Editing Phosphorus (section)

===Inorganic phosphates===
====Phoshoric acids====
{{main|Phosphoric acids and phosphates}}
The most prevalent compounds of phosphorus are derivatives of phosphate ({{chem2|PO4(3−)}}), a tetrahedral anion.{{r|Corbridge1995}} Phosphate is the conjugate base of phosphoric acid, which is produced on a massive scale for use in fertilisers. Being triprotic, phosphoric acid converts stepwise to three conjugate bases:
:{{chem2|H3PO4 + H2O <-> H3O+ + H2PO4-}} (''K''<sub>a1</sub>&thinsp;= 7.25×10<sup>−3</sup>)
:{{chem2|H2PO4- + H2O <-> H3O+ + HPO4(2-)}} (''K''<sub>a2</sub>&nbsp;= 6.31×10<sup>−8</sup>)
:{{chem2|HPO4(2-) + H2O <-> H3O+ + PO4(3-)}} (''K''<sub>a3</sub>&nbsp;= 3.98×10<sup>−13</sup>)

Food-grade [[phosphoric acid]] (additive [[E number|E338]]{{r|FGOVUK}}) is used to acidify foods and beverages such as various [[cola]]s and jams, providing a tangy or sour taste.{{r|Threlfall1951}} The phosphoric acid also serves as a [[preservative]].{{r|Coca-ColaGB}} Soft drinks containing phosphoric acid, including [[Coca-Cola]], are sometimes called [[phosphate soda]]s or phosphates. Phosphoric acid in soft drinks has the potential to cause dental erosion,{{r|Moynihan2002}} as well as contribute to the formation of [[Kidney stone disease|kidney stones]], especially in those who have had kidney stones previously.{{r|Qaseem2014}}

====Metal salts====
With metal [[cation]]s, phosphate forms a variety of salts. These solids are polymeric, featuring P-O-M linkages. When the metal cation has a charge of 2+ or 3+, the salts are generally insoluble, hence they exist as common minerals. Many phosphate salts are derived from hydrogen phosphate ({{chem2|HPO4(2-)}}).

Calcium phosphates in particular are widespread compounds with many applications. Among them, they are used to improve the characteristics of processed meat and [[cheese]], in [[baking powder]], and in toothpaste.{{r|Threlfall1951}} Two of the most relevant among them are [[monocalcium phosphate]], and [[dicalcium phosphate]].

====Polyphosphates====
Phosphate exhibits a tendency to form chains and rings containing P-O-P bonds. Many polyphosphates are known, including [[Adenosine triphosphate|ATP]]. Polyphosphates arise by dehydration of hydrogen phosphates such as {{chem2|HPO4(2-)}} and {{chem2|H2PO4-}}. For example, the industrially important pentasodium triphosphate (also known as [[sodium tripolyphosphate]], STPP) is produced industrially by the megatonne by this [[condensation reaction]]:
:{{chem2|2 Na2HPO4 + NaH2PO4 -> Na5P3O10 + 2 H2O}}
Sodium triphosphate is used in laundry detergents in some countries, but banned for this use in others.{{r|Hammond2000}} This compound [[water softening|softens]] the water to enhance the performance of the detergents and to prevent pipe and boiler tube [[corrosion]].{{r|Schrödter2008}}

====Oxoacids====
{{main|Phosphorus oxoacids}}
Phosphorus [[oxoacid]]s are extensive, often commercially important, and sometimes structurally complicated. They all have acidic protons bound to oxygen atoms, some have nonacidic protons that are bonded directly to phosphorus and some contain phosphorus–phosphorus bonds.{{r|Greenwood1997}} Although many oxoacids of phosphorus are formed, only nine are commercially important. Among them, hypophosphorous, phosphorous and orthophosphoric acid are particularly important.

{|class="wikitable"
|-
!Oxidation state!!Formula!!Name!!Acidic protons!!Compounds
|-
| +1||{{chem2|HH2PO2}}||[[hypophosphorous acid]]||1||acid, salts
|-
| +3||{{chem2|H3PO3}}||[[phosphorous acid]]<br />(phosphonic acid)||2||acid, salts
|-
| +3||{{chem2|HPO2}}||metaphosphorous acid||1||salts
|-
| +4||{{chem2|H4P2O6}}||[[hypophosphoric acid]]||4||acid, salts
|-
| +5||{{chem2|(HPO3)_{''n''}|}}||[[metaphosphoric acid]]s||''n''||salts (''n''&nbsp;=&nbsp;3,4,6)
|-
| +5||{{chem2|H(HPO3)_{''n''}OH}}||[[polyphosphoric acid]]s||''n''+2||acids, salts (''n''&nbsp;=&thinsp;1-6)
|-
| +5||{{chem2|H5P3O10}}||[[tripolyphosphoric acid]]||3||salts
|-
| +5||{{chem2|H4P2O7}}||[[pyrophosphoric acid]]||4||acid, salts
|-
| +5||{{chem2|H3PO4}}||(ortho)[[phosphoric acid]]||3||acid, salts
|}