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1.
The interaction between molecular oxygen and bile salts, previously observed using chemiluminescence techniques, is studied in this paper by electrochemical techniques to further highlight the nature of the interaction. A shift of half-wave potential of the first polarographic wave for the reduction of molecular oxygen was observed in solutions in the presence of bile salts. The shift could be related to different phenomena, such as adsorption of bile salt molecules on the mercury electrode, irreversibility of the oxygen reduction reaction, pH of the solution. Experimental results suggest the exclusion of the above mentioned processes and outline the occurrence of a direct interaction between oxygen and bile salts, where the hydrophobic face of bile salt monomers and/or small aggregates are involved, enhancing so dismutation of superoxide ion produced at the electrode. The presence of bile salts in solutions containing triphenylphosphine oxide, a hydrophobic surfactant, increases also the wave of reduction of molecular oxygen. As a consequence bile salts, beside the well-assessed physiological roles, can behave as oxygen carrier and as antioxidant, preventing the oxidation of biological compounds by superoxide ion. 相似文献
2.
E. Chiessi M. D'Alagni G. Esposito E. Giglio 《Journal of inclusion phenomena and macrocyclic chemistry》1991,10(4):453-469
The structure of sodium deoxycholate (NaDC) micellar aggregates has been previously reported to be helical, and two helical models have been proposed for the micellar aggregates of sodium taurodeoxycholate (NaTDC). Here we report NMR and UV-VIS studies on the interaction between acridine orange (AO) and NaDC or NaTDC aqueous micellar solutions. AO is known to aggregate in aqueous solutions. The addition of NaDC or NaTDC causes the breaking of the AO aggregates, although the binding geometry of the two bile salts with AO seems to be slightly different. The cationic dye interacts mainly with the C18 and C,9 methyl groups of the bile salt molecules. This result agrees with one of the two NaTDC helical models and with some of its possible aggregates, and confirms again the helical structure attributed to the NaDC micellar aggregates within the limits of the experimental conditions tested by us.Devoted to Professor Giovannai Battista Marini Bettolo Marconi on the occasion of his 75th birthday. 相似文献
3.
Gh. Dragan 《Journal of Thermal Analysis and Calorimetry》1986,31(3):679-691
The construction, the isothermal operation (26.2±0.06) and the calibration of a differential calorimeter of high performance are described. Its construction is based on the conduction principle by using copper resistors noninductively coiled on thin aluminium cylinders used as temperature sensors with very low inertia. Thermal flows are measured by using an ac bridge with a lock-in amplifier. The calibration, both of the height (h) and of the area (A) of the recorded peaks, is performed by using calibrated heat pulsesw
p
with errors under 0.5%. A reproducible value of ratioh/A is obtained on a large number ofw
p
values, which represents a figure of merit of the high-performance calorimeter. This value is an immediate index of the nature of the general transformation process. For a clear-cut definition of the process, the universal procedure recently established on the topoenergetic principles is applied.
Zusammenfassung Konstruktion, isotherme Betriebsweise (26.2±0.06 °C) und Kalibration eines differentiellen Kalorimeters hoher Leistungsfähigkeit werden beschrieben. Die Konstruktion basiert auf dem Leitfähigkeitsprinzip, wobei Kupferwiderstände benutzt werden, die auf als Temperaturfühler mit sehr geringer Trägheit dienenden Aluminiumzylindern aufgewickelt sind. Zur Messung des Wärmeflusses wird eine Wechselstrombrücke mit einem lock-in Verstärker verwendet. Die Kalibration der Berghöhe (h) und der Bergfläche (A) wird mit kalibrierten Wärmeimpulsenw p ausgeführt, die mit Fehlern unter 0.5% behaftet sind. Der Wert des Verhältnissesh/A wird für eine große Zahl vonw p -Werten reproduzierbar erhalten, was die Vorzüge des Hochleistungskalorimeters deutlich macht. Dieser Wert ist eine unmittelbare Kenngröße für die Natur des allgemeinen Umwandlungsprozesses. Das kürzlich entwickelte, auf dem topoenergetischen Prinzip beruhende universelle Verfahren wird zur klaren Definition des Prozesses herangezogen.
, 26,2±0,06 . , , . - . (h) () w p 0,5%. h/ w p , . . , .相似文献
4.
Gh. Dragon 《Journal of Thermal Analysis and Calorimetry》1986,31(4):941-954
The solubility behaviour of several hydrated and anhydrous sulphates has been studied isothermally (26.2±0.06 °C) by using the high-resolution calorimeter previously described. The notion of behaviour recently defined in terms of topoenergetic principles was adopted for these experiments by establishing standard experimental conditions (SEC), mainly covering the geometry of the measuring cell and the figure of merit of the overall calorimetric system. The previously defined parameters from the heat flow recorded at normal and high speed clearly show the oscillatory behaviour generally predicted by the topoenergetic theory. The measuring system used also allows the demonstration of a difference in behaviour for size fractions of the same solute. The overall solubility behaviour under the same SEC for all values of solute mass can be defined in accordance with the universal topoenergetic procedure applied to a large variety of composite and measuring systems. The resulting data associated with the individual (ontogenic) and the group (phylogenic) behaviour can provide Data Banks for general use. 相似文献
5.
Gh. Dragon 《Journal of Thermal Analysis and Calorimetry》1987,32(1):293-300
The process of dilution of aqueous concentrated solutions of the series XSO4 (X=Cu, Na2, Fe, Ni, Mn, Mg) was studied calorimetrically by considering the peak height and area as eigenvalues and the initial concentration as governing potential. The experiments were carried out under standard conditions imposed by topoenergetic principles. The results obtained with the universal procedure recently established define the individual (ontogeny) and the group (phytogeny) behaviour of all the considered solutions with respect to the overall measuring system. These data agree with many other experimental facts showing the following increasing sequence of their power: Mg< Mn < Ni < Fe< Na < Cu. The initial concentration of hydrogen-bonds can be determined by means of standard experiments with the universal topoenergetic procedure proposed for the creation of Data Banks.
Zusammenfassung Der Proze\ der Verdünnung konzentrierter wÄssriger Lösungen der Serie XSO4 (X=Cu, Na2, Fe, Ni, Mn, Mg) wurde kalorimetrisch untersucht, indem Höhe und FlÄche des Peaks als Eigenwerte und die Ausgangskonzentration als dominierendes Potential angesehen wurden. Die Experimente wurden unter von topochemischen Prinzipien auferlegten Standardbedingungen ausgeführt. Die mit der kürzlich eingeführten universellen Prozedur erhaltenen Ergebnisse kennzeichnen das (ontogene) individuelle und das (phylogene) Gruppenverhalten aller in Betracht genommenen Lösungen in Bezug auf das Gesamtme\system. Diese Daten stimmen mit anderen experimentellen Fakten überein. Die von den Kationen ausgehende Wirkung nimmt in der Reihenfolge Mg< Mn < Ni < Fe < Na < Cu zu. Die Ausgangskonzentration der Wasserstoffbindungen kann mittels Standardexperimenten nach der für die Schaffung einer Datenbank vorgeschlagenen universellen topoenergetischen Prozedur bestimmt werden.
XSO4 (X=u, Na2, Fe, Ni, Mn, Mg), , — . . , , () () . , Mg < Mn < Ni < Fe < Na < u. , .相似文献
6.
7.
J. Plank M. Gretz 《Colloids and surfaces. A, Physicochemical and engineering aspects》2008,330(2-3):227-233
The interaction between organic latex polymers and the surface of hydrating cement was investigated by measuring the zeta potential and adsorbed amount of polymer on cement. First, differently charged model latex particles were synthesized in aqueous media by well-known emulsion polymerization technique. The latex polymers were characterized by differential scanning calorimetry (DSC), dynamic light scattering (DLS) and environmental scanning electron microscopy (ESEM). Electrokinetic latex surface properties were investigated by means of streaming potential measurements using a particle charge detector (PCD). It is shown that the anionic latexes adsorb a considerable amount of Ca2+ from the cement pore solution. Next, adsorption of the latex polymers on the surface of hydrating cement was confirmed by zeta potential measurements using the electroacoustic method. A water to cement ratio in the cement paste as low as 0.5 was studied, representing actual conditions in mortar and concrete. Additionally, adsorption isotherms were determined in a sedimentation test using the depletion method. For all latex polymers, Langmuir type adsorption isotherms were found. The latex dosages required to achieve saturated adsorption on the cement surface obtained from zeta potential measurements correspond well with those determined in the sedimentation test. Electron microscopy photographs confirm that the charged latex polymers adsorb selectively on surface areas of hydrating cement showing opposite charge. This way, domains of organic latex polymers exist on the cement surface. They provide adhesion between the inorganic cement matrix and the organic polymer film formed later on by particle coalescence as a result of cement hydration and drying. 相似文献
8.
R. N. Khlestkin V. L. Khlestkina R. B. Valitov N. G. Usanov 《Reaction Kinetics and Catalysis Letters》1981,17(3-4):391-392
A correlation between the temperatures of the maximum thermal decomposition rate of salts or of the maximum heat effects, and the standard heats of formation of the respective metal oxides has been established.
, , .相似文献
9.
The interaction of H atoms having relatively low average kinetic energy (~0.025 eV) with both perfectly clean and D-covered HOPG surfaces is investigated using high resolution electron energy loss spectroscopy. From this study we confirm, in a controlled fashion, the presence of the theoretically predicted adsorption barrier since no adsorption is detected for such H atoms on HOPG. Moreover, we demonstrate that the exposure of a D saturated HOPG surface to these H atoms results in the complete removal of adatoms, with no further adsorption despite the prediction of the adsorption barrier to vanish for H dimers in para configuration. Therefore, the recombinative abstraction mechanism which competes with the adsorption process is more efficient. 相似文献
10.
Gülbanu Koyundereli Çılgı Halil Cetişli Ramazan Donat 《Journal of Thermal Analysis and Calorimetry》2014,115(2):2007-2020
Thermal decomposition of U(C2O4)2·6H2O was studied using TG method in nitrogen, air, and oxygen atmospheres. The decomposition proceeded in five stages. The first three stages were dehydration reactions and corresponded to removal of four, one, and one mole water, respectively. Anhydrous salt decomposed to oxide products in two stages. The decomposition products in nitrogen atmosphere were different from those in air and oxygen atmospheres. In nitrogen atmosphere UO1.5(CO3)0.5 was the first product and U2O5 was the second product, while these in air and oxygen atmospheres were UO(CO3) and UO3, respectively. The second decomposition products were not stable and converted to stable oxides (nitrogen: UO2, air–oxygen: U3O8). The kinetics of each reaction was investigated with using Kissinger–Akahira–Sunose and Flynn–Wall–Ozawa methods. These methods were combined with modeling equations for thermodynamic functions, the effective models were investigated and thermodynamic values were calculated. 相似文献
11.
Gülbanu Koyundereli ??lg? Halil Ceti?li Ramazan Donat 《Journal of Thermal Analysis and Calorimetry》2012,110(1):127-135
In this study the thermal decomposition kinetics of uranyl acetate dehydrate [UO2(CH3COO)2·2H2O] were studied by thermogravimetry method in flowing nitrogen, air, and oxygen atmospheres. Decomposition process involved two stages for completion in all atmosphere conditions. The first stage corresponded to the removal of two?moles of crystal water. The decomposition reaction mechanism of the second stage in nitrogen atmosphere was different from that in air and oxygen atmospheres. Final decomposition products were determined with X-ray powder diffraction method. According to these data, UO2 is the final product in nitrogen atmosphere, whereas U3O8 is the final product in air and oxygen atmospheres. The calculations of activation energies of all reactions were realized by means of model-free and modeling methods. Kissinger?CAkahira?CSunose (KAS) and Flynn?CWall?COzawa (FWO) methods were selected for model-free calculations. For investigation of reaction models, 13 kinetic model equations were tested. The model, which gave the highest linear regression, the lowest standard deviation, and an activation energy value which was close to those obtained from KAS and FWO equations, was selected as the appropriate model. The optimized value of activation energy and Arrhenius factor were calculated using the selected model equation. Using these values, thermodynamic functions (??H*, ??S*, and ??G*) were calculated. 相似文献
12.
Halil Ceti?li Gülbanu Koyundereli ??lg? Ramazan Donat 《Journal of Thermal Analysis and Calorimetry》2012,108(3):1213-1222
The thermal decomposition kinetics of UO2C2O4·3H2O were studied by TG method in a flowing nitrogen, air, and oxygen atmospheres. It is found that UO2C2O4·3H2O decomposes to uranium oxides in four stages in all atmosphere. The first two stages are the same in the whole atmosphere that correspond to dehydration reactions. The last two stages correspond to decomposition reactions. Final decomposition products are determined with X-Ray powder diffraction method. Decomposition mechanisms are different in nitrogen atmosphere from air and oxygen atmosphere. The activation energies of all reactions were calculated by model-free (KAS and FWO) methods. For investigation of reaction models, 13 kinetic model equations were tested and correct models, giving the highest linear regression, lowest standard deviation, and agreement of activation energy value to those obtained from KAS and FWO equations were found. The optimized value of activation energy and Arrhenius factor were calculated with the best model equation. Using these values, thermodynamic functions (??H *, ??S *, and ??G *) were calculated. 相似文献
13.
Lithium, sodium, potassium and ammonium bisulphate have been shown by detailed TG/DTA studies to have limited application as molten solvents. By contrast, the eutectic bisulphate systems, ammonium-potassium bisulphate and sodium-potassium bisulphate, appear to be excellent molten solvents in view of their low melting points, long liquid ranges and prolonged thermal stability at 200°. In contrast to previous studies, potassium pyrosulphate has been found to be an excellent molten solvent, provided rigorous preliminary drying procedures have been applied.
The authors would like to thank Dr. C. Barraclough and Mr. M. Beyer of the Physical Chemistry Department, Melbourne University, for assistance with the Raman spectra. 相似文献
Zusammenfassung An Hand eingehender TG/DTA-Untersuchungen wurde gezeigt, daß die Bisulfate von Lithium, Natrium, Kalium und Ammonium nur eine begrenzte Anwendung als geschmolzene Lösungsmittel finden können. Die eutektischen Bisulfat-Systeme Ammonium/ Kalium Bisulfat und Natrium/Kalium Bisulfat scheinen wegen ihrer niedrigen Schmelzpunkte, ihres weiten Flüssigkeitsbereichs und ihrer dauerhaften Thermostabilität bei 200° ausgezeichnete geschmolzene Lösungsmittel zu sein. Im Gegensatz zu früheren Untersuchungen erwies sich Kaliumpyrosulfat als ein ausgezeichnetes geschmolzenes Lösungsmittel, vorausgesetzt daß vorangehend strenge Trocknungsverfahren angewandt wurden.
Résumé On montre par une étude TG/ATD approfondie que les hydrogénosulfates de lithium, de sodium, de potassium et d'ammonium n'ont qu'une application limitée en tant que solvants fondus. Les systèmes eutectiques des hydrogénosulfates ammonium/potassium et sodium/potassium paraissent, au contraire, être des solvants fondus excellents, en raison de leurs points de fusion bas, de leurs larges intervalles d'existence à l'état liquide et de leur stabilité thermique prolongée à 200°. Contrairement à des études antérieures, on a trouvé que le pyrosulfate de potassium est un solvant fondu excellent, à la condition d'appliquer un mode opératoire rigoureux lors du séchage préliminaire.
/ , , , . , - - , 200°. , , , - .
The authors would like to thank Dr. C. Barraclough and Mr. M. Beyer of the Physical Chemistry Department, Melbourne University, for assistance with the Raman spectra. 相似文献
14.
15.
The thermal dehydrations of CoSO4 · 6H2O, NiSO4 · 6H2O and MnSO4 · H2O have been investigated by TG, DTG, and DTA in water-saturated nitrogen. The starting temperatures and the “activation energy” values for each step are reported. 相似文献
16.
Yu. M. Shapiro A. V. Kuligina V. I. Nichepurenko 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(1):25-28
The paper presents systematized data on nucleophilic addition reactions in acid-base interactions of carboxylic acids. 相似文献
17.
Howell Bob A. Alrubayyi Aeshah Ostrander Eric A. 《Journal of Thermal Analysis and Calorimetry》2019,138(4):2661-2668
Journal of Thermal Analysis and Calorimetry - To be converted into a useful commercial material, poly(vinyl chloride) (PVC) must generally be heavily plasticized. Owing to its high level of... 相似文献
18.
Marek Wesołowski 《Thermochimica Acta》1979,31(2):133-146
A survey is given concerning studies of the thermal decomposition of salicylic acid and its alkaline, alkaline earth and other metal salts. The application of thermal analysis to the detection and quantitative determination of salicylic acid and its salts is discussed. Studies on the elucidation of the mechanism of commercial-scale manufacture of salicylic acid, by using thermal methods of analysis, have been reported. 相似文献
19.
20.
Rotich M. K. Brown M. E. Glass B. D. 《Journal of Thermal Analysis and Calorimetry》2003,73(2):499-508
The effect on the stability of the isomers of aminosalicylic acid of formation of their sodium salts has been studied by use
of differential scanning calorimetry and thermogravimetry, coupled with evolved gas analysis by Fourier transform infrared
spectroscopy. X-ray powder diffraction and infrared spectroscopy provided complementary information. The DSC curves for the
sodium salts of all of the isomers showed complex dehydration/decomposition endotherms. From the initial mass losses of the
TG curves, the amounts of water per mole of salt were estimated as 0.5, 2.4 and 1.4 moles for the sodium salts of 3-aminosalicylic
acid, 4-aminosalicylic acid and 5-aminosalicylic acid, respectively. TG-FTIR results for the sodium salt of 3-aminosalicylic
acid showed the evolution of carbon dioxide in three stages: below 150°C, between 200 and 300°C and continuous formation up
to 500°C. This behaviour differs from that of 3-aminosalicylic acid itself, which forms CO2 between 225 and 290°C. For the sodium salt of 4-aminosalicylic acid, the formation of carbon dioxide starts from 250°C and
is still being formed at about 650°C. 4-aminosalicylic acid decarboxylates above 150°C. 5-aminosalicylic acid and its sodium
salt showed no evolution of carbon dioxide below 600°C.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献