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Acceleration of Sulfurous Acid Oxidation by Freezing of Aqueous Solution
Kazuhiro HONDA
Department of Applied Chemistry, Kanagawa Institute of Technology; 1030 Shimoogino, Atugi-shi 243-0292 Japan
Oxidation of sulfurous acid ( H2SO3) to sulfuric acid (H2SO4) by dissolved oxygen (O2) in an aqueous solution was remarkably enhanced by freezing. The concentration of sulfurous acid in a sample solution which froze in a −10 °C refrigerant for 60 min decreased by about 50%, and three freeze/thaw cycles resulted in perfect conversion into sulfuric acid. The difference of reaction rates in −20 °C and −10 °C refrigerants indicated that the rate-determining step of the reaction was the growth rate of ice formation in the sulfurous acid in an aqueous solution. The yield of sulfurous acid oxidation in a −10 °C refrigerant was higher than that in a −20 °C refrigerant.
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