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CATION EXCHANGE REACTIONS
Author(s) -
SALMON R. C.
Publication year - 1964
Publication title -
journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 0022-4588
DOI - 10.1111/j.1365-2389.1964.tb02225.x
Subject(s) - chemistry , magnesium , illite , potassium , bentonite , soil water , adsorption , saturation (graph theory) , cation exchange capacity , peat , divalent , inorganic chemistry , calcium , clay minerals , environmental chemistry , mineralogy , soil science , geology , organic chemistry , ecology , paleontology , mathematics , combinatorics , biology
Summary Wyoming bentonite, Blisworth illite, and a fen peat were saturated with different proportions of calcium, magnesium, and potassium, and exchange between these cations was studied by measuring their activity ratios in dilute equilibrium solutions. With both clays the activity ratio aMg/aCa in solution was linearly related to the ratio of adsorbed Mg/Ca, the former being 1.22 times larger than the latter ratio. Peat held magnesium much less strongly than calcium, and the difference increased with increasing magnesium saturation. With all three materials the activity ratio aMg/aCa+Mg in solution was curvilinearly related to the percentage magnesium saturation. Peat adsorbed potassium less strongly relative to the divalent cations than did the clays, and bentonite adsorbed potassium less strongly than illite. Decreasing the Ca:Mg ratio increased the strength with which peat adsorbed potassium, but had no effect on potassium adsorption by the clays. Exchange between magnesium and calcium in forty British soils was studied by measuring the concentration ratio [Mg]/[Ca+Mg] in equilibrium soil solutions. The relation between [Mg]/[Ca+Mg] in solution and the ratio of exchangeable Mg/(Ca+Mg) in different soils varied within the range covered by peat and bentonite or illite, suggesting that differences between soils might be due to different organic‐matter contents. The extent to which [Mg]/[Ca + Mg] in solution was altered by changes in the exchangeable magnesium content differed considerably between soils. These differences were not all explained by variations in exchange capacity, showing that different soils adsorb magnesium with differing strengths relative to calcium.