Disodium phosphate

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| Verifiedfields = changed

| Watchedfields = changed

| verifiedrevid = 457118728

| ImageFile = Disodium hydrogen phosphate.png

| ImageSize = 150px

| ImageAlt = Structural formula of disodium phosphate

| ImageFile1 = Disodium phosphate 3D spacefill.png

| ImageSize1 = 250

| ImageAlt1 = Ball-and-stick model of the component ions of disodium phosphate

| ImageCaption1 = {{legend|purple|Sodium, Na}}{{legend|orange|Phosphorus, P}}{{legend|red|Oxygen, O}}{{legend|white|Hydrogen, H}}

| ImageFile2 = Hydrogenfosforečnan sodný dodekahydrát.jpg

| IUPACName = Disodium hydrogen phosphate

| OtherNames = {{ubl|Acetest|Dibasic sodium phosphate|Disodium hydrogen orthophosphate|Disodium hydrogen phosphate|Disodium phosphate|Sodium phosphate dibasic}}

| SystematicName =

| Section1 = {{Chembox Identifiers

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| ChemSpiderID = 22625

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = 22ADO53M6F

| UNII2_Ref = {{fdacite|correct|FDA}}

| UNII2 = 94255I6E2T

| UNII2_Comment = (dihydrate)

| UNII3_Ref = {{fdacite|correct|FDA}}

| UNII3 = 70WT22SF4B

| UNII3_Comment = (heptahydrate)

| UNII4_Ref = {{fdacite|correct|FDA}}

| UNII4 = E1W4N241FO

| UNII4_Comment = (dodecahydrate)

| InChI = 1/2Na.H3O4P/c;;1-5(2,3)4/h;;(H3,1,2,3,4)/q2*+1;/p-3

| ChEMBL_Ref = {{ebicite|correct|EBI}}

| ChEMBL = 1060

| ChEBI_Ref = {{ebicite|correct|EBI}}

| ChEBI = 34683

| SMILES = OP(=O)([O-])[O-].[Na+].[Na+]

| InChIKey = BNIILDVGGAEEIG-DFZHHIFOAK

| StdInChI_Ref = {{stdinchicite|changed|chemspider}}

| StdInChIKey = BNIILDVGGAEEIG-UHFFFAOYSA-K

| StdInChI = 1S/2Na.H3O4P/c;;1-5(2,3)4/h;;(H3,1,2,3,4)/q2*+1;/p-3

| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}}

| CASNo = 7558-79-4

| CASNo_Ref = {{cascite|correct|CAS}}

| CASNo2_Ref = {{cascite|correct|CAS}}

| CASNo2 = 10028-24-7

| CASNo2_Comment = (dihydrate)

| CASNo3_Ref = {{cascite|correct|CAS}}

| CASNo3 = 7782-85-6

| CASNo3_Comment = (heptahydrate)

| CASNo4_Ref = {{cascite|correct|CAS}}

| CASNo4 = 10039-32-4

| CASNo4_Comment = (dodecahydrate)

| PubChem = 24203

| EINECS = 231-448-7

| RTECS = WC4500000

}}

| Section2 = {{Chembox Properties

| Formula = {{chem2|Na2HPO4}}

| MolarMass = {{ubl|141.96 g/mol (anhydrous)|177.99 g/mol (dihydrate)|268.07 g/mol (heptahydrate)}}

| Appearance = White crystalline solid

| RefractIndex = 1.35644 to 1.35717 at 20°C

| Odor = Odorless

| Density = 1.7 g/cm³

| MeltingPtC = 250

| MeltingPt_notes = Decomposes

| Solubility = 7.7 g/(100 ml) (20 °C)
11.8 g/(100 ml) (25 °C, heptahydrate)

| SolubleOther = Insoluble in ethanol

| pKa = 12.35

| LogP = −5.8

| MagSus = −56.6·10⁻⁶ cm³/mol

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| Section3 =

| Section4 =

| Section5 =

| Section6 =

| Section7 = {{Chembox Hazards

| ExternalSDS = [http://www.inchem.org/documents/icsc/icsc/eics1129.htm ICSC 1129]

| NFPA-H = 1

| NFPA-F = 0

| NFPA-R = 0

| MainHazards = Irritant

| FlashPt = Non-flammable

| LD50 = 17000 mg/kg (rat, oral)

}}

| Section8 = {{Chembox Related

| OtherAnions = sodium phosphite

| OtherCations = Dipotassium phosphate
Diammonium phosphate

| OtherCompounds = Monosodium phosphate
Trisodium phosphate

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Disodium phosphate (DSP), or disodium hydrogen phosphate, or sodium phosphate dibasic, is an inorganic compound with the chemical formula {{chem2|Na2HPO4|auto=1}}. It is one of several sodium phosphates. The salt is known in anhydrous form as well as hydrates {{chem2|Na2HPO4*nH2O}}, where n is 2, 7, 8, and 12. All are water-soluble white powders. The anhydrous salt is hygroscopic.{{Cite web |url=http://www.ffcr.or.jp/zaidan/FFCRHOME.nsf/7bd44c20b0dc562649256502001b65e9/916cae3da5a8a11b49256f320018877f/$FILE/D121.pdf |title=Physical data (pdf) |access-date=2007-03-06 |archive-url=https://web.archive.org/web/20110717102830/http://www.ffcr.or.jp/zaidan/FFCRHOME.nsf/7bd44c20b0dc562649256502001b65e9/916cae3da5a8a11b49256f320018877f/$FILE/D121.pdf |archive-date=2011-07-17 |url-status=dead}}

The pH of disodium hydrogen phosphate water solution is between 8.0 and 11.0, meaning it is moderately basic:

:{{chem2|HPO4(2−) + H2O ⇌ H2PO4− + OH−}}