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The degree of equivalence within the participating national metrology institutes for the measurement results of the mass fractions of the analytes Cr, Cu, Fe, Mn and Zn in an aluminium alloy was assessed. This interlaboratory comité consultatif pour la quantité de matière key comparison (CCQM-K42) was organised as an activity of the Inorganic Analytical Working Group of CCQM. In total seven laboratories participated, six of them for all analytes. Measurands were the mass fractions of the analytes in a range of 0.05 and 0.2%. As an outcome the consistency of the results for all elements investigated was acceptable, hence satisfactory comparability was established. An aluminium based certified reference material—undisclosed to the analysts which one it was—was used as test sample. For the purpose of this study homogeneity was tested at BAM. Each laboratory was free to choose any analytical method they wanted to use for the analysis. Consequently various methods of measurement were employed: instrumental neutron activation analysis, X-ray fluorescence spectrometry (XRF) using fused cast-bead method combined with reconstitution technique, inductively coupled plasma optical emission spectrometry (ICP OES) and inductively coupled plasma mass spectrometry. Metrological traceability of the measurement results to the SI unit had to be demonstrated. Therefore, methods such as spark OES or XRF (without fused cast-bead technique)—both of them being most important methods for the analysis of metals and alloys in industrial laboratories—could not be used in the frame of the key comparison.
Raman spectroscopic and 35Cl-NMR scans of Hydro-Xan®, a preparation containing the biocatalytically effective Tetrachlorinedecaoxide anion (TCDO), are described. The spectroscopic analyses showed that HydroXan® does not contain chlorite initially used in the preparation anymore. Furthermore, a structure of four equal chlorate-like ClO3-groups was indicated for TCDO by the scans. Such a structure is supported by the long-term stability of HydroXan® found at tests over 267 days.
Ab initio molecular orbital calculations at various, correlated levels of theory have been performed on eight isomers of the [H,O4,S2]- anion and six forms of [H2,O4,S2]. For the former species, the hypothetical O3SSOH- (9) ion is identified as the lowest energy isomer using second-order Mller-Plesset perturbation theory or the CCSD(T) method, with the protonated dithionite ion, O2SSO2H- (6), being only marginally (less than 5 kJ mol-1 at 25 C) higher in energy. In contrast, the B3LYP density functional predicts a rather different order of relative stabilities, with O2SSO2H- (6) as the by far most stable ion. 6 is stable with respect to dissociation into SO2 and HOSO- or into SO2- and HOSO (which is more stable than HSO2). For the species of composition H2S2O4 the cagelike dithionous acid molecule (HO)O2SSO2(OH) (14) represents the global minimum at all four levels of theory. However, also for this species, the relative stabilities predicted by the B3LYP approach differ considerably from results obtained from the conventional wave function-based methods. 14 is stabilized by two very strong intramolecular hydrogen bonds (symmetry C2). The homolytic dissociation of 14 at the SS bond is strongly endothermic, but the molecule is unstable with respect to dissociation into H2SO2 and SO2. The harmonic wavenumbers and infrared intensities of the fundamental vibrations of 6 and 14 are given.