Chloride

The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion (negatively-charged ion) Cl &minus; . The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water. 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.

Terminology
The word chloride can also refer to a chemical compound in which one or more chlorine atoms are covalently bonded in the molecule. This ambiguity is present in chemistry terminology, however it is important to remember that the inorganic, ionic-bond forming chloride ion is entirely different from a covalently bonded chlorine atom, and the term organo-halide, such as methyl chloride, is a terminological coincidence, resulting from the way that organic chemists name their molecules. As an example, compare sodium chloride, NaCl, with methyl chloride, CH3Cl. NaCl is an inorganic, ionically bonded compound, while methyl chloride is an organic covalently bonded compound, which does not contain a chloride ion. Methyl chloride does not have to be named as a chloride, and its more common name is chloromethane. NaCl must be named as a chloride because it actually contains the chloride ion.

Corrosion
The presence of chlorides, e.g. in seawater, significantly aggravates the conditions for pitting corrosion of most metals (including stainless steels and high-alloyed materials) by enhancing the formation and growth of the pits through an autocatalytic process.

Uses
Chloride is used to form salts that can preserve food such as sodium chloride. Other salts such as calcium chloride, magnesium chloride, potassium chloride have varied uses ranging from medical treatments to cement formation.

An example is table salt, which is sodium chloride with the chemical formula NaCl. In water, it dissociates into Na + and Cl &minus; ions.

Examples of inorganic covalently bonded chlorides that are used as reactants are:
 * phosphorus trichloride, phosphorus pentachloride, and thionyl chloride, all three of which reactive chlorinating reagents that have been used in a laboratory
 * disulfur dichloride (S2Cl2), used for vulcanization of rubber.

A chloride ion is also the prosthetic group present in the amylase enzyme.

Another example is calcium chloride with the chemical formula CaCl2. Calcium chloride 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 sanite fortifying roadbases for new construction. In addition, Calcium chloride is widely used as a deicer since it is effective in lowering the melting point when applied to ice.

Chloride is a chemical the human body needs for metabolism (the process of turning food into energy). It also helps keep the body's acid-base balance. The amount of chloride in the blood is carefully controlled by the kidneys. Further reading:Renal chloride reabsorption

In the petroleum industry, the chlorides are a closely monitored constituent of the mud system. The increase of the chlorides in the mud system could indicate the possibility 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.