HOI versus HOIO Selectivity of a Molten-type AgI Electrode

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• 作者：G谩bor Holl贸 ; Krist贸f K谩ly-Kullai ; Thuy B. Lawson ; Zolt谩n Noszticzius ; Maria Wittmann ; Norbert Muntean ; Stanley D. Furrow ; Guy Schmitz
• 刊名：Journal of Physical Chemistry A
• 出版年：2014
• 出版时间：July 3, 2014
• 年：2014
• 卷：118
• 期：26
• 页码：4670-4679
• 全文大小：397K
• ISSN：1520-5215

文摘

AgI electrode is often applied not only to determine iodine concentration but also to follow oscillations in the weakly acidic medium of the Bray鈥揕iebhafsky and Briggs鈥揜auscher reactions where it partly follows the hypoiodous acid (HOI) concentration. It is known that HOI attacks its matrix in the corrosion reaction: AgI + HOI + H⁺ Ag⁺ + I₂ + H₂O and the AgI electrode measures the silver ion concentration produced in that reaction. The signal of the electrode can be the basis of sensitive and selective HOI concentration measurements only supposing that an analogous corrosive reaction between AgI and iodous acid (HOIO) can be neglected. To prove that assumption, the authors calibrated a molten-type AgI electrode for I^{鈥?/sup>, Ag+, HOI, and HOIO in 1 M sulfuric acid and measured the electrode potential in the disproportionation of HOIO, which is relatively slow in that medium. Measured and simulated electrode potential versus time diagrams showed good agreement, assuming that the electrode potential is determined by the HOI concentration exclusively and the contribution of HOIO is negligible. An independent and more direct experiment was also performed giving the same result. HOIO was produced with a new improved recipe. Conclusion: an AgI electrode can be applied to measure the HOI concentration selectively above the so-called solubility limit potential.}