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当溶液中含有溴化物时,Fe(Ⅲ)络合物与银电极之间的反应较慢。如果使用碘化物、反应会加快。电流加和原理和溶度积常数可用来解释碘化物对Fe(Ⅲ)络合物氧化金属银反应加速作用机理。在电极表面上氧化形成的AgI较之溴化银更难用硫代硫酸盐络合除去。 在含有Fe(Ⅲ)络合物的溴化物和碘化物混合溶液中,卤化银在银电极表面上的生成速率随溶液中碘化物浓度的增大先是下降,然后上升。因为AgI较低的溶度积常数,AgI/Ag的阳极化曲线与Fe(Ⅲ)络合物/Fe(Ⅱ)络合物氧化还原对的阴极化曲线间较负的混合电位,在浸入含有少量碘化物和一定浓度溴化物的Fe(Ⅲ)络合物溶液的银电极表面上,优先生成AgI。
When the solution contains bromide, the reaction between the Fe (III) complex and the silver electrode is slow. The reaction will be accelerated if iodide is used. The current summation principle and the solubility product constant can be used to explain the accelerating mechanism of iodide on the oxidation reaction of Fe (Ⅲ) complex with silver metal. AgI formed on the surface of the electrode is more difficult to remove by thiosulfate complexation than silver bromide. In the mixed solution of bromide and iodide containing Fe (III) complex, the formation rate of silver halide on the silver electrode surface first decreases with the increase of iodide concentration in the solution, and then increases. Because of the lower solubility product constant of AgI, the more negative mixing potential between the anodic polarization curve of AgI / Ag and the cathodic polarization curve of the Fe (III) complex / Fe (II) complex redox pair, A small amount of iodide and a certain concentration of bromide Fe (Ⅲ) complex solution silver electrode surface, giving priority to the formation of AgI.