Polarographic Behavior of Indium in Presence of Chloride.

Electrochemical activity of various types of aqueous In(III) species at a mercury electrode

“…The rate of supply of each species to the electrode surface will be rate limiting when 0 Values of 0 i k in the range 10 -11 to 10 -14 m s -1 have been derived for 3 26 In(H O) + from measurements with a dropping mercury electrode in acidic media [2,58]. Thus the rate of electron transfer is the rate limiting step in the reduction of 3 26 In(H O) + , and its contribution to the overall electrodic reduction will be limited by its slow rate of electron transfer in agreement with experimental data [2][3][4]. As the pH is increased to values at which hydroxy species are present in non-negligible concentrations, a reversible reduction process is detected at potentials much more positive than those at which the irreversible reduction of 3 26 In(H O) + occurs.…”

“…As the pH is increased to values at which hydroxy species are present in non-negligible concentrations, a reversible reduction process is detected at potentials much more positive than those at which the irreversible reduction of 3 26 In(H O) + occurs. The reversible wave reported at E1/2 of -0.55 V (vs. SCE) [2][3][4] indicates that the contribution of the various In(III) hydroxy species to the overall electrodic reduction is governed by their rate of diffusion towards the electrode surface (also see Results and Discussion). The differences between the various In(III) species in terms of the relative rates of the elementary processes governing electrochemical reactivity, determine their relative contributions to the overall electrodic reduction.…”

“…Voltammetric waves recorded for In(III) show an irreversible wave for 3 26 In(H O) + (E1/2 = -0.95V vs. SCE) when the pH is sufficiently low to suppress hydrolysis; as the pH is increased to values at which hydroxy species are present in solution a reversible diffusion-controlled wave appears (E1/2¨= -0.55 V vs. SCE) [2][3][4]. This behaviour was also observed in the present work (Fig.…”

“…In(III) readily hydrolyses at low pH: see ref [1] for a critical review of the literature on the hydrolysis constants. Literature from the 1960s evidences that voltammetric waves recorded for free 3 26 In(H O) + with a dropping mercury electrode at a pH sufficiently low to suppress hydrolysis, show a drawn-out electrochemically irreversible wave for the 3 26 In(H O) + species with halfwave potential, E1/2, of -0.95 V (vs. saturated calomel electrode (SCE)); as the pH is increased an electrochemically reversible diffusion-controlled wave with E1/2 of -0.55 V (vs. SCE) is observed [2][3][4]. These observations suggest that In(III) hydroxy species are the predominant electroactive contributors to the electrodic reduction current [5][6][7].…”

ANION EXCHANGE OF METAL COMPLEXES. X.1 THE INDIUM—CHLORIDE SYSTEM. COMPARISON OF RESIN AND LIQUID ANION EXCHANGE

“…In particular, the polarographic work of Schufle, Stubbs, and Witman22 may be reevaluated, taking account of the irreversibility of the wave in absence of chloride. 23 Referring the half wave potentials Ei/" in mv., to the extrapolated value for zero hydrochloric acid concentration23 instead of to the perchlorate solution,22 permits the calculation of the left side of the eq.…”