Schwingungs- und Elektronenspektren der bindungsisomeren Hexakis(thiocyanato-isothiocyanato)-ruthenate(III)

Vibrational and Electronic Spectra of Bond-Isomeric Hexakis(thiocyanato-isothiocyanato)ruthenates(III) Well resolved IR, Raman, and Electronic spectra of the bond isomeric complexes (TBA)₃[Ru(NCS)_n(SCN)_6?n], n = 1–5, including the pairs of geometric isomers n = 2, 3, 4, are recorded at low temperatures (10 and 80 K). Characteristic vibrations of the N- or S-coordinated ambident ligand SCN^? occur as listed: ν_CS(N): 810–850, ν_CS(S): 690–710, δ_NCS: 450–490, δ_SCN: 420–450, ν_RuN: 300–350, ν_RuS: 270–295 cm^?1. The assignment of the complexes is based on stepwise increasing intensities of the ν_CS(N) modes with increasing number of N-coordinated ligands. Characteristic shifts and splittings in the spectra allow to distinguish the geometric bond isomers according to their different symmetries. Even the absorption spectra in the visible range show within the series of bond isomers and for the cis/trans pairs systematic alternations.     

Mechanisms of thermal transformation of zinc blende to [NaCl] in MnS crystals

Single crystals of zinc blende phase MnS transform at 200°C to single crystals of [NaCl] phase by single diffusive jumps of the cations. Dimensional changes cause random distortion of the crystal. Evidence is also presented for a second structural correspondence in which {111} zinc blende planes become {100} [NaCl] planes. The corresponding deformational mechanism might be favored at low temperatures.     

Prediction of the glass transition temperature for compatible polymer blends of varying compositions

Compatible polymer blends have been found to have widespread commercial applications. The simplest criterion for judging polymer—polymer miscibility in the solid state is the glass transition temperature (T_g), which can vary widely according to blend composition for a compatible system.Recently, an equation which predicts the T_g of intimate mixtures of compatible polymers has been derived, based on classical thermodynamics. Only a knowledge of the T_g and heat capacity increment (ΔC_p) of each pure component is required to predict the T_g at any composition.In this paper, the validity of this entropy-based relationship is investigated for a variety of commercial compatible polymer blends, including some based on poly(vinyl chloride), polystyrene, and poly(2,6-dimethyl-,4-phenylene oxide). The T_g and ΔC_p of each pure component are measured with a Perkin-Elmer DSC-2 differential scanning calorimeter, are predicted glass transition temperatures are compared with those observed experimentally.     

Einfluß zweiwertiger Anionen auf die Filmdruck-Flächenbedarfs-Isothermen von gespreiteten Octadecylamin-Monoschichten

Zusammenfassung Durch den Einsatz zweiwertiger Ionen in der wäßrigen Subphase kann die Packungsdichte gespreiteter Monoschichten wasserunlöslicher Tenside pH-abhän-gig erhöht werden. Ergebnisse für Octadecylamin auf einer Lösung von Natriumhydrogensphosphat werden angegeben.

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Summary The packing density of spread monolayers of waterinsoluble surface-active agents can be increased by use of bivalent ions in the aqueous subphase. Results for octadecyl amine spread on a solution of sodium hydrogen phosphate are given.

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Mit 2 Abbildungen     

The structure of a model intermediate for the nickel-catalyzed cyclodimerization of allene

The stoichiometric reaction between allene, zerovalent nickel and a chelating diphosphane leads to the formation of a bis-methylenenickelacyclopentane derivative whose structure has been established by X-ray crystallography.     

Advances in two-dimensional GC with glass capillary columns

A versatile two-dimensional gas chromatograph is described, consisting of 2 separate ovens, one intermediate trap, an auxiliary inlet, and the necessary hardware to effect off-line switching according to the principle of Deans. The unit has been designed for use with high resolution glass capillary columns. The performance of individual instrumental components was critically evaluated. Results showed that low dead volume glass to metal connections were required in the manifold and detector lines to minimize extra-column effects. The mass of the intermediate trap must be low to allow rapid heating. Operational parameters are discussed and examples of some applications are shown.     

Some ideas on minimization in ultra micro elemental analysis

Summary The problems encountered in the development of ultra micro methods or trace methods of elemental analysis are generally discussed. It is shown that process analyses (e.g. titrations) are preferable to meet needs of accuracy and sensitivity. Moreover, continuous systems of chemical process analyses seem to give a solution to the generally stated problems.

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Überlegungen zur Minimalisierung in der Ultramikroelementaranalyse

Zusammenfassung Die Probleme bei der Entwicklung von Ultramikro- oder Spurenmethoden in der Elementaranalyse werden allgemein diskutiert. Es wird gezeigt, daß Prozeßanalysen (z.B. Titrationen) den Anforderungen an Genauigkeit und Empfindlichkeit entsprechen. Darüber hinaus scheinen kontinuierliche Systeme chemischer Prozeßanalysen eine Lösung der aufgezeigten Probleme zu ermöglichen.

We thank the Czechoslovak Academy of Sciences, the Analytical Department of the Charles University of Prague and the High School for Chemical Technology of Pardubice for the possibility given to one of us (B.G.) to discuss with many colleagues in the SSR, the ideas presented in this article.     

The gas chromatography, thermal analysis and mass spectrometry of fluorinated lead β-diketonates Determination of traces of lead by the integrated ion-current technique

Preparative details for perfluoroalkanoylpivalylmethanes and their lead chelates are given. Thermal analysis, gas chromatography and mass spectral studies all indicate high thermal stability, but strong column interaction makes successful quantitative gas chromatography difficult. The integrated ion-current technique is applied to determine lead heptafluorobutanoylpivalylmethanate in the range 10^-9–10^-7 g of lead, but a lower detection limit of ca. 10^-14 g is indicated.     

Plasma chromatography of heroin and cocaine with mass-identified mobility spectra.

Plasma chromatography detects and identifies compounds in trace quantities at atmospheric pressure through characteristic positive and negative mobility spectra. To facilitate use of the technique to detect gas chromatographic effluents, a number of reference mobility spectra for different classes of compounds have been reported. Reference spectra for two more compounds, heroin and cocaine, are presented in this study. The primary ions found in these mobility spectra were determined to be M+, (M - H2)+, and (M - CH3CO2)+ for heroin and M+, (M - C6H5CO2)+ and (M - C6H5CO2 - CO2CH3)+ for cocaine using a directly interfaced plasma chromatograph-mass spectrometer. The identified ions agree closely with those predicted in the ion mobility spectra using mass-mobility correlation data coupled with chemical ionization mass spectrometry data. Also, an independent check demonstrating the reliability of reduced mobility values reported in earlier reference spectra was made.