Little is known about the reduction of NO2‐ and N2O by Fe2+ in the pH range from 6 to 8, a range of importance in many natural environments. Reduction of 25 mg NO2‐‐N (approximate concentration=25 ppm) and 5 mg N2O‐N in a distilled‐water medium containing 800 mg Fe2+ with a helium atmosphere in the presence and absence of Cu2+ at pH 6 and 8 was studied at 26°C. Reduction of NO2‐ to N2O (the principal product), N2 and NH4+ was rapid and quantitive at pH 8 and not greatly affected by Cu2+. However, addition of Cu2+ decreased the mole ratio of N2O to N2 in the evolved gas mixture from 4.2 to 3.1. Reduction of NO2‐ at pH 6 was incomplete, but was favored by Cu2+ addition. Nitrous oxide was the dominant reduction product at this pH value. Small quantities of NO accumulated at pH 6.Irrespective of Cu2+ addition, N2O was stable in the Fe2+ medium at pH 6. In the pH 8‐system in the presence of Cu2+ 84% of the N2O was reduced to N2. Nitrous oxide was relatively stable at pH 8 in the absence of Cu2+. Small quantities of H2 accumulated in the atmospheres of vessels containing the pH 8, plus Cu2+ N2O − N treatment. No H2 accumulated in the NO2‐ series of treatments.

Knowledge concerning the chemical reduction of NO3− to gaseous products, a process of potential practical significance as an antipollution device, is sparse. The influence of pH on chemical reduction of NO3−‐N (approximate concentration 25 ppm) by Fe2+ in the presence and absence of Cu2+ was studied over a pH range from 6 to 10. After 24‐hours of controlled pH incubations under a helium atmosphere NO3−, NO2−, N2O, NO, N2, and NH4+ were determined. The initial Fe2+/NO3− mole ratio was 8. Reduction of NO3− was negligible in the absence of Cu2+, but was pronounced above pH 7 in the presence of approximately 5 ppm Cu2+. Formation of NH4+ increased with pH and was the dominant process at pH 9 and 10. Nitrous oxide and N2 accumulations were greatest in the pH range from 8 to 8.5 and negligible at pH 6 and 10. Nitrite formation was small except at pH 9 and 10. Trace quantities of NO accumulated during incubation if the pH was allowed to drop below 6.Levels of Cu2+ and Fe2+ influenced the extent and nature of NO3− reduction at pH 8. Maximum reduction of NO3− (93%) and maximum gas production (equivalent to 61% of the original NO3−) occurred when the Fe2+/NO3− mole ratio was 12 and the Cu2+ level was approximately 10 ppm. The N2O/N2 mole ratio in the evolved gases decreased as the Cu2+ level was increased from approximately 1 to 10 ppm and as the Fe2+/NO3− mole ratio was increased from 8 to 12. Nitrate was relatively stable at a Cu2+ content of 0.1 ppm irrespective of the Fe2+/NO3− ratio.

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