Sodium arsenate

Sodium arsenate
IUPAC name Sodium dihydrogen arsenate
Other names sodium arsenate
Identifiers
CAS number	10103-60-3 Y
PubChem	23677060
RTECS number	CG1100000
Jmol-3D images	Image 1
SMILES O[As](=O)(O)[O-].[Na+]
InChI InChI=1S/AsH3O4.Na/c2-1(3,4)5;/h(H3,2,3,4,5);/q;+1/p-1
Properties
Molecular formula	NaH2AsO4
Molar mass	163.924 g/mol
Appearance	colourless solid
Density	2.53 g/cm3
Melting point	280 °C
Solubility in water	slightly soluble
Hazards
Main hazards	toxic
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Sodium arsenate is the inorganic compound with the formula NaH₂AsO₄^.H₂O. Related salts are also called sodium arsenate, including Na₂HAsO₄ and Na₃AsO₄. This particular salt is a colorless solid that is highly toxic. The potassium salt has similar properties.

The salt is the conjugate base of arsenic acid:

H₃AsO₄ H₂AsO−
4 + H⁺ (K₁ = 10^−2.19)

It is prepared in this way and crystallized by cooling a hot saturated aqueous solution, where it is highly soluble when hot (75.3 g in 100 mL at 100 °C). A fine white powder of the monohydrate crystallizes. Upon heating, the solid loses water of crystallization and then the dihydrogenarsenate anions condense to give Na₂H₂As₂O₇ and, above 230 °C, NaAsO₃.^[1]

References

1. ^ Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 602.

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