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Soil Science Society of America Journal Abstract -

Relationships Between Particle Size and Potassium Release From Biotite and Its Analogues1


This article in SSSAJ

  1. Vol. 25 No. 6, p. 473-476
    Received: Jan 3, 1961
    Accepted: Feb 16, 1961

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  1. M. M. Mortland and
  2. K. Lawton2



The relationships of particle size of biotite to K release, oxidation state of iron, cation-exchange capacity, and total charge of the mineral were studied. The first stage of alteration, accomplished by leaching 15 minutes with 0.1N NaCl, showed a marked relationship to particle size. At this point, the only K removed was that on the external surfaces of the particles, and consequently the fine particles lost a larger percentage of their total K at this stage than did the larger particles. However, by the last stage where 50% of the total K had been removed, the large particles generally had lost as much as the fine. Once the initially exchangeable K has been removed, the release of matrix K from the particles is suggested to be controlled by the concentration gradient and the geometry of the diffusion path available for the exchanging ions, Na and K. The equilibrium concentration of K in 0.1N NaCl was shown to be proportional to the total K content of biotite which had been altered to different levels of total K. The oxidation state of iron in the biotite was shown to be a function of particle size and extent of alteration.

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