POTENTIOMETRIC CHLORINE GAS SENSOR USING BACL2-KCL SOLID-ELECTROLYTE - THE INFLUENCES OF BARIUM OXIDE CONTAMINATION

The effects of BaO contamination on the behaviour of a Cl-2 gas sensor using a 0.97BaCl(2)-0.03KCl solid electrolyte have been investigated. The addition of BaO to the electrolyte is found to produce unfavourab le effects on both the measuring and reference electrodes through a si de reaction such as BaO + Cl-2 --> BaCl2 + (1/2)O-2. The presence of B aO in the vicinity of the measuring electrode results in decreases in the e.m.f. and rate of response, especially when the Cl-2 gas concentr ation is lowered to a few tens of ppm. Its presence near to the refere nce electrode, on the other hand, results in the upward deviation of t he e.m.f. over the entire range of Cl-2 concentration. The probe prepa red in vacuo, free of such BaO contamination, gives e.m.f. values in g ood agreement with the theoretical ones for Cl-2 gas concentrations be tween 10 and 1000 ppm, In contrast, the probe prepared in air shows a slower response as well as a more extensive deviation from theory in t he low Cl-2 concentration range, suggesting that the electrolyte near the measuring electrode is contaminated with BaO.