Solubility Measurements of Phases in Three Illites1

J. A. Kittrick
Department of Agronomy and Soils, Washington State University, Pullman, Washington 99164
1 Scientific paper No. 5946, College of Agriculture Research Center, Washington State University, Pullman, Washington. Project 1885.

Abstract: Goose Lake, Beavers Bend, and Fithian illites were equilibrated in the presence of goethite (or hematite) at room temperature for as long as 2.6 yr. Kaolinite of known stability was added to some samples. Samples of solution were obtained after centrifuging with, or without, immiscible displacement or column leaching. Equilibrium was indicated by constant values over a long period of time, with kaolinite solubility as an internal indicator, and most importantly, by the approach to equilibrium from both undersaturation and supersaturation. Data plots indicate that the illites contain two or more phases or components in equilibrium with each other. Statistical and graphical techniques were used to analyze hundreds of equilibrations. The constancy of pK values for various expressions indicates that bulk illite composition and pyrophyllite are likely solution-controlling phases or components, but that muscovite, leucophyllite, phlogopite, and talc are not. A muscovite-like phase, of lower K content than muscovite, fit one pK expression well, but failed on two others.

Key Words: Equilibration • Illite • Kaolinite • Phase analysis • Pyrophyllite • Solubility

Clays and Clay Minerals; April 1984 v. 32; no. 2; p. 115-124; DOI: 10.1346/CCMN.1984.0320205
© 1984, The Clay Minerals Society
Clay Minerals Society (www.clays.org)