Arsenic acid

Arsenic acid
Structural formula
Ball-and-stick model
Names
IUPAC name
Arsoric acid[1]
Other names
  • Desiccant L-10
  • Orthoarsenic acid
  • Trihydrogen arsenate
  • Zotox
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.029.001 Edit this at Wikidata
EC Number
  • 231-901-9
KEGG
RTECS number
  • CG0700000
UNII
UN number 1553, 1554
  • InChI=1S/AsH3O4/c2-1(3,4)5/h(H3,2,3,4,5) checkY
    Key: DJHGAFSJWGLOIV-UHFFFAOYSA-N checkY
  • InChI=1/AsH3O4/c2-1(3,4)5/h(H3,2,3,4,5)
    Key: DJHGAFSJWGLOIV-UHFFFAOYAY
  • O[As+](O)([O-])O
Properties
H3AsO4
Molar mass 141.942 g·mol−1
Appearance White translucent or colorless crystals, hygroscopic
Density 2.5 g/cm3
Melting point 35.5 °C (95.9 °F; 308.6 K)
Boiling point 120 °C (248 °F; 393 K) decomposes
16.7 g/(100 mL)
Solubility soluble in ethanol
Vapor pressure 55 hPa (50 °C)
Acidity (pKa) pKa1 = 2.19
pKa2 = 6.94
pKa3 = 11.5[2]
Conjugate base Arsenate
Structure
Tetrahedral at arsenic atom
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Extremely toxic, carcinogenic, corrosive
GHS labelling:
GHS05: CorrosiveGHS06: ToxicGHS07: Exclamation markGHS08: Health hazardGHS09: Environmental hazard
Danger
H301, H312, H314, H331, H350, H361, H410
P201, P202, P260, P261, P264, P270, P271, P273, P280, P281, P301+P310, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P308+P313, P310, P311, P312, P321, P322, P330, P363, P391, P403+P233, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
4
0
0
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
48 mg/kg (rat, oral)

6 mg/kg (rabbit, oral)

Related compounds
Other cations
 Sodium arsenate
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)
Three bottles of arsenic acid from the Great Exhibition: impure, pure and distilled.

Arsenic acid or arsoric acid is the chemical compound with the formula H3AsO4. More descriptively written as AsO(OH)3, this colorless acid is the arsenic analogue of phosphoric acid. Arsenate and phosphate salts behave very similarly. Arsenic acid as such has not been isolated, but is only found in solution, where it is largely ionized. Its hemihydrate form (2H3AsO4·H2O) does form stable crystals. Crystalline samples dehydrate with condensation at 100 °C.[3]

  1. ^ "Arsenic acid".
  2. ^ Perrin, D. D., ed. (1982) [1969]. Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution. IUPAC Chemical Data (2nd ed.). Oxford: Pergamon (published 1984). Entry 11. ISBN 0-08-029214-3. LCCN 82-16524.
  3. ^ Holleman, A. F.; Wiberg, E. (2001). Inorganic Chemistry. San Diego: Academic Press. ISBN 0-12-352651-5.