1-H and 14-N NMR relaxation studies on solutions of Mn(ClO4)2 in acetonitrile

Proton spin-lattice and spin-spin relaxation times of acetonitrile solutions of Mn(ClO₄)₂ between 298°KT413°K have been measured over a wide frequency range (10 kHzv90 MHz). From these data and corresponding 14-N NMR line width measurements of acetonitrile at varying temperatures, it is possible to extract structural and dynamical parameters such as the number of complexed acetonitrile molecules, their mean lifetime in the first solvation sphere of the manganese ions, and the rotational diffusion constant of the [Mn(CH₃CN)₆]²⁺ complex.     

Micellar Effects of Cationic Detergents in the Decomposition of Ecotoxic Substrates by Hydroxide Ion

The rate of decomposition of 4-nitrophenyl esters of diethylphosphoric, diethylphosphonic, and 4-toluenesulfonic acids, which are ecotoxicants, by hydroxide ion is enhanced by micelles of cationic detergents. The effect of concentrating the reagents provides for decomposition of the neurotoxins in aqueous micellar media with _1/2 60 s.     

Vapor pressures of non-aqueous electrolyte solutions. Part 1. Alkali metal salts in methanol

Precise vapor pressure data for solutions of NaCl, NaBr, NaI, NaClO₄, KBr, KI, RbI, and CsI in methanol at 25°C in the concentration range 0.02m (mol-kg^–1)0.7 are communicated and discussed. Measurements were carried out by procedures and equipment known to produce data of high precision. Polynomials of fourth degree in molalities are given for the vapor pressure of methanol solutions which can be used for calculating precise reference values as needed in indirect methods. Osmotic coefficients were calculated by taking into account the second virial coefficient of methanol vapor. Discussion of the data is based on the chemical model of electrolyte solutions taking into account short range interactions. Ion-pair association constants are compared to those of conductance measurements.     

The Interaction of O2, NO,and N2O with Surface Defects of Dispersed Titanium Dioxide

A combined study of intrinsic structural defects in reduced TiO₂ was performed using mass spectrometry, optical diffuse-reflectance spectroscopy, and UV photoelectron spectroscopy (UPS). It was found that the reduction of TiO₂ resulted in the appearance of absorption in the region 0.50 h 3.50 eV (400 2500 nm), which is formed by absorption due to free electrons (a continuum at h 1.50 eV), local centers—Ti³⁺ ions (a band at 2.00 eV), and oxygen vacancies (bands at 1.17, 2.81, and 2.55 eV). The spectrum of induced occupied electronic states in the forbidden gap and the position of oxygen vacancy levels with respect to the Fermi level were determined by UPS. The absorption of reduced TiO₂ was stable on the sample to T = 800 K in a vacuum; however, it weakened in contact with O₂, NO, and N₂O molecules beginning at T = 300 K (surface sites) and T 400 K (subsurface sites) as a result of filling oxygen vacancies with atomic oxygen in the course of dissociative adsorption. The adsorption complexes formed by the interaction of O₂, NO, and N₂O with defects were analyzed by temperature-programmed desorption. The distribution of sites over the energies of oxygen binding was found with the use of a nonuniform surface model, and specific oxygen adsorption species were revealed. It was found that the irradiation of TiO₂ activates the formation and decay of sites and results in the formation of specific O₂ and N₂O adsorption species.     

Phase Equilibria in the System CuO-Fe2O3-Sb2O4-O2

Results of X-ray phase analysis were used to construct the phase diagram of the system CuO-Fe₂O₃-Sb₂O₄-O₂ at 1000°C in air. Two Cu_2x Fe_4-3x Sb _x O₆ solid solutions (0 x 0.154 and 0.923 x 1) of, respectively, hematite and bixbyite structure were identified.     

Ionic Strength Dependence of Formation Constants and Complexation of Glutamine with Dioxovanadium(V)

The dependence of L-glutamine protonation and its complexation with dioxovanadium(V) on ionic strength (I) is reported in sodium perchlorate solution as a background salt. The measurements have been performed at 25 ± 0.1°C and various ionic strengths in the range 0.1 to 1.0 mol/l, using a combination of potentiometric and spectrophotometric techniques. The overall analysis of the present and the previous data dealing with the determination of stability constants at different ionic strengths allowed us to obtain a general equation, by which a formation constant determined at a fixed ionic strength can be calculated, with a good approximation, at another ionic strength, if 0.1 I 1.0 mol/l (NaClO₄).     

Metallreiche Phasen im ternären System Ni-Se-Te

Zusammenfassung Die metallreichen Phasen im System Ni-Se-Te wurden durch Röntgenaufnahmen bei Zimmertemp. und bei höheren Temperaturen sowie durchDTA untersucht. Bei Zimmertemp. wurden im pseudo-binären Schnitt Ni₃(Se_1-x , Te _x )₂ Phasen mit den folgenden Strukturen gefunden: rhomboedrischer Ni₃S₂-Typ fürx=0; tetragonaler (Ni,Fe)₁₁Se₈-Typ für 0,15x0,35; tetragonaler Rickardit-Typ für 0,50x0,80; Überstrukturen des Rickardit-Typs für 0,95x1. Bei höheren Temperaturen verbreitert sich das Homogenitätsgebiet der Phase mit der tetragonalen Rickardit-Struktur. Über 600–770°C tritt im ganzen Gebiet 0x1 eine kubisch.

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Metal-rich phases in the ternary system Ni-Se-Te

The metal-rich phases in the system Ni-Se-Te have been studied by X-ray diffraction at room temperature and elevated temperatures, and byDTA. At room temperature phases with the following structures were found in the pseudo-binary section Ni₃(Se_1-x , Te _x )₂: rhombohedral Ni₃S₂ type forx=0; tetragonal (Ni,Fe)₁₁Se₈ type for 0,15x0,35; tetragonal rickardite type for 0,50x0,80; superstructures of the rickardite type for 0,95x1. At higher temperatures the homogeneity range of the phase with the tetragonal rickardite structure broadens. Above 600–770°C a face-centered cubic phase exists in the whole range 0x1; a model for the structure of this phase is proposed. The compound Ni_2,6Te₂ is orthorhombic at room temperature; it becomes hexagonal at 720°C and disproportionates at 820°C; by partial substitution of Te by Se the hexagonal form is stabilized at room temperature. Similarly, the compound Ni₆Se₅ which is stable above 440°C only, is stabilized at room temperature by partial substitution of Se by Te. The phase Ni₆(Se_1-x , Te _x )₅ decomposes by a peritectoid reaction at 650° (x=0) to 590°C (x=0,3).

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Herrn Prof. Dr.H. Nowotny gewidmet.     

Transference Numbers of NaCl in Aqueous Mixtures with Organic Solvents of Moderate to Low Permittivities

Electromotive forces (emf) were measured in the transference cells: AgAgCl- Nacl (m₂) in Z NaCl (m₁) in ZAgClAg and Na_xHg_1-xNaCl (m₁) in Z NaCl (m₂) in ZNa_xHg_1-x (where Na_xHg_1-x denotes a flowing Na–amalgam electrode and Z an aqueous-organic solvent mixture) at various molalities m ₂ > m₁ of NaCl in Z = (ethylene glycol + water), (acetonitrile + water) and (1,4-dioxane + water), with mass fractions of the organic components 0.8. The transference number of Na⁺ in (ethylene glycol + water) and (1,4-dioxane + water) varies little with respect to that in pure water medium, whereas in (acetonitrile + water) it increases remarkably with increasing proportion of acetonitrile so as to approach equitransference, behavior similar to that previously found in (methanol + water) and in (ethanol + water). At acetonitrile mass fraction 0.6 NaCl is sufficiently close to equitransference to emerge as a useful salt bridge, nearly at the same level as the popular aqueous KCl.     

Measurements of relative thick target yields for PIGE analysis on light elements in the proton energy interval 2.4–4.2 MeV

In order to extend the energy range of the systematic investigation on relative thick target yields performed by ANTTILA et al² for 1E_p2.4 MeV bombarding energies, gamma spectra and yield data are presented for elements Z=3–9, 11–17, 19–21 in the energy range 2.4E_p4.2 MeV and the results are discussed from the point of view of PIGE analysis.     

Hydrophile-lipophile balance of alkyl ethoxylated surfactants as a function of intermolecular energies

Summary The semiempirical MNDO method has been used in order to examine the variation of the molecular properties of hydrocarbons C_nH_2n+2 (with 1n19) and ethylene oxide chains CH₃(CH₂CH₂O)_mCH₃ (with 1m19) as a function of their molecular length. Least-square fits of those properties have been calculated, along with two mathematical relations between the hydrophile-lipophile balance of alkyl-phenol ethoxylated surfactants and (1) the ratio of molecular lengths between their lipophilic and hydrophilic branches; (2) the intermolecular energies between the molecules of surfactant, water and hexane.     

Electrolyte mixing thermodynamics to probe ion-ion interactions

In their study of solvent-averaged ion-ion pair potentials, Pettitt and Rossky show that, at least for the given underlying Born-Oppenheimer level model, there is a remarkable well in the potential of the solventaveraged Cl^––Cl^– interaction in water; it has a minimum below-kT and near 3.6Å, the Pauling diameter for the Cl^– ion. As Pettitt and Rossky also showed, the osmotic coefficient of aqueus NaCl solution as a function of ionic strength (I) could be insensitive to this remarkable feature, even when the well implies that there is a substantial concentration of dimers at 1M or higher stoichiometric concentration. Here it is argued that the thermodynamics of mixtures of aqueous NaCl with, say, aqueous NaClO₄, should be sensitive to the presence of the well in the Cl^––Cl^– interaction. Accordingly we apply the HNC approximation to calculate the mixing coefficients that characterize the excess free energy functions of several model aqueous NaCl–NaClO₄ mixed electrolyte solutions. For reference we use a model (V₆) in which all six ion-ion pair potentials have the simple vanilla form: charged soft spheres supplemented by a dielectric image correction and an adjustable Gurney term that represents an interaction of the solvation structures about the ions. The six Gurney coefficients were adjusted to tune the model (I) close to the experimental for pure NaCl, pure NaClO₄, and an equimolar mixture, all in the range 0.1I2M. We find that the V₆ model gives mixing coefficients that agree closely with experiment. The calculations were also made for five models that incorporate, in varying degrees, the Pettitt-Rossky pair potentials. Comparison of the mixing coefficients for these models with the experimental data leads to the conclusion that the Cl^–, Cl^– well is unrealistic, although a shallower well in the same place might be acceptable.     

Salt effects on the protonation of ortho-phosphate between 10 and 50°C in aqueous solution. A complex formation model

Protonation constants of o-phosphate were studied potentiometrically, using the (H⁺)-glass electrode in aqueous NaCl, KCl and tetraethylammonium iodide solutions, at 0IIM and 10T50°C. The differences found in the protonation constants for different salt solutions are explained by a complex formation model. The formation of the species MPO ₄ ^2– , MHPO ₄ ^– , MH₂PO ₄ ⁰ , M₂PO ₄ ^– and M₂HPO ₄ ⁰ (M=Na⁺, K⁺) is hypothesized. In mixed NaCl-KCl solutions, it is possible to find the mixed metal species NaKPO ₄ ^– and NaKHPO ₄ ⁰ . Ionic strength and temperature dependence parameters are reported for all species. The relevance of Na⁺ and K⁺ complexes is discussed in connection with speciation problems of natural fluids, such as marine water and urine.     

Some remarks on the solubility of gases in liquid long-chainn-alkanes andn-alkan-1-ols

The Ostwald coefficients L_2,1 of He, Ne, Ar, Kr, Xe, N₂, O₂, CH₄ CF₄ and SF₆ dissolved in several homologous_n-alkanes,_n-C₁H₂₁₊₂, 6l16, andn-alkan-1-ols,n-C₁H₂₁₊₁OH, 1l11, were recently measured at 298.15 K and atmospheric pressure with a modified Ben-Naim/Baer apparatus. Altogether, 201 gas/liquid systems were investigated. For about half of these systems, both pressure control and measurement of the volume of gas dissolved in a given volume of solvent were achieved with a microprocessor. This improved medium-precision instrument (0.5% in most cases) combines easy handling with fully automated data retrieval, and is totallymercury-free. In this communication, the salient points of data reduction are presented, with the focus on the estimation of several important auxiliary quantities such as second virial coefficients and partial molar volumes at infinite dilution. The effect of the chain lengthl of then-alkane or then-alkan-1-ol upon solubility is demonstrated, and some correlations betweenL _2,1, or the derived Henry fugacitiesH _2,1, and appropriate molecular and/or bulk properties of the gases and the solvents are discussed.     

Kinematic Viscosities of Binary Liquid Mixtures of 2-Butanone with 1,2-Propanediol

Kinematic viscosities of the binary 2-butanone (1) + 1,2-propanediol (2) solvent system have been measured for mixtures covering the whole miscibility range expressed by 0 x _i 1, at 19 temperatures in the range –10 t/°C 80. The measured values have been used to test empirical equations that express the kinematic viscosities as functions of the composition and temperature. Excess kinematic viscosities (^E) have also been calculated. Sign and magnitude of these quantities are discussed in terms of type and nature of specific intermolecular interactions. Furthermore, derived quantities such as thermodynamic parameters of viscous flow (G, H and S), are analyzed on the basis of Eyring's model. All the investigated excess mixing properties indicate the probable existence of stable two-component adducts in this binary solvent system.     

Interaction of Dioxovanadium(V) with Alanine, Alanylalanine, and Alanylglycine

The stability constants of the systems dioxovanadium(V) with alanylalanine, alanylglycine, and alanine have been determined in aqueous solution in 0.8 pH 5 at 25°C and 0.1 mol-dm^–3 (NaClO₄), using a combination of potentiometric and spectrophotometric techniques. The compositions of the formed complexes were determined and it was shown that dioxovanadium(V) forms two mononuclear 1:1 and 1:2 species with alanine of the type VO₂L and VO₂L₂ ^–, and two mononuclear 1:1 complexes with alanylpeptides of the type VO₂HL and VO₂L^–.     

1A1⇔5T2 Spin Transition in Heterometallic Solid Phases FexNi1-x(Htrz)3(NO3)2 · H2O (Htrz = 1,2,4‐Triazole)

Solid phases Fe_xNi_1-x(Htrz)₃(NO₃)₂ · H₂O (0.4 x 0.8$) and Ni(Htrz)₃(NO₃)₂ · H₂O were synthesized and studied. The phases were studied by means of magnetochemistry, powder Xray difraction analysis, and electronic and IR spectroscopy. The heterometallic phases are described by the stoichiographic method of differentiating dissolution (DD). The values of x were determined by two methods — atomic absorption and DD. Magnetochemical data showed that the solid phases exhibit a hightemperature ¹A₁ ⁵T₂ 0.5 x 0.8 and disappears at x = 0.4. The spin transition is accompanied by thermochromism (color changed from pink to white at 0.6 x 1 and from pink to light lilac at x = 0.5). A decrease in x leads to a decrease in the temperature of the forward (under heating T_c ) and reverse (under cooling T_c ) transitions, a decrease in hysteresis value ( T_c), and a smearing of the spin transition.     

Lattice Relaxation Effect on the Electronic Structure of Helium Solutions in Calcium Fluoride Crystals

The discrete variation (DV) and molecular static methods are used to study the effects of atomic displacements near the anion vacancies and He impurity centers in the interstitial and vacancy positions on the electronic structure of CaF₂. Lattice ion displacements near the helium atom were estimated at 1% lattice constant in the former case and 4% in the latter. This leads to decreased splitting between the occupied and vacant impurity levels in the presence of isolated defects and to increased splitting for interacting defects. Effective charges are less sensitive to lattice relaxation than the electronic energy spectrum, except the case of high defect concentration.     

Proton induced X-ray emission (PIXE) analysis on thick samples exemplified on the rare earth elements

Summary Proton Induced X-ray Emission (PIXE) analysis calibration curves (i.e. intensity of analytical signal as a function of concentration c _i ) are determined on thick solid samples with rare earth element concentrations c _i 0.3g/g. The calibration curves are linear at low concentrations c _i 0.3 weight% at proton energies 1.7E _PO 2.5MeV. The precision of the quantitative analysis amounts to ±4 %. The shape of the curves at higher concentrations may be understood by simple qualitative considerations.Distortions by interelement-effects caused by additional other rare earth elements j in concentrations c _j 2 weight% are not detectable. The agreement between the experimental and the calculated intensities for different matrices is very good at low concentrations c _i 1 weight% of analyte.

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Protoneninduzierte Röntgenspektralanalyse (PIXE) dicker Proben am Beispiel der Seltenen ErdelementeI. Experimentelle Bestimmung von Eichkurven, Genauigkeit und Matrixeffekten

Zusammenfassung Es werden Eichkurven (d. h. Intensität des Analysensignals in Abhängigkeit von der Analytkonzentration c _i ) für die protoneninduzierte Röntgenspektralanalyse (PIXE) dicker Festkörperproben mit Seltenen Erdelementen im Konzentrationsbereich c _i 0,3g/g aufgenommen. Diese Eichkurven verlaufen bei niedrigen Konzentrationen c _i 0,3 Gewichts-% und Protonenenergien 1,7E_PO2,5MeV linear. Die Genauigkeit der quantitativen Analyse beträgt ±4 %. Der Verlauf der Eichkurven bei höheren Konzentrationen kann durch einfache qualitative Überlegungen verstanden werden.Es werden keine Störungen durch Interelementeffekte beobachtet, die durch zusätzliche andere Seltene Erdelemente j in Konzentrationen c _j 2 Gewichts-% hervorgerufen werden. Die Übereinstimmung der experimentellen und berechneten Intensitäten für verschiedene Matrices ist bei niedrigen Analytkonzentrationen c _i 1 Gewichts-% sehr gut.

Dedicated to Karl Gleu at the occasion of his 80th birthday     

Volumetric properties of H2O, D2O, and methanol in acetonitrile at 278.15—318.15 K

The densities of H₂O, D₂O, and MeOH solutions in acetonitrile with the solute concentrations up to 0.07 molar fractions at 278.15, 288.15, 298.15, 308.15, and 318.15 K were measured using vibrating-tube densimetry with an error 8·10^–6 g cm^–3. The limiting partial molar volumes for the H/D isotopomers of water and IaII in acetonitrile (V^– ₂ ) and the isotope effects in V^– ₂ and in excess molar volumes of acetonitrile—water mixtures were calculated. Molecules of H₂O, D₂O, and IaII form associates with acetonitrile molecules via hydrogen bonds. The associates have the packing volumes close to those in the individual solute. The water and methanol molecules were assumed to be incorporated into the acetonitrile structure without substantial changes in the latter. However, this process results in some compression of the system with a simultaneous increase in its expansibility.     

Cobalt(III) dicarboxylato bis-ethylenediamine nitrates: Preparation and characterization by thermal analysis and other analytical methods

Compounds with the general formulacis ortrans-[Coen ₂ (RCOO)₂]NO₃ were prepared by modifications of known procedures; R was H, CH₃, C₂H₅ or C₃H₇, anden was ethylenediamine. The compounds were characterized by TLC and UV-Vis spectrophotometry, and their thermal behaviour was examined via TG and DTA, and via IR spectra on heated samples.The thermal stabilities are discussed in terms of the strengths of the bonds in the solids [1] and steric hindrance; the thermal decompositions are described with the aid of hypothesized intermediates and IR spectra.Reaction steps are identified and the thermal stability sequence is discussed: thecis compounds are less stable than the correspondingtrans compounds, due to the lower reticulation effect; the sequence of thecis compounds is the reverse of the sequence of carboxylate ion basicity, while the sequence displalyed by thetrans compounds can be interpreted in terms of solid lattice stabilization.

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Zusammenfassung Unter Durchführung einiger Abänderungen des bekannten Verfahrens wurden Verbindungen der allgemeinen Formel conf-Co[en₂(RCOO)₂]NO₃ hergestellt. Der AlkylrestR war H, CH₃, C₂H₅, C₃H₇ unden war Ethylendiamin. Die Verbidungen mitconf=cis odertrans wurden mittels TLC und UV-Spektrophotometrie charakterisiert. Ihr thermisches Verhalten wurdeanhand von TG, DTA und IR-Spektren von erhitzten Proben untersucht. Die thermische Stabilität wurde untersucht und in Abhängigkeit von Bindungsstärke und sterischer Behinderung diskutirt; weiterhin wurden die thermischen Zersetzungen mit Hilfe angenommener Intermediäre und deren IR-Spektren beschrieben. Die Reaktionsschritte wurden identifiziert und eine Stabilitätsreihe aufgestellt und diskutiert: cis-Verbindungen erwiesen sich als instabiler als die entsprechenden trans-Verbindungen, was einem geringeren Vernetzungseffekt zuzuschreiben ist; Die Reihenfolge folgt im Falle voncis dem Reziproken der Carboxylationenbasizität, während die Reihenfolge im Falle vontrans mittels der Gitterstabilisierung erklärt werden kann.

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, -[Coen₂(RCOO)₂]NO₃, R=H, CH₃, C₂H₅, C₃H₇, aen= . - - - . , . . , . : - , , . - -, - .

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This work was carried out with the financial support of the Consiglio Nazionale delle Ricerche (C.N.R.), which also gave a grant to one of us (A.M.G.).