Nachweis und photometrische Bestimmung von Dimethylanilin mit Natriumchlorit in Gegenwart von Monomethylanilin und Anilin

Zusammenfassung Es wird eine colorimetrische Methode für die Bestimmung von Dimethylanilin mit Natriumchlorit vorgeschlagen.Die Bestimmung ist empfindlich und gestattet 30–300 g/ml Dimethylanilin zu bestimmen.Das Verfahren ist auch für die Bestimmung von Dimethylanilin in Gegenwart von Anilin und Methylanilin anwendbar.     

Spektrochemische Bestimmung von Spurenelementen in reinem Gold

Zusammenfassung Eine Spektrochemische Methode zur Bestimmung von Spuren der Elemente As, Sb, Fe, Mn, Pb, Ni, Bi, Cu, Pt, Pd, Cd, Rh und Ag in reinem Gold wird beschrieben. Zunächst wird das Gold durch Extraktion aus 3 N HCl mit Methylisobutylketon abgetrennt. Die Verunreinigungselemente werden dann an spektralreinem Graphitpulver mit 4% NaCl und 0,02% Co als Bezugselement adsorbiert und im Wechselstromabreißbogen 3,5 min bei 10 A angeregt. Die Spektren wurden mit einem UV-Spektrograph Q 24 auf ORWO-Spektralplatten Blau Extrahart aufgenommen. Die quantitative Bestimmungsgrenze für Mn, Pt und Ag beträgt 10^–6%, für Fe, Pb, Ni, Bi, Cu, Pd und Rh 10^–5% und für As, Sb und Cd 10^–4%. Die relative Standardabweichung überschreitet nicht 30%.

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Spectrochemical determination of trace elements in pure gold

A spectrochemical method for the determination of traces of As, Sb, Fe, Mn, Pb, Ni, Bi, Cu, Pt, Pd, Cd, Rh and Ag in pure gold is described. The gold is first separated by extraction into methyl isobutyl ketone from 3 N HCl solution and then the trace elements are adsorbed on spectrally pure carbon powder containing 4% NaCl and 0.02% Co as reference standard, and excited in an 10 A a.c. arc for 3.5 min. Emission spectra were recorded on ORWO-Blau Extrahart plates with an UV-spectrograph Q 24. Limits of detection were 10^–6% for Mn, Pt and Ag; 10^–5 % for Fe, Pb, Ni, Bi, Cu, Pd and Rh; 10^–4% for As, Sb and Cd. Relative standard deviation was not exceeding 30%.

     

Theoretical studies on di- and tetra-nuclear Ni pivalate complexes

A combination of DFT calculations and magnetic studies allow structural features of di- and tetra-nuclear nickel pivalate cage complexes to be deduced.     

Uniqueness of the Newton-Wigner position operator

It is shown that the quantum position operator of Newton and Wigner for nonzero-mass systems is uniquely determined if one imposes a quantum manifest covariance condition of the same type as the similar condition of Currie, Jordan, and Sudarshan in the framework of the Hamiltonian formalism.     

Antioxidant activity evaluation by physiologically relevant assays based on haemoglobin peroxidase activity and cytochrome c-induced oxidation of liposomes

Two new protocols for exploring antioxidant-related chemical composition and reactivity are described: one based on a chronometric variation of a haemoglobin ascorbate peroxidase assay and one based on cytochrome c-induced oxidation of lecithin liposomes. Detailed accounts are given on their design, application, critical correlations with established methods and mechanisms. These assays are proposed to be physiologically relevant and bring new information regarding a real sample, both qualitative and quantitative. The well-known assays used for evaluation of antioxidant (re)activity are revisited and compared with these new methods. Extracts of the Hedera helix L. are examined as test case, with focus on seasonal variation and on leaf, fruit and flower with respect to chromatographic, spectroscopic and reactivity properties. According to the set of assays performed, winter are the most antioxidant, followed by summer leaves, and then by flowers and fruits.     

g‐Engineering in Hybrid Rotaxanes To Create AB and AB2 Electron Spin Systems: EPR Spectroscopic Studies of Weak Interactions between Dissimilar Electron Spin Qubits

Hybrid [2]rotaxanes and pseudorotaxanes are reported where the magnetic interaction between dissimilar spins is controlled to create AB and AB₂ electron spin systems, allowing independent control of weakly interacting S= centers.     

Polyazomethines derived from polynuclear dihydroxyquinones and siloxane diamines

New polyazomethines have been synthesized based on polynuclear dihydroxy quinones (5,8-dihydroxy-1,4-naphthoquinone and 1,4-dihydroxyanthraquinone) and siloxane diamines differing by the siloxane sequence length (1,3-bis(3-aminopropyl)tetramethyldisiloxane and α,ω-bis(3-aminopropyl)oligodimethylsiloxane having about 12 siloxane units/sequence). The structures were verified by spectral analyses. Solubility tests, GPC and viscosity measurements were performed. Some properties of the resulted polymers were investigated by thermal (TGA and DSC), electrical, spectral (UV-Vis) and electrochemical (differential pulse voltammetry) methods.     

Characteristics of Ti–Nb,Ti–Zr and Ti–Al containing hydrogenated carbon nitride films

Nanocomposite Me–C–N:H coatings (Me is TiNb, TiZr or TiAl), with relatively high non-metal/metal ratios, were prepared by cathodic arc method using TiNb, TiZr and TiAl alloy cathodes in a CH₄ + N₂ atmosphere. For comparison purposes, a-C–N:H films were also produced through evaporating a graphite cathode in a similar atmosphere. The films were characterized in terms of elemental and phase compositions, chemical bonds, texture, hardness, adhesion and friction behavior by GDOES, XPS, Raman spectroscopy and XRD techniques, surface profilometry, hardness and scratch adhesion measurements, and tribological tests. The nanocomposite films consisted of a mixture of crystalline metal carbonitride and amorphous carbon nitride. The non-metal/metal ratio in the films composition was found to range between 1.8 and 1.9. For the metal containing nanocomposites, grain size in the range 7–23 nm, depending on the metal nature, were determined. As compared with the a-C–N:H, the Me–C–N:H films exhibited a much higher hardness (up to about 39 GPa for Ti–Zr–C–N:H) and a better adhesion strength, while the coefficients of friction were somewhat higher (0.2–0.3 for Me–C–N:H and 0.1 for a-C–N:H).