Stability of Soil Smectite From a Houston Black Clay *

C. D. Carson, J. A. Kittrick, J. B. Dixon and T. R. McKee
Department of Soil and Crop Sciences, Texas A & M University, College Station, TX 77843, U.S.A.
* Investigations supported by Texas Agricultural Experiment Station, College Station.
Present address: Department of Agronomy and Soils, Washington State University, Pullman, WA 99163, U.S.A.
Present address: Department of Oceanography, Texas A & M University.

Abstract: The stability of smectite separated from a Houston Black clay soil was studied by solubility methods in an acid environment. High Silicon levels (supersaturated with respect to amorphous Si) probably were due to dissolution of the smectite and slow precipitation of amorphous Silicon. Also, mica and vermiculite impurities may have contributed to high solution Si values. Solubility data from equilibrium solutions of various treatments and chemical structural analyses permitted the formulation of a solubility equation. The ΔG°f for the Houston Black smectite computed from pK values was —2433.9 ± 0.8 kcal/mole. The stability of this clay could then be determined by calculations for any desired solution environment. It was found that under some conditions this soil smectite could be more stable than Belle Fourche and Aberdeen montmorillonites. Therefore, it appears that this soil clay has the required stability area in which it can form in nature.

Clays and Clay Minerals; August 1976 v. 24; no. 4; p. 151-155; DOI: 10.1346/CCMN.1976.0240401
© 1976, The Clay Minerals Society
Clay Minerals Society (www.clays.org)