IdeaWazaWiki - User contributions [en]

Precipitation (chemistry)

2008-11-11T02:05:03Z

70.57.121.189: /* Digestion */

[[Image:Chemical precipitation diagram.png|thumb|right|Chemical Precipitation]]
{{redirect|Precipitate|the album by Interpol|Precipitate EP}}
'''Precipitation''' is the formation of a [[solid]] in a [[solution]] during a [[chemical reaction]]. When the reaction occurs, the solid formed is called the '''precipitate''', and the liquid remaining above the solid is called the '''supernate'''.

==Applications==
[[Image:Tetratolylporphyrin.jpg|thumb|right|Crystals of ''meso''-tetratolylporphyrin from refluxing [[propionic acid]] precipitate on cooling]]
Precipitation reactions can be used for making [[pigments]], removing [[salts]] from water in [[water treatment]], and in [[classical qualitative inorganic analysis]].

Precipitation is also useful to isolate the products of a reaction during [[workup (chemistry)|workup]]. Ideally, the product of the reaction is insoluble in the reaction solvent. Thus, it precipitates as it is formed, preferably [[crystallization|forming pure crystals]]. An example of this would be the synthesis of [[porphyrin]]s in refluxing [[propionic acid]]. By cooling the reaction mixture to room temperature, crystals of the porphyrin precipitate, and are collected by filtration:<ref>{{cite journal | author = A. D. Adler; F. R. Longo; J. D. Finarelli; J. Goldmacher; J. Assour; L. Korsakoff | title = A simplified synthesis for meso-tetraphenylporphine | year = 1967 | journal = [[J. Org. Chem.]] | volume = 32 | issue = 2 | pages = 476–476 | doi = 10.1021/jo01288a053 }}</ref>

:[[Image:H2TPPsyn.png|400px]]
Precipitation may also occur when an ''antisolvent'' (a solvent in which the product is insoluble) is added, drastically reducing the solubility of the desired product. Thereafter, the precipitate may easily be separated by [[filtration]], [[decanting]], or [[centrifugation]]). An example would be the synthesis of chromic tetraphenylporphyrin chloride: water is added to the DMF reaction solution, and the product precipitates.<ref>{{cite journal | doi = 10.1016/0022-1902(70)80535-8 | title = On the preparation of metalloporphyrins | year = 1970 | author = Alan D. Adler; Frederick R. Longo; Frank Kampas; Jean Kim| journal = Journal of Inorganic and Nuclear Chemistry | volume = 32 | pages = 2443 }}</ref> Precipitation is also useful in purifying products: crude bmim-Cl is taken up in [[acetonitrile]], and dropped into ethyl acetate, where it precipitates.<ref>{{OrgSynth | author = Dupont, J., Consorti, C., Suarez, P., de Souza, R. | title = Preparation of 1-Butyl-3-methyl imidazolium-based Room Temperature Ionic Liquids | collvol = 10 | collvolpages = 184 | year = 2004 | prep = v79p0236}}</ref>

In [[metallurgy]], precipitation from a [[solid solution]] is also a useful way to [[precipitation strengthening|strengthen alloy]]s; this process is known as [[solid solution strengthening]].

== Mechanism ==
Precipitation can occur when an [[solubility|insoluble]] substance is formed in the [[solution (chemistry)|solution]] due to a [[chemical reaction]] or when the solution has been [[supersaturated]] by a [[compound (chemistry)|compound]]. The formation of a precipitate is a sign of a [[chemical change]]. In most situations, the solid forms ("falls") out of the solute phase, and sinks to the bottom of the solution (though it will float if it is less dense than the solvent, or form a [[suspension (chemistry)|suspension]]).

The solid may reach the bottom of a container by means of [[settling]], [[sediment]]ation, or [[centrifugation]].

An important stage of the precipitation process is the onset of [[nucleation]]. The creation of a hypothetical solid [[particle]] includes the formation of an [[interface (chemistry)|interface]], which requires some [[energy (chemistry)|energy]] based on the relative [[surface energy]] of the solid and the solution. If this energy is not available, and no suitable nucleation surface is available, [[supersaturation]] occurs.

== Representation using chemical equations ==
An example of a precipitation reaction: Aqueous [[silver nitrate]] (AgNO<sub>3</sub>) is added to a solution containing [[potassium chloride]] (KCl) and the precipitation of a white solid, [[silver chloride]] is observed. (Zumdahl, 2005)

:AgNO<sub>3</sub> (aq) + KCl (aq) → AgCl (s) + KNO<sub>3</sub> (aq)

The silver chloride(AgCl) has formed a solid, which is observed as a precipitate.

This reaction can be written emphasizing the [[dissociation|dissociated]] [[ions]] in a combined solution. This is known as the [[ionic equation]].
:Ag<sup>+</sup> (aq) + NO<sub>3</sub><sup>-</sup> (aq) + K<sup>+</sup> (aq) + Cl<sup>-</sup> (aq) → AgCl (s) + K<sup>+</sup> (aq) + NO<sub>3</sub><sup>-</sup> (aq)

A final way to represent a precipitate reaction is known as a ''net ionic reaction''. In this case, any [[spectator ions]] (those which do not contribute to the reaction) are left out of the formula completely. This simplifies the above equations to the following:
:Ag<sup>+</sup> (aq) + Cl<sup>-</sup> (aq) → AgCl (s)

==Cation sensitivity==
Precipitate formation is useful in the detection of the type of [[cation]] in [[salt]]. To do this, an [[alkali]] first reacts with the unknown salt to produce a precipitate which is the [[hydroxide]] of the unknown salt. To identify the cation, the color of the precipitate and its solubility in excess are noted. Similar processes are often used to separate chemically similar elements, such as the [[Alkali earth metals]].

==Digestion==
Digestion, or ''precipitate ageing'', happens when a freshly-formed precipitate is left, usually at a higher [[temperature]], in the solution from which it is precipitated. It results in cleaner and bigger particles.<ref>{{cite web |url=http://www.ktf-split.hr/glossary/en_o.php?def=digestion |title=Chemical dictionary definition |accessdate=2008-02-26}}</ref> The physico-chemical process underlying digestion is called [[Ostwald ripening]].
this is wrong

==Coprecipitation==
{{main|coprecipitation}}
Coprecipitation is the carrying down by a precipitate of substances normally soluble under the conditions employed. It is an important issue in chemical analysis, where it is often undesirable, but in some cases it can be exploited. In [[gravimetric analysis]], it is a problem because undesired impurities often coprecipitate with the analyte, resulting in excess mass. On the other hand, in the analysis of trace elements, as is often the case in [[radiochemistry]], coprecipitation is often the only way of separating an element.

==References==
*Zumdahl, Steven S. ''Chemical Principles.'' 4<sup>th</sup> ed. New York: Houghton Mifflin Company, 2005.
*Mark Smith ''Principles of Science'' 1993
{{reflist}}
{{refimprove|date=February 2008}}

==Further reading==
*Banert, T., Brenner, G., Peuker, U. A. (2006), Operating parameters of a continuous sono-chemical precipitation reactor, Proc. 5. WCPT, Orlando Fl., 23.-27. April 2006.

==External links==
{{Commonscat|Solid precipitation}}
* [http://www.hielscher.com/ultrasonics/precipitation_01.htm Continuous Precipitation Using Ultrasonication (e.g. for nano-size magnetite particles)]
* http://www.answers.com/supernatant

[[Category:Separation processes]]
[[Category:Chemical processes]]

[[ca:Precipitació (química)]]
[[da:Fældningsreaktion]]
[[de:Fällung]]
[[es:Precipitado]]
[[fr:Précipité]]
[[gl:Precipitación (reacción)]]
[[it:Precipitazione (chimica)]]
[[he:תגובת שיקוע]]
[[nl:Neerslag (scheikunde)]]
[[ja:沈殿]]
[[no:Fellingsreaksjon]]
[[nn:Fellingsreaksjon]]
[[pt:Precipitação (química)]]
[[ru:Преципитат (химия)]]
[[sk:Precipitácia]]
[[su:Présipitasi]]
[[sv:Utfällning]]
[[ur:عمل ترسیب]]
[[zh:沉淀]]

Archive:Fish and Wildlife Coordination Act

2006-09-24T18:30:31Z

70.57.102.250:

The '''Fish and Wildlife Coordination Act''' (FWCA) provides the basic authority for the [[United States Fish and Wildlife Service|Fish and Wildlife Service]]'s (FWS) involvement in evaluating impacts to [[fish]] and [[wildlife]] from proposed water resource development projects. It requires that fish and wildlife resources receive equal consideration to other project features. It also requires [[List of United States federal agencies|Federal agencies]] involved with water resource development projects to first consult with the FWS and State fish and wildlife agencies regarding the impacts on fish and wildlife resources, and provide for measures to mitigate these impacts.<ref>http://www.fws.gov/habitatconservation/fwca.htm</ref>

The origional Act, enacted on March 10, 1934, authorizes the Secretaries of [[United States Secretary of Agriculture|Agriculture]] and [[United States Secretary of Commerce|Commerce]] to provide assistance to Federal and State agencies for protecting and increasing the supply of [[Game (food)|game]] and [[Fur clothing|fur]] bearing animals, as well as to study the effects of [[pollution]] on wildlife. The Act authorizes the preparation of plans to protect wildlife resources, including wildlife surveys on [[public land]]s. In addition, it directs the [[Bureau of Fisheries]] to use water resources for [[fish culture]] stations and [[Bird migration|migratory bird]] resting and [[nest]]ing areas, and requires consultation with the Bureau of Fisheries prior to the construction of any new [[dam]]s, to provide for [[fish migration]].

Amendments in 1946 require consultation with the Fish and Wildlife Service and the fish and wildlife agencies of States where any body of water is controlled or modified by any Federal agency, in order to prevent loss and damage of wildlife resources. The amendments specifically exempted the [[Tennessee Valley Authority]] from its provisions.

The 1958 amendments add provisions to require equal consideration and coordination of wildlife conservation with other water resources development programs, and authorized the [[United States Secretary of the Interior|Secretary of Interior]] to provide public [[fishing]] areas and accept donations of lands and funds.<ref>http://www.fws.gov/laws/lawsdigest/fwcoord.html</ref> These amendments also modified the [[Watershed Protection and Flood Prevention Act]].

==References==

<div class="references-small">
<references/>
</div>

== External links ==
* [http://ipl.unm.edu/cwl/fedbook/fwca.html Wording of the act] from the [[New Mexico Center for Wildlife Law]] at the [[University of New Mexico]]

[[Category:United States federal legislation]]

Archive:Fish and Wildlife Coordination Act

2006-09-24T18:17:14Z

70.57.102.250:

The '''Fish and Wildlife Coordination Act''' (FWCA) provides the basic authority for the [[United States Fish and Wildlife Service|Fish and Wildlife Service]]'s (FWS) involvement in evaluating impacts to [[fish]] and [[wildlife]] from proposed water resource development projects. It requires that fish and wildlife resources receive equal consideration to other project features. It also requires [[List of United States federal agencies|Federal agencies]] involved with water resource development projects to first consult with the FWS and State fish and wildlife agencies regarding the impacts on fish and wildlife resources, and provide for measures to mitigate these impacts.<ref>http://www.fws.gov/habitatconservation/fwca.htm</ref>

The origional Act, enacted on March 10, 1934, authorizes the Secretaries of [[United States Secretary of Agriculture|Agriculture]] and [[United States Secretary of Commerce|Commerce]] to provide assistance to Federal and State agencies for protecting and increasing the supply of [[Game (food)|game]] and [[Fur clothing|fur]] bearing animals, as well as to study the effects of [[pollution]] on wildlife. The Act authorizes the preparation of plans to protect wildlife resources, including wildlife surveys on [[public land]]s. In addition, it directs the [[Bureau of Fisheries]] to use water resources for [[fish culture]] stations and [[Bird migration|migratory bird]] resting and [[nest]]ing areas, and requires consultation with the Bureau of Fisheries prior to the construction of any new [[dam]]s, to provide for [[fish migration]].

Amendments in 1946 require consultation with the Fish and Wildlife Service and the fish and wildlife agencies of States where any body of water is controlled or modified by any Federal agency, in order to prevent loss and damage of wildlife resources. The amendments specifically exempted the [[Tennessee Valley Authority]] from its provisions.

The 1958 amendments add provisions to require equal consideration and coordination of wildlife conservation with other water resources development programs, and authorized the [[United States Secretary of the Interior|Secretary of Interior]] to provide public [[fishing]] areas and accept donations of lands and funds.<ref>http://www.fws.gov/laws/lawsdigest/fwcoord.html</ref> Thes amendments also modified the [[Watershed Protection and Flood Prevention Act]].

==References==

<div class="references-small">
<references/>
</div>

== External links ==
* [http://ipl.unm.edu/cwl/fedbook/fwca.html Wording of the act] from the [[New Mexico Center for Wildlife Law]] at the [[University of New Mexico]]

[[Category:United States federal legislation]]

Archive:Fish and Wildlife Coordination Act

2006-09-24T18:11:22Z

70.57.102.250:

The '''Fish and Wildlife Coordination Act''' (FWCA) provides the basic authority for the [[United States Fish and Wildlife Service|Fish and Wildlife Service]]'s (FWS) involvement in evaluating impacts to [[fish]] and [[wildlife]] from proposed water resource development projects. It requires that fish and wildlife resources receive equal consideration to other project features. It also requires [[List of United States federal agencies|Federal agencies]] involved with water resource development projects to first consult with the FWS and State fish and wildlife agencies regarding the impacts on fish and wildlife resources, and provide for measures to mitigate these impacts.<ref>http://www.fws.gov/habitatconservation/fwca.htm</ref>

The origional Act, enacted on March 10, 1934, authorizes the Secretaries of [[United States Secretary of Agriculture|Agriculture]] and [[United States Secretary of Commerce|Commerce]] to provide assistance to Federal and State agencies for protecting and increasing the supply of [[Game (food)|game]] and [[Fur clothing|fur]] bearing animals, as well as to study the effects of [[pollution]] on wildlife. The Act authorizes the preparation of plans to protect wildlife resources, including wildlife surveys on [[public land]]s. In addition, it directs the [[Bureau of Fisheries]] to use water resources for [[fish culture]] stations and [[Bird migration|migratory bird]] resting and [[nest]]ing areas, and requires consultation with the Bureau of Fisheries prior to the construction of any new [[dam]]s, to provide for [[fish migration]].

Amendments in 1946 require consultation with the Fish and Wildlife Service and the fish and wildlife agencies of States where any body of water is controlled or modified by any Federal agency, in order to prevent loss and damage of wildlife resources. The amendments specifically exempted the [[Tennessee Valley Authority]] from its provisions.

The 1958 amendments add provisions to require equal consideration and coordination of wildlife conservation with other water resources development programs, and authorized the [[United States Secretary of the Interior|Secretary of Interior]] to provide public [[fishing]] areas and accept donations of lands and funds.<ref>http://www.fws.gov/laws/lawsdigest/fwcoord.html</ref>

==References==

<div class="references-small">
<references/>
</div>

== External links ==
* [http://ipl.unm.edu/cwl/fedbook/fwca.html Wording of the act] from the [[New Mexico Center for Wildlife Law]] at the [[University of New Mexico]]

[[Category:United States federal legislation]]

Archive:Fish and Wildlife Coordination Act

2006-09-24T18:10:12Z

70.57.102.250:

The '''Fish and Wildlife Coordination Act''' (FWCA) provides the basic authority for the [[Fish and Wildlife Service]]'s (FWS) involvement in evaluating impacts to [[fish]] and [[wildlife]] from proposed water resource development projects. It requires that fish and wildlife resources receive equal consideration to other project features. It also requires [[List of United States federal agencies|Federal agencies]] involved with water resource development projects to first consult with the FWS and State fish and wildlife agencies regarding the impacts on fish and wildlife resources, and provide for measures to mitigate these impacts.<ref>http://www.fws.gov/habitatconservation/fwca.htm</ref>

The origional Act, enacted on March 10, 1934, authorizes the Secretaries of [[United States Secretary of Agriculture|Agriculture]] and [[United States Secretary of Commerce|Commerce]] to provide assistance to Federal and State agencies for protecting and increasing the supply of [[Game (food)|game]] and [[Fur clothing|fur]] bearing animals, as well as to study the effects of [[pollution]] on wildlife. The Act authorizes the preparation of plans to protect wildlife resources, including wildlife surveys on [[public land]]s. In addition, it directs the [[Bureau of Fisheries]] to use water resources for [[fish culture]] stations and [[Bird migration|migratory bird]] resting and [[nest]]ing areas, and requires consultation with the Bureau of Fisheries prior to the construction of any new [[dam]]s, to provide for [[fish migration]].

Amendments in 1946 require consultation with the Fish and Wildlife Service and the fish and wildlife agencies of States where any body of water is controlled or modified by any Federal agency, in order to prevent loss and damage of wildlife resources. The amendments specifically exempted the [[Tennessee Valley Authority]] from its provisions.

The 1958 amendments add provisions to require equal consideration and coordination of wildlife conservation with other water resources development programs, and authorized the [[United States Secretary of the Interior|Secretary of Interior]] to provide public [[fishing]] areas and accept donations of lands and funds.<ref>http://www.fws.gov/laws/lawsdigest/fwcoord.html</ref>

==References==

<div class="references-small">
<references/>
</div>

== External links ==
* [http://ipl.unm.edu/cwl/fedbook/fwca.html Wording of the act] from the [[New Mexico Center for Wildlife Law]] at the [[University of New Mexico]]

[[Category:United States federal legislation]]

Archive:Fish and Wildlife Coordination Act

2006-09-24T17:32:47Z

70.57.102.250:

Telefarm Towers Shoreview

2006-04-24T00:52:58Z

70.57.193.210:

'''Telefarm Towers Shoreview''' is a transmission site for [[FM radio]] and [[television]] [[broadcasting]] in [[Shoreview, Minnesota]] consisting of two guyed towers. The towers are owned by '''Telefarm, Inc.''', which is a company jointly owned by the [[Twin Cities]] stations [[WCCO-TV|WCCO]] channel 4, [[KSTP-TV|KSTP]] channel 5, and [[KARE]] channel 11. The towers are used for both analog and [[digital television]] broadcasts, plus the transmission of [[KSTC-TV|KSTC]] channel 45 (owned by the same company as KSTP) and [[KMWB]] channel 23. Some area radio stations also use the facility. The towers were initially built in the [[1970s]]. In [[1971]], one of the towers collapsed when it was partially completed, killing seven workers.

The towers were upgraded at the turn of the century to allow the addition of digital TV transmitters to meet [[Federal Communications Commission]] requirements. Because each antenna assembly weighs many [[ton]]s, the towers had to be strengthened. Work took a bit longer than expected, and KSTP notably used its original broadcast tower along [[University Avenue (Minneapolis-St. Paul)|University Avenue]] in [[St. Paul, Minnesota]] for digital transmission for about a year starting in late [[1999]] before the construction was finished.

Upgrades to the first tower were completed in [[2000]]. It now rises 437.7 meters (1436 feet) from the ground. Its geographical coordinates are {{coor dms|45|03|44.0|N|93|08|22.0|W|}}.

Work on the second tower, which rises 438.3 m (1438 ft), was finished in [[2001]]. It is located at {{coor dms|45|03|45.0|N|93|08|22.0|W|}}.

==See also==
*[[KMSP TV Tower]] – another major tower in Shoreview
*[[List of masts]]
==References==
*(November 8, 1999). [http://www.contelec.com/11-08-99-2.php KSTP-TV to flip the switch for DTV.] (press release)

==External links==
* [http://wireless2.fcc.gov/UlsApp/AsrSearch/asrRegistration.jsp?regKey=101520 FCC records for tower 1]
* [http://wireless2.fcc.gov/UlsApp/AsrSearch/asrRegistration.jsp?regKey=125253 FCC records for tower 2]

[[Category:Guyed masts]]
[[Category:Towers in Minnesota]]