PVT properties of concentrated electrolytes. VI. The speed of sound and apparent molal compressibilities of NaCl,Na2SO4, MgCl2, and MgSO4 solutions from 0 to 100°C

The sound velocities of aqueous NaCl, Na₂SO₄, MgCl₂, and MgSO₄ solutions were measured from 25 to 95°C in 10^o intervals from dilute to saturated solutions. The results were combined with our earlier data and fitted to functions of molality and temperature to within ±0.4 m-sec^–1. The adiabatic compressibilities _S were calculated from sound speeds and used to calculate the adiabatic apparent molal compressibilities . Isothermal compressibilities and isothermal apparent molal compressibilities were calculated from _S using literature values for the expansibilities and heat capacities. The values of were extrapolated to infinite dilution using the Debye-Huckel limiting law to determine partial molal compressibilities. The apparent molal compressibilities were fitted to Pitzer's equations. The Pitzer parameters for the concentration dependence of were determined as a function of temperature. Correlations of and V at various temperatures were found for the electrolytes.     

Enthalpy of dilution and heat capacity of aqueous solutions of tetrabutylammonium butyrate as a function of temperature

Enthalpies of dilution of tetrabutylammonium butyrate are reported as a function of temperature between 10° and 50°C. Heat capacities of aqueous solutions of tetrabutylammonium butyrate were measured in order to obtain values of _cp at 15°, 25°, and 35°C. These data were combined with the enthalpy of dilution data to obtain _cp as a function of molality and temperature. The apparent molal heat content _L decreased with increasing temperature in concentrated solutions but increased with increasing temperatures in dilute solutions (below0.7 m). Over the temperature range studied _cp shows a maximum as a function of molality at approximately 0.5m. The decrease in _cp with increasing concentration of hydrophobic solute is consistent with the view that the hydrophobic hydration cages, formed under the influence of the tetrabutylammonium and butyrate ions, are saturated at about 0.5m, and that at higher molalities increased overlap of the hydration cages occurs.     

Mathematical structure of chromatographic optimization based on information theory: I. Effect of mobile phase composition on precision

Summary The influence of mobile phase composition X on the precision of liquid-chromatographic analysis is interpreted in terms of the derivate of the mutual information for peak j with respect to X, d_j/dX. The sign and magnitude of d_j/dX depend on the operational conditions of X or on the details of chromatograms (e.g., resolutions R_s), but d_j/dX always indicates the direction of X toward more information _j. The sensitivity function s_j(=1/(k_j+1)) is examined on the basis of information theory. Optimization is formulated as a nonlinear programming problem.     

Apparent molal heat capacities and volumes of pyridine and methyl-substituted pyridines in aqueous solution at 25°C

We have made calorimetric measurements leading to apparent molal heat capacities of pyridine and four methyl-substituted pyridines in aqueous solution at 25.0°C. Measurements of densities of the same solutions have led to apparent molal volumes. The results are as follows: pyridine, _C ^° = 305.7 J–°K^–1-mole^–1 and _V ^° = 77.5 cm³-mole^–1; 2-methylpyridine, _C ^° = 370.0 J–°K^–1-mole^–1 and _V ^° = 94.3 cm³-mole^–1; 3-methylpyridine, _C ^° = 380.2 J–°K^–1-mole^–1 and _V ^° = 93.7 cm³-mole^–1; 4-methylpyridine, _C ^° = 378.9 J–°K^–1-mole^–1 and _V ^° = 94.3 cm³-mole^–1; 2,6-dimethylpyridine, _C ^° = 441.8 J–°K^–1-mole^–1 and _V ^° = 109.9 cm³-mole^–1. These _C ^° and _V ^° values are discussed in terms of effects of substitution of CH₃-for H– in the various solute molecules.The research reported here was carried out in the Department of Chemistry, University of Lethbridge, Lethbridge, Alberta, Canada T1K 3M4.     

Tris(pyrazol-1-yl)-s-triazine (TPT): X-ray crystallographic,computational, and gas-phase electron diffraction studies

The conformation of the TPT molecule has been analyzed using experimental and computational techniques. The solid-state molecular structure shows similar conformational features to those in the 2-pyrimidine and phenyl derivatives although a different pattern of bond angles in the triazine ring was observed. The AM1 calculations predicted two conformations of comparable stability (E=1.8 kcal/mol) differing in the orientation of one pyrazole ring. While the minimum energy conformation corresponds to a model displayingC _3h symmetry ( ₁= ₂= ₃=0°), the other minimum ( ₁= ₂=0°, ₃=180°) is close to that observed in the solid state. The electron diffraction results are consistent with a planar or nearly planar conformation in agreement with the preceding studies.On leave from the Depto. Química. Universidade Federal Rural do Rio de Janeiro. Itaguai (RJ) 23851 Brazil.     

Basis extension in the Roothaan method

Quantum-chemical calculations show that in the Roothaan method, even when the Hartree-Fock energy limit is achieved, the basis set extension can significantly influence other molecular characteristics. In this work we study the influence of an additional (orthogonal to an initial basis set) orbital on one-electron levels, total energy, and quantities that are calculated as average values of one-electron operators. We assume that the initial M-dimensional basis is sufficiently good, so that adding orbital does not lead to the redistribution of occupied and virtual levels. Then, each occupied (M+1)-dimensional MO _i is approximately the same as the corresponding M-dimensional MO _i ⁰ and differs from it only by admixture of the other orbitals _k ⁰ and the function . The coefficients of _k ⁰ and in _i are considered to be small parameters, and molecular characteristics of interest are expanded in power series with respect to them. It has been established that a decrease in the total energy during the basis extension corresponds to the quadratic in these parameters terms while quantities calculated as average values of one-electron operators change linearly during the basis extension. A shift of one-electron levels _i during the basis extension is examined. It is shown that the MacDonald rule is satisfied if integrals containing the energy shift operator for electron interaction are small with respect to integrals <F⁰_j ⁰> where F⁰ is the Fock operator in the initial basis. An an illustration, results of calculations for H₂ and HeH₊ molecules in an ellipsoidal basis are given.Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 22, No. 1, pp. 3–11, January–February, 1986.     

Volumetric Properties of Some α-Amino Acids in Aqueous Guanidine Hydrochloride at 5, 15, 25, and 35°C

The infinite-dilution apparent molar volumesV ₂ ^o for glycine, DL-alanine, DL--amino-n-butyric acid, DL-valine, DL-leucine, and L-serine in 6 mol-kg^–1 aqueous guanidine hydrochloride were determined at 5, 15, 25, and 35°C from precise density measurements. Using these data, the standard volumes of transfer, _t V°, from water to 6m> aqueous guanidine hydrochloride solution were calculated. A linear relationship was found between V ₂ ^o and temperature. Both V ₂ ^o and _t V° vary linearly with increasing number of carbon atoms in the alkyl chain of the amino acids. The results show that the apparent molar volumes at infinite dilution for (NH ₃ ⁺ ,COO^-) groups increase with increasing temperature and those for CH₂ and the other alkyl chains are almost constant. These results also shows that guanidine hydrochloride has stronger interactions with amino acids than urea. These phenomena are discussed in terms of the cosphere overlap model.     

Effect of surfactants on the cleavage of the N?O bond in O-(2,4-dinitrophenyl)-cyclohexanone oxime

Kinetics of cleavage of N–O bond in O-(2,4-dinitrophenyl)-cyclohexanone oxime with hydroxide ions both in the presence and absence of surfactants has been studied. The reaction is accelerated by cationic micelles, slightly by non-ionic micelles and there is no effect of anionic micelles. A plot of the rate constant vs. [surfactant] shows a maximum corresponding to the CMC of surfactant.

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NO O-(2,4-) - , - (). , , - . , .

     

Kinetic studies on the thermal decomposition of glucose and fructose

The thermal decompositions of glucose and fructose were studied by means of the Derivatograph. From the melting temperature up to 300 these monosaccharides decompose and give brown caramel matter. The TG curves as functions of time were taken at various heating rates (0.5–10/min) by the Derivatograph and the activation energies of the decompositions were determined by Ozawa's method.

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Zusammenfassung Die thermische Zersetzung von Glukose und Fruktose wurde mit Hilfe des Derivatographen studiert. Diese Monosaccharide erleiden von der Schmelztemperatur bis zu 300 C eine Zersetzung und ergeben braune Karamelstoffe. Die verschiedenen Zeitspannen zugeordneten TG-Kurven wurden vom Derivatographen bei verschiedenen Aufheizgeschwindigkeiten (von 0.5C/min bis zu 10C/min) registriert und die Aktivierungsenergie der Zersetzung wurde mittels der Methode von Ozawa bestimmt.

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Résumé On a étudié la décomposition thermique du glucose et du fructose à l'aide du Derivatograph. Ces monosaccharides subissent une décomposition à partir de la température de fusion jusqu' à 300C en donnant des caramels bruns. Les courbes TG ont été enregistrées en fonction du temps avec diverses vitesses de chauffage (de 0.5 C/min jusqu'à 10C/min) et l'énergie d'activation de la décomposition a été déterminée par la méthode d'Ozawa.

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. 300 . ( 0,5/ 10/) .

     

The dependence of build-up233U,232U,233Pa and fission products from ThO2 irradiated in HFETR on integral thermal neutron fluxes and neutron spectra

In this paper the dependence of build-up²³³U,²³²U,²³³Pa and fission products from ThO₂ irradiated in HFETR on integral thermal neutron fluxes and neutron spectra have been investigated. The yields of all above nuclides in ThO₂ increase with the increase of integral thermal neutron fluxes at different neutron spectra. The values of²³³U/²³²Th increase with the increases of _th and decreases with the increase of fast/thermal neutron ratios (_f/_th). The values of²³²U/²³³U increase with the increase of both _th and _f/_th ratio. The amount of fission products relative to original irradiated thorium decreases with the increase of _f/_th ratios. These results could be used to evaluate the behaviour of thorium-based nuclear fuel in reactor.     

Influence of the sample mass and the presence of the reaction products on the thermoanalytical results

It has been known from the very beginning of the thermal analysis that the transport processes can significantly influence the thermoanalytical results. In this paper, three characteristic examples are given to show that this problem is more complex and arises more frequently than it is generally believed. The studied reactions are the carbon monoxide evolution from calcium oxalate, the thermal degradation of polytetrafluoroethylene, and the thermal decomposition of azodicarbonamide. TG and DSC experiments were carried out with sample masses varying between 0.05 and 8 mg. The necessity of the development of new kinetic models is concluded.

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Zusammenfassung Seit den Anfängen der Thermoanalyse ist bekannt, dass Transportprozesse die thermoanalytischen Ergebnisse weitgehend beeinflussen können. Es werden hier drei Beispiele beschrieben, die zeigen, dass dieses Problem weitauf komplizierter ist und häufiger auftritt als allgemein angenommen wird. Die untersuchten Reaktionen sind die Kohlenmonoxidabspaltung aus Calziumoxalat, die thermische Zersetzung von Polytetrafluoräthylen und der thermische Zerfall von Azodicarbonamid. Die TG- und DSC- Untersuchungen wurden mit Probenmassen zwischen 0.05 und 8 mg durchgeführt. Es wird auf die Notwendigkeit der Entwicklung neuer kinetischer Modelle geschlossen.

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, . , , . , . , 0,05 8 . .

     

Dehydration of lithium triphosphate pentahydrate,Li5P3O10· 5H2O

The kinetics of isothermal-isobaric dehydration of Li₅P₃O₁₀·5H₂O in vacuum (p=10^–1 hPa) and in water vapour atmosphere ( =23·hPa) was investigated by TG in the temperature range 40–140°. It was shown that the initial non-degradation removal of 1/10 of the crystal water, the rate of which is sensitive to , proceeds according to the laws of reversible topochemical reactions. In the next, irreversible degradation stage, where the bulk of the crystal water is removed, the kinetic characteristics of the process and the DSC effects exhibit a low sensitivity to the water vapour pressure. The peculiarities of Li₅P₃O₁₀·5H₂O dehydration were considered in comparison with the thermal behaviour of Na₅P₃O₁₀·6H₂O and K₅P₃O₁₀·4H₂O.

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Zusammenfassung Die Kinetik der isotherm-isobaren Dehydratisierung von Li₅P₃O₁₀·5H₂O in Vakuum (p=10^–4 hPa) und in Wasserdampfatmosphäre ( =23 hPa) wurde durch TG im Temperaturbereich von 40–140° untersucht. Es wurde gezeigt, daß die anfängliche, noch keine Zersetzung zur Folge habende Eliminierung von 1/10 des Kristallwassers, deren Geschwindigkeit von abhängt, nach den Gesetzen der reversiblen topochemischen Reaktionen abläuft. Im nächsten irreversiblen Zersetzungsschritt, in dem die Hauptmenge des Kristallwassers austritt, sind die kinetischen Kennwerte des Prozesses und die DSC-Effekte nur wenig vom Wasserdampfdruck abhängig. Die Besonderheiten der Dehydratisierung von Li₅P₃O₁₀·5H₂O werden im Vergleich mit dem thermischen Verhalten von Na₅P₃O₁₀·6H₂O und K₅P₃O₁₀·4H₂O erörtert.

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40–140° - Li₅P₃O₁₀ · 5₂ (=10^–4 ) (=23 ). , 1/10 , . , - . L₅₃₁₀·5₂ Na₅P₃O₁₀·6H₂O K₅₃₁₀·4₂.

     

Dependence of the thermal decomposition of CuSO4·5H2O on the experimental conditions

The mechanism of thermal decomposition of CuSO₄·5H₂O is greatly influenced by the experimental conditions. Under conventional conditions, in an open crucible, the first partial reaction takes place in one step involving solid and gaseous phases. If a sample holder which creates a self-generated atmosphere is used, the reaction is separated into two consecutive processes. First the sample melts in an incongruent way, and thereafter the saturated solution formed beside solid CuSO₂·3H₂O evaporates under boiling. These two processes can be completely distinguished in the DTA curve. The selectivity of the examinations can be further increased through application of the quasi-isothermal heating technique.The two modes of decomposition can be correlated with the special phenomenon that, if the decomposition occurred according to the former mechanism, then the intermediate CuSO₄·3H₂O had stoichiometric composition, while in the latter case the compound consequently contained about 2.5% more water than that calculated.

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Zusammenfassung Der Mechanismus der thermischen Zersetzung von CuSO₄·5H₂O wird durch experimentelle Bedingungen in grossem Masse beeinflusst. Unter herkömmlichen Bedingungen, in einem offenen Tiegel, spielt sich die erste Teilreaktion in einem Schritt ab und hat sowohl feste als auch gasförmige Produktephasen zur Folge. Wird ein Probenhalter benutzt, der eine selbstgenerierte Atmosphäre erzeugt, wird die Reaktion in zwei konsekutive Vorgänge unterteilt. Zuerst schmilzt die Probe inkongruent, die dabei entstandene gesättigte Lösung (neben festem CuSO₄·3H₂O) dampft dann beim Verkochen ein. Diese beiden Vorgänge können mittels der DTA-Kurve vollkommen voneinander unterschieden werden. Die Selektivität der Untersuchung kann durch Anwendung der quasi-isothermen Heiztechnik weiter verbessert werden.Die zwei Zersetzungsarten stimmen mit der Beobachtung überein, dass bei der Zersetzung nach dem ersteren Mechanismus das Zwischenprodukt CuSO₄·3H₂O eine stöchiometrische Zusammensetzung besitzt, während es im letzteren Fall stets ungefähr 2,5% Wasser mehr enthält, als berechnet.

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. , . , . , , , . . . , , . , 2,5% .

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The authors thank Prof. E. Pungor for valuable discussions, and Miss I. Czene and Miss J. Forizs for their technical assistance.     

The use of thermal analysis in medical science with special reference to nephroliths

The applications of thermal methods in medical science have been summarized, with special regard to kidney stones. Complex thermal analysis can be used successfully for examination of human and animal urinary calculi, bones, odontoliths biological tissues (proteins, skin, callus, nail) etc.

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Zusammenfassung Es wurden die Anwendungen der Thermoanalyse auf medizinischem Gebiet unter besonderer Berücksichtigung von Nierensteinen zusammenfassend behandelt. Komplexe thermoanalytische Methoden eignen sich zur Prüfung von menschlichen und tierischen Harnsteinen, Knochen, Zahnstein, biologischem Gewebe (Proteine, Haut, Nägel, usw.)

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Résumé Revue des applications des méthodes thermoanalytiques dans le domaine médical avec mention particulière pour les calculs rénaux. L'emploi des méthodes d'analyse thermique mixtes donnent de bons résultats pour l'examen des calculs rénaux animaux et humains, du tartre dentaire et des tissus biologiques (protéines, peau, ongles), etc.

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, . , (, , , ) .

     

Interaction of tribenzyltitanium with butadiene

It has been established that the interaction of (C₆H₅CH₂)₃Ti with butadiene does not change the parameters of ESR spectra. Only the hydrodynamic radius of this complex increases.

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, (C₆H₅CH₂)₃Ti . .

     

Oxidation of trimethoxybenzenes to benzoquinones with hydrogen peroxide in the presence of heteropolyacid

Trimethoxybenzenes were oxidized to dimethoxy-p-benzoquinones in fairly good yields (50–60%) with hydrogen peroxide in the presence of heteropolyacid in the solvent of acetic or formic acid.

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-- (50–60%) , , .

     

Relationships between glass transition and melting temperatures and chemical structures of polypyromellitimides

At temperatures above 350° polypyromellitimides exhibit continuously increasing deformations. The temperatures of glass transition and melting were determined in their homologous series.For the determinations, thermomechanical and combined thermogravimetric massspectrometric measurements were performed. Glass transition temperatures were also calculated on the basis of the structure of the repeating unit. Conclusions could be drawn on the structures and rigidities of the molecules. The roles of groups introduced into the diamine fragment could be determined.

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Zusammenfassung Polypyromellitimide weisen bei Temperaturen oberhalb von 350 °C ständig zunehmende Deformationen auf. Die Temperaturen des Glas-Überganges und des Schmelzens wurden in ihren homologen Reihen bestimmt.Zur Bestimmung wurden thermomechanische und kombinierte thermogravimetrischmassenspektrometrische Messungen durchgeführt. Die Glas-Übergangstemperaturen wurden auch auf Grund der Struktur der sich wiederholenden Einheit errechnet. Schlüsse über die Struktur und Rigidität der Moleküle konnten gezogen werden. Die Rolle der in das Diamin-Fragment eingeführten Gruppen konnte bestimmt werden.

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Résumé Les polypyromellitimides montrent des déformations qui augmentent de manière continue aux températures supérieures à 350°. On a déterminé dans leurs séries homologues les températures de transition vitreuse et de fusion.Ces déterminations ont été complétées par des essais thermomécaniques ainsi que par des mesures combinées en thermogravimétrie et en spectrométrie de masse. Les températures de transition vitreuse ont également été calculées sur la base de la structure unitaire. On en déduit des conclusions sur la structure et la rigidité des molécules. Le rôle des groupes introduits dans le fragment diamine a pu être déterminé.

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350° . . -- . . . . , .

     

Oxidative coupling of alkylbenzenes to diaryls catalyzed by the palladium(II)-heteropolyacid system

Oxidative coupling of alkylbenzenes (benzene, toluene, o-xylene, durene) is shown to proceed in the presence of palladium salts and heteropolyacids under the action of oxygen with a high yield of diaryls. The addition of mercury salts and variation of the solvent affect the reaction rate and isomer composition of the products.

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, (, , -, ) . .

     

Studies of the chemical exchange kinetics of glycinate ions in mixed ligand complexes of copper (II) and glycylglycine

Nuclear magnetic resonance studies of the chemical exchange kinetics of glycinate ions in binary and ternary complexes of copper(II) and glycylglycine indicate the increase in the exchange rate of glycinate ions in the ternary complex. This phenomenon is assumed to be due to the glycinate ion coordination in the axial—equatorial position.

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(II) . . , - - .

     

Thermal and mechanical studies on the cure time optimisation of polysulphide resin

The effect of two commercially available metal oxide curing agents, PbO₂ and MnO₂, on the cure time, kinetic parameters and ultimate tensile strength of the polysulphide polymer was investigated. The kinetic parameters for the thermal decomposition of the two systems were evaluated from their TG data. Both the energy of activation and pre-exponential factor showed a systematic increase with increase in cure and levelled off after the reaction. The cure time was also followed by determining the mechanical properties of the samples at regular intervals. The ultimate tensile strength values and the kinetic parameters follow similar trend with respect to the cure time. The kinetic parameters and the ultimate tensile strength for the PbO₂ cured polysulphide system were on the higher side.

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Zusammenfassung Es wurde der Einfluß von zwei im Handel erhältlichen Metalloxidhärtemitteln. PbO₂ und MnO₂, auf die Aushärtungszeit, die kinetischen Parameter und die Zugfestigkeit von Polysulfidpolymeren untersucht. Die kinetischen Parameter für die thermische Zersetzung der zwei Systeme wurden aus deren TG-Daten ermittelt. Sowohl die Aktivierungsenergie als auch der präexponentielle Faktor wachsen mit fortschreitender Aushärtung ständig an und erreichen nach Verlauf der Reaktion einen konstanten Wert. In gleichmäßigen Zeitabschnitten wurde die Aushärtungszeit auch durch Bestimmen der mechanischen Eigenschaften der Proben verfolgt. In Bezug auf die Aushärtungszeit zeigen die Zugfestigkeit und die kinetischen Parameter einen ähnlichen Verlauf. Die kinetischen Parameter und die Zugfestigkeit von mit PbO₂ gehärteten Polysulfidsystemen zeigen bessere Werte.

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, , , . , . . , . , . , , .

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We thank Dr. R. Ramaswamy for supplying the resin and Dr. K. V. C. Rao and Director, VSSC for the kind permission to publish this work.