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This article in SSSAJ

  1. Vol. 22 No. 6, p. 503-508
    Received: Feb 17, 1958
    Accepted: May 13, 1958

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Kinetics of Potassium Release from Biotite1

  1. M. M. Mortland2



Data presented suggest that the rate of K release from biotite by leaching with NaCl is independent of the amount of K in the mineral during the depletion of a large proportion of the total K content. Optical and X-ray diffraction data show that weathering of biotite to vermiculite proceeds from the outside edge in toward the center of the particle. The 14Å. layers were found to have about 4 times the diffraction intensity of the 10Å. layers. Observation was made of the actual weathering front. The dependence of rate of K release on leaching rate, NaCl concentration, temperature, time, and particle size was evaluated and an empirical equation derived relating these variables. A theory is presented that the apparent zero-order type of reaction results from the maintenance of a constant concentration of reactive K similar to the principle of a saturated solution of a material in equilibrium with its solid phase. The logarithmic portion of the curve is suggested as the place where a “saturated solution” of reactive K can no longer be maintained and rate of release becomes dependent on the amount of unreacted K.

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