Analytische Aspekte der Oxydation organischer Stickstoffverbindungen mit Chromsäure. XXIII

Zusammenfassung Die früher beschriebene Halbmikromethode zur Bestimmung von Isonitrosogruppen in organischen Verbindungen wurde in den Mikromaßstab übergeführt. Sie beruht auf der Reaktion der Substanz mit Eisen(III)-sulfat in verd. Schwefelsäure. Dabei wird der Oximstickstoff als Distickstoffoxid frei, das mit Kupfer zu elementarem Stickstoff reduziert und im Mikroazotometer gemessen wird. Für die Berechnung des Oximstickstoffgehaltes aus den abgelesenen Gasvolumina wurden Werte für die konstante und proportionale Volumenkorrektur mit Hilfe der Methode der Regressionsgeraden experimentell festgestellt. Beide Werte sind den bei der N-N-Gruppenbestimmung benützten Volumenkorrekturen fast gleich. Die Bestimmung von Oximgruppen ist durch die Anwesenheit von Nitro- oder Aminogruppen nicht gestört. Diese Gruppen können aus derselben Einwaage durch nachfolgende Oxydation mit Chromsäure bestimmt werden.

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Analytical aspects of the oxidation of organic nitrogen compounds with chromic acid. XXIII

Summary The semimicro method previously described for the determination of isonitroso groups in organic compounds has been converted to the microscale. It is based on the reaction of the material with iron(III)-sulfate in dilute sulfuric acid. The oxime nitrogen is thus liberated as dinitrogen oxide, which is reduced to elementary nitrogen by copper and measured in the mieroazotometer. To calculate the oxime nitrogen content from the read-off gas volume, values for the constant and proportional volume correction with the aid of the regression lines were established experimentally. Both values are almost equal in the case of the determination of the volume corrections employed in the determination of the N-N-groups. The presence of nitro-or amino groups does not interfere with the determination of oxime groups. These groups may be determined from the same sample by subsequent oxidation with chromic acid.

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XXII. Mitteilung s.¹.     

Investigation of the physico-chemical structure of oxycellulose after storage for two years and determined by derivatograph

The effect of ageing for a period of two years upon chemically pre-oxidized and irradiated cellulose was investigated. Changes in the chemical structure and energy excitation of atomic groups of oxycellulose skeleton were evaluated from the qualitative and quantitative points of view. The numerical interpretation and complex comparison of the quantities (activation energy, energy quantity EW, values of the thermal effect (areas of DTA peaks) and weight losses) of four degradation phases of pyrolysis were employed, when applying the oxidation pyrolysis method with derivatograph.

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Zusammenfassung Die Wirkung einer zweijährigen Alterung von chemisch voroxydierter und bestrahlter Zellulose wurde untersucht. Veränderungen der chemischen Struktur und die energetische Anregung von Atomgruppen des Oxyzellulosegerüsts wurden unter qualitativen und quantitativen Gesichtspunkten studiert. Eine numerische Interpretation und ein komplexer Vergleich der Größen (Aktivierungsenergie, EnergiemengeEW, Werte der thermischen Effekte — DTA-Peakflächen, Gewichtsverluste) von 4 pyrolytischen Abbauphasen wurden vorgenommen, wobei für die oxydative Pyrolyse ein Derivatograph verwendet wurde.

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, , . . , , EW, ( ) .

     

Flow injection analysis : Part IX. A New Approach to Continuous Flow Titrations

Studies of dispersion patterns in nonsegmented streams, flowing through narrow open tubes, show that it is possible to obtain highly reproducible concentration gradients within a sample zone injected into the moving stream. By varying the geometry of the flow path, low, medium and high dispersion patterns can be achieved; the high dispersion pattern forms the basis for a new approach to continuous flow titrimetry. In this type of titration, discrete samples are passed through a gradient device and are then mixed with a continuously flowing stream of titrant of fixed concentration. The new technique has been tested for potentiometric as well as spectrophotometric end-point indication. A simple one-channel system allows titrations to be performed automatically in less than 1 min.     

Dialkyldithiocarbamate als Reagentien zur gas-chromatographischen Bestimmung von Metallen

Zusammenfassung Kleine Mengen Ni, Cu und Zn in wäßrigen Lösungen können nach Ausschütteln ihrer Dipropyldithiocarbamatochelate gas-chromatographisch bestimmt werden. Arbeitsbedingungen für den 0,01–1 ppm-Bereich werden angegeben. Die Reproduzierbarkeit der Bestimmung wird durch Zusatz eines inneren Standards verbessert.

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Dialkyldithiocarbamates as reagents for the gas-chromatographic determination of metalsII. Determination of zinc, copper and nickel as dipropyldithiocarbamato chelates after extraction from aqueous solution

Summary Small amounts of Ni, Cu and Zn in aqueous solutions can be determined by gas chromatography after extraction of their dipropyldithiocarbamatochelates. Working details for the 0.01–1 ppm range are reported. Reproducibility is markedly improved by addition of an inner standard.

Die Untersuchungen wurden in dankenswerter Weise durch Mittel der Deutschen Forschungsgemeinschaft und des Verbands der chemischen Industrie unterstützt.     

Impedance study of Ni–Co electro-deposition on Fe powder particles in fluidised bed systems

The electrochemical impedance method was applied during the electrochemical deposition of a binary Ni–Co coating on iron powder in a fluidised bed electrode system. The influence of the suspension density on the charge transfer in the course of the electro-deposition process was studied. At a potential of −900 mV (vs. Ag/AgCl/3 M KCl), when the binary Ni–Co layer was formed, the impedance data were characterised by two semicircles with the semicircle at high frequencies being larger in magnitude. A contribution of the diffusion process to the overall current was observed. The optimal suspension density for the charge transfer in the bed was 10×10⁻³–15×10⁻³ (i.e., 4–6 g of iron powder in 50 ml of electrolyte). The most probable mechanism of the charge transfer for the studied concentrations of powder particles is the convective mechanism. The iron particles dispersed in the electrolyte were considered to act as either a depolariser or an additional working electrode depending on the applied electrode potential and on the suspension density.     

Rapid determination of protein in plant material by flow injection spectrophotometry with trinitrobenzenesulfonic acid

The rapid determination of protein in plant material based on spectrophotometric determination of amino acids in protein hydrolysates with trinitrobenzenesulfonic acid has been adapted to flow injection analysis. With the manifold described, a routine sampling rate of 120 samples/h is possible, though this, as well as sensitivity, can easily be varied. The method was calibrated against the Kjeldahl method and a good correlation was obtained between the two methods over a wide range of protein values for beans.     

A set of four soil reference materials with certified values of total element contents and their extractable fractions

A set of certified reference materials of four natural soils denoted as CRM 7001-4 was prepared. They consist of light sandy soils with normal and elevated, silty clay loam with normal, and loam with elevated element levels. Certified and/or information values were established for the total contents of the elements As, Ba, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, V, Zn, and their fractions, extractable with aqua regia, and boiling and cold 2 mol L^–1 nitric acid, from results of a 28 laboratory intercomparison using various methods of atomic absorption spectrometry, optical emission spectrometry, mass spectrometry, electrochemical methods, spectrophotometry, instrumental neutron activation analysis, and X-ray fluorescence.     

The infrared spectra and normal coordinate analysis of syn and anti acetaldoxime

The infrared spectra of mixtures of syn and anti acetaldoxime and its deuterated analogues CH₃CHNOD, CD₃CHNOH, CD₃CDNOH and CH₃CDNOH have been recorded. The syn and anti isomers of CH₃CHNOH, CD₃CHNOH, CD₃CDNOH and CH₃CDNOH have been separated by gas chromatography [1]. The infrared spectra of separated isomers in CS₂ solution have been recorded and the assignment of ten in-plane vibrations made. From a normal coordinate analysis the Urey-Bradley force field, the potential energy distribution and additional information about assignments have been obtained.For the anti isomer the simple Urey-Bradley force field gives satisfactory agreement between the calculated and measured frequencies. For the syn isomer it is necessary to take into account the interactions between atoms separated by three bonds.     

Thermal Analysis of the System Na3AlF6–NaVO3

Summary. The phase diagram of the system Na₃AlF₆–NaVO₃ was determined by means of thermal analysis. The system is a simple binary eutectic one. The eutectic point was estimated at x(NaVO₃) = 0.975 and t _eut = 617°C. The XRD patterns of samples after thermal analysis revealed the presence of cryolite and NaVO₃ only supporting the above assumption of a simple eutectic binary system.     

Micellar ultrafiltration preconcentration of strontium by anionic micellar solution

Th anionic micellar system of the sodium dodecylsulphate (SDS) with di-2-ethylhexylphosphoric acid (D2EHPA) chelating ligand reagent in acctate buffer solutions was studied. The influence of the concentration and the composition of the micellar system for strontium preconcentration was determined. Different pH values of solutions as well as different concentration ratios of the ligand to the surfactant were used.