Surface chemistry and nonadecanoic acid adsorbate layers on TiO2(100) surfaces prepared at ambient conditions

The surface and adsorbate chemistry of the TiO₂(100) surface prepared at high temperatures and ambient conditions were studied by means of angle resolved X-ray photoelectron spectroscopy (AR-XPS), Low Energy Electron Diffraction (LEED) and Atomic Force Microscopy (AFM) based nanoshaving studies. The TiO₂(100) surface shows a 1 × 1 structure with a 1 × 3 superstructure assigned to surface defects. A significant hydroxide surface concentration was revealed by means of AR-XPS measurements. The adsorbate formation of nonadecanoic acid (NDCA) from ethanolic solution led to disordered sub-monolayer surface coverage. The weak interaction between the carboxylic acid group and the TiO₂ surface is assumed to be a combination of the neutral to acid behavior of the TiO₂ surface and the stable hydroxide surface layer created under ambient conditions.     

Synthetic macro-reference samples for the calibration of instruments in inorganic bulk analysis

Summary Basic considerations are discussed and conditions are described for the careful production of oxide macro-samples in the mass range of 200 to 750 g, starting from compounds of tested purity. Solid state reactions were performed at high temperatures. Compounds sensitive to heating were added after heat treatment in a way which ensured homogeneity. The uptake of CO₂/H₂O during manipulations was controlled. The homogeneity of the samples was investigated as well as the success of the experimental approach to their desired, nominal analysis. Even after only moderate mechanical homogenisation, nominal and experimental values were found to be identical (within the limits of repeatability of the test methods), provided compounds with a sufficiently small grain size and of high enough a purity were used. The results obtained on these samples showed that spending a greater analytical effort to achieve the desired analysis, was unnecessary. A thoroughly performed control analysis — e.g., by reconstitution of the sample portion — was sufficient to exclude erroneous production steps. Then the nominal analysis was used to establish the internal laboratory certificate.

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Synthetische Makroreferenz-Proben zur Eichung von Instrumenten für die anorganische Bulk-Analyse

     

Zur Bestimmung der Bildungsenthalpie von SeCl4 und SeOCl2

Determination of the Enthalpies of Formation of SeCl₄ and SeOCl₂ The enthalpies of formation were derived for SeCl₄ and SeOCl₂ from the enthalpy of solution in NaOH. The determination is based on the enthalpy of formation for SeO₂, NaCl, and NaOH as well as on their enthalpy of solution. Results see ?Inhaltsübersicht”?.     

Thermal degradation of metal novolak precursors for high temperature superconductors: thermogravimetric and mass spectroscopy studies

High temperature superconductor (HTS) materials were prepared from novolak metal precursors in a special annealing process. In the present paper the thermal behaviour of pure cresol novolaks and novolak metal salt (nitrate) precursors was investigated by means of simultaneous thermogravimetric analysis and mass spectroscopy in air. The results show significant differences in thermal stability between the pure novolaks and the novolak metal precursors, with respect to the process as well as the products of decomposition. The main volatile products for the precursors are CO₂, H₂O and NO, thus indicating that the thermal degradation results in the formation of metal oxides at a temperature of about 300 °C.     

Determination of titanium and zirconium wear debris in blood serum by means of HNO3/HF pressurized digestion using ICP – optical emission spectrometry

A ‘one bottle’ method to determine particulate debris of titanium and zirconium in blood serum was developed. Inductively coupled plasma – optical emission spectrometry (ICP-OES) was used to simultaneously detect both elements at concentrations above 50 ng/mL. Pressurized digestion by means of nitric and hydrofluoric acid in PTFE^TM-containers in a specific time-heat-pressure protocol apparatus was applied to assure complete solvation of particles including oxides. Total decomposition of the matrix was achieved and reasonable detection limits were accomplished. The amount of remaining carbon did not cause any matrix problems during measurement. Received: 10 October 1997 / Revised: 5 December 1997 / Accepted: 9 December 1997     

Untersuchungen zum System Te/O/Br

Investigations on the System Te/O/Br The melting point diagram of the system TeBr₄? TeO₂ was obtained by total pressure measurements and DTA measurements. A Congruent melting composition Te₆O₁₁Br₂ exists, the melting point is 570°C. The enthalpy of formation and the standard entropy of the species TeOBr₂,g was derived from measurements of the total pressure over Te₆O₁₁Br₂/TeBr₄ and from the transport behaviour of the TeO₂ with Br₂. From the decomposition-pressure measurements over Te₆O₁₁Br₂/TeO₂ follow the partial pressure. The enthalpy of formation ΔH°(Te₆O₁₁Br₂,f,298) = ?453.5 kcal/Mol was obtained from the enthalpy of solution. The transport-behaviour of TeO₂ with HBr, with Tebr₄ and Br₂ and that of Te₆O₁₁Br₂ is clear with the thermodynamic data of TeObr₂.     

Indirect determination of arsenic by flotation spectrophotometry

An indirect method of arsenic determination in the submicrogram range via the determination of molybdenum is presented here. High sensitivity is achieved by combination of the chemical amplification during formation of dodecamolybdoarsenic acid (arsenic: molybdenum ratio 1 12) with multiplication due to the formation of ion-association complexes during flotation-spectrophotometric molybdenum determination with crystal violet (molar ratio 1 2). Thus, the amplification factor relating to arsenic is 24.Dodecamolybdoarsenic acid is formed in a weakly acidic medium and is quantitatively extracted byn-butanol. Back extraction of the heteropoly acid to the aqueous phase and its simultaneous destruction provides the basis for the reaction of released molybdate ions with thiocyanate ions. The molybdenum-thiocyanate complex forms a sparingly soluble ion-association complex with crystal violet which can be floated with toluene on the phase boundary (film flotation). After separation of the aqueous phase the floated molybdenum compound is dissolved in acetone and the resulting free crystal violet ions are subjected to photometric determination at 590 nm as equivalent of the concentration of arsenic. The molar absorptivity of crystal violet is 3.2 · 10⁵1 · mol^–1 · cm^–1. Beer's law is obeyed in a concentration range from 0.01 to 1 g Mo · ml^–1 (0.001–0.1 g As · ml^–1). The resulting detection limit for arsenic is 1 ng · ml^–1.     

Phosphinsubstituierte chelatliganden: XI. NMR-spektroskopische untersuchungen (1H, 13C, 31P, 55Mn) an halogentricarbonylmangan-chelatkomplexen mit phosphino-thioformamid- und -thioformimidoester-liganden

A series of halotricarbonylmanganese chelate complexes, fac-(CO)₃Mn(X)L (X = Cl (a), Br (b), I (c)), with thioformamide (L = Ph₂PC(S)NRMe; R = H (1), Me (2), Ph (3)) and the isomeric thioformimidoester (L = Ph₂PC(NR)SMe; R = Me (4), Ph (5)) ligands were prepared by thermal CO substitution of the pentacarbonylmanganese halides. The IR and NMR data indicate P,S-coordination of the ambidentate ligands and uniform Z configuration in 3–5. Due to the large linewidth of the NMR signals, the ⁴J(PH) and ³J(PC) coupling constants could not be determined for the thioamide complexes 1–3. Coordination of the thioimide 4 causes an increase in ⁴J(PH) whereas ³J(PC) remains unchanged. δ(³¹P) shows a downfield coordination shift as usual for manganese complexes. The broad ⁵⁵Mn NMR signals cover a range of +90 to ?730 ppm (rel. KMnO₄) with the imidoester complexes 4 and 5 at the low-field side. The normal halogen dependence Cl < Br < I is observed for ⁵⁵Mn shielding.