POTENTIOMETRIC DETERMINATION OF PROTON ACTIVITIES IN SOLUTIONS CONTAINING HYDROFLUORIC-ACID USING THERMALLY OXIDIZED IRIDIUM ELECTRODES

A robust sensor based on iridium oxide is shown to be suitable for use in determining proton activities in solutions containing hydrofluoric acid. Fabricated by a thermal growth process, the low-impedance sensor possesses analytical utility for regulating acidity levels in etching media and pickling-baths. The thermally oxidized electrodes function satisfactorily in hydrofluoric acid solutions with concentrations up to 28 mol dm-3 and show responses comparable to electrodes prepared by the more involved method of reactive sputtering.