Abstract The speciation of gases formed in the vapor phase above HNO3-H2O mixtures at room temperature is measured and characterized using Fourier-transform infrared (FTIR) spectroscopy. Although studies of speciation of compounds have been performed in the solution phase, this study focuses solely on the gas phase species formed over HNO3-H2O mixtures and their concentrations as a function of time. The nitric acid concentration in the experiments range from 14 to 4 M. The NO2, NO, and N2O (collectively known at NOx) gases are measured by FTIR at 1585, 1850, and 2208 wavenumbers, respectively. The concentrations of these NOx species ranges from 0 to 3 ppm and change over time as a function of acid concentration. Two purities of commercially available HNO3 are used to prepare the HNO3-H2O mixtures. An analysis of thermodynamic data shows that the formation of NOx gases without the presence of a catalyst are thermodynamically favorable.

中文翻译：

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从硝酸/水系统产生的含氮物种的表征

摘要 使用傅里叶变换红外 (FTIR) 光谱测量和表征室温下 HNO3-H2O 混合物上方气相中形成的气体的形态。尽管已在溶液相中进行了化合物形态的研究，但本研究仅关注在 HNO3-H2O 混合物上形成的气相物种及其作为时间函数的浓度。实验中的硝酸浓度范围为 14 到 4 M。NO2、NO 和 N2O（统称为 NOx）气体分别通过 FTIR 在 1585、1850 和 2208 波数处测量。这些 NOx 物质的浓度范围为 0 到 3 ppm，并且随着时间的推移作为酸浓度的函数而变化。两种纯度的市售 HNO3 用于制备 HNO3-H2O 混合物。