trans‐Bis(benzoato‐O)tetrakis(methanol‐O)iron(II): ligand bulk is not structure‐determining

The title compound, [Fe(C₇H₅O₂)₂(CH₄O)₄], is a centrosymmetric six‐coordinate Fe^II complex coordinated by two axial monodentate benzoate ligands and four methanol ligands in the equatorial plane [Fe—O_benzoate 2.0935 (7) Å, and Fe—O_methanol 2.1310 (7) and 2.1290 (7) Å]. The benzoate ligands adopt monodentate ligation, rather than a bridged polymeric structure, because of strong intra‐ and intermolecular hydrogen bonds to the methanol ligands. This structure is nearly identical to that obtained with a much bulkier carboxyl­ate ligand [Chavez, Que & Tolman (2001). Chem. Commun. pp. 111–112].     

Mean amplitudes of vibration and perpendicular amplitude correction coefficients for 1,2,4,5-hexatetraene and 1,2,4-pentatriene

Mean amplitudes of vibration (u) and perpendicular amplitude correction coefficients (K) for 1,2,4,5-hexatetraene and 1,2,4-pentatriene were computed from spectroscopic data. Values at 298°K for all interatomic distances are given and discussed.     

Reproducibility of Mooney viscosity measurements made at different laboratories—A discussion of the problem

A cross-check with 12 participants has shown considerable differences between Mooney viscosity readings of different laboratories on four polymers. The mean difference for the identically prepared polymers was 7·7 MU (Mooney units) and the differences for individual polymers up to 11 MU. When the samples were prepared by the individual participants the differences were 7·4 MU for this viscosity range. The author attributes these differences partly to non-compliance with the standards as to the instruments and sample preparation and partly to vagueness of the standards themselves.Although definite amendments to the standards can be suggested, improvement of the instruments cannot be achieved at short notice. The differences between the measurements of different laboratories should therefore be ascertained through routine testing of standard samples; they could then be taken into account in the polymer delivery specifications.     

Das Elektronenspektrum eines vinylogen Tropons (Die photochemische darstellung des 2-Hydroxy-guaj-azulens)

Irradiation of guaj-azulene-2-sulfonic acid (VII) in 40 percent aqueous or methanolic sulfuric acid with light of 370 nm wave-length yields 2-hydroxy-guaj-azulene (V) or 2-methoxy-guaj-azulene (X) respectively. The former compound (V) exhibits a keto-enol tautomerism V ? VI, the equilibrium constant of which is strongly dependent on solvent. The keto form VI contains the π-electron system of a vinylogue tropone IV. The theoretical analysis of the electronic spectrum of VI, using a CI-model of the PARISER-PARR-POPLE type, supports the previously proposed assignement of the electronic transitions observed in tropone (I), benzotropone (II) and naphthotropone (III).     

Ein neues Prinzip enzymatischer Analyse

Zusammenfassung An wasserunlösliche Träger fixierte Enzyme lassen sich wie anorganische Katalysatoren zur Analyse verwenden. Sie können laufend wieder verwendet werden und es können mit einer definierten Aktivität statt einer mehr als 10000 Bestimmungen ausgeführt werden. Am Beispiel der Glucose-Bestimmung wird eine einfache Meßanordnung beschrieben, mit der nicht enteiweißte Proben analysiert werden können. Die Pufferlösung wird ständig umgepumpt. Über einen neuartigen Probenapplikator werden die Probelösungen (ca. 60/h) exakt dosiert in den Strom eingespeist. Meßdetektor ist eine O₂-empfindliche Elektrode. Das Meßergebnis liegt in < 1 min vor.

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A new principle of enzymatic analysis

Enzymes fixed to a water-insoluble carrier can be applied for analysis in the same way as inorganic catalysators. They can be used continuously and with a single defined activity more than 10000 determinations can be carried out instead of only one. For the example of a glucose determination a simple apparatus is described for analysing non-deproteinised samples. The buffer solution is pumped continuously and the samples (ca. 60/h) are fed into the circuit accurately dosed by a novel applicator. An O₂-sensitive electrode is used as detector. The result is obtained within < 1 min.

     

Monotonicity properties of the quantum mechanical particle density: an elementary proof

The negative quantum mechanical particle density in its dependence on the potential in the Hamiltonian is a nonlinear operator. We give an explicit proof of the monotonicity of this operator for a large class of admissible thermodynamic equilibrium distribution functions. In particular the zero temperature case is included.