humic acid

a brown, melanin-tinted mixture of polymers, found in lignite, peat, and soils, where it acts as a cation exchange agent: used in drilling fluids and inks.
[1835-45]

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      one of two classes of natural acidic organic polymer that can be extracted from humus found in soil, sediment, or aquatic environments. The process by which humic acid forms in humus is not well understood, but the consensus is that it accumulates gradually as a residue from the metabolism of microorganisms. Its structure is unlike that of proteins or carbohydrates, the two most common organic polymers found in biological material; instead, humic acid can be characterized as a loose assembly of aromatic polymers of varying acidity and reactivity.

      Humic acid has the average chemical formula C187H186O89N9S1 and is insoluble in strong acid (pH = 1). A 1:1 hydrogen-to-carbon ratio indicates a significant degree of aromatic character (i.e., the presence of benzene rings in the structure), whereas a low oxygen-to-carbon ratio indicates fewer acidic functional groups than occur in fulvic acid, (fulvic acid) the other acidic organic polymer that can be extracted from humus. Transition and heavy metals—for example, Fe3+ or Pb2+—as well as other compounds having aromatic or hydrophobic (water-insoluble) chemical structures (i.e., organic pesticides or anthropogenic hydrocarbons), react strongly with humic acid. This property makes it an effective agent in sequestering many of the pollutants in terrestrial and aquatic environments.

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Universalium. 2010.

Look at other dictionaries:

  • Humic acid — is one of the major components of humic substances [http://www.ihss.gatech.edu/whatarehs.html] which are dark brown and major constituents of soil organic matter humus that contributes to soil chemical and physical quality and are also precursors …   Wikipedia

  • humic acid — n. a brown powder consisting of organic acids, derived from humus …   English World dictionary

  • humic acid — noun a dark brown humic substance that is soluble in water only at pH values greater than 2 the half life of humic acid is measured in centuries • Hypernyms: ↑humic substance * * * noun : any of various organic acids that are insoluble in alcohol …   Useful english dictionary

  • humic acid — Humin Hu min, n. [L. humus the earth, ground.] (Chem.) A bitter, brownish yellow, amorphous substance, extracted from vegetable mold, and also produced by the action of acids on certain sugars and carbohydrates; called also {humic acid}, {ulmin} …   The Collaborative International Dictionary of English

  • humic acid — hu·mic acid hyü mik , yü n any of various organic acids obtained from humus …   Medical dictionary

  • humic acid — noun Date: 1843 any of various organic acids obtained from humus …   New Collegiate Dictionary

  • humic acid — noun a complex mixture of organic acids produced by the decomposition of vegetable matter …   Wiktionary

  • Humic — Hu mic, a. [L. humus the earth, ground: cf. F. humique.] (Chem.) Pertaining to, or derived from, vegetable mold; as, humic acid. See {Humin}. [1913 Webster] …   The Collaborative International Dictionary of English

  • humic substance — noun an organic residue of decaying organic matter • Hypernyms: ↑organic compound • Hyponyms: ↑fulvic acid, ↑humic acid, ↑humin …   Useful english dictionary

  • humic — HÚMIC, humice, adj.n. (Despre sol) Bogat în humus. – Din fr. humique. Trimis de gall, 13.09.2007. Sursa: DEX 98  húmic adj. m., pl. húmici; f. sg. húmică, pl. húmice …   Dicționar Român

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