Advanced pH measuring system with safety mechanism for elevated temperature aqueous solutions

An in-situ pH measuring system for high temperature aqueous solutions was developed using YSZ membrane tubes and a new pressure balanced regulator system. Air was filled inside the tube, the pressure of which being balanced with that of high temperature aqueous side by the regulator system. The Pt coated inside surface functioned as the oxygen electrode. Owing to the regulator system and some improvement in the shape of the tube and its cooling condition, the damage of the full stabilized membrane tube was almost prevented. In the temperature range from 150 to 275degC, the potential of the YSZ tube electrode was confirmed to show the one to one correlation to the potentials of the Pt oxygen and hydrogen electrode, respectively in air and hydrogen saturated aqueous solutions. The pH measurement by the YSZ tube was, also, confirmed not to be affected by other redox couples in solutions. (author)