SOLID-STATE PROBE FOR SO2-SO3 BASED ON NA2SO4-I ELECTROLYTE

Conductivity measurements as a function of temperature and partial pressures of SO3, SO2, and O2, and transference experiments indicate that the transport number of Na + ions is unity in Na2S04-I. A concentration cell based on this electrolyte [formula omitted] produces emf's that are in agreement with those calculated from the Nernst equation when equilibrium is assumed between the gas species at the electrodes. The cell can be used for monitoring the SO2/SO3 pollution in air, and in combination with an oxygen probe can be used for the determination of SO2/SO3 concentrations in coal combustion reactors, for the evaluation of the partial pressure of S2 in coal gasification systems, and for emission control in nonferrous smelters using sulfide ores. The probe is similar to that developed recently by Gauthier et aL (4, 5) using K2SO4 as the electrolyte, but can operate at higher pressures of SO3. Because of the greater polarizing power of the Na+ ion compared to the K + ion, Na2S2O7 is less stable and can be formed only at a considerably higher pressure of SO3 than that required for K2S2O7. © 1979, The Electrochemical Society, Inc. All rights reserved.