A kinetic study of sulfur dioxide in aqueous solution with radioactive tracers

A kinetic study was made of the homogeneous reactions in the sulfur dioxide‐sodium bisulfite‐water system, with a radioactive tracer technique. By operating this system at chemical equilibrium but at isotopic disequilibrium the influence of the diffusion of sulfur dioxide into and out of the aqueous solution could be divorced from the kinetic effects of the chemical reaction. It was then possible to follow the rate of reaction of this system by analyzing the radioactive sulfur‐35 in the form of gaseous sulfur dioxide, with the Bernstein‐Ballentine technique. Data were collected at temperatures of 0° to 20°C. and at pH ranges from 1.25 to 4.3. Analysis and correlation of the experimental data by different kinetic models demonstrated that the classical reaction SO2 + H2O ⇌ H+ + HSO3− represented the experimental data best from a macroscopic viewpoint. Because of the low pH conditions employed it was not possible to obtain rate data for the reaction SO2 + OH− ⇌ HSO3. Forward and reverse rate constants are reported for the first time for this system.