Solid state electrochemical sensor for chlorine and hydrogen chloride gas trace analysis

Two potentiometric sensors are tested for chlorine gas trace analysis. The solid electrolyte is a chloride ion conductor: PbCl2 doped with KCI or a two layer SrCl2-KCl/PbCl2-KCl material. The reference electrode is based on the Pb-PbCl2 or Ag-AgCl system, respectively. A thin film of ruthenium dioxide is used as the measuring electrode. The operating chlorine partial pressure range extends from 1 to 10(-7) atm. The response time is between 2 and 3 min for 3 vpm (volume per million) of injected chlorine. The present work describes the influence of the operating temperature, the relative humidity, the amount of chlorine and the number of cycles on the sensor response. The sensor response is successfully explained by taking into account the chlorine adsorbed on the test room and by the Deacon reaction. By taking advantage of this reaction, the chlorine gas potentiometric gauge based on SrCl2-KCl electrolyte is used to measure trace quantities of hydrogen chloride gas, in a humid atmosphere. (C) 1999 Elsevier Science S.A. All rights reserved.