Reversed phase liquid chromatographic retention behavior of polystyrene homopolymers

Summary Isocratic and gradient elution high performance liquid chromatographic measurements of the retention behavior of polystyrene homopolymers with molecular weights ranging from 2 kD to 390 kD were performed using mixed methylene chloride-methanol mobile phases of varying composition and a C-18 chemically bonded stationary phase supported on either 100 Å or 300 Å mean pore diameter silica. Isocratic measurements of the capacity factor, k, for different molecular weight homopolymers as a function of the volume fraction of methylene chloride, , permit determination of the critical composition, _c, which renders k=1 and the local slope, S=–lnk/_c of the lnk- isotherm at =_c, and also the dependence of _c and S on the degree of polymerization, M. Linear gradient elution measurements of _c and S were also performed and compared to the corresponding isocratic measurements. The general retention behavior and the dependence of _c and S on M compare favorably to the predictions of the theory of homopolymer retention and fractionation developed by Boehm, Martire, Armstrong, and Bui (BMAB). Comparison is also made between the present work and the experimental observations of other workers on related chromatographic systems involving hompolymer retention.     

Apparent molar heat capacity and relative enthalpy of aqueous NaOH between 323 and 523K

The apparent molar heat capacity, C _p,, of aqueous NaOH has been measured at temperatures between 50 and 250°C and molalities from 0.05 to 1.5 mol-kg^–1. Enthalpies of dilution L were also determined at 99°C and apparent molar relative enthalpies L were calculated up to 1.9 m. Measurements were performed by means of a flow calorimetric apparatus constructed in our laboratory and standardized for C _p, and L with aqueous Na₂SO₄ and with the formation of water from its ions, respectively. Characteristics and performance of this calorimeter are described in detail. Pitzer's semiempirical equations are used for the representation of the results and a general fitting of C _p, data is reported using also recent literature values measured between 4 and 55°C. The fitted parameters are finally utilized, through an integration procedure, to derive a general equation to calculate L at any temperature between 4 and 250°C.     

Study of the thermal decompositions of some transition metal perchlorates

The thermal decompositions of nickel(II), copper(II), cobalt(II) and manganese(II) perchlorates were studied by thermal analysis and kinetic measurements. Anhydrous perchlorates could not be prepared by heating and outgassing the samples in vacuum; oxides were obtained as the main solid decomposition products. In the case of cobalt and manganese perchlorates, oxidation of the metal ions was observed during the decomposition. In most cases the decompositions of the perchlorates followed the Avrami-Erofeyev kinetics. A correlation was found between the stabilities of the perchlorates and the effective field strengths of the cations.

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Zusammenfassung Die thermische Zersetzung von Nickel(II), Kupfer(II)-, Kobalt(II)- und Mangan(II)-perchloraten wurde mittels Thermoanalyse und kinetischer Messungen untersucht. Durch Erhitzen und Entgasen der Proben im Vakuum konnten keine wasserfreien Perchlorate hergestellt werden; Oxide wurden als feste Hauptzersetzungsprodukte erhalten. Im Falle der Perchlorate von Kobalt und Mangan wurde die Oxidation der Metallionen während der Zersetzung beobachtet. In den meisten Fällen verlief die Zersetzung der Perchlorate nach der Kinetik von Avrami-Erofeyev. Eine Korrelation wurde zwischen den Stabilitäten der Perchlorate und der tatsächlichen Feldstärke der Kationen gefunden.

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Résumé La décomposition thermique des perchloartes de nickel(II), de cuivre(II), cobalt(II) et de manganèse(II) a été étudiée par analyse thermique et mesures cinétiques. Les perchlorates anhydres n'ont pas pu être préparés par chauffage et traitement sous vide de échantillons; les oxydes ont été obtenus comme produits solides principaux de décomposition. Dans le cas des perchlorates de cobalt et de manganèse, l'oxydation des ions métalliques a été observée pendant la décomposition. Dans la plupart des cas, la décomposition des perchlorates a suivi la cinétique d'Avrami-Erofeyev. Une corrélation a été trouvée entre la stabilité des perchlorates et les intensités effectives des champs des cations.

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, , . ; . , . . .

     

Transient phenomena in o-xylene oxidation in a fluidized bed reactor

The effect of stirring a vanadium-titanium-tellurium catalyst on the yield of the selective oxidation products for oxidation of o-xylene in fluidized bed reactors has been studied. It is shown that the stirring of catalyst pellets increases the yield of phthalic anhydride.

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-- - . , .

     

Influence of oxygen on semiconducting properties of polycrystalline zinc oxide in its surface region

The influence of oxygen adsorption on electrical conductivity of sintered ZnO has been studied. The concentration of conduction electrons and their mobility were determined by Hall effect method in the temperature range 200–550 K. It was found that adsorbed oxygen decreases the conduction electron concentration as well as their mobility.

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ZnO. 200–550 . , , .

     

Ammoxidation of 3- and 4-picolines over V2O5?SnO2/γ?Al2O3 catalyst

The ammoxidation of 3- and 4-picolines has been studied over V₂O₅–SnO₂/–Al₂O₃ catalysts prepared by surface impregnation technique. Best results were obtained for the generation of cyanopyridines in the temperature range 400–450°C and sub-stoichiometric value with respect to O₂. Catalysts that were calcined above 700°C showed no activity.

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3- 4- V₂O₅–SnO₂/–Al₂O₃, . 400–450°C O₂. , 700 K, .

     

Synthesis and thermal study of some adducts of morpholine with nickel(II) nitrite,sulphate and perchlorate

The preparations of the nickel-morpholine (Morph) complexes Ni(NO₂)₂·3Morph and Ni(ClO₄)₂·4Morph·2H₂O are described. The thermal treatment of this perchlorate and of NiSO₄·2Morph led to the isolation of Ni(ClO₄)₂·2Morph·2H₂O and NiSO₄·Morph. The magnetic moments, diffuse reflectance spectra and infrared spectra of these compounds are all compatible with a pseudo-octahedral environment around the nickel atom.

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Zusammenfassung Die Darstellung der Nickel-Morpholin(Morph)-Komplexe Ni(NO₂)₂·3Morph und Ni(ClO₄)₂·4Morph·2H₂O wird beschrieben. Die thermische Behandlung dieses Perchlorates und von NiSO₄·2Morph ergibt Ni(ClO₄)₂·2Morph·2H₂O und NiSO₄Morph. Magnetisches Moment sowie diffuse Reflektionsspektren und Infrarotspektren dieser Verbindungen sind kompatibel mit einer pseudooktaedrischen Koordination des Nickelatoms.

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, () : Ni(NO₂)₂·, NiSO₄·2 Ni(ClO₄)₂·4·2H₂O. NiSO₄· Ni(ClO₄)₂·2·2H₂O. , , .

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The authors are indebted to Consejeria de Cultura y Educación de la Comunidad Autónoma de Murcia for financial support.     

Solvent effects on chemical processes. 4. Complex formation between naphthalene and theophylline in binary aqueous-organic solvents

The standard free energy change for complex formation is written as a sum of effects arising from solvent-solvent interactions (the general medium effect), solvent-solute interactions (the solvation effect), and solute-solute interactions (the intersolute effect). The general medium effect is given by gA(–_o), where g is a curvature correction factor to the solvent surface tension , A is the change in surface area as the two solvent cavities containing the substrate (naphthalene) and ligand (theophylline) collapse into a single cavity containing the complex, and _o is the value of surface tcnsion at which there is no net solvophobic interaction; is defined to be the value appropriate to the equilibrium mean solvation shell composition. The solvation effect is modeled by equilibrium stoichiometric formation of solvated species. All data are related to the fully aqueous system to give _MG^o, the solvent effect on the free energy change, as an explicit function of solvent composition. Solvent effects on bimolecular association are related to solvent effects on the solubilities of the substrate, ligand, and complex. Approximation methods for interpreting such systems are described and are applied to the naphthalene-theophylline complex. It is shown that complex destabilization in mixed aqueous-organic solvents (relative to the fully aqueous system) may receive contributions from both the general medium and the solvation effects, and that these contributions can be quantitatively estimated.     

Preparation and study of Mn-containing silicates of zeolite structure

The Cu–SiO₂ catalyst prepared by ion exchange method shows a longer life for the dehydrogenation of methanol, as compared with those of Cu catalysts prepared by other methods. This suggests that the highly dispersed Cu particles on the support cannot be easily aggregated during the reaction.

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Cu–SiO₂, , , , . , .

     

Thermal decomposition of calcium sulphate in carbon monoxide

Simultaneous TG and DTA studies were performed on analytical grade calcium sulfate and on samples of natural gypsum and phosphogypsum in carbon monoxide atmosphere. The decomposition temperatures and mechanism are influenced by the mineral impurities of the sample and the heating rate as well as the CO content of the gas atmosphere.

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Zusammenfassung Simultane TG- und DTA-Untersuchungen von analytisch reinem Calciumsulfat und Proben von natürlichem Gips und Phosphogips wurden in Kohlenmonoxidatmosphäre ausgeführt. Temperatur und Mechanismus der Zersetzung werden durch mineralische Verunreinigungen der Probe, durch die Aufheizgeschwindigkeit und durch den CO-Gehalt der Gasatmosphäre beeinflußt.

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. - , , .

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The authors are indebted to Professor M. Veiderma for fruitful discussions and continuous support. The scholarship from Finnish Government to one of us (R. K.) is gratefully acknowledged.     

Differential thermal analysis of fluxed melts and its application to the system NiFe2O4-BaO-B2O3

The application of DTA to fluxed melts is discussed, and an apparatus for the determination of the solubility of crystalline materials in molten solutions is described. An exploratory study of the crystallization of nickel ferrite from barium borate fluxes is also described, and solubility curves are presented for fluxes which favour crystal growth. The heat of solution of nickel ferrite was found to be 73 ± 2 Kjoule mole^–1.

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Zusammenfassung Es wurde über die Anwendung der DTA Methode bei der Untersuchung von Flußmittel enthaltenden Schmelzen berichtet und ein Apparat zur Bestimmung der Löslichkeit von kristallinischen Substanzen in Flüssen beschrieben. Eingehend wurden die Kristallisation von Nickelferrit aus Bariumborat-Flüssen untersucht und Löslichkeitskurven für den Kristallwachstum begünstigende Flüssen gegeben. Die Lösungswärme von Nickelferrit betrug 73 ± 2 Kjoule Mol^–1.

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Résumé On a décrit l'application de la méthode ATD à l'étude des fusions avec fondant et un appareil adapté à la détermination de la solubilité des substances crystallines dans les fondants. On a étudié la cristallisation de ferrite de nickel des flux de borate de baryum. Des courbes de solubilité pour des flux favorisant les grossissement des cristaux sont présentées. La chaleur de solution du ferrite de nickel a été trouvée 73 ± 2 kjoule mole^–1.

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A ( ). , . 73±2 ^–1.

     

n-Butane oxidation over a vanadium-phosphorus catalyst

The activity of vanadium-phosphorus oxide catalysts with respect to maleic anhydride formation in n-butane oxidation has been found to correlate with the concentration of V⁴⁺ ions in the catalysts. The steady catalytic activitv of the samples examined is achieved more rapidly upon prereduction.

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, - - . , .

     

Order and disorder in mixed metal linear chains: The homo and heterobimetallic EDTA (M(H2O)4OIOII)[M′(EDTA)] · 6H2O complexes (M = Mg,Mn, Co,Zn and Ni; M′ = Co,Ni, Cu and Zn)

Summary Polymetallic solid solutions of the ethylenediaminetetracetic acid (EDTA) and six divalent metal ions exist in the range: MgMnCoZnNiCu(EDTA) · 6H₂O where + + + + + =2, 01, 0,,2, 0, 1.This type of structure is characterized by the presence of two different octahedral carboxylate-bridged coordination sites forming infinite zig-zag chains. Visible and i.r. spectra and t.g.a. analysis show that there is occupational preference for the two coordination sites in the crystalline structure.Due to this preference, and also to the structural features, the heterobimetallic MM(EDTA) · 6H₂O compounds constitute a structurally new class of materials which can be described as ordered alternating-heterobimetallic polymeric coordination complexes.     

Kinetics and mechanism of isothermal dehydration of LiKC4H4O6 · H2O single-crystals

The kinetics of isothermal dehydration of LiKC₄H₄O₆.H₂O single-crystals was investigated in the [001] crystallographic direction under a dynamic vacuum of 6.7×10^–5 Pa with a quartz crystal microbalance. The removal of H₂O molecules may be described by a diffusion equation for a semi-infinite medium. The diffusion coefficients vary from 2.13×10^–11 cm² s^–1 at 391.7 K to 9.9×10^–9 cm² s^–1 at 453.2 K. The scanning electron microscope data provide some evidence that the dehydration is not a topochemical reaction. From the experimental data it is concluded that the anhydrous product is in the state of premelting. This explains the anomalous diffusion energyE _D=37±1 kcal mol^–1 and preexponential factorD ₀=5×10⁹ cm² s^–1.

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Zusammenfassung Die Kinetik der Entwässerung von LiKC₄H₄O₆.H₂O in [001] — Richtung unter dynamischem Vakuum wurde mit einer Quarzkristall-Mikrowaage verfolgt. Die Abgabe von Wasser kann mit einer Diffusionsgleichung für ein halb-unendliches Medium beschrieben werden, die Diffusionskoeffizienten variieren von 2, 13 · 10^–11 cm²s^–1 bei 391,7 K bis 9,9 · 10^–9 cm² s^–1 bei 453,2 K. Rasterelektronenmikroskopische Aufnahmen zeigen, daß die Entwässerung nicht topochemisch abläuft. Nach dem experimentellen Ergebnis befindet sich das entwässerte Produkt in einem Vorschmelz-Stadium. Daraus erklären sich die anomalen Werte für die DiffusionsenergieE _D=(37±1) kcal mol–1 und den präexponentiellen FaktorD ₀=5 · 10⁹ cm² s^–1.

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6,7 · 10. LiKC₄H₄O₆.H₂O [001]. . 2,13·10^{–11 2 –1} 391,7 9,9·10^{–9 2 –1} 453,2 . , . , «», E =37±1 ·^{– 1} ₀=5·10⁹²·^–1.

     

Reduction of NO by carbon monoxide on tin dioxide

The reduction of NO by carbon monoxide on SnO₂ has been studied in the temperature range from 90 to 450°C. The complicated temperature dependence of the reaction rate is due to the interaction of CO an CO₂ with the catalyst.

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NO SnO₂ 90–450°C. , CO CO₂ .

     

Thermoanalytical and thermogastitrimetric investigation of oil-shales

From thermoanalytical curves (DTG, TG) recorded in an oxygen atmosphere, the moisture and carbonate contents of oil-shales were determined with acceptable accuracy. The nature of the carbonates was predicted from the shape of the DTG curves above 550°C Dolomite (ankeritc) as found in Gérce oil-shale, and calcite in Pula-9 oil-shale. The clay content was determined from the signal of a water-detector recorded in a nitrogen atmosphere. The peaks at 80°C and 150°C for Gérce oil-shale were attributed to montmorillonite, and the sharp peak at 525°C for Pula-9 oil-shale to kaolinite.The volatile and fixed carbon contents of the oil-shales were calculated from the thermogastitrimetric curves.

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Zusammenfassung Feuchtigkeits- und Carbonatgehalt von Ölschiefern werden aus in Sauerstoffatmosphäre aufgenommenen thermoanalytischen Kurven (DTG, TG) mit annehmbarer Genauigkeit bestimmt. Die Natur der Carbonate wurde aus dem Verlauf der DTG-Kurve oberhalb 550 °C vorausgesagt. Dolomit (Ankerit) wurde im Gérce-Ölschiefer, Calcit im Pula-9-Ölschiefer gefunden. Der Gehalt an Tonen wurde aus dem in Stickstoffatmosphäre erhaltenen Signal eines Wasserdetektors bestimmt. Die Peaks bei 80 und 150 °C in der DTG-Kurve des Gérce-Ölschiefers werden Montmorillonit, der scharfe Peak bei 525 °C im Falle von Pula-9-ölschiefer Kaolinit zugeschrieben. Die Gehalte der Ölschiefer an flüchtigem und fixiertem Kohlenstoff werden aus gastitrimetrischen Kurven berechnet.

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(, ) , , . 550°. (), -9-. . , 80 150° , 525° -9 — . , .

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The authors are indebted to J. Kristóf (Dept. of Anal. Chem., Univ. of Veszprém) for carrying out the continuous water measurements; to K. Labdy (Central Laboratory, Univ. of Veszprém) for the elemental analysis results; to I. Vassányi (Dept. of Mineralogy, Univ. of Veszprém) for the diffractometric results; and to I. Koncz (Hydrocarbon Research and Development Institute, Nagykanizsa) for donating the oil-shale samples.     

Temperature measurements with a differential calorimeter

A differential microcalorimeter was used for the reading of transition temperatures. The inherent factors in both the instrument and the sample which may introduce variables in temperature measurements carried out with the calorimeter were studied together with modifications of the reading methods. An accurate technique is described for the preparation of the sample and measurement of temperature. The proposed method, when applied to organic standards of very high and of decreasing purity, gives an accuracy of temperature reading in the order of ±0.1°, and confirms a relationship between experimental and theoretical values.

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Zusammenfassung Ein Differentialmikrokalorimeter wurde zur Bestimmung der Übergangstemperaturen angewandt. Man untersuchte die Faktoren sowohl seitens des Instruments wie der Probe, durch welche Variablen in den mit dem Kalorimeter ausgeführten thermometrischen Messungen eingeführt werden können, weiterhin wurden Modifikationen der Ablesemethoden vorgeschlagen. Ein sicheres Verfahren zur Probebereitung und Temperaturmessung wird beschrieben. Die Methode gab bei der Anwendung von organischen Standardstoffen sehr hoher und minderer Reinheit eine Genauigkeit von ±0.1°.

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Résumé On a utilisé un microcalorimètre pour la détermination des températures de transition. On a étudié les facteurs inhérents à la fois à l'instrument et à l'échantillon, susceptibles d'introduire des variations dans les mesures thermométriques et l'on a proposé des modifications. On décrit une technique précise pour préparer l'échantillon et mesurer la température. La méthode proposée, appliquée à des étalons organiques de très haute pureté, ainsi que de pureté moins élevée, donne une précision de l'ordre de ±0.1° dans la lecture de la température et confirme une relation entre les valeurs expérimentales et théoriques.

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. . , ± 0.1° .

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The authors wish to thank Prof. G. Milazzo of the Istituto Superiore di Sanitgt (Rome) for assistance in the work.     

Energetic state of hydrogen on Os-black

Hydrogen adsorption on Os-black has been studied by the TPD method in the range from –85 to 450°C. Energetic inhomogeneity of hydrogen chemisorbed at adsorption temperatures of 150 to 450°C has been elucidated.

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OS (–85)–450°C. , 150 450°C.

     

Isothermal and nonisothermal gravimetry of nontronite dehydroxylation

A pure typical nontronite from Czechoslovakia (Sampor) was analysed by the title techniques in the range 570–1070 K. The isothermal dehydroxylation of nontronite, recorded at 630–730 K, was described reasonably, in the decomposition range =0.05–0.95, by diffusioncontrolled mechanismsD ₃ andD ₄. Application of the current solid-state reaction equations to the non-isothermal curve gave very poor results, except in the limited decomposition range =0.10 to 0.55. A unimolecular mechanism equation (Fm ₁) and also a second-order (SO) mechanism gave the best linearization of the curve. The activation energies estimated from the isothermal (D ₃,D ₄) and non-isothermal (F ₁) experiments were 125 and 151 kJ·mol^–1, respectively. Reduced time plots indicate the probable presence of a sequence of different mechanism for both techniques.

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Zusammenfassung Mittels der Titeltechniken wurde im Bereich 570–1070 K ein reines typisches Nontronit aus der SSR (Sampor) untersucht. Die isotherme Dehydroxylierung von Nontronit bei 630–730 K konnte im Bereich der Zersetzung von =0,05–0,95 durch die diffusionsbestimmten MechanismenD ₃ undD ₄ befriedigend beschrieben werden. Eine Anwendung der Gleichungen für Feststoffreaktionen auf die nichtisotherme Kurve ergab mit Ausnahme des Bereiches =0,10–0,55 nur sehr unzureichende Ergebnisse. Eine Gleichung für einen monomolekularen (F ₁) Mechanismus sowie für einen mechanismus zweiter Ordnung (SO) ergaben die beste Linearisierung der Kurve. Die aufgrund der isothermen (D ₃,D ₄) und nichtisothermen (F ₁) Experimente geschätzten Aktivierungsenergien betragen 125 bzw. 151 kJ·mol^–1. Es wird angenommen, daß es sich bei beiden Techniken um eine Sequenz verschiedener Mechanismen handelt.

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570–1070 (). , 630–730 =0,05–0,95, - D ₃ D ₄. , =0,10–0,55. (F ₁), . , (D ₃,D ₄) (F ₁) , , , 125 151 ·^–1. .