UV-Photolyse von 5-Joduracil / UV Photolysis of 5-Iodouracil

1972 ◽  
Vol 27 (5) ◽  
pp. 501-504 ◽  
Author(s):  
E. Gilbert ◽  
G. Wagner ◽  
D. Schulte-Frohlinde
Keyword(s):  
Main Product ◽  
Ph Value ◽  
Product Distribution ◽  
Reaction Products ◽  
Value Addition ◽  
Uv Photolysis ◽  
Ph Values ◽  
Constant Ph ◽  
Ph Range

UV Photosylis (254 nm) of 5-iodouracil in aqueous, oxygenated solution in presence of KI, FeSO4, KBr and K2SO4 was investigated over a pH-range of 1—6. Uracil, isodialuric acid, and isobarbituric acid were identified as photoproducts.At a constant pH-value (pH=1) at high KI-concentrations (10-1 mole/1) the main product is uracil. With decreasing KI-concentrations the yield of uracil decreases and isobarbituric acid appears as a photoproduct. On further decreasing KI-concentrations (< 10-2 mole/1) the yield of isobarbituric acid decreases and the formation of isodialuric acid commences.UV Photolysis of iodouracil at constant KI-concentrations (10—1 mole/1) and increasing pH (pH = 1—6) yields similar results with one exception. At higher pH-values on account of isodialuric acid at least four further compounds are formed. The yield of these products increases with increasing pH value. Addition of KBr and K2SO4 has no effect on the product distribution.The possible mechanisms for the formation of the reaction products are discussed.

Survival of Bacillus cereus Vegetative Cells and Spores during In Vitro Simulation of Gastric Passage

2012 ◽  
Vol 75 (4) ◽  
pp. 690-694 ◽  
Author(s):  
SIELE CEUPPENS ◽  
MIEKE UYTTENDAELE ◽  
KATRIEN DRIESKENS ◽  
ANDREJA RAJKOVIC ◽  
NICO BOON ◽  
...  
Keyword(s):  
Bacillus Cereus ◽  
Acid Resistance ◽  
In Vitro Experiments ◽  
Vegetative Cells ◽  
Ph Values ◽  
Constant Ph ◽  
In Vitro Simulation ◽  
Ph Range

The enteric pathogen Bacillus cereus must survive gastric passage in order to cause diarrhea by enterotoxin production in the small intestine. The acid resistance and the survival after gastric passage were assessed by in vitro experiments with acidified growth medium and gastric simulation medium with B. cereus NVH 1230-88 vegetative cells and spores. First, batch incubations at constant pH values for 4 h, which represented different physiological states of the stomach, showed that spores were resistant to any gastric condition in the pH range of 2.0 to 5.0, while vegetative cells were rapidly inactivated at pH values of ≤4.0. Second, a dynamic in vitro gastric experiment was conducted that simulated the continuously changing in vivo conditions due to digestion dynamics by gradually decreasing the pH from 5.0 to 2.0 and fractional emptying of the stomach 30 to 180 min from the start of the experiment. All of the B. cereus spores and 14% (±9%) of the vegetative cells survived the dynamic simulation of gastric passage.

scholarly journals Zinc adsorption in highly weathered soils

2008 ◽  
Vol 43 (1) ◽  
pp. 131-139 ◽  
Author(s):  
José Carlos Casagrande ◽  
Marcio Roberto Soares ◽  
Ernesto Rinaldi Mouta
Keyword(s):  
Ionic Strength ◽  
Ph Value ◽  
Batch Adsorption ◽  
Adsorption Mechanisms ◽  
Ionic Strength Effect ◽  
Ph Values ◽  
Effects Of Ph ◽  
Ph Range ◽  
Highly Weathered Soils ◽  
Zinc Adsorption

The objective of this work was to assess the effects of pH and ionic strength upon zinc adsorption, in three highly weathered variable charge soils. Adsorption isotherms were elaborated from batch adsorption experiments, with increasing Zn concentrations (0-80 mg L-1), and adsorption envelopes were constructed through soil samples reactions with 0.01, 0.1 and 1 mol L-1 Ca(NO3)2 solutions containing 5 mg L-1 of Zn, with an increasing pH value from 3 to 8. Driving force of reaction was quantified by Gibbs free energy and separation factor. Isotherms were C-, H- and L-type and experimental results were fitted to nonlinear Langmuir model. Maximum adsorption ranged from 59-810 mg kg-1, and Zn affinity was greater in subsoil (0.13-0.81 L kg-1) than in the topsoil samples (0.01-0.34 L kg-1). Zinc adsorption was favorable and spontaneous, and showed sharply increase (20-90%) in the 4-6 pH range. No effect of ionic strength was observed at pH values below 5, because specific adsorption mechanisms predominated in the 3-5 pH range. Above pH 5, and in subsoil samples, Zn was adsorbed by electrostatic mechanisms, since ionic strength effect was observed. Despite depth and ionic strength effects, Zn adsorption depends mainly on the pH.

THE DECOMPOSITION OF 2-METHYL-Δ2-OXAZOLINE IN AQUEOUS SOLUTION

1963 ◽  
Vol 41 (7) ◽  
pp. 1662-1670 ◽  
Author(s):  
R. Greenhalgh ◽  
R. M. Heggie ◽  
M. A. Weinberger
Keyword(s):  
Aqueous Solution ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Water Concentration ◽  
Acidity Function ◽  
First Order ◽  
Ph Values ◽  
Constant Ph ◽  
Kinetic Expression ◽  
Ph Range

Nuclear magnetic resonance has been used to follow the decomposition of aqueous solutions of 2-methyl-Δ2-oxazoline (0.29 M) at constant pH values in the range −1 to 14. The decomposition is first order with respect to total oxazoline at any specific pH, but deviates from the simple reaction of water with the protonated species above pH 5. At neutral pH values this is shown to be partially due to a second reaction involving 2-methyl-Δ2-oxazoline and O-acetylethanolamine which yields N-2-acetoxyethyl N′-2-hydroxyethyl acetamidate. The decrease in rate constant at pH < 2 is accounted for by variation in the water concentration, which is related to the acidity function. A kinetic expression is derived for the decomposition over the whole pH range studied. The decomposition of the amidate is also discussed.

Isotope Effects of Uranium by Ion Exchange in the System Dowex 50 / α-Hydroxyisobutyrate

1974 ◽  
Vol 29 (3-4) ◽  
pp. 190-194 ◽  
Author(s):  
Jorma Aaltonen ◽  
Klaus G. Heumann ◽  
Pikka Pietilä
Keyword(s):  
Ion Exchange ◽  
Isotope Effect ◽  
Separation Factor ◽  
Ph Value ◽  
Isotope Effects ◽  
Uranyl Ions ◽  
Distribution Factor ◽  
Ph Values ◽  
Ion Exchange Column ◽  
Ph Range

In this investigation the isotope effect of uranium in the system Dowex 50 resin/ α- hydroxyisobutyrate solution was studied by mass spectrometry. A recycle ion exchange column was used for the separation experiments. The dependence of the isotope effect on the pH value and on the concentration of the α-hydroxyisobutyrate solution used as eluent was investigated. In the case of a 0.07 ᴍ and a 0.22 ᴍ α-hydroxyisobutyrate solution the elementary separation factor of uranium was calculated to be 1.00019 and 1.00006, respectively. In both cases an enrichment of 235U in relation to 238U was found in the solution.In addition the distribution factor of the uranyl ions in the investigated system was determined in the pH range between 2 and 6. The distribution factor depends strongly on the pH value. With increasing pH values the distribution factor decreases.The results obtained for the elementary separation factor and the distribution factor are compared with other investigations.

Effect of pH on Fenton process using estimation of hydroxyl radical with salicylic acid as trapping reagent

2008 ◽  
Vol 58 (4) ◽  
pp. 873-879 ◽  
Author(s):  
Chen-Yu Chang ◽  
Yung-Hsu Hsieh ◽  
Kai-Yuan Cheng ◽  
Ling-Ling Hsieh ◽  
Ta-Chih Cheng ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Hydroxyl Radical ◽  
Ph Value ◽  
Formation Rate ◽  
Fenton Process ◽  
Reaction Products ◽  
Reaction Conditions ◽  
Ph Values ◽  
The Difference ◽  
The Relationship

This study estimates the yield of hydroxyl radical using salicylic acid as the trapping reagent and investigates the relationship between hydroxyl radical and pH value. The formation and variation of hydroxyl radical under different pH values were evaluated using reaction products, 2,3-DHBA, 2,5-DHBA, and catechol. The formation rate of hydroxyl radical was dependent on the ratio of ferrous ion to hydrogen peroxide and pH values. The difference between various pH values was explored. The kinetics and mechanisms of hydroxyl radical reactions were established in the Fenton process. Experimental results showed that the best reaction conditions were 8.5 mM H2O2, 1.25 mM Fe2 + , Fe2 + /H2O2=0.147 at pH 3 and the formation rate constant of hydroxyl radical was 1.12 × 1011 M−1 s−1.

Sectroscopic study of stability and molecular species of 12-tungstophosphoric acid in aqueous solution

2008 ◽  
Vol 86 (10) ◽  
pp. 996-1004 ◽  
Author(s):  
Ivanka Holclajtner-Antunović ◽  
Danica Bajuk-Bogdanović ◽  
Marija Todorović ◽  
Ubavka B Mioč ◽  
Joanna Zakrzewska ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Molecular Species ◽  
Ph Value ◽  
Equilibrium Composition ◽  
Keggin Structure ◽  
Special Importance ◽  
Keggin Anion ◽  
Ph Values ◽  
Ir And Nmr Spectroscopy ◽  
Ph Range

The various molecular species of 12-tungstophosporic acid (WPA) in aqueous solutions of different pH values (from 1 to 11.5) were investigated by UV, IR, and NMR spectroscopy. The dependence of the attained equilibrium composition in solution on time, concentration of WPA, and type of buffer used was studied. Obtained results indicate that the buffer type and pH value greatly determine the equilibrium composition in the solution. The Keggin structure of the WPA is sustained only up to pH 1.5. With further increase in pH, the decomposition of Keggin anion does not lead directly to the monovacant lacunary anion. Between 1.5 and 2.0, the structures with 2 phosphorus atoms from the Dawson series are dominant as intermediate species. In the pH range 3.5–7.5, WPA is present in the form of the monovacant lacunary Keggin anion. These results are of special importance for the biomedical and catalytic applications of heteropoly compounds (HPCs) and for an improved understanding of the mechanism of their functioning.Key words: heteropolyacids of the Keggin structure, hydrostability, UV, IR and NMR spectroscopy.

scholarly journals Disproportionation and Polymerization of Plutonium(IV) in Dilute Aqueous Solutions

1983 ◽  
Vol 26 ◽  
Author(s):  
T. W. Newton ◽  
V. L. Rundberg
Keyword(s):  
Ionic Strength ◽  
Aqueous Solutions ◽  
Rate Constants ◽  
Second Order ◽  
Disproportionation Reaction ◽  
Reaction Products ◽  
Constant Ph ◽  
Low Concentrations ◽  
Dilute Aqueous Solutions ◽  
Ph Range

ABSTRACTThe rates of polymerization and disproportionation of Pu(IV) have been studied using low concentrations: (1.7 − 10) × 10−6M Pu, (0.8 − 12) × 10−4M HCI and 0.01M ionic strength. Osmium(II) complexes such as the tris−4,41−2,21−bipyridine complex were found to react rapidly with Pu(IV) but very slowly, if at all, with Pu(IV) polymer, Pu(lll), or Pu(V). Thus, it is possible to determine unreacted Pu(IV) in the presence of reaction products by using Os(II) complexes. Disproportionation reaction products, Pu(IlI) and Pu(V), were determined using their reactions with Ce(IV) sulfate. We find −d[Pu(IV)]/dt = k'[Pu(IV)]2 at constant pH. Log k1 varies from about 4.25 at pH 3 to about 7.0 at pH 4.1 (units for k1 are M−1min−1). The [H+] dependence varies from about −2 to −3 over the pH range studied. The measured rate is the sum of those for polymerization and disproportionation; the latter reaction amounts to about 75% of the total at pH 3 and 20% at pH 4. The second-order rate constants for disproportionation are very much larger than expected on the basis of extrapolation from 0.2 to 1.OM HClO, solutions. The products of the reaction do not affect the rate, but U(VI), aged Pu(IV) polymer, and CO2 increase the rate.

scholarly journals Sorption of heavy metals by natural biopolymers

2017 ◽  
Vol 35 (7-8) ◽  
pp. 595-601 ◽  
Author(s):  
Natalya V Efimova ◽  
Alla P Krasnopyorova ◽  
Galina D Yuhno ◽  
Anastasia A Scheglovskaya
Keyword(s):  
Functional Group ◽  
Ph Value ◽  
Kinetic Properties ◽  
Hydrolysis Lignin ◽  
Second Order Reaction ◽  
Equilibrium Solutions ◽  
Sorption Equilibrium ◽  
Ph Values ◽  
Ph Range ◽  
Modified Lignin

The sorption properties of modified hydrolysis lignin towards Cu[Formula: see text], Zn[Formula: see text], Ni[Formula: see text], Co[Formula: see text] ions in the pH range from 2 to 8 at temperature of 298.15 K solution are studied. The analysis of kinetic curves of ions sorption on modified lignin at pH 7 shows that sorption equilibrium in heterogenic system ion–metal–sorbent is attained in 30–60 min. Obtained results indicate good equilibrium kinetic properties of sorbent. Supposed that reaction between sorbate and functional group of sorbent are the second-order reaction and they interact between each other in ratio 1:1. The character of the obtained electrokinetic curve suggests that the zeta potential of modified lignin strongly depends on the pH. The dependencies of cations metals sorption coefficients on the pH value of water phase are S-shaped. Maximal extraction of studied cations is observed at pH values of equilibrium solutions close to neutral ones.

Influence of Ionic Strength and pH-value on the Silicon Dioxide Polishing Behaviour of Slurries Based on Pure Silica Suspensions

2010 ◽  
Vol 1249 ◽  
Author(s):  
Ulrich Kuenzelmann ◽  
Kathrin Estel ◽  
Johann W Bartha ◽  
Erwin-Peter Meyer ◽  
Herbert Barthel
Keyword(s):  
Ionic Strength ◽  
Fumed Silica ◽  
Ph Value ◽  
Acidic Ph ◽  
Experimental Conditions ◽  
Ph Values ◽  
Pure Silica ◽  
Silica Sols ◽  
Ph Range ◽  
Silica Suspensions

AbstractIn this study, the effect of the addition of electrolytes in a given ionic strength to various high-purity silica suspensions was investigated by measurement of the removal rates (RR's) in CMP processes on oxide layers under the same experimental conditions. As so-called slurries the following suspensions were used: i) silica sols produced by the Stöber process, ii) conventional silica sols based on alkali silicate as well as iii) suspensions of fumed silica, with the same SiO2 concentration in each suspension. Ionic strength of the added electrolyte was adjusted to e.g. 0.065 mol/l, with the electrolytes being HCl, NH4Cl, KOH, or binary mixtures of these substances.These investigations revealed significant differences of the polishing behaviour between the different types of silica dispersions as slurries. While for the Stöber sols investigated, the RR's are highest in the acidic range and almost negligible in the alkaline pH range, fumed silica suspensions show an entirely different behaviour: RR is very low for acidic pH-values, and increases with the alkalinity of the slurry. In contrast to these observations, the RR's of slurries based on conventional silica sols are highest around the neutral point, and show a decrease for both more alkaline and acidic pH-values. In comparison to the other two types of material, these suspensions have a high amount of electrolyte background, originating from their manufacturing process.A model is developed to explain these results in a comprehensive manner. It involves effects of the electrolyte type and the ionic strengths as well as influences of the particle size.

scholarly journals Appearance of Platelet-Clumping Substance after Acidification of Plasma

Blood ◽  
1968 ◽  
Vol 31 (3) ◽  
pp. 348-357 ◽  
Author(s):  
HIROH YAMAZAKI ◽  
HIROSHI MURASE ◽  
TATSUO SHIMAMOTO ◽  
TAKIO SHIMAMOTO
Keyword(s):  
Calcium Ions ◽  
Standard Error ◽  
Room Temperature ◽  
Ph Value ◽  
Platelet Rich Plasma ◽  
Final Concentration ◽  
Ringer’S Solution ◽  
Ph Values ◽  
Edta Plasma ◽  
Ph Range

Abstract 1. The pH values of heparinized plasma from ten normal rabbits were from 7.53 to 7.80. The average pH and standard error was 7.69 ± 0.03. These plasmas did not show platelet-clumping activity when exposed to the platelet-saline suspension from the same or other normal rabbits. The platelet-clumping substance was not observed in all ten cases after alkalinization of the plasma to pH values ranging from 8.32 to 9.40. On the contrary, immediately after acidification of the plasmas, the platelet-clumping substance appeared at pH values from 4.90 to 6.82 at room temperature. The range of the lower pH value, in which the platelet-clumping substance was observed, was 4.90-5.60 (5.15 ± 0.07 in average) and the upper range was 5.95-6.82 (6.27 ± 0.12 in average). The pH range at which the strongest clumping of platelets appeared was 5.22-5.95 (5.61 ± 0.07 in average). The platelet-clumping substance did not disappear after the pH of the acidified plasma was reneutralized to the original value. 2. No clumping was found after the addition of citrated, oxalated, EDTA-plasma or serum even when they were acidified. After the pH value of the citrated, oxalated or EDTA-plasma was changed from 4.85 ± 0.39 to 7.55 ± 0.03 and in the presence of calcium ions (10 mM.), platelet-clumping activity was observed. After the addition of citrate (0.38 percent in final concentration), oxalate (0.2 percent in final concentration), or EDTA (0.1 percent in final concentration) to the heparinized plasma the platelet-clumping substance did not disappear. In the case of serum, the platelet-clumping activity did not appear after the pH changes. 3. The platelet-clumping substance in the acidified plasma was heat-labile; it was detected after BaSO4-adsorption and defibrination; it was stable in storage at 4 C., and it was not dialyzable against Ringer’s solution for 72 hours. It induced platelet clumping not only in citrated platelet-rich plasma but also in the platelet-saline suspension. 4. The properties of the platelet-clumping substance in the acidified plasma were compared with that of substances known to have platelet-clumping activity and the experimental evidences showing the differences to ADP, thrombin, ADP-cofactor and thrombocyte agglutinating factors have been detailed.

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