Oxidation of aqueous sulfite ion by nitrogen dioxide

The formation of products from the reaction of nitrogen dioxide, with and without the presence of oxygen, in aqueous sulfite and hydrogen sulfite solutions has been studied by Raman spectroscopy.The products observed include nitrite, nitrate, sulfate and dithionate ions.The product distribution at low pH is complicated by the formation of nitrogen sulfonates from the reaction of nitrite ion with hydrogen sulfite ion.A possible mechanism is presented for the reaction of aqueous nitrogen dioxide with sulfite ion to generate the observed products.From the product distribution observed, we obtain a branching ratio for • the reactions 503•-+ 503•---> 503 + 503 2 -503•-+ 503•---> 5206 2of k7 /kg = 1.8 ± 0.2 at 20°C in 0.8 M NaOH and derive values of k7 = 3.5 x loB M-1 s-1 and kg = 2.0 x loB M-1 s-1 .I •-• '. 1