Calcium chloride

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Calcium chloride
Kristallstruktur Calciumchlorid.png
Calcium chloride CaCl2.jpg
Names
IUPAC name
Calcium chloride
Other names
Calcium(II) chloride, calcium dichloride, E509
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.030.115
EC Number
  • 233-140-8
E number E509 (acidity regulators, ...)
PubChem CID
RTECS number
  • EV9800000
UNII
Properties
CaCl2
Molar mass 110.98 g·mol−1
AppearanceWhite powder, hygroscopic
Odor Odorless
Density
  • 2.15 g/cm3 (anhydrous)
  • 2.24 g/cm3 (monohydrate)
  • 1.85 g/cm3 (dihydrate)
  • 1.83 g/cm3 (tetrahydrate)
  • 1.71 g/cm3 (hexahydrate) [1]
Melting point 772–775 °C (1,422–1,427 °F; 1,045–1,048 K)
anhydrous [2]
260 °C (500 °F; 533 K)
monohydrate, decomposes
175 °C (347 °F; 448 K)
dihydrate, decomposes
45.5 °C (113.9 °F; 318.6 K)
tetrahydrate, decomposes [2]
30 °C (86 °F; 303 K)
hexahydrate, decomposes [1]
Boiling point 1,935 °C (3,515 °F; 2,208 K)anhydrous [1]
Anhydrous:
74.5 g/100 mL (20 °C) [3]
Hexahydrate:
49.4 g/100 mL (−25 °C)
59.5 g/100 mL (0 °C)
65 g/100 mL (10 °C)
81.1 g/100 mL (25 °C) [1]
102.2 g/100 mL (30.2 °C)
α-Tetrahydrate:
90.8 g/100 mL (20 °C)
114.4 g/100 mL (40 °C)
Dihydrate:
134.5 g/100 mL (60 °C)
152.4 g/100 mL (100 °C) [4]
Solubility
Solubility in ethanol
  • 18.3 g/100 g (0 °C)
  • 25.8 g/100 g (20 °C)
  • 35.3 g/100 g (40 °C)
  • 56.2 g/100 g (70 °C) [5]
Solubility in methanol
  • 21.8 g/100 g (0 °C)
  • 29.2 g/100 g (20 °C)
  • 38.5 g/100 g (40 °C) [5]
Solubility in acetone 0.1 g/kg (20 °C) [5]
Solubility in pyridine 16.6 g/kg [5]
Acidity (pKa)
  • 8–9 (anhydrous)
  • 6.5–8.0 (hexahydrate)
−5.47·10−5 cm3/mol [1]
1.52
Viscosity
  • 3.34 cP (787 °C)
  • 1.44 cP (967 °C) [5]
Structure
  • Pnnm, No. 58 (anhydrous)
  • P42/mnm, No. 136 (anhydrous, >217 °C) [6]
  • 2/m 2/m 2/m (anhydrous)
  • 4/m 2/m 2/m (anhydrous, >217 °C) [6]
a = 6.259 Å, b = 6.444 Å, c = 4.17 Å (anhydrous, 17 °C) [6]
α = 90°, β = 90°, γ = 90°
Octahedral (Ca2+, anhydrous)
Thermochemistry
  • 72.89 J/mol·K (anhydrous) [1]
  • 106.23 J/mol·K (monohydrate)
  • 172.92 J/mol·K (dihydrate)
  • 251.17 J/mol·K (tetrahydrate)
  • 300.7 J/mol·K (hexahydrate) [2]
108.4 J/mol·K [1] [2]
  • −795.42 kJ/mol (anhydrous) [1]
  • −1110.98 kJ/mol (monohydrate)
  • −1403.98 kJ/mol (dihydrate)
  • −2009.99 kJ/mol (tetrahydrate)
  • −2608.01 kJ/mol (hexahydrate) [2]
−748.81 kJ/mol [1] [2]
Pharmacology
A12AA07 ( WHO ) B05XA07 ( WHO ), G04BA03 ( WHO )
Hazards
Main hazards Irritant
Safety data sheet See: data page
GHS pictograms GHS-pictogram-exclam.svg [7]
GHS Signal word Warning
H319 [7]
P305+351+338 [7]
NFPA 704 (fire diamond)
[8]
Flammability code 0: Will not burn. E.g. waterHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformReactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no codeCalcium chloride
0
2
1
Lethal dose or concentration (LD, LC):
1,000-1,400 mg/kg (rats, oral) [9]
Related compounds
Other anions
Other cations
Supplementary data page
Refractive index (n),
Dielectric constantr), etc.
Thermodynamic
data
Phase behaviour
solidliquidgas
UV, IR, NMR, MS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)
Infobox references

Calcium chloride is an inorganic compound, a salt with the chemical formula CaCl2. It is a white coloured crystalline solid at room temperature, and it is highly soluble in water. It can be created by neutralising hydrochloric acid with calcium hydroxide.

Contents

Calcium chloride is commonly encountered as a hydrated solid with generic formula CaCl2(H2O)x, where x = 0, 1, 2, 4, and 6. These compounds are mainly used for de-icing and dust control. Because the anhydrous salt is hygroscopic, it is used as a desiccant. [10]

Uses

De-icing and freezing-point depression

Bulk CaCl2 for de-icing in Japan Cacl2 storage for winter road in japan.jpg
Bulk CaCl2 for de-icing in Japan

By depressing the freezing point of water, calcium chloride is used to prevent ice formation and is used to de-ice. This application consumes the greatest amount of calcium chloride. Calcium chloride is relatively harmless to plants and soil. As a deicing agent, it is much more effective at lower temperatures than sodium chloride. When distributed for this use, it usually takes the form of small, white spheres a few millimeters in diameter, called prills. Solutions of calcium chloride can prevent freezing at temperatures as low as −52 °C (−62 °F), making it ideal for filling agricultural implement tires as a liquid ballast, aiding traction in cold climates. [11]

It is also used in domestic and industrial chemical air dehumidifiers. [12]

Road surfacing

Calcium chloride was sprayed on this road to prevent weathering, giving it a wet appearance even in dry weather. Calcium chloride on a dirt road.jpg
Calcium chloride was sprayed on this road to prevent weathering, giving it a wet appearance even in dry weather.

The second largest application of calcium chloride exploits hygroscopic properties and the tackiness of its hydrates. Calcium chloride is highly hygroscopic and its hydration is an exothermic reaction. A concentrated solution keeps a liquid layer on the surface of dirt roads, which suppresses the formation of dust. It keeps the finer dust particles on the road, providing a cushioning layer. If these are allowed to blow away, the large aggregate begins to shift around and the road breaks down. Using calcium chloride reduces the need for grading by as much as 50% and the need for fill-in materials as much as 80%. [13]

Food

The average intake of calcium chloride as food additives has been estimated to be 160–345 mg/day. [14] Calcium chloride is permitted as a food additive in the European Union for use as a sequestrant and firming agent with the E number E509. It is considered as generally recognized as safe (GRAS) by the U.S. Food and Drug Administration. [15] Its use in organic crop production is generally prohibited under the US National Organic Program. [16]

In marine aquariums, calcium chloride is one way to introduce bioavailable calcium for calcium carbonate-shelled animals such as mollusks and some cnidarians. Calcium hydroxide (kalkwasser mix) or a calcium reactor can also be used.

As a firming agent, calcium chloride is used in canned vegetables, in firming soybean curds into tofu and in producing a caviar substitute from vegetable or fruit juices. [17] It is commonly used as an electrolyte in sports drinks and other beverages, including bottled water. The extremely salty taste of calcium chloride is used to flavor pickles without increasing the food's sodium content. Calcium chloride's freezing-point depression properties are used to slow the freezing of the caramel in caramel-filled chocolate bars. Also, it is frequently added to sliced apples to maintain texture.

In brewing beer, calcium chloride is sometimes used to correct mineral deficiencies in the brewing water. It affects flavor and chemical reactions during the brewing process, and can also affect yeast function during fermentation.

In cheesemaking, calcium chloride is sometimes added to processed (pasteurized/homogenized) milk to restore the natural balance between calcium and protein in casein. It is added before the coagulant.

Calcium chloride is used to prevent cork spot and bitter pit on apples by spraying on the tree during the late growing season. [18]

Drying tubes are frequently packed with calcium chloride. Kelp is dried with calcium chloride for use in producing sodium carbonate. Anhydrous calcium chloride has been approved by the FDA as a packaging aid to ensure dryness (CPG 7117.02). [19]

The hydrated salt can be dried for re-use but will dissolve in its own water of hydration if heated quickly and form a hard amalgamated solid when cooled.

Miscellaneous applications

Calcium chloride is used in concrete mixes to accelerate the initial setting, but chloride ions lead to corrosion of steel rebar, so it should not be used in reinforced concrete. [20] The anhydrous form of calcium chloride may also be used for this purpose and can provide a measure of the moisture in concrete. [21]

Calcium chloride is included as an additive in plastics and in fire extinguishers, in wastewater treatment as a drainage aid, in blast furnaces as an additive to control scaffolding (clumping and adhesion of materials that prevent the furnace charge from descending), and in fabric softener as a thinner.

The exothermic dissolution of calcium chloride is used in self-heating cans and heating pads.

In the oil industry, calcium chloride is used to increase the density of solids-free brines. It is also used to provide inhibition of swelling clays in the water phase of invert emulsion drilling fluids.

CaCl2 acts as flux material, decreasing the melting point, in the Davy process for the industrial production of sodium metal through the electrolysis of molten NaCl.

Similarly, CaCl2 is used as a flux and electrolyte in the FFC Cambridge process for titanium production, where it ensures the proper exchange of calcium and oxygen ions between the electrodes.

Calcium chloride is also used in the production of activated charcoal.

Calcium chloride is also an ingredient used in ceramic slipware. It suspends clay particles so that they float within the solution, making it easier to use in a variety of slipcasting techniques.

Calcium chloride dihydrate (20 percent by weight) dissolved in ethanol (95 percent ABV) has been used as a sterilant for male animals. The solution is injected into the testes of the animal. Within one month, necrosis of testicular tissue results in sterilization. [22] [23]

Hazards

Calcium chloride can act as an irritant by desiccating moist skin. Solid calcium chloride dissolves exothermically, and burns can result in the mouth and esophagus if it is ingested. Ingestion of concentrated solutions or solid products may cause gastrointestinal irritation or ulceration. [24]

Consumption of calcium chloride can lead to hypercalcemia. [25]

Properties

Flame test of CaCl2 Flame Test Ca.jpg
Flame test of CaCl2

Calcium chloride dissolves in water, producing chloride and the aquo complex [Ca(H2O)6]2+. In this way, these solutions are sources of "free" calcium and free chloride ions. This description is illustrated by the fact that these solutions react with phosphate sources to give a solid precipitate of calcium phosphate:

3 CaCl2 + 2 PO3−
4
→ Ca3(PO4)2 + 6 Cl

Calcium chloride has a very high enthalpy change of solution, indicated by considerable temperature rise accompanying dissolution of the anhydrous salt in water. This property is the basis for its largest-scale application.

Molten calcium chloride can be electrolysed to give calcium metal and chlorine gas:

CaCl2 → Ca + Cl2

Preparation

Structure of the polymeric [Ca(H2O)6] center in crystalline calcium chloride hexahydrate, illustrating the high coordination number typical for calcium complexes. Ca(aq)6 improved image.tif
Structure of the polymeric [Ca(H2O)6] center in crystalline calcium chloride hexahydrate, illustrating the high coordination number typical for calcium complexes.

In much of the world, calcium chloride is derived from limestone as a by-product of the Solvay process, which follows the net reaction below: [10]

2 NaCl + CaCO3 → Na2CO3 + CaCl2

North American consumption in 2002 was 1,529,000 tonnes (3.37 billion pounds). [26]

In the US, most of calcium chloride is obtained by purification from brine.[ citation needed ]

As with most bulk commodity salt products, trace amounts of other cations from the alkali metals and alkaline earth metals (groups 1 and 2) and other anions from the halogens (group 17) typically occur, but the concentrations are trifling.

Occurrence

Calcium chloride occurs as the rare evaporite minerals sinjarite (dihydrate) and antarcticite (hexahydrate). The related minerals chlorocalcite (potassium calcium chloride, KCaCl3) and tachyhydrite (calcium magnesium chloride, Ca Mg 2 Cl 6·12H2O) are also very rare.

See also

Related Research Articles

Potassium ferrocyanide chemical compound

Potassium ferrocyanide is the inorganic compound with formula K4[Fe(CN)6]·3H2O. It is the potassium salt of the coordination complex [Fe(CN)6]4−. This salt forms lemon-yellow monoclinic crystals.

Sodium hydroxide Chemical compound with formula NaOH

Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations Na+
and hydroxide anions OH
.

Brine A highly concentrated solution of a salt in water

Brine is a high-concentration solution of salt (NaCl) in water (H2O). In different contexts, brine may refer to salt solutions ranging from about 3.5% (a typical concentration of seawater, on the lower end of solutions used for brining foods) up to about 26% (a typical saturated solution, depending on temperature). Lower levels of concentration are called by different names: fresh water, brackish water, and saline water.

Sodium chloride Chemical compound with formula NaCl

Sodium chloride, commonly known as salt, is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g/mol respectively, 100 g of NaCl contains 39.34 g Na and 60.66 g Cl. Sodium chloride is the salt most responsible for the salinity of seawater and of the extracellular fluid of many multicellular organisms. In its edible form of table salt, it is commonly used as a condiment and food preservative. Large quantities of sodium chloride are used in many industrial processes, and it is a major source of sodium and chlorine compounds used as feedstocks for further chemical syntheses. A second major application of sodium chloride is de-icing of roadways in sub-freezing weather.

Sodium carbonate chemical compound

Sodium carbonate, Na2CO3, (also known as washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, water-soluble salts. All forms have a strongly alkaline taste and give moderately alkaline solutions in water. Historically it was extracted from the ashes of plants growing in sodium-rich soils. Because the ashes of these sodium-rich plants were noticeably different from ashes of wood (once used to produce potash), sodium carbonate became known as "soda ash". It is produced in large quantities from sodium chloride and limestone by the Solvay process.

Potassium chloride

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The compound hydrogen chloride has the chemical formula HCl and as such is a hydrogen halide. At room temperature, it is a colourless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hydrogen chloride gas and hydrochloric acid are important in technology and industry. Hydrochloric acid, the aqueous solution of hydrogen chloride, is also commonly given the formula HCl.

Magnesium chloride chemical compound

Magnesium chloride is the name for the chemical compound with the formula MgCl2 and its various hydrates MgCl2(H2O)x. These salts are typical ionic halides, being highly soluble in water. The hydrated magnesium chloride can be extracted from brine or sea water. In North America, magnesium chloride is produced primarily from Great Salt Lake brine. It is extracted in a similar process from the Dead Sea in the Jordan Valley. Magnesium chloride, as the natural mineral bischofite, is also extracted (by solution mining) out of ancient seabeds, for example, the Zechstein seabed in northwest Europe. Some magnesium chloride is made from solar evaporation of seawater. Anhydrous magnesium chloride is the principal precursor to magnesium metal, which is produced on a large scale. Hydrated magnesium chloride is the form most readily available.

Sodium sulfate chemical compound

Sodium sulfate (also known as sodium sulphate or sulfate of soda) is the inorganic compound with formula Na2SO4 as well as several related hydrates. All forms are white solids that are highly soluble in water. With an annual production of 6 million tonnes, the decahydrate is a major commodity chemical product. It is mainly used for the manufacture of detergents and in the kraft process of paper pulping.

Barium chloride chemical compound

Barium chloride is the inorganic compound with the formula BaCl2. It is one of the most common water-soluble salts of barium. Like most other barium salts, it is white, toxic, and imparts a yellow-green coloration to a flame. It is also hygroscopic, converting first to the dihydrate BaCl2(H2O)2. It has limited use in the laboratory and industry.

Praseodymium(III) chloride chemical compound

Praseodymium(III) chloride is the inorganic compound with the formula PrCl3. It is a blue-green solid that rapidly absorbs water on exposure to moist air to form a light green heptahydrate.

Lithium chloride Chemical compound

Lithium chloride is a chemical compound with the formula LiCl. The salt is a typical ionic compound, although the small size of the Li+ ion gives rise to properties not seen for other alkali metal chlorides, such as extraordinary solubility in polar solvents (83.05 g/100 mL of water at 20 °C) and its hygroscopic properties.

Aluminium chloride chemical compound

Aluminium chloride (AlCl3), also known as aluminium trichloride, is the main compound of aluminium and chlorine. It is white, but samples are often contaminated with iron(III) chloride, giving it a yellow color. The solid has a low melting and boiling point. It is mainly produced and consumed in the production of aluminium metal, but large amounts are also used in other areas of the chemical industry. The compound is often cited as a Lewis acid. It is an example of an inorganic compound that reversibly changes from a polymer to a monomer at mild temperature.

Efflorescence migration of a salt to the surface of a porous material

In chemistry, efflorescence is the migration of a salt to the surface of a porous material, where it forms a coating. The essential process involves the dissolving of an internally held salt in water, or occasionally in another solvent. The water, with the salt now held in solution, migrates to the surface, then evaporates, leaving a coating of the salt.

Manganese(II) chloride chemical compound

Manganese(II) chloride is the dichloride salt of manganese, MnCl2. This inorganic chemical exists in the anhydrous form, as well as the dihydrate (MnCl2·2H2O) and tetrahydrate MnCl2·4H2O), with the tetrahydrate being the most common form. Like many Mn(II) species, these salts are pink, with the paleness of the color being characteristic of transition metal complexes with high spin d5 configurations.

Cobalt(II) chloride chemical compound

Cobalt(II) chloride is an inorganic compound of cobalt and chlorine, with the formula CoCl
2
. It is a sky blue crystalline solid.

Sodium bisulfate sodium bisulfate

Sodium bisulfate, also known as sodium hydrogen sulfate, is the sodium salt of the bisulfate anion, with the molecular formula NaHSO4. Sodium bisulfate is an acid salt formed by partial neutralization of sulfuric acid by an equivalent of sodium base, typically in the form of either sodium hydroxide (lye) or sodium chloride (table salt). It is a dry granular product that can be safely shipped and stored. The anhydrous form is hygroscopic. Solutions of sodium bisulfate are acidic, with a 1M solution having a pH of around 1.

Calcium hypochlorite is an inorganic compound with formula Ca(ClO)2. It is the main active ingredient of commercial products called bleaching powder, chlorine powder, or chlorinated lime, used for water treatment and as a bleaching agent. This compound is relatively stable and has greater available chlorine than sodium hypochlorite (liquid bleach). It is a white solid, although commercial samples appear yellow. It strongly smells of chlorine, owing to its slow decomposition in moist air. It is not highly soluble in hard water, and is more preferably used in soft to medium-hard water. It has two forms: dry (anhydrous); and hydrated (hydrous).

Disodium phosphate chemical compound Na2HPO4

Disodium phosphate (DSP), or sodium hydrogen phosphate, or sodium phosphate dibasic, is the inorganic compound with the formula Na2HPO4. It is one of several sodium phosphates. The salt is known in anhydrous form as well as forms with 2, 7, 8, and 12 hydrates. All are water-soluble white powders; the anhydrous salt being hygroscopic.

Calcium nitrite is an inorganic compound with chemical formula Ca(NO2)2. In this compound, as in all nitrites, nitrogen is in a +3 oxidation state. It has many applications such as antifreeze, rust inhibitor of steel and wash heavy oil.

References

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  15. 21 CFR § 184.1193
  16. 7 CFR § 205.602
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