Calorimetric investigations of hydrogen-bonded liquid crystal binary mixtures

Journal of Thermal Analysis and Calorimetry - Double hydrogen-bonded liquid crystals formed between methyl malonic acid (MM) and p-n-alkyloxy benzoic acids (nBAO) are characterized. Variation in...     

Calorimetric investigations of high density polyethylene/polyaniline composites

Summary Electrically conductive composites containing high density polyethylene (HDPE) and polyaniline (PANI) - dodecylbenzenesulfonic acid (DBSA) complex were prepared in situ by bulk oxidative polymerization of aniline (ANI) in presence of DBSA. Their thermal behaviour and crystallinity parameters were studied for the first time by using differential scanning calorimetry (DSC). It was found that the presence of the conductive complex does not affect the crystalline structure of the matrix polymer neither during in situ polymerization of ANI in powdered HDPE nor upon heating of HDPE/PANI·DBSA composite up to 180°C followed by fast cooling.     

Calorimetric investigations of urease inhibition by heavy metal ions

The subject of this publication is calorimetric investigations on the inhibitor effect of heavy metal ions on the enzyme urease. The obtained results allow quantification of the inhibitors (Cd²⁺-, As³⁺-, Zn²⁺-, Pb²⁺-ions) via the initial reaction rate of enzymatically catalysed urea hydrolysis. The interpretation potential of the calorimetric measurements is underlined by the determination of the inhibiting mechanisms for the example of Cd²⁺- and As³⁺-ions, the findings on the time regime of the inhibition process, and the detection of heavy metal ions in the ppm range. The use of several different buffer substance revealed the influence of the latter on the intensity of heavy metal inhibition. This opens the path to both the selective analysis of heavy metals via pattern recognition and to the improvement of detection sensitivity.     

Calorimetric and dielectric investigations of smectic liquid crystals with aerosil

Two strongly polar 4-(4-cyanobenzyloxy)benzylidene 4- n -alkylanilines were synthesized for the first time and mixed with the hydrophilic aerosil A 300. The compounds, showing a rich polymorphism, and the mixtures were investigated by calorimetric and dielectric methods. Phase transitions of first and second order were detected. Neither the phase transition temperatures nor dielectric relaxation times are strongly influenced by addition of aerosil up to 20%.     

Calorimetric investigations on molecular interactions in a mixed layer adsorbed on a homogeneous surface

The adsorption and differential heats of adsorption of mixtures of methanol and tetrahydrofuran (mole ratio 11), methanol and cyclopentane (11 and 14) and tetrahydrofuran and cyclopentane (11 and 14) on a graphitized carbon black (Sterling MT) surface were determined.The dependence of the intermolecular interactions on the composition of the adsorbed layer was established. From an analysis of the experimental results, the mechanism of adsorption of the equimolar methanol-tetrahydrofuran mixture was described, in which both homomolecular. and heteromolecular association were taken into consideration.

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Zusammenfassung Es wurde die Adsorption und die differentiellen Adsorptionswärmen äqnimolarer Gemische aus Methanol mit Tetrahydrofuran bzw. aus Methanol und Tetra-hydrofuran mit Cyclopentan (Molverhältnis 11 bzw. 14) an mit Graphit überzogenen Ruß Sterling MT Oberflächen bestimmt.Dabei wurde die Abhängigkeit der intermolekularen Wechselwirkungen von der Zusammensetzung der adsorbierten Schicht aufgedeckt. Ausgehend von der Analyse der experimentellen Ergebnisse wurde der Mechanismus der Adsorption eines Methanol-Tetrahydrofurangemisches beschrieben, wobei sowohl homoals auch heteromolekulare Assoziation berücksichtigt wurde.

     

Calorimetric methods for catalytic investigations of novel catalysts based on metallized S-layer preparations

The contribution will show the first results from calorimetric screening of novel catalysts. Biotemplated platinum nanoclusters were prepared on the basis of S-layer—bacterial surface proteins—on different supports. Methods were contrived and examined, permitting both the investigation of catalytic bulk material, and the investigation of sensory interesting coatings. The calorimetric measurements were carried out using conventional calorimetric technique (DSC 111, firm SETARAM) and miniaturized calorimetric systems (integrated circuit calorimeter - IC-calorimeter and a sensor platform). The results of the calorimetric investigations to the selected model reactions (oxidation of hydrogen, carbon monoxide and propane) demonstrate the interesting characteristics of these new catalysts.     

Calorimetric investigations of the influence of waste aluminosilicate on the hydration of different cements

The aim of this work is to compare the influence of addition of waste aluminosilicate catalyst on the initial periods of hydration of different cements, i.e. calcium aluminate cements of different composition and Portland cement, basing on the calorimetric studies. Cement pastes containing up to 25 mass% of additive were studied, where the water/(cement+additive) ratio was 0.5. An attempt was undertaken to explain the mechanism of action of introduced aluminosilicate in the system of hydrating cement, particularly in the case of calcium aluminate cement pastes. It was found that the presence of fine-grained additive caused in all studied cases the increase of the amount of released heat in the first period after the addition of water. In the case of aluminate cements with aluminosilicate addition, a significant reduction of induction time and faster precipitation of hydration products were observed compared to the reference sample (without additive). In the experimental conditions, the additive caused the acceleration of aluminate cements hydration, and the mechanism of its action is probably complex and can encompass: nucleative action of small grains and formation of new chemical compounds.     

Calorimetric,dilatometric and microscopic investigations of the system sodium stearate-stearic acid

Summary AT-x phase diagram of the system sodium stearate (NaSt)-stearic acid (HSt) has been determined by DTA. It shows the existence of five defined association compounds, three of them (2 NaSt · 3 HSt, NaSt · HSt and 3 NaSt · 2 HSt) with an incongruent melting point and the others (5 NaSt · 2 HSt and 5 NaSt · HSt) with a congruent melting point. The latter two compounds pass through various mesomorphic phases before melting. The components do not form solid solutions and are even non-miscible in the mesomorphic state below 200 °C. Mutual miscibility is only observed above this temperature in the subneat and neat region, occurring in the HSt composition range from 0 to 15 and from 0 to 5 mole% respectively. The existence of molecular associations in the liquid state is very probable, particularly in the composition range between 30 and 40 mole% stearic acid. This might result in a liquid structure similar to that present in the melt of anhydrous soaps.

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Zusammenfassung EinT-x Zustandsdiagramm des Natriumstearat (NaSt)- Stearins?ure (HSt)-Systems wurde mittels DTA bestimmt. Es weist fünf definierte assoziierte Verbindungen auf, drei (2 NaSt · 3 HSt, NaSt · HSt und 3 NaSt · 2 HSt) mit einem inkongruenten Schmelzpunkt und zwei (5 NaSt · 2 HSt und 5 NaSt · HSt) mit einem kongruenten Schmelzpunkt. Die zwei letzteren Verbindungen durchlaufen verschiedene mesomorphe Phasen, bevor sie schmelzen. Die Komponenten bilden keine festen L?sungen und sind im mesomorphen Zustand unter 200 °C nicht einmal miteinander mischbar. Nur bei h?heren Temperaturen sind sie v?llig mischbar, und zwar in der “subneat” und “neat” Region, die im HSt-Bereich von 0 bis 15 bzw. von 0 bis 5 Mol% reicht. Die Existenz molekularer Assoziate im flüssigen Zustand ist sehr wahrscheinlich, vor allem im Bereich zwischen 30 und 40 Mol% Stearins?ure. Dies k?nnte zur Bildung von Strukturen in der Flüssigkeit führen ?hnlich, wie dies bei der Schmelze wasserfreier Seifen der Fall ist.

     

Calorimetric investigations of the solvent effect on complex formation between pyridine derivatives and molecular iodine

The heats of solution of isoquinoline and 2,4-lutidine and heats of 11 complex formation with molecular iodine inn-hexane, cyclohexane, CCl₄, benzene, and chlorobenzene have been determined by the calorimetric method. The heats of transfer of the donor and donor-acceptor complex from nonsolvating medium (n-hexane) to the particular solvent were calculated and discussed in terms of donor and solvent properties and solute-solute-solvent interactions.Presented at the IV International Symposium on Solute-Solute-Solvent Interactions, Vienna, September 11–16, 1978, pp. 152–154.     

Calorimetric investigations on the action of alarm pheromones in the hornet Vespa crabro

This study investigated the effects of alarm pheromone components on the heat production rates of hornets (Vespa crabro) by means of direct calorimetry. In a flow-through system, pheromones from hornets, honeybees (Apis mellifera) and yellowjackets (Vespula vulgaris) were sucked through a measuring vessel containing a group of hornet workers. The locomotive reaction of hornet workers was recorded as an increase of the heat production rate. Hornets exhibited a strong response to their own alarm pheromone components, mainly 2-methyl-3-butene-2-ol (MBO). They also reacted intensively upon the main alarm pheromone component of the honey bee, isopentylactetate (IPA), but less pronounced to alarm pheromone components of yellowjackets. The metabolic response of hornets to MBO was dose-dependent. The heat production rates of provoked hornet workers were similar to those of flying hornets. (z)-9-Pentacosene, a substance which is believed to be a thermoregulative brood pheromone, induced no metabolic reaction.     

Reactions of cyclochlorotriphosphazatriene with 2-mercaptoethanol. Calorimetric and spectroscopic investigations of the derived products

Abstract

The reactions of hexachlorocyclotriphosphazatriene, N₃P₃Cl₆ (1) with 2-mercaptoethanol, 2-HS-CH₂-CH₂-OH (2), in (1:1, 1:2 and 1:3) mole ratios, in excess of NaH, in THF and diethylether solutions yield a total of 6 novel products: one mono spiro, N₃P₃Cl₄[O-CH₂-CH₂-S] (3); one mono-substituted open chain, N₃P₃Cl₅[S-CH₂-CH₂-OH] (4); one dispiro, N₃P₃Cl₂[O-CH₂-CH₂-S]₂ (5); one tri-substituted open chain, N₃P₃Cl₃[S-CH₂-CH₂-OH]₃ (6); one tris-spiro, N₃P₃[O-CH₂-CH₂-S]₃ (7) and one disubstituted open chain, N₃P₃Cl₄[S-CH₂-CH₂-OH]₂ (8) derivatives. The spiro products (3, 5 and 7) are formed as the major products in this system and all of the synthesized compounds are found to be stable at room temperature. The structures of the derived compounds were elucidated by elemental analysis, TLC-MS, ³¹P and ¹H NMR spectral data. For evaluation of melting behavior of derivatives (6) and (7), thermal transition peaks and their corresponding enthalpies were determined via DSC technique.     

Calorimetric and spectroscopic investigations into the stability of SiCl4 and SnCl4 complexes.

The enthalpy values for the reaction of acetoacetanilides with SiCl₄ and SnCl₄ have been determined by solution calorimetry at 298 K in 1.2-dichloroethane. Stable compounds were isolated and identified by elementary analysis and spectroscopic methods.     

Calorimetric investigations of association equilibria: the pyridine-iodine complex in cyclohexane and in carbon tetrachloride

The results of two independent calorimetric investigations of the pyridine- iodine complex are reported. “Best” values are reported as K_m = 128 1/mol and ΔH° = -8.4 kcal mol^?1 for the formation of the complex in cyclohexane at 25°C, and K_m = 104 and ΔH° = -7.9 kcal mol^?1 in carbon tetrachloride. Evidence is presented to support the contention that association constants for weak complexes determined by calorimetric methods can be as reliable as those determined by spectrometric methods, and that values of ΔH° determined by the calorimetric method are much more reliable than those derived from the temperature dependence of equilibrium constants.     

Calorimetric experiments on social insects

Direct calorimetric experiments on the social insects: honeybees, bumblebees and hornets are described as function of castes, age, number of animals in a group, temperature, sound generation, hibernation and influence of pheromones. Two honeybee subspecies, the European bee Apis mellifera carnica and the Egyptian bee Apis mellifera lamarckii, were compared calorimetrically in their energy metabolism which differed considerably in favour of the more alert Egyptian form.

Moreover, thermoelectric cooling boxes for camping were applied as simple heat conduction calorimeters and as artificial nesting facilities for bumblebees and hornets. Their colonies could be monitored calorimetrically and thermometrically throughout the season. In spring, initial nests with only a few workers and one queen were collected in the field and transferred to these boxes where they continued their normal development up to full size of several hundred individuals. By this means, energy turnover of insect colonies could be evaluated under varying conditions.     

Calorimetric investigations of the MBr−NdBr3 melts (M=Li,Na, K,Cs)

Present work is a part of thermodynamic research program on the MX?LnX₃ system (M=alkali metal,X=Cl, Br andLn=lanthanide). Molar enthalpies of mixing in the LiBr?NdBr₃, NaBr?NdBr₃ and KBr?NdBr₃ liquid binary systems have been determined at temperature 1063 K by direct calorimetry in the whole range of composition. Investigated systems are generally characterized by negative enthalpies of mixing with minimum atX _NdBr3≈0.3–0.4. These enthalpies decrease with decrease of ionic radii of alkali metals. Molar enthalpies of solid-solid and solid-liquid phase transitions of K₃NdBr₆ and Cs₃NdBr₆ have been also determined by differential scanning calorimetry (DSC). K₃NdBr₆ is formed at 689 K from KBr and K₂NdBr₅ with enthalpy of 44.0 kJ·mol^?1 whereas Cs₃NdBr₆ is stable at ambient temperature and undergoes phase transition in the solid state at 731 K with enthalpy of 8.8 kJ·mol^?1. Enthalpies of melting have been also determined.     

Calorimetric study of water adsorption on saponite

The isotherms and differential heats of water vapor adsorption on Na- and Ca-saponite samples are measured. It is shown that the successive stages of hydration of the internal surface of this mineral appear as waves or inflections in the adsorption isotherms and maxima in the dependences of the differential heat on the adsorption value. The compositions of Na⁺ and Ca²⁺ aquacations in single- and double-layer saponite hydrates are determined. The heats of interaction between water molecules and interlayer Na⁺ cations in single-layer saponite hydrates and between Na⁺ cations and the ion exchanger matrix are estimated.     

微量热法研究非离子型表面活性剂微乳液

用微量热法研究了由正十六烷／正己醇／水／烷基聚氧乙烯醚组成的微乳液中水的状态，对微乳液中水的模式对热效应的影响进行了解释。在微乳液具有异常流变性的水油比范围内，测定了体系在负触变性状态恢复期间的热效应。