Komplexometrische Bestimmung von Metallkationenverunreinigungen in Reinchemikalien

Zusammenfassung Ein Verfahren zur quantitativen summarischen Bestimmung von Metallionenverunreinigungen in flüssigen Chemikalien (Reinheitsprüfung) durch komplexometrische Titration mit photometrischer Endpunktsanzeige wird beschrieben. Als Indikator dient Eriochromschwarz T; erfaßbar ist zirka 1 g in 20 ml. Durch einfaches Einengen des Ausgangsmaterials lassen sich noch Metallionengehalte von 0,01 ppm mit einer Genauigkeit von einigen Prozent bestimmen.

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Summary A procedure is described for the quantitative summary determination of metal ion impurities in liquid chemicals (purity tests) through complexo-metric titration with photometric endpoint indication. Eriochrome black T serves as indicator. Approximately 1 g can be detected in 20 ml. Metal ion contents as low as 0.01 ppm can still be determined with a precision of several per cent by simple concentration of the starting material.

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Résumé On décrit un procédé de dosage total quantitatif des impuretés à l'état d'ions métalliques dans les produits chimiques liquides (contrôle de la pureté) par titrage complexométrique avec détection du point équivalent par photométrie. On utilise le noir ériochrome T comme indicateur. La limite de dilution est d'environ 1 g/20 ml. On peut encore doser des teneurs en ions métalliques de 0,01 ppm avec une erreur de quelques pour cent simplement en diminuant la quantité initiale de substance.

     

Synthesis of [ethylene-1-(eta(5)-4,5,6,7-tetrahydro-1-indenyl)-2- (eta(5)-4',5',6',7'-tetrahydro-2'-indenyl)]titanium dichloride, the elusive isomer of the Brintzinger-type ansa-titanocenes

We present a short synthesis of 1-(2-indenyl)-2-(3-indenyl)ethane (5) and a method for its conversion to the ansa-metallocene [ethylene(eta5-inden-1-yl)(eta5-inden-2-yl)]titanium dichloride (13). The synthetic strategy applied to prepare bisindene 5 relies on the efficient alkylation of 2-(phenylsulfonyl)indane followed by HMPA-assisted E1cB-elimination of phenylsulfinate. This tandem sequence circumvents the predisposition of indene to undergo C(1)-alkylation and enables access to C(2)-substituted indenes. The key step in the synthesis of the title ansa-titanocene (4) features a previously unreported equilibration step to generate the bis(indenide anion) of 5. Complexation with TiCl4.(THF)2 followed by hydrogenation of the product metallocene furnishes ansa-titanocene 4.     

The pH dependence of phenolphthalein: A 13c NMR study

The pH dependence of the ¹³C NMR spectra of phenolphthalein has been measured and interpreted. The spectrum of the neutral compound 1 is compared with the spectra of the dianion 4, the trianion5 and the carbocation7. At the first time spectroscopic evidence for the carbinol 6 is given.     

Evaluation of multidimensional (ion-exchange/reversed-phase) protein separations using linear and step gradients in the first dimension

The performance characteristics of multidimensional liquid chromatographic protein separations were evaluated using on-line electrospray mass detection, and a novel workflow for automated LC/MS data processing. Two-dimensional ion exchange/reversed-phase LC separations of Escherichia coli cytosol were conducted using either a continuous linear or discontinuous step gradient in the first dimension. Chromatographic profiles of the top 100 most abundant components were characterized to assess overall separation reproducibility within each mode, and to characterize differences in component distribution between the two modes of operation. Analysis of the resulting data indicates that multidimensional separations of complex protein mixtures can be done reproducibly. Furthermore, under the conditions employed within this study, a linear first dimension gradient was more effective at fractionating the protein mixture, distributing fewer major components to multiple second dimension cycles than an equivalent step gradient. The application of on line mass spectrometry, and automated processing of the resulting data, proved valuable for producing component level analysis of multidimensional protein separations.     

Advanced kinetic tools for the evaluation of decomposition reactions

Summary An advanced kinetic study on the thermal behaviour of pyrotechnic ignition mixtures has been carried out by differential scanning calorimetry using different B/KNO3 mixtures (50:50, 30:70, 20:80) as a model reaction. The experimental conditions applied (isochoric conditions/closed crucibles and isobaric conditions/open crucibles) as well as the composition of the mixtures noticeably influences the relative thermal stabilities of the energetic materials. The kinetic study focused on the prediction of the thermal stability of the different mixtures both in extended temperature ranges and under temperature conditions at which ordinary investigation would be very difficult. Using advanced numerical tools [1], thermal ageing and influence of the complex thermal environment on the heat accumulation conditions were computed. This can be done for any surrounding temperature profile such as isothermal, non-isothermal, stepwise, modulated, shock, adiabatic conditions and additionally for temperature profiles reflecting real atmospheric temperature changes (yearly temperature profiles of different climates with daily minimal and maximal fluctuations). Applications of accurate decomposition kinetics enabled the determination of the time to maximum rate under adiabatic conditions (TMR_ad) with a precision given by the confidence interval of the predictions. This analysis can then be applied for the examination of the effects of the surrounding temperature for safe storage or transportation conditions (e.g. determination of the safe transport or storage temperatures).     

THE SUNBURNING ULTRAVIOLET METER: DESIGN AND PERFORMANCE

Abstract— A meter for measuring the skin sunburn effectiveness of a light source is being used in an extensive network to provide solar data for correlation to skin cancer incidence. The solar radiation measured also affects a wide variety of organisms. The intensity of this band of radiation is also strongly affected by ozone concentration so that the output correlates with ozone thickness.
The meter spectral response is essentially the excitation spectrum of magnesium tungstate phosphor which is similar to the erythema action spectrum (EAS). In addition to the waterproofed, dose reading embodiment, a cheaper, easily transportable, batteryless, intensity reading meter with the same spectral response has been developed.
The deviation of any sunburn meter from the ideal erythema action spectrum can be calculated by convolution of a series of solar spectra against each of the two response spectra. Plotting the change in output against the change in input results in straight lines. Either log-log coordinates are required, or, as is done here, decibels can be used on linear coordinates. The angle between the straight lines is taken as the error. An error angle of 6.5° is calculated for the present meter.