Quantum yields have been obtained for the disappearance of nitrogen dioxide in photolysis at 3660 A and at concentrations below 4×10—7 mole per liter in nitrogen at one atmosphere pressure. The effects of small amounts of added nitric oxide and oxygen on the quantum yields were also observed. From these data and an assumed mechanism it was possible to calculate the rates of reaction of atomic oxygen with nitric oxide and nitrogen dioxide relative to the rate of reaction of atomic oxygen with molecular oxygen. These relative rates were converted to absolute rates using Benson and Axworthy's rate constant for the O+O2 reaction.

Nitrogen dioxide was irradiated at 3660 A in the presence of HN03. Both N02 and HNOs were decomposed. The proposed mechanism for HN03 decomposition is 0 + HN03 OH + NO3 followed by OH + HN03 H20 + N03. The specific rate constant for the O + HNO3 reaction is estimated to be ~1010 1. mole-1 sec-1. Quantum yields are reported as a function of N02, HNOs, and NO pressures.(1) This paper presents results of one phase of research carried out at the Jet Propulsion Laboratory, California Institute of Technology, under Contract No. NAS 7-100, sponsored by the National Aeronautics and Space Administration.

A red sludge-like deposit was found in several tile systems in Florida citrus groves. This deposit prevented the tile from functioning properly by blocking the passageway through which water entered the title. The deposit was found to be due primarily to "iron bacteria" which oxidize and precipitate reduced iron in the drainage water. Chemical analyses indicated a large proportion of the material was organic-probably bacterial cell bodies and waste products. The inorganic portion was mainly hydrated iron and aluminum oxides. Bacteriological studies of the material indicated the following genera of bacteria were responsible for the formation of the deposits: Gallionella, Leptrothrix, Thiothrix, Thiobacillus, Crenothrix and Cladothrix. The predominating genera within a tile line varied with location. The deposits occur in both bituminous pipe and clay tile whether installed in sawdust filter or wrapped with fiberglass. The relative amounts of the deposit in tile at various locations were related to the amounts of reduced iron extracted from the soils with an aluminum chloride solution.

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Nitrogen dioxide was irradiated at 3660 and 4047 Å at various pressures of NO2, with and without CO2, NO, and N2 as added gases. The data indicate a primary dissociation at 3660 Å and shorter wavelengths corresponding to energies greater than the ON–O bond energy. At 4047 Å, the data are explained by an excited-molecule mechanism. Isotopic oxygen scrambling experiments at 4047 Å indicate the probability of reactions to produce oxygen atoms at that wavelength, but photolysis of NO2 at trace concentrations and high inert-gas pressures indicates that these atoms are not derived from the unimolecular decomposition of the photoactivated molecule. The inhibition of the quantum yield by NO addition was pressure-dependent, lending further support to the premise that oxygen atoms are important in the mechanism at 4047 Å. It is postulated that the reaction NO2*+NO2→N2O3+O is the source of atomic oxygen.