Thomas Steiger

Sulphur compounds: Part 149. Structures, relative stabilities and vibrational spectra of several isomeric forms of sulphoxylic acid (H2SO2) and its anion (HSO2'−): an ab initio study

Abstract The ground state geometries, energies, atomic charges, dipole moments, and vibrational wavenumbers of four isomeric forms of H 2 SO 2 and two isomere of HSO 2 − have been calculated at the HF and MP2 levels of theory using 6-31G ∗ basis sets. The correlation energy has also been included up to the fourth order of Moller-Plesset perturbation theory (MP4). The two most stable isomers of H 2 SO 2 are two retamers of the chain-like HOSOH structure of C 2 , and C 8 symmetry, the C 8 conformer being less stable by about 8 kJ mol −1 . The sulphuric acid structure HS(O)OH was found to be less stable by about 56 kJ mol −1 . The geometries obtained are compared to known structures of organic derivatives of H 2 SO 2 . The anion HSO 2 − containing an SH bond is more stable than the HOSO − isomer by 23 kJ mol −1 . The calculated vibrational wavenumbers are discussed in terms of recent experimental data.

Sulfur compounds. Part 162. Geometries and energies of the radical anion SO2− and of three isomeric structures of the dithionite anion S2O42−

Abstract Ab initio molecular orbital calculations indicate that the isolated S 2 O 4 2− anion may exist as either O 2 S-SO 2 2− ( 2 ), OSSO 3 2− ( 3 ), or SOSO 3 2− ( 4 ), the geometries and energies of which have been calculated with the MP2/ 6-311 + G(2d,p)//6-31G ∗ approximation. The order of decreasing stability is 4 > 3 > 2 . The dissociation of S 2 O 4 2− ( 2 ) into two radical anions SO 2 − is exothermic by 271 kJ mol − in the gas phase. The bond length and valence angle of SO 2 − are 149.5 pm and 115.6°. The decomposition of aqueous dithionite is discussed.

COMAR: the international database for certified reference materials—an overview

Abstract COMAR is an international database for certified reference materials. This paper describes the history, structure, content, maintenance and present situation of the database.

Investigations of Structure and Stability of the Tetrachlorinedecaoxide Anion Complex (TCDO)

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. Untersuchungen zur Struktur und Stabilitat des Tetrachlordecasauerstoff-Anions (TCDO) Es werden raman- und 35Cl-NMR-spektroskopische Untersuchungen am HydroXan®, einem Praparat, das das biokatalytisch wirksame Tetrachlordecaoxid-Anion (TCDO) enthalt, beschrieben. Die Untersuchungen zeigen, dass HydroXan® das Ausgangsprodukt Chlorit nicht mehr enthalt. Untersuchungen des Depolarisationsgrades der Ramanbanden legen fur das TCDO eine Struktur nahe, in der vier gleichwertige chloratahnliche ClO3-Gruppen vorhanden sind. Langzeituntersuchungen uber 267 Tage liefern Anhaltspunkte zur Stabilitat des HydroXans®.

Quality in Measurement and Testing

Technology and todayʼs global economy depend on reliable measurements and tests that are accepted internationally. As has been explained in Chap. 1, metrology can be considered in categories with different levels of complexity and accuracy. Scientific metrology deals with the organization and development of measurement standards and with their maintenance. Industrial metrology has to ensure the adequate functioning of measurement instruments used in industry as well as in production and testing processes. Legal metrology is concerned with measurements that influence the transparency of economic transactions, health, and safety. All scientific, industrial, and legal metrological tasks need appropriate quality methodologies, which are compiled in this chapter.