抄録
Dissolution of nitrogen oxides (NO and NO2) into water was studied with regard to the intake process of NOx by living body. NOx mixed with N2 was passed in bubblers at 25°C. NO2- and NO2-+NO3- were analyzed with colorimetric methods. NO dissolves physically in the absence of O2 and obeys Henry's law. NO2 (20-80 ppm (v/v)) dissolves and gives rise to equal amounts of NO2- and NO3- regardless of the existence of O2. The rate of NO2 dissolution is proportional to the gaseous concentration of NO2. The dissolution of NO+NO2 (NO: 230-630 ppm (v/v)), NO2: (25-70 ppm (v/v)) produces NO2- exclusively in the absence of O2. The rate depends linearly upon the gaseous concentration of NO2 irrespective of the concentration of NO. The rate constant of the dissolution of NO+NO2 approximately equals that of NO2, which suggests that both reactions proceed with the identical rate determining step. The dissolution of NO in the existence of O2 (NO: 100-470 ppm (v/v), O2: 50%) likely proceeds with the gaseous oxidation of NO and the subsequent dissolution of NO+NO2. The rate constant k of the oxidation of NO with O2 was calculated according to the above mechanism. The value of k thus obtained agreed well with that reported by Stedman and Niki.
