Studies of the Electrochemical Kinetics of Indium: III . Systems and In + Combined Sulfate‐Chloride Electrolyte

Abstract

In previous papers the kinetics of the deposition and dissolution of indium in indium sulfate solutions at pH 2.5 had been studied by a galvanostatic method of single current pulses. Continuing this work and using a similar experimental technique, kinetics of the deposition and dissolution of indium in indium chloride and combined indium sulfate‐chloride solutions at pH 2.5 have been studied. The analysis of experimental data obtained by polarization in indium chloride solutions indicates that in the wide range of c.d.'s up to the cathodic and anodic processes occur near the equilibrium potential. When the c.d.'s are higher, it was found that the first cathodic reaction step is rate‐determining, and that during anodic polarization disproportionation reactions probably take place.The curves obtained by cathodic polarization in the combined sulfate‐chloride solutions show steep increases in the overvoltage of ca 400 mv, at certain characteristic c.d.'s, depending on the concentration of chloride in the solutions. It is concluded that in the range of c.d.'s before the steep increases, deposition of indium occurs by analogous mechanism as in the pure chloride medium. In the range after the steep increases, deposition of indium occurs as in the pure sulfate medium. The mechanism of this rapid change in the deposition of indium is discussed. From the analysis of the results of the anodic polarization in the combined electrolytes, it follows, that the third reaction step is rate‐determining in accordance with the observations for the pure sulfate and chloride solutions.