| Formula =
| Entropy = 153.36 J K−1 mol−1
| DeltaHf = −167 kJ·mol−1
| OtherAnions = Fluoride
The chloride ion
. is the anion
(negatively charged ion) Cl−
. It is formed when the element chlorine
) gains an electron
or when a compound
such as hydrogen chloride
is dissolved in water or other polar solvents. Chloride salts such as sodium chloride
are often very soluble in water.Green, John, and Sadru Damji. "Chapter 3." Chemistry
. Camberwell, Vic.: IBID, 2001. Print. It is an essential electrolyte
located in all body fluids responsible for maintaining acid/base balance, transmitting nerve impulses
and regulating fluid in and out of cells. Less frequently, the word chloride
may also form part of the "common" name of chemical compound
s in which one or more chlorine atom
s are covalently bonded
. For example, methyl chloride, with the standard name chloromethane
(see IUPAC books) is an organic compound with a covalent C−Cl bond in which the chlorine is not an anion.
A chloride ion is much larger than a chlorine atom, 167 and 99 pm, respectively. The ion is colorless and diamagnetic. In aqueous solution, it is highly soluble in most cases; however, some chloride salts, such as silver chloride, lead(II) chloride, and mercury(I) chloride are slightly soluble in water. In aqueous solution, chloride is bound by the protic end of the water molecules.
Occurrence in nature
Sea water contains 1.94% chloride. Some chloride-containing minerals include the chlorides of sodium ( halite
or NaCl), potassium ( sylvite
or KCl), and magnesium ( bischofite
), hydrated MgCl2. The concentration of chloride in the blood is called serum chloride
, and this concentration is regulated by the kidneys
. A chloride ion is a structural component of some proteins, e.g., it is present in the amylase
Role in commerce
industry is a major consumer of the world's energy budget. This process converts sodium chloride into chlorine and sodium hydroxide, which are used to make many other materials and chemicals. The process involves two parallel reactions:
2 Cl− → + 2 e−
2 + 2 e− → H2 + 2 OH−
Water quality and processing
Another major application involving chloride is desalination
, which involves the energy intensive removal of chloride salts to give potable water
. In the petroleum industry
, the chlorides are a closely monitored constituent of the mud system
. An increase of the chlorides in the mud system may be an indication of drilling into a high-pressure saltwater formation. Its increase can also indicate the poor quality of a target sand.
Chloride is also a useful and reliable chemical indicator of river / groundwater fecal contamination, as chloride is a non-reactive solute and ubiquitous to sewage & potable water. Many water regulating companies around the world utilize chloride to check the contamination levels of the rivers and potable water sources.http://www.gopetsamerica.com/substance/chlorides.aspx
Chloride salts such as sodium chloride
are used to preserve food.
The presence of chlorides, e.g. in seawater
, significantly aggravates the conditions for pitting corrosion
of most metals (including stainless steels, aluminum, aluminum alloys, and high-alloyed materials) by enhancing the formation and growth of the pits through an autocatalytic process.
Role in biology
Chloride is an essential electrolyte
, trafficking in and out of cells through chloride channel
s and playing a key role in maintaining cell homeostasis
and transmitting action potentials
in neurons. Characteristic concentrations of chloride in model organisms are: in both E. coli
and budding yeast are 10-200mM (media dependent), in mammalian cell 5-100mM and in blood plasma 100mM.
Reactions of chloride
Chloride can be oxidized but not reduced. The first oxidation, as employed in the chlor-alkali process, is conversion to chlorine gas. Chlorine can be further oxidized to other oxides and oxyanions including hypochlorite
(ClO−, the active ingredient in chlorine bleach), chlorine dioxide
(), and perchlorate
In terms of its acid-base properties, chloride is a very weak base
as indicated by the negative value of the pKa of hydrochloric acid. Chloride can be protonated by strong acid
s, such as sulfuric acid:
NaCl + H2SO4 → NaHSO4 + HCl
Ionic chloride salts reaction with other salts to exchange anions. The presence of chloride is often detected by its formation of an insoluble silver chloride
upon treatment with silver ion:
Cl− + Ag+ → AgCl
The concentration of chloride in an assay can be determined using a chloridometer
, which detects silver ions once all chloride in the assay has precipitated via this reaction.
Chlorided silver electrodes
are commonly used in electrophysiology
. Molleman, Areles (2003). "Patch Clamping: An Introductory Guide to Patch Clamp Electrophysiology". Wiley & Sons. .
An example is table salt, which is sodium chloride
with the chemical formula
NaCl. In water
, it dissociates into Na+ and Cl− ions. Salts such as calcium chloride
, magnesium chloride
, potassium chloride
have varied uses ranging from medical treatments to cement formation.Green, John, and Sadru Damji. "Chapter 3." Chemistry
. Camberwell, Vic.: IBID, 2001. Print.
Calcium chloride (CaCl2) is a salt that is marketed in pellet
form for removing dampness from rooms. Calcium chloride is also used for maintaining unpaved roads and for fortifying roadbases for new construction. In addition, calcium chloride is widely used as a de-icer
, since it is effective in lowering the melting point
when applied to ice."Common Salts." Test Page for Apache Installation. Web. 22 Mar. 2011. .
Examples of covalently bonded chlorides are phosphorus trichloride
, phosphorus pentachloride
, and thionyl chloride
, all three of which are reactive chlorinating reagent
s that have been used in a laboratory
Chlorine can assume oxidation state
s of −1, +1, +3, +5, or +7. Several neutral chlorine oxide
s are also known.