Oxalic acid
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| Names | |||
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Preferred IUPAC name
Oxalic acid
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Systematic IUPAC name
Ethanedioic acid
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| Other names
Wood bleach
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| Identifiers | |||
144-62-7 
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| 3D model (Jmol) | Interactive image | ||
| 3DMet | B00059 | ||
| 385686 | |||
| ChEBI |
CHEBI:16995
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| ChEMBL |
ChEMBL146755
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| ChemSpider |
946
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| DrugBank |
DB03902
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| ECHA InfoCard | 100.005.123 | ||
| EC Number | 205-634-3 | ||
| 2208 | |||
| KEGG |
C00209 
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| MeSH | Oxalic+acid | ||
| PubChem | 971 | ||
| RTECS number | RO2450000 | ||
| UNII |
9E7R5L6H31
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| UN number | 3261 | ||
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| Properties | |||
| C2H2O4 | |||
| Molar mass | 90.03 g·mol−1 (anhydrous) 126.065 g mol−1 (dihydrate) |
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| Appearance | White crystals | ||
| Odor | odorless | ||
| Density | 1.90 g cm−3 (anhydrous) 1.653 g cm−3 (dihydrate) |
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| Melting point | 189 to 191 °C (372 to 376 °F; 462 to 464 K) 101.5 °C (214.7 °F; 374.6 K) dihydrate |
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| 143 g/L (25 °C) | |||
| Solubility | 237 g/L (15 °C) in ethanol
14 g/L (15 °C) in diethyl ether |
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| Vapor pressure | <0.001 mmHg (20 °C) | ||
| Acidity (pKa) | 1.25, 4.14 | ||
| -60.05·10−6 cm3/mol | |||
| Pharmacology | |||
| QP53AG03 (WHO) | |||
| Hazards | |||
| Main hazards |  T |
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| Safety data sheet | External MSDS | ||
| NFPA 704 | |||
| Flash point | 166 °C (331 °F; 439 K) | ||
| Lethal dose or concentration (LD, LC): | |||
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LDLo (lowest published)
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1000 mg/kg (dog, oral) 1400 mg/kg (rat) 7500 mg/kg (rat, oral) |
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| US health exposure limits (NIOSH): | |||
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PEL (Permissible)
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TWA 1 mg/m3 | ||
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REL (Recommended)
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TWA 1 mg/m3 ST 2 mg/m3 | ||
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IDLH (Immediate danger)
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500 mg/m3 | ||
| Related compounds | |||
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Related compounds
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oxalyl chloride disodium oxalate calcium oxalate phenyl oxalate ester |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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 (what is ?) |
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| Infobox references | |||
Oxalic acid is an organic compound with the formula C2H2O4. It is a colorless crystalline solid that forms a colorless solution in water. Its condensed formula is HOOCCOOH, reflecting its classification as the simplest dicarboxylic acid. Its acid strength is much greater than that of acetic acid. Oxalic acid is a reducing agent and its conjugate base, known as oxalate (C
2O2−
4), is a chelating agent for metal cations. Typically, oxalic acid occurs as the dihydrate with the formula C2H2O4·2H2O. Excessive ingestion of oxalic acid or prolonged skin contact can be dangerous.
The preparation of salts of oxalic acid from plants had been known, at the latest, since 1745, when the Dutch botanist and physician Herman Boerhaave isolated a salt from sorrel. By 1773, François Pierre Savary of Fribourg, Switzerland had isolated oxalic acid from its salt in sorrel.
In 1776, Swedish chemists Carl Wilhelm Scheele and Torbern Olof Bergman produced oxalic acid by reacting sugar with concentrated nitric acid; Scheele called the acid that resulted socker-syra or såcker-syra (sugar acid). By 1784, Scheele had shown that "sugar acid" and oxalic acid from natural sources were identical.
In 1824, the German chemist Friedrich Wöhler obtained oxalic acid by reacting cyanogen with ammonia in aqueous solution. This experiment may represent the first synthesis of a natural product.
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