Reactions of Some Iron, Zinc, and Manganese Chelates in Various Soils
1956
Wallace, A. | Lunt, O. R.
Polyamine-polyacetate chelating agents were previously reported to be fixed on the clay portion of soils. Further studies have been made to characterize the method of fixation on clays. From these studies it has been postulated that ferric iron EDTA can become attached to clay through an Fe-O-clay linkage on the edges of clay crystals. Divalent zinc and manganese EDTA chelates did not fix on clays. The degree of fixation in relation to the cation exchange capacity of different clay minerals indicated the fixation occurs principally on the edges of the clay rather than on the basal planes. This theory is supported by X-ray examination. Some divalent metal chelates other than EDTA fixed readily on clays while others did not. A new chelating agent, APCA, was examined which was extremely stable under alkaline soil conditions. Iron APCA was not adsorbed on clay in the pH range encountered in calcareous soils. Zinc and manganese APCA, in contrast, readily fixed on clay. For certain chelating agents in various soils, there was an isotopic exchange which sometimes was of considerable magnitude between the chelated iron and the natural iron of the soil.
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