Disodium hydrogen arsenate
Names
IUPAC name
Disodium hydrogen arsorate
Other names
Sodium arsenate dibasic
Identifiers
ChEBI
ECHA InfoCard 100.029.002 Edit this at Wikidata
EC Number
  • 231-902-4
UNII
Properties
H15Na2AsO11 (heptahydrate)
Molar mass 312.01 g/mol (heptahydrate)
Appearance white solid
good
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 poison
GHS labelling:
GHS06: ToxicGHS08: Health hazardGHS09: Environmental hazard
Danger
H301, H331, H350, H410
P201, P202, P261, P264, P270, P271, P273, P281, P301+P310, P304+P340, P308+P313, P311, P321, P330, P391, P403+P233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Disodium hydrogen arsenate is the inorganic compound with the formula Na2HAsO4.7H2O. The compound consists of a salt and seven molecules of water of crystallization although for simplicity the formula usually omits the water component. The other sodium arsenates are NaH2AsO4 and Na3AsO4, the latter being called sodium arsenate. Disodium hydrogen arsenate is highly toxic. The salt is the conjugate base of arsenic acid. It is a white, water-soluble solid.[1]

Being a diprotic acid, its acid-base properties is described by two equilibria:

H
2AsO−
4 + H2O ⇌ HAsO2−
4 + H3O+  (pKa2 = 6.94)
HAsO2−
4 + H2O ⇌ AsO3−
4 + H3O+  (pKa3 = 11.5)

Related compounds

References

  1. ^ Grund, S. C.; Hanusch, K.; Wolf, H. U. "Arsenic and Arsenic Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a03_113.pub2. ISBN 978-3527306732.
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