ANODIC POLARIZATION IN MOLTEN SILICATES

The anodic polarization in binary sodium silicates containing 22-40 mol% Na2O equilibrated with air was studied at 1000 degrees C by means of voltammetry and double-step chronoamperometry. The electrochemical oxidation of the oxide ions produced by condensation reactions of silicate species is a two-electron process kinetically controlled by mass transport of O2- to the anode. The oxygen atoms generated by the oxidation rapidly dimerize to produce dissolved oxygen which is further transformed into gaseous oxygen in the saturated bulk liquid. In basic liquids, the voltammetric peak corresponding to oxygen evolution is preceded by a prewave which has been explained by the formation of chemisorbed peroxide ions via an electrochemical reaction which involves dissolved and adsorbed oxide ions.