Analytical Sciences

Mechanism of the NO₂ Conversion to NO₂^- in an Alkaline Solution

Xinyu CHEN, Kenji OKITSU, Norimichi TAKENAKA, and Hiroshi BANDOW

Department of Applied Materials Science, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka 599-8531, Japan

The reaction of NO₂ and NaOH aqueous solution at room temperature was studied for elucidating the behavior of gaseous NO₂ in an alkaline solution. Experimental runs related to NO₂ absorption have been carried out in various pH solutions. The nitrite and nitrate ions formed in these absorption solutions were quantitatively analyzed. In the case of pH 5 - 12, both of the nitrite and nitrate ions were formed simultaneously. On the other hand, only the nitrite ion was formed when the pH of the absorption solution was higher than 13. In this paper, a new reaction mechanism was proposed to explain the selective formation of nitrite ion in the 10 M alkaline solution. In order to confirm the new reaction mechanism, H₂¹⁸O was used as part of the absorption solution for detecting oxygen gas production. The amounts of reaction products: ¹⁸O¹⁸O, ¹⁸O¹⁶O and ¹⁶O¹⁶O, were quantitatively determined. It was confirmed that the new reaction proceeds mainly in the 10 M alkaline solution.

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