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This article in SSSAJ

  1. Vol. 21 No. 1, p. 29-34
    Received: Jan 9, 1956
    Accepted: Apr 11, 1956

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Replaceability of Ammonium Fixed in Clay Minerals as Influenced by Ammonium or Potassium in the Extracting Solution1

  1. J. J. Hanway,
  2. A. D. Scott and
  3. G. Stanford2



Fixed NH4 in vermiculite and bentonite was completely released by distillation in NaOH solutions. Small amounts of K in the solutions, however, blocked this release of NH4. If the amount of K was in excess of 2 K ions per 100 Na ions, no fixed NH4 was released from vermiculite. With smaller amounts of K present, the amount of fixed NH4 released decreased as the K/Na ratio in solution was increased. In an equilibrium NaCl extraction, small amounts of either fixable ion, NH4 or K, in the solution prevented the release of fixed NH4. There was no blocking from the NH4 in the NaOH distillations since it was lost from the alkaline systems. In the salt solutions, NH4 was more effective than K in blocking the release of fixed NH4. The blocking effect of a gixen fixable/nonfixable ion ratio in the neutral salt solutions increased as the amount of salt extractant per gram of mineral was increased. This is due to the preferential adsorption of the fixable cations. Higher K/Na ratios were required to block the release of fixed NH4 in neutral salt solutions than in alkaline solutions. Ten K ions per 100 Na ions in NaCl were not as effective as 2 K ions per 100 Na ions in NaOH. Higher K/Na or NH4/Na ratios were required to block the release of fixed NH4 from bentonite than from vermiculite. The NH4/Na ratio required to completely prevent the release of fixed NH4 from bentonite by NaCl was 0.04 as compared to 0.02 for vermiculite.

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