Hydrolysis of Protactinium(V). III. Determination of Standard Thermodynamic Data

Hydrolysis constants of protactinium(V) at tracer scale were deduced from the variations of partition coefficient of Pa(V) in the system: TTA/toluene/Pa(V)/H₂O/H⁺/Na⁺/ClO^– ₄, as a function of TTA and proton concentrations, ionic strength (0.1 3 M), and temperature (10 60°C). Extrapolations of theses constants to zero ionic strength were performed using the SIT model. Standard thermodynamic data (under atmospheric pressure) related to the two hydrolysis equilibria involved, were derived from the temperature dependence of the hydrolysis constants at infinite dilution.     

A density-functional calculation of dynamic dipole polarizabilities of noble gas atoms

Using a very simple trial function and unperturbed electron densities calculated by a new procedure, the frequency-dependent dipole polarizability () of Ne, Ar, Kr and Xe has been calculated in the range 0 0.45 a.u., by a Karplus-Kolker-type variation-perturbation method. Results progressively worsen for larger systems so that, for Xe, (0) is only 75% of the experimental value. Probable reasons for this are discussed.     

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.     

Dissociation equilibrium between uncharged and charged local anesthetic lidocaine in a surface-adsorbed film

The dissociation equilibrium between uncharged local anesthetic lidocaine (LC) and charged local anesthetic LC (LCH⁺) in a surface-adsorbed film was investigated by measuring the surface tension and pH of aqueous solutions of a mixture of hydrochloric acid and LC. The surface tension values decreased slightly with increasing total molality m_t at 0X₂0.5, where X₂ is the mole fraction of LC in the mixture, while they decreased rapidly with increasing m_t at 0.5<X₂1. It was shown from the pH measurements that almost all LC molecules were changed into LCH⁺ ions by protonation at 0X₂0.5 and both forms coexisted only at 0.5<X₂1. The quantities of the respective LC and LCH⁺ transferred from the aqueous solution to the adsorbed film, i.e., their surface densities, were calculated by applying the thermodynamic equations derived to the surface tension and pH data. A greater quantity of LC than LCH⁺ existed in the adsorbed film at the coexisting composition. The partitioning behavior of LC and LCH⁺ in the adsorbed film was characterized by three composition regions: (1) slight partitioning of low surface-active LCH⁺ in the region at 0X₂0.5, (2) preferential partitioning of LC at 0.5<X₂<around 0.7, and (3) negative partitioning of LCH⁺ at around 0.7X₂1. The present results clearly indicate that uncharged local anesthetics transfer into hydrophobic environments such as cell membranes more than charged ones.     

Kinetics and mechanism of the reaction of aquachromium(III) with l-ascorbic acid in aqueous media

The kinetics of the reaction of l-ascorbic acid (H2A) with aquachromium(III) has been studied over the range 0.04 [H2A]T 0.16 mol dm–3, 3.5 pH 6.0, 25.0 t 50.0C, 0.03 I 1.0 mol dm–3 (KNO3) and 0% [MeOH] 20% (v/v). The reaction takes place via an outer-sphere association between Cr3+/CrOH2+ and H2A, followed by transformation of the outer- into an inner-sphere complex by slow interchange. The anation rate constants for Cr3+ and CrOH2+ species (k1 and k2) at 25C and I=1.0moldm–3 (KNO3) are 1.68×10–4 and 2.14×10–4s–1, respectively. H and S for the k1 and k2 paths are 27.0±2kJmol–1, –227±5J K–1mol–1 and 57.2± 4kJmol–1, –123±14JK–1mol–1, respectively. Anation of Cr(H2O)3+6 and Cr(H2O)5OH2+ follow an Ia path.     

Ionic strength dependence of formation constants. Part 4. Potentiometric study of the system Cu2+-Ni2+-citrate

Summary The ternary Cu²⁺-Ni²⁺-citrate (cit^3–) system was investigated potentiometrically in aqueous solution, at different temperatures, 10t45°C, and ionic strengths, 0.03I0.8 mol dm^–3, using potassium nitrate or tetraethylammonium bromide as background salt. Since the citrate anion forms weak complexes with potassium, the stability constants here reported differ according to whether the potassium association is considered or not. In the presence of both Cu²⁺ and Ni²⁺, the mixed metal species, [CuNi(cit)₂H_–2]^4– is formed with citrate in solution, in addition to the various binary complexes. We have obtained the dependence for all the formation constants on ionic strength and temperature. The previous suggestions concerning a general equation for describing the dependence, log =f(I), are confirmed; from the study of log =f(T) we have obtained the values of thermodynamic parameters. The dependence of H on ionic strength is discussed.     

Spectrophotometric Determination of the Polyiodohalides of Organic Nitrogen-Containing Cations

The following biologically active diiodohalides of organic cations were studied: N-cetylpyridinium, trimethylbenzylammonium, triethylbenzylammonium, and N,N-dimethylmorpholinium diiodochlorides; N-cetylpyridinium, tetramethylammonium, tetrabutylammonium, and N,N-dimethylmorpholinium diiodobromides; and N,N-dimethylmorpholinium and butyroylcholinium triiodides. A simple and rapid procedure was proposed for the determination of the above compounds; it is based on the conversion of organic diiodohalides into the corresponding triiodides (_{300 nm} 4 × 10⁴; _{370 nm} 2 × 10⁴) in the presence of excess potassium iodide (RSD 2%). An extraction–spectrophotometric method was developed for the quantitative determination of the biologically active compounds in pharmaceutical dosage forms based on their ion associates with anionic dyes, erythrosine (m _min = 1.25–3.30 g; RSD 3%) and Bromothymol Blue (m _min = 3.85 g; RSD = 3%), or a cationic dye—1,3-dimethyl-2-(4-morpholinophenyl)azobenzimidazolium phenylsulfate (m _min = 2.32–8.26 g; RSD 4%). The developed procedures were used for monitoring drug substances in model pharmaceutical preparations (RSD 4%).     

Thermodynamics of Proton Association of Polyacrylates and Polymethacrylates in NaCl(aq)

Enthalpies of protonation of polyacrylates and polymethacrylates with different molecular weights in aqueous NaCl solutions, 0 I 2 mol-L^–1 were determined by titration calorimetry at 25°C. H values are dependent on both the neutralization degree, , and the molecular weight of polyacids. T S of protonation was obtained using pK values already reported and the present H results. Empirical equations for the dependence on I, , and molecular weight are reported for both H and T S.     

The antiferromagnetic and ferrimagnetic properties of iron selenides with NiAs-type structure

The magnetic properties of the NiAs-type iron selenides have been investigated by susceptibility measurements between 100 and 450 K. Hexagonal -Fe_1-x Se exhibits both antiferromagnetism and ferrimagnetism depending on composition. For antiferromagnetic alloys with 0.02x0.10 (50.5 to 52.5 at % Se) the transition to the paramagnetic state is assumed to occur in the unstable range between room temperatur and about 573K. Ferrimagnetism is observed at compositions near Fe₇Se₈ (0.10x0.16; 52.5 to 54.3 at % Se) withCurie temperatures varying only slightly with composition. In Fe₇Se₈ the ferriparamagnetic transition is observable at 453 K. The characteristic discontinuities in the magnetization curves of Fe₇Se₈ in both superstructures (3c, 4c) are related to the rotation of the magnetic moments from a direction close to [001] into (001).The antiferromagnetism of Fe_0.89Se (52.8 at % Se) changes abruptly into ferrimagnetism when the temperature is raised above 160 K. The similar abrupt changes of the magnetic susceptibilities in the antiferromagnetic region are possibly associated with a crystallographic transformation. In the range of monoclinic -Fe_1-x Se with 0.24x0.36 (56.8 to 61.0 at % Se) only Fe₃Se₄ is ferrimagnetic above room temperature; alloys containing more selenium are ferrimagnetic far below room temperature. In Fe_0.69Se (59.1 at % Se) the transition from ferrimagnetism to paramagnetism was observed at 145 K. The saturation magnetization and the magnetic moments obtained from neutron diffraction are compared with values calculated from a simple ionic model.

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Die antiferromagnetischen und ferrimagnetischen Eigenschaften von Eisenseleniden mitNiAs-Struktur

Zusammenfassung Die magnetischen Eigenschaften von Eisenseleniden mit NiAs-Struktur wurden mittels Suszeptibilitätsmessungen zwischen 100 und 450 K untersucht. Hexagonales -Fe_1-xSe zeigt abhängig von der Konzentration sowohl Antiferromagnetismus als auch Ferrimagnetismus. In antiferromagnetischen Legierungen mit 0,02x0,10 (50,5 bis 52,5 At % Se) verläuft die Umwandlung in den paramagnetischen Zustand im nichfstabilen Bereich zwischen Raumtemperatur und 573 K. Ferrimagnetismus wurde in der Nähe von Fe₇Se₈ (0,10x0,16; 52,5 bis 54,3 At % Se) beobachtet mitCurietemperaturen, die sich nur wenig mit der Konzentration ändern. Fe₇Se₈ zeigt die ferri-paramagnetische Umwandlung bei 453 K. Die charakteristischen Diskontinuitäten der Magnetisierungskurven von Fe₇Se₈ in beiden Überstrukturen (3fache und 4fachec-Achse) hängen mit der Drehung der magnetischen Momente aus einer [001]-nahen Richtung in die (001)-Ebene zusammen. Der Antiferromagnetismus von Fe_0,89Se (52,8 At % Se) geht bei 160 K sprunghaft in Ferrimagnetismus über. Ähnliche sprunghafte Änderungen der magnetischen Suszeptibilitäten im antiferromagnetischen Bereich sind möglicherweise mit einer kristallographischen Umwandlung verbunden. Im Phasenbereich von monoklinem -Fe_1-x Se mit 0,24x0,36 (56,8 bis 61,0 At % Se) ist einzig Fe₃Se₄ oberhalb Raumtemperatur ferrimagnetisch; Legierungen mit mehr Selen sind weit unterhalb Raumtemperatur ferrimagnetisch. In Fe_0,69Se (59,1 At % Se) wurde der Übergang von Ferri- zu Paramagnetismus bei 145 K beobachtet. Die Sättigungsmagnetisierung und die magnetischen Momente aus Neutronenbeugungsexperimenten wurden mit Werten verglichen, die mit einem einfachen ionischen Modell berechnet wurden.

     

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.     

Effect of the dispersity of substances on the macrokinetics of thermal analysis under non-isothermal conditions

The effect of the dispersity of the sample on the topochemical mechanism and on the kinetic parameters of thermolysis (A _sB_s + C_g) under non-isothermal conditions is discussed. For correctness of the experiment, a ratio of maximum and minimum particle diameters 6 is a necessary condition. The topochemical mechanism of the process should be determined separately for the initial and final stages.

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Zusammenfassung Die Wirkung der Dispersion der Probe auf den topochemischen Mechanismus und die kinetischen Parameter der Thermolyse (A_s B_s + C_g) unter nichtisothermen Bedingungen wird diskutiert. Die Genauigkeit des Experiments setzt ein Verhältnis der maximalen und minimalen Teilchendurchmesser von 6 voraus. Der topochemische Mechanismus sollte für die Anfangs- und Endphase des Vorganges einzeln bestimmt werden.

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Résumé L'effet de la dispersion de l'échantillon sur le mécanisme topochimique et sur les paramètres cinétiques de la thermolyse (A_s B_s + C_g) en conditions non-isothermes est discuté. La conditions nécessaire pour qu'une expérience soit correcte est que le rapport entre les valeurs maximale et minimale des diamètres des particules soit 6. Le mécanisme topochimique du processus devrait être déterminé séparément pour les étapes initiale et finale.

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(A + ) . d ./d 6; .

     

Photoakustikspektroskopische Untersuchungen an Filtergl?sern

Zusammenfassung Verschiedene Filtergläser wurden mit Hilfe der Photoakustikspektroskopie im Bereich 300800 nm untersucht. Die Ergebnisse zeigten, daß die PAS wertvolle spektroskopische Informationen liefern kann, die die Transmissionsmessungen ergänzen können. Absorptionsmaxima, die durch Transmissionsmessung nicht erfaßbar sind (T10^–5), können bestimmt und den farbgebenden Kationen zugeordnet werden.

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Investigation of filter glasses by photo-acoustic spectroscopy

Summary Various filter glasses were investigated in the range of 300800 nm by photo-acoustic spectroscopy. The results showed that PAS is able to deliver valuable spectroscopic information supplementary to transmission measurements. Absorption maxima which are not detectable by transmission measurements (T10^–5) can be determined and attributed to the dyeing cations.

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Die Arbeit wurde durch Mittel der Deutschen Forschungsgemeinschaft und des Verbandes der Chemischen Industrie — Fonds der Chemie — sowie der Fa. Henkel KGaA unterstützt, wofür wir an dieser Stelle herzlich danken. Den Glaswerken Schott in Mainz danken wir für die Überlassung der untersuchten Filtergläser.     

A toxic reagent-free method for normal-phase matrix solid-phase dispersion extraction and reversed-phase liquid chromatographic determination of aldrin,dieldrin, and DDTs in animal fats

A method for the determination of aldrin, dieldrin, DDT, DDE, and DDD contamination in animal fats (beef tallow, lard, and chicken fat) without using toxic reagents is developed, that uses high-performance liquid chromatography after the sample has been prepared by matrix solid-phase dispersion (MSPD) with acidic alumina oxide. A reversed-phase C₁-silica column with a mobile phase of 50% (v/v) ethanol solution (in water) and a photo-diode array detector were used for the determination. Average recoveries of the target compounds (0.2–5.0 g g^–1) ranged from 84–98%, with coefficients of variation of <5%. The limits of quantitation were 0.16 g g^–1 for AD, 0.10 g g^–1 for DD, 0.06 g g^–1 for DDT, 0.07 g g^–1 for DDE, and 0.05 g g^–1 for DDD. No toxic reagents were used at all.     

DSC of sun-exposed chloroquine phosphate

Pharmaceutical intended for use in the tropics are required to maintain their stability under the most severe storage conditions. Chloroquine phosphate, a common antimalarial formulation, was exposed to the sun of the roof top under the extreme heat of the Saharan climate during the hot and dry season (February to June) at an average day temperature of 43°. The heat of meltingH determined by differential scanning calorimetry decreased from 60.1 J/g to 33.2 J/g after exposure for 73 days, corresponding to 49% decomposition. Differential scanning calorimetry is shown by this work to be a rapid and reliable technique for the routine quality control of chloroquine phosphate powders and tablet formulations.

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Zusammenfassung Für die Verwendung in den Tropen vorgesehene Arzneimittel müssen unter extremen Bedingungen lagerfähig sein. Chloroquin-Phosphat, ein bekanntes Mittel gegen Malaria, wurde auf einem Dach der Sonne unter der extremen Wärme des Sahara-Klimas während der Hitze- und Trockenperiode (Februar bis Juni) bei einer durchschnittlichen Tagestemperatur von 43 °C ausgesetzt. Die durch DSC bestimmte SchmelzwärmeH nahm von 60.1 J/g nach 73 tägiger Hitzeeinwirkung auf 33,2 J/g ab, was einem Zersetzungsgrad von 49% entspricht. DSC erwies sich als eine schnelle und zuverlässige Technik zur routinemäßigen Qualitätskontrolle von Chloroquin-Phosphat in Pulver- oder Tablettenform.

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, , . (-) 43°. (H) , 73 , 60,1 / 33,2 /, ' 49% . , .

     

Contribution to the formulation of a structural model by the determination of kinetic data

The processes involved in the isothermal dehydration of hexaoxytelluric acid, Te(OH)₆, are studied and the kinetic equations and activation energies corresponding to these processes are determined. The results are in agreement with a previously proposed structural model.

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Zusammenfassung Die an der isothermen Dehydratisierung der Hexaoxytellursäure Te(OH)₆ beteiligten Vorgänge wurden untersucht und die diesen Vorgängen entsprechenden kinetischen Gleichungen und Aktivierungsenergien bestimmt. Die Ergebnisse sind mit einem früher vorgeschlagenen strukturellen Modell in Übereinstimmung.

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Résumé On a étudié les réactions qui interviennent lors de la déshydratation isotherme de l'acide hexaoxytellurique Te(OH)₆ et déterminé les équations cinétiques ainsi que les énergies d'activation correspondantes. Les résultats sont en accord avec un modèle structural proposé préalablement.

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, , ()₆, . .

     

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).     

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.     

Variations in the cooling transitions of potassium nitrate

Because of questions concerning the suitability of potassium nitrate as a dynamic temperature standard for DTA, the relation between the experimental procedure and the resulting curves was ascertained for the Standard Reference Material KNO₃. The material behaves differentlyon cooling in open pans than in cylindrical holders because confinement in the latter case initiates reversion to the room temperature form. Under the conditions of use as a dynamic temperature reference material, the curves are accurately reproducible.

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Zusammenfassung Zur Überprüfung der Eignung von Kaliumnitrat als dynamische Temperatur-Eichsubstanz für die DTA, wurde der Zusammenhang des Versuchsvorganges und der erhaltenen Kurven für das Standard-Referenz-Material KNO₃ untersucht. Die Substanz verhält sich bei der Kühlung in offenen Tiegeln und in zylindrischen Behältern unterschiedlich, da in letzteren die Begrenztheit die Reversion zur Zimmertemperatur-Form in Gang setzt. Unter den für das dynamische Temperatur-Referenz-Material gegebenen Bedingungen sind die Kurven gut reproduzierbar.

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Résumé En raison de l'emploi du nitrate de potassium comme étalon de température en ATD, on a étudié l'influence des conditions d'expérience sur les courbes obtenues. Le comportement de ce corps est différent si on effectue le refroidissement dans des capsules ouvertes ou dans des creusets cylindriques. Dans ce dernier cas, le manque d'espace initie le retour à la forme stable delà température ambiante. Dans les conditions d'emploi comme matériau de température étalon, les courbes sont exactement reproductibles.

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. - , , .

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One of us is indebted to the U. S. National Science Foundation for support of part of this study.     

Aromatization of natural propane using modified molecular-shape selective zeolites

The conversion of propane into aromatic hydrocarbons has been studied at 400–540°C, using H-ZSM-11, Zn-ZSM-11, H-ZSM-5 and Zn-ZSM-5 zeolites. The zinc-exchanged forms of ZSM-11 and ZSM-5 were more active and gave better aromatic selectivity. The aromatics yield increased with the temperature and BTX selectivity increased with space velocity.

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400–540°C H-ZSM-11, Zn-ZSM-11, H-ZSM-5 Zn-ZSM-5. , . .

     

Thermal decomposition of ethyl and isopropyl amine perchlorates

Thermal decomposition of ethyl and isopropyl amine perchlorates has been studied by methods such as DTA, TG, isothermal weight loss measurements and the decomposition products have been analyzed in a mass spectrometer. Activation energy values for thermal decomposition have been calculated from-t plots. The proton transfer dissociation mechanism proposed for the thermal decomposition of ammonium perchlorate (AP) has been extended to explain the decomposition products of these twosubstituted amine perchlorates.

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Zusammenfassung Die thermische Zersetzung von Äthyl- und Isopropylaminperchloraten wurde durch die Methoden der DTA, TGA sowie durch isotherme Gewichtsverlustmessungen untersucht und die Zersetzungsprodukte in einem Massenspektrometer analysiert. Die Werte der Aktivierungsenergien der thermischen Zersetzung wurden aus-t Funktionen berechnet. Der für die thermische Zersetzung von Ammoniumperchlorat (AP) vorgeschlagene Proton-Übergangs-Dissoziationsmechanismus wurde erweitert um die Zersetzungsprodukte dieser zwei substituierten Aminperchlorate zu erklären.

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Résumé On a étudié, par des méthodes comme l'ATD, la TG et les mesures de pertes de poids isothermes, la décomposition thermique des perchlorates d'amines éthylique et isopropylique et on a analysé les produits de décomposition dans un spectromètre de masse. On a calculé les valeurs de l'énergie d'activation de la décomposition thermique à partir des fonctions-t. On a étendu le mécanisme de dissociation du transfert de protons, proposé pour la décomposition thermique du perchlorate d'ammonium (AP), afin d'expliquer la formation des produits de décomposition de ces deux perchlorates d'amines substitués.

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- , . -. -t. , , .