Oxalic acid

Oxalic acid
Structural formula of oxalic acid
Skeletal formula of oxalic acid
Space-filling model of oxalic acid
Oxalic acid dihydrate
Oxalic acid dihydrate
Names
IUPAC name
1,2-ethanedioic acid
Preferred IUPAC name
Oxalic acid[1]
Systematic IUPAC name
Ethanedioic acid[1]
Other names
Wood bleach
(Carboxyl)carboxylic acid
Carboxylformic acid
Dicarboxylic acid
Diformic acid
Identifiers
3D model (JSmol)
3DMet
385686
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.005.123 Edit this at Wikidata
EC Number
  • 205-634-3
2208
KEGG
MeSH Oxalic+acid
RTECS number
  • RO2450000
UNII
UN number 3261
  • InChI=1S/C6H6O6/c3-1(4)2(5)6/h(H,3,4)(H,5,6) checkY
    Key: MUBZPKHOEPUJKR-UHFFFAOYSA-N checkY
  • OC(=O)C(=O)O
Properties
C2H2O4
Molar mass 90.034 g·mol−1 (anhydrous)
126.065 g·mol−1 (dihydrate)
Appearance White crystals
Odor Odorless
Density 1.90 g/cm3 (anhydrous, at 17 °C)[2]
1.653 g/cm3 (dihydrate)
Melting point 189 to 191 °C (372 to 376 °F; 462 to 464 K)
101.5 °C (214.7 °F; 374.6 K) dihydrate
  • In g/L:
  • 46.9 (5 °C)
  • 57.2 (10 °C)
  • 75.5 (15 °C)
  • 95.5 (20 °C)
  • 118 (25 °C)
  • 139 (30 °C)
  • 178 (35 °C)
  • 217 (40 °C)
  • 261 (45 °C)
  • 315 (50 °C)
  • 376 (55 °C)
  • 426 (60 °C)
  • 548 (65 °C)
[3]
Solubility 237 g/L (15 °C) in ethanol
14 g/L (15 °C) in diethyl ether[4]
Vapor pressure <0.001 mmHg (20 °C)[5]
Acidity (pKa) pKa1 = 1.25
pKa2 = 4.14[6]
Conjugate base Hydrogenoxalate
−60.05·10−6 cm3/mol
Thermochemistry[7]
91.0 J/(mol·K)
109.8 J/(mol·K)
−829.9 kJ/mol
Pharmacology
QP53AG03 (WHO)
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Corrosive
GHS labelling:
GHS05: CorrosiveGHS07: Exclamation markGHS08: Health hazard
Danger
H302+H312, H318, H402
P264, P270, P273, P280, P301+P312+P330, P302+P352+P312, P305+P351+P338+P310, P362+P364, P501
NFPA 704 (fire diamond)
Flash point 166 °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)[8]
NIOSH (US health exposure limits):
PEL (Permissible)
TWA 1 mg/m3[5]
REL (Recommended)
TWA 1 mg/m3 ST 2 mg/m3[5]
IDLH (Immediate danger)
500 mg/m3[5]
Safety data sheet (SDS) External MSDS
Related compounds
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Oxalic acid is an organic acid with the systematic name ethanedioic acid and chemical formula HO−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 comes from the fact that early investigators isolated oxalic acid from flowering plants of the genus Oxalis, commonly known as wood-sorrels. It occurs naturally in many foods. Excessive ingestion of oxalic acid or prolonged skin contact can be dangerous.

Oxalic acid has much greater acid strength than acetic acid. It is a reducing agent[9] and its conjugate bases hydrogen oxalate (HC2O4) 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.

  1. ^ a b "Front Matter". Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. pp. P001–P004. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
  2. ^ Record in the GESTIS Substance Database of the Institute for Occupational Safety and Health
  3. ^ Apelblat, Alexander; Manzurola, Emanuel (1987). "Solubility of oxalic, malonic, succinic, adipic, maleic, malic, citric, and tartaric acids in water from 278.15 to 338.15 K". The Journal of Chemical Thermodynamics. 19 (3): 317–320. doi:10.1016/0021-9614(87)90139-X.
  4. ^ Radiant Agro Chem. "Oxalic Acid MSDS". Archived from the original on 2011-07-15. Retrieved 2012-02-02.
  5. ^ a b c d NIOSH Pocket Guide to Chemical Hazards. "#0474". National Institute for Occupational Safety and Health (NIOSH).
  6. ^ Bjerrum, Jannik; Sillén, Lars Gunnar; Schwarzenbach, Gerold Karl; Anderegg, Giorgio (1958). Stability constants of metal-ion complexes, with solubility products of inorganic substances. London: Chemical Society.
  7. ^ CRC handbook of chemistry and physics : a ready-reference book of chemical and physical data. William M. Haynes, David R. Lide, Thomas J. Bruno (2016-2017, 97th ed.). Boca Raton, Florida. 2016. ISBN 978-1-4987-5428-6. OCLC 930681942.{{cite book}}: CS1 maint: location missing publisher (link) CS1 maint: others (link)
  8. ^ "Oxalic acid". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  9. ^ Ullmann's Encyclopedia of Industrial Chemistry. Wiley. 2005. pp. 17624/28029. doi:10.1002/14356007. ISBN 9783527306732.