New synthetic and structural aspects in the chemistry of alkylaluminum fluorides. The mutual influence of hard and soft ligands and the hybridization as rigorous structural criterion

A general synthetic strategy starting from metal alkyls is reported based on the hydrogen difluoride anion as a suitable reagent for obtaining organometallic fluorides. The newly prepared compounds are [Me(4)N][(i-Bu)(2)AlF(2)] (1), [Ph(4)P][(i-Bu)(2)AlF(2)] (2), and [Ph(4)P][AlF(4)] (3), containing the tetrahedral anions [(i-Bu)(2)AlF(2)](-) and [AlF(4)](-). The actual structures are prototypes that allowed a comparison of inorganic and organometallic fluorides in the frame of the hard and soft acid and base principle, by means of ab initio calculations. A new theoretical model is designed to put in equation form the qualitative statements of the Bent rule. The model allows the rationalization of the tendencies of bond angle variation in [R(2)MX(2)] systems containing a main group metal (M), in terms of hybridization of the central atom and the reciprocal influence of hard and soft ligands.     

Iranian natural clinoptilolite and its synthetic zeolite P for removal of cerium and thorium from nuclear wastewaters

The ion-exchange behaviors of an Iranian natural clinoptilolite and its modified forms as well as a relevant synthetic zeolite P were investigated toward cerium and thorium from nuclear wastewaters. Column experiments were performed on different exchangers in various conditions and the effect of parameters such as particle size, pH, temperature, and time were considered. The distribution coefficient, cation exchange capacity and some thermodynamic parameters were calculated. Ion-exchange isotherms and break-through curves were plotted. As a result, the selectivity of synthetic zeolite P from Iranian natural clinoptilolite toward cerium and thorium was compared with that of natural and cationic forms of clinoptilolite     

Study of a glassy carbon electrode in amperometric detection using d.c., normal and differential pulse techniques

The results of a comparative study on d.c., normal pulse and differential pulse techniques applied to anodic amperometric detection at a glassy carbon electrode in a voltammetric flow-through cell are presented. The important aspects examined are response time, linearity, limit of detection and selectivity. It is shown that the d.c. mode is the most favourable as long as no adsorption of oxidation products takes place. If strong adsorption occurs, normal pulse detection is recommended, although the limit of detection is somewhat larger.     

Bestimmung von Melment in Zementmischungen durch UV-Spektralphotometrie

Ohne Zusammenfassung

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Determination of melment in cement mixtures by UV-spectrophotometry

     

Der Dreistoff: Vanadium-Silicium-Germanium

Zusammenfassung V-Si-Ge-Legierungen werden aus den Komponenten hergestellt und röntgenographisch untersucht. V₃Si und V₃Ge bilden eine lückenlose Mischreihe. Ebenso gehen die T1-Phasen V₅Si₃ und V₅Ge₃ homogen über, was auch für die C-stabilisierten Phasen mit teilweise aufgefüllter Mn₅Si₃-Struktur gilt. V₁₁Ge₈ löst praktisch kein Silicid und steht mit V₅(Si, Ge)₃ und (Ge, Si)-Mischkristall im Gleichgewicht. Im Disilicid erfolgt ein Si/Ge-Austausch bis etwa 11 (1000°C Homogenisierungstemp.). Bei dieser Temp. tritt nach kurzen Glühzeiten das sogenannte Digermanid (V₁₇Ge₃₁) noch nicht in Erscheinung.

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V-Si-Ge-alloys have been prepared out of the components and examined. V₃Si and V₃Ge do form a contineous solid solution, the same is true for V₅Si₃ and V₅Ge₃ either for the W₅Si₃-structure or for the carbon stabilized Mn₅Si₃-type phases. V₁₁Ge₈ does not dissolve any silicide. There are equilibria between V₁₁Ge₈, V₅(Si,Ge)₃ and a (Ge, Si)-solid solution. Silicon can be substituted by germanium in VSi₂ up to 11 (1000°C homogenizing temperature). At this temperature the so called digermanide (V₁₇Ge₃₁) does not occur after a short anneal.

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Mit 1 Abbildung     

Low-temperature infrared and raman studies: XI. The vibrational behaviour of ammonium perchlorate- its phase changes and the rotational freedom of its ions

An infrared, Raman and X-ray diffraction study on NH₄CIO₄. was conducted in the temperature ranges 300 to 17 °K, 300 to 130 °K and 300 to 120 °K respectively. The infrared studies also included the deuterated salt. The spectra are discussed and vibrational assignments made. Changes in the infrared spectra, as well as intensity measurements of the vibrational bands indicate anomalous behaviour in the region 100–110 °K as well as 17–50 °K. Possible reasons for these changes are proposed. The rotational behaviour of the ammonium ion upon cooling and hydrogen bonding are discussed.     

Koordinationschemische Untersuchungen an Zinkdialkylen. X. Über die Reaktion von Zinkdimethyl mit sekundären Aminen

Dimethyl zinc reacts with diethyl amine, piperidine and morpholine forming definite 1:2- or 1:1-complexes. The weaker basic secondary amines pyrroline, pyrazolidine and imidazoline cause the evolution of methane and the formation of the corresponding zinc amides. In this way zinc pyrrolide, zinc pyrazolide and zinc imidazolide were obtained in form of pure substances.     

Spektralphotometrische Bestimmung von Spurenelementen der Schwefelwasserstoffgruppe mit Natriumpyrrolidindithiocarbamidat

Zusammenfassung Es wird eine direkte, photometrische Bestimmungsmethode für Kupfer in Eisenwerkstoffen mit Natriumpyrrolidindithiocarbamidat beschrieben. Nach Auflösen der Probe wird der Cu-PyDTC-Komplex in Anwesenheit von Maskierungsmitteln mit Tetrachlorkohlenstoff extrahiert und photometriert. Die Methode ist der Kupferbestimmung mit Diäthyldithiocarbamidat durchaus gleichwertig, das Na-PyDTC besitzt aber gegenüber dem DDTC den Vorteil größerer Anwendungsbreite, da es auch im sauren Gebiet verwendbar ist. Gegenüber anderen bekannten Bestimmungsverfahren bietet die beschriebene Arbeitsweise den Vorteil größerer Schnelligkeit bei gesteigerter Genauigkeit und Reproduzierbarkeit.

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Summary A direct photometric method is described for the determination of copper in ferrous material with sodium pyrrolidinedithiocarbamate (Na-PyDTC). After dissolution of the sample the Cu-PyDTC complex is extracted with carbon tetrachloride in presence of masking agents and is determined by photometry. The method can be favourably compared to the determination of copper with diethyldithiocarbamate (DDTC), yet Na-PyDTC is superior to DDTC with regard to the range of applicability as it can be used also in acid medium. In contrast to other methods already known the recommended procedure permits more rapid determinations of increased accuracy and reproducibility.

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IV. Mitt.: Kovács, E., H. Guyer u. W. Lüscher: diese Z. 208, 321 (1965).

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Kovács, E.; Produktions A.G. Meilen (Schweiz); H. Guyer, Hilger and Watts Ltd., German Office, Dortmund (Deutschland)

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Der Direktion der Georg Fischer Aktiengesellschaft, Schaffhausen (Schweiz), danken wir für die Bewilligung zur Veröffentlichung der vorstehenden Arbeit. Herrn W. Lüscher danken wir für die Ausführung der zahlreichen Extraktionen und photometrischen Messungen.