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Calcium chloride is an inorganic compound, a salt with the chemical formula Template:Chem2. It is a white crystalline solid at room temperature, and it is highly soluble in water. It can be created by neutralising hydrochloric acid with calcium hydroxide.
Calcium chloride is commonly encountered as a hydrated solid with generic formula Template:Chem2, where n = 0, 1, 2, 4, and 6. These compounds are mainly used for de-icing and dust control. Because the anhydrous salt is hygroscopic and deliquescent, it is used as a desiccant.<ref name=Ullmann>Robert Kemp, Suzanne E. Keegan "Calcium Chloride" in Ullmann's Encyclopedia of Industrial Chemistry 2000, Wiley-VCH, Weinheim. {{#invoke:doi|main}}</ref> Template:TOC limit
HistoryEdit
Calcium chloride was apparently discovered in the 15th century but wasn't studied properly until the 18th century.<ref name="Peck-1954">Template:Cite book</ref> It was historically called "fixed sal ammoniac" (Template:Langx<ref name="Hartmann-1816">Template:Cite book</ref>) because it was synthesized during the distillation of ammonium chloride with lime and was nonvolatile (while the former appeared to sublime); in more modern times (18th–19th cc.) it was called "muriate of lime" (Template:Langx<ref name="Hartmann-1816" />).<ref name="Ottley-1826">Template:Cite book</ref>
UsesEdit
De-icing and freezing-point depressionEdit
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 de-icing 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.<ref name="Aqueous-Solutions-Aps-2016">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
It is also used in domestic and industrial chemical air dehumidifiers.<ref name="humantouchofchemistry.com-2014">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Road surfacingEdit
The second largest application of calcium chloride exploits its hygroscopic nature and the tackiness of its hydrates; calcium chloride is highly hygroscopic and its hydration is an exothermic process. 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%.<ref name="Road-Management-Engineering-Journal-1998">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
FoodEdit
In the food industry, calcium chloride is frequently employed as a firming agent in canned vegetables, particularly for canned tomatoes and cucumber pickles.<ref>Template:Cite book</ref><ref>Template:Cite journal</ref><ref>Template:Cite book</ref><ref>Template:Cite journal</ref> It is also used in firming soybean curds into tofu and in producing a caviar substitute from vegetable or fruit juices.<ref>Template:Cite book</ref><ref>Template:Cite book</ref><ref>Template:Cite book</ref> It is also used to enhance the texture of various other products, such as whole apples, whole hot peppers, whole and sliced strawberries, diced tomatoes, and whole peaches.<ref name="Luna-Guzmán-2000">Template:Cite journal</ref><ref name="StarChefs Studio-2004">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
The firming effect of calcium chloride can be attributed to several mechanisms:<ref name="Luna-Guzmán-2000"/>
- Complexation, since calcium ions form coordination complexes with pectin, a polysaccharide found in the cell wall and middle lamella of plant tissues.<ref name="Luna-Guzmán-2000"/>
- Membrane stabilization, since calcium ions contribute to the stabilization of the cell membrane.<ref name="Luna-Guzmán-2000"/>
- Turgor pressure regulation, since calcium ions influence cell turgor pressure, which is the pressure exerted by the cell contents against the cell wall.<ref name="Luna-Guzmán-2000"/>
Calcium chloride's freezing-point depression properties are used to slow the freezing of the caramel in caramel-filled chocolate bars.Template:Citation needed Also, it is frequently added to sliced apples to maintain texture.<ref name="Sitbon-2011">Template:Cite book</ref>
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.<ref>Template:Cite book</ref><ref>Template:Cite book</ref><ref>Template:Cite book</ref><ref>Template:Cite book</ref><ref>Template:Cite book</ref>
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.<ref>Template:Cite book</ref>
Calcium chloride is also commonly used as an "electrolyte" in sports drinks and other beverages; as a food additive used in conjunction with other inorganic salts it adds taste to bottled water.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="Why Your Bottled Water Contains Four Different Ingredients-2014">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="Brands Of Bottled Water With Electrolytes-2024">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
The average intake of calcium chloride as food additives has been estimated to be 160–345 mg/day.<ref name="Calcium Chloride SIDS Initial Assessment Profile-2002">Calcium Chloride SIDS Initial Assessment Profile, UNEP Publications, SIAM 15, Boston, 22–25 October 2002, pp. 13–14.</ref> 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.<ref name=FSA6>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It is considered as generally recognized as safe (GRAS) by the U.S. Food and Drug Administration.<ref name="21-CFR-1193">21 CFR § 184.1193</ref> Its use in organic crop production is generally prohibited under the US National Organic Program.<ref name="CFRTitle7Part205Section602c">7 CFR § 205.602 Template:Webarchive</ref>
The elemental calcium content in calcium chloride hexahydrate (CaCl2·6H2O) is approximately 18.2%. This means that for every gram of calcium chloride hexahydrate, there are about 182 milligrams of elemental calcium.
For anhydrous calcium chloride (CaCl2), the elemental calcium content is almost twice higher, that is around 36.1% (for every gram of anhydrous calcium chloride there are about 361 milligrams of elemental calcium).
Calcium chloride has a very salty taste and can cause mouth and throat irritation at high concentrations, so it is typically not the first choice for long-term oral supplementation (as a calcium supplement).<ref name="Calcium-Chloride-2023">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="pmid11165888">Template:Cite journal</ref> Calcium chloride, characterized by its low molecular weight and high water solubility, readily breaks down into calcium and chloride ions when exposed to water. These ions are efficiently absorbed from the intestine.<ref name="Calcium chloride CaCl2 Human health tier II assessment-2014">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Calcium chloride has the potential to release heat energy upon dissolution in water. This release of heat can lead to trauma and burns in the mouth, throat, esophagus, and stomach. In fact, there have been reported cases of stomach necrosis resulting from burns caused by accidental ingestions of big amounts of undissolved calcium chloride.<ref name="pmid23283618">Template:Cite journal</ref><ref name="pmid32903978">Template:Cite journal</ref>
The extremely salty taste of calcium chloride is used to flavor pickles without increasing the food's sodium content.<ref>Template:Cite journal</ref>
Calcium chloride is used to prevent cork spot and bitter pit on apples by spraying on the tree during the late growing season.<ref name="Cork Spot and Bitter Pit of Apples-2024">"Cork Spot and Bitter Pit of Apples", Richard C. Funt and Michael A. Ellis, Ohioline.osu.edu/factsheet/plpath-fru-01</ref>
Edit
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).<ref name="FDA Compliance Articles-1995">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
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.
Metal reduction fluxEdit
Similarly, Template:Chem2 is used as a flux and electrolyte in the FFC Cambridge electrolysis process for titanium production, where it ensures the proper exchange of calcium and oxygen ions between the electrodes.
Medical useEdit
Calcium chloride infusions may be used as an intravenous therapy to prevent hypocalcemia.<ref>Template:Cite book</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite book</ref><ref>Template:Cite book</ref>
Calcium chloride is a highly soluble calcium salt. Hexahydrate calcium chloride (CaCl2·6H2O) has solubility in water of 811 g/L at 25 °C.<ref name=crc /> Calcium chloride when taken orally completely dissociates into calcium ions (Ca2+) in the gastrointestinal tract, resulting in readily bioavailable calcium. The high concentration of calcium ions facilitates efficient absorption in the small intestine.<ref name="Calcium chloride CaCl2 Human health tier II assessment-2014"/><ref name="pmid2110852"/> However, the use of calcium chloride as a source of calcium taken orally is less common compared to other calcium salts because of potential adverse effects such as gastrointestinal irritation and discomfort.<ref name="pmid2110852">Template:Cite journal</ref><ref name="pmid17507729">Template:Cite journal</ref><ref>Template:Cite book</ref>
When tasted, calcium chloride exhibits a distinctive bitter flavor alongside its salty taste. The bitterness is attributable to the calcium ions and their interaction with human taste receptors: certain members of the TAS2R family of bitter taste receptors respond to calcium ions; the bitter perception of calcium is thought to be a protective mechanism to avoid ingestion of toxic substances, as many poisonous compounds taste bitter. While chloride ions (Cl⁻) primarily contribute to saltiness, at higher concentrations, they can enhance the bitter sensation. The combination of calcium and chloride ions intensifies the overall bitterness. At lower concentrations, calcium chloride may taste predominantly salty. The salty taste arises from the electrolyte nature of the compound, similar to sodium chloride (table salt). As the concentration increases, the bitter taste becomes more pronounced: the increased presence of calcium ions enhances the activation of bitterness receptors.<ref name="pmid17108952">Template:Cite journal</ref><ref>Template:Cite journal</ref><ref name="pmid9177340">Template:Cite journal</ref>
Other applicationsEdit
Template:More citations needed 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.<ref name="Federal Highway Administration-1999">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The anhydrous form of calcium chloride may also be used for this purpose and can provide a measure of the moisture in concrete.<ref name="National Research Council (U.S.). Building Research Institute-1962">Template:Cite book</ref>
Calcium chloride is included as an additive in plastics and in fire extinguishers, 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.Template:Citation needed
The exothermic dissolution of calcium chloride is used in self-heating cans and heating pads.Template:Citation needed
Calcium chloride is used as a water hardener in the maintenance of hot tub water, as insufficiently hard water can lead to corrosion and foaming.Template:Citation needed
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.Template:Citation needed
Calcium chloride (Template:Chem) acts as flux material, decreasing the melting point, in the Davy process for the industrial production of sodium metal through the electrolysis of molten Template:Chem.Template:Citation needed
Calcium chloride is also used in the production of activated charcoal.Template:Citation needed
Calcium chloride can be used to precipitate fluoride ions from water as insoluble Template:Chem.Template:Citation needed
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.Template:Citation needed
For watering plants to use as a fertilizer, a moderate concentration of calcium chloride is used to avoid potential toxicity: 5 to 10 mM (millimolar) is generally effective and safe for most plants—that is Template:Convert of anhydrous calcium chloride (Template:Chem) per liter of water or Template:Convert of calcium chloride hexahydrate (Template:Chem·6Template:Chem) per liter of water.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> Calcium chloride solution is used immediately after preparation to prevent potential alterations in its chemical composition.<ref>Template:Cite journal</ref><ref>Template:Cite book</ref> Besides that, calcium chloride is highly hygroscopic, meaning it readily absorbs moisture from the air.<ref name="left-standing">Template:Cite journal</ref> If the solution is left standing, it can absorb additional water vapor, leading to dilution and a decrease in the intended concentration.<ref name="left-standing"/> Prolonged standing may lead to the precipitation of calcium hydroxide or other insoluble calcium compounds, reducing the availability of calcium ions in the solution<ref name="prolonged-standing">Template:Cite book</ref> and reducing the effectiveness of the solution as a calcium source for plants.<ref name="prolonged-standing"/> Nutrient solutions can become a medium for microbial growth if stored for extended periods.<ref name="wei-2019">Template:Cite journal</ref> Microbial contamination may alter the composition of the solution and potentially introduce pathogens to the plants.<ref name="wei-2019"/> When dissolved in water, calcium chloride can undergo hydrolysis, especially over time, which can lead to the formation of small amounts of hydrochloric acid and calcium hydroxide: Template:Chem+2Template:Chem ⇌ Template:Chem+2Template:Chem. This reaction can lower the pH of the solution, making it more acidic.<ref>Template:Cite journal</ref> Acidic solutions may harm plant tissues and disrupt nutrient uptake.<ref>Template:Cite journal</ref>
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.<ref name="Koger-1977">Template:Cite journalTemplate:Primary source inline</ref><ref name="pmid21774835">Template:Cite journalTemplate:Primary source inline</ref>Template:Primary source inline
Cocaine producers in Colombia import tons of calcium chloride to recover solvents that are on the INCB Red List and are more tightly controlled.<ref name="Smith-2020">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
HazardsEdit
Although the salt is non-toxic in small quantities when wet, the strongly hygroscopic properties of non-hydrated calcium chloride present some hazards. It 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.<ref name="Dow Chemical Company-2006">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Consumption of calcium chloride can lead to hypercalcemia.<ref name="www.drugs.com">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
PropertiesEdit
Calcium chloride dissolves in water, producing chloride and the aquo complex Template:Chem2. 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:
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.
Aqueous solutions of calcium chloride tend to be slightly acidic due to the influence of the chloride ions on the hydrogen ion concentration in water. The slight acidity of calcium chloride solutions is primarily due to the increased ionic strength of the solution, which can influence the activity of hydrogen ions and lower the pH slightly. The pH of calcium chloride in aqueous solution is the following:<ref name="Speight-2016">Template:Cite book</ref><ref name="Rumble-2024">Template:Cite book</ref>
| Concentration (mol/L) | Approximate pH |
|---|---|
| 0.01 | 6.5 – 7.0 |
| 0.1 | 6.0 – 6.5 |
| 1.0 | 5.5 – 6.0 |
Molten calcium chloride can be electrolysed to give calcium metal and chlorine gas:
PreparationEdit
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:<ref name=Ullmann/>
North American consumption in 2002 was 1,529,000 tonnes (3.37 billion pounds).<ref name="Calcium Chloride SIDS Initial Assessment Profile">Calcium Chloride SIDS Initial Assessment Profile, UNEP Publications, SIAM 15, Boston, 22–25 October 2002, page 11.</ref> In the US, most calcium chloride is obtained by purification from brine. 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.<ref name=Ullmann/>
OccurrenceEdit
Calcium chloride occurs as the rare evaporite minerals sinjarite (dihydrate) and antarcticite (hexahydrate).<ref name="www.mindat.org-2020-sinjarite">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="www.mindat.org-2020-anthracite">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="ima-mineralogy.org">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Another natural hydrate known is ghiaraite – a tetrahydrate.<ref name="www.mindat.org-2020-ghiarite">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="ima-mineralogy.org"/> The related minerals chlorocalcite (potassium calcium chloride, Template:Chem2) and tachyhydrite (calcium magnesium chloride, Template:Chem2) are also very rare.<ref name="www.mindat.org-202-chlorocalcite">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="www.mindat.org-2020-tachydrite">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="ima-mineralogy.org"/> The same is true for rorisite, CaClF (calcium chloride fluoride).<ref name="www.mindat.org-rorisite">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="ima-mineralogy.org"/>
See alsoEdit
ReferencesEdit
External linksEdit
- International Chemical Safety Card 1184
- Product and Application Information (Formerly Dow Chemical Calcium Chloride division) Template:Webarchive
- Report on steel corrosion by chloride including CaCl2 Template:Webarchive
- Collection of calcium chloride reports and articles
- Calcium chloride, Anhydrous MSDS
- Difusivity of calcium chloride
- Centers for Disease Control and Prevention, National Institutes of Occupational Safety and Health, "Calcium Chloride (anhydrous)"
Template:Calcium compounds Template:Chlorides Template:Mineral supplements Template:Urologicals, including antispasmodics Template:Salt topics