorph crystallizes first, followed by the crystallization of different polymorphs via a sequence of increasingly stable phases.
However, aragonite, whose stability lies between those of vaterite and calcite, seems to be the exception to this rule, as aragonite does not form as a precursor to calcite under ambient conditions.

Aragonite occurs in majority when the reaction conditions inhibit the formation of calcite and/or promote the nucleation of aragonite.
For example, the formation of aragonite is promoted by the presence of magnesium ions, or by using proteins and peptides derived from biological E170 Calcium carbonate.

Some polyamines such as cadaverine and Poly(ethylene imine) have been shown to facilitate the formation of aragonite over calcite.
Solid-state NMR analysis has revealed that poly-aspartate-stabilized ACC contains water molecules that undergo millisecond-timescale flips, illustrating dynamic hydration as a key factor in delaying crystallization.

SELECTION BY ORGANISMS of E170 CALCIUM CARBONATE:
Organisms, such as molluscs and arthropods, have shown the ability to grow all three crystal polymorphs of E170 Calcium carbonate, mainly as protection (shells) and muscle attachments.
Moreover, they exhibit a remarkable capability of phase selection over calcite and aragonite, and some organisms can switch between the two polymorphs.
The ability of phase selection is usually attributed to the use of specific macromolecules or combinations of macromolecules by such organisms.

OCCURRENCE of E170 CALCIUM CARBONATE:
GEOLOGICAL SOURCES
Calcite, aragonite and vaterite are pure E170 Calcium carbonate minerals.
Industrially important source rocks which are predominantly E170 Calcium carbonate include limestone, chalk, marble and travertine.

BIOLOGICAL SOURCES of E170 CALCIUM CARBONATE:
Eggshells, snail shells and most seashells are predominantly E170 Calcium carbonate and can be used as industrial sources of that chemical.
Oyster shells have enjoyed recent recognition as a source of dietary calcium, but are also a practical industrial source.

Dark green vegetables such as broccoli and kale contain dietarily significant amounts of E170 Calcium carbonate, but they are not practical as an industrial source.
Annelids in the family Lumbricidae, earthworms, possess a regionalization of the digestive track called calciferous glands,
Kalkdrüsen, or glandes de Morren, that processes calcium and CO2 into E170 Calcium carbonate, which is later excreted into the dirt.
The function of these glands is unknown but is believed to serve as a CO2 regulation mechanism within the animals' tissues.
This process is ecologically significant, stabilizing the pH of acid soils.

EXTRATERRESTRIAL of E170 CALCIUM CARBONATE:
Beyond Earth, strong evidence suggests the presence of E170 Calcium carbonate on Mars.
Signs of E170 Calcium carbonate have been detected at more than one location (notably at Gusev and Huygens craters).
This provides some evidence for the past presence of liquid water.

GEOLOGY of E170 CALCIUM CARBONATE:
Carbonate is found frequently in geologic settings and constitutes an enormous carbon reservoir.
E170 Calcium carbonate occurs as aragonite, calcite and dolomite as significant constituents of the calcium cycle.
The carbonate minerals form the rock types: limestone, chalk, marble, travertine, tufa, and others.
In warm, clear tropical waters corals are more abundant than towards the poles where the waters are cold.

E170 Calcium carbonate contributors, including plankton (such as coccoliths and planktic foraminifera), coralline algae, sponges, brachiopods, echinoderms, bryozoa and mollusks, are typically found in shallow water environments where sunlight and filterable food are more abundant.

Cold-water carbonates do exist at higher latitudes but have a very slow growth rate.
The calcification processes are changed by ocean acidification.
Where the oceanic crust is subducted under a continental plate sediments will be carried down to warmer zones in the asthenosphere and lithosphere.

Under these conditions E170 Calcium carbonate decomposes to produce carbon dioxide which, along with other gases, give rise to explosive volcanic eruptions.

CARBONATE COMPENSATION DEPTH
The carbonate compensation depth (CCD) is the point in the ocean where the rate of precipitation of E170 Calcium carbonate is balanced by the rate of dissolution due to the conditions present.
Deep in the ocean, the temperature drops and pressure increases.
Increasing pressure also increases the solubility of E170 Calcium carbonate.

E170 Calcium carbonate is unusual in that its solubility increases with decreasing temperature.
The carbonate compensation depth ranges from 4,000 to 6,000 meters below sea level in modern oceans, and the various polymorphs (calcite, aragonite) have different compensation depths based on their stability.

ROLE IN TAPHONOMY of E170 CALCIUM CARBONATE:
E170 Calcium carbonate can preserve fossils through permineralization.
Most of the vertebrate fossils of the Two Medicine Formation—a geologic formation known for its duck-billed dinosaur eggs—are preserved by E170 Calcium carbonate permineralization.

This type of preservation conserves high levels of detail, even down to the microscopic level.
However, it also leaves specimens vulnerable to weathering when exposed to the surface.
Trilobite populations were once thought to have composed the majority of aquatic life during the Cambrian, due to the fact that their E170 Calcium carbonate-rich shells were more easily preserved than those of other species, which had purely chitinous shells.

CALCINATION EQUILIBRIUM of E170 CALCIUM CARBONATE:
Calcination of limestone using charcoal fires to produce quicklime has been practiced since antiquity by cultures all over the world.
The temperature at which limestone yields calcium oxide is usually given as 825 °C, but stating an absolute threshold is misleading.
E170 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 E170 Calcium carbonate.
At room temperature the equilibrium overwhelmingly favors E170 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, E170 Calcium carbonate begins to outgas CO2 into air.
However, 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.

This partial pressure is not achieved until the temperature is nearly 800 °C.
For the outgassing of CO2 from E170 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 of E170 CALCIUM CARBONATE:
WITH VARYING CO2 PRESSURE
E170 Calcium carbonate is poorly soluble in pure water (47 mg/L at normal atmospheric CO2 partial pressure as shown below).
The equilibrium of its solution is given by the equation (with dissolved E170 Calcium carbonate on the right):

CaCO3 ⇌ Ca2+ + CO2−3
Ksp = 3.7×10−9 to 8.7×10−9 at 25 °C
where the solubility product for [Ca2+][CO2−3] is given as anywhere from Ksp = 3.7×10−9 to Ksp = 8.7×10−9 at 25 °C, depending upon the data source.

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 CO2−3 cannot exceed the value of Ksp.
This seemingly simple solubility equation, however, must be taken along with the more complicated equilibrium of carbon dioxide with water (see carbonic acid).

Some of the CO2−3 combines with H+ in the solution according to
HCO3− ⇌ H+ + CO2−3
Ka2 = 5.61×10−11 at 25 °C

HCO3− is known as the bicarbonate ion.
Calcium bicarbonate is many times more soluble in water than E170 Calcium carbonate—indeed it exists only in 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(aq) ⇌ H2CO3
Kh = 1.70×10−3 at 25 °C

And dissolved carbon dioxide is in equilibrium with atmospheric carbon dioxide according to
PCO2 / [CO2] = Hv
Hv = 29.76 atm/(mol/L) at 25 °C (Henry volatility), and PCO2 is the CO2 partial pressure.

For ambient air, PCO2 is around 3.5×10−4 atm (or equivalently 35 Pa).
The last equation above fixes the concentration of dissolved CO2 as a function of PCO2, independent of the concentration of dissolved E170 Calcium carbonate.

At atmospheric partial pressure of CO2, dissolved CO2 concentration is 1.2×10−5 moles per liter.
The equation before that fixes the concentration of H2CO3 as a function of CO2 concentration.
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 constraint that the solution must be electrically neutral, i.e., the overall charge of dissolved positive ions [Ca2+] + 2 [H+] must be cancelled out by the overall charge of dissolved negative ions [HCO3−] + [CO2−3] + [OH−], make it possible to solve simultaneously for the remaining five unknown concentrations.

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 that the solution will be slightly alkaline with a maximum E170 Calcium carbonate solubility of 47 mg/L.

As ambient CO2 partial pressure is reduced below atmospheric levels, the solution becomes more and more alkaline.
At extremely low PCO2, 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 E170 Calcium carbonate.

For PCO2 = 10−12 atm, the [Ca2+][OH−]2 product is still below the solubility product of Ca(OH)2 (8×10−6).
For still lower CO2 pressure, Ca(OH)2 precipitation will occur before E170 Calcium carbonate precipitation.
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.
Water in aquifers underground can be exposed to levels of CO2 much higher than atmospheric.

As such, water percolates through E170 Calcium carbonate rock, the CaCO3 dissolves according to one of the trends above.
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 E170 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.
Two hydrated phases of E170 Calcium carbonate, monohydrocalcite CaCO3•H2O and ikaite CaCO3•6H2O, may precipitate from water at ambient conditions and persist as metastable phases.

WITH VARYING PH, TEMPERATURE AND SALINITY: E170 CALCIUM CARBONATE SCALING IN SWIMMING POOLS
In contrast to the open equilibrium scenario above, many swimming pools are managed by addition of sodium bicarbonate (NaHCO3) to the concentration of about 2 mmol/L as a buffer, then control of pH through use of HCl, NaHSO4, Na2CO3, NaOH or chlorine formulations that are acidic or basic.
In this situation, dissolved inorganic carbon (total inorganic carbon) is far from equilibrium with atmospheric CO2.

Progress towards equilibrium through outgassing of CO2 is slowed by the slow reaction
H2CO3 ⇌ CO2(aq) + H2O;
limited aeration in a deep water column; and periodic replenishment of bicarbonate to maintain buffer capacity (often estimated through measurement of total alkalinity).

In this situation, the dissociation constants for the much faster reactions
H2CO3 ⇌ H+ + HCO3− ⇌ 2 H+ + CO32−
allow the prediction of concentrations of each dissolved inorganic carbon species in solution, from the added concentration of HCO3−.

Rearranging the equations given above, we can see that [Ca2+] = Ksp / [CO32−], and [CO32−] = Ka2 [HCO3−] / [H+].
Therefore, when HCO3− concentration is known, the maximum concentration of Ca2+ ions before scaling through CaCO3 precipitation can be predicted from the formula:
[Ca2+]max = Ksp / Ka2 × [H+] / [HCO3−]

The solubility product for E170 Calcium carbonate (Ksp) and the dissociation constants for the dissolved inorganic carbon species (including Ka2) are all substantially affected by temperature and salinity, with the overall effect that [Ca2+]max increases from freshwater to saltwater, and decreases with rising temperature, pH, or added bicarbonate level.

Scaling is commonly observed in electrolytic chlorine generators, where there is a high pH near the cathode surface and scale deposition further increases temperature.
This is one reason that some pool operators prefer borate over bicarbonate as the primary pH buffer, and avoid the use of pool chemicals containing calcium.

SOLUBILITY of E170 CALCIUM CARBONATE IN A STRONG OR WEAK ACID SOLUTION:
Solutions of strong (HCl), moderately strong (sulfamic) or weak (acetic, citric, sorbic, lactic, phosphoric) acids are commercially available.
They are commonly used as descaling agents to remove limescale deposits.

The maximum amount of E170 Calcium carbonate that can be "dissolved" by one liter of an acid solution can be calculated using the above equilibrium equations.
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 [Ca2+] ≈ 0.5 [A−].

When the concentration decreases, [HCO3−] becomes non-negligible so that the preceding expression is no longer valid.
For vanishing acid concentrations, one can recover the final pH and the solubility of E170 Calcium carbonate in pure water.
In the case of a weak monoacid (here we take acetic acid with pKa = 4.76) with decreasing total acid concentration [A] = [A−] + [AH].

For the same total acid concentration, the initial pH of the weak acid is less acid than that of the strong acid; however, the maximum amount of E170 Calcium carbonate which can be dissolved is approximately the same.
This is because in the final state, the pH is larger than 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 E170 Calcium carbonate.

The calculation in the case of phosphoric acid (which is the most widely used for domestic applications) is more complicated since the concentrations of the four dissociation states corresponding to this acid must be calculated together with [HCO3−], [CO2−3], [Ca2+], [H+] and [OH−].
where [A] = [H3PO4] + [H2PO4−] + [HPO2−4] + [PO3−4] is the total acid concentration.
Thus phosphoric acid is more efficient than a monoacid since at the final almost neutral pH, the second dissociated state concentration [HPO2−4] is not negligible.

PHYSICAL and CHEMICAL PROPERTIES of E170 CALCIUM CARBONATE:
Appearance: White, odorless powder
Molecular Formula: CaCO₃
Density: 2.7 g/cm³
Solubility: Insoluble in water
Melting Point: 825°C (decomposes)
Boiling Point: N/A (decomposes upon heating)
Flash Point: Not applicable
Vapor Pressure: Not applicable
Chemical Formula: CaCO₃
Grade name: GSC / Gulcal
Colour: Bright White
B.D. gm/ml: 0.40 to 0.9 gm /ml

Phase: Calcite/Aragonite
Loss of Drying: < 1. %
Residue on 325 Mesh: < 0.10%
Soluble Alkali: < 0.15
Solution Test: Clear
pH: 9.5-10.2
Particle Size (D50) Different Grades: 2–8 Microns
Purity as CaCO₃ %: 98%
CAS number: 471-34-1
EC number: 207-439-9

Grade: Ph Eur, BP, USP, JP, FCC
Hill Formula: CaCO₃
Chemical formula: CaCO₃
Molar Mass: 100.09 g/mol
HS Code: 2836 50 00
Density: 2.8 g/cm³
Melting Point: 825 °C (decomposition)
pH value: 8.0 (H₂O) (slurry)
Bulk density: 300 - 1400 kg/m³
Solubility: 0.017 g/l

Physical state: Solid
Color: Light gray
Odor: No data available
Melting point/freezing point: 800 °C - Decomposes on heating.
Initial boiling point and boiling range: 800 °C
Flammability (solid, gas): The product is not flammable.
Upper/lower flammability or explosive limits: No data available
Flash point: No data available
Autoignition temperature: Not auto-flammable
Decomposition temperature: No data available
pH: 8.0

Viscosity:
Viscosity, kinematic: No data available
Viscosity, dynamic: No data available
Water solubility: 0.017 g/l at 20 °C - Slightly soluble
Partition coefficient: n-octanol/water:
Not applicable for inorganic substances
Vapor pressure: No data available
Density: 2.8 g/cm³
Relative density: No data available
Relative vapor density: No data available

Particle characteristics: No data available
Explosive properties: No data available
Oxidizing properties: None
Other safety information:
Bulk density: ca. 300 - 1,400 kg/m³
Molecular Weight: 100.09 g/mol
Hydrogen Bond Donor Count: 0
Hydrogen Bond Acceptor Count: 3
Rotatable Bond Count: 0
Exact Mass: 99.9473347 Da

Monoisotopic Mass: 99.9473347 Da
Topological Polar Surface Area: 63.2 Å²
Heavy Atom Count: 5
Formal Charge: 0
Complexity: 18.8
Isotope Atom Count: 0
Defined Atom Stereocenter Count: 0
Undefined Atom Stereocenter Count: 0
Defined Bond Stereocenter Count: 0
Undefined Bond Stereocenter Count: 0

Covalently-Bonded Unit Count: 2
Compound Is Canonicalized: Yes
Chemical formula: CaCO3
Molar mass: 100.0869 g/mol
Appearance: Fine white powder or colorless crystals; chalky taste
Odor: odorless
Density: 2.711 g/cm3 (calcite) 2.83 g/cm3 (aragonite)
Melting point: 1,339 °C (2,442 °F; 1,612 K) (calcite) 825 °C (1,517 °F; 1,098 K) (aragonite)
Boiling point: decomposes

Solubility in water: 0.013 g/L (25 °C)
Solubility product (Ksp): 3.3×10−9
Solubility in dilute acids: soluble
Magnetic susceptibility (χ): −3.82×10−5 cm3/mol
Refractive index (nD): 1.59
Crystal structure: Trigonal
Space group: 32/m
Std molar entropy (S⦵298): 93 J/(mol·K)
Std enthalpy of formation (ΔfH⦵298): −1207 kJ/mol

FIRST AID MEASURES of E170 CALCIUM CARBONATE:
-Description of first-aid measures
*General advice:
Show this material safety data sheet to the doctor in attendance.
*If inhaled:
After inhalation:
Fresh air.
*In case of skin contact:
Take off immediately all contaminated clothing.
Rinse skin with
water/ shower.
*In case of eye contact:
After eye contact:
Rinse out with plenty of water.
Call in ophthalmologist.
Remove contact lenses.
*If swallowed:
After swallowing:
Immediately make victim drink water (two glasses at most).
Consult a physician.
-Indication of any immediate medical attention and special treatment needed.
No data available

ACCIDENTAL RELEASE MEASURES of E170 CALCIUM CARBONATE:
-Environmental precautions:
Do not let product enter drains.
-Methods and materials for containment and cleaning up:
Cover drains.
Collect, bind, and pump off spills.
Observe possible material restrictions.
Take up dry.
Dispose of properly.
Clean up affected area.

FIRE FIGHTING MEASURES of E170 CALCIUM CARBONATE:
-Extinguishing media:
*Suitable extinguishing media:
Carbon dioxide (CO2)
Foam
Dry powder
*Unsuitable extinguishing media:
For this substance/mixture no limitations of extinguishing agents are given.
-Further information:
Prevent fire extinguishing water from contaminating surface water or the ground water system.

EXPOSURE CONTROLS/PERSONAL PROTECTION of E170 CALCIUM CARBONATE:
-Control parameters:
--Ingredients with workplace control parameters:
-Exposure controls:
--Personal protective equipment:
*Eye/face protection:
Use equipment for eye protection.
Safety glasses
*Body Protection:
protective clothing
*Respiratory protection:
Recommended Filter type: Filter A
-Control of environmental exposure:
Do not let product enter drains.

HANDLING and STORAGE of E170 CALCIUM CARBONATE:
-Conditions for safe storage, including any incompatibilities:
*Storage conditions:
Tightly closed.
Dry.

STABILITY and REACTIVITY of E170 CALCIUM CARBONATE:
-Chemical stability:
The product is chemically stable under standard ambient conditions (room temperature) .
-Possibility of hazardous reactions:
No data available