The Electrode Potential of Zinc Amalgam in Alkaline Zincate Solutions

Abstract

The electrode potential of zinc amalgams has been measured in potassium hydroxide solutions containing dissolved zincate. Curvature in the Nernst plots was observed at high zincate concentrations in agreement with the results of other workers. The curvature is explained as being due to the dependence of the hydroxyl and zincate ion activity on concentration in strong potassium hydroxide solutions. The data yield a value of −1.205V (vs. SHE) for the standard potential of the zinc, zincate ion electrode (I.U.P.A.C.—Stockholm convention) and −205.86 kcal for the free energy of formation of the zincate ion at 25°C.

The electrodeposition and dissolution of zinc and amalgamated zinc in alkaline solutions

“…This change cannot be Davies equation [25] for the activity coefficients, since measured directly since the potential of the RE also the activity coefficients of KOH and I& Zn (OH) [26].…”

The Behavior of the Amalgamated Zinc Electrode in Supersaturated Alkaline Zincate Solutions

“…E* is determined to be Ϫ1.211 V reported by Dirkse 2 and Boden et al 3 To calculate the equilibrium potential from above Eq. 4 or 5, we need to know the activity or activity coefficients for zincate and hydroxyl ions in the presence of each other.…”

“…[1][2][3][4][5] Many authors studied the equilibrium potential of the zinc electrode in unsaturated and nearsaturated zincate solutions. Non-Nernstian behavior was observed at high zincate concentration.…”

“…2 It was also explained as being due to the dependence of the hydroxyl and zincate ion activities on concentration in strong potassium hydroxide solutions. 3 The junction potential between the electrolyte in the reference electrode and the electrolyte under test was also a major contributor to this non-Nernstian behavior. 4 Another suggestion was that the zincate ion was somewhat acidic and a neutralization reaction took place between the zincate and the potassium hydroxide as the potassium hydroxide concentration increased.…”

The Behavior of the Zinc Electrode in Alkaline Solutions: III . The Equilibrium Potential

“…One suggestion is that the activities of zincate and hydroxide ions are dependent on the ionic strength of the electrolyte (5). One suggestion is that the activities of zincate and hydroxide ions are dependent on the ionic strength of the electrolyte (5).…”