Schwingungsspektren und Kraftkonstanten von Hexamethyldisilan,Hexaphenyldisilan und 1,1,1-Trimethyl-2,2,2-triphenyldisilan

The Raman and infrared spectra of (CH₃)₃SiSi(CH₃)₃ (I), (CD₃)₃SiSi(CD₃)₃, (C₆H₅)₃SiSi(C₆H₅)₃ (II), (CH₃)₃SiSi(C₆H₅)₃ (III), and (CD₃)₃SiSi(C₆H₅)₃ are reported. Assignments are based on symmetry G ₃₆ ⁺ (free internal rotation) forI, D_3d forII, and C_3v forIII. Normal coordinate treatment has been done using some simplifications in the phenyl coordinates. The SiSi stretching force constant inI amounts to 1,65 N/cm. In compoundsII andIII strong vibrational coupling is elucidated byPED calculations.     

Exact spin-pairing energies at the crossovers in octahedral d 4, d 5, d 6, and d 7 transition metal complexes

Exact spin-pairing energies are calculated by direct diagonalization of the relevant ligand field plus interelectronic repulsion matrices for the configurations d ⁴, d ⁵, d ⁶, and d ⁷ of octahedral transition metal ions. The results are presented in terms of /B as function of = C/B for the range of values =3.0 to 8.0. Comparison with the quantity resulting from a simplified approach in which configuration interaction is neglected or considered on an approximate basis only reveals significant differences. Useful estimates of spin-pairing energies are provided, in addition, on the basis of empirical magnetic and electronic spectral data.

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Zusammenfassung Exakte Spinpaarungsenergien für die Konfigurationen d ⁴, d ⁵, d ⁶ und d ⁷ oktaedrischer Übergangsmetallionen werden durch direkte Diagonalisierung der entsprechenden Matrizen des Ligandenfeldes sowie der Elektronenwechselwirkung berechnet. Die Ergebnisse für /B werden in Abhängigkeit von = C/B für den Wertebereich =3.0 bis 8.0 angegeben. Ein Vergleich mit der Größe , die bei einer vereinfachten Behandlung unter Vernachlässigung oder näherungsweiser Berücksichtigung der Konfigurationswechselwirkung erhalten wird, zeigt auffallende Unterschiede. Nützliche Abschätzungen der Spinpaarungsenergie werden außerdem unter Benutzung empirischer magnetischer und elektronenspektroskopischer Daten erhalten.

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Résumé Les énergies exactes de couplage de spin sont calculées par diagonalisation directe du champ de ligand correspondant en plus des matrices de répulsion électronique pour les configurations d ⁴, d ⁵, d ⁶ et d ⁷ des ions octaédriques des métaux de transition. Les résultats sont présentés en termes de /B en fonction de = C/B dan l'intervalle =3,0 à 8,0. On trouve des différences significatives par comparaison de avec les valeurs résultant d'une approche simplifiée sans interaction de configuration ou avec interaction de configuration approchée. De plus, des estimations des énergies de couplage de spin sont obtenues à partir de données empiriques magnétiques et spectrales.

     

Untersuchung der Temperaturabhängigkeit derg ik -Tensoren von Polyäthyleneinkristallen

Zusammenfassung Es wurden die Kristallitgröße und die Änderungen der parakristallinen Gitterstörungen aus den Linienbreiten des Röntgenweitwinkeldiagramms von lösungskristallisiertem linearem Polyäthylen bei den Temperaturen 15°K, 73°K, 173°K und Zimmertemperatur bestimmt. Es wurde eine Zunahme der Gitterstörungen mit fallender Temperatur gefunden.

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Summary The crystallite size and the paracrystalline distortions in polyethylene single crystals were evaluated by the measurement of the linewidth in the X-ray wide angle diagram at four different temperatures (15°K, 73°K, 173°K and 297°K). An increase of the lattice distortions with decreasing temperature was found.

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Mit 3 Abbildungen

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Vorgetragen auf der Arbeitssitzung des Fachausschusses Physik der Hochpolymeren in der Frühjahrstagung 1970 des Regionalverbandes Hessen-Mittelrhein-Saar der Deutschen Physikalischen Gesellschaft in Darmstadt, 10.–13. März 1970.     

Preconcentration of manganese,cobalt, yttrium,zirconium, niobium,ruthenium, europium and protactinium by various hydroxides

Summary The removal of trace elements from dilute water solutions by hydroxide precipitates was investigated. The co-precipitation yields of manganese, cobalt, ruthenium, europium and protactinium onto beryllium, zinc, iron, lanthanum and titanium hydroxides were studied in the pH region from 3 to 11, while those of manganese, cobalt, yttrium, zirconium, niobium, ruthenium, europium, and protactinium onto the same hydroxides were investigated in sea-water media. The influence of some other factors, such as the presence of neutral electrolyte and NH₄ ⁺ ions, aging of hydroxide precipitates etc. on the co-precipitation yields were also examined.

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Zusammenfassung Die Entfernung von Spurenelementen aus verdünnten wäßrigen Lösungen durch Hydroxidniederschläge wurde untersucht. Die mitgefällten Anteile Mn, Co, Ru, Eu und Pa in den Hydroxiden von Be, Zn, Fe, La und Ti wurden im pH-Bereich 3–11 untersucht, während die Anteile von Mn, Co, Yt, Zr, Nb, Ru, Eu und Pa in den gleichen Hydroxiden in Meerwasser studiert wurden. Der Einfluß einiger anderer Faktoren auf die Mitfällung, wie die Anwesenheit neutraler Elektrolyte und von NH₄-Ionen, die Alterung der Hydroxidniederschläge usw. wurden ebenfalls geprüft.

     

A CNDO/INDO crystal orbital model for transition metal polymers of the 3d series—basis equations

The crystal orbital formalism in the tight-binding approximation is combined with a recently developed CNDO/INDO model for transition metal species of the 3d series in order to allow band structure calculations on the Hartree-Fock (HF) SCF level for one-dimensional (1D) chains with organometallic unit cells. The band structure approach based on the CNDO and INDO approximation can be used for any atom combination up to bromine under the inclusion of the 3d series. The matrix elements for the tight-binding Hamiltonian are derived for an improved CNDO and INDO framework. The total energy of the 1D chain is partitioned into one-center contributions and into two-center increments of the intracell and intercell type. Semiempirical band structure calculations on simple model systems are compared with available ab initio data of high quality.     

Prospects of thermal analysis in polymer research

A survey and an analysis of the publications concerned in thermal analysis (TA) published in four renowned journals during the years 1965–1974 were performed. The published data were evaluated from three points of view: TA methods used for polymers, properties and phenomena studied by TA methods, types of polymers investigated by TA methods. From the statistical data were derived the future trends for the application of particular TA methods in polymer science.     

The influence of “two-phase” synthesis conditions on blown film extrusion of LDPE

LDPE synthesized under two-phase conditions is known to have a good balance of blown film properties. Good optical properties and high impact strength are characteristic for two-phase LDPE grades. In order to obtain systematic information, LDPE was synthesized at several different pressures with two different melt index levels. Blown film was extruded at different output rates and melt temperatures. The influence on haze and dart drop impact was studied. Two-phase conditions were found to improve haze and dart drop impact and the improvement was impressive, especially for the low melt index grades. By increasing the output rate, the dart drop values were further improved. The influence of melt temperature on dart drop impact goes through an optimum and overall haze decreases with increasing melt temperature. For films made from two-phase grades, dart drop impact decreases as internal haze increases. For corresponding internal haze values, the films made from single-phase grades have lower dart drop values and they are somewhat scattered.     

Kinetic study of copper(II) complexation with 9-ethyl-3-carbazolecarboxaldehyde-thiosemicarbazone and kinetic-spectrophotometric determination of copper(II)

The kinetics of complexation reaction of Cu(II) with 9-ethyl-3-carbazolecarboxaldehyde-thiosemicarbazone (ECCAT) has been examined spectrophotometrically. The ligand was synthesized for the first time. The complexation reaction was carried out in a DMF-water medium at 35°C. The complex has maximum absorbance at 393 nm. Kinetic and activation parameters of the complexation reaction were calculated by the Arrhenius and Eyring equations using the data obtained from investigating the effect of temperature on reaction rates under the specified conditions. We also proposed reaction rate equations. Based on the studied complexation reaction, a simple kinetic method for the spectrophotometric determination of copper(II) has been developed. The calibration graphs are linear in the concentration range 0.2–1.9 μg/mL. The species that caused interference were investigated. The text was submitted by the authors in English.     

Zur Ermittlung und rechnerischen Überprüfung thermodynamischer Daten aus experimentell gefundenen Werten, 10. Mitt.: Zur Frage der Parameterzahl und Fehlerverteilung bei einigen Rechenansätzen für binäre thermodynamische Systeme

Zusammenfassung Es wird eine vergleichende Untersuchung über die Anwendungsmöglichkeit zweier dreiparametriger und zweier zweiparametriger Ansätze angestellt. Die Bestimmung der Konstanten erfolgt nach der Methode der kleinsten Quadrate, die entstehenden Fehlerquadratsummen werden als Funktion der Iterationszahl dargestellt und verglichen. Ebenso wird mit den Verbesserungen _i und den mittleren Fehlern der einzelnen Parameter verfahren. Es ergibt sich, daß der Ansatz vonWilson für stark assoziierende Systeme mit nahezu horizontaler Grenztangente die kleinste Fehlerverteilung aufweist. Die beiden dreiparametrigen Ansätze vonRedlich-Kister und vonMusil-Breitenhuber zeigen sich für das Systemn-Hexan-Methylamin besser geeignet als für die Systeme Benzol-Methanol und CCl₄-Methanol. Die Problematik der Parameterzahl wird an Hand der Fehlerverteilung bei den Ansätzen vonMB undRK aufgezeigt und diskutiert.Das Programm wurde in der Programmiersprache FORTRAN erstellt und mit der UNIVAC-490-Computer-Anlage des Grazer Rechenzentrums gerechnet.

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Four thermodynamical statements are tested with regard to their applicability to binary systems, two statements having three and two only two parameters. The least square method ofGauss shows that theWilson statement has the smallest dispersion of errors for systems with nearby horizontal boundary tangent. [vv], _i and are shown as functions of the number of iterations. The problem of the parameters' number is shown and discussed by means of the dispersion of errors for theMusil-Breitenhuber (MB) andRedlich-Kister (RK)-statements.The programme is written in FORTRAN and has been used the UNIVAC-490-Computer of the Graz Computer Centre.

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Herrn Professor Dr.Robert Fischer zum 65. Geburtstag in Dankbarkeit und Verehrung gewidmet.

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bis 6. Mitt.:F. Gölles, Mh. Chem.92, 981 (1961);93, 191, 201 (1962);94, 1108 (1963);95, 1656 (1964);96, 1366 (1965);7. bis 9. Mitt.:F. Gölles undA. Höpfner, Mh. Chem.97, 368, 911 (1966);99, 230 (1968).     

Selective pressurized liquid extraction of polychlorinated biphenyls from fat-containing food and feed samples influence of cell dimensions, solvent type, temperature and flush volume

Sulphuric acid impregnated silica was used for the lipid free extraction of polychlorinated biphenyls from fat containing food and feed matrices using pressurized liquid extraction on a Dionex ASE300, with 34 mL cells. Data were compared to a previous publication where extractions had been performed on a Dionex ASE200, with 33 mL cells. Four different fat/fat retainer ratios (FFRs) were tested (0.100, 0.075, 0.050 and 0.025) at 50 and 100 degrees C using n-pentane, n-hexane or n-heptane as extraction solvent. The best results were obtained with a FFR of 0.025 when applying a temperature of 100 degrees C. Both n-pentane and n-heptane were capable of replacing n-hexane as extraction solvent. A flush volume of 60% was sufficient as suggested in US Environmental Protection Agency Method 3545. The applicability of the method was demonstrated for naturally contaminated fish meal as well as various spiked and certified materials.