Showing papers on "Ammonia published in 1980"

On the Gaseous Exchange of Ammonia between Leaves and the Environment: Determination of the Ammonia Compensation Point

Abstract: Whole shoots of Phaseolus vulgaris L. and other species were exposed to a range of partial pressures of gaseous ammonia in air and the resulting fluxes were measured. Net uptake is linear with partial pressure in the range 5 to 50 nanobars and is zero at a finite partial pressure, termed the ammonia compensation point. Below the compensation point, ammonia (or possibly other volatile amines) is evolved by the leaves. The compensation points in several species are near the low partial pressures found in unpolluted air and approximate to the Km of glutamine synthetase in vitro. In P. vulgaris L., the compensation point increases with temperature.

4 – Ammonia Assimilation

Abstract: Publisher Summary This chapter focuses on ammonia assimilation and discusses the mechanisms by which the ammonia produced is incorporated into organic compounds. Nitrate and dinitrogen gas, two of the major sources of inorganic nitrogen available to plants, are reduced to ammonia before the nitrogen is incorporated into organic matter. Ammonia is released and reassimilated in large amounts at different stages of the plant's metabolism. Nitrate is the major source of inorganic N available to the leaves of most land plants; ammonia is not present in the xylem stream leaving the roots. Thus, the ammonia assimilated is normally generated in situ from the reduction of nitrate through nitrite. Ammonia is not normally transported into a leaf but is rather a product of nitrate reduction; however, it can also be generated within the leaf by two other ways: (1) by the breakdown of asparagine through transaminase or asparaginase and (2) in photorespiration.

Nitrate and Nitrite Reduction

Abstract: Publisher Summary This chapter describes nitrate and nitrite reduction. Nitrate is the predominant form of nitrogen available to most cultivated plants grown under normal field conditions. Although ammoniacal fertilizers are used almost exclusively, the ammonia derived from these fertilizers is oxidized to nitrate by soil organisms. Nitrification is extremely rapid when the soil is well aerated, moist, and above 7°–10°C. Certain bacteria can utilize nitrate nitrogen as the sole nitrogen source for the synthesis of all nitrogen containing compounds of the cell. This nitrate assimilation can occur under both aerobic and anaerobic conditions. Nitrate reduction by partially purified enzyme preparations is frequently stimulated by phosphate. Nitrate reduction, mediated by either reduced pyridine nucleotides or reduced viologen dyes, is inhibited by cyanide and azide; however, pyridine-nucleotide-mediated reduction of cytochrome c is insensitive to these inhibitors. A reactivation of an inactive nitrate reductase apoenzyme extracted from molybdenum-deficient plants can be achieved by the addition of acid-treated nitrate reductase or by addition of phosphate buffer washes of nitrate reductase absorbed on adenosine monophosphate -Sepharose.

Ammonia production by intestinal bacteria: the effects of lactose, lactulose and glucose.

Abstract: Ammonia production by eight groups of intestinal bacteria was measured, and the effect on ammonia production of lowered pH and ambient ammonia concentration was determined. Endogenous ammonia production from bacterial protoplasm was also examined. To examine the mechanisms by which fermentable substrates reduce ammonia formation in a faecal incubation system, the effect of lactose, lactulose or glucose on ammonia release by pure cultures of intestinal bacteria was studied. The largest amounts of ammonia were generated by gram-negative anaerobes, clostridia, enterobacteria, and Bacillus spp. Gram-positive non-sporing anaerobes, streptococci and micrococci formed modest amounts, and lactobacilli and yeasts formed very little ammonia. All groups of bacteria formed less ammonia at pH 5.0 than at pH 7.0 and production of ammonia was not inhibited when 30 mmol ammonia/litre was included in the medium. Small amounts of ammonia were formed due to endogenous metabolism of bacterial cells. Washed cell suspensions of four isolates of Bacteroides, one clostridial isolate and two streptococcal isolates formed less ammonia from alanine, methionine or histidine after growth in the presence of either lactose or lactulose. In contrast, the Bacteroides isolates formed more ammonia from aspartate than from either lactose or lactulose. Also, cultures of gram-negative anaerobes and enterobacteria, and to a lesser extent clostridia and streptococci, formed significantly less ammonia in nutrient broth when lactose, lactulose or glucose was included in the medium. This decrease in ammonia formation was not due to a fall in pH of the medium. Ammonia production by gram-positive non-sporing anaerobes was not affected by carbohydrate fermentation. These results suggest that gram-negative anaerobic bacteria make a major contribution to ammonia generated from peptides and amino acids in vivo, and that ammonia may be formed from bacterial cells in the colon. Fermentation of lactose and lactulose may repress the formation and inhibit the activity of enzymes responsible for ammonia release. In the human colon these substrate effects may decrease the amount of ammonia available to exert a toxic effect on the host, and thus contribute to the beneficial effects of lactulose when it is used in the treatment of portosystemic encephalopathy.

Production of nitrous oxide by ammonia-oxidizing chemoautotrophic microorganisms in soil.

Abstract: Gas chromatographic studies showed that nitrous oxide was produced in each instance when sterilized (autoclaved) soil was incubated after treatment with ammonium sulfate and inoculation with pure cultures of ammonia-oxidizing chemoautotrophic microorganisms (strains of Nitrosomonas, Nitrosospira, and Nitrosolobus). Production of N(2)O in ammonium-treated sterilized soil inoculated with Nitrosomonas europaea increased with the concentration of ammonium and the moisture content of the soil and was completely inhibited by both nitrapyrin and acetylene. Similar effects of nitrapyrin, acetylene, ammonium concentration, and soil moisture content were observed in studies of factors affecting N(2)O production in nonsterile soil treated with ammonium sulfate. These observations support the conclusion that, at least under some conditions, most of the N(2)O evolved from soils treated with ammonium or ammonium-producing fertilizers is generated by chemoautotrophic nitrifying microorganisms during oxidation of ammonium to nitrite.

N2O reduction by Vibrio succinogenes.

Abstract: Vibrio succinogenes grew anaerobically at the expense of formate oxidation, with nitrous oxide (N2O) serving a terminal oxidant. N2O was quantitatively reduced to dinitrogen (N2). In the presence of 5 x 10(-2) atm (ca. 5 kPa) of acetylene (C2H2), which inhibits the reduction of N2O, growth of V. succinogenes was completely inhibited. Nitrate was reduced to nitrite or to ammonia, depending on the extent of availability of formate, but N2 was not produced by reduction of nitrate. During the reduction of nitrate to ammonia, all eight electrons transported to a molecule of nitrate appeared to be coupled for energy-yielding reactions.

Ammonia gas concentrations over the Southern Ocean

Abstract: Ammonia is the only common, soluble, basic gas in the atmosphere and as such plays an important neutralising, sometimes rate-determining, role in the chemistry of acid gases such as SO2, H2SO4 and HNO3. It also constitutes a reservoir of labile nitrogen in the atmosphere and so must be included in any attempt to describe the cycling of nitrogen through the global environment. We report here values of ammonia concentration measured in Southern Ocean air which are considerably lower than any previously reported1–5. For our analyses ammonia was collected on oxalic acid-impregnated filters and determined colormetrically. In air apparently devoid of contact with land for several thousands of kilometres of travel the mean concentration of ammonia gas was 0.06 μg m−3 (STP). Concentrations in air apparently affected by the Australian continent were several times higher than in the maritime air.

Reactivity of stratospheric aerosols to small amounts of ammonia in the laboratory environment

Abstract: Trace ammonia in laboratory air reacts easily with sulfuric acid aerosol samples to form crystalline ammonium sulfate. Argon atmospheres, however, protect sampling surfaces from ammonia contamination. It is found that atmospheric aerosols treated in this way contain only sulfuric acid. After an hour exposed to laboratory air, these same samples convert to ammonium sulfate. Aerosol particles have been collected, using argon control, to determine if the absence of crystalline sulfate is common. But so far there is no evidence that aerosols are neutralized by ammonia in the stratosphere.

Process for the production of ammonia and the corresponding synthesis gas

Abstract: A process to produce ammonia from a hydrocarbon feedstock, involving basically the following steps: Dividing the feedstock into two fractions, Subjecting the first fraction to a primary steam reforming reaction, at high pressure and moderate temperature, Combining the effluent from the primary reforming with the second fraction of the feedstock, and subjecting the mixture thereof to a secondary adiabatic reforming reaction with an amount of air in excess to that needed for ammonia synthesis, Subjecting the synthesis gas produced to a CO shift conversion reaction, and then to CO 2 removal by solvent scrubbing, while the gas released by pressure letdown of said solvent is preferably recycled back upstream of the secondary reforming, Methanation of the residual carbon oxides, Removing the excess nitrogen present in the gas by cryogenic separation, Compressing and feeding the final synthesis gas into an ammonia synthesis loop, Recycling the purge gas from said ammonia synthesis loop to upstream the cryogenic separation.

Reaction mechanism of ammonia decomposition on tungsten

Abstract: The mechanism of ammonia decomposition on a clean tungsten surface was studied by direct and simultaneous measurements of the reaction rate and the amounts and behaviour of adsorbed species during the course of the reaction in the temperature range 773–1473 K under an ammonia pressure of 10–6–10–3 Pa. The order of the reaction rate with respect to ammonia pressure changed with temperature from first order to fractional at 1473 and 773 K, respectively. No hydrogen was adsorbed on the surface in any form above 973 K and an increase in the hydrogen partial pressure (PH2) during the reaction had no effect on either the reaction rate or on the amount of surface nitrogen (θN). Under higher ammonia pressures, up to 100 Pa, thick surface nitride layers were formed during the decomposition, which decomposed at the same rate in vacuo as in the steady-state NH3 decomposition, provided the uptake of nitrogen was the same. It was also found that the rate of nitrogen desorption from the surface depended only on θN, being faster with increasing θN, whereas the rate of nitrogen uptake from ammonia decreased with increasing θN and increased with ammonia pressure (PNH3). On the basis of these data, it was concluded that the overall reaction proceeds through a reaction mechanism of “dynamic balance” between two consecutive ratedetermining steps; the supply and consumption of surface nitrogen.

Preparation of l-glutamic acid by fermentation

Abstract: PURPOSE: To increase the concentration of glucose or sucrose in the culturing medium to more than 1.5 times the one obtainable by the conventional process, and to increase the amount of L-glutamic acid accumulated in the medium, by culturing L-glutamic acid-producing bacteria under specific conditions. CONSTITUTION: L-glutamic acid-producing bacteria (e.g. Brevibacterium devaricatum, Corynebacterium acetoacidiphilum) are inoculated in a liquid medium containing glucose or sucrose as main carbon source, and aerobically cultured. When the concentraion of the sucrose is decreased to a predetermined value below 10 g/1, glucose or sucrose is added to the medium, and at the same time, aqueous ammonic (or ammonia gas) or an alkali hydroxide is added to the medium to keep the ammonium ion concentration in the medium between 0.3 and 10 g/d1. The aqueous ammonia raises the concentration, while the alkali hydroxide lowers. COPYRIGHT: (C)1979,JPO&Japio

Effect of ammonia on photosynthetic carbon fixation in isolated spinach leaf cells

Abstract: Ammonia stimulated photosynthetic 14CO2 fixation in isolated spinach cells under conditions of saturating light intensity and adequate CO2 supply. Increasing temperature increased photosynthesis and promoted the stimulation of photosynthesis by ammonia. Ammonia increased carbon traffic into organic acids and amino acids without affecting the total, 14C incorporation in the neutral fraction, although the relative distribution of 14C incorporation in the neutral fraction as a percentage of the total soluble 14C incorporation was decreased. The increased carbon flow into the amino acid fraction led to an increase of, 14C incorporation, principally into glutamine, glutamate, and aspartate. The role of ammonia in photosynthetic carbon metabolism is discussed.

Physiological ecology of acetylene reduction (nitrogen fixation) in a Delaware salt marsh.

Abstract: The effects of several fixed nitrogen compounds on acetylene reduction activity (nitrogen fixation) of surface sediments from a Delaware salt marsh were studied. Ammonia addition caused little decrease in activity early in the summer but resulted in a considerable decrease (85–95%) in activity late in the summer and early in the fall. Nitrate caused a near complete suppression of activity at all times. Other compounds such as glutamate, urea, and yeast extract caused a slight increase in activity in tallSpartina sediments and caused more than a 2.5-fold increase in shortSpartina sediments. There was a lag period (1–2 days) before the commencement of in vitro acetylene reduction activity during the spring and early summer, but this lag period was not present in the late summer. The addition of chloramphenicol to samples from a shortSpartina zone caused decreases in activity similar to those obtained with ammonia, whereas chlorate amendments yielded results which, when compared on an electron basis, were comparable to those obtained with nitrate. These results indicated that the observed lag period may be the result of a physiological response to the in situ levels of ammonia and/or nitrate. It is suggested here that in situ nitrogenase activity may be controlled by two processes: (a) repression and derepression of nitrogenase synthesis mediated by the levels of ammonia, and (b) competition for reducing power (electrons) and energy (ATP) between the processes of nitrate reduction and nitrogen fixation.

Process for purifying urea-containing waste water and process for preparing melamine

Abstract: An improved process for the removal of urea from urea-containing waste water by hydrolysis and desorption of the ammonia and carbon dioxide thus formed. Urea-containing waste water is treated in a process for the separation of ammonia and carbon dioxide from mixtures thereof, which process has (a) an ammonia separation zone wherefrom ammonia, substantially free of carbon dioxide and water, is obtained, (b) a carbon dioxide separation zone wherefrom carbon dioxide, substantially free of ammonia and water is obtained, and (c) a desorption zone wherefrom water, substantially free of carbon dioxide and ammonia is obtained. The urea is substantially completely hydrolyzed and the ammonia and carbon dioxide produced thereby can be recovered.

Reactions of coordinated dinitrogen. 8. Formation of ammonia by protonation of a molybdenum-dinitrogen complex and isolation and characterization of the molybdenum-containing product

Abstract: This is the first reported conversion of metal-coordinated dinitrogen into ammonia in which the fate of the metal has been determined. This reaction is shown in the following equation, where triphos = PhP(CH/sub 2/CH/sub 2/PPh/sub 2/)/sub 2/ and L = PPh/sub 3/:2Mo(N/sub 2/)/sub 2/(triphos)(L) + 8HBr ..-->.. 2NH/sub 4/Br + 2MoBr/sub 3/(triphos) + 3N/sub 2/ + 2L. The metal complex which is a new subclass of bis(dinitrogen) complexes of molybdenum, reacted in tetrahydrofuran (THF) solution with anhydrous hydrogen bromide to produce ammonium bromide. No hydrazine or hydrazinium bromide was detected among the reaction products. Ammonium bromide was detected by infrared spectroscopy among the reaction products after solvent and excess HBr had been removed in vacuo. The yield of ammonia was determined quantitatively by the indophenol method after either aqueous, nonaqueous (ethanol), or two-phase (dichloromethane-water) extraction of ammonium bromide from the residue. The molybdenum-containing product slowly decomposed during the dichloromethane-water extraction step. Isolation of pure MoBr/sub 3/(triphos) was carried out in a separate experiment in which only N/sub 2/ evolution was measured. All volatiles were removed from the reaction vessel and the resulting yellow solid was washed with ethanol and dried. Its identity was confirmed by elemental analysis.

Process for the production of crystalline aluminosilicates and their use as catalysts and catalyst supports

Abstract: OF THE DISCLOSURE Crystalline alumonosilicates having a silica to alumina molar ratio greater than 12 are produced by mixing a source of silica, a source of alumina, a source of alkali metal, water and a source of ammonium ions, e.g. ammonia or an ammonium salt, in the absence of an alcohol or alkylene oxide, in the molar proportions (expressed in the case of the silica and alumina sources in terms of the equivalent moles of the oxide, in the case of the alkali metal source in terms of the equivalent moles of the hydroxide [MOH] and in the case of the source of ammonium ions in terms of free ammonia): SiO2 : A1203 greater than 12:1 MOH : A12O3 in the range from 1:1 to 20:1 SiO2 : NH3 in the range from 1:1 to 200:1 H2O : MOH in the range from 30:1 to 300:1 and maintaining the composition at elevated temperature, such as 120 to:210°C, for a period such that crystallisation occurs, typically greater than 4 hours. The crystalline aluminosilicates so-prepared are useful as catalysts and catalyst supports.

Process for controlling nitrogen oxides in exhaust gases and apparatus therefor

Abstract: In a process and an apparatus for controlling oxides of nitrogen in exhaust gases from combustion equipment by decomposing the oxides, in the presence of oxygen, with ammonia blown into the equipment and associated ducting at temperatures within the range from 700° to 1300° C., a catalyst assembly is arranged, with the catalytic surfaces of the component units substantially in parallel to the direction of exhaust gas flow, in a region where the temperature of the gas after the decomposing treatment is between 300° and 500° C., and the gas after the decomposing treatment is caused to pass through the catalyst assembly to decompose residual nitrogen oxides and ammonia in the gas to innocuous substances. An additional supply of ammonia, in an amount from 0.5 to 1.5 times equivalent (in molar ratio) to the amount of nitrogen oxides in moles in the gas is introduced into the space immediately upstream of the catalyst assembly, thereby to accelerate the decomposition of the oxides in the gas to make it harmless.

The solubility of cellulose in liquid ammonia/salt solutions

Abstract: The dissolution of cellulose in solutions of liquid ammonia and ammonium thiocyanate is discussed. Viscosity measurements on dilute solutions of cellulose in this solvent over a range of shear rates and shear stresses are reported. A four-bulb Ubbelohde suspended level viscometer was used for the measurements. Plots of log [η] versus log M gave Mark-Houwink coefficients of a = 0.95 and K = 6.686 × 10−5 at 25°C for [η] as dl/g. The Bloomfield equation was used to calculate effective bond lengths (b) from limiting viscosity numbers of cellulose in solutions of ammonia/ammonium thiocyanate and Cuene, respectively. Results indicate that cellulose may have similar configurations in both solvents and also that the ammonia solutions are true cellulose solutions. Miscibility of the cell- ulose/ammonia/ammonium thiocyanate solutions with organic solvents, such as glycerol, is also reported. Further, a few interesting characteristics of the liquid ammonia/ammonium salt solutions, discussed briefly, are the convenient boiling point, the rheological behavior, and the relatively high concentration of cellulose obtainable.