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

Abstract

Conductivity measurements as a function of temperature and partial pressures of SO₂, SO₂, and O₂, and transference experiments indicate that the transport number of Na⁺ ions is unity in Na₂SO₄I. A concentration cell based on this electrolyte Pt, O′₂+SO′₂+SO′₃/Na₂SO₄I/SO_2″ + SO_2″ + O_2″, 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 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, Na₂S₂0₇ is less stable and can be formed only at a considerably higher pressure of S0₃ than that required for K₂S₂O₇.