Share on Facebook Share on Twitter Email
Answers.com

phosphate

 
Dictionary: phos·phate   (fŏs'fāt') pronunciation
Home > Library > Literature & Language > Dictionary
n.
  1. A salt or ester of phosphoric acid.
  2. A fertilizer containing phosphorus compounds.
  3. A soda fountain drink made by blending carbonated water with flavored syrup.

[PHOSPH(O)- + -ATE2.]

phosphatic phos·phat'ic (fŏs-făt'ĭk) adj.

Search unanswered questions...

Enter a question here...
Search: All sources Community Q&A Reference topics

Food and Nutrition: phosphates
Top
Home > Library > Food & Cooking > Food and Nutrition

Salts of phosphoric acid; the form in which the element phosphorus is normally present in foods and body tissues. See also polyphosphates.

Dental Dictionary: phosphates
Top
Home > Library > Health > Dental Dictionary
(fos′fāts)
n.pl

The organic compounds of phosphorus. The blood phosphate level is normally 2.5 mg to 5 mg/100 mL. It is low in rickets and early hyperparathyroidism and high in tetany and nephritis.

Britannica Concise Encyclopedia: phosphate
Top
Home > Library > Miscellaneous > Britannica Concise Encyclopedia

Any of numerous chemical compounds related to phosphoric acid (H3PO4). Phosphate salts are inorganic compounds containing the phosphate ion (PO43-), the hydrogen phosphate ion (HPO42-), or the dihydrogen phosphate ion (H2PO4-), along with any cation. Phosphate esters are organic compounds in which the hydrogens of phosphoric acid are replaced by organic groups (e.g., methyl, ethyl, phenyl), with one of their carbon atoms bonding to an oxygen atom in the phosphate group. Nucleic acids and ATP both contain phosphate; bones and teeth contain calcium phosphate. Phosphate rock (mainly calcium phosphate) is one of the four most important basic chemical commodities. Phosphates were formerly used in detergents, which washed into rivers and lakes, causing water blooms of algae and bacteria (see eutrophication); such use is now generally outlawed or regulated. Phosphates are still used in fertilizers, baking powder, and toothpaste.

For more information on phosphate, visit Britannica.com.

Archaeology Dictionary: phosphate
Top
Home > Library > Science > Archaeology Dictionary

(phosphorus) [Ma]

Phosphates are naturally present in all soils at varying levels. Anthropogenically derived phosphates have their sources in a wide range of organic materials with the result that in occupation areas, burials, food-processing areas, latrine areas and animal compounds and droveways the phosphate levels in the soil can be considerably enhanced. Once in the soil, phosphate is generally fixed in an insoluble form to inorganic aluminium, calcium, and iron components, or associates with organic molecules to form insoluble complexes. Fixed in this way it can survive for long periods. In archaeology, identifying concentrations of phosphates through phosphate analysis is extremely useful for the recognition and definition of settlement sites, and mapping the different levels of activity within a site. Phosphates can also be used to identify the presence of burials in ground where all physical traces have vanished.
 
Columbia Encyclopedia: phosphate
Top
Home > Library > Miscellaneous > Columbia Encyclopedia
phosphate, salt or ester of phosphoric acid, H3PO4. Because phosphoric acid is tribasic (having three replaceable hydrogen atoms), it forms monophosphate, diphosphate, and triphosphate salts in which one, two, or three of the hydrogens of the acid are replaced, respectively. Because replaceable hydrogens remain in monophosphates and diphosphates, they are sometimes called acid phosphates. The most important inorganic phosphate is calcium phosphate, Ca3(PO4)2. It makes up the larger part of phosphate rock, a mineral that is abundantly distributed throughout the world. Since calcium phosphate is only slightly soluble in water, it is not very suitable as a source of the phosphorus necessary for plant life; however, by treating it with sulfuric acid the soluble calcium acid phosphate known as superphosphate of lime is formed. Other important inorganic phosphates include ammonium phosphate, important as a fertilizer; trisodium phosphate, used in detergents and for softening water; and disodium phosphate, used to some extent in medicine and in preparing baking powders. Various acid phosphates, e.g., those of calcium, magnesium, and sodium, are sometimes present in carbonated beverages. Microcosmic salt, used in certain bead tests in chemical analysis, is sodium ammonium phosphate. Organic phosphates play an important role in metabolism. For example, in the metabolism of sugars (which have hydroxyl groups, -OH, in their molecules), phosphate esters are often formed as an intermediate compound. Formation of these esters is called phosphorylation. Nucleotides are phosphate esters that play an important role in the conservation and use of the energy released in the metabolism of foods in the body; adenosine triphosphate is an important nucleotide. DNA and RNA (see nucleic acid) are complex polymeric organic phosphates.

Veterinary Dictionary: phosphate
Top
Home > Library > Animal Life > Veterinary Dictionary

Any salt or ester of phosphoric acid.
1. Phosphates are widely distributed in the body, the largest amounts being in the bones and teeth. They are continually excreted in the urine and feces, and must be replaced in the diet. Inorganic phosphates function as buffer salts to maintain the acid–base balance in blood, saliva, urine and other body fluids. The principal phosphates in this buffer system are monosodium and disodium phosphate. Organic phosphates, in particular adenosine triphosphate (ATP), are used to store the chemical bond energy released during the oxidation of compounds such as glycogen or fatty acids, which may later be expended in muscle contraction. This is thought to occur through the hydrolysis of the so-called high-energy phosphate bond present in ATP, phosphocreatine and certain other body compounds. See also hypophosphatemia, hyperphosphatemia.
2. used extensively in agricultural industry as fertilizers and organic compounds as cleaning agents.

  • p. binders — usually aluminum carbonate or hydroxide preparations, used to bind phosphates and limit their absorption from the intestine. Used in the treatment of the hyperphosphatemia of renal failure.
  • p. buffer — important phosphate-containing buffers.
  • p. buffered saline — a special phosphate buffered saline used in tissue cultures and for the storage and transport of bovine embryos. Abbreviated PBS.
  • p. calculi — see struvite urolith.
  • dietary p. — supplementation of the diet with phosphate in some form is a very common practice in farm animals. Materials used include rock phosphate (defluorination may be necessary), sodium dihydrogen phosphate produced by the agricultural chemical industry, calcium triphosphate and bone meal or flour.
  • inorganic p. — any salt of phosphoric acid.
  • p. retention — a phenomenon resulting from reduced glomerular filtration; contributes to a chronic hypocalcemic state.
  • p. ridge — see mineralization front.
  • p. rock — see rock phosphate.
  • p. yielding endonucleases — a class of ribonuclease involved in the usually fairly rapid turnover of RNA in the cell that degrades RNA by cleavage of the phosphodiester bonds within the molecule.
Wikipedia: Phosphate
Top
Home > Library > Miscellaneous > Wikipedia

A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in agriculture and industry.[1][2][3] At elevated temperatures in the solid state, phosphates can condense to form pyrophosphates.

Contents

Chemical properties

The general chemical structure of an organophosphate.
This is the structural formula of the phosphoric acid functional group as found in a weakly acidic aqueous solution. In more basic aqueous solutions, the group donates the two hydrogen atoms and ionizes as a phosphate group with a negative charge of 2. [4]

The phosphate ion is a polyatomic ion with the empirical formula PO3−4 and a molar mass of 94.973 g/mol. It consists of one central phosphorus atom surrounded by four identical oxygen atoms in a tetrahedral arrangement. The phosphate ion carries a negative three formal charge and is the conjugate base of the hydrogen phosphate ion, HPO2−4, which is the conjugate base of H2PO−4, the dihydrogen phosphate ion, which in turn is the conjugate base of H3PO4, phosphoric acid. It is a hypervalent molecule (the phosphorus atom has 10 electrons in its valence shell). Phosphate is also an organophosphorus compound with the formula OP(OR)3. A phosphate salt forms when a positively-charged ion attaches to the negatively-charged oxygen atoms of the ion, forming an ionic compound. Many phosphates are not soluble in water at standard temperature and pressure. The sodium, potassium, rubidium, caesium and ammonium phosphates are all water soluble. Most other phosphates are only slightly soluble or are insoluble in water. As a rule, the hydrogenphosphates and the dihydrogenphosphates are slightly more soluble than the corresponding phosphates. The pyrophosphates are mostly water soluble.

In dilute aqueous solution, phosphate exists in four forms. In strongly-basic conditions, the phosphate ion (PO3−4) predominates, whereas in weakly-basic conditions, the hydrogen phosphate ion (HPO2−4) is prevalent. In weakly-acid conditions, the dihydrogen phosphate ion (H2PO−4) is most common. In strongly-acid conditions, aqueous phosphoric acid (H3PO4) is the main form.

H3PO4
H2PO−4
HPO2−4
PO3−4

More precisely, considering the following three equilibrium reactions:

H3PO4 is in equilibrium with H+ + H2PO−4
H2PO−4 is in equilibrium with H+ + HPO2−4
HPO2−4 is in equilibrium with H+ + PO3−4

the corresponding constants at 25°C (in mol/L) are (see phosphoric acid):

K_{a1}=\frac{[\mbox{H}^+][\mbox{H}_2\mbox{PO}_4^-]}{[\mbox{H}_3\mbox{PO}_4]}\simeq 7.5\times10^{-3} (pKa1 2.12)
K_{a2}=\frac{[\mbox{H}^+][\mbox{HPO}_4^{2-}]}{[\mbox{H}_2\mbox{PO}_4^-]}\simeq 6.2\times10^{-8} (pKa2 7.21)
K_{a3}=\frac{[\mbox{H}^+][\mbox{PO}_4^{3-}]}{[\mbox{HPO}_4^{2-}]}\simeq 2.14\times10^{-13} (pKa3 12.67)
Phosphoric acid speciation.png

The speciation diagram obtained using these pK values shows three distinct regions. In effect H3PO4, H2PO−4 and HPO2−4 behave as separate weak acids. This is because the successive pK values differ by more than 4. For each acid the pH at half-neutralization is equal to the pK value of the acid. The region in which the acid is in equilibrium with its conjugate base is defined by pH ≈ pK ± 2. Thus the three pH regions are approximately 0-4, 5-9 and 10-14. This is idealized as it assumes constant ionic strength, which will not hold in reality at very low and very high pH values.

For a neutral pH as in the cytosol, pH=7.0

\frac{[\mbox{H}_2\mbox{PO}_4^-]}{[\mbox{H}_3\mbox{PO}_4]}\simeq 7.5\times10^4 \mbox{ , }\frac{[\mbox{HPO}_4^{2-}]}{[\mbox{H}_2\mbox{PO}_4^-]}\simeq 0.62 \mbox{ , } \frac{[\mbox{PO}_4^{3-}]}{[\mbox{HPO}_4^{2-}]}\simeq 2.14\times10^{-6}

so that only H2PO−4 and HPO2−4 ions are present in significant amounts (62% H2PO−4, 38% HPO2−4 Note that in the extracellular fluid (pH=7.4), this proportion is inverted (61% HPO2−4, 39% H2PO−4).

Phosphate can form many polymeric ions such as diphosphate (also known as pyrophosphate), P2O4−7, and triphosphate, P3O5−10. The various metaphosphate ions (which are usually long linear polymers) have an empirical formula of PO−3 and are found in many compounds.

Biochemistry of phosphates

In biological systems, phosphorus is found as a free phosphate ion in solution and is called inorganic phosphate, to distinguish it from phosphates bound in various phosphate esters. Inorganic phosphate is generally denoted Pi and can be created by the hydrolysis of pyrophosphate, which is denoted PPi:

P2O4−7 + H2O is in equilibrium with 2 HPO2−4

However, phosphates are most commonly found in the form of adenosine phosphates, (AMP, ADP and ATP) and in DNA and RNA and can be released by the hydrolysis of ATP or ADP. Similar reactions exist for the other nucleoside diphosphates and triphosphates. Phosphoanhydride bonds in ADP and ATP, or other nucleoside diphosphates and triphosphates, contain high amounts of energy which give them their vital role in all living organisms. They are generally referred to as high energy phosphate, as are the phosphagens in muscle tissue. Compounds such as substituted phosphines, have uses in organic chemistry but do not seem to have any natural counterparts.

The addition and removal of phosphate from proteins in all cells is a pivotal strategy in the regulation of metabolic processes.

Reference ranges for blood tests, showing inorganic phosphorus in purple at right, being almost identical to the molar concentration of phosphate.

Phosphate is useful in animal cells as a buffering agent. Phosphate salts that are commonly used for preparing buffer solutions at cell pHs include Na2HPO4 , NaH2PO4 , and the corresponding potassium salts.

An important occurrence of phosphates in biological systems is as the structural material of bone and teeth. These structures are made of crystalline calcium phosphate in the form of hydroxyapatite. The hard dense enamel of mammalian teeth consists of fluoroapatite, an hydroxy calcium phosphate where some of the hydroxyl groups have been replaced by fluoride ions.

Insect exoskeleta are constructed of chitin containing crystalline calcium phosphate as a strengthening material.

Geochemistry of phosphates

Phosphates are the naturally occurring form of the element phosphorus, found in many phosphate minerals. In mineralogy and geology, phosphate refers to a rock or ore containing phosphate ions. Inorganic phosphates are mined to obtain phosphorus for use in agriculture and industry.[1][2][3]

The largest phosphorite or rock phosphate deposits in North America lie in the Bone Valley region of central Florida, United States, the Soda Springs region of Idaho, and the coast of North Carolina. Smaller deposits are located in Montana, Tennessee, Georgia and South Carolina near Charleston along Ashley Phosphate road. The small island nation of Nauru and its neighbor Banaba Island, which used to have massive phosphate deposits of the best quality, have been mined excessively. Rock phosphate can also be found on Egypt, Israel, Morocco, Navassa Island, Tunisia, Togo and Jordan, countries that have large phosphate mining industries.

Phosphorite mines are primarily found in:

North America: United States of America, especially North Carolina, with lesser deposits in Florida, Idaho and Tennessee.

Africa: Morocco, mainly near Khouribga and Youssoufia; Senegal, Togo, Tunisia and Western Sahara.

Middle East: Israel, Jordan, Iraq, at the town of Akashat, near to the Jordanian borders.

Oceania: Australia, Makatea, Nauru, Ocean Island.

In 2007, at the current rate of consumption, the supply of phosphorus was estimated to run out in 345 years.[5] However, scientists are now claiming that a "Peak Phosphorus" will occur in 30 years and that "At current rates, reserves will be depleted in the next 50 to 100 years."[6]

Ecology of phosphates

In ecological terms, because of its important role in biological systems, phosphate is a highly sought after resource. Consequently, it is often a limiting reagent in environments, and its availability may govern the rate of growth of organisms. Addition of high levels of phosphate to environments and to micro-environments in which it is typically rare can have significant ecological consequences. For example, booms in the populations of some organisms at the expense of others, and the collapse of populations deprived of resources such as oxygen (see eutrophication). In the context of pollution, phosphates are a principal component of total dissolved solids, a major indicator of water quality.

Calcium hydroxyapatite and calcite precipitates can be found around bacteria in alluvial topsoil.[7] As clay minerals promote biomineralization, the presence of bacteria and clay minerals resulted in calcium hydroxyapatite and calcite precipitates.[7]

Phosphate deposits can contain significant amounts of naturally occurring heavy metals. Mining operations processing phosphate rock can leave tailings piles containing elevated levels of cadmium, lead, nickel, copper, chromium, and uranium. Unless carefully managed, these waste products can leach heavy metals into groundwater or nearby estuaries. Uptake of these substances by plants and marine life can lead to concentration of toxic heavy metals in food products.[8]

See also

References

  1. ^ a b "Phosphate Primer". http://fipr1.state.fl.us/PhosphatePrimer. 
  2. ^ a b Lynn A. Kuntz (June 2006). "Figuring Out Phosphates". http://www.foodproductdesign.com/articles/661ingredient2.html. 
  3. ^ a b Lynn A. Kuntz (June 2006). "Food Product Design". http://www.foodproductdesign.com/articles/661ingredient2.html. 
  4. ^ Campbell, Neil A.; Reece, Jane B. (2005). Biology (Seventh ed.). San Francisco, California: Benjamin Cummings. pp. 65. ISBN 0-8053-7171-0. 
  5. ^ "How Long Will it Last?". New Scientist 194 (2605): 38–9. May 26, 2007. ISSN 4079 0262 4079. 
  6. ^ Leo Lewis (2008-06-23). "Scientists warn of lack of vital phosphorus as biofuels raise demand". The Times. http://business.timesonline.co.uk/tol/business/industry_sectors/natural_resources/article4193017.ece. 
  7. ^ a b Schmittner KE, Giresse P (1999). "Micro-environmental controls on biomineralization: superficial processes of apatite and calcite precipitation in Quaternary soils, Roussillon, France". Sedimentology 46 (3): 463-76. doi:10.1046/j.1365-3091.1999.00224.x. 
  8. ^ Gnandil, K.; Tchangbedjil, G.; Killil, K.; Babal, G.; Abbel, E. (March). "The Impact of Phosphate Mine Tailings on the Bioaccumulation of Heavy Metals in Marine Fish and Crustaceans from the Coastal Zone of Togo". Mine Water and The Environment 25 (1): 56-62. 

External links


This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Translations: Phosphate
Top
Home > Library > Literature & Language > Translations

Dansk (Danish)
n. - fosfat

Nederlands (Dutch)
fosfaat, (mv) fosfaatmest, prik (drank) met kleine hoeveelheid fosfaat

Français (French)
n. - (Chim) phosphate, (Agric) phosphates, engrais phosphatés

Deutsch (German)
n. - Phosphat

Ελληνική (Greek)
n. - (χημ.) φωσφορικό άλας

Italiano (Italian)
fosfato, concime fosfatico

Português (Portuguese)
n. - fosfato (m) (Quím.)

Русский (Russian)
фосфат

Español (Spanish)
n. - fosfato

Svenska (Swedish)
n. - fosfat

中文（简体）(Chinese (Simplified))
磷酸盐, 磷酸果汁汽水, 磷肥

中文（繁體）(Chinese (Traditional))
n. - 磷酸鹽, 磷酸果汁汽水, 磷肥

한국어 (Korean)
n. - 인산염 , 인산 비료, 탄산수

日本語 (Japanese)
n. - リン酸塩, リン酸肥料, 炭酸飲料

العربيه (Arabic)
‏(الاسم) فسفات : ملح حامض الفسفوريك, سماد الفسفات‏

עברית (Hebrew)
n. - ‮זרחה, פוספט‬

If you are unable to view some languages clearly, click here.

To select your translation preferences click here.


 
 

 

Copyrights:

Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.  Read more
Food and Nutrition. A Dictionary of Food and Nutrition. Copyright © 1995, 2003, 2005 by A. E. Bender and D. A. Bender. All rights reserved.  Read more
Dental Dictionary. Mosby's Dental Dictionary. Copyright © 2004 by Elsevier, Inc. All rights reserved.  Read more
Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 2006 Encyclopædia Britannica, Inc. All rights reserved.  Read more
Archaeology Dictionary. The Concise Oxford Dictionary of Archaeology. Copyright © 2002, 2003 by Oxford University Press. All rights reserved.  Read more
Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2003, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/.  Read more
Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.  Read more
Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Phosphate".  Read more
Translations. Copyright © 2007, WizCom Technologies Ltd. All rights reserved.  Read more