Study of air pollution particulates by X-ray photoelectron spectroscopy

Summary This paper discusses the application of X-ray photoelectron spectroscopy to the determination of the chemical composition of sulfur and nitrogen species in air pollution particulates. Core electron chemical shift measurements are augmented by the determination of relative concentrations and volatility of particulate species.

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Untersuchung von Verunreinigungsteilchen in der Luft durch Röntgenphotoelektronen-Spektroskopie

Zusammenfassung Die Anwendung der Röntgenphotoelektronen-Spektroskopie auf die Bestimmung der chemischen Zusammensetzung von Schwefel und Stickstoff enthaltenden Verunreinigungsteilchen in Luft wird diskutiert. Messungen der chemischen Verschiebung werden ergänzt durch die Bestimmung der relativen Konzentrationen und der Flüchtigkeit der Verbindungen.

Presented at the 6th Annual Symposium on Recent Advances in the Analytical Chemistry of Pollutants, April 21–23, 1976; Vienna, Austria.     

Proton magnetic shielding and susceptibility effects in single crystals of ferrocene

The proton NMR in single crystals of ferrocene has been studied by multiple pulse techniques at room temperature. In crystals of natural shape with plane faces the angular dependence of the resonance frequency due to the anisotropy of the shielding and due to the bulk susceptibility was found to be of about equal size, making analysis of the data practically impossible. By using a single crystal sphere the shape dependent part of the susceptibility contribution could be eliminated. In addition, the resolution obtained by the multiple pulse technique is considerably higher for spheres than for non-spherical crystals. As the ferrocene molecules rotate rapidly about their fivefold axes at room temperature, the shielding tensor σ must be axially symmetric. Having this in mind, the data could be analyzed to yield both the shielding tensor with Δσ = σ₆ - σ_⊥ = ?6.5 ± 0.1 ppm, σ_iso = ?4.2 ± 0.5 ppm from a spherical sample of TMS and the anisotropy of the susceptibility Δ _x = 30 × 10^?6 cgs units.     

Vibrational and lifetime line broadenings in ESCA

The line profile of the narrow, symmetric 1s line from neon, recorded with the new ESCA instrument with X-ray monochromatization, is analyzed. The natural linewidth of this line is found to be 0.23 ± 0.02 eV, in good agreement with theoretical calculations of the oscillator strengths for Auger transitions and X-ray emission. Spectra from molecules show frequently asymmetric core electron lines under high resolution. This rules out previous explanations based on a chemical influence on the natural lifetime. Contrary to earlier assumptions, vibrational excitations are shown to be important in core electron spectra. For methane, the vibrational energy spacing is large enough to allow the vibrational lines to be partly resolved. Recent results from accurate PNO CI calculations on methane agree well with the experimental findings. The Franck-Condon transitions in the C1s and N1s lines from CO and N₂ are shown to be well described in the harmonic approximation and approximating the potential curves of the highly excited core hole states with the potential curve for the ground state of NO⁺, X¹ Σ⁺. Knowledge of vibrational excitations in core electron spectra is shown to be valuable in the analysis of high resolution X-ray emission spectra of free molecules.     

2-Nitrodiphenylamine as a versatile high-potential reversible oxidation-reduction indicator

The use of 2-nitrodiphenylamine as a reversible indicator has been investigated in the titration of iron(II) with cerium(IV) sulphate, potassium dichromate and sodium vanadate in sulphuric acid media. Accurate results can be obtained with cerium(IV) sulphate in 0.5–5.0 M acid, with potassium dichromate in 5.0–7.0 M acid, and with sodium vanadate in 5.0–7.5 M acid. With cerium(IV) sulphate the titrations are preferably conducted in 2.0 M sulphuric acid or in a 1.0 M. sulphuric acid-1.0 M pechloric acid medium. Tungstic acid, acetic acid, arsenic(III) and manganese(II) do not interfere. In titrations of iron(II) with dichromate and vanadate, the colour changes at the end-point are much more vivid with 2-nitrodiphenylamine than with ferroin.     

Thermal analysis and synthesis of pentazinc hexahydroxide dicarbonate: Investigations by thermogravimetry,thermo molecular beam analysis and x-ray measurements

A combination of thermobalance and X-ray camera is described which allows simultaneous thermogravimetric (TG) and X-ray measurements under high vacuum. During these measurements the sample is positioned in the sample holder of the camera in the usual fashion and is X-raved while the temperature is varied. The molecular beam of the gaseous decomposition products flows through a connecting tube which acts as a molecular beam former between camera and thermobalance. The molecular beam is directed towards the empty balance pan. The orifice through which the beam exits as well as the pan have special shapes that allow transfer of the angular momentum of the decomposition beam to the balance. The exerted force is a function of time and corresponds to the first derivative of the TG curve. i.e. to the DTG curve. The integrated curve is directly proportional to the change in mass of the probe. A quantitative evaluation is possible if the molecular composition of the beam is known. The calibration of the molecular beam and the evaluation of the measurements will be discussed. The results show that simultaneous detection of X-ray scattering and indirect TG curves allows a better interpretation of decomposition reactions.An additional investigation shows that thermal synthesis of chemical com- pounds can also be studied by thermogravimetry. Based on the same compound as described in the analysis. the pyrosynthesis is demonstrated. The special instrumentation and the test conditions are discussed.     

Dipole moments of some diphenyl thioethers: Absolute conformation of bis(o-nitrophenyl) sulphide

The electric dipole moments of three diphenyl thioethers have been measured in benzene solution at 25· and the conformational analysis of bis(o-nitrophenyl) sulphide has been carried out by vector addition. The results show that this compound exists in a twisted conformation with the phenyl rings considerably rotated from coplanarity with respect to the C-S-C plane and indicate that in o,o′-disubstituted derivatives of diphenyl sulphide steric rather than conjugative effects operate in determining the conformational preference.     

Conversions of 2-thioxo-1,3-dithiol-4,5-dicarboxylic acid dimethyl ester — The path to a new heterocyclic system, (4H,6H)-1,3-dithiolo[4,5-d]pyrimidine-2,5,7-trione and 5,6-dimercaptouracil derivatives

The conversions of 2-thioxo-1,3-dithiol-4,5-dicarboxylic acid methyl ester into anhydride, mono- and diamide, and monoamide methyl ester were demonstrated. The new heterocyclic system, (4H,6H)-1,3-dithiolo[4,5-d]pyrimidine-2,5,7-trione, was obtained by oxidative rearrangement-cyclization of 2-oxo-1,3-dithiol-4,5-dicarboxylic acid diamide with phenyliodosyl(hydroxy)tosylate and used to synthesize previously unknown 5,6-dimercaptouracil derivatives, including nickel dithiolene complex.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1270–1275, September, 1992.     

Silicon clusters: chemistry and structure

The chemical reactions of size selected silicon cluster ions (containing up to 70 atoms) have been studied with a number of different reagents using injected ion drift tube techniques. Both kinetic and equilibrium measurements have been performed as a function of temperature, and the influence of cluster annealing on chemical reactivity explored. Unlike metal clusters, where bulk behavior appears to be approached with around 30 atoms, large silicon clusters (n up to 70) are much less reactive than bulk silicon surfaces. These results suggest that the clusters in the size range examined here are not small crystals of bulk silicon, but have compact, high coordination number structures with few dangling bonds.     

Reaction of some sympathomimetic amines with sodium 1,2-naphthoquinone-4-sulphonate

Summary The condensation products of 4 sympathomimetic amines with 1,2-naphthoquinone-4-sulphonic acid have been prepared and examined. A spectrophotometric procedure based on the chloroform-soluble orange-red condensation product is described. The same products were investigated fluorimetrically after reduction with sodium borohydride. The results obtained are satisfactory.

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Zusammenfassung Die Kondensationsprodukte vier sympathicomimetischer Amine mit 1,2-Naphthochinon-4-sulfonsäure wurden dargestellt und untersucht. Ein spektralphotometrisches Verfahren auf der Grundlage des chloroformlöslichen, orangeroten Kondensationsproduktes wurde beschrieben. Die gleichen Produkte wurden auch fluoreszenzanalytisch nach ihrer Reduktion mit Natriumborhydrid untersucht. Die Ergebnisse sind befriedigend.