Limescale is the hard, off-white, chalky deposit found in kettles, hot-water boilers and the inside of inadequately maintained hot-water central heating systems. It is also often found as a similar deposit on the inner surface of old pipes and other surfaces where "hard water Hard water is water that has high mineral content . Hard water minerals primarily consist of calcium (Ca2+), and magnesium (Mg2+) metal cations, and sometimes other dissolved compounds such as bicarbonates and sulfates. Calcium usually enters the water as either calcium carbonate (CaCO3), in the form of limestone and chalk, or calcium sulfate (" has evaporated.

These types of limescale differ slightly due to their origins.

The type found deposited on the heating elements of water heaters etc. has a main component of calcium carbonate Calcium carbonate is a chemical compound with the chemical formula Ca , precipitated out of the (hot) water. Hard water Hard water is water that has high mineral content . Hard water minerals primarily consist of calcium (Ca2+), and magnesium (Mg2+) metal cations, and sometimes other dissolved compounds such as bicarbonates and sulfates. Calcium usually enters the water as either calcium carbonate (CaCO3), in the form of limestone and chalk, or calcium sulfate ( contains 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. Calcium is also the fifth most abundant dissolved ion in seawater by both molarity and mass, after sodium, chloride, (and often magnesium Magnesium is a chemical element with the symbol Mg, atomic number 12 and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust, where it constitutes about 2% by mass, and ninth in the known Universe as a whole. This preponderance of magnesium is related to the fact that it is easily) bicarbonate In inorganic chemistry, bicarbonate is an intermediate form in the deprotonation of carbonic acid. Its chemical formula is HCO3− and/or similar salts Salt is a mineral that is composed primarily of sodium chloride. It is essential for animal life in small quantities, but is harmful to animals and plants in excess. Salt flavor is one of the basic tastes, making salt one of the oldest, most ubiquitous food seasonings. Salting is an important method of food preservation.

Calcium bicarbonate Calcium bicarbonate (Ca2), also called calcium hydrogen carbonate, does not refer to a known solid compound; it exists only in aqueous solution containing the ions calcium (Ca2+), dissolved carbon dioxide (CO2), bicarbonate (HCO3–), and carbonate (CO32–). The relative concentrations of these carbon-containing species depend on the pH; is soluble in water, however at temperatures above 70 °C (158 °F) the soluble bicarbonate is converted to poorly-soluble carbonate, leading to deposits in places where water is heated.[1] Local boiling “hot spots” can also occur when water is heated, resulting in the concentration and deposition of salts from the water.

Calcium cations 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. An anion , from the Greek word ἀνω (anο), meaning "up", is an ion with more electrons than protons, giving it a net negative charge (since electrons are negatively from hard water can also combine with soap SOAP, originally defined as Simple Object Access Protocol, is a protocol specification for exchanging structured information in the implementation of Web Services in computer networks. It relies on eXtensible Markup Language as its message format, and usually relies on other Application Layer protocols (most notably Remote Procedure Call (RPC) and, which would normally dissolve in soft water. This combination often forms scum which precipitates out in a thin film on the interior surfaces of baths, sinks, and drainage pipes. Soap usually contains salts of anions 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. An anion , from the Greek word ἀνω (anο), meaning "up", is an ion with more electrons than protons, giving it a net negative charge (since electrons are negatively from neutralized fatty acids In chemistry, especially biochemistry, a fatty acid is a carboxylic acid with a long unbranched aliphatic tail , which is either saturated or unsaturated. The most occurring natural fatty acids have an even number of carbon atoms because their biosynthesis involves acetyl-CoA, a coenzyme carrying a two-carbon-atom group (see fatty acid synthesis) or similar chemical compounds A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together in a defined spatial arrangement by chemical bonds. The calcium salts of these anions are less soluble Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a liquid solvent to form a homogeneous solution of the solute in the solvent. The solubility of a substance fundamentally depends on the used solvent as well as on temperature and pressure. The extent of the solubility of a substance in a in water.

The type found on air-dried cooking utensils, dripping taps and bathroom tiling consists of calcium carbonate mixed with all the other salts that had been dissolved in the water, prior to evaporation Evaporation is a type of vaporization of a liquid, that occurs only on the surface of a liquid. The other type of vaporization is boiling, that instead occurs on the entire mass of the liquid. Evaporation is also part of the water cycle.

It can also be found on taps where hard water Hard water is water that has high mineral content . Hard water minerals primarily consist of calcium (Ca2+), and magnesium (Mg2+) metal cations, and sometimes other dissolved compounds such as bicarbonates and sulfates. Calcium usually enters the water as either calcium carbonate (CaCO3), in the form of limestone and chalk, or calcium sulfate ( has been continually running through and has deposited calcium carbonate Calcium carbonate is a chemical compound with the chemical formula Ca . This can be a help to start with by protecting the inside of the tap, but can build up, reducing water flow and can eventually block the tap.

Contents

Effects

Other than being unsightly and harder to clean, limescale can impair the operation of various components or damage them.

In kettles, limescale acts as an insulator, impairing heat transfer. Additionally, it can damage the heating element, which overheats due to accruing limescale.

Prevention

In kettles, one can add crystals of citric acid Citric acid is a weak organic acid, and it is a natural preservative and is also used to add an acidic, or sour, taste to foods and soft drinks. In biochemistry, it is important as an intermediate in the citric acid cycle and therefore occurs in the metabolism of virtually all living things. It can also be used as an environmentally benign to water, which act as chelating agents Chelation is the formation or presence of two or more separate bindings between a polydentate (multiple bonded) ligand and a single central atom. Usually these ligands are organic compounds, and are called chelants, chelators, chelating agents, or sequestering agents (it binds to the metal ions, inactivating them). Adding some carbonated water with low amounts of dissolved Ca and Mg kations (the cheapest mineral water is usually the best for this purpose) also works by dissolving carbonate again as bicarbonate. In kettles and coffee machines the water will not boil long enough for all the carbonate to percipitate out, and the bicarbonate will stay disolved in the water.

Alternatively, one may use a ball of steel wire, whose surface area attracts much of the limescale, to reduce the accumulation. The ball can then be cleaned coarsely via squeezing (breaking off the brittle limescale), or finely via a descaling agent.

Treatment

Main article: Descaling agent An anti-scaling agent, also known as descaling agent, anti-limestone, anti-limescale, anti-lime or anti-scale are preparations to prevent the buildup or to remove limescale and fouling. Anti-scaling agent agents usually contain acids such as acetic acid, lactic acid, citric acid, phosphoric acid, hydrochloric acid, sulfamic acid to remove

Limescale can be removed via various descaling agents and penetrating tools.

It can also be removed via a scouring pad, though this may damage the underlying surface.

See also

References

  1. ^ Centre for Water Science — Cranfield University. Calcium Carbonate. Last accessed April 19, 2007.
This chemistry Chemistry is the science of matter and the changes it undergoes. The science of matter is also addressed by physics, but while physics takes a more general and fundamental approach, chemistry is more specialized, being concerned with the composition, behavior, structure, and properties of matter, as well as the changes it undergoes during chemical-related article is a stub. You can help Wikipedia by expanding it.

Categories: Water Categories: Amorphous liquids | Inorganic compounds | Natural resources | Health effectors | Transparent materials | Fouling | Limestone Limestone is a geological rock formed primarily from calcium carbonate and in water. It is produced principally during periods when there is a high proportion of carbon dioxide in the atmosphere. It varies greatly in its hardness and in the materials included in it so its commercial uses vary |

Personal tools
Namespaces
">
Variants
Views
">
Actions
Search">
The Central London Railway was a railway company established in 1889 to construct a deep-level underground "tube" railway in London. Funding for construction was obtained in 1895 through a syndicate of financiers and construction work took place from 1896 to 1900. When opened in 1900, the railway served 13 stations and ran completely
Navigation
Interaction
Toolbox
Print/export
Languages

 

The above information uses material from Wikipedia and is licensed under the GNU Free Documentation License The purpose of this License is to make a manual, textbook, or other functional and useful document "free" in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a.
Some facts may not have been fully verified for accuracy. [Disclaimers Wikipedia is an online open-content collaborative encyclopedia, that is, a voluntary association of individuals and groups working to develop a common resource of human knowledge. The structure of the project allows anyone with an Internet connection to alter its content. Please be advised that nothing found here has necessarily been reviewed by]
This page was last archived by our server on Fri Jul 30 21:09:10 2010. [ refresh local cache ]
Displaying this page or its contents does not use any Wikimedia Foundation's resources.
The owners of this site proudly support the Wikimedia Foundation.

[Hide]▼
'Limescale' Blogs
Comment on Do electronic limescale inhibitors work? by Wendy
boakes.org
Comment on Do electronic limescale inhibitors work? by Wendy

Wendy

2008-10-15 18:04:40

gary williams! please report on your observations! I live in Utah too! I ve been reading this discussion with interest. It seems the electronic descalers work, but only under certain conditions, and we have yet to . ...

Google Blogs Search: Limescale,
Thu Apr 2 00:17:28 2009
[Hide]▲