On the theory of adsorption kinetics of ionic surfactants at fluid interfaces

The kinetic equation to describe the adsorption process of ionic surfactants (derived in part 1) will be solved numerically. The results show the effect of parameters such as ion valencyz, thickness of theDL x ^–1, and surfactant parameters_eq,K, andK _ads on the adsorption process. The results can be used to decide whether the model can explain experimental data on charged surfactant molecules or not.Nomenclature c concentration - c_e bulk concentration in equilibrium - C =c/c _e dimensionless concentration - D diffusion coefficient - e proton charge - F Faraday's constant - f ₀ =e/kTdimensionless potential - k Bolzmann's constant - K _ads rate constant of adsorption - K _des rate constant of desorption - K(f ₀) coefficient of electrostatic deceleration - K = _eq /c _e Henry's constant - R gas law constant - t time - T absolute temperature - z electrovalence - ₀ adsorption of ions - _eq equilibrium value of _o - = ₀/ _eq dimensionless adsorption - , constants - dielectric constants - x Debye-Hückel reciprocal distance - =Dt/K ² dimensionless time - electric potential     

TPD study of catalyst surface acidity

Acidity of catalyst surfaces of different nature such as -Al₂O₃, natural zeolite-clinoptilolite, and synthetic zeolite zeokar by adsorption of ammonia over a wide temperature range has been studied. Ammonia is adsorbed on the catalysts with different strengths, as evidenced by the presence of different types of acid sites.

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(-Al₂O₃, - , () . , , .

     

Influence of cyclodextrins on nitrosation of drugs

The World Health Organization issued a nitrosation procedure (NAP Test) which allows to carry out nitrosation under standard conditions. It has proved that the in vitro reaction rates of the fast nitrosatable drugs piperazine, cimetidine and ethambutol are not influenced by -, - and -cyclodextrin. On the contrary, -, -cyclodextrin and heptakis-2,6-di-O-methyl--cyclodextrin enhance the nitrosation of the slower nitrosatable 1-ephedrine and fencamfamine significantly. This possible reaction must be considered if nitrosatable drugs are formulated with cyclodextrins to be administered to human beings.     

Studies on lanthanoid sulfites. Part VIII. Thermogravimetric study of europium sulfite trihydrate

When Eu₂(SO₃)₃·3H₂O is heated in air it forms after dehydration two sulfite-sulfate phases: Eu₂(SO₃)₂SO₂ and Eu₂SO₃(SO₄)₂. The latter phase is thermally remarkably stable and decomposes above 700°C via Eu₂O₂SO₄ to Eu₂O₃. Anhydrous Eu₂(SO₃)₃ and Eu₂O₂SO₄ were also found as intermediates before Eu₂O₃ when the TG experiments were carried out in nitrogen but in other details the decomposition mechanism differs from that in air.

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Zusammenfassung Eu₂(SO₃)₃·3H₂O bildet durch Erhitzen in Luft nach Dehydratation zwei Sulfit-Sulfat-Phasen: Eu₂(SO₃)₂SO₄ und Eu₂SO₃(SO₄)₂·Letztere ist thermisch bedeutend stabiler und zersetzt sich oberhalb 700°C über Eu₂O₂SO₄ zu Eu₂O₃. Bei Durchführung der TG-Experimente in Stickstoff wurden als Zwischenprodukte vor Eu₂O₃ auch wasserfreies Eu₂(SO₃)₃ und Eu₂O₂SO₄ gefunden, in anderen Details weicht jedoch der Mechanismus der Zersetzung von dem der Zersetzung in Luft ab.

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- Eu/SO_3/2SO₄ Eu₂SO₃/SO_4/2. 700° Eu₂O₃ Eu₂O₂SO₄. Eu₂/SO_3/3 Eu₂O₂SO₄ , .

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For Part VII, see ref. 6.     

Preparation of cobalt doped γ-Fe2O3 and Mn-Zn ferrites by the thermal decomposition of the hydrazine precursors

Fine particle cobalt doped-Fe₂O₃ and Mn-Zn ferrites have been prepared by the thermal decomposition of N₂H₅Co _x Fe_1–x (N₂H₃COO)₃.H₂O wherex=1–10 atom% and (N₂H₅)₃Mn_xZn_1–x Fe₂(N₂H₃COO)₉· 3H₂O wherex=0.2–0.8, respectively. Formation of these oxide materials has been confirmed by thermogravimetry and X-ray powder diffraction patterns. The fine particle nature of these oxide materials is evident from particle size analysis and surface area measurements.

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Zusammenfassung Mit fein verteiltem Kobalt versetztes-Fe₂O₃ sowie Mn-Zn Ferrite wurden durch thermische Zersetzung von N₂H₅Co _x Fe_1–x (N₂H₃COO)₃·H₂O mit jc=1–10 Atomprozent bzw. (N₂H₅)₃Mn _x Zn_1–x Fe₂(N₂H₃COO)₉·3H₂O mitx=0,2–0,8 hergestellt. Die Bildung dieser Oxidstoffe wurde durch Thermogravimetrie und Pulverdiffraktionsmethoden bekräftigt. Die Feinkornstruktur dieser Oxidstoffe wird durch Korngrößenverteilungs- und Oberflächenmessungen augenscheinlich.

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N₂H₅Co _x Fe_1–x (N₂H₃COO)₃·H₂O, x-1–10 %, (N₂H₅)₃Mn _x Zn_1–x Fe₂(N₂H₃COO)₉ · 3H₂O, x=0,2–0,8, , , -Fe₂O₃ Mn-Zn . . .

     

Reaction of triphenyl phosphite ozonide with thioacetals

Kinetic regularities in the reaction of triphenyl phosphite ozonide with several thioacetals in CH₂Cl₂ solution at –15°C have been studied. The consumption rate of ozonides is described by the kinetic equation W=k₀[(C₆H₅O)₃P·O₃]+k₁[(C₆H₅O)₃P·O₃][R₁R₂C(SR₃)₂] Rate constants k₀ and k₁ for the thioacetals: (CH₃H₇S)₂CH₂, (C₆H₅S)₂CH₂, (C₆H₅CH₂S)₂CH, (n=C₁₂H₂₅–S)₂CH₂, (C₃H₇S)₂C(H)CH₃, (C₃H₇S)₂C(H)C₆H₅, (C₃H₇S)₂C(CH₃)C₆H₅ and (C₃H₇S)₂C(H)C₁₀H₉, increases with increasing the electron-donating power of subtituents R_i.

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CH₂Cl₂ –15°C. : W=k₀[(C₆H₅O)₃P·O₃]+k₁[(C₆H₅O)₃P·O₃][R₁R₂C(SR₃)₂] k₀ k₁ (C₃H₇S)₂CH₂, (C₆H₅S)₂CH₂, (C₆H₅CH₂S)₂CH₂, (n-C₁₂H₂₅S)₂CH₂, (C₃H₇S)₂C(H)CH₃, (C₃H₇S)₂C(H)C₆H₅, (C₃H₇S)₂C(CH₃)C₆H₅, (C₃H₇S)₂C(H)C₁₀H₉. .

     

Kinetics and mechanism of the hydrolysis of sodium carboxymethylcellulose (Na-CMC) by a cellulase complex

TheSomogyi-Nelson colorimetric method is applied in a new manner more suitable for evaluating the kinetics of the enzyme hydrolysis of sodium carboxymethylcellulose (Na-CMC) catalyzed by the cellulase complex. By means of selective inhibition of a chosen enzyme from the cellulase complex it became possible to trace the effect of the other enzymes included in its composition.

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Kinetik und Mechanismus der Hydrolyse von Natriumcarboxymethylcellulose (Na-CMC) durch einen Cellulase-Komplex

Zusammenfassung Die kolorimetrische Methode nachSomogyi undNelson wird nach einem neuen Verfahren zur Verfolgung der Kinetik der hydrolytischen Spaltung von Natriumcarboxymethylcellulose (Na-CMC), katalysiert durch den Cellulase-Komplex, angewandt. Durch selektive Inhibierung eines bestimmten Enzyms des Cellulase-Komplexes kann man die Wirkung der anderen zu seiner gesamten Zusammensetzung gehörenden Enzyme verfolgen.

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Symbols Used E enzyme (E—cellulase;E—exo-cellobiohydrolase;E—-glucosidase) - [E] _w weight concentration of enzymeE - S substrate (Na-CMC—sodium carboxymethylcellulose) - [S]₀ weight concentration of substrateS - I inhibitor (I—lactose;I—calcium chloride;I—condurrite-B-epoxide) - P product (P—oligosaccharides;P—cellobiose;P—D-glucose) - P end product (K , K , K ) - DP degree of polymerization - DS degree of substitution - ES enzyme-substrate complex (E S, E S, E S) - EP enzyme-product complex (E P, E P) - EI enzyme-inhibitor complex (E I, E I, E I) - M _s molecular mass of substrateS - K _s substrate constant (K _s , K _s , K _s ) - K _I inhibitor constant (K _I , K _I , K _I ) - K _m Michaelis-Menten constant - k ₊₁,k ₊₂ (k ₊₂ ,k ₊₂ ,k ₊₂ ) forward rate constants - k _–1 reverse rate constant - ₀ initial rate of reaction - V maximal reaction rate - A change in absorbance - molar absorption coefficient - wavelength Herrn Prof. Dr.Hans Tuppy zum 60. Geburtstag herzlichst gewidmet.     

New chiral acyclic analogs of 2′-deoxynucleosides

Convenient methods for the synthesis of chiral 2,3-seco-2-deoxynucleosides were developed. An isopropylidene protective group was used to block the 3,5-hydroxy groups in 2,3-seco-uridine. Conversion of the hydroxymethyl group to a methyl group was accomplished by chlorination with a mixture of CCl₄ and Ph₃P with subsequent reduction with n-Bu₃SnH. 2,3-seco-2-Deoxyuridine was obtained after deacetonation. The (S) enantiomer was similarly synthesized starting from 1-(-D-arabinofuranosyl)uracil. 3-O-tert-Butyldimethylsilyl-5-O-(p-monomethoxytrityl)-2,3-seco-2-deoxyuridine, which has optically active centers at C₍₁₎ and C₍₄₎, was also synthesized.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 822–826, June, 1988.The authors thank Professor M. Ya. Karpeiskii for his constant interest in this research.     

Thermal Behaviour of some dioxane adducts ofM(C6F5)2 (M=Pd,Pt)

The thermal treatment of the pentafluorophenyl derivativesM(C₆F₅)₂Dx_n [M=Pd (n=2, 3) or Pt (n=2); Dx=dioxane] leads to the formation of the new dioxane adducts M(C₆F₅)₂Dx (M=Pd, Pt) and Pt(C₆F₅)₂Dx_1.5. Calculations of the order of reaction and the activation energy of some of the decomposition reactions are described. The values were determined by the Coats-Redfern and Freeman-Carroll methods. Structural data on the isolated intermediates were obtained by infrared spectroscopy and magnetic susceptibility measurements.

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Zusammenfassung Die thermische Behandlung der PentafluorphenylderivateM(C₆F₅)₂Dx_n [M=Pd (n=2, 3) oder Pt (n=2); Dx=Dioxan] führt zu der Bildung der neuen DioxanaddukteM(C₆F₅)₂Dx (M=Pd, Pt) und Pt(C₆F₅)₂Dx_1.5. Die Berechnungen der Reaktionsordnung und der Aktivierungsenergie einiger Zersetzungsreaktionen werden beschrieben. Die Werte wurden durch die Methoden von Coats-Redfern und Freeman-Carroll bestimmt. Die Strukturangaben der isolierten Zwischenprodukte wurden durch Infrarotspektroskopie und Messung der magnetischen Suszeptibilität erhalten.

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(₆F₅)₂, M=Pd n=2, 3 Pt _n=2, - , -M(C₆F₅)₂ (=Pd, Pt) (₆F₅)_21,5. , — —. .

     

Kinetics of chlorine isotope exchange reaction between sodium chloride-36 and triphenyltin chloride in mixed solvents

Isotope exchange reaction between NaCl-36 and triphenyltin chloride in dioxane-water (8020% w/w) and ethanol-water (9010% w/w) mixed solvents has been studied at 25, 35 and 50 °C. The exchange reaction was found to proceed via a bimolecular S_N2, limiting mechanism with reaction rates depending on the solvent used. Inhibition of the exchange in ethanol-water is probably due to solvation of chloride ion through hydrogen bond formation. The rate laws for the exchange reactions are: R_e=3.24×10⁹ e^–65550/RT [Rh₃SnCl] [NaCl] in dioxanewater and R_e=6.61×10⁸ e^–69600/RT [Ph₃SnCl] [NaCl] in ethanol-water, where is the degree of dissociation of NaCl and R_e is the rate of exchange in mol l^–1 s^–1. The activation parameters H^*, S^* and G^* are reported.     

Universal system for liquid stationary phase classification on the basis of thermodynamical data

Summary Equations modifying Rohrschneider's relationship between I and thermodynamical characteristics values are derived. Polarity in chromatography is discussed as a possibility of stationary phases or absorbents to enter into intermolecular interactions and is determined on the basis of the partial molar free energies of solution (G) of six test substances. A simple method for the calculation of stationary phase polarity in terms of G from retention indices and McReynolds constants is given. Equations are presented for the calculation of stationary phase selectivity utilizing G data tabulated for selected test substances. The thermodynamical basis of selecting a reference phase for a unified system expressing the selectivity of stationary phases which can also be applied for adsorbents is suggested. The energy equivalent to an index unit, G_i.u., is discussed.     

Relative enthalpies and related thermodynamic functions of some organic compounds by drop calorimetry

The values of thermodynamic functions of the following eight organic compounds under non-reacting conditions within the temperature range 298.15 – 550 K are given: N,N dimethylformamide, CHO · N(CH₃)₂; 4-nitro-1-chlorobenzene, Cl · C₆H₄ · NO₂; sodiump-nitrophenoxide, NO₂ · C₆H₄ · ONa; 1-methyl-2-pyrrolidone, 4,4-dinitrodiphenyl ether, (NO₂ · C₆H₄)₂O; 4,4-diaminodiphenyl ether, (NH₂ · C₆H₄)₂O; bis-(4-aminophenyl)methane, (NH₂ · C₆H₄)₂CH₂; bis(4-maleic acidimidphenyl)methane, The relative enthalpy was obtained from calorimetric data by drop calorimetry. The heat capacity and relative entropy are functions derived from the foregoing. The equations of the temperature variation of the relative enthalphy were obtained by computer processing of the calorimetric data by the least squares method. The parameters of solid-liquid transitions were determined from the discontinuity of the temperature variation of the relative enthalpy.

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Zusamenfassung Die Werte der thermodynamischen Funktionen folgender 8 organischer Verbindungen werden unter nicht-reagierenden Bedingungen im Temperaturbereich von 298.15 bis 550 K angegeben: Dimethylformamid, CHO · N(CH₃)₂;p-Nitrochlorbenzol, Cl · C₆H₄NO₂; Natrium-p-Nitrophenoxid, NO₂ · C₆H₄ONa; N-Methylpyrrolidon, 4-4-Dinitrodiphenyläther, (NO₂ · C₆H₄)₂O; 4-4-Diaminodiphenyläther, (NH₂C₆H₄)₂O; 4-- 4-Diaminodiphenylmethan, (NH₂ · C₆H₄)₂CH₂; 4-4-bis-Maleinimid-Diphenylmethan, Die relative Enthalpie wird aus kalorimetrischen Daten der Temperaturgefällekalorimetrie erhalten. Die Wärmekapazität und die relative Entropie sind Funktionen der erwähnten Werte. Die Gleichungen der Temperaturänderung der relativen Enthalpie wurden mittels Computerverarbeitung der kalorimetrischen Daten, mit der Methode der kleinsten Quadrate erhalten. Die Parameter der fest-flüssig Übergänge wurden an Hand der Diskontinuität der Temperaturänderung der relativen Enthalpie bestimmt.

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Résumé On donne les valeurs des fonctions thermodynamiques des 8 composés organiques suivants, en conditions non réactionnelles, dans l'intervalle de températures 298.15–550 K: diméthylformamide CHO · N(CH₃)₂,p-nitrochlorobenzène Cl · C₆H₄ · NO₂,p-nitrophé noxysodium NO₂ · C₆H₄ · ONa, N-méthylpyrrolidone dinitrodiphényl-4,4 éther (NO₂ · C₆H₄)₂O, diaminodiphényl-4,4 méthane (NH₂ ·H ₄CH₂, 4-4 bis maléinimide diphénylméthane L'enthalpie relative a été obtenue à partir de données calorimétriques fournies par un calorimètre à chute. La chaleur spécifique et l'entropie relative sont des fonction dérivées de la précédente. Les équations donnant la variation de l'enthalpie relative en fonction de la température sont obtenues par traitement des données calorimétriques sur ordinateur par la méthode des moindres carrés. Les paramètres des transitions solide-liquide ont été déterminés à partir de la discontinuité de la variation de l'enthalpie relative avec la température.

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, 298,15–550 , : — · N(CH₃)₂;- — l · ₆₄ · NO₂.- -NO₂·₆₄·ONa; N-—₃·N··₂·₂₂; 4,4- — (NO₂·₆₄)₂; 4,4- — (NH₂·₆₄)₂; 4,4- — (NH₂·₆₄)₂₂; 4,4-- —(₆₄.N. . :. )₂₂. . , . . - .

     

Thermal analyses of aerosols

Thermal analysis as an analytical tool has been applied to the study of suspended liquid and solid matter in air. The aerosol is heated in a glass pipe, and the light scattering coefficient is used for thein situ detection of aerosol. Results of thermal analysis of the Los Angeles smog, and of St. Louis aerosol on dry and humid days, are presented, all indicating distinctly different thermo-nephelograms. On polluted days in St. Louis, over 50% of the light scattering coefficient is lost at about 100, which indicates the presence of H₂SO₄.

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Zusammenfassung Die Thermoanalyse wurde als analytische Methode zur Untersuchung von in Luft suspendierten flüssigen und festen Substanzen eingesetzt. Das Aerosol wird in einem Glasrohr beheizt und Lichtstreuungskoeffizient zumin situ Nachweis des Aerosols verwendet. Die Ergebnisse der Thermoanalyse von Smog aus Los Angeles und von Aerosol aus St. Louis an trockenen und feuchten Tagen werden bekanntgegeben; diese zeigen deutlich verschiedene Thermonephelogramme. An Tagen bei besonders starker Verschmutzung in St. Louis, gehen mehr als 50% des Lichtstreuungskoeffizienten bei etwa 100 verloren, was auf Gegenwart von H₂SO₄ zurückzuführen ist.

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Résumé Application de l'analyse thermique comme moyen d'analyse des matériaux liquides et solides en suspension dans l'air. L'aérosol est chauffé dans un tube de verre et le coefficient de diffusion de la lumière est utilisé pour analyserin situ l'aérosol. Les résultats de l'analyse du brouillard de Los Angeles et de l'aérosol de St. Louis par temps sec et humide sont présentés, indiquant tous des néphélogrammes thermiques différents. Les cas de pollution à St. Louis se traduisent par une déperdition du coefficient de diffusion de la lumière de plus de 50% à 100 environ, ce qui indique la présence de H₂SO₄.

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, , . , . - - , . - , 50% 100C, .

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This research was supported by the U.S. Environmental Protection Agency, National Environmental Research Center, Atmospheric Aerosol Research Section, Research Triangle Park, N.C.     

Thermochemical data of barium peroxide from thermogravimetric measurements

Decomposition temperatures of barium peroxide in equilibrium with the oxygen pressure in the gas phase have been determined by thermogravimetric measurements at temperatures from 670 to 843. Enthalpies and entropies of the reaction BaO₂= =BaO+0.5O₂ and of the formation of BaO₂ have been calculated.

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Zusammenfassung Zersetzungstemperaturen von mit dem Sauerstoffdruck in der Gasphase in Gleichgewicht stehendem Bariumperoxyd wurden thermogravimetrisch im Temperaturbereich von 670 bis zu 843 ermittelt. Enthalpie- und Entropiewerte der Reaktion BaO₂= =BaO+0.5 O₂ und der Bildung von BaO₂ wurden errechnet.

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Résumé On a déterminé les températures de décomposition du peroxyde de baryum en équilibre avec la pression d'oxygène de la phase gazeuse, par mesures thermogravimétriques entre 670 et 843. On a calculé les enthalpies et les entropies correspondant à la réaction BaO₂=BaO+0.5 O₂ et à la formation de BaO₂.

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, , , 670 843. BaO₂= + +0.5 O₂ BaO₂.

     

Simultaneous measurement of thermal properties in ferroelectric crystals

Simultaneous measurement of the influence of the electric field on specific heat, thermal conductivity and pyroelectric coefficient is described as a summary of previous papers. From these coefficients, which are determined by means of a flux calorimeter, the behaviour of other properties, such as thermal diffusivity and electrocaloric coefficient, is deduced.The data are compared with the findings obtained by other authors with traditional methods.

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Zusammenfassung In Zusammenfassung vorhergehender Arbeiten wurde die simultane Messung des Einflusses von elektrischen Feldern auf spezifische Wärme, Wärmeleitfähigkeit und pyroelektrischen Koeffizienten beschrieben. Auf Grundlage dieser Konstanten, die mittels eines Fluxkalorimeters bestimmt wurden, konnte das Verhalten anderer Eigenschaften wie z. B. thermische Diffusionskonstante und elektrokalorischer Koeffizient abgeleitet werden. Die Daten wurden mit durch herkömmliche Methoden erhaltenen Ergebnissen anderer Autoren verglichen.

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, . , , , . , .

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This work has been supported by the Spanish C.A.I.C. y T.     

Application of solvent extraction and synchronous spectrofluorimetry to the determination of the formation constant for a 1:1 complex of carbazole withβ-cyclodextrin in water-dimethyl sulfoxide medium

Extraction of carbazole in heptane was performed at 25±1°C with an aqueous dimethyl sulfoxide (DMSO) medium containing -cyclodextrin (CD) at consecutive concentrations in the range of 0–10 mM. The fluorescence intensity of carbazole remaining in the heptane phase was measured by synchronous scanning fluorimetry. The apparent formation constant (K _f) for a 1:1 carbazole: CD inclusion complex in water-DMSO medium was determined by using a linear plot of the distribution ratio calculated from the fluorescence intensities vs. the -CD concentration. The values thus obtained ranged from 477 M^–1 in a 10% v/v DMSO medium to 12.1 M^–1 in a 60% v/v medium. Good linear relationships were observed between logK _f and the DMSO concentration ([DMSO]), and also between logK _f and the logarithm of the distribution coefficient (K _d) for carbazole. The formation constant in 100% water was estimated to be approximately 1.0×10³ M^–1 on the basis of the logK _f vs. [DMSO] and the logK _f vs. logK _d correlations.     

Preparation-Proprietes physico-chimiques enthalpie de formation de l'hydrure d'aluminium AlH3α′

Résumé L'hydrure d'aluminium AlH₃- a été obtenu par action de LiAlH₄ sur AlCl₃ ou ZnCl₂ dans l'éther éthylique. La décomposition thermique a été étudiée par thermogravimé trie sous pression réduite (10^–2 torr). La capacité calorifique molaire à 298 K, l'enthalpie de décomposition, ainsi que l'enthalpie de formation ont été déterminées avec un microcalorimètre Calvet.

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Aluminium hydride,-AlH₃, was prepared by reaction of LiAlH₄ on A1C1₃ or ZnCl₂ in diethyl ether. Thermogravimetry was used to investigate its thermal decomposition under low pressure (10^–2 torr). The molar heat capacity at 298 K, the heat of decomposition, and the heat of formation, were measured with a Calvet microcalorimeter.

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Zusammenfassung Aluminiumhydrid AlH₃- wurde durch Einwirkung von LiAlH₄ auf AlCl₃ oder ZnCl₂ in DiÄthylether hergestellt. Die Thermo gravimetrie wurde zur Untersuchung der thermischen Zersetzung bei niedrigem Druck (10^–2 torr) herangezogen. Die molare WÄrmekapazitÄt bei 298 K, die Zersetzungsenthalpie sowie die Bildungsenthalpie wurden mit einem Calvet-Mikrokalorimeter bestimmt.

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— - l₃ LiAlH₄ ll₃ ZnCl₂ . (10^–2 ) . 298 , .

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Ce travail a été effectué dans le cadre d'un contrat de recherches passé par le laboratoire de Thermochimie Minérale avec la Direction des Recherches et Moyen d'Essai. Nous remercions bien vivement cet organisme de l'aide qu'il nous a apportée.     

NMR studies of the interaction between tris-acetylacetonates of Fe(III), Cr(III) and diethyldichloride of Sn (IV)

Paramagnetic relaxation rate of CH₂ protons has been found to be higher than that of CH₃ protons of SnEt₂Cl₂ in the presence of tris-acetylacetonate of Cr(III) in chloroform at 298 K, which supports the specific interactions between these compounds. The revealed ligand exchange between Cr(AA)₃, Fe(AA)₃ and SnEt₂Cl₂ takes place with the equilibrium shifted to the side of initial reactants.

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, -CH₂ CH₃- SnEt₂Cl₂ - Cr(III) 298 K, . Cr(AA)₃, Fe(AA)₃ SnEt₂Cl₂, .

     

Spectral properties and temperature-dependence of semiconductivity of various doped bismuth trioxide polycrystals

Several samples of Nb₂O₅-doped Bi₂O₃ and Y₂O₃-doped Bi₂O₃ were carefully prepared and sintered at 700° for 3 hours. Extensive measurements were carried out on these samples, including X-ray diffraction spectra, infrared absorption spectra and the temperature-dependence of the DC-electrical conductivity in the solid state. The results obtained were discussed, correlated and interpreted. Finally, the optimum compositions were established and recommended for doped-Bi₂O₃ in the electronics industry.

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Zusammenfassung Einige Proben von mit Nb₂O₅ und Y₂O₃ gedopten Bi₂O₃ wurden hergestellt und bei 700 °C 3 Stunden gesintert. Von den Proben wurden Röntgendiffraktogramme und IR-Absorptionsspektren aufgenommen und die Temperaturabhängigkeit der elektrischen Gleichstromleitfähigkeit im festen Zustand gemessen. Die erhaltenen Ergebnisse werden diskutiert, zueinander in Beziehung gesetzt und interpretiert. Optimale Zusammensetzungen werden ermittelt und für gedoptes Bi₂O₃ in der Elektronikindustrie empfohlen.

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Bi₂O₃, Nb₂O₅ Y₂O₃, 3 700°. , . . , .

     

Kinetic isotope effect in proton exchange processes between methanol and water in inert solvents

The kinetic isotope effect in proton exchange between methanol and water in CCl₄ solution was studied by¹H and²H NMR and kinetic IR spectroscopy. The exchange rate increases in the series CD₃OH+H₂O3OD+H₂O3OD+D₂O. It has been concluded that the limiting step of the reaction involves the formation of an H-bonded cyclic intermediate.

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¹H ²H - CCl₄. , CD₃OH+H₂O3OD+H₂O3OD+D₂O. , - -.