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Solubility and Hydrolysis of Aluminum in Soil Solutions and Saturated‐paste Extracts
Author(s) -
Richburg John S.,
Adams Fred
Publication year - 1970
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/sssaj1970.03615995003400050019x
Subject(s) - hydrolysis , solubility , chemistry , monomer , soil water , ion , solubility equilibrium , aqueous solution , inorganic chemistry , nuclear chemistry , organic chemistry , soil science , geology , polymer
Three Coastal Plains soils that had exhibited different “critical” pH values for maximum cotton yields in field experiments were analyzed for Al solubility. Fertilized soil was used to verify critical pH by a root‐growth experiment in a growthchamber and to obtain displaced soil solutions (⅓‐bar moisture) and water extracts from saturated pastes. Extracts were also obtained from saturated pastes made with 0.01 M and 0.05 M KCl and with 0.0033 M and 0.0167 M CaCl 2 . Solutions were analyzed for pH, Ca, Mg, Mn, K, NH 4 + , Al, and SO 4 2‐ ; the remaining ions required for electrical neutrality were assumed to be Cl ‐ and NO 3 ‐ . A computer program, involving successive iterations of numerous equilibrium equations, was used to solve for ion activities and ion‐pair concentrations, including the Al‐ion species of Al 3+ , AlOH 2+ , Al 6 (OH) 15 3+ , and AlSO 4 + . The ion‐product of (Al 3+ ) (OH ‐ ) 3 was considerably larger and much more pH‐dependent with AlOH 2+ as the hydrolytic product than with Al 6 (OH) 15 3+ . Calculated (Al 3+ ) values were much lower for polymeric hydrolysis than for monomeric hydrolysis.