SILVER BETA-ALUMINA AS A POTENTIOMETRIC GAS SENSOR FOR ARSENIC OXIDES, ASOX

A potentiometric solid-state sensor for measuring gaseous arsenic oxides and/or arsine was constructed by using a silver p-alumina solid electrolyte with Ag metal as the reference electrode. The operation of this sensor depends on the in situ formation of Ag3AsO4 at the surface of the electrolyte and can be represented by the following galvanic cell Ag/Ag+ - β-alumina/AsOx(g), O2(g), Pt The partial pressures of the arsenic oxides at the working electrode were defined by mixing arsine (AsH3), diluted in nitrogen, with oxygen, or by passing air over a constant temperature bed of arsenolite (As2O3). The EMF of the above galvanic cell was measured as a function of P(AsH3), P(O2), P(As4O6), and temperature. Any change in arsine concentration produced a fast, highly reproducible response in EMF, The EMF of the sensor varied linearly over a wide range of P(AsOx) at temperatures between 963 and 1173 K, the optimum operational temperature being ~973 K. The EMF of the sensor was also a linear function of temperature. However, in spite of the highly reproducible results, the electrode reaction was found to be kinetically controlled. When operated at temperatures above 973 K, the sensor exhibited good selectivity to AsH3 in the presence of CO2, SO2, and H2. © 1990, The Electrochemical Society, Inc. All rights reserved.