HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Reneau,, R. B. Articles by Fiskell, J. G. A. Search for Related Content PubMed Articles by Reneau,, R. B., Jr. Articles by Fiskell, J. G. A. GeoRef GeoRef Citation Agricola Articles by Reneau,, R. B. Articles by Fiskell, J. G. A.

Mineralogical Properties of Clays from Panama Soils¹

ABSTRACT

Panama soil clays from eight Alfisols were studied extensively by X-ray diffraction, DTA, and infrared spectroscopy. Composition of these clays was examined before and after sequential selective dissolution with citrate-dithionite and hot 0.5N NaOH for removal of amorphous components. Vermiculite was the dominant mineral in three clays, and smectite in four others. In one soil, a poorly crystalline mineral was present and this clay had an unusally large low-temperature endotherm which was attributed to a combination of halloysite, an expandable phyllosilicate, and amorphous materials. In the other clays the shape of the high-temperature endotherms indicated presence of kaolinite ranging in content from 19 to 27%. Infrared spectra showed a large absorption band of 3,450 cm^-1 for water adsorbed to clay surfaces indicating the presence of halloysite and/or 2:1 expanding phyllosilicates. Absorption bands at 910 cm^-1 found for some clays was attributed to A1-O-H bending presumably from halloysite. Mica content ranges from 1.4 to 12.0%. Considerable interlayer hydroxy-A1 and hydroxy Fe appears to be present in the expanding phyllosilicates from incomplete collapse of spacings after K saturation and heating to 550C. After sequential dissolutions, and allowing for CEC of kaolinite and mica, CEC of the expanding phyllosilicate fractions ranges from 61 to 152 meq/100 g at pH 4.8 and increased about 15% more when measured at pH 8.2.

¹ Florida Agricultural Experiment Stations Journal Series no. 3657. Contribution by Department of Soil Science, University of Florida, Gainesville 32601, presented before Div. S-9, Soil Science Society of America, Aug. 1970 at Tucson, Ariz. A major portion of this work is from a dissertation by the senior author supported by funds from Battelle Memorial Institute for study of a proposed sea-level canal by nuclear excavation in eastern Panama.

² Research Associate, now Assistant Professor at Virginia Polytechnic Institute, and Professor of Soils, respectively.

Received for publication August 30, 1971. Accepted for publication March 1, 1972.