Oxalic Acid | Formula, Uses, & Facts | Britannica

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External Websites

• National Center for Biotechnology Information - PubMed Central - Toxic and signalling effects of oxalic acid
• USDA Agricultural Marketing Service - Oxalic acid (PDF)
• CORE - Spectrophotometric Determination of Oxalic Acid in Dietary Sources Through Catalytic Titration with Hexavalent Chromium (PDF)
• Research Online at ECU - Oxalic acid: A blooming organic acid for postharvest quality preservation of fresh fruit and vegetables (PDF)
• CAMEO Chemicals - Oxalic Acid
• WebMD - Foods High in Oxalates
• Healthline - Oxalate (Oxalic Acid): Good or Bad?
• Frontiers - Frontiers in Nuclear Engineering - Methods for the destruction of oxalic acid decontamination effluents
• CiteSeerX - Microbial Metabolism of Oxalic Acid (PDF)
• Mount Sinai - Oxalic acid poisoning Information
• ACS Publications - Oxalic Acid Recovery from High Iron Oxalate Waste Solution by a Combination of Ultrasound-Assisted Conversion and Cooling Crystallization
• U.S. Environmental Protection Agency - Oxalic Acid

Ask the Chatbot a Question Also known as: ethanedioic acid Written and fact-checked by Britannica Editors Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Britannica Editors Last updated Dec. 19, 2025 •History Table of Contents Table of Contents Ask the Chatbot

oxalic acid, a colourless, crystalline, toxic organic compound belonging to the family of carboxylic acids. Oxalic acid is widely used as an acid rinse in laundries, where it is effective in removing rust and ink stains because it converts most insoluble iron compounds into a soluble complex ion. For the same reason, it is the chief constituent of many commercial preparations used for removing scale from automobile radiators.

Also called: ethanedioic acid (Show more) Related Topics: dicarboxylic acid (Show more) On the Web: Research Online at ECU - Oxalic acid: A blooming organic acid for postharvest quality preservation of fresh fruit and vegetables (PDF) (Dec. 19, 2025) (Show more) See all related content

The formula of oxalic acid is (C2H2O4); its usual form is that of the crystalline hydrate, (COOH)2·2H2O. Known as a constituent of wood sorrel as early as the 17th century, oxalic acid was first prepared synthetically in 1776. It is manufactured by heating sodium formate in the presence of an alkali catalyst, by oxidizing carbohydrates with nitric acid, by heating sawdust with caustic alkalies, or by fermentation of sugar solutions in the presence of certain molds.

The Editors of Encyclopaedia Britannica This article was most recently revised and updated by Adam Augustyn.