A General Approach for Calculating Speciation and Poising Capacity of Redox Systems with Multiple Oxidation States: Application to Redox Titrations and the Generation of pepsilon-H Diagrams

摘要

Providing detailed descriptions of complex systems in terms ofproton and redox equilibria is a challenge faced by many chemists. In the environmental chemistry field a number of comprehensive texts have advanced the use of pH and pepsilon as master variaalbes in defining the geochemistry of aquatic systems in equilibrium with the atmosphere and soils (1-3). These variables define the classic pepsilon-pH diagram as described by Sillen in this Journal (4). Derivatives of concentration with respect to pH and pepsilon define proton buffer capacity and electron poising capacity, respectively. These concepts build directly of the conventional quantitative analysis curriculum emphasizing acid-base, metal complexation, and redox equilibria. Analysis of relevant geochemical systems to produce pepsilon-pH diagrams is interesting for many students and nicely integrates many of the concepts introduced in quantitative analysis.