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
CAS Number	144-62-7 (anhydrous) ; 6153-56-6 (dihydrate) ;
3D model (JSmol)	Interactive image;
3DMet	B00059;
Beilstein Reference	385686
ChEBI	CHEBI:16995 ;
ChEMBL	ChEMBL146755 ;
ChemSpider	946 ;
DrugBank	DB03902 ;
ECHA InfoCard	100.005.123
EC Number	205-634-3;
Gmelin Reference	2208
KEGG	C00209 ;
MeSH	Oxalic+acid
PubChem CID	971;
RTECS number	RO2450000;
UNII	9E7R5L6H31 ; 0K2L2IJ59O (dihydrate) ;
UN number	3261
CompTox Dashboard (EPA)	DTXSID0025816 ;
	InChI InChI=1S/C6H6O6/c3-1(4)2(5)6/h(H,3,4)(H,5,6) Key: MUBZPKHOEPUJKR-UHFFFAOYSA-N ;
	SMILES OC(=O)C(=O)O;
Properties
Chemical formula	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); 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
Solubility in water	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);
Solubility	237 g/L (15 °C) in ethanol 14 g/L (15 °C) in diethyl ether
Vapor pressure	<0.001 mmHg (20 °C)
Acidity (pKa)	pKa1 = 1.25; pKa2 = 4.14
Conjugate base	Hydrogenoxalate
Magnetic susceptibility (χ)	−60.05·10−6 cm3/mol
Thermochemistry
Heat capacity (C)	91.0 J/(mol·K)
Std molar; entropy (S⦵298)	109.8 J/(mol·K)
Std enthalpy of; formation (ΔfH⦵298)	−829.9 kJ/mol
Pharmacology
ATCvet code	QP53AG03 (WHO)
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	Corrosive
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H302+H312, H318, H402
Precautionary statements	P264, P270, P273, P280, P301+P312+P330, P302+P352+P312, P305+P351+P338+P310, P362+P364, P501
NFPA 704 (fire diamond)	3 1 0 ACID
Flash point	166 °C (331 °F; 439 K)
	Lethal dose or concentration (LD, LC):
LDLo (lowest published)	1000 mg/kg (dog, oral); 1400 mg/kg (rat); 7500 mg/kg (rat, oral)
	NIOSH (US health exposure limits):
PEL (Permissible)	TWA 1 mg/m3
REL (Recommended)	TWA 1 mg/m3 ST 2 mg/m3
IDLH (Immediate danger)	500 mg/m3
Safety data sheet (SDS)	External MSDS
Related compounds
Related compounds	oxalyl chloride; disodium oxalate; calcium oxalate; phenyl oxalate ester;
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

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 (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.

^ ^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.
^ Record in the GESTIS Substance Database of the Institute for Occupational Safety and Health
^ 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.
^ Radiant Agro Chem. "Oxalic Acid MSDS". Archived from the original on 2011-07-15. Retrieved 2012-02-02.
^ ^a ^b ^c ^d NIOSH Pocket Guide to Chemical Hazards. "#0474". National Institute for Occupational Safety and Health (NIOSH).
^ 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.
^ 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)
^ "Oxalic acid". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
^ Ullmann's Encyclopedia of Industrial Chemistry. Wiley. 2005. pp. 17624/28029. doi:10.1002/14356007. ISBN 9783527306732.

[iupac2013-1] "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.

[GESTIS-2] Record in the GESTIS Substance Database of the Institute for Occupational Safety and Health

[apel1987-3] 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.

[PGCH-5] 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).

[Oxalic_Acid:_Uses-9] Ullmann's Encyclopedia of Industrial Chemistry. Wiley. 2005. pp. 17624/28029. doi:10.1002/14356007. ISBN 9783527306732.

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