Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

The reduction kinetics of bromate ions with thiocyanate was studied polarographically and the dynamics of the BrO₃^-/SCN^- system was studied spectrophotometrically in the medium of perchloric acid in both cases. The reduction in the presence of an at least ten-fold excess of SCN^- ions is governed by the kinetics equation – d[Br(V)]/dt = a[Br(V)][SCN^-][H⁺]²/(1 + b[SCN^-]), where a = 19.2 ± 0.9 mol^-3 dm⁹, b = 4.4 ± 0.5 mol^-l dm³ at 20°C. A mechanism was proposed, based on the transfer of oxygen atom from HBrO₃ to SCN^- ion. The dynamic system BrO₃^-/SCN^-/HClO₄ is non-monotonous in character. According to the conditions, the production of bromine has a sigmoidal course preceded by a lag phase or the bromine concentration passes through a maximum.