Ultraviolet Absorption of Mixtures of NO, NO2 and H2O

In considerable amounts of NO containing small amounts of NO2 a continuous absorption occurs in the ultraviolet, obscuring both the absorption of NO and that portion of the absorption of NO2 which lies below 2500A. The behavior of this absorption with respect to temperature and the partial pressures of the constituents is rather convincing evidence that it is due to N2O3. When very small amounts of water are also present a group of bands occurs in the near ultraviolet, lying in the same region but not resembling the longer wave-length NO2 absorption. These bands appear diffuse under low dispersion but possess an ordered arrangement. With increase of temperature the intensity of the bands decreases rapidly. They begin in the vicinity of 3850A, extending to shorter wavelengths. The first members are broader and more diffuse than those that follow, indicating a predissociation process in the carrier, which is probably HONO.