TheInfoListRev V5.1.84
Xfr/

Topic summary

Oxalic acid

Oxalic acid
Oxalic acid dihydrate
Names IUPAC name
1,2-ethanedioic acid
Preferred IUPAC name
Oxalic acid
Systematic IUPAC name
Ethanedioic acid
Other names
  • Wood bleach
  • (Carboxyl)carboxylic acid
  • Carboxylformic acid
  • Dicarboxylic acid
  • Diformic acid
Identifiers
3D model (JSmol)
385686 ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard100.005.123EC Number
  • 205-634-3
2208 KEGG
MeSHOxalic+acid
RTECS number
  • RO2450000
UNII
UN number3261
  • InChI=1S/C6H6O6/c3-1(4)2(5)6/h(H,3,4)(H,5,6)
    Key: MUBZPKHOEPUJKR-UHFFFAOYSA-N
  • OC(=O)C(=O)O
Properties C2H2O4Molar mass
  • 90.034 g⋅mol (anhydrous)
  • 126.065 g⋅mol (dihydrate)
Appearance White crystals OdorOdorless Density
  • 1.90 g/cm (anhydrous, at 17 °C (63 °F))
  • 1.653 g/cm (dihydrate)
Melting point
  • 189–191 °C (372–376 °F; 462–464 K) (anhydrous)
  • 101.5 °C (214.7 °F; 374.6 K) (dihydrate)
Boiling pointdecomposes (see article for details)
  • 46.9 g/L @ 5 °C (41 °F)
  • 57.2 g/L @ 10 °C (50 °F)
  • 75.5 g/L @ 15 °C (59 °F)
  • 95.5 g/L @ 20 °C (68 °F)
  • 118 g/L @ 25 °C (77 °F)
  • 139 g/L @ 30 °C (86 °F)
  • 178 g/L @ 35 °C (95 °F)
  • 217 g/L @ 40 °C (104 °F)
  • 261 g/L @ 45 °C (113 °F)
  • 315 g/L @ 50 °C (122 °F)
  • 376 g/L @ 55 °C (131 °F)
  • 426 g/L @ 60 °C (140 °F)
  • 548 g/L @ 65 °C (149 °F)
Solubility in ethanol237 g/L @ 15 °C (59 °F) Solubility in diethyl ether14 g/L @ 15 °C (59 °F) Vapor pressure
  • 2.34×10 mmHg @ 20 °C (68 °F)
  • 0.54 mmHg @ 105 °C (221 °F)
Acidity (pKa) 1.25 and 4.28 Conjugate baseHydrogenoxalate−60.05×10 cm/molThermochemistry 91.0 J/(mol·K)109.8 J/(mol·K)−829.9 kJ/molPharmacology QP53AG03 (WHO) Hazards Occupational safety and health (OHS/OSH):
Main hazards
Corrosive GHS labelling: DangerH302+H312, H318, H402P264, P270, P273, P280, P301+P312+P330, P302+P352+P312, P305+P351+P338+P310, P362+P364, P501NFPA 704 (fire diamond)
3
1
0
ACID
Flash point166 °C (331 °F; 439 K) Lethal dose or concentration (LD, LC):
  • 1000 mg/kg (dog, oral)
  • 1400 mg/kg (rat)
  • 7500 mg/kg (rat, oral)
NIOSH (US health exposure limits):NIOSH Pocket Guide to Chemical Hazards. "#0474". National Institute for Occupational Safety and Health (NIOSH).
PEL (Permissible)
TWA 1 mg/m
REL (Recommended)
  • TWA 1 mg/m
  • ST 2 mg/m
IDLH (Immediate danger)
500 mg/mSafety data sheet (SDS) External MSDSRelated compounds
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X markNverify (  ?)

Oxalic acid is an organic acid with the systematic name ethanedioic acid and chemical formulaHO−C(=O)−C(=O)−OH, also written as (COOH)2 or (CO2H)2 or H2C2O4. It is the simplest dicarboxylic acid. It is a white crystalline solid that forms a colorless solution in water. Its name is derived from early investigators who isolated oxalic acid from flowering plants of the genus Oxalis, commonly known as wood-sorrels. It occurs naturally in many foods. It can be toxic when ingested in significant quantities, and contact with concentrated forms can cause chemical burns.

Oxalic acid is a much stronger acid than acetic acid. It is a reducing agent and its conjugate baseshydrogenoxalate (HC2O−4) and oxalate (C2O2−4) are chelating agents for metal cations. It is used as a cleaning agent, especially for the removal of rust, because it forms a water-soluble ferric iron complex, the ferrioxalate ion. Oxalic acid typically occurs as the dihydrate with the formula H2C2O4·2H2O.

Wikipedia source