Polarization measurements on solid platinum—molten sodium sulphate—sodium chloride interfaces

Electrochemical studies in sodium sulphate—sodium chloride melts at 900° are reported. The limiting reactions which occur during electrolysis of fused sodium sulphate are suggested to be the SO₃ reduction to S^2? and O^2? and the SO^2?₄ oxidation to SO₂ and O₂ at the cathode and anode, respectively. Additions of sodium chloride into the sulphate do not reduce its stability range.A relevant finding is that platinum is anodically passivated in sulphate melts. Voltammetric scans made to elucidate its passivation mechanism show that the anodically polarized platinum is continuously modified and passes through three states of passivation. Moreover, it is observed that the platinum samples used as cathodes are attacked by the sulphate reduction products.