ChemInform Abstract: pH Measurement in Strong KOH Solutions with a Bismuth Electrode.

ChemInform Abstract

The aim of the investigation reported is to develop a pH indicating electrode of small dimensions usable in KOH solutions of pH 14-16. Freshly prepared Pt/Bi and Pt/Bi/BiOx electrodes show a linear E-pH curve, whose slope alters with time. Therefore, these electrodes are only suited for short-time pH measurements (∼ 15-30 min). The slope is shown to be constant if the electrode is aged by immersion in conc. KOH solution and the electrodes are applicable for several hours. ESCA and SEM studies of bismuth electrode surface morphology and composition suggest that at freshly prepared electrodes the formation of Bi₂O₃ or Bi(OH)₃ is the potential determining process. At the aged electrodes this process may involve various Bi oxide species, and a reaction running off via the solution seems to be possible.