Sodium dihydrogen arsenate

Sodium dihydrogen arsenate
Names
	IUPAC name Sodium dihydrogen arsorate
	Other names sodium arsenate monobasic, sodium dihydroarsenate
Identifiers
CAS Number	10103-60-3 ;
3D model (JSmol)	Interactive image;
PubChem CID	23677060;
CompTox Dashboard (EPA)	DTXSID8058611 ;
	InChI InChI=1S/AsH3O4.Na/c2-1(3,4)5;/h(H3,2,3,4,5);/q;+1/p-1 Key: XCVRTGQHVBWRJB-UHFFFAOYSA-M;
	SMILES O[As](=O)(O)[O-].[Na+];
Properties
Chemical formula	NaH4AsO4 (monohydrate)
Molar mass	163.9 g/mol
Appearance	colourless solid
Density	2.53 g/cm3
Solubility in water	slightly soluble
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	toxic
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Sodium dihydrogen arsenate is the inorganic compound with the formula NaH₂AsO₄. Related salts are also called sodium arsenate, including Na₂HAsO₄ (disodium hydrogen arsenate) and NaH₂AsO₄ (sodium dihydrogen arsenate). Sodium dihydrogen arsenate is a colorless solid that is highly toxic.

The salt is the conjugate base of arsenic acid:

H₃AsO₄ ⇌ H₂AsO⁻
₄ + H⁺ (K₁ = 10^−2.19)

In the laboratory, it is prepared in this way, crystallizing from a hot saturated aqueous solution, where it is highly soluble when hot (75.3 g in 100 mL at 100 °C). It is obtained as the monohydrate.

Upon heating, solid NaH₂AsO₄H₂O, loses water of crystallization and converts to the pyroarsenate salt Na₂H₂As₂O₇.^[1]

References

^ Schenk, P. W. (1963). Brauer, G. (ed.). Arsenic, Antimony, Bismuth" in Handbook of Preparative Inorganic Chemistry. Vol. 1 (2nd ed.). New York: Academic Press. p. 602.

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[1] Schenk, P. W. (1963). Brauer, G. (ed.). Arsenic, Antimony, Bismuth" in Handbook of Preparative Inorganic Chemistry. Vol. 1 (2nd ed.). New York: Academic Press. p. 602.

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