A CHEMICALLY PLAUSIBLE E-PH DIAGRAM OF THE RU-H2O SYSTEM AT 25-DEGREES-C IN NON-COMPLEXING AQUEOUS ACIDIC SOLUTIONS - A REEXAMINATION

The thermodynamic E-pH diagram for the Ru-H2O system in acidic solutio ns is almost totally dominated by crystalline RuO2. Actually, there ex ists a considerable solution chemistry in this system, even in non-com plexing solutions. In a review of the chemistry and themodynamics of i norganic ruthenium compounds, Rard [Chem. Rev., 85, 1 (1985)] has pres ented a ''chemically plausible'' E-pH diagram of the Ru-H2O system in non-complexing aqueous solutions. This contribution presents a condens ed overview of the redox chemistry of ruthenium in non-complexing acid solutions (perchloric acid, methanesulfonic acid,...), mainly based o n the results of several years of research in this laboratory. Finally , this paper presents a more realistic version of the ''chemically pla usible'' E-pH diagram of the Ru-H2O system in non-complexing aqueous a cidic solutions.