oxalic acid

noun

ox·​al·​ic acid (ˌ)äk-ˈsa-lik- 

: a poisonous strong acid (COOH)₂ or H₂C₂O₄ that occurs in various plants (such as spinach) as oxalates and is used especially as a bleaching or cleaning agent and as a chemical intermediate

Examples of oxalic acid in a Sentence

Recent Examples on the Web

This gene encodes a protein called OXO, short for oxalate oxidase, which breaks down oxalic acid, the fungus’s key weapon for invading and killing plant tissues. — Steve Strauss, The Conversation, 22 July 2026

Products designed to dissolve rust stains, including those made with oxalic acid, are often effective at lifting discoloration without damaging porcelain when used according to the manufacturer’s directions. — Jessica Safavimehr, Southern Living, 16 July 2026

Using a product like Bar Keeper's Friend, which contains oxalic acid, a natural rust remover, can help bring your cookware back to life. — Kelly Vaughan, Martha Stewart, 23 June 2026

These involve removal of thorium from REE containing acidic solution, as well as the selective extraction of REEs using oxalic acid. — Aditya Jadhav, Interesting Engineering, 10 June 2026

Word History

Etymology

French (acide) oxalique, from Latin oxalis

First Known Use

1788, in the meaning defined above

Rhymes for oxalic acid

• antacid
• placid

Medical Definition

oxalic acid

noun

ox·​al·​ic acid (ˌ)äk-ˌsal-ik- 

: a poisonous strong acid (COOH)₂ or H₂C₂O₄ that occurs in various plants as oxalates and is used especially as a bleaching or cleaning agent and as a chemical intermediate