In aquatic systems a reaction between tetrathionate and cyanide results in the formation of thiocyanate. We have studied kinetics of the reactions of tetrathionate with free cyanide and two cyanide complexes, hexacyanoferrate(II) and hexacyanoferrate(III), at the environmentally relevant conditions. For the reaction between tetrathionate and free cyanide, the rate constant and the activation energy, but not the reaction order, strongly depend on pH. Our observations allow to propose the following pathways of thiocyanate formation by the reactions of free cyanide with tetrathionate: (1) tetrathionate reacts relatively slow with hydrogen cyanide at acidic and neutral conditions; and (2) tetrathionate reacts relatively fast with cyanide anion under highly alkaline conditions. Depending on environmental conditions, the half-lives of the reaction between free cyanide and tetrathionate will be in the ranges of hours to several years. Reactions of tetrathionate with hexacyanoferrate(II) and hexacyanoferrate(III) have no environmental significance as they are slower than the decomposition of tetrathionate. Strategy for improvement of analytical protocols for analysis of tetrathionate and cyanide is proposed based on the detected kinetics parameters.

在水生系统中，连四硫酸盐和氰化物之间的反应导致形成硫氰酸盐。我们研究了在环境相关条件下连四硫酸盐与游离氰化物以及两种氰化物配合物六氰基铁酸盐（II）和六氰基铁酸盐（III）的反应动力学。对于连四硫酸盐和游离氰化物之间的反应，速率常数和活化能，但不是反应级数，很大程度上取决于 pH 值。我们的观察结果提出了游离氰化物与连四硫酸盐反应形成硫氰酸盐的以下途径：（1）连四硫酸盐在酸性和中性条件下与氰化氢反应相对缓慢； (2)连四硫酸盐在强碱性条件下与氰化物阴离子反应较快。根据环境条件，游离氰化物和连四硫酸盐之间的反应半衰期将在数小时至数年范围内。连四硫酸盐与六氰基铁酸盐(II)和六氰基铁酸盐(III)的反应没有环境意义，因为它们比连四硫酸盐的分解慢。根据检测到的动力学参数，提出了连四硫酸盐和氰化物分析方法的改进策略。