Showing papers on "Ammonia published in 1970"

Synthesis of glutamate in Aerobacter aerogenes by a hitherto unknown route

Abstract: In order to grow in a simple salts medium in which ammonia provides the sole source of nitrogen, micro-organisms must possess some mechanism for the synthesis of amino acids from ammonia and intermediary metabolites. In many bacteria this requirement is fulfilled by the enzyme glutamate dehydrogenase (EC 1.4.1.4), which reductively aminates 2-oxoglutarate to glutamate. In other bacteria (particularly in some species of Bacillus) analogous amino acid dehydrogenases (e.g. alanine dehydrogenase and leucine dehydrogenase) functionally replace glutamate dehydrogenase and glutamate is then formed by an aminotransferase reaction. Available kinetic data indicate that amino acid dehydrogenases generally have high Km values for ammonia (above 5mM; see Sanwal & Zink, 1961; Wiame, Pierard & Ramos, 1962), and one might therefore expect that when bacteria are growing in a simple salts medium the intracellular free ammonia concentration always would be relatively large. When growth takes place in the presence of a large excess of ammonia, the intracellular free ammonia content is difficult to assess without washing the organisms (which is undesirable, since it may cause changes in 'pool' composition; see Britten, 1965). But, when organisms are cultured in a chemostat under conditions where growth is limited by the availability of ammonia, the intracellular free ammonia can be easily determined by extracting the organisms with 0.25% HC104 and applying the extracts to the columns of a Technicon automatic amino acid analyser; washing these organisms is unnecessary since the extracellular free ammonia concentration is negligible (Herbert, 1958). With ammonia-limited chemostat cultures of Aerobacter aerogenes, growing at a dilution rate of 0.3h-1 in the medium of Tempest (1965) at pH6.5 and 35°C, the intracellular free ammonia concentration was found to be less than 0.005% of the bacterial dry weight * Present address: Novo Industri A/S, Fuglebakkevej 115, 2200 Copenhagen N, Denmark. (below 0.5mM), well below theKm value for amnmonia (3-4mM) of A. aerogenes glutamate dehydrogenase. This observation prompted a detailed quantitative study of the relationship between growth condition and bacterial glutamate dehydrogenase activity of

Oxidation of Inorganic Nitrogen Compounds

Abstract: Nitrogen plays an integral part in life processes of a biological cell since the synthesis of cellular proteins, amino acids, purines, pyrimidines, nucleic acids, and enzymes is dependent on this essential element. The biological conversion of the oxidized inorganic nitrogen compounds to the ammonia or amino level appears to be an essential metabolic aspect of almost all plants and many microogranisms. They play a vital role in providing nitrogen to many forms of life, including some particular microorganisms and virtually all animals as well as man ; the latter systems lack the ability to reduce more oxidized states of nitrogen and, therefore, they fulfill their obligate nitrogen requirements from the exogenous supply of organic nitrogen and ammonia. It is obvious , therefore, that the inorganic nitrogen is the ultimate nitrogen source for all forms of life on this earth. In nature the nitrogen atom exists in the following oxidation states: N205 or HNOa (+5), N02 (+4), N20a or HN02 (+3), NO or H2N20a (+2), the (+1) oxidation states as represented by N20, HNO, H2N202 and NOzNH2; Nz(O)NHzOH (-1), NHzNH2 ( 2), and finally the most reduced state of nitrogen, NHa (-3). Each of these compounds has been implicated in the inorganic nitrogen metabolism of either intact organisms or their cell-free preparation (51). Although the (+6) oxidation state as represented by NOa, a short-lived compound, has been reported (74), its metabolic role if any is unknown at present. The biological oxidation of reduced inorganic nitrogen compounds is catalyzed predominantly by the bacterial genera Nitrosomonas and Nitro­ bacter, which oxidize ammonia to nitrite and nitrite to nitrate respectively, a process commonly known as nitrification. These bacteria are obligate chemoautotrophs which derive their energy from the respective primary inorganic oxidations that are coupled to the cellular biosynthetic reactions involving the reduction of carbon dioxide by mechanisms very similar to those of the carbon reduction cycle in photosynthetic organisms. The basic mechanisms of the respiratory and intermediary metabolism of the nitrifying bacteria have been reviewed previously by Lees (44, 45) and by Aleem & Nason (13), and very recently in excellent review articles by Peck (55) and by Wallace & Nicholas (73).

Inorganic nitrogen assimilation of ditylum brightwellii, a marine plankton diatom1,2

Abstract: SUMMARY Apparent Km values for nitrite reductase, glutamic dehydrogenase, and nitrate reductase are of the order 10−4 molar for nitrite, ammonia, and nitrate, respectively while half-saturation constants for the corresponding uptake mechanisms approximate 10−6 molar. Ammonium and nitrate are accumulated in the vacuolated cells of the diatom (about 10 and 40 mmoles/liter cell volume, respectively) and these intracellular pools serve as substrate for the assimilatory enzymes. Nitrite is either not accumulated or is concentrated, in a very small cellular compartment. Ammonium and nitrate in the external medium exert modifying effects on uptake and assimilatory mechanisms which can be distinguished from effects of the ions accumulated within the cells. Several of these effects are described and fitted into a general scheme of nitrogen assimilation by D. brightwellii.

Synthesis of Amino Acids by the Heating of Formaldehyde and Ammonia

Abstract: The heating of formaldehyde and ammonia yields a product that, on hydrolysis, is converted into seven amino acids: aspartic acid, glutamic acid, serine, proline, valine, glycine, and alanine. Glycine is the predominant amino acid. Inasmuch as formaldehyde and ammonia have been identified as compounds in galactic clouds, these experimental results are interpreted in a cosmochemical and geochemical context.

The effect of uncomplicated potassium depletion on urine acidification

Abstract: Studies were performed on normal human subjects to determine the effects of potassium depletion on urine acidification. Depletion was induced by ingestion of a low potassium diet either alone or in combination with a potassium-binding resin, and the response of each subject to an acute ammonium chloride load in the potassium-depleted state was compared to his normal response. Urine pH was significantly higher during potassium deficiency if sufficient potassium depletion had been induced. No differences in blood acid-base parameters, urinary flow rate, or urinary fixed buffer excretion rate were found to account for this change; however, the increase in urine pH was accompanied by a concomitant increase in net acid and ammonium excretion. It is proposed that these changes during potassium depletion reflect an increase in ammonia diffusion into the urine, presumably as a result of increased renal ammonia production. In addition, it is speculated that changes in ammonia metabolism may be a physiologic control mechanism for potassium conservation.

Ammonia and ammonium sulfate in the troposphere over the United Kingdom

Abstract: Ammonia occurs in the troposphere chiefly as ammonia gas or as ammonium sulfate The principal source of the ammonia, at least in the UK, appears to be the urea in animal urine The ammonia thus released is converted on a time scale of hours into ammonium sulfate, the conversion process being quite rapid in the dark, as well as in the light, and over a range of relative humidity (RH) values The most significant mechanisms probably are reaction with sulfur dioxide and oxygen in mist or cloud droplets and reactions with sulfuric acid droplets from power-station plumes There is no positive evidence for appreciable reaction on solid particulates, but the possibility cannot at present be excluded Photochemical reactions probably make only a small contribution A direct gasphase reaction between ammonia and sulfur dioxide does not seem possible at the concentrations and temperatures concerned It is important to elucidate the mechanisms so that ammonium sulfate levels in the troposphere and their effects, eg, on visibility, can be predicted

Non-exchangeable binding of ammonium and amino nitrogen by Norway Spruce raw humus.

Abstract: The capacity of an originally acid Norway spruce raw humus to fix isotopically labelled ammonium and amino nitrogen in a form resistant to cold 1N HCl treatment was studied. The amount fixed was determined after a reaction period of 24 hours (the humus pretreated with propylene oxide), using the amount of labelled N in the HCl-leached humus residue as a basis for calculating the amount of added N fixed. The nitrogen sources used were ammonium chloride, glycine and cyanamide. It was found that the fixation of added ammonium and glycine N was exceedingly low in the H+-saturated raw humus (pH 3.3–3.4), but the fixation rate was rapidly increased by increasing the pH during the aerobic incubation. Maximum fixation was obtained at a final pH of 10–11. Within the acid range the fixation was constantly higher for added glycine-N than ammonium-N. On the alkaline side of the neutral point the amount of fixation tended to be similar for ammonium and glycine. In treatments with N15-labelled ammonium, it was shown that small but fully detectable amount of added N were present in the soluble organic N fraction of the HCl extract, the quantities increasing with increasing soil pH during the incubation. The fixation was increased by increasing temperature and decreased by oxidative pretreatment of the humus before the addition of N. In the nitrogen gas atmosphere the fixation figures were 40 to 50 per cent lower than for corresponding treatments in air atmosphere. When various N compounds were added in equimolar concentrations the highest fixation was recorded for cyanamide. In studying the stability of fixed N to acid hydrolysis, it was found that 54 per cent of the fixed N resisted eight hours' refluxing with 6N HCl, the corresponding figure for the native raw humus N being 19 per cent. About one third of the fixed N was liberated as ammonia during the acid hydrolysis.

Process for removal of ammonia from waste water streams

Abstract: Ammonium ions are selectively removed from aqueous solutions containing alkali and/or alkaline earth cations by cation exchange with zeolite F. This is a synthetic crystalline aluminosilicate having a silica-to-alumina oxide mol ratio of about 2 which is derived from a potassium-rich reaction mixture. This zeolite possesses unusual cation exchange capacity and unpredictable selectivity for the ammonium ion.

Method for making metal oxide sols in polar organic solvents

Abstract: Sols of Sb2O3, SnO2, TiO2 and ZrO2 in organic polar liquids are prepared by reacting a soluble salt of the metal with water and ammonia in a solution of the liquid. The reaction produces the metal oxide in colloidal dispersion and an insoluble ammonium salt, which precipitates and is filtered off. Sols in liquids which are solvents for organic polymers are used to incorporate metal oxides into the polymers to provide flame resistance and other desirable properties.

I. Studies of Cavities Containing One and Two Electrons in Metal-Ammonia Solutions. II. Accurate 'Effective' Intermolecular Pair Potentials in Gaseous Argon.

Abstract: The “effective” intermolecular potential in gaseous argon has been determined, accurate through first order in density, for various assumed argon–argon potentials and the triple‐dipole interaction. This potential should lead to the correct radial‐distribution function. The calculations do not agree with the 1965 analysis of experimental data by Mikolaj and Pings [Phys. Rev. Letters 15, 849 (1965) ]. Our results suggest a density dependence of the minimum of the effective potential of only about 17 ρ (in degrees Kelvin), where ρ is the density in grams per cubic centimeter. This constant has a sizeable temperature dependence but only a small variation proportional to density. The contribution of other nonadditive effects is briefly examined as is the small contribution of nonadditive effects to the x‐ray structure factor of the liquid.

Optimal Thermal Design of an Autothermal Ammonia Synthesis Reactor

Abstract: T h e treatment of variational problems has received considerable attention in the chemical engineering literature in the past decade. These can be classified as control or design problems. In chemical engineering, one would expect the most useful results to come from the solution of the design rather than the control problems, because in controlling a process one can, through feedback, correct and control by specifying the control algorithm (the functional relationship between corrective action and error) and not the control action function-e.g., valve stem position us. time. The solution to the variational control problem would yield the control action function, and while there are cases-e.g., batch processes-in which this would be useful, in most process control problems we are free to exert corrective action after the process has started and error has been measured. This is obviously not true in design problems; the configuration is first set and then the process is operated. This situation is more compatible to the nature of variational problem solutions. Thus it was decided to study variational problems that arise in design. Beginning with Temkin and Pyzhev (1960) and Denbigh (1944, there has developed a considerable literature (Aris, 1961) on the processing conditions under which a chemical reaction should be carried out in order to obtain maximum yield or selectivity. Although this work is of great value, there are two shortcomings: The process variables such as temperature, pressure, and concentration are not under direct control of the designer-for example, the designer

Automated determination of ammonium and nitrate in soil extracts by distillation

Abstract: Automated procedures for the determination of ammonium and nitrate in soil extracts are described. Distillation of the extract with magnesium oxide, with subsequent determination of ammonia by the automated indophenol method, is used for ammonium. For ammonium plus nitrate, the nitrate is reduced with titanium(III) sulphate during distillation with magnesium oxide, and ammonia determined as before. The method has wider application, for example, to the analysis of fertilisers and water samples.

Separation of low-boiling gas mixtures

Abstract: A process for the recovery of hydrogen from an ammonia synthesis purge gas comprising ammonia, hydrogen, nitrogen and methane wherein ammonia is first separated from the purge gas and the gas substantially free of ammonia is subsequently cooled to very low temperatures, e.g., -300 DEG F., thereby obtaining a liquid phase and a hydrogen-rich gaseous phase.

Factors affecting the urinary excretion of urea nitrogen in cattle. III. High plasma urea nitrogen concentrations

Abstract: The relationship between urinary urea nitrogen excretion, the filtered load of urea nitrogen, and the plasma urea nitrogen concentration were studied in cows intravenously infused with 0.5–10 g urea nitrogen per hour. These levels of infusion resulted in ranges of plasma urea nitrogen concentration of 12–63 mg/100 ml, of filtered urea nitrogen of 3–19 g/hr, and of urinary urea nitrogen excretion of 2.5–12.7 g/hr. There were linear relationships between the filtered load of urea nitrogen and the plasma urea nitrogen concentration (r = 0.91), between urinary urea nitrogen excretion and the filtered load of urea nitrogen (r = 0.92), and between urinary urea nitrogen excretion and the plasma urea nitrogen concentration (r = 0.97). It was concluded that the amount of urea excreted in the urine was regulated more by the plasma urea concentration than by renal processes such as glomerular filtration rate (GFR), the concentrating ability of the kidneys, or urine flow rate. The capacity of the bovine kidneys to excrete urea and mechanisms involved in the renal excretion of urea are discussed. The successful use of 51Cr-EDTA for the estimation of GFR in cattle is reported in an appendix. __________________ *Part II, Aust. J. Agric. Res., 21: 145 (1970).

Volatilization of ammonia from submerged tropical soils.

Abstract: A laboratory study was made of the losses of nitrogen through ammonia volatilization from four flooded, tropical soils. The soils used varied considerably in pH, organic matter content, and cation exchange capacity. Losses were measured from the unamended soils, and from ammonium sulphate and urea-treated soils. Two rates of nitrogen application (approximately 50 and 200 kg/ha N) and two methods of application (simulated field broadcast and fertilizer incorporation) of the nitrogen were used. Losses of ammonia were detected for each of the unamended soils, including an acid sulphate soil of pH 3.6. Increased application of both ammonium sulphate and urea resulted in increased losses of ammonia through volatilization. Incorporation of the nitrogen into the mud of the flooded soils significantly decreased losses due to volatilization. It was concluded that the initial or ‘aerobic’ pH of the soils was the soil characteristic most closely related to the magnitude of losses due to volatilization.

Ab Initio SCF MO Study of the Interaction of Lithium with Ammonia

Abstract: An ab initio molecular orbital study of the stability and electronic structure of lithium–ammonia complexes was made. A complex of lithium with one ammonia molecule is predicted to be stable by 20 kcal/mole relative to a free lithium atom and a free ammonia molecule. The bonding in the complex is primarily through sharing of the lone pair of electrons on ammonia between the ammonia molecule and the lithium atom. The unpaired electron orbital is rearranged upon formation of the complex so that it has very low density in the region of the ammonia with the exception of a sharp peak in density near the nitrogen nucleus. The complex with two ammonia molecules is nearly isoenergetic with the one ammonia complex plus an ammonia molecule. Addition of a second ammonia causes an increase in the preferred lithium–nitrogen distance and an increase in the occupancy of the nitrogen orbitals by the unpaired electron. Ammonia appears repulsive to the unpaired electron in the diammonia complex, also. The implications of these results for models of the monomer in metal–ammonia solutions are discussed.

The thermal decomposition of ammonium metavanadate, i

Abstract: The stoichiometry of the various stages involved in the thermal decomposition of ammonium metavanadate has been shown to correspond to a stepwise decrease in the ratio of ammonia and water to V2O5, with V2O5 being the final product in vacuum, in air and in argon. In ammonia, VO2 is formed. The actual stages and intermediates are dependent upon the prevailing atmosphere. Chemical analyses, together with infrared absorption spectra and X-ray powder data, have enabled the intermediates and products to be characterized and the structural changes involved in the decomposition to be discussed.

Bonding with ammonium polymer salts

Abstract: Water-soluble ammonium salts of ethylene-acrylic acid copolymers are used to coat or bond various substrates with water insoluble ethylene-acrylic acid copolymers by first applying the salt alone or with polyvinyl alcohol to the substrate from aqueous solutions or dispersions and then drying the treated substrate. During the drying step ammonia is evolved leaving the ethylene-acrylic acid copolymer on the substrate. This invention has been used to coat articles with a temporary coating, and to prepare floor polishes, paper coatings, non-woven fabrics and water-proof wood.

Hydrogen purification and recycle in hydrogenating heavy mineral oils

Abstract: Heavy mineral oils with high nitrogen contents are hydrogenated in two stages, with gas effluent from only the first stage being scrubbed to remove ammonia and then sent to the second stage with hydrogen makeup, the gas effluent from the second stage being recycled without scrubbing as the hydrogen feed for the first stage, the first stage effluent undergoes separation in two high pressure zones to produce light liquid hydrocarbons as a product of the process.