Standard electrode reaction rate constants for the one-electron reduction of Eu(CF3SO3)(3) on mercury in different concentrations of the supporting electrolyte tetrabutylammonium perchlorate in dimethylsulfoxide have been measured by single and double potential step chronocoulometry. Simulation programs were developed to extract the standard reaction rate constants from chronocoulometric experiments. The k(s)-values agreed well with data obtained from cyclic voltammetry and from ac techniques. The reaction rate constants depended on the concentration of the supporting electrolyte. Correlations of the k(s)-values with electrolyte properties are discussed. (C) 2005 Elsevier B.V. All rights reserved.