Nitrogen—Inorganic Forms

Bacterial strain GR-1 was isolated from activated sludge for its ability to oxidize acetate with perchlorate as electron acceptor. Sequencing of 16S rDNA revealed the isolate to belong to the β subgroup of Proteobacteria. When strain GR-1 was grown on acetate and perchlorate, the release of chloride was proportional to the disappearance of perchlorate, showing that this compound was completely reduced. In addition to perchlorate, strain GR-1 used chlorate, oxygen, nitrate and Mn(IV) as electron acceptor. The oxidation of acetate is coupled to the reduction of perchlorate and chlorate, whereas chlorite reduction is not affected by the addition of acetate. Strain GR-1 disproportionates chlorite into molecular oxygen and chloride. As a consequence, the strain oxidizes acetate by simultaneously reducing perchlorate to chlorite and molecular oxygen to water. Comparison of growth yields with oxygen, chlorate and perchlorate and calculated ΔG
0′ values confirms this finding.

Transformation of (per)chlorate into chloride by a newly isolated bacterium: reduction and dismutation

Determination of nitric oxide using fluorescence spectroscopy

Spectrophotometric determination of nitrate using chromotropic acid

The increased interest in the problem of surface and ground water pollution by nitrate has emphasized the need for a simple, sensitive and reliable method for the determination of nitrate in waters. According to methods of analysis commonly employed for the determination of nitrate in water, the presence of appreciable amounts of chloride would result in a low value for nitrate. Even the most widely used methods for nitrate determination are not specific and involve lengthy procedures such as separation of interferences or concentration of sample solution. A simple, sensitive and specific method for the deter­ mination of nitrate in microgram ranges applicable for water and air samples is described. The method is directly applicable to water samples without recourse to evaporation or separation procedures. The proposed method was evolved as a result of the exhaustive study of the nitrate-chromotropic acid reaction in concentrated sulfuric medium. Nitrate reacts with chromotropic acid in about 75$ v/v sulfuric acid medium giving a water-soluble yellow product. Spectrophotometric measurement of the absorbance of the color at lt-10 millimicrons provides a means for the determination of nitrate in the concentration range of 0 .2 to 20 milligrams per liter. Many commonly occurring materials such as oxidizing

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A. M. Hartley

Papers

Spectrophotometric Determination of Nitrate with 2,6-Xylenol Reagent.