A STUDY OF THE AG(S) AG2SO4(I) HIGH-TEMPERATURE REFERENCE ELECTRODE/

Ag(s)/Ag2SO4(l) reference electrodes for use in hot corrosion research were fabricated and their properties were studied at 927 degrees C (1 200 degrees K). The McDanel(TM) MV 30 mullite tube was used as sheath of the reference electrode and concentrations of the tested electrolyt es were varied from 0.1 to 10 m/o Ag2SO4 (l) + Na2SO4 (l). 10 m/o Ag2S O4 was always used as electrolyte in the reference electrode. The work ing electrodes with less than 2 m/o Ag2SO4 showed marked potential dri ft as the Ag2SO4 concentration was lowered, showing poor potential sta bility. However, the initial values of cell voltages obeyed Nernstian behavior for all range of Ag2SO4 concentrations in the working electro des, which showed that Ag(s)/Ag2SO4(l) electrodes behaved reversibly. Galvanostatic polarization was performed on a pair of 10 m/o Ag2SO4 re ference electrodes to test the reversibility. The polarizability was 3 .5 mV/10 mu A with no hysteresis loop on the polarization curve, showi ng that the reversibility was satisfactory. The potential of gold elec trode in molten Na2SO4 was measured under pure oxygen atmosphere with 10 m/o Ag2SO4 electrode as a reference potential. The results showed t hat the potential of gold electrode could be explained by the 2 Na + S O3 + 1/2 O-2 <-> Na2SO4 cell reaction.