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Aluminum in Soils: IV. The Role of Aluminum in Soil Acidity
Author(s) -
Heddleson M. R.,
McLean E. O.,
Holowaychuk N.
Publication year - 1960
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/sssaj1960.03615995002400020008x
Subject(s) - chemistry , soil water , titration , soil ph , cation exchange capacity , hydrolysis , titration curve , inorganic chemistry , ion exchange resin , ion exchange , adsorption , aluminium , nuclear chemistry , environmental chemistry , ion , soil science , organic chemistry , geology
Samples of soils representing a wide range of pH and extractable Al were treated with increments of acid and base and incubated for 3 months. The extractable Al and exchange acidity were measured. Samples were also treated with increments of AlCl 3 and measurements of extractable Al and exchange acidity again made. Various resin titrations were made in order to compare the reaction of TEA with both Al and H, and to observe the acid properties of Al ions. An increase in both extractable Al and exchange acidity was found following treatment of soils with acid. The increase was much greater in mildly acid soils than in highly acid samples. The increase in extractable Al and exchange acidity was generally of the same order of magnitude. Acid, strongly weathered soils were found to adsorb much less Al than did neutral, less weathered soils treated with increments of AlCl 3 . Apparently Al was near equilibrium in acid soils but not in mildly acid or neutral samples. Al resin was shown to titrate similar to a weak acid while H resin titration more nearly resembled a strong acid. Titration of Al resin with KOH in absolute alcohol indicated that hydrolysis was necessary for Al to exhibit acid properties. Results show that soil acidity is composed of both H and Al and that measurement of acidity by TEA measures at least part of the Al.