calcium chloride

Calcium chloride
IUPAC name	Calcium chloride
Other names	Calcium(II) chloride, Calcium dichloride, E509
Identifiers
CAS number	10043-52-4 Y, 22691-02-7 (monohydrate) 10035-04-8 (dihydrate) 25094-02-4 (tetrahydrate) 7774-34-7 (hexahydrate)
PubChem	24854
EC number	233-140-8
RTECS number	EV9800000
Properties
Molecular formula	CaCl2
Molar mass	110.98 g/mol (anhydrous) 128.999 g/mol (monohydrate) 147.014 g/mol (dihydrate) 183.045 g/mol (tetrahydrate) 219.08 g/mol (hexahydrate)
Appearance	white solid
Density	2.15 g/cm3 (anhydrous) 1.835 g/cm3 (dihydrate) 1.83 g/cm3 (tetrahydrate) 1.71 g/cm3 (hexahydrate)
Melting point	772 °C (anhydrous) 260 °C (monohydrate) 176 °C (dihydrate) 45.5 °C (tetrahydrate) 30 °C (hexahydrate) [1]
Boiling point	1935 °C (anhydrous)
Solubility in water	74.5 g/100mL (20 °C) 59.5 g/100 mL (0 °C)
Solubility in alcohol	soluble
Acidity (pKa)	8-9 (anhydrous) 6.5-8.0 (hexahydrate)
Structure
Crystal structure	Orthorhombic (deformed rutile), oP6
Space group	Pnnm, No. 58
Coordination geometry	octahedral, 6-coordinate
Hazards
MSDS	External MSDS
EU Index	017-013-00-2
EU classification	Irritant (Xi)
R-phrases	R36
S-phrases	(S2), S22, S24
LD50	1000 mg/kg (oral, rat)
Related compounds
Other anions	calcium fluoride calcium bromide calcium iodide
Other cations	magnesium chloride strontium chloride barium chloride
Supplementary data page
Structure and properties	n, εr, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Calcium chloride, CaCl₂, is a common salt. It behaves as a typical ionic halide, and is solid at room temperature. It has several common applications such as brine for refrigeration plants, ice and dust control on roads, and in concrete. The anhydrous salt is also widely used as a desiccant, where it will absorb so much water that it will eventually dissolve in its own crystal lattice water. It can be produced directly from limestone, but large amounts are also produced as a by-product of the Solvay process. Because of its hygroscopic nature, the anhydrous form must be kept in tightly-sealed containers. It is used to turn kelp into a solid.

Chemical properties

Calcium chloride can serve as a source of calcium ions in a solution; unlike many other calcium compounds, which are insoluble, calcium chloride is able to dissociate.

3 CaCl₂ + 2 K₃PO₄ (aq) → Ca₃(PO₄)₂ (s) + 6 KCl (aq)

Molten CaCl₂ can be electrolysed to give calcium metal and chlorine gas:

CaCl₂ (l) → Ca (s) + Cl₂ (gas)

Uses in industry

Because the anhydrous salt is strongly hygroscopic, air or other gases may be channeled through a column of calcium chloride to remove moisture. In particular, calcium chloride is usually used to pack drying tubes to exclude atmospheric moisture from a reaction set-up while allowing gases to escape. It cannot, however, be used to dry alkaline gases such as ammonia because it will form addition products. It is used to dry kelp, which is then used to produce soda ash. It can also be added to liquids to remove suspended or dissolved water. The dissolving process is highly exothermic and rapidly produces temperatures of around 60 °C (140 °F). In this capacity, it is known as a drying agent or desiccant. It is converted to a brine as it absorbs the water or water vapor from the substance to be dried:

CaCl₂ + 2 H₂O → CaCl₂·2H₂O

Aided by the intense heat evolved during its dissolution, calcium chloride is also used as an ice-melting compound. Unlike the more-common sodium chloride (rock salt or halite), it is relatively harmless to plants and soil; however, recent observations in Washington state suggest it may be particularly harsh on roadside evergreen trees.^[2] 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 millimetres in diameter, called prills (see picture at top of page).

Used for its hygroscopic property, it can be applied to keep a liquid layer on the surface of the roadway, which holds dust down.^[3] It is used in concrete mixes to help speed up the initial setting, but chloride ion leads to corrosion of steel rebar, so it should not be used in reinforced concrete.^[4] The anhydrous form of calcium chloride may also be used for this purpose and can provide a measure of the moisture in concrete.^[5]

Aqueous calcium chloride (in solution with water) lowers the freezing point as low as −52 °C (−62 °F), making it ideal for filling agricultural implement tires as a liquid ballast, aiding traction in cold climates.^[6]

Calcium Chloride is also commonly used as an additive in swimming pool water as it increases the "Calcium Hardness" value for the water. Low Calcium Hardness values in pool water cause pool water to be corrosive on equipment, pumps and metal fittings.

Other industrial applications include use as an additive in plastics, as a drainage aid for wastewater treatment, as an additive in fire extinguishers, as an additive in control scaffolding in blast furnaces, and as a thinner in fabric softener.

North American consumption in 2002 was 1,687,000 tons (3.7 billion pounds).^[7] A Dow Chemical Company manufacturing facility in Michigan, houses about 35% of the total U.S. production capacity for calcium chloride.^[8]

Uses in food

As an ingredient, it is listed as a permitted food additive in the European Union for use as a sequestrant and firming agent with the E number E509, and considered as generally recognized as safe (GRAS) by the U.S. Food and Drug Administration.^[9] The average intake of calcium chloride as food additives has been estimated to be 160-345 mg/day for individuals.^[10] Ingestion of concentrated or pure calcium chloride products may cause gastrointestinal irritation or ulceration.^[11] The anhydrous form has been approved by the FDA as a packaging aid to ensure dryness (CPG 7117.02).^[12]

Calcium chloride is commonly used as an electrolyte and has an extremely salty taste, as found in sports drinks and other beverages such as Smartwater and Nestle bottled water. It can also be used as a preservative to maintain firmness in canned vegetables or in higher concentrations in pickles to give a salty taste while not increasing the food's sodium content. It is even found in snack foods, including Cadbury Caramilk chocolate bars (purpose unknown).

It can be used to make a caviar substitute from vegetable or fruit juices^[13] or added to processed milk to restore the natural balance between calcium and protein for the purposes of making cheese such as brie and stilton. Calcium chloride's exothermic properties are exploited in many 'self heating' food products where it is activated (mixed) with water to start the heating process, providing a non-explosive, dry fuel that is easily activated.

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 it can also affect yeast function during fermentation.

Uses in drugs

Calcium chloride can be injected as intravenous therapy for the treatment of hypocalcaemia (low serum calcium). It can be used for insect bites or stings (such as Black Widow Spider bites); sensitivity reactions, particularly when characterized by urticaria (hives); magnesium intoxication; as an aid in management of the acute symptoms in lead colic; in cardiac resuscitation, particularly after open heart surgery. Parenteral calcium can be used when epinephrine has failed to improve weak or ineffective myocardial contractions. Calcium chloride injection may antagonize cardiac toxicity as measured by electrocardiogram (ECG/EKG).^[14]

It can help to protect the myocardium from dangerously-high levels of serum potassium in hyperkalemia. Calcium chloride can be used to quickly treat Calcium Channel Blocker toxicity, from the side effects of drugs such as Diltiazem (Cardizem)—helping avoid potential heart attacks.

The aqueous form of calcium chloride is used in genetic transformation of cells by increasing the cell membrane permeability, inducing competence for DNA uptake (allowing DNA fragments to enter the cell more readily).

It can also be used in the reef aquarium hobby for adding bio-available calcium in solution for calcium-using animals such as algae, snails, hard tube worms, and corals although the use of calcium hydroxide (kalkwasser mix) or a calcium reactor is the preferred method of adding calcium. However, calcium chloride is the quickest method to increase calcium levels as it dissolves readily in water.

Precautions

Calcium chloride is an irritant, particularly on moist skin.

Dry calcium chloride reacts exothermically when exposed to water. Burns can result in the mouth and esophagus if humans or other animals ingest dry calcium chloride pellets. Small children are more susceptible than adults (who generally have had experience trying to eat hot food, and can react accordingly) so calcium chloride pellets should be kept out of their reach.

Natural occurrence

Natural occurrence of a dihydrate (mineral sinjarite) and hexahydrate (antarcticite) is very rare and connected mainly with dry lakes and brines. Chlorocalcite KCaCl₃ is a related mineral (also very rare).

References

1. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0070494398
2. ^ "De-icer damaging thousands of trees on mountain passes". The Seattle Times. 19 March 2008. http://seattletimes.nwsource.com/html/localnews/2004291523_treekill19m.html. Retrieved 18 March 2008. 
3. ^ "Dust: Don't Eat It! Control It!". Road Management & Engineering Journal. US Roads (TranSafety Inc.). 1 June 1998. http://www.usroads.com/journals/rmej/9806/rm980603.htm. Retrieved 9 August 2006. 
4. ^ "Accelerating Concrete Set Time". 1 June 1999. http://www.fhwa.dot.gov/infrastructure/materialsgrp/acclerat.htm. Retrieved January 16 2007. 
5. ^ National Research Council (U.S.). Building Research Institute (1962). Adhesives in Building: Selection and Field Application; Pressure-sensitive Tapes. National Academy of Science-National Research Council. pp. 24-5. 
6. ^ "Agricultural Tire Hydroinflation". www.firestoneag.com. Firestone Tires. December 2007. http://www.firestoneag.com/tiredata/info/info_hydro_2.asp. Retrieved 3 December 2007. 
7. ^ Calcium Chloride SIDS Initial Assessment Profile, UNEP Publications, SIAM 15, Boston, October 22-25, 2002, page 11.
8. ^ Calcium Chloride Chemical Profile, The Innovation Group, www.the-innovation-group.com, printed September 9, 2005.
9. ^ 21 CFR § 184.1193
10. ^ Calcium Chloride SIDS Initial Assessment Profile, UNEP Publications, SIAM 15, Boston, October 22-25, 2002, pages 13-14.
11. ^ "Product Safety Assessment (PSA): Calcium Chloride". Dow Chemical Company. May 2, 2006. http://www.dow.com/productsafety/finder/cacl_2.htm. 
12. ^ "CPG 7117.02". FDA Compliance Articles. US Food and Drug Administration. March 1995. http://www.fda.gov/ora/compliance_ref/cpg/cpgfod/cpg500-400.html. Retrieved 3 December 2007. 
13. ^ "Apple Caviar Technique". StarChefs Studio. StarChefs.com. April 2004. http://www.starchefs.com/events/studio/techniques/FAdria/index.shtml. Retrieved 9 August 2006. 
14. ^ "CALCIUM CHLORIDE INJECTION USP". RxMed. http://www.rxmed.com/b.main/b2.pharmaceutical/b2.1.monographs/CPS-%20Monographs/CPS-%20(General%20Monographs-%20C)/CALCIUM%20CHLORIDE%20INJECTION%20USP.html. Retrieved 2008-10-08. 

• Greenwood, Norman N.; Earnshaw, A. (1997), Chemistry of the Elements (2nd ed.), Oxford: Butterworth-Heinemann, ISBN 0-7506-3365-4 
• Handbook of Chemistry and Physics, 71st edition, CRC Press, Ann Arbor, Michigan, 1990.

External links

• International Chemical Safety Card 1184
• Calcium Chloride Handbook from Dow Chemical (pdf 1.6 MB)
• Report on steel corrosion by chloride including CaCl₂
• Collection of calcium chloride reports and articles
• MSDS sheet for Calcium Chloride