Mikroanalyse von Eisen und Stahl. I. Silicium

Zusammenfassung Es wird ein Verfahren zur mikroanalytischen Bestimmung von Silicium in Eisen und Stahl mit Einwaagen von 10 bis 100 mg beschrieben. Das Silicium wird photometrisch als Silikomolybdänsäure bestimmt. Der Zeitbedarf für eine Einzelbestimmung beträgt etwa 25 Minuten, der relative Fehler im Mittel ±1 bis 2%.

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Summary A method is described for the microanalytical determination of silicon in iron and steel with samples from 10 to 100 mg. The silicon is determined photometrically as silicomolybdic acid. The time required for a single determination is around 25 minutes; the relative error is ± 1 to 2%.

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Résumé On décrit un procédé de dosage micro-analytique du silicium dans le fer et dans l'acier sur des prises d'essai de 10 à 100 mg. On dose le silicium par photométrie à l'état d'acide silicomolybdique. La durée d'un seul dosage est d'environ 25 minutes, l'erreur relative ± 1 à 2% en moyenne.

     

Fine structure at the carbon 1s K edge in vapours of simple hydrocarbons

Electron yield spectra in the range of 280 ? ?ω ? 300 eV which basically resemble the absorption spectra, have been measured for gaseous methane, ethane, ethylene, benzene and acetylene using synchrotron radiation. The spectra being fairly simple compared to the valence shell absorption are characterized by weak maxima for energies below the ionization threshold for C 1s for methane and ethane whereas additional strong resonances are observed in the spectra from molecules containing π-electrons. The nature of these excitations is discussed on the basis of their term values using information from XPS-measurements.     

Polyurethane foams as selective sorbents for noble metals : Quantitative extraction and separation of rhodium from iridium in hydrochloric acid containing tin(II) chloride

The distribution of rhodium(III) between polyether-type polyurethane foam and 0.5–5.0 mol dm^?3 hydrochloric acid in the presence of small amounts of tin(II) chloride is described. The distribution of rhodium is affected by the extraction temperature, acid concentration and the Sn(II):Rh ratio. The capacity of the polyurethane foam for rhodium is in excess of 0.5 mmol g^?1. Rhodium is presumably sorbed in the form of a chloro(trichlorostannato)rhodium(III/I) complex anion. Iridium is not extracted by the foam under corresponding conditions and can be separated quantitatively from rhodium.     

Microscopic theory of laser gain in semiconductor quantum wells

Received: 31 October 1997/Accepted: 31 October 1997     

Quantification of total petrol hydrocarbons (TPH) in soil by IR-spectrometry and gas chromatography – conclusions from three proficiency testing rounds

Due to the utilisation of 1,1,2-trichlorotrifluoroethane (CFE) as extraction solvent the IR-spectrometric determination of total petrol hydrocarbon (TPH) in soil according to ISO/TR 11046 has been replaced by gas chromatography/flame ionisation detection (GC/FID) after extraction with a halogen-free solvent according to ISO/DIS 16703:2001. The results obtained with both methods by field laboratories in three proficiency testing (PT) rounds are compared. The consensus means obtained with GC/FID are typically 10%–20% (ranging between 0% and 25%) higher than those found with IR-spectroscopy. On the contrary, coefficients of variation (CV) are roughly double in case of GC/FID and are briefly discussed against the background of the Horwitz equation. Received: 19 November 2001 Accepted: 17 March 2002     

Time evolution of strange-particle densities in hot hadronic matter

The kinetic equations for production in hot nuclear matter of rare, strange antibaryons are studied numerically. Strange antibaryons are confirmed as viable characteristic signatures of the quark-gluon plasma. We find four orders of magnitude enhancement in the abundance of $\text{Ω}$ multiply-strange antibaryons. Strange antibaryon production in the hadronic gas phase is shown to have a relatively slow characteristic time constant of ～ 10^?21 sec to be compared with the 100 times faster equilibration in quark-gluon plasma.     

Synthese und Molekülstruktur zweier 1-Sila-3-alanata-cyclobutan-Derivate mit AlC2Si-Heterozyklus

Synthesis and Molecular Structure of Two 1-Sila-3-alanata-cyclobutane Derivatives with Four-membered AlC₂Si-Heterocycles The C? H acidic bis(trimethylsilyl)methyl compounds Me₃C? AlR₂ und Me₃C? CH₂? AlR₂ (R ? CH(SiMe₃)₂) are deprotonated by treatment with the sterically high shielded base LiCH(SiMe₃)₂ in the presence of 1,3,5-trimethylhexahydrotriazinane. The deprotonation occurs at a methyl group of one of the element-organic substituents, and the formed carbanions are stabilized by coordination to the unsaturated Al atoms yielding four-membered heterocycles. Both products were characterized by a crystal structure determination each showing bent ring systems.     

Über gerade unimodulare Gitter der Dimension 32, III

Let A_j, B_j be complex B-spaces, j = 0, 1, A_θ and B_θ–the complex-interpolation spaces generated by the couples (A₀, A₁) and (B₀, B₁), resp., by CALDERON'S/LIONS'S method. Let T: A₀ ∧ A₁ → B₀ → B₁ be an operator satisfying some conditions such as continuity, estimates etc. in terms of the norms of A_j, B_j (j = 0, 1). We consider the question which one of these properties is inherited to T when A₀ → A₁ and B₀ → B₁ are equipped with the norm of A_θ and B_θ.     

A comparison of experimental and theoretical photoelectron energy distribution curves for solid argon and krypton

We present a comparison of recent experimental data and recent theoretical calculations of the photoelectron energy distribution curves for solid argon and krypton. These comparisons are significant in that they support the idea that the valence states of the solid rare gases are band like and of non-negligible width (Ar is about 1.5 eV wide and Kr is about 2 eV wide). Furthermore, in order to obtain reasonable agreement between theory and experiment, the the calculations needed were selfconsistent Hartree-Fock in nature and were corrected for both long range correlation effects (polarization) and short range effects (relaxation).