Zur Thermodynamik der Metallcarbonate. 4. Mitteilung. Potentiometrische Untersuchungen am System Mn2+?CO2?H2O

The solubility and the complex equilibria in the system Mn²⁺-CO₂-H₂O have been investigated at 25°C in solutions of the constant ionic strength 3 M (Na)ClO₄. From experimental data the following values for equilibrium constants and Gibbs free energies of formation are deduced: A predominance area diagram for the system Mn²⁺-H₂-CO_2(g)-H₂S_(g) including MnCO_3(ppt.), α-MnS and Mn²⁺ is given.     

Na-Li-[V3O8] insertion electrodes: Structures and diffusion pathways

The potential insertion-electrode compounds Na_1.2[V₃O₈] (NaV) and Na_0.7Li_0.7[V₃O₈] (NaLiV) were synthesized from mixtures of Na₂CO₃, Li₂CO₃ and V₂O₅, which were melted at 750° and subsequently cooled to room temperature. The structures of NaV and LiV contain sheets of polymerized (VO_n) polyhedra, which are topologically identical to the sheet of polymerized polyhedra in Li_1.2[V₃O₈] (LiV). Vanadium occurs in three different coordination environments: [2+3] V(1), [2+2+2] V(2) and [1+4+1] V(3). Calculated bond-valence sums indicate that V⁴⁺ occurs preferentially at the V(3) site, which agrees with the general observation that [6]-coordinated V⁴⁺ prefers [1+4+1]-rather than [2+2+2]-coordination. The M-cations Na and Li occur at three distinct sites, M(1), M(2) and M(3) between the vanadate sheets. The M(1)-site is fully occupied and has octahedral coordination. The M(2) sites are partly occupied in NaV and NaLiV, in which they occur in [4]- and [6]-coordination, respectively. Li partly occupies the M(3) site in NaLiV, in which it occurs in [3]-coordination. The M(2) and M(3) sites in NaLiV occur closer to the vanadate sheets than the M(2) sites in NaV and LiV. The shift in these cation positions is a result of the larger distance between the vanadate sheets in NaLiV than in LiV, which forces interstitial Li to move toward one of the vanadate sheets to satisfy its coordination requirements. Bond-valence maps for the interstitial cations Na and Li are presented for NaV, NaLiV and LiV. These maps are used to determine other potential cation positions in the interlayer and to map the regions of the structure where the Na and Li have their bond-valence requirements satisfied. These regions are potential pathways for Na and Li diffusion in these structures, and are used to explain chemical diffusion properties of Na and Li in the Na-Li-[V₃O₈] compounds.     

Reaction behaviour of dinuclear copper(I) complexes with m-xylyl-based ligands towards dioxygen

Intramolecular ligand hydroxylation was observed during the reactions of dioxygen with the dicopper(I) complexes of the ligands L(1)(L(1)=alpha,alpha'-bis[(2-pyridylethyl)amino]-m-xylene) and L(3)(L(3)=alpha, alpha'-bis[N-(2-pyridylethyl)-N-(2-pyridylmethyl)amino]-m-xylene). The dinuclear copper(I) complex [Cu(2)L(3)](ClO(4))(2) and the dicopper(II) complex [Cu(2)(L(1)-O)(OH)(ClO(4))]ClO(4) were characterized by single-crystal X-ray structure analysis. Furthermore, phenolate-bridged complexes were synthesized with the ligand L(2)-OH (structurally characterized [Cu(2)(L(2)-O)Cl(3)] with L(2)=alpha, alpha'-bis[N-methyl-N-(2-pyridylethyl)amino]-m-xylene; synthesized from the reaction between [Cu(2)(L(2)-O)(OH)](ClO(4))(2) and Cl(-)) and Me-L(3)-OH: [Cu(2)(Me-L(3)-O)(mu-X)](ClO(4))(2)xnH(2)O (Me-L(3)-OH = 2,6-bis[N-(2-pyridylethyl)-N-(2-pyridylmethyl)amino]-4-methylphenol and X = C(3)H(3)N(2)(-)(prz), MeCO(2)(-) and N(3)(-)). The magnetochemical characteristics of compounds were determined by temperature-dependent magnetic studies, revealing their antiferromagnetic behaviour [-2J(in cm(-1)) values: -92, -86 and -88; -374].     

A rapid automated method for wine analysis based upon sequential injection (SI)-FTIR spectrometry

A new process control methodology for the simultaneous determination of sugars, alcohols and organic acids in wine based on multivariate evaluation of mid-IR transmission spectra of wine samples is presented. In addition to ethanol several lower level wine components (glucose, fructose, glycerol, citric-, tartaric-, malic-, lactic- and acetic acid) were determined. To establish a multivariate calibration model a set of 72 calibration solutions was prepared and measured, using a novel, fully automated sequential injection (SI) system with Fourier transform infrared (FTIR) detection. The resulting spectra were evaluated using a partial least square (PLS) model. The developed PLS model was then applied to the analysis of real wine samples containing 79–91 g L^–1 ethanol, 5.9–8.1 g L^–1 glycerol, 0.4–6.9 g L^–1 glucose, 1.5–7.5 g L^–1 fructose, 0.3–1.6 g L^–1 citric acid, 1.0–1.7 g L^–1 tartaric acid, 0.02–3.2 g L^–1 malic acid, 0.4–2.8 g L^–1 lactic acid and 0.15–0.60 g L^–1 acetic acid, yielding results which were in good agreement with those obtained by an external reference method (HPLC-IR). The short analysis time (less than 3 min) together with high reproducibility makes the newly developed method applicable to process control and screening purposes (average of the standard deviations calculated from four repetitive measurements of six different real samples: ethanol: 0.55 g L^–1, glycerol: 0.037 g L^–1, glucose: 0.056 g L^–1, fructose: 0.036 g L^–1, citric acid: 0.020 g L^–1, tartaric acid: 0.010 g L^–1, malic acid: 0.052 g L^–1, lactic acid: 0.012 g L^–1 and acetic acid: 0.026 g L^–1).     

Investigations of the long-term measuring stability of cold-cathode gauges

Cold-cathode ionization gauges (CCGs) are used widely for pressure reading in vacuum systems due to large measuring range, robustness and relative low cost. Amongst the many advantages of CCGs, however, these instruments are restricted in use by decreasing measuring accuracy over operating time as internal electrodes become contaminated. Thus, to guarantee a consistently high measuring accuracy, this gauge type needs to be calibrated regularly after a fixed operating time period. With the aim of quantifying the useful lifetime of CCGs we investigated the measuring behavior of different commercial CCGs in several long-term-operation tests. After a first calibration, the gauges were operated in a vacuum atmosphere with a high fraction of hydrocarbons for several thousand hours at varying high-vacuum pressures. After use, the gauges were re-calibrated and changes in their characteristics analyzed. To compare the operating states of the used CCGs a new basic quantity was introduced: the so-called pressure dose. Using this quantity it should be possible to verify roughly the effective lifetime of CCGs until their pressure readings become erroneous due to contamination effects. It was found that the pressure reading of all tested CCGs become inaccurate after a pressure dose of about 1 mbarh. PACS 07.30.Dz; 84.47.+w     

A new condensation principle

We generalize (A), which was introduced in [Sch], to larger cardinals. For a regular cardinal >₀ we denote by (A) the statement that and for all regular >,is stationary in It was shown in [Sch] that can hold in a set-generic extension of L. We here prove that can hold in a set-generic extension of L as well. In both cases we in fact get equiconsistency theorems. This strengthens results of [Rä00] and [Rä01]. is equivalent with the existence of 0^#.Mathematics Subject Classification (1991): Primary 03E55, 03E15, Secondary 03E35, 03E60