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This article in SSSAJ

  1. Vol. 49 No. 4, p. 1070-1073
    Received: Oct 13, 1983
    Accepted: Feb 15, 1985

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Titration Method for Determination of Clay-Sized Carbonates1

  1. P. R. Bloom,
  2. K. Meter and
  3. J. R. Crum2



The carbonate content of soil clay suspension samples obtained by the pipet method was determined by the titration of the excess acid after reaction with an acetic acid buffer. The clay samples were reacted with a pH 4.0 buffer and titrated after 30-min of bubbling with air. Two variations of the method were evaluated. One was for use with an automatic titration and the other for manual titration. The accuracy of the two methods was demonstrated using a suspension of clay-sized reagent grade CaCO3. The coefficient of variation for the determination of CaCO3 in soil clays by the automatic titration method was <0.15 for samples containing <4 mg of CaCO3. The precision was greater for samples with CaCO3 contents up to 26 mg. With greater quantities of CaCO3 the 30-min reaction time was insufficient for complete dissolution because the rate of CaCO3 dissolution decreases with increasing suspension pH. The coefficient of variation for the manual titration method was <0.05 for all samples analyzed. The maximum quantity of CaCO3 that could be determined by the manual titration method was 55 mg.

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