An Evaluation of Job's Method of Continuous Variations as Applied to Soil Organic Matter‐Metal Ion Interactions

Abstract

AbstractThe literature dealing with the application of Job's method of continuous variations to the study of soil organic matter‐metal ion interactions has been reviewed, and an introduction to the fundamental chemistry necessary for an understanding of these interactions is presented. The method of continuous variations was applied to simple systems consisting of metal ions and mixtures of discrete ligands. The behavior of these “model” systems was compared to that of the more complicated soil organic matter systems. Following a consideration of the fundamental principles of Job's method and of its boundary conditions and limitations, it was concluded that this method is not directly applicable to the study of soil organic matter‐metal ion interactions. This conclusion was substantiated by experiments carried out on the simple “model” systems as well as those on fulvic acid itself. Explanations are proposed to account for the deceptive results which were obtained when this method was erroneously applied by other workers to the investigation of soil organic matter‐metal ion interactions in the past. Possible interferences, due to scattering of light, during the study of soil organic matter‐metal ion reactions by UV‐visible absorption spectroscopy are considered.