The Generalized Two--Layer Model. Experimental Data. Data Compilation and Treatment Methods. Properties of Hydrous Ferric Oxide, Cation Sorption on Hydrous Ferric Oxide. Anion Sorption on Hydrous Ferric Oxide. Use of the Model and Data Base. The Coulombic Effect. Coherence and Extrapolation of Results. References. Appendices. Author Index. Subject Index.