CHEMICAL-REACTION OF PLATINUM WITH PBO-SIO2 MELT UNDER DIRECT-CURRENTELECTROLYSIS

Platinum electrodes were immersed in lead silicate glasses of (100-x) PbO.xSiO(2) (mol%, x=0-50) melts and dc voltage was applied to keep a constant current, 6 mA, at 900 degrees C. After electrolysis the inter faces between Pt electrodes and the melt were analysed by electron pro be microanalysis and x-ray diffraction analysis. In SiO2 rich melts in which Pt solubility and conductivity are low it was found that the cu rrent is carried mainly by Pb2+ and O2- ions. It was also found that c athode Pt reacts with lead to form a Pt-Pb alloy and anode Pt reacts w ith O-2 gas to form a dark thin film consisting of Pt-Pb-O compound. I n low SiO2 and PbO melts in which Pt solubility and conductivity are h igh, it was found that the current is carried mainly by platinum ions. It was also found that the anode Pt dissolves into the melt and preci pitates on the cathode Pt. These phenomena were discussed based on the redox potential, conductivity of the melt and solubility of platinum in the melt.