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This article in SSSAJ

  1. Vol. 41 No. 6, p. 1092-1097
    Received: Nov , 1976
    Accepted: June 24, 1977

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Estimated Association Constants for Some Complexes of Trace Metals with Inorganic Ligands1

  1. Shas V. Mattigod and
  2. Garrison Sposito2



Chemical equilibrium studies of trace metals in soils by an ion-association model require reliable data on thermodynamic association constants for various metal-ligand complexes. Therefore, available experimental data at 25°C were compiled for complexes of the transition metal cations Mn2+, Fe2+, Nl2+, Cu2+, and Zn2+ with the ligands CO32-, HCO3-, SO42-, HSO4-, PO43-, HPO42-, H2PO4-, Cl-, and OH-. However, experimental values of the thermodynamic association constants for many of the complexes were not available. This lack of information was alleviated by employing the theoretical model of Kester and Pytkowicz and the semiempirical models of Nieboer and McBryde, and Van Panthaleon Van Eck to make estimates of the as yet unmeasured association constants. These estimated constants were tabulated in a compact form along with the experimental values. This compilation of 100 association constants, although provisional, should prove helpful in a variety of studies on trace metal equilibria in soils until more reliable experimental data become available.

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