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1.
Physico-chemical properties of Chitosan films 总被引:1,自引:0,他引:1
Luminita Balau Gabriela Lisa M. I. Popa V. Tura V. Melnig 《Central European Journal of Chemistry》2004,2(4):638-647
Chitosan films obtained by dry phase inversion were prepared from an aqueous solution of chitosan in acetic acid. The films,
of thickness less than 20 μm, were transparent, very flexible and had smooth surfaces. Increasing the film thickness induced
an increase of the internal tensions and the consequent formation of a rough surface. Structural investigations by X-ray diffraction
and Fourier transform IR analysis, showed that the chitosan films, as prepared, are amorphous. Further annealing to evaporate
acetic acid and water traces, changed the amorphous phase into a more ordered phase, characterized by diffraction peaks at
2θ values of 9, 17, 20 and 23 degrees. Thermal investigations by TG, DTG, and DTA revealed that the decomposition of the chitosan
films as prepared proceeds in two stages, starting from 180°C and 540°C. 相似文献
2.
Richard Vytlacil 《Monatshefte für Chemie / Chemical Monthly》1980,111(5):1075-1086
In the ternary system silver chloride-lithium chloride-sodium chloride the kinetics of the galvanic deposition of silver on graphite electrodes was investigated as well as its dissolution without current in the molten salt saturated with chlorine gas.In addition the emf-values were measured in the temperature range between 923 K and 1,173 K by means of, the formation cell graphite/Ag(s)/AgCl(l)–LiCl(l)–NaCl(l)/Cl2 graphite From these data the partial molar free excessGibbs energies were calculated. Using the equation for a multicomponent system as suggested byRedlich-Kister
1
G
AgCl
E
values were obtained by a non-linear fitting process, where the fit was performed for all investigated temperatures and over the entire concentration range in the ternary system. With the parameters obtained the partial and integral excess valuesG
i
E
,G
E
,H
i
E
,H
E
,S
i
E
andS
E
were calculated. 相似文献
3.
Pyrazoles as molecular probes to study the properties of co-crystals by solid state NMR spectroscopy
Concepción López Rosa M. Claramunt M. Ángeles García José Elguero 《Central European Journal of Chemistry》2004,2(4):660-671
Equimolar mixtures of 3,5-dimethylpyrazole (1) with four NH-imidazoles (2–5) have been studied by13C and 15N CPMAS NMR and by DSC. In three cases, the solid mixture behaves as the sum of the individual components [imidazole (2), 2-methylimidazole (3) and 2,4(5)-dimethylimidazole (5)]. In one case [4,5-dimethylimidazole (4)], the mixture corresponds to a new species in which the dynamic behavior of1 no longer exists. 相似文献
4.
Jinzhang Gao Yongjun Liu Wu Yang Lumei Pu Jie Yu Quanfang Lu 《Central European Journal of Chemistry》2005,3(3):377-386
A plasma induced degradation process has been studied to treat 4-nitrotoluene (4-NT) present as an aqueous pollutant. The
plasma was locally generated from a glow discharge around a tip of a platinum anode in an electrolytic solution. The influence
of initial pH and Fe2+ on the degradation was examined. Major intermediates resulting from the degradation process were identified. Amongst the
aromatic intermediates, p-hydroxybenzoic acid was the predominant degradation product. The formation of oxalic acid, malic
acid was also observed. The final products of degradation were NH
4
+
, NO
3
−
and CO2. Based on the analysis of intermediates and the kinetic considerations, the degradation was shown to follow a pseudo-first
order reaction hence, a possible reaction pathway was proposed. 相似文献
5.
An attempt was made to study the oxidation of manganese by air in synthetic waters. A series of batch experments were performed
at differnet values of concentration, temperature and pH. Unoxidized manganese in the solution was determined by formaldoxime
spectrometric method. Results of these studies indicated that the air oxidation of manganese soluble in water can be effectively
performed in basic media and that oxidation yield increasedwith an increase in pH and concentration. The yield was very high
in the presence of manganese dioxide, sepiolite or clinoptilolite in solution and, the oxidation was almost completed especially
at high values of pH and concentration. The reaction was found to be first order with respect to Mn2+ with a very low activation energy. A yield of 62% was obtained for the air oxidation of wastewater taken from the treatment
plant of Corum Municipality. 相似文献
6.
Friedrich Asinger Alfons Saus Magdalena von Wachtendonk 《Monatshefte für Chemie / Chemical Monthly》1980,111(2):385-398
Thiomorpholine as well as alkyl substituted thiomorpholines and their Sdioxides, respectively, are transformed into the corresponding N-Aminothiomorpholines by nitrosation (1–5) followed by the reduction with zinc in acetic acid/acetic acid anhydride under simultaneous formation of the corresponding N-acetyl derivates, and hydrolysis by hydrochloric acid (6–9). Examples of this method are described. 4-Aminothiomorpholines and their Sdioxides react with aldehydes or ketones to give azomethines (10–31). Acylation with mono-and dicarbonic acid chlorides leads to the N-acyl derivatives32–44.Mannich condensation is also possible. By oxidation with yellow mercury oxide tetracenes are formed (46–47).
Teil der DissertationM. Schmitz, Techn. Hochschule Aachen, 1975. 相似文献
7.
Stanisław Zieliński Lechosław Lomozik Anna Wojciechowska 《Monatshefte für Chemie / Chemical Monthly》1981,112(11):1245-1252
The formation of the lanthanide (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Lu) complexes with proline and hydroxyproline has been investigated by potentiometric methods as well as by a turbidimetric one which has provided some additional conclusions. It has been found that 11 and a slight amount of 21 complexes are formed. The deviation from the typical course of the formation function is discussed. It is suggested that the perturbations of complex formation in the systems are caused by hydrolysis. The stability constants of the complexes are reported.
Potentiometrische Untersuchungen an Lanthanid-Komplexen von Prolin und Hydroxyprolin
Zusammenfassung Die Bildung von Lanthanid-Komplexen (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Lu) mit Prolin und Hydroxyprolin wurde potentiometrisch und mit Hilfe von Trübungsmessungen untersucht. Es wurde festgestellt, daß sich Komplexe der Zusammensetzung 11 und in kleiner Menge auch 21 bilden. Die Abweichung von typischem Verlauf der Bildungskurven wurde untersucht. Es wurde dabei festgestellt, daß für die Störungen in der Komplexbildung die Hydrolyse verantwortlich ist. Die Stabilitätskonstanten wurden bestimmt.相似文献
8.
Substituted azafulvenes were generated by dehydrogenation of 5-methyl-substituted pyrromethenones withDDQ and characterized by UV- and1H-NMR-spectroscopy. Their electrophilic properties were demonstrated using several quenchers and furthermore they were used for a synthesis of verdinoid bile pigments (which easily can be converted to rubinoid systems by the action of NaBH4) with nearly any desired unsymmetrical alkyl substitution patter: The azafulvene spezies was generated by the action ofDDQ on a 5-methylpyrromethenone and was quenched by an 5-unsubstituted pyrromethenone. The resulting rubinoid adduct was dehydrogenated immediatly byDDQ — yields were good to high.
39. Mitt.:Falk, H., Höllbacher, G., Hofer, O., Müller, N., Mh. Chem.112, 391 (1981). 相似文献
9.
Heinz Falk Günther Höllbacher Otmar Hofer Norbert Müller 《Monatshefte für Chemie / Chemical Monthly》1981,112(3):391-403
A force field model was designed with respect to the special needs of bile pigments. It is parametrized and tested using partial structures of bile pigments as well as an integral pigment; the solution structures of the molecules were previously deduced using independent experimental methods.
38. Mitt::Falk, H., Schlederer, T., Wolshann, P., Mh. Chem.112, 199 (1981). 相似文献
10.
Mineralization procedures for blood and urine suitable for the determination of arsenic by Hydride Generation Atomic Absorption
Spectrometry (HGAAS) are studied on model samples, and the results are utilized in biological monitoring investigations. The
objective of this work is to obtain good total As recoveries for both matrices regardless of added As species (As(III), As(V),
DMA, MMA, AsB, or AsC). Prior to the HGAAS analyses, preparation procedures were controlled under optimised conditions by
graphite furnace atomic absorption spectrometry (GFAAS). Two preparation procedures for urine give As recoveries close to
100% by HGAAS: a) dry ashing at 420°C with Mg(NO3)2 on a hot plate, and b) microwave oven decomposition with (NH4)2S2O8. For blood samples, As recoveries by HGAAS range between 95 and 108% for all species when using dry ashing after a pretreatment
of samples with HNO3 and H2O2 in a microwave oven. Wet digestion with (NH4)2S2O8 in a microwave oven gives recoveries very near 100% for As
inorg.
and MMA. For other As species in spiked blood samples, recoveries of less than 20% As are found. Precision and detection
limits obtained by both techniques are evaluated as well. For arsenic concentrations of 20 μg dm−3 or more in blood and urine, a chemical modifier is recommended for GFAAS analysis; it may or may not be proceeded by a mineralization
step. For low As levels encountered in the unexposed population, the HGAAS technique provides reliable results only if a very
complete mineralization procedure is used. 相似文献
11.
Hansjörg Meyer Hanskarl Müller-Buschbaum 《Monatshefte für Chemie / Chemical Monthly》1981,112(1):51-57
Solid state reaction of CuO and Al2O3 with a flux of PbO about 930°C and reaction time of 8d gives the new compound Cu2Al4O7. The red single crystals were examined by energydispersive microanalysis and X-ray diffraction methods. Cu2Al4O7 has cubic symmetry, space group
,a=908.0 pm. The typical coordination of Cu+ (CN=6 and CN=12) and the interstitial arrangement of the AlO4-tetrahedra are discussed with respect to related compounds. 相似文献
12.
Jerzy L. Gębicki 《Central European Journal of Chemistry》2004,2(2):371-387
The recombination of thiocyanate anion radicals, (SCN)
2
−
, formed pulse radiolytically within the water pools of reverse micelles stabilized with anionic AOT and nonionic Igepal surfactants,
was proved as an indicator reaction to study intermicellar exchange. It was found that the exchange process is slower inIgepal
than in AOT reverse micelles with the same water to surfactant ratio. The apparent activation enthalpy and entropy of the
exchange process were determined in different alkanes. For the AOT and Igepal reverse micelles the activation parameters increase
with the droplet size, but for the AOT systems they do not significantly change with the increase of droplet concentration.
For non-percolated systems the activation parameters for Igepal reverse micelles approach those for AOT reverse micelles.
This result supports existing suggestions that the mechanism of intermicellar exchange does not differ in principle between
reverse micelles stabilized with ionic and nonionic surfactants. 相似文献
13.
The structure and the biosorption properties of fungal biomass of Aspergillus niger originated from citric acid fermentation industry was investigated. This waste biomass, produced in high quantity in carefully
controlled industrial processes, has certain favourable characteristics that may be improved for its usefulness. In environmental
chemistry, it is known for the removal of heavy metals cations. In this work, different alkaline treatments (1M NaOH/20°C/24
h and 10M NaOH/107°C/6 h) were used to evaluate the dependence of sorption properties of biomass on the cell wall composition.
The biosorption was studied by the batch method, with the biomass concentration of 1 g/l, at pH 6. The adsorption of lead
was more effective than that of cadmium. The biosorption capacity was evaluated using the biosorption isotherm derived from
the equilibrium data. At pH 6, the maximmum lead biosorption capacity estimated with the Langmuir model was 93 mg/g dry biomass. 相似文献
14.
Axel-Rüdiger Schulze Hanskarl Müller-Buschbaum 《Monatshefte für Chemie / Chemical Monthly》1981,112(2):149-156
The hitherto unknown compound Ca3Ga4O9 was prepared and investigated by X-ray single crystal methods. Ca3Ga4O9 has orthorhombic symmetry:a=1435.8;b=1682.5;c=532.1 pm; space group C
2v
11
–Cmm2,Z=6. The tetrahedra network (circles of 4 and 5 GaO4-tetrahedra) and the surrounding of Ca2+ are described and discussed with respect to other oxogallates. 相似文献
15.
Titus Constantinescu Petre Ionita Ion Chiorescu Gabriela Ionita 《Central European Journal of Chemistry》2003,1(4):465-476
Ten novel and stable free radicals of nitronyl-, imino-nitroxide and hydrazyl type compounds were synthesized and their physico-chemical
properties investigated. UV-Vis and ESR spectroscopic data, as well as the lipophilicities and specific hydrophobic areas
of the compounds are compiled. The reaction of these radical compounds with nitric oxide and nitrogen dioxide was also investigated.
The radicals synthesized, show selectivity in their reaction with these nitric oxides, depending on their structure (nitronyl-nitroxide
radicals react with NO, while hydrazyl radicals react with NO2). The processes are easily monitored by UV-Vis or ESR spectroscopy. 相似文献
16.
Pavel Tlustoš Jiřina Száková Alena Stárková Daniela Pavlíková 《Central European Journal of Chemistry》2005,3(4):830-851
Twelve soil samples differing in physicochemical properties and total element contents were extracted by three sequential
extraction procedures to determine As, Cd, Pb, and Zn bound to individual soil fractions and are defined by individual operational
procedures. In the case of arsenic, two additional sequential extraction schemes were designed entirely for fractionation
of soil containing arsenic were tested. The results confirmed that determination of element proportions bound to individual
soil fractions is strongly dependent on the extracting agent and/or procedure applied within individual extracting schemes.
As expected, absolute values of the elements released among the individual extracting procedures are weakly comparable. More
reliable results were determined for the more mobile soil elements i.e. cadmium and zinc, in the fractions characterizing
the most mobile proportions of investigated elements where significant correlations with basic soil characteristics were observed.
In contrast, ambiguous results were observed for As and Pb, for both the individual extraction procedures and the effect of
the soil characteristics. Regardless of the studied element, the poorest results were determined for reducible and oxidizable
soil fractions. The application of at least two independent procedures or modification of the extraction scheme according
to element investigated and/or particular soil characteristics can also be helpful in definition of element pattern in soils
in further research. 相似文献
17.
H. S. Singh V. P. Singh B. S. Arya G. R. Varma 《Monatshefte für Chemie / Chemical Monthly》1981,112(11):1253-1260
Kinetics of oxidation of xylitol and galactitol by hexacyanoferrate(III) ion in aqueous alkaline medium is reported. The reaction rate is of first order with respect to hexacyanoferrate(III) in each substrate. The reaction is first order at lower concentrations of xylitol and galactitol and tends towards zero order as the concentration increases. Similarly first order kinetics was obtained with respect to hydroxide ion at lower concentrations and tends to lower order at higher concentration in the oxidation of xylitol; in the oxidation of galactitol the reaction is first order with respect to hydroxide ion even up to manyfold variation. The course of reaction has been considered to proceed through the formation of an activated complex between [K Fe(CN)6]2– and substrate anion which decomposes slowly into radical and [K Fe(CN)6]3–. A probable reaction mechanism is proposed.
Kinetik und Mechanismus der Oxidation von Xylit und Galaktit mit Hexacyanoferrat(III) in wäßriger, alkalischer Lösung
Zusammenfassung Das Geschwindigkeitsgesetz der Titelreaktion ist in beiden Fällen erster Ordnung bezüglich Hexacyanoferrat(III). Die Oxidation ist erster Ordnung bei niedrigen Konzentrationen von Xylit und Galaktit und geht bei Erhöhung der Konzentration gegen null. In gleicher Weise wurde eine Kinetik erster Ordnung bezüglich Hydroxyl bei niedrigen Konzentrationen und eine erniedrigte Ordnung bei höheren Konzentrationen für die Oxidation von Xylit beobachtet; bei Galaktit bleibt die Oxidation auch bei höheren Hydroxyl-Konzentrationen erster Ordnung. Es wird angenommen, daß die Reaktion über einen aktivierten Komplex zwischen [KFe(CN)6]2– und dem Substrat-Anion verläuft; dieser Komplex zerfällt in [KFe(CN)6]3– und ein Substrat-Radikal. Ein möglicher Reaktionsmechanismus wird vorgeschlagen.相似文献
18.
Paul Peringer 《Monatshefte für Chemie / Chemical Monthly》1980,111(6):1245-1252
The mixed mercury complexes (2XC6H4)2N3HgY (X=CH3, F, Cl, Br, I;Y=SC2H5, SC6H5, SeC6H5) have been prepared. Both the Hg–S and Hg–Se bonds and, in contrast to other mixed triazenato-mercury compounds, the triazenato-mercury bonds have been shown to be kinetically labile on the NMR time scale by means of77Se and199Hg NMR spectroscopy. Evidence has been obtained for the presence of (2XC6H4)2N3HgY together with HgY
2 and [(2XC6H4)2N3]2Hg in solution. 相似文献
19.
A. Mierczynska J. Friedrich H. -E. Maneck G. Boiteux J. K. Jeszka 《Central European Journal of Chemistry》2004,2(2):363-370
In this work we present the preparation of conductive polyethylene/carbon nanotube composites based on the segregated network
concept. Attention has been focused on the effect of decreasing the amount of filler necessary to achieve low resistivity.
Using high- and low-grade single-walled carbon nanotube materials we obtained conductive composites with a low percolation
threshold of 0.5 wt.% for high-grade nanotubes, about 1 wt% for commercial nanotubes and 1.5 wt% for low-grade material. The
higher percolation threshold for low-grade material is related to low effectiveness of other carbon fractions in the network
formation. The electrical conductivity was measured as a function of the single-walled carbon nanotubes content in the polymer
matrix and as a function of temperature. It was also found that processing parameters significantly influenced the electrical
conductivity of the composites. Raman spectroscopy was applied to study single wall nanotubes in the conductive composites. 相似文献
20.
Claudia Mureşanu Lucian Copolovici Florina Pogącean 《Central European Journal of Chemistry》2005,3(4):592-604
The inhibitory effect of para-nitrophenol on the catalytic reaction of catalase was investigated. Michaelis-Menten kinetic parameters were determined from
Lineweaver-Burk plots obtained in the absence or in the presence of the inhibitor. The inhibitor pattern, revealed by the
Lineweaver-Burk plots, suggested a fully mixed inhibition mechanism. Spectrophotometric monitoring of the indicator reaction:
in conjunction with initial rate measurements was employed for the kinetic determination of the inhibitor. Calibration plots
of initial rate vs. para-nitrophenol concentration were linear in the concentration range 0.9·10−5–2.5·10−5 mol/L and the detection limit was 3·10−6 mol/L (417 μg/L) para-nitrophenol. Interferences from other phenolic compounds like orto-cresole, meta-and orto-nitrophenol were observed. 相似文献