For a Pt cathode, the following equation is given for the electrode processes: Pt(OH)2 + 2e- = Pt + 20H- or PtO + 2H+ + 2e- = Pt + H2O. After anodization in 0.1M H2SO4 at 1.5 V (vs. SCE), the Pt electrode is partially covered with PtO2. Under open-circuit conditions, PtO2 decomps. to PtO in the presence of Pt. The electrode potential decreases rapidly and gradually reaches a stable value. The stabilized Pt electrode also responds to pH according to the above-mentioned equation. After soaked in permanganate solution, the Pt electrode is covered with MnO2. The potential vs. pH behavior is close to that predicted for the following reactions: MnO2 + 4H+ + 2e- = Mn2+ + 2H2O (pH 2-7) or 2MnO2 + 2H+ + 2e- = Mn2O3 + H2O (pH 8-12).

Key words: TITRATION, OXIDATION, PLATINUM, METAL ELECTRODE, ACIDITY, NEUTRALIZATION, POTASSIUM PERMANGANATE, ELECTRODE POTENTIAL