Experiences with reference electrodes in sulphate melts

The construction and the experiences with a reference electrode of the type PT/0.1 Ag₂SO₄ + 0.9 (Na, K)₂SO₄/ mullite in sulphate melts at 1173 K are reported. After an “ageing” period of approx. 200 h, during which the potential can change by up to 80 mV, the potential is stable within ± 10 mV over many hundreds of hours. Additional investigations reveal that the potential is established by formation of a silver or AgPt alloy layer, respectively, on the Pt-wire. This kind of reference electrode is suitable for long term experiments, eg corrosion tests.