B10 Amperometric Oxygen Measurement

Description
An oxygen electrode with a teflon oxygen permeable membrane is used to measure the oxygen dissolved in aqueous solutions. The current flowing through the system increases as the concentration of dissolved oxygen increases. First the electrode is calibrated with water equilibrated with air. Then the oxygen content of a hydrogen peroxide solution is measured. Next, several aliquots of potassium permanganate are added. The first one reacts very slowly. Subsequent aliquots react rapidly because the manganese products catalyze the reaction. When the solution is saturated with oxygen, the meter stops moving.

Equation
4 H⁺ + O₂ + 4 e^- --> 2 H₂O

5 H₂O₂ + 2 MnO₄^- + 6 H⁺ --> 8 H₂O + 5 O₂ + 2 Mn²⁺

Reference