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This article in SSSAJ

  1. Vol. 43 No. 2, p. 318-323
     
    Received: Aug 28, 1978
    Published: Mar, 1979


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doi:10.2136/sssaj1979.03615995004300020016x

Analytical Properties of the Soluble, Metal-Complexing Fractions in Sludge-Soil Mixtures: IV. Determination of Carboxyl Groups in Fulvic Acid1

  1. Kenneth M. Holtzclaw and
  2. Garrison Sposito2

Abstract

Abstract

A detailed experimental examination of the titration behavior and reaction with calcium acetate of a series of model organic acids led to the conclusion that the standard Ca(OAc)2 method for the determination of COOH groups in organic matter would be ineffective for sludge-derived fulvic acid. In particular, it was shown that positive interferences from SO3H groups and acidic OH groups could be expected. A modified Ca(OAc)2 method was developed, consisting of: (i) conversion of fulvic acid to K/H fulvate, (ii) reaction with 1N calcium acetate, (iii) distillation of the acetic acid product, and (iv) titration of the acetic acid with 0.1N NaOH, in which these positive interferences do not occur. The modified method was applied successfully to two representative sludge-derived fulvic acids, a soil-derived fulvic acid, and two model humic polymers, all of which exhibited positive interferences with the standard Ca(OAc)2 method.

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