Disodium hydrogen phosphite is the name for inorganic compounds with the formula Na₂HPO₃•(H₂O)_x. The commonly encountered salt is the pentahydrate.^[1] A derivative of phosphorous acid (HP(O)(OH)₂), it contains the anion HPO₃²⁻. Its common name suggests that it contains an acidic hydrogen atom, as in sodium hydrogen carbonate. However, this name is misleading as the hydrogen atom is not acidic, being bonded to phosphorus rather than oxygen. The salt has reducing properties. It is white or colorless solid, and is little studied.

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Disodium hydrogen phosphite

Names
IUPAC name sodium phosphonate pentahydrate
Other names Sodium phosphate dibasic pentahydrate, sodium phosphite
Identifiers
CAS Number	anhydrous: 13708-85-5 Y pentahydrate: 13517-23-2 Y
3D model (JSmol)	Interactive image anhydrous: Interactive image
ChemSpider	21106436 Y
ECHA InfoCard	100.033.848
PubChem CID	anhydrous: 16211071 pentahydrate: 22463763
UNII	anhydrous: X65D416703 Y pentahydrate: UM5UZ43YVE Y
CompTox Dashboard (EPA)	DTXSID20889617
InChI InChI=1S/2Na.O3P/c;;1-4(2)3/q2*+1;-3/p+1 Y Key: XWGAABYWOLJBFF-UHFFFAOYSA-O Y InChI=1/2Na.O3P/c;;1-4(2)3/q2*+1;-3/p+1 Key: XWGAABYWOLJBFF-IKLDFBCSAK
SMILES O=P([O-])([O-])[H].[Na+].[Na+] anhydrous: [H+].[Na+].[Na+].[O-]P([O-])[O-]
Properties
Chemical formula	HNa2O3P
Molar mass	125.958 g·mol−1
Appearance	white solid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

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