This report reviews general approaches for determining the chemical species of ionic materials and outlines a feasible approach to the analytical speciation of Cr(III) and (VI), and Fe(II) and (III) in an aqueous solution. The results of the speciation are related to existing models through redox electrode potential measurements. An ion chromatographic technique based on the separation of anionic species was selected for the speciation. Nonspecific (conductivity) and specific (electronic absorption spectrometry) detection alternatives are discussed, and detection limits are projected into the low parts per billion range. The results of the present work suggest a technique for the quantitative characterization of certain elemental species in an aqueous phase. The significance of the results with respect to geochemical meodeling will depend upon the application of the methodology in a variety of geochemical environments. 57 refs., 5 figs., 2 tabs.