INTERACTION OF SULPHUR DIOXIDE AND HYDROGEN UNDER SILENT ELECTRICAL DISCHARGE

Interaction of SO₂ and H₂ under silent electric discharge is time-continuous and irreversible. An initial rapid fall of the pressure (p) is followed by a slower change and the attainment of a stationary stage. The time variation of the conductivity, i, is synchronous with but less pronounced than that of p. The formation of SO as an unstable inter­mediate product is suggested. Besides Hz and undecomposed SO₂, the reaction products consist of sulphur, H₂SO₃, H₂SO₄, SO₃, O₂ O₃ and H₂S. Ozone is produced prior to H₂S. The decrease of p is attributed to the condensation of the products of decomposition or/and their 'clean up' by the annular film of sulphur produced under the discharge. In agreement with the general finding due to Joshi the current i, at a given applied potential V, depends on V-V_m, where V_m is the 'threshold potential'. Production of SO and SO₃ reduces V_m and tends to increase i. The deposition of sulphur on the annular walls inhibits the reaction.