Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

A spectrocoulometric macrocell with a direct-view optical probe was designed and constructed, where the optical signal is transferred by light-conducting glass or quartz fibres permitting to work at wavelengths above 410 or 300 nm. The method of measurement on the proposed equipment is described; it was tested in the study of the mechanism and kinetics of oxidation of Fe(bipy)₃²⁺ ions (bipy = 2,2'-bipyridyl) with the use of potentiostatic coulometric electrolysis with open-circuit relaxation at a suitable time. The primary product of electrolysis, Fe(bipy)₃³⁺, undergoes a follow-up hydrolytic reaction with the formation of a binuclear complex. The rate constant of the reaction of the first order involves the contributions, k_Bi, from all bases present in solution; the corresponding values for H₂O, OH^-, bipy, and CH₃COO^- ions at a ionic strength 0·5 mol dm^-3 and 25 °C were determined as k_OH = (5·0 ± 0·6) . 10⁵ mol^-1 dm³ s^-1, k_bipy = (1·3 ± 0·2) . 10^-1 mol^-1 dm³ s^-1, k_Ac = (5·8 ± 1·0) . 10^-2 mol^-1 dm³ s^-1, and k_H2O is not significant with respect to experimental errors.