A solid-state probe for SO2/SO3 based on Na2SO4 I electrolyte

Conductivity measurements as a function of temperature and partial pressures of SOs, SO2, and O2, and transference experiments indicate that the transport number of Na + ions is unity in Na2SO4-I. A concentration cell based on this electrolyte Pt, O2' + SO2' + SOs'/Na2SO4-I/SOa" + SO~" + O~", Pt 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 SO#SOs pollution in air, and in combination with an oxygen probe can be used for the determination of SO=/SOs concentrations in coal combustion reactors, for the evaluation of the partial pressure of $2 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 K=SO4 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, Na2S207 is less stable and can be formed only at a considerably higher pressure of S03 than that required for K~20~.