Literature data for the redox potential of the aqueous sulfur‐polysulfide redox couple have been correlated by accounting for the complex equilibration of various sulfur‐bearing species in alkaline electrolyte. For electrolytes wherein the ratio of zero‐valent sulfur to total sulfide ranges from 0.1 to 3.0, the pH ranges from 10.6 to 13.8, and the temperature ranges from 25 to 90°C, the redox potential is correlated by the expressionE=E0−RT6Fln)(CHS−4COH−4CS42−This equation represents the redox potentials to within 2% at all compositions and temperatures, except for the electrolyte with a normalsulfur/normalsulfide ratio of 3.0 at 80°C, for which the deviation is 6%.

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The kinetics of the aqueous polysulfide redox couple were investigated using a potential step technique in a solution 1M in S0 and 1.3M in total S2−, at pH 12. The low overpotential region (−20 to +20 mV) on cobalt and platinum electrodes was investigated from 25° to 80°C. The active species concentration was found to be several orders of magnitude lower than those of any of the major (poly)sulfide ions, and its temperature dependence corresponded to an Enormala of about 10 kcal/ mol. These results are consistent, with the active species being S2− . Deviations were found at temperatures above 45°C between experimental data and the simple analytical form for the current response for an electrode reaction with one rate‐determining step. The results agree with a new model that considers two rate‐determining steps, one of which is the reaction S42−⇆2S2− . The rate constants for this reaction determined using this new model agree with those measured for similar reactions.