oxalic acid

from The American Heritage® Dictionary of the English Language, 4th Edition

• n. A poisonous, colorless crystalline organic acid, HOOCCOOH·2H2O, found in many plants, such as spinach, and used as a bleach and rust remover.

from Wiktionary, Creative Commons Attribution/Share-Alike License

• n. A colourless, crystalline dicarboxylic acid, (COOH)2, found in rhubarb, spinach and other plants, often as crystals of the calcium salt.

from the GNU version of the Collaborative International Dictionary of English

• adj. a dibasic acid (HO.CO.CO.OH), existing combined in oxalis as an acid potassium oxalate, and in many plant tissues as the calcium oxalate. It is prepared on a large scale, by the action of fused caustic soda or potash on sawdust, as a white crystalline substance, which has a strong acid taste, and is poisonous in large doses. It is used in dyeing, calico printing, bleaching flax and straw, the preparation of formic acid, and in salts of lemon for removing ink stains, mold, etc.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• n. a toxic colorless crystalline organic acid found in oxalis and other plants; used as a bleach and rust remover and in chemical analysis