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Solution Activities of Aluminum and Silicon in Highly Weathered Soils that contain Gibbsite and Kaolinite
Author(s) -
Weaver R. M.,
Bloom P. R.
Publication year - 1977
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1977.03615995004100040042x
Subject(s) - gibbsite , kaolinite , aluminosilicate , oxisol , dissolution , aluminium , chemistry , soil water , allophane , boehmite , inorganic chemistry , clay minerals , mineralogy , geology , catalysis , organic chemistry , soil science
Solution activities of aluminum (Al 3+ ) and monosilicic acid (Si(OH) 4 ) in dilute acid suspensions of six Brazilian Oxisols were measured over a period of 145 days. The steady state activity function of pH‐⅓pAl ranged from 1.86 to 2.69, while that of pSi(OH) 4 ranged from 3.69 to 4.22. Although all of the soils contained kaolinite and gibbsite, the observed solute activity functions of pH‐⅓pAl and pSi(OH) 4 deviated considerably from those expected for a thermodynamic equilibrium between gibbsite and kaolinite. It was found that the solution activities of Al and Si(OH) 4 in these soils appeared to result from the dissolution of a surface aluminosilicate component (R) of variable composition‐{[Al(OH) 3 ] (1‐ x ) [SiO 2 ] x } R rather than gibbsite and kaolinite.