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Spin crossover in halogenated ethyltetrazole complexes of Fe(ii) was earlier explained1 within the model of ordering arising from non-specific molecular interactions and is now analysed by using a quasi-chemical approximation taking into account specific interactions in HS-LS associates. Non-specific molecular interactions are also included employing the formalism of excess energies. The equations obtained predict both incomplete and two-step spin crossover and provide a rational explanation of these phenomena. A comparison is given of these two approaches to the description of critical phenomena in spin crossover.

The theoretical model taking into account interactions of a spin-crossover molecule with its two nearest neighbours has been applied to the data on spin crossover equilibria in a series of Fe(ii) complexes with halogenated ethyltetrazoles. Transition curves of different shapes, varying from a gradual to a two-step and incomplete spin crossover, have been successfully described by this model. The observed variation of the shape of transition curve originates from ligand-ligand interactions of neighbouring complexes achieved via electrostatic dipole-dipole interactions and hydrogen bonding.

Spin crossover in halogenated ethyltetrazole complexes of Feii was earlier explained1within the model of orderingarising from non-specific molecular interactions and is now analysed by using a quasi-chemical approximation taking into account specific interactionsin HS-LS associates. Non-specific molecular interactions are also included employing the formalism of excess energies. The equations obtained predict both incomplete and two-step spin crossover and provide a rational explanation of these phenomena. A comparison is given of these two approaches to the description of critical phenomena in spin crossover.

The theoretical model taking into account interactions of a spin-crossover molecule with its two nearest neighbours has been applied to the data on spin crossover equilibria in a series of Feii complexes with halogenated ethyltetrazoles. Transition curves of different shapes, varying from a gradual to a two-step and incomplete spin crossover, have been successfully described by this model. The observed variation of the shape of transition curve originates from ligand-ligand interactions of neighbouring complexes achieved viaelectrostatic dipole-dipole interactions and hydrogen bonding.

Summary 1. The behaviour of ethioniamide and its sulfoxide has been examined for studying the way and the rate of decomposition in different liquid culture-media.

Zusammenfassung 1.Unter Einsatz von Glucose, Fructose, Galaktose, Saccharose und Maltose wird gezeigt, daß bei der Vergärung ihrer Lösungen (5% und mehr) durch gesunde ausgewaschene Preßhefe eine von Art und Einsatzmenge des Zuckers abhängige Restreduktion hinterbleibt. Sie ist von der Hefemenge praktisch unabhängig und läßt sich auch bei extrem verlängerter Gärdauer oder bei wiederholtem Zusatz frischer Hefe nicht völlig beseitigen.2.Papyrographisch treten — abgesehen von stickstoffhaltigen Produkten (mit Ninhydrin positiv) — beim Besprühen mit den üblichen Zuckerreagentien in Erscheinung bei Glucose 3, bei Saccharose 3, bei Fructose 1–2, bei Galaktose 1, bei Maltose mindestens 4 Saccharide.3.Zum Nachweis stickstoffhaltiger Substanzen (mit Ninhydrin positiv) neben Sacchariden auf dem gleichen Chromatogramm wird ein kombiniertes Sprühver-fahren (Ninhydrin und Diphenylamin/Anilin/Phosphorsäure) angegeben.4.Bei den die Restreduktion verursachenden Substanzen handelt es sich im wesentlichen um Saccharide, die nicht durch Reversion bzw. durch übliche Transglykosidierung entstanden sein dürften.