Calcium chloride
Overview
 
Calcium chloride, CaCl2, is a salt of calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

 and chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...

. It behaves as a typical ion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...

ic halide
Halide
A halide is a binary compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative than the halogen, to make a fluoride, chloride, bromide, iodide, or astatide compound. Many salts are halides...

, and is solid
Solid
Solid is one of the three classical states of matter . It is characterized by structural rigidity and resistance to changes of shape or volume. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a...

 at room temperature
Room temperature
-Comfort levels:The American Society of Heating, Refrigerating and Air-Conditioning Engineers has listings for suggested temperatures and air flow rates in different types of buildings and different environmental circumstances. For example, a single office in a building has an occupancy ratio per...

. Common applications include brine
Brine
Brine is water, saturated or nearly saturated with salt .Brine is used to preserve vegetables, fruit, fish, and meat, in a process known as brining . Brine is also commonly used to age Halloumi and Feta cheeses, or for pickling foodstuffs, as a means of preserving them...

 for refrigeration plants, ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...

 and dust control on roads, and desiccation
Desiccation
Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic substance that induces or sustains such a state in its local vicinity in a moderately sealed container.-Science:...

. Because of its hygroscopic nature, anhydrous calcium chloride must be kept in tightly-sealed air-tight containers.
Calcium chloride can serve as a source of calcium ions in a solution
Solution
In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...

 as calcium chloride is soluble.
Encyclopedia
Calcium chloride, CaCl2, is a salt of calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

 and chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...

. It behaves as a typical ion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...

ic halide
Halide
A halide is a binary compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative than the halogen, to make a fluoride, chloride, bromide, iodide, or astatide compound. Many salts are halides...

, and is solid
Solid
Solid is one of the three classical states of matter . It is characterized by structural rigidity and resistance to changes of shape or volume. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a...

 at room temperature
Room temperature
-Comfort levels:The American Society of Heating, Refrigerating and Air-Conditioning Engineers has listings for suggested temperatures and air flow rates in different types of buildings and different environmental circumstances. For example, a single office in a building has an occupancy ratio per...

. Common applications include brine
Brine
Brine is water, saturated or nearly saturated with salt .Brine is used to preserve vegetables, fruit, fish, and meat, in a process known as brining . Brine is also commonly used to age Halloumi and Feta cheeses, or for pickling foodstuffs, as a means of preserving them...

 for refrigeration plants, ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...

 and dust control on roads, and desiccation
Desiccation
Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic substance that induces or sustains such a state in its local vicinity in a moderately sealed container.-Science:...

. Because of its hygroscopic nature, anhydrous calcium chloride must be kept in tightly-sealed air-tight containers.

Properties

Calcium chloride can serve as a source of calcium ions in a solution
Solution
In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...

 as calcium chloride is soluble. This property can be useful for displacing ions from solution. For example, phosphate
Phosphate
A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...

 is displaced from solution by calcium:
3 CaCl2 (aq) + 2 K3PO4 (aq) → Ca3(PO4)2 (s) + 6 KCl (aq)


Molten calcium chloride can be electrolysed
Electrolysis
In chemistry and manufacturing, electrolysis is a method of using a direct electric current to drive an otherwise non-spontaneous chemical reaction...

 to give calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

 metal and chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...

 gas:
CaCl2 (l) → Ca (s) + Cl2 (g)


Calcium chloride has a very high enthalpy change of solution
Enthalpy change of solution
The enthalpy of solution, enthalpy of dissolution, or heat of solution is the enthalpy change associated with the dissolution of a substance in a solvent at constant pressure resulting in infinite dilution....

.

The anhydrous salt is deliquescent; it can accumulate enough water in its crystal lattice to form a solution.

Preparation

Calcium chloride can be produced directly from limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

, but large amounts are also produced as a by-product of the Solvay process
Solvay process
The Solvay process, also referred to as the ammonia-soda process, is the major industrial process for the production of soda ash . The ammonia-soda process was developed into its modern form by Ernest Solvay during the 1860s...

. North American consumption in 2002 was 1,687,000 tons (3.7 billion pounds).
A Dow Chemical Company manufacturing facility in Michigan, houses about 35% of the total U.S. production capacity for calcium chloride.

Occurrence

Calcium chloride occurs as the rare evaporite
Evaporite
Evaporite is a name for a water-soluble mineral sediment that result from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporate deposits, marine which can also be described as ocean deposits, and non-marine which are found in standing bodies of...

 minerals sinjarite (dihydrate) and antarcticite (hexahydrate). A related mineral chlorocalcite (potassium calcium chloride, KCaCl3) is also very rare.

Desiccant

Drying tube
Drying tube
A drying tube or guard tube is a tube-like piece of apparatus used to house a disposable solid desiccant, wherein at one end the tube-like structure terminates in a ground glass joint for use in connecting the drying tube to a reaction vessel, for the purpose of keeping that reaction vessel free of...

s are frequently packed with calcium chloride. Kelp
Kelp
Kelps are large seaweeds belonging to the brown algae in the order Laminariales. There are about 30 different genera....

 is dried with calcium chloride for use producing sodium carbonate
Sodium carbonate
Sodium carbonate , Na2CO3 is a sodium salt of carbonic acid. It most commonly occurs as a crystalline heptahydrate, which readily effloresces to form a white powder, the monohydrate. Sodium carbonate is domestically well-known for its everyday use as a water softener. It can be extracted from the...

. Adding solid calcium chloride to liquids can remove dissolved water. Calcium chloride is also used in products such as DampRid and Dri-Z-Air which is advertised as an air moisture absorber. Anhydrous calcium chloride has been approved by the FDA as a packaging aid to ensure dryness (CPG 7117.02).

These hygroscopic properties are also applied to keep a liquid layer on the surface of the roadway, which holds dust down.

Deicing and freezing point depression

By depressing the freezing-point
Freezing-point depression
Freezing-point depression describes the phenomenon in which the freezing point of a liquid is depressed when another compound is added, meaning that a solution has a lower freezing point than a pure solvent. This happens whenever a non-volatile solute is added to a pure solvent, such as water...

 calcium chloride is used to prevent ice formation and to deice
Deicing
For snow and ice control on roadways and similar facilities, see Snow removalDe-icing is defined as removal of snow, ice or frost from a surface...

. This is particularly useful on road surfaces. Calcium chloride dissolution is exothermic, and is relatively harmless to plants and soil; however, recent observations in Washington state suggest it may be particularly harsh on roadside evergreen trees. It is also more effective at lower temperatures than sodium chloride. When distributed for this use, it usually takes the form of small white balls a few millimeters in diameter, called prills. Solutions of calcium chloride can prevent freezing at temperature as low as −52 °C (−62 °F), making it ideal for filling agricultural implement tires as a liquid ballast, aiding traction in cold climates.

Source of calcium ions

Calcium chloride is used to increase the hardness
Hard water
Hard water is water that has high mineral content . Hard water has high concentrations of Ca2+ and Mg2+ ions. Hard water is generally not harmful to one's health but can pose serious problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers, cooling...

 in swimming pools. This reduces the erosion of the concrete in the pool. By Le Chatelier's principle
Le Châtelier's principle
In chemistry, Le Chatelier's principle, also called the Chatelier's principle, can be used to predict the effect of a change in conditions on a chemical equilibrium. The principle is named after Henry Louis Le Chatelier and sometimes Karl Ferdinand Braun who discovered it independently...

 and the common ion effect, increasing the concentration of calcium in the water will reduce the dissolution of calcium compounds essential to the structure of concrete.

In marine aquarium
Marine aquarium
A marine aquarium is an aquarium that keeps marine plants and animals in a contained environment. Marine aquaria are further subdivided by hobbyists into fish only , fish only with live rock , and reef aquaria. Fish only tanks often showcase large or aggressive marine fish species and generally...

s calcium chloride is added to introduce bioavailable
Bioavailability
In pharmacology, bioavailability is a subcategory of absorption and is used to describe the fraction of an administered dose of unchanged drug that reaches the systemic circulation, one of the principal pharmacokinetic properties of drugs. By definition, when a medication is administered...

 calcium for calcium carbonate shelled animals such as mollusks and cnidarians. Calcium hydroxide
Calcium hydroxide
Calcium hydroxide, traditionally called slaked lime, is an inorganic compound with the chemical formula Ca2. It is a colourless crystal or white powder and is obtained when calcium oxide is mixed, or "slaked" with water. It has many names including hydrated lime, builders lime, slack lime, cal, or...

 (kalkwasser mix) or a calcium reactor
Calcium reactor
In marine and reef aquariums, a calcium reactor is a device used to create a balance of alkalinity in the system. An acidic solution is produced by injecting carbon dioxide into a chamber with salt water and calcium rich media. The carbon dioxide lowers the pH by producing a solution high in...

 can also be used to introduce calcium, however calcium chloride addition is the fastest method and has minimal impact on pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

.

Food

As an ingredient, it is listed as a permitted food additive in the European Union for use as a sequestrant
Sequestrant
A sequestrant is a food additive whose role is to improve the quality and stability of the food products. Sequestrants form chelate complexes with polyvalent metal ions, especially copper, iron and nickel, which serve as catalysts in the oxidation of the fats in the food...

 and firming agent
Firming agent
Firming agents are food additives added in order to precipitate residual pectin, thus strengthening the structure of the food and preventing its collapse during processing.Typical firming agents are:* Calcium carbonate...

 with the E number
E number
E numbers are number codes for food additives that have been assessed for use within the European Union . They are commonly found on food labels throughout the European Union. Safety assessment and approval are the responsibility of the European Food Safety Authority...

 E509,
and considered as generally recognized as safe (GRAS)
Generally recognized as safe
Generally recognized as safe is an American Food and Drug Administration designation that a chemical or substance added to food is considered safe by experts, and so is exempted from the usual Federal Food, Drug, and Cosmetic Act food additive tolerance requirements.-History:On January 1, 1958,...

 by the U.S. Food and Drug Administration.
The average intake of calcium chloride as food additives has been estimated to be 160–345 mg/day for individuals.

As a firming agent
Firming agent
Firming agents are food additives added in order to precipitate residual pectin, thus strengthening the structure of the food and preventing its collapse during processing.Typical firming agents are:* Calcium carbonate...

 calcium chloride is used in canned vegetables, in firming soy bean curds into tofu
Tofu
is a food made by coagulating soy milk and then pressing the resulting curds into soft white blocks. It is part of East Asian and Southeast Asian cuisine such as Chinese, Japanese, Korean, Indonesian, Vietnamese, and others. There are many different varieties of tofu, including fresh tofu and tofu...

 and in producing a caviar
Caviar
Caviar, sometimes called black caviar, is a luxury delicacy, consisting of processed, salted, non-fertilized sturgeon roe. The roe can be "fresh" or pasteurized, the latter having much less culinary and economic value....

 substitute from vegetable or fruit juices
Spherification
Spherification is the culinary process of shaping a liquid into spheres which visually and texturally resemble caviar. The technique was originally discovered by Unilever in the 1950s Spherification is the culinary process of shaping a liquid into spheres which visually and texturally resemble...

. It is commonly used as an electrolyte
Electrolyte
In chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....

 in sports drinks and other beverages including Smartwater
Glacéau
Energy Brands, also doing business as Glacéau, is a privately owned subsidiary of Coca-Cola Company based in Whitestone, New York City that manufactures and distributes various lines of enhanced water. Founded in May 1996 by J...

 and Nestle
Nestlé
Nestlé S.A. is the world's largest food and nutrition company. Founded and headquartered in Vevey, Switzerland, Nestlé originated in a 1905 merger of the Anglo-Swiss Milk Company, established in 1867 by brothers George Page and Charles Page, and Farine Lactée Henri Nestlé, founded in 1866 by Henri...

 bottled water. The extremely salty taste of calcium chloride is used to flavor pickles
Pickled cucumber
A pickled cucumber is a cucumber that has been pickled in a brine, vinegar, or other solution and left to ferment for a period of time, by either immersing the cucumbers in an acidic solution or through souring by lacto-fermentation.-Gherkin:A gherkin is not only...

 while not increasing the food's sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

 content. Calcium chloride's freezing-point depression properties are used, for example, in Cadbury Caramilk
Cadbury Caramilk
Caramilk is a caramel-filled candy bar made by Cadbury Adams in Canada. It was first sold in 1968.Variations available, some of them limited editions, include Caramilk made with dark chocolate maple, chocolate, or cappuccino. The standard bar is not actually made with chocolate, and is simply...

 chocolate bars to slow the freezing of the caramel.

In brewing
Brewing
Brewing is the production of beer through steeping a starch source in water and then fermenting with yeast. Brewing has taken place since around the 6th millennium BCE, and archeological evidence suggests that this technique was used in ancient Egypt...

 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. Calcium chloride is sometimes added to processed milk to restore the natural balance between calcium and protein in casein
Casein
Casein is the name for a family of related phosphoprotein proteins . These proteins are commonly found in mammalian milk, making up 80% of the proteins in cow milk and between 60% and 65% of the proteins in human milk....

 for the purposes of making cheese such as brie
Brie (cheese)
Brie is a soft cow's cheese named after Brie, the French region from which it originated . It is pale in color with a slight grayish tinge under a rind of white mold; very soft and savory with a hint of ammonia...

, Pélardon
Pélardon
Pélardon, formerly called paraldon, pélardou and also péraudou, is a French cheese from the Cévennes range of the Languedoc-Roussillon region. It is a traditional cheese made from goat's milk. It is round soft-ripened cheese covered in a white mold weighing approximately 60 grams, with a...

 and stilton
Stilton (cheese)
Stilton is a type of English cheese, known for its characteristic strong smell and taste. It is produced in two varieties: the well-known blue and the lesser-known white. Both have been granted the status of a protected designation of origin by the European Commission, together one of only...

.

Medicine

Calcium chloride can be injected as intravenous therapy
Intravenous therapy
Intravenous therapy or IV therapy is the infusion of liquid substances directly into a vein. The word intravenous simply means "within a vein". Therapies administered intravenously are often called specialty pharmaceuticals...

 for the treatment of hypocalcaemia
Hypocalcaemia
In medicine, hypocalcaemia is the presence of low serum calcium levels in the blood, usually taken as less than 2.1 mmol/L or 9 mg/dl or an ionized calcium level of less than 1.1 mmol/L or 4.5 mg/dL. It is a type of electrolyte disturbance...

. It can be used for magnesium intoxication. Calcium chloride injection may antagonize cardiac toxicity as measured by electrocardiogram
Electrocardiogram
Electrocardiography is a transthoracic interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the outer surface of the skin and recorded by a device external to the body...

.
It can help to protect the myocardium from dangerously high levels of serum potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...

 in hyperkalemia
Hyperkalemia
Hyperkalemia refers to the condition in which the concentration of the electrolyte potassium in the blood is elevated...

. Calcium chloride can be used to quickly treat Calcium Channel Blocker toxicity, from the side effects of drugs such as Cardizem — helping avoid potential heart attacks.
Aqueous calcium chloride is used in genetic transformation
Transformation (genetics)
In molecular biology transformation is the genetic alteration of a cell resulting from the direct uptake, incorporation and expression of exogenous genetic material from its surroundings and taken up through the cell membrane. Transformation occurs naturally in some species of bacteria, but it can...

 of cells by increasing the cell membrane permeability, inducing competence
Competence (biology)
In microbiology, genetics, cell biology and molecular biology, competence is the ability of a cell to take up extracellular DNA from its environment...

 for DNA uptake (allowing DNA fragments to enter the cell more readily).

Other

Calcium chloride is used in concrete mixes to help speed up the initial setting, but chloride ion leads to corrosion of steel rebar
Rebar
A rebar , also known as reinforcing steel, reinforcement steel, rerod, or a deformed bar, is a common steel bar, and is commonly used as a tensioning device in reinforced concrete and reinforced masonry structures holding the concrete in compression...

, so it should not be used in reinforced concrete
Reinforced concrete
Reinforced concrete is concrete in which reinforcement bars , reinforcement grids, plates or fibers have been incorporated to strengthen the concrete in tension. It was invented by French gardener Joseph Monier in 1849 and patented in 1867. The term Ferro Concrete refers only to concrete that is...

. The anhydrous form of calcium chloride may also be used for this purpose and can provide a measure of the moisture in concrete.

Calcium chloride is used in swimming pool water as a pH buffer and to adjust the calcium hardness of the water.

Calcium chloride is included as an additive in plastics and in fire extinguisher
Fire extinguisher
A fire extinguisher or extinguisher, flame entinguisher is an active fire protection device used to extinguish or control small fires, often in emergency situations...

s, in wastewater treatment as a drainage aid, in blast furnace
Blast furnace
A blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally iron.In a blast furnace, fuel and ore and flux are continuously supplied through the top of the furnace, while air is blown into the bottom of the chamber, so that the chemical reactions...

s as an additive to control scaffolding (clumping and adhesion of materials that prevent the furnace charge from descending), and in fabric softener
Fabric softener
Fabric softener is used to prevent static cling and make fabric softer. It is available as a liquid, crystals and dryer sheets.- Varieties :...

 as a thinner.

The exothermic dissolution of calcium chloride is used in self-heating cans and heating pad
Heating pad
A heating pad is a pad used for warming of parts of the body in order to manage pain. Localized application of heat causes the blood vessels in that area to dilate, enhancing perfusion to the targeted tissue...

s.

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.

Toxicology

Calcium chloride can act as an irritant
Irritation
Irritation or exacerbation, in biology and physiology, is a state of inflammation or painful reaction to allergy or cell-lining damage. A stimulus or agent which induces the state of irritation is an irritant...

 by desiccating moist skin. Solid calcium chloride dissolves exothermically
Exothermic reaction
An exothermic reaction is a chemical reaction that releases energy in the form of light or heat. It is the opposite of an endothermic reaction. Expressed in a chemical equation:-Overview:...

 and burns
Burn (injury)
A burn is a type of injury to flesh caused by heat, electricity, chemicals, light, radiation or friction. Most burns affect only the skin . Rarely, deeper tissues, such as muscle, bone, and blood vessels can also be injured...

 can result in the mouth
Mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....

 and esophagus
Esophagus
The esophagus is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. During swallowing, food passes from the mouth through the pharynx into the esophagus and travels via peristalsis to the stomach...

if calcium chloride is ingested. Ingestion of concentrated solutions or solid calcium chloride products may cause gastrointestinal irritation or ulceration.

External links

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