Liquid sulfur has been reduced coulometrically in fused eutectic at 420°C. Nernstian behavior is observed for the cell C, , , . The standard potentials of the sulfur/sulflde couple at 450 °C with respect to the appropriate standard platinum reference electrode are −1.008, −1.039, and −1.219v on the molar, molal, and mole fraction scales, respectively. Voltammetric studies showed an anodic wave at +0.03v ascribed to and a cathodic wave at −0.92v ascribed to . The diffusion coefficient of the (poly)sulfide ion was found to be at 420°C by chronopotentiometric measurements. The observed blue color of sulfur‐sulfide solutions is ascribed to polysulfide ions.