an polyunsaturated fatty acid, having 18 carbon atoms and two double bonds, essential for human nutrition; it is found in linseed, sunflower and other vegetable oils

(chemistry) a yellowish hygroscopic solid, H₃PO₃; a mild reducing agent

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

(organic chemistry) A white crystalline acid, C₂H₄(N(CH₂COOH)₂)₂, (and its sodium salt), a strong chelating agent with many industrial and analytical uses.

(inorganic chemistry) HIO₄ or H₅IO₆, the oxyacids of iodine in which iodine has the highest oxidation number; H₅IO₆ is a white crystalline substance (HIO₄ is not stable), and both are strong oxidizing agents.

(organic chemistry) A class of organic compounds having two acyl groups bonded to the same oxygen atom. They react with water to give carboxylic acids.

(organic chemistry) Any organic compound having two carboxylic acid functional groups.

(organic chemistry) Any of three isomeric aromatic organic benzenedicarboxylic acids, C₆H₄(COOH)₂; especially the ortho- isomer manufactured from naphthalene, used in the synthesis of dyes, perfumes and other compounds.

(chemistry) a solid white acid, H₂SeO₄, having the same structure and similar reactions as sulphuric acid

(chemistry) 2,4,6-trinitrophenol, C₆H₂(NO₂)₃, prepared by the nitration of phenol or of aspirin; a toxic, yellow, explosive substance used in dyes, explosives, and as an antiseptic